• Proceedings of the Korean Information Science Society Conference
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• 2007.10d
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• pp.456-461
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• 2007

기존의 P2P기반의 분산컴퓨팅 시스템을 일반 응용수행자가 사용하기 위해서는 수동적으로 시스템에 위탁하여 수행하여 왔다. 이러한 구조에서 응용수행자가 자신이 원하는 응용을 계산도구로서 분산컴퓨팅 시스템을 활용하여 수행하고 최종 결과를 받아오는 것은 복잡하고 어려운 과정이었다. 본 논문에서는 이러한 과정을 간편화하고 분산컴퓨팅 시스템의 참여도를 높이기 위하여 웹 서비스 Open API를 사용한 개방형 분산컴퓨팅 시스템을 구현하였다. 본 논문은 국내의 P2P기반 분산컴퓨팅 시스템인 Korea@Home 데스크톱 그리드 시스템을 소개하고 이 시스템에서 효율적으로 Open API를 제공하기 위하여 REST 웹 서비스를 구현하고 응용수행자의 편의를 위한 인터페이스로 자바 클래스를 제공하였다. 응용수행자는 제공되는 인터페이스를 통하여 간단한 프로그래밍 지식으로 Korea@Home 데스크톱 그리드 시스템을 웹 서비스 방식으로 이용할 수 있다.

• Geophysics and Geophysical Exploration
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• v.18 no.2
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• pp.54-63
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• 2015

Petrophysical parameters such as porosity and fluid saturation which provide useful information for reservoir characterization could be estimated by rock physics model (RPM) using seismic velocity and resistivity. Therefore, accurate P-wave velocity and resistivity information have to be obtained for successful estimation of the petrophysical parameters. Compared with the individual inversion of electromagnetic (EM) or seismic data, the joint inversion using both EM and seismic data together can reduce the uncertainty and gives the opportunity to use the advantages of each data. Thus, more reliable petrophysical properties could be estimated through the joint inversion. In this paper, for the successful estimation of petrophysical parameters, we proposed an effective method which applies a grid-search method to find the porosity and fluid saturation. The relations of porosity and fluid saturation with P-wave velocity and resistivity were expressed by using RPM and the improved resistivity distribution used to this study was obtained by joint inversion of seismic and EM data. When the proposed method was applied to the synthetic data which were simulated for subsea reservoir exploration, reliable petrophysical parameters were obtained. The results indicate that the proposed method can be applied for detecting a reservoir and calculating the accurate oil and gas reserves.

• Journal of Soil and Groundwater Environment
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• v.21 no.6
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• pp.179-191
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• 2016

In addition to the measurement of the concentration of soil contaminants, the new idea of indicative parameters was proposed to validate the remedial works through the monitoring for the changes of soil characteristics after applying the clean up technologies. The parameters like CFU (colony forming unit), pH and soil texture were recommended as indicative parameters for land farming. In case of soil washing, water content and the particle size distribution of the sludge were recommended as indicative parameters. The sludge is produced through the particle separation process in soil washing and it is usually treated as a waste. The parameters like water content, organic matter content, CEC (cation exchange capacity) and CFU were recommended as indicative parameters for the low temperature thermal desorption method. Besides the indicative parameter, sampling methods in stock pile and the optimal minimum amount of composite soil sample were proposed. The rates of sampling error in regular grid, zigzag, four bearing, random grid methods were 17.3%, 17.6%, 17.2% and 16.5% respectively. The random grid method showed the minimum sampling error among the 4 kinds of sampling methods although the differences in sampling errors were very little. Therefore the random grid method was recommended as an appropriate sampling method in stock pile. It was not possible to propose a value of optimal minimum amount of composite soil sample based on the real analytical data due to the dynamic variation of $CV_{fund{\cdot}error}$. Instead of this, 355 g of soil was recommended for the optimal minimum amount of composite soil sample under the assumption of ISO 10381-8.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.1
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• pp.8-18
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• 2000

