三维编织复合材料声发射源定位分析研究

采用声发射检测技术,基于声发射波的传播特性和最小二乘法理论确立了三维编织复合材料性能分析和内部缺陷的定位方法.通过实验对比了工业CT扫描和声发射检测两种方式确定损伤源位置的差异,表明声发射源定位具有一定的准确性.     

考虑光伏动态特性的功角电压交互失稳机理分析

在大容量直流和高比例新能源集中接入电网的背景下,研究了考虑光伏动态特性影响的直流大功率扰动引发功角电压交互失稳问题。首先,从理论上推导了两机等值系统发电机转子运动方程和电动机负荷运动方程;然后,分析了直流大功率扰动引发功角和电压交互作用导致系统失稳的物理机理;最后,进一步分析了光伏低电压穿越期间不同有功/无功特性对系统稳定性的影响规律,通过吉泉直流实际系统算例进行了仿真验证。研究结果表明,两侧发电机功角拉开和负荷母线电压跌落(电动机电阻减小)形成恶性循环最终导致系统失稳,不同的光伏低电压穿越有功/无功特性对系统稳定性的影响需要通过理论结合仿真综合分析。     

55m砖烟囱小角度切口爆破拆除

为了成功爆破拆除一座55m高的砖结构烟囱,根据周围环境、烟囱高度及其结构特点,选取了合适的爆破倾倒方向和合理的爆破参数,采用了精准的爆破起爆网路。在实际工程中,砖烟囱爆破切口圆心角多数在200°~220°,通过对烟囱倾倒需满足的条件进行计算,确定其满足条件的爆破圆心角范围。设计了小角度爆破切口,其对应圆心角为185°,并且在爆破前进行预处理。起爆后,烟囱按照设计方向顺利倾倒,取得了较好的爆破效果。振动监测结果均在安全允许范围内,验证了砖烟囱小角度切口爆破拆除的可行性,可为类似工程提供参考。     

Concepts and fuzzy logic

Weights are used to measure relative importance of multiple attributes or objectives, which influence evaluation or decision results to a great degree. Thus, analyzing weight sensitivity is an important work for a multi-attribute evaluation or decision. A measuring method based on the inclined angle of two vectors is proposed in this paper in order to solve the weight sensitivity of a multi-attribute evaluation with isotonicity characteristic. This method uses the cosine of the inclined angle to measure the weight sensitivity based on preferences or preference combinations. Concepts of sensitivity space, degree, and angle are given, and the relevant measurement method is discussed and proved. Also, this method is used for the choice of the water environment protection projects in Heyuan City.     

Contact angle estimation and composite locomotive strategy of a stair-climbing mobile platform

This paper presents a stair-climbing mobile platform built on the Rocker–Bogie mechanism which enables to effectively climb up/down various sizes of stairs in indoor environments without violating its mobile stability. First, the link parameters of Rocker–Bogie mechanism are optimally chosen via the Taguchi method in order to make the trajectory of its center of mass (CM) as smooth as possible, which implies high mobile stability as well as excellent adaptability during climbing up/down stairs. Based on this optimization result, the proposed mobile platform is compactly and lightly constructed suitable for indoor applications by placing all motors and sensors inside the hollow links in order to prevent undesired interferences with stairs as well as to protect themselves from external impact. A simple, robust and cost-effective estimation algorithm is proposed to detect the contact angles between wheels and a stair with high fidelity. Through the kinematic and kinetic analysis combined with the wheel-stair contact angle information, a composite locomotive strategy is established not only to minimize the slip during climbing up a stair but also to prevent falling down during climbing down a stair. The extensive experiments against various types of stairs successfully demonstrate the capability of the proposed mobile platform to effectively and safely climb up/down stairs.     

无人飞艇低空航测系统在1:500大比例尺地形图航测中的应用

利用无人飞艇搭载组合宽角相机进行低空低速航空摄影,获取高分辨率、高清晰度、宽像幅、大航摄基高比影像,实现平面和高程测量精度的提高;采用地面标志布设像控标志点,提高坐标量测精度和空三加密精度;采用新的无人飞艇低空航测生产技术,实现满足国家规范要求的航测内业直接采集1∶500地形图平面和高程数据生产方式,解决了长期以来大比例尺航测成图内业高程测量精度达不到要求的难题,提高了航测生产效率,试验表明该技术具有较强的实用性和应用潜力。     

基于Matlab的定角度SPR传感器仿真

从理论上分析表面等离子体共振（SPR）的条件,给出了k层Kretschmann棱镜耦合模型下的反射率R大小的公式,编写了Matlab仿真软件,仿真了4层Kretschmann棱镜耦合模型下的反射率R大小与入射光波长、银膜厚度、棱镜折射率的关系。分析了仿真结果,得出了采用定角度方式时各装置参数的选择依据。     

Effects of display method,text display rate and observation angle on comprehension performance and subjective preferences for reading Chinese on an LED display

This study examined the effects of display method, text display rate, and observation angle on comprehension performance and subjective preferences for Chinese characters presented on an LED display. The factors and levels studied were as follows: four text display methods (rapid serial visual presentation ‘RSVP’, leading, paged view scrolling, and continuous scrolling), three text display rates (160 characters per min ‘cpm’, 240 cpm, and 320 cpm), and seven observation angles (−75°, −60°, −30°, 0°, 30°, 60°, and 75°). The results indicated that a display rate of 160 cpm was in general superior to 240 and 320 cpm for comprehension scores and subjective evaluations. The effects of display method and observation angle were found to be non significant. However, there was a significant interaction between display method and display rate. The results of this study were used to make ergonomics recommendations applicable to LED displays for determining optimum dynamic text display methods for Chinese characters.     

基于引导角的轮式移动机器人轨迹跟踪控制

首先,基于拉格朗日方程建立移动机器人模型;然后,根据侧向误差和角度误差的关系设计引导角,将该引导角作为虚拟输入,结合Backstepping方法设计基于移动机器人运动学模型的轨迹跟踪控制律,并给出参数选取条件;最后,以驱动轮力矩作为控制输入,并考虑到机器人受到的外部扰动,将运动学控制律扩展得到基于动力学模型的控制律.仿真结果表明了所设计控制律的有效性.     

固液界面效应影响竖壁沟流波动研究

基于最小能量原理分析的竖壁沟流流动模型,认为当壁面为存在接触角滞后的非理想表面时,其控制方程的边界条件与滞后接触角有关,并分析了流量存在波动时沟流厚度的波动原因和范围.实验研究了一些液体在不同表面上的沟流流动,结果表明了沟流波动与界面效应有关的假设的合理性,沟流的实际厚度介于由滞后角限定的某一范围内,并且与沟流平均流量有关.若流率波动未超出由滞后接触角及沟流基础流量限定的范围时,沟流只在厚度方向发生波动;若流率波动超出这一范围,则沟流在宽度方向也开始伸缩.