Analyzing vortex breakdown flow structures by assignment of colors to tensor invariants

Topological methods are often used to describe flow structures in fluid dynamics and topological flow field analysis usually relies on the invariants of the associated tensor fields. A visual impression of the local properties of tensor fields is often complex and the search of a suitable technique for achieving this is an ongoing topic in visualization. This paper introduces and assesses a method of representing the topological properties of tensor fields and their respective flow patterns with the use of colors. First, a tensor norm is introduced, which preserves the properties of the tensor and assigns the tensor invariants to values of the RGB color space. Secondly, the RGB colors of the tensor invariants are transferred to corresponding hue values as an alternative color representation. The vectorial tensor invariants field is reduced to a scalar hue field and visualization of iso-surfaces of this hue value field allows us to identify locations with equivalent flow topology. Additionally highlighting by the maximum of the eigenvalue difference field reflects the magnitude of the structural change of the flow. The method is applied on a vortex breakdown flow structure inside a cylinder with a rotating lid.     

心灵深处的遇合——读莫砺锋先生的《杜甫评传》

莫砺锋先生的《杜甫评传》是《中国思想家评传丛书》之一种。该书在继承前人成果后自创新说,围绕"思想"这一宗旨,贯穿整部著作的叙述。通过阅读《杜甫评传》发现其在对杜甫与传统文化的关系,对杜诗的解读及对历史人物的评价方面都有其独到之处。     

Stress wave propagation in supporting bolts: A test for bolt support quality

A test method for the non-destructive determination of bolt length, anchoring length, and bolt body force is described. This addresses the problems of low accuracy, limited number of data, and untimely warning signs encountered with existing test methods. Numerical simulations of the bolt, resin, and rock system show that the length accuracy when using the velocity wave is lower than when using the acceleration wave. It is accepted practice to use the acceleration wave for length tests because of improved signal to noise ratios of the waveforms. Laboratory and in situ underground tests showed that the precision of the measurements meets field requirements. Using this method the anchor properties of each single bolt and, thus, the safety of the entire roadway support may be evaluated.     

Modeling and experimental investigation for electrolytic corrosion prevention in high frequency micro EDM using deionized water

The characteristics of the prevention of electrolytic corrosion during micro electrical discharge machining (EDM) using deionized water and high frequency bipolar pulse were investigated. Electrolytic corrosion during micro EDM using deionized water was analyzed using an equivalent electrical circuit based on the electrical double layer theory. Based on the analysis and experimental verification, a narrow positive pulse duration should be provided to the workpiece to prevent corrosion. A negative voltage with zero average applied voltage (V_{avg, app}) is also essential for this purpose. If V_{avg, app} is positive or negative, electrolytic corrosion occurs on the workpiece or tool, respectively. Micro holes and 3D structures without corrosion were successfully fabricated using a high frequency bipolar pulse with a pulse duration of 0.2?μs and a period of 1?μs, as well as V_{avg, app}?=?0?V.     

子带自适应滤波器组参数的选取及其影响

为了研究自适应滤波在噪声消除,干扰抑制以及雷达信号处理中的广泛应用,对滤波器各影响因素进行了分析,提出了各参数的设计规则.以自适应滤波理论为基础,将信号划分成不同的子带通过原型分析综合滤波器组,将处理后的各路信号叠加可恢复原信号.选择合理的参数设置滤波器可以使系统的综合性能最优,同时可以将信号在传输过程中造成的损失减小到最低.通过大量仿真验证了该参数选取规则的准确性和有效性.     

Feasibility study of the application of voltage contrast to printed circuit board

Voltage contrast (VC) has been a powerful tool for the failure analysis of integrated circuits and multichip module. As the packing density of printed circuit board (PCB) is increasing, conventional failure analysis methods to detect open or short circuit in PCBs are no longer adequate, and voltage contrast method could be a method for this purpose. However, unlike the cases of integrated circuits and multichip module, there are many areas in PCB that will produce serious charging effect when examine under the scanning electron microscope. One of the areas is the presence of solder mask on PCB.This work examines the feasibility of using voltage contrast for PCB failure analysis. Specially designed PCB is used for experimentation, and it is found that positive bias on one track and zero bias on another copper track provide a better image contrast as compared to negative and zero biases on the tracks. Also, the variation of the image contrast with different spacing between inter copper tracks has studied. It is found that the variation depends on the presence of solder mask and its location. The variation can be very different for negative bias case as compared to the positive bias case.Finite element analysis is also performed to explain the experimental observations. All the observations can be well explained by the charging effect of the solder masks. The charging effect of solder mask is indeed very significant in affecting the image contrast, and it could reduce the contrast to almost zero in some cases.     

在DNA损伤修复信号传导通路中ATM介导的BCA1及RAD51作用机理的研究

为阐明毛细血管扩张性共济失调突变基因(Ataxia telangiectasia mutated,ATM)介导的乳癌基因1(Breast cancer gene 1,Brca1)磷酸化及其下游DNA修复相关蛋白(DNA damage repair protein 51,RAD51)在DNA损伤修复信号传导通路中作用机理,以源于正常人皮肤的成纤维细胞系GM细胞(Originated from human skinfibroblast GM Cell,GM0639)为对照,用免疫共沉淀与Western blot方法,观察60Co γ射线照射后共济失调症(Ataxia telangiectasia,AT)细胞、ATM转染的AT细胞(ATM+-AT)和GM细胞的BRCA1及RAD51蛋白表达的变化.经0、5、10、20Gy辐照后,AT细胞通过免疫共沉淀及Western Blot法分析其中ATM和BRCA1蛋白以及BRCA1和RAD51蛋白之间的相互作用以及PI3K抑制剂对ATM磷酸化其下游基因的影响.0Gy照射ATM+-AT和GM细胞未出现BRCA1表达条带;照射后,GM细胞、ATM细胞BRCA1和RAD51蛋白均有表达,而AT细胞无表达;PI3K抑制剂Wortmannin对经电离辐射照射后的AT、ATM+-AT和GM细胞中BRCA1蛋白表达具有抑制作用;照射后ATM+-AT和GM细胞中BRCA1和RAD51蛋白均有表达.因此,电离辐射照射后,BRCA1由ATM介导磷酸化后可进一步与RAD51相互作用,这是信号通路传导过程中的一个级联反映,从而修复损伤的DNA,保持基因组的稳定性.     

河流无线测控系统的设计

利用计算机技术和无线电通信技术实现远距离无线测控是实现自动控制的要求。提出了基于nRF24E1芯片为核心，集成了单片机／D转换器及无线收发器，扩展极少数外围设备组成的远程无线测控系统的设计思想及设计原理。系统由测控系统中心与现场测报单元两部分组成。在实验的基础上设计了单片机无线测挖电路，试验证明它达到了预定的控制效果。     

通孔氧化铝模板的制备和光学特性

采用阳极氧化法,制备了二维有序纳米通孔氧化铝模板.研究了工艺参数对通孔有序性、孔径、模板厚度等的影响,测量了通孔氧化铝模板的光透过、光吸收和光发射等光学特性.结果表明,在波长360 nm附近通孔氧化铝模板的光透过谱线和光吸收谱线发生突变,波长大于360 nm时,光透过增强;波长小于360 nm时,光吸收增强.通孔氧化铝模板的光致发光强度和峰位与激发光波长有关,光致发光谱范围在340～600 nm.     

基于AR2010微控制器的GPS接收机设计

AR2010型PDA/GPS芯片是一款集成了GPS控制器的SoC芯片，它使用MIPS的32位CPU内核并包含了GPS及各种外围设备控制器，主要介绍了基于这款芯片的GPS软件机的设计。