Sharif Digital Repository

In a graph G a vertex v dominates all its neighbors and itself. A set D of vertices of G is (vertex) dominating set if each vertex of G is dominated by at least one vertex in D. The (vertex) domination number of G, denoted by γ (G), is the cardinality of a minimum dominating set of G. A set D of vertices in G is efficient dominating set if every vertex of G is dominated by exactly one vertex of D. For natural numbers n and k, where n > 2 k, a generalized Petersen graphP (n, k) is obtained by letting its vertex set be {u1, u2, ..., un} ∪ {v1, v2, ..., vn} and its edge set be the union of {ui ui + 1, ui vi, vi vi + l} over 1 ≤ i ≤ n, where subscripts are reduced modulo n. We prove a necessary... 

Based on the quasi-adiabatic model, the parameters of the bubble interior for a moving single bubble sonoluminescence in water, adiponitrile, and N-methylformamide are calculated for various fluid viscosities. By using a complete form of the hydrodynamic force, the bubble trajectory is calculated for a moving single bubble sonoluminescence (m-SBSL). It is found that as the fluid viscosity increases, the unique circular path changes to an ellipsoidal and then linear form and along this incrementally increase of viscosity the light intensity increases. By using the Bremsstrahlung model to describe the bubble radiation, gradual increase of the viscosity results in brighter emissions. It is... 

SnO2 is an important functional material having a wide range of applications in gas sensors and optoelectronic devices. There is a great interest for finding new cost-effective and straight-forward methods for production of these particles. In this research, hydrogel thermal decomposition method (HTDM) is used for production of high purity SnO2 nano-particles. Cost effective reactants and green routs of production are the advantages of polysaccharide based hydrogel as starting material for this method. Visual observations indicated that there is very little tendency for agglomeration in the SnO2 nano-particles produced by this method which can be considered as an advantage for this method... 

A complete study of the hydrodynamic force on a moving single bubble sonoluminescence in N-methylformamide is presented in this work. All forces exerted, trajectory, interior temperature and gas pressure are discussed. The maximum values of the calculated components of the hydrodynamic force for three different radii at the same driving pressure were compared, while the optimum bubble radius was determined. The maximum value of the buoyancy force appears at the start of bubble collapse, earlier than the other forces whose maximum values appear at the moment of bubble collapse. We verified that for radii larger than the optimum radius, the temperature peak value decreases  

The mutual interaction of two oscillating gas bubbles in different concentrations of sulfuric acid is numerically investigated. A nonlinear oscillation for spherical symmetric bubbles with equilibrium radii smaller than 10 μm at a frequency of 37 kHz in a strong driving acoustical field Pa =1.8 bar is assumed. The calculations are based on the investigation of the secondary Bjerknes force with regard to adiabatic model for the bubble interior which appears as repulsion or attraction interaction force. In this work the influence of the various concentrations of sulfuric acid in uncoupled and coupled distances between bubbles has been investigated. It is found that the sign and value of the... 

A simple catalyst LiClO4/Et3N has been developed and demonstrated to efficiently catalyze Michael addition reactions of active methylene compounds to conjugated ketones, nitriles, esters and nitroalkenes with remarkably high yields and in short reaction time. The Michael addition to nitroalkenes and α,β-unsaturated ketones proceeds quantitatively in the usual way, giving the monoaddition product. © 2008 Elsevier B.V. All rights reserved  

BACKGROUND AND OBJECTIVES: It is suggested that activation of the transverse abdominis muscle has a stabilizing effect on the lumbar spine by raising intra-abdominal pressure without added disc compression. However, its feedforward activity has remained a controversial issue. In addition, research regarding bilateral activation of trunk muscles during a unilateral arm movement is limited. The aim of this study was to evaluate bilateral anticipatory activity of trunk muscles during unilateral arm flexion.MATERIALS AND METHODS: Eighteen healthy subjects (aged 25 ± 3.96 years) participated in this study and performed 10 trials of rapid arm flexion in response to a visual stimulus. The... 

Objectives: Previous research has shown inconsistent findings regarding muscle endurance in chronic low back pain (CLBP). Questions also remain about muscle endurance in patients with clinical instability. The aim of this study was to investigate trunk muscles strength and endurance in CLBP patients with and without clinical instability. Methods: 32 CLBP patients (15 with and 17 without clinical instability) and 39 matched healthy subjects participated in this study. The standing extension test was performed to assess the strength and endurance of the lumbar extensors while recording their electromyographic activity. The patients' disability was evaluated using the Oswestry and Roland-Morris... 

Based on a quasi-adiabatic model, the parameters of the bubble interior for a moving single bubble sonoluminescence (m-SBSL) in water are calculated. By using a complete form of the hydrodynamic force, a unique circular path for the m-SBSL in water is obtained. The effect of the ambient pressure variation on the bubble trajectory is also investigated. It is concluded that as the ambient pressure increases, the bubble moves along a circular path with a larger radius and all bubble parameters, such as gas pressure, interior temperature and light intensity, increase. A comparison is made between the parameters of the moving bubble in water and those in N-methylformamide. With fluid viscosity... 

This article proposes a novel index along with a user-friendly platform for resilience evaluation of the urban water distribution networks (WDN). WDN is of great importance in preserving the safety and sustainability of communities and cities. Resilience of a given system results in its sustainability. In recent years, many studies have focused on resilient urban WDN. However, these studies did not provide a comprehensive evaluation index and platform that could simultaneously consider hydraulic analysis, resilience parameters, and significant uncertainties. In this study, a novel resilience index was defined, and a user-friendly and practical platform (REWAT) was developed to calculate the... 

