Influence of cleaning modes on the microstructure and performance of 5083 alloy substrate

Yunkai Li,Chunming Wang,Gaoyang Mi 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.9

In this study, the paint layer was removed on the surface of 5083 aluminum alloy using laser cleaning and mechanical grinding. The microstructure and performance of experimental samples were carefully investigated using scanning electron microscope, energy disperse spectroscopy and other methodologies. The results showed that compared with mechanical grinding, laser cleaning can improve the surface paint coating of aluminum alloy more effectively. The surface of the matrix formed uniformly distributed volcanic craters and small holes emerged at the spot junction after laser cleaning. The carbon and oxygen content on the substrate surface after laser cleaning was much lower than that after mechanical grinding. In addition, the corrosion resistance and coating adhesion of the substrate were obviously improved using laser cleaning. It was closely associated with refinement of the grains and reduction in surface roughness. We concluded that laser cleaning can be widely used to replace mechanical grinding in manufacturing on the premise of meeting industrial needs.

Contrast-Enhanced Harmonic Ultrasonography for the Assessment of Prostate Cancer Aggressiveness: a Preliminary Study

Yunkai Zhu,Yaqing Chen,Jun Jiang,Ren Wang,Yongchang Zhou,Huizhen Zhang 대한영상의학회 2010 Korean Journal of Radiology Vol.11 No.1

Objective: To determine whether contrast-enhanced harmonic ultrasonography can be used to predict the aggressiveness of prostate cancer. Materials and Methods: Contrast-enhanced harmonic ultrasonography was performed in 103 patients suspected of prostate cancer before biopsy. Time intensity curves were reconstructed for systematic biopsy sites and sonographic abnormalities. The characteristics of the curves were described using hemodynamic indices including arrival time (AT), time-to-peak (TTP), and peak intensity (PI). The differences of hemodynamic indices between high-grade and low-grade cancer were analyzed and the correlations between the hemodynamic indices and biopsy Gleason score were studied. Results: Prostate cancer was detected in 41 of 103 patients and there were significant differences in the hemodynamic indices between the biopsy sites of the non-malignant patients and prostate cancer lesions (p < 0.05). The prostate biopsies revealed 154 prostate cancer lesions, including 31 low-grade lesions and 123 high-grade lesions. The hemodynamic indices AT and TTP of highgrade tumors were significantly shorter than those of low-grade tumors (p = 0.001, 0.002). In addition, high-grade peripheral zone (PZ) tumors had higher PI than low-grade PZ tumors (p = 0.009). The PZ prostate cancer Gleason score correlated with PI, AT and TTP, with Spearman correlation coefficients of 0.223, -0.335, and -0.351, respectively (p = 0.013, < 0.001 and < 0.001). Conclusion: Contrast-enhanced ultrasound measurements of hemodynamic indices correlate with the prostate cancer Gleason score. Objective: To determine whether contrast-enhanced harmonic ultrasonography can be used to predict the aggressiveness of prostate cancer. Materials and Methods: Contrast-enhanced harmonic ultrasonography was performed in 103 patients suspected of prostate cancer before biopsy. Time intensity curves were reconstructed for systematic biopsy sites and sonographic abnormalities. The characteristics of the curves were described using hemodynamic indices including arrival time (AT), time-to-peak (TTP), and peak intensity (PI). The differences of hemodynamic indices between high-grade and low-grade cancer were analyzed and the correlations between the hemodynamic indices and biopsy Gleason score were studied. Results: Prostate cancer was detected in 41 of 103 patients and there were significant differences in the hemodynamic indices between the biopsy sites of the non-malignant patients and prostate cancer lesions (p < 0.05). The prostate biopsies revealed 154 prostate cancer lesions, including 31 low-grade lesions and 123 high-grade lesions. The hemodynamic indices AT and TTP of highgrade tumors were significantly shorter than those of low-grade tumors (p = 0.001, 0.002). In addition, high-grade peripheral zone (PZ) tumors had higher PI than low-grade PZ tumors (p = 0.009). The PZ prostate cancer Gleason score correlated with PI, AT and TTP, with Spearman correlation coefficients of 0.223, -0.335, and -0.351, respectively (p = 0.013, < 0.001 and < 0.001). Conclusion: Contrast-enhanced ultrasound measurements of hemodynamic indices correlate with the prostate cancer Gleason score.

