• Journal of Korea Multimedia Society
• /
• v.8 no.1
• /
• pp.34-45
• /
• 2005

In this paper, a novel implementation of a person verification system based on depth-weighted Hausdorff distance (DWHD) using the surface curvature of the face is proposed. The definition of Hausdorff distance is a measure of the correspondence of two point sets. The approach works by finding the nose tip that has a protrusion shape on the face. In feature recognition of 3D face image, one has to take into consideration the orientated frontal posture to normalize after extracting face area from original image. The binary images are extracted by using the threshold values for the curvature value of surface for the person which has differential depth and surface characteristic information. The proposed DWHD measure for comparing two pixel sets were used, because it is simple and robust. In the experimental results, the minimum curvature which has low pixel distribution achieves recognition rate of 98% among the proposed methods.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.22 no.4
• /
• pp.423-429
• /
• 2011

Cooperative spectrum sensing is proposed to overcome some problem such as multipath fading and shadowing and to improve spectrum sensing performance. There are different combining methods for cooperative spectrum sensing: hard decision method and soft decision method. In this paper, we analysis the performance of cooperative spectrum sensing with distance based weight that is kind of a soft decision rule for cognitive radio(CR) systems and CR systems sense the spectrum of the licensed user by using a energy detection method. Threshold is determined in accordance with the constant false alarm rate(CFAR) algorithm for energy detection. The signal of licensed user is OFDM signal and the wireless channel between a licensed user and CR systems is modeled as Gaussian channel. From the simulation results, the cooperative spectrum sensing with distance based weight combining(DWC) and equal gain combing(EGC) methods shows higher spectrum sensing performance than single spectrum sensing does. And the detection probability performance with the DWC is higher than that with the EGC.

• Journal of Ocean Engineering and Technology
• /
• v.36 no.5
• /
• pp.340-352
• /
• 2022

This article presents a modeling method for the uncorrelated measurement error of the ultra-short baseline (USBL) acoustic positioning system for aiding navigation of underwater vehicles. The Mahalanobis distance (MD) and principal component analysis are applied to decorrelate the errors of USBL measurements, which are correlated in the x- and y-directions and vary according to the relative direction and distance between a reference station and the underwater vehicles. The proposed method can decouple the radial-direction error and angular direction error from each USBL measurement, where the former and latter are independent and dependent, respectively, of the distance between the reference station and the vehicle. With the decorrelation of the USBL errors along the trajectory of the vehicles in every time step, the proposed method can reduce the threshold of the outlier decision level. To demonstrate the effectiveness of the proposed method, simulation studies were performed with motion data obtained from a field experiment involving an autonomous underwater vehicle and USBL signals generated numerically by matching the specifications of a specific USBL with the data of a global positioning system. The simulations indicated that the navigation system is more robust in rejecting outliers of the USBL measurements than conventional ones. In addition, it was shown that the erroneous estimation of the navigation system after a long USBL blackout can converge to the true states using the MD of the USBL measurements. The navigation systems using the uncorrelated error model of the USBL, therefore, can effectively eliminate USBL outliers without loss of uncontaminated signals.

• Journal of the Korean Institute of Gas
• /
• v.27 no.4
• /
• pp.78-84
• /
• 2023

Recently, the world's countries are tightening regulations on CO2 and air pollutants emission to solve them. In addition, eco friendly vehicles is increasing to replace automobiles in internal combustion engine. The government is supporting the expansion of hydrogen refueling infrastructure according to the hydrogen economy road map. In particular, refueling station is important to secure the safety that supplies high-pressure hydrogen with a wide LFL range. This paper is on guidelines for the determination safety distances to ensure worker safety from accident as jet fire. The safety distance is set according to the procedure of the EIGA doc 075/21. For accident frequency is upper 3.5E-05 per annum, safety distance is decided via consequence analysis where the risk of harm is below individual harm exposure threshold.

• Journal of the Korean Ceramic Society
• /
• v.39 no.1
• /
• pp.92-98
• /
• 2002

To investigate the electrode structural effect on the ferroelectric electron emission, the electric field distribution in a 2-dimensional structure was calculated as a function of upper electrode diameter, and the switching charge density and emission charge were measured simultaneously. The simulation of the electric field distribution showed that an asymmetric electrode structure could cause a stray field on the bare surface of the ferroelectric cathode near the edge of upper electrode. The distance of stray field from the electrode edge increased with increasing ferroelectric thickness, but it did not depend on the upper electrode diameter. The switching charge density increased more on the cathode with smaller upper electrode diameter. This was attributed to the stray field on the bare ferroelectric surface near the electrode edge, because the stray field for the asymmetric ferroelectric cathode enhanced polarization switching near the electrode edge. From the switching charge density, the distance of stray field from the electrode edge was calculated as about 11-14${\mu}{\textrm}{m}$. The threshold voltage of electron emission was 61-68 kV/cm, which was almost 3 times lager than the coercive voltage. The threshold voltage was not determined just by coercive voltage, but by strength and distance of the stray-field, which largely depended on the geometrical structure of ferroelectric cathode.

