共查询到20条相似文献，搜索用时 31 毫秒
1.
LIU Guang-hui CHEN Chuan-bo 《浙江大学学报(A卷英文版)》2007,8(8):1210-1217
When the edges of a convex polygon are traversed along one direction,the interior of the convex polygon is always on the same side of the edges. Based on this characteristic of convex polygons,a new algorithm for computing the convex hull of a simple polygon is proposed in this paper,which is then extended to a new algorithm for computing the convex hull of a planar point set. First,the extreme points of the planar point set are found,and the subsets of point candidate for vertex of the convex hull between extreme points are obtained. Then,the ordered convex hull point sequences between extreme points are constructed separately and concatenated by removing redundant extreme points to get the convex hull. The time complexity of the new planar convex hull algorithm is O(nlogh) ,which is equal to the time complexity of the best output-sensitive planar convex hull algorithms. Compared with the algorithm having the same complexity,the new algorithm is much faster. 相似文献
2.
A new, general type of planar linkages is presented, which extends the classical linkages developed by Kempe consisting of two single-looped kinematic chains of linkages, interconnected by revolute hinges. Together with a locking device, these new linkages have only one degree of freedom (DOF), which makes them ideal for serving as deployable structures for different purposes. Here, we start with a fresh matrix method of analysis for double-loop planar linkages, using 2D transformation matrices and a new symbolic notation. Further inspection for one case of Kempe’s linkages is provided. Basing on the inspection, by means of some novel algebraic and geometric techniques, one particularly fascinating solution was found. Physical models were built to show that the derivation in this paper is valid and the new mechanisms are correct. 相似文献
3.
MAO De-can LUO Yao-zhi YOU Zhong 《浙江大学学报(A卷英文版)》2007,8(7):1084-1090
A new, general type of planar linkages is presented, which extends the classical linkages developed by Kempe consisting of two single-looped kinematic chains of linkages, interconnected by revolute hinges. Together with a locking device, these new linkages have only one degree of freedom （DOF）, which makes them ideal for serving as deployable structures for different purposes. Here, we start with a fresh matrix method of analysis for double-loop planar linkages, using 2D transformation matrices and a new symbolic notation. Further inspection for one case of Kempe＇s linkages is provided. Basing on the inspection, by means of some novel algebraic and geometric techniques, one particularly fascinating solution was found. Physical models were built to show that the derivation in this paper is valid and the new mechanisms are correct. 相似文献
4.
A Novel Electromagnetic Bandgap Structure for Filter 总被引：1，自引：0，他引：1
Electromagnetic bandgap (EBG) materials are periodic structures capable of prohibiting the propagation of electromagnetic waves within a certain band of frequencies. This characteristic of EBG has wide application. The structures to be studied here are mainly planar EBG materials of two dimensions, which are periodic arrays of holes etched in the ground plane of a conventional microstrip line. EBG structures are calculated with finite-difference time-domain (FDTD) method in this paper. Technique of the perfectly matched layer is used for the absorption of electromagnetic waves in FDTD. The FDTD method is programmed with the blend of C^ and Matlab languages, which makes the program both simple and fast computing. A kind of new EBG structure is brought out through a lot of experiments and analyses. A filter with wide stop-band and another filter with two stop-bands are designed. 相似文献
5.
A continuum damage mechanics （CDM） meso-model was derived for both intraply and interply progressive failure behaviors of a 2D woven-fabric composite laminate under a transversely low velocity impact.An in-plane anisotropic damage constitutive model of a 2D woven composite ply was derived based on CDM within a thermodynamic framework,an elastic constitutive model with damage for the fibre directions and an elastic-plastic constitutive model with damage for the shear direction.The progressive failure behavior of a 2D woven composite ply is determined by the damage internal variables in different directions with appropriate damage evolution equations.The interface between two adjacent 2D woven composite plies with different ply orientations was modeled by a traction-separation law based interface element.An isotropic damage constitutive law with CDM properties was used for the interface element,and a damage surface which combines stress and fracture mechanics failure criteria was employed to derive the damage initiation and evolution for the mixed-mode delamination of the interface elements.Numerical analysis and experiments were both carried out on a 2D woven glass fibre/epoxy laminate.The simulation results are in agreement with the experimental counterparts,verifying the progressive failure model of a woven composite laminate.The proposed model will enhance the understanding of dynamic deformation and progressive failure behavior of composite laminate structures in the low velocity impact process. 相似文献
6.
Fundamental principles from structural dynamics, random theory and perturbation methods are adopted to develop a new response spectrum combination rule for the seismic analysis of non-classically damped systems, such as structure-damper systems. The approach, which is named the perturbation spectrum method, can provide a more accurate evaluation of a non-classically damped system＇s mean peak response in terms of the ground response spectrum. To account for the effect of non-classical damping, all elements are included in the proposed method for seismic analysis of structure, which is usually approximated by ignoring the off-diagonal elements of the modal damping matrix. Moreover, as has been adopted in the traditional Complete Quadratic Combination （CQC） method, the white noise model is also used to simplify the expressions of perturbation correlation coefficients. Finally, numerical work is performed to examine the accuracy of the proposed method by comparing the approximate results with exact ones and to demonstrate the importance of the neglected off-diagonal elements of the modal damping matrix. In the examined cases, the proposed method shows good agreement with direct time-history integration. Also, the perturbation spectrum method leads to a more efficient and economical calculation by avoiding the integral and complex operation. 相似文献
7.
