• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.212-212
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• 2000

This study was performed to construct a hot strip speed measuring system and check over whether the measured speed can be used for improving the mass flow of the head-end part of a hot strip in the 7-stand finishing mill. Because the mass flow in hot rolling mill affects the looper operation and the thickness and width control of a strip, accurate measurement of strip speed ie important. The measured speed was compared with the roll speeds of No. 6 and No.7 stand to check the performance of the system and analyzed to find how to apply the speed. As a result, it is shown that the accuracy of the system is enough, strip thickness error can be reduced by -275∼+200$\mu\textrm{m}$ using the measured speed and the existing FSU model has low accuracy for predicting forward slip rate. A neural network was developed to calculate forward slip rate instead of FSU model. The test result of the neural network shows that the neural network is more accurate than the FSU model.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1996년도 춘계학술대회논문
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• pp.101-109
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• 1996

Mini-mill process which is one of the new steel -marking technologies to be able to produce the hot rolled coils by thin slab caster of ISP(In-Line Strip Production) type, will be completed in the Kwangyang Steel Works of POSCO in August, 1996, SEt-Up Model of finishing mill which consists of 5 stands is the most basic and essential in mini-mill plant. Therefore, the simulation program of Finishing-mill Set-Up model were developed in this research , using new temeprature prediction model, roll gap model and rolling physical model. Using the developed FSU program , pass schedules to produce the strips with target strip thickness of 1.8mm, 2.0mm, 2.3mm, 2.7mm an d3.0mm were also determined respectively.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.73.3-73
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• 2001

Finishing mill (FM) is set up with rolling conditions (rolling speed, rolling force, roll gap, etc.) calculated by a FSU (Finisher Setup) model considering the temperature, qualities and size of a transfer bar and a strip at the entry and exit of FM before the transfer bar is rolled through FM. If the accuracy of setup is low mass flow unbalance occurs, so that the accuracies of the strip thickness and width become lower or rolling operation fault occurs. Therefore, to enhance the performance of the FSU model and to improve mass flow and the thickness accuracy of a strip in the 7-stand finishing mill using a hot strip speed measurement system. This study is being performed. In this paper, the speed measurement system, a developed neural network for predicting ...

• Journal of the Korean Data and Information Science Society
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• 제14권4호
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• pp.1067-1082
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• 2003

In this paper, we propose a randomized response model with discrete quantitative attribute by three-stage cluster sampling for obtaining discrete quantitative data by using the Liu & Chow model(1976), when the population was made up of sensitive discrete quantitative clusters. We obtain the minimum variance by calculating the optimum number of fsu, ssu, tsu under the some given constant cost. And we obtain the minimum cost under the some given accuracy.

• 대한기계학회논문집A
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• 제24권11호
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• pp.2836-2844
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• 2000

Thickness control of hot-rolled strips has become an important issue in recent years because of the need for improving the quality of the hot-rolled strip. In this study, a modifying method of rolling force set-up with consideration of spread was developed to improve the thickness uniformity at the finishing rolling units in hot rolling. Through the analysis of real production data it was found that the accuracy of the rolling force determined from the finishing mill set-up (FSU) model dominantly governed the thickness uniformity in rolled plates at the front. Based on this analysis , several examples were selected to calculate the spread of rolled plate using three dimensional rigid thermo-viscoplastic finite element program. FE analysis results were used to train the neural network system that can predict the spread hot-rolled plate and the rolling force was modified based on the predicted value of spread. The modified rolling forces were closer to the measured rolling force so it can be expected that the accuracy of thickness uniformity of hot-rolled plate will be improved.

• 대한의용생체공학회:의공학회지
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• 제25권3호
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• pp.171-182
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• 2004

본 연구에서는 의료 영상과 유한요소 해석을 이용하여 골절된 척추체의 치료를 위해 골 시멘트를 주입하는 추체 성형술(vertebroplasty)에 영향을 미치는 여러 인자들에 대해 생체 역학적으로 분석하여 평가하고자 하였다. 의료 영상을 통해 구현된 모델들은 분석하고자 하는 인자에 대하여 크게 단분절과 다분절 유한요소 모델의 2 가지 형태로 구분하였다. 단분절 유한요소 모델을 통해 골다공증의 정도, 주입된 골 시멘트의 양, 골 시멘트의 주입량 및 환자에게 주입된 골 시멘트 양의 적절성을 평가하였으며, 골 시멘트의 주입이 척추체의 구조적 안정성에 미치는 효과를 분석하기 위하여 척추체 상종판에 수직 압축하중을 가하여 이때의 최대 수진 변위량을 분석하였다. 또한 단분절 척추체의 강성도(stiffness) 값을 산출한 뒤, 정상 상태의 척추체의 강성도 값으로 정규화 하였다. 다분절 유한요소 모델의 경우, 압박 골절 상태를 적용하여 척추 만곡의 변화가 인체에 미치는 영향을 분석하기 위하여 골절의 정도를 3 가지로 구현하였으며, 모델의 최상부에 압축 하중을 가한 후의 척추 만곡의 변화 정도를 분석하였다. 추체 성형술에 대한 다양한 인자들에 대한 분석 결과, 추체 성형술을 통해 환자의 골밀도가 상대적으로 높은 경우(BMD 50mg/$m\ell$이상)와 환자의 척추체 망상골 부피의 약 15%에 해당하는 골 시멘트 주입 시 가장 큰 척추체의 구조적 안정성의 증가 효과를 가져올 것으로 예측되었다. 또한 척추 골절이 미치는 영향에 대한 분석 결과, -2.8$^{\circ}$의 정상적인 후만곡을 가지는 T12∼L2 운동 분절이 골절의 모델링 후 약 9∼17$^{\circ}$의 큰 전만곡을 가지게 되었으며 이러한 척추 만곡의 변화는 동일한 하중 하에서 급격한 척추 만곡의 변화를 야기하는 것으로 나타났다. 또한 골절의 정도가 심할수록 척추 변형은 더욱 크게 증가하는 것으로 나타났다. 이러한 연구 결과들로부터, 전반적으로 추체 성형술은 골 시멘트의 주입량 또는 골밀도에 상관없이 약화된 척추체의 자체의 구조적 안정성의 증가 효과를 가져왔으며 골절로 인해 추체의 높이가 손상되었을 경우 이를 회복하는 것이 중요한 인자의 하나임을 나타내는 결과로 사료되어진다.

