• Structural Engineering and Mechanics
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• v.77 no.2
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• pp.151-165
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• 2021

This paper aims to present a novelty damage detection method to identify damage locations by the simultaneous use of both the energy and displacement damage indices. Using this novelty method, the damaged location and even the damaged floor are accurately detected. As a first method, a combination of the instantaneous frequency energy index (EDI) and the structural acceleration responses are used. To evaluate the first method and also present a rapid assessment method, the Displacement Damage Index (DDI), which consists of the error reliability (β) and Normal Probability Density Function (NPDF) indices, are introduced. The innovation of this method is the simultaneous use of displacement-acceleration responses during one process, which is more effective in the rapid evaluation of damage patterns with velocity vectors. In order to evaluate the effectiveness of the proposed method, various damage scenarios of the ASCE benchmark problem, and the effects of measurement noise were studied numerically. Extensive analyses show that the rapid proposed method is capable of accurately detecting the location of sparse damages through the building. Finally, the proposed method was validated by experimental studies of a six-story steel building structure with single and multiple damage cases.

• The Journal of Advanced Prosthodontics
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• v.10 no.5
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• pp.388-394
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• 2018

PURPOSE. To measure axial displacement of different implant-abutment connection types and materials during screw tightening at the recommended torque by using a contact scanner for two-dimensional (2D) and three-dimensional (3D) analyses. MATERIALS AND METHODS. Twenty models of missing mandibular left second premolars were 3D-printed and implant fixtures were placed at the same position by using a surgical guide. External and internal fixtures were used. Three implant-abutment internal connection (INT) types and one implant-abutment external connection (EXT) type were prepared. Two of the INT types used titanium abutment and zirconia abutment; the other INT type was a customized abutment, fabricated by using a computer-controlled milling machine. The EXT type used titanium abutment. Screws were tightened at $10N{\cdot}cm$, simulating hand tightening, and then at the manufacturers' recommended torque ($30N{\cdot}cm$) 10 min later. Abutments and adjacent teeth were subsequently scanned with a contact scanner for 2D and 3D analyses using a 3D inspection software. RESULTS. Significant differences were observed in axial displacement according to the type of implant-abutment connection (P<.001). Vertical displacement of abutments was greater than overall displacement, and significant differences in vertical and overall displacement were observed among the four connection types (P<.05). CONCLUSION. Displacement according to connection type and material should be considered in choosing an implant abutment. When adjusting a prosthesis, tightening the screw at the manufacturers' recommended torque is advisable, rather than the level of hand tightening.

• Journal of The Korean Society of Integrative Medicine
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• v.11 no.1
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• pp.13-20
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• 2023

Purpose : The purpose of this study is to compare the balance ability between subjects with chronic ankle instability and normal people and the center of pressure displacement during the sit to stand and stand to sit. Methods : The subjects of this study were 63 who met the inclusion criteria and were classified into normal group (n=33) and chronic ankle instability group (n=30). The displacement of the center of pressure during sit to stand and stand to sit was measured. And the limit of stability and Y-balance tests were performed to measure the balance ability. Independent t-test was conducted to compare center of pressure displacement and balance ability between groups, and pearson correlation was conducted to analyze the correlation between the center of pressure displacement and balance ability. Results : In the case of the center of pressure displacement, there was a significant difference between the two groups during sit to stand and stand to sit. In the case of balance, both limit of stability and Y-balance test showed significant differences between the two groups. At the time of sit to stand, the center of pressure displacement showed a significant correlation with balance abilities, and at the time of stand to sit, the center of pressure displacement showed a significant correlation with Y-balance test. Conclusion : Chronic ankle instability shows that there is a lot of sway in the body due to compensation to replace the decrease in ankle joint range of motion when performing sit to stand and stand to sit due to sensory input damage such as decrease in ankle range of motion and decrease in ankle proprioception. Chronic ankle instability is expected to have a negative effect on our daily lives in life. The results of this study will serve as the basis for the dynamic approach to objective evaluation, treatment, and prevention of chronic ankle instability.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4A
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• pp.507-515
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• 2008

