Negative Effects Of Interference Research Articles

Inverter drive signal processing via DFT and EKF

Two algorithms for estimating both the positive sequence fundamental symmetrical component and the frequency of the voltage system at the terminals of an inverter-fed three-phase motor are presented in this paper. The first one is based on the discrete Fourier transform of the instantaneous symmetrical component of the positive sequence and yields off-line estimates. The accuracy is improved by the application of flat-top windows which reduce leakage and negative interference effects. This algorithm can be used for microcomputer based tests and diagnostics of inverter drives. The second one is based on the extended Kalman filtering of the instantaneous symmetrical component of the positive sequence and gives on-line unbiased estimates. The harmonic components are rejected because they are treated as measurement errors. The EKF algorithm may lead to the development and implementation of adaptive control techniques. Several results obtained from these algorithms are reported and compared in this paper.

A Parametric Study of the Effects of Coal Seam Properties on Gas Drainage Efficiency

Summary A parametric study is conducted to investigate the effects of reservoir properties on gas drainage efficiency. It is found that when a coal seam is opened to production, the gas desorption and production rates increase to a maximum value and then decline. The magnitude of the early desorption peak was found to be a function of (1) the ability of the micropore matrix to supply gas to the macropore system, and (2) the coal seam's conductivity to water. The desorbing gas was observed to create a localized, high-gas-saturation bank in the area enclosed by the pressure transient. The gas bank provided an internal pressure maintenance to the reservoir, while it decreased the relative permeability to brine. This created a competing effect with respect to water production. Because water removal strongly influences the pressure decline and, consequently, the desorption rate, a unique production mechanism was observed. The study explored the interference effects on gas and water flow in multiple-well systems. It was found that the pressure drawdown caused by the multiple wells enhanced the desorption of gas into the macropore system and caused a positive interference effect on the gas flow rate. The water rate, however, encountered the more conventional negative interference effect.

ON THE TOPOLOGY OF THE GENETIC FINE STRUCTURE

From the classical researches of Morgan and his school [1], the chromosome is known as a linear arrangement of hereditary elements, the genes. These elements must have an internal structure of their own. At this finer level, within the gene the question arises again: what is the arrangement of the sub-elements? Specifically, are they linked together in a linear order analogous to the higher level of integration of the genes in the chromosome? Until recently, the sensitivity of genetic analysis has been insufficient to answer this question. Mapping of a genetic structure is done by observing the recombination of its parts, and recombination involving parts of the structure that are very close together is a rare event. Observation of such rare events requires very many offspring and a selective trick for detecting the few individuals in which the event is recorded. It is for this reason that microorganism are the material of choice for studies of genetic fine structure, and have made it feasible to extend the fineness of genetic mapping by orders of magnitude. In favorable systems, the attainable resolution reaches the level of the molecular subunits of the hereditary material. and experimental testing of the linear arrangement of the finest structural details is therefore possible. A number of cases have been investigated on this level [2]. As a rule, closely linked mutations affecting the same characteristic can be seriated in an unambiguous way, suggesting a linear model. However, the (i.e., recombination frequencies) between mutations are not always strictly additive, and certain complexities (negative interference effects [3,4]) make quantitative analysis difficult. As pointed out by Muller [5] in regard to similar difficulties encountered in mapping on the chromosomal level, strict additivity of should not be taken as the criterion for the linear character of an array. A crucial examination of the question should be made from the point of view of topology, since it is a matter of how the parts of the structure are connected to each other, rather than of the distances between them. Experiments to explore the topology should ask qualitative questions (e.g., do two parts of the structure touch each other or not?) rather than quantitative ones (how far apart are they?). In what follows, such an investigation is attempted for a small portion of the genetic structure of a virus, the rII region of phage T4. Using only qualitative tests, an examination is made of the topology of this structure at the molecular level.