• Journal of the Korean Society of Safety
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• v.3 no.2
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• pp.35-48
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• 1988

Modern technological progress demands the use of materials at high temperature and high pressure. One of the most critical factors in considering such applications - perhaps the most critical one - is creep behavior. In this study the stress exponents n were determined during creep over the temperature range of $90^{\circ}C\;to\;500^{\circ}C$ (0.4 - 0.85 Tm) and stress range of 0.64 kgt/$mm^2$ in order to investigate the creep hehavior. The stress dependence of rapture time (n') were determined over the temperature range of $200^{\circ}C\;to\;240^{\circ}C$ and stress range of 8.13 kgt/$mm^2$ to 9.55 kgt/$mm^2$ in order to investigate to creep rupture property. And the stress transient dip tests were also carried out for the internal stress ${\sigma}i$ over the temperature range of $90^{\circ}C\;to\;500^{\circ}C$ and stress range of 0.64kgt/$mm^2$ to 17.2 kgt/$mm^2$. The creep tests for constant temperature and stress transient dip tests were conducted in air with Al 7075 alloy under constant tensile load. At around the temperature range $200^[\circ}C\;-\;230^{\circ}C$ and the stress level 8.13 - 9.55 (kgt/$mm^2$), the temperature range $280^{\circ}C\;-\;310^{\circ}C$ and the stress level 1.85 - 2.55 (kgt/$mm^2$), the temperature range $380^{\circ}C\;-\;410^{\circ}C$ and the stress 1.53 - 0.91 (kgt/$mm^2$), the stress exponent in had the value of 6.2 - 6.65 but at around the temperature range $90^{\circ}C\;-\;120^{\circ}C$ and the stress level 10 - 17.2(kgt/$mm^2$), the value of 1.3, and at around the temperature range $470^{\circ}C\;-\;500^{\circ}C$, the stress level 0.62 - 1.02 (kgt/$mm^2$) the value of 1-1. Besides these results, at around the temperature $200^{\circ}C\;-\;240^{\circ}C$ the stress dependence of rupture time (n') had the value of 6.3. Finally, it was found that the value n calculated by considering the applied stress dependence of the internal stress were in good agreement with those obtained for the creep test. Then, it was concluded that the change in n was mainly attributed to the difference of the applied stress dependence of the internal stress and the ratio of the internal stress to the applied stress, and the creep rupture life may be represented as.

• Korean Journal of Soil Science and Fertilizer
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• v.32 no.4
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• pp.365-374
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• 1999

To obtain informations on vertical movements of water and solute in rice paddy field during the growing season, soil water contents and bulk electrical conductivities (${\sigma}_a$) were monitored using Time Domain Reflectometry. Soil water contents with depth showed ${\varepsilon}$-shaped profiles constituting of partly saturated zones at top and bottom layers and unsaturated zones (20-100cm) between them. Analysis by fitting with a van Genuchten-type model showed that soil water contents at 60cm were affected by both water supplied from surface water and groundwater, but at 80cm mainly affected by groundwater. Water percolation at the rate of 2cm $day^{-1}$ rates were, but large fluctuation from 10 to 38cm $day^{-1}$ in C1 layer (60-90cm). Therefore, it can be said that any water or solute entering C1 layer is very rapidly transported to C2 layer, especially during the period of high groundwater table staying, and retarded to a relatively constant percolation rate in C2 layer. This can be manifested by the fact that rapid decrease and steady increase of electrical conductivities at 50 and 110cm depth respectively, were found around that period.

• Korean journal of applied entomology
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• v.43 no.3 s.136
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• pp.211-215
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• 2004

Temperature-fecundity of the melon aphid, Aphis gossypii Glover, was studied at constant temperatures ranging from 15 to $32.5^{\circ}C$ under $60-70\%$ RH and a photoperiod of 16 : 8 (L : D) A life table parameters were constructed using the results. The longevity of A. gossypii gradually increased with decreasing temperature below $27.5^{\circ}C$. Also fecundity increased with decreasing temperature and the highest fecundity was 61.8 nymphs per female at $17.5^{\circ}C$. However. daily fecundity increased with increasing temperatures up to $22.5^{\circ}C$ showing 5.9 nymphs per day and thereafter decreased. Longevity and fecundity of the adult in the greenhouse with an average temperature of $21^{\circ}C$ and $65.6\%$ RH, were 20.0 days and 59.6, respectively, which were longer and higher than those in the growth chamber with similar conditions. net reproductive rate (Ro) was 54.9 at $17.5^{\circ}C$ while intrinsic rate of increase ($r_m$) and finite rate of increase ($\lambda$) were the highest 0.5 and 1.6 at $30^{\circ}C$, respectively. doubling time (DT) and mean generation time (T) were the shortest 1.4 and 6.8 at $30^{\circ}C$ indicating that optimal temperature for the development is $30^{\circ}C$.

