检索结果-内蒙古大学图书馆

Fast and accurate position verification algorithms for dose delivery system in proton therapy scanning nozzle system

引用

NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 2021年 986卷 164719-164719页

作者： Lin, Yinjie Tan, Ping Guo, Huidong Zhang, Lige Lei, Hao Yu, Yecheng Li, Xingyu Huazhong Univ Sci & Technol State Key Lab Adv Electromagnet Engn & Technol Sch Elect & Elect Engn Wuhan 430074 Hubei Peoples R China

The spot position and size of a proton beam are critical parameters in the scanning dose delivery system. They need to be validated efficiently and accurately. But the traditional methods work poorly in some non-ideal cases. In this study, we develop effective means for the position verification algorithm, including the student's t distribution fitting algorithm, the Slope method, as well as the improved Gaussian fitting algorithm. And we verify the accuracy of them experimentally. That is several times higher than the one of the traditional fitting algorithms. The root mean square error (RMSE) of the improved Gaussian fitting algorithm is less than 0.2 mm as the signal-to-noise ratio (SNR) is higher than 30 dB even when a damaged strip exists around the beam spot. Furthermore, we implement the proposed Gaussian fitting arithmetic and the Slope method in Field Programmable Gate Arrays (FPGA) to test their efficiency. If the clock frequency of the chip with enough calculation resources is higher than 10 MHz, the computing time can be less than 6 mu s and 4 mu s, respectively. Finally, we conduct a simulation experiment. The result shows that RMSE of the proposed three methods are all less than 0.3 mm as the SNR is around 25 dB.

关键词： Proton therapy Ionization chamber fitting algorithm

来源：评论

学校读者我要写书评

暂无评论

Toward automatic measurement of the linewidth-enhancement factor using optical feedback self-mixing interferometry with weak optical feedback

引用

IEEE JOURNAL OF QUANTUM ELECTRONICS 2007年第7-8期43卷 527-534页

作者： Yu, Yanguang Xi, Jiangtao Chicharo, Joe F. Bosch, Thierry Zhengzhou Univ Coll Informat Engn Zhengzhou 450052 Peoples R China Univ Wollongong Sch Elect Comp & Telecommun Engn Wollongong NSW 2522 Australia ENSEEIHT F-31071 Toulouse France

This paper proposes an approach for automatically measuring the linewidth-enhancement factor (LEF) of semiconductor lasers using optical feedback self-mixing interferometry (OFSMI), which works in weak optical feedback regime and where the external target is subject to simple harmonic vibration with unknown vibration frequency and magnitude. According to well-known Lang-Kobayashi theory the waveforin of the modulated optical output power from the OFSMI system is influenced by multiple parameters, including the LEF, the optical feedback level factor, and the parameters related to the movement of external target. In order to estimate LEF, other parameters must also be considered and, hence, a multiple parameter estimation strategy is required. We propose a solution for this multiple parameter estimation problem based on the principle of data-to-theoretical model match. In particular, a strategy for minimizing a cost function in order to achieve the best fitting is proposed with which all the unknown parameters can be estimated. The performance of the proposed approach is tested using experimental data in comparison with other two approaches. It is seen that, over different experimental signals, the standard deviation for estimated LEF is less than 4.58% on average, which shows that results have excellent consistency. Moreover, the proposed approach also provides a solution for vibration measurement (that is, vibration frequency and magnitude)

关键词： fitting algorithm linewidth-enhancement factor (LEF) optical feedback interferometry self-mixing effect semiconductor laser

来源：评论

学校读者我要写书评

暂无评论

Sensitivity Analysis and Classification algorithms Comparison for Underground Target Detection

引用

IEEE ACCESS 2019年 7卷 116227-116246页

作者： Duan, Shihong Li, Yue Wan, Yadong Wang, Peng Wang, Zhen Li, Na Univ Sci & Technol Beijing Sch Comp & Commun Engn Beijing 100083 Peoples R China Sunkaisens Beijing Technol Ltd Beijing 100071 Peoples R China Univ Sci & Technol Beijing Sch Math & Phys Beijing 100083 Peoples R China

