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A New Method for Dynamic Analysis of Spatial Lattice Structures Based on Mode Selection and Mode Construction Techniques

  • Luo, Y.F.;Liu, Y.P.;Hu, Z.Y.;Xiong, Z.
    • International journal of steel structures
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    • v.17 no.3
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    • pp.1157-1170
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    • 2017
  • The traditional mode superposition method (MSM) is inefficient when applied to dynamic analyses of spatial lattice structures. The inapplicability and inefficiency of the MSM associated with spatial lattice structures are investigated and summarized in this paper. Based on mode selection and mode construction, a new modal set is constructed named Eigen-Loaddependent Ritz (Eigen-LDR) mode. Additionally, the computational procedure of the Eigen-LDR modes is presented. Furthermore, based on the constructed Eigen-LDR modes, a modified MSM, named the Eigen-LDR mode superposition method (EL-MSM), is proposed. Two typical spatial lattice structures, namely, a latticed shell and a spatial truss, are built as numerical examples. Seismic response analyses using the EL-MSM, including mode-superposition time history analysis and mode-superposition response spectrum analysis, are conducted simultaneously. The numerical results illustrate the accuracy, efficiency and generality of the method proposed in this paper.

Implementation of Omni-directional Image Viewer Program for Effective Monitoring (효과적인 감시를 위한 전방위 영상 기반 뷰어 프로그램 구현)

  • Jeon, So-Yeon;Kim, Cheong-Hwa;Park, Goo-Man
    • Journal of Broadcast Engineering
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    • v.23 no.6
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    • pp.939-946
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    • 2018
  • In this paper, we implement a viewer program that can monitor effectively using omni-directional images. The program consists of four modes: Normal mode, ROI(Region of Interest) mode, Tracking mode, and Auto-rotation mode, and the results for each mode is displayed simultaneously. In the normal mode, the wide angle image is rendered as a spherical image to enable pan, tilt, and zoom. In ROI mode, the area is displayed expanded by selecting an area. And, in Auto-rotation mode, it is possible to track the object by mapping the position of the object with the rotation angle of the spherical image to prevent the object from deviating from the spherical image in Tracking mode. Parallel programming for processing of multiple modes is performed to improve the processing speed. This has the advantage that various angles can be seen compared with surveillance system having a limited angle of view.

Evaluation of the Availability of the Wide Coverage Volume Axial Mode in Pediatric Cardiac CT (소아 심장 CT검사 시 Wide Coverage Volume Axial Mode의 유용성 평가)

  • Park, Ki Seok;Kim, Dong Hyun
    • Journal of the Korean Society of Radiology
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    • v.13 no.5
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    • pp.683-689
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    • 2019
  • We are trying to evaluate usefulness of Wide Coverage Volume Axial Mode by comparing and analyzing for exposure doses to patients and video quality extracted from two materials. First material is a computer tomography scanning of paediatric cardiac made by using High Pitch Mode, which is designed for diagnosing Congenital cardiac diseases. Second material is computer tomography scanning of paediatric cardiac made by using Wide Coverage Volume Axial Mode. When we did computer tomography scanning of paediatric cardiac, we used High Pitch Mode and Wide Coverage Volume Axial Mode to 50 patients of each, overall 100 patients. Also, we compared exposure doses to patients using videos got from each protocol. Then we compared video quality by calculating SNR and CNR by setting ROI of each. Not only exposure doses to patients were reduced by 13.07 %, but also SNR and CNR were improved when testing used Wide Coverage Volume Axial Mode rather than using High Pitch Mode. Wide Coverage Volume Axial Mode reduced testing time by using high-speed scanner. Furthermore, we can find out that Wide Coverage Volume Axial Mode is an useful method through improving video quality and reducing exposure doses to patients than using High Pitch Mode from ASiR-V, which is low-dose technology.

