• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.1035-1036
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• 2009

• Journal of Industrial Technology
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• v.36
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• pp.65-69
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• 2016

Deflection of the vertical is used in geodetic surveying associated with geoid network construction for geoid modeling and ellipsoid decision and obtained by gravity survey, astronomic survey etc. Technique of astronomic survey and gravity survey is very complex and requires a significant amount of time until gathering data. So this study is to determined a various method which evaluates deflection of the vertical and components about deflection of the vertical using GPS results and orthometric height value decided by leveling. Results of components about deflection of the vertical using GPS/leveling is that ${\xi}$ conponent is distributed $-2.11^{{\prime}{\prime}}{\pm}0.62$, ${\eta}$ component is distributed $1.75^{{\prime}{\prime}}{\pm}0.71$. Decision of component about deflection of the vertical using GPS is less complex than existing astronomic survey. Decision of component about deflection of vertical line using GPS is not complicated than astronomic surveying and can determine in a very short time. So it will be important means to determine the exact orthometric height, topographic study and diastrophism if can periodically calculate.

• Journal of the Korea Institute of Military Science and Technology
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• v.9 no.3
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• pp.12-19
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• 2006

A gun barrel of infantry fighting vehicle is supported like a type of cantilever. Temperature of a gun barrel is increased by heat transfer due to the combustion of propellant charge during the firing. Thus, the muzzle of a gun barrel is deflected in accordance with its temperature and the accuracy rate is decreased by deflection of the muzzle. In this study, deflection of a gun barrel is estimated by measuring its restoration rate because measuring the deflection rate is difficult due to the vibration of the gun barrel during the firing. In order to obtain the relations between deflection rate and restoration rate of the 40mm gun barrel of Next Infantry Fighting Vehicle(NIFV) under varying temperature, measurement of deflection rate and restoration rate is carried out using 5.56mm Remington rifle barrel. Effect of the estimated deflection rate of a gun barrel of NIFV on the hit probability is also analyzed.

• Smart Structures and Systems
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• v.24 no.5
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• pp.607-616
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• 2019

The video deflectometer based on digital image correlation is a non-contacting optical measurement method which has become a useful tool for characterization of the vertical deflections of large structures. In this study, a novel imaging model has been established which considers the variations of pitch angles in the full image. The new model allows deflection measurement at a wide working distance with high accuracy. A monocular video deflectometer has been accordingly developed with an inclination sensor, which facilitates dynamic determination of the orientations and rotation of the optical axis of the camera. This layout has advantages over the video deflectometers based on theodolites with respect to convenience. Experiments have been presented to show the accuracy of the new imaging model and the performance of the monocular video deflectometer in outdoor applications. Finally, this equipment has been applied to the measurement of the vertical deflection of Yingwuzhou Yangtze River Bridge in real time at a distance of hundreds of meters. The results show good agreement with the embedded GPS outputs.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.6
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• pp.354-359
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• 2000

A new method of measuring residual stress in micromachined film is proposed. An estimation of residual stress is performed by using least squares fit with an appropriate deflection modeling. an exact value of residual stress is obtained without any of the ambiguities that exist in conventional buckling method, and a good approximation is also obtained by using a few data points. Therefore, the test structures area could be greatly decreased by using this method. The measurement can be done more easily and simply without any actuation or any specific measuring equipment. The structure and fabrication processes described in this paper are simple and widely used in surface micromachining. In addition, in-situ measurement is available by using the proposed method when the test structure and the measurement structure are fabricated on a wafer simultaneously.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.5
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• pp.487-493
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• 2004

This study was conducted to develope a capacitive micromachined ultrasonic transducer (cMUT) which enable to high efficient non-contact transmit and receive the ultrasonic wave in air. Theoretical analysis and finite element analysis of the behavior of membrane (such as resonance frequency, membrane deflection, collapse deflection and collapse voltage) of the cMUT were performed. The design parameters of the cMUT such as the dimension and thickness of membrane, thickness of sacrificial layer, thickness and size of electrode were estimated. The resonance frequency of the membrane increased as the thickness of the membrane increased but decreased as the diameter of the membrane increased. The deflection of the membrane increased as d-c bias voltage increased. The collapse voltage of the membrane was analyzed.

