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Nucleation and growth behavior of coating film on Mg–Al–Zn alloy with different surface topographies via plasma electrolytic oxidation

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Journal of Magnesium and Alloys 2022年第8期10卷 2185-2192页

作者： Nisa Nashrah Sung Hun Baek Young Gun Ko Materials Electrochemistry group School of Materials Science and EngineeringYeungnam UniversityGyeongsan 38541Republic of Korea

This work was made to investigate how nucleation and growth behavior of the coating film were affected by surface topographies of Mg–Al–Zn alloy substrate during the initial stage of plasma electrolytic oxidation(PEO).To satisfy this end,a single substrate was prepared by mechanical treatment exhibiting rough and smooth regions with an equal area on the *** rough region with prominent hills and grooves induced the breakdown of passive film,which was indicated by an early appearance of plasma discharge on the rough region since nucleation of coating film occurred preferentially around the ***,the coating film grown on the grooves was somewhat thicker and more porous than the film grown on the hills and smooth *** was due to the fact that the growth of the coating film was found to be localized in the presence of rough region,which was in line with the discharge ***,the nucleation and growth behavior during the initial stage of PEO will be discussed schematically on the basis of microstructural interpretation.

关键词： Mg alloy Surface roughness Plasma electrolytic oxidation Coating film

Evolution of biomass particles during pelletization process

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Particuology 2024年第3期86卷 182-187页

作者： Hamid Rezaei Maryam Tajilrou Jun Sian Lee Kanages Singaraveloo Anthony Lau Shahab Sokhansanj Biomass and Bioenergy Research group Department of Chemical and Biological EngineeringUniversity of British ColumbiaVancouverCanada

Pulverizing is an essential unit operation in co-firing biomass with *** are only compatible with pellet forms of fibrous biomass materials and crush them down to their original forming particle *** is why the data on the size distribution of the particles forming a biomass pellet is crucial to achieving optimum combustion *** current study determines the internal particle size distribution of pellets after wet disintegration,following Iso 17830 standard,and aims to suggest improvements to the mentioned standard based on new measured *** were carried out on white wood pellets(no bark)and brown wood pellets containing bark at four water temperatures:20,40,60,and 95℃,with or without *** particle size distribution of the pre-pelletizer wood particles was also measured and compared with particles in the formed *** water temperature of 20℃ was found to be adequate for the complete disintegration of pellets,and no mechanical stirring was *** 30% of particles in the disintegrated pellets were 0.5-1.0 *** changes the particle size distribution to smaller *** disintegrated bark pellets contained more fines than white pellets.

关键词： Wood pellets Particle sizes distribution Wet disintegration Stirring Water temperature

Unsupervised Electric Motor Fault Detection by Using Deep Autoencoders

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维普期刊数据库

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IEEE/CAA Journal of Automatica Sinica 2019年第2期6卷 441-451页

作者： Emanuele Principi Damiano Rossetti Stefano Squartini Francesco Piazza the Department of Information engineering Università Politecnica delle Marche Loccioni group Angeli di Rosora IEEE

Fault diagnosis of electric motors is a fundamental task for production line testing, and it is usually performed by experienced human operators. In the recent years, several methods have been proposed in the literature for detecting faults automatically. Deep neural networks have been successfully employed for this task, but, up to the authors' knowledge, they have never been used in an unsupervised scenario. This paper proposes an unsupervised method for diagnosing faults of electric motors by using a novelty detection approach based on deep autoencoders. In the proposed method, vibration signals are acquired by using accelerometers and processed to extract LogMel coefficients as features. Autoencoders are trained by using normal data only, i.e., data that do not contain faults. Three different autoencoders architectures have been evaluated: the multilayer perceptron(MLP) autoencoder, the convolutional neural network autoencoder, and the recurrent autoencoder composed of long short-term memory(LSTM) units. The experiments have been conducted by using a dataset created by the authors, and the proposed approaches have been compared to the one-class support vector machine(OC-SVM) algorithm. The performance has been evaluated in terms area under curve(AUC) of the receiver operating characteristic curve, and the results showed that all the autoencoder-based approaches outperform the OCSVM algorithm. Moreover, the MLP autoencoder is the most performing architecture, achieving an AUC equal to 99.11 %.

