• Journal of Advanced Navigation Technology
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• v.18 no.4
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• pp.347-352
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• 2014

In this paper, we propose a Markovian queueing model(M/M/1)-based call admission control to reduce forced terminating rate of non-real secondary user's call for Multi-services Cognitive Radio Networks. A existing control has a problem that the forced terminating rate increases because of adopting a policy of spectrum priority allocation to real calls. In our scheme the rate can be reduced as the call that has no useful spectrum waits in a queue until getting an available spectrum. Our scheme use a neural-net based prediction of primary user's reappearance. Through the simulation, we analysis the call forced terminating rate, access delay and spectrum utilization efficiency, and then show that our scheme can more reduce the forced terminating rate of the call, compared to that of the existing algorithm.

• Korean Journal of Metals and Materials
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• v.49 no.4
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• pp.275-280
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• 2011

This paper focuses on reliability prediction of long-term creep strength for Modified 9Cr-1Mo steel (Gr. 91) which is considered as one of the structural materials of next generation reactor systems. A "Z-parameter" method was introduced to describe the magnitude of standard deviation of creep rupture data to the master curve which can be plotted by log stress vs. The larson-Miller parameter (LMP). Statistical analysis showed that the scattering of the Z-parameter for the Gr. 91 steel well followed normal distribution. Using this normal distribution of the Z-parameter, the various reliability curves for creep strength design, such as stress-time temperature parameter reliability curves (${\sigma}$-TTP-R curves), stress-rupture time-reliability curves (${\sigma}-t_{r}-R$ curves), and allowable stress-temperature- reliability curves ([${\sigma}$]-T-R curves) were reasonably drawn, and their results are discussed.

• International Journal of Precision Engineering and Manufacturing
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• v.3 no.2
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• pp.95-101
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• 2002

The propagation rate(da/dt) prediction parameter and the microstructure properties of creep crack in domestic 3.3NiCrMov steel were investigated at 550$\^{C}$ by using 0.5" CT specimen under constant load(4090N) and constant Ct(300∼4000N/mhr) condition that was maintained during crack growth of 1mm distance. C＊ usually increased with crack length though load was reduced in order to maintain constant Ct value as crack growth and considerably showed the scatter band, but Ct depended on load line displacement rate and represented a good relation with da/dt. At constant toad and Ct region, crack growth slope was 0.900 and 0.844 each, in the other hand C＊ slope was 0.480. Fully coalesced area(FCA) ahead of crack tip was increased as Ct value increase to the critical value, and after that value FCA decreased. The average diameter ditribution of cavity in FCA showed the greatest value about 1.5 ㎛ when Ct=2000N/mhr. The increasing of Ct in FCA view point enlarged the size of damage area and the size reached to maximum 800 ㎛ when Ct=2000N/mhr.

• Journal of Ocean Engineering and Technology
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• v.13 no.3 s.33
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• pp.100-107
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• 1999

Due to the high temperature and pressure, the materials of pipeline in power plant are degraded by creep damage. So far, many conventional measurement techniques such as replica method, electric resistance method, adn hardness test method for creep damage have been used. Among them, the replica method has mainly been used for the inspection of components. But this technique is restricted to the applications at the surface of the objects and cannot be used to material inside. In this paper, the measuring methods of evaluation by using ultrasonic attenuation and electric resistance for the creep detection of creep damage in the form of cavities on grain boundaries or intergranular microcracks were carried out. Absolute measuring method of quantitave ultrasonic attenuation technique for 1Cr0.5Mo material degradation was analyzed for determining the creep degradation steps using life prediction formula. As a result of measurement for creep specimens, we founded that the coefficient of utrasonic attenuation was increased as the increase of creep life fracton(${phi}c$) and the decreasing rate of wlwctric resistance was also increased.

• Journal of Korea Multimedia Society
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• v.8 no.12
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• pp.1649-1657
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• 2005

In this paper, a fast implementation of JPEG is discussed and its application to multimedia service is presented for mobile wireless internet. A fast JPEG player is developed based on several fast algorithms for mobile handset. In the color transformation, RCT is adopted instead of ICT for JPEG source. For the most time-consuming DCT part, the binDCT can reduce the decoding time. In upsampling and RGB conversion, the transformation from YCbCr to RGB 16 bit is made at one time. In some parts, assembly language is applied for high-speed. Also, an implementation of multimedia in mobile handset is described using MJPEG (Motion JPEG) and QCELP(Qualcomm Code Excited Linear Prediction Coding). MJPEG and QCELP are used for video and sound, which are synchronized in handset. For the play of MJPEG, the decoder is implemented as a S/W upon the MSM 5500 baseband chip using the fast JPEG decoder. For the play of QCELP, the embedded QCELP player in handset is used. The implemented multimedia player has a fast speed preserving the image quality.

• Journal of Mechanical Science and Technology
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• v.20 no.3
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• pp.335-344
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• 2006

A comprehensive review of through thickness transverse residual stress distributions in a range of as-welded and mechanically bent components made up of a range of steels has been carried out, and simplified generic transverse residual stress profiles for a plate and pipe components have been proposed. The geometries consisted of welded pipe butt joints, T-plate joints, tubular T-joints, tubular Y-joints and a pipe on plate joints as well as cold bent tubes and pipes. The collected data covered a range of engineering steels including ferritic, austenitic, C-Mn and Cr-Mo steels. Measured residual stress data, normalised with respect to the parent material yield stress, has shown a good linear correlation versus the normalised depth of the region containing the residual stress resulting from the welding or cold-bending process. The proposed simplified generic residual stress profiles based on the mean statistical linear fit of all the data provides a reasonably conservative prediction of the stress intensity factors. Whereas the profiles for the assessment procedures are fixed and case specific, the simple bilinear profiles for the residual stresses obtained by shifting the mean and bending stress from the mean regression line have been proposed and validated.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.04a
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• pp.42-45
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• 2005

