• Proceedings of the Korea Concrete Institute Conference
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• 1994.04a
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• pp.7-12
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• 1994

In structural analysis of prestressed concrete continuous flexural mambers, secondary effects produced by tendon forces should be reasonably estimated. The secondary moment at service load stags is normally used for ultimate required moment caculation in strength design. This concept has to be reviewed when precise analysis is performed considering construction step, time dependent properties of concrete and tendon. An ultimate moment computation proposed, concept and structural behavior. The previously proposed procedure by other researcher and the proposed procedure are compared and reviewed for the currently constructed precast prestressed concrete bridge.

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.1
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• pp.1-8
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• 1999

In the present paper an attempt has been made to simulate the secondary injection-primary flow interaction in the conical rocket nozzle and to derive the performance of secondary injection thrust vector control(SITVC) system. Complex three-dimensional flowfield induced by the secondary injection is numerically analyzed by solving unsteady three-dimensional Euler equation with Beam and Warming's implicit approximate factorization method. Emphasized in the present study is the effect of secondary injection such as secondary mass flow rates and the momentum of secondary/primary nozzle flow mass rates upon the gross system performance parameters such as thrust ratio, specific impulse ratio and deflection angle. The results obtained in terms of system performance parameters show that lower secondary mass flow rate is advantageous for to reduce secondary specific impulse loss. It is further found that the nozzle with secondary jet injected downstream and interacting with fast primary flow is preferable for efficient and stable SITVC over the wide range of use with the penalty of side specific impulse loss.

• Journal of Engineering Education Research
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• v.16 no.5
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• pp.9-17
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• 2013

The purpose of this study is to analyze elementary and secondary school teachers' recognition about engineering education in elementary and secondary school. For this, we surveyed elementary and secondary school teachers. The result of this study is as follow. First, most teachers perceived that engineering positively affect national competitiveness and development. They also found that engineering education helps student to select natural science and engineering field career. Moreover, they perceived that engineering contents are not applied in elementary and secondary schools curriculums, hence it does not stimulate interest in engineering. Therefore, they perceived that if engineering education contents are systematically applied in formal curriculum, it will have a positive effect on current engineering education. Second, most teachers perceived that roles of engineering education are to make students learn creative design and problem solving process and inform about the engineering field career. They perceived that the best grade to start engineering education is 4~6 grade in elementary school and the best way to apply engineering education is through distributing engineering education contents to related subjects. They also perceived that technology subject has the most relation to engineering education and science subjects; mathematics subject follow after.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.10
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• pp.835-842
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• 2003

A three dimensional numerical analysis has been conducted for a stoker type incinerator which has the capacity of 1.5 ton/hr. The objective of the present study is to predict the effects of swirl induced by secondary air and to find an optimal operating condition of the incinerator. In this study, combustion characteristics such as distributions of temperature, velocity and concentration of each species have been examined with various injection types of secondary air and with different flow rates of secondary air in the incinerator. It is found that the secondary air injection on the combustion process makes the path of fluid particle longer in the combustor and enhances the mixing between air and combustion gas by arousing a swirl. Therefore, the injection type of secondary air can be an important key in the design process of incinerator.

• Particle and aerosol research
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• v.9 no.2
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• pp.111-125
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• 2013

Among the hazardous air pollutions(HAPs), characteristics of secondary organic aerosols are not well understood. In this study, the current state for the measurement and analysis of representative secondary PAHs such as oxy-PAHs and nitro-PAHs are presented with the discussion of their toxicity. Also, further research directions for the secondary PAHs are suggested. It was found that the chemical reaction mechanisms and products of PAHs in the air are poorly identified and their toxicities are not well studied. Moreover ambient concentrations of those secondary PAHs are not well documented. Sampling methodologies of those secondary PAHs are similar with PAHs but the analytical protocols for those secondary PAHs are more complicated than PAHs. Future management directions are suggested along with future research directions.

