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41.
Investigation of the hydro-mechanical behaviour of fouled ballast   总被引:1,自引:0,他引:1  
In this study, a fouled ballast taken from the site of Sénissiat, France, was investigated. For the hydraulic behaviour, a large-scale cell was developed allowing drainage and evaporation tests to be carried out with monitoring of both suction and volumetric water content at various positions of the sample. It was observed that the hydraulic conductivity of fouled ballast is decreasing with suction increase, as for common unsaturated soils. The effect of fines content was found to be negligible. For the mechanical behaviour, both monotonic and cyclic triaxial tests were carried out using a large-scale triaxial cell. Various water contents were considered. The results were interpreted in terms of shear strength and permanent axial strain. It appeared that the water content is an important factor to be accounted for since any increase of water content or degree of saturation significantly decreases the shear strength and increases the permanent strain. Constitutive modelling has been attempted based on the experimental results. The model in its current state is capable of describing the effects of stress level, cycle number and water content.  相似文献   
42.
Micromixer based on viscoelastic flow instability at low Reynolds number   总被引:1,自引:0,他引:1  
We exploited the viscoelasticity of biocompatible dilute polymeric solutions, namely, dilute poly(ethylene oxide) solutions, to significantly enhance mixing in microfluidic devices at a very small Reynolds number, i.e., Re≈0.023, but large Peclet and elasticity numbers. With an abrupt contraction microgeometry (8:1 contraction ratio), two different dilute poly(ethylene oxide) solutions were successfully mixed with a short flow length at a relatively fast mixing time of <10 μs. Microparticle image velocimetry was employed in our investigations to characterize the flow fields. The increase in velocity fluctuation with an increase in flow rate and Deborah number indicates the increase in viscoelastic flow instability. Mixing efficiency was characterized by fluorescent concentration measurements. Our results showed that enhanced mixing can be achieved through viscoelastic flow instability under situations where molecular-diffusion and inertia effects are negligible. This approach bypasses the laminar flow limitation, usually associated with a low Reynolds number, which is not conducive to mixing.  相似文献   
43.
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   
44.
This study examined the impact of parental involvement on adolescents' academic achievement in Korean families. The major strengths of the current research are the study of multiple dimensions of parental involvement, the longitudinal design and the consideration of mediating variables. Structural equation modelling was used to examine the direct and indirect effects of parental involvement on students' academic achievement using data from a nationally representative sample of middle school students from the Korea Youth Panel Survey. Results indicated: (1) parental involvement dimensions positively influenced achievement through its effects on student self‐concept and locus of control; and (2) parents' increased participation in involvement practices (monitoring, educational expectation and affection) increases students' self‐concept and locus of control.  相似文献   
45.
Users of the Internet are stripped of voice inflections, body language, and other common cues of conversation-only their words are left. Some claim that the lack of these social cues and the lack of hierarchy in the structure of the Internet provide the potential for equality in cyberspace. Many others have shown, though, that the issues of power in cyberspace are similar to the issues of power in physical space. This article examines an intersection of feminism and cyberspace in the ethos of online discussion. It is a rhetorical analysis of two popular feminist newsgroups, alt.feminism and soc.feminism. Do these newsgroups create a feminist and inclusive space online? What are the rhetorical strategies that make an online space more or less inclusive of women? Usenet newsgroups reveal the rhetorical power of these bare words. Although no formal means of discrimination is built into Usenet newsgroup discussions, discrimination does occur through the subtle and not so subtle use of language. This article looks at how various characteristics of language are used on the two newsgroups. Though the ethos on such discussion forums is dynamic, the analysis reveals examples of how sarcastic questioning, strong assertions, accusatory disagreements, and sexistcomments can create a hostile and noninclusive ethos.  相似文献   
46.
This article examines the policy cycle and vernacular globalization in the context of higher education reform in Vietnam. Through an analysis of the development of the Vietnam National University—Hochiminh City as part of the post‐1986 reconstruction of Vietnamese higher education, the article considers the complex interrelationship between globalized policy discourses, national interests and history in Vietnam, and the specific politics of policy implementation within one institution. Vietnam National University—Hochiminh City was created through an amalgamation of a number of smaller universities, and against the backdrop of social and economic restructuring aimed at promoting industrialization and a market orientation within socialist governance. The article reveals the dynamic tension between these local and global influences on higher education policy and practice, and more specifically, the dilemmas associated with top‐down policy implementation when a new organization consists of older organizations with powerful provenance and reputations. In so doing the article demonstrates the necessity to globalize policy theory.  相似文献   
47.
48.
Sexual responses were conditioned in male Japanese quail using the opportunity to copulate with a female as the unconditioned stimulus (US). The conditioned stimulus (CS) was a 3-D object made of a taxidermically prepared female quail head mounted on a terry-cloth body. Both appetitive conditioned responses (approach and proximity to the CS) and consummatory conditioned responses (mount and cloacal contact directed toward the CS) developed when 2-min presentations of the CS were followed immediately by the US, but not when the CS and US were separated by trace intervals of 10 or 20 min (Experiment 1). Postconditioning sexual satiation suppressed conditioned cloacal contact responses more than conditioned approach to the CS (Experiment 2), and “acute” extinction suppressed both conditioned mounting and conditioned cloacal contact responses more than conditioned approach to the CS (Experiment 3). These results demonstrate a functional dissociation between conditioned appetitive and consummatory responses and imply that the motivational and/or associative mechanisms underlying the two types of behavior are distinct.  相似文献   
49.
A recent “third wave” of neural network (NN) approaches now delivers state-of-the-art performance in many machine learning tasks, spanning speech recognition, computer vision, and natural language processing. Because these modern NNs often comprise multiple interconnected layers, work in this area is often referred to as deep learning. Recent years have witnessed an explosive growth of research into NN-based approaches to information retrieval (IR). A significant body of work has now been created. In this paper, we survey the current landscape of Neural IR research, paying special attention to the use of learned distributed representations of textual units. We highlight the successes of neural IR thus far, catalog obstacles to its wider adoption, and suggest potentially promising directions for future research.  相似文献   
50.
E-books have increasingly penetrated the academic world. However, despite efforts from Vietnamese universities and colleges to establish and broaden their e-books collection, students seem reluctant to use these digital books. This study aims to examine the barriers to using e-books in libraries among Vietnamese students. Data were obtained from 355 undergraduate students who were interested in e-books. The findings demonstrate that some key barriers impeding students from using e-books include the lack of computers and e-books in libraries, limited information and knowledge about e-books and their preference of using print books. Interestingly, female students tend to perceive the barriers to be stronger than their male counterparts. This study’s findings have important implications for universities, libraries and publishers who seek to promote e-books to students.  相似文献   
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