《天津大学学报(英文版)》2020,(4)
We developed the high-gravity coupled liquid–liquid interface reaction technique on the basis of the rotating packed bed(RPB) reactor for the continuous and ultrafast synthesis of silver sulfi de(Ag_2S) quantum dots(QDs) with near-infrared(NIR) luminescence. The formation of Ag_2S QDs occurs at the interface of microdroplets, and the average size of Ag_2S QDs was 4.5 nm with a narrow size distribution. Ag_2S QDs can disperse well in various organic solvents and exhibit NIR luminescence with a peak wavelength at 1270 nm under 980-nm laser excitation. The mechanism of the process intensifi cation was revealed by both the computational fl uid dynamics simulation and fl uorescence imaging, and the mechanism is attributed to the small and uniform droplet formation in the RPB reactor. This study provides a novel approach for the continuous and ultrafast synthesis of NIR Ag_2S QDs for potential scale-up. 相似文献
8.
A Fractional Characteristic Study of Liquid and Vapor Interface in Lennard—Jones Fluids 总被引：3，自引：0，他引：3
LIUChao ZENGDanling 《重庆大学学报(英文版)》2002,1(1):61-66
The molecular dynamic simulation results for the liquid-vapor interface of the pure Lennard-Jones fluid are presented.The thermodynamic properties,the surface tension and the effective thickness of interfacial layer are determined.The rough characteristic of the liquid-vapor interface is discussed with fractional Brownian motion theory.Thereupon the fractal dimension d of the liqud-vapor interface is obtained. 相似文献
9.
The study of the interfacial and bond behaviour of reinforced cement-based materials is important for understanding the mechanical behaviour of such composites. This paper presents extensive experimental, theoretical and finite element analyses of pull-out tests of galvanised steel strips with different geometries, in lightweight cement-based material blocks with different densities and mechanical properties. The theoretical model proposed here is capable of determining the pull-out strength and bond stress versus the slip relationship between components of reinforced cement-based materials. This bond-slip relationship is then implemented in finite element simulation through the user-defined subroutine of ABAQUS software. Based on the results, a trilinear bond-slip model is suitable for modelling the interface between a steel strip and a cement-based material interface. 相似文献
10.
HUJi-yun YUCui-ping YINXue-gang 《重庆大学学报(英文版)》2004,3(2):43-47
A mathematical model of electromechanical coupling system for a planar inertial vibrating machine is built by setting up dynamical equations of discrete systems with a matrix methodology proposed. The substance of the transient behavior of the machine is unveiled by analyzing the results of the computer simulation to the model, and new methods are presented for diminishing the transient amplitude of the vibrating machine and improving the transient behavior. The reliable mathematical model is provided for intelligent control of the transient behavior of the equipment. 相似文献
11.
This paper introduces the advances of ultra-wideband(UWB)and super-wideband(SWB)planar antennas based on the printed monopole,microstrip slot and other planar antenna designs in the last decade.A brief history of the ultra- wideband antennas is first provided.Several types of planar antennas for UWB systems with band-notched designs are reviewed.Special SWB planar antenna designs with the bandwidth ratio greater than 10:1 including metal-plate and printed monopole antennas and tapered slot antennas are presented and compared. 相似文献
12.
Peak-power reduction by the lattice-reduction-aided closest point search for MIMO broadcast channels
In this letter, we present a modified vector-perturbation precoding scheme for the multiple-input multiple-output broadcast channel, where a perturbation vector is chosen to take into account both the instantaneous power and the instantaneous peak power of the transmitted signal. This perturbation vector is obtained by using the closest point search, with the aid of the lattice-reduction algorithm. Simulation results show that the proposed scheme yields a tradeoff among power efficiency, peak-to-average power ratio reduction, and complexity. 相似文献
13.
Sedimentation tanks and clarifiers play a significant role in an active sludge system, and the efficiency of the whole system is closely related with the design and operation of the sedimentation tanks. This paper focuses on the sludge concentration in each cross-section of the sedimentation tank. We measured the sludge concentration to explore its distribution inside the tank, carried in-situ tests to research the fluid pattern and real operational rules of the sedimentation tank. We also used the computational fluid dynamics (CFD) software, PHOENICS 3.5, to simulate the solid-liquid two-phase fluid inside the tank and describe the sludge concentration distribution. The numerical results indicate obviously a sludge-water interface and a compression interface inside the sedimentation tank, a stratified sedimentary region with uniform concentration and a compression region with high concentration at the bottom of the tank. Although the simulated concentrations deviated slightly from those of in-situ tests, they were still acceptable for identifying the sludge interfaces and fluid pattern inside a sedimentation tank, which are important parameters for optimizing the tank size and improving the settling efficiency. 相似文献
14.
