近阈值电压下可容错的末级缓存结构设计

近阈值电压技术通过降低晶体管的电源电压来降低芯片能耗和提升能效。但是,近阈值电压技术会在Cache中引起大量位错误,严重影响末级缓存的功能。针对近阈值电压下超过1%的位错误率造成的Cache故障问题,该文提出一种基于传统6T SRAM单元的可容错的末级缓存结构(FTLLC)。该策略对缓存条目中的错误进行了低错纠正和多错压缩,提高了Cache中数据保存的可靠性。为了验证FTLLC的有效性,该文在gem5中实现了该结构,并运行了SPEC CPU2006测试集进行仿真实验。结果表明,对于650 mV电压下65 nm工艺的末级缓存,FTLLC与Concertina压缩机制相比在4-Byte粒度下末级缓存可用容量增加了24.9%,性能提高了7.2%,末级缓存的访存缺失率下降了58.2%,而面积和能耗开销仅有少量增加。     

氮杂多环芳烃~（13）C－NMR化学位移的理论探讨

本文主要是对氮原子以ｓｐ~２杂化，孤氮电子占据ｓｐ~２杂化轨道，以这种形式成键的氮杂交变多环芳烃中的１１个化合物的~（１３）Ｃ－ＮＭＲ的化学位移进行了计算。该计算依据ＣＮＤＯ方法一个联系分子电荷密度，键级和键长等参数的半经验公式。同时利用环电流、空间效应以及针对氮原子的屏蔽效应和去屏蔽效应的影响，通过分子动力学的考虑，得到理论上计算的化学位移，该计算结果与实验值吻合得很好，通过时~（１３）Ｃ－ＮＭＲ化学位移的回归分析表明，回归系数达到０．９９，非常好地反映了氮杂多环芳烃~（１３）Ｃ－ＮＭＲ化学位移与分子微观结构之间的关系，同时表明我们在处理诸多化学位移时考虑到的因素是合理可行的。     

Prototype studies on the forward MWDC tracking array of the external target experiment at HIRFL-CSR

A prototype of the forward tracking array consisting of three multiwire drift chambers (MWDC) for the external target experiment (CEE) at the Heavy Ion Research Facility at the Lanzhou -Cooling Storage Ring (HIRFL-CSR) has been assembled and tested using cosmic rays. The signals from the anode wires are amplified and fed to a Flash-ADC to deliver the drift time and charge integration. The performances of the array prototype are investigated under various high voltages. For the tracking performances, after the space-time relation (STR) calibration and the detector displacement correction, the standard deviation of 223 μm of the residue is obtained. The performances of the forward MWDCs tracking array meets the requirements of CEE in design.     

探究性教学情景下的大学物理课堂评估策略

为了评估大学物理探究性教学情景下的学生综合素质,本文作者研究课堂评估法在探究性课题教学过程中各阶段的实施策略,并进行相应教学实验,得出针对大学物理探究性教学情景下的课堂评估实施原则、方式、标准.实践表明课堂评估法与探究性教学实现了有机融合,促进了学生综合素质的提高,是一种行之有效的评估学生综合素质的教学评价方法.     

基于FPGA的对击锤力能参数测量仪设计

为实现在锻造生产中对击锤打击能量、打击力等力能参数的测量,设计了一种基于FPGA与USB2.0的四通道、高速同步数据采集系统;硬件采用两个压电式加速度传感器和两个位移传感器,FPGA选用Altera公司的EP2C5Q240I8,通过对打击过程中524 ms内的加速度和位移数据的采集,计算出力能参数,并通过USB2.0将数据实时上传到PC机进行处理;重点介绍系统硬件电路设计、USB2.0控制逻辑和FPGA内部状态机模块设计;系统采样频率达到1 MHz,数据传输速率达到30 MB/s,现场测试证明,该系统能够在强冲击、大振动环境下稳定可靠工作,为锻造质量控制提供了可靠的科学依据。     

