• The Journal of Korea Robotics Society
• /
• v.1 no.1
• /
• pp.9-16
• /
• 2006

The Mobile robots are increasingly being used to perform tasks in unknown environments. The potential of robots to undertake such tasks lies in their ability to intelligently and efficiently search in an environment. An algorithm has been developed for robots which explore the environment to measure the physical properties (dust in this paper). While the robot is moving, it measures the amount of dust and registers the value in the corresponding grid cell. The robot moves from local maximum to local minimum, then to another local maximum, and repeats. To reach the local maximum or minimum, simple gradient following is used. Robust estimation of the gradient using perturbation/correlation, which is very effective when analytical solution is not available, is described. By introducing the probability of each grid cell, and considering the probability distribution, the robot doesn't have to visit all the grid cells in the environment still providing fast and efficient sensing. The extended algorithm to coordinate multiple robots is presented with simulation results.

• Proceedings of the Korean Society for Quality Management Conference
• /
• 2007.04a
• /
• pp.461-465
• /
• 2007

The BMAP/M/N/O queueing system operating in Markovian random environment is investigated. The stationary distribution of the system is calculated. Loss probability and other performance measures are calculated. Numerical experiments which show the necessity of taking into account the influence of random environment and correlation in input flow are presented.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.30 no.4
• /
• pp.39-45
• /
• 2007

The BMAP/M/N/0 queueing system operating in Markovian random environment is investigated. The stationary distribution of the system is derived. Loss probability and other performance measures of the system also are calculated. Numerical experiments which show the necessity of taking into account the influence of random environment and correlation in input flow are presented.

• Journal of Korea Water Resources Association
• /
• v.42 no.10
• /
• pp.857-866
• /
• 2009

In this study, basic data is consisted annual maximum rainfall at 56 stations that has the rainfall records more than 30years in Korea. The 14 probability distributions which has been widely used in hydrologic frequency analysis are applied to the basic data. The method of moments, method of maximum likelihood and probability weighted moments method are used to estimate the parameters. And 4-tests (chi-square test, Kolmogorov-Smirnov test, Cramer von Mises test, probability plot correlation coefficient (PPCC) test) are used to determine the goodness of fit of probability distributions. This study emphasizes the necessity for considering the variability of the estimate of T-year event in hydrologic frequency analysis and proposes a framework for evaluating probability distribution models. The variability (or estimation error) of T-year event is used as a criterion for model evaluation as well as three goodness of fit criteria (SLSC, MLL, and AIC) in the framework. The Jackknife method plays a important role in estimating the variability. For the annual maxima of rainfall at 56 stations, the Gumble distribution is regarded as the best one among probability distribution models with two or three parameters.

• Wind and Structures
• /
• v.14 no.2
• /
• pp.113-131
• /
• 2011

Excessive wind-induced motion in tall buildings can cause discomfort, affect health, and disrupt the daily activities of the occupants of a building. Dynamic vibration absorbers such as the tuned mass dampers (TMDs) can be used to reduce the wind-induced motion below a specified tolerable serviceability limit state (SLS) criterion. This study investigates whether the same probability of not exceeding specified wind-induced motion levels can be achieved by torsionally sensitive structures without/with linear/nonlinear TMDs subjected to partially correlated wind forces, if they are designed to just meet the same SLS criterion. For the analyses, different structures and the uncertainty in the response, wind load and perception of motion is considered. Numerical results indicate that for structures that are designed or retrofitted without or with optimum linear TMDs and satisfying the same SLS criterion, their probability of exceeding the considered criterion is very consistent, if the inherent correlation between the wind forces is considered in design. However, this consistency deteriorates if nonlinear TMDs are employed. Furthermore, if the correlation is ignored in the design, in many cases a slightly unconservative design, as compared to the designed by considering correlation, is achieved.