关键词： Autoencoder convolutional neural networks electric motor fault detection long short-term memory neural networks novelty detection

Development of anti-corrosive coating on AZ31 Mg alloy subjected to plasma electrolytic oxidation at sub-zero temperature

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Journal of Magnesium and Alloys 2022年第7期10卷 1915-1929页

作者： S.Fatimah M.P.Kamil D.I.Han W.Al-Zoubi Y.G.Ko Materials Electrochemistry group School of Materials Science and EngineeringYeungnam UniversityGyeongsan 38541Republic of Korea

Plasma electrolytic oxidation(PEO)is a promising surface treatment to generate adherent and thick anti-corrosive coating on light-weight metals(Al,Mg,Ti,etc.)using an eco-friendly alkaline *** energy plasma,however,inevitably generates porous structures that limit their practical *** present study proposes a straight-forward simple method by utilizing sub-zero electrolyte(268 K)to alter the plasma characteristics during formation of the protective coating on AZ31 Mg alloy via PEO with a comparison to the electrolyte at room temperature(298 K).In refrigerated electrolyte,the formation of micro-defects is suppressed relatively at the expense of low coating growth,which is measured to be twice lower than that at 298 K due to the temperature-dependent soft plasma discharges contributing to the development of the present *** a consequence,corrosion resistance of the sample processed at 268 K is superior to that of 298K,implying that the effect of coating thickness is less dominant than that of *** phenomenon is interpreted in relation to the ionic movement and oxide solidification controlled by soft plasma discharges arising from the temperature gradient between electrolyte and surface of the substrate during PEO.

关键词： AZ31 Mg alloy Plasma electrolytic oxidation Sub-zero electrolyte Anti-corrosive coating Corrosion

Spectral hole burning effects initiated by uniform signal intensities in a gain-flattened EDFA

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Chinese Optics Letters 2011年第2期9卷 11-14页

作者： A.R.Sarmani S-J Sheih F.R.Mahamd Adikan M.A.Mahdi Wireless and Photonics Networks Research Center Faculty of Engineering Universiti Putra Malaysia Taiwan International Securities group Department of Electrical engineering Faculty of Engineering Universitiy of Malaya

Spectral hole burning （SHB） effects in a gain-flattened erbium-doped fiber amplifier （EDFA） are demonstrated to be significant in the presence of large signal power around the 1530-1532-nm wavelength range. These are the first effects reported in a setup employing equivalent power level distribution of 40 channels ranging from 1530 to 1561 nm. To explain this, the introduction of a new local population variable into the laser equation is required to support the original inversion ratio that is determined by the pump lasers. In the analysis section, spectroscopic parameters and high signal powers are considered to be other contributing parameters to the change in the gain characteristics. An improvement to this theoretical basis is suggested by implementing mathematical modeling to validate similarities between the gain shape of simulation to that obtained in the experiment.

关键词： Erbium Fiber amplifiers Pumping (laser) Spectroscopic analysis

Process-scheme-driven automatic construction of NC machining cell for aircraft structural parts

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Chinese Journal of Aeronautics 2013年第5期26卷 1324-1335页

作者： Chen Shulin Zheng Guolei Zhou Min Du Baorui Chu Hongzhen School of Mechanical engineering and Automation Beihang University Shenyang Aircraft Industry (group) Corporation Ltd.

In order to enhance the NC programming efficiency and quality of aircraft structural parts （ASPs）, an intelligent NC programming pattern driven by process schemes is presented. In this pattern, the NC machining cell is the minimal organizational structure in the technological process, consisting of an operation machining volume cell, and the type and parameters of the machining operation. After the machining cell construction, the final NC program can be easily obtained in a CAD/CAM system by instantiating the machining operation for each machining cell. Accordingly, how to automatically establish the machining cells is a key issue in intelligent NC program- ming. On the basis of the NC machining craft of ASP, the paper aims to make an in-depth research on this issue. Firstly, some new terms about the residual volume and the machinable volume are defined, and then, the technological process is modeled with a process scheme. Secondly, the approach to building the machining cells is introduced, in which real-time complement machining is mainly considered to avoid interference and overcutting. Thirdly, the implementing algorithm is designed and applied to the Intelligent NC Programming System of ASP. Finally, the developed algorithm is validated through two case studies.

