• Journal of the Korean Ceramic Society
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• v.35 no.1
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• pp.5-10
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• 1998

Mullitization in a multicomponent oxide system(alumina-kaolin-quartz-feldspar-talc) was studied as a function of sintering temperature from 1200 to 1500$^{\circ}C$ based upon a quantitative X-ray diffraction analysis. In the present study mullite grew as wiskers and its formation reaction showed characteristic there stages as follows In the first stage(1255-1295$^{\circ}C$) an appreciable mullitization(nucleation) occurred while corun-dum dissolution into glass (increasing glass content ) limited the rate of the reaction. At 1295-1335$^{\circ}C$ (second state) the reaction was significantly enhanced with a considerable glass consumption and with no appreciable change in corundum content. Finally (above 1335$^{\circ}C$) the reaction rate was attenuated re-markably with an apparent decrease in glass consumption rate. The impingement of mullite whiskers by oth-er whiskers and crystals was speculated to cause mullite growth in thickness direction with a slow growth rate resulting in the diminished reaction rate in the final stage.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.11
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• pp.853-864
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• 2017

This paper proposes a false alarm rate reduction technique for detection of small targets in a terrestrial environment. CFAR algorithm is useful in homogeneous background, but it is not easy to detect targets in non-homogeneous background. In particular, when the clutter power is not significantly different from the target signal, it is difficult to detect the target due to high false alarm rate. To solve these difficulties, this study presents the false alarm rate reduction technique based on CFAR algorithm, matched filter and binary integration technique. The parameters are studied through the theoretical analysis and the validity of the proposed study is examined by the test results.

• Journal of Animal Reproduction and Biotechnology
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• v.36 no.2
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• pp.82-90
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• 2021

In the present study, we examined if deep uterine artificial insemination (DUAI) can improve the pregnancy rate of artificial insemination (AI) using epididymal spermatozoa (ES) in Hanwoo cattle. The estrus cycles of 88 Hanwoo cows were synchronized, and 17 cows were artificially inseminated using the DUAI method with ES, 20 cows were artificially inseminated via the uterine body (BUAI) method with ES, and as a control, 51 cows were inseminated by using the BUAI method with ejaculated spermatozoa from 1 proven bull after frozen thawing. The pregnancy rate of the DUAI method (58.8%) was higher than that of the BUAI method (25.0%, p = 0.0498). The motility of ES was examined immediately after thawing and after 3 and 6 h of incubation. The rapid progressive sperm motility of the control group was significantly higher than that of the ES group immediately after thawing and after 3 and 6 h of incubation (p < 0.05). The straight line velocity and average path velocity of the ES group after 6 h of incubation were significantly lower than those in the control group (p < 0.05). The linearity and amplitude of lateral head of ES were lower than those at 6 h (p < 0.05). The flagellar beat cross frequency and hyperactivation of ES were lower than the control spermatozoa immediately after thawing and at 3 h (p < 0.05). These motility parameters suggested that ES had a low motility and fertilization ability compared to the control spermatozoa. After frozen-thawing and 3 h of incubation, the percentage of live spermatozoa with intact acrosomes in the ES was significantly lower than that in ejaculated spermatozoa (p < 0.05). Our findings suggested that the DUAI method can overcome the low pregnancy rate of ES, despite the low motility, viability, and fertilization ability of ES.

• Journal of Aquaculture
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• v.22 no.1
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• pp.1-4
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• 2009

A 10-week feeding trial was conducted to investigate the effects of feeding rate on growth and body composition of adult flounder during the summer season. Three replicated groups of the fish (initial mean weight of $535{\pm}4.1\;g$) were hand-fed a extruded diet twice a day at the different feeding rates of satiation (100%), 90%, 80% and 70% of satiation for 10 weeks. Mean Water temperature was $19.2{\pm}2.8^{\circ}C$ during the feeding trial. Weight gain and condition factor increased significantly with increase in daily feeding rate (P<0.05), but there was no significant difference in weight gain of fish fed the diet between 100% and 90% of satiation. Survival and feed efficiency were not significantly different among all groups. Proximate composition of dorsal muscle was not significantly affected by feeding rate. Based on the results of this study, optimum feeding rate for growth and condition factor of adult flounder (535-928 g) seemed to be 90% of satiation.

• Corrosion Science and Technology
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• v.12 no.2
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• pp.85-92
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• 2013

This work is concerned with an evaluation of dynamic boric acid corrosion (BAC) of low alloy steel for reactor pressure vessel of a pressurized water reactor (PWR). Mockup test method was newly established to investigate dynamic BAC of the low alloy steel under various conditions simulating a primary water leakage incident. The average corrosion rate was measured from the weight loss of the low alloy steel specimen, and the maximum corrosion rate was obtained by the surface profilometry after the mockup test. The corrosion rates increased with the rise of the leakage rate of the primary water containing boric acid, and the presence of oxygen dissolved in the primary water also accelerated the corrosion. From the specimen surface analysis, it was found that typical flow-accelerated corrosion and jet-impingement occurred under two-phase fluid of water droplet and steam environment. The maximum corrosion rate was determined as 5.97 mm/year at the leakage rate of 20 cc/min of the primary water with a saturated content of oxygen within the range of experimental condition of this work.

