• 한국공간구조학회논문집
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• 제11권2호
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• pp.63-70
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• 2011

축사는 비닐하우스 다음으로 자연재해에 취약한 농촌시설물이다. 축사의 경우 측벽 없이 지붕만 있는 형태가 가장 많이 사용되고 있는데, 태풍이 불면 지붕 전제가 날아가 많은 피해가 발생하는 실정이다. 그래서 농가에서는 태풍피해예방을 위한 측벽에 윈치 커튼설치하여 피해를 예방하고 있는 실정이다. 본 논문에서는 측벽 개방에 따른 축사지붕에 위치별 풍압 계수 분포특성에 대해서 알아보고자 한다. 측벽유무에 관계없이 축사지붕면의 피크외압계수분포에서 풍향각 $0^{\circ}$로 불어오는 방향에 대해서 불리하게 작용하고 있는 것을 알 수 있다. 그러나 측벽의 유무에 따라 피크외압계수가 풍향각과 처마의 길이에 영향을 받는 것을 확인할 수 있었다.

• Wind and Structures
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• 제31권4호
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• pp.287-298
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• 2020

This paper presents an experimental investigation on the surface pressures on the CAARC standard tall building model concerning the effects of freestream turbulence. Two groups of incidence turbulence are generated in the wind tunnel experiment. The first group has an approximately constant turbulence intensity of 10.3% but different turbulence integral scale varying from 0.141 m to 0.599 m or from 0.93 to 5.88 in terms of scale ratio (turbulence integral scale to building dimension). The second group presents similar turbulence integral scale but different turbulence intensity ranging from 7.2% to 13.5%. The experimental results show that the mean pressure coefficients on about half of the axial length of the side faces near the leading edge slightly decrease as the turbulence integral scale ratio that is larger than 4.25 increases, but respond markedly to the changes in turbulence intensity. The root-mean-square (RMS) and peak pressure coefficients depend on both turbulence integral scale and intensity. The RMS pressure coefficients increase with turbulence integral scale and intensity. As the turbulence integral scale increases from 0.141 m to 0.599 m, the mean peak pressure coefficient increases by 7%, 20% and 32% at most on the windward, side faces and leeward of the building model, respectively. As the turbulence intensity increases from 7.2% to 13.5%, the mean value of peak pressure coefficient increases by 47%, 69% and 23% at most on windward, side faces and leeward, respectively. The values of cross-correlations of fluctuating pressures increase as the turbulence integral scale increases, but decrease as turbulence intensity increases in most cases.

• Geomechanics and Engineering
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• 제29권6호
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• pp.697-706
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• 2022

In order to explore the stable anchoring conditions of coal side under the mining disturbance of soft section coal pillar in Wangcun Coal Mine of Chenghe Mining Area, the distribution model of the anchoring support pressure at the coal pillar side was established, using the strain-softening characteristics of the coal to study the distribution law of anchoring coal side support pressure. The analytical solution for the reinforcement anchorage stress in the coal pillar side was derived with the inelastic state mechanical model. The results show that the deformation angle of the roadway side and roof increases with the roof subsidence due to the mining influence at the adjacent working face, the plastic deformation zone extends to the depth of the coal side, and the increase of anchorage stress can effectively control the roof subsidence and further deterioration of plastic zone. The roadway height and the peak support pressure have a certain influence on the anchorage stress, the required anchorage stress of the coal side rises with the roadway height and the peak support pressure. The required anchorage stress of the coal pillar side decreases as the cohesion between the coal seam and the roof and floor and the anchor length increases. Then, applied the research result to Wangcun coal mine in Chenghe mining area, the design of anchor cable reinforcement support was proposed for the section of coal pillars side that has been anchored and deformed, which achieved great results and effectively controlled the convergence and deformation of the side, providing a safety guarantee for the roadway excavation and mining.

