• Nuclear Engineering and Technology
• /
• v.51 no.1
• /
• pp.45-53
• /
• 2019

Thermal-hydraulic passive safety systems (PSSs) are incorporated into many advanced reactor designs on the bases of simplicity, economics and inherent safety nature. Several factors among which are the critical parameters (CPs) that influence failure and reliability of thermal-hydraulic (t-h) passive systems are now being explored. For simplicity, it is assumed in most reliability analyses that the CPs are independent whereas in practice this assumption is not always valid. There is need to critically examine the dependency influence of the CPs on reliability of the t-h passive systems at design stage and in operation to guarantee safety/better performance. In this paper, two multivariate analysis methods (covariance and conditional subjective probability density function) were presented and applied to a simple PSS. The methods followed a generalized procedure for evaluating t-h reliability based on dependency consideration. A passively water-cooled steam generator was used to demonstrate the dependency of the identified key CPs using the methods. The results obtained from the methods are in agreement and justified the need to consider the dependency of CPs in t-h reliability. For dependable t-h reliability, it is advisable to adopt all possible CPs and apply suitable multivariate method in dependency consideration of CPs among other factors.

• Proceedings of the IEEK Conference
• /
• 2003.07b
• /
• pp.667-670
• /
• 2003

Ni-silicide has low thermal stabiliy. This point is obstacle to apply NiSi to devices. So In this paper, we have studied for obtain thermal stability and analysis of dopant dependency of NiSi. And then we applied Ni-silicide to devices. To improvement of thermal stability, we deposit Ni70/Co10/Ni30/TiN100 to sample. Co midlayer is enhanced thermal stability of NiSi. Co/Ni/TiN, this structure show very difference between n-poly and p-poly in sheet resistance. But Ni/Co/Ni/TiN, structure show less difference. Also junction leakage is good.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.17 no.4
• /
• pp.396-403
• /
• 2004

The dielectric properties of Y-ray irradiated and thermally aged polyetheretherketone (PEEK) have been investigated. Results of the temperature dependency of dielectric properties indicated that the glass transition temperature of aged PEEK increased as radiative and thermal ageing. The frequency dependency of dielectric properties implied that the magnitude of radiation and thermal induced dipoles, ions increased as radiative and thermal ageing. The values of relaxation intensity calculated using Cole-Cole's circular arc can be useful for evaluation of degradation level of PEEK.

• Structural Engineering and Mechanics
• /
• v.44 no.3
• /
• pp.289-303
• /
• 2012

Existing plane stress solutions for thin plates and disks have shown several qualitative features which are difficult to handle with the use of commercial numerical codes (non-existence of solutions, singular solutions, rapid growth of the plastic zone with a loading parameter). In order to understand the effect of temperature and pressure-dependency of the yield criterion on some of such features as well as on the distribution of residual stresses and strains, a semi-analytic solution for a thin hollow disk fixed to a rigid container and subject to thermal loading and subsequent unloading is derived. The material model is elastic-perfectly/plastic. The Drucker-Prager pressure-dependent yield criterion and the equation of incompressibity for plastic strains are adopted. The distribution of residual stresses and strains is illustrated for a wide range of the parameter which controls pressure-dependency of the yield criterion.

• Bulletin of the Korean Chemical Society
• /
• v.23 no.2
• /
• pp.325-329
• /
• 2002

In this study, the dependency of the behavior of propagating front on the reaction condition in frontal polymerization reaction has been studied. We have used some multifunctional acrylates as a monomer and ammonium persulfate as an initiator for the polymerization reactions. In frontal polymerization, a method of producing polymeric materials via a thermal front that propagates through the unreacted monomer/initiator solution, the behavior of self propagating front shows various dynamic patterns depending on the reaction condition. We have obtained some spin modes of propagating front in the number of 'hot spots' or 'spin heads' by changing the reaction condition. The effect of the reactor tube diameter on the mode of propagating front has also been studied by using some reactor tubes with different size of tube diameter and it has been examined in some detail by adopting an experimental method of two-tubes system.

