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FHSST Physics/Atomic Nucleus/Radioactivity

= Radioactivity =

As was said before, the nucleus experiences the intense struggle between the electric repulsion of protons and nuclear attraction of the nucleons to each other. It therefore should not be surprising that there are many nuclei that are unstable. They can spontaneously (i.e. without an external push) break in pieces. When the fragments reach the distances where the short range nuclear attraction disappears, they fiercely push each other away by the electric forces. Thus accelerated, they move in different directions like small bullets making destruction on their way. This is an example of nuclear radioactivity but there are several other varieties of radioactive decay.

Discovery of radioactivity
Nuclear radioactivity was discovered by Antoine Henri Becquerel in 1896. Following Wilhelm Roentgen who discovered the X-rays, Becquerel pursued his own investigations of these mysterious rays.

The material Becquerel chose to work with contained uranium. He found that the crystals containing uranium and exposed to sunlight, made images on photographic plates even wrapped in black paper. He mistakenly concluded that the sun's energy was being absorbed by the uranium which then emitted X-rays. The truth was revealed thanks to bad weather.katie

On the 26th and 27 February 1896 the skies over Paris were overcast and the uranium crystals Becquerel intended to expose to the sun were returned to a drawer and put over (by chance) the photographic plates. On the first of March, Becquerel developed the plates and to his surprise, found that the images on them were clear and strong. Therefore the uranium emitted radiation without an external source of energy such as the sun. This was the first observation of the nuclear radioactivity.

Later, Becquerel demonstrated that the uranium radiation was similar to the X-rays but, unlike them, could be deflected by a magnetic field and therefore must consist of charged particles. For his discovery of radioactivity, Becquerel was awarded the 1903 Nobel Prize for physics.

Nuclear alpha, beta, and gamma rays
Classical experiment that revealed complex content of the nuclear radiation, was done as follows. The radium crystals (another radioactive element) were put at the bottom of a narrow straight channel made in a thick piece of lead and open at one side. The lead absorbed everything except the particles moving along the channel. This device therefore produced a flux of particles moving in one direction like bullets from a machine gun. In front of the channel was a photoplate that could register the particles.

Without the magnetic field, the image on the plate was in the form of one single dot. When the device was immersed into a perpendicular magnetic field, the flux of particles was split in three fluxes, which was reflected by three dots on the photographic plate.

One of the three fluxes was straight, while two others were deflected in opposite directions. This showed that the initial flux contained positive, negative, and neutral particles. They were named respectively the $$\alpha$$ $$\beta$$, and $$\gamma$$ particles.

The $$\alpha$$-rays were found to be the $${}^4$$He nuclei, two protons and two neutrons bound together. They have weak penetrating ability, a few centimeters of air or a few sheets of paper can effectively block them. The $$\beta$$-rays proved to be electrons. They have a greater penetrating power than the $$\alpha$$-particles and can penetrate 3mm of aluminum. The $$\gamma$$-rays are not deflected because they are high energy photons. They have the same nature as the radio waves, visible light, and the X-rays, but have much shorter wavelength and therefore are much more energetic. Among the three, the $$\gamma$$-rays have the greatest penetrating power being able to pass through several centimeters of lead and still be detected on the other side.

Danger of the ionizing radiation
The $$\alpha$$, $$\beta$$, and $$\gamma$$ particles moving through matter, collide with atoms and knock out electrons from them, i.e. make positive ions out of the atoms. This is why these rays are called ionizing radiation.

Apart from ionizing the atoms, this radiation destroys molecules. For humans and all other organisms, this is the most dangerous feature of the radiation. Imagine thousands of tiny tiny bullets passing through your body and making destruction on their way. Although people do not feel any pain when exposed to nuclear radiation, it harms the cells of the body and thus can make people sick or even kill them. Illness can strike people years after their exposure to nuclear radiation. For example, the ionizing particles can randomly modify the DNA (long organic molecules that store all the information on how a particular cell should function in the body). As a result, some cells with wrong DNA may become cancer cells.

Fortunately, our body is able to repair some damages caused by radiation. Indeed, we are constantly bombarded by the radiation coming from the outer space as well as from the inner parts of our own planet and still survive. However, if the number of damages becomes too large, the body will not cope with them anymore.

There are established norms and acceptable limits for the radiation that are considered safe for human body. If you are going to work in contact with radioactive materials or near them, make sure that the exposure dose is monitored and the limits are adhered to.

You should understand that no costume can protect you from $$\gamma$$-rays! Only a thick wall of concrete or metal can stop them. The special costumes and masks that people wear when handling radioactive materials, protect them not from the rays but from contamination with those materials. Imagine if few specks of radioactive dirt stain your everyday clothes or if you inhale radioactive atoms. They will remain with you all the time and will shoot the bullets at you even when you are sleeping.

In many cases, a very effective way of protecting yourself from the radiation is to keep a certain distance away. Radiation from nuclear sources is distributed equally in all directions. Therefore the number $$n$$ of dangerous particles passing every second through a unit area (say $$1 cm^2$$) is the total number $$N$$ of particles emitted during 1 second, divided by the surface of a sphere

$$n=\frac{N}{4\pi r^2}\ $$,

where $$r$$ is the distance at which we make the observation. From this simple formula, it is seen that the radiation intensity falls down with increasing distance quadratically. In other words, if you increase the distance by a factor of 2, your exposure to the radiation will be decreased by a factor of 4.

Decay law
Unstable nuclei decay spontaneously. A given nucleus can decay next moment, next day or even next century. Nobody can predict when it is going to happen. Despite this seemingly chaotic and unscientific situation, there is a strict order in all this.

Atomic nuclei, being microscopic objects, are ruled by quantum probabilistic laws. Although we cannot predict the exact moment of its decay, we can calculate the probability that a nucleus will decay within this or that time interval. Nuclei decay because of their internal dynamics and not because they become old or somehow rotten.

To illustrate this, let us imagine that yesterday morning we found that a certain nucleus was going to decay within 24 hours with the probability of 50%. However, this morning we found that it is still alive. This fact does not mean that the decay probability for another 24 hours increased. Not at all! It remains the same, 50%, because the nucleus remains the same, nothing wrong happened to it. This can go on and on for centuries.

Actually, we never deal with individual nuclei but rather with huge numbers of identical nuclei. For such collections (ensembles) of quantum objects, the probabilistic laws become statistical laws. Let us assume that in the above example we had 1 million identical nuclei instead of only one. Then by this morning only half of these nuclei would survive because the decay probability for 24 hours was 50%. Among the remaining 500000 nuclei, 250000 will decay by tomorrow morning, then after another 24 hours only 125000 will remain and so on.

The number of unstable nuclei that are still alive continuously decreases with time according to the curve shown in Fig. 15.2

If initially, at time $$t=0$$, their number is $$N_0$$, then after certain time interval $$T_{1/2}$$ only half of these nuclei will remain, namely, $$\frac12 N_0$$. Another one half of the remaining half will decay during another such interval. So, after the time $$2T_{1/2}$$, we will have only one quarter of the initial amount, and so on. The time interval $$T_{1/2}$$, during which one half of unstable nuclei decay, is called their half-life time. It is specific for each unstable nucleus and vary from a fraction of a second to thousands and millions of years. A few examples of such lifetimes are given in Table 15.2

Radioactive dating
Examining the amounts of the decay products makes possible radioactive dating. The most famous is the Carbon dating, a variety of radioactive dating which is applicable only to matter which was once living and presumed to be in equilibrium with the atmosphere, taking in carbon dioxide from the air for photosynthesis.

Cosmic ray protons blast nuclei in the upper atmosphere, producing neutrons which in turn bombard nitrogen, the major constituent of the atmosphere. This neutron bombardment produces the radioactive isotope $${}^{14}_{6}$$C. The radioactive carbon-14 combines with oxygen to form carbon dioxide and is incorporated into the cycle of living things.

The isotope $${}^{14}_{6}$$ decays (see Table 15.2) inside living bodies but is replenished from the air and food. Therefore, while an organism is alive, the concentration of this isotope in the body remains constant. After death, the replenishment from the breath and food stops, but the isotopes that are in the dead body continue to decay. As a result the concentration of $${}^{14}_{6}$$C in it gradually decreases according to the curve shown in Fig. 15.2. The time $$t=0$$ on this Figure corresponds to the moment of death, and $$N_0$$ is the equilibrium concentration of $${}^{14}_{6}$$C in living organisms.

Therefore, by measuring the radioactive emissions from once-living matter and comparing its activity with the equilibrium level of emissions from things living today, an estimation of the time elapsed can be made. For example, if the rate of the radioactive emissions from a piece of wood, caused by the decay of $${}^{14}_{6}$$C, is one-half lower than from living trees, then we can conclude that we are at the point $$t=T_{1/2}$$ on the curve 15.2, i.e. it is elapsed exactly one half-life-time period. According to the Table 15.2, this means that the tree, from which this piece of wood was made, was cut approximately 5730 years ago.

This is how physicists help archaeologists to assign dates to various organic materials.


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Macroeconomics/Central Banks

Central banks are national banks that primarily control the monetary policy of the national economy, through changes in the interest rate. However, they also perform other duties, such as holding reserves of foreign currency, bankrolling government borrowing, and acting as the 'banker's bank', or the 'lender of last resort'.

There are two types of central bank, those that are state-controlled or at best quasi-independent, and those that are fully independent such as the US Federal Reserve and UK Bank of England (since 1997). Due to the potential for political interference in economic policy, with aims other than macroeconomic stability, the potential for infamous boom and bust cycles in an economy is greater for non-independent central banks.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Macroeconomics/Central Banks


text:
Using Ratpoison

This is a book that is aimed to help the average user work with the simple yet powerful window manager Ratpoison. Please note that this book is very far from finished, but if you want to help, feel free to write some!

