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We demonstrated a simple method for the device design of a staggered herringbone micromixer (SHM) using numerical simulation. By correlating the simulated concentrations with channel length, we obtained a series of concentration versus channel length profiles, and used mixing completion length Lm as the only parameter to evaluate the performance of device structure on mixing. Fluorescence quenching experiments were subsequently conducted to verify the optimized SHM structure for a specific application. Good agreement was found between the optimization and the experimental data. Since Lm is straightforward, easily defined and calculated parameter for characterization of mixing performance, this method for designing micromixers is simple and effective for practical applications. 相似文献
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Jingwei Miao Omar Hasan Sonia Ben Mokhtar Lionel Brunie Kangbin Yim 《International Journal of Information Management》2013
Message routing in mobile delay tolerant networks inherently relies on the cooperation between nodes. In most existing routing protocols, the participation of nodes in the routing process is taken as granted. However, in reality, nodes can be unwilling to participate. We first show in this paper the impact of the unwillingness of nodes to participate in existing routing protocols through a set of experiments. Results show that in the presence of even a small proportion of nodes that do not forward messages, performance is heavily degraded. We then analyze two major reasons of the unwillingness of nodes to participate, i.e., their rational behavior (also called selfishness) and their wariness of disclosing private mobility information. 相似文献
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Elizabeth B. Rush Jodi A. Quas Ilona S. Yim Mariya Nikolayev Steven E. Clark Rakel P. Larson 《Child development》2014,85(3):1292-1305
Few studies have investigated how stress affects eyewitness identification capabilities across development, and no studies have investigated whether retrieval context in conjunction with stress affects accuracy. In this study, one hundred fifty‐nine 7‐ to 8‐ and 12‐ to 14‐year‐olds completed a high‐ or low‐stress laboratory protocol during which they interacted with a confederate. Two weeks later, they attempted to identify the confederate in a photographic lineup. The lineup administrator behaved in either a supportive or a nonsupportive manner. Participants who experienced the high‐stress event and were questioned by a supportive interviewer were most accurate in rejecting target‐absent lineups. Results have implications for debates about effects of stress on eyewitness recall, how best to elicit accurate identifications in children, and developmental changes in episodic mnemonic processes. 相似文献
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Evaluating Strategic Approaches to Competitive Displacement: The Case of the U.S. Newspaper Industry
Bozena I. Mierzejewska Dobin Yim Philip M. Napoli Henry C. Lucas Jr. Abrar Al-Hasan 《Journal of Media Economics》2017,30(1):19-30
The concept of competitive displacement is central to theories of media evolution, and the threat that the Internet has posed to printed newspapers provides an ongoing case study on the topic. In particular, this situation offers an opportunity to examine the strategic efforts of print newspapers to prevent competitive displacement, as well as the effectiveness of these strategies. This article addresses these issues through an analysis of a unique data set, constructed from 20 years of newspaper circulation data, as well as data on local market characteristics, newspaper staffing and content variety, and state-level Internet penetration. Specifically, this article examines whether, and to what extent, these competitive strategies impacted local print newspaper circulation trends over this 20-year time period. This analysis focuses on the following strategic responses: (a) newspapers’ launching of online versions (a diversification strategy within the language of media evolution literature); and (b) newspapers’ efforts to cover a greater variety of subject areas, as measured by the number of editors and special editorial sections produced. (The authors characterize these as a “mimicking” strategy from media evolution literature, as this strategy essentially represents an effort to simulate the much greater content variety that readers can find online). This article examines the relationships between these circulation, strategic, and Internet penetration variables over a 20-year time period, while also taking into account relevant characteristics of local newspaper markets. 相似文献
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Jongho Shin Alexander McCarthy-Donovan Hyeyoung Hwang Sonyoung Yim EunJin Seo 《International Journal of Science Education》2013,35(9):1478-1503
The purpose of the study was to examine whether gender differences exist in the mean levels of and relations between adolescents’ home environments (parents’ view of science, socio-economic status (SES)), motivations (intrinsic and instrumental motivations, self-beliefs), and pursuit of science careers. For the purpose, the Programmed for International Student Assessment 2006 data of Korean 15-year-old students were analysed. The results of the study showed that girls had lower levels of science intrinsic and instrumental motivations, self-beliefs, and science-career pursuit (SCP) as well as their parents’ values in science less than boys. Gender similarities, rather than gender differences, existed in patterns of causal relationship among home environments, motivations, and SCP. The results showed positive effects for parents’ higher value in science and SES on motivations, SCP, and for intrinsic and instrumental motivations on SCP for girls and boys. These results provide implications for educational interventions to decrease gender differences in science motivations and SCP, and to decrease adolescents’ gender stereotypes. 相似文献
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Jaehoon Yim 《Educational Studies in Mathematics》2010,73(2):105-120
This study investigated how children tackled a task on division by fractions, and how they formulated numerical algorithms
from their strategies. The task assigned to the students was to find the length of a rectangle given its area and width. The
investigation was carried out as follows: First, the strategies invented by eight 10- or 11-year-old students, all identified
as capable and having positive attitudes towards mathematics, were categorised. Second, the formulation of numerical algorithms
from the strategies constructed by nine students with similar abilities and attitudes towards mathematics was investigated.
The participants developed three types of strategies (making the width equal to 1, making the area equal to 1, and changing
both area and width to natural numbers) and showed the possibility of formulating numerical algorithms for division by fractions
referring to their strategies. 相似文献
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Micromixers with floor-grooved microfluidic channels have been successfully demonstrated in experiment. In this work, we numerically simulated the mixing within the devices and used the obtained concentration versus channel length profiles to quantitatively characterize the process. It was found that the concentration at any given cross-section location of the microfluidic channel periodically oscillates along the channel length, in coordination with the groove-caused helical flow during the mixing, and eventually converges to the neutral concentration value of two the mixing fluids. With these data, the specific channel length required for each helical flow to complete, the mixing efficiency of the devices, and the total channel length required to complete a mixing were easily defined and quantified, and were used to directly and comprehensively characterize the micromixing. This concentration versus channel length profile-based characterization method was also demonstrated in quantitatively analyzing the micromixing within a classic T mixer. It has clear advantages over the traditional concentration image-based characterization method that is only able to provide qualitative or semiquantitative information about a micromixing, and is expected to find an increasing use in studying mixing and optimizing device structure through numerical simulations. 相似文献
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Kathryn Kohnert Jennifer Windsor Dongsun Yim 《Learning disabilities research & practice》2006,21(1):19-29
We report results from 2 language‐based processing tasks designed to investigate the performance of linguistically diverse learners. The tasks were the Competing Language Processing Task (CLPT) and Non‐Word Repetition (NWR). Participants were 100 school‐age children in 1 of 3 different experimental groups: monolingual English‐speaking children with specific or primary language impairment (LI), typical English‐only‐speaking children (EO), or typical Spanish–English bilingual children (BI). On both CLPT and NWR, EO group performance was best and LI group performance was poorest, with BI group performance falling in between. Likelihood ratios indicated that performance on these tasks does not provide compelling diagnostic power for separating typically developing bilinguals from monolingual children with LI. One exception is that children who obtained an NWR score of 93 percent or higher could be ruled out of the LI group with a high degree of confidence. 相似文献