To develop operating strategies in polymer electrolyte membrane (PEM) fuel cell-powered applications, precise computationally efficient models of the fuel cell stack voltage are required. Models are needed for all operating conditions, including Transients. In this work, Transient evolutions of voltage, in Response to load changes, are modeled with a sum of three exponential decay functions.Amplitude factors are correlated to steady-state operating data (temperature, humidity, average current, resistance, and voltage). The obtained time constants reflect known processes of the membrane heat/water transport. These model parameters can form the basis for the prediction of voltage overshoot/undershoot used in computational-based control systems, used in real-time simulation. Furthermore, the results provide an empirical basis for the estimation of the magnitude of temporary voltage loss to be expected with sudden load changes, as well as a systematic method for the analysis of experimental data. Its applicability is currently limited to thin membranes with low to moderate humidity gases, and with adequately high reactant-gas stoichiometry.

Space Vector Current Regulators (SPCR) have low harmonic currents in steady state, but they have slower Transient Response compared to other control methods such as hysteresis current regulator. In this paper a new method is proposed to improve Transient Response of SPCR compared to conventional methods. The proposed technique is based on adjustment of zero vector time intervals and modifying the current regulator PI controller output. The proposed method is used in Transients. In steady state, the conventional SPCR method is used. The proposed technique can be applied to existing SPCR systems with no change in the hardware and minimum changes in the DSP software. Simulation results indicate that with the proposed method, the magnitude of current error is reduced compared to the conventional SPCR method. The performance of the proposed method is verified experimentally with a laboratory setup using Texas Instruments TMS320F2407A Digital Signal Processor (DSP) and tested on a 1.5 KW induction motor.

Background and Aim: Transient ischemic attack (TIA) most often manifests by sudden loss of motor, sensory or visual function. Recurrent TIA have been accepted as unproven indication of urgent anticoagulation therapy. The aim of this study was to evaluate the frequency of recurrent TIA and in hospital and short term prognosis after treatment with anticoagulants. Materials and Methods: Our cross-sectional was conducted on patients with TIA in Shafa hospital in Kerman in 2019. For All patients with recurrent TIA heparin (1000u/h) started and TCCD and CT angiography were done for all of them and the patients with significant stenosis referred for angioplasty or endarterectomy. The other patients received 5-7 days heparin and after that warfarin. Heparin or warfarin were disconnected whenever the patient had stroke. In hospital and short-term (three-month) prognosis were evaluated. Demographic information (age, sex) and vascular risk factors were included in a checklist, as well as patients' telephone numbers for follow-up after discharge, Results: Of the 120 patients with TIA, only 15(12. 5 %) had recurrent TIA. 4 patients had significant stenosis and referred for angioplasty or endarterectomy. 11 patients received anticoagulants. 4 (36. 3%) patients had stroke in hospital (3) or in 3 months fallow up (1). 7 (63. 7%) were well at the end of 3th month. Results showed no significant relationship between Response to treatment and age, sex and vascular risk factors. Conclusion: More than 63% patients with recurrent TIA and no significant stenosis had good short term prognosis with anticoagulant therapy.

In this study, the analysis of Transient thermoelastic Response of a functionally graded (FG) non-axisymmetric viscoelastic cylinder is presented. The material properties are assumed to be time-dependent and radially and circumferentially non-homogeneous. The finite element (FE) formulations of the thermoelastic problem are obtained using the virtual work method and all the coupling terms are considered. According to material dependencies and nonlinearity of the constitutive equation, an iterative-based FE solution is suggested in order to solve thermo-elastic equations. The effects of material in homogeneities on the time-dependent Response of mechanical and thermal components are investigated. From the results of this study, it is concluded that, using appropriate material inhomogeneities can improve the magnitudes of stress components, especially shear stress.

Maintaining network stability and encouraging generation companies to involve in stability maintaining are major concerns of independent system operator (ISO) in deregulated power system. Excitation system of synchronous generators is effective and well-known equipment which has a significant effect on network stability. Therefore, improving performance of this system can enhance network stability. But utilizing of the methods, which improve performance of excitation system, imposes cost on generation companies. This paper proposes a motivation mechanism for enhancing Transient stability which encourages generation companies to improve performance of excitation system. In this mechanism beside excitation system Response improving methods, a Transient stability constrained optimal power flow is solved in order to ensure maintaining Transient stability in different contingencies. A 4-buses test system, the IEEE 14-buses test system, and the IEEE 118-buses test system are used to illustrate effectiveness of the proposed mechanism. Implementation results show that the proposed mechanism not only provides required Transient stability margin with minimum operation cost, but also does not restrict generators production capability.