检索结果-南通市图书馆

The UV-Decomposition on a Class of *** and Optimality Conditions

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Acta Mathematicae Applicatae Sinica 2007年第1期23卷 29-38页

作者： Wei Wang Li-Ping Pang Zun-Quan Xia School of Mathematics Liaoning Normal University Dalian 116029 China Department of Physics Dalian University of Technologe Dalian 116024 China. Department of Applied Mathematics Dalian University of Technology Dalian 116024 China

In this paper, the uV-theory and P-differential calculus are employed to study second-order expansion of a class of D,C, functions and minimization problems. Under certain conditions, some properties of the u-Lagrangian, the second-order expansion of this class of functions along some trajectories are formulated. Some first and second order optimality conditions for the class of D,C, optimization problems are given.

关键词： Nonlinear programming nonsmooth optimization optimality condition,uv-decomposition,D.C. optimization

Accelerometer error estimation and compensation for three-axis gyro-stabilized camera mount based on proportional multiple-integral observer

在线全文

学校读者我要写书评

暂无评论

science china(Technological sciences) 2014年第12期57卷 2387-2395页

作者： LI Shu Sheng ZHONG Mai Ying ZHAO Yan School of Instrument science & Opto-engineering Beihang University

This paper deals with the problem of accelerometer error estimation and compensation for a three-axis gyro-stabilized camera mount. In a dynamic environment, the aircraft motion acceleration affects the accelerome ：er output and causes a degradation of attitude steady accuracy. In order to improve control accuracy, this paper proposes a proportional multiple-integral observer- based control strategy to estimate and compensate the accelerometer error. The basic idea of this paper is to approximate the error property by using a q-order polynomial function and extend the error and its derivatives as augmented states. Then a proportional multiple-integral observer is developed to estimate the error, with which the relationship between the error and the imbalance torque is formulated. The estimated value is compared to an angle threshold, the result of which is used to compen- sate the accelerometer output. Through static and vehicle-mounted experiments, it is demonstrated that compared with the tra- ditional method, the proposed method can improve the attitude steady accuracy effectively.

关键词： three-axis gyro-stabilized camera mount accelerometer error estimation and compensation proportional multiple-integralobserver imbalance torque

k-step adaptive cluster sampling with Horvitz-Thompson estimator

在线全文

学校读者我要写书评

暂无评论

International Journal of Biomathematics 2018年第2期11卷 299-317页

作者： Quangyu Zhu Liyong Fu Central South University of Forestry and Technology 498 Shaoshan Nanlu Changsha 410004 Hunan P. R. China Research Institute of ForestResource Information Techniques Chinese Academy of Forestry Beijing 100091 P. R. China Center for Statistical Genetics Pennsylvania State University Loc T3436 Mailcode CH69500 University Drive Hershey PA 17033 USA

Adaptive cluster sampling （ACS） has been widely used for data collection of environment and natural resources. However, the randomness of its final sample size often impedes the use of this method. To control the final sample sizes, in this study, a k-step ACS based on Horvitz-Thompson （HT） estimator was developed and an unbiased estimator was derived. The k-step ACS-HT was assessed first using a simulated example and then using a real survey for numbers of plants for three species that were characterized by clustered and patchily spatial distributions. The effectiveness of this sampling design method was assessed in comparison with ACS Hansen-Hurwitz （ACS-HH） and ACS- HT estimators, and k-step ACS-HT estimator. The effectiveness of using different k- step sizes was also compared. The results showed that k-step ACS^HT estimator was most effective and ACS-HH was the least. Moreover, stable sample mean and variance estimates could be obtained after a certain number of steps, but depending on plant species, k-step ACS without replacement was slightly more effective than that with replacement. In k-step ACS, the variance estimate of one-step ACS is much larger than other k-step ACS （k 〉 1）, but it is smaller than ACS. This implies that k-step ACS is more effective than traditional ACS, besides, the final sample size can be controlled easily in population with big clusters.

关键词： Finalized sample size k-step adaptive cluster sampling plant species sample design inlprovement unbiased estimator.

