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- South China University of Technology
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Laser Ablation - From Fundamentals to Applications || Nanosecond Laser Ablation: Mathematical Models, Computational Algorithms, Modeling
摘要： The basic mathematical models, computational algorithms, and results of mathematical modeling of various modes of laser action on metals are considered. It is shown that for mathematical description and analysis of the processes of laser heating, melting, and evaporation of condensed media, various theoretical approaches are used: continuum, kinetic, atomistic, etc. Each of them has its own field of applicability, its advantages, and disadvantages. Mathematical description of ns-laser ablation is usually carried out within the framework of continuum approach in the form of hydrodynamic models that take into account reaction of irradiated material to varying density, pressure, and energy both in the target and in the vapor-gas medium. Within the framework of continuum approach, a multiphase, multifront hydrodynamic model and computational algorithm were constructed that were designed for modeling ns-PLA of metal targets embedded in gaseous media. It is shown that proposed model and computational algorithm allow to carry out the simulation of interrelated mechanisms of heterogeneous and homogeneous evaporation of metals manifested as a series of explosive boiling. Modeling has shown that explosive boiling in metals occurs due to the presence of a near-surface temperature maximum. It has been established that in ns-PLA, exposure regimes can be realized in which a phase explosion is the main mechanism of material removal. The verification of reliability of obtained results was carried out by comparing experimental data and calculations with atomistic models.
关键词： explosive boiling,phase explosion,hydrodynamic model,laser action,nanosecond pulse,mathematical modeling,subsurface temperature maximum
更新于2025-09-12 10:27:22
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[IEEE 2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting - Atlanta, GA, USA (2019.7.7-2019.7.12)] 2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting - On a Unified Apporach Towards the Modeling of Nonlocal Hydrodynamic Non-classical Response from Plasmonic Nanotopologies
摘要： In this work, we present a unified approach to model the optical response from a classical local and a nonclassical nonlocal hydrodynamic interface. The modeling is based on a boundary integral equation (BIE) representation. This representation is general for both 2D and 3D problems and can be numerically solved by the Method of Moments (MoM) algorithm. An example is then demonstrated for the 2D and 3D case. A very good agreement with the generalized Mie theory has been demonstrated.
关键词： Boundary Integral Equations (BIEs),Plasmonics,Nonlocal Hydrodynamic Model,Multiphysics Modeling
更新于2025-09-12 10:27:22
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Appropriate Nonlocal Hydrodynamic Models for the Characterization of Deep‐Nanometer Scale Plasmonic Scatterers
摘要： The interaction between light and plasmonic systems with deep-nanometer characteristics, which is essentially governed by quantum mechanical effects, has been extensively studied by the nonlocal hydrodynamic approach. Several hydrodynamic models, supplemented by additional boundary conditions, have been introduced in order to describe the collective motion of the free electron gas in metals. Four hydrodynamic models, namely the hard wall hydrodynamic model (HW-HDM), the curl-free hydrodynamic model, the shear forces hydrodynamic model, and the quantum hydrodynamic model (Q-HDM), are thoroughly investigated. The investigation studies the mode structure (the natural modes or, in quantum optics, the quasi-normal modes) of the spherical core–shell topology, which is complemented by the plane wave response from the system. The results of the above hydrodynamic models are also compared with those of the specular reflection method. It is demonstrated that the choice of a particular hydrodynamic model strongly affects the natural frequencies and modes in the mode structure of the topology and thus drastically modifies the simulated fields in the near and far regions. Contrary to HW-HDM and Q-HDM, the other two hydrodynamic models fail to predict the particles’ response accurately, showing artifactual mode hybridization.
关键词： additional boundary conditions,natural (quasi-normal) modes,nonlocal hydrodynamic models,scattering
更新于2025-09-11 14:15:04
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Representing hydrodynamically important blocking features in coastal or riverine lidar topography
摘要： New automated methods are developed for identifying narrow landscape features that cause hydrodynamic blocking and might have critical impacts for management models of river flooding, coastal inundation, climate change, or extreme event analysis. Lidar data processed into a fine-resolution raster (1 m × 1 m) can resolve narrow blocking features in topography but typically cannot be directly used for hydrodynamic modeling. For practical applications such data are abstracted to larger scales, which can result in a loss of hydrodynamic blocking effects. The traditional approach to resolving hydrodynamic blocking features is to represent them as cell boundaries within a customized unstructured grid that is tuned to the spatial features. A new automated edge-blocking approach is developed, which allows application of an arbitrarily structured (Cartesian) mesh at coarser scales and provides contiguous representation of blocking features along Cartesian cell boundaries. This approach distorts the shape of a blocking feature (i.e., making it rectilinear along grid cell faces) but retains its critical hydrodynamic blocking height characteristics and spatial continuity within the topographic model.
