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EIS diagnosis on the corrosion behavior of TiN coated NiTi surgical alloy
Dazhi Yang,Chenglong Liu,Xiaopeng Liu,Min Qi,Guoqiang Lin 한국물리학회 2005 Current Applied Physics Vol.5 No.5
In this work titanium nitride (TiN) coatings were deposited on NiTi surgical alloy by arc ion plating (AIP). The open circuittesting and electrochemical impedance spectroscopy (EIS) have been employed to study the corrosion performance of the TiNcoated samples in Troyde.s simulated body uid. It was found that the TiN coating showed a good corrosion resistance at the begin-ning of long-term immersion; with the increase of immersion time, however, the corrosion resistance of the coating deteriorated afternearly 24 h of immersion; moreover, the large areas of the coating had fallen o the substrate after 30 days of immersion..
Dazhi Wang,Zhao Li 한국자기학회 2018 Journal of Magnetics Vol.23 No.2
This paper presents an improved 2-D analytical model to predict the magnetic field distributions and torque characteristics for a flux focusing disk-type permanent magnet eddy current coupling. Due to the inhomogeneous physical properties in the permanent magnet regions, based on the equivalent magnetic circuit method, a fictitious magnetization for the iron cores is introduced to simplify the complexity of modeling. The magnetic flux density distributions are derived when the eddy current generated in the copper plate and its back iron is reasonably concerned in 2-D Cartesian coordinates. Then, the explicit expression of torque is given and the torque-speed characteristics are analyzed. In the end, the calculated results of the proposed model are compared with those obtained from the magnetic equivalent circuit model and 3-D finite-element simulations.
Dazhi Wang,Di Zheng,Shuo Li,Zhao Li,Bingxue Liang,Yongliang Ni Korean Magnetics Society 2018 Journal of Magnetics Vol.23 No.4
In this paper, a precise electromagnetic–thermal model of axial-flux permanent magnet (PM) eddy current couplers is proposed to calculate the eddy current loss and predict the copper plate node temperature. With subloop calculation method, the quasi 3-D electromagnetic field analytical model is established in cylindrical coordinate. Based on the electromagnetic field analytical model, magnetic field distribution, eddy current losses of PM, copper plate and copper back iron are analyzed under various loads. The eddy current loss of each loop in the copper plate is calculated, at the rated slip speed. Then, the thermal resistance network is carried out, in which the previously obtained eddy current losses are heat sources for calculating the copper plate node temperature. In the thermal study, the influence of various loads on copper plate node temperature rise is analyzed. Finally, the analytical predicted results are compared with the results of finite element method and measurement. The comparison results confirm the validity of the electromagnetic–thermal model.
The Focused Electrode Ring for Electrohydrodynamic Jet and Printing on Insulated Substrate
Zeshan Abbas,Dazhi Wang,Liangkun Lu,Zhaoliang Du,Xiangyu Zhao,Kuipeng Zhao,Meng Si,Penghe Yin,Xi Zhang,Yan Cui,Junsheng Liang 한국정밀공학회 2022 International Journal of Precision Engineering and Vol.23 No.5
Drop-on-demand electrohydrodynamic jet (DoD E-Jet) printing is considered a well-known type of fabrication method contemporary since it can be used to print high-resolution microstructures (< 1 μm) on various insulating substrates. This paper presents a numerical study of DoD E-Jet printing using a novel combination of needle and focused electrode ring to print stable and consistent microdroplets on a Polyethylene terephthalate substrate. Primarily, a phase field method was used to generate a stable cone-jet morphology that can allow the production of high-resolution micron/nano structures on PET substrates. The numerical simulation of cone-jet morphology was performed by COMSOL multiphysics software. Further, the impact of key parameters such as flow rate and dc positive pulse voltage was studied on cone-jet morphology through numerical simulation. Subsequently, optimized operating parameters i.e., f = 5.3 . 10 –15 m 3 s −1 , V n = 1.9 kV and V r = 0.7 kV were achieved by performing a series of numerical experiments. Then, optimized parameters by simulation were directly used to print arrays of stable droplets on PET substrate using the focused electrode ring in different locations by regulating distance 0.2 mm to 1.3 mm between needles to focused electrode ring. The minimum size of stable microdrop was measured 3 μm on PET substrate (thickness = 0.2 mm) using a 50 μm size quartz capillary maintaining a distance of 0.2 mm between combined needle and focused electrode ring. The experimental results proved that the simulation model is useful for printing different microstructures on insulating substrates and creating a promising production path for micro-electro mechanical system and nano-electro mechanical system (MEMS and NEMS).
