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21.
Integration of microfluidic devices with pressure-driven, self-powered fluid flow propulsion methods has provided a very effective solution for on-chip, droplet blood testing applications. However, precise understanding of the physical process governing fluid dynamics in polydimethylsiloxane (PDMS)-based microfluidic devices remains unclear. Here, we propose a pressure-driven diffusion model using Fick''s law and the ideal gas law, the results of which agree well with the experimental fluid dynamics observed in our vacuum pocket-assisted, self-powered microfluidic devices. Notably, this model enables us to precisely tune the flow rate by adjusting two geometrical parameters of the vacuum pocket. By linking the self-powered fluid flow propulsion method to the sedimentation, we also show that direct plasma separation from a drop of whole blood can be achieved using only a simple construction without the need for external power sources, connectors, or a complex operational procedure. Finally, the potential of the vacuum pocket, along with a removable vacuum battery to be integrated with non-PDMS microfluidic devices to drive and control the fluid flow, is demonstrated. 相似文献
22.
Liang Xiong Lyu Fen Li Kang Wu Pan Deng Seung Hee Jeong Zhigang Wu Han Ding 《国家科学评论(英文版)》2019,6(5):970
Soft robotics with new designs, fabrication technologies and control strategies inspired by nature have been totally changing our view on robotics. To fully exploit their potential in practical applications, untethered designs are preferred in implementation. However, hindered by the limited thermal/mechanical performance of soft materials, it has been always challenging for researchers to implement untethered solutions, which generally involve rigid forms of high energy-density power sources or high energy-density processes. A number of insects in nature, such as rove beetles, can gain a burst of kinetic energy from the induced surface-energy gradient on water to return to their familiar habitats, which is generally known as Marangoni propulsion. Inspired by such a behavior, we report the agile untethered mobility of a fully soft robot in liquid based on induced energy gradients and also develop corresponding fabrication and maneuvering strategies. The robot can reach a speed of 5.5 body lengths per second, which is 7-fold more than the best reported, 0.69 (body length per second), in the previous work on untethered soft robots in liquid by far. Further controlling the robots, we demonstrate a soft-robot swarm that can approach a target simultaneously to assure a hit with high accuracy. Without employing any high energy-density power sources or processes, our robot exhibits many attractive merits, such as quietness, no mechanical wear, no thermal fatigue, invisibility and ease of robot fabrication, which may potentially impact many fields in the future. 相似文献
23.
Despite the growing interest and importance of pre-service teachers’ cross-cultural experiences, a review of the literature shows that few studies have discussed the international teaching practicum experiences of pre-service teachers from Asian countries. Bridging this gap, this qualitative case study examined the perceptions and experiences of 15 Korean social studies pre-service teachers who participated in an international teaching practicum in the United States. The findings of the study demonstrated that although participants encountered difficulties in speaking a foreign language and adjusting to a different culture, they also gained confidence and self-efficacy by negotiating and actively participating in the teaching and learning process. This international teaching practicum also helped participants promote their own understanding of multiculturalism and their different perspectives of the teachers’ roles, teaching pedagogies, and local education systems. This study offers implications for future multicultural professional development in teacher education and contributes to developing a body of research and scholarship on international teaching practicums from Asian contexts that have, to date, been largely underexplored. 相似文献
24.
Su Ye Sohn Gi Young Jang Byung Min Choi 《Journal of Zhejiang University. Science. B》2010,11(7):539-541
Congenital atresia of the left main coronary artery is a rare occurrence, and surgical revascularizationbypass graft is required.
We here report a rare case of congenital coronary anomaly in an infant. A 10-month-old male infant was admitted to the hospital
with heart failure symptoms. Echocardiographic examinations revealed mitral valve regurgitation and ischemic changes of the
anterolateral papillary muscle and chordae. Coronary angiography showed atresia of the left main coronary artery with a severe
hypoplastic left anterior descending artery and a circumflex coronary artery. Unfortunately, sudden cardiac arrest occurred
after catheterization and the infant did not recover despite of immediate cardiopulmonary resuscitation. Further studies are
needed to find a newer diagnostic method to detect coronary anomaly in an infant, and coronary angiography, if necessary,
has to be performed very carefully. 相似文献
25.
26.
