• The Korean Journal of Ceramics
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• v.1 no.2
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• pp.81-85
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• 1995

PST-series spcimens with stoichimetric and nonstoichimtric compositins were prepared and the effects of compositionl modification on phase formation and dielectric presponse were investigated. The phases formed on calcination were mainly perovskite and trace amount of phyrochlore(s), with an increase of the latter phase(s) as the composition became more ononstoichiometric. The sintered samples showed thermal hysteresis and diffuseness in phase transition with a small degree of frequency relaxation. Temperatures corresponding to maximum values of dielectric constant and loss were relatively insensitive to the composition change while the maximum values were very sensitive to that.

• Animal cells and systems
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• v.3 no.1
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• pp.47-52
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• 1999

Change of proteins was confirmed during low temperature acclimation of overwintering larva, and some biochemical characteristics of the induced antifreeze protein-1 (AFP-1) were investigated in Protaetia brevitarsis. As the freezing point depression by the action of induced AFPs, a considerable thermal hysteresis was observed in the haemolymph and in partially purified proteins. AFP-1 was purified from the cold acclimation larvae by ammonium sulfate precipitation ion exchange chromatography, gel permeation chromatography, and electroelution. The purified AFP-1 was determined to be a glycoprotein (approximately 320 kDa, pl 5.8) composed of a single type of subunit (80 kDa). The high contents of hydrophilic amino acids (Asp, Glu, Lys, Asn, Gln, Arg, Ser, Thr) were also confirmed, showing similarity with antifreeze proteins from other insects.

• Journal of Magnetics
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• v.1 no.2
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• pp.94-100
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• 1996

A hysteresis loop tracer using a pulsed high magnetic field of 113.4 kOe, which is suitable for rare earth based permanent magnets, is constructed. The high pulsed magnetic field is generated by discharging a large capacitance charge (5 mF) with a voltage of 600 V into an air solenoid with the inner diameter of 14 mm, outer diameter of 36 mm and the lingth of 34 mm. A computer simulation method is used for the construction of an electromagnet to optimize the many parameters such as the discharge current, generated pulsed magnetic field intensity, thermal dissipation, capacitance, charged voltage, period of damping oscillation and solenoid geometry. By using the hysteresis loop tracer constructed in this work, we are able to measure hystersis loops of several rare earth based permanent magnets with large values of the remanent magnetization, coercvity and energy product.

• Electrical & Electronic Materials
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• v.9 no.2
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• pp.132-137
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• 1996

Pb(Zr$_{x}$Ti$_{1-x}$ )O$_{3}$ solutions prepared by sol-gel processing with different Zr/Ti ratio were coated on Pt/SiO$_{2}$/Si substrates using spin coating method. Coated films were annealed by rapid thermal annealing at 650.deg. C for 20sec to fabricate Pb(Zr, Ti)O$_{3}$ ferroelectric thin films. Electrical properties of the films such as dielectric constant and loss, ferroelectric hysteresis, fatigue, switching time, and leakage current were measured. Hysteresis of the films with different Zr/Ti ratio yield Pr ranging 10-21.mu.C/cm$^{2}$, E$_{c}$ ranging 37.5-137.5kV/cm. Hysteresis curve was changed from square-type to slim type according to increasing Zr contents. Switching time was faster than 180ns, and leakage current was about 20.mu.A/cm$^{2}$. The film underwent above 10$^{8}$ cycles of reversed polarization showed fatigue with increased coercive field and decreased remnant polarization.tion.

• International Journal of Automotive Technology
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• v.5 no.4
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• pp.297-302
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• 2004

This paper presents the low cycle thermal fatigue of the engine exhaust manifold subject to thermo-mechanical cyclic loading. As a failure of the exhaust manifold is mainly caused by geometric constraints of the less expanded inlet flange and cylinder head, the analysis is based on the exhaust system model with three-dimensional temperature distribution and temperature dependent material properties. The result show that large compressive plastic deformations are generated at an elevated temperature of the exhaust manifold and tensile stresses are remained in several critical zones at a cold condition. From the repetition of these thermal shock cycles, maximum plastic strain range (0.454%) could be estimated by the stabilized stress-strain hysteresis loops. It is used to predict the low cycle thermal fatigue life of the exhaust manifold for the thermal shock test.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.1
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• pp.139-145
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• 2007

This paper presents the low cycle thermal fatigue of the engine exhaust manifold subject to thermomechanical cyclic loadings. The analysis includes the FE model of the exhaust system, temperature dependent material properties, and thermal loadings. The result shows that at an elevated temperature, large compressive plastic deformations are generated, and at a cold condition, tensile stresses are remained in several critical zones of the exhaust manifold. From the repetitions of thermal shock cycles, plastic strain ranges could be estimated by the stabilized stress-strain hysteresis loops. The method was applied to assess the low cycle thermal fatigue for the engine exhaust manifold. It shows a good agreement between numerical and experimental results.

