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Sökning: hsv:(TEKNIK OCH TEKNOLOGIER) hsv:(Annan teknik)

  • Resultat 1-10 av 6399
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  • Angenendt, Knut, et al. (författare)
  • Ionic liquid structures from large DFT calculations using mindless configurations
  • 2010
  • Ingår i: Journal of Physical Chemistry C. - 1932-7447. ; 114, s. 20577-20582
  • Tidskriftsartikel (refereegranskat)abstract
    • Three different popular imidazolium based ionic liquids (ILs); EMI-BF4, EMI-PF6, and EMI-TFSI, have been modeled by DFT calculations (B3LYP/6-311+G*) using large, up to 130 atom cluster models, for a better understanding of the structure and ion ion interactions in these ILs and ILs in general. Particular emphasis has been put on the role of appropriate starting structures and how the present large models differ from the ion-pair models of ILs generally used. The system size normalized ion ion interaction energies are shown to converge rapidly, and conformational equilibria and higher order properties like IR spectra are shown to be valuable as quality criteria. The explicit inclusion of an IL environment by the large cluster approach is also compared to using an implicit, continuum, strategy via SCRF C-PCM calculations.
  • Bengtsson, Lars, 1963- (författare)
  • Avancerad Elektrisk Mätteknik
  • 1996
  • Bok (övrigt vetenskapligt)abstract
    • Boken är avsedd för fortsättnigskurser i elektrisk mätteknik på högskolenivå. Den lämpar sig också väl som kompletteringslitteratur för kurser i signalbehandling. Innehållet är framför allt koncentrerat till analog och digital frekvensanalys, brusreducerande mätmetoder och AD/DA-omvandlingsmetoder. Ett kapitel tar upp signalbehandling och sambanden mellan analys i tid och rum. Fouriertransformen och faltningsintegralen gås igenom i detalj. Boken avslutas dels med ett kapitel om snabba förlopp i transmissionsledningar, dels med ett kapitel om GPIB-bussen. I appendix finns även en beskrivning av RS-232-kommunikation.
  • Bengtsson, Lars, 1963- (författare)
  • Electrical Measurement Systems and Methods
  • 2014
  • Bok (övrigt vetenskapligt)abstract
    • This book treats a wide range of aspects on electrical measurement systems and the methods used to acquire data from electronic systems. That includes sensors and sensor design, amplifiers such as differential and charge amplifiers, ADCs and DACs, digital oscilloscopes, cable theory and probes, noise and noise coupling, common and normal mode signals. This first part (chapters 1-8) doesn’t require any advanced mathematics and is aimed towards undergraduates. The second part (chapters 9-17) is on an advanced level (master level) and treats transform theory (Fourier, Laplace, z) and how to handle signals in frequency space. We cover the sampling theorem (Nyquist), resolution bandwidth, frequency spectrum distortions like aliasing and leakage and how to apply windows in a frequency spectrum. We also cover systems and signal processing in time-space, including convolution and correlation, filter theory and filter design (both analog and digital). The last chapters concern the statistical aspects on measurement systems and signals, like point and interval estimations, curve fitting and uncertainty estimations according to the GUM method.
  • Carini, Giovanni, et al. (författare)
  • Hypersonic attenuation in cesium borate glasses: Relaxation and anharmonicity
  • 2009
  • Ingår i: MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING. 15th International Conference on Internal Friction and Mechanical Spectroscopy (ICIFMS-15). Perugia, ITALY. JUL 20-25, 2008. - 0921-5093. ; 521-22, s. 247-250
  • Konferensbidrag (refereegranskat)abstract
    • The internal friction and the sound velocity in a cesium borate glass (Cs(2)O)(0.14)(B(2)O(3))(0.86) were measured at ultrasonic and hypersonic frequencies by Brillouin scattering measurements over the temperature range between 15 and 300 K. The analysis of the experimental results show that, in addition to thermally activated local motions of structural defects, the vibrational anharmonicity contributes substantially to the temperatures dependences of both the hypersonic loss and velocity. It has been also proved that above 150 K the vibrational anharmonicity appears to be governed by the Akhiezer mechanism of phonon viscosity.
  • Chen, Zhe, et al. (författare)
  • Nano-scale characterization of white layer in broached Inconel 718
  • 2017
  • Ingår i: Materials Science and Engineering A. - Elsevier. - 0921-5093. ; 684, s. 373-384
  • Tidskriftsartikel (refereegranskat)abstract
    • The formation mechanism of white layers during broaching and their mechanical properties are not well investigated and understood to date. In the present study, multiple advanced characterization techniques with nano-scale resolution, including transmission electron microscopy (TEM), transmission Kikuchi diffraction (TKD), atom probe tomography (APT) as well as nano-indentation, have been used to systematically examine the microstructural evolution and corresponding mechanical properties of a surface white layer formed when broaching the nickel-based superalloy Inconel 718.TEM observations showed that the broached white layer consists of nano-sized grains, mostly in the range of 20–50 nm. The crystallographic texture detected by TKD further revealed that the refined microstructure is primarily caused by strong shear deformation. Co-located Al-rich and Nb-rich fine clusters have been identified by APT, which are most likely to be γ′ and γ′′ clusters in a form of co-precipitates, where the clusters showed elongated and aligned appearance associated with the severe shearing history. The microstructural characteristics and crystallography of the broached white layer suggest that it was essentially formed by adiabatic shear localization in which the dominant metallurgical process is rotational dynamic recrystallization based on mechanically-driven subgrain rotations. The grain refinement within the white layer led to an increase of the surface nano-hardness by 14% and a reduction in elastic modulus by nearly 10% compared to that of the bulk material. This is primarily due to the greatly increased volume fraction of grain boundaries, when the grain size was reduced down to the nanoscale.
