• Journal of Navigation and Port Research
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• v.39 no.1
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• pp.69-75
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• 2015

The concrete purpose of this study is to suggest actually a debt ratio to optimize the capital structure providing a kind of approach to estimate the proper debt ratio with an analytical model and empirical data in Korean shipping industry. The mathematical and analytical model is started from the first equation about ROE, return of net operating income on equity, with an independent variable, debt ratio. It is constructed with several parameters, ROS(return of operating income on sales), TAT(total assets turnover), and NFCL(net finance cost to liabilities). There could not be a certain relationship between debt ratio and ROS or TAT, while some correlation or causality between debt ratio and NFCL. In other words, most of firms with high debt ratio is likely to burden higher finance cost than others with low one. In this case, there is a linearity relationship between debt ratio and NFCL, so then the second equation considering this relation could be included within the analytical approach of this paper. To be short, if the criteria of adequate debt ratio has to be defined as some level of debt ratio to optimize ROE, the ROE could be illustrated as a quadratic equation to debt ratio from two equations. Next, this research estimated those parameters' numbers through the single regression method with data over 12 years of Korean shipping industry, and identified empirically the fact that optimal debt ratio would be approximately 400%. To conclude, if that industry's sales and operating incomes are stable, the debt ratio could be accepted until twice of 200% had forced in order to guarantee its financial safety in past time.

• Progress in Medical Physics
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• v.24 no.1
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• pp.61-67
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• 2013

In this study, we developed and evaluated the patient respiration training method which can help to avoid the problems for the limitation of RGRT applicable patient cases. By using the MEMS (micro-electro-mechanical-system) acceleration sensor, we measured movement of motion phantom. We had compared the response of MEMS with commercially introduced real time patient monitoring (RPM) system. We measured the response of the MEMS with 1 dimensional motion phantom movement for 2.5, 3.0, 3.5 second of period and the 2.0, 3.0, 4.0 cm of the amplitudes. The measured period error of the MEMS system was 0.6~6.0% compared with measured period using RPM system. We found that the shape of MEMS signals were similar with RPM system. From this study, we found the possibility of MEMS as patient training system.

• Journal of Korea Water Resources Association
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• v.41 no.8
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• pp.761-772
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• 2008

The object of this study is to develop the model that solves the numerically difficult problems in hydraulic engineering and to demonstrate the applicability of this model by means of various test examples, such as, verification in the gradually varied unsteady condition, three steady flow problems with the change of bottom slope with exact solution, and frictional bed with analytical solution. The governing equation of this model is the integral form of the Saint-Venant equation satisfying the conservation laws, and finite volume method with the Riemann solver is used. The evaluation of the mass and momentum flux with the HLL Riemann approximate solver is executed. MUSCL-Hancock scheme is used to achieve the second order accuracy in space and time. This study introduce the new and simple technique to discretize the source terms of gravity and hydrostatic pressure force due to longitudinal width variation for the balance of quantity between nonlinear flux and source terms. The results show that the developed model's implementation is accurate, robust and highly stable in various flow conditions with source terms, and this model is reliable for one-dimensional applications in hydraulic engineering.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.36 no.1
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• pp.54-59
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• 2000

This paper presents a control system that uses a fuzzy algorithm in controlling the depth of a model midwater trawl net, and experimental results carried out in the circulating water channel by using a model trawl winch system.The fuzzy controller calculates the length of the warp to be changed, based on the depth error between the desired depth and actual depth of the model trawl net and the ratio of change in the depth error. The error and the error change are calculated every sampling time. Then the control input, i.e. desirable length of the warp, is determined by inference from the linguistic control rules which an experienced captain or navigator uses in controlling the depth of the trawl winch controller and the length of the warp is changed. Two kinds of fuzzy control rules were tested, one was obtained from the actual operations used by a skilled skipper or navigator, and the other was a modified from the former by considering the hydrodynamic characteristics of the model trawl system.Two kinds of fuzzy control were tested, one was obtained fro the actual operations used by a skilled skipper or navigator, and the other was a modified from the former by considering the hydrodynamic characteristics of the model trawl system.The results of these model experiments indicate that the proposed fuzzy controllers rapidly follow the desired depth without steady-state error although the desired depth was given in one step, and show robustness properties against changes in the parameters such as the change of the towing sped. Especially, a modified rule shows smaller depth fluctuations and faster setting times than those obtained by a field oriented rule.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.5
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• pp.331-339
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• 2020

In this study, ways to reduce the edge pressure at the bottom plate of the caisson breakwater were considered. The water depth, freeboard, design wave height and period, and the location of the center of gravity on the super-structure of the breakwater were selected as key design variables that influence the edge pressure, and analyzed how the edge pressure changes according to the change of this key variables. The pressure distribution formulae suggested in the design standard was applied for the calculation of design wave forces. Based on the wave forces, the required effective self-weight of the super-structure and the minimum width of the caisson were determined to have a safety factor of 1.2 against sliding and overturning. From the results, it was found that the edge pressure rapidly increased as the water depth increased, and could exceed the allowable bearing capacity when it reached a certain water depth which is 20 m within the analysis conditions. It was also confirmed that the edge pressure gradually increased linearly as the freeboard increased, but decreased with the increase of the wave height and period. This edge pressure could be significantly reduced up to more than 20% by moving the center of gravity of the super-structure to the seaside, which is 5% of the caisson width. Based on the analysis results and the recently conducted research results, a method was proposed to reduce the edge pressure that can be used in the design.

