• 한국기계가공학회지
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• 제2권2호
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• pp.60-66
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• 2003

For the estimation of chatter lobe boundary it is very important to calculate the natural mode of cutting process. There are many time series algorithms for getting the natural mode of structural endmilling dynamics considering the cutting process. In this study, we have compared several time series methods such as AR algorithm, ARX, ARMAX, ARMA, Box Jenkins, Output Error, Recursive ARX, Recursive ARMAX considering the sampling frequency. As a results, the ARX, ARMAX and IV 4 are more desirable algorithms for the calculation of modal parameters such as natural frequency and damping ratio In endmilling operation. Also these algorithms may be adopted for the natural mode estimation of endmilling operation for chatter lobe prediction.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1995년도 추계학술발표회논문집(2)
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• pp.879-884
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• 1995

The results of performance assessment analyses have shown that the long-lived radionuclides such as I-129 control the potential individual dose impact to the public. I-129 is difficult-to-measure(DTM) in low-level waste because it is non-gamma emitting radionuclides and exists at extremely low concentrations in radioactive waste generated by nuclear reactors. In this study, computer modeling technique to predict release rate of I-129 is developed to provide another tools far performance assessment of land disposal facilities and characteristics of radwaste. Model suggested in this study will give conservative values of I-129 release rate far determination of radwaste characteristics. More detailed approach is implemented to account for release conditions of fuel source-nuclides. 1-131 concentration measured from reactor coolant and released fraction from tramp fuel have dominant roles in calculating release rate of I-129 with fuel defect conditions.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 추계학술대회 논문집
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• pp.93-95
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• 2007

Studies on ski-end shape control at the top end of rolling plate in heavy thick plate mill by using FEM analysis and measuring system have been performed. Plate shape behaviour at the top-end on rolling by the two different methods in finishing rolling process has been observed. One is to minimize the height of ski-end by using pass line based on the relational model between shape factor and pick-up and the other one is to prevent turn down problem caused by the impact between table roller and down bended plate on rolling by using roll speed difference. To minimize the height of ski-end, the prediction models based on the FEM analysis and measuring data was developed. The control method of ski - end shape on finishing rolling process was applied in actual mill and the height of ski-end was reduced by about 50% compared with conventional operation.

• 도시과학
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• 제8권2호
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• pp.25-28
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• 2019

Hefei has suffered from heavy air pollution, especially car exhaust and industry emissions. The smoke contains PM2.5 and PM10. These smoke will enter people's bodies and have a bad impact on the human body. This review is about PM2.5. This review covers the sources and hazards of PM2.5. It introduces the use of modelling methods to analyze PM2.5 pollution in various places and proposes treatment measures. These cities were heavily polluted by PM2.5, and after the local government's management and renovation, there has been a significant improvement. However, there are still many shortcomings in the process of pollution improvement. This review combines the means used in the process of pollution prevention and control in Handan City, Beijing. Hefei now suffers from some of the same pollution as these cities did in the past.

• 한국소음진동공학회논문집
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• 제17권3호
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• pp.249-256
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• 2007

Aircraft noise is a serious problem to inhabitants near airports. INM is one of programs for determining the predicted noise impact in the vicinity of airports. It has been widely used for engineers to evaluate aircraft noise. However it is difficult to predict aircraft noise in case of lack of exact INM input data. The exact informations about a fighter plane are not known well for a security problem. This study presents methods of reducing errors between measurement and simulation when the exact INM input data is not known. Especially we adjusted the thrust force of aircraft engine and reduced the error.

• 국제학술발표논문집
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• The 9th International Conference on Construction Engineering and Project Management
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• pp.1043-1050
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• 2022

Markov chains and Monte Carlo Simulation were applied to account for the probabilistic nature of pavement deterioration over time using data collected in the field. The primary purpose of this study was to evaluate pavement network performance of Western Australia (WA) by applying the existing pavement management tools relevant to WA road construction networks. Two approaches were used to analyze the pavement networks: evaluating current pavement performance data to assess WA State Road networks and predicting the future states using past and current pavement data. The Markov chains process and Monte Carlo Simulation methods were used to predicting future conditions. The results indicated that Markov chains and Monte Carlo Simulation prediction models perform well compared to pavement performance data from the last four decades. The results also revealed the impact of design, traffic demand, and climate and construction standards on urban pavement performance. This study recommends an appropriate and effective pavement engineering management system for proper pavement design and analysis, preliminary planning, future pavement maintenance and rehabilitation, service life, and sustainable pavement construction functionality.

