• The Journal of Engineering Geology
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• v.33 no.4
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• pp.573-586
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• 2023

Joints or weak planes can induce anisotropy in the strength and deformability of fractured rock masses. Comprehending this anisotropic behavior is crucial to engineering geology. This study used plaster as a friction material to mold specimens with a single joint. The strength and deformability of the specimens were measured in true triaxial compression tests. The measured results were compared with three-dimensional numerical analysis based on the distinct element method, conducted under identical conditions, to assess the reliability of the modeled values. The numerical results highlight that the principal stress conditions in the field, in conjunction with joint orientations, are crucial factors to the study of the strength and deformability of fractured rock masses. The strength of a transversely isotropic rock mass derived numerically considering changes in the dip angle of the joint notably increases as the intermediate principal stress increases. This increment varies depending on the dip of the joint. Moreover, the interplay between the dip direction of the joint and the two horizontal principal stress directions dictates the strength of the transversely isotropic rock mass. For a rock mass with two joint sets, the set with the steeper dip angle governs the overall strength. If a rock bridge effect occurs owing to the limited continuity of one of the joint sets, the orientation of the set with longer continuity dominates the strength of the entire rock mass. Although conventional three-dimensional failure criteria for fractured rock masses have limited applicability in the field, supplementing them with numerical analysis proves highly beneficial.

• Journal of the Korean earth science society
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• v.21 no.6
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• pp.675-682
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• 2000

25 seismic shot gathers were obtained to study the two dimensional subsurface shear wave velocities in a landfilled area near the Keum river estuary. Borehole(BH#1 and BH#2) tests at two sites were made in the same area. Standard Penetration Tests were also performed at the same time. The 2-D shear wave velocity structure resulted from the inversion of the seismic data shows that the subsurface of the studied area consists of the upper 1${\sim}$3 meter thick layer(200 m/sec${\sim}$700 m/sec), the middle 5${\sim}$8 m thick low velocity layer(100 m/sec${\sim}$400 m/sec), and the lower layer of 1000m/sec or higher shear wave velocities. The thickness of the low velocity layer decreases from the BH #1 site to the BH #2 site. The depth to the basement also decreases toward the BH #2 site. The examination of the S wave velocity structure, the description of the geologic contents, and the Standard Penetration Test values indicate that the middle layer of low shear wave velocity may be related to the clay content of the layer. On the other hand, the Standard Penetration test values increase with depth, showing no significant relationship with the geologic contents of the subsurface. This study shows that the inversion of surface waves can be effective in the study of the shear wave velocity, especially in the area where low velocity layers can be found. The method of inversion of surface waves also can be used as a viable technique to overcome the limit of the seismic refraction method.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.3
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• pp.292-298
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• 2013

A signal processing technique is introduced in this paper in order to estimate the lengths of missile targets. To measure the length of a target, it is necessary to know the information on the target's location and aspect angle. Chirp waveforms and stretch processing are used to estimate the location and angle of a missile as well as HRRP(High Resolution Range Profile). RELAX(relaxation) algorithm, which is one of the spectral estimation techniques, were used to find scattering centers of a missile from HRRP. From the information on the distribution of one-dimensional(1-D) scattering centers on a target, we can discriminate the length of a missile.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.3
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• pp.49-60
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• 2002

A systematic design approach for Power distribution network (PDN) is presented aiming at applications to DRAM module designs. Three main stages are comprised in this design approach: modeling and simulation of a PDN based on a two-dimensional transmission line structure employing a partial element equivalent circuit (PEEC); verification of the simulation results through comparison to measured values; and design space scanning with PDN parameters. Impedance characteristics for do-coupling capacitors are analyzed to devise an effective way to stabilize power and ground plane Performance within a target level of disturbances. Self-impedance and transfer-impedance are studied in terms of distance between circuit features and the size of do-coupling capacitors. A simple equation has been derived to find the do-coupling capacitance values yielding impedance lower than design target, and thereby reducing the overall computation time. The effectiveness of the design methodology has been demonstrated using a DRAM module with discrete do-coupling capacitors and a strip structure.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.12
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• pp.56-65
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• 2001

This paper proposes an algorithm for the capacitance extraction of general 3-dimensional conductors in an ideal uniform dielectric that uses a high-order quadrature approximation method combined with the typical first-order collocation method to enhance the accuracy and adopts an efficient matrix-vector product algorithm for the model-order reduction to achieve efficiency. The proposed method enhances the accuracy using the quadrature method for interconnects containing corners and vias that concentrate the charge density. It also achieves the efficiency by reducing the model order using the fact that large parts of system matrices are of numerically low rank. This technique combines an SVD-based algorithm for the compression of rank-deficient matrices and Gram-Schmidt algorithm of a Krylov-subspace iterative technique for the rapid multiplication of matrices. It is shown through the performance evaluation procedure that the combination of these two techniques leads to a more efficient algorithm than Gaussian elimination or other standard iterative schemes within a given error tolerance.

