• Nuclear Engineering and Technology
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• v.46 no.6
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• pp.837-846
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• 2014

A lead slowing down spectrometer (LSDS) is under development for analysis of isotopic fissile material contents in pyro-processed material, or spent fuel. Many current commercial fissile assay technologies have a limitation in accurate and direct assay of fissile content. However, LSDS is very sensitive in distinguishing fissile fission signals from each isotope. A neutron spectrum analysis was conducted in the spectrometer and the energy resolution was investigated from 0.1eV to 100keV. The spectrum was well shaped in the slowing down energy. The resolution was enough to obtain each fissile from 0.2eV to 1keV. The detector existence in the lead will disturb the source neutron spectrum. It causes a change in resolution and peak amplitude. The intense source neutron production was designed for ~E12 n's/sec to overcome spent fuel background. The detection sensitivity of U238 and Th232 fission chamber was investigated. The first and second layer detectors increase detection efficiency. Thorium also has a threshold property to detect the fast fission neutrons from fissile fission. However, the detection of Th232 is about 76% of that of U238. A linear detection model was set up over the slowing down neutron energy to obtain each fissile material content. The isotopic fissile assay using LSDS is applicable for the optimum design of spent fuel storage to maximize burnup credit and quality assurance of the recycled nuclear material for safety and economics. LSDS technology will contribute to the transparency and credibility of pyro-process using spent fuel, as internationally demanded.

• Atmosphere
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• v.24 no.2
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• pp.151-158
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• 2014

This study investigated a method for the discrimination of precipitation type using thickness of geopotential height at 1000~850 hPa and improved Matsuo's scheme over South Korea using 7 upper-level observations data during winter time from 2003 to 2008. With this research, it was suggested that thickness between snow and rain should range from 1281 to 1297 gpm at 1000~850 hPa. This threshold was suitable for determining precipitation type such as snow, sleet and rain and it was verified by investigation at 7 upper-level observation and 10 surface observation data for 3 years (2009~2011). In addition, precipitation types were separated properly by Matsuo's scheme and its improved one, which is a fuction of surface air temperature and relative humidity, when they lie in mixed sectors. Precipitation types in the mixed sector were subdivided into 5 sectors (rain, rain and snow, snow and rain, snow, and snow cover). We also present the decision table for monitoring and predicting precipitation types using model output of Korea Local Analysis and Prediction System (KLAPS) and observation data.

• Atmosphere
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• v.27 no.2
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• pp.119-131
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• 2017

We present and discuss the Tropopause Folding Turbulence Detection (TFTD) algorithm for the Korean Communication, Ocean, Meteorological Satellite (COMS) which is originally developed for the Tropopause Folding Turbulence Product (TFTP) from the Geostationary Operational Environmental Satellite (GOES)-R. The TFTD algorithm assumes that the tropopause folding is linked to the Clear Air Turbulence (CAT), and thereby the tropopause folding areas are detected from the rapid spatial gradients of the upper tropospheric specific humidity. The Layer Averaged Specific Humidity (LASH) is used to represent the upper tropospheric specific humidity calculated using COMS $6.7{\mu}m$ water vapor channel and ERA-interim reanalysis temperature at 300, 400, and 500 hPa. The comparison of LASH with the numerical model specific humidity shows a strong negative correlation of 80% or more. We apply the single threshold, which is determined from sensitivity analysis, for cloud-clearing to overcome strong gradient of LASH at the edge of clouds. The tropopause break lines are detected from the location of strong LASH-gradient using the Canny edge detection based on the image processing technique. The tropopause folding area is defined by expanding the break lines by 2-degree positive gradient direction. The validations of COMS TFTD is performed with Pilot Reports (PIREPs) filtered out Convective Induced Turbulence (CIT) from Dec 2013 to Nov 2014 over the South Korea. The score test shows 0.49 PODy (Probability of Detection 'Yes') and 0.64 PODn (Probability of Detection 'No'). Low POD results from various kinds of CAT reported from PIREPs and the characteristics of high sensitivity in edge detection algorithm.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.6
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• pp.158-165
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• 2004

The DC motor in a vehicle may cause noise and vibration because of high speed revolution, which can make a driver feel uncomfortable. There have been various studies attempting to solve these problems, focusing mostly on the causes of and ways to reduce noise and vibration. It is suggested that the noise in a DC motor may be primarily due to interaction between a brush and a commutator. Brush noise, the most common noise in a DC motor, results from a brush bounced from the surface of the commutator, fluctuation of the friction between the brush and the commutator, and the impact on the brush when passing over slots of the commutator. Based on the noise test, one of the most important design parameters was shown to be the roundness of the commutator. As the DC motor is used, the roundness of the commutator gets bigger with subsequent increase of the level of brush noise and vibration. There must be a threshold in order to prevent the brush noise from getting worse. Using the method of CAE is more efficient than the real test for purposes of looking for various design parameters to maintain the roundness of the commutator. In this study, the design process to reduce the brush noise is presented with the use of a computer model. The design parameters to reduce the brush noise and vibration are proposed by using FEM. The design parameters are used to reduce the noise and vibration of a DC motor and it is verified with the test results on a fan DC motor in a vehicle. This method may be applicable to various DC motor.

