Coherent States for Generalized Laguerre Functions

We explicitly construct a Hamiltonian whose exact eigenfunctions are the generalized Laguerre functions. Moreover, we present the related raising and lowering operators. We investigate the corresponding coherent states by adopting the Gazeau-Klauder approach, where resolution of unity and overlapping properties are examined. Coherent states are found to be similar to those found for a particle trapped in a P\"oschl-Teller potential of the trigonometric type. Some comparisons with Barut-Girardello and Klauder-Perelomov methods are noticed.Comment: 12 pages, clarifications and references added, misprints correcte

Simulation of turbulent explosion of hydrogen-air mixtures

Spherically expanding turbulent premixed hydrogen-air flames are computed using the Reynolds-Averaged Navier-Stokes (RANS) approach. The mean reaction rate is modelled using unstrained and strained flamelets, and an algebraic model. Since the temperature and mass fraction evolve differently in hydrogen flames because of non-unity Lewis numbers, two reaction progress variables are used in the calculations. The computed turbulent burning velocity is compared to measured values to validate the computational models. The strained flamelets model captured the experimental variations quite well while the other two models over estimated the burning velocity of stoichiometric hydrogen-air flames. All of these models under estimated the burning velocity for a lean flame which is thermo-diffusively unstable, indicating a need to include these instability effects in turbulent combustion modelling. A comparative analyses of stoichiometric hydrogen- and methane-air flames are also performed to understand their relative behaviour for a given turbulent combustion condition signified by u" /s0 L and Λ/δ. Although the gross behaviour is observed to be similar, there is a significant difference in the normalised turbulent flame speeds, st/s0 L, of these flames. A detailed analysis showed that the mean reaction rate increases very sharply, at least by two order of magnitude, near the leading edge for the hydrogen flames compared to the methane flames. Since this behaviour is controlled not only by turbulence and its interaction with flame but also by chemical kinetics, one must also consider chemical kinetics parameters such as activation temperature, in addition to u" /s0 L and Λ/δ to characterise st/s0 LThis is the accepted manuscript. The final version is available from Elsevier at http://www.sciencedirect.com/science/article/pii/S0360319914009744

Simulation of spherically expanding turbulent premixed flames

Statistically spherical expanding turbulent premixed flames are computed using unsteady Reynolds-Averaged Navier-Stokes (URANS) approach. Mean reaction rate is closed using strained and unstrained flamelet models and an algebraic model. The flamelets are parametrised using the scalar dissipation rate in the strained flamelet model. It is shown that this model is able to capture the measured growth rate of methane-air turbulent flame ball, which is free of thermo-diffusive instability. The spherical flames are observed to accelerate continuously. The flame brush thickness grows in time and the role of turbulent diffusion on this growth seems secondary compared to the convection due to the fluid velocity induced by the chemical reaction. The spherical flames have larger turbulent flame speed, the leading edge displacement speed st, compared to the planar flames for a given turbulence and thermo-chemical condition. The computational results suggest st/s0 L " Rent with 0.57 # n # 0.58, where Ret is the turbulence Reynolds number and s0 L is the unstrained planar laminar flame speed, for both spherical and planar flames.This is an Accepted Manuscript of an article published by Taylor & Francis inCombustion Science and Technology on 16 September 2013, available online: http://wwww.tandfonline.com/10.1080/00102202.2013.808629

Monitoring the Health of Computer Networks with Visualization - VAST 2012 Mini Challenge 1 Award: "Efficient Use of Visualization"

The complex computer networks of large organisations contain many machines of many types, used in many geographic locations. Although system administrators should monitor the health of each machine, they need to do so within the context of the whole computer network. Our visualization presents the health of a fictitious financial institution's computer network at a snapshot in time and over a time range, and preserves the important aspects of each facility's administrative and geographic context. Using the "Bank of Money" VAST Challenge dataset, our visualization allowed us to correctly identify several areas of concern, as well as hypothesise about their causes

Gasoline flame behavior at elevated temperature and pressure

Freely propagating laminar premixed flames of stoichiometric mixtures of gasoline surrogate and iso-octane with air are computed using three chemi- cal kinetics mechanisms of varied complexity and detail. A good agreement of the computed burning velocities with past experimental data is observed. The burning velocities of these mixtures at temperature of 850 ≤ T ≤ 950 decrease with pressure up to about 3 MPa and starts to increase beyond this pressure. This contrasting behavior is related to the role of pressure dependent reaction involving OH and the influence of this radical on the fuel consumption rate. The results suggest that the overall order of the com- bustion reaction is larger than two at pressures higher than 3 MPa. Hence, one must be cautious in extending the commonly used laminar flame speed correlation with pressure to thermo-chemical conditions of interest for future engines.KACS

