1,720,963 research outputs found
Sobolev regularity theory for the non-local elliptic and parabolic equations on open sets
No full textWe study the zero exterior problem for the elliptic equation Delta alpha/2u - lambda u = f, x E D ; u|Dc =0 as well as for the parabolic equation ut = Delta alpha/2u + f, t > 0, xED; u(0,')|D= u0, u|[0,T]xDc = 0. Here, alpha E (0, 2), lambda > 0 and D is a C',' open set. We prove uniqueness and existence of solutions in weighted Sobolev spaces, and obtain global Sobolev and Ho center dot lder estimates of solutions and their arbitrary order derivatives. We measure the Sobolev and Ho center dot lder regularities of solutions and their arbitrary derivatives using a system of weights consisting of appropriate powers of the distance to the boundary. The range of admissible powers of the distance to the boundary is sharp.
TOWARD ENERGY-EFFICIENT ERROR CONTROL IN 3G BROADCAST VIDEO
No full textEnergy use is a key issue in battery-operated mobile devices. In order to extend battery life, mobiles showing video often allow a controlled drop in quality, which is tolerable when the shortcomings of a small screen are combined with the imperfections of visual perception. Both energy consumption and video quality are affected by the Reed-Solomon codes and interleaving levels used in 3G video broadcast services. We explore the effect of these elements of MAC-layer error control, and show how they can be manipulated to save energy while maintaining acceptable video quality through a controlled reduction in the number of parity symbols in the Reed-Solomon code and the level of interleaving. © 2002-2012 IEEE.
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Reducing Application Launch Time by Using Execution-time Prefetching Techniques
Full text link학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2013. 2. 신현식.최근 모바일 기기의 사용이 보편화되면서 프로그램 실행의 응답성은 사용자의 체험에 큰 영향을 주는 요소가 되었다. 특히, 응용프로그램의 기동시간은 기기에 대한 사용자의 체감성능을 평가하는 중요한 지표로 사용된다. 하지만 플래시 기반의 디스크가 시스템 디스크로 사용되는 경우에도 사용자들은 긴 응용프로그램 기동시간을 자주 경험한다. 프로세서나 디스크 장치는 병렬성을 이용하여 성능을 개선하는 반면, 응용프로그램 기동 시에는 자원들의 사용이 직렬화되기 때문이다.
응용프로그램의 기동시간 단축을 위하여 본 논문에서는 새로운 실행시간 프리페칭 기법을 제안한다. 응용프로그램의 최초 기동 시 접근되는 블록을 정확히 파악하고, 이후 기동 시 이 블록들을 효율적인 방법으로 디스크캐시에 적재함으로써 기동시간을 단축시킨다. 핵심 전략은 프로세서와 디스크의 사용을 병렬화하고 디스크의 내부병렬성과 멀티코어의 활용을 유도하였다. 또, 프리페칭 시간을 단축하기 위하여 디스크의 특성에 따라 다양한 병합, 논리블록번호 정렬, 프리페치 수준의 의존성 해결 기법을 사용하였다.
제안한 프리페칭 기법을 리눅스 커널 3.5.0에 구현하였고 많이 사용되는 응용프로그램을 이용하여 성능을 평가하였다. 하드디스크 기반의 데스크탑 워크로드에서 콜드스타트 시간 대비 평균 52%의 기동시간을 단축하였고 SSD를 사용한 경우 34.1%가 단축하였다. 또, SSD를 사용하는 모바일용 Meego 플랫폼에서 평균 28.1 ~ 34.1%의 기동시간을 단축하였고, 안드로이드 플랫폼이 탑재된 갤럭시 넥서스 폰에서 평균 12.8%의 기동시간을 단축하였다. 마지막으로, 유저 수준에서 구현한 프리페쳐를 사용한 경우, SSD를 사용하는 환경에서 평균 21.7 ~ 28.5%의 기동시간을 단축하였다.
제안한 기법을 기존의 환경에 구현하여 운용하는데 경미한 오버헤드를 유발하는 한편, 시스템의 응답속도를 개선하고 사용자의 체감 속도를 향상시킴으로서 데스크탑 PC와 스마트폰의 성능향상에 유의미한 기여를 할 것이다.Recently, as mobile devices are widely used, an application responsiveness is of great importance to user experience. Among many metrics, application launch performance is one of important indices to evaluate user-perceived system performance. However, users suffer from long application launch delay even if they use flash-based disk as their system disks. It is mainly because system resources are used in serialized manner during application launch process while processors and disk drives improve their performance by exploiting parallelism.
