• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.3
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• pp.96-102
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• 2015

Traditional propellants emit toxic gases such as carbon dioxide and hydrogen chloride during combustion which are harmful to the environment. This study established a synthetic process of a high nitrogen containing derivative of tetrazine, 3,3-Azobis(6-Amino-1,2,4,5-Tetrazine) (DAAT), which can be applied as solid fuels for a solution to environmental concerns. Also, this paper described the detailed process and the analytic results of properties, which were not mentioned in previous reports. The compound was characterized by NMR, IR spectroscopy, and thermal, impact, and friction stability were measured. In addition, the heats of formation (${\Delta}H_f$) and detonation properties (pressure and velocity) of DAAT were calculated using Gaussian 09 and EXPLO5 programs.

• Advances in concrete construction
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• v.12 no.6
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• pp.499-505
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• 2021

Geopolymer binders fascinate the attention of researchers as a replacement to cement binder in conventional concrete. One-ton production of cement releases one ton of carbon-dioxide in the atmosphere. In the replacement of cement by geopolymer material, there are two advantages: one is the reduction of CO₂ in the atmosphere, second is the utilization of Fly ash and Ground granulated blast furnace slag (GGBFS) are by-products from coal and steel industries. This paper focuses on the mechanical properties of steel fiber reinforced geopolymer concrete. The framework considered in this research work is geopolymer source (Fly ash, GGBFS and crimped steel fibre) and alkaline activator which consists of NaOH and Na₂SiO₃ of molarity 8M. Here the Na₂SiO₃ / NaOH ratio was taken as 2.5. The variables considered in this experimental work include Binder content (360,420 and 450 kg/m³), the proportion of Fly ash and GGBS (70-30, 60-40 and 50-50) for three different grades of Geopolymer concrete (GPC) GPC 20, GPC 40 and GPC 60. The percentage of crimped steel fibres was varied as 0.1%, 0.2%, 0.3%, 0.4% and 0.5%. Generally, the inclusion of steel fibres increases the flexural and split tensile strength of Geopolymer concrete. The optimum dosage of steel fibres was found to be 0.4% (by volume fraction).

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.9
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• pp.1561-1565
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• 2007

According to thermal degradation on power transformers, it is known that electrical, mechanical and chemical characteristics for power transformer's oil-paper are changed. In the chemical property, especially, when the kraft paper is aged, the cellulose polymer chains break down into shorter lengths. It causes decrease in both tensile strength and degree of polymerization of paper insulation. Also the paper breakdown is accompanied by an increase in the content of various furanic compounds within the dielectric liquid. It is known that furanic components in transformer oil come only from the decomposition of insulating paper rather than from the oil itself. Therefore the analysis of furanic degradation products provides a complementary technique to dissolved gas analysis for monitoring transformers when we evaluate the aging of insulating paper by the total concentration of carbon monoxide and carbon dioxide dissolved in oil only. Recently, the analysis of furanic compounds by high performance liquid chromatography(HPLC) using IEC 61198 method for estimating degradation of paper insulation in power transformers has been used more conveniently for assessment of oil-paper. It is know that the main products which is produced by aging are 2-furfuryl alcohol, 2-furaldehyde(furfural), 2-furoic acid, 2-acetylfuran, 5-methyl-2-furaldehyde, and 5-hydroxymethyl-2-furaldehyde. For investigating the accelerated aging process of oil-paper samples we manufactured accelerating aging equipment and we estimated variation of insulations at $140^{\circ}C$ temp. during 500 hours. Typical transformer proportions of copper, silicon steel and iron have been added to oil-paper insulation during the aging process. The oil-paper insulation samples have been measured at intervals of 100 hours. Finally we have analyzed that 2-furoic acid and 2-acetylfuran products of furanic compounds were detected by HPLC, and their concentrations were increased with accelerated aging time.

• Korean Journal of Materials Research
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• v.20 no.3
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• pp.117-124
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• 2010

Titanium dioxide ($TiO_2$) particles deposited on different quantitative Fe-treated carbon nanotube (CNT) composites with high photocatalytic activity of visible light were prepared by a modified sol-gel method using TNB as a titanium source. The composites were characterized by BET, XRD, SEM, TEM and EDX, which showed that the BET surface area was related to the adsorption capacity for each composite. From TEM images, surface and structural characterization of for the CNT surface had been carried out. The XRD results showed that the Fe-ACF/$TiO_2$ composite mostly contained an anatase structure with a Fe-mediated compound. EDX results showed the presence of C, O, and Ti with Fe peaks in the Fe-CNT/$TiO_2$ composites. The photocatalytic activity of the composites was examined by degradation of methylene blue (MB) in aqueous solution under visible light, which was found to depend on the amount of CNT. The highest photocatalytic activity among the different composites was related to the optimal content of CNT in the Fe-CNT/$TiO_2$ composites. In particular, the photocatalytic activity of the Fe-CNT/$TiO_2$ composites under visible light was better than that of the CNT/$TiO_2$ composites due to the introduction of Fe particles.

