• Korean Journal of Crystallography
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• v.13 no.3_4
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• pp.148-151
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• 2002

The molecular and crystal structure of metalaxyl C/sub15/H/sub21/NO₄, was determined by single crystal x-ray diffraction study. Crystallographic data for, title compound P2₁/c, a=7.849(4) Å, b=13.081(5) Å, c=15.100(3) Å, β=101.8(2)°, V= 1517.6(3) ų, Z=4. The molecular. Structure model was solved by direct method and refined by full-matrix least- squares. The final reliable factor, R, is 0.067 for 1694 independent reflections (F/sub o//sup 2/>4σ(F/sub o//sup 2/)). The molecular structure of title compound shows an intramolecular hydrogen bond: Cl2-Hl2A…O1.

• Korean Journal of Crystallography
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• v.8 no.2
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• pp.111-118
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• 1997

The structrue of hydroxy-bisbenzoyloxy-allyloxycalix[4]arene (C45H36O6) has been determined by X-ray crystallography. The crystals are monoclinic, space group P21, unit cell constants a=11.045(3), b=33.545(2) c=10.319(4)Å, β=113.86(2)˚, Z=4, V=3496.0(1.8) Å3, DC=1.28 gcm-3. The intensity data were collected on an Enraf-Noninus CAD-4 Diffractometer with a graphite monochromated Mo-Kα radiation. The structure was solved by direct method and refined by full-matrix least-squares calculations to a final R value of 0.076 for 2945 observed reflections. Two independent enantiomeric molecules are crystallized in a 1:1 racemate mixture. They have the flattened cone conformation with the flattening hydroxy1 pheny1 rings. There is an intramolecular hydrogen bond in both molecules.

• Steel and Composite Structures
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• v.9 no.2
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• pp.103-118
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• 2009

It has been reported that more than thirty five percent of steel bridges in the USA are structurally deficient because of structural degradations. The degraded structures need either full replacement or rehabilitation such that they are able to provide the required services for a longer period of time. The cost for repair in most cases is far less than the cost of replacement. Moreover, repair method generally takes less time than replacement and also reduces service interruption time. Modern advanced composites have been used in aerospace and automotive fields since World War II. In the recent past, because of the high strength-to-weight ratio and high stiffness-to-weight ratio, these composite materials have been introduced to civil engineering infrastructures primarily for repair and rehabilitation of concrete structures. However, only a few preliminary studies on repair of corroded steel structures using theses composite materials are reported in the literature available in the public domain. Thus, in this study, a series of laboratory tests was undertaken to evaluate the effectiveness of this repair method using carbon fiber reinforced polymer composite. The paper discusses the test method and test results obtained from these tests.

• Korean Journal of Crystallography
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• v.6 no.2
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• pp.98-102
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• 1995

The crystal structure of -Ethyl-1,4-dihydro-7-methyl-1,8-naphthyridin-4-one-3-carboxylic acid [Nalicixic Acid] has been determined from single crystal X-ray diffraction study; C12H12N2O3, monoclinic, P21/c, a=8.910(2)Å, b=13.145(3)Å, c=9.370(3)Å, β =100.06(2)°, V=1080.6Å, T=293K, Z=4, CuKα(λ=1.5418Å). The molecular structure was solved by direct method and refined by full-matrix least squares to a final R=0.055 for 1555 unique observed [F0>4σ(F0)] reflections and 166 parameters. The conformation of the molecule is stabilized by an intramolecular O(17)-H(17)…O(14) hydrogen bond [2.525(2)Å, 144.3(10)°].

