Search results for: metallic nanoparticle arrays

Authors: S. M. Hamidi, M. Afsharnia

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Gas sensors based on magneto-plasmonic (MP) structures have attracted much attention due to the high signal to noise ratio in these type of sensors. In these sensors, both the plasmonic and the MO properties of the resulting MP structure become interrelated because the surface Plasmon resonance (SPR) of the metallic medium. This interconnection can be modified the sensor responses and enhanced the signal to noise ratio. So far the sensor features of multilayered structures made of noble and ferromagnetic metals as Au/Co/Au MP multilayer with TiO2 sensor layer have been extensively studied, but their SPR assisted sensor response need to the krestchmann configuration. Here, we present a systematic study on the new MP structure based on one-dimensional nano-grating Au/ Co/ Au/ TiO2 multilayer to utilize as an inexpensive and easy to use gas sensor.

Keywords: Magneto-plasmonic structures, Gas sensor, nano-garting

Procedia PDF Downloads 447

Authors: G. E. Gandomkar, E. Bekhradinassab, S. Sabbaghi, M. M. Zerafat

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The reduction of water content in crude oil emulsions reduces pipeline corrosion potential and increases the productivity. Chemical emulsification of crude oil emulsions is one of the methods available to reduce the water content. Presence of demulsifier causes the film layer between the crude oil emulsion and water droplets to become unstable leading to the acceleration of water coalescence. This research has been performed to study the improvement performance of a chemical demulsifier by silica nanoparticles. The silica nano-particles have been synthesized by sol-gel technique and precipitation using poly vinyl alcohol (PVA) and poly ethylene glycol (PEG) as surfactants and then nano-particles are added to the demulsifier. The silica nanoparticles were characterized by Particle Size Analyzer (PSA) and SEM. Upon the addition of nanoparticles, bottle tests have been carried out to separate and measure the water content. The results show that silica nano-particles increase the demulsifier efficiency by about 40%.

Keywords: demulsifier, dehydration, silicon dioxide, nanoparticle

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Authors: Min-Ah Woo, Min-Cheol Lim, Hyun-Joo Chang, Sung-Wook Choi

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We developed a paper-based colorimetric sensor utilizing magnetic nanoparticles conjugated with aptamers (MNP-Apts) against E. coli O157:H7. The MNP-Apts were applied to a test sample solution containing the target cells, and the solution was simply dropped onto PVDF (polyvinylidene difluoride) membrane. The membrane moves the sample radially to form the sample spots of different compounds as concentric rings, thus the MNP-Apts on the membrane enabled specific recognition of the target cells through a color ring generation by MNP-promoted colorimetric reaction of TMB (3,3',5,5'-tetramethylbenzidine) and H₂O₂. This method could be applied to rapidly and visually detect various bacterial pathogens in less than 1 h without cell culturing.

Keywords: aptamer, colorimetric sensor, E. coli O157:H7, magnetic nanoparticle, polyvinylidene difluoride

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Authors: Kristina Zuzek, Xuan Xu, Awais Ikram, Richard Sheridan, Allan Walton, Saso Sturm

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Recycling of end-of-life REEs based Nd-Fe-B magnets is an important strategy for reducing the environmental dangers associated with rare-earth mining and overcoming the well-documented supply risks related to the REEs. However, challenges on their reprocessing still remain. We report on the possibility of direct electrochemical recycling and reprocessing of Nd-Fe(B)-based magnets. In this investigation, we were able first to electrochemically leach the end-of-life NdFeB magnet and to electrodeposit Nd–Fe using a 1-ethyl-3-methyl imidazolium dicyanamide ([EMIM][DCA]) ionic liquid-based electrolyte. We observed that Nd(III) could not be reduced independently. However, it can be co-deposited on a substrate with the addition of Fe(II). Using advanced TEM techniques of electron-energy-loss spectroscopy (EELS) it was shown that Nd(III) is reduced to Nd(0) during the electrodeposition process. This gave a new insight into determining the Nd oxidation state, as X-ray photoelectron spectroscopy (XPS) has certain limitations. This is because the binding energies of metallic Nd (Nd0) and neodymium oxide (Nd₂O₃) are very close, i. e., 980.5-981.5 eV and 981.7-982.3 eV, respectively, making it almost impossible to differentiate between the two states. These new insights into the electrodeposition process represent an important step closer to efficient recycling of rare piles of earth in metallic form at mild temperatures, thus providing an alternative to high-temperature molten-salt electrolysis and a step closer to deposit Nd-Fe-based magnetic materials. Further, we propose a new concept of recycling the sintered Nd-Fe-B magnets by direct recovering the 2:14:1 matrix phase. Via an electrochemical etching method, we are able to recover pure individual 2:14:1 grains that can be re-used for new types of magnet production. In the frame of physical reprocessing, we have successfully synthesized new magnets out of hydrogen (HDDR)-recycled stocks with a contemporary technique of pulsed electric current sintering (PECS). The optimal PECS conditions yielded fully dense Nd-Fe-B magnets with the coercivity Hc = 1060 kA/m, which was boosted to 1160 kA/m after the post-PECS thermal treatment. The Br and Hc were tackled further and increased applied pressures of 100 – 150 MPa resulted in Br = 1.01 T. We showed that with a fine tune of the PECS and post-annealing it is possible to revitalize the Nd-Fe-B end-of-life magnets. By applying advanced TEM, i.e. atomic-scale Z-contrast STEM combined with EDXS and EELS, the resulting magnetic properties were critically assessed against various types of structural and compositional discontinuities down to atomic-scale, which we believe control the microstructure evolution during the PECS processing route.

