AIR DIRECT FIRED LINE MAKE UP

Wednesday, March 5, 2008

Air direct fired line make up

make

In software development, make is a utility for automatically building large applications. Files specifying instructions for make are called Makefiles. make is an expert system that tracks which files have changed since the last time the project was built and invokes the compiler on only those source code files and their dependencies. Before make's introduction, the Unix build system would most likely consist of "make" and "install" shell scripts accompanying a program's source. Being able to combine the commands for the different targets into a single file, and being able to abstract out dependency tracking and archive handling, was an important step in the direction of modern build environments. BSD make, which is derived from Adam de Boor's work on a version of make capable of building targets in parallel, and survives with varying degrees of modification in FreeBSD, NetBSD and OpenBSD. Most notably, it has conditionals and iterative loops which are applied at the parsing stage and may be used to conditionally, and programmatically, construct the makefile, including generation of targets at runtime. GNU make, which is part of most GNU/Linux installations and is frequently used in conjunction with the GNU build system. Its departures from traditional make are most noticeable in pattern-matching in dependency graphs and build targets, as well as a number of functions which may be invoked to have the make utility do things like collect a list of all files in the current directory. POSIX includes standardization of the basic features and operation of the make utility, and is implemented with varying degrees of completeness in Unix-based versions of make. In general, simple makefiles may be used between various versions of make with reasonable success. Some versions of GNU make and BSD make will look first for files named "GNUmakefile" and "BSDmakefile" respectively, which allows one to put makefiles which use implementation-defined behaviour in separate locations. In its basic form, Make requires the programmer to manually track all dependencies between files in the project. This process is error prone, since a forgotten or an extra dependency might not be immediately obvious, but instead surfaces as subtle bugs in the software. It is possible to create make files that generate some of these dependencies, but a more common solution is to use one of the available generators to make, e.g. Automake toolchain provided from the GNU Project. Another problem not well handled by make is the tailoring of a build process to a given platform. E.g, the compiler used on one platform might not accept the same options as the one used on another. This problem is typically handled by generating platform specific build instructions, which in turn are processed by make. Common tools for this process are Autoconf and Cmake. The syntax used by Make includes the use of tab, a whitespace character. Many editors do not provide very clear visual clues to the presence of tabs rather than spaces, and tab characters are not represented uniformly across editors in any case, with size varying from as little as 2 spaces to 8 spaces. Thus, the syntax of make is often subject to criticism. Some projects, such as Apache Ant, have attempted to redo make with a better syntax, with mixed success. For programmers using makefile generators, this issue is likely unimportant. With the advent of modern Integrated Development Environments, especially on non-Unix platforms, many programmers do not manually manage dependency tracking, or even the listing of which files are part of a project. Instead, the task is automated by the integrated environment. Likewise, many modern programming languages have language-specific ways of listing dependencies which are more efficiently tracked through the use of language-specific build utilities. These approaches typically have the drawback that support for arbitrary build instructions is limited. A makefile consists of lines of text which define a file (or set of files) or a rule name as depending on a set of files. Output files are marked as depending on their source files, for example, and source files are marked as depending on files which they include internally. After each dependency is listed, a series of lines of tab-indented text may follow which define how to transform the input into the output, if the former has been modified more recently than the latter. In the case where such definitions are present, they are referred to as "build scripts" and are passed to the shell to generate the target file. The basic structure is:[1] A makefile also can contain definitions of variables and inclusion of other makefiles. Variables in makefiles may be overridden in the command line arguments passed to the make utility. This allows users to specify different behaviour for the build scripts and how to invoke programs, among other things. For example, the variable "CC" is frequently used in makefiles to refer to a C compiler, and the user may wish to provide an alternate compiler to use.

