• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.4
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• pp.580-597
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• 2013

Three materials SUS304, 9% Ni steel and Al 5083-O alloy, which are considered possible candidate for International Maritime Organization (IMO) type B Cargo Containment System, were studied. Monotonic tensile, fatigue, fatigue crack growth rate and Crack Tip Opening Displacement tests were carried out at room, intermediate low ($-100^{\circ}C$) and cryogenic ($-163^{\circ}C$) temperatures. The initial yield and tensile strengths of all materials tended to increase with decreasing temperature, whereas the change in elastic modulus was not as remarkable. The largest and smallest improvement ratio of the initial yield strengths due to a temperature reduction were observed in the SUS304 and Al 5083-O alloy, respectively. The fatigue strengths of the three materials increased with decreasing temperature. The largest increase in fatigue strength was observed in the Al 5083-O alloy, whereas the 9% Ni steel sample showed the smallest increase. In the fatigue crack growth rate test, SUS304 and Al 5083-O alloy showed a decrease in the crack propagation rate, due to decrease in temperature, but no visible improvement in da/dN was observed in the case of 9% Ni steel. In the Crack Tip Opening Displacement (CTOD) test, CTOD values were converted to critical crack length for the comparison with different thickness specimens. The critical crack length tended to decrease in the case of SUS304 and increase for the Al 5083-O alloy with decreasing temperature. In case of 9% Ni steel, change of critical crack length was not observed due to temperature decrease. In addition, the changing material properties according to the temperature of the LNG tank were analyzed according to the international code for the construction and equipment of ships carrying liquefied gases in bulk (IGC code) and the rules of classifications.

• Korean Journal of Microbiology
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• v.7 no.3
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• pp.115-124
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• 1969

The mash of Takjoo, Korean flour wine, is fermented through two brewing processes ; the primary brewing process to saccharify and the main one to produce ethyl alcohol. The activities of acid proteinase (pH3), weak acid proteinase (pH 6), and alkaline proteinase (Ph 80 on the processes are determined with time by the Folin phenol method as a strength of casein digestion. Hydrogen ion concentration, the content of total organic acids, protein, free amino acids and oligopeptides, which effect the activities of proteinase, are also measured. The results are briefly summarized as follows : 1. In general, the activities of acid proteinase and weak acid proteinase in the mesh of primary brewing process are stronger than those in main brewing process. 2. The activities of acid proteinase are remarkably stronger than those of weak acid proteinase in both processes. It reveals that they decrease slowly through the fermentation. Activities of alkaline proteinase are weaker than others. 3. As the raw materials are mixtured, the total amount of organic acids is equivalent to 0.150 mg/ml acetic acid in the mesh of primary brewing process and 0.02 mg/ml acetic acid in the main one. They increase gradually with time. 4. Hydrogen ion concnetration shows 3.9 in the mesh of main brewing process and 3.28 in the primary one. They increase to the maximum in 60-72 hrs., and decrease since 108 hrs. 5. The content of crude protein shows 66.90mg/ml in the mesh of main brewing process, while shows 64.29mg/ml in the mesh of primary one. they decrease slowly with time. it seems that a small content of crude protein, as a substrate, converts into amino acids and soluble nitrogen compounds by proteinase. 6. The content of free amino acids and oligopeptides shows 0.36 mg/ml in the mesh of primary brewing process and 0.24mg/ml in the main brewing process. It is evident that the reason they increase continuously through the fermentation is the effect of proteinase. 7. According to the results, the strong activities of proteinase in primary brewing process has been derived from the decrease of hydrogen ion concentration due to the production of organic acids.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.2
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• pp.1-7
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• 2018

Suspension bridge cables made of high strength steel wires require periodical maintenance in accordance with the axial force of cable-band bolts, since the bolts in suspension bridges can undergo tension decrease due to creep of cable wires, bolt relaxation, load fluctuation, and cable re-arrangement, etc. Consequently, this study is aimed at investigating and subsequently evaluating the critical factors with respect to the bolt tension-decrease phenomenon in SR suspension bridge in Korea, based on field monitoring, theoretical studies, and field record management works. From the observation, it is interesting to note that the decrease in the bolt tension force is typically accompanied by plastic deformation of the zinc plating layers in the cable wires. In addition, a framework corresponding to generic methodologies to characterize the deformation in terms of the bolt tension-decrease and long-term history management has been developed in this exploratory study.

