Pipeline computing

The ASC differs from the conventional scalar computer in that it is a pipeline computer with a full set of hardware vector instructions in addition to the standard scalar instructions. The vector hardware includes arithmetic operations such as add, subtract, multiply, divide, vector dot product, as well as vector instructions for shifting, logical operations, comparisons, format conversions, normalization, merge, order, search, peak pick, select, replace, MIN, and MAX. Although an ASC may have one to four pipes, the configuration described below will be that of the two pipe machine at NRL. 

Pipeline Computing A strategy that parallelizes over a sequence of operations applied independently to multiple inputs. 

Magatao, L., Arruda, L., and Neves, F. A mixed integer programming approach for scheduling commodities in a pipeline. Computers Chemical Engineering, 28(1-2) 171 - 185, 2004. 

MirHassani, S. and Fani Jahromi, H. Scheduling multi-product tree-structure pipelines. Computers chemical engineering, 35(1) 165-176, 2011. 

P. M. Kogge, The Architecture of Pipelined Computers. Hemisphere Publishing Corporation, 1981. 

Tracer Type. A discrete quantity of a foreign substance is injected momentarily into the flow stream and the time interval for this substance to reach a detection point, or pass between detection points, is measured. From this time, the average velocity can be computed. Among the tracers that have historically been used are salt, anhydrous ammonia, nitrous oxide, dyes, and radioactive isotopes. The most common appHcation area for tracer methods is in gas pipelines where tracers are used to check existing metered sections and to spot-check unmetered sections. 

Coal Slurry Pipelines. The only operating U.S. coal slurry pipeline is the 439-km Black Mesa Pipeline that has provided the 1500-MW Mohave power plant of Southern California Edison with coal from the Kayenta Mine in northern Arizona since 1970. It is a 457-mm dia system that aimuaHy deHvers - 4.5 x 10 t of coal, the plant s only fuel source, as a 48.5—50% slurry. Remote control of slurry and pipeline operations is achieved with a SCADA computer system. In 1992 coal deHvery cost from mine to power plant was calculated to be 0.010/tkm ( 0.015/t-mi) (28). 

As a pipeline is heated, strains of such a magnitude are iaduced iato it as to accommodate the thermal expansion of the pipe caused by temperature. In the elastic range, these strains are proportional to the stresses. Above the yield stress, the internal strains stiU absorb the thermal expansions, but the stress, g computed from strain 2 by elastic theory, is a fictitious stress. The actual stress is and it depends on the shape of the stress-strain curve. Failure, however, does not occur until is reached which corresponds to a fictitious stress of many times the yield stress. 

Clearly the key to maximum performance was being able to keep the pipeline full. This observation stiU. holds tme for today s computers. 

There are many reasons that it might be difficult to keep the pipelines full. The most obvious is a data dependency, where a previously initiated computation must pass through all stages of the pipeline before the next operation can be commenced. 

In this example, the evaluation of X and Z can be overlapped within the multiplication pipeline, but work caimot begin on the evaluation of lU until the result of the computation of Z is known. The pipeline must empty, and the result, Z, must be retrieved before the pipeline can be refilled for the evaluation of lU. 

On a vector computer having vector registers that hold 64 floating-point numbers, this loop would be processed 64 elements at a time. The first 64 elements of Y would be fetched from memory and stored in a vector register. Each iteration of the loop is independent of the previous iteration, so this loop can be fliUy pipelined, with successive iterations started every clock cycle. Once the pipeline is filled, the result, X, will be produced one element per clock cycle and will be stored in another vector register. The results in the vector register will then be stored back into main memory or used as input to a subsequent vector operation. 

The rapid development of microelectronics has enabled many similar measurements to be made with data collecting systems and then stored electronically. The raw data can then be downloaded to the data processing installation, where they can be plotted and evaluated at any time [1]. This applies particularly to monitoring measurements on pipelines for intensive measurements, see Section 3.7. Figure 3-1 shows an example of a computer-aided data storage system. 

Fig. 3-1 Computer-aided data storage system for monitoring the cathodic protection of a long-distance pipeline.

A check on the cathodic protection of the pipeline should be carried out annually according to Section 10.4, where, of course, only the on potential should be measured. This value should also be compared with the values of the measurements in Section 10.4. If there are no changes in the on potentials and the protection current densities for the individual sections of the pipeline, it can be concluded that the off potential has not changed. The values can easily be compared using computers and represented in plots. If the protection current and potential distribution have changed, or in any case every 3 years, the off potentials as well as the on potentials should be measured. 

A complete solution for calculating the inductive coupling between a high-voltage line and metal conductors (e.g., pipelines) is possible with the help of series expansion [10,11] and computers. The following section provides advice on these calculations. 

To determine the pipeline potentials, the resultant induced field strengths have to be included in the equations in Section 23.3.2. Such calculations can be carried out with computers that allow detailed subdivision of the sections subject to interference. A high degree of accuracy is thus achieved because in the calculation with complex numbers, the phase angle will be exactly allowed for. Such calculations usually lead to lower field strengths than simplified calculations. Computer programs for these calculations are to be found in Ref. 16. 

Electric field measurement at the boundary of a metal container filled with charged material. Examples include pipelines and storage vessels. The electric field can be used to calculate charge density (3-5.1). Eield meters can also be lowered into containers such as silos to determine the local fields and polarities. Quantitative interpretation of the reading requires correction for field intensification and is sometimes accomplished using computer simulations. 

Goldberg, D.E. (1983) Computer-aided gas pipeline operation using genetic algorithms and rule learning (Doctoral dissertation. University of Michigan). Dissertation Abstracts International, 44(10), p. 3174B (University Microfilms No. 8402282). 

Because of their role as the link between producing and market areas, interstate natural gas pipelines play a crucial role in balancing supply and demand. To do so, the interstate pipelines continually monitor pipeline performance. These companies rely heavily on computers to gather, analyze and retain information on the performance of their pipelines, and to control the flow of gas in remote sections of the line. 

Interstate pipelines also use computer simulation programs to calculate pipeline capacity, pressures, horsepower, fuel and other physical characteristics and properties of their systems. Using this information and incorporating variables such as ambient temperatures, facility outages, and changes in market patterns, transmission companies can run daily studies to determine how much natural gas their systems will deliver under expected operating conditions. 

Another tool the interstates use to maintain their pipelines is a device known as an intelligent pig. Propelled through the pipeline with the gas stream, these devices, taking thousands of measurements with electronic sensors that can be analyzed later by computers, can inspect pipeline interior walls for corrosion or other defects and remove accumulated debris from a section of pipeline. Pipelines also use state-of-the-art coating and cathodic protection to battle corrosion. 

Gould, T. L., el. al., Engineering Methods and Computer Applications For Design and Operation, of Two-Phase Pipeline Systems, The University of Michigan, Amn Arbor, Mich., 1973. 

More recently, the Southern Gas Association s Gas Machinery Research Council and Pipeline and Compressor Research Council cooperated with Southwest Research Institute to develop a software package that enhances reciprocating compressor operation. Several major American and foreign compressor manufacturers (and some other interested companies) have cooperated with Southwest Research Institute or developed their own proprietary pulsation-reduction design computer programs. 

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