COMPARISON OF FLUX AND RESIDENT CONCENTRATION BREAKTHROUGH CURVES IN STRUCTURED SOIL COLUMNS

Kim, Dong-Ju Korean Society of Soil and Groundwater Environment 1997 지하수토양환경 Vol.2 No.2

오염물질 이동현상 연구에서는 침출수 혹은 잔존수농도 형태가 사용되는데 이의 선택은 모니터링 방법에 의존하게 된다. 파과곡선 실험에서 모니터링 농도 형태에 관한 선택은 임의적이며, 각 농도 형태에서 얻어진 운송 파라미터들은 동등하며 다공성매질의 수리적 특성을 각각 대표하는 것으로 알려져왔다. 그러나, 현장상태의 구조적 발달을 보이는 토양에서는 농도 형태별 운송계수의 동등성이 의문시 된다. 본 연 구에서는 불교란 현장시료(직경 20cm, 높이 20cm)에 대하여 두가지 농도 형태에 의한 파과곡선 실험을 시행하므로써 모니터링 방법에 따른 농도 형태와 그에 따른 운송 파라미터들을 비교분석 하였다. 침출수 농도와 잔존수 농도는 토양상부에서 20cm와 loom 떨어진 지점에서 EC-meter와 TDR 을 이용하여 각각 측정하였다. 연구결과, 침출수 농도는 잔존수 농도보다 첨두농도가 훨씬 높게 그리고 첨두농도의 운송시간이 짧게 나타났음을 알 수 있었다. 따라서 침출수농도곡선으로부터 추정된 운송파 라미터들은 잔존수농도곡선으로부터 추정된 수치들과 상당한 차이를 보였으며 그 차이는 CLT 모델보다 CDE 모델에서 더 크게 나타났다. 특히 CDE 모델에서는 침출수곡선으로부터 도출된 계수값들이 잔존수곡선으로부터 도출된 계수값들보다 훨씬 크게 나타났다. 이는 구조토양내에 존재하고 있는 대공극을 통한 오염물질 우회통과와 평형조건에서의 CDE 모델이 연구대상토양에서의 오염물질 이동현상을 표현하는데 부적합하였기 때문인 것으로 사료된다. 분자 분산에 대한 동수리학적 확산의 비와 Peclet number와의 상관관계를 나타내는 도표영역에서 두가지 농도는 모두 역학적 확산이 오염물질 운송을 좌우하는 영역에 속하였다. 그러나 분자분산은 토양내 대공극부분보다 matrix 부분에서의 오염물질 확산에 더 많은 기여를 하는 것으로 나타났으며 이는 공극유속과 확산계수사이에 존재하는 비선형성에 기인하기 때문인 것으로 사료된다. In many solute transport studies, either flux or resident concentration has been used. Choice of the concentration mode was dependent on the monitoring device in solute displacement experiments. It has been accepted that no priority exists in the selection of concentration mode in the study of solute transport. It would be questionable, however, to accept the equivalency in the solute transport parameters between flux and resident concentrations in structured soils exhibiting preferential movement of solute. In this study, we investigate how they differ in the monitored breakthrough curves (BTCs) and transport parameters for a given boundary and flow condition by performing solute displacement experiments on a number of undisturbed soil columns. Both flux and resident concentrations have been simultaneously obtained by monitoring the effluent and resistance of the horizontally-positioned TDR probes. Two different solute transport models namely, convection-dispersion equation (CDE) and convective lognormal transfer function (CLT) models, were fitted to the observed breakthrough data in order to quantify the difference between two concentration modes. The study reveals that soil columns having relatively high flux densities exhibited great differences in the degree of peak concentration and travel time of peak between flux and resident concentrations. The peak concentration in flux mode was several times higher than that in resident one. Accordingly, the estimated parameters of flux mode differed greatly from those of resident mode and the difference was more pronounced in CDE than CLT model. Especially in CDE model, the parameters of flux mode were much higher than those of resident mode. This was mainly due to the bypassing of solute through soil macropores and failure of the equilibrium CDE model to adequate description of solute transport in studied soils. In the domain of the relationship between the ratio of hydrodynamic dispersion to molecular diffusion and the peclet number, both concentrations fall on a zone of predominant mechanical dispersion. However, it appears that more molecular diffusion contributes to the solute spreading in the matrix region than the macropore region due to the nonliearity present in the pore water velocity and dispersion coefficient relationship.

