ejaasaari/simplewiki-2025-04-01 huggingface dataset:
The article about graphical symbols is at Logo Logo is a programming language that is easy to learn. It is used to teach students and children to program a computer. It was developed to process lists of words. It was like the language LISP. History. In 1967, the first Logo ran on a mainframe computer, a machine called a teletype was used to type in and printout the results. There was no screen. In 1969, it was used to control a Floor Turtle. Commands were added to send the turtle forwards and backwards, and to turn the turtle to left or right. This turtle had pen with different colors. When it moved, it left a trail on the floor. Versions. When a new version of Logo was developed to draw graphics on a screen, it used the same commands. This was called Turtle graphics. There are 170 versions of Logo. Many of them are open source and free. There are three Logo textbooks that can be downloaded free. Logo is usually an interpreted language. Examples. Hello World. Load the Logo program. Type the next line in the command box.  print [Hello World!] The computer replies.  Hello World! Example Showing Graphics and Functional Programming. A spiral drawn using recursion.  Using the editor, type in this new definition.  to spiral :size  if :size &gt; 30 [stop] ; a condition stop  fd :size rt 15 ; many lines of action  spiral :size *1.02 ; the tailend recursive call  end Type this in the command box.  spiral 10 On the screen you will see. Other websites. Logo Programs Online books
Lisp (used to be called LISP) is a programming language. It is among the oldest programming languages that are still used today. Only Fortran is one year older. Lisp was designed by John McCarthy in 1958. The best-known versions of LISP are Common Lisp, Scheme and Clojure. Many concepts that are used in modern programming languages were first created in Lisp. Linked lists are a very important data structure in Lisp.  The basic concepts behind Lisp are easy to learn. Logo is another version of Lisp that was made for children. Logo can help young children develop skills and become efficient within the programming language. Simple examples (Scheme). In Lisp, operations are written in prefix notation, and they start and end with parentheses. For example, the formula formula_1 is written as: Because Lisp is a functional language, Lisp programs often use recursion to solve problems. Here is a Scheme program that finds the factorial of a number. The function (factorial n) starts by testing if formula_2 or not. If formula_3, then (factorial 0) is 1. If formula_4, then (factorial n) returns the product of formula_5 and the factorial of formula_6.  (if  (= n 0)  1  (* n (factorial (- n 1))))) Linked lists are an important idea in Lisp. The list without any things in it is known as the "empty" or "nil list", and is written as '(). A list that has things in it is written as '(dog cat).  The operation car is used to get the first thing of a list. For example, The operation cdr returns everything in the list except for the first thing. Here is a hello world program in Scheme:
In mathematical logic and computer science, lambda calculus, also λ-calculus, is a formal system (a system that can be used to figure out different logical theories and ideas). It was made to explore different ways of creating and using mathematical functions, and it lays out rules for doing this. It is also a tool for exploring recursion, and it has been used to explain what a computable function is. It was made by Alonzo Church and Stephen Cole Kleene in the 1930s. In 1936, Church used lambda calculus to show that there is no solution to the Entscheidungsproblem. Lambda calculus can be called the smallest universal programming language. At its core, lambda calculus is made up of just one "transformation rule" (something called "variable substitution") and just one way to define a function. Each "function definition" has a list of the function's "parameters", which are all of the variables that can be used in that function. Variable substitution is where specific variables in a function are replaced by other values (for example, the value formula_1 could take the place of every spot in a function where the variable formula_2 appears). This is called a transformation rule because it can be used to "transform" lambda expressions by changing around their values. Lambda calculus is considered "universal" because it can be used to both create and find the answer to any computable function. This is exactly what a Turing machine can do, so lambda calculus and Turing machines are said to be equivalent. However, lambda calculus focuses more on the use of transformation rules. It does not care about the actual machine that puts those rules into place. It is an approach more related to software than to hardware. There is no way to answer the question of whether two lambda calculus expressions are the same as each other (in more specific words, there is no general algorithm that can show that two lambda expressions are equivalent). This was the first problem where the idea of undecidability could be proven. Later, undecidability was also proven for the halting problem, where it was shown that there is no general way to show whether or not a program will keep running forever. Lambda calculus has had large effects on lots of functional programming languages, such as LISP, ML, and Haskell.
