• Title/Summary/Keyword: 손상저감

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A Study of the Prediction of the Temperature Reduction of Tire Sidewalls According to the Shape of the Cooling Fins (냉각핀 형상에 따른 타이어 사이드월의 표면온도 저감 효과 예측에 관한 연구)

  • Park, Jae Hyen;Jung, Sung Pil;Chung, Won Sun;Chun, Chul Kyun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.40 no.4
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    • pp.245-253
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    • 2016
  • The friction and deformation of a tire causes heat generation, which causes a temperature rise of the tire. This temperature rise can be a source of tire damage. The object of this study is to investigate the cooling effect of the application of a fin to the tire side to suppress the temperature rise. Eight different fin shapes were considered, and the sidewall surface temperature reduction owing to the cooling fin shape was numerically analyzed. In addition, the flow characteristics and heat transfer characteristics of the vortex of the pin rear were compared.

Seismic Fragility Functions of a SDOF Nonlinear System with an Energy Dissipation Device (에너지 소산형 감쇠기가 설치된 단자유도 비선형 시스템의 지진취약도 함수)

  • Park, Ji-Hun;Yun, Soo-Yong
    • Journal of the Earthquake Engineering Society of Korea
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    • v.16 no.2
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    • pp.1-13
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    • 2012
  • Seismic fragility functions are derived for probabilistic evaluation of seismic control performance of energy dissipation devices installed in reinforced concrete structures. Displacement-dependent dampers are added to the nonlinear single-degree-of-freedom systems with different natural periods and hysteretic characteristics of which stiffness and strength has uncertainty. Nonlinear time history analysis is conducted for those SDOF systems and the result is processed statistically to obtain seismic fragility functions in the form of log normal distribution. Variation of seismic fragility functions for different parameters of SDOF systems and dampers are investigated and the seismic control performance is assessed probabilistically.

Design of Tower Damper Gain Scheduling Algorithm for Wind Turbine Tower Load Reduction (풍력터빈 타워 하중 저감을 위한 타워 댐퍼 게인 스케줄링 알고리즘 설계)

  • Kim, Cheol-Jim;Kim, Kwan-Su;Paek, In-Su
    • Journal of the Korean Solar Energy Society
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    • v.38 no.2
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    • pp.1-13
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    • 2018
  • This paper deals with the NREL (National Renewable Energy Laboratory) 5-MW reference wind turbine. The controller which include MPPT (Maximum power point tracking) control algorithm and tower load reduction control algorithm was designed by MATLAB Simulink. This paper propose a tower damper algorithm to improve the existing tower damper algorithm. To improve the existing tower damper algorithm, proposed tower damper algorithm were applied the thrust sensitivity scheduling and PI control method. The thrust sensitivity scheduling was calculated by thrust force formula which include thrust coefficient table. Power and Tower root moment DEL (Damage Equivalent Load) was set as a performance index to verify the load reduction algorithm. The simulation were performed 600 seconds under the wind conditions of the NTM (Normal Turbulence Model), TI (Turbulence Intensity)16% and 12~25m/s average wind speed. The effect of the proposed tower damper algorithm is confirmed through PSD (Power Spectral Density). The proposed tower damper algorithm reduces the fore-aft moment DEL of the tower up to 6% than the existing tower damper algorithm.

Development of a Signal Conditioner to Improve the Measurement Reliability of a Microseismic Monitoring System (미소진동 모니터링 시스템의 측정 신뢰도 향상을 위한 시그널 컨디셔너 개발)

  • Cheon, Dae-Sung;Han, Cheol-Min;Lee, Jang Baek
    • Tunnel and Underground Space
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    • v.30 no.1
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    • pp.1-14
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    • 2020
  • Microseismic monitoring is utilized for the performance verification and safety management of the structure by detecting fine levels of damage. In order to construct a highly reliable microseismic monitoring system, the role of signal conditioner is critical. The signal conditioner helps with accurate data collection and precision control of the device, and performs additional functions such as signal conversion, linearization, and amplification. In this technical report, noise reduction signal conditioner suitable for mining sites was developed and reviewed for the purpose of implementing more precise monitoring by supplementing the previously developed microseismic monitoring system.

Hydrophysical effect of vegetation cover factors on soil erosion (토양침식에 대한 식생피복 인자의 수문물리적 영향)

  • Seung Sook Shin;Sang Deog Park;Sang Jin Son
    • Proceedings of the Korea Water Resources Association Conference
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    • 2023.05a
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    • pp.343-343
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    • 2023
  • 식생피복(Vegetation cover)은 대기 중의 강우와 토양 사이에서 침식으로부터 표토를 보호하는 역할을 한다. 자유 낙하하는 강우의 물방울은 식생을 통과하면서 차단(interception), 수관통과(throughfall), 수간유하(stemflow)의 형태로 변화한다. 식생은 강우입자의 운동에너지와 수량을 감소시키고, 지표면에 도달하는 시간을 지연시킴에 따라 지표유출(overland flow) 저감에 기여한다. 유출수의 흐름과정에서 식물의 줄기, 낙엽, 뿌리 등은 유속을 감소시키는 장애물로 작용하여 궁극적으로 토양침식은 감소한다. 토양침식은 식생피복이 증가함에 따라 일반적으로 감소하며, 지수함수의 관계를 갖는다. 식생의 종류와 구조 그리고 잎의 모양 등에 따라 수문물리적인 반응이 달라진다. 캐노피를 갖는 지상식물(canopy cover plant)은 물방울의 운동에너지를 갖는 반면, 지피식물(ground cover plant)은 낙하고가 작기 때문에 운동에너지는 적으며, 특히 낙엽층은 지표면을 보호하여 토양침식의 저감효과가 더욱 크다. 산불지역의 식생피복에 따른 토양침식 측정 자료에 따르면, 강우운동에너지는 식생피복이 증가함에 따라 지상피복(canopy cover)에 의한 감소보다는 지면피복(ground cover)과 낙엽피복(litter cover)에 의한 감소효과가 상대적으로 컸다. 식생피복에 의해 차단되는 강우의 손실량보다 침투량 증가에 의한 손실량이 상대적으로 많았다. 낙엽피복에 대한 강우모의 실험 결과에 따르면, 낙엽의 피복율이 증가함에 따라 지수적으로 토양침식량은 감소하였다. 낙엽 피복율의 40% 이상은 토양침식량을 현격이 감소시킨 반면, 피복율의 70% 이상은 지표유출량을 현저히 감소시켰다. 낙엽 피복율이 70%이상이면, 유출계수가 33%가 감소하였으나, 토양침식민감도는 94%로 크게 감소하였다.

