Sharif Digital Repository

The problem of degrees of freedom states that there are several ways to take advantage of the multiple joints of the body to perform a motor skill. This issue was first raised by Nikolai Bernstein. In previous studies on the Bernstein hypothesis, movement coordination has often been evaluated by calculating variance changes in joint movements and using statistical indicators, and synergy analysis has not been used.In this study, the effect of exercise on balance skills in healthy individuals was investigated using synergy analysis. For this purpose, movement data of 8 healthy individuals were recorded in two sessions before and after exercise while maintaining their balance on the balance... 

Our body makes use of many degrees of freedom in muscle space. As a result, there are many solutions for activating muscles when performing a specific task. “how our central nervous system (CNS) controls abundant degrees of freedom?” has been a popular question for researchers in the field of motor control since Bernstein. The existence of muscle synergies is one of the proposed hypothesis, and there is experimental evidence that they are encoded in our CNS as building blocks. The aim of this study is to study the effect of training on the number, structures, and activation profiles of muscle synergies that are used for maintaining balance. For this purpose, electromyography data from 28... 

Stroke is the main cause of disability in the world and the third cause of death, so spreading rehabilitation technique for post stoke patients is one of the most important targets un these days. The first prototype hand rehabilitation device was designed and fabricated in RCSTIM in 2008. Since the first prototype had been proved its effectiveness in clinical tests in the next phase industrial production of the device had to be considered at first all of the problems that had been observed during the clinical tests had to be solved for the future production. In the first series of experiments, clinical limitation and the interaction between the patient and the physiotherapist with the device... 

Spinal cord injury (SCI) is one of the most important causes of disability in the youth and costs enormous expenses for the government. Most SCI subjects use wheelchair as their main way of locomotion while standing and walking can benefit them in various aspects. The role of lower extremity muscles has been investigated in paraplegic gait with active orthoses or in partial weight support condition. However, due to the large expenses of active orthoses, their application have been limited to clinical trials and yet most SCI individuals use traditional AFO and KAFO for walking. The role and significance of trunk and upper extremity muscles (TUEM) has been investigated only in balance... 

Strongly correlated materials are kind of materials in which novel electric and magnetic properties will appear as a result of strong correlations among their electrons like “heavy fermion materials”. Kondo lattice model is a model to describe heavy fermion materials. If we are merely interested in the magnetic properties of heavy fermions we can replace the Kondo lattice Model with the simpler model called the Kondo-necklace model which consists of the interactions only among the spins of the itinerant (conduction) and localized electrons (magnetic impurities) and also the interactions between the spins of the itinerant electrons. In this thesis we investigate the properties of the one... 

In this study, electrochemical oxygen reduction reaction (ORR) was studied on Cu, Pd, Rh, Pd-Cu and Rh-Cu alloys in alkaline solution. Pd-Cu and Rh-Cu alloys were prepared by electrochemical methods. On copper electrode it is found that direct oxygen reduction is accompanied by the electrochemical reductions of copper oxides. Also, mechanism and kinetics of reaction change as the amount of copper oxides increase on the surface. For electrodeposited alloys, it is indicated that the reactivity of Pd-Cu and Rh-Cu alloys toward oxygen reduction is higher than pure Pd and pure Rh. The maximum reactivity among Pd-Cu alloys is related to the sample with 24.5% copper content while the maximum... 

Cavity Quantum Electro-Dynamics (CQED) in Weak, Strong and Ultra-Strong coupling Regimes are studied. A MATLAB m-file is written which is able to solve any arbitrary CQED configuration. This program demands input data such as number of Quantum Dots, number of energy levels of each Quantum Dot, energies of each energy level of Quantum Dots, Number of cavity modes, eign-frequency of each cavity mode, coupling constant, dipole strength of each allowed transition of Quantum Dots and initial state of system from user and begins to solve the Schrodinger equation for annihilation and atomic ladder operators. In addition, coefficients of each possible ket will be calculated. Since, any approximation... 

In this study a new Ni(II)-¬oxazoline complex was synthesized by reaction of Ni(CH3COO)2.4H2O and 2-(2׳-hydroxyphenyl)-2-oxazoline ligand in MeOH solvent. The resulting complex bis[2-(2׳-hydroxyphenyl)-2-oxazolinato]Ni(II), was characterized by different spectroscopic methods. X-ray diffraction showed that this complex is four coordinated with a square planner geometry. The complex was applied as an efficient homogeneous catalyst in C-C coupling Heck reaction of arylhalides with olefins such as methylacrylate. Investigation of the catalytic activity of the complex in Heck reaction between arylhalides and olefins showed high yield and selectivity. For example reaction between iodobenzene and... 

This study investigates the effect of titanium dioxide and magnesium oxide additives on hydroxyapatite synthesized by sol-gel and composite with the predominant phase of hydroxyapatite by in situ method to improve mechanical properties. Scaffold samples were synthesized with nanometer-sized hydroxyapatite and composite powder particles by gel casting and sintered at 1200 ° C. Then, to evaluate the synthesized powders, simultaneous thermal analysis (STA), X-ray diffraction test, FTIR test, FESEM, EDS, and MAP analysis were used. Also, to evaluate the mechanical properties of the scaffolds, a compressive test was used, and to evaluate the scaffolds' density, the Archimedes method was used.... 

Given the complex structure of electronic waste and the difficulty of recycling it by traditional methods, the focus is mainly on biohydrometallurgy method, and in particular on bioleaching. To recover metals, various microorganisms are utilized in this method. In light of previous studies, cyanogenic bacteria have been widely used for the extraction of basic and precious metals. Among the species, indigenous microorganisms have a higher ability to resist toxic environments in the bioleaching of metals due to their adaptation by rapid changes in their metabolic system over time. The main objective of this study is to isolate indigenous microorganisms from electronic waste landfill for their... 

Downhole temperature measurement is one of the key tools for monitoring and analyzing the performance of production wells, evaluating water injection, and identifying multiphase flows within wells. The development of fiber optic technology and tools such as distributed temperature sensors has enabled the recording of high-resolution and detailed temperature profiles. These data, which measure temperature over a wide range along the wellbore, allow researchers to analyze complex downhole processes and identify fluid entry from various reservoir layers. However, accurately distinguishing the contribution of each layer to the total flow rate, especially under multiphase flow conditions and... 

Due to the prominence of the evaluation of the consequences of rising temperatures, this paper examines the effects of temperature variation on mortality across different demographic groups in Iran. I use a rich weekly data set from 2009 to 2017 across different demographic groups to understand the potential health impacts of climate change in a developing country. Using several fixed effect regressions, I discover that for an additional day with a mean temperature over 25°C, mortality rate increases by 2.56% relative to the effects of an extra day in 0-5 °C, in the weekly temperature exposure horizon. I test for the harvesting effect by comparing the estimates at weekly and monthly...