• Title/Summary/Keyword: Earth parameter

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Analysis of thermally induced vibration of cable-beam structures

  • Deng, Han-Qing;Li, Tuan-Jie;Xue, Bi-Jie;Wang, Zuo-Wei
    • Structural Engineering and Mechanics
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    • v.53 no.3
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    • pp.443-453
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    • 2015
  • Cable-beam structures characterized by variable stiffness nonlinearities are widely found in various structural engineering applications, for example in space deployable structures. Space deployable structures in orbit experience both high temperature caused by sun's radiation and low temperature by Earth's umbral shadow. The space temperature difference is above 300K at the moment of exiting or entering Earth's umbral shadow, which results in structural thermally induced vibration. To understand the thermally induced oscillations, the analytical expression of Boley parameter of cable-beam structures is firstly deduced. Then, the thermally induced vibration of cable-beam structures is analyzed using finite element method to verify the effectiveness of Boley parameter. Finally, by analyzing the obtained numerical results and the corresponding Boley parameters, it can be concluded that the derived expression of Boley parameter is valid to evaluate the occurrence conditions of thermally induced vibration of cable-beam structures and the key parameters influencing structural thermal flutter are the cable stiffness and thickness of beams.

On the Surface Moisture Availability Parameters to Estimate the Surface Evaporation (증발량 추정을 위한 지표면 가용 수분 계수)

  • Jin, Byoung-Hwa;Hwang, Soo-Jin
    • Journal of Environmental Science International
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    • v.4 no.5
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    • pp.41-41
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    • 1995
  • In order to discuss the differences among the SMP(Surface Moisture Availability Parameter), by previous researchers on the basis of their own theoretical and empirical background, we assessed the SMP according to the soil types and volumetric soil water contents. The results are as follows. There are differences among all the five SMAPs. There''s a tendency that the larger grain size, the higher value of parameters. And they divided into two groups for their value: one group has parameters with exponential function and the other with cosine and linear function. The maximum difference between the two groups appears when the volumetric soil water contents are 0.07$m^3m^{-3}$ for sand, 0.l1$m^3m^{-3}$ for loam, 0.12 for clay, and 0.13$m^3m^{-3}$ for silt loam. So, these differences must be considered when we estimate the surface evaporation rate. From field data, the paddy field soil around Junam reservoir is classified as a silt has high wetness, 0.56. So, the parameter obtained from the field measurement is much higher than that of Clapp and Hornberger(1978)''s Table. This study treated the SMP for a certain point of time in winter season. But if we measured the soil water contents continuously, we could obtain better time-dependent parameter.

Selecting Optimal Basis Function with Energy Parameter in Image Classification Based on Wavelet Coefficients

  • Yoo, Hee-Young;Lee, Ki-Won;Jin, Hong-Sung;Kwon, Byung-Doo
    • Korean Journal of Remote Sensing
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    • v.24 no.5
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    • pp.437-444
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    • 2008
  • Land-use or land-cover classification of satellite images is one of the important tasks in remote sensing application and many researchers have tried to enhance classification accuracy. Previous studies have shown that the classification technique based on wavelet transform is more effective than traditional techniques based on original pixel values, especially in complicated imagery. Various basis functions such as Haar, daubechies, coiflets and symlets are mainly used in 20 image processing based on wavelet transform. Selecting adequate wavelet is very important because different results could be obtained according to the type of basis function in classification. However, it is not easy to choose the basis function which is effective to improve classification accuracy. In this study, we first computed the wavelet coefficients of satellite image using ten different basis functions, and then classified images. After evaluating classification results, we tried to ascertain which basis function is the most effective for image classification. We also tried to see if the optimum basis function is decided by energy parameter before classifying the image using all basis functions. The energy parameters of wavelet detail bands and overall accuracy are clearly correlated. The decision of optimum basis function using energy parameter in the wavelet based image classification is expected to be helpful for saving time and improving classification accuracy effectively.