To optimize launch performance, this dissertation presents a new execution-time prefetching technique, which monitors accessed blocks accurately during the first launch of each application and prefetches them into disk caches in the optimized order at their subsequent launches. The key idea is to overlap processor computation with disk I/O while exploiting internal parallelism on disk drives effectively. In order to optimize prefetch performance, we employ various merge, logical-block-number sort, and prefetch-level dependency resolution schemes.
We implemented the proposed prefetcher on Linux kernel 3.5.0 and evaluated it by launching a set of widely-used applications. Experiments demonstrate an average of 52% reduction of application launch time on an HDD-based system and 34.1% reduction on an SSD-based system as compared to cold start performance. We also achieve an average of 28.1 ~ 31.4% reduction on mobile Meego platform using an SSD as a system disk. And We port the proposed prefetcher to Android platform and achieve an average of 12.8% reduction of widely-used android applications on Galaxy Nexus phone. In addition, We implemented the proposed prefetcher at user-level which does not require kernel modification. It demonstrated an average of 21.7 ~ 28.5% reduction of application launch time on SSDs.
The proposed scheme incurs little overhead from its implementation and operations in the existing environment. It is expected to make significant contributions to performance enhancement of desktop PCs and smartphones by improving both system and user-perceived performance.제 1 장 서 론 1
1.1 연구 동기 1
1.2 연구 내용 및 의의 3
1.3 논문의 구성 8
제 2 장 연구 배경 9
2.1 범용 디스크 드라이브 9
2.1.1 하드디스크 드라이브 9
2.1.2 NAND 플래시 기반 Solid-State Drive (SSD) 10
2.1.3 하이브리드 하드디스크 12
2.2 리눅스의 디스크 입출력 부 시스템 14
2.2.1 리눅스의 디스크 입출력 스택 14
2.2.2 리눅스의 디스크캐시 16
2.2.3 입출력 스케쥴러의 종류 및 특징 18
2.2.4 입출력 플러그/언플러그 20
2.2.5 프리페치 성공 시 절약되는 프로세서 시간 분석 21
2.3 응용프로그램의 빠른 기동을 위한 기존 연구 23
2.3.1 응용프로그램의 빠른 기동을 위한 디스크캐싱 기법 23
2.3.2 범용 워크로드의 빠른 응답을 위한 디스크캐싱 기법 26
2.3.3 그 외의 기법들 29
제 3 장 응용프로그램 기동 시의 동작 특성 분석 31
3.1 기동 시나리오 31
3.2 기동 시 발생되는 디스크 입출력 분석 32
3.3 프로세서와 디스크의 활성화 패턴 분석 34
제 4 장 커널 수준 실행시간 프리페쳐의 설계, 구현 및 평가 37
4.1 실행시간 프리페쳐의 소개 및 목표 37
4.2 기동시퀀스 수집 41
4.3 프리페치시퀀스 스케쥴러 44
4.3.1 익스텐트-의존성 (Extent-Dependency) 분석 44
4.3.2 블록 간 의존성 해결을 위한 메타데이터 쉬프트 46
4.3.3 거리기반 병합 50
4.3.4 거리기반 빈공간채움 병합 51
4.3.5 논리블록번호 정렬 52
4.3.6 플러그/언플러그 52
4.4 응용프로그램과 프리페쳐 동작의 병렬화 54
4.4.1 하드디스크를 사용하는 시스템 54
4.4.2 SSD를 사용하는 시스템 56
4.4.3 다중 디스크를 사용하는 시스템 57
4.5 기동시퀀스의 유효성 관리 57
4.6 운영체제 부트 프리페쳐 58
4.7 유휴시간 프리페쳐 인터페이스 59
4.8 실험 환경 60
4.9 응용프로그램 기동시간 64
4.10 운영 및 저장 공간 오버헤드 78
4.11 커널 수준 프리페쳐의 안전성 80
제 5 장 유저 수준 실행시간 프리페쳐의 설계, 구현 및 평가 83
5.1 유저 수준 프리페쳐의 소개 및 구조 83
5.2 응용프로그램의 프리페치시퀀스 생성 85
5.2.1 디스크 입출력 정보 수집 85
5.2.2 기동시퀀스 추출 85
5.2.3 프리페치시퀀스 스케쥴 86
5.3 블록-파일 사상 (Map) 86
5.3.1 블록-파일 사상의 소개 86
5.3.2 기동시퀀스 관련 파일 목록의 수집 88
5.4 유저 수준의 프리페쳐 프로그램 생성 89
5.5 응용프로그램 기동 관리자 90
5.6 유저 수준의 프리페쳐의 장점 및 단점 93
5.7 실험 환경 93
5.8 응용프로그램 기동시간 94
5.9 운영 및 저장 공간 오버헤드 95
제 6 장 결론 및 향후 연구 방향 96
6.1 결론 96
6.2 향후 연구 방향 99
참고문헌 102
Abstract 113Docto
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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