Calculating torque, back-EMF, inductance, and unbalanced magnetic force for a hybrid electrical vehicle by in-wheel drive application.

To use a Hybrid Excitation Synchronous Machine (HESM) in a hybrid electrical vehicle (HEV), its performance indicators such as back-EMF, inductance and unbalanced magnetic force should be computed preferably by an analytical method. First, the back-EMF is calculated by considering alternate-teeth and all-teeth non-overlapping and overlapping windings. The effects of three types of magnetization patterns including the radial, parallel and Halbach magnetizations on the back-EMF waveform have also been investigated. Then, the self-inductance of the stator and rotor windings, the mutual inductance between the stator and rotor windings, and the mutual inductance between the stator phases are computed. Next, the components of the unbalanced magnetic force (UMF) in the direction of the x and y axes and its amplitude are computed. Moreover, the effects of the magnetization patterns on those magnetic pulls are investigated. To minimize the UMFs, symmetry must be implemented in the excitation sources; therefore, first the stator winding then the permanent magnet and rotor winding are modified in such a way that the UMFs are reduced. Increasing the temperature leads to a weakening of the magnet's residual flux density, which strongly affects the performance characteristics of the electric machine such as Back-EMF and UMF. Finally, the ratio of the permanent magnet flux to the rotor flux is determined in such a way that the average torque is maximized. In this section, the effects of three magnetization patterns will be investigated.

Determination of the optimal location for constructing solar photovoltaic farms based on multi-criteria decision system and Dempster-Shafer theory.

Considering environmental concerns regarding air pollution which is induced by burning fossil fuels to generate electrical power, utilizing solar energy as a green and sustainable energy source is of great interest. This study proposes a novel framework to determine the optimal location for constructing solar photovoltaic (PV) farms. To locate the suitable areas for PV farms, firstly, a fuzzy-based method is utilized to homogenize the input parameters, thereafter, the analytical hierarchy process (AHP) and Dempster-Shafer (DS) methods are independently used. In the AHP method, the proper weight for each input parameter is generated utilizing a pairwise comparison matrix. However, the DS method identifies output in different confident levels. Finally, southeast of Fars province in Iran as a region with high sunny hours in the year is selected, and the applicability of proposed methods is examined. The results show that 32% of the case study is located at high and good suitability classes in the fuzzy_AHP method. However, it is 18.56%, 16.70%, 16.32% according to 95%, 99% and 99.5% confident levels in the fuzzy_DS method, respectively. Comparisons of the fuzzy_AHP and fuzzy_DS methods at 20 points with various solar radiation intensities and the number of dusty days parameters indicate that the fuzzy_DS method can more reliably determine the optimal PV farm locations. Additionally, as the fuzzy_DS method determines the optimal locations with different confident levels, this method can benefit decision-makers to determine the risks associated with selecting a specific site for constructing solar PV farms.

Gene expression feature selection for prostate cancer diagnosis using a two-phase heuristic-deterministic search strategy.

Here, a two-phase search strategy is proposed to identify the biomarkers in gene expression data set for the prostate cancer diagnosis. A statistical filtering method is initially employed to remove the noisiest data. In the first phase of the search strategy, a multi-objective optimisation based on the binary particle swarm optimisation algorithm tuned by a chaotic method is proposed to select the optimal subset of genes with the minimum number of genes and the maximum classification accuracy. Finally, in the second phase of the search strategy, the cache-based modification of the sequential forward floating selection algorithm is used to find the most discriminant genes from the optimal subset of genes selected in the first phase. The results of applying the proposed algorithm on the available challenging prostate cancer data set demonstrate that the proposed algorithm can perfectly identify the informative genes such that the classification accuracy, sensitivity, and specificity of 100% are achieved with only nine biomarkers.

The Effects of Ambulatory Accelerations on the Stability of a Magnetically Suspended Impeller for an Implantable Blood Pump.

