Full Research Paper
Nader Nezafati; Fathollah Moztarzadeh; Saeed Hesaraki; Nasim Nosoudi
Volume 2, Issue 4 , June 2008, Pages 277-283
Abstract
Calcium phosphate cements are among the formable calcium phosphate cements which are widely used for reconstruction of hard tissue injuries. Unfortunately, due to low mechanical strength, the application of such materials is only limited to non-load bearing like skull. We have investigated some mechanical ...
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Calcium phosphate cements are among the formable calcium phosphate cements which are widely used for reconstruction of hard tissue injuries. Unfortunately, due to low mechanical strength, the application of such materials is only limited to non-load bearing like skull. We have investigated some mechanical and characteristics of a calcium phosphate cement which was reinforced with glass fiber. Compressed strength, setting time, phase composition and microstructure of the composite cement were among the cases which were investigated using appropriate techniques. The results indicated that adding only 15 weight percent of glass fiber (with about 100µm diameter) which was prepared using sol-gel method, does not show any meaningful change in the setting time of calcium phosphate cement This period of time was estimated about 20 minutes. Compressed strength of the cements without any fibers was 0.635MPa which was increased by adding fiber to 3.69MPa.The toughness of the cement was changed from 0.098KJ/m2 for cement without any fibers to 0.545KJ/m2 cement containing fibers. The XRD pattern of the composite samples which were maintained in the Ringer's solution showed that the reactant materials of the cement have almost thoroughly converted to hydroxyapatite which in this case does not show much difference with the non-fiber samples. As a whole, it seems that using glass fiber prepared by sol-gel method can considerably increase mechanical strength and toughness of calcium phosphate. This occurs without any effect on the quality of the cement.
Full Research Paper
Fluid-Structure Interaction in Biological Media / FSI
Bahman Vahidi; Nasser Fatouraee
Volume 2, Issue 4 , June 2008, Pages 285-296
Abstract
Arterial embolism is one of the major killers of the people who have heart diseases. In cerebral arteries, the danger of embolism is that the ruptured particles are carried into the brain, provoking neurological symptoms or a stroke. In this research, for the first time, we have presented a numerical ...
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Arterial embolism is one of the major killers of the people who have heart diseases. In cerebral arteries, the danger of embolism is that the ruptured particles are carried into the brain, provoking neurological symptoms or a stroke. In this research, for the first time, we have presented a numerical model to study the complete blockage of the human common carotid artery resulted from the physical motion of a blood clot bulk with spherical geometry in it. In the numerical model, a transient flow was assumed in an axisymmetric finite length tube. The incompressible Navier-Stokes equations were used as the governing equations for the fluid and a linear elastic model was utilized for the blood clot bulk. In order to model the contact conditions between the blood clot and arterial wall, an axisymmetric rigid contact model was used. The arbitrary Lagrangian-Eulerian formulation (ALE) was applied to analyze the solid large displacements inside fluid flow. The results indicated that during contact between stenosis and the clot, separation and reattachment regions were occurred on the stenosis extensively which are susceptible to thrombosis onset and growth. By abruption of the clot from the arterial wall during its passage through the stenosis, an extensive recirculation zone occurred downstream of the stenosis and beneath the moving clot bulk. Analysis of the clot motion and deformation have showed that when the clot passed the stenosis completely, the areas near the clot peak had a large tendency to expand which indicated the propensity of these areas to disperse.
Full Research Paper
Mehran Baboli; Seyed Ali Ghorashi; Namdar Saniei; Alireza Ahmadian
Volume 2, Issue 4 , June 2008, Pages 297-303
Abstract
Ultra Wide Band (UWB) signals are widely used in medical applications. In this paper, we developed a novel non-contact monitoring system to measure the heart rates of patients using UWB signals. The work is performed in two stages. First, a simulated UWB system including a model for human body is developed, ...
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Ultra Wide Band (UWB) signals are widely used in medical applications. In this paper, we developed a novel non-contact monitoring system to measure the heart rates of patients using UWB signals. The work is performed in two stages. First, a simulated UWB system including a model for human body is developed, where heart is simulated using simple layered model, and then its rate is detected. In second stage, real experiments are carried out on human body using UWB radar with 3.2 GHz bandwidth, and a new practical wavelet based algorithm is proposed to detect heart rate. The proposed algorithm has a high precision (98%) and accuracy (92%) and appears to be promising for future monitoring systems.
Full Research Paper
Biological Computer Modeling / Biological Computer Simulation
Pejman Ghassemi; Mohammad Hossein Miranbaygi
Volume 2, Issue 4 , June 2008, Pages 305-315
Abstract
In this research we present a new method to evaluate changes in size and refractive index of Titanium dioxide (TiO2) nanoparticles which are the main component of anti-UV creams. The main objective of this research is assessing the impact of changing in size and refractive index of TiO2 on the polarization ...
