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PUSH-PULL PHENOMENON OF A DIELECTRIC PARTICLE IN A RECTANGULAR WAVEGUIDE
摘要： The electromagnetic force acting on a Rayleigh particle placed in a rectangular waveguide is studied. The particle is excited using the lowest order TE 10 mode. It is determined that the particle is laterally trapped at the high intensity region of the electric ?eld and either pushed away from or pulled toward the light source. This push-pull phenomenon depends on whether the frequency of the light wave is above or below the cuto? frequency (i.e., the particle can be pushed or pulled by tuning the frequency). While conventional optical tweezers rely on a balance of scattering and gradient force in the propagation direction, the phenomenon predicted here switches between the two forces near the lowest cuto? in a waveguide.
关键词： TE 10 mode,electromagnetic force,rectangular waveguide,gradient force,optical tweezers,scattering force,Rayleigh particle,push-pull phenomenon
更新于2025-09-16 10:30:52
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Calculation of electric field gradient in spherical quantum dots
摘要： We have calculated the ground and excited energy states of the quantum dot as a function of the depth of con?ning potential well and radius R. Based on the calculated energies and wave functions, the electric ?eld gradient induced by the non-spherical charge at the impurity is investigated as a function of dot radius and the con?ning potential. For Deuterium dot with spherical con?ning potential, the expectation value of the quadrupole moment operator is carried out. The calculations show that the con?ning potential and the impurity charge have a great in?uence on the electric ?eld gradient and the quadrupole moment. It is found that as the con?ning potential increases, the peak position of the electric ?eld gradient shifts toward smaller dot radii and its amplitude increases with the increase of con?ning potential.
关键词： quadrupole moment,electronic structure,Spherical quantum dot,electric ?eld gradient
更新于2025-09-16 10:30:52
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In situ Construction of Gradient Heterojunction using Organic VOx Precursor for Efficient and Stable Inverted Perovskite Solar Cells
摘要： Inverted perovskite solar cells (PSCs) have attracted tremendous attention recently but the energy levels between the perovskite absorber and conventional hole transport layers (HTL) are mismatch, resulting in the lower open-circuit voltages (Voc) than that of regular PSCs. Herein, a gradient heterojunction (GHJ) based on poly(3,4?ethylenedioxythiophene: polystyrenesulphonate) (PEDOT:PSS)/PEDOT:PSS-VOx was constructed in situ by low-temperature annealing and used as HTL of the inverted PSCs. This GHJ structure fabricated conveniently by doping a small amount of triisopropoxyvanadium oxide isopropyl alcohol solution into the PEDOT:PSS solution during spin-coating can efficiently facilitate charge separation and improve charge extraction efficiency, leading to significantly improved PSC performance with Voc up to 1.02 V and power conversion efficiency (PCE) to 18.0%. More impressively, owing to the more hydrophobic surface and lower acidity than the PEDOT:PSS layer after the formation of high work function VOx mainly on the surface of HTL, the GHJ-based PSCs show excellent long-term stability, which retain over 80% or 70% of their initial PCEs after exposure to full spectrum illumination in N2 for 750 h or in air for 175 h, respectively. These results illustrate the significant advantages of the in situ formed VOx-modified HTLs in gradient structures using organic VOx precursors, providing important clues in constructing GHJ for inverted PSCs with high efficiency and stability.
关键词： Gradient heterojunction,Hole transport layer,Stability,Power conversion efficiency,Perovskite solar cells
更新于2025-09-12 10:27:22
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Controlled generation of chimera states in SQUID metasurfaces using DC flux gradients
摘要： SQUID (Superconducting QUantum Interference Device) metasurfaces, subject to a time-independent (dc) flux gradient and driven by a sinusoidal (ac) flux field, support chimera states that can be generated with zero initial conditions. The dc flux gradient and the amplitude of the ac flux can thus control the number of desynchronized clusters of such a generated chimera state (i.e., its “heads”) as well as their location and size. The combination of three measures, i.e., the synchronization parameter averaged over the period of the driving flux, the strength of incoherence, and the discontinuity measure, is used to predict the emergence or not of a chimera state and its multiplicity on the parameter plane of the dc flux gradient and the ac flux amplitude. Moreover, the full-width half-maximum of the distribution of the values of the synchronization parameter averaged over the period of the ac driving flux, allows to distinguish chimera states from non-chimera, partially synchronized states. Our findings are relevant from the pointview of both theory and applications. The SQUID oscillator provides an excellent physical example of systems with inertia and driving, for which chimera states have been under-examined. Finally, in the parameter regime under consideration, SQUID lattices are systems which are experimentally realisable and have very important applications in metamaterials science.
