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Total hip Arthroplasty is one of the most common surgeries in elderly people around the world. In spite of many successful cases, a few failures are still reported, a significant number of which relates to the effects of stress shielding. Many scientists have been working on solving this problem by enhancing the material and/or the geometry of the hip prostheses' stems. For example, hollow-stemmed hip prostheses have been designed and tested. In this study, 30 hollow-stemmed samples were designed which were different in terms of geometry and dimension of their holes as well as the materials defined for them. Then, they were tested through finite element modeling along with validating and verifying the results using experimental and convergence tests. The results including displacements, maximum stress values and consequent safety factors were compared based on the reactions of the samples against various static loads including the loads predefined by ISO 7206-4 as well as the loads which had been previously obtained. D 2 designs show the least stiffness compared to other designs. Designs with 132.66 mm2 hole area are the most promising layouts for reducing weight and providing the most amount of medullary space for revascularization of the femur. In spite of designs which predictably help revascularization more than D 2 designs, these designs which are of the multi-hole patterns seemed to represent the best outcomes in terms of preventing stress shielding and consequently the best pattern for creating holes in the stem according to the precedence of stress shielding over other problems. The results prove the possibility of representing a promising structure which helps to reduce the weight, stress shielding and the lack of revascularization of the femur. [ABSTRACT FROM AUTHOR]

With the onset of the warm and cold season, the temperature inside the building goes far away from the human comfort condition, so an optimal energy source is needed to reach the desired temperature. Naturally, the earth is a massive source of heat that is easily accessible under the buildings, yards, and squares of the city; therefore, the geothermal heat exchangers can be used in depth of the ground to drain the heat from the earth. In optimizing heat transfer equipment to achieve higher energy efficiency, the focus is on reducing the size of the heat exchanger on the one hand and increasing the intensity of heat transfer area on the other hand. Helical heat exchangers are compact and can be used in geothermal systems to receive energy. In this paper, a conical coil tube geothermal heat exchanger is simulated according to the environmental conditions of Tehran, the capital city of Iran, and the potential of using such system is examined by changing the geometric parameters and operational requirements. The coil diameter, coil pitch and the angle of conic of the helical tube are varied for the heat exchanger buried at a depth of 3 m from the earth surface. The soil temperature profile is obtained from the air temperature data Synoptic Meteorological Station. Design parameters are coil diameter, coil pitch, cone angle, length to width ratio of the fin, number of fins and Reynolds number. Taguchi algorithm is applied to find the best geometric parameters. Finally, different volume fractions of Al 2 O 3 nanoparticles are added to the optimized geometry to enhance the heat transfer rate. Results indicate that the optimized geometry considering thermal-hydraulic performance in the range of this study is θ = 0 ° ,   D c = 1000   m m ,   P c = 60   m m ,   R e = 3000 ,   R = 1   a n d   F n = 6 for cone angle, coil diameter, coil pitch, Reynolds number, length to width ratio of fin and number of fins respectively. Changing the objective to increase heat transfer (Nusselt number) the optimized values alter to θ = 3.14 ° ,   D c = 1000   m m , P c = 80   m m ,   R e = 4993 ,   R = 1.5   a n d   F n = 6 . Heat flux on the surface of the tube increases to 18% for 0.5% volume fraction of nanoparticles. [ABSTRACT FROM AUTHOR]

