检索结果-南通市图书馆

Representing conics by low degree rational DP curves

同方期刊数据库博看期刊评论

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science C(Computers and Electronics) 2010年第4期11卷 278-289页

作者： qian-qian HU Guo-jin WANG Department of Mathematics Zhejiang University Hangzhou 310027 China College of Statistics and Mathematics Zhejiang Gongshang University Hangzhou 310018 China

A DP curve is a new kind of parametric curve defined by Delgado and Pena （2003）; Jt has very good properties when used in both geometry and algebra, i.e., it is shape preserving and has a linear time complexity for evaluation. It overcomes the disadvantage of some generalized Ball curves that are fast for evaluation but cannot preserve shape, and the disadvantage of the B6zier curve that is shape preserving but slow for evaluation. It also has potential applications in computer-aided design and manufacturing （CAD/CAM） systems. As conic section is often used in shape design, this paper deduces the necessary and suffi- cient conditions for rational cubic or quartic DP representation of conics to expand the application area of DP curves. The main idea is based on the transformation relationship between low degree DP basis and Bemstein basis, and the representation tbeory of conics in rational low degree B6zier form. The results can identify whether a rational low degree DP curve is a conic section and also express a given conic section in rational low degree DP form, i.e., give positions of the control points and values of the weights of rational cubic or quartic DP conics. Finally, several numerical examples are presented to validate the effectiveness of the method.

关键词： Conic sections Bernstein basis DP basis Rational low degree Bezier curves Rational low degree DP curves

Model optimization method and connected-pipe experiment of a liquid fuel ramjet engine

在线全文

学校读者我要写书评

暂无评论

航空动力学报 2013年第6期28卷 1277-1285页

作者： MA qian-rong GUO Xin WU Hu CHOU qian School of Power and Energy Northwest Polytechnical University Aero-Engine Altitude Simulated Key Laboratory China Gas Turbine EstablishmentAviation Industry Corporation of China

The optimization method of a mathematical model and connected-pipe experimental technique for a test in altitude test facility (ATF) of a liquid fuel ramjet engine was *** optimization of the simple mathematical model was divided into two ***,using the test engine's geometry configuration size data,a preliminary adjustment was ***,using experimental test data,the components' experiential coefficients were modified *** was laid on the simulation technique of flight condition and parameters measurement *** experimental technique was applied to a ramjet ATF test *** comparison results show that the optimized-model has higher precision and the nozzle gross thrust difference drops from 12% to about 4%.

关键词： ramjet engine model optimization altitude test facility(ATF) connected-pipe experiment simulation technique

Pumping into a cool future:electrocaloric materials for zero-carbon refrigeration

在线全文

学校读者我要写书评

暂无评论

Frontiers in Energy 2022年第1期16卷 19-22页

作者： Xiaoshi qian Interdisciplinary Research Center for Engineering Science School of Mechanical EngineeringShanghai Jiao Tong UniversityShanghai 200240China

Existing commercial heat pumps,such as air conditioners(A/C)and refrigerators,possess a coefficient of performance(COP)up to and in some cases even higher than ***,most existing space heating techniques rely heavily on fossil fuels as their direct(burning)or secondary(electric heating)energy *** heating is responsible for 45%of building emissions.

关键词： heating carbon coefficient

Advances on topological materials

在线全文

学校读者我要写书评

暂无评论

Frontiers of physics 2020年第4期15卷 33-34页

作者： qian Niu Department of Physics The University of Texas at AustinAustinTX 78712USA

Topological materials refer to solid structures with topo-logically protected electronic states or other degrees of freedom.A prime example is a Chern insulator in which the occupied bands of states are organized with a non-trivial topology as characterized by a nonzero Chern in-teger,exhibiting gapless chiral excitations on the bound-aries,which are robust against scatterings.

关键词： topological trivial excitation

Deeply missing my career idol and role model--Professor Perry ***

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

Frontiers of Environmental Science & Engineering 2023年第9期17卷 257-258页

作者： Yi qian School of Environment Tsinghua UniversityBeijing 100084China

Upon hearing the news of Professor Perry ***’s passing,I felt deeply saddened and heartbroken,and was unable to contain my emotions.I couldn’t help but reminiscing about the cherished moments we shared together and the valuable lessons I learned from him over the years.I first met Professor Perry *** in *** the opportunity of attending a conference in the United States,I visited Professor McKinney at the University of Kansas,the first American expert in my field that I had ever known of.I told him that I was very interested in Professor McCarty’s research on aerobic bio-filters and wanted to learn more.“Let me give Perry a call,”he said immediately,and in less than five minutes,Perry and I became *** turned out that Professor McKinney had been Professor McCarty’s teacher and mentor in the past.I changed my flight immediately and flew to California the next day,where I met Professor McCarty,a world-renowned expert in water pollution control,and visited the aerobic bio-filter he established and their water pollution control *** had inspiring yet amiable conversations,and a friendship that lasted for over 30 years ensued.

