• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.3
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• pp.199-206
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• 2014

In this paper, a scheme to evaluate the response variability for functionally graded material (FGM) beam with varying sectional area is presented. The randomness is assumed to appear in a spatial domain along the beam axis in the elastic modulus. The functionally graded material categorized as composite materials, however without the drawbacks of delamination and occurrence of cracks due to abrupt change in material properties between layers in the conventional composite materials. The functionally graded material is produced by the gradual solidification through thickness direction, which endows continuous variation of material properties, which makes this material performs in a smooth way. However, due to difficulties in tailoring the gradients, to have uncertainty in material properties is unavoidable. The elastic modulus at the center section is assumed to be random in the spatial domain along the beam axis. Introducing random variables, defined in terms of stochastic integration, the first and second moments of responses are evaluated. The proposed scheme is verified by using the Monte Carlo simulation based on the random samples generated employing the spectral representation scheme. The response variability as a function of correlation distance, the effects of material and geometrical parameters on the response variability are investigated in detail. The efficiency of the proposed scheme is also addressed by comparing the analysis time of the proposed scheme and MCS.

• The Korean Journal of Food And Nutrition
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• v.20 no.1
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• pp.1-8
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• 2007

Tortillas were prepared using rice and wheat flour. The experimental design incorporated thee independent variables(rice, wheat flour and moisture content) producing 14 samples of different proportions of each variable for each tortilla. The following were analysed using Design Expert 6 to unveil the influences of these variables on tensile strength and color(L, a, b). Results indicated that tensile strength increased with increasing rice and wheat flour content, however, decreased with increasing moisture content. Lighteness(L), of the tortilla increased with increased rice content whereas yellowness(b) increased with increased wheat flour content. The model suggests that tensile strength and color(L, a, b) in tortillas are highly correlated(SD Comment - give correlation coefficient and p-value). As well, the numerical optimization method suggests that the ratio of wheat flour to rice flour to moisture content which maximizes the three responses(tensile strenth, L and b) is 18.26 : 33.92 : 39.24%, 28.15 : 25.77 : 37.50%.

• Journal of Korea Foundry Society
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• v.11 no.6
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• pp.475-481
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• 1991

In this study the fabrication technology and mechanical properties of AC8A/$Al_2O_3$ Composites by squeeze casting process were investigated to develope for application as the piston materials that require good friction, wear resistance, and thermal stability. AC8A/$Al_2O_3$ composistes without a porosity and the break of preform were fabricated at the melt temperature of $740^{\circ}C$, the preform temperature of $500^{\circ}C$, and mold temperature of $400^{\circ}C$ under the applied pressure of $1200kg/cm^2$ as the results of the observation of microstructures. As the results of this study, the tensile strength of AC8A/$Al_2O_3$ composites was not increased linearly with $Al_2O_3$ volume fraction and so it seemed not to agree with the rule of mixture, which had been used often in metal matrix composite. Also the tensile strength after thermal fatigue test was little different from that before the test. Consequently it was thought that AC8A/$Al_2O_3$ composites fabricated under our experimental conditions had a good thermal stability and subsequently a good interface bonding. Wear rate(i.e., volume loss per unit sliding distance) of AC8A/$Al_2O_3$ composites was decreased with $Al_2O_3$ volume fraction and the sliding speed at both room temperature and $250^{\circ}C$ and so there was a good correlation between wear rate and hardness. Also the wear rate of AC/8A20% $Al_2O_3$ composities was obtained the value of $1.65cm^3/cm$ at sliding speed of 1.14m/sec as compared with about $3.0\;{\times}10^{-8}cm^3/cm$ hyereutectie Al-Si alloy(Al-16%Si-2%Cu-1%Fe-1%Ni), which applied presently for piston materials. The wear behavior of $Al_2O_3$ composites was observed to a type of abrasive wear by the SEM view of wear surface.

• Korean Journal of Agricultural Science
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• v.28 no.1
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• pp.8-17
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• 2001

This study was carried out to obtain a basic intonation for the development of a new com hybird with tillers. Materials used in this study were 20 lines having three to four tillers per plant including the PI213749 U.S. line with non-tillers. These 20 lines were compared for the botanical characteristics and genetic distances were measured using RAPD analysis. Flowering date of the K15 was very earlier, while the K07 was very late in flowering date. Stem height and ear height were similar except for K04 and the K15. K06, K13 and K19 lines were appeared to be resistant to lodging due to decreased ear height. Number of tillers per plant of lines used were shown three to five on average. K09 showed the highest kernel yield, while the K08 was low. Among characteristics measured tiller per plant and flowering dates, and silking dates showed a positive correlation, while 100 kernels weight, flowering date and ear height were shown a negative with tillers per plant. A total of 17 bands by RAPD analysis using four per primer were appeared and these lines were classified into three groups, especially the third group could be classified into of four sub-groups.