• Journal of the Korea Concrete Institute
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• v.14 no.5
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• pp.782-788
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• 2002

Several non-destructive test methods have been developed to estimate compressive strength of concrete in other countries. However, their applications are limited in domestic concrete due to their inaccuracies. The purpose of this study is to propose an aging coefficient of compressive strength of structural concrete in rebound number method and ultrasonic pulse velocity method for domestic concrete. The test variables include type of aggregate, curing condition, and compressive strength. Two approaches are used to estimate aging coefficient. One is evaluated by uniform linear regression equation for all ages and shows uniform strength reduction coefficient regardless of material properties and the other is evaluated by individual regression equation for each ages and shows nonuniform strength reduction and rebound increasing coefficients which decrease with increasing of rebound number and compressive strength. The latter result which can include the effect of rebound number and compressive strength is more resonable than the former.

• Journal of Korean Society of Steel Construction
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• v.21 no.5
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• pp.505-514
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• 2009

This paper describes the structural behavior and the ultimate strengths of circular hollow steel (CHS) sections based on a series of compression tests. The ultimate strengths of CHS section columns are mainly dependent on both diameter-thickness ratio and column slenderness ratio. For the CHS sections with a high diameter-thickness ratio, an elastic or an inelastic local buckling may occur prior to the overall buckling, and it may decrease the column strength. Test sections were fabricated from SM400 steel plate of 2.8 mm and 3.2 mm in thickness and were tested to failure. The diameter-thickness ratios of the test sections ranged from 45 to 170 to investigate the effect of local buckling on the column strength. The compression tests indicated that the CHS sections of lower diameter-thickness ratio than the yield limit in the current design specifications showed an inelastic local buckling and a significant post-buckling strength in the local mode. Their ultimate stresses were larger than the nominal yield stress. It was known that the allowable stresses of the sections predicted by the Korean Highway Bridge Design Specifications (2005) were too conservative in comparison with test results. The Direct Strength Method which was newly developed was calibrated for application to the CHS sections by the experimental and numerical results. The Direct Strength Method proposed can predict properly the ultimate strength of CHS section columns whether a local buckling and an overall buckling occur nearly simultaneously or not.

• Restorative Dentistry and Endodontics
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• v.32 no.5
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• pp.445-458
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• 2007

The purpose of this study was to evaluate the bond strength of a new Single step system with different curing mode composites, and to evaluate the effect of the intermediate resins which have different hydrophilicity on bonding ability by means of the micro shear bond testing and TEM examination for the adhesive interface. The adhesive used in this study was an experimental single step system (Bisco Inc., Schaumburg IL). Experimental groups were produced by using six kinds of intermediate resin having different hydrophilicity that was hydrophilic, hydrophobic and most hydrophobic resin and as filled or not after applying adhesive. Each experimental group was further divided into two subgroups whether the adhesive was light cured or not. Dual cured composite (Bis Core, Bisco Ltd., Schaumburg, IL) was placed on the adhesive layer as light cure or self cure mode. The results or bond strength were statistically analyzed using one way ANOVA and multiple comparisons are made using Tukey's test at ${\alpha}\;<\;0.05$ level. The results of this study were as follows ; 1. The application of intermediate resin did not increase the bond strength for light cured composite. 2. The bond strength of an experimental adhesive with self cured composite was significantly increased by the application of intermediate resin layer. 3. The bond strength of adhesive was irrespective of the cure or not of itself before intermediate resin layer applied. 4. As applied hydrophilic resin layer was, the initial bond strength was higher than both hydrophobic and most hydrophobic one used but there was no significance. Using a single step adhesive with dual/self cured composite, the incompatibility between both of them should be solved by the application of intermediate hydrophobic resin to reduce the adhesive permeability. However, Single step adhesive can be used in the light cured composite restoration without any decrease of the initial bond strength.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.2
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• pp.585-589
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• 2015

Physical inactivity may an important outcome in the prognosis of breast cancer. Physical activity levels decrease significantly for breast cancer patients following the treatment and remain low after oncology treatment is completed. The aim of this study was to determine physical activity levels and to examine associations among physical activity, comorbidity, functional capacity, peripheral muscle strength, and psychosocial status in breast cancer patients. Forty breast cancer survivors were included in this study. Demographic and clinical characteristics were recorded. Physical activity was assessed with a short form of the International Physical Activity Questionnaire (IPAQ). We defined comorbid diseases according to the Charlson Comorbidity Index (CCI). Functional capacity was evaluated with a six-minute walk test (6MWT). Peripheral muscle strength was measured for quadriceps femoris muscle with a hand-held dynamometer. Psychosocial status was measured with the Hospital Anxiety Depression Scale (HADS). Forty percent of patients were inactive. The IPAQ total score was significantly related with quadriceps muscle strength (r=0.492; p<0.001) and HADS depression score (r=0.341; p<0.05). Marked correlations were also observed between IPAQ walking score and quadriceps muscle strength (r=0.449; p<0.001), HADS depression score (r=0.341; p<0.05), and CCI (r=-0.433; p<0.001). The CCI score was also markedly associated with quadriceps muscle strength (r=-0.413; p<0.001). 6MWT distance was not significantly correlated with any of the parameters. Regression analyses revealed that psychosocial status and peripheral muscle strength were significant predictors of physical activity estimated with the IPAQ short form and when combined, they explained 35% of the variance. Comorbidities, peripheral muscle strength and psychosocial status partially explain the variability of physical activity level in breast cancer survivors. These results suggest that physical inactivity contributes to worsening health in breast cancer survivors.

