• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.12
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• pp.5216-5220
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• 2010

Rheological measurement of a thermotropic liquid crystalline poymer (TLCP) is not an easy task since their rheological responses are strongly influenced by a thermal history during a processing and thus the reproducibility of the measurement is poor. In order to find out a cause for the strong influence of the thermal history, rheological measurements and DSC observations of the TLCP having various thermal histories were carried out. It was observed that the TLCP used in this study shows liquid-like behavior at a temperature above a crystal-nematic transition temperature ($280^{\circ}C$), but at the same time crystallization can occur at this temperature range and as a consequence the viscosity of the polymer continuously increases. When the samples are heated beyond the $320^{\circ}C$, all crystals thus formed and the thermal histories were observed to disappear. Crystallization rate of the samples annealed above $320^{\circ}C$ was very low at even the lowed temperature ($280^{\circ}C\;{\sim}\;320^{\circ}C$). Therefore, it is concluded that rheological measurements of TLCP used in this study must be performed after annealed above the nematic-isotropic transition temperature for better reproducibility.

• Journal of the Korean Society of Clothing and Textiles
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• v.21 no.6
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• pp.1003-1009
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• 1997

To study the time course of increased cold tolerance, the physiological responses were measured during the course of a 2-yr study (Feb. 1995~Feb. 1996) of four female college students, whose cold tolerance was proved to be increased through wearing cool clothing in daily life from Sep. 1994 to Feb. 1995. To determine their cold tolerance, subjects rested at 25$\pm$1$^{\circ}C$, then were exposed to 15$\pm$1$^{\circ}C$, 50$\pm$5% R.H. for 90min in Feb. 1995 and Feb. 1996. Subjects' rectal temperatures, mean skin temperatures, heat production, shivering onset, thermal sensations, and comfort showed no significant changes, when they were measured in 1995 and 1996. Based on these results, we can safely assume that mild cold acclimatization coming from wearing cool clothing lasts at least oneyear, that is until the following year. One of the possible explanations for this is that the subjects did not increase their clothing thermalresistances after the cold acclimatization.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.191-194
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• 2003

The results from a systematic study of the response of a Ti-6Al-4V alloy under quasi-static and dynamic loading at different strain rates and temperatures are presented. It has been shown that the work-hardening rate decreased as the strain rate and the strain increased. The correlations and predictions using modified KHL (Khan-Huang-Liang) viscoplastic constitutive model are compared with those from JC (Johnson-Cook) model and experimental observations. Overall, KHL model correlations and predictions compared much more favorably than the corresponding JC model predictions and correlations.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.981-982
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• 1998

We fabricated sampled fiber grating by double-exposure method. First, a short-period grating was written into the hydrogen-loaded single mode fiber and then the refractive index was modulated over it by an amplitude mask. It was observed that several transmission dips appear due to the index modulation. The thermal and strain responses were measured over $40-180^{\circ}C$ and $0-1800\mu\varepsilon,$ respectively. The dips have the same and linear sensitivity to both physical quantities over the range of measurement.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.6
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• pp.686-695
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• 2012

This paper proposes a noncontact thermography technique for fatigue crack evaluation under a cyclic tensile loading. The proposed technique identifies and localizes an invisible fatigue crack without scanning, thus making it possible to instantaneously evaluate an incipient fatigue crack. Based on a thermoelastic theory, a new fatigue crack evaluation algorithm is proposed for the fatigue crack-tip localization. The performance of the proposed algorithm is experimentally validated. To achieve this, the cyclic tensile loading is applied to a dog-bone shape aluminum specimen using a universal testing machine, and the corresponding thermal responses induced by thermoelastic effects are captured by an infrared camera. The test results confirm that the fatigue crack is well identified and localized by comparing with its microscopic images.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.6
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• pp.433-440
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• 2000

To flexibly evaluate performance and reliability of a real-time system which is intrinsically characterized by stringent timing constraints to generate correct responses, we propose fuzzyrandom variables and build a discrete event model embedded with fuzzy-random variables. Also, we adapt fuzzy-variables to a path-space approach, which derives the upper and lower bounds of reliability by using a semi-Markov model that explicitly contains the deadline information. Consequently, we propose certain formulas of state automata properly transformed by fuzzy-random variables, and present numerical examples applying the formulas to RTP(Rapid Thermal Process) to show that a complex system can be properly evaluated based on this model by computer simulation.

• Korean Journal of Psychosomatic Medicine
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• v.3 no.1
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• pp.91-97
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• 1995

Pain is a complex symptom consisting of a sensation underlying potenial disease and associated emotional state. Acute pain is a reflex biological response to injury, in contrast, chronic pain consists of pain of a mininum of 6 months duration and associates with physical, emotional past experience, economic resources of the patient, family and society. Moreover, chronic pain is characterized by physiological affective and behavioral responses that are quite different than those of acute pain. The different type of stimuli exciting pain receptor are mechanical, thermal and chemical stimli and chronic pain are concerned with three of all stimli. The major three components of pain central(Analgesia) system in the brain and spinal cord are 'periaqueductal gray area of the mesencephalon', 'the raphe magnus nucleus' and 'pain inhibitory complex located in the dorsal horns of the spinal cord'. But unfortunately, the central biochemical mechanisms of chronic pain are not clearly defined. To proper management of chronic pain, comprehensive urderstanding as a psychosomatic aspect and multidisciplinary therapeuti-team approach must be emphasized.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.9 no.4
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• pp.99-107
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• 2000

In this study, a static and dynamic characteristics analysis system for machine tool spindle systems with 3 lobe sliding bearing is developed based on Timoshenko theory, finite element method and windows programming techniques. And the characteristics value of 3 lobe sliding bearing such as eccentricity ratio, attitude angle, friction coefficient , stiffness coefficients, damping coefficients and so on, are determined by using the thermal equilibrium conditions of spindle systems. Since the developed system has various analysis modules related to static deformation analysis, modal analysis, frequency responses analysis and so on, it can be utilized to perform systematically the design an devaluation process of spindle systems with 3 lobe sliding bearing under windows GUI environment.

• Journal of Electrical Engineering and Technology
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• v.9 no.6
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• pp.1900-1908
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• 2014

This paper establishes a compact and practical model for a water-wall system comprising supercritical once-through boilers, which can be used for automatic control or simple analysis of the entire boiler-turbine system. Input and output variables of the water-wall system are defined, and balance equations are applied using a lumped parameter method. For practical purposes, the dynamic equations are developed with respect to pressure and temperature instead of density and internal energy. A comparison with results obtained using APESS, a practical thermal power plant simulator developed by Doosan Heavy Industries and Construction, is presented with respect to steady state and transient responses.

• Advances in materials Research
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• v.8 no.4
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• pp.259-274
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• 2019

Flexoelectric effect has a major role on mechanical responses of piezoelectric materials when their dimensions become submicron. Applying differential quadrature (DQ) method, the present article studies dynamic characteristics of a small scale beam made of piezoelectric material considering flexoelectric effect. In order to capture scale-dependency of such piezoelectric beams, nonlocal elasticity theory is utilized and also surface effects are included for better structural modeling. Governing equations have been derived by utilizing Hamilton's rule with the assumption that the scale-dependent beam is subjected to thermal environment leading to uniform temperature variation across the thickness. Obtained results based on DQ method are in good agreement with previous data on pizo-flexoelectric beams. Finally, it would be indicated that dynamic response characteristics and vibration frequencies of the nano-size beam depends on the existence of flexoelectric influence and the magnitude of scale factors.