• Earthquakes and Structures
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• 제24권1호
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• pp.37-51
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• 2023

Türkiye has made significant changes and updates in both seismic risk maps and design codes over time, as have other countries with high seismic risk. In this study, the last two seismic design codes and risk maps were compared for the Aegean Region (Western Türkiye) where the earthquake risk has once again emerged with the 2020 Izmir Earthquake (Mw=6.9). In this study, information about the seismicity of the Aegean Region was given. The seismic parameters for all provinces in the region were compared with the last two earthquake risk maps. The spectral acceleration coefficients of all provinces have increased and differentiated with the current seismic hazard map as a result of the design spectra used on a regional basis have been replaced by the geographical location-specific design spectra. In addition, section damage limits were obtained for all provinces within the scope of the last two seismic design codes. Structural analyses for a sample reinforced-concrete building were made separately for each province using pushover analysis. The deformations in the cross-sections were compared with the limit states corresponding to the damage levels specified in the last two seismic design codes for the region. Target displacement requests for all provinces have decreased with the current code. The differentiation of geographical location-specific design spectra both in the last two seismic design code and between provinces has caused changes in section damages and building performance levels. The main aim of this study is to obtain and compare both seismic and structural analysis results for all provinces in the Aegean Region (Western Türkiye).

• 대한조선학회논문집
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• 제60권6호
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• pp.424-432
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• 2023

This study deals with the design of a safety device around a leisure boat propeller. The safety device is to be designed to minimize performance degradation attached to propulsors in coastal waters. These devices, important for preventing propeller accidents, negatively gives influence boat performance, especially at higher speeds. In order to minimize the negative effect, the accelerating ducts, normally used in ESDs (Energy Saving Devices) have been chosen as a safety device. The present study aims to design an optimal duct (minimizing negative effect) through the parametric study. Based on the Marine 19A nozzle, the nozzle's thickness and angle were varied to obtain the optimum parameter in the preliminary design by the computational fluid dynamics program Star-CCM+ Ver. 15.02. In the detailed design, a NACA 4-digit Airfoil shape resembling the Marine 19A by modification at the trailing edge was chosen and the optimum shape was chosen according to variation of camber, thickness, and incidence angle for optimization. The optimally designed duct shows a speed decrease of about 10% in the sea trial result, which is much smaller than the normal speed decrease of at least 30%. The present designing method can give wide applications to the leisure boat because the wake is almost the same due to using the outboard propulsor.

• 대한교통학회지
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• 제33권4호
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• pp.323-336
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• 2015

Surrogate safety measure(SSM)를 이용하여 도로상의 위험을 측정하는 방식은 사고의 직접적인 원인과 연관된 차량의 거동을 분석 대상으로 한다는 장점을 가지고 있으나, 한 지점에 국한된 정보를 이용하기 때문에 위험을 연속적으로 분석하는 데에 제약이 있다. 이러한 한계를 극복하기 위해 본 연구에서는 RTK-DGPS를 이용하여 차량들의 궤적을 얻는 방안을 제시하고, 이를 통해 time-to-collision(TTC), deceleration rate to avoid collision(DRAC), acceleration noise(AN) 등의 SSM을 산출하는 데에 필요한 문제들을 고려한 방법론을 설정하였다. 또한 본 연구에서는 검토된 방법론을 이용하여 운전 중 발생하는 다양한 차량거동 변화를 관찰하기 위하여 영동고속도로 북수원IC-군포IC 구간을 대상으로 실험을 수행한 결과를 제시하였다. 그 결과 궤적 기반 SSM 지표값이 다양한 주행 상황에서의 위험성을 합리적으로 설명할 수 있음을 확인하였다. 본 연구는 향후 다양한 구간특성 및 운전자 특성에 따른 위험상황을 설명하는 연구를 수행하고, 위험구간 감지 및 위험한 운전행태의 감지를 통한 사고예방에 활용될 수 있을 것으로 판단되며, 이를 통하여 위험도로 개선 및 교통사고 줄이기 사업을 효율적으로 추진하는 데에 기여할 수 있을 것이다.

