线路分闸时的电弧现象分析

从开关电器电弧产生的一般机理、物理过程，电弧熄灭的随机性等方面进行了分析，就电气操作过程中带电作业时发生的拉弧现象进行了探讨，针对线路分闸时出现电弧现象的原因提出了有效的防制措施。     

Encoding of conditioned fear in central amygdala inhibitory circuits

The central amygdala (CEA), a nucleus predominantly composed of GABAergic inhibitory neurons, is essential for fear conditioning. How the acquisition and expression of conditioned fear are encoded within CEA inhibitory circuits is not understood. Using in vivo electrophysiological, optogenetic and pharmacological approaches in mice, we show that neuronal activity in the lateral subdivision of the central amygdala (CEl) is required for fear acquisition, whereas conditioned fear responses are driven by output neurons in the medial subdivision (CEm). Functional circuit analysis revealed that inhibitory CEA microcircuits are highly organized and that cell-type-specific plasticity of phasic and tonic activity in the CEl to CEm pathway may gate fear expression and regulate fear generalization. Our results define the functional architecture of CEA microcircuits and their role in the acquisition and regulation of conditioned fear behaviour.     

电流速断保护的灵敏性校验方法

文章根据无时限电流速断保护具有快速性的优点和灵敏性差、保护范围小的缺点,着重研究了这种继电保护灵敏性的校验方法,并说明了不同校验方法的适用条件和适用场合。     

Horizontal and vertical components of head movement are controlled by distinct neural circuits in the barn owl

To generate behaviour, the brain must transform sensory information into signals that are appropriate to control movement. Sensory and motor coordinate frames are fundamentally different, however: sensory coordinates are based on the spatiotemporal patterns of activity arising from the various sense organs, whereas motor coordinates are based on the pulling directions of muscles or groups of muscles. Results from psychophysical experiments suggest that in the process of transforming sensory information into motor control signals, the brain encodes movements in abstract or extrinsic coordinate frames, that is ones not closely related to the geometry of the sensory apparatus or of the skeletomusculature. Here we show that an abstract code underlies movements of the head by the barn owl. Specifically, the data show that subsequent to the retinotopic code for space in the optic tectum yet before the motor neuron code for muscle tensions there exists a code for head movement in which upward, downward, leftward and rightward components of movement are controlled by four functionally distinct neural circuits. Such independent coding of orthogonal components of movement may be a common intermediate step in the transformation of sensation into behaviour.     

塔吊专用三速电动机不断电切换方案的设计

分析了塔吊三速电动机的工作状态,针对4／8／32极电动机设计中存在的问题提出新的不断电切换的变极方案,并较详细地叙述了32／8极电动机的设计过程．     

PWM控制的开关电源

分析了采用整流-逆变-整流主电路结构的典型PWM控制的开关电源,并利用MATLAB建立了一个基于PID控制的开关电源模型.利用该模型对电力机车110 V高频大容量开关电源进行了仿真,给出了仿真结果.     

三层交换及虚拟网技术的应用研究

第三层交换技术是将网络层的功能融入交换机，将第二层交换机与第三层路由器两者的优势集成在一起，在各个层次提高网络速度性能的一种网络技术．用三层交换机可取代传统路由器充当局域网路由器，采用三层交换技术还可有效地提高网络的性能和安全性，并使网络管理员对网络管理更加灵活方便．因此，三层交换和VLAN技术已经成为中小型校园网建设的有效解决方案。     

模糊极小圈的若干性质

通过研究模糊极小圈的性质,在模糊拟阵中定义了一种新的连通性,由这种连通性研究了一个闭模糊拟阵与其对偶模糊拟阵的秩函数的性质,给出了一个模糊拟阵为连通模糊拟阵的等价刻画.最后,研究了两个连通模糊拟阵的直和以及模糊连通分支的性质.     

基于链型等效电路的鼠笼式异步电机启动研究

采用链型等效电路,对影响启动的高次谐波建立谐波等效电路,推导出参数的计算公式,通过分析和计算,绘制出鼠笼式异步电机的转矩-转差率(T-s)曲线,为电机设计和绕组选择提供评估参考.仿真结果表明即使高次谐波含量很小,也可能造成较大的转矩下凹,从而影响启动.     

