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71.
A 66-kV network generally is grounded through a neutral grounding resistor. In this network a single-phase ground-fault current is limited to as small as 100 to 400 A. There are parallel four-circuit transmission lines mounted on the same tower in the 66-kV network. In such transmission lines, the load and the fault currents could induce circulating current that flows through the lines. Since the circulating current has zero-phase-sequence and negative-phase-sequence components, it could cause unwanted operation of a balance ground relay using zero-phase-sequence current. However, it is difficult to compensate for the circulating current by the conventional vector compensation scheme. This paper presents a new balance ground relay to deal with the circulating current. In the relay from the ground-fault inception until first tripping, the difference current Δ3I2d of negative-phase-sequence current 3I2d of the differential current between two protected lines is used as an input current. The Δ3I2d is the difference current of 3I2d between, before and during faults. After the first tripping, the difference current of positive-phase-sequence load current and zero-phase-sequence current of the forementioned differential current are used as an input current. Consequently, a higher sensitivity of the ground-fault protection for these lines has been achieved. The correct operation of the new balance ground relay was confirmed when a single-phase-ground-fault occurred in the parallel four-circuit transmission lines, to which the relay is applied. 相似文献
72.
Oxidation and gel-forming ability of chicken white (breast) and red (leg) muscle myofibrillar proteins during storage at 0°C were examined. Breast myofibril gels exhibited greater shear moduli than leg myofibril gels throughout 8 days storage. Shear moduli of both breast and leg gels in the intermediate temperature zone (45–55°C) decreased during storage, but at >55°C, they either increased or remained unchanged. Lipid oxidation was inhibited by washing myofibrils with antioxidants propyl gal-late, ascorbate, and tripolyphosphate. However, these antioxidants did not affect the content of protein carbonyls, and only slightly decreased the amine content during storage. Storage affected the kinetic process of myofibril gelation independently of antioxidant treatments. 相似文献
73.
Phospholipase A2 [EC 3.1.1.4] treatment of pig kidney Na+,K(+)-ATPase [EC 3.6.1.3] labeled with fluorescence probes at the alpha-chain reduced the extent of the fluorescence intensity change of an N-[p-(2-benzimidazolyl)phenyl]maleimide (BIPM) probe at Cys-964 to below one-third of the control level accompanying the accumulation of phosphoenzymes. However, it only induced a slight decrease in that of a fluorescence isothiocyanate (FITC) probe at Lys-501 with a large decrease in the rate of change. The addition of phosphatidylserine (PS) or phosphatidylinositol (PI) to the phospholipase-treated BIPM-FITC-labeled enzyme increased the rate of the FITC fluorescence change. Phospholipase treatment of the BIPM-enzyme greatly reduced the Na+,K(+)-ATPase activity. The addition of PS or PI to the treated enzyme induced reactivation. These data and others suggest that Cys-964 and Glu-953 (Rb+ protectable dicyclohexyl carbodiimide binding site) are located in the vicinity of the surface area of the enzyme where hydrocarbon chains of phospholipids are present, and conserved H-bonding amino acids, Thr-955 and Ser-962, are located rather near the center of a domain forming a cation binding route or cage with other hydrophobic transmembrane segments. These data may indicate that the interaction between the BIPM probe and the hydrocarbon chains of phospholipids changes in such a way as to sense the change in the binding state of various ligands accompanying the sequential appearance of reaction intermediates of the enzyme. 相似文献
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76.
多属性神经网络地震反演在NB油田水平井钻探中的应用 总被引:2,自引:0,他引:2
NB油田位于渤海海域,为新近系河流相稠油油田,储层横向分布不稳定,砂体厚度薄、连通性较差,油水关系复杂,开发设计部署了大量水平井。选择神经网络反演方法,建立地震属性与储层参数的非线性关系,进而根据其关系反演得到储层参数数据体,利用该数据体沿层切片提取储层预测信息,研究储层发育规律,指导该油田水平井的部署和钻探,取得了较好的效果,降低了钻探风险。用神经网络地震反演方法进行储层预测研究,指导水平井钻探,在渤海海域尚属首次。 相似文献
77.
清代皇家园林规划设计控制的量化研究——以圆明三园、清漪园为例 总被引:1,自引:0,他引:1
本文通过量化分析探索了清代皇家园林规划设计的控制规律及相关理论。 相似文献
78.
严峻的能源短缺、居高不下的原油价格、日益严重的环境问题已经成为制约中国经济、社会发展的瓶颈。改变现有的以化石能源为主的能源结构, 相似文献
79.
基于多信道预约可冲突避免的多址接入协议 总被引:3,自引:0,他引:3
本文为多跳分布多无线网络提出了一套灵活而有效的自适应获取冲突避免(AACA)的多址接入协议。在该协议中,各节点竞争公共信道,利用RTS/CTS对话形式来预约各业务信道,成功预约后的分组传输不会受到其他节点的干扰。它使用任意确定数目信道,以异步方式工作,并且使得各节点利用半双工无线电台就可以灵活、简便地实现资源预约。分析和比较结果说明,所提出的多信道预约协议可以有效地解决隐藏终端、暴露终端以及侵入终端的问题。 相似文献
80.