A Development of Earth Parameters and Equivalent Resistivity Estimation Algorithm for ITS Facility Stabilization (ITS설비의 안정화를 위한 대지파라미터 및 등가대지저항률 추정 알고리즘 개발)

  • Lee, Jong-Pil;Lim, Jae-Yoon;Ji, Pyeong-Shik
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.62 no.4
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    • pp.186-191
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    • 2013
  • Earth equipments are essential to protect ITS facilities from abnormal situation. In this research, an estimation algorithm of earth parameters and equivalent resistivity is introduced. Traditional estimation methods can be divided into graphic method and numerical method. The result of graphic method is varied by the ability of expert or repeated calculation and it is hard to estimate the parameters precisely. The numerical method requires special techniques such as optimizing theory, and numerous calculations, whose results can be varied with initial values. The proposed algorithm is based on the relationship between apparent resistances and earth parameters and approximates the nonlinear characteristics of earth using ANN(artificial neural networks). The effectiveness of proposed method is verified in case studies.

Application of Bayesian Approach to Parameter Estimation of TANK Model: Comparison of MCMC and GLUE Methods (TANK 모형의 매개변수 추정을 위한 베이지안 접근법의 적용: MCMC 및 GLUE 방법의 비교)

  • Kim, Ryoungeun;Won, Jeongeun;Choi, Jeonghyeon;Lee, Okjeong;Kim, Sangdan
    • Journal of Korean Society on Water Environment
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    • v.36 no.4
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    • pp.300-313
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    • 2020
  • The Bayesian approach can be used to estimate hydrologic model parameters from the prior expert knowledge about the parameter values and the observed data. The purpose of this study was to compare the performance of the two Bayesian methods, the Metropolis-Hastings (MH) algorithm and the Generalized Likelihood Uncertainty Estimation (GLUE) method. These two methods were applied to the TANK model, a hydrological model comprising 13 parameters, to examine the uncertainty of the parameters of the model. The TANK model comprises a combination of multiple reservoir-type virtual vessels with orifice-type outlets and implements a common major hydrological process using the runoff calculations that convert the rainfall to the flow. As a result of the application to the Nam River A watershed, the two Bayesian methods yielded similar flow simulation results even though the parameter estimates obtained by the two methods were of somewhat different values. Both methods ensure the model's prediction accuracy even when the observed flow data available for parameter estimation is limited. However, the prediction accuracy of the model using the MH algorithm yielded slightly better results than that of the GLUE method. The flow duration curve calculated using the limited observed flow data showed that the marginal reliability is secured from the perspective of practical application.

Changes in the Earth's Spin Rotation due to the Atmospheric Effects and Reduction in Glaciers

  • Na, Sung-Ho;Cho, Jungho;Kim, Tu-Hwan;Seo, Kiweon;Youm, Kookhyoun;Yoo, Sung-Moon;Choi, Byungkyu;Yoon, Hasu
    • Journal of Astronomy and Space Sciences
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    • v.33 no.4
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    • pp.295-304
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    • 2016
  • The atmosphere strongly affects the Earth's spin rotation in wide range of timescale from daily to annual. Its dominant role in the seasonal perturbations of both the pole position and spinning rate of the Earth is once again confirmed by a comparison of two recent data sets; i) the Earth orientation parameter and ii) the global atmospheric state. The atmospheric semi-diurnal tide has been known to be a source of the Earth's spin acceleration, and its magnitude is re-estimated by using an enhanced formulation and an up-dated empirical atmospheric S2 tide model. During the last twenty years, an unusual eastward drift of the Earth's pole has been observed. The change in the Earth's inertia tensor due to glacier mass redistribution is directly assessed, and the recent eastward movement of the pole is ascribed to this change. Furthermore, the associated changes in the length of day and UT1 are estimated.

Establishment of Guardrail Distance for Safety of Reinforced Earth Retaining Wall by Vehide Collision (차량충돌에 대한 보강토 옹벽 안전성 확보를 위한 가드레일 설치거리)

  • Park, Kwon;Hong, Ki-Nam;Ahn, Kwang-Kuk
    • Journal of the Korean Society of Safety
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    • v.24 no.5
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    • pp.57-62
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    • 2009
  • In this study, the numerical analyses regarding the distance between the guardrail and the reinforced earth wall as parameter were performed to determine the safe distance of guardrail installed on reinforced earth wall from the reinforced earth wall. The analyses were fulfilled by increasing the distance between the guardrail and reinforced earth wall from 150mm to 750mm. The computer program used in this research is LS-DYNA, which is very' popular in analysis of vehicle collision. Ford single unit truck in NCAC was employed as the model of vehicle and the velocity of vehicle collision was 80km/hr. As a results of analyses, the safety of guardrail was secured regardless of the distance between the guardrail and block of reinforced earth wall. However, to secure the safety of block of reinforced earth wall the distance between the guardrail and block of reinforced earth wall should be over 600mm.

