一种流媒体Caching策略

It is expected that by 2003 continuous media will account for more than 50% of the data available on origin servers, this will provoke a significant change in Internet workload. Due to the high bandwidth requirements and the long-lived nature of digital video, streaming server loads and network bandwidths are proven to be major limiting factors. Aiming at the characteristics of broadband network in residential areas, this paper proposes a popularity-based server-proxy caching strategy for streaming media. According to a streaming media popularity on streaming server and proxy, this strategy caches the content of the streaming media partially or completely. The paper also proposes two formulas that calculate the popularity coefficient of a streaming media on server and proxy, and caching replacement policy. As expected, this strategy decreases the server load, reduces the traffic from streaming server to proxy, and improves client start-up latency.     

Modeling of D-STATCOM in distribution systems load flow

This paper presents modeling of Distribution STATCOM (D-STATCOM) in load flow calculations for the steady- state voltage compensation. An accurate model for D-STATCOM is derived to use in load flow calculations. The rating of this device as well as the direction of required reactive power injection for voltage compensation in the desired value (1 p.u.) is de- rived and discussed analytically and mathematically by the phasor diagram method. Furthermore, an efficient method for node and line identification used in load flow calculations is presented. The validity of the proposed model is examined by using two standard distribution systems consisting of 33 and 69 nodes, respectively. The best location of D-STATCOM for under voltage problem mitigation approach in the distribution networks is determined. The results validate the proposed model for D- STATCOM in large distribution systems.     

The relationship between parental bonding and peer victimization: examining child stress and hopelessness as mediators

The purpose of the current study was to investigate a two-stage model in which parent-related stress and hopelessness each served as mediators of the relationship between perceived parental bonding and South Korean adolescent peer victimization. This study also examined whether the mediating relationships differed by the gender of parents and adolescents. A casual chain with three links and four sets of variables were analyzed using structural equation modeling. Data were collected from 800 adolescents attending 10 middle schools in the Busan region of South Korea. Results indicated that both maternal and paternal parental bonding were negatively associated with stress, stress was positively associated with hopelessness, and hopelessness was positively associated with South Korean adolescent peer victimization. Most importantly, the significant negative associations between both maternal and paternal parental bonding and peer victimization were mediated by both stress and hopelessness. Furthermore, gender differences in these relationships existed for both parents and adolescents. Limitations and implications to practice were discussed.     

Zum Verlauf des Zweitspracherwerbs im Migrationskontext

Zusammenfassung Die Entwicklung der mündlichen und schriftlichen Kenntnisse in Deutsch und der Sprache des Herkunftslandes bei Angeh?rigen der ersten und zweiten Einwanderergeneration aus den Gastarbeiter-Anwerbel?ndern, bei Aussiedlern und neuen Zuwanderergruppen wird beschrieben und Erkl?rungsfaktoren für Unterschiede werden mit Hilfe bivariater und multivariater Verfahren untersucht. Die Deutschkenntnisse der ersten Generation steigen zwischen 1984 und 2001 kaum an, wohingegen Aussiedler und Zuwanderer in kurzer Zeit relativ gute Fortschritte aufweisen. Die meisten Befragten sind bilingual. Defizite bei Deutschkenntnissen variieren nach Herkunftsland. Der Zweitspracherwerb erfolgt im Generationenverlauf, d.h. in Deutschland geborene Personen mit Migrationshintergrund haben in der Regel bessere Deutschkenntnisse als die erste Generation. Die Aufenthaltsdauer hat per se keinen Einfluss auf den Spracherwerb, ebenso wie das Geschlecht, w?hrend das Einwanderungsalter und die Schulbildung entscheidende Faktoren sind. Personen mit niedrigem Einwanderungsalter, Personen, die eine weiterführende Schule im Herkunftsland oder eine h?here Schule in Deutschland abgeschlossen haben, haben eine h?here relative Chance, gute mündliche und schriftliche Deutschkenntnisse zu erwerben.      

