Micromixer based on viscoelastic flow instability at low Reynolds number

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.     

Neural information retrieval: at the end of the early years

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.     

Why Do University Students Refrain from Using E-Books in Libraries? Empirical Evidence from Vietnam

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.     

Promoting the Purchase of Textbooks in the Vietnamese Higher Education Sector

Higher education textbooks sales account for a significant portion of the overall book market. This study makes an important contribution to the extant literature by examining students’ purchase of original textbooks in a developing market, Vietnam. Notably, it seeks to investigate why students do not purchase original textbooks as well as the difference in purchase behavior between different groups of students. The findings reveal that some key obstacles to students’ purchase behavior include high prices, insufficient availability, low perceived value, and the emergence of pirated textbooks. Another notable finding is that senior students who are female tend to purchase more textbooks. In light of these findings, marketing strategies are suggested for publishers, bookstores and universities who aim to promote the sales and consumption of original textbooks.     

Public Opinion Polls,Chicken Soup and Sample Size

Cooking and tasting chicken soup in three different pots of very different size serves to demonstrate that it is the absolute sample size that matters the most in determining the accuracy of the findings of the poll, not the relative sample size, i.e. the size of the sample in relation to its population.     

Marketing International Scholarly Journals to Vietnamese Researchers

There is a significantly growing interest in publishing in international scholarly journals in Vietnam. On the one hand, Vietnamese researchers can be potential authors of interesting articles that provide new insights into the emerging economic context. On the other hand, they can be target consumers and subscribers of journals in their quest for academic and practical knowledge. This paper aims to propose marketing initiatives for publishers and editors who seek to promote their journals to researchers in emerging countries, particularly Vietnam. These marketing solutions build upon an understanding of barriers for researchers in international publications.     

Changing views of teachers and teaching in Vietnam

In order for Vietnam to seek better international integration into an increasingly globalised world, the Vietnamese Government has launched educational reforms requiring teachers to adopt ‘Western’ constructivist pedagogies. This paper reports on an action research study in a Vietnamese teacher training institution which found that Vietnamese student teachers were willing to accommodate and accept change and were often very enthusiastic about the ‘Western ideas’ of teaching and learning, but that their unquestioning respect for the authority of their tutors remained firmly fixed. The data also showed that the students’ tutors had a relatively limited exposure to the ‘Western theories’ and their implications and therefore did not model or demonstrate the theories effectively. The paper draws on these findings to argue that the focus for transforming Vietnamese teachers’ practice should be on promoting the responsibility of teacher educators to introduce student teachers to new ideas about the processes of teaching and learning. This strategy is likely to be more supportive of student teachers’ development as it allows them to separate the processes of teaching from culturally dominant beliefs about roles which are part of their established identities.     

Temperature-induced droplet coalescence in microchannels

This paper reports a technique for temperature-induced merging of droplets in a microchannel. The multiphase system consists of water droplet and oil as the dispersed phase and the carrying continuous phase. A resistive heater provides heating in a rectangular merging chamber. The temperature of the chamber is controlled by the voltage applied to the heater. The merging process of two neighboring droplets was investigated with different applied voltage, flow rate ratio between water and oil and total flowrate. Merging is found to be effective at high flow rate ratio, high temperature, and low total flowrate. The presented technique could be used for merging and mixing in droplet-based lab-on-a-chip platforms.     

Students’ academic performance and various cognitive processes of learning: an integrative framework and empirical analysis

The main aim of this study is to test a conceptualised framework that involved the integration of achievement goals, self‐efficacy and self‐esteem beliefs, and study‐processing strategies. Two hundred and ninety (178 females, 112 males) first‐year university students were administered a number of Likert‐scale inventories in tutorial classes. Data were analysed through structural equation modelling procedures. The results provided support, in part, for the hypothesised relationships; for example, both self‐efficacy and self‐esteem exerted positive effects on deep processing, and academic performance was influenced positively by mastery goals and deep processing. Similarly, surface processing exerted a negative effect on academic performance. One key finding was the positive effect that self‐esteem exerted on self‐efficacy. Finally, a one‐way MANOVA indicated statistically significant differences between men and women in their self‐esteem; women reported higher self‐esteem than men. This study provides support for the amalgamation of key motivational and learning theories and accentuates the importance of achievement goals, self‐efficacy and study‐processing strategies as possible mediators of students’ academic performance.