• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.23-32
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• 2022

Although PSCB girder bridges account for 4% of the bridges in use on highways, they do not account for much, but 98% of PSCB girder bridges are 1^st type and 2^nd type of bridge. Also, the total length of the PSCB girder bridge is 16% (192km) of the total length of the highway bridge. Thus, the PSCB girder bridge can be one of the bridge types where maintenance is important. In order to analyze the damage types of PSCB girder bridges, a detailed analysis was conducted by selecting 62 places (477 spans) precision safety diagnosis reports considering ratio of the construction method and snow removal environment exposure class. Analysis of report and a field investigation was conducted, and as a result, most of the causes of deterioration damage were caused by rainwater (salt water) flowing into the bridge pavement soaking in between the top flange and the interface. After concrete slab deteriorate occurred then bridge pavement cracking and breaking increased and exfoliation of concrete occurred by corrosion and expansion of the reinforcing bars occurred. In addition, the cause of cracks in the longitudinal direction on the bottom of the top flange is considered to be cracks caused by restrained drying shrinkage. In conclusion, for reasonable maintenance considering the characteristics of PSCB girder bridges, it should be suggested in the design aspect that restrained drying shrinkage crack on top flange. Also, it is believed that differentiated maintenance method should be proposed according to snow removal environment exposure class.

• Journal of the Society of Disaster Information
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• v.19 no.2
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• pp.280-291
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• 2023

Purpose: As fire accidents happen at the production and storage sites of superabsorbent polymers for convenience of daily life, an experimental study was conducted to secure basic data to establish practical preventive measures against them. Method: The sample container (20cm width × 20cm length) was made into a rectangular cuboid with the heights of 3cm, 5cm, 7cm, and 14cm, respectively, to allow access to the infinite flat plane. The front and back of the container were covered with a 300-mesh stainless steel mesh for one-dimensional heat transfer. The sample container was placed in the center of the thermostatic bath, which was heated to a predetermined temperature by setting the thermostat program in advance, and it was determined to be 'ignited' when the central temperature of the sample rose by more than 20℃ above the set temperature, and "unignited" when it was maintained at an approximate value of the set temperature. Result: The critical autoignition temperature was calculated to be 217.5℃ when the height of the sample container was 3 cm, 212.5℃ when it was 5 cm, 202.5℃ when it was 7cm, and 187.5℃ when it was 14cm. The ignition induction time to reach the maximum temperature was 34hours for 3cm, 76hours for 5cm, 143hours for 7cm, and 318hours for 14cm. Conclusion: ① As the size of the container increased, the autoignition temperature decreased and the induction time to reach the maximum temperature increased. ② An apparent activation energy was calculated to be 44.92kcal/mol, with a correlation of 96.93%.

• Information Display
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• v.23 no.4
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• pp.12-21
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• 2022

