• KOREAN JOURNAL OF CROP SCIENCE
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• v.28 no.4
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• pp.391-418
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• 1983

Urea and ammonium sulfate without and with sulfur group, respectively, were compared with respect to their nutritive effects on the rice plants, Suweon 264 and Jinheung, under the nursery trial on the protected upland and lowland seedbed, the pot trials with their various combination ratios and with added sodium sulfate to urea and the trials on the paddy fields which have undergone urea and ammonium sulfate application for many years. The rice seedlings fertilized with ammonium sulfate surpassed those with urea in growth performance and nutrients absorption of the rice seedlings at nursery period. Such stimulating effect of ammonium sulfate on the growth and nutrients uptake was more remarkable under the upland nursery than under the lowland one. The pot trial with the various combination ratios of urea and ammonium sulfate revealed that the chlorophyll content in leaf blade increased with the increment of sulfate ratio in the combination and the sole application of urea caused the chlorosis of leaf which was more conspicuous in Suweon 264 than in Jinheung. Fertilized with the same active ingradient amount of nitrogen, the rice plants supplied with ammonium sulfate surpassed those with urea in the chlorophyll content consistently under the nursery, the pot and the paddy field trials. The photosynthesis of flag leaf at heading stage increased with the combination rate of ammonium sulfate in the pot trial. The sulfur applicated as supplementary element of nitrogen in the nursery, the pot and the field trials were observed to be in positive relationship to the nitrogen and potassium content, but to be in negative correlation to the calcium content. The sulfur content in the rice plants was higher at early growth stage and decreased with the advance in growth stage. The nitrogen content also showed a similiar tendency to the sulfur content, and the N/S ratio was higher at early growth stage than at later one. The N/S ratio was negatively correlated with the chlorophyll content. In the field experiment, ammonium sulfate surpassed urea in the number of productive tiller, dry matter production and unhulled rice yields, but much stimulating effect of ammonium sulfate on the grain production was shown to be less effective than that on the straw production. The nitrogen and major nutrients content in the rice straw at harvest were higher in the paddy field with long-term ammonium sulfate application than in that with long-term urea application, suggesting that the former might have greater potentiality in nutrients supply than the latter.

• Journal of the Korea Institute of Building Construction
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• v.3 no.1
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• pp.139-146
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• 2003

The special requirements of high-performance concrete(HPC) could be enhanced property over others such as compressive strength, durability, and construction practices. In order to satisfy these requirements a series of laboratory trial mixes and following mock-up test of reinforced concrete wall at field were performed in this study. The objective of this study was to quantitatively evaluate the workability, compressive strength, and the increased heat of hydration caused by the increase of the specific weight of cement according to various variables. Six example series designed about a minimum compressive strength of 500kgf/$\textrm{cm}^2$ at 28 days, and an approximately slump and slump flow of 25cm and 60cm respectively were tested. The selection process of the specific weight of water and the percentage of fly-ash transposition determined to be most suitable for the production of HPC is presented in the following paper.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.560-564
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• 2009

This paper introduces measurement and evaluation of vibration of the ship propulsion machinery (ISO 20283-4). ISO 20283-2 for measurement of structural vibration on ships was finalized last year and ISO 20283-4 was drafted and reviewed by particulate ISO members now. As the importance and core field in ISO 20283-4, the torsional vibration of propulsion system for sea going vessels should be analysed in design stage and it should be confirmed by the its measurement during the sea trial. Criteria for evaluation of torsional loadings are defined by IACS (International Association of Classification Societies) UR M68. In this paper, the author introduced the important and controversial matters during the review of ISO 20283-4.

• Bulletin of the Korean Chemical Society
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• v.33 no.2
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• pp.433-442
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• 2012

The promise of stem cell therapy for various clinical applications seems getting realistic. An increasing number of researchers, from virtually every discipline of natural sciences, are flocking into this new world. Only ten years ago, gene therapy was the medicine for the 21st century. The possibility was endless. Although the science itself underlying gene therapy was very young, the field was exploding under the optimism that this new medicine would revolutionize both the basic and clinical sciences. For many reasons, the initial target was cancer. Here, we will focus on the results of cancer gene therapy clinical trials using liposome or nonviral gene carrier, hoping that the lesson from here will be a guideline for the new generation of cell-based therapies.

