Three phase induction motor drives are widely used in modern industry due to appearance of high speed power electronic devices and microprocessors. Simulation results under device faults in inverter stage of an induction motor drive shows that there are undesirable affects in motor voltages and motor speed. Experimental results confirm the existence of motor speed oscillation. This study shows that after fault occurrence, it is possible to drive the motor in single-phase mode. However, there is large low frequency speed oscillation. Simulation results show that it is possible to reduce motor speed oscillation by injection of proper current harmonic to motor under single-phase operation.

Background and Aim: Different surgical techniques have been proposed for crown exposure among patients under orthodontic treatment. The aim of this study was to investigate periodontal indices in closed flap operation technique used for impacted teeth crown exposure.Materials and Methods: In this descriptive study (2001-2003) 20 patients (15 females and 5 males), age ranging from 15 to 20 years, were participated. Following the performance of closed flap operation technique, in 12 patients impacted canine and central incisors were exposed and treated orthodontically. Periodontal parameters including sulcular depth, width of keratinized gingiva and attachment loss were recorded. Results: The mean of gingival sulcus depth was 1.50±0.43, the means of keratinized gingival in central incisors and canines were 3.07±0.53 and 2.30±0.42, respectively. In one patient, attachment loss was reported.Conclusion: Considering the optimal sulcular depth and keratinized gingiva, the closed flap operation technique seems suitable.

It has been shown recently that in many industrial factories, for example rolling and looming, single controller and drive must control a number of multi-phase machines simultaneously. The major difficulty in utilizing this approach is using common single controller for two motors.The most recent solution for this problem is to serialize the stator windings in an appropriate manner.Replacing three-phase machines with multi-phase ones opens the way to implement this method. In addition, a number of multi-phase machines can be controlled independently, by a suitable drive switching. In this paper, a new modeling method is presented to models these two machines separately. Then, every machine has been simulated in any arbitrary reference frame. Finally, the two methods are compared and the simulation results evince the advantages of the suggested method.Furthermore, designing a controller in separate models alleviates the design burden in comparison to previous methods.

The accurate prediction of wellbore temperature distribution helps to accurately estimate well pressure profile and bottom-hole pressure (BHP) which is important in the under-balanced drilling (UBD) operation. In this paper effect of temperature variation due to heat transfer of drilling fluid with the formation and also oil and gas production from the reservoir into the annulus in under-balanced drilling condition were investigated. Gas-liquid two-phase flow model considering thermal interaction with the formation is used to numerically simulate a well with real dimensions. Based on drilling fluids flow and heat transfer characteristics in wells, conservations of mass and momentum and energy equations have been developed to compute BHP and wellbore temperature and pressure profile. After temperature and pressure validation of the numerical model, the effect of heat transfer between drilling fluid inside the well and the formation was considered on the pressure distribution and bottom-hole pressure. The results of two-phase flow, considering thermal effect gives better results compared to two-phase flow with geothermal temperature distribution analysis and better accuracy in comparison with other models.

Parallel connection of two or even more single-phase inverter modules is a successful solution to increase the reliability and the efficiency of an inverter at moderate power levels. Stable operation and proper current sharing among parallel inverter modules is a key issue, especially when they are connected to a common load through unequal output filter impedances. In this paper, a new formulation and consequently a proper current sharing control algorithm for parallel connected inverter modules with the possibility of unequal filter impedances is proposed. Also a dual-loop voltage control with the filter current as the inner loop feedback signal, considering the effect of digital control delay, is adopted. The controller parameters are designed according to a frequency domain analysis. Finally, theoretical achievements are confirmed by experimental test results on a test rig with two 250 W parallel connected single phase inverters.

Introduction: Use of different methods for GnRH administration in ART cycles is a controversy.Microdose regimens in poor- responder patients are very useful and this has been determined by some studies, but it is not clear how this regimen affects patients with first (IVF/ICSI) cycle. Materials & Methods: In a prospective, randomized, clinical trial study at The Research and Clinical Center for Infertility and Madar Hospital, Yazd, we compared 140 patients who were candidates for IVF/ICSI for the first time. 70 patients received Microdose flare (A Group) and 70 patients were administered GnRH in long luteal phase (B group). Number of oocytes, follicles, embryos and the pregnancy outcome were compared in both groups. In microdose group, after administration of 21 contraceptive pills in the last cycle from day 3 , GnRH was given to patients ( 0.05 cc twice a day) and H MG from day 5 (3 vials a day). In long protocol, the patients received 0.5 cc Buserelin daily from day 21 subcutaneously and with the beginning of bleeding , the dosage was decreased to half. HMG was given three times a day. As the follow up of some patients was difficult and their pregnancy outcome was unknown, 14 patients of A group and 3 patients of B group were left out from the study. The data was analyzed by chi-square and T test. Results: Number of oocytes, embryos and outcome of pregnancy were not different the in two groups. However, the number of mature follicles in long method was higher but not significant statistically. Conclusion: The Microdose flare regimen thus offers no further advantage for patients with first cycle of IVF/ICSI.    

Because most part of Iran country is located in a dry climate، construction of water conveyance tunnels is inevitable. One of the major challenges in the building of these tunnels is inflow of water into the tunnel during the construction and operation phase. The Rozieh water conveyance tunnel whose length is 3200 meters is a part of water conveyance project to the Semnan city and it is located 30 Kilometers NE of the Semnan city. In accordance with the drilled boreholes، the tunnel route has been classified into eight zones from a geotechnical view. Then the permeability coefficients of host rock were calculated using back analysis approach done on the basis of numerical simulation results and water inflow quantity during the construction phase. In following، a parametric study was done on the lining and cement injection zone permeability and the thickness of cement injection zone. According to this study، the effect of injection zone thickness variation on the water inflow quantity is negligible. So with the assumption of 3 meters thickness for the injection zone، the permeability coefficient of host rock after injection were evaluated. Dependent on the initial rock permeability، cement injection could reduce the rock permeability 10 to 1000 times. In addition، the water inflow into the tunnel was calculated using hydro-mechanical coupling analysis. According to this analysis، the water inflow calculated by the hydro-mechanical coupling analysis is 50 to 70 percent less than the hydraulic analysis.