• 한국운동역학회지
• /
• 제13권3호
• /
• pp.15-26
• /
• 2003

This study was conducted to investigate the performance times, CM position and CM speed, pole chord length and pole chord angle, whole body angular momentum(X axis), and grip width in pole vault event according to the event and phase; touch down, pole plant, take-off, maximum pole bending pole straight, pole release, peak height, and foot contact, pole contact, free flight. The pole vaulting of four male elite vaulters including six trial were filmed using two video digital cameras at 60 Hz at 56th national athletic match, and data were collected through the DLT method of three dimensional cinematography. In general the better jumper is, the longer the performance time is. And the greater CM speed is, and the better his transformation ability of CM horizontal speed into vertical speed is. As he uses a longer pole, his grip is higher, and it is a enough for him to rock back his body, so that he pulls and pushes the pole well keeping his hips close to. An greater maximum angular momentum and early positioning of the hips parallel to the bar makes his body far side of the bar and his bar clearance easier. Specially our national jumper needs to have more powerful braking force during foot contact phase, and take his body on the pole after maximum pole bending, and pull and push the pole strongly keeping his hips close to. Also he needs to have stronger muscular strength in order to control the longer pole and use the pole of proper tension more efficiently.

• 한국안전학회지
• /
• 제17권1호
• /
• pp.11-17
• /
• 2002

The purpose of this study was to present the method to choose the optimization machining condition for the wire electric machine. This was completed by examining the ever-changing quality of the material and by improving the function of the wire electric discharge machine. Precision metal mold products and the unmanned wire electric discharge machining system were used and then applied in industrial fields. This experiment uses the wire electric discharge machine with brass wire electrode of 0.25mm. To measure the precision of the machining surface, average values are obtained from 3 samples of measures of center-line average roughness by using a third dimension gauge and a stylus surface roughness gauge. In this experiment, we changed no-node voltage to 7 and 9, pulse-on-time to $6{\mu}s,\;8{\mu}s$ and $10{\mu}s$, pulse-off-time to $8{\mu}s,\;10{\mu}s$ and $13{\mu}s$, and experimented on wire tension at room temperature by 1000gf, 1200gf, and 1400gf, respectively.

• 천문학회보
• /
• 제39권2호
• /
• pp.74.2-74.2
• /
• 2014

Magnetohydrodynamics(MHD) dynamo depends on many factors such as viscosity ${\gamma}$, magnetic diffusivity ${\eta}$, magnetic Reynolds number $Re_M$, external driving source, or magnetic Prandtl number $Pr_M$. $Pr_M$, the ratio of ${\gamma}$ to ${\eta}$ (for example, galaxy ${\sim}10^{14}$), plays an important role in small scale dynamo. With the high PrM, conductivity effect becomes very important in small scale regime between the viscous scale ($k_{\gamma}{\sim}Re^{3/4}k_fk_f$:forcing scale) and resistivity scale ($k_{\eta}{\sim}PrM^{1/2}k_{\gamma}$). Since ${\eta}$ is very small, the balance of local energy transport due to the advection term and nonlocal energy transfer decides the magnetic energy spectra. Beyond the viscous scale, the stretched magnetic field (magnetic tension in Lorentz force) transfers the magnetic energy, which is originally from the kinetic energy, back to the kinetic eddies leading to the extension of the viscous scale. This repeated process eventually decides the energy spectrum of the coupled momentum and magnetic induction equation. However, the evolving profile does not follow Kolmogorov's -3/5 law. The spectra of EV (${\sim}k^{-4}$) and EM (${\sim}k^0$ or $k^{-1}$) in high $Pr_M$ have been reported, but our recent simulation results show a little different scaling law ($E_V{\sim}k^{-3}-k^{-4}$, $EM{\sim}k^{-1/2}-k^{-1}$). We show the results and explain the reason.

• 한국환경과학회지
• /
• 제20권2호
• /
• pp.175-183
• /
• 2011

This study was conducted to survey the subjective symptoms of workers and users in selected 5 public facility groups(offices, performance halls, private crammers, wedding halls and indoor sports facilities), located in Seoul, Daejeon and Chungnam Province. Overall as subjective symptoms that were worse at public facilities than those usual, following responses appeared: I have a headache, My eyes are dry or feel irritated or itching, I feel eyestrain or my eyes are bloodshot, My nose was stuffy, I have a cough, I feel dry in the throat or inflammation happens, I feel oppressed in the breast or sometimes have difficulty in breathing, My skin gets dry, My skin is itching or has some spots, I feel like vomiting, I feel easily tired or sleep, I lose my concentration and I feel my memory is falling, I feel dizzy, I feel depressed, I feel being sharp and feel tension, I feel muscular pain or stiffness on shoulders, back and neck. Also, we compare with normal subjective symptoms scores and subjective symptoms scores in public facilities. The highest subjective symptoms score in at normal was my skin gets dry(2.35 points) and subjective symptoms score in public facilities was I feel eyestrain or my eyes are bloodshot(2.61 points).

