Predicting Cascading Failures in Power Grids using Machine Learning Algorithms

Although there has been notable progress in modeling cascading failures in power grids, few works included using machine learning algorithms. In this paper, cascading failures that lead to massive blackouts in power grids are predicted and classified into no, small, and large cascades using machine learning algorithms. Cascading-failure data is generated using a cascading failure simulator framework developed earlier. The data set includes the power grid operating parameters such as loading level, level of load shedding, the capacity of the failed lines, and the topological parameters such as edge betweenness centrality and the average shortest distance for numerous combinations of two transmission line failures as features. Then several machine learning algorithms are used to classify cascading failures. Further, linear regression is used to predict the number of failed transmission lines and the amount of load shedding during a cascade based on initial feature values. This data-driven technique can be used to generate cascading failure data set for any real-world power grids and hence, power-grid engineers can use this approach for cascade data generation and hence predicting vulnerabilities and enhancing robustness of the grid

An investigation on electro discharge micro-drilling of SiC-20% BN composite

SiC-20% BN composite is a newly developed material having potential applications in several engineering industries. Machining of such type of advanced ceramic composites by conventional methods is not only difficult to perform but it is also very costly. Electro discharge machining is seen as a potential process for such materials because it does not exert any mechanical force on tool and work piece and it is also independent of hardness of the work piece. In the present research the characteristic features of electro discharge micro-drilling of SiC-20% BN composite are studied through experimental investigation. The measured responses are material removal rate (MRR), tool wear rate (TWR) and relative electrode wear (REW). The optimal parameter settings for the responses are determined with the help of a statistical analysis. SEM micrographs of the holes were taken to illustrate the material removal mechanism of the ceramic composite. In the present research study it has been proved that EDM is a potentially successful technique for micro-hole drilling in this new generation composite

Laser surface modification of 316 L stainless steel with bioactive hydroxyapatite

Laser-engineered net shaping (LENS (TM)), a commercial additive manufacturing process, was used to modify the surfaces of 316 L stainless steel with bioactive hydroxyapatite (HAP). The modified surfaces were characterized in terms of their microstructure, hardness and apatite forming ability. The results showed that with increase in laser energy input from 32 J/mm(2) to 59 J/mm(2) the thickness of the modified surface increased from 222 +/- 12 mu m to 355 +/- 6 mu m, while the average surface hardness decreased marginally from 403 +/- 18 HV03 to 372 +/- 8 HV0.3. Microstructural studies showed that the modified surface consisted of austenite dendrites with HAP and some reaction products primarily occurring in the inter-dendritic regions. Finally, the surface-modified 316 L samples immersed in simulated body fluids showed significantly higher apatite precipitation compared to unmodified 316 L samples. (C) 2013 Elsevier B.V. All rights reserved

Synthesis of boron nitride from boron containing poly(vinyl alcohol) as ceramic precursor

A ceramic precursor, prepared by condensation reaction from poly(vinyl alcohol) (PVA) and boric acid (H3BO3) in 1:1, 2:1 and 4:1 molar ratios, was synthesized as low temperature synthesis route for boron nitride ceramic. Samples were pyrolyzed at 850A degrees C in nitrogen atmosphere followed by characterization using Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD)

Laser processing of Ti composite coatings reinforced with hydroxyapatite and bioglass

Composite coatings of titanium reinforced separately with hydroxyapatite (HAp) and bioglass (BG) were deposited on titanium substrate using Laser Engineered Net Shaping (LENS (TM)). The microstructure, phase constituents, in vitro electrochemical, tribological and biological properties of these composite coatings deposited using different laser powers was studied. The composite coatings showed several reaction products such as Ca2P2O2, CaTiO3, Na2Ca2Si3O9 due to high temperature interaction of HAp and BG with Ti. The average top surface hardness of the Ti substrate was 148 +/- 5 HV and that of the composite coatings was between 720 and 740 HV. As a result, the composite coatings exhibited significant increase in the in vitro wear resistance. The incorporation of HAp and BG in Ti increased the corrosion current, possibly due to the presence of residual stresses, but shifted the corrosion potential towards noble direction due bioactive reinforcements. In vitro proliferation of mouse embryonic fibroblast cells (NIH3T3) was found to be more on composite coatings than on titanium substrate demonstrating their superior cell-materials interactions

In vitro tribological and biocompatibility evaluation of sintered silicon nitride

