• Journal of Ocean Engineering and Technology
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• v.5 no.2
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• pp.58-66
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• 1991

Not only difference of fatigue crack growth and propagation behavior resulted from the grain size, the hardness ratio and volume fraction in M.E.F. dual phase steel composed of martensite in hard phase and ferrite in soft phase, but also the effects of the plastic constraint were investigated by fracture mechanics and microstructural method. The main results obtained are as follows: 1) The fatigue endurance of M.E.F. steel increases with decreasing the grain size, increasing the ratio of hardness and volume fraction. 2) The initiation of slip and crack occures faster as the stress level goes higher. These phenomena result from the plastic constraint effect of the second phase. 3) The crack propagation rate in the constant stress level is faster as the grain size gets larger, the ratio of hardness lower and volume fraction smaller.

• Journal of Korea Foundry Society
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• v.10 no.4
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• pp.309-315
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• 1990

Aluminum alloy matrix composites reinforced by SiC particles were prepared by rheocompocasting, a process which consists of the incoporation and distribution of reinforcement by stirring within a semi-solid alloy. When the volume fraction of SiCp and stirring speed were fixed, the dispersion of SiCp in Al-matrix alloy depended on stirring time and solid volume fraction in slurry. The results were as follows : 1) As a dispersed SiCp during stirring at $647^{\circ}C$ in 6063-Al alloy, SiC was better dispersed than that other temperature, where solid volume fraction was 43% in slurry. 2) When increased solid fraction in slurry, rate of dispersing SiC increased during stirring and porosities decreased in matrix alloy after casting. 3) Inspite of stirring with 800rpm, since solid particles of matrix alloy in slurry joined each other and occured joining growth, so that SiC was not dispersed into solid particle.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.08a
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• pp.184-196
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• 2004

An Eulerian finite element analysis for the steady state rolling process is addressed. This analysis combines the crystal plasticity theory fur texture development as well as the continuum damage mechanics for growth of micro voids. Although an Eulerian analysis for steady state rolling has many advantages, it needs an initial assumption about the shape of control volume. However, the assumed control volume does not match the final shapes. To effectively predict the correct shape in an assumed control volume, a free surface correction algorithm and a streamline technique are introduced. Applications to plate rolling, clad rolling, and shape rolling will be given and the results will be discussed in detail.

• Journal of Welding and Joining
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• v.16 no.2
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• pp.64-72
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• 1998

This study aims a investigating the effect of volume fraction of chromium carbide phase(VFC) of hardfaced iron/chromium alloys on fracture toughness. The alloys were deposited twice on a mild steel plate using self-shielding flux cored arc welding process. In order to examine VFC effect, different VFC (0.28∼0.62) were employed by changing the Cr and C content, while the ratio of Cr/C was fixed in the range of 5.7∼6.6. Fracture toughness was constant as increasing VFC because fracture surface was developed in the eutectic phase which was growing parallel with introduced sharp notch in the hypoeutectic alloys, but fracture toughness did not decreased in spite of increasing volume fraction of coarse primary chromium carbide phase which was easily craced at the low stress because the growth direction of chromium carbide phase were more irregular as increasing VFC in the hypereutectic alloys.

• Coupled systems mechanics
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• v.10 no.6
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• pp.545-560
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• 2021

An in situ experiment imaged via X-ray computed tomography was performed on a continuous glass fiber mat reinforced epoxy resin composite. The investigated dogbone specimen was subjected to uniaxial cyclic tension. The reconstructed scans (i.e., gray level volumes) were registered via Digital Volume Correlation. The calculated maximum principal strain fields and correlation residual maps exhibited strain localization areas within the material bulk, thus indicating damage inception and growth toward the specimen surface. Strained bands and areas of elevated correlation residuals were mainly concentrated in the narrowest gauge section of the investigated specimen, as well as on the specimen ligament edges. Gray level residuals were laid over the corresponding mesostructure to highlight and characterize damage development within the material bulk.