The dynamic response of moored crane-ship is studied. Governing equations for the dynamic response of a crane-ship coupled with the pendulum motion of the payload are derived based on Lagrange＇s equations. The boom is modeled based on finite element method, while the payload is modeled as a planar pendulum of point mass. The dynamic response was studied using numerical method. The calculation results show that the large-amplitude responses occur at wave periods near the natural period of the payload. Load swing angle is smaller for crane-ship with flexible boom, in comparison with rigid boom. The ship surge motions have large vibrations for crane-ship with flexible boom, which were not observed for a rigid boom. The analysis identifies the significance of key parameters and reveals how the system design can be adjusted to avoid critical conditions. 相似文献
15.
卢东强 《上海大学学报(英文版)》2004,8(1):8-12
Based on the complex dispersion relation for the two-dimensional free-surface waves generated by a moving body in the steady Oseen flows, the effect of viscosity on wavelength and wave amplitude was investigated by means of an asymptotic method and a numerical analysis. A comparison between the asymptotic and numerical analysis for the viscous decay factor demonstrates the validity of the perturbation expansions for the wave profile. The numerical result shows that the wavelength of viscous wave is slightly elongated in comparison with that of inviscid wave. 相似文献
16.
This paper presents the results of an experimental research on reinforced concrete beams strengthened with an external carbon fibre reinforced polymer(CFRP) layer under long-term load action that lasted for 330 d.We describe the characteristics of deflection development of the beams strengthened with different additional anchorages of the external carbon fibre composite layer during the period of interest.The conducted experiments showed that the additional anchorage influences the slip of the external layer with respect to the strengthened element.Thus,concrete and carbon fibre composite interface stiffness decreases with a long-term load action.Therefore,the proposed method of analysis based on the built-up-bars theory can be used to estimate concrete and carbon fibre composite interface stiffness in the case of long-term load. 相似文献
17.
The steady-state electrical conductivity,as well as the dielectric propertiesbetween 2×10~(-4)Hz and 100 kHz,and at 1 GHz,are reported for urease compressed powdersamples of low hydration.The results show that the large,low frequency dielectricdispersion,known as α-dispersion,is due to the build-up of a space charge of protons atthe sample-electrode interfaces.A smaller dispersion,appearing at higher frequencies,isconcluded to be associated with hindered motions of the peptide residues in the molecularstructure of urease.The extent of these polypeptide backbone motions is shown to bestrongly depended on the extent of enzyme hydration.This work is contributed to the de-velopment of conductimetric biosensors. 相似文献
18.
GUO Yun-fei WEI Wei XUE An-ke MAO Dong-cai 《浙江大学学报(A卷英文版)》2006,7(10):1717-1722
INTRODUCTION For the filtering problem of multi-measurement nonlinear system with parameter perturbation, we need to consider the following aspects. First, although the parameter uncertainty does not change the system configuration, it makes the filter designed based on a fixed parameter unsuitable for an alterable parameter. Second, there are false alarms in the raw measure- ments which are received by multiple sensors. Third, since the optimal nonlinear Bayesian estimation is impossible… 相似文献
19.
This paper proposes an engineering approach to examine the stability margin of cascade circuits. The proposed measurement injects an external perturbation current into the cascade interface and measures the load-side response current. The system stability margin can be figured out by comparing the magnitudes of the perturbation current and the response current. The proposed measurement is strictly derived in theory, implemented with details, and demonstrated by experiment. 相似文献
20.
Sensing Escherichia coli O157：H7 via frequency shift through a self-assembled monolayer based QCM immunosensor 总被引：1，自引：0，他引：1
Wang LJ Wu CS Hu ZY Zhang YF Li R Wang P 《Journal of Zhejiang University. Science. B》2008,9(2):121-131
By means of the specific immuno-recognition and ultra-sensitive mass detection, a quartz crystal microbalance (QCM) biosensor for Escherichia coli O157H7 detection was developed in this work. As a suitable surfactant, 16-mercaptohexadecanoic acid (MHDA) was introduced onto the Au surface of QCM, and then self-assembled with N-hydroxysuccinimide (NHS) raster as a reactive intermediate to provide an active interface for the specific antibody immobilization. The binding of target bacteria with the immobilized antibodies decreased the sensor's resonant frequency, and the frequency shift was correlated to the bacterial concentration. The stepwise assembly of the immunosensor was characterized by means of the electrochemical techniques. Using the immersion-dry-immersion procedure, this QCM biosensor could detect 2.0×102 colony forming units (CFU)/ml E. coli O157H7. In order to reduce the fabrication time, a polyelectrolyte layer-by-layer self-assembly (LBL-SA) method was adopted for fast construction. Finally, the reproducibility of this biosensor was discussed. 相似文献