• Journal of Korean Society of Environmental Engineers
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• v.27 no.12
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• pp.1305-1310
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• 2005

As a way to the optimum design of the collector well lateral in riverbed filtration, experiments were performed using sand tanks which were connected to form a model lateral system. Measured were the residual hydraulic heads along the laterals, the discharge rates at each sand tank and the production rates at the collector well while the model laterals were operated with various scenarios of changing parameters including water level of the collector well, the lateral diameter and length, and the hydraulic conductivity of the sand. Results showed that riverbed filtration could be more efficient when the resistance in the lateral was weak compared with the resistance in the sand, which was indicated by the more flattened distribution of the residual hydraulic heads along the lateral. Results also showed that the discharge rate increased exponentially with the approach to the collector well, and that the exponent increased as the lateral diameter decreased and/or the hydraulic conductivity of the sand increased. It was also seen that the well production increased with the increase in the lateral length and diameter although the marginal productivity decreased. It could be concluded that the axial flow velocity in the lateral was an important factor governing the efficiency of a lateral in riverbed filtration and that the maximum entrance velocity to the collector well, over which the efficiency decreased drastically, was about 1 m/sec under the conditions of this study.

• Journal of the Korean Geotechnical Society
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• v.36 no.2
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• pp.17-28
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• 2020

With respect to the tensile strength of volcanic rocks in Jeju Island, a comparative study was conducted using the existing research results and the test results performed in this study. In addition, the characteristics and effectiveness of the cohesion and internal friction angle estimated from the Brazilian tensile strength and unconfined compressive strength of Jeju volcanic rocks were investigated. As results, the Brazilian tensile strength of Jeju volcanic rocks was closely related to absorption, and decreased exponentially as the absorption increased. It was confirmed that the internal friction angle was closely related to the ratio of unconfined compressive strength to Brazilian tensile strength (σ_c / σ_t), and increased logarithmically as the ratio of σ_c / σ_t increased. In addition, the ratios of σ_c / σ_t of Jeju volcanic rocks were in the range of 5~20 depending on the magnitude of internal friction angle. In the case of cohesion, it was closely related to the absorption and Brazilian tensile strength. The cohesion exponentially decreased as the absorption increased, such as the relation between the Brazilian tensile strength and absorption. It was confirmed that there was a linear relation between the cohesion and Brazilian tensile strength.

• Korean Journal of Food Science and Technology
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• v.28 no.3
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• pp.538-544
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• 1996

A highly viscous biopolymer from alkali-tolerant Bacillus sp. was purified and its rheological properties were studied. 1% (w/v) solution of purified biopolymer showed pseudoplastic fluid behavior with the yield stress similar to those of xanthan and guar gum, and its consistency index was exponentially dependent on concentration and temperature. The concentration dependency of consistency index exhibited two rectilinear plots with different slopes at 1% concentration and pseudoplastic property increased with the increase of biopolymer concentration. The biopolymer solution exhibited a low temperature dependency and the activation energy of flow was 1.16 kacl/g mol. The apparent viscosity was very dependent on the change of pH and the addition of salt. However, no organic solvent effects were observed effects of viscosity synergism with the addition of viscosifier were not observed.

• Food Science and Preservation
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• v.8 no.1
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• pp.102-108
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• 2001

Flow properties of the concentrated pigment solutions extracted from purple-fleshed sweet potatoes were determined using a cone and plate rotational viscometer for soluble solids concentration range of 25 to 65% at temperature range of 20 to 60 $^{\circ}C$. The purple-fleshed sweet potato pigment solutions exhibited Newtonian behavior. Temperature dependency for the viscosity of the solution followed the Arhenius relationship with activation energy values between 14.23 and 43.00 kJ/mol, which increased linearly with soluble solids concentration. A relationship between viscosity, temperature and soluble solids concentration was investigated. At the same temperature, the viscosity of the concentrated pigment solutions increased exponentially as the concentration increased with higher degree of such phenomena at lower temperatures.