Energy-Aware Traffic Engineering in Hybrid SDN/IP Backbone Networks

Yunkai Wei,Xiaoning Zhang,Lei Xie,Supeng Leng 한국통신학회 2016 Journal of communications and networks Vol.18 No.4

Software defined network (SDN) can effectively improvethe performance of traffic engineering and will be widely used inbackbone networks. Therefore, new energy-saving schemes musttake SDN into consideration; this action is extremely importantowing to the rapidly increasing energy consumption in telecom andInternet service provider (ISP) networks. Meanwhile, the introductionof SDN in current networks must be incremental in mostcases, for technical and economic reasons. During this period, operatorsmust manage hybrid networks in which SDN and traditionalprotocols coexist. In this study, we investigate the energyefficienttraffic engineering problem in hybrid SDN/Internet protocol(IP) networks. First, we formulate the mathematical optimizationmodel considering the SDN/IP hybrid routing mode. Theproblem is NP-hard; therefore, we propose a fast heuristic algorithmnamed hybrid energy-aware traffic engineering (HEATE) asa solution. In our proposed HEATE algorithm, the IP routers performshortest-path routing by using distributed open shortest pathfirst (OSPF) link weight optimization. The SDNs perform multipathrouting with traffic-flow splitting managed by the global SDNcontroller. The HEATE algorithm determines the optimal settingfor the OSPF link weight and the splitting ratio of SDNs. Thus, thetraffic flow is aggregated onto partial links, and the underutilizedlinks can be turned off to save energy. Based on computer simulationresults, we demonstrate that our algorithm achieves a signifi-cant improvement in energy efficiency in hybrid SDN/IP networks.

Energy-Aware Traffic Engineering in Hybrid SDN/IP Backbone Networks

Wei, Yunkai,Zhang, Xiaoning,Xie, Lei,Leng, Supeng The Korea Institute of Information and Commucation 2016 Journal of communications and networks Vol.18 No.4

Software defined network (SDN) can effectively improve the performance of traffic engineering and will be widely used in backbone networks. Therefore, new energy-saving schemes must take SDN into consideration; this action is extremely important owing to the rapidly increasing energy consumption in telecom and Internet service provider (ISP) networks. Meanwhile, the introduction of SDN in current networks must be incremental in most cases, for technical and economic reasons. During this period, operators must manage hybrid networks in which SDN and traditional protocols coexist. In this study, we investigate the energy-efficient traffic engineering problem in hybrid SDN/Internet protocol (IP) networks. First, we formulate the mathematical optimization model considering the SDN/IP hybrid routing mode. The problem is NP-hard; therefore, we propose a fast heuristic algorithm named hybrid energy-aware traffic engineering (HEATE) as a solution. In our proposed HEATE algorithm, the IP routers perform shortest-path routing by using distributed open shortest path first (OSPF) link weight optimization. The SDNs perform multipath routing with traffic-flow splitting managed by the global SDN controller. The HEATE algorithm determines the optimal setting for the OSPF link weight and the splitting ratio of SDNs. Thus, the traffic flow is aggregated onto partial links, and the underutilized links can be turned off to save energy. Based on computer simulation results, we demonstrate that our algorithm achieves a significant improvement in energy efficiency in hybrid SDN/IP networks.

A Fast Analytic Model of Axial Flux Permanent Magnet Machines with Static/Dynamic Axis Eccentricity

Baocheng Guo,Yunkai Huang 한국자기학회 2016 Journal of Magnetics Vol.21 No.4

This paper presents a general analytical model to calculate the characteristics of axial-flux permanent-magnet machines with axis eccentricities. The radial and tangential magnetic flux densities in the air gap under normal conditions were first obtained using a combination of Maxwell’s equations and Schwarz-Christoffel (SC) transformation. Next, equations for the radii were deduced to investigate the static/dynamic eccentricities. The back electromotive forces (EMFs) were calculated and compared with those obtained from finite element (FE) analysis. The analytical predictions show good agreement with the FE results. Detection approaches were obtained by comparing with normal conditions, and the analytical model was verified experimentally.

An Improved Conformal Mapping Method for Static Angular Eccentricity Analysis of Axial Flux Permanent Magnet Machines

Baocheng Guo,Yunkai Huang,Fei Peng 한국자기학회 2018 Journal of Magnetics Vol.23 No.1

This paper presents an improved and simple analytical model to study the static angular eccentricity of single stator single rotor axial-flux permanent-magnet (AFPM) machine. The magnetic flux densities in the air gap under normal and static angular eccentricity are calculated by using a combination of Maxwell’s equations and Schwarz-Christoffel (SC) transformation. The original contribution of the model is that angular eccentricity is obtained without extra transformations. Thus the proposed approach is simpler than existing methods. The calculated back electromotive forces (EMFs) and cogging torque by the proposed method are compared with those obtained from the finite element (FE) model, the results show acceptable accuracy of the proposed method. In this way, the effectiveness of the proposed method is verified.