Keywords: electrochemistry, Nd-Fe-B, pulsed electric current sintering, recycling, reprocessing

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Authors: R. O. Ocaya, J. J. Terblans

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The laws of Newtonian mechanics allow ab-initio molecular dynamics to model and simulate particle trajectories in material science by defining a differentiable potential function. This paper discusses some considerations for the coding of ab-initio programs for simulation on a standalone computer and illustrates the approach by C language codes in the context of embedded metallic atoms in the face-centred cubic structure. The algorithms use velocity-time integration to determine particle parameter evolution for up to several thousands of particles in a thermodynamical ensemble. Such functions are reusable and can be placed in a redistributable header library file. While there are both commercial and free packages available, their heuristic nature prevents dissection. In addition, developing own codes has the obvious advantage of teaching techniques applicable to new problems.

Keywords: C language, molecular dynamics, simulation, embedded atom method

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Authors: M. A. Islam, P. J. Hazell, J. P. Escobedo, M. Saadatfar

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Quasistatic compression and micro structural characterization of closed cell aluminium foams of different pore size and cell distributions has been carried out. Metallic foams have good potential for lightweight structures for impact and blast mitigation and therefore it is important to find out the optimized foam structure (i.e. cell size, shape, relative density, and distribution) to maximize energy absorption. In this paper, we present results for two different aluminium metal foams of density 0.5 g/cc and 0.7 g/cc respectively that have been tested in quasi-static compression. The influence of cell geometry and cell topology on quasistatic compression behavior has been investigated using computed tomography (micro-CT) analysis. The compression behavior and micro structural characterization will be presented.

Keywords: metal foams, micro-CT, cell topology, quasistatic compression

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Authors: M. Valentini, D. Melisi, M. A. Nitti, R A. Picca, M. C. Sportelli, E. Bonerba, G. Casamassima, N. Cioffi, L. Sabbatini, G. Tantillo, A. Valentini

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In recent years antimicrobial coatings are receiving increasing attention due to their high demand in medical applications as well as in healthcare and hygiene. Research and technology are constantly involved to develop advanced finishing which can provide bacteriostatic growth without compromising the other typical properties of a textile as durability and non-toxicity, just to cite a few. Here we report on the antimicrobial coatings obtained, at room temperature and without the use of solvents, by means of the ion beam co-sputtering technique of an Ag target and a polytetrafluoroethylene one. In particular, such method allows to conjugate the well-known antimicrobial action of silver with the anti-stain and water-repellent properties of the fluoropolymer. Moreover, different Ag nanoparticle loadings (φ) were prepared by tuning the material deposition conditions achieving a fine control on film thickness and their antimicrobial/anti-stain properties.

Keywords: antimicrobial, ion beam sputtering, nanocoatings, anti-stain

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Authors: Syed Javed Arif, Mohd Ayyub Khan, Saleem Anwar Khan

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In this paper, a simple method is presented for measurement of power frequency deviations. A phase locked loop (PLL) is used to multiply the signal under test by a factor of 100. The number of pulses in this pulse train signal is counted over a stable known period, using decade driving assemblies (DDAs) and flip-flops. These signals are combined using logic gates and then passed through decade counters to give a unique combination of pulses or levels, which are further encoded. These pulses are equally suitable for both control applications and display units. The experimental circuit developed gives a resolution of 1 Hz within the measurement period of 20 ms. The proposed circuit is also simulated in Verilog Hardware Description Language (VHDL) and implemented using Field Programing Gate Arrays (FPGAs). A Mixed signal Oscilloscope (MSO) is used to observe the results of FPGA implementation. These results are compared with the results of the proposed circuit of discrete components. The proposed system is useful for frequency deviation measurement and control in power systems.

