A UNIQUENESS THEOREM FOR HOLOMORPHIC MAPPINGS IN THE DISK SHARING TOTALLY GEODESIC HYPERSURFACES

In this paper,we prove a Second Main Theorem for holomorphic mappings in a disk whose image intersects some families of nonlinear hypersurfaces(totally geodesic hypersurfaces with respect to a meromorphic connection) in the complex projective space P^(k).This is a generalization of Cartan’s Second Main Theorem.As a consequence,we establish a uniqueness theorem for holomorphic mappings which intersect O(k^(3)) many totally geodesic hypersurfaces.

The Mechanism of Voltage Instability Analysis Considering Load Characteristic

Load characteristics are the main factor to affect voltage stability. In addition, load modeling reflecting the actual load characteristics has been a well—known difficult problem and unsolved so far, It is mainly due to the fact that the load composition, amount and characteristics are always changing. This paper introduces the slip into the equivalent impedance load model to analyze load characteristic, the varying slip is employed to indicate?time-varying load characteristic precisely, and considering the dissimilar load behaviors, discusses node voltage, power during the changes of load characteristic, obtains voltage inflexion and power inflexion, and then analyzes the mechanism of power system voltage instability based on static voltage stability region. An example indicates the feasibility of the method.

Solution-processed D-A-π-A-D radicals for highly efficient photothermal conversion

Organic donor-acceptor semiconductors exhibit great potential in photothermal conversion.However,it is still challenging to achieve pure organic materials with broad absorption comparable with inorganic materials such as graphene.Herein,two D-AD type DPA-BT-O4 and NDI-TPA-O4 and three D-A-π-A-D type Th-O4,Th2-O4,and IDT-O4 were readily prepared via two high-yield steps and simple air oxidization.The stability can be attributed to their multiple resonance structures based on the aromatic nitric acid radical mechanism.Compared with the D-A-D radicals,the conjugation extension of the D-A-π-A-D radicals endows them with a narrowed band gap and broad absorption in powder.Interestingly,the IDT-O4 powder with aggregation-induced radical effect exhibits broad absorption between 300 and 2500 nm,which is comparable with graphene and other inorganic materials.Under irradiation of 0.9 W/cm^(2)(808 nm),the temperature of IDT-O4 powder rises to 250℃within 60 s.The water evaporation conversion efficiency of 94.38%and an evaporation rate of 1.365 kg/m^(2)h^(−1)under one sun illumination were achieved.IDT-O4 stands as one of the most efficient photothermal conversion materials among pure organic materials via a rational design strategy.

Stable Electron Spin Pan on Aromatic Oxalic Acid Radical

The stability of organic radicals in ambient condition is important for their practical application.During the development of organic radical chemistry,the electron-withdrawing and steric hindrance groups are usually introduced to improve the stability of radicals via reducing the reactivity of radicals with oxygen in air.Herein,the electron-withdrawing carbonyl groups are introduced to construct a planar aromatic oxalic acid radical(IDF-Og)with two-dimensional electron spin pan structure.Interestingly,IDF-Og exhibited a low optical bandgap of 0.91 eV in film,however,the multiple quinone resonance structures between electron-withdrawing ketone and phenol radicals contribute to the high stability of open-shell radical IDF-Og without protection of large steric hindrance groups.Under the irradiation of 808 nm(1.2 W.cm^(-2)),IDF-Og reaches 147 c in powder state.This work provides an efficient synthesis route for the open-shell electron spin pan system,which is different from the famous fullerene,carbon nanotube and graphene.The electron spin pan can be extended to spin tube or spin sphere system based on the design strategy of aromatic inorganic acid radicals in future.

中国熊蜂多样性、人工利用与保护策略

熊蜂是众多野生植物和农作物的重要传粉者,在维持自然和农业生态系统平衡中发挥着十分重要的作用。中国地形多样、植被丰富,是全球熊蜂多样性的热点地区,但过去缺乏系统调查研究,中国熊蜂多样性现状及其利用特性不详。本文介绍了近20年在中国熊蜂资源系统调查及其人工利用方面取得的主要研究结果:(1)2002–2017年采集熊蜂标本5万余号,先后揭示了一系列疑难类群的分类地位,确认中国已知熊蜂125种,占全球熊蜂已知物种总数的50%,表明中国是全球熊蜂物种资源最丰富的国家;(2)首次报道了中国熊蜂物种名录,其中22种为中国特有种。我国青藏高原东部向黄土高原、秦岭山地和四川盆地过渡的地带,是全球熊蜂多样性分布中心;(3)1998–2017年,明亮熊蜂(Bombus lucorum)、密林熊蜂(B.patagiatus)、红光熊蜂(B.ignitus)、火红熊蜂(B.pyrosoma)、重黄熊蜂(B.picipes)和兰州熊蜂(B.lantschouensis)6种本土熊蜂先后被驯养成功,其中密林熊蜂和兰州熊蜂的繁殖性状优良,已应用于我国设施作物传粉服务。同时,我们从栖息地、食物资源、外来物种、农药使用等方面提出了保护中国熊蜂资源的策略,以期为野生传粉昆虫特别是熊蜂资源的保护与可持续利用提供参考资料。

