• Journal of Bio-Environment Control
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• v.32 no.1
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• pp.57-63
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• 2023

The external weather conditions including temperature and wind speed in the Saemangeum reclaimed land is different from that of the inland, affecting the internal environment of the greenhouse. Therefore, it is important to select an appropriate covering material considering the insulation effect according to the type and characteristics of the covering material considering the weather condition in the Saemangeum reclaimed land. A hexahedral insulation chamber was designed to evaluate the insulation efficiency of each glass-clad material in the outside weather condition in reclaimed land. In order to evaluate the insulation effect of each covering material, a radiator was installed and real-time power consumption was monitored. 16-mm PC (polycarbonate), 16-mm PMMA (polymethyl methacrylate), 4-mm greenhouse glass, and 16-mm double-layered glass were used as the covering materials of the chamber. In order to understand the effect of the external wind directions, the windward and downwind insulation properties were evaluated. As a result of comparing the thermal insulation effect of each greenhouse cover material to single-layer glass, the thermal insulation effect of double-layer glass was 16.9% higher, while PMMA and PC were 62.5% and 131.2% higher respectively. On average the wind speed on the windward side was 53.1% higher than that on the lee-wind side, and the temperature difference between the inside and outside of the chamber at the wind ward side was found to be 52.0% larger than that on the lee ward side. During the experiment period, the overall heating operation time for PC was 39.2% lower compared to other insulation materials. Showing highest energy efficiency, and compared to PC, single-layer glass power consumption was 37.4% higher.

• 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%.

• Membrane Journal
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• v.32 no.1
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• pp.43-49
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• 2022

Solid-state supercapacitors with high safety and robust mechanical properties are attracting global attention as next-generation energy storage devices. As an electrode of a supercapacitor, an economical carbon-based electrode is widely used. However, when an aqueous electrolyte is introduced, the charge transfer resistance increases because the interfacial contact between the hydrophobic electrode surface and aqueous electrolyte is not good. In this regard, we propose a method to obtain higher electrochemical performance based on improved interfacial properties by treating the electrode surface with oxygen plasma. The surface hydrophilization induced by the enriched oxygen functionalities was confirmed by the contact angle measurement. As a result, the degree of hydrophilization was easily adjusted by controlling the power and duration of the oxygen plasma treatment. As the electrolyte of the supercapacitor, PVA/H₃PO₄, which is a typical solid-state aqueous electrolyte, was used. Free-standing membranes of PVA/H₃PO₄ electrolyte were prepared and then pressed onto the electrode. The optimal condition was to perform oxygen plasma treatment for 5 seconds with a low power of 15 W, and the energy density of the supercapacitor increased by about 8%.

• The Journal of the Convergence on Culture Technology
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• v.9 no.4
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• pp.587-592
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• 2023

Plant growth is regulated by a variety of factors, including organic matter availability. Organic nutrients are carbohydrate molecules from photosynthetic products produced by tissues associated with carbon and energy fixation called "sources". These compounds flow through plant vascular bundles into non-photosynthetic or growing tissues called "sinks". Among these possible compounds, the disaccharide fructosyl glucose, sucrose, is the most representative. During the transport of sucrose, the pathway from the source to the sinks can include hydrolysis of sucrose into glucose and fructose derivatives or direct transfer of sucrose. Among the enzymes involved in this, β-D-fructofuranosidase is the most important. Soluble neutral β-D-fructofuranosidase, one of several isoenzymes, is located in intracellular protoplasts and helps plant cells metabolize sucrose to produce energy. In order to track the activity of this enzyme during the course of plant growth, histological methods were used for the most effective immunolocalization. As a result, the activity was higher in the phloem and epidermis than in the mesophyll tissue in the leaf. In the growing stem, activity was high in the phloem, epidermis, and cortex. The activity of the root, which is a sink tissue, was high in all parts, but especially the highest in the root tip part. It is thought that this is because it helps unloading of sucrose in sink tissues that require sucrose degradation and plays a role in hydrolysising sucrose.

