• 한국자동차공학회논문집
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• 제11권1호
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• pp.7-17
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• 2003

Highly accurate control of an air-fuel ratio is very important to reduce exhaust gas emissions of gaseous-fuel engines. In order to achieve this purpose, a precise engine model is required to estimate engine performance from the engine design process which is applied to the design of an engine controller. Engine dynamics are considered to develop a dynamic engine model of a gaseous-fuel engine. An effective air mass ratio is proposed to study variations of the engine dynamics according to the water vapor and the gaseous-fuel in the mixture. The dynamic engine model is validated with the LPG engine under steady and transient operating conditions. The experimental results in the LPG gaseous-fuel engine show that the estimation of the air flow and the air-fuel ratio based upon the effective air mass ratio is more accurate than that of a normal engine model.

• Biotechnology and Bioprocess Engineering:BBE
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• 제6권1호
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• pp.42-50
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• 2001

The activity of immobilized cell-support particle aggregates is influenced by physical and biochemical elements, mass transfer, and physiology. Accordingly, the mathematical model discussed in this study is capable of predicting the steady state and transient concentration profiles of the cell mass and substrate, plus the effects of the substrate and product inhibition in an immobilized cell-support aggregate. The overall mathematical model is comprised of material balance equations for the cell mass, major carbon source, dissolved oxygen, and non-biomass products in a bulk suspension along with a single particle model. A smaller bead size and higher substrate concentration at the surface of the particle, resulted in a higher supply of the substrate into the aggregate and consequently a higher biocatalyst activity.

• Nuclear Engineering and Technology
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• 제49권7호
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• pp.1555-1562
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• 2017

A loose part monitoring system is used to identify unexpected loose parts in a nuclear reactor vessel or steam generator. It is still necessary for the mass estimation of loose parts, one function of a loose part monitoring system, to develop a new method due to the high estimation error of conventional methods such as Hertz's impact theory and the frequency ratio method. The purpose of this study is to propose a mass estimation method using a Markov decision process and compare its performance with a method using an artificial neural network model proposed in a previous study. First, how to extract feature vectors using discrete cosine transform was explained. Second, Markov chains were designed with codebooks obtained from the feature vector. A 1/8-scaled mockup of the reactor vessel for OPR1000 was employed, and all used signals were obtained by impacting its surface with several solid spherical masses. Next, the performance of mass estimation by the proposed Markov model was compared with that of the artificial neural network model. Finally, it was investigated that the proposed Markov model had matching error below 20% in mass estimation. That was a similar performance to the method using an artificial neural network model and considerably improved in comparison with the conventional methods.

• 한국컴퓨터그래픽스학회논문지
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• 제5권1호
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• pp.27-33
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• 1999

본 논문은 유연한 비정형 물체의 애니메이션을 위한 효율적인 기법을 제안한다. 비정형 물체를 표현하기 위해 질량-스프링 모텔이 사용되었다. 지금까지 많은 기법들이 부드러운 객체의 사실적인 애니메이션을 생성하기 위해 질량-스프링 모델을 사용하였다. 질량-스프링 모텔의 애니메이션을 수행하기 위한 가장 손쉬운 접근법은 명시적 오일러 방법 (explicit Euler method)인데, 이 방법은 '불안정성 문제'라는 잘 알려진 문제가 발생한다는 단점을 가지고 있다. 이 불안정성 문제를 해결하기 위한 해법으로 암시적 적분법이 사용될 수 있다. 그러나, 이 암시적 방법의 가장 결정적인 약점은 대규모의 선행 시스템을 풀어야 한다는 것이다. 본 논문은 암시적 방법의 근사(approximation)를 이용하여 질량-스프링 모델을 빠른 시간에 애니메이션 할 수 있는 기법을 제시한다. 제안된 기법은 n 개의 질점이 O(n) 개의 스프링으로 연결되어 있을 때, 각 질점의 상태를 O(n) 시간에 안정적으로 갱신할 수 있다. 본 논문은 사실적인 결과를 위해 비정형 물체와 공기와의 상호 작용도 고려하였다.

• Journal of the Korean Data and Information Science Society
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• 제22권2호
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• pp.287-296
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• 2011

36명의 여대생을 대상으로 체 지방 감소효과에 대한 실험을 실시하였다. 이 실험에서 처리는 매일 섭취하는 식사종류 및 양에 대한 식사일지 작성과 카메라 폰으로 찍어 실험관리자에게 전송하여 매주상담을 받는 것이다. 실험관리자는 체 지방 및 관련된 자료를 일주일마다 측정하여 8주간의 반복측정자료를 얻었다. 이 실험자료를 이용하여 혼합모형의 일종인 변량계수모형을 이용하여 추정 및 유의성 검정을 실시한 결과, 유의한 고정인자들은 처리 전체지방 값, 비만지수, 확장기 혈압, 총 콜레스테롤 및 시간이다. 처리 후 시간에 따른 체 지방 감소는 2차 함수의 관계가 성립된다. 변량인자인 개체효과와 개체와 시간과의 교호작용에서 1차 함수의 관계가 존재한다. 처리 후 시간이 지남에 따라 체 지방 량은 점점 감소하였으며, 실험실시 8주 후에는 평균 2.1kg 감소한 효과가 있음을 보여주었다.

