InP quantum dots-based electroluminescent devices

Indium phosphide(InP) quantum dots(QDs) have shown great potential to replace the widely applied toxic cadmiumcontaining and lead perovskite QDs due to their similar emission wavelength range and emission peak width but without intrinsic toxicity. Recently, electrically driven red and green InP-based quantum-dot light-emitting diodes(QLEDs) have achieved great progress in external quantum efficiency(EQE), reaching up to 12.2% and 6.3%, respectively. Despite the relatively poor device performance comparing with cadmium selenide(CdSe)-and perovskite-based QLEDs, these encouraging facts with unique environmental friendliness and solution-processability foreshadow the enormous potential of InP-based QLEDs for energy-efficient, high-color-quality thin-film display and solid-state lighting applications. In this article, recent advances in the research of the InP-based QLEDs have been discussed, with the main focus on device structure selection and interface research, as well as our outlook for on-going strategies of high-efficiency InP-based QLEDs.

Numerical simulations of dense granular flow in a two-dimensional channel:The role of exit position

Molecular dynamics simulations have been performed to elucidate the influence of exit position on a dense granular flow in a two-dimensional channel. The results show that the dense flow rate remains constant when the exit is far from the channel wall and increases exponentially when the exit moves close to the lateral position. Beverloo’s law proves to be successful in describing the relation between the dense flow rate and the exit size for both the center and the lateral exits.Further simulated results confirm the existence of arch-like structure of contact force above the exit. The effective exit size is enlarged when the exit moves from the center to the lateral position. As compared with the granular flow of the center exit, both the vertical velocities of the grains and the flow rate increase for the lateral exit.

Head-on Collision of Solitary Waves Described by the Toda Lattice Model in Granular Chain

We study the head-on collision of two solitary waves in a precompressed granular chain using the discrete element method.Our study takes the Toda chain solution as the initial condition for the simulations.The simulation covers the dynamical evolution of the collision process from the start of the incident wave to the end of the collision.The interaction has a central collision region of about five-grain width in which two solitary waves merge completely and share only one peak.Four stages,i.e.,the pre-in-phase traveling stage,lag-phase collision state,lead-phase collision state,and post-in-phase traveling stage,are identified to describe the complex collision processes.Our results may be helpful for explaining the existence of long-lived solitary waves seen in the simulations by Takato and Sen[Europhys.Lett.100(2012)24003].

Research on Real-time Data Sharing in Power Integrated Automation System

The Power Integrated Automation System has a large amount of the real-time data, it needs to achieve data sharing in different modules in its own system, sometimes even needs to be shared with the other systems. The thesis discusses the characteristics and the ways of the real-time data sharing in the first place. Then, it compares the merits and drawbacks in different ways. Besides, it gives a viable resolution in different aspects, such as the design of the real-time database, the framework of the communication system and the design of the communication software, as well as the real-time data sharing in different systems.

Construction of NiCo_(2)O_(4) nanoflake arrays on cellulose-derived carbon nanofibers as a freestanding electrode for high-performance supercapacitors

Cellulose has a wide range of applications in many fields due to their naturally degradable and low-cost characteristics,but few studies can achieve cellulose-nanofibers by conventional electrospinning.Herein,we demonstrate that the freestanding cellulose-based carbon nanofibers are successfully obtained by a special design of electrospinning firstly,pre-oxidation and high-temperature carbonization(1600℃),which display a superior electrical conductivity of 31.2 S·cm^(-1)and larger specific surface area of 35.61 m^(2)·g^(-1)than that of the polyacrylonitrile-based carbon nanofibers(electrical conductivity of 18.5 S·cm^(-1),specific surface area of 12 m^(2)·g^(-1).The NiCo_(2)O_(4)nanoflake arrays are grown uniformly on the cellulose-based carbon nanofibers successfully by a facile one-step solvothermal and calcination method.The as-prepared cellulose-based carbon nanofibers/NiCo_(2)O_(4)nanoflake arrays are directly used as electrodes to achieve a high specific capacitance of 1010 F·g^(-1)at 1 A·g^(-1)and a good cycling stability with 90.84%capacitance retention after 3000 times at 10 A·g^(-1).Furthermore,the all-solid-state symmetric supercapacitors assembled from the cellulose-based carbon nanofibers/NiCo_(2)O_(4)deliver a high energy density of 62 W·h·kg(-1) at a power density of 1200 W·kg^(-1).Six all-solid-state symmetric supercapacitors in series can also power a‘DHU’logo consisted of 36 light emitting diodes,confirming that the cellulose-based carbon nanofiber is a promising carbon matrix material for energy storage devices.

