• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
• /
• 1999.02a
• /
• pp.51-53
• /
• 1999

The crystallization mechanism of an amorphous $Bi_{2}$$Sr_{2}$$Ca_{2 x}$$Cd_{x}$$Cu_{3}$$O_{y}$ phase were studied from the relations between crystallization and volume changes by dilatometry. Further, the effect of addition of CdO on the crystallization mechanism and superconductivity was discussed. The shrinkage of the amorphous $Bi_{2}$$Sr_{2}$$Ca_{2 x}$$Cd_{x}$$Cu_{3}$$O_{y}$ occurred with the crystallization of $Bi_{2}$$Sr_{2}$Cu$O_{6}$ phase decrease with increasing CdO content with a minimum at x=0.4. Better superconductivity was obtained in the specimens formation less amount of the$Bi_{2}$$Sr_{2}$Cu$O_{6}$ phase during the crystallization process.

• Structural Engineering and Mechanics
• /
• v.29 no.6
• /
• pp.659-671
• /
• 2008

A procedure to analyse the space frame structure fixed at base as well as resting on sliding bearing using total or absolute displacement in dynamic equation is developed. In the present method, the effect of ground acceleration is not considered as equivalent force. Instead, the ground acceleration is considered as a known value in the acceleration vector at degree of freedom corresponding to base of the structure when the structure is in non-sliding phase. When the structure is in sliding phase, only a force equal to the maximum frictional resistance is applied at base. Also, in this method, the stiffness matrix, mass matrix and the damping matrix will not change when the structure enters from one phase to another. The results obtained from the present method using absolute displacement approach are compared with the results obtained from the analysis of structure using relative displacement approach. The applicability of the analysis is also demonstrated to obtain the response of the structure resting on sliding bearing with restoring force device.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.14 no.5
• /
• pp.408-414
• /
• 2002

The instability of two-phase loop thermosyphons (TLTs) was investigated experimentally. Three orifice type inserts were used to study the effect of change in the pressure drop in the flow channel of the TLT on the flow instability and temperature fluctuation. It is observed that a decrease in the size of the orifice insert from 3.7mm (no insert) to 0.71mm drastically reduced the fluctuation of the temperature, especially at the evaporator section of the TLT With the orifice type insert of 0.71 mm for the TLT, the overall temperature fluctuation was almost completely eliminated, especially at higher power input to the TLT.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.7 no.5
• /
• pp.81-88
• /
• 1999

In order to understand the relationship between the phase angle of piston ring and oil consumption was measured by analyzing $CO_2$concentration in exhaust gas. The use of hydrogen fuel not gasoline makes this possible because all of the carbon component in exhaust gas can be assumed to be produced from oil. As a result of experiment, it is known that the oil consumption varies periodically and a specific location of ring end gap was found at each peak of oil consumption. Therefore, it was found that the oil consumption was not constant even at the same operating conditions and this is because the relative locations of top and 2'nd ring end gap change arbitrarily.

• Structural Engineering and Mechanics
• /
• v.77 no.3
• /
• pp.315-327
• /
• 2021

Here, in this research we have studied a two dimensional problem in a homogeneous orthotropic magneto-thermoelastic medium with higher order dual-phase-lag heat transfer with combined effects of rotation and hall current in generalized thermoelasticity due to time harmonic sources. As an application the bounding surface is subjected to uniformly distributed and concentrated loads (mechanical and thermal source). Fourier transform technique is used to solve the problem. The expressions for displacement components, stress components and temperature change are derived in frequency domain. Numerical inversion technique has been used to obtain the results in physical domain. The effect of frequency has been depicted with the help of graphs.

• Nuclear Engineering and Technology
• /
• v.39 no.2
• /
• pp.123-128
• /
• 2007

In order to apply a static fault-tree (FT) method to a system or a plant whose configuration changes dynamically, condition gates and a post processing method are used to effectively accommodate these changes. An operator's performance change, which can be caused by these configuration changes, should also be considered to assess the risk to a plant in a more realistic manner. This study aims to develop an integrated framework to accommodate various configuration changes and their effect on an operator’s performance by using the FT model. We applied a condition-based human reliability assessment (CBHRA) method to consider various conditions endured by an operator. That is, we integrated the CBHRA method with the conventional post processing method for modeling the system configuration changes. The effect of the condition monitoring systems installed in a plant is also considered. In this study, we show an example application of the integrated framework to a probabilistic safety assessment for the shutdown phase of a nuclear power plant.

• The Journal of Korea Robotics Society
• /
• v.4 no.4
• /
• pp.320-326
• /
• 2009

This paper proposed a new magnetic field detection algorithm to detect metal pieces in food producing processes. This algorithm can detect mixed metal pieces by sensing magnetic field. Some metal pieces are passed through an over-current circuit to magnetize them. The magnetic field sensor can detect the change in the magnetic field on theconveyor belt caused by the flow of the metal pieces in the food product. However, such a method detects the output of signals that change their amplitude and phase according to the movement of the conveyor belt with the food product, in which the equilibrium of the positive signal that is created in the receiver coil loses its balance due to the magnetized material. This includes not only the signal elements resulting from the effect of the alternating magnetic fields of the mixed metals, but also the signal elements resulting from the effect of the alternating magnetic fields of the examined object itself.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.2 no.3
• /
• pp.208-217
• /
• 1990

A rectangular test section is devised by assuming two dimensional melting of a solid phase change material heated from two sides which are maintained at constant temperature and allowing a free expansion due to density difference between solid and liquid. The timewise melting shape is recorded photographically by the shadow graph method for several experimental conditions. The analysis shows that the melting process consists of four regimes. At first, the pure conduction heat transfer is dominant, and as time goes by natural convection grows and plays a role greatly. Experiments are carried out varying not only the wall temperature but height of the wall. Each effect of them on the melting process is obtained in the form of combination of dimensionless parameters, $Ste^{0.8}\;FoRa^{0.2}$. An algebraic correlation is suggested, which predicts the melted fraction well.

• Journal of the Korean Ceramic Society
• /
• v.31 no.3
• /
• pp.305-311
• /
• 1994

In this paper, a change of fracture toughness and hardness in PZT-PYW ceramics system before and after poling treatment was measured to investigate the effect of composition on the mechanical properties in PZT-PYW ceramics. The hardness of the PZT-PYW ceramics increased with increasing mole fraction of PYW. The fracture toughness achieved maximum values for x=0.03. Both of the hardness and the fracture toughness also increased with poling treatment. The variation of both hardness and fracture toughness with increasing PYW mole fracture was explained by the change in microstructures such as grain size and second phase. The difference in hardness and fracture toughness in the electrically poled and unpoled specimens was also explained on the bases of internal stress.

• Bulletin of the Korean Chemical Society
• /
• v.23 no.12
• /
• pp.1749-1753
• /
• 2002

The effect of concentration fluctuations on the changes of azimuth and ellipticity are analytically obtained in a binary chiral liquid mixture, when the incident light is completely linearly polarized above (or below) the horizontal at 45°. The important results are as follows;(1) When the binary liquid is in the critical region far from the cr5itical point, the ellipticity change is proportional to isothermal compressibility factor and the fifth order of frequency and shows the logarithmic divergence. (2) In the case that the system is in the critical region far from the critical point, the azimuth change is solely due to the molecular contribution. As the system approaches to the critical point, the effect of fluctuations becomes important. If it is in the extreme close to the critical point, the term due to the concentration fluctuations is comparable to or larger than the molecular contribution.