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崔鎔湜,金永鎭,李鎭鎬 成均館大學校 科學技術硏究所 1991 論文集 Vol.42 No.1
The objective of this paper is to develop a computational model and a software for predicting fatigue growth life of collinear multiple surface cracks under constant amplitude loadings and variable amplitude loadings. After examining crack growth rate data for CT specimens and surface crack specimens, empirical equations for surface crack geometry are proposed to predict the crack growth rate. In order to verify the proposed algorithm, a life prediction program has been developed. Several case studies were performed to check the accuracy of the proposed model and to verify the usefulness of the developed program. A good agreement was observed between the numerical results based on the proposed model and the published experimental data.
옥시칼본계 화합물의 포오틀랜드 시멘트 광물에 대한 흡착거동
김창은,최진호,유종석 연세대학교 산업기술연구소 1983 논문집 Vol.15 No.2
The rheological properties of the cement mineral-sodium gluconate-water system were investigated by determining the adsorbed amount of sodium gluconate, the sedimentation velocity of cement particles, and viscosity of the cement paste. IR and SEM were used to analyze the adsorbed phase on cement minerals. The results of experiment were as follow: 1. In the case of containing gypsum, the adsorbed amount of sodium gluconate on OPC could be calculated from the sum of that on each mineral component. 2. In general, the fluidity of the cement paste was increased with the equilibrium concentration. 3. There were maximum values of the amount adsorbed and viscosity at equilibrium concentration of 0.3% for C₃A in the solution system. 4. The adsorbed phase of sodium gluconate on C₃A could be identified by the IR analysis with the wavelength region of 3200??(-OH), 2800??(C-H), and 1600??( ?? ) 5. As shown in microstructure analysis with SEM, the layered type structure of hydrated C₃A could incorporate with polar compound or ionic species to form a interlamella complex. Due to the large surface area of layed structure of C₃AHx, the extraordinary high amount of gluconate anion adsorbed C₃A matrix could be well explained also comparing with hydrated C₃S.
Choy, Jin-Ho,Choi, Suk-Yong,Byeon, Song-Ho,Chun, Sung-Ho,Hong, Seung-Tae,Jung, Duk-Young,Choe, Won-Young,Park, Yung-Woo Korean Chemical Society 1988 Bulletin of the Korean Chemical Society Vol.9 No.5
The ratio of trivalent to divalent copper has been determined by the redox titration for two superconducting phases of $YBa_2Cu^{3+}_{2x}Cu^{2+}_{3-2x}O_{6.5+x}$ with the onset temp. of 60K (x = 0.23 ${\pm}$ 0.01) and 90K (x = 0.35 ${\pm}$ 0.02), and for the insulating one (x ${\cong}$ 0) which was kept in an ambient atmosphere for 72 hrs. It is found that $T_c$, and the ratio of $Cu^{3+}/Cu^{2+}$ depend strongly on the annealing temperature and time. A typical orthorhombic phase can easily be obtained by a slow cooling or stepwise cooling at $PO_2$ = 1 atm, and shows a high Tc (ca. 90K) superconductivity.
Intercalation of Vitamer into LDH and Their Controlled Release Properties
Choy, Jin-Ho,Son, You-Hwan Korean Chemical Society 2004 Bulletin of the Korean Chemical Society Vol.25 No.1
Biofunctional nanohybrids are synthesized from layered double hydroxide (LDH) and the vitamins such as ascorbic acid and topopherol acid succinate. Either ion exchange or copricipitaion leads to successful intercalation of the vitamins into gallery space of LDH that offers a new route to safe preservation of bioactivity as well as controlled release. Intercalations of vitamins are clearly reflected on the increase in the basal spacing of ZnAl-(Nitrate) LDH from 8.5 ${\AA}$ to 10.5 ${AA}$ for ascorbate, and 49.0 ${AA}$ for tocopherol acid succinate, respectively. No significant change in UV-Vis and IR absorption characteristics of the intercalated vitamins strongly supports the safe maintenance of their bioactivities without any deterioration of chemical and structural integrity. Furthermore, it is shown that the hybridized vitamins could be discharged in a controlled kinetics.
Perovskite-Like Strontium Titanium Zirconium Oxide Solid Solutions Prepared at Atmospheric Pressure
Choy, Jin-Ho,Kim, Ha-Suck,Kwon, Young-Uk,Kim Chong Hee Korean Chemical Society 1985 Bulletin of the Korean Chemical Society Vol.6 No.6
Perovskite type oxides of $SrTiO_3,SrZrO_3,and\;SrTi_{1-x}Zr_xO_3$ have been systematically synthesized at $1250^{\circ}C$and $1550^{\circ}C$ with specimens containing additions of up to x=0.9 of zirconium by solid state reactions and characterized by X-ray diffraction. X-ray diffraction studies showed that the compound $SrTi_{1-x}Zr_xO_3$ has cubic structure. The lattice paramters of $SrTi_{1-x}Zr_xO_3$ solid solutions obey the Vegard's law and fairly large increase in volume can acompany the formation of this solution with increasing Zr content(X). Assuming the lattice constants of perovskite type compounds $A(B_{1-x}B'_x)O_3$where $B_{1-x}B'_x$ is $Ti_{1-x}Zr_x$, to be a linear function of the ionic radii of B and B' ions, the disordered ion pair of $Ti^{4+}$and $Zr^{4+}$ was verified from the lattice constants of a series compounds varying x=0,0.05, 0.25, 0.5, 0.75, 0.9, and 1.0 with known isovalent pairs.