Table of Contents

 * /Introduction/
 * /Your first steps/
 * /Basic Keystrokes/
 * /Advanced Usage/
 * /Aliasing/
 * /Rebinding keys/
 * /Splitting Windows/
 * /The Config File/
 * /Advanced Commands/
 * Pulling it all together: an example configuration file
 * /Tips and Tricks/
 * /Where to Go from Here/
 * /External Resources/

Ratpoison

title: Using Ratpoison


text:
Talk:Using Ratpoison

Organizing the book
I noticed your new book Using Ratpoison. It seems to get very professional. I just want to let you know at an early stage, that a prefered way of creating subpages is "/" or ":" (without spaces before and afterwards), where "/" gives you the additional advantage that you get an automatic link back to your main page. Have a look at the discussion at Hierarchy naming scheme or the recent conversion at Talk:How To Build A Computer. I'd therefore recommend to organize your book like this: Using Ratpoison       <- should be what you currently call Table of Contents Using Ratpoison/Cover <- Move your cover here (you can link from the bookshelf here) Using Ratpoison/Introduction <- move "What is Ratpoison" and "Pros and cons" here Using Ratpoison/Your first steps and so on. Avoid having too many subpages if you don't have the content yet. For your book, 3 or 4 subpages are enough (more can be easily created later as soon as you have enough content). If there are questions, just ask. --Andreas 10:11, 23 Mar 2005 (UTC)
 * Thank you very much for your feedback. This is in fact my first wikibook, so I am glad for any hints that I can get. I will edit the pages subsequently as soon as I can find some spare time. Etnoy 08:16, 26 Mar 2005 (UTC)

I hope you don't mind me taking the liberty here to implement this. Don't forget that the pipe character '|' can be used to show a link name that differs from the link path, for clarity's sake. Orethrius van Degaurde 07:04, 18 Jun 2005 (UTC)
 * Actually, it looks like Etnoy has this well in-hand, the bookshelf just needs a little cleanup. Orethrius van Degaurde 07:09, 18 Jun 2005 (UTC)

Reorganisation
I merged the two ToCs, it might be prudent to delete the old one. Orethrius van Degaurde 07:21, 18 Jun 2005 (UTC)

 * Actually, now that I think of it, this should go in the ToC, and the Cover should go here. Orethrius van Degaurde 07:21, 18 Jun 2005 (UTC)

 * Done! Hope that's made it a little more prettiful.  Orethrius van Degaurde 07:28, 18 Jun 2005 (UTC)

title: Talk:Using Ratpoison


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FHSST Physics/Atomic Nucleus/Nuclear Reactions

= Nuclear Reactions =

Those of you who studied chemistry, are familiar with the notion of chemical reaction, which, in essence, is just regrouping of atoms that constitute molecules. As a result, reagent chemical compounds are transformed into product compounds.

In the world of nuclear particles, similar processes are possible. When nuclei are close to each other, nucleons from one nucleus can jump into another one. This happens because there are attractive and repulsive forces between the nucleons. The complicated interplay of these forces may cause their regrouping. As a result, the reagent particles are transformed into product particles. Such processes are called nuclear reactions.

For example, when two isotopes $${}^3_2$$He collide, the six nucleons constituting them, can rearrange in such a way that the isotope $${}^4_2$$He is formed and two protons are liberated. Similarly to chemical reactions, this process is denoted as

The same as in chemical reactions, nuclear reactions can also be either exothermic (i.e. releasing energy) or endothermic (i.e. requiring an energy input). The above reaction releases 12.86MeV of energy. This is because the total mass on the left hand side of Eq. (15.3) is in 12.86MeV greater than the total mass of the products on the right hand side (you can check this using Table 15.1).

Thus, when considering a particular nuclear reaction, we can always learn if it releases or absorbs energy. For this, we only need to compare total masses on the left and right hand sides of the equation. Now, you can understand why it is very convenient to express masses in the units of energy.

Composing equations like (15.3), we should always check the superscripts and subscripts of the nuclei in order to have the same number of nucleons and the same charge on both sides of the equation. In the above example, we have six nucleons and the charge +4 in both the initial and final states of the reaction. To make the checking of nucleon number and charge conservation easier, sometimes the proton and neutron are denoted with superscripts and subscripts as well, namely, $${}^1_1p$$and $${}^1_0n$$.

In this case, all we need is to check that sum of superscripts and sum of subscripts are the same on both sides of the equation.


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FHSST Physics/Atomic Nucleus/Detectors

= Detectors =

How can we observe such tiny tiny things as protons and $$\alpha$$-particles? There is no microscope that would be able to discern them. From the very beginning of the sub-atomic era, scientists have been working on the development of special instruments that are called particle detectors. These devices enable us either to register the mere fact that certain particle has passed through certain point in space or to observe the trace of its path (the trajectory). Actually, this is as good as watching the particle. Although the particle sizes are awfully small, when passing through some substances, they leave behind visible traces of tens of centimeters in length. By measuring the curvature of the trajectory of a particle deflected in electric or magnetic field, a physicist can determine the charge and mass of the particle and thus can identify it.

Geiger counter
The most familiar device for registering charged particles is the Geiger counter. It cannot tell you anything about the particle except the fact that it has passed through the counter. The counter consists of a thin metal cylinder filled with gas. A wire electrode runs along the center of the tube and is kept at a high voltage ($$\sim 2000$$V) relative to the cylinder. When a particle passes through the tube, it causes ionization of the gas atoms and thus an electric discharge between the cylinder and the wire. The electric pulse can be counted by a computer or made to produce a click in a loudspeaker. The number of counts per second tells us about intensity of the radiation.

Fluorescent screen
The very first detector was the fluorescent screen. When a charged particle hits the screen, a human eye can discern a flash of light at the point of impact. In fact, we all use this kind of detectors every day when watching TV of looking at a computer (if it does not have an LCD screen of course). Indeed, the images on the screens of their electron-ray tubes are formed by the accelerated electrons.

Photo-emulsion
Another type of particle detector, dating back to Becquerel, is the nuclear photographic emulsion. Passage of charged particles is recorded in the emulsion in the same way that ordinary black and white photographic film records a picture. The only difference is that nuclear photoemulsion is made rather thick in order to catch a significant part of the particle path. After the developing, a permanent record of the charged particle trajectory is available.

Wilson's chamber
In the fields of sub-atomic physics and nuclear physics, Wilson's cloud chamber is the most fundamental device to observe the trajectories of particles. Its basic principle was discovered by C. T. R. Wilson in 1897, and it was put to the practical use in 1911.

The top and the side of the chamber are covered with round glasses of several centimeters in diameter. At the bottom of the chamber, a piston is placed. The air filled in the chamber is saturated with vapor of water. When pulling down the piston quickly, the volume of the chamber would be expanded and the temperature goes down. As a result, the air inside would be supersaturated with the vapor. If a fast moving charged particle enters the chamber when it is in such a supersaturated state, the vapor of water would condense along the line of the ions generated by the particle, which is the path of the particle. Thus we can observe the trace, and also take a photograph. To make clear the trace, a light is sometimes illuminated from the side. When placing the cloud chamber in a magnetic field, we can obtain various informations about the charged particle by measuring the curvature of the trace and other data. The bubble chamber and the spark chamber have taken place of the cloud chamber which is nowadays used only for the educational purposes. Wilson's cloud chamber has however played a very important role in the history of physics.

Bubble chamber
Bubble chamber is a particle detector of major importance during the initial years of high-energy physics. The bubble chamber has produced a wealth of physics from about 1955 well into the 1970s. It is based on the principle of bubble formation in a liquid heated above its boiling point, which is then suddenly expanded, starting boiling where passing charged particles have ionized the atoms of the liquid. The technique was honoured by the Nobel prize award to D. Glaser in 1960. Even today, bubble chamber photographs provide the aesthetically most appealing visualization of subnuclear collisions.

Spark chamber
Spark chamber is a historic device using electric discharges over a gap between two electrodes with large potential difference, to render passing particles visible. Sparks occurred where the gas had been ionized. Most often, multiple short gaps were used, but wide-gap chambers with gaps up to 40 cm were also built. The spark chamber is still of great scientific value in that it remains relatively simple and cheap to build as well as enabling an observer to view the paths of charged particles.

title: FHSST Physics/Atomic Nucleus/Detectors


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FHSST Physics/Atomic Nucleus/Nuclear Energy

= Nuclear Energy =

Nuclei can produce energy via two different types of reactions, namely, fission and fusion reactions. Fission is a break up of a nucleus in two or more pieces (smaller nuclei). Fusion is the opposite process: Formation of a bigger nucleus from two small nuclei.

A question may arise: How two opposite processes can both produce energy? Can we make an inexhaustible souce of energy by breaking up and then fusing the same nuclei? Of course not! The energy conservation law cannot be circumvented in no way. When speaking about fusion and fission, we speak about different ranges of nuclei. Energy can only be released when either light nuclei fuse or heavy nuclei fission.

To understand why this is so, let us recollect that for releasing energy the mass of initial nuclei must be greater than the mass of the products of a nuclear reaction. The mass difference is transformed into the released energy. And why the product nuclei can loose some mass as compared to the initial nuclei? Because they are more tightly bound, i.e. their binding energies are lager.

Fig. 15.3 shows the dependence of the binding energy $$B$$ per nucleon on the number $$A$$ of nucleons constituting a nucleus. As you see, the curve reaches the maximum value of $$\sim9$$MeV per nucleon at around $$A\sim50$$. The nuclei with such number of nucleons cannot produce energy neither through fusion nor through fission. They are kind of ashes and cannot serve as a fuel. In contrast to them, very light nuclei, when fused with each other, make more tightly bound products as well as very heavy nuclei do when split up in lighter fragments.

In fission processes, which were discovered and used first, a heavy nucleus like, for example, uranium or plutonium, splits up in two fragments which are both positively charged. These fragments repel each other by an electric force and move apart at a high speed, distributing their kinetic energy in the surrounding material.

In fusion reactions everything goes in the opposite direction. Very light nuclei, like hydrogen or helium isotopes, when approaching each other to a distance of a few fm ($$1fm = 10^{-13}$$cm), experience strong attraction which overpowers their Coulomb (that is electric) repulsion. As a result the two nuclei fuse into a single nucleus. They collapse with extremely high speeds towards each other. To form a stable nucleus they must get rid of the excessive energy. This energy is emitted by ejecting a neutron or a photon.


