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Published: 20 September 2019
IOP Conference Series: Materials Science and Engineering, Volume 595; doi:10.1088/1757-899x/595/1/011001
Abstract: The National Conference on Thermodynamics with International Participation (NACOT2019) held in Galaţi is the 22nd meeting of a series of conferences initiated in 1990 by the Romanian Society of Thermotechnics (SRT). NACOT2019 was organized by the Department of Thermal Systems and Environmental Engineering, Faculty of Engineering from "Dunărea de Jos" University of Galati in collaboration with the Romanian Association of Frigotehnists and Cryogenics (AFCR). More than 80 academicians, researchers, industry professionals, experts in thermodynamics from 14 countries participated and presented papers at the event. The conference topics included: applied thermodynamics, heat and mass transfer, fluid mechanics and CFD, refrigeration and heat pumps, power plants and CHP, internal combustion engines, renewable energy, energy use and storage, environmental impact of energy conversion. The conference offered participants the opportunity to present new research, discuss the results, exchange ideas and establish links between different research directions in the field. The format of the conference was based on plenary presentations, oral presentations, poster presentations, and presentations of equipment and technologies. The NACOT2019 organizing committee thanks the reviewers, plenary speakers and sponsors. NACOT2019 organizing committee
Published: 20 September 2019
IOP Conference Series: Materials Science and Engineering, Volume 595; doi:10.1088/1757-899x/595/1/011002
Abstract: All papers published in this volume of IOP Conference Series: Materials Science and Engineering have been peer reviewed through processes administered by the proceedings Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.
Measurement Science and Technology; doi:10.1088/1361-6501/ab466d
Abstract: In concrete structures, damage is identified by the appearance of cracks on the surface. Monitoring the level of tensile stress in the material provides an indication of microcrack localization, which leads to the formation of a crack in the medium. In this study, the stress in the substrate leading to the localized cracking in a concrete substrate is evaluated using surface mounted PZT patches. The PZT patches are used in a local electrical impedance (EI) measurement mode and for distributed stress wave measurements. The EI measurements from PZT patches sensitively detect the tensile stress in the substrate. The localization of damage resulting in the formation of a crack in the concrete medium is detected sensitively by stress wave measurements. A frequency-dependent attenuation factor, which is independent of the intervening material effects is presented for quantifying the changes in the stress waves. The localization of microcracks leading to the formation of a crack is detected by the attenuation factor measurements of stress waves significantly before visual detection of a surface crack. The combined use of the EI measurement with the distributed stress wave attenuation allows for detecting stress and microcracking in the concrete leading up to the formation of a localized crack. The attenuation factor gives an indication of the crack opening once the crack is formed.
Environmental Research Letters; doi:10.1088/1748-9326/ab466e
Abstract: Past studies on CO2 utilization in the concrete industry have primarily focused on maximizing sequestered CO2, while focusing less on CO2 avoidance possible by reducing binder use through the addition of CO2 to concrete formulations. In this paper, we study the net CO2 reduction and cost benefits achievable by reducing binder loading while adding CO2 via three approaches: carbonation during curing, carbonation during mixing, or carbonation with recycled concrete aggregate. These techniques are evaluated for a cohort of concrete formulations representing the diverse mixture designs found in the U.S. ready-mixed and precast industries. Each formulation is optimized for reduced binder loading where the use of CO2 directly in the formulation recovers the lost compressive strength from reduced binder. We show that over an order of magnitude more CO2 can be avoided when binder reduction is jointly implemented with CO2 utilization compared to utilizing CO2 alone. As a result, nearly 40% of the annual CO2 emissions from the U.S. concrete industry could, in principle, be eliminated without relying on novel supplemental materials, alternative binder, or carbon capture and sequestration. The recently amended 45Q tax credit will not incentivize this strategy, as it only considers carbon sequestration. However, we find that the saved material cost from reduced binder use on its own may provide a significant economic incentive to promote the joint strategy in practice. We conclude that the real value of CO2 utilization in concrete hinges on exploiting CO2-induced property changes to yield additional emission reduction, not by maximizing absorbed CO2.
