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Acoustics/Sonar

SONAR (sound navigation and ranging) is a technique that uses sound propagation under water to navigate or to detect other vessels. There are two kinds of sonar: active and passive.

History
The French physicist Paul Langevin, working with a Russian émigré electrical engineer, Constantin Chilowski, invented the first active sonar-type device for detecting submarines in 1915. Although piezoelectric transducers later superseded the electrostatic transducers they used, their work influenced the future of sonar designs. In 1916, under the British Board of Inventions and Research, Canadian physicist Robert Boyle took on the project, which subsequently passed to the Anti- (or Allied) Submarine Detection Investigation Committee, producing a prototype for testing in mid-1917, hence the British acronym ASDIC.

By 1918, both the U.S. and Britain had built active systems. The UK tested what they still called ASDIC on HMS Antrim in 1920, and started production of units in 1922. The 6th Destroyer Flotilla had ASDIC-equipped vessels in 1923. An anti-submarine school, HMS Osprey, and a training flotilla of four vessels were established on Portland in 1924.

The U.S. Sonar QB set arrived in 1931. By the outbreak of World War II, the Royal Navy had five sets for different surface ship classes, and others for submarines. The greatest advantage came when it was linked to the Squid anti-submarine weapon.

Active sonar
Active sonar creates a pulse of sound, often called a "ping", and then listens for reflections of the pulse. To measure the distance to an object, one measures the time from emission of a pulse to reception. To measure the bearing, one uses several hydrophones, and measures the relative arrival time to each in a process called beamforming.

The pulse may be at constant frequency or a chirp of changing frequency. For a chirp, the receiver correlates the frequency of the reflections to the known chirp. The resultant processing gain allows the receiver to derive the same information as if a much shorter pulse of the same total energy were emitted. In practice, the chirp signal is sent over a longer time interval; therefore the instantaneous emitted power will be reduced, which simplifies the design of the transmitter. In general, long-distance active sonars use lower frequencies. The lowest have a bass "BAH-WONG" sound.

The most useful small sonar looks roughly like a waterproof flashlight. One points the head into the water, presses a button, and reads a distance. Another variant is a "fishfinder" that shows a small display with shoals of fish. Some civilian sonars approach active military sonars in capability, with quite exotic three-dimensional displays of the area near the boat. However, these sonars are not designed for stealth.

When active sonar is used to measure the distance to the bottom, it is known as echo sounding.

Active sonar is also used to measure distance through water between two sonar transponders. A transponder is a device that can transmit and receive signals but when it receives a specific interrogation signal it responds by transmitting a specific reply signal. To measure distance, one transponder transmits an interrogation signal and measures the time between this transmission and the receipt of the other transponder's reply. The time difference, scaled by the speed of sound through water and divided by two, is the distance between the two transponders. This technique, when used with multiple transponders, can calculate the relative positions of static and moving objects in water.

Analysis of active sonar data
Active sonar data is obtained by measuring detected sound for a short period of time after the issuing of a ping; this time period is selected so as to ensure that the ping's reflection will be detected. The distance to the seabed (or other acoustically reflective object) can be calculated from the elapsed time between the ping and the detection of its reflection. Other properties can also be detected from the shape of the ping's reflection:
 * When collecting data on the seabed, some of the reflected sound will typically reflect off the air-water interface, and then reflect off the seabed a second time. The size of this second echo provides information about the acoustic hardness of the seabed.
 * The roughness of a seabed affects the variance in reflection time. For a smooth seabed, all of the reflected sound will take much the same path, resulting in a sharp spike in the data.  For a rougher seabed, sound will be reflected back over a larger area of seabed, and some sound may bounce between seabed features before reflecting to the surface. A less sharp spike in the data therefore indicates a rougher seabed.

Sonar and marine animals
Some marine animals, such as whales and dolphins, use echolocation systems similar to active sonar to locate predators and prey. It is feared that sonar transmitters could confuse these animals and cause them to lose their way, perhaps preventing them from feeding and mating. A recent article on the BBC Web site (see below) reports findings published in the journal Nature to the effect that military sonar may be inducing some whales to experience decompression sickness (and resultant beachings).

High-powered sonar transmitters may indirectly harm marine animals, although scientific evidence suggests that a confluence of factors must first be present. In the Bahamas in 2000, a trial by the United States Navy of a 230 decibel transmitter in the frequency range 3 – 7 kHz resulted in the beaching of sixteen whales, seven of which were found dead. The Navy accepted blame in a report published in the Boston Globe on 1 January 2002. However, at low powers, sonar can protect marine mammals against collisions with ships.

A kind of sonar called mid-frequency sonar has been correlated with mass cetacean strandings throughout the world’s oceans, and has therefore been singled out by environmentalists as causing the death of marine mammals. International press coverage of these events can be found at this active sonar news clipping Web site. A lawsuit was filed in Santa Monica, California on 19 October 2005 contending that the U.S. Navy has conducted sonar exercises in violation of several environmental laws, including the National Environmental Policy Act, the Marine Mammal Protection Act, and the Endangered Species Act.

Passive sonar
Passive sonar listens without transmitting. It is usually employed in military settings, although a few are used in science applications.

Speed of sound
Sonar operation is affected by sound speed. Sound speed is slower in fresh water than in sea water. In all water sound velocity is affected by density (or the mass per unit of volume). Density is affected by temperature, dissolved molecules (usually salinity), and pressure. The speed of sound (in feet per second) is approximately equal to 4388 + (11.25 × temperature (in °F)) + (0.0182 × depth (in feet) + salinity (in parts-per-thousand)). This is an empirically derived approximation equation that is reasonably accurate for normal temperatures, concentrations of salinity and the range of most ocean depths. Ocean temperature varies with depth, but at between 30 and 100 metres there is often a marked change, called the thermocline, dividing the warmer surface water from the cold, still waters that make up the rest of the ocean. This can frustrate sonar, for a sound originating on one side of the thermocline tends to be bent, or refracted, off the thermocline. The thermocline may be present in shallower coastal waters, however, wave action will often mix the water column and eliminate the thermocline. Water pressure also affects sound propagation. Increased pressure increases the density of the water and raises the sound velocity. Increases in sound velocity cause the sound waves to refract away from the area of higher velocity. The mathematical model of refraction is called Snell's law.

Sound waves that are radiated down into the ocean bend back up to the surface in great arcs due to the effect of pressure on sound. The ocean must be at least 6000 feet (1850 meters) deep, or the sound waves will echo off the bottom instead of refracting back upwards. Under the right conditions these waves will then be focused near the surface and refracted back down and repeat another arc. Each arc is called a convergence zone. Where an arc intersects the surface a CZ annulus is formed. The diameter of the CZ depends on the temperature and salinity of the water. In the North Atlantic, for example, CZs are found approximately every 33 nautical miles (61 km), depending on the season, forming a pattern of concentric circles around the sound source. Sounds that can be detected for only a few miles in a direct line can therefore also be detected hundreds of miles away. Typically the first, second and third CZ are fairly useful; further out than that the signal is too weak, and thermal conditions are too unstable, reducing the reliability of the signals. The signal is naturally attenuated by distance, but modern sonar systems are very sensitive.

Identifying sound sources
Military sonar has a wide variety of techniques for identifying a detected sound. For example, U.S. vessels usually operate 60 Hz alternating current power systems. If transformers are mounted without proper vibration insulation from the hull, or flooded, the 60 Hz sound from the windings and generators can be emitted from the submarine or ship, helping to identify its nationality. In contrast, most European submarines have 50 Hz power systems. Intermittent noises (such as a wrench being dropped) may also be detectable to sonar.

Passive sonar systems may have large sonic databases, however most classification is performed manually by the sonar operator. A computer system frequently uses these databases to identify classes of ships, actions (i.e., the speed of a ship, or the type of weapon released), and even particular ships. Publications for classification of sounds are provided by and continually updated by the U.S. Office of Naval Intelligence.

Sonar in warfare
Modern naval warfare makes extensive use of sonar. The two types described before are both used, but from different platforms, i.e., types of water-borne vessels.

Active sonar is extremely useful, since it gives the exact position of an object. Active sonar works the same way as radar: a signal is emitted. The sound wave then travels in many directions from the emitting object. When it hits an object, the sound wave is then reflected in many other directions. Some of the energy will travel back to the emitting source. The echo will enable the sonar system or technician to calculate, with many factors such as the frequency, the energy of the received signal, the depth, the water temperature, etc., the position of the reflecting object. Using active sonar is somewhat hazardous however, since it does not allow the sonar to identify the target, and any vessel around the emitting sonar will detect the emission. Having heard the signal, it is easy to identify the type of sonar (usually with its frequency) and its position (with the sound wave's energy). Moreover, active sonar, similar to radar, allows the user to detect objects at a certain range but also enables other platforms to detect the active sonar at a far greater range.

Since active sonar does not allow an exact identification and is very noisy, this type of detection is used by fast platforms (planes, helicopters) and by noisy platforms (most surface ships) but rarely by submarines. When active sonar is used by surface ships or submarines, it is typically activated very briefly at intermittent periods, to reduce the risk of detection by an enemy's passive sonar. As such, active sonar is normally considered a backup to passive sonar. In aircraft, active sonar is used in the form of disposable sonobuoys that are dropped in the aircraft's patrol area or in the vicinity of possible enemy sonar contacts.

Passive sonar has fewer drawbacks. Most importantly, it is silent. Generally, it has a much greater range than active sonar, and allows an identification of the target. Since any motorized object makes some noise, it may be detected eventually. It simply depends on the amount of noise emitted and the amount of noise in the area, as well as the technology used. To simplify, passive sonar "sees" around the ship using it. On a submarine, the nose mounted passive sonar detects in directions of about 270°, centered on the ship's alignment, the hull-mounted array of about 160° on each side, and the towed array of a full 360°. The no-see areas are due to the ship's own interference. Once a signal is detected in a certain direction (which means that something makes sound in that direction, this is called broadband detection) it is possible to zoom in and analyze the signal received (narrowband analysis). This is generally done using a Fourier transform to show the different frequencies making up the sound. Since every engine makes a specific noise, it is easy to identify the object.