Accurate prediction of the fate and transport of contaminants in soils and sediments is very Important to environmental risk assessment and effective remediation of contaminated soils and sediments. The fate and transport of contaminants in subsurface are affected by geosorbents, especially carbonaceous materials including black carbon. Various physical and chemical treatment methods have been developed to separate different kinds of carbonaceous materials from soils and sediments. However, the effects of these separation methods on the properties of remaining carbonaceous materials including sorption capacity and linearity are unclear. The objective of this study is to determine if the chemical and thermal treatment methods previously used to separate different carbonaceous material fractions affect the properties of carbonaceous materials including longer term sorption capacity of hydrophobic organic contaminants. The results indicate that treatments with hydrochloric acid (HCl)/hydrofluoric acid (HF), trifluoroacetic acid (TFA), sodium hydroxide (NaOH) may not affect the sorption capacity of black carbon reference materials such as char and soot, however, treatments with acid dichromate $(K_2Cr_2O_7/H_2SO_4)$ and heat $(375^{\circ}C)$ for 24 hours in sufficient of oxygen) decrease the sorption capacity of them. The results of longer term sorption isotherm indicate that 2 days might be enough for trichloroethene (TCE) to equilibrate apparently with treated black carbon reference materials. The results suggest that acid dichromate and heat treatments may not appropriate method to investigate sorption properties of black carbon in soils and sediments.

• ETRI Journal
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• v.39 no.5
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• pp.672-682
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• 2017

Video compression exploits statistical, spatial, and temporal redundancy, as well as transform and quantization. In particular, the transform in a frequency domain plays a major role in energy compaction of spatial domain data into frequency domain data. The high efficient video coding standard uses the type-II discrete cosine transform (DCT-II) and type-VII discrete sine transform (DST-VII) to improve the coding efficiency of residual data. However, the DST-VII is applied only to the Intra $4{\times}4$ residual block because it yields relatively small gains in the larger block than in the $4{\times}4$ block. In this study, after rearranging the data of the residual block, we apply the DST-VII to the inter-residual block to achieve coding gain. The rearrangement of the residual block data is similar to the arrangement of the basis vector with a the lowest frequency component of the DST-VII. Experimental results show that the proposed method reduces the luma-chroma (Cb+Cr) BD rates by approximately 0.23% to 0.22%, 0.44% to 0.58%, and 0.46% to 0.65% for the random access, low delay B, and low delay P configurations, respectively.

• Economic and Environmental Geology
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• v.52 no.5
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• pp.499-508
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• 2019

Based on the preliminary surveys for the occurrences of the Muwellut chrome-nickel mineralized zone ($800km^2$) in northwestern Myanmar, Bophivum area was selected as the detailed exploration area after considering data source, geological potential, metallogenic province, necessity of resource development on target mineral, exploration activity, grade, ore deposit type, nearby operating mine, infrastructure and exploration prediction effect. From 2013 to 2016, KIGAM and DGSE carried out geological and geochemical survey with 1:1,000 scale, magnetic survey(areal extent, $1.672km^2$), trench survey(19 trench, total length 392 m), pitting survey(18 pit, total depth 42.6m), exploration drilling(6holes 600m, 2015; 13holes 617.4m). We analyzed Cr and Ni contents of 77 drill cores with specific gravity in Yangon DGSE analytical center. Considering surface geological survey, geochemical exploration, magnetic survey, trench survey and drilling data, we divided Bophivum area into 8 blocks. Resource estimation are divided into measured and indicated resources. Measured resource is about 9,790t and indicated resource is about 12,080t with the average grade of Cr 11.8% and Ni 0.34%. In case of Bophivum area, if we develop by tying up Webula chrome mineralized zone in the south, it will be possible to upgrade the medium-scale mine. Geologically, the ophiolite belt are distributed in the western and eastern part in Myanmar. So, the exploration technology obtained from exploation in Bophivum area will be helpful to discover the hidden chromitite ore body in Myanmar ophiolite belt in the future.

• Spatial Information Research
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• v.14 no.1 s.36
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• pp.129-150
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• 2006

Mineral potential mapping is an important procedure in mineral resource assessment. The purpose of this study is to analyze mineral potential using weight of evidence model and a Geographic Information System (GIS) environment to identify areas that have not been subjected to the same degree of exploration. For this, a variety of spatial geological data were compiled, evaluated and integrated to produce a map of potential mineral in the Gangreung area, Korea. for this, a spatial database considering mineral deposit, topographic, geologic, geophysical and geochemical data was constructed for the study area using a GIS. The used mineral deposits were non-metallic(Kaolin, Porcelainstone, Silicastone, Mica, Nephrite, Limestone and Pyrophyllite) deposits of sedimentary type. The factors relating to mineral deposits were the geological data such as lithology and fault structure, geochemical data, including the abundance of Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, Pb, Si, Sr, V, Zn, $Cl^-,\;F^-,\;{PO_4}^{3-},\;{NO_2}^-,\;{NO_3}^-,\;SO_{42-}$, Eh, PH and conductivity and geophysical data, including the Bouguer and magnetic anomalies. These factors were used with weight of evidence model to analyze mineral potential. Probability models using the weight of evidence were applied to extract the relationship between mineral deposits and related factors, and the ratio were calculated. Then the potential indices were calculated by summation of the likelihood ratio and mineral potential maps were constructed from Geographic Information System (GIS). The mineral potential maps were then verified by comparison with the known mineral deposit areas. The result showed the 85.66% in prediction accuracy.