改进型四波束Butler矩阵的幅度加权

在4×4Butler矩阵基础上,在保持波束数目和指向不变的情况下,通过增加4个功分器和4个180^。移相器,对矩阵进行改进。将天线阵列扩展为8单元线阵,并对改进后的矩阵进行近似切比雪夫分布幅度加权,仿真结果表明加权后副瓣电平明显改善,最后对半功率覆盖范围和波束交叉电平的影响进行分析。     

聚氨酯-丙烯酸酯的前端自由基聚合

由甲苯二异氰酸酯（TDI）、聚醚二元醇（N210、220）、丙烯酸-2-羟丙酯（HPA）制得端烯基聚氨酯-丙烯酸酯大分子;然后通过前端自由基聚合;制备了聚氨酯-丙烯酸酯共聚物。研究了引发剂浓度对前端速度和温度分布的影响。FTIR显示前端聚合产物与间歇聚合产物有相似的红外吸收;TGA分析表明;前端聚合产物具有更好的热稳定性。     

Frontal polymerization preparation of poly(acrylamide‐co‐acrylic acid)/activated carbon composite hydrogels for dye removal

A series of poly(acrylic acid‐co‐acrylamide) (PAA)/activated carbon (AC) composite hydrogels were rapidly prepared via frontal polymerization (FP). It was found that an increase in the concentration of AC caused an increase in the front velocity (V_f) and the highest front temperature (T_max). It may be attributed to that AC particles could increase the liquid viscosity of reaction mixture and remain the reaction heat during FP. The Fourier transform infrared and scanning electron microscopy (SEM) confirmed that AC particles had entered the hydrogel network, and many spherical AC particles with an average diameter of 0.5–1 μm had been dispersed homogeneously in the PAA hydrogel matrix. The swelling behavior showed that the equilibrium swelling values of hydrogels increased when the concentration of AC particles increased. Adsorption studies showed that incorporation of AC particles into PAA hydrogel matrix could increase the sites of interaction between the hydrogels and crystal violet molecules and result in an increase of adsorption capacities of hydrogels toward dyes. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

肺下叶结核64例临床X线特征及误诊研究

目的探讨研究肺下叶结核患者的临床X线特征及误诊因素。方法选择本院2005年9月至2010年11月间收治的64例肺下叶结核患者为研究对象,对其进行临床X线检查并归纳其特性。结果临床X线表现主要包括小叶肺炎样与流沙样征象,具体还有粟粒型、空洞型、结核球型等表现。文中共有12例患者被延误诊,平均延误时间为1.8个月,分别被误诊为支气管肺炎、肺脓疡、肺癌、大叶性肺炎。结论由于肺下叶结核为少发部位且临床表现缺乏特异性,同时X线的表现具有多样性和隐蔽性导致易被误诊。因此应注意消除肺下叶结核临床误诊减少延误的主要事项。     

一种基于遗传算法的波束设计方法

提出了基于遗传算法优化思想的波束设计方法,借助计算机对二十元阵进行波束优化设计。结果表明,使用该方法设计的波束与常规方法相比,获得了更低的旁瓣级,充分说明了方法的可行性和有效性,为多元任意阵的波束设计提供了有益参考。     

敌我识别器多点应答问题的研究

针对二次雷达系统中天线旁瓣使目标在雷达显示器上形成多点应答现象，提出了4种多点应答问题解决办法：在询问机通过和波束发射询问信号的同时通过另一天线发射抑制波束实现发射旁瓣抑制：通过比较询问机和差波束接收信号幅度实现接收旁瓣抑制；通过调节发射机功率开关控制询问机功率实现功率控制旁瓣抑制；通过控制接收机灵敏度实现灵敏度控制旁瓣抑制．     

Efficiency of 4,4′‐bis(N,N‐diethylamino) benzophenone for the polymerization of dimethacrylate resins in thick sections

The efficiency of 4,4′‐bis(N,N‐diethylamino)benzophenone (DEABP) for the polymerization of dimethacrylate monomers in thick sections ( 1 – 2 mm) was studied. DEABP (λ_max = 365 nm) represents a complete initiating system as it contains both ketone and amine functional groups. During irradiation, DEABP photobleaches at a fast rate causing deeper penetration of light through the underlying layers, but the photoinitiation efficiency (rate of polymerization per photon absorption rate) is relatively poor. As a result, irradiation of methacrylate monomers at 365 nm results in a slow average polymerization rate and a reduced monomer conversion for thick sections due to the light attenuation caused by the high absorptivity of DEABP and photolysis products. These results highlight the inherent interlinking of light attenuation and photobleaching rate in polymerization of thick sections. Copyright © 2011 Society of Chemical Industry     

Resting frontal EEG asymmetry as an endophenotype for depression risk: Sex-specific patterns of frontal brain asymmetry.

Resting frontal electroencephalographic (EEG) asymmetry has been hypothesized as a marker of risk for major depressive disorder (MDD), but the extant literature is based predominately on female samples. Resting frontal asymmetry was assessed on 4 occasions within a 2-week period in 306 individuals aged 18–34 (31% male) with (n = 143) and without (n = 163) lifetime MDD as defined by the Diagnostic and Statistical Manual of Mental Disorders, 4th edition (American Psychiatric Association, 1994). Lifetime MDD was linked to relatively less left frontal activity for both sexes using a current source density (CSD) reference, findings that were not accounted for solely by current MDD status or current depression severity, suggesting that CSD-referenced EEG asymmetry is a possible endophenotype for depression. In contrast, results for average and linked mastoid references were less consistent but demonstrated a link between less left frontal activity and current depression severity in women. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Numerical and experimental study on nugget formation in resistance spot welding for three pieces of high strength steel sheets

A resistance spot welding for three pieces of high strength steel sheets was selected as a research subject and the nugget formation processes at the various welding conditions were investigated by both experimental measurement and FEM simulation. The FEM program developed by the authors considered the coupling of the electrical field, thermal field and mechanical field. The interface elements were used to model the transient contact states between two worksheets or between a worksheet and an electrode. The electrical resistance and thermal–mechanical properties of the interface elements change with the contact state, and can have different values from the worksheets and electrodes. The nugget sizes and its formation process predicted by FEM agreed very well with experimental results. The welding conditions (current, cycles and force) to produce sound nuggets for both two pieces and three pieces of high strength steel sheets were accurately estimated by the simulation.     

Preserved monitoring and control processes in temporal lobe epilepsy.

Objective: The aim of this study was to assess an aspect of metamemory never examined before in patients with temporal lobe epilepsy (TLE): the ability to upgrade the accuracy of one's memory predictions after study. Method: Four lists of different levels of difficulty and relatedness were presented to 15 TLE patients and 15 control participants, who were asked to predict their subsequent recall both before and after studying each list. Results: The results showed clear impairment in recall in TLE patients. However, both TLE patients and controls showed an improvement in accuracy in their poststudy predictions compared with their prestudy predictions, showing that both groups were able to upgrade their metamemory predictions. Unexpectedly, prediction accuracy was overall higher in TLE patients than in controls. Moreover, study time was allocated in both groups taking into account the characteristics of the list. Conclusion: These results confirm and extend findings of Howard et al. (2010) of intact metamemory in TLE patients, and provide further support to the dissociation between memory and metamemory in this clinical population. (PsycINFO Database Record (c) 2010 APA, all rights reserved)