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Role of structural anisotropy in geometric birefringence of high-birefringence index-guiding PCFs: analysis by moment of inertia
摘要： We have studied the role of structural anisotropy on the geometric birefringence of four typical high-birefringence (HB) index-guiding photonic crystal fibers (PCFs) with the same air-silica structure and circular, ellipse, and rectangle air holes, respectively. The normalized difference between the moment of inertia ΔI in x and y direction of the PCF structure is utilized to quantificationally describe the structural anisotropy. We demonstrate that the phase birefringence B increases monotonously when the normalized ΔI rises in different cases of PCFs structures. In order to obtain high birefringence B, it can be an effective method to optimize the parameters of the structure to increase the normalized ΔI. This work can be not only a reference of founding the essence of geometric birefringence and proposing the optimal design of HB-IG-PCFs, but also an enlightenment for bringing the different method (compared to the finite element) into the investigation of PCFs.
关键词： Photonic crystal fiber (PCF),Polarization maintenance,Structural anisotropy,Geometric birefringence,Birefringence,Moment of inertia
更新于2025-09-04 15:30:14
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Shock induced damage and fracture in SiC at elevated temperature and high strain rate
摘要： Large-scale molecular dynamics simulations are used to investigate shock-induced damage and fracture in 3C-SiC single crystals at an elevated initial temperature of 2000 K and a high tensile strain rate of ~1010 s-1. Three crystal orientations have been evaluated: [001], [110] and [111]. A comprehensive comparison has been made between cases at 2000 K and at 300 K to address the effects of high temperature on the mechanical performance of SiC under shock loading. Results show that for shock compression, the high temperature decreases the longitude elastic wave speeds as well as the shock stresses. The shock-induced plasticity is mainly in the form of deformation twinning at 300 K, but twinning is absent at 2000 K. The high temperature decreases the structural phase transition threshold pressure in SiC from ~90 GPa at 300 K (for all three orientations) to ~75 GPa in [001], ~57 GPa in [110] and ~64 GPa in [111] at 2000 K, with corresponding particle velocities of 2.75 km/s, 2.0 km/s, and 2.25 km/s, respectively, in agreement with trends observed in recent experiments. The spall fracture behavior reveals that high temperature reduces the spall strength with an average spall strength of ~20.7 GPa in [001], ~21.4 GPa in [110] and ~22.5 GPa in [111] at 2000 K in the classical spall regime, which are about 33% lower than strengths measured at 300 K. However, in the micro-spall regime the spall strengths are very similar at both temperatures. The corresponding thresholds of particle velocity to trigger spall decrease at elevated temperature except for [001] loading, as well as the thresholds for generating overdriven phase transition waves.
关键词： Structural phase transformation,High temperature,Silicon carbide,Plasticity,Spall
更新于2025-09-04 15:30:14
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Influence of rare earth material (Sm3+) doping on the properties of electrodeposited Cu2O films for optoelectronics
摘要： Herein, we report samarium (Sm) dopant concentration effect on Cu2O films characteristics prepared by electrodeposition method. XRD patterns of the films indicated that pristine and Sm:Cu2O films have polycrystalline cubic structure with (111) preferred orientation. It was seen from the SEM photographs pinhole free dense triangle shaped grains for undoped Cu2O thin films and the grain size was decreased as concentration of samarium was increased. Raman spectroscopy showed peaks at 108, 146, 217, 413 and 637 cm?1 which conformed the Cu2O phase formation and intensity of the peaks was decreased with a increase in dopant concentration. UV–Vis spectra exhibited that the absorption value of Cu2O films is increased gradually with reduction in band gap value for the increase of samarium content. Photoluminescence (PL) spectra revealed that all films display a visible light emissions and its intensity was reduced due to increase in doping concentration. Photosensitivity observation study indicated that the photocurrent of deposited Cu2O films was increased along with the increase in dopant material concentration.