• Journal of Ecology and Environment
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• v.46 no.4
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• pp.282-291
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• 2022

Background: The Arctic permafrost stores enormous amount of carbon (C), about one third of global C stocks. However, drastically increasing temperature in the Arctic makes the stable frozen C stock vulnerable to microbial decomposition. The released carbon dioxide from permafrost can cause accelerating C feedback to the atmosphere. Soil organic matter (SOM) composition would be the basic information to project the trajectory of C under rapidly changing climate. However, not many studies on SOM characterization have been done compared to quantification of SOM stocks. Thus, the purpose of our study is to determine soil properties and molecular compositions of SOM in four different Arctic regions. We collected soils in different soil layers from 1) Cambridge Bay, Canada, 2) Council, Alaska, USA, 3) Svalbard, Norway, and 4) Zackenberg, Greenland. The basic soil properties were measured, and the molecular composition of SOM was analyzed through pyrolysis-gas chromatography/mass spectrometry (py-GC/MS). Results: The Oi layer of soil in Council, Alaska showed the lowest soil pH and the highest electrical conductivity (EC) and SOM content. All soils in each site showed increasing pH and decreasing SOC and EC values with soil depth. Since the Council site was moist acidic tundra compared to other three dry tundra sites, soil properties were distinct from the others: high SOM and EC, and low pH. Through the py-GC/MS analysis, a total of 117 pyrolysis products were detected from 32 soil samples of four different Arctic soils. The first two-axis of the PCA explained 38% of sample variation. While short- and mid-hydrocarbons were associated with mineral layers, lignins and polysaccharides were linked to organic layers of Alaska and Cambridge Bay soil. Conclusions: We conclude that the py-GC/MS results separated soil samples mainly based on the origin of SOM (plants- or microbially-derived). This molecular characteristics of SOM can play a role of controlling SOM degradation to warming. Thus, it should be further investigated how the SOM molecular characteristics have impacts on SOM dynamics through additional laboratory incubation studies and microbial decomposition measurements in the field.

• Journal of Bio-Environment Control
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• v.18 no.4
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• pp.475-480
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• 2009

These studies were carried out to find the effect of packing materials and storage temperature to enhance the storability of Salicornia europaea. The fresh weight loss was less than 2% at below $10^{\circ}C$ and non-perforated package, but $25^{\circ}C$ and perforated package treatment showed more than 4% of fresh weight loss that result to deteriorate quality. The carbon dioxide and oxygen contents remained 1~2% and above 15% in non-perforated package, and these contents were in proportion to gas permeability of packing materials. All the temperature treatments except 25c showed rapidly increasing ethylene concent from 7days after storage, and the highest ethylene content was $2^{\circ}C$ treatment that should appear chilling injury. The off-odor and deterioration ratio were lowest in $5^{\circ}C$ among the temperature treatments and $50{\mu}m$ thickness ceramic film treatment at $5^{\circ}C$ storage, while packing materials did not show any trends among the temperature treatments. The shelf life based on visual quality showed highest in $50{\ss}|$ thickness ceramic film packing and $5^{\circ}C$ treatment, and that was 28days.

• Korean Journal of Soil Science and Fertilizer
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• v.34 no.6
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• pp.380-386
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• 2001

This study was conducted to investigate the influence of the root zone temperature on the changes in soil physicochemical environment and the growth of the apple trees. Root zone temperatures applied were 20. 25. 30. and $35^{\circ}C$. A pot experiment of 4-year-old fruit-bearing Fuji/M.26 apple trees was done from May 15. 1997 to August 15. 1997. Shoot length and shoot number of 4-year-old Fuji/M.26 was longest at $30^{\circ}C$ but decreased at $35^{\circ}C$. Oxygen concentrations in soil air were maintained from 17 to 18% at $20^{\circ}C$ but fluctuated from 10 to 14% at the end at $35^{\circ}C$. Carbon dioxide concentrations in soil air was highest at $35^{\circ}C$. Organic matter contents in soil decreased as root zone temperature and duration of treatment increased. Nitrate and ammonium contents in soil increased with rising root zone temperature in the beginning but nitrate contents decreased at $35^{\circ}C$ as time progressed. Nitrate content was higher in 10~15cm subsoil than in 25~30cm subsoil.