This article describes the effects of ambulatory accelerations on the stability of a magnetically suspended impeller for use in implantable blood pumps. A magnetic suspension system is developed to control the radial position of a magnetic impeller using coils in the pump casing. The magnitude and periodicity of ambulatory accelerations at the torso are measured. A test rig is then designed to apply appropriate accelerations to the suspension system. Accelerations from 0 to 1 g are applied to the suspended impeller with ambulatory periodicity while the radial position of the impeller and power consumption of the suspension system are monitored. The test is carried out with the impeller suspended in air, water, and a glycerol solution to simulate the viscosity of blood. A model is developed to investigate the effects of the radial magnetic suspension system and fluid damping during ambulatory accelerations. The suspension system reduces the average displacement of the impeller suspended in aqueous solutions within its casing to 100 µm with a power consumption of below 2 W during higher magnitude ambulatory accelerations (RMS magnitude 0.3 g). The damping effect of the fluid is also examined and it is shown that buoyancy, rather than drag, is the primary cause of the damping at the low displacement oscillations that occur during the application of ambulatory accelerations to such a suspension system.

Optimization of Centrifugal Pump Characteristic Dimensions for Mechanical Circulatory Support Devices.

The application of artificial mechanical pumps as heart assist devices impose power and size limitations on the pumping mechanism, and therefore requires careful optimization of pump characteristics. Typically new pumps are designed by relying on the performance of other previously designed pumps of known performance using concepts of fluid dynamic similarity. Such data are readily available for industrial pumps, which operate in Reynolds numbers region of 10. Heart assist pumps operate in Reynolds numbers of 10. There are few data available for the design of centrifugal pumps in this characteristic range. This article develops specific speed versus specific diameter graphs suitable for the design and optimization of these smaller centrifugal pumps concentrating in dimensions suitable for ventricular assist devices (VADs) and mechanical circulatory support (MCS) devices. A combination of experimental and numerical techniques was used to measure and analyze the performance of 100 optimized pumps designed for this application. The data are presented in the traditional Cordier diagram of nondimensional specific speed versus specific diameter. Using these data, nine efficient designs were selected to be manufactured and tested in different operating conditions of flow, pressure, and rotational speed. The nondimensional results presented in this article enable preliminary design of centrifugal pumps for VADs and MCS devices.

In-vitro investigation of cerebral-perfusion effects of a rotary blood pump installed in the descending aorta.

This study describes use of a cardiovascular simulator to replicate the hemodynamic responses of the cerebrovascular system with a mechanical circulatory support device operating in the descending aorta. To do so, a cerebral autoregulation unit was developed which replicates the dilation and constriction of the native cerebrovascular resistance system and thereby regulates the cerebral flow rate within defined limits. The efficacy of the replicated autoregulation mechanism was investigated by introducing a number of step alterations in mean aortic pressure and monitoring the cerebral flow. The steady responses of the cerebral flow to changes in mean aortic pressure were in good agreement with clinical data. Next, a rotary pump, modeling a mechanical circulatory support device, was installed in the descending aorta and the hemodynamic responses of the cerebral system were investigated over a wide range of pump operating conditions. Insertion of a mechanical circulatory support device in the descending aorta presented an improved cardiac output as a result of afterload reduction. It was observed that the primary drop in cerebral flow, caused by the pump in the descending aorta, was compensated over the course of five seconds due to a gradual decrease in cerebrovascular resistance. The experimental results suggest that the implantation of a mechanical circulatory support device in the descending aorta, a less invasive procedure than typical mechanical circulatory support implantation, will not have an adverse effect on the cognitive function, provided that the cerebral autoregulation is largely unimpaired.

Numerical and in vitro investigation of a novel mechanical circulatory support device installed in the descending aorta.

