• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.98-101
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• 2003

The Alkali-Aggregate Reaction (AAR) may cause a serious failure in the concrete structures. Several researchers in some nations have performed the continuous studies to prevent failure of a concrete structures by the AAR distress as well as the studies to manifest the mechanism. The ASTM Standards to prevent failure by potential AAR aggregates were established in 1950. The KS F2545 and KS F 2546 were established to test the susceptibility of aggregate to potential AAR in 1982. But the researches on the AAR have not been performed affluently in Korea because the distress due to AAR has seldom been reported officially. In this study, the Chemical Method and Scanning Electron Microscopy (SEM) were used to verifying the cause of the pattern crack on the surface and internal crack in the plain concrete pavement. It can be concluded that the distress of a specific site in plain concrete pavement was mainly due to AAR, and the chemical method and SEM may be the effective tools for verifying the cause of AAR distresses.

• International Journal of Highway Engineering
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• v.17 no.2
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• pp.13-20
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• 2015

PURPOSES: This paper describes the expansion caused by the alkali-aggregate reaction (AAR) in concrete pavement currently in service. It also discusses the effects of joints installed to release the stress induced by the AAR expansion. METHODS: The expansion effect on concrete pavement was verified by a visual inspection and long-term measurement of the joint width of a cut-section. The behaviors of 16 newly installed joints were monitored as part of the investigation and long-term monitoring was carried out for three years after cutting. RESULTS: The behavior of a bridge was affected when AAR occurred in the connected pavement. The newly installed joints shrank in the longitudinal direction of the bridge after cutting. The width of the joints decreased over the six months after cutting. A large portion of the joint width (8.5cm) was found to have closed nine months after cutting. It had ultimately shrunk by about 92 percent when the final measurement was taken. CONCLUSIONS : The expansion of the pavement due to AAR was quantitatively described by visual inspection and the long-term monitoring of the newly cut joints. However, the width of the new joints decreased over the six to nine months after cutting. Additional research should be conducted to determine a means of controlling the expansion due to AAR in the pavement.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.1
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• pp.7-15
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• 2017

Ambient Adjusted line Rating(AAR) method for overhead transmission lines considering Risk Tolerance(RT) was proposed in this paper. AAR is suitable for system operators to plan their operation strategy and maintenance schedule because this can be designed as a seasonal line rating. Several candidate transmission lines are chosen to apply the proposed method in the paper. As a result, it is shown that system reliability was significantly enhanced through maximizing transfer capability, solving the system constraints.

• Computers and Concrete
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• v.12 no.5
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• pp.627-650
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• 2013

This paper deals with application of a non-linear continuum model for reinforced concrete affected by alkali-aggregate reaction (AAR) to analysis of some nuclear structures. The macroscopic behaviour of the material affected by AAR is described by incorporating a homogenization/averaging procedure. The formulation addresses the main stages of the deformation process, i.e., a homogeneous deformation mode as well as that involving localized deformation, associated with formation of macrocracks. The formulation is applied to examine the mechanical behaviour of some reinforced concrete structures in nuclear power facilities located in Quebec (Canada). First, a containment structure is analyzed subjected to 45 years of continuing AAR. Later, an inelastic analysis is carried out for the spent fuel pool taking into account the interaction with the adjacent jointed rock mass foundation. In the latter case, the structure is said to be subjected to continuing AAR that is followed by a seismic event.

• Proceedings of the Korea Concrete Institute Conference
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• 1993.10a
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• pp.103-107
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• 1993

The Alkali Aggregate Reaction(AAR), reported first by T. E. Stanton in 1940, is a reaction between certain siliceous aggregate and hydroxyl ions present in the pore fluid of a concrete. The damage of concrete structures, deteriorated by AAR, have been reported since using the crushed stones caused by the exhaustion of natural aggregates. This study was performed to investigate the AAR of crushed stones using chemical analysis, polarization microscope, XRD, chemical method(KS F 2545, ASTM C 289), mortar bar method(KS F 2546, ASTM C 227) and Scanning Electron Microscope(SEM) and Energy Dispersive X-ray Analysis (EDXA) of reaction products by AAR in mortar bar.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.5
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• pp.67-73
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• 2017

The concrete pavement slabs that suffer expansion due to the Alkali-Aggregate Reaction(AAR) increase and the increase consequently causes unexpected displacement of bridge abutment. As the expansion due to the AAR is greater than that due to the temperature change, lethal load can act on bridge abutment. Therefore appropriate preventive measures may be necessary. The degree of expansion by AAR depends on the severity of AAR and geometry condition of concrete pavement and road structure. In order to prevent damage to bridge, it is effective to release the expansion force of the concrete. It would be advantageous to replace the concrete pavement with asphalt for a long section of concrete pavement.

