Performance Evaluation of a Parallel Pipeline Computational Model for Space-Time Adaptive Processing

This paper presents further results on the design and implementation of various optimizations based on our earlier work of developing a parallel pipelined model for the computational intensive applications that have multiple processing tasks. Performance evaluation of this model was done by using a real-time airborne radar application that employs a Space-Time Adaptive Processing (STAP) algorithm. This paper focuses on the following four issues: (1) The tradeoffs between increasing the throughput and reducing the latency are examined in more detail when allocating processors among different processing tasks. (2) A multi-threaded design is incorporated into the pipeline model and implemented on a massively parallel computer with symmetric multi-processor nodes, which shows enhanced performance. (3) The disk I/O is incorporated into the parallel pipeline to study its effect on performance in which two I/O task designs have been implemented: embedding I/O in the pipeline or having a separate I/O task. By using a double buffering approach together with the asynchronous I/O, the overall pipeline performance scales well as the number of processors increases. (4) From the comparison of the two I/O implementations, it is discovered that the latency may be improved when merging multiple tasks into a single task. The effect of reorganizing the task structure of the pipeline is discussed in detail. All the performance results shown in this work demonstrate the linear scalability the parallel pipeline model can achieve using a production radar application. Although this paper focuses on the implementation of the parallel pipeline model and uses the results from a STAP application to support the claims of the discovered properties for this pipeline, this model is also applicable to many other types of applications with similar computational characteristics.     

Comparative incidence of de novo nonlymphoid malignancies after liver transplantation under tacrolimus using surveillance epidemiologic end result data

BACKGROUND: An increased incidence of de novo nonlymphoid malignancies has been shown in immunocompromised patients. However, the true risk over time compared to the general population has not been determined. METHODS: One thousand consecutive patients were carefully followed for an average of 77.8+/-11.1 (range, 56.3-96.3) months after primary liver transplantation at a single center. All de novo nonlymphoid malignancies were recorded. Each malignancy was compared with a standard Occupational Cohort Mortality Analysis Program population matched for age, sex, and length of follow-up using modified life table technique and surveillance epidemiology end result (SEER) data. RESULTS: Fifty-seven patients accounted for de novo malignancies and contributed 4795.3 total person years, a mean+/-SD of 36+/-21 (median, 36; range, 6-74) months after liver transplantation. Twenty-two of these malignancies were skin malignancies including two melanomas. Oropharyngeal cancers (n=7) were found to be 7.6 times higher (P<0.05) and respiratory malignancies (n=8) were 1.7 times higher (P>0.05) compared to the SEER incidence rate. Female reproductive system malignancies including breast cancer (n=3) were 1.9 times lower (P>0.05) and genitourinary malignancies were (n=5) 1.5 times lower (P>0.05) than their matched cohorts. No differences was observed in gastrointestinal malignancies (n=5). There was a significant difference in survival of the patients after diagnosis of malignancy depending on the type of cancer. There were two Kaposi's sarcomas, two metastatic unknown primaries, one thyroid, one brain, and one ophthalmic malignancies in the series. Mortality for Kaposi's and metastatic disease of unknown primary was 100% within 5 months, while the 1-year mortality for oropharyngeal cancer was 57.1% and that for lung cancers was 62.5%. Long-term survival for skin cancer was highest: 86.4% at 3 years (P=0.015 by log-rank test). CONCLUSION: An increased incidence of de novo cancers in the chronically immunocompromised patient demands careful long-term screening protocols which will help to facilitate the diagnosis at an early stage of the disease. This is particularly true for oropharyngeal cancers where the risk is more than 7 times higher compared to SEER incidence data matched for age, sex, and length of follow-up.     

Influence of the dislocation density on the performance ofheteroepitaxial indium phosphide solar cells

The authors point out that heteroepitaxial indium phosphide solar cells developed to date have low efficiency due to misfit dislocations. Dislocations act as recombination centers and strongly influence the solar cell performance. Calculations have been made to study the dependence of heteroepitaxial InP solar cell efficiency on dislocation density. The effects of surface recombination velocity and cell emitter thickness are also considered. Calculated results are compared with the available experimental results on representative InP solar cells. It is shown that heteroepitaxial InP cells with over 20% AM0 efficiency could be fabricated if dislocation density can be reduced to <10⁵ cm^-2 and the surface recombination velocity reduced to <10⁵ cm/s     

Retarding behaviour of organic solvents in permanganate-sulphite-initiated polymerization of acrylamide

Redox polymerization of acrylamide initiated by a new redox couple, potassium permanganate-sodium sulphite, has been studied under atmospheric oxygen at 35 ± 0.2° C. The rate of polymerization has been found to vary with the half power of the redox components and the first power of the monomer concentration. The energy of activation has been calculated to be 8.29 kcal/(deg. mol.). The effect of various additives such as neutral salts and surface-active agents has been studied qualitatively. The retarding effect of organic solvents on the rate of polymerization has also been studied both qualitatively and quantitatively. An interpretation of the observed results has been proposed.     

