Speed sensorless field oriented control of ac induction motor using model reference adaptive system

In order implement the vector control technique, the motor speed information is required. Incremental encoder, resolvers and tachogenerator, are used to reveal the speed. These sensors require careful mounting and alignment and special attention is required with electrical noises. Sensorless speed vector control is greatly used and applied in induction machine drives instead of scalar control and vector control for their robustness and reliability, and very low maintenance cost. In this project MRAS based techniques are used to estimate the rotor speed based on rotor flux estimation, the estimated speed in the MRAS algorithm is used as a feedback for the vector control system. The model reference adaptive control system is predicated on the comparison between the outputs of adjustable model and reference model. The error between them is employed to drive a suitable adaptation mechanism which generates the estimated rotor speed for the adjustable model. And indirect vector control scheme controls the flux and torque by restricting the torque and flux errors with respective hysteresis bands, and motor flux and torque are controlled by the stator voltage space vectors using optimum inverter switching table. Modeling and simulation of the induction machine and the vector control drives implemented in MATLAB/SIMULINK. Simulation results of proposed MRAS and indirect vector control technique are presented

An improved fast scanning algorithm based on distance measure and threshold function in region image segmentation

Segmentation is an essential and important process that separates an image into regions that have similar characteristics or features. This will transform the image for a better image analysis and evaluation. An important benefit of segmentation is the identification of region of interest in a particular image. Various algorithms have been proposed for image segmentation and this includes the Fast Scanning algorithm which has been employed on food, sport and medical image segmentation. The clustering process in Fast Scanning algorithm is performed by merging pixels with similar neighbor based on an identified threshold and the use of Euclidean Distance as distance measure. Such an approach leads to a weak reliability and shape matching of the produced segments. Hence, this study proposes an Improved Fast Scanning algorithm that is based on Sorensen distance measure and adaptive threshold function. The proposed adaptive threshold function is based on the grey value in an image’s pixels and variance. The proposed Improved Fast Scanning algorithm is realized on two datasets which contains images of cars and nature. Evaluation is made by calculating the Peak Signal to Noise Ratio (PSNR) for the Improved Fast Scanning and standard Fast Scanning algorithm. Experimental results showed that proposed algorithm produced higher PSNR compared to the standard Fast Scanning. Such a result indicate that the proposed Improved Fast Scanning algorithm is useful in image segmentation and later contribute in identifying region of interesting in pattern recognition

Challenges of being a researcher in Africa: A narrative synthesis of literature

Background: The importance of research in the development agenda of Africa has received better recognition in recent years, with an increasing number of publications by African researchers. However, the number and quality of the research outputs are not on a par with the health problems and population size of the continent. This review was carried out with the aim of identifying the challenges researchers face in Africa. Materials and Methods: We conducted a narrative synthesis of the available literature. We searched for relevant articles on PubMed, Hinari and Google Scholar databases. We searched for additional articles from the reference lists of studies identified through the search. The date of the last search was 05 April 2018. We thematically synthesized the results in terms of individual, institutional and policy challenges. Results: We retrieved 610 articles, of which 12 were eligible for inclusion. Limited institutional research capacity, including a shortage of local funds, shortage of skilled researchers and weak infrastructure, were the prevailing challenges. A lack of technical capacity in scientific writing, including lack of English language writing skills, were the common individual-level challenges. A further finding was that research evidence generated in Africa was not generally used to inform the policy-making process. Conclusions: The challenge for researchers in Africa is primarily the weak capacity of research institutes that are not well equipped to produce the next generation of researchers. Efforts should be made to strengthen their capacity to improve the production of skilled scientists and visibility of research work in Africa. Ethiop. J. Health Dev. 2019; 33(4):229-238] Key words: Scientist, research, researcher, challenge, Africa, narrative, systematic revie