• Journal of Korean Society of Forest Science
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• v.90 no.1
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• pp.124-132
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• 2001

This study was conducted to reveal the relationship between physiological characteristics and growth by family for open-pollinated progeny stand of Korean white pine in Gapyung site. Average growth performance of total 25 families for 18 years old progeny stand in this study site showed 5.9m in mean height, 8.9cm in mean DBH, $12.0m^2$ in basal area per hectare and $46.5m^3$ in volume per hectare, respectively. By the analysis result of growth performance for all 25 families, family No. 20 showed the most excellent growth and middle in family No. 10. On the other hand, family No. 3 represented the worst growth among the 25 families. The change of seasonal photosynthesis rate by increasing luminous intensity was the same tendency as the growth pattern of all 25 families and showed the same results in all four seasons. In the seasonal analysis, the photosynthesis rate was increased as the season has changed from winter to summer. Chlorophyll contents was also increased from winter to summer. Especially, family No. 20 which is the best in growth performance has more chlorophyll contents than the others. In addition, family No. 20 was also better than other families in the weight of assimilation tissue(g), length of needle(cm), width of needle(cm), and number of Stoma. However, in water utilization rate, family No. 3 which is the worst in the growth performance showed the best result that is reverse tendency compared with the photosynthesis rate. The changes of water utilization rate represented to be increased as the season has changed from winter to summer.

• Journal of Korean Society of Forest Science
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• v.111 no.4
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• pp.482-489
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• 2022

This study aimed to determine the optimal planting density of Fraxinus rhynchophylla assessed from the early growth performance at various planting densities over the 7-year period after planting. The study site was in Pyeongchang County, South Korea, and seedlings of 2-year-old (bare-root seedlings) F. rhynchophylla were planted at four densities (3,000, 5,000, 7,000, and 10,000 trees ha^-1) in March 2015. The survival rate, root-collar diameter (RCD), and height (H) were measured from 2015 to 2021, and the H/D (H/RCD) ratio and stem volume were calculated. The survival rate (84-97%) and H/D ratio (54.5-59.2%) were not affected by the planting density during the study period, but the RCD, H, and stem volume were significantly higher for 7,000 trees ha^-1 than for other planting densities. Especially, the stem volume (cm³ tree^-1) at 7 years after planting was highest for 7,000 trees ha^-1 (1,356.1), followed by 10,000 trees ha^-1 (958.6), 5,000 trees ha^-1 (773.0), and 3,000 trees ha^-1 (579.5). As the planting density increased, F. rhynchophylla seedlings showed initial rapid growth due to light competition, but relatively low growth at excessive planting densities. In the future, use of a suitable planting density considering planting costs should provide outstanding growth performance of F. rhynchophylla on plantations.

• The Journal of the Convergence on Culture Technology
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• v.9 no.3
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• pp.861-866
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• 2023

Unlike conventional smart farms that require chemical fertilizers and large spaces, aquaponics farming, which utilizes the symbiotic relationship between aquatic organisms and crops to grow crops even in abnormal environments such as environmental pollution and climate change, is being actively researched. Different crops require different environments and nutrients for growth, so it is necessary to configure the ratio of aquatic organisms optimized for crop growth. This study proposes a method to measure the degree of growth based on area and volume using image processing techniques in an aquaponics environment. Tilapia, carp, catfish, and lettuce crops, which are aquatic organisms that produce organic matter through excrement, were tested in an aquaponics environment. Through 2D and 3D image analysis of lettuce and real-time data analysis, the growth degree was evaluated using the area and volume information of lettuce. The results of the experiment proved that it is possible to manage cultivation by utilizing the area and volume information of lettuce. It is expected that it will be possible to provide production prediction services to farmers by utilizing aquatic life and growth information. It will also be a starting point for solving problems in the changing agricultural environment.

• Journal of Korea Foundry Society
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• v.11 no.3
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• pp.217-227
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• 1991

The present study was conducted to estimate the fatigue crack growth rate of the Mo-Ni alloyed ductile cast iron for the influence of austempering temperature and time. The fatigue crack growth rate was affected by retained austenite. Retained austenite volume were higher with the ductile cast irons which were austempered at $360^{\circ}C$ than austempered at $260^{\circ}C$, and the fatigue crack growth rate of the former was lower than that of the latter. Also, the fatigue growth rate of the former was the lowest at austempering for 1 hour and that of the latter was the lowest at austempering for 3 hours.

• Korean journal of applied entomology
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• v.19 no.3 s.44
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• pp.153-155
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• 1980

In pot experiment, relations between bulb nemationde, Ditylenchus dipsaci, and growth and yield of garlic were followed. There was no effect of height growth on bulb nematode, but growth of volume was reduced at more than 250 nematodes per pot. Yield loss of garlic was more than $20\%$ when nematode density was about 30 per bulb in late-April. Tolerance limit should be about 20 nematodes per bulb at early growing stage. Reproduction of bulb nematode was good when initial population had been low.