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11.
The main contribution of this paper is to develop an adaptive output-feedback control approach for a class of uncertain nonlinear systems with unknown time-varying delays in the pure-feedback form. Both the non-affine nonlinear functions and the unknown time-varying delayed functions related to all state variables are considered. These conditions make the controller design difficult and challenging because the output-feedback controller should be designed using only the output information. In order to overcome these conditions, we design an observer-based adaptive dynamic surface controller where the time-delay effects are compensated by using appropriate Lyapunov–Krasovskii functionals and the function approximation technique using neural networks. A first-order filter is added to the control input to avoid the algebraic loop problem caused by the non-affine structure. It is proved that all the signals in the closed-loop system are semi-globally uniformly bounded and the tracking error converges to an adjustable neighborhood of the origin. 相似文献
12.
This study examines audience uses of three types of interactivity, user motivations for visiting an online newspaper, and the relationship between user motivations and use of the different types of interactive features. There are three types of interactivity on a continuum: medium, human/medium, and human interactivity. In an online survey of 542 respondents, results indicate that medium interactive features were used most frequently and human interactive features used the least. Three motivations for using online newspapers emerged—information seeking/surveillance, socialization, and entertainment. In addition, further analysis found that although all three motivations were predictors of use of medium interactive features, the information seeking/surveillance motivation was not a significant predictor of use of human/medium and human interactive features. 相似文献
13.
Hyunju Lee Jungsook Yoo Kyunghee Choi Sung-Won Kim Joseph Krajcik Benjamin C. Herman 《International Journal of Science Education》2013,35(12):2079-2113
Our guiding presupposition in this study was that socioscientific issues (SSI) instruction, given the humanistic features that comprise this type of instruction, could play a role as a vehicle for cultivating character and values as global citizens. Our main objective was to observe how and to what extent SSI instruction might contribute to this. In order to achieve this aim, we implemented a SSI program on genetic modification technology for 132 ninth-grade students over 3–4 weeks and identified its educational effects using a mixed method approach. Data sources included student responses to questionnaire items that measure the students' character and values, records of student discussions, and semi-structured interviews with the students and their teachers. Results indicated that the students became more sensitive to moral and ethical aspects of scientific and technological development and compassionate to diverse people who are either alienated by the benefits of advanced technology or who are vulnerable to the dangers of its unintended effects. In addition, the students felt more responsible for the future resolution of the genetic SSI. However, the students struggled to demonstrate willingness and efficacy to participate within broader communities that entailed action toward SSI resolution. 相似文献
14.
Sehee Hong Sung-Kyung Yoo Sukkyung You Chih-Chun Wu 《Journal of Experimental Education》2013,81(4):419-439
This study focused on comparing the longitudinal associations between two types of parental involvement (i.e., mathematics value and academic reinforcement) and high school students’ mathematics achievement, using data from the Longitudinal Study of American Youth(LSAY). Results, based on multivariate autoregressive cross-lagged modeling, indicated that parents’ academic reinforcement had no effect on students’ mathematics achievement and vice versa; however, a statistically significant positive reciprocal influence existed between parents’ mathematics value and students’ mathematics achievement throughout high school. This result not only reaffirms that parental involvement is a multidimensional construct but also implies that parental involvement has a domain-specific effect. Results from multigroup analyses revealed that students’ gender did not have a differential effect on these associations. 相似文献
15.
Yoonsook Chung Jungsook Yoo Sung-Won Kim Hyunju Lee Dana L. Zeidler 《International Journal of Science and Mathematics Education》2016,14(1):1-27
Communication skills are one of the most important competencies for 21st century global citizens. Our guiding presupposition was that socioscientific issues (SSIs) could be used as an effective pedagogical tool for promoting students’ communication skills by increasing peer interactions, stimulating students’ reasoning, and in constructing shared social knowledge. We implemented a SSI program on gene modification (GM) technology to 132 9th graders in South Korea and investigated to what extent this SSI instruction contributed to enhancing students’ communication skills. Data sources included pre- and post-scores on the Communication Skills Questionnaire (CSQ), semi-structured interviews with the students and instructor, and classroom observations. The results demonstrated that SSI instruction could bring about a moderately large impact on students’ ability to understand the key ideas of others and to value others’ perspectives, as well as a marginal positive effect on developing active assertions. However, SSI instruction appeared to have a lesser impact on students’ ability to develop shared understanding. Overall, this research indicates the potential that even a limited SSI classroom could have in terms of promoting students’ communication skills in the context of their regular science class. 相似文献
16.