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.17 no.3
• /
• pp.191-201
• /
• 2015

Measuring and mapping connectivity among habitats is a key component of sustainable urban planning and design process. In this study, we examined how functional corridors connect forest bird habitats in a metropolitan area of Korea using graph theory-based techniques. High-quality forest habitat was defined as a function of forest cover, presence of residential areas, and road networks. We then constructed a network of high-quality forest habitats using the FunConn (functional connectivity) tools, and computed metrics ($T_i$) of patch importance based on the minimum ($Q_1$) and the 25th percentile ($Q_{25}$) rank least-cost distance values. We investigated the relative influence of two values of patch importance on forest bird species richness. As a result, the patch importance index based on the $Q_{25}$ effective distance threshold was most positively correlated with species richness (P < 0.001) after controlling for the area effect. Thus, using the $Q_{25}$ effective distance threshold, we mapped not only the locations of important habitat patches and functional corridors, but also the network backbone of forest bird habitats. The network developed in this study can help guide urban planning for biodiversity conservation.

• Journal of Korean Institute of Industrial Engineers
• /
• v.32 no.1
• /
• pp.42-50
• /
• 2006

The multi-criteria group decision making (MCGDM) problem is to determine the best compromise solution in a set of competing alternatives that are evaluated under conflicting criteria by decision maker (DM)s. In this paper, we propose a mixed-integer programming (MIP) model to solve MCGDM. The existing method based on minimizing a distance measure such as Median Approach can not guarantee the best compromise solution because the element of median point vector is defined with respect to each criteria separately. However, by considering all criteria simultaneously, we generate median point that is better for locating the best compromise solution. We also utilize the concept of spatial dispersion index (SDI) to produce a threshold value, which is used as a guideline to choose either the Utopian Approach or the Median Approach. And we suggest using CBITP (Convex hull of individual maxima Based Interactive Tchebycheff Procedure) to provide DMs with various Pareto-optimal solutions so that DMs have broad range of selection.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.6 no.4
• /
• pp.255-261
• /
• 2013

In this paper, we compare two methods that improve the reliability of soft output at the receiver of MIMO communications. The receiver complexity of spatially mutiplexed MIMO system is in proportion to the number of candidate vectors. Low complexity receiver techniques involving a small number of candidate vectors, provide soft output values of low reliability. In order to improve the low reliability of soft output, two previous methods can be used; the first method involves a clipping threshold, the second method uses Euclidian distance instead of squared Euclidian distance. In the paper, we address the theoretical similarity of the two methods, then we compare the two methods from the perspective of hardware implementation.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.1 no.1
• /
• pp.53-59
• /
• 2008

In this paper, we compare two methods that improve the reliability of soft output at the receiver of MIMO communications. The receiver complexity of spatially mutiplexed MIMO system is in proportion to the number of candidate vectors. Low complexity receiver techniques involving a small number of candidate vectors, provide soft output values of low reliability. In order to improve the low reliability of soft output, two previous methods can be used; the first method involves a clipping threshold, the second method uses Euclidian distance instead of squared Euclidian distance. In the paper, we address the theoretical similarity of the two methods, then we compare the two methods from the perspective of hardware implementation.

• Computers and Concrete
• /
• v.5 no.4
• /
• pp.375-388
• /
• 2008

Crack opening governs many transfer properties that play a pivotal role in durability analyses. Instead of trying to combine continuum and discrete models in computational analyses, it would be attractive to derive from the continuum approach an estimate of crack opening, without considering the explicit description of a discontinuous displacement field in the computational model. This is the prime objective of this contribution. The derivation is based on the comparison between two continuous variables: the distribution if the effective non local strain that controls damage and an analytical distribution of the effective non local variable that derives from a strong discontinuity analysis. Close to complete failure, these distributions should be very close to each other. Their comparison provides two quantities: the displacement jump across the crack [U] and the distance between the two profiles. This distance is an error indicator defining how close the damage distribution is from that corresponding to a crack surrounded by a fracture process zone. It may subsequently serve in continuous/discrete models in order to define the threshold below which the continuum approach is close enough to the discrete one in order to switch descriptions. The estimation of the crack opening is illustrated on a one-dimensional example and the error between the profiles issued from discontinuous and FE analyses is found to be of a few percents close to complete failure.