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FHSST Physics/Atomic Nucleus/Nuclear Reactors

= Nuclear Reactors =

Since the discovery of radioactivity it was known that heavy nuclei release energy in the processes of spontaneous decay. This process, however, is rather slow and cannot be influenced (speed up or slow down) by humans and therefore could not be effectively used for large-scale energy production. Nonetheless, it is ideal for feeding the devices that must work autonomously in remote places for a long time and do not require much energy. For this, heat from the spontaneous-decays can be converted into electric power in a radioisotope thermoelectric generator. These generators have been used to power space probes and some lighthouses built by Russian engineers. Much more effective way of using nuclear energy is based on another type of nuclear decay which is considered next.

Chain reaction
The discovery that opened up the era of nuclear energy was made in 1939 by German physicists O. Hahn, L. Meitner, F Strassmann, and O. Frisch. They found that a uranium nucleus, after absorbing a neutron, splits into two fragments. This was not a spontaneous but induced fission

that released $$\sim185$$MeV of energy as well as two neutrons which could cause similar reactions on surrounding nuclei. The fact that instead of one initial neutron, in the reaction (15.4) we obtain two neutrons, is crucial. This gives us the possibility to make the so-called chain reaction schematically shown in Fig. 15.4.

In such process, one neutron breaks one heavy nucleus, the two released neutrons break two more heavy nuclei and produce four neutrons which, in turn, can break another four nuclei and so on. This process develops extremely fast. In a split of a second a huge amount of energy can be released, which means explosion. In fact, this is how the so-called atomic bomb works.

Can we control the development of the chain reaction? Yes we can! This is done in nuclear reactors that produce energy for our use. How can it be done?

Critical mass
First of all, if the piece of material containing fissile nuclei is too small, some neutrons may reach its surface and escape without causing further fissions. For each type of fissile material there is therefore a minimal mass of a sample that can support explosive chain reaction. It is called the critical mass. For example, the critical mass of $${}^{235}_{92}{\rm U}$$is approximately 50 kg. If the mass is below the critical value, nuclear explosion is not possible, but the energy is still released and the sample becomes hot. The closer mass is to its critical value, the more energy is released and more intensive is the neutron radiation from the sample.

The criticality of a sample (i.e. its closeness to the critical state) can be reduced by changing its geometry (making its surface bigger) or by putting inside it some other material (boron or cadmium) that is able to absorb neutrons. On the other hand, the criticality can be increased by putting neutron reflectors around the sample. These reflectors work like mirrors from which the escaped neutrons bounce back into the sample. Thus, moving in and out the absorbing material and reflectors, we can keep the sample close to the critical state.

How a nuclear reactor works
In a typical nuclear reactor, the fuel is not in one piece, but in the form of several hundred vertical rods, like a brush. Another system of rods that contain a neutron absorbing material (control rods) can move up and down in between the fuel rods. When totally in, the control rods absorb so many neutrons, that the reactor is shut down. To start the reactor, operator gradually moves the control rods up. In an emergency situation they are dropped down automatically.

To collect the energy, water flows through the reactor core. It becomes extremely hot and goes to a steam generator. There, the heat passes to water in a secondary circuit that becomes steam for use outside the reactor enclosure for rotating turbines that generate electricity.

Nuclear power in South Africa
By 2004 South Africa had only one commercial nuclear reactor supplying power into the national grid. It works in Koeberg located 30 km north of Cape Town. A small research reactor was also operated at Pelindaba as part of the nuclear weapons program, but was dismantled.

Koeberg Nuclear Power station is a uranium Pressurized Water Reactor (PWR). In such a reactor, the primary coolant loop is pressurised so the water does not boil, and heat exchangers, called steam generators, are used to transmit heat to a secondary coolant which is allowed to boil to produce steam. To remove as much heat as possible, the water temperature in the primary loop is allowed to rise up to about $$300^{\circ}$$C which requires the pressure of 150 atmospheres (to keep water from boiling).

The Koeberg power station has the largest turbine generators in the southern hemisphere and produces 1800 megawatts of electrical power. Construction of Koeberg began in 1976 and two of its Units were commissioned in 1984-1985. Since then, the plant has been in more or less continuous operation and there have been no serious incidents.

Eskom that operates this power station, may be the current technology leader. It is developing a new type of nuclear reactor, a modular pebble-bed reactor (PBMR). In contrast to traditional nuclear reactors, in this new type of reactors the fuel is not assembled in the form of rods. The uranium, thorium or plutonium fuels are in oxides (ceramic form) contained within spherical pebbles made of pyrolitic graphite. The pebbles, having a size of a tennis ball, are in a bin or can. An inert gas, helium, nitrogen or carbon dioxide, circulates through the spaces between the fuel pebbles. This carries heat away from the reactor.

Ideally, the heated gas is run directly through a turbine. However since the gas from the primary coolant can be made radioactive by the neutrons in the reactor, usually it is brought to a heat exchanger, where it heats another gas, or steam.

The primary advantage of pebble-bed reactors is that they can be designed to be inherently safe. When a pebble-bed reactor gets hotter, the more rapid motion of the atoms in the fuel increases the probability of neutron capture by $${}^{238}_{92}$$U isotopes through an effect known as Doppler broadening. This isotope does not split up after capturing a neutron. This reduces the number of neutrons available to cause $${}^{235}_{92}$$U fission, reducing the power output by the reactor. This natural negative feedback places an inherent upper limit on the temperature of the fuel without any operator intervention.

The reactor is cooled by an inert, fireproof gas, so it cannot have a steam explosion as a water reactor can.

A pebble-bed reactor thus can have all of its supporting machinery fail, and the reactor will not crack, melt, explode or spew hazardous wastes. It simply goes up to a designed "idle" temperature, and stays there. In that state, the reactor vessel radiates heat, but the vessel and fuel spheres remain intact and undamaged. The machinery can be repaired or the fuel can be removed.

A large advantage of the pebble bed reactor over a conventional water reactor is that they operate at higher temperatures. The reactor can directly heat fluids for low pressure gas turbines. The high temperatures permit systems to get more mechanical energy from the same amount of thermal energy.

Another advantage is that fuel pebbles for different fuels might be used in the same basic design of reactor (though perhaps not at the same time). Proponents claim that some kinds of pebble-bed reactors should be able to use thorium, plutonium and natural unenriched Uranium, as well as the customary enriched uranium. One of the projects in progress is to develop pebbles and reactors that use the plutonium from surplus or expired nuclear explosives.

On June 25, 2003, the South African Republic's Department of Environmental Affairs and Tourism approved ESKOM's prototype 110MW pebble-bed modular reactor for Koeberg. Eskom also has approval for a pebble-bed fuel production plant in Pelindaba. The uranium for this fuel is to be imported from Russia. If the trial is successful, Eskom says it will build up to ten local PBMR plants on South Africa's seacoast. Eskom also wants to export up to 20 PBMR plants per year. The estimated export revenue is 8 billion rand a year, and could employ about 57000 people.


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J2ME Programming/The J2ME Platform

Java 2 Platform, Micro Edition, or J2ME, is a collection of Java APIs targeting embedded consumer products such as PDAs, cell phones and other consumer appliances.

J2ME has become a popular option for creating games for cell phones, as they can be emulated on a PC during the development stage and easily uploaded to the phone. This contrasts with the difficulty of developing, testing, and loading games for other special gaming platforms such as those made by Nintendo, Sony, and others, as expensive system-specific hardware and kits are required.

Often, introductions of J2ME gloss over areas that the beginning J2ME developer might improve their learning process  and hopefully this set of articles will remove that obstacle. What we will cover is the history leading up to J2ME's birth and beyond. We will also cover the complexity of the whole J2ME API ecological system and hopefully this will help you in your J2ME development projects and applications.

Overall, the change from analogue to digital in both devices and infrastructure serving those devices has been the third unseen character in this J2ME evolution. Changes from analogue methods of cellular communication to such standards as CDMA, TDMA,and WCDMA. Also, drastic changes in the vehicle computing and digital TV realm involving new standards such as DVB, MHP, HAVi, MPEG4, OSGi, etc. have changed how computer languages such as Java and the J2ME platform interact with this new area.

A brief history of Java on Mobile Devices (pre-platform and pre-jcp)
This history is called pre-platform and occurs before the 1999 Sun event of renaming java portions as platform editions. In the 1992 time span Sun Microsystems Engineers and  Venture Capital funded Startups contributed to a project called Green  to bring new Virtual Machine execution framework to embedded devices. The device was called Star7 and was powered by a SPARC CPU.

The language which was called OAK at the time and its features were the result of the merge of FirstPerson, ON, and Sun Microsystems. Although, not mentioned in this brief history. The first JVM was in fact completed by ON and based on Smalltalk according to The official Wiki version of history of Java Language. Thus, the having the small foot print of a Virtual Machine not only benefited the birth of Java but its steady climb during this period into browsers and the start of its rebirth into mobile devices.

Although Sun Microsystems concluded that some of its role during this period was to drive the Consumer Device market away from WINTEL to SPARC processors it was the application killer app side that survived this risky startup time period.

PersonalJava (pJava)
Sun's second exploration of java on mobile devices was centered around the idea of deploying a subset of JDK1.1.8 on mobile devices that have a more in depth display as opposed to just a character display. At this time, around 1998, one of the target devices for PersonalJava was set boxes as evidence by press such as McNealy touts Java on set boxes.

As the PersonalJava spec was introduced in 1998 it was nicknamed pJava by Sun Microsystems. Because pJava uses a subset of JDK1.1.8, SUN Microsystems released a pJava Emulation Environment to assist developers in testing their applets and applications for pJava Compliance.

EmbeddedJava
EmbeddedJava was based on JDK1.1.6  and was targeted for those mobile devices that only had a character display.

JavaPhone
The Mobile device OEMs found that the PersonalJava and EmbeddedJava solutions lacked those APIs that would allow access to pure telephony functionality on Mobile Devices. Thus JavaPhone API was designed by Sun Microsystems to be vertical expansion of PersonalJava to add telephony functionality to deployed java solutions on Mobile devices.

JavaTV
JavaTV is designed to provide java apis for the set box and headless network terminals beyond what PersonalJava provides that are specific to the iTV/DTV platform such as HAVi, DVB-MHP, and etc.

AutoJava
AutoJava was also a 1998 Sun Microsystems push into telematics (Auto) and did not get enough traction to survive as a separate api.

