• Korean Journal of Acupuncture
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• v.31 no.3
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• pp.125-135
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• 2014

Objectives : Warm needling is the method combining the effects of acupuncture and moxibustion. In modern clinics, warm needling is only affected by treatment time or frequency. We need to study the physical characteristics of warm needles currently used in clinics in order to develop more efficient and economical treatments. Methods : We collected various warm needle specimens and analyzed chemical constitutions, measured heat transfer velocity, micro Vicker's hardness and specific resistance. We studied the relationship between heat transfer velocity and micro Vicker's hardness as well as that between heat transfer velocity and specific resistance. Results : The heat transfer velocity of the Silver_HL was 3.3 mm/sec, of the Au alloy group was 1.3~2.6 mm/sec, and Silver_IN, Silver_ZK and SS groups was less than 0.3 mm/sec. We therefore concluded that the needle composed of Ag has the best heat transfer velocity. In the Micro Vicker's hardness test, Vicker's hardness of the Au alloy group was 159~170 Hv, of Silver_HL was 181 Hv, and of the Silver_IN, Silver_ZK, SS group was 450.8~519 Hv. In the Silver_IN, Silver_ZK and SS groups, hardness was inversely proportial to thermal conductivity. In the specific resistance test, the specific resistance of Silver_HL was the lowest, that of the Au alloy group was the second lowest, and that of the Silver_IN, Silver_ZK, SS groups were the highest. Conclusions : We concluded that the needle composed of Ag has the best heat transfer velocity, highest electric conductivity and thermal conductivity, therefore the needle composed of Ag is suitable for warm needling.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.2
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• pp.129-135
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• 2011

An ice-making model has been developed and analyzed in this study. The effects of the following on the ice formation on the outer surface of a tube in which a refrigerant flows and boils are numerically investigated: thermal resistance of the refrigerant and thermal resistance of the ice formed on the outer surface of the tube. The ice thickness and related variables are analyzed in the case of the refrigerants R22 and R134a by using the expressions for phase-change heat transfer and boiling heat transfer coefficient. Vapor qualities of the refrigerants range from 0 to 0.8. As a result, up to the first 30 min, the internal convection resistance is higher than the thermal resistance of the ice on the external surface of the tube. However, after about 30 min, the thermal resistance of the ice increases remarkably due to the increase in the ice thickness. Thus, the heat flux to the refrigerant decreases, and further, the refrigerant quality and the boiling heat transfer coefficient also decrease. As the heat transfer coefficient of R22 is higher than that of R134a, the mass of the ice formed when R22 is used is higher than that formed when R134a is used.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.6
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• pp.1087-1094
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• 2010

We have developed a cylindrical multi-terminal capacitive-conductive sensor that could be attached to the internal surface of cooling system pipe to evaluate capacitance and conductivity of heat transfer fluid. It was used as measuring system to diagnose insulating condition, by which was kept a insulating resistance of inner stack and at the same time was cooled electrochemical heat of reaction of FCEV(fuel cell electric vehicle) stack that used a compressed hydrogen gas reacting with oxygen in accordance with variation on thermal degradation of nonconductive heat transfer fluid. Also to assess diagnosis characteristics of heat transfer fluid, i.e. coolant, we have performed accelerated aging test using developed sensor attached to cooling system. Consequently, it was measured dielectric and electric resistance of coolant to estimate and analyse for dielectric properties by degradation condition.

• International Journal of Korean Welding Society
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• v.2 no.1
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• pp.1-10
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• 2002

The thermal contact conductance at different temperatures and with different electrode forces and zinc coating morphology was measured by monitoring the infrared emissions from the one dimensionally simulated contact heat transfer experiments. The contact heat transfer coefficients were presented as a function of the harmonic mean temperature of the two contacting surfaces. Using these contact heat transfer coefficients and experimentally measured temperature profiles, the electrical contact resistivities both for the faying interface and electrode-workpiece interface were deduced from the numerical analyses of the one dimension simulation welding. It was found that the average value of the contact heat transfer coefficients for the material with zinc coating (coating weight from 0 g/$mm^2$to 100 g/$mm^2$) ranges from 0.05 W/$mm^2$$^{\circ}C$ to 2.0 W/$mm^2$$^{\circ}C$ in the temperature range above 5$0^{\circ}C$ harmonic mean temperature of the two contacting surfaces. The electrical contact resistivity deduced from the one dimension simulation welding and numerical analyses showed that the ratio of electrical contact resistivity at the laying interface to the electrical contact resistivity at the electrode interface is smaller than one far both bare steel and zinc coated steel.

