氨水工质浓度可调型功冷联供循环

本文提出一个新型氨水工质功冷联供循环,由氨水Rankine子循环和氨吸收式制冷子循环通过吸收、分离及换热过程耦合而成,可采用燃气轮机排烟等中低温热源驱动.通过设置分流、吸收式冷凝实现系统内氨水工质浓度变换,兼顾动力子循环加热蒸发和冷凝过程不同的浓度需求,达到改善换热过程匹配和提高透平作功能力的目的.计算表明,当透平进气温度为450℃时,循环热效率达25%～28%,??效率达45%～53%;且存在最佳分流比使热效率及??效率达到最佳.     

通过低熵合金实现铂金属d轨道的调控（英文）

对催化剂中活性位电子结构的精准调控是实现精准催化最有效的手段之一,常见的方法包括调控晶格应力、电荷转移等。在掺杂材料体系中,人们已经运用原子晕效应等理论来解释异原子活性位几何、电子结构的改变给基底材料所带来的物理、化学性质的改变,进而实现对催化等性能的调控。本文以低熵合金为研究对象,通过第一性原理计算提出了轨道及自旋调控的新途径来尝试实现对催化的精准调控,即通过改变Pt原子的d轨道来实现对催化性能的调控。分别模拟了Pt和Pt-Fe合金在不同的吸附位点下对O₂分子的吸附过程。结果发现,Fe原子的掺入在削弱表面Pt原子对O₂分子吸附的情况下却没有影响其解离。通过投影态密度(PDOS)分析得到Pt-Fe合金中Fe-3d和Pt-5d轨道有较强的杂化,从而导致了Pt的d轨道发生偏移的同时产生了自旋极化现象。部分Pt的电子态移动到费米能级之上,与O₂-π^*产生交叠,进而导致了Pt-Fe合金中的Pt-5d与O₂-π^*的杂化程度明显高于纯Pt体系。理论研究表明,通过这种低...     

CO2加氢合成二甲醚的催化剂的制备

先采用均匀沉淀法制备出CuO—ZnO催化剂,然后以CuO—ZnO催化剂作为晶核采用水热合成法制备出CuO—ZnO／HZSM-5（氢型ZSM-5分子筛）复合催化剂．利用X射线衍射和氨程序升温脱附手段对复合催化剂进行表征,并应用于CO2催化加氢合成二甲醚的反应．研究结果表明,在相同的反应条件下,这种CuO—ZnO／HZSM-5复合催化剂与采用物理混合法制备出的复合催化剂相比具有更好的催化效果,不但提高了CO2的转化率、二甲醚的选择性以及二甲醚和甲醇的总选择性,同时还改善了催化剂的稳定性．     

Analysis of secondary electron emission using the fractal method

Based on the rough surface topography with fractal parameters and the Monte–Carlo simulation method for secondary electron emission properties, we analyze the secondary electron yield(SEY) of a metal with rough surface topography. The results show that when the characteristic length scale of the surface, G, is larger than 1 × 10^-7, the surface roughness increases with the increasing fractal dimension D. When the surface roughness becomes larger, it is difficult for entered electrons to escape surface. As a result, more electrons are collected and then SEY decreases. When G is less than 1 × 10^-7,the effect of the surface topography can be ignored, and the SEY almost has no change as the dimension D increases. Then,the multipactor thresholds of a C-band rectangular impedance transfer and an ultrahigh-frequency-band coaxial impedance transfer are predicted by the relationship between the SEY and the fractal parameters. It is verified that for practical microwave devices, the larger the parameter G is, the higher the multipactor threshold is. Also, the larger the value of D,the higher the multipactor threshold.     

利用三维构效关系确定互变异构抑制剂的活性构象

HPPD酶抑制剂NTBC存在多种互变异构体,其优势构象受溶液环境影响显著,不同的观测手段确定NT-BC的优势结构存在差异.本文首次采用了三维构效关系CoMFA和CoMSIA对NTBC类似物的5种可能的活性构象进行了研究.根据NTBC类似物以离子为活性构象得到的CoMFA模型具有最佳预测能力,推测NTBC以离子形式与HPPD键合,该结论与文献通过动力学实验预测的结合模式相吻合,这对进一步研究HPPD与NTBC的作用机理以及开发高效抑制剂提供了理论依据.     