JavaOS
JavaOS targets the underlying RealTimeOS (RTOS) structure of the OS that typically is deployed on Mobile Devices or Embedded Devices. JavaOS was launched by SUN Microsystems in the fall of 1996 and was based on the JDK1.0. ChorusOS which was bought during JavaOS development by SUN Microsystems was later spun off as ChorusOS.

Birth of J2ME
As you can see by this NewsFlash in the spring of 1998 the Mobile Device market was being stormed by java but not in a very structured fashion. As you can see from an Interview of the Father of KVM Sun was behind the scenes responding to this fragmentation in the Mobile Device space by innovating a new JVM for Mobile Devices and the first set of J2ME platform specs and as a project was nicknamed Spotless.

J2ME is Alive
In the time period of 1998-1999 SUN Microsystems reveals its behind the scenes work in defeating fragmentation in the Mobile Device space by announcing the formation of the Java Community Process and reorganizing these fragments of java apis for mobile devices into the J2ME, Microediton Platform. Let us now go over how J2ME is organized against API fragmentation in the Mobile Device space.

J2ME Configurations
Sun Microsystems came up with the idea that a configuration API would cover the runtime aspects of J2ME deployed on a device. The smallest J2ME configurations are actually subsets of the largest J2ME configuration. The runtime aspects are covered by having these specific classes in the configuration api:

 * Core Java classes
 * Java programming language features
 * Virtual Machine features

Currently, there are the configurations of CLDC (Connected Limited Device Configuration) and CDC (Connected Device Configuration).

Connected Limited Device Configuration
The CLDC covers devices below 512k size of memory for the JVM environment and removes JNI, user defined class loaders, some class verification items of the class verification process (the reason why we MIDlet Preverify MIDlets compiled to be deployed on CLDC devices) and reflection to fit into this small footprint. The JVM on CLDC devices is called KVM (K-VirtualMachine), nicknamed K-VirtualMachine for kilobyte. The application lifecycle concepts from javaTV and the installation concepts of javaPhone found their way into this Connected Limited Device Configuration. The JSRs for CLDC are:

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 * This Connected Limited Device Configuration 1.0 targets devices with 128k to 512k memory (256kROM/256RAM or less), limited power or battery operation, connectivity to some network at low speeds, and user interface.
 * This Connected Limited Device Configuration 1.1 targets devices with 160K or more memory, processor speeds of 8-32MHZ, limited power or battery operation, and user interface. This configuration adds extends CLDC1.0 to included floating point math.

Connected Device Configuration
The CDC covers devices above the 512k size of memory for the JVM environment. The garbage collector is a separate pluggable item into the CVM deployed on CDC devices. The threads are implemented not as OS specific but as fully implemented threads within the CVM and are known as Green Threads. Threads can also be implemented as OS native threads. Class file verification takes place in the CVM on the device just as in J2SE java platform on desktop systems. The JVM on CDC devices is known as a CVM or the C-VirtualMachine. The JSRs for CDC are:

 * This Connected Device Configuration 1.0 targets devices with 512k minimum ROM/128k minimum RAM, connectivity to some network, supports a complete installation of a complete JVM, and more full featured user interfaces compared to CLDC.
 * This Connected Device Configuration 1.1 extends/updates the CDC1.0 to update J2SE APIs used in CDC1.0 to J2SE 1.4 APIs. Memory size was increased from 128k ROM to 256k ROM.

J2ME Profiles
Profiles provide APIs that focus on a specific group of devices. These devices typically have the same or similar user interfaces (screen and inputs), how the device connects to the network, how the device stores data, and etc. Currently, the Profile Name indicates the Family name of this group of devices or a common functionality with this group of devcies. For example, the MIDP (MID Profile) is for the group of Mobile Information Devices. J2ME Profiles are:

Mobile Information Device Profile
The Mobile Information Device Profile extends and enhances the CLDC to provide a Java environment to develop applications on Mobile information appliances and voice communication devices. The JSRs for this profile are:

 * This Mobile Information Device Profile 1.0 extends the CLDC1.0 java environment in a vertical way to support MIDlet application development on devices targeted in the CLDC1.0 spec by providing a GUI toolkit, persistent data storage, messaging, networking components, and security.  Although, attributes of JavaPhone and Java Telephony are mentioned in the spec; JavaPhone telephony attributes are not included as classes in MIDP1.0 but later on completed as a separate JSR and API package.
 * This Mobile Information Device Profile 2.0 extends MIDP1.0 to include https networking, the domain security model with digital certificates, formally includes OTA provisioning, push architecture of MIDlets responding to events, game functionality added to LCDUI, small xml parser, and a base sound API.
 * This Mobile Information Device Profie 3.0 extends MIDP2.0 to allow MIDlets to be auto-launched, run in background within the same VM, and enable inter-MIDlet communication. Extended functionality includes secure record stores/removable record stores, IPv6, multiple network interfaces per device, and additional MIDlet provisioning in addition to OTA.

Foundation Profile
The Foundation Profile is what can be called a vertical specification profile. A vertical specification profile specifies the targeted family of devices by memory size and the optional profiles that may plugin more functionality in addition to this profile. The GUI APIs are often Profiles plugged in on top of this Profile. Typical rich network devices include set top boxes (iTV), auto-computing (telematics), and etc. The JSRs for this profile are:

hi am the one who wrote it.
 * This Foundation Profile 1.0 targets devices with 128k minimum ROM/512k minimum RAM, connectivity to some network, and no graphical user interface provided by this profile on top of the CDC1.0.
 * This Foundation Profile 1.1 is on top of the CDC1.1 which supports J2SE 1.4 APIs. Targeted devices memory is increased to 256k minimum ROM/512k minimum RAM. Some APIs included to specify functionality for IPv6, security, and more math support.

Personal Profile
This Personal Profile provides high web fidelity to device with a rich network connection and can use the heavy weight applet classes that were part of the PersonalJava spec. While Personal Profile, JSR62, supports PersonalJava1.1.x and PersonalJava1.2.x of the PersonalJava Application Environment; Personal Profile 1.1 supports the adoption of the subset of J2SE1.4 APIs as Personal Profile 1.0 was based on the subset of J2SE1.3 APIs. The JSRs for this profile are:

 * This Personal Profile 1.0 targets devices with 1.5Megs of minimum ROM/1Megs of minimum RAM, and a robust network connection is on top of the CDC1.0 and Foundation Profile1.0 and allows applications developed with pJava Emulation Environment Specification 1.1.x and 1.1.2 to run on devices targeted by this profile.
 * This Personal Profile 1.1 extends the Personal Profile 1.0 to update APIs to J2SE 1.4 and to make sure optional Graphics Packages derived from J2SE 1.4 APIs can be deployed on top of this profile. Devices targeted now are of minimum memory size of 3.5Megs ROM/3.5 RAM.

Personal Basis Profile
This Personal Basis Profile provides a basic graphical user interface, i.e. the AWT lighweight APIs, on top of the CDC and Foundation Profile and is considered as a subset to the Personal Profiles. This profile also provides the xlet classes required for JavaTV. The JSRs for this profile are:

 * This Personal Basis Profile 1.0 is deployed on top of the CDC1.0 and Foundation Profile 1.0 targeting devices with 2Megs minimum ROM/1Megs minimum RAM. the lightweight AWT apis are based on JDK1.1 not JDK1.3 APIs to meet the smaller foot print requirements.
 * This Personal Basis Profile 1.1 extends the Personal Basis Profile 1.0 by updating all APis to derived from J2SE 1.4 APIs to be compatible with optional graphics APIs such as AGUI.

Information Module Profile
This Information Module Profile supports embedded network connected devices without a graphical user interface. This profile is a subset of the MIDP1.0 profile without the LCDUI classes of MIDP1.0. The typical devices target are modems, household devices, and industrial metering devices. While IMP is a subset of MIDP1.0, IMP-NG is a subset of MIDP2.0. The JSRs for this profile are:

 * This Information Module Profile is a subset of  MIDP1.0 missing the LCDUI classes.
 * This Information Module Profile-Next Generation si a subset of mIDP2.0 without the LCDUI classes.

Digital Set Top Box Profile
This Digital Set Top Box Profile is a subset of JavaTV and is targeted for the smaller set top boxes that deploy OCAP. Thus, this profile differs from the javaTV (CDC, PP PBP) setup in that its on top of CLDC not CDC to support a smaller device memory foot print. However, several concepts are borrowed from the JavaTV items in Personal Basis Profile such as the xlet lifecycle. The JSR for this profile is:

 * This Digital Set Top Box Profile is a subset of Personal Java and JavaTV and is based on the current java classes in OCAP. Xlets developed with this Profile are upward compatible with the JavaTV (CDC, PP, and PBP) combination.

J2ME Optional Packages and APIs
During 1999 to 2001 the concept of J2ME Optional Packages and APIs was introduced to provide additional packages and APIs on top of J2ME Profiles to add specific functionality to certain classes of devcies. Some profile JSRs were changed to this new Optional Package concept:

 * The RMI Optional Package provides interoperable J2SE RMI support on top of the CDC and Foundation Profile.
 * The PDA Optional Package is on top of the CLDC and provides optional APIs common to PDAs and handsets. For example, the PIM functionality in JavaPhone makes its re-introduciton into J2ME Platform devices within this ooptional package. FileConnection API is added to allow GCF to access removable media storage.

J2ME Technology for the Wireless Industry
Due to the increasing complexity of J2ME, JTWI was proposed in 2002. The J2ME Technology for the Wireless Industry, also known as, sets a clear architecture concept of what optional packages and APIs match up with which Profiles. This concept covers CLDC1.0, CLDC1.1, CDC1.0, and MIDP2.0 family of devices. The optional packages and APIs are:

 * The Wireless Messaging API provides classes to support messaging application development on the J2ME Platform.
 * The Mobile Media API supports audio and multimedia on both the CLDC and CDC of the J2ME Platform.

