在线氧化分光光度法测定铁的价态

1 引言 铁的价态影响着铁在生态系统中的迁移性、生物可利用性以及毒性.本研究基于Fe3+与钛铁试剂在酸性条件下生成蓝紫色络合物的反应原理,建立了顺序注射在线氧化测定铁的价态的光度分析方法.     

Streamlined,two-column,simulated countercurrent chromatography for binary separation

We report on a numerical and experimental study of two-column versions of streamlined, multicolumn, semi-continuous chromatography for binary separation. The systems combine a flexible node design, cyclic flow-rate modulation, and relayed operation of the inlet/outlet ports to extend the mass-transfer zone over the largest possible length, while keeping it inside the system at all times. One advantage of these streamlined designs is the simplicity of their physical realization: regardless of the number of columns, they only require two pumps to supply feed and desorbent into the system, while the flow rates of liquid withdrawn from the system are controlled by material balance using simple two-way valves. In one case, an extra pump is needed to recirculate the fluid in closed-loop. A rigorous model-based optimization approach is employed in the optimal design of the cycles to generate solutions that are physically realizable in the experimental set-ups. The optimized schemes for two-column operation supply fresh feed into the middle of the system where the composition of the circulating fluid is closest to that of the feedstock fluid, and recover the purified products, extract and raffinate, alternately at the downstream end of the unit, while desorbent is continuously supplied into the upstream end of the system. By internally recycling part of the non-pure cut fraction, the scheme with a step of closed-loop recycling significantly reduces its solvent consumption. The feasibility and effectiveness of the reported two-column processes have been verified experimentally on the linear separation of nucleosides by reversed phase subject to 99% purity constraints on both products. It is shown that our processes compare favorably against single-column batch chromatography, steady-state recycling, and four-column, open-loop SMB, for the same amount of adsorbent; they are also better than the four-column, closed-loop SMB at high feed throughputs.     

Water-compatible iminium activation: highly enantioselective organocatalytic Michael addition of malonates to α,β-unsaturated enones

The highly enantioselective Michael addition of malonates to α,β-unsaturated ketones in water was reported to be catalyzed by a primary-secondary diamine catalyst containing a long alkyl chain. This asymmetric Michael addition process was found to be effective for a variety of α,β-unsaturated ketones.     

电子产品环境与可靠性试验应力研究

本文从有关标准入手,论述了环境试验与可靠性试验的基本概念及相互关系,重点介绍了环境试验和可靠性试验在应力施加上的异同点,指出了进行这两项试验的重要性。     

宽带GaN单片功率放大器研究

基于GaN HEMT器件在微波功率方面的优越性能,设计并实现了宽带GaN单片功率放大器.简述了AlGaN/GaN异质结构的优势以及现状,同时结合热分析的方法给出了所选GaN HEMT器件的基本尺寸和性能,并采用ICCAP提取了合适的大信号模型,通过器件性能优选拓扑结构,最终运用宽带匹配的方法并结合较先进的仿真软件设计了一款GaN宽带单片功率放大器.测试结果表明,单片放大器脉冲工作方式下在2～7 GHz频带内,小信号增益G＞18 dB,输入回损＜-10 dB,脉冲饱和输出功率Po＞5 W,功率增益GP＞15 dB,典型功率附加效率25%(测试条件为脉宽100μs,占空比10%).GaN HEMT器件具有较高的功率密度和良好的宽带特点.     

一种基于DFT滑动窗的实时FSK解调算法

介绍一种FSK调制信号的解调算法方案,并在DFT滑动窗理论基础上完成实时运算。首先根据傅里叶变换中频域与时域的运算关系,针对已知FSK信号的特定频率完成相应的运算参数配置,达到优化硬件资源的目的;同时,根据此优化设计完成的滑动窗运算可以达到实时性,极大地降低了在通信FSK解调系统中对调频信号到数字码的转换时间,达到提高整体通信速度的目的。     

国外多种数据链综合应用研究

从网络中心战对数据链发展的要求出发,结合外军数据链发展情况及特点,着重论述了多种数据链综合应用所面临的技术挑战及解决途径。分析了建设全球信息栅格面临的技术困难,并提出我军数据链综合应用需从以主用数据链为主实现多数据链信息共享、数据链距离扩展及数据链、与计算机互联网络的互联等方向的几点启示。     

B位非化学计量比对0.6BCN-0.4BZN陶瓷性能的影响

采用传统固相反应法,制备了Ba(Co0.6Zn0.4)1/3Nb2/3O3(0.6BCN-0.4BZN)微波介质陶瓷。系统研究了Ba(Co0.6Zn0.4)(1/3+x)Nb2/3O3陶瓷中B位(Zn,Co)离子的非化学计量比(x=-0.015,-0.009,-0.003,0,0.003,0.009,0.015)对该微波介质陶瓷性能的影响。结果表明:少量的B位离子缺量,可以促进烧结的致密化。x为-0.009时所制陶瓷密度最大,达到理论密度的99%以上。在1400℃下烧结20h,可以获得εr=35.35,Q.f=40787GHz(f=5.180GHz),τf=-3×10-6/℃的0.6BCN-0.4BZN陶瓷。     

PIN型非晶硅薄膜太阳电池仿真研究

运用AMPS软件,对TCO/p-a-SiC:H/i-a-Si:H/n-a-Si:H/metal型非晶硅薄膜太阳电池进行了仿真研究,重点模拟和分析了电池性能参数随i层和n层厚度变化的规律.结果表明,为了获得电池转换效率和短路电流密度的最大值,n 层非晶硅薄膜应尽可能地减小厚度,而i层非晶硅薄膜厚度最好控制在500～700 nm范围内.     

基于FPGA的嵌入式三态以太网的设计

采用Xilinx的ISE、EDK设计工具,利用Virtex-5 LXT芯片实现嵌入式三态以太网.主要介绍了嵌入式以太网的系统结构,在硬件设计方面,详细阐述了基于EDK的嵌入式模块设计以及MARVELL的88E1111-RCJ物理层接口芯片的外围电路设计;在软件方面,详细阐述了采用VHDL进行MAC控制器的时序控制设计和采用C++进行MicroBlaze的嵌入式模块的设计,最后给出了仿真结果.