• Journal of Power System Engineering
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• v.6 no.3
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• pp.57-63
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• 2002

This paper describes the acoustic analysis of mid duty truck. The focus of the analysis is on structure borne engine noise with major contributions of 2nd order. It has been previously recognized that the noise contribution of each transfer path of structure borne noise can be varied with the charateristics of each mounts and vibro acoustic sensitivity of car body. The structure of car body will be split up into three major sub components, which are modeled separately, the engine, the frame and the cab. The acoustic performance is evaluated on three levels: engine to frame transfer, frame to cab transfer, and panel contribution from cab to driver. In order to perform these analyses, analytical models are created for the engine, frame, cab and acoustic cavity. The models are linked through a coupled fluid structure calculation, and through FRF Based Substructuring for the structural couplings. Based on the structural coupling calculations, a transfer path analysis is performed to identify the most important transfer paths. These paths are then the focussing points for applying modifications to the structure or the mount system. Finally, a number of modification are proposed and their effect is quantified.

• Journal of the Korean earth science society
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• v.26 no.8
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• pp.790-799
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• 2005

We investigate the optical properties of aerosols over Gongju by an indirect method using the pound measurement, Sky-radiometer. The analysis period is from January to December, 2004. Skyrad. pack.3 is used to estimate the optical properties, such as the aerosol optical thickness (AOT), single scattering albedo (SSA), ${\AA}ngstron$ exponent $({\alpha})$ and size distribution, of aerosols from the ground measured radiance data. And qualify control is applied to minimize the cloud-contaminated data and improve the quality of analysis results. The 12-month average of AOT, ${\alpha}$, and SSA are 0.46, 1.14, and 0.91, respectively. The average volume spectra of aerosols shows a bi-modal distribution, the first peak at fine mode and the second peak at coarse mode. AOT and coarse particles clearly increases while SSA decreases during the Asian dust events. The optical properties of aerosols at Gongju vary with?seasons, but those are not influenced by the wind direction.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.1
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• pp.124-132
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• 2013

Damage location and extent could be detected by the inverse analysis on dynamic response of the damaged structure. In general, detection of damage location is possible by the observation of the mode shape difference between undamaged and damaged structure and assessment of stiffness reduction is possible by the observation of the natural frequency difference of them. The study on damage detection by the dynamic response in civil structures is reported enough and in practical use, but in building structures it is reported seldom due to several problems. The purpose of this study is to present the damage detection method on shear building structures by mode shape. The damage location index using 1st mode shape is observed theoretically to find out damage location. The damage detection method is applied to numerical analysis model such as MATLAB and MIDAS GENw for the verification. Finally the shaking table test on 3 story shear building is performed for the examination of the damage detection method. In shaking table results, as the story stiffness decrease by 25% the 1st mode frequency increase by 12%, and the damage location index represents minus at damaged story.

• The Journal of the Petrological Society of Korea
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• v.13 no.2
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• pp.81-102
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• 2004

The plutonic rocks in Seonsan area are divided into dioritic-syenitic rock, gneissose granite, biotite granite and fine grained biotite granite. These rocks intruded into the Pre-cambrian metamorphic complex and are all covered by the Cretaceous Nakdong formation. According to modal minerals, dioritic-syenitic rock corresponds to quartz monzonite, granodiorite, tonalite fields, whereas all the other plutonic rocks fall in granite field. Petrochemically the dioritic-syenitic rock is lower in SiO$_2$ content, differentiation index and Larsen index than all the other plutonic rocks. About the zircon morphology, dioritic-syenitic rock shows (100) dominant type but other granitic rocks exhibit mixed types between (100) and (110) type. The dioritic-syenitic rock could be crystallized in higher temperature than the other plutonic rocks. The plutonic rocks correspond to calc-alkaline rock series, and belong to I-type granite and mostly magnetite-series in magmatic origin. In plutonic processes, the dioritic-syenitic rock with 5kb vapor pressure could intrude into the metamorphic batement at 17km deep below the surface. Later the gneissose granite with lower 3kb vapor pressure could intrude at 10km deep. Sequentially the biotite granite with 0.7kb could intrude at 2km deep. Finally the fine grained biotite granite with 3kb vapor pressure could intrude at 10km deep.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.5
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• pp.482-489
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• 2010

This paper describes the test procedure, instrumentation, verification methodology and the results of the ground vibration test(GVT) and force vibration test(FVT) of the SmartUAV aircraft to estimate experimentally dynamic characteristics of the aircraft. Bungee cords are used to emulate free-free boundary conditions of the test aircraft. The SmartUAV is excited by three shakers and one-hundred frequency response functions(FRF's) is measured. The FRF's are reduced and analyzed to identify the dynamics parameters of the SmartUAV. To extract modal parameters of the SmartUAV such as, natural frequencies and damping ratios, the poly-reference least square complex exponential method is used in the time domain. The mode shape coefficients are estimated with the least squares frequency domain method to identify the vibration modes. The FVT was performed by fixed sine frequency with three shakers on the x, y and z direction and vibration characteristics of structures and detail equipments are measured.

