• Title/Summary/Keyword: Caching

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Video Retrieval System supporting Adaptive Streaming Service (적응형 스트리밍 서비스를 지원하는 비디오 검색 시스템)

  • 이윤채;전형수;장옥배
    • Journal of KIISE:Computing Practices and Letters
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    • v.9 no.1
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    • pp.1-12
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    • 2003
  • Recently, many researches into distributed processing on Internet, and multimedia data processing have been performed. Rapid and convenient multimedia services supplied with high quality and high speed are to be needed. In this paper, we design and implement clip-based video retrieval system on the Web enviroment in real-time. Our system consists of the content-based indexing system supporting convenient services for video content providers, and the Web-based retrieval system in order to make it easy and various information retrieval for users in the Web. Three important methods are used in the content-based indexing system, key frame extracting method by dividing video data, clip file creation method by clustering related information, and video database construction method by using clip unit. In Web-based retrieval system, retrieval method ny using a key word, two dimension browsing method of key frame, and real-time display method of the clip are used. In this paper, we design and implement the system that supports real-time display method of the clip are used. In this paper, we design and implement the system that supports real-time retrieval for video clips on Web environment and provides the multimedia service in stability. The proposed methods show a usefulness of video content providing, and provide an easy method for serching intented video content.

Dynamic Query Processing Using Description-Based Semantic Prefetching Scheme in Location-Based Services (위치 기반 서비스에서 서술 기반의 시멘틱 프리페칭 기법을 이용한 동적 질의 처리)

  • Kang, Sang-Won;Song, Ui-Sung
    • Journal of KIISE:Databases
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    • v.34 no.5
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    • pp.448-464
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    • 2007
  • Location-Based Services (LBSs) provide results to queries according to the location of the client issuing the query. In LBS, techniques such as caching and prefetching are effective approaches to reducing the data transmission from a server and query response time. However, they can lead to cache inefficiency and network overload due to the client's mobility and query pattern. To solve these drawbacks, we propose a semantic prefetching (SP) scheme using prefetching segment concept and improved cache replacement policies. When a mobile client enters a new service area, called semantic prefetching area, proposed scheme fetches the necessary semantic information from the server in advance. The mobile client maintains the information in its own cache for query processing of location-dependent data (LDD) in mobile computing environment. The performance of the proposed scheme is investigated in relation to various environmental variables, such as the mobility and query pattern of user, the distributions of LDDs and applied cache replacement strategies. Simulation results show that the proposed scheme is more efficient than the well-known existing scheme for range query and nearest neighbor query. In addition, applying the two queries dynamically to query processing improves the performance of the proposed scheme.

A Hashing Scheme using Round Robin in a Wireless Internet Proxy Server Cluster System (무선 인터넷 프록시 서버 클러스터 시스템에서 라운드 로빈을 이용한 해싱 기법)

  • Kwak, Huk-Eun;Chung, Kyu-Sik
    • The KIPS Transactions:PartA
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    • v.13A no.7 s.104
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    • pp.615-622
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    • 2006
  • Caching in a Wireless Internet Proxy Server Cluster Environment has an effect that minimizes the time on the request and response of Internet traffic and Web user As a way to increase the hit ratio of cache, we can use a hash function to make the same request URLs to be assigned to the same cache server. The disadvantage of the hashing scheme is that client requests cannot be well-distributed to all cache servers so that the performance of the whole system can depend on only a few busy servers. In this paper, we propose an improved load balancing scheme using hashing and Round Robin scheme that distributes client requests evenly to cache servers. In the existing hashing scheme, if a hashing value for a request URL is calculated, the server number is statically fixed at compile time while in the proposed scheme it is dynamically fixed at run time using round robin method. We implemented the proposed scheme in a Wireless Internet Proxy Server Cluster Environment and performed experiments using 16 PCs. Experimental results show the even distribution of client requests and the 52% to 112% performance improvement compared to the existing hashing method.

Concurrency Control and Consistency Maintenance of Cached Spatial Data in Client-Server Environment (클라이언트-서버 환경에서 캐쉬된 공간 데이터의 동시성 제어 및 일관성 유지 기법)

  • Shin, Young-Sang;Hong, Bong-Hee
    • Journal of KIISE:Databases
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    • v.28 no.3
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    • pp.512-527
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    • 2001
  • In a client-server spatial database, it is desirable to maintain the cached data in a client side to minimize the communication overhead across a network. This paper deals with the issues of concurrency and consistency of map updates in this environment. A client transaction to update map data is an interactive work and takes a long time to complete it. The map update in a client site may affect the other sites'updates because of dependencies between spatial data stored at different sites. The concurrent updates should be propagated to the other clients as well as the server to keep the consistency of map replicated in a client cache, and also the communication overhead of the update propagation should be minimized not to lose the benefit of caching. The newly proposed cache region locking with CR lock and CX lock controls the update dependency due to spatial relationships. CS lock and COD lock are suggested to use optimistic detection-based approaches for guaranteeing the consistency of cached client data. The cooperative update protocol uses these extended locking primitives and Spatial Relationship-based 2PC (SR-based 2PC). This paper argues that the concurrent updates of cached client spatial data can be achieved by deciding on collaborative updates or independent updates based on spatial relationships.