• Geophysics and Geophysical Exploration
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• v.19 no.2
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• pp.67-75
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• 2016

To investigate spatial and temporal variations of low-frequency (${\leq}5Hz$) ambient seismic noise, we analyzed the noise data recorded for one whole year of 2014 at surface accelerometer stations in South Korea. After decomposed into low-frequency (LF; < 1 Hz) and high-frequency (HF; ${\geq}1Hz$) components, the root-mean-squared (RMS) amplitudes and power spectral densities (PSD) of the noise data were computed. The RMS amplitudes were larger on islands and near-shore stations, but also large RMS amplitudes were observed at inland stations in large cities only for HF components. The RMS amplitudes of HF components were larger in the daytime than at nighttime and during weekdays than on Sunday and holidays. This indicates the HF components are closely related to human activities. On the contrary, daily and weekly variations were not clear in the LF components while they showed seasonal variations with its maximum during the winter and a good correlation with significant wave height. Therefore, we interpret the mechanism of LF components is closely related to natural phenomena such as sea. The amplitude of LF components decreased as an exponential function of the distance to the center of typhoons. The exponential index of -0.76 suggested that ambient seismic noise included both surface and body waves. Peak frequencies of the PSD curves were near 0.34 Hz indicating the double frequency. No temporal variation in the peak frequency was clearly noticed.

• Journal of Korean Society of Forest Science
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• v.103 no.1
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• pp.51-58
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• 2014

Genetic diversity and genetic structures were estimated in seven natural populations of Phellodendron amurense Rupr in South Korea using ISSR markers. The average of polymorphic loci per primer and the proportion of polymorphic loci per population were 4.5 and 78.8% respectively with total 27 polymorphic loci from 6 ISSR primers. The Shannon's diversity index(I) was 0.421 and the expected heterozygosity($H_e$) was 0.285, which was similar to the heterozygosity (hs =0.287) inferred by Bayesian method. In AMOVA, 7.6% of total genetic variation in the populations was resulted from the genetic difference among populations and the other 92.4% was resulted from the difference among individuals within populations. Genetic differentiation(${\theta}^{II}$) and inbreeding coefficient(f) for total population were estimated to be 0.066 and 0.479 by Bayesian method respectively. In Bayesian clustering analysis, seven populations were assigned into three groups. This result was similar to the results of genetic relationships by UPGMA and PCA. The first group included Hwachoen, Gapyeong, Bongpyeong and Yongpyeong population, and the second included two populations in Sancheong region. Muju population was discretely assigned into the third group in spite of the geographically short distance from the Sancheong region. There was no significant correlation between genetic relationship and geographic distribution among populations in Mantel's test. For conservation of the phellodendron trees, it would be effective to consider the findings resulted from this study with ecological traits and life histories of this species.

• The Korean Journal of Physiology
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• v.2 no.2
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• pp.83-92
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• 1968

