• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.4
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• pp.495-500
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• 1999

The carrageenans are linear, sulfated Polysaccharides extracted from various species of the Rhodophyta (marine red algae). The carrageenan backbone is based on a repeating disaccharide sequence of $\beta$-D-galactopyranose residues linked glycosidically through position 1 and 3, and $\alpha$-D-galactopyranose residues linked glycosidically through position 1 and 4. Carrageenans are typical food polysaccharides in that food applications overwhelmingly dominate their end uses. Other applications, hewer, including cosmetics, pharmaceuticals, industrial suspensions and paints are also of importance But because of its high degree of gelling and viscosity with low solubility, carrageenan is limited to use beyond $0.03\%$ as food additives. Response Surface Methodology was applied for optimizing the processing parameters of ultrasound treatment in order to produce low-molecular-weight carrageenan. The use of ultrasound significantly reduced viscosity of $\lambda$-carrageenan solutions. Optimal parameters for ultrasound reduction of carrageenan molecular weight were: temperature, $10^{\circ}C$; ultrasound intensity, 121.64 $W/cm^2$ ; tarrageenan concentration, $2\%$; treatment time, 40 min. As the gel permeation chromatogram of dextran standards (M.W.= 500,000 ; 260,000 ; 167,000 ; 71,400 ; 42,000) and ultrsound treated carrageenan, the molecular weight of ultrasound treated carrageenan were approximately 200,000 (peak 1) and 60,000 (peak 2), respectively.

• Journal of the Korean Society for Railway
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• v.17 no.5
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• pp.355-364
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• 2014

The restrained volume changes of concrete due to variations of temperature and moisture produce transverse cracks in continuously reinforced concrete tracks (CRCTs). Such cracks are known to significantly affect the behaviors and long-term performance of CRCT. To investigate the effects of the transverse cracks on the behavior of CRCT and to develop more reasonable maintenance standards for cracks, in this study, the stress distribution of the track concrete layers (TCL) and the hydraulically stabilized base course (HSB) with transverse cracks were numerically predicted by a three dimensional finite element analysis when CRCT was subjected to train loads. The results indicate that the bending stresses of TCL and vertical stresses at the interfaces between TCL and HSB increased as the cracks were deepened. In addition, vertical stresses were locally concentrated near reinforcing steel in cracks in TCL when full-depth cracks developed, which may lead to punch-outs in CRCTs. Comparably, the effects of crack width and spacing were not as significant as crack depth. This study indicates that ensuring the long-term performance of CRCTs requires adequate maintenance not only for crack width and spacing but also for crack depth. Our results also show that locating HSB joints between sleepers is beneficial to the long-term performance of CRCTs.

• Journal of the Korean Society for Railway
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• v.16 no.3
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• pp.189-195
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• 2013

Recent trains have broadband train communication networks to improve train operation safety and to provide passengers with multimedia services. Compared to glass optical fiber, plastic optical fiber (POF) has a large diameter; it also provides the good durability and maintainability necessary to railway applications. This paper suggests an All-IP broadband train communication network that connects all devices in the train through a POF interface. Performance tests according to Korean railroad standards shows that this POF interface is usable in the range of vibration and temperature conditions encountered in trains. A dedicated Layer-2 switch with the POF interface is developed for the construction of the All-IP train communication network. A prototype 1Gbps train communication network was set up in a trial-run of train on a metro line using the developed Layer-2 switch and POF. On-track tests indicated the feasibility of the POF train communication network. POF has an additional advantage of economic feasibility, and it is expected to start a trend toward broadband train communication networks using POF.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.24 no.3
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• pp.107-112
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• 2018

The purpose of this study was to investigate the migration levels of lead (Pb), cadmium (Cd) and arsenic (As) from polycarbonate food contact materials into food simulant at different temperatures ($70^{\circ}C$ and $100^{\circ}C$). The method was validated by linearity of calibration curves, limit of detection (LOD), limit of quantification (LOQ), recovery, precision and uncertainty. All of 200 samples, including bottles, cups, containers, ladles, spoons and tongs were purchased from domestic markets and analyzed by inductively coupled plasma mass spectrometry (ICP-MS). Mean concentrations of positive samples were higher at $100^{\circ}C$ than $70^{\circ}C$ as showing a dependency of migration temperature. The migration concentrations ranged from not-detected (ND) to $4.67{\mu}g/L$, ND to $0.49{\mu}g/L$L and ND to $2.91{\mu}g/L$ for Pb, Cd and As, respectively, which were far below the migration limits of Korea standards and specifications for food utensils, containers and packages.

