3D finite element numerical simulation of advanced detection in roadway for DC focus method

Within the roadway advanced detection methods, DC resistivity method has an extensive application because of its simple principle and operation. Numerical simulation of the effect of focusing current on advanced detection was carried out using a three-dimensional finite element method （FEM）, meanwhile the electric-field distribution of the point source and nine-point power source were calculated and analyzed with the same electric charges. The results show that the nine-point power source array has a very good ability to focus, and the DC focus method can be used to predict the aquifer abnormality body precisely. By comparing the FEM modelling results with physical simulation results from soil sink, it is shown that the accuracy of forward simulation meets the requirement and the artificial disturbance from roadway has no impact on the DC focus method.

NUMERICAL INVESTIGATION OF TOROIDAL SHOCK WAVES FOCUSING USING DISCONTINUOUS GALERKIN FINITE ELEMENT METHOD

A numerical simulation of the toroidal shock wave focusing in a co-axial cylindrical shock tube is inves- tigated by using discontinuous Galerkin （DG） finite element method to solve the axisymmetric Euler equations. For validating the numerical method, the shock-tube problem with exact solution is computed, and the computed results agree well with the exact cases. Then, several cases with higher incident Mach numbers varying from 2.0 to 5.0 are simulated. Simulation results show that complicated flow-field structures of toroidal shock wave diffraction, reflection, and focusing in a co-axial cylindrical shock tube can be obtained at different incident Mach numbers and the numerical solutions appear steep gradients near the focusing point, which illustrates the DG method has higher accuracy and better resolution near the discontinuous point. Moreover, the focusing peak pres- sure with different grid scales is compared.

Focused Wave Properties Based on A High Order Spectral Method with A Non-Periodic Boundary

In this paper, a numerical model is developed based on the High Order Spectral （HOS） method with a non-periodic boundary. A wave maker boundary condition is introduced to simulate wave generation at the incident boundary in the HOS method. Based on the numerical model, the effects of wave parameters, such as the assumed focused amplitude, the central frequency, the frequency bandwidth, the wave amplitude distribution and the directional spreading on the surface elevation of the focused wave, the maximum generated wave crest, and the shifting of the focusing point, are numerically investigated. Especially, the effects of the wave directionality on the focused wave properties are emphasized. The numerical results show that the shifting of the focusing point and the maximum crest of the wave group are dependent on the amplitude of the focused wave, the central frequency, and the wave amplitude distribution type. The wave directionality has a definite effect on multidirectional focused waves. Generally, it can even out the difference between the simulated wave amplitude and the amplitude expected from theory and reduce the shifting of the focusing points, implying that the higher order interaction has an influence on wave focusing, especially for 2D wave. In 3D wave groups, a broader directional spreading weakens the higher nonlinear interactions.

Highlights in focus issue on prostate cancer

In September 2013, the Translational Andrology and Urology （FAU） launched a focus issue on“Prostate Cancer”, which was guest-edited by Dr. Jer-Tsong Hsieh and Dr. Ganesh Raj from University of Texas Southwestern Medical Center at Dallas, USA.

Formal Methods for Commercial Applications Issues vs. Solutions

It was advocated that in 21st century, most of software will be developed with benefits of formal methods. The benefits include faults found in earlier stage of software development, automating, checking the certain properties and minimizing rework. In spite of their recognition in academic world and these claimed advantages, formal methods are still not widely used by commercial software industry. The purpose of this research is to promote formal methods for commercial software industry. In this paper we have identified issues in use of formal methods for commercial applications and devised strategies to overcome these difficulties which will provide motivations to use formal methods for commercial applications.

Method for the Determination of Sudan Dyes in Foods-High Performance Liquid Chromatography Jointly Issued by AQSIQ and SAC

Sudan Red are the chemosynthesis dyes of series of azo, which are mainly used as coloring additives in ma- nufacturing of some products, such as the wax, the oil-dyes, the petrol, and etc. In the process of food production, Sudan Dyes are banned to be used as food dyes in our country.

