Cardiovascular Biomechanics
Sara Barati; Nasser Fatouraee; Malikeh Nabaei
Volume 15, Issue 4 , March 2022, , Pages 355-366
Abstract
Transcatheter aortic valves have become the standard procedure for high-risk patients with severe aortic valve stenosis. This minimally invasive procedure can expand to a wider range of patients with a lower risk of surgery. The complications after the implantation and the structural malfunction of these ...
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Transcatheter aortic valves have become the standard procedure for high-risk patients with severe aortic valve stenosis. This minimally invasive procedure can expand to a wider range of patients with a lower risk of surgery. The complications after the implantation and the structural malfunction of these prostheses are the obstacles of this transition. Design optimization of the stents of these prostheses can improve their performance and reduce the post-operative complications associated with them. Since all prostheses are crimped before implantation, the designs should guarantee an acceptable structural performance after expansion, especially self-expandable stents for which the fatigue behavior strongly depends on the strain. This study applies a simple, cost-effective optimization framework to optimize the geometric parameters of these stents regarding the maximum strain during the crimping process. The design parameters include diameter profile, cell size, number of repeating components, and strut cross-section. The simplified models are evaluated and verified by the 3D simulations. The results show that the middle cells' height, number of cells, and strut width have the most prominent effect on the maximum crimping strain of the stent. The maximum strain of the optimized stent in the selected design space was 0.52. This stent had a width of 0.2 mm, thickness of 0.3 mm, the number of cells and patterns of 3 and 15, respectively, and the diameter profile associated with the diameter ratio of 1.05. This framework can be applied to a wide range of stent designs and tremendously reduce the cost of stent design and optimization.
Speech processing
Mohammad Bahador Najafi; Mansour Vali
Volume 14, Issue 2 , July 2020, , Pages 97-107
Abstract
After Alzheimer, Parkinson's disease is known as the most common malignant disease of the nervous system. One of the common obstacles of this disease is the expansion of speech disorders. Since the speech production in humans is made by combination of vibration of the vocal cords (phonatory section) ...
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After Alzheimer, Parkinson's disease is known as the most common malignant disease of the nervous system. One of the common obstacles of this disease is the expansion of speech disorders. Since the speech production in humans is made by combination of vibration of the vocal cords (phonatory section) and then passage through the resonator in vocal tract (articulatory section), it is expected that both of these sections to be impaired. In this study, by using a noninvasive method, it is intended to diagnose Parkinson's disease from speech signal of each subject; for this purpose, using 3 sustain vowels in Persian language recorded from 48 people (27 people with Parkinson's disease and 21 healthy people), it has been evaluated to assess the extent of damage to both phonatory and articulatory sections. The phonatory model can include features such as jitter, shimmer, fundamental frequencies, opening and closing cycling time of the glottal pulses. On the other hand, for the articulatory section, features such as first, second, and third formmants, zero crossing rates, MFFCs, and LPC are investigated. In this study, 38 feature categories were extracted and four statistical parameters of mean, standard deviation, skewness and kurtosis were calculated. Genetic Algorithm was used to identify the optimum features. Then, using the SVM, KNN and the Decision Tree classifiers, the optimum extracted features are classified to determine whether a person is patient or healthy. Finally for the main aim of this study, the results of both phonatory and articulatory sections were compared and challenged. The results of this study showed that phonatory features with accuracy of 96.1±1.2% were more useful than articulatory section in diagnosing of Parkinson. Also it was proved that vowel /u/ has more significant role in the diagnosis of Parkinson's disease compared to other vowels by accuracy of 97.6%.
Biological Computer Modeling / Biological Computer Simulation
Reza Vosoughi; Armin Allahverdy; Sajjad Shafiekhani; Amir Homayoun Jafari
Volume 11, Issue 4 , February 2018, , Pages 291-301
Abstract
In recent decades, due to the increased prevalence of diabetes and its chronic complications, glucose measurement, modeling of glucose-insulin system and glucose control have been especially important. Since the type I diabetes does not secrete insulin, cells do not absorb glucose, and thus the blood ...
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In recent decades, due to the increased prevalence of diabetes and its chronic complications, glucose measurement, modeling of glucose-insulin system and glucose control have been especially important. Since the type I diabetes does not secrete insulin, cells do not absorb glucose, and thus the blood glucose level increase. In order to control your blood sugar, insulin should besubcutaneously injected into the body under complex, controlled conditions. If the level of insulin increases beyond the natural physiological range, there is a risk of death. There are various treatments for diabetes, the main treatment of which is insulin therapy. Monitoring the patient's blood sugar level continuously during the day and night is a very good treatment strategy, since it controls the patient's blood sugar level in a safe area with the lowest amount of insulin injected at the required times. This mechanism avoid the hyperglycemia (blood glucose levels greater than 120 mg/dl) and hypoglycemia (blood sugar less than 65 mg / dl). To achieve this goal, a two delay model has been developed to model blood glucose levels continuously during time. Some of the parameters of this model are estimated using the genetic algorithm to achieve the best fitness between the dynamics of the model with the experimental data obtained in this study. As a result, the developed model of this study can dynamically obtain blood glucose continuously during time, consequently it can predicts the insulin dynamics required to be injected into the patient to control the amount of blood glucose in the normal range. Therefore this controlling system is capable of preventing hypoglycemia and hyperglycemia.
Biomedical Signal Processing / Medical Signal Processing / Biosignal Processing
Amin Janghorbani; Mohammad Hasan Moradi; Abdollah Arasteh
Volume 7, Issue 2 , June 2013, , Pages 163-174
Abstract
Acute hypotension episodes (AHEs) are one of the hemodynamic instabilities with high mortality rate that is frequent among many groups of patients. Prognosis of acute hypotension episodes can help clinicians to diagnose the cause of this physiological disorder and select proper treatment based on this ...
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Acute hypotension episodes (AHEs) are one of the hemodynamic instabilities with high mortality rate that is frequent among many groups of patients. Prognosis of acute hypotension episodes can help clinicians to diagnose the cause of this physiological disorder and select proper treatment based on this diagnosis. In this study two groups of features, physiological and chaotic features, were extracted from the physiological time series to be applied for prediction of AHEs in the future 1 hour time interval. The best set of the features from the extracted features were selected using Genetic Algorithm (GA) and were classified by SVM. The prediction accuracy for physiological features was 87.5% and for chaotic features was 85%. In order to improve prediction accuracy, physiological and chaotic features were employed simultaneously in feature selection and the best combination of these features was selected by GA and classified by SVM. The best prognosis accuracy, which was achieved in this study by classification of the selected features, was 95% that was better than other previously studies on the same database.
Biomechanical Motor Control / Motor Control of Human Movement
Hamed Ghomashchi; Ali Esteki; Ali Motie Nasrabadi; Fereydoun Nowshiravan Rahatabad
Volume 4, Issue 3 , June 2010, , Pages 177-185
Abstract
In this study a simple inverted pendulum model with PID controller and delayed feedback is used to model standing-still postural control system for the purpose of achieving useful information about its underlying control structure. Using the Genetic algorithm and an experimental study results, the model ...
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In this study a simple inverted pendulum model with PID controller and delayed feedback is used to model standing-still postural control system for the purpose of achieving useful information about its underlying control structure. Using the Genetic algorithm and an experimental study results, the model and the controller parameters were estimated in a way that the model mimics real experimental sway patterns. The controller parameters found meaningful interpretations and it is shown that degeneration of postural control system affects the values of the parameters. Our findings indicate that although the simple models are not able to describe complexities of postural control system and interactions between its components, they can help us to improve our understanding of postural control system, its performance, its features and the way that the features change.
