1,348 research outputs found
Fuzzy Logic Control of Switched Reluctance Motor Drives
In this chapter, the electromechanical behavior of switched reluctance motor (SRM) is first modeled by analyzing the related nonlinear differential equations. In the model, the estimation of rotor speed is also considered. After modeling, the effects of torque ripple, radial force, and acoustic noise are investigated. As we know, torque ripple and acoustic noise are two of the main disadvantages of a switched reluctance motor. Thus, a fuzzy logic current compensator is proposed both for reducing the peak of radial force and for decreasing acoustic noise effects. In the parts that torque reduces, the fuzzy logic current compensator injects additional current for each phase current to overcome the torque ripple. Also, the fuzzy logic current compensator reduces speed estimation error. The speed estimation is carried out using a hybrid sliding mode observer which estimates the rotor position and speed for a wide speed range. These new approaches have been simulated using MATLAB/SIMULINK for a nonlinear model of switched reluctance motor. The simulation results indicate that proposed methods decrease the maximum radial force and the torque ripple while the maximum torque is preserved. Also, these results show that proposed methods will estimate the rotor position and speed with high precision for all speeds from near zero speeds up to rated speed. These procedures have the advantages of simple implementation on the every switched reluctance motor drive without extra hardware, low cost, high reliability, low vibration, and excellent performance at long term
Sleep Disturbances in Patients with Rheumatoid Arthritis
BACKGROUND: Sleep problems are frequent in chronic diseases like rheumatoid arthritis (RA). The present study was conducted to determine frequency of sleep disturbances and their relations with disease severity.METHODS: The present case-control study was performed on 100 rheumatoid patients who were referred to the rheumatology clinic at the Avicenna hospital. A hundred age- and sex- matched healthy individuals were recruited in the study as a control group. Pittsburgh Sleep Quality questionnaire, Insomnia Severity Index questionnaire and EpworthSleepiness Scale were used. The disease activity was calculated with the disease activity score 28. The collected data were analyzed using SPSS version 19.RESULTS: Mean scores of the sleep quality were 6.2±4.3 in patients and 4.6±2.5 in control group. 28% of the patients had good sleep quality whereas 72% had poor sleep quality. Daytime sleepiness was present in24.8% of the patients and 15% of the control group. Multiple logistic regressions showed that insomnia, pain and disease intensity were the most important factors that determine patients' sleep quality.CONCLUSION: The present study showed that sleep disturbances are frequent in patients with RA and may contribute to disease severity. It is recommended that rheumatoid patients be evaluated for sleep disturbances during routine examinations.KEY WORDS: Rheumatoid arthritis, Sleep quality, Insomnia, Daytime sleepines
Possible signatures of mixed-parity superconductivity in doped polar SrTiO3 films
Superconductors that possess both broken spatial inversion symmetry and
spin-orbit interactions exhibit a mix of spin singlet and triplet pairing.
Here, we report on measurements of the superconducting properties of
electron-doped, strained SrTiO3 films. These films have an enhanced
superconducting transition temperature and were previously shown to undergo a
transition to a polar phase prior to becoming superconducting. We show that
some films show signatures of an unusual superconducting state, such as an
in-plane critical field that is higher than both the paramagnetic and orbital
pair breaking limits. Moreover, nonreciprocal transport, which reflects the
ratio of odd versus even pairing interactions, is observed. Together, these
characteristics indicate that these films provide a tunable platform for
investigations of unconventional superconductivity
Molecular Identification and Sequencing of Mannose Binding Protein (MBP) Gene of Acanthamoeba palestinensis
"nBackground: Acanthamoeba keratitis develops by pathogenic Acanthamoeba such as A. palÂesÂtinenÂsis. Indeed this species is one of the known causative agents of amoebic keratitis in Iran. Mannose Binding Protein (MBP) is the main pathogenicity factors for developing this sight threatening disease. We aimed to characterize MBP gene in pathogenic Acanthamoeba isolates such as A. palestinensis."nMethods: This experimental research was performed in the School of Public Health, Tehran University of Medical Sciences, Tehran, Iran during 2007-2008. Â A. palestinensis was grown on 2% non-nutrient agar overlaid with Escherichia coli. DNA extraction was performed using phenol-chloroform method. PCR reaction and amplification were done using specific primer pairs of MBP. The amplified fragment were purified and sequenced. Finally, the obtained fragment was deposited in the gene data bank."nResults: A 900 bp PCR-product was recovered after PCR reaction. Sequence analysis of the purified PCR product revealed a gene with 943 nucleotides. Homology analysis of the obÂtained sequence showed 81% similarity with the available MBP gene in the gene data bank. The fragment was deposited in the gene data bank under accession number EU678895"nConclusion: MBP is known as the most important factor in Acanthamoeba pathogenesis casÂcade. Therefore, characterization of this gene can aid in developing better therapeutic agents and even immunization of high-risk people
INVENTION OF A SHOOTING DEVICE FOR PARAPLEGIA AND QUADRIPLEGIA AND PROPOSING A NEW FIELD OF SPORT IN PARA OLYMPIC MATCHES
This paper describes the design of a special laser based shooting device designed for paraplegics. The device helps the disabled persons to take part in the sports activities. By this invention, a new field which is shooting is suggested to be included in Para Olympic matches. The device consists of two main parts, the gun and the target. A six link mechanism was designed to carry out the shooting task. Laser localisation and Image processing techniques were used to design the target. The device was built following the above design procedures. After that it has been tested for operation and safety. Also software fitness has been checked considering the ability to save and retrieve the player's data and shooting results correctly. The tests ensured perfect operation of the device in all the above mentioned aspects
Investigating the impact of Total Quality Management (TQM) on innovation in iranian oil companies
Today, the concept of innovation has captured the attention of many scholars and scientists of different fields, and has gained a paramount importance in modern ever changing organizations for competing with rival’s organized management and to survive in the cycle of change. The purpose of the present study is to answer the key question of whether total quality management is able to have any impact on the incremental and radical innovation of Iranian oil companies through cultural changes. This study should be considered as an applicable one in terms of its purpose, a descriptive - correlational one in terms of the method it has followed and a field study in terms of its way of data collection. The sample of the study consisted of 30 Iranian oil Companies, all of which we have thoroughly investigated. The results of the study derived from data analysis done by means of equation modeling method verified all the hypotheses of the study except for hypotheses 2 and 6. According to our results it is possible to increase the rate of innovation in companies by increasing the level of total quality management.Keywords: Total Quality Management (TQM), cultural changes, incremental and radical innovation, Iranian oil Companie
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