Super-twisting observer-based sliding mode control with fuzzy variable gains and its applications to fully-actuated hexarotors     

Ngo Phong Nguyen  Wonhee Kim  Jun Moon 《Journal of The Franklin Institute》2019,356(8):4270-4303

In this paper, we consider the super-twisting observer-based sliding mode control algorithm with fuzzy variable gains (STOSMC) for the fully-actuated hexarotor. Our hexarotor has full actuation due to six titled propellers that allows to control position and orientation (attitude) simultaneously, and resolves the singularity problem of the rotational matrix by using the quaternion modeling framework. We show that the proposed STOSMC for the hexarotor guarantees finite-time convergence of the estimation error and asymptotic stability of the hexarotor. In simulations, we demonstrate the nonsingularity and fully-actuated control performance of the hexarotor by considering extreme position and attitude control scenarios. Moreover, the simulation results show that the hexarotor achieves the fast and precise tracking performance to the desired position and the desired attitude and the chattering phenomenon is reduced compared with the fixed-gains observer-based super-twisting sliding mode control due to the fuzzy mechanism.  相似文献   

Less than expected—The minor role of foreign firms in upgrading domestic suppliers—The case of Vietnam     

Thi Xuan Thu Nguyen  Javier Revilla Diez 《Research Policy》2019,48(6):1573-1585

Vietnam is an important case for studying the impact of foreign firms’ backward linkages on local firms’ productivity. As an emerging economy Vietnam became the second most popular FDI destination after China in Pacific Asia since 2014. Our empirical analysis for Vietnam as a whole demonstrates a significant difference in the productivity growth between domestic suppliers who have a direct linkage with foreign firms and non-suppliers. This is also true for the Southeast Region (SE) with Ho-Chi-Minh City as economic center. However, in the Red River Delta (RRD), that difference is not statistically significant. Based on in-depth interviews with domestic suppliers, we reveal that in the RRD, effects of foreign firms on the productivity upgrading of domestic suppliers are indirect and limited while internal factors like absorptive capacity are more important for the productivity growth. These regional differences can be traced back to different regional specializations which still persist from the pre-reform era.  相似文献   

Web document summarization by exploiting social context with matrix co-factorization     

Minh-Tien Nguyen  Viet Cuong Tran  Xuan Hoai Nguyen  Le-Minh Nguyen 《Information processing & management》2019,56(3):495-515

In the context of social media, users usually post relevant information corresponding to the contents of events mentioned in a Web document. This information posses two important values in that (i) it reflects the content of an event and (ii) it shares hidden topics with sentences in the main document. In this paper, we present a novel model to capture the nature of relationships between document sentences and post information (comments or tweets) in sharing hidden topics for summarization of Web documents by utilizing relevant post information. Unlike previous methods which are usually based on hand-crafted features, our approach ranks document sentences and user posts based on their importance to the topics. The sentence-user-post relation is formulated in a share topic matrix, which presents their mutual reinforcement support. Our proposed matrix co-factorization algorithm computes the score of each document sentence and user post and extracts the top ranked document sentences and comments (or tweets) as a summary. We apply the model to the task of summarization on three datasets in two languages, English and Vietnamese, of social context summarization and also on DUC 2004 (a standard corpus of the traditional summarization task). According to the experimental results, our model significantly outperforms the basic matrix factorization and achieves competitive ROUGE-scores with state-of-the-art methods.  相似文献   

Bidirectional longitudinal relationship between Chinese children's compounding awareness and vocabulary knowledge from Grades 3 to 6     

Ruibo Xie  Xinchun Wu  Thi Phuong Nguyen  Ying Zhao  Jie Feng 《Journal of Research in Reading》2020,43(4):482-495

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A Comparison of the Effects of Two Different Online Homework Systems on Levels of Knowledge Retention in General Chemistry Students     

Nabulsi  Leena  Nguyen  Amy  Odeleye  Oluwatobi 《Journal of Science Education and Technology》2021,30(1):31-39

Journal of Science Education and Technology - Online homework systems have been shown to help student achievement in chemistry courses. This study sought to compare the levels of knowledge...  相似文献   

Synergizing geriatric research and education in an allied health profession with an older adult community advisory board: development and process outcomes     

An Thi Nguyen  Sharon Burnside  Kristin Junge  Emily Kling Somerville  Marian Keglovits 《Educational gerontology》2020,46(8):486-496

