• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05a
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• pp.81-86
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• 2002

이전에 Magnetic Fluid를 이용하여 의료기기 등에 사용할 목적으로 Linear Actuator를 설계, 제작하였다. 그러나 이 모델은 공극의 높은 자기저항으로 인해 펌핑 압력이 낮고, 그 부피 또한 크다. 따라서 본 논문에서는 Yoke를 이용하여 Linear Actuator를 소형화하고 자기저항을 최소화함으로써 펌핑 압력을 향상시켰다. 또한 Linear Actuator의 3D해석을 통하여 Yoke의 폭, 두께, 간격에 대한 최적 크기를 계산하고 설계하였으며, 실제 제작 및 실험을 하였다.

• Journal of the Korea Computer Graphics Society
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• v.25 no.1
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• pp.1-11
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• 2019

More force must be applied when dragging a wet compared with a dry cloth lying on the table. Increased force is needed because the fluid between the cloth and the surface of the table produces an adhesion force. In this paper, we study the adhesion force between a wet cloth and the surface of an object. To compute the adhesion force, we used the adhesion force model used in textile research based on real-world experiments and also considered the effect of wrinkles, which, to our knowledge, has not been investigated in previous work. Furthermore, we studied the phenomenon in which a wet cloth adheres to the surface of an object and that in which a wet cloth adheres to itself when undergoing self-collision.

• Journal of the Korea Society for Simulation
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• v.31 no.1
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• pp.29-41
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• 2022

As one of the alternatives to solve the problem of unstable food supply and demand imbalance caused by abnormal climate change, the need for plant factories is increasing. Airflow in plant factory is recognized as one of important factor of plant which influence transpiration and heat transfer. On the other hand, Digital Twin (DT) is getting attention as a means of providing various services that are impossible only with the real system by replicating the real system in the virtual world. This study aimed to develop a digital twin model for airflow prediction that can predict airflow in various situations by applying the concept of digital twin to a plant factory in operation. To this end, first, the mathematical formalism of the digital twin model for airflow analysis in plant factories is presented, and based on this, the information necessary for airflow prediction modeling of a plant factory in operation is specified. Then, the shape of the plant factory is implemented in CAD and the DT model is developed by combining the computational fluid dynamics (CFD) components for airflow behavior analysis. Finally, the DT model for high-accuracy airflow prediction is completed through the validation of the model and the machine learning-based calibration process by comparing the simulation analysis result of the DT model with the actual airflow value collected from the plant factory.

• Journal of the Korea Convergence Society
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• v.8 no.12
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• pp.291-298
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• 2017

In recent years, the increase of secondary controls within vehicles requires a mechanism to integrate various controls into a single device. This paper presents control performance of an integrated magnetorheological (MR) haptic device which can adjust various in-vehicle comfort instruments. As a first step, the MR fluid-based haptic device capable of both rotary and push motions within a single device is devised as an integrated multi-functional instrument control device. Under consideration of the torque and force model of the proposed device, a magnetic circuit is designed. The proposed MR haptic device is then manufactured and its field-dependent torque and force are experimentally evaluated. Furthermore, an inverse model compensator is synthesized under basis of the Bingham model of the MR fluid and torque/force model of the device. Subsequently, haptic force-feedback maps considering in-vehicle comfort functions are constructed and interacts with the compensator to achieve a desired force-feedback. Control performances such as reflection force are experimentally evaluated for two specific comfort functions.

• Journal of Digital Convergence
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• v.14 no.6
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• pp.245-251
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• 2016

A numerical model is developed to predict distributions of current density and temperature. Also the complete fuel cell performances were compared. In this study the effect of flow field design and flow direction on current density and temperature distribution as well as full cell performance. The complete three-dimensional Navier-Stokes equations were solved with convergence of electro-chemical reactions terms. In this paper, the two different flow field design were simulated, straight channel and rectangular serpentine flow channel, which is commonly used. The effect of flow direction, co-flow and counter-flow, was also analyzed. The current density and temperature is higher with abundant oxygen not fuel. Also, temperature distribution was able to be drawn by using computer simulation. In this paper, the relationship among flow pattern, flow field design and current denstity distribution.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1999.04a
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• pp.8-8
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• 1999