• Journal of the Korea Society for Simulation
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• v.29 no.2
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• pp.119-127
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• 2020

This study numerically investigated a structural behavior subjected to consecutive explosions. To this end, a small scale one-way reinforced slab (RC) with fixed-fixed boundary condition was considered as the target structure, and a commercial software, LS-DYNA, was utilized for finite element (FE) analysis. Prior to performing FE analysis, preliminary tests were carried out to verification of a computational model for the one-way RC slab. In the numerical simulation, identical blast loads were consecutively applied to the structure, and cumulative damage assessment were carried out based on its maximum dynamic displacements. As a result of the numerical simulation, it was found that maximum displacements considering permanent deformation due to a prior explosion were almost linearly increased in every explosion until the hazardous damage threshold.

• Journal of Korean Biological Nursing Science
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• v.10 no.1
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• pp.88-95
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• 2008

Purpose: The purpose of this study was to examine the effect of neuropathic pain by peripheral nerve injury on mass and Type I and II fiber cross-sectional areas on hindlimb muscles of the neuropathic pain model rat. Method: Adult male Sprague-Dawley rats (body weight 200-220 g) were assigned to one of two groups: a neuropathic pain group (n=7) that had a ligation of the left L5 spinal nerve, a control group (n=5), a naive rat without any procedures. Withdrawal threshold, activity, body weight and food intake were measured daily. At 8 days after neuropathic pain, all rats were anesthetized and the soleus and plantaris muscles were dissected from the both hindlimbs. Body weight, food intake, muscle weight and Type I and II fiber cross-sectional area of the dissected muscles were determined. Result: The neuropathic pain group showed a significant decreases (p<.05) as compared with the control rats, in diet intake, body weight, muscle weight and Type II fiber cross-sectional area of the left (affected side) soleus and plantaris muscles, and the right (unaffected side) muscle weight of plantaris and Type II fiber cross-sectional area of the soleus muscle. Conclusion: The hindlimb muscle atrophy occurs in both affected and unaffected side due to neuropathic pain by the peripheral nerve injury. The hindlimb muscle atrophy of the affected side is more pronounced than that of the unaffected side.

• Journal of the Korean Data and Information Science Society
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• v.21 no.6
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• pp.1155-1169
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• 2010

This study considers movement-based registration (MBR). In MBR, a mobile station (MS) performs location registration whenever the number of entering cells reaches the specified movement threshold M. MBR is simple and its implementation is quite straightforward. However, it may result in more registrations than other similar schemes. An improved MBR scheme called MBIR (MBR with implicit registration) was proposed to reduce registration cost of MBR and its approximated performance was analyzed. In this study, we point out some problems of the previous analysis method and propose an exact analysis method of MBIR. Using the exact analysis method, we show that the previous analysis includes considerable errors and improvement of MBIR in our study seems to be larger than in the previous study.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.9
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• pp.1627-1634
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• 2017

In this work, a junctionless transistor with different film thickness of amorphous InGaZnO has been fabricated and it's instability has been analyzed with different film thickness under positive and negative gate stress as well as light illumination. It was found that the threshold voltage shift and the variation of drain current have been increased with decrease of film thickness under the condition of gate stress and light illumination. The reasons for the observed results have been explained by stretched-exponential model and device simulation. Due to the reduced carrier trapping time with decrease of film thickness, electrons and holes can be activated easily. Due to the increase of vertical channel electric field reaching the back interface with decrease of film thickness, more electrons and holes can be accumulated in back interface. When one decides the film thickness for the fabrication of junctionless transistor, the more significant device instability with decrease of film thickness should be consdered.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.9
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• pp.2043-2052
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• 1997

The object-oriented coding technique which is one of the coding methods in very low bit rate environment is suitable for videophone image sequence. The selection of source model affect image analysis. In this paper, an image analysis method for the object-oriented coding is presented. The process is composed of changed region detection andmotion estimateion. First, we use the standard deviation of frame difference as thrreshold to extract themoving area. If thesum of gray values in mask is greater than the threshold, the center pixel of the mask is regarded as moving region. After moving is detected in changed region by edge operator, observation point is determined from moving region. The motion is estimated by 6-parameter mapping method with determined observation point. The experimantal resutls show that the proposed method can significantly improve the image quality.

• Journal of the Korea Society of Computer and Information
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• v.10 no.4 s.36
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• pp.385-396
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• 2005

In this paper, a new structural approach to on-line signature verification is presented. A primitive pattern is defined as a part segmented by a local minimal position of speed. And a structural description of signature is composed of subpatterns which are defined as such forms as rotation shape, cusp shape and bell shape, acquired by composition of the primitives regarding the directional changes. As the matching method to find identical parts between two signatures, a modified DP(dynamic programming) matching algorithm is presented. And also, variation and complexity of local parts are computed from the training samples, and reference model and decision boundary are derived from these. Error rate, execution time and memory usage are compared among the functional approach, the parametric approach and the proposed structural approach. It is found that the average error rate can be reduced from 14.2% to 4.05% when the local parts of a signature are weighted and the complexity is used as a factor of decision threshold. Though the error rate is similar to that of functional approaches. time consumption and memory usage of the proposed structural approach are shown to be very effective.