Impact of Torsion Space-Time on ttˉt\bar{t} observables at Hadron Colliders

Starting from the effective torsion space-time model, we study its effects on the top pair production cross section at hadron colliders. We also study the effect of this model on top pair asymmetries at the Tevatron and the LHC. We find that torsion space-time can explain forward-backward asymmetry according to measured anomaly at Tevatron. We find an allowed region in the parameters space which can satisfy simultaneously all $t\bar{t}$ observables measured at Tevatron and LHC.Comment: 17 pages, 6 figures. arXiv admin note: substantial text overlap with arXiv:1207.064

Physical Modeling of Graphene Nanoribbon Field Effect Transistor Using Non-Equilibrium Green Function Approach for Integrated Circuit Design

The driving engine for the exponential growth of digital information processing systems is scaling down the transistor dimensions. For decades, this has enhanced the device performance and density. However, the International Technology Roadmap for Semiconductors (ITRS) states the end of Moore’s law in the next decade due to the scaling challenges of silicon-based CMOS electronics, e.g. extremely high power density. The forward-looking solutions are the utilization of emerging materials and devices for integrated circuits. The Ph.D. dissertation focuses on graphene, one atomic layer of carbon sheet, experimentally discovered in 2004. Since fabrication technology of emerging materials is still in early stages, transistor modeling has been playing an important role for evaluating futuristic graphene-based devices and circuits. The GNR FET has been simulated by solving a numerical quantum transport model based on self-consistent solution of the 3D Poisson equation and 1D Schrödinger equations within the non-equilibrium Green’s function (NEGF) formalism. The quantum transport model fully treats short channel-length electrostatic effects and the quantum tunneling effects, leading to the technology exploration of graphene nanoribbon field effect transistors (GNRFETs) for the future. A comprehensive study of static metrics and switching attributes of GNRFET has been presented including the performance dependence of device characteristics to the GNR width and the scaling of its channel length down to 2.5 nanometer. It has been found that increasing the GNR width deteriorate the off-state performance of the GNRFET, such that, narrower armchair GNRs improved the device robustness to short channel effects, leading to better off-state performance considering smaller off-current, larger ION/IOFF ratio, smaller subthreshold swing and smaller drain-induced barrier-lowering. The wider armchair GNRs allow the scaling of channel length and supply voltage resulting in better on-state performance such as higher drive current, smaller intrinsic gate-delay time and smaller power-delay product. In addition, the width-dependent characteristics of GNR FETs is investigated for two GNR semiconducting families (3p,0) and (3p+1,0). It has been found that the GNRs(3p+1,0) demonstrates superior off-state performance, while, on the other hand, GNRs(3p,0) shows superior on-state performance. Thus, GNRs(3p+1,0) are promising for low-power design, while GNRs(3p,0) indicate a more preferable attribute for high frequency applications

Probing the top quark chromoelectric and chromomagnetic dipole moments in single top tWtW-channel at the LHC

We study the effects of chromoelectric and chromomagnetic dipole moments (CEDM and CMDM) on the production cross section of single top $tW$-channel at the LHC based on the effective Lagrangian approach. We show that the impact of CEDM and CMDM could be large. Using the experimental measurement of the $tW$-channel cross section, constraints on CEDM and CMDM are extracted. These constraints are comparable with the ones obtained from the top pair analysis.Comment: 13 pages, 4 figure

On dynamics of multi-mode systems: process damping effect & FRF modification

Dynamic response of machining systems is the primary information required for determining stability behavior. For the sake of simplicity, machining systems are normally treated as single mode systems in many researches. However, considering multi-mode characteristics and effects of multiple modes introduce new features to machining dynamics. In this thesis, two topics are studied on systems with multiple modes. First, the effect of process damping in multi-mode milling systems is investigated. Stability lobes diagrams are constructed through frequency domain solution and a time domain model is presented to simulate vibrations of the cutting tool. Effects of modes with different frequencies on stability frontier at low speeds are presented and verified experimentally. As the second part of this research, a methodology is developed to modify the dynamic response of structures with respect to their multi-mode characteristics. Using this methodology, the transfer function of a structure can be modified through interaction of structure’s modes. Tool-tip transfer function of a milling machine tool is suppressed and verification has been done through hammer impact tests. Keywords: Multi-mode systems, Process damping, Stability lobes diagram, Chatter, FRF modification, Modes interaction

Experimental Optimization of Using Natural Pozzolan in Chloride Ion Exposed Concrete via Taguchi Method

Concrete durability is one of the most important concerns in the field of construction. The environmentally friendly materials that can provide the durability are of great value in the construction of concrete structures. The use of natural pozzolans is one of the cheapest and most efficient methods in this field, which offers a good performance from environmental and economic point of view and satisfies required engineering parameters. In this study, the effect of using natural pozzolan in the manufacture of concrete exposed to sulfate and chloride ion of Oman sea water was investigated. The Taguchi optimization method was used to reduce the number of samples prepared, reduce the cost of experiments and achieve an optimal mix design. The four parameters, namely water to cement ratio, different percentages of natural pozzolan, super-plasticizer and cement grade with different ratios, were considered as problem variables. The Taguchi optimization method proposed 8 mix designs based on the defined levels for the variables. By constructing 96 samples, two parameters of permeability and water absorption from Oman Sea and drinking water were investigated in the samples. By introducing the results of the experiments into the Taguchi method, the final optimal design was presented by this method, and by constructing 12 additional samples and conducting permeability and water absorption experiments, the behavior of this optimal mix design was verified. The appropriate performance of the Taguchi method was demonstrated by obtaining the optimal mix designs from the Taguchi method, constructing this mix design and comparing the results with the regulation limitations. The results showed that it is acceptable to use natural pozzolan under moderate to severe chloride and sulfate ion attacks, but it is not recommended in the extreme environmental conditions

