• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.629-634
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• 2001

Recently, to consider financial and constructive aspect, usage of Admixture, like Blast-Furnace Slag and Fly-Ash, are increased. Also the use of cold-weather-concrete is increased. Blast-furnace Slag, a by-product of steel industry, have many advantage, to reduce the heat of hydration, increase in ultimate strength and etc. But it also reduces early-age strength, so it is prevented from using of Blast-Furnace Slag at cold-weather-concrete. In this study, for the purpose of increasing usage of Blast-Furnace Slag at cold-weather-concrete, it is investigated the strength properties of concrete subjected to frost damage for the cause of early age curing. According to this study, if early curing is carried out before having frost damage, the strength of concrete, subjected to frost damage, is recovered. And that properties is not connected with the frost cause.

• Nuclear Engineering and Technology
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• v.45 no.3
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• pp.393-400
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• 2013

Concrete undergoing early frost damage in cold weather will experience significant loss of not only strength, but also of permeability and durability. Accordingly, concrete codes like ACI-306R prescribe a minimum compressive strength and duration of curing to prevent frost damage at an early age and secure the quality of concrete. Such minimum compressive strength and duration of curing are mostly defined based on the strength development of concrete. However, concrete subjected to frost damage at early age may not show a consistent relationship between its strength and durability. Especially, since durability of concrete is of utmost importance in nuclear power plant structures, this relationship should be imperatively clarified. Therefore, this study verifies the feasibility of the minimum compressive strength specified in the codes like ACI-306R by evaluating the strength development and the durability preventing the frost damage of early age concrete for nuclear power plant. The results indicate that the value of 5 MPa specified by the concrete standards like ACI-306R as the minimum compressive strength to prevent the early frost damage is reasonable in terms of the strength development, but seems to be inappropriate in the viewpoint of the resistance to chloride ion penetration and freeze-thaw. Consequently, it is recommended to propose a minimum compressive strength preventing early frost damage in terms of not only the strength development, but also in terms of the durability to secure the quality of concrete for nuclear power plants in cold climates.

• Journal of the Korea Concrete Institute
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• v.12 no.3
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• pp.47-55
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• 2000

Protections from the frost damage at early ages are one of the serious problems to be considered in cold weather concreting. Frost damage at early ages brings about the harmful influences on the concrete structures such as surface cracks and declination of strength development. Therefore, in this paper, protecting periods of frost damage at early ages according to the standard specifications provided in KCI(Korean Concrete Institute) are suggested by appling logistic curve, which evaluates the strength development of concrete with maturity. W/B, kinds of cement and curing temperatures are selected as test parameters. According to the results, the estimation of strength development by logistic curve has a good agreement between calculated values and measured values. As W/B and compressive strength for protecting from frost damages at early ages increase, it is prolonged. It shows that the protecting periods of FAC(Fly Ash Cement) and BSC(Blast-furnace Slag Cement) concrete are longer than those of OPC(Ordinary Portland Cement) concrete. The protecting peridos from frost damage at early age by JASS are somewhat shorter than those by this paper.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.316-321
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• 2000

The role of fatigue on the surface damage of 5% chrome cold milling work roll is evaluated. Uniaxial and torsional fatigue tests are carried out, and the baseline data for fatigue life evaluation are established. An appropriate multiaxial fatigue parameter is developed from the fatigue data. Fatigue tests are also performed under compressive mean stresses, and a mean stress model is formulated. A computer program is developed to assess the interaction of fatigue and grinding of the roll. The fatigue damage is computed for selected servicing conditions. It is found that the fatigue damage can be an important issue when the effect of mean stress is ignored, however the fatigue damage is negligibly small when the effect of mean stress including the residual stresses currently used is fully accounted. The result indicates that spalling due to the growth of thermal shock cracks is more important than fatigue damage in roll surface failure.

• Korean Journal of Oriental Medicine
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• v.18 no.1
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• pp.25-34
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• 2012

Objective : This study was carried out with focus on written by Joh, Taek-seung (曺澤承) and Joh, Byeong-who(曺秉矦) in the relation of father and son in 1933. This book is a medical book including rare data, which has never been reported to academic circles all this while. Method : First, this study looked into the authors of this book and its history of publication. Further, this study analyzed the composition and contents of this book. Lastly, this study summed up the meaning of this book from the standpoint of medical history. Result : The authors were Confucian doctors who were active in the latter era of the Joseon Dynasty and also in the period of Japanese colonial rule. They lived in Haenam district of Jeonlanam-do, and cured its neighboring local residents while studying. They published the book of by putting together their own medical experiences. The authors suggested their remedial prescription according to gender and age whereas Zhang Zhongjing(張仲景) suggested the remedial prescription according to Six-Meridian Pattern Identification & Syndrome Differentiation(六經辨證). In addition, the authors of gave weight to the relationship with internal damage. Additionally, the authors not only thought much of the relationship between internal damage and external damage but also thought of the weakness and strength of the healthy qi, and the new and the old of a disease as an important clue to medical treatment. It seems that such contents was influenced by (東醫寶鑑). Conclusion : shows the results of the research on which was spontaneously conducted in Joseon.

