• 대한수학회보
• /
• 제26권1호
• /
• pp.47-52
• /
• 1989

Methods of Riemannian geometry has played an important role in the study of compact transformation groups. Every effective action of a compact Lie group on a differential manifold leaves a Riemannian metric invariant and the study of such actions reduces to the one involving the group of isometries of a Riemannian metric on the manifold which is, a priori, a Lie group under the compact open topology. Once an action of a compact Lie group is given an invariant metric is easily constructed by the averaging method and the Lie group is naturally imbedded in the group of isometries as a Lie subgroup. But usually this invariant metric has more symmetries than those given by the original action. Therefore the first question one may ask is when one can find a Riemannian metric so that the given action coincides with the action of the full group of isometries. This seems to be a difficult question to answer which depends very much on the orbit structure and the group itself. In this paper we give a sufficient condition that a subgroup action of a compact Lie group has an invariant metric which is not invariant under the full action of the group and figure out some aspects of the action and the orbit structure regarding the invariant Riemannian metric. In fact, according to our results, this is possible if there is a larger transformation group, containing the oringnal action and either having larger orbit somewhere or having exactly the same orbit structure but with an orbit on which a Riemannian metric is ivariant under the orginal action of the group and not under that of the larger one. Recently R. Saerens and W. Zame showed that every compact Lie group can be realized as the full group of isometries of Riemannian metric. [SZ] This answers a question closely related to ours but the situation turns out to be quite different in the two problems.

• 정보보호학회논문지
• /
• 제11권6호
• /
• pp.89-103
• /
• 2001

그룹 기반 통신 응용 서비스의 요구가 증가함에 따라 유·무선 네트워크상에서 사용 가능한 멀티캐스트 기반 구조에 대한 연구가 활발히 진행되고 있다. 하지만 멀티캐스트 구조에 대한 안전성과 효율성 및 확장성 부분에 대한 해결책은 아직 미비한 상태이다. 본 연구에서는 유·무선 통합 멀티캐스트 서비스 지원을 위해, PKI(Public Key Infrastructure) IPsec, 도메인 Subgroup 및 구조적 이원화 기법 등에 기초하여 확장성을 제공하는 안전한 멀티캐스트 키 관리 구조를 제안한다. 또한 멀티캐스트 키 관리 서비스를 위하여, 수신자 지정 그룹 서명 방식 및 키 갱신 기법을 새로이 제안함으로서 안전성과 신뢰성을 보장하고 있다. 이를 근거로 새로이 제안된 방식과 기존의 방식들을 안전성, 효율성 및 확장성 부분에서 비교 분석함으로서 그 효용성을 검증한다.

• International Journal of Oral Biology
• /
• 제46권4호
• /
• pp.184-189
• /
• 2021

When luting indirect restorations with dual-cure resin cement (DCRC), excess cement can be easily removed by performing tack cure of DCRC for a few seconds. The purpose of this study was to evaluate whether different tack cure times affect polymerization shrinkage (PS) of the selected DCRC. One dual-cure resin cement (G-CEM LinkAce, GC) was used for measuring PS in light-cure (LC group), self-cure (SC group), and two tack-cure modes. In the first tack-cure subgroup, tack cure was performed for 1, 2, 3, and 5 seconds, followed by light cure after 2 minutes of remnant removal time in each case (TC-LC groups). In the other tack-cure subgroup, tack cure was performed for the same lengths of time, but followed by self-cure in each case (TC-SC groups). PS was measured by a modified bonded disc method for 1,800 seconds. One-way analysis of variance followed by Duncan's post hoc test was used to determine any statistically significant differences among the test groups (α = 0.05). When the DCRC was self-cured after tack cure, PS was significantly lower than when it was only self-cured (p < 0.05); however, tack cure time did not affect PS (p > 0.05). When the DCRC was light-cured, PS was not affected by tack cure or tack cure time (p > 0.05). Therefore, tack cure within 5 seconds did not negatively affect the final PS when the DCRC was light-cured after cement remnant removal.