• Journal of Welding and Joining
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• v.20 no.1
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• pp.76-82
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• 2002

In these days, many advanced nations have enforced import restrictions against things emitting electromagnetic wave which has report that it is so harmful. In general, electromagnetic wave is composed of electric wave and magnetic wave. The reflection of electromagnetic wave is mainly reflected by conductive materials and the magnetism loss is generated by magnetic ferrite. The magnetism loss of ferrite is separated by eddy current loss, residual magnetism loss and hysteresis loss. Thermal sprayed coating is intended to manufacture because of simple processes and high efficient electromagnetic wave shielding. The high efficient thermal sprayed coatings were made from the magnetic ferrite materials that characterizes absorption of electromagnetic wave, and the electric conductive materials that characterize emitting of electromagnetic wave. This study was manufactured thermal sprayed coatings to improve absorption-efficiency, and measured the electromagnetic wave shielding efficiency. As the experimental results, high electromagnetic wave shield efficiency was obtained at wave frequency 2GHz to thermal sprayed ferrite coatings manufactured by size distribution range of spray powders, $38~88\mu\textrm{m}$.

• Korean Journal of Materials Research
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• v.10 no.10
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• pp.703-708
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• 2000

As the engine design changes to get high efficiency and performance of commercial diesel engine, surface w wear of the earn follower becomes an important issue as applied load increasing at the contact face between cam follower and cam. We developed the ceramic cam follower made of sili$\infty$n nitride ceramic which was more wear resistant than the cast iron or sintered metal cam follower. Ceramic cam follower was made by direct brazing of thin ceramic disk to steel body using an active brazing alloy without the interlayer. In-situ crowning(R), resulted from the difference of thermal expansion coefficient between ceramic and carbon steel after direct brazing without any stress-relieving inter]ayer, could be controlled. When a earbon steel was heated above $A_{c1}$ point and then c$\infty$led, the expansion curve represented a hysteresis. Appropriate crowning was achieved below the $A_{c1}$ point(about $723^{\circ}C$) and crowning increased with brazing temperature exponentially above the $A_{c1}$ point. Optimum brazing temperature range was from 700 to $720^{\circ}C$. We developed successfully the ceramic cam follower having appropriate crowning and being inexpensive. Also we could successfully control the crowning of ceramic earn follower by hysteresis behavior of thermal expansion of earbon steel during direct brazing process.

• Journal of Environmental Policy
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• v.12 no.2
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• pp.17-32
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• 2013

The potential impact of water temperature on air temperature in response to recent anthropogenic global warming has been noticed. To predict climate, induced change in river aquatic environment, it is necessary to understand the thermal constrains of fish species and the timing of the projected river temperature. As a preliminary study, air-water temperature relationship was analyzed on the basis of the observed data during the time period of 2009-2011 and the number of data corresponds to 873-1083. As a result of analyzing the auto-and cross-correlation coefficient between air-water temperature, high correlation is shown (~0.9). It is also found that the correlation coefficient of air temperature is higher than that of water temperature at the lag time less than approximately 10 days. Observed data was divided into two groups to investigate hysteresis: rising limb and falling limb. For some stations there is strong evidence that hysteresis exist between air-water temperature relationships. Consequently it is recommended that seasonal hysteresis needs to be included in determining an airwater relationship.

• Electrical & Electronic Materials
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• v.9 no.8
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• pp.836-850
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• 1996

In this study, we have analyzed structural analysis and measured ferroelectric characteristics of PZT thin films prepared by sol gel process with different sintering conditions and different Zr/Ti mot%. When the Zr mot% of PZT thin film was increased, it was found that the remanent. polarization and coercive field were decreased and increased, respectively. Also, the maxium dielectric constant of PZT(50/50) thin film was 786.8. We got double hysteresis(anti-fcrroelectric) curve from PbZrO$_{3}$ thin film. As heating rate goes up, pyrochlore phase of PZT thin film was decreased and dielectric and ferroelectric characteristics were improved. As a result of variation of sintering temperature and time 500.deg. C-800.deg. C and 5 sec.-8 hours, respectively, we got optimal sintering temperature and time. The optimium sintering temperature and time of conventional furnace method and rapid thermal processing method were 650.deg. C-700.deg. C for 30-60 minutes and 700.deg. C/20 seconds-2 minutes, respectively.