• Journal of the Korean Geosynthetics Society
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• v.19 no.2
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• pp.13-21
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• 2020

In Korea, small reservoirs have been constructed for the supply of agricultural water, but most of them have been over 50 years from the year of construction. Aging agricultural reservoirs are being investigated for serious defects such as leaks and movements in slope, which are very vulnerable to safety. Accordingly, grouting methods are used to reinforce aging agricultural reservoirs in Korea. However, cement used as a grouting injection material consumes natural resources and generates a large amount of greenhouse gases during production. In addition, there is a problem that sufficient reinforcement is not made due to various factors such as the injection amount, the compounding ratio, the injection pressure, and etc. Therefore, due to these problems, the development of new materials and methods that can replace the grouting method and cement is required. In order to solve these problems, this study conducted an laboratory test on the surface stabilizer used to secure the stability of road and rail slopes. In addition, the program was analyzed and the reinforcing effect was examined when the surface stabilizer was used as reinforcement material for aging agricultural reservoir. As a result of the laboratory test, when the surface stabilizer is mixed, the increase of cohesion is possible up to 9% and there is no change in the friction angle. The results of the program analysis showed that the 1.0m reinforcement of slopes increased the factor of safety by 1.4 times, making it possible to reinforce the aging agricultural reservoir using surface stabilizers. And as a reinforcement method, it was analyzed that it is most appropriate to reinforce the slope and the bottom of slope simultaneously.

• Korean Chemical Engineering Research
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• v.46 no.6
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• pp.1095-1099
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• 2008

In this study, we investigated that hydrate formation and phase behavior of the $THF+H_2$ binary clathrate hydrates. In order to confirm the binary clathrate hydrate formation we employed the Raman and NMR spectroscopies that are known to be quite powerful tools, particularly for examining the cage occupancy pattern of guest molecules. In addition, we traced the P-T profiles from clathrate hydrate formation and dissociation process, which made it possible for the resulting phase equilibrium boundary to be clearly established. In the binary clathrate hydrate matrix we further identified that the relatively large THF molecules can only occupy the large $5^{12}6^4$ cavities, while the small $H_2$ molecules are entrapped in the empty $5^{12}$ cavities in structure-II, making the hydrate to be stable above 273 K even at relatively low pressure condition. Considering that pure $H_2$ hydrate can be produced at the extreme pressures higher that 1,000 bar, we can conclude that the water-soluble second guest inclusion induces $H_2$ storage and transportation to be readily achievable under much milder conditions.

• Journal of the Korean Chemical Society
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• v.33 no.3
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• pp.326-331
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• 1989

Superconducting fiber of high Tc $YBa_2Cu_3O_{7-{\sigma}}$ was successfully prepared by the sol-gel method. The stoichiometric mixture of Y, Ba and Cu nitrates was dissolved in water, to which citric acid solution was added. Then ammonium hydroxide was added to the mixture in order to increase the pH to a value between 5.8 and 6.2. The mixture was heated carefully to form a homogeneous colloid sol at 358 K. The solution was viscous enough to draw a long gel fiber, which was then heated at 1223K for 8 hrs. under oxygen partial pressure of $Po_2$ = 1 atm., cooled slowly and annealed at 723K for 13 hrs.. The reacted superconducting sample maintained a fiber form with some shrinkage of its volume. The superconducting transition temperatures (Tc, onset and Tc, offset) of $YBa_2Cu_3O_{7-{\sigma}}$ have been determined to be approximately 95K and 82K, respectively. The superconducting phase was also confirmed by Meissner effect at liquid nitrogen boiling temperature.

