• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4C
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• pp.265-273
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• 2006

This study aims at evaluation of the fire resistance performance of cementitious materials for fire protection of tunnel. For this purpose, the research procedure was divided into three parts. First, base mix proportion with different material type were determined by fire test. Second, the fire test of cementitious materials for fire resistance were performed on base mix proportions to evaluated their performance. Third, the performance of cementitious materials for fire resistance compare to the target value and existing commercial products. If the performance of developed cemetitious materials for fire resistance were satisfied the target value, this studies were stopped. But, this research return to first process if the performance of cementitious materials for fire resistance are not satisfied the target value. As a result of this study, the spalling did not happen for develop and existing commercial product. Also, developed cementitious materials for fire resistance are shown with excellent compressive strength, flexural strength, and bond strength, because it used a height density aggregate. And developed cementitious materials has sufficient resistance for fire.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.9
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• pp.4661-4664
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• 2012

Mammographic breast density is a known risk factor for breast cancer. To conduct a survey to estimate the distribution of mammographic breast density in Korean women, appropriate sampling strategies for representative and efficient sampling design were evaluated through simulation. Using the target population from the National Cancer Screening Programme (NCSP) for breast cancer in 2009, we verified the distribution estimate by repeating the simulation 1,000 times using stratified random sampling to investigate the distribution of breast density of 1,340,362 women. According to the simulation results, using a sampling design stratifying the nation into three groups (metropolitan, urban, and rural), with a total sample size of 4,000, we estimated the distribution of breast density in Korean women at a level of 0.01% tolerance. Based on the results of our study, a nationwide survey for estimating the distribution of mammographic breast density among Korean women can be conducted efficiently.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.82.1-82.1
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• 2010

We have investigated the spatial configuration of stars within the tidal radius of metal poor globular cluster NGC 6626 in the bulge direction. Data were obtained in near-IR J,H,Ks bands with wide-field ($20'\times20'$) detector, WIRCam at CFHT. To trace the stellar density around target cluster, we sorted cluster's member stars by using a mask filtering algorithm and weighting the stars on the color-magnitude diagram. From the weighted surface density map, we found that the stellar spatial distributions within the tidal radius appear asymmetric and distorted features. Especially, we found that more prominent over-density features are extending toward the direction of Galactic plane rather than toward the directions of the Galactic center and its orbital motion. This orientation of the stellar density distribution can be interpreted with result of disk-shock effect of the Galaxy that the cluster had been experienced. Indeed, this over-density feature are well represented in the radial surface density profile for different angular sections. As one of the metal poor globular clusters with extended horizontal branch (EHB) in the bulge direction, NGC 6626 is kinematically decoupled from the normal clusters and known to have disk motion of peculiar motion. Thus, our result will be able to add further constraints to understand the origin of this cluster and the formation of bulge region in early universe.

• Advances in biomechanics and applications
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• v.1 no.1
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• pp.15-22
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• 2014

Computed tomography (CT) is being utilized in orthopaedics and related research to estimate bone strength. These applications benefit from calibration of Hounsfield units to mineral density typical of long bone, up to $1750mg/cm^3$. This study describes a method for establishing repeatable calibration of Hounsfield units to density, and determines the effects of imaging medium on calibration accuracy. Four hydroxyapatite standards were imaged in air on 7 occasions over 19 weeks using a helical multi-slice CT scanner. Each standard was scanned 5 times in different media: porcine soft tissue, water, and air. Calibrated densities were highly repeatable (CV<3.5%). No difference in density was observed between water and soft tissue conditions (p>0.08). This work provides a model for determining repeatable scanner-specific density calibration, demonstrates that the linear relationship between Hounsfield units and density extends to values typical of cortical bone, and supports the practice of imaging calibration standards in an environment similar to that of the target bone.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2009.01a
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• pp.136-141
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• 2009

This paper proposed a framework for handover method in continuously tracking a person of interest across cooperative pan-tilt-zoom (PTZ) cameras. The algorithm here is based on a robust non-parametric technique for climbing density gradients to find the peak of probability distributions called the mean shift algorithm. Most tracking algorithms use only one cue (such as color). The color features are not always discriminative enough for target localization because illumination or viewpoints tend to change. Moreover the background may be of a color similar to that of the target. In our proposed system, the continuous person tracking across cooperative PTZ cameras by mean shift tracking that using color and shape histogram to be feature distributions. Color and shape distributions of interested person are used to register the target person across cameras. For the first camera, we select interested person for tracking using skin color, cloth color and boundary of body. To handover tracking process between two cameras, the second camera receives color and shape cues of a target person from the first camera and using linear color calibration to help with handover process. Our experimental results demonstrate color and shape feature in mean shift algorithm is capable for continuously and accurately track the target person across cameras.

