Identifying the criterion spontaneously minimized during the take-off phase of a sub-maximal long jump through optimal synthesis

Optimal synthesis of human movement or the prediction of the kinematics of a new movement require not only that the multi-body system be modeled but also that a performance criterion is specified. For sub-maximal movements the selection of a suitable performance criterion, able to generate realistic dynamic behavior is difficult. A two-dimensional simulation model of the take-off phase of a sub-maximal long jump was developed to study the effect of criterion choice on the realism of simulated movements. A parametric optimization technique was employed to obtain solutions to the constrained equations of motion. Seven different criteria were evaluated, by comparing simulated movements with an actual performance, to identify the criterion which most closely approximated that spontaneously minimized by the athlete. Synthesis of the take-off phase of a sub-maximal long jump was found to be sensitive to the chosen criterion, with a criterion based on minimizing joint intersegmental forces found to perform well.     

A URI-based approach for addressing fragments of media resources on the Web

To make media resources a prime citizen on the Web, we have to go beyond simply replicating digital media files. The Web is based on hyperlinks between Web resources, and that includes hyperlinking out of resources (e.g., from a word or an image within a Web page) as well as hyperlinking into resources (e.g., fragment URIs into Web pages). To turn video and audio into hypervideo and hyperaudio, we need to enable hyperlinking into and out of them. The W3C Media Fragments Working Group is taking on the challenge to further embrace W3C??s mission to lead the World Wide Web to its full potential by developing a Media Fragment protocol and guidelines that ensure the long-term growth of the Web. The major contribution of this paper is the introduction of Media Fragments as a media-format independent, standard means of addressing media resources using URIs. Moreover, we explain how the HTTP protocol can be used and extended to serve Media Fragments and what the impact is for current Web-enabled media formats.     

An exploratory study of the impact of antipatterns on class change- and fault-proneness

Antipatterns are poor design choices that are conjectured to make object-oriented systems harder to maintain. We investigate the impact of antipatterns on classes in object-oriented systems by studying the relation between the presence of antipatterns and the change- and fault-proneness of the classes. We detect 13 antipatterns in 54 releases of ArgoUML, Eclipse, Mylyn, and Rhino, and analyse (1) to what extent classes participating in antipatterns have higher odds to change or to be subject to fault-fixing than other classes, (2) to what extent these odds (if higher) are due to the sizes of the classes or to the presence of antipatterns, and (3) what kinds of changes affect classes participating in antipatterns. We show that, in almost all releases of the four systems, classes participating in antipatterns are more change-and fault-prone than others. We also show that size alone cannot explain the higher odds of classes with antipatterns to underwent a (fault-fixing) change than other classes. Finally, we show that structural changes affect more classes with antipatterns than others. We provide qualitative explanations of the increase of change- and fault-proneness in classes participating in antipatterns using release notes and bug reports. The obtained results justify a posteriori previous work on the specification and detection of antipatterns and could help to better focus quality assurance and testing activities.     

Notch sensitivity of thermoset and thermoplastic laminates loaded in tension

Inplane tensile fracture of unnotched and notched thermoset graphite-epoxy and thermoplastic graphite-PEEK composite laminates is examined. Both fibre-dominated quasi-isotropic and matrix dominated ±45 angle-ply layups were investigated.Classical lamination theory predictions of elastic and strength properties of unnotched specimens are compared with experiments. Several notched geometries, i.e. centre-notched, double-edge notched and open-hole specimens subjected to tensile loading to fracture were examined. The notched strength of the quasi-isotropic laminates was analysed by a damage zone model, where damage around the notch is represented by an equivalent crack with cohesive force acting between the crack surfaces.Good agreement between experimental and calculated strength was observed for the graphite-epoxy laminates which failed in a collinear manner. For the graphite-PEEK laminates discrepancies between predicted and experimental strength are related to observed deviations from collinear crack growth. The angle-ply graphite-PEEK laminates showed larger notch sensitivity than the corresponding graphite-epoxy, probably due to less degree of stress relieving damage formation around the notch.     

