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Global dimension and left derived functors of Hom

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Science china Mathematics 2007年第6期50卷 887-898页

作者： Li-xin MAO & Nan-qing DING institute of Mathematics, nanjing institute of Technology, nanjing 211167, china Department of Mathematics, nanjing university, nanjing 210093, china institute of Mathematics Nanjing Institute of Technology Nanjing China Department of Mathematics Nanjing University Nanjing China

It is well known that the right global dimension of a ring R is usually computed by the right derived functors of Hom and the left projective resolutions of right R-modules. In this paper, for a left coherent and right perfect ring R, we characterize the right global dimension of R, from another point of view, using the left derived functors of Hom and the right projective resolutions of right R-modules. It is shown that rD(R)≤n (n≥2) if and only if the gl right Proj-dim MR≤n - 2 if and only if Extn-1(N, M) = 0 for all right R-modules N and M if and only if every (n - 2)th Proj-cosyzygy of a right R-module has a projective envelope with the unique mapping property. It is also proved that rD(R)≤n (n≥1) if and only if every (n-1)th Proj-cosyzygy of a right R-module has an epic projective envelope if and only if every nth Vroj-cosyzygy of a right R-module is projective. As corollaries, the right hereditary rings and the rings R with rD(R)≤2 are characterized.

关键词： global dimension projective resolution envelope

Formation flying in elliptic orbits with the J_2 perturbation

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Research in Astronomy and Astrophysics 2012年第11期12卷 1563-1575页

作者： Xi-Yun Hou, Yu-Hui Zhao and Lin Liu School of Astronomy and Space Science, nanjing university, nanjing 210093, china institute of Space Environment and Astrodynamics, nanjing university, nanjing 210093, china School of Astronomy and Space Science Nanjing University Nanjing 210093 China institute of Space Environment and Astrodynamics Nanjing University Nanjing 210093 China

Relative dynamics between the chief satellite and the deputy ones in for- marion flying is crucial to maintaining the formation. A good choice of the forma- tion usually requires a lower control frequency or less control energy. For formation flying missions in highly elliptic orbits, the well-known C-W equation is not accu- rate enough. Instead, Lawden＇s equation is often used. First, the solution to Lawden＇s equation with a very simple form is deduced. Then the J2 perturbation is added. It is found that Lawden＇s solution is not necessarily valid when the J2 perturbation is con- sidered. Completely discarding Lawden＇s solution and borrowing the idea of mean orbit elements, two rules to initialize the formation are proposed. The deviation speed is greatly reduced. Different from previous studies on the J2 perturbation, except for the relatively simple expression for the semi-major axis, the tedious formulae of the long period terms and the short period terms of other orbital elements are not used. In addition, the deviation speed is further reduced by compensation of the nonlinear effects. Finally, a loose control strategy of the formation is proposed. To test the ro- bustness of this strategy, a third body perturbation is added in numerical simulations.

关键词： celestial mechanics

Research on heart sound identification technology

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Science china(Information Sciences) 2012年第2期55卷 281-292页

作者： CHENG XieFeng1,3,MA Yong2,LIU Chen1,ZHANG XueJun1 & GUO YuFeng11School of Electronic Science and Engineering,nanjing university of posts and telecommunications,nanjing 210003,china 2School of Computer Science and Technology,nanjing university of Science and Technology,nanjing 210094,china 3Key Lab of Broudbard Wireless Communication and Sensor Network Technology(nanjing university of posts and telecommunications),Ministry of Education,nanjing 210094,china School of Electronic Science and Engineering Nanjing University of Posts and Telecommunications Nanjing China Ministry of Education Key Lab of Broudbard Wireless Communication and Sensor Network Technology (Nanjing University of Posts and Telecommunications) Nanjing China School of Computer Science and Technology Nanjing University of Science and Technology Nanjing China

In this article,both the basic principles and the experimental methods of identity recognition technology based on heart sounds are ***,the characteristics of heart sounds and the feasibility of heart sounds as a biometric were analyzed.A synthetic model of heart sounds was then developed based on a family of wavelets;Finally,the characteristic parameters of heart sounds were extracted by using the heart sounds linear band frequency cepstra(HS-LBFC)with a specified configuration,and the similarity distance was adopted for heart sound *** highlight the difference in two heart sound signals between the time and frequency domains,a construction method of the heart sound wavelet,a calculation method of the parameters of a synthetic model,selection of the characteristic parameters of heart sounds and the corresponding data processing technology were *** experimental results showed that the proposed method exhibited excellent performance and practicability.

