• Korean Journal of Remote Sensing
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• v.35 no.5_1
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• pp.751-761
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• 2019

Mt. Baekdu, Mt. Aso, Mt. Sakurajima, Mt. Kikai and etc are distributed around the Korean Peninsula. Recently signs of eruption of Mt. Baekdu are increasing, raising concerns over possible damage to volcanic ash from seasonal winds during the winter eruption. Therefore, detailed procedures for investigation and countermeasures for volcanic ash spread and damage are required. But the standards for the warning and alarm signal of volcanic ash presented by Korea Ministry of Government Legislation are vague, with "when damage is expected" and "when serious damage is expected". In this study, to analyze the damage threshold and to apply the cases of overseas damage to the country, a survey was conducted on the establishment of domestic spatial information by public institutions with public confidence. As a result of the investigation of damage from volcanic ash overseas, the details of the damage cases were different depending on the type of life or income sources of each country. Therefore, instead of applying the volcanic ash damage cases abroad in Korea, spatial information analysis was performed to reflect domestic social and natural characteristics. In addition, we selected the areas to be considered in the event of volcanic ash damage in Korea. Finally, domestic volcanic ash damages should be classified as health, residential, road, railroad, aviation, power, water, agriculture, livestock, forest, and soil. When establishing the volcanic ash alarm optimized for Korea in the future, overseas volcanic ash damage cases and domestic spatial information construction in this study will be helpful in policy establishment.

• Composites Research
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• v.16 no.4
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• pp.44-50
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• 2003

The damage zone around a crack tip occurring before the fracture is a significant domain. which affects the toughening mechanism of materials. In this study. the growth process of damage zone in the vicinity of crack tip for rubber-modified epoxy resin is investigated using an acoustic emission(AE) analysis. The weight fractions of rubber(CTBN 1300$\times$B) in rubber-modified epoxy resin are 5 wt% and 15 wt%. The fracture toughness($K_{IC}$) and the fracture energy($G_{IC}$) were measured using 3 point bending single-edge notched specimens. The damage zone and rubber particles distributed around the crack tip were observed by a polarized optical microscope and an atomic force microscope(AFM). The damage zone around crack tip of rubber-modified epoxy resin was formed at 13 % loading and developed until 57 % loading of the fracture load. The crack initiated at 57 % loading grew repeatedly in the stick-slip propagation behavior. Based on time-frequency analysis, it was confirmed that AE signals with frequency bands of 0.15~0.20 MHz and 0.20~0.30 MHz were generated from cavitation and stable/unstable cracking inside the damage zone.

• Smart Structures and Systems
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• v.15 no.4
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• pp.1121-1137
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• 2015

This study presents probabilistic-based damage identification technique for highlighting damage in metallic structures. This technique utilizes distributed piezoelectric transducers to generate and monitor the ultrasonic Lamb wave with narrowband frequency. Diagnostic signals were used to define the scatter signals of different paths. The energy of scatter signals till different times were calculated by taking root mean square of the scatter signals. For each pair of parallel paths an error function based on the energy of scatter signals is introduced. The resultant error function then is used to estimate the probability of the presence of damage in the monitoring area. The presented method with an autofocusing feature is applied to aluminum plates for method verification. The results identified using both simulation and experimental Lamb wave signals at different central frequencies agreed well with the actual situations, demonstrating the potential of the presented algorithm for identification of damage in metallic structures. An obvious merit of the presented technique is that in addition to damages located inside the region between transducers; those who are outside this region can also be monitored without any interpretation of signals. This novelty qualifies this method for online structural health monitoring.

• International Journal of High-Rise Buildings
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• v.3 no.2
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• pp.121-145
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• 2014

The story shear force distributions of most seismic design codes generally reflect the influences of higher vibration modes based on the elastic deformations of structures. However, as the seismic design allows for the plastic behavior of a structure, the story shear force distribution shall be effective after it is yielded due to earthquake excitation. Hence this study conducted numerical analyses on the story shear force distributions of most seismic design codes to find out the characteristics of how a structure is damaged between stories. Analysis results show that the more forces are distributed onto high stories, the lower its concentration is and the more energy is absorbed. From the results, this study proposes the optimum story shear force distribution and its calculation formula that make the damages uniformly distributed onto whole stories. Consequently, the story damage distribution from the optimum calculation formula was considerably more stable than existing seismic design codes.