XO(X=Ti,Mn)decorated hollow multi-channel carbon sub-micro fiber networks as freestanding cathode for LieS batteries

Lithium-sulfur(Lisingle bondS)batteries are considered as one of the most promising high-energy storage devices due to the high theoretical capacity(1675 mA·h·g^(-1))and large energy density(2600 W·h·kg^(-1)).However,the poor conductivity of sulfur and“shuttle effect”of soluble polysulfide intermediates limit practical applications of Lisingle bondS batteries.Herein,four kinds of carbon sub-micro fibers with different structures were designed and prepared,the effect of structure on Lisingle bondS battery was studied.On this basis,the XO(X=Ti,Mn)decorated hollow multi-channel carbon sub-micro carbon fibers(HMCMFs)were prepared by electrospinning and carbonization.The HMCMFs can not only supply nanopores for relieving the expansion of sulfur but also served as high conductivity freestanding substrate for sulfur loading,meanwhile the decorated XO(X=Ti,Mn)can provide powerful chemical adsorption to polysulfide intermediates and limit“shuttle effect”Therefore,the TiO-HMCMFs/S composite shows high specific capacity of 900 mA·h·g^(-1)and maintain stable specific capacities up to∼600 mA·h·g^(-1)over 300 cycles at 0.1 A·g^(-1).This work offers a facile method to build efficient sulfur cathode to acquire Lisingle bondS batteries with high performance.

Design,fabrication,and dynamic mechanical responses of fiber-reinforced composite lattice materials

Fiber-reinforced composites are a popular lightweight materials used in a variety of engineering applications,such as aerospace,architecture,automotive,and marine construction,due to their attractive mechanical properties.Constructing lattice materials from fiber-reinforced composites is an efficient approach for developing ultra-lightweight structural systems with superior mechanical proper-ties and multifunctional benefits.In contrast to corrugated,foam,and honeycomb core materials,composite lattice materials can be manufactured with various architectural designs,such as woven,grid,and truss cores.Moreover,lattice materials with open-cell topology provide multifunctional advantages over conventional closed-cell honeycomb and foam structures and are thus highly desirable for developing aerospace systems,hypersonic vehicles,long-range rockets and missiles,ship and naval structures,and protective systems.The objective of this study is to review and analyze dynamic mechanical behavior performed by different researchers in the area of composite lattice materials and to highlight topics for future research.

Efficient and stable hybrid perovskite-organic lightemitting diodes with external quantum efficiency exceeding 40 per cent

Light-emitting diodes(LEDs)based on perovskite semiconductor materials with tunable emission wavelength in visible light range as well as narrow linewidth are potential competitors among current light-emitting display technologies,but still suffer from severe instability driven by electric field.Here,we develop a stable,efficient and highcolor purity hybrid LED with a tandem structure by combining the perovskite LED and the commercial organic LED technologies to accelerate the practical application of perovskites.Perovskite LED and organic LED with close photoluminescence peak are selected to maximize photon emission without photon reabsorption and to achieve the narrowed emission spectra.By designing an efficient interconnecting layer with p-type interface doping that provides good opto-electric coupling and reduces Joule heating,the resulting green emitting hybrid LED shows a narrow linewidth of around 30 nm,a peak luminance of over 176,000 cd m^(−2),a maximum external quantum efficiency of over 40%,and an operational half-lifetime of over 42,000 h.

