• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.21 no.3
• /
• pp.119-123
• /
• 2011

Carbon nanotilaments (CNFs) could be synthesized on nickel catalyst layer-deposited silicon oxide substrate using $C_2H_2$ and$H_2$ as source gases under thermal chemical vapor deposition system. By the incorporation of $SF_6$ as a cyclic modulation manner, the geometries of carbon coils-related materials, such as nano-sized coil and wave-like nano-sized coil could be observed on the substrate. The characteristics (formation density and morphology) of as-grown CNFs with or without $SF_6$ incorporation were investigated. Diameter size reduction for the individual CNFs-related shape and the enhancement of the formation density of CNFs-related material could be achieved by the incorporation of $SF_6$ as a cyclic modulation manner. The cause for these results was discussed in association with the slightly increased etching ability by $SF_6$ addition and the sulfur role in SF 6 for the geometry change.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2002.05a
• /
• pp.275-278
• /
• 2002

The performance of Terfenol-D, the commercially available magnetostrictive material, is highly dependent on the prestress, magnetic field intensity and temperature. This paper presents an experimental investigation of the temperature effect on the magnetostriction in Terfenol-D. The effects of both prestress and magnetic field on the magnetostriction are also presented. Experimental results show that both the prestress and magnetic field on the magnetostriction are significant. It is also observed that the displacement decreases slightly to around 40$^{\circ}C$, then increases to 80$^{\circ}C$. It indicates that the displacement decreases due to the reduced magnetization, and increases due to the thermal expansion, as the temperature increases. It means that the reduced magnetization affects more in the displacement change up to 40$^{\circ}C$, and the thermal expansion affects more in the displacement change beyond 40$^{\circ}C$.

• Journal of Integrative Natural Science
• /
• v.4 no.3
• /
• pp.222-226
• /
• 2011

Cyclic AMP receptor protein(CRP) is involved in the activation of many genes corresponding to catabolite enzymes in Escherichia coli. In this study, mutant CRP(S128A) was used to elucidate the effect of Ser 128 on the cAMP-induced structural change. Based on the protease digestion and thermal analysis, serine 128 in CRP affects the cAMP binding capability and then structural change of CRP protein. In addition, CD spectra in near UV region revealed that S128A CRP retained the sensitive conformation to thermal effect relative to that of wild-type CRP, in spite of identical Tm values in the absence of cAMP.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2014.05a
• /
• pp.216-217
• /
• 2014

Optimum finishing position, thickness and phase change temperature of winter and summer season were selected and suitability of finishing materials was evaluated based on temperature measurement of specimens applying the coating material mixed phase change materials(PCM). As a result, when finishing position was interior and finishing thickness of coating material mixed n-Octadecane(28℃ PCM) was 4mm, thermal performance was effective. n-Octadecane in summer season and n-Hexadecane(18℃ PCM) in winter season are indicated effective on energy savings, respectively.

• Proceedings of the KSME Conference
• /
• 2001.06a
• /
• pp.517-522
• /
• 2001

The purpose of this study is to investigate the thermal embrittlement and the mechanical properties of 2.25Cr-1Mo steel aged at high temperature and stress for 250 hours. Original, aged artificially material were tested to obtain the hardness and impact absorbed energy. Hardness and impact absorbed energy decreased with the increasing aging time. The carbide morphology with the thermal embrittlement was found to contribute to the mechanical property change by X-Ray diffraction method.

• Journal of the Korean Society for Precision Engineering
• /
• v.18 no.2
• /
• pp.126-131
• /
• 2001

One of the major obstacles in testing or evaluating precisely the thermal behavior of a machine tool is the difficulty in measuring the heat transfer coefficients on the surfaces by a conventional method. This paper presents a new approach based on the inverse method to identify the values of heat transfer coefficients by using temperature changes measured on the surfaces of a machine tool during a short period in its operating. In the present method, a machine tool structure is modeled by the finite element method and the characteristic curves of the temperature change at several points on machine tool surfaces are theoretically derived in the form that they contain the heat transfer coefficient as an unfixed heat source are approximated so that the theoretical characteristic curves of temperature change fit the measured ones as closely as possible.

• Advanced Composite Materials
• /
• v.17 no.3
• /
• pp.301-317
• /
• 2008

The energy release rate associated with crack growth in adhesive double cantilever beam (DCB) specimens, including the effect of residual stresses, was formulated using beam theory. Because of the rotation of the asymmetric arms in the adhesive DCB specimens due to temperature change, it is necessary to correct the evaluated fracture toughness of the DCB specimens, specifically in the case of a large temperature change. This study shows that the difference between the true toughness and an apparent toughness due to the consequence of ignoring residual stresses can be calculated for a given specimen geometry and thermo-mechanical properties (e.g. coefficient of thermal expansion). The calculated difference in the energy release rates based on the present correction method is compared with that from FEM in order to verify the present correction method. The residual stress effects on the evaluation of the adhesive fracture toughness are discussed.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.32 no.12
• /
• pp.931-937
• /
• 2008

A high motive pressure thermal vapor compressor(TVC) for a commercial multi-effect desalination(MED) plant is designed to have a high entraining performance and its robustness is also considered in the respect of operating stability at the abrupt change of the operating pressures like the motive and suction steam pressure which can be easily fluctuated by the external disturbance. The TVC having a good entraining performance of more than entrainment ratio 6.0 is designed through the iterative CFD analysis for the various primary nozzle diameter, mixing tube diameter and mixing tube length. And then for a couple of TVC having a similar entrainment ratio, the changes of the entrainment ratio are checked along the motive and suction pressure change. The system stability is diagnosed through the analyzing the changing pattern of the entrainment ratio.

• Proceedings of the Korean Institute of Intelligent Systems Conference
• /
• 1995.10b
• /
• pp.15-24
• /
• 1995

This paper describes a system that can be used to recognize an unknown material regardless of the fuzzy neural network(FNN). There are some problems to realize the recognition system using temperature response. It requires too many memories to store the vast temperature response data and it has to be filtered to remove noise which occurs in experiment. And the temperature response is influenced by the change of ambient temperature. So, this paper proposes a practical method using curve fitting to remove above problems of memories and noise. and FNN is proposed to overcome the problem caused by the change of ambient temperature. Using the FNN which is learned by temperature responses on fixed ambient. Temperatures and known thermal conductivity, the thermal conductivity of the material can be inferred on various ambient temperatures. So the material can be recognized by the thermal conductivity.

• 유체기계공업학회:학술대회논문집
• /
• 1999.12a
• /
• pp.46-51
• /
• 1999

This paper describes the control charcteristics of thermal/flow systems. In thermal/flow systems, the transport lag plays as a dead time causing a deterioration of the controllability. Besides this, such many parameters including the temperature, pressure, and flow rate affect the system response that a control scheme which can deal with multi-input is required. Particularly in a refrigerant compressor test facility, the evaporator and condenser interact each other so that the change in the evaporator pressure cause the condenser pressure to change or vice versa. Therefore, to control the evaporator pressure, not only the cooling water flow rate in the evaporator but also the coolant flow rate in the condenser is considered. Meanwhile, the conventional PID controllers, which is suitable for a single input system, shows a large overshoot for a disturbance input. In this work, the predictive control scheme is introduced and its applicability is discussed for thermal/flow systems.