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Surface Wettability and Chemistry of Oz.ne Perfusion Processed Porous Collagen Scaffold

Journal of Bionic Engineering 2011年第3期8卷 223-233页

作者： Chaoz.ng Liu Shirley z. shen 乙hiwu Han School of Mechanical and Systems Engineering University of Newcastle Newcastle upon Tyne NEI 7R U UK Polymer Composite & Nanomaterials CSIRO Manufacturing & Infrastructure Technology Highett Vic 3190 Australia Key Laboratory of Bionic Engineering (Ministry of Education China) Jilin University Changchun 130022 P. R. China

Crosslinking treatment of collagen has often been used to improve the biological stability and mechanical properties of 3D porous collagen scaffolds. However, accompanying these improvements, the collagen fibril surface becomes hydrophobic nature resulting in a reduced surface wettability. The wetting of the collagen fibril by culture medium is reduced and it is difficult for the medium to diffuse into the 3D structure of a porous collagen scaffold. This paper reports a ＂perfusion processing＂ strategy using oz.ne to improve the surface wettability of chemical crosslinked collagen scaffolds. Surface wettability, surface composition and biological stability were analyz.d to evaluate the effectiveness of this surface processing strategy. It was observed that oz.ne perfusion processing improved surface wettability for both exterior and interior surfaces of the porous 3D collagen scaffold. The improvement in wettability is attributed to the incorporation of oxygen-containing functional groups onto the surface of the collagen fibrils, as confirmed by X-ray Photoelectron Spectroscopy （XPS） analysis. This leads to a significant improvement in water taking capability without compromising the bulk biological stability and mechanical properties, and confirms that oz.ne perfusion processing is an effective tool to modify the wettability both for interior and exterior surfaces throughout the scaffold.

关键词： scaffold collagen surface modification hydrophilicity oz.ne perfusion

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Interfacial bonding mechanism in Al/coated steel dissimilar refill friction stir spot welds

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Journal of Materials Science & Technology 2019年第6期35卷 1027-1038页

作者： z. shen Y. Ding J. Chen B. Shalch Amirkhiz.J.z. Wen L. Fu A.P. Gerlich School of Materials Science and Engineering Northwestern Poly technical University Xi'an 710072 China Shanxi Key Laboratory of Friction Welding Technologies Northwestern Polytechnical University Xi'an 710072 China State Key Laboratory of Solidification Processing Northwestern Poly technical University Xi'an 710072 China Centre of Advance Materials Joining Department of Mechanical and Mechatronics Engineering University of Waterloo 200 University Ave. Waterloo N2L3G1 Ontario Canada CanmetMATERIALS Natural Resources Canada Hamilton L8P 0A5 Canada

Defect-free dissimilar Al/z.nc coated steel and Al/AlSi coated steel welds were successfully fabricated by refill friction stir spot welding. However, Al alloy and uncoated steel could not be welded under the same welding condition. Al-z. eutectic layer formed at the Al/z.nc coated steel interface showed nonuniformity in thickness and nanoscale intermetallic(IMC) produced was discontinuous. The bonding formation between the Al-z. layer and the surrounding materials was attributed to a liquid/solid reaction mechanism. Bonding formation at Al alloy and AlSi coated steel interface was attributed to a solid/solid reaction mechanism, as the joining process did not involve with melting of base metals or AlSi coating materials. Kissing bond formed at the weld boundary acted as a crack initiation and propagation site,and the present study showed that weld strength of Al 5754/AlSi coated steel was greatly influenced by properties of original IMC layer.

关键词： Refill friction stir spot welding Al alloy Steel Coated materials Joining mechanism

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Transient Characteristics and Accommodative Current Limiting Strategy for Bidirectional Interlinking Converters in Hybrid AC/DC Microgrids

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CSEE Journal of Power and Energy Systems 2024年第4期10卷 1575-1588页

作者： Xia shen z.ikang Shuai Wen Huang Chao shen Yang shen z.John shen College of Electrical and Information Engineering Hunan UniversityChangsha 410082China Department of Electrical and Computer Engineering Illinois Institute of TechnologyChicagoIL 60616 USA