Another use of the passive sonar is to determine the target's trajectory. This process is called Target Motion Analysis (TMA), and the resultant "solution" is the target's range, course, and speed. TMA is done by marking from which direction the sound comes at different times, and comparing the motion with that of the operator's own ship. Changes in relative motion are analyzed using standard geometrical techniques along with some assumptions about limiting cases.

Passive sonar is stealthy and very useful. However, it requires high-tech components (band pass filters, receivers) and is costly. It is generally deployed on expensive ships in the form of arrays to enhance the detection. Surface ships use it to good effect; it is even better used by submarines, and it is also used by airplanes and helicopters, mostly to a "surprise effect", since submarines can hide under thermal layers. If a submarine captain believes he is alone, he may bring his boat closer to the surface and be easier to detect, or go deeper and faster, and thus make more sound.

In the United States Navy, a special badge known as the Integrated Undersea Surveillance System Badge is awarded to those who have been trained and qualified in sonar operation and warfare.

In World War II, the Americans used the term SONAR for their system. The British still called their system ASDIC. In 1948, with the formation of NATO, standardization of signals led to the dropping of ASDIC in favor of sonar.

title: Acoustics/Sonar


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Acoustics/Threshold of Hearing/Pain

The threshold of hearing is the Sound pressure level SPL of 20 µPa (micropascals) = 2 × 10−5 pascal (Pa). This low threshold of amplitude (strength or sound pressure level) is frequency dependent. See the frequency curve in Fig. 2 below

The absolute threshold of hearing (ATH) is the minimum amplitude (level or strength) of a pure tone that the average ear with normal hearing can hear in a noiseless environment.

The threshold of pain is the SPL beyond which sound becomes unbearable for a human listener. This threshold varies only slightly with frequency. Prolonged exposure to sound pressure levels in excess of the threshold of pain can cause physical damage, potentially leading to hearing impairment.

Different values for the threshold of pain:

The Threshold of hearing is frequency dependent, and typically shows a minimum (indicating the ear's maximum sensitivity) at frequencies between 1 kHz and 5 kHz. A typical ATH curve is pictured in Fig. 1. The absolute threshold of hearing represents the lowest curve amongst the set of equal-loudness contours, with the highest curve representing the threshold of pain.

In psychoacoustic audio compression, the ATH is used, often in combination with masking curves, to calculate which spectral components are inaudible and may thus be ignored in the coding process; any part of an audio spectrum which has an amplitude (level or strength) below the ATH may be removed from an audio signal without any audible change to the signal.

The ATH curve rises with age as the human ear becomes more insensitive to sound, with the greatest changes occurring at frequencies higher than 2 kHz. Curves for subjects of various age groups are illustrated in Fig. 2. The data is from the United States Occupational Health and Environment Control, Standard Number:1910.95 App F

../../Human Vocal Fold/ - Acoustics - ../../How an Acoustic Guitar Works/

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

title: Acoustics/Threshold of Hearing/Pain


text:
False Friends of the Slavist/Map pismo

pismo

title: False Friends of the Slavist/Map pismo


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False Friends of the Slavist/Map pьsъ

pьsъ

title: False Friends of the Slavist/Map pьsъ


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SanDisk Sansa MP3 Players/e100

Unknown artist, unknown album
Some have complained of lots of songs having unknown artist and unknown album. That problem has been tentatively tracked down to a USB cable that truncates the files. Since the ID3 tags are at the end of the files, those could easily be missing if the last 1Kb of the file is truncated. Try another cable, and see if that fixes the problem.

title: SanDisk Sansa MP3 Players/e100


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Acoustics/Acoustic Loudspeaker

The purpose of the acoustic transducer is to convert electrical energy into acoustic energy. Many variations of acoustic transducers exist, although the most common is the moving coil-permanent magnet transducer. The classic loudspeaker is of the moving coil-permanent magnet type.

The classic electrodynamic loudspeaker driver can be divided into three key components:

 * 1) The Magnet Motor Drive System
 * 2) The Loudspeaker Cone System
 * 3) The Loudspeaker Suspension

The Magnet Motor Drive System
The main purpose of the Magnet Motor Drive System is to establish a symmetrical magnetic field in which the voice coil will operate. The Magnet Motor Drive System is comprised of a front focusing plate, permanent magnet, back plate, and a pole piece. In figure 2, the assembled drive system is illustrated. In most cases, the back plate and the pole piece are built into one piece called the yoke. The yoke and the front focusing plate are normally made of a very soft cast iron. Iron is a material that is used in conjunction with magnetic structures because the iron is easily saturated when exposed to a magnetic field. Notice in figure 2, that an air gap was intentionally left between the front focusing plate and the yoke. The magnetic field is coupled through the air gap. The magnetic field strength (B) of the air gap is typically optimized for uniformity across the gap. [1]

Figure 2 Permanent Magnet Structure

When a coil of wire with a current flowing is placed inside the permanent magnetic field, a force is produced. B is the magnetic field strength, $$l$$ is the length of the coil, and $$I$$ is the current flowing through the coil. The electro-magnetic force is given by the expression of Laplace :

$$d\underline F = I\underline {dl}  \times \underline B $$

$$\underline B$$ and $$\underline {dl}$$ are orthogonal, so the force is obtained by integration on the length of the wire (Re is the radius of a spire, n is the number of spires and $$\underline e_x$$ is on the axis of the coil):

$$\underline F = 2\pi R_eBnI\underline e_x$$

This force is directly proportional to the current flowing through the coil.

Figure 3 Voice Coil Mounted in Permanent Magnetic Structure

The coil is excited with the AC signal that is intended for sound reproduction, when the changing magnetic field of the coil interacts with the permanent magnetic field then the coil moves back and forth in order to reproduce the input signal. The coil of a loudspeaker is known as the voice coil.

The loudspeaker cone system
On a typical loudspeaker, the cone serves the purpose of creating a larger radiating area allowing more air to be moved when excited by the voice coil. The cone serves a piston that is excited by the voice coil. The cone then displaces air creating a sound wave. In an ideal environment, the cone should be infinitely rigid and have zero mass, but in reality neither is true. Cone materials vary from carbon fiber, paper, bamboo, and just about any other material that can be shaped into a stiff conical shape. The loudspeaker cone is a very critical part of the loudspeaker. Since the cone is not infinitely rigid, it tends to have different types of resonance modes form at different frequencies, which in turn alters and colors the reproduction of the sound waves. The shape of the cone directly influences the directivity and frequency response of the loudspeaker. When the cone is attached to the voice coil, a large gap above the voice coil is left exposed. This could be a problem if foreign particles make their way into the air gap of the voice coil and the permanent magnet structure. The solution to this problem is to place what is known as a dust cap on the cone to cover the air gap. Below a figure of the cone and dust cap are shown.

Figure 6 Cone and Dust Cap attached to Voice Coil

The speed of the cone can be expressed with an equation of a mass-spring system with a damping coefficient \xi :

$$m\frac + \xi v + k\int {v \, dt} = Bli$$

The current intensity $$i$$ and the speed $$v$$ can also be related by this equation ($$U$$ is the voltage, $$R$$ the electrical resistance and $$L_b$$ the inductance) :

$$L_b \frac + Ri = U - Blv$$

By using a harmonic solution, the expression of the speed is :

$$v = \frac$$

The electrical impedance can be determined as the ratio of the voltage on the current intensity :

$$Z = \frac{U}{i} = R + jL\omega + \frac$$

The frequency response of the loudspeaker is provided in Figure 7.

Figure 7 Electrical impedance

A phenomena of electrical resonance is observable around the frequency of 100 Hz. Besides, the inductance of the coil makes the impedance increase from the frequency of 400 Hz. So the range of frequency where the loudspeaker is used is 100 – 4000 Hz

The loudspeaker suspension
Most moving coil loudspeakers have a two piece suspension system, also known as a flexure system. The combination of the two flexures allows the voice coil to maintain linear travel as the voice coil is energized and provide a restoring force for the voice coil system. The two piece system consists of large flexible membrane surrounding the outside edge of the cone, called the surround, and an additional flexure connected directly to the voice coil, called the spider. The surround has another purpose and that is to seal the loudspeaker when mounted in an enclosure. Commonly, the surround is made of a variety of different materials, such as, folded paper, cloth, rubber, and foam. Construction of the spider consists of different woven cloth or synthetic materials that are compressed to form a flexible membrane. The following two figures illustrate where the suspension components are physically at on the loudspeaker and how they function as the loudspeaker operates.

Figure 8 Loudspeaker Suspension System

Figure 9 Moving Loudspeaker

Modeling the loudspeaker as a lumped system
Before implementing a loudspeaker into a specific application, a series of parameters characterizing the loudspeaker must be extracted. The equivalent circuit of the loudspeaker is key when developing enclosures. The circuit models all aspects of the loudspeaker through an equivalent electrical, mechanical, and acoustical circuit. Figure 9 shows how the three equivalent circuits are connected. The electrical circuit is comprised of the DC resistance of the voice coil, $$R_e$$, the imaginary part of the voice coil inductance, $$L_e$$, and the real part of the voice coil inductance, $$R_{evc}$$. The mechanical system has electrical components that model different physical parameters of the loudspeaker. In the mechanical circuit, $$M_m$$, is the electrical capacitance due to the moving mass, $$C_m$$, is the electrical inductance due to the compliance of the moving mass, and $$R_m$$, is the electrical resistance due to the suspension system. In the acoustical equivalent circuit, $$M_a$$ models the air mass and $$R_a$$ models the radiation impedance[2]. This equivalent circuit allows insight into what parameters change the characteristics of the loudspeaker. Figure 10 shows the electrical input impedance as a function of frequency developed using the equivalent circuit of the loudspeaker. Figure 9 Loudspeaker Analogous Circuit

Figure 10 Electrical Input Impedance

Function of the enclosure
The loudspeaker emits two waves : a front wave and a back wave. With a reflection on a wall, the back wave can be added with the front wave and produces destructive interferences. As a result, the sound pressure level in the room is not uniform. At certain positions, the interaction is additive, and the sound pressure level is higher. On the contrary, certain positions offer destructive interaction between the waves and the sound pressure level is lower.

