• Journal of Korean Ophthalmic Optics Society
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• v.8 no.2
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• pp.31-35
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• 2003

Several poly(6-dialkylamino-1,3,5-triazine-2,4-dithioxylene) derivatives were synthesized by the polycondensation of 6-dialkylamino-1,3,5-triazine-2.4-dithiol with m- and p-dibromide xylene in a cetyltrimethyl ammonium bromide at $70^{\circ}C$ for 24h. The synthesized derivatives had refractive Indexes of 1.580~1.697 and had molar absorptivity of 97~196.6. In these derivatives, we knew that they are a polymer having high refraction indexes without double refraction because they contain triazine rings and sulfur atoms with high electron density.

• Journal of Pharmaceutical Investigation
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• v.13 no.1
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• pp.1-9
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• 1983

The effect of humidity on crystallization and polymorphic transformation of hydrous aluminum oxide under various humidity at $37^{\circ}$ was examined by means of X-ray diffraction, scanning electron micrograph, IR spectra and DTA. The humidity was an important factor influencing crystallization of hydrous aluminum oxide. The growth or crystal was strongly accelerated by humidity. The aging process is assumed that it is composed of two seperate steps, an increase of the diffraction around $36{\sim}42^{\circ}$, and an appearance and its development of the peak at $18{\sim}20^{\circ}$ of $2{\theta}$ value. The former is considered to be nucleation and the latter correspond to the growth period on crystallization. The crystalline form of aging products was various depending on the degree of humidity, directly it leads to the eventual formation of bayerite in more than 72%, $b{\"{o}}hmite$ in 50% and resembled to Nordstandite in 0% relative humidity, respectively but once formed, it was mostly stable in each surroundings and does not transform to the other more stable form in solid state even after aging for five years. The mechanism responsible for aging is further polymerization process of six-membered rings by deprotonation-dehydration reaction in which positively charged polynuclear hydroxy aluminum complexes formed in the presence of moisture are joined at their edges by double hydroxide bridges.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.9
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• pp.733-739
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• 2008

The X-ring is a elastomer with X-shaped cross-section used as a mechanical seal or gasket. Such a X-ring was equipped in a groove and compressed between two or more parts, acts as a seal on the interface. This study aims to detect contact stress and deformed shape of a X-shaped ring shell under various compressive contact conditions. A contact stress analysis was carried out by finite element analysis. The effect of compression rates and thickness design variable was analyzed. X-ring kept up the double seal until a compression rate of 20%. The maximum stresses of the X-ring was occurred at the top and bottom corner. The maximum contact stress of X-ring was rapidly increased according with the compression rate. The X-rings with thickness design variable from 1.3 mm to 1.5 mm had comparative low stress levels.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.10 no.5
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• pp.53-59
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• 2011

In this paper wideband dipole antenna that is usable as PCS/WCDMA/WiBro/WiMax public relay station antenna is proposed. The proposed antenna that designed by using double ring structure improves bandwidth performance of existing dipole antenna to wideband performance. To verify wideband performance and isotropic radiation pattern of the proposed antenna, simulation and fabrication have progressed its radiation characteristic has measured and then compared with calculated result. Measured result is similar to calculated result and has gain of 2dB VSWR of 2:1 over 1.75~3GHz. It is considered that the dipole antenna that designed in this paper can be usable as PCS/WCDMA/WiBro/WiMax public relay station antenna.

• Journal of Radiation Protection and Research
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• v.28 no.4
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• pp.291-298
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• 2003

The KN-12 transport cask has been designed to transport 12 PWR spent nuclear fuel assemblies and to comply with the regulatory requirements for a Type B(U) package. The containment boundary of the cask is defined by a cask body, a cask lid, lid bolts with nuts, O-ring seals and a bolted closure lid. The containment vessel for the cask consists of a forged thick-walled carbon steel cylindrical body with an integrally-welded carbon steel bottom and is closed by a lid made of stainless steel, which is fastened to the cask body by lid bolts with nuts and sealed by double elastomer O-rings. In the cask lid an opening is closed by a plug with an O-ring seal and covered by the bolted closure lid sealed with an O-ring. The cask must maintain a radioactivity release rate of not more than the regulatory limit for normal transport conditions and for hypothetical accident conditions, as required by the related regulations. The containment requirements of the cask are satisfied by maintaining a maximum air reference leak rate of $2.7{\times}10^{-4}ref.cm^3s^{-1}$ or a helium leak rate of $3.3{\times}10^{-4}cm^3s^{-1}$ for normal transport conditions and for hypothetical accident conditions.

• Journal of Korean Society for Atmospheric Environment
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• v.20 no.6
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• pp.759-771
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• 2004

This study analyzed concentrations of volatile organic compounds (VOCs) produced from incineration of plastic wastes at $600^{\circ}C$. The plastic wastes used in this study included polyethyleneterephthlate (PETE), high density polyethylene (HOPE), polyvinyl chloride (PVC), low density polyethylene (LOPE), polypropylene (PP), polystyrene (PS) and other. Plastic wastes were heated from room temperature upto $600^{\circ}C$ providing the compressed air inside of a small-scale electric furnace for 90 minutes and then they were oxidized (incinerated) for 60 minutes at $600^{\circ}C$ maintaining the same air supply. VOCs emitted from the incineration process were sampled using an air sampling pump and Tedlar air bags for 150 minutes and then the components and concentrations of the VOCs were analyzed by a GC-MS. The most prominent chemical structure of the VOCs obtained from the incineration process of the HOPE, LOPE and PP, which include ethylene groups in their main chains, was identified as aliphatic hydrocarbons such as 1-hexene. However, aromatics such as benzene were major chemical structure from the incineration of PETE, PVC and PS which include benzene rings in their main chains. This study estimated the total VOC production from the incineration of the plastic wastes based on the real plastic waste production and the emission factors. 64% and 27% of the total VOC emissions consisted of aliphatic hydrocarbons and aromatics, respectively, which have double bonds within their molecular structure and thus a high ground level ozone formation potential.

