• Journal of the Korean GEO-environmental Society
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• v.4 no.1
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• pp.19-28
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• 2003

Current methods for lateral thrust calculations are based on the classical formulations of Rankine or Coulomb. However, the previous studies indicate that lateral earth pressures acting on the wall stem, which is the function of deformation parameters of the backfill, are close to the active condition only in the top half of the wall stem and in the lower half of the wall stem, the lateral earth pressures are significantly in excess of the active pressures. This paper presents the compressible inclusion function of EPS which can results in reduction of static earth pressure by accomodating the movement of retained soil. A series of model tests were conducted to evaluate the reduction of static earth pressure using EPS inclusion and determine the optimum stiffness of EPS. Also, field test was conducted to evaluate the reduction of static earth pressure using EPS inclusion. Based on field test it is found that the magnitude of static earth pressure can be reduced about 20% compared with classical active earth pressure.

• Journal of the Korean Geotechnical Society
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• v.23 no.4
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• pp.47-58
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• 2007

The usage of Integral abutment bridges has been increased worldwide because of reducing bridge maintenance costs and resisting seismic loads. Although these attributes make the integral abutment bridge an increasingly popular choice, back-abutment interaction issues remain unresolved. Hence, the earth pressure behavior of an integral abutment bridge having 90 m long PSC beam bridge for the first time in Korea was analyzed by conducting long term monitoring in this study. Based on this study, the results were as follows; the ratio of maximum passive movement to the abutment height (H) of 0.0027 and the maximum passive earth pressure coefficient of 4.8 were developed at 0.82H from the bottom of the abutment during summer season. During winter season, the ratio of maximum active movement to H of 0.0011 and the maximum active earth pressure coefficient of 0.7 were developed at the same location as in summer season. The new earth pressure distributions having a trapezoid type were proposed based on this study.

• Computers and Concrete
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• v.20 no.4
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• pp.469-481
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• 2017

This paper aims to analytically investigate the effect of shear stress at the concrete-steel interface on the mechanical behavior of the circular steel tube-confined concrete (STCC) stub columns with active and passive confinement subjected to axial compression. Nonlinear 3D finite element models divided into the four groups, i.e. circumferential-grooved, talc-coated, lubricated, and normal groups, with active and passive confinement were developed. An innovative method was used to simulate the actively-confined specimens, and then, the results of the finite element models were compared with those of the experiments previously conducted by the authors. It was revealed that both the predicted peak compressive strength and stress-strain curves have good agreement with the corresponding values measured for the confined columns. Then, the mechanical properties of the active and passive specimens such as the concrete-steel interaction, longitudinal and hoop stresses of the steel tube, confining pressure applied to the concrete core, and compressive stress-strain curves were analyzed. Furthermore, a parametric study was performed to explore the effects of the concrete compressive strength, steel tube diameter-to-wall thickness ratio, and prestressing level on the compressive behavior of the STCC columns. The results indicate that reducing or removing the interfacial shear stress in the active and passive specimens leads to an increase in the hoop stress and confining pressure, while the longitudinal stress along the steel tube height experiences a decrease. Moreover, prestressing via the presented method is capable of improving the compressive behavior of STCC columns.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.734-741
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• 2008

At-rest and active earth pressure in plane strain condition have been applied to the design of cylindrical retaining walls. But many researchers have indicated that the earth pressure on the cylindrical retaining walls would be smaller than in plane strain condition due to wall deformation and stress relief. In this paper, the distribution of earth pressure acting on diaphragm wall of a shaft in dry sand was predicted by using the convergence confinement method and model test was performed to verify the estimated values. Test results showed that the earth pressure acting on the diaphragm wall of a shaft was expected to be 1.1~1.5 times larger than active earth pressure of plane strain condition and 0.7~0.9 times less than at-rest earth pressure.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.229.2-229.2
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• 2014

Graphene, an allotrope of carbon, is a two-dimensional material having a unique electro-mechanical property that shows significant change of the electrical conductance under the applied strain. In addition of the extraordinary mechanical strength [1], graphene becomes a prospective candidate for pressure sensor technology [2]. However, very few investigations have been carried out to demonstrate characteristics of graphene sensor as a device form. In this study, we demonstrate a pressure sensor using graphene double layer as an active channel to generate electrical signal as the response of the applied vertical pressure. For formation of the active channel in the pressure sensor, two single graphene layers which are grown on Cu foil (25 um thickness) by the plasma enhanced chemical vapor deposition (PECVD) are sequentially transformed to the poly-di-methyl-siloxane (PDMS) substrate. Dry and wet transfer methods are individually employed for formation of the double layer graphene. This sensor geometry results a switching characteristic which shows ~900% conductivity change in response to the application of pulsed pressure of 5 kPa whose on and off duration is 3 sec. Additionally, the functional reliability of the sensor confirms consistent behavior with a 200-cycle test.

• Geomechanics and Engineering
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• v.38 no.3
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• pp.285-305
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• 2024

This study investigates the behaviour of hunchback retaining walls supporting unsaturated sandy backfill under active earth pressure conditions. Utilizing a horizontal slice method and a unified effective stress methodology, the influence of various factors on lateral earth pressure, including the position of the hunch along the wall, friction angles, and wall heights, is explored. The results suggest that relocating the hunch position from close to the wall's top to near its base leads to a significant decrease (ranging from 54% to 81%) in lateral earth pressure. However, as the hunch position transitions from near the top to mid-height, the point of application of active thrust shifts upward initially, then slightly downward as the hunch position approaches the toe. Notably, the reduction in lateral earth pressure is more pronounced for shorter wall heights and higher friction angles. Building upon these findings, an Artificial Neural Network (ANN)-based model is developed to accurately predict the lateral earth pressure coefficient and point of application, achieving R² values of 0.94 and 0.93, respectively. In addition, an analytical model based on Coulomb's earth pressure theory is presented and compared with ANN models. These models are anticipated to assist designers and practitioners in optimizing hunchback retaining walls for unsaturated backfill.

• 제어로봇시스템학회:학술대회논문집
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• 1994.10a
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• pp.100-105
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• 1994

In this paper, we discuss a method for design of an ambulance stretcher which call decrease blood pressure fluctuation caused by ambulance acceleration. Recently, a lot of stretchers which can isolate the vertical vibration to reduce body resonances (4-10 Hz) have been used during ambulance transport. However, we have found that blood pressure of a patient laying in the stretcher fluctuates when the ambulance accelerates or decelerates. Since the enforced change of the blood pressure may deteriorate the patent's condition, a stretcher to cancel head-to-foot acceleration and to decrease the blood pressure variation (BPV) is expected for safe transport. We propose a method to design a stretcher which is tilted according to an adequate angle to cancel head-to-foot acceleration by gravity when the ambulance accelerates or decelerates. A control method of the stretcher is constructed by means of simulation analysis using acceleration data measured during ambulance transport. It is confirmed that the active controlled stretcher proposed has good performance for the BPV reduction.

• Korean Journal of Optics and Photonics
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• v.5 no.4
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• pp.457-460
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• 1994

Dependence of saturation energy density and small signal gain coefficient on the active gas pressure in XeCl laser amplifier has been investigated. The saturation energy density was increased almost linearly as 1.3, 1.45, 2.0, and $2.3mJ/\textrm{cm}^2$ when the pressure of Xe and He were 30 and 2000 mb, and the pressure of HC] was varied as 34, 52, 73, and 92 mb. Whereas the small signal gain coefficient was measured to be 6.5, 7.5, 7.0, 7.0 %/cm, which shows that the small signal gain did not varies not so much.o much.

• Tribology and Lubricants
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• v.15 no.4
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• pp.304-313
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• 1999

High-speed rotors set a lot of high vibration and stability problems especially when the speed of rotation is going through the first or the second critical speed. The aim of this paper is to investigate the possibility of an active control of a rigid rotor with squeeze film damper which has a good configuration of easily controlled end seal clearances and/or adjustment of a feed pressure. A theoretical method is presented and some numerical results are compared with test measurements. Both results show that the vibration or bit sizes are decreased when the end seal gap decreases with constant supply pressure, and when the supply oil pressure increases with constant seal gap. The experimental results show also a pleasing similarity on both orbit sizes and their decrement ratio compared with theoretical analysis. The possibility of an active control with the squeeze film damper was verified by adjusting the seal gap and the supply pressure.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.1199-1213
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• 2011

Slurry type shield would be very effective for the tunnelling in a sandy ground, but low slurry pressure could cause a tunnel face failure or a ground settlement in front of the tunnel face. Thus, the stability of tunnel face could be maintained by applying an excess slurry pressure that is larger than the active earth pressure. However, the slurry pressure should increase properly because an excessively high slurry pressure could cause the slurry flow out or the passive failure of the frontal ground. It is possible to apply the high slurry pressure without passive failure if a horizontal impermeable layer is located in the ground in front of the tunnel face, but its location, size, and effects are not clearly known yet. In this research, two-dimensional model tests were carried out in order to find out the effect of a horizontal impermeable layer for the slurry shield tunnelling in a saturated sandy ground. As results, larger slurry pressure could be applied to increase the stability of the tunnel face when the impermeable layer was located in the ground above the crown in front of the tunnel face. The most effective length of the impermeable grouting layer was 1.0~1.5D, and the location was 1.0D above the crown level. The safety factor could be suggested as the ratio of the maximum slurry pressure to the active earth pressure at the tunnel face. It could also be suggested that the slurry pressure in the magnitude of 3.5~4.0 times larger than the active earth pressure at the initial tunnel face could be applied if the impermeable layer was constructed at the optimal location.