• 대한교통학회지
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• 제34권4호
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• pp.341-353
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• 2016

고속도로는 중 장거리 차량 통행을 담당하고 있으며, 공공기관들의 지방이전 등으로 인해 직장과 거주지 간의 거리가 멀어짐에 따라 운전자들의 통행거리는 증가 추세를 보이고 있다. 이러한 이유로 고속도로에서는 피로나 졸음으로 인한 운전자요인 사고의 비중이 매우 높다. 하지만 기존의 사고예측 연구에서는 주로 도로요인, 환경요인, 차량요인 등 외적인 조건만을 고려하였을 뿐 도로구간별 운전자의 통행행태를 고려하지 못하였다. 본 연구에서는 대용량 내비게이션 경로자료를 활용하여 통행행태기반의 사고지표(운전피로도지표)를 제안하고, 교통사고와의 관계를 살펴보았다. 분석결과 개발된 지표와 교통사고와는 높은 상관성을 보이는 것으로 나타났으며, 이를 통해 시설물 위주에서 통행행태기반으로 교통사고 예측연구의 패러다임 변화가 필요함을 확인할 수 있었다. 본 연구에서 제안한 지표는 다양한 분야에서 활용이 가능할 것이다. 교통사고(졸음, 부주의운전 등)를 사전에 방지하기 위한 정보제공, 고속도로 안전진단 핵심요소기술로의 활용, 휴게소 및 졸음쉼터 입지 우선순위 선정 시, 피로한 구간에 대하여 운전자에게 주의환기를 위한 방법(노면요철, 그루빙 등)을 적용해야하는 구간 선정 시 활용이 가능할 것이다.

• 한국환경보건학회지
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• 제42권5호
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• pp.333-344
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• 2016

Objectives: This study aimed to examine risk-accepting personality traits and associated factors among farmers. Methods: Data were collected from farmers aged over 40 living in Goryeong, North Gyeongsang-do Province, Korea. Study participants were enrolled in the Korean Rural Cohort study from 2011 to 2014. Surveys for the risk perception of farming were made through face-to-face interviews. Chi-square tests and logistic regression analysis were conducted adjusting for gender, age, marital status, and education. Results: Several factors such as gender, age, marital status, age first worked as a farmer, duration of farming, and history of pesticide poisoning were associated with risk-accepting personality traits among farmers. Farmers with risk-accepting personalities tend to be older, less educated, and have self-employed health insurance. Farmers who started farming after the age of 50 are likely to be risk averse compared to farmers who started farming before the age of 20 (OR=0.41, 95% CI; 0.21, 0.82). Frequent spraying of pesticides was marginally associated with higher risk acceptance among female farmers (OR=1.61, 95% CI: 0.99, 2.64). Male farmers who had experienced pesticide poisoning in their lifetime showed higher odds of risk-accepting personality traits (OR=2.20, 95% CI: 1.03, 4.72) Conclusion: Risk-acceptors were more likely to spray pesticides frequently and to experience more pesticide poisoning compared to risk-averse individuals. This result suggests that farming hazards are to some degree driven by risk-accepting personality traits. Further investigation of how risk-accepting behaviors influence farming practices and pesticide poisoning is needed.

• 한국통신학회논문지
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• 제40권4호
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• pp.678-691
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• 2015

최근 정보통신 생태계는 스마트 기기의 대중화와 대용량 데이터 스트리밍을 필요로 하는 다양한 인터넷 서비스들의 출현과 함께 인터넷 및 모바일 데이터 트래픽이 급속도로 증가하게 되었다. 이에 따라 원활한 인터넷 접속문제, 네트워크의 혼잡 및 정체, 그리고 통신사업자들의 지속적인 네트워크 투자 비용증대 등 다양한 문제들이 초래되었다. 이렇게 데이터 중심의 패러다임으로 변화된 통신 생태계 속에서 초기 상호접속체제들은 사업자들 간 균형 있는 혜택과 공정한 분배 그리고 차세대 네트워크 구축을 위한 경제적 유인을 형성할 수 없다는 측면에서 논란이 가중되고 있다. 따라서 더욱 복잡해진 All-IP 네트워크 환경에 부합할 수 있는 진화된 인터넷 상호접속체제의 도입이 필요한 상황이다. 이에 본 연구에서는 국내 인터넷 상호접속제도의 핵심이슈를 발굴하고 인터넷 초기에서 현재까지의 인터넷 상호접속체제를 전반적으로 분석한 후, 실증연구를 통하여 트래픽 최적화, 비용 최적화, 네트워크 투자 최적화의 세 가지 측면에 부합될 수 있는 인터넷 상호접속체제를 제시하고자 한다.