关键词： Flux gradient,SQUID Metasurfaces,Chimera states,Superconducting metamaterials
更新于2025-09-12 10:27:22
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Non-Photochemical Pulsed-Laser-Induced Nucleation in a Continuous-Wave-Laser-Induced Phase-Separated Solution Droplet of Aqueous Glycine Formed by Optical Gradient Forces
摘要： A centimeter-sized, laser-induced phase-separated (LIPS) solution droplet, which was formed by tightly focusing a continuous-wave near-infrared laser beam at the glass/solution interface of a millimeter-thick layer of glycine in D2O with a supersaturation ratio, S, of 1.36 was irradiated with a single unfocused nanosecond near-infrared laser pulse in order to study the effect of non-photochemical laser-induced nucleation (NPLIN) on the droplet, as well as to help characterize the behavior of the LIPS droplet. Additionally, a control NPLIN experiment was conducted on an S = 1.50 supersaturated solution of glycine/D2O in the same cell to better understand the differences between NPLIN in a LIPS droplet and an ordinary supersaturated solution. These experiments revealed that NPLIN could nucleate crystals within a LIPS droplet, although the growth of these crystals was inhibited during the first 5 min of the droplet’s relaxation. For the first 40 min of its relaxation, the LIPS droplet was observed to be more labile to spontaneous nucleation than the control S = 1.50 solution, although the growth of spontaneously nucleated crystals was also inhibited during the first 5 min of the droplet’s relaxation. This suggests that although the macroscopic phase boundary between the LIPS droplet and the surrounding solution disappeared after approximately 5 min, the full microscopic relaxation of the LIPS droplet took at least 40 min. The resulting crystals were analyzed using powder X-ray diffraction, and 100% of crystals formed within the LIPS droplet induced by NPLIN with linearly polarized light and by spontaneous nucleation were α-glycine, while crystals formed outside of the LIPS droplet were mixtures of α- and γ-glycine. The results suggest that the LIPS droplet and the surrounding solution are not equilibrium phases of aqueous glycine, but phases in which optical gradient forces have induced a partitioning of large and small solute clusters.
关键词： Polymorphism,Optical gradient forces,Laser-induced phase separation,Non-photochemical laser-induced nucleation,Glycine
更新于2025-09-12 10:27:22
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Size-dependent instability of organic solar cell resting on Winkler-Pasternak elastic foundation based on the modified strain gradient theory
摘要： The present study employs the modified strain gradient theory (MSGT) in conjunction with the refined shear deformation plate theory to explore the buckling behaviour of simply supported and clamped OSC. The Winkler-Pasternak elastic foundation is implemented to idealise the foundation. The size-dependent effect of the OSC is captured by the three length scale parameters within the MSGT. The Hamilton principle is used to derive the equations of motion and the boundary conditions, and the Galerkin procedure is subsequently implemented to obtain the critical buckling load. Subsequently, the framework is extended to the thermally induced buckling behaviour, and three types of temperature rise patterns, namely uniform, linear and nonlinear temperature variations, along the thickness of the OSC are considered. Several verification studies are conducted to illustrate the accuracy of the present method. Besides, size-dependent material properties are taken into consideration during the numerical experiments. Thorough studies are conducted to demonstrate the difference between critical buckling loads and temperature variations obtained from the MSGT, the modified couple stress theory (MCST), and the classical plate theory (CPT) models. Furthermore, the effects of length scale parameter (hl), the aspect ratio (ab), the length-to-thickness ratio (ah) and the Winkler-Pasternak elastic foundation parameters on the buckling behaviour of the OSC are also revealed by the numerical results.
