• Journal of Communications and Networks
• /
• v.15 no.2
• /
• pp.228-239
• /
• 2013

Peer-to-peer (P2P) systems have proved the most effective and popular file sharing applications in recent years. Previous studies mainly focused on equal service and differentiated service strategies when peers have no initial data before their downloads. For an upload-constrained P2P file sharing system, we model both the equal service process and the differentiated service process when the initial data distribution of peers satisfies some special conditions. Moreover, we show how to minimize the time required to distribute the file to any number of peers. The proposed fluid-based models can reveal the intrinsic relations among the initial data amount, the peer set size, and the minimum last finish time. The closed-form expressions derived from the extended models can closely approximate chunk-based models and systems, especially for relatively large files. As an application of the extended models, we show how to provide differentiated service efficiently to multiple peer sets. Since no limits are imposed on the upload bandwidth of peers or the size of each peer set, we believe that our analytic process and the results achieved can provide not only fundamental insights into bandwidth allocation and data scheduling but also a helpful reference for both improving system performance and building an effective incentive mechanism for P2P file sharing systems.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.10 no.1
• /
• pp.27-36
• /
• 1998

A three-dimensional numerical model of water circulation has been developed. The model employs the equations on $\sigma$-coordinate and the finite element method for numerical integration. To verify accuracy of the model, a series of numerical experiments have been conducted. The experiments include wind-driven currents in an one-dimensional channel, wind-driven currents in a square lake, and tidal current distributions in Masan-Jinhae Bay. The simulation results showed good agreements with the analytic solutions for wind-driven current and the field data sets in Masan-Jinhae Bay. The model can be used widely for modeling of water circulation in the waters with a complex geometry.

• Journal of the Chungcheong Mathematical Society
• /
• v.24 no.1
• /
• pp.19-34
• /
• 2011

A bounded linear operator T on a complex Banach space X is said to have property (I) provided that T has Bishop's property (${\beta}$) and there exists an integer p > 0 such that for a closed subset F of ${\mathbb{C}}$ ${X_T}(F)={E_T}(F)=\bigcap_{{\lambda}{\in}{\mathbb{C}}{\backslash}F}(T-{\lambda})^PX$ for all closed sets $F{\subseteq}{\mathbb{C}}$, where $X_T$(F) denote the analytic spectral subspace and $E_T$(F) denote the algebraic spectral subspace of T. Easy examples are provided by normal operators and hyponormal operators in Hilbert spaces, and more generally, generalized scalar operators and subscalar operators in Banach spaces. In this paper, we prove that if T has property (I), then the quasi-nilpotent part $H_0$(T) of T is given by $$KerT^P=\{x{\in}X:r_T(x)=0\}={\bigcap_{{\lambda}{\neq}0}(T-{\lambda})^PX$$ for all sufficiently large integers p, where ${r_T(x)}=lim\;sup_{n{\rightarrow}{\infty}}{\parallel}T^nx{\parallel}^{\frac{1}{n}}$. We also prove that if T has property (I) and the spectrum ${\sigma}$(T) is finite, then T is algebraic. Finally, we prove that if $T{\in}L$(X) has property (I) and has decomposition property (${\delta}$) then T has a non-trivial invariant closed linear subspace.

• The Journal of Asian Finance, Economics and Business
• /
• v.9 no.6
• /
• pp.363-372
• /
• 2022

The purpose of this study is to investigate COVID-19's impact on firm survival, as well as the management accounting system's role in adjusting operation efficiency for business survival. Two sets of data comprising small enterprises in the service sector were used. The first business group serves customers who have changed their lifestyle to a new normal. The second business group serves customers who are affected by social distancing measures. The data was collected based on an in-depth interview method. The data was then evaluated using content analysis and analytic comparison. The results show that the COVID-19 situation positively impacts the business survival of the service businesses group that serves customers who have changed lifestyles. However, COVID-19 has a negative effect on the survival of service business groups that serve customers affected by social distancing measures. In addition, the management accounting used during COVID-19, small enterprises have analyzed the operating environment and used the information stored in the database to determine goals for the operation. This study provides comprehensive economic effects and the utilization of management accounting systems. The accounting systems helped to decide to adjust the operation process during the quick changing of the environment of the small enterprise in the service sector.