• 농촌지도와개발
• /
• 제29권4호
• /
• pp.225-250
• /
• 2022

This study aims to examine the effects of infant's social development forest experience activities through meta-analysis. The final nine studies(total of 165 in the experimental group and 159 in the control group) were selected as a method of systematic review. Meta-analysis on overall effect size estimation, chi-square test, significance analysis, publication bias analysis, and subgroup analysis was performed using the R program. The overall effect size of 9 studies was 1.59, indicating a large effect size. As a result of subgroup analysis of the sub-factors of sociality, autonomy showed the largest effect size at 1.47, the adjusted effect size of cooperation was 1.34, the effect size adjusted for peer interaction was 1.29, and the adjusted effect size for perspective-taking ability was 0.97. All were found to have a statistically significant effect. To analyze the moderating effect, a meta-regression analysis was conducted on the participation period(4, 5~6, 7~8weeks), the number of sessions(6~10, 11~15, 16~20), the frequency per week(1, 2, 5), and the participation time(40, 60, 90, 120, 150min), but there was no statistical difference. Although not statistically significant, the effect size was larger when the participation period was 4 weeks, the number of sessions was 16 to 20, the frequency was 2 times per week, and the participation time was 40 minutes. This results can be usefully utilized by policy makers and forest commentators related to the vitalization of forest education through forest experience activities.

• 천문학회보
• /
• 제46권1호
• /
• pp.33.1-33.1
• /
• 2021

The overprediction of the number of satellite galaxies in the LCDM paradigm compared to that of the Milky Way (MW) and M31 (the "missing satellites" problem) has been a long-standing issue. Recently, a large host-to-host scatter of satellite populations has been recognized both from an observational perspective with a larger sample and from a theoretical perspective including baryons, and it is crucial to collect diverse and complete samples with a large survey coverage to investigate underlying factors contributing to the diversity. In this study, we discuss the diversity in terms of galaxy assembly history, using satellite populations of both observed systems and simulated systems from IllustrisTNG. In addition to previously studied satellite systems, we identify satellite candidates from 25deg2 of Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) Wide layer around NGC 4437, a spiral galaxy of about one-fourth of the MW mass, paired with a ~2 magnitude fainter dwarf spiral galaxy NGC 4592. Using the surface brightness fluctuations (SBF) method, we confirm five dwarf galaxies as members of the NGC 4437 group, resulting in a total of seven members. The group consists of two distinct subgroups, the NGC 4437 subgroup and the NGC 4592 subgroup, which resembles the relationship between the MW and M31. The number of satellites is larger than that of other observed and simulated galaxy groups in the same host stellar mass range. However, the discrepancy decreases if compared with galaxy groups with similar magnitude gaps (V12 ~ 2), defined as the V-band magnitude difference between the two brightest galaxies in the group. Using simulated galaxy groups in IllustrisTNG, we find that groups with smaller V12 have richer satellite systems, host more massive dark matter halos, and have assembled more recently. These results show that the host-to-host scatter of satellite populations can be attributed to the diversity in galaxy assembly history and be probed by V12 to some degree and that NGC 4437 group is likely a recently assembled galaxy group with a large halo mass compared to galaxy groups of similar luminosity.

• 대한치과교정학회지
• /
• 제54권2호
• /
• pp.89-107
• /
• 2024

Objective: This systematic review aimed to provide a comparative analysis of the treatment outcomes, including hard and soft tissues, postoperative stability, temporomandibular disorders (TMD), and quality of life (QoL), in patients with facial asymmetry who underwent orthognathic surgery. Methods: The primary objective was to address the question, "How do different factors related to surgery affect the outcomes and stability of orthognathic surgery in the correction of facial asymmetry?" A meta-analysis was conducted on the outcome parameters, such as skeletal, dental, and soft tissue symmetry, TMD, QoL, and relapse, using the Hartung-Knapp-Sidik-Jonkman method for random-effects models. Subgroup analyses were conducted considering surgery-related factors such as surgical techniques (one-jaw vs. two-jaw), use of the surgery-first approach, utilization of computer simulation, and analytical methods employed to evaluate asymmetry (2D vs. 3D). Results: Forty-nine articles met the inclusion criteria. The metaanalysis demonstrated a significant improvement in the symmetry of hard and soft tissues. The subgroup analysis indicated that the treatment outcomes showed significant improvement, regardless of the factors related to surgery. Changes in TMD signs and symptoms varied according to the surgical technique used. Quality of life improved in the facial, oral, and social domains. Skeletal relapse was observed during the follow-up. Conclusions: Our findings support the positive outcomes of orthognathic surgery in the treatment of facial asymmetry in terms of skeletal and soft tissue improvements, stability, relief of TMD symptoms, and enhancement of QoL. However, most of the included studies showed a low certainty of evidence and high heterogeneity.

