A Note on Heuristic Methods in Optimal System Reliability

Many optimization techniques have been used to solve redundancy allocation problems, most of which result in noninteger solutions. A few, including dynamic programming and integer programming, as well as a host of heuristic methods give integer solutions. This note critically reviews six promising heuristic approaches. The advantages and disadvantages of each of the approaches are discussed. An extended approach is presented which incorporates some of the ideas of the previous methods for solving a general non series-parallel system. The extended approach appears to be quite efficient and is general. The simplicity and efficiency of the approach will lend itself to solving large practical problems.     

Abstracts

Journal of the American Oil Chemists' Society -     

One dimensional polar mechanical and dielectric responses of the ferroelectric ceramic PZT 65/35 due to domain switching

The constitutive relations and rate laws proposed by Chen and Peercy[l] have been successfully implemented in describing the one dimensional polar mechanical and dielectric responses of the ferroelectric ceramic PZT 65/35 to a slowly varying cyclic electric field ($\text{period > 1 s}$). In particular, we are interested in the consequences of domain switching due to the applied field and the results associated with the butterfly and hysteresis loops. An extensive experimental program has been carried out to obtain simultaneous time resolved measurements of the mechanical strain, the electric displacement and the applied field. The excellent agreement between numerical and experimental results indicates that we are beginning to gain considerable insight into the fundamentals of domain switching.     

OSA uniform color scale samples: A unique set

The Optical Society of America, in early 1977, published a set of uniformly scaled coor samples based on specifications developed after long years of study by its Committee on Uniform Color Scales. The model for arranging and specifying the samples is based on an octahedral unit which consists of a cluster of 12 colors equally different from a central color and from each of its nearest neighbors. This space lattice, extended to accommodate all samples that can be produced within the gamut of present-day colorants, is described, together with the adopted system of notation. The lattice provides three sets of square grids and four sets of triangular grids that correspond to the seven pairs of parallel faces of a cuboctahedron. Horizontal, vertical, and oblique cleavage planes through the lattice are described and illustrated. The OSA-UCS set consists of 558 samples: 424 represent a regular 2-unit sampling of OSA-UCS committee space; 134 additional samples are provided in the much used, near-neutral, central-lightness region of color space. The set is unique because each sample in the regular set is represented in six different uniform color scales. These appear as linear arrays that pass in six different directions through each sample. The samples are intended for use by artists and designers as well as by scientists. With a relatively small number of samples, material is provided for constructing color scales and charts with colors uniformly spaced in six directions in any chosen part of color space. The OSA-UCS set provides a “storehouse of color-contrast information in efficient form.” It provides useful color research material such as has never before been available.     

Evaluation of two commercial lateral-flow test kits for detection of animal proteins in animal feed

Performance characteristics were evaluated for two lateral-flow test kits, Reveal for Ruminant in Feed (Neogen Corporation) and FeedChek (Strategic Diagnostics Inc.), designed to detect ruminant or terrestrial animal proteins in feeds. The stringent acceptance criteria used were developed by the Center for Veterinary Medicine Office of Research to identify test kits with comparable selectivity and sensitivity to microscopy and PCR assay, the analytical methods used by the U.S. Food and Drug Administration (FDA). Guidelines were developed for evaluating the selectivity, sensitivity, ruggedness, and specificity of these kits. These guidelines further stated that ruggedness and specificity testing would be performed only after a test passed both the selectivity and sensitivity assessments. Acceptance criteria for determining success were developed using a statistical approach requiring 90% probability of achieving the correct response, within a 95% confidence interval. A minimum detection level of 0.1% bovine meat and bone meal, consistent with the sensitivity of the methods used by the FDA, was required. Selectivity was assessed by testing 60 dairy feed samples that contained no added animal proteins; sensitivity was determined by evaluating 60 samples (per level of fortification) of the same feed that contained 0.025, 0.05, 0.1, 0.25, 0.5, 1, or 2% bovine meat and bone meal. The Reveal test passed the selectivity assessment but failed the sensitivity assessment, detecting only samples fortified at the 2% level and then only 17 to 33% of those samples, when read according to the label directions. The FeedChek test passed the sensitivity assessment but failed the selectivity assessment, with rates for false-positive results ranging from 34 to 38%, depending on the user. The sensitivity of the Reveal test was affected by the concentration of trace minerals present in the feed; concentrations toward the high end of the normal range prevented the detection of true positive feed samples containing bovine meat and bone meal. Better sensitivity assessments were obtained when lamb meal was used either alone or in combination with bovine meat and bone meal. The FeedChek test was not affected by the concentration of trace minerals or by the type of animal meal used. These results indicate that neither of the two tests is adequate for routine regulatory use.     