Power transmission is moving energy from where it is made to where it is used. Power is defined formally as units of energy per unit time. In SI units: 1 watt = 1 joule/s = 1 newton * metre/second (1W=1J/s=1N·m/s). Electrical power. With widespread establishment of power grids, power transmission has came to be associated most often with electric power transmission.  Mechanical power. Electrical power transmission has replaced mechanical power transmission in all but the very shortest distances. From the start of the industrial revolution until the end of the 19th century mechanical power transmission was the norm. Factories were fitted with overhead driveshafts providing rotary power. Drivebelts would provide power to individual machines on the shop floor. Mechanical power may be transmitted directly using a solid structure such as a driveshaft; transmission gears can adjust the amount of torque or force vs. speed in much the same way an electrical transformer adjusts voltage vs current. Chemicals and fuels. Chemical energy is transmitted by moving fuels to generate power in distant places. Pipelines and other large infrastructure projects transport natural gas, petroleum and petroleum products for use as fuel.
Ocean surface waves are surface waves that occur in the upper layer of the ocean. They usually result from wind. Some are made by geologic effects like earthquakes or vulcanicity and may travel thousands of miles before striking land. They range in size from small ripples to huge tsunamis. There is little actual forward motion of individual water particles in an unbroken wave, despite the large amount of energy and momentum it may carry forward. When a wave hits shallow water, it "breaks" because the bottom moves more slowly than the top.  Wave formation. The great majority of large breakers one sees on an ocean beach result from distant winds. Three factors influence the formation of these "wind waves": All of these factors work together to determine the size and shape of ocean waves. The greater each of the variables, the larger the waves. Waves are measured by: Waves in a given area typically have a range of sizes. For weather reporting and for scientific analysis of wind wave statistics, their size over a period of time is usually expressed as "significant wave height." This figure represents the average height of the highest one-third of the waves in a given time period (usually twelve hours) or in a specific storm system or event. Given the variability of wave size, the largest individual waves are likely to be twice the reported significant wave height for a particular day or storm.
A crest is the point on a wave with the greatest positive value or upward displacement in a cycle. A trough is the opposite of a crest. When the crest and the trough of two waves of equal magnitude and frequency intersect or collide when in phase with each other the result is called constructive interference and the magnitudes double (above and below the line), when 180° out of phase the result is destructive interference with each other the resulting wave is the undisturbed line that is in the middle of the diagram having zero amplitude. In other words, the wave crest is called a peak.
A trough is a box-like drinking vessel for farm animals. Other senses of the word refer to things that are lower than their surroundings, like a trough: See also trow.
Nausea is a general feeling of unease and discomfort in the stomach, often with the urge to vomit. The word "nausea" comes from the Latin word for seasickness. Nausea is a symptom, rather than an illness or disease. The causes for it very often are not in the stomach itself, but somewhere else in the body. Nausea is often caused by a stomach virus. Nausea is usually harmless, in the short term. A good treatment for it can be not to take solid food (and to only drink non-alcoholic drinks, like water). Nausea can also occur during pregnancy, and is quite normal in that context. People can suffer nausea without vomiting.
Anxiety is distress or uneasiness of mind caused by a fear of danger or misfortune. Very often, people with anxiety also feel worries. There can also be physical symptoms, like having a headache or an upset stomach. Anxiety is a very common human emotion and is often associated with fear, panic, and the fight or flight response. The amount of stress needed to cause anxiety will vary from person to person however, basics include: losing one's job, the death of a loved one, or an accident, to name a few. In most people, anxiety will settle over time and one will return to normal state.  Some people suffer a lot of anxiety over a long period of time which controls them and makes their lives difficult. These conditions are called anxiety disorders and can be treated by therapy and medicine. General anxiety symptoms are things such as; continual tiredness / exhaustion, inability to relax, lack of confidence, low self-esteem, fear of public places, fear of socialising, frequent feelings of irrational anxiety / fear, compulsive behavior, worrying about making mistakes, regular nightmares, disturbed sleep patterns, excessive crying, headaches, stomach problems, diarrhea, nausea, aching muscles, and so on. Symptoms of anxiety attacks are things like; sweating, shaking and tremors, palpitations, shortness of breath, hyperventilating, racing heart beat, tingling in hands and feet, feeling of impending doom, feeling you are having a heart attack. There are more, but these are the usual ones. Medicine. These symptoms, more or less, define anxiety but they can also be signs of other problems, so the first port of call has to be a doctor or other health care professional. They will be able to define what the problem is exactly, and propose the appropriate treatment. A doctor’s first line treatment is usually through drug-based medication; for example antidepressants, anti-anxiety tablets and beta blockers. These can be very effective, but they all have side effects, some worse than others. This can tend to put folks off continuing with them. Note however, that many drugs that have been taken for a longer time, need to be stopped in a special way (usually, with the help
Wave power means the use of ocean surface waves and the capture of that energy to do useful work—including electricity generation, desalination, and the pumping of water (into reservoirs). It makes use of the kinetic energy of the waves that are driven by the wind. Power from ocean surface wave motion might produce much more energy than tides. Tests have shown that it is possible to produce energy from waves, particularly in Scotland in the UK. But the technology is not as well developed as other renewable energy such as wind power or solar power.