챔버 내부의 질소 농도에 따른 3D프린팅 출력물의 인장 강도에 관한 연구

허용정,이송연 한국반도체디스플레이기술학회 2022 반도체디스플레이기술학회지 Vol.21 No.1

Scaffolds are the structures that safely protect sensors in various parts of the body. Because of scaffolds must protect sensors from load, the tensile strength of the scaffolds must be higher than 750 kgf/㎠. Currently, the tensile strength of scaffolds made with the 3d printer is 714 kgf/㎠. We confirm that the tensile strength of the scaffolds increase using air with high nitrogen concentration. In this study, we conducted experiments to find nitrogen concentrations in which the tensile strength of the specimen is higher than 750 kgf/㎠. The nitrogen control device and the nitrogen concentration sensor were installed in the chamber type 3d printer. The nitrogen concentration inside the 3d printer was changed by 5 % from 80 % to 100 %. Specimens of ASTM D 638 standard were produced under changed nitrogen concentration. We measured the tensile strength of specimens. We compared the tensile strength of specimens produced under each nitrogen concentration. We confirmed that when air with nitrogen concentration of 90 % was used, the tensile strength of scaffolds were 762 kgf/㎠.

폭 함수를 기반으로 한 Clark 모형의 매개변수 추정

박상현,김주철,정관수 한국수자원학회 2013 한국수자원학회논문집 Vol.46 No.6

본 연구에서는 Clark 모형의 시간-면적곡선의 구성 방법과 적용성을 검토하고 모멘트 원리에 의한 도달시간, 저류상수를 합리적으로 산정하기 위한 방법론을 고찰해 보았다. 격자 기반으로 폭 함수를 구성하고 운동과정을 순수 이류현상으로 가정하여 시간-면적곡선으로 사용하였다. 또한 도달시간과 저류상수는 모멘트 법의 원리에 따라 Clark 모형 구조에 적용하여 해석적으로 산정할 수 있는 방법을 제시하였다. 적용성 검토를 위해 (1) HEC-1에서 기본적으로 제공하는 좌우 대칭형상인 무차원 시간-면적곡선을 적용하고 매개변수 산정은 관측유출수문곡선과 계산된 유출수문곡선의 오차를 최소화하는 HEC-1의 최적화 기법 사용, (2) HEC-1에 폭 함수 기반의 시간-면적곡선을 적용하고 매개변수 산정은 HEC-1의 최적화 기법 사용, (3) 폭 함수 기반의 시간-면적곡선을 이용하여 모멘트 원리에 따라 매개변수를 직접 산정하는 방법을 적용하였다. 방법별로 산정된 Clark 모형의 매개변수들을 HEC-1을 이용하여 직접유출량을 산정하고 관측 직접유출량과 비교하여 얻은 결과는 다음과 같다. (1) 정량적으로 비교하기 위해 산정한 첨두유량과 첨두발생 시간의 상대오차 및 효율계수 E(Efficiency Coefficient)를 비교한 결과, 시간-면적곡선을 폭 함수로 대체하여 HEC-1으로부터 추정된 매개변수가 관측값을 잘 반영하였다. (2) Clark 모형의 올바른 적용을 위해서는 HEC-1에서 기본적으로 제공하는 좌우 대칭형상인 무차원 시간-면적곡선보다는 적용 대상유역의 배수구조가 적절하게 반영된 시간-면적곡선의 사용이 합리적일 것으로 판단된다. (3) 본 연구 방법은 첨두유량과 첨두시간의 상대오차 범위와 재현정도를 나타내는 효율계수를 비교하여 볼 때 대체로 양호하게 모의되었고, 대상유역별 유량측정성과인 하천평균유속과 비교했을 때 본 연구 방법이 다소 실제 유속에 접근하고 있음을 확인하였다. (4) 본 연구에서 모멘트 원리를 기반으로 제안한 매개변수 추정을 위한 방법은 유역의 이류현상과 저류현상을 정량적으로 계량할 수 있는 효율적인 관계식으로 사용할 수 있음을 확인하였다. (5) 본 방법에 의해 계산된 수문곡선이 대부분 관측수문곡선의 우측으로 왜곡되고 첨두유량은 과소평가 되는 것을 보이고 있다. 이것은 평균과 분산만을 고려하여 유역을 하나의 평균이송속도로 모의한 본 연구의 한계점으로 판단된다. 만약 모멘트의 왜곡도를 고려하고 유역을 지표면과 하천으로 나누어 평균이송속도를 모의한다면 물리적인 특성을 충분히 반영하여 매개변수를 추정 할 수 있을 것으로 판단된다. This paper presents the methodology for construction of time-area curve via the width function and thereby rational estimation of time of concentration and storage coefficient of Clark model within the framework of method of moments. To this end time-area curve is built by rescaling the grid-based width function under the assumption of pure translation and then the analytical expressions for two parameters of Clark model are proposed in terms of method of moments. The