• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.2
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• pp.263-268
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• 2016

A rapid increase of data amount, used in ship-to-ship transmission of safety and logistics information, ships in the inland sea have trouble transmitting real-time information transmission due to an increase in traffic load caused by data transmitted by land station and offshore ships. In this study, therefore, communication is carried out by adaptively controlling the detailed beam width based on the distribution of offshore ships in land station durable in marine environment. Then after the adaptive sector system enabling real-time communication support between ships concentrated in an inland sea and land station is applied, the performance verification is conducted based on the respective Call Blocking Rates of an omnidirectional antenna, fisted sector system, and adaptive sector system. The performance verification result shows that adaptive sector system has better performance than the fixed sector system as the density of ship, q value, increases, and that the smaller the beam width is, the better performance of adaptive sector system will be.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.6
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• pp.148-156
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• 2018

The integrity assessment of the bridge behavior is generalized by field data of a static load-deformation curve and dynamic properties such as impact factors and natural frequencies. Evaluating it with numerical analysis is a reasonable method. The results of the mockup test and the numerical analysis are corresponded with each other since the behavior of service load proceeds in elastic region. In case of the dynamic behavior of structure, especially for the analysis of vibration, the result of the mockup test differs from the result of numerical analysis a little due to the geometric shape and non-homogeneous materials. In order to converge on these tolerances, this study suggested several numerical models, analyzed the sensitivity and finally offered a practical modeling method for the estimation of bridge on the basis of the result of mockup test. Based on the model substituted concrete section for strands section, the natural frequency of the model composed with axial stiffness of strands or the model applied the modified modulus of elasticity was closest with the result of the mockup test.

• The Journal of Engineering Geology
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• v.27 no.2
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• pp.119-124
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• 2017

The waviness of Large Discontinuity rock is the one of important elements that judges the stability of rock slope. When the waviness of large discontinuity is measured in the field, there are many limitations Therefore this research was carried out to measure waviness of large rock discontinuities using 3D laser scanner to supplement this problem. This research established one 3D model that actual X, Y and Z coordinates through the integrated data gained from one that calculates waviness of base lock using CAD program was compared and analyzed to that of disc-clinometer. As its results, the high reliability of results could be recognized as it belongs to mechanical tolerance $1{\sim}2^{\circ}$ and the results belong to the measured values of Mean DIP and Mean are all within $1^{\circ}$. So, the investigation method of waviness of large discontinuity rock face using 3D laser scanner was verified as more prompt, effective and reliable method than conventional direct site measuring method.

• The Journal of Engineering Geology
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• v.27 no.2
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• pp.133-141
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• 2017

In this study, filter conditions by difference in grading between core material and filter material used for dam construction was applied as evaluation condition for surrounding ground conditions near excavation site in a bid to identify the risk of land subsidence resulting from the erosion of soil particles. To that end, filter conditions proposed for the test was evaluated and the risk of land subsidence depending on grain size conditions was also evaluated using the filter conditions developed by COE. Consequently, evaluation diagram that can be used to determine the risk of land subsidence using grain size conditions obtained from ground investigation data was developed, which is expected to help evaluate the possibility of land subsidence depending on changes to the stratum. To simulate the particle flow process, PFC3D program was used. It's not only intended to determine the land subsidence pattern caused by falling ground water level but also predict and evaluate the land subsidence caused by soil erosion using grain size condition which can be verified by numerical analysis approach.

• Journal of Sensor Science and Technology
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• v.5 no.3
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• pp.93-100
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• 1996

Polycrystalline $Sr_{2}(Ta_{1-x}Nbx)_{2}O_{7}$ and $La_{2}Ti_{2}O_{7}$ ceramics having very high Curie temperatures were synthesized by the conventional oxide mixing method (CON) and the molten salt synthesis method (MSS). Physical characteristics and phase relationship of calcined powders, as well as the sintering behavior, the grain-orientation and dielectric properties of sintered ceramics were investigated as a function of composition and firing temperature. The single $A_{2}B_{2}O_{7}$ phase was synthesized by using the MSS method at 100 - $150^{\circ}C$ lower temperature compared to the CON method. As Nb content increased in $Sr_{2}(Ta_{1-x}Nbx)_{2}O_{7}$ ceramics, the Curie temperature and the dielectric constant at Curie temperature were raised, and the sintering behavior and the degree of grain-orientation were also improved at the same time. The use of MSS-derived powders made it possible to lower the sintering temperature and to improve the dielectric properties of the sintering samples. However, the piezoelectric properties as well as the grain-orientation were not improved any further by the MSS route.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.1
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• pp.1-10
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• 2020

The application of multiphase flows is increasingly being applied to analyze phenomena such as single phase flows where the fluid boundary changes continuously over time or the problem of mixing a liquid phase and a gas phase. In particular, multiphase flow models that take into account incompressible Newtonian fluids for liquid and gas are often applied to solve the problems of the free water surface such as wave fields. In general, multi-phase flow models require time-based the surface tracking of each fluid's phase boundary, which determines the accuracy of the final calculation of the model. This study evaluates the advection performance of representative VOF-type boundary tracking techniques applied to various CFD numerical codes. The effectiveness of the FCT method to control the numerical flux to minimize the numerical diffusion in the conventional VOF-type boundary tracking method and advection calculation was mainly evaluated. In addition, the possibility of tracking performance of free surface using CIP method (Yabe and Aoki, 1991) was also investigated. Numerical results show that the FCT-VOF method introducing an anti-diffusive flux to precent excessive diffusion is superior to other methods under the confined conditions in this study. The results from this study are expected to be used as an important basic data in selecting free surface tracking techniques applied to various numerical codes.