• Journal of Plant Biotechnology
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• v.49 no.3
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• pp.171-177
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• 2022

The precise homeostatic regulation of local auxin accumulation in xylem precursors of cambium stem cell tissues is one of the most important mechanisms for plant vascular patterning and radial secondary growth. Walls are thin (WAT1), a novel intracellular auxin transporter, contributes directly to the auxin accumulation maxima in xylem precursors. According to recent research, the auxin signaling activated pathway-related gene network was significantly enriched during the secondary growth of Panax ginseng storage roots. These imply that during P. ginseng root secondary growth, specific signaling mechanisms for local auxin maxima in the vascular cambial cells are probably triggered. This study identified four WAT1-like genes, PgWAT1-1/-2 and PgWAT2-1/-2, in the P. ginseng genome. Their expression levels were greatly increased in nitratetreated storage roots stimulated for secondary root growth. PgWAT1-1 and PgWAT2-1 were similar to WAT1 from Arabidopsis and tomato plants in terms of their subcellular localization at a tonoplast and predicted transmembrane topology. We discovered that overexpression of PgWAT1-1 and PgWAT2-1 was sufficient to compensate for the secondary growth defects observed in slwat1-copi loss of function tomato mutants. This critical information from the PgWAT1-1 and PgWAT2-1 genes can potentially be used in future P. ginseng genetic engineering and breeding for increased crop yield.

• Journal of the Korean BIBLIA Society for library and Information Science
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• v.33 no.4
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• pp.115-137
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• 2022

This research aims to suggest the way of activation of book curation in secondary school libraries by analyzing examples of book curation and the recognition of the persons in charge of secondary school libraries. A documentary research and a survey is conducted. 192 school librarians are chosen for that survey in Incheon region secondary school. 4 teacher librarians of Incheon region secondary school and a professor of library and information science are interviewed. Also an investigation is executed by visiting school libraries. Augmentation of the persons in charge of secondary school libraries, coordinating and information sharing with educational teachers, establishment of manual for book curation operation, publishing examples of subject selection are suggested for the measure of activation of book curation.

• Journal of Korean Society of Forest Science
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• v.97 no.5
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• pp.501-507
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• 2008

The data of crown width with 4 directions, DBH, tree height, and coordinate for sample trees were collected from 30 permanent sample plots in secondary fore st of the Maoershan Experimental Forestry Farm, Northeast China. In this paper, the competition of individual trees in stand were discussed for secondary forest by using iterative Hegyi competition index and crown overlap index that represented the competitive and cooperative interactions among neighboring trees. Active competitors of subject tree in the competition zone were selected to calculate the iterative competition index. Using the results of crown classification based on the equal crown projection area, a new distance dependent competition index called crown overlap index (COI) was developed for secondary forest. The COI performed well in describing the crown competition rather than crown competition factor (CCF). The individual-based competition index discussed in this paper will provide more precise for developing individual tree growth models for secondary forest and it can also use to adjust the stand structure for spatial optimal management.

• Journal of Nutrition and Health
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• v.11 no.1
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• pp.17-20
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• 1978

The materials carcinogenic agent, nitrosoamine, is distributed in food circumstances, and is formed when both nitrite and secondary amine are present. Nitrites are added to fishes as a color fixative or preservative and secondary amines exist in fishes. In order to find the distribution and contents of secondary amines, analysis of 19 kinds of fish was conducted. The results showed that, significant differences were not observed in the quantity of secondary amines in 19 kinds of fish by district. The highest value was 20.29 ppm in Theragra chalocogramma and the lowest was 0.022 ppm in Ostrea denselamellosa. Six fishes below 1 ppm were Nibea imbricata, Misgurnus mizolepis, Astroconger myriaster, Evynnis Japonica, Ostrea denselamellosa and Solen gouldi. Dimethyl amine only was identified and diethylamine or diphenylamine was not detected in all kinds of 19 fishes.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.4
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• pp.495-503
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• 2000

The present numerical study investigates flow characteristics and heat transfer enhancement of the viscoelastic non-Newtonian fluid in a 2:1 rectangular duct. The combined effect of temperature-dependent viscosity, buoyancy and secondary flow caused by second normal stress difference are all considered. The Reiner-Rivlin model is used as a viscoelastic fluid model to simulate the secondary flow and temperature-dependent viscosity model is adopted. Three types of thermal boundary conditions involving different combinations of heated walls and adiabatic walls are considered in this study. Calculated Nusselt numbers are in good agreement with experimental results in both the thermal developing and thermally developed regions. The heat transfer enhancement can be explained by the combined viscoelasticity-driven secondary flow, buoyancy-induced secondary flow and temperature-dependent viscosity.