반도체 기반 양자점 (QD)소재와 CsPbX3 (X=Cl, Br, I)기반 perovskite 양자점 또는 나노결정 소재(PNC)는 매우 우수한 양자효율과 좁은 발광 선폭으로 고색재현성 디스플레이 색변환 소재 또는 발광 소재로서 각광을 받고 있다. 그러나, 기존 화학적 합성법을 통해 제조되는 QD 및 PNC 소재는 취약한 열 및 화학적 안정성으로 인해 장기 내구성의 개선이 요구된다. 이들 QD 및 PNC 소재는 모두 완전 무기 소재인 산화물 기반 유리 소재내에 생성이 가능하며, 이를 통해 장기 내구성을 근본적으로 개선할 수 있다. 반도체 기반 QD 함유 유리소재 (QDEG)의 경우, 유리 내 core/shell 구조를 가진 QD의 생성으로 양자효율의 향상이 가능했으나, 콜로이드 기반 양자점 (cQD)과 달리 다중 shell의 형성이 어려워 양자효율이 제한되고, 발광 선폭이 넓어 고색재현성 디스플레이용 색변환 소재로 적용되기에는 아직 한계가 있다. 한편, Perovskite 양자점 (또는 나노결정) 함유 유리소재 (PNEG) 소재는 QDEG과 달리 콜로이드 기반의 PNC (c-PNC)가 가지는 우수한 양자효율과 20 nm 수준의 좁은 선폭을 유리 내에서도 가지며, c-PNC 대비 열적, 화학적 및 광학적 안정성이 획기적으로 향상되어 실질적인 응용 가능성을 높이고 있다. 특히, 일반적인 용융-급랭법으로 제조하여 대량생산에 용이하고, 분말 또는 판상 등 다양한 형태로의 제작이 가능한 장점이 있다. 현재까지 제조된 PNEG의 최대 PL-QY는 450 nm 여기 시 녹색 및 적색에서 약 60% 수준이며, Al₂O₃ 분말을 이용할 경우 최대 80% 수준까지 달성이 가능하다. 또한, PNEG과 blue LED를 이용하여 백색 LED를 구현할 경우 color filter를 적용하지 않을 때, NTSC 대비 최대 약 130 % 수준의 높은 색재현 영역을 보여 주고 있으며, 실제 LCD용 BLU로 적용 시 기존 상용 c-QD 소재와 동등 이상의 색재현 영역을 보이고 있어, 실질적인 응용 가능성이 매우 높음을 확인하였다. PNEG의 상업적인 응용을 위해서는 몇 가지 추가적인 연구 개발이 필요하다. 기존 c-QD 또는 c-PNC는 나노 수준 크기의 입자가 액상에 분산된 형태로 입도 제어가 용이하나, PNEG의 경우 분말 제조 시 유리 형성 후 분쇄를 통해 제조되며, 입도가 대개 수십 ㎛ 이하로 작아질 경우 PL-QY가 저하되어, 향후 잉크젯 공정 응용을 위해서는 고효율의 분말 제조공정 개발이 필요하다. 또한, 유리 소재의 경우 절연체로서 기존 QD 소재 대비 electro-luminescence(EL) 소자의 활성층으로 사용하는데 제약이 있어 PNEG을 이용한 EL 소자 제작에 대한 연구도 필요하다. 마지막으로, 기존 c-PNC 소재와 같이 Pb가 함유되지 않은 PNEG 소재의 개발이 선결되어야 할 것으로 판단된다. 이와 같은 해결 과제들에도 불구하고, PNEG 소재는 기존 c-QD 소재 대비 매우 우수한 안정성을 기반으로 고품위 고색재현 디스플레이용 색변환 소재로서 다양한 응용에 활용될 수 있을 것으로 기대된다.

• Journal of the Korean Applied Science and Technology
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• v.39 no.2
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• pp.368-376
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• 2022

Spontaneous ignition occurs in industrial sites or anywhere in our lives, and is a phenomenon in which a substance ignites itself without an ignition source in the atmosphere. As the rate of chemical reaction increases, the heat generated increases, and the risk of spontaneous ignition increases. In this study, safe raw materials used for food and cosmetics were mixed to prepare coal spontaneous ignition prevention agents specifically among various spontaneous ignition phenomena. The effect of suppressing spontaneous combustion of coal was confirmed through lab and field tests with low-calorie, low-grade coal from Indonesia. As a result of the outdoor field test, the ignition prevention agent manufactured in this study compared with the control group(Fire after 90 days) showed excellent ignition inhibitors for more than 120 days. In addition, CO concentration control was confirmed by comparing the concentration of carbon monoxide for 50 days at the indoor coal yard. It was confirmed that the results were better than the comparative group coal and the existing anti-firing method. In addition, the possibility of coal fire prevention agents for indoor coal farms will be applied from 2024 was confirmed by studying the environment and safety of workers' working environments through official test such as soil and water quality test, MSDS of coal fire prevention agents in consideration of working workers, water quality, and eye irritation tests.

• Journal of the Korean Society of Food Science and Nutrition
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• v.43 no.8
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• pp.1296-1303
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• 2014

This study was conducted to develop predictive models for the growth of Bacillus cereus on carrot treated with slightly acidic electrolyzed water (SAcEW) and ultrasonication (US) at different storage temperatures. In addition, the inactivation of B. cereus by US with SAcEW was investigated. US treatment with a frequency of 40 kHz and an acoustic energy density of 400 W/L at $40^{\circ}C$ for 3 min showed the maximum reduction of 2.87 log CFU/g B. cereus on carrot, while combined treatment of US (400 W/L, $40^{\circ}C$, 3 min) with SAcEW reached to 3.1 log CFU/g reduction. Growth data of B. cereus on carrot treated with SAcEW and US at different temperatures (4, 10, 15, 20, 25, 30, and $35^{\circ}C$) were collected and used to develop predictive models. The modified Gompertz model was found to be more suitable to describe the growth data. The specific growth rate (SGR) and lag time (LT) obtained from the modified Gompertz model were employed to establish the secondary models. The newly developed secondary models were validated using the root mean square error, bias factor, and accuracy factor. All results of these factors were in the acceptable range of values. After compared SGR and LT of B. cereus on carrot, the results showed that the growth of B. cereus on carrot treated with SAcEW and US was slower than that of single treatment. This result indicates that shelf life of carrot treated with SAcEW and US could be extended. The developed predictive models might also be used to assess the microbiological risk of B. cereus infection in carrot treated with SAcEW and US.