Underground target detection technology has been widely used in urban construction and resource exploration. With the development of industrial modernization, the demand for underground target detection is becoming more specific, such as the material and shape of underground targets. Therefore, it is necessary to classify the properties of underground targets. In this paper, sensitivity analysis was performed on the spheroid model and the approximate forward model at first, and the influence of the target properties on the model output is obtained. Secondly, we utilized the fitting algorithm to obtain the model parameters of the simulation data (model response of targets with varying shapes and materials), and analyzed the influence of the fitting algorithm on the classification results at different SNR. Finally, eight machine learning algorithms: support vector machine (SVM), neural network (NN), quadratic discriminant analysis (QDA), Gaussian process (GP), decision tree (DT), random forest (RF) and AdaBoost were used in this study to compare the obtained results. From the above analysis, we found that the shape (radius) have a greater influence on the model than the material (permeability) in the spheroid model. According to the approximate forward model, we found that it is not feasible to classify targets when the orientation is unknown. The influence of the fitting algorithm on the classification performances is related to the noise level. The obtained results using neural network demonstrated that the proposed method outperformed in material-based classification and shape-based classification. In the material-based classification, the classifier generally has a weaker ability to distinguish between permeable materials.

关键词： Underground target detection sensitivity analysis fitting algorithm machine learning classification algorithms comparison

来源：评论

学校读者我要写书评

暂无评论

ANALYSIS OF SPECTROSCOPIC ELLIPSOMETRIC MEASUREMENTS

引用

COMPUTER PHYSICS COMMUNICATIONS 1992年第1期69卷 201-214页

作者： VERBRUGGEN, MHW DENIJS, JMM Faculty of Applied Physics Eindhoven Univers0ity of Technology P.O. Box 513 5600 MB Eindhoven The Netherlands

In recent years spectroscopic ellipsometry has been successfully applied to non-destructively characterize multi-layer materials and to monitor surface processes as a function of time. The extraction of the relevant parameters of these samples from the spectroscopic data requires extensive computer analysis. For this purpose the sample is described by means of a stratified-layer theory in combination with an effective medium approximation. The computer program presently discussed performs this analysis of spectroscopic-ellipsometric data for any arbitrary model and any arbitrary number of data points. It applies a least-squares fitting procedure based on a modified Levenberg-Marquardt routine. A special feature of the program is the implementation of linked lists to obtain a very efficient data structure that allows a high flexibility of the program.

关键词： SPECTROSCOPIC ELLIPSOMETRY EFFECTIVE MEDIUM APPROXIMATION LEVENBERG-MARQUARDT LINKED LISTS fitting algorithm

来源：评论

学校读者我要写书评

暂无评论

QPA: A Quantization-Aware Piecewise Polynomial Approximation Methodology for Hardware-Efficient Implementations

引用

IEEE TRANSACTIONS ON VERY LARGE SCALE INTEGRATION (VLSI) SYSTEMS 2023年第7期31卷 931-944页

作者： Geng, Haoran Chen, Xiaoliang Zhao, Ning Du, Yuan Du, Li Nanjing Univ Sch Elect Sci & Engn Nanjing 210023 Peoples R China

Piecewise polynomial approximation (PPA) on nonlinear functions plays an important role in high-precision computing. In this article, we proposed QPA, an integration of error-flattened quantization-aware PPA methods, to generate the optimized coefficients for efficient hardware implementations targeting any polynomial order. QPA incorporated four key features to minimize the fitting error and the hardware cost, including using the Remez algorithm to compute the minimax fitting polynomial, combining the fitting and quantization operations to get an error-flattened characteristic, assigning specific coefficient bit width to each multiplier to reduce the hardware cost, and fine-tuning the truncated coefficients to further reduce the fitting error. Experimental results showed that our methods consistently achieved the lowest fitting error compared with the state-of-the-art error-flattened piecewise approximation methods. We synthesized the proposed designs with 28-nm TSMC CMOS technology. The results showed that the proposed designs achieved up to 37.0% area reduction and 50.5% power consumption reduction compared to the state-of-the-art error-flattened piecewise linear (PWL) method, and up to 27.0% area reduction, 21.4% delay reduction, and 20.8% power consumption reduction compared to the state-of-the-art error-flattened piecewise quadratic (PWQ) method.

