发动机冷却系统仿真模拟及节温器的影响分析

本文基于MATLAB/Simulink仿真平台,建立了某型柴油活塞发动机冷却系统的一维仿真模型,研究了冷却系统对环境温度、气缸散热量等参数的敏感性,并分析了节温器对冷却系统敏感性及冷启动过程中动态特性的影响.结果表明,节温器对流量的分配和调节作用可以有效地增强系统对外部扰动的适应能力,使系统的工作更加稳定;对冷却系统参数的敏感性分析,可用于研究系统的工作特性,为系统的设计和运行控制提供依据;节温器的时间常数对冷却系统的动态特性影响显著,较小的时间常数有利于保证发动机的稳定工作.     

ICP-AES法测定硅酸盐岩石中15个元素

本法采用ICP-AES法并应用阶梯减光器,分步稀释和分步曝光相结合的方法,分析岩石中一些高含量的造岩元素,同时也分析岩石中次要、痕量元素。方法使用自制的3.5kW的高频等离子体发生器,采用三种混合酸(HNO_3、HF、HClO_4)分解样品,一次冲稀,两次摄谱。在2400 A—3800 A波段,测定Cr、Mn、V、Be、Cu、Y、La、Ni等8个元素;在3600A—5000A波段,采用三阶梯减光器,测定Ti、     

柴油发动机润滑系统流动与传热仿真研究

柴油发动机相比于汽油机有多方面的优势,但其较高的热负荷同样对润滑系统的设计和运行提出了更高的要求。本研究以某型柴油机为参照,基于MATLAB建立了润滑系统的数学模型,模拟了系统的流动和传热状况。和商业软件GT-suite的对比表明,仿真程序的计算结果精确可靠。基于仿真程序,本文研究了不同系统参数对流动和传热的影响,并据此提出了润滑系统的优化建议。     

卢卡斯光子筛的聚焦特性研究

介绍了一种基于卢卡斯数编码设计的轴上四焦点光子筛,其各焦距分布与黄金分割比密切相关.实验上利用相移数字全息验证了设计器件具有轴上四焦点聚焦特性,测量结果表明:轴向焦距和横向焦斑光强分布与理论设计值一致.该振幅型光子筛具有体积小、重量轻、易加工等优点,可应用于X波段显微和生物细胞阵列成像等领域.     

Nanoscale thermal transport: Theoretical method and application

With the size reduction of nanoscale electronic devices, the heat generated by the unit area in integrated circuits will be increasing exponentially, and consequently the thermal management in these devices is a very important issue. In addition, the heat generated by the electronic devices mostly diffuses to the air in the form of waste heat, which makes the thermoelectric energy conversion also an important issue for nowadays. In recent years, the thermal transport properties in nanoscale systems have attracted increasing attention in both experiments and theoretical calculations. In this review, we will discuss various theoretical simulation methods for investigating thermal transport properties and take a glance at several interesting thermal transport phenomena in nanoscale systems. Our emphasizes will lie on the advantage and limitation of calculational method, and the application of nanoscale thermal transport and thermoelectric property.     

混凝土声发射信号源定位精度的细观模型计算分析*

混凝土内部在断裂时会产生相应的声发射信号,通过这一信号,混凝土内部损伤断裂区域可以被定位。然而,混凝土是一种多相非均匀材料,而声发射定位算法是基于均匀介质假设进行计算的,因此采用该算法对其定位会产生一定的误差,有必要从细观的角度研究混凝土非均匀性对定位精度的影响。本文基于随机骨料模型以及时差定位算法（基于遗传算法）,建立了一种用于估计混凝土声发射定位误差的定量估算模型。本文采用该模型定量估算分析了混凝土细观组分对其声速的影响,并在该分析结构的基础上继续分析了骨料含量以及声速取值偏差对定位精度的影响。     

Simulations of monolayer SiC transistors with metallic 1T-phase MoS2 contact for high performance application

We preform a first-principles study of performance of 5 nm double-gated (DG) Schottky-barrier field effect transistors (SBFETs) based on two-dimensional SiC with monolayer or bilayer metallic 1T-phase MoS₂ contacts. Because of the wide bandgap of SiC, the corresponding DG SBFETs can weaken the short channel effect. The calculated transfer characteristics also meet the standard of the high performance transistor summarized by international technology road-map for semiconductors. Moreover, the bilayer metallic 1T-phase MoS₂ contacts in three stacking structures all can further raise the ON-state currents of DG SiC SBFETs in varying degrees. The above results are helpful and instructive for design of short channel transistors in the future.