• Structural Engineering and Mechanics
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• v.61 no.1
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• pp.161-169
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• 2017

This study aimed to develop a simple and effective method to facilitate the experimental research on mechanical properties of masonry under biaxial compressive stress. A series of tests on full-scale brick masonry panels under biaxial compression have been performed in limited principal stress ratios oriented at various angles to the bed joints. Failure modes of tested panels were observed and failure features were analyzed to reveal the mechanical behavior of masonry under biaxial compression. Based on the experimental data, the failure curve in terms of two orthotropic principal stresses has been presented and the failure criterion of brick masonry in the form of the tensor polynomial has been established, which indicate that the anisotropy for masonry is closely related to the difference of applied stress as well as the orientation of bed joints. Further, compared with previous failure curves and criteria for masonry, it can be found that the relative strength of mortar and block has a considerable effect on the degree of anisotropy for masonry. The test results demonstrate the validity of the proposed experimental method for the approximation of masonry failure under biaxial compressive stress and provide valuable information used to establish experimentally based methodologies for the improvement of masonry failure criteria.

• Journal of Advanced Marine Engineering and Technology
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• v.12 no.1
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• pp.53-61
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• 1988

Most of the recent for the flow field hydrofoil in partially cavitating condition are the ones which are linearized, and the problem of cavity end region for hydrofoil is not verified. This paper deals with a study on characteristics of end region flow field for partially cavitating hydrofoil by using a characteristics of shear turbulence flow and nonlinear cavity flow theory. The results obtained as follows : 1) Shear layer thickness is decreased gradually going to the end section of hydrofoil. When attack angle is large, it is appeared largely at the region of partial cavitation after its collapsing. 2) The fluctuation velocity of a second-degree relative direction have minimum value at the front of hydrofoil or at the end of hydrofoil. The difference for the validity of attack angle is appeared largely at the surrounding of .chi.$_{e}$ point. 3) The fluctuation velocity of transverse direction decrease from the maximum thickness of cavitation to the end of hydrofoil, but it undergoes largely the effect of pressure recovery. The difference is larger at the region of partial cavitation after its collapsing than at the of hydrofoil. 4) The distribution of Reynolds stress have maximum values at the region of partial cavitation after its collapsing and the end of foil, and the larger attack angle, the larger the distribution of value.e.

• Journal of the Korea Safety Management & Science
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• v.4 no.4
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• pp.137-146
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• 2002

In order to investigate the effect of irradiation by $^{60}Co-\gamma$rays as well as the e thermal treatment on the dielectric deterioration in ethylene propylene rubber, insulating material for electric cables used in atomic power plants, charging discharging current, residual built- up voltage and dielectric properties are measu discussed in this study. Variance in the characteristic of relative dielectric constant as a function of tem was observed in relatively high dose of irradiation. Since glass transition tem appeared at tens of degree Celsius below zero, the characteristic is attributed orientation polarization. Dielectric loss is generally increased, with increasing d irradiation in the characteristic of dielectric loss as a function of temperature, No d loss by thermal treatment was observed. Dielectric resistance decreases with increa of irradiation in the characteristic of charging current as a function of temperature be considered that dielectric resistance seems to be recovered by thermal treatm characteristic of discharging current as a function of time in the specimen less ir become similar to that of the unirradiated, when thermal treated. A peak is shown residual built- up voltage as a function of time, and the corresponding time of the shorten as increasing dose of irradiation. It is also observed that the corresponding the peak is lengthened by thermal treatment.

• Journal of Plant Biology
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• v.17 no.2
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• pp.87-94
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• 1974

This survey has been carried out on ten species(Erythronium japonicum, Symplocarpus renifolius, Adonis amurensis var. ramosa, Corydalis turtschaninovii var. genuina, Primula sieboldii forma spontanea, Anemone raddeana, Gagea Iutea, Heloniopsis japonjca, Hylomecon japonicum, and Convallaria majalis var. keiskei in the undergrowth of a forest of deciduous broad-leaved trees in the Kwangnung area of Kyung-Ki Province. They always bloom towards the end of March which is earlier than most of the other plants do. They completely finish up their matter productions before foliage of the deciduous trees, which are the upper strata plants, grows broader or to cite in other terms, before the relative light intensity in the lower strata is fallen to the lowest degree to become to insufficient to allow for photosynthesis. These phanerophytes naturally wither down between June and July. The above mentioned phenomenon clearly demonstrates a kind of the ecological niches and habitat segregation in terms of using sunlight to her greatest advantage. Soon after these herbs wither they make their own winter buds-life form-around their roots and then go into hibernation. The intensity of light in this forest zone was measured through the use of a lux meter in order to investigate it's seasonal variations. In additions, an intensive survey on the duration of their efflorescence was fullfilled.

• Macromolecular Research
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• v.12 no.3
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• pp.263-268
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• 2004

We have synthesized a water-soluble polyimide precursor, poly(amic acid) amine salt (PAD), from pyromellitic dianhydride (PMDA), 4,4'-oxydianiline, and N,N -dimethylethanolamine (DMEA) and have investigated in detail its properties with respect to the degree of salt formation (D$\_$sf/). The maximum value of D$\_$sf/ we obtained upon precipitation of the precursor solution into acetone was 79%. We synthesized a PAD having a D$\_$sf/ of 100% (PAD100) by the solid state drying of an organic solution. The precursors showed different solubility depending on the D$\_$sf/ to make up to 4 wt% solutions in water containing a small amount of DMEA. PAD100 is completely soluble in pure water. We investigated the imidization behavior of PAD in aqueous solution using various spectroscopic methods, which revealed that PAD 100 has faster imidization kinetics relative to that of the poly(amic acid)-type precursors. The resulting polyimide films prepared from an aqueous precursor solution possess almost similar physical and thermal properties as those prepared from N-methyl-2-pyrrolidone(NMP) solution. Therefore, we have demonstrated that PAD can be used as a water-based precursor of polyimide; this procedure avoids the use of toxic organic solvents, such as NMP.