Figure 11 Loudspeaker without baffle producing destructive interferences

The solution is to put a baffle round the loudspeaker in order to prevent the back wave from interfering with the front wave. The sound pressure level is uniform in the room and the quality of the loudspeaker is higher.

Figure 12 Loudspeakers with infinite baffle and enclosure

Loudspeaker-external fluid interaction
The external fluid exerts a pressure on the membrane of the loudspeaker cone. This additive force can be evaluate as an additive mass and an additive damping in the equation of vibration of the membrane.

$$ - (m + MS)\omega ^2 \xi + i\omega (C + RS)\xi  + K\xi  = fe^{i\omega t} $$

When the fluid is the air, this additive mass and additive damping are negligible. For example, at the frequency of 1000 Hz, the additive mass is 3g.

Loudspeaker-internal fluid interaction
The volume of air in the enclosure constitutes an additive stiffness. This is called the acoustic load. In low frequencies, this additive stiffness can be four times the stiffness of the loudspeaker cone. The internal air stiffness is very high because of the boundary conditions inside the enclosure. The walls impose a condition of zero airspeed that makes the stiffness increase.

Figure 13 Stiffness of the loudspeaker cone and stiffness of the internal air

The stiffness of the internal air (in red) is fourth time higher than the stiffness of the loudspeaker cone (in blue). That is why the design of the enclosure is relevant in order to improve the quality of the sound and avoid a decrease of the sound pressure level in the room at some frequencies.

title: Acoustics/Acoustic Loudspeaker


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User:Luvtheheaven

See my wikipedia page to see who I am. For now. I'm not sure how often I'll be using wikibooks, so you might want to try to contact me at wikipedia, if you want to at all. I'll update this page if I decide to use this much. I most likely will be using te wikibooks only for The Muggles Guide to Harry Potter.

title: User:Luvtheheaven


text:
General Biology/Classification of Living Things/Eukaryotes

 * 1) Protists
 * 2) Plants
 * 3) Fungi
 * 4) Animals
 * 5) *Phyla
 * 6) *Chordates


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User talk:165.230.104.137

You (or someone using your IP address) edited the Template:Engineering bookshelf. Then, you used "Save Page" and it worked! Everyone could see the results of your test: "Headline text", "Link title", "Media:Example.ogg", and "Insertformulahere". I went and deleted them.

To make things easier for us, if you want to test the "edit this page" feature again, do it in the Sandbox. The sandbox is a same place to experiment with wiki syntax without (accidentally) defacing part of Wikibooks. Welcome to Wikibooks! --Kernigh 00:15, 8 March 2006 (UTC)

title: User talk:165.230.104.137


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Acoustics/Car Mufflers

Introduction
A car muffler is a component of the exhaust system of a car. The exhaust system has mainly 3 functions:

 * 1) Getting the hot and noxious gas from the engine away from the vehicle
 * 2) Reduce exhaust emission
 * 3) Attenuating the noise output from the engine

The last specified function is the function of the car muffler. It is necessary because the gas coming from the combustion in the pistons of the engine would generate an extremely loud noise if it were sent directly in the ambient air surrounding engine through the exhaust valves. There are 2 techniques used to dampen the noise: absorption and reflection. Each technique has its advantages and disadvantages.

The absorber muffler
The muffler is composed of a tube covered by sound absorbing material. The tube is perforated so that some part of the sound wave goes through the perforation to the absorbing material. The absorbing material is usually made of fiberglass or steel wool. The dampening material is protected from the surrounding by a supplementary coat made of a bend metal sheet.

The advantage of this method is low back pressure with a relatively simple design. The inconvenience of this method is low sound damping ability compared to the other techniques, especially at low frequency. The mufflers using the absorption technique are usually sports vehicle because they increase the performances of the engine because of their low back pressure. A trick to improve their muffling ability consists of lining up several "straight" mufflers.

The reflector muffler
Principle: Sound wave reflection is used to create a maximum amount of destructive interferences

Definition of destructive interferences
Let's consider the noise a person would hear when a car drives past. This sound would physically correspond to the pressure variation of the air which would make his ear-drum vibrate. The curve A1 of the graph 1 could represent this sound. The pressure amplitude is a function of the time at a certain fixed place. If another sound wave A2 is produced at the same time, the pressure of the two waves will add. If the amplitude of A1 is exactly the opposite of the amplitude A2, then the sum will be zero, which corresponds physically to the atmospheric pressure. The listener would thus hear nothing although there are two radiating sound sources. A2 is called the destructive interference.

Definition of the reflection
The sound is a traveling wave i.e. its position changes in function of the time. As long as the wave travels in the same medium, there is no change of speed and amplitude. When the wave reaches a frontier between two mediums which have different impedances, the speed, and the pressure amplitude change (and so does the angle if the wave does not propagate perpendicularly to the frontier). The figure 1 shows two medium A and B and the 3 waves: incident transmitted and reflected.

Example
If plane sound waves are propagating across a tube and the section of the tube changes, the impedance of the tube will change. Part of the incident waves will be transmitted through the discontinuity and the other part will be reflected.

Animation

Mufflers using the reflection technique are the most commonly used because they dampen the noise much better than the absorber muffler. However they induce a higher back pressure, lowering the performance of the engine (an engine would be most efficient or powerful without the use of a muffler).

The upper right image represents a car muffler's typical architecture. It is composed of 3 tubes. There are 3 areas separated by plates, the part of the tubes located in the middle area are perforated. A small quantity of pressure "escapes" from the tubes through the perforation and cancel one another.

Some mufflers using the reflection principle may incorporate cavities which dampen noise. These cavities are called Helmholtz Resonators in acoustics. This feature is usually only available for up market class mufflers.

Back pressure
Car engines are 4 stroke cycle engines. Out of these 4 strokes, only one produces the power, this is when the explosion occurs and pushes the pistons back. The other 3 strokes are necessary evil that don't produce energy. They on the contrary consume energy. During the exhaust stroke, the remaining gas from the explosion is expelled from the cylinder. The higher the pressure behind the exhaust valves (i.e. back pressure), the higher the effort necessary to expel the gas out of the cylinder. So, a low back pressure is preferable in order to have a higher engine horsepower.

Muffler modeling by transfer matrix method
This method is easy to use on computer to obtain theoretical values for the transmission loss of a muffler. The transmission loss gives a value in dB that correspond to the ability of the muffler to dampen the noise.

Example

P stands for Pressure [Pa] and U stand for volume velocity [m3/s]

$$\begin{bmatrix} P1 \\ U1 \end{bmatrix}$$=$$\begin{bmatrix} T1 \end{bmatrix} \begin{bmatrix} P2 \\ U2 \end{bmatrix}$$  and   $$\begin{bmatrix} P2 \\ U2 \end{bmatrix}$$=$$\begin{bmatrix}  T2 \end{bmatrix} \begin{bmatrix} P3 \\ U3 \end{bmatrix}$$  and   $$\begin{bmatrix} P3 \\ U3 \end{bmatrix}$$=$$\begin{bmatrix}  T3 \end{bmatrix} \begin{bmatrix} P4 \\ U4 \end{bmatrix}$$

So, finally: $$\begin{bmatrix} P1 \\ U1 \end{bmatrix}$$= $$\begin{bmatrix} T1 \end{bmatrix} \begin{bmatrix} T2 \end{bmatrix} \begin{bmatrix} T3 \end{bmatrix} \begin{bmatrix} P4 \\ U4 \end{bmatrix}$$

with

$$\begin{bmatrix} T_i \end{bmatrix}$$=$$\begin{bmatrix} cos (k L_i) & j sin (k L_i) \frac{\rho c}{S_i}  \\ j sin (k L_i) \frac{S_i}{\rho c} & cos (k L_i) \end{bmatrix}$$

Si stands for the cross section area

k is the wave number

$$\ \rho $$ is the medium density

c is the speed of sound of the medium

Results

of the graph above.

Comments
The higher the value of the transmission loss and the better the muffler.

The transmission loss depends on the frequency. The sound frequency of a car engine is approximately between 50 and 3000 Hz. At resonance frequencies, the transmission loss is zero. These frequencies correspond to the lower peaks on the graph.

The transmission loss is independent of the applied pressure or velocity at the input.

The temperature (about 600 Fahrenheit) has an impact on the air properties : the speed of sound is higher and the mass density is lower.

The elementary transfer matrix depends on the element which is modelled. For instance the transfer matrix of a Helmotz Resonator is $$\begin{bmatrix} 1 & 0 \\ \frac{1}{Z} & 1 \end{bmatrix}$$ with $$\ Z = j \rho ( \frac{\omega L_i}{S_i} - \frac{c^2}{\omega V})$$

The transmission loss and the insertion loss are different terms. The transmission loss is 10 times the logarithm of the ratio output/input. The insertion loss is 10 times the logarithm of the ratio of the radiated sound power with and without muffler.