Nonparametric Inference in a Simple Change-point Model

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 2008年第9期24卷 1483-1496页

作者： Zhan Feng Wang Yao Hua Wu and Lin Cheng Zhao Department of Statistics and Finance University of Science and Technology of China Hefei 230026 P. R. China

In this paper, we consider a change point model allowing at most one change, X($\tfrac{i}{n}$\tfrac{i}{n}) = f($\tfrac{i}{n}$\tfrac{i}{n}) + e($\tfrac{i}{n}$\tfrac{i}{n}), where f(t) = α + θ $I_{(t_0 ,1)} $I_{(t_0 ,1)} (t), 0 ≤ t ≤ 1, {e($\tfrac{1}{n}$\tfrac{1}{n}), ..., e($\tfrac{n}{n}$\tfrac{n}{n})} is a sequence of i.i.d. random variables distributed as e with 0 being the median of e. For this change point model, hypothesis test problem about the change-point t0 is studied and a test statistic is constructed. Furthermore, a nonparametric estimator of t0 is proposed and shown to be strongly consistent. Finally, we give an estimator of jump θ and obtain it’s asymptotic property. Performance of the proposed approach is investigated by extensive simulation studies.

关键词： sample median change point extreme distribution Bahadur representation

Fabrication of a Bi-layer Tubular Scaffold Consisted of a Dense Nanofibrous Inner Layer and a Porous Nanoyarn Outer Layer for Vascular Tissue Engineering

在线全文

学校读者我要写书评

暂无评论

Journal of Donghua University(English Edition) 2014年第5期31卷 718-722页

作者： CHEN Jian-feng LIU Wei WU Tong LI Da-wei ZHANG Jian-guang WANG Nan-ping MO Xiu-mei State KeyLaboratory for Modifications of Chemical Fibers and Polymer Materials- Coilege of Material Science and EngineeringDonghua University Shanghai 201620 China Biomaterials and Tissue Engineering Laboratory College of Chemistry Chemical Engineering and Biotechnology DonghuaUniversity Shanghai 201620 China Shanghai Fisheries Research Institute Shanghai 201620 China

Recent years, it has attracted more attentions to increase the porosity and pore size of nanofibrous scaffolds to provide the for the cells to grow into the small-diameter vascular grafts. In this study, a novel bi-layer tubular scaffold with an inner layer and an outer layer was fabricated. The inner layer was random collagen/poly （ L-lactide-co-caprolactone ） I P （ LLA- CL） ] nanofibrous mat fabricated by conventional electrospinning and the outer layer was aligned collagen/P （LLA-CL） nanoyarns prepared by a dynamic liquid dectrospinning method. Fourier transform infrared spectroscopy （FTIR） was used to characterize the chemical structure. Scanning electron microscopy （ SEM ） was employed to observe the morphology of the layers and the cross- sectioned bi-layer tubular scaffold. A liquid displacement method was employed to measure the porosities of the inner and outer layers. Stress-strain curves were obtained to evaluate the mechanical properties of the two different layers and the bi-layer membrane. The diameters of the nanofibers and the nanoyarns were （480 ± 197 ） nm and （ 19.66 ± 4.05 ） μm, respectively. The outer layer had a significantly higher porosity and a larger pore size than those of the inner layer. Furthermore, the bi-layer membrane showed a good mechanical property which was suitable as small-diameter vascular graft. The results indicated that the bi-layer tubular scaffold had a great potential application in small vascular tissue engineering.

关键词： nanoyarn poly ( L-lactide-co-caprolactone ) [ P ( LLA-CL ) ] bi-layer tubular scaffold porous structure small vascular tissueengineering

Cooperative Compressive Spectrum Sensing in Cognitive Underw ater Acoustic Communication Networks

在线全文

学校读者我要写书评

暂无评论

Journal of Donghua University(English Edition) 2015年第4期32卷 523-529页

作者：左加阔陶文凤包永强赵力邹采荣 School of Internet of Things Nanjing University of Posts and Telecommunications Key Laboratory of Underwater Acoustic Signal Processing of ministry of education Southeast University School of Communication Engineering Nanjing Institute of Technology

Because of the specific of underwater acoustic channel,spectrum sensing entails many difficulties in cognitive underwater acoustic communication( CUAC) networks, such as severe frequency-dependent attenuation and low signal-to-noise ratios. To overcome these problems, two cooperative compressive spectrum sensing( CCSS) schemes are proposed for different scenarios( with and without channel state information). To strengthen collaboration among secondary users( SUs),cognitive central node( CCN) is provided to collect data from SUs. Thus,the proposed schemes can obtain spatial diversity gains and exploit joint sparse structure to improve the performance of spectrum sensing. Since the channel occupancy is sparse,we formulate the spectrum sensing problems into sparse vector recovery problems,and then present two CCSS algorithms based on path-wise coordinate optimization( PCO) and multi-task Bayesian compressive sensing( MT-BCS),*** results corroborate the effectiveness of the proposed methods in detecting the spectrum holes in underwater acoustic environment.

