Performance Optimisation of Single-Phase Variable Reluctance Shaded-Pole Motor

Shaded pole induction motors’ theoretical analysis is quite difficult because of the presence of strong harmonic components and the elliptical rotating field. The change of air gap reluctance is affecting the air gap flux distribution and thus the performance of the motor. In the study, the effect of the change in the SPIM’s stator, rotor and squirrel cage on the performance of the motor is analysed by the Finite Element Method. The flux distributions and torque values of the closed-interpoles type and the stator with different interpoles clearances are obtained. The effects of single and double cage structures in the rotor part and the effects of copper and aluminium cage materials in the squirrel cage were analysed. According to the analyses, it was determined that the single cage motor with aluminium cage material exhibited the best torque performance with a torque value of 132.78 mNm

Morbidly adherent placenta and cesarean section methods. A retrospective comparative multicentric study on two different skin and uterine incision

Objectives: Morbidly adherent placenta (MAP) is one of leading causes of maternal mortality, with an increasing rate because of repeated cesarean sections (CS). The primary objective of this study is to compare two techniques of skin and uterine incisions in patients with MAP, evaluating the maternal fetal impact of the two methods. Retrospective multicentric cohort study.Material and methods: A total of 116 women with MAP diagnosis were enrolled and divided in two groups. Group one, comprised of 81 patients, abdominal entry was performed by Pfannenstiel skin incision plus an upper transverse lower uterine segment (LUS) incision (transverse-transverse), which was 2–3 cm above the MAP border, with the uterus in the abdomen. In group two, comprised of 35 patients, abdominal entry was performed by an infra-umbilical midline abdominal incision, by vertical-vertical technique, and the pregnant uterus was incised by a midline incision (vertical) from the fundus till the border of the MAP. Total surgery time, blood loss, blood product consumption, total hospital stay, cosmetic outcomes, and postoperative complications were investigated.Results: Total time of surgery was significantly shorter in group 1 (p < 0.05). Intraoperative blood loss was higher in group 2. Difference between preoperative and postoperative Hb and Htc levels were 3.30 ± 1.04 and 12.99 ± 5.07 respectively (p = 0.012; p = 0.033). The use of erythrocyte suspension (ES), fresh frozen plasma (FFP), and cryoprecipitate and thrombocyte suspension (TS) were found to be significantly lower in patients of group 1than vertical-vertical group (p = 0.008, p = 0.009, p = 0.001, p = 0.001, respectively). There was no difference in terms of total length of hospital stay between groups.Conclusions: In a subgroup of patients diagnosed for MAP, the transverse-transverse incision resulted in less bleeding, less blood and blood product use, and had better cosmetic results than vertical-vertical incision. Moreover, the total time of surgery, crucial for MAP patients, seems to be shorter also in transverse-transverse incision than in vertical-vertical incision

Archaeogenetic analysis of Neolithic sheep from Anatolia suggests a complex demographic history since domestication

Yurtman, ozer, Yuncu et al. provide an ancient DNA data set to demonstrate the impact of human activity on the demographic history of domestic sheep. The authors demonstrate that there may have been multiple domestication events with notable changes to the gene pool of European and Anatolian sheep since the Neolithic. Sheep were among the first domesticated animals, but their demographic history is little understood. Here we analyzed nuclear polymorphism and mitochondrial data (mtDNA) from ancient central and west Anatolian sheep dating from Epipaleolithic to late Neolithic, comparatively with modern-day breeds and central Asian Neolithic/Bronze Age sheep (OBI). Analyzing ancient nuclear data, we found that Anatolian Neolithic sheep (ANS) are genetically closest to present-day European breeds relative to Asian breeds, a conclusion supported by mtDNA haplogroup frequencies. In contrast, OBI showed higher genetic affinity to present-day Asian breeds. These results suggest that the east-west genetic structure observed in present-day breeds had already emerged by 6000 BCE, hinting at multiple sheep domestication episodes or early wild introgression in southwest Asia. Furthermore, we found that ANS are genetically distinct from all modern breeds. Our results suggest that European and Anatolian domestic sheep gene pools have been strongly remolded since the Neolithic