Serum IL-21 level and its relation to activity and severity of alopecia areata

Background: Alopecia areata (AA) is a non-cicatricial alopecia that is postulated to be a hair-specific autoimmune disease, with genetic factors playing a role in disease susceptibility and severity. The disease presentation ranges from circular patches on the scalp to complete hair loss with devastating psychosocial consequences.Patients and methods: This was a case control study carried out on 40 patients diagnosed as alopecia areata. They were recruited from the outpatient clinic of Dermatology, Andrology and STDs Department, Mansoura University Hospitals. In addition 40 normal healthy subjects with matched age and sex were selected to act as a control group.Results: Serum levels of IL-21 were significantly increased in AA patients, and showed significant positive correlation with activity of the disease. Higher serum levels of IL-21 in active cases support its role as predictor of disease activity. There were no significant differences in IL-21 level with different SALT scores. Receiver Operating Characteristic (ROC) curve analysis of IL-21 was conducted to evaluate the sensitivity and specificity of serum IL-21 as a diagnostic index for AA. The AUC-ROC of IL-21 was excellent (0.962); and the best cut off point for IL-21 was determined to be 22.22 pg/ml. It was good predictive value. Its accuracy was 86.3%.Conclusions: The results of this study indicate that the serum IL-21 could be promising marker in the diagnosis of alopecia areata, and also can be used as prognostic marker of its activity

Enhancement of data transmission for mobile multi hop relay worldwide interoperability for microwave access network

Mobile Multi-hop Relay (MMR) Worldwide Interoperability for Microwave Access (WiMAX) uses Non-Transparent Relay Station (NT-RS) to extend the Base Station (BS) coverage and improve the channel quality and throughput of the network. Nevertheless, the use of NT-RS in MMR WiMAX network increases the delay of relaying packets across multiple hops. Transmission Control Protocol (TCP) and Automatic Repeat reQuest (ARQ) are used to achieve the data transmission reliability in the wireless systems. However, the setting of ARQ parameters are optimised for single hop network and it does not consider the Quality of Service (QoS) limits required of WiMAX networks. In addition, the TCP is adapted to deal with the congestion in the wired network without considering the QoS requirements. In order to enhance the performance of data transmission over MMR WiMAX networks, resource management, transmission control and error control mechanisms should be optimised for MMR WiMAX network. Therefore, this research proposes resource management schemes to decrease the delay of relaying the packets across multiple hops scenario. Transmission control mechanism is then proposed to optimise the transmission control for MMR WiMAX network. Lastly, ARQ parameters are optimised to enhance the link utilisation in order to achieve the QoS rates required. The proposed algorithms performances are evaluated through simulation work. The proposed resource management schemes reduce the delay of relaying packets across multiple hops by 33% and 40% for the second and third hops respectively. Therefore, the link layer throughput is enhanced by 35% and 53% and TCP throughput by 30% and 40% for the second and third hops correspondingly. The proposed transmission control scheme reduces the timeout occurrences which increase the resource utilisation up to 90% and hence the TCP throughput is enhanced by 26% to 75% for different hops. In conclusion, the optimised ARQ parameters for MMR WiMAX network reduce the TCP packet loss by 8%, 44% and 64% for the first, second and third hops. Hence, the link layer and TCP performances are improved by 10% to 140% for diverse scenarios

A comparison among Different Methods for Estimating Regression Parameters with Autocorrelation Problem under Exponentially Distributed Error

