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Relevant bibliographies by topics / Temperature dependent electrical transport

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Academic literature on the topic 'Temperature dependent electrical transport'

Author: Grafiati

Published: 6 September 2023

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Journal articles on the topic "Temperature dependent electrical transport"

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Sallam, M. M., B. A. El-Sayed, and A. A. Abdel-Shafi. "The temperature dependent electrical transport in biphenyl derivatives." Current Applied Physics 6, no. 1 (January 2006): 71–75. http://dx.doi.org/10.1016/j.cap.2004.12.006.

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Wu, H. Y., W. Wang, and W. J. Lu. "Temperature-dependent electrical transport mechanism in amorphous Ge2Sb2Te5films." physica status solidi (b) 253, no. 9 (June 7, 2016): 1855–60. http://dx.doi.org/10.1002/pssb.201600045.

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VAISH, RAHUL, and KALIDHINDI B. R. VARMA. "ELECTRICAL TRANSPORT STUDIES IN 3Na2O–6.5B2O3 GLASSES." Journal of Advanced Dielectrics 01, no. 03 (July 2011): 331–36. http://dx.doi.org/10.1142/s2010135x11000355.

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Transparent 3Na2O–6.5B2O3 (NBO) glasses were fabricated via the conventional melt-quenching technique. X-ray powder diffraction (XRD) combined with Differential Scanning Calorimetric (DSC) studies carried out on the as-quenched samples confirmed their amorphous and glassy nature, respectively. The frequency and temperature dependent of the dielectric constant, electric modulus and electrical conductivity of the transparent NBO glasses were investigated in the 100 Hz–10 MHz frequency range. The electrical modulus and conductivity data have been rationalized using Jonscher's universal law. The bulk dc conductivity at various temperatures was extracted from the electrical relaxation data. The activation energy associated with dc conductivity is 0.52 ± 0.01eV, which is ascribed to the motion of Na+ ions in the glass matrix.

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Muchharla, Baleeswaraiah, T. N. Narayanan, Kaushik Balakrishnan, Pulickel M. Ajayan, and Saikat Talapatra. "Temperature dependent electrical transport of disordered reduced graphene oxide." 2D Materials 1, no. 1 (May 29, 2014): 011008. http://dx.doi.org/10.1088/2053-1583/1/1/011008.

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Sinha, S., P. L. Srivastava, and R. N. Singh. "Temperature-dependent structure and electrical transport in liquid metals." Journal of Physics: Condensed Matter 1, no. 9 (March 6, 1989): 1695–705. http://dx.doi.org/10.1088/0953-8984/1/9/014.

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Li, Zhen, Yongsen Han, Ji Liu, Daomin Min, and Shengtao Li. "Investigation of temperature-dependent DC breakdown mechanism of EP/TiO₂ nanocomposites." Applied Physics Letters 121, no. 5 (August 1, 2022): 052901. http://dx.doi.org/10.1063/5.0097351.

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In dielectric science, the electrical breakdown strength of a polymeric material significantly decreases with elevated temperatures, which restricts the development of advanced electrical and electronic applications toward miniaturization. In the present study, to clarify the temperature-dependent DC breakdown mechanisms of epoxy resin (EP)/TiO2 nanocomposites, the effects of nanoparticle incorporation and temperature on charge transport and molecular chain dynamics were studied. The results indicate that space charge accumulation and electric field distortion are reduced by nanoparticle incorporation to enhance the deep trap level, while space charge accumulation, electric field distortion, and molecular displacement are all accelerated as temperature increases. To further investigate the influence of carrier traps and molecular chain dynamics on temperature-dependent breakdown, a DC breakdown simulation model that involves bipolar charge transport, molecular chain dynamics, and breakdown criterion equations is established. The calculated breakdown strengths of EP/TiO2 nanocomposites show great accordance with the experimental results, which indicates that temperature-dependent DC breakdown mechanisms are dominated by the synergetic effects of carrier traps and segment chain dynamics. Through the analysis of the breakdown model, a transition of the dominant mechanism (from segment chain to backbone dynamics) near the glass-transition temperature for DC breakdown of EP/TiO2 nanocomposites is discovered.

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Park, Jae Young, Hwangyou Oh, Ju-Jin Kim, and Sang Sub Kim. "The temperature-dependent electrical transport mechanism of single ZnO nanorods." Nanotechnology 17, no. 5 (February 7, 2006): 1255–59. http://dx.doi.org/10.1088/0957-4484/17/5/016.

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Sahu, A. K., S. K. Satpathy, and Banarji Behera. "Dielectric and frequency-dependent transport properties of lanthanum-doped bismuth ferrite." Journal of Advanced Dielectrics 09, no. 04 (August 2019): 1950031. http://dx.doi.org/10.1142/s2010135x19500310.

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Polycrystalline samples of Bi[Formula: see text]LaxFeO3 [[Formula: see text], 0.6, 0.7 and 0.8] were synthesized through high temperature solid state reaction method. The structural studies of the compounds were done using X-ray diffraction technique. Dielectric constant and dielectric loss were studied for various frequencies (100[Formula: see text]Hz–104[Formula: see text]Hz) at different temperatures. The temperature-dependent non-Debye type relaxation process was suggested in the materials from the analysis of frequency-dependent electrical data at different temperatures. Temperature dependence of dc and ac conductivity at various frequencies showed negative temperature coefficient of resistance (NTCR) behavior. The frequency dependence of ac conductivity at different temperatures obeyed Jonscher’s universal power law. The temperature dependence of dc and ac conductivity was fitted to Arrhenius equation. The activation energies at different temperature ranges were calculated to know the charge species involved in the conduction process.

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Hui, Zhenzhen, Xuzhong Zuo, Longqiang Ye, Xuchun Wang, and Xuebin Zhu. "Solution Processable CrN Thin Films: Thickness-Dependent Electrical Transport Properties." Materials 13, no. 2 (January 16, 2020): 417. http://dx.doi.org/10.3390/ma13020417.

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Thickness is a very important parameter with which to control the microstructures, along with physical properties in transition-metal nitride thin films. In work presented here, CrN films with different thicknesses (from 26 to 130 nm) were grown by chemical solution deposition. The films are pure phase and polycrystalline. Thickness dependence of microstructures and electrical transport behavior were studied. With the increase of films thickness, grain size and nitrogen content are increased, while resistivity, zero-field sensitivity and magnetoresistance are decreased. In the temperature range of 5–350 K, all samples exhibited semiconductor-like properties with dρ/dT < 0. For the range above and below the Néel temperature, the resistivity can be fitted by the thermal activation model and the two-dimensional weak localization (2D-WL) model, respectively. The ultra-low magnetoresistance at a low temperature under high magnetic fields with a large zero-field sensitivity was observed in the CrN thin films. The zero-field sensitivity can be effectively tuned to 10−2 K−1 at 5 K with a magnetoresistance of less than 1% at 2 K under 14 T by reasonably controlling the thickness.

