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排序方式: 共有238条查询结果,搜索用时 0 毫秒
1.
The time-domain electromagnetic interference measurement system 总被引:5,自引:0,他引:5
A novel real-time broad-band time-domain electromagnetic interference (TDEMI) measurement system for the 30-1000-MHz frequency range is described. The signals from the antenna are sampled, analog-to-digital (A/D) converted and digitally processed. The fast-Fourier transform (FFT), the Welch- and Bartlett periodograms are digitally computed. Compared with state-of-the-art EMI measurement systems, the novel described TDEMI system samples the complete phase and amplitude information of the EMI simultaneously over the whole frequency band under consideration. With the presented time domain measurement system the measurement time can be reduced by a factor of 10. The digital processing of EMI measurements allows emulation in real-time of the various modes of conventional analogous equipment, e.g., peak, average, rms and quasi-peak detector and also introduces new concepts of analysis, e.g., phase spectra, short-time spectra, statistical evaluation and FFT-based time-frequency analysis methods. 相似文献
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3.
V. A. Ivanshin M. V. Eremin J. Deisenhofer H.-A. Krug von Nidda A. Loidl R. M. Eremina 《Journal of Superconductivity and Novel Magnetism》2002,15(6):523-525
The electron spin resonance (ESR) measurements were performed in single crystals of La1 ? x Sr x MnO3 (0.05 ≤ x ≤ 0.125) in order to study the interplay of crystal field, Dzyaloshinsky–Moriya interaction, Jahn–Teller (JT) effect, and orbital order. The angular dependence of the ESR linewidth of an untwinned La0.95Sr0.05MnO3 single crystal has been analyzed in the high-temperature approximation, which takes into account the microscopic geometry of the four nonequivalent Mn positions in the orthorhombic unit cell. A strong mixing of the |3z 2 ? r 2> and |x 2 ? y 2> states for the real orbital configuration was found. Magnetic inhomogeneities observed in the ESR spectra across the composition range 0.075 ≤ x ≤ 0.125 can be attributed to the presence of ferromagnetic clusters (magnetic spin polarons) in the paramagnetic state. New polaronic models are proposed. 相似文献
4.
Gary Krug 《The Journal of communication》1995,45(2):204-209
5.
Krug HF 《Metal-Based Drugs》1995,2(2):91-98
Organometals induce platelet aggregation and inorganic metal ions such as Cd(2+) or Pb(2+) sensitise human blood platelets to aggregating agents and this action is associated with the liberation of arachidonic acid and eicosanoid formation. The same mechanism is observed using human leukaemia cells (HL-60) when treated with MeHgCl or Et(3)PbCl. The fatty acid liberation within human platelets and HL-60 cells could only be inhibited with phospholipase A(2) inhibitors of different specificity.Preincubation of the cells with pertussis toxin reduces the activation induced by Et(3)PbCl to a great extent. The non-catalytic B subunit, that only mediates the binding of the toxin to the cell membranes, has no effect at all. When summarised, these results suggest that one possible mechanism for the stimulation of phospholipase A(2) by Et(3)PbCl functions via a G-protein dependent pathway. 相似文献
6.
R. Hackl M. Opel P. F. Müller G. Krug B. Stadlober R. Nemetschek H. Berger L. Forró 《Journal of Low Temperature Physics》1996,105(3-4):733-742
Experimental results for the electronic Raman effect in differently doped cuprate superconductors will be presented. We show that the B2g-symmetry data are generally closely related to ordinary transport and are therefore most likely originating from the carriers, while the response at B1g symmetry cannot be assigned to a specific type of excitations. In the superconducting state the B2g pair breaking peaks scale with the transition temperature over a wide doping range. All results consistently suggest a strong anisotropy of the gap and can be modeled by assuming
symmetry for the order parameter. 相似文献
7.
