• Journal of the Korea Furniture Society
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• v.12 no.1
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• pp.47-55
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• 2001

Violin bridge blank cut from maple wood with good quality has typical pattern of the radial direction in the side edge with minimal dispersion. This experimental study was designed and carried out to examine the effect of the physical and macroscopical characteristics on the compressive creep of violin bridge blank which had been imported from European manufacturer. This research arose from the idea that the maple solid wood with heterogeneous wood density and ray direction in the side edge would have uneven rheological property of violin bridge blank which is supposed to be pressed by the tension of strings. Experimentally, the compressive creep of bridge blank became smaller with the higher density of imported maple wood and showed clear density-dependence for the duration of load under the string tension of 5 kgf. Every bridge blank showed the behavior of primary creep stage(stress stabilization) having logarithmic regression creep curve with high correlation coefficient under the designed stress level. Even though the relationship between compressive creep and ray direction on the side edge of bridge was not so clear contrary to expectation, we could conclude that wood density and ray direction should be the quality decisive factors affecting the acoustical characteristics and performance of the bridge, the core member of violin-family bow instruments.

• Water for future
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• v.23 no.4
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• pp.445-457
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• 1990

In order to predict the dispersion of a thermal discharge with strong turbulent and buoyant effects, the development of a numerical model using turbulence model and its application are significantly increased. In this study, a 3-dimensional steady-state model for the surface discharge of heated water into quiescent water body is developed. For the model closure of turbulent terms the 4-equation turbulence model is used. For economic numerical simulation, the elliptic governing equations are transformed to the partially parabolic equations. In general, the simulated results by the present model agree well to the experimental results by Pande and Rajaratnam. The model characteristics are presented in comparison with the predicted results of the 2-equation turbulence model by McGuirk and Rodi. Applying the 4-equation turbulence model to the Korea nuclear unit 1 at Kori site, feasibility and efficiency of the present model are validated.

• IEMEK Journal of Embedded Systems and Applications
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• v.13 no.2
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• pp.83-91
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• 2018

With the development of IT (Information Technology) technology, embedded system and network technology are combined and used in various environments such as military environment as well as everyday life. In this paper, we propose a new airdropped distributed mobility model (ADMM) modeling the dispersion falling of the direct shot of a cluster bomb, and we compare and analyze some representative MANET routing protocols in ADMM in ns-3 simulator. As a result of the analysis, we show OLSR routing protocol is promising in ADMM environment in the view points of packet delivery ratio (PDR), end to end delay, and jitter. In addition, we propose a new adaptation scheme for OLSR, AND-OLSR (Average Node Distance based adaptive-OLSR) to improve the original OLSR in ADMM environment. The new protocol calculates the average node distance, adapts the period of the control message based on the average node distance increasing rate. Through the simulation study, we show that the proposed AND-OLSR outperforms the original OLSR in PDR and control message overhead.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1318-1327
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• 2008

Geotechnical sites in urban areas may have embedded structures such as utility lines and underground concrete structures, which cause difficulties in site investigation. This study is a preliminary research to establish knowledge base for developing an optimal technique for site investigation in urban areas. Surface-wave method and resistivity survey, which are frequently adopted for non-destructive site-investigation for geotechnical sites, were investigated to characterize effects of adjacent structures. In case of surface wave method, patterns of wave propagation were investigated for typical sets of multi-layered geotechnical profiles by numerical simulation based on forward modeling theory and field experiments for small-size model tests and real-scale tests in the field. In case of resistivity survey, 3-D finite element analyses and field tests were performed to investigate effects of adjacent concrete structures. These theoretical and experimental researches for surface-wave method and resistivity survey resulted in establishing physical criteria to cause interference of adjacent structures in site investigation at urban areas.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.8
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• pp.1-7
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• 2008

In this paper, we propose a lossy MTM transmission line unit cell and retrieve the parameter values related with radiation effects. Based on this unit cell model, we plot dispersion diagrams and analyze resonance conditions. We also discuss the input impedance or admittance behavior when we terminate the load as open or short. Then, we examine the quality factor and return loss bandwidth. We also design a very compact unit cell antenna using the provided lossy MTM-TL model. The results based on EM simulations and measurements are shown to be in good agreement with those based on circuit simulation.