• 한국정밀공학회지
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• 제21권2호
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• pp.130-137
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• 2004

A dynamic model of railway reducer is developed by the lumped parameter method. The model accounts for shafts, bearings flexibilities, gyroscopic effects and the force couplings among the transverse and torsion motions due to gearing. Vibration/noise analysis as well as strength of gear teeth, and bearing life are considered. Excitation forces of railway reduction are considered as the mass unbalance of the rotors, misalignment and a function of gear transmission error which comes from the modified tooth surface. A campbell diagram, in which the excitation sources caused by the mass unbalance of the rotors, misalignment and the transmitted errors of the gearing are considered, shows that, at the operating speed, there are not the critical speed. The program which can be used to analyze and predict vibration/noise characteristics by mass unbalance, misalignment and gear transmission error of railway reduction is developed with this system model.

• 오토저널
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• 제5권3호
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• pp.45-55
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• 1983

This paper discussed about Application Technique of Numerical Methods for large structure. The dynamic behaviours of a vehicle were investigated through finite element modelling. After dividing a vehicle body into three substructures, Basic Mass System was composed of 60 flexual modes which was obtained from the dynamic characteristics of each substructure using Modal Synthesis Method. Engine, transmission and rear axle, etc. were added to Basic Mass Model, consequently Full Mass System was constructed by 72 degree of freedoms. Full Mass System was analyzed over the frequency range 0.5-50.0 Hz under the loading conditions which were Stationary Gaussian Random Process. Results and discussions provided the guidelines to eliminate resonances among the parts and to improve the Ride Quality. The Absorbed Power was used as a standard to determine the Ride Quality. The RMS value of driver's vertical acceleration was obtained 0.423g from the basic model and 0.415g from the modified model.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.308-313
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• 2003

Thermal mass flow meters (TMFMs) are most widely used for measuring mass flow rates in the semiconductor industry. A TMFM should have a short response time in order to measure the time-varying flow rate rapidly and accurately. Therefore it is important to study transient heat transfer phenomena in the sensor tube of a TMFM that is the most critical part in the TMFM. In the present work, a simple numerical model for transient heat transfer phenomena of the sensor tube of a TMFM is presented. Numerical solutions for the tube and fluid temperatures in a transient state are obtained using the proposed model and compared with experimental results to validate the proposed model. Based on numerical solutions, heat transfer mechanism in a transient state in the sensor tube is explained. Finally, a correlation for predicting the response time of a sensor tube is presented. The correlation is verified by experimental results.

• Water Engineering Research
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• 제1권3호
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• pp.171-185
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• 2000

A mathematical model to adequately predict complex mixing characteristics of sorptive polluants in natural streams with pools-and-riffes has been developed. In this model, sorption of pollutants onto the bed sediment as well as mass storage and exchange in the storage zones were incorporated into one-dimensional mass balance equatins. The geometric and hydraulic characteristics of the pool-riffle sequences were properly conceptualized. Simulations with parameters of pool-and-riffle streams better fit the measured data in overall shape and peak concentration than simulations with parameters for uniform channels. The analyses on the characteristics of the storage zone model parameters reveal that a linear relationship between the logrithm of the storage zone volume ratio and a function of the friction factor exists. A linear relatiohship might also be tenatively assumed between the logarithm of the dimensionless mass exchange coefficient and the logarithm of the aspect ratio of the storage zone if some of the high values of the dimensionless mass exchange coefficient collected on the successive bed forms are excluded.

• Journal of Astronomy and Space Sciences
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• 제14권1호
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• pp.1-17
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• 1997

The results of a restricted numerical simulation for the color gradients within globular clusters have been presented. The standard luminosity function of M3 and Salperter's initial mass functions were used to generate model clusters as a fundamental population. Color gradients with the sample clusters for both King and power law cusp models of surface brightness distributions are discussed in the case of using the standard luminosity function. The dependence of color gradients on several parameters for the simulations with Salpter's initial mass functions, such as slope of initial mass functions, cluster ages, metallicities, concentration parameters of King model, and slopes of power law, are also discussed. No significant radial color gradients are shown to the sample clusters which are regenerated by a random number generation technique with various parameters in both of King and power law cusp models of surface brightness distributions. Dynamical mass segregation and stellar evolution of horizontal branch stars and blue stragglers should be included for the general case of model simulations to show the observed radial color gradients within globular clusters.