• Smart Structures and Systems
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• 제14권1호
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• pp.39-54
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• 2014

Node layout optimization of structural wireless systems is investigated as a means to prolong the network lifetime without, if possible, compromising information quality of the measurement data. The trade-off between these antagonistic objectives is studied within a multi-objective layout optimization framework. A Genetic Algorithm is adopted to obtain a set of Pareto-optimal solutions from which the end user can select the final layout. The information quality of the measurement data collected from a heterogeneous WSN is quantified from the placement quality indicators of strain and acceleration sensors. The network lifetime or equivalently the network energy consumption is estimated through WSN simulation that provides realistic results by capturing the dynamics of the wireless communication protocols. A layout optimization study of a monitoring system on the Great Belt Bridge is conducted to evaluate the proposed approach. The placement quality of strain gauges and accelerometers is obtained as a ratio of the Modal Clarity Index and Mode Shape Expansion values that are computed from a Finite Element model of the monitored bridge. To estimate the energy consumption of the WSN platform in a realistic scenario, we use a discrete-event simulator with stochastic communication models. Finally, we compare the optimization results with those obtained in a previous work where the network energy consumption is obtained via deterministic communication models.

• 에너지공학
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• 제16권3호
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• pp.128-148
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• 2007

원자력 연구개발사업의 품질보증은 사업 고유의 속성을 반영하지 못하는 무분별한 품질보증요건의 선정 및 적용으로 인해 불필요한 요건이 포함되거나 필요한 요건이 배제될 가능성이 있을 뿐만 아니라, 이로 인한 자원낭비의 비경제성이 우려되고 있다. 본 연구에서는 원자력 연구개발사업의 속성을 반영하는 품질보증요건의 중요도 평가방법론을 제시하였다. 이 방법론은 기본적인 분석틀로서 QFD(Quality Function Deployment)를 활용하며, 계산과정에서 퍼지개념을 도입하여 인간 판단의 모호함에 따른 불확실성을 결과에 반영하고, 피설문자의 응답확신도를 활용함으로써 설문의 내용을 보다 유용하게 분석에 반영할 수 있다는 특징을 가지고 있다. 특정 원자력 연구개발사업에 제시된 방법론을 적용함으로써 그 실용성을, 다양한 시나리오 분석을 통해 유효성을 확인하였다. 시나리오 분석 결과에 따르면, 퍼지개념과 응답확신도를 활용함에 따라 기존의 방법론과 비교하여 품질보증요건의 중요도에 유의할만한 수준의 변화를 가져올 수 있음을 확인하였다. 또한, 사업 속성요인의 수준변화가 품질보증요건의 중요도에 직간접적으로 반영되고 있음을 확인하였다. 본 연구는 원자력 연구개발사업의 속성을 반영하는 품질보증요건 중요도 산출방법론이라는 점과 QFD의 새로운 응용분야를 개척하였다는 점에서 그 의미를 찾을 수 있다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권8호
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• pp.2140-2156
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• 2023

The Wireless Sensor Network (WSN), is constructed out of teeny-tiny sensor nodes that are very low-cost, have a low impact on the environment in terms of the amount of power they consume, and are able to successfully transmit data to the base station. The primary challenges that are presented by WSN are those that are posed by the distance between nodes, the amount of energy that is consumed, and the delay in time. The sensor node's source of power supply is a battery, and this particular battery is not capable of being recharged. In this scenario, the amount of energy that is consumed rises in direct proportion to the distance that separates the nodes. Here, we present a Hybrid Firefly Glow-Worm Swarm Optimization (HF-GSO) guided routing strategy for preserving WSNs' low power footprint. An efficient fitness function based on firefly optimization is used to select the Cluster Head (CH) in this procedure. It aids in minimising power consumption and the occurrence of dead sensor nodes. After a cluster head (CH) has been chosen, the Glow-Worm Swarm Optimization (GSO) algorithm is used to figure out the best path for sending data to the sink node. Power consumption, throughput, packet delivery ratio, and network lifetime are just some of the metrics measured and compared between the proposed method and methods that are conceptually similar to those already in use. Simulation results showed that the proposed method significantly reduced energy consumption compared to the state-of-the-art methods, while simultaneously increasing the number of functioning sensor nodes by 2.4%. Proposed method produces superior outcomes compared to alternative optimization-based methods.