Air direct fired line make up

line

A line can be described as an ideal zero-width, infinitely long, perfectly straight curve (the term curve in mathematics includes "straight curves") containing an infinite number of points. In Euclidean geometry, exactly one line can be found that passes through any two points. The line provides the shortest connection between the points. In two dimensions, two different lines can either be parallel, meaning they never meet, or may intersect at one and only one point. In three or more dimensions, lines may also be skew, meaning they don't meet, but also don't define a plane. Two distinct planes intersect in at most one line. Three or more points that lie on the same line are called collinear. This intuitive concept of a line can be formalized in various ways. If geometry is developed axiomatically (as in Euclid's Elements and later in David Hilbert's Foundations of Geometry), then lines are not defined at all, but characterized axiomatically by their properties. While Euclid did define a line as "length without breadth", he did not use this rather obscure definition in his later development. More abstractly, one usually thinks of the real line as the prototype of a line, and assumes that the points on a line stand in a one-to-one correspondence with the real numbers. However, one could also use the hyperreal numbers for this purpose, or even the long line of topology. In Euclidean geometry, a ray, or half-line, given two distinct points A (the origin) and B on the ray, is the set of points C on the line containing points A and B such that A is not strictly between C and B. In geometry, a ray starts at one point, then goes on forever in one direction.

Air direct fired line make up

fired

Pit firing is the oldest known method of firing clay. Unfired pots are nestled together in a pit in the ground and are then covered with burnable materials such as wood shavings, leaves, metal oxides, salts, sawdust and dried manure. The top of the pit may be protected with moist clay, shards, larger pieces of wood or metal baffles. The filled pit is then set on fire and carefully tended until most of the inner fuel has been consumed. The final pit temperature is generally low to moderate, approaching 2000 °F (1100 °C). This is in the range of temperatures used by ancient Native American potters or those used for earthenware. After cooling, pots are removed and cleaned to reveal dramatic patterns and colors left by ash and salt deposits. Pots may then be waxed and buffed to create a smooth glossy finish.

Air direct fired line make up

direct

Direct current (DC or "continuous current") is the unidirectional flow of electric charge. Direct current is produced by such sources as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may flow in a conductor such as a wire, but can also be through semiconductors, insulators, or even through a vacuum as in electron or ion beams. In direct current, the electric charges flow in the same direction, distinguishing it from alternating current (AC). A term formerly used for direct current was Galvanic current. Direct current may be obtained from an alternating current supply by use of a current-switching arrangement called a rectifier, which contains electronic elements (usually) or electromechanical elements (historically) that allow current to flow only in one direction. Direct current may be made into alternating current with an inverter or a motor-generator set. The first commercial electric power transmission (developed by Thomas Edison in the late nineteenth century) used direct current. Because of the advantage of alternating current over direct current in transforming and transmission, electric power distribution today is nearly all alternating current. For applications requiring direct current, such as third rail power systems, alternating current is distributed to a substation, which utilizes a rectifier to convert the power to direct current. See War of Currents. Direct current is used to charge batteries, and in nearly all electronic systems as the power supply. Very large quantities of direct-current power are used in production of aluminum and other electrochemical processes. Direct current is used for some railway propulsion, especially in urban areas. High voltage direct current is used to transmit large amounts of power from remote generation sites or to interconnect alternating current power grids. Within electrical engineering, the term DC is a synonym for "constant". For example, the voltage across a DC voltage source is constant as is the current through a DC current source. The DC solution of an electric circuit is the solution where all voltages and currents are constant. It can be shown that any voltage or current waveform can be decomposed into a sum of a DC component and a time-varying component. The DC component is defined to be the average value of the voltage or current over all time. The average value of the time-varying component is zero. DC is commonly found in many low-voltage applications, especially where these are powered by batteries, which can produce only DC, or solar power systems, since solar cells can produce only DC. Most automotive applications use DC, although the alternator is an AC device which uses a rectifier to produce DC. Most electronic circuits require a DC power supply. Applications using fuel cells (mixing hydrogen and oxygen together with a catalyst to produce electricity and water as byproducts) also produce only DC. Many telephones connect to a twisted pair of wires, and internally separate the AC component of the voltage between the two wires (the audio signal) from the DC component of the voltage between the two wires (used to power the phone).

