• Korean Journal of Radiology
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• v.20 no.5
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• pp.830-843
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• 2019

Objective: To examine the potential of intravoxel incoherent motion (IVIM) and blood oxygen level-dependent (BOLD) magnetic resonance imaging for detecting renal changes after iodinated contrast-induced acute kidney injury (CI-AKI) development in a diabetic rabbit model. Materials and Methods: Sixty-two rabbits were randomized into 2 groups: diabetic rabbits with the contrast agent (DCA) and healthy rabbits with the contrast agent (NCA). In each group, 6 rabbits underwent IVIM and BOLD imaging at 1 hour, 1 day, 2 days, 3 days, and 4 days after an iohexol injection while 5 rabbits were selected to undergo blood and histological examinations at these specific time points. Iohexol was administrated at a dose of 2.5 g I/kg of body weight. Further, the apparent transverse relaxation rate (R2^*), average pure molecular diffusion coefficient (D), pseudo-diffusion coefficient (D^*), perfusion fraction (f) were calculated. Results: The D and f values of the renal cortex (CO) and outer medulla (OM) were significantly decreased compared to baseline values in the 2 groups 1 day after the iohexol injection (p < 0.05). A marked reduction in the D^* values for both the CO and OM was also observed after 1 hour in each group (p < 0.05). In the OM, a persistent elevation of the R2^* was detected for 4 days in the DCA group (p < 0.05). Histopathological changes were prominent, and the pathological features of CI-AKI aggravated in the DCA group until day 4. The D, f, and R2^* values significantly correlated with the histological damage scores, hypoxia-inducible transcription factor-1α expression scores, and serum creatinine levels. Conclusion: A combination of IVIM and BOLD imaging may serve as a noninvasive method for detecting and monitoring CI-AKI in the early stages in the diabetic kidney.

• Journal of the Earthquake Engineering Society of Korea
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• v.16 no.1
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• pp.1-12
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• 2012

In this paper, the reduction factors to calculate the site coefficients of an embedded foundation are estimated, considering the effect of a poor backfill for the seismic design of a building built on an embedded foundation. This is determined by utilizing in-house finite element software, P3DASS, which has the capability of horizontal pseudo 3D seismic analysis with nonlinear soil. The 30m thick soil on stiff rock was assumed to be homogeneous, elastic, viscous and isotropic, and equivalent circular rigid foundations with radii of 10-70m were assumed to be embedded 0, 10, 20, and 30 m in the soil. Seismic analyses were performed with 7 bedrock earthquake records de-convoluted from the outcrop records; the scaling of the peak ground accelerations were to 0.1 g. The study results show that the site coefficients of a poor-backfilled foundation are gradually reduced as the foundation embedment ratio increases, except in the case of a small foundation embedded deeply in the weak soft soil. In addition, it was found that the deviation of the site coefficients due to the foundation size was not significant. Therefore, the typical reduction factors of an embedded foundation with poor backfill are proposed in terms of the shear wave velocity and site class. This is in order to find the site coefficients of an embedded foundation by multiplying the reduction factor by a site coefficient of a surface foundation specified in the design code. They can then be interpolated to determine the intermediate shear wave velocity.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.4
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• pp.1-15
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• 2010

In this study, the reduction factor of the code-defined site coefficient due to the embedment of a foundation was estimated for the seismic analysis of a building built on a soft soil site. This was done by utilizing the in-house finite element software P3DASS, which has the capability of pseudo 3D seismic analysis with nonlinear soil layers. A 30m thick soft soil site laid on the rock was assumed to be homogeneous, elastic, viscous and isotropic, and equivalent circular rigid foundations with radii of 10-70m were considered to be embedded at 0, 10, 20 and 30m in the soil layer. Seismic analyses were performed with 7 bedrock earthquake records deconvoluted from the outcrop records of which the effective ground acceleration was scaled to 0.1g. The study results showed that the site coefficients are gradually reduced except in the case of a small foundation embedded deeply in the weak soil layer, and it was estimated that the deviation of the site coefficients due to the foundation size was not significant. The standard reduction factor due to the foundation embedment were calculated adding the standard deviation to the average of 5 reduction factors calculated for 5 different foundation radii. Standard reduction factors for the site amplification factor were proposed for the practical amplification and the codes of KBC, etc., in accordance with the average shear wave velocity of the site, and the site class.