Desalination means any process that removes the excess salt and other minerals from water in order to obtain fresh water suitable for animal consumption or irrigation. Most desalination is by distillation. Some is by reverse osmosis or other methods. The main purpose is to make water for people to use. The salt is usually carried away as brine but in some places the solid salt is extracted.  Desalination of brackish water is done in the United States in order to meet treaty obligations for river water entering Mexico. Several Middle Eastern countries have energy reserves so great that they use desalinated water for agriculture. Saudi Arabia's desalination plants account for about 24% of total world capacity. The world's largest desalination plant is the "Jebel Ali" Desalination Plant (Phase 2) in UAE. It uses multi-stage flash distillation, dual-purpose and it is capable of producing 300 million cubic meters of water per year. Methods. The traditional process used in these operations is vacuum distillation — essentially the boiling of water at less than atmospheric pressure, and thus a much lower temperature than normal. Due to the reduced temperature, energy is saved.
Solar energy is a type of energy that comes from the sun's heat. People have been using solar energy for thousands of years in different ways, such as heating, cooking, and drying. Nowadays, it is also used to create electricity in areas where other sources of power are not available, such as remote locations and even outer space. The cost of generating electricity from solar energy is decreasing, making it a more affordable option. Since the sun provides heat and light constantly, solar energy is considered a renewable energy source and an alternative to non-renewable resources like coal and oil. Energy uses. Solar energy is used in various ways today, including: Energy from the Sun. After passing through the Earth's atmosphere, most of the Sun's energy is in the form of visible light and infrared light radiation. Plants convert the energy in sunlight into chemical energy (sugars and starches) through the process of photosynthesis. Humans regularly use this store of energy in various ways, as when they burn wood off fossil fuels, or when simply eating plants, fish and animals. Solar radiation reaches the Earth's upper atmosphere with the power of 1366 watts per square meter (W/m2). Since the Earth is round, the surface nearer its poles is angled away from the Sun and receives much less solar energy than the surface nearer the equator. At present, solar cell panels convert, at best, about 15% of the sunlight hitting them into electricity.  The dark disks in the third diagram on the right are imaginary examples of the amount of land that, if covered with 8% efficient solar panels, would produce slightly more energy in the form of electricity than the world needed in 2003. Types of technologies. Many technologies have been developed to make use of solar radiation. Some of these technologies make direct use of the solar energy (e.g. to provide light, heat, etc.), while others produce electricity. Solar power plants. Solar power plants convert sunlight into electricity, either directly using photovoltaics (PV), or indirectly using "concentrated solar power" (CSP). Concentrated solar power systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam. Photovolta
Photovoltaics (PVs) are arrays of cells containing a solar photovoltaic material that converts solar radiation or energy from the sun into direct current electricity. Due to the growing demand for renewable energy sources, the manufacturing of solar cells and photovoltaic arrays has advanced considerably in recent years, and costs have dropped. Solar photovoltaics are growing rapidly, from a small base, to a total global capacity of 130,000 MW at the end of 2013. More than 100 countries use solar PV. Installations may be ground-mounted (and sometimes integrated with farming and grazing) or built into the roof or walls of a building. Panels. Photovoltaic solar panels come in many different voltages. The most common are 12 volts, 24 volts, and 48 volts. Like batteries, multiple solar panels can be connected together to produce higher voltages, for example, two 48 volt panels connected together would produce 96 volts. The inverter, batteries, and solar panels in a system are usually all of the same voltage. The advantage of a higher-voltage system is that thinner wire is used, which is less expensive and easier to pull through conduit. The disadvantage of a higher-voltage installation is that electric shock and arc flash become more of a hazard, so installations above 48 volts are usually only found in solar power plants or commercial buildings. A photovoltaic installation typically includes an array of solar panels, an inverter, rechargeable batteries (for use at night), a charge controller (a device that prevents the batteries from over-charging), two GFCI circuit breakers (one before the inverter and one after), and interconnection wiring. There is sometimes also a transformer after the inverter, which can power 240 volt heavy appliances such as a clothes dryer or oven. The transformer is often part of the inverter and can't be seen. Everything past the inverter (or transformer if there is one) is set up like a normal utility-fed installation (breaker panel, lights, outlets, switches, etc.). If there is no transformer, only 120 volt devices may be used. Installations without a transformer must be labelled as such on the breaker panel to
