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The radiation from power-bus structures on high-speed printed circuit boards due to the switching noise current of digital integrated circuits is investigated. The study is based on an analytical cavity-resonator model for a rectangular parallel-plate structure. Based on the application of the field-equivalence principle, the radiated field is calculated from the electric edge-field distribution. For typical board dimensions, several cavity-mode resonances occur within the typical frequency range of interest, leading to relatively high maximum values for radiated emission. The evaluation of the radiation patterns reveals that all (0, nth) resonances have equal maximum amplitudes in the whole mode spectrum. This allows the setting up of an engineering equation for quantifying the noise-current-related maximum radiated field strength, including the dielectric and ohmic loss. Among all geometrical and material parameters, the dielectric thickness is one of the most effective ones to control radiated emission. The theoretical results are well confirmed by accurate measurements carried out in an anechoic room.  相似文献   
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In this paper, by applying a non linear model for the electromagnetic inverse scattering, a technique for the dielectric profiling of a planarly layered medium is investigated and applied to void localization and diagnostics inside a homogeneous lossless slab (one-dimensional geometry). Data are collected under plane wave multifrequency normal incidence. Suitable finite dimensional representations for the unknown functions are introduced and their influence on the model is discussed. The resulting functional equation is solved by the method of weighted residuals and the solution algorithm amounts to minimizing a non quadratic function, where particular attention is devoted to reduce the occurrence of local minima. Finally, the inversion algorithm is validated by applications to both simulated and experimental data.  相似文献   
4.
Pervasive computing is as much about the user as it is about the technology. So, the Fifth International Conference on Pervasive Computing emphasized desirability rather than just feasibility. Featured themes included user benefits, human-computer interaction, group and social interactions, context awareness, finding and positioning people and objects, and personal privacy.  相似文献   
5.
A team of faculty members at the University of Denver changed the learning environment in key courses in the Department of Engineering from predominately teacher centered to student centered. Through this funded project new grading methods were implemented, classrooms were renovated and wired with studio layouts to facilitate learning, the Engineering Circuits Laboratory was rewired and instrumented for automated data acquisition and reporting, and two new pedagogical approaches were developed. At the onset of the project, six goals were established related to student learning. The introduction of industry standard hardware and software provided students with unprecedented hands‐on experience and project related activities stimulated faculty innovations in other current and future courses. Assessment results indicate that the new grading system improved the clarity of expectations for students before assignments were given resulting in increased reported motivation for learning in many courses. Even though course GPAs did not always reflect higher achievement on graded work, faculty members firmly believe that deeper understanding was achieved because more complex material was assimilated.  相似文献   
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Results from this laboratory have shown that bone metabolism is directly related to extracellular pH and that high concentrations of tobramycin released from impregnated polymethylmethacryrate (PMMA) beads has pH-dependent toxic effects on bone. In the present study, beneficial effects of calcium hydroxide-impregnated PMMA were investigated regarding tobramycin toxicity and bone metabolism in chick embryo tibiae in vitro. Also using Ca(OH)2 as a pH regulator, the antibiotic efficacy of tobramycin-impregnated PMMA was evaluated with respect to inhibition of Staphylococcus aureus growth. When Ca(OH)2 was added to PMMA beads containing tobramycin, the beads released hydroxyl and calcium ions into the culture medium and released more antibiotic than beads containing only tobramycin. Bone metabolism (glycolysis, total protein synthesis, and collagen synthesis) was enhanced by Ca(OH)2-impregnated beads with or without tobramycin. Additionally, bacterial growth was inhibited more strongly when S. aureus was incubated with tobramycin- and Ca(OH)2-impregnated PMMA disks than with disks containing only tobramycin. This study demonstrates the feasibility of adding Ca(OH)2 to tobramycin-impregnated PMMA beads as a regulator of local pH and a promoter of bone metabolism for protection of bone when high concentrations of tobramycin are used to treat osteomyelitis. It also suggests that lower concentrations of antibiotic may be effective if Ca(OH)2 and tobramycin are administered simultaneously.  相似文献   
8.
Drug users are particularly at risk for contracting the human immunodeficiency virus and serve as a major mechanism for spreading the virus to other sectors of the population. As a result drug abuse treatment and potential behavioral change strategies are primary public health issues. The purpose of this article is to review the contributions included in this special edition, which represent an effort to describe the most current thinking in the field with a blend of theoretical, review, and empirical articles. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
9.
BACKGROUND: Common etiopathogenic factors may explain the association of systemic sarcoidosis with inflammatory bowel disease. METHODS: We report two cases of such an association: one of sarcoidosis that developed 2 years after proctocolectomy for ulcerative colitis and one of sarcoidosis and Crohn's colitis. Factors like increased cellular immunity or circulating immunocomplexes or autoantibodies may have a role. Exogenous agents or familiarity may also be involved. CONCLUSIONS: It is postulated that the association between sarcoidosis and inflammatory bowel disease (both ulcerative colitis and Crohn's disease) does not occur by chance alone and that the two conditions may share some genetic or immunologic alterations. The two diseases, however, follow an independent clinical course.  相似文献   
10.
A 1-yr follow-up study was conducted on families randomly assigned to settle custody disputes either in mediation or through adversary procedures. Consistent with Time 1 reports, at Time 2 fathers who mediated were substantially more satisfied than were fathers who litigated. Fathers who mediated also complied more with child support orders. Contrary to prediction, the greater satisfaction and compliance of fathers did not lead to increased satisfaction among mothers who mediated. In contrast to Time 1, at follow-up mothers who mediated were significantly less satisfied than were mothers who litigated, but selective attrition may account for these differences. The psychological adjustment of mothers and fathers was not significantly different between settlement groups at Time 2, but mothers in both groups reported less satisfaction with dispute settlement and less dysphoria at Time 2 than they had reported at Time 1. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
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