期刊文献+
共找到9篇文章
< 1 >
每页显示 20 50 100
Method to generate training samples for neural network used in target recognition
1
作者 何灏 罗庆生 +2 位作者 罗霄 徐如强 李钢 《Journal of Beijing Institute of Technology》 EI CAS 2012年第3期400-407,共8页
Training neural network to recognize targets needs a lot of samples.People usually get these samples in a non-systematic way,which can miss or overemphasize some target information.To improve this situation,a new meth... Training neural network to recognize targets needs a lot of samples.People usually get these samples in a non-systematic way,which can miss or overemphasize some target information.To improve this situation,a new method based on virtual model and invariant moments was proposed to generate training samples.The method was composed of the following steps:use computer and simulation software to build target object's virtual model and then simulate the environment,light condition,camera parameter,etc.;rotate the model by spin and nutation of inclination to get the image sequence by virtual camera;preprocess each image and transfer them into binary image;calculate the invariant moments for each image and get a vectors' sequence.The vectors' sequence which was proved to be complete became the training samples together with the target outputs.The simulated results showed that the proposed method could be used to recognize the real targets and improve the accuracy of target recognition effectively when the sampling interval was short enough and the circumstance simulation was close enough. 展开更多
关键词 pattern recognition training samples for neural network model emulation space coordinate transform invariant moments
下载PDF
Reduced Imaging Time and Improved Image Quality of 3D Isotropic T2-Weighted Magnetic Resonance Imaging with Compressed Sensing for the Female Pelvis
2
作者 Hao Mei Feng Xiao Ming Deng 《Journal of Beijing Institute of Technology》 EI CAS 2023年第5期579-585,共7页
This study is to compare three-dimensional(3D)isotropic T2-weighted magnetic resonance imaging(MRI)with compressed sensing-sampling perfection with application optimized contrast(CS-SPACE)and the conventional image(3D... This study is to compare three-dimensional(3D)isotropic T2-weighted magnetic resonance imaging(MRI)with compressed sensing-sampling perfection with application optimized contrast(CS-SPACE)and the conventional image(3D-SPACE)sequence in terms of image quality,estimated signal-to-noise ratio(SNR),relative contrast-to-noise ratio(CNR),and the lesions’conspicuous of the female pelvis.Thirty-six females(age:51,28-73)with cervical carcinoma(n=20),rectal carcinoma(n=7),or uterine fibroid(n=9)were included.Patients underwent magnetic resonance(MR)imaging at a 3T scanner with the sequences of 3D-SPACE,CS-SPACE,and twodimensional(2D)T2-weighted turbo-spin echo(TSE).Quantitative analyses of estimated SNR and relative CNR between tumors and other tissues,image quality,and tissue conspicuity were performed.Two radiologists assessed the difference in diagnostic findings for carcinoma.Quantitative values and qualitative scores were analyzed,respectively.The estimated SNR and the relative CNR of tumor-to-muscle obturator internus,tumor-to-myometrium,and myometrium-to-muscle obturator internus was comparable between 3D-SPACE and CS-SPACE.The overall image quality and the conspicuity of the lesion scores of the CS-SPACE were higher than that of the 3D-SPACE(P<0.01).The CS-SPACE sequence offers shorter scan time,fewer artifacts,and comparable SNR and CNR to conventional 3D-SPACE,and has the potential to improve the performance of T2-weighted images. 展开更多
关键词 compressed sensing sampling perfection with application-oriented contrasts(space)using variable flip angle evolutions three-dimensional(3D)imaging magnetic resonance imaging(MRI) PELVIS
下载PDF
Sequential RBF Surrogate-based Efficient Optimization Method for Engineering Design Problems with Expensive Black-Box Functions 被引量:6
3
作者 PENG Lei LIU Li +1 位作者 LONG Teng GUO Xiaosong 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2014年第6期1099-1111,共13页
As a promising technique, surrogate-based design and optimization(SBDO) has been widely used in modern engineering design optimizations. Currently, static surrogate-based optimization methods have been successfully ... As a promising technique, surrogate-based design and optimization(SBDO) has been widely used in modern engineering design optimizations. Currently, static surrogate-based optimization methods have been successfully applied to expensive optimization problems. However, due to the low efficiency and poor flexibility, static surrogate-based optimization methods are difficult to efficiently solve practical engineering cases. At the aim of enhancing efficiency, a novel surrogate-based efficient optimization method is developed by using sequential radial basis function(SEO-SRBF). Moreover, augmented