            يهتم الانحدار الخطي المتعدد بدراسة وتحليل العلاقة بين المتغير المعتمد ومجموعة من المتغيرات المستقلة ومن هذه العلاقة يتم التنبؤ بقيم المتغيرات, وفي هذا البحث تم دراسة انموذج الانحدار الخطي المتعدد ولثلاثة متغيرات بوجود مشكلة الارتباط الذاتي للاخطاء عندما يتوزع الخطأ العشوائي توزيع اسيا, وتمت المقارنة بين ثلاثة طرائق (طريقة المربعات الصغرى العامة, طريقة (M) الحصينة وطريقة لابلاس الحصينة) باستعمال المحاكاة ومن خلال المقياس الاحصائي متوسط مربعات الخطأ ولاحجام العينات (15, 30, 60, 100) وتطبيق افضل طريقة على بيانات تجربة حقيقية تمثل اصناف السجائر وفقا لتصنيف لجنة التجارة الفيدرالية الامريكية.Multiple linear regressions are concerned with studying and analyzing the relationship between the dependent variable and a set of explanatory variables. From this relationship the values of variables are predicted. In this paper the multiple linear regression model and three covariates were studied in the presence of the problem of auto-correlation of errors when the random error distributed the distribution of exponential. Three methods were compared (general least squares, M robust, and Laplace robust method). We have employed the simulation studies and calculated the statistical standard mean squares error with sample sizes (15, 30, 60, 100). Further we applied the best method on the real experiment data representing the varieties of cigarettes according to the US Federal Trade Commission

Genom Editing of Saccharomyces Cerevisiae Using CRISPR-Cas9 System: A Review Study

Saccharomyces cerevisiae is an important yeast has been exploited for a long time to produce alcohol or bread. Moreover, genetically engineered S. cerevisiae cells continue to be used as cell factories for production of biofuels, pharmaceutical proteins and food additives. Genetically modified strain of S. cerevisiae created using traditional methods is laborious and time consuming. Recently, originally an immune system in archaea and bacteria, Clustered regularly interspaced short palindromic repeats “CRISPR” and CRISPR-associated “Cas” have been used exploited  as a flexible tool for genome editing. Until now, this tool has been applied to many organisms including yeast. Here, we review the importance of S. cerevisiae as an industrial platform and the use of CRISPR/Cas system and its applications in research and industry of this yeast. &nbsp

Assessment Resistance Potential to Moisture Damage and Rutting for HMA Mixtures Reinforced by Steel Fibers

Rutting is mainly referring to pavement permanent deformation, it is a major problem for flexible pavement and it is a complicated process and highly observed along with many segments of asphalt pavement in Iraq. The occurrence of this defect is related to several variables such as elevated temperatures and high wheel loads. Studying effective methods to reduce rutting distress is of great significance for providing a safe and along-life road. The asphalt mixture used to be modified by adding different types of additives. The addition of additives typically excesses stiffness, improves temperature susceptibility, and reduces moisture sensitivity. For this work, steel fibres have been used for modifying asphalt mixture as they incorporated in the specimens by three percentages designated as 0.5, 1.0 and 1.5 % by the weight of asphalt mixture. The evaluation process based on conducting Marshall Test, Compressive strength test, and the wheel tracking test. The optimum asphalt content was determined for asphalt mixture. The results of the Marshall quotient and the index of retained strength of modified mixtures were increased by 44.0 and 17.38% respectively with adding 1.0% of steel fibres compared with the conventional mixture. The rut depth and dynamic stability were determined by using a wheel tracking test at two various testing temperatures of 45 and 55°C and two applied stresses of 70 and 80 psi. Results show that adding 1% of steel fibres to asphalt mixtures is very effective in increase the rutting resistance and reduce moisture damage

The Relationship between the Education of Forensic Accounting & Accounting Students Competence in Sudanese Universities.

Forensic accountant plays a significant role in decreasing risk of financial & managerial misstatement in companies. The aim of this study is to investigate the relationship between the education of (FA) & accounting students competence with reference to Sudanese universities. In order to achieve this aim, Descriptive and inferential statistics were used to generalize the results and conclude the findings. The data has been collected through a well-structured questionnaire is designed and will be distributed to a randomly chosen sample of business & economic staff members in some Sudanese universities. Statistical package for the social sciences (SPSS) was used to analyze data and test hypotheses. The results of the study suggest that the inclusion of forensic accounting topics within the curriculum of the accounting department in Sudanese universities developed the characteristics and skills required for a forensic accountant.Also, the study concludes thatthe studying of (FA) increase the ability detect the financial misstatement disputes in the future. The study recommends that there is a necessity for the Coordination between the academic & professional bodies on how to develop the (FA) in the Sudanese environment