Zone 3 relay blocking scheme to prevent cascaded events

Defense systems are needed to prevent catastrophic failures of a power grid due to cascaded events. Cascaded events can be attributed to improper operations of protective relays. The most challenging problem for the design and implementation of a defense system is the performance in accuracy and speed in a real time environment. Protective devices are normally designed to operate fast in order to isolate the fault(s). This paper proposes a new methodology to distinguish line overloads from actual faults for distance relays. In order to distinguish between line flow transfers from a line outage and an actual fault, the line outage distribution factor (LODF) and generation shift factor (GSF) based power flow estimation method, and a secure peer to peer (P2P) communication structure are adopted. Computer simulations of cascaded events for a 6-bus system and the Korean power grid have been performed to establish the feasibility of the proposed scheme. Supported by Ministry of Science & Technology of Korea and Korea Science & Engineering Foundation Through ERC (Engineering Research Center) Program.     

Analysing meritocratic (in)equality in Singapore: ideology,curriculum and reproduction

In this article I first discuss how in Singapore the concept of meritocracy captures both elitist and egalitarian aspirations, and the ways in which its education policies have for a long time vacillated between these conflicting dimensions. I then argue that critical studies of meritocracy need to go beyond an understanding of the term as an inherently unstable concept instantiated problematically in policy and practice. Rather, as I develop the argument further, the dynamics of meritocracy needs to be appreciated as an ideology that is negotiated by dominant social groups as these seek to legitimize particular distributions of social resources. Such dominant ideologies, however, are not only produced in the education system; they are also reproduced through it, often in far more complex ways. To see how these ideologies and their tensions animate the very mechanism that sits at the centre of the reproduction of (in)equality, viz. the curriculum, the rest of the article provides an account of how one particular subject area is differently taught in an elite and a mainstream school.     

Language Use Among Singaporean Pre-School Children

This paper highlights the findings pertaining to the receptive and expressive language competencies of young children. The purpose of this paper is to evaluate the relative sensitivity of five different language measures as a means for assessing pre-schoolers' oral language proficiency. The results show few significant differences in language scores as a function of age, sex or SES. There was a complex pattern of intercorrelations among the language measures used. Results of a home environment questionnaire administered to parents revealed homogeneity in home environments for stimulating child learning and cognitive development across socioeconomic groups. The findings are discussed in relation to the utility of these measures in assessing pre-schoolers' linguistic competencies.     

Challenges and issues in designing inquiry on the Web

The purpose of this study is to discuss major issues in designing inquiries on the web. Instructional designers face a lot of difficulties and challenges to deal with in the course of designing inquiry experiences for learners in the online environment, a complex and ill‐structured learning environment. Facilitating inquiry or using an inquiry‐based learning approach on the web has both advantages and disadvantages. Instructional designers need to acknowledge the design issues arising in each and every phase of the design process. Utilising appropriate design strategies, instructional designers can provide positive learning experiences for their online learners. For this purpose, three representative cases in the context of teacher professional development were examined and six major issues were identified as follows: (1) seeking a balance between a system‐generated guide and human facilitator, (2) visual representation of the inquiry process, (3) motivating learners with the right question, (4) engaging learners in various learning activities, (5) guiding the inquiry process with various scaffolds, and (6) maximising learning by coordinating resources, tools and the community of inquiry. This study explains each issue in great detail and provides possible guides for instructional designers to handle the issue.     

Cultivating sustained teachers’ professional learning within a centralised education system

This study investigates how sustained professional learning for teachers within a centralised system was cultivated. Specifically, the sustained professional learning was initiated by officers from the headquarters (HQ) and involved interested teachers across schools in Singapore. Qualitative instruments were used to collect and analyse the data in examining the partnerships perceived by the participants. The enablers responsible to bring about sustained professional learning are proposed. A contribution of this study is to clarify how resources in the HQ and its schools can be bridged. Deliberate bridging of resources is critical particularly at the initial stage of the partnerships. This bridging is made possible through dedicated appointed champions. The appointed champions are passionate about the educational innovations and are willing to invest their time to understand the teachers’ needs. This paper argues that the enablers can offer opportunities for lateral networks to be forged within a hierarchical system.     

Continuity and Discontinuity Between Training and School Experience: Follow-up Studies of Former Students of the Institute of Education

The present report is based on three pilot projects that aimed to explore and describe teachers' perceptions of their training and the transition experience of teachers in the shift from being a student on a teacher training programme to being a full-fledged teacher in the primary or secondary school. The three studies were prompted by the concern for a possible lack of fit, even under the best circumstances, between pre-service training and the work of a full-time teacher in a typical school. In the main, then, this report focuses on the continuity between campus-based training and teaching practice and full-time teaching experience.     

