A multimedia interactive conferencing application for personalworkstations

The multimedia interactive conferencing application (MICA), a personal-workstation application for multipoint visual teleconferencing, is described. MICA allows people at two or more locations to share visual material such as documents, photographs, and computer screens in a highly interactive way. It supports the distribution, storage, retrieval, and high-quality display of visuals, real-time interaction by pointing and annotation, and meeting services facilities. The context of multimedia teleconferencing and computer-supported cooperative work is established, relating earlier research to the design of MICA. The services MICA offers are outlined. The handling, compression, and display of multiple media, and the design of a suitable user interface for MICA are discussed     

1.4-/spl mu/m InGaAsP-InP strained multiple-quantum-well laser for broad-wavelength tunability

InGaAsP-InP strained multiple-quantum-well (MQW) lasers for extended wavelength tunability in external cavity operation were designed, fabricated, and tested. The active layer was a strain compensated structure consisting of three 3.2/spl plusmn/0.3 nm and three 6.4/spl plusmn/0.3 nm 1.0% compressive strained wells and five 10.3/spl plusmn/0.3 nm 0.45% tensile strained barrier layers. A 2-/spl mu/m-wide ridge waveguide laser of length 250 /spl mu/m, when used in a grating external cavity and with no coatings to alter the reflectivity of the facets, was observed to operate over a range >110 nm. The lasers were designed for applications in trace gas and liquid detection with the goal to maximize the tunable range when operated in external cavities and with no facet coatings.     

Cyclic code weight spectra and BIST aliasing

In built-in self-test for logic circuits, test data reduction can be achieved using a linear feedback shift register. The probability that this data reduction will allow a faulty circuit to be declared good is the probability of aliasing. Based on the independent bit-error model, we show that the code spectra for the cyclic code generated by the feedback polynomial can be used to obtain an exact expression for the aliasing probability of a multiple input signature register when the test length is a multiple of the cycle length. Several cases are examined and, as expected, primitive feedback polynomials provide the best performance. Some suggestions to avoid peaks in the aliasing probability are given.     

Performance and Modeling of the MWIR HgCdTe Electron Avalanche Photodiode

The operation of the mid-wave infrared (MWIR) HgCdTe cylindrical electron injection avalanche photodiode (e-APD) is described. The measured gain and excess noise factor are related to the collection region fill factor. A two-dimensional diffusion model calculates the time-dependent response and steady-state pixel point spread function for cylindrical diodes, and predicts bandwidths near 1 GHz for small geometries. A 2 μm diameter spot scan system was developed for point spread function and crosstalk measurements at 80 K. An electron diffusion length of 13.4 μm was extracted from spot scan data. Bandwidth data are shown that indicate bandwidths in excess of 300 MHz for small unit cells geometries. Dark current data, at high gain levels, indicate an effective gain normalized dark density count as low as 1000 counts/μs/cm² at an APD gain of 444. A junction doping profile was determined from capacitance–voltage data. Spectral response data shows a gain-independent characteristic.     

Process simulation for HgCdTe infrared focal plane array flexible manufacturing

The strategy and status of a process simulator for the flexible manufacture of HgCdTe infrared focal plane arrays is described. It has capabilities to simulate Hg vacancy and interstitial effects and cation impurity diffusion, for various boundary conditions in one dimension. Numerical complexity of these problems stems from the necessity of solving diffusion equations for each defect that are coupled to each other via nonlinear interaction terms. The simulator has already led to the prediction of heretofore unexplained experimental data. Current extensions of the one-dimensional simulator planned over the next few years include the addition of Te antisites, antisite-Hg vacancy pairs, and In-Hg vacancy pairs, ion implantation, and various energetic processes (such as ion milling). The sequential effect of various processes will be possible with the input to the simulator looking much like a process run sheet.     

Electrooptical Characterization of MWIR InAsSb Detectors

InAs_1?x Sb _x material with an alloy composition of the absorber layer adjusted to achieve 200-K cutoff wavelengths in the 5-μm range has been grown. Compound-barrier (CB) detectors were fabricated and tested for optical response, and J _dark–V _d measurements were taken as a function of temperature. Based on absorption coefficient information in the literature and spectral response measurements of the midwave infrared (MWIR) nCBn detectors, an absorption coefficient formula α(Ε, x, T) is proposed. Since the presently suggested absorption coefficient is based on limited data, additional measurements of material and detectors with different x values and as a function of temperature should refine the absorption coefficient, providing more accurate parametrization. Material electronic structures were computed using a k·p formalism. From the band structure, dark-current density (J _dark) as a function of bias (V _d) and temperature (T) was calculated and matched to J _dark–V _d curves at fixed T and J _dark–T curves at constant V _d. There is a good match between simulation and data over a wide range of bias, but discrepancies that are not presently understood exist near zero bias.     

The detection of polyphosphate in broiler chicken breast muscle

The relationship between the concentration of sodium and phosphorus (as P₂O₅) in commercially processed broiler chicken breast muscle as a result of injection of various levels of sodium polyphosphate and sodium chloride has been studied and a routine analytical method which can confirm the presence or absence of the addition of these chemicals has been developed. The method is applicable to frozen, thawed or cooked broilers and is independent of moisture and protein content. Since polyphosphates may contain potassium as well as sodium salts, the relationship between these two elements in untreated commercially processed broiler breast muscle has also been measured and compared with treated birds. The analytical procedure has been applied to a survey of deep frozen broilers purchased from three local supermarkets.     

PSOBLAP: Particle Swarm Optimization-Based Bandwidth and Link Availability Prediction Algorithm for Multipath Routing in Mobile Ad Hoc Networks

Wireless Personal Communications - In mobile ad hoc network (MANET), optimal path identification is the main problem for implementing the Multipath routing technique. MANET desires an efficient...     

Design and Characterization of Fabry–Pérot MEMS-Based Short-Wave Infrared Microspectrometers

Microspectrometers based on the monolithic integration of a microelectromechanical system (MEMS) Fabry–Pérot filter and a Hg _x Cd_1–x Te-based infrared detector are discussed and measured results presented. The microspectrometers are designed to operate in the 1.5 μm to 2.6 μm wavelength range. Design equations are presented which account for the mechanical and optical characteristics of the device. Measurements indicate linewidths as narrow as 55 nm, switching times of 40 μs, and a tuning range of 380 nm, which is limited by snap-down. Optical characterization of the distributed Bragg mirrors and the Fabry–Pérot filter are presented, and these are shown to be in good agreement with simple first-order analytical models. Bowing of the movable Fabry–Pérot mirror due to stress gradients is identified as the dominant source of linewidth broadening.     

Design and Analysis of Microstrip Patch Antenna Using Periodic EBG Structure for C-Band Applications

Wireless Personal Communications - In this paper, an Electromagnetic Band Gap structured microstrip patch antenna is presented. The proposed antenna consists of a rectangular patch which is fed by...