We presented a BGA(Ball Grid Array) package for RF circuit modules and extracted its electrical parameters. As the frequency of RF system devices increases, the effect of its electrical parasitics in the wireless communication system requires new structure of RF circuit modules because of its needs to be considered of electrical performance for minimization and module mobility. RF circuit modules with BGA packages can provide some advantages such as minimization, shorter circuit routing, and noise improvement by reducing electrical noise affected to analog and digital mixed circuits, etc. We constructed a BGA package of ITS(Intelligent Transportation System) RF module and measured electrical parameters with a TDR(Time Domain Reflectometry) equipment and compared its electrical parasitic parameters with PCB RF circuits. With a BGA substrate of 3${\times}$3 input and output terminals, we have found that self capacitance of BGA solder ball is 68.6fF, and self inductance 146pH, whose values were reduced to 34% and 47% of the value of QFP package structure. S11 parameter measurement with a HP4396B Network Analyzer showed the resonance frequency of 1.55GHz and the loss of 0.26dB. Routing length of the substrate was reduced to 39.8mm. Thus, we may improve electrical performance when we use BGA package structures in the design of RF circuit modules.

• Wind and Structures
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• v.26 no.5
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• pp.331-341
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• 2018

A numerical study on the flow over a square cylinder in the vicinity of a wall is conducted for different Couette-Poiseuille-based non-uniform flow with the non-dimensional pressure gradient P varying from 0 to 5. The non-dimensional gap ratio L (=$H^{\ast}/a^{\ast}$) is changed from 0.1 to 2, where $H^{\ast}$ is gap height between the cylinder and wall, and $a^{\ast}$ is the cylinder width. The governing equations are solved numerically through finite volume method based on SIMPLE algorithm on a staggered grid system. Both P and L have a substantial influence on the flow structure, time-mean drag coefficient ${\bar{C}}_D$, fluctuating (rms) lift coefficient ($C_L{^{\prime}}$), and Strouhal number St. The changes in P and L leads to four distinct flow regimes (I, II, III and IV). Following the flow structure change, the ${\bar{C}}_D$, $C_L{^{\prime}}$, and St all vary greatly with the change in L and/or P. The ${\bar{C}}_D$ and $C_L{^{\prime}}$ both grow with increasing P and/or L. The St increases with P for a given L, being less sensitive to L for a smaller P (< 2) and more sensitive to L for a larger P (> 2). A strong relationship is observed between the flow regimes and the values of ${\bar{C}}_D$, $C_L{^{\prime}}$ and St. An increase in P affects the pressure distribution more on the top surface than on bottom surface while an increase in L does the opposite.

• Progress in Medical Physics
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• v.26 no.4
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• pp.215-222
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• 2015

In this work, we performed a proof-of-concept experiment for phase-contrast x-ray imaging (PCXI) based on a single antiscatter grid and a polychromatic x-ray source. We established a table-top setup which consists of a focused-linear grid having a strip density of 200 lines/inch, a microfocus x-ray tube having a focal-spot size of about $5{\mu}m$, and a CMOS-type flat-panel detector having a pixel size of $48{\mu}m$. By using our prototype PCXI system and the Fourier demodulation technique, we successfully obtained attenuation, scattering, and differential phase-contrast images of improved visibility from the raw images of several selected samples at x-ray tube conditions of $90kV_p$ and 0.1 mAs. Further, fusion image (e.g., the attenuation+the scattering) may have an advantage in displaying details of the sample's structures that are not clearly visible in the conventional attenuation image. Our experimental results indicate that single-grid-based approach seems a useful method for PCXI with great simplicity and minimal requirements on the setup alignment.