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Implementation of XML Query Processing System Using the Materialized View Cache-Answerability (실체뷰 캐쉬 기법을 이용한 XML 질의 처리 시스템의 구현)

  • Moon, Chan-Ho;Park, Jung-Kee;Kang, Hyun-Chul
    • The KIPS Transactions:PartD
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    • v.11D no.2
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    • pp.293-304
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    • 2004
  • Recently, caching for the database-backed web applications has received much attention. The results of frequent queries could be cached for repeated reuse or for efficient processing of the relevant queries. Since the emergence of XML as a standard for data exchange on the web, today's web applications are to retrieve information from the remote XML sources across the network, and thus it is desirable to maintain the XML query results in the cache for the web applications. In this paper, we describe implementation of an XML query processing system that supports cache-answerability of XML queries, and evaluate its performance. XML path expression, which is one of the core features of XML query languages including XQuery, XPath, and XQL was considered as the XML query. Their result is maintained as an XML materialized view in the XML cache. The algorithms to rewrite the given XML path expression using its relevant materialized view proposed in [13] were implemented with RDBMS as XML store. The major issues of implementation are described in detail. The results of performance experiments conducted with the implemented system showed effectiveness of cache-answerability of XML queries. Comparison with previous research in terms of performance is also Provided.

A Study of Educational System for Medical Technologists in Korea (한국(韓國)의 의료기사(醫療技士) 교육제도(敎育制度)에 관(關)한 조사(調査) 연구(硏究))

  • Song, Jae-Kwan;Lee, Gun-Sub;Kim, Byong-Lak;Kim, Chung-Rak;Cho, Jun-Suk;Huh, Joon;Lee, Joon-Il
    • Journal of radiological science and technology
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    • v.6 no.1
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    • pp.131-181
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    • 1983
  • After the investigation on, and the analysis of, the educational system for medical technicians and the present educational situation for medical technologies in this country, the following conclusions were drawn. 1. As of March 1983 the current academic system for education in medical technologies included the regular 4-year college courses and those of the 2-year professional junior college courses. But except in the cases on clinical pathology and physical therapy, there were no college-level departments. Particularly, no educational institutions, at whatever level, had a department for working therapies. 2. The total number of credits needed for graduation from a department of medical technologies was 150 points at a regular 4-year college and 85 to 96 points at a 2-year professional college. The obligatory minimum number of credits for a student at a professional college was set at 80 points and above. 3. As for the number of the educational institutions for medical technologies in this country, there were one regular college and 14 professional colleges, a total of 15 institutions. As many as 14 colleges had departments of clinical pathology, 12 had departments of Radiotechnology, 11 had departments of physical therapy, 12 had departments of dental technology, and eight had departments of dental hygiene. 4. The total capacity of the professional colleges in admitting new enrollment each year were 1,920 for clinical pathology, 1,552 for radiology, 1,012 for physical therapy, 1,334 for dental technologies, 828 for dental hygiene, an aggregate of 6,646 for all of the professional college departments. 5. The total number of graduates from the 12 professional colleges by department during the period of 1965-83 were 7,595 for clindical pathology, 4,768 for radiology, 2,821 for physical therapy, 3,000 for dental technologies, and 1,787 for dental hygiene, totalling 19,971 for all departments in the professional colleges. 6. In the state examination for licensed medical technicians, 12,446 have passed from among the total of 26,609 participants, representing a 45% passing ratio. By departments the ratios showed 44% for clinical pathology, 39.7% for radiology, 51.2% for physical therapy, 42.5% for dental technology, 72.5% for dental hygiene and 73.1% for working therapy. 7. As for the degree of satisfaction shown by the people in this field, 52.2 percent of the teaching staffs who responed to the questionaires said they were satisfied with their present profession, while the great majority of medical technicians(66%) replied that they were indifferent to the problem. 8. The degree of satisfaction shown by the students on their enrollment in this particular academic field was generally in the framework of indifference(43.7%), but mere students(36.5%) were satisfied with their choice than those were not satisfied(14.4%) 9. As for the student's opinions on the lectures and practicing hours, a good many students replied that, among such courses as general science and humanities courses the basic medical course, the major course and practicing hours, the hours provided for the general courses(47.1%) and practicing(47.6%) were insufficient. 10. When asked about the contents of their major courses, comparatively few students (23.6%) replied that the courses were too difficult, while a convincing majority(58.5%) said they were neither difficult nor easy. As for the appropriateness of the number of the present teaching staffs, a great majority(71.0%) of the students replied that the level of the teaching personnel in each particular field was insufficient. 11. Among the students who responded to the poll, good part of them(49.5%) wanted mandatory clinical practicing hours, and the the majority of them(64.6%) held the view that the experimental and practicing facilities of their schools were insufficient. 12. On the necessity of the attached hospitals, 71.1% of the teaching staffs and 58.0% of the medical technicians had the opinion that this kind of facility was indispensable. 13. As for the qualifications for applicants to the state examination in the licensing system for medical technicians, 52.2% of the teacher's and 36% of the medical technicians replied that the present system granting the qualifications according to the apprenticeship period should be abolished. 14. On the necessity of improving the present system for education in medical technologies, an overwhelming majority(94.4% of the :caching staffs, 92.0% of the medical technicians and 91.9% of students) of these polled replied that the present system should be changed for the better. 15. On the method of changes for the present educational system, a great majority(89.4% of the teaching staffs, 80.4% of the medical technicians and 90.1% of the students) said that the system must be changed so that it fits into the reality of the present day. 16. As for the present 2-year program for the professional colleges, 61.6% of the teachers, 72.0% of the medical technicians and 38.8% of the students expressed the hope that the academic period would be extended to four regular years, hemming a full-fledged collegelevels program. 17. On the life-long eductional system for medical technicians, there was a considerable number of people who expressed the hope that an open university system(38.9% of the teaching staffs, 36.0% of the medical technicians) and a graduate school system would be set up. 18. As for the future prospects for medical technicians as professionals, the optimists ana pessimists were almost equally divided, and 41.1% of the teaching staffs 36.0% of. the technicians and 50.5% of the students expressed an intermediate position on this issue.

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