• The Korea Journal of Herbology
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• v.36 no.1
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• pp.51-57
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• 2021

Objects : In this study, I aimed to determine the size and administration Method of pills preparation in Treatise on Cold Damage Diseases. Methods : I investigated the Treatise on Cold Damage Diseases, Newly Revised Materia Medica, Variorum of the Classic of Materia Medica, The Korean Herbal Pharmacopoeia, and recent studies. Results : There were four kinds of pills preparation. Each size of pill preparation was equal to the Odongja, Tanwhan, Yolk, and quarter of daily dosage of Decoction. One pill of Tanwhan was equivalent to 16 pills of Odongja, and one Yolk was equal to 40 pills of Odongja. The Diameter of Odongja was 6.5 mm, Tanwhan was 16.37897 mm, and Yolk was 22.11484 mm. Jeodangwhan was equal to one quarter daily dosage of Jeodangtang. Maximum size to swallow with water was Odongja and daily dosage, which was 16 pills, includes one square-inch-spoon of powder preparation. When we made the pill preparation, it is difficult to make 16 pills using one square-inch-spoon of powder. Therefore, Zhang Zhongjing made one dosage started from 10 pills to 20 pills to find out optimum dose. Due to the difficulty of making precise size of pills and considerable amount of daily dosage, there was no smaller size than Odongja. When the size of Pill preparation was larger than Odongja, it was ground or boiled slightly to make suspensions. Conclusions : These results suggest that the sizes of Pill preparation in the Treatise on Cold Damage Diseases were true compared with reality.

• Transactions of Materials Processing
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• v.20 no.1
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• pp.48-53
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• 2011

Fasteners are used to join the various electronic products and machines. So, the quality and reliability of the fastener are strongly requested. In this study, the analyses of the multi-stage cold forging of TORX screws for storage parts are carried out. In manufacturing of TORX screws, crack and folding defects are observed. Therefore, the analysis is focused on the prediction of the defects. Based on the analysis results, the upper die and process conditions are redesigned to reduce the defects. The upper die shape for preform forming is redesigned to prevent folding and sharp shape change. The Cockroft-Latham damage criterion is introduced to predict the crack initiation. Analysis results shows that the maximum Cockroft-Latham damage value is decreased by 40% in the forming using the modified upper die.

• Journal of the Korean Association of Geographic Information Studies
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• v.26 no.1
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• pp.89-113
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• 2023

This study aimed to identify heat wave vulnerable areas and discuss spatial typology and policy directions through spatial coincidence analysis of heat wave damage. By utilizing the climate change vulnerability assessment of the Intergovernmental Panel on Climate Change (IPCC) and Spatial Statistics Comparison Analysis, this study examined cities, counties, and districts in South Korea for five years (2015-2019), including 2018, when the heat wave was most extreme. It was determined that the number of heat wave days (exposure) was the most impactful among various factors for heat wave vulnerability. Sensitivity and adaptive capacity to heat waves were found to vary according to regional characteristics. The relationship between heat wave vulnerability and damage was categorized into four types through spatial coherence. Hot to Hot and Cold to Cold types have a positive relationship between vulnerability and damage, while Hot to Cold and Cold to Hot types have a negative relationship. The findings suggest that since different types of regions have distinct characteristics and conditions, policies and research for improvement should be directed to address each region separately. This study may be used as basic data for establishing heat-related policies in the future, as it categorizes regions by considering both heat vulnerability and damage and examines the direction of response by type.

• Smart Structures and Systems
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• v.31 no.5
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• pp.485-500
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• 2023

Machine learning-based structural health monitoring (ML-based SHM) methods are researched extensively in the recent decade due to the availability of advanced information and sensing technology. ML methods are well-known for their pattern recognition capability for complex problems. However, the main obstacle of ML-based SHM is that it often requires pre-collected historical data for model training. In most actual scenarios, damage presence can be detected using the unsupervised learning method through anomaly detection, but to further identify the damage types would require prior knowledge or historical events as references. This creates the cold-start problem, especially for new and unobserved structures. Modal-based methods identify damages based on the changes in the structural global properties but often require dense measurements for accurate results. Therefore, a two-stage hybrid modal-machine learning damage detection scheme is proposed. The first stage detects damage presence using Principal Component Analysis-Frequency Response Function (PCA-FRF) in an unsupervised manner, whereas the second stage further identifies the damage. To solve the cold-start problem, mode shape assessment using the first mode is initiated when no trained model is available yet in the second stage. The damage identified by the modal-based method would be stored for future training. This work highlights the performance of the scheme in alleviating the cold-start issue as it transitions through different phases, starting from zero damage sample available. Results showed that single and multiple damages can be identified at an acceptable accuracy level even when training samples are limited.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.10a
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• pp.200-204
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• 1994

Low temperature associated damage mechanism is not well known for asphalt concrete. Many studies have related the thermal cracking of pavement in the roadway in cold region with overall shrinkage of the pavement surface under assumption of homogeneous material. This study, however, was intiated based on the assumption that thermal incompatibility of materials (heterogeneous) in asphalt concrete mixture would be the primary cause of the damages. Acoustic emission technique and microscopic obsevation were employed to evaluate damage mechanism of asphalt concrete due to low temperature. The first method showed the sufficient evidence that asphalt concrete could be damaged by lowered temperature only. The second method showed that the damage by temperature resulted in micro-cracks at the interface between asphalt matrix and aggregate particle. It was concluded that these damage mechanisms were the primary cause of major thermal cracking of asphalt pavement in cold region.