Synthesis of Imidazole‐Based AIEgens with Wide Color Tunability and Exploration of their Biological Applications

Research on aggregation‐induced emission (AIE) has become increasingly popular recently and various AIE luminogens (AIEgens) have been developed based on tetraphenylethene, hexaphenylsilole, distyrylanthracene, tetraphenylpyrazine, etc. However, facile tuning of the AIEgen emissions in a wide range remains challenging. Herein, a novel series of AIEgens is reported, based on imidazole‐cored molecular rotors, with facile synthesis and emission colors covering the whole visible spectrum. Moreover, these imidazole derivatives exhibit biological functions unique among the AIEgens, including mitochondria‐specific imaging and antifungal activity. Benefiting from the easy preparation and the tunable emission, the imidazole derivatives are expected to not only diversify the family of AIEgens but also enrich their biological applications.     

海天背景下红外小目标检测的背景抑制及海天线检测方法

针对复杂海天背景下红外弱小目标难以检测与识别的问题,提出了基于海天线检测实现远距离弱小目标识别的方法。该方法对采集到的红外图像进行相关处理。通过用多级小波变换方法抑制背景杂波噪声提高目标信杂比;然后使用多方向Gabor滤波融合方法增强海天线边缘,并通过霍夫变换方法实现海天线定位和检测;最后通过定位海天线确定海天线附近区域的目标搜寻范围,缩小目标点潜在区,从而提高弱小目标在海天背景下的检测和识别概率。     

Nanoplasmonic-gold-cylinder-array-enhanced terahertz source

Photoconductive antennas (PCAs) based on nanoplasmonic gratings contact electrodes have been proposed to satisfy the demand for high power, efficiency and responsivity terahertz (THz) sources. Reducing the average photo-generated carrier transport path to the photoconductor contact electrodes was previously considered the dominant mechanism to improve PCAs'' power. However, considering the bias in a real device, the electric field between gratings is limited and the role of surface plasmonic resonance (SPR) field enhancement is more important in improving THz radiation. This paper, based on SPR, analyzes the interaction between incident light and substrate in nano cylinder array PCAs and clearly shows that the SPR can enhance the light absorption in the substrate. After the optimization of the structure size, the proposed structure can offer 87% optical transmission into GaAs substrate. Compared with conventional PCAs, the optical transmission into the substrate will increase 5.8 times and the enhancement factor of substrate absorption will reach 13.7 respectively.     

Training sequence design and channel estimation of OFDM-CDMA broadband wireless access networks with diversity techniques

In this paper, an OFDM-CDMA system employing various diversity schemes is considered for a possible candidate of broadband wireless access networks and broadcasting applications. With an emphasis on a preamble design for multi-channel separation, we address a channel estimation based on the time-domain windowing and its imperfectness in OFDM-based multiple-antenna transmission systems. By properly designing each preamble for multiple antennas to be orthogonal in the time domain, the channel estimation can be applied to the HIPERLAN/2 and IEEE 802.11a standards in the case of more than two transmit antennas. Also, the effect of diversity techniques on the performance of OFDM-CDMA based broadband wireless access networks is investigated and the maximum achievable diversity gain for a two-path Rayleigh fading environment is evaluated. Simulation results show that the OFDM-CDMA system applying a space-time-frequency diversity with a full-rate full diversity code can give the diversity of D=4 and D=8 for both multi-user cases of maximum user and half user capacities, respectively.     

意大利移动市场考察报告

截至2002年4月底,意大利的移动通信用户数已超过5200万,普及率高达88%,用户规模仅次于德国,是欧洲第二大移动通信市场。目前,意大利共有4家GSM移动运营商:TIM,OmnitelVodafone,Wind和Blu,分别占有市场份额的46.7%、34.4%、15.3%和3.6%。意大利的运营商早在1998年就开始了移动互联网业务的市场培育工作,现在,移动互联网业务收入在意大利各运营商的总业务收入中已经占到10%～15%的比例。意大利的3G牌照是通过拍卖的方式颁发,OmnitelVodafone,TIM,Wind,IPSE2000,Wind,和H3G五家运营商获得了3G执照。ReportofStudyTouro     

一种频率可重构微带天线的快速优化设计方法

该文针对目前频率可重构微带天线的优化设计常依赖于反复实验的现状,提出了一种快速有效的频率可重构微带天线优化设计方法,该方法将新型量子遗传算法与通用的空域矩量法结合,在计算阻抗矩阵时利用了直接矩阵操作技术,大大节约了计算时间。利用该方法,优化出一副可工作在十个甚至更多的窄频段的变频圆柱共形可重构微带天线,优化结果与相关软件结果的比较显示了该文方法的正确性及高效性。     

大功率LED照明灯有限元热设计与高效系统开发

随着LED亮度要求的不断提高,LED的温度分布和采用的散热手段对LED的可靠性有很大影响。利用ANSYS软件对LED照明的散热问题进行了详细的模拟计算。基于100 WLED实验和模拟结果的一致性,分析比较了不同结构和加载方式对200 WLED温度分布的影响。采用增加散热片个数及其长度、Al锭厚度、灯头的直径等因素,对LED的散热进行了优化设计,结合基于VC++的二次开发系统,较好实现了LED热模拟分析。研究发现LED照明灯的传热方向主要是轴向,轴向散热设计可提高LED开发效率;点阵排列LED灯的温度分布呈现一定的温度梯度;在基于实验验证的模拟可以较好实现不同功率的LED灯散热设计。模拟分析为LED的散热方案优化设计提供了有效的参考依据和手段。     

La基高k栅介质的研究进展

SiO2作为栅介质已无法满足MOSFET器件高集成度的需求,高k栅介质材料成为当前研究的热点。综述了高k栅介质材料应当满足的各项性能指标和研究意义,总结了La基高k栅介质材料的最新研究进展,以及在改正自身缺点时使用的一些实验方法,指出了有可能成为下一代MOSFET栅介质的几种La基高k材料。La基高k材料的研究为替代SiO2的芯片制造工艺提供优异的候选材料及理论指导,这是一项当务之急且浩大的工程。