Second-Harmonic Generation and Spectrum Modulation by Active Nonlinear Metamaterial

The nonlinear properties of a metamaterial sample composed of double-layer metallic patterns and voltage controllable diodes are experimentally investigated. Second harmonics and spectrum modulations are clearly observed in a wide band of microwave frequencies, showing that this kind of metamaterial is not only tunable by low DC bias voltage, but also behaves strong nonlinear property under a small power incidence. These properties are difficult to be found in normal, naturally occurring materials.Comment: 14 pages, 4 figure

Synchronization of delayed stochastic reaction–diffusion Hopfield neural networks via sliding mode control

Synchronization of stochastic reaction–diffusion Hopfield neural networks with s-delays via sliding mode control is investigated in this article. To begin with, we choose suitable functional space for state variables, then the system is transformed into a functional differential equation in an infinite-dimensional Hilbert space by using appropriate functional analysis technique. Based on above preliminary preparation, sliding mode control (SMC) is constructed to drive the error trajectory into the designed switching surface. Specifically, the switching surface is constructed as linear combination of state variables, which is related to control gains. Then novel SMC law is designed which involving delay, reaction diffusion term, and reaching law. Furthermore, the criterion of mean-square exponential synchronization for stochastic delayed reaction–diffusion Hopfield neural networks with s-delays is given in the form of matrix form. This criterion is less restrictive and easy to check in computer. Meanwhile, a different novel Lyapunov–Krasovskii functional (LKF) mixed with Itô’s formula, Young inequality, Hanalay inequality is employed in this proof procedure. At last, a numerical example is presented to validate the availability of theoretical result. The simulation is based on the finite difference method, and numerical result coincides with the theoretical result proposed

Insight into Bioactivity of In‐situ Trapped Enzyme‐Covalent‐Organic Frameworks

Selecting a suitable support material for enzyme immobilization with excellent biocatalytic activity and stability is a critical aspect in the development of functional biosystems. The highly stable and metal‐free properties of covalent‐organic frameworks (COFs) make them ideal supports for enzyme immobilization. Herein, we constructed three kinds of COFs via a biofriendly and one‐pot synthetic strategy at room temperature in aqueous solution. Among the three developed COFs (COF‐LZU1, RT‐COF‐1 and ACOF‐1), the horseradish peroxidase (HRP)‐incorporated COF‐LZU1 is found to retain the highest activity. Structural analysis reveals that a weakest interaction between the hydrated enzyme and COF‐LZU1, an easiest accessibility by the COF‐LZU1 to the substrate, as well as an optimal conformation of enzyme together promote the bioactivity of HRP‐COF‐LZU1. Furthermore, the COF‐LZU1 is revealed to be a versatile nanoplatform for encapsulating multiple enzymes. The COF‐LZU1 also offers superior protection for the immobilized enzymes under harsh conditions and during recycling. The comprehensive understanding of interfacial interactions of COF host and enzyme guest, the substrate diffusion, as well as the enzyme conformation alteration within COF matrices represents an opportunity to design the ideal biocatalysts and opens a broad range of applications of these nanosystems

Fault severity assessment of rolling bearings method based on improved VMD and LSTM

In order to solve the problem of selection of appropriate wavelet basis function and clearly show the physical meaning of Empirical Mode Decomposition (EMD), an improved Variational Mode Decomposition (VMD) method with Long Short-Term Memory (LSTM) neural network is proposed. With the Cuckoo Search (CS) algorithm, the central frequency updating rules of VMD are optimized. And the low efficiency and local optimum problem is avoided. Meanwhile the decomposition layer number is found by the instantaneous frequency theory. For improving the prediction accuracy in traditional regression prediction methods, a LSTM neural network is designed for regression prediction of time sequence characteristics. The proposed method is implemented on actual bearings data which is derived from the bearing laboratory of Case West Reserve University in the United States and the University of Cincinnati Bearing Data Center. The experimental results showed that the improved VMD method was more robust and more accurate than the other traditional methods. And it has some practical value for real application and guiding significance for theory