关键词： Electrodeposition,Cu2O films,Optoelectronics,Structural properties,Samarium doping,Optical properties,Photosensitivity
更新于2025-09-04 15:30:14
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WS2 nanodots-modified TiO2 nanotubes to enhance visible-light photocatalytic activity
摘要： WS2 nanodots-modified TiO2 nanotubes (TNT/WND) composites were fabricated via one-pot hydrothermal method for the first time. The physical and photophysical properties of the as-prepared photocatalysts were characterized by XRD, TEM, HRTEM, BET, UV-vis, and PL. The results demonstrated that WS2 nanodots have been successfully anchored on the inner wall of TiO2 nanotubes. TNT/WND composites showed excellent photocatalytic activity toward photodegradation of rhodamine B (RhB) under visible-light, which mainly attributed to the synergistic effect from relative low recombination rate of the photogenerated electron-hole pairs and high specific surface area.
关键词： Semiconductors,Photocatalysis,WS2 nanodots,Structural,TiO2 nanotubes,Nanocomposites
更新于2025-09-04 15:30:14
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Cardiomyocyte-Driven Structural Color Actuation in Anisotropic Inverse Opals
摘要： Biohybrid actuators composed of living tissues and artificial materials have attracted increasing interest in recent years because of their extraordinary function of dynamically sensing and interacting with complex bioelectrical signals. Here, a compound biohybrid actuator with self-driven actuation and self-reported feedback is designed based on an anisotropic inverse opal substrate with periodical elliptical macropores and a hydrogel filling. The benefit of the anisotropic surface topography and high biocompatibility of the hydrogel is that the planted cardiomyocytes could be induced into a highly ordered alignment with recovering autonomic beating ability on the elastic substrate. Because of the cell elongation and contraction during cardiomyocyte beating, the anisotropic inverse opal substrates undergo a synchronous cycle of deformation actuations, which can be reported as corresponding shifts of their photonic band gaps and structural colors. These self-driven biohybrid actuators could be used as elements for the construction of soft-bodied structural color robot, such as a biomimetic guppy with a swinging tail. Besides, with the integration of a self-driven biohybrid actuator and microfluidics, the advanced heart-on-a-chip system with the feature of microphysiological visuality has been developed for integrated cell monitoring and drug testing. This anisotropic inverse opal-derived biohybrid actuator could be widely applied in biomedical engineering.
关键词： cardiomyocyte,microfluidics,inverse opal,heart on a chip,structural color,actuator
更新于2025-09-04 15:30:14
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Nonlinearities Associated with Impaired Sensors in a Typical SHM Experimental Set-Up
摘要： Structural Health Monitoring (SHM) gives a diagnosis of a structure assessing the structural integrity and predicting the residual life through appropriate data processing and interpretation. A structure must remain in the design domain, although it can be subjected to normal aging due to usage, action of the environment, and accidental events. SHM involves the integration of electronic devices in the inspected structure that sometimes are Piezoelectric Transducers (PZT). These are lightweight and small and can be produced in different geometries. They are used both in guided wave-based and electromechanical impedance-based methods. The PZT bonding requires essential steps such as preparation of the surfaces, application of the adhesive, and assembly that make the bonding process not so easy to be realised. Furthermore, adhesives are susceptible to environmental degradation. Transducer debonding or non-uniform distributed glue underneath the sensor causes the reduction of the performance and can affect the reliability of the SHM system. In this paper, a sensor diagnostic method for the monitoring of the PZT operational status is proposed in order to detect bonding defect/damage between a PZT patch and a host structure. The authors propose a method based on the nonlinear behaviour of the contact PZT/structure that allows the identification of the damaged PZT and the geometrical characterization of the debonding. The feasibility of the diagnostic procedure is demonstrated by numerical studies and experiments, where disbonds were created by inhibiting the adhesive action on a part of the interface through Te?on ?lm. The proposed method can be used to evaluate the sensor functionality after an extreme loading event or over a long period of service time.
关键词： impaired sensor,Structural Health Monitoring,Time of Flight,subharmonics
更新于2025-09-04 15:30:14