Bead Manufacture by Extrusion/spheronization - a Statistical Design for Process Optimization

Our recent experience in developing bead formulations for a hydrophilic drug using an extrusion/spheronization technique highlighted several critical processing factors. It was observed that the yield of beads of desired size fraction was significantly affected by water level, water temperature, extrusion speed, spheronization speed, and spheronization time. To further elucidate the roles of these factors, a split-plot factorial design was used to evaluate their effects on the yield of desired size beads, and to determine the optimal levels to maximize the yield. Several 18 kg batches of beads were manufactured using a predetermined level of each factor. The finished beads were sieved using #14 and #20 mesh screens and the yields of beads between #14-20 mesh screen were determined. It was observed that the temperature of water used at the granulation stage significantly affected the bead formation. Using room temperature water for granulation, the significant factors were water level, extruder speed, spheronization speed, spheronization dwell time, and the interactions of water level with extruder speed and spheronization speed with dwell time. Whereas using 50 °C water, significant factors were water level, extruder speed, spheronization speed, and the interaction of water level with spheronization speed. The best fitting regression model describing the relationship between the found yields and the factors was used to find the levels of each factor that would optimize the yield. Two scale-up batches at 100 kg each were manufactured using the optimal process conditions to verify the room temperature model. The yields from the two scale-up batches were within 0.4% of the predicted yield using the regression model.     

Studies on effects of metal vapour in an experimental self-blastinterrupter

Low rate of energy transfer in self-blast interrupters results in slow build-up of pressure in the expansion-volume. The arcing continues (for 20 to 30 ms) till the pressure in the arcing chamber is sufficient to flush the arc and the arc-product from the inter-electrode space. To promote the energy transfer and the efficiency of a self-blast interrupter, use of metal-vapour as an energy transport acceleration device has been investigated for the first time on an experimental self-blast interrupter. The results indicate an appreciable rise in rate of energy transfer to the expansion-volume gas in the interrupter. Different energy transfer rates observed during experimentation with the metal-vapours of aluminium, silver and copper confirm the feasibility of using and controlling of such a mechanism in a self-blast interrupter     

Psychophysiological correlates of infant temperament: stability of behavior and autonomic patterning from 5 to 18 months

The stability of infant temperament and autonomic patterning (heart period and cardiac vagal tone) was examined longitudinally when infants were 5, 10, and 18 months of age. Behavioral measures of reactivity and regulation to frustration tasks, and maternal perceptions of infant temperament were obtained at each age along with baseline measures of cardiac activity. No stability was found from 5 to 10 months while some stability of behavior and autonomic patterning was identified from 10 to 18 months, with the exception of negative reactivity. High levels of cardiac vagal tone (V) were associated with negative reactivity at 18 months. When examining groups based on degrees of reactivity and regulation, we found infants who responded negatively to frustration but who also displayed more regulatory behavior to have higher V.     

Phase equilibria of the Si-Ge-Ti system relevant to the reactions between SiGe alloys and Ti

The semiconductor-rich region of the Si-Ge-Ti ternary isotherm at 900°C was determined by metallography, x-ray diffraction, and electron microprobe analysis. The sample alloys were prepared by arc-melting. These alloys were brought to equilibrium by annealing at 900°C for 400 h. It was confirmed that at 900°C, TiSi₂ and TiGe₂ form a continuous solid solution Ti(Si_1−yGe_y)₂ with the C54 crystal structure. It was also shown that, other than Ti(Si_1−yGe_y)₂ and Si_1−xGe_x, there is not any binary or ternary phase within the Si-Ge-TiGe₂-TiSi₂ trapezoid region. Between the Ti(Si_1−yGe_y)₂ and Si_1−xGe_x single-phase fields is the Ti(Si_1−yGe_y)₂-Si_1−xGe_x two-phase region. The tie-lines for this two-phase region were determined. The tie-lines tilt slightly toward the TiSi₂ and Ge corners. In other words, at equilibrium, the silicon to germanium atomic ratio is larger in Ti(Si_1−yGe_y)₂ than in Si_1−xGe_x (x>y). This tendency for tie-lines to tilt toward the TiSi₂ and Ge corners had been proposed in the literature as the reason for the interesting microstructure evolution during the reactions between SiGe alloys and Ti. In addition, the possible diffusion paths for the reactions between SiGe alloys and Ti were discussed based on the obtained isotherm. Recognizing Si and Ge have higher mobilities in Ti(Si_1−yGe_y)₂, it is predicted that for SiGe the extent of concentration change is large but occurs over a shorter distance, and for TiSi₂ the extent of concentration change is small but occurs over a longer distance.     

An iterative Newton-Raphson method to solve the inverse admittivity problem

By applying electrical currents to the exterior of a body using electrodes and measuring the voltages developed on these electrodes, it is possible to reconstruct the electrical properties inside the body. This technique is known as electrical impedance tomography. The problem is nonlinear and ill conditioned meaning that a large perturbation in the electrical properties far away from the electrodes produces a small voltage change on the boundary of the body. This paper describes an iterative reconstruction algorithm that yields approximate solutions of the inverse admittivity problem in two dimensions. By performing multiple iterations, errors in the conductivity and permittivity reconstructions that result from a linearized solution to the problem are decreased. A finite-element forward-solver, which predicts voltages on the boundary of the body given knowledge of the applied current on the boundary and the electrical properties within the body, is required at each step of the reconstruction algorithm. Reconstructions generated from numerical data are presented that demonstrate the capabilities of this algorithm.