Evaluation of laboratory methods for the study of driver behavior: Relations between simulator and street performance.

Road performance data on 304 taxi drivers were obtained by pairs of trained observers using behavioral checklists. Drivers did not know they were being observed. 66% of the drivers then agreed to participate in the laboratory study, which involved performance on 2 different driving simulators and on 4 perceptual–motor tests. Officially recorded accidents and violations over a 5-yr period were obtained for each S for comparison with performance data. Results show that few of the scores from the simulators or tests were significantly correlated with road performance; however, a number of significant relations were found between perceptual–motor test performance and simulator performance. Although these correlations were not high, they tended to be more significant than those between performance on the 2 simulators. Age was negatively correlated with simulator performance. Relations between all performance measures and officially recorded accident and violation data were low. Some significant predictors of certain classes of violations were achieved from road performance measures obtained in the study. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conviction proneness and the authoritarian juror: Inability to disregard information or attitudinal bias?

In Exp I, 120 undergraduate mock jurors completed the Mitchell-Byrne Authoritarianism Scale and rendered verdicts and gave probability of guilt estimates for trial evidence involving 2 levels of admissibility of wiretap evidence (inadmissible and admissible) and 2 levels of incrimination value of wiretap evidence (exonerating and incriminating). Results support a pro- and antidefendant bias rather than a differential cognitive ability model. Exp II, involving 160 undergraduates, determined whether repeating and emphasizing judge's instructions to jurors to disregard inadmissible evidence would reduce authoritarians' tendency to incorporate it. Authoritarian Ss were more likely to convict, especially in the presence of incriminating evidence, regardless of its admissibility and judge's emphasis. The 2 studies suggest that authoritarians are characterized by an antidefendant bias that influences their responses to trial evidence and that is not easily overcome by emphasizing the judge's instructions. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Token economies and unpredictable reward in family settings: A descriptive report.

202 graduate students were trained as behavior assistants, and they in turn trained and supervised indigenous mediators in projects with 84 volunteer families under a quadratic model composed of instructor, assistant instructors, behavior assistants, and mediators. The techniques combined unpredictable reward, stimulus variability, and intermittent reinforcement with token economy procedures. Greater positive effects were associated with larger families, younger children, availability of a greater variety of back-up rewards in exchange for tokens, longer duration of contact with the family, and provision of a training manual to behavior assistants. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of a role conflict questionnaire for women: Some preliminary findings.

Describes a 252-item questionnaire which assesses 8 potential role-conflict areas: Time Management, Relations with Husband, Household Management, Financial, Child Care, Expectations for Self, Expectations of Others, and Guilt. Preliminary data from 242 female respondents suggest that the greatest role conflict for women today involves their self-image and that those areas which deal directly with self-concept are more stressful. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Determining Component Reliability and Redundancy for Optimum System Reliability

The usual constrained reliability optimization problem is extended to include determining the optimal level of component reliability and the number of redundancies in each stage. With cost, weight, and volume constraints, the problem is one in which the component reliability is a variable, and the optimal trade-off between adding components and improving individual component reliability is determined. This is a mixed integer nonlinear programming problem in which the system reliability is to be maximized as a function of component reliability level and the number of components used at each stage. The model is illustrated with three general non linear constraints imposed on the system. The Hooke and Jeeves pattern search technique in combination with the heuristic approach by Aggarwal et al, is used to solve the problem. The Hooke and Jeeves pattern search technique is a sequential search routine for maximizing the system reliability, RS (R, X). The argument in the Hooke and Jeeves pattern search is the component reliability, R, which is varied according to exploratory moves and pattern moves until the maximum of RS (R, X) is obtained. The heuristic approach is applied to each value of the component reliability, R, to obtain the optimal number of redundancies, X, which maximizes RS (R, X) for the stated R.