• Structural Engineering and Mechanics
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• 제37권1호
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• pp.17-37
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• 2011

This paper presents a new Internet-based computational framework for the realistic simulation of multi-scale response of structural systems. Two levels of parallel processing are involved in this frame work: multiple local distributed computing environments connected by the Internet to form a cluster-to-cluster distributed computing environment. To utilize such a computing environment for a realistic simulation, the simulation task of a structural system has been separated into a simulation of a simplified global model in association with several detailed component models using various scales. These related multi-scale simulation tasks are distributed amongst clusters and connected to form a multi-level hierarchy. The Internet is used to coordinate geographically distributed simulation tasks. This paper also presents the development of a software framework that can support the multi-level hierarchical simulation approach, in a cluster-to-cluster distributed computing environment. The architectural design of the program also allows the integration of several multi-scale models to be clients and servers under a single platform. Such integration can combine geographically distributed computing resources to produce realistic simulations of structural systems.

• International Journal of Concrete Structures and Materials
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• 제10권1호
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• pp.1-13
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• 2016

The progressive collapse analysis of reinforced concrete (RC) moment-frame buildings under extreme loads is discussed from the perspective of modeling issues. A threat-independent approach or the alternate path method forms the basis of the simulations wherein the extreme event is modeled via column removal scenarios. Using a prototype RC frame building, issues and considerations in constitutive modeling of materials, options in modeling the structural elements and specification of gravity loads are discussed with the goal of achieving consistent models that can be used in collapse scenarios involving successive loss of load-bearing columns at the lowest level of the building. The role of the floor slabs in mobilizing catenary action and influencing the progressive collapse response is also highlighted. Finally, an energy-based approach for identifying the proximity to collapse of regular multi-story buildings is proposed.

• 한국생산제조학회지
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• 제22권3호
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• pp.364-371
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• 2013

Because of the increases in international oil prices and the level of global warming, the automotive industry has much interest in developing green cars with high fuel efficiencies. In addition, researchers in Korea are actively responding to high oil prices and $CO_2$ emission regulations in many ways. One example is, the multi-mode hybrid system, which is being studied to improve its performance. Because a multi-mode hybrid system is able to overcome the weaknesses of a system that uses simple planetary gears, excellent fuel efficiency and driving performances are the key features of the system. This paper analyzes the driving performance of the power-train system of GM-2MT70, which consists of one engine, two electric motors, one simple planetary gear, one double planetary gear, two clutches, and two brakes. The driving performance of the system's steady state is analyzed using performance modeling. The dynamic performance is analyzed using Matlab Simulink.

• 한국경영정보학회:학술대회논문집
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• 한국경영정보학회 2008년도 춘계학술대회
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• pp.52-63
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• 2008

Virtuality is a product of the information age, and as it plays a larger role in the activities of individuals, groups and organizations, the issue of how human behavior varies between virtual and physical space has become one of the most important questions facing the management environment of today. The purpose of this article is to examine how virtuality shapes individuals' social relationships within and outside their work groups. We developed a conceptual framework that explores the links between virtuality and social network based on computer-mediated communication theory and social network theory. Using data from 172 individuals of 42 project teams in 5 global business consulting firms, we tested cross-level hypotheses. The results of hierarchical linear modeling (HLM) indicate that virtuality significantly influences individual's internal tie strength as well as external bridging ties. The results also show the effects of virtual process via CMC vary along with the virtual context.

• 대한토목학회논문집
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• 제37권5호
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• pp.905-914
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• 2017

본 연구는 공동주택의 부산광역시 554개 국가기초구역과 1832세대의 개별세대주택을 대상으로, 기존의 건축 단지특성과 보행친화특성이 공동주택가격에 끼치는 영향에 대하여 분석하였다. 개별세대주택과 국가기초구역의 다양한 공간구역 특성을 바탕으로 보다 정확한 다층적인 분석을 위해, multi-level models 을 이용하였다. 분석 결과, Level-2의 국가기초구역별 보행친화특성은 전체분산의 약 77%를 잠재적으로 설명하였으며, 그 중 범죄안전특성에서 가장 많은 영향을 미치는 것으로 나타났다. 이것은 이전연구에서 많이 다뤄졌던 개별세대 공동주택별 분석보다, 한국에서 새롭게 제정된 국가기초구역에 따른 공간별 분석이 더욱 전체적으로 의미가 있다는 것을 의미한다. 이 연구결과는 요동치는 한국의 주택가격을 건강하고 안정적으로 유지할 수 있는 보행친화적인 도시설계 및 주택정책에 기여할 수 있을 것이라 생각한다.

• 전기학회논문지
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• 제64권8호
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• pp.1193-1201
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• 2015

This paper presents a study of circulating current of modular multi-level converter (MMC) based a high voltage direct current (HVDC) system under unbalanced grid conditions. Due to the connection of a dependent DC source in each phase, the MMC system inherently generates the power ripple of double-line-frequency components in the AC-side and as a result, the additional sinusoidal current named circulating current flows through the each arm. Reliability improvement of HVDC system under an unbalanced grid condition is one of the important criteria. Generally, the modeling of the circulating current is based on the power relation between DC-side and AC-side. However, the method is not perfectly matched in the MMC system due to the difference of the structural characteristic. In this paper, improved modeling method of circulating current is proposed, which is based on the inner arm power. The proposed method is verified by several simulations to have good agreement of the circulating current components.