Links

 * General Information about Filter Design & Implementation
 * More information about the Transfer Matrix Method
 * General information about car mufflers

title: Acoustics/Car Mufflers


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Template:General Biology/GettingStarted

 * 1) Introduction
 * 2) Matter
 * 3) Chemical Building Blocks of Life
 * 4) History and Origin of Life

title: Template:General Biology/GettingStarted


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Template:General Biology/Cells

 * 1) Cell Structure
 * 2) Membranes
 * 3) Cell-Cell Interactions
 * 4) Energy and Metabolism
 * 5) Respiration
 * 6) Photosynthesis
 * 7) How Cells Divide
 * 8) Sexual Reproduction

title: Template:General Biology/Cells


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Template:General Biology/Genetics

 * 1) Inheritance
 * 2) DNA, The Genetic Material
 * 3) Gene Expression
 * 4) Gene Regulation
 * 5) Mutation
 * 6) Recombinant DNA Technology

title: Template:General Biology/Genetics


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Acoustics/Active Control

Introduction
The principle of active control of noise, is to create destructive interferences using a secondary source of noise. Thus, any noise can theoretically disappear. But as we will see in the following sections, only low frequencies noises can be reduced for usual applications, since the amount of secondary sources required increases very quickly with frequency. Moreover, predictable noises are much easier to control than unpredictable ones. The reduction can reach up to 20 dB for the best cases. But since good reduction can only be reached for low frequencies, the perception we have of the resulting sound is not necessarily as good as the theoretical reduction. This is due to psychoacoustics considerations, which will be discussed later on.

Control of a monopole by another monopole
Even for the free space propagation of an acoustic wave created by a punctual source it is difficult to reduce noise in a large area, using active noise control, as we will see in the section.

In the case of an acoustic wave created by a monopolar source, the Helmholtz equation becomes:

$$\Delta p + k^2 p = - j\omega \rho _0 q$$

where q is the flow of the noise sources.

The solution for this equation at any M point is:

$$p_p (M) = \frac\frac$$

where the p mark refers to the primary source.

Let us introduce a secondary source in order to perform active control of noise. The acoustic pressure at that same M point is now:

$${\rm{p(M) = }}\frac\frac + \frac\frac$$ It is now obvious that if we chose $$q_s =  - q_p \frace^{ - jk(r_p  - r_s )}$$ there is no more noise at the M point. This is the most simple example of active control of noise. But it is also obvious that if the pressure is zero in M, there is no reason why it should also be zero at any other N point. This solution only allows to reduce noise in one very small area.

However, it is possible to reduce noise in a larger area far from the source, as we will see in this section. In fact the expression for acoustic pressure far from the primary source can be approximated by:

$$p(M) = \frac\frac(q_p + q_s e^{ - jkD\cos \theta } )$$

As shown in the previous section we can adjust the secondary source in order to get no noise in M. In that case, the acoustic pressure in any other N point of the space remains low if the primary and secondary sources are close enough. More precisely, it is possible to have a pressure close to zero in the whole space if the M point is equally distant from the two sources and if: $$D < \lambda /6$$ where D is the distance between the primary and secondary sources. As we will see later on, it is easier to perform active control of noise with more than on source controlling the primary source, but it is of course much more expensive.

A commonly admitted estimation of the number of secondary sources which are necessary to reduce noise in an R radius sphere, at a frequency f is:

$$N = \frac$$

This means that if you want no noise in a one meter diameter sphere at a frequency below 340 Hz, you will need 30 secondary sources. This is the reason why active control of noise works better at low frequencies.

Active control for waves propagation in ducts and enclosures
This section requires from the reader to know the basis of modal propagation theory, which will not be explained in this article.

Ducts
For an infinite and straight duct with a constant section, the pressure in areas without sources can be written as an infinite sum of propagation modes:

$$p(x,y,z,\omega ) = \sum\limits_{n = 1}^N {a_n (\omega )\phi _n (x,y)e^{ - jk_n z} }$$

where $$\phi$$ are the eigen functions of the Helmoltz equation and a represent the amplitudes of the modes.

The eigen functions can either be obtained analytically, for some specific shapes of the duct, or numerically. By putting pressure sensors in the duct and using the previous equation, we get a relation between the pressure matrix P (pressure for the various frequencies) and the A matrix of the amplitudes of the modes. Furthermore, for linear sources, there is a relation between the A matrix and the U matrix of the signal sent to the secondary sources: $$A_s = KU$$ and hence: $$A = A_p  + A_s  = A_p  + KU$$.

Our purpose is to get: A=0, which means: $$A_p + KU = 0$$. This is possible every time the rank of the K matrix is bigger than the number of the propagation modes in the duct.

Thus, it is theoretically possible to have no noise in the duct in a very large area not too close from the primary sources if the there are more secondary sources than propagation modes in the duct. Therefore, it is obvious that active noise control is more appropriate for low frequencies. In fact the more the frequency is low, the less propagation modes there will be in the duct. Experiences show that it is in fact possible to reduce the noise from over 60 dB.

Enclosures
The principle is rather similar to the one described above, except the resonance phenomenon has a major influence on acoustic pressure in the cavity. In fact, every mode that is not resonant in the considered frequency range can be neglected. In a cavity or enclosure, the number of these modes rise very quickly as frequency rises, so once again, low frequencies are more appropriate. Above a critical frequency, the acoustic field can be considered as diffuse. In that case, active control of noise is still possible, but it is theoretically much more complicated to set up.

Active control and psychoacoustics
As we have seen, it is possible to reduce noise with a finite number of secondary sources. Unfortunately, the perception of sound of our ears does not only depend on the acoustic pressure (or the decibels). In fact, it sometimes happen that even though the number of decibels has been reduced, the perception that we have is not really better than without active control.

Active control systems
Since the noise that has to be reduced can never be predicted exactly, a system for active control of noise requires an auto adaptable algorithm. We have to consider two different ways of setting up the system for active control of noise depending on whether it is possible or not to detect the noise from the primary source before it reaches the secondary sources. If this is possible, a feed forward technique will be used (aircraft engine for example). If not a feed back technique will be preferred.

Feedforward
In the case of a feed forward, two sensors and one secondary source are required. The sensors measure the sound pressure at the primary source (detector) and at the place we want noise to be reduced (control sensor). Furthermore, we should have an idea of what the noise from the primary source will become as he reaches the control sensor. Thus we approximately know what correction should be made, before the sound wave reaches the control sensor (forward). The control sensor will only correct an eventual or residual error. The feedforward technique allows to reduce one specific noise (aircraft engine for example) without reducing every other sound (conversations, …). The main issue for this technique is that the location of the primary source has to be known, and we have to be sure that this sound will be detected beforehand. Therefore portative systems based on feed forward are impossible since it would require having sensors all around the head.

Feedback
In that case, we do not exactly know where the sound comes from; hence there is only one sensor. The sensor and the secondary source are very close from each other and the correction is done in real time: as soon as the sensor gets the information the signal is treated by a filter which sends the corrected signal to the secondary source. The main issue with feedback is that every noise is reduced and it is even theoretically impossible to have a standard conversation.

Noise cancelling headphone
Usual headphones become useless when the frequency gets too low. As we have just seen active noise cancelling headphones require the feedback technique since the primary sources can be located all around the head. This active control of noise is not really efficient at high frequencies since it is limited by the Larsen effect. Noise can be reduced up to 30 dB at a frequency range between 30 Hz and 500 Hz.

Active control for cars
Noise reduction inside cars can have a significant impact on the comfort of the driver. There are three major sources of noise in a car: the motor, the contact of tires on the road, and the aerodynamic noise created by the air flow around the car. In this section, active control for each of those sources will be briefly discussed.

Motor noise
This noise is rather predictable since it a consequence of the rotation of the pistons in the motor. Its frequency is not exactly the motor’s rotational speed though. However, the frequency of this noise is in between 20 Hz and 200 Hz, which means that an active control is theoretically possible. The following pictures show the result of an active control, both for low and high regime.

Even though these results show a significant reduction of the acoustic pressure, the perception inside the car is not really better with this active control system, mainly for psychoacoustics reasons which were mentioned above. Moreover such a system is rather expensive and thus are not used in commercial cars.

Tires noise
This noise is created by the contact between the tires and the road. It is a broadband noise which is rather unpredictable since the mechanisms are very complex. For example, the different types of roads can have a significant impact on the resulting noise. Furthermore, there is a cavity around the tires, which generate a resonance phenomenon. The first frequency is usually around 200 Hz. Considering the multiple causes for that noise and its unpredictability, even low frequencies become hard to reduce. But since this noise is broadband, reducing low frequencies is not enough to reduce the overall noise. In fact an active control system would mainly be useful in the case of an unfortunate amplification of a specific mode.

Aerodynamic noise
This noise is a consequence of the interaction between the air flow around the car and the different appendixes such as the rear views for example. Once again, it is an unpredictable broadband noise, which makes it difficult to reduce with an active control system. However, this solution can become interesting in the case an annoying predictable resonance would appear.

Active control for aeronautics
The noise of aircraft propellers is highly predictable since the frequency is quite exactly the rotational frequency multiplied by the number of blades. Usually this frequency is around some hundreds of Hz. Hence, an active control system using the feedforward technique provides very satisfying noise reductions. The main issues are the cost and the weigh of such a system. The fan noise on aircraft engines can be reduced in the same manner.

title: Acoustics/Active Control


text:
Template:General Biology/Classification

 * 1) Classification and Domains of Life
 * 2) General Biology/Classification of Living Things/Viruses
 * 3) Prokaryotes
 * 4) Eukaryotes
 * 5) Protists
 * 6) Plants
 * 7) Fungi
 * 8) Animals
 * 9) *Phyla
 * 10) *Chordates

title: Template:General Biology/Classification


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Template:General Biology/Evolution

 * 1) Introduction
 * 2) Evolution of Life
 * 3) Animal Evolution
 * 4) Human Evolution

title: Template:General Biology/Evolution


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Template:General Biology/Tissues

 * 1) Tissues
 * 2) *Epithelial tissue
 * 3) *Connective tissue
 * 4) *Muscle tissue
 * 5) Systems
 * 6) *Digestive system
 * 7) *Circulatory system
 * 8) *Lymphatic system
 * 9) *Respiratory system
 * 10) *Nervous system
 * 11) *Sensory systems
 * 12) *Homeostasis

title: Template:General Biology/Tissues


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Talk:Compiler Construction/Case Study 1B

Some comments on this:
 * 1. It might be easier if you could make the source code available separately.
 * 2. Traditionally lex/flex files are *.l, yacc/bison file *.y (make has rules to deal with these file extensions automatically).
 * 3. A Makefile would be nice at some point.
 * 4. In order to be used, the code should be under a different license to GFDL. I would suggest licensing it to be used by anyone for any purpose, as its purpose is merely to be a tutorial/guide to compiler constuction.