• 한국운동역학회지
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• 제18권4호
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• pp.59-65
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• 2008

본 연구는 일상생활에서 흔히 접하게 되는 시설물 중 낙상의 위험이 큰 계단과 경사로 오르기 동안 젊은 성인과 노인들의 압력중심이동 경로와 족저압 변화에 대해 알아보았다. 측정도구는 MatScan system(Tekscan, USA)을 사용하였다. 보행 조건(평지 보행, 계단 오르기, 경사로 오르기)에 따른 족저 영역별 족저압의 차이를 알아보기 위해 일원배치분산분석(One-way ANOVA)을 사용하였다. 압력중심 이동경로는 젊은 성인의 경우 평지 보행과 비교해 계단 오르기에서 조금 짧아졌으며 전족부에서는 외전하는 경향이 나타났다. 경사로 오르기에서는 대체적으로 내전되는 경향이 나타났고 특히 입각기 말기에 엄지발가락으로 압력중심이 이동하였다. 노인의 경우 평지 보행과 비교해 계단 오르기에서 압력중심 이동 경로가 짧아졌으며 앞뒤로 이동이 많았으며 전족부에서는 외전되었다. 경사로 오르기에서는 압력중심이 좌우로 이동하는 경향이 나타났다. 족저 영역별 최고 족저압은 젊은 성인의 경우 평지보행과 비교해 경사로 오르기 에서 2-3번째 중족골두 영역과 후족부 영역의 최고 족저압이 유의하게 감소하였다. 노인의 경우 첫 번째 중족골두 영역은 계단 오르기에서 최고 족저압이 증가하고 경사로 오르기에서 최고 족저압이 감소하였고, 두 번째 중족관절 영역과 후족부 영역은 평지 보행과 비교해 경사로 오르기에서 최고 족저압이 감소하였다. 같은 기울기의 계단과 경사로 오르기 동안 최고 족저압은 대체적으로 경사로 오르기에서 변화가 크게 나타났다.

• 생명과학회지
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• 제20권11호
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• pp.1704-1710
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• 2010

본 연구는 뇌졸중 발병 후 재활운동에 참가하는 환자들을 대상으로 재활운동 3개월이 지난 시점에서 1차 실험을 하였고, 6개월이 지난 시점에서 2차 실험을 하여 운동역학적 비교분석을 하였다. 실험에 사용된 장비는 영상분석기, 족저압분석기, 근전도분석기를 사용하였다. 대상자는 7명으로 하였으며 통계방법은 t-test분석 이용하였다. 결과는 엉덩관절의 최대신전 피크 값과 최대신전 피크 모멘트 값에서 통계적으로 유의한 차이를 나타내었다(p<0.05). 족저압의 비교에서는 환측 다리의 족저압에서 일반적인 걷기 동작시에 족저압의 중심이동거리에서 통계적으로 유의한 차이를 나타내었다(p<0.05). 근전도 분석에서는 대퇴사두근 중의 대퇴직근과 외측광근의 근력에서 통계적으로 유의한 차이를 나타내었다(p<0.05).

• Wind and Structures
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• 제8권5호
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• pp.357-372
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• 2005

Mean and extreme pressure distributions on a large cantilevered flat roof model are measured in a boundary layer wind tunnel. The largest peak suction values are observed from pressure taps beneath conical "delta-wing type" corner vortices that occur for oblique winds, then the characteristics and causes of the local peak suctions are discussed in detail. Power spectra of fluctuating wind pressures measured from some typical taps located at the roof edges under different wind directions are presented, and coherence functions of fluctuating pressures are also obtained. Based on these results, it is verified that the peak suctions are highly correlated with the conical vortices. Furthermore, according to the characteristics of wind loads on the roof, an aerodynamic solution to minimize the peak suctions by venting the leading edges and the corners of the roof is recommended. The experimental results show that the suggested strategy can effectively control the generation of the conical vortices and make a reduction of 50% in mean pressures and 25% in extreme local pressures at wind sensitive locations on the roof.

