Overview of development, design, testing and application of compact gas-insulated DC systems up to ±550 kV

The development of high-voltage direct current gas-insulated switchgear assemblies(DC GIS)of rated voltages up to±550 kV has been completed.DC GIS provide a compact technical solution with a high functional density,optimized for projects with limited space as in offshore HVDC converter platforms,onshore HVDC converter stations and transition stations between different transmission media.Up to now,no standards for testing of gas-insulated DC systems are available,although pre-standardization work is in progress within CIGRE.Some tests can be performed as required in AC GIS standards.Special aspects of DC voltage stress,like the electric field distribution of insulators influenced by the accumulation of electrical charge carriers and the operation-related inhomogeneous temperature distribution,must be considered by additional electric and thermoelectric tests.For DC GIS,the experience of long-term performance is limited today.Although ageing is expected to be of lower importance,tests are recommended.This contribution summarizes the physical and technical background to design and develop compact DC switchgear assemblies using gas-insulated technology.It explains the developed modules of the substation and gives an overview of the performed tests.Furthermore,it provides an insight in the on-going standardization activities and describes applications in converter and transition stations,showing its space-saving characteristics.

ZnO Interface Modified LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)Toward Boosting Lithium Storage

In this work,an amorphous ZnO was coated on LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)(NCM)using a sol-gel strategy method.The NCM coated with 1 wt.%Zn O and a thickness of about 3 nm exhibits an improved cycling performance,accompanied by a lower capacity fading(from 194.8 to 133.8 m Ah g^(-1),i.e.,68%)than that of the pristine one(i.e.,only 34%)after 300 cycles at 0.2 C.The cyclic voltammetry(CV)and electrochemical impedance spectroscopy(EIS)indicate that the Zn O coating can improve extraction/insertion of Li+and inhibit the increase in impedance of the NCM cathode material.This approach may benefit the performance improvement of the Ni-rich cathode materials in Lithium-ion batteries(LIBs).

Topography modulates effects of nitrogen deposition on microbial resource limitation in a nitrogen-saturated subtropical forest

Background:Nitrogen(N)saturation theory proposes that an ecosystem might switch from N limitation to carbon(C),phosphorus(P),or other nutrient limitations if it receives continuous N input.Yet,after N limitation is removed,which nutrient is the most limited and whether topography modulates such change is rarely tested at a microbial level.Here,we conducted a two-year N addition experiment under two different topography positions(i.e.a slope and a valley)in a N-saturated subtropical forest.Soil enzyme activity was measured,and ecoenzymatic stoichiometry indexes were calculated as indicators of microbial resource limitation.Results:In the valley,two-year N addition changed the activity of all studied enzymes to various degrees.As a result,microbial C limitation was aggravated in the valley,and consequently microbial decomposition of soil labile organic C increased,but microbial P limitation was alleviated due to the stoichiometry balance.On the slope,however,N addition did not significantly change the activity of the studied enzymes,and did not alter the status of microbial resource limitation.Conclusions:These results indicate that C is a more limited element for microbial growth than P after removing N limitation,but we also highlight that topography can regulate the effect of N deposition on soil microbial resource limitation in subtropical forests.These findings provide useful supplements to the N saturation theory.

