• The Journal of the Korea Contents Association
• /
• v.7 no.12
• /
• pp.303-310
• /
• 2007

Compressed video bitstreams are intended for real-time transmission over communication networks. Because video compression algorithms eliminate the temporal, spatial, and statistical redundancies, the coded video bitstreams are very sensitive to transmission errors. We propose an error resilient video coding technique to limit the effect of error propagation in low bit-rate video coding. The success of error resilient coding techniques relies on how accurately the transmission errors can be detected. To detect the transmission error, we propose a very simple error detection technique based on data hiding Next, we conceal the corrupted MB data using intra MB refresh and motion compensation with the estimated motion vector and compare the simulation results. This method will be useful in video communication in error Prone environment such as WCDMA networks.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.38 no.8
• /
• pp.857-862
• /
• 2014

The research on a thermal stress control layer (TSCL) begins to undertake to reduce residual stress and strain in the vicinity of the joined region between the hardfacing layer and the base part. The goal of this paper is to estimate the material combination and the thickness of TSCL for the Stellite21 hardfaced STD61 hot working tool steel via three-dimensional finite element analysis (FEA). TSCL is created by the combination of Stellite21 and STD61. The thickness of TSCL ranges from 0.5 mm to 1.5 mm. The influence of the material combination and the thickness of TSCL on temperature, thermal stress and thermal strain distributions of the hardfaced part have been investigated. The results of the investigation have been revealed that a proper material combination of TSCL is Stellite21 of 50 % and STD61 of 50 %, and its appropriate thickness is 1.0 mm.

• Journal of Mushroom
• /
• v.6 no.1
• /
• pp.38-41
• /
• 2008

Studies were processed to confirm the difference of the shiitake productivity according to different spawn shapes(sawdust, plug-shaped and liquid spawns) on middle-temperature type strain. A tendency of fruiting was similar among three treatments, and treatments inoculated with plug-shaped spawn and liquid spawn produced over 50 % of total yield until 2nd flushing period and 80 % of total yield until 4th flushing period. In investigation of deformed fruit-bodies, all of three treatments occurred until 2nd flushing period. However, in rate of deformed fruit-bodies, treatment inoculated with liquid spawn was lower than others. In investigation of yield, the amount produced on treatment inoculated with liquid spawn was 411 g per medium and it was highest among treatments. And the amount of fruit-bodies over 10 g was higher than others. Also, the number of fruit-bodies between sawdust and plug-shaped spawn was different, but each weight of fruit-bodies among three treatments was not different.

• Journal of the Korea Concrete Institute
• /
• v.28 no.6
• /
• pp.665-672
• /
• 2016

This study is conducted to investigate the effect of phase change materials (PCM) on hydration heat and strength characteristics of cement mortar. Two types of Barium and Strontium-based PCMs were used in this study and the addition ratio of each PCM to the cement mortar ranged from 1% to 5% by cement weight. Flow test, semi-adiabatic temperature rise test, compressive strength and flexural strength test were carried out to examine the PCM effect on heat and mechanical properties of cement mortar. Test results indicated that PCMs used in this study were effective to control hydration heat of cement mortar, and Barium-based PCM slightly reduce flow value. The compressive and flexural strength of cement mortar with PCM decreased with increasing the adding mount of PCM. The prediction model for compressive strength of cement mortar with different addition levels of PCMs are suggested in this study.

• Journal of Satellite, Information and Communications
• /
• v.9 no.4
• /
• pp.91-96
• /
• 2014

This paper proposed an adaptive threshold method for detecting flame candidate regions in a infrared image and it adapts according to the contrast and intensity changes in the image. Conventional flame detection systems uses fixed threshold method since surveillance environment does not change, once the system installed. But it needs a adaptive threshold method as requirements of surveillance system has changed. The proposed adaptive threshold algorithm uses the dynamic behavior of flame as featured parameter. The test result is analysed by comparing test result of proposed adaptive threshold algorithm and conventional fixed threshold method. The analysed data shows, the proposed method has 91.42% of correct detection rate and false detection is reduced by 20% comparing to the conventional method.

