Effects of post-sintering annealing treatment between 300 and 1000°C for up to 8 hrs time periods followed by either furnace cooling (FC) or air-cooling (AC) on the hard magnetic properties of some Nd-Fe-B based sintered magnets was investigated. It was shown that the intrinsic coercivity (Hci), second quadrant DEMAGNETIZATION LOOP SHAPE and thus the energy density (BH)maxvaried considerably as a result of the annealing treatment. However, no significant changes occurred in the remanence (J) values of the magnets. Annealing at 500°C for 1 hr followed by FC resulted in a considerable deterioration in the DEMAGNETIZATION LOOP SHAPEs and thus in (BH) max values in all the magnets. These changes were almost recoverable. By annealing at 500°C, followed by AC, no deterioration in the DEMAGNETIZATION LOOP SHAPE occurred for any of the magnets and thus there were some increases in (BH)max values of the magnets due to increase in their Hci values. The highest Hci in magnets A and C was obtained by a standard annealing treatment for 1 hr at 6000C, while in magnet B, the highest Hci occurred after an annealing treatment for 2 hrs at 500°C, both followed by AC. No deterioration in the DEMAGNETIZATION LOOP SHAPE was identified for any of the magnets either in FC or AC from 6000C. However, the coercivity enhancement in magnet A and in particular, in magnet B, was found to be much higher after AC than FC. In all the annealing treatments, the improvement in Hci and/or (BH)max values occurred in the first 1 or 2 hrs of annealing. Any further annealing beyond these times resulted in significant falls in the magnetic properties. Thus, long term annealing for up to 300 hrs at 400°C resulted in dramatic reductions in the hard magnetic properties, which could only be partially recovered. This behavior has been related to the oxidation of the magnets during long term annealing in a roughing pump vacuum. In this paper, the changes in Hci and (BH)max values during these annealing treatments are related to possible microstructural changes reported elsewhere.

Spirometry and flow-volume LOOP show the abnormal pattern of pulmonary dysfunction and the site of the obstruction of upper and peripheral airways.For determining the SHAPE of flow - volume LOOP in obstruction of carina and bronchus we examined 19 patients with large airway obstruction documented with fiberoptic bronchoscopy via pulmonary function testing and flow-volume LOOP performing. Two patients about 70% obstruction of carina had F-V LOOP compatible with upper aiway obstrucion. 10 patients with obstruction of right or left main or intermedius bronchus had PFT criteria of restrictive pulmonary dysfunction but no change in F-VLOOP. In seven patients with lobar bronchus obstruction this obstruction did not change the SHAPE of flow-volume LOOP. We reached to the conclusion that F-V LOOP in obstruction of carina is the same as fixed upper airway obstruction but obstruction in main and intermediate bronchus’s show normal F-V LOOP with restrictive pattern, and obstruction of lobar bronchus dose not significantly change the SHAPE of F-V LOOP or pulmonary function parameters.

It is very important to improve the parameters of the electric motor in order to improve its performance. One of the ways to improve the performance of electric motors is to use permanent magnets in the structure of induction motors. These types of motors are known as line start motors. The use of permanent magnets eliminates ohmic losses and increases efficiency. Due to the fact that permanent magnetism plays the most important role in these motors, the smallest change in the magnetic properties of the used magnet will cause malfunction of the machine. One of the important phenomena that changes the properties of the core magnet is the phenomenon of DEMAGNETIZATION. Although this phenomenon has very destructive effects on engine performance, the design of electric motors is still done without considering this issue. In this article, a line start motor is designed. The numerical simulation results show that the performance and efficiency of the motor in the DEMAGNETIZATION mode are significantly reduced. Also, the increased current in demagnetized motors causes a further decrease in the magnet's magnetic properties. This effect is progressively repeated many times until the property of the applied permanent magnet is lost. Finally, an analytical model was presented for examining and designing electric motors, considering the effects of DEMAGNETIZATION. The results showed that the use of the analytical model of motor design considering the effects of DEMAGNETIZATION can be a suitable alternative to the use of conventional methods in the design of electric motors.

