A new MnxOy/carbon nanorods derived from bimetallic Zn/Mn metal–organic framework as an efficient oxygen reduction reaction electrocatalyst for alkaline Zn-Air batteries

Journal of Solid State Electrochemistry - In this work, nanorods like bimetallic Zn/Mn metal–organic-frameworks (MOFs) are proposed as the precursor for preparing MnxOy/porous carbon...     

Wide-viewing-angle switchable image splitter obtained using varied-line-spacing H-PDLC Bragg grating

We propose the use of a varied-line-spacing (VLS) holographic polymer-dispersed liquid crystal (H-PDLC) Bragg grating as a switchable image splitter to generate a compatible three-dimensional (3D) stereogram and to increase the viewing angle of the observer. To fabricate the VLS grating, a cylindrical lens is adopted to form a cylindrical wave, which interferes with a plane wave, generating an H-PDLC grating with a continuously varying period. The proposed holographic optical element (HOE)-based image splitter comprises two VLS H-PDLC gratings. It can be attached on a designed pattern, with two rectangles taking the place of conventional liquid crystal display panel pixels, and can separate them into right and left viewing fields with a wider range. Experimental results show that the movement of the eyes of the observer can reach 37.6 mm. A theoretical simulation indicates that a shorter focal length of the cylindrical lens can yield a larger movement range. Switching between two-dimensional and 3D modes can be performed by applying an external alternating-current voltage at ~80 V. The contrast ratio of the diffracted images induced by crosstalk is greater than 60%, which indicates the feasibility of the proposed HOE for 3D image splitting.     

纳米银掺杂的高效率全息聚合物分散液晶光栅制备

报道了一种基于掺杂纳米银聚合物分散液晶(PDLC)材料的高衍射率全息电控光栅的制备及特性。通过在原有聚合物分散液晶材料体系中添加适量的纳米银颗粒以制备体全息光栅,实验研究了掺杂不同质量比的纳米银颗粒对全息聚合物分散液晶(H-PDLC)体光栅的衍射效率、驱动阈值电压、响应时间的影响。实验结果表明,通过掺杂纳米银材料,能够优化聚合物和液晶两相分离结构,使聚合物与液晶分离更加彻底,显著提高H-PDLC体光栅的一级衍射效率,同时能改善体光栅的电光特性,缩短响应时间。初步分析表明,由于纳米银颗粒的表面等离子体效应和体系折射率匹配的优化改善了H-PDLC光栅的特性。     

Natural convection in shallow enclosures with multiple conducting partitions

Laminar natural convection and conduction in shallow enclosures having multiple partitions with finite thickness and conductivity have been studied. An approximate analytical solution is obtained by using the parallel flow approximation in horizontal shallow enclosures heated isothermally at two vertical ends while adiabatic on horizontal end walls. The same problem is solved also using a finite difference formulation and the control volume method. The study covers the range ofRa from 105 to 107,A=H/L0.2, C=1/L from 0 to 0.15, and the thermal conductivity ratio of partition to fluidk _r from 10^–4 to 10¹¹. The partition numberN was varied from 0 to 5. The Prandtl number was 0.72 (for air). The results are reduced in terms ofNu as a function ofRa, k, and various geometrical parameters (A, C). The streamlines and isotherms are produced to visualize the flow and temperature fields.Es wird der kombinierte Einfluß von laminarer Naturkonvektion und Leitung in flachen Behältern mit mehreren Trennwänden endlicher Dicke und Leitfähigkeit untersucht. Eine analytische Näherungslösung läßt sich über die Parallelstromapproximation bezüglich horizontaler flacher Behälter finden, deren zwei vertikale Begrenzungswände isotherm beheizt sind, während die Horizontalflächen adiabat sein sollen. Das selbe Problem wird unter Verwendung eines Differenzverfahrens und der Kontrollvolumen-Methode gelöst und zwar für die Parameterbereiche 105 Ra 10⁷;A=H/L<0.2;>C=1/L 0.15; 10^–4k_r 1011, wobei der letzte Parameter das Verhältnis der Leitfähigkeit von Trennwand und Fluid bezeichnet. Die Zahl der TrennwändeN variierte Zwischen 0 und 5, die Prandtl-Zahl betrug 0.72 (Luft). Die Ergebnisse werden in dimensionsloser Form gemäß der BeziehungNu =f (Ra, k _r ,A, C) mitgeteilt bzw. durch Diagrammdarstellungen der Stromlinien- und Isothermenfelder veranschaulicht.Financial support from the Natural Sciences and Engineering Council Canada is acknowledged. Financial support to A. Kangni from Canadian Fellowship Program For French Speaking Countries is also acknowledged.     

Enhanced wavelength-sensitivity of volume holographic grating with dual-photoinitiation system in polymer-dispersed liquid crystal

We propose a method to improve the wavelength-sensitivity of a volume holographic grating by mixing dual-photoinitiation dopants, namely, rose bengal (RB)/N-phenylglycine (NPG) system and methylene blue (MB)/p-toluenesulfonic acid (PTSA) system, which enable the fabrication of gratings upon both green and red light illumination. The RB/NPG green light photoinitiation system is chosen in combination with the red-active MB/PTSA system because RB and MB absorb light near 567 and 665 nm independently. In this case, the holographic gratings, recorded in polymer-dispersed liquid crystal, can be fabricated simultaneously by two different visible laser lights with an output wavelength of 532 and 632.8 nm. The electro-optical performances of the gratings exposed upon 532 and 632.8 nm have been implemented: the diffraction efficiencies (DE) are 75% and 57% respectively when the exposure time is optimised to 2 min and 17 min; the threshold voltage is approximately 2.9 V/μm. The enhanced wavelength-sensitivity of holographic gratings allows for the storage of three-dimensional (3D) images on the same hologram plate, and these 3D images are easily reconstructed by both red and green light.