共查询到17条相似文献，搜索用时 674 毫秒
1.
The co-effect of transmitted power fluctuation and system nonlinearity produce deviations in scatterometer measurement results . An internal calibration method to deal with this problem is proposed. The method can result in more precise scatterometric measurements in a wide range. The basic principle of the method is combining real-transmitted-power detection with the calibration of system nonlinearity. A practical scheme to implement the method is also presented, which is developed based on a special designed mechanism of a microwave radiometer-scatterometer combined system. 相似文献
2.
We presented a wireless endoscope system developed on the embedded Linux platform. This wireless endoscope system consists of three parts： the endoscope capsule, the portable equipment and the image workstation, which make this system wireless and portable. Hardware design of this system and software design of the portable equipment are described. In clinical use, patients swallow the endoscope capsule for gastrointestinal inspection. The portable equipment receives images of gastrointestinal tract via the radio frequency module while it sets and reads back parameters of the capsule via the low frequency module. Acquired image data can be saved as a FAT32 format file in an universal serial bus disk. Images can be processed and reviewed at an Microsoft Windows PC workstation in the next stage. The image acquired by this wireless endoscope system is quite effective with clear details of gastrointestinal tract. However, the endoscope capsule was large, making it difficult to swallow. So the printed circuit board design of endoscope capsule needs to be improved. 相似文献
3.
A simple method for calculating the 3D coordinates of points on a moro object in a multi-camera system is proposed.It simplifies the algorithms used in traditional computer vision system by eliminating the calculation of the CCD( charge coupled device) camera parameters and the relative position between cameras,and using solid geometry in the calculation procedres instead of the calculation of the complex matrixes,The algorithm was used in the research of generating a virtual magnified 3D image of a micro object to be operated in a micro operation system,and the satisfactory results were obtained.The application in a virtual tele-operation system for a dexterous mechanical gripper is under test. 相似文献
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A laser collimating system based on 2-D position sensitive detector (PSD) is presented in this paper. The working principle of PSD is depicted in detail. A calibration device was developed to check the nonlinearity errors of PSD and a multilayer feedforward neural network based on error back-propagation algorithm was used to compensate errors. With the aid of computer-based data acquisition system, an automatic dynamic measuring process was realized. A series of experiments, including comparison tests with laser interferometer, were done to evaluate the performance of the measuring system. The experimental results show that the spatial straightness errors of guide rails can be measured with high accuracy. The maximum differences between the device and laser interferometer are 0. 027 mm in Y direction, and 0. 053 mm in X direction in the measuring distance of 6 m. 相似文献
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A system for measuring the quality parameters of elevator guide rails is developed. The quality parameters the system can measure include straightness, flatness, squareness, width and height of the rail. The system consists of six parts:main guideway, auxiliary guideway, reference rail, saddle, control casing and measured rail. The guide rail to be measured is mounted on a bed. The straightness errors of surfaces are checked by five linear displacement sensors mounted on the saddle. The deviation of readings from the sensor, which is in contact with top guiding surface, gives the straightness error of the surface and height of the rail. The other four sensors are used to measure side guiding surfaces respectively and give other parameters including flatness on the surfaces, squareness, width and height of the rail. A novel calibration method is also developed to calibrate the straightness motion error of the system in horizontal and vertical directions. The deflection deformation of the measured rail is fitted by using a fourth-order polynomial. Experimental results show that the uncertainty of the system on the side surfaces after compensating the straightness motion error is less than 0. 01 mm, and the uncertainty of the system on the top surface after compensating the straightness motion error and the deflection deformation of the rail is less than 0.03 mm. 相似文献
6.
In this paper, a collection of three-dimensional(3D)numerical breast models are developed based on clinical magnetic resonance images(MRIs). A hybrid contour detection method is used to create the contour, and the internal space is filled with different breast tissues, with each corresponding to a specified interval of MRI pixel intensity. The developed models anatomically describe the complex tissue structure and dielectric properties in breasts. Besides, they are compatible with finite-difference-time-domain(FDTD)grid cells. Convolutional perfect matched layer(CPML)is applied in conjunction with FDTD to simulate the open boundary outside the model. In the test phase, microwave breast cancer detection simulations are performed in four models with varying radiographic densities. Then, confocal algorithm is utilized to reconstruct the tumor images. Imaging results show that the tumor voxels can be recognized in every case, with 2 mm location error in two low density cases and 7 mm─8 mm location errors in two high density cases, demonstrating that the MRI-derived models can characterize the individual difference between patients' breasts. 相似文献
7.
To improve the efficiency of the management of large farms, a digitalized system of economic statistics is designed based on the Internet platform of the digitalized agricultural integrated system of Friendship Farm, the largest farm in the world. The system can also realize data storage by using the access databank technology. A dynamic website system, based on ASP technology, is used to implement the on-line inquiry of the statistical index of the agricultural economy and the diagrams of the index every year. Furthermore, it can provide the value of comprehensive indicators of farms' economic profits for every year and a trend chart of the comprehensive appraisal of economic development, by using principal component analysis. An early-warning indicator boundary is decided based on the majority principle. The system can realize the farm's terminal data input with effective data-collecting channels and a normative gathering scope and system. This system breaks through the stand-alone database system in agricultural digitalized research to realize the database system in the Internet environment by integrating the existing technologies in China. The system lays a foundation for the further integrated research on the network platform of the digitalized agricultural integrated system in Friendship Farm. 相似文献
8.
