• Title/Summary/Keyword: force standard

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The Effect of Wind Force on Stability of Agricultural Structures - Numerical Calculation of Wind Pressure Coefficients - (풍하중이 농업시설물의 구조적 안정성에 미치는 영향 -수치해석에 의한 풍력계수분포 산정-)

  • 최홍림;손정익
    • Journal of Bio-Environment Control
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    • v.3 no.1
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    • pp.10-19
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    • 1994
  • Wind load is known to be one of major forces to influence the stability of agricultural structures. General flow fields were calculated to determine flow characteristics over the envelop of the following three types of greenhouses with arched roof : single span, twin span greenhouses, and two single span greenhouses apart 3m inbetween. Pressure coefficients along the envelop of greenhouse were numerically calculated by the k-$\varepsilon$ turbulence model, which lead to determine wind forces on it. Curvilinear coordinate for an arched roof and the upwind scheme were adopted for the study. The calculated pressure coefficients were validated with the avaliable data of Japanese Standard and NGAM Standard. The Magnitude of calculated forces over the envelop was not in good accordance with data except the windward wall. Even tile data of Japanese and NGAM Standard for validation deviated a lot from each other in quantity and quality. Such discrepancy may be attributed to different geometric and/or flow configuration conditions for experiments, or the insenstivity of the k-$\varepsilon$ turbulence model to recirculation flow.

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A Study on the Characteristics of the Flow around a Sunken Vessel (침선어초 주위의 유동특성에 관한 연구)

  • 양찬규;김현주
    • Journal of Ocean Engineering and Technology
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    • v.14 no.4
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    • pp.9-16
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    • 2000
  • This paper deals with the numerical and experimental study on the characteristics of the flow around a sunken vessel. Numerical simulation of the two dimensional steady flow on the midship section are carried out by the CFD code which is developed by using finite volume method and which includes the standard $textsc{k}$-$\varepsilon$ model with standard wall function. A experimental study is also carried out for the 1/100 scale model in circulating water channel. A velocity fields around the ship are measuremed by using particle image velocimetry technique. And the fluid forces acting on the ship hull by uniform current are measured by two axis load cell. The computed and measured velocity fields on the midship section are compared with each other in the view point of velocity dstribution and reattachement length, which shows good agreement in quality. The drag force on the vessel also showed the same tendency in both computational and experimental results. However, the quantitative disagreements are shown due to the three dimensional effect of the experiment. The result are used to determine the functional efficiency and stability of the vessel as a artificial reef.

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Failure Mode of Structural Components Considering Column Axial Forces and Partial Masonry Infills for School Buildings Constructed in the 1980s (기둥 축력과 조적허리벽을 고려한 1980년대 학교교사 구조요소의 파괴모드 평가)

  • Jeong, Su-Hyeon;Choi, Myeong-Ho;Lee, Chang-Hwan
    • Journal of Korean Association for Spatial Structures
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    • v.22 no.3
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    • pp.57-64
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    • 2022
  • As earthquakes have increased in Korea recently, people are paying attention to the seismic performance of buildings built in the past. Many school buildings in Korea were built based on standard drawings before the seismic design was applied. However, since school buildings are often designated as emergency evacuation facilities in case of disasters such as earthquakes, seismic evaluation and retrofit must be done quickly. This study investigated the failure modes among structural components (beams, columns, and joints), focusing on 1980s standard drawings for school buildings. The effects of column axial force, partial masonry infills, and different material strengths for concrete and rebar were considered for detailed evaluation. As a result, most of the joints were found to be the weakest among structural components. Column axial forces tended to make the joints more vulnerable, and partial masonry infills increased the possibility of joint failure and shear failure in columns.

Hip Protector against the Impact by Fall Using Air-bag (에어백을 이용한 신체충격완화장치)

  • Park, Ji-Soo;Kim, Choong-Hyun
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.21 no.4
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    • pp.639-643
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    • 2012
  • The hip protector has been developed using the air-bag which has the capability of attenuating an impact. The impact force using the PVC air-bag was decreased by values of 27.5% on average, compared to the impact force without the air-bag. In the experiment, the standard deviation of the impact force attenuation rate was 0.78%. It means that the dimensions of the air-bag have no significant effects to reduce the impact. We believe that it is possible to design light and cheap hip protectors with air-bag to prevent the femur fracture.