• Progress in Superconductivity and Cryogenics
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• v.21 no.1
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• pp.18-24
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• 2019

This study was carried out to investigate the effect of milling of boron (B), which is one of raw materials of $MgB_2$, on the critical current density ($J_c$) of $MgB_2$. B powder used in this study is semi-amorphous B (Pavezyum, Turkey, 97% purity, 1 micron). The size of B powder was reduced by planetary milling using $ZrO_2$ balls (a diameter of 2 mm). The B powder and balls with a ratio of 1:20 were charged in a ceramic jar and then the jar was filled with toluene. The milling time was varied from 0 to 8 h. The milled B powders were mixed with Mg powder in the composition of (Mg+2B), and the powder mixtures were uniaxially pressed at 3 tons. The powder compacts were heat-treated at $700^{\circ}C$ for 1 h in flowing argon gas. Powder X-ray diffraction and FWHM (Full width at half maximum) were used to analyze the phase formation and crystallinity of $MgB_2$. The superconducting transition temperature ($T_c$) and $J_c$ of $MgB_2$ were measured using a magnetic property measurement system (MPMS). It was found that $B_2O_3$ was formed by B milling and the subsequent drying process, and the volume fraction of $B_2O_3$ increased as milling time increased. The $T_c$ of $MgB_2$ decreased with increasing milling time, which was explained in terms of the decreased volume fraction of $MgB_2$, the line broadening of $MgB_2$ peaks and the formation of $B_2O_3$. The $J_c$ at 5 K increased with increasing milling time. The $J_c$ increase is more remarkable at the magnetic field higher than 3 T. The $J_c$ at 5 K and 4 T was the highest as $4.37{\times}10^4A/cm^2$ when milling time was 2 h. The $J_c$ at 20 K also increased with increasing milling time. However, The $J_c$ of the samples with the prolonged milling for 6 and 8 h were lower than that of the non-milled sample.

• Journal of Environmental Science International
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• v.30 no.8
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• pp.659-671
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• 2021

The physicochemical properties of soil and the yield and quality of rice (Oryza sativa L. cv. Sailmi) were assessed using Italian ryegrass (Lolium multiflorum Lam. cv. Kowinearly)-rice double cropping systems in the paddy fields at Goseong and Miryang in southern Korea. The average temperatures during the ripening period were approximately 1 ℃ higher than the optimal temperature for rice ripening and the sunshine duration was reduced by frequent rainfall. Consequently, it was slightly below the optimal conditions required for rice ripening. In the soil at Goseong, winter Italian ryegrass cropping increased the pH, electrical conductivity, and the contents of organic matter, total nitrogen (T-N), available P₂O₅, K, Ca, and Mg than winter fallowing. Particularly, the contents of T-N and available P₂O₅increased significantly. In the soil at Miryang, Italian ryegrass slightly increased the electrical conductivity and the T-N, Mg, and Na contents. Therefore, winter Italian ryegrass cropping improved the physicochemical properties of paddy soils; however, Italian ryegrass-rice double cropping slightly reduced the culm length at both Goseong and Miryang, without markedly changing the panicle length or number compared to fallow-rice cropping. Furthermore, at Goseong, Italian ryegrass-rice double cropping slightly decreased the spikelet number and milled rice yield, and increased the ripened grain rate; however, at Miryang, contrasting results were observed. In addition, fallow-rice cropping revealed no differences in the head rice or opaque rice rates. The protein content was slightly increased in Italian ryegrass-rice double cropping, without significant changes in the amylose content or Toyo value, compared to that in fallow-rice cropping. The peak and breakdown viscosities were slightly decreased. These results indicate that winter Italian ryegrass cropping might alter rice taste but may not exhibit remarkable negative effects on rice cultivation. Therefore, Italian ryegrass-rice double cropping system is recommended for paddy fields in southern Korea. Nevertheless, to increase the rice yield and quality, fertilization standards for rice cropping that consider the changes in the T-N and organic matter contents in paddy fields caused by winter Italian ryegrass cropping need to be established.

