Fluid-structure Interaction Simulation of Bileaflet and Monoleaflet Mechanical Heart Valve Flow Dynamics

In this study, opening and closing behavior of monoleaflet and bileaflet prosthetic heart valves was simulated using 2D and 3D Fluid Structure Interaction (FSI) models. The FSI models were based on the arbitrary Lagrangian-Eulerian (ALE) method for moving boundaries. Leaflet and diaphragm motions were described by means of user-defined functions following the experimental setup in a previous study. The hemodynamic performance of monoleaflet valves at the opening angle of 45, 60, 75, 80, and 85 was compared and results from this study demonstrated that the optimal opening angle should fall between 75 and 80. As the opening angle further increased, even though the calculated flow parameters continued to improve, the large angle could prevent the valve to close properly, which might lead to the failure of the heart valve. Furthermore, the hemodynamic performance of bileaflet and monoleaflet heart valves following the design of St. Jude bileaflet valve with 85 of opening angle and Bjork-Shiley monoleaflet valve with 75 of opening angle was compared. Results demonstrated that the flow in the monoleaflet valve design had a lower maximum velocity compared to the bileaflet design during both opening and closing phases which resulted in lower chance for flow to transition to turbulence. The mean pressure gradients across the monoleaflet and bileaflet valves were similar and resulted in an analogous EOA for these valves. According to the results of this study, the bileaflet valve had higher chance of developing cavitation bubbles during the valve closure because of higher pressure drops across the valve.Mechanical & Aerospace Engineerin

A Pareto Front Approach to Bi-objective of Distillation Column Operation Using Genetic Algorithm

In this paper, an exergy analysis approach is proposed for optimal design of distillation column by using Genetic algorithm. First, the simulation of a distillation column is performed by using the shortcut results and irreversibility in each tray is obtained. The area beneath the exergy loss profile is used as Irreversibility Index for exergy criteria. Then, two targets optimization algorithm (SA, Simulated Annealing) is used to maximize recovery and minimize irreversibility index in a column by six different variables (Feed Condition, Reflux Rate, Number of theoretical stage, Feed Trays (Feed Splitting, three variables)). SA uses one objective function for the purpose or alters two targets optimization to one target optimization. Then, GA optimization algorithm is used for two targets optimization except Pareto set which is used instead of objective function; finally, the results are compared with SA results. Then, one pump-around is considered to obtain better results (OPT2). Irreversibility index criterion is compared with exergetic efficiency, constant and variable feed composition splitters are considered.Key words: Exergy analysis; Irreversibility index; Genetic algorithm; Process optimization; Distillation colum

Means-end relations and a measure of efficacy

Propositional dynamic logic (PDL) provides a natural setting for semantics of means-end relations involving non-determinism, but such models do not include probabilistic features common to much practical reasoning involving means and ends. We alter the semantics for PDL by adding probabilities to the transition systems and interpreting dynamic formulas 〈α〉 ϕ as fuzzy predicates about the reliability of α as a means to ϕ. This gives our semantics a measure of efficacy for means-end relations.<br/

Means-end Relations and a Measure of Efficacy

Abstract. Propositional dynamic logic (PDL) provides a natural setting for semantics of means-end relations involving non-determinism, but such models do not include probabilistic features common to much practical reasoning involving means and ends. We alter the semantics for PDL by adding probabilities to the transition systems and interpreting dynamic formulas 〈α〉ϕ as fuzzy predicates about the reliability of α as a means to ϕ. This gives our semantics a measure of efficacy for means-end relations. Keywords: Means-end relations, fuzzy modal logic, propositional dynamic logic, efficacy 1

Means-end relations and a measure of efficacy

Propositional dynamic logic (PDL) provides a natural setting for semantics of means-end relations involving non-determinism, but such models do not include probabilistic features common to much practical reasoning involving means and ends. We alter the semantics for PDL by adding probabilities to the transition systems and interpreting dynamic formulas ¿ as fuzzy predicates about the reliability of a as a means to ¿. This gives our semantics a measure of efficacy for means-end relations