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Zhang, Tong, Liuan Li, and Jin-Ping Ao. "Temperature-dependent electrical transport characteristics of a NiO/GaN heterojunction diode." Surfaces and Interfaces 5 (December 2016): 15–18. http://dx.doi.org/10.1016/j.surfin.2016.08.004.

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Dissertations / Theses on the topic "Temperature dependent electrical transport"

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Kaya, Savas. "Electrical transport in strained silicon quantum wells on vicinal substrates." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313699.

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Webb, Alexander James. "Temperature dependence and touch sensitivity of electrical transport in novel nanocomposite printable inks." Thesis, Durham University, 2014. http://etheses.dur.ac.uk/10764/.

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Printed electronics is an established industry allowing the production of electronic components such as resistors, and more complex structures such as solar cells, from functional inks. Composites, a mixture of two or more materials with different physical and/or chemical properties that combine to create a new material with properties differing from its constituent parts, have been important in areas such as the textile and automotive industries, and are significant in printed electronics as inks for printed circuit components, touch and vapour sensors. Here, the functional performance and physical behaviour of two screen printable multi-component nanocomposite inks, formulated for touch-pressure sensing applications, are investigated. They each comprise a proprietary mixture of electrically conducting and insulating nanoparticles dispersed in an insulating polymer binder, where one is opaque and the other transparent. The opaque ink has a complex surface structure consisting of a homogeneous dispersion of nanoparticles. The transparent inks structure is characterised by large aggregates of nanoparticles distributed through the printed layer. Temperature dependent electrical transport measurements under a range of compressive loadings reveal similar non-linear behaviour in both inks, with some hysteresis observed, and this behaviour is linked to the inks structures. A physical model comprising a combination of linear and non-linear conduction contributions, with the linear term attributed to direct connections between conductive particles and the non-linear term attributed to field-assisted quantum tunnelling, has been developed and used successfully to describe the underpinning physical processes behind the unique electrical functionality of the opaque ink and, to a lesser extent, the transparent ink.

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Whitfield, Thomas Britain. "An analysis of copper transport in the insulation of high voltage transformers." Thesis, University of Surrey, 2001. http://epubs.surrey.ac.uk/843581/.

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Examination of the paper insulation and copper stress braiding during stripdown of a number of Current Transformers (FMK type 400kV) has revealed the presence of dark deposits. Copper foils are often interspersed within layers of paper insulation and mineral oil found in transformer windings. The dark deposits were often found in association with these foils, affecting several layers of paper in addition to the layer in contact with the copper foil. This thesis describes the research undertaken to identify these deposits and establish a mechanism for the transportation through the paper layers. Preliminary investigation using scanning electron microscopy (SEM) in conjunction with energy dispersive X-ray analysis (EDX) has shown these dark deposits to be copper based. X-ray photoelectron spectroscopy was used to show that the transport of the copper deposit through the paper insulation was working under the influence of a diffusion controlled process, related to Fick's law. Laboratory studies in support of work designed to eliminate the problem have shown that corrosion of copper occurs in mineral oils containing a trace of oxygen. This corrosion is non protective in character and leads to migration of copper into adjacent layers of paper. It has been shown that the transport of copper through several layers of paper can be measured by XPS and that the concentration from one paper winding to the next declines in accord with Fick's law for non-steady state diffusion. Measurements of surface concentrations by XPS correlate well with measurements made with atomic absorption spectroscopy on solutions of extracts of the contaminated paper. The laboratory measurements have allowed determination of the diffusion coefficients and activation energy for the transport process and thus give a basis for interpretation of the diffusion profiles found in the transformer in terms of time and temperature of operation. The diffusion process is temperature dependant. The results have been used to produce long term prediction curves.

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Falasco, Gianmaria, Manuel V. Gnann, Daniel Rings, Dipanjan Chakraborty, and Klaus Kroy. "Effective time-dependent temperature in hot Brownian motion." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-183309.

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Falasco, Gianmaria, Manuel V. Gnann, Daniel Rings, Dipanjan Chakraborty, and Klaus Kroy. "Effective time-dependent temperature in hot Brownian motion." Diffusion fundamentals 20 (2013) 63, S. 1-2, 2013. https://ul.qucosa.de/id/qucosa%3A13640.

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Hai, Md. "Minimizing temperature dependent spectral shift in SOI DPSK demodulators." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=104852.

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Silicon on insulator (SOI) photonic devices are becoming popular due to their compatibility with complementary metal oxide semiconductor (CMOS) technology. Over the last five years, we have seen several practical demonstrations of high-speed optical modulators, switches, filters designed on SOI platform. Some of these devices were made utilizing one fundamental property of light: Interference. However, interference-based SOI devices show disastrous spectral phase shift with temperature change which result in the necessity of integrating active temperature control circuits to stabilize them. In this work we present a 50 Gb/sec SOI Mach-Zehnder interferometer (MZI) differential phase shift keying (DPSK) demodulator which exhibits over 90% improvement in thermal stability with 0.05 nm/C of its spectral profile compared to 0.9 nm/C for a noncompensated demodulators. Our proposed method is a fully passive way of minimizing temperature dependant spectral shift in DPSK demodulators, which employs the waveguide engineering method. A full analytical approach to address the problem is derived first, which is followed by extensive numerical simulations to find out the exact device dimensions. Through this, we present a step by step approach to design the demodulator by achieving required waveguide geometry. After we get the design values of our device parameters we calculate the spectral shift with temperature change by our customized computer program and observe improved performance of the device with temperature change. With the values of design variables, we fabricate our device through Canadian Microelectronics Corporation (CMC). The waveguide width of our device varies from 280 nm to 450 nm at different stage of the device while its height was fixed to 220 nm. For thermally non-compensated demodulator, waveguide width was 450 nm throughout the device. Both thermally compensated and non-compensated demodulators are built on the same chip. Experimental result of the fabricated device is presented and we compare different performance metric of the demodulator with and without the proposed temperature compensation technique.
La recherche sur les composantes photoniques en silicium sur isolant (SOI) est devenue populaire en raison de leur compatibilité avec la technologie des semi-conducteur en métal complémentaire d'oxyde (CMOS). Pendant les cinq dernières années, nous avons vu plusieurs démonstrations pratiques de modulateurs optiques à grande vitesse, de commutateurs, et de filtres en SOI. Certaines de ces composantes utilisent une propriété fondamentale de lumière : l'interférence. Pourtant, les composantes en SOI à base d'interférence montrent un changement de phase spectral désastreux avec le changement de température qui s'ensuit d'une nécessité d'intégrer des circuits de contrôle actifs de température pour les stabiliser. Dans ce travail nous présentons un interféromètre Mach-Zehnder (MZI) en SOI à 50 Gb/sec pour la modulation de phase différentielle (DPSK). Le démodulateur a une stabilité thermale de 0.05 nm/0C qui est 90% meilleure que les démodulateurs non-compensés qui eux ont un profil spectral de 0.9 nm/0C. Notre méthode propose une façon complètement passive de minimiser l'effet de la température sur le changement spectral des démodulateurs DPSK. Une approche analytique complète suivi pardes simulations numériques permettent de définir les dimensions exactes du démodulateur. Nous présentons la géométrie due démodulateur. En utilisant les paramètres obtenus, nous calculons le changement spectral avec le changement de température en utilisant notre programme informatique conçu pour observer la performance du démodulateur. Le démodulateur a été fabriqué par la société de microélectrique Canadian (CMC). La largeur de la guide d'onde du démodulateur varie de 280 nm 450 nm et la hauteur est fixe à 220 nm. Pour le démodulateur non-compensé, la largeur du guide d'onde est 450 nm. Les démodulateurs tant compensés que non-compensés sont construits sur le même fragment. Les résultats expérimentaux sont présentés et nous comparons les différentes performances du démodulateur avec et sans la technique de compensation proposée.

