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Mesh Generation Based on Virtual Geometry
Peng Wei,Chen Wenliang,Bao Yidong 한국소성가공학회 2010 기타자료 Vol.2010 No.6
Finite element mesh generation algorithm often requires the ability to abstract and modify the topology of a boundary representation model. A method based on virtual geometry for mesh generation is proposed to modify the model topology without changing the geometry of the model. By this method, a tool is given to adjust the model topology for optimal meshing, while leaving the geometry or shape of the model, and the accuracy of the resulting mesh in representing the model, unchanged. Our practical examples show that the proposed method is effective and reliable for mesh generation in molding analysis field.
Rigid Surface Matching by Shape Analysis and Correspondences Filtering
Peng Wei,Ji Weixi,Chen Wenliang,Shao Kun 한국정밀공학회 2018 International Journal of Precision Engineering and Vol.19 No.9
Surface matching technology, as a fundamental part of computer graphics, has a wide range of applications in engineering domain. In this paper, we propose a novel matching method for best fitting a given source model onto a target model by a combination of the following: point clustering, region similarity matching and correct pairing searching. Mesh segmentation is used to aggregate points into several sub-regions, and then paired regions are obtained by distance distribution. An indirect searching strategy is presented, in which bad paired triples are removed by filtering operation and the remaining candidates are traversed until the correct pairing is found. Experimental results on a variety of mechanical models demonstrate that our method exhibits high reliability and robustness for automatic shape alignment.
Control of Radial Force in Double Stator Type Bearingless Switched Reluctance Motor
Peng, Wei,Xu, Zhenyao,Lee, Dong-Hee,Ahn, Jin-Woo The Korean Institute of Electrical Engineers 2013 Journal of Electrical Engineering & Technology Vol.8 No.4
Modeling and control of radial force in the double stator type bearingless switched reluctance motor (BLSRM) is researched. The rotational torque is controlled independently from the radial force control. And the radial force is constant which is independent from the rotor position. In order to realize steady suspension, analytical models of torque and radial force for the proposed structure are derived. Meanwhile, in order to realize steady suspension, control scheme for proposed BLSRM is proposed. In the control method, the radial force can be controlled in arbitrary direction and magnitude by selecting some combinations of radial force windings. The validities of structure and control method are verified by the experimental results.
Vibration analysis and dynamic performance improvement of high-frequency injection method
Peng, Wei,Qiao, Mingzhong,Jiang, Chao,Lu, Xihao,Zhu, Peng The Korean Institute of Power Electronics 2021 JOURNAL OF POWER ELECTRONICS Vol.21 No.2
This paper analyzes and compares the typical rotating high-frequency voltage injection (RTHF) method and the typical pulsating high-frequency voltage injection (PSHF) method in terms of torque ripple and vibration. Analysis and experiment results indicate that the PSHF performs better when it comes to torque pulsation and vibration. In addition, it is more suitable for rim motors which have strict restrictions on vibration. However, the estimated rotor position in PSHF has multiple convergence points. In addition, the filters used in PSHF can degrade the dynamic response of the PMSM sensorless field oriented control (SLFOC) system. An improved PSHF method compensated by Hall signals is proposed to accelerate the estimation process and improve the system stability in the presence of sudden load disturbances. The improved method is verified on an 11 kW rim motor experimental platform.
Assessing the Vulnerability of Network Topologies under Large-Scale Regional Failures
Peng, Wei,Li, Zimu,Liu, Yujing,Su, Jinshu The Korea Institute of Information and Commucation 2012 Journal of communications and networks Vol.14 No.4
Natural disasters often lead to regional failures that can cause network nodes and links co-located in a large geographical area to fail. Novel approaches are required to assess the network vulnerability under such regional failures. In this paper, we investigate the vulnerability of networks by considering the geometric properties of regional failures and network nodes. To evaluate the criticality of node locations and determine the critical areas in a network, we propose the concept of ${\alpha}$-critical-distance with a given failure impact ratio ${\alpha}$, and we formulate two optimization problems based on the concept. By analyzing the geometric properties of the problems, we show that although finding critical nodes or links in a pure graph is a NP-complete problem, the problem of finding critical areas has polynomial time complexity. We propose two algorithms to deal with these problems and analyze their time complexities. Using real city-level Internet topology data, we conducted experiments to compute the ${\alpha}$-critical-distances for different networks. The computational results demonstrate the differences in vulnerability of different networks. The results also indicate that the critical area of a network can be estimated by limiting failure centers on the locations of network nodes. Additionally, we find that with the same impact ratio ${\alpha}$, the topologies examined have larger ${\alpha}$-critical-distances when the network performance is measured using the giant component size instead of the other two metrics. Similar results are obtained when the network performance is measured using the average two terminal reliability and the network efficiency, although computation of the former entails less time complexity than that of the latter.