Bewertung von Ausfallvarianten für die Netzsicherheitsanalyse

Übersicht Für die On-line-Netzsicherheitsüberwachung wird eine adaptive Güteindex-Prozedur zur dynamischen Erstellung von Ausfallisten vorgestellt. Mit den bisher bekannten Güteindex-Verfahren konnten aufgrund des Verdeckungseffektes meist nicht alle tatsächlich kritischen Varianten als solche erkannt und deklariert werden. In der neuen Prozedur werden die Ergebnisse der Ausfallsimulationsrechnung der unmittelbaren Systemvergangenheit für die Erstellung der aktuellen Ausfalliste verwendet. Mit einer linearen Korrekturfunktion werden dabei die verdeckungseffektbehaftetenG ₂-Werte des Standard-Güteindex-Verfahrens in verbesserte Werte transformiert.

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Contingency assessment for power system security analysis

Contents An adaptive procedure for dynamic contingency selection in the on-line security assessment is proposed. Because of the masking effect in conventional performance index algorithms a possibly large number of critical contingencies is misclassified. In the new procedure results of former security checks are used for evaluating the current contingency list. A linear corrective function is applied to transform the standard second orderG-values into improved values.

     

Electrical properties of monoazacrown ether-substituted phthalocyanines

D.c. conductivities of polycrystalline monoazacrown ether-substituted phthalocyanines (M=2H, Ni, Zn, Pb, Cu) and diphthalocyanine (M=Lu) are measured as Au-MPc-Au sandwiches to be of the order 10^–10–10^–12 S m^–1. Chemical doping with oxidants (e.g. NOBF₄) and enhancing the stacking of planar phthalocyanine moieties through the formation of alkali metal adducts with sodium and potassium ions leads to increase in conductivity of the order 10¹–10². The low conductivity and the diamagneticity of the bis(phthalocyaninato)-lutetium can be ascribed to the lack of radical nature in LuH(Pc)₂. For the a.c. conductivities, lead and lutetium complexes form a group with higher conductivities and the rest show lower conductivity. The conduction activation energies calculated from Arrhenius plots exhibit the lowest value (0.40 eV) for the lutetium compound.Part of this work was presented at NATO-ASI on Semiconductor Materials and Processing Technologies, Erice, Sicily, 1–13 July 1991.     

A new microsecond pulse-heating system to investigate thermophysical properties of solid and liquid metals

A new discharge system for resistive self-heating has been constructed for the measurement of accurate thermophysical properties. A constant-current pulse is used to heat metals over a time interval of 50 to 100 s, reaching temperatures up to the boiling point. New techniques have been developed to obtain sound speeds in the pulse-heated sample, emissivities, and vapor pressure. A new pyrometer allows the extension of the measured temperature range down to the melting point of copper.     

The effect of appraisers in estimating metabolic rate with the Edholm scale

A study was made of the appraisers' effect on the estimation of metabolic rate with the Edholm scale and a table of the ISO 7243 heat stress standard. The appraisers, five experienced and five inexperienced persons, estimated the metabolic rate of three different work tasks from videotapes. Analysis of variance indicated significant ( [Formula: see text] ) differences in the appraisers' recordings of the activities. The appraisers were grouped according to the similarity of the estimated values they gave. The groups thus contained both experienced and inexperienced appraisers, and it was not possible to classify the appraisers into experienced and inexperienced groups according to their earlier experience. The metabolic rates according to the Edholm scale were higher than according to the ISO 7243 table. The differences in metabolic rates given by the individual observers varied from 38 to 118 W/m(2). The variations in the estimation of metabolic rates were greater when the Edholm scale was used. This variation caused considerable variation also in the predicted mean vote, PMV index. It is recommended that the appraisers be selected carefully, because it is not possible to know whether a randomly selected appraiser is an 'average' or an 'extreme' appraiser without a test. Before conducting extensive field surveys where several appraisers estimate the metabolic rates, it would be useful to arrange training in order to calibrate the levels of the Edholm scale as well as ISO method among the appraisers because training clearly unified the estimation.     

High-resolution photoelastic pressure sensor using low-birefringence fiber

The effect of birefringence induced in a single-mode fiber by a lateral force has been applied to measure the absolute value of force or pressure with high resolution. A sensor configuration with an extended detecting surface has been investigated by means of calibrated weights. The sensor is sensitive to an incremental force of 2 x 10(-3) N, independently of the length of the fiber. The maximum force applied was 10 N/m of fiber length.