• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.567-572
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• 2002

This research investigates experimentally an effect on the quality performances of the high flowing concrete according to binder types. The purpose of this study is to determine the optimum mix proportion of the high flowing concrete having good flowability, viscosity and no-segregation. For this purpose, two types using belite cement＋lime stone powder(LSP) and furnace slag cement+lime stone powder are selected and tested by design factors including water cement ratio, fine and coarse aggregate volume ratio. As test results of this study, the optimum mix proportion for binder types is as followings. 1) One type based belite cement ; water cement ratio $51^{\circ}C$, fine aggregate volume ratio $43^{\circ}C$ and coarse aggregate volume ratio $53^{\circ}C$, replacement ratio of LSP $42.7^{\circ}C$. 2) Another type based slag cement : water cement ratio $41^{\circ}C$, fine aggregate volume ratio $47^{\circ}C$ and coarse aggregate volume ratio $53^{\circ}C$, replacement ratio of LSP $13.5^{\circ}C$.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.407-410
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• 2005

This research investigates experimentally an effect on the properties of the combined high flowing concrete by mix design factors. The purpose of this study is to determine the optimum mix proportion of the combined high flowing concrete having good flowability, viscosity, no-segregation and design strength(40.0MPa). For this purpose, trial mixings used belite cement+lime stone powder(LSP) are tested by mix design factors including water-cement ratio($47.9\~54.0\%$), fine aggregate volume ratio($41\~45\%$) and coarse aggregate volume ratio($41\~45\%$). As test results of this study, the optimum mix proportion for the combined high flowing concrete is as followings. Water-cement ratio $51.0\%$, fine aggregate volume ratio $43{\pm}1\%$ and coarse aggregate volume ratio $0.30{\pm}0.05m^3/m^3$ and replacement ratio of LSP $42.7\%$.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.9 s.186
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• pp.164-173
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• 2006

The cooling capacity of a micro-heat pipe is mainly governed by the magnitude of capillary pressure induced in the wick structure. For microchannel wicks, a higher capillary pressure is achievable for narrower and deeper channels. In this study, a metallic micro-heat pipe adopting high-aspect-ratio microchannel wicks is fabricated. Micromachining of high-aspect-ratio microchannels is done using the laser-induced wet etching technique in which a focused laser beam irradiates the workpiece placed in a liquid etchant along a desired channel pattern. Because of the direct writing characteristic of the laser-induced wet etching method, no mask is necessary and the fabrication procedure is relatively simple. Deep microchannels of an aspect ratio close to 10 can be readily fabricated with little heat damage of the workpiece. The laser-induced wet etching process for the fabrication of high-aspect-ratio microchannels in 0.5mm thick stainless steel foil is presented in detail. The shape and size variations of microchannels with respect to the process variables, such as laser power, scanning speed, number of scans, and etchant concentration are closely examined. Also, the fabrication of a flat micro-heat pipe based on the high-aspect-ratio microchannels is demonstrated.

• Journal of the Korean Society for Railway
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• v.4 no.1
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• pp.23-30
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• 2001

The dynamic characteristics such as natural frequency, mode shape and damping ratio are most important parameters in the high-speed railway bridges rather than general roadway bridges. Also, the need to know the dynamic behavior of bridges greatly increased in recent years. In the early of 1990s, to design the high-speed railway bridges, damping ratio recommended in general code was 2.5～7.5%. However, these values were not applied in all cases. Therefore, obtaining the damping value of specific structures is important to get the correct variable for design of high-speed railway bridges. The purpose of this study is mainly to obtain the damping ratio of high-speed railway bridges. The average damping ratio of high-speed railway bridges evaluated from a field test is about 2.4%.