• Physical Therapy Korea
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• v.17 no.3
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• pp.20-30
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• 2010

This study examined whether any changes by mental task types on postural control in chronic stroke persons. Sixteen chronic stroke persons (mean age=53.75 yr) and sixteen age-and gender-matched healthy controls (mean age=54.44 yr) took part in this study. Participants randomly performed three different tasks on the stable and unstable surfaces. The no mental task was to stand while holding a 100 g weight in each hand, the arithmetic task (mental task) was to perform a silent 1-backwards counting while standing and holding a 100 g weight in each hand, and the simple task (mental task) was to stand and hold with both hands a tray (200 g) on which a glass filled with water has been placed. Sway path and sway velocity of the center of pressure (COP) were measured to assess standing postural control by task performance using the force platform. According to the results, in stroke group, total sway path and total sway velocity of COP was significantly decreased during arithmetic and simple task compared to no mental task on the stable surface (p<.05), and sway path (anteroposterior AP, mediolateral ML) of COP, total and sway velocity (AP, ML, total) of COP was significantly decreased during arithmetic and simple task compared to no mental task on the unstable surface (p<.05). Especially, sway path (AP, total) of COP and sway velocity (AP, ML, total) of COP was significantly decreased under the simple task when compared to the arithmetic task on the unstable surface (p<.05). In healthy control group, sway path (AP, ML, total) of COP and sway velocity (AP, ML, total) of COP was significantly decreased during arithmetic and simple task compared to no mental task on the stable and unstable surface (p<.05), and sway path (AP, total) of COP and sway velocity (AP, ML, total) of COP was significantly decreased under the simple task when compared to the arithmetic task on the unstable surface (p<.05). In conclusion, the findings of this study showed that arithmetic and simple task improved standing postural control for chronic stroke patients and the type of arithmetic and simple tasks were critical factor that reduced standing postural sway in dual-task conditions. Future research should determine whether dual-task conditions, including simple task, would be effective as a training program for standing postural control of stroke patients.

• The Korean Journal of Mycology
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• v.35 no.2
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• pp.109-114
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• 2007

Oudemansiella radicata, edible and medicinal mushroom belonging to Agaricales of Basidiomycota, has been known to exhibit outstanding curative effects on the fungal infection and hypertension caused by high blood pressure. Neutral saline soluble (0.9% NaCl), hot water soluble and methanol soluble substances (hereinafter referred to Fr, NaCl, Fr. HW and Fr. MeOH, respectively) were extracted from fruiting body of the mushroom. In vitro cytotoxicity test showed that Fr. NaCl was not cytotoxic against NIH3T3 and Sarcoma 180 at the concentration of $10{\sim}1,000\;{\mu}g/ml$. Intraperitoneal injection with Fr. NaCl exhibited antitumor activity with life prolongation effect of $42.9{\sim}66.7%$ in mice inoculated with Sarcoma 180. Fr. NaCl improved the immunopotentiating activity of B lymphocyte by increasing the alkaline phosphatase activity by $1.4{\sim}3$ folds compared with controlled and LPS groups, respectively. Intraperitoneal injection with Fr. MeOH increased the numbers of peritoneal exudate cells and circulating leukocytes by 3.5 and 2.5 folds, respectively. Therefore, the antitumor effect exhibited on mouse Sarcoma 180 cells was likely due to immune-modulating activity of crude polysaccharides extracted from fruiting body of O. radicata.

• Clean Technology
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• v.17 no.4
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• pp.314-324
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• 2011

Several amide derivatives have been used as additives for base oil of metal working fluids and pressure working oils. In this paper, a series of succinic acid alkyl half-amide derivatives were synthesized as over 97% yields by ring-opening reaction of succinic anhydride and several amines and were soluble in 100 N base oil within 1 wt% concentration. The structures of the synthesized amides were confirmed by $^1H$-NMR, FT-IR spectrum and GC analysis. Anti-corrosion properties of the amides in sea water were evaluated through ASTM D665 method and weight loss method. As the results of anti-corrosion properties, the properties of the amides with shorter alkyl chain and high concentration showed better performance than those with longer alkyl chain and low concentration. Also, the dialkyl amides showed better anti-corrosion properties than those of the monoalkyl amides. Inhibition efficiency% (IE%) was over 93% in the concentration of 40 ppm and corrosion rate (CR) was below 0.5 mm/year in the same concentration.