Keywords: frequency measurement, digital control, phase locked loop, encoder, Verilog HDL

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Authors: Daniel Y. Abebe, Jaehyouk Choi

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This study aims to evaluate the effective size and hysteresis characteristics of Circular Hollow Steel (CHS) damper. CHS damper is among steel dampers which are used widely for seismic energy dissipation because they are easy to install, maintain and are low cost. CHS damper dissipates seismic energy through metallic deformation due to the geometrical elasticity of circular shape and fatigue resistance around connection part. After calculating the effective size, which is found to be height to diameter ratio of √ ("3”), nonlinear FE analyses were conducted to evaluate the hysteresis characteristics. To verify the analysis simulation quasi static loading was carried out and the result was compared and satisfactory result was obtained.

Keywords: SS400 steel, circular hollow steel damper, effective size, quasi static loading, FE analysis

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Authors: A. A. Gadgeel, S. T. Mhaske

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Hexadecyltrimethylammonium bromide (HTAB) modified nano silica were used as pore stabilizer for the preparation of interconnected macroporous copolymer foam of glycidyl methacrylate (GMA), divinylbenzene (DVB) and tert-butyl acrylate (BA). The polymerization of air infused aqueous foam is carried out through free radical thermal initiator. The porosity of the polymerized foam depends on the concentration of HTAB used to control the hydrophobic and hydrophilic behavior of silica nanoparticle. Modified silica particle results to form closed cell foam with 74% of porosity for 60% of air infusion during aqueous foaming. The preliminary structure of microfoam was observed through optical microscopy, whereas for a better understanding of morphology SEM was used. The proposed route is an eco-friendly route for synthesizing polymeric microporous polymer as compared to other chemical and additive-based routes available.

Keywords: air-infused, interconnected microporous, porosity, aqueous foam

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Authors: Si Mon Kueh, Tom J. Kazmierski

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There are about 1% of the world population suffering from the hidden disability known as epilepsy and major developing countries are not fully equipped to counter this problem. In order to reduce the inconvenience and danger of epilepsy, different methods have been researched by using a artificial neural network (ANN) classification to distinguish epileptic waveforms from normal brain waveforms. This paper outlines the aim of achieving massive ANN parallelization through a dedicated hardware using bit-serial processing. The design of this bit-serial Neural Processing Element (NPE) is presented which implements the functionality of a complete neuron using variable accuracy. The proposed design has been tested taking into consideration non-idealities of a hardware ANN. The NPE consists of a bit-serial multiplier which uses only 16 logic elements on an Altera Cyclone IV FPGA and a bit-serial ALU as well as a look-up table. Arrays of NPEs can be driven by a single controller which executes the neural processing algorithm. In conclusion, the proposed compact NPE design allows the construction of complex hardware ANNs that can be implemented in a portable equipment that suits the needs of a single epileptic patient in his or her daily activities to predict the occurrences of impending tonic conic seizures.

Keywords: Artificial Neural Networks (ANN), bit-serial neural processor, FPGA, Neural Processing Element (NPE)

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Authors: Teodora Mocan, Lucian Mocan, Cornel Iancu, Flaviu A. Tabaran, Bartos Dana, Matea Cristian

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Antimicrobial resistance, which threatens the efficacy of the existing antibiotics represents a worldwide public health issue. At the current time, vancomycin is the only responsive treatment although has significant cytotoxicity, is partially effective and it is poorly retained by infected tissues. From a clinical point of view, attractive alternative approaches for treating such Meticillin-Resistant Staphylococcus Aureus (MRSA) strains would be using agents that cause physical damage to the bacteria. Modular nanopharmaceuticals systems are being designed to address all of these multifunctional capabilities for the ideal bacterial treatment, with the ability to mix and match appropriate functions. Here we present a novel method of selective laser photothermal ablation of MRSA bacteria mediated by gold nanoparticles bound to PBP antibody against PBP protein located on the MRSA surface.

Keywords: MRSA, laser, nanoparticle, antibody

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Authors: N. David, H. O. Gao

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Air pollution is a serious environmental threat on a global scale and can cause harm to human health, morbidity and premature mortality. Reliable monitoring and control systems are therefore necessary to develop coping skills against the hazards associated with this phenomenon. However, existing environmental monitoring means often do not provide a sufficient response due to practical and technical limitations. Commercial microwave links that form the infrastructure for transmitting data between cell phone towers can be harnessed to map rain at high tempo-spatial resolution. Rainfall causes a decrease in the signal strength received by these wireless communication links allowing it to be used as a built-in sensor network to map the phenomenon. In this study, we point to the potential that lies in this system to indirectly monitor areas where air pollution is reduced. The relationship between pollutant wash-off and rainfall provides an opportunity to acquire important spatial information about air quality using existing cell-phone tower signals. Since the density of microwave communication networks is high relative to any dedicated sensor arrays, it could be possible to rely on this available observation tool for studying precipitation scavenging on air pollutants, for model needs and more.