THE DECISION OF OPTIMUM BASIS FUNCTION IN IMAGE CLASSIFICATION BASED ON WAVELET TRANSFORM

  • Yoo, Hee-Young;Lee, Ki-Won;Jin, Hong-Sung;Kwon, Byung-Doo
    • Proceedings of the KSRS Conference
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    • 2008.10a
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    • pp.169-172
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    • 2008
  • Land-use or land-cover classification of satellite images is one of the important tasks in remote sensing application and many researchers have been tried to enhance classification accuracy. Previous studies show that the classification technique based on wavelet transform is more effective than that of traditional techniques based on original pixel values, especially in complicated imagery. Various wavelets can be used in wavelet transform. Wavelets are used as basis functions in representing other functions, like sinusoidal function in Fourier analysis. In these days, some basis functions such as Haar, Daubechies, Coiflets and Symlets are mainly used in 2D image processing. Selecting adequate wavelet is very important because different results could be obtained according to the type of basis function in classification. However, it is not easy to choose the basis function which is effective to improve classification accuracy. In this study, we computed the wavelet coefficients of satellite image using 10 different basis functions, and then classified test image. After evaluating classification results, we tried to ascertain which basis function is the most effective for image classification. We also tried to see if the optimum basis function is decided by energy parameter before classifying the image using all basis function. The energy parameter of signal is the sum of the squares of wavelet coefficients. The energy parameter is calculated by sub-bands after the wavelet decomposition and the energy parameter of each sub-band can be a favorable feature of texture. The decision of optimum basis function using energy parameter in the wavelet based image classification is expected to be helpful for saving time and improving classification accuracy effectively.

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Application of the Artificial Coral Reef as a Coastal Erosion Prevention Method with Numerical-Physical Combined Analysis (Case Study: Cheonjin-Bongpo Beach, Kangwon Province, South Korea)

  • Hong, Sunghoon;Jeong, Yeon Myeong;Kim, Taeyoon;Huynh, Van Men;Kim, Inho;Nam, Jungmin;Hur, Dong Soo;Lee, Jooyong;Kwon, Soonchul
    • Journal of Ocean Engineering and Technology
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    • v.35 no.1
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    • pp.75-81
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    • 2021
  • Artificial Coral Reefs (ACRs) have been introduced to help solve coastal erosion problems, but their feasibility has not been assessed with field data. This study conducted a feasibility analysis of ACRs on their erosion mitigation effects by performing a case study of Cheonjin-Bongpo beach, South Korea. A numerical-physical combined analysis was carried out using a SWAN model simulation and physical model test with a scale of 1/25 based on field observations of Cheonjin-Bongpo beach. Both Dean's parameter and the surf-scaling parameter were applied to comparative analysis between the absence and presence conditions of the ACR. The results for this combined method indicate that ACR attenuates the wave height significantly (59~71%). Furthermore, ACR helps decrease the mass flux (~50%), undertow (~80%), and maximum wave set up (~61%). The decreases in Dean's parameter (~66%) and the surf-scaling parameter suggest that the wave properties changed from the dissipative type to the reflective type even under high wave conditions. Consequently, an ACR can enhance shoreline stability.

Implementation and Validation of Earth Acquisition Algorithm for Communication, Ocean and Meteorological Satellite

  • Park, Sang-Wook;Lee, Young-Ran;Lee, Byoung-Sun;Hwang, Yoo-La;Lee, Un-Seob
    • Journal of Astronomy and Space Sciences
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    • v.28 no.4
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    • pp.345-354
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    • 2011
  • Earth acquisition is to solve when earth can be visible from satellite after Sun acquisition during launch and early operation period or on-station satellite anomaly. In this paper, the algorithm and test result of the Communication, Ocean and Meteorological Satellite (COMS) Earth acquisition are presented in case of on-station satellite anomaly status. The algorithms for the calculation of Earth-pointing attitude control parameters including those attitude direction vector, rotation matrix, and maneuver time and duration are based on COMS configuration (Eurostar 3000 bus). The coordinate system uses the reference initial frame. The constraint calculating available time-slot to perform the earth acquisition considers eclipse, angular separation, solar local time, and infra-red earth sensor blinding conditions. The results of Electronics and Telecommunications Research Institute (ETRI) are compared with that of the Astrium software to validate the implemented ETRI software.