• Korean Journal of Hazardous Materials
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• v.2 no.1
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• pp.18-26
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• 2014

We analyzed the demand of competent authorities requiring adequate technical information for initial investigation of chemical accidents. Reflecting technical reports on chemical accident response by environmental agencies in the U.S. and Canada, we presented information on environmental diffusion and toxic effects available for the first chemical accident response. Hydrogen fluoride may have the risk potential to corrode metals and cause serious burns and eye damages. In case of inhalation or intake, it could have severe health effects. The substance itself is inflammable, but once heated, it decomposes producing corrosive and toxic fume. In case of contact with water, it can produce toxic, corrosive, flammable or explosive gases and its solution, a strong acid, may react fiercely with a base. In case of hydrogen fluoride leak, the preventive measures are to decrease steam generation in exposed sites, prevent the transfer of vapor cloud and promptly respond using inflammable substances including calcium carbonate, sodium bicarbonate, ground limestone, dried soil, dry sand, vermiculite, fly ash and powder cement. The method for fire fighting is to suppress fire with manless hose stanchions or monitor nozzles by wearing the whole body protective clothing equipped with over-pressure self-contained breathing apparatus from distance. In case of transport accident accompanied with fire, evacuation distance is 1,600m radius. In cae of fire, fire suppression needs to be performed using dry chemicals, CO₂, water spray, water fog, and alcohol-resistance foam, etc. The major symptoms by exposure route are dyspnoea, bronchitis, chemical pneumonia and pulmonary edema for respiration, skin laceration, dermatitis, burn, frostbite and erythema for eyes, and nausea, diarrhea, stomachache, and tissue destruction for digestive organs. In atmosphere, its persistency is low, and its bioaccumulation in aquatic organism is also low.

• Geophysics and Geophysical Exploration
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• v.26 no.4
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• pp.211-228
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• 2023

Ground-penetrating radar (GPR) surveys are commonly used to monitor embankments, which is a nondestructive geophysical method. The results of GPR surveys can be complex, depending on the situation, and data processing and interpretation are subject to expert experiences, potentially resulting in false detection. Additionally, this process is time-intensive. Consequently, various studies have been undertaken to detect cavities in GPR survey data using deep learning methods. Deep-learning-based approaches require abundant data for training, but GPR field survey data are often scarce due to cost and other factors constaining field studies. Therefore, in this study, a deep- learning-based model was developed for embankment GPR survey cavity detection using data augmentation strategies. A dataset was constructed by collecting survey data over several years from the same embankment. A you look only once (YOLO) model, commonly used in computer vision for object detection, was employed for this purpose. By comparing and analyzing various strategies, the optimal data augmentation approach was determined. After initial model development, a stepwise process was employed, including box clustering, transfer learning, self-ensemble, and model ensemble techniques, to enhance the final model performance. The model performance was evaluated, with the results demonstrating its effectiveness in detecting cavities in embankment GPR survey data.

• Korean Journal of Optics and Photonics
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• v.35 no.4
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• pp.150-156
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• 2024

One of the key factors in research regarding long-distance laser beam propagation, as in free-space optical communication or laser power transmission, is the transmission efficiency of the laser beam. As a way to improve efficiency, we perform extensive numerical simulations of the effect of modifying the laser beam's profile, especially replacing the fundamental Gaussian beam with a super-Gaussian beam. Numerical simulations of the transmitted power in the ideal diffraction-limited beam diameter determined by the optical system of the transmitter, after about 1-km propagation, reveal that the second-order super-Gaussian beam can yield superior performance to that of the fundamental Gaussian beam, in both single-channel and coherently combined multi-channel laser transmitters. The improvement of the transmission efficiency for a 1-km propagation distance when using a second-order super-Gaussian beam, in comparison with a fundamental Gaussian beam, is estimated at over 1.2% in the singlechannel laser transmitter, and over 4.2% and over 4.6% in coherently combined 3- and 7-channel laser transmitters, respectively. For a range of the propagation distance varying from 750 to 1,250 m, the improvement in transmission efficiency by use of the second-order super-Gaussian beam is estimated at over 1.2% in the single-channel laser transmitter, and over 4.1% and over 4.0% in the coherently combined 3- and 7-channel laser transmitters, respectively. These simulation results will pave the way for future advances in the generation of higher-order super-Gaussian beams and the development of long-distance optical energy-transfer technology.