• Earthquakes and Structures
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• v.16 no.6
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• pp.691-704
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• 2019

This study simulates the responses of large-scale bridge piers under pseudo-dynamic tests to investigate the performance of four types of numerical models that consider the nonlinear behavior of the pier and the rocking behavior of the footing. In the models, beam-column elements with plastic hinges are used for the pier, two types of foundation models (rotational spring and distributed spring models) are adopted for the footing behavior, and two types of viscous damping models (Rayleigh and dashpot models) are applied for energy dissipation. Results show that the nonlinear pier model combined with the distributed spring-dashpot foundation model can reasonably capture the behavior of the piers in the tests. Although the commonly used rotational spring foundation model adopts a nonlinear moment-rotation property that reflects the effect of footing uplift, it cannot suitably simulate the hysteretic moment-rotation response of the footing in the dynamic analysis once the footing uplifts. In addition, the piers are susceptible to cracking damage under strong seismic loading and the induced plastic response can provide contribution to earthquake energy dissipation.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.23 no.4
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• pp.729-735
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• 2013

The recent issue of distributed denial of service attack paralyze major government and financial institution in internet sites. They threatened to the cyber security. There hasn't been easy defense of now using attack. There seems to be increases in damage. In this paper, The recent continue to evolve of distributed denial of service attack. DNS target of distributed denial of service attack give specific examples. but, DNS target of DDoS attacks about defense is insufficient. The DNS Cyber-shelter system was created based on the Cyber-shelter system for DDoS attack in Kisa.. We proposal DNS Cyber-shelter system.

• Journal of the Society of Disaster Information
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• v.10 no.2
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• pp.304-311
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• 2014

Disaster Resources are the resources used in the disaster fields such as fire, typhoon, flood, collapse, flood damage, distress, relief, sanitary, explosion and so forth. The resources are distributed by the several institutes including governmental agencies, public institution, and private sectors. When the large scale disaster is occurred, many kinds of the disaster resources are needed. But it is not easy to know where institutes has the needed resources, because the resource management systems are all distributed in the each institute. To integrate or connect the resource data among the systems, it need the several kinds of coordinations such as terms, classification, and resource exchange protocols. In this paper, we propose the standard specifications and how to connect and exchange the data among the systems.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.4
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• pp.312-319
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• 2014

When distributed generation such as a wind power system is connected to the grid, it should meet grid requirements like IEEE Std. 1547, which regulates the anti-islanding method. Since the islanding may cause damage on electrical equipments or safety hazards for utility line worker, a distributed generation should detect it as soon as possible. This paper proposes a hybrid anti-islanding method coupled with the active and passive detection methods. To enhance the harmonic extraction capability for an active harmonic injection method, cascaded second-order band-pass filter and signal processing scheme are employed. Simulation and experiments are carried out under the islanding test condition specified in IEEE Std. 1547. Passive over/under voltage and over/under frequency methods are combined with the active method to improve the detection speed under certain condition. The simulation and experimental results are presented to verify that the proposed hybrid anti-islanding method can effectively detect the islanding.

• Journal of Environmental Science International
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• v.23 no.8
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• pp.1385-1394
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• 2014

Metcalfa pruinosa was considered to be a very harmful invasive species, due to its high species density in nature and wide range of its host plants. M. pruinosa was distributed in 28 sites among 143 sites. M. pruinosa has wide range and diverse host plants of 52 families 110 species including crop, fruits and forest trees. At present, the identified host plant of M. pruinosa are composed of 62 families and 145 species in total since their first appearance was reported. M. pruinosa was found in roadside 46.7%, followed by forests 33.3% and orchard 20%. Nymphs and adults cause damage to crop and orchard by sucking juice, outbreak of fungi through secretion of wax, and reduction of plant assimilation due to the nectar of nymphs. Also, it reduces the merchantable quality of fruits and thus causes economic damage. It is judged that M. pruinosa has been moved along major road via the traffic vehicles.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.6
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• pp.1374-1379
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• 2015

Malicious network attacks such as DDoS has no clear measures, the damage is also enormous. In particular, in addition to a network failure, such as leakage of personal information and damage of the communication charge in the case of zombie smartphone is infected, is expected damages of various users. In this study, we extract the zombie smartphone's phenomena and features that appear while the zombie service is running and introduce a corresponding technique to prevent zombie smartphone.