• Journal of the Korean Society of Visualization
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• v.21 no.1
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• pp.67-73
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• 2023

In the study, pool boing critical heat flux (CHF) was experimentally investigated depending on the length of heaters. A smooth silicon oxide surfaces are used as the boiling surfaces. As the results of pool boiling experiments based on distilled water in ambient pressure condition, the CHF decreased as the length of the heater increased. By the high speed imaging, it was shown that the number of vapor columns increased as the length of the heater increased. Comparing the number of vapor columns and the CHF according to the heater length, the change in the CHF according to the heater length was analyzed based on the hydrodynamic instability.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.6A
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• pp.881-891
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• 2008

The purpose of the present study is to investigate the influence of seasonal temperature variation on the thermal stresses in roller compacted concrete dam(RCD) structures. Using the finite element code, DIANA performs 2-D transient temperature and resultant stress analysis for RCD. Time variability of the mesh geometry is considered in order to simulate successive phases of the structure's construction. The main analysis variables are construction sequence, concrete temperature and ambient temperature. The results show principal tensile stress of hot-weathering concrete is higher than that of cold-weathering concrete. In some case the index of thermal cracking excesses 1.0, RCD also needs thermal management on placing temperature according to weather condition.

• Nuclear Engineering and Technology
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• v.56 no.3
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• pp.832-845
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• 2024

Reactor cavity cooling systems (RCCSs) comprising passive safety features use the atmosphere as a coolant, which cannot be lost. However, their drawback is that they are easily affected by atmospheric disturbances. To realize the commercial application of the two types of passive RCCSs, namely RCCSs based on atmospheric radiation and atmospheric natural circulation, their safety must be evaluated, that is, they must be able to remove heat from the reactor pressure vessel (RPV) surface at all times and under any condition other than under normal operating conditions. These include both expected and unexpected natural phenomena and accidents. Moreover, they must be able to eliminate the heat leakage emitted from the RPV surface during normal operation. However, utilizing all of the heat emitted from the RPV surface increases the degree of waste heat utilization. This study aims to understand the characteristics and degree of passive safety features for heat removal by comparing RCCSs based on atmospheric radiation and atmospheric natural circulation under the same conditions. It was concluded that the proposed RCCS based on atmospheric radiation has an advantage in that the temperature of the RPV could be stably maintained against disturbances in the ambient air.

• Magazine of the Korean Society of Agricultural Engineers
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• v.16 no.1
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• pp.3263-3291
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• 1974

Experimental work of grain bin was carried out to develop the methods of natural air in-bin drying and storage. The method is considered to be more economical, labour saving, and an effective countermeasure to grain loss. To examine the possibility of farm use of the grain bin and to analyze the related factors concerned with in-bin grain drying and storage, ambient air conditions (especially the change of air temperature and relative humidity) and grain quality during drying and storage periods were investigated. A laboratory model bin was constructed to investigate the effect of different forced air conditions on the drying characteristics of rice. In addition, a grain bin with 2.2m diameter and 1.8m height, considered to be the optimum size for the average Korean farm, was constructed and tested to examine the drying and storing characteristics of rice. The weather data analyzed in this study was the nine-year (from 1964 to 1972) record of air temperature and relative humidity in the Suweon area, and the thirty-year (from 1931 to 1960) record of pentad normal relative humidity and air temperature in the Seoul area. From the results of the weather data analyses, the adequate air delivery hours (which was arbitrary defined as the condition to give less than 75% relative humidity) to dry the rice during October were about nine hours (from approximately 10 A.M. to 7 P.M, ) a day, in which the average air temperature was about 15.9$^{\circ}C$ and average relative humidity was 66%. The occurence of days having three hours of such conditions was 1, 2, and 1-day within the 1st, 2nd add last 10-day periods for the month of October, respectively. Therefore, it may be considered that the weather condition in October was satisfactory for the forced natural air drying. The results of the laboratory model bin test were analyzed to obtain the drying curve and drying rate for different drying stages and grain layers in the bin corresponding to various conditions of forced natural air. A drying experiment with a prototype grain bin showed that an approximate 5 percent grain moisture gradient through a 1.6 meter grain deposit was observed after 80 hours of intermittent drying, giving an over dried zone in the lower grain layers and an extremely high grain moisture zone in the upper layers. This indicates that an effective measure should be taken to reduce this high moisture gradient. In order to investigate the drying characteristics of bulk grain in a layerturning operation a grain bin test was performed. This showed a significant improvement of uniform drying. In this test, approximate 107 hours were required to dry a depth of 1.6 meter of grain from an initial moisture content of 22.2 percent to a moisture content of 16.7 percent using an air delivery rate of 2.8 cubic meter per a minute per every cubic meter of grain. This resulted in a 2 percent moisture gradient from the top to the bottom of the bin. During storage period, till the end of June the average temperature of grain was 2~3$^{\circ}C$ higher than ambient air temperature. But during July when the grain moisture content went up slightly (less than 1 percent), the average temperature of the grain also increased to 3~5$^{\circ}C$ higher than ambient air temperature. It is therefore recommended that for safe grain storage, grain should not be stored in sheet metal bins after mid May. From the above results, in-bin rice drying and storage can be used effectively on Korean farms. It is strongly recommended that the use of grain-bin system should be implemented for farm use to improve farm drying and storage of rice.

