• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.165-168
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• 2008

A numerical analysis was conducted to predict the heat transfer characteristics of a solar receiver which is subject to very high heat fluxes and temperatures for solar thermal applications. The concentration ratio of the solar receiver ranges 1000 and the concentrated heat is required to be transported to a certain distance for specific applications. This study deals with a solar receiver according to internal geometry variation incorporating high-temperature heat pipe. The isothermal characteristics in the receiver section is of major concern. The diameter of the solar thermal receiver was 120 mm and the length was 400 mm and the angle of receiver end wall set $90^{\circ},\;60^{\circ},\;45^{\circ},\;30^{\circ}$. And the diameter of the heat pipe was 12.7 mm, 48 axial channels of the same dimensions were attached to the outer wall of the receiver with even spacing in the circumferential direction. The channels are changed to high-temperature sodium heat pipes. Commercial softwares were employed to deal with the radiative heat transfer inside the receiver cavity and the convection heat transfer along the channels. The numerical results are compared and analyzed from the view point of high-temperature solar receiver.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.4
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• pp.359-364
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• 2014

This paper describes the development of needle type probe that measures temperature and injects medicine for both diagnosis and treatment of musculoskeletal pain syndrome (MPS). The size of trigger points is from several micrometers to millimeter. Therefore, it is required to develop a medical device that is capable of not only finding the trigger points by temperature measurement, but also injecting medicine at the exact location for treatment. To challenge these difficulties, thermocouple was fabricated on the surface of a needle using metal deposition process. Special type of stainless-constantan thermocouple was achieved from the stainless body of a needle itself and deposited constantan metal film. In particular, parylene coating enables to limit the temperature sensitive area to the end of the needle tip. Fabricated needle type probe produces $3.25mV/^{\circ}C$ of thermoelectric sensitivity and compared its performance with commercial T-type thermocouple in animal muscle sample.

• Ocean and Polar Research
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• v.34 no.2
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• pp.265-273
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• 2012

A new algorithm was developed, not only to detect the existence of a thermocline, but also to extract the thermocline parameters (such as thermocline thickness, mixed layer thickness, maximum temperature gradient, and temperature difference of thermocline), using the vertical profile of water temperature. According to Kappa analysis, in order to find adequate threshold values of vertical water temperature gradients ${\Delta}T$ ($^{\circ}C/m$), agreement and reliability were 87% and 0.74 respectively, in the conditions of maximum ${\Delta}T{\geq}0.5$ and surface and bottom layers ${\Delta}T<{\mid}0.2{\mid}$. Also, three different kinds of methods, viz. 1. Gradient method, 2. Hyperbolic tangent method, and 3. Differential hyperbolic tangent method, were tested to extract the key parameters of a thermocline. Comparing the results of three different methods, the differential hyperbolic tangent method was the most appropriate to extract the start and end point of a thermocline curve.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.1
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• pp.189-205
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• 1996

The twin-roll type strip continuous casting process(or direct rolling process) of steel materials is characterized by two rotating water cooled rolls receiving a steady supply of molten metal which solidifies onto the rolls. A solidification analysis of molten metal considering phase transformation and thermofluid is performed using finite diffefence method with curvilinear coordinate to reduce computing time and molten region analysis with arbitrary shape. An enthalpy-specific heat method is used to determine the temperatures inthe roll and the steel. The temperature distribution of cooling roll is calculated using two dimensional finite element method, because of complex roll shape due to cooling hole in rolls and improvemnt accuracy of calculation result. The energy equaiton of cooling roll is solved simultanuously with the conservation equaiton of molten metal in order to consider heat transfer through the cooling roll. The calculated roll temperature is compared to experimental results and the heat transfer coefficient between cooling roll surface and rolling material(steel) is also determined from comparison of measured roll temperature and calculated temperature.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.12
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• pp.645-651
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• 2015

This paper presents an experimental study on the freeze drying process for poly ${\gamma}$ glutamic acid. The physical properties of poly ${\gamma}$ glutamic acid are measured during the freeze-drying process. The moisture contents of poly ${\gamma}$ glutamic acid according to the glass transient temperature are obtained by DSC (Differential Scanning Calorimetry) analysis. The end point of primary drying for the poly ${\gamma}$ glutamic acid with a thickness of 3 mm is obtained by measuring the thickness of the dried layer, the amount of moisture evaporation, the moisture content, and the pressure in the drying vacuum chamber during the freeze-drying process. By considering the variation in the glass transient temperature with respect to the moisture content of the material, a control schedule for the heating plate temperature is suggested during the secondary drying process.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.2
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• pp.313-318
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• 2020

Since the engineering plastics having a melting point of higher than 300 degrees have a high mechanical rigidity, chemical resistance, friction and abrasion performance, those are being highlighted as metal replacement materials in various industries. In this study, 3D printer nozzle with excellent heat dissipation characteristics are designed and analytically verified to form engineering plastics with high melting points in 3D printers based on the melt-lamination modeling method. In order to insulate between the heat block heated to a melting point of filament material and the upper part of the nozzle where the filament is transferred, the heat brake part with low thermal conductivity was designed to have two separate parts, and a cooling fin structure is further applied to the heat brake part to lower steady-state temperature by air convection. Optimized structural design on FDM nozzle part reduces the temperature at the heat sink and at the end part of heat brake by 50% and 14% respectively, compared to the conventional BCnozzle structure.

• Membrane Journal
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• v.22 no.5
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• pp.301-308
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• 2012

Phosphazene diagnostic membranes were prepared to measure blood glucose level of diabetics. Final absorbances at 680nm through activated phosphazene membranes were measured at various temperature and humidity by varing concentration of glucose in blood. Measuring temperature and humidity did not seriously affected the end-point results of varing absorbance values as time (K/S). The effects of storage temperatures on the measurements of glucose concentration were studied after activated phosphazene diagnostic membranes were stored at various temperatures for 3 days, 1 week, 3 weeks, and 5 weeks. The stabilities of phosphazene dianostic membranes were confirmed even at RH 80%.

• The Korea Journal of Herbology
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• v.37 no.2
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• pp.23-31
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• 2022

Objectives : The purpose of this research was to find out the efficacy of Castanea crenata Inner Shell (CCIS) on the skin by comparing the difference effect between only MTS (microneedle therapy system) and the CCIS essence application after MTS treatment. Methods : The present author performed once a week and total 3 times of MTS treatment. The treatment time took about 5 ~ 10 minutes and the depth of the needle was adjusted according to the participant's skin condition. In the control group, essence base was applied after MTS and in the experimental group, CCIS powder dissolved essence was applied. One week after each treatment, the change of skin condition was measured. Two weeks after the end of the clinical trial, the skin condition was checked again. Results : In the case of the test group and the control group, there was a significant decrease in thermography temperature and there was a significant increase in skin tone. In the case of pores and pigmentation, there was no significant difference on both group. In the case of moisture, there was a significant increase only in the test group. Conclusion : The MTS treatment itself showed good effects on thermography temperature and skin tone. But in the case of the moisture effect, it was much better when the CCIS essence was applied to the skin after MTS treatment. This study suggests that CCIS essence increases the efficacy of MTS on the point of moisture.

• Environmental Engineering Research
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• v.24 no.4
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• pp.680-689
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• 2019

Temperature effects on the generation of brake wear particles from railway vehicles were generated, with a particular focus on the generation of ultrafine particles. A real scale brake dynamometer test was repeated five times under low and high initial temperatures of brake discs, respectively, to obtain generalized results. Size distributions and temporal patterns of wear particles were analyzed through visualization using clustered heatmaps. Our results indicate that high initial temperature conditions promote the generation of ultrafine particles. While particle concentration peaked within the range of fine sized particles under both low and high initial temperature, an additional peak occurred within the range of ultrafine sized particles only under high initial temperature. The timing of peak occurrence also differed between low and high initial temperature conditions. Under low initial temperature fine sized particles were generated intensively at the latter end of braking, whereas under high initial temperature both fine and ultrafine particles were generated more dispersedly along the braking period. The clustered correlation heatmap divided particle sizes into two groups, within which generation timing and concentration of particles were similar. The cut-off point between the two groups was approximately 100 nm, confirming that the governing mechanisms for the generation of fine particles and ultrafine particles are different.

• Corrosion Science and Technology
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• v.6 no.3
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• pp.103-111
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• 2007

The effect of stress factors on the growing process of stress corrosion cracking (SCC) of the sensitized 18-8 stainless steel in high temperature water was investigated using equations of crack growth rate derived from applying electric circuits to SCC corrosion paths. Three kinds of cross sections have to be considered when electric circuit is constructed using total current. The first is ion flow passage area, $S_{sol}$, of solution in crack, the second is total dissolving surface area, $S_{dis}$, of metal on electrode of crack tip and the third is dissolving cross section, $S_{met}$, of metal on grain boundary or in base metal or in welding metal. Stress may affect each area. $S_{sol}$ may depend on applied stress, $\sigma_{\infty}$, related with crack depth. $S_{dis}$ is expressed using a factor of $\varepsilon(K)$ and may depend on stress intensity factor, K only. SCC crack growth rate is ordinarily estimated using a variable of K only as stress factor. However it may be expected that SCC crack growth rate depends on both applied stress $\sigma_{\infty}$ and K or both crack depth and K from this consideration.$\varepsilon(K)$ is expressed as ${\varepsilon}(K)=h_2{\cdot}K^2+h_3{\cdot}K^3$ when $h_{2}$ and $h_{3}$ are coefficients. Also, relationships between SCC crack growth rate, da/dt and K were simulated and compared with the literature data of JBWR-VIP-04, NRC NUREG-0313 Rev.2 and SKIFS Draft. It was pointed out in CT test that the difference of distance between a point of application of force and the end of starter notch (starting point of fatigue crack) may be important to estimate SCC crack growth rate. An anode dissolution current density was quantitatively evaluated using a derived equation.