Showing papers by "University of Windsor published in 1991"

Feeder reconfiguration for loss reduction: an application of distribution automation

Abstract: The authors present a comparison of various methods applied to feeder reconfiguration for loss minimization. A new linear programming method using transportation techniques and a new heuristic search method are proposed for comparison with a previously developed heuristic technique which was based on an optimal load flow analysis. The methods are compared on simulations of both a small feeder distribution system, and a larger system based on a model of a public utility commission 44 kV distribution system. This study indicates that linear programming, in the form of transportation algorithms, is not suitable for real-time application to feeder reconfiguration, whereas heuristic approaches, although not optimal, can provide substantial savings if properly formulated and are suitable for real-time implementation. >

Hydrophobic behavior of insulators coated with RTV silicone rubber

Abstract: Room temperature vulcanizing (RTV) silicone rubber coatings are applied to electrical insulators to improve their subsequent insulation strength, particularly under wet conditions. Under prolonged wetting the hydrophobicity of the coating is reduced temporarily and the insulator protection is lost. After a dry period, a recovery of the hydrophobicity takes place. To investigate this phenomenon, the surface was subjected to various wetting conditions with and without electrical stress. Measurements of the contact and the sliding angles were used to determine the state of the surface. Using water, the surface free energy of the RTV was calculated from the contact angle measurements as a function of time of exposing the surface to salt-fog. The surface free energies due to London dispersion and hydrogen bonding forces on the surface of RTV coatings were calculated from the contact angle measurements using both water and methylene iodide. Good agreement was obtained with the literature value for a virgin RTV surface. The chemical changes of the surface are shown to be responsible for the loss of hydrophobicity. >

Relationships between denitrification, microbial biomass and indigenous soil properties

Abstract: The relationships between denitrification, soil microbial biomass and selected soil properties were investigated in 13 soils which varied in physical and chemical properties. It was hypothesized that estimates of biomass C may be directly related to the background (unamended) denitrification rates. Denitrification potential (with C and NO−3 amendments) was also compared to biomass C and the indigenous soil properties. The background and potential denitrification rates were measured in these soils during 75 h of anacrobiosis. Background denitrification was highly correlated with biomass C. organic C content and moisture content at field capacity (−33 kPa). Soil organic C was also highly correlated with microbial biomass C. Nitrate was not limiting for most soils as in all but two soils the residual NO−3 content following incubation exceeded 10mg N kg−1. Hence. NO−3 concentration was not strongly correlated with the background denitrification rate. The denitrification potential was 5 times greater than background denitrification. In our study, C was the factor limiting denitrification. Further, microbial biomass appeared to be a sensitive indicator of both soil C content and background denitrification. There was no significant relationship between any of the other soil chemical and physical properties measured and the denitrification potential.

Residential real estate brokerage as a principal-agent problem

Abstract: We analyze the terms of the brokerage contract between a house seller and his agent, using the established literature on the principal-agent problem. Considering the influence of moral hazard and adverse selection, we predict a number of features of the contract. Many of these features are not present in observed contracts. To account for this discrepancy, we discuss certain aspects of the real estate market which are not included in the standard principal-agent model but may explain the difference. Standard principal-agent theory neglects important contract design considerations, namely robustness and costs of complexity. In general, the commission contract performs poorly by failing to allocate risk efficiently or to provide agent incentives. It favors established agents and precludes contractual diversity. Finally, we contrast the brokerage contract for real estate with the dealership contract for used cars, but find no compelling answer as to why there are few used house dealers.

Suppression mechanism of leakage current on RTV coated porcelain and silicone rubber insulators

Abstract: The results of a study on the suppression of leakage current on room temperature vulcanizing (RTV) silicone rubber coated porcelain suspension insulators in a salt-fog chamber are reported. A comparative study of the performance of coatings on different parts of suspension insulators with RTV is reported. The results of attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy are reported. On the basis of these results, a suppression mechanism for leakage current is suggested. A mechanism for the suppression of leakage current on RTV coated porcelain and silicone rubber insulators dealing with the temporary loss of hydrophobicity and its return is suggested. >