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Zhang, Zhaohui. "Spin-dependent electrical and thermal transport in magnetic tunnel junctions." APS, 2012. http://hdl.handle.net/1993/31947.

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Thermoelectricity can directly convert a temperature difference into a voltage or charge current. Recently, the development of spin caloritronics has introduced spin as another degree of freedom in traditional thermoelectrics. This discovery bodes a new generation of magnetic random access memories (MRAMs), where thermal spin-transfer torque (TSTT) rather than voltage driven spin-transfer torque (STT) is used to switch the magnetization in magnetic tunnel junctions (MTJs). To advance the rising trend of spin caloritronics, the coupling of charge, spin, and heat flow during electron transport in MTJs was systematically studied in this thesis. To begin with, the static transport properties of MTJs were studied by observing current dependent tunnel magnetic resistance (TMR). The observed decrease of TMR with a biased current is attributed to the change in spin polarization of the free ferromagnetic layer. A phenomenological model has been built based on the current dependent polarization, which agrees with our experimental results. Next, the Seebeck rectification effect in MTJs was studied. By applying microwave currents to MTJs, an intrinsic thermoelectric coupling effect in the linear response regime of MTJs was discovered. This intrinsic thermoelectric coupling contributes a nonlinear correction to Ohm's law. In addition, this effect can be controlled magnetically since the Seebeck coefficient is related to magnetization configuration. Finally, TSTT in MTJs was systematically studied. A laser heating technique was employed to apply a temperature difference across the tunnel barrier and ferromagnetic resonance (FMR) spectra were measured electrically through spin rectification. By analyzing the FMR spectra, TSTT in MTJs was observed and the angular dependence of TSTT was found to be different from dc-biased STT. By solving the Landau-Lifshitz-Gilbert equation including STT, the experimental observations were well explained. The discovery of Seebeck rectification refines the previous understanding of magneto-transport and microwave rectification in MTJs and provides a new possibility for utilizing spin caloritronics in high-frequency applications. The study of TSTT in MTJs shows clear experimental evidence of TSTT in MTJs. Further optimization of the design of MTJs may succeed in decreasing the necessary switching fields strength or even achieve a switching by only TSTT in MTJs.
February 2017

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Ohlendorf, Gerd, Denny Richter, Jan Sauerwald, and Holger Fritze. "High-temperature electrical conductivity and electromechanical properties of stoichiometric lithium niobate." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-192902.

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High temperature properties such as electrical conductivity (σ) and resonance behaviour of stoichiometric lithium niobate (LiNbO3) are determined in the temperature range from 20 to 950 °C. The activation energy of the conductivity is found to be 0.9 and 1.7 eV in the temperature range from 500 to 750 °C and from 800 to 950 °C, respectively. During thermal treatments in ambient air up to 950 °C and back, the conductivity remains unchanged at a given temperature, i.e., the crystal is stable under these conditions. The oxygen partial pressure (pO2) dependence of the conductivity shows two distinct ranges. At 750 °C, the property remains unchanged down to 10−15 bar. Below 10−15 bar, the conductivity increases according to σ ~ (pO2)−1/5. Z-cut LiNbO3 plates can be excited to thickness mode vibrations up to at least 900 °C. At this temperature, the quality factor Q is found to be between 30 and 100. As for changes of the conductivity, a decrease of the resonance frequency is observed below 10−15 bar indicating a correlation of both properties. In order to evaluate the lithium evaporation, the crystals are tempered at 900 °C in ambient air for 24 h. A depth profile of the constituents does not indicate lithium loss within the accuracy of the secondary ion mass spectroscopy. The preliminary results underline the potential of stoichiometric LiNbO3 for high-temperature applications and justify its closer investigation.

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Sirisathitkul, C. "Studies of transport phenomena at ferromagnet/semiconductor interfaces." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325445.

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Green, Paul Elijah. "View-dependent precomputed light transport using non-linear Gaussian function approximations." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/35605.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, February 2006.
Includes bibliographical references (p. 43-46).
We propose a real-time method for rendering rigid objects with complex view-dependent effects under distant all-frequency lighting. Existing precomputed light transport approaches can render rich global illumination effects, but high-frequency view-dependent effects such as sharp highlights remain a challenge. We introduce a new representation of the light transport operator based on sums of Gaussians. The non-linear parameters of the representation allow for 1) arbitrary bandwidth because scale is encoded as a direct parameter; and 2) high-quality interpolation across view and mesh triangles because we interpolate the average direction of the incoming light, thereby preventing linear cross-fading artifacts. However, fitting the precomputed light transport data to this new representation requires solving a non-linear regression problem that is more involved than traditional linear and non-linear (truncation) approximation techniques. We present a new data fitting method based on optimization that includes energy terms aimed at enforcing good interpolation. We demonstrate that our method achieves high visual quality for a small storage cost and fast rendering time.
by Paul Elijah Green.
S.M.

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Books on the topic "Temperature dependent electrical transport"

1

George C. Marshall Space Flight Center., ed. [Computational modeling of properties]: [final report]. Marshall Space Flight Center, AL: National Aeronautics and Space Administration, George C. Marshall Space Flight Center, 1995.

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United States. National Aeronautics and Space Administration., ed. [Computational modeling of properties]: [final report, 12 Mar. 1993 - 11 Jul. 1994]. [Washington, DC: National Aeronautics and Space Administration, 1994.

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Plastics in Automotive Engineering PIAE EUROPE. VDI Verlag, 2019. http://dx.doi.org/10.51202/9783181023433.

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Der VDI-Bericht ist ausschließlich als PDF erschienen! / Sie möchten gerne mehr erfahren? Inhalt Plastic components: future requirements Zukünftige Anforderungen an Kunststoffbauteile Volvo Cars recycled plastics strategy – Kick-starting with a recycled-plastics demo car 1 S. Tostar, Volvo Car Group, Gothenburg, Sweden Sustainable materials for the interior parts 5 Nachhaltige Materialien für das Interieur 17 C. Schütz, L. Lewerdomski, E. Körner, C. Winkelmann, Volkswagen AG, Wolfsburg Interior-Trends/Trends im Fahrzeuginnenraum Antimicrobial treatment of textiles and decorative materials for passenger transport and car-sharing concepts 29 Antimikrobielle Ausstattung von Textilien und Dekormaterialien für Personentransport und Carsharing Konzepte 43 M. Schneider, A. Cordella, car i.t.a. GmbH & Co. KG, Kirkel-Limbach Simulation/Simulation Elasto-viscoplastic temperature-dependent material model for a talc-filled PP/PE copolymer 57 Elasto-viskoplastisches temperaturabhängi...