2-유체 인젝터의 분무연소에 대한 통찰 및 구조에 대한 이해와 연료-공기 혼합과 연소반응의 물리적 이해에 필요한 수치적 모델의 개발 및 검증을 위해서는 2유체 시스템에서 액체 및 기체 각각의 기본적 특성인 액적크기, 액적속도, 액적의 질량플럭스(flux), 가스상의 속도측정 등이 필요하다. 특히, 액체분무에서는 액적의 크기를 예측하는 것이 매우 중요한 과제이며, 액적의 크기에 영향을 주는 인자들로는 노즐의 형태, 분사액체의 물성치(점도, 표면장력, 밀도), 주위기체의 조건(온도, 압력, 응축과 증발현상), 분사압력 등이 있다. 그러나, 실제 분무액적의 크기는 분포를 가지므로 같은 SMD를 가지더라도 그 분포의 정도는 크게 다를 수 있어 결과적으로 분무액적의 크기를 평균값만으로 표현하는 것은 불충분할 뿐만 아니라 그 적용에도 한계를 가지게 된다. 따라서 분무액적의 평균크기와 함께 그 분포의 정도 등을 함께 나타내려는 시도가 많은 과학자들에 의하여 연구되었다.

• Journal of the Korean Society for information Management
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• v.5 no.1
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• pp.131-152
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• 1988

It is purposed in this paper to improve the retrieval cffect~venebs through the use of the seman-- t r knowledge of search terms in a computerbased search system. This study is developed it1 three stages include the experimentation of index terms or1 the probab~listir model, indexing with relational operators, and knowledgebase design. The sl~bject experimerltrd is the specific fklds of Chemical Engineering, ' Fluid Flow' and 'Combustion: As for the system ~rnplementatlon. two kinds of search method a r e done. Orie is to search terms related to one specialty word, the other is to retriele the articles based or1 the gueries.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.2
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• pp.216-223
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• 2011

TVC is a kind of ejector which entrains low pressure working fluid by using the high pressure working fluid. While most papers relating with ejectors treat the working fluid as an ideal gas for convenience, the fluid doesn't behave as the ideal gas when phase change occurs. In this study, numerical analysis is conducted by applying Redlich-Kwong equation of state instead of ideal gas equation of state. Two turbulent models are compared for the better prediction and SST k-${\omega}$ model is preferred rather than realizable k-${\epsilon}$ model by comparison. Energy loss at the diffuser inlet and throat using the real gas equation of state is relatively greater than that using ideal gas law. For the real gas case, pressure increase due to shock train at the diffuser outlet is relatively smaller than the ideal gas case, but both cases have the same pressure increase due to a pseudo shock.

• Journal of Energy Engineering
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• v.19 no.3
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• pp.143-150
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• 2010

Line source method of borehole system assumes the entire surrounding medium is uniform. However, thermal properties of grouting region are considerably different from those of surrounding soil. In this study we investigate the effect of grouting materials on the solution of line source method with the aid of numerical analysis. This numerical model generates the temperature of borehole fluid with which line source solution can be obtained. Then this solution can be compared with input condition of numerical model. The results of this comparison show that thermal conductivity and borehole thermal resistance of line source solution are approximately 86% and 91% of the input condition of numerical model. Chart method is developed in this study to find the numerical input conditions (thermal conductivity and borehole thermal resistance) from the line source solution. Thermal response test of test borehole is conducted, the results of which are approximately consistent with the Chart method. Thermal property changes of grouting materials on the line source solution are also examined.

• Tunnel and Underground Space
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• v.27 no.3
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• pp.132-145
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• 2017

Shock loss was not applied for the tunnel ventilation of road tunnel in the past. However, pressure losses due to the shock loss can be significant in network double-deck road tunnel in which combining and separating road structures exist. For the optimum ventilation design of network double-deck road tunnel, this study conducted 3D CFD numerical analysis for the shock loss at the combining and separating flows. The CFD model was made with the real-scale model that was the standard section of double-deck road tunnel. The shock loss coefficient of various combining and separating angles and road width was obtained and compared to the existing design values. As a result of the comparison, the shock loss coefficient of the $30^{\circ}$ separating flow model was higher and that of the two-lane combining flow model was lower. Since the combining and separating angles and road width can be important for the design of shock loss estimation, it is considered that this study can provide the accurate design factors for the calculation of ventilation system capacity. In addition, this study conducted 3D CFD analysis in order to calculate the shock loss coefficient of both combining and separating flows at flared intersection, and the result was compared with the design values of ASHRAE. The model that was not widened at the intersection showed three times higher at the most, and the other model that was widened at the intersection resulted two times higher shock loss coefficients.