• Computers and Concrete
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• v.19 no.1
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• pp.1-6
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• 2017

Prestressed concrete I-girders are subject to different load types at their construction stages. At the time of strand release, i.e., detensioning, prestressed concrete girders are under the effect of dead and prestressing loads. At this stage, the camber, total net upward deflection, of prestressed girder is summation of the upward deflection due to the prestressing force and the downward deflection due to dead loads. For the calculation of the upward deflection, it is generally considered that prestressed concrete I-girder behaves linear-elastic. However, the field measurements on total net upward deflection of prestressed I-girder after detensioning show contradictory results. In this paper, camber calculations with the linear-elastic beam and elastic-stability theories are presented. One of a typical precast I-girder with 120 cm height and 31.5 m effective span length is selected as a case study. 3D finite element model (FEM) of the girder is developed by SAP2000 software, and the deflections of girder are obtained from linear and nonlinear-static analyses. Only geometric nonlinearity is taken into account. The material test and field measurement of this study are performed at prestressing girder plant. The results of the linear-elastic beam and elastic-stability theories are compared with FEM results and field measurements. It is seen that the camber predicted by elastic-stability theory gives acceptable results than the linear-elastic beam theory while strand releasing.

• Smart Structures and Systems
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• v.32 no.5
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• pp.297-308
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• 2023

Dynamic deflection is important for evaluating the performance of a long-span cable-stayed bridge, and its continuous measurement is still cumbersome. This study proposes a dynamic deflection monitoring method for cable-stayed bridge based on Bi-directional Long Short-term Memory (BiLSTM) neural network taking advantages of the characteristics of spatial variation of cable acceleration response (CAR) and main girder deflection response (MGDR). Firstly, the relationship between the spatial and temporal variation of the CAR and the MGDR is described based on the geometric deformation of the bridge. Then a data-driven relational model based on BiLSTM neural network is established using CAR and MGDR data, and it is further used to monitor the MGDR via measuring the CAR. Finally, numerical simulations and field test are conducted to verify the proposed method. The root mean squared error (RMSE) of the numerical simulations are less than 4 while the RMSE of the field test is 1.5782, which indicate that it provides a cost-effective and convenient method for real-time deflection monitoring of cable-stayed bridges.

• Smart Structures and Systems
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• v.13 no.6
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• pp.975-991
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• 2014

The objective of this study is to develop a reliable method for locating cracks in a beam using data fusion of fractal dimension features of operating deflection shapes. The Katz's fractal dimension curve of an operating deflection shape is used as a basic feature of damage. Like most available damage features, the Katz's fractal dimension curve has a notable limitation in characterizing damage: it is unresponsive to damage near the nodes of structural deformation responses, e.g., operating deflection shapes. To address this limitation, data fusion of Katz's fractal dimension curves of various operating deflection shapes is used to create a sophisticated fractal damage feature, the 'overall Katz's fractal dimension curve'. This overall Katz's fractal dimension curve has the distinctive capability of overcoming the nodal effect of operating deflection shapes so that it maximizes responsiveness to damage and reliability of damage localization. The method is applied to the detection of damage in numerical and experimental cases of cantilever beams with single/multiple cracks, with high-resolution operating deflection shapes acquired by a scanning laser vibrometer. Results show that the overall Katz's fractal dimension curve can locate single/multiple cracks in beams with significantly improved accuracy and reliability in comparison to the existing method. Data fusion of fractal dimension features of operating deflection shapes provides a viable strategy for identifying damage in beam-type structures, with robustness against node effects.

• Journal of the Society of Naval Architects of Korea
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• v.57 no.6
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• pp.373-380
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• 2020

We have developed the hybrid prototype load cell structures. These developed load cell structures may increase the reliability of the load sensing by deriving the load values through the double sensing method through the vertical maximum deflection and bending stress of the simple beams. For this purpose, the structure design was performed so that the load value, the deflection and stress value could be output to the same value through the optimal structure design. The structurally designed dimensions reaffirmed the accuracy of the design through the structural analysis program and the matching of the load value and the deflection value. Based on the designed structural dimension, the prototype form was constructed through laser cutting and production using hot rolled steel materials. The developed prototype load cell structure can be used as good educational material in various subjects such as material mechanics, steel structure design, measurement engineering, and mechatronics engineering. It is also believed that the measurement system ideas can inform the occurrence of errors in the event of a problem, and if a major accident caused by a sensing error is predicted, it will show good utilization to prevent accidents.