3,043 research outputs found

    Robert G. Dixon, Jr.—Teacher, Colleague, and Friend

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    A Tribute to Arno Cumming Becht: Introduction

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    Judge Training: Judging Individual Events, Judging Parliamentary Debate, Judging Lincoln-Douglas Debate

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    This article provides a tournament di-rector with a self-contained judge training packet that can be copied and handed to judges or modified with your tournament specific information. This article ex-plains the mechanics of judging Individual Events, Parliamentary Debate, and Lincoln-Douglas Debate by providing lay judges with help in terms of how to express their thoughts about the event they just watched. The following material does not, nor should any judge training, mandate what is good or bad in a perfor-mance, but rather describes how to provide valuable feedback based on their ed-ucated reactions to the performances

    Depth-dependent target strengths of gadoids by the boundary-element method

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    Author Posting. © Acoustical Society of America, 2003. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 114 (2003): 3136-3146, doi:10.1121/1.1619982.The depth dependence of fish target strength has mostly eluded experimental investigation because of the need to distinguish it from depth-dependent behavioral effects, which may change the orientation distribution. The boundary-element method (BEM) offers an avenue of approach. Based on detailed morphometric data on 15 gadoid swimbladders, the BEM has been exercised to determine how the orientation dependence of target strength changes with pressure under the assumption that the fish swimbladder remains constant in shape and volume. The backscattering cross section has been computed at a nominal frequency of 38 kHz as a function of orientation for each of three pressures: 1, 11, and 51 atm. Increased variability in target strength and more abundant and stronger resonances are both observed with increasing depth. The respective backscattering cross sections have been averaged with respect to each of four normal distributions of tilt angle, and the corresponding target strengths have been regressed on the logarithm of fish length. The tilt-angle-averaged backscattering cross sections at the highest pressure have also been averaged with respect to frequency over a 2-kHz band for representative conditions of insonification. For all averaging methods, the mean target strength changes only slightly with depth.This work began with sponsorship by the European Commission through its RTD-program, Contract No. MAS3-CT95-0031 (BASS), and was completed with support by the Office of Naval Research, Contract No. N000140310368

    The Performance of Observer-based Residuals for Detecting Intermittent Faults: The Limitations

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    AbstractIn this paper a broad nonlinear system is considered. Attention is focused upon both performance of a high-gain observer-based residual and the investigation of residual effectiveness for detecting faults in actuators/components. Residual performances for different fault positions and various system complexities are compared. Both qualitative and quantitative evidence for selected fault positions indicated the performance and the effectiveness of the residuals decrease by ascending the system complexity. The poor performance of residuals in the more complex system may cause No Fault Found (NFF). The methods may be extended to the more general class of nonlinear systems and different observers. Efficiency of the proposed approach is demonstrated through the intermittent failure case in a vehicle suspension system

    Ubiquitous energy storage

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    This paper presents a vision of a future power system with "ubiquitous energy storage", where storage would be utilized at all levels of the electricity system. The growing requirement for storage is reviewed, driven by the expansion of distributed generation. The capabilities and existing applications of various storage technologies are presented, providing a useful review of the state of the art. Energy storage will have to be integrated with the power system and there are various ways in which this may be achieved. Some of these options are discussed, as are commercial and regulatory issues. In two case studies, the costs and benefits of some storage options are assessed. It is concluded that electrical storage is not cost effective but that thermal storage offers attractive opportunities

    Comparing Kirchhoff-approximation and boundary-element models for computing gadoid target strengths

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    To establish the validity of the boundary-element method (BEM) for modeling scattering by swimbladder-bearing fish, the BEM is exercised in several ways. In a computation of backscattering by a 50-mm-diam spherical void in sea water at the four frequencies 38.1, 49.6, 68.4, and 120.4 kHz, agreement with the analytical solution is excellent. In computations of target strength as a function of tilt angle for each of 15 surface-adapted gadoids for which the swimbladders were earlier mapped, BEM results are in close agreement with Kirchhoff-approximation-model results at each of the same four frequencies. When averaged with respect to various tilt angle distributions and combined by regression analysis, the two models yield similar results. Comparisons with corresponding values derived from measured target strength functions of the same 15 gadoid specimens are fair, especially for the tilt angle distribution with the greatest standard deviation, namely 16°

    Intense-Field Ionization of Monoaromatic Hydrocarbons using Radiation Pulses of Ultrashort Duration: Monohalobenzenes and Azabenzenes

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    Using 50-fs, 800-nm pulses, we study the intense-field ionization and fragmentation of the monohalobenzenes C_(6)H_(5)-X (X=F, Cl, Br, I) and of the heterocyclics azabenzene C5H5N (pyridine) and the three diazabenzenes C_(4)H_(4)N_(2) (pyridazine, pyrimidine, and pyrazine). Avoiding focal intensity averaging we find indications of resonance-enhanced MPI. In the monohalobenzenes the propensity for fragmentation increases for increasing Z: fluorobenzene yields predominantly C6H5Fn+, while iodobenzene yields atomic ions with charges up to I^(8+). We ascribe this to the heavy-atom effect: the large charge of the heavy halogens' nuclei induces ultrafast intersystem crossing to dissociative triplet states
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