排序方式： 共有95条查询结果，搜索用时 15 毫秒
41.
In this work, the cruise control problem of high-speed trains’ movements is investigated. Both cases of a single high-speed train and multiple high-speed trains are under consideration. Different with most existing studies where the centralized control or the decentralized control methods are adopted based on a single point mass model of the train, in this paper, a distributed control mechanism is proposed by virtue of the graph theory, and the high-speed train’s model is built as a cascade of point masses connected by flexible couplers. For a single high-speed train, the neighboring cars interact through the coupling force with each other, which can be described by a connected topological graph by regarding each car as a node. Besides, the speed information communication among the cars is considered to be described by another directed topological graph. A distributed control strategy is then developed, with which all the cars of a train track a desired speed asymptotically and the neighboring cars keep a safety distance from each other. For the multiple high-speed trains running on a railway line, the in-train force interaction topology and the speed information communication topology of all the trains are more complex than those of a single train. A new cluster consensus technique is developed, by which a distributed control law is designed. Under the control law, the trains can track the desired speeds asymptotically, the headway distance between adjacent trains and the distance between the neighboring cars of a train can be kept in appropriate ranges. Finally, simulations are provided to illustrate the effectiveness of the obtained theoretical results. 相似文献
42.
Trang Thi Thuy Nguyen M. Obaidul Hamid 《Journal of Language, Identity & Education》2017,16(3):142-156
This article examines the impact of subtractive schooling, including language use in education, on the identity of a group of ethnic minority students in Central Highlands of Vietnam. Drawing on semistructured interview data, a deeper look is taken into the ways in which these students identify themselves with their languages, cultures, and social relations. Findings reveal that the subtractive power of the school language and the institutional milieu profoundly influenced their identity construction by creating the conditions for (a) the devaluation of their language and cultural identity as a consequence of the invasion of their sociocultural territory by the dominant language and culture and (b) the segregation and disunity that affected their identity construction through social relations. Although subtractive schooling apparently facilitated students’ integration into the mainstream, its invisible power forced them not only to integrate but also to bear the full burden of constructing new identities to adjust to the school environment and the mainstream society. 相似文献
43.
The preservation of confidentiality has become a major issue for the majority of applications that process personal information, the sensitivity of this information requires creators to set rules for the sharing and use of access control policies. A great deal of research has already been conducted in educational environments. However, one aspect that has not received much attention is the important role of Information Security, especially in newer education environments such as the e-learning environment. In this article we seek to propose a policy of security in such a way to affect views of profiles for each user to control the information accessed by this user. 相似文献
44.
45.
Bandar Alhamdan Khalid Al-Saadi Aspa Baroutsis Anna Du Plessis Obaidul M. Hamid 《比较教育学》2014,50(4):490-505
This paper reports on an investigation into the representation of teachers in newspapers in five countries. An innovative methodology was used to develop a method of inquiry that supports a deeper understanding of media representations of teachers which can also be used by other researchers in comparative education. The paper explores relevant literature on teachers' work and media studies, and describes the decisions made about the selection of newspapers from the five countries and the analytical framework. Central to the project was the development of an analytic framework which we applied to our analysis of the media data collected from the five countries. The process revealed the construction of four categories of teacher identity: the caring practitioner; the transparent (un)professional; the moral and social role model; and the transformative intellectual. The aim was not to generalise categories but to offer them as they were found in newspapers during this time frame. The data analysis demonstrates the applicability of the innovative methodology while the project also contributes to locally translated understandings of teacher representations. The paper concludes with a reflection on the effectiveness of the methodology for comparative research. 相似文献
46.
Active Noise Control (ANC) systems are increasingly used to reduce environmental noises. A hybrid ANC system is a combination of feedforward and feedback structures in which the anti-noise signal is generated using both structures. Employing the advantages of feedforward and feedback structures enables a hybrid structure to have a high performance in controlling unwanted noise. The step size of filters used in ANC systems plays an essential role in its performance. Any variation from the appropriate value leads to divergence or inefficiency of the noise controller system. These parameters are often set experimentally, which is a time-consuming task. In addition, there is no guarantee that the system can adapt itself to situational changes. The objective of this paper is to propose a new self-tuning hybrid ANC method. Using this technique, the system continuously estimates the parameters during its operation. Results of computer simulations demonstrate the robustness of the proposed method. 相似文献
47.
