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Fundamentals of Transportation/Decision Making

Decision Making is the process by which one alternative is selected over another. Decision making generally occurs in the planning phases of transportation projects, but last minute decision making has been shown to occur, sometimes successfully. Several procedures for making decisions have been outlined in effort to minimize inefficiencies or redundancies. These are idealized (or normative) processes, and describe how decisions might be made in an ideal world, and how they are described in official documents. Real-world processes are not as orderly.

Applied systems analysis is the use of rigorous methods to assist in determining optimal plans, designs and solutions to large scale problems through the application of analytical methods. Applied systems analysis focuses upon the use of methods, concepts and relationships between problems and the range of techniques available. Any problem can have multiple solutions. The optimal solution will depend upon technical feasibility (engineering) and costs and valuation (economics). Applied systems analysis is an attempt to move away from the engineering practice of design detail and to integrate feasible engineering solutions with desirable economic solutions. The systems designer faces the same problem as the economist, "efficient resource allocation" for a given objective function.

Systems analysis emerged during World War II, especially with the deployment of radar in a coordinated way. It spread to other fields such as fighter tactics, mission planning and weapons evaluation. Ultimately the use of mathematical techniques in such problems came to be known as operations research, while other statistical and econometric techniques are being applied. Optimization applies to cases where data is under-determined (fewer observations than dependent variables) and statistics where data is over-determined (more observations than dependent variables). After World War II, techniques spread to universities. Systems analysis saw further mathematical development and application to a broad variety of problems.

It has been said of Systems Analysis, that it is:
 * "A coordinated set of procedures which addresses the fundamental issues of design and management: that of specifying how men, money and materials should be combined to achieve a higher purpose" - De Neufville
 * "... primarily a methodology, a philosophical approach to solving problems for and for planning innovative advances" - Baker
 * "Professionals who endeavor to analyze systematically the choices available to public and private agencies in making changes in the transportation system and services in a particular region" - Manheim
 * "Systems analysis is not easy to write about: brief, one sentence definitions frequently are trivial" - Thomas

The most prominent decision-making process to emerge from systems analysis is rational planning, which will be discussed next, followed by some critiques and alternatives.

How does one (rationally) decide what to do?

The figure identifies three layers of abstraction. The first layer (top row) describes the high level process, which we can summarize in six steps. A second layer details many of the components of the first layer. A third layer, identified by the blue box, "abstract into model or framework" depends on the problem at hand

Overview data
The first step is observational, review and gather data about the system under consideration. An understanding of the world around is required, including specifying the system.

The problem (defined in the next step) lies within a larger system, that comprises
 * 1) Objectives - measure the effectiveness or performance
 * 2) Environment - things which affect the system but are not affected by it
 * 3) Resources - factor inputs to do the work
 * 4) Components - set of activities or tasks of the system
 * 5) Management - sets goals, allocates resources and exercises control over components
 * 6) Model of how variables in 1-5 relate to each other

the detailed objectives are identified in the following step, and the detailed model for analysis of the problem is specified in the step after that.

 For instance in the case of intercity transportation in California, data about existing demand conditions, existing supply conditions, future demand expectations, and proposed changes to supply would be important inputs. Changes in technology and environmental conditions are important considerations for long-term projects. We would also want to know the certainty of the forecasts, not just a central tendency, and the potential for alternative scenarios which may be widely different.

Define the problem
The second step is to define the problem more narrowly, in a sense to identify needs.

 Rather than an amorphous issue (intercity transportation), we might be interested in a more detailed question, e.g. how to serve existing and future demands between two cities (say metropolitan Los Angeles and San Francisco). The problem might be that demand is expected to grow and outstrip supply.

Formulate goal
The third step is to formulate a goal. For major transportation projects, or projects with intense community interest, this may involve the public. For instance

 To serve future passenger demand between Los Angeles and San Francisco, quickly, safely, cleanly, and inexpensively.

The goal will need to be testable, the process below "formulate goal" in the flowchart suggests this process in more detail.

The first aspect is to operationalize the goal. We need to measure the adverbs in the goal (e.g. how do we measure "quickly", "safely", "cleanly", or "inexpensively"). Some are straight-forward. "Quickly" is a measure of travel time or speed. But it needs to account for both the access and egress time, the waiting time, and the travel time, and these may not be weighted the same.

The second step is identifying the decision criteria. Each adverb may have a certain value, but it might be that an alternative has not merely have the most points in one area, but establish at least minimum satisfactory points in all areas. So a very fast mode must meet a specific safety test, and going faster does not necessarily mean it can also be more dangerous (despite what a rational economist might think about trade-offs).

The third is to weight those criteria. E.g. how important is speed vs. safety? This is in many ways a value question, though economics can try to value each of these aspects in monetary form, enabling Evaluation. For instance, many Negative externalities have been monetized, giving a value of time in delay, a value of pollution damages, and a value of life.

Generate alternatives
Examining, evaluating, and recommending alternatives is often the job of professionals, engineers, planners, and economists. Final selection is generally the job of elected or appointed officials for important projects.

There are several sub-problems here, the first is to generate alternatives. This may require significant creativity. Within major alternatives, there may be many sub-alternatives, e.g. the main alternative may be mode of travel, the sub-alternatives may be different alignments. For network problems there may be many combinations of alternative alignments. If the analyst is lucky, these are separable problems, that is, the choice of one sub-alignment is independent of the choice of alternative sub-alignments.

 * 1) Algorithms-systematic search over available alternatives
 * 2) Analytical
 * 3) Exact numerical
 * 4) Heuristic numerical
 * 5) Generate alternatives selectively, evaluate subjectively
 * 6) Fatal flaw analysis
 * 7) Simple rating schemes
 * 8) Delphi exercises
 * 9) Generate alternatives judgmentally, evaluate scientifically using system model

A critical issue is how many alternatives to consider. In principle, an infinite number of more or less similar alternatives may be generated, not all are practical, and some may be minor variations. In practice a stopping rule to consider a reasonable number of alternatives is used. Major exemplars of the alternatives may be used, with fine-tuning awaiting a later step after the first set of alternatives is analyzed. The process may be iterative, winnowing down alternatives and detailing alternatives as more information is gained throughout the analysis.

 Several major alternatives may be suggested, expand highways, expand air travel, or construct new high-speed rail line, along with a no-build alternative.

Abstract into model or framework
"All Models are Wrong, Some Models are Less Wrong than Others"—Anonymous

"All Models are Wrong, Some Models are Useful"—George Box

The term Model refers here to a mathematical representation of a system, while a Framework is a qualitative organizing principle for analyzing a system. The terms are sometimes used interchangeably.

Framework Example: Porter’s Diamond of Advantage

To illustrate the idea of a framework, consider Porter's Diamond of Advantage

Michael Porter proposes four key determinants of competitiveness, which he calls the "Diamond of Advantage," based on cases from around the world:
 * 1) factor conditions, such as a specialized labor pool, specialized infrastructure and sometimes selective disadvantages that drive innovation;
 * 2) home demand, or local customers who push companies to innovate, especially if their tastes or needs anticipate global demand;
 * 3) related and supporting industries, specifically internationally competitive local supplier industries, creating a high quality, supportive business infrastructure, and spurring innovation and spin-off industries; and
 * 4) industry strategy/rivalry, involving both intense local rivalry among area industries that is more motivating than foreign competition and as well as a local "culture" which influences individual industries' attitudes toward innovation and competition.

Model Example: The Four-Step Urban Transportation Planning System

Within the rational planning framework, transportation forecasts have traditionally followed the sequential four-step model or urban transportation planning (UTP) procedure, first implemented on mainframe computers in the 1950s at the Detroit Area Transportation Study and Chicago Area Transportation Study (CATS).

Land use forecasting sets the stage for the process. Typically, forecasts are made for the region as a whole, e.g., of population growth. Such forecasts provide control totals for the local land use analysis. Typically, the region is divided into zones and by trend or regression analysis, the population and employment are determined for each.

The four steps of the classical urban transportation planning system model are:
 * Trip generation determines the frequency of origins or destinations of trips in each zone by trip purpose, as a function of land uses and household demographics, and other socio-economic factors.
 * Destination choice matches origins with destinations, often using a gravity model function, equivalent to an entropy maximizing model. Older models include the fratar model.
 * Mode choice computes the proportion of trips between each origin and destination that use a particular transportation mode. This model is often of the logit form, developed by Nobel Prize winner Daniel McFadden.
 * Route choice allocates trips between an origin and destination by a particular mode to a route. Often (for highway route assignment) Wardrop's principle of user equilibrium is applied, wherein each traveler chooses the shortest (travel time) path, subject to every other driver doing the same. The difficulty is that travel times are a function of demand, while demand is a function of travel time.

See Modeling for a deeper discussion of modeling questions.

Ascertain performance
This is either an output of the analytical model, or the result of subjective judgment.

Sherden identifies a number of major techniques for technological forecasting that can be used to ascertain expected performance of particular technologies, but that can be used within a technology to ascertain the performance of individual projects. These are listed in the following box:

 "Major techniques for technological forecasting
 * Delphi method: a brain-storming session with a panel of experts.
 * Nominal group process: a variant of the Delphi method with a group leader.
 * Case study method: an analysis of analogous developments in other technologies.
 * Trend analysis: the use of statistical analysis to extend past trends into the future.
 * S-curve: a form of trend analysis using an s-shaped curve to extend past trends into the future.
 * Correlation analysis: the projection of development of a new technology past developments in similar technologies.
 * Lead-user analysis: the analysis of leading-edge users of a new technology predict how the technology will develop.
 * Analytic hierarchy process: the projection of a new technology by analyzing a hierarchy of forces influencing its development.
 * Systems dynamics: the use of a detailed model to assess the dynamic relationships among the major forces influencing the development of the technology.
 * Cross-impact analysis: the analysis of potentially interrelated future events that may affect the future development of a technology.
 * Relevance trees: the breakdown of goals for a technology into more detailed goals and then assigning probabilities that the technology will achieve these detail goals.
 * Scenario writing: the development of alternative future views on how the new technology could be used."

