• Journal of KIISE:Databases
• /
• v.30 no.1
• /
• pp.95-107
• /
• 2003

The broadcast environment has asymmetric communication aspect that is typically much greater communication bandwidth available from server to clients than in the opposite direction. In addition, most of mobile computing systems allow mostly read-only transactions from mobile clients for retrieving different types of information such as stock data, traffic information and mews updates. Since previous concurrency control protocols, however, do not consider such a particular characteristics, the performance degradation occurs when previous schemes are applied to the broadcast environment. In this paper, we propose the efficient concurrency control for query transaction in broadcast environment. The following requirements are satisfied by adapting weak consistency that is the appropriate correctness criterion of read-only transactions: (1) the mutual consistency of data maintained by the server and read by clients (2) the currency of data read by clients. We also use the serialization graph scheme to check the weak consistency efficiently. As a result, we improved a performance by reducing unnecessary aborts and restarts of read-only transactions caused when global serializability was adopted.

• Journal of KIISE:Databases
• /
• v.29 no.6
• /
• pp.477-491
• /
• 2002

The broadcast environment has asymmetric communication aspect that is typically much greater communication bandwidth available from server to clients than in the opposite direction. In addition, mobile computing systems generate mostly read-only transactions from mobile clients for retrieving different types of information such as stock data, traffic information and news updates. Since previous concurrency control protocols, however, do not consider such a particular characteristics, the performance degradation occurs when previous schemes are applied to the broadcast environment. In this paper, we propose optimistic concurrency control based on timestamp interval for broadcast environment. The following requirements are satisfied by adapting weak consistency that is the appropriate correctness criterion of read-only transactions: (1) the mutual consistency of data maintained by the server and read by clients (2) the currency of data read by clients. We also adopt the timestamp Interval protocol to check the weak consistency efficiently. As a result, we improved a performance by reducing unnecessary aborts and restarts of read-only transactions caused when global serializability was adopted.

• Electronics and Telecommunications Trends
• /
• v.13 no.2 s.50
• /
• pp.29-42
• /
• 1998

이제까지 대부분의 소프트웨어 작성자들은 순차 유지적(sequential consistency) 메모리모델을 기본으로 생각하여 프로그램을 작성하였다. 그러나 이 모델은 쓰기버퍼, 명령어 재배치 등과 같은 하드웨어적인 성능증가뿐 아니가 소프트웨어적인 성능증가기법들을 사용하는 데 많은 제약으로 작용하였다. 따라서 대규모 성능이 우수한 프로그램 실행환경을 채택하고 있다. 이러한 유연한 메모리모델은 분류하기에 따라 매우 다양하지만 일반적으로 process consistency, weak consistency, release consistency 등을 예로 들 수 있다. 본 고에서는 가장 일반적이고 대표적인 메모리 모델인 sequential consistency에 대해 여러 예를 통해 살펴보고, 이제까지 제안되거나 분류된 여러 메모리 모델에 대해 살펴보고 결론을 맺는다.

• Communications for Statistical Applications and Methods
• /
• v.22 no.1
• /
• pp.81-93
• /
• 2015

Validity of the stationary bootstrap of Politis and Romano (1994) is proved for U-statistics under strong mixing. Weak and strong consistencies are established for the stationary bootstrap of U-statistics. The theory is applied to a symmetry test which is a U-statistic regarding a kernel density estimator. The theory enables the bootstrap confidence intervals of the means of the U-statistics. A Monte-Carlo experiment for bootstrap confidence intervals confirms the asymptotic theory.

• Journal of Internet Computing and Services
• /
• v.2 no.5
• /
• pp.71-79
• /
• 2001

Replication in distributed databases is to improve efficiency, availability, and autonomy, But applying the strict consistency in real systems is very difficult. In this paper, I introduce a hybrid protocol permitting group update through eager update propagation and weakening consistency through lazy update, This protocol manages replica version number for the group update consistency and generates partially ordered replica spanning tree for the serializability of lazy update transactions. It preserves weak consistency by combining synchronous and asynchronous update mechanism. Study of performance analysis for the efficiency of the protocol be included in next paper.

