Synthesis of Hollow Three-Dimensional Channels LiNi_(0.5)Mn_(1.5)O_4 Microsphere by PEO Soft Template Assisted with Solvothermal Method

A appropriate size with three-dimension(3 D) channels for lithium diffusion plays an important role in constructing highperforming LiNi_(0.5)Mn_(1.5)O_4(LNMO) cathode materials, as it can not only reduce the transport path of lithium ions and electrons, but also reduce the side effects and withstand the structural strain in the process of repetitive Li~+ intercalation/deintercalation. In this work, an e fficient method for designing the hollow LNMO microsphere with 3 D channels structure by using polyethylene oxide(PEO) as soft template agent assisted solvothermal method is proposed. Experimental results indicate that PEO can make the reagents mingle evenly and nucleate slowly in the solvothermal process, thus obtaining a homogeneous distribution of carbonate precursors. In the final LNMO products, the hollow 3 D channels structure obtained by the decomposition of PEO and carbonate precursor in the calcination can provide abundant electroactive zones and electron/ion transport paths during the charge/discharge process, which benefits to improve the cycling performance and rate capability. The LNMO prepared by adding 1 g PEO possesses the most outstanding electrochemical performance, which presented an excellent discharge capacity of 143.1 mAh g~(-1) at 0.1 C and with a capacity retention of 92.2% after 100 cycles at 1 C. The superior performance attributed to the 3 D channels structure of hollow microspheres, which provide uninterrupted conductive systems and therefore achieve the stable transfer for electron/ion.     

Waveguide external cavity narrow linewidth semiconductor lasers

Narrow linewidth light source is a prerequisite for high-performance coherent optical communication and sensing.Waveguide-based external cavity narrow linewidth semiconductor lasers(WEC-NLSLs)have become a competitive and attractive candidate for many coherent applications due to their small size,volume,low energy consumption,low cost and the ability to integrate with other optical components.In this paper,we present an overview of WEC-NLSLs from their required technologies to the state-of-the-art progress.Moreover,we highlight the common problems occurring to current WEC-NLSLs and show the possible approaches to resolving the issues.Finally,we present the possible development directions for the next phase and hope this review will be beneficial to the advancements of WEC-NLSLs.     

不同晶相结构ZrO2负载铜基催化剂用于二乙醇胺脱氢反应

通过制备不同晶相结构〔单斜相(m-ZrO_2)、四方相(t-ZrO_2)和无定型(a-ZrO_2)〕ZrO_2载体,再通过沉积沉淀法制得Cu/m-ZrO_2、Cu/t-ZrO_2和Cu/a-ZrO_2催化剂,分别用于催化二乙醇胺脱氢合成亚氨基二乙酸反应。采用XRD、氮气物理吸附脱附、XPS、H_2-TPR、CO_2-TPD对催化剂的结构进行了表征。结果表明,Cu/m-ZrO_2催化剂界面更加有利于Cu~+/Cu~0稳定存在,具有更多的碱性位点,且抗氧化性较好。在二乙醇胺脱氢反应中,Cu/m-ZrO_2催化剂性能最好,反应时间为2.5 h,亚氨基二乙酸收率为97.64%。     

Covalent triazine framework with efficient photocatalytic activity in aqueous and solid media

Covalent triazine frameworks (CTFs) have been recently employed for visible light-driven photocatalysis due to their unique optical and electronic properties. However, the usually highly hydrophobic nature of CTFs, which originates from their overall aromatic backbone, leads to limitations of CTFs for applications in aqueous media. In this study, we aim to extend the range of the application media of CTFs and design hybrid material of a CTF and mesoporous silica (SBA-15) for efficient photocatalysis in aqueous medium. A thiophene-containing CTF was directly synthesized in mesopores of SBA-15. Due to the high surface area and the added hydrophilic properties by silica, the hybrid material demonstrated excellent adsorption of organic molecules in water. This leads not only to high photocatalytic performance of the hybrid material for the degradation of organic dyes in water, but also for efficient photocatalysis in solvent-free and solid state. Furthermore, the reusability, stability and easy recovery of the hybrid material offers promising metal-free heterogeneous photocatalyst for broader applications in different reaction media.     

