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排序方式: 共有159条查询结果,搜索用时 31 毫秒
1.
This paper extends an analysis developed for tubular permanent-magnet machines to account for the effect of fringing associated with the finite length of the ferromagnetic armature core. The magnetic field distribution, established by using an analytical technique formulated in the cylindrical coordinate system, provides an accurate means of evaluating the effect of the fringing flux on the thrust force and the back-electromotive force. Finite-element calculations confirm the analytically derived results. In Part II of the paper, the analysis is used to predict the cogging force that results from end effects and to facilitate minimization of the force. 相似文献
2.
John M. Jewell James Jaganathan Ishwar D. Aggarwal 《Journal of the American Ceramic Society》1991,74(4):788-796
The effect of controlled heterogeneous nucleation by platinum on the crystallization of a ZrF4 -BaF2 -LaF3 -AlF3 -NaF (ZBLAN) glass was studied. Various levels of platinum were incorporated into this glass by a combination of PtCl2 -doping and melting-atmosphere variation. The effect of doping levels and melting conditions on the incorporation of platinum and the subsequent nucleation of crystals was studied by optical microscopy, scanning electron microscopy, differential scanning calorimetry (DSC), and X-ray diffraction. Increased platinum in the glass resulted in an increased number of nucleation sites for the growth of β-ZrF4 -BaF2 crystals. Analysis of isothermal and ramp-rate DSC measurements indicated that the crystallization of this glass changed from surface controlled to bulk controlled with an increased number of nuclei. This was confirmed by optical microscopy. In addition, Avrami analysis of the isothermal crystallization data gave an accurate approximation of the number of nuclei in the glass. 相似文献
3.
Yeddanapudi S.R.K. Yuan Li McCalley J.D. Chowdhury A.A. Jewell W.T. 《Power Systems, IEEE Transactions on》2008,23(2):287-295
Asset management is an important activity in present day distribution system planning and operation. Utilities are constantly striving to optimize the use of resources available for maintenance while ensuring system reliability is within satisfactory limits. This paper proposes a method to allocate maintenance resources to various distribution system assets. To determine the effects of maintenance, a predictive reliability assessment tool is developed. This paper describes the model on which this tool is based. The results obtained from reliability assessment can be used along with an optimizer to allocate resources to various maintenance tasks in a distribution system. 相似文献
4.
IA Wilson RL Stanfield DA Jewell JB Ghiara DH Fremont EA Stura 《Canadian Metallurgical Quarterly》1994,3(2-3):155-162
The response exhibited by the immune system to viral and other foreign antigens consists of antibody-mediated and T cell-mediated immunity. Structural and molecular biological studies have shown that the antibody response is tailored to provide exquisite specificity by generating binding pockets that are complementary in shape as well as in charge to the antigen. On the other hand, the cellular response uses T-cell receptors (TCRs) and the major histocompatibility complex (MHC) antigens. Structural information on the TCRs is not yet available, but the crystal structures of several MHC class I molecules have shown how one MHC molecule can bind many different peptide sequences that share only the common anchor residue positions that determine allele specificity. MHC class I interactions with the peptide backbone at the N and C termini explain the high specificity of the binding groove for peptide ligands and suggest a universal mode of recognition for peptides to MHC class I molecules. Peptide-MHC class II interactions are less well understood, although recent structural work has shown important differences in the binding clefts of MHC class I and II that lead to longer peptides being bound to class II molecules. Detailed analysis at the molecular level has indicated that conformational changes in both antibodies and MHC molecules occur upon antigen binding.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
5.
Jiabin Wang Weiya Wang Jewell G.W. Howe D. 《Industrial Electronics, IEEE Transactions on》2002,49(3):640-648
This paper describes the design, analysis and characterization of a linear permanent magnet generator and capacitive energy storage system for generating electrical power from a single stroke of a salient-pole armature. It is suitable for applications that require relatively low levels of electrical power, such as remote electronic locks. An electromagnetic analysis of the generator is described, and a design optimization methodology for the system is presented. Finally, the performance of a prototype is validated against measurements 相似文献
6.
7.
Robert A. Jewell 《应用聚合物科学杂志》1968,12(5):1137-1145
The thermal degradation of several polyimidazopyrrolone (pyrrone) films was studied in air and in vacuum over the range of 100–1000°C. by thermogravimetric analysis (TGA), with the use of both isothermal heating and programmed heating rates of 2, 3, 5, and 7.5°C./min. At pressures of 10?6 torr or less, maximum weight losses average 30% at 800°C. Rates of volatilization and activation energies were derived to provide comparison between these ladder-type polymers. Mass spectrometric analysis of the pyrolysis gases evolved under vacuum conditions showed that CO, CO2, and H2O were the primary volatile products and that they were formed throughout the period of weight loss. Approximate correlation between changes in weight and changes in the total pressure for the vacuum tests indicates that mass spectrometric results could provide quantitative as well as qualitative data. The importance of sample history prior to heating and of sample geometry in developing meaningful and reproducible TGA results is aptly demonstrated. The ability of these materials to absorb readily 5–7 wt.-% of water under ambient conditions and the effect of this property upon weight loss measurements are shown. 相似文献
8.
9.
Carbon-13 chemical shifts are reported for tetralin, hydrophenanthrenes and hydropyrenes and their alkyl substituted derivatives. Mono- and di- plus tri-aromatic fractions of hydrogenated phenanthrene and pyrene were also examined by carbon-13 n.m.r. and, wherever possible, the components in them identified. 相似文献
10.
N E Jewell D B Turner P Willett G J Sexton 《Journal of molecular graphics & modelling》2001,20(2):111-121
Many 3D QSAR methods require the alignment of the molecules in a dataset, which can require a fair amount of manual effort in deciding upon a rational basis for the superposition. This paper describes the use of FBSS, a program for field-based similarity searching in chemical databases, for generating such alignments automatically. The CoMFA and CoMSIA experiments with several literature datasets show that the QSAR models resulting from the FBSS alignments are broadly comparable in predictive performance with the models resulting from manual alignments. 相似文献