Keywords: air pollution, commercial microwave links, rainfall, washout

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Authors: Amine Mezni, Merfat Algethami, Ali Aldalbahi, Arwa Alrooqi, Abel Santos, Dusan Losic, Sarah Alharthi, Tariq Altalhi

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In situ synthesis of carbon nanotubes featuring different diameters (10-200 nm), lengths (1 to 100 µm) and periodically nanostructured shape was performed in a custom designed chemical vapor deposition (CVD) system using nanoporous anodic alumina (NAA) under different conditions. The morphology of the resulting CNTs/NAA composites and free-standing CNTs were analyzed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The results confirm that highly ordered arrays of CNTs with precise control of nanotube dimensions in the range 20-200 nm with tube length in the range < 1 µm to > 100 μm and with periodically shaped morphology can be fabricated using nanostructured NAA templates prepared by anodization. This technique allows us to obtain tubes open at one / both ends with a uniform diameter along the pore length without using any metal catalyst. Our finding suggests that this fabrication strategy for designing new CNTs membranes and structures can be significant for emerging applications as molecular separation/transport, optical biosensing, and drug delivery.

Keywords: carbon nanotubes, CVD approach, composites membrane, nanoporous anodic alumina

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Authors: Yong Ho Jeon, Youn Mi Lee, Yong Yoon Lee

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Effects of cold plasma treatment on various plant seed germination were studied. The seeds of hot pepper, cucumber, tomato and arabidopsis were exposed to plasma and the plasma was generated in various devices. The germination speed was evaluated compared to an unexposed control. A positive effect on germination speed was observed in all tested seeds but the effects strongly depended on the type of the used plasma device (Argon-DBD, surface-DBD or MARX generator), time of exposure (6s~10min or 1~10shots) and kind of seeds. The SEM images showed that arrays of gold particles along the cell wall were observed on the surface of cucumber seeds showed a germination-accelerating effect by plasma treatment, which was the same as untreated. However, when treated with the high dose plasma, gold particles were not arrayed at the seed surface, it seems that due to the surface etching. This may suggest that the germination is not promoted by etching or damage of surface caused by the plasma treatment. Seedling growth improvement was also observed by indirect plasma treatment. These lead to an important conclusion that the effect of charged particles on plasma play the essential role in plant germination and indirect plasma treatment offers new perspectives for large scale application.

Keywords: cold plasma, cucumber, germination, SEM

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Authors: Ahmet Yonetken, Ayhan Erol

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Intermetallic materials advanced technology materials that have outstanding mechanical and physical properties for high temperature applications. Especially creep resistance, low density and high hardness properties stand out in such intermetallics. The microstructure, mechanical properties of %80Cr-%10Ti and %10WC powders were investigated using specimens produced by tube furnace sintering at 1000-1400°C temperature. A composite consisting of ternary additions, a metallic phase, Ti,Cr and WC have been prepared under Ar shroud and then tube furnace sintered. XRD, SEM (Scanning Electron Microscope), were investigated to characterize the properties of the specimens. Experimental results carried out for composition %80Cr-%10Ti and %10WC at 1400°C suggest that the best properties as 292HV and 5,34g/cm3 density were obtained at 1400°C.

Keywords: ceramic-metal, composites, powder metallurgy, sintering

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Authors: Mohammad Khodaei, Mahmood Meratien, Alireza Valanezhad, Serdar Pazarlioglu, Serdar Salman, Ikuya Watanabe

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Pore size and morphology plays a crucial role on mechanical properties of porous scaffolds. In this research, titanium scaffold was prepared using space holder technique. Sodium chloride and ammonium bicarbonate were utilized as spacer agent separately. The effect of the hardness of spacer on the cell morphology was investigated using scanning electron microscopy (SEM) and optical stereo microscopy. Image analyzing software was used to interpret the microscopic images quantitatively. It was shown that sodium chloride, due to its higher hardness, maintain its morphology during cold compaction, and cause better replication in porous scaffolds.

