• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.04a
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• pp.121-128
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• 1999

This paper presents a time domain method for soil-structure interaction analysis for seismic loadings. It is based on the finite element formulation incorporating analytical frequency-dependent infinite elements for the far field soil. The dynamic stiffness matrices of the far field region formulated using the present method in frequency domain can be easily transformed into the corresponding matrices in time domain. At first, the equivalent earthquake forces are evaluated along the interface between the near and the far fields from the free-field response analysis carried out in frequency domain, and the results are transformed into the time domain. An efficient procedure is developed for the convolution integrals to evaluate the interaction force along the interface, which depends on the response on the interface at the past time instances as well as the concurrent instance. Then, the dynamic responses are obtained for the equivalent earthquake force and the interaction force using Newmark direct integration technique. Since the response analysis is carried out in time domain, it can be easily extended to the nonlinear analysis. Example analysis has been carried out to verify the present method in a multi-layered half-space.

• The Journal of the Acoustical Society of Korea
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• v.15 no.1
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• pp.23-33
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• 1996

In this paper we point out that if the classical principal domain for bispectra is utilized to determine a second-order Volterra model's output, such and output will be incomplete. This deficiency is associated with the periodic nature of the DFT. For this reason, the objective of this paper is to present an "extended" principal domain for Volterra kernels which leads to an improved estimate of the nonlinear system's response. In order to define the extended principal domain, we derive a new discrete frequency-domain Volterra model from a discrete time-domain Volterra model utilizing 2-dimensional DFT and the relationship between the quadratic component of the Volterra model and a square filter. The effect of the extended domain on the model output is interpreted in terms of the periodicity of DFT. Through computer simulations, we demonstrate the effects of the extended principal domain on the Volterra modeling. The simulation results indicate that the extended principal domain plays and important role in computing Volterra model outputs and estimating Volterra model coefficients.

• Journal of the korean Society of Automotive Engineers
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• v.3 no.1
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• pp.61-68
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• 1981

There are three types in frequency response accelerometer; one is lightly damped piezp type, another is oil damping stainguage type and the third is electro induction type accelerometer within electromagnetic damping. The usable frequency range of lightly damped accelerometers is limited to 0.2 of their mounted natural frequency for amplitude distortion of less than 5 percents. There have been situation where the measured motion contains unforeseen high - frequency components, which are regarded as such due to the accelerometer transfer function. There are several way to overcome amplitude distortion of the higher than anticipated frequency components; (I) to make use of the accelerometer with natural frequency three times and more as high as the measured frequency, (II) to establish data-analysis techniques which will account for the amplitude distortion, (III) to set up a notch filter circuit which has a transfer function that is the reciprocal of the accelerometer transfer function, and so on. This paper makes a report of the method as to(III), i. e., set up a few notch filter circuits, it is discussed what happens when the transfer functions, are in discord as to natural frequency of the filter and accelerometer damping vs. filter damping. And especially as for the cantilever strain gauge type accelerometer made by oneself with ease, it was compared and discussed between the ideological value and the experimental value of actual designed circuit in case of the mismatching of the transfer functions, and it was considered whether to be practicable or not, the result of which was as following; the useful frequency range of the accelerometer can be extended to near resonance if (a) the accelerometer mounted natural frequency and the filter center frequency are matched within .+-. 2 percent and (b) the damping ratios are matched within two factors. Therefore, we obtained the good result in improvement for extending frequency response characteristics of accelerometer.

• Journal of the Earthquake Engineering Society of Korea
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• v.27 no.1
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• pp.69-75
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• 2023

In Korea, most nuclear power plants were designed based on the design response spectrum of Regulatory Guide 1.60 of the NRC. However, in the case of earthquakes occurring in the country, the characteristics of seismic motions in Korea and the design response spectrum differed. The seismic motion in Korea had a higher spectral acceleration in the high-frequency range compared to the design response spectrum. The seismic capacity may be reduced when evaluating the seismic performance of the equipment with high-frequency earthquakes compared with what is evaluated by the design response spectrum for the equipment with a high natural frequency. Therefore, EPRI proposed the inelastic energy absorption factor for the equipment anchorage. In this study, the seismic performance of welding anchorage was evaluated by considering domestic seismic characteristics and EPRI's inelastic energy absorption factor. In order to reflect the characteristics of domestic earthquakes, the uniform hazard response spectrum (UHRS) of Uljin was used. Moreover, the seismic performance of the equipment was evaluated with a design response spectrum of R.G.1.60 and a uniform hazard response spectrum (UHRS) as seismic inputs. As a result, it was confirmed that the seismic performance of the weld anchorage could be increased when the inelastic energy absorption factor is used. Also, a comparative analysis was performed on the seismic capacity of the anchorage of equipment by the welding and the extended bolt.

