• Wind and Structures
• /
• 제30권3호
• /
• pp.299-316
• /
• 2020

Based on wind tunnel tests, this paper investigates the aerodynamic behavior of a large span canopy roof with elliptical plan and hyperbolic paraboloid shape. The statistics of pressure coefficients and the peak factor distributions are calculated for the top and bottom faces of the roof, and the Gaussian or non-Gaussian characteristics of the pressure time-histories in different areas of the roof are discussed. The cross-correlation of pressures at different positions on the roof, and between the top and bottom faces is also investigated. Combination factors are also evaluated to take into account the extreme values of net loads, relevant to the structural design of canopies.

• 한국조명전기설비학회:학술대회논문집
• /
• 한국조명전기설비학회 1989년도 추계학술발표회논문집
• /
• pp.25-30
• /
• 1989

고압 나트륨-수은 방전에서 파인 D선의 파란 날개아 빨간 날개 최대값의 이동과 분압 사이의 관계들을 나타내는 식을 유도했고 이식으로 실험을 해서 타당성과 유용성을 검증했다. 반데르 왈스 모델이 나트륨과 수은 원자 사이의 상호작용에 대한 계산으로서 사용된다. 모노크로메타로부터 쉽게 측정되어지는 변수 (빨간 날개 최대값의 이동과 파란 날개 최대값의 이동)로부터 나트륨-수은 방전에서의 나트륨, 수은 압력을 구하는데 유용하고 편리한 식을 유도하였고 이를 이용하여 400W 나트륨등의 나트륨 분압을 구하였다.

• 대한족부족관절학회지
• /
• 제7권1호
• /
• pp.36-40
• /
• 2003

Purpose: To investigate the relationship between radiographic parameters of the forefoot and plantar pressure in patients with hallux valgus. Materials and Methods: Plantar pressures of 21 patients with hallux valgus were examined with EMED-ST system. The data were compared with the parameters on the simple weightbearing dorsoplantar radiographs of the feet. The radiographic parameters that were measured were hallux valgus angle, 1-2 intermetatarsal angle, relative lengths of the metatarsals which were measured with the methods described by Maestro et al. and Okuda et al. Results: Statistically significant correlation was found between peak pressures under 2, 3 metatarsal heads and the relative lengths of 2, 3 metatarsals which were measured with the method described by Maestro et al. However they could explain only 13% of the pressures under the 2, 3 metatarsal heads by multivariate analysis. Conclusion: These results suggest that we cannot predict the plantar pressures under the foot with the parameters on the simple weightbearing dorsoplantar radiographs of the feet.

• Wind and Structures
• /
• 제26권1호
• /
• pp.11-24
• /
• 2018

Full-scale measurements of wind action on the open roof structure of the WuXi grand theater, which is composed of eight large-span free-form leaf-shaped space trusses with the largest span of 76.79 m, were conducted during the passage of Typhoons HaiKui and SuLi. The wind pressure field data were continuously and simultaneously monitored using a wind pressure monitoring system installed on the roof structure during the typhoons. A detailed analysis of the field data was performed to investigate the characteristics of the fluctuating wind pressure on the open roof, such as the wind pressure spectrum, spatial correlation coefficients, peak wind pressures and non-Gaussian wind pressure characteristics, under typhoon conditions. Three classical methods were used to calculate the peak factors of the wind pressure on the open roof, and the suggested design method and peak factors were given. The non-Gaussianity of the wind pressure was discussed in terms of the third and fourth statistical moments of the measured wind pressure, and the corresponding indication of the non-Gaussianity on the open roof was proposed. The result shows that there were large pulses in the time-histories of the measured wind pressure on Roof A2 in the field. The spatial correlation of the wind pressures on roof A2 between the upper surface and lower surface is very weak. When the skewness is larger than 0.3 and the kurtosis is larger than 3.7, the wind pressure time series on roof A2 can be taken as a non-Gaussian distribution, and the other series can be taken as a Gaussian distribution.

• 대한물리의학회지
• /
• 제13권1호
• /
• pp.147-154
• /
• 2018

PURPOSE: This study examined the ability of experimental socks combined with a functional insole to reduce plantar foot pressure in healthy subjects. METHODS: The study enrolled 15 subjects. An in-shoe measurement device was used to measure the peak plantar pressure while walking. The peak forefoot, midfoot, and hindfoot plantar pressure data were collected under two conditions: the subjects were wearing their own socks and while they were wearing the experimental socks. The paired t-test was used to determine the differences in peak plantar pressure between the two conditions at all three positions. RESULTS: Wearing the experimental socks resulted in a significantly higher peak plantar pressure in the medial forefoot and midfoot areas than wearing one's own socks (p<.05), and also in significantly lower peak plantar pressure in the medial and lateral hindfoot (p<.05). However, there were no significant differences of peak plantar pressure between experimental and own socks in middle and lateral forefoot (p>.05). CONCLUSION: The experimental socks combined with a functional insole decreased plantar pressure in the hindfoot and supported the medial longitudinal arch. However, it is necessary to change the design and material of the forefoot area in the functional insole to prevent foot ulcer at that location in people with diabetes mellitus.