光电化学氮还原:一种可持续的氨合成方法

氨是一种重要的化工产品和非碳基能源载体,全球年产量已达2亿吨.目前,氨的工业化生产主要依赖Haber-Bosch工艺,其能耗高且污染严重.因此亟需开发一种低碳环保的替代工艺以实现氨合成工业的可持续发展.现阶段主要有三种比较有发展潜力的新型氨合成工艺,即电催化、光催化和光电化学氮还原产氨技术.这些氮还原技术都可在温和环境条件下合成氨,具有能耗低、零排放等优势,被认为是替代Haber-Bosch工艺的有效途径,受到广泛关注.其中,与前两者相比,光电化学氮还原具有明显优势:与电催化氮还原相比,光电化学氮还原能够实现从太阳能到化学能的直接转化,具有较高的能量转化效率;而与光催化氮还原相比,光电化学氮还原系统中的外加偏压能够加速激子分离,有效提高太阳能到化学能的转化效率.在光电化学氮还原过程中,其核心组件光电阴极材料的性能决定了反应的氨产量、选择性和稳定性.本文总结了近年来光电化学氮还原领域的最新进展,特别是其中涉及的光阴极材料.首先,详细介绍了光电化学氮还原所涉及的基本原理和面临的主要瓶颈.其次,逐一总结了已报道的用于光电化学氮还原的光电阴极材料,包括氧化物(氧化铜、氧化亚铜、碘氧化铋、溴化氧铋和矾酸铋)、硫化物(硫化铜、硫化铟和硫化钼)、硒化物(硒化钼)、黑硅和黑磷等,并特别对其中所涉及的催化机理问题作了重点分析.最后,对该领域面临的未来发展方向和可能的解决方案提出了建议.其中,开发具有合适的能带结构、快速的激子分离、高的催化活性和选择性以及优异的稳定性的光阴极材料是光电化学氮还原技术走向实际应用的关键.此外,为了实现上述目标,本文还提出了八点切实可行的技术方案:高效的共催化剂、单原子和多原子团簇催化剂、异质结工程、三维有序结构、保护层、无偏压的光电化学系统、可靠的氨检测技术,以及硝酸盐还原等,以期在一定程度上推动光电化学氮还原领域的进一步发展.

Effect of bombarding energy on ion beam assisted deposited DLC film on UHMWPE

Diamond-like carbon (DLC) films on ultra-high molecular weight polyethylene substrates were prepared at CHn+ ion bombarding energies of 200-1000eV at room temperature using ion beam assisted deposition technique. The wear tests exhibited a high wear resistance for all DLC films. X-ray photoelectron spectfoscopy and Raman spectroscopy analysis indicated that DLC film was amorphous with a characteristic high fracdion of sp3 bonds in the structure of mixed sp:2+ sp3 bonding at an optimal bombardingenergy of 600eV.

Macro-and Micro-physical Characteristics of Different Parts of Mixed Convective-stratiform Clouds and Differences in Their Responses to Seeding

This study investigates the cloud macro-and micro-physical characteristics in the convective and stratiform regions and their different responses to the seeding for mixed convective-stratiform clouds that occurred in Shandong province on 21 May 2018,based on the observations from the aircraft,the Suomi National Polar-Orbiting Partnership(NPP)satellite,and the high-resolution Himawari-8(H8)satellite.The aircraft observations show that convection was deeper and radar echoes were significantly enhanced with higher tops in response to seeding in the convective region.This is linked with the conversion of supercooled liquid droplets to ice crystals with released latent heat,resulting in strengthened updrafts,enhanced radar echoes,higher cloud tops,and more and larger precipitation particles.In contrast,in the stratiform cloud region,after the Silver Iodide(AgI)seeding,the radar echoes become significantly weaker at heights close to the seeding layer,with the echo tops lowered by 1.4–1.7 km.In addition,a hollow structure appears at the height of 6.2–7.8 km with a depth of about 1.6 km and a diameter of about 5.5 km,and features such as icing seeding tracks appear.These suggest that the transformation between droplets and ice particles was accelerated by the seeding in the stratiform part.The NPP and H8 satellites also show that convective activity was stronger in the convective region after seeding;while in the stratiform region,a cloud seeding track with a width of 1–3 km appears 10 km downstream of the seeding layer 15 minutes after the AgI seeding,which moves along the wind direction as width increases.

Nanoscale Multilayered ZrAlN/ZrB_(2) Coatings Synthesized by Magnetron Sputtering

Multilayered ZrAlN/ZrB2 coatings containing alternating bilayer periods were synthesized by dc magnetron sputtering technique. The intensities of ZrN （111） or ZrN （200） textures in the structure of the nanolayers depended on the bilayer period as well as N2 gas partial pressure during deposition. Nanoindentation testing showed that hardness and internal stress of the nanolayers varied with the bilayer period and crystallographic orientation in the coatings. The hardness of the nanolayers with bilayer periods of 3-6 nm was enhanced （-27%） over the rule-of-mixture value. A low percent of N2 in processing gas was proved to be benefitial to the synthesis of high hard nanoscale multilayered coatings.