• 대기
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• 제26권1호
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• pp.35-45
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• 2016

Initialization of the global seasonal forecast system is as much important as the quality of the embedded climate model for the climate prediction in sub-seasonal time scale. Recent studies have emphasized the important role of soil moisture initialization, suggesting a significant increase in the prediction skill particularly in the mid-latitude land area where the influence of sea surface temperature in the tropics is less crucial and the potential predictability is supplemented by land-atmosphere interaction. This study developed a new soil moisture initialization method applicable to the KMA operational seasonal forecasting system. The method includes first the long-term integration of the offline land surface model driven by observed atmospheric forcing and precipitation. This soil moisture reanalysis is given for the initial state in the ensemble seasonal forecasts through a simple anomaly initialization technique to avoid the simulation drift caused by the systematic model bias. To evaluate the impact of the soil moisture initialization, two sets of long-term, 10-member ensemble experiment runs have been conducted for 1996~2009. As a result, the soil moisture initialization improves the prediction skill of surface air temperature significantly at the zero to one month forecast lead (up to ~60 days forecast lead), although the skill increase in precipitation is less significant. This study suggests that improvements of the prediction in the sub-seasonal timescale require the improvement in the quality of initial data as well as the adequate treatment of the model systematic bias.

• 한국수산과학회지
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• 제35권4호
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• pp.356-365
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• 2002

One of the most important factors that cause eutrophication is nutrient materials containing nitrogen and phosphorus which stem from excreation of terrestial sources and release from sediment. Therefore, to improve water quality, the reduction of these nutrients loads should be indispensible. At this study, the three-dimensional numerical hydrodynamic and ecosystem model, which was developed by Institute for Resources and Environment of Japan, were applied to analyze the processes affecting the eutrophication. The residual currents, which were obtained by integrating the simulated tidal currents over 1 tidal cycle, showed the presence of a typical counterclockwise eddies between Gyewha and Garyuk island. Density driven currents were generated westward at surface and eastward at the bottom in Saemankeum area where the fresh waters are flowing into, The ecosystem model was calibrated with the data surveyed in the field of the study area in annual average. The simulated results were fairly good coincided with the observed values within relative error of $30\%$. The simulations of DIN and DIP concentrations were performed using ecosystem model under the conditions of $40\~100\%$ pollution load reductions from pollution sources. In study area, concentration of DIN and DIP were reduced to $59\%$ and $28\%$ in case of the $80\%$ reduction of the input loads from fresh water respectively. But pollution loads from sediment had hardly affected DIN and DIP concentration, The $95\%$ input load abatement is necessary to meet the DIN and DIP concentration of second grade of ocean water quality criteria.

• International Journal of Control, Automation, and Systems
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• 제4권3호
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• pp.325-332
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• 2006

The dynamic responses of human standing postural control were investigated when subjects were exposed to long-term horizontal vibration. It was hypothesized that the motion of standing posture complexity mainly occurs in the mid-sagittal plane. The motor-driven support platform was designed as a source of vibration. The AC Servo-controlled motors produced anterior/posterior (AP) motion. The platform acceleration and the trunk angular velocity were used as the input and the output of the system, respectively. A method was proposed to identify the complexity of the standing posture dynamics. That is, during AP platform motion, the subject's knee, hip and neck were tightly constrained by fixing assembly, so the lower extremity, trunk and head of the subject's body were individually immovable. Through this method, it was assumed that the ankle joint rotation mainly contributed to maintaining their body balance. Four subjects took part in this study. During the experiment, the random vibration was generated at a magnitude of $0.44m/s^2$, and the duration of each trial was 40 seconds. Measured data were estimated by the coherence function and the frequency response function for analyzing the dynamic behavior of standing control over a frequency range from 0.2 to 3 Hz. Significant coherence values were found above 0.5 Hz. The estimation of frequency response function revealed the dominant resonance frequencies between 0.60 Hz and 0.68 Hz. On the basis of our results illustrated here, the linear model of standing postural control was further concluded.

• 한국기계가공학회지
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• 제12권2호
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• pp.27-33
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• 2013

In this study we analyzed the on-road driving performance of two parallel-type diesel-hybrid buses which have been driven in Daegu metropolitan area. A real-time on-board data logger was facilitated to measure the vehicle information such as vehicle speed, idle stop, state of charge of battery, and engine operating conditions. These diesel-hybrid buses ran as a commuter at Daegu Exco area and Dalsung industrial complex. The driving pattern in Exco area comprised more frequent idle stop and relatively lower speed than at Dalsung area, where comprised no idle stop. Due to those different driving patterns, the fuel economy at Dalsung showed $3.7\;km/{\ell}$, which is about 8% higher than that of Exco. The main causes of this come from the higher portion of regenerative braking and higher speed which moves to the operating points of diesel engine with a lower fuel consumption.

