• Journal of the Korean Society for Heat Treatment
• /
• v.17 no.5
• /
• pp.271-277
• /
• 2004

Zr-xNb alloys (x = 0.2, 0.8, 1.5 wt.%) were prepared to study the characteristics of the phase transformation in Zr-Nb system. The samples were heat treated at ${\beta}$-temperature ($1020^{\circ}C$) for 20 min and then cooled with different cooling rate. The microstructures of the specimens having the same compositions were changed with cooling rate and Nb content. The Widmanst$\ddot{a}$tten structure was observed on the furnace-cooled sample. The relationship between ${\alpha}$-Widmanst$\ddot{a}$tten and ${\beta}$-phase was the {0001}${\alpha}$//{110}${\beta}$, <11$\bar{2}$0>//<111>. The ${\beta}$-phase in Widmanst$\ddot{a}$tten structure of Zr-Nb alloys containing Nb more than solubility limit was identified as ${\beta}_{Zr}$ phase which was a stable phase at high temperature. In the water quenched samples, two kinds of martensite structures were observed depending on the Nb-concentration. The lath martensite was formed in Zr-0.2, 0.8 wt.% Nb alloys and the plate martensite having twins was formed in Zr-1.5 wt.% Nb alloy.

• Korean Journal of Veterinary Research
• /
• v.40 no.4
• /
• pp.769-775
• /
• 2000

This study was investigated the ovarian response following superovulation treatment at different day of diestrus. The criterion for the presence or absence of a dominant follicle based on their morphological examination. Dominant follicle was puntured 48 hrs before the oneset of superovulation treatment by ultrasonography guided aspiration needle. Superovulation was induced by subcutaneous administration of FSH twice a day for 4 day in a decreasing regimen. There was no significant different between presence of dominont follicle and progesterone concentration/diameter of corpus luteum in HanWoo. Number of corpus luteum of donor after superovulation treatment was not significantly different in FSH administration at day 9, 11 and day 13 of estrus($14.5{\pm}4.5$, $15.5{\pm}5.6$ and $11.0{\pm}5.5$, respectively). But, the diameter of CL was significantly correlate(R2 = 0.757) with progesterone levels on day of superovulatory induction. After 7 days of artificial insemination, the embryos at 7 days were collected by uterine flushing after dominant follicle aspiration and superovulation treatment, and evaluated their quality by morphological criteria. Fifty five embryos with excellent, good and fair grade were transferred into 24 recipient cows. Seventeen offsprings, 1 of triplet, 4 of twins and 6 of singlet, were yield from 10 recipient cow. In conclusion, the present study showed that 1) dominant follicle can be determined by ultrasonography with rectal palpation by morphological evaluations, 2) superovulation response after follicular aspiration was not differ at day 9, 11 and 13 of estrus, 3) dominant follicle did not affect to progesterone concentration and diameter of CL, and 4) diameter of CL was significantly correlate to the level of progesterone concentrations in HanWoo.

• Analytical Science and Technology
• /
• v.5 no.2
• /
• pp.203-211
• /
• 1992

Fracture behavior and martensite substructure of Ni-36.5at.%Al alloy were investigated with the addition of vanadium which is known as scavenging element of grain boundary. The fracture surfaces were examined by scanning electron microscopy and the EDX spectrometer was applied for composition analysis of fracture surfaces. The substructure of martensite was studied by transmission electron microscopy. By addition of vanadium, fracture surfaces show mixed modes of intergranular and transgranular fracture and more Al content is found on the grain boundaries. For Ni-36.5at.%Al alloy, the planar faults observed in the martensite plates are the internal twins. By increasing the vanadium content, the modulated structure with stacking faults and dislocations dominates while the twinned martensite disappears. The stacking fault is determined to be extrinsic due to the substitution of V for Al. It is concluded that the segregation of sulfur on the high-energy state stacking fault area suppresses the intergranular fracture.