In the present work, dense silicon nitride (Si3N4) was developed using pressureless sintering for biomedical applications. The Si3N4 samples with 15 wt% sintering additives (Al2O3 + Y2O3) were sintered at 1700 degrees C for 2 h followed by characterization in terms of phase constituents, mechanical, in vitro tribological and biological properties. In vitro tribological tests in simulated body fluid (SBF) revealed that the wear rate and coefficient of friction of Si3N4 reduced by one order of magnitude in the presence of 10% fetal bovine serum (FBS). The in vitro biocompatibility evaluations using human osteoblast-like cells (MG63) confirmed that the sintered Si3N4 samples were non-cytotoxic. (C) 2017 Elsevier B.V. All rights reserved

In vitro assessment of corrosion resistance and biocompatibility of tantalum-niobium oxide surface-functionalized Mg alloy

Magnesium alloys have been considered as temporary biomaterials for orthopedic applications. Despite having great mechanical (bone-like) characteristics and osseointegration, magnesium alloys deteriorate quickly in physiological conditions. Modifying the Mg alloy surface with tantalum-based thin films is an effective process to reduce the rate of corrosion and improve biocompatibility. In the present work, tantalum-niobium oxide nanocomposite thin films were successively deposited on Mg-Al6-Zn1.5-Cu2-Ge0.5 Mg alloys via reactive magnetron sputtering to improve anticorrosion and biocompatibility. Crystallographic structure, surface morphology and chemical compositions were characterized using XRD, TEM, FE-SEM, EDS and XPS. Electrochemical and hydrogen evolution experiments were used to evaluate the resistance to corrosion of the samples. The biocompatibility of the samples was evaluated by cell viability using the osteoblast cell line (MC3T3-E1). Results revealed the existence of the composite thin-film in the crystalline form and the cauliflower-like clustered morphology. Enhancement in the corrosion resistance of nanocomposite coatings was confirmed by a decrease in current density (Icorr) during the polarization studies. The wettability studies revealed the hydrophilic character of the coatings and they are bioactive in simulated body fluid (SBF) after 5 days by the mineralization of calcium phosphate. The hemocompatibility assessment proved that the coatings were blood compatible in nature. MTT (3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide) assay on MC3T3-E1 cells showed that tantalumniobium oxide thin films are biocompatible and can stimulate cellular proliferation and differentiation. Overall

In vitro and in vivo degradation assessment and preventive measures of biodegradable Mg alloys for biomedical applications

Magnesium (Mg) and its alloys have been widely explored as a potential biodegradable implant material. However, the fast degradation of Mg-based alloys under physiological environment has hindered their widespread use for implant applications till date. The present review focuses on in vitro and in vivo degradation of biodegradable Mg alloys, and preventive measures for biomedical applications. Initially, the corrosion assessment approaches to predict the degradation behavior of Mg alloys are discussed along with the measures to control rapid corrosion. Furthermore, this review attempts to explore the correlation between in vitro and in vivo corrosion behavior of different Mg alloys. It was found that the corrosion depends on experimental conditions, materials and the results of different assessment procedures hardly matches with each other. It has been demonstrated the corrosion rate of magnesium can be tailored by alloying elements, surface treatments and heat treatments. Various researches also studied different biocompatible coatings such as dicalcium phosphate dihydrate (DCPD), beta-tricalcium phosphate (beta-TCP), hydroxyapatite (HA), polycaprolactone (PCL), polylactic acid (PLA), and so on, on Mg alloys to suppress rapid degradation and examine their influence on new bone regeneration as well. This review shows the need for a standard method of corrosion assessment to predict the in vivo corrosion rate based on in vitro data, and thus reducing the in vivo experimentation

Effect of activation on boron nitride coating on carbon fiber

Boron nitride (BN) thin coating has been formed on the surface of chemically activated polyacrylonitrile (PAN) carbon fibers by dip coating method. The chemical activation of PAN fibers was carried out by two different chemicals, i.e. nitric acid (HNO(3)) and silver nitrate (AgNO(3)) solution. The chemical activation changes the surface properties, e.g. surface area and surface microstructure of the carbon fibers. These surface modifications ultimately influence properties of boron nitride coating on carbon fibers. The boron nitride coating on carbon fibers showed better crystallinity, strength and oxidation resistance when carbon fibers were activated by HNO(3). This improvement in strength and oxidation resistance is attributed to better crystallinity of boron nitride coating on HNO(3) activated PAN fibers. (C) 2010 Elsevier Ltd and Techna Group S.r.l. All rights reserved