Relationship between Quality of Sleep and Mental Health among Students Living in Dormitories

Abstract: Introduction: This study was carried out to investigate the sleep quality and its relationship with mental health among students living in dormitories. Methods: In this cross-sectional study, 277 students residing in dormitories of Tehran University of Medical Sciences were selected through stratified random sampling procedure. A demographic questionnaire, Pittsburgh Sleep Quality Index (PSQI) and General Health Questionnaire (GHQ-28) were used for data collection. Chi-square, Spearman and logistic regression were used to analyze the data. Results: The prevalence of sleep disturbance was 73.3% (68.1-78.5) in this sample and the prevalence of poor mental health was 34.4% (28.7-39. 9). The findings showed a significant relationship between quality of sleep and mental health (P<0.001). Conclusion: Our study displayed a significant relationship between quality of sleep and mental health. So interventionist programs are suggested to improve the sleep quality of students ant to prevent mental health disorders among students living in dormitories

Strategic Analysis of Agriculture Students’ Employability by SWOT Technic

Without a doubt, having a high education will help you land a good career, but employers demand more from their workforce to benefit their business. The job market is tough these days. Employees that want to be competitive must possess a variety of employability skills. The primary goal of this study is to show the employability skills required of graduates in agriculture. The study site was at Iran\u27s Bu-Ali-Sina University\u27s Faculty of Agriculture in Hamadan province. There were 45 participants in the study; of these, 15 were lecturers, 15 were employers, and 15 were B.Sc. and M.Sc.-level students. Based on the result of the SWOT analysis strategy for agricultural students\u27 employability are include “Prepare suitable work environment for students to gain work experience”, “before entering the job market, Holding entrepreneurial conferences and seminars to encourage entrepreneurs and explain government support for entrepreneurship”, “also giving government facility and support their new business”, “Increasing practical lessons than theoretical”, “and providing capital for starting a new business”, “To avoid a mental problem student should be chosen according to their interest field”, “and Increasing government funding to provide job opportunity for new graduates youths.

Sleep Quality of Students living in Dormitories in Tehran University of Medical Sciences (TUMS) in 2011

Background & Objectives: Sleep quality is an important factor in student life and affects in their learning process. Sleep problems are related to increased health concerns, irritability, depression, fatigue, attention and concentration difficulties, along with poor academic performance. The aim of this paper is to conduct a survey based on a questionnaire that would characterize the quality of sleep in students living in dormitories of Tehran University of Medical Sciences (TUMS). Methods: We conducted a cross-sectional study using the ..

Evaluation of Posterior Superior Alveolar Canal on Cone Beam Computed Tomography Images

Objectives The posterior superior alveolar artery (PSAA) is one of the branches of the maxillary artery that is located on the lateral wall of the maxillary sinus. The aim of the present study was to evaluate the detectability, position, and diameter of the posterior superior alveolar (PSA) canal and its relationship with the alveolar ridge using cone-beam computed tomography (CBCT).Methods A total of 257 CBCT images were evaluated. The PSA canal location was categorized into three forms of intra-osseous, below the membrane, and on the outer cortex of the lateral sinus wall. The distance between the lower border of the artery and the alveolar crest, the distance between the artery and the medial wall of the sinus, and the diameter of the artery were all measured. The prevalence of sinusitis and mucous retention cyst was also determined. The Chi-square test and independent t-test were used for statistical analysis.Results The most common type of PSA canal was intra-osseous, followed by beneath the mucosal membrane and on the outer cortex of the lateral sinus wall. The lowest distance between the PSA canal and medial sinus wall and ridge crest, and canal diameter were higher in males (P&lt;0.05). In addition, sinus pathologies were significantly more common in males than females (P&lt;0.05).Conclusion The most common type of PSA canal was intra-osseous, and the distances between the lower border of the canal and the alveolar crest and ridge height decreased with aging; thus, it should be considered during implant surgery

Circulating and Eddy Current Losses in Coreless Axial Flux PM Machine Stators with PCB Windings

Printed circuit board (PCB) stators in coreless axial flux permanent magnet (AFPM) machines have been proposed, designed, and studied for use in multiple industries due to their design flexibility and reduction of manufacturing costs, volume, and weight compared to conventional stators. This paper investigates mechanisms and methods of approximating open circuit losses in PCB stators within example wave and spiral winding topologies for a dual rotor, single stator configuration using 3D FEA, analytical hybrid techniques and experiments. The effect of rotor magnet shape, end winding, and active conductor geometry on eddy currents is studied, and some mitigation techniques are proposed. Through stator equivalent circuit analysis, circulating current losses caused by mechanical abnormalities and magnetic circuit asymmetry are assessed. Possible strategies and schemes to minimize circulating current losses are also described. The tradeoff between stator loss components and some practical design considerations are outlined in detail. The open circuit power losses of a prototype coreless AFPM motor were experimentally tested using multiple example PCB stators and emulated rotor asymmetries, with the findings being comparable to the FEA and hybrid analytical methods results