Giant electrocaloric response in the prototypical Pb(Mg,Nb)O3_{3} relaxor ferroelectric from atomistic simulations

An atomistic effective Hamiltonian is used to investigate electrocaloric (EC) effects of Pb(Mg$_{1/3}$Nb$_{2/3}$)O$_{3}$ (PMN) relaxor ferroelectrics in its ergodic regime, and subject to electric fields applied along the pseudocubic [111] direction. Such Hamiltonian qualitatively reproduces (i) the electric field-versus-temperature phase diagram, including the existence of a critical point where first-order and second-order transitions meet each other; and (ii) a giant EC response near such critical point. It also reveals that such giant response around this critical point is microscopically induced by field-induced percolation of polar nanoregions. Moreover, it is also found that, for any temperature above the critical point, the EC coefficient-versus-electric field curve adopts a maximum (and thus larger electrocaloric response too), that can be well described by the general Landau-like model proposed in [Jiang et al, Phys. Rev. B 96, 014114 (2017)] and that is further correlated with specific microscopic features related to dipoles lying along different rhombohedral directions. Furthermore, for temperatures being at least 40 K higher than the critical temperature, the (electric field, temperature) line associated with this maximal EC coefficient is below both the Widom line and the line representing percolation of polar nanoregions.Comment: 6 pages, 5 figure

Andreev Reflection without Fermi surface alignment in High Tc_{c}-Topological heterostructures

We address the controversy over the proximity effect between topological materials and high T$_{c}$ superconductors. Junctions are produced between Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ and materials with different Fermi surfaces (Bi$_{2}$Te$_{3}$ \& graphite). Both cases reveal tunneling spectra consistent with Andreev reflection. This is confirmed by magnetic field that shifts features via the Doppler effect. This is modeled with a single parameter that accounts for tunneling into a screening supercurrent. Thus the tunneling involves Cooper pairs crossing the heterostructure, showing the Fermi surface mis-match does not hinder the ability to form transparent interfaces, which is accounted for by the extended Brillouin zone and different lattice symmetries

Multichannel fiber Bragg grating for temperature field monitoring

We demonstrate a multichannel fiber Bragg grating (MC-FBG) based distributed temperature field sensor with millimeter-order spatial resolution. The MC-FBG was designed by using the layer peeling (LP) algorithm with a tailored group delay characteristic and fabricated using seamless UV-inscription. We have achieved a 21-channel MC-FBG with 0.2 nm bandwidth of each channel and 0.5 nm channel gap. The sensor was tested by using a temperature field distribution. Experimental results show that the sensor had a spatial resolution of 3 mm and could measure a maximum temperature gradient of 7.85 °C/mm

Treatment of port wastes according to the paradigm of the circular economy

The problem of the presence of waste in the marine environment has recently taken on the dimensions of a complex and global challenge. In an effort to reduce both the economic and environmental costs of managing port waste, many ports are looking for sustainable solutions for marine waste management. Plasma-assisted gasification (PAG) is an innovative combination of two technologies, namely plasma treatment and gasification, which can be used to efficiently convert carbon-containing wastes to a clean syngas (H2 + CO). The latter can be used to generate electricity directly in gas engines, dual-fuel generators, gas turbines or fuel cells. PAG provides several key benefits which allow removing all the environmental, regulatory and commercial risks typically associated with the potential eco-toxicity of leachable bottom ash produced by incinerators or other thermal processes. PAG does not produce any waste (zero waste), reduces the need for landfilling of waste, and produces a high-value construction material (Plasmarok) which is recognized as a product. All these reasons make PAG a technology capable of optimally solving waste management in ports in line with a circular economy logic. This study is based upon the IMPATTI-NO Project (Interreg IT-FR Maritime Program 2014–2020) which implements several laboratory applications aimed at the chemical-physical treatment of the non-recyclable waste containing plastics deriving from the collection of beached waste and wastes collected by fishermen’s trawls and passenger ships. To demonstrate the effectiveness of PAG for the treatment of port waste, IMPATTI-NO performs experimental tests that simulate PAG pilot plants using artificial samples representative of port waste. This paper describes the research path developed so far and the preparatory elements that led to the definition of specifications for the sampling and collection of port waste

Broadband Radio Spectral Observations of Solar Eclipse on 2008-08-01 and Implications on the Quiet Sun Atmospheric Model

Based on the joint-observations of the radio broadband spectral emissions of solar eclipse on August 1, 2008 at Jiuquan (total eclipse) and Huairou (partial eclipse) at the frequencies of 2.00 -- 5.60 GHz (Jiuquan), 2.60 -- 3.80 GHZ (Chinese solar broadband radiospectrometer, SBRS/Huairou), and 5.20 -- 7.60 GHz (SBRS/Huairou), the authors assemble a successive series of broadband spectrum with a frequency of 2.60 -- 7.60 GHz to observe the solar eclipse synchronously. This is the first attempt to analyze the solar eclipse radio emission under the two telescopes located at different places with broadband frequencies in the periods of total and partial eclipse. With these analyses, the authors made a new semiempirical model of the coronal plasma density of the quiet Sun and made a comparison with the classic models.Comment: 10 pages, 4 figures, published on Sci. China Ser. G, 2009, Vol.52, page 1765-177

Manipulating Multiple Order Parameters via Oxygen Vacancies: The case of Eu0.5Ba0.5TiO3-{\delta}

Controlling functionalities, such as magnetism or ferroelectricity, by means of oxygen vacancies (VO) is a key issue for the future development of transition metal oxides. Progress in this field is currently addressed through VO variations and their impact on mainly one order parameter. Here we reveal a new mechanism for tuning both magnetism and ferroelectricity simultaneously by using VO. Combined experimental and density-functional theory studies of Eu0.5Ba0.5TiO3-{\delta}, we demonstrate that oxygen vacancies create Ti3+ 3d1 defect states, mediating the ferromagnetic coupling between the localized Eu 4f7 spins, and increase an off-center displacement of Ti ions, enhancing the ferroelectric Curie temperature. The dual function of Ti sites also promises a magnetoelectric coupling in the Eu0.5Ba0.5TiO3-{\delta}.Comment: Accepted by Physical Review B, 201

Signature splitting inversion and backbending in 80Rb

High spin states of 80Rb are studied via the fusion-evaporation reactions 65Cu+19F, 66Zn+18O and 68Zn+16O with the beam energies of 75 MeV, 76 MeV and 80 MeV, respectively. Twenty-three new states with twenty-eight new \gamma transitions were added to the previously proposed level scheme, where the second negative-parity band is significantly pushed up to spins of 22^{-} and 15^{-} and two new sidebands are built on the known first negative-parity band. Two successive band crossings with frequencies 0.51 MeV and 0.61 MeV in the \alpha=0 branch as well as another one in the \alpha=1 branch of the second negative-parity band are observed for the first time. Signature inversions occur in the positive- and first negative-parity bands at the spins of 11\hbar and 15\hbar, respectively. The signature splitting is seen obviously in the second negative-parity band, but the signature inversion is not observed. It is also found that the structure of the two negative-parity bands is similar to that of its isotone ^{82}Y. Signature inversion in the positive-parity yrast band with configuration \pi g_{9/2} \otimes \nu g_{9/2} in this nucleus is discussed using the projected shell model (PSM)