Simulation of Horizontal-Two-Dimension Focused Waves Using A Two-Layer Boussinesq-Type Model

Accurate simulation of the horizontal-two-dimension(H2D)focused wave group in deep water requires high accuracy of a numerical model.The two-layer Boussinesq-type model(Liu and Fang,2016;Liu et al.,2018)with the highest spatial derivative of 2 has high accuracy in both linear and nonlinear properties.Based on the further development of the velocity equations(Liu et al.,2023),the H2D numerical model for water waves is established with the prediction-correction-iteration model in the finite difference method,and a composite fourth-order Adams-Bashforth-Moulton scheme is used for time integration.The wave generation method proposed by Hsiao et al.(2005)is applied and calibrated in this H2D model.The numerical calculations lead to the following three main conclusions:First,compared with the analytical solution of Stokes linear waves,the calculated velocity profiles show higher accuracy by using the improved velocity formulas.Second,the simulations of the focused multidirectional wave group are carried out,and good agreements are found,demonstrating that the present H2D numerical model shows high accuracy in simulating focused multidirectional wave groups,and the effectiveness of the improved velocity formulas is also validated.Furthermore,the velocity profiles throughout the computational domain at the time of maximum wave crest are given.Finally,the FFT method is used to obtain the amplitude with different frequencies for several locations,and the changes of the wavelet energy spectrum at different locations are presented for several cases.

Numerical simulation and response analysis of microspherical focused logging in inclined micro-fractured formation

Tight and unconventional reservoirs have become the focus with the progress of petroleum exploration and development.Micro-fractures in these reservoirs can effectively improve reservoir permeability,and well-developed micro-fractures can serve to directly improve productivity.Compared with the centered electrical well logging method,the Micro Spherical Focused Logging(MSFL)is more suitable for microfracture identification due to its high resolution and near borehole wall measuring method.In this study,an anisotropic model is used to depict micro-fractured formation.First,a forward model with microfractured formation,borehole,logging instrument and surrounding rock is established.Subsequently,MSFL responses under different micro-fracture porosity,resistivity,dip angle and borehole radius,are calculated based on the finite element method(FEM).Finally,the MSFL responses under different microfracture parameters are analyzed with the response laws clarified.

在役螺栓超声三维成像监测数据的智能化分析方法

螺栓是一种常见的机械连接件,一旦失效,可能会导致设备损坏、结构崩塌,甚至危及人身安全。因此,在役螺栓的监测一直受到广泛关注。将相控阵超声全聚焦技术应用于螺栓在役监测,开发了专用系统和阵列探头,实现了三维成像可视化监测,改变了螺栓监测数据单一的现状。针对大量三维图像化数据处理的关键问题,提出了智能化分析方法,对比分析了决策树、支持向量机和神经网络算法的适用性,最终开发了基于决策树算法的智能分析评价软件模块并取得了较好的检测效果。

一种温度补偿调焦红外系统丢包检测方法

在红外技术广泛应用于当前军事、安防、医疗等领域背景下,如何提高红外系统信号的传输质量和传输可靠性,成为了一个亟待解决的问题。本文通过研究温补技术在红外系统中的丢包应用问题,提出了一种失同步触发判断丢包检测方法,并对其性能进行了系统分析、测量和验证。本研究为提高红外系统信号传输质量和信号完整性、可靠性提供了一种新的解决思路和技术方法。

改进型密集阵列全聚焦成像算法的碳纤维复合材料板损伤定位研究

本文针对各向异性碳纤维复合材料板的损伤定位问题,提出改进型密集阵列全聚焦成像方法。首先,考虑碳纤维复合材料板的各向异性,通过实验分析超声导波在板中的传播特性,得到沿不同传播方向的群速度值。其次,对密集型传感器阵列的参数进行分析和优化研究,分别对不同阵列参数即阵元间距和阵元数量进行指向性函数的数值分析,优化阵列的参数,以保证阵列主瓣较窄、旁瓣较低且无栅瓣。然后,提出了一种考虑碳纤维复合材料板各向异性的改进型密集传感器阵列板结构缺陷定位算法。使用超声导波在碳纤维复合材料板中沿不同传播方向的群速度值,对全聚焦算法进行修正,并利用虚拟聚焦原理对板结构进行全聚焦成像。最后,通过布置碳纤维复合材料孔洞损伤实验,对基于密集阵列全聚焦成像方法的定位精度进行分析。实验结果表明,改进型密集阵列全聚焦成像算法的定位精度为1.00 mm,相较于使用单一群速度值,该方法在定位孔洞损伤缺陷时具有更高的精度。