交换式网络的技术性能分析

在新的网络应用需求面前,交换式网络为传统共享介质网络的升级与改造提供了良好的解决方案。分析了交换网络的优点,并对3ComSuperStackSwitch1000交换机所具有的性能进行了介绍。     

反激式开关电源的分析与研究

分析了反激式开关电源中变换器的两种工作模式和PWM控制模式．指出了电流控制模式在反激式开关电源中的使用优势及存在问题,并提出相关解决措施。     

Investigation on apoptosis of neuronal cells induced by Amyloid beta-Protein

Objective: To construct a PC12 cell strain with neuronal differentiation, and observe the apoptosis and pro-liferation activity effects induced these cells by Amyloid beta-Protein (Aβ3-43). Methods: 1) PC12 cells in logarithmic growth phase were subcultured for 24 h. After the culture fluid was changed, the cells were treated with Rat-β-NGF and cultured for 9 days. 2) Neuronal differentiation of PC 12 cells in logarithmic growth phase were divided into four groups:control group (0), experimental group (1), experimental group (2) and experimental group (3). The concentrations of Aβ in the four groups were 0 μmol/L, 1.25 μmol/L, 2.5 μmol/L and 5 μmol/L, respectively. The cells were harvested at 24, 48 and 72 h later and stained with AnnexinV-FITC/PI after centrifugation and washing. Then flow cytometry was conducted to examine the apoptosis percentage. 3) NGF-induced PC12 cells were selected and Aβ with different concentrations was added. The final concentrations of Aβ were 0 μmol/L, 1.25 μmol/L, 2.5 μmol/L and 5 μmol/L, respectively. After the cells were incubated in an atmosphere of 5% CO2 at 37 ℃ in an incubator for 72 h, the OD values were examined. Results: 1)Neuronal differentiated PC12 cell lines were successfully established. 2) Flow cytometric examination indicated that Aβ(1.25, 2.5, and 5.0 μmol/L) could effectively induce apoptosis of neuronal-differented cells at the 24 h, 48 h and 72 h time points. 3) Aβ (0-5.00 μmol/L) had no obvious effect on proliferation or restraining of the neuronal differentiation of the PC 12 cells after a 72 h interacting process. Conclusion: This investigation revealed successful neuronal differentiation of the PC12 cell strain. The induction of apoptosis of the neurocytes by various concentrations of Aβ was observed and the in-fluence of Aβ on induced proliferation of PC 12 cells by Rat-β-NGF was revealed. This study may provide basis for future research on the molecular cure of AD and interdiction of AD evolution.     

一项数学调查引发的思考

应用型本科“大学数学”教学改革的主要方向之一是由原来的以理论教学为重点转向对知识的应用方面。改革的负作用是容易出现数学教学偏重符号演算和解题技巧训练,忽视概念教学的倾向。对此,本文提出了相应的教学建议。     

Turning on and off recurrent balanced cortical activity

The vast majority of synaptic connections onto neurons in the cerebral cortex arise from other cortical neurons, both excitatory and inhibitory, forming local and distant 'recurrent' networks. Although this is a basic theme of cortical organization, its study has been limited largely to theoretical investigations, which predict that local recurrent networks show a proportionality or balance between recurrent excitation and inhibition, allowing the generation of stable periods of activity. This recurrent activity might underlie such diverse operations as short-term memory, the modulation of neuronal excitability with attention, and the generation of spontaneous activity during sleep. Here we show that local cortical circuits do indeed operate through a proportional balance of excitation and inhibition generated through local recurrent connections, and that the operation of such circuits can generate self-sustaining activity that can be turned on and off by synaptic inputs. These results confirm the long-hypothesized role of recurrent activity as a basic operation of the cerebral cortex.     

基于ATM的话音交换技术

利用ＡＴＭ网络进行电路仿真通信是当前ＡＴＭ应用研究的一个热点问题,通过对话音ＡＴＭ电路仿真技术进行分析,指出了这种工作方式在实际应用中存在的一些问题．在此基础上,提出了一种基于ＮａｔｉｖｅｍｏｄｅＡＴＭ的话音通信方式,并对其应用方式和关键技术进行了分析．实践证明,基于Ｎａｔｉｖｅｍｏｄｅ的工作方式提高了带宽利用率和系统整体效率,适用于语音数据集成的应用环境．