Sharif Digital Repository

To help walking, using assistive devices can be considered to reduce the loads caused by weight and to effectively decrease the propulsive forces. In this study, a mobility Saddle-Assistive Device (S-AD) supporting body weight while walking was evaluated on two healthy volunteers. This device is based on the support of body weight against gravity with the help of a saddle, which is not used in other passive mobility assistive devices. To prove the efficiency of this device, the experimental results obtained while walking with this device were compared with those related to walking without the assistive device. The results showed that this device could significantly reduce the forces and... 

The majority of the people with incomplete spinal cord injury lose their walking ability, due to the weakness of their muscle motors in providing torque. As a result, developing assistive devices to improve their conditionis of great importance. In this study, a combined application of the saddle-assistive device (S-AD) and mechanical medial linkage or thosis was evaluated to improve the walking ability in patients with spinal cord injury in the gait laboratory. This mobile assistive device is called the saddle-assistive device equipped with medial linkage or thosis (S-ADEM). In this device, a mechanical orthosis was used in a wheeled walker as previously done in the literature. Initially,... 

Physical problems caused by fractures, aging, stroke, and accidents can reduce foot power; these, in the long term, can dwindle the muscles of the waist, thighs, and legs. These conditions provide the basis for the invalidism of the harmed people. In this study, a saddle-walker was designed and evaluated to help people suffering from spinal cord injury and patients with lower limb weakness. This S-AD works based on body weight support against the previously report designs. This saddle-walker consisted of a non-powered four-wheel walker helping to walk and a powered mechanism for the sit-to-stand (STS) transfer. A set of experiments were done on the STS in the use of the standard walker and... 

Titanium does not react well with the human tissues and due to its bio-inert nature the surface modification has yet to be well-studied. In this study, the sonoelectrochemical process has been carried out to generate TiO2 nanotube arrays on implantable Ti 6–4. All the prepared nanotubes fill with the vancomycin by immersion and electrophoresis method. Drug-releasing properties, antibacterial behavior, protein adsorption and cell attachment of drug-modified nanotubes are examined by UV–vis, flow cytometry, modified disc diffusion, BSA adsorption, and FESEM, respectively. The most uniform morphology, appropriate drug release, cell viability behavior and antibacterial properties can be achieved... 

A significant portion of Iranian flat breads are produced in semi-industrial, indirect-heating ovens. Therefore, an efficient oven design and a proper selection of operating conditions are crucial to improve the product quality and reduce energy consumption. In the present study, a mathematical model is developed to simulate a semi-industrial, indirect-heating, continuous oven performance during contact baking of an Iranian flat bread, referred to as Taftoon. Individual modes of heat transfer are considered among various components of the baking system to estimate the system performance and the bread quality in terms of design and operating conditions. The predictions of this model are in... 

A gradient derived base layer extractive phase was synthesized and applied for the determination of volatile organic compounds (VOCs) in saliva samples using the headspace cooled in–tube microextraction (HS–CITME) method. The base layers from three different sols of phenyltriethoxysilane (PTES), octyltrimethoxysilane (OTMS) and methyltrimethoxysilane (MTMS) as nonpolar precursors were individually dip coated on the stainless steel wires (SSW). Then, the hydrolyzed polar precursor aminopropyltriethoxysilane (APTES) reacted with the silanol groups already formed on the surface of SSWs via controlled rate infusion (CRI) method. The presence of polar and non–polar functional groups on the... 

In this paper, the coupled equations of nonlinear vibrations of a rigid two-dimensional rotor supported on tilting-pad-journal-bearing under harmonic excitation have been studied using second-order multiple scales method. By considering a nonlinear quadratic model for tilting-pad-journal-bearings, the governing coupled nonlinear differential equations of motion are presented. The frequency response function of the system, the effect of excitation force on the response, and stability of the system are discussed in different operating conditions using the method of multiple scales and validated with a numerical method. The results show that the system may have hardening or softening behavior... 

The gas chromatography retention indices of 168 pesticides were used to construct a robust quantitative structure - retention relationship (QSRR) model. After outlier detection by Cook's influence measurement, the remaining compounds were subjected to two different modeling strategies. The first one was stepwise multiple linear regression (stepwise-MLR). Results of this method revealed that 81.7 percent of variances of the response could be explained by the model. The other strategy was kernel orthogonal projection to latent structure (KOPLS). R2 and RMSE values for the prediction set established by Monte Carlo cross validation of the KOPLS were 0.906 and 0.093, respectively. Y-randomization... 

