Thermal Management Enables Bright and Stable Perovskite Light-Emitting Diodes

The performance of lead-halide perovskite light-emitting diodes (LEDs) has increased rapidly in recent years. However, most reports feature devices operated at relatively small current densities (<500 mA cm⁻²) with moderate radiance (<400 W sr⁻¹ m⁻²). Here, Joule heating and inefficient thermal dissipation are shown to be major obstacles toward high radiance and long lifetime. Several thermal management strategies are proposed in this work, such as doping charge-transport layers, optimizing device geometry, and attaching heat spreaders and sinks. Combining these strategies, high-performance perovskite LEDs are demonstrated with maximum radiance of 2555 W sr⁻¹ m⁻², peak external quantum efficiency (EQE) of 17%, considerably reduced EQE roll-off (EQE > 10% to current densities as high as 2000 mA cm⁻²), and tenfold increase in operational lifetime (when driven at 100 mA cm⁻²). Furthermore, with proper thermal management, a maximum current density of 2.5 kA cm⁻² and an EQE of ≈1% at 1 kA cm⁻² are shown using electrical pulses, which represents an important milestone toward electrically driven perovskite lasers.     

New version of continuous–discrete cubature Kalman filtering for nonlinear continuous–discrete systems

For nonlinear continuous–discrete systems, this paper elaborates a new accurate implementation of continuous–discrete cubature Kalman filter (CD-CKF). As the main contribution of this work, the new Kalman prediction stage begins by integrating the nonlinear continuous model for all the cubature sample vectors; the prior estimate state and covariance prediction are based on the weighted statistics of these integrated cubature sample vectors and the Gauss–Legendre approximation scheme. The new square root form CD-CKF is also derived and accurately implemented by combining with the modified variable stepsize NIRK. As the advantages of proposed approach, the complicated and error-prone processes of solving covariance differential equation or calculating derivatives are avoided, while the positive semi-definiteness of prior error covariance are numerically guaranteed. Simulations of traffic control scenarios further confirm the new approach’s superior filtering performance in both reliability and accuracy.     

Comparison of joint angle,velocity and acceleration estimators for hydraulically actuated manipulators to a novel dynamical approach

Excavators are used for a wide range of applications like earthworks and material handling. Assistance systems are becoming more common to support the operator. For monitoring and control based assistance functions the angular position, velocity and acceleration of the joints from the working implement are required. Commercial systems often use inertial measurement units, consisting of triaxial accelerometers and gyroscopes, to accomplish an estimation of those states. A novel joint angle, velocity and acceleration estimation for hydraulic manipulators is proposed and compared to state of the art methods. A decentralized kinematic filter using no information about the underlying system and a centralized kinematic filter taking the system kinematics into account are implemented as state of the art approaches. Both filters only use inertial measurement units to obtain information about the current state of the system. The novel centralized dynamic filter uses the same information as the centralized kinematic filter and extends it by a dynamic model containing additional information about the angular acceleration due to pressure readings of the hydraulic cylinders. Kalman filtering is used to combine the derived system and measurement models with the sensor information. The methods are evaluated on a material handling excavator for single and coupled movements of the working implement. The novel centralized dynamic filter enables improvements for the angular acceleration estimation compared to the decentralized and centralized kinematic filter. Less noise of the acceleration estimation and a better tracking of the actual acceleration are shown.     

Nanocellulose-based films and their emerging applications

Extensive research has been directed towards the reinvention of paper for advanced applications. Nanocellulose-based films, a novel class of specialty paper primarily made of nanocellulose, demonstrate an ideal combination of sustainability and enhanced or novel properties. Enormous efforts have been devoted to enhancing these intrinsic properties and/or creating novel functions to expedite and expand the use of these materials in high-end fields such as touchscreen, solar cells, and nanogenerators. We review state-of-the-art advances in nanocellulose-based films and their utilization in several emerging and promising fields. We begin with an introduction of four types of nanocellulose-based films distinguished by their functional material loads (e.g., synthetic macromolecular polymers, 0D, 1D, and 2D nanomaterials), which involves their manufacturing techniques, structure design, properties, novel functions, and underlying principles. Additionally, we summarize the value-added applications of nanocellulose-based films in flexible electronics, energy converting or harvesting devices, and water treatment. Finally, we provide a critical viewpoint on the remaining challenges and future opportunities in this field.     

Policy translation and configuration using dynamic template

To solve the problem of complex,cumbersome and error-prone configuration of security devices caused by the heterogeneous configuration modes in complex networks,a dynamic template-based scheme for translating and configuring policy was proposed.In detail,considering the code’s features,the code-based template for translating policies was constructed to configure the command line conversion,and the keyword comparison method was used to ensure the accuracy of policy configuration.Experiments show that the scalability and the accuracy of the proposed scheme.     