Crystallographic engineering of Zn anodes for aqueous batteries

With their intrinsic safety and environmental benignity,aqueous Zn-ion batteries(ZIBs)have been considered the most appropriate candidates for replacing alkali metal systems.However,polycrystalline Zn anodes in aqueous environments still pose enormous issues,such as dendrite growth and side reactions.Although many efforts have been made to address these obstacles through interphase modification and electrolyte design,researchers have not been able to improve the inherent thermodynamic stability and ion deposition behavior of the Zn anode.It is imperative to understand and explore advanced anode construction methods from the perspective of crystallinity.This review delves into the feasibility of precisely regulating the crystallographic features of metallic zinc,examines the challenges and merits of reported strategies for fabricating textured zinc,and offers constructive suggestions for the large-scale production and commercial application of aqueous ZIBs.

Fluidized Electrocatalysis

Particle-based electrocatalysts need to be glued on an electrode,where fast and slow steps of the reaction are spatially and temporally convoluted near the particles.Since the particles are under continuous electrochemical stress,decay in their catalytic performance(a.k.a.,fatigue)often occurs due to degradation of the active materials,detachment of particles and deteriorating kinetics.Here we report that these problems are well addressed by fluidizing the particles.The catalysts,instead of being fixed on an electrode,are now fluidized in the electrolyte.Reaction occurs when individual particles collide with the electrode,which collectively delivers a continuous,scalable and stable electrochemical current.Since the catalysts now work in rotation,they experience much faster kinetics and avoid the buildup of excessive electrochemical stress,leading to orders of magnitude higher particle-average efficiency and greatly enhanced fatigue resistance.Proof-ofconcepts are demonstrated using Pt/C catalysts for three well-known reactions,including oxygen evolution,hydrogen evolution and methanol oxidation reactions,all of which suffer severe performance decay using Pt/C under different mechanisms.Fluidized electrocatalysis breaks the spatial and temporal continuum of electrocatalytic reactions,and makes them drastically more fatigue resistant.It is material-and reaction-agnostic,and should be a general approach to enhance electrocatalytic reactions.

Self-Healing Microcapsule-Thickened Oil Barrier Coatings

Low-viscosity oils could potentially act as self-healing barrier coatings because they can readily fow and reconnect to heal minor damage.For the same reason,however,they typically do not form stable coatings on metal surfaces.Increasing viscosity helps to stabilize the oil coating,but it also slows down the healing process.Here,we report a strategy for creating highly stable oil coatings on metal surfaces without sacrifcing their remarkable self-healing properties.Low-viscosity oil flms can be immobilized on metal surfaces using lightweight microcapsules as thickeners,which form a dynamic network to prevent the creep of the coating.When the coating is scratched,oil around the opening can rapidly fow to cover the exposed area,reconnecting the particle network.Use of these coatings as anticorrosion barriers is demonstrated.Te coatings can be easily applied on metal surfaces,including those with complex geometries,both in air or under water,and remain stable even in turbulent water.Tey can protect metal in corrosive environments for extended periods of time and can self-heal repeatedly when scratched at the same spot.Such a strategy may ofer efective mitigation of the dangerous localized corrosion aggravated by minor imperfections or damage in protective coatings,which are typically hard to prevent or detect,but can drastically degrade metal properties.

Wear calculation of sandblasting machine based on EDEM-FLUENT coupling

Sandblasting machines are widely used in chemical, mechanical and other engineering fields. The internal flow field of the sandblasting machine belongs to a complex gas-solid two-phase flow, and impact by the continuous abrasive sand can cause the machine to wear or even fail. In this study, the EDEM-FLUENT coupling method was used to calculate the transient flow field of the gas phase and the motion, dynamic and collision characteristics of the sand. Air in the sandblasting machine was treated as the ideal gas and the continuous phase. The sand was regarded as the discrete phase solid in the computation. Using the Archard wear model, the wear amount of the sandblasting machine was calculated and the wear law was analysed, to provide a theoretical basis for optimising the design and operation method of the blasting machine.

Wear calculation of sandblasting machine based on EDEM-FLUENT coupling

Sandblasting machines are widely used in chemical,mechanical and other engineering fields.The internal flow field of the sandblasting machine belongs to a complex gas-solid two-phase flow,and impact by the continuous abrasive sand can cause the machine to wear or even fail.In this study,the EDEM-FLUENT coupling method was used to calculate the transient flow field of the gas phase and the motion,dynamic and collision characteristics of the sand.Air in the sandblasting machine was treated as the ideal gas and the continuous phase.The sand was regarded as the discrete phase solid in the computation.Using the Archard wear model,the wear amount of the sandblasting machine was calculated and the wear law was analysed,to provide a theoretical basis for optimising the design and operation method of the blasting machine.

Welcome to Accounts of Materials Research

I am an immigrant,and I came from chemistry.My first few quarters at the Materials Science and Engineering Department at Northwestern as an Assistant Professor were filled with the stress but also the excitement of learning to excel in a new language(e.g.,teaching materials courses that I never took myself)and adapting to a new culture(e.g.,the discipline of materials is diverse and dynamic yet still shares some basic guiding principles).1,2 It turned out to be a transformative experience that I quickly found rewarding.