A novel robotic plasma magnetron mole with a 50 cm long cathode was designed, fabricated, and operated. The reason for this endeavor is to alleviate the problems of unacceptable resistive heating of stainless steel vacuum tubes in the BNL Relativistic Heavy Ion Collider (RHIC). The magnetron mole was successfully operated to copper coat an assembly containing a full-size, stainless steel, cold bore, RHIC magnet tubing connected to two types of RHIC bellows, to which two additional pipes made of RHIC tubing were connected. To increase the cathode lifetime, a movable magnet package was developed, and the thickest possible cathode was made, with a rather challenging target to substrate (de facto anode) distance of less than 1.5 cm. Achieving reliable steady state magnetron discharges at such a short cathode to anode gap was rather challenging, when compared to commercial coating equipment, where the target to substrate distance is 10's cm; 6.3cm is the lowest experimental target to substrate distance found in the literature. Additionally, the magnetron developed during this project provides unique omni-directional uniform coating. The magnetron is mounted on a carriage with spring loaded wheels that successfully crossed bellows and adjusted for variations in vacuum tube diameter, while keeping the magnetron centered. Electrical power and cooling water were fed through a cable bundle. The umbilical cabling system is driven by a motorized spool. Excellent coating adhesion was achieved. Measurements indicated that well-scrubbed copper coating reduced secondary electron yield to 1, i.e., the problem of electron clouds can be eliminated. Room temperature RF resistivity measurement indicated that a 10 µm copper coated stainless steel RHIC tube has a conductivity close to that of pure copper tubing. Excellent coating adhesion was achieved. The device details and experimental results are described. [ABSTRACT FROM AUTHOR]

To match the reflectance profile of desert colors including dark brown, light brown and olive green in the visible-near IR (Vis-NIR) bands, five selected colored pigments were utilized to print woven cotton/nylon fabrics. Multi-walled carbon nanotube particles (MWCNT's) were also added to some of the printing pastes. The reflectance of printed fabrics was evaluated by using spectrophotometric technique. The effect of adding MWCNT's, on washing; light and crocking fastness alongside with colorimetric values of printed samples was evaluated. Furthermore, the water absorption time was measured in order to determine wettability of each printed sample. The results demonstrated that the presence of MWCNT's in concentration range of 0.04-0.12 g kg−1 in printing formulations was found to cause considerable decline in Near Infrared (NIR) reflectance while a surprising increase in visible reflectance of samples was observed. Color characteristics of printed fabrics were noticeably changed even at concentrations as low as 0.12 g kg−1 MWCNTs in printing formulations. Presence of MWCNTs in printing formulations was found to cause a significant increase in wetting time of samples. Also, the results indicated that air permeability of printed samples containing MWCNT's were higher than samples printed with no MWCNTs. Phenomena imposed by MWCNT's presence on pigment printed samples showed very good fastness levels in crocking, washing and light fastness tests. In dark brown sample, adding MWCNTs to the pigment printing pastes could tune the overall reflectance in order to match the standard reflectance profile accepted for use in concealment color of desert areas. © 2013 Wiley Periodicals, Inc. Col Res Appl, 40, 93-98, 2015 [ABSTRACT FROM AUTHOR]

In this article, He's energy balance method is applied for calculating angular frequencies of nonlinear Duffing oscillators. This method offers a promising approach by constructing a Hamiltonian for the nonlinear oscillator. We illustrate that the energy balance is very effective and convenient and does not require linearization or small perturbation. Contrary to the conventional methods, in energy balance, only one iteration leads to high accuracy of the solutions. It is predicted that the energy balance method finds wide applications in engineering problems. [ABSTRACT FROM AUTHOR]

In this study, based on kinematics data in steppage gait, a finite element model of human gait with ankle-foot orthosis (AFO) has been proposed to optimize the role of AFO through minimizing stress in the patients' sole. The required kinetics data for the model were captured through a force plate and then analysed by 3D-DOCTOR and ANSYS software. In the proposed three-dimensional finite element model the transmitted tension in soft tissue and bones during gait was calculated. By changing the thickness and materials of different layers of sole in AFO the tension variations have been assessed. Unlike previous studies, the effect of orthosis on tension generated in bones and muscles has been dynamically and continuously modelled and the contact between AFO and sole has been considered in this model. By using the optimized sole the stress distribution has been changed by +50.38% in the forefoot, +15% in the midfoot and -37.79% in the hindfoot. The tension reduction in the sole can improve the effect of AFO during abnormal gait. It is possible to design each orthosis sole based on the kinetics data of each patient. [ABSTRACT FROM AUTHOR]

