• Smart Structures and Systems
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• v.25 no.1
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• pp.65-80
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• 2020

In order to protect a structure over its full life cycle, a novel tuned mass damper (TMD), the so-called semi-active eddy current pendulum tuned mass damper (SAEC-PTMD), which can retune its frequency and damping ratio in real-time, is proposed in this study. The structural instantaneous frequency is identified through a Hilbert-Huang transformation (HHT), and the SAEC-PTMD pendulum is adjusted through an HHT-based control algorithm. The eddy current damping parameters are discussed, and the relationship between effective damping coefficients and air gaps is fitted through a polynomial function. The semi-active eddy current damping can be adjusted in real-time by adjusting the air gap based on the linear-quadratic-Gaussian (LQG)-based control algorithm. To verify the vibration control effect of the SAEC-PTMD, an idealized linear primary structure equipped with an SAEC-PTMD excited by harmonic excitations and near-fault pulse-like earthquake excitations is proposed as one of the two case studies. Under strong earthquakes, structures may go into the nonlinear state, while the Bouc-Wen model has a wild application in simulating the hysteretic characteristic. Therefore, in the other case study, a nonlinear primary structure based on the Bouc-Wen model is proposed. An optimal passive TMD is used for comparison and the detuning effect, which results from the cumulative damage to primary structures, is considered. The maximum and root-mean-square (RMS) values of structural acceleration and displacement time history response, structural acceleration, and displacement response spectra are used as evaluation indices. Power analyses for one earthquake excitation are presented as an example to further study the energy dissipation effect of an SAECPTMD. The results indicate that an SAEC-PTMD performs better than an optimized passive TMD, both before and after damage occurs to the primary structure.

• Journal of the Korea Society for Simulation
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• v.25 no.1
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• pp.35-43
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• 2016

Increasing the proportion of an embedded system in automotive industry, test methods for evaluation and fault detection of the embedded system have been researched. HILS is a test method that is used in the development and test of complex real-time embedded systems. In this study, we defined the HILS method of the ECU, one of the embedded systems used in automobiles. Our method is to create a test model that can provide a virtual vehicle environment to the ECU on the basis of the actual vehicle data. The test model has reference information that can transmit the sensor signal and CAN Message into the ECU from HILS tester. In this study, the HILS can detect faults of the target ECU.

• International Journal of Automotive Technology
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• v.8 no.2
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• pp.203-209
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• 2007

As the vehicle electronic control technology quickly grows and becomes more sophisticated, a more efficient means than the traditional in-vehicle driving test is required for the design, testing, and tuning of electronic control units (ECU). For this purpose, the hardware-in-the-loop simulation (HILS) scheme is very promising, since significant portions of actual driving test procedures can be replaced by HIL simulation. The HILS incorporates hardware components in the numerical simulation environment, and this yields results with better credibility than pure numerical simulations can offer. In this study, a HILS system has been developed for ESP (Electronic Stability Program) ECUs. The system consists of the hardware component, which that includes the hydraulic brake mechanism and an ESP ECU, the software component, which virtually implements vehicle dynamics with visualization, and the interface component, which links these two parts together. The validity of HIL simulation is largely contingent upon the accuracy of the vehicle model. To account for this, the HILS system in this research used the commercial software CarSim to generate a detailed full vehicle model, and its parameters were set by using design data, SPMD (Suspension Parameter Measurement Device) data, and data from actual vehicle tests. Using the developed HILS system, performance of a commercial ESP ECU was evaluated for a virtual vehicle under various driving conditions. This HILS system, with its reliability, will be used in various applications that include durability testing, benchmarking and comparison of commercial ECUs, and detection of fault and malfunction of ESP ECUs.

