Seismic behavior of beam-to-column connections with elliptic slit dampers

Saeed Farahi Shahri,Seyed Roohollah Mousavi 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.26 No.3

The rigid steel connections were suffered severe damage because of low rotational capacity during earthquakes. Hence, many investigations have been conducted on the connections of steel structures. As a solution, steel slit dampers were employed at the connections to prevent brittle failure of connections and damage of main structural members. Slit damper is a plate or a standard section with a number of slits in the web. The objective of this paper is to improve the seismic performance of steel slit dampers in the beam-to-column connection using finite element modeling. With reviewing the previous investigations, it is observed that slit dampers were commonly fractured in the end parts of the struts. This may be due to the low participation of struts middle parts in the energy dissipation. Thus, in the present study slit damper with elliptic slits is proposed in such a way that end parts of struts have more energy absorption area than struts middle parts. A parametric study is conducted to investigate the effects of geometric parameters of elliptic slit damper such as strut width, strut height and plate thickness on the seismic performance of the beam-to-column connection. The stress distribution is improved along the struts in the proposed slit damper with elliptic slits and the stress concentration is decreased in the end parts of struts. The average contributions of elliptic slit dampers, beam and other sections to the energy dissipation are about 97.19%, 2.12% and 0.69%, respectively.

Correction of Prompt Gamma Distribution for Improving Accuracy of Beam Range Determination in Inhomogeneous Phantom

Park, Jong Hoon,Kim, Sung Hun,Ku, Youngmo,Lee, Hyun Su,Kim, Young-su,Kim, Chan Hyeong,Shin, Dong Ho,Lee, Se Byeong,Jeong, Jong Hwi Korean Society of Medical Physics 2017 의학물리 Vol.28 No.4

For effective patient treatment in proton therapy, it is therefore important to accurately measure the beam range. For measuring beam range, various researchers determine the beam range by measuring the prompt gammas generated during nuclear reactions of protons with materials. However, the accuracy of the beam range determination can be lowered in heterogeneous phantoms, because of the differences with respect to the prompt gamma production depending on the properties of the material. In this research, to improve the beam range determination in a heterogeneous phantom, we derived a formula to correct the prompt-gamma distribution using the ratio of the prompt gamma production, stopping power, and density obtained for each material. Then, the prompt-gamma distributions were acquired by a multi-slit prompt-gamma camera on various kinds of heterogeneous phantoms using a Geant4 Monte Carlo simulation, and the deduced formula was applied to the prompt-gamma distributions. For the case involving the phantom having bone-equivalent material in the soft tissue-equivalent material, it was confirmed that compared to the actual range, the determined ranges were relatively accurate both before and after correction. In the case of a phantom having the lung-equivalent material in the soft tissue-equivalent material, although the maximum error before correction was 18.7 mm, the difference was very large. However, when the correction method was applied, the accuracy was significantly improved by a maximum error of 4.1 mm. Moreover, for a phantom that was constructed based on CT data, after applying the calibration method, the beam range could be generally determined within an error of 2.5 mm. Simulation results confirmed the potential to determine the beam range with high accuracy in heterogeneous phantoms by applying the proposed correction method. In future, these methods will be verified by performing experiments using a therapeutic proton beam.

Evaluation of Scatter Reduction Effect of the Aft-Multiple-Slit (AMS) System Using MC Simulation

Jina Chang(장지나),Tae-Suk Suh(서태석),Doh-Yun Jang(장도윤),Hong-Seok Jang(장홍석),Siyong Kim(김시용) 대한방사선종양학회 2010 Radiation Oncology Journal Vol.28 No.4

목 적: 본 연구에서는 콘빔 CT에서 산란선 제거를 위한 aft-multple-slit (AMS) 시스템을 설계하였다. 예비 연구로서 본 시스템의 효용성을 검증하기 위해 MC 시뮬레이션을 수행하였다. 대상 및 방법: 가상 시뮬레이션은 산란선과 산란선+일차선을 계산할 수 있는 MCNPX의 radiography tally 5를 이용하였다. AMS는 빔의 발산성을 고려한 각이 동일한 아크 형태이고, 길이 방향에서의 산란선을 막는다. AMS의 효용성을 위한 평가는 AMS를 사용하지 않았을 때의 일차선과 산란선을 비교함으로써 수행되었다. 2D projection 영상을 얻기 위해 전체의 AMS는 한번의 갠트리 회전 후 AMS에 의해 가려진 부분의 영상 획득을 위해 다시 한 번 회전하는 구조이다. 결 과: 일차선의 2D projection 영상은 모든 AMS의 폭에서 그리고 AMS를 사용하지 않았을 때에도 동일하였으나 일차선+산란선의 2D projection 영상은 slit의 폭에 따라 결과가 변했다. Slit의 폭을 5 mm, 10 mm, 15 mm, 20 mm로 하였을 때 평균 산란성 제거율은 29%, 15%, 9%, 8%였다. 결 론: 본 연구에서는 AMS를 이용한 콘빔 CT의 산란선 제거 효과를 평가하였다. MC 시뮬레이션을 이용한 본 시스템의 사전 연구에서는 상당한 산란선 제거 효과를 보여주었다. Purpose: We designed the aft-multiple-slit (AMS) system to reduce scatter in cone-beam computed tomography(CBCT). As a preliminary study, we performed a Monte Carlo N-Particle Transport Code (MCNP) simulation to verify the effectiveness of this system. Materials and Methods: The MCNPX code was used to build the AMS geometry. An AMS is an equi-angled arc to consider beam divergence. The scatter-reduced projection images were compared with the primary images only and the primary plus scatter radiation images with and without AMS to evaluate the effectiveness of scatter reduction. To obtain the full 2 dimensional (2D) projection image, the whole AMS system was moved to obtain closed septa of the AMS after the first image acquisition. Results: The primary radiation with and without AMS is identical to all the slit widths, but the profiles of the primary plus scattered radiation varied according to the slit widths in the 2D projection image. The average scatter reduction factors were 29%, 15%, 9%, and 8% when the slit widths were 5 mm, 10 mm, 15 mm, and 20 mm, respectively. Conclusion: We have evaluated the scatter reduction effect of the AMS in CBCT imaging using the Monte Carlo (MC) simulations. A preliminary study based on the MCNP simulations showed a mount of scatter reduction with the proposed system.