• Journal of the Korean Geotechnical Society
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• v.36 no.11
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• pp.7-20
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• 2020

In this study, the dynamic behavior of a single pile foundation was investigated by using an analytical and numerical studies. The emphasis was given on quantifying a function about the coefficient of dynamic horizontal subgrade reaction from 3D analysis. Based on the numerical analysis, a modified correction factor (α), which is used to obtain the coefficient dynamic horizontal subgrade reaction, was proposed by considering shear wave velocity of soil and confining stress. It was found that the prediction by pseudo-static analysis using the proposed coefficient is in good agreement with the general trends observed by dynamic analysis, and it represents a practical improvement in the prediction of behavior for pile foundations subjected to dynamic loads.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.170-170
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• 2017

기후변화 따른 스마트팜 돈사 외부 환경의 변화에 대응하고, 사육 환경을 능동적으로 개선하기 위한 연구가 수행 중이다. 돈사 내 열전달 요소 간 상호 역학성 분석을 위해서 고려해야할 사항은 입기구, 보온 등, 열풍기, 단열제, 위치, 방향, 돈사의 연평균 온도, 습도, 연중 일사량, 가축의 열복사 등 상호 복잡하게 연관되어 있는 물리량이다. 돈사 전체 열손실, 자연발생 에너지량, 강제발생 에너지량, 난방용량 등을 고려한 순간 열부하 산정을 위한 여러 방법 중 우선적으로 CFD(Computational Fluid Dynamics)를 이용하였다. 순간 열부하 산정을 위한 해석 도구 선정에 있어서 다양한 유체 및 기체 전산 유체역학 Solver(Fluent, Open-FOAM, Blender)를 고려하였다. 공간 Mech를 수행하기 위한 도구로는 공개 소프트웨어 인 FreeFem++ 3.51-4 (http://www.freefem.org)를 이용하였다. 이 과정에서 일부 기체 (암모니아)의 농도를 난수로 변화시키는 기법을 적용하여 가상적으로 돈사의 환경을 Pseudo 시뮬레이션 하였다. 결과적으로 Fluent에 비하여 OpenFOAM을 이용하여 얻은 열유동의 방향(속도)과 크기 백터가 상대적으로 크게 나타났다. Fluent가 시계열 상에서 혼합 기체 물리량 변화를 무시할 수 있는 안정되고 균일한 환경에 적합하기 때문인 것으로 판단되었다. Blender의 경우 Lattice Boltzmann methods 과 Smoothed-particle hydrodynamics 방법을 이용한 유체/입자 동력학 모델링을 제공함에 있어 시각적 효과를 강조하는 기능에 중점을 두었다. Fluent와 Blender에서 제공하는 해석 연산 모듈의 정확성 검증을 위해선 공간 분해능을 높인 정밀 계측 시스템을 이용하여 검증할 필요가 있다. Open-FOAM를 이용한 열부하 분석 수행이 상대적으로 높은 절대값을 보이는 특성은 열부하 제어 시스템의 Overshoot를 유발할 가능성이 있으므로 이에 대한 해석 모델의 보정이 추가적으로 필요할 것이다. CFD의 한계인 시간 복잡도를 낮추고 상대적으로 높은 시계열 분해능을 확보할 경우 돈사 내 환기시스템에 맞는 소요 환기량 실시간 산정이 가능해지고 외부기상 및 돈사내부 복사열을 활용함과 동시에 돈군 순환에 상응하는 실시간 열부하 관리 시스템 도출이 가능할 것이다.

• Journal of the Korean Institute of Landscape Architecture
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• v.28 no.6
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• pp.62-76
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• 2001

This study is to offer the basic information and materials for the restoration of the urban forest and the ecologically healthy and continuous green belt through the investigation and the analysis on the vegetation in Hwasan Park, Chonju-City. The flora of Hwasan Neighborhood park was composed of 86 families 230 genera, 261 species, 35 varieties, 1 formae or 298 Taxa. Among them, calculation of Pte-Q Index represented 0.60, Fisher's Index. Some characteristics of the plants in this area have represented such as Th-D1-R5 type in biological type, erect form(64.6%) in growth type, 30 taxa in naturalized plants. The life form spectra investigated from Hwasan neighborhood park was recognized as the following M"17.4%, N:11.4%, E:0.3%, Ch:0%, H:29.8%, G:6.7%, HH:0%, Th:34.2%. By the Z-M method 5 plant communities and 3 afforestation were recognized; Quercus variabilis community, Q.acutissima community, Q.serrata community, Sorbus alnifolia community, Pinus densiflora community, P.rigida afforestation, Robinia pseudo-acacia afforestation and Larix leptolepis afforestation. The actual vegetation map constructed on the grounds of the communities classified and other data. The pattern of successional trend of tree species might be suggested: L. leptoleipis, P. rigida and P. densifloralongrightarrowQ.variabilis and Q.acutissimalongrightarrowS.alnifolia and Q.serratalongrightarrowCarpinus tschonoskii community. Three measurements of species diversity (richness index(SR), Shannon-Wiener index(H'), evenness index(J')) and their relationship with community type were studied in the surveyed plant communities. Q.serrata community was higher in SR, H', J' than the other communities, whereas R.pseduo-acacia afforestation was low. Finally, The vegetation of the Hwasan neighborhood park must not allowed any more. Nothing ca be better than native states in preserving the ecosystems.tems.

