• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제14권3호
• /
• pp.1363-1376
• /
• 2020

An improved clustering scheme based on user group is proposed. Every two users are grouped among N-users in the allowed system according to their link gain from large to small. Each user group is numbered sequentially. Two user clusters are obtained according to the principle of maximizing link gain difference for the users in the first and last user groups. The remaining user groups are added to the two existing user clusters according to the parity of the group number. The clustering should be clustered again among the users in either user cluster if the throughput summation of a user cluster in NOMA is less than that of these users in orthogonal multiple access. The simulation results show that the proposed clustering scheme can increase the system throughput by about 8% compared with the hybrid clustering scheme when the number of users requiring service is 12.

• Journal of Computing Science and Engineering
• /
• 제7권1호
• /
• pp.21-29
• /
• 2013

The introduction of recommender systems to existing online services is now practically inevitable, with the increasing number of items and users on online services. Popular recommender systems have successfully implemented satisfactory systems, which are usually based on collaborative filtering. However, collaborative filtering-based recommenders suffer from well-known problems, such as popularity bias, and the cold-start problem. In this paper, we propose an innovative collaborative-filtering based recommender system, which uses the concepts of Experts and Novices to create fine-grained recommendations that focus on being novel, while being kept relevant. Experts and Novices are defined using pre-made clusters of similar items, and the distribution of users' ratings among these clusters. Thus, in order to generate recommendations, the experts are found dynamically depending on the seed items of the novice. The proposed recommender system was built using the MovieLens 1 M dataset, and evaluated with novelty metrics. Results show that the proposed system outperforms matrix factorization methods according to discovery-based novelty metrics, and can be a solution to popularity bias and the cold-start problem, while still retaining collaborative filtering.

• 한국정보과학회논문지:시스템및이론
• /
• 제30권7_8호
• /
• pp.331-340
• /
• 2003

가격대비 성능이 좋은 저가의 상업용 SMP가 클러스터 시스템의 노드로 많이 사용되고 있다. 본 논문에서는 이러한 SMP 클러스터 상에서 KDSM을 확장해 소프트웨어 분산공유메모리를 구현하고 성능을 평가하였다. 본 논문의 SDSM 시스템은 HLRC 메모리 모델을 제공한다. 또한 같은 SMP 노드내에서 실행되는 프로세스 간에는 메모리 공유를 통해 페이지 획득 및 메시지 전달을 줄여 성능을 향상시켰다. 100Mbps Fast Ethernet으로 연결된 8노드의 2-way 펜티엄-III SMP 클러스터 상에서 구현되었고 통신계층은 TCP/IP를 사용한다. 8개의 응용프로그램을 실행시켜 얻은 성능 평가에서는 기존의 단일프로세스 프로토콜과 비교해 최대 33%의 성능 향상과 13%-52%의 페이지 획득 감소가 나타났다.

• Bulletin of the Korean Chemical Society
• /
• 제35권5호
• /
• pp.1379-1384
• /
• 2014

${\alpha}-Fe_2O_3$ spherical particles having an average diameter of ca. 420 nm and ${\alpha}-Fe_2O_3$ fine particles (< 10 ${\mu}m$ particle size) were prepared to examine as catalysts for CO oxidation. Kinetic studies on the catalytic reactions were performed in a flow reactor using an on-line gas chromatography system operated at 1 atm. The apparent activation energies and the partial orders with respect to CO and $O_2$ were determined from the rates of CO disappearance in the reaction stage showing a constant catalytic activity. In the temperature range of $150-275^{\circ}C$, the apparent activation energies were calculated to be 13.7 kcal/mol on the ${\alpha}-Fe_2O_3$ spherical submicron clusters and 15.0 kcal/mol on the ${\alpha}-Fe_2O_3$ fine powder. The Pco and $Po_2$ dependencies of rate were investigated at various partial pressures of CO and $O_2$ at $250^{\circ}C$. Zero-order kinetics were observed for $O_2$ on both the catalysts, but the reaction order for CO was observed as first-order on the ${\alpha}-Fe_2O_3$ fine powder and 0.75-order on the ${\alpha}-Fe_2O_3$ spherical submicron clusters. The catalytic processes including the inhibition process by $CO_2$ on the ${\alpha}-Fe_2O_3$ spherical submicron powder are discussed according to the kinetic results. The catalysts were characterized using XRD (X-ray powder diffraction), FE-SEM (field emission-scanning electron microscopy), HR-TEM (high resolution-transmission electron microscopy), and $N_2$ sorption measurements.

