• Journal of the Korean Society for Heat Treatment
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• v.25 no.2
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• pp.74-79
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• 2012

This study has been carried out to investigate the precipitation behavior of ${\chi}$ phase and effect of ${\chi}$ phase precipitation on the impact toughness of 25%Cr-7%Ni-4%Mo super duplex stainless steel. It was proved that the ${\chi}$ phase was a intermetallic compound, which represented the higher chromium and molybdenum concentration than the matrix phases, and also showed the higher molybdenum concentration than the ${\sigma}$ phase. The ${\chi}$ phase was precipitated at the interface between ferrite and austenite or inside the ferrite matrix in the early stage of aging. The number of ${\chi}$ phase precipitates increased with increasing aging time, however, after showing the maximum value, the number was decreased due to the gradual transformation of ${\chi}$ phase into ${\sigma}$-phase. Aging ferrite phase was decomposed by the $r^2$ phase and ${\sigma}$-phase. Impact toughness rapidly decreased with time in the initial stage of aging at ${\chi}$ phase start to precipitate. Thus, the impact toughness was greatly influence for the precipitation of ${\chi}$ phase.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.311-314
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• 1998

The effects of the additions of transition metal oxides on ZrO$_2$ - Y$_2$O$_3$ (Y$_2$O$_3$ - containing tetragonal zirconia polycrystals : Y-TZP) system has been studied by investigating fracture toughness and phase stability of the sintered specimens. In the specimens sintered at 1450$^{\circ}C$ for 2hrs in air the phase transformation from tetragonal to monoclinic was observed. The ratios of monoclinic phase to tetragonal phase were changed with the additions of CoO, Fe$_2$O$_3$ and MnO$_2$, respectively, from 0.00 to 8.00wt%. The fracture toughness was increased with increasing the monoclinic to tetragonal phase ratio and was maximum at the ratio of about 18%. However, the hardness was decreased with increasing the ratio. The additions of CoO, Fe$_2$O$_3$ and MnO$_2$ together into Y-TZP resulted in more complex behaviors of fracture toughness and hardness. The specimen with the additions of 1.5wt% Fe$_2$O$_3$, 3.0wt% Al$_2$O$_3$ and 1.5wt% CoO showed the monoclinic to tetragonal phase ratio of 18% and the highest toughness of 10.8 MPa.m$\^$$\frac{1}{2}$/ and Vickers hardness of 1201kgf/mm$^2$.

• Journal of the Korean Chemical Society
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• v.38 no.2
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• pp.122-128
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• 1994

Macrocyclic ligand has been known to selectively bind with metal ions so that ability applied for the transport of metal ions across the emulsion liquid membrane in this study. The metal ions are transproted from the source phase to the receiving phase by the carrier of the organic phase. Several factors involved in the transport of metal ions acrose the emulsion membrane we reported here and these factors provided the informations for the selective seperation of some metal ion. Stability constants for cation-macrocyclic ligand and metal ion-anion receiving phase interaction are examined as parameters for the prediction of metal ion transport selectivities. $Pb^{2+}$ was transported higher rates than the other metal ions in the mixture solution. The interaction of metal ion to anion in receiving phase is important. $S_2O_3^{2-}$- in replacement of $NO_3^-$ in the receiving phase enhances the transport of $Pb^{2-}$since $Pb^{2-}-S_2O_3^{2-}$interaction is greater than $Pb^{2+}-NO_3^-$ interaction.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.4
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• pp.339-346
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• 2005

It is complex to realize the reference voltage vector by the space vector PWM method in three-leg two-phase inverter In this paper a new PWM technique for three-leg two-phase inverter fed two-phase induction motor is poroposed assuming that three-leg two-phase inverter is equivalent circuit for 'four-leg two-phase inverter with the connected two windings'. From assumption, six sectors are decreased to four sectors, and simple sinusoidal PWM method instead of SVPWM is applied to three-leg two-phase inverter. Also, the switching pattern to determine the switching periods at each sector is proposed. Practical verification of theoretical predictions is presented to confirm the capabilities of the new techniques.

• Korean Journal of Applied Biomechanics
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• v.12 no.2
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• pp.77-90
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• 2002