Teachers' pedagogical beliefs and their planning and conduct of computer-mediated classroom lessons

In this study, we observed and interviewed six teachers from two Singapore primary school classrooms. The schools were reportedly achieving high levels of computer integration as reflected in a nationwide questionnaire survey. Out of the 18 lessons that we observed, 14 lessons have incorporated some elements of constructivist teaching. However, closer examination revealed that the underlying orientation of the lessons was inclined towards information acquisition and regurgitation. Five out of the six teachers we interviewed were reportedly inclined towards constructivist notion of teaching. The teachers accounted for the inconsistency between their espoused beliefs and the teacher-centric teaching practice as due to contextual constraints. The teachers expressed that the need to complete the syllabi according to stipulated schedules so as to get the students ready for examination was the main barriers that prevented them from engaging in more constructivist teaching. This case study therefore highlights that although it is necessary for teachers to hold pedagogical beliefs that are compatible with the constructivist notion of teaching and learning, this is an insufficient condition to shift traditional teaching practice. Changes in assessment systems and substantial professional development are further conditions that have to be addressed.     

The role of lexical knowledge and related linguistic components in typical and poor language comprehenders of Chinese

The present study adapted the “Blueprint of the Reader” in comprehending language by Perfetti [2000, C. M. Brown & P. Hagoort. (Eds.), The neurocognition of language (pp. 167–208). Oxford, UK: Oxford University Press] as a framework for understanding Chinese language and reading comprehension in a group of 361 secondary Forms 1, 3 and 4 Cantonese-speaking Chinese students (mean age of 15 years) in Hong Kong. This framework with some modifications was tested with nine specially designed Chinese language and reading tasks with reasonably high reliability and surface validity. The main hypothesis was that lexical knowledge consisting of derivational morphology; correction of characters, words and sentences; segmentation of text into phrases and sentences; and writing to dictation should explain considerable individual variations, as shown in the English literature. This was tested with component analyses and multiple regression analyses. The total battery accounted for 66.80% of the variation while lexical knowledge alone explained 33.51% of the individual variation in the overall school performance in Chinese reading and writing. The second hypothesis was that subgroups of poor and good language and reading comprehenders in Chinese would be expected to show overlapping yet different component structures and their performance in the individual component tasks would be expected to differ as tested with analyses of variance. The results confirmed this hypothesis. Task analyses of the written protocols of essay writing and of morphological processing (prefixing and suffixing) provided insight into well-formed and poorly formed writing and word formation according to principles of Chinese psycholinguistics and yielded information for theory-based practice.     

A microfluidic co-culture system to monitor tumor-stromal interactions on a chip

The living cells are arranged in a complex natural environment wherein they interact with extracellular matrix and other neighboring cells. Cell-cell interactions, especially those between distinct phenotypes, have attracted particular interest due to the significant physiological relevance they can reveal for both fundamental and applied biomedical research. To study cell-cell interactions, it is necessary to develop co-culture systems, where different cell types can be cultured within the same confined space. Although the current advancement in lab-on-a-chip technology has allowed the creation of in vitro models to mimic the complexity of in vivo environment, it is still rather challenging to create such co-culture systems for easy control of different colonies of cells. In this paper, we have demonstrated a straightforward method for the development of an on-chip co-culture system. It involves a series of steps to selectively change the surface property for discriminative cell seeding and to induce cellular interaction in a co-culture region. Bone marrow stromal cells (HS5) and a liver tumor cell line (HuH7) have been used to demonstrate this co-culture model. The cell migration and cellular interaction have been analyzed using microscopy and biochemical assays. This co-culture system could be used as a disease model to obtain biological insight of pathological progression, as well as a tool to evaluate the efficacy of different drugs for pharmaceutical studies.     

Single cell kinase signaling assay using pinched flow coupled droplet microfluidics

Droplet-based microfluidics has shown potential in high throughput single cell assays by encapsulating individual cells in water-in-oil emulsions. Ordering cells in a micro-channel is necessary to encapsulate individual cells into droplets further enhancing the assay efficiency. This is typically limited due to the difficulty of preparing high-density cell solutions and maintaining them without cell aggregation in long channels (>5 cm). In this study, we developed a short pinched flow channel (5 mm) to separate cell aggregates and to form a uniform cell distribution in a droplet-generating platform that encapsulated single cells with >55% encapsulation efficiency beating Poisson encapsulation statistics. Using this platform and commercially available Sox substrates (8-hydroxy-5-(N,N-dimethylsulfonamido)-2-methylquinoline), we have demonstrated a high throughput dynamic single cell signaling assay to measure the activity of receptor tyrosine kinases (RTKs) in lung cancer cells triggered by cell surface ligand binding. The phosphorylation of the substrates resulted in fluorescent emission, showing a sigmoidal increase over a 12 h period. The result exhibited a heterogeneous signaling rate in individual cells and showed various levels of drug resistance when treated with the tyrosine kinase inhibitor, gefitinib.