Türkiye-Suriye ekonomik ilişkileri 2002-2007

Türkiye ile Suriye arasındaki ekonomik ve ticari ilişkiler Soğuk Savaş yıllarında gerek siyasi çatışmalar gerekse farklı kutuplara olan yakınlıklar nedeniyle istenilen düzeyde olmamıştır. İki ülke arasındaki ekonomik ilişiler 1990’lı yıllarda Suriye’nin serbest piyasa ekonomisine geçiş sürecine girmesiyle birlikte canlanmaya başlamıştır. Bu süreçte Suriye Hükümeti, dışa açılım ve yatırımların teşvik edilmesi, özel sektöre daha büyük önem verilmesi, yabancı sermayenin ülkeye çekilmesi, bankacılık, borsa ve kur politikaları konularında çalışmalar yapmaktadır. Suriye ile olan dış ticaretimiz, iki ülke arasında yaşanan siyasi gerginlikler başta olmak üzere Suriye’nin uyguladığı kotalar ve gümrüklerden olumsuz etkilenmesine rağmen, son yıllarda sürekli yükselen bir eğilim izleyerek önemli ilerlemeler kaydetmiştir. Hafız Esad’ın 2000 yılında ölmesinin ardından başa geçen oğlu Beşşar Esad Suriye’de yeni bir dönemin başlangıcını temsil etmektedir. Beşşar Esad’ın ifadesiyle babasıyla arasında herhangi bir fark olmamasına rağmen kendisi çağın gereklerine göre hareket ettiğini iddia etmektedir. Nitekim Beşşar Esad ile birlikte Suriye yüzünü daha çok Batı’ya dönmüştür. Türkiye ve Suriye arasında Özellikle Hatay Sorunu, Su Sorunu ve Suriye’nin PKK’ya desteği nedeniyle gergin bir süreç izleyen Türkiye-Suriye Siyasi ve Ekonomik ilişkileri son dönemde iyileşme sürecine girmiştir. Bölgede yaşanan gelişmeler iki ülkeyi dostluk çerçevesinde iyi ilişkiler kurmaya mecbur bırakmıştır. Coğrafi yakınlık ve iki ülke toplumu arasında var olan derin tarihi ilişkiler, ticari ilişkilerin gelişmesinde önemli rol oynamaktadır. ABSTRACT . Economic and commercial relations between Turkey and Syria during the Cold War couldn’t be in desired level due to proximity of different poles or political conflicts. Economic relations between two countries in 1990s began to revive with the process of transition of Syria’s economic attachment to the free market economy. İn the process the Government of Syria is working on the subjects such as openig to outside stimulation to investments, giving greater importance to the private sector withdrawing of foreing capital into the country, banking, stocking and exchanging policies. Our trade with Syria has made significant progress by following continowly rising trend despite being negatively affected due to guota and customs of Syria’s implementation Beşşar Esad who began to administer after Hafız Esad died in 2000 represents a new beginning era in Syria. Beşşar Esad claims that he acts according to age needed although there is no difference between he and his father. However Syria turned their face to the West with the statement of Beşar Esad. Economic and political relations between Turkey and Syria following tense process because of especially Hatay problem, water problem and Syria’s support to PKK has begun the healing process recently. Developments in the region forced two countries to establish good relationship. Geographical proximity and deep historical relations between two countries plays an important role in the development of commercial relations

Energy conservation by using energy efficient electric motors

This paper deals with energy conservation by installing energy-efficient (EE) motors instead of standard efficiency motors. This transition become a necessity as a direct result of limitation in energy sources and escalating energy prices. As electric motors use about three quarters of the total electric energy in Bahrain, attempts to conserve the energy consumed by electric motors recently received intensive research efforts. Therefore, the energy efficiencies of energy efficient motors are compared with those of standard efficiency motors ranging from 5 to 300 HP. To provide more clarification in this regard, full design details of 200 HP standard-efficiency and energy-efficient motors are compared. Pay back periods when replacing standard-efficiency motors with energy-efficient motors, with reference to Bahrain's market, have been discussed. Finally the energy-conservation capability of EE motors in the petrochemical industry has been discussed.Energy conservation Energy-efficient motors Pay-back periods

Performance analysis of solar cell arrays loaded with passive loads

The dynamic behaviour of the linear first-order passive circuit is of considerable importance to engineers. However, dynamic responses of these circuits when powered with solar cell arrays have not received much attention. Further to this, to date, no closed-form solution was reported for the transient response of these circuits due to difficulties arising from the complicated traditional model of the external characteristic of solar cell arrays. To overcome this difficulty, in this paper, a new model is proposed for external characteristic of solar cell arrays. The closed-form transient response of R-L and R-C circuits obtained from this model are compared with their counterparts obtained from the traditional model by using the fourth-order Runge-Kutta numerical method and very close agreement is obtained between the two sets of results. Also a closed-form solution is provided for direct estimation of the maximum power point voltage and current.