Two-stage adaptive PMD compensation in 40-Gb/s OTDM optical communication system

An experiment of two-stage adaptive compensation for polarization mode dispersion (PMD) in a 40-Gb/s optical time-division multiplexed communication system is reported. The PMD monitoring technique based on degree of polarization was adopted. The particle swarm optimization (PSO) algorithm was introduced in adaptive PMD compensation. The comparison was made to estimate the effectiveness between PSO algorithms with global neighborhood structure (GPSO) and with local neighborhood structure (LPSO).The LPSO algorithm is shown to be more effective to search global optimum for PMD compensation than GPSO algorithm. The two-stage PMD compensator is shown to be effective for both first- and second order PMD, and the compensator is shown to be bit rate independent. The optimum searching time is within one hundred milliseconds.     

利用LNG冷(火用)与工业余热的闭式Brayton循环的进一步分析

以超临界状态的LNG作为冷源,以工业余热作为热源的闭式Brayton循环,可以有效的利用LNG的冷(?)并回收工业余热。本文以(?)效率为评价准则,兼顾LNG冷(?)和工业余热的利用,对该循环进行了热力学分析。在分析过程中,利用以前分析所得的结论[1],选取的循环自变量数为4,针对不同的自变量、不同的LNG冷(?)和工业余热利用情况,对多种循环方案作了进一步(考虑了循环与冷、热源的匹配)较详细的热力学分析,并得出较明确的性能表达。     

多元掺杂尖晶石型Li1.02MxMn2-xQyO4-y正极材料的电化学特性

The effect of doping on the electrochemical performance was studied for spinel type Li_1.02M_xMn_2-xQ_yO_4-y used as cathode material in lithium-ion battery. TG/DTA curves of the precursor(the raw materials) doped with different elements were studied. The spinel materials Li_1.02Mn₂O₄, Li_1.02Co_0.02Cr_0.01La_0.01Mn_1.96F_0.02O_3.98, Li_1.02Co_0.02Cr_0.01 La_0.01Mn_1.96Cl_0.02O_3.98, Li_1.02Co_0.02La_1.02Mn_1.97Cl_0.02O_3.98, Li_1.02Co_0.02Cr_0.01Mn_1.97O₄, were prepared by solid-state reaction method after the pretreatment of conversion under low temperature and uniform mixing. X-ray diffraction patterns showed that all the samples had perfect spinel structure. SEM indicated that the particles of the samples had uniform size and were distributed evenly. The results of the charge/discharge curves showed that Li_1.02Co_0.02Cr_0.01La_0.01Mn_1.96F_0.02O_3.98 had better performance than other materials according to the inhibition of decline of reversible capacity of spinel Li_1.02M_xMn_2-xQ_yO_4-y. Therefore, cycle performance had been improved so obviously that 93.9% of the initial capacity were preserved after 100 cycles. Furthermore, electrochemical impedance tests were carried out with the spinel Li_1.02Co_0.02Cr_0.01La_0.01Mn_1.96F_0.02O_3.98 as working electrode, Lithium as counter electrode and reference electrode. Results showed that this material possessed good charge/discharge reversible capability and had the lowest impedance in 3.95～4.25 V range (on the stage of charge / discharge).     

基于Zynq的不规则物体体积测量系统的设计与实现

为解决工业生产中原始物料体积的快速、准确测量与分级问题,设计了一种以Zynq-7000可扩展处理平台为核心的基于机器视觉的不规则物体体积测量系统。该系统通过摄像头采集物料图像,结合ARM与FPGA技术,并使用Vivado开发软件在ZyBo开发平台中进行了软硬件协同设计,最终实现了不规则物体体积测量算法的硬件加速。实验结果表明该系统可以准确的计算出不规则物体的体积,并能够达到工业生产的实时性要求,这将有效地提升原始物料分级的准确性,提高企业的经济效益和社会效益。