The aim of this study was to investigate the effects of maturation on power and sprint performance adaptations following 6 weeks of plyometric training in youth soccer players during pre-season. Sixty male soccer players were categorized into 3 maturity groups (Pre, Mid and Post peak height velocity [PHV]) and then randomly assigned to plyometric group and control group. Vertical jump, standing long jump, and 20-m sprint (with and without ball) tests were collected before- and after-intervention. After the intervention, the Pre, Mid and Post-PHV groups showed significant (P ≤ 0.05) and small to moderate effect size (ES) improvement in vertical jump (ES = 0.48; 0.57; 0.73), peak power output (E = 0.60; 0.64; 0.76), standing long jump (ES = 0.62; 0.65; 0.7), 20-m sprint (ES = ?0.58; ?0.66), and 20-m sprint with ball (ES = ?0.44; ?0.8; ?0.55) performances. The Post-PHV soccer players indicated greater gains than Pre-PHV in vertical jump and sprint performance after training (P ≤ 0.05). Short-term plyometric training had positive effects on sprinting and jumping-power which are important determinants of match-winning actions in soccer. These results indicate that a sixty foot contact, twice per week program, seems effective in improving power and sprint performance in youth soccer players. 相似文献
48.
Output feedback stabilization of switching discrete-time linear systems with parameter uncertainties
Hamza Bibi Fazia Bedouhene Ali Zemouche Hamid Reza Karimi Houria Kheloufi 《Journal of The Franklin Institute》2017,354(14):5895-5918
This paper deals with observer-based control design for a class of switched discrete-time linear systems with parameter uncertainties. The main contribution of the paper is to propose a convenient way based on Finsler’s lemma to enhance the synthesis conditions, expressed in terms of Linear Matrix Inequalities (LMIs). Indeed, this judicious use of Finsler’s lemma provides additional decision variables, which render the LMIs less conservative and more general than all those existing in the literature for the same class of systems. Two numerical examples followed by a Monte Carlo evaluation are proposed to show the superiority of the proposed design technique. 相似文献
49.
Nasrin Ziamajidi Hamid Behrouj Roghayeh Abbasalipourkabir Fatemeh Lotfi 《Indian journal of clinical biochemistry : IJCB》2018,33(2):147-153
Diabetes mellitus (DM) is one of the most prevalent diseases in the world, which is strongly associated with liver dysfunction. Hyperglycemia, through an oxidative stress pathway, damages various tissues. Herbal medicine is a good candidate to ameliorate hyperglycemia and oxidative stress. In this study, the effects of aqueous Allium sativum (garlic) extract (AGE) on gene expression of inducible nitric oxide synthases (iNOS) and production of nitric oxide (NO) were evaluated in the liver tissue of diabetic rats. Four groups of rats contained normal control rats, garlic control rats (AGE), Streptozotocin (STZ) + nicotinamide-induced diabetic rats (DM), and diabetic rats treated with garlic (DM + AGE). Glucose levels and liver enzymes activities were determined by colorimetric assay in the serum. Gene expression of iNOS by real-time PCR, NO levels by Griess method, oxidative stress parameters by spectrophotometric method and histopathological examination by hematoxylin and eosin staining method were evaluated in the liver tissues. Glucose levels, activities of liver enzymes, oxidative stress markers, iNOS gene expression, and NO production increased significantly in diabetic rats in comparison with control rats, whereas after oral administration of garlic, these parameters decreased significantly, close to the normal levels. Hence, the beneficial effects of garlic on the liver injury of diabetes could be included in the hypoglycaemic and antioxidant properties of garlic via a decrease in gene expression of iNOS and subsequent NO production. 相似文献
50.
The paper presents the results of an international questionnaire survey of the attitudes of senior authors towards scholarly publishing. It was commissioned by the Publishers Association (PA) and the International Association of Scientific, Technical and Medical Publishers (STM). A total of 5,513 authors participated. The questionnaire included 22 closed questions and one open‐ended question that 1,943 authors used to freely express their views. Using QSR N6 textual analysis software, their comments were processed and themes extracted. The main concerns of the authors were the peer‐review process, faster publishing, better access to journals, journal prices, and issues related to electronic publishing. 相似文献