레이저 슬릿빔을 이용한 한옥 서까래 형상 측정

홍성민(Sung Min Hong),이건수(Gun Soo Lee),박강(Kang Park) (사)한국CDE학회 2012 한국 CAD/CAM 학회 학술발표회 논문집 Vol.2012 No.2

최근 많은 사람들의 친환경적 생활의 요구에 맞춰 우리 전통 한옥의 수요가 늘고 있으며 한옥 부재 가공의 자동화가 필요한 실정이다. 이를 위해 가공에 적합한 새로운 가공기계가 필요하며 기계에 투입되는 원목의 가공 가능 여부를 판단하기 위해 형상의 측정이 필요하다. 이 논문에서는 가공기계에 투입하는 목재를 레이저 슬릿빔(slit-beam)과 카메라를 이용하여 형상을 측정하는 방법을 제시한다. 광 삼각법은 카메라와 물체, 레이저간의 위치를 서로 연결한 삼각형으로 비례관계를 이용해 이미지평면상의 픽셀좌표를 물체의 좌표로 기하학적으로 계산하는 방법이다. WSTM(Whole-Space Tabulation Method)는 실험을 통해 각 높이당 픽셀 좌표 값을 LUT(Loockup Table)에 저장하고, 물체를 측정하여 그 픽셀값을 LUT 를 이용해 물체 좌표로 변환하는 방법이다. 이 논문에서는 위 두 가지 방법을 사용하여 목재의 휨을 측정하고 두 방법간의 정확도를 비교해 보았다.

빔셰이퍼 마스크를 이용한 레이저 빔의 강도 분포 제어

오재용(Jaeyong Oh),박덕수(Deogsu Park),신보성(Bosung Shin) 한국레이저가공학회 2012 한국레이저가공학회지 Vol.15 No.2

In this paper, we have made a proposal concerning the beam shaping mask(BSM) using random-array slits to control intensity distribution profile of laser beam and demonstrated its proprieties experimentally. When a lot of slits are set out irregularly, diffraction patterns of light does not appear but granularity patterns as a bundle of fibers appear. Intensity distribution profile is controlled by densities distribution of circular slits arrayed randomly because the number of slits and its area means amount of light energy through BSM. Namely as the number of slits in high intensity area is increased and that in low intensity area decreased, amount of light energy is same over all local parts. So gaussian intensity distribution could be changed to flat-top.

Evaluation of Scatter Reduction Effect of the Aft-Multiple-Slit (AMS) System Using MC Simulation

장지나,서태석,장도윤,장홍석,김시용 대한방사선종양학회 2010 Radiation Oncology Journal Vol.28 No.4

Purpose: We designed the aft-multiple-slit (AMS) system to reduce scatter in cone-beam computed tomography (CBCT). As a preliminary study, we performed a Monte Carlo N-Particle Transport Code (MCNP) simulation to verify the effectiveness of this system. Materials and Methods: The MCNPX code was used to build the AMS geometry. An AMS is an equi-angled arc to consider beam divergence. The scatter-reduced projection images were compared with the primary images only and the primary plus scatter radiation images with and without AMS to evaluate the effectiveness of scatter reduction. To obtain the full 2 dimensional (2D) projection image, the whole AMS system was moved to obtain closed septa of the AMS after the first image acquisition. Results: The primary radiation with and without AMS is identical to all the slit widths, but the profiles of the primary plus scattered radiation varied according to the slit widths in the 2D projection image. The average scatter reduction factors were 29%, 15%, 9%, and 8% when the slit widths were 5 mm, 10 mm, 15 mm, and 20 mm, respectively. Conclusion: We have evaluated the scatter reduction effect of the AMS in CBCT imaging using the Monte Carlo (MC) simulations. A preliminary study based on the MCNP simulations showed a mount of scatter reduction with the proposed system.