This study serves the purpose of understanding about correct jump and landing motion through Kinematical Analysis of Straddle Jump to Push up Motion at target by four elite sports aerobics athletes have more than four years career. And further more that make good assistance for coaches effective guidance through an offer basic data and correct diagnosis, evaluate of motions. It was picture-taked by two-video camera for Straddle Jump to Push up Motions. Camera speeds are 60 frame/sec. There are Kinematical Variation elements for analysis, the displacement of COG, each angle displacement left/right of shoulder-joint, each angle displacement left/right of knee-joint and each speed left/right of tip of the toes. Every each person accomplished severaly 3 times and we have acquired this conclusion. The conclusions were as follows; 1. Each situation for displacement of COG showed low height of COG by phase 1, 4, 5(79.05${\pm}9.07,\;46.41{\pm}3.65,\;18.66{\pm}0.54cm$) and It showed high height of COG by phase 2, 3($120.80{\pm}6.13,\;148.12{\pm}9.19cm$). 2. Each displacement left, right of shoulder-joint flexion by phase 1($91.07{\pm}8.30,\;90.77{\pm}5.72$deg/sec)and It showed maximal extension angles by phase 2($102.48{\pm}10.00,\;102.39{\pm}10.51$deg/sec). in part of phase 3, left of shoulder-joint angle($94.43{\pm}4.12$deg/sec) showed flexion phase 1, the other right shoulder-joint angle(88.38${\pm}$4.98deg/sec) showed more a little lower than phase 1, in last phase that showed most low by phase 4($70.58{\pm}13.72,\;54.24{\pm}11.58$deg/sec). 3. Each displacement left, right of hip joint showed maximal extent conditions by phase 2, 3($160.35{\pm}22.68,\;1534.77{\pm}5.40$deg/sec, $150.04{\pm}12.79,\;145.54{\pm}13.00$deg/sec) beside, ankle-joint showed minimal angle by phase 1, 4($93.59{\pm}18.92,\;85.37{\pm}13.23$deg/sec, $66.60{\pm}15.77,\;80.60{\pm}16.57$deg/sec). 4. Each displacement left, right of hip joint showed maximal extent conditions by phase 2($157.15{\pm}9.13,\;163.52{\pm}8.18$deg/sec), and right of hip joint showed minimal angle by phase 3($110.87{\pm}13.81,\;77.53{\pm}8.95$deg/sec) It showed alike condition of low angle by phase 1, 4($91.04{\pm}2.31,\;96.26{\pm}2.20$deg/sec). 5. Each displacement left, right of knee-joint showed maximal extent conditions by phase 1, 3, 4($173.46{\pm}2.95,\;171.51{\pm}5.44$deg/sec, $172.24{\pm}4.49,\;171.26{\pm}0.65$deg/sec, $162.78{\pm}2.13,\;164.10{\pm}5.97$deg/sec) but It showed flexion only left of knee-joint by phase 2($164.45{\pm}7.51,\;159.38{\pm}3.48$deg/sec). 6. Each speed left, right of the tip of the toes showed most fastest when someone jumped with lift up leges by phase 1, 2($321.32{\pm}67.91,\;316.90{\pm}41.97$cm/sec, $410.06{\pm}153.06,\;399.77{\pm}189.34$cm/sec), It showed more less speed than phase 1,2 by phase 3($169.74{\pm}67.17,\;150.00{\pm}63.80$cm/sec) and It showed most slow speed than phase 1,2,3 by phase 4($87.22{\pm}34.90,\;85.72{\pm}52.23$cm/sec).

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.4
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• pp.412-417
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• 1998

This paper suggests the drive characteristics of a Switched Reluctance Motor(SRM) by 2-phase excitation method. T This scheme excites 2 phases simultaneously, which is similar to 2-phase excitation method of a step motor. In this s scheme. the torque is produced by mutual inductances as well as self inductances. The abrupt change of a phase e excitation produces mechanical stresses and it results in vibration and noise. The acoustic noise is reduced remarkably t through the sequential phase excitation in the 2-phase excitation. Operational principle and characteristic comp없1son t to that of the conventional SRM show that this excitation scheme has some advantages including torque ripple and n noise reduction.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.179-180
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• 2010

• Korean Journal of Materials Research
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• v.24 no.2
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• pp.116-122
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• 2014

$Bi_2Sr_2CaCu_2O_x$(Bi-2212) and $Bi_2Sr_2Ca_2Cu_3O_y$(Bi-2223) high-Tc superconductors(HTS) have been manufactured by plasma spraying, partial melt process(PMP) and annealing treatment(AT). A Bi-2212/2223 HTS coating layer was synthesized through the peritectic reaction between a 0212 oxide coating layer and 2001 oxide coating layer by the PMP-AT process. The 2212 HTS layer consists of whiskers grown in the diffusion direction. The Bi-2223 phase and secondary phase in the Bi-2212 layer were observed. The secondary phase was distributed uniformly over the whole layer. As annealing time goes on, the Bi-2212 phase decreases with mis-orientation and irregular shape, but the Bi-2223 phase increases because a new Bi-2223 phase is formed inside the pre-existing Bi-2212 crystals, and because of the nucleation of a Bi-2223 phase at the edge of Bi-2212 crystals by diffusion of Ca and Cu-O bilayers. In this study the spray coated layer showed superconducting transitions with an onset Tc of about both 115 K, and 50 K. There were two steps. Step 1 at 115 K is due to the diamagnetism of the Bi-2223 phase and step 2 at 50 K is due to the diamagnetism of the Bi-2212 phase.

• International Journal of Railway
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• v.2 no.2
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• pp.70-79
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• 2009

An optimal driving strategy of a train in a long journey on a nonsteep track has four phases: an initial power phase, a long hold speed phase, a coast phase and a final brake phase. The majority of the journey is speed holding. On a track with steep gradients, it becomes necessary to vary the strategy around steep sections of track because it is not possible to hold a constant steep on steep track. Instead we must interrupt the speed hold phase with a power phase. The aim of this paper is to show that there is a unique power phase that satisfies the necessary conditions for an optimal journey. The problem is developed and solved for various cases, from a simple single steep gradient to a complicated multiple steep gradient section. For each case, we construct a set of new conditions for optimality of the power phase that minimises the energy used during the power phase subject to a weighted time penalty. We then use the new necessary conditions to develop a calculate scheme for finding an optimal power phase for a steep incline. We also present an example to confirm the uniqueness of an optimal power phase.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.3
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• pp.684-687
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• 1998

The biggest problem common on to all forms of Phase Shift Interferometer is unwrapping the phase. Simple phase unwrapping algorithms assume that every pixel is within radians of its neighbors. If this is true, any reasonable algorithm will return the correct unwrapped phase. If not, correct unwrapped phase will not be obtained. In rough surface, frequently, neighboring pixels have phase steps greater than. This paper proposes the new method which makes phase steps smaller than by sub-pixel movement.