methodology in this study based on the analytical expressions mentioned before is compared with both (1) the traditional optimization method of Clark model provided by HEC-1 in which the symmetric time-area curve is used and the difference between observed and simulated hydrographs is minimized (2) and the same optimization method but replacing time-area curve with rescaled width function in respect of peak discharge and time to peak of simulated direct runoff hydrographs and their efficiency coefficient relative to the observed ones. The following points are worth of emphasizing: (1) The optimization method by HEC-1 with rescaled width function among others results in the parameters well reflecting the observed runoff hydrograph with respect to peak discharge coordinates and coefficient of efficiency; (2) For the better application of Clark model it is recommended to use the time-area curve capable of accounting for irregular drainage structure of a river basin such as rescaled width function instead of symmetric time-area curve by HEC-1; (3) Moment-based methodology with rescaled width function developed in this study also gives rise to satisfactory simulation results in terms of peak discharge coordinates and coefficient of efficiency. Especially the mean velocities estimated from this method, characterizing the translation effect of time-area curve, are well consistent with the field surveying results for the points of interest in this study; (4) It is confirmed that the moment-based methodology could be an effective tool for quantitative assessment of translation and storage effects of natural river basin; (5) The runoff hydrographs simulated by the moment-based methodology tend to be more right skewed relative to the observed ones and have lower peaks. It is inferred that this is due to consideration of only one mean velocity in the parameter estimation. Further research is required to combine the hydrodynamic heterogeneity between hillslope and channel network into the construction of time-area curve.

장입한 수소량이 Zr-2.5Nb 압력관의 K<SUB>1H</SUB>에 미치는 영향

김상재(Sang-jai Kim),김영석(Young-suk Kim),임경수(Kyung-soo Im),송택호(Song-taek Ho) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.8

The aim of this study was to obtain a better understanding of delayed hydride cracking (DHC) of Zr-2.5Nb pressure tube with hydrogen concentration. DHC tests were conducted at 280℃ on Curved Compact Tension (CCT) and Cantilever Beam (CB) specimens with 60, 80, 100 ppm H to determine the threshold stress intensity factor, K1H in axial and radial directions of the Zr-2.5Nb tube, respectively. Over a hydrogen concentraion range of 80~100 ppm, K1H for the Zr-2.5Nb tube 5.84 ㎫√m in the axial direction and 8.4 ㎫√m in the radial direction, both of which were constant independent of hydrogen concentraion, However, at 60ppm, K1H increased unexpectedly to a higher value. Based on the results, K1H for Zr-2.5Nb tube is discussed with the fracture surface and a supersaturated concentration of hydrogen.