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Optimal Design of Press-Fitted Axle Shaft Considering Stress Relief (압입축의 손상저감을 위한 최적설계 연구)

  • Ko, Jaechun;Lee, Jongsoo;Choi, Ha-Young
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.22 no.5
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    • pp.859-864
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    • 2013
  • Creation of a stress relief groove is a fairly simple yet high-performance method. During the application of this method, it is important to consider the location and size of the groove in order to achieve better performance. Consequently, this research proposes an approach for optimizing the application of the stress relief groove method to a press-fitted assembly. In a boss design, the position and diameter of the groove are configured as design variables and the design of experiments is applied. Based on this information, a 3D model is built and analyzed using the finite element analysis software ABAQUS. Meta-models are created using back-propagation neural networks. Then, deterministic optimization results obtained from a genetic algorithm are compared with the results of the finite element analysis. The temperature sensitivity of the optimized model is analyzed, and finally, reliability-based design optimization is conducted for enhancing the design quality.

Cutting of Concrete Block Using Detonating Cords (도폭선을 이용한 콘크리트 블록 절단 연구)

  • Kim, Jung-Gyu;Kim, Jong-Gwan
    • Explosives and Blasting
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    • v.37 no.4
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    • pp.17-25
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    • 2019
  • The method to remove the head of the cast-in-place pile using the detonating cord and horizontal separation plate was proposed in this paper. Plain concrete block was fabricated. Through the blasting test of the concrete block, the charge weight and the burden required for cutting the pile head were identified. The degree of damage of concrete blocks after cutting the head was checked using AUTODYN 2D. As a result of the experiment, it was found that the concrete block was cut using the 10 g/m detonating cord and horizontal separation plate, and the directional cutting of the block using the horizontal separation plate and the block damage caused by the detonating cord were reduced.

Rock Surface Protection According to Decrease of Blasting Vibration (진동저감 대책을 통한 절취면 보호)

  • Hong, Seong-Min;Song, Ha-Lim;Kang, Choo-Won;Chang, Ho-Min
    • Explosives and Blasting
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    • v.30 no.2
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    • pp.21-28
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    • 2012
  • Blasting methods are frequently used in case of forming slope artificially like slope cutting and open-cut method in the downtown area because of many economical and effective advantages. It is important that blasting work is carried out maintaining original strength of rock and not to damage rock face. And it is also considered that blasting method to decrease ground vibration is essential to the point of blast damages due to the ground vibration. In this study, to form a smooth plane of rock slope face, many trial blasts were carried out in this way that explosives were installed in detonating cord by equal interval in different charging method and stemming method. Using 4 blasting patterns in total 60 blast holes and 20 times of blasts were carried out. At the same time ground vibration measurements were carried out 15~102m away from the blast source, and total number of 310 data were obtained. Measured data for ground vibration velocity were analyzed so as to study blasting method to protect slope plane while decreasing blast vibration in an effective way.

Chattering Reduction of Variable Structure Controller for Position System of Induction Motor (유도전동기의 위치제어 시스템을 위한 가변구조제어기의 떨림저감)

  • Kim, Young-Jo;Kim, Hyun-Jung
    • Journal of the Korean Institute of Telematics and Electronics T
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    • v.35T no.2
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    • pp.39-47
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    • 1998
  • It has been known that variable structure control(VSC) has theoretically powerful control technique of providing fast response, no overshoot, and very robust control with respect to system parameter variations and disturbances. However, the technique has not become more widely extended in the industrial circles because chattering phenomenon which may excite high-frequency unmodelled plant dynamics and damage to system components exists. In this paper, a modified variable structure control(MVSC) is developed to alleviate these problems which are applied to the position control of induction motor. While the conventional VSC makes the structure of the system change with high-frequency switching on the center of the one switching surface, in the MVSC two switching surface are used to establish a sliding sector. The structure of the system will be changed with low-frequency switching. Therefore, the proposed algorithm has the properties of reducing chattering, retaining the benefits achieved in the conventional VSC, and working even under the influences of parameter variations. Experimental results show the effectiveness of the control strategy proposed here for the position control of induction motor.

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A Study on Crack Control of Tunnel Lining Concrete with Large Section (대단면 터널 라이닝 콘크리트의 균열저감 연구)

  • Kim, Wan-Young
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.11a
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    • pp.509-512
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    • 2008
  • The lining concrete of water tunnel is a much capability to occur crack due to drying shrinkage and vibrator compaction etc. Because of crack of concrete induce structural problem and decrease durability of concrete, it is need to reduce crack of concrete. In this an Analytical study to analyze the effect of curing of concrete and compaction on the lining concrete. As the results, it was found that control of construction condition into curing of concrete and compaction improve on construction efficiency of the lining concrete.

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