• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 1999년도 봄 학술발표회 논문집
• /
• pp.121-128
• /
• 1999

This paper presents a time domain method for soil-structure interaction analysis for seismic loadings. It is based on the finite element formulation incorporating analytical frequency-dependent infinite elements for the far field soil. The dynamic stiffness matrices of the far field region formulated using the present method in frequency domain can be easily transformed into the corresponding matrices in time domain. At first, the equivalent earthquake forces are evaluated along the interface between the near and the far fields from the free-field response analysis carried out in frequency domain, and the results are transformed into the time domain. An efficient procedure is developed for the convolution integrals to evaluate the interaction force along the interface, which depends on the response on the interface at the past time instances as well as the concurrent instance. Then, the dynamic responses are obtained for the equivalent earthquake force and the interaction force using Newmark direct integration technique. Since the response analysis is carried out in time domain, it can be easily extended to the nonlinear analysis. Example analysis has been carried out to verify the present method in a multi-layered half-space.

• Structural Engineering and Mechanics
• /
• 제52권5호
• /
• pp.971-995
• /
• 2014

The parts of semi-rigid connected and partially embedded piles in elastic soil, above the soil and embedded in the soil are called the first region and second region, respectively. The upper end of the pile in the first region is supported by linear-elastic rotational spring. The forth order differential equations of both region for critical buckling load of partially embedded and semi-rigid connected pile with shear deformation are established using small-displacement theory and Winkler hypothesis. These differential equations are solved by differential transform method (DTM) and analytical method and critical buckling loads of semirigid connected and partially embedded pile are obtained, results are given in tables and graphs are presented for investigating the effects of relative stiffness of the pile and flexibility of rotational spring.

• Geomechanics and Engineering
• /
• 제16권6호
• /
• pp.609-618
• /
• 2018

A new mechanical model for predicting the vibration of a pipe pile embedded in longitudinally layered visco-elastic media with radial inhomogeneity is proposed by extending Novak's plain-strain model and complex stiffness method to consider viscous-type damping. The analytical solutions for the dynamic impedance, the velocity admittance and the reflected signal of wave velocity at the pile head are also derived and subsequently verified by comparison with existing solutions. An extensive parametric analysis is further performed to examine the effects of shear modulus, viscous damping coefficient, coefficient of disturbance degree, weakening or strengthening range of surrounding soil and longitudinal soft or hard interbedded layer on the velocity admittance and the reflected signal of wave velocity at the pile head. It is demonstrated that the proposed model and the obtained solutions provide extensive possibilities for practical application compared with previous related studies.

• 분석과학
• /
• 제22권2호
• /
• pp.136-140
• /
• 2009

AMS (Accelerator Mass Spectrometry)를 이용한 방사성 탄소연대측정법으로 퇴적물 및 토양시료를 측정하기 위한 화학적 전처리법의 유기물 회수율을 개선하기 위하여, 초음파를 이용한 방법을 개발하였다. 일반적으로 널리 쓰이는 부식산 전처리법 중 단계 마다 사용되는 스터링법을 대신하여, 초음파 (ultrasonic)를 사용하고 초음파 출력, 반응 온도, 반응 시간 등 실험조건을 결정하였다. 유기물 함유량이 적어 연대측정이 불가능했던 시료에 대한 탄소 회수율이 6배 향상되어 다량의 시료를 얻기 힘든 연대측정분야에서는 매우 중요한 개선이 이루어졌다. 또한 동일 시료에 대해 초음파법과 스터링법으로 처리한 시료의 연대측정결과를 비교하여 초음파법이 회수율 향상 이외에는 연대측정결과에 영향을 미치지 않음을 확인하여 실용성이 있음을 증명하였다.

• 분석과학
• /
• 제29권6호
• /
• pp.261-268
• /
• 2016

TXRF는 시료전처리 없이 분말상 시료의 정량분석이 가능하여 토양시료를 효율적으로 분석할 수 있다. 기존의 내부표준법을 이용한 분석법은 매질 효과 및 형광신호의 겹침으로 인한 간섭 효과로 인해 정확도가 떨어진다. 이를 개선하기 위해 외부표준법을 적용하여 용액화한 토양시료와 분말상 토양시료를 분석하였다. 용액화한 토양시료의 경우 개별표준물질로 만든 표준용액으로 작성한 검량선으로 분석하였는데, 내부 및 외부표준법 간 유의미한 차이가 없었다. 반면 분말상 토양시료로 부유용액을 만들어 검량선을 작성한 후 이를 이용하여 분말상 토양시료를 분석한 결과, 전반적으로 외부표준법을 적용한 결과가 내부표준법의 그것에 비해 정확도가 높았다. 두 가지 표준토양시료로 교차검증한 결과, Al, Fe, K, Ca, Ti, Ba, Mn, Sr, Rb, Cu 등 10개의 원소들에 대해 ${\pm}20%$ 내외의 상대오차가 측정되었다.