Keywords: Spacer, Titanium Scaffold, Pore Morphology, Space Holder Technique

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Authors: Safia Akram

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In this article, the effects of peristaltic transport with double-diffusive convection in nanofluids through an asymmetric channel with different waveforms is presented. Mathematical modelling for two-dimensional and two directional flows of a Jeffrey fluid model along with double-diffusive convection in nanofluids are given. Exact solutions are obtained for nanoparticle fraction field, concentration field, temperature field, stream functions, pressure gradient and pressure rise in terms of axial and transverse coordinates under the restrictions of long wavelength and low Reynolds number. With the help of computational and graphical results the effects of Brownian motion, thermophoresis, Dufour, Soret, and Grashof numbers (thermal, concentration, nanoparticles) on peristaltic flow patterns with double-diffusive convection are discussed.

Keywords: nanofluid particles, peristaltic flow, Jeffrey fluid, magnetic field, asymmetric channel, different waveforms

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Authors: M. Tang, S. M. Wen, D. W. Liu

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This paper presents the influences on the entrainment of serpentines by grinding and reagents during copper–nickel sulfide flotation. The previous bench flotation tests were performed to extract the metallic values from the ore in Yunnan Mine, China and the relatively satisfied results with recoveries of 86.92% Cu, 54.92% Ni, and 74.73% Pt+Pd in the concentrate were harvested at their grades of 4.02%, 3.24% and 76.61 g/t, respectively. However, the content of MgO in the concentrate was still more than 19%. Micro-flotation tests were conducted with the objective of figuring out the influences on the entrainment of serpentines into the concentrate by particle size, flocculants or depressants and collectors, as well as visual observations in suspension by OLYMPUS camera. All the tests results pointed to the presences of both “entrapped-in” serpentines and its coating on the hydrophobic flocs resulted from strong collectors (combination of butyl xanthate, butyl ammonium dithophosphate, even after adding carboxymethyl cellulose as effective depressant. And fine grinding may escalate the entrainment of serpentines in the concentrate.

Keywords: serpentine, copper and nickel sulfides, flotation, entrainment

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Authors: Mohamed Elbehery

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Historical textiles in the burial environment or in museums are exposed to many types of stains and dirt that are associated with historical textiles by multiple chemical bonds that cause damage to historical textiles. The cleaning process must be carried out with great care, with no irreversible damage, and sediments removed without affecting the original material of the surface being cleaned. Science and technology continue to provide innovative systems in the bio-cleaning process (using pure enzymes) of historical textiles and artistic surfaces. Lipase and α-amylase were immobilized on nanoparticles of alginate/κ-carrageenan nanoparticle complex and used in historical textiles cleaning. Preparation of nanoparticles, activation, and enzymes immobilization were characterized. Optimization of loading time and units of the two enzymes were done. It was found that, the optimum time and units of amylase were 4 hrs and 25U, respectively. While, the optimum time and units of lipase were 3 hrs and 15U, respectively. The methods used to examine the fibers using a scanning electron microscope equipped with an X-ray energy dispersal unit: SEM with EDX unit.

Keywords: nanoparticles, enzymes, immobilization, textiles

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Authors: Muhammad Khalil, Nader Abuelfoutouh, Gasser Abdelal, Adrian Murphy

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Nowadays, the direct effects of lightning to aircrafts are of great importance because of the massive use of composite materials. In comparison with metallic materials, composites present several weaknesses for lightning strike direct effects. Especially, their low electrical and thermal conductivities lead to severe lightning strike damage. The lightning strike direct effects are burning, heating, magnetic force, sparking and arcing. As the problem is complex, we investigated it gradually. A magnetohydrodynamics (MHD) model is developed to simulate the lightning strikes in order to estimate the damages on the composite materials. Then, a coupled thermal-electrical finite element analysis is used to study the interaction between the lightning arc and the composite laminate and to investigate the material degradation.

Keywords: composite structures, lightning multiphysics, magnetohydrodynamic (MHD), coupled thermal-electrical analysis, thermal plasmas.

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Authors: Simone Dell'Agnello