• Journal of the Optical Society of Korea
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• v.13 no.1
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• pp.48-52
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• 2009

Micro-hole targets are studied to generate energetic protons from laser-thin foil targets by using 2-dimensional particle-in-cell simulations. By using a small hole, the maximum energy of the accelerated proton is increased to 4 times higher than that from a simple planar target. The main proton acceleration mechanism of the hole-targets is the electrostatic field created between the fast electrons accelerated by the laser pulse ponderomotive force combined with the vacuum heating and the target rear surface. But in this case, the proton angular distribution shows double-peak shape, which means poor collimation and low current density. By using a small cone-shaped hole, the maximum proton energy is increased 3 times higher than that from a simple planar target. Furthermore, the angular distribution of the accelerated protons shows good collimation.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.55 no.9
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• pp.401-408
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• 2006

In a multi-sensor multi-target tracking systems, the local sensors have the role of tracking the target and transferring the measurements to the fusion center. The measurements from the same target can arrive out of sequence called the out-of-sequence measurements(OOSMs). Out-of-sequence measurements can arise at the fusion center due to communication delay and varying preprocessing time for different sensor platforms. In general, the track fusion occurs to enhance the tracking performance of the sensors using the measurements from the sensors at the fusion center. The target informations can wive at the fusion center with the clutter informations in cluttered environment. In this paper, the OOSM update step with MPDA(Most Probable Data Association) is introduced and tested in several cases with the various clutter density through the Monte Carlo simulation. The performance of the MPDA with OOSM update step is compared with the existing NN, PDA, and PDA-AI for the air target tracking in cluttered and out-of-sequence measurement environment. Simulation results show that MPDA with the OOSM has compatible root mean square errors with out-of-sequence PDA-AI filter and the MPDA is sufficient to be used in out-of-sequence environment.

• Nuclear Engineering and Technology
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• v.55 no.3
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• pp.919-926
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• 2023

To analyze the cause of the destruction of thin, carbon-backed lithium fluoride targets during a measurement of the fusion of ⁷Li and ¹⁷O, we estimate theoretically the lifetimes of carbon and LiF films due to sputtering, thermal evaporation, and lattice damage and compare them with the lifetime observed in the experiment. Sputtering yields and thermal evaporation rates in carbon and LiF films are too low to play significant roles in the destruction of the targets. We estimate the lifetime of the target due to lattice damage of the carbon backing and the LiF film using a previously reported model. In the experiment, elastically scattered target and beam ions were detected by surface silicon barrier (SSB) detectors so that the product of the beam flux and the target density could be monitored during the experiment. The areas of the targets exposed to different beam intensities and fluences were degraded and then perforated, forming holes with a diameter around the beam spot size. Overall, the target thickness tends to decrease linearly as a function of the beam fluence. However, the thickness also exhibits an increasing interval after SSB counts per beam ion decreases linearly, extending the target lifetime. The lifetime of thin LiF film as determined by lattice damage is calculated for the first time using a lattice damage model, and the calculated lifetime agrees well with the observed target lifetime during the experiment. In experiments using a thin LiF target to induce nuclear reactions, this study suggests methods to predict the lifetime of the LiF film and arrange the experimental plan for maximum efficiency.

• Journal of the Korean Solar Energy Society
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• v.22 no.3
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• pp.31-37
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• 2002

This experimental study represents the results of an analysis on the characteristics of flux density distributions in the focal region of solar concentrator. The characteristics of flux density distributions are investigated to optimally design and position a cavity receiver. This deemed very useful to find and correct various errors associated with a dish concentrator. We estimated the flux density distribution on the target placed along with focal lengths from the dish vertex to experimentally determine the focal length. It is observed that the actual focal point exists when the focal length is 2.17 m. We also evaluated the position of flux centroid, and it was found that there were errors within 2 cm from the target center. The total integrated power of 2467 W was measured under focal flux distributions, which corresponds to the intercept rate of 85.8%. As a result of the percent power within radius, approximately 90% of the incident radiation is intercepted by about 0.06 m radius.

• Journal of Korean Society of Transportation
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• v.23 no.2
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• pp.83-92
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• 2005

We try to evaluate the stock level of Korean transportation infrastructure comparing Korean SOC stock level with those of OECD countries. In order to do so, we work on indices to show the transportation infrastructure stock levels of various countries. Among several indices, we select the effective road-extension rate per population density and the effective railroad-extension rate per population density corresponding to road and railroad. We compare Korean road and railroad stock levels with those of OECD countries, to make use of the effective road-extension rate per population density and effective railroad-extension rate per population density. We choose the Britain, Greece, Portugal, and Sweden to compare Korea because their sizes of population and territory are similar to those of Korea. Using International comparison, we arrive at the conclusion that Korean road and railroad stock levels are 63.4% and 53.2% of those of four countries respectively. In addition, we estimate the target level of road and railroad stocks and compute the target level of investments in road and railroad based on the result.