• Applied Chemistry for Engineering
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• v.10 no.6
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• pp.832-837
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• 1999

Stability of a cathode material was determined by Tafel plot in 1 M LiOH solution. The stabilized $LiM_xMn_{2-x}O_4$ (x=0.05~0.1) electrode resulted in overpotential of 0.13~0.15 mV at 100 mA. This overpotential was 0.05 mV lower than that of the spinel structured $LiMn_2O_4$ electrode. Conductivity test at various potentials showed that the conductivity of $LiM_xMn_{2-x}O_4$ was higher than that of the spinel structured $LiMn_2O_4$ and the bulk resistance of $LiM_xMn_{2-x}O_4$ due to the dissolution of $Mn^{2+}$ was lowered.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.3 s.174
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• pp.667-675
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• 2000

Force measuring devices should be calibrated to guarantee their test results. In order to establish the force standards in Korea, deadweight machines of 5 kN, 20 kN, 100 kN and 500 kN capacity and a hydraulic force standard machine of 2 MN capacity were installed at the Korea Research Institute of Standards and Science(KRISS). As heavy industries in Korea have been developed, we should measure large forces over 2 MN capacity precisely in industries. We developed a 10 MN force standard machine with built-in force transducers which is more compact and cheaper than hydraulic force standard machines which have been widely used as large force standards in most national metrology laboratories. Test results reveal that the relative expanded uncertainty of the force machine is less than 4.1 $\times$ 10-4 in the range of 1 MN-4.5 MN.

• Korean Journal of Materials Research
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• v.11 no.4
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• pp.266-271
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• 2001

Effect of Cd addition on the stress corrosion cracking(SCC) resistance of Al-Cu-Mn cast alloy was investigated by C-ring test and electrical conductivity measurement. With increasing Cd contents, the electrical conductivity and the SCC resistance were increased. The PFZ and coarse precipitates along the grain boundary were observed from TEM micrographs. The fracture made of the alloys was confirmed as intergranular type and showed brittle fracture surface. As a result, it was concluded that the SCC mechanism of these alloys is the anodic dissolution model. The maximum hardness was increased from 127Hv in the Cd-free alloy to 138∼145Hv in the Cd addition alloys.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.707-710
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• 2002

Spinel $LiMn_2O_4$ and $LiMn_{1.9}Mg_{0.05}Zn_{0.05}O_4$ powders were synthesized by solid-state method at $800^{\circ}C$ for 36h. Crystal structure and electrochemical properties were analyzed by X-ray diffraction, charge-discharge test, cyclic voltammetry and ac impedance to $LiMn_2O_4$ and $LiMn_{1.9}Mg_{0.05}Zn_{0.05}O_4/Li$. All cathode material showed spinel structure in X-ray diffraction. $LiMn_{1.9}Mg_{0.05}Zn_{0.05}O_4/Li$ cell substituted $Mg^{2+}$ and $Zn^{2+}$ showed excellent discharge capacities than other cells, which it presented about 120mAh/g at the 1st cycle and about 73mAh/g at the 250th cycle, respectively. AC impedance of $LiMn_{1.9}Mg_{0.05}Zn_{0.05}O_4/Li$ cells showed the similar resistance of about $65{\sim}110{\Omega}$ before cycling.

• Korean Journal of Materials Research
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• v.27 no.12
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• pp.643-651
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• 2017

Four types of high Mn TWIP(Twinning Induced Plasticity) steels were fabricated by varying the Mn and Al content, and the tensile properties were measured at various strain rates and temperatures. An examination of the tensile properties at room temperature revealed an increase in strength with increasing strain rate because mobile dislocations interacted rapidly with the dislocations in localized regions, whereas elongation and the number of serrations decreased. The strength decreased with increasing temperature, whereas the elongation increased. A martensitic transformation occurred in the 18Mn, 22Mn and 18Mn1.6Al steels tested at $-196^{\circ}C$ due to a decrease in the stacking fault energies with decreasing temperature. An examination of the tensile properties at $-196^{\circ}C$ showed that the strength of the non-Al added high Mn TWIP steels was high, whereas the elongation was low because of the martensitic transformation and brittle fracture mode. Although a martensitic transformation did not occur in the 18Mn1.9Al steel, the strength increased with decreasing temperature because many twins formed in the early stages of the tensile test and interacted rapidly with the dislocations.

