Search

The high overpotential caused by the slow kinetics of oxygen reduction (ORR) and oxygen evolution (OER) has greatly limited the practical application of lithium‐oxygen (Li−O2) batteries. The adoption of force‐field‐assisted system based on a newly developed piezocatalysis is promising in reducing the overpotential. Herein, a force‐assisted Li−O2 battery is first established by employing MoS2/Pd nanocomposite cathode, in which the piezoelectric polarization as well as built‐in electric field are formed in MoS2 piezoelectric catalyst under ultrasound activation, leading to the continuously separated electrons and holes to enhance the ORR and OER kinetics. Moreover, the introduction of Pd can promote the electrons transfer and further inhibit the complexation of electron–hole pairs, contributing to enhanced catalytic activity in the decomposition/generation of discharge products, resulting in reduced discharge/charge overpotentials. Thus, the force‐assisted MoS2/Pd‐based Li−O2 battery is capable of adjusting the output and input energies by the assisted ultrasonic wave. An ultra‐low charging platform of 2.86 V and a high discharging platform of 2.77 V are achieved. The proposed unique force‐assisted strategy can also be applied to lithium carbon dioxide battery system through the effective reduction and separation of CO2 and CO32−, providing significant insights in achieving efficient energy conversion for metal−air batteries. [ABSTRACT FROM AUTHOR]

The atmospheric pressure measurement is closed related to the aircraft flight and it is the key factor directly affecting the aviation flight safety. With the development of aircraft, the barometric altitude measurement technology is more and more prominent and important. According to the barometric altitude measurement principle and the general barometric altitude measurement methods, four kinds of measurement methods of bellows, vibration cylinder, silicon resonant and silicon piezoresistance are analyzed with the principle and compared from the application.

This work develops a polarisation-tunable reflector that is based on a guided-mode resonant (GMR) filter with an integrated liquid-crystal (LC) polarisation rotator. The GMR filter serves as a linear polariser that strongly reflects linearly polarised light with high polarisation extinction ratio of 20:1 and sharp reflection band of ~20 nm in width. The LC polarisation rotator comprising an LC cell and quarter-wave plate can electrically control the polarisation orientation of the reflected light from the GMR. The required applied voltage for arbitrary polarisation rotation between 0° and 180° is less than 4.1 V. This dynamically tunable polarised reflector is also compact, integrable into optical circuits, and easily fabricated, showing high potential for practical and widespread applications. [ABSTRACT FROM AUTHOR]

Our understanding of relevant internal controls at the post-implementation phase remains limited in spite of general guidance from professional frameworks or standards. In this study, based on the COBIT 5 framework, we reviewed 56 studies from relevant academic journals from 1998 to 2014 to form an initial list of information technology (IT) internal control items for the post-implementation phase of enterprise resource planning (ERP) systems. An expert survey was conducted to validate the list, and 45 control items were ranked using the Delphi method. The proposed items may assist companies and auditors in focusing on essential internal control issues during the ERP system post-implementation phase. [ABSTRACT FROM AUTHOR]

Low-temperature sintering of 0.5Pb(Zn1/3Nb2/3)O3–0.5Pb(Zr0.47Ti0.53)O3 ceramics (0.5PZN–0.5PZT) was investigated using Li2CO3 as sintering aids. The addition of Li2CO3 significantly improved the sinterability of 0.5PZN–0.5PZT ceramics, resulting in a reduction of sintering temperature from 1100 to 950 °C. Moreover, the effect of Li2CO3 addition on the dielectric and piezoelectric responses in 0.5PZN–0.5PZT systems was systematically studied in this work. The analysis of x-ray diffraction patterns and scanning electron microscopy indicated that the solubility limit of Li ions in perovskite structures was near 0.5 wt % in Li2CO3 form. Below the solubility limit, Li+ ions entered the six-fold coordinated B sites of oxygenic octahedral center and enhanced the compositional fluctuation in nanoscale, resulting in the increase of the degree of diffuseness γ. While at high doping level above the solubility limit, γ decreased subsequently, which was attributed to the formation of pyrochlore phase. Raman analysis on the B-site cation order correlates well with the dielectric measurement results. The large improvements in the piezoelectric properties such as the coupling factor and piezoelectric constant were also observed for doped specimens. Optimized parameters, such as d33=278 pC/N, kp=0.50, and [variant_greek_epsilon]max=8800, were achieved by doping 0.5 wt % Li2CO3 in low-temperature sintered 0.5PZN–0.5PZT systems, which shows great promise as practical materials for multilayered piezoelectric device applications. The observed improvement in the electric properties can be attributed to the grain size effect. After doping, the clamping effect caused by oxygen vacancies and grain boundary phases on domain wall motion was largely reduced due to the increase of grain size; therefore, a significant reduced coercive field and an increased remanent polarization were observed in doped 0.5PZN–0.5PZT systems. [ABSTRACT FROM AUTHOR]

Relaxor ferroelectrics of 0.5Pb(Zn1/3Nb2/3)O3–0.5Pb(Zr0.47Ti0.53)O3 (0.5PZN–0.5PZT) near the morphotropic phase boundary (MPB) were prepared using the conventional oxide mixing method. The influence of sintering temperature on the phase transition and dielectrical response in the relaxor-ferroelectric-system 0.5PZN–0.5PZT has been investigated. X-ray diffraction analysis indicated that the phase of the material changed from an initially rhombohedral structure to a MPB structure and then a tetragonal structure when the sintering temperature is increased from 900 to 1250 °C. The corresponding grain size is enlarged from 1.1 μm for predominantly rhombohedral to 2.5 μm for more than 60% tetragonal, which obeys the common grain-growth law. The dielectric studies revealed that the indicator of the degree of diffuseness γ decreased with the increase of the sintering temperature from 900 to 1150 °C, indicating that the dielectric relaxor behavior was weakened, while at high sintering temperature above 1250 °C, γ increased subsequently, which was attributed to the Pb vacancy due to the formation of a pyrochlore phase. Raman analysis on the B-site cation order correlates well with the dielectric measurement results. [ABSTRACT FROM AUTHOR]