• Journal of Korean Society for Atmospheric Environment
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• 제20권E1호
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• pp.29-33
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• 2004

In environmental studies, decisions are often made on the analytical data indicating certain contaminants as being 'detected' or 'non-detectible.' Since detection limits are analytical method specific, one has to first review the concepts and definitions associated with analytical method systems and specifications. In this study, the experimental analytical values for a series of low level standards (for an ionic species) were used as an example to estimate two different method detection limits (MDL). The scores of EPA's MDL and Pallesen's MDL determined by real analytical scores are 0.0575 and 0.0561 mg/L, respectively for our nitrate data. These scores determined by two different MDL models are roughly similar, while there are apparent differences between two methods with respect to statistical and systematical procedure. However, determination of MDL for one's laboratory provides some practical applications which helps to assure one's regulating authorities that one's measured scores are accurate.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.1106-1116
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• 2008

Single-pole transmission structures which are supported by drilled shaft foundations are usually subjected to large overturning moments with modest vertical and lateral loads. To analyze the behavior of the drilled shaft under such loading conditions, an analytical model was developed based on beam-column and subgrade reaction methods. Field model tests were performed to calibrate the developed analytical model in which additional subgrade spring models were adopted. The field test results estimated from the calibrated analytical model were compared with those calculated by one spring model and other commercial program. According to the comparison study, the developed analytical model was proven to be a useful tool to analyze the laterally loaded behavior of foundations for single-pole structures.

• Structural Engineering and Mechanics
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• 제54권4호
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• pp.607-622
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• 2015

This paper presents a comparative study of analytical method and finite element method (FEM) for analysis of a continuous contact problem. The problem consists of two elastic layers loaded by means of a rigid circular punch and resting on semi-infinite plane. It is assumed that all surfaces are frictionless and only compressive normal tractions can be transmitted through the contact areas. Firstly, analytical solution of the problem is obtained by using theory of elasticity and integral transform techniques. Then, finite element model of the problem is constituted using ANSYS software and the two dimensional analysis of the problem is carried out. The contact stresses under rigid circular punch, the contact areas, normal stresses along the axis of symmetry are obtained for both solutions. The results show that contact stresses and the normal stresses obtained from finite element method (FEM) provide boundary conditions of the problem as well as analytical results. Also, the contact areas obtained from finite element method are very close to results obtained from analytical method; disagree by 0.03-1.61%. Finally, it can be said that there is a good agreement between two methods.

• Advances in Computational Design
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• 제5권1호
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• pp.55-89
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• 2020

For the first time, an accurate analytical solution, based on coupled three-dimensional (3D) piezoelasticity equations, is presented for free vibration analysis of the angle-ply elastic and piezoelectric flat laminated panels under arbitrary boundary conditions. The present analytical solution is applicable to composite, sandwich and hybrid panels having arbitrary angle-ply lay-up, material properties, and boundary conditions. The modified Hamiltons principle approach has been applied to derive the weak form of governing equations where stresses, displacements, electric potential, and electric displacement field variables are considered as primary variables. Thereafter, multi-term multi-field extended Kantorovich approach (MMEKM) is employed to transform the governing equation into two sets of algebraic-ordinary differential equations (ODEs), one along in-plane (x) and other along the thickness (z) direction, respectively. These ODEs are solved in closed-form manner, which ensures the same order of accuracy for all the variables (stresses, displacements, and electric variables) by satisfying the boundary and continuity equations in exact manners. A robust algorithm is developed for extracting the natural frequencies and mode shapes. The numerical results are reported for various configurations such as elastic panels, sandwich panels and piezoelectric panels under different sets of boundary conditions. The effect of ply-angle and thickness to span ratio (s) on the dynamic behavior of the panels are also investigated. The presented 3D analytical solution will be helpful in the assessment of various 1D theories and numerical methods.