  • Cherednichenko, Sergey, 1970-, et al. (författare)
  • Online Detection of H2O and CO in the Humid Raw Gas from the Gasifier Using Terahertz Spectroscopy
  • 2013
  • Ingår i: ICPS, 13 International Conference on Polygeneration Strategies, Sept.5-13, Vienna, Austria. - 978-3-950275483 ; s. 51-58
  • Konferensbidrag (refereegranskat)abstract
    • The integration of a gasifier with a complex multistage synthesis process, such as SNG synthesis, demands a fast monitoring of the gasifier performance. However, despite the availability of standard analyzers for determination of dry gas composition, there are still many practical difficulties remaining in the online measurement of tar and steam in the raw gas. For the detection of steam concentration, electromagnetic waves at terahertz frequencies (102-104 GHz) are promising with regard to development of a robust online measurement device for industrial application. The main reason for the high potential is the low risk for interference with the wide range of other molecules and that the transmission of electromagnetic waves at THz frequencies is rather low sensitive to deposits and particulate matter in the course of the beam compared to the conventional and well established wavelengths like infrared. In the present work, a THz gas spectrometer was designed and constructed to check the feasibility of applying this measurement technique at industrial scale. For this purpose, continuous flows of raw gas with various water and CO contents from the Chalmers gasifier as well as a flue gas with known water content from the biomass combustor were introduced to the spectrometer set-up. H2O and CO compositions in each stream were determined in an online manner. The results confirmed the possibility of applying strong rotational water lines at 448 and 380 GHz to develop reliable devices for online measurement of water vapor with excellent error interval. However, some difficulties were encountered for simultaneous detection CO concentration with water within the frequency range studied in this work (300-500 GHz).
  • Cherednichenko, Sergey, 1970-, et al. (författare)
  • Terahertz Gas Spectrometer
  • 2014
  • Ingår i: Swedish Microwave Days March 11-12, 2014, Gothenburg, Sweden.
  • Konferensbidrag (refereegranskat)abstract
    • We present a 300-500GHz gas spectrometer built for and practically tested at the 2–4-MW indirect gasifier at the Chalmers Power Center. The primary goal is precise online measurements of H2O vapor and CO concentrations in the producer gas. Experimentally obtained H2O vapor concentration resolution was about 1% at the conditions of 50% VMR and 400 deg.C.
  • Chernikova, Dina, 1982-, et al. (författare)
  • Development of the Neutron-Gamma-Neutron (NGN) approach for the fresh and spent fuel assay
  • 2012
  • Ingår i: Proceedings of The 53nd Annual Meeting of the Institute of Nuclear Materials Management.
  • Konferensbidrag (övrigt vetenskapligt)abstract
    • In connection with current safety and complexity limitations for installations which use keV neutrons for irradiation in the fresh and spent fuel assay, in medicine, geophysical and detection fields, there is a long felt need of effective, light, inexpensive systems with longer lifetimes and the possibility to ”switch off” the source during transportation and work break. The present paper discusses an opportunity of creating a novel technique based on using a pulsed neutron generator, hydrogen moderator and beryllium, which will enable creation of a compact and inexpensive facility capable to satisfy all requirements. The main idea of the proposed method consists in using photonuclear reaction in beryllium due to gamma irradiation originating from (n,gamma) reaction in a hydrogen containing moderator. After the neutron pulse of a modern compact DD neutron generator in hydrogen-containing moderator, high-energy neutrons (approximately 2.5 MeV) get slowed down mainly by elastic scattering to near thermal energies. At thermal energies, the neutrons diffuse through the material until they undergo thermal capture (capture is dominated by hydrogen neutron absorbers). When a hydrogen atom captures a thermal neutron, it turns into deuterium with the release of a large component of 2.23 MeV gamma-rays. Beryllium is one of the few elements in nature that undergoes a photonuclear reaction with this gamma energy range (e.g. deuterium has a low energy 2.225 MeV photonuclear threshold). Thus, as the beryllium has lower neutron-binding energy, 1.667 MeV (photonuclear reaction threshold), a photonuclear reaction will take place with emission of neutrons with energy defined by the kinematic equation. Thus, this method allows to obtain a high quality epithermal neutron beam without using a complex system with particle accelerator or radioisotope sources with limited decay time. The proposed method has been studied using Monte Carlo simulations, which made it possible to define the theoretical limits of the use of the NGN approach in industrial applications. The paper will presents the results of these investigations.
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