Explanatory Diagnosis of an Ontology Stream via Reasoning About Actions

International audienceExplanatory diagnosis of an ontology stream aims to explain the changes hidden in the ontology stream by a sequence of actions. In this paper, we present a framework for explanatory diagnosis of an ontology stream, which allows the actions to be uncertain. In order to capture the semantics of actions, we introduce a new update operator and effect-guided bold-repair. By combining these operators with a query mechanism of description logics EL ++ supporting inconsistency-tolerant semantics, we present a formal definition for the explanatory diagnosis problem of ontology streams

Asymmetric Phenotypes of Sterile Hybrid Males From Reciprocal Crosses Between Species of the Anopheles gambiae Complex

Haldane’s rule of speciation states that sterility or inviability affects the heterogametic sex of inter-species hybrids. Darwin’s corollary to Haldane’s rule implies that there are asymmetric phenotypes in inter-species hybrids from reciprocal crosses. Studying the phenotypes of F1 hybrids among closely related species of malaria mosquitoes can assist researchers in identifying the genetic factors and molecular mechanisms of speciation. To characterize phenotypes of sterile hybrid males in the Anopheles gambiae complex, we performed crosses between laboratory strains of An. merus and either An. gambiae or An. coluzzii. The reproductive tracts had normal external morphology in hybrid males from crosses between female An. merus and male An. gambiae or An. coluzzii. Despite being sterile, these males could copulate with females for a normal period of time and could transfer a mating plug to induce female oviposition and monogamy. In contrast, the entire reproductive tracts in hybrid males from crosses between female An. gambiae or An. coluzzii and male An. merus were severely underdeveloped. These males had atrophic testes and reduced somatic organs of the reproductive system including male accessary glands and ejaculatory duct. In addition, hybrid males with underdeveloped reproductive tracts displayed a shorter copulation time with females and failed to induce female oviposition and monogamy due to their inability to form and transfer a plug to females during mating. The asymmetry of the phenotypes associated with hybrid male sterility suggests that different genetic factors and molecular mechanisms are responsible for reproductive isolation in reciprocal crosses among species of the An. gambiae complex

A Comparative Study of 2 Techniques to Avoid Bone Cement Loosening and Displacement After Percutaneous Vertebroplasty Treating Unstable Kummell Disease

Objective Percutaneous vertebroplasty (PVP) is currently the most common surgical procedure for unstable Kummell disease (KD), but cement loosening or displacement often occurs after PVP. We had been using percutaneous pediculoplasty (PPP) or a self-developed bone cement bridging screw system to avoid this severe complication. This study intends to compare these novel surgical procedures through a 2-year follow-up evaluation. Methods From May 2017 to May 2021, 77 patients with single-level unstable KD were included in the PPP group, and 42 patients received the PVP-bone cement bridging screw system were included in the screw group. The changes in the vertebral body index (VBI), bisegmental Cobb angle, visual analogue scale (VAS) and Oswestry Disability Index (ODI) and the cement loosening rate and displacement rate at different follow-up time points were used to evaluate the clinical efficacy. Results There was no significant difference in VBI or bisegmental Cobb angle between the 2 groups (p > 0.05) before operation, immediately after operation and at 6-month follow-up, while at 1-year and 2-year postoperative evaluations, the screw group had higher VBI and bisegmental Cobb angle than the PPP group (p 0.05), while at 2-year follow-up, the screw group still had higher VAS and ODI scores than the PPP group (p < 0.05). No bone cement displacement occurred in both groups, but the rate of bone cement loosening was 14.29% in group PPP, and 0 in screw group (p < 0.05). Conclusion This 2-year follow-up study shows that the PVP-bone cement bridging screw system combined therapy had better midterm treatment efficacy than the PVP-PPP combined therapy in patients with unstable KD, and the bone cement bridging screw system is a preferred therapy with better anti cement loosening ability