• Bulletin of the Korean Chemical Society
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• v.11 no.5
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• pp.427-430
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• 1990

Cholesteryl aniline ($C_{33}H_{51}N$) is monoclinic, space group $P2_1$, with a = 9.020(3), b = 6.000(1), c = 27.130(9)${\AA},\;{\beta} = 98.22(2)^{\circ}$, Z = 2, Dc = 1.06 g/cm$^3$ and Dm = 1.04 g/cm$^3$. A diffraction data set was collected with Mo-$K_{\alpha}$ radiation (${\lambda} = 0.7107 {\AA}$) on a diffractometer with a graphite monochromator to a maximum 2${\theta}$ value of 50$^{\circ}$, by the ${\omega}-2{\theta}$ scan technique. The coordinates of the non-hydrogen atoms and their anisotropic temperature factors were refined by full-matrix least-squares methods to final R of 0.058. In cholesteryl group, bond distances were normal except in tail part, where high thermal vibration resulted in apparent shortening of the C-C distances. The crystal structure consists of bilayers of thickness $d_{001} = 27.13 {\AA}$, in each of which there is the tail to tail arrangement of molecules aligned in the unit cell with their long axes approximately parallel to the [104] axis. The two halves of the double layer are related to each other by the screw axis.

• Archives of Pharmacal Research
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• v.16 no.2
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• pp.134-139
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• 1993

The molecular structure of acemetacin, 1-(4-chlorobenzoyl)-5-methoxy-2-methyl-1H-indole-3-acetic acid carboxymethyl ester, was determined by single cystal X-ray diffraction analysis. The compound was recrystallized from a mixture of acetone and water in triclinic, space group P1, with a=7.796(1), b=10.245(2), c=13.542(3)$\AA,\;\alpha=97.35(1),\;\beta=96.34(1),\;\gamma=107.06(1)^\circ$, and Z=2. The calculated density is 1.422; the observed value is $1.42\;g/cm^3$. The structure was solved by the direct method and refined by full matrix least-squares procedure to the final R value of 0,037 for 2960 independent reflections. There are water molecules, which are thought to be co-crystallized during the evaporation procedure, with the ratio of one water per compound molecule in the crystal. The conformation of the compound is found to be very similar to that of indomethacin. The molecules are stabilized by three O-H.....O type intermolecular hydrogen bonds between the oxygen of water molecule and those of the compound.

• Steel and Composite Structures
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• v.38 no.6
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• pp.739-749
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• 2021

This paper introduces an improved design equation to evaluate the resisting capacity of circular reinforced concrete (RC) columns partially strengthened with outer steel tube. When RC column members are required to be strengthened according to the change in the loadings considered and/or the deterioration progress in columns, wrapping up RC column with steel circular tube, which takes the form of concrete filled steel tube (CFST), has been popularly considered because of its structural advantage induced from the confinement effect. However, the relatively high construction cost of steel tube is restricting its use to the required region, while deriving the shape of a partial CFST column. To evaluate the resisting capacity of a partial CFST column, numerical analyses need to be performed, and a numerical model proposed in the previous study for the numerical analysis of full CFST columns is used to conduct parametric studies for the introduction of a design equation. The bond-slip effect developed along the interface between the in-filled concrete and the exterior steel tube is taken into consideration and the validity of the numerical model has been established through correlation studies between experimental data and numerical results for partial CFST circular columns. Moreover, parametric studies make it possible to introduce a design equation for determining the optimum length of outer steel tube which produces partial CFST circular columns.

• Tunnel and Underground Space
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• v.28 no.1
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• pp.97-110
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• 2018

The application of sprayed waterproofing membrane with high adhesion and ductility is considered to be promising as a measure for repair and reinforcement of a tunnel structure. Therefore, a powder-type and one-component membrane prototype with high tensile and bond strengths was made in this study. Then, its reinforcement effect on a shield segment was evaluated by carrying out a series of full-scale loading tests of segment specimens on which the membrane was sprayed. From the tests, it was confirmed that the initial cracking loads increased by approximately 34% due to cracking retardation by membrane coating. Even though the increase of failure loads were not so high as cracking loads, the strain-softening behaviors were observed from specimens coated by the membrane. Therefore, it is expected that the membrane coated on the inner surface of a lining might be effective in preventing its brittle failure.