The purpose of this study was to assess, evaluate, and compare the competitive advantages of the human resource development systems of advanced countries. The Global Human Resource Development Index was utilized for this study, since it has been validated through an expert panel’s content review and analytic hierarchy process. Using a sample of 34 OECD member countries, the following conclusions were drawn. First, Switzerland, Sweden, and United States ranked top three in order in National Human Resource Development (NHRD) competitiveness and such Nordic countries as Sweden, Finland, Denmark, Norway, and Iceland showed outstanding NHRD competitiveness. Second, thirty-four countries differed significantly in key aspects of supply, demand, environment, and supporting systems of NHRD. Strong, intermediate, and weak groups classified based on NHRD competitiveness significantly differed from one another in all factors of the NHRD system. Third, changes in NHRD competitiveness between 2005 and 2011 did not exhibit specific patterns depending on the level of economic development. Fourth, little changes in NHRD system occurred in a short period of time. The most significant positive changes in NHRD competitiveness were identified in only two cases of Luxemburg (△6) and Poland (△6) among 34 countries. Only striking case of decrease in NHRD competitiveness was Israel (▽6). The findings of this research will be able to assist each country in identifying its strengths and weaknesses in the NHRD system. 相似文献
27.
Linda Serra Hagedorn Hye Sun Moon Scott Cypers William E. Maxwell Jaime Lester 《Community College Journal of Research & Practice》2013,37(3):223-242
ABSTRACT In this article, the authors introduce a novel way, using the metaphor of a baseball game, to evaluate and measure community college student progress for those whose stated goal is to transfer to a 4-year institution and, ultimately, earn a bachelor's degree. The proposed framework of “the Transfer Game” is an outgrowth of the Transfer and Retention of Urban Community College Students (TRUCCS) project, which is a longitudinal study of 5,000 community college students from the 9-campuses of the Los Angeles Community College District. The goal of the project is to explain how the “all-American game” provides a method to measure, comprehend, and visualize student progression, and identify the factors that predict both success and barriers. The framework provides a scholarly comparison of the all-American game of baseball to the All-American invention of the community college. 相似文献
28.
ABSTRACT Research on media substitution theory has examined substitutional and/or complementary relationships between new and existing media. This study focuses on the growth of mobile platforms and investigates the relationship between mobile devices and personal computers. Using Nielsen’s panel data that provide electronically recorded media usage (N = 2,396), this study analyzes yearly changes in time allocation to mobile devices and PCs at total and content-specific usage levels during mobile 4G transition. Results suggest a complementarity dynamic between mobile devices and PCs; however, the patterns were more nuanced in light of the role of individual and structural factors when determining media choice. 相似文献
29.
Allan Jeong 《Distance Education》2005,26(3):367-383
This paper proposes a set of methods and a framework for evaluating, modeling, and predicting group interactions in computer‐mediated communication. The method of sequential analysis is described along with specific software tools and techniques to facilitate the analysis of message–response sequences. In addition, the Dialogic Theory and its assumptions are presented to establish a theoretical framework and guide to using sequential analysis in computer‐mediated communication research. Step‐by‐step instructions are presented to illustrate how sequential analysis can be used to measure the way latent variables (e.g., message function, response latency, communication style) and exogenous variables (e.g., gender, discourse rules, context) affect how likely a message is to elicit a response, the types of responses elicited by the message, and whether or not the elicited sequence of responses (e.g., claim → challenge → explain) mirror the processes that support group decision‐making, problem‐solving, and learning. 相似文献
30.
The purpose of this study is to develop the evaluation factors for the Subject Guide for Korean Modern Literature, which is provided by the National Library of Korea, to enhance the guides as an effective public service. In the study, the following final evaluation factors were identified: four evaluation domains (use, content, format, and collaboration), 23 evaluation components, and 67 evaluation items and questions. The results of the study showed that key evaluation components included the reliability of the website, user communication, accessibility to the subject guides, book search capability, provision of information in a consistent format, and the scope of the subject guides. When the subject-specific bibliography system of the National Library of Korea was examined by applying the developed evaluation factors, it was found that the system satisfied only 37 (55.2%) of 67 evaluation items: 8 (40%) of 20 items on use, 13 (66%) of 20 items on content, 15 (88%) of 17 items on format, and 1 (10%) of 10 items on collaboration. Accordingly, the entire subject-specific bibliography system that is currently in use needs to be reviewed, and changes and improvements need to be made utilizing the derived evaluation factors. In particular, it is imperative to develop a strategy to facilitate collaboration among users and librarians in charge, and a more effective subject guide system. 相似文献