Rate alternatives
The performance of each of the alternatives is compared across decision criteria, and weighted depending on the importance of those criteria. The alternative with the highest ranking would be identified, and this information would be brought forward to decision-makers.

Compute optimal decision
The analyst is generally not the decision maker. The actual influence of the results of the analysis in actual decisions will depend on:
 * 1) Determinacy of evaluation
 * 2) Confidence in the results on the part of the decision maker
 * 3) Consistency of rating among alternatives

Implement alternatives
A decision is made. A project is constructed or a program implemented.

Evaluate outcome
Evaluating outcomes of a project includes comparing outcome against goals, but also against predictions, so that forecasting procedures can be improved. Analysis and implementation experience lead to revisions in systems definition, and may affect the  values that underlay that definition. The output from this "last" step in is used as input to earlier steps in subsequent analyses. See e.g. [http://dx.doi.org/doi:10.1016/j.tranpol.2010.04.010 Parthasarathi, Pavithra and David Levinson (2010) Post-Construction Evaluation of Trafﬁc Forecast Accuracy. Transport Policy ]

Relationship to other models
We need a tool to "Identify Needs" and "Evaluate Options". This may be the transportation forecasting model.

Problem PRT: Skyweb Express

The Metropolitan Council of Governments (the region's main transportation planning agency) is examining whether the Twin Cities should build a new Personal Rapid Transit system in downtown Minneapolis, and they have asked you to recommend how it should be analyzed

1. What kind of model should be used. Why?

2. What data should be collected.

Form groups of 3 and take 15 minutes and think about what kinds of models you want to run and what data you want to collect, what questions you would ask, and how it should be collected. Each group should have a note-taker, but all members of the group should be able to present findings to the class.

Thought Questions

 * Is the "rational planning" process rational?
 * Compare and contrast the rational planning process with the scientific method?

Some Issues with Rational Planning
Nevertheless, some issues remain with the rational planning model:

Problems of incomplete information

 * Limited Computational Capacity
 * Limited Solution Generating Capacity
 * Limited input data
 * Cost of Analysis

Problems of incompatible desires

 * Conflicting Goals
 * Conflicting Evaluation Criteria
 * Reliance on Experts (What about the People?)

Alternative Planning Decision Making Paradigms: Are They Irrational?
No one really believes the rational planning process is a good description of most decision making, as it is highly idealized. Alternatives normative and positive paradigms to the rational planning process include:

Several strategies normatively address the problems associated with incomplete information:
 * Satisficing
 * Decomposition hierarchically into Strategy/Tactics/Operations.

Other strategies describe how organizations and political systems work:
 * Organizational Process
 * Political Bargaining

Some do both:
 * Incrementalism

The paper Montes de Oca, Norah and David Levinson (2006) Network Expansion Decision-making in the Twin Cities. Journal of the Transportation Research Board: Transportation Research Record #1981 pp 1-11 describes the actual decision making process for road construction in the Twin Cities


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User talk:Chiragarora

hi \ i am chemical engg

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

title: User talk:Chiragarora


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Ido/Lesson III7

Using Computers
Some of these words have not been oficially adopted:

Exemplo-frazi

 * La dominaco-programo en mea komputoro* es Ubuntu Linux.

 * Komputorala reto esas irga grupo di inter-konektita komputori.

 * La ¨Internet¨ esas mond-vasta, publike acesebla serio di inter-konektita reti komputorala.

 * La ¨World Wide Web¨ esas sistemo konsistanta ek inter-ligita ¨hypertext¨-arkivi quan onu povas acesar per la ¨Internet¨.

 * Onu povas uzar la komputorala programaro, nome ¨Web Browser¨, por vidar ret-situi ed por pilotadar inter li per ¨hyperlinks¨.

 * The operating system in my computer is Ubuntu Linux.

 * A computer network is an interconnected group of computers.

 * The Internet is a worldwide, publicly accessible series of interconnected computer networks.

 * The World Wide Web is a system of interlinked hypertext documents accessed via the Internet.

 * One can use a ¨Web Browser¨ to view ¨Web pages¨ and to navigate among them by using hyperlinks.

title: Ido/Lesson III7


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User talk:68.253.184.204

Apologies. I haven't edited here for a little while and the above template has been changed and appears to be quite threatening. What I intended to say was that a recent edit of yours appeared to be unconstructive or inappropriate and that it was reverted. If you feel that it was justified then I apologise.

--Xania talk 21:23, 31 March 2008 (UTC)

title: User talk:68.253.184.204


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User talk:FirstCoolBreeze

--Xania talk 21:27, 31 March 2008 (UTC)

title: User talk:FirstCoolBreeze


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Wikijunior:Europe/Serbia

Serbia (Република Србија / Republika Srbija in Serbian language) is a country located in south eastern Europe in the Balkan peninsula. Its neighbours are Bosnia & Hercegovina, Croatia, Hungary, Romania, Bulgaria, North Macedonia, Albania and Montenegro (which was part of a union between Serbia and Montenegro until 2006). Within Serbia there are officially two autonomous regions: Vojvodina and Kosovo Metohija, however, in February 2008 Kosovo declared itself independent from Serbia although the many countries in the world have not recognised this independence including Serbia. The capital of Serbia is Belgrade. Other big cities in Serbia are Novi Sad and Niš. The currency of Serbia is the dinar.

Serbia's History
Serbia has a long history and has been part of many different countries and empires over the centuries including the Roman Empire, Ottoman Empire and, more recently, Yugoslavia. During the 1990s Serbia (the dominant part of Yugoslavia, especially after other countries became independent) fought several wars directly or indirectly in the region. The Yugoslav Army (mostly under the command of Serbs) fought wars in Slovenia and Croatia and the Yugoslav Government (then consisting of just Serbia and Montenegro) aided and funded paramilitary groups during the Bosnian War. At the end of the 1990s Serbia was bombed by NATO and withdrew from Kosovo (which is populated mostly by Albanians but considered to be the birthplace of the Serbian people and their church).

Serbia's Geography
Serbia a landlocked country in Central and South-eastern Europe, covering the southern part of the Pannonian Plain and the central part of the Balkan Peninsula. Serbia is bordered by Hungary to the north; Romania and Bulgaria to the east; the Republic of Macedonia, Kosovo and Albania to the south; and Croatia, Bosnia and Herzegovina and Montenegro to the west.

The Serbian climate varies between a continental climate in the north, with cold winters, and hot, humid summers, and a more Adriatic climate in the south with hot, dry summers and autumns and relatively cold winters with heavy inland snowfall.

At 2656 metres, Prokletije is Serbia's highest mountain although this mountain is located in Kosovo. The highest mountain entirely within Serbia is Stara planina at 2168 metres.

Serbia's People
The people of Serbia are a mixture of many nationalities. 7 million people live in Serbia. The majority of people who live in Serbia are Serbian. Other nationalities include Hungarians, Muslims (Serbian and Bosnian), Albanians, Slovaks and Roma.

The most spoken language is Serbian but many people speak other languages like Hungarian and Albanian.

Most people in Serbia are Orthodox Christians but there are also large numbers of Muslims and Catholics (especially in Vojvodina).

Serbia's Sights
Tourism in Serbia is mostly focused on the villages and mountains of the country. The most famous mountain resorts are Zlatibor, Kopaonik, and the Tara. There are also many spas in Serbia, one the biggest of which is Vrnjačka Banja. Other spas include Soko Banja and Niška Banja. There is a significant amount of tourism in the largest cities like Belgrade, Novi Sad and Niš, but also in the rural parts of Serbia like the volcanic wonder of Đavolja varoš, Christian pilgrimage across the country and the cruises along the Danube, Sava or Tisza. There are several popular festivals held in Serbia, such as the EXIT Festival and the Guča trumpet festival. Nightlife in Belgrade and Novi Sad is popular with locals and tourists alike and the largest clubs in Belgrade attract clubbers from all over south-eastern Europe.

There are 4 UNESCO World Heritage Sites in Serbia including a collection of monasteries and churches located in Kosovo. Gamzigrad-Romuliana, Palace of Galerius in the east of the country dates back to the 3rd Century CE and was built by the Romans. Studenica Monastery, in the west, is Serbia's largest monastery.

title: Wikijunior:Europe/Serbia


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Khepera III Toolbox/The Toolbox/Modules/odometry track

The odometry_track module implements the odometry equations for a differential-drive vehicle and allows to track the robot's position ($$x$$, $$y$$, $$\theta$$) over time. Fosamax Class Action blog

Description
odometry_track_start sets up a sOdometryTrack structure and reads the odometry calibration values from /etc/khepera/odometry. If that file is not available (or does not contain a valid configuration), default values are used. After calling this function, the initial position can be changed by modifying the result fields of the structure. odometry_track_start also reads the current motor positions and should therefore be called immediately before entering the main loop.

Inside the main loop, odometry_track_step is called to read the new motor positions and update the position estimate in the result fields.

Calibration
The default calibration values should give acceptable results on most Khepera III robots. Through a calibration procedure, the precision can be significantly improved, however.