• Journal of Bio-Environment Control
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• v.14 no.2
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• pp.95-105
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• 2005

This study was carried out to file up using effect and requirement of energy for environmental design data of Pleurotus eryngii growing houses. Heating and cooling Degree-Hour (D-H) were calculated and compared for. some Pleurotus eryngii growing houses of sandwich-panel (permanent) o. arch-roofed(simple) type structures modified and suggested through field survey and analysis. Also thermal resistance (R-value) was calculated for the heat insulating and covering materials of the permanent and simple-type, which were made of polyurethane or polystyrene panel and $7\~8$ layers heat conservation cover wall. The variations of heating and cooling D-H simulated for Jinju area was nearly linearly proportional to the setting inside temperatures. The variations of cooling D-H was much more sensitive than those of heating D-H. Therefore, it was expected that the variations of required energy in accordance with setting temperature or actual temperature maintained inside of the cultivation house could be estimated and also the estimated results of heating and cooling D-H could be effectively used far the verification of environmental simulation as well as for the calculation of required energy amounts. When the cultivation floor areas are all equal, panel type houses to be constructed by various combinations of materials were found to by far more effective than simple type pipe house in the aspect of energy conservation maintenance except some additional cost invested initially. And also the energy effectiveness of multi-span house compared to single span together with the prediction of energy requirement depending on the level insulated for the wall and roof area could be estimated. Additionally, structural as well as environmental optimizations are expected to be possible by calculating periodical and/or seasonal energy requirements for those various combinations of insulation level and different climate conditions, etc.

• Journal of Food Hygiene and Safety
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• v.37 no.2
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• pp.97-106
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• 2022

Listeria monocytogenes (L. monocytogenes) is one of gram-positive foodborne pathogens with a very high fatality rate. Unlike most foodborne pathogens, L. monocytogenes is capable of growing at low temperatures, such as in refrigerated foods. Thus, various physical and chemical prevention methods are used in the manufacturing, processing and distribution of food. However, there are limitations to the methods such as possible changes to the food quality and the consumer awareness of synthetic preservatives. Thus, the aim of this study was to evaluate the anti-listeria activity of lactic acid bacteria (LAB) isolated from kimchi and characterize the bacteriocin produced by Lactococcuslactis which is one of isolated strains from kimchi. The analysis on the anti-listeria activity of a total of 36 species (Lactobacillus, Weissella, Lactobacillus, and Lactococcus) isolated from kimchi by the agar overlay method revealed that L. lactis NJ 1-10 and NJ 1-16 had the highest anti-listeria activity. For quantitatively analysis on the anti-listeria activity, NJ 1-10 and NJ 1-16 were co-cultured with L. monocytogenes in Brain Heat Infusion (BHI) broth, respectively. As a result, L. monocytogenes was reduced by 3.0 log CFU/mL in 20 h, lowering the number of bacteria to below the detection limit. Both LAB strains showed anti-listeria activity against 24 serotypes of L. monocytogenes, although the sizes of clear zone was slightly different. No clear zone was observed when the supernatants of both LAB cultures were treated with proteinase-K, indicating that their anti-listerial activities might be due to the production of bacteriocins. Heat stability of the partially purified bacteriocins of NJ 1-10 and NJ 1-16 was relatively stable at 60℃ and 80℃. Yet, their anti-listeria activities were completely lost by 60 min of treatment at 100℃ and 15 min of treatment at 121℃. The analysis on the pH stability showed that their anti-listeria activities were the most stable at pH 4.01, and decreased with the increasing pH value, yet, was not completely lost. Partially purified bacteriocins showed relatively stable anti-listeria activities in acetone, ethanol, and methanol, but their activities were reduced after chloroform treatment, yet was not completely lost. Conclusively, this study revealed that the bacteriocins produced by NJ 1-10 and NJ 1-16 effectively reduced L. monocytogenes, and that they were relatively stable against heat, pH, and organic solvents, therefore implying their potential as a natural antibacterial substance for controlling L. monocytogenes in food.