The 2nd version of the JTWI2.0 was split along CLDC and CDC configuration lines into is and

Conclusion
Although, other OS specific solutions such as extending C/C++ to the mobile platform has gotten its first burst of adoption; preliminary work in the forms of javaPhone, javaTV, embeddedJava, PersonalJava, and establishment of the J2ME Platform provided the basis for the successful push of J2ME and its steady climb to become the market leader on mobile devices. While, not all of JavaPhone functionality is in full MIDP devices as of yet; this other API brings rest of the JavaPhone to the J2ME Platform:

 * The Mobile Telephony API provides the classes to control the calls on both CLDC and CDC devices.

As we head into the future of Mobile Devices, the Java Community Process Contributors to the J2ME Platform have been busy creating new JSRs to cover new advances Mobile Technology. For example:

 * Specifies the API to manage message boxes and their content on mobile devices.
 * Specifies the API for contactless communication such as through RFID tags and etc.

Trademark Notices
J2ME, Java and all Java-based marks are trademarks or registered trademarks of Sun Microsystems, Inc. in the U.S. and other countries.

title: J2ME Programming/The J2ME Platform


text:
Talk:J2ME Programming/The J2ME Platform

Transeferred Introduciton to J2ME from wikipedia to here for preparation to moving to wikibook J2Me

Authors of this Article from wikipedi are:
 * Fred Grott(Shareme)
 * DJ Clayworth

Now editing to change wikipedia links to proper w:NmaeEntry and need to adjust for use of WEB reference templates Shareme 14:24, 26 Mar 2005 (UTC)

I made changes in the copied Template:Web reference so that Accessed on Month Day, Year is no longer displayed to come into line with wikibooks style Shareme 18:47, 26 Mar 2005 (UTC)

Navigation template is Template:J2ME Navigation

Shareme 19:43, 26 Mar 2005 (UTC)

Volunteer
My name is Laurence Burton and I am an experienced J2ME programmer, but not an experienced wikipedia contributor. I was browsing wikipedia today and I got an itch to do some contributing. Would you folks be interested in some help? If so, what would be the best way for me to begin?

title: Talk:J2ME Programming/The J2ME Platform


text:
FHSST Physics/Atomic Nucleus/Nuclear Fusion

= Nuclear Fusion =

For a given mass of fuel, a fusion reaction like

yields several times more energy than a fission reaction. This is clear from the curve given in Fig. 15.3. Indeed, a change of the binding energy (per nucleon) is much more significant for a fusion reaction than for a fission reaction. Fusion is, therefore, a much more powerful source of energy. For example, 10 g of deuterium which can be extracted from 500 litres of water and 15 g of tritium produced from 30 g of lithium would give enough fuel for the lifetime electricity needs of an average person in an industrialised country.

But this is not the only reason why fusion attracted so much attention from physicists. Another, more fundamental, reason is that the fusion reactions were responsible for the synthesis of the initial amount of light elements at primordial times when the universe was created. Furthermore, the synthesis of nuclei continues inside the stars where the fusion reactions produce all the energy which reaches us in the form of light.

Thermonuclear reactions
If fusion is so advantageous, why is it not used instead of fission reactors? The problem is in the electric repulsion of the nuclei. Before the nuclei on the left hand side of Eq. (15.5) can fuse, we have to bring them somehow close to each other to a distance of about a femtometer. This is not an easy task! They both are positively charged and refuse to approach each other. What we can do is to make a mixture of the atoms containing such nuclei and heat it up. At high temperatures the atoms move very fast. They fiercely collide and loose all the electrons. The mixture becomes plasma, i.e. a mixture of bare nuclei and free moving electrons. If the temperature is high enough, the colliding nuclei can overcome the electric repulsion and approach each other to a fusion distance. When the nuclei fuse, they release much more energy than was spent to heat up the plasma. Thus the initial energy investment pays off. The typical temperature needed to ignite the reaction of the type (15.5) is extremely high. In fact, it is the same temperature that our sun has in its center, namely, about 15 megakelvins. This is why the reactions (15.3), (15.5), and the like are called thermonuclear reactions.

Human-made thermonuclear reactions
The same as with fission reactions, the first application of thermonuclear reactions was in weapons, namely, in the hydrogen bomb, where fusion is ignited by the explosion of an ordinary (fission) plutonium bomb which heats up the fuel to solar temperatures while compressing it immensely.

In an attempt to make a controllable fusion, people encounter the problem of holding the plasma. It is relatively easy to achieve a high temperature (with laser pulses, for example). But as soon as plasma touches the walls of the container, it immediately cools down. To keep it from touching the walls, various ingenious methods are tried, such as strong magnetic field and laser beams directed to plasma from all sides. In spite of all efforts and ingenious tricks, no fusion reactor has demonstrated that it can produce more energy than it consumed creating and containing the plasma. A giant thermonuclear reactor is being planned by the international community to be built in Cadarache, France. It will be the largest of its kind, and theoreticians predict that it may be within the parameters needed to sustain a fusion reaction and extract energy.

Cold fusion
To visualize the struggle of the nuclei approaching each other, imagine yourself pushing a metallic ball towards the top of a slope shown in Fig. 15.5. The more kinetic energy you give to the ball, the higher it can climb. Your purpose is to make it fall into the narrow well that is behind the barrier.

In fact, the curve in Fig.15.5 shows the dependence of relative potential energy $$V_{\rm eff}$$ between two nuclei on the distance $$R$$ separating them. The deep narrow well corresponds to the strong short-range attraction, and the $$\sim1/R$$ barrier represents the Coulomb (electric) repulsion. The nuclei need to overcome this barrier in order to touch each other and fuse, i.e. to fall into the narrow and deep potential well. One way to achieve this is to give them enough kinetic energy, which means to rise the temperature. However, there is another way based on the quantum laws.

As you remember, when discussing the motion of the electron inside an atom (see What the atom is made of), we said that it formed a cloud of probability around the nucleus. The density of this cloud diminishes at very short and very long distances but never disappears completely. This means that we can find the electron even inside the nucleus though with a rather small probability.

The nuclei moving towards each other, being microscopic objects, obey the quantum laws as well. The probability density for finding one nucleus at a distance R from another one also forms a cloud. This density is non-zero even under the barrier and on the other side of the barrier. This means that, in contrast to classical objects, quantum particles, like nuclei, can penetrate through potential barriers even if they do not have enough energy to go over it! This is called the tunneling effect.

The tunneling probability strongly depends on thickness of the barrier. Therefore, instead of lifting the nuclei against the barrier (which means rising the temperature), we can try to make the barrier itself thinner or to keep them close to the barrier for such a long time that even a low penetration probability would be realized.

How can this be done? The idea is to put the nuclei we want to fuse, inside a molecule where they can stay close to each other for a long time. Furthermore, in a molecule, the Coulomb barrier becomes thinner because of electron screening. In this way fusion may proceed even at room temperature.

This idea of cold fusion was originally (in 1947) discussed by F. C. Frank and (in 1948) put forward by A. D. Sakharov, the father of Russian hydrogen bomb, who at the latest stages of his career was worldwide known as a prominent human rights activist and a winner of the Nobel Prize for Peace. When working on the bomb project, he initiated research into peaceful applications of nuclear energy and suggested the fusion of two hydrogen isotopes via the reaction (15.5) by forming a molecule of them where one of the electrons is replaced by a muon.

The muon is an elementary particle (see Elementary particles) which has the same characteristics as an electron. The only difference between them is that the muon is 200 times heavier than the electron. In other words, a muon is a heavy electron. What will happen if we make a muonic atom of hydrogen, that is a bound state of a proton and a muon? Due to its large mass the muon would be very close to the proton and the size of such atom would be 200 times smaller than that of an ordinary atom. This is clearly seen from the formula for the atomic Bohr radius

$$R_{\mbox{Bohr}}=\frac{\bar{h}^2}{me^2}$$

where the mass is in the denominator.

Now, what happens if we make a muonic molecule? It will also be 200 times smaller than an ordinary molecule. The Coulomb barrier will be approximately 200 times thinner and the nuclei 200 times closer to each other. This is just what we need! Speaking in terms of the effective nucleus-nucleus potential shown in Fig. 15.5, we can say that the muon modifies this potential in such a way that a second minimum appears. Such a modified potential is (schematically) shown in Fig. 15.6

The molecule is a bound state in the shallow but wide minimum of this potential. Most of the time, the nuclei are at the distance corresponding to the maximum of the probability density distribution (shown by the thin curve). Observe that this density is not zero under the barrier (though is rather small) and even at $$R=0$$. This means that the system can (with a small probability) jump from the shallow well into the deep well through the barrier, i.e. can tunnel and fuse.

Unfortunately, the muon is not a stable particle. Its lifetime is only ≈ 10−6 s. This means that a muonic molecule cannot exist longer than 1 microsecond. As a matter of fact, from a quantum mechanical point of view, this is quite a long interval.

The quantum mechanical wave function (that describes the probability density) oscillates with a frequency which is proportional to the energy of the system. With a typical binding energy of a muonic molecule of about 300 eV this frequency is 1017 Hz or 100 PHz.

This means that the particle hits the barrier with this frequency and during 1 microsecond it makes $$10^{11}$$ attempts to jump through it. The calculations show that the penetration probability is ≈ 10−7. Therefore, during 1 microsecond nuclei can penetrate through the barrier 10000 times and fusion can happen much faster than the decay rate of the muon. Cold fusion via the formation of muonic molecules was done in many laboratories, but unfortunately, it cannot solve the problem of energy production for our needs. The obstacle is the negative efficiency, i.e. to make muonic cold fusion we have to spend more energy than it produces. The reason is that muons do not exist like protons or electrons. We have to produce them in accelerators. This takes a lot of energy. Actually, the muon serves as a catalyst for the fusion reaction. After helping one pair of nuclei to fuse, the muon is liberated from the molecule and can form another molecule, and so on. It was estimated that the efficiency of the energy production would be positive only if each muon ignited at least 1000 fusion events. Experimentalists tried their best, but by now the record number is only 150 fusion events per muon. This is too few. The main reason why the muon does not catalyze more reactions is that it is eventually trapped by a $${}^4$$He nucleus which is a by-product of fusion. Helium captures the muon into an atomic orbit with large binding energy, and it cannot escape.

Nonetheless, the research in the field of cold fusion continues. There are some other ideas of how to keep nuclei close to each other. One of them is to put the nuclei inside a crystal. Another way out is to increase the penetration probability by using molecules with special properties, namely, those that have quantum states with almost the same energies as the excited states on the compound nucleus. Scientists try all possibilities since the energy demands of mankind grow continuously and therefore the stakes in this quest are high.


