• Nuclear Engineering and Technology
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• v.47 no.4
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• pp.488-499
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• 2015

Acceleration sensors are usually used to measure the vibration of a structure. Although this is the most accurate method, it cannot be used remotely because these are contact-type sensors. This makes measurement difficult in areas that cannot be easily approached by surveyors, such as structures located in high or dangerous areas. Therefore, a method that can measure the structural vibration without installing sensors is required for the vibration measurement of structures located in these areas. Many conventional studies have been carried out on non-contact-type vibration measurement methods using cameras. However, they have been applied to structures with relatively large vibration displacements such as buildings or bridges, and since most of them use targets, people still have to approach the structure to install the targets. Therefore, a new method is required to supplement the weaknesses of the conventional methods. In this paper, a method is proposed to measure vibration displacements remotely using a camera without having to approach the structure. Furthermore, an estimation method for the measurement resolution and measurement error is proposed for the vibration displacement of a cylindrical structure measured using the proposed measurement method. The proposed methods are described, along with experimental results that verify their accuracy.

• Journal of the Society of Disaster Information
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• v.4 no.2
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• pp.10-27
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• 2008

When the ground is excavated adjacent to the existing tunnel, which is loaded by the surcharge on the ground surface, the tunnel stability would be very sensitive to the deformation of the ground induced by the horizontal displacement of braced wall. The stability of the existing surcharged tunnel could be controlled by pre-loading on the braced wall. In this paper, it was investigated, if it would be possible to keep the existing surcharged tunnel stable by preventing the horizontal displacement of a braced wall by imposing the pre-loading during the ground excavation. For this purpose, large scale model tests were performed in a scale 1/10 at the test pit which was 2.0m in width and 6.0m in height and 4.0m in length. Isotropic test ground was constructed homogeneously by wet sand. Model tunnel was constructed in the test ground. Surcharge was loaded on the ground surface above the tunnel. During the tests, the behavior of model tunnel and model braced wall was measured. Numerical analyses were also performed in the same condition as the tests. And their results were compared to that of the model tests. Consequently, the effect of a surcharge could be compensated by imposing the pre-loading on the braced wall. The existing tunnel and the braced wall could be kept stable by preventing the horizontal displacement of the braced wall through pre-loading, although the tunnel is surcharged.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11b
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• pp.23-26
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• 2004

Monolayers of lipids on a water surface have attracted much interest as models of biological membranes, but also as precursors of multilayer systems promising many technical applications. Until now, many methodologies have been developed in order to gain a better understand. Photoisomerization in monolayers of a novel azobenzene compound, azobenzene dendrimer, was investigated for the first time by means of the absorption spectrum and Maxwell displacement current(MDC) technique. Dendrimers are well-defined macromolecules exhibiting a tree-like structure, first derived by the cascade molecule approach According to the absorption spectrum, trans-to-cis conversion ratio was estimated to the third generation of azobenzene dendrimer deposited onto a glass substrate. Temperature-dependent induced charge with trans-cis isomerization was also measured by means of MDC technique.

• Transactions of the Korean hydrogen and new energy society
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• v.29 no.5
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• pp.497-502
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• 2018

In Korea, passenger car and van using LPG fuel including taxi constantly increased due to the high cost of fuel. Recently, the emission standard has continuously tightened in the world. In this investigation was conducted the greenhouse gas emission characteristics of LPG vehicles according to the displacement and weight. Exhaust emission characteristics of 13 test LPG vehicles from about 1.0 L to 3.0 L displacements were measured and analyzed by using chassis dynamometer and emission analyzer. It is revealed that the greenhouse gas emission was showed the increasing tendency as the displacement and curb weight increased. Also, greenhouse gas emission of SC03 driving cycle has highest value and that of HWFET driving cycle shows the lowest value.

