A new analysis method for early detection and prevention of cascading events

This paper introduces a new analysis method for early detection and prevention of power system cascading events. It uses the vulnerability index (VI) and margin index (MI) to evaluate the vulnerability and security of the individual system parts, as well as the whole system during an operating state. It identifies the vulnerable parts of the power system using the topology processing and operation index methods. For a given disturbance, it calculates the power flow, evaluates the vulnerability and security, identifies the vulnerable part, finds the transmission line overload and bus voltage problems, and predicts the possible successive events. The approach defines the control means using the following methods for early detection and prevention of cascading events: network contribution factor (NCF), generator distribution factor (GDF), load distribution factor (LDF), and selected minimum load shedding (SMLS). This approach has been tested using the IEEE RTS-96 24-bus system and promising results have been obtained. The proposed approach allows the power system operator to detect initial stages of cascading events and assert actions that will prevent such events from unfolding.     

Cutter mark cross method for improvement of contact stiffness by controlling distribution of real contact area

Contact surfaces do not make contact perfectly because such surfaces have a lot of asperities. The real contact area is much smaller than the nominal contact area, and the real contact areas has a non-uniform distribution because of the waviness in the contact surface. The contact stiffness is influenced not only by the deformation of the asperities, but also by the distribution of the real contact areas. In general, a contact surface with a uniform distribution of the real contact areas has greater contact stiffness. However, this requires a grinding finish and costs more than the cutting finish. In this study, a method for uniformly distributing the real contact areas easily, is proposed to improve the contact stiffness of a contact surface finished by cutting. The method is called the cutter mark cross (CMC) method. The allowable waviness in the CMC method is shown. In addition, the effect of the CMC method is investigated by experimentation. The results show that the real contact areas can be distributed uniformly using the CMC method. The horizontal and vertical contact stiffness can also be improved.     

LUBRICATION FILM FORMATION MECHANISM OF SLIPPER PAIRS IN LOW SPEED HIGH TORQUE HYDRAULIC MOTORS

Pressure-flow analytical formulas of lubrication film of slipper pairs on camshaft connect- ing rod type low speed high torque (LSHT) hydraulic motors are put forward. The bottom surface of slipper pairs is rectangle, and the effect of squeeze flow and pressure differential flow is considered. The dynamic process of lubrication film formation through squeezing is numerically studied by com- puter simulation. Effects of supply pressure, initial lubrication film thickness, velocity damping coef- ficient, loading impact and gravity, etc are studied. Advantages of novel slipper pairs with large oil cavity area are pointed out.     

山区弱电系统的接地设计与降阻措施探讨

通过对山区弱电系统在接地上普遍存在的土壤电阻率高,可用场地小,地势险峻、地形复杂等因难因素的分析;讨论了山区弱电系统在接地设计和降阻改造的措施。提出了综合地利用自然接地体,在适当地区设置外延接地及沿道路外延降阻方法。通过分析、讨论认为只要充分采取合理、有效的降阻措施,是能够有效降低山区弱电系统的接地电阻,保证弱电系统安全运行。     

Modafinil Administration to Preadolescent Rat Impairs Non-Selective Attention,Frontal Cortex D2 Expression and Mesolimbic GABA Levels

The misuse of psychostimulants is an increasing behavior among young people, highlighting in some countries the abuse of modafinil (MOD) as a neuropotentiator. However, several clinical trials are investigating MOD as an alternative pharmacological treatment for attentional deficit and hyperactivity disorder (ADHD) in children and adolescents. On the other hand, the early use of psychostimulants and the misdiagnosis rates in ADHD make it crucial to investigate the brain effects of this type of drug in young healthy individuals. The aim of this work was to evaluate the effects of chronic MOD treatment on neurochemicals (γ-aminobutyric acid and glutamate), dopamine receptor 2 (D₂) expression and behavior (non-selective attention “NSA”) in the mesocorticolimbic system of young healthy Sprague–Dawley rats. Preadolescent male rats were injected with MOD (75 mg/kg, i.p.) or a vehicle for 14 days (from postnatal day 22 to 35). At postnatal day 36, we measured the GLU and GABA contents and their extracellular levels in the nucleus accumbens (NAc). In addition, the GLU and GABA contents were measured in the ventral tegmental area (VTA) and D₂ protein levels in the prefrontal cortex (PFC). Chronic use of MOD during adolescence induces behavioral and neurochemical changes associated with the mesocorticolimbic system, such as a reduction in PFC D₂ expression, VTA GABA levels and NSA. These results contribute to the understanding of the neurological effects of chronic MOD use on a young healthy brain.     