Lagrangian multiplier method is adopted to solve the problems involving expensive constraints. In order to study the performance of SEO-SRBF, several numerical benchmark functions and engineering problems are solved by SEO-SRBF and other well-known surrogate-based optimization methods including EGO, MPS, and IARSM. The optimal solutions, number of function evaluations, and algorithm execution time are recorded for comparison. The comparison results demonstrate that SEO-SRBF shows satisfactory performance in both optimization efficiency and global convergence capability. The CPU time required for running SEO-SRBF is dramatically less than that of other algorithms. In the torque arm optimization case using FEA simulation, SEO-SRBF further reduces 21% of thematerial volume compared with the solution from static-RBF subject to the stress constraint. This study provides the efficient strategy to solve expensive constrained optimization problems. 展开更多
关键词 surrogate-based optimization global optimization significant sampling space adaptive surrogate radial basis function
下载PDF
Combinatorial and Statistical Applications of Generalized Stirling Numbers 被引量:2
4
作者 R.B.Corcino 徐利治 E.L.Tan 《Journal of Mathematical Research and Exposition》 CSCD 北大核心 2001年第3期337-343,共7页
Here illustrated are certain combinatorial and statistical applications of the generalized Stirling numbers with integer parameters.
关键词 sample space probability function unbiased estimator.
下载PDF
A novel unsupervised approach for multilevel image clustering from unordered image collection 被引量:2
5
作者 Lai KANG Lingda WU Yee-Hong YANG 《Frontiers of Computer Science》 SCIE EI CSCD 2013年第1期69-82,共14页
A novel unsupervised approach to automatically constructing multilevel image clusters from unordered im- ages is proposed in this paper. The whole input image col- lection is represented as an imaging sample space (... A novel unsupervised approach to automatically constructing multilevel image clusters from unordered im- ages is proposed in this paper. The whole input image col- lection is represented as an imaging sample space (ISS) con- sisting of globally indexed image features extracted by a new efficient multi^view image feature matching method. By mak- ing an analogy between image capturing and observation of ISS, each image is represented as a binary sequence, in which each bit indicates the visibility of a corresponding feature. Based on information theory-inspired image popularity and dissimilarity measures, we show that the image content and distance can be quantitatively described, guided by which an input image collection is organized into multilevel clusters automatically. The effectiveness and the efficiency of the pro- posed approach are demonstrated using three real image col- lections and promising results were obtained from both qual- itative and quantitative evaluation. 展开更多
关键词 multilevel image clustering imaging sample space (ISS) unordered image collection
原文传递
Limited Spatial Transferability of the Relationships Between Kriging Variance and Soil Sampling Spacing in Some Grasslands of Ireland:Implications for Sampling Design 被引量:3
6
作者 SUN Xiaolin WANG Huili +3 位作者 Dermot FORRISTAL FU Weijun Hubert TUNNEY Chaosheng ZHANG 《Pedosphere》 SCIE CAS CSCD 2019年第5期577-589,共13页
Sampling plays an important role in acquiring precise soil information required in modern agricultural production worldwide, which determines both the cost and quality of final soil mapping products. For sampling desi... Sampling plays an important role in acquiring precise soil information required in modern agricultural production worldwide, which determines both the cost and quality of final soil mapping products. For sampling design, it has been proposed possibile to transfer the relationships between kriging variance and sampling grid spacing from an area with existing information to other areas with similar soil-forming environments. However, this approach is challenged in practice because of two problems: i) different population vaxiograms among similar areas and ii) sampling errors in estimated variograms. This study evaluated the effects of these two problems on the transferability of the relationships between kriging variance and sampling grid spacing, by using spatial data simulated with three variograms and soil samples collected from four grasslands in Ireland with similar soil-forming environments. Results showed that the variograms suggested by different samples collected with the same grid spacing in the same or similar areas were different, leading to a range of mean kriging variance (MKV) for each grid spacing. With increasing grid spacing, the variation of MKV for a specific grid spacing increased and deviated more from the MKV generated using the population variograms. As a result, the spatial transferability of the relationships between kriging variance and grid spacing for sampling design was limited. 展开更多