• Animal Bioscience
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• v.36 no.11
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• pp.1769-1774
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• 2023

Objective: Resting comfort may influence sleep-related lying postures in cattle. This study aimed to investigate the effects of bed cleanliness on tucked (TSP) and extended (ESP) head positions in sleep-related lying postures. Methods: The study was conducted over two experimental periods. In each period, four Japanese Black fattening cattle were assigned to the cleaning treatment (CL), in which bedding material was replaced once during each experimental period. Four cattle were assigned to the control treatment (CON) with no bed cleaning. Daily duration, bout frequency, and bout length of sleep-related lying postures were measured, and bed moisture, ammonia concentration in the air, plasma cortisol, and serotonin concentration were also measured within one week before and after cleaning treatment in each period. Results: The bed moisture and ammonia concentrations decreased in CL after bed cleaning. Following bed cleaning, the duration and bout frequency of TSP in CL decreased compared to that observed in CON, whereas ESP in CL increased after bed cleaning. Total duration of sleep-related lying postures and cortisol and serotonin levels did not differ between CL and CON. Conclusion: These results suggest that cattle in sleep-related lying postures shifted from tucked head positions to extended head positions in response to improved bed cleanliness.

• Smart Structures and Systems
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• v.23 no.6
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• pp.653-667
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• 2019

Using cross-ties to connect cables together when forming a cable network is regarded as an efficient method of mitigating cable vibrations. Cross-ties have been extended and fixed on bridge decks or towers in some engineering applications. However, the dynamics of this kind of system need to be further studied, and the effects of extending cross-links to bridge decks/towers on the modal response of the system should be assessed in detail. In this paper, a system of two cables connected by an inter-supported cross-link with another lower cross-link extended to the ground is proposed and analyzed. The characteristic equation of the system is derived, and some limiting solutions in closed form of the system are derived. Roots of cable system with special configurations are also discussed, attention being given to the case when the two cables are identical. A predictable mode behavior was found when the stiffness of inter-connection cross-link and the cross-link extended to the ground were the same. The vector of mode energy distribution and the degree of mode localization index are proposed so as to distinguish global and local modes. The change of mode behaviors is further discussed in the case when the two cables are not identical. Effects of cross-link stiffness, cross-link location, mass-tension ratio, cable length ratio and frequency ratio on $1^{st}$ mode frequency and mode shape are addressed.

• Journal of KSNVE
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• v.5 no.1
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• pp.29-35
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• 1995

This paper presents the simultaneous optimal design of structure and LQG control systems for the improvement of riding comforts of active vehicle suspension systems. The performance index of riding comforts is extended to include frequency-weighted acceleration in the quadratic cost functional. Janeway human response curve with respect to acceleration is used to verify the usefulness of the presented method. The method is applied to a half model of an active vehicle suspension systems with elastic body moving on randomly profiled road. The values of stiffness of suspensions are used for the structural design variables. The conjugate gradient method is used for optimization. The simulated results of simultaneous optimization with frequency-weighted cost functional are compared with those without frequency- weighted cost functional.

• The Korean Journal of Emergency Medical Services
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• v.17 no.3
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• pp.115-137
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• 2013

Purpose: The purpose of this study was to investigate the extended job of paramedic after the 1st job description in 2000 by the National Health Personnel Licensing Examination Board. Methods: This study was carried out from May 2012 to July 2013 on the Developing A Curriculum (DACUM) method to analysts 330 responses among 400 questionnaires (response rate 82.5%) after analysing 30 pilot questionnaires. In order to enhance validity and reliability of this job description, 2 job analysts in universities and 10 EMT-Paramedics in hospitals and fire stations were recruited. Results: There were differences between 166 (year 2000) and 240 (2012) in task element. There were higher answering at triaging patient(2.64 frequency, 4.15 importance), calling for help(2.68 frequency, 4.07 importance) in disaster emergency care. There were higher answering at measuring vital sign (3.95 frequency, 4.22 importance), measuring ECG(3.84 frequency, 4.14 importance), wound care(3.48 frequency, 3.86 importance), bleeding control & wound care(3.46 frequency, 3.86 importance), applying $O_2$(3.40 frequency, 3.94 importance) in physician assistant. Conclusion: Scope of extended practice as a physician assistant in hospital setting recommended us to replace the present curriculum and national exam with new curriculum and national written & skill test.

• Earthquakes and Structures
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• v.25 no.4
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• pp.269-282
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• 2023

This study investigates a rocking seismic isolation (RSI) system as a seismic protection measure against narrow-band ground-motions generated by earthquakes. Structures supported over RSIs are considered capable of reducing the lateral demands and damage of the main structural system through lifting and rocking. This lifting and rocking during earthquake activity is provided by free-standing columns. A single-degree-of-freedom (SDOF) system supported on a RSI system is subjected to narrow-band seismic motions and its response is compared to an analog system without RSI. The comparison is then extended to reinforced concrete linear frames with and without RSI; three-bay frames with 11 and 17 storeys are considered. It is found that the RSI systems significantly reduce acceleration and displacement demands in the main structural frames, more noticeably if the first structural mode dominates the response and for ratios of the predominant frequency of the ground motion to the predominant frequency of the main frame near one. It is also found that the RSI system is more effective in reducing lateral accelerations and displacements of the main structure when the aspect ratio, b/h, and size, R, of the free-standing columns decrease, although the rocking stability of the RSI system is also reduced.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1989.04a
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• pp.66-70
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• 1989

Methods for identification of modal properties of linear structures are presented. The extended Kalman filtering technique is empolyed. The state equation is formulated by two different ways, namely by the time domain and frequency domain approaches. Verifications are carried out by using simulated records of ground acceleration and structural response. Then the techniques are applied to the estimation of modal parameters of a scaled model for a 3-story building which is installed on a shaking table.