检索结果-南通市图书馆

An Efficient Approach for Fuzzy Project Network Analysis

在线全文

学校读者我要写书评

暂无评论

Systems Science and Systems engineering 2002年第1期11卷 83-89页

作者： HU Jing-song department of Management Science & engineering, qingdao university, qingdao 266071,china department of Management Science & engineering Qingdao University Qingdao 266071 China

In this paper we present two-level linear programming method for determining latest dates and slack times in project network models with triangular fuzzy number or trapezoidal fuzzy number. Compared with the well-known fuzzy network techniques in literature, the approach always produces the meaningful latest dates and slack times. Practically we have generalized critical path method by accepting imprecise, fuzzy data for the duration of the activities.

关键词： network analysis fuzzy equations linear programming

Preparation, characterization, viscosity and thermal conductivity of CaCO_3 aqueous nanofluids

在线全文

学校读者我要写书评

暂无评论

Science china(Technological Sciences) 2010年第2期53卷 360-368页

作者： ZHU HaiTao1, LI ChangJiang2, WU DaXiong1, ZHANG CanYing1 & YIN YanSheng2 1 College of Materials Science and engineering, qingdao university of Science and Technology, qingdao 266042, china 2 department of Materials, Ocean university of china, qingdao 266003, china College of Materials Science and engineering Qingdao University of Science and Technology Qingdao China department of Materials Ocean University of China Qingdao China

CaCO3 aqueous nanofluids were prepared by dispensing aqueous CaCO3 paste into distilled water under ultrasonic vibration. The actual microstructures of the CaCO3 nanofluids with different particle volume fractions were characterized by freeze etching replication transmission electron microscopy (FERTEM). Thermal conductivity and rheological behavior of the nanofluids were measured by standard analyzers. The results show that CaCO3 paste as raw material for nanofluids is advantageous to reducing aggregation of primary nanoparticles. The effective viscosities and effective thermal conductivities of the CaCO3 nanofluids are related to the aggregates of nanoparticles and can be well predicted by the modified Krieger & Dougherty formula and the modified Hamilton & Crosser model, respectively.

关键词： CaCO3 nanofluid thermal conductivity viscosity microstructure

Approximately optimal tracking control for discrete time-delay systems with disturbances

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2008年第2期18卷 225-231页

作者： Gongyou Tang a,,Huiying Sun b,Haiping Pang c a College of Information Science and engineering,Ocean university of china,qingdao 266100,china b College of Information and electrical engineering,Shandong university of Science and Technology,qingdao 266510,china c College of Automation and Electronic engineering,qingdao university of Science and Technology,qingdao 266042,china College of Information Science and engineering Ocean University of China Qingdao 266100 China College of Information and electrical engineering Shandong University of Science and Technology Qingdao 266510 China College of Automation and Electronic engineering Qingdao University of Science and Technology Qingdao 266042 China

Optimal tracking control (OTC) for discrete time-delay systems affected by persistent disturbances with quadratic performance index is considered. By introducing a sensitivity parameter,the original OTC problem is transformed into a series of two-point boundary value (TPBV) problems without time-advance or time-delay terms. The obtained OTC law consists of analytic feedforward and feedback terms and a compensation term which is the sum of an infinite series of adjoint vectors. The analytic feedforward and feedback terms can be found by solving a Riccati matrix equation and two Stein matrix equations. The compensation term can be obtained by using an iteration formula of the adjoint vectors. Observers are constructed to make the approximate OTC law physically realizable. A simulation example shows that the approximate approach is effective in tracking the reference input and robust with respect to exogenous persistent disturbances.