关键词 Key Words. geostatistics population variogram sampling error sampling grid spacing soil-forming environment soil information soil mapping spatial variability
原文传递
Sampling Designs for Validating Digital Soil Maps: A Review 被引量:6
7
作者 Asim BISWAS Yakun ZHANG 《Pedosphere》 SCIE CAS CSCD 2018年第1期1-15,共15页
Sampling design(SD) plays a crucial role in providing reliable input for digital soil mapping(DSM) and increasing its efficiency.Sampling design, with a predetermined sample size and consideration of budget and spatia... Sampling design(SD) plays a crucial role in providing reliable input for digital soil mapping(DSM) and increasing its efficiency.Sampling design, with a predetermined sample size and consideration of budget and spatial variability, is a selection procedure for identifying a set of sample locations spread over a geographical space or with a good feature space coverage. A good feature space coverage ensures accurate estimation of regression parameters, while spatial coverage contributes to effective spatial interpolation.First, we review several statistical and geometric SDs that mainly optimize the sampling pattern in a geographical space and illustrate the strengths and weaknesses of these SDs by considering spatial coverage, simplicity, accuracy, and efficiency. Furthermore, Latin hypercube sampling, which obtains a full representation of multivariate distribution in geographical space, is described in detail for its development, improvement, and application. In addition, we discuss the fuzzy k-means sampling, response surface sampling, and Kennard-Stone sampling, which optimize sampling patterns in a feature space. We then discuss some practical applications that are mainly addressed by the conditioned Latin hypercube sampling with the flexibility and feasibility of adding multiple optimization criteria. We also discuss different methods of validation, an important stage of DSM, and conclude that an independent dataset selected from the probability sampling is superior for its free model assumptions. For future work, we recommend: 1) exploring SDs with both good spatial coverage and feature space coverage; 2) uncovering the real impacts of an SD on the integral DSM procedure;and 3) testing the feasibility and contribution of SDs in three-dimensional(3 D) DSM with variability for multiple layers. 展开更多
关键词 calibration geographical space Latin hypercube sampling model-based design spatial coverage three-dimensional(3D) digital soil mapping
原文传递
A NEW TEST PROCEDURE FOR NEW BETTER THAN USED IN INCREASING CONVEX ORDERING
8
作者 LIXiaohu 《Journal of Systems Science & Complexity》 SCIE EI CSCD 2004年第4期492-499,共8页
A new nonparametric procedure is developed to test the exponentiality against the strict NBUC property of a life distribution. The exact null distribution is derived by the theory of sample spacings, and the asymptoti... A new nonparametric procedure is developed to test the exponentiality against the strict NBUC property of a life distribution. The exact null distribution is derived by the theory of sample spacings, and the asymptotic normality is also established by the large sample theory of L-statistics. Finally, the lower and upper tailed probability of the exact null distribution and some numerical simulation results are presented as well. 展开更多
关键词 increasing convex ordering L-statistic NBUC sample spacings simulation
原文传递
Exact Confidence Limits for the Parameter of an Exponential Distribution in the Accelerated Life Tests under Type-ⅠCensoring
9
作者 De-qiang ZHENG Xiang-zhong FANG 《Acta Mathematicae Applicatae Sinica》 SCIE CSCD 2021年第2期393-408,共16页
Life data frequently arise in many reliability studies,such as accelerated life tests studies.This paper considers the part of life data where failure and censoring observations may exist.To develop statistical method... Life data frequently arise in many reliability studies,such as accelerated life tests studies.This paper considers the part of life data where failure and censoring observations may exist.To develop statistical methods and theory for the analysis of these data,a new approach was proposed to obtain the exact lower and upper confidence limits for the mean life of the exponential distribution with Type-I censoring data.It is assumed that the acceleration factor is a random variable,and that the distribution of the acceleration factor is known from some empirical information or the meta analysis.A method for constructing the lower and upper confidence limits for the parameter based on an ordering relation among the sample space was proposed.Simulation studies and analyses of two examples suggest that the proposed method performed well. 展开更多
关键词 mean life confidence limit acceleration factor sample space ordering relation
原文传递
上一页 1 下一页 到第
使用帮助 返回顶部