• Science of Emotion and Sensibility
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• v.8 no.4
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• pp.415-422
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• 2005

The purpose of the present study was to investigate the differences of nonlinear characteristics of electroencephalogram (EEG) depending on different sensitivities of behavioral activation system (BAS) and behavioral inhibition system (BIS) of young and elderly groups. The EEGs from Fpl and Fp2 electrodes were recorded during resting condition. The young and elderly groups consisted of 19 and 31 healthy right-handed volunteers, respectively. We estimated 1/f scaling exponent which reflects the nonlinear dynamical complexity of EEG. As results, we found the differences of 1/f scaling exponent between young ant elderly BAS sensitive groups. The 1/f scaling exponent of young BAS sensitive group showed significantly higher values than those of elderly BAS sensitive group at the left prefrontal area (Fpl). The young BAS sensitive group had also a tendency to higher 1/f scaling exponent at the right prefrontal area (Fp2). Decrease of the 1/f scaling exponent indicates the increase of complexity and the decrease of the amount of information related to the statistical distribution. Therefore, the elderly BAS sensitive group has higher complexity than young BAS sensitive group, though they were all classified as BAS sensitive group by BAS/BIS scale. Our results suggest the possibility of correlation between BAS sensitivity an4 age.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.2
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• pp.265-274
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• 2011

In this paper, it is studied on wide radiating slot antenna's miniaturization for ultra wide-band(UWB) technologies and notch structure to prevent interference between UWB systems and existing wireless systems for using Wi-Fi service of IEEE standards 802.11 a/n. Proposed antenna that wide slot is decreased from $\lambda/2$ to $\lambda/4$ length of resonant frequency has decreased by 72 % compared with conventional antenna. And optimized T-shaped CPW-fed stub has satisfied UWB bandwidth for 3.0~11.8 GHz. Then, creating 2-order Hilbert curve slot line in the stub's patch area, 4.9~5.6 GHz that centered frequency is 5 GHz is eliminated. Finally, the designed antenna constructed on FR4-epoxy has $20{\times}15\;mm^2$ dimension. The measured results that are obtained return loss under -10 dB through 3.2~11.8 GHz without Wi-Fi bandwidth, a linear phase characteristic, a stable group delay, and omnidirectional radiation patterns are presented.

• Journal of the Korean Chemical Society
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• v.55 no.1
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• pp.63-69
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• 2011

This work discusses the fabrication, development and potential response behaviors of $Ag^+$ ion-selective electrodes ($Ag^+$-ISE) based on N,N'-bis(2-hydroxybenzyl)-1,3-diaminopropane (L1) and N,N'-bis(2-hydroxybenzyl)-2,2-dimethyl-1,3-diaminopropane (L2) as carriers. The observations indicated that the resulting electrode based on L1 toward $Ag^+$ showed stable near-Nernst slope approaching 58.7 mV/dec and the optimum potential response characteristics in a linear range at least five orders of magnitude with a detection limit of $1.0{\times}10^{-6}M$. The proposed electrode displayed the preferential selectivity to $Ag^+$ against other tested cations. The excellent potential analytical characteristics could lead to the successful applications of silver assay in significant real samples, indicating that the proposed $Ag^+$-ISE showed a significant advancement of measurement capabilities. But for the electrode based on L2, the poor potential response characteristics were observed in total experiment process.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.7
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• pp.1694-1704
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• 2015

In this paper, a robust trajectory tracking control method of a wheeled mobile robot is newly proposed combining the PDC and the ISMC. The PDC is a relatively simple and easy control method for nonlinear system compared to the other non-linear control methods. And the ISMC can have robust and stable control characteristics against model uncertainties and disturbances from the initial time by placing the states on the sliding plane with desired nominal dynamics. Therefore, the proposed PDC+ISMC trajectory tracking control method shows robust trajectory tracking performance in spite of external disturbance. The tracking performance of the proposed method is verified through simulations. Even though the disturbance increases, the proposed method keeps the performance of the PDC method when there is no disturbance. However, the PDC trajectory tracking control method has increasing tracking error unlike the proposed method when the disturbance increases.

• KIPS Transactions on Software and Data Engineering
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• v.2 no.10
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• pp.713-722
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• 2013

This paper proposes a method of using depth information to detect the hand region in real-time based on the cascade method. In order to ensure stable and speedy detection of the hand region even under conditions of lighting changes in the test environment, this study uses only features based on depth information, and proposes a method of detecting the hand region by means of a classifier that uses boosting and cascading methods. First, in order to extract features using only depth information, we calculate the difference between the depth value at the center of the input image and the average of depth value within the segmented block, and to ensure that hand regions of all sizes will be detected, we use the central depth value and the second order linear model to predict the size of the hand region. The cascade method is applied to implement training and recognition by extracting features from the hand region. The classifier proposed in this paper maintains accuracy and enhances speed by composing each stage into a single weak classifier and obtaining the threshold value that satisfies the detection rate while exhibiting the lowest error rate to perform over-fitting training. The trained classifier is used to classify the hand region, and detects the final hand region in the final merger stage. Lastly, to verify performance, we perform quantitative and qualitative comparative analyses with various conventional AdaBoost algorithms to confirm the efficiency of the hand region detection algorithm proposed in this paper.