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There are laser retroreflectors on the Moon and no laser retroreflectors on Mars. Here we describe the design, construction, qualification and imminent deployment of next-generation, optimized laser retroreflectors on the Moon and on Mars (where they will be the first ones). These instruments are positioned by time-of-flight measurements of short laser pulses, the so-called 'laser ranging' technique. Data analysis is carried out with PEP, the Planetary Ephemeris Program of CfA (Center for Astrophysics). Since 1969 Lunar Laser Ranging (LLR) to Apollo/Lunokhod laser retro-reflector (CCR) arrays supplied accurate tests of General Relativity (GR) and new gravitational physics: possible changes of the gravitational constant Gdot/G, weak and strong equivalence principle, gravitational self-energy (Parametrized Post Newtonian parameter beta), geodetic precession, inverse-square force-law; it can also constraint gravitomagnetism. Some of these measurements also allowed for testing extensions of GR, including spacetime torsion, non-minimally coupled gravity. LLR has also provides significant information on the composition of the deep interior of the Moon. In fact, LLR first provided evidence of the existence of a fluid component of the deep lunar interior. In 1969 CCR arrays contributed a negligible fraction of the LLR error budget. Since laser station range accuracy improved by more than a factor 100, now, because of lunar librations, current array dominate the error due to their multi-CCR geometry. We developed a next-generation, single, large CCR, MoonLIGHT (Moon Laser Instrumentation for General relativity high-accuracy test) unaffected by librations that supports an improvement of the space segment of the LLR accuracy up to a factor 100. INFN also developed INRRI (INstrument for landing-Roving laser Retro-reflector Investigations), a microreflector to be laser-ranged by orbiters. Their performance is characterized at the SCF_Lab (Satellite/lunar laser ranging Characterization Facilities Lab, INFN-LNF, Frascati, Italy) for their deployment on the lunar surface or the cislunar space. They will be used to accurately position landers, rovers, hoppers, orbiters of Google Lunar X Prize and space agency missions, thanks to LLR observations from station of the International Laser Ranging Service in the USA, in France and in Italy. INRRI was launched in 2016 with the ESA mission ExoMars (Exobiology on Mars) EDM (Entry, descent and landing Demonstration Module), deployed on the Schiaparelli lander and is proposed for the ExoMars 2020 Rover. Based on an agreement between NASA and ASI (Agenzia Spaziale Italiana), another microreflector, LaRRI (Laser Retro-Reflector for InSight), was delivered to JPL (Jet Propulsion Laboratory) and integrated on NASA’s InSight Mars Lander in August 2017 (launch scheduled in May 2018). Another microreflector, LaRA (Laser Retro-reflector Array) will be delivered to JPL for deployment on the NASA Mars 2020 Rover. The first lunar landing opportunities will be from early 2018 (with TeamIndus) to late 2018 with commercial missions, followed by opportunities with space agency missions, including the proposed deployment of MoonLIGHT and INRRI on NASA’s Resource Prospectors and its evolutions. In conclusion, we will extend significantly the CCR Lunar Geophysical Network and populate the Mars Geophysical Network. These networks will enable very significantly improved tests of GR.

Keywords: general relativity, laser retroreflectors, lunar laser ranging, Mars geodesy

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Authors: D. Varadaradjou, H. Kebir, J. Mespoulet, D. Tingaud, S. Bouvier, P. Deconick, K. Ameyama, G. Dirras

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The development of new architecture metallic alloys with controlled microstructures is one of the strategic ways for designing materials with high innovation potential and, particularly, with improved mechanical properties as required for structural materials. Indeed, unlike conventional counterparts, metallic materials having so-called harmonic structure displays strength and ductility synergy. The latter occurs due to a unique microstructure design: a coarse grain structure surrounded by a 3D continuous network of ultra-fine grain known as “core” and “shell,” respectively. In the present study, pure harmonic-structured (HS) Nickel samples were processed via controlled mechanical milling and followed by spark plasma sintering (SPS). The present work aims at characterizing the mechanical properties of HS pure Nickel under room temperature dynamic loading through a Split Hopkinson Pressure Bar (SHPB) test and the underlying microstructure evolution. A stopper ring was used to maintain the strain at a fixed value of about 20%. Five samples (named B1 to B5) were impacted using different striker bar velocities from 14 m/s to 28 m/s, yielding strain rate in the range 4000-7000 s-1. Results were considered until a 10% deformation value, which is the deformation threshold for the constant strain rate assumption. The non-deformed (INIT – post-SPS process) and post-SHPB microstructure (B1 to B5) were investigated by EBSD. It was observed that while the strain rate is increased, the average grain size within the core decreases. An in-depth analysis of grains and grain boundaries was made to highlight the thermal (such as dynamic recrystallization) or mechanical (such as grains fragmentation by dislocation) contribution within the “core” and “shell.” One of the most widely used methods for determining the dynamic behavior of materials is the SHPB technique developed by Kolsky. A 3D simulation of the SHPB test was created through ABAQUS in dynamic explicit. This 3D simulation allows taking into account all modes of vibration. An inverse approach was used to identify the material parameters from the equation of Johnson-Cook (JC) by minimizing the difference between the numerical and experimental data. The JC’s parameters were identified using B1 and B5 samples configurations. Predictively, identified parameters of JC’s equation shows good result for the other sample configuration. Furthermore, mean rise of temperature within the harmonic Nickel sample can be obtained through ABAQUS and show an elevation of about 35°C for all fives samples. At this temperature, a thermal mechanism cannot be activated. Therefore, grains fragmentation within the core is mainly due to mechanical phenomena for a fixed final strain of 20%.