• Journal of the Korean Institute of Gas
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• v.18 no.3
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• pp.20-30
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• 2014

To develop a unconventional gas reservoir, an analysis of tight rock property are required. Especially, conventional measurements are difficult to be applied to unconventional resources such as tight gas reservoir because the permeability are extremely low compared to a conventional gas reservoir. In this study, an apparatus was developed for measuring low permeability and porosity based on a pressure pulse decay method under unsteady state conditions. The apparatus was applied for measuring the porosity and permeability of tight sand core samples from Gyeongsang basin in Korea. As a validation of the measurement, regression analysis was carried out using the dimensionless pseudo-pressure between the measured data and analytical solution. The results show the correlation coefficients above 0.96. Therefore, it is believed that the apparatus has a high accuracy.

• YAKHAK HOEJI
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• v.38 no.3
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• pp.250-264
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• 1994

Omeprazole(OMZ)-cholestyramine(CHL) and various OMZ-Dowex resin complexes were prepared by reaction between OMZ and activated resins in 0.1N NaOH solution. And their physical properties were tested by means of infrared(IR), differential scaning caloimeter(DSC), X-ray diffraction. Chemical stability of OMZ-CHL was increased markedly compared with OMZ and the decomposition of OMZ-CHL followed the pseudo first-order kinetics and the rate constants were $2.743{\times}10^{-4}/day$ at $20^{\circ}C$, $7.83{\times}10^{-3}day^{-1}$ under 80% RH and $1.68{\times}10^{-2}day^{-1}$ under UV radiation, respectively. On the other hand, the rate constants of OMZ were $2.996{\times}10^{-4}day^{-1}$ at $20^{\circ}C$, $1.17{\times}10^{-2}day^{-1}$ under 85% RH, and $4.07{\times}10^{-2}day^{-1}$ under UV radiation, respectively. The rates of dissolution of OMZ-CHL bulk and OMZ-CHL tablet were 100% and more than 85% in 15 minutes, respectively, which were increased than OMZ base and OMZ-tablet. In the acute toxicological test, the value of oral $LD_{50}$(mouse) was 4.608 g/kg. OMZ-CHL was pelletized using lactose, polyethyle neglycol(PEG), D-sorbitol, Avicel PH 101, sodium laurylsulfate and polyvinylpyrrolidone(PVP) K-30, and enteric coated with HPMCP, Myvacet, acetone, ethanol and cetanol, of which dissolution rate was found to be more than 85% in 10 minutes. From the above results, it was found that OMZ-CHL is a useful means for development of new oral dosage forms of OMZ.

• Applied Chemistry for Engineering
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• v.7 no.4
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• pp.794-801
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• 1996

$TiO_2$ fine powders were synthesized via hydrolysis reaction of titanium isopropoxide in isopropanol solvent and the reaction rates were studied by use of UV spectroscopic method. The reactions were controlled to proceed to pseudo-first-order reaction in the presence of excess water in isopropanol solvent. The rate constants which varied with temperature and concentration of water were calculated by Guggenheim method. Reactions using $D_2O$ were also carried out to determine the catalytic character of water. n value of water molecules in transition state and the thermodynamic parameters showed that the reaction proceeded by $S_N2$ mechanism. $TiO_2$ powders synthesized in this reaction were almost spheric forms and had average particle size of $0.3{\mu}m$ diameter.

• Microbiology and Biotechnology Letters
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• v.48 no.4
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• pp.525-532
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• 2020

A continuous fermentation process was carried out to enhance hyaluronic acid (HA) production using Streptococcus zooepidemicus cells. During the 1st stage continuous operation from 8 h with a dilution rate of 0.029/h (D1), HA was produced in the range of 7.5-10 g/l. During the 2nd stage from 44 h with a dilution rate of 0.036/h (D2), HA production (8.28 g/l) was initially reduced to a small extent due to increase of dilution rate from D1 to D2, and then a new pseudo-steady state was formed within a few hours with a concurrent small variations of HA production. The HA amount produced during the latter part of the 2nd stage was stably maintained in the range of 8.28-9.48 g/l, about 4.7% less amount compared to the 1st stage. Due to 24% increase of dilution rate from D1 to D2, however, maximum volumetric productivity (DP) amounting to 0.341 g/l/h was obtained at 96 h during the 2nd stage. This maximum productivity obtained from the continuous culture turned out only a small increase (3%) as compared to the corresponding batch fermentation. However, it should be noted that, in the case of batch process, one run typically consists of serial stages of growth culture plus one final production culture. This implies that, if the continuous fermentation that practically needs no dead time necessary for the multi-stage growth cultures is run for longer period, the total amount of the accumulated HA would be far greater than the amount obtained from the corresponding batch culture performed for the identical period.