Vibrotactile Guidance Cues for Target Acquisition

Three experiments examined the use of vibrotactile cues to guide an operator toward a target. Vibrotactile stimulation on the hand can provide spatially stabilizing cues for feedback of subtle changes in position. When such feedback is present, a deviation from the point of origin results in tactile stimulation indicating the direction and magnitude of the positional error. Likewise, spatial deviation from a desired position displayed tactually can provide robust position guidance and stabilization sufficient to improve the acquisition time and accuracy of fine cursor control. A major advantage of this mode of information representation is that it can be present at the same time as visual cues with minimal cross-modal interference. Our findings suggest that performance is actually enhanced when both tactile and visual cues are present. Although previous studies have suggested that various forms of tactile feedback can provide position guidance and stabilization, to our knowledge, this work is the first that details the effect of tactile feedback on target acquisition directly.     

Teletraffic performance of GSM900/DCS1800 in street microcells

Studies the teletraffic issues of the Global System of Mobile Communications at 900 MHz (GSM900), and its sister, the Digital Communication System at 1800 MHz (DCS1800). The teletraffic simulations have the essential elements of GSM900 and DCS1800, but they are not be exact simulations of these two systems. The approach is to site microcellular base stations, using the microcellular prediction tool MIDAS, into a fictitious city and into parts of two real cities. The radio coverage plots are then imported into a teletraffic simulator TELSIM. The simulator is loaded with the basic GSM900 and DCS1800 parameters to give an indication of the teletraffic performance of these systems in the three environments     

Optical beam forming techniques for phased array antennas

Three optical beam forming techniques are identified as applicable to large spaceborne phased array antennas. They are 1) the fiber replacement of conventional RF phased array distribution and control components, 2) spatial beam forming, and 3) optical beam splitting techniques. Two novel optical beam forming approaches, i.e., the spatial beam forming with a “smart pixel” spatial light modulator (SLM) and the optical beam splitting approaches are conceived with integrated quasi-optical components. Also presented are the transmit and receive array architectures with the new SLM.     

VSNR: a wavelet-based visual signal-to-noise ratio for natural images.

This paper presents an efficient metric for quantifying the visual fidelity of natural images based on near-threshold and suprathreshold properties of human vision. The proposed metric, the visual signal-to-noise ratio (VSNR), operates via a two-stage approach. In the first stage, contrast thresholds for detection of distortions in the presence of natural images are computed via wavelet-based models of visual masking and visual summation in order to determine whether the distortions in the distorted image are visible. If the distortions are below the threshold of detection, the distorted image is deemed to be of perfect visual fidelity (VSNR = infinity) and no further analysis is required. If the distortions are suprathreshold, a second stage is applied which operates based on the low-level visual property of perceived contrast, and the mid-level visual property of global precedence. These two properties are modeled as Euclidean distances in distortion-contrast space of a multiscale wavelet decomposition, and VSNR is computed based on a simple linear sum of these distances. The proposed VSNR metric is generally competitive with current metrics of visual fidelity; it is efficient both in terms of its low computational complexity and in terms of its low memory requirements; and it operates based on physical luminances and visual angle (rather than on digital pixel values and pixel-based dimensions) to accommodate different viewing conditions.     

Videomicroscopic comparison of bull sperm and leukocyte chromosome areas as related to gender

Chromosomal areas from metaphase spreads of male bovine leukocytes were digitized and sex chromosomes identified using videomicroscopy. Autosomal areas were ranked in descending order within a cell and assigned to two categories based on alternating rank. X and Y chromosome areas were assigned to respective categories. Areas were divided by 4 to make their sum equivalent to sperm DNA content. Data were analyzed before and after inclusion of sex chromosomal areas. Before X and Y inclusion, rank contributed to difference in chromosomal areas. Rank by category interaction and category effects did not contribute to area variation. After X and Y inclusion, area variation was due to rank by category interaction, rank, and category. Differences between sums of chromosomal areas across categories was 3.57%. Head areas of morphologically normal sperm with intact acrosomes were digitized using the same optics as chromosomal areas. Sum of corrected chromosomal areas per category was used in discriminant analysis to assign sperm head areas to two categories with .5 prior probabilities. Assignment resulted in 1037 sperm in one category and 1177 in the other. Difference between largest sperm head area classes across categories was 3.2%. Discrimination of sperm head areas, based on sum of chromosomal area and measured with computerized videomicroscopy, may be used to evaluate sex of bovine spermatozoa.     

Channel capacity limits for multiple-access channels with slowRayleigh fading

The complex-valued collaborative coding multiple-access (CVCCMA) technique has been shown to offer efficient simultaneous transmission by multiple users over a common radio channel, without the use of orthorgonal codes nor subdivisions in time or frequency. The authors describe the capacity calculation for a T user CVCCMA system in a slow Rayleigh fading environment with additive white Gaussian noise (AWGN). The capacity, in terms of bits per channel use has also been derived by simulation for different values of T with MPSK modulation     

Allpass filter using reflection coefficient of lossless networks

An approach to the design of analogue allpass filters and phase shift networks is presented which leads to designs which are more readily realised in practical circuits than by using the usual approach of using bridged T or lattice networks     

On parallel PIC versatility and the structure of parallel PIC approaches

We discuss insights gained from an effort to develop a versatile parallel PIC code (PICARD – PIC with arbitrary rebalancing and decompositions). Because of the highly dynamic nature of PIC, it is sometimes necessary to tailor decomposition strategies on a problem-by-problem basis instead of solely on the basis of the algorithm. The dynamics of a problem may dictate the particular strategy to be used. Thus, finding a general operational method for parallel PIC applications is important. We find approaches to partitioning the mesh and particle domains which provide some trade-off opportunities, but the relationship enforced between the partition layouts in addition to the way one chooses to manage the problem's dynamics defines categories of strategies which are independent of the partitioning technique used. The overall strategy enforced is as important as the individual techniques applied to partition the domains. Three strategy groups arise from the analysis and form the basis of widely disparate parallel PIC operational methods. These distinct solutions are obtained from rather simple parametric choices. We introduce the concept of rubber boundaries as a means to bring a compromise between what are commonly referred to as Lagrangian and Eulerian particle mappings. We show several parallel PIC strategies that are as yet unexplored. © 1997 John Wiley & Sons, Ltd.