• Earthquakes and Structures
• /
• v.23 no.1
• /
• pp.35-57
• /
• 2022

This article presents a computationally efficient framework for multi-objective seismic design optimization of steel moment-resisting frame (MRF) structures based on the nonlinear dynamic analysis procedure. This framework employs the uniform damage distribution philosophy to minimize the weight (initial cost) of the structure at different levels of damage. The preliminary framework was recently proposed by the authors based on the single excitation and the nonlinear static (pushover) analysis procedure, in which the effects of record-to-record variability as well as higher-order vibration modes were neglected. The present study investigates the reliability of the previous framework by extending the proposed algorithm using the nonlinear dynamic design procedure (optimization under multiple ground motions). Three benchmark structures, including 4-, 8-, and 12-story steel MRFs, representing the behavior of low-, mid-, and high-rise buildings, are utilized to evaluate the proposed framework. The total weight of the structure and the maximum inter-story drift ratio (IDRmax) resulting from the average response of the structure to a set of seven ground motion records are considered as two conflicting objectives for the optimization problem and are simultaneously minimized. The results of this study indicate that the optimization under several ground motions leads to almost similar outcomes in terms of optimization objectives to those are obtained from optimization under pushover analysis. However, investigation of optimal designs under a suite of 22 earthquake records reveals that the damage distribution in buildings designed by the nonlinear dynamic-based procedure is closer to the uniform distribution (desired target during the optimization process) compared to those designed according to the pushover procedure.

• Journal of Korean society of Dental Hygiene
• /
• v.19 no.5
• /
• pp.743-752
• /
• 2019

Objectives: Grip strength is a measure for assessing overall muscle strength, muscle mass, and nutritional status, and is a useful tool for early examination of a person's general health. Thus, this study analyzed the association between oral health-related factors and grip strength, using the 6th Korea National Health and Nutrition Examination Survey (KNHANES) data. Methods: Data were analyzed using the IBM SPSS version 25.0 (IBM Co., Armonk, NY, USA) software with a complex sampling analysis of stratified and clustered variables, all with weighted values, applied for every analysis conducted. From the 6th KNHANES data, a total of 26,101 people were selected as the study population. A complex sample generalized linear model analysis was performed for participants' sociodemographic characteristics, health status, use of oral care products, and factors such as adult mastication and speaking habits. Results: Grip strength was found to be higher among men compared to women. Grip strength was the highest in the 20-39 year old group. Furthermore, grip strength was statistically significantly higher among married and employed individuals, and in the right hand (p<0.001). Grip strength was statistically significantly higher among people who perceived themselves to have good health and among those who did not have health-related problems in the past two weeks (p<0.001). It was also higher among those who used interdental brushes and electronic toothbrushes (p<0.001), but decreased with greater discomfort in mastication and speaking among adults (p<0.05). Conclusions: Grip strength was found to be associated with oral health-related factors and therefore, these could be helpful tools in evaluating both general and subjective health statuses. In general, oral care products are small in size with oral care involving the use of hands and certain precise motions and actions to remove foreign substances in the oral cavity. As shown in the findings, grip strength declines with increased age and as a result, the use of oral care products should be strongly recommended in order to promote better general health.

• Journal of the Korean Society of Earth Science Education
• /
• v.5 no.1
• /
• pp.20-30
• /
• 2012