• Korean Journal of Materials Research
• /
• v.25 no.12
• /
• pp.678-682
• /
• 2015

The electrical property of polymer matrix composites with added carbon powder is studied based on the temperature dependency of the conduction mechanism. The temperature coefficient of the resistance of the polymer matrix composites below the percolation threshold (x) changed from negative to positive at 0.20 < x < 0.21; this trend decreased with increasing of the percolation threshold. The temperature dependence of the electrical property(resistivity) of the polymer matrix composites below the percolation threshold can be explained by using a tunneling conduction model that incorporates the effect of the thermal expansion of the polymer matrix composites into the tunneling gap. The temperature coefficient of the resistance of the polymer matrix composites above the percolation threshold has a positive value; its absolute value increased with increasing volume fraction of carbon powder. By assuming that the electrical conduction through the percolating paths is a thermally activated process and by incorporating the effect of thermal expansion into the volume fraction of the carbon power, the temperature dependency of the resistivity above the percolation threshold can be well explained without violating the universal law of conductivity.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.22 no.2
• /
• pp.151-157
• /
• 2009

This paper reports the resistance change of conductive carbon nanotube (CNT) thin-films according to the temperature variation. Resistance of conductive CNT thin-films intrinsically has good thermal sensitivity, but shows environmental dependency. In order to reduce environmental effects, we spin-coated polydimethylsiloxane (PDMS) on the conductive CNT thin-films. We observed that conductive CNT thin-films with a PDMS encapsulation layer showed little environmental dependency, but more linear and stable temperature dependencies. If proper encapsulation is provided, conductive CNT thin-films can be used for temperature sensor applications.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
• /
• 2003.02a
• /
• pp.167-170
• /
• 2003

The thermal and hydraulic characteristics of the cooling passage for HTS power cable should be carefully investigated to get the highly reliable and economic operation. In this study, the pressure drop and temperature change of the coolant flowing the corrugated passage was estimated using the simple one-dimensional approach, and the temperature distribution in the radial direction was calculated. The results show the dependency of the mass flow rate, thermal conductivities on the cooling performance of the HTS cable.

• Nuclear Engineering and Technology
• /
• v.50 no.5
• /
• pp.731-737
• /
• 2018

In this research paper, the thermal transport in thorium dioxide is investigated by using nonequilibrium molecular dynamics. The thermal conductivity of bulk thorium dioxide was measured to be 20.8 W/m-K, confirming reported values, and the phonon mean free path was estimated to be between 7 and 8.5 nm at 300 K. It was observed that the thermal conductivity of thorium dioxide shows a strong dependency on temperature; the highest thermal conductivity was estimated to be 77.3 W/m-K at 100 K, and the lowest thermal conductivity was estimated to be 4.3 W/m-K at 1200 K. In addition, by simulating thorium dioxide structures with different lengths at different temperatures, it was identified that short wavelength phonons dominate thermal transport in thorium dioxide at high temperatures, resulting in decreased intrinsic phonon mean free paths and minimal effect of boundary scattering while long wavelength phonons dominate the thermal transport in thorium dioxide at low temperatures.

• Steel and Composite Structures
• /
• v.22 no.1
• /
• pp.91-112
• /
• 2016

In this paper, post-buckling behavior of sandwich plates with functionally graded (FG) face sheets under uniform temperature rise loading is examined based on both sinusoidal shear deformation theory and stress function. It is supposed that the sandwich plate is in contact with an elastic foundation during deformation, which acts in both compression and tension. Thermo-elastic non-homogeneous properties of FG layers change smoothly by the variation of power law within the thickness, and temperature dependency of material constituents is considered in the formulation. In the present development, Von Karman nonlinearity and initial geometrical imperfection of sandwich plate are also taken into account. By employing Galerkin method, analytical solutions of thermal buckling and post-buckling equilibrium paths for simply supported plates are determined. Numerical examples presented in the present study discuss the effects of gradient index, sandwich plate geometry, geometrical imperfection, temperature dependency, and the elastic foundation parameters.