• Composites Research
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• v.35 no.2
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• pp.61-68
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• 2022

Composite materials have been used in aerospace industry and many applications because of many advantages such as specific strength and stiffness and corrosion resistance etc. However, it is vulnerable to impacts, these impact lead to formation of cracks in composite laminate and failure of structures. In this paper, we analyzed Mode I fracture toughness of Carbon/Epoxy laminates using acoustic emission signal. DCB test was carried out to analyze Mode I failure characterization of Carbon/Epoxy laminates, and AE sensor was attached to measure AE signal induced by failure of specimen. Fracture toughness was calculated using cumulative AE energy and measured crack length using camera. The calculated fracture toughness was applied in FE model and the result of FE analysis compared with DCB test results. The results show good agreement with between FEM and DCB test results.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.28 no.3
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• pp.237-246
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• 1995

Larvae of the freshwater shrimp, Macrobrachium nipponense were reared in the laboratory at constant condition $(25^{\circ}C,\;7\%o)$, and their feeding rate, oxygen consumption rate, and growth rate were measured in regular intervals of time during larval development. Regression equations describing rates of feeding, growth and respiration as functions of time during individual larval molt cycles were inserted in a simulation model in order to analyse time-dependent patterns of variation as well as in bioenergetic efficiencies. Absolute values for feeding, growth, respiration and assimilation showed clear changes during the molt cycle, The absolute and specific values of respiration (R: R/C) showed small variation during the individual molt cycles. Significance of respiration in relation to growth (G) increased within the carbon budget, respiration rate (R/C) outbalanced growth rate (G/C) in late premolt. When the portion of metabolizable carbon is respired (R/G), metabolic coefficient was < 1 (i.e. R$(K_2)$ decreased concurrently, In cumulative carbon budget, total feeding was $491.54\;{\mu}g$ C/ind., assimilation was $85.3\%$, respiration was $47.7\%$, and growth was $37.6\%$ from hatching to postlarval stage.

• Korean Journal of Environmental Agriculture
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• v.14 no.1
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• pp.82-87
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• 1995

The standardization of test procedures and reproducibility of the toxicity data are prerequisite for the toxicity testing with the earthworm culturing in the laboratory. No in-depth study on culturing conditions of earthworms has been conducted in Korea, even of massive cultural practice is common for composting and production of biochemicals. The earthworms, Lumbricus rubellus and Eisenia foetida, were cultured in three kinds of artificial soil substrates(I, II and III) based on the OECD Guideline, which consist of different ratios of components (sand, sphagnum peat and kaolinite), and fed with a mixture of grain powders. During the period of culturing, the body weight and reproduction parameters were measured. L. rubellus showed the best results for increasing body weight and cocoon production in the artificial soil substrate(I) compared with E. foetida. The cocoon production was significantly high in both species cultured in the artificial soil substrate(I) among the three kinds of soil substrates, but the cumulative cocoon production of L. rubellus was 11 cocoon per worm compared with 3.7 cocoons per worm of E.foetida. L. rubellus, therefore, was more prolific than E. foetida in these culture schemes. The cumulative mortality in both species was less than 10%, and the number of juvenile worms per cocoon ranged from 1.5 to 2.3 and thus did not show any relationships with soil substrates or species. From these data, the culture of L. rubellus in the laboratory could be standardized, but for E. foetida, further study would be necessary to establish the optimal growth conditions in the laboratory.

• Management & Information Systems Review
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• v.31 no.3
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• pp.307-321
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• 2012

This paper examines the spillover effect between Korea stock market and Chinese stock market according to increasing economic power of Chinese. Chinese stock market start the transaction one hour and half early than Korea stock market. Especially we focuses the response of Korea stock market after Chinese stock market starts. So we analyze the return an volatility of Korea stock market after 10:30. We employee daily and intraday stock return and volatility. The sample period ranges from January 2008 to April 2010 total 28 months. Our results show that the gap of open price between Korea and Chinese stock market affect the five minute return and volatility of Korea stock market but don't affect the ten minute return and volatility. Recently, this spillover effect has increased more and more. This shows the rapid increase of economic power of Chinese to affect the Korea capital market.

• Korean Journal of Agricultural and Forest Meteorology
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• v.24 no.1
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• pp.1-12
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• 2022

Tilia amurensis is an important honey plant. As T. amurensis mainly distributes mountainous area with various elevations in Korea, accurate prediction of blooming time at the different elevation would benefit forest beekeepers. In this study, we measured time-dependent blooming progress of T. amurensis in Mt. Gariwang area ranging from 500-1500m. Additionally we collected blooming data from web and published literatures and estimated the variation of blooming time relative to the geographic locations. Flowers began to bloom from July 6 to July 22 with full blooming on July 14 in location where elevation is 638m in Mt. G ariwang area in 2021. Based on these databases, a growing degree day (G DD) model was developed for prediction of T. amurensis blooming progress using average daily temperatures. Using the starting date of G DD accumulation of January 1 and base temperature of 5 ℃, blooming period ranging from 10% to 90% of cumulative blooming rate was estimated as 860-1198 degree days (DD). This corresponded to the beginning to the end of July in Mt. Gariwaning area in 2021. This model could explain the phenological variations of T. amurensis flower blooming possibly affected by elevation within geographic area, latitude or year relative to the climate change, and aid forest beekeepers for better timing of nectar foraging by honey bees.