• Tunnel and Underground Space
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• v.26 no.3
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• pp.166-180
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• 2016

The present study numerically simulated the CO2 injection into the saline aquifer of CO2CRC Otway pilot project and the resulting hydrological-mechanical coupled process in the storage site by TOUGH-FLAC simulator. A three-dimensional numerical model was generated using the stochastic geological model which was established based on well log and core data. It was estimated that the CO2 injection of 30,000t over a period of 200 days increased the pressure near the injection point by 0.5 MPa at the most. The pressure increased rapidly and tended to approach a certain value at an early stage of the injection. The hydrological and mechanical behavior observed from the CO2 flow, effective stress change and stress-strength ratio revealed that the CO2 injection into the saline aquifer under the given condition would not have significant effects on the mechanical safety of the storage site and the hydrological state around the adjacent fault.

• Steel and Composite Structures
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• v.31 no.6
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• pp.575-589
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• 2019

The main focus of this study is to numerically investigate the influence of strong earthquake and tsunami-induced wave impact on the response and behavior of a cable-stayed steel bridge with large caisson foundations, by assuming that the earthquake and the tsunami come from the same fault motion. For this purpose, a series of numerical simulations were carried out. First of all, the tsunami-induced flow speed, direction and tsunami height were determined by conducting a two-dimensional (2D) tsunami propagation analysis in a large area, and then these parameters obtained from tsunami propagation analysis were employed in a detailed three-dimensional (3D) fluid analysis to obtain tsunami-induced wave impact force. Furthermore, a fiber model, which is commonly used in the seismic analysis of steel bridge structures, was adopted considering material and geometric nonlinearity. The residual stresses induced by the earthquake were applied into the numerical model during the following finite element analysis as the initial stress state, in which the acquired tsunami forces were input to a whole bridge system. Based on the analytical results, it can be seen that the foundation sliding was not observed although the caisson foundation came floating slightly, and the damage arising during the earthquake did not expand when the tsunami-induced wave impact is applied to the steel bridge. It is concluded that the influence of tsunami-induced wave force is relatively small for such steel bridge with large caisson foundations. Besides, a numerical procedure is proposed for quantitatively estimating the accumulative damage induced by the earthquake and the tsunami in the whole bridge system with large caisson foundations.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.9
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• pp.78-84
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• 2022

An air circuit breaker (ACB) is an electrical protection device that interrupts abnormal fault currents that result from overloads or short circuits in a low-voltage power distribution line. The ACB consists of a main circuit part for current flow, mechanism part for the opening and closing operation of movable conductors, and arc-extinguishing part for arc extinction during the breaking operation. The driving mechanism of the ACB is a spring energy charging type. The faster the contact opening speed of the movable conductors during the opening process, the better the breaking performance. However, there is a disadvantage that the durability of mechanism decreases in inverse proportion to the use of a spring capable of accumulating high energy to configure the breaking speed faster. Therefore, to simultaneously satisfy the breaking performance and mechanical endurance of the ACB, its driving mechanism must be optimized. In this study, a dynamic model of the ACB was developed using the MDO(Mechanism Dynamics Option) module of CREO, which is widely used in multibody dynamics analysis. To improve the opening velocity, the Taguchi design method was applied to optimize the design parameters of an ACB with many linkages. In addition, to evaluate the improvement in the operating characteristics, the simulation and experimental results were compared with the MDO model and improved prototype sample, respectively.

• The Journal of the Convergence on Culture Technology
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• v.9 no.3
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• pp.845-850
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• 2023

In this paper, we propose a method for diagnosing ball bearing vibration using transfer learning. STFT, which can analyze vibration signals in time-frequency, was used as input to CNN to diagnose failures. In order to rapidly learn CNN-based deep artificial neural networks and improve diagnostic performance, we proposed a transfer learning-based deep learning learning technique. For transfer learning, the feature extractor and classifier were selectively learned using a VGG-based image classification model, the data set for learning was publicly available ball bearing vibration data provided by Case Western Reserve University, and performance was evaluated by comparing the proposed method with the existing CNN model. Experimental results not only prove that transfer learning is useful for condition diagnosis in ball bearing vibration data, but also allow other industries to use transfer learning to improve condition diagnosis.