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FHSST Physics/Atomic Nucleus/Elementary Particles

= Elementary Particles =

In our quest for the elementary building blocks of the universe, we delved inside the atomic nucleus and found that it is composed of protons and neutrons. Are the three particles, $$e$$, $$p$$ and $$n$$, the blocks we are looking for? The answer is no. Even before the structure of the atom was understood, Becquerel discovered the radioactivity (see Discovery of radioactivity) that afterwards puzzled physicists and forced them to look deeper - inside protons and neutrons.


text:
FHSST Physics/Atomic Nucleus/Beta Decay

= Beta Decay =

Among the three types of radioactivity, the $$\alpha$$ and $$\gamma$$ rays were easily explained. The emission of $$\alpha$$ particle is kind of lop-sided fission reaction, when an initial nucleus spontaneously decays in two fragments one of which is the nucleus $${}^4_2$$He (i.e. $$\alpha$$ particle). The $$\gamma$$ rays are electromagnetic quanta (photons) emitted by a nuclear system when it transits from one quantum state to another (similar to an atom emitting visible light when an electron drops to a lower energy level).

The $$\beta$$ rays posed the puzzle. On the one hand, they are just electrons and you may think that it looks simple. But on the other hand, they are not the electrons from the atomic shell. It was found that they come from inside the nucleus! After the $$\beta$$-decay, the charge of the nucleus increases in one unit,

$${}^A_Z\left(\mbox{parent nucleus}\right)\,\longrightarrow\,{}^A_{Z+1}\left(\mbox{daughter nucleus}\right)+e\ ,$$

which is in accordance with the charge conservation law.

There was another puzzle associated with the $$\beta$$ decay: The emitted electrons did not have a fixed energy. Measuring their kinetic energies, you could find very fast and very slow electrons as well as the electrons with intermediate speeds. How could identical parent nuclei, after losing different amount of energy, become identical daughter nuclei? Perhaps energy is not conserved in the quantum world? The possibility was so astounding that even Niels Bohr put forward the idea of statistical nature of the energy conservation law.

To explain the first puzzle, it was first suggested that neutron is a bound state of proton and electron. At that time, some physicists believed that if something is emitted from an object, it must be present in that object before the emission. They could not imagine that a particle could be created from vacuum.

The naive $$(pe)$$ model of the neutron contradicted the facts. Indeed, it was known already that the $$pe$$ bound state is the hydrogen atom. A neutron is much smaller than the hydrogen atom. Therefore, it would be unusually tight binding, and perhaps with something else involved that keeps the size small. By the way, this something else could also save the energy conservation law. In 1930, Wolfgang Pauli suggested that in addition to the electron, the $$\beta$$ decay involves another particle, $$\nu$$, that is emitted along with the electron and carries away part of the energy. For example,

This additional particle was called neutrino (in Italian the word neutrino means small neutron). The neutrino is electrically neutral, has extremely small mass (maybe even zero, which is still a question in 2004) and very weakly interacts with matter. This is why it was not detected experimentally till 1956. The bar over $$\nu$$ in Eq. (15.6) means that in this reaction actually the anti-neutrino is emitted (see the discussion on anti-particles further down in Sec. Elementary particles: Particle Physics).

title: FHSST Physics/Atomic Nucleus/Beta Decay


text:
FHSST Physics/Atomic Nucleus/Particle Physics

=Particle Physics =

In an attempt to explain the $$\beta$$ decay and to understand internal structure of the neutron a new branch of physics was born, the particle physics. The only way to explore the structure of sub-atomic particles is to strike them with other particles in order to knock out their constituent parts. The simple logic says: The more powerful the impact, the smaller parts can be knocked out.

At the beginning the only source of energetic particles to strike other particles were the cosmic rays. Earth is constantly bombarded by all sort of particles coming from the outer space. Atmosphere protects us from most of them, but many still reach the ground.

Antiparticles
In 1932, studying the cosmic rays with a bubble chamber, Carl Anderson made a photograph of two symmetrical tracks of charged particles. The measurements of the track curvatures showed that one track belonged to an electron and the other was made by a particle having the same mass and equal but positive charge. These particles were created when a cosmic $$\gamma$$ quantum of a high energy collided with a nucleus.

The discovered particle was called positron and denoted as $$e^+$$ to distinguish it from the electron, which sometimes is denoted as $$e^-$$. It was the first antiparticle discovered. Later, it was found that every particle has its mirror reflection, the antiparticle. To denote an antiparticle, it is used bar over a particle symbol. For example, $$\bar{p}$$ is the anti-proton, which has the same mass as an ordinary proton but a negative charge.

When a particle collides with its mirror reflection, they annihilate, i.e. they burn out completely. In this collision, all their mass is transformed into electromagnetic energy in the form of $$\gamma$$ quanta. For example, if an electron collides with a positron, the following reaction may take place

$$\begin{matrix}e^-+e^+\,\longrightarrow\,\gamma+\gamma\ ,\end{matrix}$$

where two photons are needed to conserve the total momentum of the system.

In principle, stable antimatter can exist. For example, the pair of $$\bar{p}$$ and $$e^+$$ can form an atom of anti-hydrogen with exactly the same energy states as the ordinary hydrogen. Experimentally, atoms of anti-helium were obtained. The problem with them is that, surrounded by ordinary matter, they cannot live long. Colliding with ordinary atoms, they annihilate very fast.

There are speculations that our universe should be symmetric with respect to particles and antiparticles. Indeed, why should preference be given to matter and not to anti-matter? This implies that somewhere very far, there must be equal amount of anti-matter, i.e. anti-universe. Can you imagine what happens if they meet?

Muon, mesons, and the others
In yet another cosmic-ray experiment a particle having the same properties as the electron but $$\sim$$207 times heavier, was discovered in 1935. It was given the name muon and the symbol $$\mu$$. For a long time it remained unnecessary particle in the picture of the world. Only the modern theories harmonically included the muon as a constituent part of matter (see Elementary particles: Quarks and leptons).

The same inexhaustible cosmic rays revealed the $$\pi$$ and $$K$$ mesons in 1947. The $$\pi$$ mesons (or simply pions) were theoretically predicted twelve years before by Yukawa, as the mediators of the strong forces between nucleons. The $$K$$ mesons, however, were unexpected. Furthermore, they showed very strange behaviour. They were easily created only in pairs. The probability of the inverse process (i.e. their decay) was $$10^{13}$$ times lower than the probability of their creation.

It was suggested that these particles possess a new type of charge, the strangeness, which is conserving in the strong interactions. When a pair of such particles is created, one of them has strangeness $$+1$$ and the other $$-1$$, so the total strangeness remains zero. When decaying, they act individually and therefore the strangeness is not conserving. According to the suggestion, this is only possible through the weak interactions that are much weaker than the strong interactions (see Sec. Elementary particles: Forces of nature) and thus the decay probability is much lower.

The golden age of particle physics began in 1950-s with the advent of particle accelerators, the machines that produced beams of electrons or protons with high kinetic energy. Having such beams available, experimentalists can plan the experiment and repeat it, while with the cosmic rays they were at the mercy of chance. When the accelerators became the main tool of exploration, the particle physics acquired its second name, the high energy physics.

During the last half a century, experimentalists discovered so many new particles (few of them are listed in Table 15.5) that it became obvious that they cannot all be elementary. When colliding with each other, they produce some other particles. Mutual transformations of the particles is their main property.

Physicists faced the problem of particle classification similar to the problems of classification of animals, plants, and chemical elements. The first approach was very simple. The particles were divided in four groups according to their mass: leptons (light particles, like electron), mesons (intermediate mass, like pion), baryons (heavy particles, like proton or neutron), and hyperons (very heavy particles).

Then it was realized that it would be more logical to divide the particles in three families according to their ability to interact via weak, electromagnetic, and strong forces (in addition to that, all particles experience gravitational attraction towards each other). Except for the gravitational interaction, the photon ($$\gamma$$ quantum) participates only in electromagnetic interactions, the leptons take part in both weak and electromagnetic interactions, and hadrons are able to interact via all forces of nature (see Elementary particles: Forces_of_nature).

In addition to conservation of the strangeness, several other conservation laws were discovered. For example, number of leptons is conserving. This is why in the reaction (15.6) we have an electron (lepton number $$+1$$) and anti-neutrino (lepton number $$-1$$) in the final state. Similarly, the number of baryons is conserving in all reactions.

The quest for the constituent parts of the neutron has led us to something unexpected. We found that there are several hundreds of different particles that can be knocked out of the neutron but none of them are its parts. Actually, the neutron itself can be knocked out of some of them! What a mess! Further efforts of experimentalists could not find an order, which was finally discovered by theoreticians who introduced the notion of quarks.


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FHSST Physics/Atomic Nucleus/Quarks and Leptons

= Quarks and Leptons =

While experimentalists seemed to be lost in the maze, the theoreticians groped for the way out. Using an extremely complicated mathematical technique, they managed to group the hadrons in such families which implied that all known (and yet unknown) hadrons are built of only six types of particles with fractional charges. The main credit for this (in the form of Nobel Prize) was given to M. Gell-Mann and G. Zweig.

At first, they considered a subset of the hadrons and developed a theory with only three types of such truly elementary particles. When Murray Gell-Mann thought of the name for them, he came across the book "Finnegans Wake" by James Joyce. The line "Three quarks for Muster Mark!" appeared on page 383 of that book (the word quark there is a merging of the words quart and quack, among others). He needed a name for three particles and this was the answer. Thus the term quark was coined.

Later, the theory was generalized to include all known particles, which required six types of quarks. Modern theories require also that the number of different leptons should be the same as the number of different quark types. According to these theories, the quarks and leptons are truly elementary, i.e. they do not have any internal structure and therefore are of a zero size (pointlike). Thus, the world is constructed of just twelve types of elementary building blocks that are given in Table 15.4. Amazingly enough, the electron that was discovered before all other particles, more than a century ago, turned out to be one of them!