• Fire Science and Engineering
• /
• v.13 no.3
• /
• pp.3-17
• /
• 1999

Smoldering is a non-flaming combustion mode, characterized by thermal degradation and c charring of the virgin material, evolution of smoke and emission of visible glow. A big fire may @ occur even in a confined environment having a limited amount of oxygen, due to smoldering c combustion through a porous solid material. This paper presents a theoretical analysis on the effect of smoldering combustion on fire occurrence based on a report about fire investigation of a real f fire accident. It is assumed that the propagation of the smolder wave is one-dimensional, d downward, opposing an upward forced flow and steady in a frame of reference moving with the s smolder wave. Smoldering combustion is modeled by a one-step reaction mechanism, without c considering pyrolysis. It is found that dominant parameters controlling smoldering combustion i include mass flux of oxidizer entering the reaction zone and void fraction of solid fuel. It is also found that the mechanism of transition to flaming is critically influenced by these two parameters.

• Proceedings of the Optical Society of Korea Conference
• /
• 2003.07a
• /
• pp.144-145
• /
• 2003

열상카메라는 빛이 전혀 없는 야간에도 선명한 영상을 획득할 수 있도록 구성된 장비이다. 이러한 열상카메라는 야간 영상 획득에 있어서 많은 분야에서 사용되고 또한 반드시 사용되어야만 한다. 또한 열상카메라를 구성하기 위하여 사용되는 렌즈의 재질은 온도에 대한 굴절률의 변화가 크고 경도가 낮아 외부 환경에 대한 영향성이 크다. 열상카메라의 성능에 영향을 주는 외부 환경 요소로는 열상카메라가 사용되는 환경에서 발생하는 진동의 요인과 내부 및 외부로부터 받는 온도에 대한 요인이다. (중략)

• Smart Media Journal
• /
• v.9 no.1
• /
• pp.38-44
• /
• 2020

Due to the high dependence on electric energy, electric fires make up a significant portion of fires in Korea. Electric arcs by short circuits or poor contact cause three of four electrical fires. An electric arc is a discharge phenomenon of electrical current between the insulators, which instantaneously produces high temperature. In order to reduce the fire due to electric arc, this study aims to predict the electric arc risk. We collected arc data from the arc detectors and converted into graphs based on temporal arc data. We used machine learning for training converted graph with different number of temporal arc data. To measure the performance of the learning model, we use the test data. In the results, when the number of temporal arc data was 20, the prediction rate was high as 86%.

• Journal of the Microelectronics and Packaging Society
• /
• v.17 no.3
• /
• pp.17-26
• /
• 2010

Pb-Sn solder is rapidly being replaced by lead-free solder for board-level interconnection in microelectronic package assemblies due to the environmental protection requirement. There is a general lack of mechanical reliability information available on the lead-free solder. In this study, thermo-mechanical behaviors of wire-bond plastic ball grid array (WB-PBGA) package assemblies are characterized by high-sensitivity moire interferometry. Experiments are conducted for two types of WB-PBGA packages that have Pb-Sn solder and lead-free solder as joint interconnections. Using real-time moire setup, fringe patterns are recorded and analyzed for several temperatures. Bending deformations of the assemblies and average strains of the solder balls are investigated and compared for the two type of WB-PBGA package assemblies. Results show that shear strain in #3 solder ball located near the chip shadow boundary is dominant for the failure of the package with Pb-Sn solder, while normal strain in #7 most outer solder ball is dominant for that with lead-free solder. It is also shown that the package with lead-free solder has much larger bending deformation and 10% larger maximum effective strain than the package with Pb-Sn solder at same temperature level.

• Journal of the Korea Concrete Institute
• /
• v.25 no.5
• /
• pp.497-508
• /
• 2013

This paper introduces a numerical model which can evaluate the fire-resistant capacity of reinforced concrete members. On the basis of the transient heat transfer considering the heat conduction, convection and radiation, time-dependent temperature distribution across a section is determined. A layered fiber section method is adopted to consider non-linear material properties depending on the temperature and varying with the position of a fiber. Furthermore, effects of non-mechanical strains of each fiber like thermal expansion, transient strain and creep strain are reflected on the non-linear structural analysis to take into account the extreme temperature variation induced by the fire. Analysis results by the numerical model are compared with experimental data from the standard fire tests to validate an exactness of the introduced numerical model. Also, time-dependent changes in the resisting capacities of reinforced concrete members exposed to fire are investigated through the analyses and, the resisting capacities evaluated are compared with those determined by the design code.