石墨烯上生长GaN纳米线

采用金属Ga升华法在石墨烯/蓝宝石衬底上生长了高质量GaN纳米线,研究了不同的生长条件,如NH3流量、反应时间、催化剂和缓冲层等对GaN纳米线形貌的影响,采用扫描电子显微镜(SEM)对GaN纳米线进行表征.研究发现,在适当的NH3流量且无催化剂时,衬底上可以生长出粗细均匀的GaN纳米线.反应时间为5 min时,纳米线密集分布在衬底上,表面光滑.在石墨烯/蓝宝石上预先低温生长GaN缓冲层,然后升温至1 100℃进行GaN纳米线生长,获得了具有择优取向的GaN纳米线结构.研究表明,石墨烯和缓冲层对获得GaN纳米线结构有序阵列具有重要的作用.     

CMOS缓冲器的时延估算模型

随着集成电路生产工艺的进展，互连线在集成电路设计中的影响越来越大。为了减小互连线的影响，通常在芯片互连中插入缓冲器，但这样做会增加时延。因此，为了精确地对系统进行时延估计，必须对缓冲器的时延进行估算。基于Sakurai的器件模型，提出了一种新的缓冲器时延估算模型。     

具有反馈式光缓存的OPS节点结构性能研究

对反馈式光分组交换节点的性能进行深入分析,并针对现有反馈式光分组交换节点结构的不足,提出一种改进的反馈式光分组交换节点结构,即SMOP-TWC交换结构.最后,本文使用仿真实验的方法对SMOP-TWC交换结构的性能进行深入研究.     

面向存储系统的低功耗SoC设计

降低存储系统功耗是SoC设计中的重要问题,基于对程序执行与器件特性的分析,在SDRAM中引入数据缓冲区,给出针对多进程数据访问特性的实现方法,降低了程序运行时外存设备的功耗。在EMI中实现了指令FIFO,并给出定制方法,降低了程序运行时的SDRAM能耗。实验与仿真表明,该方法能有效降低程序运行时SoC存储系统整体功耗。     

一种无片外电容LDO的稳定性分析

电路如果存在不稳定性因素,就有可能出现振荡。本文对比分析了传统LDO和无片电容LDO的零极点,运用电流缓冲器频率补偿设计了一款无片外电容LDO,电流缓冲器频率补偿不仅可减小片上补偿电容而且可以增加带宽。对理论分析结果在Cadence平台基上于CSMC0.5um工艺对电路进行了仿真验证。本文无片外电容LDO的片上补偿电容仅为3pF,减小了制造成本。它的电源电压为3.5～6 V,输出电压为3.5 V。当在输入电源电压6 V时输出电流从100μA到100mA变化时,最小相位裕度为830,最小带宽为4.58 MHz     

MEMS镍平面弹簧非线性力学性能仿真及研究

工程应用中,平面微弹簧存在弹性系数的非线性现象且难以被忽略,弹簧结构的几何非线性是引起这种现象的主要原因。针对特定形状的弹簧运用Ansys软件进行了非线性有限元静力学仿真,计算出弹簧弹性力F与弹性形变x之间的对应关系,并与采用MEMS微细加工技术制得弹簧样品实测实验结果比较,相对误差低于3.2%,验证了分析模型的可靠性。而后设计了5种不同平面形状的微弹簧,仿真计算它们的力学性能曲线,以及改变弹簧臂宽度厚度后的力学性能曲线,分别进行比较以讨论影响非线性的主要因素,为弹簧的设计工作提供参考依据。     

基于插入WO3缓冲层并五苯有机场效应晶体管性能的研究

The pentacene-based organic field effect transistor （OFET） with a thin transition metal oxide （WO3） layer between pentacene and metal （AI） source/drain electrodes was fabricated. Compared with conventional OFET with only metal AI source/drain electrodes, the introduction of the WO3 buffer layer leads to the device performance enhancement. The effective field-effect mobility and threshold voltage are improved to 1.90 em2/（V.s） and 13 V, respectively. The performance improvements are attributed to the decrease of the interface energy barrier and the contact resistance. The results indicate that it is an effective approach to improve the OFET performance by using a WO3 buffer layer.     

基于SIMD技术的图像卷积处理器体系结构研究

SIMD处理机特别适合于要求大量高速向量或矩阵计算的场合,数据缓存系统和对准网络是它的关键部件。而图像卷积是图像处理技术中最基本也是最重要的一项技术,文章根据数字图像的卷积定理对数字图像的卷积运算进行了分析,在此基础上提出了一种基于SIMD处理机的可变卷积模板的图像卷积处理器的体系结构。该处理器内部包含有接口部件、控制部件、数据缓存系统、对准电路和执行部件等。它的极高效率的数据缓存系统和对准电路成为该处理器最有特色的部分,它从根本上解决了图像卷积中的数据复用带来的CPU重复访问主存储器的问题。实现了3×3、5×5、7×7、9×9、11×11、13×13和15×15卷积模板的图像卷积运算的变换而无需另行更改硬件电路的特点。最后,对这个图像卷积处理器体系结构的性能进行了缜密的分析。     

Role of dual SiOx: H based buffer at the p/i interface on the performance of single junction microcrystalline solar cells

In p-i-n structure a-Si solar cell a buffer layer with proper characteristics plays important role in improving the p/i interface of the cell, reducing mismatch of band gaps and number of recombination centres. However for p-i-n structure microcrystalline ( µc-Si: H) cell which has much less light induced degradation than a-Si:H cell, not much work has been done on development of proper buffer layer and its application to µc-Si:H cell. In this paper we have reported the development of two intrinsic oxide based microcrystalline layer having different characteristics for use as buffer layers at the p/i interface of µc-Si:H cell. Previously SiO_x:H buffer layer has been used at the p/i interface which showed positive effects. To explore the possibility of improving the performance of p-i-n structure µc-Si:H cell further we have thought it interesting to use two buffer layers with different characteristics at the p/i interface. The two buffer layers have been characterized in detail and applied at the p/i interface of the µc-Si:H cell with positive effects on all the PV parameters mainly improves the open circuit voltage (V_oc) and enhances short circuit current (I_sc). The maximum initial efficiency obtained is 8.97% with dual buffer which is 6.7% higher than that obtained by using conventional single buffer layer at the p/i interface. Stabilized efficiency of the cell with dual buffer is found to be ~9.5% higher than that with single buffer after 600 h of light soakings.     

Load’s temporal characteristics for annulling forced vibrations of linear elastic plates

We consider trapezoidal load-time pulses with linearly increasing and affinely decreasing durations equal to integer multiples of the time period of the first bending mode of vibration of a linearly elastic structure. For arbitrary spatial distributions of loads applied to monolithic and laminated orthotropic plates, it is shown through numerical solutions that plates’ vibrations become miniscule after the load is removed. This phenomenon is independent of the dwell time (i.e., the time duration between the rising and the falling portions) during which the load is kept constant. The primary reason for this response is that for such time-dependent loads, nearly all of plate’s strain energy is concentrated in deformations corresponding to the fundamental bending mode of vibration. Thus plate’s deformations can be studied by taking the mode shape of the 1st bending mode as the basis function and reducing the problem to that of solving a single second-order ordinary differential equation. We have verified this postulate by comparing strain energies computed from the 3-dimensional deformations of different plate geometries and boundary conditions with those determined by using the single degree of freedom (DoF) model. Thus for trapezoidal time-dependent loads applied on plates, the 1 DoF model provides reasonably accurate results and saves considerable computational effort.