조명 소프트웨어를 이용한 추적식 디쉬형 집광기의 배광분포 분석 및 자연채광 성능 예측

오승진(Oh Seung Jin),한현주,신상웅,천원기(Chun wongee) 한국태양에너지학회 2012 한국태양에너지학회 학술대회논문집 Vol.2012 No.3

Daylighting software is an important component to predict the performance of daylighting system in advance of a field demonstration study with installing them in buildings. PHOTOPIA is a powerful software to generate a candela distribution curve(CDC) of an active daylighting system like a tracking dish concentrator. With PHOTOPIA, a set of candela distribution curves was generated under clear sky conditions and different solar altitude angles. The candela distribution curves were then imported to RADIANCE for rendering and analysis on the daylighting performance of a tracking dish concentrator when it installed in a actual class room without windows. As a result, the daylight collection efficiency of the dish concentrator was 68.4% when we assumed that there was no tracking error. It was found that candela(cd) and total lumens(lm) increased with solar altitude rising, whereas the distribution angle was fixed. The illuminance uniformity on the work plane in the class room was relatively low, 0.12, while the illuminance uniformity on the area of 2.7m to which the light was illuminated was considerably high, 0.60. The maximum illuminance was 1,3401ux with a solar altitude angle of 80 degrees.

Comparison of Trough-Based and Area Under the Curve-Based Therapeutic Drug Monitoring of Vancomycin: An In Silico Study

윤응준,이현승,박형두,이수연 대한진단검사의학회 2022 Laboratory Medicine Online Vol.12 No.4

Background: Recent American guideline published in 2020 recommend using 24-h area under the curve (AUC)/minimum inhibitory concentration instead of vancomycin serum concentration (Ctrough) for vancomycin therapeutic drug monitoring (TDM). However, Ctrough-based TDM is widely used in clinical practice. Thus, this retrospective study aimed to compare Ctrough-based and AUC-based TDM. Methods: We evaluated patients’ TDM data with at least one vancomycin trough measurement. Patients younger than 18 years, admitted to an intensive care unit, or on renal replacement therapy were excluded. The variables of Ctrough-based and AUC-based TDM were simulated using MwPharm++ (Mediware, Czech Republic) with vancomycin two-compartment model. The therapeutic range was 400-600 mg*h/L and 15-20 mg/L for AUC and Ctrough, respectively. We evaluated the correlation between Ctrough and AUC, the attainment rate of AUC target range, and changes in vancomycin dose and Ctrough when AUC-based TDM is applied. Results: One hundred and four patients were enrolled. Ctrough and AUC correlated moderately (R=0.707, P <0.001). Among 31 patients with Ctrough of 15-20 mg/L, the AUC of only 18 patients was within the target range (18/31, 58.1%). In addition, most patients with Ctrough of 10-15 mg/L had the AUC within the target range (57/66, 86.4%). The respective vancomycin dose and Ctrough were expected to be significantly lower in AUC-based TDM simulation than those in Ctrough-based TDM simulationConclusions: Ctrough of 15-20 mg/L for vancomycin monitoring is not appropriate for attaining AUC target range. Targeting either AUC or lower Ctrough is recommended for vancomycin TDM.

한국의 미세먼지 발생요인 분석: 공간계량모형의 적용

강희찬 한국환경경제학회 2019 자원·환경경제연구 Vol.28 No.3

In this paper, we conducted panel data analysis considering spatial correlation between regions, which were not considered in previous papers in analyzing the causes of fine dust concentration in Korea. Many existing researchers implicitly assume the independence of the effects of incomes and other explanatory variables of adjoining countries(or regions). Using panel data on fine dust concentration, this paper has established that existing EKC can be established even when considering the spatial correlation of the region, and when these effects are not taken into account, it can be underestimated or overestimated on the effects and causes of fine dust concentration. 본 논문에서는 한국의 미세먼지 발생원인을 분석하는 과정에서 기존 논문에서는 고려하지 않았던 지역 간 공간상관성(Spatial correlation)을 고려한 패널계량분석을 진행하였다. 기존 환경쿠즈네츠곡선(EKC, Environmental Kuznets Curve)에 대한 연구들에서, 인접한 국가 및 지역 간에 오염물질의 상호영향이 존재할 가능성이 있음에도 각 유닛이 독립이라고 가정한다. 본 논문에서는 한국의 미세먼지농도에 대한 지역 패널데이터를 이용하여 기존 EKC가 지역의 상호상관성을 고려하는 때도 성립할 수 있으며, 이러한 영향을 고려하지 않았을 때 미세먼지농도의 원인에 대해 과소 혹은 과대 추정될 수 있음을 규명하였다.

