Synthesis of C_f/TiAl_3 Composite by Infiltration-In Situ Reaction

Infiltration-in situ reaction synthesis of Cf /TiAl3 composite was investigated. The as-cast material was obtained by titanium particles, carbon fibers and pure aluminum. Titanium particles and carbon fibers were mixed and pressed to form a preform firstly, and then molten pure aluminum was pressed into the preform, subsequently, cooled rapidly. In situ reaction samples were obtained by heating the as-cast material from 600 to 1000 °C for 1 h. The microstructural evolution of in situ reaction samples was an...     

Synthesis of monodisperse CdS nanowires and their photovoltaic applications

Cadmium sulphide (CdS) nanowires with a monodisperse diameter of 3.6 nm and an aspect ratio of 10–170 were successfully synthesized using a simple and reproducible hot coordinating solvents method. The morphology and optical properties of the CdS nanocrystals were investigated using transmission electron microscopy (TEM), high-resolution TEM (HRTEM) ultraviolet–visible (UV–Vis) absorption spectroscopy and photoluminescence (PL) spectroscopy. It was found that using a long alkyl chain phosphonic acid-octadecylphosphonic acid (ODPA) causes a low diffusion rate and low reactivity which help to control the morphology of the nanocrystals. The timing of the injection process was also found to have critical effect on the morphology of the nanocrystals. Sharp peaks in both the UV–Vis absorption and PL spectra indicate that the size distribution of the diameter is nearly monodisperse. The photovoltaic properties of photovoltaic devices made with a blend of our nanowires and poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) were also investigated. Devices made with the nanowires were found to have double the I_sc observed in devices made with lower aspect ratio CdS nanorods. The possible reason of low photocurrent and high V_oc is maybe due to the presence of ligand in the nanocrystals.     

FlexPDA: A Flexible Programming Framework for Deep Learning Accelerators

There are a wide variety of intelligence accelerators with promising performance and energy efficiency, deployed in a broad range of applications such as computer vision and speech recognition. However, programming productivity hinders the deployment of deep learning accelerators. The low-level library invoked in the high-level deep learning framework which supports the end-to-end execution with a given model, is designed to reduce the programming burden on the intelligence accelerators. Unfortunately, it is inflexible for developers to build a network model for every deep learning application, which probably brings unnecessary repetitive implementation. In this paper, a flexible and efficient programming framework for deep learning accelerators, FlexPDA, is proposed, which provides more optimization opportunities than the low-level library and realizes quick transplantation of applications to intelligence accelerators for fast upgrades. We evaluate FlexPDA by using 10 representative operators selected from deep learning algorithms and an end-to-end network. The experimental results validate the effectiveness of FlexPDA, which achieves an end-to-end performance improvement of 1.620x over the low-level library.     

18位高精度音频∑-△DAC设计

采用基于过采样∑-△DAC调制技术设计的音频D/A转换器,对量化噪声进行有效整形,提高了分辨率和带内信噪比(SNR).重点对Sigma-delta设计进行了详细分析,给出了有关电路结构和仿真结果.芯片已在TSMC 0.18μm CMOS工艺上流片成功,在工作频率6.144MHz时动态范围达128.6dB,信噪比109.5dB,总谐波失真达-117.2dB.     

基于ADAMS锻造操作机钳杆机构的优化设计

通过对锻造操作机钳杆机构工作原理的分析,确定了设计变量、约束条件并建立了目标函数,同时也确定了以夹紧力最大为主要设计目标的数学模型.将所确定的设计变量、目标函数转化为ADAMS函数语言,并对该机构进行了参数化设计以及优化计算,找到了影响夹紧力的主要因素,得出了在夹紧力最大为2.2044e 005N时,机构杠杆大臂长度L=1.8762m、小臂长度l=0.6616m,得到了钳杆优化过程夹紧力变化曲线,对ADAMS优化功能的一些问题做了介绍.     

17aα-D-高炔雌二醇-3-乙酯对辐射和化学损伤小鼠的防护作用及其雌活性的实验研究

采用我所自行合成的新型雌激素类化合物17aα-D-高炔雌二醇-3-乙酯,观察其对受致死剂量（8．0Gr）^137Csγ射线照射IRM-2小鼠30d存活率的影响,以及药物对注射环磷酰胺（CY）所致的IRM-2小鼠造血系统损伤的保护作用,比较了其与炔雌二醇（EE2）对昆明种雌性小鼠的雌活性。结果表明,5mg／kg、7．5mg／kg、10me/kg三个不同剂量17aα-D-高炔雌二醇-3-乙酯药物注射组,30d存活率分别比单纯照射对照组提高55％、85％、75％（P〈0．01）,保护指数分别为1．99、2．56、2．46;同时,药物可明显保护环磷酰胺所致的小鼠造血系统功能的损伤。与EE2相比,该药物雌活性约为其1／10000。因此,17aα-D-高炔雌二醇-3-乙酯对γ射线及化学药物损伤均有明显的保护作用,而且该药的雌活性低,毒副作用小。     

Complementary metamaterial transmission line for monoband and dual‐band bandpass filters application

A novel composite right‐/left‐handed transmission line (CRLH TL) and its equivalent circuit model are proposed based on cascaded complementary single split ring resonator (CCSSRR). It features an intrinsically balanced wider band and an additional transmission zero above the right‐handed band relative to CRLH TL using complementary single split ring resonator and complementary split ring resonators. Moreover, two single negative (SN) metamaterial (MTM) TLs constructed by using complementary electric inductive‐capacitive resonator on the conductor strip and on the ground, respectively, are researched. Both SN MTM TLs exhibit electric resonance above the fundamental magnetic resonance. For application, a monoband (MB) bandpass filter (BPF) covered WLAN band, and a dual‐band (DB) BPF covered satellite DMB band and WiMAX band are designed, fabricated, and measured. The SN MTM TLs are adopted for the sake of deep and wide out‐of‐band suppression while CRLH MTM TLs using square‐shaped and Sierpinski‐shaped CCSSRR are critical factors of the MB and DB behavior. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.     

基于移动代理入侵检测模型的研究

本文提出一种基于代理的入侵检测系统采用了移动代理和多代理合作技术,解决了传统的检测系统数据量过大、对入侵事件反应不及时的问题,它的移动代理技术,起到了主机负载均衡的效果。这个入侵检测系统采用了特征匹配和数据统计相结合的方式对入侵事件进行检测,大大降低了误警率。该检测系统由代理系统、存储系统、控制系统、分析系统和响应系统六部分组成,具有良好的分布性能和可扩展性。它将基于网络和基于主机的入侵检测系统有机地结合在一起,提供集成化的检测、报告和响应功能。     

18位高精度音频Σ-ΔDAC设计

采用基于过采样Σ-ΔDAC调制技术设计的音频D/A转换器,对量化噪声进行有效整形,提高了分辨率和带内信噪比(SNR)。重点对Sigma-delta设计进行了详细分析,给出了有关电路结构和仿真结果。芯片已在TSMC 0.18μm CMOS工艺上流片成功,在工作频率6.144MHz时动态范围达128.6dB,信噪比109.5dB,总谐波失真达-117.2dB。