AES中字节代换和列混合的硬件可逆设计

针对AES硬件实现占用大量资源的缺点,对其两个核心计算部件(字节代换和列混合)进行了硬件可逆设计.该设计采用模块复用技术,使字节代换及其逆变换模块最大限度地共享GF(2<'8>)域中的模逆运算单元,而使列混合及其逆变换模块最大限度地共享p(x)乘运算单元,以较小的硬件代价实现了字节代换模块和列混合模块的硬件可逆设计.最后在Xilinx的FPGAVirtexE xev2000e-6上进行了仿真验证,实验结果表明,与其他同类设计相比,新设计方案明显减少了硬件开销.     

Effect of Sintering Temperature on Magnetic and Electrical Properties of GdBaCo<Subscript>2</Subscript><Emphasis Type="Italic">O</Emphasis><Subscript>5 + <Emphasis Type="Italic">δ</Emphasis></Subscript>

In this study, we report the results of an investigation into the sintering temperature dependence of magnetic and transport properties for GdBaCo₂ O _{5 + δ} synthesized through a sol-gel method. The lowering of sintering temperature leads to the increase of oxygen content and the reduction of grain size. The increase of oxygen content results in the enhancement of magnetic interactions and the weakening of Coulomb repulsion effect, while the reduction of grain size improves the magnetoresistance effect. Metal-insulator transition accompanied with spin-state transition is observed in all samples.     

Walnut-inspired microsized porous silicon/graphene core–shell composites for high-performance lithium-ion battery anodes

Silicon is considered an exceptionally promising alternative to the most commonly used material, graphite, as an anode for next-generation lithium-ion batteries, as it has high energy density owing to its high theoretical capacity and abundant storage. Here, microsized walnut-like porous silicon/reduced graphene oxide (P-Si/rGO) core–shell composites are successfully prepared via in situ reduction followed by a dealloying process. The composites show specific capacities of more than 2,100 mAh·g^?1 at a current density of 1,000 mA·g^?1, 1,600 mAh·g^?1 at 2,000 mA·g^?1, 1,500 mAh·g^?1 at 3,000 mA·g^?1, 1,200 mAh·g^?1 at 4,000 mA·g^?1, and 950 mAh·g^?1 at 5,000 mA·g^?1, and maintain a value of 1,258 mAh·g^?1 after 300 cycles at a current density of 1,000 mA·g^?1. Their excellent rate performance and cycling stability can be attributed to the unique structural design: 1) The graphene shell dramatically improves the conductivity and stabilizes the solid–electrolyte interface layers; 2) the inner porous structure supplies sufficient space for silicon expansion; 3) the nanostructure of silicon can prevent the pulverization resulting from volume expansion stress. Notably, this in situ reduction method can be applied as a universal formula to coat graphene on almost all types of metals and alloys of various sizes, shapes, and compositions without adding any reagents to afford energy storage materials, graphene-based catalytic materials, graphene-enhanced composites, etc.

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采用变回水温度控制策略的空气源热泵空调系统研究

为了提高空气源热泵空调系统运行性能,研究了一套采用变回水温度控制策略的空气源热泵机组的制冷性能。实验研究表明,变回水温度工况可满足室内冷负荷需求。与传统采用定12℃回水温度的空气源热泵空调系统相比,COP更高,耗电量更小,是一种高效节能的空气源热泵空调系统控制方法。此外,所建立的Dymola模型从理论上验证了实验结果,在此基础上模拟实际空调系统的能耗,模拟结果表明,COP由3.99提高至4.39,提高了10%。     

基于Opencv的絮体颗粒跟踪与沉速测量系统研究

针对饮用水处理过程混凝剂投加量对处理结果的直接影响,提出了一个以絮体的沉降速度(作为主控,等效粒径、数量等参数作为辅控的多源数据融合的混凝剂投药模型。本文基于Open CV机器视觉库,以VS2010为平台,采用C++语言,编写絮体检测和沉降速度测量在线系统的软件,实现了絮体各个参数和沉降速度的实时监测。     

车辆防碰预警系统的设计

介绍了一种以ATmega16单片机为控制核心的车辆防碰预警系统,提出了解决收发一体式超声波测距电路难题的新方法;由于温度对超声波波速的影响,增加了温度补偿电路来消除误差;设计的自动增益控制(AGC)电路,有效地解决了回波信号过于微弱而导致系统测量误差加大的难题;在此基础上,设计了相应的超声波测距系统的软件;对系统进行了测试,如主要试验参数:灵敏度、测距、频率等;并将所测数据与实际数据进行了对比;结果表明,该预警系统具有较高的测量精度。     

靶场仿真中分布式异构网关技术研究

为快速、高效地实现试验与训练领域各靶场、设施和仿真的互操作、重用和可组合,构建实物的、虚拟的、构造的(LVC)分布式网络,研究了目前主要存在的高级分布式仿真架构,包括分布式交互仿真(DIS)、高层体系架构(HLA)及试验与训练使能体系结构(TENA);在对它们的异同进行分析比较的基础上,确定以TENA网关对异构靶场进行无缝连接是实现靶场互联的最佳方案;对网关进行了总体设计并对关键技术进行了分析,网关原型的建立为网关的深入研究和开发奠定了基础。     

动态偏置射频宽带功放设计

射频宽带功率放大器是目前功率放大器的主要发展趋势。为了提高射频宽带功率放大器的增益平坦度与效率,采用推挽结构LDmos晶体管,使用ADS软件对动态偏置电路和匹配电路进行仿真设计。详细介绍了动态偏置功率放大器的工作原理及其实现方法。实现了多倍频程带宽、确保带内增益平坦、提高功率附加效率。仿真结果表明该功率放大器对于100MHz~400MHz的信号,在整个输入功率变化范围内,功率附加效率（PAE）与传统的功放相比提高了5~15%左右。