Analysis of Typical Fault-Tolerant Architectures using HARP

HARP (the Hybrid Automated Reliability Predictor) is a software package that implements advanced reliability modeling techniques. We present an overview of some of the problems that arise in modeling highly reliable fault-tolerant systems; the overview is loosely divided into model construction and model solution problems. We then describe the HARP approach to these difficulties, which is facilitated by a technique called behavioral decomposition. The bulk of this paper presents examples of the dependability evaluation of some typical fault-tolerant systems, including a local-area network, two well-known fault-tolerant computer systems (C.mmp and SIFT), and an example of a flight control system. HARP has been used to solve very large models. A system consisting of 20 components distributed among 7 stages produced a Markov chain with 24 533 states and over 335 000 transitions (without coverage). Depending on the system used to run this example, the run time took anywhere from 4 to 8 hours. HARP is undergoing beta testing at approximately 20 sites. It is written in standard FORTRAN 77, consists of nearly 30000 lines of code and comments, and has been tested under several operating systems. The graphics interface (written in C) runs on an IBM PC AT, and produces text files that can be used to solve the system on the PC (for very small systems), or can be uploaded to a larger machine. HARP is accompanied by an Introduction and Guide for Users. For information on obtaining a copy of HARP, contact one of the authors.     

Developmental aspects of the feeling of knowing.

Prior reports that feeling-of-knowing (FOK) accuracy increases through childhood and remains constant during adulthood are inconclusive because (a) they used absolute FOK judgments that can be contaminated by differences in the threshold for claiming to know, (b) they used measures of FOK accuracy that are not invariant across different degrees of recognition-test difficulty, and (c) they did not rule out the possibility that age-related differences in FOK accuracy may be caused by changes in the reliability of FOK judgments. We avoided these methodological problems in two studies by using relative FOK judgments, by computing Goodman-Kruskal gamma coefficients to assess FOK accuracy, and by assessing the test–retest reliability of the subjects' FOK judgments. We found that 6-year-olds had less reliable FOK judgments but greater FOK accuracy than 10-year-olds or 18-year-olds. Moreover, 18- and 70-year-olds had equally reliable FOK judgments and equivalent FOK accuracy. Possible reasons for the greater FOK accuracy of youngsters included their lower rate of commission errors and more frequent recognition of correct answers for their commissions. Implications are drawn for the study of metacognitive development. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Improved high resolution image processing of bright field electron micrographs: II. Experiment

The new methods of nonlinear image processing are applied to high resolution experimental micrographs of chlorinated copper phthalocyanine taken on the Kyoto 500 kV electron microscope. With these new methods of image processing the phase and amplitude of the specimen transmission function are reconstructed from a defocus series of conventional transmission electron micrographs (bright field). Strong scattering, partial coherence and statistical noise have been included. Both of these new methods are based on the MAP (maximum a posteriori) criterion generalized to include reconstruction from multiple input images. In a companion paper (the first part of this two-part report) the theory behind these methods was presented and in this paper it is tested on actual experimental micrographs. A significant increase in resolution has been obtained with computer image processing. The point-to-point resolution obtained here with computer image processing of 500 kV electron micrographs is of the order of 1.2–1.4 Å which represents a 30–50% increase in resolution.     

Conceptualizing the influence of social agents of behavior change: A meta-analysis of the effectiveness of HIV-prevention interventionists for different groups.

A meta-analysis of 166 HIV-prevention interventions tested theoretical predictions about the effects of experts, lay community members, and similar and dissimilar others, as agents of change. In general, expert interventionists produced greater behavior change than lay community members, and the demographic and behavioral similarity between the interventionist and the recipients facilitated behavioral change. Equally importantly, there were differences across groups in the efficacy of various sources, especially among populations of low status and/or power. These findings support the hypothesis that unempowered populations are more sensitive to characteristics of the interventionists who can facilitate access to various resources. In addition, they suggest the need to ensure the availability of health professionals from diverse demographic and behavioral backgrounds. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Data communications using ATM: architectures, protocols, andresource management

The introduction of ATM is being propelled by the need for fast data communications in public and private networks. What is needed is a clear picture of protocol architectures and traffic characteristics of the various applications to be supported both now and in the future. The authors discuss ATM network architectures with special focus on the support of connectionless LAN interconnection and show which benefits can be obtained from the introduction of a connectionless server in an ATM network. They outline issues related to the use of existing protocols when ATM networks are introduced and show which protocol complexities have to be handled by gateways and servers, again using the example of connectionless LAN interconnection. Having presented network and protocol architectures the issue of data communication in ATM, resource allocation, is treated     

Demands on cognitive processing: implications for verbalisation in complex work environments

Cognition, Technology & Work - Verbalisation (or talk-aloud protocols) has been used as a technique for knowledge elicitation in research for some time. It allows the researcher some degree of...     