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Pirota, Kleber Roberto, Angela Knobel, Manuel Hernandez-Velez, Kornelius Nielsch, and Manuel Vázquez. Magnetic nanowires: Fabrication and characterization. Edited by A. V. Narlikar and Y. Y. Fu. Oxford University Press, 2017. http://dx.doi.org/10.1093/oxfordhb/9780199533053.013.22.

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This article describes the fabrication and characterization of magnetic nanowires, focusing on the magnetic properties of patterned arrays of metallic magnetic nanowires electrodeposited into the pores of anodized-alumina membranes. It also discusses the complex magnetization processes, both in isolated nanowires and in collectively patterned arrays. After providing an overview of the state-of-the-art on fabrication techniques of nanowires, the article considers the microstructure of magnetic nanowires and the magnetic properties of single nanowires. It then examines the collective behavior of arrays where the interactions among the magnetic entities play an important role, along with the transport properties of magnetic nanowires, the temperature-dependent effects (such as magnetoelastic-induced anisotropy), and the dynamic properties of magnetization such as ferromagnetic resonance characteristics and spin-wave excitations in ferromagnetic nanowires. Finally, it presents an overview of future research directions.

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Panigrahi, Muktikanta, and Arpan Kumar Nayak. Polyaniline based Composite for Gas Sensors. IOR PRESS, 2021. http://dx.doi.org/10.34256/ioriip212.

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In this research work, we have demonstrated the synthesis, spectroscopic characteristics, thermal behaviour and DC conductivity of a few nanostructured composites, substituted conducting polymers (ICPs) and composites of ICPs. The physical properties of aforementioned composites are significantly changed by the doping with HCl, H2SO4, HNO3, H3PO4, or acrylic acid. The charge transport properties of these polymeric materials have been studied in detail because of their potential application in gas sensors. In the current work, varieties of conducting polymer based materials such as PANI-ES/Cloisite 20A nanostructured composite, acrylic acid (AA) doped PANI polymer, N-substituted conducting polyaniline polymer, DL−PLA/PANI-ES composites, poly methyl methacrylate (PMMA) based polyaniline composite, and inorganic acid doped polyaniline are sucessfuly synthesized using aniline/aniline hydrochloride as precursors in acidic medium. Particularly, AA based synthesised PANI polymer was found with higher solubility The spectroscopic, thermal stability, enthalpy of fusion, room temperature DC conductivity and temperature dependent DC conductivity measurements with and without magnetic was carried out with as-synthesized materials. The FTR/ATR−FTIR spectra indicated the presence of different functional groups in the as-prepared composite materials. The UV−Visible absorption spectroscopic analysis showed the presence of polaron band suggesting PANI-ES form. The Room temperature DC conductivity, temperature variation DC conductivity (in presence and absence of magnetic field), and magnetoresistance (MR) of as-prepared conducting polyaniline based were analysed. The highest room temperature DC conductivity value was obtained from H2SO4 doped based composite materials and all prepared conductive composites were followed ohms law. The low temperature DC conductivity was carried out in order to study the semiconducting nature of prepared materials. The Mott type VRH model was found to be well fitted the conductivity data and described the density of states at the Fermi level which is constant in this temperature range. From MR plots, a negative MR was observed, which described the quantum interference effect on hopping conduction. We discuss different gas analytes i.e., NO2, LPG, H2, NH3, CH4, and CO of conducting polymer based materials.

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Fisher, David. Mechanical Properties of MAX Phases. Materials Research Forum LLC, 2021. http://dx.doi.org/10.21741/9781644901274.

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MAX Phase Materials are uniquely structured carbide and nitride materials which combine the rigidity, oxidation-resistance and high-temperature strength of ceramic materials with such metallic properties as good machinability, thermal-shock resistance, damage-tolerance and good transport properties. Potential applications include microelectronic layers, coatings for electrical contacts, thermal shock-resistant refractories, high-temperature heating elements, neutron-irradiation resistant nuclear applications, thermal barriers, protective aerospace coatings, and bio-compatible materials. The book reviews theoretical and experimental research up to early 2021 and references 185 original resources with their direct web links for in-depth reading.

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Sobczyk, Eugeniusz Jacek. Uciążliwość eksploatacji złóż węgla kamiennego wynikająca z warunków geologicznych i górniczych. Instytut Gospodarki Surowcami Mineralnymi i Energią PAN, 2022. http://dx.doi.org/10.33223/onermin/0222.