关键词： visited career missing

Derivative-free reinforcement learning:a review

在线全文

学校读者我要写书评

暂无评论

Frontiers of Computer Science 2021年第6期15卷 75-93页

作者： Hong qian Yang YU National Key Laboratory for Novel Software Technology Nanjing UniversityNanjing 210023China

Reinforcement learning is about learning agent models that make the best sequential decisions in unknown *** an unknown environment,the agent needs to explore the environment while exploiting the collected information,which usually forms a sophisticated problem to ***-free optimization,meanwhile,is capable of solving sophisticated *** commonly uses a sampling-andupdating framework to iteratively improve the solution,where exploration and exploitation are also needed to be well ***,derivative-free optimization deals with a similar core issue as reinforcement learning,and has been introduced in reinforcement learning approaches,under the names of learning classifier systems and neuroevolution/evolutionary reinforcement *** such methods have been developed for decades,recently,derivative-free reinforcement learning exhibits attracting increasing ***,recent survey on this topic is still *** this article,we summarize methods of derivative-free reinforcement learning to date,and organize the methods in aspects including parameter updating,model selection,exploration,and parallel/distributed ***,we discuss some current limitations and possible future directions,hoping that this article could bring more attentions to this topic and serve as a catalyst for developing novel and efficient approaches.

关键词： reinforcement learning derivative-free optimization neuroevolution reinforcement learning neural architecture search

Modeling the measurement precision of Fringe Projection Profilometry

在线全文

学校读者我要写书评

暂无评论

Light(Science & Applications) 2023年第11期12卷 2480-2497页

作者： Shenzhen Lv qian Kemao School of Computer Science and Engineering Nanyang Technological UniversitySingaporeSingapore

Three-dimensional(3D)surface geometry provides elemental information in various sciences and precision *** Projection Profilometry(FPP)is one of the most powerful non-contact(thus non-destructive)and non-interferometric(thus less restrictive)3D measurement techniques,featuring at its high ***,the measurement precision of FPP is currently evaluated experimentally,lacking a complete theoretical model for *** propose the first complete FPP precision model chain including four stage models(camera intensity,fringe intensity,phase and 3D geometry)and two transfer models(from fringe intensity to phase and from phase to 3D geometry).The most significant contributions include the adoption of a non-Gaussian camera noise model,which,for the first time,establishes the connection between camera’s electronics parameters(known in advance from the camera manufacturer)and the phase precision,and the formulation of the phase to geometry transfer,which makes the precision of the measured geometry representable in an explicit and concise *** a result,we not only establish the full precision model of the 3D geometry to characterize the performance of an FPP system that has already been set up,but also explore the expression of the highest possible precision limit to guide the error distribution of an FPP system that is yet to *** theoretical models make FPP a more designable technique to meet the challenges from various measurement demands concerning different object sizes from macro to micro and requiring different measurement precisions from a few millimeters to a few micrometers.

关键词： sizes concerning formulation

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

日本数字疗法管理及医保支付的经验与启示

卫生软科学 2025年第1期39卷 90-94页

作者：邢倩何达上海市卫生和健康发展研究中心/上海市医学科学技术情报研究所上海201199

通过梳理日本数字疗法的应用现状、医保支付路径及标准,发现日本数字疗法的准入在传统医疗器械框架下进行,得益于独立的分类管理和监管策略,以及产学研数据共享和数字疗法的快速发展。但较为有限的卫生技术评估基础导致数字疗法评估维... 详细信息

通过梳理日本数字疗法的应用现状、医保支付路径及标准,发现日本数字疗法的准入在传统医疗器械框架下进行,得益于独立的分类管理和监管策略,以及产学研数据共享和数字疗法的快速发展。但较为有限的卫生技术评估基础导致数字疗法评估维度不全面,伦理审查和社会影响有潜在隐患。基于此提出未来我国可探索以真实世界证据为准绳,尝试快速审查与支付的地区试点,确保多方利益和伦理考量,定期进行影响评估以保障数字疗法健康发展。

关键词：数字疗法政策保障医疗保险日本

Rational cubic/quartic Said-Ball conics

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

Applied Mathematics(A Journal of Chinese Universities) 2011年第2期26卷 198-212页

作者： HU qian-qian WANG Guo-jin Department of Mathematics Zhejiang University Hangzhou 310027 College of Statistics and Mathematics Zhejiang Gongshang University Hangzhou 310018.

In CAGD, the Said-Ball representation for a polynomial curve has two advantagesover the B′ezier representation, since the degrees of Said-Ball basis are distributed in a step *** advantage is that the recursive algorithm of Said-Ball curve for evaluating a polynomialcurve runs twice as fast as the de Casteljau algorithm of B′ezier curve. Another is that theoperations of degree elevation and reduction for a polynomial curve in Said-Ball form are simplerand faster than in B′ezier form. However, Said-Ball curve can not exactly represent conics whichare usually used in aircraft and machine element design. To further extend the utilizationof Said-Ball curve, this paper deduces the representation theory of rational cubic and quarticSaid-Ball conics, according to the necessary and su？cient conditions for conic representation inrational low degree B′ezier form and the transformation formula from Bernstein basis to Said-Ballbasis. The results include the judging method for whether a rational quartic Said-Ball curve is aconic section and design method for presenting a given conic section in rational quartic Said-Ballform. Many experimental curves are given for confirming that our approaches are correct ande？ective.

关键词： Rational Said-Ball curve Rational B′ezier curve conics.