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Medical Image Segmentation Based on Morphology Algorithm and FCM Algorithm
Shigang Wang,Zhinan Rong,Xueshan Gao 보안공학연구지원센터 2016 International Journal of Signal Processing, Image Vol.9 No.10
Fuzzy c-means algorithm is an unsupervised clustering algorithm, its clustering process can reduce the human intervention, and it is suitable for processing medical images of uncertainty and ambiguity. When simply using FCM algorithm in brain image segmentation will leads to the condition of low accuracy. On the basis of FCM algorithm, this paper proposes a new method which combines FCM algorithm and morphology algorithm. The result of simulation shows that this method can accurately and efficiently segment the brain image. The new algorithm is an effective method for image segmentation.
Study on failure mechanism of line contact structures of nuclear graphite
Jia Shigang,Yi Yanan,Wang Lu,Liu Guangyan,Ma Qinwei,Sun Libin,Shi Li,Ma Shaopeng 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.8
Line contact structures, such as the contact between graphite brick and graphite tenon, widely exist in high-temperature gas-cooled reactors. Due to the stress concentration effect, the line contact area is one of the dangerous positions prone to failure in the nuclear reactor core. In this paper, the failure mechanism of line contact structures composed of IG11 nuclear graphite column and brick were investigated by means of experiment and finite element simulation. It was found that the failure process mainly includes three stages: firstly, the damage accumulation in nuclear graphite material led to the characteristic yielding of the line contact structure, but no macroscopic failure can be observed at this stage; secondly, the stresses near the contact area met Mohr failure criterion, and a crack initiated and propagated laterally in the contact zone, that is, local macroscopic failure occurred at this stage; finally, a second crack initiated in the contact area and developed in to a Y-shape, resulting in the final failure of the structure. This study lays a foundation for the structural design and safety assessment of hightemperature gas-cooled reactors
Modeling and Analysis of a Novel Two-Axis Rotary Electromagnetic Actuator for Fast Steering Mirror
Yongjun Long,Chunlei Wang,Xin Dai,Xiaohui Wei,Shigang Wang 한국자기학회 2014 Journal of Magnetics Vol.19 No.2
This paper focuses on the modeling and analysis a novel two-axis rotary normal-stress electromagnetic actuator with compact structure for fast steering mirror (FSM). The actuator has high force density similar to a solenoid, but its torque output is nearly a linear function of both its driving current and rotation angle, showing that the actuator is ideal for FSM. In addition, the actuator is designed with a new cross topology armature and no additional axial force is generated when the actuator works. With flux leakage being involved in the actuator modeling properly, an accurate analytical model of the actuator, which shows the actuator’s linear characteristics, is obtained via the commonly used equivalent magnetic circuit method. Finally, numerical simulation is presented to validate the analytical actuator model. It is shown that the analytical results are in a good agreement with the simulation results.
Yongjun Long,Jinqiu Mo,Xiaohui Wei,Chunlei Wang,Shigang Wang 한국자기학회 2014 Journal of Magnetics Vol.19 No.3
This paper develops a moving-magnet electromagnetic actuator for fast steering mirror (FSM). The actuator achieves a reasonable compromise between voice coil actuator and piezoelectric actuator. The stroke of the actuator is between the strokes of a piezoelectric actuator and a voice coil actuator, and its force output is a linear function of air gap and excitation current within our FSM travel range. Additionally, the actuator is more reliable than voice coil actuator as the electrical connection in the actuator is static. Analytically modeling the actuator is difficult and time-consuming. Alternatively, numerous finite element simulations are carried out for the actuator analysis and design. According to the design results, a real prototype of the actuator is fabricated. An experimental test system is then built. Using the test system, the force output of the fabricated actuator is evaluated. The test results validate the actuator analysis and design.
Design of a Rotary Electromagnetic Actuator with Linear Torque Output for Fast Steering Mirror
Yongjun Long,Jinqiu Mo,Xinshu Chen,Qinghua Liang,Yaguang Shang,Shigang Wang 한국자기학회 2015 Journal of Magnetics Vol.20 No.1
This paper focuses on the design of a flux-biased rotary electromagnetic actuator with compact structure for fast steering mirror (FSM). The actuator has high force density and its torque output shows linear dependence on both excitation current and rotation angle. Benefiting from a new electromagnetic topology, no additional axial force is generated and an armature with small moment of inertia is achieved. To improve modeling accuracy, the actuator is modeled with flux leakage taken into account. In order to achieve an FSM with good performance, a design methodology is presented. The methodology aims to achieve a balance between torque output, torque density and required coil magnetomotive force. By using the design methodology, the actuator which will be used to drive our FSM is achieved. The finite element simulation results validate the design results, along with the concept design, magnetic analysis and torque output model.
Xin Dai,Qinghua Liang,Chao Ren,Jiayong Cao,Jinqiu Mo,Shigang Wang 한국자기학회 2015 Journal of Magnetics Vol.20 No.3
In this study, we propose an analytical model for studying magnetic fields in radial-flux permanent-magnet eddy-current couplings by considering the effects of slots and iron-core protrusions on the eddy currents. We focus on the analytical prediction of the air-gap field by considering the influence of eddy currents induced in conducting bars. In the proposed model, the permanent magnet region is treated as the source of a timevarying magnetic field and the moving-conductor eddy current problem is solved based on the resolution of time-harmonic Helmholtz equations. The spatial harmonics in the air gap and in slots, as well as the time harmonics are all considered in the analytical calculation. Based on the proposed field model, the electromagnetic torque is computed by using the Maxwell stress tensor method. Nonlinear finite element analysis is performed to validate the analytical model. The proposed model can be used for permanent-magnet eddy-current couplings with any slot?pole combination.
Zhiping Lei,Yazhou Li,Zhao Lei,Xue Yang,Jingchong Yan,Zhanku Li,Hengfu Shui,Shibiao Ren,Zhicai Wang,Ying Kong,Shigang Kang 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.117 No.-
Large-scale preparation of cheap and high-performance carbonaceous materials is in urgent need due tothe huge demand of carbonaceous materials-organic binder composites for Joule heating. Here, carbonbasedelectrothermal composites with high electrical conductivity were fabricated by adjusting the morphologyand structure of pitch-based carbonaceous materials (PC) through the use of graphene asstructure-directing agent to tune the orientation and carbonization of coal pitch. It is demonstrated thatthe addition of graphene can effectively promote the formation of graphitized carbon, increase the contentof sp2C, reduce defective carbon and increase the graphite interlayer spacing. 1% graphene-added PCPVDFcomposite exhibits 290% increase in the carrier concentration, 190% enhancement in mobility, and67% reduction in the volume resistivity compared to PC-PVDF composite. Molecular simulations elucidatethat the graphene edges favor pitch carbonization and improve the orientation factor and energy gap ofcarbon materials. This study provides clues for design of low-cost pitch-derived carbon materials-bindercomposites.