Doxorubicin-conjugated pH-responsive gold nanorods for combined photothermal therapy and chemotherapy of cancer

Cancer chemotherapy can be hindered by drug resistance which leads to lower drug efficiency.Here,we have developed a drug delivery system that tethers doxorubicin to the surface of gold nanorods via a pHsensitive linkage(AuNRs@DOX),for a combined photothermal and chemical therapy for cancer.First,AuNRs@DOX is ingested by HepG2 liver cancer cells.After endocytosis,the acidic pH triggers the release of doxorubicin,which leads to chemotherapeutic effects.The gold nanorods are not only carriers of DOX,but also photothermal conversion agents.In the presence of an 808 nm near-infrared laser,AuNRs@DOX significantly enhance the cytotoxicity of doxorubicin via the photothermal effect,which induces elevated apoptosis of hepG2 cancer cells,leading to better therapeutic effects in vitro and in vivo.

Carbon‑Based Fibers: Fabrication, Characterization and Application

In recent years,the carbon-based fibers(CBFs)including carbon fibers,carbon nanotube fibers and graphene fibers have received extensive attention due to excellent thermal,electrical and mechanical properties.Here,the current status of CBFs is reviewed from the following aspects:sprecursors,preparation,performance and application.The precursor systems including acrylonitrile copolymers,pitch,cellulose and lignin,carbon nanotube,graphene and other rare synthetic polymeric precursors.The relationship of preparation method and performance of CBFs is presented.In addition,this review gives the overview of application and future development of CBFs.

介电-量子点-介电夹层结构设计实现外量子效率超过20%的发光场效应晶体管

新兴的量子点(QD)发光场效应晶体管(QLEFET)能够以较低成本产生高颜色纯度的发光,并且其光电特性易于调节.研究人员在设计器件结构和理解深层物理机制等方面已作了大量尝试,但由于界面处的电荷/激子损耗和QD层与相邻载流子传输层之间存在着较大的能量势垒,目前QLEFET的整体性能仍然偏低.鉴于此,本文采用一个介电层-QD-介电层的(DQD)的三明治夹层结构设计买现了外量子效率(EQE)超过20%的QLEFET.该DQD结构可以通过调节能带排列进一步调控器件中载流子行为,从而使激子复合区移动进入QD发光层.此外,通过抑制表面陷阱和界面电荷转移诱导的荧光碎灭引起的激子损耗,有效提高了激子的辐射复合.本研究提出的DQD夹层结构设计是一种改善QLEFET电致发光胜能的全新概念,也可以将其应用到其他材料体系中,促进QD在新型光电器件中的开发应用.

Kinetics and mechanism of hexavalent chromium removal by basic oxygen furnace slag

Basic oxygen furnace slag（BOFS） has the potential to remove hexavalent chromium（Cr（VI））from wastewater by a redox process due to the presence of minerals containing Fe2＋. The effects of the solution p H, initial Cr（VI） concentration, BOFS dosage, BOFS particle size, and temperature on the removal of Cr（VI） was investigated in detail through batch tests. The chemical and mineral compositions of fresh and reacted BOFS were characterized using scanning electron microscope（SEM） equipped with an energy dispersive spectrometer（EDS）system and X-ray diffractometer（XRD）. The results show that Cr（VI） in wastewater can be efficiently removed by Fe2＋released from BOFS under appropriate acidic conditions. The removal of Cr（VI） by BOFS significantly depended on the parameters mentioned above. The reaction of Cr（VI） with BOFS followed the pseudo-second-order kinetic model. Fe2＋responsible for Cr（VI） removal was primarily derived from the dissolution of Fe O and Fe3O4 in BOFS. When H2SO4 was used to adjust the solution acidity, gypsum（Ca SO4·2H2O）could be formed and become an armoring precipitate layer on the BOFS surface, hindering the release of Fe2＋and the removal of Cr（VI）. Finally, the main mechanism of Cr（VI） removal by BOFS was described using several consecutive reaction steps.

