用MOCVD方法在GaAs衬底上低温生长ZnO薄膜

采用二乙基锌(DEZn)和水(H2O)作为生长源,利用金属有机化学气相沉积(MOCVD)的方法,在100～400℃低温范围内,在GaAs(001)衬底上制备了ZnO薄膜.利用X射线衍射(XRD),室温PL,AFM,SEM研究了薄膜的晶体结构特性、发光特性及表面形貌特性.XRD分析表明ZnO薄膜具有很强的c轴取向,(002)峰的FWHM平均值为0.3°.当生长温度达到400℃时从SEM测量结果可以观察到薄膜表面呈六角状结晶.随着生长温度的升高,薄膜的晶粒尺寸变大,结晶质量得到提高但同时表面变粗糙.室温PL测量显示薄膜在370nm附近有强的近带边发射,没有观测到深能级发射峰.     

2008年一季度元器件价格将快速下跌

当元器件市场的季节性需求高峰过去以后,大多数供货商们仍然握有大量的存货。许多供货商对今年的消费需求持高度谨慎的态度。目前,过剩的库存是他们今年的主要问题之一。事实上,由于需求的不确定性和产能扩张,库存过剩是2008年1季度的现实问题。假日需求的情况仍然是一个未知数,iSuppli公司预测,电子元器件的供货将足以满足市场的需求。     

SQI优化思路

在GSM无线网络中,对无线质量的评估是通过RXQUAL来实现的。但是无线网络的语音是经过话音编码及信道编码两个过程的,RXQUAL只能反映出网络在空中接口上的传输质量,并不能反映终端用户对无线网络语音保真度的最终感受。为此爱立信提出了一个能够表达终端用户对无线网络质量直接感受的指标—SQI。     

小波去噪与信号相似性在电泳信号方面的应用

根据信号与噪声在小波变换下的不同特性．文章讨论了一种基于小波变换的信号去噪方法。因为不同的小波基有各自的特点和优点。文章中选择了几种典型的小波进行了比较．井提出一种信号相似性理论判别方法。数值实验及实际运用都证明了上述方法的有效性。     

Mechanical Strain‐Tunable Microwave Magnetism in Flexible CuFe2O4 Epitaxial Thin Film for Wearable Sensors

Purely mechanical strain‐tunable microwave magnetism device with lightweight, flexible, and wearable is crucial for passive sensing systems and spintronic devices (noncontact), such as flexible microwave detectors, flexible microwave signal processing devices, and wearable mechanics‐magnetic sensors. Here, a flexible microwave magnetic CuFe₂O₄ (CuFO) epitaxial thin film with tunable ferromagnetic resonance (FMR) spectra is demonstrated by purely mechanical strains, including tensile and compressive strains, on flexible fluorophlogopite (Mica) substrates. Tensile and compressive strains show remarkable tuning effects of up‐regulation and down‐regulation on in‐plane FMR resonance field (H_r), which can be used for flexible tunable resonators and filters. The out‐of‐plane FMR spectra can also be tuned by mechanical bending, including H_r and absorption peak. The change of out‐of‐plane FMR spectra has great potential for flexible mechanics‐magnetic deformation sensors. Furthermore, a superior microwave magnetic stability and mechanical antifatigue character are obtained in the CuFO/Mica thin films. These flexible epitaxial CuFO thin films with tunable microwave magnetism and excellent mechanical durability are promising for the applications in flexible spintronics, microwave detectors, and oscillators.     

透析3G在中国面临的重重困局(1)--牌照与标准选择

探讨了中国3G牌照何时发放、发放数量、牌照与标准是否捆绑、3G产业链如何搭建、频率如何分配、市场容量和终端等问题，并对此提出了建设性的意见。     

Phase Transition VO2 Thin Films for Optical Switches

This paper presents a method to make vanadium dioxide (VO₂) crystallites on silicon substrates by reactive ion beam sputtering. The thickness of the thin film is about 100nm. The phase transition temperature of VO₂ is 65°C. The transmittance of the semiconducting phase VO₂ is about 50% and it is reduced to as low as 3% in metal phase at the infrared wavelenghth spectrum. The extinction ratio of the optical switches is 12dB. and the insertion loss is of 1-2dB. The switching time is about 1ms.     

解读美军标MIL-STD-461F

针对美国现行军用标准MIL-STD-461F的新增内容CS106,以及与MIL-STD-461D/462D、MIL-STD-461E的差异,从测试一般要求和测试详细要求两个方面进行了介绍。提出了实验室的对应措施。     

Regulating Fe Aggregation State via Unique Fe?N?V Pre-Coordination to Optimize the Adsorption-Catalysis Effect in High-Performance Lithium-Sulfur Batteries

Lithium-sulfur batteries (LSBs) suffer from uncontrollable shuttling behavior of lithium polysulfides (LiPSs: Li₂S_x, 4 ≤ x ≤8) and the sluggish reaction kinetics of bidirectional liquid-solid transformations, which are commonly coped through a comprehensive adsorption-catalysis strategy. Herein, a unique Fe N V pre-coordination is introduced to regulate the content of “dissociative Fe³⁺” in liquid phase, realizing the successful construction of N-doped micro-mesoporous “urchin-like” hollow carbon nanospheres decorated with single atom Fe-N₄ sites and VN nanoparticles (denoted as SA-Fe/VN@NMC). The strong chemisorption ability toward LiPSs and catalyzed Li₂S decomposition behavior on VN, along with the boosted reaction kinetics for sulfur reduction on SA-Fe sites are experimentally and theoretically evidenced. Moreover, the nanoscale-neighborhood distribution of VN and SA-Fe active sites presents synergistic effect for the anchoring-reduction-decomposition process of sulfur species. Thus SA-Fe/VN@NMC presents an optimized adsorption-catalysis effect for the whole sulfur conversion. Therefore, the SA-Fe/VN@NMC based Li-S cells exhibit high cyclic stability (a low decay of 0.024% per cycle over 700 cycles at 1 C, sulfur content: 70 wt%) and considerable rate performance (683.2 mAh g⁻¹ at 4 C). Besides, a high areal capacity of 5.06 mAh cm⁻² is retained after 100 cycles under the high sulfur loading of 5.6 mg cm⁻². This work provides a new perspective to design the integrated electrocatalysts comprising hetero-formed bimetals in LSBs.     

An energy‐efficient utility‐based distributed data routing scheme for heterogenous sensor networks

A utility‐based distributed data routing algorithm is proposed and evaluated for heterogeneous wireless sensor networks. It is energy efficient and is based on a game‐theoretic heuristic load‐balancing approach. It runs on a hierarchical graph arranged as a tree with parents and children. Sensor nodes are considered heterogeneous in terms of their generated traffic, residual energy and data transmission rate and the bandwidth they provide to their children for communication. The proposed method generates a data routing tree in which child nodes are joined to parent nodes in an energy‐efficient way. The principles of the Stackelberg game, in which parents as leaders and children as followers, are used to support the distributive nature of sensor networks. In this context, parents behave cooperatively and help other parents to adjust their loads, while children act selfishly. Simulation results indicate the proposed method can produce on average more load‐balanced trees, resulting in over 30% longer network lifetime compared with the cumulative algorithm proposed in the literature. Copyright © 2014 John Wiley & Sons, Ltd.