Solar cells are semiconductor devices that convert light to electricity. They have many applications. They have long been used in situations where electrical power from the grid is unavailable, such as in remote area power systems, Earth-orbiting satellites and space probes, consumer systems, e.g. handheld calculators or wrist watches, remote radiotelephones and water pumping applications. More recently, they are starting to be used in assemblies of solar modules connected to the electricity grid through an inverter, often in combination with net metering. Solar cells are regarded as one of the key technologies of solar energy towards a sustainable energy supply. Three generations of development. First. The first generation photovoltaic consists of a large-area, single layer p-n junction diode, which is capable of generating usable electrical energy from light sources with the wavelengths of sunlight. These cells are typically made using a silicon wafer. First generation photovoltaic cells (also known as silicon wafer-based solar cells) are the dominant technology in the commercial production of solar cells, accounting for more than 86% of the solar cell market. Second. The second generation of photovoltaic materials is based on the use of thin-film deposits of semiconductors. These devices were initially designed to be high-efficiency, multiple junction photovoltaic cells. Later, the advantage of using a thin-film of material was noted, reducing the mass of material required for cell design. This contributed to a prediction of greatly reduced costs for thin film solar cells. Currently (2007) there are different technologies/semiconductor materials under investigation or in mass production, such as amorphous silicon, poly-crystalline silicon, micro-crystalline silicon, cadmium telluride, copper indium selenide/sulfide. Typically, the efficiencies of thin-film solar cells are lower compared with silicon (wafer-based) solar cells, but manufacturing costs are also lower, so that a lower price in terms of $/watt of electrical output can be achieved. Another advantage of the reduced mass is that less support is needed when placing panels on rooftops and it allows fitting panels on light materials or flexible materials, even textiles. This allows for portable roll
An alternating current (AC) is an electric current of which magnitude and direction vary, unlike direct current, whose direction remains constant. This means that the direction of current flowing in a circuit is constantly being reversed back and forth. This is done with any type of AC voltage source.  The usual waveform of an AC power circuit is a sine wave, because this leads to the most efficient transmission of energy. However, in certain applications different waveforms are used, such as triangular or square waves. Inexpensive power inverters produce a square wave with a pause between the change in direction. When one speaks of alternating current one mostly refers to the form in which electricity is delivered to businesses and residences. The AC comes from a power plant. The direction of the electricity switches back 60 times every second (or 50 times in some parts of the world). This happens so fast that a light bulb does not stop glowing. Both audio and radio signals carried on electrical wire are also examples of alternating current. In these applications, an important goal is often the recovery of information encoded (or modulated) onto the AC signal. History. Nikola Tesla experimented with electrical resonance and studied various lighting systems. He invented an induction motor, new types of generators and transformers, and a system of alternating current power transmission. William Stanley, Jr. designed one of the first practical devices to transfer AC power efficiently between isolated circuits. Using pairs of coils wound on a common iron core, his design, called an induction coil, was an early precursor of the modern transformer. The system used today was devised in the late nineteenth century, largely by Nikola Tesla. Contributions were also made by George Westinghouse, Lucien Gaulard, John Dixon Gibbs,Wilhelm Siemens and Oliver Shallenger. AC systems overcame the limitations of the direct current system used by Thomas Edison to distribute electricity efficiently over long distances.  The Mill Creek hydroelectric plant was built near Redlands, California in 1893. Designed by Almirian Decker, it used 10,000 volt three-phase electric power which eventually became the standard method for power stations throughout the world. How it Works. AC power is cheaper and easier to make electronic devices. The power switches for AC
Direct current (DC or "continuous current") is the flow of electricity in a single direction, from the negative to the positive terminals (potential, poles). The direct current always flow in the same direction, distinguishing it from the alternating current (AC). Direct current used to be called "Galvanic current". Batteries are some of the main sources of direct current (DC), but many other sources also exist such as bridge rectifiers in power supply, solar panels, etc. Typically, the current goes through a conductor and other things that can carry DC. DC is also sent through a vacuum as in electron beams or ion beams. The first commercial electric power transmission was developed by Thomas Edison in the late nineteenth century using direct current. Today nearly all electric power distribution uses alternating current because of the advantages with transformers and transmission. High-voltage direct current is often used for transporting electricity to places far away. For applications requiring direct current, the alternating current is typically distributed to a substation and then converted to direct current. Long after the usage of direct current had been established, physicists realized that the current was made of negative electric charges, the electrons, and that the actual flow was from the negative to the positive pole (and so-called "holes" flow in the opposite direction), but by convention, the usage of the term was never changed.