• Korean Journal of Environment and Ecology
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• v.31 no.6
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• pp.557-563
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• 2017

Gastrodia elata (Orchidaceae) is a perennial parasitic plant that has a unique lifestyle of being in a symbiotic interaction with fungi. The underground root of Gastrodia is used for medicinal treatment to cure high blood pressure, stroke, leukemia, headaches, and especially neurasthenia. This study is intended to investigate the effect of the global warming on the ecological responses of Gastrodia. We cultivated the small tuber of Gastrodia with the oak wood lot and mulberry fungus under control (ambient $CO_2$ concentration + ambient temperature, ACAT), temperature treatment (ambient $CO_2$ concentration+elevated temperature, ACET), and $CO_2$+temperature treatment (elevated $CO_2$ concentration+elevated temperature, ECET). The elevated $CO_2$ concentration was about twice in the ambient air while the elevated temperature was about $2^{\circ}C$ higher than the control group. And then we observed the growth and production of reproductive organs and the underground root. The observation showed that the number of flower stalk was highest at ACET and lowest at ECET. The flower stalk was longest at ACET and shortest at ECET. The inflorescence was longest at ACAT and shortest at ECET. The seed capsule was heaviest at ACET and lightest at ECET. The aboveground biomass was highest at ACET and lowest at ECET. The number of rhizomes was highest at ACET and lowest at ECET. The total rhizome biomass was highest at ACET and lowest at ECET. The average rhizome biomass was highest at ACET and lowest at ECET. The results showed that the growth of Gastrodia increased because of more active growth of Gastrodia elata when only the temperature increased and decreased when both $CO_2$ concentration and temperature increased, indicating the poor growth of Gastrodia elata under the global warming condition. Therefore, the Gastrodia elata plantation should be maintained at the temperature of $20-25^{\circ}C$ and not be exposed to a high $CO_2$ concentration.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.2
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• pp.59-66
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• 2019

Small bridges carry out only general inspections based on visual inspection. The Bridges with more than 30 years of public use need to be decided on whether or not they will be reconstruction according to aging. However, there are some situations that need to be determined only by appearance condition, which is insufficient in terms of safety maintenance. In this paper, the condition evaluation and the load carrying capacity evaluation were carried out for aged small bridges. A comparison of the evaluation results was conducted to examine the appropriateness of the maintenance related to the decision making of the reconstruction. As a result of reviewing, two of the bridges showed that there are no abnormality in the safety of the state evaluation, but the load capacity were insufficient. Thus evaluation the safety and performing the reconstruction decision of aged small bridges by visual inspection alone with may cause problems. Therefore, it is necessary to carry out additional research on the ambient measurement and load carrying capacity evaluation for the maintenance of the bridges, and to supplement it through application of the bridge management system.

• Journal of Biosystems Engineering
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• v.12 no.2
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• pp.16-27
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• 1987

Greenhouse farming was introduced to the Korean farmers in the middle of 1950's and its area has been increased annually. The plastic greenhouse, which is covered with polyethylene or polyvinyl chloride film, has been rapidly spread in greenhouse farming since 1970. The greenhouse farming greatly contributed to the increase of farm household income and the improvement of crop productivity per unit area. Since the greenhouse farming is generally practiced during winter, from November to March, the thermal environment in the plastic greenhouse should be controlled in order to maintain favorable condition for plant growing. Main factors that influence the thermal environment in the plastic greenhouse are solar radiation, convective and radiative heat transfer among the thermal component of the greenhouse, and the use of heat source. The objective of this study was to develop a simulation model for thermal environment of the plastic greenhouse in order to determine the characteristics of heat flow and effects of various ambient environmental conditions upon thermal environments within the plastic greenhouse. The results obtained are summarized as follows: 1. Simulation model for thermal environment of the plastic greenhouse was developed, resulting in a good agreement between the experimental and predicted data. 2. Solar radiation being absorbed in the plant and soil during the daytime was 75 percent of the total solar radiation and the remainder was absorbed in the plastic cover. 3. About 83 percent of the total heat loss was due to convective and radiative heat transfer through the plastic cover. Air ventilation heat loss was 5 to 6 percent of total heat loss during the daytime and 16 to 17 percent during the night. 4. The effectiveness of thermal curtain for the plastic greenhouse at night was significantly increased by the increase of the inside air temperature of the greenhouse due to the supplementary heat. 5. When the temperature difference between the inside and outside of the greenhouse was small, the variation of ambient wind velocity did not greatly affect on the inside air temperature. 6. The more solar radiation in the plastic greenhouse was, the higher the inside air temperature. Because of low heat storage capacity of the plant and soil inside the greenhouse and a relatively high convective heat loss through the plastic cover, the increase of solar radiation during the daytime could not reduce the supplymentary heat requirement for the greenhouse during the night.