• Animal cells and systems
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• v.2 no.2
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• pp.217-222
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• 1998

Green peach aphid, Myzus persicae(Sulzer) (Homoptera: Aphididae), interacts with many predatory insects in potato fields during the summer. The concept of the predator complex associated with green peach aphids was applied to explain the interactions between the aphid and its predators. The predator power of the predator complex was determined by two factors: the number of predators and the relative feeding capacity. The dynamics of the green peach aphid population was expressed by the number of individuals while the predator power was used to characterize the predator complex. Cumulative degree-days for green peach aphids were used as a time scale to analyze phonology and dynamics patterns of the aphid and its predator complex. The patterns of population changes in aphids were similar during the period of study(1993-1995) although the highest density of aphids fluctuated significantly from year to year. However, the predator power appeared more stable than the green peach aphid population over the three year period. The results indicated that the predator complex plays an important role to suppress the aphid populations during the latter part of the season and that the applications of control measures for green peach aphids in between the initiation and the peak timing of aphid populations are critical to minimize the damage on potatoes.

• Journal of Life Science
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• v.16 no.7 s.80
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• pp.1225-1228
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• 2006

Cyclic AMP receptor protein (CRP) complexed with cAMP binds to DNA and induces sharp DNA bending around ${\sim}90$ degree. Previous publication (5), however, reported that mutant CRP:cGMP complex showed high migration rate relative to mutant CRP:cAMP complex on native polyacrylamide gel. To confirm DNA structural change in the presence of CRP and cyclic nucleotide, molar cyclization factor $(j_M)$ [13] was measured with 6 constructed DNA fragments. Nonlinear regression analysis of $j_M$ data indicated that mutant CRP did not induce DNA bending in the presence of cGMP but bent DNA in the presence of cAMP without any helical twist change in DNA.

• Journal of the Korean Society of Food Culture
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• v.10 no.1
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• pp.19-28
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• 1995

The relationship of obesity and related behaviors was analyzed among 361 primary school children, 4th and 5th grade, in one of private school in Seoul in July 1994. Compared to 1985 Korean Children's Growth Standard, the surveyed children have shown remarkable growth, which is the secular trend in growth of Korean children accompanied with rapid economic growth. But the relative incremental weight was far larger than that of height and this trend was more evident among children over 50th percentile, which shows a wide prevalence of obesity of the surveyed children. By WLI index, 15% of the children was overweight and 13% was obese. The higher the WLI, the more frequent and stronger stress they had. The nutrition knowledge score of obese children was higher compared to others. They were especially sensitive to their physical fitness but many normal or underweight-children also experienced stress due to their body weight and have tried to lose weight by incorrect methods. On the other hand many obese children thought they were optimal or underweight. These results reasserts the importance of nutrition education focused on children aheading puberty. They need to know the correct degree of obesity and to get appropriate education through teachers, dietitians, parents and doctors. The findings of this study could be applied to a nutrition implementation policy to ensure better physical fitness of children aheading puberty in the future.

• The Korean Journal of Ecology
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• v.11 no.4
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• pp.213-225
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• 1988

The plant communities of the eastern ridge in Mt. Cheonma, Central Korea, Quercus mongolica, Q mongolica-Acer pseudo-sieboldianum, and Q. mongolica-Rhododendron schlippenbachii communities in the northern slope and Q. variabilis and Q. cutissima communities in the southern slope were detected by Zurich-Montpellier method. The undergrowth of Q mongolica community in the northern slope was dominated by Ainsliaea acerifolia, Carex siderosticta, Astilbe chinensis var. davidii, Heloniopsis orientalis, Pseudostellaria palibiniana, ranging 3.3 to 2.2 in dominance-sociability, while the those of Q variabilis and Q acutissima in the southern slope were dominated by Spodiopogon cotulifer, Artemisia keiskeana, Carex humilis, Atractylodes japonica, Lysimachia clethroides and Disporum smilacinum with similar degree in dominance-sociability to that of Q mongolica community. The two communities were considered as regenerating forest after severe disturbance judging by their age structure. The relationship between Shannon's diversity index (H') and Simpson's dominance index (i) was in reciprocal proportion in both two communities. The Q. mongolica and Q. variabilis communities were showed 13 and 12 m respectively. Seasonal changes of undergrowth coverage in the two communities were seemed to be affected especially with soil moisture among environmental factors such as temperature, light intensity, relative humidity and organic matter.

• Journal of the Korean Ceramic Society
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• v.29 no.8
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• pp.667-673
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• 1992

The alumina-zirconia composite powders of core particle ZrO2 coated with Al2O3 were prepared by the hydrolysis-deposition of the mixed aluminum salt solution of Al2(SO4)3-Al(NO3)3-Urea. The effects of hydrolysis reaction and coating parameters on characteristics of coated powders and composites were also investigated. The degree of coating could be estimated from the ratio of tetra-/mono-ZrO2 present at the room temperature after heat-treating coated powders at 120$0^{\circ}C$ and the result of TEM observations. When the content of ZrO2 in the dispersed coating system, the coating time, and the volume ratio of water/solution were 50 mg/g, 180 min, and 5, respectively the coating efficiency was maximum (the ratio of tetra-/mono-ZrO2 was 87/13). The relative densities of coated Al2O3-ZrO2 composites sintered at 1$650^{\circ}C$ for 4 hrs were about 91~98% and the maximum ratio of tetra-/mono-ZrO2 in Al2O3-20wt% ZrO2 composites was 62/38.