关键词： Aircraft structural part (ASP) Automatic programming Machining cell Process planning Process scheme Residual volume

Determination of critical parameters in the analysis of road tunnel fires

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International Journal of Mining Science and Technology 2019年第2期29卷 187-198页

作者： Ali Haghighat Kray Luxbacher Department of Mining & Minerals engineering Virginia Tech Fire Life Safety Tunnel Ventilation GroupAECOM

The analysis of the fluid characteristics downstream of a fire source in transportation tunnels is one the most important factor in the emergency response, evacuation, and the rescue service studies. Some crucial parameters can affect the fluid characteristics downstream of the fire. This research develops a statistical analysis on the computational fluid dynamics(CFD) data of the road tunnel fire simulations in order to quantify the significance of tunnel dimensions, inlet air velocity, heat release rate, and the physical fire size(fire perimeter) on the fluid characteristics downstream of the fire source. The selected characteristics of the fluid(response variables) were the average temperature, the average density, the average viscosity, and the average velocity. The prediction of the designed statistical models was assessed; then the significant parameters' effects and the parameters interactive effects on different response variables were determined individually. Next, the effect of computational domain length on the selection of the significant parameters downstream of the fire source was analyzed. In this statistical analysis, the linear models were found to provide the statistically good prediction. The effect of the fire perimeter and the parameters interactive effects on the selected response variables downstream of the fire, were found to be insignificant.

关键词： Road tunnel fire Two-level fractional factorial design Statistical two-level design CFD Fire dynamics

Proper orthogonal decomposition analysis of coherent motions in a turbulent annular jet

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Applied Mathematics and Mechanics(English Edition) 2021年第9期42卷 1297-1310页

作者： Y.ZHANG M.VANIERSCHOT Department of Mechanical engineering Group T Leuven CampusCelestijnenlaan 300Leuven B-3001Belgium

A three-dimensional incompressible annular jet is simulated by the large eddy simulation(LES)method at a Reynolds number Re=*** time-averaged velocity field shows an asymmetric wake behind the central bluff-body although the flow geometry is *** proper orthogonal decomposition(POD)analysis of the velocity fluctuation vectors is conducted to study the flow dynamics of the wake *** distribution of turbulent kinetic energy across the three-dimensional POD modes shows that the first four eigenmodes each capture more than 1%of the turbulent kinetic energy,and hence their impact on the wake dynamics is *** results demonstrate that the asymmetric mean flow in the near-field of the annular jet is related to the first two POD modes which correspond to a radial shift of the stagnation *** modes 3 and 4 involve the stretching or squeezing effects of the recirculation region in the radial *** addition,the spatial structure of these four POD eigenmodes also shows the counter-rotating vortices in the streamwise direction downstream of the flow reversal region.

关键词： coherent structure proper orthogonal decomposition(POD) turbulent annular jet large eddy simulation(LES)

Synthesis and spectral properties of Nd-doped glass-ceramics in SiO_2-CaO-MgO system prepared by sol-gel method

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Journal of Rare Earths 2013年第6期31卷 595-599页

作者： Masoud Eslami Zohreh Hamnabard Ali Nemati Materials Science & engineering Department Sharif University of Technology Materials Research School Ceramic Group

SiO2-CaO-MgO glass and glass-ceramic powder doped with Nd3＋ were synthesized with sol-gel method. Tetraethylorthosilicate （TEOS）, Ca（NO3）2？4H2O, Mg（NO3）2？6H2O, Nd（NO3）3？6H2O, ethanol, distilled water, and HNO3 were used as starting materials. The synthesized powder’s properties were examined with simultaneous thermal analysis （STA）, X-ray diffraction （XRD）, photoluminescence （PL） and scanning electron microscopy （SEM） analysis. The STA curves showed that the softening point and crystallization temperatures were shifted to higher temperatures with increasing dopant content. Regarding XRD patterns of glass samples, Nd was found to act as an intermediate oxide in glass matrix. The XRD patterns of glass-ceramic samples indicated that bredigite and akermanite crystallized in the glass matrix after heat treating at 900 oC. The fluorescence spectra showed that glass-ceramics emitted much stronger irradiation than glasses with the same dopant content. The SEM images illustrated uniform and homogeneous distribution of applied oxides in glass and glass-ceramic compositions.

关键词： glass glass-ceramic synthesis sol-gel method spectral properties rare earths