• Advances in nano research
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• v.16 no.1
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• pp.11-26
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• 2024

In this study, free vibration analysis of FG porous spherical cap reinforced by graphene platelets resting on Winkler-type elastic foundation has been surveyed for the first time. Three different types of porosity patterns are considered for the spherical cap whose two types of porosity patterns in the metal matrix are symmetric and the other one is uniform. Besides, five GPL patterns are assumed for dispersing of GPLs in the metal matrix. Tsai-Halpin and extended rule of the mixture are used to determine the Young modulus and mass density of the shell, respectively. Employing 3D FEM elasticity in conjunction with Hamilton's Principle, the governing motion equations of the structure are obtained and solved. The impact of various parameters including porosity coefficient, various porosity distributions in conjunction with different GPL patterns, the weight fraction of graphene Nano fillers, polar angles and stiffness coefficient of elastic foundation on natural frequencies of FG porous spherical cap reinforced by GPLs have been reported for the first time.

• Nuclear Engineering and Technology
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• v.53 no.9
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• pp.3068-3084
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• 2021

Investigations of large commercial aircraft impact effect on nuclear power plant (NPP) buildings have been drawing extensive attentions, particularly after the 9/11 event, and this paper aims to experimentally assess the damage and vibrations of NPP buildings subjected to aircraft crash. In present Part I, two shots of reduce-scaled model test of aircraft impacting on NPP building were carried out. Firstly, the 1:15 aircraft model (weighs 135 kg) and RC NPP model (weighs about 70 t) are designed and prepared. Then, based on the large rocket sled loading test platform, the aircraft models were accelerated to impact perpendicularly on the two sides of NPP model, i.e., containment and auxiliary buildings, with a velocity of about 170 m/s. The strain-time histories of rebars within the impact area and acceleration-time histories of each floor of NPP model are derived from the pre-arranged twenty-one strain gauges and twenty tri-axial accelerometers, and the whole impact processes were recorded by three high-speed cameras. The local penetration and perforation failure modes occurred respectively in the collision scenarios of containment and auxiliary buildings, and some suggestions for the NPP design are given. The maximum acceleration in the 1:15 scaled tests is 1785.73 g, and thus the corresponding maximum resultant acceleration in a prototype impact might be about 119 g, which poses a potential threat to the nuclear equipment. Furthermore, it was found that the nonlinear decrease of vibrations along the height was well reflected by the variations of both the maximum resultant vibrations and Cumulative Absolute Velocity (CAV). The present experimental work on the damage and dynamic responses of NPP structure under aircraft impact is firstly presented, which could provide a benchmark basis for further safety assessments of prototype NPP structure as well as inner systems and components against aircraft crash.

• Journal of Environmental Impact Assessment
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• v.18 no.2
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• pp.89-97
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• 2009

Korean society is faced with various new problems arising from the development projects of new towns, industrial cities, large-scale residential complexes, etc. started from the 1970s. Particularly with the construction of residential and industrial complexes by the roadsides, they are openly exposed to road traffic noise and vibration. Thus, the objective of this study is to examine using noise maps how increasing traffic volume affects road traffic noise and what problems it causes in areas where new towns or complexes are constructed by development projects. According to the results of this study, in areas around the sites of development projects, the noise level increased by road traffic noise compared to that before development and was 1.16~6.92 times higher than the environmental noise standard, but measures to reduce road traffic noise was lukewarm. In addition, areas with soundproof facilities showed a noise level 1~3 step lower than other areas, and in individual buildings, the noise level on the side facing the road was 1~2 step higher than that on the rear side.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.06a
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• pp.540-543
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• 2007

In this paper, we propose a new approach to reduce the audible noise generated by TFT-LCD module in mobile applications. We also analyzed impact factors which effect on the audible noise. It is expected that this noise source comes from various impact factors such as vibration of flexible printed-circuit board (FPCB) and LCD panel, and static electricity charged in window and back-light unit. Windowless type and window type models are evaluated to analyze noise level due to the static electricity charged in window. To obtain reliable and reproducible data, we constructed controllable test jig and measurement set-up.

• Journal of Environmental Impact Assessment
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• v.22 no.6
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• pp.739-744
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• 2013

Recently, railroad construction becomes an alternative considering environmental merits such as mass transportation, safety, economy and energy efficiency. Also railroad can have 3 to 4 times better in economy compared to road construction. However, long line and unavoidable sensitive areas hinders railroad construction often resulted in ecosystem degradation. This paper reviewed 27 cases of EIS submitted during 2003-2006 and reviewed major issues on Animal-Plants and Landscape. Noise-Vibration (13.5%), Water Quality (13.5%), Wastes (10.8%) appeared to be most frequent factors to supplement. Route selection in the railroad is the most sensitive issues so that public participation and hearing should be involved in the early stage of the process and social and cultural factors also must be considered to make a final decision on the railroad route location and selection.