Providing Motor Positions from Other Sources
The functions mentioned above read the motor positions automatically with the khepera3_drive_getposition function. If this is not desired, the functions odometry_track_start_pos and odometry_track_step_pos can be used.


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Wikijunior:Europe/Azerbaijan

Azerbaijan is a medium-sized country in the South Caucasus region. Mostly the country is located in West Asia, but a small part in the North is on the borders of Europe, because the Caucasus Mountains are a division between Eastern Europe and Western Asia. Until 1991, Azerbaijan was a part of the Soviet Union (USSR). The capital city is Baku and the country shares borders with Russia, Georgia, Armenia, Iran and Turkey. The country is a member of the Council of Europe, but it is not a member of the European Union. Azerbaijan is one of the six independent Turkic states and an active member of the Turkic Counsil and the TÜRKSOY community. Azerbaijan uses the Azerbaijani Manat as its currency.

Azerbaijan's History
The area of present-day Azerbaijan was settled beginning in about the 8th century BC by the Medes, an ancient Aryan tribe. It became part of the Persian Empire in the 6th century BC. Between the 1st and 3rd centuries AD, the Romans conquered the area of present-day Azerbaijan. Christianity began to spread there in the 3rd century. It was part of the Sassanid empire from 252 until the Muslim conquest of Persia, then it became under Umayyad rule. The Umayyad Caliphate spread Islam in the region. At the beginning of the 11th century, the territory was gradually seized by the waves of Oghuz Turks from Central Asia, who adopted a Turkoman ethnonym at the time. The first of these Turkic dynasties established was the Seljuk Empire, who entered the area now known as Azerbaijan by 1067. Notorious was the Shirvanshah dynasty, they stayed in the region untill the Safavids took control in 1501. Azerbaijan remained under Iranian rule from the earliest advent of the Safavids up to the course of the 19th century. In 1920 the Azerbaijani were taken over by the Soviet Union or the USSR. In 1991 Azerbaijan became independent from the Soviet Union. After becoming independent, Azerbaijan and Armenia fought as war called the Nagorno-Karabakh War which killed more than 30,000 people on both sides. Since the 1990s Azerbaijan has become more prosperous, mostly because of large amounts of oil.

Azerbaijan's Geography
Azerbaijan covers an area of about 86,600 km2 (about 33,400 sq mi). Azerbaijan borders the Caspian Sea to the east, Georgia and Russia to the north, Iran to the south, and Armenia to the south-west and west. The capital of Azerbaijan is the ancient city of Baku, which has the largest and best harbour on the Caspian Sea.

Azerbaijan is located in both Europe and Asia. The highest mountain in the country is Bazardüzü which is 4466 metres above sea level. Another interesting feature of Azerbaijan are the mud volcanoes - half of all mud volcanoes in the world are situated in Azerbaijan.

Azerbaijan's People
The population of Azerbaijan is just under 10 million. Azerbaijani, Russian, Lezgin,and Talysh are the languages that are spoken by the people who live in the country. The national language is Azerbaijani or Azeri and almost 93 percent of the population speak it. Azerbaijani language is similar to Turkish language as they are both Turkic languages from the Oghuz tribe.

People from Azerbaijan are called Azerbaijani or Azeris, there is a significant amount of Azerbaijanis in the north of Iran (see: ; Talyshs and Lezgins the largest minority groups in Azerbaijan, followed by Armenians if the break-away Nagorno Karabakh region considered. The majority of people in the country are considered Muslim but there are also small numbers of Russian Orthodox Christians. However, Azerbaijan is one of the most secular countries in West Asia.

Education is required for the first eight years, but some children continue their education.

Azerbaijan's Sights
Azerbaijan has two UNESCO World Heritage Sites: The Walled City of Baku (and Shirvanshahs' Palace and the Maiden Tower) all in the capital, Baku and Gobustan Rock Art - a site full of ancient art from 4,000 to 40,000 years ago.

Tourism was extremely popular during the 1980s but because of wars in the 1990s tourists went elsewhere. Tourism has only recently become important again in Azerbaijan. Religious, spa and health care tourism is becoming more and more popular every year. Castles, national parks, two Heritage Sites, skiing in the winter and swimming in the summer are activities that tourists can do while visiting Azerbaijan.

title: Wikijunior:Europe/Azerbaijan


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User talk:193.120.116.178

--Xania talk 22:05, 31 March 2008 (UTC)

title: User talk:193.120.116.178


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Adventist Youth Honors Answer Book/Arts and Crafts/Glass Painting

1. Know the primary colors, the secondary colors, and how to mix the primary colors to obtain the secondary colors.
Red, Blue and Yellow are the primary colors. Green, Violet, and Orange are the secondary colors. Red and Blue make Violet. Blue and Yellow make Green. Red and Yellow make Orange.

2. Know the materials used in painting, mounting, and hanging a glass painting.

 * Glass
 * Paint
 * transparent paints - allow light to pass through them
 * opaque paints - achieve the desired color, but are not transparent
 * Other mediums for frosted, iridescent, or crackling effects
 * Paint brush
 * Sponges - can be used instead of or in addition to paint brushes. Good if you want to paint the entire surface a single color.
 * Rubbing alcohol - for cleaning the glass before painting. Don't paint dirty glass!
 * Paper towel - also for cleaning.
 * Sticky stencils (optional)
 * Patterns - can be placed on the inside of a glass and then the design can be copied (similar to tracing).

3. Make and display a glass painting for each of the following designs: animal, flower, and landscape or seascape.
Begin by thoroughly cleaning the glass with alcohol and a paper towel. You can use a picture frame (paint right on the backside of the glass), a drinking glass, or a jar. For glasses and jars, place the pattern on the inside of the vessel. It will help if you tape the pattern to the glass (flat or round) so it doesn't move around as you paint.

Then begin your painting. If you drip paint on the glass by accident do not despair. Once it dries you can scrape it off with an X-acto knife, but care must be taken. You don't want to cut yourself or scrape off too much of the surrounding work. If paint drips on an unpainted section, you can simply wipe it off before it dries.

If painting on a round object, your painting surface will likely be oriented in a vertical position. Be careful not to use too much paint in the brush, or dripping can almost be guaranteed.

If using a picture frame, a background can be cut from matte or poster board, and the paint can be applied on the reverse side of the glass.

When painting on the reverse side of the glass, the painting can be realistic or abstract. Realistic reverse paintings are more challenging to create as one must, for example, in painting a face, to put the pupil of an eye on the glass before the iris, exactly the opposite of normal painting. If this is neglected the artist will not be able to correct the error as he will not get in between the glass and the paint already applied. In other words, you must work from the foreground to the background rather than painting the back ground and then laying a foreground over it.

4. Make a silhouette painting and mount for hanging.
A silhouette is a view of an object or scene consisting of the outline and a featureless interior, with the silhouetted object usually being black. The term was initially applied in the 18th century to portraits or other pictorial representations cut from thin black card.

The term has been extended to describe the sight or image of a person, object or scene that is backlit, and appears dark against a lighter background.

To make a silhouette on glass, it is easiest to start with a picture frame. Place a reverse-image pattern behind the glass and color it with opaque black paint on the reverse side of the glass. Allow this to dry, and then (if desired) paint a background over the silhouette using colors. As long as the original layer of black paint is dry, it will not be affected by the background you lay over it. The finished product should be viewed from the front.

The background is not necessary, or it can be a printed design on a piece of stock card or paper that lies behind the glass in a frame. The silhouette can be the main feature of the piece, or it can be an accent if placed off to the side, in a corner, or along an edge of the glass.

Here is a small gallery of images to give you a few ideas:

5. Make a hand-painted mirror picture by removing the back coating of the mirror from the picture area and painting the design on the back of the mirror glass.
Decide where on the mirror you would like to paint the design. Do you want it in the center? In a corner? Once you decided, flip the mirror over and use masking tape to mask around the area you wish to paint. Remember that this is a reverse-image, so if you wanted your picture to appear on the right, you will have to mark the area on the left. Once the area is masked, apply some paint stripper to the area within the tape. Read and follow the directions for the paint stripper. It will tell you how long to let it set before scraping. It will also tell you what kind of gloves you will need to protect your skin.

Once the paint stripper has done its work, you should be able to scrape most of the paint off and rinse the mirror. If you can't get it all scraped off, use steel wool to get that last little bit.

With the mirror backing removed, you should now have a transparent area in which to paint your picture.

Reverse painting on glass is an art form consisting of applying paint to a piece of glass and then viewing the image by turning the glass over and looking through the glass at the image.

This art form has been around for many years. A number of clock faces were created using this technique in the early to mid 1800s, but it started to become popular again in the late 1990s. The painting can be realistic or painting. Realistic reverse paintings are more challenging to create as one must, for example, in painting a face, to put the pupil of an eye on the glass before the iris, exactly the opposite of normal painting. If this is neglected the artist will not be able to correct the error as he will not get in between the glass and the paint already applied. No such care need be taken with the abstract form, but with this form you do not have a good idea what the piece will look like until you are finished painting it. This process is not like stained or leaded glass work in that it is not intended to hang in a window with light coming through the piece. Hanging on a wall, framed or unframed, with a lot of light directed towards the piece provides best viewing.