• 대한기계학회논문집A
• /
• 제41권5호
• /
• pp.415-420
• /
• 2017

과소 구동 전동의수는 가벼우며 비교적 경제적이라는 장점이 있다. 본 연구에서는 적응파지가 가능한 과소 구동 전동의수를 대상으로 경제적인 파지력 제어 시스템을 제안하였다. 근전도 신호로 구동되는 메인 케이블의 장력으로 파지력이 결정되므로 장력에 따라 사용자의 피부에 부착된 진동모터를 구동하는 촉감기반 피드백 시스템을 구성하였다. 진동 신호에 대한 사용자의 감각적 판단을 기반으로 파지력을 추정하고 제어하기 위하여 파지력과 진동 신호 간의 적절한 변환 관계를 수립하고 시제품 성능시험을 하였다. 최소한의 훈련으로 사용자들은 비교적 정확하게 파지력을 제어할 수 있었다.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2007년도 추계학술대회 논문집
• /
• pp.1188-1195
• /
• 2007

The vertical forces in rail fasteners at areas of bridge transitions near the embankment and on the pier will occur due to different deformations of adjoining bridges caused by the trainloads, the settlement of supports, and the temperature gradients. The up-lifting forces is not large problem in the blast track because the elasticity of blast and rail pad buffs up-lifting effect. But, it is likely to be difficult to ensure the serviceability of the railway and the safety of the fastener in the end in that concrete slab track consist of rail, fastener, and track in a single body, delivering directly the up-lifting force to the fastener if the deck is bended because of various load cases, such as the end rotation of the overhang due to the vertical load, the bending of pier due to acceleration/braking force and temperature deviation, the settlement of embankment and pier, the temperature deviation of up-down deck and front-back pier, and the rail deformation due to wheel loads. The analysis of the rail fastener is made to verify the superposed tension forces in the rail fastener due to various load cases, temperature gradients and settlement of supports. The potential critical fasteners with the highest uplift forces are the fastener adjacent to the civil joint. The main influence factors are the geometry of the bridge such as, the beneath length of overhang, relative position of bridge bearing and fastener, deflection of bridge and the vertical spring stiffness of the fastener.

• 소성∙가공
• /
• 제18권4호
• /
• pp.336-341
• /
• 2009

Hydroformed parts have higher dimensional accuracy, structural strength, and dimensional repeatability. Particularly in the automotive industry, manufacturing of parts with complex shapes from tubular materials sometimes requires one or more pre-forming operations such as bending before the hydroforming process. The pre-bending process is an important process for the successful hydroforming in the case where the perimeter of the blank is nearly the same as that of final product. The bendability of a tube depends on the parameters such as the bending radius, welding methods, mechanical properties and hardness. Through the stainless steel tubes bent by rotary draw bending machine, this study shows the following : (1) The influence on spring back ratio variation with stress level in the welded bent tube. (2) The Cross-section ovality variation with weld seam position and bending radius. (3) The relation between elongation and thickness reduction of tension zone with weld seam position and bending radius. (4) Workability evaluation of bent stainless steel tubes through the hardness of materials and hardness increment. The results of this study may help to understanding of characteristics on bendability of stainless steel tubes.

• 건축역사연구
• /
• 제14권1호
• /
• pp.107-122
• /
• 2005

The purpose of this study is to analyse Herzog & de Meuron's surface, which represents contemporary architectural trends toward surface. Semper's Bekleidung theory and the important architectural theories about surface were compared according to the conceptual opposition between representation and re-presentation, which is borrowed from Kastern Harris, and again Martin Heidegger. Representation means a sort of translation into a different medium. It doesn't preserve the material identity of what it represent. Re-presentation, however, celebrates the material employed. The tension between representation and re-presentation have activated the architectural history Contemporary architects have emphasized re-presentation at the expense of representation. This trends relate with digital technology, which demands surface or skin independent from depth or interior. Buildings that deserve to be called works of architecture invite us to attend to material in a different way Re-presenting its materials, the work of architecture reveals its being. Such revelation requires that materials work in a way that invites us to step back from our usual involvement with things. It's the poetics of re-presentation, which is emboded in the Herzog & de Meuron's architectural works.

• Structural Engineering and Mechanics
• /
• 제61권4호
• /
• pp.463-473
• /
• 2017

Reinforced concrete is a complex material to be modeled in finite element domain. A proper material model is necessary to represent the nonlinear behaviour accurately. Though the nonlinear analysis of RC structures evolved long back, still an accurate and reliable model to predict the realistic behaviour of components are limited. It is observed from literature that there are three well-known models to represent the nonlinear behaviour of concrete. These models include Chu model (1985), Hsu model (1994) and Saenz model (1964).A new stress-strain model based on Weibull distribution has been proposed in the present study. The objective of the present study is to analyze a reinforced concrete beam under flexural loading by employing all the models. Nonlinear behaviour of concrete is considered in terms of stress vs. strain, damage parameter, tension stiffening behaviour etc. The ductility of the RC beams is computed by using deflection based and energy based concepts. Both deflection ductility and energy based ductility is compared and energy based concept is found to be in good correlation with the experiments conducted. The behavior of RC beam predicted using ABAQUS has been compared with the corresponding experimental observations. Comparison between numerical and experimental results confirms that these four constitutive models are reliable in predicting the behaviour of RC structures and any of the models can be employed for analysis.

• 한국수산과학회지
• /
• 제38권5호
• /
• pp.316-322
• /
• 2005

In order to develop a floating breakwater, which can efficiently control long period waves, vertical plates are attached in pontoon. Wave control and dynamic behaviors of the newly developed vertical plates type are verified from numerical analysis and hydraulic experiment. As a result, for the wave control and energy dissipation, the newly developed vertical plates type is more efficient than the conventional pontoon type. For the floating body motion, the wave transmission, depending on incident wave period, is decreased at the natural frequency. Dimensionless drift distance has similar trend of the reflection rate of wave transformation near natural frequency except maximum and minimum values. Dimensionless maximum tension is 17 percent of the weight of floating breakwater in case of the conventional pontoon type and 18 percent or 14 percent in case of the newly developed vertical plates type. Thus, it is shown that the wave control is improved by the vertical plates type. In addition, by adjusting the interval of the front and back vertical plate, we would control proper wave control.