• Communications for Statistical Applications and Methods
• /
• v.12 no.3
• /
• pp.783-795
• /
• 2005

We consider to obtain an estimate of bivariate survival function for the right censored data with the assumption that the two components of censoring vector are independent. The estimate is derived from an ad hoc approach based on the representation of survival function. Then the resulting estimate can be considered as an extension of the Susarla- Van Ryzin estimate to the bivariate data. Also we show the consistency and weak convergence for the proposed estimate. Finally we compare our estimate with Dabrowska's estimate with an example and discuss some properties of our estimate with brief comment on the extension to the multivariate case.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.7 no.2
• /
• pp.341-347
• /
• 2012

In cloud computing, a enterprise or a client can use resources of computers that they are not own them. In case of Web 2.0 applications, such as Facebook, it is difficult to predict the maximum popularity of the service. But, the cloud computing may give a solution about this problem without high cost, thus becomes wildly popular. One of the advantage of cloud computing is providing a high availability. To provide the availability when the cloud computing that has shared-nothing architecture, strict consistency is not well with cloud computing. So, some consistency was proposed including the eventual consistency that was weaken the traditional consistency and has been adopted to many cloud applications. In this paper, we observe various consistency criteria that can adjust to cloud computing and discuss about some consistency that can be adapted to many applications of cloud computing.

• The Korean Journal of Community Living Science
• /
• v.23 no.1
• /
• pp.51-59
• /
• 2012

This study was conducted to investigate the rheological properties of mulberry powder on the weak flour using color, Rapid Visco Amalyzer(RVA), farinogram, alveogram. The lightness(L value) and yellowness(b value) decreased and the redness(a value) increased with increment of mulberry powder content. On the RVA data, the weak flour with 1% of mulberry powder showed the highest initial pasting temperature and peak viscosity, while the addition of mulberry powder reduced final viscosity. On the farinogram data, the consistency of the flour containing mulberry powder was decreased with increments of mulberry powder. This meant that mulberry powder could weaken the batter. Water absorption of the samples with mulberry powder was decreased more than the control. The development time of flour with mulberry powder was also decreased more than control, but the differences were not significant. The stability of the flour with adding mulberry powder was decreased. The Pmax value of the flour was decreased significantly by adding mulberry powder. Extensibility and swelling index were both increased, but there were no significant differences.

• Journal of Korea Multimedia Society
• /
• v.10 no.4
• /
• pp.421-431
• /
• 2007

Due to the rapid development of wireless communication technology, demands on data services in mobile computing environment are gradually increasing. In mobile computing environments, a mobile host began to use cache to overcome the weak point. Caching at mobile host could reduce the bandwidth consumption and query response time, but mobile host must maintain cache consistency. In this paper, we propose a cache consistency strategy to consider the period of data usage. The server allows an effective broadcasting by classifying data into two groups of periodic and non-periodic. By classifying the data, it prevent from elimination of cache after disconnection of periodic data by using expired time. By storing IR(Invalidation Report) messages, this scheme divides cached data by selection after disconnection. Consequently, we have shown much improvement in total consumption of bandwidth than the conventional scheme.

• Journal of the Korea Society of Computer and Information
• /
• v.17 no.5
• /
• pp.41-48
• /
• 2012

A Vehicular Ad-hoc Network (VANET) is a vehicular specific type of a mobile ad-hoc network, to provide temporary communications among nearby vehicles. Mobile node of VANET consumes energy and resource with participating in the member of network. In a VANET, data replication and cooperative caching have been used as promising solutions to improve system performance. Existing cooperative caching scheme in a VANET mostly focuses on weak consistency is not always satisfactory. In this paper, we propose an efficient cache management scheme to maintain strong data consistency in a VANET. We make an adaptive scheduling scheme to broadcast Invalidation Report (IR) in order to reduce query delay and communication overhead to maintain strong data consistency. The simulation result shows that our proposed method has a strength in terms of query delay and communication overhead.