• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.732-739
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• 2005

The determination of sound pressure radiated from periodic plate structures is fundamental in the estimation of noise level in aircraft fuselages or ship hull structures. As a robust approach to this problem, here a very general and comprehensive analytical model is developed for predicting the sound radiated by a vibrating plate stiffened by periodically spaced orthogonal symmetrical beams subjected to a sinusoidally time varying point load. In this these, we experiment with the numerical analysis using the space harmonic series and the SYSNOISE for measuring the vibration mode and character of response caused by sound radiation with adding the harmonic point force in the thin isotropic plate supported by the rectangular lattice reinforcement. We used the reinforcements, beams of open type section like the style of 'ㄷ' letter; the space of the beams were chosen to be 0.2m, 0.3m, 0.4m. We studied the behavior of sound pressure levels, analysis of vibration mode between support points, connection between frequency function and sound pressure levels, and connection between position function and sound pressure levels.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.10
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• pp.923-930
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• 2010

Finite element models of dynamic systems can be updated in two stages. In the first stage, mass and stiffness matrices are updated neglecting damping, and in the second stage, damping matrices are estimated with the mass and stiffness matrices fixed. Three methods to estimate damping matrices for this purpose are proposed in this paper. The methods include one for proportional damping systems and two for non-proportional damping systems. Method 1 utilizes orthogonality of normal modes and estimates damping matrices using the modal parameters extracted from the measured responses. Method 2 estimates damping matrices from impedance matrices which are the inverse of FRF matrices. Method 3 estimates damping using the equation which relates a damping matrix to the difference between the analytical and measured FRFs. The characteristics of the three methods are investigated by applying them to simulated discrete system data and experimental cantilever beam data.

• Journal of Advanced Navigation Technology
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• v.8 no.2
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• pp.155-162
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• 2004

Recently, significant interest is shown to creation rather inexpensive global systems communications on base of Low-Earth-Orbit Satellite Networks (LEOSN). One of problems of design and creation LEOSN is development of the stream control methods and estimation it's efficiency in such networks. The given problem is complicated, that the topology of the satellite networks varies in time. It essentially hinders the analytical decision of the given problem. An effective way of overcoming of these difficulties is simulation modeling. For realization of research experiments on learning the information streams routing algorithms in LEOSN a special program complex SANET was developed. In the given paper principles of development of LEOSN simulation models and architecture of the manager by the process of a simulation modeling of the unit are considered. Methods of promotion of modeling time and architecture of a simulator complex offered in the article allow to boost essentially efficiency of simulation analysis and to ensure simulation modeling of the satellite networks consisting of several hundreds space vehicles.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.294-294
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• 2018

복잡한 수문 수리지질학적 조건을 고려할 수 있는 SWAT-MODFLOW 지표수-지하수 통합모형과 대수층-하천-양수정 시스템을 단순화한 Hunt (1999) 해석해를 죽산천 인근 지역에 각각 적용하여 지하수 양수로 인한 하천수 감소량을 모의하고 그 결과를 비교하였다. 하천으로부터 약 1 km 이내에 위치한 천부 지하수 관정들 중에서 취수계획량이 $100m^3$/일을 초과하는 18개의 관정을 선별하고 지하수 양수량 대비 하천수 감소량(하천수 감소비)을 산정한 결과 대부분의 관정에서 해석해와 모델링 결과의 차이가 0.2 미만으로 매우 작은 것으로 나타났다. 따라서 해석해가 하천-대수층 시스템을 단순화한 조건에 대해 유도되었음에도 불구하고 정밀한 모델링에 준하는 결과를 나타낼 수 있는 것으로 분석되었다. 그러나, 양수기간이 장기화되거나 하천과 관정간의 이격거리가 증가함에 따라 해석해와 모의결과의 차이가 다소 증가하는 경향을 나타내었다. 해석해가 대수층 저류량의 감소와 하천수량의 감소가 장기적으로 균형을 이루는 동적 평형 상태를 구현할 수 없고 하천수위의 급격한 변화에 따른 하천수와 지하수간의 상호 교환량의 불규칙한 패턴 또한 모사할 수 없는 한계가 있지만 양수기간 5년 이내의 하천수 감소량의 평균적인 거동은 수치모의 결과와 유사한 것으로 평가되었다.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.327-327
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• 2016