A study was planned to evaluate the effects of removal of the cingulate cortex upon the occurrence of any behavior commonly displayed by the rat, and to compare the effects of cingulectomy with those of removal of the parietal, parieto-occipital, or occipital regions. The subjects were 54 male albino rats (Holtzman strain, body weight $200{\sim}330\;gm$) including 14 rats in which the cingulate gyri between splenium and genu of the corpus callosum were bilaterally ablated by suction (cingulate group), 9 animals which had their parietal cortices (chiefly area 7) partially removed (parietal group), 9 rats whose parietal and occipital regions (chiefly areae 7 & 17), 13 animals in which the occipital cortices (chiefly area 17) were removed bilaterally (occipital group), and 9 normal rats (normal control group). Eighteen observation cages, each of which housed a subject and was provided with food and water ad lib., were arranged in 6 rows on a rack and the behavior of each subject was scanned by an observer at a distance of 1.5 m from the rack. The observer scanned the first and second rows 6 times in 1 min, then proceeded to the 3rd and 4th rows, scanning for another 1 min, and finally to the 5th and 6th rows. The speed of scanning was such that behavioral observations of all of the 18 rats were completed in 3 min, each subject receiving 6 observations. The scanning was repeated every 3 min for 18 min, which constituted one observation session and was followed by a 72 minutes' recess. The whole procedure was repeated through 24 hours so that a total of 576 behavioral observations were made on each subject in 16 observation sessions. Behaviors checked were sleeping, lying, lying and sniffing, standing, standing and sniffing, exploring, eating, drinking, grooming (included were washing, licking, and scratching), and others. Results obtained were as follows: 1. The cingulate group ate significantly more often than the normal control, the parietal, and the parieto-occipital groups. 2. Exploration was significantly less frequent in the cingulate group than in the normal control, the parietal, and the occipital groups. There was, in the case of the cingulate group, a significant negative correlation between the occurrence of eating and the exploratory activity. 3. The general activity, as judged from the value obtained by adding the occurrence of exploration, eating, drinking, grooming, and standing and sniffing, was significantly increased in the cingulate group compared with those of any other groups including the normal control. 4. Though statistically insignificant, the cingulate group slept least often among all the animal groups tested. 5. The parieto-occipital group tended to groom less, and the parietal group to eat less often than the normal control group did, but the difference was not significant. There were no significant differences among all the groups except the cingulate group as regards other behaviors analyzed. Based on the above results, it was inferred that the cingulate cortex exerts an inhibitory influence upon the occurrence of eating and general activity, while it tends to facilitate the occurrence of sleep.

• The Korean Journal of Pain
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• v.20 no.2
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• pp.138-142
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• 2007

Background: Depression is a frequent comorbid disease of chronic pain patients. This study was conducted to evaluate the prevalence of depression and to correlate associated factors and depression in patients with lumbar spinal stenosis. Methods: The data of this survey was collected from 97 patients that visited our pain clinic for the management of lumbar spinal stenosis. Depression was examined by a self-reported survey using the Korean version of the Beck Depression Inventory (BDI). The Oswestry Disability Index (ODI) and the life satisfaction scale score were also obtained. Demographic and clinical characteristics (including spouse status, employment status, smoking status, the number of patients with multiple painful areas, the number of patients with combined disease, pain duration, visual analogue scale, Roland 5-point scale and walking distance) were obtained from an interview with the patient. The patients were divided into group N ($BDI{\leq}14$, n = 43) and group 0 (BDI > 14, n = 54) according to the BDI scale. Of the 97 patients, 55,7% had a high BDI score. Results: The patients in group N had a higher rate of employment (48.0%, P < 0.05) and had higher life satisfaction scale scores ($9.4{\pm}2.5$, P < 0.01) as compared to group D patients. The BDI score showed a close correlation with employment status and the life satisfaction scale. Conclusions: Many lumbar spinal stenosis patients had high BDI scores. Employment status and the life satisfaction scale were closely correlated with the BDI score.

• Journal of Broadcast Engineering
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• v.24 no.6
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• pp.1085-1095
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• 2019

In this paper, we perform a subjective quality assessment on low-resolution surveillance videos, which are encoded with a very low target bit-rate to use in an ultra-low band transmission system and investigate the encoding effects on the perceived video quality. The test videos are collected based on their spatial and temporal characteristics which affect the perceived quality. H.265/HEVC encoder is used to prepare the impaired sequences for three target bit-rates 20, 45, and 65 kbps and subjective quality assessment is conducted to evaluate the quality from a viewing distance of 3H. The experimental results show that the quality of encoded videos, even at target bit-rate of 45 kbps can satisfy the users. Also we compare objective image/video quality assessment methods on the proposed dataset to measure their correlation with subjective scores. The experimental results show that the existing methods poorly performed, that indicates the need for a better quality assessment method.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.4
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• pp.35-43
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• 2016

Recently, the pipeline system for waste transportation has been increasingly constructed as new solution for the waste collection and disposal system by constantly increasing domestic waste which issued as social problem. The pipeline system is constructed through long distance, so proper long-term monitoring system is necessary which available to detect the damage location for the effective maintenance. In this paper, the experimental study is carried out to evaluate the applicability of optical strain gauge sensor based on FBG for the long-term monitoring system. Three test parameters such as pressure leaking, blockage and deformation are considered as typical damages for real-scale pipeline test specimen. In order to measure flexural and volumetric strain and temperature, three FBG sensors are installed at each monitoring sections. From the test results, this study suggested effective methods of sensor installation and arrangement. Also the sensor spacing for the design of monitoring system using FBG sensor is derived by the correlation of distances from deformation between sensor responses.