• Journal of Navigation and Port Research
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• v.39 no.3
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• pp.179-184
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• 2015

The purpose of this study is to provide appropriate methodology to ensure the safety and integrity of the production riser in offshore structure. In order to select integrity estimation methodology for production riser, level I and II Non-destructive Damage Evaluation (NDE) methods that were applied to existing structures are classified and reviewed. Numerical analysis is performed to verify the applicability and capability on damage detection of reviewed methods. As a result, the damage detection methodology using modal strain energy is more sensitive in detection of the damage than other methods. In practice, the number of sensors is limited due to the environmental and financial conditions. The impact on damage detection performance by reducing the number of sensors is systematically investigated through a series of numerical analyses and the results are discussed. The optimal number of sensor for the integrity estimation of production riser is recommended.

• Composites Research
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• v.31 no.1
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• pp.37-41
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• 2018

The aim of the current work is to characterise a piecewisely-integrated composite bumper beam based on the IIHS bumper crash protocol. IIHS bumper crash FE analysis for an aluminium type bumper beam was carried out to get the information about the dominant loading types at several regions in the bumper beam during crash. In the meantime, robust stacking sequences against tension and compression have been searched for using FE analysis of a coupon type model. After determining most effective stacking sequences for tension and compression, three-point bending simulation was preliminarily carried out to investigate the combination performance of them. Finally, IIHS bumper crash FE analysis for the piecewisely-integrated composite bumper beam, which consisted of the combination of tension effective stacking sequence and compression efficacious stacking sequence, was conducted and the result was compared with other types of composite bumper beams. It was found that the newly suggested piecewisely-integrated composite bumper beam showed superior crashworthy behaviour to those of uni-modal stacking sequence composite bumper beams.

• Tribology and Lubricants
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• v.35 no.3
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• pp.158-168
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• 2019

This paper presents the investigation of two types of rotordynamic modeling issues for 2.2 kW-class, rated speed of 1,800 rpm, squirrel-cage type induction motors. These issues include the lamination structure of rotor cores, and the radial clearance of ball bearings that support the shaft of the motor. Firstly, we focus on identifying the effects of rotor core lamination on the rotordynamic analysis via a 2D prediction model. The influence of lamination is considered as the change in the elastic modulus of the rotor core, which is determined by a modification factor ranging from 0 to 1.0. The analysis results show that the unbalanced response of the rotor-bearing system significantly varies depending on the value of the modification factor. Through modal testing of the system, the modification factor of 0.079 is proven to be appropriate to consider the effects of lamination. Next, we investigate the influence of ball bearing clearance on the rotordynamic analysis by establishing a bearing analysis model based on Hertz's contact theory. The analysis results indicate that negative clearance greatly changes the bearing static behavior. Rotordynamic analysis using predicted bearing stiffness with various clearances from -0.005 mm to 0.010 mm reveals that variations in clearance result in a slight difference in the displacement of the system up to 18.18. Thus, considering lamination in rotordynamic analysis is necessary as it can cause serious analysis errors in unbalanced response. However, considering the effect of the bearing clearance is optional because of its relatively weak impact.

• Economic and Environmental Geology
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• v.45 no.4
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• pp.351-363
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• 2012

In order to develop the evaluation techniques for the potential sulfide ore reserves, the relationships between the modal vol.%, grain sizes and textural characteristics of the constituent minerals (e.g., sulfides, oxides and skarn minerals) and the Spectral Induced Polarization (SIP) phase differences are examined for the nine rock cores collected from the Gagok Pb-Zn skarn deposit. The Gagok Pb-Zn skarn deposit occurs mainly along the intrusive contact between the Cretaceous granitic rocks and Cambrian Myobong slate and Pungchon limestone. The nine rock cores have been grouped into three showing distinctive SIP phase differences: the highest (Group I), intermediate (Group II) and lowest (Group III). In relation with the modal vol.% of minerals, Group I is characterized by higher pyrrhotite (25-38 vol.%) and amphibole (40-55 vol.%); Group II by intermediate pyrrhotite (7-13 vol.%) and higher garnet (44-68 vol.%); and lower pyrrhotite (1-7 vol.%) and higher pyroxene (24-66 vol.%) stand for Group III. Furthermore, the grains of all the major constituent minerals become smaller from Group I (<5 mm) through Group II (<2.5 mm) to Group III (<1.6 mm). In particular, the pyrrhotite contents and their grain sizes show logarithmic correlation with the SIP phase differences, Although we present here the results solely from nine samples, the systematic interrelations especially for pyrrhotite indicate the potential ability of SIP measurements as a new mine-evaluation technique for the sulfide ore reservoir.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.1A
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• pp.61-73
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• 2009

In this paper, hybrid health monitoring techniques using acceleration-impedance features are newly proposed to detect two damage-type in steel plate-girder bridges, which are girder's stiffness-loss and support perturbation. The hybrid techniques mainly consists of three sequential phases: 1) to alarm the occurrence of damage in global manner, 2) to classify the alarmed damage into subsystems of the structure, and 3) to estimate the classified damage in detail using methods suitable for the subsystems. In the first phase, the global occurrence of damage is alarmed by monitoring changes in acceleration features. In the second phase, the alarmed damage is classified into subsystems by recognizing patterns of impedance features. In the final phase, the location and the extent of damage are estimated by using modal strain energy-based damage index method and root mean square deviation (RMSD) method. The feasibility of the proposed hybrid technique is evaluated on a laboratory-scaled steel plate-girder bridge model for which hybrid acceleration-impedance signatures were measured for several damage scenarios. Also, the effect of temperature on the accuracy of the impedance-based damage monitoring results are experimentally examined from combined scenarios of support damage cases and temperature changes.