• Smart Structures and Systems
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• 제26권1호
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• pp.35-47
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• 2020

This paper proposes the use of transmissibility functions combined with a machine learning algorithm, Artificial Neural Networks (ANNs), to assess damage in a truss bridge. A new approach method, which makes use of the input parameters calculated from the transmissibility function, is proposed. The network not only can predict the existence of damage, but also can classify the damage types and identity the location of the damage. Sensors are installed in the truss joints in order to measure the bridge vibration responses under train and ambient excitations. A finite element (FE) model is constructed for the bridge and updated using FE software and experimental data. Both single damage and multiple damage cases are simulated in the bridge model with different scenarios. In each scenario, the vibration responses at the considered nodes are recorded and then used to calculate the transmissibility functions. The transmissibility damage indicators are calculated and stored as ANNs inputs. The outputs of the ANNs are the damage type, location and severity. Two machine learning algorithms are used; one for classifying the type and location of damage, whereas the other for finding the severity of damage. The measurements of the Nam O bridge, a truss railway bridge in Vietnam, is used to illustrate the method. The proposed method not only can distinguish the damage type, but also it can accurately identify damage level.

• Journal of Radiation Protection and Research
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• 제48권2호
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• pp.90-99
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• 2023

Background: Quantitative risk assessments should be accompanied by uncertainty analyses of the risk models employed in the calculations. In this study, we aim to develop a computational code named SUMRAY for use in cancer risk projections from radiation exposure taking into account uncertainties. We also aim to make SUMRAY publicly available as a resource for further improvement of risk projection. Materials and Methods: SUMRAY has two versions of code written in R and Python. The risk models used in SUMRAY for all-solid-cancer mortality and incidence were those published in the Life Span Study of a cohort of the atomic bomb survivors in Hiroshima and Nagasaki. The confidence intervals associated with the evaluated risks were derived by propagating the statistical uncertainties in the risk model parameter estimates by the Monte Carlo method. Results and Discussion: SUMRAY was used to calculate the lifetime or time-integrated attributable risks of cancer under an exposure scenario (baseline rates, dose[s], age[s] at exposure, age at the end of follow-up, sex) specified by the user. The results were compared with those calculated using another well-known web-based tool, Radiation Risk Assessment Tool (RadRAT; National Institutes of Health), and showed a reasonable agreement within the estimated confidential interval. Compared with RadRAT, SUMRAY can be used for a wide range of applications, as it allows the risk projection with arbitrarily specified risk models and/or population reference data. Conclusion: The reliabilities of SUMRAY with the present risk-model parameters and their variance-covariance matrices were verified by comparing them with those of the other codes. The SUMRAY code is distributed to the public as an open-source code under the Massachusetts Institute of Technology license.

• Spatial Information Research
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• 제17권4호
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• pp.431-443
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• 2009

최근 탁수문제는 댐과 저수지관리 업무에서 중요한 이슈중의 하나가 되고 있으며, 고탁수를 유발하는 주요원인은 강우강도 에너지에 의한 유사량이다. 기존의 연구들은 다양한 작물형태를 고려하지 않아 정확한 토양 침식 및 유사량을 계산할 수 없었다. 본 연구에서는 IKONOS 위성영상으로부터 추출한 인삼밭 레이어를 이용하여 토양침식량과 유사량의 저감효과를 분석하였으며, 인삼밭의 면적과 점유비율은 각각 $0.290km^2$와 0.94%로 나타났다. GIS 기반 RUSLE 모델을 이용하여 인삼밭을 고려한 토양침식량의 저감효과를 분석한 결과는 0.9%로 낮게 나타났으며, 이는 인삼밭의 면적이 다른 농경지에 비해 상대적으로 작기 때문으로 해석된다. 미래의 토지이용변화를 반영하기 위해, 본 연구에서는 논, 밭, 과수원 그리고 기타 재배지들이 인삼밭 지역으로 전환된다는 시나리오를 고려하여 토양침식과 유사량의 저감효과를 평가하였다. 시나리오에 따른 인삼밭의 저감효과를 분석한 결과, 밭지역을 인삼밭으로 전환한 시나리오 (1)과 모든 농경지를 인삼밭으로 전환한 (4)가 인삼밭을 고려하지 않은 기존의 연구와 비교할 때 31.3% 및 34.8% 더 높은 저감효과를 나타내었다. 본 연구에서 제시한 방법론은 고탁수와 관련된 저수지관리를 지원하기 위한 매우 효과적인 도구가 될 수 있을 것이다.

