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1.
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
2.
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
3.
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
4.
Drawing on data from a merged data set from a student survey and a parent survey that were conducted in the Emirate of Abu Dhabi in 2013, this article uses a multilevel framework to investigate the effects of individual characteristics and the classroom and school environments on high school students’ school engagement in a modernising education system that is different from Western ones. The results of the three-level model revealed that while students’ attributes remained strong predictors of their school engagement, the social and organisational environment of classrooms and school also greatly shaped the extent to which students emotionally and cognitively engaged with their school and learning. This study provided evidence to support the interactive nature of the impact of multilevel environments on student engagement. The policy and research implications were also discussed in the empirical context of Abu Dhabi. 相似文献
5.
Let G be a weighted graph with adjacency matrix A=[aij]. An Euclidean graph associated with a molecule is defined by a weighted graph with adjacency matrix D=[d/ij], where for i≠j, dij is the Euclidean distance between the nuclei i and j. In this matrix dij can be taken as zero if all the nuclei are equivalent. Otherwise, one may introduce different weights for different nuclei.Balasubramanian (1995) computed the Euclidean graphs and their automorphism groups for benzene, eclipsed and staggered forms of ethane and eclipsed and staggered forms of ferroeene. This paper describes a simple method, by means of which it is possible to calculate the automorphism group of weighted graphs. We apply this method to compute the symmetry of tetraammine platinum(Ⅱ) with C2v and C4v point groups. 相似文献
6.
Xue-li BAI Qi ZHANG Noman MASOOD Waqas MASOOD Yun ZHANG Ting-bo LIANG 《Journal of Zhejiang University. Science. B》2013,14(3):185-194
Pancreatic cystic neoplasms(PCNs) are a diverse group of neoplasms in the pancreas,and are more increasingly encountered with widespread abdominal screening and improved imaging techniques.The most common types of PCNs are serous cystic neoplasms(SCNs),mucinous cystic neoplasms(MCNs),and intraductal papillary mucinous neoplasms(IPMNs).Clinicians frequently feel bewildered in the differential diagnosis and subsequent management among the various types of lesions in the pancreas,which may lead to overtreatment or delayed treatment.The current review provides recent developments in the understanding of the three most common types of PCNs,the latest modalities used in preoperative diagnosis and differential diagnosis,as well as the most up to date management.Suggestions for diagnosis and differential diagnosis of SCNs,MCNs,and IPMNs are also provided for young surgeons.Better understanding of these neoplasms is essential for clinicians to make accurate diagnosis and to provide the best management for patients. 相似文献
7.
Deb Risisky Syed Masood Asghar Madeline Chaffee Nancy DeGennaro 《The Journal of perinatal education》2013,22(3):136-144
A qualitative nonexperimental thematic analysis was conducted at a hospital-based midwifery practice to explore the views of participants in group prenatal care and its impact on pregnancy, birth, and postnatal care. Ten women and three support people, recruited through purposive sampling, shared their feedback on the program. The findings conveyed three broad themes: program experience, midwife relationship, and support. Women enjoyed the opportunity for in-depth learning, and peer-group support led to normalizing of pregnancy concerns. Having support people as participants also helped during pregnancy, birth, and child care. The findings showed the enhanced opportunity for education, learning, and interpersonal support provided by CenteringPregnancy to expectant mothers had a positive impact on their pregnancy experiences. 相似文献
8.
MOGHANI Ghorban Ali ASHRAFI Ali Reza HAMADANIAN Masood 《Journal of Zhejiang University. Science. B》2005,(3)
Let G be a weighted graph with adjacency matrixA=[aij]. An Euclidean graph associated with a molecule is defined by a weighted graph with adjacency matrix D=[dij], where for i≠j, dij is the Euclidean distance between the nuclei i andj. In this matrix dij can be taken as zero ifall the nuclei are equivalent. Otherwise, one may introduce different weights for different nuclei. Balasubramanian (1995) computed the Euclidean graphs and their automorphism groups for benzene, eclipsed and staggered forms of ethane and eclipsed and staggered forms of ferrocene. This paper describes a simple method, by means of which it is possible to calculate the automorphism group of weighted graphs. We apply this method to compute the symmetry of tetraammine platinum(Ⅱ) with C2v and C4v point groups. 相似文献
9.
Output reversibility involves dynamical systems where for every initial condition and the corresponding output there exists another initial condition such that the output generated by this initial condition is a time-reversed image of the original output with the time running forward. Through a series of necessary and sufficient conditions, we characterize output reversibility in linear discrete-time dynamical systems in terms of the geometric symmetry of its eigenvalue set with respect to the unit circle in the complex plane. Furthermore, we establish that output reversibility of a linear continuous-time system implies output reversibility of its discretization. In addition, we present a control framework that allows to alter the system dynamics in such a way that a discrete-time system, otherwise not output reversible, can be made output reversible. Finally, we present numerical examples involving a discretization of a Hamiltonian system that exhibits output reversibility and an example of a controlled system that is rendered output reversible. 相似文献
10.
ABSTRACTA multilevel framework was applied to investigate the effects of teacher characteristics, school environment, and district level HRM practices on teacher commitment. Drawing on the results from a public school teacher survey conducted in the Emirate of Abu Dhabi in 2014, four forms of teacher commitment (commitment to school, to students, to teaching, and to community) were tested, which provided empirical evidence to further the development of teacher commitment as a multi-foci construct. The results of the three-level model revealed differentiating effects of some individual and organisational variables on different forms of teacher commitment and highlighted that nationality, multiple interpersonal support, and collegial relationships were the most consistent and strong variables to predict teacher commitment. This study suggested that the social and interpersonal environment of school played a significant role in influencing teacher commitment. Results were discussed in relation to improving the commitment of teachers in the empirical context of Abu Dhabi public schools. 相似文献