Ductile Fracture Behaviour of SA 533B Pressure Vessel Steel Under Mixed Mode (I/II) Loading (혼합 모드(I/II) 하중에 의한 SA533B 압력용기강의 연성파괴 특성에 관한 연구)

  • O, Dong-Jun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.11
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    • pp.1829-1834
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    • 2001
  • The aim of this study is to investigate the ductile fracture behavior under mixed mode (I/II) loading using SA533B pressure vessel steel. Anti-symmetric 4-point (AS4P) bonding tests were performed to obtain the J-R curves under two different mixed mode (I/II) loadings. In addition, the fractographic examination of fracture surfaces was carried out to compare with those of pure Mode I and Mode II. In conclusions, the J-R curves under Mixed Mode (I/II) loading were located between those of Mode I and Mode II loadings. When the mixture ratio of mixed mode (I/II) loading was high, the J-R currie of mixed mode (I/II) loading approached that of pure mode I loading after some amount of crack propagation. In contrast with the above fact, if the mixture ratio was low, the J-R curve looked after that of pure mode II loading. The fractographic evidences such as the shape of dimples under different loading conditions supported these conclusions.

Performance Analysis of the Inversion Schemes in the Spotlight-mode SAR(Synthetic Aperture Radar) (Spotlight-mode SAR(Synthetic Aperture Radar)에서의 Inversion 기법 성능 분석)

  • 최정희
    • Journal of the Institute of Electronics Engineers of Korea SP
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    • v.40 no.1
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    • pp.130-138
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    • 2003
  • The classical image reconstruction for stripmap-mode Synthetic Aperture Radar is the Range-Doppler algorithm. When the spotlight-mode SAR system was envisioned, Range-Doppler algorithm turned out to fail rapidly in this SAR imaging modality. Thus, what is referred to as Polar format algorithm, which is based on the Plane wave approximation, was introduced for imaging from spotlight-mode SAR raw- data. In this paper, we have studied for the raw data processing schemes in the spotlight-mode Synthetic Aperture Radar. We apply the Wavefront Reconstruction scheme that does not utilize the approximation in spotlight-mode SAR imaging modelity, and compare the performance of target imaging with the Polar format inversion scheme.

Ductile Fracture Behavior of AS4P Under Mixed Mode (I/II) Loading

  • Oh, Dong-Joon
    • Journal of Mechanical Science and Technology
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    • v.16 no.4
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    • pp.476-484
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    • 2002
  • The aim of this study is to investigate the ductile fracture behavior under mixed mode (I/II) loading using SA533B pressure vessel steel. Anti-symmetric 4-point (AS4P) bending tests were performed to obtain the J-R curves under two different mixed mode (I/II) loadings. In addition, finite element analysis using Rousselier Ductile Damage Theory was carried out to predict the J-R curves under mixed mode (I/II) loadings. In conclusions, the J-R curves under. Mixed Mode (I/II) loading were located between those of Mode I and Mode II loading. When the mixity of mixed mode (I/II) loading was high, the J-R curve of mixed mode (I/II) loading approached that of pure mode I loading after some amount of crack propagation. In contrast with the above fact, if the mixity was low, the J-R curve took after that of pure mode II loading. Finally, it was found that the predicted J-R curves made a good agreement with the test data through the tuning procedures of $\beta$ values at the different mixed mode (I/II) loading.

Development and Application of Mode II Fracture Toughness Test Method Using Rock Core Specimen (시추코어를 이용한 암석의 mode II 파괴인성 시험법 개발과 적용)