Peng Wei,Wan-Fen Pu,Lin Sun,Daibo Li,Xudong Ji 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.60 No.-
APG can be employed as a promising foaming agent due to its largely independent of temperature and salinity. Aiming at the APGs foam, we conducted the experiments about adsorption behaviors, surface viscoelasticity, bulk foam properties and core flooding under conditions of high-temperature and -salinity. Our results demonstrated that APG (n = 10) foam presents a good foam performance and foam properties are highly depended on the surface viscoelasticity and are not completely determined by the adsorbing capacity at the interface of gas–water. In the porous media, an appropriate foam quality of APG foam is contributed to increase the foam strength and gas trapping.
Free-Form Surface Flattening Based on Rigid Registration and Energy Optimization
Peng Wei,Qiao Kai,Bao Yidong,Zhang Chaoyang,Ji Weixi 한국정밀공학회 2022 International Journal of Precision Engineering and Vol.23 No.8
Fundamental technology of Computer Aided Design, free-form surface flattening is important for both practical and scientific point of view in mechanical engineering. This paper proposed a flattening algorithm by using a local rigid registration and a global energy optimization. Firstly, each 3D element is aligned to the plane by minimizing the distance between the original 3D element and its corresponding planar element. Then, a global optimization operator is used to stitch and optimize these best-aligned local elements by iteratively minimizing a quadratic energy function composed of linear elastic energy, which makes the internal force of the nodes reach the equilibrium state. The experimental results show that this method is stable and reliable, and can obtain good surface flattening effect under free boundary conditions.
Peng, Wei,Zhang, Jian,Chang, Da,Shen, Zhuo-Wen,Shang, Yuanqi,Song, Donghui,Ge, Qiu,Weng, Xuchu,Wang, Ze Korean Society of Magnetic Resonance in Medicine 2017 Investigative Magnetic Resonance Imaging Vol.21 No.4
Purpose: Caffeine is the most widely consumed psychostimulant. It is often adopted as a tool to modulate brain activations in fMRI studies. However, its pharmaceutical effect on task-induced deactivation has not been fully examined in fMRI. Therefore, the purpose of this study was to examine the effect of caffeine on both activation and deactivation under sustained attention. Materials and Methods: Task fMRI was acquired from 26 caffeine naive healthy volunteers before and after taking caffeine pill (200 mg). Results: Statistical analysis showed an increase in cognition-load dependent task activation but a decrease in load dependent de-activation after caffeine ingestion. Increase of attention and memory task activation and its load-dependence suggest a beneficial effect of caffeine on the brain even though it has no overt behavior improvement. The reduction of deactivation by caffeine and its load-dependence indicate reduced facilitation from task-negative networks. Conclusion: Caffeine affects brain activity in a load-dependent manner accompanied by a disassociation between task-positive network and task-negative network.
Role of water-soluble polymer on foam-injection process for enhancing oil recovery
Peng Wei,Wan-Fen Pu,Lin Sun,Yong Pu,Daibo Li,Ying Chen 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.65 No.-
Role of polymer on foam transportation in porous media is still not entirely illustrated. In this study, we performed the foam injection process in cores and the parallel-layered micromodel, respectively. Combined with a series of static investigations, we found that adding polymer to foam could not only effectively generate a viscous force, but also create a protective enclosure around the bubble (i.e., viscoelastic film). This synergistic effect was supposed to increase the foam apparent viscosity, promote the foam strength in the low-quality regime, create the shear-thickening behavior, and restraint the defoaming effect of crude oil. The microflow experiments indicated that polymer-enhanced foam was capable of sharply increasing the sweep efficiency and EOR. Meanwhile, the presence of viscoelastic liquid films contributed to the microflow behaviors.