Electromagnetic torque detecting for optimization of in-mould electromagnetic stirring in the billet and bloom continuous casting

ABSTRACT

In this paper, an electromagnetic torque device based on the theoretical model was established to determine the optimum frequency accurately and conveniently in billet and bloom continuous casting with in-mould electromagnetic stirring (M-EMS). Magnetic characteristics with M-EMS was investigated by numerical simulation and physical experiment with the application of electromagnetic torque device and gauss meter. In addition, the effects of stirring frequency with M-EMS on macro segregation and equiaxed crystal ratio were compared and analysed for 55SiCr with 150?mm?×?150?mm billet caster and BU with 310?×?360?mm bloom caster by a series of plant trials, respectively. The results showed that maximum magnetic flux density and maximum electromagnetic torque occurred with different frequency and same current in M-EMS, and central equiaxed crystal ratio and macro segregation has been significantly improved by optimum frequency with M-EMS.     

Electrochemical energy storage applications of carbon nanotube supported heterogeneous metal sulfide electrodes

Electrochemical system centered on hierarchically carbon-based metal sulphide assemblies are of great fame for competent supercapacitors. Herein, the synthesis of a hierarchical CNT anchored MoS₂–Bi₂S₃ nanocomposite is reported. Attractively, a vertically grown Bi₂S₃ nanorods supported on MoS₂ nanosheets with carbon framework acts as a highly effective electrode in alkaline electrolyte. More interestingly, this hierarchical structure and synergetic upshot of CNT and composites provide excess coverage of active sites with improved conductivity and stability. Advancing from the physical and compositional properties of nanocomposites, the specific capacitance of MoS₂–Bi₂S₃@CNT composites is measured to be 1338 F/g at 10 mV/s, columbic efficiency of 99.5% over 10000 cycles and long-term stability (60% retention at 0.5 A g^?1 over 2000 cycles and 34.6% up to 10000 cycles). The success of this MoS₂–Bi₂S₃@CNT composite may be attributed to the structural advantages, admirable cyclic stability, and better capacitance retention for supercapacitor applications.     

Excellent supercapacitive performance of graphene quantum dots derived from a bio-waste marigold flower (Tagetes erecta)

Marigold flower (MG; Tagetes erecta) derived Graphene quantum dots (GQDs) have been successfully reported for the fabrication of supercapacitor electrodes in charge storage devices. The GQDs have been synthesized through a hydrothermal route using biomass viz. Waste material (MG) without adding any hazardous chemicals. The successful formation of GQDs as elaborated has been confirmed by various analytical characterization techniques. The as-synthesized GQDs have been electrodeposited on the Ni foil (working electrode) with the help of PVDF (binder) and subsequently, cyclic voltammetry (CV) has been conducted to access specific capacitance, energy density, and other parameters. Moreover, the galvanometric charge/discharge (GCD) technique has been employed due to its accuracy and reliability. Maximum areal specific capacitance has been found as 1.6008 F/cm² with the current density of 2.0 A/g even after loading a little amount of material on the electrode. The high magnitude of columbic efficiency (160.08), energy density (17.78 Wh/kg), and specific capacitance of 200 F/g at current density 2.0 A/g within a voltage range of −0.55 V to +0.25 V in 2 M KOH electrolyte solution indicate a good electrocapacitive performance of the as-synthesized material. Moreover, the as-synthesized GQDs have shown excellent capacitive retention after 1000th cycles which clearly embarks its sustainable electrocapacitive nature and henceforth offers outstanding potential for the applications in energy storage devices like supercapacitors.     

基于激光闪光法的立式热扩散率测量装置研究

介绍了基于激光闪光法的立式热扩散率测量装置,利用脉冲激光对样品进行均匀加热,使样品内部产生一维热流,并通过红外探测器测量样品温升信号,采用立式真空加热炉控制测量温度环境,实现室温至1600℃的热扩散率测量。用该装置测量厚度为1. 1 mm,直径为10 mm的不锈钢样品,测量结果与PTB参考数据的偏差小于1%。     

Distributed two‐stage state estimation with event‐triggered strategy for multirate sensor networks

This paper investigates the state estimation issue for a class of wireless sensor networks (WSNs) with the consideration of limited energy resources. First, a multirate estimation model is established, and then, a new event‐triggered two‐stage information fusion algorithm is developed based on the optimal fusion criterion weighted by matrices. Compared with the existing methods, the presented fusion algorithm can significantly reduce the communication cost in WSNs and save energy resources of sensors efficiently. Furthermore, by presetting a desired containment probability over the interval [0,1] with the developed event‐triggered mechanism, one can obtain a suitable compromise between the communication cost and the estimation accuracy. Finally, a numerical simulation for the WSN tracking system is given to demonstrate the effectiveness of the proposed method.