Keywords: 3D simulation, fragmentation, harmonic structure, high strain rate, Johnson-cook model, microstructure

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Authors: Enerit Sacdanaku, Idriz Haxhiu

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This study was conducted in the area of Vlora Bay, Albania. Data about Sea Turtles Caretta caretta and Chelonia mydas, belonging to two periods of time (1984–1991; 2008–2014) are given. All data gathered were analyzed using recent methodologies. For all turtles captured (as by catch), the Curve Carapace Length (CCL) and Curved Carapace Width (CCW) were measured. These data were statistically analyzed, where the mean was 67.11 cm for CCL and 57.57 cm for CCW of all individuals studied (n=13). All untagged individuals of marine turtles were tagged using metallic tags (Stockbrand’s titanium tag) with an Albanian address. Sex was determined and resulted that 45.4% of individuals were females, 27.3% males and 27.3% juveniles. All turtles were studied for the presence of the epibionts. The area of Vlora Bay is used from marine turtles (Caretta caretta) as a migratory corridor to pass from the Mediterranean to the northern part of the Adriatic Sea.

Keywords: Caretta caretta, Chelonia mydas, CCL, CCW, tagging, Vlora Bay

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Authors: Lincy Stephen, N. Yogesh, G. Vasantharajan, V. Subramanian

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This paper presents the design and simulation of a five band metamaterial absorber at microwave frequencies. The absorber unit cell consists of squares and strips arranged as the top layer and a metallic ground plane as the bottom layer on a dielectric substrate. Simulation results show five near perfect absorption bands at 3.15 GHz, 7.15 GHz, 11.12 GHz, 13.87 GHz, and 16.85 GHz with absorption magnitudes 99.68%, 99.05%, 96.98%, 98.36% and 99.44% respectively. Further, the proposed absorber exhibits polarization insensitivity and wide angle receptivity. The surface current analysis is presented to explain the mechanism of absorption in the structure. With these preferable features, the proposed absorber can be excellent choice for potential applications such as electromagnetic interference (EMI) shielding, radar cross section reduction.

Keywords: electromagnetic absorber, metamaterial, multi- band, polarization insensitive, wide angle receptive

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Authors: Elżbieta Cygan-Bączek, Piotr Wyżga, Sławomir Cygan

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In the presented work, the main goal was to investigate the retention properties, defined as the ability of the matrix material to hold diamond particles in relation to metallized (Ti, Si, Cr, Co, Cu, Ni) and non-metallized diamond crystals. For this purpose, diamond-impregnated specimens were tested for wear rate on abrasive sandstone using a test rig specially designed to simulate tool application conditions. The tests that involved 3- and 2-body abrasion ranked the alloys in different orders. The ability of the matrix to retain diamond crystals was determined using the electron microskopy (SEM, TEM). The specimens were also characterized by X-ray diffraction (XRD) and hardness. The conducted research has shown that Si and Ti metallized diamonds, apart from mechanical jamming in the matrix, are also connected in a metallurgical manner, ensuring the improvement of the retention properties of the matrix material.

Keywords: diamond, metallic-diamond segments, retention, abrasive wear resistance

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Authors: Dilip K. Paul

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The most popular mesoporous molecular sieves, Mobil Composition of Matter (MCM) are keenly studied by researchers because of these materials possess amorphous silica wall and have a long range of ordered framework with uniform mesopores. These materials also possess large surface area, which can be up to more than 1000 m2g−1. Herein the investigation is focused upon the synthesis and characterization of chromium and aluminum doped MCM-41 using XRD and FTIR. Acid-base properties of Cr-Al-MCM 41 was investigated by molecularly sensitive transmission FT-IR spectroscopy by adsorbing pyridine. In addition, these MCM nanomaterial was used to catalyze C-C bond formation from acetaldehyde adsorption. The assignment of all infrared peaks during adsorption of pyridine provided detail information on the presence of acid-base sites which in turn helped us to explain the roles of these in the condensation reaction of aldehyde. Reaction mechanisms of C-C bond formation is therefore explored to shed some light on this elusive reaction detail.