Performance Comparison of Analytical Models for Rotor Eccentricity: A Case Study of Active Magnetic Bearing

Zhi Cao,Yunkai Huang,Baocheng Guo,Jianning Dong,Fei Peng 한국자기학회 2020 Journal of Magnetics Vol.25 No.2

This paper applies two different analytical methods, i.e., the perturbation method and superposition method, to calculate the magnetic flux density distribution and the magnetic force of the active magnetic bearing (AMB) with the rotor eccentricity. These two methods are thoroughly analyzed, compared and validated by the finite element model (FEM). The perturbation method is theoretically complex while the superposition method is intuitive. The valid range of the superposition method is larger than the perturbation method. However, the superposition method requires longer computation time. The main contribution of this paper is assessing the effectiveness of two analytical methods for predicting the AMB performance with the rotor eccentricity and giving a comprehensive guideline for engineers to choose the proper analytical method to design AMB.

A New Rotor Structure for High Speed Flywheel Permanent Magnet Synchronous Machine

Zichong Zhu,Yunkai Huang,Jianning Dong,Fei Peng 한국자기학회 2019 Journal of Magnetics Vol.24 No.3

This paper presents a new rotor design with assembled permeable retaining sleeve (APRS) to improve performances of a high speed permanent magnet synchronous machine (PMSM). The APRS consists of equal number of permeable and nonmagnetic parts, which are alternately arranged and assembled together circumferentially via keyways. Electromagnetic and mechanical characteristics of the rotor applied to a high speed flywheel PMSM are analyzed using finite element method. Machine performances are compared to an original design with commonly used rotor structure. It shows that phase inductance of the high speed machine increases dramatically due to smaller effective air gap, which may benefit suppressing inverter current harmonics. Also, permanent magnet usage reduces by 9.4 % to obtain identical back electromotive force and torque constant. In addition, a smaller skin depth owing to high-permeability material and the circumferential segmentation of the retaining sleeve effectively reduce rotor eddy current. Associated loss decreases by 40.7 % under open-circuit condition. A prototype rotor is fabricated and preliminary experimental tests are performed to confirm the analysis results.

Aberrant Effective Connectivity of the Ventral Putamen in Boys With Attention-Deficit/Hyperactivity Disorder

Zhihui Lan,Yunkai Sun,Lei Zhao,Yang Xiao,Changxiao Kuai,Shao-Wei Xue 대한신경정신의학회 2021 PSYCHIATRY INVESTIGATION Vol.18 No.8

Objective The connectivity alterations in the putamen were found in revealing the neural correlates of attention-deficit/hyperactivity disorder (ADHD), but whether the effective connectivity of the putamen is atypical in ADHD remains unclear. Investigating this abnormality contributes to describing the neural circuit of ADHD at the level of macrostructural organization. Methods Data were acquired from thirty-two boys with ADHD and fifty-two matched typically developing controls (TDC) from Peking University (Peking) dataset deposited at the Neuroimaging Informatics Tools and Resources Clearinghouse (NITRC) platform. We examined the effective connectivity of the putamen using Granger causality analysis (GCA) and then determined whether these connections could differentiate ADHD from TDC. Results Compared with TDC, the ADHD group showed decreased effective connectivity from the left ventral rostral putamen (VRP) to left calcarine (CAL), right medial part of the superior frontal gyrus, left orbital part of superior frontal gyrus and left middle occipital gyrus (MOG). Increased effective connectivity from the left inferior occipital gyrus and right lingual gyrus to left VRP was also found in ADHD. The result of the classification accuracy showed that 72.3% of participants were correctly classified using support vector machine. Moreover, GCA values from the left VRP to left CAL and left MOG were significantly correlated with hyper/impulsive scores of patients with ADHD. Conclusion The findings may help extend our understanding of the ADHD-related neural loops.

Research on the Characteristics of AC Copper Loss and Suppression Method in Slotless Permanent Magnet Motor

Chenglong Chu,Yunkai Huang 한국자기학회 2023 Journal of Magnetics Vol.28 No.4

Due to the absence of magnetic teeth on the stator to restrict the magnetic field, the windings of the slotless motor are directly exposed to the air gap magnetic field. Consequently, this exposure results in a more irregular distribution of current in the windings and a notable increase in AC loss. Therefore, it is the key point in the design of slotless permanent magnet motor (SPMM) to study the characteristics of AC copper loss in detail and the effective suppression method. According to the structural characteristics of SPMM, this paper proposes to reduce the gap between wires (WDG) to reduce the AC copper loss. And the corresponding winding production method - winding extrusion potting (WEP) for toroidal windings is also introduced. In addition, the measurement method of WDG is demonstrated through experiments, and the accurate value of WDG before and after using this suppression method are obtained. The research results indicate a 46 % reduction in AC copper loss attributed to circulating current. Ultimately, the experimental outcomes of the prototype align well with the theoretical analysis and computational findings.