• The Journal of the Petrological Society of Korea
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• v.24 no.3
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• pp.181-191
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• 2015

The Bakseok of Geunjeongjeon Hall in Gyeongbokgung Palace is platy floor stone acting as drainage, protected glaring and sliding. The Bakseoks were composed of anisotropic medium-grained biotite granite with a weak myrmekitic texture. Interpretation of transportation process for the Bakseok and original granite provenance trace of and analyze of identity based on ancient writings and detail field survey. As a result, the very similar granite with the Bakseok in lithology, composition mineral, texture and geochemical characteristics was found around Mt. Nakgasan in the Seokmodo Island. There were interpreted stonework process of the Bakseok used exfoliation granite dome with physical weathering properties in Seokmodo Island, to get platy stone economically stonework at the state level as a minimized on burden of supply and men power.

• Journal of the Semiconductor & Display Technology
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• v.7 no.4
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• pp.29-33
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• 2008

Rapid increase of integrity for recent semiconductor industry highly demands the development of removal technology of contaminated particles in the scale of a few microns or even smaller. It is known that the surface cleaning technology using $CO_2$ snow has its own merits of high efficiency. However, the detailed removal mechanism of particles using this technology is not yet fully understood due to the lack of sophisticated research endeavors. The detachment mechanism of particles from the substrates is known to be belonged in four types; rebounding, sliding, rolling and lifting. In this study, a modeling effort is performed to explain the detachment mechanism of a contaminant particle due to the rebounding caused by the vertical collision of the $CO_2$ snow. The Hertz and Johnson-Kendall-Roberts(JKR) theories are employed to describe the contact, adhesion and deformation mechanisms of the particles on a substrate. Numerical simulations are followed for several representative cases, which provide the perspective views on the dynamic characteristics of the particles as functions of the material properties and the initial inter-particle collision velocity.

• Journal of the Earthquake Engineering Society of Korea
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• v.18 no.4
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• pp.161-170
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• 2014

Newmark-type deformation analysis has rarely been done in Korea due to the popularity of simple pseudo-static limit equilibrium analysis and detailed time-history FE/FD dynamic analysis. However, the Korean seismic dam design code updated in 2011 prescribes Newmark-type deformation analysis as a major dynamic analysis method for the seismic evaluation of fill dams. In addition, a design PGA for dynamic analysis is significantly increased in the code. This paper aims to study the seismic evaluation of four existing large fill dams through advanced FEM/Newmark-type deformation analyses for the artificial earthquake time histories with the design PGA of 0.22g. Dynamic soil properties obtained from in-situ geo-physical surveys are applied as input parameters. For the FEM/Newmark analyses, sensitivity analyses are performed to study the effects of input PGA and $G_{max}$ of shell zone on the Newmark deformation. As a result, in terms of deformation, four fill dams are proved to be reasonably safe under the PGA of 0.22g with yield coefficients of 0.136 to 0.187, which are highly resistant for extreme events. Sensitivity analysis as a function of PGA shows that $PGA_{30cm}$ (a limiting PGA to cause the 30 cm of Newmark permanent displacement on the critical slip surface) is a good indicator for seismic safety check. CFRD shows a higher seismic resistance than ECRD. Another sensitivity analysis shows that $G_{max}$ per depth does not significantly affect the site response characteristics, however lower $G_{max}$ profile causes larger Newmark deformation. Through this study, it is proved that the amplification of ground motion within the sliding mass and the location of critical slip surface are the dominant factors governing permanent displacements.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.5 no.4
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• pp.47-63
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• 1994