This paper presents comparisons between flow fields for turbulent flow over square cylinder with two different angles of incidence in free stream at Reynolds number of Re = 3400. The present numerical results were obtained using a two-dimensional finite-volume code which solves governing equations. The pressure field was obtained with well known SIMPLE algorithm. The central difference scheme was employed for the discretization of convection and diffusion terms. The v2f and standard k-ε model were used for simulation of turbulent flow. Time averaged velocity, root mean square velocities and streamlines in the downstream of square cylinders are presented. A number of quantities such as Strouhal number, drag coefficient and the length of the wake are calculated for the case of angle of incidence α=0°, 45° with two turbulent models. Strouhal number and the length of the wake are larger for the case ofα=45° because of the sharp corners in it which results in more diffusion of turbulence in the downstream of the cylinder. On the other hand, with comparison of results obtained by v2f and standard k-εmodels with experiment, it is obvious that v2f leads to much more accurate results. [ABSTRACT FROM AUTHOR]

Perturbation methods depend on small parameters which are difficult to find for real-life nonlinear problems. He's parametrized perturbation method, which does not need small parameters, is one of the newest analytical methods to solve nonlinear equations. In this letter some nonlinear heat transfer equations are used as examples to illustrate the simple solution procedures of this method. Comparison of the results obtained by the new method with exact solutions reveals that the method is tremendously effective. [ABSTRACT FROM AUTHOR]

In this paper, nonlinear dispersive equations and seventh-order Sawada–Kotera equation are solved using homotopy perturbation method (HPM) and variational iteration method (VIM). The results obtained by the proposed methods are then compared with that of Adomian decomposition method (ADM). The comparisons demonstrate that the two obtained solutions are in excellent agreement. The numerical results calculated show that the methods can be accurately implemented to these types of nonlinear equations. The results of HPM and VIM confirm the correctness of those obtained by Adomian decomposition method. [ABSTRACT FROM AUTHOR]

Abstract: This letter applies energy balance method and variational iteration method to a nonlinear oscillation of a mass attached to a stretched wire. Comparison of the period of oscillation and obtained solutions with the exact one shows that both methods are very effective and convenient and quite accurate to nonlinear engineering problems. [Copyright &y& Elsevier]

INRODUCTION: Bispectral Index is an objective tool to assess electroencephalographic activity and measure the effect of certain sedatives and hypnotics on the brain. In addition, there are certain subjective tools such as the observer's assessment of alertness and sedation which are used. The correlation between BIS and the concentration of propofol in the brain, and the relationship between these subjective and objective tools in assessing sedation levels are the subject of this study. METHODS: Thirty healthy volunteers enrolled in this prospective observational study. They were sedated with a target controlled infusion of propofol with an initial target of 0.8 µg.mL(-1) and an increase in target to 0.2 µg.mL(-1) ten minutes after equilibration of the predicted and set target concentrations. In each sedation score, the Bispectral Index value and predicted effect site concentration of propofol were recorded and analyzed. Analysis of variance and significant differences between groups were analyzed by paired t-test. Correlations between Bispectral Index and effect site concentration of propofol at each sedation score and the relationship of BIS and effect site concentration of propofol to each sedation score were assessed and analyzed by nonparametric Spearman's rho. RESULTS: The means of Bispectral Index and effect site concentration of propofol at each sedation score showed a significant difference with the following score. Additionally, Bispectral Index and effect site concentration of propofol showed a significant negative correlation in sedation scores 3 and 2 when inducing sedation. In other sedation scores or when reversing the sedation, no strong correlation was noted. CONCLUSION: Both Bispectral Index and effect site concentration of propofol indicate a good estimate of sedation levels; however their correlations are significant and negative only at moderate and deep sedation levels, and during the induction of sedation. [ABSTRACT FROM AUTHOR]