• 농촌계획
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• 제22권2호
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• pp.31-43
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• 2016

In existing method, research for landscape resource is driven by professional (or with the participation of local people at Tokenism level), and usually hinder local residents from reflecting their appreciations on the landscape resources in their own ways and eventually ends up with indistinguishable landscape planning. To avoid this, a profound understanding of what landscape they experience in their daily life and how they perceive it should be empirically analysed carefully. The purpose of this study is to apply walking behavior as a method to examine local residents' subjective perceptions and consider its usability. The researcher walked the site(Sucheongri) with the residents, carrying a GPS device, taking photographs of the landscape objects they described, and recording the relevant explanations. After gathering photographs and explanations which represent the research participants' individual subjective perception, the researcher analysed the explanation using open coding, based on grounded theory. By the analysis, 117 landscape objectives are identified and 18 reason factors for landscape perception were deduced from the explanation. Those factors could be classified as 'positive feeling inducing' and 'negative feeling inducing', and also as 'personal emotion based' and 'community based emotion'. By comparison between feeling map by conventional method and feeing map by new method, usability of new method was empirically reveled. Walking behavior makes it easier for researcher to get more abundant data in quantitative aspect and profound understanding with affection of respondent by allowing them to 'go beyond' the perceptions they remember. Finally new method with walking gives professionals a contextual understanding of a place and more resident-oriented plans and management on sites.

• Journal of Advanced Marine Engineering and Technology
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• 제29권3호
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• pp.297-305
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• 2005

The evaporation heat transfer coefficient of $CO_2$ (R-744) in a horizontal tube was investigated experimentally. The experiments were conducted without oil in a closed refrigerant loop which was driven by a magnetic gear pump. The main components of the refrigerant loop are a receiver. a variable-speed pump. a mass flow meter. a pre-heater and evaporator (test section). The test section consists of a smooth. horizontal stainless steel tube of 7.75 mm inner diameter. The experiments were conducted at mass flux of 200 to $500\;kg/m^{2}s$. saturation temperature of $-5^{\circ}C\;to\;5^{\circ}C$. and heat flux of 10 to $40\;kW/m^2$. The test results showed the evaporation heat transfer of $CO_2$ has greatly effect on more nucleate boiling than convective boiling. The evaporation heat transfer coefficients of $CO_2$ are highly dependent on the vapor quality. heat flux and saturation temperature. The evaporation heat transfer coefficient of $CO_2$ is very larger than that of R-22 and R-134a. In making a comparison between test results and existing correlations. the present experimental data are the best fit for the correlation of Jung et al. But it was failed to predict the evaporation heat transfer coefficient of $CO_2$ using by the existing correlation. Therefore. it is necessary to develop reliable and accurate predictions determining the evaporation heat transfer coefficient of $CO_2$ in a horizontal tube.

• 시스템엔지니어링학술지
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• 제18권2호
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• pp.75-93
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• 2022

Machine learning (ML) data-driven meta-model is proposed as a surrogate model to reduce the excessive computational cost of the physics-based model and facilitate the real-time prediction of a nuclear power plant's transient response. To forecast the transient response three machine learning (ML) meta-models based on recurrent neural networks (RNNs); specifically, Long Short Term Memory (LSTM), Gated Recurrent Unit (GRU), and a sequence combination of Convolutional Neural Network (CNN) and LSTM are developed. The chosen accident scenario is a control element assembly withdrawal at power concurrent with the Loss Of Offsite Power (LOOP). The transient response was obtained using the best estimate thermal hydraulics code, MARS-KS, and cross-validated against the Design and control document (DCD). DAKOTA software is loosely coupled with MARS-KS code via a python interface to perform the Best Estimate Plus Uncertainty Quantification (BEPU) analysis and generate a time series database of the system response to train, test and validate the ML meta-models. Key uncertain parameters identified as required by the CASU methodology were propagated using the non-parametric Monte-Carlo (MC) random propagation and Latin Hypercube Sampling technique until a statistically significant database (181 samples) as required by Wilk's fifth order is achieved with 95% probability and 95% confidence level. The three ML RNN models were built and optimized with the help of the Talos tool and demonstrated excellent performance in forecasting the most probable NPP transient response. This research was guided by the Systems Engineering (SE) approach for the systematic and efficient planning and execution of the research.