• Structural Engineering and Mechanics
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• 제19권3호
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• pp.281-295
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• 2005

An analytical method is presented to solve the elastodynamic problem of finitely long hollow cylinder subjected to torsional impact often occurs in engineering mechanics. The analytical solution is composed of a solution of quasi-static equation satisfied with the non-homogeneous boundary condition and a solution of dynamic equation satisfied with homogeneous boundary condition. The quasi-static solution is obtained directly by solving the quasi-static equation satisfied with the non-homogeneous boundary condition. The solution of the non-homogeneous dynamic equation is obtained by means of finite Hankel transform on the radial variable, r, Laplace transform on time variable, t, and finite Fourier transform on axial variable, z. Thus, the solution for finitely long, hollow cylinder subjected to torsion impact is obtained. In the calculating examples, the response histories and distributions of shear stress in the finitely long hollow cylinder subjected to an exponential decay torsion load are obtained, and the results have been analyzed and discussed. Finally, a dynamic finite element for the same problem is carried out by using ABAQUS finite element analysis. Comparing the analytical solution with the finite element solution, it can be found that two kinds of results obtained by means of two different methods agree well. Therefore, it is further concluded that the analytical method and computing process presented in the paper are effective and accurate.

• 대한토목학회논문집
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• 제28권4B호
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• pp.413-419
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• 2008

본 연구에서는, 바닥의 수심이 반경의 임의 차수의 제곱 꼴로 표현되는 다양한 형태의 축 대칭 지형 위를 통과하는 장파의 해석해를 유도하였다. 첫 번째 지형은 둔덕 위에 원기둥 모양의 섬이 있는 경우이며 두 번째는 원형의 섬이 있는 경우이다. 해를 구하기 위하여 변수 분리법, Taylor 급수전개법 및 Frobenius 급수법을 사용하였다. 유도된 해석해를 기존에 유도된 해석해와 비교를 하여 그 정확성을 검증 하였다. 또한, 입사파의 주기, 둔덕의 반지름 및 차수를 가지는 경우에 대하여 분석하였다.

• 분석과학
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• 제37권5호
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• pp.271-279
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• 2024

Bisphenols and phthalates are endocrine-disrupting chemicals that are commonly used in packaging and as plasticizers. However, they pose health risks through ingestion, inhalation, and dermal contact. Accurate analysis of these pollutants is challenging owing to their low concentration and their presence in complex oil matrices. Therefore, they require efficient extraction and detection methods. In this study, an analytical method for the simultaneous quantification of bisphenols and phthalates in corn oil is developed. The dynamic multiple reaction monitoring mode of liquid chromatography-tandem mass spectrometry is used according to the different polarities of bisphenols and phthalates. The method is validated by assessing system suitability, linearity, accuracy, precision, homogeneity, and stability. The determination coefficients are higher than 0.99, which is acceptable. The percentage recovery and coefficient of variation of the accuracy and precision confirm that this analytical method is capable of simultaneously quantifying bisphenols and phthalates in corn oil. The bisphenols and phthalates in the formulations and pretreatment samples are stable for 7 d at room temperature and 24 h in an auto-sampler. Therefore, this validated analytical method is effective for the simultaneous quantification of bisphenols and phthalates in oils.

• 한국환경과학회지
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• 제23권2호
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• pp.181-192
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• 2014

In Korea, the chemical oxygen demand($COD_{sed}$) in freshwater sediments has been measured by the potassium permanganate method used for marine sediment because of the absence of authorized analytical method. However, this method has not been fully verified for the freshwater sediment. Therefore, the use or modification of the potassium permanganate method or the development of the new $COD_{sed}$ analytical method may be necessary. In this study, two modified $COD_{sed}$ analytical methods such as the modified potassium permanganate method for $COD_{Mn}$ and the modified closed reflux method using potassium dichromate for $COD_{Cr}$ were compared. In the preliminary experiment to estimate the capability of the two oxidants for glucose oxidation, $COD_{Mn}$ and $COD_{Cr}$ were about 70% and 100% of theoretical oxygen demand(ThOD), respectively, indicating that $COD_{Cr}$ was very close to the ThOD. The effective titration ranges in $COD_{Mn}$ and $COD_{Cr}$ were 3.2 to 7.5 mL and 1.0 to 5.0 mL for glucose, 4.3 to 7.5 mL and 1.4 to 4.3 mL for lake sediment, and 2.5 to 5.8 mL and 3.6 to 4.5 mL for river sediment, respectively, within 10% errors. For estimating $COD_{sed}$ recovery(%) in glucose-spiked sediment after aging for 1 day, the mass balances of the $COD_{Mn}$ and $COD_{Cr}$ among glucose, sediments and glucose-spiked sediments were compared. The recoveries of $COD_{Mn}$ and $COD_{Cr}$ were 78% and 78% in glucose-spiked river sediments, 91% and 86% in glucose-spiked lake sediments, 97% and 104% in glucose-spiked sand, and 134% and 107% in glucose-spiked clay, respectively. In conclusion, both methods have high confidence levels in terms of analytical methodology but show significant different $COD_{sed}$ concentrations due to difference in the oxidation powers of the oxidants.