• Wind and Structures
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• v.31 no.5
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• pp.403-418
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• 2020

To investigate the effects of central buckles on the dynamic behavior and flutter stability of long-span suspension bridges, four different connection options between the main cable and the girder near the mid-span position of the Aizhai Bridge were studied. Based on the flutter derivatives obtained from wind tunnel tests, formulations of self-excited forces in the time domain were obtained using a nonlinear least square fitting method and a time-domain flutter analysis was realized. Subsequently, the influences of the central buckles on the critical flutter velocity, flutter frequency, and three-dimensional flutter states of the bridge were investigated. The results show that the central buckles can significantly increase the frequency of the longitudinal floating mode of the bridge and have greater influence on the frequencies of the asymmetric lateral bending mode and asymmetric torsion mode than on that of the symmetric ones. As such, the central buckles have small impact on the critical flutter velocity due to that the flutter mode of the Aizhai Bridge was essentially the symmetric torsion mode coupled with the symmetric vertical mode. However, the central buckles have certain impact on the flutter mode and the three-dimensional flutter states of the bridge. In addition, it is found that the phenomenon of complex beat vibrations (called intermittent flutter phenomenon) appeared in the flutter state of the bridge when the structural damping is 0 or very low.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.4
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• pp.113-122
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• 2018

A hydraulic breaker is an attachment of an excavator, and it crushes stones. Recently, research to reduce the impact and noise of breakers are ongoing. In this paper, a method to improve the upper, lower, and side dampers, which act as insulation for the attenuation of vibration during breaker operation, is studied through testing and simulation. To obtain the nonlinear material constants required for the simulation, the biaxial tensile test was performed with urethane, which is a material used for dampers. The existing parts and the improved parts were compared and evaluated using the LS-DYNA program. As a result, 50% of the equivalent stress was reduced in the bracket body of the hydraulic breaker, and the equivalent stress of the side damper was also decreased. We verified that the fatigue conditions were satisfied by performing a fatigue analysis.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.13 no.2
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• pp.51-59
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• 2017

Steam jets ejected from a rupture zone of high energy pipes may cause damage to adjacent structures. This event could lead to more serious accidents in nuclear power plants. Therefore, to prevent serious accidents, high energy pipes of nuclear power plants are designed according to the ANSI / ANS 58.2 technical standard. However, the US Nuclear Regulatory Commission (USNRC) has recently pointed out non-conservatism in existing high energy pipe fracture evaluation methods, and required the assessment of the unsteady load of the jet caused by a potential feedback mechanism as well as the impact range of steam jet, the jet impact loads and the blast wave effects at the initial breakage stage. The potential feedback mechanism refers to a phenomenon in which a vortex formed by impingement jets amplifies vortex itself and induces jet vibration in a shear layer. In this study, CFD methodology using the LES turbulence model is established and numerical analysis is carried out to evaluate the dynamic behavior of impingement jets and the potential feedback mechanism during jet impingement. Obtained results have been compared with an empirical correlation and experiment.

• Journal of Environmental Impact Assessment
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• v.20 no.2
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• pp.123-131
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• 2011

The objective of this study is to prepare the effective management plan of environmental noise with a noise map, and the guideline on the management plan of environmental noise was suggested through the review of existing application examples. The management plan of environmental noise with a noise map includes the practical contents in the stages of subdivision of management areas, establishment of reduction measures, opinion collection, post investigation, and reformulation of management plan. First, the classification of management regions is performed considering the excess degree of noise standard and the facility type in the phase of subdivision of management areas. Second, the optimal management plan is established through the investigation of regional characteristics and various noise reduction measures in the phase of establishment of reduction measures, which includes the examination of noise reduction effects with a noise map and the budget planning with the costing of noise reduction measures. Third, the opinion survey with a local resident and a expert is carried out in order to prove the validity of the management plan in the phase of opinion collection, and the management plan is modified with gathered opinions. Fourth, the post examination plan with noise measurement is performed in order to verify the real effect of noise reduction measures according to the management plan in the phase of post investigation. Finally, the amendment of the management plan as well as the improvement of a noise map is carried out at a regular cycle in the phase of reformulation of management plan.

• Proceedings of the Korean Geotechical Society Conference
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• 1993.06a
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• pp.83-116
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• 1993

This article analyzed the dynamic compaction incuced vibration of man made waste landfill. General dynamic properties and compaction-condition-related dynamic properties were analyzed. from the results, it was turned out that the shear modulus G=17496-58320 t/m2, dannpln ratio D=14~58%, dominant frequency f=6-14Hz. Also, it was turned out that the propagation velocitis of low amplitude shear wave and compressive wave were increased as the number of impact increased, the relation between peak particle velocity, and impact distance was wpp=5.08.[D/r E]-1.4, the peak particle velocity was high at the lower part of the waste fill layer and the range of dynamically improved area was about 6-10m.