Ribosomal DNA Variation in Daphnia pulex

Abstract: Variation in the ribosomal DNA (rDNA) gene family was surveyed in five cyclically parthenogenetic populations of Daphnia pulex from central Illinois and in obligately parthenogenetic clones from Illinois and Ontario. A total of 37 distinct rDNA repeat types were identified on the basis of restriction-site and repeat-length polymorphism in a sample of 90 isolates. Repeat-type diversity was high within cyclic populations; however, individuals possessed only a small subset of the repeat-type variation present in each population. The distribution of repeat types within and among individuals suggested that new variants spread within rDNA arrays much faster than arrays carrying the variants spread within populations. This observation is contrary to a model developed by Ohta and Dover for strictly sexual organisms. Previous surveys of isozyme and mitochondrial DNA variation in these populations showed that gene flow among them is limited. Hierarchical analysis of rDNA restriction-site variation was consistent with this observation and showed that genetic divergence accumulates between populations for rDNA almost as rapidly as it does for single-copy nuclear genes (isozymes). Analysis of rDNA variation in obligately parthenogenetic clones provided evidence that both intraand interchromosomal exchanges occur between rDNA arrays in the absence of meiosis. Moreover, individuals reproducing by obligate parthenogenesis possessed fewer rDNA repeat types, on average, than did individuals from cyclic populations, suggesting that there is a net loss of rDNA repeat-type variability within obligately clonal lineages over time. Preliminary analyses of two additional species, D. pulicaria and D. obtusa, revealed several restriction-site polymorphisms that were found in more than one of the three species. The existence of such shared polymorphisms advises caution in the use of multigene-family variation to infer phylogenies among species when levels of intraspecific variation have not been assessed.

Coping with stress in families with children who have mental retardation : an evaluation of the double ABCX model

Abstract: The Double ABCX model of family stress and coping was evaluated using path analysis to determine the causal ordering of variables in 86 families raising children with mental retardation The families' use of resources (B) and their perception of the stressor event (C) were examined to determine their relation to the stressor (A) and the stress experiences (X) The causal ordering of the model suggested an ACBX relation rather than an ABCX relation Results were discussed in terms of the consistency of these findings with two models of clinical intervention

A unified treatment of the non-relativistic and relativistic hydrogen atom: III. The reduced Green functions

Abstract: For pt.I see ibid p.79-94. This is the second in a series of three papers in which it is shown how the radial part of non-relativistic and relativistic hydrogenic bound-state calculations involving the Green functions can be presented in a unified manner. In this paper the nonrelativistic Green function is examined in detail; new functional forms are presented and a clear mathematical progression is shown to link these and most other known forms. A linear transformation of the four radial parts of the relativistic Green function is given which allows for the presentation of this function as a simple generalization of the non-relativistic Green function. Thus, many properties of the non-relativistic Green function are shown to have simple relativistic generalizations. In particular, new recursion relations of the radial parts of both the non-relativistic and relativistic Green functions are presented, along with new expressions for the double Laplace transforms and recursion relations between the radial matrix elements. A novel proof of the Sturmian form of the radial Green functions is given in an appendix.

Genetic consequences of passive dispersal in pond‐dwelling copepods

Abstract: Pond-dwelling copepods have colonized habitats throughout North America after glaciers have receded. Most species are passively transported via resting eggs into new habitats. Colonists originating in a glacial refugium could lose some of the ancestral genetic diversity when they establish new populations and the attenuation may be substantial in populations far removed from the refugium due to multiple founder events. Genetic variation was measured in Heterocope septentrionalis from 27 populations at arctic sites near potential refugia and those more recently deglaciated to determine the effects of postglacial dispersal on patterns of genetic relatedness and diversity. Some populations were more distant, genetically, from others within the same site than those from other more distant sites. Eleven polymorphic enzyme loci were significantly more variable (F [1,294 df] = 5.94, P < 0.025) among individuals from populations near the Alaskan refuge than those at the eastern limit of their distribution. Because populations are typically extremely large and stable this loss of genetic diversity is attributed primarily to repeated founder events during colonization. This result suggests profound genetic changes may occur on a continental scale in passively dispersed copepods due to founder events alone. Their potential for divergence and speciation is greater than currently recognized.

