Texture has been investigated as a cue for reconstructing 3-D structure. There are various textures in a natural scene. In this paper, the regularity of alignment of texture elements was manipulated to investigate its effect on human perception. The results show that the regularity affects human perception when only the texel density gradient is given as cue or the density cue is inconsistent with the compression cue. We introduce a model based on a MAP estimation to account for the result from a viewpoint of an integration of 3-D cues. The model simultaneously estimates texture properties and 3-D surface orientation by using prior knowledge about texture and 3-D surface. The performance of the model accounts for the experimental result well.

This paper presents a novel four-sector shaped-beam antenna suitable for base station antennas in 60-GHz wireless local area networks (LANs). The antenna has a plateau configuration, whose four side walls have four linearly arranged microstrip antennas. Each trapezoidal facet excites a shaped beam in the elevation plane in order to meet link-budget requirement between base station and remote terminal, taking account of directional patters of remote terminal antennas. Low-loss curved microstrip-line is applied to connect the three-dimensional antennas with active circuits mounted on a flat carrier plate. This antenna has been adopted as the base station antenna in 60-GHz wireless LANs. The first-stage transmission experiment confirms the usefulness of shaped-beam antennas in the 60-GHz band.

Ultra-low-power-consumption and high-speed DCFL circuits have been fabricated by using 0.2-µm Y-shaped gate E/D-heterojunction-FETs (HJFETs) with a high-aspect-ratio gate-structure, which has an advantage of reducing the gate-fringing capacitance (Cf) to about a half of that of a conventional low-aspect-ratio one. A fabricated 51-stage ring oscillator with the 0.2-µm Y-shaped gate n-AlGaAs/i-InGaAs E/D-HJFETs shows the lowest power-delay product of 0.21 fJ with an unloaded propagation delay of 34.9 ps at a supply voltage (VDD) of 0.4 V. We also analyze the DCFL switching characteristics by taking into account the intrinsic gate-to-source capacitance (Cgsint) and the Cf. The analysis results for the power-delay products agree well with our experimental results. Our analysis also indicates the DCFL circuit with the high-aspect-ratio Y-shaped gate E/D-HJFETs can reduce the power-delay products by 35% or more below 0.25-µm gate-length as compared to conventional ones with the low-aspect-ratio Y-shaped gate HJFETs. These results clarify that the Cf-reduction of the Y-shaped gate HJFETs is more effective in improving the power-delay products than reducing the gate-length.

We have developed a fabrication technique for high-performance high-thermal-stability InP/InGaAs heterojunction bipolar transistors (HBTs) for use in 40-Gb/s ICs. The HBT's T-shaped emitter electrode structure simplifies the fabrication process and enables high controllability of spacing between the emitter and the base electrodes. A highly-C-doped base, grown by gas-source MBE, and a new Pt-based metal system results in a low base resistance. An InP subcollector suppresses thermal runaway of HBTs at high collector current better than a conventional InGaAs subcollector does. Using these techniques, we fabricated a very-high-performance HBT with an extremely high cutoff frequency fT of 235 GHz. The RF measurements show that the collector current at the peak cutoff frequency is inversely proportional to collector thickness. We also fabricated a static 1/2 frequency divider, that can be used for 40-Gb/s optical transmission systems, operating up to 44 GHz. This divider confirmed that the developed HBT is applicable to 40-Gb/s optical transmission ICs.

Acquisition of three-dimensional information of a real-world scene from two-dimensional images has been one of the most important issues in computer vision and image understanding in the last two decades. Noncontact range acquisition techniques can be essentially classified into two classes: Passive and active. This paper concentrates on passive depth extraction techniques which have the advantage that 3-D information can be obtained without affecting the scene. Passive range sensing techniques are often referred to as shape-from-x, where x is one of visual cues such as shading, texture, contour, focus, stereo, and motion. These techniques produce 2.5-D representations of visible surfaces. This survey discusses aspects of this research field and reviews some recent advances including video-rate range imaging sensors as well as emerging themes and applications.

In a DC 50 V/3.3 A circuit, the spatial distributions of the spectral intensities of breaking arcs near the cathode for silver contacts were measured on the contact surfaces of three different shapes: flat and spherical (1 mm radius and 2 mm radius) and the arc temperature and the metal-vapor quantity were calculated from the spectral intensities. The influence of the contact shape on the arc temperature and the metal-vapor quantity were also examined, as well as the arc tracks on the contact surfaces and the gain and loss of the contacts. Findings show the distributions of spectral intensities are non-symmetrical from the beginning to the extinction of the breaking arc for the flat contact: However, they are symmetrical in the latter half of the breaking in spite of the number of breaking arcs and the shape of contact surface for the spherical contact. The relationship between the area of the arc tracks on the cathode and the shape of contact surface is the same as the relationship between the existent areas of measured spectra and the shape of the contact surface. For the spherical contacts, the arc temperature and the metal-vapor quantity are affected a little by the radius of the curved of contact surface and the number of breaking arcs. However, the longer the arc duration, the higher the metal-vapor quantity is in the latter period of the breaking arc. For the flat contacts, the metal-vapor quantity is lower than those for the spherical contacts. The gain and loss of the contacts are less and the arc duration is shorter for the flat contact than for the spherical contact.