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User talk:90.204.45.232

You have been blocked from editing Wikibooks English for a period of 2 hours due to deletion of large quantities of text from pages. --Xania talk 22:27, 31 March 2008 (UTC)

title: User talk:90.204.45.232


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User talk:67.162.226.16

Welcome!
Welcome to Wikibooks, a collection of open-content textbooks! You don't have to log in to read or edit articles on Wikibooks, but creating an account is quick, free and non-intrusive, requires no personal information, and gives you many benefits, including:
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title: User talk:67.162.226.16


text: User talk:68.106.16.254

title: User talk:68.106.16.254


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User talk:Andre316~enwikibooks

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title: User talk:Andre316~enwikibooks


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User talk:62.249.233.80

Join Us!
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title: User talk:62.249.233.80


text:
Principles of Economics/Costs to Firm

Average fixed cost

The above graph adopts the axes we will be using quite often in economics: quantity on the x and price on the y. Fixed costs for a firm are unchanging but are spread over additional units, resulting in lower average fixed costs.

Total fixed cost

At any particular production point, we can show the total fixed cost as the pink rectangle. No matter where the gray line is placed, the area of the pink rectangle will be constant. Average is the height at a particular point; total is the area.

Average and marginal variable cost

The green curve is the marginal cost, the cost of producing an additional unit of a good and includes only variable cost (no fixed cost). This curve starts very high but rapidly falls through increasing returns to scale (increasing productivity), then starts rising as resources become more scarce and costly and/or less suitable. The pink average variable cost curve trails the marginal cost, rising when marginal cost is higher than the average and falling when marginal cost is lower. The average variable cost is flat at the point when it is the same as the marginal cost.

Individual Supply

The new pink line, average total cost, combines average fixed cost with average variable cost. This leads to the firm's individual supply curve, which is for intents identical to the marginal cost and so also colored green.

title: Principles of Economics/Costs to Firm


text: User talk:66.61.19.113

title: User talk:66.61.19.113


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Principles of Economics/Supply

Firm's production position

(Review the section on firm's costs if this looks strange.)

Long term, the firm produces at the point where marginal cost (and hence supply curve) intersects average total cost because at any higher point additional firms enter the industry and at any lower point the firm will earn negative profits (to be discussed later). This position is represented by the green point at Q*, equilibrium quantity. Extending this point to the y axis, we call this price P*, equilibrium price. The firm has to consider its fixed costs, which it satisfies at this level of output and price, along the green supply curve.

Market long run supply

In perfect competition, all the firms are more or less equal, in which the combination of their individual supply curves results in another market supply curve identical to them except that it is a multiple as large (stretched). (However, we will continue to show it as the same size.) We can remove everything else about the firm to see just this green supply curve. The 'common' component of the supply curve that textbooks often discuss is the positive-slope half, but we cannot ignore the first component.

Firm's short run minimum position

The minimum position at which the firm will produce instead of shutting down is shown by this alternative green point along its marginal cost / supply curve, where it intersects average variable cost. If a firm cannot sell for as much as what it costs to produce that additional unit (ignoring the fixed cost, which is unavoidable in the short run), and the units before that are unproductive as well, then the firm will close down and choose to suffer the fixed cost and not incur additional expenses from operating.

Firm's short and long run positions

Here both short and long run minimum positions for a firm's continued operation are shown. The long run position involves more output, indicating that a firm producing zero profits will produce at a higher level than one that is incurring losses from fixed costs will. It also requires a higher market price at P*, indicating that an industry has to be more profitable than the bare minimum for operating in the short run, in order to be worth it for the firm to not shut down. Producing at the long run position - where marginal cost/supply and hence market price (for supposedly all producers are doing the same thing) equals average total cost, ensures that the fixed costs are covered.

title: Principles of Economics/Supply


text: User talk:203.89.173.10

title: User talk:203.89.173.10


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Principles of Economics/Budget Constraints

Budget

This is the basic budget curve (often a line). Its slope is an indication of relative prices (opportunity cost of one good for another) because at any point along the line one has to give up something for more of another. The point indicated by the gray lines is one way of dividing up the budget (in quantity of money terms) between two goods (in quantity terms).

Budgets at differing incomes

Different incomes will have differing budget constraint positions. Lower incomes will be closer to the origin, while higher incomes are farther. As the graph shows, higher incomes allow one to buy more of one or both goods without necessarily having to give up some of any good.

Budgets and changing prices

When the price of the good with price along x axis (good Q1 in this case) increases in comparison with the other good, the budget constraint rotates clockwise. This is because the budget can no longer buy as much of the first good (1). When the other good's (2) price increases, the constraint rotates counterclockwise, indicating fewer bought (Q2).

Increase in cost of good 1

When there is an increase in the cost of good 1, the consequences will be most severe for one who buys all good 1 and no good 2, while it will have no effect on those who buy all good 2, hence the y intersection does not change while the x intersection changes notably. The increase moves the new x intercept closer to the origin, indicating fewer can be bought. A decrease in price would move the new x intercept to the right. If the quantity of good 1 purchased is to remain constant, some of good 2 will be sacrificed, and vice versa.

Increase in cost of good 2

When there is an increase in the cost of good 2, a similar situation occurs, except that the axes to which the changes act on are changed.


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Bartending/Cocktails/Bloody Mary

A Bloody Mary is a popular cocktail containing vodka, tomato juice, and usually other spices or flavorings such as Worcestershire Sauce,Tabasco sauce, beef consommé or Bouillon Cube, Horseradish, Celery salt, Black pepper, Cayenne Pepper, Lemon Juice, & Celery salt.

Preparation and serving
A Bloody Mary, as well as the non-alcoholic Virgin Mary, is commonly served in the morning (as are mimosas and screwdrivers).

While there is not much complexity in mixing vodka and tomato juice, more elaborate versions of the drink have become trademarks of the bartenders who make them. A common garnish is a celery stalk when served in a tall glass, often over ice. A beer chaser may also be served with the Bloody Mary, although this varies from region to region.

Ingredients
Bloody Mary recipe courtesy of the New York School of Bartending: Garnish with celery stalk.
 * 1 oz. to 1 1/2 oz.vodka in a Highball glass filled with ice.
 * Fill glass with tomato juice
 * 1 dash celery salt
 * 1 dash ground black pepper
 * 1 dash Tabasco
 * 2-4 dashes of Lea & Perrin's Worcestershire sauce
 * 1/8 tsp. horseradish (pure, never creamed)
 * Dash of lemon or lime juice

May be shaken vigorously or stirred lazily, as desired. Garnish with a celery stalk; a skewer of olives, pickles, carrots, mushrooms, or other vegetables; or even meat or fish (salami, shrimp, etc.) and cheese (see photos). Occasionally, pickled asparagus spears or pickled beans are also used.

Prepackaged Bloody Mary mixes that combine the spicy, non-alcoholic components of a Bloody Mary are commercially available.

Variations in alcohol

 * Bloody Philip : Thailand Lao Khao (literally white liquor} 80 proof, rice distilled, replacing vodka in equal measure
 * Bloody Bishop : Sherry in equal measure to vodka
 * Bloody Fairy, Red Fairy : Absinthe replacing the vodka.
 * Bloody Geisha : Sake replacing vodka.
 * Bloody Maria : Tequila replacing vodka.
 * Brown Mary or Whiskey Mary : Whiskey replacing the vodka.
 * Bloody Pirate : Dark rum replacing vodka.
 * Bloody Scotsman : Scotch replacing vodka.
 * Bloody Maureen : Guinness replacing vodka.
 * Michelada Clementina (or simply "Chelada") : Mexican beer replacing vodka, usually flavored with a couple of dashes of Worcestershire sauce and Maggi Sauce and Tabasco sauce. Usually the proportion of beer equals the tomato juice.
 * Ruddy Mary : Gin replacing vodka. Popular in UK. Sometimes known as a Red Snapper.
 * Red Eye, Calgary Red Eye, or Saskatchewan Red Eye : Beer replacing vodka, usually in a 50/50 mixture with Clamato in place of the tomato juice.
 * Red Eye: 1 Pint Glass, 1 Shot Of Vokda, Filled Half Way With Beer, Then Topped Up With Tomato Juice, Then An Egg Cracked In (DO NOT STIR) Then Drunk.
 * Red Hammer : Through the 1950s in the north eastern USA, while vodka was scarce, gin instead of vodka was known as a Bloody Mary; once vodka became readily available in those regions, the traditional vodka-based Bloody Mary was known as a Red Hammer for a time
 * Virgin Mary, Bloody Shame, or Bloody Virgin : Without alcohol; the second term is commonly used in Australia.

Variations in mixers
The original Bloody Mary created at Harry's New York Bar in Paris, was only vodka and tomato juice
 * Bloody Bull : Beef bouillon and tomato juice. The drink originated at Brennan's restaurant in New Orleans and is served at Commander's Palace as well as other Brennan Family Restaurants.
 * Bull Shot : Beef bouillon or beef consommé in place of tomato juice. It may also contain salt, pepper, lemon juice, Tabasco sauce and Worcestershire sauce.
 * Caesar, Bloody Caesar, or Clammy Mary : Clamato replacing tomato juice, much more popular in Canada than the traditional Bloody Mary.
 * Bloody Eight or Eight Ball : V8 replacing tomato juice, or a mixture, usually equal parts
 * '''Harry's Original

Variation in drink format

 * Frozen Bloody Mary : Placed in a blender with ice.
 * Flaming Bloody Mary : A small amount of 151 rum is floated on top and a string hangs outside the glass and is ignited for a cold weather drink.
 * Flaming, Frozen Bloody Mary : A frozen Bloody Mary is topped with 151 rum and ignited. Also called "Bloody Fire and Ice". (Note be sure to use a ceramic mug to avoid shattered glass)

Miscellaneous

 * Bloodless Mary : Without tomato juice
 * Bleeding Mary : Without tomato juice, 1:1 Tabasco to vodka.
 * Screaming Emo : Traditional Bloody Mary, but with a habanero pepper added to it for more heat.
 * Screw Mary : Equal parts vodka, orange juice, and tomato juice or V8, spiced to taste.

title: Bartending/Cocktails/Bloody Mary


text:
Principles of Economics/Demand

Demand

(Review material from the indifference curve section if this seems unfamiliar.)