• Archives of Pharmacal Research
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• v.22 no.6
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• pp.585-591
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• 1999

The linker which plays a role in connecting a polymer with a scaffold has become an important part n solid-phase reaction. To develop a new linker for alcohols and carbohydrates, dihydropyran moiety was selected in this study. New linker, 1-($4^{l},5^{l}$-dihydro-5H-pyranyl)-7-hydroxyheptan-3-one (5) was synthesized via four steps from $\delta$-valerolactone. This can be called as DDHP-linked Wang resin due to double dihy-dropyran rings. To the one pyran ring of new linker 5 was added Wang resin and other alcohols and carbohydrates as scaffolds were then added successfully to the another pyran ring. Carbohydrate and hydroxyl resins were connected via new linker in a 70% loading yield. The detachment of glucose moiety in the presence of PPTS (2 equiv.) in 1:1 n-buteanol/1,2-dichloroethane at $60^{\circ}C$ for 12 h was carried out quantitatively. When certain combinatorial chemical works are carried out using this dihydropyran linker, Wang resin itself can be recovered. Its fact is particularly very important in industry, because recovered resins can be recycled.

• Journal of electromagnetic engineering and science
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• v.14 no.3
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• pp.299-305
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• 2014

A wideband circularly polarized (CP) antenna with a single feed is proposed for use in global navigation satellite systems. Its primary radiation elements are composed of two orthogonal bowtie dipoles, which are equipped with double-printed vacant-quarter rings to allow direct matching of the antenna to a single $50-{\Omega}$ coaxial line and to produce CP radiation. The crossed bowtie dipole is appropriately incorporated with a planar metallic reflector to produce the desired unidirectional radiation pattern as well as to achieve a wideband characteristic in terms of impedance matching and axial ratio (AR) bandwidths. The designed antenna was fabricated and measured. The prototype antenna with an overall 1.2-GHz frequency size of $0.48{\lambda}_o{\times}0.48{\lambda}_o{\times}0.25{\lambda}_o$ produced a measured ${\mid}S_{11}{\mid}$<-10 dB bandwidth of 1.05-1.79 GHz and a measured 3-dB AR bandwidth of 1.12-1.64 GHz. It also showed right-hand CP radiation with a small gain variation (${\pm}0.3dB$) and high radiation efficiency (>93%) over the operational bandwidth.

• Bulletin of the Korean Chemical Society
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• v.19 no.10
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• pp.1095-1099
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• 1998

The crystal structure of an acetylene sorption complex of dehydrated fully Mn(Ⅱ)-exchanged zeolite X, Mn46Si100Al92O384·30C2H2 (a=24.705(3) Å) has been determined by single-crystal X-ray diffraction techniques. The structure was solved and refined in the cubic space group Fd3 at 21(l) ℃. The complex was prepared by dehydration at 380 ℃ and 2 x 10-6 Torr for 2 days, followed by exposure to 300 Torr of acetylene gas for 2 h at 24 ℃. The structure was refined to the final error indices, R1=0.060 and R2=0.054 with 383 reflections for which I > 3σ(Ⅰ). In the structure, Mn2+ ions are located at two different crystallographic sites; sixteen Mn2+ ions at site I are located at the centers of the double six rings and thirty Mn2+ ions are found at site Ⅱ in the supercage, respectively. Each of these latter Mn2+ ions is recessed ca. 0.385(2) Å into the supercage from its three-oxygen plane. Thirty acetylene molecules are sorbed per unit cell. Each Mn2+ ion at site Ⅱ lies on a threefold axis in the supercage of the unit cell, close to three equivalent trigonally arranged zeolite framework oxygen atoms (Mn(Ⅱ)-O=2.135(9) Å) and symmetrically to both carbon atoms of a C2H2 molecules. At these latter distances, the Mn(Ⅱ)-C interactions are weak (Mn(Ⅱ)-C=2.70(5) Å), probably resulting from electrostatic attractions between the divalent cations and the polarizable π-electron density of the acetylene molecules.

• Anatomy and Cell Biology
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• v.51 no.4
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• pp.243-250
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• 2018

Because of its embryonic origin, the thyroid gland is predisposed to multiple anatomical variations and developmental anomalies. These include the pyramidal lobe, the origin of levator glandular thyroidae, the absence of the isthmus, ectopic thyroid, accessory thyroid tissues, etc. These anatomical variations are clinically significant to surgeons, anatomists, and researchers. The present study was designed to report anatomical variations and developmental anomalies of the thyroid gland in Ethiopian population. The study was conducted on 40 cadavers used for routine dissection classes. The thyroid gland was exposed and observed for any variations and developmental anomalies. The length, width, and thickness of the lobes were measured using a vernier caliper. Differences in the incidence of pyramidal lobe and absence of the isthmus between sexes were tested using a Pearson chi-square test. The mean length, width, and thickness of the right lobe were 4.24 cm, 1.8 cm, and 1.6 cm, respectively, whereas it was 4.08 cm, 1.8 cm, and 1.6 cm, respectively for that of the left lobe. The pyramidal lobe was noted in 52.5% of the cadavers. The levator glandulae thyroidae were prevalent in 40% of the cadavers. The isthmus mainly overlies the 2nd to 4th tracheal rings and was absent in 7.5% of the cadavers. Accessory thyroid tissue and double pyramidal lobes were noted in 2.5% of the cadavers. Most of the variations of the thyroid gland were seen frequently in female but it was not statically significant. Different clinically important and rare variations of the thyroid gland were found.