Air direct fired line make up

air

There is no definite boundary between the atmosphere and outer space. It slowly becomes thinner and fades into space. Three quarters of the atmosphere's mass is within 11 km of the planetary surface. In the United States, people who travel above an altitude of 80.5�km (50 statute miles) are designated astronauts. An altitude of 120�km (~75 miles or 400,000 ft) marks the boundary where atmospheric effects become noticeable during re-entry. The Kármán line, at 100�km (62 miles or 328,000 ft), is also frequently regarded as the boundary between atmosphere and outer space. Ionosphere: is the part of the atmosphere that is ionized by solar radiation. It plays an important part in atmospheric electricity and forms the inner edge of the magnetosphere. It has practical importance because, among other functions, it influences radio propagation to distant places on the Earth. It is located in the thermosphere and is responsible for auroras. Mesosphere: From the Greek word "μέσος" meaning middle. The mesosphere extends from about 50�km (160,000 ft) to the range of 80 to 85�km (265,000 – 285,000 ft), temperature decreasing with height. This is also where most meteors burn up when entering the atmosphere. Stratosphere: From the Latin word "stratus" meaning a spreading out. The stratosphere extends from the troposphere's 7 to 17�km (23,000 – 60,000 ft) range to about 50�km (160,000 ft). Temperature increases with height. The stratosphere contains the ozone layer, the part of the Earth's atmosphere which contains relatively high concentrations of ozone. "Relatively high" means a few parts per million—much higher than the concentrations in the lower atmosphere but still small compared to the main components of the atmosphere. It is mainly located in the lower portion of the stratosphere from approximately 15 to 35�km (50,000 – 115,000 ft) above Earth's surface, though the thickness varies seasonally and geographically. Troposphere: From the Greek word "τρέπω" meaning to turn or change. The troposphere is the lowest layer of the atmosphere; it begins at the surface and extends to between 7�km (23,000 ft) at the poles and 17�km (60,000 ft) at the equator, with some variation due to weather factors. The troposphere has a great deal of vertical mixing due to solar heating at the surface. This heating warms air masses, which makes them less dense so they rise. When an air mass rises the pressure upon it decreases so it expands, doing work against the opposing pressure of the surrounding air. To do work is to expend energy, so the temperature of the air mass decreases. As the temperature decreases, water vapor in the air mass may condense or solidify, releasing latent heat that further uplifts the air mass. This process determines the maximum rate of decline of temperature with height, called the adiabatic lapse rate. It contains roughly 80% of the total mass of the atmosphere. 50% of the total mass of the atmosphere is located in the lower 5 km of the troposphere. Atmospheric pressure is a direct result of the total weight of the air above the point at which the pressure is measured. This means that air pressure varies with location and time, because the amount (and weight) of air above the earth varies with location and time. Atmospheric pressure decreases with height, dropping by 50% at an altitude of about 5.6�km (18,000 ft). Equivalently, about 50% of the total atmospheric mass is within the lowest 5.6�km. This pressure drop is approximately exponential, so that pressure decreases by approximately half every 5.6�km. However, because of changes in temperature throughout the atmospheric column, as well as the fact that the force of gravity begins to decrease at great altitudes, a single equation does not model atmospheric pressure through all altitudes (it is modeled in 7 exponentially decreasing layers, in the equations given above). Below the turbopause at an altitude of about 100�km (not far from the mesopause), the Earth's atmosphere has a more-or-less uniform composition (apart from water vapor) as described above; this constitutes the homosphere.