• Geophysics and Geophysical Exploration
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• v.14 no.3
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• pp.242-248
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• 2011

By applying analytic method to the uniform model, the intrinsic and scattering quality factor ($Q_i^{-1}$ and $Q_s^{-1}$) was separated for the southeastern part of Korean Peninsula. The Multiple Lapse Time Window Analysis method was used to fit theoretical values with observations obtained 759 earthquake data. While previous study for the Korean Peninsula showed very low $Q_i^{-1}$ and $Q_s^{-1}$ reflecting inactive seismicity, southeastern Korea exhibited relatively high $Q_i^{-1}$ and $Q_s^{-1}$ values interpreted as higher seismicity than the other region in the peninsula.

• Geophysics and Geophysical Exploration
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• v.25 no.4
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• pp.242-251
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• 2022

Automatic differentiation automatically calculates the derivatives of a function using the chain rule once the forward operation of a function is defined. Given the recent development of computing libraries that support automatic differentiation, many researchers have adopted automatic differentiation techniques to solve geophysical inverse problems. We analyzed the advantages, disadvantages, and performances of automatic differentiation techniques using the gradient calculations of seismic full waveform inversion objective functions. The gradients of objective functions can be expressed as multiplications of the derivatives of the model parameters, wavefields, and objective functions using the chain rule. Using numerical examples, we demonstrated the speed of analytic differentiation and the convenience of complex gradient calculations for automatic differentiation. We calculated derivatives of model parameters and objective functions using automatic differentiation and derivatives of wavefields using analytic differentiation.

• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.238-243
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• 2003

As there are many advantages on underground caverns, such as safety and operation, they can also be used for gas storage purpose. When liquefied gas is stored underground, the cryogenic temperature of the gas will affect the stability of the storage cavern. In order to store the liquefied gas successfully, it is essential to estimate the exact temperature distribution of the rock mass around the cavern. In this study, an analytic solution and a conceptual model that can estimate three-dimensional temperature distribution around the storage cavern are suggested. When calculating the heat transfer within a solid, it is likely to consider the solid as the intersection of two or more infinite or semi-infinite geometries. Therefore heat transfer solution for the solid is expressed by the product of the dimensionless temperatures of the geometries, which are used to form the combined solid. Based on the multi-dimensional transient heat transfer theory, the analytic solution is successfully derived by assuming the cavern shape to be of simplified geometry. Also, a conceptual model is developed by using the analytic solution of this study. By performing numerical experiments of this multi-dimensional model, the temperature distribution of the analytic solution is compared with that of numerical analysis and theoretical solutions.

• Proceedings of the IEEK Conference
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• 2003.07d
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• pp.1621-1624
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• 2003

As the entities participating Grid become larger, performance requirement for the LDAP-based GIS(Grid Information Service) goes beyond that provided by a stand-alone single LDAP server. This entails the exploration of distributed LDAP systems. This paper presents the performance evaluation respectively for a distribution-based and a replication-based LDAP model. The analysis is based on an analytic performance model for each distributed system which is obtained by applying the M/M/1 queuing model. The performance evaluation made to these analytic models reveals that the distribution-based and the replication-based model show a significant tradeoff in their performance with respect to the system size as well as the amount of system load.

• Journal of Korean Society for Quality Management
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• v.32 no.3
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• pp.29-44
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• 2004

Obtaining and fully understanding the true requirements of customers is hard task. However, successful use of quality function deployment(QFD) depends on capturing customers' requirements and reflecting them during the design of a product. One of common mistakes in QFD is to perform analysis using an inconsistent house of quality(HoQ) chart. This article presents a model for prioritizing customer attributes and design characteristics in order to make a product more attractive to customers. The proposed model modifies the analytic hierarchical process(AHP) with simple pairwise comparison. Our exploration using of QFD identifies how practitioners maintain consistency, whist quantifying HoQ speedily from the customer's perspectives. This paper also identifies and justifies an alternative position on QFD that is supported by statistical examples.

• Korean System Dynamics Review
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• v.5 no.1
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• pp.35-47
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• 2004

Analyzers adopt a variety of techniques in analyzing public policy. Based on the results of exploration, they explain problems and suggest prescriptions such as policy alternatives. By doing so, however, they have different degree of confidence in their own results according to what techniques they adopt. This study explores whether system dynamics apporach gives analyzers more confidence on their own simulation results than other approaches do. This study designed an experiment. Three research teams are organized. Each of them applies different analytic techniques on the same policy issue, i.e., introduction of transportation tax. It flnds that researchers using S,D. simulation technique are most confident on what they predict, while researchers adopting survey techniques show moderate degree of confidence on their results. Researchers using regression are least confident.

• Journal of the Korean Geophysical Society
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• v.6 no.4
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• pp.213-219
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• 2003

This study in on the development of analytic model that can predict the hysterisis response of steel-concrete under the periodic loads. Analytic value and experimental value including developed model were compared and interpreted. From the comparing interaction between torque and shear was focused on the its importance.

• The Journal of the Acoustical Society of Korea
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• v.18 no.8
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• pp.48-53
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• 1999

This paper presents an analytic derivation of the erroneous effect when the sliding-DFT is implemented in a recursive way with the finite-bit approximation of the twiddle factors. The analysis result is obtained in a closed form equation of the noise-to-signal power ratio(NSR) employing the zero-mean white Gaussian signal as the target input of the DFT. The parameters of the wordlength used in representing the twiddle factors and the blocklength of the DFT appear in the NSR explicitly as its function variables. The derivation is based on the error dynamic equation which is derived from the recursive SDFT, and on the analytic exploration of the statistical characteristics of the approximation coefficients treating them as random variables of having spatial distributions. The analytically derived results are verified through the comparison with the data actually measured from the computer simulation experiment.

• Geophysics and Geophysical Exploration
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• v.8 no.1
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• pp.97-103
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• 2005

Recent development of marine magnetic gradient systems, using arrays of sensors, has made it possible to survey large contaminated areas very quickly. However, underwater Unexploded Ordnances (UXO) can be moved by water currents. Because of this mobility, the cleanup process in such situations becomes dynamic rather than static. This implies that detection should occur in near real-time for successful remediation. Therefore, there is a need for a fast interpretation method to rapidly detect signatures of underwater objects in marine magnetic data. In this paper, we present a fast method for location and characterization of underwater UXOs. The approach utilises gradient interpretation techniques (analytic signal and Euler methods) to locate the objects precisely. Then, using an iterative linear least-squares technique, we obtain the magnetization characteristics of the sources. The approach was applied to a theoretical marine magnetic anomaly, with random errors, over a known source. We demonstrate the practical utility of the method using marine magnetic gradient data from Japan.

• Geophysics and Geophysical Exploration
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• v.2 no.1
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• pp.43-53
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• 1999

Numerical modeling and inversion for electromagnetic exploration methods are essential to understand behaviour of electromagnetic fields in complex subsurface. In this study, a finite element method was adopted as a numerical scheme for the 2.5-dimensional forward problem. And a finite element equation considering linear conductivity variation was proposed, when 2.5-dimensional differential equation to couple eletric and magnetic field was implemented. Model parameters were investigated for near-field with large source effects and far-field with responses dominantly by homogeneous half-space. Numerical responses by this study were compared with analytic solutions in homogeneous half-space. Blocky inversion model was modified to be applied to the forward calculation in this study and it was also adopted in the inversion algorithm. Resolution for isolated bodies were investigated to confirm possibility and limitation of inversion for electromagnetic exploration data.