From the indifference curves we can see that people value things differently and alter what they demand (no pun intended) to best utilize their money. This naturally leads to the demand curve, which in many ways is similar to the sum of many individuals' indifference curves (but not entirely). The curve is often shaped similarly. The blue line in this graph is the basic demand curve. Note that the y axis is P, not Q2.

Quantity demanded

The quantity demanded is a specific quantity, given a demand curve and a price level. In this graph the price level of the market for the good, P*, has been extended to the y axis, price. At any quantity and given any demand curve, there should be only one natural equilibrium quantity demanded. This point is marked Q*. No trade occurs beyond this point.

Consumer surplus

Consumer surplus is a measure of the benefit or welfare to the consumers of trading with a particular good. It can be defined as the amount of money that they save from making the transaction, or the amount that they are willing to pay to buy the good under discussion. Different consumers have different preferences (indifference curves) and thus obtain different levels of happiness with the trade. In graphs, they are always arranged so that the most happy consumer - the one willing to pay the highest price - is placed rightmost, while the least happy consumer - the one barely willing to make the trade - is placed leftmost (at the equilibrium point).

In the graph, it is the area under the demand curve and above the price level, to the left of the equilibrium point, and is shaded blue. (To the left because no trade happens beyond the equilibrium.) At the equilibrium point the consumer is barely happy with the price offered and so there is no consumer surplus.

title: Principles of Economics/Demand


text: User talk:76.86.244.205

title: User talk:76.86.244.205


text:
User:Spradlig

Gabe Spradlin
I am the owner of ControlTheoryPro.com. Few web resources provide practical help on the design of real world controllers. University courses speak in generalities about design. So do most web sites. I plan for ControlTheoryPro.com to be more design and modeling oriented.

Abbreviated Resume
I've worked in the Aerospace industry for more than 10 years. During that time I've worked as a contractor to
 * AlliedSignal (now Honeywell) in the aircraft engines division
 * Lockheed Martin in Space Shuttle astronaut training

I've also worked directly for
 * Boeing (twice)
 * Embedded Software for the Apache attack helicopter
 * Guidance, Navigation and Control subsystem for the International Space Station

I currently work for
 * Ball Aerospace & Technologies Corp. in pointing control for laser communications

While getting my BSME I worked for the Colorado Space Grant College on
 * DATA-CHASER Space Shuttle payload
 * 2 University Explorer class satellite proposals

title: User:Spradlig


text: User talk:195.189.142.226

title: User talk:195.189.142.226


text:
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Template talk:Bigwelcome

We want to make our welcome message as helpful as possible, so please comment on it below. For comparison, you can see our other welcome template. Questions we're interested in: You can start a new section below by clicking the + tab at the top; please put your username in the subject line. – Mike.lifeguard  | talk 05:33, 1 April 2008 (UTC)
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Too long on one side, short on the other - L10nM4st3r
There are three boxes on the right and one on the left. Would it be possible to move a box to the left to save some vertical space? L10nM4st3r / Roar at me 19:09, 29 June 2022 (UTC)
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title: Template talk:Bigwelcome


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title: User:ComaVN~enwikibooks/monobook.js


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Template:ChessStub

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Category:Chess stub

Category for Chess related articles that are a Chess stub.

title: Category:Chess stub


text: User talk:88.203.117.113

title: User talk:88.203.117.113


text:
Khepera III Toolbox/The Toolbox/Modules/odometry goto

The odometry_goto module implements a simple feedback algorithm a differential-drive vehicle to move towards a given position ($$x$$, $$y$$). It uses the odometry_track module to estimate the current position of the robot.

Description
This module is always used in combination with the odometry_track module.

odometry_goto_start sets up a sOdometryGoto structure and assigned a sOdometryTrack structure to it. The latter must have been initialized beforehand (but could have been initialized much earlier and used already).

The target position is set with odometry_goto_set_goal. Inside the main loop, odometry_goto_step, called right after odometry_track_step, calculates the new wheel speeds and put them inside the result structure. These speed values should be set khepera3_drive_set_speed. Note that the target position may be changed at any time. The odometry_goto_step function will calculate the motor speeds for the currently configured target position.

In addition to the motor speeds, the result structure provides a two more useful fields:
 * closetogoal: Set as soon as the robot comes so close to the target position that it starts decelerating.
 * atgoal: Set if the robot has reached the target position.


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Embedded Control Systems Design/Process control vs system control

Broadly speaking there are two fundamentally different types of control systems: Another major difference between process and system control is the large scale at which the former is implemented.
 * Process control occurs typically in the chemical or food processing industry, oil and gas refineries, etc. These kind of installations have as components devices such as valves, temperature sensors, flow rate sensors, etc., and need to control the continuous flow of material through a large set of subsequent operations.
 * System control deals with the appropriate functioning of (semi-)autonomous devices, i.e., making sure that it performs the expected set of actions at the appropriate times. This involves switching between various control actions, decision making under uncertainty, etc.

=Process control= In general, looking at process control there will be multiple sensors, actuators and controllers distributed over a sometimes very large area. Such a system always has a lot of distributed hardware.

Despite this distributed nature, it is necessary to have a central control to oversee, manage and monitor everything at a distance. This does not how ever mean to ‘control’ everything. Every slave will mostly have its own processing capabilities to control its immediate surroundings.

To use a metaphor: it can be seen as an army general and subordinate platoons. The general (central control) needs to know what is going on with each platoon in the battle field to make upper level strategic decisions and give orders. While each platoon (slaves) decides for itself how it will perform these orders and then report the result back to the general.

To bring it back into the engineering world. The central control will be used to monitor safety issues, functioning levels and set system levels and properties. This is also called the human-machine interface or HMI.

Each slave in the plant or factory will be controlling the temperature, flow rate or volume of a smaller section of the whole. These are individually independent and are able to function as a complete unit on its own.

The actual control happens locally, with the SCADA main controller collecting and interpreting all the data throughout the complete system. Also the main controller is used to change and set operating levels.

Connecting all these independent systems is where it starts to get tricky. Everything has to function in combination, and means that information needs to be inter exchanged: information from an upstream or down stream slave may be necessary for it to make proper controlling decisions.

There are many ways to implement such a distributed hardware-centralise controller system. One such an implementation is called SCADA.

Design considerations
During the design of a distributed hardware system, there are some designs considerations and decisions to be made that will have noticeable effects in the end product.

The four main aspects, although there are many others, to consider are: safety, cost, optimisation and robustness. In a design such as this, there is a definite link between these four, and changing one has an automatic effect on the rest. The designer is constantly faced by such trade-off decisions.

Main considerations
Safety: As with any system where humans are involved safety is of very high importance. In some situations more so that in others: a nuclear energy plant vs. a water bottling plant for instance.

With an increase in safety measures, there is also an increase of eventual implementation cost (extra shut valves, redundant controllers) and a decrease in robustness. Safety could also mean a better communication system to ensure that the correct data is transmitted between the central control and slaves, and between individual slaves.

Implementing multiple master stations running in parallel for in case onse should fail, linking to a single SCADA main terminal. Safety is, as control, also localised but not limited to being locally implemented. The main controller can and will have some safety control.

Robustness: It is wished for the system to keep functioning even with some interferences and non intentional events. Robustness means a decrease in safety.

The question then arises: Should small problems be allowed? Small issues can be corrected by the slaves themselves. If handled incorrectly, these small problems can lead to much bigger ones. Cascading failures of interconnected parts result from small problems not being correctly handled.

Cost: Eventually it is wished for the design to be implemented, therefore costs kept to a minimum for the system to be lucrative to the market. But with cutting costs, you have a decrease in safety and robustness.

Optimisation: With this design factor the goal is to have an increase in quality, and cost minimisation (minimal product or raw material waste). With optimisation again comes the decrease of robustness.

Thus, the most difficult part of such a design is finding the optimal balance between cost, robustness, optimisation and safety for each project.

Human influence/interface
Due to the nature of this kind of systems and an ever changing environment (different products to be manufactured, or a change in the product mixture) there needs to be human interaction with the system. Also it is necessary for a human to be able to tell at a glance if a problem exists, where and what kind of problem.

The importance of proper human-machine interaction was shown in the Three Mile Island accident. Incomplete and incorrect information is thought to be the eventual reason for an otherwise preventable accident.

This adds to the safety side of the design decisions, added redundancy, and then increase in cost. But from the Three Mile Island accident, the necessity of proper and timely system information can be seen.

Furthermore the human interface is an easily reachable tool for information or hardware that would otherwise be difficult to reach. It should also have an attention grabbing setup to be able to make a system assessment at a glance.

Interdependency
Although previously said that all the slaves can operate independently, in a major industrial system this is not the case for each and every part. Some are directly dependent on information from another slave.

For instance, if a valve is to control the flow rate into some container, it needs to know to shut off if the container gets full. It is therefore necessary to have a reliable inter-slave communication network.

This interdependency shifts some of the central systems responsibility to manage safety, to a more localised area.

Data handling
Because eventually all the independent systems have to work together to form the final product, some sort of data handling system is necessary. This is where the central control system comes into play and fulfils its main role.

Due to the fact that lots of the actual control and safety is managed by the slaves system, a SCADA installation deals mostly with a bottom-up data structure. The main controller does not need all the information that is available in the complete system.

The central controller can thus be seen as an information gathering unit. This data, other than the safety information, could be calculating trends and monitoring quality.