Bidirectional interlinking converter(BIC)is the core equipment in a hybrid AC/DC microgrid connected between AC and DC ***,the variety of control modes and flexible bidirectional power flow complicate the influence of AC faults on BIC itself and on DC sub-grid,which potentially threaten both converter safety and system *** study first investigates AC fault influence on the BIC and DC bus voltage under different BIC control modes and different pre-fault operation states,by developing a mathematical model and equivalent sequence ***,based on the analysis results,a general accommodative current limiting strategy is proposed for BIC without limitations to specific mode or operation *** amplitude is predicted and constrained according to the critical requirements to protect the BIC and relieving the AC fault influence on the DC bus *** with conventional methods,potential current limit failure and distortions under asymmetric faults can also be ***,experiments verify feasibility of the proposed method.

关键词： Bidirectional interlinking converter current limiting fault characteristic hybrid AC/DC microgrid variation/oscillation of DC bus voltage

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A New Pulse Delta-Sigma CO2 NDIR Gas Detector

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Optics and Photonics Journal 2016年第8期6卷 219-225页

作者： Steven z. Y. shen Chi-Feng Chen Hilbert C. S. shen Department of Optics and Photonics National Central University Taiwan

This work describes the implementation and the modeling of an infrared gas sensor with pulse delta-sigma sensing architecture. Beyond the conventional technique of constant periodic heating of infrared light source, our proposed delta-sigma architecture with closed-loop feedback system is built with the hybrid combination of a CO2 infrared sensor with a specific wavelength filter, an infrared MEMS heater, a chopper amplifier, threshold comparator, ARM based MPU and discrete electronic devices. After a modeling of system, we built a model for the description of relationship between gas concentration and sensor by the duty of heating. The measurement results show a good linear behavior of signal and it proves to be a practical for all the NDIR measuring techniques and this work also gives a new approach not only to measure gas concentration fast but also obtain the high resolution.

关键词： Carbon Dioxide Delta-Sigma Gas Sensor NDIR Sensitivity

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Stability Investigation and Improvement for DC Cascade Systems with Simplified Impedance-based Stability Criterion

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CSEE Journal of Power and Energy Systems 2024年第3期10卷 1044-1052页

作者： Junbin Fang z.ikang Shuai Yang Li z.ibing Wang Xiangyang Wu Xia shen z.John shen College of Electrical and Information Engineering Hunan UniversityChangsha 410082China Renewable Energy Department of China Electric Power Research Institute Beijing 100192China Department of Electrical and Computer Engineering Illinois Institute of TechnologyChicagoIL 60616USA IEEE

In DC distributed power systems(DPSs),the complex impedance interactions possibly lead to DC bus voltage oscillation or *** previous research,the stability analysis of DPSs is implemented based on mathematical analysis in control *** specific mechanisms of the instability of the cascade system have not been intuitively *** this paper,the stability analysis of DPSs based on the traditional Nyquist criterion is simplified to the resonance analysis of the seriesconnected port impedance(z.R+jX)of source and load *** reveals that the essential reason for impedance instability of a DC cascade system is that the negative damping characteristic(Rz.ro-crossing *** simplified stability criterion for DC cascade systems can be concluded as:in the negative damping frequency ranges(Rz.ro-crossing point of the reactance component(i.e.,X=0).According to the proposed stability criterion,the oscillation modes of cascade systems are classified.A typical one is the internal impedance instability excited by the negative damping,and the other one is that the external disturbance amplified by negativity in a low stability ***,the impedance reshaping method for stability improvement of the system can be further *** validity of the simplified criterion is verified theoretically and experimentally by a positive damping reshaping method.

关键词： DC cascaded system,impedance model impedance reconstruction stability criterion

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A NEW MECHANISM OF ULTRASOUND ATTENUATION IN SINTERED METAL POWDERS

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Acta Metallurgica Sinica(English Letters) 1996年第5期9卷 338-342页

作者： z. C. shen( International Centre for Materials Physics, Chinese Academy of Sciences, shenyang 110015, China Suz.ou Professional University, Suz.ou 215002, China)

This paper analyz.s the anomalous power-law dependence of the ultrasound attenuation on frequency by means of a percolation model. It was suggested that the anomaLous ultrasound attenuation is associated with strongly localiz.d eigen modes (to be called fracton) in disordered systems. There exits a steplike increase in the density of vibrational states at crossover frequency ω(co).Computer simulation of vibration spectrum in disordered system is also reported. The density of vibrational states is consistent with the results of relevant experiment outlined above.