하천 인근에서 지하수를 채수할 경우 지하수위 저하로 인해 하천으로의 지하수 유출이 감소하거나 하천수가 역으로 지하수계로 유입되어 하천수 감소(stream depletion) 현상이 발생한다. 이러한 지하수 양수로 인한 하천수 감소량을 산정하기 위한 방법으로 현지 계측, 수치해석 모델링, 해석해 적용 등이 있으며, 이 중에서 해석해를 이용하는 방법은 실제 하천수-지하수 연계시스템을 단순화한 조건에서 유도되었다는 단점이 있지만 비용이나 시간적 측면에서는 가장 유리하다. 본 연구에서는 Hunt(1999)가 개발한 해석해를 전산프로그램화하고 이를 하천변에 위치한 실제 지하수 관정 109개에 적용하여 양수로 인한 지하수위 강하 및 하천수 감소량을 산정하여 대수층 및 하천의 수리특성, 하천과 관정간의 이격거리에 따른 변동 특성을 분석하였다. Hunt 해석해로 양수 시간에 따른 하천수 감소량을 계산한 결과, 양수후 5년 뒤에는 지하수 양수량 대비 하천수 감소량의 비율이 80%를 초과하는 관정이 대부분인 것으로 나타났으며, 특히 수리확산계수가 $1,000m^2/d$를 넘고 하천고갈인자(Stream Depletion Factor, SDF)값이 100 보다 작은 범위에서는 양수의 영향이 크게 발생하는 것으로 분석되었다.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.220-220
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• 2019

천부대수층-심부대수층-하천-양수정 시스템에 대해 개발된 Ward & Lough 해석해와 국내 시험유역을 대상으로 개발된 양수량 대비 하천수 감소량 산정공식 (한강홍수통제소, 2018)을 광주천인근에 실제로 위치한 지하수 관정에 적용하여 지하수 취수로 인해 하천의 수량에 미치는 영향을 분석하였다. 분석 대상관정은 하천에서 약 67 m 떨어진 공업용수 공급을 위한 지하수개발 이용시설로서 착정심도 100 m, 착정구경 150 mm, 취수계획량 $200m^3$/일, 수중펌프 5 Hp 등의 시설제원을 가진다. 해석해 및 경험공식 적용을 위한 기본 입력자료로 투수량계수, 저류계수 등의 수리상수값은 해당 관정의 지하수개발 이용 영향조사서에서 발췌하였고, 측정되지 않은 일부 입력값은 문헌조사를 통해 적절한 값을 가정하여 사용하였다. 하천의 수량에 미치는 지하수 양수 영향을 예측한 결과 지하수 허가기간 5년동안 취수계획량의 약 80 %를 넘는 하천수 감소율이 발생하는 것으로 분석되었다. 연구 대상관정과 같이 하천에 매우 근접한 지역에서 지하수를 이용할 경우 하천수 취수에 준하는 영향을 보일 수 있기 때문에 수자원의 효율적인 이용을 위해서는 하천수와 하천 인근 지하수의 통합적 관리가 필요할 것이다.