• Journal of Biomedical Engineering Research
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• v.24 no.2
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• pp.133-140
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• 2003

In this study, muscle activity was measured using surface EMG (sEMG) during a voluntary maneuver (ankle dorsiflexion) in the supine position was compared pre and post gait training. Nine patients with incomplete spinal cord injury participated in a supported treadmill ambulation training (STAT), twenty minutes a day, five days a week for three months. Two tests, a gait speed test and a voluntary maneuver test, were made the same day, or at least the same week, pre and post gait training. Ten healthy subjects' data recorded using the same voluntary maneuvers were used for the reference. sEMG measured from ten lower limb muscles was used to observe the two features of amplitude and motor control distribution pattern, named response vector. The result showed that the average gait speed of patients increased significantly (p〈0.1) from 0.47$\pm$0.35 m/s to 0.68$\pm$0.52 m/s. In sEMG analysis, six out of nine patients showed a tendency to increase the right tibialis anterior activity during right ankle dorsiflexion from 109.7$\pm$148.5 $mutextrm{V}$ to 145.9$\pm$180.7 $mutextrm{V}$ but it was not significant (p〈0.055). In addition, only two patients showed increase of correlation coefficient and total muscle activity in the left fide during left dorsiflexion. Patients' muscle activity changes after gait training varied individually and generally depended on their muscle control abilities of the pre-STAT status. Response vector being introduced for quantitative analysis showed good Possibility to anticipate. evaluate, and/or guide patients with SCI, before and after gait training.

• Journal of Bio-Environment Control
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• v.25 no.2
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• pp.106-110
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• 2016

In this study, a planting density-growth-harvest (PGH) chart was developed to easily read the growth and harvest factors such as crop growth rate, relative growth rate, shoot fresh weight, shoot dry weight, harvesting time, marketable rate, and marketable yield of common ice plant (Mesembryanthemum crystallinum L.). The plants were grown in a nutrient film technique (NFT) system in a closed-type plant factory using fluorescent lamps with three-band radiation under a light intensity of $140{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ and a photoperiod of 12 h. Growth and yield were analyzed under four planting densities ($15{\times}10cm$, $15{\times}15cm$, $15{\times}20cm$, and $15{\times}25cm$). Shoot fresh and dry weights per plant increased at a higher planting density until reached an upper limit and yield per area was also same tendency. Crop growth rate, relative growth rate and lost time were described using quadratic equation. A linear relationship between shoot dry weight and fresh weights was observed. PGH chart was constructed based on the growth data and making equations. For instance, with within row spacing (= 20 cm) and fresh weight per plant at harvest (= 100 g), we can estimate all the growth and harvest factors of common ice plant. The planting density, crop growth rate, relative growth rate, lost time, shoot dry weight per plant, harvesting time, and yield were $33plants/m^2$, $20g{\cdot}m^{-2}{\cdot}d^{-1}$, $0.27g{\cdot}g^{-1}{\cdot}d^{-1}$, 22 days, 2.5 g/plant, 26 days after transplanting, and $3.2kg{\cdot}m^{-2}$, respectively. With this chart, we could easily obtain the growth factors such as planting density, crop growth rate, relative growth rate, lost time and the harvest factors such as shoot fresh and dry weights, harvesting time, marketable rate, and marketable yield with at least two parameters, for instance, planting distance and one of harvest factors of plant. PGH charts will be useful tools to estimate the growth and yield of crops and to practical design of a closed-type plant production system.

• Journal of Astronomy and Space Sciences
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• v.22 no.3
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• pp.329-352
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• 2005

Long term observations of full-disk Lyman-o irradiance have been made by the instruments on various satellites. In addition, several sounding rockets dating back to the 1950s and up through the present have measured the $Lyman-{\alpha}$ irradiance. Previous full disk $Lyman-{\alpha}$ images of the sun have been very interesting and useful scientifically, but have been only five-minute 'snapshots' obtained on sounding rocket flights. All of these observations to date have been snapshots, with no time resolution to observe changes in the chromospheric structure as a result of the evolving magnetic field, and its effect on the Lyman-o intensity. The $Lyman-{\alpha}$ Imaging Solar Telescope(LIST) can provide a unique opportunity for the study of the sun in the $Lyman-{\alpha}$ region with the high time and spatial resolution for the first time. Up to the 2nd year development, the preliminary design of the optics, mechanical structure and electronics system has been completed. Also the mechanical structure analysis, thermal analysis were performed and the material for the structure was chosen as a result of these analyses. And the test plan and the verification matrix were decided. The operation systems, technical and scientific operation, were studied and finally decided. Those are the technical operation, mechanical working modes for the observation and safety, the scientific operation and the process of the acquired data. The basic techniques acquired through the development of satellite based solar telescope are essential for the construction of space environment forecast system in the future. The techniques which we developed through this study, like mechanical, optical and data processing techniques, could be applied extensively not only to the process of the future production of flight models of this kind, but also to the related industries. Also, we can utilize the scientific achievements which are obtained throughout the project And these can be utilized to build a high resolution photometric detectors for military and commercial purposes. It is also believed that we will be able to apply several acquired techniques for the development of the Korean satellite projects in the future.