Apart from that, it looks great.

Jonmmorgan 03:03, 8 March 2006 (UTC)

After further thought, I withdraw some of these comments. What is there is good for a tutorial. Incidental details like a Makefile are probably outside the scope of this book, though they need to be bundled with separately available source code for greater usefulness.

The licensing should not be a problem as you dual-license with Creative Commons.

211.28.122.32 13:03, 20 March 2006 (UTC)

 * And yes, that was me forgetting to sign in - very careless :).

 * Jonmmorgan 13:05, 20 March 2006 (UTC)

I really like this tutorial.

Unfortunately the "Interpreting" section has not been finished yet and i have a question how to build this interpreter. (By the way I do not know if this is the right place to ask my question.)

When interpreting, what's the best way to make a goto (goto, gotosub) jump? Will I have to parse the ast again to find the node with the matching line number and continue execution there? I could imagine that this might be difficult to code in one recursive function.

Can somebody help me? Wiegi 20:03, 25 September 2007 (UTC)


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Orthopaedic Surgery/Staging of Tumours

Benign soft tissue tumors are classified using the musculoskeletal tumor society staging system. Arabic numerals denote benign condidtions and Roman numerals malignant. Stage 1 inactive Stage 2 active Stage 3 locally aggressive. Marginal section is appropriate for the first two categories whereas wide local excision is appropriate for the third.

Superficial lesions less than 1.5 cm especially with slow growth characteristics,assymtomatic, non-fixed and soft are suitable for excisional biopsy, otherwise incisional biopsy if fine needle or core biopsy is not your preferred approach. Beware the ganglion cyst that isn't. Upon encountering instead a solid tumor which does not appear to be a giant cell tumor of tendon sheath or a schwannoma, or a hemangioma which have fairly characteristic appearances, avoid the temptation to proceed directly to marginal resection, instead, perform an incisional biopsy. If a malignant lesion is encountered then close, observing meticulous hemostasis. Layered closure, tourniquet deflated first to confirm hemostasis, compressive bulky dressing. After the fact is the wrong time to then check for adenopathy. It is also too late to take back that esmarch exsanguination. It is also too late to take back the transverse incision and the subcutaneous flap, and the exposure of major neurovascular structure that might have been avoided. In other words, plan the approach to even benign lesions as if you are about to encounter an unexpected malignant fibrous histiocytoma, or synovial sarcoma or epithelioid sarcoma.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=8727762

title: Orthopaedic Surgery/Staging of Tumours


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Template:French/Table

border="1" bordercolor="#edebe8" ! colspan="" |

title: Template:French/Table


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Orthopaedic Surgery/Immunology

 * Immune response

The ability of our bodies to distinguish self from non-self is essential to our survival but under certain circumstances inter alia rheumatoid arthritis, this defense aparatus can be turned on the bodies normal tissues. Antigens

 * Inflammation

Inflammation is a term which has ancient origins, which originally describe the characteristic clinical manifestations of calor, rubor, dolor, tumor and functio laesa. Inflammation is a stereotypical set of cellular responses that give rise to local and systemic physiologic changes, classically in response to infection but also in response to injury and irritation. All are circumstances which warrant a change in behavior and a shift in priorities in a timely manner to confront a threat which may not be entirely evident absent this response. Indeed when the immune system is compromised this early warning system fails to promote the necessary cascade of events that give rise to a robust response to the offending agent, actual or potentially injurious circumstance. Inflammation plays a propitious role in all normal healing responses and thus it is not the enemy but rather the messenger albeit the bearer of bad news which is ignored at our peril.

The ubiquitous nature of this cellular response may lead us to conclude that it is always the source of pain where it occurs without aparent cause and thus we tend to assume this mechanism is at work for any malady involving pain even if dolor and functio laesa i are the only manifestations, tendinopathies may be an example of this tendency.

 * Platelets

 * Endothelium

 * Neutrophils

 * Monocytes and Macrophages

 * T-lymphocytes

 * Fibroblasts

 * Mast Cells

 * Neurones

 * Aspirin and NSAIDS

 * Corticosteroids

Message in a bottle.

We inject a glucocorticoid without giving it much thought. It is our one blunt instrument for influencing the immune system which is slowly revealing its secrets through the laborious efforts of clinical investigators and basic scientists. Meanwhile, if it hurts and it is not getting better and if a surgery does not seem warranted then odds are we are likely to see if bathing the problem area in glucocorticoid will help out. The practice came into being on the premise that many painful conditions were caused by inflammation and thus might respond to an anti-inflammatory. Many conditions previously felt to involve inflammation are later found to be some other process for which we stuggle even to find a suitable name.Yet we are left without an explanation for what seems at least to be a substantial degree of effectiveness to the injection of a glucocorticoid. Glucocorticoid effects a variety of cell types unrelated to inflammation. Its influence in these cases may be via some other mechanism, involving the gene expression of the targeted cells. The influence of the glucocorticoid is not necessarily helpful or neutral, it may also be harmful beyond simply side effects like fat atrophy and skin depigmentation. Cellular apoptosis, tendon rupture or a more insidious state of arrested remodeling, halting a productive healing process in the interest of alleviating acute symptoms and in the process creating a cycle of chronic or recurrent difficulties if not inciting the rupture of a tendon or the deterioration of joint cartilage. Approaching 60 years since the discovery of a glucocorticoid receptor and the first clinical use of systemic steroids for the treatment of rheumatoid arthritis and we as yet to not have complete knowledge of the molecular mechanism of action of glucocorticoids. A dermatologist may use a short course of systemic steroids 30 times a week in his office population, a rheumatologist may have innumerable patients on low dose prednisone for years. Chronic COPD for the pulmonologists.

Glucocorticoids act on most cells, the molecule binds to a carrier molecule within the cell and is transported to the nucleus where it influences, usually down regulates DNA transcription.

Cyclooxygenase COX is the major enzymatic target of most of the anti-inflammatory medications we use as clinicians. This enzyme controls the arachidonic acid metabolism and is present in three isoforms; types 1 and 2 are periferal and type 3 central.

 * Modalities

 * CAM

 * New Horizons

Injectable corticosteroids

Inflammation, pathways of gene expression

http://content.nejm.org/cgi/content/extract/353/16/1711?maxtoshow=&HITS=&hits=&RESULTFORMAT=1&andorexacttitle=and&fulltext=cortisone+mechanism+of+action&andorexactfulltext=and&searchid=1&FIRSTINDEX=20&sortspec=relevance&resourcetype=HWCIT

title: Orthopaedic Surgery/Immunology


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Orthopaedic Surgery/Lateral Epicondylitis

Tendinopathy of the common extensor origin also referred to as tendinosis, has replaced the previous moniker, tennis elbow and lateral epicondylitis. In what seems to be a trend to make our nomenclature less assertive as to our professed understanding of the workings of this condition we hope to take a step back and give a broader more fundamental look at the issue. In light of the lack of histologic evidence implicating inflammation it seems appropriate to defenestrate the term epicondylitis from our working clinical vocabulary. Steroid injections work frequently enough that they are commonly perceived as useful and certainly something to try at least a time or two before any surgical intervention. Histology usually does not include evidence for acute or chronic inflammation. Why then do we use steroid injection? Two reasons seem likely, first it has been the traditional recommendation and secondly, it seems to work by golly, not always but pretty often.

How is this possible in view of the science which tells us there is no inflammation. Recent efforts attempt to tease out an answer. It seems that needling alone, or needling with injection of blood can also meet with success in alleviating symptoms. While this seems to have merit, it has yet to be adopted widely. This may be that the process of drawing blood is inconvenient in the clinic setting, or it may be that it does not work so well. Lidocaine injection takes place from time to time to verify relief of symptoms when considering whether a patient can be predicted to improve with a surgery. The usual scenario is the patient referred having had umpteen cortisone injections and unwilling to have another. I don't believe I have ever seen lidocaine alone, with needling of the tendon origing to affect a lasting benefit. Is it in fact the needling rather than the steroid. Are we rebooting the healing computer by micotrauma to the tendinous origin, seems doubtful but maybe at some point in the subacute phase this could play a role.

Alternatively, does the steroid in fact cause the partially ruptured fibers which are the source of the symptoms to rupture thus relieving the symptoms. I am reminded of the chymopapain era though, or the clostridial enzyme era (has that passed?) how does it know when to stop dissolving tissue?

Surgery often seems ultimately successful and accomplishes in essence the completion of a tear with variable degrees of removal of grossly abnormal appearing tissue on the assumption that the tissue in situ is a potential source for the pain. Studies seem to indicate that release whether arthroscopic or percutaneous or open seem about equivalent. In view of this success, it seems reasonable to conclude that when steroid injection works it is in essence accomplishing the same thing. When it does not work it may be that while completing some tear it may be setting the ground work for the adjacent tissue to fail and herein lies the concern.