• Human Ecology Research
• /
• v.56 no.2
• /
• pp.175-193
• /
• 2018

This study identified the rate of income poverty and multidimensional poverty, correlation between income poverty and multidimensional poverty, and adjusted multidimensional poverty rate. We also analyzed the factors that affected the number of poverty dimension and the probability of belonging to the poor or not in 3,159 elderly households including 474 poor households and 2,685 middle class households. First, in poor households, the employment poverty rate was the highest and the housing poverty rate was the lowest. In middle class households, the relation poverty rate was the highest and the employment poverty rate was the lowest. Second, in poor households, correlation between asset poverty and relation poverty had the highest coefficient of .205 and asset poverty and housing poverty had the lowest coefficient of .149. In middle class households, the correlation between income poverty and relation poverty had highest coefficient of -.290 and employment poverty and relation poverty had the lowest coefficient of .038. Third, in poor households, the number of average poverty dimension was 4.30, but the number of average poverty dimensions of middle class households was 2.310. Fourth, the variable affecting the number of poverty dimensions in poor households were gender, age, level of education, marital status; however, the significant variables were gender, education level, marital status, income poverty in the middle class households. The variable that affected the probability of belonging to the poor or not in poor households was age. However, the significant variables were gender, education level, marital status, residence, and income poverty in middle class households.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.27 no.7A
• /
• pp.695-704
• /
• 2002

Watermark detection plays a crucial role in multimedia copyright protection and has traditionally been tackled using correlation-based algorithms. However, correlation-based detection is not actually the best choice, as it does not utilize the distributional characteristics of the image being marked. Accordingly, an efficient watermark detection scheme for DWT coefficients is proposed as optimal for non-additive schemes. Based on the statistical decision theory, the proposed method is derived according to Bayes decision theory, the Neyman-Pearson criterion, and the distribution of the DWT coefficients, thereby minimizing the missed detection probability subject to a given false alarm probability. The proposed method was tested in the context of robustness, and the results confirmed the superiority of the proposed technique over conventional correlation-based detection method.

• Journal of the Institute of Electronics Engineers of Korea CI
• /
• v.40 no.1
• /
• pp.39-49
• /
• 2003

Watermark detection has a crucial role in copyright protection of and authentication for multimedia and has classically been tackled by means of correlation-based algorithms. Nevertheless, when watermark embedding does not obey an additive rule, correlation-based detection is not the optimum choice. So a new detection algorithm is proposed which is optimum for non-additive watermark embedding. By relying on statistical decision theory, the proposed method is derived according to the Bayes decision theory, Neyman-Pearson criterion, and distribution of wavelet coefficients, thus permitting to minimize the missed detection probability subject to a given false detection probability. The superiority of the proposed method has been tested from a robustness perspective. The results confirm the superiority of the proposed technique over classical correlation- based method.

• Journal of the Korean Society of Radiology
• /
• v.15 no.7
• /
• pp.1015-1020
• /
• 2021

This study retrospectively analyzed the test results of 113 healthy postmenopausal women without special diseases among patients who visited a medical institution in Busan from January 2020 to June 2021. The purpose of the study was to investigate the effect of BMI (Body Mass Index) on bone density in menopause women, the analysis of the lumbar and femur of patients with low weight (BMI<18.5) showed a significant probability (p-value) of 0.000, and the normal weight (18.5≦BMI<23.0) of the femur. In overweight (23.0≦BMI<25.0), the significance probability (p-value) of the lumbar region was 0.021 and the significance probability (p-value) of the femur was 0.034, confirming the correlation. However, in patients with high obesity (30.0≦BMI<40.0), the p-value of the lumbar region was 0.127, and the p-value of the femur was 0.093, indicating that there was no correlation between BMI and bone density.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.13 no.1
• /
• pp.9-17
• /
• 2001

A probability of failure of armor units on rubbJe-mound breakwater are evaluated by using the direct method for reliability analysis, which is represented as a function of safety factor that has been extensively used in practical design. The reliability function is fonnulated based on Hudson formula suggested for designing the stable size of armor units on rubble-mound breakwater. Several kinds of stability coefficient are applied separately to calculate the probability of failure with respect to the type of armor units, breaking/nonbreaking and the correlation coefficients between random variables. [n addition, the sensitivity analyses are carried out to investigate quantitatively into the effects of each random variable in the reliability function on the probability of failure.