= System control = Most of the examples in the rest of this Wikibook are system control applications.


text:
Principles of Economics/Trade

Differences between entities

Different entities will have different possibility curves, which allow for trade to be done. In this case, each society might decide to produce at these two indicated positions because their output is relatively higher for those positions. However, should they choose to have the same output position, that position will be significantly lower than their optimal positions. This is the case for entities that do not trade.

Trade

Trade between these two entities can be done after they each produce at their optimal (depending on where society wants to allot its resources) and then exchanging goods at a fair ratio. The result of fair exchange is the pink line connecting them. The result is a higher possibility for each society through trade than each can reach without, as shown by the comparison between the center gray point and the pink point.

Specialization

These different entities can then take actions to specialize in one field. Specialization causes the PPF to take the concave outward form as the graph shows, because choosing to produce more of one good allows one to produce far more combined goods.

Trade with specialization

Specialization increases the benefits from trade. In these graphs, the benefit is the horizontal and vertical increase from the center gray point to the pink point. The specialized PPF curves are more separate, allowing the societies (or entities in general) to produce at more different positions.

title: Principles of Economics/Trade


text: User talk:Prantik Saha Anindya

title: User talk:Prantik Saha Anindya


text:
Principles of Economics/Graphs

Graph reading

The first step to understanding economics models is comprehending graphs. Here the x axis is Q, quantity, and the y axis is P, price. The point at the top right indicates Q* quantity of a good each being sold at price P*; the horizontal and vertical lines are there for facilitation/marker purposes. The point to its left has only half the extent x-axis-wise, and therefore involves half the quantity. The point below the first has only half the extent y-axis-wise, and therefore involves half the price.

This graph is used for demand / supply curves, and for production cost curves.

The supply curve is an upsloping curve from left to right, and shows that whenever the market price of a good increases, more producers are willing to produce, and there for there is more goods produced for price 2, if price 2 is greater than price 1.

The demand curve is a downsloping curve from left to right, and it shows that when the price is very high, there are few consumers demanding little quantity, but when the price is low, there are many more consumers, demanding more quantity. Ideally, if the price reaches zero, than infinite quantity is demanded.

Production costs curve show the Law of Diminishing Returns, which shows that total costs decline as more quantity is produced, because fixed costs are divided into more units. In fact, fixed costs always decline. Variable costs however, can decline because of gains in efficiency, but after a certain quantity, variable costs increase because of inefficiency e.g. due to congested access to fixed resources. Thus unit variable costs are drawn as a stretched out U shape. Unit total cost is a stretched out U shape, which sits above unit variable cost, and gets closer to it, because unit fixed cost is included in total cost, total cost never quite touches unit variable cost. Marginal cost is the cost of producing one more unit, and unlike unit total cost and unit variable cost, it is not an average unit cost, but determines the direction of change of average cost for the next unit. If the marginal cost equals the average total cost, than after the next unit is produced, the average total cost doesn't change, but if it is less than the average, then next average cost will be lower than the current average cost. Conversely, if marginal cost is greater than the average cost, than the next average cost will rise. This means marginal cost, which represents to the change in total cost over the change in quantity, or the additional total cost to produce 1 more unit, doesn't incorporate the fixed cost, as none of the additional total cost is additional fixed cost. So marginal cost will intersect average total cost at its minimum point, because average total cost will rise when the marginal cost is greater than the average total cost, and in fact, the same can be applied to average variable cost.

Graph reading continued

This may appear to be a similar graph, but it is entirely different because here the y axis is the quantity Q2 of another good. The top right point involves Q* of good 1 and Q2* of good 2. The point to its left involves half as much of good 1, while the point below it involves half as much of good 2.

This graph is called the a graph of possible production, where shared available resources are used to produce two alternatives at varying quantities. If more of good 1 is produced, less of good 2 is produced. The characteristics of the curve is that:
 * 1) convex quarter shape, from 12pm to 3pm
 * 2) convex shape is explained by suitability of some resources for good 1, and some for good 2, so that more quantity is produced of good 1 and good 2 when Q1 = Q2, because specialised resources are allocated most efficiently.

title: Principles of Economics/Graphs


text:
Principles of Economics/Types of Goods

Ordinary goods

Ordinary goods have the indifference curves you have so far seen. As one has more of a good, one obtains less marginal utility from another of that good; the reverse is true for goods that one is relatively lacking. Remember that in these problems the utility results from the use of goods, not how much the goods can be sold for.

Perfect complements

Perfect complements are goods that are useless without the other. Therefore, having more of a good than is required by the other good brings no benefit whatsoever. This is demonstrated in the graph, where having more of good 1 while holding good 2 constant does not increase utility.

Perfect substitutes

Perfect substitutes are goods that exactly substitute for one another at a certain ratio. Having relatively more of a good does not reduce marginal utility because there is no 'relatively more'; you have the same amount of the one substitutable (combined) good.

Ordinary goods often fall in between these two extremes. It's easy to imagine a mostly complementary set of goods to have curve with a rather pointy edge, while a mostly substitutable set of goods would have a curve that is barely bent.

title: Principles of Economics/Types of Goods


text:
Talk:Geometry for Elementary School/Copying a line segment

What is this? If I need to copy a line segment here is what i would do. Measure the existing line segment AB, go to the point T and with my ruler I draw another line segment of length equal to AB. Why do I have to go through all these circle drawings? Why does my simple solution not work?
 * Good question. The reason is the Greek "rules of the game".
 * See Compass and straightedge constructions
 * The ruler to be used is assumed to be infinite in length, has no markings on it and only one edge, and is known as a straightedge. APH (talk)

I also think this construction method is unnecessary. If all you need is to copy line AB to T at any direction, use a compass to measure the length of AB, draw a circle centerred at T with radius AB. You can have as many lines as you need that are equal to AB, i.e. all lines from T to any point on the circle.

To copy a line with the same direction, simply construct a parallelogram BATC, where AB equals TC. (This takes about three steps.)


text:
Principles of Economics/Budget Compensation

Increase in price of good 1

In this case an increase in the price of good 1 (along x axis) shifts the budget curve (black) inward. One can no longer obtain as high an indifference curve (blue) as before; the new indifference curve is closer to the origin and entails a lower utility than the original.

Compensated budget

We can draw a compensated budget, compensating one for the increase in the price of a good by increasing their money overall. However, such a double change will lead to a shift in the way the consumer allocates resources between the two goods. The compensated budget curve (which looks like a line), pink in the graph, has the same slope as the new budget curve but has an optimal point on the original indifference curve (just like the original budget). This new compensated budget allows a consumer to attain exactly the same level of utility despite the fact that the price of a good has increased.

Income and substitution effects

The key position of the compensated budget is the position of resource (money) apportionment that a consumer would make, here labeled with the purple point. The compensated budget offers effectively the same income as the original budget (because it is compensated and the same utility as before is reachable). Therefore, any change in the allotment of what goods a consumer wants to buy, going from the original point to the compensated point, must come entirely from the substitution effect.

Because any shift from original to new budget must result from the combined effect of substitution and income effect, the remainder of the shift is attributable to the income effect. Alternatively, the shift from the purple point to the left blue point (final budget optimal point) involves no change in resource apportionment ratios because the new and compensated budget curves have the same slope (a unit of good 1 is worth the same multiple as much as a unit of good 2). Hence we come to the same conclusion.

If the final blue point is to the left of the purple point, the two effects are acting in harmony and the good along the x axis is considered a normal good.

Contradicting effects

For this consumer, the indifference curves look significantly different. The compensatory budget is still placed in the same location. The main difference is that now the new optimal allocation with the new budget - the lower blue point - is to the right of the purple point.

Contradicting effects part 2

The purple substitution effect does not change because the first blue point and purple point remain in the same positions. However, the blue income effect now goes counter to the substitution effect (though it is still smaller than the substitution effect). In other words, the two effects are acting in opposite directions.

If the final blue point is to the right of the purple point but to the left of the initial blue point, the two effects are acting in opposite directions, the substitution effect is stronger, and the good along the x axis is considered an inferior good.

If the final blue point is to the right of the initial blue point, the two effects are acting in opposite directions, the income effect is stronger, and the good along the x axis is considered a giffen good. A giffen good is one where a consumer buys more of it when the price increases - very, very rare but possible in certain very limited cases (often involving poverty).


text:
User talk:Spradlig

Welcome!
Welcome, Spradlig!

Come introduce yourself at the new users page. If you have any questions, you can ask there or contact me personally.-- – Mike.lifeguard  | talk 16:27, 1 April 2008 (UTC)

Pages
Hello Spradlig, welcome to wikibooks!

I've seen your pages Semilog and Loglog. These pages are supposed to be part of the MATLAB Programming book, correct? To make sure that a page is inside a book (and not floating around by itself) you have to title the pages like this: "Book Name/Page Name". For instance, you should write:

 * MATLAB Programming/Semilog not Semilog
 * MATLAB Programming/Loglog not Loglog

Pages that aren't properly inserted in a book could end up getting lost or deleted. If you need any help fixing this, or if you have questions, let me know on my user talk page. --Whiteknight (Page) (Talk) 00:51, 22 April 2008 (UTC)

 * Thanks for the reply! You like control systems? I've written most of the Control Systems book myself, and have helped a class project at Embedded Control Systems Design. Moving pages is easy, you don't need to be an admin. Click the move tab at the top of the page, and change the titles to include "MATLAB Programming/" in front of the page names.
 * When you create a link inside the MATLAB book, you can use the shorthand:  This will automatically put the page inside the MATLAB book, and you don't need to worry about moving it or adding the book title to the link. If you need help, don't hesitate to ask! --Whiteknight (Page) (Talk) 00:59, 22 April 2008 (UTC)

title: User talk:Spradlig


text:
User talk:Kj

Welcome!
Welcome, Kj!

