Optimized Hierarchical Power Oscillations Control for Distributed Generation Under Unbalanced Conditions

Control structures have critical influences on converter-interfaced distributed generations (DG) under unbalanced conditions. Most of previous works focus on suppressing active power oscillations and ripples of DC bus voltage. In this paper, the relationship between amplitudes of the active power oscillations and the reactive power oscillations are firstly deduced and the hierarchical control of DG is proposed to reduce power oscillations. The hierarchical control consists of primary and secondary levels. Current references are generated in primary control level and the active power oscillations can be suppressed by a dual current controller. Secondary control reduces the active power and reactive power oscillations simultaneously by optimal model aiming for minimum amplitudes of oscillations. Simulation results show that the proposed secondary control with less injecting negative-sequence current than traditional control methods can effectively limit both active power and reactive power oscillations.Comment: Accepted by Applied Energ

Effects of Autonomous Learning Software on Chinese Learners’ English Performance and Course Assessment

Based on the construction of an autonomous learning platform for college English learners, a one-year teaching reform experiment has been carried out and 204 subjects were involved. Data collection was conducted mainly through questionnaires and the subjects’ autonomous learning achievements, regular grades, final exam performance, and English listening achievements. The software SPSS17.0 was applied to analyze those data. The results reveal that the experimental class’ achievements on the self-learning platform are positively correlated with their achievements in the final examination. In addition, the correlation between the experimental class’ regular grades and final exam performance is more statistically significant than the control class; moreover, the experimental class performed significantly better than the control class in the English listening test. The vast majority of the students in the experimental class hold positive attitudes towards the software; however, there is still some room to improve it

A Preliminary Probe into Lin Shu’s Creative Translation

Lin Shu is a renowned translator in Chinese history for his abundant influential translating works. He plays a very important role in introducing western literature to China and is well known for his unique translating methods. Nevertheless, his creative translation approaches of omission, addition and alteration also make him target of sharp criticism. This paper, through a deliberate comparison between Lin Shu’s versions and the original works, finds that many of Lin Shu’s omission, addition and alteration of the original is out of his careful consideration rather than arbitrary behaviors. The concrete examples and full analysis revealed that Lin Shu is quite creative in the translation process. His translation can be considered as a creative rebellion against the original. A careful study shows that it is Lin Shu’s illiteracy of foreign languages and the use of classical Chinese that make his translation a big hit shortly after their publication and give Lin Shu and his translation a special status in the literary world of China

Implementing the CSILE/KB Program of University of Toronto in English Teaching in China

This paper first proposes that Aims of English Teaching should go beyond communicative competence according to Bloom's taxonomy. Then it mainly analyzes that teaching English as a foreign language in China can learn from CSILE/KB Program of University of Toronto in terms of goal setting, active roles of thinking scaffolding and comprehensive English competence acquirement.To bring TEFL to a new stage,the integration of TEFL with KB and MOOCS is put forward and some suggestions are made in the end

A Generic Framework for Constraint-Driven Data Selection in Mobile Crowd Photographing

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Mobile crowd photographing (MCP) is an emerging area of interest for researchers as the built-in cameras of mobile devices are becoming one of the commonly used visual logging approaches in our daily lives. In order to meet diverse MCP application requirements and constraints of sensing targets, a multifacet task model should be defined for a generic MCP data collection framework. Furthermore, MCP collects pictures in a distributed way in which a large number of contributors upload pictures whenever and wherever it is suitable. This inevitably leads to evolving picture streams. This paper investigates the multiconstraint-driven data selection problem in MCP picture aggregation and proposes a pyramid-tree (PTree) model which can efficiently select an optimal subset from the evolving picture streams based on varied coverage needs of MCP tasks. By utilizing the PTree model in a generic MCP data collection framework, which is called CrowdPic, we test and evaluate the effectiveness, efficiency, and flexibility of the proposed framework through crowdsourcing-based and simulation-based experiments. Both the theoretical analysis and simulation results indicate that the PTree-based framework can effectively select a subset with high utility coverage and low redundancy ratio from the streaming data. The overall framework is also proved flexible and applicable to a wide range of MCP task scenarios

CXCR4/SDF1 mediate hypoxia induced chondrosarcoma cell invasion through ERK signaling and increased MMP1 expression

BACKGROUND: Chondrosarcoma is a disease that does not respond to conventional cytotoxic chemotherapy and expression of MMP1 is a marker for a poor prognosis. The mechanism of increased MMP1 expression in chondrosarcoma is not completely known. Our goal is to identify molecular pathways that could serve as therapeutic targets. Chondrosarcoma become hypoxic as they grow, are capable of eliciting an angiogenic response, and typically metastasize to the lungs. The present study determined the effect of hypoxia and specifically HIF-1a on expression of CXCR4 and MMP1 and their role in chondrosarcoma cell invasion. RESULTS: CXCR4 and its ligand, SDF1, are upregulated in primary chondrosarcoma tumors compared to normal articular cartilage, and CXCR4 was upregulated in chondrosarcoma cell line JJ compared to normal chondrocytes. Hypoxia and specifically HIF-1a increased CXCR4 and MMP1 expression in JJ cell line and chondrosarcoma invasion in vitro. The hypoxia mediated increase in MMP1 expression and chondrosarcoma invasion could be inhibited by siRNA directed at HIF-1a or CXCR4, the CXCR4 inhibitor AMD3100, as well as with ERK inhibitor U0126 and ERK siRNA. CONCLUSIONS: Chondrosarcoma cell invasion is increased by hypoxia induced expression of CXCR4 and MMP1 and is mediated by HIF-1a and ERK. Both invasion and MMP1 can be inhibited with CXCR4 blockade, suggesting that CXCR4/SDF1 signaling may be a therapeutic target for chondrosarcoma