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992.
Tongxiang Liang Wenzhen Sun Y. -H. Wang H. -D. Li Q. -L. Wu Y. -J. Yan 《Journal of Materials Science》1996,31(19):5159-5161
A multilayer AIN-W cofired body has been developed using the pressless sintering technique. Effects of additives, such as Y2O3, CaO, La2O3, MgO, Al2O3 and SiO2, on the sheet resistance of W conductor were studied. The sheet resistance of the W conductor increases with increasing additives in the W paste. However, the oxides can be divided into two groups. The effect of the first group on sheet resistance is different from that of the second group. 相似文献
993.
本文主要阐述使用红外热象仪检测运行中的电力设备所发现的问题。文中通过若干实例介绍了用红外热象仪检测带电运行的发电机、电容器及连接头,并查出带有严重缺陷的部位,从而避免事故发生。 相似文献
994.
本文综述了机械合金化Al-Al_3Ti材料的发展现状,论述了增强体Al_3Ti的性质和机械合金化制备的Al-Al_3Ti的组织与性能。采用机械合金化制备的Al-Al_3Ti具有理想的组织。相当高的强度与塑性,良好的热强性。目前对机械合金化制备的Al-Al_3Ti的研究不够深入,还需进行大量的工作。 相似文献
995.
996.
997.
Synchronous fiber-optic CDMA using hard-limiter and BCH codes 总被引:3,自引:0,他引:3
Jyh-Horng Wu Jingshown Wu 《Lightwave Technology, Journal of》1995,13(6):1169-1176
In this paper, synchronons code division multiple access (S/CDMA) for fiber-optic local area networks is considered. The performance of the fiber-optic S/CDMA network with negligible thermal and shot noises is interference limited. Here we derive the bit error rate of the S/CDMA system as a function of code length and number of active users, and the performance characteristics are also discussed. Furthermore, we analyze the performance of the fiber-optic S/CDMA system with an ideal optical hard-limiter, and the error probability with error control coding is also derived. In addition, the optimization between the S/CDMA and BCH codes of a constant bandwidth system is presented. The results show that by using an ideal hard-limiter in conjunction with BCH codes in this system, the influence of interference arising from other users can be greatly reduced, and the number of active users can also be increased significantly 相似文献
998.
We have made reasonably comprehensive measurements of action potential activity in the Aplysia californica abdominal ganglion to determine the amount of feedback the central nervous system (CNS) receives from a movement which it initiates. Voltage-sensitive dye measurements of action potential activity of cells in the ganglion were made during the gill-withdrawal reflex elicited by siphon stimulation. We compared recordings in two situations which differed dramatically in the amount the gill moved. In the control sea water, the gill withdrawal was normal; in low-Ca2+, high-Mg2+ sea water, the gill movement was blocked. Both the timing and the number of spikes of the individual neurons were similar in the two situations. Histograms of the summed spike activity versus time and histograms of the number of active neurons versus time in the two conditions were also similar. Finally, two numerical measures of trial-to-trial differences, a paired t-test and a measure we named fractional similarity, did not indicate larger differences between two trials in the different sea waters than two trials in the same sea water. Feedback from sensory neurons activated by the gill movement itself does not make a large contribution to the spike activity in the abdominal ganglion. Apparently the Aplysia CNS issues the command for the withdrawal and does not make adjustments for the magnitude of the actual withdrawal. It may not even receive the information necessary for such adjustments to be made. A second motivation for these experiments was to test whether removing the feedback might simplify the neuronal activity that occurs during the gill-withdrawal reflex. This did not occur. 相似文献
999.
1000.
The laser-induced thermal grating technique has been used to determine the thermal diffusivity of liquids and liquid mixtures. But the dynamic behaviour of the transient thermal grating has not yet been thoroughly investigated, and the systematic errors, which result from the departures from one-dimensional heat conduction, have scarcely been studied quantitatively. In this paper. a three-dimensional numerical simulation and results of the transient thermal grating technique are presented, which enable a good understanding of the dynamic behaviour of the transient thermal grating. The results of this simulation are important for the proper design of the experimental setup to keep the systematic errors for the diffusivity measurement small. Based on the simulation method, the systematic errors were analyzed quantitatively. Here, the following effects were studied: (I) sample thickness, (2) intersection angle, (3) absorption, (4) Gaussian beam intensity distribution and focusing of heating laser beam, and (5) heating pulse duration and laser power. This error analysis makes it possible to specify the criteria for optimum measuring conditions, to correct the measured thermal-diffusivity values for systematic errors, and to estimate the accuracy of the measurements. 相似文献