关键词： Refined shear deformation plate theory,Strain gradient elasticity theory,Thermal buckling,Organic solar cell,Mechanical buckling,Elastic foundation
更新于2025-09-12 10:27:22
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Experimental Investigations on the Effects of Multicomponent Laser Boriding on steels
摘要： In this investigation, the effects of the multicomponent (Ni+Cr+B4C) laser boriding on the microstructure, microhardness, ductility and toughness of AISI 1020 steel are studied. Thick, hard, non-acicular and uniform boride layer are obtained as a result of laser boriding. The impact test results indicate that the laser borided specimens treated at higher energy densities of the laser beam have better ductility and toughness as compared with the specimens treated with lower energy densities of the laser beam as well as the continuous and the interrupted borided specimens.
关键词： Microstructure,Multicomponent boriding,Laser beam,Hardness gradient,Steel,Ductility and Toughness
更新于2025-09-12 10:27:22
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Controllable fabrication of unidirectional liquid spreading surface through confining plasma eruption and femtosecond laser double pulses
摘要： The e?cient and simple fabrication of a self-driven, continuous, and controllable unidirectional liquid spreading surface is an enormous challenge. In this paper, we present a maskless, one-step, and controllable method to fabricate unidirectional high-speed liquid spreading surfaces. The method con?nes the eruption of plasma by using oblique glass and femtosecond (fs) laser double pulses. The oblique glass is used to regulate plasma density via plasma con?nement, and the double-pulse is used to control the ?nal processing energy by changing pulse delay. The gradient structure size can be controlled by adjusting the laser energy, pulse delay and the tilted glass angle. Moreover, It has even can both achieved a high-speed and unidirectional spreading. A 1 μL droplet ?ows approximately 7 mm in 640 ms with no increase of the corresponding width using the gradient grating structure fabricated under double pulses with a pulse delay of 1 ps. Using di?erent gradient channel assembly, a selective ?ow along designed direction can be achieved. The selective ?ow phenomenon is observed through customized liquid diode. By manufacturing continuous and adjustable gradient structure, the method is potential to control liquid ?ow in microsystem.
关键词： Wettability gradient surface,Liquid diode,Plasma con?nement,Unidirectional liquid,Double pulse,Femtosecond laser
更新于2025-09-12 10:27:22
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Investigation on Ti6Al4V laser metal deposition using Taguchi based grey approach
摘要： An optimization of laser metal deposition process considering tensile strength, clad hardness, clad grain size and clad porosity as performance characteristics were investigated. The influence of laser power and laser scan speed on the thermal gradient and cooling rate with regard Ti6Al4V powder coating on Ti6Al4V substrate was focused. Taguchi’s experimental design approach is employed for planning the experiments and analyzing the dependency of input variables on desired performance measures such as micro hardness, tensile strength, porosity and grain size. The laser scan speed is found as the dominant factor on the clad hardness while laser power has the influencing effect on grain size of the substrate. GRA is opted for determining the multi performance machining characteristics of laser metal deposition process. The experimental outcomes reveal that the proposed method of multi objective optimization considerably enhances the multi performance machining characteristics.
关键词： Laser metal deposition,Ti6Al4V,Grain size,Thermal gradient,Grey relational approach,Laser scan speed
更新于2025-09-12 10:27:22
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Regimes of two-color light bullet formation in a gradient waveguide
摘要： In this paper we concentrate on the remarkable role of a gradient waveguide in two-color light bullet formation. We study generation of the second harmonic in such an inhomogeneous nonlinear medium, taking into account diffraction and relatively weak temporal dispersion. Using the averaged Lagrangian method we consider all possible combinations of the range of group velocities (normal or anomalous dispersion) and waveguide geometry (focusing or defocusing waveguide). Stability conditions for a propagating two-color light bullet are derived analytically. We demonstrate the formation of a stable two-component light bullet in a parabolic planar quadratically nonlinear waveguide either at anomalous or at normal group velocity dispersion. We discuss also the results of numerical simulation con?rming our analytical ?ndings. Besides that, simulation allows us to expand the scope of the study and to show light bullet propagation at a certain phase mismatching and the formation of a stable coupled localized structure from a signal at the fundamental frequency as well.
关键词： diffraction,second harmonic generation,two-color light bullet,waveguide geometry,averaged Lagrangian method,group velocities,stability conditions,gradient waveguide,temporal dispersion,numerical simulation
更新于2025-09-12 10:27:22