MRSA 폐렴 환자에서 Vancomycin trough 농도 및 AUC24/MIC의 항 미생물학적 효과 비교

손기호 한국병원약사회 2013 병원약사회지 Vol.30 No.3

American Journal of Health-System Pharmacy (AJHP) recommended targeting vancomycin trough concentrations of 10 mg/L or more because of therapeutic failure and potential risk of developing vancomycin resistance. Therefore, new dosage guidelines that could achieve these higher targets were needed. However, these higher trough levels have potential risk, such as renal toxicity. The purpose of this study is to compare the antimicrobial effect of the trough vancomycin level and vancomycin area under the concentration-time curve from 0 to 24 h (AUC24)/minimum inhibitory concentration(MIC). A retrospective, observational study set within pharmacist-managed clinical pharmacokinetic service in a teaching hospital was performed. Patients with MRSA pneumonia and vancomycin therapy between November 2009 and July 2010 were included (n=45). No difference between the MRSA positive group (n=17) and the MRSA negative group (n=28) were showed in the demo-graphic data and vancomycin trough level (p=0.925). However significant difference between the MRSA positive group (n=17) and MRSA negative group (n=28) were showed in AUC24/MIC 666.97 (95% CI, 419.18-1,295.51) and 1272.21 (95% CI, 1,011.6-1,389.46) respectively. (p=0.025)In conclusion, targeted exposure using AUC24/MIC compared trough concentrations is a more realistic target in patients with MRSA pneumonia.

지니계수를 활용한 기초지방자치단체의 농촌어메니티 자원 분포 집중도 - 전북 순창군을 사례로 -

박재철 한국농촌건축학회 2011 농촌건축 : 한국농촌건축학회논문집 Vol.13 No.4

This study aims to understand the degree of inequality of surveyed rural amenity resources according to resources and region in basic self governing body by estimating the Gini Coefficient and Lorenz Curve. Case Study was performed in Sunchang basic self governing body which full survey of rural amenity resources was completed. The Gini Coefficient was applied to measure the concentration of amenity resources in 11 Eup-Myun regions, Sunchang county of Jeonbuk province. The results demonstrate significantly different variation according to Eup-Myun regions and amenity variables. This result would be used as a basic data for rational rural planning based on amenity resources through identifying distributional concentration of rural amenity resources in basic self governing body.

Modeling non-Fickian pollutant mixing in open channel flows using two-dimensional particle dispersion model

Park, Inhwan,Seo, Il Won Elsevier 2018 Advances in water resources Vol.111 No.-

<P><B>Abstract</B></P> <P>The non-Fickian particle dispersion model was developed in this study to model two-dimensional pollutant mixing in open channel flows. The proposed model represents shear dispersion using step-by-step arithmetic calculations, which consist of horizontal transport and vertical mixing steps, instead of using Fick's law. In the sequential calculations, the model directly applied the effect of vertical variations of both longitudinal and transverse velocities, whereas the Fickian dispersion model incorporates the effect of shear flow in the dispersion coefficients. Furthermore, in order to avoid the numerical diffusion errors induced by the grid tracking method of previously developed non-Fickian dispersion models, this model adopted the particle tracking technique to trace each particle. The simulation results in the straight channel show that the proposed model reproduced the anomalous mixing, which shows a non-linear increase of variance with time and large skewness coefficient in the initial period. However, in the Taylor period, the variance and skewness of the concentration curves approached the Fickian mixing. The simulation results in the meandering channel reveal that the proposed model adequately reproduced the skewed concentration–time curves of the experimental results whereas the Fickian dispersion model, CTM-2D, generated symmetrical curves. Further comparison between the simulation results and the tracer test results conducted in the Hongcheon River shows that the proposed model properly demonstrated the two-dimensional mixing without adopting Fick's law.</P>