• 한국분무공학회지
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• 제24권3호
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• pp.114-121
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• 2019

The effect of injector driving current pattern on fuel injection rate of solenoid diesel common rail injector was studied by computer simulation. The time resolved fuel injection rate and injected quantity per stroke of a common rail injector driven with the five current patterns were computer simulated. The fuel injection rate and injected quantity per stroke according to the rail pressure and fuel injection period were also computer simulated. When the common rail injector was driven with the five driving current patterns of peak & hold, there was no difference in the fuel injection rate in the peak section regardless of all the current patterns of the five cases. On the other hand, the magnitude of the hold current value influenced the injection rate and injected quantity per stroke. That is, in the current pattern of three cases where the hold current value is equal to or more than a constant value of the peak current value, the fuel injection rates for the given common rail rail pressure and injection period are same one another. On the other hand, the current pattern of the two cases, in which the hold current value is smaller than a certain value, there is a large fluctuation in the fuel injection rate.

• Journal of Mechanical Science and Technology
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• 제20권9호
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• pp.1436-1448
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• 2006

This paper describes the effects of injection rate shaping on the combustion, fuel consumption and emission of $NO_x$ and soot of a medium duty diesel engine. The focus is on the influence of four different injection rate shapes, square type 1, square type 2, boot and ramp, with a variation of maximum injection pressure and start of injection (SOI). The experiments were carried out on a 1 liter single cylinder research diesel engine equipped with an amplifier-piston common rail injection system, allowing the adjustment of the injection pressure during the injection event and thus injection rate as desired. Two strategies to maintain the injected fuel mass constant were followed. One where rate shaping is applied at constant injection duration with different peak injection pressure and one strategy where rate shaping is applied at a constant peak injection pressure, but with variable injection duration. Injection rate shaping was found to have a large effect on the premixed and diffusion combustion, a significant influence on $NO_x$ emissions and depending on the followed strategy, moderate or no influence on soot emission. Only small effects on indicated fuel consumption were found.

• 한국공간구조학회논문집
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• 제13권1호
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• pp.97-104
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• 2013

Recent tall buildings tend to have unconventional shapes as a prevailing, which is effective for suppressing across-wind responses. Suppression of across-wind responses is a major factor in tall building projects, and the so called aerodynamic modification method is comprehensively used. The purpose of the present study is to investigate the pressure fluctuations on tapered and setback tall buildings, including peak pressures, power spectra and coherences through the synchronous multi-pressure sensing system techniques. And flow measurements around the models were conducted to investigate the condition of vortex shedding. The results show that by tapering and setback, different distributions of mean pressure coefficients at leeward surface were found, which is caused by the geometric characteristics of the models. And the power spectra of wind pressures at sideward surface become wideband and the peak frequencies are different depending on heights, which makes the correlation near the Strouhal component low or even negative. The differences in shedding frequencies were also confirmed by the flow fields around the models.

• 센서학회지
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• 제26권3호
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• pp.186-191
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• 2017

In this study, we investigated the simultaneous detection properties of organic vapor, pressure difference, and magnetic field using a single rugate-structured free-standing porous silicon (RFPS) thin film. Both the wavelength and the intensity of the rugate peaks were changed in the reflectivity spectrum measured at the thin film surface while the organic vapor was exposed to the RFPS thin film. However, when the pressure difference and the magnetic field were exposed to the film, only the rugate peak intensity was changed. Therefore, it is possible to distinguish whether or not the organic vapor is detected by simultaneously changing the rugate peak wavelength and intensity. In addition, a method of distinguishing between the pressure difference and the magnetic field detection signal has been derived by rapidly modulating the direction of the magnetic field. This study shows that it is possible to simultaneously detect and distinguish various objects using a single RFPS thin film, and it is found that porous silicon can be utilized as a sensor sufficiently.