Evidance for an Oxygen Diffusion Model for the Electric Pulse Induced Resistance Change Effect in Oxides

Electric pulse induced resistance (EPIR) switching hysteresis loops for Pr0.7Ca0.7MnO3 (PCMO) perovskite oxide films were found to exhibit an additional sharp "shuttle peak" around the negative pulse maximum for films deposited in an oxygen deficient ambient. The device resistance hysteresis loop consists of stable high resistance and low resistance states, and transition regions between them. The resistance relaxation of the "shuttle peak" and its temperature behavior as well as the resistance relaxation in the transition regions were studied, and indicate that the resistance switching relates to oxygen diffusion with activation energy about 0.4eV. An oxygen diffusion model with the oxygen ions (vacancies) as the active agent is proposed for the non-volatile resistance switching effect in PCMO.Comment: 7 pages, 5 figure

Improvement of ride quality for patient lying in ambulance with a new hydro-pneumatic suspension

© The Author(s) 2019. Instability caused by emergency braking and steering during ambulance operation would easily lead to a sharp rise of blood pressure in patient’s head, which would further cause a secondary injury to the patient. Furthermore, the vibration generated by uneven road would result in patient’s nausea and deterioration of patient’s condition. This article proposes a pitch–roll-interconnected hydro-pneumatic suspension system which can achieve the resistance control for pitch, roll, and bounce modes of ambulances to improve the stability and attenuate the vibration for the lying patients. The ambulance with pitch–roll-interconnected hydro-pneumatic suspension is characterized by 7 degrees of freedom dynamic model, in which the characteristics of pitch–roll-interconnected hydro-pneumatic suspension are explicitly formulized using hydrodynamic equation derivation. A motion-mode energy spectral density method is proposed to decouple the vibration energy for bounce, pitch, and roll modes in frequency domain. Subsequently, the parameter design approach incorporated with the suspension characteristic equations and motion-mode energy spectral density method is also presented to optimize the lying patient’s ride comfort and ambulance’s handling stability. The numerical simulation results show that the proposed pitch–roll-interconnected hydro-pneumatic suspension system can simultaneously provide pitch–roll–stiffness and damping without generating additional bounce-stiffness, resulting in superior ride comfort and handling stability compared to the conventional suspension

A low cost desktop electrochemical metal 3D printer

Additive manufacturing (AM), or 3D printing as it is more commonly known, is the process of creating 3D objects from digital models through the sequential deposition of material in layers. Electrochemical 3D printing is a relatively new form of AM that creates metallic structures through electrochemical reduction of metal ions from solutions onto conductive substrates. The advantage of this process is that a wide range of materials and alloys can be deposited under ambient conditions without thermal damage and more importantly at low cost, as this does not require expensive laser optics or inert gas environments. Other advantages include the fact that this process can be both additive and subtractive through reversal of potential allowing for recycling of components through electrochemical dissolution. However, one main limitation of this technology is speed. Here, a novel electrochemical 3D printer design is proposed using a meniscus confinement approach which demonstrates deposition rates three orders of magnitude higher than equivalent systems due to improved mass transport characteristics afforded through a mechanical electrolyte entrainment mechanism. Printed copper structures exhibit a polycrystalline nature, with decreasing the grain size as the potential is increased resulting in a higher Vickers hardness and electronic resistivity

Monte Carlo Simulation of HERD Calorimeter

The High Energy cosmic-Radiation Detection (HERD) facility onboard China's Space Station is planned for operation starting around 2020 for about 10 years. It is designed as a next generation space facility focused on indirect dark matter search, precise cosmic ray spectrum and composition measurements up to the knee energy, and high energy gamma-ray monitoring and survey. The calorimeter plays an essential role in the main scientific objectives of HERD. A 3-D cubic calorimeter filled with high granularity crystals as active material is a very promising choice for the calorimeter. HERD is mainly composed of a 3-D calorimeter (CALO) surrounded by silicon trackers (TK) from all five sides except the bottom. CALO is made of 9261 cubes of LYSO crystals, corresponding to about 55 radiation lengths and 3 nuclear interaction lengths, respectively. Here the simulation results of the performance of CALO with GEANT4 and FLUKA are presented: 1) the total absorption CALO and its absorption depth for precise energy measurements (energy resolution: 1\% for electrons and gamma-rays beyond 100 GeV, 20\% for protons from 100 GeV to 1 PeV); 2) its granularity for particle identification (electron/proton separation power better than $10^{-5}$); 3) the homogenous geometry for detecting particles arriving from every unblocked direction for large effective geometrical factor ($>$3 ${\rm m}^{2}{\rm sr}$ for electron and diffuse gamma-rays, $>$2 ${\rm m}^{2}{\rm sr}$ for cosmic ray nuclei); 4) expected observational results such as gamma-ray line spectrum from dark matter annihilation and spectrum measurement of various cosmic ray chemical components

Experimental demonstration of counterfactual quantum key distribution

Counterfactual quantum key distribution provides natural advantage against the eavesdropping on the actual signal particles. It can prevent the photon-number-splitting attack when a weak coherent light source is used for the practical implementation. We realized the counterfactual quantum key distribution in an unbalanced Mach-Zehnder interferometer of 12.5-km-long quantum channel with a high-fringe visibility of 96:4%. As a result, we obtained secure keys against the noise-induced attack (eg. the vacuum attack) and passive photon-number-splitting attack.Comment: 5 pages, 3 figure

Dirac Line-nodes and Effect of Spin-orbit Coupling in Non-symmorphic Critical Semimetal MSiS (M=Hf, Zr)

Topological Dirac semimetals (TDSs) represent a new state of quantum matter recently discovered that offers a platform for realizing many exotic physical phenomena. A TDS is characterized by the linear touching of bulk (conduction and valance) bands at discrete points in the momentum space (i.e. 3D Dirac points), such as in Na3Bi and Cd3As2. More recently, new types of Dirac semimetals with robust Dirac line-nodes (with non-trivial topology or near the critical point between topological phase transitions) have been proposed that extends the bulk linear touching from discrete points to 1D lines. In this work, using angle-resolved photoemission spectroscopy (ARPES), we explored the electronic structure of the non-symmorphic crystals MSiS (M=Hf, Zr). Remarkably, by mapping out the band structure in the full 3D Brillouin Zone (BZ), we observed two sets of Dirac line-nodes in parallel with the kz-axis and their dispersions. Interestingly, along directions other than the line-nodes in the 3D BZ, the bulk degeneracy is lifted by spin-orbit coupling (SOC) in both compounds with larger magnitude in HfSiS. Our work not only experimentally confirms a new Dirac line-node semimetal family protected by non-symmorphic symmetry, but also helps understanding and further exploring the exotic properties as well as practical applications of the MSiS family of compounds.Comment: 5 figure

Time variable cosmological constant of holographic origin with interaction in Brans-Dicke theory

Time variable cosmological constant (TVCC) of holographic origin with interaction in Brans-Dicke theory is discussed in this paper. We investigate some characters for this model, and show the evolutions of deceleration parameter and equation of state (EOS) for dark energy. It is shown that in this scenario an accelerating universe can be obtained and the evolution of EOS for dark energy can cross over the boundary of phantom divide. In addition, a geometrical diagnostic method, jerk parameter is applied to this model to distinguish it with cosmological constant.Comment: 10 pages, 9 figure