• Journal of Bio-Environment Control
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• v.16 no.1
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• pp.67-71
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• 2007

This study was conducted to find out the influence of cultivation season for fresh parsley in modified atmosphere storage. As the qualities of fresh parsley grown in different seasons; autumn, winter, summer were compared, the chlorophyll and vitamin C showed the highest content in autumn and winter cultivation, respectively, but the firmness was the highest in summer cultivation treatment. These fresh parsleys grown in different seasons packaged with 0.04mm ceramic film and stored at $0^{\circ}C$. The shelf life of these parsleys were 84 days in winter cultivation treatment, while parsleys cultivated in autumn and summer were able to be stored for 77 days and 56 days, respectively. The fresh weight loss of parsley was much more higher in summer than in both autumn and winter cultivation treatments. The carbon dioxide and ethylene contents in packages in summer were more than twice as high in autumn and winter cultivation treatment. There were not different between autumn and winter cultivation treatment in the two kinds of gas contents. This result should be caused by higher field heat that increased a respiration remarkably during the early storage. The highest field heat produced by summer cultivation resulted in remarkable decreases of firmness, chlorophyll and vitamin C during MA storage. As the results, the fresh parsley showed highest storability in winter cultivation treatment. The field heat of fresh parsley should be eliminated just after harvest for a long term storage.

• Journal of Bio-Environment Control
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• v.16 no.4
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• pp.420-425
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• 2007

This study was conducted to find out the effect of vitamin C treatments on the storability of several baby vegetables; endive, green romaine lettuce, pak-choi, red romaine, lollo rosa, and ssamchoo. The vitamin C was treated by the foliar spray which was carried out 3 times before harvest or dipping in vitamin C solution for 5 minutes after harvest. The vitamin C contents of 6 different baby vegetables were higher in vitamin C treatments than control, whereas the difference of vitamin C content between treatments was disappeared after storage. The fresh weight of ssamchoo and lollo rosa lettuce treated by vitamin C was maintained higher than that of control. There was not significant difference in visual quality among treatments, though some of baby vegetables treated by washing with vitamin C showed better visual quality than the others. The contents of carbon dioxide, oxygen and ethylene in MAP with baby vegetables did not show any difference among treatments. As the result, high concentrated vitamin C treatment, such as the foliar spray and washing (dipping) had a role of increasing functionality, but the enhanced functionality, high vitamin C, did not affect storability in baby vegetables.

• Asian-Australasian Journal of Animal Sciences
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• v.17 no.2
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• pp.263-270
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• 2004

A repeated $4{\times}4$ Latin square design was conducted with eight ileal cannulated castrates to examine the effect of source of starch and fiber on nutrient balance and energy metabolism. Pigs were fed on one of the four experimental diets: Control diet (C) mainly based on cooked rice; and diets P, S and W with the inclusion of either raw potato starch, sugar beet pulp or wheat bran supplementation, respectively. With the exception of an increased (p<0.05) energy loss from methane production with diet S observed, no significant differences (p>0.05) in the ratio of metabolizable energy (ME)/digestible energy, the utilization of ME for fat deposition and for protein deposition, energy loss as hydrogen and urinary energy were found between diets. The efficiency of utilization of ME for maintenance was lower (p<0.05) with diets P and S than with diet C. The inclusion of fiber sources (sugar beet pulp or wheat bran) or potato starch reduced the maintenance energy requirement. The fecal energy excretion was increased (p<0.05) with either sugar beet pulp or wheat bran supplementation, while it was unaffected (p>0.05) by addition of potato starch. In comparison with diets C and P, a lowered ileal or fecal digestibility of energy with diets S and W was observed (p<0.05). Feeding sugar beet pulp caused increased (p<0.05) daily production of methane and carbon dioxide and consequently increased energy losses from methane and carbon dioxide production, while it did not influence the daily hydrogen production (p>0.05). An increased (p<0.05) proportion of NSP excreted in feces was seen by the supplementation of wheat bran. Higher NSP intake caused an increased daily amount of NSP in the ileum, but the ileal NSP proportion as a percentage of NSP intake was unaffected by diets. Feeding potato starch resulted in increased daily amount of starch measured in the ileum and the proportion of ileal starch as a percentage of starch intake, while no significant influence on fecal starch was found. Higher (p<0.05) daily amount of fecal starch and the proportion of fecal starch as a percentage of starch intake were found with fiber sources supplementation compared with diets C and P. By increasing the dietary NSP content the fecal amount of starch increased (p<0.01).