• 분석과학
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• 제25권2호
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• pp.91-101
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• 2012

2010년부터 지정악취물질로 관리 중인 유기지방산은 큰 반응성과 그에 따른 낮은 회수율 등의 문제로 인해, 분석이 난해한 성분으로 알려져 있다. 악취공정시험기준에서는 대기 중에 존재하는 유기지방산을 분석하는 방법으로 알칼리함침필터법과 알칼리흡수용액법을 제시하고 있다. 본 연구에서는 유기지방산의 분석기법을 전반적으로 비교검토하였다. 그러나 이들 지정분석방법에 대한 객관적인 검증이 쉽지않다는 점을 감안할 때, 유기지방산의 새로운 대안 분석방안으로 고체흡착관-저온농축탈착법 등을 고려할 필요가 있다. 고체흡착관으로 시료를 채취하고 저온농축열탈착기를 이용하여 분석할 경우, 공정시험기준상에 제시한 분석방법들에 비해 상당히 간편하고 검정이 용이하다는 이점이 있다. 본 연구에서는 이러한 분석방법에 대한 고찰에 덧붙여, 표준시료의 준비, 시료의 채취단계, 최종적인 검출단계에 대한 부분에 대해서도 검토하였다. 유기지방산의 현장시료를 채취 및 분석하기 위해서, 용기채취법의 적용은 심각한 오차를 수반할 수 있다는 점을 확인하였다. 또한 현장에서 채취한 시료의 유기지방산을 분석할 때, GC/FID에 의존할 경우, 여러 가지 간섭 성분의 영향을 배제하기 어렵다. 따라서 유기지방산의 분석에는 GC/MS를 이용하여 정량뿐 아니라 정성적인 부분까지 동시에 검토하는 것이 중요하다.

• Journal of Microbiology and Biotechnology
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• 제34권8호
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• pp.1617-1626
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• 2024

Various antibiotic-resistant bacteria (ARB) are known to induce repeated pulmonary infections and increase morbidity and mortality. A thorough knowledge of antibiotic resistance is imperative for clinical practice to treat resistant pulmonary infections. In this study, we used a reads-based method and an assembly-based method according to the metagenomic next-generation sequencing (mNGS) data to reveal the spectra of ARB and corresponding antibiotic resistance genes (ARGs) in samples from patients with pulmonary infections. A total of 151 clinical samples from 144 patients with pulmonary infections were collected for retrospective analysis. The ARB and ARGs detection performance was compared by the reads-based method and assembly-based method with the culture method and antibiotic susceptibility testing (AST), respectively. In addition, ARGs and the attribution relationship of common ARB were analyzed by the two methods. The comparison results showed that the assembly-based method could assist in determining pathogens detected by the reads-based method as true ARB and improve the predictive capabilities (46% > 13%). ARG-ARB network analysis revealed that assembly-based method could promote determining clear ARG-bacteria attribution and 101 ARGs were detected both in two methods. 25 ARB were obtained by both methods, of which the most predominant ARB and its ARGs in the samples of pulmonary infections were Acinetobacter baumannii (ade), Pseudomonas aeruginosa (mex), Klebsiella pneumoniae (emr), and Stenotrophomonas maltophilia (sme). Collectively, our findings demonstrated that the assembly-based method could be a supplement to the reads-based method and uncovered pulmonary infection-associated ARB and ARGs as potential antibiotic treatment targets.