After Gell-Mann, who used a funny name (quark) for an elementary particle, the fundamental physics was flooded with such names. For example, the six quark types are called flavors (for cottage cheese, this is appropriate indeed), the three different states in which each quark can be, are called colors (red, green, blue) etc. Modern physics is so complicated and mathematical, that people working in it, need such kind of jokes to spice unsavoury dish with flavors. The funny names should not confuse anybody. Elementary particles do not have any smell, taste, or colour. These terms simply denote certain properties (similar to electric charge) that do not exist in human world.

Hadrons
There are particles that are able to interact with each other by the so-called strong forces. Another name for these forces is nuclear forces. They are very strong at short distances ($$\sim 10^{-15}$$m), and very quickly vanish when the distance between the particles increases. All these particles are called hadrons. The protons and neutrons are examples of hadrons. As you remember, we learned about the existence of huge variety of particles when trying to look inside a nucleon, more particularly, the neutron. So, what the neutron is made of? Can we get the answer at last, after learning about the quarks? Yes, we can. According to modern theories, all hadrons are composed of quarks. The quarks can be combined in groups of two or three. The boundstates of two quarks are called mesons, and the boundcomplexes of three quarks are called baryons. No other numbers of quarks can form observable particles (Recently, experimentalists and theoreticians started to actively discuss the possibility of the existence of pentaquarks, exotic particles that are bound complexes of five quarks.).

Nucleons are baryons and therefore consist of three quarks while the pion is a meson containing only two quarks, as schematically shown in Fig. 15.7. Comparing this figure with Table 15.4, you can see why quarks have fractional charges. Counting the total charge of a hadron, you should not forget that anti-quarks have the opposite charges. The baryon number for an anti-quark also has the opposite sign (negative). This is why mesons actually consist of a quark and anti-quark in order to have total baryon number zero.

Particle reactions
At the early stages of the particle physics development, in order to find the constituent parts of various particles, experimentalists simply collided them and watched the fragments. However, this straightforward approach led to confusion. For example, the reaction between the $$\pi^-$$ meson and proton,

would suggest (if naively interpreted) that either $$K^0$$ or $$\Lambda^0$$ is a constituent part of the nucleon while the pion is incorporated into the other fragment. On the other hand, the same collision can knock out different fragments from the same proton. For example,

which leads to an absurd suggestion that neutron is a constituent part of proton.

The quark model explains all such puzzles nicely and logically. Similarly to chemical reactions that are just rearrangements of atoms, the particle reactions of the type (15.8 and 15.9) are just rearrangements of the quarks. The only difference is that, in contrast to chemistry where the number of atoms is not changing, the number of quarks before the collision is not necessarily equal to their number after the collision. This is because a quark from one colliding particle can annihilate with the corresponding antiquark from another particle. Moreover, if the collision is sufficiently powerful, the quark-antiquark pairs can be created from vacuum.

It is convenient to depict the particle transformations in the form of the so-called quark flow diagrams. On such diagrams, the quarks are represented by lines that may be visualized as the trajectories showing their movement from the left to the right.

For example, the diagram given in Fig. 15.8, shows the quark rearrangement for the reaction (15.8). As you can see, when the pion collides with proton, its $$\bar{u}$$ quark annihilates with the $$u$$ quark from the proton. At the same time, the $$s\bar{s}$$ pair is created from the vacuum. Then, the $$\bar{s}$$ quark binds with the $$d$$ quark to form the strange meson $$K^0$$, while the $$s$$ quark goes together with the $$ud$$ pair as the strange baryon $$\Lambda^0$$.

The charge-exchange reaction (15.9) is a more simple rearrangement process shown in Fig. 15.9. You may wonder why the quark and antiquark of the same flavor in the $$\pi^0$$ meson do not annihilate. Yes they do, but not immediately. And due to this annihilation, the lifetime of $$\pi^0$$ is 100 million times shorter than the lifetime of $$\pi^{\pm}$$ (see Table 15.3).

Despite its simplicity, the quark-flow diagram technique is very powerful method not only for explaining the observed reactions but also for predicting new reactions that have not yet been seen in experiments. Knowing the quark content of particles (which is available in modern Physics Handbooks), you can draw plenty of such diagrams that will describe possible particle transformations. The only rule is to keep the lines continuous. They can disappear or emerge only for a quark-antiquark pair of the same flavor.

However, the continuity of the quark lines is valid only for the processes caused by the strong interaction. Indeed, the $$\beta$$-decay of a free neutron (caused by the weak forces),

as well as the $$\beta$$-decay of the nuclei, indicate that quarks can change flavor. In particular, the $$\beta$$-decay (15.10 or 15.6) happens because the $$d$$ quark transformes into the $$u$$ quark,

due to the weak interaction, as shown in Fig. 15.10

Quark confinement
At this point, it is very logical to ask if anybody observed an isolated quark. The answer is no. Why? And how can one be so confident of the quark model when no one has ever seen an isolated quark?

Basically, you can't see an isolated quark because the quark-quark attractive force does not let them go. In contrast to all other systems, the attraction between quarks grows with the distance separating them. It is like a rubber cord connecting two balls. When the balls are close to each other, the cord is not stretched and the balls do not feel any force. If, however, you try to separate the balls, the cord pulls them back. The more you stretch the cord, the stronger the force becomes (according to the Hook's law of elasticity). Of course, a real rubber cord would eventually break. This does not happen with the quark-quark force. It can grow to infinity. This phenomenon is called the confinement of quarks.

Nonetheless, we are sure that the nucleon consists of three quarks having fractional charges. A hundred years ago Rutherford, by observing the scattering of charged particles from an atom, proved that its positive charge is concentrated in a small nucleus. Nowadays, similar experiments prove the existence of fractional point-like charges inside the nucleon.

The quark model actually is much more complicated than the quark-flow diagrams. It is a consistent mathematical theory that explains a vast variety of experimental data. This is why nobody doubts that it reflects the reality.


text:
FHSST Physics/Atomic Nucleus/Forces of Nature

=Forces of Nature =

If asked how many types of forces exist, many people start counting on their fingers, and when the count exceeds ten, they answer plenty of. Indeed, there are gravitational forces, electrical, magnetic, elastic, frictional forces, and also forces of wind, of expanding steam, of contracting muscles, etc.

If, however, we analyze the root causes of all these forces, we can reduce their number to just a few fundamental forces (or fundamental interactions, as physicists say).

For example, the elastic force of a stretched rubber cord is due to the attraction between the molecules that the rubber is made of. Looking deeper, we find that the molecules attract each other because of the electromagnetic attraction between the electrons of one molecule and nuclei of the other. Similarly, if we depress a piece of rubber, it resists because the molecules refuse to approach each other too close due to the electric repulsion of the nuclei. Therefore the elasticity of rubber has the electromagnetic origin.

Any other force in the human world can be analyzed in the same manner. After doing this, we will find that all forces that we see around us (in the macroworld), are either of gravitational or electromagnetic nature. As we also know, in the microworld there are two other types of forces: The strong (nuclear) forces that act between all hadrons, and the weak forces that are responsible for changing the quark flavors.

Therefore, all interactions in the Universe are governed by only four fundamental forces: Strong, electromagnetic, weak and gravitational. These forces are very different in strength and range. Their relative strengths are given in Table 15.5. The most strong is the nuclear interaction. The strength of the electromagnetic forces is one hundred times lower. The weak forces are nine orders of magnitude weaker than the nuclear forces, and the gravity is 38 orders of magnitude weaker! It is amazing that this subtle interaction governs the cosmic processes. The reason is that the gravitational forces are of long range and always attractive. There is no such thing as negative mass that would screen the gravitational field, like negative electrons screen the field of positive nuclei.

Towards the unified force
Physicists always try to simplify things. Since there are only four fundamental forces, it is tempting to ask "If only four, then why not only one?". Can it be that all interactions are just different faces of one master force?

The first who started the quest for unification of forces was Einstein. After completing his general theory of relativity, he spent 30 years in unsuccessful attempts to unify the electromagnetic and gravity forces. At that time, it seemed logical because both of them were infinite in range and obeyed the same inverse square law. Einstein failed because the unification should be done on the basis of quantum laws, but he tried to do it using the classical concepts.

Electro-weak unification
Now it is known that despite the similarities in form of the gravity and electromagnetic forces, the gravity will be the last to yield to unification. The more implausible unification of the electromagnetic and weak forces turned out to be the first successful step towards the unified interaction.

In 1979, the Nobel prize was awarded to Weinberg, Salam, and Glashow, who developed a unified theory of electromagnetic and weak interactions. According to that theory, the electromagnetic and weak forces converge to one electro-weak interaction at very high collision energies. The theory also predicted the existence of heavy particles, the $$W$$ and $$Z$$ (vector bosons), with masses around 80000MeV and 90000MeV, respectively. These particles were discovered in 1983, which brought experimental verification to the new theory.

Grand unification
The next step was to try to combine the electro-weak theory with the theory of the strong interactions (i.e. quark theory) in a single theory. This work was called the grand unification. Currently, physicists discuss versions of such theory that predicts the convergence of the three forces at awfully high energies $$\sim10^{17}$$MeV. The quarks and leptons in this theory, are the unified leptoquarks.

The grand unification is not that successful as the electro-weak theory. It has the problem of mathematical consistency and contradicts to at least one experiment. The matter is that it predicts the proton decay,

$$p\,\longrightarrow\, e^+ +\pi^0\ $$,

that does not conserve both the baryon and lepton numbers, with the lifetime of $$\sim10^{29}$$years. The measurements show, however, that the lifetime of the proton is at least $$10^{32}$$ years.

Theory Of Everything
Some people believe that the grand unification has an inherent principal flaw. According to them, one cannot unify the forces step by step (leaving the gravity out), and the correct way is to combine all four forces in the so-called theory of everything.

There are few different approaches to unifying everything. One of them suggests that all fundamental particles (quarks and leptons) are just vibrating modes of string loops in multidimensional space. The electron is a string vibrating one way, the up-quark is a string vibrating another way, and so on. The other approach introduces a new level of fundamental particles, the preons, that could be constituent parts of quarks and leptons. The quest goes on.