• 한국지하수토양환경학회:학술대회논문집
• /
• 한국지하수토양환경학회 2005년도 INTERNATIONAL SYMPOSIUM ON SOIL & GROUNDWATER ENVIRONMENT
• /
• pp.235-237
• /
• 2005

• 한국지하수토양환경학회:학술대회논문집
• /
• 한국지하수토양환경학회 2001년도 추계학술발표회
• /
• pp.148-150
• /
• 2001

Solid-phase microextraction (SPME) was investigated to understand the BTEX extraction behavior of SPME in groundwater. Analytical procedure was conducted In both conventional and headspace mode. And the conventional direct extraction method and the headspace analysis method were compared. Data obtained with direct and headspace SPME were very similar and showed successful results. In headspace analysis, the linearity was better and RSD (relative standard deviation, %) was smaller than direct extraction.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2000년도 가을 학술발표회논문집(I)
• /
• pp.87-92
• /
• 2000

The real situation of an underground reinforced concrete(RC) structure with the surrounding soil medium subjected to seismic load is quite difficult to be simulated through an expensive work and, even if it is possible to arrange such an experiment, it will be too expensive. So development of analytical method can be applied usefully to seismic design and seismic retrofit through an analysis of seismic behavior and seismic performance evaluation. A path-dependent constitutive model for soil that can estimate the response of soil layer is indispensible for dealing with kinematic interaction of RC/soil entire system under seismic loads. And interface model which deals with the dynamic interaction of RC/soil entire system is also necessary. In this study, finite element analysis program that can consider path-dependent behavior of RC and soil, and interfacial behavior between RC and soil is developed for rational seismic analysis of RC/soil entire system. Using this program, nonlinear behavior of interface between RC and soil is analyzed, and the effect of interfacial behavior to entire system is investigated.

• 한국환경농학회지
• /
• 제17권4호
• /
• pp.371-378
• /
• 1998

Pesticide has played important role in Korean and Austrailian agriculture. In addition, pesticides are the most reliable tools pests in agriculture. Recently, it is highly recommended that the use of pesticide should be concerned with both atricultural and environmental aspect, also legislation on environmental contamination has been fortified to the world. Particularly, the attention on agrochemicals has been focused on the soil abuse and the water contamination at present time. In spite of this kind of concern, a few research about pesticides using in Australia and Korean have been conducted to their behaviors under australian and korean environment to avoid environmental contamination by pesticides. Thus, the research organizations need facilities to analyze the characteristics of each pesticide and the environmental fate of pesticides. The conventional analytical method to detect pesticides and their metabolites can not be overcome to reduce time, expenditure, and complexity of analysis even though the methods are accurate and precise. For example, High performance liquid chromatography(HPLC), and gas chromatography (GC) used until now are less choice detectors and often lower sensitive. In contrast to the conventional analytical methods, biosensors are so fast in analysis and has high productivity and analyze multi=sample simultaneously. Therefore, it is biosensing analytical method that we could consider as an alternative method intead of the conventional methods.

• 한국지하수토양환경학회지:지하수토양환경
• /
• 제9권3호
• /
• pp.33-37
• /
• 2004

본 실험에 사용된 토양은 유류 유출사고가 발생한 후 7년 동안 방치 되어왔던 지역에서 채취되었으며 정성분석을 수행한 결과 풍화된 형태의 경유로 오염된 사실이 확인되었다. 토양 중 경유의 정량은 1999년 7월에 개정된 토양오염 공정시험방법 (시험법 1)과 US EPA method 8015b (시험법 2)에 준하여 이루어졌으며, 또한 2002년 7월에 개정되어 현재 시행되고 있는 토양오염공정시험방법 (시험법 3)과의 비교를 위하여 일부 추가 시료에 대한 정량분석이 수행되었다. 시험법 1을 적용하였을 때 분석에 사용된 총 46개의 시료 중 4개의 시료에서만 유류성분이 검출되었으며 시험법 2를 적용하였을 때는 모든 시료에서 유류성분이 검출되었으며 43개 시료의 농도가 토양오염우려기준인 2000mg/kg을 초과하였다. 시험법 2와 3에 의하여 수행된 결과를 이용하여 1차 회귀직선식을 도출해보면, 기울기 값이 0.9845로 높은 정의 상관관계($r^2$=0.99)를 보여주었다. 이들 결과로 볼 때 시험법 2와 3은 시험법 1과 비교하여 토양 중 풍화가 진행된 경유를 정량 할 경우 보다 적절한 방법으로 판단되었으며 시험법 2와 시험법 3은 거의 같은 수준의 정확성과 재현성을 보여주었다.