• Journal of Applied Biological Chemistry
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• v.44 no.3
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• pp.135-139
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• 2001

To observe the changes in isotopic composition (${\delta}^{15}N$) of $NO_3{^-}$ during denitrification, an incubation experiment using soil treated with nitrification inhibitor (2-chloro-6-trichloromethyl-pyridine) under water-saturated condition was conducted for 153 h. The $NO_3-N$ concentration decreased from 73.3 to $20.6mg\;kg^{-1}$ during the incubation period, with denitrification rate constant of $0.00905h^{-1}$, and ${\delta}^{15}N$ values of $NO_3-N$ increased from +0.9 to +25.5‰ with decreasing the $NO_3-N$ concentration. The increase in the ${\delta}^{15}N$ values of $NO_3-N$ is due to kinetic isotope fractionation, which always results in $^{15}N$ enrichment of the substrate. The isotopic fractionation factor calculated in this study was 1.0196, an indication that 1.96% more $^{14}NO_3{^-}$ reacted at a given time interval than a comparable number of $^{15}NO_3{^-}$. The ${\delta}^{15}N$ values measured through the incubation study showed a good agreement with the results calculated from the Fochts isotope fractionation model. Our results suggest that when the ${\delta}^{15}N$ of $NO_3{^-}$ is used for tracing the fate of N, the kinetic isotope fractionation associated with denitrification must be taken into consideration.

• The Journal of Korean Academy of Prosthodontics
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• v.31 no.4
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• pp.482-505
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• 1993

The purpose of this study was to evaluate the fracture characteristics and the effect of resin bonding of laminate porcelain. In order to characterize the indentation-induced crack, Young's moduli and characteristic indentation dimensions were measured. The fatigue life under three point flexure test was measured using the electro-dynamic type fatigue machine, and the crack propagation with thermocycling was investigated on the condition of 15 second dwell time each in $5^{\circ}C\;and\;55^{\circ}C$ bath. The Vickers indentation pattern and the fracture surface were examined by an optical microscope and a scanning electron microscope (SEM). The results obtained were summarized as follows ; 1. Young's moduli(E) of the laminate porcelain and the resin cement used in this experiment were $62.56{\pm}3.79GPa$ and $15.01{\pm}0.12GPa$, respectively. 2. The initial crack size of the laminate porcelain was $69.19{\pm}5.94{\mu}m$ when an indentation load of 9.8N was applied, and the fracture toughness was $1.065{\pm}0.156MPa\;m^{1/2}$. 3. The fatigue life of laminate porcelain showed the constant fracture range at the stress level 27.46-35.30MPa. 4. When a cyclic flexure load was applied, the fatigue life of resin-bonded laminate porcelain was more decreased than that of laminate porcelain. 5. When a thermocycling was conducted, the crack growth rate of resin-bonded laminate porcelain was more increased than that of laminate porcelain. 6. Fracture surface showed the radial crack, the lateral crack, and the macroscopic crack branching region beneath the plastic deformation region when an indentation load of 9.8N was applied.

• Korean Journal of Environmental Biology
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• v.27 no.4
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• pp.353-362
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• 2009

This study attempted to compare the litter decomposition rate of Arundinella hirta and Miscanthus sinensis var. purpurascens which collected from serpentine soil acting potentially toxic concentration of heavy metals and non-serpentine soil by using the microcosm method for 192 days under constant humidity and $23^{\circ}C$. The contents of Ni, Fe, Mg and Cr in the serpentine and nonserpentine soil originated litter showed high differences between them. The litter samples from serpentine site have lower C/N than non-serpentine litter, but the soluble carbohydrate content was shown almost similar between two plant litter. The mass loss rates of leaf litter from serpentine area were slower than those from non-serpentine site. During the experimental period, the remained dry weight of A. hirta and M. sinensis var. purpurascens litter collected from serpentine site were 64.7%, 65.0% of initial dry weight and litter samples from non-serpentine site showed 54.2%, 50.7%, respectively. K and Na were leached rapidly at the initial decomposition periods, but Ca showed immobilization and other metal elements reserved at the decomposing litter for a long time. The decomposing A. hirta litter from non-serpentine soil showed higher values of $CO_2$ evolution, microbial biomass-C, and microbial biomass-N than those in serpentine soil originated litter acting nutrient stresses and exhibited rapid decay rate. The microbial biomass and microbial respiration of decaying litter were positively correlated with litter decomposition rate, and these relationships showed more rapid slope in non-serpentine soil originated litter than that in serpentine soil.