• Journal of KIISE:Information Networking
• /
• v.30 no.5
• /
• pp.581-594
• /
• 2003

Recently, a location management is being more important in mobile communication systems due to an explosive increase of mobile users. Current systems have used a concept of location area. Based on this concept, a mobile user performs a location update whenever it moves into a new location area. However, this scheme can not avoid unnecessary location updates when a mobile user moves around with high movement rate as compared to call arrival rate. That results in tremendous location management cost. To overcome this drawback, our proposal divides service areas into two sets: One is a set of areas that mobile users move with high speed and another is a set of areas that they move with low speed. After establishing these two sets, this paper employs different location tracking schemes for each sets. Generally, most mobile users with high speed have a low CMR and a regular direction until they arrive at their destination. Using such the moving behavior, systems can predict a mobile user's next location area in advance. When the mobile user moves into the predicted location, our proposal does not perform a location update. Thus, it can reduce overall location management cost. The Markov model is used to analyze the performance of our proposal. Using the model, this paper compares our proposal with IS-41 and TLA. The analytic results show that as CMR grows lower, an overall cost of our proposal becomes less, particularly if a mobile user frequently moves into the specific location are predicted by mobile systems. Also, our proposal has a better performance than other two schemes when the communication cost between HLR and VLR is high.

• Journal of Service Research and Studies
• /
• v.7 no.4
• /
• pp.51-68
• /
• 2017

Financial technology (FinTech) is an emerging financial service sector include innovations in financial literacy and investment, retail banking, education, and crypto-currencies like bitcoin. One of the crucial branch of financial technology-third-party payment (TPP) is undergoing rapid growth, with online/mobile systems replacing offline financial systems. System quality and user attitudes are key perceptions driving third-party payment usage, the importance of these perceptions, however, may be different with countries as users' thinking varies from country to country. Thus, the purpose of this study is to elaborate how factors differ from China to Korea by drawing on the unified theory of acceptance and use of technology (UTAUT2). Additionally, this study also aims to propose a multi-attribute evaluation of the third-party online payment system based on analytic hierarchy process (AHP), fuzzy sets and technique for order performance by similarity to ideal solution (TOPSIS), to examine the relative importance of the perceptions influencing new technology adoption intention. The results showed that the price value has the most significant influence on Chinese perceptions, while the perceived credibility has the most significant effect on Korean perceptions. Sub-criteria also performs different results to Chinese and Korean third-party online payment system.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.2
• /
• pp.613-624
• /
• 2013

The purpose of this study is to identify the priorities with respect to the characteristics of tourism resources development plan between the South and the North Korea. Through a preliminary investigation 287 lists of questions were distributed from May 14, 2012 to December 5, 2012 and from among them 252 lists were used. Expert Choice 11.5 was used to do pairwise comparisons and priorities assessment. Based upon the results of empirical analysis, the priority order sets of the domain of tourism resources development plan should be related to the development contents, the development objects, the development patterns, and the development subjects in the South Korea. Those should be related to the development subjects, the development objects, the development contents, and the development patterns in the North Korea.

• Journal of the Korean Geotechnical Society
• /
• v.15 no.5
• /
• pp.229-240
• /
• 1999

The groundwater flow and grout flow in individual rock joint and jointed rock mass are studied using various methods of analysis such as (i) the finite difference method, (ii) channel network analysis and (iii) joint network analysis. The flow behaviour is investigated in two distinguishable scales of observation: one for a rough joint of a laboratory scale having variable aperture, and the other for field- scale rock masses having three sets of intermittent joints. In the former case, the aperture-dependent channel flow is identified for both water and grout flows. The comparison of the flow rate in a rough joint is made between the finite difference analysis and existing analytical solution. In the latter case, the effects of increasing number of joints on the groundwater inflow into a circular opening of various diameters are analyzed using both the joint network method and Goodman's analytic solution. Comparisons are made between the two methods. The boundary effects in the joint network method are discussed. The inhomogeneity of joint network and its impacts on the groundwater inflow are also discussed.

• Education of Primary School Mathematics
• /
• v.15 no.2
• /
• pp.77-89
• /
• 2012

Considerable efforts have been attempted to identify what makes high-quality mathematics instruction, including diversity and variability across different educational systems and cultural contexts. As the instructional elements related to effective mathematics teaching can be commonly applied to different content domains, they may be efficient in selecting such teaching. However, such elements may not reflect on the specific but essential features of each domain. This paper compared and contrasted two sets of measurement teaching practices, which were recognized as good instruction, in terms of how the key elements of measurement domain were implemented. As such this paper is expected to accumulate significant knowledge about elements of effective mathematics instruction that are specialized in a particular content domain of measurement. This paper suggests that domain-specific approach be considered in studying good mathematics teaching.

• School Mathematics
• /
• v.15 no.3
• /
• pp.633-650
• /
• 2013

The aim of this paper is to explore and understand, using in-depth interviews, the participant's interests and discourse analytic expressions in studying the notion of infinity and limit. In addition we tried to understand how the participant's ways of dealing with math and thinking patterns on the polygons whose boundary is infinite but area is finite as they brought up such examples. Further follow-up questions are posed on the infinite sum of a smallest number close to 0 and the sum of infinite sets of different smallest numbers close to 0. Larger aspects of two pre-service teachers' subjective thinking patterns and colloquial discourses were sketched by contrasting the three posed tasks. Cross case discussions are provided with several suggestions for the future research directions.