AMIRKABIR
Year:2009 | Volume:20 | Issue:70-A|Papers Count:17

Investigating behavior of natural human ankle shows that its kinetic and kinematics function could be compared with mechanism that contains mechanical elements such as spring, damper and actuator. Hence, designing appropriate mechanism could result an artificial ankle that helps amputees properly. Researches demonstrate prosthesis works well if its biomechanical behaviors be according to the natural limb and residual limbs consume metabolic energy correspond to normal human. In this research, biomechanical behaviors of normal ankle joint in level-walking are studied and these behaviors are estimated by using simple mechanical elements such as spring and actuator. Then, a model will be suggested and according to this model a prototype ankle prosthesis will be designed.

Polyvinyl alcohol (PVA) hydrogels were crosslinked by different molecular weight of diisocyanate chains (168, 2400 and 6000 glmol) in order to profit from the physical-chemical advantages of both PVA hydrogels and urethane groups. Fourier transform infrared spectroscopy employed to confirm urethane formation and the absence of the isocyanate peaks (NCO) at 2270 em-1. With increasing crosslinker chain length, water uptake reduced from 450% for PVA to 120% and the ultimate tensile strength increased from 34 MPa to 54 MPa. The cell viability evaluated by 3- (4, 5-DimethyIthiazol-2-yl) -2, 5-diphenyItetrazolium bromide (MIT) assay on rabbit isolated chondrocytes. In addition, the amounts of proteoglycan secreted by cells in the vicinity of the samples were assessed by dimethyl methylene blue staining protocol which confirmed the highest level for sample 3. The spherical morphology of the isolated cells on the samples verified with scanning electron microscopy (SEM). It can be concluded that crosslinking of the PVA with polyurethane chains (6000 glmol) may consider as a suitable candidate for natural cartilage replacement.

In this study, the blood flow domain inside the diaphragm-type Ventricular Assist Device has been analyzed using numerical Fluid-Structure Interaction method. In the performed analysis, the motion and deformation of the diaphragm, the interaction of blood with the diaphragm and leaflet of valves, the control of opening and closing of the inlet and outlet valves, and also the contact of the valves leaflet with the seats were taken into the account. The blood and driving fluid were modeled as viscous, Newtonian and isothermal, and their flow was also assumed to be laminar. Because of the presence of pulsatile flow, analysis type for fluid and solid domains was the transient dynamic. The results show that during the complete cardiovascular cycle, some wakes appear inside the blood chamber and around the inlet and outlet channels, which generally formed during the diastolic phase. In the systolic phase, these wakes continually move toward the outlet channel and finally, they go to the cardiovascular circulation system.

In this study, a dynamic model of human walking has been made according to the kinematics data of neuropathic patients with drop foot in order to evaluate the role of foot orthosis on generated torque in joints of patients on the sagittal plane. The required kinematics data for the model have been captured through filming by high speed camera and then software analysis. In the dynamic model, the role of foot orthosis has been substituted by a spring and damper between ankle and shank. By changing the constant of spring the generated torque has been examined. Unlike previous researches, the role of orthosis on generated torque has been modeled by muscles and this can improve the role of foot orthosis during abnormal walking.

Layered double hydroxides (LDHs) are nanolayered materials with positively charged layers. A variety of negatively charged biomolecules can be hybridized with LDHs to evolve into bio-LDH nanohybrids, including vitamins, drugs and DNA strands. In this research, Mg-AI-LDH containing drug was synthesized by coprecipitation and anion exchange methods. The LDH structure was characterized by X-Ray Diffraction, FTIR, SEM and STA techniques. Thein vitro release profile of nanohybrids was analyzed by UV spectrophotometer. It was concluded that the present biocompatible hydrotalcite-like compound can be an excellent host material for encapsulating Ibuprofen and can playa role as a delivery vehicle for controlled release.

Unique characteristics of carbon nanotubes are of intense interest in composites applications. The exceptional properties of carbon nanotubes such as mechanical, electrical, chemical, and even their bioactivity, promise introducing new generations of versatile composite materials. Simultaneous use of several properties of carbon nanotubes, as composite matrix reinforcements, may have the potential to apply this unique material to bone tissue-engineering issues such as replacement, healing, and growth of bone. In this paper, some approaches to carbon nanotubes applications in bone tissue engineering are reviewed and a new field of applicable researches is introduced.

In this study, magnetic (Fe3O4) nanoparticles were prepared by controlled chemical co-precipitation technique in alkine medium under N2 gas at room temperature. The obtained powders were characterized by the commonly used bulk techniques of scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infra-red (FTIR), X-ray diffraction (XRD), simultaneously analysis (STA), vibrating sample magnetometer (VSM) and BET analyses, Also the effect of some parameters on the size of Fe3O4 nanoparticles, such as stirring rate and concentration of NaOH was studied. The results indicated that smaller particles can be synthesized by increasing the stirring rate and decreasing the NaOH concentration, which in current case this corresponded to 35 nm using 0.9 M NaOH at 750 rpm.The VSM analysis showed a saturation magnetization range of (82-96 emu/g) and coercivity of (83-119 Oe) for particles between (35-96 nm), respectively. In addition, the highest specific area of 41 m2/g was obtained at 0.9 M NaOH at 750 rpm and the smallest value of 15 m2/g at 1.5 M of NaOH at 450 rpm using BET analysis. Eventually, the rheological properties of magnetite nanoparticles were examined and the results showed that nano-ferrofluid containing magnetite had a shear thining behavior.

In this research, an athlete's body on sagittal plane in the tension phase of snatch weightlifting has been modeled for calculating the generated torques in joints. Then, by means of descending gradient algorithm, the generated torque in joints has been minimized and the power of athlete has been maximized. The method of weightlifting has been captured by high speed camera and the films have been analyzed through motion analysis software. Consequently, the required kinematic data for mathematical model of weightlifter have been produced. In this research, unlike previous research activities, instead of studying the effect of body parameters and sport facilities, the technique of weightlifting has been modified in aid of mathematical modeling in order to enhance the power of athlete.This method is a new experiment to apply modeling for optimization of motions and techniques.

Patients with spinal cord injury in C5/C6 levels are capable of controlling the voluntary movements of the shoulder joints, but some muscles involved in the movement of the elbow joint are paralyzed. By using FES as well as an appropriate stimulation of paralyzed muscles, these patients can be assisted with their essential daily living activities. One of the major problems of using FES for reanimation of paralyzed arm is providing voluntary commands for FES control. In this paper, the feasibility of using synergy has been investigated. The kinematical data of four basic arm movements have been recorded and preprocessed. Afterwards, synergy was implemented in a hierarchical architecture using machine learning techniques (inductive learning and neural networks). Cross correlation between learned and recorded trajectories is above 99% over all recordings, confirm the performance of proposed method.

Multi-phase drive systems have several advantages over conventional three-phase drives such as: reducing the amplitude of torque pulsations, increasing the torque per ampere ratio for the same volume machine, reducing the current per phase without increasing the voltage per phase, and higher reliability.An additional possibility, opened up by the use of multiphase machines, is independent control of a set of series connected motors, supplied from a single voltage source inverter using a appropriate phase transposition in the motor winding connections. Input-output linearization method can be used to linearization of the relation between the induction motor inputs and outputs. Decouple torque and stator flux control of series-connected two-motor five-phase induction motor can be obtained using the linearized model. Simulation results confirm the effectiveness of the proposed control method.