• Economic and Environmental Geology
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• v.29 no.6
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• pp.677-687
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• 1996

The Buckchang deposits which is located in the Ockcheon metamorphic zone, are emplaced along $N20-30^{\circ}E$ trending fissure sets. So it is a sort of fissure-filling ore deposits. The results of mineral paragenetic studies suggest two stages of hydrothermal mineralization; stage I: base-metal sulfides stage, stage II: late base-metal sulfides, electrum and silver-bearing sulfosalts stage. The silver-bearing sulfosalts occured as the Buckchang mine are mainly argentite and, minor of canfieldite, tetrahedrite, etc. Au:Ag ratios of the electrums show a highly limited range of nearly 1:1 in atomic %. The temperature, salinity and pressure of the Buckchang deposits estimated from fluid inclusion and sulfur isotope studies are as follows; stage I: $174{\sim}250^{\circ}C$, 0.35~4.01 NaCl eq. wt.%, 0.40~1.00 Kbar, stage II: $138{\sim}222^{\circ}C$, 1.9~8.4 NaCl eq. wt.%, 0.22~0.53 Kbar. The estimated oxygen and sulfur fugacity during stage I mineralization, based on phase relation of associated minerals, range from $10^{-39.7}{\sim}10^{-44.7}$ atm. and $10^{-13.4}{\sim}10^{-18.1}$ atm., respectively. All these evidences suggest that the Buckchang deposits are polymetallic epithermal ore deposits.

• Analytical Science and Technology
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• v.10 no.1
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• pp.66-74
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• 1997

Influence of the axial dispersion on immobilized enzyme catalytic bed was investigated in order to examine the kinetic behavior of the biocatalysis. The enzyme employed in this study was the tyrosinase(EC 1.14.18.1) immobilized on carbon support : this system requires two substrates of phenol and oxygen. This enzyme has potential application for phenol degradation in waste water. A simulated reactor was a packed-bed reactor of 2.54cm in diameter and 10cm long, loaded with the immobilized carbon particle with an average diameter of $550{\mu}m$. A phenol feed in the strength of 55.5mM(5220ppm) was used to observe the behavior of the immobilized enzyme column at three different dissolved oxygen levels of 0.08445mM(2.7ppm), 0.1689mM(5.4ppm) and 0.3378mM(9.5ppm) with the flow rates in the range of 60(1mL/s) to 180mL/min(3mL/s). Examination of the Biot number and Damkolher numbers of the immobilized system enables us to eliminate the contribution of external mass transfer to set of differential equations derived from the dispersion model. Solution of the equation was finally obtained numerically with the application of the Danckwert boundary conditions and the assumed zero-and first order rates on the non-linear two substrate enzyme kinetics. Higher conversion of phenol was observed at the low flow rates and at the higher oxygen concentration. Comparison of axial dispersion and plug flow model showed that no detectable difference was observed in the column outlet conversion between the axial and the plug flow models which was in complete agreement with the previous studies.

• Journal of KIISE:Computing Practices and Letters
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• v.8 no.3
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• pp.344-355
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• 2002

Having a variety of good characteristics against other pattern recognition techniques, Multilayer Perceptron (MLP) has been used in wide applications. But, it is known that Error Backpropagation (EBP) algorithm which MLP uses in learning has a defect that requires relatively long leaning time. Because learning data in pattern recognition contain abundant redundancies, in order to increase learning speed it is very effective to use online-based teaming methods, which update parameters of MLP pattern by pattern. Typical online EBP algorithm applies fixed learning rate for each update of parameters. Though a large amount of speedup with online EBP can be obtained by choosing an appropriate fixed rate, fixing the rate leads to the problem that the algorithm cannot respond effectively to different leaning phases as the phases change and the learning pattern areas vary. To solve this problem, this paper defines learning as three phases and proposes a Instant Learning by Varying Rate and Skipping (ILVRS) method to reflect only necessary patterns when learning phases change. The basic concept of ILVRS is as follows. To discriminate and use necessary patterns which change as learning proceeds, (1) ILVRS uses a variable learning rate which is an error calculated from each pattern and is suppressed within a proper range, and (2) ILVRS bypasses unnecessary patterns in loaming phases. In this paper, an experimentation is conducted for speaker verification as an application of pattern recognition, and the results are presented to verify the performance of ILVRS.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.5
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• pp.608-614
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• 2018

In addition to the diffusion of ICT technology, various protocols of short range wireless communication technology are being applied for efficient information operation. However, due to limitations of short-range wireless communication, communication is not smooth in places where frequency environment is poor, such as frequency confusion and warehouse type factory. When an alternative is needed. The development of LED technology and expansion of infrastructure through LED based visible light communication is attracting attention as an alternative and spreading the usage in wide range now a days. In addition, the infrastructure has been expanded with solar panels in response to the development of smarthome built-in with renewable energy. In this situation, visible light communication using PD has been limitedly applied in a near environment where the receiving angle of the PD and the ambient light ensure the LoS and the influence of the ambient light is small. In order to solve this problem, we have implemented visible light communication using LED lighting with large current infrastructure and solar panel with large receiving area, and proposed a circuit for restoring accurate data even in ambient light. Through this study results, it is expected that visible light communication can be more widely used and this result used as the base data for visible light communication research using the solar panel as the receiver.