• Steel and Composite Structures
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• v.2 no.4
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• pp.247-258
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• 2002

The high-temperature material properties of steel are very important to the fire resistance analysis of high-strength bolt connections. This paper reports on the results of the experimental studies on the high-temperature properties of 20 MnTiB steel which is widely used in high-strength bolts, and the friction coefficient of 16Mn steel plates at elevated temperature which is a necessary parameter for bolted frictional connection analysis. The test data includes yield strength, limit strength, modulus of elasticity, elongation and expansion coefficient of 20MnTiB steel at elevated temperature, and the friction coefficients between two 16Mn steel plates under elevated temperatures and after cooling. Based on the data from the tests, the mathematical models for predicting the mechanical properties of 20MnTiB steel and friction coefficients of 16Mn steel plates have been established.

• Journal of the Korean Society for Heat Treatment
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• v.8 no.2
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• pp.113-119
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• 1995

We have reported that an Fe-17wt%Mn alloy exhibits the highest damping capacity in the Fe-Mn binary system. In the present work, the effects of copper content on the damping capacity, atmospheric corrosion and mechanical properties were studied. The damping capacities were measured at room temperature for the air cooled Fe-17wt%Mn alloy having copper content from 0.1wt% to 1.1wt%. The damping capacity of the Fe-17wt %Mn alloy was decreased with increasing copper content. However, the addition of Copper was found to improve mechanical properties and atmospheric corrosion resistance. These mechanical properties were attributed to the formation of stress-induced martensite during tensile test.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.277-284
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• 2000

Using the large diameter (D ＝ 2,500mm, L ＝ 40m) batter steel pipe piles, designed as compression piles but used as reaction piles during the static compression load test of socketed test piles (D ＝ 1,000mm, L ＝ 40m), static pile load tests for large diameter instrumented rock-socketed piles were performed. The reaction steel pipe piles were driven 20m into the marine deposit and weathered rock layer and then l0m socketed with reinforced concrete through the weathered rock layer and into hard rock layer. Steel pipe and concrete in the steel pile part, and concrete and rebars in the socketed parts were instrumented to measure strains in each part. The pullout amounts of reaction pile heads were also measured with LVDT. During the static pile load test, total compressional load of about 20MN was loaded on the head of test piles, but load above 20MN was not loaded due to lack of loading capacity of loading system. Over the course of the study, maximum pullout amount up to 7mm was measured in the heads of reaction piles when loaded op to 10MN and 1mm of pullout amount was measured. More than 85% of pullout load was transfered in the residual weathered rock layer and about 10% in the soft rock layer, which was somewhat different transfer mechanism in the static compressional load tests.

• Journal of Powder Materials
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• v.29 no.6
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• pp.517-522
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• 2022

We investigate the austenite stability in nanocrystalline Fe-7%Mn-X%Mo (X = 0, 1, and 2) alloys fabricated by spark plasma sintering. Mo is known as a ferrite stabilizing element, whereas Mn is an austenite stabilizing element, and many studies have focused on the effect of Mn addition on austenite stability. Herein, the volume fraction of austenite in nanocrystalline Fe-7%Mn alloys with different Mo contents is measured using X-ray diffraction. Using a disk compressive test, austenite in Fe-Mn-Mo alloys is confirmed to transform into strain-induced martensite during plastic deformation by a disk d. The variation in austenite stability in response to the addition of Mo is quantitatively evaluated by comparing the k-parameters of the kinetic equation for the strain-induced martensite transformation.

• Communications for Statistical Applications and Methods
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• v.4 no.2
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• pp.435-444
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• 1997

The objective of this study is to investigate the problem of goodness of fit testing based on nonparametric function estimation techniques for the random censorship model. The small and large sample properties of the proposed test, $E_{mn}$, were investigated and it is shown that under the proportional hazard model $E_{mn}$ has higher power compared to the powers of the Kolmogorov -Smirnov, Kuiper, Cramer-von Mises, and analogue of the Cramer-von Mises type test statistic.