• Computers and Concrete
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• v.16 no.4
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• pp.625-642
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• 2015

Prestressed concrete bridges with corrugated steel webs have emerged as one of the promising bridge forms. This structural form provides excellent structural efficiency with the concrete flanges primarily taking bending and the corrugated steel webs primarily taking shear. In the design of this type of bridges, the flexural ductility and deformability as well as strength need to be carefully examined. Evaluation of these safety-related attributes requires the estimation of full-range behaviour. In this study, the full-range behaviour of beam sections with corrugated steel webs is evaluated by means of a nonlinear analytical method which uses the actual stress-strain curves of the materials and considers the path-dependence of materials. In view of the different behaviour of components and the large shear deformation of corrugated steel webs with negligible longitudinal stiffness, the assumption that plane sections remain plane may no longer be valid. The interaction between shear deformation and local bending of flanges may cause additional stress in flanges, which is considered in this study. The numerical results obtained are compared with experimental results for verification. A parametric study is undertaken to clarify the effects of various parameters on ductility, deformability and strength.

• Journal of the Korean earth science society
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• v.40 no.4
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• pp.315-328
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• 2019

Since the Coastal Zone Color Scanner (CZCS)/Nimbus-7 was launched in 1978, a variety of studies have been conducted to retrieve ocean color variables from multi-satellites. Several algorithms and formulations have been suggested for estimating ocean color variables based on multi band data at different wavelengths. Chlorophyll-a (chl-a) concentration is one of the most important variables to understand low-level ecosystem in the ocean. To retrieve chl-a concentrations from the satellite observations, an appropriate algorithm depending on water properties is required for each satellite sensor. Most operational empirical algorithms in the global ocean have been developed based on the band-ratio approach, which has the disadvantage of being more adapted to the open ocean than to coastal areas. Alternative algorithms, including the semi-analytical approach, may complement the limits of band-ratio algorithms. As more sensors are planned by various space agencies to monitor the ocean surface, it is expected that continuous monitoring of oceanic ecosystems and environments should be conducted to contribute to the understanding of the oceanic biosphere and the impact of climate change. This study presents an overview of the past and present algorithms for the estimation of chl-a concentration based on multi-satellite data and also presents the prospects for ongoing and upcoming ocean color satellites.

• Advances in Computational Design
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• v.4 no.3
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• pp.307-326
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• 2019

A low computational cost semi-analytical method is developed, based on eigenfunction expansion, to study the vibration of rectangular plates subjected to a series of moving sprung masses, representing a bridge deck under multiple vehicle or train moving loads. The dynamic effects of the suspension system are taken into account by using flexible connections between the moving masses and the base structure. The accuracy of the proposed method in predicting the dynamic response of a rectangular plate subjected to a series of moving sprung masses is demonstrated compared to the conventional rigid moving mass models. It is shown that the proposed method can considerably improve the computational efficiency of the conventional methods by eliminating a large number of time-varying components in the coupled Ordinary Differential Equations (ODEs) matrices. The dynamic behaviour of the system is then investigated by performing a comprehensive parametric study on the Dynamic Amplification Factor (DAF) of the moving loads using different design parameters. The results indicate that ignoring the flexibility of the suspension system in both moving force and moving mass models may lead to substantially underestimated DAF predictions and therefore unsafe design solutions. This highlights the significance of taking into account the stiffness of the suspension system for accurate estimation of the plate maximum dynamic response in practical applications.

• Journal of Climate Change Research
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• v.5 no.3
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• pp.199-208
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• 2014

According to "IPCC guide line for national greenhouse gas inventories" each country should develop the 'Country-specific emission factor' and apply it to estimate greenhouse gases emissions from landfill. It could reflect properties of country and make estimation more accurate. For that accuracy, developed country-specific emission factor should be assessed and be verified consistently. Developed emission factors should be assessed in terms of Representative, Emission Property, Accuracy and Uncertainty, but there is no study about weighted assessment factors under each emission variable. This study do survey targeting public officials, professors and other experts for Analytical Hierarchy Process(AHP), mostly use to make decisions, to weight assessment factors. We investigated the weighted values per Emission factor for Representative, Emission property, Accuracy and Uncertainty on AHP survey, and Representative factor was the highest, and then in the order of Emission property (0.26), Accuracy(0.22), Uncertainty (0.15).