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排序方式: 共有854条查询结果,搜索用时 15 毫秒
791.
在气体绝缘变电站GIS(gas insulated substation)中,隔离开关进行分合母线时引起的特快速暂态过电压VFTO(very fast transient overvoltage)威胁站内设备安全,深入认识VFTO的特点并提出适当的抑制措施对于保障GIS变电站的安全具有重要意义.选取深圳某550 kV ... 相似文献
792.
793.
针对某极贫磁铁矿石性质特点,采取粗粒湿式预选技术对某极贫磁铁矿进行了有效经济的选别,获得了较好的选别指标,为开发利用极贫磁铁矿资源提供了科学的理论依据. 相似文献
794.
Yinxiu CAO Hongchi TIAN Kun YAO Yingjin YUAN 《Frontiers of Chemical Science and Engineering》2011,5(3):318
Due to its merits of drought tolerance and high yield, sweet potatoes are widely considered as a potential alterative feedstock for bioethanol production. Very high gravity (VHG) technology is an effective strategy for improving the efficiency of ethanol fermentation from starch materials. However, this technology has rarely been applied to sweet potatoes because of the high viscosity of their liquid mash. To overcome this problem, cellulase was added to reduce the high viscosity, and the optimal dosage and treatment time were 8 U/g (sweet potato powder) and 1 h, respectively. After pretreatment by cellulase, the viscosity of the VHG sweet potato mash (containing 284.2 g/L of carbohydrates) was reduced by 81%. After liquefaction and simultaneous saccharification and fermentation (SSF), the final ethanol concentration reached 15.5% (v/v), and the total sugar conversion and ethanol yields were 96.5% and 87.8%, respectively. 相似文献
795.
为了进行超长寿命疲劳破坏行为的可靠性研究,对GCr15钢超长寿命疲劳S-N试验数据进行了统计评估,采用Bansqun模型描述了其S-N曲线关系,建立了其概率S-N曲线模型,并采用SEV方法和Murakami方程分别预测了钢中最大夹杂尺寸和其相对应的疲劳强度。结果表明:其超长寿命疲劳S-N数据能较好地服从三参数威布尔分布,其概率S-N曲线形式都呈现持续下降的趋势;在验证了最大夹杂尺寸服从Gumbel分布的基础上,SEV方法预测的最大夹杂尺寸随着钢体积的增大而线性增加,Murakami方程预测的结果揭示了其概率S-N曲线呈现持续下降的原因。 相似文献
796.
Different stages of the Very High Cycle Fatigue (VHCF) crack evolution in tool steels have been explored using a 20 kHz ultrasonic fatigue testing equipment. Extensive experimental data is presented describing VHCF behaviour, strength and crack initiating defects in an AISI H11 tool steel. Striation measurements are used to estimate fatigue crack growth rate, between 10?8 and 10?6 m/cycle, and the number of load cycles required for a crack to grow to critical dimensions. The growth of small fatigue cracks within the “fish‐eye” is shown to be distinctively different from the crack propagation behaviour of larger cracks. More importantly, the crack initiation stage is shown to determine the total fatigue life, which emphasizes the inherent difficulty to detect VHCF cracks prior to failure. Several mechanisms for initiation and early crack growth are possible. Some of them are discussed here: crack development by local accumulation of fatigue damage at the inclusion – matrix interface, hydrogen assisted crack growth and crack initiation by decohesion of carbides from the matrix. 相似文献
797.
根据斜沟煤矿13号煤层赋存条件,运用FLAC3D数值模拟,主要研究了底层4.5m大采高综放全厚开采14.6m特厚煤层工作面煤壁前方支承压力作用及顶煤和顶板垮落特征等特征,对类似条件工作面的生产具有一定的指导意义. 相似文献
798.
Partial discharge (PD) degradation phenomena is one of the most important factors to decide the performance and the lifetime of the high voltage apparatus. During PD degradation tests of an epoxy specimen with an internal void, PD often change to a large number of very small PD known as swarming pulsive microdischarges (SPMD). Because the appearance of SPMD is concerned with the degradation of the insulating materials, the insulation diagnosis with the detection of SPMD becomes possible. However, SPMD cannot be detected with the conventional PD Detector because the PD magnitude of SPMD is too small. The computer-aided partial discharge analyzing system (CAPDAS) has been developed to detect and analyze the SPMD. Furthermore, a new PD parameter, the SPMD ratio has been introduced for quantitative analysis of SPMD. In this paper, the time variation of SPMD characteristics of a CIGRE Method-II specimen are investigated by using the CAPDAS. Further, the effect of the frequency of the applied voltage on SPMD is also investigated at 60 Hz and a very low frequency of 0.1 Hz. As a result, the comparison of PD magnitudes measured at 60 Hz with those at 0.1 Hz enables a quantitative analysis of SPMD characteristics to be possible by using only the conventional PD detector. 相似文献
799.
Single crystals of CdTe were obtained by the very fast vapor growth technique. The four major defects, namely, multi-grains,
lamellar, lateral, and micro-twins, which are fatal to the single crystallinity, were eliminated or limited by increasing
the growth stability. This investigation indicates that the latent heat under high growth rate conditions should not be neglected.
A model is developed to explain the effects of latent heat on the growth stability at the interface. A relationship between
crystal morphologies and growth conditions was established. It strongly suggests that the above defects are growth stability
related. The origin of twinning, dominated by growth stability, is discussed in this paper. 相似文献
800.
LLDPE及VLDPE对LDPE/HDPE共混物拉伸性能的影响 总被引:6,自引:0,他引:6
研究了线性低密度聚乙烯(LLDPE)和极低密度聚乙烯(VLDPE)对高密度聚乙烯(HDPE)/低密度聚乙烯(LDPE)共混物拉伸性能的影响。由于LLDPE或VLDPE的加入,改善了HDPE与LDPE间的相互作用,提高了HDPE/LDPE共混物的拉伸性能。 相似文献