• Journal of Korean Academy of Nursing
• /
• v.47 no.3
• /
• pp.357-366
• /
• 2017

Purpose: The aim of this study was to determine the influence of various factors on preterm labor symptoms (PLS) and preterm birth (PB). Methods: This prospective cohort study included 193 women in the second stage of pregnancy. Multiple characteristics including body mass index (BMI), smoking, and pregnancy complications were collected through a self-report questionnaire. Pregnancy stress and PLS were each measured with a related scale. Cervical length and birth outcome were evaluated from medical charts. Multiple regression was used to predict PLS and logistic regression was used to predict PB. Results: Multiple regression showed smoking experience, pregnancy complications and pregnancy specific stress were predictors of PLS and accounted for 19.2% of the total variation. Logistic regression showed predictors of PB to be twins (OR=13.68, CI=3.72~50.33, p<.001), shorter cervix (<25mm) (OR=5.63, CI=1.29~24.54, p<.05), BMI >25 ($kg/m^2$) (OR=3.50, CI=1.35~9.04, p<.01) and a previous PB (OR=4.15, CI=1.07~16.03, p<.05). Conclusion: The results of this study show that the multiple factors affect stage II pregnant women can result in PLS or PB. And preterm labor may predict PB. These findings highlight differences in predicting variables for pretrm labor and for PB. Future research is needed to develop a screening tool to predict the risk of preterm birth in pregnant women.

• Journal of the Korean Ceramic Society
• /
• v.33 no.2
• /
• pp.228-234
• /
• 1996

It is very important to understand the domain structures of ferroelectric BaTiO3 in the poling process. Especially because {111} twinning is frequently observed in most BaTiO3 ceramics it is required to know the relations between the ferroelectric domains and the structural twin. In this study the domain structures of a {111} twinned crystal sample were observed under a polarizing microscope. and the relation between the {111} twin and the domain configurations could be classified into two types of 'V'-shape and linear shape penetrating perpendicular to the twin boundary. Domain formation obeys the symmetry of the {111} twining when a new domain structure is developed by heat treatment and surface deformation due to domain formation is also occured symmetrically between the both sides of the{111} twin boundary. This symmetrical behavior of the domains could be interpreted with the "head-to-tall" orientation of the domains across the {111} twin boundary.

• Clinical and Experimental Reproductive Medicine
• /
• v.25 no.2
• /
• pp.217-231
• /
• 1998

The effectiveness of intrauterine insemination (IUI) combined with controlled ovanan hyperstimulation (COH) in the treatment of infertility with various etiologies was compared in a total of 152 cycles. Patients received a maximum of three IUI cycles for the treatment. Severe male ($<2\times10^6$ motile sperm) or age factor (> 39 y) patients were excluded in this study. Pregnancy was classified as clinical if a gestational sac was seen on ultrasound. The overall clinical pregnancy rate was 7.9% per cycle (12/152) and 9.7% per patient (12/124). The pregnancy rates were 0% in unstimulated natural (0/18), 7.5% in CC (3/40), 8.2% in CC+hMG (4/49), 5.9% in GnRH-a ultrashort (1/17), 5.9% in GnRH-a long (1/17) and 27.3% in dual suppression cycles (3/11), respectively. The pregnancy rate was higher in dual suppression cycle than other stimulated cycles, but this was not significant. The multiple pregnancy rates were 25.0% (2 twins and 1 triplet). No patient developed ovarian hyperstimulation. Abortion rates were 66.7% in CC (2/3) and 100% in ultrashort cycles (1/1). The livebirth rate was 5.9% per cycle (9/152) and 7.3% per patient (9/124). There were no differences in age, duration of infertility, follicle size, total ampules of gonadotropins and days of stimulation between pregnant and non-pregnant groups. However, significant(P<0.05) differences were observed in the level of estradiol $(E_2)$ on the day of hCG injection ($3,266.6{\pm}214.2$ vs $2,202.7{\pm}139.4$ pg/ml) and total motile sperm count ($212.1{\pm}63.4$ vs $105.1{\pm}9.9\times10^6$) between pregnant group and non-pregnant group. These results suggest that IUI combined with successful ovarian stimulation tends to improve the chance of pregnancy as compared to IUI without COH and a total motile sperm count may be considered predictive of the success for pregnancy.

