• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.544-544
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• 2014

Energy harvesting technology, which scavenges electric power from ambient, otherwise wasted, energy sources, has been explored to develop self-powered wireless sensors and possibly eliminate the battery replacement cost for wireless sensors. Among ambient energy sources, vibration energy can be converted into electric power through a piezoelectric energy harvester. For the last decade, although tremendous advances have been made in design methodology to maximize harvestable electric power under a given vibration condition, the research in reliability assessment to ensure durability has been stagnant due to the complicated nature of the multiple failure modes of a piezoelectric energy harvester, such as the interfacial delamination, fatigue failure, and dynamic fracture. Therefore, this study presents the first-ever system reliability analysis for multiple failure modes of a piezoelectric energy harvester using the Generalized Complementary Intersection Method (GCIM), while accounts for the energy conversion performance. The GCIM enables to decompose the probabilities of high-order joint failure events into probabilities of complementary intersection events. The electromechanically-coupled analytical model is implemented based on the Kirchhoff plate theory to analyze its output performances of a piezoelectric energy harvester. Since a durable as well as efficient design of a piezoelectric energy harvester is significantly important in sustainably utilizing self-powered electronics, we believe that technical development on system reliability analysis will have an immediate and major impact on piezoelectric energy harvesting technology.

• 정보처리학회논문지A
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• 제10A권2호
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• pp.111-122
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• 2003

군사용 워게임 시뮬레이션 모델들의 상호연동을 위해서는 국제표준연동(HLA : High Level Architecture)구조를 반드시 갖추어야하며 타 모델과 연동시 발생되는 시스템 오버헤드를 줄이기 위해서는 병렬 시뮬레이션 엔진 도입이 효과적이다. 그러나 기존 군사용 워게임 시뮬레이션 모델엔진의 이벤트 처리는 순차적 이벤트-드리븐 방식으로 처리하고 있다. 이는 병렬로 처리 시 글로벌 자료영역에 대한 동시참조등의 문제점들이 발생하기 때문이다. 아울러 기존 시뮬레이션 플랫폼으로 다중 CPU 시스템을 사용하여도 여러 개의 CPU를 다 활용하지 못하는 결과를 초래하고 있다. 따라서 이 논문에서는 군사용 워 게임 모델의 시스템 처리능력 향상과 글로벌 자료 영역에 대한 동시참조, 대외적인 시뮬레이션 시간처리, 장애 회복(Crash Recovery)시 병행 처리된 이벤트들의 순서를 보장 할 수 있는 객체모델에 기반한 병렬 시뮬레이션 엔진으로의 전환을 제안한다 이 전환된 병렬 시뮬레이션 엔진은 다중 CPU 시스템(SMP)상에서도 병렬 실행이 가능하도록 설계하고 구현하였다.

• 한국인공지능학회지
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• 제11권2호
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• pp.1-6
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• 2023

This paper presents a comprehensive scheme for assessing the importance of multiple microgrids (MGs) network that includes distributed energy resources (DERs), renewable energy systems (RESs), and energy storage system (ESS) facilities. Due to the uncertainty of severe weather, large-scale cascading failures are inevitable in energy networks. making the assessment of the structural vulnerability of the energy network an attractive research theme. This attention has led to the identification of the importance of measuring energy nodes. In multiple MG networks, the energy nodes are regarded as one MG. This paper presents a modified PageRank algorithm to assess the importance of MGs that include multiple DERs and ESS. With the importance rank order list of the multiple MG networks, the core MG (or node) of power production and consumption can be identified. Identifying such an MG is useful in preventing cascading failures by distributing the concentration on the core node, while increasing the effective link connection of the energy flow and energy trade. This scheme can be applied to identify the most profitable MG in the energy trade market so that the deployment operation of the MG connection can be decided to increase the effectiveness of energy usages. By identifying the important MG nodes in the network, it can help improve the resilience and robustness of the power grid system against large-scale cascading failures and other unexpected events. The proposed algorithm can point out which MG node is important in the MGs power grid network and thus, it could prevent the cascading failure by distributing the important MG node's role to other MG nodes.

• 대한가정학회지
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• 제27권1호
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• pp.165-179
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• 1989

The purpose of this study is to examine the difference between wife and husband in the level of stress recognition and distress subsequent to the life events, and thus 5 kinds of study questions have been established for the achievement of this purpose. Data were obtained from 371 couples who resided in Seoul through Likert-Type questionaire, and Frequency, Percentage, Mean, T-Test, One Way ANOVA, Pearson ${\gamma}$ Correlation, Multiple Regression, Cronbach ${\alpha}$ Coefficient were calculated. As the result of this studay, the experiences subsequent to life events, the level stress recognition and distress was different from wife and husband, and it was generally shown that those are higher for wife rather than husband.

