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Finite-time stability involves dynamical systems whose trajectories converge to an equilibrium state in finite time. In this paper, we consider a general class of fully actuated mechanical systems described by Euler–Lagrange dynamics and the class of underactuated systems represented by mobile robot dynamics that are required to reach and maintain the desired trajectory in finite time. An approach known as the terminal sliding mode control (TSMC) involves non-smooth sliding surfaces such that, while on the sliding surface, the error states converge to the origin in finite time thus ensuring finite-time tracking. The main advantage of this control scheme is in fast converging times without excessive control effort. Such controllers are known to have singularities in some parts of the state space and, in this paper, we propose a method of partitioning the state space into two regions where the TSMC is bounded and its complement. We show that the region of bounded TSMC is invariant and design an auxiliary sliding mode controller predicated on linear smooth sliding surface for the initial conditions outside this region. Furthermore, we extend these results to address TSMC for underactuated systems characterized by the mobile robot dynamics. We demonstrate the efficacy of our approach by implementing it for a scenario when multiple dynamic agents are required to move in a fixed formation with respect to the formation leader. Finally, we validate our results experimentally using a wheeled mobile robot platform. 相似文献
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The purpose of the paper is to explore Students' perception of university teaching behaviours in Pakistan. Three hundred and fifty students from the six public sector Pakistani universities returned questionnaires. Assessment framework, learning activities and instructional strategies emerged from factor analysis as common factors. Students' views on five conceptual variables were also analysed: instructional design, active teaching, learning activities, questioning styles; and assessment framework. University teaching in Pakistan was found to be driven by assessment. This is a matter of concern for all stake holders, including the administration of the universities, teachers, students and the Higher Education Commission. A teaching behaviour paradigm shift is required, switching from knowledge-oriented teaching behaviour focused on successful passage through assessment, to teaching behaviour focused upon the development of transferable skills demanded by external markets. 相似文献
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Akhtar Ali Keith J. Topping Riaz H. Tariq 《美中教育评论》2010,7(5):66-77
This paper explores entrepreneurial attributes among the students of The Islamia University of Bahawalpur, a public sector Pakistani university. Multistage sampling was employed to maximize the representation. Five hundred and twenty one master＇s level students from thirty departments returned completed questionnaires. Three factors emerged： self efficacy, efficiency and commitment, and entrepreneurial inclinations. The majority of the students exhibited positive entrepreneurial attributes. However, there was no significant difference between negative and positive entrepreneurial attributes. There was no significant impact of demographic variables such as gender, parental income and profession on entrepreneurial attributes. Impact on practice and policy is discussed. 相似文献
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Upward social mobility has been evident among British ethnic minority communities since the 1960s, and education appears to have had a key role in this process. Despite this, social scientists have been slow to consider the link between education, ethnicity and social stratification. The role of higher education has been particularly neglected. Although there has been some suggestion of an ethnic bias in the allocation of university places, previous work in this area has been limited by the nature of the data that have been available and by the types of analysis that have been conducted. This article includes detailed consideration of the key stages of the university application procedure, and particular attention is given to the role of candidates' predicted and actual A-level grades. Although young people from ethnic minority backgrounds are admitted into university in large numbers, it is suggested that higher education has an ambivalent role in relation to ethnic equality. Institutional biases mean that ethnic minority candidates are filtered into the new university sector, and it is concluded that biases in education and the labour market combine to create a cumulative pattern of ethnic disadvantage. 相似文献
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Masood Badri Asma Al Rashedi Guang Yang Jihad Mohaidat Arif Al Hammadi 《Education and Information Technologies》2016,21(2):471-497
Offering an online integrated high-school course or subject for the first time involves many challenges. Better understanding the factors that affect students’ willingness to participate in the experience could provide support for better implementation of such a strategic initiative. In addition, it is important to understand how personal factors can influence the success of such an endeavour. This study develops a comprehensive structural equation model that captures most causal factors related to offering a high-school course online for the first time. A sample of public and private secondary school students (Grades 10, 11 and 12) in Abu Dhabi were administered an online survey regarding offering free online courses. The instrument was reviewed by other experts in curriculum, information technology and teaching and learning. The final instrument contained dimensions related to student perception of ease of use of e-learning, usefulness, self-efficacy, skills, style, student self-reported performance in certain subjects, use of social media, school support, teacher support, general support, access to the internet, and preferences behavioural intentions to use e-learning. The analysis provides a structural equation model with acceptable statistical fits and with many significant causal relationships. The paths representing direct and indirect effects of the construct predictors on intention to use provided statistical evidence of the validity of the 13 component predictors. Results show significant links between intention to use e-learning, perception of easiness, perception of usefulness, and other factors such as user characteristics and support. Use of social network affect intention to use e-learning indirectly thorough other variables. Limitations and implications of the study in general and as it concerns Abu Dhabi are highlighted. 相似文献
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Tariq Ashraf 《International Information and Library Review》2013,45(3):148-152
The beginning of the 21st century is marked with the developments made in the field of information and technology. The primary role of the information is to equip the citizens to make informed choices. Information is life blood that sustains political, social and business decisions. It may pertain to quality, quantity, standard, and prices of products or services that are needed to make an informed decision. This is particularly true in a country where government and its numerous administrative agencies have expanded in a bewildering manner.The Right to Information Act, passed by the Indian Parliament in the year 2005 has proved to be a landmark for good governance and in helping common people, especially the poor and underprivileged, get their dues from the government. The act has emerged as the most potent tool to empower ordinary citizens to combat state corruption and to play an important and active role in participatory democracy. Drafted by civil society itself, the law is unique in the sense that it has been the result of years of struggle by civil society, NGOs and media. 相似文献
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Prasanthi Mannava Afshan Masood Ambika K. Devi 《Indian journal of clinical biochemistry : IJCB》2015,30(1):113-116
Albright hereditary osteodystrophy (AHO) is a rare hereditary metabolic disorder that may or may not be associated with resistance to parathyroid hormone (pseudohypoparathyroidism) or other hormones. The disorder is commonly characterized by a constellation of dysmorphic physical features and with biochemical levels that demonstrate hypocalcaemia and hyperphosphatemia. We report here a clinical case of a 14 year old male with AHO and we discuss his clinical features, radiographic and laboratory findings along with treatment. 相似文献