• Journal of the Korean Geotechnical Society
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• v.16 no.5
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• pp.179-191
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• 2000

본 연구에서는 화강토 지반상의 자립식 diaphragm wall의 거동을 연구하기 위하여 벽체의 근입깊이비, 지하수위 및 굴착조건(연속 및 단계굴착)을 변화시키면서 원심모형시럼을 수행하였다. 원심모형실험시 지반굴착은 흙과 동일한 밀도로 혼합된 zine chloride 용액이 배수되도록 밸브를 조작하여 실시하였으며, 굴착에 의해 발생되는 지반의 변형괴 벽체의 변위 및 휨모멘트를 시간경과에 따라 측정하였다. 실험결과, 벽체의 근입깊이비가 증가함에 따라 벽체의 휨모멘트는 증가하는 반면, 굴착과정동안 배면측에서의 간극수압 감소속도는 감소하였다. 최종 굴착단계에서 굴착후 시간경과에 따른 침하량은 굴착과정중의 침하？에 비해 5~7% 정도를 나타내었다. 최대표면침하량과 벽체변위를 굴착깊이로 정규화한 결과 최대 침하량은 벽체 변위량의 0.8~1.2배9평균0.91배)사이에 분포하였다. 굴착깊이로 전규화한 벽체변위와 근입깊이와의 관계는 지수함수식으로 제안하였다. 파괴면은 직선적인 형태로 파괴면내의 배면측 지반은 벽체를 향하여 하향의 변위를 일으키면서 벽체의 회전에 의해 파괴되었으며, 퐈괴면의 각도는 66~72.5$^{\circ}$정도로 이론적인 파괴면의 각도보다 크게 평가되었다.

• Korean Journal of Materials Research
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• v.4 no.3
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• pp.312-318
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• 1994

In this paper the breakdown and dielectric characteristics of purified transformer oil dissolved with $SF_6$ Gas are investigated with a few decade MHz frequency voltage. The results are as follows. 1) High frequency current is a approximately proportional to the square root of high frequency voltage in purified transformer oil. 2) As frequency increase breakdown voltage decrease inversely proportional to the square root of frequency and the high frequency breakdown voltage is lower about 35 percentage than that of AC 3) The breakdown voltage of high frequency has a little increase with the pressure increase of dissolved $SF_6$, Air and Ar Gas. 4) As voltage freguency increases the value of the dielectric loss tangent has increased almost exponentially and the dielectric constant ($\varepsilon$) has tended to decrease with a slope[0.6% MHz]. 5) When dissolved with $SF_6$ Gas, oil electrical characteristics has more increased about 25% than in Air or Ar gas with high voltage frequency.

• Journal of the Korean Data and Information Science Society
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• v.28 no.6
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• pp.1257-1260
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• 2017

Single-person households recently have been rapidly increasing and one reason may be the increment in elderly single-person. Since the change of living patterns is relevant to the government policy direction, it is important to understand how single-person households are clustered and which factors have influence on them. In this study, we tried to detect spatial clusters of single-person households and low-income elderly single-person households after adjusting for deprivation index. A recently developed fused lasso for Poisson data was used for data analysis and we provided the details on how to use it in R. From these analysis results, we observed the effect of socioeconomic level on the clusters and explained the reason why spatial clusters are shown after adjusting for deprivation index.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.707-711
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• 2007

낙동강과 밀양강의 합류지점에 위치한 김해시 딴섬 지역의 지표면하 $25{\sim}35\;m$ 구간에 형성되어 있는 고투수성 충적층 내 염소이온의 수리분산특성을 연구하기 위한 수렴흐름 추적자시험(convergent flow tracer test)이 수행되었다. 추적자로는 IW-1공과 IW-2공에서 각각 염소이온 5kg이 순간주입(instantaneous injection) 되었으며, PW공에서 일정한 양수율(2,500 m3 /day)로 채수하면서 염소이온농도를 관측하였다. 염소이온 주입 후 경과시간에 따른 염소이온농도 자료를 이용하여 농도이력곡선과 누적질량회수곡선이 산출되었으며, 관측된 염소이온농도의 정규분포를 검증하기 위한 일반통계분석이 수행되었다. 그리고, 농도이력의 증가/감소 구간에서의 함수를 추정하였으며, 두 시험에서 동일한 시간에 관측된 염소이온농도의 상관성이 분석되었다. 본 현장에서 수행된 추적자시험에 의한 종분산지수의 추정은 CATTI 코드(Sauty and Kinzelbach, 1992)에 의해 해석되었다. 추정된 종분산지수는 IW-1공과 PW공 구간에서는 0.4152 m, IW-2공과 PW공 구간에서는 0.4158 m 로서 매우 유사한 값으로 나타났다. 이는 추적자시험이 수행된 충적층에서의 용질이송이 방사상으로 비교적 균일함을 의미하는 것이다. 본 연구에서 수행된 추적자시험의 규모(2 m)를 Xu and Eckstein(1995)이 제시한 방정식에 대입하여 산정된 종분산지수는 0.0458 m 이었다. 이러한 결과는, 본 연구지역에서 수렴흐름 추적자시험에 의해 추정된 고투수성 충적층의 종분산지수가 일반적인 자연대수층에 비해 9.1배 정도 높다는 것을 의미한다. 이는 시험대수층의 투수성이 매우 높아 염소이온의 용질이송이 매우 빠르게 발생되었기 때문이다. 본 연구에서 추정된 종분산지수를 Gelhar et al.(1992)의 연구 결과와 비교 분석한 결과에서도 시험규모에 비해 매우 높은 수리분산이 발생된 것으로 나타났다. 그리고 염소이온의 확산면적을 추정하기 위해, 수렴흐름 추적자시험에 의한 종분산지수와 시험대수층의 평균선형유속을 이용하여 종분산계수를 구하였다. 현장에서 수행된 양수시험에 의한 평균선형유속 22.44 m/day와 평균 종분산지수 0.4155 m를 적용하여 산정된 종분산계수는 $9.32\;m^2/day$이었다. 따라서, 시험부지 내 충적층에서 일정한 양수율$(2,500\;m^3/day)$로 지하수를 개발할 시에 양수정 주변지역으로 유입되는 염소이온의 확산면적은 1일 $9.32\;m^2$ 정도일 것으로 나타났다.

