ScholarBank@NUShttps://scholarbank.nus.edu.sgThe DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Sun, 11 Aug 2024 11:24:11 GMT2024-08-11T11:24:11Z50121- Engineering resonance frequency charts of PZT rings of different sizes and at different clamping conditionshttps://scholarbank.nus.edu.sg/handle/10635/58253Title: Engineering resonance frequency charts of PZT rings of different sizes and at different clamping conditions
Authors: Xu, Y.; Koc, B.; Uchino, K.; Chew, L.L.
Abstract: For developing ring type ultrasonic motors and piezoelectric transformers, the method by V. Stephenson for the computation of resonance frequency of piezoceramic rings was extended. Engineering charts of the resonance frequencies of PZT rings with different sizes and at different clamping conditions were constructed. The resonance frequencies obtained from the charts were in good agreement with the experiments. Some interesting features of the resonance frequency with respect to the ring dimensions (the outside and inside diameters, OD and ID) were found. The resonance frequency for rings with the same outside diameter decreased with decreasing OD/ID ratio. Clamping of the outer circumference of the ring reduced the resonance frequency. There was a minimum in the curve of the resonance frequency versus OD/ID, when the inside of the ring was clamped. These features provided methods to reduce the resonance frequency so as to miniaturize ultrasonic motors and other piezoelectric devices using PZT rings.
Fri, 01 Jan 1999 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/582531999-01-01T00:00:00Z
- Vibratory in-plane tunneling gyroscopehttps://scholarbank.nus.edu.sg/handle/10635/32688Title: Vibratory in-plane tunneling gyroscope
Authors: CHUA, BEE LEE; LI, HOLDEN KING HO; XU, YUAN; TAY, FRANCIS ENG HOCK; CHEN, WILLIAM TZE-YOU
Abstract: A gyroscope comprising: a proof mass; a frame supporting the proof mass; a connection arrangement connecting the proof mass and the frame, the connection arrangement having a first stiffness in a first direction and a second stiffness in a second direction substantially perpendicular to the first direction, one of the stiffness being significantly greater than the other stiffness; and a pair of elements adapted to sense relatively motion therebetween in either the first or the second direction. Also disclosed is a gyroscope comprising: a proof mass; a frame supporting the proof mass and connected to only one edge thereof by a connection arrangement extending between the proof mass and the frame in a first direction, the connection arrangement having a first stiffness in the first direction and a second stiffness in a second direction substantially perpendicular to the first direction, the first stiffness being significantly greater than the second stiffness; and a pair of elements adapted to sense relative motion therebetween in the first direction.
Tue, 04 Jan 2005 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/326882005-01-04T00:00:00Z
- Time-domain Green's functions for microstrip structures using Cagniard-de Hoop methodhttps://scholarbank.nus.edu.sg/handle/10635/117204Title: Time-domain Green's functions for microstrip structures using Cagniard-de Hoop method
Authors: Xia, M.-Y.; Chan, C.H.; Xu, Y.; Chew, W.C.
Abstract: Time-domain Green's functions are required for transient analyzes of many structures using the time-domain integral equation method. In this paper, we express the generalized reflection coefficient of the microstrip structure in terms of a geometric optics series so that by applying the Cagniard-de Hoop method to each term of the series, we can derive the time-domain Green's function. It is demonstrated that this series converges rapidly and there are two contributing waves from each source image if the observation point is beyond the total internal refraction location. The two waves are the direct wave from the image and the head wave from the image to the critical point, and then laterally along the surface to the observer. Each contribution is a definite integral that is evaluated for each point in space and time. Therefore, the derived Green's function is efficient for time-domain simulations compared with conventional approach, in which for each point in space and frequency a Sommerfeld type integral is involved and then the frequency-domain data is converted into time-domain by discrete Fourier transform. This rigorous Green's function can also be used to check the accuracy of other approximate methods such as those using the discrete complex image theory.
Tue, 01 Jun 2004 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1172042004-06-01T00:00:00Z
- 3-dimensional implementation of the field iterative method for cavity modelinghttps://scholarbank.nus.edu.sg/handle/10635/111307Title: 3-dimensional implementation of the field iterative method for cavity modeling
Authors: Wang, C.-F.; Xu, Y.; Gan, Y.-B.
Abstract: The analysis of electromagnetic scattering from cavity structure is very important to many practical applications. The field iterative method (FIM) is one of the promising methods to deal with the cavity problem. In this paper, 3-dimensional (3D) FIM has been implemented using Rao-Wilton-Glisson (RWG) basis function and an accurate equivalent model of the cavity. Two testing procedures, a newly developed point matching and conventional Galerkin's methods, have been discussed for better and simpler implementation of the 3D FIM. Numerical results show that the accuracy of the 3D implementation of FIM using the newly developed point matching method is the same as that of the conventional Galerkin's method. The numerical results also show that the simpler implementation of 3D FIM using the point matching method converges very fast for all the tested cases.
Thu, 01 Jan 2004 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1113072004-01-01T00:00:00Z
- Modal method analysis of multilayered coated circular waveguide using a modified characteristic equationhttps://scholarbank.nus.edu.sg/handle/10635/111435Title: Modal method analysis of multilayered coated circular waveguide using a modified characteristic equation
Authors: HU FU-GANG; Wang, C.-F.; Xu, Y.; Gan, Y.-B.
Abstract: In this paper, the modal method is applied to analyze coated circular waveguide terminated by a perfect electric conductor (PEC) plate. The key to this method is the accurate calculation of the propagation constants of modes in coated circular waveguide. To overcome numerical difficulties, such as overflow, encountered in solving characteristic equation, the characteristic equation is modified using Hankel function of the second kind instead of Bessel function of the first kind in the coated layers. The modified characteristic equation can be accurately solved to obtain the propagation constants even for very large circular waveguide with highly lossy coatings. To verify the modified characteristic equation, the attenuation and scattering property of circular waveguide structure have been simulated. Simulation results agree well with the reference results.