C. el Dsoki V. Landersheim H. Kaufmann T. Bruder P. Krug T. Bohn C. Müller 《Materialwissenschaft und Werkstofftechnik》2006,37(12):1006-1017
The fatigue behaviour of spray compacted aluminium materials. Material properties for component design data: From specimen to component. Spray compacted, high performance aluminium alloys (DISPAL = DISpersion hardened Aluminium) are characterised by their high strength, high Young’s modulus, good wear resistance and low coefficient of thermal expansion. These properties vindicate both the application of these materials and the increasing interest of the automobile manufacturers. Within the framework of a bilateral project, tests were carried out by varying different parameters under both strain‐ and load‐controlled conditions in order to describe the fatigue behaviour of these materials. 相似文献
8.
Jonathan D. Krug Andrew Dart Carlton L. Witherspoon Jerome Gilberry Quentin Malloy Surender Kaushik 《Aerosol science and technology》2017,51(7):868-878
Under the National Ambient Air Quality Standard (NAAQS) for airborne lead, measurements are conducted by means of a high-volume total suspended particulate matter (Hi-Vol TSP) sampler. In the decade between 1973 and 1983, there were 12 publications that explored the sampling characteristics and effectiveness of the Hi-Vol TSP, yet there persists uncertainty regarding its performance. This article presents an overview of the existing literature on the performance of the Hi-Vol TSP, and identifies the reported sampler effectiveness with respect to four factors: particle size (reported effectiveness of 7%–100%), wind speed (?36% to 100%), sampler orientation (7%–100%), and operational state (107%–140%). Effectiveness of the Hi-Vol TSP was evaluated with a solid, polydisperse aerosol in a controlled wind tunnel setting. Isokinetic samplers were deployed alongside the Hi-Vol TSP to investigate three wind speeds (2, 8, and 24 km h?1), three sampler orientations (0°, 45°, 90°), and two operational states (on, off) for aerosols with aerodynamic diameters from 5 to 35 µm. Results indicate that particle diameter was the largest determining factor of effectiveness followed by wind speed. Orientation of the sampler did not have a significant effect at 2 and 8 km h?1 but did at 24 km h?1. In a passive state, the Hi-Vol TSP was collected between 1% and 7% of available aerosol depending on particle size and wind speed. Results of this research do not invalidate results of previous studies but rather contribute to our overall understanding of the Hi-Vol TSP's size-selective performance. While results generally agreed with previous studies, the Hi-Vol TSP was found to exhibit less dependence on these four factors than previously reported.© 2017 American Association for Aerosol Research 相似文献
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10.
A. A. Wereszczak K. Breder M. K. Ferber T. P. Kirkland E. A. Payzant C. J. Rawn E. Krug C. L. Larocco R. A. Pietras M. Karakus 《Journal of Materials Science》2002,37(19):4235-4245
Dimensional changes and creep deformation of a silica/zircon (74%/24%, respectively) and a high silica (93% silica and 3% zircon) ceramic were characterized and compared. All specimens were tested with a thermal profile that consisted of a 300°C/h heating rate to 1475 or 1525°C, followed by a one-hour isothermal hold (where each specimen was compressively crept under a static stress of 2.07, 4.14, or 6.21 MPa). The specimens were cooled at a rate of 900°C/h under stress. Dimensional changes were interpreted from apparent thermal expansion behavior during heating as well as before-and-after dimensional measurements. The silica/zircon ceramic generally exhibited less total contraction than the high silica ceramic for a specific test condition even though it crept faster at all stresses and temperatures during the one-hour isothermal/isostress segment. This indicates that the total contraction for both was dominated by reinitiated sintering and subsequent cristobalite formation that occurred during the heating segment. Minimum creep rate during the one-hour isothermal/isostress segment was examined as a function of stress and temperature for both ceramics using a power-law creep model. Creep-rate stress exponents (n) and activation energies (Q) were equivalent (within 95% confidence) for both ceramics showing that their different contents of zircon (3 vs. 24%) did not affect them. Lastly, n 1.3–1.4 and Q 170 kJ/mol indicate that diffusion-assisted crystallization of cristobalite, combined with power-law sintering owing to the high concentration of porosity (28–30%) was likely the rate-limiting mechanism in the creep deformation for both ceramics. 相似文献