• Journal of Aquaculture
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• v.20 no.1
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• pp.31-40
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• 2007

To find out the effect of the spat planting time and environmental factors in the arkshell, Scapharca broughtonii (Schrenck), we investigated the growth, survival rate of arkshell and habitat characteristics in Gamak Bay, Yeoja Bay and Saryang Island. We planted artificial spats of arkshell in Gamak Bay and Yeoja Bay at November 2004, and also planted domestic and Chinese natural spats in Saryang Island at March 2005. We measured growth, survival rate of arkshell, physiochemical parameters of the water mass (water temperature, salinity, dissolved oxygen, nutrients and chlorophyll a) and characteristics of the sediment (oxygen penetration depth, oxygen microprofiles, ignition loss and chemical oxygen demand) by monthly. The cumulative survival ratio of arkshell in Gamak Bay was the highest at December, whereas the ratio of arkshell in Yeoja Bay was recorded as 0% at October. The monthly growth rates of arkshell length in Gamak Bay and Yeoja Bay were the highest in May and the growth rate of the Korean arkshell in Saryang Island was higher than Chinese ones significantly. The high mortality (> 65%) of the arkshell in Yeoja Bay during summer probably caused by high water temperature, inflow of low salinity water, and low dissolved oxygen concentration in sediment. The concentrations of nutrient and sediment COD were considered to play an important role in the monthly survival ratio of arkshell in Gamak Bay and Sarayng Island. We suggest that the growth and mortality of arkshell might be influenced to the planting time of spat and the habitat characteristics.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.1
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• pp.38-47
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• 2007

The initiation of fatigue cracks in a simulated aircraft structure with a series of rivet holes was detected by acoustic emission(AE), then the crack length was determined by surface acoustic wave(SAW) technique. With the initiation and growth of fatigue cracks, AE events increased intermittently to form a stepwise incremental curve of cumulative AE events whereas the crack length increased more or less monotonically. With the SAW technique employed, the crack sizing for 13 different cracks including some short cracks was performed. With the reference to the measurement by traveling microscope, cracks in the range of $1{\sim}8mm$ long were reliably sized by the SAW technique. Although it was impossible to size the short fatigue cracks in the range shorter than 1 mm, the SAW technique still appeared practically useful for a range of crack lengths often found in aircraft structures.

• Nuclear Engineering and Technology
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• v.27 no.5
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• pp.775-783
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• 1995

This study is to assess the effects of increasing wall thickness on the safety margin of pressure tube in operating and of lowering initial hydrogen concentration on the DHC growth in respect to the improvement of the reliability of pressure tube in CANDU reactors. The pressure tube with thicker wall of 5.2 mm shows much higher safety margin for flaw tolerance by 25％ than the current 4.2mmm tube. The thicker pressure tubes have a great benefit in LBB assessment including the initial crack depth at which DHC occurs, the crack length at onset of leaking and the available time for action. The resistance for the pressure tube ballooning at LOCA accident is also increased with the thicker tube. The calculations for Heq concentration after 20 years of operation as a function of wall thickness and initial hydrogen concentration show that the 5.2 mm nil thickness tube with 5 ppm initial hydrogen concentration is the most resistant to DHC. with the lower initial hydrogen concentration, TSS temperature for the precipitation or hydride decreases and the crack growth during cooldown reduces.

• Journal of Digital Convergence
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• v.13 no.3
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• pp.1-10
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• 2015

Carrier billing services market is growing according to the technical development. This study investigated the limiting factor in carrier billing services and suggested the improvement factor for it using the Delphi Method. The amount money to use in carrier billing charges should be provided in their credit based and the accumulated payment using a text message is displayed and also telecommunications carriers and carrier billing firms are the least responsible for consumer harm. It also provides administrative responsibility for communications carriers and billing services company for non recognition and payment. The service provider to prove negligence not proven by consumer and telecommunications billing service delinquency rate is applied at a rate such as a credit card and it also should integrate retail payment and service fee. This study will contribute to the communication billing services market growth through improved communication billing service. Further research is needed to continue the study of the factors that emerged from communication and billing services due to emerging technologies and services.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4B
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• pp.322-331
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• 2011

Recently, the social issues such as low birth rate, an aging population has brought about decreasing labor productivity and productive population. To relieve these problems, the government has planned to set up smart working infrastructure and will raise the number of smart worker to around 30 percent of the total working population by 2015. This study scrutinizes to the meaning of smart working with the concepts of new work pattern and open innovation. The empirical analysis result shows 56.9% of SMBs thought a need for such system and 60.1% of them answered to adopt it. And the market related to smart working of SMBs will increase to 17.5% every year to the point that by 2014. It will be worth 1.54 trillion won and create up to 38,000 job positions. While prior researches on SMB suggested key drivers and guideline for innovation, this study gives some implications of impact and ripple effect of smart working as an innovation factor based on empirical analysis.