• Journal of the Geological Society of Korea
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• v.54 no.5
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• pp.579-584
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• 2018

It is crucial to determine a mixing ratio using an end-member mixing analysis when there is seawater intrusion. In this study, an error from the calculation of the mixing ratio between seawater and freshwater based on the principles of uncertainty was determined. I present the errors in the calculated mixing ratios as a function of the chemical difference between the mean seawater concentrations and standard deviations. The error is caused by: (1) the mixing ratio between seawater and freshwater; (2) the difference between the mean concentration and the standard deviation; and (3) the difference of the tracer concentration between freshwater and seawater (inversely). In particular, the error may determine hydrogeochemical process (either precipitation or dissolution) when a value of ionic delta (difference between measured and theoretical concentration) is close to zero during cation exchange by seawater intrusion.

• Proceeding of EDISON Challenge
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• 2017.03a
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• pp.236-240
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• 2017

다양한 분야에서 복합재료의 중요성이 강조되면서 각각의 재료 특성에 따른 물성을 미시역학적으로 구하는 것에 대한 다양한 방법이 제시되고 있다. 본 논문에서는 5개의 혼합 법칙을 선정하여 전산구조해석을 통한 유한요소해석을 비교 검증한다. 그 과정에서 산출된 결과를 통하여 복합재료의 탄성거동의 오차가 1% 미만인 것을 확인하였고, 프로그램의 해석이 적절하다는 것을 검증하였다. 또한 프로그램과 가장 유사한 혼합 법칙이 무엇인지 확인하고, 체적 비에 따른 오차를 비교하여 가장 적합한 체적 비를 선정하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.1
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• pp.88-95
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• 2015

This paper considers the effects of propellant mixture ratio and loading errors on the performance of a liquid rocket. Propellant residuals generated by error sources are analyzed for a launch vehicle model whose first stage consists of a cluster rocket of four 75-tonf class engines using a statistical Monte-Carlo approach and then the optimal fuel biases minimizing residuals are computed. The results are validated through comparison with analytic method using approximate formula, which have been applied for other space launch vehicles.

• Journal of the Korea Institute of Building Construction
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• v.20 no.2
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• pp.155-162
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• 2020

Since the third industrial revolution has been started in the 1980s, the form of buildings has been varied and atypical by the development of building technology. Such free-form building has a curved shape unlike the existing standard buildings, and to realize this, it is necessary to manufacture the free-from panel. The shape of the free-form panel must satisfy a limited error ratio compared with the design shape, and the technology to produce free-form panels is very difficult. However, there are many problems such as enormous cost and construction waste generation when implementing free-from construction. Therefore, the development of free-form panel manufacturing technology should be made to solve the problems caused by the free-form construction. In this study, the error rate analysis of the mixed mortar panel was conducted by selecting the proper mixing ratio of the mixed mortar for the shape of the free-form panel.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.10a
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• pp.87-91
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• 2004

It is definitely required to control dispersion of the rocket engine performance in order to accomplish the mission of launch vehicle successfully. We performed the dispersion analysis of gas generator cycle LRE (liquid rocket engine) accompanied with ANASYN. As a result, the vacuum thrust dispersion of the engine was $+5.34\%,\;-5.27\%$ and the mixture ratio deviated $+9.07\%,\;-9.82\%$ from the nominal value due to the errors of components and engine inlet condition of propellants. By applying the gas generator regulator only, the dispersion of the engine performance increases. Error in turbine efficiency is the most influential factor to the dispersion of engine performance.

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.1
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• pp.53-59
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• 2016

Ultrasonic nonlinear evaluation is generally utilized for detection of not only defects but also microdamage such as corrosion and plastic deformation. Nonlinearity is determined by the amplitude ratio of primary wave second harmonic wave, and the results of its comparison are used for evaluation. Owing to the experimental features, the experimental nonlinearity result contains system nonlinearity and material nonlinearity. System nonlinearity is that which is unwanted by the user; hence, it acts as an error and interrupts analysis. In this study, a bulk wave mixing technique is implemented in order to minimize the system nonlinearity and obtain the reliable analysis results. The biggest advantage of this technique is that experimental nonlinearity contains less system nonlinearity than that for the conventional nonlinear ultrasonic technique. Theoretical and experimental verifications are performed in this study. By comparing the results of the bulk wave mixing technique with those of the conventional technique, the strengths, weaknesses, and application validity of the bulk wave mixing technique are determined.

• Aerospace Engineering and Technology
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• v.9 no.1
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• pp.93-97
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• 2010

The analysis of specific impulse of the liquid rocket engine employing gas generator cycle with LOx/kerosene as propellant has been performed. The relative error of performance of 300 ton level engine is 0.1%s for specific impulse and 12% for optimal combustion pressure comparing with the published data. The difference of the performance model and the material property models of gas generator product gas are the presumed major reason of discrepancy. The optimal condition of 30 ton level engine is combustion pressure of 68 bar and mixture ratio of 2.2 for maximum specific impulse. This optimal condition can be changed by performance models.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.236-236
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• 2012

QMS(Quadruple Mass Spectrometer)를 사용하여 혼합 기체의 조성비를 측정하는 기술로 He, $NF_3$, $CF_4$, $SF_6$가 포함된 공정에서 사용되는 가스를 사용하여 실제 조성비를 정량적으로 구하는 방법을 연구하였다. 실험을 위해 압력을 $1{\times}10^{-8}Torr$로 배기하였고, 반복 실험을 통하여 최적의 값으로 QMS를 튜닝을 한 후 He, $NF_3$, $CF_4$, $SF_6$가스에 대한 감도를 구하였다. 측정된 감도 값을 바탕으로 총 10회의 반복 측정한 데이터를 이용하여 농도 값을 얻었다. 사용된 가스는 한국표준과학연구원 표준가스실에 제작한 가스이다. 실험 데이터를 이용한 농도와 실제 농도를 비교한 결과 5% 이내의 오차 범위에서 농도 측정이 가능했다.

• Aerospace Engineering and Technology
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• v.12 no.1
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• pp.200-206
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• 2013

A performance sensitivity of liquid rocket engine to propellant density or supply pressure change was studied. The analysis program was verified to have 1% error comparing with the measured data of a turbopump-gas generator system. The engine combustion pressure decreases as fuel supply pressure increases due to decreased mixture ratio which reduces the turbine power. The engine combustion pressure increases as fuel density increases because the total propellant flow rate is increased substantially even though mixture ratio is slightly decreased. The engine combustion pressure increases when the oxidizer density or supply pressure increases.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.4
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• pp.361-371
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• 2012

In order to improve the efficiency of the branch-and-bound method for mixed-discrete nonlinear programming, a nonuniform convergence tolerance scheme is proposed for the continuous subproblem optimizations. The suggested scheme assigns the convergence tolerances for each continuous subproblem optimization according to the maximum constraint violation obtained from the first iteration of each subproblem optimization in order to reduce the total number of function evaluations needed to reach the discrete optimal solution. The proposed tolerance scheme is integrated with five branching order options. The comparative performance test results using the ten combinations of the five branching orders and two convergence tolerance schemes show that the suggested non-uniform convergence tolerance scheme is obviously superior to the uniform one. The results also show that the branching order option using the minimum clearance difference method performed best among the five branching order options. Therefore, we recommend using the "minimum clearance difference method" for branching and the "non-uniform convergence tolerance scheme" for solving discrete optimization problems.