• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.9
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• pp.729-738
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• 2021

Feedback flow control using an artificial neural network was numerically investigated for NACA0015 Airfoil to suppress flow separation on an airfoil. In order to achieve goal of flow control which is aimed to reduce the size of separation on the airfoil, Blowing&Suction actuator was implemented near the separation point. In the system modeling step, the proper orthogonal decomposition was applied to the pressure field. Then, some POD modes that are necessary for flow control are extracted to analyze the unsteady characteristics. NARX neural network based on decomposed modes are trained to represent the flow dynamics and finally operated in the feedback control loop. Predicted control signal was numerically applied on CFD simulation so that control effect was analyzed through comparing the characteristic of aerodynamic force and spatial modes depending on the presence of the control. The feedback control showed effectiveness in pressure drag reduction up to 29%. Numerical results confirm that the effect is due to dramatic pressure recovery around the trailing edge of the airfoil.

• The Journal of the Korea Contents Association
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• v.22 no.3
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• pp.62-70
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• 2022

This study investigates the temporal structure and movement of floating people near university areas in Daegu metropolitan city, South Korea, before and after Covid-19. In order to determine Daegu's position, the current study compares Daegu and Seoul. The floating population is used as an index to reveal people's various activities in the area known as the local business district, which surrounds the university campus. The information was provided by mobile phone manufacturers. A municipal authority managed a public website where mobile data was made available. Several statistical and visualization techniques were used after the data pre-processing steps. As a result, the floating population fluctuation patterns in both cities in the first half of 2019 and 2020 were comparable. When the Covid-19 diffusion rate in Daegu stabilized in the second half of 2020, the floating population in Daegu increased slightly over the previous year, while the population in Seoul decreased due to the second wave of Covid-19.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.10a
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• pp.24-34
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• 2021

Estimation of the presence of people in real time is extremely useful for businesses in providing better services. Many companies and researchers have attempted various researches in order to count the number of floating population in specific space. Recently, as part of smart cities and digital twins, commercialization of measuring floating populations using Wi-Fi signals has become active in the public and private sectors. This paper explains the floating population measuring system from the perspective of general consumers(non-experts) who uses current population data. Specifically, it presents a method of estimating the floating population based on MAC-address values collected from smartphones. By distinguishing Real MAC-address and Random MAC-address values, we compare the estimated number of smartphone devices and the actual number of people caught on CCTV screens to evaluate the accuracy of the proposed method. And it appeared to have a similar correlation between the two datas. As a result, we present a method of estimating the floating population based on analyzing Wi-Fi Probe Requests

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.11a
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• pp.353-354
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• 2007

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.801-804
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• 1999

The interest in workability and quality control of concrete is increasing as to improve quality of concrete structure according to industrialization. Therefore, it is the aim of this study to evaluate the quality of flowing concrete and systematize quality control by analyzing the data of the quality control of concrete through a basic quality control system for improvement of the concrete in pumping flowing concrete for construction industy.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1998.05a
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• pp.173-176
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• 1998

FCC (Fluid Catalystic Cracking) 장치는 중질유의 원유와 잔사유로부터 가솔린과 heating oil. 디젤연료 제조 등에 사용되고 있다. 이 장치는 50년 동안 fine-powder 유동화에 중요하게 응용되고 있으며, 현재 세계적으로 약 350여 개의 장치가 조업되고 있다. FCC 장치에서 미세한 분해촉매는 촉매에 의한 중질유의 분해가 일어나는 상승관 (riser)과 촉매의 재생이 일어나는 재생반응기(regenerator) 사이에서 높은 속도로 순환되고 있다. (중략)

• Proceedings of the Korea Concrete Institute Conference
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• 1990.04a
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• pp.16-19
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• 1990

The effect of superplasticizers on the fluidity performance in fresh concrete and physical properties in hardened concrete have been analyzed and investigated under mix proportions of water cement ratio of 0.4, 0.6, crushed stone aggregates, and addition rates of superplasticizers of 0.0, 0.5, 1.0 and 1.5 in the practical range. It is the aim of this study to provide the fundamental data on the workability improvement and engineering properties of crushed stone concrete using superplasticizers comparing with conventional concrete for the practical use and research data accumulation of superplastized concrete.

• Journal of the Korean Society of Safety
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• v.13 no.2
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• pp.76-87
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• 1998

This study was carried out to investigate the effect of on temperature control from actuating method, recycling ratio and the position (top, middle and bottom) of set and controlled temperature within the reactor in adiabatic ebullated recycling condition, when the disturbance was occurred. Estimation of the solution were performed numerically using the finite difference method. It was assumed that the reaction is in constant with heat of reaction and the physical properties(density, heat capacity and viscosity, etc) of the reactants are same condition within the reactor.

• Membrane Journal
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• v.1 no.1
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• pp.13-23
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• 1991

열유도 상분리법을 이용하여 제조되는 분리막의 구조 변화를 열역학 및 속도론적 관점에서 고찰하였다. Polypropylene과 희석제로서 n-alkanes, n-fatty acids, n,n-bis(2-hydroxyethyl) tallowamine을 model system으로 하였다. 고분자/희석제 system의 상변화의 종류에 따라 다양한 형태의 분리막구조가 얻어졌다. 분리막의 구조에 영향을 미치는 변수로서 고분자/희석제간의 interaction parameter, 희석제의 분자 크기, 용액의 조성, 냉각 조건, 희석제의 결정화 온도 등이며, 각 변수의 역할을 전자현미경을 사용하여 규명하였다. 열유동 상분리법에 의하여 제조된 분리막은 inter-spherulitic 및 intra-spherulitic pore의 이중 구조로 이루어짐을 확인하였다.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2001.11a
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• pp.97-98
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• 2001

폐기물 소각로는 주입 폐기물의 성상이 균일하지 못하므로 폐기물의 불완전 연소에 의한 유해중간 생성물들이 생성되므로 논란이 되어왔다. 이를 제어하기 위해서는 공기량, 공기 주입방법, 공기 예열온도등에 운전조건들의 선정이 매우 중요하다. 이를 위해 진행되어온 연구는 크게 실험적 방법과 수치 해석적 방법의 두 범주로 나뉘어진다. 이에 본 연구에서는 수치해석적 방법으로 광주 상무신도심에 설치 가동중인 200톤/일 용량의 소각로내의 열유동 현상을 해석하기 위하여 고체 폐기물이 매우 빠르게 탈휘(devolatilization)되는 것으로 가정, 메탄가스로 단순화(Chen et al, 1999)하였다. (중략)