Neuropsychological functioning of hydrocephalic children

Abstract: A group of 30 five- to eight-year-old hydrocephalic children was administered a comprehensive battery of neuropsychological tests. As a group, they displayed a pattern of lower PIQ than VIQ. Their performance was within the average range of many neuropsychological tests, but they performed poorly on some measures of complex visuospatial functioning. It is concluded that hydrocephalic children at this early age exhibit relatively reduced efficiency in processing complex or novel nonverbal stimuli. The possibility of dysfunction in the posterior regions of the right cerebral hemisphere is discussed.

Syndrome of nonverbal learning disabilities: Age differences in neuropsychological, academic, and socioemotional functioning

Abstract: Previous research has suggested that changes in the manifestations of the nonverbal learning disabilities syndrome (NLD) occur over the lifespan and that they do so in a manner that is consistent with the tenets of the NLD model (Rourke, 1989). Although the model would predict that age-related changes would also be evident within the childhood years, no study has yet examined this possibility. Based on the tenets of the model, specific predictions were formulated regarding developmental changes in the features of the NLD syndrome that would be expected to occur across the middle childhood and early adolescent years. The pattern of neurocognitive and socioemotional changes observed within the context of the cross-sectional data provided strong support for the predictions. Due to methodological limitations, no firm conclusions regarding the developmental manifestations of the NLD syndrome could be derived from the results of the longitudinal study. At most, these results suggested that some improvements in areas of neurocognitive deficiency may occur with the implementation of an appropriate remedial intervention program.

Quantum defects and the 1/n dependence of Rydberg energies : second-order polarization effects

Abstract: The principal result of this paper is a general expression for the second-order dipole polarization energy of a Rydberg electron resulting from the term -${\mathrm{\ensuremath{\alpha}}}_{1}$/${\mathit{r}}^{4}$ in the asymptotic potential, where ${\mathrm{\ensuremath{\alpha}}}_{1}$ is the core polarizability. It is shown that the second-order term contributes even as well as odd powers of 1/n in a 1/n expansion of the energies for Rydberg states. The results are used to extend the interpretation of the terms in a quantum-defect expansion. It is shown that the Ritz expansion for the quantum defect, which contains only even inverse powers of the effective quantum number ${\mathit{n}}^{\mathrm{*}}$, provides a powerful method for deducing the even-order terms in the second-order energy. Least-squares fits to high-precision variational calculations for the Rydberg states of helium, using 1/n and quantum-defect expansions, are presented. The results reveal well-defined ``Ritz defects,'' which represent the degree to which the data cannot be represented by a Ritz expansion for the quantum defect. The implications for extrapolations of quantum defects are discussed. Finally, it is shown that the second-order polarization energy plays a significant role in understanding the quantum defects for the alkali metals.

Purification of glucose-inducible outer membrane protein OprB of Pseudomonas putida and reconstitution of glucose-specific pores.

Abstract: A 43,000 molecular-weight, glucose-inducible, organic acid-repressible protein (OprB) was identified in the outer membrane of Pseudomonas putida. OprB was surface expressed in whole cells, had a high beta-sheet content, and was heat modifiable, as demonstrated by 125I-labeling, circular dichroism spectroscopy, and mobility on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. OprB was extracted from outer membrane preparations by using 2% Lubrol PX with 10 mM EDTA and purified by DEAE-Sephacel ion exchange chromatography following ammonium sulfate precipitation. Reconstitution experiments with black lipid membranes showed that OprB formed small, cation-selective pores which bound glucose (KS = 110 mM) and other carbohydrates. However, the binding site of OprB appeared to be distinct from that of the maltodextrin-specific porin LamB from Escherichia coli.

Porcelain insulator maintenance with RTV silicone rubber coatings

Abstract: The selection, application and performance of RTV (room-temperature vulcanizing) coatings for the maintenance of porcelain insulators are examined. The ability of coating systems to suppress leakage current, thereby eliminating the cause of wood pole fires and flashover, is discussed. The conditions associated with the temporary loss of coating hydrophobicity and its return are also discussed. Coating life expectancy is considered in terms of the pollution conditions, the frequency of maintenance cleaning, and the formulation of the RTV coating system. It is concluded that RTV coating systems perform by virtue of the fact that they are able to suppress leakage current. This enables insulation systems to attain increased flashover performance of about 30% over uncoated insulations. Under severe conditions of pollution, the effectiveness of the coating systems is temporarily lost, showing only some improvement over uncoated insulation. However, after maintenance cleaning, the coating systems return to their initial state with only a slight loss in their ability to suppress leakage. >

