• 한국시뮬레이션학회논문지
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• 제28권2호
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• pp.149-158
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• 2019

본 연구에서는 전장이나 재난 환경과 같은 인간이 투입되기 힘든 환경에서 인간을 대신하여 부상자 구조 및 위험물 처리 목적으로 개발된 구조로봇의 효율적 개발을 위한 통합 M&S 프레임워크를 소개한다. 개발된 통합 M&S 프레임워크는 계층화, 모듈화된 통합운동제어 소프트웨어의 구조에 기인하여 통합운동제어 소프트웨어 구조는 동일하게 이용하며 로봇 플랫폼을 시뮬레이션 프로그램으로 대체하여 SILS(Software-in-the-Loop Simulation) 개념의 M&S를 가능하게 하였다. 이를 활용하여 로봇 설계 및 로봇 제어 기술의 성능 검증 등의 개발 전 과정을 효율적으로 수행하였고, 비정형 환경에서의 원격 운용성 향상도 가져왔다. 통합 M&S 프레임워크의 적극적인 활용을 통해 구조로봇의 성공적인 개발 및 성능 확인을 완료하였으며, 구조로봇의 주요 기술 중 하나인 가변형상 제어를 통한 주행 안정화 기술 개발 과정에 적용된 통합 M&S 프레임워크의 사례를 통해 효용성을 확인한다.

• 한국항공우주학회지
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• 제47권6호
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• pp.397-404
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• 2019

항공우주시스템에서 절단/분리 시스템에 널리 사용되는 선상성형장약은 복합화약 충전량의 불균일로 인해 과량의 복합화약을 충전해야 하며 제작 공정의 특성상 라이너 및 복합화약 형상을 자유자재로 조절하기 어렵다는 단점을 가지고 있다. 이를 개선하기 위하여 라이너를 단독으로 제작하여 균일한 복합화약량을 충전할 수 있는 정밀선상성형장약에 대한 연구 개발이 진행되고 있다. 본 연구에서는 정밀선상성형장약이 적정 복합화약량을 갖도록 설계하고 설계된 정밀선상성형장약의 최적 침투 관통 성능을 확인하기 위하여 라이너로부터 표적까지의 거리에 단차를 두어 이격거리에 따른 침투 관통 성능시험을 수행하였다. 정밀선상성형장약의 침투 관통 성능시험 결과를 바탕으로 AUTODYN 기반의 수치 해석 환경을 구축하였다. 수치해석 및 시험 결과의 비교 분석을 통해 정밀선상성형장약의 침투 관통 메커니즘과 특성을 분석하였다.

• 센서학회지
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• 제31권5호
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• pp.337-342
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• 2022

Hydrogen (H₂) gas is widely preferred for use as a renewable energy source owing to its characteristics such as environmental friendliness and a high energy density. However, H₂ can easily reverse or explode due to minor external factors. Therefore, H₂ gas monitoring is crucial, especially when the H₂ concentration is close to the lower explosive limit. In this study, metal oxide materials and their p-n heterojunctions were synthesized by a hydrothermal-assisted dip-coating method. The synthesized thin films were used as sensing materials for H₂ gas. When the H₂ concentration was varied, all metal oxide materials exhibited different gas sensitivities. The performance of the metal oxide gas sensor was analyzed to identify parameters that could improve the performance, such as the choice of the metal oxide material, effect of the p-n heterojunctions, and operating temperature conditions of the gas sensor. The experimental results demonstrated that a CuO/ZnO gas sensor with a p-n heterojunction exhibited a high sensitivity and fast response time (134.9% and 8 s, respectively) to 5% H₂ gas at an operating temperature of 300℃.

• 한국프랜차이즈경영연구
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• 제7권2호
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• pp.5-14
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• 2016

Purpose - Competitive industry structure and recent economic depression challenge a survival of Korean small- and medium-sized food franchising companies (SMFCs), albeit the explosive growth of the Korean food service industry for last few decades. Against this backdrop, it examines how these SMFCs overcome liabilities of smallness and resource scarcity to strengthen competitive advantage in the market. To tackle this, in this article we focus on corporate entrepreneurship and human resources as a knowledge-based asset for these SMFCs. Furthermore, the ratio of employee turnover is high in SMFCs. We view that such brain-drain may result in poor performance of the Korean SMFCs. As such, we pay attention to the role of organizational commitment to an organization as a solution for enhancing individual-level employees' loyalty toward their organization. Research design, data, and methodology - Our research question is to what extent corporate entrepreneurship (i.e., innovative organizational culture, organizational autonomy, and administrative innovation) affects an individual-level attitude toward the organization and, in turn, employee creativity and satisfaction in the Korean SMFCs context. We collected data from employees in SMFCs for three months. A total of 126 valid questionnaires were collected, and analyzed the data using partial least squares path modeling. Results - The reliable and valid measurement model feed into testing the structural model. Our findings suggest that innovative organizational culture and organizational autonomy positively affect employee commitment. Particularly, organizational autonomy has a greater effect than innovative culture on employee commitment. However, the relationship between administrative innovation and employee commitment is not significant. We also find that employee commitment positively affects both employee creativity and satisfaction. Conclusions - Our contribution to the existing franchising business and management literature is twofold. First, the conceptual model includes three antecedents in the organizational entrepreneurship dimension to organizational commitment. Second, we conceptualize organizational commitment as employee commitment, and validate its impact on employee creativity and job satisfaction at an individual performance level. Overall, this article suggests that it is critically important for the Korean SMFCs to develop corporate entrepreneurship in order to facilitate employees' positive attitudes toward their organizations.