Sung-Kyung Yoo 《Asia Pacific Education Review》2001,2(1):94-100
This study explored whether, and how, ethnicity and individualism-collectivism are related to depression symptomatology and
attitudes toward seeking professional help using a comparison of university students in the United States and South Korea.
Eighty eight American college students and 95 South Korean college students participated in the study. Canonical correlation
analyses revealed that low ratings on vertical individualism in American culture are related to more positive attitudes toward
seeking professional help. On the basis of these findings some tentative counseling implications are considered and directions
for future research are proposed. 相似文献
17.
Joan P. Yoo Elizabeth Palley 《International Journal of Disability, Development & Education》2014,61(4):362-376
This article examines the development of South Korean special education policy and suggests that different strategies of policy diffusion influenced the design of the policy at different times. Historically, South Korea relied on external pressures and influences, particularly US law and UN guidelines, to develop much of its human rights law, including special education. This article suggests that development of democratic infrastructure in South Korea led to improvements in the legislative development process in relation to current special education law, and this led to legislation that better identifies and addresses the needs of children with disabilities. 相似文献
18.
Sung-Kyung Yoo Sehee Hong Nanhee Sohn Karen M. O’Brien 《Asia Pacific Education Review》2014,15(2):271-281
The study examined client’s perceptions of working alliance as a mediator and moderator between client expectations of counseling success and counseling outcome. Participants were 284 adult clients in counseling in university or community counseling centers or private practices in South Korea. Level of functioning at the start of counseling was used to control for counseling outcome. Results of structural equation modeling analyses indicated that working alliance fully mediated the relationship between client expectations of counseling success and counseling outcome. In addition, moderation of counseling expectations by working alliance on counseling outcome was supported. Implications for research and practice are discussed. 相似文献
19.
Kyoung-Sae Na Soyoung Irene Lee Hyun Ju Hong Myoung-Ja Oh Geon Ho Bahn Kyunghee Ha Yun Mi Shin Jungeun Song Eun Jin Park Heejung Yoo Hyunsoo Kim Yun-Mi Kyung 《Child abuse & neglect》2014
In the last few decades, changing socioeconomic and family structures have increasingly left children alone without adult supervision. Carefully prepared and limited periods of unsupervised time are not harmful for children. However, long unsupervised periods have harmful effects, particularly for those children at high risk for inattention and problem behaviors. In this study, we examined the influence of unsupervised time on behavior problems by studying a sample of elementary school children at high risk for inattention and problem behaviors. The study analyzed data from the Children's Mental Health Promotion Project, which was conducted in collaboration with education, government, and mental health professionals. The child behavior checklist (CBCL) was administered to assess problem behaviors among first- and fourth-grade children. Multivariate logistic regression analysis was used to evaluate the influence of unsupervised time on children's behavior. A total of 3,270 elementary school children (1,340 first-graders and 1,930 fourth-graders) were available for this study; 1,876 of the 3,270 children (57.4%) reportedly spent a significant amount of time unsupervised during the day. Unsupervised time that exceeded more than 2 h per day increased the risk of delinquency, aggressive behaviors, and somatic complaints, as well as externalizing and internalizing problems. Carefully planned afterschool programming and care should be provided to children at high risk for inattention and problem behaviors. Also, a more comprehensive approach is needed to identify the possible mechanisms by which unsupervised time aggravates behavior problems in children predisposed for these behaviors. 相似文献
20.
This paper proposes an adaptive approximation design for the decentralized fault-tolerant control for a class of nonlinear large-scale systems with unknown multiple time-delayed interaction faults. The magnitude and occurrence time of the multiple faults are unknown. The function approximation technique using neural networks is employed to adaptively compensate for the unknown time-delayed nonlinear effects and changes in model dynamics due to the faults. A decentralized memoryless adaptive fault-tolerant (AFT) control system is designed with prescribed performance bounds. Therefore, the proposed controller guarantees the transient performance of tracking errors at the moments when unexpected changes of system dynamics occur. The weights for neural networks and the bounds of residual approximation errors are estimated by using adaptive laws derived from the Lyapunov stability theorem. It is also proved that all tracking errors are preserved within the prescribed performance bounds. A simulation example is provided to illustrate the effectiveness of the proposed AFT control scheme. 相似文献