• 한국소음진동공학회논문집
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• 제22권10호
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• pp.974-984
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• 2012

플랫 블레이드 와이퍼의 블레이드의 누름압 분포를 조정하여 역전과정에서 발생되는 진동을 저감하는 방법을 제시하였다. 블레이드와 유리면 사이에 길이방향으로 불균일한 누름압 분포를 도입, 고무스트립에 점진적인 역전을 유도함으로써 역전과정에서 발생하는 충격력을 저감하였다. 블레이드 내의 바디스프링 형상을 이전 연구에서 제시된 방법을 통해 구해진 형태를 적용함으로써 누름압 분포를 조정하였다. 이 방법을 적용하여 전체 길이에 균일한 누름압과 불균일한 누름압을 발생시키는 두 종류의 블레이드를 개발한 다음 누름압을 측정하여 확인하였다. 두 블레이드에서 발생하는 수직방향 및 횡방향 진동을 측정 비교한 결과, 불균일한 누름압을 가진 블레이드가 균일한 누름압의 블레이드에 비해 훨씬 작은 수직방향 진동을 나타냄을 확인하였다.

• Wind and Structures
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• 제28권5호
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• pp.299-313
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• 2019

In order to examine the effects of different wind deflectors on the wind load distribution characteristics of extra-large cooling towers, a comparative study of the distribution characteristics of wind pressures on the surface of three large cooling towers with typical wind deflectors and one tower without wind deflector was conducted using wind tunnel tests. These characteristics include aerodynamic parameters such as mean wind pressures, fluctuating wind pressures, peak factors, correlation coefficients, extreme wind pressures, drag coefficients and vorticity distribution. Then distribution regularities of different wind deflectors on global and local wind pressure of extra-large cooling towers was extracted, and finally the fitting formula of extreme wind pressure of the cooling towers with different wind deflectors was provided. The results showed that the large eddy simulation (LES) method used in this article could be used to accurately simulate wind loads of such extra-large cooling towers. The three typical wind deflectors could effectively reduce the average wind pressure of the negative pressure extreme regions in the central part of the tower, and were also effective in reducing the root of the variance of the fluctuating wind pressure in the upper-middle part of the windward side of the tower, with the curved air deflector showing particularly. All the different wind deflectors effectively reduced the wind pressure extremes of the middle and lower regions of the windward side of the tower and of the negative pressure extremes region, with the best effect occurring in the curved wind deflector. After the wind deflectors were installed the drag coefficient values of each layer of the middle and lower parts of the tower were significantly higher than that without wind deflector, but the effect on the drag coefficients of layers above the throat was weak. The peak factors for the windward side, the side and leeward side of the extra-large cooling towers with different wind deflectors were set as 3.29, 3.41 and 3.50, respectively.

• 한국지진공학회논문집
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• 제27권5호
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• pp.193-202
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• 2023

In this paper, a dynamic centrifuge model test was conducted on a 24.8-meter-deep excavation consisting of a 20 m sand layer and 4.8 m bedrock, classified as S3 by Korean seismic design code KDS 17 10 00. A braced excavation wall supports the hole. From the results, the mechanism of seismically induced earth pressure was investigated, and their distribution and loading points were analyzed. During earthquake loadings, active seismic earth pressure decreases from the at-rest earth pressure since the backfill laterally expands at the movement of the wall toward the active direction. Yet, the passive seismic earth pressure increases from the at-rest earth pressure since the backfill pushes to the wall and laterally compresses at it, moving toward a passive direction and returning to the initial position. The seismic earth pressure distribution shows a half-diamond distribution in the dense sand and a uniform distribution in loose sand. The loading point of dynamic thrust corresponding with seismic earth pressure is at the center of the soil backfill. The dynamic thrust increased differently depending on the backfill's relative density and input motion type. Still, in general, the dynamic thrust increased rapidly when the maximum horizontal displacement of the wall exceeded 0.05 H%.

• Tribology and Lubricants
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• 제30권5호
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• pp.284-290
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• 2014

The influence of round embossed surface on slider bearing characteristics and its load carrying capacity is discussed for thin film effect of embossed slider bearing. For the numerical computation of lubrication parameters such as pressure, load capacity and shear stress that are normalized and a Reynolds equation is used for the analysis of embossed slider bearing characteristics. For this purpose, the finite difference method of central difference scheme is used in this study. In a slider bearing with embossed form, several simulation parameters such as pressure, load capacity and shear stress of the bearing can be obtained according to independent parameters such as the slope of the slider bearing and number of embossing in the upper slider. Also this results can be summarized and be stored in sequential data file for latter analysis. After all, their distribution of the pressure and shear stress parameters can be displayed and be analyzed easily by using the developed program with matlab GUI technique. The independent parameters such as a number of embossing and a slope of the embossed surface slider are used for discussing simulation parameters of pressure distribution, shear stress and load carrying capacity of the round embossing. These study results reported in this paper should be applied to the other shaped slider bearing with a rectangular embossed surface or rectangular waved surface.

• 대한인간공학회지
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• 제27권1호
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• pp.53-60
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• 2008

The purpose of this study is to provide basic data, such as exerting muscle power of the lower-extremity, EMG test and pressure distribution for designing ergonomic workstation in sitting posture. The exerting muscle power of the lower-extremity was measured by PRIMUS in 4 postures of 90$^{\circ}$, 120$^{\circ}$, 150$^{\circ}$ and 180$^{\circ}$. And performed ANOVA test on Max. and Mean 100%MVC. In EMG test for surveying muscle mobiligation, 5 muscles(Rectus Femoris, Vastus Lateralis, Gastrocnemius, Soleus, Tibialis Anterior) were employed. Additional experiment in pressure distribution in sitting posture by Pliance(16$\time$16 poles), Max. pressure was measured and performed ANOVA test on the results. Concludingly, sitting posture with 120$^{\circ}$ lower-extremity is the best design criterion for ergonomic workstation in sitting posture.