• 한국초전도ㆍ저온공학회논문지
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• 제7권2호
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• pp.1-6
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• 2005

The Particle Image Velocimetry (PIV) technique can be used to obtain a whole-field view of thermal counterflow velocity profile in He II. Using commercially available microspheres, we have been able to visualize the normal fluid velocity in He II thermal counterflow; however, the measured velocities are less than predicted from the two fluid model. None the less, the PIV is a useful tool for observing the counterflow field in He II flow, particularly where the flow is complex as occurs through channel constrictions or around bluff objects. The present paper shows recent results using PIV to observe He II counterflow. Two cases are discussed: 1D channel flow and turbulent flow around a circular cylinder.

• 자원ㆍ환경경제연구
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• 제15권2호
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• pp.201-245
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• 2006

본 연구는 일반균형모형을 이용하여 배출권 거래로 인한 일반균형효과와 온실가스 저감비용의 효율성에 대해 알아보았다. 모든 국가가 교토의정서를 비준하고 연합을 형성한 국가끼리 배출권 거래를 한다는 가정 하에서 분할함수형태의 온실가스저감게임을 구성하였고, 전지구를 미국과 미국 이외의 OECD 국가군, 구소련연방, 개도국으로 나누어 연합구조별로 각 국가군에 미치는 영향을 일반균형모형으로 분석한 결과 대연합 하에서 기후변화협약은 연합을 형성하지 않은 ${\phi}$연합구조에 비해 동일한 환경적 효과를 달성하는데 978억 달러를 줄일 수 있어서 효율적인 것으로 나타났다. 하지만, 이 중 약 절반을 미국이 가지고 OEC가 20%를 가지는 반면 배출권 판매국인 구소련연방과 개도국은 각각 18%와 10%만을 가지는 것으로 나타나 배출권 구매국이 전체 연합이익의 약 70%를 가지는 것을 확인하였다. 개도국이 연합에 참여하지 않으면 2010년 Annex-I 국가의 저감량의 최대 22%를 상쇄하는 유출량을 발생하므로 기후변화협약의 본래의 목적인 온실가스 저감 및 안정화를 위해서는 개도국이 연합에 참여하여 유출량을 줄여야 한다. 하지만, 전지구적 배출권 거래시 Annex I 국가가 상당량의 연합이익을 가져가고 개도국의 에너지 산업은 위축되므로 기후변화협약의 안정성을 위해 추가지원금을 제안하고 개도국을 연합에 참여하도록 유인할 필요가 있다.

• Journal of Advanced Marine Engineering and Technology
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• 제38권2호
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• pp.195-201
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• 2014

Flexible risers have been used extensively in recent years for floating and early production systems. Such risers offer the advantage of having inherent heave compliance in their catenary thereby greatly reducing the complexity of the riser-to-rig and riser-to subsea interfaces. Another advantage with flexible risers is their greater reliability. Concerns about fatigue life, gas permeation and pigging of lines have been overcome by extensive experience with these risers in production applications. In this paper, flexible riser analysis results were compared through coupled and uncoupled dynamic analyses methods. A time domain coupled analysis capability has been developed to model the dynamic responses of an integrated floating system incorporating the interactions between vessel, moorings and risers in a marine environment. For this study, SPM (Single Point Mooring) system for an FSU in shallow water was considered. This optimization model was integrated with a time-domain global motion analysis to assess both stability and design constraints of the flexible riser system.

• Structural Engineering and Mechanics
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• 제34권1호
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• pp.15-38
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• 2010

In order to predict the shear strengths of reinforced concrete beams, many deterministic models have been developed based on rules of mechanics and on experimental test results. While the constant and variable angle truss models are known to provide reliable bases and to give reasonable predictions for the shear strengths of members with shear reinforcement, in the case of members without shear reinforcement, even advanced models with complicated procedures may show lack of accuracy or lead to fairly different predictions from other similar models. For this reason, many research efforts have been made for more accurate predictions, which resulted in important recent publications. This paper develops probabilistic shear strength models for reinforced concrete beams without shear reinforcement based on deterministic shear strength models, understanding of shear transfer mechanisms and influential parameters, and experimental test results reported in the literature. Using a Bayesian parameter estimation method, the biases of base deterministic models are identified as algebraic functions of input parameters and the errors of the developed models remaining after the bias-correction are quantified in a stochastic manner. The proposed probabilistic models predict the shear strengths with improved accuracy and help incorporate the model uncertainties into vulnerability estimations and risk-quantified designs.