• Applied Chemistry for Engineering
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• v.26 no.2
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• pp.132-137
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• 2015

BEA-zeolite was modified by alkaline solution to introduce mesoporosity in the crystals and the homogeneous chiral Co(III) salen was immobilized in the mesopores. The dinuclear chiral Co(salen)-$GaCl_3$ catalyst immobilized on mesoporous BEA-zeolite showed high activity for the regioselective ring opening of terminal epoxides by carboxylic acids. Various chiral monoester derivatives could be synthesized with moderate enantioselectivity (47~69 ee%) from racemic epoxides through above reaction. When the chiral (S)-ECH was used as a reactant, it was efficiently resolved by carboxylic acid with a high enantioselectivity in the presence of heterogenized chiral salen catalyst, and the ring opened product afforded optically pure monoester epoxide (R)-GB (up to 98 ee%) through the ring closing in the basic solution by elimination of HCl. The heterogeneous catalyst could be fabricated easily, and the catalytic activity was retained for several times reuse without any further regeneration step.

• Journal of the Korean Geotechnical Society
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• v.36 no.1
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• pp.29-38
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• 2020

These days the circular cross section cofferdam has been frequently used for the earth retaining structures or cut off wall such as ventilating opening, intake tower in cofferdam, shaft for emergency. By the arching effect, the circular cross section type cofferdam has more advantage than a polygon cofferdam in terms of the structural forces and moment. This paper shows the proper approach to analyze the circular cross section cofferdam using 2D Finite Element Method (FEM) for the circular stiffener (ring beam) evaluation. Besides, the various shapes of cofferdam indluding circular cross section have modeled the 3D Finite Element Mothod (FEM). The circular cross section cofferdam shows the minimum reaction force compared with the other shapes of cofferdam.

• Advances in pediatric surgery
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• v.16 no.2
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• pp.101-107
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• 2010

Herniorrhaphy of Indirect inguinal hernia (IIH) is one of the most frequently performed surgical procedures in children. The overall incidence of inguinal hernias in childhood ranges from 0.8 to 4.4 %. The incidence is up to 10 times higher in boys than girls, especially much higher in premature infants. IIHs in children are basically an arrest of embryologic development rather than an acquired weakness, which explains the increased incidence in premature infants. In normal development, the processus vaginalis closes, obliterating the peritoneal opening of the internal ring between 36th and 40th week of gestation. This process is often incomplete, leaving a small patent processus in many newborns. However, closure continues postnatally, and the rate of patency is inversely proportional to age of the child. The presence of a patent processus vaginalis is a necessary but not sufficient variable in developing a congenital IIH. In other words, all congenital IIHs are preceded by a patent processus vaginalis, but not all patent processus vaginalis go on to become IIHs. The overall incidence of IIH in population is approximately 1 to 2 % and the incidence of a processus vaginalis is approximately 12 to 14%, clinically appreciable IIH should develop in approximately 8 to 12 % of patients with a patent processus vaginalis. Although the classic open inguinal hernia repair remains the gold standard for most pediatric surgeons, laparoscopic repair is being performed in many centers. Like open technique, laparoscopic technique is fundamentally a high ligation of the indirect hernia sac with or without internal ring ligation. The advantages of laparoscopic approach include the ease of examining the contralateral internal ring, the avoidance of access damage to vas and vessels during mobilization of cord, decreased operative time, and an ability to identify unsuspected direct or femoral hernias. Almost all groin hernias in children are IIHs and occur as a result of incomplete closure of processus vaginalis. The treatment is repair by high ligation of hernia sac, which can be done by an open or laparoscopic technique. The contralateral side can be explored by laparoscopy or left alone, open exploration is no longer indicated due to potential risk of infertility.

