（六）风电场送出线路距离保护影响分析

从感应发电机基本原理出发,在转子转速旋转磁场坐标下,建立感应发电机简化三阶动态模型。从电路角度分析了风电场送出线电压、电流主频不同的机理,因此依据工频傅氏算法的相量距离保护元件的动作性能受到严重影响。利用Prony等算法分别提取保护安装处电压、电流工频及转速频率分量,可以准确测量出故障线路阻抗;基于线路时域微分方程模型的解微分方程算法距离元件不受信号频率影响。PSCAD／EMTDC仿真结果验证了分析的正确性。（详见2013年第33卷第6期）     

快速响应磁控电抗器抑制特高压操作过电压研究

针对高电压等级电网的过电压限制与无功补偿存在矛盾的问题,提出了一种大容量并具有快速响应能力的磁控电抗器的设计方案.磁控电抗器的本体采用单相双绕组结构,保证了运行可靠性;接入电网的三相电抗器组的工作绕组以星形联结,中性点接小电抗,控制绕组为三角形联结以减小输出谐波;通过对低压控制回路直流电压的调节实现对电抗器输出容量的控制.提出2种励磁方式实现了磁控电抗器响应速度的大幅提高;也可采用控制绕组短接的方法实现电抗器容量的突增,以限制线路的操作过电压水平.应用一条1000 kV特高压线路模型,对采用常规并联高压电抗器和磁控高压电抗器时对三相对称合闸过电压的限制效果进行了计算分析,结果表明应用快速响应磁控电抗器可以对特高压线路操作过电压进行有效限制.     

基于CYME的配电网可靠性评估应用

配电网供电可靠性直接影响用户的用电质量,应用电力系统分析软件CYME,对配电网进行建模分析。研究比较了不同供电半径和不同典型结构配电网的供电可靠性,并针对实际配电网算例,分析了不同开关动作时间下的配电网可靠性的情况;从各个负荷点可靠性的角度,寻找出该配电网中可靠性较差的负荷点,进而提出了具有针对性的网架优化方案,为配电网可靠性评估分析及应用提供了参考。     

基于多孔氧化铝模板的ZnO纳米线的制备

首先制备了优良的多孔氧化铝有序孔洞阵列,以其为模板,采用直流电化学沉积的方法,在其规则排列的孔中沉积得到锌纳米线;然后将其在高温下氧化,得到氧化锌纳米线.利用X射线衍射谱、扫描电子显微镜等手段研究了它们的微结构性质.X射线衍射谱表明,用电化学沉积方法得到的锌和氧化锌纳米线均为多晶结构.     

Ob ject-Based Classification Metho d for PolSAR Images with Improved Scattering Powers and Contextual Features

This paper proposes a new object-based classification method for Polarimetric synthetic aperture radar (PolSAR) images, which considers scattering powers from an improved model-based polarimetric decomposition approach, as well as the spatial and textural features. With the decomposition, the scattering ambiguities between ori-ented buildings and vegetation are reduced. Furthermore, various contextual features are extracted from the ob ject and incorporated into the K-nearest neighbors (k-NN) based classification. To reduce the feature redundancy, a new Supervised locally linear embedding (S-LLE) dimen-sionality reduction method is introduced to map the high dimensional polarimetric signatures into the most compact low-dimensional structure for classification. Experimental results with Airborne synthetic aperture rada (AIRSAR) C-band PolSAR image demonstrate the superior perfor-mance to other methods.     

Experimental Investigation of Heat Transfer in Microchannel with Inlet Cavitation Structure

Heat transfer of R134 a through the microchannel with an inlet reentrant cavitation structure was investigated for high flux thermal management of electronic devices.The cavitating flow patterns,pressure,and heat transfer characteristics were studied in the range of effective heat fluxes from 0 to 138.4 W/cm2 with mass flow velocities from 2.12 to 5.23 m/s.A stable and ideal starting point of two phase flow and heat transfer was commendably provided by the inlet cavitation orifice.There existed an axis deviation liquid jet after the micro-orifice.The refrigeration vapor was generated from the cavitation structure but liquidized at the downstream of the channel.The wall temperature along flow orientation presented an opposite trend under the test states with or without heat input.The cavitation structure can significantly suppress the flow oscillation in microchannels and the outlet pressure fluctuation reduced about 72%compared with the fluctuation at the entrance.The heat transfer coefficient had been distinctly impacted by heat flux at lower heat input and then maintained the value nearly constant of 11.0 W/(cm²·K)with the critical heat flux of 88.4 W/cm2.     

乳化石蜡脱模剂配方选择

采用了石蜡、水、乳化剂为主要原料制备了一种水基型脱模剂,介绍了脱模剂的配方、制备工艺、脱模效果及性能测试。     

Multi-user security of the tweakable Even-Mansour cipher

Dear editor, Data security, including data privacy security and data integrity security, are usually achieved by a cryptographic algorithm.Block ciphers axe wid...     

板坯连铸结晶器铜板热机耦合应力分析

通过对大板坯连铸结晶器铜板热电偶的实测温度数据的分析,获得了铜板温度场分布的基本规律,在考虑钢水、铸坯、铜板以及接触面介质的物理参数随温度变化的前提下,依托有限元软件ANSYS对结晶器铜板的动态温度场、耦合应力场进行动态仿真,获得了铜板在三排热电偶高度上的温度分布与耦合应力应变规律,研究结果为了解铜板的应力/变形情况以及铸坯缺陷分析提供了较好的数据参考.     

地热资源在供热空调开发利用中的研究现状和进展

本文首先回顾了国内外地热资源在供热空调方面的应用历程及研究现状,重点介绍了当前地热供暖空调的新技术。其次,就目前系统开发设计中遇到的问题提出并分析了应采取的措施,为地热资源的合理利用提供了依据。