关键词： Discrete systems Time-delay systems Disturbances Optimal control Tracking control

Analysis on cohesive crack opening displacement considering the strain softening effect

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science china(Physics,Mechanics & Astronomy) 2006年第1期49卷 88-101页

作者： WANG Limin1, XU Shilang2 & ZHAO Xiqiang3 1. Mechanics department, Shandong university of Technology, Zibo 255049, china 2. Civil engineering department, Dalian university of Technology, Dalian 116024, china 3. Mathematics department, Ocean university of china, qingdao 266071, china Mechanics department Shandong University of Technology Zibo China Civil engineering department Dalian University of Technology Dalian China Mathematics department Ocean University of China Qingdao China

In order to investigate the crack propagation in quasi-brittle materials like rock, ceramic and concrete, Hillerborg and his co-researchers abstracted the fracture process zone in front of a stress free crack in terms of a “fictitious crack zone”. On the fictitious crack zone, cohesive stresses distribute following a given softening relationship of stress vs. crack opening. Based on the polynomial or power series expression of cohesive crack opening displacement, the relationship of the cohesive stress vs. the crack opening displacement is established using elastic theory and integral equation, and some unknown physics variables are obtained using variation approach. The calculation results gained in this paper are close to the experimentally test ones.

关键词： cohesive crack, softening, dissipation work, variation approach.

Lattice dynamical simulation of methane hydrate

在线全文

学校读者我要写书评

暂无评论

Journal of Natural Gas Chemistry 2010年第1期19卷 43-46页

作者： Lin Wang, Shunle Dong Physics department, College of Information Science and engineering, Ocean university of china, qingdao 266100, Shandong, china Physics department College of Information Science and Engineering Ocean University of China Qingdao 266100 Shandong China

INS （Inelastic Neutron Scattering） spectrum of methane hydrate was measured on MARI （a direct-geometry chopper spectrometer） at Ruther-ford Appleton Laboratory, UK. Compared with ice Ih, it is found that the whole spectrum of methane hydrate moves toward high-energy by about 1.5 meV. Using lattice dynamical （LD） technique, computer simulations of methane hydrate were carried out. In the simulations, four potential models （BE TIP3P, TIP4P, MCY） were employed to calculate the phonon density of states （PDOS）. Comparing the calculated PDOS spectrum with the experimental spectrum, it is found that BF, TIP4P, and TIP3P potential lattices give out well-separated translational and librational bands while MCY potential lattice is unstable to do so and this model is not suitable to describe hydrate system.

关键词： methane hydrate inelastic neutron scattering lattice dynamical simulation

The correlation of flare's location on solar disc and the sudden increase of total electron content

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2002年第1期47卷 82-85页

作者： ZHANG Donghe, XIAO Zuo & CHANG Qingdepartment of Geophysics, Peking university, Beijing 100871, china qingdao Research Center, china Research Insitute of Radio-wave Propagation, qingdao 266071, china department of Electronic engineering, Beijing Universit department of Geophysics Peking University Beijing China qingdao Research Center China Research Insitute of Radio-wave Propagation Qingdao China department of Electronic engineering Beijing University of Aeronautics and Astronautics Beijing China

The correlation of flare’s location on solar disc with the value of sudden increase of total electron content is analyzed with flare’s parameters observed by GOES satellite from 1997 to 1999 and total electron content derived from GPS data observed by international GPS Service for Geo-dynamics. It is found that, besides the flare’s maximum X-ray flux, flare’s location on solar disc has some relation with the value of SITEC during the flare. The ionospheric response to a flare with a smaller maximum X-ray flux and nearer angular distance to the Sun’s central meridian line may be stronger than that of the flare with a larger maxi-mum X-ray flux and far angular distance. To the flares with the same class of maximum X-ray flux, the nearer the angu-lar distance to the Sun’s meridian, the stronger the ionospheric response.

关键词： flare SITEC GPS.

