• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.7
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• pp.645-653
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• 2013

Seoul National University flap(SNUF) blade is a small-scale rotor blade incorporating a small trailing-edge flap control surface driven by piezoelectric actuators at higher harmonics for vibration attenuation. Initially, the blade was designed using two-dimensional cross-section analysis and geometrically exact one-dimensional beam analysis, and its material configuration was finalized. A flap-deflection angle of ${\pm}4^{\circ}$ was established as the criterion for enhanced vibration reduction based on an earlier simulation. The flap-linkage mechanism was designed and static bench tests were conducted for verifying the performance of the flap-actuation mechanism. Different versions of test beds were developed and tested with the designed flap and the selected APA 200M piezoelectric actuators. Through significant improvements, a maximum deflection of ${\pm}3.7^{\circ}$ was achieved. High-frequency experiments were conducted for evaluating the performance, and the transfer function of the test bed was determined experimentally. With the static tests almost complete, the rotor power required for testing the blade in a whirl tower (centrifugal environment) was calculated, and further preparations are underway.

• Journal of the Korean Geosynthetics Society
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• v.14 no.3
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• pp.31-42
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• 2015

The Reinforced subgrade for railroad (RSR) was constructed for one way railway line with the dimension of 5 m high, 6 m wide and 20 m long to evaluate its performance under train design load. The RSR has characteristics of short length (0.3-0.4 H) of reinforcement and rigid wall, 30 and 40 cm vertical spacing of reinforcement installation. To enhance economics and constructability, three kinds of connections (welding, hinge & bolt, bold wire) were also designed to realize the integration between rigid wall and reinforced subgrade. Two times of static loading tests were done on the full size railroad subgrade. The maximum applied pressure was 0.98 MPa (the maximum test load 5.88 MN), which corresponds to 19.6 times of the design load for railroad subgrade, 50 kPa. The performance on the RSR was evaluated with the safety on the failure, subgrade bearing capacity and settlement, horizontal displacement of wall, and reinforcement strain. Based on the full scale test, we confirmed that the RSR with the conditions of 0.35 H (35% of height) short reinforcement length, hinge & bolt type connection for integration between rigid wall and reinforced subgrade, and 40cm vertical spacing of reinforcement installment shows good performance under train design load.

• The Journal of Information Technology
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• v.3 no.3
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• pp.27-37
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• 2000

Although an insurance criterion for reliance is unified, the difference in evaluation mechanism in every country is already ambiguity. In other words, the aspect of objectivity would be a little because it is true that the vulnerability evaluation include evaluator, scenario and tools (TSVES) applying in test, depth and scope of evaluation. But evaluation results can be difference in accordance with each evaluation elements. By using TSVES to evaluating network security vulnerability, first, we expected the evaluation results is impartiality, objectivity, repeatability, reproducibility, appropriateness and soundness of results. Second, it could be transferred manual ways into automation ways, and then expected easiness and safety of extension and modification in a quality of products as well as a dramatical reduction of waste of time and energy.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.10
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• pp.5290-5298
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• 2013

In order to apply a mechanical deck joint to the prefabricated steel grid composite decks, shear resistance of a joint composed of concrete shear key and high-tension bolt is experimentally evaluated by the push-out test. Shear resistance evaluated by the test is compared with resistance estimated by empirical and design equations based on the shear friction theory. Test results show that joint specimens bonded by epoxy have about 10% more shear resistance than specimens with strengthened shear key by steel plates, but in the case of specimens with strengthened shear key there is smaller resistance deviation than specimens bonded by epoxy. In comparison with resistances estimated by empirical and design equations, the deck joint can be safely designed. But because the existed shear resistance of deck joint is underestimated by the ACI-318, application of the LRFD design equation could be more reasonable.

• Journal of the Korean GEO-environmental Society
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• v.15 no.7
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• pp.59-66
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• 2014

Nowadays, some studies are performed in order to introduce the Limit State Design method widely used in foreign work sites. LRFD (Load Resistance Factor Design) method is widely used in the fields in which the data accumulation is possible - such as deep foundations, and shallow foundations, etc. The limit state design in the retaining walls is insufficient in the country owing to difficulties applying load tests. The limit state design method for retaining wall structures are studied based upon the National Retaining wall Design Standard legislated in 2008 by Ministry of Land, Transport, and Maritime Affairs. In this paper several retaining walls were calculated according to LRFD design criteria analysis using the general program with limit state design method and the factor of safety for sliding and overturning. Comparing with their results, the Taylor's series simple reliability analysis was performed. In the analysis results of retaining wall section, safety factors calculated by LRFD were found to be lowered than those calculated in current WSD, and it is possibly judged to be economic design by changing wall dimensions. In the future, pre-assessment of the geotechnical data for ensuring the reliability and the studies including reinforced retaining walls with ground anchor are needed.