Thu, 01 Jan 2004 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1114352004-01-01T00:00:00Z
- Advanced numerical techniques for large PEC cavity modelinghttps://scholarbank.nus.edu.sg/handle/10635/111532Title: Advanced numerical techniques for large PEC cavity modeling
Authors: Wang, C.F.; Xu, Y.; HU FU-GANG; Gan, Y.B.
Abstract: Air intake structures greatly affect the overall electromagnetic scattering response of real airborne targets. This has motivated the development of accurate and efficient methods to model the electromagnetic scattering of such structures. This paper summarizes the work done on several newly developed numerical techniques in the Temasek Laboratories at National University of Singapore (NUS) for electromagnetic scattering from large PEC cavities.
Sat, 01 Jan 2005 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1115322005-01-01T00:00:00Z
- Modeling of interior scattering from 3D cavity using FE-BI method with higher-order tetrahedral elementhttps://scholarbank.nus.edu.sg/handle/10635/111607Title: Modeling of interior scattering from 3D cavity using FE-BI method with higher-order tetrahedral element
Authors: HU FU-GANG; Wang, C.-F.; Gan, Y.-B.; Xu, Y.
Abstract: Finite element-boundary integral (FE-BI) method is a powerful tool to model electromagnetic scattering from three-dimensional large, deep, and arbitrarily-shaped cavities. The FE-BI method with higher-order tetrahedral element has been implemented to evaluate the interior electromagnetic scattering from typical and unconventional cavity structure. Using this method, we can understand the underlying phenomena of scattering from various cavities, which will benefit the design of realistic cavity structure. © 2005 IEEE.
Sat, 01 Jan 2005 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1116072005-01-01T00:00:00Z
- Integral equation formulation for modeling electromagnetic scattering from indented screenshttps://scholarbank.nus.edu.sg/handle/10635/111596Title: Integral equation formulation for modeling electromagnetic scattering from indented screens
Authors: Xu, Y.; Wang, C.-F.; Gan, Y.-B.; HU FU-GANG
Abstract: Two integral equation were derived using the equivalence principle and image theory. Both integral equations involve only current density on the cavity walls. It was found that the problem of electromagnetic scattering from 3D cavity with an infinite ground plane was formulated as a system of boundary integral equation for the electric current density on the cavity walls and the interface between the cavity and free space using equivalence principle and image theory. It was also found that the numerical solution of integral equation was more accurate than that of integral equation.
Thu, 01 Jan 2004 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1115962004-01-01T00:00:00Z
- A domain decomposition method for analysis of electromagnetic scattering from cavitieshttps://scholarbank.nus.edu.sg/handle/10635/111514Title: A domain decomposition method for analysis of electromagnetic scattering from cavities
Authors: Xu, Y.; Wang, C.-F.; Gan, Y.-B.; HU FU-GANG
Abstract: A non-overlapping domain decomposition method is applied to solve surface integral equations for electromagnetic scattering from cavities. This scheme allows the cavity to be divided into sub-domains and can be solved in a serial or parallel manner. Thus, the memory requirement and CPU time for modeling cavity structures can be dramatically reduced. Moreover, interior resonance problem is eliminated from this scheme, which occurs in the Generalized Network Formulation. © 2005 IEEE.
Sat, 01 Jan 2005 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1115142005-01-01T00:00:00Z
- Two integral equations for modeling electromagnetic scattering from indented screenshttps://scholarbank.nus.edu.sg/handle/10635/111503Title: Two integral equations for modeling electromagnetic scattering from indented screens
Authors: Xu, Y.; Wang, C.-F.; Gan, Y.-B.
Abstract: This paper discusses three aspects for characterizing electromagnetic scattering from indented screens or cavity structures using integral equations. The first aspect is on the derivations of two integral equations using physical models. Both integral equations involve only the electric current density on the cavity walls. The second aspect is on numerical verification of the two integral equations by calculating monostatic scattering from three-dimensional rectangular cavity structures. The numerical results show the correctness of the two integral equations. The third aspect is on the comparison of the numerical behavior of the two integral equations, as regards accuracy and convergence. © 2005 IEEE.
Sat, 01 Jan 2005 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1115032005-01-01T00:00:00Z
- On interior resonance problem of integral equations for modeling electromagnetic scattering from cavitieshttps://scholarbank.nus.edu.sg/handle/10635/111619Title: On interior resonance problem of integral equations for modeling electromagnetic scattering from cavities
Authors: Xu, Y.; Wang, C.-F.; HU FU-GANG; Gan, Y.-B.
Sat, 01 Jan 2005 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1116192005-01-01T00:00:00Z
- Field iterative method for PEC cavity modelinghttps://scholarbank.nus.edu.sg/handle/10635/111576Title: Field iterative method for PEC cavity modeling
Authors: Wang, C.F.; Gan, Y.B.; Xu, Y.; Thiele, G.A.
Abstract: The field iterative method (FIM) based on an accurate equivalent model of large PEC cavity is discussed. The FIM employs a two-stage iterative process that yields the actual fields or currents, that include diffraction effects and demonstrated the edge condition. It is observed that the accuracy of the FIM based on the simple equivalent model can be significantly improved by introducing a relaxation factor to the magnetic field on the cavity walls. The result shows that the accuracy of the 3D implementation of the FIM using the newly developed point matching method is the same as that of the conventional Galerkin's method.
Thu, 01 Jan 2004 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1115762004-01-01T00:00:00Z