摘要:

Based on the Faraday rotation effect, the magnetic field induced by the current in a power line changes the polarization of laser light which passes through a single mode fiber. Accordingly, a current sensor is built. This paper describes a 2‐frequency laser fiberoptic interferometer for current measurement. Two fiber coils with diameters of 15 cm and 10 cm, and 100‐turns were built to sense 60Hz power currents with a range from 0.161kA to 1.392kA. The results show that this system can be used quite satisfactorily for large current sensing.

ISSN:0253-3839    

DOI:10.1080/02533839.1992.9677384

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

In this paper, the purpose is to discuss the relationships among different voltage patterns on the surface so as to compare the noise sensitivity in the voltage measurements for two current patterns frequently used in electric current computed tomography (ECCT). The relationship between the voltage and current patterns on the boundary of homogeneity and concentrically symmetric inhomogeneity can be represented by a pseudo operatorR(σ) for a 32‐electrode system. Thus, using the eigencurrents and their corresponding eigenvalues forR,which are called characteristic resistances, any arbitrary voltage patterns can be synthesized. The two currents studied here are a set of spatial trigonometric patterns and a set of an “adjacent‐pair” patterns. Comparing the synthesized and experimentally measured surface voltages for the two current patterns, the sensitivity to noise for systems using these two types of current patterns may be obtained. Based upon the results, it is shown that the system with the trigonometric current patterns is better than the one with adjacent‐pair current patterns for producing the impedance images.

ISSN:0253-3839    

DOI:10.1080/02533839.1992.9677385

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

This paper presents new techniques for analyzing eigenvalue assignment robustness of uncertain systems. The root locus approach is used to ensure that the roots of the characteristic polynomials with coefficient variations remain in some distinct but desired regions. No restrictions are imposed on the shapes of the specified regions. An algorithm is proposed to calculate the allowable coefficient bounds. The proposed methods are applicable to the continuous‐time case as well as to the discrete‐time case.

ISSN:0253-3839    

DOI:10.1080/02533839.1992.9677386

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

In this paper, the problem of token ring networks interconnected by a backbone ring is considered. The token ring networks connect each other through bridges. The bridge nodes themselves form the “backbone” ring. Each bridge node is modeled as two queues, one is for the local ring to send messages to the backbone ring and the other is for the backbone ring to send packets to the local ring. With the assumptions that the packet length distribution is exponential, the token walk time is constant, and the service discipline is exhaustive, we find that the interarrival time distribution of the bridge queues is close to exponential when the inter‐ring traffic is small. The Kolmogorov‐Smirnov test is used to determine the distribution of the interarrival time at the bridge queues. When exponential distribution of interarrival time at bridge queues is accepted, the arrival processes of the two queues are Poisson.

ISSN:0253-3839    

DOI:10.1080/02533839.1992.9677387

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A new method for the planning of the position and orientation of an end‐effector along a spline path in Cartesian space is presented. The method is developed using parallel computation. This parallel algorithm for path planning is a function of Cartesian displacement which is determined by the system's speed profile. In positional path planning, the algorithm interpolates a spline path directly based on thecircular arc generation methodinstead of composing piecewise‐straight line segments. In rotational path planning, the algorithm eliminates thewobbling approach vectorwhich conventional methods had suffered. When initial data is determined, position and orientation of the end‐effector can be computed in parallel. If the algorithm is executed by three processors, the computational time is reduced by a factor of 1.67. For four and eight processors, the computational time is further reduced by a factor of 2.0 and 2.22, respectively. When the straight line case of the scheme is executed serially, the computing time is about two thirds of that of the conventional method. An example implemented in a UNIX system shows that the algorithm elegantly solves the problem of the wobbling approach vector.