• Journal of Bio-Environment Control
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• v.12 no.2
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• pp.68-71
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• 2003

Experiments were conducted to investigate optimal ionic salt strength in nutrient solution for small plug seedlings of ‘Nokgwang’ and ‘Kwari’ green pepper. Plant height increased with increasing ionic salt strength. total leaf area was 72％ greater in ‘Nokgwang’ and 18% greater in ‘Kwari’with 2.0 ionic salt strength than that with 1.0 strength. Dry weight per plant tended to increase at higher ionic salt strengths in ‘Kwari’, but to decrease in ‘Nokgwang’ Chlorophyll content increased with increasing ionic salt strength in both cultivars. Photosynthetic rate, stomatal conductance, and transpiration rate were higher for plants fertilized with 1.5 strength than other strengths in both cultivars. Photosynthetic rate peaked at 8.74 $\mu$mol$.$m$^{-2}$ s$^{-1}$ in ‘Nokgwang’ and 5.70 $\mu$mol$.$m$^{-2}$ s$^{-1}$ in‘Kwari’with 1.5 ionic salt strength.

• Journal of the Korea Concrete Institute
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• v.25 no.2
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• pp.241-250
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• 2013

As the amount of construction wastes increase, reuse of demolished concrete is being considered in research areas. Reflecting these interests, this experiment was performed to clarify concrete's mechanical property and workability using recycled aggregate as a coarse aggregate. Eleven cases of concrete specimens were produced by changing the rates of replacement of coarse recycled aggregate, replacement of fly ash, design strength, and moisture state of coarse aggregate. Compressive and tensile split strength tests were taken to study the mechanical properties of hardened concrete. To verify flowability of fresh concrete, a slump test and a flow curve test using ICAR Rheometer were performed. It was found that using recycled aggregate and fly ash leads good workability by testing slump and flow curve. The yield stress of fresh concrete decreased with increase of recycled aggregate substitution rate. Through the test, it was confirmed that there is inversely proportional relationship between the slump and yield stress roughly. Recycled aggregate concrete containing fly ash has considerably lower plasticity viscosity than not containing fly ash. Strength test results showed that recycled aggregate tended to decrease compressive and tensile strength of concrete, when recycled aggregate was used as a coarse aggregate. Using over 30% recycled aggregate caused significant decreases in compressive and tensile strength. Replacing 30% cement with fly ash was helpful to improve the long-term strength of concrete.

• Journal of the Korean Institute of Landscape Architecture
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• v.46 no.6
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• pp.120-126
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• 2018

The study conducted an experiment in which residual aggregate and polypropylene fibers are mixed in concrete, and an experiment in which granite and polypropylene fibers are mixed. Two types of experiments, in particular, changed the amount of polypropylene fibers, and examined the mechanical properties of slump, compressive strength, tensile strength and the like. To establish a light and easy-to-use material for landscape construction and packaging material development by comparing two kinds of experimental results, comparing and analyzing residual aggregate as experimental materials and materials using granite soil to prevent partial destruction due to cracks in drying shrinkage. The more the amount of the PP fibers increases in concrete, the more the volume of the PP fibers increases, the less the slump is determined. As a result of the compressive strength, the cast-down earth concrete is measured to be about 59% to 71% of the concrete strength. As the amount of PP fibers mixed in increased, the compression strength showed a relative decrease. As a result of tensile strength, it is found that the granite concrete is about 68-67% of concrete tensile strength. It was found that the compression strength decreased as the amount of PP fibers mixed in concrete or fire-gant concrete was increased. Then, when polypropylene fibers are mixed in the concrete and the concrete, it is found that tensile strength is increased. By analyzing these results, a fixed amount of PP fiber is mixed in the concrete mixed with the granite soil and utilized for various structures in the field of landscape construction or materials related to packaging, the prevention and improvement effect of the structure is determined.