• Journal of Advanced Marine Engineering and Technology
• /
• 제39권9호
• /
• pp.911-917
• /
• 2015

본 논문에서는 함정용 디젤연료를 단기통 커먼레일 디젤엔진에 적용하여 연료분사압력 변화에 따른 분사율 특성, 거시적 분무 특성 및 연료분사시기와 연료압력변화에 따른 연소 및 배기가스 배출특성을 분석하는데 초점을 두었다. 분사율 특성은 Bosch법을 적용한 분사율 측정 시험 장치를 이용하여 분석하였고, 거시적 분무 특성은 정적용기 및 초고속 카메라를 이용하여 분석하였다. 또한, 연료분사시기 및 연료압력 변화를 정밀하게 제어할 수 있는 단기통 엔진을 이용하여 연소 및 배기가스 배출특성을 분석하였다. 30MPa과 50MPa의 분사조건에서 초기 분사율은 50MPa의 분사조건에서 크게 나타났으며, 분무 발달(투과) 또한 동일시간대에서 큰 것으로 분석되었다. 연료분사시기가 지각될수록 실린더 내부 최대 압력과 최대 열발생량은 떨어지는 경향으로 나타났으며, 고압분사조건에서 실린더 내부 최대압력과 최대 열발생량은 다소 큰 것으로 분석되었다. 고압분사조건에서 도시평균유효압력은 낮은 것으로 분석되었고, 연료분사시기가 TDC 쪽으로 지각될수록 도시평균유효압력 및 토크는 증가하는 것으로 나타났다. 연료분사시기가 $BTDC20^{\circ}$(30MPa)와 $BTDC15^{\circ}$(50MPa)에서 질소산화물 발생수준이 가장 높았으며, 일산화탄소는 $BTDC30^{\circ}$를 기준으로 지각될수록 저감되었다.

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

• 한국의류산업학회지
• /
• 제15권4호
• /
• pp.613-619
• /
• 2013

This study compares the gait characteristics of elderly women during barefoot walking and walking with sneakers. We measured foot angles, max foot pressure, peak plantar pressure of each plantar region, velocity of Center of Pressure(COP), and axis shifting of COP with an RS-scan system. Elderly women's foot angles were narrower when walking with sneakers than when barefoot walking. We found that the subtalar joint angle (representing ankle joint flexibility) affected walking stability. Regarding the peak plantar pressure of each foot region, pressures were high in the medial regions and the pressures greatly varied depending on the region measured during barefoot walking. The COP moved significantly faster when walking with sneakers than barefoot walking and suggests that elderly women walked faster in sneakers. Axis shifting of the COP decreased during walking with sneakers and indicated that gait balance improved when walking with sneakers. The findings of the present study can be utilized as foundational data for elderly women's gait characteristics as well as data for the production of functional footwear. Future research that focuses on various types of shoes, age groups, and gender are recommended for the development of more functional footwear for stable gaits.

• Geomechanics and Engineering
• /
• 제11권5호
• /
• pp.639-655
• /
• 2016

The effect of particle breakage and intermediate principal stress ratio on the behaviour of crushable granular assemblies under true triaxial stress conditions is studied using the discrete element method. Numerical results show that the increase of intermediate principal stress ratio $b(b=({\sigma}_2-{\sigma}_3)/({\sigma}_1-{\sigma}_3))$ results in the increase of dilatancy at low confining pressures but the decrease of dilatancy at high confining pressures, which stems from the distinct increasing compaction caused by breakage with b. The influence of b on the evolution of the peak apparent friction angle is also weakened by particle breakage. For low relative breakage, the relationship between the peak apparent friction angle and b is close to the Lade-Duncan failure model, whereas it conforms to the Matsuoka-Nakai failure model for high relative breakage. In addition, the increasing tendency of relative breakage, calculated based on a fractal particle size distribution with the fractal dimension being 2.5, declines with the increasing confining pressure and axial strain, which implies the existence of an ultimate graduation. Finally, the relationship between particle breakage and plastic work is found to conform to a unique hyperbolic correlation regardless of the test conditions.

• Wind and Structures
• /
• 제16권1호
• /
• pp.93-115
• /
• 2013

This paper describes a study of the influence of a dynamically flexible building structure on pressures inside and net pressures on the roof of low-rise buildings with a dominant opening. It is shown that dynamic interaction between the flexible roof and the internal pressure results in a coupled system that is similar to a two-degree-of-freedom mechanical system consisting of two mass-spring-damper systems with excitation forces acting on both the masses. Two resonant modes are present, the natural frequencies of which can readily be obtained from the model. As observed with quasi-static building flexibility, the effect of increased dynamic flexibility is to reduce the first natural frequency as well as the corresponding peak value of the admittance, the latter being the result of increased damping effects. Consequently, it is found that the internal and net roof pressure fluctuations (RMS coefficients) are also reduced with dynamic flexibility. This model has been validated from experiments conducted using a cylindrical model with a leeward end flexible diaphragm, whereby good match between predicted and measured natural frequencies, and trends in peak admittances and RMS responses with flexibility, were obtained. Furthermore, since significant differences exist between internal and net roof pressure responses obtained from the dynamic flexibility model and those obtained from the quasi-static flexibility model, it is concluded that the quasi-static flexibility assumption may not be applicable to dynamically flexible buildings. Additionally, since sensitivity analyses reveal that the responses are sensitive to both the opening loss coefficient and the roof damping ratio, careful estimates should therefore be made to these parameters first, if predictions from such models are to have significance to real buildings.