• Steel and Composite Structures
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• v.21 no.2
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• pp.357-371
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• 2016

Column base connections are critical components in steel structures because they transfer axial forces, shear forces and moments to the foundation. Exposed column bases are quite commonly used in low- to medium-rise buildings. To investigate shear transfer in exposed column base plates, four large scale specimens were subjected to a combination of axial load (compression or tension) and lateral shear deformations. The main parameters examined experimentally include the number of anchor rod, arrangement of anchor rod, type of lateral loading, and axial force ratio. It is observed that the shear resisting mechanism of exposed column base changed as the axial force changed. When the axial force is in compression, the resisting mechanism is rotation type, and the shear force will be resisted by friction force between base plate and mortar layer. The specimens could sustain inelastic deformation with minimal strength deterioration up to column rotation angle of 3%. The moment resistance and energy dissipation will be increased as the number of anchor rods increased. Moreover, moment resistance could be further increased if the anchor rods were arranged in details. When the axial force is in tension, the resisting mechanism is slip type, and the shear force will be resisted by the anchor rods. And the shear resistance was reduced significantly when the axial force was changed from compression to tension. The test results indicated that the current design approach could estimate the moment resistance within reasonable acceptance, but overestimate the shear resistance of exposed column base.

• Fire Science and Engineering
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• v.27 no.6
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• pp.26-31
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• 2013

This study, to evaluate the technology of the fire resistance design of Reinforced Concrete columns based on fire resistance performance design, was suppose to use as basic data for performance design through a measure of temperature and deformation using heat transfer analysis and Heat-load test of the Reinforced Concrete columns as parameter is the axial load ratio. In accordance with axial load without eccentricity, the load ratio of 0.30, 0.35, 0.40 and 0.47 were imposed on columns. As a result of this study, 0.40 or more of axial load ratio can be ensured that the fire resistance performance was considered satisfactory.

• Interaction and multiscale mechanics
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• v.1 no.4
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• pp.397-409
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• 2008

The interfacial thermal resistance of pristine and defective carbon nanotubes (CNTs) embedded in low-density polyethylene matrix is studied in this paper. Interface thermal resistance in nanosystems is one of the most important factors that lead to the large variation in thermal conductivities in literature and the novelty of this paper lies in the estimation of the interfacial thermal resistance for defective nanotubes-systems. Thermal properties of CNT nanostructures are estimated using molecular dynamics (MD) simulations and the simulations were carried out for various temperatures by rescaling the velocities of carbon atoms in the nanotube. This paper also deals with the mesoscale thermal conductivities of composite systems, using effective medium theories by considering the size effect in the form of interfacial thermal resistance and also using the conventional micromechanical methods like Hashin-Shtrikman bounds and Wakashima-Tsukamoto estimates.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.7
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• pp.512-520
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• 2007

The design of a ground-source heat pump system includes specifications for a ground loop heat exchanger where the heat transfer rate depends on the effective thermal conductivity of the ground and the effective thermal resistance of the borehole. To evaluate these heat transfer properties, in-situ thermal response tests on four vertical test boreholes with different grouting materials were conducted by adding a monitored amount of heat to circulating water. The line-source method is applied to the temperature rise in an in-situ test and extended to also give an estimate of borehole effective thermal resistance. The effect of increasing thermal conductivity of the grouting materials from 0.818 to $1.104W/m^{\circ}C$ resulted in overall increases in effective thermal conductivity by 15.8 to 56.3% and reductions in effective thermal resistance by 13.0 to 31.1%.

• Journal of Power System Engineering
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• v.17 no.2
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• pp.70-77
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• 2013

An experimental study was carried out to understand the heat transfer performance of a miniature loop heat pipes using water-based copper nanoparticles suspensions as the working fluid. The suspensions consisted of deionized water and copper nanoparticles with an average diameter of 80 nm. Effects of the cupper mass concentration and the operation pressure on the average evaporation and condensation heat transfer coefficients, the critical heat flux and the total heat resistance of the mLHPs were investigated and discussed. The pressure frequency also depends upon the evaporator temperature which has been maintained from $60^{\circ}C$ to $90^{\circ}C$. The Investigation shows 60% filling ratio gives the highest inside pressure magnitude of highest number pressure frequency at any of setting of evaporator temperature and 5wt% results the lowest heat flow resistance.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.546-549
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• 2009

In this paper, we investigated the effects of different source/drain (S/D) electrode materials in thin film transistors (TFTs) based on indium-gallium-zinc oxide (IGZO) semiconductor. A transfer length and effective resistances between S/D electrodes and amorphous IGZO thin-film transistors were examined. Intrinsic TFT parameters were extracted by the transmission line method (TLM) using a series of TFTs with different channel lengths measured at a low drain voltage. The TFTs fabricated with Cu S/D electrodes showed the lowest contact resistance and transfer length indicating good ohmic characteristics, and good transfer characteristics with a field-effect mobility (${\mu}_{FE}$) of 10.0 $cm^2$/Vs.