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Hard coal mining is characterised by features that pose numerous challenges to its current operations and cause strategic and operational problems in planning its development. The most important of these include the high capital intensity of mining investment projects and the dynamically changing environment in which the sector operates, while the long-term role of the sector is dependent on factors originating at both national and international level. At the same time, the conditions for coal mining are deteriorating, the resources more readily available in active mines are being exhausted, mining depths are increasing, temperature levels in pits are rising, transport routes for staff and materials are getting longer, effective working time is decreasing, natural hazards are increasing, and seams with an increasing content of waste rock are being mined. The mining industry is currently in a very difficult situation, both in technical (mining) and economic terms. It cannot be ignored, however, that the difficult financial situation of Polish mining companies is largely exacerbated by their high operating costs. The cost of obtaining coal and its price are two key elements that determine the level of efficiency of Polish mines. This situation could be improved by streamlining the planning processes. This would involve striving for production planning that is as predictable as possible and, on the other hand, economically efficient. In this respect, it is helpful to plan the production from operating longwalls with full awareness of the complexity of geological and mining conditions and the resulting economic consequences. The constraints on increasing the efficiency of the mining process are due to the technical potential of the mining process, organisational factors and, above all, geological and mining conditions. The main objective of the monograph is to identify relations between geological and mining parameters and the level of longwall mining costs, and their daily output. In view of the above, it was assumed that it was possible to present the relationship between the costs of longwall mining and the daily coal output from a longwall as a function of onerous geological and mining factors. The monograph presents two models of onerous geological and mining conditions, including natural hazards, deposit (seam) parameters, mining (technical) parameters and environmental factors. The models were used to calculate two onerousness indicators, Wue and WUt, which synthetically define the level of impact of onerous geological and mining conditions on the mining process in relation to: —— operating costs at longwall faces – indicator WUe, —— daily longwall mining output – indicator WUt. In the next research step, the analysis of direct relationships of selected geological and mining factors with longwall costs and the mining output level was conducted. For this purpose, two statistical models were built for the following dependent variables: unit operating cost (Model 1) and daily longwall mining output (Model 2). The models served two additional sub-objectives: interpretation of the influence of independent variables on dependent variables and point forecasting. The models were also used for forecasting purposes. Statistical models were built on the basis of historical production results of selected seven Polish mines. On the basis of variability of geological and mining conditions at 120 longwalls, the influence of individual parameters on longwall mining between 2010 and 2019 was determined. The identified relationships made it possible to formulate numerical forecast of unit production cost and daily longwall mining output in relation to the level of expected onerousness. The projection period was assumed to be 2020–2030. On this basis, an opinion was formulated on the forecast of the expected unit production costs and the output of the 259 longwalls planned to be mined at these mines. A procedure scheme was developed using the following methods: 1) Analytic Hierarchy Process (AHP) – mathematical multi-criteria decision-making method, 2) comparative multivariate analysis, 3) regression analysis, 4) Monte Carlo simulation. The utilitarian purpose of the monograph is to provide the research community with the concept of building models that can be used to solve real decision-making problems during longwall planning in hard coal mines. The layout of the monograph, consisting of an introduction, eight main sections and a conclusion, follows the objectives set out above. Section One presents the methodology used to assess the impact of onerous geological and mining conditions on the mining process. Multi-Criteria Decision Analysis (MCDA) is reviewed and basic definitions used in the following part of the paper are introduced. The section includes a description of AHP which was used in the presented analysis. Individual factors resulting from natural hazards, from the geological structure of the deposit (seam), from limitations caused by technical requirements, from the impact of mining on the environment, which affect the mining process, are described exhaustively in Section Two. Sections Three and Four present the construction of two hierarchical models of geological and mining conditions onerousness: the first in the context of extraction costs and the second in relation to daily longwall mining. The procedure for valuing the importance of their components by a group of experts (pairwise comparison of criteria and sub-criteria on the basis of Saaty’s 9-point comparison scale) is presented. The AHP method is very sensitive to even small changes in the value of the comparison matrix. In order to determine the stability of the valuation of both onerousness models, a sensitivity analysis was carried out, which is described in detail in Section Five. Section Six is devoted to the issue of constructing aggregate indices, WUe and WUt, which synthetically measure the impact of onerous geological and mining conditions on the mining process in individual longwalls and allow for a linear ordering of longwalls according to increasing levels of onerousness. Section Seven opens the research part of the work, which analyses the results of the developed models and indicators in individual mines. A detailed analysis is presented of the assessment of the impact of onerous mining conditions on mining costs in selected seams of the analysed mines, and in the case of the impact of onerous mining on daily longwall mining output, the variability of this process in individual fields (lots) of the mines is characterised. Section Eight presents the regression equations for the dependence of the costs and level of extraction on the aggregated onerousness indicators, WUe and WUt. The regression models f(KJC_N) and f(W) developed in this way are used to forecast the unit mining costs and daily output of the designed longwalls in the context of diversified geological and mining conditions. The use of regression models is of great practical importance. It makes it possible to approximate unit costs and daily output for newly designed longwall workings. The use of this knowledge may significantly improve the quality of planning processes and the effectiveness of the mining process.

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Book chapters on the topic "Temperature dependent electrical transport"

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Jahana, R., S. Kawaji, T. Okamoto, T. Fukase, T. Sakon, and M. Motokawa. "Transport Properties of the Half-Filled Landau Level in GaAs/AlGaAs Heterostructures: Temperature Dependence of Electrical Conductivity and Magnetoresistance of Composite Fermions." In Materials Science in Static High Magnetic Fields, 181–90. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/978-3-642-56312-6_13.

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Suryavanshi, Manmath, P. Karuppanan, Abhay Kumar Gautam, and Sreeteja Reddy Kotha. "A Temperature Dependent Modified TEAM Model." In Lecture Notes in Electrical Engineering, 357–68. Singapore: Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-19-2631-0_32.

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Farkas, Gábor. "Temperature-Dependent Electrical Characteristics of Semiconductor Devices." In Theory and Practice of Thermal Transient Testing of Electronic Components, 139–69. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-86174-2_4.

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Heer, R., J. Smoliner, J. Bornemeier, and H. Brückl. "Temperature Dependent Transport in Spin Valve Transistor Structures." In Nonequilibrium Carrier Dynamics in Semiconductors, 159–62. Berlin, Heidelberg: Springer Berlin Heidelberg, 2006. http://dx.doi.org/10.1007/978-3-540-36588-4_35.

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Njuguna, M. K., C. Yan, J. Bell, and P. Yarlagadda. "Temperature Dependent Electrical Resistivity in Epoxy—Multiwall Carbon Nanotube Nanocomposites." In Engineering Asset Management and Infrastructure Sustainability, 713–23. London: Springer London, 2012. http://dx.doi.org/10.1007/978-0-85729-493-7_55.

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Schweitzer, Ludwig. "Frequency Dependent Electrical Transport in the Integer Quantum Hall Effect." In Anderson Localization and Its Ramifications, 65–82. Berlin, Heidelberg: Springer Berlin Heidelberg, 2003. http://dx.doi.org/10.1007/978-3-540-45202-7_6.

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Steffen, Robert P. "Effect of RSR13 on Temperature-Dependent Changes in Hemoglobin Oxygen Affinity of Human Whole Blood." In Oxygen Transport to Tissue XX, 653–61. Boston, MA: Springer US, 1998. http://dx.doi.org/10.1007/978-1-4615-4863-8_77.

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Verma, Prateek Kishor, Akash Singh Rawat, and Santosh Kumar Gupta. "Temperature-Dependent Analog, RF, and Linearity Analysis of Junctionless Quadruple Gate MOSFETs for Analog Applications." In Lecture Notes in Electrical Engineering, 355–66. Singapore: Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-32-9775-3_32.

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Fritsch, G., A. Schulte, and E. Lüscher. "Low Temperature Transport Properties: The Electrical Resistivity of Some Amorphous Alloys." In Amorphous and Liquid Materials, 368–90. Dordrecht: Springer Netherlands, 1987. http://dx.doi.org/10.1007/978-94-009-3505-1_29.

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Thong, Trinh Quang, Nguyen Anh Minh, Nguyen Trong Tinh, Trieu Viet Phuong, and Dao Huy Du. "Measurement Setup for Temperature-Dependent Electrical Property of ZnO-Based Thermoelectric Thin Films." In Advances in Engineering Research and Application, 541–47. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-64719-3_60.

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Conference papers on the topic "Temperature dependent electrical transport"

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Thakore, B. Y., P. H. Suthar, S. G. Khambholja, P. N. Gajjar, N. K. Bhatt, A. R. Jani, S. K. Tripathi, Keya Dharamvir, Ranjan Kumar, and G. S. S. Saini. "Temperature Dependent Electrical Transport Properties of Ni-Cr and Co-Cr Binary Alloys." In INTERNATIONAL CONFERENCE ON ADVANCES IN CONDENSED AND NANO MATERIALS (ICACNM-2011). AIP, 2011. http://dx.doi.org/10.1063/1.3653657.

