• Structural Engineering and Mechanics
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• v.87 no.2
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• pp.151-164
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• 2023

The latest earthquake's costly repairs and economic disruption were brought on by excessive residual drift. Self-centering systems are one of the most efficient ways in the current generation of seismic resistance system to get rid of and reduce residual drift. The mechanics and behavior of the self-centering system in response to seismic forces were impacted by a number of important factors. The amount of post-tensioning (PT) force, which is often employed for the standing posture after an earthquake, is the first important component. The energy dissipater element is another one that has a significant impact on how the self-centering system behaves. Using the damper as a replaceable and affordable tool and fuse in self-centering frames has been recommended to boost energy absorption and dampening of structural systems during earthquakes. In this research, the self-centering steel moment frame connections are equipped with cushion flexural dampers (CFDs) as an energy dissipator system to increase energy absorption, post-yielding stiffness, and ease replacement after an earthquake. Also, it has been carefully considered how to reduce permanent deformations in the self-centering steel moment frames exposed to seismic loads while maintaining adequate stiffness, strength, and ductility. After confirming the FE model's findings with an earlier experimental PT connection, the behavior of the self-centering connection using CFD has been surveyed in this study. The FE modeling takes into account strands preloading as well as geometric and material nonlinearities. In addition to contact and sliding phenomena, gap opening and closing actions are included in the models. According to the findings, self-centering moment-resisting frames (SF-MRF) combined with CFD enhance post-yielding stiffness and energy absorption with the least amount of permeant deformation in a certain CFD thickness. The obtained findings demonstrate that the effective energy dissipation ratio (β), is increased to 0.25% while also lowering the residual drift to less than 0.5%. Also, this enhancement in the self-centering connection with CFD's seismic performance was attained with a respectable moment capacity to beam plastic moment capacity ratio.

• The Journal of Korean Society for Radiation Therapy
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• v.14 no.1
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• pp.79-84
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• 2002

The main cause factor for effective the output, especially in small & irregular shaped field of electron beam therapy, are collimation system, insert block diameter and energy. In the absorption deose of treatment fields, we should consider the lateral build-up ratio (LBR), which the ratio of dose at a point at depth for a given circular field to the dose at the same point for a 'broad-field', for the same incident fluence and profile. The LBR data for a small circular field are used to extract radial spread of the pencil beam, ${\sigma}$, as a function of depth and energy. It's based on elementary pencil beam. We consider availability of the factor, ${\sigma}$, in the small & irregular fields electron beam treatment.

• New Physics: Sae Mulli
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• v.68 no.11
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• pp.1167-1172
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• 2018

Carbon nanotubes (CNTs) are structures of carbon atoms bonded together in hexagonal honeycomb shapes, with multi-walled CNTs having a very high thermal conductivity of $3000W/m{\cdot}K$ and single-walled CNTs having a conductivity of $6000W/m{\cdot}K$. In this work, the transmittance and the thermal diffusivity of a multi-walled carbon nanotube dispersion with a concentration of 1.5 M were measured using a single beam method, a dual beam method, and the thermal lens effect. The nonlinear optical coefficients were obtained by using the z-scan method, which moved the sample in the direction of propagation of the single laser beam, propagation and the thermal diffusivity was measured using a double laser beam. As a pump beam, a diode-pumped solid state (DPSS) laser with a wavelength of 532 nm and an intensity of 100 mW was used. As the probe beam, a He-Ne laser having a wavelength of 633 nm and an intensity of 5 mW was used. The experimental result shows that when the concentrations of the sample were 9.99, 11.10, 16.65, and 19.98 mM, the nonlinear absorption coefficients were 0.046, 0.051, 0.136 and 0.169 m/W, respectively. Also, the nonlinear refractive indices were 0.20, 0.51, 1.25 and $1.32{\times}10^{-11}m^2/W$, respectively, and the average thermal diffusivity was $1.33{\times}10^{-6}m^2/s$.

• Journal of Korean Society of Steel Construction
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• v.18 no.3
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• pp.385-393
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• 2006

In Korea, the effective utilization of wod structure is encour aged to preserve natural resources and the global environment.ote demand for wod. The efective combination of structural la minated timber and other materials is expected to extend the potential of building structures. This research examines the moment resis tance-type jointing method using structural laminated timber and H-section stel aiming at development of the two-direction frame for lar ge 9 mm and 12 mm) of the H section. Therefore, we conducted the experiment with bending test of the joints to investigate the s tifnes, strength, strain distributions of laminated timber an d of the flange of the H section, and failure paterns. As shown in the results, t he joints with a flange thicknes of 9 mm and 12 m have superi or strength with a flange thicknes of 9 mm and 12 mm were very large, whic h confirmed the high level of energy absorption of such structure s.

• Earthquakes and Structures
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• v.6 no.1
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• pp.89-110
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• 2014

Nonlinear dynamic analyses are carried out to investigate the influence of the pinching hysteretic response of the exterior RC beam-column joints on the seismic behavior of multistory RC frame structures. The effect of the pinching on the local and global mechanisms of an 8-storey bare frame and an 8-storey pilotis type frame structure is evaluated. Further, an experimental data bank extracted from literature is used to acquire experimental experience of the range of the real levels that have to be considered for the pinching effect on the hysteretic response of the joints. Thus, three different cases for the hysteretic response of the joints are considered: (a) joints with strength and stiffness degradation characteristics but without pinching effect, (b) joints with strength degradation, stiffness degradation and low pinching effect and (c) joints with strength degradation, stiffness degradation and high pinching effect. For the simulation of the beam-column joints a special-purpose rotational spring element that incorporates the examined hysteretic options developed by the authors and implemented in a well-known nonlinear dynamic analysis program is employed for the analysis of the structural systems. The results of this study indicate that the effect of pinching on the local and global responses of the examined cases is not really significant at early stages of the seismic loading and especially in the cases when strength degradation in the core of exterior joint has occurred. Nevertheless in the cases when strength degradation does not occur in the joints the pinching may increase the demands for ductility and become critical for the columns at the base floor of the frame structures. Finally, as it was expected the ability for energy absorption was reduced due to pinching effect.