Keywords: mesoporous nanomaterial, MCM 41, FTIR studies, acid-base studies

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Authors: Su Jeong Lee, Tae Il Lee, Jung Han Kim, Chul-Hong Kim, Gee Sung Chae, Jae-Min Myoung

Abstract:

The contact resistance between source/drain electrodes and semiconductor layer is an important parameter affecting electron transporting performance in the thin film transistor (TFT). In this work, we introduced a transparent and the solution prossable single-walled carbon nanotube (SWCNT)/Al-doped ZnO nano particle (AZO NP) bilayer electrodes showing low contact resistance with indium-oxide (In2O3) sol gel thin film. By inserting low work function AZO NPs into the interface between the SWCNTs and the In2O3 which has a high energy barrier, we could obtain an electrical Ohmic contact between them. Finally, with the SWCNT-AZO NP bilayer electrodes, we successfully fabricated a TFT showing a field effect mobility of 5.38 cm2/V∙s at 250 °C.

Keywords: single-walled carbon nanotube (SWCNT), Al-doped ZnO (AZO) nanoparticle, contact resistance, thin-film transistor (TFT)

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Authors: Nazar Hussain, Debaraj Mukherjee

Abstract:

Carbohydrate-derived chiral intermediates which contain arrays of defined stereocenters have found enormous applications in organic synthesis due to their inherent functional group, stereochemical and structural diversities as well as their ready availability. Stereodiversity of these classes of molecules has motivated synthetic organic chemistry over the years. One major challenge is control of relative configuration during construction of acyclic fragments. Here, we show that The Diels Alder addition of arynes to appropriately substituted vinyl/aryl glycals followed by π-extension via pyran ring opening smoothly furnished meta-disubstituted fused aromatic cores containing a stereo-defined orthogonally protected chiral side chain. The method is broad in terms of aryl homologation affording benzene, naphthalene, and phenanthrene derivatives. Base-induced deprotonation followed by cleavage of the allylic C-O bond appears to be the crucial steps leading to the development of aromaticity, which is the driving force behind the annulative π-extension process. The present protocol can be used for the synthesis of meta-disubstituted naphthalene aldehydes and substrates for aldolases.

Keywords: vinyl/C-2 aryl glycal, arynes, cyclization, ring opening

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Authors: Celine Bonnaud, Isabelle Billard, Nicolas Papaiconomou, Eric Chainet

Abstract:

Thanks to their high magnetization and low mass, permanent magnets (NdFeB and SmCo) have quickly became essential for new energies (wind turbines, electrical vehicles…). They contain large quantities of neodymium, samarium and dysprosium, that have been recently classified as critical elements and that therefore need to be recycled. Electrochemical processes including electrodissolution followed by electrodeposition are an elegant and environmentally friendly solution for the recycling of such lanthanides contained in permanent magnets. However, electrochemistry of the lanthanides is a real challenge as their standard potentials are highly negative (around -2.5V vs ENH). Consequently, non-aqueous solvents are required. Ionic liquids (IL) are novel electrolytes exhibiting physico-chemical properties that fulfill many requirements of the sustainable chemistry principles, such as extremely low volatility and non-flammability. Furthermore, their chemical and electrochemical properties (solvation of metallic ions, large electrochemical windows, etc.) render them very attractive media to implement alternative and sustainable processes in view of integrated processes. All experiments that will be presented were carried out using butyl-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide. Linear sweep, cyclic voltammetry and potentiostatic electrochemical techniques were used. The reliability of electrochemical experiments, performed without glove box, for the classic three electrodes cell used in this study has been assessed. Deposits were obtained by chronoamperometry and were characterized by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The IL cathodic behavior under different constraints (argon, nitrogen, oxygen atmosphere or water content) and using several electrode materials (Pt, Au, GC) shows that with argon gas flow and gold as a working electrode, the cathodic potential can reach the maximum value of -3V vs Fc+/Fc; thus allowing a possible reduction of lanthanides. On a gold working electrode, the reduction potential of samarium and neodymium was found to be -1.8V vs Fc+/Fc while that of dysprosium was -2.1V vs Fc+/Fc. The individual deposits obtained were found to be porous and presented some significant amounts of C, N, F, S and O atoms. Selective deposition of neodymium in presence of dysprosium was also studied and will be discussed. Next, metallic Sm, Nd and Dy electrodes were used in replacement of Au, which induced changes in the reduction potential values and the deposit structures of lanthanides. The individual corrosion potentials were also measured in order to determine the parameters influencing the electrodissolution of these metals. Finally, a full recycling process was investigated. Electrodissolution of a real permanent magnet sample was monitored kinetically. Then, the sequential electrodeposition of all lanthanides contained in the IL was investigated. Yields, quality of the deposits and consumption of chemicals will be discussed in depth, in view of the industrial feasibility of this process for real permanent magnets recycling.

Keywords: electrodeposition, electrodissolution, ionic liquids, lanthanides, rcycling

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