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In this research we present a new method to evaluate changes in size and refractive index of Titanium dioxide (TiO2) nanoparticles which are the main component of anti-UV creams. The main objective of this research is assessing the impact of changing in size and refractive index of TiO2 on the polarization state of backscattered light. The proposed technique is based on modeling the propagated polarized laser beam inside a phantom and evaluating the change in the polarization of backscattered light. The phantom is simulated by software to have the polarization properties of anti-UV creams. As scattering particles (TiO2) in these creams configure polarization properties, then through modeling we have simulated the phantom with matrix of resin epoxy that has unit refractive index including Titanium dioxide nanoparticles. It will be shown that size parameter and relative refractive index of these particles influence cream's properties like purity, quality, coating power and degree of filtration and directly affect its polarization properties. The measurement technique which is presented here is based on scattering polarimetry. To assess the scattering phenomenon, the polarization state of incident and backscattered light is analyzed by simulating a laboratory polarimeter. Then polarization information of the simulated phantom is extracted as Mueller matrix and degree of polarization index. All modeling and simulations are performed in MATLAB 2006 and the results are presented towards the end part of the paper. The main outcome of this research is the ability of extracting and the recognition of those elements of the Mueller matrix which are very sensitive to changes in size parameter and relative refractive index of TiO2. That will define the main markers for quality assessment of anti-UV creams.
Full Research Paper
Cardiovascular Biomechanics
Mansour Alizadeh; Iman Mohebbi Nejad
Volume 2, Issue 4 , June 2008, Pages 317-324
Abstract
Mechanical characteristic of arteries is very important for stent producing and cardiovascular implants. In this study mechanical behavior of a piece of left anterior descending coronary artery with specified dimension and separated layers which was prepared by holtzapfel and tested under tensile test ...
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Mechanical characteristic of arteries is very important for stent producing and cardiovascular implants. In this study mechanical behavior of a piece of left anterior descending coronary artery with specified dimension and separated layers which was prepared by holtzapfel and tested under tensile test bas been considered. Ogden hyperelastic model has been implemented for the experimental data and related parameters were obtained. These parameters have been optimized. The obtained results showed that by using the same experimental data the Ogden model can be fitted well with holtzapfel model and the errors fall within acceptable range.
Full Research Paper
Mohammad Ali Ardakani; Vahid Reza Nafisi
Volume 2, Issue 4 , June 2008, Pages 325-333
Abstract
Hot-wire anemometry (HWA) is a suitable method for pulmonary research and routine tests. This anemometry method has high frequency response, calibration stability, low pressure drop and desired precision over whole clinical range of human respiration. Nevertheless, flow direction detection in inspiratory ...
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Hot-wire anemometry (HWA) is a suitable method for pulmonary research and routine tests. This anemometry method has high frequency response, calibration stability, low pressure drop and desired precision over whole clinical range of human respiration. Nevertheless, flow direction detection in inspiratory and expiratory phases is one of the main problems in this method. We apply the obstacle-wake probe as a solution. In this probe, an obstacle is inserted between 2 bot-wire sensors; and the effects of the shape and relative position of the obstacle and hot-wire sensors are discussed. Finally the results are used in manufacturing a clinical spirometer. It satisfies common clinical/research demands along with inspiratory/expiratory flow direction detection.
Full Research Paper
Neuro-Muscular Engineering
Hamid Reza Kobravi; Abbas Erfanian Omidvar
Volume 2, Issue 4 , June 2008, Pages 335-349
Abstract
In this paper an adaptive robust fuzzy controller based on sliding mode control (SMC) approach is proposed to control the knee joint position using quadriceps electrical stimulation and it has been tested on three subjects. The proposed method is based on SMC. The main advantage of SMC derives from the ...
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In this paper an adaptive robust fuzzy controller based on sliding mode control (SMC) approach is proposed to control the knee joint position using quadriceps electrical stimulation and it has been tested on three subjects. The proposed method is based on SMC. The main advantage of SMC derives from the property of robustness to system uncertainties and external disturbances. However, a large value has to be applied to the control gain when the boundary of uncertainties is unknown. Unfortunately, this large control gain may cause chattering on the sliding surface and therefore deteriorate the system performance. In this paper a robust control strategy proposed which is based on the combination of sliding mode, fuzzy logic systems, and an adaptive compensator to reduce the system uncertainties while alleviating the effects of chattering. The fuzzy logic system is used to identify the muscle-joint dynamics. The parameters of this fuzzy system were estimated using another fuzzy system. The controller is evaluated through the simulation studies on a virtual patient and experimental studies on intact subjects. The results show that the adaptive robust controller provides an accurate tracking of desired knee-joint angle for different subjects and different days and can generate control signals to compensate the muscle fatigue and reject the external disturbance.
Technical note
Nasrin Ghazanshahi
Volume 2, Issue 4 , June 2008, Pages 351-356
Abstract
Peritoneal Dialysis (PD) units treat renal failure, partially replacing kidney function by removing metabolic wastes and fluid through selective diffusion and osmosis across the peritoneum. A prototype of PD unit is designed and made for the first time in IROST. Our unit features are control of filling ...
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Peritoneal Dialysis (PD) units treat renal failure, partially replacing kidney function by removing metabolic wastes and fluid through selective diffusion and osmosis across the peritoneum. A prototype of PD unit is designed and made for the first time in IROST. Our unit features are control of filling dialysate flow to peritoneal cavity and draining from it, warming the dialysate to body temperature and controlling the dialysate temperature before filling, Control and monitoring fill time, dwell time, drain time, number of cycles on the basis of dialysis type, computing the ultra filtration, reporting and storing capability, computer connection capability, programming for individual patient, etc. In this unit, all controls and monitoring of different parameters are based on digital and microprocessor system.