In this study, a method predicting the displacement response of structures from the measured dynamic strain signal is proposed by using mode decomposition technique. Evaluation of bridge stability is normally focused on the bridge completed. However, dynamic loadings including wind and seismic loadings could be exerted to the bridge under construction. In order to examine the bridge stability against these dynamic loadings, the prediction of displacement response is very important to evaluate bridge stability. Because it may be not easy for the displacement response to be acquired directly on site, an indirect method to predict the displacement response is needed. Thus, as an alternative for predicting the displacement response indirectly, the conversion of the measured strain signal into the displacement response is suggested, while the measured strain signal can be obtained using fiber optic Bragg-grating (FBG) sensors. As previous studies on the prediction of displacement response by using the FBG sensors, the static displacement has been mainly predicted. For predicting the dynamic displacement, it has been known that the measured strain signal includes higher modes and then the predicted dynamic displacement can be inherently contaminated by broad-band noises. To overcome such problem, a mode decomposition technique was used. Mode decomposition technique estimates the displacement response of each mode with mode shape estimated to use POD from strain signal and with the measured strain signal decomposed into mode by EMD. This is a method estimating the total displacement response combined with the each displacement response about the major mode of the structure. In order to examine the mode decomposition technique suggested in this study model experiment was performed.

• Proceedings of the KIEE Conference
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• 2008.09a
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• pp.69-71
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• 2008

We have developed a current range extension method to obtain the ratio error and phase displacement of a current transformer (CT) by using absolute evaluation method and two different CTs. The method was applied to CTs under test with the current ratios of the range of 5,000 A / 1 A - 20,000 A / 1 A. The ratio error and phase displacement of the CT under test obtained in this study are consistent with those measured at the national institute in Germany using the same CT under test within an expanded uncertainty (k = 2) in the overall current ratios.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.186-189
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• 2006

Since the columns with flexure-shear failure have lower ductility than those with flexural failure, shear capacity curve models shall be applied as well as flexural capacity curve in order to determine ultimate displacement for seismic design or performance evaluation. In this paper, a proposed modified shear capacity curve model is compared with the other models such as the CALTRANS model, Aschheim et al.'s model, and Priestley et al.'s model. Four shear capacity curve models are applied to the 4 full scale and 7 small scale circular bridge column test results and the accuracy of each model is discussed. It may not be fully adequate to drive a final decision from the application to the limited number of test results, however the proposed model provides the better prediction of failure mode and ultimate displacement than the other models for the selected column test results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.127-131
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• 2008

This paper deals with the performance evaluation of piezoelectric unimorph actuator. In the unimorph design, the thickness ratio of substrate to piezoelectric material and the elastic modulus ratio of substrate to piezoelectric material are important parameters. There exists only one structural configuration that satisfies the optimal condition among them, and actuators using that configuration exhibit better actuating displacements. Another design parameter is the piezoelectric coefficient which can be improved due to the induced tensile stress and voltages. The application of the tensile stress to the piezoelectric material makes it get higher piezoelectric coefficient and the total displacement performance of the unimorph actuator is improved. Finally, the piezoelectric actuator system with spring elements is fabricated and it shows higher actuating displacement capability.

• Journal of the Korean Society of Industry Convergence
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• v.19 no.3
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• pp.160-166
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• 2016

This study proposes the development and performance evaluation of electronic proportional control valve having an LVDT. The electronic proportional control valve is composed of hydraulic valve, proportional solenoid and controller. LVDT is to reduce the steady state error for the reference input of the controller by the feedback signal to detect the displacement of the spool. Designed LVDT is applied to the common proportional valve. In order to evaluate the performance of the developed valve, the hydraulic test equipment was developed and flow tests were carried out. From experimental results, it was proved that the hysteresis was less than 1% based on the maximum flow rate.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.3
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• pp.279-284
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• 2008

We have developed two absolute evaluation technology of inductor using current transformer (CT) comparator. One is the method that the reactance of inductor is obtained by analysing the equivalent circuit of CT with inductor connected to series at secondary terminal of CT. The other is the method that the reactance of inductor is obtained by comparing phase displacement of current flowing on inductor by using CT comparator. These technologies have the advantage to apply up to rated current and voltage of inductor. The method was applied to inductors under test in the range of $100 {\mu}H{\sim}1\;H$. The inductance of the inductor under test obtained in this study are consistent with those measured by LCR meter using the same inductor within an expanded uncertainty (k = 2) in the overall range of inductance.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.10a
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• pp.569-576
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• 2001

In this study a procedure for evaluation of performance point using direct displacement-based design method was developed to enhance the applicability of the method. Parametric study has been performed for the natural period of the structure, yield strength, and the stiffness after the first yield. The proposed method was also applied to a 10-story steel frame. To verify the accuracy of the result, the results from capacity spectrum analysis and time history analysis were compared. The results of the proposed method turned out to match well with the results of capacity spectrum method and the time history analysis.