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Anjum, Nafisa, Riffat Ara Islam Ritu, Washik Adnan, Md Ittehad Hasan, and Md Faysal Nayan. "Numerical Analysis to Determine the Temperature-Dependent Charge Transport in CNTFET." In 2021 IEEE International Women in Engineering (WIE) Conference on Electrical and Computer Engineering (WIECON-ECE). IEEE, 2021. http://dx.doi.org/10.1109/wiecon-ece54711.2021.9829666.

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Wagenknecht, David, Karel Carva, and Ilja Turek. "Spin-dependent electrical transport at finite temperatures from the first principles." In Spintronics X, edited by Henri Jaffrès, Henri-Jean Drouhin, Jean-Eric Wegrowe, and Manijeh Razeghi. SPIE, 2017. http://dx.doi.org/10.1117/12.2273315.

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Ma, Weigang, Tingting Miao, and Xing Zhang. "Thermal and Electrical Transport Characteristics of Polycrystalline Gold Nanofilms." In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22328.

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The in-plane thermal and electrical conductivities of several suspended polycrystalline gold nanofilms with thickness of 20.0–54.0 nm have been measured simultaneously at 100–310 K. Both the thermal and electrical conductivities drop greatly compared to the corresponding bulk value, and the electrical conductivity reduction is larger. Fits to the temperature-dependent electrical conductivity confirm that the scattering of electrons by softened phonons is significant and cannot be reconciled with the classical size-effect model considering only surface and grain boundary. Taking into account the enhanced electron-phonon scattering, the electrical conductivity is well predicted over the whole temperature range and the obtained Debye temperature agrees well with the calculated value from the elastic continuum model. Furthermore, a new model on the thermal transport of metallic nanofilm is proposed based on the Energy Conservation Law, in which the electron-phonon scattering induced electron energy decrease is supposed to be counteracted by the phonon energy increase. The present model greatly improves the prediction of thermal conductivity in thin films compared to the corresponding result directly from electrical thermal analogy applied to bulk metals.

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Samuel, B. A., C. M. Lentz, and M. A. Haque. "Experimental Study of Structure-Electrical Transport Correlation in Single Disordered Carbon Nanowires." In ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-11739.

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We present experimental results characterizing the changes in electrical transport of single disordered carbon nanowires (diameter 150–250 nm) to the changes in microstructure within the nanowires induced by synthesis temperature. The material system studied is a nanoporous, semiconducting disordered carbon nanowire obtained from the pyrolysis of a polymeric precursor (polyfurfuryl alcohol). Unlike the other allotropes of carbon such as diamond, graphite (graphenes) and fullerenes (CNT, buckyballs), disordered carbons lack crystalline order and hence can exhibit a range of electronic properties, dependent on the degree of disorder and the local microstructure. Such disordered carbon nanowires are therefore materials whose electronic properties can be engineered to specifications if we understand the structure-property correlations. Using dark DC conductivity tests, measurements were performed from 300K to 450K. The charge transport behavior in the nanowires is found to follow an activation-energy based conduction at high temperatures. The conductivity for nanowires synthesized from 600°C to 2000°C is calculated and is linked to changes in the microstructure using data obtained from SEM, TEM and Raman spectroscopy. The electrical properties of the nanowire are shown to be linked intrinsically to the microstructure and the degree of disorder, which in turn can be controlled to a great extent just by controlling the pyrolysis temperature. This ability to tune the electrical property, specifically conductivity, and map it to the structural changes within the disordered material makes it a candidate material for use in active/passive electronic components, and as versatile transducers for sensors.

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Tang, Gong Yue, and Chun Yang. "Joule Heating Induced Temperature Gradient Focusing in a Microfluidic Channel With a Sudden Change in Cross Section." In ASME 2008 First International Conference on Micro/Nanoscale Heat Transfer. ASMEDC, 2008. http://dx.doi.org/10.1115/mnht2008-52197.

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Temperature gradient focusing is a recently developed technique for spatially focusing and separating ionic analytes in microchannels. The temperature gradient required for temperature gradient focusing can be generated either by an imposed temperature gradient or by Joule heating resulted from an applied electric field that also drives buffer flow. In this study, a numerical model describing the Joule heating induced temperature development and temperature gradient focusing is developed. The model consists of a set of governing equations including the Poisson-Boltzmann equation, the Laplace equation, the Navier-Stokes equations, the energy equations and the mass transport equation. As the thermophysical and electrical properties including the liquid dielectric constant, viscosity and electric conductivity are temperature-dependent, these governing equations are coupled, and therefore the coupled governing equations are solved numerically by using a CFD based numerical method. The numerical simulations agree well with the experimental results, suggesting that the valid mathematical model presented in this study.

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Tang, Gongyue, Chun Yang, Cheekiong Chai, and Haiqing Gong. "Electroosmotic Flow and Mass Species Transport in a Microcapillary Under Influences of Joule Heating." In ASME/JSME 2003 4th Joint Fluids Summer Engineering Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/fedsm2003-45124.

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This study presents a numerical analysis of Joule heating effect on the electroosmotic flow and species transport, which has a direct application in the capillary electrophoresis based BioChip technology. A rigorous mathematic model for describing the Joule heating in an electroosmotic flow including Poisson-Boltzmann equation, modified Navier-Stokers equations and energy equation is developed. All these equations are coupled together through the temperature-dependent parameters. By numerically solving aforementioned equations simultaneously, the electroosmotic flow field and the temperature distributions in a cylindrical microcapillary are obtained. A systematic study is carried out under influences of different geometry sizes, buffer solution concentrations, applied electric field strengths, and heat transfer coefficients. In addition, sample species transport in a microcapillary is also investigated by numerically solving the mass transfer equation with consideration of temperature-dependant diffusion coefficient and electrophoresis mobility. The characteristics of the Joule heating, electroosmotic flow, and sample species transport in microcapillaries are discussed. The simulations reveal that the presence of the Joule heating could have a great impact on the electroosmotic flow and sample species transport.

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Miller, A., R. J. Manning, and P. J. Bradley. "Optical Nonlinearities and Cross-Well Transport In Multiple Quantum Well Structures." In Quantum Wells for Optics and Opto-Electronics. Washington, D.C.: Optica Publishing Group, 1989. http://dx.doi.org/10.1364/qwoe.1989.mc1.

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Multiple quantum well (MQW) semiconductors provide a number of nonlinear optical effects associated with well resolved, room temperature, exciton absorption features. Refractive nonlinearities arising from the saturation of the exciton by phase space filling, and the electric field induced quantum confined Stark effect (QCSE) can both be used to produce nonlinear characteristics at low laser powers. We use these effects to monitor optically created excess carrier dynamics in GaAs/AlGaAs MQW structures at room temperature on picosecond timescales. In particular, we have determined the time constants relating to cross-well carrier diffusion by thermionic emission from quantum wells, and tunnelling through 60Å barriers in the presence of an electrical field. Measurement of the temperature dependence of four wave mixing decay rates allows a study of the thermionic emission process, while the voltage dependence of the build up time of the crosswell photocurrent establishes the latter. The differential emission rates for both processes will be discussed.