This article presents a model to simulate the behavior of a magnetic shape memory alloy while harvesting vibratory energy. In this type of energy harvester, magnetic shape memory alloy element is placed in the air gap of a ferromagnetic core which conducts the magnetic flux. Two apparent coils are wound around a ferromagnetic core: one to produce bias magnetic field by passing a rectified electric current and the other to serve as an energy pickup coil. Applying compressive time-variant strain field to magnetic shape memory alloy element changes its dimensions and magnetic properties as well. Presence of the bias magnetic field returns magnetic shape memory alloy element to its initial state... 

An analytic expression for energy and angular dependence of a secondary charged lepton in the decay of a polarized top quark with anomalous tWb couplings in the presence of all anomalous couplings are derived. The angular distribution of the b-quark is derived as well. It is presented that the charged lepton spin correlation coefficient is not very sensitive to the anomalous couplings. However, the b-quark spin correlation coefficient is sensitive to anomalous couplings and could be used as a powerful tool in the search for non-SM coupling. © 2007 IOP Publishing Ltd  

In this paper we study the noncommutative effects to the lepton spectrum from the decay of a polarized top quark. It is shown that the lowest contribution comes from the quadratic terms of the noncommutative parameter. The deviations from the standard model are significant for small values of the noncommutative characteristic scale. However, the charged lepton spin correlation coefficient has a remarkable deviation from the standard model from very low values of the noncommutative characteristic scale to 1 TeV. © 2006 The American Physical Society  

In this paper, a modified partial derivative method is developed to predict the linear and nonlinear dynamic coefficients of tilting-pad journal bearings with journal and pad perturbation. To this end, Reynolds equation and its boundary conditions along with equilibrium equations of the pad are used. Finite difference, partial derivative method, and perturbation technique have been employed simultaneously for solving these equations. The accuracy of the results is investigated by comparing the linear dynamic coefficients of three types of tilting-pad journal bearings with those published the literature. It is shown that the nonlinear dynamic coefficients depend on Sommerfeld number,... 

Vapor pressure and liquid density of 20 pure alcohols were correlated using an artificial neural network (ANN) system and statistical associating fluid theory (SAFT) equation of state. The SAFT equation has five adjustable parameters as temperature-independent segment diameter, square-well energy, number of segment per chain, association energy and association volume. These parameters can be obtained by a non-linear regression method using the experimental vapor pressure and liquid density data. In continue, the vapor pressure and liquid densities of pure alcohols were estimated by using an artificial neural network (ANN) system. In the neural network system, it is assumed that thermodynamic... 

In this study a system for real-time analysis of some involving factors in the efficiency of gas-liquid separators is developed based on the weighing method. An ultrasonic atomizer generates water drops in a size range of 1-10 μm with the same frequency during the test. A cyclone separator is selected and effect of the developing flow rate and shape of the mini-riser as a part of connecting assembly to the cyclone separator is investigated. Further an efficient electrostatic precipitator (ESP) with outcome of single-phase airflow is employed in the downstream of the cyclone to separate remaining droplets and produce the same pressure loss during the test. Circular, triangular, rectangular... 

In this experimental study the effect of physical and thermal properties of various FRP bars on their performance under elevated temperatures are investigated. The parameters included the bars' diameter, type of fiber, type of resin, fiber to matrix ratio, and thermal properties were studied. Moreover, ANOVA (ANalysis Of VAriance) was performed in order to investigate the contribution of each variable on the obtained results. The results showed that in addition to the temperature, the bars' diameter, type of fiber, type of resin, and thermal properties (Tg and Td) of the FRP bars have contributions to the results, while the fiber to matrix ratio was found to be an ineffective factor. It was... 

This paper presents the creep behavior of various FRP (GFRP, CFRP, and hybrid) bars in order to investigate the effects of different parameters, including the applied stress levels, bar diameter, and the type of fiber and resin in the creep behavior of FRP bars. The creep strains versus time curves were experimentally obtained for 83 days. Moreover, a statistical study, including analysis of variance (ANOVA) and linear Bayesian regression was conducted to investigate the contribution of the studied parameters. The results showed that in GFRP bars the ratio of ultimate creep strain to the initial elastic strain decreased when the applied stresses on the bars exceeded 30% of their ultimate... 

In this paper, a modified partial derivative method is developed to predict the linear and nonlinear dynamic coefficients of tilting-pad journal bearings with journal and pad perturbation. To this end, Reynolds equation and its boundary conditions along with equilibrium equations of the pad are used. Finite difference, partial derivative method, and perturbation technique have been employed simultaneously for solving these equations. The accuracy of the results is investigated by comparing the linear dynamic coefficients of three types of tilting-pad journal bearings with those published the literature. It is shown that the nonlinear dynamic coefficients depend on Sommerfeld number,...