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981.
Ippolito L.J. Jr. Russell T.A. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1993,81(6):923-929
The effects of rain and other propagation concerns for new applications areas, currently in operation or planned for implementation by the end of this decade, are described. The areas include: VSAT systems employing low operating margins and/or low elevation angles; traditional communications applications operating with inclined geosynchronous orbits; and mobile and personal communications applications employing networks of low earth orbit (LEO) satellites. Prediction modeling and analysis techniques applicable to these areas are described. Analytical results for a range of operational parameters involving low-margin, low elevation angle, inclined geosynchronous, and LEO systems are presented 相似文献
982.
Michael H. Zimmerman K. T. Faber Edwin R. Fuller Jr. Keith L. Kruger Keith J. Bowman 《Journal of the American Ceramic Society》1996,79(5):1389-1393
Untextured and highly textured iron titanate specimens were produced by vacuum filtering iron titanate-ethanol suspensions in the absence and presence of a strong magnetic field, respectively. Crystallographic texture was assessed by measuring X-ray pole figures on surfaces parallel and perpendicular to the field direction for several peaks in each system. Morphological texture was assessed by measuring grain size as a function of angle to a reference direction. Results indicate that magnetic field processing imposes a strong, fiber-type texture on the order of 30 times random, with the b -axis parallel to the applied field. Additionally, morphological texturing is absent for the grain sizes studied in this work. 相似文献
983.
984.
Hilsenroth Mark J.; Holdwick Daniel J. Jr.; Castlebury Frank D.; Blais Mark A. 《Canadian Metallurgical Quarterly》1998,35(2):163
This study investigates the relationship between therapy attendance with DSM-IV criteria for the cluster B personality disorders (antisocial [ANPD]; borderline [BPD]; histrionic [HPD]; and narcissistic [NPD]). Ninety patients who were found to meet DSM-IV criteria for an Axis II disorder (cluster A personality disorders?=?10; ANPD?=?20, BPD?=?25, HPD?=?5, NPD?=?14; cluster C personality disorders?=?16). Total number of DSM-IV criteria for BPD (r?=?.33, p?=?.001) and ANPD (r?=?–.22, p?=?.04) were significantly related to the number of psychotherapy sessions attended by a patient. Stepwise regression indicated that the 5 individual criteria BPD-1, NPD-4, BPD-8, HPD-8, and ANPD-7 (in order of entry into the regression equation) were independent and nonredundant predictors that explained 31% of variance found in the number of psychotherapy sessions attended by patients. The presence or absence of 3 of these individual criteria provided a good balance of positive predictive power (.78–.95) and overall correct classification rate (.53–.69) for therapy continuation. Clinical and research implications of personality characteristics are discussed in relation to the termination and continuation of psychotherapy. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
985.
J. D. Warthen Jr. W. F. Schmidt R. E. Doolittle R. T. Cunningham 《Journal of chemical ecology》1995,21(1):69-79
tert-Butyl 4- (and 5-) chloro-trans-2-methylcyclohexane-1-carboxylate (TML), a mixture of four majortrans and four minorcis isomers, is used as an attractant for detecting and monitoring the male Mediterranean fruit fly (medfly),Ceratitis capitata (Wiedemann). The eight isomers (racemic mixtures) were isolated by HPLC, and their relative attractiveness in the field was determined. A quantitative structure-activity relationship (QSAR) was proposed that related a molecular measurement (Å3) of the TML structure to male medfly captures. More recently, thetrans-TML enantiomers were synthesized in sufficient quantities for field testing. This paper reports the computer-aided molecular modeling, via Chem-X, of thetrans-TML enantiomers and the staggered and superimposed fitting with the most attractive isomer, (1S,2S,4R)-TML-C, to determine common volumes and surface areas from Van der Waals (VdW) maps. Observations of structure-activity relationships (SAR) are reported for the staggered fittings. 相似文献
986.
Testing the Interactivity Principle: Effects of Mediation, Propinquity, and Verbal and Nonverbal Modalities in Interpersonal Interaction 总被引:5,自引:0,他引:5
Judee K. Burgoon Joseph A. Bonito Artemio Ramirez Jr. Norah E. Dunbar Karadeen Kam Jenna Fischer 《The Journal of communication》2002,52(3):657-677
Early channel reliance research compared different modes of communication to assess relationships among nonverbal and verbal cues. Emerging communication technologies represent a new venue for gaining insights into the same relationships. In this article, the authors advance a principle of interactivity as a framework for decomposing some of those relationships and report an experiment in which physical proximity—whether actors are in the same place ("co-located") or interacting at a distance ("distributed")—and the availability of other nonverbal environmental, auditory, and visual information in distributed modes is varied. Results indicate that both proximity and availability of nonverbal cues affect communication processes, social judgments participants make about each other, and task performance. The authors discuss implications about gains and losses due to presence of nonverbal features. 相似文献
987.
988.
An analytical and numerical study of the accuracy of the beam propagation method that includes approximate treatments of wide-angle propagation based on Pade rational functions is presented. The investigation identifies the error terms associated with a sequence of higher order operators and the range of validity of different approximant operators is studied through examination of two-dimensional (2-D) waveguide structures. An analytical model for the general error in Pade-based wide-angle schemes is developed and compared with numerical simulations of simple waveguiding devices for which the exact solution is known. Guidelines for determining the range of error pertinent to the Pade operator are established 相似文献
989.
Applying wavelets to mammograms 总被引:2,自引:0,他引:2
This article briefly reviews the challenges faced as technology moves toward digital mammography, presents a necessarily brief overview of multiresolution analysis, and finally, gives current and future applications of wavelets to several areas of mammography. Topics covered include data compression and teleradiology, feature enhancement and classification, wavelets, fractals and texture, and de-noising 相似文献
990.
Microelectromechanical wavelength tuning is demonstrated for the first time in a resonant-cavity light-emitting diode. The device utilizes a deformable-membrane top mirror suspended by an air gap above a diode-active region and bottom mirror. Applied membrane-substrate bias produces an electrostatic force which reduces the air-gap thickness, and therefore, the resonant wavelength. We report broad tunability of nearly 40 nm and spectral linewidths as narrow as 1.9 nm (2.6 meV) for operation near 950 nm 相似文献