小波变换的地下含水层分层法

根据电测井曲线可以了解地层构造.为了找出含水砂层,基于人工分层的原理,利用小波变换过零点理论对电测井曲线进行计算机自动分层,将地下土层分为含水层和隔水层.介绍小波变换原理,给出用Matlab软件实现测井曲线计算机自动分层的方法.实验结果表明,用该方法研究实测井信号,结果与人工方法基本一敛,证明了小波变换用于测井信号分析与处理的有效性.论文工作对合理利用地下水资源有非常重要的意义.     

A Phase Engineering Strategy of Perovskite-Type ZnSnO3:Nd for Boosting the Sonodynamic Therapy Performance

The sensitization performance of sonosensitizers plays a key role in the sonodynamic therapy (SDT) effect. Herein, ZnSnO₃:Nd nanoparticles with R3c phase/amorphous heterogeneous structure are developed by phase engineering strategy and applied as an ideal sonosensitizer. In the crystalline perovskite-type ZnSnO₃:Nd, the substitution of the Zn²⁺ with Nd³⁺ causes the O 2p non-bonded state to move toward the Fermi level, which optimizes the band structure for ultrasound sensitization by reducing bandgap. Meanwhile, the unequal charge substitution can also form electron traps and oxygen vacancies to shorten the electron migration distance, which accelerates the electron–hole separation and inhibits carrier recombination, thus improving the acoustic sensitivity. Moreover, the dangling bonds exposed on the surface of amorphous ZnSnO₃:Nd provide more active sites, and the localized states of the amorphous phase may also promote carrier separation, resulting in synergistic SDT effect. In particular, the Zn²⁺ released from ZnSnO₃:Nd in the acidic tumor microenvironment (TME) reduces the adenosine triphosphate production by inhibiting the electron transport chain , which promotes the tumor cell apoptosis through destroying the redox balance of TME. Combining the inherent second near infrared and computed tomography imaging capabilities, this ZnSnO₃:Nd nanoplatform shows a promising perspective in clinic SDT field.     

A d-axis based current differential protection scheme for an active distribution network

The emergence of distributed generators has changed the operational mode and fault characteristics of the distribu tion network, in a way which can severely influence protection. This paper proposes a d-axis-based current differential protection scheme. The d-axis current characteristics of inverter-interfaced distributed generators and synchronous generators are analyzed. The differential protection criterion using sampling values of the d-axis current component is then constructed. Compared to conventional phase-based current differential protection, the proposed protection reduces the number of required communication channels, and is suitable for distribution networks with inverter interfaced distributed generators with complex fault characteristics. Finally, a 10 kV active distribution network model is built in the PSCAD platform and protection prototypes are developed in RTDS. Superior sensitivity and fast speed are verified by simulation and RTDS-based tests.     

Edge Fracture Prediction Using Uncoupled Ductile Fracture Models for DP780 Sheet

This paper is a contribution to the prediction of edge fracture behavior using uncoupled ductile fracture models. A fully integrated simulation framework for the edge fracture prediction is proposed with the shear-induced pre-damage considered. User-defined material subroutines are coded with uncoupled ductile fracture models (Lou-Huh, Oh, Brozzo) incorporated, which are calibrated using the fracture strains of various loading paths. A series of 3D numerical simulations are performed and compared with the results of hole-expansion tests. The effects of pre-damage field and fracture models are analyzed and discussed.

     

火箭结构系统纵向模态自动辨识方法

针对工程中需要从火箭结构系统的整体模态中识别纵向模态,根据模态有效质量理论,提出了一种识别火箭结构系统纵向模态的自动辨识方法.以具有集中质量系统的振动特性作为算例,通过有限元软件,建立了具有集中质量系统的梁模型,利用自动辨识的方法,自动辨识出系统的纵向模态,并与应用模态分析法所计算的系统模态信息相比较,这种自动辨识方法不仅能准确的辨识出振动系统的纵向模态,而且还具有自动高效的识别特点.为准确快速建立液体火箭POGO振动系统的动力学模型等工程系统的模型提供理论依据.     

冷凝式天然气快速热水器的应用探讨

根据对冷凝式燃气快速热水器节能效果的理论分析,产通过试验得出冷凝式天然气快速热水器热效率与其排烟温度的关系,试验结果表明冷凝式天然气快速热水器有很好的实用价值。     

无线传感器网络的信任模型研究

无线传感器网络环境下的信任模型作为密码技术的有效补充,在抵抗内部攻击、识别故障节点等方面发挥着重要作用,可应用于安全路由、安全数据融合等,用以提高系统的安全性、可靠性和公平性;分析了无线传感器网络环境下信任模型的特性,详细介绍了信任模型的评价指标;选取4种典型的信任模型进行评述,分析其优势和不足,并根据各项评价指标进行比较;最后指出目前研究中存在的问题,并展望了进行后续研究的切入点。     

基于SOPC的1553B通信系统设计

为满足航天相机与卫星平台的通信,在深入研究了1553B总线协议及接口技术的基础上,设计了一种基于SOPC(system onprogrammable chip)的1553B通信系统,详细描述了硬件构成及驱动软件和应用软件的编写,并应用于航天相机控制系统中;利用Xil-inx公司Vertex-ⅡPro系列的FPGA芯片,在其嵌入式硬核PowerPC405上构建SOPC平台,并移植实时操作系统Vxworks,进行任务实时调度,使系统工作在RT模式下,实现了航天相机与卫星的通信。     

Asymptotic powers for matched trend tests and robust matched trend tests in case-control genetic association studies

The matched trend test (MTT), developed using a conditional logistic regression, has been proposed to test for association in matched case-control studies to control the bias of known confounding effects and reduce the potential impact of population stratification. The MTT requires a known genetic model. When the genetic model is unknown, a Monte Carlo robust test, MAX, has been proposed for the analysis of matched case-control studies. The MAX statistic takes the maximum of three MTTs optimal for three common genetic models. We derive the asymptotic power for MTTs and robust tests. In particular, we derive the asymptotic p-value for MAX. Using these analytical results, we conduct simulation studies to compare the performance of MAX and the two-degree-of-freedom Chi-square test for matched case-control studies, where the latter is implemented in most computing software. Our simulation results show that MAX is always asymptotically more powerful than the two-degree-of-freedom Chi-square test under common genetic models. Our results provide guidelines for the analysis of genetic association using matched case-control data. An illustration of our results to a real matched pair case-control etiologic study of sarcoidosis is given.     

A hybrid immune model for unsupervised structural damage pattern recognition

This paper presents an unsupervised structural damage pattern recognition approach based on the fuzzy clustering and the artificial immune pattern recognition (AIPR). The fuzzy clustering technique is used to initialize the pattern representative (memory cell) for each data pattern and cluster training data into a specified number of patterns. To improve the quality of memory cells, the artificial immune pattern recognition method based on immune learning mechanisms is employed to evolve memory cells. The presented hybrid immune model (combined with fuzzy clustering and the artificial immune pattern recognition) has been tested using a benchmark structure proposed by the IASC–ASCE (International Association for Structural Control–American Society of Civil Engineers) Structural Health Monitoring Task Group. The test results show the feasibility of using the hybrid AIPR (HAIPR) method for the unsupervised structural damage pattern recognition.