An important parameter in characterizing mobile communication channel is delay spread. This paper presents the results of measured delay profiles and calculated distribution funcations of delay spread for typical cellular service environments at Taejon and vicinities. The measurement system uses 1023 chip length, 5 Mbps PN code and sliding correlation method. It has been evaluated by using commercial hardware channel simulator for reliability of out data. As results the value of mean delay spread is 2.08 $\mu\textrm{s}$for suburban area. 2.12 $\mu\textrm{s}$ for urban area and 1.3 $\mu\textrm{s}$ for national/local road. Delay spread is less then 3.4$\mu\textrm{s}$, 2.8$\mu\textrm{s}$ and 1.5 $\mu\textrm{s}$ for probability of 50% and 4.5$\mu\textrm{s}$, 4.2$\mu\textrm{s}$ and 2.9$\mu\textrm{s}$ for probability of 90% at each tested site. The difference of delay spread is within 7% between going and returning status along same street. In this experiment, we found delay spread for suburban area is larger than reported foreign test results.

• Journal of Ocean Engineering and Technology
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• v.29 no.2
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• pp.191-198
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• 2015

In this study, we proposed a new type of dual-buoy wave energy converter (WEC) exploiting multi-resonance and analyzed the experimental results from a model test in a 2-D wave flume. A dual-buoy WEC using multi-resonance has two advantages: high efficiency at the resonant frequencies and the potential to extend the frequency range available to extract wave power from the WEC. The suggested WEC was composed of an outer buoy and an inner buoy sliding vertically inside the outer buoy. As the power take-off device, a linear electric generator (LEG) consisting of permanent magnets and coils fixed at each buoy was adopted. Electricity was produced by the relative heave motion between the two buoys. To search for the optimal shape of a dual-buoy WEC, we conducted experiments on the heave motion of a two-body system in regular waves without an LEG installed. Model tests with six combinations of experimental models were conducted in order to find the motion characteristics of a dual-buoy WEC. It was found that model 2, which included a ring-shaped appendage to move the resonant frequency of the outer buoy toward a high value, showed a higher relative heave response amplitude operator (RAO) curve than model 1. In addition, the double-peak shape of the heave RAO curve shown for model 2 indicated the extension of the frequency range for extracting wave power in irregular waves.

• Journal of the Korean housing association
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• v.23 no.1
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• pp.79-88
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• 2012

The purpose of this study is to determine the personalizing characteristics of detached housing that reflect the housing needs according to the residents' participation in the back-to-countryside community village. For this study, 15 households of Jagun-maul at Namwon in Jeonbuk provided responses to the semi-structured questionnaire on housing consciousness, housing needs, and views on lifestyle. In addition, 15 plans were analyzed about the shape of the plan, the composition of LDK, the type of access, and the type of special space. The results were as follows. 1) The number of households under the elementary education stage was larger than the number of households above the middle education stage. Most of the households revealed the housing consciousness of 'house as resting place'. Households under the elementary education stage showed a housing consciousness for family-oriented life and households above the middle education stage showed a housing consciousness to interact with neighbors. 2) Households under the elementary education stage preferred LK style while households above the middle education stage preferred LDK style. Most of the floor plans had a front entrance and sliding door for the access from living room to garden. 3) Special spaces such as a loft, 'Ondolbang' (room with underfloor heating), study, maru, 'Toenmaru' (narrow wooden porch), family room, workroom, and toilet with outside door were arranged on each floor plan.

• International Journal of Fluid Machinery and Systems
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• v.6 no.4
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• pp.200-205
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• 2013

In order to investigate the characteristics of unsteady flow in a mixed flow pump guide vane under the small flow conditions, several indicator points in a mixed flow pump guide vane was set, the three-dimensional unsteady turbulence numerical value of the mixed flow pump which is in the whole flow field will be calculated by means of the large eddy simulation (LES), sub-grid scale model and sliding mesh technology. The experimental results suggest that the large eddy simulation can estimate the positive slope characteristic of head & capacity curve. And the calculation results show that the pressure fluctuation coefficients of the middle section in guide vane inlet will decrease firstly and then increase. In guide vane outlet, the pressure fluctuation coefficients of section will be approximately axially symmetrical distribution. The pressure fluctuation minimum of section in guide vane inlet is above the middle location of the guide vane suction surface, and the pressure fluctuation minimum of section in which located the middle and outlet of guide vane. When it is under the small flow operating condition, the eddy scale of guide vane is larger, and the pressure fluctuation of the channel in guide vane being cyclical fluctuations obviously which leads to the area of eddy expanding to the whole channel from the suction side. The middle of the guide vane suction surface of the minimum amplitude pressure fluctuation to which the vortex core of eddy scale whose direction of fluid's rotation is the same to impeller in the guide vane adhere.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.10a
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• pp.907-910
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• 2011

