二烷氧基对苯乙炔聚合物发光材料的研究 Ⅰ.相转移催化合成中间体1,4-二丁氧基苯

以对苯二酚和溴代正丁烷为原料、乙醇和甲苯为溶剂,在碱性条件下,采用相转移催化剂合成二烷氧基对苯乙炔聚合物发光材料的中间体1,4-二丁氧基苯,考察了不同相转移催化剂和反应条件对产品收率的影响。实验结果表明,以双十八烷基甲基胺氯化苄季铵盐(C_(18)H_(37))2N~+MeCH_2PhCl~-为相转移催化剂,在原料配比n(对苯二酚):n(溴代正丁烷)=1:2.2、催化剂用量(基于对苯二酚的物质的量)2.0%、反应温度60℃、反应时间3.0 h的条件下,1,4-二丁氧基苯的收率达93.6%。通过IR和~1H NMR表征,对产品进行了分析和确认。     

潜式沉箱-群桩-平台型复合结构的水动力特性

通过点压力试验对由潜式沉箱-群桩-平台组合成的新型复合结构受到的波浪压力进行系统研究。分析了时域内不同位置的压强特点,并对整个结构最大压力的空间分布进行探讨,给出了不同位置压强与相对波高（H/S）的关系,为结构设计应用提供参考。     

VBLAST系统的译码算法研究

对已有的传统译码算法如迫零算法（ZF）、最小均方（MMSE）算法、连续抵消（SIC）算法等的性能进行了研究,并在此基础上提出将迫零算法与连续抵消算法、最小均方算法与连续抵消算法相结合,构成迫零-连续抵消算法（ZF-SIC）与最小均方-连续抵消算法（MMSE-SIC）,从而明显改善系统的误码性能。此外,对收发两端采用不同天线数时的系统误码性能进行了仿真与分析,同时仿真分析了系统采用QPSK与16QAM调制方式的误码性能,最后给出仿真分析结果。     

模拟通信时分干扰效果研究

时分干扰信号是时分多目标干扰中的基本干扰信号形式,对模拟通信的时分干扰效果进行了研究,建立了时分干扰效果研究模型,对单边带话、调幅话、调频话3种通信样式在不同干扰重复周期、干扰占空比、干信比参数下的性能进行仿真分析,得出了时分干扰针对模拟通信进行干扰的规律特点,为通信对抗中时分多目标干扰试验科目的有效开展和结果分析提供了技术支持。     

电荷泵型LED驱动器的CMOS误差放大器设计

结合电荷泵型LED驱动器的工作要求,从减小输出电压纹波、稳定输出电压出发,设计了一款误差放大器。该误差放大器具有较大的工作电压范围,使电荷泵型LED驱动器高效率低噪声工作。基于CHRT0．35μm CMOS MIXED SIGNAL TECHNOLOGY进行仿真,结果表明,在2．7～5V工作电压范围内,开环电压增益约等于72dB,相位裕度约等于65°,单位增益带宽约等于4．6MHz,共模抑制比CMRR约等于113dB,电源抑制比PSRR约等于100dB。     

Polycyclic aromatic hydrocarbon residues in human milk, placenta, and umbilical cord blood in Beijing, China

This paper provides the results of an investigation on dietary intakes and internal doses of polycyclic aromatic hydrocarbons (PAHs) for nonsmoking women from Beijing, China. Concentrations of PAHs were measured by gas chromatography/mass spectrometry (GC/MS) for human milk, placenta, and umbilical cord blood samples from 40 nonsmoking women and for 144 composite food samples covering major food categories. Information on food consumption and estimated ingestion doses of PAHs by the cohort was also collected individually. Relationship among the studied human samples and relative importance of breastfeeding to the total exposure dose of infants were addressed. The median (mean and standard deviation) total concentrations of 15 PAHs in human milk, placenta, and umbilical cord blood with (or without) fat normalization were 278 (9.30 ± 5.75), 819 (35.9 ± 15.4), and 1370 (5.521 ± 3.71) ng/g of fat, respectively, and the corresponding levels of benzo[a]pyrene equivalent (B[a]P(equiv)) were 11.2 (0.473 ± 0.605), 16.2 (0.717 ± 0.318), and 13.1 (0.140 ± 0.225) ng/g of fat, respectively. The calculated intake of B[a]P(equiv) by Beijing cohort varied from 0.609 to 4.69 ng·kg(-1)·day(-1) with a median value of 1.93 (2.09 ± 0.921 mean ± standard deviation) ng·kg(-1)·day(-1). Significant correlations were found among human milk, placenta, and umbilical cord blood (p < 0.05) for low-molecular-weight PAHs, indicating selective transfer potential of individual PAHs from mother to fetus. Internal dose of PAHs was not in proportion to amounts of food ingestion, daily dietary intake, lifestyle, and social-demographic characteristics of the participants (p > 0.05). Ingested doses of PAHs (3.00-102 ng·kg(-1)·day(-1)), which were much higher than the inhaled doses (0.152-8.50 ng·kg(-1)·day(-1)), were 3-4 orders of magnitude lower than the recommended reference doses, unlikely to impose any obvious risk based on current knowledge.     

双腔室自激振荡喷嘴频率特性研究

摘要：作为对双腔室自激振荡喷嘴这一新型喷嘴的探索,基于流体网络理论建立了双腔室自激振荡脉冲射流喷嘴的相似网络模型,理论分析了双腔室自激振荡喷嘴频率特性。模型计算结果表明：双腔室自激振荡喷嘴结构参数对系统的固有频率有重要的影响,系统结构参数间存在最优匹配关系,并与文献中介绍的单腔室结构参数的最佳配比关系有较大的不同,双腔室自激振荡喷嘴较单腔室自激振荡喷嘴可以提高脉冲射流峰值压力。分析结果对双腔室自激振荡喷嘴结构设计具有一定的借鉴价值。     

面向物联网的光载WiFi链路与波长分配协议

A novel Wireless Fidelity (WiFi) over fiber link and a wavelength assignment protocol are proposed to provide sufficient bandwidth and extensive coverage range for the various applications in the Internet of Things (IoT). The performance of the WiFi over fiber-based wireless IoT network is evaluated in terms of error vector magnitude (EVM) and data throughput for both the up and down links between the WiFi central control system and remote radio units (RRUs). The experimental results illustrate the reliability of the fiber transmission of 64 Quadrature Amplitude Modulation (64QAM) WiFi signals by direct analog modulation. In order to efficiently utilize the wavelength resources, we also demonstrated the wavelength assignment protocol by employing optical switching configurations in Central Station (CS) to realize the wavelength switching, and the simulation results indicate the queuing size and the corresponding queue delay for different numbers of available wavelengths.     

局部注射不同浓度骨保护素对大鼠正畸牙移动影响的研究

目的：研究局部注射不同浓度骨保护素对大鼠牙齿移动的影响。方法：选用10周龄雄性sD大鼠60只,分为实验组与对照组,实验组分0．5mg／kgOPG组和0．05mg／kgOPG组,每组20只。在右上颌第一磨牙施加40G左右力使其移向近中。在实验组和对照组大鼠右上颌第一磨牙腭侧粘骨膜下分别注入重组人骨保护素rhOPG—Fe和...     

高速公路边坡防护中压力分散型锚索施工探讨

简要介绍了压力分散型锚索的施工顺序和锚索的张拉工序,以汕昆高速公路边坡防护工程为例,阐述了不同长度锚索的差异荷载及伸长量计算,指出压力分散型锚索现场施工时,要做好理论计算,并严格按照规定程序进行张拉。