Optimized sliding mode current controller for power converters with non-minimum phase nature     

Alireza Goudarzian  Adel Khosravi  Heidar Ali Raeisi 《Journal of The Franklin Institute》2019,356(15):8569-8594

This paper proposes a unified method to design an optimized type of the hysteresis modulation-based sliding mode current controller for non-minimum phase power converters in continuous conduction mode. The traditional sliding mode controlled converters have a slow transient voltage response at heavy loads, a large overshoot at light loads and during abrupt output resistance variations. To solve these problems, an optimized feedback control scheme is used according to the output resistance to adjust the coefficients of the controller. The basic idea of this controller is to suggest a new way for reduction of the sensitivity function amplitude of the closed loop system. The presented approach is developed for three basic DC/DC converters; i.e. boost, buck-boost and quadratic boost converters. Generally, the certain advantages of the suggested control approach are: (i) a fast transient response can be achieved in heavy load conditions, (ii) the voltage overshoot can be effectively reduced during load variations; (iii) the transient voltage overshoot can be eliminated in light load conditions; (iv) the closed loop control sensitivity can be reduced and therefore, the performance specification of a control system can be improved compared with the conventional sliding mode current control. To show the reliability of the suggested control scheme, simulations and experimental results for the derived systems are developed. Several conditions are performed to confirm the effectiveness of the proposed controller.  相似文献   

Raising teachers’ voices: an in-depth qualitative inquiry into teachers’ working conditions and professional development needs in Khyber Pakhtunkhwa,a province of Pakistan     

Takbir Ali 《Teacher Development》2018,22(1):78-104

This study documented in detail teachers’ voices about their working conditions, professional development needs and opportunities to cater to these needs. The study reported in this paper was conducted as part of a large-scale study that used mixed methods to assess teachers’ professional development needs. The qualitative data reported in this paper were collected using focus group discussion with teachers (N = 481), classroom observation (N = 66), post-observation interviews with teachers (N = 24) and analysis of qualitative responses from survey questionnaires (N = 200). By bringing together a collection of teachers’ voices, the findings of the study illuminate a hope for positive change in teaching and learning in public schools in Khyber Pakhtunkhwa, provided that teachers are genuinely considered as part of the solution and are facilitated with necessary physical and structural resources and psychological incentives. The education system needs to create conditions in schools that support teachers’ work and their continued professional growth.  相似文献   

Design of a H_∞ model reference tracking control for interconnected nonlinear systems by decentralized dynamic output-feedback     

Ali Sghaier Tlili 《Journal of The Franklin Institute》2018,355(17):8313-8345

This study investigates the problem of robust tracking control for interconnected nonlinear systems affected by uncertainties and external disturbances. The designed H_∞ dynamic output-feedback model reference tracking controller is parameterized in terms of linear matrix inequalities (LMIs), which is formulated within a convex optimization problem readily implementable. The resolution of such a problem, guarantying not only the quadratic stability but also a prescribed performance level of the resulting closed-loop system, enables to calculate concurrently the robust decentralized control and observation gain matrices. The established LMI conditions are computed in a single-step resolution to obtain all the controller/observer parameters and therefore to overcome the problem of iterative algorithm based on a multi-stage resolution leading in most cases to conservative and suboptimal solutions. Numerical simulations on diverse applications ranging from a numerical academic example to coupled inverted double pendulums and a 3-strongly interconnected machine power system are provided to corroborate the merit of the proposed control scheme.  相似文献   

Study on Impact of Iron and Folic Acid on the Plasma Trace Minerals in Pregnant Anemic Women     

Amit Kumar Mani Tiwari  Abbas Ali Mahdi  Sanjay Mishra 《Indian journal of clinical biochemistry : IJCB》2018,33(1):31-37

Iron deficiency anemia is one of the causes that lead to significant mortality and morbidity among pregnant women and fetus. The present study was undertaken to explore oral iron supplementation can modify the metal contents in pregnant anemic women. Iron and folic acid supplementations was given to 500 anemic women (mild = 200, moderate = 200, and severe = 100) and 100 age matched non-anemic controls daily for 100 days. Blood index values and plasma trace minerals were estimated as per standard protocols. Haemoglobin and ferritin levels were found significantly increased (p < 0.001) in anemic and control subjects after treatment. Moreover, the serum transferring receptor levels and total iron binding capacity were found significantly decreased in all treated groups. Iron (Fe), zinc (Zn) and copper (Cu) levels were found increased (p < 0.01) after oral iron supplementation groups. Moreover, selenium (Se) manganese (Mn) and were found to be decreased in all treated groups. Data provides the conclusion that iron and folic acid supplementation recovered the essential trace minerals, except manganese, which may lead to various complications including peroxidation of vital body molecules resulting in increased risk for pregnant women as well as fetus.  相似文献   

Urinary Urea,Uric Acid and Hippuric Acid as Potential Biomarkers in Multiple Sclerosis Patients     