• Journal of The Geomorphological Association of Korea
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• v.25 no.2
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• pp.1-14
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• 2018

The main objective of this paper is to classify properties of the locational environment for each debris type by calculating likelihood ratio based on the correlation between the distributions for each type of debris landform. A total of 8 thematic maps, like as elevation, slope, aspect, curvature, topographic wetness index (TWI), soil drainage, geology, and landcover including with GIS spatial information generally used in this type of debris landform analysis. The results of this study showed that the block stream had a high likelihood ratio compared to talus in areas with relatively high elevation; and concerning slope, the block stream had a high likelihood ratio in a relatively low region than talus. Concerning aspect, a clear correlation could not be analyzed for each debristype, and concerning curvature, the block stream displayed a developed slope on the more concave valley than the talus. Analysis concerning TWI, the block stream displayed a higher likelihood ratio in wider sections than talus, and concerning soil drainage, the talus and block stream both displayed a high likelihood ratio in regions with well-drained soil. The talus displayed a high likelihood ratio in the order of metamorphic rocks, sedimentary rocks, and granite, while the block stream displayed a high likelihood ratio in the order of volcanic rocks, granite, and sedimentary rocks. In addition, concerning landcover, the likelihood ratio had the most concentrated distributed compared to natural bare land only concerning talus. Based on the likelihood ratio result, it can be used as basic data for extracting the possible areas of distribution for each debris type through the GIS spatial integration method.

• International Journal of Automotive Technology
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• v.6 no.3
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• pp.259-268
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• 2005

In order to analyze the sheet drawability, the measurement of the plastic strain ratio was carried out for the 5182 aluminum alloy sheets in which were cold rolled without lubrication and subsequent recrystallization annealing. The average plastic strain ratio of the 5182 aluminum sheets was 1.50. It was considered that the higher plastic strain ratio was resulted from the ND//<111> component evolved during rolling and maintained during annealing. The AA5182/polypropylene/AA5182 (AA/PP/AA) sandwich sheets of the 5182 aluminum alloy skin sheet and the polypropylene core sheet with high formability have been developed for application for automotive body panels in future light weight vehicles with significant weight reduction. The AA/PP/AA sandwich sheets were fabricated by the adhesion of the core sheet and the upper and lower skin sheets. The AA/PP/AA sandwich sheet had high plastic strain ratio (1.58), however, the planar anisotropy of the sandwich sheet was little changed after fabrication. The optimum combination of directionality of the upper and lower skin sheets having high plastic strain ratio and low planar anisotropy was calculated theoretically and an advanced process for producing the sandwich sheets with high plastic strain ratio was proposed. The developed sandwich sheets have a high average plastic strain ratio of 1.55 and a low planar anisotropy of 0.17, which was improved more by 3.2 times than that of 5182 aluminum single sheet.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.05a
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• pp.154-155
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• 2017

With the recent development in construction industry, industrial by-products fly ash(FA) and blast furnace slag(BS) have been used in large quantities as an alternative to cement, as a solution for environmental problems and resource exhaustion. This study analyzed the basic characteristics according to the changes in replacement ratio and mixing ratio of FA and BS in high strength SCMs concrete, from which in turn it sought to find the optimal mixing ratio for high strength concrete The results showed that in unhardened concrete the more the replacement ratio and FA mixing ratio increases the slump flow will increase while amount of air decreases, and setting time is delayed. In hardened concrete the more the replacement ratio and FA mixing ratio increases the more the overall compression strength decreases, but until 28 days of material age the larger of the BS ratio displayed the best compression strength.

• Journal of Nutrition and Health
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• v.27 no.10
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• pp.967-978
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• 1994

This study was done to investigate the effect of age and dietary linolenic acid content and the linolenic acid/linoleic acid(LNA/LA) ratio on the lipid metabolism and formation of PGI2 and TXA2. The male Sprague-Dawley rats were fed 6 different with 0.2, 0.4, 0.6 of LNA/LA ratio within either 8% LNA(high LNA) or 4% LNA(low LNA) of fatty acid content for different feeding period(1, 4, 12 month). The dietary fat used were sesame oil, perilla oil, soybean oil and beef tallow. The concentration of serum total lipid, total cholesterol and HDL-C were increased with aging. Triglyceride concentration was decreased in 0.2 ratio of LNA/LA. The lipid content of liver showed similar tendency to that of serum. The ratio of PGI2/TXA2 was increased in 1 month rats and antithrombotic effect was reduced significantly with increasing age. The PGI2/TXA2 ratio was tended to be higher in diet of 0.2 and 0.4 LNA/LA ratio at high LNA level and in diet of 0.6 LNA/LA ratio at low LNA level. Especially PGI2/TXA2 ratio was increased linearly with rising LNA/LA ratio at low LNA level. It seemed that the LNA content and LNA/LA ratio had interaction to increase the antithrombotic effect bychanging TXA2 synthesis. And the dietary fatty acid related effect lowering the serum and liver lipid content, excepting triglyceride, was increased when dietary n3/n6 ratio was high(0.6) at both high and low n3 level. Therefore, it could not be recommended to consume large amount of n3 fatty acid or high ratio of n3/n6 to prevent cardiovascular diseases. These results suggested that the dietary fatty acid ratio of n3/n6 could be determined based on the n-3 content of dietary fat to reduce the risk of cardiovascular disease.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.2
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• pp.185-193
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• 2005