Come introduce yourself at the new users page. If you have any questions, you can ask there or contact me personally.-- – Mike.lifeguard  | talk 16:28, 1 April 2008 (UTC)

title: User talk:Kj


text:
User talk:Tissa jayasekera

Welcome!
Welcome, Tissa jayasekera!

Come introduce yourself at the new users page. If you have any questions, you can ask there or contact me personally.-- – Mike.lifeguard  | talk 16:28, 1 April 2008 (UTC)

title: User talk:Tissa jayasekera


text:
User talk:Jredmond

Welcome!
Welcome, Jredmond!

Come introduce yourself at the new users page. If you have any questions, you can ask there or contact me personally.-- – Mike.lifeguard  | talk 16:28, 1 April 2008 (UTC)

title: User talk:Jredmond


text:
Wikijunior:Ancient Civilizations/Toltecs

What Countries Did They Live In?
The Toltec civilization began in what is now southern Mexico then spread north through the rest of Mexico.

What did they believe?
The Toltec believed in two gods. One was Quetzalcoatl, the “Sovereign Plumed Serpent”. This was the god of learning, culture, philosophy, fertility, holiness, and gentility. The other god is Tezcatlipoca, the “Smoked Mirror”. This god was war-like.

Who did they battle with?
The Toltecs were pre-Columbian Native Americans. They took over most of central Mexico between the 10th and 12th century. Toltecs once ruled the Mayans. The Mayans and the Toltecs clashed. They tried to compromise but the Toltecs took over. The Toltecs were later taken over by the Chichimecs in 1200 A.D.


text:
Talk:Horticulture/Vinca

It is amusing to see that vinca is considered an invasive weed in parts of the U.S., as I have a customer with a large hillside vinca groundcover that has been ailing over the past two years. It is an important plant in her landscape as it provides erosion control and is (or at least has been) relatively easy to care for.

I am wondering what soil conditions and annual rainfall is normative in its native range. What sort of soil type, soil pH, and irrigation regimen should I expect vinca to flourish under?

title: Talk:Horticulture/Vinca


text: User talk:209.62.160.42

title: User talk:209.62.160.42


text: User talk:124.40.47.45

title: User talk:124.40.47.45


text: User talk:172.214.200.33

title: User talk:172.214.200.33


text:
Principles of Economics/Labor Production

Marginal product of labor

In firms, people start off rather productive, but as more people are added, specialization occurs, with the result that the marginal product of labor (the next worker's labor productivity) increases. After the critical point at which this has reached its maximum, the MPL begins to decline as additional workers become less productive. In the short run this is most acute, where a constant amount of available capital limits productivity. After a certain point, adding workers begins to reduce overall (total) productivity; this is reflected by a negative MPL.

Firms' production frontier

The gold line is the typical firm's production frontier. It is the sum of each worker's marginal productivity (taking the integral of MPL from 0 to L). At first the production frontier increases faster, then it increases slower, then it stops increasing, before beginning a decline (which should never happen if the firm is money-conscious).

Isoprofit lines set

Isoprofit lines are lines composed of amounts of labor and its total output that yield the same amount of profit for the firm. There are an infinite number of isoprofit lines, one above another, similarly to how there are an infinite number of indifference curves. The isoprofit line that is tangent to the production frontier is also the highest isoprofit line that the firm can reach.

Isoprofit lines part 2

There are a variety of isoprofit lines that may be drawn. Realistically, their slopes will be flatter than the ones shown here, and their y axis will be higher.

The slope is equal to wage divided by price of output.

The y intercept is profit divided by price of output.


text:
Principles of Economics/Wage

Firm's isoprofit line

This purple isoprofit line is more realistic of a firm, for it intersects the production frontier somewhere to the right of the maximum marginal product of labor. The y intercept is the profit to the firm after subtracting costs of hiring labor. However, this amount does not translate to economic profit; in perfect competition the default height of the y intercept (the intermediate profit) is equal to the fixed cost of the firm, with the result that there is no economic profit.

Labor hired

The point where the highest isoprofit line overlaps with the production frontier is where the firm will produce. Any higher isoprofit line is unattainable and any lower isoprofit line will generate less than optimal profits. The result is that more workers are hired than the one that helps increase profit the most (has the highest marginal product of labor, MPL). The slope of the isoprofit line determines where this position actually is. The right brown point is the position of the firm's labor hired.

Wage rate

In perfect competition, firms can only afford to hire workers at the same amount of profit they can generate for the firm. Extending the right brown point (position at which hiring stops) gives the wage rate. Supposedly, all firms in the industry are equally productive and thus reach this same point, which brings about labor equilibrium. First, we must multiply the graph, which is in terms of units production in the y axis, to currency (P). This changes the marginal product of labor MPL into marginal revenue product MRP (or marginal revenue of labor MRL). The MRL definition is clearest because in perfect competition it makes clear sense for a firm to hire workers - marginal cost of labor - at the same amount as the marginal revenue of labor.

Wage loss and surplus

A firm's loss and profit can also be shown through the MPL. Since MRP reflects earnings and the wage rate W* reflects expenses, the firm's surplus is the green area in the graph - the area under the MRP but above W*. The firm's losses is the red area in the graph - the area under W* but above MRP. Since the firm stops hiring at the far right corner of the surplus area, there is no additional loss pass that point. In perfect competition the two areas (loss and surplus) cancel each other out, but with the green area exactly fixed cost larger than the red area.

title: Principles of Economics/Wage


text: User talk:205.122.90.54

title: User talk:205.122.90.54


text:
User:Lkirilova

Hi,I'm Lora Kirilova :)nice to meet you!

title: User:Lkirilova


text:
User talk:Lkirilova

Welcome, Lkirilova!

Come introduce yourself at the new users page. If you have any questions, you can ask there or contact me personally.

It looks like you've done quite a bit of good work already, great!

--Xania talk 18:06, 1 April 2008 (UTC)

title: User talk:Lkirilova


text:
Talk:Microeconomics

A much more developed and detailed book on the same topic can be found under the title Principles of Economics. Please contribute there instead of on this work. --Yunzhong Hou 18:11, 1 April 2008 (UTC)

 * Principles of Economics refers back here, I think this should not be abandoned--Bquast (discuss • contribs) 12:29, 9 February 2014 (UTC)

Manual of Subject and Illustrative Examples
I have no idea what style this Wikibook would want. Could someone please make a manual of style for each of the following: ?
 * Definitions (should they be italicized or bolded?)
 * Names (should they be italicized, bolded, or kept as normal?)
 * Reading level (should the reading level be intermediate or advanced?)
 * etc.

"Where needed, we use R for statistical programming. The graphics are also created using R, the needed code can be revealed by clicking on the graphic." What if I do not have experience with R statistical programming? Could I still provide visual images not using such programming languages?

title: Talk:Microeconomics


text:
Issues in Digital Technology in Education

Table of Contents

 * /Web 2.0 Learning Environments/
 * /The Net Generation/
 * /Blended Learning/
 * /Online Communities/
 * /Accessibility and Usability/
 * /Games for Learning/
 * /Virtual Learning Environments/
 * /Moderating Online Discussions For Learning/
 * /Assessing Online Discussions/
 * /Computers in the Early Childhood Classroom/
 * /Adult E-Learning in Education for Sustainable Development/
 * /Assistive Technology in Education: A Critical analysis of the “Highs” and the “Lows"/
 * /E-Portfolios/
 * /Open Educational Resources/
 * /Autism and Technology/
 * /Inclusion of Students with a Disability in Higher Education and the Internet/
 * /Online learning communities as an integral part of blended learning strategy/
 * /The Reality of Internet Filtering/Blocking/
 * /Second Life/


text:
Futurebasic/Language/Reference/octstring

Function
(+)	Appearance		(+)	Standard		(+)	Console

Syntax
octalString$ = OCT$(expr)

Description
This function is a string of octal (base-8) digits which represent the integer value of expr. The returned string will consist of either 3, 6 or 11 characters, depending on which of DEFSTR BYTE, DEFSTR WORD or DEFSTR LONG is currently in effect.

Note that if the value of expr is too large to fit in the currently selected DEFSTR size, the string returned by OCT$ will not represent the true value of expr. In FB, integers are stored in standard "2's-complement" format, and the values returnet by OCT$ reflect this storage scheme. You need to keep this in mind when interpreting the results of OCT$, especially when expr is a negative number.