This paper proposes a character segmentation algorithm of steel plate images composed of adaptive binarization by the SCW (Sliding Concentric Windows) technique, the object labelling by CCA (Connected Component Analysis), and 2D projection method. The SCW technique carries out the grayscale-to-binary image conversion in consideration of local characteristics of images. The character decision algorithm followed by the labelling technique by CCA (Connected Component Analysis) determines the character area effectively reducing the noise effect. The 2D projection with horizontal and vertical directions produces a tight bounding box for a character based on the cross points. Experimental results indicate that the proposed algorithm segments the characters in steel plate images effectively. The proposed algorithm can be applied to the devices with limited resources due to its excellent performance and low complexity.

• Journal of Powder Materials
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• v.17 no.6
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• pp.456-463
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• 2010

This paper describes the results of the application of Cr-Diamond-like carbon (DLC) films for efficiency improvement through surface modification of spur gear parts in the hydraulic gear pump. Cr-DLC films were successfully deposited on SCM 415 substrates by a hybrid coating process using linear ion source (LIS) and magnetron sputtering method. The characteristics of the films were systematically investigated using FE-SEM, nano-indentation, sliding tester and AFM instrument. The microstructure of Cr-DLC films turned into the dense and fine grains with relatively preferred orientation. The thickness formed in our Cr buffer layer and DLC coating layer were obtained the 487 nm and $1.14\;{\mu}m$. The average friction coefficient of Cr-DLC films considerably decreased to 0.15 for 0.50 of uncoated SCM415 material. The hardness and surface roughness of Cr-DLC films were measured 20 GPa and 10.76 nm, respectively. And then, efficiency tests were performed on the hydraulic gear pump to investigate the efficiency performance of the Cr-DLC coated spur gear. The experimental results show that the volumetric and mechanical efficiency of hydraulic gear pump using the Cr-DLC spur gear were improved up to 2~5% and better efficiency improvement could be attributed to its excellent microstructure, higher hardness, and lower friction coefficient. This conclusion proves the feasibility in the efficiency improvement of hydraulic gear pump for industrial applications.

• Tribology and Lubricants
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• v.32 no.3
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• pp.101-105
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• 2016

Trap effect of groove is evaluated in a lubricating system using computational fluid dynamics (CFD) analysis. The simulation is based on the standard k-ε turbulence model and the discrete phase model (DPM) using a commercial CFD code FLUENT. The simulation results are also capable of showing the particle trajectories in flow field. Computational domain is meshed using the GAMBIT pre-processor. The various grooves are applied in order to improve lubrication characteristics such as reduction of friction loss, increase in load carrying capacity, and trapping of the wear particles. Trap effect of groove is investigated with variations in cross-sectional shape and Reynolds number in this research. Various cross-sectional shapes of groove (rectangular, triangle, U shaped, trapezoid, elliptical shapes) are considered to evaluate the trap effect in simplified two-dimensional sliding bearing. The particles are assumed to steel, and defined a single particle injection condition in various positions. The “reflect” boundary condition for discrete phase is applied to the wall boundary, and the “escape” boundary condition to “pressure inlet” and “pressure outlet” conditions. The streamlines are compared with particles trajectories in the groove. From the results of numerical analysis in the study, it is found that the cross-sectional shapes favorable to the creation of vortex and small eddy current are effective in terms of particle trapping effect. Moreover, it is found that the Reynolds number has a strong influence on the pattern of vortex or small eddy current in the groove, and that the pattern of the vortex or small eddy current affects the trap effect of the groove.