• Journal of Broadcast Engineering
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• v.20 no.6
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• pp.938-949
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• 2015

In this paper, we propose a robust speed-limit sign recognition system which is durable to any sign changes caused by exterior damage or color contrast due to light direction. For recognition of speed-limit sign, we apply CNN which is showing an outstanding performance in pattern recognition field. However, original CNN uses multiple hidden layers to extract features and uses fully-connected method with MLP(Multi-layer perceptron) on the result. Therefore, the major demerit of conventional CNN is to require a long time for training and testing. In this paper, we apply randomly-connected classifier instead of fully-connected classifier by combining random forest with output of 2 layers of CNN. We prove that the recognition results of CNN with random forest show best performance than recognition results of CNN with SVM (Support Vector Machine) or MLP classifier when we use eight speed-limit signs of GTSRB (German Traffic Sign Recognition Benchmark).

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.6
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• pp.798-805
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• 2010

There are no domestic researches of plate fin heat exchanger in the field of cryogenic such as LNG FPSO liquefaction plant. In this study, condensing heat transfer characteristics of nitrogen according to three kinds of fin type in the plate fin heat exchanger were analyzed through simulation and experiment to secure independent technologies. In the simulation, nitrogen was condensed at 69bar and $-140^{\circ}C$ in serrated and wavy fin of plate-fin heat exchanger. The serrated fin shows the highest value of local heat transfer coefficient, followed by wavy and plain fin. The experimental results were shown errors less than 12% comparing with the simulation results.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.11
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• pp.1013-1021
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• 2007

Design and performance analysis of the jet pump to transfer fuel between tanks in the smart UAV fuel supply system were carried out through one dimensional flow analysis and the flow analysis using a commercial CFD code. From the analysis results, it was proved that the jet pump was designed with the flow ratio of 2.23 that is the fundamental requirement of the jet pump design. The comparison results showed that the primary nozzle pressure is higher in the CFD analysis than in one dimensional flow analysis, mainly due to the underestimated loss coefficient of the primary nozzles. Consequently, the loss coefficients of the jet pump components should be determined more precisely for the design of the jet pumps with high performance.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.217.1-217.1
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• 2014

반도체 및 디스플레이 산업은 많은 공정들에서 저온 플라즈마 반응을 이용한다. 특히 소자 제작을 위한 실리콘 박막의 증착은 저온 플라즈마 공정의 주요 공정이다. 하지만 실리콘 박막을 합성하는데 있어서 저온 플라즈마에서 형성되는 실리콘 나노 입자는, 오염입자로써 박막의 특성을 악화시켜 소자생산 수율을 악화시키는 주요 원인이 되고 있다. 따라서 플라즈마에서 입자 형성의 원인이 되는 화학반응 및 입자들의 성장 매커니즘에 대한 연구는, 1980년대 플라즈마 공정에서 입자 합성이 보고된 이래 공정의 최적화를 위해 꾸준히 연구되어왔다. 이러한 매커니즘의 연구들은, 플라즈마 화학반응에 의해 실리콘 입자 핵을 만들어 내는 과정과 입자들이 충돌에 의해 성장해가는 과정으로 나눠진다. 플라즈마 화학 반응 과정은 아레니우스 방정식에 의해 정의된 반응계수를 이용하여 플라즈마 내 전자와 이온, 중성 화학종들이 전자 온도와 전자 밀도, 챔버 온도 등에 의해 결정되는 현상을 모사한다. 또한 이 과정에서 실리콘을 포함하는 화학종들의 반응에 의해 핵이 생성 되가는 양상을 모사한다. 생성된 핵은 충돌에 의해 입자가 성장해 가는 과정의 가장 작은 입자로써 이용된다. 입자들이 성장해가는 과정은 입자들이 서로 충돌하면서 다양한 입경의 입자로 분화되어가는 현상을 모사한다. 이 과정에 의해 다양한 입경분포로 분화된 입자들은 플라즈마 내 전자에 의해 하전되며, 이러한 하전 양상은 입경에 따라 다른 분포를 보인다. 본 연구에서는 입자의 하전 분포를 고려하여, 입자들의 성장의 주요 원인인 입자간의 충돌을 대표하는 충돌주파수를 수정하는 방식을 채택하여 보다 정밀한 입자 성장 양상을 모델링하였다. Inductively coupled plasma (ICP) 타입의 저온 플라즈마 반응기에서 합성된 입자들을 Particle Beam Mass Spectrometer (PBMS)와 Scanning Electron Microscope (SEM)를 이용하여 입경분포를 측정한 데이터와 모델링에 의해 계산된 결과를 비교하여 본 모델의 유효성을 검증하였다. 검증을 위해 100~300 mtorr의 챔버 압력 조건과 100~350 W의 입력 전력 조건들을 달리하며 측정한 결과와 계산한 데이터를 조건별로 비교하였다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.7
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• pp.785-790
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• 2011