• 한국구조물진단유지관리공학회 논문집
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• 제23권1호
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• pp.27-35
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• 2019

기존의 중-장경간 철도교량에는 주로 강박스 거더교가 적용되어 왔다. 하지만 강박스 거더교는 교량 아래의 공간확보가 불리하고, 주거더가 얇은 박판의 박스형상으로 이루어져 진동에 의한 울림소음이 발생하여 소음에 대한 많은 민원이 제기 되고 있다. 이와 같은 이유로 강박스 거더교를 대체할 수 있는 장지간 철도교량의 개발에 대한 필요성이 대두되었다. 본 논문에서는 이러한 이유로 최근에 개발된 강합성 하로 철도교에 대한 특징을 소개하고, 이 철도교의 주요 적용 지간인 40m와 50m 교량을 대상으로 실제 운행열차인 KTX 하중의 운행속도를 반영하여 상용유한요소프로그램인 MIDAS Civil을 이용하여 시간이력해석을 수행하였다. 또한 해석결과를 분석하여 대상교량의 동적거동 특성을 확인하고 철도설계기준에서 제시하고 있는 동적성능 기준을 만족하는지에 대해 검토하였다. 그 결과, 검토 대상 교량 모두 동적안전성 기준을 만족하였으나 지간 40m의 경우 연직가속도 값이 상당히 크게 나와 이에 대한 개선 방안을 제시하고, 단면을 수정하여 연직가속도의 감소를 확인하였다.

• 한국구조물진단유지관리공학회 논문집
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• 제26권3호
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• pp.29-38
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• 2022

본 연구에서는 실규모의 2층 철골 구조물에 7종의 건축 및 비건축 비구조요소를 설치하여 진동대 실험을 수행하였다. 진동대 실험은 현행 비내진상세와 면진장치를 적용한 실험으로 두 차례 수행되었으며 본 연구에서는 무정전전원장치(UPS)의 내진성능에 대하여 실험 및 분석하였다. 비내진정착상세로는 UPS 하단에 ㄷ형강 다리부가 설치되었고, 면진장치로는 고감쇠고무와 와이어로프로 구성된 개발 복합면진장치가 사용되었다. 지진하중모사를 위하여 ICC-ES AC156 (2010)에 따라 인공지진파를 생성 후, 동일 지진파의 크기를 점증하여 가진하였다. 진동대실험을 통해 복합면진장치의 적용여부에 따른 UPS의 거동 및 동적 특성(응답가속도, 응답변위, 동증폭계수, 고유진동수, 감쇠비)을 비교 및 분석하였다. 실험결과, 복합면진장치를 적용함에 따라 UPS의 고유진동수가 감소하여 응답가속도 및 증폭계수가 크게 감소하는 것으로 확인되었다.

• Journal of Korean Vacuum Science & Technology
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• 제6권2호
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• pp.92-96
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• 2002

In this paper, we treated the Ni$_3$Al based alloy samples with intense pulsed ion beams (IPIB) at the beam parameters of 250KV acceleration voltage, 100 - 200 A/cm$^2$ current density and 60 u pulse duration. We simulated the thermal-mechanical process near the surface of Ni$_3$Al based alloy with our STEIPIB codes. The surface morphology and the cross-section microstructures of samples were observed with SEM, the composition of the sample surface layer was determined by X-ray Energy Dispersive Spectrometry (XEDS) and the microstructure on the surface was observed by Transmission Electron Microscope (TEM). The results show that heating rate increases with the current density of IPIB and cooling rate reached highest value less than 150 A/cm$^2$. The irradiation of IPIB induced the segregation of Mo and adequate beam parameter can improve anti-oxidation properly of IC6 alloy. Some craters come from extraneous debris and liquid droplets, and some maybe due to the melting of the intersection region of interphase. Increasing the pulse number enlarges average size of craters and decreases number density of craters.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.761-767
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• 2011

