Attack Simulation Model and Channel Statistics in Underwater Acoustic Sensor Networks

In recent years,underwater acoustic wireless sensor networks have been used in many areas.There have been many field trials of acoustic propagation models and statistics for shallow water conditions.However,field trials are limited environmentally and,hence,not widely accepted.Simulations of the impulse response of a shallow underwater acoustic channel allows less expensive system tests that are reproducable.This paper presents a shallow water acoustic channel model based on the actual acoustic propagation ...     

Multi-Axis Projection Based Giant Component Formation in Random Unit-Disk Graphs

This paper proposes a multi-axis projection (MAP) based giant component formation strategy via the Maximal Independent Set (MIS) in a random unit-disk graph.We focus on the problem of virtual back-bone construction in wireless ad hoc and sensor networks,where the coverage areas of the nodes are disks with identical radii.In the simulation,we show that the MAP-based giant component has the ability to connect most nodes and serves as a backbone in the network.The algorithm is localized and may play an important role in efficiently constructing a virtual backbone for ad hoc and sensor networks.     

Effects of Ru on microstructure stability and mechanical properties of Ni_3Al single crystal alloy

The effect of Ru on microstructure stability and stress rupture properties of a Ni_3Al single-crystal alloy was investigated. The experimental results showed that the addition of 2%Ru(mass fraction) improved the microstructure stability due to the restraint of harmful Y-NiMo phase formation during the thermal exposure at the high temperature above 1 000℃.And the reason may be that the addition of Ru increased the degree of Mo supersaturation in bothγandγ' phases,and hence suppressed the precipitation of ...     

Influence of Mg_5Ga_2 compound on microstructures and electrochemical properties of Mg-5%Hg-22%Ga alloy

The Mg-5%Hg-22%Ga(mole fraction) alloy was melted.Aging at 573-673 K for different times was carried out to ensure the fine dispersion of the Mg_5Ga_2 compound.Scanning electron microscopy(SEM),X-ray diffractometry(XRD) and energy spectrum analysis(ESA) were employed to characterize the microstructures and phases of the Mg-5%Hg-22%Ga alloy.The electrochemical and corrosion behaviors of the above alloy were studied by potentiodynamic,galvanostatic and electrochemical impedance spectroscopy(EIS) measuremen...     

基于原子模型的非局域连续模型

在传统的连续模型中,本构关系,例如胡克定律、热传导的傅立叶定律是宏观现象的表征.在原子尺度下,传统连续模型具有很大的局限性,其中一个原因就是传统连续模型忽略了原子间相互作用的非局域性.本文在不采用任何经验的本构假设和局部均匀变形假设(如Cauchy-Born假设)的情况下,严格基于原子模型,构造了一个连续模型,将原子间相互作用力的非局域性和非线性性自然地嵌入到模型中.此模型可以有效表现原子尺度的非均匀变形.     

油气水流量测量仪的混合器设计及仿真研究

为了保证油气水流量测量的精度,研制了一种不占用中心通道的静态混合器,仿真和试验表明,在产生很小压差的情况下,混合器可以达到良好的混合效果,为油气水流量精确测量提供了有效的均相方法.     

改革电子电路实验教学 培养学生创新能力

实验教学是高职院校实践性教学的主要环节,对学生创新思维和创新能力的培养起着至关重要的作用。文章以电子电路分析与实践课程教学为例,介绍了实验教学在课程设置、实验教学内容、实验教学手段上进行的探索和创新。实践表明,实验教学探索与改革收到了良好的效果,提升了学生的学习兴趣,基础型实验有助于学生掌握基本实验技术和技能,而自主设计综合创新型实验则有利于对学生进行知识、能力与素质的综合培养。     

高校院级科研实验室仪器设备共享管理浅析

随着高等教育的不断发展,高校资产规模的日益扩大,学院科研实验室占有的仪器设备在数量、价值上都有明显增加。因此,如何提高科研实验室仪器设备的使用效益,探索共享管理模式以及该模式在运行中的环节建设十分必要。通过对华南理工大学生物科学与工程学院科研实验室仪器设备共享管理具体实施情况的分析,对这共享管理模式下的仪器设备管理方式和管理系统的建设提出了自己的看法。     

瓜环的缚酸行为及催化环己醇合成环己烯研究

文中以实验室合成的Q[n](n=5～8)与一定浓度的硫酸作用,形成瓜环硫酸盐晶体。运用酸碱滴定法,对该产物的酸度进行测定,通过计算得出不同瓜环的缚酸比例,进而总结出瓜环缚酸的规律。另采用该瓜环硫酸盐催化环己醇合成环己烯,既减少硫酸用量,降低了实验操作的危险性和实验室污染,又增加了瓜环的应用范围。对催化剂用量、反应时间对产率的影响进行了研究,收到了较满意的效果。     

基于晶体管GP模型的Multisim仿真建模方法

在现代电子电路设计中,先对电路进行前期软件仿真已经是必不可少的环节,然而仿真结果的可信度和真实度又取决于建立的仿真模型正确与否.Multisim仿真软件提供了部分型号三极管的仿真模型,但不够全面.对于特定三极管,需要在仿真软件中建立相应的仿真模型,以得到较理想的仿真结果.利用三极管的数据手册,介绍在Mulitism仿真软件中建立三极管GP模型的方法,并对2N3903型三极管的仿真模型与实物分别进行了直流扫描和交流特性对比分析.从直流扫描分析结果中可以看出:在饱和区,仿真曲线与实测曲线基本上一致;在放大区,仿真曲线与实测之间有一定的差异,但是平均相对误差小于10%.主要原因是晶体管存在分散性,而数据手册提供的是平均特性.从波特图仿真与实测结果中可以看出仿真的3dB通频带要比实际3dB通频带宽,主要原因是仿真模型中只考虑了三极管的极间电容影响,没有考虑三极管衬底电容的影响.实验结果表明利用该方法建立的仿真模型与实测数据基本上一致.