Linalyl oleate as a frying oil autoxidation inhibitor

Linalyl oleate (LO), an interesterification product of linalyl acetate (LA) and methyl oleate catalyzed with sodium methoxide, was studied to determine its effectiveness in retarding oxidative changes in soybean oil heated continuously at 180±5°C for 32 h. The identity of LO was established by GC-MS and NMR. LO was tested at levels of 0.05 and 0.1% and compared with the more commonly used synthetic autoxidation inhibitor methyl silicone (MS) at levels of 5 and 10 ppm. FA changes and conjugated dienoic acid formation were monitored. First-order kinetic equations were used to model the decreases in linoleate (18∶2)/palmitate and linolenate (18∶3)/palmitate ratios. Plots of the data show an inflection point at ∼11 h. Oils with either level of MS and LO had lower reaction rate constants before the inflection points, and lower conjugated diene values and higher 18∶2 and 18∶3 percentages at the end of the 32-h heating period than did oil without additives and with LA. LO could replace methyl silicone in soybean oil during deep-fat frying but at levels about 100 times greater. [We propose to use the term “autoxidation inhibitor” for substances that inhibit autoxidation when added to fats and oils at low concentrations and whose mechanism of action may be unknown. Some may wish to call such substances “antioxidants” but others wish to reserve this term for substances that end free radical chains by hydrogen radical donation. Some refer to methyl silicone as a “polymerization inhibitor”, but this term suggests more about its mechanism of action than seems warranted.]     

Phospholipid fatty acid composition and stereospecific distribution of soybeans with a wide range of fatty acid composition

Phospholipid (PL) fatty acid composition and stereospecific distribution of 25 genetically modified soybean lines with a wide range of compositions were determined by gas chromatography and phospholipase A₂ hydrolysis. Pl contained an average of 55.3% phosphatidylcholine, 26.3% phosphatidylethanolamine, and 18.4% phosphatidylinositol. PL class proportions were affected by changes in overall fatty acid composition. PL fatty acid composition changed with oil fatty acid modification, especially for palmitate, stearate, and linolenate. Stereospecific analysis showed that saturated fatty acids were primarily located at the sn-1 position of all PL, and changes of the saturates in PL were largely reflected on this position. Oleate was distributed relatively equally between the sn-1 and sn-2 positions. Linoleate was much more concentrated on sn-2 than on sn-1 position for all PL. Linolenate was distributed relatively equally at low concentration but preferred sn-2 position at high concentration.     

Detergency studies at low solution concentrations

Summary Tests made with mixtures of Santomerse No. 1 or No. 3 with TSPP at 0.05% (in synthetic sea water) indicate optimum soil removal for combinations of 80% TSPP and 20% Santomerse. At this solution concentration TSPP alone removed more soil than either Santomerse product. Tests made in hard water at 0.075% solution concentration with Santomerse combined with various alkaline soap builders in 1:1 ratios of Santomerse No. 3 to anhydrous alkaline builders permitted arrangement of the alkalies in decreasing order of effectiveness as follows: TSP TSPP TSPP—Orthosilicate (1:1) TSPP—TSP (1:1) Orthosilicate and metasilicate Sodium carbonate Further tests at the same solution concentration were made with hydrous builders on an “as received” basis but with Santomerse No. 1 to builder ratios of 67:33 or 75:25. The order of efficiency of the builders was the same as for the previous tests, and there were negligible differences between the two ratios tested. Detergent testing of several of the alkaline soap builders indicated relatively high soil removal at low solution concentrations in comparison with Santomerse No. 1 and accounts for improved detergency of its mixtures with alkali. Burnt umber peptization values tend to corroborate detergent findings. This paper was presented at the Chicago fall meeting of the American Oil Chemists’ Society, October 25–27.