Effectiveness of percutaneous nephrostomy in reversing obstructive renal failure

A retrospective analysis of 34 patients of obstructive renal failure, initially managed by percutaneous nephrostomy was performed. Pre procedure blood biochemical profile was compared with upto one week follow-up of blood chemistry. There was a decline of 71.1% and 56.08% (P-values 0.0001 and 0.0028) in the mean values of serum creatinine and blood urea nitrogen respectively at 7 days after the procedure. Improvement in blood biochemical profile was solely dependent on performance of percutaneous nephrostomy

A WiFi-based Reliable Network Architecture for Rural Regions

WiFi is being considered as an attractive option in providing low cost Internet connectivity to rural areas, and thereby reducing Digital Divide with urban areas. Most of the WiFi-based Long Distance network architectures extend Internet to rural regions through a single gateway node which is connected to high speed Internet. If the gateway node fails in such single gateway-based rural networks, the entire network gets collapsed. In this paper, we propose a reliable and low-cost WiFi based rural network architecture using multi-gateway concept. The proposed network architecture also allows load balancing among the available gateways. In such multi-gateway architecture, the network recovers from gateway failure and reestablishes the ongoing communication within 2-4 seconds time. The simulation results in NS-2 validate the claims of the paperKeywords—Digital Divide, WiFi, WiFi based Long Distance Network

A Mechanistic Model on Catalyst Deactivation by Coke Formation in a CSTR Reactor

A mechanistic model on catalyst deactivation by coke formation in a continuous stirred tank reactor (CSTR) has been developed in the paper. Catalyst deactivation by coke formation was treated as a surface reaction. Four reaction mechanisms representing coke formation through different routes were proposed. The evolved system of ordinary differential equations (ODEs) was solved numerically using MATLAB. This approach was validated by applying it to the skeletal isomerization of 1-pentene over ferrierite. Simulation results were compared qualitatively to those obtained from the literature. Simulation results indicated that coke formation is an extremely rapid process with fast formation of coke components on the strongest acid sites leading to final coke. The coke deposition is slower at higher residence times resulting in more stable product formation and weaker deactivation. The results obtained from this work revealed that the developed model is indeed able to successfully demonstrate the most essential features of catalyst deactivation by coke formation and are in agreement with the findings in the literature. Future work is aimed to extend the study to different reactors such as a plug flow reactor, in addition to analysis of the reaction system’s sensitivity to variables such as temperature and pressure

Mammographic criteria for determining the diagnostic value of microcalcifications in the detection of early breast cancer

Objective: To evaluate the importance of microcalcifications in the detection of breast carcinoma in conventional mammography.Methods: This prospective study was carried out at Aga Khan University Hospital (AKUH). Mammograms of 68 patients with microcalcifications were evaluated. Craniocaudal and oblique views of both breasts were acquired on routine basis with cone compression and magnified views when required.Results: Among 68 patients with microcalcifications, 61 (89%) had clustered microcalcifications while 7 patients (10.29%) had scattered microcalcifications. Microcalcifications can occur in benign and malignant diseases. While evaluating clustered microcalcifications, few criteria have been established to determine malignant clustered microcalcifications, these include specific and nonspecific criteria. Among specific and statistically significant criteria for malignant microcalcifications, which were identified in this study, were irregularity of size, irregularity of density, linear or branched shape and Le Gal\u27s type V distribution. In a cluster total number of \u3e30 microcalcifications and at least 10 microcalcifications/cm2 of a cluster are also important in diagnosing a malignant cluster, but are included in nonspecific criteria because they can be present in benign diseases also. Scattered bilateral microcalcifications are usually present in benign breast diseases, but in this study, two patients with breast cancer had profuse bilateral scattered microcalcifications.CONCLUSION: This study shows that specific and statistically significant criteria for malignant microcalcifications, are irregularity of size, irregularity of density, linear or branched shape and Le Gal\u27s type V distribution. Scattered bilateral microcalcifications are usually present in benign breast diseases, but irregular shape and development of new calcifications among diffusely scattered bilateral calcifications, on follow up study, should also raise suspicion for being malignant