Steroids are often used very early within days or weeks of symptom onset and indeed sometimes a quick cure is achieved. How efficient. What we do not know is whether the early injection of steroid might in some cases interfere with normal healing processes and prevent the successful resolution of the problem in a time frame like 3 to 4 months. Instead with injection at 3 weeks we have a period of relief and then relapse and eventually a chronic problem, perhaps one requiring surgery.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=16452759


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Chinese (Mandarin)/Pronunciation of Initials

Remember, since hearing is very important for learning to speak, audio samples and the voices of native speakers should be your constant companions.


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Chinese (Mandarin)/Pronunciation of Finals

Rolled finals
Rolled finals (儿化音) are a phenomenon in spoken Mandarin. People from northern China like to roll their tongue when saying specific words (usually nouns and verbs) in daily dialogues. On the other hand, people from southern China rarely do that. Foreign Chinese learners are not quite suggested to learn so, as this is sometimes considered as a northern China accent instead of standard Mandarin. This table's purpose is to enable Chinese learners to recognize and understand them when hearing somebody using them.


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Chinese (Mandarin)/Table of Initial-Final Combinations

^ Chinese ^ | <>

Table of Possible Combinations of Chinese Initials and Finals
The table below shows all possible combinations of initials and finals in Pinyin (not including -r modified syllables). It also does not reflect the use of tones. Some combinations may only be valid with the use of one tone, while others may be valid with multiple tones.

 * Colour Legend:
 * {| class="wikitable"

! align="left" | "regular" initial or final Final is in Group a or is a direct combination of: ! align="left" style="background: rgb(204, 204, 204);" | Final of i, u, ü groups is a modified combination of:
 * i+Group a final
 * u+Group a final
 * ü+Group a final
 * i+Group a final
 * u+Group a final
 * ü+Group a final
 * syllable is direct combination of initial and final (or follows rules for standalone initials and finals, explained in pronunciation basics)
 * style="background: rgb(255, 255, 204);"| syllable is modified combination of initial and final
 * }
 * style="background: rgb(255, 255, 204);"| syllable is modified combination of initial and final
 * }

 * Modified i, u, and ü group finals:
 * The following finals in the i, u, and ü groups are a modified combination of i, u or ü with a group a final:
 * ie=i+ê
 * iu=i+ou
 * in=i+en
 * ing=i+eng
 * ui=u+ei
 * un=u+en
 * ong=u+eng
 * üe=ü+ê
 * ün=ü+en
 * iong=i+u+eng

^ Chinese ^ | <>


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Chinese (Mandarin)/Using Tones

Using Tones
Every syllable in Chinese has a clearly defined pitch of voice associated with it to distinguish characters with the same sound from each other. Unfortunately, there is no indication of the tone given when reading a character, so the tones for words must be individually memorized. To help with this, pinyin uses four easily-remembered diacritical marks to tell you what the tones of words are. The diagram to the right shows the pitch changes of the four tones on a five-bar scale going from lowest (1), to highest (5), while the five tone marks are:

 * 1) First tone (阴平)( ˉ ), high level.
 * 2) Second tone (阳平)(ˊ), middle rising.
 * 3) Third tone (上声)( ˇ ), low dipping.
 * 4) Fourth tone (去声)(ˋ), high falling.
 * 5) Tone of unstressed syllable (轻声)(without any marks), low level.

Tone marks are always placed over vowels, never consonants. If there is more than one vowel in the syllable, the mark placement is determined by three simple rules.
 * 1) If there is an a, the tone goes on the a. No pinyin syllable contains both an a and an e.
 * 2) In the ei and ou combinations, the first vowel takes the tone mark.
 * 3) In all other cases, the last vowel gets the tone mark.

Pronouncing the tones
Say the first tone as if you were singing a high note. The second tone is pronounced like a question in English, with your pitch rising at the end of the syllable. Third tones are low and extended, noticeably longer than the other tones because of the dip. The fourth tone is said abruptly and forcefully, like a curt command in English. The neutral tone's pitch depends on the tone that precedes it. It is described more fully below, but in general, they are pronounced quickly and softly. The classic example used to show the difference tones make is:

In many cases, several characters can have exactly the same syllable and tone. For example, along with 马, the characters 码 and 蚂 are also pronounced exactly the same (mǎ). 马 can be used alone to mean the animal "horse." It can also be combined with other characters for new meanings. 马上mǎshàng-immediately; 马球mǎqiú-polo; 马路mǎlù-street; etc. Other characters with the same pronunciation will be used differently as well. 数码相机shùmǎ xiàngjī-digital camera; 蚂蚁mǎyǐ-ant; etc. Since these characters alone sound exactly the same in conversation, the only way to distinguish them is through context.

Tone changes
The third tone, with its dip-and-rebound, is hard to fit into a continuous sentence. This is why the third-tone changes depending on its environment. There are two rules:

 * 1) If a third tone comes before another third tone, then it is pronounced as a second tone.
 * 2) If a third tone comes before any other tone, then it only dips, and doesn't rebound and is called a half-third tone (see image).

Because of these broad rules, the majority of third tones you encounter will be spoken as second tones or half-third tones. Be mindful of this because the written tone marks remain unchanged despite the differences in actual pronunciation.

Neutral Tones
Some syllables don't have a tone and carry no tone mark. They are not stressed, and they take their tone from the syllable before them:

 * 1) If it follows a first- or second-tone syllable, then the toneless syllable is mid-range.
 * 2) If it follows a third-tone syllable, then the toneless syllable is high, as if the dip-and-rebound of the third-tone continues right into it.
 * 3) If it follows a fourth-tone syllable, then the toneless syllable is low, as if the fall of the fourth-tone continues right into it.

Test and Review
Mandarin One: Lesson One

title: Chinese (Mandarin)/Using Tones


text:
Talk:Abstract Algebra/Hypercomplex numbers

Old comment
This is not a correct definition of hypercomplex numbers. Squares of imaginary units of -1 are a special case, occuring for complex numbers, quaternions, octonions, etc.

Revision 20/10/17
A new start has been made on this chapter, noting that the term is historical only, and giving the main instances and their structure. Rgdboer (discuss • contribs) 03:07, 21 October 2017 (UTC)


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User talk:68.219.181.172

Please stop adding nonsense to Wikibooks. It is considered vandalism. If you would like to experiment, use the sandbox. Thank you.

title: User talk:68.219.181.172


text:
User talk:Flexxelf

Welcome
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Image:Figure1.pdf
You uploaded file which is not used at Wikibooks. You should be aware that we are not a free hosting service and unused files are being deleted. --Derbeth talk 10:02, 8 March 2006 (UTC)

title: User talk:Flexxelf


text:
User talk:JOPSOUND

Welcome
Hello and welcome to Wikibooks!

Here are some tips to help you get started:
 * You can sign your name on Talk and vote pages using four tildes, like this: ~~~~.
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You will find more resources in Community Portal. If you want to ask a question, visit the Study help desk, the Staff lounge, IRC channel or ask me personally on my talk page.

Good luck! --Derbeth talk 10:04, 8 March 2006 (UTC)

Copyright problem with Image:JOPSOUND.jpg
--Derbeth talk 10:04, 8 March 2006 (UTC)

title: User talk:JOPSOUND


text:
User talk:J Darnley

Welcome
Hello and welcome to Wikibooks!

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You will find more resources in Community Portal. If you want to ask a question, visit the Study help desk, the Staff lounge, IRC channel or ask me personally on my talk page.

Good luck! --Derbeth talk 10:05, 8 March 2006 (UTC)

Copyright problem with Image:Plotof-twothirdsxsquaredplusone.png
--Derbeth talk 10:05, 8 March 2006 (UTC)
 * I could have sworn I put PD-self on all the images I uploaded. Well I added that one now. --J Darnley 09:46, 9 March 2006 (UTC)

title: User talk:J Darnley


text: Template:Nld

title: Template:Nld


text:
User talk:Patsissons

Welcome
Hello and welcome to Wikibooks!

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 * See list of templates which can save your time
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 * Explore, be bold in editing pages, and have fun!

You will find more resources in Community Portal. If you want to ask a question, visit the Study help desk, the Staff lounge, IRC channel or ask me personally on my talk page.

Good luck!--Derbeth talk 10:16, 8 March 2006 (UTC)

Image:Uofa stat222 Sol2-06.pdf
You uploaded file which is not used at Wikibooks. You should be aware that we are not a free hosting service and unused files are being deleted. --Derbeth talk 10:16, 8 March 2006 (UTC)
 * File is now referenced properly on one of the wikibook pages --Patsissons 19:01, 9 March 2006 (UTC)

Hello. Regarding your request: as far as I am aware, both naming conventions (: and /) are acceptable here - there's no need to convert anything. tsca ✉ 20:55, 10 March 2006 (UTC)

title: User talk:Patsissons


text:
User talk:Ann222

Welcome
Hello and welcome to Wikibooks!

Here are some tips to help you get started:
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You will find more resources in Community Portal. If you want to ask a question, visit the Study help desk, the Staff lounge, IRC channel or ask me personally on my talk page.

Good luck! --Derbeth talk 10:17, 8 March 2006 (UTC)

title: User talk:Ann222


text:
User:Ksyrie

zh:User:Ksyrie

title: User:Ksyrie


text:
User talk:Zocky

Welcome
Hello and welcome to Wikibooks!

Here are some tips to help you get started:
 * You can sign your name on Talk and vote pages using four tildes, like this: ~~~~.
 * Remember to conduct any editing experiments in the sandbox.
 * Check out our help page if you need additional help.
 * Eventually, you might want to read the Manual of Style and Policies and Guidelines.
 * Take a look at Naming policy
 * See list of templates which can save your time
 * Remember to maintain a Neutral point of view.
 * Explore, be bold in editing pages, and have fun!

You will find more resources in Community Portal. If you want to ask a question, visit the Study help desk, the Staff lounge, IRC channel or ask me personally on my talk page.