关键词： biometric wavelet family of heart sounds synthetic model of heart sounds heart sounds linear band frequency cepstra(HS-LBFC)

Design of Groupband Data Modem using OQAM Technique

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The Journal of china Universities of posts and telecommunications 1997年第1期4卷 7-15页

作者： Zhang Dengyin (Department of Computer Engineering, nanjing university of posts and telecommunications, nanjing 210003, P.R.china) Zheng Baoyu (Department of Graduate Students, nanjing university of posts and telecommunications, nanjing 210003,

An orthogonally multiplexed QAM(OQAM) system allows transmission speed to be very close to the Nyquist rate with little sensitivity to delay and signal distortions of transmission medium when a large number of channels are used. Its circuit complexity can be largely overcome by introducing digital signal processing(DSP) technology. In this paper, the implementation of groupband data modem using OQAM technique is presented, where OQAM system is realized by means of cascading a discrete cosine transformer(DCT) and a weighting network. The proper algorithm of evaluating FIR filter and DCT provides further reduction of the computation complexity which drops to 35.6% of that of Hirosaki's scheme .

关键词： data modem OQAM DCT weighted network

A new measure to characterize multifractality of sleep electroencephalogram

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Science Bulletin 2006年第24期51卷 3059-3064页

作者： MA Qianli1,2,NING Xinbao1,WANG Jun2 & BIAN Chunhua1 1. State Key Laboratory of Modern Acoustics,Department of Electronics Science and Engineering,institute for Biomedical Electronic Engi-neering,nanjing university,nanjing 210093,china 2. Province Key Laboratory of Image Processing & Image Communica-tion,College of telecommunications and Information Engineering,nanjing university of posts & telecommunications,nanjing 210003,china State Key Laboratory of Modern Acoustics Department of Electronics Science and Engineering Institute for Biomedical Electronic Engineering Nanjing University Nanjing China Province Key Laboratory of Image Processing & Image Communication College of Telecommunications and Information Engineering Nanjing University of Posts & Telecommunications Nanjing China

Traditional methods for nonlinear dy-namic analysis,such as correlation dimension,Lyapunov exponent,approximate entropy,detrended fluctuation analysis,using a single parameter,cannot fully describe the extremely sophisticated behavior of electroencephalogram (EEG). The multifractal for-malism reveals more “hidden” information of EEG by using singularity spectrum to characterize its nonlin-ear dynamics. In this paper,the zero-crossing time intervals of sleep EEG were studied using multifractal analysis. A new multifractal measure Δasα was pro-posed to describe the asymmetry of singularity spec-trum,and compared with the singularity strength range Δα that was normally used as a degree indi-cator of multifractality. One-way analysis of variance and multiple comparison tests showed that the new measure we proposed gave better discrimination of sleep stages,especially in the discrimination be-tween sleep and awake,and between sleep stages 3 and 4.

关键词： sleep electroencephalogram multifractality.

Differential AR algorithm for packet delay prediction

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Progress in Natural Science:materials International 2006年第4期16卷 437-440页

作者： JIAO Liangbao, ZHANG De and BI Houjie institute of Acoustics, State Key Laboratory of Modern Acoustics, nanjing university, nanjing 210093, china institute of Communication Technique, nanjing university, nanjing 210093, china institute of Acoustics State Key Laboratory of Modern Acoustics Nanjing University Nanjing 210093 China institute of Communication Technique Nanjing University Nanjing 210093 China

Different delay prediction algorithms have been applied in multimedia communication, among which linear prediction is attractive because of its low complexity. AR (auto regressive) algorithm is a traditional one with low computation cost, while NLMS (normalize least mean square) algorithm is more precise. In this paper, referring to ARIMA (auto regression integrated with moving averages) model, a differential AR algorithm (DIAR) is proposed based on the analyses of both AR and NLMS algorithms. The prediction precision of the new algorithm is about 5-10 db higher than that of the AR algorithm without increasing the computation complexity. Compared with NLMS algorithm, its precision slightly improves by 0.1 db on average, but the algorithm complexity reduces more than 90% . Our simulation and tests also demonstrate that this method improves the performance of the average end-to-end delay and packet loss ratio significantly.