楔块耦合的碳纤维增强复合材料褶皱缺陷全聚焦成像

褶皱是碳纤维增强复合材料中最主要的缺陷类型之一,当使用超声相控阵对复合材料薄板进行检测时,由于采集系统非线性效应和电子串扰等干扰会引发盲区现象,掩盖了薄板内的褶皱信息。为削弱盲区影响,考虑在相控阵与复合材料薄板(小于10 mm)之间增加楔块,提出楔块耦合的最短路径射线追踪全聚焦方法。基于费马原理与斯涅耳定律,建立楔块耦合的多层介质超声波传播模型;制备含褶皱缺陷的碳纤维增强复合材料试样,搭建超声相控阵数据采集系统,采集全矩阵数据;将楔块耦合的最短路径射线追踪全聚焦方法和传统全聚焦方法的成像效果进行对比。结果表明,基于楔块耦合的最短路径射线追踪全聚焦方法能减小试样表面盲区深度,修正声时偏差,削弱盲区影响,恢复出试样内的褶皱缺陷。相比传统全聚焦方法,纤维褶皱长度、褶皱顶部高度、褶皱角度这3个参数表征的精准程度分别提高了5.9%、4.1%、4.2%。该文为碳纤维增强复合材料薄板褶皱缺陷的检测提供了新思路。

现代风险导向审计实务探讨

随着经济社会的持续快速发展,现代风险导向审计迎来崭新局面,如何立足时代背景,全面优化提升审计工作质效,满足高标准审计要求,备受业内关注。基于此,本文通过介绍现代风险导向审计的内涵,分析现代风险导向审计的计划、实施和完成等流程。在探讨审计环境、审计规范与信息化建设等方面存在的问题及原因的基础上,结合相关实践经验,提出优化内部审计环境、完善风险导向内部审计规范、加强内部审计信息化建设、建立完善的审计人才管理制度等优化路径。

邓小平对工农城乡关系战略重构的探索

以邓小平同志为主要代表的中国共产党人在探索中国式现代化进程中,主张经济发展以农业为战略重点、首先解决农村问题、让农民富起来。这是基于中国生产力水平、产业结构、要解决的现实问题和要实现的战略目标的重大变化,对社会主义革命和建设时期实行以重工业为中心、城市先行发展、产业发展目标重于增收目标的突破演进。这是在国民经济由以农业为主转变为以工业为主后,着眼于社会主义现代化建设“三步走”战略全局对工农城乡关系的战略重构,形成的促进工农城乡协调发展的新方略,既成为工业化新进程中巩固农业农村在经济社会发展中基础地位的保障,又促进了城乡二元结构的破解和农业农村向现代化的演进,对如何构建与社会主义现代化建设第一二步战略相适应的工农城乡关系的时代之问作出了回答。

基于分割环阵的CFRP分层缺陷超声全聚焦成像

碳纤维复合材料在钻孔加工时易产生分层缺陷,分层缺陷严重影响了构件的力学性能,存在严重的安全隐患。针对碳纤维复合材料孔边分层缺陷的检测,提出一种基于分割环形阵列的1/4矩阵全聚焦成像方法。设计了R4×S8、R3×S12、R3×S16和R4×S12四种分割环形阵列结构,通过数值仿真对比分析了各阵列的聚焦声场特点,最终确定分割环阵探头为5 MHz的R4×S12探头。使用该探头对碳纤维复合材料孔边分层试块的上层、中层、下层缺陷进行全矩阵采集,利用VTK工具包分别进行全矩阵三维成像和1/4矩阵三维成像。结果表明,1/4矩阵方法比全矩阵方法三维成像的缺陷对比度更高,1/4矩阵方法的缺陷尺寸表征误差更小,误差不超过6%。与全矩阵成像相比,1/4矩阵成像信噪比提升范围为3.43~7.61 dB,有效提升了图像质量。

大型螺栓阵列超声全聚焦成像的场能强化算法研究

大型螺栓大多用于连接需要承受重载和剧烈振动的构件,由于处于关键承载位置,其可靠性和稳定性对于工业结构的安全至关重要。阵列超声全聚焦成像能够提供高灵敏度、高分辨率的三维成像,为螺栓监测/检测提供了更好的质量和可靠性评价能力。但对于大型螺栓监测/检测而言,由于常规全聚焦方法使用单个阵元发射,造成在远离探头的部分超声能量较小,检测灵敏度下降。针对上述问题,提出了一种多反射场能量叠加强化的方法,针对所有反射能量场进行场能重建,将多层声场能量累加,使得缺陷处的信号增强。实验结果表明,随着声场能量层数增加,缺陷处的信号逐步增强,缺陷信噪比提高,可以检出常规全聚焦方法无法检出的小缺陷,证明该方法可以有效提高对微小缺陷的检测能力,提高全聚焦技术对螺栓的检测深度。