1-(2-Hydroxyethyl)-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid ([hemim][NTf2]) was synthesized as a new functionalized ionic liquid to study the effect of addition of the hydroxyl group to the imidazolium cation on aliphatic/aromatic separations. For this purpose, liquid-liquid equilibrium (LLE) data for {heptane + toluene or benzene + 1-(2-hydroxyethyl)-3-methylimidazolium bis (trifluoromethylsulfonyl)imide ([hemim][NTf2])} systems were measured at 313.2 K and atmospheric pressure. The measured LLE data were correlated using three basically distinct thermodynamic models; that is, nonrandom two-liquid (NRTL), Othmer-Tobias, and Hand correlations. Results show that... 

Switched Reluctance Motors (SRMs) are widely used in high-speed and low voltage applications because of their attractive features such as robustness and simplicity. No winding on the rotor of this type of motors allows reaching high speed which is desired for many applications. Drive circuits of SRMs also play an important role in their performance and operation. In this paper, a new bifilar drive circuit for this type of motors has been proposed. This novel configuration has been tested and investigated by PSIM software. Results show that the new bifilar drive circuit highly reduces the voltage stresses on semiconductor switches, and also considerably reduces the switching losses which are... 

A cell spheroid is a three-dimensional (3D) aggregation of cells. Synthetic, in-vitro spheroids provide similar metabolism, proliferation, and species concentration gradients to those found in-vivo. For instance, cancer cell spheroids have been demonstrated to mimic in-vivo tumor microenvironments, and are thus suitable for in-vitro drug screening. The first part of this paper discusses the latest microfluidic designs for spheroid formation and culture, comparing their strategies and efficacy. The most recent microfluidic techniques for spheroid formation utilize emulsion, microwells, U-shaped microstructures, or digital microfluidics. The engineering aspects underpinning spheroid formation... 

Background: Patients who have shoulder pain usually have compensatory or contributory deviation of shoulder motion during arm elevation. In the traditional scapulohumeral rhythm, the share of the acromioclavicular (AC) and the sternoclavicular (SC) joint movements and also the role of AC internal rotation angle are unknown. Objectives: The main purpose of this study was to measure and compare the segmentary scapulohumeral rhythm (SSHR) during scapular arm elevation at a steady rotational speed in athletes with and without impingement syndrome. Patients and Methods: Using a speedometer, the maximum speed of arm elevation was measured in 21 men in each of the involved and uninvolved groups.... 

Regarding the increasing number of electrical devices in the smart homes that leads to increase in total electricity consumption and cost, it is essential to use energy management methods to reduce the electricity cost. However, this can cause resident's dissatisfaction. Hence, it is important to define a method in which cost and dissatisfaction be optimized simultaneously. Among different services, an electric vehicle is the one that can be used as an energy storage system, so it can reduce the daily cost despite of increasing the total energy consumption. In this paper, we study the effect of the EV on the cost and dissatisfaction in our proposed method. © 2018 IEEE  

Using solid-state power amplifiers for next generation of weather radars becomes feasible by pulse compression techniques. In this study a 1.5 kW solid-state power amplifier (transmitter) for C-band weather radars is designed and fabricated by GaN high electron mobility transistor (HEMT) technology. An experimental setup based on heterodyne receiver with 16-bit digitiser is developed to investigate the behavior of the power amplifier under different cooling methods and back-off points. Several measurements with shaped LFM pulse show an approximately identical pulse to pulse (P2P) stability for 3 dB compression, P1dB and 2 dB back-off points while the best sidelobe level (SLL) is achieved for... 

Application of Probabilistic Safety Assessment (PSA) to a Uranium hexafluoride (UF 6) production process is presented in this paper. The process is constituted from three main units: UF 4 conversion to UF 6, condensation of produced UF 6 gas and tail gas treatment. Radioactive gas is present in all parts of the process and occurrence of high pressure or high temperature in the process equipments may lead to radioactive release to workplace and environment. The work is mainly based on PSA experience in nuclear power plants. Accordingly for the process, eight group of Initiating Events (IE) that lead to UF 6 gas release have been identified using HAZOP study. For each IE, based on related... 

In self-controlling hyperthermia therapy, once the desired temperature is reached, the heat generation ceases and overheating is prevented. In order to design a system that generates sufficient heat without thermal ablation of surrounding healthy tissue, a good understanding of temperature distribution and its change with time is imperative. This study is conducted to extend our understanding about the heat generation and transfer, temperature distribution and temperature rise pattern in the tumor and surrounding tissue during self-controlling magnetic hyperthermia. A model consisting of two concentric spheres that represents the tumor and its surrounding tissue is considered and temperature... 

This study investigates the aerodynamic loads and energy losses of a typical 600 kW wind turbine with S816 airfoil blade under two different icing conditions. Three sections at different radial positions were considered to estimate the icing effect along the blade. Ice accretion simulations in wet and dry regimes were carried out using the NASA LEWICE 3.2 computer program. The airflow simulations were performed with CFD method and SST k -ω turbulence model. The results of these simulations, including streamlines, surface pressure, skin friction, lift, and drag coefficients, were inspected for both clean and iced airfoils. In the case of wet iced airfoil, a separation bubble was created in...