声表面波谐振器无源无线传感虚拟仪器系统

分析了在通用硬件平台上结合软件设计的声表面波谐振器无源无线传感虚拟仪器系统。该系统通过设计虚拟仪器实现部分硬件功能,控制闭环系统实现自动检测,并采用数字信号处理方法提高检测系统的精度,从而避免了通常的复杂硬件系统,降低硬件成本,并使检测更灵活。本文介绍了设计原理和系统构成,并对系统的误差进行了分析。实验表明:该仪器系统能够达到5m的无线检测距离。     

UG应用技法

通过使用UG规律曲线和自由曲面建立的命令，一步一步掌握UG高级建模方法。     

单一水文站洪水波计算方法

本文介绍应用水力学方法计算洪水波绳套曲线。应用动力波模式的格戈夫方法,精度较高,特别适用于洪水期流量涨落变幅较大的场合,应用扩散波模式的琼斯方法,易于掌握和计算。以上两种方法都只需要用一个水文站的资料即可计算。对两种方法计算所得结果,用实测原型资料进行了验证。本文还对影响绳套曲线变化的惯性项进行了分析、探讨。     

A computational fluid dynamics investigation of a novel flooded-bed dust scrubber with vibrating meshOA

This work proposes a vibrating mesh screen as an alternative to the static mesh screen currently used in conventional flooded-bed dust scrubbers for removing airborne coal mine dust in the continuous mining environment. Fundamental assessments suggest that a vibrating screen may improve the dust collection efficiency of scrubber systems and mitigate the clogging issues associated with the conventional design.To evaluate this hypothesis, computational fluid dynamics(CFD) simulations were carried ...     

High-speed ground moving target detection research using triangular modulation FMCW

The frequency modulated continuous wave (FMCW) radar has the characteristics of low probability of interception, good hidden property and the ability to counter anti-radiation missiles. This paper proposes a new method for high-speed ground moving target detection (GMTD) using triangular modulation FMCW. According to the characteristic of the opposite range shift induced by the upslope and downslope modulation FMCW, the upslope and downslope are imaged, respectively. After compensation of continuous motion of the platform and time difference between upslope and downslope signals for imaging, the moving target can be detected through displaced phase center antenna (DPCA) technology. When the moving target is detected, the moving target image is extracted, and correlation processing is used to obtain the range shift, which can be used to estimate the target radial velocity, and further to find the real position of the target. The effectiveness of this method is verified by the result of computer simulation. __________ Translated from Journal of Xidian University, 2008, 35(4): 586–591 [译自: 西安电子科技大学学报(自然科学版)]     

如何提高米波雷达的方位精度

分析了米波波段背靠背双天线雷达实测原始点迹数据,列出了不同情况下目标点迹参数的分布,对比了中心法、峰值法、幅度加权法三种方法获得的目标方位数据的分布与特性。比较表明：对米波雷达而言,采用幅度加权方法获取目标方位,其精度较高。     

考虑非线性大变形的轮胎模态分析

轮胎的动态特性是影响包括操纵稳定性、行驶平顺性在内的车辆整体性能的重要指标之一。建立了考虑轮胎的实际边界条件、复杂材料特性的有限元模型，进行了考虑非线性大变形的模态分析。同时分析了影响模态频率的各个因素，主要包括轮胎胎压、轮胎侧壁材料和轮胎胎体质量。     

Reversed and Anomalous Doppler Effects in Photonic Crystals and other Time-dependent Periodic Media

We predict that reversed and anomalous non-relativistic Doppler shifts can be observed under some circumstances when light reflects from a shock wave front propagating through a photonic crystal, or material with a periodic modulation of the dielectric. This theoretical prediction is generalizable and applies to wave-like excitations in a variety of periodic media. An experimental observation of this effect has recently been made (Seddon, N. and Bearpark, T. Science, 302 (2003) 1537) and we provide a brief discussion of this experiment.     

超声纵波换能器用于平测时的测距修正方法研究

研究了超声纵波换能器用于平测时的测距修正方法.首先,根据弹性波理论分析了利用平测布置代替对测布置测量波速时的实际物理意义;然后,分析了两种换能器布置方式的真实传播距离并通过设计混凝土试件切割-测量实验进行了两种布置方式的声时对比;最后,根据实验数据在对测回归直线方程的基础上提出了计算换能器平测布置修正测距的最小二乘法....     

基于脑电技术的MOOC平台用户体验优化策略研究

目的 通过脑电技术与主观问卷相结合的方式,测量MOOC平台用户体验水平,探索影响MOOC平台用户体验的主要因素,提出设计优化建议。方法 通过脑电技术采集各被试者在使用MOOC平台时的脑电信号特征,结合用户体验量表获取用户的主观评价。采用频域分析的方法提取节律波能量值并进行定量化分析,洞察节律波能量与主观评价的内在联系,从而实现MOOC平台用户体验水平的定量化分析。结论 中国大学MOOC平台用户体验优于学堂在线平台,MOOC平台可用性、可寻性是影响用户注意力、脑力负荷、唤醒度的重要影响因素,MOOC平台愉悦性是影响用户情绪的主要因素。