In this paper, we present an analysis of the microstrip lines whose strip conductors are of various cross-sections, such as rectangular cross-section, triangle cross-section, and half-cycle cross-section. The method employed is the boundary integral equation method (BIEM). Numerical results for these microstrip lines demonstrate various shape effects of the strip conductor on the characteristics of lines. The processing technique on the convergence of the Green's function is also described.

A fractal image coding scheme using classified range regions is proposed. Two classes of range regions, shade and nonshade, are defined here, A shade range region is encoded by the average gray level, while a nonshade range region is encoded by IFS parameters. To obtain classified range regions, the two-stage block merging scheme is proposed. Each range region is produced by merging primitive square blocks. Shade range regions are obtained at the first stage, and from the rest of primitive blocks nonshade range regions are obtained at the second stage. Furthermore, for increasing the variety of region shape, the 8-directional block merging scheme is defined by extension of the 4-directional scheme. Also, two similar schemes for encoding region shapes, each corresponding to the 4-directional block merging scheme and the 8-directional block merging scheme, are proposed. From the results of simulation by using a test image, it was demonstrated that the variety of region shape allows large shade range regions to be extracted efficiently, and these large shade range regions are more effective in reduction of total amount of codebits with less increase of degradation of reconstructed image quality than large nonshade range regions. The 8-directional merging and coding scheme and the 4-directional scheme reveal almost the same coding performance, which is improved than that of the quad-tree partitioning scheme. Also, these two schemes achieve almost the same reconstructed image quality.

In the task of forming high-level object-centered models from low-level image-based features, parts serve as an intermediate representation. A representation of parts for object recognition should be rich, stable, and invariant to changes in the viewing conditions. In addition, it should be capable of describing partially occluded shapes. This paper describes a method for decomposing shapes into parts. The method is based on pairs of negative curvature minima which have a good continuation at their boundary tangents. A measure of good continuation is proposed by using the coefficients of cocircularity, smoothness, and proximity. This method could recover parts in a direct computation, therefore efficient in calculation than the former. Currently, we assume that the shape is a closed planar curve.

This paper describes a factorization-based algorithm that reconstructs 3D object structure as well as motion from a set of multiple uncalibrated perspective images. The factorization method introduced by Tomasi-Kanade is believed to be applicable under the assumption of linear approximations of imaging system. In this paper we describe that the method can be extended to the case of truly perspective images if projective depths are recovered. We established this fact by interpreting their purely mathematical theory in terms of the projective geometry of the imaging system and thereby, giving physical meanings to the parameters involved. We also provide a method to recover them using the fundamental matrices and epipoles estimated from pairs of images in the image set. Our method is applicable for general cases where the images are not taken by a single moving camera but by different cameras having individual camera parameters. The experimental results clearly demonstrates the feasibility of the proposed method.

This paper studies how the self-similarity of traffic changes through shaper (buffered leaky bucket) and switch in ATM networks by numerical experiments. Further the applicability of CAC algorithm to shaped self-similar traffic is also investigated. Numerical experiments show self-similarity of total output traffic from shapers and switch is kept while connection-wise self-similarity is broken.

This paper proposes a new approach to recover the sign of local surface curvature of object from three shading images using neural network. The RBF (Radial Basis Function) neural network is used to learn the mapping of three image irradiances to the position on a sphere. Then, the learned neural network maps the image irradiances at the neighbor pixels of the test object taken from three illuminating directions of light sources onto the sphere images taken under the same illuminating condition. Using the property that basic six kinds of surface curvature has the different relative locations of the local five points mapped on the sphere, not only the Gaussian curvature but also the kind of curvature is directly recovered locally from the relation of the locations on the mapped points on the sphere without knowing the values of surface gradient for each point. Further, two step neural networks which combines the forward mapping and its inverse mapping one can be used to get the local confidence estimate for the obtained results. The entire approach is non-parametric, empirical in that no explicit assumptions are made about light source directions or surface reflectance. Results are demonstrated by the experiments for real images.

Channel holding time distributions in typical cross- and cigar-shaped urban microcells is determined. Practical low-tier-user behaviors in urban areas, such as turning at intersections, entering a buildings, as well as variable user speed and direction are considered. The results are useful in analyzing system traffic and in choosing the best cell shape in urban microcellular systems.

A multimedia coding standard, MPEG4 has frozen its Committee Draft (CD) as the MPEG4 version 1 CD, last October. It defines Audio-Visual (AV) coding Algorithms and their System Multiplex/Composition formats. Founding on Object-base concept, Video part adopts Shape Coding technology in addition to conventional Texture Coding skills. Audio part consists of voice coding tools (HVXC and CELP core) and audio coding tools (HILN and MPEG2 AAC or Twin VQ). Error resilience technologies and Synthetic and Natural Hybrid Coding (SNHC) technologies are the MPEG4 specific features. System part defines flexible Multiplexing of audio-visual bitstreams and Scene Composition for user-interactive re-construction of the scenes at decoder side. The version 1 standardization will be finalized in 1998, with some possible minute changes. The expected application areas are real-time communication, mobile multimedia, internet/intranet accessing, broadcasting, storage media, surveillance, and so on.