A Practical Algorithm for Simulation of Transient Performance of Chopper-Controlled R-L and Dc Drive Loads

This paper presents a practical algorithm for obtaining transient response of chopper-controlled active and passive loads. Core algorithm given for simulating transient response of chopper-controlled R-L load is extended to chopper-controlled DC drive, covering both the continuous and discontinuous current modes of operation. Although chopper-controlled loads are taken as case studies, with a little effort the core algorithm can be readily extended to handle the transient response of the other system which manifests periodic discontinuous forcing functions of different types. Transient current and speed responses of chopper-controlled DC drive, which are obtained from application of the proposed algorithm are compared with their counterparts obtained from detailed numerical solution of the state-space model of the drive using fourthorder Runge-Kutta method, and the advantages of proposed algorithm are discussed

A study on performance increasing in SSVEP based BCI application

People which are afflicted with neurological conditions or neurodegenerative diseases can’t control own muscles by neural pathways. Brain computer interface (BCI) systems offer these people another alternative path from their own neural pathways. This alternative pathway is the direct use of brain signals by a computer without using any vocal muscle. The steady state visual evoked potential (SSVEP) approach currently provides the high performance and reliable communication for the implementation of a non-invasive BCI. In SSVEP based BCI systems, Electroencephalography (EEG) signal detection time (signal window length) and accuracy are the most important performance parameters. Performance is usually measured by Information Transfer Rate (ITR).In the presented paper a SSVEP based BCI robot control application is introduced and system performance is analyzed for different signal window lengths. At first, the number of eye blinks of the subjects is determined by fast eye artifact detection method (FEAD) which based on visual eye blink detection. These eye blink counts are used for system activation. System usability is improved by this control. Two consecutive eye blinks which detecting by FEAD method are used for system activation. System deactivation is also provided by the same command. Synchronous and asynchronous experiments are performed on four healthy subjects for performance analyses. EEG data is analyzed in details by asynchronous experiments. During the synchronous experiments, subjects are tried to complete a predefined route which has twelve steps by navigating the robot (Lego Mindstorms EV3). The minimum energy combination (MEC) and canonical correlation analysis (CCA) methods are applied to EEG segments that are different in length in order to detect SSVEPs in both type experiments. ITR values are calculated for different signal window lengths. The results show that the detection accuracy of the MEC method is similar to that of the CCA method, although it is higher than that of the CCA method in situations where the SSVEP has low strength. In synchronous experiments, using MEC method a system peak ITR of 133.33 bit/min is reached for one subject with a 0.9 s signal window length. This ITR value is higher than previously published studies in the literature for SSVEP based BCI systems. Keywords: Brain computer interface (BCI), Steady state visual evoked potential (SSVEP), Minimum energy combination (MEC), Canonical correlation analysis (CCA

SOLAR TO AC POWER SOURCE FOR REMOTE AREAS USING SEIG

Photovoltaic generators (PVG) are increasingly used to provide electricity in remote areas. However, in many applications the DC generated electricity by a PVG need to be converted to AC. Traditionally DC to AC inverters have been widely used for this purpose. In this paper, a different system is proposed in which a self excited induction generator (SEIG) driven by a permanent magnet DC motor (DCM) and powered from a PVG through a maximum power point tracker (MPPT) are used. A step-up chopper is utilized as an MPPT unit. The proposed system is modelled in time domain, and a detailed transient and steady-state analysis are presented. The main reason behind analyzing the system in the time domain is because of the fact that for unknown speeds, the methods developed for steady-state analysis of SEIGs can not be applied. The presented work shows that the full available power of the PVG can be harnessed by selecting suitable values for the duty cycle and the frequency of the step up chopper and the excitation capacitor of the SEIG. It is also shown that with such a combination power utilization efficiency of more than 83% can be achieved

Regular paper Improved Modeling and Analysis of a High-Performance ac/dc Converter for High-Frequency Power Distribution System

This paper presents an improved modeling and detailed analysis for determining the steady-state and transient performance of a high-performance ac/dc converter topology that can be utilized in high-frequency power distribution systems. The output voltage is regulated by controlling the turn on time of the anti-parallel semiconductor control switches. Both the steady-state and transient performance is explored in details. It is shown that the converter has almost unity power factor of close to 99%, input current is almost sinusoidal with a total harmonic distortion of less than 2%, a conversion efficiency of close to 96% and very low inrush current of around 110% can be achieved, when appropriate circuit components are used. Based on predetermined value of the input current total harmonic distortion, consideration is given to the design of important circuit components