[5] However, above about 100�km, the Earth's atmosphere begins to have a composition which varies with altitude. This is essentially because, in the absence of mixing, the density of a gas falls off exponentially with increasing altitude, but at a rate which depends on the molar mass. Thus higher mass constituents, such as oxygen and nitrogen, fall off more quickly than lighter constituents such as helium, molecular hydrogen, and atomic hydrogen. Thus there is a layer, called the heterosphere, in which the earth's atmosphere has varying composition. As the altitude increases, the atmosphere is dominated successively by helium, molecular hydrogen, and atomic hydrogen. The precise altitude of the heterosphere and the layers it contains varies significantly with temperature. After loss of the hydrogen, helium and other hydrogen-containing gases from early Earth due to the Sun's radiation, primitive Earth was devoid of an atmosphere. The first atmosphere was formed by outgassing of gases trapped in the interior of the early Earth, which still goes on today in volcanoes. [6] The modern atmosphere is sometimes referred to as Earth's "third atmosphere", in order to distinguish the current chemical composition from two notably different previous compositions. The original atmosphere was primarily helium and hydrogen. Heat from the still-molten crust, and the sun, plus a probably enhanced solar wind, dissipated this atmosphere. About 4.4 billion years ago, the surface had cooled enough to form a crust, still heavily populated with volcanoes which released steam, carbon dioxide, and ammonia. This led to the early "second atmosphere", which was primarily carbon dioxide and water vapor, with some nitrogen but virtually no oxygen. This second atmosphere had approximately 100 times as much gas as the current atmosphere, but as it cooled much of the carbon dioxide was dissolved in the seas and precipitated out as carbonates. The later "second atmosphere" contained largely nitrogen and carbon dioxide. However, simulations run at the University of Waterloo and University of Colorado in 2005 suggest that it may have had up to 40% hydrogen.[7] It is generally believed that the greenhouse effect, caused by high levels of carbon dioxide and methane, kept the Earth from freezing. One of the earliest types of bacteria was the cyanobacteria. Fossil evidence indicates that bacteria shaped like these existed approximately 3.3 billion years ago and were the first oxygen-producing evolving phototropic organisms. They were responsible for the initial conversion of the earth's atmosphere from an anoxic state to an oxic state (that is, from a state without oxygen to a state with oxygen) during the period 2.7 to 2.2 billion years ago. Being the first to carry out oxygenic photosynthesis, they were able to produce oxygen while sequestering carbon dioxide in organic molecules, playing a major role in oxygenating the atmosphere. Photosynthesising plants would later evolve and continue releasing oxygen and sequestering carbon dioxide. Over time, excess carbon became locked in fossil fuels, sedimentary rocks (notably limestone), and animal shells. As oxygen was released, it reacted with ammonia to release nitrogen; in addition, bacteria would also convert ammonia into nitrogen. But most of the nitrogen currently present in the atmosphere results from sunlight-powered photolysis of ammonia released steadily over the aeons from volcanoes. As more plants appeared, the levels of oxygen increased significantly, while carbon dioxide levels dropped. At first the oxygen combined with various elements (such as iron), but eventually oxygen accumulated in the atmosphere, resulting in mass extinctions and further evolution. With the appearance of an ozone layer (ozone is an allotrope of oxygen) lifeforms were better protected from ultraviolet radiation. This oxygen-nitrogen atmosphere is the "third atmosphere". 200 – 250 million years ago, up to 35% of the atmosphere was oxygen (as found in bubbles of ancient atmosphere were found in an amber). This modern atmosphere has a composition which is enforced by oceanic blue-green algae as well as geological processes. O2 does not remain naturally free in an atmosphere, but tends to be consumed (by inorganic chemical reactions, and by animals, bacteria, and even land plants at night), and CO2 tends to be produced by respiration and decomposition and oxidation of organic matter. Oxygen would vanish within a few million years due to chemical reactions and CO2 dissolves easily in water and would be gone in millennia if not replaced. Both are maintained by biological productivity and geological forces seemingly working hand-in-hand to maintain reasonably steady levels over millions of years (see Gaia theory). Air pollution is a chemical, physical (e.g. particulate matter) or biological agent that modifies the natural characteristics of the atmosphere in an unwanted way. Stratospheric ozone depletion due to air pollution (chiefly from chlorofluorocarbons) has long been recognized as a threat to human health as well as to the earth's ecosystems.