We discuss the uniqueness of 3-D shape reconstruction of a polyhedron from a single shading image. First, we analytically show that multiple convex (and concave) shape solutions usually exist for a simple polyhedron if interreflections are not considered. Then we propose a new approach to uniquely determine the concave shape solution using interreflections as a constraint. An example, in which two convex and two concave shapes were obtained from a single shaded image for a trihedral corner, has been given by Horn. However, how many solutions exist for a general polyhedron wasn't described. We analytically show that multiple convex (and concave) shape solutions usually exist for a pyramid using a reflectance map, if interreflection distribution is not considered. However, if interreflection distribution is used as a constraint that limits the shape solution for a concave polyhedron, the polyhedral shape can be uniquely determined. Interreflections, which were considered to be deleterious in conventional approaches, are used as a constraint to determine the shape solution in our approach.

In a DC 50 V/5 A circuit, the relationship between the number of breaking arcs and the spatial distribution of the spectral intensity of breaking arcs of long duration near the cathode in palladium contact were examined through substitution of the contact surfaces of three different shapes: flat and spherical (1 mm radius and 2 mm radius). Findings show the distribution of spectral intensity in Pd arcs to be influenced remarkably by the shape of contact surface and the number of breaking arcs. However, the temperature of Pd arcs was affected neither by the shape of contact surface nor by the number of breaking arcs. The metal-vapor quantity present differed for flat and spherical surface contacts; however, it was not affected by the radius of the curved contact surfaces or by the number of breaking arcs. Additionally, the longer the duration of the breaking arc, the more metal-vapor was presented in the beginning of the arc. Furthermore, arc tracks on contact surfaces were observed with microscopes, clarifying that the relationship between the area of the clouded white metal on the cathode and the shape of contact surface is the same as the relationship between the existent area of measured spectra and the shape of the contact surface.

The proposed GCRA (Generic Cell Rate Algorithm) traffic shaper consists of a regulator and a scheduler. It can shape multiple incoming VBR (Variable Bit Rate) cell streams simultaneously to be strictly conforming according to the GCRA algorithm when the cells depart for the ATM output link. The impact of cell emission conflicts is considered and resolved by using an EDD (Earliest-Due-Date) scheduler and a feedback signal from the scheduler to the regulator. The call admission control condition and the cell delay bound are derived. Simulation results demonstrate that the output cell streams of the proposed GCRA traffic shaper do not contain any non-conforming cells and the scheduler queue size is significantly reduced. Meanwhile, the delay performance is almost not affected by the use of the feedback mechanism.

In this paper, a new traffic shaping mechanism for ATM networks, the RC Shaper, is proposed and studied. The objective of a shaping mechanism is, to smoothen the traffic by reducing the burstiness. Using the analogies between the RC low pass filter and the proposed shaper, performance measures such as burstiness reduction factor and cell mean waiting time of the shaper can be obtained. In this current exploratory stage of study, the shaper is used to shape the well-known Markov Modulated Poisson Process. Behaviour of the shaper is established through examining the burstiness reduction achieved by the device. Another performance measure obtained for the shaper is the cell mean waiting time. Difference in shaping each connection individually and a group of connections collectively is also observed. From our results, it seems better to shape VCs within a virtual path `aggregately' instead of shaping each of these VCs individually. Comparison with fixed-rate shaper is reported and difference in multiplexing shaped and unshaped cell streams is also observed.

High-speed display of 3-D objects in virtual reality environments is one of the currently important subjects. Shape simplification is considered an efficient method. This paper presents a method of hierarchical cube-based segmentation for shape simplification and multiresolution model construction. The relations among shape simplification, resolution and visual distance are derived firstly. The first level model is generated from scattered range data by cube-base segmentation with the first level cube size. Multiresolution models are then generated by re-sampling polygonal patch vertices of each former level model with hierarchical cube-based segmentation structure. The results show that the algorithm is efficient for constructing multiresolution models of free-form shape 3-D objects from scattered range data and high compression ratio can be obtained with little noticeable difference during the visualization.

In this paper, a new method capable of effectively coding arbitrarity-shaped image regions is presented. The image region is spanned into the 8 8 rectangular block and its intermediate luminances are interpolated. After all liminances in the 8 8 block are obtained from pixels in the region, they are transformed by 8 8 DCT. The proposed extension/interpolation (EL) method is compared with conventional ones, such as SA-DCT, mean stuffing, etc., under three aspects: peak signal-to-noise ratio (PSNR), hardware complexity, and the flexibility for improvement of performance. Simulation results show that the performance of the proposed method is superior to that of the conventional ones. In addition, we introduce an improved version by repetitively performing the EL method.