• Tribology and Lubricants
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• v.32 no.5
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• pp.166-171
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• 2016

Electric vehicle ownership is expanding for two reasons: its technology features have enhanced fuel economy, and the number of vehicle emissions regulations is increasing. Battery performance has a large influence on the capability of electric vehicles, and even though battery thermal management has been actively researched, specific technological improvements to battery performance are not being presented. For instance, many industrial applications utilize vortex tubes as components for refrigeration machines because of their numerous intrinsic benefits. If electric vehicles incorporate vortex tubes for battery cooling, performance and efficiency advancements are possible. This study uses a counter-flow vortex tube to investigate its temperature separation characteristics, based on the back pressure of the cold air exit and the difference between the inlet and back pressures. The experiment uses a vortex tube with the following parameters: six nozzle holes, a 20 mm inner vortex diameter (D), a 14D tube length, a 0.7D cold exit orifice diameter, and a nozzle area ratio of 0.142. The measurements prove that the temperature difference between the hot air and cold air decreased because of the flow resistance of the hot air and the backflow phenomenon at the cold air exit. The flow resistance causes the temperature difference to decrease, and the back pressure of the cold air exit influences the flow resistance. The results show that the back pressure significantly influences the efficiency of temperature separation.

• Steel and Composite Structures
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• v.43 no.4
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• pp.483-500
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• 2022

Cold-formed steel wall panels sheathed with gypsum plasterboard have shown superior thermal and structural performance in fire. Recent damage caused by fire events in Australia has increased the need for accurate fire resistance ratings of wall systems used in low- and mid-rise construction. Past fire research has mostly focused on light gauge steel framed (LSF) walls under uniform axial compression and LSF floors under pure bending. However, in reality, LSF wall studs may be subject to both compression and bending actions due to eccentric loading at the wall to-roof or wall-to-floor connections. In order to investigate the fire resistance of LSF walls under the effects of these loading eccentricities, four full-scale standard fire tests were conducted on 3 m × 3 m LSF wall specimens lined with two 16 mm gypsum plasterboards under different combinations of axial compression and lateral load ratios. The findings show that the loading eccentricity can adversely affect the fire resistance level of the LSF wall depending on the magnitude of the eccentricity, the resultant compressive stresses in the hot and cold flanges of the wall studs caused by combined loading and the temperatures of the hot and cold flanges of the studs. Structural fire designers should consider the effects of loading eccentricity in the design of LSF walls to eliminate their potential failures in fire.

• Corrosion Science and Technology
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• v.9 no.2
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• pp.67-73
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• 2010

Niobium microalloying is effective in hot-rolled and cold-rolled steels by providing a fine-grained microstructure resulting in increased strength. To optimize the strengthening effect, alloy design and hot-rolling conditions have to be adapted. As a key issue the dissolution and precipitation characteristics of Nb are discussed in particular with regard to the run-out table conditions. It is then considered how the hot-rolled microstructure and the solute state of Nb interact with the hot-dip galvanizing cycle. The adjusted conditions allow controlling the morphology and distribution of phases in the cold-rolled annealed material. Additional precipitation hardening can be achieved as well. The derived options can be readily applied to produce conventional HSLA and IF high strength steels as well as to modern multiphase steels. It will be explained how important application properties such as strength, elongation, bendability, weldability and delayed cracking resistance can be influenced in a controlled and favorable way. Examples of practical relevance and experience are given.

• Transactions of Materials Processing
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• v.11 no.1
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• pp.24-35
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• 2002

Recent trend and future prospect of flat rolling of steel has been summarized based on the earlier reports. Key technology in the plate rolling is to have ultra fine microstructure having high resistance against crack propagation during application. Heavy accelerated cooling facility and high power rolling mill will be helpful to develope the high toughness steel. Precise modeling of properly prediction based on deformation and transformation imposed on microstructure of steel during processing is highly anticipated. For the hot strip rolling process, new trend is lies on the production of ultra-thin gauged hot strip to substitute cold rolled strip. For the substitution of cold rolled strip into hot rolled strip widely, high formable property of hot strip is highly required. For the formabilit, the ferritic rolling of extra low carbon steel under high lubricated condition is essential. Recently introduced semi-continuous thin slab and rolling mill line is very plausible to develope those kinds of products easily In the view groin facility combination. New idea to modify the existing continuous hot strip mill line to produce the ultra thin-gauged hot strip in an economic way is suggested in this report.