The present study composed a diesel-atkinson cycle of high expansion as a method of achieving high efficiency in diesel cycle engines. It also interpreted the cycle engine thermodynamically analysis to determine the possibility of the improvement of thermal efficiency and clarified the characteristics of several factors . According to the result of theoretical analysis, heat efficiency was highest when expansion-compression ratio Reど:1. In addition. diesel engines with high apparent compression ratio had higher expansion-compression ratio than otto engines and consequently their effect of high expansion was high. which in turn enhanced thermal efficiency. When the atkinson cycle was implemented in a real diesel engine by applying the miller cycle through the variation of the closing time of the intake valve, the effective compression ratio and the quantify of intake air decreased and as a result, the effect of high expansion was not observed. Accordingly. the atkinson cycle can be implemented when the quantity of intake air is compensated by supercharge and the effective compression ratio is maintained at its initial level through the reduction of the clearance volume. In this case. heat efficiency increased by $4.1\%$ at the same expansion-compression ratio when the apparent compression ratio was 20 and the fuel cut off ratio was 2. As explained above, when the atkinson cycle was used for diesel cycle. heat efficiency was improved. In order to realize high expansion through retarding the intake value closing time, the engine needs to be equipped with variable valve timing equipment, variable compression ratio equipment and supercharged Pressure equipment. Then a diesel-atkinson cycle engine is realized.

• Korea journal of population studies
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• v.11 no.2
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• pp.67-76
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• 1988

The purpose of this study was to find out the factors affecting birth sex ratio which had revealed alarmingly higher in recent years. This study was conducted to get hold of the basic data such as the sex ratio of live births which had been delivered at 5 general hospitals in Taegu from 1982 to 1986. And author chose Dongsan Medical Center from those 5 hospitals for further detailed study, and reviewed 1,286 medical records of mothers who had birth in each February and March from 1984 to 1987. Of these 1,286 deliveries, 30 cases were twin deliveries, which added the total children numbers to 1,316. The findings of this study were as follows: The average of birth sex ratio( 114.5) for 5 years at five general hospitals in Taegu was slightly higher than the traditional birth sex ratio( 102-107) and the highest was 123.4 in 1985. There was no significant difference in birth sex ratio by mother's educational level, her religion nor father's occupation. The birth sex ratio of the cases whose mother was above 35 years old was significantly high(400.0), that of the cases who were born to the mothers who had more than 3rd parity was significantly high(309.5), and that of the cases whose mother had more than two daughters and no son was also significantly high (330.7). The birth sex ratio of the cases who did not have ultrasonogram on their prenatal visits was 87.8. In contrast to this, that of the cases who had ultrasonogram was significantly higher( 135.5). Of the mothers who have more than two daughters and no son' 80.4% (45 cases) had ultrasonogram and their newborn's birth sex ratio was significantly high(542.9). Of the cases who were born to more than 3rd parity mothers, 75.6%(65 cases) of their mothers had ultrasonogram and their sex ratio was significantly high(441.6). It was revealed by this study that the birth sex ratio is changed to significantly high due to sex confirmation of the fetus by ultrasonogram. Thus it is recommended that the value related to having equality of sexes must be ingrained by changing the various social systems and value systems which is now aggrevating the son preference and should provide controlling system which can prohibit the ultrasonogram for sex confirmation only.