• Bulletin of the Korean Chemical Society
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• v.28 no.9
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• pp.1477-1484
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• 2007

Artificial neural networks (ANNs), for a first time, were successfully developed for the prediction partial molar heat capacity of aqueous solutions at infinite dilution for various polar aromatic compounds over wide range of temperatures (303.55-623.20 K) and pressures (0.1-30.2 MPa). Two three-layered feed forward ANNs with back-propagation of error were generated using three (the heat capacity in T = 303.55 K and P = 0.1 MPa, temperature and pressure) and six parameters (four theoretical descriptors, temperature and pressure) as inputs and its output is partial molar heat capacity at infinite dilution. It was found that properly selected and trained neural networks could fairly represent dependence of the heat capacity on the molecular descriptors, temperature and pressure. Mean percentage deviations (MPD) for prediction set by the models are 4.755 and 4.642, respectively.

• Journal of Pharmaceutical Investigation
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• v.36 no.1
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• pp.31-38
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• 2006

Using a Rheometries Dynamic Analyzer (RDA II), the dynamic viscoelastic properties of a semi-solid ointment base (vaseline) in large amplitude oscillatory shear flow fields were measured over a temperature range of $25{\sim}45^{\circ}C$ and the linear viscoelastic behavior in small amplitude oscillatory shear flow fields was investigated over a wide range of angular frequencies. In this article, the nonlinear viscoelastic behavior was reported from the experimentally obtained data and the effect of temperature on this behavior was discussed in detail. In addition, the angular frequency and temperature dependencies of a linear viscoelastic behavior were explained. Finally, the applicability of a time-temperature superposition principle originally developed for polymeric materials was examined using a shift factor. Main results obtained from this study can be summarized as follows : (1) At very small strain amplitude region, vaseline shows a linear viscoelastic behavior independent of the imposed deformation magnitudes. Above a critical strain amplitude $({\gamma}_{0}=0.1{\sim}0.2%)$, however, vaseline exhibits a nonlinear viscoelastic behavior ; indicating that both the storage modulus and dynamic viscosity are sharply decreased with increasing deformation magnitude. (2) In large amplitude oscillatory shear flow fields, an elastic behavior (storage modulus) has a stronger strain amplitude dependence and begins to show a nonlinear behavior at a smaller strain amplitude region than does a viscous behavior (dynamic viscosity). (3) In small amplitude oscillatory shear flow fields, the storage modulus as well as the loss modulus are continuously increased as an increase in angular frequency and an elastic nature is always superior to a viscous behavior over a wide range of angular frequencies. (4) A time-temperature superposition principle can successfully be applicable to vaseline. This finding allows us to estimate the dynamic viscoelastic behavior of vaseline over an extraordinarily extended range (11 decades) of angular frequencies inaccessible from the experimentally measured range (4 decades).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.335-338
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• 1997

Platinum-Cobalt alloy thin films were deposited on A1$_2$O$_3$substrate by magnetron cosputtering for RTD temperature sensors with wide temperature ranges. We made Pt-Co alloy resistance patterns on the A1$_2$O$_3$substrate by lift-off method and fabricated Pt-Co alley RTD temperature sensors by using Pt-wire, Pt-paste. We investigated the physical and electrical characteristics of theme films under various conditions, input power, working vacuum, annealing temperature and time, and also after annealing these films. The resistivity and sheet resistivity of these films were decreased with increasing the annealing temperature. At input power of Pt : 4.4 W/cm$^2$, Co : 6.91 W/cm$^2$, working vacuum of 10 mTorr and annealing conditions of 800$^{\circ}C$ and 60 min, the resistivity and sheet resistivity of Pt-Co thin films was 15${\mu}$$\Omega$$.$cm and 0.5$\Omega$/ , respectively, and the TCR value of Pt-Co alloy thin films with thickness of 3000${\AA}$ was 3740ppm/$^{\circ}C$ in the temperature range of 25∼600$^{\circ}C$. These results indicate that Pt-Co alloy thin films hove potentiality for the RTD with wide temperature ranges.