• Journal of the Society of Disaster Information
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• v.20 no.3
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• pp.584-592
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• 2024

Purpose: The biggest concern in cold wave situations is that the fire extinguishing water initially supplied through dry pipes with empty pipes consumes enthalpy and freezes as it rapidly approaches the surface temperature of steel pipes that have been exposed to sub-zero outdoor air for a long time. It has no choice but to be. Method: Therefore, the study found that ice crystals were generated during transport, making it difficult to transport fire extinguishing water, and as a result of the review, when the heat load passed through the piping material, the heat loss per unit length from the piping to the surroundings was 0.946. Results: When calculating the volume of the main pipe, it was calculated that the fire extinguishing water supplied at a temperature of 15 degrees from the underground pipe would have a volume of 3.33m³ to reach the first branch point. If we calculate the heat required until this volume reaches below zero, we get 316.350 kcal. When the results were reviewed using the related formula, the time required for the fire extinguishing water to completely freeze up to the first branch of the steel pipe was found to be 3,412 seconds. Conclusion: Fire-fighting water, which must reach from the main pipe to the branch pipe and nozzle in good condition, must minimize heat loss through the pipe surface along the transfer path. To achieve this, it is necessary to supplement insulation of the main pipe and branch pipes. In this study, the use of inorganic perlite material or flame-retardant rubber foam insulation was proposed through analysis of insulation properties.

• Korean Chemical Engineering Research
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• v.62 no.4
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• pp.327-334
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• 2024

The risks associated with coal dust explosion were investigated by analyzing various characteristics affecting the possibility of explosion. Samples were collected directly from two regions of the transfer process where the most explosions occurred in coal-fired power plants, and the composition ratio and average particle diameter that could affect the experiment were considered. As experimental items, explosion intensity, particle size and distribution, moisture content, dust concentration, minimum ignition energy, minimum ignition temperature, and oxygen concentration that affect the explosion were evaluated. As a result, the explosion intensity was found to have a maximum explosion pressure of 7.1 bar at a dust concentration of 500 g/m³ in sample A, and the maximum explosion pressure increase rate was 366 bar/s. In terms of dust particle diameter and particle size distribution, sample A had an average diameter of 35 ㎛ (D 50%), which was smaller than sample B. The moisture content was 5.7% in sample A, which was more than twice as high as 2.5% in sample B. The minimum explosion concentration was 400 g/m³ in sample A, which was lower than 2,000 g/m³ in sample B, so it had a risk. Since neither sample exploded at 1,000 mJ, it is judged that if the minimum energy is 500 mJ or higher, it can be regarded as dust with a low sensitivity to ignition compared to similar previous studies. The minimum ignition temperature was 532℃ in sample A and 634℃ in sample B, so sample A was more dangerous than sample B. The marginal oxygen concentration was 18.0% in both samples, so it is judged that there is a constant risk of explosion in the atmosphere.

• Clean Technology
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• v.20 no.3
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• pp.306-313
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• 2014

Nanoporous $TiO_2$ films are commonly used as working electrodes in dye-sensitized solar cells (DSSCs). So far, there have been attempts to synthesize films with various $TiO_2$ nanostructures to increase the power-conversion efficiency. In this work, vertically aligned rutile $TiO_2$ nanorods were grown on fluorinated tin oxide (FTO) glass by hydrothermal synthesis, followed by deposition of an anatase $TiO_2$ film. This new method of anatase $TiO_2$ growth avoided the use of a seed layer that is usually required in hydrothermal synthesis of $TiO_2$ electrodes. The dense anatase $TiO_2$ layer was designed to behave as the electron-generating layer, while the less dense rutile nanorods acted as electron-transfer pathwaysto the FTO glass. In order to facilitate the electron transfer, the rutile phase nanorods were treated with a $TiCl_4$ solution so that the nanorods were coated with the anatase $TiO_2$ film after heat treatment. Compared to the electrode consisting of only rutile $TiO_2$, the power-conversion efficiency of the rutile-anatase hybrid $TiO_2$ electrode was found to be much higher. The total thickness of the rutile-anatase hybrid $TiO_2$ structures were around $4.5-5.0{\mu}m$, and the highest power efficiency of the cell assembled with the structured $TiO_2$ electrode was around 3.94%.