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Li, Yong Bing, Zhong Qin Lin, Li Li, and Guan Long Chen. "Numerical Analysis of Transport Phenomena in Resistance Spot Welding Process." In ASME 2009 Fluids Engineering Division Summer Meeting. ASMEDC, 2009. http://dx.doi.org/10.1115/fedsm2009-78210.

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Resistance Spot Welding (RSW) is a very complicated process involving electro-magnetic, thermal, fluid flow, mechanical and metallurgical variables. Since weld nugget area is close and unobservable with experimental means, numerical methods are mainly used to reveal the nugget formation mechanism. Traditional RSW models focus on the electro-thermal behaviors in the nugget, and do not have the ability to model mass transport caused by induced magnetic forces in the molten nugget. In this paper, a multi-physics model, which comprehensively considers the coupling of electric, magnetic, thermal and flow fields during RSW, temperature-dependent physical properties and phase transformation, is used to investigate the heat and mass transport laws in the weld nugget and to reveal the interaction of the heat and mass transports. Results show that the heat transport behaviors in the weld nugget, the profile of the nugget, and the thermal field evolution are significantly changed when the mass transport is considered. At the same time, a good agreement is also found between experimental and numerically calculated nugget sizes. As a result, when predicting crystal growth process, the effects of the mass transport should be considered in order to obtain a more accurate prediction results.

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Shimpalee, S., S. Dutta, and J. W. Van Zee. "Numerical Prediction of Local Temperature and Current Density in a PEM Fuel Cell." In ASME 2000 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/imece2000-1360.

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Abstract The heat generation inside polymer electrolyte membrane (PEM) fuel cells affects fuel cell performance significantly. A numerical model for three-dimensional single fuel cell is developed by including the energy equation and the phase change aspects. A control volume approach is used and source terms for species transport equations, heat generation, and phase change model are introduced to incorporate the coupled flow physics in commercial flow solvers. Details of local current density distribution and temperature profiles are obtained and predictions from this model are compared with previous conclusions. The results reveal that the water evaporation and condensation generated by temperature change in fuel cell control humidity of the membrane and vary the local current density value. Further, the temperature distributions are dependent on the amount of heat generation created by electrical losses and water phase change. The predictions also present that the performance of the fuel cell relies not only on the inlet humidity condition but also on the temperature change inside the fuel cell.

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Reports on the topic "Temperature dependent electrical transport"

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Weiss, W. Jason, Chunyu Qiao, Burkan Isgor, and Jan Olek. Implementing Rapid Durability Measure for Concrete Using Resistivity and Formation Factor. Purdue University, 2020. http://dx.doi.org/10.5703/1288284317120.

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The durability of in-place concrete is a high priority issue for concrete pavements and bridges. Several studies have been conducted by INDOT to use electrical resistivity as a measure of fluid transport properties. Resistivity is dependent on the chemistry of the cement and supplementary cementitious system used, as such it has been recommended that rather than specifying resistivity it may be more general to specify the formation factor. Samples were tested to establish the current levels of performance for concrete pavements in the state of Indiana. Temperature and moisture corrections are presented and acceptable accelerated aging procedure is presented. A standardized testing procedure was developed (AASHTO TP 119–Option A) resulting in part from this study that provides specific sample conditioning approaches to address pore solution composition, moisture conditioning, and testing procedures. An accelerated aging procedure is discussed to obtain later age properties (91 days) after only 28 days.

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Efthimion, P. C., D. K. Mansfield, B. C. Stratton, E. Synakowski, A. Bhattacharjee, H. Biglari, P. H. Diamond, et al. Observation of temperature dependent transport in TFTR. Office of Scientific and Technical Information (OSTI), October 1990. http://dx.doi.org/10.2172/6780591.

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Chan, Mun Keat. Magnetometry and electrical transport measurements of high temperature superconductors. Office of Scientific and Technical Information (OSTI), February 2017. http://dx.doi.org/10.2172/1343729.

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Friedman, Shmuel, Jon Wraith, and Dani Or. Geometrical Considerations and Interfacial Processes Affecting Electromagnetic Measurement of Soil Water Content by TDR and Remote Sensing Methods. United States Department of Agriculture, 2002. http://dx.doi.org/10.32747/2002.7580679.bard.

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Time Domain Reflectometry (TDR) and other in-situ and remote sensing dielectric methods for determining the soil water content had become standard in both research and practice in the last two decades. Limitations of existing dielectric methods in some soils, and introduction of new agricultural measurement devices or approaches based on soil dielectric properties mandate improved understanding of the relationship between the measured effective permittivity (dielectric constant) and the soil water content. Mounting evidence indicates that consideration must be given not only to the volume fractions of soil constituents, as most mixing models assume, but also to soil attributes and ambient temperature in order to reduce errors in interpreting measured effective permittivities. The major objective of the present research project was to investigate the effects of the soil geometrical attributes and interfacial processes (bound water) on the effective permittivity of the soil, and to develop a theoretical frame for improved, soil-specific effective permittivity- water content calibration curves, which are based on easily attainable soil properties. After initializing the experimental investigation of the effective permittivity - water content relationship, we realized that the first step for water content determination by the Time Domain Reflectometry (TDR) method, namely, the TDR measurement of the soil effective permittivity still requires standardization and improvement, and we also made more efforts than originally planned towards this objective. The findings of the BARD project, related to these two consequential steps involved in TDR measurement of the soil water content, are expected to improve the accuracy of soil water content determination by existing in-situ and remote sensing dielectric methods and to help evaluate new water content sensors based on soil electrical properties. A more precise water content determination is expected to result in reduced irrigation levels, a matter which is beneficial first to American and Israeli farmers, and also to hydrologists and environmentalists dealing with production and assessment of contamination hazards of this progressively more precious natural resource. The improved understanding of the way the soil geometrical attributes affect its effective permittivity is expected to contribute to our understanding and predicting capability of other, related soil transport properties such as electrical and thermal conductivity, and diffusion coefficients of solutes and gas molecules. In addition, to the originally planned research activities we also investigated other related problems and made many contributions of short and longer terms benefits. These efforts include: Developing a method and a special TDR probe for using TDR systems to determine also the soil's matric potential; Developing a methodology for utilizing the thermodielectric effect, namely, the variation of the soil's effective permittivity with temperature, to evaluate its specific surface area; Developing a simple method for characterizing particle shape by measuring the repose angle of a granular material avalanching in water; Measurements and characterization of the pore scale, saturation degree - dependent anisotropy factor for electrical and hydraulic conductivities; Studying the dielectric properties of cereal grains towards improved determination of their water content. A reliable evaluation of the soil textural attributes (e.g. the specific surface area mentioned above) and its water content is essential for intensive irrigation and fertilization processes and within extensive precision agriculture management. The findings of the present research project are expected to improve the determination of cereal grain water content by on-line dielectric methods. A precise evaluation of grain water content is essential for pricing and evaluation of drying-before-storage requirements, issues involving energy savings and commercial aspects of major economic importance to the American agriculture. The results and methodologies developed within the above mentioned side studies are expected to be beneficial to also other industrial and environmental practices requiring the water content determination and characterization of granular materials.

