• Korean Journal of Agricultural Science
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• v.50 no.3
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• pp.497-505
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• 2023

This study evaluated the impact of rain shelters made of plastic film on spring frost damage and fruit quality in Asian pears ('Niitaka') over two years. In 2021, during the coldest spring days (between 0:00 am and 7:00 am), temperatures dropped to -1.20 - 0.43℃ at 120 cm and -1.33 - 0.57℃ at 200 cm above ground level in the control. Conversely, the rain shelter treatment maintained higher temperatures, -0.40 - 0.87℃ at 120 cm and -0.43 - 0.77℃ at 200 cm. Flower damage was significantly lower in the rain-sheltered group, with incidences of 1.3 and 6.9% at 120 and 200 cm, respectively, compared with 18.1 and 22.6% in the control group. Visual observations verified the prevention of frost adhesion on flower organs in the sheltered group, compared with noticeable pistil death and petal browning in the control group. In 2022, when temperatures remained above 0℃, fruitlet stalk length was 5 - 6 mm longer in the sheltered group. The cumulative impact of rain shelters was evident in the improved fruit quality over the two years. This study suggests resilient cultivation strategies in the face of climate change to reduce frost damage, increase productivity, improve fruit quality, and potentially increase incomes of the farmers.

• Journal of the Korea Institute of Building Construction
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• v.24 no.2
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• pp.193-202
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• 2024

This research delves into the evaluation of the suitability of ultrasonic pulse velocity as a diagnostic tool for early detection of frost damage in concrete. The investigation involves the measurement of compressive strength and ultrasonic pulse velocity concerning the depth of freezing for individual mortar specimens, followed by an analysis of their microstructure and their interrelation. The findings indicate a consistent decrease in both compressive strength and ultrasonic pulse velocity with increasing freezing depth. Furthermore, a correlation between compressive strength and ultrasonic pulse velocity concerning the depth of early frost damage is established. Consequently, the study asserts the potential of utilizing the ultrasonic pulse velocity method for early detection of frost damage in concrete, with prospects for quantifying the depth of damage through further research endeavors.

• Journal of the Korean GEO-environmental Society
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• v.15 no.10
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• pp.5-13
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• 2014

In this research, in order to study insulation effect of commercial XPS and recycled PE aggregates for prevention of frost heave in the roadbed of railroad track from the freezing temperature, model tests were carried out in the large freezing room. For this, thermal conductivities were measured for various dry densities, water contents, temperatures and mixing ratios of PE aggregates. From the tests, it can be seen that thermal conductivities of roadbed decrease with the increase of the ratio of mixed PE aggregates. However it was sensitive to the changes of temperature and water content due to the amount of water in the voids. From the model test of railroad track, it can be seen that the time to reach $0^{\circ}C$ was longer for XPS than that for the PE aggregates. Also the test shows best insulation effect can be achieved when XPS board was installed above the PE aggregate layer rather than the opposite order.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.11a
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• pp.23-25
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• 2013

In this study, the results are compared with the case of the concrete with embedded heating wire to verify the performance of the IB made in order to improve the workability and affordability, and to determine the effectiveness of early frost damage prevention. The IB was made using the 5W heating wire and layed on the upper surface of the concrete. The temperature was reduced to below 0℃ approximately within 24 hours, then approached the external temperature thereafter. On the other hand, when the 20W heating wire was used to make the IB and applied the same way, the temperature remained around -2 to 3℃ on the average even through the temperature was reduced to below 0℃, due to the heating wire with relatively large heating capacity. It appeared to reach 85% of the direct heating by embedding the heating wire relatively deeper in the concrete. However, it was determined that using the IB made with the 20W heating wire will prevent the early frost damage to some degree in -10℃.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.11a
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• pp.47-49
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• 2012

Under this study, the characteristics of concrete intensity condition following the curing method under the extremely low temperature environment have been contemplated, and as a result, in the event of insulation + heat cable curing, the intensity and accumulated temperature accomplishment period is required for two times of requiring initial frost damage prevention than the case of heating + heat insulation curing method due to the insufficient calories supplied in general.

• Nuclear Engineering and Technology
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• v.44 no.5
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• pp.523-534
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• 2012