Plant vs. Animal Prototype for Designing Bio-inspired PEMFC Flow Fields: Corn Veins or Murray’s Law?

Designing bio-inspired flow fields holds great potential in improving the performance of Proton Exchange Membrane Fuel Cell(PEMFC).Two kinds of biological prototypes are widely used:plant prototype and animal prototype.It remains a question which one of these prototypes is more appropriate for the scenario of PEMFC.Here,a comparative study was conducted to compare bionic flow fields based on animal and plant prototypes.First,a Corn Leaf Vein Mathematical Model(CLMM)was established by extracting structural parameters from corn leaves of two growth stages.Then the obtained CLMM and well-known Murray’s law were employed to design bionic flow fields corresponding to the plant and animal prototypes,respectively,which have been subsequently compared by numerical investigations.The results demonstrate that the flow field guided by Murray’s law outperforms the counterpart based on the structural parameters of CLMM in terms of PEMFC net output power,mass transport,water management and pressure drop,suggesting that animal circulation system is more suitable to the bionic flow field design of PEMFC than plant leaf veins.The work may also offer valuable insights into the design of other flow fields related to electrochemical energy conversion.

Influence of modeling approaches and structural parameters on impact resistance of the human porous cranium

Failure mechanism and impact resistance of a human porous cranium are studied in detail by means of theoretical and numerical methods.It is hypothesized that pore distribution of a cranium directly affects cranial energy absorption,and a stretched beam model and a real beam model are taken as the example for the verification.Meanwhile,for the purpose of comparison with numerical results,a theoretical model is also proposed for the prediction of residual velocity and contact force of the impactor for an impacted skull.Compared with the real beam model,the stretched beam model containing through-thickness pores is easily deformed under the impact,thereby buffering well the external impact energy.The energy absorption efficiency of both the stretched beam model and real beam model is concerned with the threshold velocity for penetration which is directly related to the size of the structural damage area.Overall,there is good agreement between numerical and theoretical results.In addition,the effect of structural geometric parameters(shape and size of the impactor)on the impact resistance of the skull bone is theoretically investigated.The study provides reference for the evaluation of the energy absorption and failure mechanism of the skull under impact loads.

Computational Studies of Porous Head Protection Structures for Human Cranium under Impact Loading

This paper looks into the effects of various porous structures used in the construction of the shell of a protective helmet on the energy absorption capacity and their efficacy in protecting the head/skull against impact force.It is well known that porous structures are very effective for energy absorption;hence,they have been widely used to reduce the negative effects of impact and explosion loads on the human skull.Porous shell structures,made from titanium alloy(Ti–6Al–4V)and,comprised of several periodic topological configurations,namely the more common rectangle and hexagonal honeycomb,as well as those having auxetic properties,namely the concave honeycomb and double-arrow,are studied by means of numerical modeling.The reliability of the numerical model is validated with the published experimental results.For the double-arrow configurations,the study involves three different densities,and the structural energy absorption capacity of the double-arrow shells increases with density.For the same density,the energy absorption capacity of the rectangular shell is the best,and that of the honeycomb is the worst.The superior performance of the rectangular configuration is partly derived from the fact that the orientation of the struts in this structure is aligned along the direction of the impact force.Further comparison of energy absorption capacity is made between the porous shell and a shell having a traditional titanium monolayer.The severe plastic deformation in the solid titanium shell(traditional monolayer shell)is detrimental to the overall effectiveness of head protection gear.Apart from this,compared with the Kevlar composite laminated shell of the same mass,both the solid and porous titanium shells provide considerable protection to the human head.The comprehensive comparisons show that the porous design on the titanium shell is beneficial for mitigating the risks of traumatic brain injuries(TBIs).