Non-linear screening of external charge by doped graphene

We solve a nonlinear integral equation for the electrostatic potential in doped graphene due to an external charge, arising from a Thomas-Fermi (TF) model for screening by graphene's $\pi$ electron bands. In particular, we study the effects of a finite equilibrium charge carrier density in graphene, non-zero temperature, non-zero gap between graphene and a dielectric substrate, as well as the nonlinearity in the band density of states. Effects of the exchange and correlation interactions are also briefly discussed for undoped graphene at zero temperature. Nonlinear results are compared with both the linearized TF model and the dielectric screening model within random phase approximation (RPA). In addition, image potential of the external charge is evaluated from the solution of the nonlinear integral equation and compared to the results of linear models. We have found generally good agreement between the results of the nonlinear TF model and the RPA model in doped graphene, apart from Friedel oscillations in the latter model. However, relatively strong nonlinear effects are found in the TF model to persist even at high doping densities and large distances of the external charge.Comment: 12 pages including 6 figure

Scalable and Reliable Middlebox Deployment

Middleboxes are pervasive in modern computer networks providing functionalities beyond mere packet forwarding. Load balancers, intrusion detection systems, and network address translators are typical examples of middleboxes. Despite their benefits, middleboxes come with several challenges with respect to their scalability and reliability. The goal of this thesis is to devise middlebox deployment solutions that are cost effective, scalable, and fault tolerant. The thesis includes three main contributions: First, distributed service function chaining with multiple instances of a middlebox deployed on different physical servers to optimize resource usage; Second, Constellation, a geo-distributed middlebox framework enabling a middlebox application to operate with high performance across wide area networks; Third, a fault tolerant service function chaining system

Effect of Slice Thickness on the Accuracy of Linear Measurements Made on Cone Beam Computed Tomography Images (InVitro)

Objective: Cone beam computed tomography (CBCT) is applied for the imaging of the maxillofacial and dental structures, particularly for surgical treatments and dental implants. The aim of this study was to assess the effect of slice thickness on the accuracy of CBCT linear measurements. Methods: In this diagnostic accuracy study, forty-two titanium pins with the same dimensions were inserted into seven dry sheep mandibles. The length of the pins before the insertion was carefully measured by a digital caliper, (0.01mm accuracy). Imaging of the mandible performed using CBCT New Tom VGi. After image reconstruction by NNT Viewer, linear measurements were made on cross-sectional slices (thicknesses of 0.125, 0.5, 1 and 2mm) by three radiologists. The accuracy of measurements assessed using descriptive indices and compared between different slice thicknesses by repeated measures ANOVA.Results: Repeated measures ANOVA showed a significant difference between different slice thicknesses (P=0.024). According to the least significant difference (LSD) test, the difference in absolute errors was significant in all thicknesses (P=0.024). Measurements at 0.125 mm thickness were significantly different from others, with a higher error rate (mean absolute error=0.17). Measurements at 0.5mm thickness showed a significant difference with those at 0.125 and 2mm (mean absolute error=0.15). Measurements at 2mm thickness were significantly different from those at 0.125 mm thickness (mean absolute error=0.13).The average error rate was lower in 2mm thickness and the measurements were more accurate.Conclusion: A statistically significant difference was seam between CBCT measurements and actual sizes in different slice thicknesses. The differences were below 1mm, and clinically acceptable

Study of inter story drift demands of multi-story frames with RBS connection

RBS connections are one of the most common deformable connections in the world. The plastic hinge will be placed in a conducted mode at a specific area in the beam using this type of connection. It is worth to mention that reducing the sectional area of the beam flange, in general, will cause a reduction in the strength and lateral stiffness of the structure. Hence, the effect of fabrication of the RBS connection, on the frame stiffness and lateral displacement of steel bending frames is analyzed. Regarding the high effect of drift on building’s damages, the effect of fabrication of RBS connections on increasing or decreasing of the frame drift are analyzed. In order to investigate the effect of fabrication of RBS connections, the results of RBS connection are compared with the results of cover plate connection. Keywords: Steel rigid connection; RBS connection; Cover plate connection; Drift; Time History

The effect of acceptance and commitment therapy on emotional stability and alexithymia in female students

