Electron-Hole Generation and Recombination Rates for Coulomb Scattering in Graphene

We calculate electron-hole generation and recombination rates for Coulomb scattering (Auger recombination and impact ionization) in Graphene. The conduction and valence band dispersion relation in Graphene together with energy and momentum conservation requirements restrict the phase space for Coulomb scattering so that electron-hole recombination times can be much longer than 1 ps for electron-hole densities smaller than $10^{12}$ cm$^{-2}$.Comment: 13 pages, 7 figure

The strength of nuclear shell effects at N=126 in the r-process region

We have investigated nuclear shell effects across the magic number N=126 in the region of the r-process path. Microscopic calculations have been performed using the relativistic Hartree-Bogoliubov approach within the framework of the RMF theory for isotopic chains of rare-earth nuclei in the r-process region. The Lagrangian model NL-SV1 with the inclusion of the vector self-coupling of omega meson has been employed. The RMF results show that the shell effects at N=126 remain strong and exhibit only a slight reduction in the strength in going from the r-process path to the neutron drip line. This is in striking contrast to a systematic weakening of the shell effects at N=82 in the r-process region predicted earlier in the similar approach. In comparison the shell effects with microscopic-macroscopic mass formulae show a near constancy of shell gaps leading to strong shell effects in the region of r-process path to the drip line. A recent analysis of solar-system r-process abundances in a prompt supernova explosion model using various mass formulae including the recently introduced mass tables based upon HFB approach shows that whilst mass formulae with weak shell effects at N=126 give rise to a spread and an overproduction of nuclides near the third abundance peak at A~190, mass tables with droplet models showing stronger shell effects are able to reproduce the abundance features near the third peak appropriately. In comparison, several analyses of the second r-process peak at A~130 have required weakened shell effects at N=82. Our predictions in the RMF theory with NL-SV1, which exhibit weaker shell effects at N=82 and stronger one at N=126 in the r-process region, support the conjecture that a different nature of the shell effects at the magic numbers may be at play in r-process nucleosynthesis of heavy nuclei.Comment: 14 pages, 8 figures; submitted to Physical Review C. Part of this work was presented at Nuclear Physics in Astrophysics II, 20th International Nuclear Physics Divisional Conference of the European Physical Society, at Debrecen, Hungary, May 16-20, 200

Experimental investigation on hardness, tensile strength, and microstructure of Al-3,1Cu cast-alloy after T6-tempered

This research aims to investigate Brinell hardness and tensile strength properties of Al-3,1Cu cast-alloy after T6- tempered treatment and evaluate its microstructural changes. This experiment was first performed by using an electric furnace to melt the metal alloy. The liquid metal was then poured into a rectangular metal mold, and the properties of the cast sample material were improved by using T6 heat treatment. Furthermore, the cast product was processed following acceptable tensile and impact tests standards. The results showed an increase in Brinell hardness and tensile strength after T6-Tempered treatment on the cast product. The observation of the microstructure also showed that the precipitate that grows evenly in α was finely dotted

Carrier Recombination and Generation Rates for Intravalley and Intervalley Phonon Scattering in Graphene

Electron-hole generation and recombination rates for intravalley and intervalley phonon scattering in Graphene are presented. The transverse and the longitudinal optical phonon modes ($E_{2g}$-modes) near the zone center ($\Gamma$-point) contribute to intravalley interband carrier scattering. At the zone edge ($K(K')$-point), only the transverse optical phonon mode ($A'_{1}$-mode) contributes significantly to intervalley interband scattering with recombination rates faster than those due to zone center phonons. The calculated recombination times range from less than a picosecond to more than hundreds of picoseconds and are strong functions of temperature and electron and hole densities. The theoretical calculations agree well with experimental measurements of the recombination rates of photoexcited carriers in graphene.Comment: 6 pages, 9 figure

Biological landmark Vs quasi-landmarks for 3D face recognition and gender classification

Face recognition and gender classification are vital topics in the field of computer graphic and pattern recognition. We utilized ideas from two growing ideas in computer vision, which are biological landmarks and quasi-landmarks (dense mesh) to propose a novel approach to compare their performance in face recognition and gender classification. The experimental work is conducted on FRRGv2 dataset and acquired 98% and 94% face recognition accuracies using the quasi and biological landmarks respectively. The gender classification accuracies are 92% for quasi-landmarks and 90% for biological landmarks

Numerical Investigation of Heat Transfer Enhancement in a Circular Tube with Rectangular Opened Rings

Turbulent forced convection of coolant air flow (10 m/s velocity) in a steel tube of 50 cm long having outside diameter of 60 mm and inside diameter of 30 mm with constant outside surface temperature of 1000, 1200 and 1400 Ko is numerically analyzed. The renormalization group k-ε model is used to simulate turbulence in ANSYS - FLUENT 14.5. An opened ring of rectangular cross section (5x7 mm) is fitted in the tube and separated by 8cm pitch. Results of temperature and velocity distribution along the tube center line for the case of tube with internal ribs were compared with that of plain tube , these results show that the use of internal ribs enhance the heat transfer rate and found to possess the highest performance factors for turbulent flow

Effect of energy spectrum law on clustering patterns for inertial particles subjected to gravity in Kinematic Simulation

We study the clustering of inertial particles using a periodic kinematic simulation. Particles clustering is observed for different pairs of Stokes number and Froude number and different spectral power laws (1.4 6 p 6 2.1). The main focus is to identify and then quantify the effect of p on the clustering attractor - by attractor we mean the set of points in the physical space where the particles settle when time tends to infinity. It is observed that spectral power laws can have a dramatic effect on the attractor shape. In particular, we observed a new attractor type which was not present in previous studies for Kolmogorov spectra (p = 5/3)

To Assess Sleep Quality among Pakistani Junior Physicians (House Officers): A Cross‑sectional Study

Background: Sleep deprivation among junior physicians (house officers) is of growing concern. In developed countries, duty hours are now mandated, but in developing countries, junior physicians are highly susceptible to develop sleep impairment due to long working hours, on‑call duties and shift work schedule. Aim: We undertook the study to assess sleep quality among Pakistani junior physicians. Subjects and Methods: A cross‑sectional study was conducted at private and public hospitals in Karachi, Pakistan, from June 2012 to January 2013. The study population comprised of junior doctors (house physicians and house surgeons). A consecutive sample of 350 physicians was drawn from the above‑mentioned study setting. The subject underwent two validated self‑administered questionnaires, that is, Pittsburgh Sleep Quality Index (PSQI) and Epworth Sleepiness Scale (ESS). Results: A total of 334 physicians completely filled out the questionnaire with a response rate of 95.4% (334/350). Of 334 physicians, 36.8% (123/334) were classified as “poor sleepers” (global PSQI score > 5). Poor sleep quality was associated with female gender (P = 0.01), excessive daytime sleepiness (P < 0.01), lower total sleep time (P < 0.001), increased sleep onset latency (P < 0.001), and increased frequency of sleep disturbances (P < 0.001). Abnormal ESS scores (ESS > 10) were more prevalent among poor sleepers (P < 0.01) signifying increased level of daytime hypersomnolence.Conclusion: Sleep quality among Pakistani junior physicians is significantly poor. Efforts must be directed towards proper sleep hygiene education. Regulations regarding duty hour limitations need to be considered.Keywords: Epworth sleepiness scale, Excessive daytime sleepiness, House officers, Junior physicians, Pittsburgh sleep quality index, Poor sleepers, Sleep disturbances, Sleep qualit