Hanaa B. Atya  Sahar A. Ali  Mohamed I. Hegazy  Fathia Z. El Sharkawi 《Indian journal of clinical biochemistry : IJCB》2018,33(2):163-170

Urine is a proven source of metabolite biomarkers and has the potential to be a rapid, noninvasive, inexpensive, and efficient diagnostic tool for various human diseases. Despite these advantages, urine is an under-investigated source of biomarkers for multiple sclerosis (MS). The objective was to investigate the level of some urinary metabolites (urea, uric acid and hippuric acid) in patients with MS and correlate their levels to the severity of the disease, MS subtypes and MS treatment. The urine samples were collected from 73 MS patients-48 with RRMS and 25 with SPMS- and age matched 75 healthy controls. The values of urinary urea, uric acid and hippuric acid in MS patients were significantly decreased, and these metabolites in SPMS pattern showed significantly decrease than RRMS pattern. Also showed significant inverse correlation with expanded disability status scale and number of relapses. Accordingly, they may act as a potential urinary biomarkers for MS, and correlate to disease progression.  相似文献   

Robust simultaneous fault detection and control for a class of nonlinear stochastic switched delay systems under asynchronous switching     

Hossein Shokouhi-Nejad  Amir Rikhtehgar Ghiasi  Mohammad Ali Badamchizadeh 《Journal of The Franklin Institute》2017,354(12):4801-4825

This paper concerns the simultaneous fault detection and control (SFDC) problem for a class of nonlinear stochastic switched systems with time-varying state delay and parameter uncertainties. The switching signal of detector/controller unit (DCU) is assumed to be with switching delay, which results in the asynchronous switching between the subsystems and DCU. By constructing a switching strategy depending on the state and switching delays, new sufficient conditions expressed by a set of linear matrix inequalities (LMIs) is derived to design DCU gains. This problem is formulated as an H_∞ optimization problem and both mean square exponential stability and fault detection of augmented system are considered. A numerical example is finally exploited to verify the effectiveness and potential of the achieved scheme.  相似文献   

和田地区中小学"维汉"双语教育三种主要模式及分析     

艾力·伊明 《新疆教育学院学报》2011,27(1):35-41

科学的双语教育理论应该建立在科学地划分双语教育类型的基础上.文章按照学校的语言文化环境将和田地区中小学的双语教育模式大体分为民族学校模式、汉族学校模式、民汉合校模式等三个类型,从理论依据、教学目标、操作程序、操作策略等角度对其进行分析.  相似文献   

Acceptance of mobile technologies and M-learning by university students: An empirical investigation in higher education     

Al-Rahmi  Ali Mugahed  Al-Rahmi  Waleed Mugahed  Alturki  Uthman  Aldraiweesh  Ahmed  Almutairy  Sultan  Al-Adwan  Ahmad Samed 《Education and Information Technologies》2022,27(6):7805-7826

Education and Information Technologies - Mobile-learning (M-learning) apps have grown in popularity and demand in recent years and have become a typical occurrence in modern educational systems,...  相似文献   

Minimization of students’ cognitive load in a virtual chemistry laboratory via contents optimization and arrow-textual aids     

Ali  Numan  Ullah  Sehat  Khan  Dawar 《Education and Information Technologies》2022,27(6):7629-7652

Education and Information Technologies - Virtual Chemistry Laboratories (VCLs) are used as an alternative to the physical laboratories, where users can enhance their performance for hands-on...  相似文献   

Training Transfer and Transfer Motivation: The Influence of Individual,Environmental, Situational,Training Design,and Affective Reaction Factors     

Muhammad Awais Bhatti  Sharrifah Ali  Mohd Faizal Mohd Isa  Mohamed Mohamed Battour 《Performance Improvement Quarterly》2014,27(1):51-82

The purpose of this study is to examine the effects of individual, environmental, training design, and affective reaction factors on training transfer and transfer motivation. To determine the relationship between these factors and their influence on training transfer and to test the model, the researchers collected data from employees in the Malaysian banking sector. Structural equation modeling with Amos 16 was used to test the model and determine the relationship. The study suggested that training stakeholders should manage the training program effectively. Transfer is maximized when trainees have social support, high performance self‐efficacy, and transfer motivation. Stakeholders (e.g., trainers, trainees, supervisors, and peers) are important to the training transfer process, as are learner readiness, trainee reaction, instrumentality, and training retention. This study revealed that perceived content validity and transfer design work together and influence the trainee's performance self‐efficacy. In other words, if trainers want to improve the performance self‐efficacy level of trainees, they need to explain how the trainee can transfer the learned skills at the workplace and make sure the content of the training is similar to the actual job. The main objective of training programs is to align the employee's expertise with organizational goals. Organizations can achieve their desired objectives only when employees transfer the learned skills on the job. Unfortunately, employees often transfer only a small percentage of skills they have learned in training. To effectively manage their training programs, organizations need to identify and focus on the factors that resist effective training transfer.  相似文献