• Horticultural Science & Technology
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• v.31 no.6
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• pp.821-827
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• 2013

The purpose of this study was to investigate the effects of three kinds of horticultural activities (HAs) on attention concentration of elementary students. We selected 20 students using a Wee Class counseling office at J elementary school in Yeongcheon, and divided them into experimental and control groups composed of ten students each. The experimental group participated in three HAs including flower arrangement, planting, and pressed flower. Each HA was composed of three sessions and a session proceeded for a week. For the examinations of attention concentration, two groups responded the questionnaires before a week of the first session and at the end of the 9th session, only the experimental group participated in the measurement using grid by Harris before a week of the first session and at the end of each HA every week. The results of questionnaire survey showed that the scores of problem in emotion and problem in controlling, and the total score decreased 9.2, 7.8, and 19.0 points, respectively (P < 0.05), indicating that the attention concentration of the experimental group improved compared with the control. In the measurements using grid by Harris, the flower arrangement, planting, and pressed flower activities increased the scores by 2.22, 2.49, and 2.41 points compared with the pre-HA of 6.00, respectively (P < 0.05), that means the improvements of attention concentration. At the post-HAs, the flower arrangement, planting, and pressed flower activities increased the scores by 1.12, 1.39 and 1.31 points compared with the control group of 7.10, respectively (P < 0.05). In conclusion, the indoor HAs improved the attention and concentration of elementary students irrespective of kind of activities.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.6
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• pp.481-486
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• 2010

ENIG (electroless Ni immersion gold) is one of surface finishing which has been most widely used in fine pitch SMT (surface mount technology) and BGA (ball grid array) packaging process. The reliability for package bondability is mainly affected by interfacial reaction between solder and surface finishing. Since the behavior of IMC (intermetallic compound), or the interfacial reaction between Ni and solder, affects to some product reliabilities such as solderability and bondability, understanding behavior of IMC should be important issue. Thus, we studied the properties of ENIG with P contents (9 wt% and 13 wt%), where the P contents is one of main factors in formation of IMC layer. The effect of P content was discussed using the results obtained from FE-SEM(field-emission scanning electron microscope), EPMA(electron probe micro analyzer), EDS(energy dispersive spectroscopy) and Dual-FIB(focused ion beam). Especially, we observed needle type irregular IMC layer with decreasing Ni contents under high P contents (13 wt%). Also, we found how IMC layer affects to bondability with forming continuous Kirkendall voids and thick P-rich layer.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.1
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• pp.25-31
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• 2010

In this study, we investigated the morphology and thermal stability of interfacial phases in joint between lead free solder(Sn-3.0Ag-0.5Cu) and electroless Ni-W-P under bump metallizations(UBM) with different tungsten contents as a function of thermal aging. Content of phosphorus of each deposits was fixed at 8 wt.%, and content of tungsten was variated each 0, 3, 6 and 9 wt.%. Specimens were prepared by reflowing at $255^{\circ}C$, aging range was $200^{\circ}C$ and up to 2 weeks. After reflow process, in the electroless Ni(W)-P/solder joint, the interfacial intermetallic compound(IMC) was showed both $(Cu,Ni)_6Sn_5$ and $(Ni,Cu)_3Sn_4$. UBM and generated IMC at the interface of lead free solder was proportionally increased with aging time. The thickness of IMC was increased because the generation rate of $Ni(W)_3P$ decreased with increasing contents of W.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.203-210
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• 2003

격자망식 전선배치에 의한 전기비저항 측정기법을 이용한 침출수 누출감지시스템을 개발하여 그 적용성을 평가하기 위하여 현장모형시험을 수행하였다. 현장모형시험을 수행한 결과 침출수 누출지점에서 전기비저항이 크게 감소하여 누출지점을 정확하게 감지할 수 있었다. 격자망식 전선배치에 의한 전기회로적인 효과로 인하여 전기비저항이 감소된 지점과 동일 전선상에 연결된 다른 센서에서의 측정값도 다소 감소하는 경향을 나타내었다. 이를 보정하기 위하여 P-SPICE를 이용하여 전기회로 시뮬레이션을 수행하여 전기회로 효과를 정량적으로 평가하였다 P-SPICE 시뮬레이션의 결과를 토대로 보정계수를 도출하여 현장모형시험결과를 보정하였으며, 보정된 겉과에 의하면 전기회로적 특성에 의한 영향을 효과적으로 제거되어 누출지점에서의 전기비저항 감소가 명확하게 나타났다.