关键词： fitting Hardware Approximation algorithms Table lookup Partitioning algorithms Adders Very large scale integration Approximate computing error-flattened fine-tuning rounding fitting algorithm piecewise polynomial approximation (PPA) prequantization Remez algorithm VLSI architecture

来源：评论

学校读者我要写书评

暂无评论

A new approach to characterising aspheric surfaces

引用

PRECISION ENGINEERING-JOURNAL OF THE INTERNATIONAL SOCIETIES FOR PRECISION ENGINEERING AND NANOTECHNOLOGY 2010年第1期34卷 171-179页

作者： Sun, W. McBride, J. W. Hill, M. Univ Southampton Sch Engn Sci Highfield SO17 1BJ Hants England

In this paper, a new approach to fitting aspheric surfaces in three-dimensional space is proposed, based on the nonlinear least-squares algorithm. For the conditions tested, there are good indications that this method provides better results than conventional solutions as all the surface parameters can be estimated simultaneously based on the design equation, thus allowing the result to be directly compared to design parameters. Conventionally, aspheric surfaces can be fitted with simplified surface models, such as a second order surface or polynomial model. Using this approach the estimated parameters cannot be compared with the design values, breaking the link between the designed and measured surface. The new method is developed here and tested on computer simulated aspheric surfaces. Both ideal surfaces and surfaces with random irregularities are considered. Issues regarding the application of the fitting method to real measured surfaces are discussed. (C) 2009 Elsevier Inc. All rights reserved.

关键词： Aspheric surfaces fitting algorithm Nonlinear least-squares

来源：评论

学校读者我要写书评

暂无评论

The measurement techniques for angular 3-D pinholes based on capacitive probe

引用

MEASUREMENT 2017年 97卷 145-148页

作者： Ma Yu-Zhen Ma Ling Zheng Yi-Zhong Univ Jinan Sch Mech Engn Jinan 250022 Peoples R China Tianjin Univ State Key Lab Measurement Technol & Instruments Tianjin 300072 Peoples R China

Based on the measurement progress of straight through pinholes, the measuring for angular is challenging because the probe is inconvenient to stretch into the pinhole exactly. In the paper, an adjustable five dimensional system, which is mainly composed of a three-coordinate measuring machine (CMM), a turntable, a visual sensor and a capacitive probe, is employed to accomplish the measurement for a circular workpiece with angular multi-pinholes. The CMM traces the coordinates while the capacitive probe moves, a precise turntable turns the workpiece at desired angle to guarantee the pinhole and the probe in the same orientation. A binocular visual sensor and a capacitive probe is for alignment and measuring, respectively. A comprehensive algorithm of combining projection and the least-squares fitting is put forward for fitting spatial axis equation of 3-D pinholes. Finally, a reliable and entire measurement system is set up and the optimal equation of the spatial axis is obtained. (C) 2016 Elsevier Ltd. All rights reserved.

关键词： Angular 3-D pinholes Capacitive probe Three-dimensional coordinates Axis fitting algorithm Circular workpiece

来源：评论

学校读者我要写书评

暂无评论

AN INEXPENSIVE LOW-FREQUENCY IMPEDANCE ANALYZER BASED ON DIRECT SAMPLING

引用

ELECTROCHIMICA ACTA 1993年第14期38卷 2079-2082页

作者： SKOU, E [a]Department of Chemistry Odense University DK-5230 Odense M Denmark

An impedance analyzer is described which used direct sampling of the stimulating and response signals into a laboratory data acquisition system. The analyzer uses subsampling in order to extend the range to frequencies higher than the sampling frequency. An algorithm which computes the optimum sampling rate is described. The analyzer can be used in the frequency range from above 10(5) Hz to below 10(-2) Hz. In the range from 50 kHz to 0.01 Hz the relative amplitude error was found to be less than 0.01% and the phase error to be less than 0.1 degree.