Estimating Cohesive Sediment Erosion and Deposition Rates in Wide Rivers

Sediment erosion and deposition rates are two of the most important factors that influence fluvial geomorphology. Several experimental devices have been constructed to estimate cohesive sediment erosion rate. However, estimated erosion rates may not be reliable for large rivers due to limited soil sampling and a high dependency of cohesive sediment behaviour on several physical, mechanical, and electrochemical properties of the sediment and eroding fluid. A new methodology has been developed to estimate the erosion and deposition rate of wide rivers using in-situ measurements. To test this methodology, an acoustic Doppler current profiler (ADCP) was used to collect bathymetry and velocity profiles over a study area along the Red River in Winnipeg, Canada. Sediment concentration profiles along an 8.5 km reach of the river were measured several times under different flow conditions. Finally, an advection-dispersion equation was numerically solved using measured and calculated streamwise dispersion coefficients, flow and channel characteristics to calculate net erosion and deposition over the study area. Moreover, an exponential relationship was obtained between the river discharge and longitudinal dispersion coefficient for the Red River.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Wave-current induced erosion of cohesive riverbanks in northern Manitoba, Canada

The field of cohesive soil erosion is still not fully understood, in large part due to the many soil parameters that affect cohesive soil erodibility. This study is focused on two channels, 2-Mile and 8-Mile channels in northern Manitoba, Canada, that were built to connect Lake Winnipeg with Playgreen Lake and Playgreen Lake with Kiskikittogisu Lake, respectively. The banks of the channels consist of clay rich soils and alluvial deposits of layered clay, silts and sands. The study of erosion at the sites is further complicated because the flow-induced erosion is combined with the effects of significant wave action due to the large fetch length on the adjacent lakes, particularly Lake Winnipeg that is the seventh largest lake in North America. The study included three main components: field measurements, laboratory experiments and numerical modelling. Field measurements consisted of soil sampling from the banks and bed of the channels, current measurements and water sampling. Grab soil samples were used to measure the essential physical and electrochemical properties of the riverbanks, and standard ASTM Shelby tube samples were used to estimate the critical shear stress and erodibility of the soil samples using an erosion measurement device (EMD). Water samples were taken to estimate the sediment concentration profile and also to monitor changes in sediment concentration along the channels over time. An Acoustic Doppler Current Profiler (ADCP) was used to collect bathymetry and current data, and two water level gauges have been installed to record water levels at the entrance and outlet of the channels. The MIKE 21 NSW model was used to simulate waves using historical winds and measured bathymetry of the channels and lakes. Finally, results from the wave numerical model, laboratory tests and current measurement were used to estimate the effect of each component on erodibility of the cohesive banks

Microwave characterization of carbon nanotube yarns for UWB medical wireless body area networks

Carbon nanotube (CNT) yarns are novel CNT-based materials that extend the advantages of CNT from the nanoscale to macroscale applications. In this study, we have modeled CNT yarns as potential data transmission lines. Test structures have been designed to measure electrical properties of CNT yarns, which are attached to these test structures using gold paste. DC testing and microwave S-parameter measurements have been conducted for characterization. The observed frequency independent resistive behavior of the CNT yarn is a very promising indicator that this material, with its added values of mechanical resilience and thermal conductivity, could be invaluable for a range of applications such as body area networks. A model is developed for the CNT yarn, which fits the measured data collected and agrees in general with similar data for non-yarn CNTs

The Therapeutic Effectiveness of Risperidone on Negative Symptoms of Schizophrenia in Comparison with Haloperidol: A Randomized Clinical Trial

Introduction: A number of research studies have shown that the new generation of neuroleptic medications can more effectively contribute to treating negative symptoms of schizophrenia compared with the first generation by influence cognitive functioning. The present study examined the therapeutic effectiveness of manufactured Risperidone and Haloperidol in Iran on treating the negative symptoms of schizophrenia. Methods: This randomized clinical trial (RCT) study examined 100 hospitalized patients who met DSM-IV. TR criteria for schizophrenia were sampled at Razi psychiatric hospital in Tehran, Iran. After two weeks of stopping neuroleptic medications, the patients were randomly assigned into two groups, Risperidone and Haloperidol group. During 8 weeks of the study, baseline and weekly assessments were performed by completing brief psychiatric report scale (BPRS). Results: Both Risperidone and Haloperidol were effective in treating the negative symptoms of schizophrenia and improvements in both groups were initiated in the second week of treatment. The most prominent response rate was the second week in Haloperidol group and the eighth week in Risperidone group but this difference was not statistically significant. Discussion: Prescribing Risperidone or Haloperidol for treating negative symptoms of schizophrenia can be influenced by other criteria including side effects, previous treatment histories of patients and their families and a patient`s or physician` preference in prescribing a medication. Studies in other countries show that Haloperidol has better therapeutic effects in treating the negative symptoms of schizophrenia in comparison with Risperidone. Further studies on the therapeutic effectiveness of Risperidone and Haloperidol are suggested