A Hybrid Filtering Stage Based Quasi-type-1 PLL under Distorted Grid Conditions
Yunlu Li,Dazhi Wang,Wei Han,Zhenao Sun,Tianqing Yuan 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.3
For three-phase synchronization applications, the synchronous reference frame phase-locked loop (SRF-PLL) is probably the most widely used technique due to its ease of implementation and satisfactory phase tracking performance under ideal grid conditions. However, under unbalanced and distorted grid conditions, its performance tends to worsen. To deal with this problem, a variety of filtering stages have been proposed and used in SRF-PLLs for the rejection of disturbance components at the cost of degrading the dynamic performance. In this paper, to improve dynamic performance without compromising the filtering capability, an effective hybrid filtering stage is proposed and incorporated into the inner loop of a quasi-type-1 PLL (QT1-PLL). The proposed filtering stage is a combination of a moving average filter (MAF) and a modified delay signal cancellation (DSC) operator in cascade. The time delay caused by the proposed filtering stage is smaller than that in the conventional MAF-based and DSC-based PLLs. A small-signal model of the proposed PLL is derived. The stability is analyzed and parameters design guidelines are given. The effectiveness of the proposed PLL is confirmed through experimental results.
Forecasting by General Type-2 Fuzzy Logic Systems Optimized with QPSO Algorithms
Yang Chen,Dazhi Wang 제어·로봇·시스템학회 2017 International Journal of Control, Automation, and Vol.15 No.6
With the development of a-planes representation result of general type-2 fuzzy sets, the optimizationand application of general type-2 fuzzy logic systems (GT2 FLSs) based on general type-2 fuzzy sets (GT2 FSs)has become a hot topic in current academic research. The efficient and energy conserving permanent magneticdrive (PMD) presents relatively high uncertainty as an emerging technology. The paper studies on forecasting problemsbased the data of torque and revolutions per minute (rpm) of PMD. In the proposed GT2 FLSs design, theantecedent, input measurement primary membership functions of GT2 FSs are chosen as Gaussian type-2 membershipfunctions with uncertain standard deviation. While the consequent parameters are selected as deterministicvalues. Quantum particle swarm optimization (QPSO) algorithms are used to optimize all the parameters of thesuggested GT2 FLSs. The torque and rpm data of PMD are used to train and test the proposed advanced FLSs forecastingmethods. Simulation studies and convergence analysis show the effectiveness of the proposed GT2 FLSsmethods compared with their type-1 (T1) and interval type-2 (IT2) methods for forecasting.
Chengshuo Zhang,Dazhi Fu,Fengshan Wang,Xinping Zhong,Lei Yang,Gang Wu,Baifeng Li,Jialin Zhang 대한외과학회 2021 Annals of Surgical Treatment and Research(ASRT) Vol.100 No.4
Purpose: Oxidized cellulose is available in many forms, but manufactured using either a regenerated or non-regenerated process. In this study, we evaluated the effects of 2 different hemostatic agents for the treatment of local bleeding in patients undergoing hepatic resection. Methods: This was a monocentric, parallel-group, randomized, and controlled clinical trial to compare oxidized regenerated cellulose gauze (ORCG) with oxidized non-regenerated cellulose gauze (ONRCG) in patients undergoing hepatectomy. The primary endpoint was the time to hemostasis at the target bleeding site. The secondary endpoints were the postoperative drainage volume on the first 2 days after surgery and the hospital stay. Results: There was no significant difference between the ORCG and ONRCG groups in time to hemostasis from column analysis (238.8 ± 121.6 seconds vs. 193.7 ± 85.3 seconds, P = 0.068), and there were no differences in the rates of hemostatic success between the 2 groups at 120 seconds (18.4% vs. 24.3%; odds ratio [OR], 0.703; 95% confidence interval [CI], 0.231–2.136) and 300 seconds (71.1% vs. 89.2%; OR, 0.298; 95% CI, 0.085–1.041). However, the ONRCG group was superior to the ORCG group in hemostasis according to the survival analysis (log-rank test, P = 0.044). Moreover, there were also no significant differences between the 2 groups in postoperative drainage volume on the first 2 days (P = 0.436, P = 0.381) and hospital stay (P = 0.537, P = 0.200). Conclusion: ONRCG was not inferior to ORCG as a hemostatic agent in patients undergoing liver resection.