基于EAP无线安全认证系统的设计和实现

网络安全一直是计算机领域受关注的课题。现有802．11设备采用的WEP技术存在一定的安全隐患,无法保证无线局域网的安全。基于IEEE802.1x／EAP协议规范,提出了一种有效的认证／授权模式,并探讨了在Linux环境下无线局域网中安全认证系统认证端的设计与实现。     

双波长波片导致的脉冲分离对双色场辐射太赫兹波的影响

由于群速度的偏振依赖性,飞秒激光脉冲入射到双波长波片时出射光脉冲会分离为两个具有一定时间延迟的飞秒激光脉冲。从实验和理论模拟两方面研究了双波长波片导致的脉冲分离现象对飞秒激光双色场成丝辐射太赫兹(THz)波效率的影响。实验结果表明,脉冲分离导致的时间延迟会降低双色场辐射THz波的效率,可通过零级双波长波片缩短分离脉冲之间的时间延迟,有效提高THz波的产生效率。     

Fluorobenzotriazole (FTAZ)‐Based Polymer Donor Enables Organic Solar Cells Exceeding 12% Efficiency

The fluorobenzotriazole (FTAZ)‐based copolymer donors are promising candidates for nonfullerene polymer solar cells (PSCs), but suffer from relatively low photovoltaic performance due to their unsuitable energy levels and unfavorable morphology. Herein, three polymer donors, L24 , L68 , and L810 , based on a chlorinated‐thienyl benzodithiophene (BDT‐2Cl) unit and FTAZ with different branched alkyl side chain, are synthesized. Incorporation of a chlorine (Cl) atom into the BDT unit is found to distinctly optimize the molecular planarity, energy levels, and improve the polymerization activity. Impressively, subtle side chain length of FTAZ realizes a dramatic improvement in all the device parameters, as revealed by the short‐current density (J_sc) improved from 7.41 to 20.76 mA cm^?2, fill‐factor from 36.3 to 73.5%, and even the open‐circuit voltage (V_oc) from 0.495 to 0.790 V. The best power conversion efficiency (PCE) of 12.1% is obtained from the L810‐based device, which is one of the highest values reported for FTAZ‐based PSCs so far. Notably, the corresponding external quantum efficiency curve keeps a very prominent value up to 80% from 500 to 800 nm. The notable performance is discovered from the reduced energy loss, improved molecular face‐on orientation, the down‐shifted energy levels, and optimized absorption coefficient regulated by side‐chain engineering.     

干熄炉内环形集气道压降及阻力系数的研究

借助CFD商业软件CFX数值模拟了干熄炉环形集气道内气体的湍流流动,并计算了各斜道区的压力分布。计算结果与现场实测数据吻合较好,验证了数值模拟的准确性。借鉴管路计算中局部阻力系数的概念,进一步计算了斜道区不同压砖情况下的压力损失系数。三种几何尺寸模型的计算结果表明,所得到的压力损失系数具有一定的通用性,可为干熄炉大型化环形集气道的设计提供参考。     

我国城市绿地建设水平的区域差异研究

我国城市绿地建设存在一定的地区差异,这种差异直接反映在人均公共绿地面积、建成区绿地率和建成区绿化覆盖率这三项绿地指标上。以省为单位,依据这三项绿地指标进行聚类分析,可将全国31个省、自治区、直辖市分为城市绿化先进区、达标区、未达标区和缺乏区四类。我国城市绿地建设水平自东向西呈阶梯状由高到低变化,主要是受地形地貌、城市建设资金投入、发展理念等因素的影响。     

位相调制三倍频激光束聚焦特性的衍射模型

基于三次谐波转换过程中位相扰动的传输变换 ,理论上研究了非线性晶体表面周期性纹波对三倍频激光束聚焦特性的影响 ,建立了多级衍射模型。该理论模型能解析地分析多级衍射峰的强度分布及角度分布 ,可为高功率激光驱动器三倍频器的设计提供理论依据     

Al-Ni-Co微细球形粉末的制备及SLM成形研究

采用气雾化(IGA)制备了Al-Ni-Co粉末,初筛后的最大粉末粒径小于150μm。分别采用霍尔流速计、XRD、SEM、VSM等测试方法研究了不同粒径范围Al-Ni-Co微粉的微观形貌、相成分、磁性能等。研究表明：微粉的球化率在95%左右;50～80μm范围微粉的流动性相对最好;20μm以下微粉因为粒径偏小,成分偏析较为严重;80～150μm微粉因为粒径过大,表面吸附卫星小颗粒,粗糙度较差;Al-Ni-Co微粉的磁性为软磁,相组成为AlNi和FeCo相。综合比较微观结构、相成分及粉末占比量,选取20～80μm的Al-Ni-Co微粉采用SLM法制备了6组Al-Ni-Co圆柱形磁体,热处理后磁体的密度、磁性等综合性能达到铸造Al-Ni-Co磁体的性能水平。     

糙米结合酚的分离纯化、结构表征及体外抗氧化活性

本研究以糙米为材料,通过碱解得到结合态酚粗提物,采用多种色谱手段分离纯化得到4种单体物质,通过高效液相色谱-质谱(LC-MS)、核磁共振(NMR)等波谱学方法鉴定其化学结构.4个单体化合物分别为6-羟基-2-氧代-1,2,3,4-四氢喹啉-4-羧酸甲酯(1)、4-羧甲氧基-6-羟基-2-喹诺酮(2)、4-羧基-6-羟基...     

Experimental Verification of Doppler Effect with the Refraction Method

The traditional methad of measuring Dopplr Effect is either reflection or dispersion.This article clarifies that it can also verify the Doppler Effect with the refraction method.We have designed the experimental system with the method of optical heterodyne,using the refraction light beam from a prism,and made the experiment.The experimental results are in accordance with the theoreticai calculation.It is very useful in some particular case,such as in Negative-Index Materials(NIM),to verify the Doppler Effect with this method.     

开关磁阻发电机最大输出功率的控制原则

对开关磁阻发电机的工作原理进行了介绍,基于线性模型下对开关磁阻发电机的输出功率进行了分析计算,根据推导出来的公式使用MATLAB建立了开关磁阻发电机的数学模型,针对影响开关磁阻发电机输出功率的设计参数和控制变量如开通角、关断角、母线电压、转速等逐一进行了仿真计算,提出了实现开关磁阻发电机最大输出功率的控制原则,并进行了部分实验验证.