Since the "Low Carbon, Green Growth" as a social requirements is attracted public attention, the policies and investments of the railway which have been less estimated than road is re-considered. Since the starting the commercial service (2004. April), the KTX have been operated successfully while transport passengers over 100million for years. And also the project for development of KHST (Korea High Speed Train ; G7) had been accomplished with a good result, the first trainset of KTX-II which base on G7 project was manufactured and testing now. On the other hand, the world's technology of the high speed train is more faster, and changing to a distributed traction system. To catch up the world's leading technology, the HEMU(High-speed Electric Multiple Unit) project will secure new technology and aims to promote the technology of domestic high-speed train. The authors indicates the result of detail review such as a curve, slope of the track and electrical dead section of the catenary to test at 400kph and also the performance simulation of the developed rolling stock in this paper. As the result, the authors devise the test scenario to perform a maximum speed test (stability at max. speed, acceleration & deceleration etc) with the restricted conditions such as track length, track available time etc by considering above result.

• Journal of Astronomy and Space Sciences
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• 제36권4호
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• pp.235-248
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• 2019

This paper suggests a relative orbit control strategy for the CubeSat Astronomy by NASA and Yonsei using Virtual Telescope Alignment eXperiment (CANYVAL-X) mission whose main goal is to demonstrate an essential technique, which is an arrangement among two satellites and a specific celestial object, referred to as inertial alignment, for a next-generation virtual space telescope. The inertial alignment system is a relative orbit control system and has requirements for the relative state. Through the proposed orbit control strategy, consisting of separation, proximity keeping, and reconfiguration, the requirements will be satisfied. The separation direction of the two CubeSats with respect to the orbital plane is decided to provide advantageous initial condition to the orbit controller. Proximity keeping is accomplished by differential atmospheric drag control (DADC), which generates acceleration by changing the spacecraft's effective cross section via attitude control rather than consuming propellant. Reconfiguration is performed to meet the requirements after proximity keeping. Numerical simulations show that the requirements can be satisfied by the relative orbit control strategy. Furthermore, through numerical simulations, it is demonstrated that the inertial alignment can be achieved. A beacon signal had been received for several months after the launch; however, we have lost the signal at present.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.846-851
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• 2005

The purpose of this paper is that investigates the dynamic behavior characteristic of W.T.S(Wind turbine System) and carries out the evaluation analysis during operating W.T.S. To investigate the dynamic behavior characteristic of W.T.S, the experiments to measure vibration of the blade from the attached accelerometer on the flap and edge section of the blade that is one of the most important elements of dynamic characteristic of W.T.S are performed. Natural frequency and mode shape are calculated with commercial program (ANSYS) using the measured vibration acceleration that receives the signal with F.F.T Analyzer from the accelerometer. For validation of these experiments, the finite element analysis is performed with commercial F.E.M program (ANSYS) on the basis of the natural frequency and mode shape. The results indicate that experimental values have good agreements with the finite element analysis.

• 한국정밀공학회지
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• 제23권1호
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• pp.113-120
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• 2006

This paper proposed the control algorithm fur aspheric surface grinding and was verified by the experiment. The functions of the algorithm were simultaneous control of the position and interpolation of the aspheric curve. The non-linear formula of the tool position was derived from the aspheric equations and the shape of the tool. The function was partitioned by an certain interval and the control parameters were calculated at each control section. The movement in a session was interpolated with acceleration and velocity. The position error was feed-backed by rotary encorder. The concept of feedback algorithm was correcting position error by increasing or decreasing the speed. In the experiment, two-axis machine was controlled to track the aspheric surface by the proposed algorithm. The effect of the control and process parameters was monitored. The result showed that the maximum tracking error was under sub-micro level for the concave and convex surfaces.