• 한국가족관계학회지
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• 제23권1호
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• pp.75-95
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• 2018

Objectives: This study aims to examine a school adjustment trajectory of adolescents from continued single parent families and its associated factors by comparing it to that of adolescents of two-parent families. Methods: We selected 4th grade students from Korean Youth & Youth Panel Survey (KCYPS). Using a multi-level growth modeling, we followed the trajectory of school adjustment until 9th grade and the effects of family income, parenting styles, and academic motivations of adolescents on the intercepts and the slopes. Results: Adolescents' school adjustment were decreased from 4th grade to 7th grade and then increased from 7th to 9th grade. The adolescents of continued single parent families showed a lower school adjustment than those of two parent families and this trend remained constant during the period. The effects of family income, parenting style, and academic motivation were confirmed to explain the gap between the adolescents of single parent and two parent families. Conclusions: The results imply that an earlier intervention is necessary to reduce the gap. We need to offer income support and decent quality of work for single parent family to reduce the economic hardship and also provide parental education that is designed to enhance academic expectations and motivations.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.833-835
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• 2002

In this paper, we propose multi-resolutional representation of B-rep solid models using the selective Boolean operations on non-manifold geometric models. Since the union and subtraction operations of the selective Boolean operations are commutative, the integrity of the model is guaranteed for reordering design features. A multi-resolution representation is established using a non-manifold merged set model and a feature modeling tree reordered according to some criterion of level of detail (LOD). Then, a solid model for a specified LOD can be extracted from this multi-resolution model using the selective Boolean operations.

• 산업경영시스템학회지
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• 제41권1호
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• pp.102-109
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• 2018

This paper seeks to present a multi-control method that can contribute to effective control of the production line with multiple bottleneck processes. The multi-control method is the production system that complements shortcomings of CONWIP and DBR, and it is designed to determine the raw material input according to the WIP level of two bottleneck processes and WIP level of total process. The effectiveness of the production system developed by applying the multi-control method was verified by the following three procedures. Raw material input conditions of the multi-control method are as follows. First, raw materials are go into the production line when the number of the total process WIP is lower than established number of WIP in total process and first process is idle. Second, raw materials are introduced when the number of WIP of two bottleneck processes is lower than the established number of WIP of each bottleneck process. Third, raw materials are introduced when the first process and in front of bottleneck process are idle even if the number of WIP in the total process is less than established number of WIP of the total process. The production line with two bottleneck processes was selected as the condition for production environment, and the production process modeling of CONWIP, DBR and multi-control production method was defined according to the production condition. And the optimum limited WIP level suitable for each system was obtained by applying a genetic algorithm to determine the total limited number of WIP of CONWIP, the limited number of WIP of DBR bottleneck process, the number of WIP in the total process of multi-control method and the limited number of WIP of bottleneck process. The limited number of WIP of CONWIP, DBR and multi-control method obtained by the genetic algorithm were applied to ARENA modeling, which is simulation software, and a simulation was conducted to derive result values on the basis of three criteria such as production volume, lead time and number of goods in-progress.

• 한국농공학회논문집
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• 제58권4호
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• pp.21-35
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• 2016

This study is to evaluate the applicability of SWAT (Soil and Water Assessment Tool) model for multi-purpose dams and multi-function weirs operation in Namhan river basin ($12,577km^2$) of South Korea. The SWAT was calibrated (2005 ~ 2009) and validated (2010 ~ 2014) considering of 4 multi-purpose dams and 3 multi-function weirs using daily observed dam inflow and storage, evapotranspiration, soil moisture, and groundwater level data. Firstly, the dam inflow was calibrated by the five steps; (step 1) the physical rate between total runoff and evapotranspiration was controlled by ESCO, (step 2) the peak runoff was calibrated by CN, OV_N, and CH_N, (step 3) the baseflow was calibrated by GW_DELAY, (step 4) the recession curve of baseflow was calibrated by ALPHA_BF, (step 5) the flux between lateral flow and return flow was controlled by SOL_AWC and SOL_K, and (step 6) the flux between reevaporation and return flow was controlled by REVAPMN and GW_REVAP. Secondly, for the storage water level calibration, the SWAT emergency and principle spillway were applied for water level from design flood level to restricted water level for dam and from maximum to management water level for weir respectively. Finally, the parameters for evapotranspiration (ESCO), soil water (SOL_AWC) and groundwater level fluctuation (GWQMN, ALPHA_BF) were repeatedly adjusted by trial error method. For the dam inflow, the determination coefficient $R^2$ was above 0.80. The average Nash-Sutcliffe efficiency (NSE) was from 0.59 to 0.88 and the RMSE was from 3.3 mm/day to 8.6 mm/day respectively. For the water balance performance, the PBIAS was between 9.4 and 21.4 %. For the dam storage volume, the $R^2$ was above 0.63 and the PBIAS was between 6.3 and 13.5 % respectively. The average $R^2$ for evapotranspiration and soil moisture at CM (Cheongmicheon) site was 0.72 and 0.78, and the average $R^2$ for groundwater level was 0.59 and 0.60 at 2 YP (Yangpyeong) sites.