• The Korean Journal of Zoology
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• v.31 no.1
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• pp.1-10
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• 1988

A syrnpatnc sample of Rana nigrnmaculata sand R plancyi (Anura) from Kwangu, Korea was investigated to clarify their taxonornic status and to estimate the degree of genic variation, genetic relatedness, and reproductive isolation between them, based on electrophoretic analysis, marphometric data, mating call, mating season, and habitat. All the characters measured including morphometric, genetic, behavioral, and ecological suggest that they are distinct species and R nigrnmaculata might have originated from R plancyi (tropical form about three and a half million years ago. An adult female was found to be Fl hybrid between two species The hybrid female possessed fettile eggs and morphologically intermediate to the parental species in head parts, hind limb, and web characters. The differences in mating call, mating behavior, breeding season, and habitat strongly suggest that postmating isolating mechanism is operating, even though very rare hybrid is found.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.05a
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• pp.123-126
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• 2005

Eye Glass Display (EGD) with microdisplay to realize the virtual display can make the large screen, so virtual image has been developed by using microdisplay panel. This paper shows study of low cost lens design and simulation for microdisplay system with 0.6"LCoS panel. Lens design optimized consider to spherical aberration, astigmatism, distortion, and chromatic aberration. Code V is used and it designed an aspheric lens about exit pupil 6mm, eye relief 20mm and 35 degree of field of view (FOV). With the application this aspheric lens to liquid crystal on silicon (LCOS) type's microdisplay, virtual image showed 50 inch at 2m. One side of the aspheric lens was constituted from diffractive optical element (DOE) for the improvement in a performance. It had less than 2.5% of distortion value and modulation transfer function in axial had 20% of resolution with 32 lp/mm spatial frequency. The optical system is suitable for display of 15.6 mm-diagonal with SVGA.

• Journal of Information Processing Systems
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• v.6 no.1
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• pp.53-66
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• 2010

The energy efficiency is a key design issue to improve the lifetime of the underwater sensor networks (UWSN) consisting of sensor nodes equipped with a small battery of limited energy resource. In this paper, we apply a hexagon tessellation with an ideal cell size to deploy the underwater sensor nodes for two-dimensional UWSN. Upon this setting, we propose an enhanced hybrid transmission method that forwards data packets in a mixed transmission way based on location dependent direct transmitting or uniform multi-hop forwarding. In order to select direct transmitting or uniform multi-hop forwarding, the proposed method applies the threshold annulus that is defined as the distance between the cluster head node and the base station (BS). Our simulation results show that the proposed method enhances the energy efficiency compared with the existing multi-hop forwarding methods and hybrid transmission methods

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.3
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• pp.1213-1237
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• 2019

Vehicular Ad-hoc Network (VANET) facilities envision future Intelligent Transporting Systems (ITSs) by providing inter-vehicle communication for metrics such as road surveillance, traffic information, and road condition. In recent years, vehicle manufacturers, researchers and academicians have devoted significant attention to vehicular communication technology because of its highly dynamic connectivity and self-organized, decentralized networking characteristics. However, due to VANET's high mobility, dynamic network topology and low communication coverage, dissemination of large data packets (e.g. multimedia content) is challenging. Clustering enhances network performance by maintaining communication link stability, sharing network resources and efficiently using bandwidth among nodes. This paper proposes a mobility-based, multi-hop clustering algorithm, (MBCA) for multimedia content broadcasting over an IEEE 802.11p-LTE-enabled hybrid VANET architecture. The OMNeT++ network simulator and a SUMO traffic generator are used to simulate a network scenario. The simulation results indicate that the proposed clustering algorithm over a hybrid VANET architecture improves the overall network stability and performance, resulting in an overall 20% increased cluster head duration, 20% increased cluster member duration, lower cluster overhead, 15% improved data packet delivery ratio and lower network delay from the referenced schemes [46], [47] and [50] during multimedia content dissemination over VANET.

• Journal of Korea Multimedia Society
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• v.24 no.3
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• pp.355-372
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• 2021

Recently, high-performance HMDs (Head-Mounted Display) are becoming wireless due to the growth of virtual reality technology. Accordingly, environmental constraints on the hardware usage are reduced, enabling multiple users to experience virtual reality within a single space simultaneously. Existing multi-user virtual reality platforms use the user's location tracking and motion sensing technology based on vision sensors and active markers. However, there is a decrease in immersion due to the problem of overlapping markers or frequent matching errors due to the reflected light. Goal of this study is to develop a multi-user virtual reality moving platform in a single space that can resolve sensing errors and user immersion decrease. In order to achieve this goal hybrid sensing technology was developed, which is the convergence of vision sensor technology for position tracking, IMU (Inertial Measurement Unit) sensor motion capture technology and gesture recognition technology based on smart gloves. In addition, integrated safety operation system was developed which does not decrease the immersion but ensures the safety of the users and supports multimodal feedback. A 6 m×6 m×2.4 m test bed was configured to verify the effectiveness of the multi-user virtual reality moving platform for four users.