Spatially controlled lithium deposition on Li_(x)Cu_(y)P_(z) arrays enabling highly stable lithium metal batteries

Lithium(Li)metal is a potential anode for high-energy-density batteries because of its low potential and ultrahigh capacity.Nevertheless,the Li dendrites formation,the ununiform Li deposition,and the growth of Li dendrites hamper its application,especially under high deposition capacity/high rate.Here,a spatially controlled Li deposition mode with array-oriented morphology is achieved based on the novel mixed ion/electron-conducting Li_(x)Cu_(y)P_(z) arrays constructed on Cu foil,which can be facile fabricated via an in-situ transformation of metal phosphide.Theoretic calculations indicate the excellent lithiophilicity and low Li diffusion barrier of the arrays,especially for the Li_(2)CuP phase,which are conducive to ho-mogenizing the Li nucleation/deposition of Li.Moreover,such mixed conducting arrays promote fast Li+diffusion via the continuous Li+pathways as well as modulate the Li+flux/electric field.Furthermore,the arrays with enlarged specific surface area and open spaces reduce the local current density and alle-viate the volume fluctuation of Li.Consequently,a dendrite-free Li anode is obtained under a high rate(20 mA cm^(–2))or a high deposition capacity(10 mAh cm^(–2)).In addition,even if the negative/positive ratio reduces to only 1.1,the full cells still perform outstanding stability for over 200 cycles.This work empha-sizes the importance of the design of the framework in terms of the intrinsic properties and structure and reveals a pathway for developing Li metal batteries.

Identification and mapping of genes for improving yield from Chinese common wild rice (O.rufipogon Griff.) using advanced backcross QTL analysis

To identify useful genes from wild rice which have been lost or weakened in cultivated rice has become more and more important for modern breeding strategy. In this study, a BC4 population derived from 94W1, an accession of common wild rice (Oryza rufipogon Griff.) from Dongxiang in Jiangxi Province of China, as the donor, and a high-yielding Indica cultivar (O. sativa L.), 'Guichao 2', as the recipient, was used to identify quantitative trait loci (QTL) associated with yield and its components. Based on the analysis for the genotype of BC4F1 population with 87 SSR markers distributed throughout the genome and investigation of the plant height, yield and yield components of BC4F2, a total of 52 QTLs, were detected. Of 7 QTLs associated with grain yield per plant, 2 QTLs on chromosome 2 and chromosome 11 for grain yield, explaining 16% and 11% of the phenotypic variance respectively, were identified. The alleles from Dongxiang common wild rice in those two loci could increase the yield of 'Guichao 2' by

The Hardy Rubber Tree Genome Provides Insights into the Evolution of Polyisoprene Biosynthesis

Eucommia ulmoides, also called hardy rubber tree, is an economically important tree; however, the lack of its genome sequence restricts the fundamental biological research and applied studies of this plant species. Here, we present a high-quality assembly of its ~l.2-Gb genome （scaffold N50 = 1.88 Mb） with at least 26 723 predicted genes for E. ulmoides, the first sequenced genome of the order Garryales, which was obtained using an integrated strategy combining Illumina sequencing, PacBio sequencing, and BioNano mapping. As a sister taxon to lamiids and campanulids, E. ulmoides underwent an ancient genome triplication shared by core eudicots but no further whole-genome duplication in the last ~125 million years. E. ulmoides exhibits high expression levels and/or gene number expansion for multiple genes involved in stress responses and the biosynthesis of secondary metabolites, which may account for its considerable environmental adaptability. In contrast to the rubber tree （Hevea brasiliensis）, which produces cis-polyisoprene, E. ulmoides has evolved to synthe- size long-chain trans-polyisoprene via farnesyl diphosphate synthases （FPSs）. Moreover, FPS and rub- ber elongation factor/small rubber particle protein gene families were expanded independently from the H. brasiliensis lineage. These results provide new insights into the biology of E. ulmoides and the origin of polyisoprene biosynthesis.