• Journal of the Korean Wood Science and Technology
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• v.46 no.2
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• pp.155-165
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• 2018

The objective of the research was to evaluate the effect of particle pre-treatment on physical, mechanical, and durability of jatropha fruit hulls (JFH) particleboard. The pre-treatments included were immersing in cold water, hot water, and acetic acid solution. After each treatment, the particles were dried up to 3% moisture content. Urea-formaldehyde (UF) resin was used to fabricate particleboards with board size, thickness and density target of 25 cm by 25 cm, 0.80 cm, and $0.70g/cm^3$, respectively. Board pressed at $130^{\circ}C$ for 10 minutes, and $25kg/cm^2$ pressure. The evaluation of particleboard followed the JIS A 5908-2003. Whilist their resistance to subterranean termite test (mass loss, mortality, antifeedant value and feeding rate) refers to the Indonesian standard (SNI 01.7207-2006). The physical and mechanical properties of particleboards showed that all pre-treatments decreased the pH of particles. Overall, all particle immersing treatments resulted of better physical and mechanical properties of particleboard than those of untreated ones. The acetic acid treatment resulted the best physical and mechanical properties of particleboard. Based on the mass loss of JFH particleboard, hot water and acetic acid treated particleboards were classified into weak resistance to subterranean attack. The other two treatments were classified into very weak resistance. Hot water treated particleboard provided the highest mortality and antifeedant as much as 87.40% and 34.20%, respectively. Based on antifeedant classification, hot water treated particleboards were classified into moderately strong resistance, while other treatments were categorized into weak resistance. The lowest feeding rate value ($45.30{\mu}g/termite/day$) was attained by hot water treatment.

• International Journal of Highway Engineering
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• v.20 no.3
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• pp.1-9
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• 2018

PURPOSES : In order to evaluate a crack resistance at cold joint, sealing tape was adopted to apply at cold joint instead of typical tack coat material(RSC-4). The sealing tape was made by hot sealing material. The crack resistance as function of environmental and traffic loading was measured with visual observation. METHODS : In this study, the crack resistance was evaluated as function of environmental and traffic loading. The freeze-thaw method was adopted for environmental loading of asphalt pavement. condition. The damage of cold joint under freeze-thaw action is initiated by ice expansion load and accelerated by the interfacial damage between new and old asphalt pavement. The traffic loading was applied with wheel tracking machine on the cold joint area of the asphalt pavement for 3 hours at $25^{\circ}C$. The evaluation of crack resistance was measured with visual observation. The freeze-thaw results shows that the sealing tape was significantly increased the crack resistance based on. RESULTS : To estimate the crack resistance at cold joint area due to the environmental loading, the Freeze-thaw test was conducted by exposing the product to freezing temperature(approximately $-18^{\circ}C$) for 24 hours, and then allowing it to thaw at $60^{\circ}C$ for 24 hours. The tack coat material(RSC-4) was debonded after 21 cycles of the Freeze-thaw test. The first crack was observed after 14 freeze-thaw cycle with RSC-4 material. But, the sealing tape was not debonded after 24 cycle test. Also, the sealing tape shows the better performance of the crack resistance under the traffic loading with wheel track test. The crack was generated the under traffic loading with RSC-4(tack coating), however, the crack was not shown with sealing tape. It indicates that the sealing tape has a strong resistance of tensile stress due to traffic loading. CONCLUSIONS :Based on limited laboratory test result, a performance of crack resistance using the sealing tape is better than that of general tack coat material(RSC-4). It means that the sealing tape is possible to extend a pavement service life because the crack, one of the main pavement distresses, will be delayed.

• Korean Journal of Human Ecology
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• v.18 no.5
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• pp.1087-1092
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• 2009

From the environmental adaptation point of view, the clothing habits made by the thermal sensation and clothing weight of elderly women have changed according to the thermal sensation and health condition. The purpose of this study was to obtain the basic data for developing healthy and comfortable clothing for elderly women. Clothing weight, thermal sensation, clothing microclimate, resistance to cold and heat of 198 elderly women in Taejeon were surveyed from October 9, 2007 to October 19, 2007. 1. Clothing weight per body surface area was $830.4g/m^2$ of total clothing weight, $242.8g/m^2$ of underwear clothing weight, $617.3g/m^2$ of outerwear clothing weight, $419.8g/m^2$ of upper clothing weight, and $420.4g/m^2$ of lower clothing weight. 2. More than 90% of the respondents replied that they felt comfortable when the temperature inside the clothing was $33.5^{\circ}C$ and humidity inside the clothing was 30.2%. 3. The elderly women were more sensible to cold than to hot, those who felt cold had a tendency to wear heavier clothing. 4. The appeal rate for physical pain of older and lower income people, especially those with an income under 1,000,000 won, was higher than that of others. On the other hand, the lower the subjective economic level, the younger they were, and the more the monthly average income was, the higher the rate of mental pain. 5. The heavier the total clothing weight was, the higher the appeal rate for general pain.

• Journal of Applied Reliability
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• v.13 no.3
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• pp.207-216
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• 2013

This paper, we classified LED failure mechanisms that occur due to the delamination and analyzed each of the mechanism that gives the LED PKGs the effect. Usually, the LED is composed of several materials which are LED chips, gold wire, phosphor, epoxy resin, adhesive, reflector and lead frame. These different materials are usually delaminated in trouble conditions which are huge temperature difference, hot and humid or mechanical shocked. When the components are delaminated, a luminance will be lost and moisture be absorbed easily, a thermal resistance be increased attendantly. In this paper, we experimented to investigate failure mechanism of the thermal resistance and failure mechanism of the decrease of luminance that occur due to the delamination. A thermal shock test was performed to reproduce this phenomena by subjecting samples to a cold-hot cyclling process between $-30^{\circ}C$(15min) and $110^{\circ}C$(15min). The samples were inspected at 200, 600 and 1,000 cycles. We measured feature of LED using the spatial analyzer, optical microscope, thermal resistance, photometer, scanning electron microscope (SEM). As a result, the progression of the crack and the thermal resistance and decrease in luminance are proportional to number of thermal shock.

• Journal of the Society of Disaster Information
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• v.20 no.2
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• pp.390-397
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• 2024

Purpose: In this study, PCM was used to give thermal performance to concrete and analyze its effect on durability to prevent disasters that may occur in concrete when exposed to hot and cold environments. Method: After preparing concrete specimens containing 10, 30, and 50% of the two types of PCMs compared to the cement volume, the pore volume, freeze melting resistance, and scaling resistance were evaluated. Result: Regardless of the type, when PCM powder was mixed with concrete, the amount of pores decreased, and when 10% and 30% were mixed, the freeze-melting resistance was also improved. It was also confirmed that the higher the mixing amount, the better the scaling resistance. Conclusion: When mixing powdered PCM into concrete, it is believed that durability can be improved to a certain level by the filling effect, and additional various studies should be supported for actual field application.

• Nuclear Engineering and Technology
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• v.39 no.5
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• pp.591-602
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• 2007

The results of Reactivity-Initiated Accidents (RIA) experiments have been analysed and the main variables affecting the fuel failure propensity identified. Fuel burn-up aggravates the mechanical loading of the cladding, while corrosion, or better the hydrogen absorbed in the cladding as a consequence of corrosion, may under some conditions make the cladding brittle and more susceptible to failure. Experiments point out that corrosion impairs the fuel resistance for RIA transient occurring at cold conditions, whereas there is no evidence of important embrittlement effects at hot conditions, unless the cladding was degraded by oxide spalling. A fuel failure threshold correlation has been derived and compared with experimental data relevant for BWR and PWR fuel. The correlation can be applied to both cold and hot RIA transients, account taken for the lower ductility at cold conditions and for the different initial enthalpy. It can also be used for non-zero power transients, provided that a term accounting for the start-up power is incorporated. The proposed threshold is easy to use and reproduces the results obtained in the CABRI and NSRR tests in a rather satisfactory manner. The behaviour of advanced PWR alloys and of MOX fuel is discussed in light of the correlation predictions. Finally, a probabilistic approach has been developed in order to account for the small scatter of the failure predictions. This approach completes the RIA failure assessment in that after determining a best estimate failure threshold, a failure probability is inferred based on the spreading of data around the calculated best estimate value.