• Journal of the Korean GEO-environmental Society
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• v.18 no.11
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• pp.13-18
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• 2017

In a banking process for construction of a complex, non-compaction construction has been applied in most sites, which is a method that soils are compacted by the equipment load without being compacted separately. However, there are no specific descriptions in the construction manual or specifications, so it is unclear to evaluate the excavation volume. Hence, this study is a basic study to compare the soil conversion factor at a design stage and the actual soil conversion factor of a banking ground under a non-compaction condition in order to examine the feasibility in constructing the ground for construction of the complex and to examine appropriateness of the earth work in the site by conducting an indoor, field, and load-settlement test and proposing a reasonable soil conversion factor. Under the non-compaction condition, the soil conversion factor C is set to be 1.0 at the design stage, but the result of the field test was 0.86 which is smaller than the value at the design stage. It was expected that this result would increase the banking volume, and the construction result actually showed a difference in the banking volume. Therefore, for the baking ground under the non-compaction condition, it is necessary to apply the value C suitable for the site condition after performing test by considering the site's condition and the banking height.

• Journal of the Korean Geosynthetics Society
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• v.22 no.3
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• pp.1-10
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• 2023

Recently, numerous structures have been constructed near the Nakdong river estuary, with pile foundations embedded in sand and gravel layers. In this study, the side resistance for six drilled shafts embedded in that region was evaluated based on the results of bi-directional and static axial compressive pile load tests. Subsequently, these results were compared with the side resistance calculated using domestic and foreign design codes such as FHWA (1999), KDS (2021), and AIJ (2004). Based on the test results, the evaluated side resistances ranged from 120 to 444kPa. However, the estimated values obtained from the design codes ranged from 69.3 to 170kPa, which were less than 50% of the evaluated values. It was observed that the empirical methods and correlations used in design codes provide a conservative estimation of the side resistance for drilled shafts embedded in sand and gravel layers. It implies that a suitable domestic approach should be developed to accurately estimate the side resistance of pile in sandy gravel and gravel layers near the Nakdong river estuary.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.5
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• pp.87-92
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• 2005

This paper presents a design concept of smart UAV console system and the analysis of its dynamic response to shock and vibration. The console system design is determined by two main elements; the shape design and the mechanical design. The shape design refers to the human engineering aspects according to the military standards for ship borne equipment. The goal of the mechanical design is to provide the required shock and vibration endurance. The endurance of the system is numerically verified by means of Finite Element Method. The results of verification show that six resilient mounts installed on the console allow to sufficiently decrease the influence of the input impact wave on endurance of the system.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.1381-1388
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• 2011

Recently, Because of weight lighting and tighten safety regulations of the railway vehicle railroad weight lighting and safety improvement technology is internationally required. Slide step for moving the passenger to high flatform in the railroad vehicle is recognized of important parts. However, Due to high price and weight, it is limited. In this research, In order to apply for railroad, it was redesigned to optimize part count and reduce the price and weight. By choosing honeycombcore as a part for enduring high weight and weight lighting, We produce honeycombpanel of sandwich structure which a different kind connected by using existing stainless(STS304)steel and thermo plasticity glue. Finally, we can find that honeycombpanel is suitable for weight lighting and high weight. As well as, with test result, we can prove that low-high platform railway system will be optimized, if steps are applied to honeycombpanel.

• Journal of the Korean GEO-environmental Society
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• v.11 no.4
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• pp.51-59
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• 2010

This article is a case study for the example of the foundation design, in the project area of the silty sand layer that is spread shallowly with loose status, to make the site for a structure and build it up. The site is located on the dredged and reclaimed land in Gun-San and In-Cheon that is formed the silty sand layer with loose status range around 10 meters underground level, the solid ground for the lower pile is shown around 20 meters underground level. Therefore, this area has to be done by ground improvement when applying for the shallow method of foundation. Dynamic compaction method considering the conditions of the design loads in each zone has to be decided through comparative review on the method of foundations and pilot field test was conducted, and drilling investigation and plate bearing test were achieved as well. The analysis results of the tests prove that stability against bearing capacity was acquired by ground improvement effect.