ISSN:0253-3839    

DOI:10.1080/02533839.1989.9677193

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A one‐layer model describing wave‐induced turbulent flows near a smooth bottom is presented. A time‐invariant effective viscosity model, which is more realistic under natural conditions, is specified near a smooth bottom. The first and second order solutions are presented. These include the velocity profile, shear stress, friction Investigated. These include the velocity profile, shear stress, friction factor and mass transport. The present study simplifies much of the mathematical complexity in many of the existing models. Furthermore, the results compare favorably with available observations, indicating that the approach adopted in the present model is physically sound.

ISSN:0253-3839    

DOI:10.1080/02533839.1989.9677194

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Several methods were employed to evaluate the residual strength of reinforced concrete columns exposed to different durations of fire. These methods included the analytical method, ultrasonic tests, hammer tests and load tests. Fifty columns were involved in the tests. Calculated temperatures and residual strengths of the test columns were compared with those measured. Comparisons were also made between results from load tests and those from nondestructive tests. The results showed that using analytical procedures is acceptable while the nondestructive test methods are accurate only for shorter durations of fire.

ISSN:0253-3839    

DOI:10.1080/02533839.1989.9677195

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The objective of this study is to investigate the amplification spectra of the single layered soil medium subjected to various SH sources from distinct locations. The source of model I is treated as a harmonic plane SH source, of which the generated wave propagates in one direction. To make the source approach the seismic mechanism, the harmonic line SH source is adopted as the one used by model II, by which the amplification spectra at distinct locations can be obtained. Frequently, the applied duration of the seismic source is limited, so the generalized ray theory is a powerful mathematic tool for dealing with the propagation problem of waves generated by a transient line SH source. This is the source of model III in this study. Then the obtained results show that the amplification effects decrease with an increasing damping factor, and the spectra vary with distinct sources, locations and even applied durations.

ISSN:0253-3839    

DOI:10.1080/02533839.1989.9677196

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The oxide/water interface of metal oxides has been identified as the most important inorganic mineral phase in water body and soil in controlling trace metal ion concentrations due to their relatively high surface area, abundance, and coating of clay minerals. In this paper, the effects of external and internal mass transport limitations on cadmium adsorption onto porous amorphous aluminum oxide/solution interfaces were studied. A modified two‐stage rate model was developed and used to interpret the time dependent experimental results. The effects of pH, aluminum oxide concentration, metal concentration and background electrolyte were performed and discussed.

ISSN:0253-3839    

DOI:10.1080/02533839.1989.9677197

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Noise properties of a bidirectional optical fiber transmission system using Raman amplification are analyzed. Analytical expressions for both forward and backward amplified spontaneous emission (ASE) noise are established in terms of system parameters. The signal to ASE noise ratio (SNR) and the achievable repeater length are discussed. Based on the results, we find that there exist optimum pump and initial power levels for the maximum SNR and repeater spacing. The maximum system transmission length and accumulated ASE noise for a multiple‐amplifier system are calculated. A maximum system transmission length up to 5,000 km with 12 dB SNR is then predicted.

ISSN:0253-3839    

DOI:10.1080/02533839.1989.9677198

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

To design a reliable and economical induction motor, it is necessary to be able to predict accurately the temperature distribution within the motor. In this paper, a 3D thermal model of an induction motor is presented. Except for providing a more accurate representation of the problem, the proposed model can also reduce computer memory and time. The finite element method (FEM) is used to analyze the three dimensional (3D) heat flow equation which describes the thermal model. Galerkin's procedure is used to derive the element equations and first order tetrahedral elements are used to discretize the field region. Galerkin's time‐stepping scheme is employed to treat time differential terms. Values of surface heat transfer coefficients are obtained from the empirical formula and heat losses are revised by the factory test. Application of the proposed method to the analysis of a 9,000 HP induction motor yields temperature distribution very close to the experimental data.

ISSN:0253-3839    

DOI:10.1080/02533839.1989.9677199

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Communications networks with multiple parallel channels become more feasible more than before because of the decreasing cost of equipments. Advantages of using multiple parallel channels to connect terminals include better reliability and fault‐tolerance capability, higher throughput and lower delay, easier implementing priority schemes, and more adaptable to provide various kinds of network services. We analyze in this paper the performances of four different channel selection methods in a network with multiple parallel channels. The basic idea is that the performance can be significantly improved by transmitting multiple copies of the same packet simultaneously. We also evaluate the performance deterioration caused by channel failures. The deterioration is observed to be significant if users do not know which channels are out of order. However, an efficient fault‐diagnosis technique is very helpful to alleviate the deterioration. Some easily implementable priority schemes, which are called priority by diversity, priority by privilege, and priority by diversity and privilege, are discussed and evaluated. By appropriately adjustig the values of the control parameters, one can get a suitable priority scheme to achieve the desired performance.

ISSN:0253-3839    

DOI:10.1080/02533839.1989.9677200

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

This paper presents the utilization of boundary element method (BEM) to analyze the elasto‐plastic deformation of upsetting problems. Method of successive elastic solutions is used in the nonlinear analysis; both the linear strain hardening and the power law relation are used as constitutive equations of the material. For the later model the slope of strain hardening at each step is modified to a more correct prediction to make the deformation step larger and to obtain better convergence. The result may verify the stress‐strain curve as it does, and verify the similar pattern of the plastic zone propagation as Roll's result by finite element method. It is shown that various frictional conditions and width‐height ratios of the workpiece also influence the propagation behavior of plastic zones.

ISSN:0253-3839    

DOI:10.1080/02533839.1989.9677201

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

In this paper, the effects of transverse mean velocity and temperature gradients on the acoustic propagation in a straight annular duct are studied so as to be the basis of further analyzing the sound propagation in nonuniform annular ducts. The wave equation governing this acoustic field is a difficult eigenvalue problem. The eigenvalue is solved by an IMSL package which is proposed to find suitable initial guess. By using the initial guess, in addition to the iterative process, the final results have been found. The results are proved to be of good accuracy by comparing with published data, and the errors are under 2.0%. From this paper we also find that, under the influence of the unsymmetric boundary condition, the attenuations of the axial symmetric radial mode are different from other modes, and this property of the former mode can not be expected by ray acoustic arguments, on the other hand, the attenuations of the lowest mode and the spinning modes can be expected.

ISSN:0253-3839    

DOI:10.1080/02533839.1989.9677202

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor