• Tribology and Lubricants
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• v.28 no.5
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• pp.240-245
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• 2012

In this study, we developed a new carrier finger to prevent scratches in a sheet metal forming line. The developed carrier finger was designed to have a streamlined shape with a larger radius of curvature at the edges, as well as a smaller contact area. To evaluate the scratch alleviation effect, a sliding contact analysis and scratch test using the pin on a plate wear tester were conducted for both the old and new carrier fingers. The results show that, for both transverse and longitudinal movements of the strip, the newly designed carrier finger reduces both the friction and scratch depth by its streamlined shape, which decreases the pressure spike at the edge.

• Tribology and Lubricants
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• v.25 no.1
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• pp.25-30
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• 2009

본 연구에서는 pin-on-disk 마찰 시험기를 통하여 Hexagonal 배열 $40{\mu}m$ Dimple 패턴의 효과를 실험하였다. 마찰 실험은 미끄럼 속도가 $0.06{\sim}0.34m/s$로 하였으며 마찰하중은 $20{\sim}100\;N$의 범위로 하였고, Dimple의 밀도는 $10{\sim}25%$의 범위로 제작하여 실험을 행하였다. 일반적으로 속도가 증가하고 하중이 감소할수록 마찰계수는 감소하는 경향을 나타내었으며, Dimple에 의한 마찰저감 효과는 속도가 $0.14{\sim}0.26m/s$의 범위에서 나타났다. $40{\mu}m$ Hexagonal 배열 Dimple 패턴의 마찰 특성에서는 밀도가 12.5%에서 가장 좋은 경향을 나타내었다.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.1
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• pp.111-116
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• 2001

A practical scheme to reduce failure of the PCB(Printed Circuit Board) of a monitor is introduced using deformed mode shape under mechanical shock. When the monitor is given critical shock loads, cracks are commonly initiated at the tip of a hole on the PCB. Accordingly, a deformed mode shape of the PCB is obtained using a FEM code to define a weak point on the PCB under mechanical shock, and then the position and direction of the hole is determined to prevent the failure at the critical mode shape. Also, the stress intensity factor around the weak point on the PCB is calculated to check the possibility of fracture by normal tensile stress. In conclusion, present research is useful to assist the practical design of components-layout on the PCB.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.12
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• pp.1245-1254
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• 2008

Proposing a method for the estimation of the social cost for global warming impact (external cost) is the aim of this paper. Both the endpoint approach and conjoint analysis were applied to estimating the social cost for global warming. The endpoint approach was used to assess the damage on the safeguard subjects by global warming due to the emission of greenhouse gases into the atmosphere. The conjoint analysis was used to estimate the economic values for safeguard subjects which measure the social preferences and willingness to pay (WTP) on safeguard subjects. The economic values of human health and social asset were estimated at 62,261,700 Won / DALY (yr) and 10,000 Won / 10,000 Won, respectively. Moreover, cost factors of GHGs were calculated by multiplying the damage factor which is quantified the unit damage on safeguard subject and the economic value. In the case of CO$_2$, the cost factor was calculated at 13.52 Won / kg (13,520 Won / ton). External cost of products or services can be calculated by multiplying the GHG inventory result of products or services by the cost factor of each GHG. inventory.

• Geotechnical Engineering
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• v.14 no.1
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• pp.109-126
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• 1998

The use of fly ash as a contaminant barrier material was studied. Mixing ratio of fly ash to bentonite to meet the requirements for landfill liners was determined. The hydraulic behavior exhibited by the fly ash-bentonite liner and the effects of CaO were investigated through hydraulic conductivity tests under various conditions and microscopic analyses including XRD, SEM, helium porosimetry, and image analysis. The hydraulic conductivity of compacted fly ash decreased with the addition of bentonite, which was due mainly to the expanding of bentonite and partly to the filling of voids by chemical reaction products among constituents of the artificial liner. Because of insufficient CaO content, and rich in content but low-reactive $SiO_2$ contained in the fly ashes used, pozzolanic reaction and resulting effects in the artificial liner were not significant. The reactions among constituting materials and their resulting effects on hydraulic conductivity were controlled not by the apparent amounts of each constituent, but by reaction activities of the materials in the artificial liner.