Good luck! --Derbeth talk 11:06, 8 March 2006 (UTC)

False Friends
Dear Zocky, thanks for all your additions and corrections to the maps. You seem to know Serbo-Croatian and Slovenian quite well, so you might be just the one to translate some sentences we still need, especially the ones at the head of Talk:False Friends of the Slavist. Also, if you like and have some time, look at the translations needed for Croatian, Bosnian, Serbian and Slovenian. Thanks! --Daniel Bunčić 12:37, 8 March 2006 (UTC)

Have you voted yet? :-) --Daniel Bunčić 15:41, 12 March 2006 (UTC)

title: User talk:Zocky


text:
Understanding Darcs/More patch theory

It's all patches
Before moving on, we would like to make one very minor point clear: in the day to day operation of darcs, we talk about pulling and pushing patches, and of recording and reverting changes. This is just a user interface convention. In patch theory terms, all of these are just patches. The patches which you pull and push are named patches, patches which contain a name and a list of unnamed patches. So in fact, when you pull a single named patch from somebody else's repository, you are pulling a sequence of potentially many primitive patches. What does this mean for merging?

Merging a sequence of patches
In the last chapter, we saw that dealing with simple, non-conflicting merges consists mainly of making an inverse patch and commuting that inverse with the other side's patches. Let us now explore a slightly more complicated scenario, where we have to merge against a non-conflicting sequence of patches. We do this with a variant of the darcs hackathon shopping list. As usual, Arjan and Ganesh are working together to write the shopping list. They both start from a common file shplst containing apples bananas cookies

As before, Arjan inserts "beer" in line 3 of shplst and records the change. He then decides to add another item on the end of the list, this time, "pasta" and records his second change. In darcs notation, Arjan has brought us from an initial context $$o$$, to a new context $$a$$ with beer in it, and then to yet another context $$c$$ with pasta as well..

FIXME: will be fleshed out: i want to show what happens when Ganesh pulls two patches in

title: Understanding Darcs/More patch theory


text: Template:Clear

title: Template:Clear


text:
Visual Basic .NET/Controls

Like its predecessor, Visual Basic .NET excels in creating graphical user interfaces. Although the programmer still has the option of creating controls and setting their properties programatically (i.e., by hand writing the code), he usually will create many, if not all of the controls in the interface by selecting items from the toolbox and adding to a particular form. While working with forms, you can use the toolbox to drag different controls to the form you are designing, resize them and relocate them using the mouse, and set the control's properties in a corresponding properties window to quickly develop the user interface. Events handlers for each control's most common event can be quickly created by double-clicking on the control to create a new event handler and be send to that event handler in the code window.

Some of these controls are described below.

TextBox
A TextBox is used to get and display text, this one can be in several fonts, size and color. By default, a TextBox will only display text on a single line. If you require more than one line you can set its Multiline property to true.

Passwords
If you need a TextBox for accepting a password you should set it's PasswordChar property to a character. The character you choose will be displayed in the TextBox instead of what is actually typed. Good characters to choose include * and ● and any letter you will type.

Clipboard
You can copy the selected text to the clipboard by using the TextBox.Copy method. Use the TextBox.Paste method to paste text into the Textbox from the clipboard. TextBox.Cut places the selected text into the clipboard and removes the text from the TextBox.

To restrict text
To restrict text from being entered into a TextBox create an event handler for the KeyPress event.

This example is for a TextBox named TextBox1. It will allow only numbers (0 - 9), 1 decimal point and 1 minus sign to be entered.

Labels
Labels are used to display text. Unlike the textbox, it is not meant to accept input from the user. Often a Label is used to describe another control, and is often used as a prompt for a Textbox.label display read-only text as far as the user is concerned

Buttons
Buttons are controls that are usually raised that the user most often can click on to perform some action defined by the programmer. Once the programmer has added the button control to a form, he can define an event handler to perform an action when the button is clicked.

Checkboxes
A check box indicates a two-way choice or state (true/false) which can be edited by the user. Check boxes are shown on the screen as a square box that can contain white space (for false) or a check mark (for true). Adjacent to the check box is normally shown a caption describing the meaning of the check box. Inverting the state of a check box is done by clicking the mouse on the button, or the caption. Visual Basic allows the programmer to set the caption through the check box's text property.

Radio Buttons
A radio button allows the user to choose exactly one of a predefined set of options. Radio buttons are arranged in groups of two or more and displayed on screen a list of circular holes that can contain white space (for unselected) or a dot (for selected). Each radio button can show a caption describing the choice that this radio button represents. This is done by setting the radio button's text property.

RichTextBox
Can easily save Richtext files with Colours and Fonts. Has all the qualities of a textbox but with built in save method(richtextbox1.savefile(pathname)) and openfile(Richtextbox1.openfile(filename)).

Other controls not visible at design time
Some of the controls you can add while designing your form do not actually appear on the form, but you can still use the toolbox to add them to the form, where they are keep in a tray below the form for easy reference.

OpenFileDialog
An OpenFileDialog displays the standard "Open" dialog. It lets the user browse for a file. This code is a function that returns the file path.

SaveFileDialog
A SaveFileDialog displays the standard "Save" dialog. It lets the user browse for a directory to save files and enter a filename. It can (optionally) automatically append extensions to the filename.

FontDialog
A FontDialog lets the user to select a font from a list of installed fonts.

ColorDialog
A ColorDialog lets the user select predefined color or specify a custom color.

Timer Control
A Timer Control is a control that will execute code at intervals. It is not visible at runtime. The interval can be set in the properties in the measurement of milliseconds. The timer control will continue to repeat its code at your interval until the control is stopped.

de:Visual Basic .NET: Einstieg in Windows Forms Visual Basic .NET/Contrôles

title: Visual Basic .NET/Controls


text:
User:Nightstallion/monobook.js

// User:Lupin/popups.js - please include this line

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/* default subset - try to use a cookie some day */ chooseCharSubset(0); } }

/* select subsection of special characters */ function chooseCharSubset(s) { var l = document.getElementById('specialchars').getElementsByTagName('p'); for (var i = 0; i < l.length ; i++) { l[i].style.display = i == s ? 'inline' : 'none'; l[i].style.visibility = i == s ? 'visible' : 'hidden'; } }

addLoadEvent(addCharSubsetMenu);

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// Script from User:Haza-w/Interiot2.js document.write(' ')

title: User:Nightstallion/monobook.js


text:
User:Neilgravir~enwikibooks

Hi, you can see my Wikipedia user page here.

title: User:Neilgravir~enwikibooks


text:
Talk:XML - Managing Data Exchange/VoiceXML

My chapter seems to be pretty good as far as the content goes. I think I need to go through the checklist to make its appearance consistent with the rest of the chapters.

Editorial Board Suggestions
I admit that I didn't fully understand this chapter; some of the information is a little too technical for me. I understood the chapter better when I saw the VoiceXML code examples and their corresponding dialogs. It made me think of automated phone menus or surveys that prompt callers for voice responses--scenarios that are more familiar to me. Even though the chapter explains that inputs can be in more forms than just speech, such as touch tone inputs, I think more familiar examples will help the reader understand the concepts of VoiceXML. Based on my initial reading of the chapter, here are my questions/suggestions:

Overall

''VoiceXML is created to generate audio dialogs that allows the use of synthesized speech, digitized audio, recognition of spoken and DTMF(Dual Tone Multi-Frequency Touch-tone or push-button dialing. Pushing a button on a telephone keypad generates a sound that is a combination of two tones, one high frequency and the other low frequency) key input, recording of spoken input, telephony, and mixed initiative conversations. The major goal of VoiceXML is to bring the advantages of the XML language to generate interactive voice response applications. VoiceXML sets an integration environment between voice services and data services taking advantage of the client-server paradigm.'' The parentheses need to be corrected, but aside from that, what are some examples of using synthesized speech, digitized audio, etc. in relation to VoiceXML? This didn't really ring clear to me.
 * Definitely use the checklist.
 * The chapter should have learning objectives.
 * Provide more familiar details of VoiceXML applications. In particular, correct and flesh out the following segment:
 * Just an idea--I wonder if it would make more sense to move the VoiceXML code examples before the VoiceXML elements. This may help reinforce the concepts, and when you discuss the VoiceXML elements, you could refer to the example code elements the reader has already previewed. Also, then there would be no need for the  element code example because it already exists in the form and menu code examples, and both of these examples simply can be referenced when discussing the  element and the rest of the elements.
 * Other element examples--even though the form and menu examples include the vxml, field, grammar, block, and prompt elements, the samples of code do not always include one of the listed attributes for these elements (might be nice). Furthermore, the  element in the sample code includes  and I didn't see any content in the chapter that explains the src and type attributes for the  element. Perhaps some comments in the code or more explanation in the chapter would be helpful.
 * In the Form example, there is --should the property element be explained further in its own section, as are the vxml, field, grammar, etc. elements?
 * Provide additional comments for all code examples and tables to help transition between content.
 * The exercises mention choosing options from a keyboard. Maybe I'm not familiar enough with the chapter, but I didn't understand how this is using VoiceXML.

Implementation platform requirements This section kind of lost me. The bolded terms confused me. Is "document acquisition" the hardware/software requirements? Similarly, I wasn't too sure what "audio output" and "audio input" were correlated with--it could just be the way these terms are being referenced (i.e. colon, comma, period). The bulleted list confused me as well. There doesn't seem to be a sentence that transitions to the bulleted list. Is the list a summary of implementation platform requirements? The list also contains a few ambiguous Its that should be clarified.

VoiceXML architectural model

 * The model references component titles with capital letters (e.g. Document Server). Should this style be continued throughout the chapter? There are times these components are referenced with capital and lowercase letters, and the way these are referenced should remain consistent throughout the chapter. I think the component references are more distinguished when they're used like titles with capital letters.
 * The last bullet in this section doesn't seem as though it should be a part of the list. It's an example of how the model works, so it probably should just be a paragraph after the list.
 * The graphic is a little blurry. You could replace it with the following graphic:

Christinaserrano 04:38, 24 March 2006 (UTC)

Professor
The editorial board has provided much good advice, and it should be considered carefully when making the revision.