• The Journal of Korean Academy of Prosthodontics
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• v.41 no.3
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• pp.369-378
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• 2003

Statement of Problem: Recently, resin cements have become more widely used and have been accepted as prominent luting cements. Current resin cements exhibit less microleakage than conventional luting cements. However, the constant contact with water and exposure to occlusal forces increase microleakage even in resin cements inevitably. Most bonding resins have been modified to contain a hydrophilic resin such as 2-hydroxyethylmethacrylate (HEMA) to overcome some of the problems associated with the hydrophobic nature of bonding resins. By virtue of these modifications, bonding resins absorb a significant amount of water, and there may also be significant stresses at bonding interfaces, which may adversely affect the longevity of restorations. Therefore the reinforcement of water stability of resin cement is indispensable in future study. Purpose: This study was conducted to examine the influence of water retention on microleakage of two resin cements over the period of 6 months. Materials and Methods: 32 extracted human teeth were used to test the microleakage of a single full veneer crown. Two resin cements with different components and adhesive properties - Panavia F (Kuraray Co., Osaka, Japan) and Super-Bond C&B (Sun Medical Co., Kyoto, Japan)- were investigated. The storage medium was the physiological saline solution changed every week for 1 month, 3 months, and 6 months. One group was tested after storage for 1 day. At the end of the each storage period, all specimens were exposed to thermocycling from $5^{\circ}C$ to $55^{\circ}C$ of 500 cycles and chewing simulation of 50,000 cycles, and then stained with 50% silver nitrate solution. The linear penetration of microleakage was measured using a stereoscopic microscope at ${\times}40$ magnification and a digital traveling micrometer with an accuracy of ${\pm}3{\mu}m$. Values were analyzed using two-way ANOVA test, Duncan's multiple range tests (DMRT). Results : Statistically significant difference of microleakage was shown in the 3-month group compared with the1-day or 1-month group in both systems (p<0.05) and there were statistically significant differences in microleakage between the 3-month group and the 6-month group in both systems (p<0.05). The two systems showed different tendency in the course of increased microleakage during 3 months. In Panavia F, microleakage increased slowly throughout the periods. In Super-Bond C&B, there was no significant increase of microleakage for 1 month, but there was statistically significant increase of microleakage for the next 2 months. For the mean microleakage for each period, in the 3-month group, microleakage of Super-Bond C&B was significantly greater than that of Panavia F. On the other hand, in the 6-month group, microleakage of Panavia F was significantly greater than that of Super-Bond C&B (p<0.05). Conclusion: Within the limitation of this study, water retention of two different bonding systems influence microleakage of resin cements. Further studies with the longer observation periods in viro are required in order to investigate water stability and the bonding durability of the resin cement. CLINICAL IMPLICATIONS Microleakage at the Cement-tooth interfaces did not necessarily result in the failure of the crowns. But it is considered to be a major factor influening the longerity of restorations. Further clinical approaches for decreasing the amount of microleakage are required.

• Korean Journal of Mineralogy and Petrology
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• v.36 no.4
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• pp.355-363
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• 2023

In this study, we explore the nature of clumped isotopes of H₂O molecule using quantum chemical calculations. Particularly, we estimated the relative clumping strength between diverse isotopologues, consisting of oxygen (¹⁶O, ¹⁷O, and ¹⁸O) and hydrogen (hydrogen, deuterium, and tritium) isotopes and quantify the effect of temperature on the extent of isotope clumping. The optimized equilibrium bond lengths and the bond angles of the molecules are 0.9631-0.9633 Å and 104.59-104.62°, respectively, and show a negligible variation among the isotopologues. The calculated frequencies of the modes of H₂O molecules decrease as isotope mass number increases, and show a more prominent change with varying hydrogen isotopes over those with oxygen isotopes. The equilibrium constants of isotope substitution reactions involving these isotopologues reveal a greater effect of hydrogen mass number than oxygen mass number. The calculated equilibrium constants of clumping reaction for four heavy isotopologues showed a strong correlation; particularly, the relative clumping strength of three isotopologues was 1.86 times (HT¹⁸O), 1.16 times (HT¹⁷O), and 0.703 times (HD¹⁷O) relative to HD¹⁸O, respectively. The relative clumping strength decreases with increasing temperature, and therefore, has potential for a novel paleo-temperature proxy. The current calculation results highlight the first theoretical study to establish the nature of clumped isotope fractions in H₂O including ¹⁷O and tritium. The current results help to account for diverse geochemical processes in earth's surface environments. Future efforts include the calculations of isotope fractionations among various phases of H₂O isotopologues with a full consideration of the effect of anharmonicity in molecular vibration.