• Proceedings of the Korea Concrete Institute Conference
• /
• 2006.11a
• /
• pp.933-936
• /
• 2006

Many non-destructive inspection methods have recently been developed for concrete structures. However, these methods can obtain only physical information of concrete, such as crack depth, delamination or position of reinforcement etc. near its surface. If chemical information is required, sampling and componential analyses may be earned out. Non-destructive method that can detect deterioration factors such as carbonation, chloride content or sulfate attack would be an outstanding innovation in inspection methodologies. In this research, near-infrared spectroscopy and X-ray fluorescence analysis were applied for componential analysis for concrete. These methods are very effective compared to traditional methods, therefore, working efficiency and maintenance cost will be improved.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.18 no.4
• /
• pp.415-422
• /
• 2015

The flow field structures of dual jet-in-cross-flow were examined experimentally for in-lined perforated damage holes configuration using particle image velocimetry. Ensemble averaged in-plane velocity and vorticity data in the jet were determined to study the mean jet structure. Jets are formed by pressure differences between upper and lower airfoil surface. The flow structure of vicinity of the thru holes consist of a vortical structure that wrap around the jets like a horseshoe and develop further downstream through a pair of stream-wise vortices. The shape, size and location of the horseshoe vortex were found to be dependent on the angle of attack. In spite of the existence of battle damage holes, the effect on the control force was insignificant when the damage size was not large enough.

• 한국가시화정보학회:학술대회논문집
• /
• 2006.12a
• /
• pp.141-144
• /
• 2006

In this study, one-way fluid structure interaction analysis(FSI) on wind turbine blade was performed. Both a quantitative fluid analysis on 3-bladed wind turbine and a structural analysis using the surface pressure data resulting from fluid analysis were carried out. Streamlines and angle of attack was easily acquired from analysis results, we showed the inlet velocity that the stall begins to occur. In the structural analysis, structural displacement and maximum stress of the two comparative models was calculated. The location that has maximum stress was found. The pressure difference between back and front part of the blade increases as the inlet velocity increase. The torque and maximum with regard to inlet velocity was also presented.

• 한국가시화정보학회:학술대회논문집
• /
• 2002.11a
• /
• pp.63-66
• /
• 2002

The Flow patterns around two cylinders in various arrangements were studied by a discrete vortex method. The flow for the surface of each cylinder was represented by arranging bound vortices at adequate intervals. The viscous diffusion of fluid was represented by the random walk method. The vortex distributions, streaklines, timelines and velocity vectors around two cylinders were calculated for centre-to-centre pitch rations of P/D=1.5 and 2.5, attack angles of $\alpha=0^{\circ},\;30^{\circ},\;60^{\circ},\;and\;90^{\circ}$, correspond to the photographs by flow visualization and the flow intereference between two cylinders in var ious arrangements was clearly visualized by a numerical simulation.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.15 no.2
• /
• pp.580-599
• /
• 2021

Software-Defined Networking (SDN) has three key features: separation of control and forwarding, centralized control, and network programmability. While improving network management flexibility, SDN has many security issues. This paper systemizes the security threats of SDN using spoofing, tampering, repudiation, information disclosure, denial of service, and elevation of privilege (STRIDE) model to understand the current security status of SDN. First, we introduce the network architecture and data flow of SDN. Second, we analyze security threats of the six types given in the STRIDE model, aiming to reveal the vulnerability mechanisms and assess the attack surface. Then, we briefly describe the corresponding defense technologies. Finally, we summarize the work of this paper and discuss the trends of SDN security research.