Superconductor Science and Technology; doi:10.1088/1361-6668/ab4665
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Materials Research Express; doi:10.1088/2053-1591/ab4668
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Materials Research Express; doi:10.1088/2053-1591/ab4663
Abstract: Nickel oxide (NiO) is one of the most promising transparent conducting oxides for optoelectronic and electrochemical devices. Sol-gel prepared NiO thin films were calcined at different annealing temperatures (AT) and characterized by XRD, Raman, AFM, UV-vis-NIR spectroscopy, and water contact angle () measurements. Raman spectra showed two main bands at 560 and 1079 cm−1, arising from O–O planar and Ni–O stretching vibrations, respectively. AFM analysis illustrated that AT enhances the silkworm-like morphology and the films' roughness. XRD, Raman, and AFM confirmed the crystallinity improvement after annealing. The films are highly transparent (40 – 97%) and their bandgap decreased from 4.05 to 3.88 eV. The refractive index, porosity, packing density as well as the dispersion parameters were sensitive to AT. The un-annealed film is hydrophilic. The films' wettability decreased significantly with AT. Based on the obtained results, the films are a candidate for electrochemical, transparent heat mirrors and optical windows applications.
New Journal of Physics; doi:10.1088/1367-2630/ab466f
Abstract: We study the elastic scattering time τS of ultracold atoms propagating in optical disordered potentials in the strong scattering regime, going beyond the recent work of J. Richard et al., Phys. Rev. Lett. 122 100403 (2019). There, we identified the crossover between the weak and the strong scattering regimes by comparing direct measurements and numerical simulations to the first order Born approximation. Here we focus specifically on the strong scattering regime, where first order Born approximation is not valid anymore and the scattering time is strongly influenced by the nature of the disorder. To interpret our observations, we connect the scattering time τS to the profiles of the spectral functions that we estimate using higher order Born perturbation theory or self-consistent Born approximation. The comparison reveals that self-consistent methods are well suited to describe τS for Gaussian-distributed disorder, but fails for laser speckle disorder. For the latter, we show that the peculiar profiles of the spectral functions, as measured independently in V. Volchkov et al., Phys. Rev. Lett. 120, 060404 (2018), must be taken into account. Altogether our study characterizes the validity range of usual theoretical methods to predict the elastic scattering time of matter waves, which is essential for future close comparison between theory and experiments, for instance regarding the ongoing studies on Anderson localization
Materials Research Express; doi:10.1088/2053-1591/ab465e
Abstract: A series of epitaxial thin films of PrNi0.5Mn0.5O3-δ (~12 nm) were grown on single crystal LSAT [(LaAlO3)0.3(Sr2AlTaO6)0.7] substrate by pulsed laser deposition method. With a purpose to vary oxygen content in the films, the in-situ oxygen annealing time was varied (0 to 5 min)during the thin film formation. One film was not annealed after the deposition in order to create high oxygen deficiency. This oxygen-deficient film grew with a different tensile strain. In spite of oxygen variation, all the films of this series show epitaxial growth [00l] on LSAT. Temperature-dependent resistivity and magnetization measurement were performed over a temperature range of 300K to10K. All the films show insulating behavior. The temperature-dependent magnetization shows two transitions in the system finally leading to a magnetically frustrated state at low temperatures. These results indicate that Ni and Mn sub-lattices order in antiparallel spin-states in these thin films. A comparative study of magnetization in polycrystalline bulk PrMn0.5Ni0.5O3 and these thin films shows that the epitaxial strain and oxygen content strongly influences the overall magnetic behavior of this system.
Materials Research Express; doi:10.1088/2053-1591/ab4676
Abstract: In the present study, the effects of boron and zirconium on the microstructure and high-temperature tensile properties of Nimonic 105 superalloy were evaluated. For this purpose, three alloys with different contents of boron and zirconium (0.003 wt.% B-0 wt. % Zr, 0.013 wt.% B-0 wt.% Zr, 0.003 wt.% B- 0.16%wt.% Zr) were prepared via VIM+ ESR process. Optical and scanning electron microscopes, X-ray diffraction analysis and tensile testing at 25 and 700 ̊C were used to describe the alloys structure and properties. The results showed that the microstructure of the 0.003 wt.% B-0 wt. % Zr alloy consisted of thin-film (Cr, Mo)23C6 and blocky (Ti, Mo)C phases in the γ matrix. The addition of zirconium changed the type of carbide to MC one while boron improved the formation of discrete M23C6-type carbide. The XRD analysis results revealed an increase in the lattice misfit of the γ/γ´ phase for the B and Zr-added alloy, a decrease in the M23C6/γ misfit for the B-added alloy and the MC/γ phase misfit for the Zr-added alloy. In addition, a significant effect of zirconium on grain size were observed in the alloys. Boron and zirconium decreased the ductility at room temperature by 3 % and 6 % and increased it at 700 ̊C by 7 % and 13 %, respectively. Moreover, boron and zirconium increased the high-temperature yield strength by 9 % and 13% and ultimate tensile strength by 9 % and 16 %, respectively.