Xing-guang Duan Gui-bin Bian Hong-hua Zhao Xing-tao Wang Qiang Huang 《浙江大学学报(A卷英文版)》2010,11(4):263-269
Hepatocellular carcinoma （HCC） is the second most common malignancy in China. As microwave ablation （MWA） is an effective method for liver cancer, a robotic surgical system with ultrasound-directed was designed to assist surgeons on positioning the needles. This robotic system includes a surgical robot with 5 degrees of freedom, a workstation for path-planning and image processing, a conventional 2D ultrasound device, and an electromagnetic （EM） tracking system. Surgery space, clinical operation requirements and optimal mechanical structure are the key factors to be considered in designing a medical robot suitable for use by surgeons. Based on the mechanics of the needle placement robot, we have conducted detailed kinematic analysis, including a combined numerical algorithm and coordinate mapping. Finally, the feasibility of the needle placement robot has been validated by experiment. 相似文献
9.
It has been shown in recent economic and statistical studies that combining forecasts may produce more accurate forecasts than individual ones,However,the literature on combining forecasts has almost exclusively focused on linear combining forecasts.In this paper,a new nonlinear combination forecasting method based on fuzzy inference system is present to overcome the difficulties and drawbacks in linear combination modeling of non-stationary time series.Furthermore,the optimization algorithm based on a hierarchical structure of learning automata is used to identify the parameters of the fuzzy system.Experiment results related to numerical examples demonstrate that the new technique has excellent identification performances and forecasting accuracy superior to other existing linear combining forecasts. 相似文献
10.
in order to evaluate the seismic reliability of water distribution system and make rehabilitation decisions correspondingly, it is necessary to assess pipelines damage states and conduct functional analysis based on pipe leak- age model. When an earthquake occurred, the water distribution system kept serving with leakage. By adding a virtual node at the centre of the pipeline with leakage, an efficient approach to pressure-driven analysis was developed for simulating a variety of low relative scenarios, and a hydraulic leakage model was also built to perform hydraulic analy- sis of the water supply network with seismic damage. Then the mean-first-order-second-moment method was used to analyse the seismic serviceability of the water distribution system. According to the assessment analysis, pipes that were destroyed or in heavy leakage were isolated and repaired emergently, which improved the water supply capability of the network and would constitute the basis for enhancing seismic reliability of the system. The proposed approach to seismic reliability and rehabilitation decision analysis on water distribution system is demonstrated effective through a case study. 相似文献
11.
针对便携式心电仪数据存储需求,设计基于SDIO接口的SD卡底层驱动程序,并移植FatFS文件系统。同时,为降低存储开销,设计2-4-8-16变长码近似Huffman算法对一阶差分后的心电数据进行无损压缩;针对实验所用心电仪采集的一些心电数据,利用该算法平均可节省3/4以上的存储空间。实验结果表明,基于SD卡的文件存储机制通用性好,心电数据压缩算法时空开销小,可较好地满足便携式心电仪的数据存储需求。 相似文献
12.
星载微波辐射计计算植被光学厚度研究 总被引：1，自引：0，他引：1
大尺度的土壤水分变化监测对于建立全球的水循环模型意义重大，是实现气候变化预测和洪涝预警的基础。星载辐射计为实现大尺度土壤水分的监测提供了有效途径。由于地表植被对地表的上行微波辐射存在衰减作用，已有的反演算法过程中需要大量的地表植被信息辅助数据来计算地表植被层的影响，其中一个重要的参数就是植被光学厚度。该文基于地表微波辐射传输模型，分析微波极化差异指数（MPDI）与植被光学厚度的关系，结果表明6．9GHz通道MPDI与地表的植被覆盖度之间存在一定的负相关关系。在此基础上，该文建立了MPDI反演植被光学厚度的方法，并应用于土壤水分反演。实验中采用2004年AMSR／AMSR—E的亮温数据计算我国植被光学厚度并进行土壤水分反演，反演结果表明MPDI计算地表植被光学厚度能够取得较好的效果。 相似文献
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本文提出一种改进的幅度比较式无线电测向体制及测向算法,给出了在某手持测向设备中的应用结果．该测向体制及算法可抵消掉由硬件电路、人体干扰及环境等因素对天线方向图造成的影响,具有测向速度快、抗干扰能力强等优点,可广泛应用于各种手持式测向设备． 相似文献
15.
王淼 《北京工业职业技术学院学报》2013,12(1):34-36
数据安全问题越来越受到重视,笔记本电脑、随身U盘以及使用越来越广泛的智能手机所带的存储卡,都存储了大量的个人隐私信息。一旦这些物品丢失,或者这些信息被窃取、篡改、破坏,后果将不堪设想。针对个人计算机数据安全的隐患,提出了一系列的防护措施,能够有效地保证个人重要数据的不丢失,个人敏感数据的不外泄。 相似文献
16.
设计了一种结构简单、体积小、易携带，并能直接外接计算机打印口(DB-25)的高速并行数据采集器，并介绍了这种采集器的设计原理、各芯片的性能特性及与打印机适配器接口的软件设计。 相似文献
17.
金向平 《金华职业技术学院学报》2008,8(4):15-18
提出了一种基于USB的便携式数据采集与控制系统设计方案。从USB数据采集控制器硬件及电路设计、USB固件开发、驱动程庭设计以及数据采集程序设计等方面介绍了数据采集控制系统软硬件的设计和实现。该系统采用双CPU结构,一个CPU负责进行数据的采集、滤波、计算等,另一个CPU作为总线接口实现与PC机的通讯。以此为核心设计的数据采集控制系统。具有测试精度高、可靠性好,使用方便、通用性强等优点。可用于各种场合的实时数据采集与控制。 相似文献