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1.
Mass transport in porous materials is universal in nature, and its worth attracts great attention in many engineering applications. Plant leaves, which work as natural hydraulic pumps for water uptake, have evolved to have the morphological structure for fast water transport to compensate large water loss by leaf transpiration. In this study, we tried to deduce the advantageous structural features of plant leaves for practical applications. Inspired by the tissue organization of the hydraulic pathways in plant leaves, analogous double-layered porous models were fabricated using agarose hydrogel. Solute transport through the hydrogel models with different thickness ratios of the two layers was experimentally observed. In addition, numerical simulation and theoretical analysis were carried out with varying porosity and thickness ratio to investigate the effect of structural factors on mass transport ability. A simple parametric study was also conducted to examine unveiled relations between structural factors. As a result, the porosity and thickness ratio of the two layers are found to govern the mass transport ability in double-layered porous materials. The hydrogel models with widely dispersed pores at a fixed porosity, i.e., close to a homogeneously porous structure, are mostly turned out to exhibit fast mass transport. The present results would provide a new framework for fundamental design of various porous structures for effective mass transport. 相似文献
2.
We present dual-mode, on-demand droplet routing in a multiple-outlet microfluidic device using an oil-based magnetic fluid. Magnetite (Fe3O4) nanoparticle-contained oleic acid (MNOA) was used as a carrier phase for droplet generation and manipulation. The water-in-MNOA droplets were selectively distributed in a curved microchannel with three branches by utilizing both a hydrodynamic laminar flow pattern and an external magnetic field. Without the applied magnetic field, the droplets travelled along a hydrodynamic centerline that was displaced at each bifurcating junction. However, in the presence of a permanent magnet, they were repelled from the centerline and diverted into the desired channel when the repelled distance exceeded the minimum offset allocated to the channel. The repelled distance, which is proportional to the magnetic field gradient, was manipulated by controlling the magnet''s distance from the device. To evaluate routing performance, three different sizes of droplets with diameters of 63, 88, and 102 μm were directed into designated outlets with the magnet positioned at varying distances. The result demonstrated that the 102-μm droplets were sorted with an accuracy of ∼93%. Our technique enables on-demand droplet routing in multiple outlet channels by simply manipulating magnet positions (active mode) as well as size-based droplet separation with a fixed magnet position (passive mode). 相似文献
3.
运动性贫血时大鼠红细胞锌卟啉、转铁蛋白受体及营养干预的影响 总被引：3，自引：2，他引：1
红细胞锌卟啉、红细胞膜转铁蛋白受体是反映铁贮备的指标,实验结果表明:运动训练导致运动性贫血大鼠红细胞锌原卟啉含量和红细胞膜转铁蛋白受体含量明显增加,且与血清铁呈高度相关,说明红细胞锌卟啉是反映缺铁性贫血的良好指标,而红细胞膜转铁蛋白受体含量能更为准确地反映红细胞内和机体铁代谢状况;抗贫血铁制剂复合营养补剂的干预显著降低了运动性贫血大鼠红细胞锌原卟啉和红细胞膜转铁蛋白受体含量,并通过对这些机体铁代谢状况指标的改善反映抗贫血铁制剂复合营养补剂对提高大鼠红细胞铁贮备和维持大鼠铁代谢稳定具有积极作用. 相似文献
4.
The primary purpose of the current research was to identify core contextual factors that facilitate or hinder the process of organizational knowledge creation practices. The grounded theory framework and negotiated coding approach were employed. Serving as the fundamental research framework was Nonaka and his colleagues' knowledge creation and conversion theory, along with their proposed knowledge creation enablers. A total of 314 codeable units from 153 individuals were used for data analysis. All answers were coded and categorized into three emerged domains—organization, team/subgroup, and individual—for both areas of facilitating and hindering factors. Limitations and implications for further research are presented in the discussion section. 相似文献
5.