The goal of this study is to estimate the force acting on the knee joint in the human body by using the Hilltype muscle model based on a musculoskeletal model of the human lower extremity in the sagittal plane. For estimating the force applied, the human leg is modeled using multi-body modeling. This leg model comprises biarticular muscles acting on two joints of the upper and lower limbs, and the muscles include some of the major muscles such as the hamstring. In order to analyze the uncertainty of the applied forces acting on the knee joint, statistical distributions of human body, leg part, parameters are required and to obtain the parameter's statistical characteristic of the part sample survey method is employed. Finally, by using the sensitivity information of the parameters, the force acting on the knee joint can be estimated.

• Applied Chemistry for Engineering
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• v.8 no.6
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• pp.893-900
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• 1997

In this study, vapor-liquid equilibria of a binary system, which consists of glycerol and water, are measured using a vaporrecirculating modified Othmer still at various subatmospheric pressures. The constituent components of the binary system considered in this study exhibit a large difference in the boiling temperatures. Since it is generally observed that the properties of a mixture greatly differ from those of the pure components, the phase equilibrium characteristics of a mixture can not be predicted from the properties of the pure components. Furthermore, an abrupt increase in the boiling temperature occurs as the concentration of the higher boiling component exceeds a certain value. Therefore, it is essential to acquire realistic phase equilibrium data of the mixture for industrial applications. Using the UNIQUAC model, the experimental vapor-liquid equilibrium data are correlated with good accuracy. The thermodynamic consistency test is also performed to ensure soundness of the data.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.4
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• pp.2401-2406
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• 2015

Pipelines are used by large heavy industries to deliver various types of fluids. Since this is important to maintain the performance of large systems, it is necessary to accurately predict remaining life of the corroded pipeline. However, predicting the remaining life is difficult due to uncertainties in the associated variables, such as geometries, material properties, corrosion rate, etc. In this paper, a statistical method for predicting corrosion remaining life is proposed using Bayesian inference. To accomplish this, pipeline failure probability was calculated using prior information about pipeline failure pressure according to elapsed time, and the given experimental data based on Bayes' rule. The corrosion remaining life was calculated as the elapsed time with 10 % failure probability. Using 10 and 50 samples generated from random variables affecting the corrosion of the pipe, the pipeline failure probability was estimated, after which the estimated remaining useful life was compared with the assumed true remaining useful life.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.4
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• pp.405-415
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• 2000

Time series of wind-induced pressure on a structure are modeled using autoregressive moving average (ARMA) model. In an AR process, the current value of the time series is expressed in terms of a finite, linear combination of the previous values and a white noise. In a MA process, the value of the time series is linearly dependent on a finite number of the previous white noises. The ARMA process is a combination of the AR and MA processes. In this paper, the ARMA models with several different combinations of the AR and MA orders are fitted to the wind-induced pressure time series, and the procedure to select the most appropriate ARMA model to represent the data is described. The maximum likelihood method is used to estimate the model parameters, and the AICC model selection criterion is employed in the optimization of the model order, which is assumed to be a measure of the temporal complexity of the pressure time series. The goodness of fit of the model is examined using the LBP test. It is shown that AR processes adequately fit wind pressure time series.

• Clean Technology
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• v.20 no.1
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• pp.22-27
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• 2014

Under low pressures of $CF_4$ and $C_2F_6$ up to 20.7 kPa, the equilibrium adsorbed quantity on activated carbon was experimentally examined using the volumetric method at various temperatures between 293.15 K and 333.15 K. To give the best fit to the experimental data curve, the two step model (i.e., Langmuir model for the first layer adsorption and then Freundlich physisorption) is suggested. The method of initial slope yielded the enthalpy of adsorption for the first step while we could apply the Clausius-Clapeyron equation to find the heat of adsorption of the second step. They are 25.9 kJ/mol and 11.8 kJ/mol, respectively, with $CF_4$, and 38.7 and 38.2 kJ/mol with $C_2F_6$.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.820-824
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• 2010

The purpose of this study is to develop basic technology of hybrid rocket vehicle by constructed and launched. This small hybrid rocket using HDPE/LN2O and Aluminium steel for its body (weight : 12.5 kg, diameter : 114 mm, height : 1.8 m) was designed. The fuel grain and injector were designed for 50 kgf thrust and burning time 2.5 sec. This rocket was loaded the data acquisition device for obtaining data of pressure and velocity during its flying and equiped an automatic ejector system using spring/motor and timer to collect the rocket more safely after launching. It was launched successfully, but found some problem that the rocket's weight was heavier than expected and the thrust was not enough to reach the designed altitude and analyzed its flight path way.