ISSN:0253-3839    

DOI:10.1080/02533839.1992.9677388

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

When a robot is constrained by more than one inequality constraints, the analysis of the contact force becomes quite involved. Moreover, the degree‐of‐freedom of the robot motion is reduced in a constrained motion. Frequently, it is desirable to analyze the motion behavior of the robot before, at, and after the contact instant. In our previous report, a robot with one inequality constraint was carefully examined. In this paper, we extend our results to the case of a robot with two inequality constraints. The mathematical model, the impact force, the elasticity and friction of the constraint surface will be discussed. In addition, a solution algorithm will be developed for the model.

ISSN:0253-3839    

DOI:10.1080/02533839.1992.9677389

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

In this study, a partitioning model of Polycyclic Aromatic Hydrocarbons (PAHs) based on PM10μsuspended particulates is evaluated. A second model based on total suspended particulates (TSP) is also evaluated. The partitioning model is in the form oflog[A(TSP)/F}= m/T + b,whereAandFstand for PAH amount in gas and particulate phases respectively,Tis the ambient temperature,mandbare constants. The PM10μand TSP sampling and analysis for PAHs were carried out year‐round in downtown Taipei from June, 1989 to May, 1990. The partitioning model derived from Langmuir adsorption was established for Fluoranthene, Pyrene and Benzo(a)anthracene/Chrysene. The performance of partitioning models for PM10#GMand TSP are close to each other except for pyrene. This is indicated by the coefficient of determination (r2) determined by the regression between the product of partitioning ratio and suspended particulates level, and the inverse of ambient temperature. When the mass of total suspended particulate in the partitioning model was substituted with the surface area of suspended particulate estimated from the cascade impactor experiments of PM10μ, the coefficients of determination for Fluoranthene and Pyrene were both increased significantly. Therefore, particle surface area is a better parameter to be applied in the partitioning model by accounting for the surface area available for adsorption.

ISSN:0253-3839    

DOI:10.1080/02533839.1992.9677390

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

On the basis of the results of Lin et al. [12], the interaction between screw dislocations and an internal crack in a two‐phase medium is analyzed. The complex potential, stress field, stress intensity factor, crack extension force and strain energy are derived. The mechanical behavior of the medium is strongly influenced by the shear modulus ratio of the two‐phase medium and the dislocations inside the internal crack. Finally, our results can be reduced to several special cases.

ISSN:0253-3839    

DOI:10.1080/02533839.1992.9677391

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The minimum void concept was used to proportionhigh strength fly ash concrete.Numerous trial batches were made to determine the optimum mix proportion. Nine beams were cast from optimum mix to investigate theflexural behaviorof this type of concrete. The requirements specified in current ACI 318 for modulus of elasticity of concrete, modulus of rupture of concrete, flexural strength of beam sections, effective moment of inertia of flexural members, maximum tension reinforcement ratio and minimum tension reinforcement for seismic design were examined for their application to high strength fly ash concrete.

ISSN:0253-3839    

DOI:10.1080/02533839.1992.9677392

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

An analytical study of natural convection from an isothermal or uniform wall‐heat‐flux vertical, heated plate embedded in a porous medium is presented. The Brinkman's equation of the non‐Darcy model with boundary effect is employed. Based on the scaling analysis of order‐of‐magnitude, two natural convection parameters are introduced;ζ= (RaxDax)½is for the isothermal case andζ*=Ra*x?Dax½for the uniform wall‐heat‐flux case, with ξ =ζ/ (1 +ζ) or ξ =ζ*/(l +ζ*). These parameters not only represent the ratio of the viscous sublayer thickness to the thermal layer thickness, but also denote a measure of the boundary effect on the buoyancy‐induced flow and heat transfer characteristics. Furthermore, we use the dimensionless variables transformation in terms of ξ to transform the governing boundary layer equations into a system of nonsimilar equations. An accurate, implicit finite difference method is thus employed to solve these nonsimilar equations. The numerical solutions obtained are found uniformly valid over the whole porous media with any porosity, ranging from pure Darcy flow to non‐Darcy flow.

ISSN:0253-3839    

DOI:10.1080/02533839.1992.9677393

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor