• Journal of the Korean Society of Safety
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• v.32 no.2
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• pp.66-71
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• 2017

The autoignition temperature (AIT) is crucial combustible characteristics which need attention in chemical process that handle hazardous materials. The AIT, also to as minimum spontaneous ignition temperature(MSIT), is the lowest temperature of a hot surface at which the substance will spontaneously ignite without any obvious sources of ignition such as a spark or flame. The AIT may be used as combustion property to specify operating, storage, and materials handling procedures for process safety. This study measured the AITs of n-propanol+acetic acid system from ignition delay time(time lag) by using ASTM E659 apparatus. The AITs of n-propanol and acetic acid which constituted binary system were $435^{\circ}C$ and $212^{\circ}C$, respectively. The experimental AITs of n-propanol+acetic acid system were a good agreement with the calculated AITs by the proposed equations with a few A.A.D.(average absolute deviation). In the case of n-propanol and acetic acid system, the minimum autoignition temperature behavior (MAITB), which is lower than the lower AIT, is shown among the two pure substances constituting the mixture.

• Journal of Environmental Science International
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• v.33 no.1
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• pp.75-85
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• 2024

An intensive observing period (IOP) of heatwaves in the urban region of Seoul in the summer of 2023 was carried out to understand the changes in air temperature and road temperature induced by environmental conditions. The temperature observed at eight points with different urban environmental conditions was compared with the temperature by the KMA/AWS to analyze the characteristics of change in air temperature by height and the change in road temperature according to environmental conditions and road sprinkler. The comparison of the average temperature observed in different urban environmental conditions with the temperature observed at KMA/AWS showed that the air temperature in asphalt and open space sites was 0.7 to 2.3℃ higher and that the one in bus stops was 0.9 to 2.3℃ higher. In terms of temperature deviations depending on residential type, the temperature in highly populated areas was about 0.1 to 0.8℃ higher than that of apartment complexes. In addition, regardless of the size of a park, the temperature in the park was lower than the temperature in dense housing areas and apartment complexes. In asphalt and residential areas, the road temperature was higher than the temperature at a height of 150 cm, Conversely, road temperature was lower than air temperature in a shaded shelter and large park. In addition, after spraying a surface road, the road temperature immediately dropped by about 3 to 4℃; however, after about 20 minutes, it rose again to the previous road temperature. This change in road temperature appeared only for the temperature of 30 cm height.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.11a
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• pp.207-208
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• 2017

The current study assumed a condition in which concrete curing was not completed correctly in the winter, in order to analyze the effect of changes in early low-temperatures in early-frost damage depth. As a result, lower external temperature early on after depositing the concrete greatly reduced the temperature in the upper parts of the concrete, and it delayed the time during which the concrete temperature restored. In addition, for early-frost damages, lower early temperature increased the expansion of frozen water, which in turn relaxes the concrete structures and increases the absorption rate, ultimately extending the depth of early-frost damage.

• International Journal of Automotive Technology
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• v.8 no.4
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• pp.395-402
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• 2007

Homogeneous Charge Compression Ignition (HCCI) shows great potential for low $NO_x$ emission but is hampered by the problem of no direct method to control the combustion process. Therefore, HCCI combustion becomes unstable easily, especially at lower and higher engine load. This paper presents a method to achieve diesel-fueled HCCI combustion, which involves directly injecting diesel fuel into the cylinder before the piston arrives at top dead center in the exhaust stroke and adjusting the valve overlap duration to trap more high temperature residual gas in the cylinder. The combustion stability of diesel-fueled HCCI combustion and the effects of engine load, speed, and valve overlap on it are the main points of investigation. The results show that: diesel-fueled HCCI combustion has two-stage heat release rate (low temperature and high temperature heat release) and very low $NO_x$ emission, combustion stability of the HCCI engine is worse at lower load because of misfire and at higher load because of knock, the increase in engine speed aids combustion stability at lower load because the heat loss is reduced, and increasing negative valve overlap can increase in-cylinder temperature which aids combustion stability at lower load but harms it at higher load.

• Corrosion Science and Technology
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• v.20 no.2
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• pp.85-93
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• 2021

The corrosion damage of materials in marine environment mainly occurs by Cl^- ions due to the breakdown of passive films. Additionally, various characteristics in seawater such as salinity, temperature, immersion time, flow rate, and biological activity also affect corrosion characteristics. In this study, the corrosion characteristics of stainless steels (STS 304 and STS 316L) and anodized aluminum alloys (AA 3003 and AA 6063) were evaluated with seawater temperature parameters. A potentiodynamic polarization experiment was conducted in a potential range of -0.25 V to 2.0 V at open circuit potential (OCP). Corrosion current density and corrosion potential were obtained through the Tafel extrapolation method to analyze changes in corrosion rate due to temperature. Corrosion behavior was evaluated by measuring weight loss before/after the experiment and also observing surface morphology through a scanning electronic microscope (SEM) and 3D microscopy. Weight loss, maximum damage depth and pitting damage increased as seawater temperature increased, and furthermore, the tendency of higher corrosion current density with an increase of temperature attributed to an increase in corrosion rate. There was lower pitting damage and lower corrosion current density for anodized aluminum alloys than for stainless steels as the temperature increased.

• Journal of the Korean Society of Safety
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• v.13 no.1
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• pp.19-25
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• 1998

In this study, proper injection molding condition has been studied through stress relaxation tests in order to experimentally investigate the effect of the condition on softening of mold product, using specimens produced under the different conditions according to the recommendation of resin manufactures. As a result, softening of the specimens was found to be strongly influenced by material melting temperature. The specimen with higher material melting temperature is found to have lower softening. However, softening of the specimen with lower mold temperature has an decrement, compared with other specimens. In particular, specimen with notch is influenced by mold temperature. The softening increase with higher injection speed and pressure. Finally in order to improve softening, material melting temperature, injection speed and injection pressure were found to be increased with low mold temperature.

• Food Science and Preservation
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• v.4 no.1
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• pp.33-38
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• 1997

In order to provide informations for designing packaging and storage condition of dry jujube (Zizyphus jujuba MILLER), moisture sorption isotherm was determined for temperatures of 20, 30 and 4$0^{\circ}C$, and quality changes were evaluated as function of temperature and water activity. Dry jujube at a given water activity showed higher equilibrium moisture content for lower temperature. Moisture isothem could be fitted by GAB model equation, giving higher C value, lower m0 and relatively constant k value with increase in temperature. Ascorbic acid was lost more highly at higher temperature and water activity, and showed negligible retention for whole range of water activity and temperature studied after 141 days. Browning increased with water activity up to 0.73 at 30 and 4$0^{\circ}C$. Dry jujube of high water activity had high L value in surface color, which represent brightness of surface color. Considering quality retention in the storage, dry jujube is desired to be dried to water activity of 0.42 and be stored at temperature below 3$0^{\circ}C$

• Fashion & Textile Research Journal
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• v.7 no.3
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• pp.309-314
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• 2005

This study was to determine whether the massage would enhance the physical relaxation in healthy women, and whether the effects of massage on the relaxation would be different by the applied regions of the body. Five healthy young women participated in the two test sessions of back and lower extremities massage in a chamber controlled at an air temperature of $28^{\circ}C$ and a relative humidity of $50{\pm}5%$. The slow stroke massage with lavender aroma oil for 30 minutes was applied to the subjects with a 10-min. and a 20-min rest time before and after the application, respectively. Rectal temperature decreased and the chest and thigh skin temperatures increased with the massage application, and the changes of the temperatures were greater with lower extremities massage than with back massage. Heart rate also decreased during massage period and tended to be lower with lower extremities massage. Systolic and diastolic blood pressure decreased with lower extremities massage. These results show that the slow stroke massage for 30 minutes can induce physiological responses related with the enhanced relaxation in healthy women, and lower extremities massage is more effective on the physical relaxation rather than back massage.

• Journal of Biosystems Engineering
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• v.25 no.4
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• pp.293-300
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• 2000

Automated greenhouse production system often require crop growth monitoring involving accurate quantification of plant physiological properties. Conventional methods are usually burdensome, inaccurate, and harmful to crops. A thermal image analysis system can accomplish rapid and accurate measurements of physiological-property changes of stressed crops. In this research a thermal imaging system was used to measure the leaf-temperature changes of several crops according to nutrient stresses. Thermal images were obtained from lettuce, cucumber, and pepper plants. Plants were placed in growth chamber to provide relatively constant growth environment. Results showed that there were significant differences in the temperature of stressed plants and non-stressed plants. In a case of the both N deficiency and excess, the leaf temperatures of cucumber were $2^{\circ}C$ lower than controlled temperature. The leaf temperature of cucumber was $2^{\circ}C$ lower than controlled temperature only when it was under N excess stress. For the potassium deficiency or excess stress, the leaf temperaures of cucumber and hot pepper were $2^{\circ}C$ lower than controls, respectively. The phosphorous deficiency stress dropped the leaf temperatures of cucumber and hot pepper $2^{\circ}C$ and $1.5^{\circ}C$ below than controls. However, the leaf temperature of lettuce did not change. It was possible to detect the changes in leaf temperature by infrared thermography when subjected to nutrition stress. Since the changes in leaf temperatures were different each other for plants and kinds of stresses, however, it is necessary to add a nutrient measurement system to a plant-growth monitoring system using thermography.

• Fire Science and Engineering
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• v.26 no.4
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• pp.1-9
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• 2012

We have examined In order to compare each other from explosion and combustion characteristics about the dusts which collects from manufacturing process of wheat flour and cosmetics manufacturing process of functional Keratin removal soap at the small and medium enterprise style. We measured explosive pressure and explosive lower limit which follows in change of concentration change at the time of talc addition uses Hartman dust explosion apparatus, also measured weight loss and endothermic quantity uses DSC and TGA. The explosion test results show that increased explosive lower limit concentration and explosive pressure decreased by the increased ratio of the talc dust. And the DSC results show that heat flux and temperature decreased by the increased ratio of the talc dust. Also increased in raising temperature causes initial smoldering temperature to move towards low temperature section and the endothermic quantity increased on a large scale. Together the TGA results show that weight loss decreased by the increased ratio of the talc dust. From this research we have assured the successive dust explosion mechanism study will play a key role as a significant safety securing guideline against the dust explosion.