• Journal of Welding and Joining
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• v.34 no.1
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• pp.41-46
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• 2016

With the recent increase in size of ships and offshore structures, there are more demand for thicker plates. As the thickness increases, it is known that fatigue life of the structures decrease. To improve the fatigue life, post weld treatments techniques, such as toe grinding, TIG dressing and hammer peening, are typically employed. However, these techniques require additional construction time and production cost. Therefore, it is of crucial interest steels with longer fatigue crack growth life compared to conventional steels. This study investigates fatigue crack growth rate (FCGR) behaviours of conventional EH36 steel and Ferrite-Bainite dual phase EH36 steel (F-B steel). F-B steel is known to have improved fatigue performance associated with the existence of two different phases. Ferrite-Bainite dual phase microstructures are obtained by special thermo mechanical control process (TMCP). FCGR behaviours are investigated by a series of constant stress-controlled FCGR tests. Considering all test conditions (ambient, low temperature, high stress ratio), it is shown that FCGR of F-B steel is slower than that of conventional EH36 steel. From the tensile tests and impact tests, F-B steel exhibits higher values of strength and impact energy leading to slower FCGR.

• The Journal of the Korea Contents Association
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• v.12 no.12
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• pp.93-102
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• 2012

This study started from the project that make the record of legendary actor's heritage in Korea. This research was focused on Sung Hee Beck's artistic footprint which was almost same steps as the Korean modern play of the centennial theater history by reviewing her; domestic royal actor; acting techniques which learn from real acting field by herself and her career. Her life shows constant resistance for the social negative reputation of the acting field, and her frantic effort to Korean play and actor's phase. Above all, this passionate actor's life contributes to society, and improve the Korean theater through 70 year's her experiences with countless roles in around 400 performances and her own valuable acting techniques. To look up legendary actress of our time, Sung Hee Beak's life gives us a chance to reflect art of acting which emphasizes its fundamental.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.6
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• pp.270-275
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• 2019

Mica capacitor is being adopted for high voltage firing unit of guided weapon system because of its superior impact enduring property relative to ceramic capacitor. Reliability of localized mica high voltage capacitors was verified through environmental test like terminal strength test, humidity test, thermal shock test and accelerated life test for application to high voltage firing unit. Failure mode of mica capacitor is a decrease of insulation resistance and its final dielectric breakdown. Main constants of accelerated life model were derived experimentally and voltage constant and activation energy were 5.28 and 0.805 eV respectively. Lifetime of mica capacitor at normal use condition was calculated to be 38.5 years by acceleration factor, 496, and lifetime at accelerated condition and this long lifetime confirmed that mica high voltage capacitor could be applied for firing unit.

• Journal of the Korean Society of Food Science and Nutrition
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• v.29 no.5
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• pp.807-813
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• 2000

One hundred fifty grams of Korean fermented soybean paste and hot pepper-soybean paste were packaged in glass jar of 232 mL and Sotred at 5, 13, 22 and 30℃. During the storage, the changes in their microbial flora and quality attributes were monitored. Carbon dioxide production rate from the stored pastes were also determined from initial change of CO₂concentration in headspace of the pack. Hot pepper-soybean pate showed much higher CO₂ production rate higher dependence of CO₂ production on temperature compared to soybean paste. Total aerobic bacteria count and lactic acid bacteria count did not change significantly through the storage. Yeast count in soybean paste decreased slowly after initial uprise while that of hot pepper-soybean paste steadily decreased. Surface color of hot pepper paste changed to dark red with slight decrease in 'L' value and slight increase in 'a' and 'b' values, whereas any significant color change was not observed in soy paste. Titratable acidity increased with time with higher increase in soybean paste, but pH stayed at constant level for both pastes. All the rates of quality change were higher with higher temperature. Pressure buildup due to CO₂ production needs to be considered first in designing the packages of the fermented pastes before their color changes and other chemical quality changes.