• 기술혁신연구
• /
• 제12권2호
• /
• pp.67-97
• /
• 2004

Practical experience with technology implementation of the upgrading of very small village industries in India suggests that innovation failures are not merely a result of the lack of proper interaction between the users and suppliers of technologies under implementation, but also a result of adoption of the primitive conception of competitiveness in their practice of technology development. The approach of promoting the small producers to become individually competitive by using labour intensive, small-scale intermediate technologies is proving to be totally inadequate for the achievement of technological efficiency in a dynamic sense. Guided by a primitive notion of competitiveness, the suppliers of intermediated technologies are thus being led into limiting their technological efforts in the sectors of direct interest to the rural industrial clusters to the transitional objectives of mainly poverty alleviation. Consequently they have not been able to target the small producers of these village industries for the objectives of business growth. This paper posits that under competitive conditions the self-employed small producer has not only to come together for access to resources, but also has to emerge as a multi-sectoral collective of producers, co-operating in production. With the aim to draw lessons that are generic and have policy implications for the development of innovation systems for local economy based rural industrial clusters and value chains, the author analyses in this paper the experience of innovation in technological systems for the sectors of leather, fruits and vegetable processing and agro processing by the People's Science Movement with the help of the Ministry of Science and Technology and other sectoral ministries in India where rural poor were required to pool the resources and capabilities for raising the scale and scope of their collective production organization.

• 한국정보과학회논문지:소프트웨어및응용
• /
• 제31권1호
• /
• pp.8-19
• /
• 2004

본 논문에서는 우리나라 우편영상에서 수취인 주소 영역을 추출하는 방법을 제안한다. 우편영상에 기입된 주소가 프린터나 타자기 둥에 의해서 인쇄된 주소일 수도 있고 사람에 의해서 필기된 주소일수도 있다. 즉, 인쇄체 우편영상과 필기체 우편영상 모두에 적용될 수 있는 수취인 주소 영역 추출 방법을 제안한다. 제안 방법에서는 이진화 된 우편영상으로부터 연결요소를 추출하고 연결요소를 결합하여 문자열을 생성한다. 그 후 문자열을 군집화하고 생성된 군집 중 몇 개의 군집을 선택함으로써 수취인 주소 영역을 결정한다. 우리나라 우편봉투에 기입되는 정보의 유형별 기입 위치 패턴에 따라 우편영상을 총 9개의 균등 영역으로 분할한 후 각 영역의 중심을 초기 값으로 갖는 9개의 군집을 생성하였고 k-Means 방법을 사용하여 군집화를 수행하였다. 군집화 과정에서 사용되는 거리함수로 우편영상의 폭 대 높이의 비율이 반영된 수정된 맨하탄 거리를 사용하였다. 제안 방법의 성능을 알아보기 위하여 실제 우편물 영상 1,988개를 사용하여 실험한 결과 약 93.56%의 우편영상에서 수취인 주소 영역을 정확하게 추출할 수 있었다.

• 농촌계획
• /
• 제21권2호
• /
• pp.103-114
• /
• 2015

The comprehensive rural village development projects (CRVDP) have been carried out as the core one of the rural development schemes in Korea since 2004. CRVDP included the various rural experience programs to increase rural income and in order to promote rural community development in the project area. This study analyzed the operating management conditions, types and characteristics of the rural experience programs targeting the 168 CRVDPs have been completed so that the recommendations and lessons which were found the usefulness, challenges and improvements to the CRVDP can be provided to be better the same kinds of rural development projects. We identified the relationships between performances such as increasing village income and utilization of rural amenity resources to the CRVDP and operational management types of the rural experience programs as well. Employing principle component analysis and cluster analysis technique, this study found 5 clusters of rural experience programs among 168 CRVDPs. The results of analysis of variance indicated that there were significant the mean differences between clusters such as the utilization of rural amenity resources(0.01), income of rural experience programs(0.1). According to the result of the Chi-squire test, there was very significant differences between internet homepage operation and clusters(0.01). Finally, the analysis of covariance about the income of rural experience programs showed that there were significant the mean differences between clusters(0.05).