For example: OCT$(-3) returns "775" when DEFSTR BYTE is in effect; "777775" when DESTR WORD is in effect; and "77777777775" when DEFSTR LONG is in effect. Note: To convert a string of octal digits into an integer, use the following technique: ÊÊÊintVar = VAL&("&o" + octalString$) intVar can be a (signed or unsigned) byte variable, short-integer variable or long-integer variable. See Appendix C: Data Types and Data Representation, to determine the range of values that can be stored in different types of integer variables.


text:
Futurebasic/Language/Reference/offsetof

Function
(+)	Appearance		(+)	Standard		(+)	Console

Syntax
byteOffset = OFFSETOF(fieldName IN {recordType|trueRecVar}) byteOffset = OFFSETOF(const [IN pseudoRecVar])

Description
Use this function to find where a particular field begins within a record. OFFSETOF returns the field's offset as a number of bytes past the beginning of the record. In the first syntax, recordType is the name of a "true record" type as defined in a BEGIN RECORD statement; trueRecVar is a variable declared as a "true record" type; fieldName is the name of a field within that "true record" type. In the second syntax, const is a symbolic integer constant, without its leading underscore character. Typically, this will be a constant which was defined within a DIM RECORD...DIM END RECORD block. pseudoRecVar.recLen is a "pseudo-record" variable declared as DIM psuedoRecVar.recLen. When you use the second syntax, OFFSETOF just returns the value of const. Because a symbolic constant always has a global scope, the IN pseudoRecVar clause is not required. The value passed as fieldName is seen by the compiler as a constant. You do not use type designator suffixes like $,&,#, etc.

title: Futurebasic/Language/Reference/offsetof


text:
Futurebasic/Language/Reference/on appleevent

Statement
(+)	Appearance		(+)	Standard			Console

Syntax
ON APPLEEVENT (eventtype&,eventClass&)Â{FN userFunction|GOSUB{lineNumber|"stmtLabel"}}

Revised
May, 2001 (Release 5)

Description
AppleEvents are used for communication between applications. (In dealing with Apple Events, you will often see applications referred to as processes.) Use this FB statement to set up and track specific types of Apple Events. Event types and classes that are to tracked are part of the ON APPLEEVENT parameters. Types and Classes Apple events are divided into general groups called Types. Those groups are subdivided into specific classes. As an example, you may have heard of Apple core events. There are events which every application should understand and handle. The class for this group is called _coreEventType. the long integer constant for this type is _"core". Either of these two forms of address is acceptable in FB, but only one (_"core") is case sensitive. If you wanted to deal with core events, you would have to tell the Apple Event Manager which of four classes might be of interest. As an example, you might want to know if the Finder (or some other process) sent a message to you to open a document. In such a case the class would be _kAEOpenDocuments or _"odoc". An event handler set up for this type and class would be entered as follows: ON APPLEEVENT(_coreEventType,_kAEOpenDocuments) ÂFN myODocHandler FB recognizes a special event class of _"TEXT". When this class in encountered, the contents of the event parameter may be more easily accessed using the APPLEEVENTMESSAGE$ function. The following simple example shows how your ON APPLEEVENT handler might look for incoming text. LOCAL FN doAppleEvent PRINT "Message received:" PRINT APPLEEVENTMESSAGE$ END FN ON appleevent(_"buba",_"TEXT") FN doAppleEvent It is often convenient to pass large blocks of data via Apple Events as handles. FB processes this automatically by pulling the data from the Apple Event and transferring it to your application as a handle. FB always copies the data, so when you are finished, you must manage disposal on your own. The following fragment shows how a handle is received and disposed. To show that the data was accepted, this routine prints the first fifty characters of the handle as ASCII text. LOCAL DIM AERec as AERecord DIM @OSErr DIM dataHandle as handle DIM n LOCAL FN doAppleEvent OSErr = FN AEGETPARAMDESC(gFBAEEvent&,Â _keyDirectObject, _"CLAS", AERec) dataHandle = AERec.dataHandle CLS PRINT "Rec'd at ";TIME$ FOR n = 1 TO 50 PRINT CHR$(PEEK([dataHandle]+n)); NEXT CALL DISPOSEHANDLE(dataHandle) END FN When this handler was set up, the class parameter for ON APPLEEVENT was _"CLAS". You can see that it was required for use in FN AEGETPARAMDESC. Note: Some handlers (like the example above) are already built in to most of the FB runtimes. In order to override a behavior, you will first have to use KILL APPLEEVENT. Only one Apple Event vector is allowed. If you create multiple ON APPLEEVENT vectors, each one overwrites the previous, so the last vector will be used. To handle multiple eventClasses and/or types in the one application, set up a vector for each, pointing all to the one handler. The handler can determine which class it has received by examining the global variable gFBAEType&. (See KILL APPLEVENT for the proper method of replacing an event vector.)

Example: CD Example: AppleEvents Folder


text:
Issues in Digital Technology in Education/Web 2.0 Learning Environments

By Kevin Pitts and Renu Kumar

Introduction

Web 2.0 is a term describing a new era in the way users interact with the World Wide Web. The term ‘Web 2.0’ was officially coined in 2004 by Dale Dougherty, a vice president of O’Reilly Media Inc. (the company famous for its technology-related conferences and books) during a team discussion on a potential future conference on the Web. The team wanted to get everyone re-excited about the Web despite the dot-com bust.1

There are a number of Web-based services and applications that demonstrate the foundations of the Web 2.0 concept. Some of these include blogs, wikis, Facebook, and YouTube. The services vary from data ‘mash-ups’, tracking, aggregation, and content filtering to social networking and collaboration services.

Whereas Web 1.0 can be thought of as static, consumptive, and individualistic, Web 2.0 can be thought of as dynamic, participatory and social. The primary tenet of Web 2.0 is that users add value. Although there is some debate whether the name Web 2.0 is deserved, there is no denying that change has occurred in the way the Web is used.

Impact on Education

The impact of Web 2.0 services and technologies on education is profound.

Web 2.0 services and technologies expand the learning options available to educators. For example, Wiki technology enables collaborative learning as users (e.g., students) collectively create, edit, link, and share web content. Blog (Web Log) technology enables active, reflective learning as users regularly publish personal content to the web and invite comments back to expand on and share experiences. Wikis, Blogs and similar Web 2.0 technologies provide a means for users to easily participate in the creation of new knowledge rather than consume pre-existing knowledge. These technologies also provide alternative assessment options for educators. The result is often a more engaging and collaborative teaching and learning experience.

Web 2.0 services and technologies foster a more open approach to learning. The ability to easily access and share educational materials, create derivative works, republish and redistribute these works provides access to a wide variety of learning materials and enables teachers and learners alike to meet specific learning needs and focus on specific outcomes. The result is often a more empowering learning experience. This openness expands beyond content. Web 2.0 services and technologies allow users to tap into the affordances of social networking. Here learners construct identities and foster wide ranging relationships resulting in a more community oriented approach to inquiry and practice.

As Web 2.0 services and technologies become more commonplace and become easier to use, particularly in the educational milieu, educators can shift their attention away from the technology itself to the pedagogy to find the best value and most appropriate uses of Web 2.0 technology in enhancing teaching and learning.

Issues and Implications

Although there are several advantages in using Web 2.0 technologies, there are also several issues that require awareness and attention. Some of these issues include: equal access, information control, intellectual property, copyright, authorship, trust, privacy, security and cultural considerations.

Web 2.0 technologies allow users to participate and express themselves; however most producers are individuals and organizations with access to technology, computer skills, and money, resulting in what has come to be known as a ‘digital divide’ been haves and have-nots with respect to digital technologies. The great strength of Web 2.0 is its participatory nature, but if one cannot participate then its effectiveness is lost. In collaborative environments (such as Wikis) questions of credibility, accuracy, authorship, and vandalism have arisen. Although open content is seen as a panacea for information and knowledge sharing, lines are being blurred in terms of rightful ownership, authorship, and copyright. Further, social networking brings to the fore issues of trust, privacy and security. The social and cultural impact of Web 2.0 technology is not yet fully understood. As such, as more and more of us adopt Web 2.0 technologies, we need to remain informed and aware of the changing nature of the Web and the benefits and drawbacks made possible by such technologies.

The Future

Tim-Berners Lee, the inventor of World Wide Web, and his colleagues at MIT propose the emergence of “Web Science” as a discipline. The goal of Web Science is to understand the growth of the Web, to describe emergent trends and patterns within it, to develop new scientific approaches to studying it, and to perform research to understand its social impact.1

This raises a question about the future of Web 2.0; that is, what’s next? Web 3.0 has been proposed as a possible future and consists of the integration of high-powered graphics (Scalable Vector Graphics or SVG) and semantic data. There have also been discussions around 3-D social networking systems and immersive 3-D internet environments that will take the best of virtual worlds (such as Second Life) and gaming environments and merge them with the Web. Others argue that Web 3.0 will be a backlash to Web 2.0 where software will ‘clean up’ after you, erasing your digital identity and path if needed. Regardless, it will be very interesting to see what the future holds.

Conclusion

The World Wide Web is evolving, and as such the way users interact with it is changing. Web 2.0 is a term used to describe a change to a more dynamic, participatory and social Web. Education is a beneficiary of such change. Web 2.0 services and technologies afford more empowering, engaging, and open learning experiences that foster more social, community-driven lines of inquiry and practice. Nonetheless, there are issues that require our awareness and attention; not the least of which revolve around privacy, security, and credibility, particularly within an educational context. The use of Web 2.0 services and technologies is becoming commonplace and is shaping the way think about and participate in the world. What is certain is the Web will continue to evolve in ways that we can in some respects predict, but in others can’t imagine. Regardless, it will be most interesting to see how it all unfolds.

Further Reading

1. Anderson, P. (2007). What is Web 2.0? Ideas, technologies, implications for education. JISC Technology and Standards Watch. Retrieved April 28, 2008, from http://www.jisc.ac.uk/media/documents/techwatch/tsw0701b.pdf

2. MacFayden, L. (2006). In a world of text, is the author king? In F. Sudweeks, H. Hrachovec, & C. Ess (Eds.), Cultural attitudes towards technology and communication (pp. 285-298). Murdoch, Australia: Murdoch University.

3. O’Reilly, T. (2005). What is Web 2.0: Design Patterns and Business Models for the next generation of software. O’Reilly Media Inc. Retrieved April 28, 2008, from http://www.oreillynet.com/pub/a/oreilly/tim/news/2005/09/30/what-is-web-20.html

4. Richardson, W. (2006). Blogs, wikis, podcasts, and other powerful tools for the classroom. Corwin Press.