• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.5
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• pp.1180-1188
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• 2015

In this paper, we propose a new subband quantizer which is a type of quad-tree for applying to digital hologram compression based on Fresenelet transform. After executing Fresnelet transform to the captured digital holgoram, we analyze effect of the designed quantizer for the reconstructed objects from analyzing average energy of each coefficient and visual importance in all subbands. We analyze distribution of coefficient and set dynamic range for each subband, and then design subband quantizer. For enhancing effectiveness of the designed quantize, we adopt a method using the coefficients which are located out of dynamic range, which are named by exception indices. From this, we can obtain more effective quantizer which has higher performance in a range of σ′ = 5.0.

• Journal of the Korean Data and Information Science Society
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• v.15 no.4
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• pp.743-752
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• 2004

In this paper, we develop the Bayesian model selection procedure using the reference prior for comparing two nested model such as the independent and intraclass models using the distance or divergence between the two as the basis of comparison. A suitable criterion for this is the power divergence measure as introduced by Cressie and Read(1984). Such a measure includes the Kullback -Liebler divergence measures and the Hellinger divergence measure as special cases. For this problem, the power divergence measure turns out to be a function solely of $\rho$, the intraclass correlation coefficient. Also, this function is convex, and the minimum is attained at $\rho=0$. We use reference prior for $\rho$. Due to the duality between hypothesis tests and set estimation, the hypothesis testing problem can also be solved by solving a corresponding set estimation problem. The present paper develops Bayesian method based on the Kullback-Liebler and Hellinger divergence measures, rejecting $H_0:\rho=0$ when the specified divergence measure exceeds some number d. This number d is so chosen that the resulting credible interval for the divergence measure has specified coverage probability $1-{\alpha}$. The length of such an interval is compared with the equal two-tailed credible interval and the HPD credible interval for $\rho$ with the same coverage probability which can also be inverted into acceptance regions of $H_0:\rho=0$. Example is considered where the HPD interval based on the one-at- a-time reference prior turns out to be the shortest credible interval having the same coverage probability.

• Journal of the Korean Geotechnical Society
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• v.21 no.6
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• pp.5-18
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• 2005

In this study, the influence of progressive consolidation from the drainage boundary on the subsequent process of consolidation was investigated. Analytical theory and numerical program f3r consolidation of clayey soil were developed based on finite difference method, in which spatial variation of permeability and volume compressibility were implemented. And model ground with normally consolidated clayey soils and a vertical drain at its center were simulated. Various types of soils with different relations between coefficient of volume compressibility and permeability and void ratio were applied. Also numerical simulations based on the properties of the normally consolidated clay at Nakdong River basin and reconstituted kaolinite soil were performed to recognize its practical impact. Consequently, it is found out that retardation of consolidation induced by progressive consolidation is very important to understand consolidation behavior on field conditions and its effect is remarkable at the initial state of consolidation, and increases with plasticity index and applied load.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.6
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• pp.537-543
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• 2016

A new approach to systematically model aerodynamic coefficients using an adaptive sampling based wind tunnel testing considering cost is proposed. The Latin Hypercube design is used for selecting initial test points. The Gaussian Process (GP) is iteratively used during the experiment to determine additional experimental points that minimizes the uncertainty reduction per incremental cost. A numerical simulation based experiment was conducted using the static aerodynamic coefficient database a fighter aircraft, which demonstrated the validity of the proposed method.

• Journal of the Ergonomics Society of Korea
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• v.30 no.6
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• pp.689-694
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• 2011

Objective: The aim of this study is to evaluate the fluctuation of signal amplitude during repetitive dynamic contraction based on surface electromyography(EMG). Background: The most previous studies were considered isometric muscle contraction and they were difference to smoothing window length by moving average filter. In practical, the human movement is dynamic state. Dynamic EMG signal which indicated as the nonstationary pattern should be analyzed differently compared with the static EMG signal. Method: Ten male subjects participated in this experiment, and EMG signal was recorded by biceps brachii, anterior/posterior deltoid, and upper/lower trapezius muscles. The subject was performed to repetitive right horizontal lifting task during ten cycles. This study was considered three independent variables(muscle, amplitude processing technique, and smoothing window length) as the within-subject experimental design. This study was estimated muscular activation by means of the linear envelope technique(LE). The dependent variable was set coefficient of variation(CV) of LE for each cycle. Results: The ANOVA results showed that the main and interaction effects between the amplitude processing technique and smoothing window length were significant difference. The CV value of peak LE was higher than mean LE. According to increase the smoothing window length, this study shows that the CV trend of peak LE was decreased. However, the CV of mean LE was analyzed constant fluctuation trend regardless of the smoothing window length. Conclusion: Based on these results, we expected that using the mean LE and 300ms window length increased reproducibility and signal noise ratio during repetitive dynamic muscle contraction. Application: These results can be used to provide fundamental information for repetitive dynamic EMG signal processing.