• Journal of Wetlands Research
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• v.24 no.1
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• pp.38-43
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• 2022

Smart sewage treatment plant means creating a safe and clean water environment by establishing an ICT-based real-time monitoring, remote control management and intelligent system for the entire sewage treatment process. The core technology of such a smart sewage treatment plant can be operation control technology using measuring instruments. This research team analyzed and suggested the operation control technologies necessary for the establishment of the intelligent business by referring to the intelligent research projects of the sewage treatment plant in progress in Korea. As a result of the analysis, a total of six removal technologies were presented, including control by scale, reflow water control, linked treated water control, chemical quantity control, winter operation control, and total organic carbon control. By size, standards that can be classified into small and medium-sized large-scale are presented, and in the case of reflow water control, the location of water quality and flow sensors capable of managing reflow water is suggested. In the case of the linked treated water control, the influence and control points of the linked treated water on the sewage treatment plant were presented, and in the case of the chemical injection volume control, a system capable of optimizing the amount of chemical injection according to the introduction of an intelligent sewage treatment plant was presented. In the case of winter operation, the sensors and pumps to be controlled are suggested when considering the decrease in nitrification due to the decrease in water temperature. In the case of total organic carbon control, an interlocking system considering the total amount of pollution in the future was proposed. These operation control scenarios are expected to be used as basic data to be used in intelligent sewage treatment algorithms and scenarios in the future.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.5
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• pp.118-127
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• 2021

Recently, the public's interest in the air environment has increased, and public health is threatened by fine particulate matter. Furthermore, the government continues efforts to improve air quality by expanding the monitoring of air pollutants and reinforcing environmental standards. Since air quality differs depending on the region in the Korean Peninsula, it is currently necessary to identify the cause and search for influencing factors. In this study, the atmospheric environment and regional differences in cities located in the Chungnam Province were observed. As a research method, regression analysis was performed for weather conditions, such as temperature, wind speed, precipitation, and season and targeted at air pollutants, such as SO₂, NO₂, CO, O₃, PM₁₀, and PM_2.5, as well as heavy metals contained in particulate matter, such as Pb, Cd, Cr, Cu, Ni, As, Mn, Fe, Al, Ca, and Mg. In the case of PM₁₀, the concentrations of Mn(0.4884) in Cheonan, CO(0.3329) in Dangjin, and Mg(0.5691) in Seosan were highest. In the case of PM_2.5, Cheonan NO₂(0.4759), Dangjin CO(0.4128), and Seosan NO₂(0.3715) were significantly affected. In summary, the influencing factors vary according to the region in Chungnam province in terms of air quality, and there is a difference in the degree of contribution. Therefore, it is considered that the Korean government's management of air quality is required for each region.

• Korean Chemical Engineering Research
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• v.61 no.1
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• pp.80-88
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• 2023

Ensuring safety in the designing of manufacturing and handling facilities for low-density polyethylene (LDPE) is difficult because there are no standards for the dust explosion characteristics of LDPE. In this study, a dust explosion test was performed on two dust samples collected from a bag filter (LDPE 1) during the LDPE manufacturing process and sedimentary dust (LDPE 2) leaked outside a facility such as a silo, and the LDPE 2 explosion test results were summarized. Particle size analysis showed that the volume-based particle diameter (median) was 95.04 ㎛ and the number density was 0-1 ㎛. The maximum explosion pressure (P_max) was 6.6 bar, and the maximum rate of explosion pressure rise was 366 [bar/s] at 1500 g/m³. Accordingly, the dust explosion index (K_st) was 99.4 bar·m/s, which was confirmed as ST-1 grade. Moreover, the minimum ignition energy and minimum ignition temperature was 10 mJ and 450 ℃, respectively. Currently, manufacturing and handling design is based on the characteristic values of high-density polyethylene (HDPE). However, as the test results show that LDPE 2 dust has a higher risk than HDPE (particle diameter 61.6 ㎛), caution is required when using the HDPE design criteria in the LDPE manufacturing process.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.16 no.3
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• pp.152-160
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• 2023

After the recent COVID-19 outbreak, more and more people are paying attention to health care. Many people feel uncomfortable in life due to muscle pain after sports or exercise as a hobby and often take a break from exercise. After exercising for a long time or exercising excessively, pain appears throughout the body within 24 to 48 hours after exercise. This pain is called delayed onset muscle soreness (DOMS). In this study, the effectiveness of the pain relief of delayed onset myalgia was verified by using a high-frequency pain therapy device that generates deep heat. EMG was measured before and after pain treatment at ordinary times, RMS values were obtained through analysis, statistical analysis was performed using the SPSS program, and it was judged to be statistically significant. In addition, statistical analysis of the RMS value between normal and after pain treatment was conducted to confirm that there was no significance, and to confirm how much it returned to normal after pain treatment. In addition, since the standards for pain are different for each person even if the size of the same pain is the same, the NRS questionnaire for the size of pain was conducted, and the size of pain felt by the subjects was analyzed using the SPSS program and statistical significance was obtained. Therefore, as a result of this study, the high-frequency pain therapy device generated deep heat in the pain area to raise the temperature, and expanded the arteries and capillaries to increase blood flow, thereby increasing blood circulation and metabolism, and alleviating the pain of delayed onset muscle pain.