An analysis of surface erosion in electrical discharge machining

An analytical model for the computation of metal erosion by a single spark in electrical discharge machining is presented. The effect of plasma channel growth on metal removal was examined and good correlation was found between theoretical and experimental results. The model was further developed to study the effects of non-rectangular current pulse shapes on metal removal and relative electrode wear to establish the optimum current pulse form required to minimize relative electrode wear.     

Studies on curcumin and curcuminoids XVII. Variation in the content of curcuminoids inCurcuma longa L. from Nenal during one season

Summary The content of curcuminoids inCurcuma longa L. before, during and after a normal harvesting period was investigated. The plant material was grown in the Kathmandu area. Bis-demethoxycurcumin was found to be the main constituent. No significant change in the curcuminoid content was observed during a 17-week sampling period.

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Studien über Curcumin und Curcuminoide. XVII. Veränderung des Gehaltes an Curcuminoiden inCurcuma longa L. (Zingiberaceae) aus Nepal warend der Ernte

Zusammenfassung Der Gehalt an Curcuminoiden inCurcuma longa L. (Zingiberaceae) wurde vor, während und nach der normalen Erntezeit untersucht. Das Pflanzenmaterial stammt aus dim Kathmandu-Tal in Nepal. Der Hauptinhaltsstoff ist Bisdemethoxycurcumin. Im Laufe von 17 Wochen konnten keine signifikante Schwankungen observiert werden.

     

Modelling perforated mediated modified atmospheric packaging of capsicum

Perforation of a film would otherwise have a low permeability is an alternative to obtain optimum oxygen and carbon dioxide concentration in modified atmosphere packages. In present study, gas exchange was studied through a macroperforated packet containing capsicum having different number of holes, 1–4, of diameter 0.3 mm at temperatures of 5 and 25 °C. A model combining the Michaelis–Menten kinetics to describe the respiration rate of the product with mass transfer equation to describe the gas transfer across the package provided a good fit to the experimental data. Its applicability was further validated in a dynamic test, subjecting a package to a variable temperature programme simulating conditions in distribution chains. Model showed good agreement between predicted and observed values for both storage conditions with constant temperatures and variable temperature conditions of distribution chain, as mean relative deviation modulus (E) value was <10%.     

Graph Convolutional Network Based Fault Detection and Identification for Low-voltage DC Microgrid

This paper presents a novel fault detection and identification method for low-voltage direct current（DC） microgrid with meshed configuration. The proposed method is based on graph convolutional network（GCN）, which utilizes the explicit spatial information and measurement data of the network topology to identify a fault. It has a more substantial feature extraction ability even in the presence of noise and bad data. The adjacency matrix for GCN is developed by considering the network topology as an inherent graph. The bus voltage and line current samples after faults are regarded as the node attributes. Moreover, the DC microgrid model is developed using PSCAD/EMTDC simulation, and fault simulation is carried out by considering different possible events that include environmental and physical conditions. The performance of the proposed method under different conditions is compared with those of different machine learning techniques such as convolutional neural network（CNN）, support vector machine（SVM）,and fully connected network（FCN）. The results reveal that the proposed method is more effective than others at detecting and classifying faults. This method also possesses better robustness under the presence of noise and bad data.     

Investigations of Ce3+ co-doped SbPO4:Tb3+ nano-ribbons and nanoparticles by vibrational and photoluminescence spectroscopy

Nano-ribbons and very small nanoparticles (size 2-5 nm) of SbPO4 doped with lanthanide ions (Ce3+ and Tb3+) are prepared at a relatively low temperature of 120 degrees C based on a solution method. Detailed vibrational and luminescence studies on these samples establish that these lanthanide ions are incorporated at Sb3+ site of the SbPO4 lattice. The excitation spectrum corresponding to the Tb3+ emission and the excited state lifetime of the 5D4 level of Tb3+ ions in the sample confirm the energy transfer from Ce3+ to Tb3+ ions in the SbPO4 host. The extent of energy transfer from Ce3+ to Tb3+ in these samples is found to be around 60%. Dispersion of these nanomaterials in silica matrix effectively shields the lanthanide ions at the surface of the nano-ribbons/nanoparticles from the stabilizing ligands resulting in the reduction in the vibronic quenching of the excited state. Our results show significant reduction in the surface contribution in the decay curve corresponding to the 5D4 level of the Tb3+ ions after incorporating the nano-ribbons/nanoparticles in silica. These nanomaterials incorporated in silica matrix can have potential applications in bio-assays and bio-imaging.     

Effect of impinging ion energy on the substrates during deposition of SiOx films by radiofrequency plasma enhanced chemical vapor deposition process

Radiofrequency (13.56 MHz) plasma enhanced chemical vapor deposition process is used for deposition of SiO_x films on bell metal substrates using Ar/hexamethyldisiloxane/O₂ glow discharge. The DC self-bias voltage developed on the substrates is observed to be varied from − 35 V to − 115 V depending on the RF power applied to the plasma. Plasma potential measurements during film deposition process are carried out by self-compensated emissive probe. The deposited films are characterized by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), nanoindentation, nano-scratch test and thermogravimetric analysis. The characterization results show strong dependency of the SiO_x films properties on the energy of the ions impinging on the substrates during deposition. Analysis of Raman spectra indicates an increase in vitreous silica content and reduction in defective Si-O-Si chemical structure in the deposited SiO_x films with increasing ion energy impinging on the substrates. The increase in inorganic (Si and O) content in the SiO_x films is further confirmed from XPS analysis. The growth of SiO_x films with more inorganic content and defect free chemical structure apparently contribute to the increase in their hardness and scratch resistance behavior. The films show higher thermal stability as the energy of the ions arriving at substrates increases with DC self-bias voltage. The possibility of using SiO_x films for surface protection of bell metal is also explored.     

Effect of dysprosia doping on structural and electrical property of stabilized zirconia for intermediate- temperature SOFCs

Present work deals with structural, micro-structural and electrical properties of dysprosia stabilized zirconia electrolyte, which have been evaluated by means of X-ray diffraction (XRD) and scanning (SEM), and complex impedance analysis respectively. The amount of dysprosia was varied from 2 to 12 mol% in zirconia. The addition of dysprosia (8-12 mol%) stabilized the cubic zirconia phase, which was analyzed from XRD analysis. SEM micrographs clearly showed the improvement in sinterability with increase in dysprosia concentration up to 6 mol% disprosia. Complex impedance analysis was performed in the temperature range from 250 to 600 °C. The results indicated a gradual decrease in impedance of both bulk and grain boundary and increase in conductivity with dysprosia doping up to 6 mol% and thereafter showing a reverse trend. The activation energies for oxygen ion migration were also found to decrease with increase in dysprosia doping which was in the range of 0.99 ? 1.28 eV. The average thermal expansion coefficient increases linearly.     

Toughening of Polylactic Acid: An Overview of Research Progress

To overcome the limitations of polylactic acid, alterations are needed to enhance its toughness, to improve handling and for various applications. Extensive studies were reported, mainly in the area of blends with renewable resource polymer blends. Better phase dispersion between the blend materials is achieved either by reactive mixing of the two components or by incorporation of a block copolymer compatibilizer, finally showing highly enhanced property. In this article, the recent research progress of different toughening processes of PLA via blending is reviewed and a detailed understanding about toughening of PLA using biodegradable or renewable polymers has been established.