• Journal of Korea Multimedia Society
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• v.23 no.11
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• pp.1388-1395
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• 2020

Daily monitoring of the heart rate can facilitate detection of heart-related diseases in their early stages. Therefore, providing an easy-to-use and noninvasive heart rate monitoring system has been a very popular research topic in the field of healthcare. One of good candidate methods is to use commonly available cameras and extract information that can help to estimate heart rate from a human face. Generally, such information can be retrieved using two different approaches: photoplethysmography (PPG) and ballistocardiography (BCG). PPG exploits slight color changes caused by blood volume variations during heartbeats; thus, it tends to be vulnerable to unstable lighting conditions. BCG exploits subtle head motions caused by pumped blood travelling through the carotid artery during heartbeats; thus, it is vulnerable to the voluntary head movements that are not related to heartbeats. Nevertheless, most related works use either to estimate the heart rate. In this paper, we propose to combine two approaches to be robust to challenging conditions. Specifically, we explore possible ways to combine raw signals obtained from two approaches and verify that the proposed combination shows better accuracies under challenging conditions, such as voluntary head movements and ambient lighting changes.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.3
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• pp.68-74
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• 1998

Performance and efficiency of deep seabed collector is a primary factor for feasibility of commercial deep ocean mining. The efficiency of manganese nodules collector depends on vehicle mobility relative to undulating seafloor and is attributed pickup head to keep altitude and elevation of it against seafloor. For this reason, motion control of pickup head relative to the changing deep-sea topography and other disturbances is of particular importance in design of pickup device. The concept of design axiom is applied to a pickup device of hybrid type in order to evaluate the concept design. Kinematic analysis conducted in absolute Cartesian coordinates gives position, velocity, and acceleration of the hydraulic cylinders which enable the pickup head to keep the preset optimal distance from seafloor. Inverse dynamic analysis provides the driving forces of hydraulic cylinders and the reaction forces at each joint. Design sensitivity analysis is performed in order to investigate the effects of possible design variables on the change of the maximum strokes of hydraulic cylinders. The direct differentiation method is used to obtain the design sensitivity coefficients.

• Nuclear Engineering and Technology
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• v.51 no.4
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• pp.1060-1068
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• 2019

This work aims to establish a model of a primary water stress corrosion crack growth rate of Alloy 690 material for the head penetration nozzles of Korean pressurized water reactors. The test material had an inhomogeneous microstructure with bands of fine-grains and intragranular carbides in the matrix of coarse-grains, which was similar to the archive materials of the head penetration nozzles. The crack growth rate was measured from the strain-hardened materials as a function of the stress intensity factor in simulated primary water at various temperatures and dissolved hydrogen contents. The effects of strain-hardening, temperature, and dissolved hydrogen on the crack growth rate were analyzed independently, and were then introduced as normalizing factors in the crack growth rate model. The crack growth rate model proposed in this work provides a key element of the tools needed to assess the progress of a stress corrosion crack when detected in thick-wall Alloy 690 components in Korean reactors.

• The Magazine of the IEIE
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• v.35 no.9
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• pp.58-69
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• 2008

디지털 케이블TV서비스는 헤드엔드(Head-End)센터로부터 QoS (Quality of Service)가 보장되는 케이블 HFC(Hybrid FiberCable)망을 통해 디지털 영상 방송이나 양방향서비스를 가입자 단말까지 제공하는 방송 통신 융합서비스이다. 본 고에서는 디지털 케이블TV 서비스를 제공하기 위한 디지털 케이블 네트워크 기술에 대해서 설명하고, 디지털 방송 및 양방향 서비스를 송출하는 방송센터시스템과 디지털 방송 기술에 대해 알아본 후 마지막으로 디지털 케이블TV의 향후 전망에 대해서 살펴보기로 한다.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.6
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• pp.681-686
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• 2007

The flow analysis was made by applying the turbulent models in the scroll volume of centrifugal compressor. The $k-{\varepsilon}.\;k-{\omega}$, Spalart-Allmaras and reynolds stress models are used in which the hybrid grid is applied for the simulation. The velocity vector the Pressure contour. the change of residual along the iteration number. and the dynamic head are simulated by solving the Navier-Stokes equations for the comparison of four example cases.