In this work, we study the dynamic behaviour for a heat equation with exponential polynomial kernel memory to be a controller for a Schrödinger system. By introducing some new variables, the time-variant system is transformed into a time-invariant one. Remarkably, the resolvent of the closed-loop system operator is not compact anymore. The residual spectrum is shown to be empty and the continuous spectrum consisting of finite isolated points are obtained. It is shown that the sequence of generalised eigenfunctions forms a Riesz basis for the Hilbert state space. This deduces the spectrum-determined growth condition for the C0-semigroup, and the exponential stability is then established. 相似文献
Neural Computing and Applications - For a class of nonlinear multi-agent systems under switching topologies with disturbances, we propose a distributed H∞ consensus control protocol based on... 相似文献
Aiming at the problem that the traditional collaborative filtering recommendation algorithm does not fully consider the influence of correlation between projects on recommendation accuracy, this paper introduces project attribute fuzzy matrix, measures the project relevance through fuzzy clustering method, and classifies all project attributes. Then, the weight of the project relevance is introduced in the user similarity calculation, so that the nearest neighbor search is more accurate. In the prediction scoring section, considering the change of user interest with time, it is proposed to use the time weighting function to improve the influence of the time effect of the evaluation, so that the newer evaluation information in the system has a relatively large weight. The experimental results show that the improved algorithm improves the recommendation accuracy and improves the recommendation quality. 相似文献
Lithium-sulfur batteries (LSBs) have been regarded as one of the most promising energy storage systems to break through the upper limit of lithium-ion batteries. However, the rampant diffusions of soluble lithium polysulfides (LiPSs) in the electrolyte induced the shuttle effect between anode and cathode, resulting in low sulfur utilization, low energy efficiency and short cycling life. Herein, we prove the rational design and construction of Ni nanoparticles filled in vertically grown N-doped bamboo-like carbon nanotubes (CNTs) on graphene nanosheets (Ni@NG-CNTs) as efficient polysulfide barrier for high-performance LSBs. The unique design integrates graphene nanosheets and CNTs into hierarchical architectures with one-dimensional (1D) CNTs, two-dimensional (2D) ultrathin nanosheets and abundant carbon nanocages. This design provides large surface area for lithium polysulfides (LiPSs) adsorption, accelerates electron transport and enhances electrochemical redox of LiPSs. Benefiting from the unique structural features, the LSBs with the Ni@NG-CNTs as polysulfide barrier keep high reversible specific capacities of 309.1 and 265.0 mAh·g−1 at 5 and 10 C rates after 500 cycles. This work provides a new strategy for constructing self-assembled hybrids of CNTs and graphene nanosheets with abundant carbon nanocages for high-performance LSBs.
Persistent luminescence nanoprobes (PLNPs) can remain luminescent after ceasing excitation. Due to the ultra-long decay time of persistent luminescence (PersL), autofluorescence interference can be efficiently eliminated by collecting PersL signal after autofluorescence decays completely, thus the imaging contrast and sensing sensitivity can be significantly improved. Since near-infrared (NIR) light shows reduced scattering and absorption coefficient in penetrating biological organs or tissues, near-infrared persistent luminescence nanoprobes (NIR PLNPs) possess deep tissue penetration and offer a bright prospect in the areas of in vivo biosensing/bioimaging. In this review, we firstly summarize the design of different types of NIR PLNPs for biosensing/bioimaging, such as transition metal ions-doped NIR PLNPs, lanthanide ions-doped NIR PLNPs, organic molecules-based NIR PLNPs, and semiconducting polymer self-assembled NIR PLNPs. Notably, organic molecules-based NIR PLNPs and semiconductor self-assembled NIR PLNPs, for the first time, were introduced to the review of PLNPs. Secondly, the effects of different types of charge carriers on NIR PersL and luminescence decay of NIR PLNPs are significantly emphasized so as to build up an in-depth understanding of their luminescence mechanism. It includes the regulation of valence band and conduction band of different host materials, alteration of defect types, depth and concentration changes caused by ion doping, effective radiation transitions and energy transfer generated by different luminescence centers. Given the design and potential of NIR PLNPs as long-lived luminescent materials, the current challenges and future perspective in this rapidly growing field are also discussed.
ABSTRACTMany researchers believe that crystallization is responsible for drastic viscosity changes near the break temperature of mould flux; however, there are no reasonable experimental data to support this view. In this study, the complete crystallization process is recorded in situ by inhibiting the volatilization of fluoride, and the relationship between viscosity change and crystallization near the break temperature is studied. Mould flux with a basicity of 0.65 had no break temperature, and no crystallization occurs within the temperature range of the viscosity test. The other three mould fluxes begin to crystallize before the break temperature, but the crystal volume fractions at the break temperature are different. The break temperature of mould flux is the crystallization temperature with a critical crystal volume fraction, which is related to the viscosity before the break temperature. The higher the viscosity, the smaller the critical crystal volume fraction. Therefore, break temperature?≤?initial crystallization temperature. 相似文献
Previous studies showed that adding hydrogen (H2) can have an opposite chemical effect on soot formation: its chemical effect enhances and suppresses soot formation in methane (CH4) and ethylene (C2H4) diffusion flames, respectively. Such opposite chemical effect of H2 (CE-H2) remains unresolved. The different CE-H2 is studied numerically in the two laminar coflow diffusion flames. A detailed chemical mechanism with the addition of a chemically inert virtual species FH2 is used to model the gas-phase combustion chemistry in this study. Particularly, a reaction pathway analysis was performed based on the numerical results to gain insights into how H2 addition to fuel affects the pathways leading to the formation of benzene (A1) in CH4 and C2H4 flames. The numerical results show that the CE-H2 in CH4 diffusion flame to prompt soot formation is ascribed that the higher mole fraction of H atom promotes the formation of A1 and Acetylene (C2H2) and leads to higher nucleation rate and eventually higher soot surface growth rate. In contrast, adding H2 to C2H4 diffusion flames decreases soot nucleation and surface growth rate. The lower soot nucleation rate is due to the lower mole fractions of pyrene (A4), while the lower soot surface growth rate is due to the lower mole fractions of H atom and C2H2, higher mole fraction of H2 and lower soot nucleation rate. Furthermore, the CE-H2 in C2H4 diffusion flames promotes the formation of A1, but suppresses the formation of A4. 相似文献