• Structural Engineering and Mechanics
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• 제87권4호
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• pp.297-304
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• 2023

Targeted introduction of explosion-resisting and energy-absorbing materials and optimization of explosion-resisting composite structural styles in underground engineering are the most important measures for modern engineering protection. They could also improve the survivability of underground engineering in wartime. In order to test explosion-resisting and energy-absorbing effects of high-performance equal-sized-aggregate (HPESA) concrete, the explosive loading tests were conducted on HPESA concrete composite plates by field simple explosion craters. Time-history curves of the explosion pressure at the interfaces were obtained under six conditions with different explosion ranges and different thicknesses of the HPESA concrete plate. Test results show that under the same explosion range, composite plate structures with different thicknesses of the HPESA concrete plate differ significantly in terms of the wave-absorbing ability. Under the three thicknesses in the tests, the wave-absorbing ability is enhanced with the growing thickness and the maximum pressure attenuation index reaches 83.4%. The energy attenuation coefficient of the HPESA concrete plate under different conditions was regressively fitted. The natural logarithm relations between the interlayer plate thickness and the energy attenuation coefficient under the two explosion ranges were attained.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권3호
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• pp.838-856
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• 2014

Enhanced network speed and the appearance of various applications have recently resulted in the rapid increase of Internet users and the explosive growth of network traffic. Under this circumstance, Internet users are eager to receive reliable and Quality of Service (QoS)-guaranteed services. To provide reliable network services, network managers need to perform control measures involving dropping or blocking each traffic type. To manage a traffic type, it is necessary to rapidly measure and correctly analyze Internet traffic as well as classify network traffic according to applications. Such traffic classification result provides basic information for ensuring service-specific QoS. Several traffic classification methodologies have been introduced; however, there has been no favorable method in achieving optimal performance in terms of accuracy, completeness, and applicability in a real network environment. In this paper, we propose a method to classify Internet traffic as the first step to provide stable network services. We integrate the existing methodologies to compensate their weaknesses and to improve the overall accuracy and completeness of the classification. We prioritize the existing methodologies, which complement each other, in our integrated classification system.

• 한국안전학회지
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• 제28권6호
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• pp.6-10
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• 2013

A numerical reproducibility of the backdraft phenomena in a compartment was investigated. The prediction performance of two combustion models, the mixture fraction and finite chemistry models, were tested for the backdraft phenomena using the FDS code developed by the NIST. The mixture fraction model could not predict the flame propagation in a fuel-air mixture as well as the backdraft phenomena. However, the finite chemistry model predicted the flame propagation in the mixture inside a tube reasonably. In addition, the finite chemistry model predicted well the backdraft phenomena in a compartment qualitatively. The flame propagation inside the compartment, fuel and oxygen distribution and explosive fire ball behavior were well simulated with the finite chemistry model. It showed that the FDS adopted with the finite chemistry model can be an effective simulation tool for the investigation of backdraft in a compartment.

• 한국ITS학회 논문지
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• 제14권5호
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• pp.44-51
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• 2015

모바일 데이터의 급속한 성장으로 인해 대용량의 백홀 구축 요구가 대두되었으며, 비용 효율 관점에서 쉽게 적은 비용을 가지고 백홀을 신속하게 구축할 수 있는 기술은 점대점 마이크로웨이브이다. 점대점 마이크로웨이브 링크에서의 공간 다이버시티 방법은, 두 개의 수신 안테나에서 오는 신호를 결합시킴으로 페이딩효과를 상쇄시켜 성능을 향상시키는 것이다. 기존의 신호 결합방법으로는 최대 전력 방법과 최소 왜곡 방법이 제안되었다. 하지만, 선택적 페이딩 채널에서 두 기법 모두가 알고리즘의 강건성 관점에서 성능저하가 보고되었다. 그래서, 본 논문에서 현실적 관점에서 효율적이며 더 성능이 향상된 신호결합 기법을 제안하고, 시뮬레이션을 통해 제안된 방법이 신호의 스펙트럼 관점에서 상당한 성능의 향상이 있음을 보인다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권3호
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• pp.872-885
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• 2015

The rapid increase of smart mobile devices and mobile applications has led to explosive growth of data traffic in cellular network. Offloading data traffic becomes one of the most urgent technical problems. Recent work has proposed to exploit opportunistic communications to offload cellular traffic for mobile data dissemination services, especially for accepting large delayed data. The basic idea is to deliver the data to only part of subscribers (called target-nodes) via the cellular network, and allow target-nodes to disseminate the data through opportunistic communications. Human mobility shows temporal and spatial characteristics and predictability, which can be used as effective guidance efficient opportunistic communication. Therefore, based on the regularity of human mobility we propose NodeRank algorithm which uses the encounter characteristics between nodes to choose target nodes. Different from the existing work which only using encounter frequency, NodeRank algorithm combined the contact time and inter-contact time meanwhile to ensure integrity and availability of message delivery. The simulation results based on real-world mobility traces show the performance advantages of NodeRank in offloading efficiency and network redundant copies.

• 복합신소재구조학회 논문집
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• 제6권1호
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• pp.38-44
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• 2015

In this paper, a finite element dynamic simulation study was performed to gain an insight about the blast wall test details for the offshore structures. The simulation was verified using qualitative and quantitative comparisons for different materials. Based on in-depth examination of blast simulation recordings, dynamic behaviors occurred in the blast wall against the explosion are determined. Subsequent simulation results present that the blast wall made of high energy absorbing high manganese steel performs much better in the shock absorption. In this paper, the existing finite element shock analysis using the LS-DYNA program is further extended to study the blast wave response of the corrugated blast wall made of the high manganese steel considering strain rate effects. The numerical results for various parameters are verified by comparing different material models with dynamic effects occurred in the blast wall from the explosive simulation.