• Journal of Industrial Technology
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• v.21 no.B
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• pp.331-339
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• 2001

Zero to tension fatigue tests and strain controlled fatigue tests were carried out to find how initial strain induced martensite, ${\alpha}^{\prime}$ affects low and high cycle fatigue behavior and fatigue crack growth mechanisms. Microscopic study and phase analysis were carried out with TEM, SEM, EDAX, Optical Microscope, Ferriscope, and X-ray diffractometry. The amount of Initial ${\alpha}^{\prime}$ was controlled from 0% to 33% by controlling the temperatures for cold working and heat treatment. Lower contents of initial ${\alpha}^{\prime}$ showed higher fatigue resistance in low cycle fatigue but lower fatigue resistance in high cycle fatigue because it is ascribed to the more transformation of ${\alpha}^{\prime}$ martensite during low cycle fatigue and higher ductility. In high cycle fatigue, fatigue life is attributed to the strength and phase transformation of austenite into ${\alpha}^{\prime}$ during fatigue was negligible. ${\gamma}$ boundary, ${\gamma}/twin$ boundary, and ${\gamma}/{\alpha}^{\prime}$ boundary were found to be the preferred site of fatigue crack initiation.

• International Journal of Industrial Entomology and Biomaterials
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• v.33 no.2
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• pp.41-49
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• 2016

We bred a mulberry cultivar named Shimgang, through local adaptability test, which is under registration as a new cultivar for fruit production. Local adaptability test had been carried out at four local places(Suwon, Chuncheon, Buan and Jinju) for five years from 2011. This variety 'Shimgang' belongs to Morus Microphylla Buckl. selected from seedlings imported from USA. Shimgang was resistant to popcorn disease and high yielding variety in fruit productivity by 111% compared to control cultivar 'Shimheung(Morus alba L.)' for three years. Although fruits of 'Shimgang' was smaller in size and lower in sugar content of mulberry fruits, it showed stronger resistance than that of 'Shimheung'. It is adaptable to every where except the places where cold and late frost damage happen frequently.

• Journal of the Korean Society for Advanced Composite Structures
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• v.6 no.2
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• pp.32-39
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• 2015

So far, square concrete filled tubular(CFT) columns have been used in a limited width thickness ratio. The reason is that local buckling occurs in steel tube easily. Once the local buckling occurs, the confinement effect of steel tube on concrete disappears. In this study, we developed welded built-up square steel tube with reinforcement which are placed at the center of the tube width acts as an anchor. 3 specimens of slender welded built-up square CFT columns and 3 specimens of slender welded built-up square steel tube columns were manufactured with parameters of width(B) of steel tube, width thickness ratio(B/t). we conducted a experimental test on the 6 specimens under eccentric load, and evaluated the structural resistance and behavior of 6 specimens.

• Korean Journal of Human Ecology
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• v.12 no.5
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• pp.747-754
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• 2003

The actual clothing conditions were surveyed to diagnose clothing condition of Korean female in the view point of the adaptation to the thermal environment according to seasonal changes. Then, clothing microclimate, physiological responses, and subjective sensation were investigated through wearing trials on human body in climatic chamber based on the results from the survey. Factors to evaluate validity of clothing condition were clothing weight, clothing microclimate, physiological response of human body, and subjective sensation. The results were as follows: 1. Clothing weight per body surface area of the season was $856g/m^{2}$, $439g/m^{2}$ in summer, $630g/m^{2}$ in fall, and $1184g/m^{2}$ in winter. Cold - resistance of Korean female in office was superior to Japanese, inferior to residents of rural areas of Korea, and similar to male in office. However, in heat - resistance, female in office was inferior to residents of rural areas of Korea. 2. In spring, fall, winter, clothing microclimate temperature was a little higher than that in summer. Therefore, it was not a desirable wearing condition even though the clothing microclimate was comfortable zone. 3. Mean skin temperature of female in office was including within the range of Winslow's comfortable zone, but the range of comfortable zone in mean skin temperature of female was more narrow than Winslow's. Thus, it has problem for female to adaptation to thermal environment.

