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.     

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.     

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 Environment for Values Learning

This study examines the impact of the environment on pupils' learning of values. The sample selected for the study was 14 secondary schools, 3 Mission and 11 government schools. In all, 3102 Secondary 1 and 2 pupils were involved in the study. The study adopted an 80% cut-off point as a decision rule for interpreting the data. Among the dimensions considered were teacher helpfulness, affiliation, peer relationship and cooperativeness, class learning environment, values of respect, trust and attitude towards school rules. The study found that sharing and caring, mutual respect between teachers and pupils and courtesy were not strongly represented. It also found a bias towards friendship over obligation to public morality. On the positive side, there was strong achievement orientation and a belief among pupils that teachers were helpful and interested in pupils.     

Information networks and social media use in public diplomacy: a comparative analysis of South Korea and Japan

This article examines how South Korean and Japanese public diplomacy organizations employ digital media to embrace the principle of ‘networked public diplomacy’ through analyses of the web and social media practices. A network analysis was used to map interorganizational information networks among core public diplomacy organizations in each country. To reveal the key organizations' communication strategies on Facebook, a content analysis was also conducted. The findings indicate that Japan had a strong internal network infrastructure achieved through dispersed connections and partnerships; however, Korea had a centralized network, including a limited number of dominant actors. The results of content analysis suggest that both South Korea and Japanese public diplomats focused on promoting their cultural products and national values through their use of texts and visual images. In addition, user profile analysis gaged the degree of users' engagement in the organizations' profiles and identified the demographic features of users. Comparative data suggest the Korean public diplomacy organization was more successful at attracting and engaging with foreign public than the Japanese public diplomacy organization. These results imply that although these two countries had similar sociopolitical backgrounds and perspectives of public diplomacy, they had distinct forms of internal information networks, communication strategies, and social networking performances with public.     

Who Says What About Whom: Young Voters' Impression Formation of Political Candidates on Social Networking Sites

Social information processing theory claims that computer-mediated communication users form impressions of others by utilizing available information in the web environment. As social networking sites offer a wider variety of cues, however, the environment has become increasingly complex. This study explores which cues influence computer-mediated communication users in a cue-rich environment. More specifically, based on the social identification and deindividuation model, we examined not only how others' opinions but also how the perceived age of the commenters and candidates influenced young people's impressions of political candidates. Participants (N = 520) were randomly placed into a 2 (positive/negative comments) × 2 (younger/older commenters) × 2 (younger/older candidate) design and exposed to a fictitious candidate's Facebook profile with unknown others' comments before reporting the candidate's trustworthiness. Although comments' valence was the strongest cue, the results showed that older commenters' opinions were more influential than young commenters'. This two-way interaction between comments' valence and commenters' age was significant only when the candidate was young, suggesting that social networking sites users utilize multiple cues depending on the situation.     

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.     

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.     

Probing transient protein-mediated DNA linkages using nanoconfinement

We present an analytic technique for probing protein-catalyzed transient DNA loops that is based on nanofluidic channels. In these nanochannels, DNA is forced in a linear configuration that makes loops appear as folds whose size can easily be quantified. Using this technique, we study the interaction between T4 DNA ligase and DNA. We find that T4 DNA ligase binding changes the physical characteristics of the DNA polymer, in particular persistence length and effective width. We find that the rate of DNA fold unrolling is significantly reduced when T4 DNA ligase and ATP are applied to bare DNA. Together with evidence of T4 DNA ligase bridging two different segments of DNA based on AFM imaging, we thus conclude that ligase can transiently stabilize folded DNA configurations by coordinating genetically distant DNA stretches.     

Relative position keeping in satellite formation flying with input saturation

This paper studies a relative position keeping problem in satellite formation flying with input saturation. The relative motion dynamics is designed with polytopic-type uncertainties by considering elliptic and noncoplanar formation, and unknown angular rate and acceleration within some boundary. A composite nonlinear feedback control law is developed by using a low-and-high gain control scheme with an algebraic Riccati inequality (ARI). In the presence of input saturation and disturbances, finite-gain _L∞$L_{\infty }$ stability of the relative motion dynamics is ensured using the proposed control law. Additionally, the domain of attraction for the stability is evaluated by formulating an optimization problem. Through numerical simulations, the validity of the proposed scheme is illustrated.