• The Journal of Korean Physical Therapy
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• 제33권3호
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• pp.162-167
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• 2021

Purpose: A hyperextended knee is described as knee pain associated with an impaired knee extensor mechanism. Additionally, a hyperextended knee may involve reduced position sense of the knee joint that decreases the individual's ability to control end-range knee extension movement. The purpose of this study was to investigate the effects of visual biofeedback information for plantar pressure distribution on knee joint angle and lower extremity muscle activities in participants with hyperextended knees. Methods: Twenty-three participants with hyperextended knees were recruited for the study. Surface electromyography signals were recorded for the biceps femoris, rectus femoris, gastrocnemius, and tibialis anterior muscle activities. The plantar pressure distribution was displayed and measured using a pressure distribution measuring plate. Knee joint angle kinematic parameters were recorded using a motion analysis system. The visual biofeedback condition was the point at which the difference between the forefoot and backfoot plantar foot pressure on the monitor was minimized. The Wilcoxon signed-rank test was used to determine the significance between the visual biofeedback condition and the preferred condition. Results: The knee joint angle was significantly decreased in the visual biofeedback condition compared to that in the preferred condition (p<0.05). The rectus femoris and gastrocnemius muscle activities were significantly different between the visual biofeedback and preferred conditions (p<0.05). Conclusion: The results of this study showed that visual biofeedback of information about plantar pressure distribution is effective for correcting hyperextended knees.

• 한국가시화정보학회지
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• 제20권2호
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• pp.78-85
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• 2022

In these days, the rapid development in prediction technology using artificial intelligent is being applied in a variety of engineering fields. Especially, dimensionality reduction technologies such as autoencoder and convolutional neural network have enabled the classification and regression of high-dimensional data. In particular, pixel level prediction technology enables semantic segmentation (fine-grained classification), or physical value prediction for each pixel such as depth or surface normal estimation. In this study, the pressure distribution of the ship's surface was estimated at the pixel level based on the artificial neural network. First, a potential flow analysis was performed on the hull form data generated by transforming the baseline hull form data to construct 429 datasets for learning. Thereafter, a neural network with a U-shape structure was configured to learn the pressure value at the node position of the pretreated hull form. As a result, for the hull form included in training set, it was confirmed that the neural network can make a good prediction for pressure distribution. But in case of container ship, which is not included and have different characteristics, the network couldn't give a reasonable result.

• Geomechanics and Engineering
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• 제30권2호
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• pp.153-167
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• 2022

This study proposes a method to analyze the distribution of coal porosity disturbances after the excavation of ultra-large-diameter water jet boreholes using a coal wetting and softening model. The high-pressure jet is regarded as a short-term high-pressure water injection process. The water injection range is the coal softening range. The time when the reference point of the borehole wall is shocked by the high-pressure water column is equivalent to the time of high-pressure water injection of the coal wall. The influence of roadway excavation with support and borehole diameter on the ultra-large-diameter jet drilling excavation is also studied. The coal core around the borehole is used to measure the gas permeability for determining the porosity disturbance distribution of the coal in the sampling plane to verify the correctness of the simulation results. Results show that the excavation borehole is beneficial to the expansion of the roadway excavation disturbance, and the expansion distance of the roadway excavation disturbance has a quadratic relationship with the borehole diameter. Wetting and softening of the coal around the borehole wall will promote the uniform distribution of the overall porosity disturbance and reduce the amplitude of disturbance fluctuations.

• 대한기계학회논문집B
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• 제29권10호
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• pp.1148-1155
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• 2005

In this study, the influence of changing combustor pressure on nitric oxide emission was investigated. Expansion of reaction region was more clear in the P$^{*}$ <1 conditions compared to the P$^{*}\geq1$ conditions, and it could be observed that flames are distinct in the P$^{*}\geq1$ conditions and that brightness is relative low and wide distribution is shown in the P$^{*}$ <1 conditions. In the respect of temperature distribution, narrow and high-temperature region was shown in the P$^{*}\geq1$ conditions. On the other hands, overall uniform temperature distributions were shown in the P$^{*}$ <1 conditions. Nitric oxide emission decreased with decreasing combustor pressure. This tendency was explained by the mean flame temperature distribution. Low NOx combustion is ascribed to wide-spread reaction region in the low combustor Pressure and oscillation were shown P$^{*}\leq0.97$, and strength and sizes of oscillation were more increased with lower pressure index. These results demonstrate that flame shape and nitric oxide emission can be controlled with changing combustor pressure.

• 척추신경추나의학회지
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• 제2권1호
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• pp.115-125
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• 2007

Objectives : The limited number of studies to date have mainly focused on the effect of obesity on the characteristics of plantar foot pressures. This study is designed to find the correlation between plantar pressure and obese index. Methods : This study assessed the body composition of 30 obese women using bioelectrical impidence analysis and Gaitview AFA-50. The static and dynamic plantar pressure was determined from electronic footprints captured using a capacitive pressure distribution platform during standing and walking. The data were analysed by independent t-test and Pearson Correlation. Results : Positive correlations were noted between body weight, body mass index(BMI), waist circumference(WC), waist-hip ratio(WHR) and difference of fore and rear plantar pressure. And negative correlations were noted between body weight, BMI, WC, WHR and difference of left and right plantar pressure. Conclusions : The findings of this pilot study suggest that body composition influences the waight distribution in overweight and obese subjects.