• Physical Therapy Korea
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• v.12 no.3
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• pp.11-21
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• 2005

The present study was aimed at investigating the effect of swimming training on brain function after focal cerebral ischemia in rats. Therefore, this study was examined on neurogenesis in dentate gyrus of hippocampus using 5-bromo-2'-deoxyuridine (BrdU) to label proliferating cells and assessed the neurological response following focal cerebral ischemia in rats using neurological motor behavioral test. In an observer-blinded fashion, twenty male Sprague-Dawley (280~310 g, 7 weeks old) rats were divided into four groups: MCAO plus swimming group (ME, $n_1$=5), MCAO plus control group (MC, $n_2$=5), SHAM plus swimming group (SE, $n_3$=5), SHAM plus control group (SC, $n_4$=5). The results of this study were as follows: 1) The limb placing time before and after swimming in the ME group were significantly longer than the MC group (p<.05), the SE group were significantly longer than the SC group (p<.01). 2) The balance beam scores before and after swimming in the ME group was higher than the SE group, the MC group was higher than the SC group but was not significantly different (p>.001). 3) The foot fault index before and after swimming training in ME group was significantly lower (i.e., improved) than the MC group (p<.001) and the SE group (p<.001), the SE group was significantly lower (i.e., improved) than the SC group (p<.001). 4) The mean number of BrdU-positive cells in the dentate gyrus in the ME group was significantly higher than the MC group (p<.001) and the SE group (p<.01). The MC group and the SE group was significantly higher than the SC group (p<.001). 5) There was significantly correlation between limb placing time and number of BrdU-positive cells on swimming training, there was positive correlation (r=.807, p<.0001) and between foot fault index and BrdU-positive cells number, there was negative correlation (r=-.503, p<.05). However, between balance beam scores and BrdU-positive cells number, there was no correlation. In conclusion, the present study demonstrates that the role of swimming training improves behavioral motor function probably by enhancing cell proliferation in that hippocampus. This study provides a model for investigating the stroke rehabilitation that underlies neurogenesis and functional ability.

• Economic and Environmental Geology
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• v.48 no.4
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• pp.313-324
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• 2015

This study constructed a 3D geological model for Uggi Nuur Fe-Mn mineralization zone in Mongolia, and the 3D geological distribution is cross-analyzed with magnetic anomaly distribution to figure out relationship between ore zone and subsurface geology. As a result of 4 step 3D modeling procedures including geological cross section, surface modeling, foliation modeling and solid modeling, the geology of the both study area is bordered by faults in NW direction with Munguntessj formation being located in the west side of the fault while Yashill formation is located on the other side of the fault. Moreover, the strike direction of foliation in the both formation shows same directional pattern with the NW faults. The magnetic anomaly distribution reveals that higher anomaly values are concentrated to near the ground surface. The analyses of 3 dimensional distribution between subsurface geology and magnetic anomaly indicates that higher anomaly is mainly distributed over the Munguntessj formation as a elongated lens bodies whereas the magnetic anomaly is evenly found in the both of Munguntessj formation and Yashill formation in the study area 2. It infers that volcanic activities associated mineralization occurred during silurian period, and the mineralized zone is thought to be realigned along the geological structures caused by later stage tectonic activities.

• Journal of the Korean earth science society
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• v.32 no.6
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• pp.548-559
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• 2011

3-D Multi-geophysical surveys were carried out around the Hwasan caldera at the Euisung Sub-basin. To overcome the limitations of resolutions in previous studies, dense gravity data and magnetotelluric (MT) data were obtained and analyzed. In this study, the independent inversion models from gravity and MT data were integrated using correlation and classification approaches for 3-D imaging of the geologic structures. A Structure Index (SI) method was proposed and applied to the integration and classification analyses. This method consists of Type Angle (TA) and Type Intensity (TI) values, which are estimated by the spatial correlation and abnormality of the physical properties. The SI method allowed the classification analysis to be effectively performed. Major findings are as follows: 1) pyroclastic rocks around the central area of the Hwasan caldera with lower density and resistivity than those of neighboring regions extended to a depth of around 1 km, 2) intrusive igneous rocks with high resistivity and density were imaged around the ring fault boundary, and 3) a basement structure with low resistivity and high density, at a depth of 3-5 km, was inferred by the SI analysis.