关键词： sintered metal powder percolating network fracton ultrasound Attenuation

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Asymmetrical Fault Current Calculation Method and Influencing Factors Analysis of Droop-Controlled Inverters

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CSEE Journal of Power and Energy Systems 2024年第2期10卷 562-573页

作者： Huimin z.ao z.ikang Shuai Jun Ge An Luo Weimin Wu z.John shen College of Electrical and Information Engineering Hunan UniversityChangsha 410006China Electrical Engineering Department Shanghai Maritime UniversityShanghai 201306China Department of Electrical and Computer Engineering Ilinois Institute of TechnologyChicagoIL 60616 USA

Since the fault dynamic of droop-controlled inverter is different from synchronous generators (SGs), protection devices may become invalid, and the fault overcurrent may damage power electronic devices and threaten the safety of the microgrid. Therefore, it is imperative to conduct a comprehensive fault analysis of the inverter to guide the design of protection schemes. However, due to the complexity of droop control strategy, existing literatures have simplified asymmetric fault analysis of droop-controlled inverters to varying degrees. Therefore, accurate fault analysis of a droop-controlled inverter is needed. In this paper, by analyz.ng the control system, an accurate fault model is established. Based on this, a calculation method for instantaneous asymmetrical fault current is proposed. In addition, the current components and current characteristics are analyz.d. It was determined that fault currents are affected by control loops, fault types, fault distance and nonlinear limiters. In particular, the influences of limiters on the fault model, fault current calculation and fault current characteristics were analyz.d. Through detailed analysis, it was found that dynamics of the control loop cannot be ignored, the fault type and fault distance determine fault current level, and part of the limiters will totally change the fault current trend. Finally, calculation and experimental results verify the correctness of the proposed method.

关键词： Asymmetrical fault analysis droop control fault current calculation method limiter transient fault characteristics

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FINITE ELEMENT ANALYSIS OF AXIAL FEED BAR ROLLING

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Acta Metallurgica Sinica(English Letters) 2007年第6期20卷 463-468页

作者： C.G. Xu G.H. Liu G.S. Ren z. shen C.P. Ma W. W. Ren Beijing Research Institute of Mechanical and Electrical Technology Beijing 100083 China

A flexible technique of hot working of bars by axial feed rolling was introduced. The process deformation, strain field, stress field, and temperature fie M of the parts are analyz.d by finite element method （ FEM）-... 详细信息

关键词： axial feed bar rolling deformation FEM (finite element method) stress field strain feld, temperature field

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Oxygen abundance in young open clusters

Oxygen abundance in young open clusters

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中国天文学会恒星分会2004年学术年会

作者： z.-X.shen X.-W.Liu H.-W.z.angD.N.C Lin

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Post-layout simulation driven analog circuit siz.ng

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Science China(Information Sciences) 2024年第4期67卷 289-300页

作者： Xiaohan GAO Haoyi z.ANG Siyuan YE Mingjie LIU David z.PAN Linxiao shen Runsheng WANG Yibo LIN Ru HUANG School of Integrated Circuits Peking University School of Computer Science Peking University Department of Electrical and Computer Engineering University of Texas at Austin Institute of Electronic Design Automation Peking University

Post-layout simulation provides accurate guidance for analog circuit design, but post-layout performance is hard to be directly optimiz.d at early design stages. Prior work on analog circuit siz.ng often utiliz.s pre-layout simulation results as the optimiz.tion objective. In this work, we propose a post-layoutsimulation-driven(post-simulation-driven for short) analog circuit siz.ng framework that directly optimiz.s the post-layout simulation performance. The framework integrates automated layout generation into the optimiz.tion loop of transistor siz.ng and leverages a coupled Bayesian optimiz.tion algorithm to search for the best post-simulation performance. Experimental results demonstrate that our framework can achieve over 20% better post-layout performance in competitive time than manual design and the method that only considers pre-layout optimiz.tion.

关键词： analog EDA transistor siz.ng Bayesian optimiz.tion post-layout simulation

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