• Journal of Welding and Joining
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• v.27 no.2
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• pp.63-68
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• 2009

Microminiature heat exchanger has been applied to the gas turbine in order to increase energy efficiency. During the production of microminiature heat exchanger, however, it is very difficult to weld tube to tubesheet. In this study, therefore, welding process of resistance ring projection was used, and weld tensile tests were performed. Sound weld joint was obtained as a result of applying resistance ring projection welding to microminiature heat exchanger to tubesheet. Cold weld occurred at under 1600A. Even though tensile strength was increased with increasing current, splash occurred and tensile strength decreased at 2000A due to the excessive current. Therefore it was determine that the optimal current is 1900A. As result of tensile tests based on ASME code for tube to tubesheet weldment, rupture position was weldment due to Fs(Fractured section) of nugget, which was smaller than tube thickness (t), and it was proven as a partial strength welding because of the average joint efficiency fr = 0.90.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.194-195
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• 2005

(100-x)Zn xMg alloy films are prepared onto cold-rolled steel substrates; where x ranged from 0 to about 38 atomic %. The alloy films show microcrystalline and grain structures respectively, according to preparation conditions such as composition ratio of zinc and magnesium or gas pressures etc.. And X-ray diffraction analysis indicates not only the presence of Zn-Mg thin films with forced solid solution but also the one of $MgZn_2$ alloy films partly. In addition the influence of Mg/Zn composition ratio and morphology of the Zn-Mg alloy films on corrosion behavior is evaluated by electro-chemical anodic polarization tests in deaerated 3% NaCl solution. From this experimental results, all the prepared Zn-Mg alloy films showed obviously good corrosion resistance to compare with 99.99% Zn and 99.99% Mg Ingots for evaporation metal. It is thought that the Zn-Mg films with effective forced solid solution prepared by plasma enhanced PVD method, produces smaller and denser grain structure so that may improve the formation of homogeneous passive layer in corrosion environment.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.2
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• pp.103-110
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• 2016

Fine wires made from platinum have been used as sensors to evaluate the convection performance of nanofluids. However, the wire sensor is difficult to handle due to its fragility. Additionally, an unrealistic convective heat transfer coefficient (h) is obtained if a rigorous calibration process combined with precision equipment is not used for measurement. This paper proposes a new evaluation apparatus for h of nanofluids that uses a thermistor sensor instead of the platinum wire. The working principles are also explained in detail. Validation experiments for pure engine oil comparing h from the two sensors confirmed numerous practical benefits of the thermistor. The proposed system can be used as a useful tool to justify the adoption of developed nanofluids.

• Journal of the Korean Ceramic Society
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• v.49 no.2
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• pp.179-184
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• 2012

The size of various alumina ceramics used in semiconductor and display industry is required to increase with increase in wafer and panel size. In this research, large alumina ceramics were fabricated by uniaxial pressing, cold isostatic pressing and filter pressing with commercial powder and thereafter sintering at $1600^{\circ}C$ in gas furnace. The large alumina ceramics exhibited dense microstructure corresponding to 98.5% of theoretical density and 99.8% of high purity. The impurities and microstructural defects of the alumina were found to influence the resistance and dielectric properties. The volume resistances in these four aluminas were almost the same while the pure alumina was higher value. The dielectric constant, dielectric loss and dielectric strength of aluminas were placed within the range of 10.3~11.5, 0.018~0.036, and 10.1~12.4 kV/mm, respectively.

• Journal of Ocean Engineering and Technology
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• v.14 no.1
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• pp.23-28
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• 2000

The fatigue crack growth behavior of the cold-rolled STS 304 steel developed for membrane material of LNG storage tank was examined experimentally at 293K, 153K and 111K. The fatigue crack growth rate(do/dN) tends to increase as the stress ratio (R) increases over the testing temperature when compared at the same stress intensity factor range($\Delta$K). The effect of R on do/dN is more explicit at low temperatures than at room temperature. The resistance of fatigue crack growth at low temperatures is higher compared with that at room temperature which is attributed to the extent of strain-induced martensitic transformation at the crack tip. The temperature dependence of fatigue crack growth resistance is gradually vanished with an increase in $\Delta$K which correlates with a decreasing fracture toughness with decreasing temperature. Fractographic examinations reveal that the differences of the fatigue crack growth characteristics between room and low temperature are mainly explained by the crack closure and the strengthening due to the martensitic transformation.

• Journal of Sericultural and Entomological Science
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• v.44 no.1
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• pp.1-3
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• 2002

The colchicine drop treatment is done on the growthpoint of the Sangilppong, which is the leading mulberry variety for mulberry dwarf resistance. So the breeding of the Sawonppong 27, that is tetraproidy, is succeeded and the chracteristics of this is as follows. The chromosome number of it is 2n=56, tetraproidy. The spring sprouting stage is midseason mulberry variety, and the leaf has a broad width shape that the oval leaf and the 3 lobed leaf exist simultaneously, The thickness of leaf is thick, the branch length and internorde length are short. The nonbudding of basal part does not exist and the cold hardness of this is stronger than the Sangilppong.