关键词： AR algorithm NLMS algorithm differential AR algorithm ARIMA model.

The Implementation of an Experimental Teleteaching System with Enhanced Document Image Display

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The Journal of china Universities of posts and telecommunications 2002年第2期9卷 30-36页

作者： HU Dong (Department of Information Engineering, nanjing university of posts and telecommunications, nanjing 210003, P.R.china) Department of Information Engineering Nanjing University of Posts and Telecommunications Nanjing 210003 P.R.China

This paper describes a flexible experimental teleteaching system,which is established by integrating an additional document camerawith desktop H.320 system to present high resolution document imageto remote student site. Special software architechture has beendesigned to manage the document image processing part, as well as thecommunication with the videoconferencing part. Based on the idea ofContent-based representation, the document im- age and video imageare synthesized into a single display, which is composed of two VideoObject Planes(VOP)with different resolutions. Automatic changedetection is used for document image processing, which makesefficient use of the transmission channel. Experimental resultsdemonstrate the performance of the system.

关键词： tele-teaching content-based representation VOP image processing

伊姆裸甲藻溶藻菌LD-B3的分离鉴定及溶藻作用

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应用海洋学学报 2024年第1期43卷 192-200页

作者：李俊佳陈磊王君玥蔡月凤申欣姬南京江苏海洋大学、江苏省海洋生物资源与环境重点实验室、江苏省海洋生物技术重点实验室江苏连云港222005 江苏海洋大学、江苏省海洋生物产业技术协同创新中心江苏连云港222005 江苏省海洋资源开发研究院江苏连云港222005

近年来,有害藻华频繁发生给海洋生态系统甚至人类健康带来严重影响。伊姆裸甲藻(Gymnodinium impudicum)是一种典型有害藻华原因种,开展其溶藻菌筛选工作,将有利于该种藻华的防控研究。本研究从伊姆裸甲藻藻华发生海域,分离一株针对藻... 详细信息

近年来,有害藻华频繁发生给海洋生态系统甚至人类健康带来严重影响。伊姆裸甲藻(Gymnodinium impudicum)是一种典型有害藻华原因种,开展其溶藻菌筛选工作,将有利于该种藻华的防控研究。本研究从伊姆裸甲藻藻华发生海域,分离一株针对藻华原因种的溶藻菌LD-B3,16S rDNA序列分析表明,该菌株属于假交替单胞菌属(Pseudoalteromonas)。菌藻共培养结果显示,2.0%终浓度LD-B3菌液添加72 h后,伊姆裸甲藻溶藻率达81.06%,且溶藻效应呈现浓度和时间依赖性。显微观察和生理参数测定结果表明,菌株LD-B3可导致伊姆裸甲藻细胞链断裂,最大光合效率(Fv/Fm)下降。溶藻方式研究发现,菌株LD-B3主要通过分泌胞外物质实现溶藻,且这类物质对温度较为敏感,初步推断其可能为蛋白类物质。本研究结果表明菌株LD-B3在伊姆裸甲藻溶藻剂开发方面有一定应用前景。

关键词：海洋生物学有害藻华伊姆裸甲藻溶藻菌假交替单胞菌

The renascence of industrial historic buildings——Taking the protective remolding and reusing of Chenguang Mechanical Factory in nanjing as an example

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Science china(Technological Sciences) 2009年第9期52卷 2502-2509页

作者： WANG YanHui Research institute of Architecture,Southeast university,nanjing 210096,china Research institute of Architecture Southeast University Nanjing China

The protective remolding and reusing of industrial historic buildings and sites is regarded as a great scientific matter in today's urban development. Based on discussing its significance and value,this paper,taking a specific example,makes a systematic discussion on the design strategy and method from the aspects of overall planning,remolding the old buildings,designing the new buildings,etc.

关键词： industrial historic buildings and sites protective remolding and reusing renascence strategy