Showing papers by "Southeast University published in 1988"

Surface normal for 3D object display in cuberille environment

Abstract: The authors present a surface normal estimate which is based on 3-D moments of gray-value distribution and works in either a gray-scaled or binary voxel-based scene. In the cuberille (voxel-based representation) environment, the voxel value is merely an average of some physical parameter throughout the cubic volume, so the surface extracted (explicitly or implicitly) from a such scene is no longer an exact representation of the actual object surface. An estimate of surface normal from the extracted surface might accumulate errors in object rendering by shading techniques. The proposed operator works directly on the original scene and gives for each surface point in the scene a quantity that measures the probability that a direction could be the normal vector to the surface at this point. Hence, it is able to preserve the structural details of objects. The operator provides superior realism of rendering even though a simple shading model is used. >

Automatic Measurement Of Deformations Of Curved Surface Using Carrier-Holography

Abstract: The present paper proposed a complete method to obtian whole-field displacements information at the curved surface of a body by using carrier-holography and rasterstereography. In the carrier-holography,the fringe pattern of interferogram consists of two parts. Ons is the displacement due to surface deformation, another is a straight fringe family with equal pitch produced by artificality and rigid body moving (if exist). the components of a displacement at every point are given from demodulating carrier-isothetics pattern by means of image processing. The space curvatures of a curved sueface are measured by the resterstereograph method. All the procedure from collecting image to printing result are completed automatically by a personal computer. For example, a model of a hyperboloidal arch dam is nonuniform heated,the thermal displacements on the arch suface are measured.

Rigorous Field Analysis Of Impedances Of Some Millimeter Wave Oscillator Cavities

Abstract: This paper presents a generalized field analysis method for calculating the external circuit impedances looking outside from the active devices of some millimeter wave oscillators For a simple oscillator model with a radial disc and a diode existing in a rectangular waveguide, the numerical results are in agreement with the experimental data Impedance characteristics for several different oscillator configruations are given, and sane useful conclusions for oscillator design are derived

The Solution Of End Effects Of Slot Line By Open Cavity Method

Abstract: An open cavity model is developed to analyse end effects of slot line. Both the reactance and radiation effects are taken into account. The nu­ merical results are compared with the published data.INTRODUCTIONSlot line is a transmission medium for micro­ wave and millimeter wave applications. Much work has been done for its guided-wave properties [1] [2]. Only few work, however, has contributed to its discontinuities, such as step or shorted end. A slot line shorted end is needed to build slot line transitions or filters. As far back as 1973, ex­ perimental characteristics of a slot line shorted end have been reported by Knorr et al [3]. Until last year no theoretical work was presented. Yang et al [4] [5] reported their results about slot line shorted end by dynamic model.In this paper an open cavity model is presented for analysing shorted end of slot line. The reac­ tance and radiation effects are both considered. The numerical results show that the reactance parts of the end effects by cavity model agree well with that in [4] [5] and radiation resistances are different from that in [5].CAVITY MODEL FOR SLOT LINE SHORTED ENDThe slot line cavity is shown in Fig. 1, which is composed of a uniform slot line with two shorted ends. The equivalent circuit for it is shown in Fig. 2. As well known, resonance frequency of this cavity is a complex value, because of radiation losses, and can be denoted ascO = cor + ju>^where o)r is the oscillation frequency of the cavity. ^ stands for losses.For a half-wave cavity the normalized equiva­ lent reactance can be found from following expres­ sionX= jwhere 6 is the propagation constant at 6) = k)r for uniform slot line.L1 = ^The radiation resistance R can be found by following procedure.It is known that the power losses caused by radiation from one end in this cavity can be written as