• Journal of Korea Port Economic Association
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• v.38 no.3
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• pp.1-13
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• 2022

The Busan-Ulsan-Gyeongsangmando(BuUlGyeong) megacity aims to grow into the second metropolitan area by strengthening the growth and connectivity of the southeast region in Korea. In order to analyze the linkage between port logistics and regional economic development, this study focused on the economic community of BuUlGyeong. The findings are as follows. First, it was found that vessel entry and departure had a positive (+) significant effect on cargo volume. Second, the cargo volume was found to have a preemptive effect on the vessel entry and exit ports and the composite index. Third, the composite Index was found to have a significant positive (+) effect on cargo volume. From the results of the variance decomposition, it can be confirmed that the composite index has a weak impact on ship entry/exit and cargo volume. Based on the above findings, some policy implications are derived. First, regional governments in BuUlGyeong should provide incentives to revitalize the maritime economy such as the expansion of maritime port infrastructure and encouraging investment. Second, since an increase in cargo transport volume at major national ports linked to the BuUlGyeong region has a positive (+) effect on economy. Therefore it is necessary to expand actively port marketing and regular service for the country and ports. Third, investments should be made continuously to expand the marine port infrastructure such as the expansion of facilities so that global shipping companies can continue to call megacities in BuUlGyeong ports for super-large ships and cruises.

• The Journal of Engineering Geology
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• v.18 no.4
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• pp.415-422
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• 2008

Pumping test was conducted to understand hydraulic conductivity for leaky confined aquifer with high permeability. Test aquifer was formed in $25{\sim}35\;m$ below ground surface at predetermined site of riverbank filtration which junction of Nakdong river and Milyang river in the Ttaan isle, Gimhae city, Korea Monitoring wells were located at intervals of 2 m and 5 m from pumping well in south-west direction (MW1 and MW2 wells) and northeast direction (MW3 and MW4 wells), respectively. Pumping test was continuously conducted for constant pumping rate of $2,500m^3/day$, hydraulic conductivity was estimated using AQTESOLV 3.5 program. Hydraulic conductivity were estimated to be $1.745{\times}10^{-3}m/sec$ for pumping well (PW), $2.452{\times}10^{-3}m/sec$ for between PW and MW1 wells, $2.161{\times}10^{-3}m/sec$ for between PW and MW2 wells, $2.270{\times}10^{-3}m/sec$ for between PW and MW3 wells and $2.591{\times}10^{-3}m/sec$ for between PW and MW4 wells. The function of hydraulic conductivity (K) as monitoring distance (d) were estimated to be logK = 0.0693logd - 2.671 for south-west direction (PW-MW1-MW2 line), logK = 0.0817logd - 2.655 for north-east direction (PW-MW3-MW 4 line). Scale exponent of hydraulic conductivity as test volume was estimated using Schulze-Makuch et al.(1999) method. Scale exponent of this aquifer was estimated to be 0.15. It means that test aquifer has very low heterogeneity. The radius of influence estimated using transmissivity, maximum groundwater level displacement, distance from pumping well and pumping rate during pumping test were 7.148 m for south-west direction and 6.912 m for north-east direction. The increasing rate of hydraulic conductivity from pumping well to maximum radius of influence were estimated to be 1.40 times for south-west direction and 1.49 times for north-east direction. Thus, heterogeneity of test aquifer was a little higher in north-east direction.