• Journal of Digital Convergence
• /
• v.14 no.1
• /
• pp.445-452
• /
• 2016

The purpose of this study was empirically to reveal how professional baseball fan's team identification and team loyalty influence on purchase intention of parent company products. For the research, a survey was conducted by 278 subjects selected from fans of Samsung Lions and LG Twins among professional baseball teams which were owned by representative electronics manufacturers. The results were as follows: First, team identification of the professional baseball fan had positive corelation with purchase intention of parent products. Second, team loyalty of the professional baseball fan had positive corelation with purchase intention of parent company products. Third, team loyalty had effective to mediate between team identification and purchase intention of parent company products. The result of studies showed that team identification was a major factor(variable) which had a positive influence on purchase intention of parent company products, and it also verified that team loyalty had mediating effects on these.

• Corrosion Science and Technology
• /
• v.2 no.3
• /
• pp.117-126
• /
• 2003

Due to excellent corrosion resistance and mechanical properties, austenitic stainless steel is widely used as the material for chemical plants. nuclear power plants, and food processing facilities. But, the zone affected by heat in the range of 400 to $800^{\circ}C$ during welding loses corrosion resistance and tensile strength since Cr-carbide precipitation like $Cr_{23}C_6$ forms at the grain boundary and thereby takes place the intergranular corrosion. In this study, AISI 304 stainless steel with the added Nb of 0.3 to 0.7 wt% was solutionized at $1050^{\circ}C$ and sensitized at $650^{\circ}C$. Specimen was welded by MIG. The phase and the microstructure of the specimens were examined by an optical microscope, a scanning electron microscope, and a x-ray diffractometer. The corrosion characteristics of specimens were tested by electrolytic etching and by double loop electrochemical potentiokinetic reactivation method(EPR) in the mixed solution of 0.5M $H_2SO_4$ + 0.01M KSCN. The melting zone had dendritic structure constituted of austenitic phase and $\delta$-ferrite phase. Cr carbide at the matrix did not appear, as Nb content increased. At the grain boundaries of the heat affected zone, the precipitates decreased and the twins appeared. The hardness increased, as Nb content increased. The hardness was highest in the order of the heat affected zone>melted zone>matrix. According to EPR curve, as the Nb content decreased, the reactivation current density(Ir) and the activation current density(la) were highest in the order of the melted zone

• Journal of Welding and Joining
• /
• v.31 no.2
• /
• pp.16-20
• /
• 2013

Titanium and its alloys have been widely using in the various field of industry application due to high corrosion resistant properties and mechanical properties. Titanium is highly reactive in the high temperature state and the formation of titanium oxide and porosities in the nuggets of fusion welding will results in the degradation of the mechanical properties. For this reason the studies of friction stir welding for titanium have been investigated recently. The FSW zones of titanium were classified by the weld nugget (WN), the linear transition boundary (TB) and the heat affected zone (HAZ). The WN along with titanium parent was characterized by the presence of twins and dislocations. The average grain size and hardness of WN has been changed according to heat input. The grain refinement resulted from the FSW increased the hardness in the stir zone. Sound dissimilar joints between SUS 304 and CP-Ti were achieved using an advancing speed of 50 mm/min and rotation speeds in the range of 700-1100 rpm. Aluminum 1060 and titanium alloy Ti-6Al-4V plates were lap joined by friction stir welding, hence the ultimate tensile shear strength of joint reached 100% of Al 1060. Mg alloy and Ti were successfully butt joined by inserting a probe into the Mg alloy plate with slightly offsetting. But Ti-Al intermetallic compound layers formed at the interface of these joints.

• Journal of the Mineralogical Society of Korea
• /
• v.18 no.3 s.45
• /
• pp.155-164
• /
• 2005

Volcanic rocks from the Mt. Mudeung area which are composed of Hwasun andesite, Mudeungsan dacite and Togok rhyolite contain plagioclase phenocrysts in common. Majority of the repeated twins observed in optical microscopy are albite twin and some are pericline twin. EPMA studies of plagioclases from Hwansun andesite, Mudeungsan dacite and Togok rhyolte indicate calcic andesine, andesine-oligoclase, nearly pure albite, respectively Albite twin and pericline twin can be easily distinguished through TEM diffraction patterns, which is quite difficult by optical microscopy. Plagioclases in volcanic rocks from the Mt. Mudeung area do not show e-reflection in (100) electron diffraction patterns, probably because of their high cooling rate, which inhibited phase separations during cooling.