气动激励装置原型机磁共振弹性成像研究

介绍:磁共振弹性成像是一种无创的对生物组织的生物力学特性进行定量分析的新技术。在诸多外部机械激励方法中,气动激励装置因其磁兼容性好而相对被广泛使用。本研究搭建了一台气动装置原型机并测试了该装置在不同频率和振幅条件下的性能。材料和方法:使用超声方法测试气动激励装置原型机在无负载条件和不同频率和振幅情况下的性能,并在磁共振弹性成像环境测试该原型机在有负载条件下的性能。结果:生物组织的弹性值与外部激励的频率和振幅、生物组织的机械力学特性以及传导管的长度和内径有关。结论:稳定可靠的机械波是磁共振弹性成像中准确可靠地重建组织弹性值的保障,气动激励装置的机械激励参数应根据不同生物组织的特性进行优化,以保证弹性值重建的可靠性。     

Studying single nanocrystals under high pressure using an x-ray nanoprobe

In this report, we demonstrate the feasibility of applying a 250-nm focused x-ray beam to study a single crystalline NbSe(3) nanobelt under high-pressure conditions in a diamond anvil cell. With such a small probe, we not only resolved the distribution and morphology of each individual nanobelt in the x-ray fluorescence maps but also obtained the diffraction patterns from individual crystalline nanobelts with thicknesses of less than 50 nm. Single crystalline diffraction measurements on NbSe(3) nanobelts were performed at pressures up to 20 GPa.     

基于Skyline软件的三维Web系统设计与研发

本文讲述基于Skyline软件的三维web地理信息系统的解决方案。重点阐述了WEB可视化技术,以及如何利用Skyline系列软件在在网络环境下搭建一种三维地理信息系统,包括Skyline系列软件中Terra Builder的建模过程和调用Terra Explorer pro接口的过程。     

High‐order sliding mode control design based on adaptive terminal sliding mode

High‐order sliding mode control techniques are proposed for uncertain nonlinear SISO systems with bounded uncertainties based on two different terminal sliding mode approaches. The tracking error of the output converges to zero in finite time by designing a terminal sliding mode controller. In addition, the adaptive control method is employed to identify bounded uncertainties for eliminating the requirement of boundaries needed in the conventional design. The controllers are derived using Lyapunov theory, so the stability of the closed‐loop system is guaranteed. In the first technique, the developed procedure removes the reaching phase of sliding mode and realizes global robustness. The proposed algorithms ensure establishment of high‐order sliding mode. An illustrative example of a car control demonstrates effectiveness of the presented designs. Copyright © 2011 John Wiley & Sons, Ltd.     

Human eyebrow recognition in the matching-recognizing framework

This paper studies the problem of automatically recognizing human eyebrows using a frontal view. In the matching-recognizing framework for image-based object classification, we design an automatic human eyebrow recognition system via fast template matching and Fourier spectrum distance. Fast template matching is used to locate the target subregion of a gallery template or a pure eyebrow image in a probe original eyebrow image, whereas Fourier spectrum distance is used to determine the final identity of the probe original eyebrow image. We conducted a number of experiments to demonstrate the efficacy of the proposed system and corroborate the validity of eyebrow recognition on the BJUT eyebrow database. Moreover, we also tested the system on the color FERET database. Experimental results show that our approach can be directly applied to face recognition by only replacing eyebrow templates with face templates, and may achieve higher accuracy in eyebrow recognition than in small face recognition. This is a strong argument for eyebrow recognition to replace face recognition as an independent biometric in certain scenarios, especially where relatively large eyebrows can be cropped.     

积石峡水电站混凝土面板堆石坝设计

积石峡水电站拦河坝为混凝土面板堆石坝,最大坝高103 m。坝址位于高山峡谷地区,河谷狭窄且不对称,岸坡陡峻。在设计中,围绕减少岸坡开挖和填筑工程量、减小坝体不均匀沉降、确保止水效果等关键技术问题,就堆石坝的布置、坝体分区、趾板布置、周边缝结构、坝顶结构等进行了优化设计,为在不对称狭窄河谷上建造高面板坝积累了成功经验。     

浅谈积石峡水电站导流及围堰施工方案

积石峡水电站施工采用全年围堰挡水、导流隧洞和泄洪排沙底孔导流、基坑全年施工的导流方式。围堰挡水阶段度汛标准为20年一遇洪水。积石峡水电站导流及泄水建筑物设计和围堰及其防渗系统设计符合工程实际水文气象条件和地形地质条件,为成功截流及主体工程施工奠定了基础,积累了宝贵的工程经验。     

金安桥水电站引水发电系统设计

金安桥水电站引水发电系统设计中面临的主要技术问题有:电站进水口结构设计、压力背管形式、钢管过缝措施、蜗壳外围混凝土结构设计、地震高烈度区厂房结构抗震设计等。对以上问题进行了多次分析研究,提出了技术可行、经济合理、施工方便、便于运行管理的工程优化方案。     

观音岩水电站右岸溢流坝段RCC温度场仿真分析

1 引言 观音岩水电站地处四川省攀枝花市,位于横断山纵谷区.挡河大坝由左岸、河中碾压混凝土重力坝和右岸粘土心墙堆石坝组成为混合坝,坝顶总长1158 m,其中混凝土坝部分长838.035 m,心墙堆石坝部分长319.965 m.混凝土坝部分坝顶高程为1139 m,心墙堆石坝部分坝顶高程为1141 m,两坝型间坝顶通过5%的坡相连.碾压混凝土重力坝部分最大坝高为159 m,心墙堆石坝部分最大坝高71 m.