• Journal of Magnetics
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• v.12 no.1
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• pp.7-11
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• 2007

We confirm the validity of the analytic expression for the temperature of the Joule heated nano-wire [C.-Y. You et al. Appl. Phys. Lett. 89, 222513 (2006)] with finite element method. The temperature of the Joule heated nano-wire is essential information for the research of the current induced domain wall movement. The analytic expression includes an adjustable parameter which must be determined. Since the physical origin of the adjustable parameter is simplification of the heat source profile, the validity of the analytic expression must be examined for wide range of the nano-wire structure. By comparison with this analytic expression with the results of full numerical finite element method, the adjustable parameter has been determined. The numerically confirmed adjustable parameter values are in the range of 0.60$\sim$0.69, which is well matched with the theoretically expected one. Furthermore, it is found that the adjustable parameter is a slow varying function of the nano-wire geometry. Based on this numerical confirmation, we can apply the analytic expression for the wide range of the nano-wire geometry with proper adjustable parameters.

• Journal of the Korean Solar Energy Society
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• v.28 no.5
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• pp.78-84
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• 2008

Heat pipes are considered to be promising candidates to enhance the heat transport capability of evacuated solar collectors in a wide temperature range. The working fluid must be selected properly considering various operating conditions of heat pipes for medium-high temperature range to avoid dry-out, local overheating, and frozen failure. The advantage of using binary mixture as heat pipe working fluid is that it can extend operating temperature range of the system as it can overcome operating temperature limit of a single fluid. Various operating temperature ranges were imposed in the experiments to simulate the actual operation of solar collectors using water-ethanol binary mixture. Tests were conducted for the coolant temperature range of -10$^{\circ}C$ to 120$^{\circ}C$, and mixing ratio range was from 0 to 1 based on mass fraction.

• Proceedings of the IEEK Conference
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• 2002.07a
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• pp.74-77
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• 2002

In this paper we present a novel temperature compensated Hall effect power IC for accurate operation of wide temperature and high current drive of the motor coil. In order to compensate the temperature dependence of Hall sensitivity with negative temperature coefficient(TC), the differential amplifier has the gain consisted of epi-layer resistor with positive TC. The material of Hall device and epi-resistor is epi-layer with the same mobility. The variation of Hall sensitivity is -38% at 150$^{\circ}C$ and 88% at - 40$^{\circ}C$. But the operating point(B$\sub$op/) and release point(B$\sub$RP/) of the Hall power IC are within ${\pm}$25%. The experimental results show very stable and accurate performance over wide temperature range of -40$^{\circ}C$ to 125$^{\circ}C$.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.1495-1498
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• 2008

We proposed driving method with variable integration time for ambient light sensing. One operation period of the proposed driving method consists of several sub-integration periods with variable integration time which can enlarge dynamic range of ambient light sensing circuit. Temperature dependent characteristic of p-intrinsic-metal (p-i-m) diode can be compensated using the proposed driving method.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.342-342
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• 2006

Atomic force microscope (AFM) enables us to stretch a single polymer chain by picking it at its two modified termini. Using this method called "nanofishing," we have studied statistical properties of single polymer chains. A force-extention curve obtained for a polystyrene with thiol termini in a cyclohexane showed a good agreement with a worm-like chain (WLC) model, and thus gave microscopic information about entropic elasticity. In this report, the experiments were performed at wide-range temperatures, resulting in wide-range solvent qualities from poor to good solvent condition. The temperature dependence of statistical properties of polystyrene was examined. The coil-strand transformation realized in a poor solvent was also discussed.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.5
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• pp.502-507
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• 1999

An improved, accurate and reliable high-voltage measuring system utilizing a bushing-type capacitor is proposed in this study. This system measures voltages and phase angles of three-phase 22.9 kV power distribution lines and provides enough current to charge a battery for a motor-driven load switch and to operate the measuring and communication circuits for the distribution automation. For reliability, epoxy resin was used as the dielectric material of the bushing-type capacitor since the dielectric strength of epoxy resin is very stable over the wide range of temperature. Capacitances were investigated and found to be stable over the wide range of temperature and applied voltage, and the results indicate that the proposed measurement system is very reliable.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.5
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• pp.1679-1688
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• 1996

Laser flash technique was applied to measure thermal properties of FGM made by a CVD method. System stability and reproducibility of this measuring system were proved and calibrated with glassy carbon used as reference material. Specimens was prepared by cutting FGM diagonally. Measurements were performed for a wide range of temperatures up to 1500K. Relative heat capacity of the FGM specimen was scattered with in $\pm$13% at room temperature and at high temperature above 1200K, and $\pm$3% at medium temperature range. On the other hand, thermal diffusivity data showed excellent reproducibility and stability through the whole temperature range. In conclusion, the multi-target radiometer can be applied to measure the thermal properties of non homogeneous materials like FGM.