Traditional implantation techniques of assist devices from the apex of left ventricle to the ascending or descending aorta are highly invasive and carry substantial complications for end-stage heart failure patients. This study has shown that the descending aorta can be a promising location to install an implantable mechanical circulatory support with minimally invasive surgery. Herein, the hemodynamic effect of an in-house prototyped pump implanted in the descending aorta was investigated numerically as well as experimentally. The objective of the experimental study is met by using the in-house simulator of the cardiovascular loop replicating congestive heart failure conditions. The objective of the numerical study was met by using the modified version of the concentrated lumped parameter model developed by the same team. The results show that the pump placement in the descending aorta can lead to an improvement in pulsatility. The pressure drop, generated at the upstream of the pump, facilitates the cardiac output as a result of after-load reduction, but at the same time, it induces a slight drop in the carotid as well as the coronary perfusion. The pressure rise, generated at the downstream of the pump, improves the blood perfusion in the renal circulation.

In vitro comparison of two different mechanical circulatory support devices installed in series and in parallel.

This study investigates the novel approach of placing a ventricular assist pump in the descending aorta in series configuration with the heart and compares it with the two traditional approaches of left-ventricle-to-ascending-aorta (LV-AA) and left-ventricle-to-descending-aorta (LV-DA) placement in parallel with the heart. Experiments were conducted by using the in-house simulator of the cardiovascular blood-flow loop (SCVL). The results indicate that the use of the LV-AA in-parallel configuration leads to a significant improvement in the systemic and pulmonic flow as the level of continuous flow is increased; however, this approach is considered highly invasive. The use of the LV-DA in-parallel configuration leads to an improvement in the systemic and pulmonic flow at lower levels of continuous flow but at higher levels of pump support leads to retrograde flow. In both in-parallel configurations, increasing the level of pump continuous flow leads to a decrease in pulsatility to a certain extent. The results of placing the pump in the descending aorta in series configuration show that the pressure drop upstream of the pump facilitates cardiac output as a result of afterload reduction. In addition, the pressure rise downstream of the pump may assist with renal perfusion. However, at the same time, the pressure drop generated at the proximal part of the descending aorta induces a slight drop in carotid perfusion, which would be autoregulated by the brain in a native cardiovascular system. The pulse wave analysis shows that placing the pump in the descending aorta leads to improved pulsatility in comparison with the traditional in-parallel configurations.

In vitro cardiovascular system emulator (bioreactor) for the simulation of normal and diseased conditions with and without mechanical circulatory support.

This article presents a new device designed to simulate in vitro flow rates, pressures, and other parameters representing normal and diseased conditions of the human cardiovascular system. Such devices are sometimes called bioreactors or "mock" simulator of cardiovascular loops (SCVLs) in literature. Most SCVLs simulate the systemic circulation only and have inherent limitations in studying the interaction of left and right sides of circulation. Those SCVLs that include both left and right sides of the circulation utilize header reservoirs simulating cycles with constant atrial pressures. The SCVL described in this article includes models for all four chambers of the heart, and the systemic and pulmonary circulation loops. Each heart chamber is accurately activated by a separate linear motor to simulate the suction and ejection stages, thus capturing important features in the perfusion waveforms. Four mechanical heart valves corresponding to mitral, pulmonary, tricuspid, and aortic are used to control the desired unidirectional flow. This SCVL can emulate different physiological and pathological conditions of the human cardiovascular system by controlling the different parameters of blood circulation through the vascular tree (mainly the resistance, compliance, and elastance of the heart chambers). In this study, four cases were simulated: healthy, congestive heart failure, left ventricular diastolic dysfunction conditions, and left ventricular dysfunction with the addition of a mechanical circulatory support (MCS) device. Hemodynamic parameters including resistance, pressure, and flow have been investigated at aortic sinus, carotid artery, and pulmonary artery, respectively. The addition of an MCS device resulted in a significant reduction in mean blood pressure and re-establishment of cardiac output. In all cases, the experimental results are compared with human physiology and numerical simulations. The results show the capability of the SCVL to replicate various physiological and pathological conditions with and without MCS.