A Study on Active Suspension system Using Time Delay Control (시간지연 제어기법을 이용한 능동 현가시스템에 관한 연구)

  • Xuan, Dong-Ji;Kim, Jin-Wan;Zhang, Jing-Yi;Kim, Young-Bae
    • Proceedings of the KSME Conference
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    • 2007.05a
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    • pp.1219-1224
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    • 2007
  • This is Presents experimental results of a force tracking controller for a quarter-car suspension system. The active suspension system was decomposed into two loops. At the main loop, the desired force signal is calculate by using a standard LQ design process. The Time Delay Control(TDC) design technique is then used to design the force controller such that the desired force signal is achieved in a robust manner when actuator or other plant uncertainties are present. The ADAMS controls module was used to realize the joint simulation of ADAMS and MATLAB, of which the results showed that the TDC strategy is reasonable and feasible.

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Chaotic Behavior of a Double Pendulum Subjected to Follower Force (종동력을 받는 이중진자의 혼돈운동 연구)

  • 장안배;이재영
    • Journal of KSNVE
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    • v.7 no.3
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    • pp.439-447
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    • 1997
  • In this study, the dynamic instabilities of a nonlinear elastic system subjected to follower forces are investigated. The two-degree-of-freedom double pendulum model with nonlinear geometry, cubic spring, and linear viscous damping is used for the study. The constant, the initial impact forces acting at the end of the model are considered. The chaotic nature of the system is identified using the standard methods, such as time histories, power density spectrum, and Poincare maps. The responses are chaotic and unpredictable due to the sensitivity to initial conditions. The sensitivities to parameters, such as geometric initial imperfections, magnitude of follower force, direction control constant, and viscous damping, etc., are analysed. Dynamic buckling loads are computed for various parameters, where the loads are changed drastically for the small change of parameters.

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Tractive Force Estimation in Real-time Using Brake Gain Adaptation (브레이크 게인 적응기법을 이용한 종방향 타이어 힘의 실시간 추정)

  • ;;Karl Hedrick
    • Transactions of the Korean Society of Automotive Engineers
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    • v.11 no.3
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    • pp.214-219
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    • 2003
  • This paper includes real-time tractive force estimation method using standard vehicle sensors such as wheel speed, brake pressure, throttle position, engine speed, and transmission carrier speed sensor. Engine map, torque converter lookup table, shaft torque observer, and brake gain adaptation method are used to estimate the tractive force. To verify this estimator, measurement which uses strain-based brake torque sensor and estimation results are presented. All results was performed using a real vehicle in a real-time.

Adaptive force regulation system in the milling process by current monitoring (전류감시를 이용한 밀링공정에서의 절삭력적응제어시스템)

  • 안동철;박영진;정성종
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1996.11a
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    • pp.690-694
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    • 1996
  • In order to regulate the cutting force at a desired level during peripheral end milling processes, a feedrate override Adaptive Control Constant system was developed. This paper presents an explicit pole-assignment PI-control law through spindle motor current monitoring and its application to cutting force regulation for feedrate optimization. An experimental set-up is constructed for the commercial CNC machining center without any major changes of the structure. A data transfer system is constructed with standard interface between an IBM compatible PC and a CNC of the machining center. Experimental results show the validity of the system.

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An Angle-Binder Drawbead Simulator for Measuring Drawbead Forces on Inclined Binder Surface (경사진 바인더면의 드로우비드력을 측정하기 위한 모의실험장치)

  • Yang, W.H.;Choi, K.Y.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2009.05a
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    • pp.180-184
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    • 2009
  • A novel set of experimental test tooling for measuring pulling and holding forces for drawbeads on binders inclined at a wide range of angles is introduced. A mechanical design featuring a single load cell, a male-female draw bead set, translation and rotation degrees of freedom, and a screw-driven clamping system has been incorporated into a standard tensile test machine. On a real time basis, restraining and holding force data with respect to draw-in displacement may be directly downloaded into a PC for data processing. The proposed experimental system represents a significant breakthrough in drawbead simulation technology due to its relatively low cost, clever design, and versatility. The system is shown to yield excellent experimental data suitable for verifying theory and numerical model predictions.

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A Comparative Study on Exciting Force for Luminaire of Naval Vessels According to Sailing Condition (함정 운항에 따른 조명등기구 가진력 비교 연구)

  • Park, Mi-You;Cho, Heung-Gi;Lee, Kowan-Woo;Yu, Young-Soo;Cho, Kyu-Lyong
    • Journal of the Korea Institute of Military Science and Technology
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    • v.15 no.4
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    • pp.390-397
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    • 2012
  • According to sailing condition, an exciting force for luminairie of naval vessels was measured and analyzed. A naval combat service support boat and P${\bigcirc}{\bigcirc}$(patrol killer guided missile) were selected as a target naval vessel. Due to their small size and fast speed, they received excessive vibration than other bigger naval vessels like destroyer. The vibration of luminairie was measured on their cruising and maximum speed. This could analyze exciting force for luminairie of naval vessels. Using this analyzed data, the validity of military standard for naval vessel was verified.