• Structural Engineering and Mechanics
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• 제90권4호
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• pp.403-415
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• 2024

We looked at how the damping qualities of epoxy composites changed when different amounts of graphite nanoplatelets (GNP) were added, from 0% to 6% by weight. A mix of free and forced vibration tests helped us find the key GNP content that makes the damper ability better the most. We also created a Representative Volume Element (RVE) model to guess how the alloys would behave mechanically and checked these models against testing data. An Artificial Neural Network (ANN) was also used to guess how these compounds would react to motion. With proper hyperparameter tweaking, the ANN model showed good correlation (R²=0.98) with actual data, indicating its ability to predict complex material behavior. Combining these methods shows how GNPs impact epoxy composite mechanical properties and how machine learning might improve material design. We show how adding GNPs to epoxy composites may considerably reduce vibration. These materials may be used in industries that value vibration damping.

• 대한교통학회지
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• 제27권3호
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• pp.91-102
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• 2009

도로설계 안전성을 평가하기 위해서는 도로의 설계 요소변화가 사고에 미치는 영향을 예측할 수 있어야 한다. 이를 위해 본 연구에서는 통계적 방법, 사고이력, 전문가의 판단, 그리고 기존문헌고찰 등 다양한 방법을 통하여, 설계요소의 특징과 사고율 및 사고빈도의 관계를 반영할 수 있는 AMF(Accident Modification Factor)를 개발하고자 하였다. 본 연구에서는 AMF를 좌회전전용차로, 우회전전용차로, 시거, 교차각 등의 항목을 대상으로 개발하였다. 개발된 AMF를 적용한 경우의 사고 예측값, 사고예측모형을 통한 예측값을 실제 사고데이터와 비교분석함으로써 적정성을 검토하였다. 분석결과, AMF를 적용한 예측값이 사고예측모형을 통한 예측 값보다 예측력이 우수함을 확인할 수 있었다. 이러한 결과는 사고를 예측함으로써 도로설계 안전성을 평가하는 알고리즘에 있어 AMF가 도로의 설계요소의 특성을 보다 효과적으로 반영하며, 지방부 교차로에서 각각의 해당요소가 사고에 미치는 영향을 판단할 수 있는 지표가 될 수 있음을 의미한다.

• 정보과학회 논문지
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• 제44권11호
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• pp.1149-1155
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• 2017

최근 통신 기술의 발달로 공간 내 환경 자극을 나타내는 다양한 센서 데이터 수집이 가능해졌다. 베이지안 네트워크는 추론 근거를 확률적으로 고려함으로써 센서 데이터의 불확실하고 불완전한 특성을 보완할 수 있다. 본 논문은 환경 자극의 심리적 영향력을 고려하여 설계된 모듈형 베이지안 네트워크 기반 대중 감성 예측 시스템을 제안한다. 또한 단일 베이지안 네트워크를 모듈화하여 공간 내 환경 자극 변동의 유연한 대응 및 효율적 추론을 수행하였다. 시스템의 성능 검증을 위해 유치원 공간에서 수집된 조도, 음량, 온도, 습도, 색 온도, 음향, 향기, 대중 감성 데이터를 기반으로 대중 감성을 예측하였다. 실험 결과, 제안하는 방법의 예측 정확도는 85%로 여타 분류 기법보다 높은 성능을 나타내었다. 정량적, 정성적 분석을 통해 대중 감성 예측을 위한 확률 기반 방법론의 가능성 및 한계를 분석하였다.

• Journal of Astronomy and Space Sciences
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• 제34권4호
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• pp.289-302
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• 2017

The key risk analysis technologies for the re-entry of space objects into Earth's atmosphere are divided into four categories: cataloguing and databases of the re-entry of space objects, lifetime and re-entry trajectory predictions, break-up models after re-entry and multiple debris distribution predictions, and ground impact probability models. In this study, we focused on reentry prediction, including orbital lifetime assessments, for space situational awareness systems. Re-entry predictions are very difficult and are affected by various sources of uncertainty. In particular, during uncontrolled re-entry, large spacecraft may break into several pieces of debris, and the surviving fragments can be a significant hazard for persons and properties on the ground. In recent years, specific methods and procedures have been developed to provide clear information for predicting and analyzing the re-entry of space objects and for ground-risk assessments. Representative tools include object reentry survival analysis tool (ORSAT) and debris assessment software (DAS) developed by National Aeronautics and Space Administration (NASA), spacecraft atmospheric re-entry and aerothermal break-up (SCARAB) and debris risk assessment and mitigation analysis (DRAMA) developed by European Space Agency (ESA), and semi-analytic tool for end of life analysis (STELA) developed by Centre National d'Etudes Spatiales (CNES). In this study, various surveys of existing re-entry space objects are reviewed, and an efficient re-entry prediction technique is suggested based on STELA, the life-cycle analysis tool for satellites, and DRAMA, a re-entry analysis tool. To verify the proposed method, the re-entry of the Tiangong-1 Space Lab, which is expected to re-enter Earth's atmosphere shortly, was simulated. Eventually, these results will provide a basis for space situational awareness risk analyses of the re-entry of space objects.