A common method for controlling a group of parallel converters in decentralized control strategy structure in an island microgrid, the use is the droop-down characteristics of frequency ω-P and voltage E-Q. However, the problem with using this method is that the reactive power is not properly distributed (in proportion to the capacity of the micronutrients) between the micronutrients, which may lead to overload in the converters. Microgrids may also suffer from dynamic stability problems such as power fluctuations, which can be increased by switching between active and reactive power control. To avoid this problem, the X / R ratio of transmission lines is an important parameter that should be carefully considered in the design of micronutrient controllers. By linearizing and simplifying conditions, the control system conversion function model becomes a single input-single output system, which is efficient enough to show the relationship between control parameters such as slope of droop characteristics and derivative sentences, virtual impedance, and voltage controllers. Using this model, stability conditions for different parameters are analyzed. Also, to improve power distribution stability, common droop strategies are modified by adjusting the slope as well as adding nonlinear sentence sections. This approach reduces the coupling between active and reactive power control and reduces the dependence of power distribution on grid parameters such as the X / R ratio. To evaluate the reliability of the proposed model, the simulation results in a sample island microgrid in MATLAB software are presented.

Permanent magnet motors have been considered for a variety of applications due to their features such as high power density and high efficiency. One of the issues that should be investigated in the design of these motors is the DEMAGNETIZATION problem. Usually, the DEMAGNETIZATION analysis is carried out in a steady state, while DEMAGNETIZATION effect in dynamic condition is more considerable due to pulse SHAPEd of armature field. Based on this fact, in this paper, dynamic DEMAGNETIZATION is investigated for an IPM V-SHAPEd magnet. This study has been done for two types of magnet, each one in static & dynamic conditions and the results are compared. Moreover, the effect of flux weakening regime on DEMAGNETIZATION is investigated.

In this paper, an analytical model is proposed for evaluating electromagnetic performances of permanent magnet vernier machines (PMVMs) under healthy and faulty conditions. The proposed model employs flexible magnetic equivalent circuit (MEC) method, which its accuracy can be selected by tunable parameters. The model is capable of considering the influence of saturation effect, skewed slots, slot leakage fluxes, and various winding arrangements for the machines with desired properties. First, the proposed model is used to predict the no-load performance of machine at healthy condition. Then, the machine loading behaviors under healthy and DEMAGNETIZATION fault conditions are analyzed by the MEC model. Moreover, the results of the proposed model are compared and validated with those of 2-D finite element method (FEM) and 3-D FEM. Eventually, a specific pattern is extracted from the stator current spectrum to detect the DEMAGNETIZATION fault.

In this research work a SHAPE from shading (SFS) technique which incorporates a Lambertian model is implemented for the automatic generation of a digital terrain model (DTM) using a single view aerial image. The developed algorithm is tested on both simulated and real data. The estimated accuracy of the generated DTM from the simulated data, which has a bilinear surface, is about ±3 cm. The real data is a scanned aerial photograph taken over a low texture hilly terrain. The generated DTM by the SFS technique is compared with a DTM acquired by the manual measurement of the stereo image of the same area using a photogram metric plotter. The estimated rimes of the discrepancies between the grid nodes of the measured and the automatically generated DTM is about ±4 meters. The unsuccessful reconstruction of the terrain surface for the real data is due to the fact that a simple Lambertian model does not take into account, in a perfect way, different nondeterministic influential factors such as the terrain alb Edo variations and the random noise. The influence of the latter case was reduced by a low pass filter applied as a preprocessing stage.

Background & Aim: Extrusion of debris from apex is one of the main factors of flare up (inflammation, pain or combination of both). Various studies have been conducted toward the amount of debris extrusion but no one compared this drawback on one – SHAPE and xp-SHAPEr system in curved root canals. So, this study aimed to determine the amount of apical debris extrusion following preparation of canal by one-SHAPE or xp-SHAPEr in curved canals of mesiobuccal root in mandibular first molars.Material & Method: This experimental study was done on 34 mandibular first molars with 30 to 40 degree curved mesiobuccal root canal. The samples were randomly divided in two groups. First group had one –SHAPE for root canal preparation while the other had xp-SHAPEr. Roots of the teeth were fixed in pre weighted fluxes till cervical area so that all apical debris were collected in vials. After desiccation process, the vials were weighted again. The difference between original and secondary weight of vials containing debris is considered as weight of debris extrusion. Data were analyzed using T-test.Results: Amount of debris extrusion in one– SHAPE group was 0.018±0.014 and in xp-SHAPEr group was 0.01±0.007 and the difference was statistically significant (0.01).Conclusion: Considering the situation and limitation of this in vitro study, xp-SHAPEr rotary system was associated with less debris extrusion compared to one – SHAPE systems.