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排序方式: 共有131条查询结果,搜索用时 15 毫秒
1.
Surface waves due to a current source on a grounded ferrite slab are investigated. Electromagnetic fields of the structure are in terms of a continuous plane wave spectrum. The spectrum of each field component is obtained numerically through the exponential-matrix method. The surface waves of the structure are extracted from the continuous spectrum by using the residue theorem and the method of steepest descent. Two types of surface waves are found and their properties are described. The surface wave modes found include dynamic surface wave modes which are closely related to the surface waves of a grounded dielectric slab, and magnetostatic surface wave modes which are related to the solution of Laplace's equation for the magnetic potential 相似文献
2.
GS Alexopoulos BS Meyers RC Young S Mattis T Kakuma 《Canadian Metallurgical Quarterly》1993,150(11):1693-1699
OBJECTIVE: The goals of this longitudinal investigation were 1) to study the rate of development of irreversible dementia in elderly depressed patients with a dementia syndrome that subsided after improvement of depression and 2) to compare it with that of depressed, never-demented patients. METHOD: The subjects were 57 elderly patients consecutively hospitalized for major depression. At entry into the study, 23 subjects also met criteria for "reversible dementia," while 34 were without dementia. After a systematic clinical evaluation, the subjects were followed up at approximately yearly intervals for an average of 33.8 months. RESULTS: Irreversible dementia developed significantly more frequently in the depressed group with reversible dementia (43%) than in the group with depression alone (12%). Survival analysis showed that the group with reversible dementia had a 4.69-times higher chance of having developed dementia at follow-up than the patients with depression alone. No clinical characteristics at entry into the study were found to discriminate the subjects who developed irreversible dementia during the follow-up period from those who remained nondemented. CONCLUSIONS: These findings suggest that geriatric depression with reversible dementia is a clinical entity that includes a group of patients with early-stage dementing disorders. Therefore, identification of a reversible dementia syndrome is an indication for a thorough diagnostic workup and frequent follow-ups in order to identify treatable neurological disorders. 相似文献
3.
Stavros Plessas Athanasios Alexopoulos Argyro Bekatorou Eugenia Bezirtzoglou 《Journal of food science》2012,77(12):C1256-C1262
Abstract: The natural mixed culture kefir was immobilized on boiled corn grains to produce an efficient biocatalyst for lactic acid fermentation with direct applications in food production, such as sourdough bread making. The immobilized biocatalyst was initially evaluated for its efficiency for lactic acid production by fermentation of cheese whey at various temperatures. The immobilized cells increased the fermentation rate and enhanced lactic acid production compared to free kefir cells. Maximum lactic acid yield (68.8 g/100 g) and lactic acid productivity (12.6 g/L per day) were obtained during fermentation by immobilized cells at 37 °C. The immobilized biocatalyst was then assessed as culture for sourdough bread making. The produced sourdough breads had satisfactory specific loaf volumes and good sensory characteristics. Specifically, bread made by addition of 60% w/w sourdough containing kefir immobilized on corn was more resistant regarding mould spoilage (appearance during the 11th day), probably due to higher lactic acid produced (2.86 g/Kg of bread) compared to the control samples. The sourdough breads made with the immobilized biocatalyst had aroma profiles similar to that of the control samples as shown by headspace SPME GC‐MS analysis. 相似文献
4.
Murat Tiryakioğlu John Campbell Nikolaos D. Alexopoulos 《Metallurgical and Materials Transactions B》2009,40(6):802-811
Several indices are available in the literature to assess the structural quality of cast Al alloys, especially Al-7 pct Si-Mg
alloys that are based on tensile test results. Some of these indices, most notably the one developed by Drouzy et al., provide a number that necessarily does not have a physical meaning, whereas the others are a measure of what fraction of
the expected tensile performance is achieved. These indices are analyzed in depth, their similarities and shortcomings are
discussed in detail, and recommendations are made. 相似文献
5.
P Saratsis L Leontides A Tzora C Alexopoulos GC Fthenakis 《Canadian Metallurgical Quarterly》1998,37(1-4):173-183
In a field investigation of 10 flocks in Southern Greece, 3367 dairy ewes were examined twice, in order to estimate the incidence risk and the aetiology of mammary abnormalities during the dry-period. Abnormal secretion, lumps, nodules, diffuse hardness, abscesses and cysts were the abnormalities detected. The cumulative incidence of mammary abnormalities during the dry-period was 5.1% (95% confidence interval: 4.4-5.8%); 47% of the cases detected developed during the first three weeks after cessation of lactation. Despite variation in the flock size, there was no between-flock variation in the risk of a ewe developing mammary abnormalities. Staphylococci (Staphylococcus aureus and coagulase-negative isolates) were the most frequently isolated bacteria from mammary samples; Actinomyces pyogenes, Clostridium perfringens, streptococci and Escherichia coli were also isolated. Resistance was encountered among the staphylococcal isolates. 相似文献
6.
Radiation properties of microstrip dipoles 总被引:1,自引:0,他引:1
Uzunoglu N. Alexopoulos N. Fikioris J. 《Antennas and Propagation, IEEE Transactions on》1979,27(6):853-858
The fundamental problem of printed antennas is addressed. The printed or microstrip dipole is considered, and its radiation characteristics are investigated. The Green's function to the problem is obtained in dyadic form by solving the problem of a Hertzian dipole printed on a grounded substrate. Input impedance computations are presented, and the numerical solution for the Sommerfeld integrals is discussed. 相似文献
7.
A distribution-free tabular CUSUM chart for autocorrelated data 总被引:1,自引:0,他引:1
Seong-Hee Kim Christos Alexopoulos Kwok-Leung Tsui James R. Wilson 《IIE Transactions》2007,39(3):317-330
A distribution-free tabular CUSUM chart called DFTC is designed to detect shifts in the mean of an autocorrelated process. The chart's Average Run Length (ARL) is approximated by generalizing Siegmund's ARL approximation for the conventional tabular CUSUM chart based on independent and identically distributed normal observations. Control limits for DFTC are computed from the generalized ARL approximation. Also discussed are the choice of reference value and the use of batch means to handle highly correlated processes. The performance of DFTC compared favorably with that of other distribution-free procedures in stationary test processes having various types of autocorrelation functions as well as normal or nonnormal marginals. 相似文献
8.
An asymptotic extraction process is developed which leads to an efficient method for the evaluation of the electric field from a Hertzian dipole in a layered geometry. This technique allows for a rapidly converging expression for the electric field which remains well behaved as the source and observation heightsz', z coincide. A useful application of this method is in the calculation of mutual impedance between printed dipoles. 相似文献
9.
10.
Certain basic radiation properties of microstrip dipoles on electrically thick substrates are investigated, and a comparison is made with the case of dipoles printed on a dielectric half-space. It is concluded that the microstrip dipole radiation properties become sensitive to substrate loss as the substrate thickness increases, with the half-space properties obtained for an adequate amount of loss. Asymptotic formulas for radiated power and efficiency are given for both the thick substrate and half-space problems, showing the behavior with increasing dielectric constant. The method of moments is used to extend the analysis to center-fed strip dipoles, and a method of improving both the efficiency and gain of a printed antenna by using a superstrate layer is discussed. 相似文献