Comparison of Knife-edge and Multi-slit Camera for Proton Beam Range Verification by Monte Carlo Simulation

박종훈,김성훈,구영모,이현수,김찬형,신동호,정종휘 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.2

The mechanical-collimation imaging is the most mature technology in prompt gamma (PG) imagingwhich is considered the most promising technology for beam range verification in proton therapy. Thepurpose of the present study is to compare the performances of two mechanical-collimation PG cameras,knife-edge (KE) camera and multi-slit (MS) camera. For this, the PG cameras were modeled by Geant4Monte Carlo code, and the performances of the cameras were compared for imaginary point and linesources and for proton beams incident on a cylindrical PMMA phantom. From the simulation results, theKE camera was found to show higher counting efficiency than the MS camera, being able to estimate thebeam range even for 107 protons. Our results, however, confirmed that in order to estimate the beamrange correctly, the KE camera should be aligned, at least approximately, to the location of the protonbeam range. The MS camera was found to show lower efficiency, being able to estimate the beam rangecorrectly only when the number of the protons is at least 108. For enough number of protons, however,the MS camera estimated the beam range correctly, errors being less than 1.2 mm, regardless of thelocation of the camera

Design of Optimal Slit Steel Damper Under Cyclic Loading for Special Moment Frame by Cuckoo Search

Masoud Zabihi-Samani 한국강구조학회 2019 International Journal of Steel Structures Vol.19 No.4

After the Northridge and Kobe earthquakes, several destruction of the structural beams were occurred. The diffi culty and cost-eff ectiveness of beam replacement after earthquakes is a major problem on steel structures. For this purpose, the idea of using replaceable connection is suggested. A slit steel damper (SSD) is introduced that leads to the further energy damping and the ability to move the plastic joint outside of structural elements. The stiff ness and damping characteristics of SSD is related to the thickness, height and number of sheets of the damper. The usage of SSD is more progressive and at the same time, the optimal design of SSDs should be proposed to meet the economical criterion and the reduction of the stress and defl ection. In this study, an optimal SSD connection is proposed to enhance the performance of the classical SSD connection to meet the criterion of AISC to utilize in special moment frames. The results demonstrated that increasing the thickness and reduction of the steel sheets in the damper had a greater eff ect on the performance of the SSD connection, in comparison with the increase in the number of sheets. Therefore, the Cuckoo Search (CS) was utilized to optimize the several SSD parameters. Furthermore, a comparison between the CS-SSD and Reduced Beam Section (RBS) which is known as a common moment steel fi xed-connection was accomplished. Results indicate that CS-SSD connection can reach the same function as the RBS connections under cycling loadings, in addition to the easy replacement capability after seismic excitations. The performance of the proposed CS optimization algorithm in designing of the optimal SSD was compared with the traditional Genetic Algorithm and the particle swarm optimization (PSO) with considering several designing constraints. High capabilities of the proposed CS optimization algorithm in terms of weight, energy absorption, stiff ness and bearing capacity of SSD connections are simultaneously clarifi ed by the results.

Flexible Vision Inspection for Seat Frame of Automobile using Slit Beam

정병묵,소범식,이상훈 한국정밀공학회 2011 International Journal of Precision Engineering and Vol. No.

Today’s world automobile market is highly competitive. Quality of automobile is considered even more important and thus efforts are being made to improve the quality of automobile parts in order to survive in such competitive market. Despite rapid development of inspection devices using the vision system, there are few inspection systems for automobile parts. The reason is because the inspection with only one camera is nearly impossible, since automobile parts are three-dimensional and large. The seat frame, one of the typical automobile parts, has various models and is assembled using more than 20subparts. This paper suggests a flexible assembly inspection system of seat frame through the following procedures: first, the inspection method is standardized so that the system can cope with not only some currently existing models but also latent models in the future. Second, 6 cameras are used for inspecting seat frame assembly; 4 cameras are for measuring accuracy, and 2 for right and left-hand sides. Third, a simple pattern matching method is proposed for checking the position of assembly parts. Finally, slit beam method is proposed for checking the existence of assembly parts. Especially, it is very effective to inspect assembly of automobile parts with 3D shape and complex background image.

Large Free Form Measurement Using Slit Beam

EunChang Heo,MinChel Kwon,ByoungChang Kim 제어로봇시스템학회 2008 제어로봇시스템학회 국제학술대회 논문집 Vol.2008 No.10

In heavy industry, 3D surface measurement of large-scale hull pieces is needed for fabrication and assembly. Until now, there is not such an efficient method as a standard ruler on 3D profile measurement of large-scale curvature plates. We suggest an efficient method of 3D profile measurement to obtain the xyz-coordinates of curvature plates. The measurement system comprises a few slit beam lines and performs profile measurement by projecting structured light source on the object surface.