• 한국멀티미디어학회논문지
• /
• 제9권8호
• /
• pp.963-970
• /
• 2006

본 논문에서는 저가형 CSTN-LCD(Color Super-Twisted Nematic Liquid Crystal Display)에 사용하는 동영상 프로세서를 제안한다. 제안된 프로세서는 SFP(SubFrame Pattern) 기법을 적용하여 계조 확장을 할 뿐 아니라 플리커(flicker)현상을 제거하였고 BFI(Black Field Insertion) 기법을 적용하여 액정의 응답시간을 보상하였다. 그리고 화질 향상을 위한 에지 강조 기법과 보간기법을 적용하였다. 하드웨어 구조는 FPGA 프로토타입 보드를 사용하여 검증하였다. 제안된 동영상 프로세서는 PDA(Personal Digital Assistants), 모바일 폰과 PMP(Portable Multimedia Player) 등에 사용되어 질 수 있다.

• 디지털산업정보학회논문지
• /
• 제18권3호
• /
• pp.83-95
• /
• 2022

A technology can be newly formed through technological convergence achieved by the intersection of two or more technological fields. As the complexity of technology development increases, related interest is increasing. Researches have been carried out on the concept, related indicators and analysis of technology convergence including method of social networks. This paper intends to suggest an analysis method of technology convergence using social networks based on the company's possessing technologies. According to the similarity of technologies among companies, a social network was constructed and the technology convergence was analyzed using k-core, a social network subgroup method. Using the result of k-core, base and element technologies for convergence was identified with their relations. Using the suggested method, technology convergence was analyzed on real technology data of defense-industry companies. When the minimum technology similarity is 0, the overall technology convergence relations between technology elements can be identified. In the scope of data in this paper, technologies of defense S/W, aircraft structure and structural materials are identified as important base technology for convergence.

• 미생물학회지
• /
• 제23권3호
• /
• pp.235-240
• /
• 1985

비유황 광합성 세균(Family Rhodospirillaceae) 에 속하는 16종에서 총 10개의 주요 형젤을 션택하여 Farris의 방볍에 따라 Phenetic 빛 C I adi s tic분석을 행 하였다. 얻어 진 phenogram과 cladistic tree를 Bergey's manual 및 다른 결과들과 비교하였다. 비유황성 광합성 세균들과 4 개 또는 5 개의 subgroup (genus)으로 나누어졌으며. 특히 Rhodospirillum tenue와 Rhodopseudomonas gelatinosa는 밀접한 유연관계가 있음을 나타내었고, 또한 R Rhodomicrobium vanielii와 Rhodopseudomonas 속의 몇몇 종들 사이에는 큰 차이점을 보이지 않는 것으로 나타 났다

• Communications for Statistical Applications and Methods
• /
• 제7권2호
• /
• pp.533-540
• /
• 2000

The problem of information related to I poission experiments, each having a distinct failure rate $\theta$i I=1,2,…,I, is considered. Instead of using a standard exchangeable prior for $\theta$=($\theta$1,$\theta$2,…,$\theta$I), we consider a partition of the experiments and take the $\theta$i's belonging to the same partition subgroup to be exchangeable and the $\theta$i's belonging to distinct subgroups to be independent. And we perform Gibbs sampling approach for Bayesian inference on $\theta$ conditional on a partition. Numerical study using real data is provided.