Everyone agrees that constructing the theory of everything would in no way mean that biology, geology, chemistry, or even physics had been solved. The universe is so rich and complex that the discovery of the fundamental theory would not mean the end of science. The ultimate theory of everything would provide an unshakable pillar of coherence forever assuring us that the universe is a comprehensible place.


text:
Using Ratpoison/Introduction

Welcome to the Using Ratpoison Wikibook.

Purpose
This is intended to be a book aimed at the intermediate/advanced GNU/Linux user who wants to start using the Ratpoison Window manager.

Thusly, only the window manager itself will be covered- this guide assumes that you have a working system running, from the kernel up to the X11 Windowing System, and it assumes you have competent grasp on Linux- this book will not teach you how to use GNU/Linux in general. Please see your distribution documentation or the Linux Guide to learn Linux in general.

Who is this guide suitable for?
Basically, any GNU/Linux or BSD user who wants to try something new or exciting, but also the user who wants to experiment with a different approach to mouse usage.

What is ratpoison?
Ratpoison is a window manager written for X Window, and principally developed by Linux users (though it should run on any operating system and platform X Window does). It is very different from most other window managers in that it is a tiling window manager and because it tries to minimize or completely eliminate the use of the mouse, in order to relieve stress on the arms and shoulders.

In keeping with this old-school approach, ratpoison is also extremely lightweight, and there are no "fat library dependencies", no fancy graphics beyond what other programs provide, and no window decoration. While this might seem odd at first, starting to use it is in fact quite simple. If you've ever used the GNU Screen terminal multiplexer or GNU Emacs, you'll be quite familiar with the interface, since most of the hotkeys and design ideas are borrowed from those programs. Indeed, the developers are very much fans of Emacs, as evidenced in one of the FAQs:
 * "I want feature XYZ."
 * "What you want is probably already in Emacs. If you don't use Emacs, start. If do use Emacs, use it more. If you *still* can't do what you want to do, you probably shouldn't do it." (sic)

Pros

 * 1) Ratpoison is extremely lightweight and will therefore start up and run very quickly; it will also run well on ancient hardware as well as more modern setups such as a 32-way SPARC.
 * 2) Rodent usage is minimized and the keyboard is promoted, relieving your arms and shoulders and decreasing the risk of injury
 * 3) Ratpoison works well with multiple monitors.
 * 4) Ratpoison key-bindings are very similar to those of GNU Screen and should be familiar to users with experience using Screen.

Cons

 * 1) High learning curve. Not particularly suited for UNIX beginners, without a lot of customization- this is a window manager written by experts for experts, so to speak.
 * 2) Some programs like the GIMP (which uses a multitude of small windows) are simply not designed to work with tiling window managers and do not work very well.
 * 3) Java GUI applications have some issues with the way Ratpoison handles window parenting and most Java GUI applications will only render as a grey box. (This problem could be solved by issuing 'export AWT_TOOLKIT=MToolkit' command before starting Java app).

Concepts
To start with, ratpoison has some radically different concepts about using a computer. First, you cannot drag windows around the "desktop", all windows are maximized to the full screen size and that cannot be changed. Because of this, you don't need window decorations, since they would steal precious space. When you look at a program, the only thing you see is the program. You are not forced to look at only one program at a time however: a window can be subdivided into a number of adjacent (but not overlapping!) frames; each of these frames holds a single program which is maximized within its frame. In Emacs terms, there is one window, split into one or more frames, in which each buffer is shown in one and only one frame.

title: Using Ratpoison/Introduction


text:
Puzzles/Escaping from Prison

Puzzles | Lateral puzzles | Escaping from Prison

Escaping From Prison

A man is inside a prison cell. The cell is completely empty except for the man and a table. There are no doors or windows to escape from. There is also a desert surrounding the prison. At the edge of the desert is a town. The man escapes and traverses the desert to reach the town without walking over the desert. How?

Solution

title: Puzzles/Escaping from Prison


text:
Puzzles/Escaping from Prison/Solution

The man hits his hand on the table until it is sore. He then uses the saw to chop the table into two halves. He puts the two halves together to make a whole. He jumps through the hole and lands in the desert. He shouts and shouts until his voice is hoarse. He jumps onto the horse and rides to the town. Before he gets to the town, he comes across a river. He then remembers that the banks close at 5pm. So he waits until 5pm and crosses the river into town.

title: Puzzles/Escaping from Prison/Solution


text:
User:Harami~enwikibooks

ja ja:User:Harami

title: User:Harami~enwikibooks


text: Template:J2ME Programming/Navigation

title: Template:J2ME Programming/Navigation


text:
J2ME Programming/Connected Limited Device Configuration

Introduction
Many people confuse the role of CLDC in J2ME application development. It alone is not a framework for application development because you need more than a configuration to produce J2ME applications. You can think of CLDC as the spec that helps define the subset of the J2ME language items such as input/output, math, and etc that the Java Virtual Machine uses as its set of rules in actually runing MIDlets under the Mobile Information Device Profile(MIDP).

Package Structure
We can get a clearer picture of this by observing what each package in the CLDC defines as the J2ME java subset. Although its not clear from the javadocs, Sun Microsystems does not separate MIDP and CLDC javadocs, these are the actual packages of CLDC:

CLDC1.0 list of Packages under java.*

 * java.lang.*
 * java.io.*
 * java.util.*

Thus, we have classes that deinfe the java language subset attributes used. How the java language subset definitions for input/output are used. Also, a language definition of the subset of java.util.* from the full java language.

Math Classes(CLDC1.0) in java.lang.* package from J2SE1.3

 * java.lang.Long
 * java.lang.Short
 * java.lang.Integer

Notice when compared to J2SE math we have no floating point(Float class) and no double(Double class).

Utility Classes(CLDC1.0) from J2SE1.3

 * java.lang.Math
 * java.util.Random

System Classes(CLDC1.0) in java.lang.* package from J2SE1.3

 * java.lang.System
 * java.lang.Object
 * java.lang.Runtime
 * java.lang.Thread
 * java.lang.Throwable
 * java.lang.String
 * java.lang.StringBuffer

Data Type Classes(CLDC1.0) in java.lang.* package from J2SE1.3 excluding math

 * java.lang.Boolean
 * java.lang.Byte
 * java.lang.Character

Collection Classes(CLDC1.0) in java.util.* package from J2SE1.3

 * java.util.Enumeration
 * java.util.Hashtable(see note in conclusion, from jdk1.1.8 not jse1.3)
 * java.util.Stack
 * java.util.Vector(see note in conclusion, from jdk1.1.8 not jse1.3)

Calendar and Time Classes(CLDC1.0) in java.util.* package from J2SE1.3

 * java.util.Calendar
 * java.util.Date
 * java.util.TimeZone

IO Classes(CLDC1.1) excluding GCF in java.io.* package from J2SE1.3

 * java.io.Writer
 * java.io.Reader
 * java.io.ByteArrayInputStream
 * java.io.ByteArrayOutputStream
 * java.io.DataInputStream
 * java.io.DataOutputStream
 * java.io.InputStream
 * java.io.OutputStream
 * java.io.InputStreamWriter
 * java.io.OuputStreamWriter
 * java.io.PrintStream

Exception Classes(CLDC1.0) in java.util.* package from J2SE1.3

 * java.util.EmptyStackException
 * java.util.NoSuchElementException

Exception Classes(CLDC1.0) in java.io.* package from J2SE1.3

 * java.io.EOFException
 * java.io.IOException
 * java.io.InterruptedException
 * java.io.UnsupportedEncodingException
 * java.io.UTFDataFormatException

Error Classes(CLDC1.0) in java.lang.* package from J2SE1.3

 * java.lang.Error
 * java.lang.VirtualMachineError
 * java.lang.OutOfMemoryError

The other clases are mixed in with MIDP in the javadocs, thus I will list the full list of CLDC classes under the javax.microedition.io.* package. The class is the capitalized name at the right sight of the dot ending the package.

CLDC1.0 list of classes under javax.microedition.io.*

 * javax.microedition.io.InputConnection
 * javax.microedition.io.Connection
 * javax.microedition.io.StreamConnection
 * javax.microedition.io.OutputConnection
 * javax.microedition.io.Datagram
 * javax.microedition.io.DatagramConnection
 * javax.microedition.io.StreamConnectionNotifier
 * javax.microedition.io.ContentConnection
 * javax.microedition.io.ConnectionNotFoundException
 * javax.microedition.io.Connector

The common aspect that sets these classes apart is that they are interfaces defining the capabilities of the input/output connections. The classes in java.io.* define the java language attributes that input/output classes in javax.microedition.io.* use as their rule set.

CLDC1.1 additional classes

 * java.lang.Float
 * java.lang.Double
 * java.lang.Math

GCF, General Connection Framework
In the J2ME platform the J2SE IO is replaced with a smaller General Connection Framework(GCF).

javax.microedition.io GCF Classes from CLDC1.0

 * javax.microedition.io.InputConnection
 * javax.microedition.io.Connection
 * javax.microedition.io.StreamConnection
 * javax.microedition.io.OutputConnection
 * javax.microedition.io.DatagramConnection
 * javax.microedition.io.StreamConnectionNotifier
 * javax.microedition.io.ContentConnection
 * javax.microedition.io.HttpConnection

Conclusion
In conclusion, under the subset of java language for CLDC we do not have floating point math, no double, no class loaders, no sockets and no serialization. A smaller IO framework known as GCF is used.

While the javadocs read MID Profile in top right corner the actual Configuration or Profile they belong to is noted down before the class method summary is listed as:

since CLDC1.0 or since MIDP1.0

Note, that not all classes are based on JDK1.3

Classes(CLDC1.0) Based on JDK1.1.8 instead of JDK1.3

 * java.util.Vector
 * java.util.Hashtable

These classes were based on JDK1.1.8 to conserve space.

CLDC1.0 Limitations

 * Unicode Translation to and from reader/writer bytes is limited
 * Does not support java.util.Properties from J2SE but limited stuff can be acquire as System.getProperty(String key) that starts with the keyword microedition

Trademark Notices
J2ME, Java and all Java-based marks are trademarks or registered trademarks of Sun Microsystems, Inc. in the U.S. and other countries.


text:
Talk:J2ME Programming/Connected Limited Device Configuration

Original Authors are:

Fred Grott

Shareme 20:47, 26 Mar 2005 (UTC)