• Structural Engineering and Mechanics
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• v.64 no.6
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• pp.793-802
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• 2017

The damage of concrete due to the expansion of alkali-aggregate reaction (AAR) and thermal-chemical reactions affecting the strength of concrete is studied. The empirical equations for the variations of expansion of AAR, compressive strength and degradation of the modulus of elasticity with time, and compressive strength with degradation of the modulus of elasticity are proposed by analysing numerous experimental data. It is revealed that the expansion of AAR and compressive strength increase with time. The proposed combination of the time variations of chemical and mechanical parameters provides a satisfactory prediction of the concrete strength. Seismic analysis of the aged Koyna dam is conceded for two different long-term experimental data of concrete incorporating the proposed AAR based properties. The responses of aged Koyna dam reveal that the crest displacement of the Koyna dam significantly increases with time while the contour plots show that major principal stress at neck level reduces with time. As the modulus of elasticity decreases with ages the stress generated in the concrete structure get reduces. On the other hand with lesser value of modulus of elasticity the structure becomes more flexible and the crest displacement becomes very high that cause the seismic safety of the dam reduce.

• KIPS Transactions on Computer and Communication Systems
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• v.6 no.4
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• pp.203-210
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• 2017

Address resolution protocol (ARP) is used for binding a logical address to a physical address in many network technologies. However, since ARP is an stateless protocol, it always abused for performing ARP-based attacks. Researchers presented many technologies to improve ARP protocol, but most of them require a high implementation cost or scarify the network performance for improving security of ARP protocol. In this paper, we present an address auto-resoultion (AAR) network system to neutralize the ARP-based attacks. The AAR turns off the communication function of ARP messages(e.g. request and reply), but does not disable the ARP table. In our system, the MAC address of destination was designed to be derived from destination IP address so that the ARP table can be managed statically without prior knowledge (e.g., IP and MAC address pairs). In general, the AAR is safe from the ARP-based attacks since it disables the ARP messages and saves network traffics due to so.

• Journal of the Korean Society of Radiology
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• v.13 no.4
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• pp.539-546
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• 2019

Liver biopsy is invasive and it is a risk of complications. Nevertheless, liver biopsy is gold standard for predicting liver fibrosis. To compensate for these shortcomings, in this study, the liver fibrosis stage was divided using Fibroscan(R) in 200 chronic hepatitis C patients. And, the usefulness and cut-off values of fibrosis index based on four factors(FIB-4), AST to platelet ratio index(APRI) and AST/ALT ratio(AAR) calculated as serum tests were investigated by analyzing ROC curve. As a result, using FIB-4 and APRI rather than AAR is appropriate for evaluation of liver fibrosis. And using APRI to predict significant Fibrosis(F2) and FIB-4 is considered useful for predicting cirrhosis(F4). By applying the advantages of the serum based liver fibrosis marker, which are convenient and repeatable, liver fibrosis follow-up term can be reduced, and furthermore, the prevalence of liver cirrhosis and hepatocellular carcinoma(HCC) can be reduced.

• The Korea Journal of Herbology
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• v.20 no.3
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• pp.9-18
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• 2005

Objectives : The purpose of this study is to investigate characteristics of cell morphology of two different agar woods (Aquilaria agallocha Roxburgh (AAR) and imitative agar wood (IAW)) using microscopic techniques. Methods : Both light and scanning electron microscopes were used to observe morphological and histological features of the cell of agar woods collected from commercial products in the market. Results : The cell morphology and tissue arrangements of AAR depending on either the adsorption of resin into vessels or no adsorption of resin were observed to compare these features with those of both IAW and Aquilaria sinensis Gilb (ASG). Conclusions : As a result, the vessels of AAR with the resin adsorption was packed with lots of yellow-brownish materials, which were quite different from those of IAW and ASG. The cell walls were thick, and had well-developed traumatic parenchyma tissues with squared cells of the same height and width, which appeared as a clump of small grains packed.