• Journal of the Korean Society of Safety
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• v.27 no.3
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• pp.1-8
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• 2012

Characteristics of smoke emission in light duty diesel vehicles was investigated according to the year of production, engine displacement volume, and mileage. The smoke emission was measured using light extinction smoke measurement method under free acceleration test mode. Total number of the tested vehicles was 180. The year of production of the tested vehicles distributed from 2002 to 2007. The displacement volumes of the tested vehicles were categorized as 2-liter, 2.5-liter, 2.7-liter, and 3-liter. The mileage of the tested vehicles distributed from 20,000 km to 400,000 km. The more recent in the year of production of the tested vehicles did not show clearly lower in smoke emissions. Smoke emission showed different values according to driver's pedal pushing pattern. Also, smoke emission peak for each free acceleration test initially increased and reach a maximum of the peak values. Afterwards, the smoke peak gradually decreased as number of test increased. A new guide line was proposed to determine the smoke value from the light duty diesel vehicles based on smoke emission peak patterns which were obtained with several repeated free acceleration tests.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.1
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• pp.6-13
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• 2008

National standard system for calibrating current transformer(CT) up to primary current of 20,000A have been established. The system consists of 20,000 A AC high current source, CT comparator, standard CT, CT under test and CT burden. An AC high current is applied tn the primary windings of both the standard CT and the CT under test, and then the CT comparator measures the ratio error and the phase displacement by comparing the secondary currents of the two transformers. As a validity check for 20,000 A CT calibration system, the comparison with the two national standard institutes(NMIs) has been performed using same CTs. The comparison results of the CTs are consistent with those measured at two NMIs within 0.004 % for ratio error and 0.1 min for phase displacement in the primary current ranges of Ip = 10 - 20,000 A with a secondary current of Is = 5 A.

• Smart Structures and Systems
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• v.17 no.6
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• pp.903-915
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• 2016

The classical Kalman filter (KF) provides a practical and efficient state estimation approach for structural identification and vibration control. However, the classical KF approach is applicable only when external inputs are assumed known. Over the years, some approaches based on Kalman filter with unknown inputs (KF-UI) have been presented. However, these approaches based solely on acceleration measurements are inherently unstable which leads poor tracking and so-called drifts in the estimated unknown inputs and structural displacement in the presence of measurement noises. Either on-line regularization schemes or post signal processing is required to treat the drifts in the identification results, which prohibits the real-time identification of joint structural state and unknown inputs. In this paper, it is aimed to extend the classical KF approach to circumvent the above limitation for real time joint estimation of structural states and the unknown inputs. Based on the scheme of the classical KF, analytical recursive solutions of an improved Kalman filter with unknown excitations (KF-UI) are derived and presented. Moreover, data fusion of partially measured displacement and acceleration responses is used to prevent in real time the so-called drifts in the estimated structural state vector and unknown external inputs. The effectiveness and performance of the proposed approach are demonstrated by some numerical examples.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.3
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• pp.296-304
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• 2001

A new method of measuring the thermal diffusivity of solid material at room temperature using photothermal displacement is proposed. The influence of the parameters, such as radius and modulation frequency of the pump beam and the sample thickness, was studied. From the minimum position of phase of measured deflection with respect to the pump beam, the thermal diffusivity of the materials can be obtained. The position where phase has the minimum value is determined using multiparameter least-square regression fitting. The experimental values for different samples obtained by applying the new method are in good agreement with the literature values.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.9
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• pp.1607-1613
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• 2003

An experimental method to measure Q-parameter in-situ is described. The basic idea comes from the fact that the side necking near a crack tip indicates the loss of stress triaxiality, which can be scaled by Q. From the out-of-plane displacement and the in-plane strain near the surface of side necking, stress field averaged through the thickness is calculated and then Q is determined from the difference between the stress field and the HRR field corresponding to the identical J-integral. To prove the validity, three-dimensional finite element analysis has been performed for a CT configuration with side-groove. Q-value which was calculated directly from the near-tip stress field is compared with that determined by simulating the experimental procedure according to the proposed method, that is, the Q-value determined from the lateral displacement and the in-plane strain. In addition, the effect of location where the displacement and strain are measured is explored.

• Journal of the Society of Naval Architects of Korea
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• v.57 no.3
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• pp.175-181
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• 2020

For the success of a structural integrity management, it is essential to acquire structural response data at some critical locations with limited number of sensors. In this study, the structural response of numerical model was estimated by data fusion approach based on the Kalman filter known as stochastic recursive filter. Firstly, transient direct analysis was conducted to calculate the acceleration and strain of the numerical standing beam model, then the noise signals were mixed to generate the numerical measurement signals. The acceleration measurement signal was provided to the Kalman filter as an information on the external load, and the displacement measurement, which was transformed from the strain measurement by using strain-displacement conversion relationship, was provided into the Kalman filter as an observation information. Finally, the Kalman filter estimated the displacement by combining both displacements calculated from each numerically measured signal, then the estimated results were compared with the results of the transient direct analysis.