• Clinical and Experimental Reproductive Medicine
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• v.30 no.1
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• pp.105-109
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• 2003

Objective s: To assess the fertilizing capacity using sperm penetration assay (SPA) to predict the outcome of the in vitro fertilization-embryo transfer (IVF-ET) outcome. Materials and Methods: Semen samples were provided by 129 patients undergoing IVF. We attempted to correlate the extent of sperm penetration under enhanced SPA protocol with the results of fertilization, cleavage, preimplantation embryo development, and pregnancy. Results: Univariate analysis demonstrated a statistically significant correlation between fertilizing capacity and motility, kinetics, fertilization, cleavage and embryo development, and pregnancy rate. By logistic regression analysis, fertilizing capacity was found to be the only variable that was statistically significant with respect to pregnancy rate. Fertilizing capacity, cleavage rate and pregnant rate were significantly higher in pregnant group. However, the fertilization rates was comparable with both group. Conclusions: Lower fertilizing capacity could denote a poorer prognosis for establishing a pregnancy, even after satisfactory fertilization rate is achieved.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.11
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• pp.1486-1496
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• 2000

The initial flame kernel development and flame propagation in a constant volume combustion chamber is analyzed by the heat release rate and the mass fraction burnt. The combustion pressure is measured with a piezoelectric type pressure sensor. In order to evaluate the effects of ignition system and ignition energy on the flame propagation, four different ignition systems are designed and tested, and the ignition energy is varied by the dwell time. Several different spark plugs are also tested and examined to analysis the effects of electrodes on flame kernel development. The results show that the when the dwell time is increased, and when the spark plug gap is extended, heat release rate and the mass burnt fraction are increased. The materials and shapes of electrodes affect the flame development, because they change the energy transfer efficiency from electrical energy to chemical energy. The diameter of electrodes influences not only the heat release rate but also the mass burnt fraction as well.

• Journal of the Korean Society for information Management
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• v.32 no.1
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• pp.43-62
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• 2015

This study was implemented to suggest various indicators of collection evaluation for collection development policy in public libraries. For the sake of the exploratory research, this study tried to show the usability of indicators of collection evaluation through actual data of a case study. Also to analyze indicators of collection evaluation, this study used the ten years circulation records of the Gwangjin District Public Library in Seoul. Majors indicators of collection evaluation were the rate of use and use factor of purchasing books by annual, the rate of use and use factor of librarian's recommended books by annual, the rate of non circulating books by annual, and the rate of use by residence annually.

• Journal of the Korean Society of Propulsion Engineers
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• v.26 no.4
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• pp.44-53
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• 2022

The depressurization rate in a thrust variable solid rocket motor is the major factor that has the greatest influence on the thrust termination performance. In this study, the depressurization rates range of model solid rocket motor was identified and major factors affecting the depressurization rate were found. It is important for actual system design to understand the depressurization rate of the system that can satisfy the target performance as well as the extinguishing characteristics of the solid propellant. The methodology for obtaining the depressurization rate model in this study is considered to be applicable to the optimal design of the thrust terminable propulsion system.

• Clinical and Experimental Reproductive Medicine
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• v.17 no.2
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• pp.167-172
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• 1990

This study was carried out to clarify the effects of various kinds of cryoprotectants which were frequently used in freezing embryos of domestic animals on the survival of frozen-thawed mouse embryos. Mouse embryos were collected by hyperstimulation induction of ICR mouse. The samples were slowly cooled ($l^{\circ}C/min$) to temperatures between $-7^{\circ}C$ and $-30^{circ}C$ before direct transfer to liquid nitrogen ($-196^{\circ}C$) and thawed rapidly ($-500^{\circ}C$/min). As cryoprotectants, Glycerol, DMSO, Ethylene glycol and Propylene glycol were used and applied each 2 cell, 8 cell, morula in embryo stage. After normal mouse embryos developed to blastocyst by in vitro culture, we observed recovery rate and developing rate of embryos at thawing. The results obtained in these experiments were as follows : 1. The in vitro development rate from the frozen-thawed 2 cell embryos to the blastocyst were 67.7% in ethylene glycol, 65.7% in Propylene glycol, 55.2% in glycerol and 50.0% in DMSO respectively. 2. The in vitro development rate from the frozen-thawed 8 cell embryos to the blastocyst were 83.6% in DMSO, 75.7% in glycerol, 52.2% in propylene glycol respectively. 3. The in vitro development rate from the frozen-thawed morula to the blastocyst were 84.2% in glycerol, 80.0% in DMSO, 66.6% in propylene glycol and 55.2% in ethylene glycol respectively.