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This paper presents a real-time digital simulator (DRTS) for possible use in testing of medical devices. The simulator runs a model of a physiological system (an organ or a group of organs) in real time and uses A/D and D/A cards to interface the simulation results to real medical equipment. With this simulator, the tests can be made as thorough as needed without much increase in cost
This paper presents a real-time digital simulator (DRTS) for possible use in testing of medical devices. The simulator runs a model of a physiological system (an organ or a group of organs) in real time and uses A/D and D/A cards to interface the simulation results to real medical equipment. With this simulator, the tests can be made as thorough as needed without much increase in cost
Joint stiffness, defined as the relation between the angular position of a joint and the torque acting about it, can be used to describe the dynamical behavior of the human ankle during posture and movement. Joint stiffness can be separated into intrinsic stiffness and reflex stiffness, which are modeled as a linear system and a Hammerstein system, respectively. A two-pathway parallel cascade model,...
Joint stiffness, defined as the relation between the angular position of a joint and the torque acting about it, can be used to describe the dynamical behavior of the human ankle during posture and movement. Joint stiffness can be separated into intrinsic stiffness and reflex stiffness, which are modeled as a linear system and a Hammerstein system, respectively. A two-pathway parallel cascade model,...
The system which provides short-term cardiovascular regulation has a very complex structure, resulting from the non-linear interaction among several different mechanisms: they include baroreceptors, peripheral chemoreceptors, lung-stretch receptors, a direct CNS response to hypoxia and hypercapnia, local vessel response to changes in blood gas content. Furthermore, during dynamic exercise a feedforward...
The system which provides short-term cardiovascular regulation has a very complex structure, resulting from the non-linear interaction among several different mechanisms: they include baroreceptors, peripheral chemoreceptors, lung-stretch receptors, a direct CNS response to hypoxia and hypercapnia, local vessel response to changes in blood gas content. Furthermore, during dynamic exercise a feedforward...
Accurate cardiac tissue-based modeling using the bidomain equations requires the incorporation of fine-scale structures observed at the 50-100 micron level. By including such features we can more easily observe how defibrillation shocks lead to total depolarization of the heart. Several modeling studies that have investigated the effect of fine scale structures on defibrillation success have been...
Accurate cardiac tissue-based modeling using the bidomain equations requires the incorporation of fine-scale structures observed at the 50-100 micron level. By including such features we can more easily observe how defibrillation shocks lead to total depolarization of the heart. Several modeling studies that have investigated the effect of fine scale structures on defibrillation success have been...
Computational modeling and simulation can provide important insights into the electrical and electrophysiological properties of cells, tissues, and organs. Commonly, the modeling is based on Maxwell's and Poisson's equations for electromagnetic and electric fields, respectively, and numerical techniques are applied for field calculation such as the finite element and finite differences methods. Focus...
Computational modeling and simulation can provide important insights into the electrical and electrophysiological properties of cells, tissues, and organs. Commonly, the modeling is based on Maxwell's and Poisson's equations for electromagnetic and electric fields, respectively, and numerical techniques are applied for field calculation such as the finite element and finite differences methods. Focus...
Two hidden Markov models (HMMs) were designed to identify sub-groups of chronic lower back pain (CLBP) subjects based on time series of lifting parameters obtained during a repetitive lifting task. Two simulation studies were conducted to determine the reliability of this approach, using data from the repetitive lifting study. The first simulation verifies that control and CLBP HMMs based on these...
Two hidden Markov models (HMMs) were designed to identify sub-groups of chronic lower back pain (CLBP) subjects based on time series of lifting parameters obtained during a repetitive lifting task. Two simulation studies were conducted to determine the reliability of this approach, using data from the repetitive lifting study. The first simulation verifies that control and CLBP HMMs based on these...
Most physical systems are nonlinear and often time-varying. Constructing accurate models for nonlinear systems require specialized model structures that include their nonlinearities, whereas models of time-varying systems must include the time courses of the model's parameters. This contribution implements a technique in which the time dependence of the system's parameters are modeled by projecting...
Most physical systems are nonlinear and often time-varying. Constructing accurate models for nonlinear systems require specialized model structures that include their nonlinearities, whereas models of time-varying systems must include the time courses of the model's parameters. This contribution implements a technique in which the time dependence of the system's parameters are modeled by projecting...
A bidomain reaction-diffusion model of the human heart was developed and potentials resulting from normal depolarization and repolarization were compared with results from a compatible monodomain model. Comparisons were made for an empty isolated heart and for a heart with fluid-filled ventricles. Both sinus rhythm and ectopic activation were simulated. The model took 2 days on 32 processors to simulate...
A bidomain reaction-diffusion model of the human heart was developed and potentials resulting from normal depolarization and repolarization were compared with results from a compatible monodomain model. Comparisons were made for an empty isolated heart and for a heart with fluid-filled ventricles. Both sinus rhythm and ectopic activation were simulated. The model took 2 days on 32 processors to simulate...
ST-segment depression in epicardial electrograms can be a "reciprocal" effect of remote myocardial ischemia (MI), and can also be due to local partial-thickness or "subendocardial" MI. Experimental studies have shown either ST elevation or depression in leads overlying a subendocardial ischemic region. Those reporting elevation have shown depression over the lateral borders of...
ST-segment depression in epicardial electrograms can be a "reciprocal" effect of remote myocardial ischemia (MI), and can also be due to local partial-thickness or "subendocardial" MI. Experimental studies have shown either ST elevation or depression in leads overlying a subendocardial ischemic region. Those reporting elevation have shown depression over the lateral borders of...
Attempts to terminate monomorphic tachycardia by rapid pacing occasionally lead to acceleration of the tachycardia rate followed by fibrillation. Previous experimental studies have shown that rapid pacing can convert a single-wave functional reentry into a stable multi-wave reentry with accelerated rate, but only when the single spiral rate is significantly lower than the rate the tissue can sustain...
Attempts to terminate monomorphic tachycardia by rapid pacing occasionally lead to acceleration of the tachycardia rate followed by fibrillation. Previous experimental studies have shown that rapid pacing can convert a single-wave functional reentry into a stable multi-wave reentry with accelerated rate, but only when the single spiral rate is significantly lower than the rate the tissue can sustain...
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