• Journal of the Optical Society of Korea
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• v.20 no.5
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• pp.557-562
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• 2016

In this paper, for the first time, the transmission performances of long-haul 100-Gb/s direct detection optical OFDM (DDO-OFDM) and coherent optical OFDM (CO-OFDM) wavelength division multiplexing (WDM) systems are compared by simulation. It provides specific guides for system parameter selection to get a high-performance and cost-effective OFDM WDM system. Specifically, the comparison involves three aspects: launched power is investigated to achieve better system performance; laser linewidth is numerically investigated to choose cost-effective laser; system dispersion tolerances with different laser linewidths are analyzed to further reveal the advantages and disadvantages of these two detecting methods, direct detection and coherent detection, in long-haul OFDM WDM system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.1C
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• pp.94-101
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• 2008

In this paper, we introduce a real-time state-of-polarization(SOP) finding system. The system divides the optical wave into linear horizontal- and vertical-SOP components and measures two different beat-signals, which are produced by superposition with reference optical source, in time domain. From these measured beat signals we can get SOP information of the signal instantly. Since the proposed scheme is a feed-forward measurement system, comparing with conventional systems which require an optical feedback loop, the measurement time becomes reduced tremendously. We also introduced a novel calibration method for compensating birefringence-related errors which may occur during the measurement. We prove the operation and performance of the proposed system through computer simulation and actual experiments.

• Korean Institute of Interior Design Journal
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• v.24 no.5
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• pp.128-135
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• 2015

The purpose of this study is to propose a planning method for increasing visitors' usage attraction by understanding user circulation in the large scale commercial complex. Focusing on the impact of anchor tenant on the pedestrian traffic arousing visitors' usage attraction flow, this study analyzed pedestrian circulation and traffic volume of Lotte World Mall, a large scale commercial complex. In this study, the change of pedestrian traffic in the commercial complex was investigated and the circulation flow of anchor tenant visitors such as movie theater in the commercial complex was simulated by computer. By analyzing both characteristics of pedestrian circulation and traffic volume in large scale commercial complex and movie theater users' pedestrian traffic with network-based computer simulation, positive relationship between pedestrian traffic to movie theater and pedestrian traffic dispersion of the whole commercial complex users was emerged. In addition, It is necessary to plan of distributing pedestrian traffic of vertical moving line in central space appropriately for using attraction function of anchor tenant.

• Journal of Applied Biological Chemistry
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• v.43 no.1
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• pp.18-24
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• 2000

A one-dimensional transport of displacing monovalent ion, $A^+$, and a trivalent ion being displaced, $B^{3+}^ in a porous exchange system such as soil was approximated using the Crank-Nicolson implicit finite difference technique and the Thomas algorithm in tandem. The variations in the concentration profile were investigated by varying the ion-exchange equilibrium constant (k) of ion-exchange reactions, the influent concentrations, and the cation exchange capacity (CEC) of the exchanger, under constant flux condition of pore water and dispersion coefficient. A higher value of k resulted in a greater removal of the native ion, behind the sharper advancing front of displacing ion, while the magnitude of the penetration distance of $A^+$ was not great. As the CEC increased, the equivalent fraction of $B^{3+}^ initially in the soil was greater, thus indicating that a higher CEC adsorbed trivalent cations preferentially over monovalent ions. Mass balance error from simulation results was less than 1%, indicating this model accounted for instantaneous charge balance fairly well.

• Nuclear Engineering and Technology
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• v.42 no.1
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• pp.9-16
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• 2010

Experimental examinations for evaluating fracutres were conducted by using transparent replicas of a single fracture in order to obtain the fracture data to contribute to the methodlogy on how to improve the definitaion of representative parameter values used for a parallel plate fracture model. Quantitative aperture distribution and quantitative tracer concentration data at each point in time were obtained by measuring the attenuation of transmitted light through the fracture in high spatial resolution. the representative aperture values evaluated from the multiple different measurement methods, such as arithmetic mean of aperture distribution measured by the optical method, transport aperture evaluated from the tracer test, and average aperture evaluated from the fracture void volume measurement converged to a unique value that indicates the accuracy of this experimental study. The aperture data was employed for verifying the numerical simulation under the assuption of Local Cubic Law and showed that the calculated flow rate through the fracture is 10%-100% larger than hydraulic test results. The quantitative tracer concentration data is also very valuable for validating existing numerical code for advection dispersion transport in-plane heterogeneous fractures.