关键词： IMPEDANCE ANALYSIS DIRECT SAMPLING fitting algorithm SAMPLING algorithm

来源：评论

学校读者我要写书评

暂无评论

Multi-surface phase-shifting algorithm using the window function fitted by the nonlinear least squares method

引用

JOURNAL OF MODERN OPTICS 2022年第3期69卷 160-171页

作者： Chang, Lin Valyukh, Sergiy He, Tingting Chen, Zhu Yu, Yingjie Shanghai Univ Dept Precis Mech Engn Shanghai 200072 Peoples R China Linkoping Univ Dept Phys Chem & Biol Linkoping Sweden

A multi-surface phase demodulation algorithm is proposed to measure surfaces of the transparent plate simultaneously. A non-linear least-squares method based on the trust region is utilized to fit the window function derived from the characteristic polynomials. The fitted window function requires fewer parameters and has a flexible form, which means the window length can be stretched freely and used flexibly. Then, a multi-surface phase demodulation technique combining the discrete Fourier principle and the fitted window function is investigated, allowing simultaneous reconstruction of the measured front surface, rear surface, and thickness variation. During the implementation of our algorithm, the processing time for the interferograms with 850x850 pixels is around 5.1s. Measurement errors caused by several factors are analyzed, including wavelength-tuning error, frequency order error, cavity length error, and average thickness error. The experimental result on a rectangular transparent plate further verifies the effectiveness of our algorithm.

关键词： Interferometry wavelength-tuning fitting algorithm non-linear least-squares error analysis

来源：评论

学校读者我要写书评

暂无评论

Automatic reorientation to generate short-axis myocardial PET images

引用

EJNMMI PHYSICS 2024年第1期11卷 70页

作者： Yang, Yuling Wang, Fanghu Han, Xu Xu, Hui Zhang, Yangmei Xu, Weiping Wang, Shuxia Lu, Lijun Southern Med Univ Sch Biomed Engn 1023 Shatai Rd Guangzhou 510515 Peoples R China Southern Med Univ Guangdong Prov Key Lab Med Image Proc 1023 Shatai Rd Guangzhou 510515 Peoples R China Southern Med Univ Guangdong Prov Peoples Hosp Guangdong Acad Med Sci PET CtrDept Nucl Med 106 Zhongshan Er Rd Guangzhou 510080 Peoples R China Univ Chinese Acad Sci Canc Hosp Zhejiang Canc Hosp Hangzhou Zhejiang Peoples R China Pazhou Lab Guangzhou 510515 Peoples R China

BackgroundAccurately redirecting reconstructed Positron emission tomography (PET) images into short-axis (SA) images shows great significance for subsequent clinical diagnosis. We developed a system for automatic redirection and quantitative analysis of myocardial PET *** total of 128 patients were enrolled for 18 F-FDG PET/CT myocardial metabolic images (MMIs), including 3 image classifications: without defects, with defects, and excess uptake. The automatic reorientation system includes five modules: regional division, myocardial segmentation, ellipsoid fitting, image rotation and quantitative analysis. First, the left ventricular geometry-based canny edge detection (LVG-CED) was developed and compared with the other 5 common region segmentation algorithms, the optimized partitioning was determined based on partition success rate. Then, 9 myocardial segmentation methods and 4 ellipsoid fitting methods were combined to derive 36 cross combinations for diagnostic performance in terms of Pearson correlation coefficient (PCC), Kendall correlation coefficient (KCC), Spearman correlation coefficient (SCC), and determination coefficient. Finally, the deflection angles were computed by ellipsoid fitting and the SA images were derived by affine transformation. Furthermore, the polar maps were used for quantitative analysis of SA images, and the redirection effects of 3 different image classifications were analyzed using correlation *** the dataset, LVG-CED outperformed other methods in the regional division module with a 100% success rate. In 36 cross combinations, PSO-FCM and LLS-SVD performed the best in terms of correlation coefficient. The linear results indicate that our algorithm (LVG-CED, PSO-FCM, and LLS-SVD) has good consistency with the reference manual method. In quantitative analysis, the similarities between our method and the reference manual method were higher than 96% at 17 segments. Moreover, our method demonstrated excellent

关键词： Positron emission tomography (PET) Automatic reorientation Regional division Image segmentation fitting algorithm

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：