非线性电阻——高能氧化锌在高压电力系统中的应用

本文介绍了氧化锌非线性电阻的伏安特性.在发电机及变压器供电网络加装高压限流熔断器和高能氧化锌非线性电阻可有效解决断路器保护的诸多不足.

交直流混合微电网保护方案的研究

交直流混合微电网中存在的分布式电源含有大量的电力电子器件,与配电网相连时,将会改变微电网的拓扑结构和潮流方向,传统的差动保护已经很难满足其保护的可靠性与速断性要求。因此,提出一种交直流相互配合的改进型差动保护方案。该方案通过分析交流母线电流变化率的大小,同时与直流侧相互配合确定保护动作区域,进而准确迅速的切除故障区域。仿真结果表明,该方案提高了交流系统保护与直流系统保护的相互配合,对交直流混合微电网的稳定运行具有重要意义。

交直流混合微电网组网和控制策略的研究与应用

交直流混合微电网中存在的分布式电源含有大量的电力电子器件,与配电网相连时,将会改变微电网的拓扑结构和潮流方向,传统的差动保护已经很难满足其保护的可靠性与速断性要求。因此,提出一种交直流相互配合的改进型差动保护方案。该方案通过分析交流母线电流变化率的大小,同时与直流侧相互配合确定保护动作区域,进而准确迅速的切除故障区域。仿真结果表明,该方案提高了交流系统保护与直流系统保护的相互配合,对交直流混合微电网的稳定运行具有重要意义。

Nonequilibrium Statistical Nature of Intergranular Brittle Fracture in Polycrystal

The brittle fracture probability and reliability are obtained in terms of dislocation mechanism of microcrack evolution. The statistical distribution functions and statistical deviations of elongation, strength, plastic work, crack extension force, fracture foughness, critical and crack length, can be derived in a unified fashion.

Dynamic tensile behaviors of AZ31B magnesium alloy processed by twin-roll casting and sequential hot rolling

The dynamic tensile behavior of twin-roll cast-rolled and hot-rolled AZ31B magnesium alloy was characterized over strainrates ranging from 0.001 to 375 s^-1 at room temperature using an elaborate dynamic tensile testing method, and the relationshipbetween its mechanical properties and microstructures. It is observed that the sheet has a strong initial basal fiber texture andmechanical twinning becomes prevalent to accommodate the high-rate deformation. The yield strength and ultimate tensile strengthmonotonically increase with increasing the strain rate, while the strain hardening exponent proportionally decreases with increasingthe strain rate due to twinning-induced softening. The total elongation at fracture distinctly decreases as the strain rate increasesunder quasi-static tension, while the effect of strain rate on the total elongation is not distinct under dynamic tension. Fractographicanalysis using a scanning electron microscope reveals that the fracture is a mixed mode of ductile and brittle fracture.

Effect of loading rate on fracture characteristics of rock

The three-point bending experiments were applied to investigating effects of loading rates on fracture toughness of Huanglong limestone. The fracture toughness of Huanglong limestone was measured over a wide range of loading rates from 9 × 10-4 to 1.537 MPa.m1/2/s. According to the approximate relationship between static and dynamic fracture toughness of Huanglong limestone, relationship between the growth velocity of crack and dynamic fracture toughness was obtained. The main conclusions are summarized as follows. （1） When the loading rate is higher than 0.027 MPa-ml/2/s, the fracture toughness of Huanglong limestone increases markedly with increasing loading rate. However, when loading rate is lower than 0.027 MPa-ml/2/s, fracture toughness slightly increases with an increase in loading rate. （2） It is found from experimental results that fracture toughness is linearly proportional to the logarithmic expression of loading rate. （3） For Huanglong limestone, when the growth velocity of crack is lower than 100 m/s, the energy release rate slightly decreases with increasing the growth velocity of crack. However, when the growth velocity of crack is higher than 1 000 m/s, the energy release rate dramatically decreases with an increase in the crack growth velocity.

Fast Diagnosis of Gonorrhea With Enhanced Luminescence Enzyme Immunoassay

Objective:To evaluate the value of enhanced luminescence enzyme immunoassay in the diagnosis of Neisseria gonorrhea(NG) infection. Methods: Anti-catalase antibody for Neisseria gonorrheae combined with enhanced luminescence enzyme immunoassay were used to test for N. gonorrhea. Results: A minimum of 1×10^4/CFU of GC in genital tract secretions or urine could be detected with the technique of luminescence enzyme immunoassay. Conclusion : The enhanced luminescence enzyme immunoassay has the advantage of high sensitivity and specificity for diagnosing NG from genitourinary tract secretion and urine.

煤矿供电系统保护装置的配置及效果质量分析

针对煤矿地面变电所与井下变电所距离过长而出现的供电系统保护装置配合等问题,提出供电系统保护装置的配置方案,从井下线路、变压器、反时限保护装置三方面进行优化配置,最后从速断性、选择性、可靠性方面对配置后的供电系统保护装置进行性能分析,结果表明:越级跳闸现象明显减少,停电范围大大缩小,系统的可靠性得到提高,煤矿的生产效率有所保障。

Outcomes of surgical management of tracheobronchial injuries a case series from a developing country

Objective： Tracheobronchial injuries are defined as injuries involving the trachea and/or bronchi from the level of the cricoid cartilage extending up to the division of the bronchi. We present a case series with most of the tracheobronchial injuries found to be sustained after penetrating trauma. Methods： A retrospective review was performed at the Aga Khan University, Karachi, Pakistan. From January 2004 to December 2009, 168 patients with thoracic trauma were treated, of whom 15 were recognized to have major tracheobronchial and pulmonary injuries. Results： The average age was 3 l years with most of the patients being male （14：1）. Among them,11 patients had penetrating trauma as the main cause of injury, 3 patients had blunt trauma from road traffic accidents, only 1 patient had combined trauma （blunt and penetrating trauma）. Eightpatients were diagnosed based on radiological findings. All the patients were treated surgically. Lobectomy was the most common intervention performed in 7 patients. The mortality rate was 7% （1 patient）. Most patients survived with no sequelae （10 patients） while 5 survived with disability. We found that penetrating trauma was the leading cause of injury in our series. The severity of injury depends upon the weapon causing the trauma. Patients in our series had multiple injuries and required surgical management. Conclusions： Tracheobronchial injuries are rare but potentially life threatening. They require quick diagnosis and management. Diagnosis tends to be difficult since there are no specialised diagnostic modalities available at present.