S型叶尖小翼对风轮近尾迹声辐射影响的实验研究

采用5因素5水平的正交实验方法,找到在不同尖速比下均具有较好功率放大效果的S型叶尖小翼结构,对其影响近尾迹流动与声辐射的特征进行了测试。发现该小翼可以打散从风轮叶尖脱落的叶尖涡结构,在测试方位面内形成多个涡量集中区域,而且使叶尖涡内高涡量区域减小,降低叶尖涡的强度。同时,该小翼还可以使叶尖附近的压力脉动衰减,高压力脉动区域缩小,降低声辐射的强度,有效降低近尾迹中的声压级,靠近风轮附近测点的最大声压级降幅超过10dB,在1倍风轮直径下游位置的声压级降幅为2~7 dB.对S型叶尖小翼影响近尾迹流动和声辐射的研究,为提高风力机性能和降噪途径的探索积累了经验.     

Study of the dose rate effect of 180 nm nMOSFETs

Radiation induced offstate leakage in the shallow trench isolation regions of SIMC 0.18 μm nMOSFETs is studied as a function of dose rate. A "true" dose rate effect (TDRE) is observed. Increased damage is observed at low dose rate (LDR) than at high dose rate (HDR) when annealing is taken into account. A new method of simulating radiation induced degradation in shallow trench isolation (STI) is presented. A comparison of radiation induced offstate leakage current in test nMOSFETs between total dose irradiation experiments and simulation results exhibits excellent agreement. The investigation results imply that the enhancement of the leakage current may be worse for the dose rate encountered in the environment of space.     

填充预等离子体通道靶激光电子加速研究北大核心CSCD

采用紧聚焦的超强短脉冲激光与固体通道靶相互作用是获得大电量、高准直相对论电子束的一种有效方式。实验中由于激光预脉冲烧蚀靶壁产生预等离子体会膨胀、填充到真空通道中,从而导致电子束品质发生变化。采用二维PIC粒子模拟程序研究了通道靶中填充预等离子体的电子加速过程。模拟结果显示,在功率密度为5.0×10^(20W/cm^(2))的超强短脉冲激光条件下,通道中填充一定密度的等离子体时激光场优先与低密度等离子体相互作用,激光脉冲与通道壁的相互作用减弱,电子加速机制由纵向场主导的真空电子加速转变为横向电场主导的等离子体电子加速,产生电子束具有更大的电荷量,但能量降低,发散角增大。     

Improved functional-weight approach to oscillatory patterns in excitable networks

Studies of sustained oscillations on complex networks with excitable node dynamics received much interest in recent years. Although an individual unit is non-oscillatory, they may organize to form various collective oscillatory patterns through networked connections. An excitable network usually possesses a number of oscillatory modes dominated by different Winfree loops and numerous spatiotemporal patterns organized by different propagation path distributions. The traditional approach of the so-called dominant phase-advanced drive method has been well applied to the study of stationary oscillation patterns on a network. In this paper, we develop the functional-weight approach that has been successfully used in studies of sustained oscillations in gene-regulated networks by an extension to the high-dimensional node dynamics. This approach can be well applied to the study of sustained oscillations in coupled excitable units. We tested this scheme for different networks, such as homogeneous random networks, small-world networks, and scale-free networks and found it can accurately dig out the oscillation source and the propagation path. The present approach is believed to have the potential in studies competitive non-stationary dynamics.     

Research progress of Pt and Pt-based cathode electrocatalysts for proton-exchange membrane fuel cells

Proton-exchange membrane fuel cells (PEMFCs) have been widely used commercially to solve the energy crisis and environmental pollution. The oxygen reduction reaction (ORR) at the cathode is the rate-determining step in PEMFCs. Platinum (Pt) catalysts are used to accelerate the ORR kinetics. Pt's scarcity, high cost, and instability in an acidic environment at high potentials seriously hinder the commercialization of PEMFCs. Therefore, studies should explore electrocatalysts with high catalytic activity, enhanced stability, and low-Pt loading. This review briefly introduces the research progress on Pt and Pt-based ORR electrocatalysts for PEMFCs, including anticorrosion catalyst supports, Pt, and Pt-based alloy electrocatalysts. Advanced preparation technology and material characterization of Pt-based ORR electrocatalysts are necessary to improve the performance and corresponding reaction mechanisms.