Erratum to: Suspended superconducting weak links from aerosol-synthesized single-walled carbon nanotubes

Erratum to Nano Research 2020,13(12):3433-3438 https://doi.org/101007/s12274-020-3032-1 The article“Suspended superconducting weak links from aerosol-synthesized single-walled carbon nanotubes"written by Jukka-Pekka Kaikkonen1(■),Abhilash Thanniyil Sebastian3,Patrik Laiho3,Nan Wei3,Marco Will-2,Yongping Liao3,Esko I.Kauppinen3,and Pertti J.Hakonen1,2(■),was originally published Online First without Open Access.     

Dynamic Flow Control Strategies of Vehicle SCR Urea Dosing System

Selective Catalyst Reduction(SCR)Urea Dosing System(UDS)directly affects the system accuracy and the dynamic response performance of a vehicle.However,the UDS dynamic response is hard to keep up with the changes of the engine's operating conditions.That will lead to low NO_χconversion efficiency or NH_3 slip.In order to optimize the injection accuracy and the response speed of the UDS in dynamic conditions,an advanced control strategy based on an air-assisted volumetric UDS is presented.It covers the methods of flow compensation and switching working conditions.The strategy is authenticated on an UDS and tested in different dynamic conditions.The result shows that the control strategy discussed results in higher dynamic accuracy and faster dynamic response speed of UDS.The inject deviation range is improved from being between-8%and 10%to-4%and 2%and became more stable than before,and the dynamic response time was shortened from 200 ms to 150 ms.The ETC cycle result shows that after using the new strategy the NH_3 emission is reduced by 60%,and the NO_χemission remains almost unchanged.The trade-off between NO_χconversion efficiency and NH_3 slip is mitigated.The studied flow compensation and switching working conditions can improve the dynamic performance of the UDS significantly and make the UDS dynamic response keep up with the changes of the engine's operating conditions quickly.     

公共健康导向下的拉萨城市空间设计探讨

21世纪以来,全球范围内频发的重大公共卫生事件对公共健康带来巨大压力,需思考城市设计与公共健康存在的内在联系,基于公共健康需求,不断优化城市设计.研究回顾公共健康与城市设计的历史与演变历程,分析国内外公共健康与城市设计的理论基础,基于此次疫情下城市设计暴露出的问题,以拉萨市为例,尝试探究引发城市公共健康问题的不利因素以及公共健康引导下城市空间设计的优化策略.     

Synthesis and Characterization of Pr0.6-xNdxCa0.4FeO3-δ with Pechini Method

Pr0.6-x NdxCa0.4 FeO3-δ （ x = 0.0, 0.2, 0.3, 0.4, 0.5, 0.6） were synthesized using Pechini method. A number of studies were conducted concerning composition, specific area, crystalline structure and microstructure of the samples by means of FT-IR, BET, XRD TG-DTA and SEM. The results show that all the samples with different doping amounts of Pr^3＋ and Nd^3＋ on A-site are fine dispersed, and mean particle size less than 100 nm. The powders have good sinterability, and the relative density is 95% after sintered at 1200 ℃ for 2 h. It is found that all specimens are entirely single phase solid solutions with orthorhombic perovskite structure, the stable perovskitetype phase is formed completely after calcination at 900 ℃.     

R-Calculus for ELP:An Operational Approach to Knowledge Base Maintenance

Sme concepts used in knowledge base maintenace,such as sequence,new law,user‘s rejection and reconstructions of a knowledge base,are first introduced,and then a framework for extended logic programming(ELP)is given,where an extended logic program is equivalent to a knowledge base.A transition system called R-calculus for ELP is provided.For a given knowledge base and a user‘s rejection,the R-calculus for ELP will deduce best revisions of the base.The soundness and the completeness of the R-calculus for ELP are proved,and the R-calculus for ELP is implemented in Prolog.In addition,the research is compared with other relevant work.     

Synthesis and Characterization of Poly （L-lactide-co-ε-caprolactone） Copolymers

A series of random and block poly（ L-lactide-co-e-caprolactone ） （ PCLA ） copolymers whh different composition are prepared using stannous octaoate as catalyst.The effects of the amount of initiator on the intrinsic viscosity have been investigated. The structure of the PCLA copolymers is characterized by means of nuclear magnetic resonance（ NMR ）, Fourier transform infrared spectrum （ FTIR ）, differential scanning calorimetry （ DSC ） and X- ray diffraction （ XRD ） methods. It is shown that the synthesis condition and the composition of copolymers obrious influence on the structure of PCLA copolymers. Hydrolytic degradation of the copolymers in a PBS solution of pH 7.4 at 37.0℃ shows that the copolymers of different composhions degrade at different rates.