• Korean Journal of Agricultural Science
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• v.36 no.1
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• pp.27-40
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• 2009

Six strains of Phycomyces blakesleeanus (DEL, A56, C9, C47, C111, and G5) were cultured in continuous light condition for 6 days. The increase in fresh and dry weight after the culture period was similar in all strains. However, the increase in fresh weight was sustained throughout the culture period in all strains, whereas the increase in dry weight was prominent only during the first 3 days of culture. The development and phototropism of macrophores was observed after 3 days of culture, These results suggest that the development and phototropism is ascribed to the increase in turgor pressure in sporangiophores where water entered. A56 and G5 showed a higher sensitivity to light than C9 and C47, whereas C111 showed no photosensitivity. Antagonistic relations were observed between photosensitivity and development of microphores, suggesting that the development and phototropism of macrophores is regulated by a common recognition factor (photoreceptor).

• Clean Technology
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• v.5 no.2
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• pp.25-35
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• 1999

Behavior of permeate flux decline was examined through the hollow fiber membrane in ultrafiltration system for Si colloidal solution. Flux decline with time was due to the growth of Si cake deposited on the membrane surface and the pore blocking by Si particles for the hollow fiber membrane. At the pseudo steady state of operation, the permeate flux of dead-end flow was 60 % to that of the cross flow. The ratio of permeate flux to the pure water flux, $J/J_w$, decreased with increasing the trans-membrane pressure, from 64.2 % for $0.5kg_f/cm^2$ to 45.7 % for $2.0kg_f/cm^2$. When the feed flow rate was 3 L/min, the pore blocking model was dominant at the initial period of filtration and was followed by the cake filtration model. And with increasing the feed flow rate from 1 L/min to 3 L/min, $R_c$ was $1.79{\times}10^{12}{\sim}2.34{\times}10^{12}m^{-1}$ which was the about 40 % decreased value to that of the 1 L/min while $R_p$ was not changed and was $1.71{\times}10^{12}m^{-1}$ approximately.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.5
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• pp.287-296
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• 2020

The wave-impact load on offshore structures can be divided into green-water and wave-slamming impact loads. These wave impact loads are known to have strong nonlinear characteristics. Although the wave impact loads are dealt with in the current classification rules in the shipping industry, their strong nonlinear characteristics are not considered in detail. Therefore, to investigate these characteristics, wave-impact loads induced by a breaking wave on a circular cylinder were analyzed. A model test was carried out to measure the wave-impact loads due to breaking waves in a two-dimensional (2D) wave tank. To generate a breaking wave, the focusing wave method was applied. A series of 2D tank tests under a horizontal wave impact was carried out to investigate the structural responses of the cylindrical structure, which were obtained from the measured model test data. According to the results, we proposed a structural damage-estimation procedure of an offshore tubular member due to a wave impact load. Furthermore, a recommended wave-impact load is suggested that considers the minimum required thickness of each member. From the experimental results, we found that the required minimum thickness is dependent on the impact pressure located in a three-dimensional space on the surface of a tubular member.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.310-313
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• 2009

Several high nitrogen stainless steel ingots(100kg) were fabricated with changing Ni and $[N]_2$ contents by Pressurized Vacuum Induction Melting(P_VIM). After free forging process, chemical compositions, microstructure and mechanical properties were estimated. Hardness was increased with the increase of $[N]_2$ content. Furthermore, microstructure including a lot of tempering twins was observed with optical microscope. Mechanical properties were estimated as function of solution treatment temperature and cooling method(air/water) under duration time of 1 hr on sample that were fabricated with Ni content under the atmospheric $[N]_2$ pressure. At solution treatment range of $1050{\sim}1100^{\circ}C$, hardness was decreased with the increase of solution temperature and there were little discrepancy of microstructure and hardness with cooling method. Computer simulation was carried out in order to inspect pass schedule in cold rolling process. When the condition of simulation was roll speed of 2.5mpm, rolling rate $15{\sim}17%$ per pass, it was ascertained that the formation such as deformation by sticking and lamellar sliver etc. was restricted from a simulation.