• Korean Journal of Food Science and Technology
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• v.51 no.6
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• pp.610-614
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• 2019

The effect of broccoli extracts on the storage stability of red beet extracts under various conditions (temperature, light condition, and pH) was analyzed. Regardless of the pH and light conditions, the absorbance of the red beet pigment at 537 nm was relatively stable (less than 10% reduction) at 4℃ for up to 5 days. The absorbance of the control extracts was rapidly reduced during storage at an ambient temperature in the dark, but the degree of reduction was relatively low at pH 3.8. As a positive control, the addition of vitamin C to the control extracts slightly inhibited the reduction (40% reduction), but the degree of the inhibition was much higher (15% reduction) with the addition of broccoli extracts (in 70% ethanol). Among all the samples, the addition of the broccoli floret extracts using 70% ethanol was the most effective method for the enhancement of the storage stability of red beet pigment at an ambient temperature in the dark.

• Asian-Australasian Journal of Animal Sciences
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• v.29 no.2
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• pp.299-306
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• 2016

Body temperature (BT) monitoring in cattle could be used to early detect fever from infectious disease or physiological events. Various ways to measure BT have been applied at different locations on cattle including rectum, reticulum, milk, subcutis and ear canal. In other to evaluate the temperature stability and reliability of subcutaneous temperature (ST) in highly fluctuating field conditions for continuous BT monitoring, long term ST profiles were collected and analyzed from cattle in autumn/winter and summer season by surgically implanted thermo-logger devices. Purposes of this study were to assess ST in the field condition as a reference BT and to determine any location effect of implantation on ST profile. In results, ST profile in cattle showed a clear circadian rhythm with daily lowest at 05:00 to 07:00 AM and highest around midnight and rather stable temperature readings (mean${\pm}$standard deviation [SD], $37.1^{\circ}C$ to $37.36^{\circ}C{\pm}0.91^{\circ}C$ to $1.02^{\circ}C$). STs are $1.39^{\circ}C$ to $1.65^{\circ}C$ lower than the rectal temperature and sometimes showed an irregular temperature drop below the normal physiologic one: 19.4% or 36.4% of 54,192 readings were below $36.5^{\circ}C$ or $37^{\circ}C$, respectively. Thus, for BT monitoring purposes in a fever-alarming-system, a correction algorithm is necessary to remove the influences of ambient temperature and animal resting behavior especially in winter time. One way to do this is simply discard outlier readings below $36.5^{\circ}C$ or $37^{\circ}C$ resulting in a much improved mean${\pm}$SD of $37.6^{\circ}C{\pm}0.64^{\circ}C$ or $37.8^{\circ}C{\pm}0.55^{\circ}C$, respectively. For location the upper scapula region seems the most reliable and convenient site for implantation of a thermo-sensor tag in terms of relatively low influence by ambient temperature and easy insertion compared to lower scapula or lateral neck.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.57 no.2
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• pp.106-112
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• 2012

In order to understand the growth and ecophy -siological response of ginseng to global warming condition, we cultivated one and two year ginseng seedlings in control (ambient $CO_2$ + ambient temperature) and global warming treatment (elevated $CO_2$ + elevated temperature) from March 2010 to July 2011. Shoot appearance and initiation of flowering were advanced by 3-4 days in global warming treatment than in control. However, timing of fruit setting and seed ripeness was similar in both control and global warming treatment. Shoot length was longer in global warming treatment than in control, and also the number of leaves was much in global warming treatment. Fresh root weight was not different between control and global warming treatment. Photosynthetic rate was higher in global warming treatment than at control. Photosynthetic rate and transpiration rate were higher in two year seedlings than in one year seedlings at control, but was not different between seedling age of ginseng in global warming treatment. Water use efficiency was higher in one year seedlings than two year seedlings at control and global warming treatment. These results demonstrated that Korean ginseng more or less positively responds to global warming situation.