• Transactions of the Korean Society of Mechanical Engineers
• /
• v.18 no.4
• /
• pp.1031-1038
• /
• 1994

Characteristics of pulsatile flow and heat transfer have been studied numerically in the constant heat flux curved tube with periodic pressure gradient. As the Womersley number increases, the phase difference between the pressure gradient and the cross section averaged axial velocity becomes larger. In case of the Womersley number $\beta = 2$, when cross section averaged axial velocity reaches periodic state with time, the reverse and the natural flow coexist at phase angle, $\lambda = 1.44\pi$ and $\lambda =1.96\pi$. For all the Womersley numbers of present investigation, the time variation of wall temperature near inner wall is higher than that of near outer wall, independent of phase angle.

• Coupled systems mechanics
• /
• v.9 no.5
• /
• pp.411-432
• /
• 2020

This research is devoted to the study of plane wave propagation in homogeneous transversely isotropic (HTI) magneto-thermoelastic rotating medium with combined effect of Hall current and two temperature due to multi-dual-phase lag heat transfer. It is analysed that, for 2-D assumed model, three types of coupled longitudinal waves (quasi-longitudinal, quasi-transverse and quasi-thermal) are present. The wave characteristics like phase velocity, specific loss, attenuation coefficients, energy ratios, penetration depths and amplitude ratios of transmitted and reflected waves are computed numerically and illustrated graphically and compared for different theories of thermoelasticity. Some particular cases are also derived from this research.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.20 no.11
• /
• pp.3695-3705
• /
• 1996

We designed the hot wind tunnel to reproduce the conditions of utility boiler and carried out its performance test, in order to investigate the particulate two-phase flow behaviour, the fouling and heat transfer characteristics to the heat exchanger. The hot wind tunnel introduces the control system to control the temperature in the test section. The particle is injected into the hot gas stream. The fouling probe (cylindrical tube) is positioned normal to the particulate gas-particle two-phase flow and cooled by the air. The temperature of gas and cooling air, and temperature in the fouling probe are measured as a function of time, giving the local and averaged heat transfer and fouling factor. The shape of particulate deposition adhered to the fouling probe is also observed.

• Transactions of Materials Processing
• /
• v.12 no.4
• /
• pp.302-307
• /
• 2003

Hot rolled strip is cooled by air and water in Run-Out-Table. In this process, phase transformation and shape deformation occurs due to temperature drop. Because of un-ideal cooling condition of ROT, irregular shape deformation and phase transformation arise in the strip. which affect the strip property and lead to the residual stress of strip. And these exert effects on the following processes, coiling process, coil cooling process, and re-coiling process. Through these processes, the residual stress becomes higher and severe. For the prediction of residual stress distribution and shape deformation of final product, Finite element(FE) based model was used. It consists of non-steady state heat transfer analysis, elasto-plastic analysis. thermodynamic analysis and phase transformation kinetics. Successive FEM simulation were applied from ROT process to coil cooling process. In each process simulation, previous process simulation results were used for the next process simulation. The simulation results were matched well with the experimental results.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.14 no.2
• /
• pp.168-174
• /
• 2002

In order to obtain a new heat transfer fluid having a high thermal capacity, micro-capsules of a phase-change material can be a successful candidate to be added into water. In this study, 25, 50, 100, and $200\mu$m diameter micro-encapsulated Lauric acids were tested by a differential scanning calorimeter. The Lauric acid itself had a single freezing curve, but the micro-encapsulated Lauric acid had double freezing curves. The second freezing dominated for $25\mu$m diameter Lauric acids. But the first freeing energy became big as the size of the capsule increased.

• Solar Energy
• /
• v.15 no.2
• /
• pp.39-46
• /
• 1995

Reported is a visual and quantitative experimental study on the two-phase flow and heat transfer characteristics of miniature two-phase closed thermosyphons with wire inserts. The visual study clearly demonstrated the two-phase flow involved in such thermosyphons. In the quantitative study, the effects on the heat transfer rate of the insert wire diameter, the ratio of heated-length to cooled length and the applied heat flux were investigated.

• Journal of Korea Society of Digital Industry and Information Management
• /
• v.10 no.4
• /
• pp.89-96
• /
• 2014

MANET has been applied to a wide variety of areas because it has advantages which can build a network quickly in a difficult situation to build a network. However, it is become a victim of malicious nodes because of characteristics such as mobility of nodes consisting MANET, limited resources, and the wireless network. Therefore, it is required to lightweight attack detection technique which can accurately detect attack without causing a large burden to the mobile node. In this paper, we propose a multistage attack detection techniques that attack detection takes place in routing phase and data transfer phase in order to increase the accuracy of attack detection. The proposed attack detection technique is composed of four modules at each stage in order to perform accurate attack detection. Flooding attack and packet discard or modify attacks is detected in the routing phase, and whether the attack by modification of data is detected in the data transfer phase. We assume that nodes have a public key and a private key in pairs in this paper.

• International conference on construction engineering and project management
• /
• 2007.03a
• /
• pp.498-508
• /
• 2007

The Build-Transfer-Lease (BTL) projects have rapidly increased under the Government support during recent years. This paper presents the risk analysis of factors affecting BTL projects in the initial phase. This study resulted in 10 significant risk factors influencing on each phase of BTL projects and then factors were grouped into each phase. The sensitivity analysis was also performed to identify risk factors with more significant influence on BTL projects. The results may useful to practitioners in order to cope with risks in initial phase of BTL projects. The paper resulted in the distribution of risks to project parties, thus it can be used as standards for risk assignment to competent authorities and private enterprises of BTL projects.

• Polymer(Korea)
• /
• v.26 no.6
• /
• pp.759-766
• /
• 2002

Regular, spherical and isotropic open-microcellular foams having low density were prepared by the high internal phase emulsion (HIPE) polymerization mainly composed of styrene monomer and water The effects of Polymerization conditions. such as the content of water, divinylbenzene as a crosslinking agent and dodecane as a chain transfer agent, were investigated based on the tell size and foam properties. The microstructural morphology was observed using scanning electron microscopy (SEM) and the compression modulus of the foam was evaluated using compression test. The dropwise feeding of the aqueous phase into the oil phase was more effective than the batch feeding in producing the uniform and stable foam. Agitation speed and surfactant strongly influenced on the cell size and the window size between water droplets. Introduction of chain transfer agent increased the cell size, whereas it decreased the window size. Compression modulus increased with the crosslinking agent, but decreased with the chain transfer agent.

• BMB Reports
• /
• v.43 no.8
• /
• pp.535-540
• /
• 2010

Patients with hemorrhagic fever with renal syndrome (HFRS) often exhibit altered serum lipid and lipoprotein profile during the oliguric phase of the disease. Serum lipid and lipoprotein profiles were assessed during the oliguric and recovery phases in six male patients with HFRS. In the oliguric phase of HFRS, the apolipoprotein (apo) C-III content in high-density lipoproteins (HDL) was elevated, whereas the apoA-I content was lowered. The level of expression and activity of antioxidant enzymes were severely reduced during the oliguric phase, while the cholesteryl ester transfer protein activity and protein level were unchanged between the phases. In the oliguric phase, electromobility of $HDL_2$ and $HDL_3$ was faster than in the recovery phase. Low-density lipoprotein (LDL) particle size was smaller and the distribution was less homogeneous. Patients with HFRS in the oliguric phase had severely modified lipoproteins in composition and metabolism.