ISSN:0253-3839    

DOI:10.1080/02533839.1995.9677676

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

This paper combines the measurements of SH and Lamb wave velocities to determine the orientation distribution function (ODF) of a. thin aluminum plate, and hence to plot the corresponding ultrasonic pole figure. The relations between the ODF of crystallities and the macroscopic elastic constants of a metal sheet are first briefly introduced. Secondly, the dispersion relations of horizontal polarized shear waves and Lamb waves in a slightly anisotropic thin plate are presented to relate the corresponding velocities with the macroscopic elastic constants. Noncontact electromagnetic acoustic transducers (EMAT) are utilized to measure the angular dependences of the horizontal polarized shear wave velocity and Lamb wave velocity of a thin metal plate. With the ultrasonic wave velocities measured, the elastic constants of a slightly anisotropic thin aluminum plate are determined inversely using a numerical algorithm. The coefficients of the ODF of the aluminum sheet can therefore be calculated, and hence, the ultrasonic pole figures of the aluminum thin plate.

ISSN:0253-3839    

DOI:10.1080/02533839.1995.9677677

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

This paper describes an accurate and efficient gate‐level timing simulator that can give the waveform at each node of the circuit. Its high accuracy is attributed to a sophisticated delay model, which includes an accurate representation of the waveform, a consistent and meaningful definition of delay, a consideration of waveform slope effects at both input and output of a gate, a consideration of the multiple charging/discharging paths in the circuit, and a consideration of the various fan‐out and cell‐size effects. In order to represent the waveform accurately, the switching delay and the slope are defined and calculated carefully with the consideration of internal charges. In order to compute the waveform accurately, the effects of internal charges are investigated and a merged PN tree is used to represent a CMOS gate. Characteristics of the PN tree are described and the methods used to evaluate conducting paths are proposed. After the conducting paths are obtained, a recursive algorithm can be applied to compute the RC time constant in series‐parallel RC networks, and then the switching delay and the slope. The results, even the circuits with transmission gates are satisfactory when compared with SPICE.

ISSN:0253-3839    

DOI:10.1080/02533839.1995.9677678

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

It was observed that the conduction‐band minimum of InAs is lower in energy than the valence‐band maximum of GaSb. This will cause the non‐rectification characteristic. Such unusual nonrectifying p‐n junction is the direct consequence of interpenetration between the GaSb valence band and the InAs conduction band, since the InAs‐GaSb superlattices can have a band gap smaller than that of either constituent materials. InAs‐GaSb superlattices have the modifiable band gap, but the absorption coefficient shall decrease rapidly when the period thickness is over 100 Å(d1=d2). It has a good spectral response in 3–5 μm region, but bad in 8–14 μm. The new proposal offered a normal incidence valence intersubband transition at ∼10μm. It is potential to fabricate the long wavelength devices.

ISSN:0253-3839    

DOI:10.1080/02533839.1995.9677679

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The Fourier series method is employed to calculate particle velocity, wavelength and wave profile of a gravity wave propagating on a vertically varying linear shear current. From the comparisons between predicted values and experimental data, it is found that highly nonlinear interaction resulting from a shear current has significant effects on the wave field, and that the lower order wave theories give poor prediction.

ISSN:0253-3839    

DOI:10.1080/02533839.1995.9677680

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Nitrided oxides are used as the CCD's gate oxides in this work. The nitridation process is carried out in NH3or N2O ambient. After irradiation of Co‐60 with a total dose of 106rads, we find that CCD with N2O nitrided gate oxide is more radiation hard than CCD with fresh gate oxide or NH3nitrided gate oxide. Detailed fabrication processes, p‐n junction leakage current, radiation effect, and anneal effect are also discussed in this work.

ISSN:0253-3839    

DOI:10.1080/02533839.1995.9677681

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A method is presented to incorporate the intersection algorithm into the elimination of spurious solution and shrinkage of ambiguous variables in qualitative simulations. Since, for a given model structure, the qualitative simulation is sound but incomplete, the spurious solutions are inevitably included in the solution set. To be appropriately applied to these solutions, it is important to reduce the spurious solutions. Since the true solution is always existing in the solution, by incorporating them into the intersection of solutions, one can quickly reduce the spurious solutions. A heat exchanger example is used to illustrate the effectiveness of this method. Through this complicated example, the simulation results show that spurious solutions can be reduced from 26 to 4, and the number of ambiguous variables is reduced from 9 to 2. Results also show that the proposed method is effective in reducing spurious solutions in qualitative simulation.

ISSN:0253-3839    

DOI:10.1080/02533839.1995.9677682

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A nonlinear finite element procedure for large deflection analysis of three dimensional frames is presented in this paper. On the basis of the beam‐column approach, the convected coordinate system is used in each element to separate the rigid‐body motions from the local deformations. In the derivation of the nonlinear stiffness matrix for the beam‐column element, the element axial shortening due to bowing is taken into account. With reference to a slightly deformed position of the beam column, the linearized coordinate transformation coefficients of the first and second orders are found and expressed explicitly by the member orientation matrix. The Newton‐Raphson method of iteration is adopted for solving the linearized system equation. Several selected examples are studied in detail. The numerical results indicate that the proposed procedure can be accurately and efficiently used to handle space frame problems with laige displacements and large rotations.

ISSN:0253-3839    

DOI:10.1080/02533839.1995.9677683

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The merit of internal model control(IMC) is that the influence of disturbance can be depressed in the lowest range. During operation, unmodeled dynamics and parameter variations may severely infringe the IMC performance. TheH8‐control theory with a weighting function can attenuate the influence of system perturbation. In this paper, we combine the characteristics of IMC andH8control, and offer a control structure to discuss the robustness problems. The development is based on employing a state‐space approach to treat optimization problems rather than using the conventional complex variable approach. The performance of the proposed control structure is illustrated through a specific chemical reactor system. The simulation results show that the proposed structure indeed overcomes the disadvantage of IMC. Moreover, it can obtain a better control performance than the conventionalH8control.

ISSN:0253-3839    

DOI:10.1080/02533839.1995.9677684

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Contrary to the parallel flow approach most often studied, the growth rates of unstable waves of the supersonic mixing layer are analyzed with the consideration of flow nonparallelism by employing the method of multiple scales. Flow parameters including Reynolds number, Mach number, velocity ratios and temperature ratios influencing on the instability‐wave solutions are investigated. The mean flow is determined by solving the compressible boundary layer equations and applying the Sutherland law relating the viscosity to the temperature. In this work, two dimensional compressible stability equations are solved to secure the spatial growth rate of instability waves of the flow.

ISSN:0253-3839    

DOI:10.1080/02533839.1995.9677685

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor