• Journal of the Korean Geotechnical Society
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• v.38 no.10
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• pp.49-60
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• 2022

Underground urbanization appears to be a promising solution in response to the shortage of construction sites in the above-ground space. In this context, an accurate evaluation of a construction site ensures the long-term performance of geosystems. This study characterizes potential sites for complex plants built in underground space using geophysical methods (i.e., seismic refraction exploration and electrical resistivity survey) and in situ tests (i.e., standard penetration tests (SPTs) and downhole tests). SPTs are conducted in nine boreholes BH-1-BH-9 to estimate the groundwater level and vertical distribution of geological structures. The seismic refraction method enables us to obtain the elastic wave velocity and thickness of each soil layer for each cross-sectional area. An electrical resistivity survey conducted using the dipole array method provides the electrical resistivity profiles of the cross-sectional area. Data obtained using geophysical techniques are used to assess the classification of the soil layer and bedrock, particularly the fracture zone. This study suggests that geotechnical information using in situ tests and geophysical methods are useful references to design an underground complex plant construction.

• Wind and Structures
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• v.31 no.2
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• pp.143-152
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• 2020

The wind design of buildings is typically based on strength provisions under ultimate loads. This is unlike the ductility-based approach used in seismic design, which allows inelastic actions to take place in the structure under extreme seismic events. This research investigates the application of a similar concept in wind engineering. In seismic design, the elastic forces resulting from an extreme event of high return period are reduced by a load reduction factor chosen by the designer and accordingly a certain ductility capacity needs to be achieved by the structure. Two reasons have triggered the investigation of this ductility-based concept under wind loads. Firstly, there is a trend in the design codes to increase the return period used in wind design approaching the large return period used in seismic design. Secondly, the structure always possesses a certain level of ductility that the wind design does not benefit from. Many technical issues arise when applying a ductility-based approach under wind loads. The use of reduced design loads will lead to the design of a more flexible structure with larger natural periods. While this might be beneficial for seismic response, it is not necessarily the case for the wind response, where increasing the flexibility is expected to increase the fluctuating response. This particular issue is examined by considering a case study of a sixty-five-story high-rise building previously tested at the Boundary Layer Wind Tunnel Laboratory at the University of Western Ontario using a pressure model. A three-dimensional finite element model is developed for the building. The wind pressures from the tested rigid model are applied to the finite element model and a time history dynamic analysis is conducted. The time history variation of the straining actions on various structure elements of the building are evaluated and decomposed into mean, background and fluctuating components. A reduction factor is applied to the fluctuating components and a modified time history response of the straining actions is calculated. The building components are redesigned under this set of reduced straining actions and its fundamental period is then evaluated. A new set of loads is calculated based on the modified period and is compared to the set of loads associated with the original structure. This is followed by non-linear static pushover analysis conducted individually on each shear wall module after redesigning these walls. The ductility demand of shear walls with reduced cross sections is assessed to justify the application of the load reduction factor "R".

• Journal of Conservation Science
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• v.32 no.2
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• pp.109-121
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• 2016

Mother-of-pearl turtle shell lacquerware refers to a decoration made of a mother-of-pearl, a turtle shell and metal wires. This lacquerware features bright color tone as it is produced by sprinkling metal powder over its entire surface. This study aimed to find out its material properties and characteristics by using an optical microscopy and conducting a SEM-EDS analysis on the cross section of lacquer coating. As a result, it was found that charcoal powder and soil powder were mixed for undercoating. Then a mixture of cinnabar lacquer and monoclinic arsenic sulfide mineral ($As_2S_3$) was coated on the undercoating and brass powder was sprinkled on top of it. Especially, a little amount of pigment was found on the lacquer layer, which is distinguished from the colors used for conventional lacquer patterns. In addition, it was also found that the cinnabar lacquer and monoclinic arsenic sulfide mineral were mixed together.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.2
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• pp.191-199
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• 2008

In this paper, we present a performance analysis and design and implementation results of a 2.4 GHz bio-radar system that can detect human heartbeat and respiration signals. In order to design a 2.4 GHz bio-radar system qualitatively, we investigate the electromagnetic properties of human tissues and calculate the target SNR of demodulation output with respect to distance. The target SNR is defined by the 90 % success ratio for detecting heartbeat signal. With this target SNR value, the performance and link budget of the bio-radar system is simulated using MATLAB. Using this link budget results, the direct conversion receiver is designed and Implemented in 4 layer printed circuit board(PCB). With output power of 0 dBm and 5 Hz bandwidth, 80 % success ratio of 50 cm is measured. Measurement results show a good agreement with simulation results.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.6
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• pp.1516-1529
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• 2023

In this paper, a motor gearbox fault-detection system based on a hierarchical flow-based model is proposed. The proposed system is used for the anomaly detection of a motion sound-based actuator module. The proposed flow-based model, which is a generative model, learns by directly modeling a data distribution function. As the objective function is the maximum likelihood value of the input data, the training is stable and simple to use for anomaly detection. The operation sound of a car's side-view mirror motor is converted into a Mel-spectrogram image, consisting of a folding signal and an unfolding signal, and used as training data in this experiment. The proposed system is composed of an encoder and a decoder. The data extracted from the layer of the pretrained feature extractor are used as the decoder input data in the encoder. This information is used in the decoder by performing an interlayer cross-scale convolution operation. The experimental results indicate that the context information of various dimensions extracted from the interlayer hierarchical data improves the defect detection accuracy. This paper is notable because it uses acoustic data and a normalizing flow model to detect outliers based on the features of experimental data.

• Korean Journal of Optics and Photonics
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• v.30 no.5
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• pp.193-196
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• 2019

The design and control of thermal flow is important for the operation of high-power laser diodes (LDs). It is necessary to analyze and improve the thermal bottleneck near the active layer of an LD. As the error in prediction of the thermal resistance of an LD is large, typically due to the hyperbolic increase and saturation to linear increase of the thermal resistance as a function of thickness, it is helpful to use a simple, modified divergence model for the improvement and optimization of thermal resistance. The characteristics of LDs are described quite well, in that the values for simulated thermal resistance curves and the thermal cross section followed are almost the same as the values from the model function. Also, the thermal-cross-section curve obtained by differentiating the thermal resistance is good for identifying thermal bottlenecks intuitively, and is also fitted quite well by the model proposed for both a typical LD structure and an improved LD with thin capping and high thermal conductivity.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.33 no.3
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• pp.66-71
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• 2015

Given the recent trend of natural planting, the recognized needs for new landscaping plants that have advantages in terms of climate change and maintenance, and expected increases in demands for grasses in Korea, this study is intended to investigate from the design point of view the techniques to use grasses and their significance through garden design by Piet Oudolf who is attracting international interests with the use of perennial plants and grasses and is leading the trends in modern planting design, thereby answering the question: how to best use grasses in landscaping spaces? The characteristics of Oudolf's garden design using grasses are summarized in the following conclusions: First, Oudolf combines perennial plants and grasses to make one-to-one correspondences or express expanded drifts. Here grasses mainly serve as an element to change over to other spaces or as a connecting element between image transitions. Second, the brown color and texture of grasses represent Oudolf's considerations on the temporal continuity of gardens. They express the lyricism and pictorialism of autumn and winter. Third, grasses serve to set layers in wide areas resulting in discordance between viewpoints and circulations. Oudolf repeatedly cross perennial plants and grasses using matrices, islands and distributed layering. Here grasses are used to express abstractive meanings in the settings of scenes.

• Journal of the Korea Society of Computer and Information
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• v.19 no.7
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• pp.59-70
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• 2014

This paper propose a new wireless multi-hop routing protocol that takes the hierarchical mesh of the hybrid WMN into account. WMN that is possible to provide various applications of wireless networks still has many open issues that should be solved despite the studies carried out over a decade. Especially, in routing protocol area, a problem degrading the routing efficiency by applying one of the routing protocols, which are designed for the MANET, to the hybrid WMN be solved above all. For the improvement of the routing performance, both good routing protocol and metric are essential. However, the recent studies are only concentrated in routing metric by use of the cross-layer design. Therefore, this paper is dedicated to the routing protocol that is essential for the performance of the routing but needed more studies. The proposed protocol in this paper is reactive, and designed to reorganize the hybrid WMN with several pseudo domains, and carry out domain-based route decision. By the simulation result for the performance analysis of the proposed protocol, the average delay for the route decision was decreased by 43% compared to AODV that is the typical reactive protocol.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.1
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• pp.80-83
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• 2017

In this paper, the X-band reconfigurable frequency selective surface having flexible geometry was proposed. The proposed RFSS is composed of patterns of cross-shaped loop with inductive stub, which can control the frequency response for C-Band and X-band by ON/OFF state of PIN diode. To minimize the parasitic effect and to obtain the high level of isolation between the unit cell of FSS and the bias circuit, we designed the grid type bias line on bottom layer through via hole. The measured transmission characteristics show good agreement with the simulation results and good stability of frequency response for different incident angles and curvatures of surface.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.3
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• pp.339-347
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• 2014

In this paper, the authors present a new design for a broad-band metamaterial(MTM) absorber that utilizes flexible substrate. The proposed MTM unit cell is constructed by a electric-inducive-capacitive(ELC) resonator and a cut-wire on the same side of the flexible polyimide substrate. To reduce the radar cross section at frequencies other than the targeted frequency bands, the metallic pattern layer of the proposed structure is placed facing toward the incident wave propagation direction. A prototype absorber was fabricated with a planar array of $33{\times}45$ unit cells. Our experiments showed that the proposed absorber exhibits a peak absorption rate of 92 % and 93 % at 9.06 GHz and 15.0 GHz, respectively, and 75 % of the full-width at half-maximum(FWHM) bandwidth is achieved. The proposed backplane-less MTM structure can be used for a broad-band microwave absorber and irregular surface applications.