• 한국건설관리학회논문집
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• 제10권5호
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• pp.135-147
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• 2009

최근 해외건설 시장은 진출국 투자 현지화 요구 등 기업의 장기적 투자를 필요로 하는 프로젝트가 증가하는 경향을 보이고 있어, 건설기업 입장에서 개별 프로젝트 중심의 한시적 의사결정보다는 중 장기적인 관점에서 투자를 고려해야하는 복합적인 진출의사결정 상황에 대한 판단을 요구하고 있다. 따라서 중 장기적 관점에서 해당 진출국 시장의 리스크를 분석하고 해당 진출국의 시장성 진출여부 등을 합리적으로 평가할 수 있는 체계가 기업 경쟁력의 핵심이 된다고 할 수 있다. 하지만 이러한 기업의 시장진출 의사결정과 관련하여 전통적으로 재무적 가치평가를 위해 활용되어 온 현금흐름할인법은 시장의 변동성이나 불확실성을 고려하는 데에 한계를 가지고 있다. 따라서 본 연구에서는 실물옵션 분석에 기초하여, 해외 건설시장진출 안의 평가에 있어 시장의 불확실성을 반영할 수 있는 모델을 개발하고자 하였다. 제안된 시장진출 의사결정모델은 실물옵션 분석을 통해 진출 여부 국가 유형 등과 같은 주요 의사결정 항목들을 통합적으로 고려하여 진출 안을 평가할 수 있으며, 시나리오 분석을 통해 제안된 시장진출의사결정 모델의 분석과정을 제시함으로써 활용성을 검증하였다. 본 연구의 시장진출 의사결정모델의 활용을 통해 해외 건설시장 진출을 계획하는 건설기업의 합리적 의사결정을 지원할 수 있을 것으로 기대된다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.2292-2296
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• 2010

2020 Korea GHG reduction goal is decreasing 4% compared with that of 2005. Effective counterplan of GHG redection goal needs to set for inductrial allocation and various reduction GHG technologies and policies for transportation have been developed. Modal shifr is one of these main policy and it focused on shifting as much freight as economically meaningful under current market conditions. It improves energy efficiency, consequently reduces GHG effect. This study is proposed as a preliminary studay of analyzing Modal shift effect. modal shift of car travelers to train is concerned in Seoul-Busan section, This study is based on a scenario which can maximize passenger occupancy rate to get the GHG reduction effect and the effect of modal shift of car to train is identified. According to this result, we can get GHG reduction effect through dealing with maximizing passenger occupancy rate on train. Therefore, in order to enhance this modal shift effect, train using rate need to increased and also improvement of policies and cost system are need to be considered to promote increasing use of train.

• The Journal of Asian Finance, Economics and Business
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• 제7권11호
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• pp.927-937
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• 2020

Global warming awareness through energy conservation is growing due to the regulatory policies issued by governments and voluntary organization that established carbon emission limits. Transportation is one of the major contributors to carbon emissions. Bike will be simultaneously saving money, getting fit and helping to reduce global warming. Web design has been identified as a key factor for the acceptance and success of the websites and electronic commerce. The purpose of this research is to investigate the effective implementation of the proposed Analytic Hierarchy Process (AHP) technique on a bike case study whose company (Bike Company) is involved in web design for a critical component in the demonstration. Survey research used a variety of data collection methods, with the most common being questionnaires and interviews of some exporters. The research results reveal that the top five key success factors are Good reputation, Transaction security, Ease of use, Promotion, and Diversified choices, which provide the guidelines and directions for decision-makers to design effective websites in the current competitive business scenario. The major findings of this study are suggesting that Internet marketing channels are securing the company's relevance, together with paving the way for methods to increase web traffic.

• 천문학회보
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• 제37권2호
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• pp.140.2-140.2
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• 2012

The silicate carbon star IRAS 09425-6040 shows very conspicuous crystalline silicate dust features and excessive emission at far infrared. To investigate properties of dusty envelopes around the object, we use radiative transfer models for axisymmetric and sphericallly symmetric dust distributions. We perform model calculations for various possible combinations of dust shells and disks with various dust species. We compare the model results with the observed spectral energy distributions (SEDs) including the IRAS, ISO, AKARI, MSX and 2MASS data. We find that a model with multiple disks of amorphous and crystalline silicate and multiple spherical shells of carbon dust can reproduce the observed SED fairly well. This supports the scenario for the origin of silicate carbon stars that oxygen-rich material was shed by mass loss when the primary star was an M giant and the O-rich material is stored in a circumbinary disk. Highly (about 75 %) crystallized forsterite dust in the disk can reproduce the conspicuous crystalline features of the ISO observational data. This object looks to have a detached silicate and H2O ice shell with a much higher mass-loss rate. It could be a remnant of the chemical transition phase. The last phase of stellar winds of O-rich materials looks to be a superwind.