• Journal of the Korean Society for Marine Environment & Energy
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• v.20 no.2
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• pp.84-90
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• 2017

In this research, a three-dimensional Computational Fluid Dynamics(CFD), scour characteristics around monopile was grasped and the effect of circular ring type scour protection on reducing protection was assessed. When Torsethaugen(1975) found that the scour area and its depth were coincided quantitatively On the ground of previous findings, after scour was assessed in terms of sea current velocity, we also found that the tendency of maximum scour depth and its width were increased as the sea current velocity was increased. The experiments were performed by attaching ring-circular typed scour protection under the bottom in order to reducing scour around the constructs of monopile type and showed reduced scour approximately by 68.5%. In addition, there were reduction of downward flow and bottom velocities, suggesting that scour protection reduce the effect of downward flow on scour.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.291.1-291.1
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• 2016

Graphene by one of the two-dimensional (2D) materials has been focused on electronic applications due to its ultrahigh carrier mobility, outstanding thermal conductivity and superior optical properties. Although graphene has many remarkable properties, graphene devices have low on/off current ratio due to its zero bandgap. Despite considerable efforts to open its bandgap, it's hard to obtain appropriate improvements. To solve this problem, heterojunction barristor was proposed based on graphene. Mostly, this heterojunction barristor is made by transition metal dichalcogenides (TMDs), such as molybdenum disulfide ($MoS_2$) and tungsten diselenide ($WSe_2$), which have extremely thickness scalability of TMDs. The heterojunction barristor has the advantage of controlling graphene's Fermi level by applying gate bias, resulting in barrier height modulation between graphene interface and semiconductor. However, charged impurities between graphene and $SiO_2$ cause unexpected p-type doping of graphene. The graphene's Fermi level modulation is expected to be reduced due to this p-doping effect. Charged impurities make carrier mobility in graphene reduced and modulation of graphene's Fermi level limited. In this paper, we investigated theoretically and experimentally a relevance between graphene's Fermi level and p-type doping. Theoretically, when Fermi level is placed at the Dirac point, larger graphene's Fermi level modulation was calculated between -20 V and +20 V of $V_{GS}$. On the contrary, graphene's Fermi level modulation was 0.11 eV when Fermi level is far away from the Dirac point in the same range. Then, we produced two types heterojunction barristors which made by p-type doped graphene and graphene treated 2.4% APTES, respectively. On/off current ratio (32-fold) of graphene treated 2.4% APTES was improved in comparison with p-type doped graphene.

• Economic and Environmental Geology
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• v.52 no.6
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• pp.555-560
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• 2019

One-dimensional shear wave velocity structure of North Korea is constrained using short (2-sec) to long period (30-sec) Rayleigh waves generated from four seismic events in China. Rayleigh waves are well recorded at the five broadband seismic stations (BRD, SNU, CHNB, YKB, KSA) which are located near to the border between North and South Korea. Group velocities of fundamental-mode Rayleigh waves are estimated with the Multiple Filter Analysis and refined by using the Phase Matched Filter. Average group velocity dispersion curve ranging from 2.9 to 3.2 km/s, is inverted to constrain the shear wave velocity structures. Relatively low group velocity dispersion curves along the path between the events to BRD at period from 4 to 6 seconds may correspond to the sedimentary sequence of the West Korea Bay Basin (WKBB) in the Yellow Sea. The low velocity zone in deep layers (14-20 km) may be related to the deep sedimentary structure in Pyongnam basin. The fast shear wave velocity structure from the surface to the depth of 14 km is consistent with the existence of metamorphic rocks and igneous bodies in Nangrim massif and Pyongnam basin.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.42 no.5 s.305
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• pp.19-26
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• 2005

In this paper, a new method for obtaining three-dimensional shape of an object by measuring relative blur between images using wavelet analysis has been described. Most of the previous methods use inverse filtering to determine the measure of defocus. These methods suffer from some fundamental problems like inaccuracies in finding the frequency domain representation, windowing effects, and border effects. Besides these deficiencies, a filter, such as Laplacian of Gaussian, that produces an aggregate estimate of defocus for an unknown texture, can not lead to accurate depth estimates because of the non-stationary nature of images. We propose a new depth from defocus (DFD) method using wavelet analysis that is capable of performing both the local analysis and the windowing technique with variable-sized regions for non-stationary images with complex textural properties. We show that normalized image ratio of wavelet power by Parseval's theorem is closely related to blur parameter and depth. Experimental results have been presented demonstrating that our DFD method is faster in speed and gives more precise shape estimates than previous DFD techniques for both synthetic and real scenes.

• Korean Journal of Acupuncture
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• v.29 no.2
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• pp.200-215
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• 2012

Objectives : The purpose of this study is to investigate the differences of pulse wave parameter between the non delivery group (single women with no childbirth experience) and the delivery group (married women who gave birth(s) in delivery). Methods : Sixty one healthy (non delivery) nulliparous women and fifty three delivery women participated in this study. We used 3 dimensional pulse analyser(3D MAC, DAEYOMEDI co., Korea), which measures radial pulse waveform non-invasively by way of tonometry method at 5 different applied pressure levels. From 114 subjects enrolled, pulse wave parameters were measured on the six locations of Chon, Kwan and Cheok of each hands. Results : Delivery group's pulse showed larger values in the following pulse wave parameters (Energy, Ap, RAI, As, Aw, h1, h2, h4, h4/h1, t, t1, t2, t4, Wm, Wm/t). Non delivery group's pulse indicated larger values in the pulse wave parameters such as Energy of left Chon, difference pulse energy between left and right hand, Ad, h5, h5/h1, t5. Conclusions : According to the analysis result, delivery group's pulse has bigger values in most part of pulse wave parameters, especially in Kwan and Cheok which correspond to Liver, Kidney, and Myeong-mun. We interpret these results that delivery women are more mature and stable in reproductive organs than non delivery group, as they have experienced delivery(deliveries) and child-caring through married life.