It would be useful to have links to topics such as synthesized speech, which is probably in Wikipedia.

I agree with moving the examples before listing all the elements. Give people concrete examples before abstract notions.

Remove details of the prior authors.

For the class presentations, see if you can find a live example to use.

Rtw 14:17, 24 March 2006 (UTC)


text: User:Kowey/Haskell

title: User:Kowey/Haskell


text:
False Friends of the Slavist/Map dětę

dete

title: False Friends of the Slavist/Map dětę


text:
Haskell/Indentation

Haskell relies on indentation to reduce the verbosity of your code. Despite some complexity in practice, there are really only a couple fundamental layout rules.

The golden rule of indentation
Code which is part of some expression should be indented further in than the beginning of that expression (even if the expression is not the leftmost element of the line).

The easiest example is a 'let' binding group. The equations binding the variables are part of the 'let' expression, and so should be indented further in than the beginning of the binding group: the 'let' keyword. When you start the expression on a separate line, you only need to indent by one space (although more than one space is also acceptable and may be clearer).

You may also place the first clause alongside the 'let' as long as you indent the rest to line up:

This tends to trip up a lot of beginners: All grouped expressions must be exactly aligned. On the first line, Haskell counts everything to the left of the expression as indent, even though it is not whitespace.

Here are some more examples:

Note that with 'case' it is less common to place the first subsidiary expression on the same line as the 'case' keyword (although it would still be valid code). Hence, the subsidiary expressions in a case expression tend to be indented only one step further than the 'case' line. Also note how we lined up the arrows here: this is purely aesthetic and is not counted as different layout; only indentation (i.e. whitespace beginning on the far-left edge) makes a difference to the interpretation of the layout.

Things get more complicated when the beginning of an expression is not at the start of a line. In this case, it's safe to just indent further than the line containing the expression's beginning. In the following example,  comes at the end of a line, so the subsequent parts of the expression simply need to be indented relative to the line that contains the , not relative to the   itself.

Here are some alternative layouts which all work:

Explicit characters in place of indentation
Indentation is actually optional if you instead use semicolons and curly braces for grouping and separation, as in "one-dimensional" languages like C. Even though the consensus among Haskell programmers is that meaningful indentation leads to better-looking code, understanding how to convert from one style to the other can help understand the indentation rules. The entire layout process can be summed up in three translation rules (plus a fourth one that doesn't come up very often):

 * 1) If you see one of the layout keywords,, insert an open curly brace (right before the stuff that follows it)
 * 2) If you see something indented to the SAME level, insert a semicolon
 * 3) If you see something indented LESS, insert a closing curly brace
 * 4) If you see something unexpected in a list, like , insert a closing brace before instead of a semicolon.

For instance, this definition...

...can be rewritten without caring about the indentation rules as:

One circumstance in which explicit braces and semicolons can be convenient is when writing one-liners in GHCi:

Indent to the first
Due to the "golden rule of indentation" described above, a curly brace within a  block depends not on the   itself but the thing that immediately follows it. For example, this weird-looking block of code is totally acceptable:

As a result, you could also write combined if/do combination like this:

It isn't about the, it's about lining up all the items that are at the same level within the.

Thus, all of the following are acceptable: or or

title: Haskell/Indentation


text:
False Friends of the Slavist/Map glava

glava

title: False Friends of the Slavist/Map glava


text:
Category:Recipes without servings

''This is an automatically generated category. Do not add recipes to this category by hand.''

These are recipes which use but have nothing listed for "Servings".

__HIDDENCAT__

title: Category:Recipes without servings


text:
Category:Recipes without cooking time

''This is an automatically generated category. Do not add recipes here by hand.''

These are recipes which use but do not have a cooking time.

__HIDDENCAT__

title: Category:Recipes without cooking time


text:
False Friends of the Slavist/Map kolo

kolo

title: False Friends of the Slavist/Map kolo


text:
Category:Very Easy recipes

''This is an automatically generated category. Do not add recipes here by hand.''

Recipes which are rated "Very Easy" (1 out of 5).

hy:Կատեգորիա:Շատ հեշտ բաղադրատոմսեր

title: Category:Very Easy recipes


text:
Category:Easy recipes

''This is an automatically generated category. Do not add recipes here by hand.''

Recipes which are rated "Easy" (2 out of 5).

hy:Կատեգորիա:Հեշտ բաղադրատոմսեր

title: Category:Easy recipes


text:
Category:Medium Difficulty recipes

''This is an automatically generated category. Do not add recipes here by hand.''

Recipes which are rated "Medium Difficulty" (3 out of 5).

hy:Կատեգորիա:Միջին դժվարությամբ բաղադրատոմսեր

title: Category:Medium Difficulty recipes


text:
Category:Difficult recipes

''This is an automatically generated category. Do not add recipes here by hand.''

Recipes which are rated "Difficult" (4 out of 5).

hy:Կատեգորիա:Դժվար բաղադրատոմսեր

title: Category:Difficult recipes


text:
Category:Very Difficult recipes

''This is an automatically generated category. Do not add recipes here by hand.''

Recipes which are rated "Very Difficult" (5 out of 5).

hy:Կատեգորիա:Շատ դժվար բաղադրատոմսեր

title: Category:Very Difficult recipes


text:
False Friends of the Slavist/Map para

para

title: False Friends of the Slavist/Map para


text:
Category:Recipes with images

__HIDDENCAT__

''This is an automatically generated category. Please do not add recipes here by hand.''

These are recipes using recipesummary which have images included, as well as recipes with have been manually tagged with this category as having images.

It is a hidden category which means that it will not appear in the list of categories shown on the recipe page.

If you want images in a recipe, you can use the template Image requested.

hy:Կատեգորիա:Պատկերով բաղադրատոմսեր

title: Category:Recipes with images


text:
Educational Technology Innovation and Impact/Multimedia Courseware/Online Demonstrations

Online demonstrations are particularly useful to show how a piece of software works or how it can be used to instruct or teach in a classroom environment. This usually involves some sort of interaction with the learning experience. As the title of this subject implies the learner has to log onto the web to take part in the learning opportunity.

A good example of this form of learning is through an online demonstration, Macromedia offer live one hour on line demonstrations. The benefit of these short interventions is that they are interactive and the learner can join education experts as they conduct live, online product demonstrations. These demonstrations are aimed at Key Stage 12 and higher education teachers, faculty, staff, and administrators that may wish to use the software as part of their teaching/learning. The software also let’s the learner combine existing learning materials such as text books or hand-outs with real-time interactivity which enables collaborative teaching and learning experiences (Macromedia Website 2006)

The Joint Information Systems Committee (JISC) offer a range of on-line learning resources for education and research purposes. JISC has commissioned a series of five exemplars which demonstrate how Further Education (FE) practitioners can use content found in online resources to support their teaching. Each of the exemplars showcases available electronic resource material for the teacher and it demonstrates how each of these materials can be used to assist in delivering the core syllabus to students/learners (JISC Website 2006)

The following link is the ‘Leisure’ exemplar; http://restricted.jisc.ac.uk/exemplars_fe/exemplars/leisure/index.html

Another good example of online collaborative methods of teaching and learning is through the use of Blogs. These are private web pages which are published by either an individual or a group of individuals. They can be personal journals/diaries and are used to comment on all sorts of topics depending on the interests of the author, often referred to as a Blogger. Most Blogs enable the visitors to post comments and/or suggestions allowing interactivity between the Blogger and the visitors. So from this it can be argued that the exemplars that JISC use, product online demonstrations and Blogs are excellent mediums for online educational purposes.

The following link is extremely useful to view live demonstrations on various e-learning products; http://elearningcentre.typepad.com/whatsnew/

References; www.adobe.com/products/breeze (accessed 27/3/06 www.jisc.ac.uk Joint Information Systems Committee Website (accessed 27/3/06)


text:
Utopia/Anarchism

What anarchy is a simple question; just life, the point is; what it is not. Anarchy is not the vandalism by loading arms or explosives as in the chaotic nature of 1790s France but it is a simplicity philosophy of far east that sourced of lao-tze or Taoism. But still on the contrary to the others, anarchy is not a style of constructing general agreement(choosing the one of the sames)

Wars are very unlikely to occur within an anarchist system, which may sound like zealous wishful thinking because it appears to imply that there will be no conflict between people because of an absence of authority (many would consider this paradoxical in itself). The reason wars are unlikely to happen is because to start and continue a war an individual must have a personal interest in it, kings, presidents, popes, lords and generals (autocrats and oligarchs) all have such an interest in practicing warfare for various reasons. Insurrectionists will also have an interest in continuing a war but will only have the objective of ending it, autocrats and oligarchs will usually wish to continue the war for as long as possible. The more important distinction between the two is that an insurrectionist is likely to be in personal danger of being killed during the war whilst the autocrat or oligarch have the possibility of assassination but are otherwise not in danger. To illustrate the distinction of an anarchist society, suppose there was an anarchist city with two neighbourhoods, for whatever reason they do not share what they have with each other, so neighbourhood A decides that they want to take what they like from neighbourhood B and to do so they will go to war with neighbourhood B (incidentally this is capitalist/fascist rather than anarchist reasoning not but it will have to suffice for the example). Everyone in neighbourhood A that wants to go to war will have to be involved, to play the part of the insurrectionist, to kill and probably die for what they want. This is a very different scenario to the one the autocrat/oligarch find themselves in where they are not personally willing to die for what they want but are willing to sacrifice others for it. So it can be seen that in an anarchist system someone would have to be willing to die for their desire to start a war in order for one to begin at all.

title: Utopia/Anarchism