Postsecondary Student Persistence and Pathways: Evidence From the YITS-A in Canada

The Youth in Transition Survey is used to follow the postsecondary education (PSE) pathways and outcomes of Canadian youth over the mid 2000s. Students starting at community colleges and four year universities are analyzed separately. First program outcomes are reported, showing the proportions of students who leave their first programs but remain in PSE by switching/transferring to other programs, institutions, or levels. Multinomial regression estimates correlates of students’ first program switching and leaving decisions. Five year graduation rates are calculated to show the importance of different pathways (across programs, institutions, and levels) to earning a PSE credential; in the aggregate and for subgroups of students. Transfers constitute important but not terribly large pathways for Canadian students to adjust their PSE and obtain PSE credentials. We calculate the resulting extent to which institution specific measures of persistence, PSE leaving, and graduation rates misstate the rates experienced by students. Compared to American students, university and community college starters in Canada have higher persistence and graduation rates and lower transfer rates across institutions. For community college starters, much of the difference is due to the relative lack of well defined pathways from community colleges to universities in Canada. We find that students with more family resources are better able to transfer across programs or institutions in order to obtain a PSE credential.     

Kinesin KIF4A is associated with chemotherapeutic drug resistance by regulating intracellular trafficking of lung resistance-related protein

Multidrug resistance (MDR) is the major impediment to cancer chemotherapy. The expression of lung resistance-related protein (LRP), a non-ATP-binding cassette (ABC) transporter, is high in tumor cells, resulting in their resistance to a variety of cytotoxic drugs. However, the function of LRP in tumor drug resistance is not yet explicit. Our previous studies had shown that Kinesin KIF4A was overexpressed in cisplatin (DDP)-resistant human lung adenocarcinoma cells (A549/DDP cells) compared with A549 cells. The expression of KIF4A in A549 or A549/DDP cells significantly affects cisplatin resistance but the detailed mechanisms remain unclear. Here, we performed co-immunoprecipitation experiments to show that the tail domain of KIF4A interacted with the N-terminal of LRP. Immunofluorescence images showed that both the ability of binding to LRP and the motility of KIF4A were essential for the dispersed cytoplasm distribution of LRP. Altogether, our results shed light on a potential mechanism in that motor protein KIF4A promotes drug resistance of lung adenocarcinoma cells through transporting LRP-based vaults along microtubules towards the cell membrane. Thus KIF4A might be a cisplatin resistance-associated protein and serves as a potential target for chemotherapeutic drug resistance in lung cancer.     

The formation experiment in the age of hypermedia and distance learning

Searching for an adequate method to investigate human development (especially the development of theoretical thinking) Vygotsky and his collaborators developed the causal genetic method. The basic idea of this method consists in the investigation of psychic functions and structures by their formation under controlled conditions (for instance via a formation experiment in classroom). But is this method also applicable in instructional settings using modern communications media?This paper is an attempt to find an answer to the question: By what means is the investigation of the formation of theoretical thinking realizable through the application of the causal-genetic method in instructional settings using hypermedia and distance learning? However, a closer examination of the question itself shows that there are three interrelated aspects, namely: the investigation and formation of theoretical thinking; distance learning using modern communications media; the causal-genetic method.It will be shown that in a formation experiment learning with a hyper-media-educational program, which is based on the theory of learning- activity, students reach a new level of cognitive development which is characterized by the growing ability of complex and dialectical thinking.     

Making the Case for Early Identification and Intervention for Young Children at Risk for Learning Disabilities

The early identification of children with learning disabilities (LD) is difficult but can be accomplished. Observation of key behaviors which are indicators of LD by preschool and kindergarten teachers can assist in this process. This early identification facilitates the use of intervention strategies to provide a positive early experience for children at risk for academic difficulties.     

圆周上的范德瓦尔登数

The big upper bound of typical van der Waerden number was investigated through calculating the van der Waerden number on a circle. And the van der Waerden number Wh (3,3) = 9, Wh (3,3,3)≥25 on a circle was calculated by computer.