Edy H. M. Shahali Lilia Halim David F. Treagust Mihye Won A. L. Chandrasegaran 《Research in Science Education》2017,47(2):257-281
This study investigated the understanding of science process skills (SPS) of 329 science teachers from 52 primary schools selected by random sampling. The understanding of SPS was measured in terms of conceptual and operational aspects of SPS using an instrument called the Science Process Skills Questionnaire (SPSQ) with a Cronbach’s alpha reliability of 0.88. The findings showed that the teachers’ conceptual understanding of SPS was much weaker than their practical application of SPS. The teachers’ understanding of SPS differed by their teaching qualifications but not so much by their teaching experience. Emphasis needs to be given to both conceptual and operational understanding of SPS during pre-service and in-service teacher education to enable science teachers to use the skills and implement inquiry-based lessons in schools. 相似文献
6.
Mihye Won Heiko Krabbe Siv Ling Ley David F. Treagust Hans E. Fischer 《Educational Assessment》2017,22(2):95-110
In this study, we investigated the value of a concept map marking guide as an alternative formative assessment tool for science teachers to adopt for the topic of energy. Eight high school science teachers marked students’ concept maps using an itemized holistic marking guide. Their marking was compared with the researchers’ marking and the scores of a multiple-choice diagnostic test. Statistical analysis revealed that teachers evaluated students’ concept maps consistently, but the concept map scores were only mildly correlated with the multiple-choice test scores. We explored what each assessment method revealed in terms of students’ understanding with one student’s performance as a showcase. Teachers’ views on using the marking guide of concept maps as an assessment tool were also included. We discuss the value of the concept map marking guide as a formative assessment tool for science teachers to create and modify in order to encourage students’ conceptual learning. 相似文献
7.
Conclusion In order to make PIHnet forum more usable and useful, we recently redesigned the forum tool based on findings from a survey,
interviews and observations of user posting patterns. We also developed a journal tool to assist teachers with their personal
reflection.
Interviews with four users showed that the new forum was easy to use and effectively helped them communicate with other members.
We are still developing the journal tool, so user experiences with the new journal tool have not been investigated yet. We
will continue to improve the tools based on critical feedback from actual users. 相似文献
8.
Kui Xie Min Kyu Kim Sheng-Lun Cheng Nicole C. Luthy 《Educational technology research and development : ETR & D》2017,65(4):1067-1103
In this study, researchers designed and implemented a 1-year professional development (PD) program that focused on supporting teachers in evaluating and selecting digital learning contents. Participants in this investigation included 109 teachers who consented to the study amongst a total of 171 teachers from five school districts across central Ohio. In addition to their participation in the PD program, they completed surveys, interviews, and self-reflections in this mixed-method study. The results revealed that teachers’ perceived TPACK increased over time throughout the PD program, suggesting that training teachers to evaluate digital contents can be an effective PD model to improve teachers’ capacity in learning technology integration. The PD program was especially effective for teachers with less prior experience in technology integration or related training. Mathematics teachers, in comparison to teachers from other disciplines, began with low TPACK; however, these initial differences gradually diminished over the course of the PD program. In terms of their motivation in digital content evaluation, teachers’ expectancy for success increased significantly while their task values remained medium high. The qualitative analyses provided additional insights and revealed design suggestions for success in future PDs. 相似文献
9.
本文研究了IPTV(网络电视)出现的背景及其提供的媒体服务的技术特性,并对比分析了美国、法国、意大利、香港等国家和地区的IPTV发展现状和成功因素。此论文通过分析这些案例,对IPTV在韩国市场的技术可能性进行了展望,同时对比分析了IPTV与有线电视的异同之处,以及与无线电视的竞争关系。最后,本文预测了IPTV进入收费市场的时机及在与有线、无线电视的激烈竞争下的生存战略。 相似文献
10.
We examined two aspects of college students' (N = 385) sense of belonging and its relations with three indicators of self-regulated learning. We also tested the mediating role of achievement goals in these relations. One aspect, sense of belonging to school, functioned as a significant predictor of self-reported metacognitive and academic time management strategies. In comparison, a second aspect, sense of belonging to peer groups, was a significant predictor of self-reported peer learning strategies. Findings from the mediation analyses indicated that sense of belonging to school was related with mastery goals, whereas sense of belonging to peer groups was related with performance goals. Further, mastery goals mediated the relations between sense of belonging to school and metacognitive and academic time management strategies. 相似文献