基于空间分辨法分析时间低相干光自聚焦效应

时间低相干光由于其瞬时宽带的物理特性,在激光惯性约束聚变中得到了广泛的关注.然而其复杂的时间尖峰结构或将诱导非线性自聚焦效应的放大.同时,传统的非线性自聚焦特征数值的测试方法中,多数材料的表面损伤先于体内自聚焦成丝损伤发生,这为对比不同激光的非线性效应带来巨大影响.本文利用短焦距透镜对熔石英进行紧聚焦,通过调节入射激光能量,在避免前表面损伤的前提下,诱导熔石英产生自聚焦成丝损伤.随后通过理论计算对光束在样品体内传输过程的光斑变化进行空间分辨处理,并得到对应细分位置的非线性数值.最终将各个位置对应的非线性相位变化值进行积分,得到前表面无损条件下材料的非线性自聚焦特征数值.测试结果表明时间低相干光的非线性自聚焦效应比传统单模脉冲激光更强.本文不仅设计了一套更加精确的对比不同激光非线性效应的测试方法,同时也探明了时间相干性对于非线性自聚焦效应的影响机制,为高功率时间低相干激光器的设计提供理论依据和参考.

超声全聚焦成像的裂纹类缺陷定量误差分析

虽然超声全聚焦成像(total focusing method,TFM)具有直观显示裂纹特征的明显优势,但通过TFM图像进行裂纹定量时不可避免地出现测量误差。该文采用模拟与实验对比的方式,分析TFM技术的裂纹定量误差。从超声波波长对缺陷深度的影响规律入手,分析和研究裂纹长度和取向的全聚焦图像测量误差原因。最后,通过模拟实验对比的方式验证裂纹定量误差。研究结果表明,裂纹上、下尖端的测量深度比实际深度均有所下沉,但两者下沉的深度基本相同,相差在0.6 mm以内,裂纹长度的测量误差范围为0~1 mm,带取向裂纹的取向测量误差基本保持在3°以内。因此,上、下尖端在深度上的测量误差对裂纹长度和取向的影响极小。经实验验证,裂纹深度、长度及取向误差的结论与模拟的结论一致。

国家区域医疗中心建设关键问题清单研究

目的总结当前国家区域医疗中心建设重点、难点问题,形成国家区域医疗中心建设关键问题清单,并提出相关策略建议。方法通过文献回顾、实地调研、深度访谈,形成国家区域医疗中心建设关键问题清单初稿;通过两轮德尔菲法咨询当地政府、输出医院、依托医院的专家,分析两轮问卷收集到的信息,筛选出重点问题。结果两轮问卷的有效回收率分别为99%、100%,专家权威系数分别为0.83、0.90,最终形成的国家区域医疗中心建设关键问题清单共有6条问题,其中管理体制机制健全的建设难点3条、人力资源管理完善的建设难点1条、医疗服务水平提升的建设难点1条、其他方面进展的建设难点1条。结论国家区域医疗中心建设面临管理机制完善、人力资源统筹管理、医疗能力提升等关键问题,政府部门应强化领导保障与协调监督责任,输出医院应完善管理体制与运营机制,依托医院应做好党建引领与配合协作,不断推进国家区域医疗中心同质化发展。

基于PARDISO直接求解器的三维自然电位正反演

近年来自然电位法在海底硫化物资源的勘探和评价中发挥了重要作用。本文开展的是基于PARDISO直接求解器的3D自然电位正反演算法研究。首先,利用有限体积法离散自然电位控制方程,采用PARDISO直接求解器提高正演计算的效率,通过数值解与解析解对比,验证了正演算法的可靠性。其次,在3D反演算法中考虑了地形因素,同时将最小支撑约束与深度加权加入目标泛函中,理论模型数据的反演结果很好地恢复了矿体的结构。最后,利用该算法对室内沙箱实验获得的自然电位数据进行反演,结果显示得出的电流密度异常与金属棒的位置基本一致。因此,本文提出的反演算法在未来大规模自然电位数据反演中具有重要作用。