• 천문학회보
• /
• 제39권2호
• /
• pp.54-54
• /
• 2014

We use dense redshift surveys of nine galaxy clusters at z ~ 0.2 to compare the galaxy distribution in each system with the projected matter distribution from weak lensing. By combining 2087 new MMT/Hectospec redshifts and the data in the literature, we construct spectroscopic samples within the region of weak-lensing maps of high (70-89%) and uniform completeness. With these dense redshift surveys, we construct galaxy number density maps using several galaxy subsamples. The shape of the main cluster concentration in the weak-lensing maps is similar to the global morphology of the number density maps based on cluster members alone, mainly dominated by red members. We cross correlate the galaxy number density maps with the weak-lensing maps. The cross correlation signal when we include foreground and background galaxies at 0.5zcl < z < 2 zcl is 10 - 23% larger than for cluster members alone at the cluster virial radius. The excess can be as high as 30% depending on the cluster. Cross correlating the galaxy number density and weak-lensing maps suggests that superimposed structures close to the cluster in redshift space contribute more significantly to the excess cross correlation signal than unrelated large-scale structure along the line of sight. Interestingly, the weak-lensing mass profiles are not well constrained for the clusters with the largest cross correlation signal excesses (>20% for A383, A689 and A750). The fractional excess in the cross correlation signal including foreground and background structures could be a useful proxy for assessing the reliability of weak-lensing cluster mass estimates.

• 한국경제지리학회지
• /
• 제7권2호
• /
• pp.315-328
• /
• 2004

본 연구는 자치단체의 행정구역을 넘어서서 확장되고 있는 산업클러스터를 지원하기 위한 산업지원체계의 구축에 관한 것이다. 많은 산업클러스터들은 두 개 혹은 그 이상의 자치단체를 넘어서서 확대되는 경향이 있는 바, 이렇듯 산업클러스터가 행정구역의 범위를 넘어서 성장함에 따라, 이를 뒷받침하는 행정지원체계에 있어서 다양한 문제가 발생할 수 있다. 무엇보다도 산업클러스터가 필요로 하는 산업지원서비스나 인프라공급이 원활히 되지 않거나 자치단체간의 이해 상충에 의해 서비스나 인프라 구축의 효율성이 저하될 수 있는 것이다. 본 연구에서는 산업클러스터를 지방정부간 협력에 의해 광역적 차원에서 구축하거나 지원하는 다양한 사례들을 검토하여 이들의 유형을 네 가지로 구분하였다. 그리고 이러한 분석으로부터 정책적 시사점을 추출한 바, 광역적 산업지원체계의 구축은 주로 '지역개발기구 설립에 의한 외자유치', '광역적 산업단지의 협력적 개발', '광역적 클러스터를 지원하는 통계 및 정책 개발, '클러스터내 기업들을 중심으로 대학, 연구기관간의 전자네트워크 구축' 등에 중점을 두는 것이 바람직한 것으로 종합되었다.

• 천문학논총
• /
• 제7권1호
• /
• pp.89-96
• /
• 1992

Recent spectroscopic observations indicate concentration of dark masses in the nuclei of nearby galaxies. This has been usually interpreted as the presence of massive black holes in these nuclei. Alternative explanations such as the dark cluster composed of low mass stars (brown dwarfs) or dark stellar remnants are possible provided that these systems can be stably maintained for the age of galaxies. For the case of low mass star cluster, mass of individual stars can grow to that of conventional stars in collision time scale. The requirement of collision time scale being shorter than the Hubble time gives the minimum cluster size. For typical conditions of M31 or M32, the half-mass radii of dark clusters can be as small as 0.1 arcsecond. For the case of clusters composed of stellar remnants, core-collapse and post-collapse expansion are required to take place in longer than Hubble time. Simple estimates reveal that the size of these clusters also can be small enough that no contradiction with observational data exists for the clusters made of white dwarfs or neutron stars. We then considered the possible outcomes of interactions between the black hole and the surrounding stellar system. Under typical conditions of M31 or M32, tidal disruption will occur every $10^3$ to $10^4$ years. We present a simple scenario for the evolution of stellar debris based on basic principles. While the accretion of stellar material could produce large amount of radiation so that the mass-to-light ratio can become too small compared to observational values it is too early to rule out the black hole model because the black hole can consume most of the stellar debris in time scale much shorter than mean time between two successive tidal disruptions. Finally we outline recent effort to simulate the process of tidal disruption and subsequent evolution of the stellar debris numerically using Smoothed Particle Hydrodynamics technique.