Simple machine defined

Briefly define what we mean by a simple machine and give five examples. 

Computerized programmable equipment is usually more cost effective where a variety of parts are to be produced or where part configuration is complex, such as a wind turbine blade. Sophisticated software for filament winding such as FGX Windows developed by Entec Composite Machines (Salt Lake City, Utah) allows the manufacturer to create patterns to wrap a pressure vessel, as an example, before winding begins. Filling in a simple menu defines the part geometry, and the computer uses this database to calculate a fiber path for the part and establish the... 

As was said in the introduction (Section 2.1), chemical structures are the universal and the most natural language of chemists, but not for computers. Computers woi k with bits packed into words or bytes, and they perceive neither atoms noi bonds. On the other hand, human beings do not cope with bits very well. Instead of thinking in terms of 0 and 1, chemists try to build models of the world of molecules. The models ai e conceptually quite simple 2D plots of molecular sti uctures or projections of 3D structures onto a plane. The problem is how to transfer these models to computers and how to make computers understand them. This communication must somehow be handled by widely understood input and output processes. The chemists way of thinking about structures must be translated into computers internal, machine representation through one or more intermediate steps or representations (sec figure 2-23, The input/output processes defined... 

A compressor surges at certain conditions of low flow, and the compressor map, a plot of head versus flow, has a surge line defining the limits. Surge controls help the machine avoid surge by increasing flow. For an air compressor, a simple spill to the atmosphere is sufficient. For a hydrocarbon compressor, recirculation from discharge to suction is used. 

If we are to discuss computer methods, we need some way of measuring the performance of an algorithm. We would like our code for molecules to be simple, natural, and easy to compute. Concepts like "simple" and "natural", although very important in any real-world cataloguing system, are difficult to define and quantify. We shall use a measure based on a machine s point of view, rather than on a human s. Though an algorithm good by such a measure may be unwieldy for human use, at best a method useful for machines will also be useful for people. At worst, such a measure provides a firm base for discussion of the merits of various methods. 

The identification of probable combustion product species for all but the most exotic propellant combinations has been well established. In conjunction with machine calculations which consider large numbers of possible product species, the likelihood of Introducing error into equilibrium performance calculations through omission of significant product species is small. With the completion of the JANAF Thermochemical Tables (18) which currently contain some 800 possible species and continues to be expanded, the task of taking all possible significant product species into consideration is well defined, although not necessarily simple. The problem of identification of probable species has been reduced to the identification of possible species which for most propellant combination is a routine task. 

Thus, the digital computer is really a very simple-minded device, which must be told how to accomplish even the most fundamental computations but which can accomplish these operations with blinding speed. Moreover, it is a tireless machine, which is content to calculate endlessly and consistently. It is also very versatile, since it is programmable and capable of accomplishing an infinite variety of computational, logical, or control operations. Finally, it is a device that can (in fact, must) communicate in a variety of ways with the outside world. It is this characteristic that defines the computer as a general-purpose experimental device. 

The values for these machine-specific parameters can be somewhat dependent on the application. For example, the flop rate can vary significantly depending on the type of operations performed. The accuracy of a performance model may be improved by using values for the machine-specific parameters that are obtained for the type of application in question, and the use of such empirical data can also simplify performance modeling. Thus, if specific, well-defined types of operations are to be performed in a parallel program (for instance, certain collective communication operations or specific computational tasks), simple test programs using these types of operations can be written to provide the appropriate values for the pertinent performance parameters. We will show examples of the determination of application specific values for a, and y in section 5.3.2. 

The main demands of broaching machines are high accuracy, good dynamic behavior, low noise emission, reliable operation, and simple automation (Hoffmann 1976). The elementary construction and exactly defined load requirements make broaching machines to be highly reliable machine tools. It can be differed between the following types of construction ... 

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