  • Jung, Yong-Bok;Park, Eui-Seob;Kim, Hyunwoo
    • Tunnel and Underground Space
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    • v.26 no.5
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    • pp.396-408
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    • 2016
  • Rock fracture mechanics has been widely applied to various fields of rock and civil engineering. But most researches covered mode I behavior, though mode II behavior is dominant in rock engineering. Until now, there is only one ISRM suggested method for mode II toughness of rock. A new SCC (Short Core in Compression) mode II toughness test method was developed considering 1) application of confining pressure, 2) easiness of notch creation, 3) utilization of existing equipment, 4) simple test procedure. The stress intensity factors were determined by 3D finite element method considering line and distributed loading conditions. The tests with granite specimens were carried out using MTS 815 rock test system with a loading rate of 0.002 mm/s. The mean value of mode II fracture toughness of granite showed $2.33MPa{\sqrt{m}}$. Mode I toughness of the same granite was $1.12MPa{\sqrt{m}}$, determined by Brazilian disk test and $K_{IIC}/K_{IC}=2.08$. The smooth fracture surface with rock powder formation also supported mode II behavior of SCC method. The SCC method can be used for the determination of mode II fracture toughness of rocks based on the current results.

Instability of High-Speed Impinging Jets(II) (고속 충돌제트의 불안정 특성)

  • Gwon, Yeong-Pil;Im, Jeong-Bin
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.22 no.4
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    • pp.450-467
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    • 1998
  • The characteristics of the unstable impinging circular jet is investigated based on the frequency characteristics and the sound field of the impinging-tones. Two symmetric modes S1 and S2, associated with low frequency and high frequency respectively, and one helical mode H have been observed. At low speed the S2 mode is dominant and switched by the S1 mode as the speed increases. When the jet speed is high the S1 mode is very active over the impinging distance from half the nozzle diameter to its ten times, while the S2 mode occurs at shorter distance corresponding to stage 2 and 3. The helical mode H seems unstable, likely to be influenced much by the experimental environment, and occurs at relatively high speed with almost the same frequency characteristics as the S2 mode. By estimating the convection speed of the unstable jet, it is found that the ratio of the convection speed to the jet speed decreases with both Strouhal number and Reynolds number and the speed of S2 mode is faster than the Si mode. When the present experimental results are compared with the previous investigations performed for the hole tone and the impinging tone with a small plate, the S1 mode is found to be associated with the ring vortex of large diameter with low speed, but the S2 mode with the vortex of small diameter with high speed. In addition, the frequency is found to be influenced by the nozzle configuration but the characteristics is almost the same. From the impinging distance and frequency range, it can be deduced that S1 mode is related with the jet column mode and S2 mode with the shear mode.

A Study on Standardization on the Flight Controller Mode in Remotely Piloted Aircraft Drone : Focused on Drone Controller Mode Preference (원격조종항공기 드론 조종기모드 표준화 연구 : 드론 조종기모드 선호도를 중심으로)

  • Park, Wontae
    • Journal of the Society of Korea Industrial and Systems Engineering
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    • v.42 no.4
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    • pp.69-75
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    • 2019
  • Remotely Piloted Aircraft (RPA) controls as a type of unmanned aerial vehicle (drone) is growing rapidly and its flight controller stick disposition is required standardization. We should standardize RPA drone flight control disposition because the flight pilot of RPA is hard to be trained so the flight controller stick differences impairs safety and wastes time and effort of flight controller industry. So this study researches the on-going standardization of RPA drone flight control disposition in Korea and foreign countries. Also this paper analyzes and researches of expert about RPA drone flight controller function and application of flight control mode. I accomplished expert research about standardization plan of unmanned flight control mode and confirm the necessity. Nowadays mode1 and 2 are mostly used in Korea so I carried out preference investigation for two modes. There were 4 preferences choices of RPA drone control mode necessity (importance) and recommendation of standardization modes. They answered that necessity of standardization is important considering pilot training, flight safety and positive development of drone industry. The result of standardization mode preference is that they prefer mode 2 (drone maker 86%, training facilities and research facilities 58%, government bureau 60%). Overall preference result shows that mode 1 24%, mode 1&2 16%, mode 2 60%. So they preferred mode 2 by 60%. The differences between two modes are the direction of throttle and pitch. Direction of throttle and pitch operate opposite way. They prefer mode 2 because mode 2 has similarities of manned flight control mode. Significance of this study is that it showed the necessity of standardization and flight control preference in a quantitative way. It will help drone standardization in related industries and development direction near future.