A video encryption method based on chaotic maps in DCT domain

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2008年第10期18卷 1299-1304页

作者： Shuguo Yang~(a,b,*) Shenghe Sun~a ~a School of electrical engineering and Automation,Harbin Institute of Technology,Harbin 150001,china ~b qingdao university of Science and Technology,qingdao 266061,china School of electrical engineering and Automation Harbin Institute of Technology Harbin 150001 China qingdao university of Science and Technology Qingdao 266061 China

This paper proposes a new and secure video encryption method based on chaotic maps in DCT domain,which is quite in keeping with the common ideas and the frequent practices of video *** select the I-frames of the video sequence as encryption objects. First,we introduce two coupling chaotic maps to scramble the DCT coefficients of every original I-frame,and receive the scrambled ***,we encrypt the DCT coefficients of the scrambled 1-frame using another chaotic *** the whole process,we use three chaotic maps and five keys;the I-frame is encrypted ***,we performed several tests and the experimental results have proved our method to be secure and efficient.

关键词： Video encryption Chaotic map I-frame Scrambling Video sequence

ABNORMAL BENDING OF MICRO-CANTILEVER PLATE INDUCECD BY A DROPLET

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Acta Mechanica Solida Sinica 2010年第5期23卷 428-436页

作者： Jianlin Liu Xueyan Zhu Xinkang Li Zhiwei Li 1(department of engineering Mechanics,china university of Petroleum,qingdao 266555,china) department of engineering Mechanics China University of Petroleum Qingdao China

The abnormal bending of a micro-cantilever plate induced by a droplet is of great interest and of significance in micro/nano-manipulations. In this study, the physical mechanism of this abnormal phenomenon induced by an actual droplet is elucidated. Firstly, the morphologies of 2D and 3D droplets axe solved analytically or numerically. Then the Laplace pressure difference acting on the cantilever plate caused by the droplet is presented. Finally, the deflections of the micro-cantilever plates driven by the capillary forces are quantitatively analyzed. These analytical results may be beneficial to some engineering applications, such as micro-sensors, MEMS and the micro/nano-measurement.

关键词： micro-cantilever plate surface tension Laplace pressure difference abnormal bending deflection

The fractal characteristic change in the Huanghe River Estuary due to the hydrodynamic conditions’variation

在线全文

学校读者我要写书评

暂无评论

Acta Oceanologica Sinica 2003年第2期22卷 191-200页

作者： Jia Yonggang, Fu Yuanbin, Xu Guohui, Shan Hongxian, Cao Xueqing Environmental engineering department, Ocean university of china, qingdao 266003,china Environmental engineering department Ocean University of China Qingdao 266003 China

The study area lies in the subaqueous delta, which came into being in 1964 - 1976. Oneoil-field road has been built for exploring petroleum to form a wave barrier. The hydrodynarnic conditions on the north side of the road are relatively violent, on the contrary the hydrodynarnic conditions on the south side of the road are nearly placid. This makes the study area a natural laboratory for studying the influence of the hydrodynarnic conditions on the fractal characteristics of the tidal flat. Selecting an area is named Case Ⅰ on the side of stronger hydrodynarnic activities and an area is named Case Ⅱ on the other side. Measuring the topography and sampling and analyzing the granulometrical composition, it is found that the hydrodynarnic conditions have fatal influence on the surface fractal dimensions and the granulometrical fractal dimensions of the area. In Case Ⅰ , which has strong hydrodynarnic conditions, the surface fractal dimensions are obviously larger than those of Case Ⅱ , and the granulometrical fractal dimensions are relatively smaller than those of Case Ⅱ , the surface fractal dimensions of Case Ⅰ decrease quickly with the increase of grid size; the granulometrical fractal dimensions are disperse, while the hydrodynarnic conditions of Case Ⅱ are just reverse. A sampling line and a core sampling on each side of the road are selected. It is found that on the south side of the road the granulometrical fractal dimensions vary regularly in the line and with the depth, the farther apart from the road, the smaller the fractal dimensions, and the deeper the sampling position the larger the fractal dimensions, while granulometrical fractal dimensions on the north side of the road have no such regularity pattern. The mechanism of the influence of the hydrodynarnic conditions on the fractal characteristics is discussed.

关键词： Tidal-flat hydrodynamic conditions surface fractal dimensions granulometrical fractal dimensions Huanghe River Estuary