The purpose of this study is to find how elementary students who have different spatial ability affects their understandings on the concept of the rotation of the earth. In order to perform this study, four 5th grade students were picked out of 85 students in Seoul. They had the same conceptual achievement on the movement of celestial bodies but had different spatial abilities. The results of this study were as follows : Regardless of their spatial ability, they understand how day and night are performed, and understand the fact that diurnal motions of moon are related to the rotation of the earth. Also, the students who had higher spatial abilities showed better understanding on the concept of the rotation of the earth and understood the reconstructed concepts in stereoscopic space. But the students who had lower spatial abilities did not fully understand the concept of the rotation of the earth and just memorized them as fragmentary concepts. As for the gender differences, the boy students who had higher spatial ability explained the concept clearly and the others who had lower spatial ability had difficulty in understanding the rotation direction of the earth related with the diurnal movement of celestial bodies. In the same manner, the girl students who had higher spatial ability explained the concepts concretely and the others who had lower spatial ability had difficulty in explaining the concepts by operating them stereoscopically. Therefore, developing teaching methods and studying data and so on, for the girl students, they should be trained to operate the stereoscopic space directly, and for the boy students, they should learn to think over objects with multi-viewpoints. And then the spatial ability on the movement of celestial bodies would be expected to be improved.

• Earthquakes and Structures
• /
• v.17 no.5
• /
• pp.447-462
• /
• 2019

This present paper concerned with the analytic modelling for vibration of the functionally graded (FG) plates resting on non-variable and variable two parameter elastic foundation, based on two-dimensional elasticity using higher shear deformation theory. Our present theory has four unknown, which mean that have less than other higher order and lower theory, and we denote do not require the factor of correction like the first shear deformation theory. The indeterminate integral are introduced in the fields of displacement, it is allowed to reduce the number from five unknown to only four variables. The elastic foundations are assumed a classical model of Winkler-Pasternak with uniform distribution stiffness of the Winkler coefficient (kw), or it is with variables distribution coefficient (kw). The variable's stiffness of elastic foundation is supposed linear, parabolic and trigonometry along the length of functionally plate. The properties of the FG plates vary according to the thickness, following a simple distribution of the power law in terms of volume fractions of the constituents of the material. The equations of motions for natural frequency of the functionally graded plates resting on variables elastic foundation are derived using Hamilton principal. The government equations are resolved, with respect boundary condition for simply supported FG plate, employing Navier series solution. The extensive validation with other works found in the literature and our results are present in this work to demonstrate the efficient and accuracy of this analytic model to predict free vibration of FG plates, with and without the effect of variables elastic foundations.

• Smart Structures and Systems
• /
• v.8 no.4
• /
• pp.399-412
• /
• 2011

This study compares the performance of two smart isolation systems that utilize superelastic shape memory alloys (SMAs) for seismic protection of bridges using energy balance concepts. The first isolation system is a SMA/rubber-based isolation system (SRB-IS) and consists of a laminated rubber bearing that decouples the superstructure from the bridge piers and a SMA device that provides additional energy dissipation and re-centering capacity. The second isolation system, named as superelastic-friction base isolator (S-FBI), combines the superelastic SMAs with a flat steel-Teflon bearing rather than a laminated rubber bearing. Seismic energy equations of a bridge structure with SMA-based isolation systems are established by absolute and relative energy balance formulations. Nonlinear time history analyses are performed in order to assess the effectiveness of the isolation systems and to compare their performance. The program RSPMatch 2005 is employed to generate spectrum compatible ground motions that are used in time history analyses of the isolated bridge. Results indicate that SRB-IS produces higher seismic input energy, recoverable energy and base shears as compared to the S-FBI system. Also, it is shown that combining superelastic SMAs with a sliding bearing rather than rubber bearing significantly reduce the amount of the required SMA material.

• 제어로봇시스템학회:학술대회논문집
• /
• 2003.10a
• /
• pp.473-478
• /
• 2003

To detect motions of bodies, we have discussed them with two viewpoints; one is a detection algorithm, and another is the hardware implementation. The former is to find small terms expansions for sine/cosine functions. We researched Maclaurin and optimum expansions, and moreover to reduce hardware amounts, revised the expansions. The expansions don't include divide calculations, and the error is within 0.01%. As for the former problem, there is another approach also; that is the cordic method. The method is based on the rotation of a vector on the complex plain. It is simple iterations and don't require large logic. We examined the precision and convergence of the method on C-simulations, and implemented on HDL. The later problem is to make FPGA within small gates. We considered approaches to eliminate a divider and to reduce the bit number of arithmetic. We researched Newton-Raphson's method to get reciprocal numbers. The higher-order expression shows rapid convergence and doesn't be affected by the initial guess. It is an excellent algorithm. Using them, we wish to design a detector, and are developing it on a FPGA.