• Progress in Medical Physics
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• v.8 no.2
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• pp.35-43
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• 1997

The knowledge of x-ray spectra is highly desirable in some investigation involves the differential penetrating power and absorption coefficient correction of various photon beam. The transmission data were obtained from the 80 kVp and 120 kVp of CT x-ray beam with the aluminium filter which is designed in a 30 cm of diameter and pipe-typed filter was prepared from 5.0 mm upto 92.3 mm of thickness. To obtain the reconstructed spectra of CT x-ray, the investigator used the iterative numerical analysis which has been extended to include the tungsten characteristics from experimental transmission data with energy interval of 2 keV. Comparison of the calculated transmission data from the reconstructed spectra with that of measurement shows good agreement in both 80 kVp and 120 kVp x-ray beams. This numerical analysis based on iteratively calculation of fractional exposure per energy interval shows the high potential of usefulness of determination the x-ray spectra from the attenuated beam in diagnostic energy range.

• Steel and Composite Structures
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• v.33 no.6
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• pp.793-803
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• 2019

Concrete-filled steel tubular (CFST) beam-columns are widely used owing to their good performance. They have high strength, ductility, large energy absorption capacity and low costs. Externally stiffened CFST beam-columns are not used widely due to insufficient design equations that consider all parameters affecting their behavior. Therefore, effect of various parameters (global, local slenderness ratio and adding hoop stiffeners) on the behavior of CFST columns is studied. An experimental study that includes twenty seven specimens is conducted to determine the effect of those parameters. Load capacities, vertical deflections, vertical strains and horizontal strains are all recorded for every specimen. Ratio between outer diameter (D) of pipes and thickness (t) is chosen to avoid local buckling according to different limits set by codes for the maximum D/t ratio. The study includes two loading methods on composite sections: steel only and steel with concrete. The case of loading on steel only, occurs in the connection zone, while the other load case occurs in steel beam connecting externally with the steel column wall. Two failure mechanisms of CFST columns are observed: yielding and global buckling. At early loading stages, steel wall in composite specimens dilated more than concrete so no full bond was achieved which weakened strength and stiffness of specimens. Adding stiffeners to the specimens increases the ultimate load by up to 25% due to redistribution of stresses between stiffener and steel column wall. Finally, design equations previously prepared are verified and found to be only applicable for medium and long columns.

• Journal of Welding and Joining
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• v.20 no.4
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• pp.525-534
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• 2002

During laser spot welding of the braun tube electron gun, phenomena such as serious spattering and oxidative reaction, etc. were occurred. The spatter occurred from weld pool affects the braun tube, namely it blocks up a very small hole on the shadow mask and causes short circuit between two roles of the electron gun. We guessed that high power density and oxidative reaction are main sources of these problems. So, we studied to prevent and to reduce spatter occurring in spot welding of the braun tube electron gun using pulsed Nd:YAG laser. The characteristics of laser output power was estimated, and the loss of laser energy by optical parameter and spatter was measured by powermeter. The effects of welding parameters, laser defocused distance and incident angle, were investigated on the shape and penetration depth of the laser welded bead in flare and flange joints. From these results, the laser peak power was a major factor to control penetration depth and to occur spatter. It was found that the losses of laser energy by optic parameter and sticked spatter affect seriously laser weldability of thin sheets. The deepest penetration depth is gotten on focal position, and a "bead transition" occurred with a slight displacement of focal position relative to the workpiece surface and the absorption rate of the laser energy is affected by the shape factor of the workpiece. When we changed the incident angle of laser beam, the penetration depth was decreased a little with increasing of the incident angle, and the bead width was increased. The spattering was prevented by considering laser beam energy and incident angle.ent angle.

• Journal of Korean Society of Steel Construction
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• v.22 no.4
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• pp.355-363
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• 2010

The objective of this study is to examine the structural performance on the Rectangular Steel Tube Column-to-H Beam connections using one-side bolts and T-stub. Although a rectangular steel tube comparing with a H-shaped steel has many advantages and is more efficient, its application is limited due to the lack of experiences and connection details. Existing steel moment connections using the rectangular steel tube are mainly using through plate diaphragms. Its processing of construction is so complicated that it is hard to apply in the field. In this study, the structural performance and the earthquake capacity for T-stub connection with one-side bolts were investigated. And it is performed a comparative analysis of strength, rigidity, total rotation and energy absorption capacity for the various connection details.

• Journal of Korean Society of Steel Construction
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• v.22 no.4
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• pp.305-312
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• 2010

The objective of this paper is to examine the structural performance of steel moment-resisting frames on the various connection details of Seismic Wide-flanged Beam-to-Rectangular Steel Tube Column connections. Although compared to an H-shaped steel tube, a rectangular steel tube has many advantages and is more efficient, its application is limited due to the lack of experience in using it and the connection details. Existing steel moment connections using the rectangular steel tube are mainly used through plate diaphragms. The processing of construction of the rectangular steel tube is so complicated that it is hard to apply it in the field. In this study, the structural performance and the earthquake capacity of the connection details that do not cut the rectangular steel tube column were investigated. A comparative analysis of the strength, rigidity, and energy absorption capacity of the welded connection details using an end-plate and a haunch was also performed.