Background: Mental disorders can cause many problems in students' academic performance and also severely affect their cognitive, emotional, moral and social development. The aim of this study was to evaluate the effectiveness of acceptance and commitment therapy (ACT) on emotional stability and alexithymia in female second-grade high school students. Methods: The present study was a quasi-experimental with a pretest-posttest design. The statistical population included all girls’ second grade students of the second secondary school in District 8 of Tehran. The sample size consisted of 118 students who were selected by stratified random sampling and assigned to two groups of 59 people as experimental and control groups). Data collection tools were emotional adjustment measure (EAM), Toronto alexithymia scale (TAS-20), and the ACT protocol. Data analysis was done using SPSS V.21 and multivariate analysis of covariance, and significance level was considered ≤ 0.05. Results: The findings showed that after adjusting the pre-test scores, ACT in the post-test has a significant effect on the Lack of regulation of emotional and physiological arousals, and despair and wishful thinking with values (F=90.143, F=178.324 respectively, P<0.001). Also, after adjusting the pre-test scores, ACT in the post-test showed a significant effect on the difficulty in identifying feelings (P<0.001, F=91.278), difficulty in describing feelings (P<0.001, F=189.328), and externally-oriented thinking (P<0.001, F=165.544). Conclusion: Based on the results, ACT training had a positive influence on emotional stability and alexithymia of high school students; the implementation of this protocol in schools and counseling centers is recommended

Study of Stiffness Effect of Panel Zone on Ductility of RBS Joint

Beam to column joint fractures on steel structures in Northridge earthquake produced some worries about the reliability of steel connections. Brittle fracture of bending joints indicated that ductility of construction materials doesn't ensure structure ductility, and structure geometry, loading type, and other specifications influence structure behavior. Stress (strain) concentration due to seismic moment changes may prevent distribution of plastic zone around joint, and this can be a justification for joint brittle fracture. RBS joint is one that came after Northridge earthquake, which is known as dog bone joint. In this kind of joint, by minimizing section of beam flange near support area (in which possibility of plastic joint formation is more), plastic joint is transferred from column side and joint area to inside beam and at proper interval with joint. To design this joint and achieve the goal of formation and development of plastic hinge in reduced area, many parameters must be considered. Panel zone is one of the most effective parts of a rigid steel joint. Resistance and stiffness value of panel zone has a large effect on behavior and performance of joints. This paper studies these kinds of joints and effects of changes in panel zone using cross-shaped substructure and ANSYS software. Regarding to the studies it was indicated that weak panel zone doesn't develop plastic hinge in beam, so collapses merely occurs in panel zone and joint area. In specimens with strong panel zone, because of elastic behavior of panel zone, all substructure energy is wasted in beam, so panel zone is not used efficiently

The Effect of Three-Dimensional Earthquake P-Wave Propagational Speed on Buried Continues Straight Steel Pipelines

The analysis and design of gas and oil pipelines is of importance given the fact that they are long and go through lands. They are laid besides the faults and sometimes cross the faults. Various studies have already investigated the design process and the damages imposed on the pipelines crossing the faults. The aim of this research is studying the effect of longitudinal wave propagation method on the amount of nonlinear strains of pipeline. In addition, it investigates the effect of wave propagation speed as well as the simplified hypothesis of the same effect of the wave on the pipeline. Many researchers study on modal analyses or two-dimensional analyses. In this paper used three-dimensional modeling with propagational P-wave. It should be mentioned that analyses carried out on both clayey and sandy soil with different propagational speed in each of them. The accuracy of the proposed analyses is validated by the comparison of the proposed solution results with some existing solutions.  According to the analyses, it became obvious that in dense soil the amounts of strain are less than soft soil. This amounts to 71 per cent in a sinusoidal wave. The average of the values of the reduced strain in different type of soil could reduce the amount of strain to be considered equal to 0.592 for clayey soils, and equal to 0.61 for sandy soil

The Effect of P-Wave Propagation on the Seismic Behavior of Steel Pipelines

Underground structures perceived as one the most vital infrastructures,which include a variety of tunnels, subway lines,gas, oil and water pipe. Plenty of studies devoted to the investigationof the effect of wave propagation method on the seismicbehavior of steel pipelines. It should be mentioned thatanalyses have been carried out on both clayey and sandy soilwith different propagation speed in each of them. The aim ofthis research is the investigation of the effect of longitudinalp-wave propagation method on the amount of nonlinear strainsof pipeline with different way such as Pipe and Psi element or2D modelling of soil. It became evident that the amounts ofMaximum tension strain produced in the pipe have the maximumdifference, equaling 3.4 per cent. In addition, it investigatesthe effect of frequency of input motion on nonlinearstrains and the effect of frequency content in the results. &nbsp