• Smart Structures and Systems
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• v.20 no.6
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• pp.769-780
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• 2017

Cable force monitoring is an essential and critical part of the safety evaluation of cable-supported bridges. A reasonable cable force monitoring scheme, particularly, sensor placement related to accurate safety assessment and budget cost-saving becomes a major concern of bridge administrative authorities. This paper presents optimal sensor placement for cable force monitoring by selecting representative sensor positions, which consider the spatial correlativeness existing in the cable group. The limited sensors would be utilized for maximizing useful information from the monitored bridges. The maximum information coefficient (MIC), mutual information (MI) based kernel density estimation, as well as Pearson coefficients, were all employed to detect potential spatial correlation in the cable group. Compared with the Pearson coefficient and MIC, the mutual information is more suitable for identifying the association existing in cable group and thus, is selected to describe the spatial relevance in this study. Then, the bond energy algorithm, which collects clusters based on the relationship of surrounding elements, is used for the optimal placement of cable sensors. Several optimal placement strategies are discussed with different correlation thresholds for the cable group of Nanjing No.3 Yangtze River Bridge, verifying the effectiveness of the proposed method.

• Journal of Korea Water Resources Association
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• v.34 no.2
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• pp.131-140
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• 2001

The present study is focused on improving the methodology for the determination of parameters involved in USLE(Universal Soil Loss Equation) based on distributed system concept and investigation of sediment delivery ratio. Generally the distributed system concept consists of grid networks throughout the watershed and sediment can be traced from grid to rid in the direction of the steepest descent. The sediment yield data together with physical data of 10 small irrigation reservoirs in Kyounggi-Do are collected. After the sediment delivery ratio of a grid is defined to be related tothe fraction of forested or covered with delivery proofing area of the grid, the preportionality coefficient(C$_1$) is introduced. The distributed system model is calibrated using the available data for 8 reservoirs and is verified with the data for the ramaining 2 reservoirs, and regression analysis is made to express the proportionality coefficient $C_1$ in terms of watershed physical characteristics. By applying this results the verification of the distributed system model for 2 reservoirs showed a fair result, which justifies the applicability of the proposed method in the present study.

• Journal of the Korean Geotechnical Society
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• v.33 no.11
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• pp.83-95
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• 2017

This study examined the magnitude and distribution of earth pressure on the excavation wall in jointed rock mass by considering different groundwater conditions under various rock types, joint inclination angles, and earth pressure coefficients. Based on a physical model test (Son and Park, 2014), extended studies were conducted considering rock-structure interactions based on the discrete element method, which can consider the joints characteristics of rock mass. The results showed that the earth pressure was highly influenced by the groundwater condition as well as the rock type, joint inclination angle, and earth pressure coefficient. The results were also compared with Peck's earth pressure for soil ground, and clearly showed that the earth pressure in jointed rock mass can be greatly different from that in soil ground.

• Korean Chemical Engineering Research
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• v.57 no.1
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• pp.58-64
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• 2019

This study presents a novel method for preparing monodisperse polyethylene glycol diacrylate (PEGDA) microparticles in a dispensing needle based microfluidic device. The microfluidic devices are manufactured by manually assembling various off-the-shelf products without using additional equipment. In this microfluidic device, the volumetric flow rates of the dispersed phase of PEGDA solution and the continuous phase of oil are controlled to generate monodisperse PEGDA droplets. The PEGDA droplet contains photo-initiator thus it is crosslinked to microparticle by photopolymerization at the ends of the device. The particle size is easily controlled by adjusting the volume flow rate and the size of the microfluidic device. The monodispersity of the particles is calculated by a coefficient of variation of 2.57%. To demonstrate the biological applications of PEGDA particles, cells are encapsulated and observed for proliferation and viability.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.55 no.5
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• pp.721-729
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• 2022

We investigated the ecological characteristics and biomass of white croaker Pennahia argentata population in the South Sea of Korea using catch data from Danish seins fishery and biological data from 2018 to 2020. Survival rate (S), which was estimated using Pauly method (1984) was 0.361 per year, and the instantaneous coefficient of total mortality (Z) was 1.019 per year. The instantaneous coefficient of natural mortality (M) and that of fishing mortality (F) were estimated as 0.351 and 0.668 per year, respectively. At first capture, age was estimated to be 1.19 years and length at this age was 18.7cm. The annual biomass was estimated with a biomass-based cohort analysis using annual catch data between 1997-2020 in Korean water. The biomass of the white croaker declined sharply from 4,000 tons in 1999 to the lowest level of approximately 1,000 tons in 2004. Post 2004, the biomass started to increase gradually and reached approximately 7,000 tons. The amount of resources was 35.7%, 34.8%, and 16.5% at age one, two, and three years, respectively, and 86.9% of all captured white croaker individuals belonged to the age group of 1-3 years.