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Nasser, Abidelfatah, Charles Gerba, Badri Fattal, Tian-Chyi Yeh, and Uri Mingelgrin. Biocolloids Transport to Groundwater. United States Department of Agriculture, December 1997. http://dx.doi.org/10.32747/1997.7695834.bard.

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The first phase of the study was designed to determine the adsorption rate of viruses and microspheres to sandy and loamy soils and determine the adsorption efficiency of various viruses to soil. The adsorption of viruses to sandy and loamy soils has been found virus type dependent. The poorest adsorption was observed for MS2 bacteriophage while the greatest adsorption was observed for PRD-1. Adsorption sites on the soil material were not found as limiting factors for adsorption of viruses on soil material. The effect of water quality on adsorption has been found as virus type dependent. The adsorption process of microspheres to soil material has been found to be similar to that of viruses and occurs within a very short period of time. Carboxylated (negatively charged) microspheres seems to adsorb more efficiently than plain microspheres to soil material. At low temperatures (10oC), and under saturated conditions no virus die-off was observed, therefore under these conditions virus can survive for long period of time. At 23oC, and saturated conditions, the greatest die-off was observed for MS2 bacteriophage, whereas, negligible die-off was for PRD-1 bacteriophage and hepatitis A virus. Considering the survival results MS2 bacteriophages is not suitable as indicator for pathogenic viruses persistence in soil material. Furthermore, temperature, is more important than any other factor for the inactivation of viruses.

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Brosh, Arieh, David Robertshaw, Yoav Aharoni, Zvi Holzer, Mario Gutman, and Amichai Arieli. Estimation of Energy Expenditure of Free Living and Growing Domesticated Ruminants by Heart Rate Measurement. United States Department of Agriculture, April 2002. http://dx.doi.org/10.32747/2002.7580685.bard.

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Research objectives were: 1) To study the effect of diet energy density, level of exercise, thermal conditions and reproductive state on cardiovascular function as it relates to oxygen (O2) mobilization. 2) To validate the use of heart rate (HR) to predict energy expenditure (EE) of ruminants, by measuring and calculating the energy balance components at different productive and reproductive states. 3) To validate the use of HR to identify changes in the metabolizable energy (ME) and ME intake (MEI) of grazing ruminants. Background: The development of an effective method for the measurement of EE is essential for understanding the management of both grazing and confined feedlot animals. The use of HR as a method of estimating EE in free-ranging large ruminants has been limited by the availability of suitable field monitoring equipment and by the absence of empirical understanding of the relationship between cardiac function and metabolic rate. Recent developments in microelectronics provide a good opportunity to use small HR devices to monitor free-range animals. The estimation of O2 uptake (VO2) of animals from their HR has to be based upon a consistent relationship between HR and VO2. The question as to whether, or to what extent, feeding level, environmental conditions and reproductive state affect such a relationship is still unanswered. Studies on the basic physiology of O2 mobilization (in USA) and field and feedlot-based investigations (in Israel) covered a , variety of conditions in order to investigate the possibilities of using HR to estimate EE. In USA the physiological studies conducted using animals with implanted flow probes, show that: I) although stroke volume decreases during intense exercise, VO2 per one heart beat per kgBW0.75 (O2 Pulse, O2P) actually increases and measurement of EE by HR and constant O2P may underestimate VO2unless the slope of the regression relating to heart rate and VO2 is also determined, 2) alterations in VO2 associated with the level of feeding and the effects of feeding itself have no effect on O2P, 3) both pregnancy and lactation may increase blood volume, especially lactation; but they have no effect on O2P, 4) ambient temperature in the range of 15 to 25°C in the resting animal has no effect on O2P, and 5) severe heat stress, induced by exercise, elevates body temperature to a sufficient extent that 14% of cardiac output may be required to dissipate the heat generated by exercise rather than for O2 transport. However, this is an unusual situation and its affect on EE estimation in a freely grazing animal, especially when heart rate is monitored over several days, is minor. In Israel three experiments were carried out in the hot summer to define changes in O2P attributable to changes in the time of day or In the heat load. The animals used were lambs and young calves in the growing phase and highly yielding dairy cows. In the growing animals the time of day, or the heat load, affected HR and VO2, but had no effect on O2P. On the other hand, the O2P measured in lactating cows was affected by the heat load; this is similar to the finding in the USA study of sheep. Energy balance trials were conducted to compare MEI recovery by the retained energy (RE) and by EE as measured by HR and O2P. The trial hypothesis was that if HR reliably estimated EE, the MEI proportion to (EE+RE) would not be significantly different from 1.0. Beef cows along a year of their reproductive cycle and growing lambs were used. The MEI recoveries of both trials were not significantly different from 1.0, 1.062+0.026 and 0.957+0.024 respectively. The cows' reproductive state did not affect the O2P, which is similar to the finding in the USA study. Pasture ME content and animal variables such as HR, VO2, O2P and EE of cows on grazing and in confinement were measured throughout three years under twenty-nine combinations of herbage quality and cows' reproductive state. In twelve grazing states, individual faecal output (FO) was measured and MEI was calculated. Regression analyses of the EE and RE dependent on MEI were highly significant (P<0.001). The predicted values of EE at zero intake (78 kcal/kgBW0.75), were similar to those estimated by NRC (1984). The EE at maintenance condition of the grazing cows (EE=MEI, 125 kcal/kgBW0.75) which are in the range of 96.1 to 125.5 as presented by NRC (1996 pp 6-7) for beef cows. Average daily HR and EE were significantly increased by lactation, P<0.001 and P<0.02 respectively. Grazing ME significantly increased HR and EE, P<0.001 and P<0.00l respectively. In contradiction to the finding in confined ewes and cows, the O2P of the grazing cows was significantly affected by the combined treatments (P<0.00l ); this effect was significantly related to the diet ME (P<0.00l ) and consequently to the MEI (P<0.03). Grazing significantly increased O2P compared to confinement. So, when EE of grazing animals during a certain season of the year is estimated using the HR method, the O2P must be re measured whenever grazing ME changes. A high correlation (R2>0.96) of group average EE and of HR dependency on MEI was also found in confined cows, which were fed six different diets and in growing lambs on three diets. In conclusion, the studies conducted in USA and in Israel investigated in depth the physiological mechanisms of cardiovascular and O2 mobilization, and went on to investigate a wide variety of ruminant species, ages, reproductive states, diets ME, time of intake and time of day, and compared these variables under grazing and confinement conditions. From these combined studies we can conclude that EE can be determined from HR measurements during several days, multiplied by O2P measured over a short period of time (10-15 min). The study showed that RE could be determined during the growing phase without slaughtering. In the near future the development microelectronic devices will enable wide use of the HR method to determine EE and energy balance. It will open new scopes of physiological and agricultural research with minimizes strain on animals. The method also has a high potential as a tool for herd management.

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