• Journal of the Korea Institute of Building Construction
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• v.14 no.5
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• pp.379-388
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• 2014

The purpose of this study is to investigate the effect of capsulated slurry phase change material (PCM) on the thermal crack in mass concrete by experimental work and FEM analysis. In this study, three conditions of samples were prepared for evaluating the level of hydration heat, i.e., a material condition, a cement paste condition and a concrete condition. Also, a compressive strength test was conducted for FEM inverse analysis. Based on the results of the experiment, exothermic function coefficients of concrete with encapsulated slurry PCM were deducted by the inverse analysis. After that, they applied to FEM analysis of the mass scale concrete structures. From the results of this experiment, $31^{\circ}C$ capsulated slurry PCM had no super cooling phenomenon in the material condition. In the cement condition, hydration heat decreased by 34.61J when PCM of 1g was mixed. In the concrete condition, PCM of 6% was deducted as the best level in hydration heat absorption. In FEM inverse analysis, rate coefficient of reaction gradually decreased when PCM mixing ratio increased. But, temperature-rise coefficient increased when PCM mixing ratio exceeded 6%. For the inversed exothermic function coefficients applying to large scale concrete structures, a thermal cracking index increased by 0.05 when PCM of 1% was mixed.

• Korean Chemical Engineering Research
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• v.60 no.4
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• pp.582-587
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• 2022

Biphasic solvents are attracting attention as energy-reducing solvents for capturing CO₂ from flue gas in combustion process. In this study, considering diethylenetriamine (DETA) and diethylethanolamine (DEEA) mixed solvents, one of the biphasic solvents by blending of two types of amines, the CO₂ absorption rates of DETA and DEEA was measured by wetted wall column. The effects of DETA and DEEA concentrations and operating temperature on the overall mass transfer coefficient were investigated. As a result, the overall mass transfer coefficient was proportional to the DETA concentration. However, in the case of the DEEA concentration, the effect was small and when the concentration was exceeded, the overall mass transfer coefficient decreased. The DETA aqueous solution showed little change in the overall mass transfer coefficient with the operating temperature, whereas the DEEA aqueous solution increased the overall mass transfer coefficient with the operating temperature. As a result of obtaining the observed reaction rate constant under the pseudo-first-order reaction assumption, it was found that the observed reaction rate constant in DETA aqueous solution was proportional to the DETA concentration, but DEEA did not fit the pseudo-first-order reaction assumption.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.05a
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• pp.185-187
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• 2012

In this paper, the MR fluid damper to the application of the paramagnetic (paramagnetic) particles dispersed in the MR fluid inside the magnet current caused by the MR damper using the principles of the internal fluid delivery yield stress variation is characterized in Silky. In other words, the current strength of the MR fluid damper according to the internal friction coefficient varies phenomenon is to use. The MR fluid damper to control the MCU that you want to use Microchip's dsPIC chips, and current control in order to improve performance by using the PWM and UART communication to an external monitor to monitor the entire system was designed. In this study using MR fluid dampers and dsPIC chip dehydration process happens when a washing machine vibration and noise, vibration and noise reduction sikidorok washing machine protection systems are proposed.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.5
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• pp.41-50
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• 2009

Following an earthquake, the major concerns for damaged buildings are their safety/risk in the event of aftershocks, and thus a quantitative damage assessment must be performed in order to evaluate their residual seismic capacity and to identify necessary actions for the damaged buildings. Post-event damage evaluation is therefore as essential for the quick recovery of a damaged community as pre-event seismic evaluation and strengthening of vulnerable buildings. The objective of this study is to develop a post-earthquake seismic evaluation method for RC frames with URM infill wall for typical school buildings. For this purpose, full-scale, one-bay, single-story specimens having different axial loads in columns are tested under cyclic loadings. During the tests, residual crack widths, which can also be found in damaged buildings, are measured in order to estimate the residual seismic capacity from the observed damage. In this paper, the relationship between the measured residual crack width and the residual seismic capacity is discussed analytically and experimentally, and reduction factors are proposed to estimate the residual seismic capacity based on the observed damage level.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.11
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• pp.1055-1063
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• 2012

Fluctuating wall pressures were measured using an array of 16 piezoelectric transducers beneath a turbulent boundary layer. The coating used in this experiment was an open-cell, urethane-type foam with a porosity of approximately 50 ppi. The ultimate objective of the coating is to provide a mechanical filter to reduce the wall pressure fluctuations. The boundary layer on the flat plate was measured by using a hot wire probe, and the CPM method was used to determine the skin friction coefficient. The wall pressure autospectra and streamwise wavenumber-frequency spectra were compared to assess the attenuation of the wall pressure field by the coating. The coating is shown to attenuate the convective wall pressure energy. However, the relatively rough surface of the coating in this investigation resulted in a higher mean wall shear stress, thicker boundary layer, and higher low-frequency wall pressure spectral levels compared to a smooth wall.