• Review of KIISC
• /
• v.33 no.4
• /
• pp.131-141
• /
• 2023

최근 코로나로 인하여 원격 근무의 증대와 디지털 트랜스포메이션(DX)으로 인한 클라우드 사용의 증가, 그리고 사이버 보안에 있어서의 끊임없는 새로운 공격의 등장과 공격 면(Attack Surface)의 확대가 증가 일로에 있다. 특히 기존 네트워크 중심의 보안 방식인 경계 보안(Perimeter Security) 방식은 새로운 네트워크 환경, 새로운 형태의 근무 형태로 인한 컴퓨팅 환경의 변화, 새로운 형태의 사이버 공격 등의 다양한 공격에 대한 방어 한계 등으로 인하여 새로운 전기를 맞이하고 있다. 즉, 기존 경계 보안의 한계를 보완하기 위한 차세대 보안 개념의 하나인 제로 트러스트 보안 방식이 최근 많은 관심을 끌고 있다. 본 고에서는 제로 트러스트 보안에 대하여, 미국 국립표준기술연구소(NIST)가 발표한 제로 트러스트 아키텍처SP 800-207을 중심으로 제로 트러스트 보안 개념, 등장 배경, 제로 트러스트 기본 구성, 제로 트러스트 도입과 성숙도 모델, 제로 트러스트 아키텍처 접근 방식 등에 대하여 살펴보고자 한다.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2023.05a
• /
• pp.265-266
• /
• 2023

In this study, a mortar was prepared using Rhodobacter capsulatus which is forming glycocalyx and immersed in a simulated sewage environment. As a result of the experiment, it was observed that bacteria continued to grow in the mortar immersed in the simulated sewage environment, and it was confirmed that glycocalyx was formed by bacteria on the surface of mortar specimen.

• Advances in aircraft and spacecraft science
• /
• v.10 no.5
• /
• pp.457-471
• /
• 2023

The paper evaluates the aerodynamic coefficients on a blunt-nose re-entry capsule with a conical cross-section followed by a cone-flare body. A computer code is developed to solve three-dimensional compressible inviscid equationsfor flow over a Space Recovery Experiment (SRE) configuration at different flare-cone half-angle at Mach 6 and angle of attack up to 5°, at 1° interval. The surface pressure variation is numerically integrated to obtain the aerodynamic forces and pitching moment. The numerical analysis reveals the influence of flare-cone geometry on the flow characteristics and aerodynamic coefficients. The numerical results agree with wind tunnel results. Increase of cone-flare angle from 25° to 35° results in increase of normal force slope, axial forebody drag, base drag and location of centre of pressure by 62.5%, 56.2% and 33.13%, respectively, from the basic configuration ofthe SRE of 25°.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.39 no.2
• /
• pp.297-306
• /
• 2019

Since the centrifugal force acts on the flow in the curved channel, a transverse water surface gradient occurs and the thalweg is biased toward the outer bank. The submerged vanes may be used to solve various engineering problems of the curved channels. In order to analyze the influence of an attack angle and the distance between the vane arrays on the river bed variation and the superelevation in a bend, movable bed hydraulic experiments were conducted in a $90^{\circ}$ curved rectangular channel of a small-size gravel bed. Installing the submerged vanes in the bend increases the maximum scour depth. But if vanes are installed in a uniform obtuse angle, the scour depth may be reduced. If the flow rate in the channel bend with vanes equals to the channel forming discharge, the location of the maximum scour depth moved to the downstream and the superelevation increased. However if the flow rate is smaller than that, the location of the maximum scour depth moved upstream and the superelevation decreased. The channel bed change and the superelevation due to the installation of the submerged vanes have been dependent on the interaction of the attack angle, the flow rate, and the distance between the arrays.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.45 no.4
• /
• pp.342-348
• /
• 2017

In this paper, film cooling characteristics at supersonic free stream conditions were examined experimentally by applying an IR-thermography. Film cooling experiments were carried out in a free-jet facility at Mach number of 3.0 and with unit Reynolds number of $42.53{\times}10^6$ and $69.35{\times}10^6$ using wedge shaped film cooling model which has a converging film cooling nozzle. Film cooling efficiency was calculated by measuring the surface temperature of PEEK(Polyether Ether Ketone) and the effects of angle of attack and blowing ratios on the film cooling efficiency were examined. The measured wall temperature was significantly reduced by the film cooling flow compared with the results without the film cooling flow. The usefulness of film cooling was also confirmed by the surface heat flux calculated using the surface temperature history of PEEK. As the blowing ratio increases the protected area of PEEK was also expanded along the direction of free stream and film cooling flow.