A plug-and-play ripple mitigation approach for DC-links in hybrid systems

© 2016 IEEE.In this paper, a plug-and-play ripple mitigation technique is proposed. It requires only the sensing of the DC-link voltage and can operate fully independently to remove the low-frequency voltage ripple. The proposed technique is nonintrusive to the existing hardware and enables hot-swap operation without disrupting the normal functionality of the existing power system. It is user-friendly, modular and suitable for plug-and-play operation. The experimental results demonstrate the effectiveness of the ripple-mitigation capability of the proposed device. The DC-link voltage ripple in a 110 W miniature hybrid system comprising an AC/DC converter and two resistive loads is shown to be significantly reduced from 61 V to only 3.3 V. Moreover, it is shown that with the proposed device, the system reliability has been improved by alleviating the components' thermal stresses

Toward integration of reading and service learning through an interdisciplinary program

This study examined the effect of an interdisciplinary program of reading and service learning on the cognitive and affective development of university students in Hong Kong. As Nussbaum (1997) stated, literature plays a vital role in educating citizens of the world through its narrative imagination and its power of promoting understanding and empathy toward the life of others. Halstead and Pike (2006) also emphasized that art can foster reflection upon action and bring about change in behavior as a result of perspective change. In this study, 24 freshmen read literary works under the theme of children's welfare and explored issues related to the welfare of children worldwide. Their reflections on these materials were expressed in writing and in a presentation. In the following semester, the students participated in voluntary services within and outside Hong Kong. All students completed a questionnaire on their humanistic concerns and sense of global citizenship at the beginning and the end of the project. Results showed that students were conscious of their changes after joining the program and stated their growth in values and knowledge. The pre-post-t-test analysis suggested that students had made significant improvement in the following areas: (1) their attitude toward serving others, especially in their personal and social values; (2) their engagement in reading literary and nonfiction works which reflect social and moral issues of the world; (3) their attention to world affairs; (4) their concern for the underprivileged; and (5) awareness of their potential in helping the poor. © 2011 The Author(s).published_or_final_versionSpringer Open Choice, 21 Feb 201

A design methodology for smart LED lighting systems powered by weakly regulated renewable power grids

The increasing use of intermittent renewable energy sources to decarbonize electric power generation is expected to introduce dynamic instability to the mains. This situation is of particular concern for mini-grids or isolated grids in which wind and/or solar power sources are the dominant or the sole power sources. In this paper, we utilize the photo-electro-thermal theory to develop a design methodology for LED lighting systems for weakly regulated voltage sources, with the objectives of minimizing the fluctuation of the human luminous perception and adopting reliable LED driver with long lifetime and robustness against extreme weather conditions. The proposed LED system, practically verified in a 10 kVA small power grid driven by an ac voltage source and a wind energy simulator, can be considered as a smart load with its load demand following the power generation. A typical swing of 40 V in the mains will cause only 15% actual light variation in a 132 W LED system when compared with 40% change in 150 W high-pressure-sodium lamp system. The design methodology enables future large-scale LED systems to be designed as a new generation of smart loads that can adapt to the voltage and power fluctuations arising from the intermittent nature of renewable energy sources. © 2011 IEEE.published_or_final_versio

Exposure to L2 online text on lexical and reading growth

With the fast-paced development of technology in today’s society, there has been emerging a shift from paper-based reading to digital online reading. While the benefits of exposure to print have been well-established in previous studies, how online reading may impact individuals’ literacy development is largely underexplored. The current study investigated if the amount of English reading experience on the Internet could predict EFL students’ lexical knowledge and reading comprehension ability. Participants were ninety-seven Vietnamese undergraduate students who were administered a website checklist and a vocabulary size test. Their reading comprehension scores were also collected as measures of their reading abilities. Descriptive statistics, hierarchical linear regression and structural equation modelling were utilized for data analysis. The results indicated that exposure to L2 online text was a significant predictor of the participants’ vocabulary size as well as their reading comprehension growth during a course of two years. Pedagogical implications are discussed

A THREE-YEAR LONGITUDINAL STUDY OF IN-CLASS SUSTAINED SILENT READING WITH TAIWANESE VOCATIONAL COLLEGE STUDENTS

This study examined the effects of three years of in-class sustained silent reading with a group of vocational college students in Taiwan. Readers outperformed comparisons on tests administered after one semester and increased their advantage on tests given at the end of the first year. The gap between the groups narrowed the second year, but readers maintained their superiority at the end of the second and third year. The initial gains were probably due, in part, to the Hawthorne Effect. It is likely that the progress made in the second and third year were more modest, because of external demands on students’ time, which limited the amount of reading students could do outside of class. Overall, the results clearly support the practice of in-school self-selected reading. Keywords:   In-class sustained silent reading; vocational college student; Hawthorne Effect; in-school self-selected readin