The objective of this study was to experimentally investigate the effect of heat curing methods on the temperature history and strength development of slab concrete exposed to $-10^{\circ}C$. The goal was to determine proper heat curing methods for the protection of nuclear power plant structures against early-age frost damage under adverse (cold) conditions. Two types of methods were studied: heat insulation alone and in combination with a heating cable. For heat curing with heat insulation alone, either sawdust or a double layer bubble sheet (2-BS) was applied. For curing with a combination of heat insulation and a heating cable, an embedded heating cable was used with either a sawdust cover, a 2-BS cover, or a quadruple layer bubble sheet (4-BS) cover. Seven different slab specimens with dimensions of $1200{\times}600{\times}200$ mm and a design strength of 27 MPa were fabricated and cured at $-10^{\circ}C$ for 7 d. The application of sawdust and 2-BS allowed the concrete temperature to fall below $0^{\circ}C$ within 40 h after exposure to $-10^{\circ}C$, and then, the temperature dropped to $-10^{\circ}C$ and remained there for 7 d owing to insufficient thermal resistance. However, the combination of a heating cable plus sawdust or 2-BS maintained the concrete temperature around $5^{\circ}C$ for 7 d. Moreover, the combination of the heating cable and 4-BS maintained the concrete temperature around $10^{\circ}C$ for 7 d. This was due to the continuous heat supply from the heating cable and the prevention of heat loss by the 4-BS. For maturity development, which is an index of early-age frost damage, the application of heat insulation materials alone did not allow the concrete to meet the minimum maturity required to protect against early-age frost damage after 7 d, owing to poor thermal resistance. However, the combination of the heating cable and the heat insulating materials allowed the concrete to attain the minimum maturity level after just 3 d. In the case of strength development, the heat insulation materials alone were insufficient to achieve the minimum 7-d strength required to prevent early-age frost damage. However, the combination of a heating cable and heat insulating materials met both the minimum 7-d strength and the 28-d design strength owing to the heat supply and thermal resistance. Therefore, it is believed that by combining a heating cable and 4-BS, concrete exposed to $-10^{\circ}C$ can be effectively protected from early-age frost damage and can attain the required 28-d compressive strength.

• Proceedings of the SAREK Conference
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• 2004.06a
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• pp.17-17
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• 2004

• Journal of the Korea Institute of Building Construction
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• v.16 no.1
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• pp.67-76
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• 2016

Concrete exposed to severely low temperature below $-20^{\circ}C$ should be provided with proper heat supplying curing to protect the concrete from early frost damage at the time of pouring.meanwhile, so far, effective heat curingmethods of the concrete under severely low temperature are not well established in Korea. For this reason, the objective of this paper is to provide effective heat curingmethod of concrete exposed to severely low temperature to protect early frost damage by varying the combination of heat curingmaterial combinations. Temperature history,maturity development and core strength results are investigated. Fourmock-up specimens simulating slab, wall and column were prepared and heat insulation, heat supplying and both were applied. Test results indicate that the combination of quadruple layer bubble sheet(4BS) and embedding of heating cable has desirable performance for a slab, and heat supplying curing inside heat enclosure and heat generationmat also shows desirable performance for a wall, and for a column, use of EPS heat insulation has proper performance against early frost damage, which reaches $45^{\circ}D{\cdot}D$ and helps the concretemaintain above $0^{\circ}C$ within 3 days. Themethodsmentioned above are believed to be optimum protection from early frost damage of the concrete under $-20^{\circ}C$.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.05a
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• pp.11-12
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• 2017

This study aims to analyze the properties of the temperature change in vertical reinforcements in outdoor wall structures in winter in relation to the different methods of bubble sheet installation, and to subsequently determine the possibility of initial frost damage to the concrete as a result of low temperature. As for the experimental variables, double bubble sheets were used as curing materials, and the curing method was to model the part where the slab and the wall intersect and the rebar is exposed, and to measure the change of temperature around the exposed rebar in accordance with the change of the coating curing. It was found that by employing curing method B, which is to install the bubble sheet between the vertical reinforcements, the most vulnerable area, which is 50mm below(④) the surface of the concrete, would be lowered to sub-zero temperature 20 hours later than when using curing method A, and that therefore it is more effective to install the bubble sheet between the vertical reinforcements for the prevention of initial frost damage.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.941-946
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• 2006

It followed in system development and SMRT(Seoul Metropolitan Rapid Transit Co)System reached to an automatic train operation(ATO) and driverless operation(DLM) from the manual operation due to the train driver. The train like the general bus or the car vehicle was not serial riding in a car and the Parallel concept which the numerous passenger rides in a car simultaneously occur frequently the charge of the train driver unmanned bitterly from existing manual handling was a possibility of doing, train open door control(ODM) which bites also ATO, it handles it minimized. Like this ATO/DLM, the control system which bites being a Wayside to Train communication for immediacy, it is a system of the Vital concept the immediacy of the citizen Data evil the radio information transmission and the train of the interface which is accurate from unmanned operation and, will decipher, will accomplish it will guarantee. It respects the passenger accident prevention and an air question environment improvement from subway platform and phul leys the screen door of Platform(PSD) with the fire tube frost it refers and part it treats and to sleep it does, ODM which bites is accuracy and immediacy of altitude and when seeing from the viewpoint which demands the trust of altitude, ODM system the trust of car incest interface in the equipment construction which is safe and the comparative analysis back of the system analysis against the control which bites and case study and other subway system it leads from the research which it sees and signal - train in base grudge to sleep it contributes it does.