• Earthquakes and Structures
• /
• v.10 no.2
• /
• pp.463-482
• /
• 2016

Air Traffic Control (ATC) towers play significant role in the functionality of each airport. In spite of having complex dynamic behavior and major role in mitigating post-earthquake problems, less attention has been paid to the seismic performance of these structures. Herein, seismic response of an existing ATC tower with a wall-frame structural system that has been designed and detailed according to a local building code was evaluated through the framework of performance-based seismic design. Results of this study indicated that the linear static and dynamic analyses used for the design of this tower were incapable of providing a safety margin for the required seismic performance levels especially when the tower was subjected to strong ground motions. It was concluded that, for seismic design of ATC towers practice engineers should refer to a more sophisticated seismic design approach (e.g., performance-based seismic design) which accounts for inelastic behavior of structural components in order to comply with the higher seismic performance objectives of ATC towers.

• Proceedings of the KIEE Conference
• /
• 1998.11c
• /
• pp.875-877
• /
• 1998

In this paper, the physical and electrical properties of electrical insulating materials due to linear low density polyethylene (LLDPE)/ethylene vinyl acetate(EVA) blends are studied. The peak of LLDPE/EVA made by blend ratio of 70:30 at $2{\theta}=21.4^{\circ}$ in the results of XRD is higher than the others. In the experiment for electrical conduction properties in order to investigate the electrical properties of specimen, it is confirmed that electrical conduction is increased with the increase of molecular motions with the increase of temperature.

• The Bulletin of The Korean Astronomical Society
• /
• v.35 no.2
• /
• pp.73.2-73.2
• /
• 2010

In order to understand internal dynamics of starless cores, molecular line emissions are usually observed. From profiles of the molecular lines, internal motions of starless cores have been deduced using a simple radiative transfer model such as the two-layer model (Myers et al.1996). This brings complexities arising from the chemical evolution. The motivation of this study is to follow the chemical evolution of a starless core that goes through gravitational contraction. For this purpose, we have performed hydrodynamical simulations with a marginally unstable Bonnor-Ebert sphere as an initial condition. We follow the chemical evolution of this core with changing conditions such as the chemical reaction rate at the dust surface and the strength of radiation field that penetrate into the core. At the core center, the molecules suffer from a higher degree of molecular depletion on the dust covered by ice rather than on the bare silicate dust. The stronger radiation field dissociates more molecules at the core envelope. From analysis on the line profile using the two-layer model, we found that the speed of inward motion deduced from the HCN F = 2-1 line adequately traces the true infall speed, when the dust is covered by ice and the core is exposed to the diffuse interstellar radiation field. Under different conditions, the two-layer model significantly underestimate the infall speed.

• IEMEK Journal of Embedded Systems and Applications
• /
• v.16 no.5
• /
• pp.163-169
• /
• 2021

In this paper, we implemented a deep learning-based automatic object tracking and handy motion control drone system and analyzed the performance of the proposed system. The drone system automatically detects and tracks targets by analyzing images obtained from the drone's camera using deep learning algorithms, consisting of the YOLO, the MobileNet, and the deepSORT. Such deep learning-based detection and tracking algorithms have both higher target detection accuracy and processing speed than the conventional color-based algorithm, the CAMShift. In addition, in order to facilitate the drone control by hand from the ground control station, we classified handy motions and generated flight control commands through motion recognition using the YOLO algorithm. It was confirmed that such a deep learning-based target tracking and drone handy motion control system stably track the target and can easily control the drone.