Removal of oil from emulsions using electrocoagulation

Abstract: An attempt has been made to remove oil from synthetic oily wastes using electrochemical treatment. The standard jar test apparatus was used with ferric sulfate as coagulant. The effects of alternating and direct current were evaluated in terms of coagulant aid in the oil removal process. The removal efficiency was found to be as high as 96% using 150 mg/L of ferric sulphate and a direct current of 100 V applied for 16 minutes. The polarity of the electrodes and the electric field gradient played an important role in the destabilization of oil emulsion.

Theoretical and experimental design of LIM in automated manufacturing systems

Abstract: A theoretical and experimental study was conducted to assess the feasibility of employing linear induction motors (LIMs) for automated manufacturing systems as the drive for fully flexible material handling systems (MHSs). Two double-sided linear induction motors with 17 and 9 A starting currents were designed and built to operate with two AC adjustable-frequency motor drives. The motors were intended for use as carts to transfer parts between the three cells in a physical simulator consisting of a load/unload cell, a manufacturing cell, and a turning cell. Experience with a working model confirms that the use of LIMs shows substantial promise for achieving cost and productivity gains in a wide variety of manufacturing systems. The physical simulator is used to demonstrate the advantages of the LIM system over the existing MHS. >

A fuzzy approach to multi-objective routing problem with applications to process planning in manufacturing systems

Abstract: In this paper a method is developed for the selection of an efficient path in a fuzzy multi-objective network. The application of the methodology developed is illustrated by a process plan selection problem in a manufacturing environment.

The impact of domestication on the genetic variability in the orange carrot, cultivated Daucus carota ssp. sativus and the genetic homogeneity of various cultivars.

Abstract: Isozyme analysis of wild and domesticated accessions indicated that domestication of the cultivated carrot Daucus carota ssp. sativus resulted in an insignificant reduction of all genetic variability and genetic distance estimates. Although they are less variable genetically, cultivated forms maintain a high proportion of observed heterozygosity. Relative to the overall genetic variability of the species, samples from four common cultivars ‘Red Cored Chantenay’, ‘Scarlet Nantes’, ‘Danvers Half Long’ and ‘A Plus’ demonstrated a high degree of genetic similarity. This is attributed to the recent development of orange cultivars and the limited gene pool utilized in their development.

Shake-and-bake algorithms for generating uniform points on the boundary of bounded polyhedra

Abstract: We present a class of shake-and-bake algorithms for generating (asymptotically) uniform points on the boundary of full-dimensional bounded polyhedra. We also report results of simulations for some elementary test problems.

Artificial testing and evaluation of RTV coatings in a salt-fog chamber

Abstract: The electrical performance of room-temperature vulcanizing (RTV) silicone rubber insulator coatings under accelerated aging in a salt-fog chamber is reported. The RTV coatings were evaluated in fog produced from saline water at 900 mu S/cm conductivity. The effect of the contaminants deposited during dry band arcing was evaluated with respect to the performance of RTV coatings. The increase of the leakage current and the corresponding decrease of the contact angle on the surface of the coating are shown to be related to contaminants on the RTV-coated surfaces. Five cleaning methods to remove the contaminants from the coated surface are examined, using leakage current and contact angle measurement as indicators of their comparative effectiveness. >

Number Theoretic Techniques in Digital Signal Processing

Abstract: Publisher Summary This chapter discusses the application of number theory to the intensive computations required in many digital signal processing (DSP) systems. DSP system is involved with the processing of streams of data that are indeterminately long. The requirement of the system is to produce processed output data at the same rate that the input data is entering the processor. This is referred to as “real-time processing.” Often the arithmetic manipulations are simple in form, but the numbers of operations that have to be computed every second can be enormous. The chapter focuses on two areas: first, the use of finite ring or field operations for computing ordinary integer computations for high-speed signal processing; second, the use of algorithms defined over finite rings or fields in which not only the arithmetic is performed over such finite structures, but also the properties of the algorithm depend on the properties of the finite field/ring over which the algorithm is defined. This is an important differentiation and the sole concern in the chapter is to examine arithmetic and general computations over finite mathematical systems.