• Journal of the Korean Society of Clothing and Textiles
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• v.20 no.6
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• pp.1084-1095
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• 1996

The purpose of this study was to compare the effect of clothing materials and the opening of the garment on the microclimate of the skin simulating system during the coupled heat and moisture transfer. To determine the effect of size and location of openness of the garment, openness was simulated by removing parts of the spacer ring of the modelling system. To evaluate the changes of humidity and temperature of air layer in the system, buffering indice, Kd and Pr, and efficiency of openness were determined. When the openness was imparted to the system, the transport rate of heat and moisture increased abruptly; at the total openness of 26.4%, which simulated the openness of neck, armhole and waist, Kd increased at least more than three times of the closed system. As the openness increased, the effect of clothing materials decreased gradually to lose its effect at the 60% openness and approached the value of nude. Temperature regulating index showed, however, higher value than nude which was apparently due to the still air layer.

• Bulletin of the Korean Chemical Society
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• v.27 no.3
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• pp.345-354
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• 2006

Ionic liquids are alternative reaction media of increasing interest and are regarded as an eco-friendly alternatives, of potential use in place of the volatile organic solvents typically used in current chemical processing methods. They are emerging as the smart and excellent solvents, which are made of positive and negative ions that they are liquids near room temperature. The nucleophilic substitution reaction is one of the important method for inserting functional groups into a carbon skeleton. Many nucleophilic substitution reactions have been found with enhanced reactivity and selectivity in ionic liquid. In this review, some recent interesting results of nucleophilic substitution reactions such as hydroxylations, ether cleavages, carbon-X (X= carbon, oxygen, nitrogen, fluorine) bond forming reactions, and ring opening of epoxides in ionic liquids are discussed.

• Bulletin of the Korean Chemical Society
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• v.32 no.spc8
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• pp.2965-2969
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• 2011

Highly efficient and rapid aminolysis of epoxides with various amines in water under microwave irradiation in the absence of catalyst was developed. Chiral ${\beta}$-amino alcohols were formed in a short time with excellent yields.

• YAKHAK HOEJI
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• v.36 no.6
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• pp.604-610
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• 1992

Synthesis of 6-aza-2´-azido-2´,3´-secouridine, 6-aza-2´,3´-diazido-2´, 3´-secouridine, and 6-aza-5´-azido-2´,3´-secouridine as potential antiviral agents is described. These acyclic nucleosides were synthesized from uridine by the method of ring opening reaction of sugar moiety. And these compounds were tested against HSV-1 and HSV-2, but the in vitro test results of these compounds were negative.

• Proceedings of the Korean Fiber Society Conference
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• 2002.04a
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• pp.352-354
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• 2002

A series of ABA type triblock copolymers of trimethylene carbonate (TMC) and $\varepsilon$-caprolactone($\varepsilon$-CL) with different molar ratio were synthesized using ethylene glycol as initiator and stannous octoate as catalyst by ring-opening bulk polymerization. The characterization of the triblock copolymers was characterized by $^1$H-NMR, $\^$13/C-NMR, FT-IR, GPC and DSC, and compared with random copolymer. (omitted)

• Journal of Photoscience
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• v.10 no.3
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• pp.241-243
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• 2003

Photoreactions of some carbonyl compounds with TiO$_2$ were investigated in methanol. Although 1,3-cyclohexanedione and phthalimide afforded 3-methoxy-2-cyclohexen-l-one and 3-methoxy-1-isoindolinone, respectively, acid anhydrides such as succinic, phthalic, and maleic anhydrides gave the monoesters of dicarboxylic acids in good to excellent yields, when they were irradiated on TiO$_2$ in methanol with 300 nm UV light.

• Macromolecular Research
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• v.11 no.6
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• pp.511-513
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• 2003

Hydroxyl groups were introduced onto the surface of a silicon wafer by O$_2$ plasma treatment. Poly(l-lactide) (1-PLA) was attached onto the surface-modified silicon wafer by the ring-opening polymerization of l-lactide using the hydroxyl group as an initiator. Lamellar single crystals of 1-PLA were grown directly on the 1-PLA-attached silicon wafer from a 0.025% solution in acetonitrile at 5$^{\circ}C$. A well-separated, lozenge-shaped, monolayered lamellar single crystal was prepared because the 1-PLA-attached silicon wafer acts as an initial nucleus.