ABSTRACT

Community advisory boards (CABs) have been used to improve research outcomes involving specific communities and populations, including older adults. There is potential to synergize the use of CABs to encompass both research activities and the education of healthcare professionals to help meet increasing demands for a geriatric healthcare workforce in aging populations worldwide. We describe the development and process outcomes of a CAB that synergizes geriatric research and education of students in an allied health profession (occupational therapy). Implementation costs from June 2017–June 2019 were recorded. In-depth interviews were conducted with CAB participants, who were community-dwelling older adults living in St. Louis, Missouri, United States. Interview data were analyzed using a constant comparison method based on a grounded theory approach. Themes were derived regarding barriers, facilitators, and benefits of CAB participation for older adults. Fourteen older adults (aged 65 and over) were initially recruited. The total direct cost of CAB implementation was 4050 United States Dollars over two years. Barriers to CAB participation for older adults included unexpected schedule conflicts due to illness and lack of understanding of the research process, while facilitators included accessible meeting spaces, staff support, flexible participation options, and financial support (e.g., transportation). Perceived benefits of CAB participation included gains in social capital, more positive views of research, and social connectedness. Key lessons learned are described and can be used to inform a novel approach to developing and implementing CABs to improve outcomes of geriatric research and education.  相似文献   

Predicting relevance based on assessor disagreement: analysis and practical applications for search evaluation     

Thomas Demeester  Robin Aly  Djoerd Hiemstra  Dong Nguyen  Chris Develder 《Information Retrieval》2016,19(3):284-312

Evaluation of search engines relies on assessments of search results for selected test queries, from which we would ideally like to draw conclusions in terms of relevance of the results for general (e.g., future, unknown) users. In practice however, most evaluation scenarios only allow us to conclusively determine the relevance towards the particular assessor that provided the judgments. A factor that cannot be ignored when extending conclusions made from assessors towards users, is the possible disagreement on relevance, assuming that a single gold truth label does not exist. This paper presents and analyzes the predicted relevance model (PRM), which allows predicting a particular result’s relevance for a random user, based on an observed assessment and knowledge on the average disagreement between assessors. With the PRM, existing evaluation metrics designed to measure binary assessor relevance, can be transformed into more robust and effectively graded measures that evaluate relevance towards a random user. It also leads to a principled way of quantifying multiple graded or categorical relevance levels for use as gains in established graded relevance measures, such as normalized discounted cumulative gain, which nowadays often use heuristic and data-independent gain values. Given a set of test topics with graded relevance judgments, the PRM allows evaluating systems on different scenarios, such as their capability of retrieving top results, or how well they are able to filter out non-relevant ones. Its use in actual evaluation scenarios is illustrated on several information retrieval test collections.  相似文献   

Reconstructing ‘Education’ through mindful attention: Positioning the mind at the center of curriculum and pedagogy     

Cuong Nguyen 《Educational Philosophy and Theory》2019,51(5):535-536

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Connections between learning and teaching: EFL teachers’ reflective practice     

Chinh Duc Nguyen 《Pedagogies: An International Journal》2017,12(3):237-255

This study explores six Vietnamese, English as a Foreign Language (EFL) teachers’ reflections on their experiences of English language learning during the early 1980s to the late 1990s. Data collected in narrative interviews with the participating teachers revealed a wide range of issues that arose during their EFL learning, central to which was the prevalence of grammar-focused practices in all EFL classes. From their perspectives as EFL teachers today, the participants see their learning experience as a way of learning to teach. In particular, they pinpoint the negative aspects of language teaching at that time in the hope that their teaching practice today will not repeat the same mistakes. However, they also reflect on positive aspects, especially their influential teachers, to inform their teaching. Based on the findings, the study suggests that language teachers’ experience of language learning should be considered part of reflective teaching as well as of teachers’ trajectories of learning to teach.  相似文献   

Voices from the Field: Perspectives of U.S. Kinesiology Chairs on Opportunities,Challenges, and the Role of Mentoring in the Chair Position     

Lynda B. Ransdell  Nhu Nguyen  Mary A. Hums  Megan Clark  Sarah B. Williams 《Quest (Human Kinetics)》2018,70(2):234-255

This study examined perspectives of U.S. collegiate kinesiology department chairs (n = 54/144; 37.5% response rate) relative to: (a) opportunities and most enjoyable aspects of being a department chair, (b) challenges and least enjoyable aspects of being a department chair, and (c) perspectives on mentoring. The majority of participants enjoyed their chair role (90%) and did not aspire to advance in administration (61%). Job-related opportunities included mentoring others, facilitating department success, and leading initiatives (e.g., curricula, policies, and finances). Job-related challenges included a lack of university support, personnel issues, and urgent requests for information. Many had a mentor for a long time (mean = 7.9 ± 7.6 years; range 1 to 28 years), and the majority (71%) did not consider their dean a mentor. Protégés appreciated their mentors’ experience, listening skills, and willingness to share information, advice, and empathy. Results from this study provide helpful information for serving as a kinesiology chair.  相似文献