关键词： cognitive underwater acoustic communication(CUAC) spectrum sensing compressive sensing path-wise coordinate optimization(PCO) multi-task Bayesian compressive sensing(MT-BCS)

Strong convergence of LAD estimates in a censored regression model

在线全文

学校读者我要写书评

暂无评论

science china Mathematics 2005年第2期48卷 155-168页

作者： FANG Yixin JIN Man ZHAO Lincheng Department of Statistics and Finance University of Science and Technology of ChinaHefei 230026China Department of Statistics and FinanceUniversity of Science and Technology of ChinaHefei 230026China Department of Statistics and FinanceUniversity of Science and Technology of ChinaHefei 230026China

A regression model with a nonnegativity constraint on the dependent variable,known as censored median regression model, is considered. Under some mild conditions, the LAD estimate of the regression coefficient is show... 详细信息

关键词： censored regression, LAD estimator, strong consistency, convergence rate, Bahadur representation.

Disc-Electrospun PCL Nanofiber Formed Micro-patterned Structure Scaffold

在线全文

学校读者我要写书评

暂无评论

Journal of Donghua University(English Edition) 2014年第5期31卷 595-598页

作者： PAN Xin LI Da-wei ZENG Zhi-wen SUN Bin-bin KE Qin-fei MO Xiu-mei College of Chemistry Chemical Engineering and Biotechnology Donghua University Shanghai 201620 China Engineering Research Center of Technical Textiles Donghua University Shanghai 201620 China College of Life and Environmental sciences Shanghai Normal University Shanghai 200234 China

Disc-electrospinning using a disc as spinneret and a rotary drum as collector is a novel technology to prepare nanofiber which has been applied in tissue engineering *** this study,nanofibrous mats with micro-patterned structure were fabricated via ***( #-caprolactone)( PCL) was dissolved in trifluoroethanol( TFE) at various concentrations( 2%-7%)( w / v)for electrospinning and the applied voltage ranged from 40 to 70 *** electron microscopy( SEM) was employed to observe the morphology of the nanofibrous *** images illustrated that the nanofibers with beads formed micro-patterned structure such as triangles and other *** average diameter of nanofibers presented various size with the concentration increased from 2% to 7%.The beads on the nanofibers constructed the vertexes of the polygons,while nanofibers bridged between adjacent *** concentration of solution and applied voltage may be two dominant factors to influence the topological structure of the nanofibrous *** cultured on the micro-patterned scaffold spread along the edges of the *** scaffold with patterned structure may have a promising application in tissue engineering.

关键词： disc-electrospun poly(ε-caprolactone)(PCL) patterned structure beaded-fibers scaffold

Individual and combined toxic effects of cypermethrin and chlorpyrifos on earthworm

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental sciences 2011年第4期23卷 676-680页

作者： Shiping Zhou Changqun Duan Wong Hang Gi Michelle Fazhong Yang Xuehua Wang Key Laboratory for Forest Resources Conservation and Use in the Southwest Mountains of china of ministry of education Southwest Forestry University Kunming 650224 China Laboratory for Conservation and Utilization of Bio-Resource & School of Life science Yunnan University Kunming 650091 China

Toxicities were assessed for a pyrethroid （cypermethrin） and an organophosphate insecticide （chlorpyrifos） individually and in combination. A series of tests were conducted on different responses （acute, chronic, behavioral） of earthworms of species Eisenia fetida andrei in the ecological risk assessment of these pesticides. The results showed that the toxicity of the mixture of cypermethrin and chlorpyrifos was significantly higher than either of these pesticides individually, especially on the earthworm’s chronic responses. At a concentration of 5 mg/kg, the mixture caused significant reductions on the growth and reproduction rates of earthworms, but did not cause any significant effect when the individual was tested. The increase in toxicity of the pesticide mixture means that the use of toxicity data obtained exclusively from single-pesticide experiments may underestimate the ecological risk of pesticides that actually present in the field.

关键词： earthworms pesticide combined effects cypermethrin chlorpyrifos