住宅小区的机械停车设备

目前国内轿车的保有量越来越大,停车问题越来越严重。本文研究城市住宅小区停车方式,开发了一种简易升降式机械停车设备。     

点云空间与反射强度融合的非结构化道路可行驶区域检测

可行驶区域检测旨在检测和提取智能车辆在道路上可行进的区域, 目前主流的检测方法主要基于三维激光雷达的空间特征实现, 难以处理路面边缘无清晰空间特征的非结构化道路. 为此, 本文提出了一种基于点云空间和反射强度融合的非结构化道路可行驶区域检测方法. 首先, 通过融合反射强度因子改进了基于空间特征的柱坐标系检测模型; 然后, 使用强度和降维空间检测对检测精度较低的环形检测模型进行优化, 并将其与柱坐标系检测模型联合使用以提高方法检测准确率; 最后, 在自录实际道路数据集上进行对比实验. 实验结果表明本文方法显著提高了非结构化道路可行驶区域检测的成功率与精确率, 在结构化道路上也具有良好效果.     

柴达木盆地西部大风山地区古近系下干柴沟组下段物源方向研究

目前普遍认为柴达木盆地西部大风山地区古近系下干柴沟组下段(E13)只发育向西南方向流动的牛鼻子梁物源所形成的冲积扇-河流-辫状河三角洲-湖泊沉积体系,对于物源方向的这种认识难以解释以下事实:第一,风2井在E31发育厚层辫状水道砂岩,而位于上倾方向碱1井的对应层位则发育薄、中厚层河口砂坝砂和分流水道砂;第二,在E13沉积时,牛鼻子梁地区是阿尔金山向东南方向延伸的古鼻梁,该古鼻梁是牛鼻子梁以北地区物源向西南方向流动的屏障;第三,牛参1井位于长期继承性发育的一里坪凹陷的西北边缘,大风山地区的古地貌要高于一里坪凹陷;第四,坪东F1断层与坪东F2断层所夹持的区域在E31时是一个继承性发育的小型断陷。在综合研究该地区的钻井、测井、二维地震资料和古地理背景的基础上,首次提出在E13沉积时,大风山地区的物源来自红三旱一号以北地区,而一里坪坳陷是牛鼻子梁物源汇聚区的新认识。这一新认识对于重新认识大风山地区的沉积体系及寻找优质有效碎屑岩储层具有重要的勘探实践意义。     

An LDMOS with large SOA and low specific on-resistance

An LDMOS with nearly rectangular-shape safe operation area (SOA) and low specific on-resistance is proposed. By utilizing a split gate, an electron accumulation layer is formed near the surface of the n-drift region to improve current conduction capability during on-state operation. As a result, the specific on-resistance can be lowered down to 74.7 mΩ·cm² for a 600 V device from simulation. Furthermore, under high-voltage and high-current conditions, electrons and holes flow as majority carriers in the n-drift region and p-type split gate, respectively. Due to charge compensation occurring between holes and electrons, the local electric field is reduced and impact ionization is weakened in the proposed device. Therefore, a higher on-state breakdown voltage at large V_GS is obtained and snap-back is suppressed as well.     

分子束外延碲镉汞探测器的变结面积I-V测试研究

碲镉汞红外探测器的表面钝化处理对器件暗电流有较大影响,决定了器件的探测性能。为了研究表面钝化层不同生长方式对暗电流的抑制效果,使用分子束外延(Molecular Beam Epitaxy, MBE)系统在Si基衬底上生长碲镉汞材料,分别通过磁控溅射和原位钝化方法生长CdTe/ZnS钝化膜层。采用半导体工艺在碲镉汞材料上制备了变面积光伏探测器。通过测试不同钝化膜层器件的暗电流,分析零偏电阻和面积乘积(R₀A)与周长面积之比(p/A)的关系。结果表明,磁控溅射生长钝化层的Si基碲镉汞器件存在较大的隧穿电流,而原位钝化生长钝化层的Si基碲镉汞器件能更有效地抑制表面漏电流。拟合器件R₀A因子随PN结面积的变化,得出原位生长钝化层的器件具有更好的钝化效果。变面积器件的制备和测试能够有效且直观地反映器件性能。