Voluntary wheel running reverses the decrease in subventricular zone neurogenesis caused by corticosterone

Adult neurogenesis within the dentate gyrus of the hippocampus can be increased by voluntary exercise but is suppressed under stress, such as with corticosterone (CORT). However, the effects of exercise and corticosterone on the cell proliferation of the other traditional neurogenic site, the subventricular zone (SVZ) have been reported with controversial results. In addition, the co-treatment effects of voluntary exercise and corticosterone have not been investigated. This study aims to determine whether corticosterone can suppress cell proliferation in the SVZ, and whether this can be reversed by voluntary exercise. In the present study, the effect of chronic (4 weeks) corticosterone treatment and wheel running simultaneously on the SVZ cell proliferation of adult Sprague-Dawley rats was examined. The results showed that cell proliferation indicated by bromodeoxyuridine (BrdU) was increased by voluntary wheel running whereas it was decreased by corticosterone treatment within the SVZ of the rats without running. For the rats with both corticosterone treatment and wheel running, it was found that the number of BrdU-labeled cells was approximately at the same level as the vehicle control group. Furthermore, these proliferating cells expressed doublecortin (DCX), a migrating neuroblast marker. Wheel running increased the percentage of BrdU-labeled cells expressing DCX in the SVZ whereas corticosterone treatment decreased this percentage. Thus, chronic injection of corticosterone can decrease the number of proliferating cells while wheel running can reverse the decrease in cell proliferation within the SVZ to normal levels. In addition, corticosterone can suppress the cell differentiation within the SVZ and this was alleviated by wheel running as indicated by the double-labeling of BrdU and DCX.published_or_final_versio

Magnetic nanoparticle density mapping from the magnetically induced displacement data: a simulation study

<p>Abstract</p> <p>Background</p> <p>Magnetic nanoparticles are gaining great roles in biomedical applications as targeted drug delivery agents or targeted imaging contrast agents. In the magnetic nanoparticle applications, quantification of the nanoparticle density deposited in a specified region is of great importance for evaluating the delivery of the drugs or the contrast agents to the targeted tissues. We introduce a method for estimating the nanoparticle density from the displacement of tissues caused by the external magnetic field.</p> <p>Methods</p> <p>We can exert magnetic force to the magnetic nanoparticles residing in a living subject by applying magnetic gradient field to them. The nanoparticles under the external magnetic field then exert force to the nearby tissues causing displacement of the tissues. The displacement field induced by the nanoparticles under the external magnetic field is governed by the Navier's equation. We use an approximation method to get the inverse solution of the Navier's equation which represents the magnetic nanoparticle density map when the magnetic nanoparticles are mechanically coupled with the surrounding tissues. To produce the external magnetic field inside a living subject, we propose a coil configuration, the Helmholtz and Maxwell coil pair, that is capable of generating uniform magnetic gradient field. We have estimated the coil currents that can induce measurable displacement in soft tissues through finite element method (FEM) analysis.</p> <p>Results</p> <p>From the displacement data obtained from FEM analysis of a soft-tissue-mimicking phantom, we have calculated nanoparticle density maps. We obtained the magnetic nanoparticle density maps by approximating the Navier's equation to the Laplacian of the displacement field. The calculated density maps match well to the original density maps, but with some halo artifacts around the high density area. To induce measurable displacement in the living tissues with the proposed coil configuration, we need to apply the coil currents as big as 10⁴A.</p> <p>Conclusions</p> <p>We can obtain magnetic nanoparticle maps from the magnetically induced displacement data by approximating the Navier's equation under the assumption of uniform-gradient of the external magnetic field. However, developing a coil driving system with the capacity of up to 10⁴A should be a great technical challenge.</p

A Three-year Longitudinal Study of In-class Sustained Silent Reading with Taiwanese Vocational College Students

This study examined the effects of three years of in-class sustained silent reading with a group of vocational college students in Taiwan. Readers outperformed comparisons on tests administered after one semester and increased their advantage on tests given at the end of the first year. The gap between the groups narrowed the second year, but readers maintained their superiority at the end of the second and third year. The initial gains were probably due, in part, to the Hawthorne Effect. It is likely that the progress made in the second and third year were more modest, because of external demands on students' time, which limited the amount of reading students could do outside of class. Overall, the results clearly support the practice of in-school self-selected reading