• International Journal of Costume and Fashion
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• 제14권2호
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• pp.81-96
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• 2014

The meanings of colors vary with time and space. For the most important events in a person's life, such as wedding or funeral, people use color to symbolize their identities or roles. Traditionally, the colors of dress had indicated the wearer's age, class, or marital status in Korea. However, Korea's exposure to western cultures has affected in many dimensions of its modern history. Especially, influenced by social change, the traditional dress has undergone many modifications in forms, silhouettes, materials, and color. However, women's mourning dress has been maintained as a long lasting tradition and the use of white in mourning dress has been regarded as a norm until recently, while men have worn a regular black suit with a black tie. But, the shift from white to black in mourning dress has been observed in recent mourning practices. To examine this change of color in Korean traditional mourning dress, a historical approach utilizing multiple resources, such as interview, observations of events, documents, and archival records was applied.

• 소음진동
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• 제9권6호
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• pp.1210-1217
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• 1999

This paper presents schematic process of identifying the principal cause to make the vibration problem of rotating circular saws. In the tandem pencil slat saw lines, feeding of cedar blocks is often stopped because excessive motro current is required in a saw motor. These events are called "kick-offs" in technical reports. Research on saw behavior at kick-offs is required to understand are reduce the frequency and severity of kick-offs events. This research aims at finding out the principal cause of kick-offs, and evloving design improvements for high cutting performance with fewer and less severe kick-offs. Measurements of critical speed, cutting force, cutting temeprature and dynamic displacements are carried out to observe the instability mechanism and also to obtain saw design parameters for the numerical analyses. And the numerical analyses involving FEM and multiple scale method are utilized to show the possibility of the principal cause.pal cause.

• Journal of Information Technology Applications and Management
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• 제10권1호
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• pp.35-46
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• 2003

This study focuses on the effect of Social Scaffolding of virtual community on its growth and thrift. The research model proposed in this study is that communities, which have goof social scaffolding, tend to grow and thrive. Social Scaffolding refers to those aspects of a site Purpose, Places, Profiles, leaders, Roles, Rules, Cyclic Events, integrating with the real world, and Subgroups. The data were collected from 100 virtual communities in Daum Communications and analyzed in this study. Multiple regression is used to analyze the relationship of variables. The result is following ; purpose, loaders, rules, integrating with the real world support the effects of social scaffolding of virtual community on its growth and thrift, but profiles, roles, cyclic events do not. The result of this study implies the importance of social scaffolding of virtual community for re-searches, and developers.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 2004년도 추계학술대회 및 정기총회
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• pp.345-348
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• 2004

Every bridge node participating in multiple piconets and forming a scatternet should schedule the inter-piconet traffics in an efficient manner. Frequent piconet switching due to short polling intervals for the links of a bridge node leads to considerable time slots loss caused by the guard time and power consumption for transceiving and processing. On the other hand, restrained piconet switching may result in failures of fulfilling QoS (Quality of Service) requirements for some links. Tn this paper, we present a QoS aware inter-piconet scheduling scheme minimizing the piconet switching events within guaranteed QoS requirements. According to simulation results, the proposed scheme is confirmed to have great improvement in throughput and number of switching events over the credit scheme as current inter-piconet scheduling scheme for the scatter mode.

• Industrial Engineering and Management Systems
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• 제14권2호
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• pp.196-209
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• 2015

Retail sales forecast is a special area of forecasting. Its unique characteristics call for unique data models and treatment, and unique forecasting processes. In this paper, we will address lessons learned and challenges encountered in retail sales forecast from a practical and technical perspective. In particular, starting with the data models of retail sales data, we proceed to address issues existing in estimating and processing each component in the data model. We will discuss how to estimate the multi-seasonal cycles in retail sales data, and the limitations of the existing methodologies. In addition, we will talk about the distinction between business events and forecast events, the methodologies used in event detection and event effect estimation, and the difficulties in compound event detection and effect estimation. For each of the issues and challenges, we will present our solution strategy. Some of the solution strategies can be generalized and could be helpful in solving similar forecast problems in different areas.

• 한국응급구조학회지
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• 제25권1호
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• pp.37-48
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• 2021

Purpose: The purpose of this study was to identify the degree of resilience, traumatic events, secondary traumatic stress, and calling reported by firefighters and to identify the factors affecting the resilience of firefighters. Methods: Data were collected using structured questionnaires and 200 fire officials working in D city were enrolled as the subjects. Data were analyzed using SPSS 24.0, and the analyses included descriptive statistics, independent t-test, ANOVA, Scheffé test, Pearson correlation coefficient, and multiple linear regression. Results: The difference in resilience according to general characteristics showed significant differences in health status (F=4.33, p=.014) and job satisfaction (F=6.13, p=.003). The factors affecting resilience were identified as calling (β=.25, p<.001), and the explanatory power for resilience was 19.2%. Conclusion: It is necessary to increase calling in order to increase resilience. Therefore, we suggest that professional education and programs that consider personal characteristics are needed to strengthen the calling.