• Journal of Fisheries and Marine Sciences Education
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• v.25 no.3
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• pp.743-755
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• 2013

This study has investigated concerns of elementary school teachers on STEAM education that is main stream of science-technology education in Korea nowadays. Emphasis on STEAM education of Ministry of education that is new policy about science-technology-refinement education for future led to teachers implement STEAM education on the field of education since 2011. The purpose of this study is to check current degree of concerns of elementary school teachers for STEAM education and explore effective ways to improve concerns of teachers about it. From this study we checked and diagnosed conditions of teachers' concerns on the current STEAM education in Korea. Through this work we found degree of teachers' concerns on the current STEAM education is very low and they are undergoing trial and error recently because of deficiency of understanding on STEAM education and insufficient time to design it and so on.

• Journal of Environmental Science International
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• v.27 no.1
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• pp.59-61
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• 2018

This study made an economic evaluation of duck using Houttuynia cordata (H. cordata) powder as feed additives after 6 weeks. A total of 300 ducks (Pekins) were randomly assigned to one of the three treatments (0%, 0.5% and 1% H. cordata powder), with 5 replicates of 20 ducks each. After 6-week feeding trial, an economic improvement in all the treatments was found in following order: T2 (1% H. cordata powder) > T1 (0.5% H. cordata powder) > control. The results suggested that the addition of H. cordata powder to duck diets provided significantly greater economic benefits, indicating sustainable environmental management of the duck industry.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.1034-1037
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• 2002

Wet wire drawing process is used to produce fine wire in the industrial field. The production of fine eire by using wet wire drawing process with appropriate dies pass schedule would be impossible without understanding of relationship between process parameters such as material properties, dies reduction, friction conditions, drawing speed etc. However, up to new, dies pass schedule of wet wire drawing process has performed by trial and error of expert. Therefore, this study investigates the relationship between process parameters quantitatively and analyzes a conventional wet wire drawing process. Using the results, the conventional pass schedule can be redesigned to reduce the wire breakage during wet wire drawing. To verily the result of this study, the wet wire drawing experiment was performed. And the results between conventional process and redesigned pass schedule were compared. As the comparison of results, the wire breakage was considerably reduced in the redesigned pass schedule more than conventional pass schedule.

• Proceedings of the KIEE Conference
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• 2008.11a
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• pp.122-124
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• 2008

Korea Electric Power Research Institute has being carried out an IEC 61580 communication service test on IED trial products developed related to power IT project "The verification of Performance of the Substation Automation System and Its Field Test". This paper describes control testing, one of the IEC 61850 conformance testing items, which consists of DO, enhanced DO, SBO and enhanced SBO with a number of test cases.

• 한국정보통신설비학회:학술대회논문집
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• 2007.08a
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• pp.223-226
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• 2007

This paper first outlines the technology used in Power Line Communications(PLC) systems, and the political support being offered to the technology, from the point of view of its effect on electromagnetic compatibility (EMC). The radio spectrum needs protection from other interferers, and there is a regime in place to provide this interference avoidance/mitigation. Nevertheless, PLC has several features that mean that it is capable of creating such interference. These features are discussed, and some published field trial results are reviewed. Difficulties in achieving compatibility between the requirements for radio protection and the requirements for operation of the PLC system mean that there is no consensus as yet as to how PLC system components can be made compliant with EMC requirements. It is concluded that there is little prospect of an accommodation between the competing demands, so that if PLC is to become widespread it will be at the expense of the radio environment.

• Journal of Korean Port Research
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• v.14 no.1
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• pp.107-114
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• 2000

Derivation of stage-discharge relationship and characteristics for Yangsan river is presented in this paper. This research has been conducted as the second one after the first trial in 1997. The determination of discharge at a Yangsan river gauging was best made by measuring the flow velocities with a current meter and rod float. The rating curve obtained through 52 stage-discharge measurements on Yangsan river basin in 1999 is represented by Q=15.3540-140.6076H+182.44372H$^2$, which is discovered to be most excellent among other curves in reliability analysis. The observed stage-discharge data for Yangsan river was tested by HEC-RAS program, and reproduction of discharge by the induced curve was investigated and compared with the computational results. The rating curve of Yangsan river shows characteristics of Yangsan river more accurately compared with those separated in terms of water levels.