• English Language & Literature Teaching
• /
• v.15 no.3
• /
• pp.59-81
• /
• 2009

The primary goal of this paper was to develop a critical point of view to critical pedagogy when applied to EFL contexts. Critical pedagogy is more concerned about how language can affect personal and social change of teachers and students than it is with how to teach language effectively or in ways that encourage critical thinking on the part of teacher and students. For this goal, this paper introduces the definition, emergence and major constructs of critical pedagogy in a broad way at first. Then, this paper presents how critical pedagogy has an impact on ELT, focusing on how critical pedagogy is applied in ELT contexts and why the application of critical pedagogy in EFL can be criticized, through the review of empirical studies. Reflection of Korean English teaching situation and applicational difficulties of critical pedagogy in Korean ELT are followed.

• 제어로봇시스템학회:학술대회논문집
• /
• 1996.10b
• /
• pp.1004-1007
• /
• 1996

Various auto-tuning methods using relay feedback are presented recently. They are composed of the consecutive procedures identifying Nyquist critical point using relay feedback and designing PID controller by one point of Nyquist plot mapping. This paper suggests a strategy to get the knowledges of Nyquist critical point and the neighborhood point of it using relay feedback. The parameters of PID controller are established by dominant pole approximation based on these knowledges. Designers can make use of the damping ratio as a time domain specification. So design flexibilities are taken in view of stability and performance of the system response considering practical system condition.

• Proceedings of the KSME Conference
• /
• 2000.11b
• /
• pp.404-409
• /
• 2000

Characteristics of secondary vortices is topologically investigated in the near-wake region of a circular cylinder where the Taylor hypothesis does not hold. The three-dimensional flow fields in the wake-transition regime were measured by a time-resolved PIV. For the analysis in a moving frame of reference, the convection velocity of the Karman vortices is evaluated from the trajectory of vortex center which is defined as the centroid of the vorticity field. Then, a saddle point is obtained by applying the critical point theory. Science the distributions of fluctuating Reynolds stresses defined by triple-decomposition are closely related with the existence of secondary vortices. the physical meaning of them is explained in conjunction with vortex center and saddle point trajectories. Finally, the temporal evolution of streamwise vortex is also discussed.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2002.05a
• /
• pp.901-904
• /
• 2002

The cutting thickness of ultra-precision machining is generally very small, only a few micrometer or even down to the order of a flew manometer. In such case, a basic understanding of the mechanism on the micro-machining process is necessary to produce a high quality surface. When machining at very small depths of cut, metal flow near a rounded tool edge become important. In this paper a finite element analysis is presented to calculate the stagnation point on the tool edge or critical depth of cut below which no cutting occurs. From the simulation, the effects of the cutting speed on the critical depths of cut were calculated and discussed. Also the transition of the stagnation point according to the increase of the depths of cut was observed.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.18 no.5
• /
• pp.1126-1133
• /
• 1994

When designing an internal gear. the bending strength around pitch point as well as that at tooth root fillet should be considered because the bending stress around pitch point may occur as high as that at tooth root fillet. In this study, including stress state around pitch point, the bending strength (tensile side and compressive side) of internal gear tooth is investigated by the use of the finite element method(FEM) with regarding many influencing factors of cutter and gear geometries. Then, the critical sections around pitch point and at tooth root fillet are determined, and the simple formulae based on nominal stresses(bending, compressive, and shear) are derived for the calculations of actual stresses as the functions of tooth thicknesses and radii of curvatures of involute and fillet curve at those critical sections. The stresses calculated by the formulae agree well with those by the FEM. And the bending stresses around pitch point and at tooth root are easily estimated by the use of those formulae, therefore, those formulae are useful for the purpose of the design or the bending strength estimation of internal gear.

• Journal of the Korean Ceramic Society
• /
• v.35 no.10
• /
• pp.1094-1100
• /
• 1998

The thermal fatigue behavior of alumina ceramics was investigated by water quenching method. Single-quench thermal shock tests were performed to decide the critical thermal shock temperature difference ($\Delta$Tc) which was found to be 225$^{\circ}C$ Cyclic thermal shock fatigue tests were performed at temperature diff-erences of 175$^{\circ}C$, 187$^{\circ}C$ and 200$^{\circ}C$ respectively. After cyclic thermal shock fatigue test the distributions of retained strength and crack were observed. Retained strength was measured by four point bending method and crack observation method bydye penetration. In terms of the retained strength distribution the critical number of thermal shock cycles(Nc) were 7 for $\Delta$T=200$^{\circ}C$, 35 for $\Delta$T=187$^{\circ}C$ and 180for $\Delta$T=175$^{\circ}C$ respec-tively. In terms of the crack observation the critical number of thermal shock cycles were 5 for $\Delta$T==200$^{\circ}C$ 20 for $\Delta$T==187$^{\circ}C$ and 150 for $\Delta$T=175$^{\circ}C$ respectively. The difference of Nc investigated by two different methods is due to the formation of the longitudinal cracks which had no effect on the four point bending strength. Therefore the thermal fatigue behavior of alumina ceramics could be more accurately described by the crack observation method than the retained strength measurement method.

• 열병합발전
• /
• s.74
• /
• pp.18-21
• /
• 2010

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.24 no.2
• /
• pp.168-179
• /
• 2013

The critical point analysis(CA) and impedance matching analysis(IA) are performed and compared for a 4-coil magnetic resonance wireless power transfer system. Because the operating frequency splits at short distance while the efficiency drops drastically at long distance in this system, the optimization technique is needed for either a specific distance or efficiency at the fixed frequency. CA uses the critical point where shows maximum efficiency in the entire range and IA uses the impedance matching technique to achieve maximum efficiency at the specific distance. Comparison result shows that IA is more efficient than CA. Also, it shows one side matching has a tradeoff relationship comparing to both side matching. By using four spiral resonant coils, the analysis was experimentally verified. The measured data agreed well with the calculated data.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.20 no.4
• /
• pp.26-33
• /
• 2016

In order to analyze supercritical transition of liquid hydrocarbon fuel which used propulsion engine, visualization of phase changing using Methylcyclohexane (MCH) was performed. Also, measurements of temperature and pressure were conducted to obtain saturation lines of MCH and Decane. delayed increase of the pressure existed near the critical point due to dramatical increase of specific heats and the critical opalescence was only observed from the end point of delaying to the critical point. Beyond the critical point, the boundary between phases disappeared and the strong density gradient was observed. As the comparison between experimental and numerical saturation lines, the numerical estimation for mixture had relatively little difference while the results of pure components had almost coincidence.

• Journal of Welding and Joining
• /
• v.31 no.6
• /
• pp.37-43
• /
• 2013

This study targets to make clear the connection between MS (Martensite start) point and welding shrinkage. We approved that a Martensite-transformed weldment may not yield state under low MS point, but also admitted the limitation of numerical calculation by inherent strain approach or thermal strain approach. Therefore, new thermal strain formulae during cooling stages were made. As a thermal strain is obtained by integrating thermal extension coefficient, a constant of integration should be decided. In our suggested formulae, the origin was based on totally remained austenite, and added strain from volume changes in Martensite transformation was based on totally transformed ferrite. Through the suggested methodology, It is verified that an MS point under a critical temperature can let weld shrinkage relax and the critical value can be obtained. For supporting this process, 15 weld-consumables were made, were tested by fillet type and were measured. As a result, a positive correlation between MS point and level of weld-distortion was obtained, but it was rather weak.