关键词： coastal inundation,climate change,hydrodynamic blocking,river flooding,lidar topography,extreme event analysis
更新于2025-09-10 09:29:36
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Blow-up of the smooth solution to the IBVP of three-dimensional quantum hydrodynamic models
摘要： The initial–boundary value problem for three-dimensional quantum hydrodynamic models is considered outside a unit ball. It is proved that the smooth solution will blow up in a finite time provided that a weighed functional associated with the initial momentum is large.
关键词： Smooth solution,Blow-up,Quantum hydrodynamic model
更新于2025-09-10 09:29:36
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Investigation on laser plasma instability of the outer ring beams on SGIII laser facility
摘要： In order to study the laser plasma instabilities (LPIs) in the context of some novel six-side laser-driven indirect designs like the six-cylinder-port hohlraum and the three-axis cylindrical hohlraum, where the laser beams inject in hohlraum with a large angle. LPI experiments in cylindrical hohlraum with only outer beams were designed and performed based on the current laser arrangement condition of SGIII laser facility for the first time. Stimulated Brillouin backscatter (SBS) was found to be the dominant instability with high instantaneous reflectivity in experiments. A typical feature was obtained in the time-resolved spectra of SBS, which maintained similar for different laser intensities of the interaction beam. The experimental data are analyzed by the hydrodynamic simulations combined with HLIP code, which is based on the ray-tracing model. By analysis of experimental data, it is argued that the mixture of gas and Au in the region of their interface is important to SBS, which indicates the need for the mixture model between the filled gas and the high Z plasma from hohlraum wall in the hydrodynamic simulations. Nonlinear saturation of SBS as well as the smoothed beam are also discussed here. Our effective considerations of the ions pervasion effect and the smoothed beam provide utilitarian ways for improvement of the current ray-tracing method.
关键词： laser plasma instabilities,hydrodynamic simulations,stimulated Brillouin backscatter,ray-tracing model,SGIII laser facility
更新于2025-09-09 09:28:46
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A blue fluorescent labeling technique utilizing micro- and nanoparticles for tracking in LIVE/DEAD® stained pathogenic biofilms of Staphylococcus aureus and Burkholderia cepacia
摘要： Strategies that target and treat biofilms are widely applied to bacterial cultures using popular live/dead staining techniques with mostly red or green fluorescent markers (eg, with SYTO? 9, propidium iodide, fluorescein). Therefore, visualizing drugs or micro- and nanoparticulate delivery systems to analyze their distribution and effects in biofilms requires a third fluorescent dye that does not interfere with the properties of the live/dead markers. The present study establishes and evaluates a model for tracking polymeric particles in fluorescently stained biological material. To this end, poly(d,l-lactide-co-glycolide) (PLGA)-based micro- and nanoparticles were used as well-established model systems, which, because of their favorable safety profiles, are expected to play important future roles with regard to drug delivery via inhalation. PLGA was covalently and stably labeled with 7-amino-4-methyl-3-coumarinylacetic acid (AMCA), after which blue fluorescent poly(ethylene glycol)-block-PLGA (PEG-PLGA) particles were prepared using a mixture of fluorescent AMCA-PLGA and PEG-PLGA. Because chitosan is known to reduce negative surface charge, blue fluorescent PEG-PLGA-particles with chitosan were also prepared. These micro- and nanoparticles were physicochemically characterized and could be clearly distinguished from live/dead stained bacteria in biofilms using confocal laser scanning microscopy.
关键词： 7-amino-4-methyl-3-coumarinylacetic acid,cystic fibrosis,PEG,PLGA,chitosan,hydrodynamic diameter,confocal laser scanning microscopy
更新于2025-09-09 09:28:46
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Current-Driven Dyakonov-Shur Instability in Ballistic Nanostructures with a Stub
摘要： We develop a compact model for the THz plasmonic unstable structures with tunable narrow-channel regions of an increased width (called plasmonic “stubs”) using the transmission line analogy and derive the dispersion equations describing unstable plasmons. The solutions of the dispersion equations in the plasmonic systems with the electron drift, which are derived using the hydrodynamic model and generalized to account for the stubs, illustrate the device physics and can be used for design and characterization of THz plasmonic-electronic sources. Our results show that adding stubs allows one to control the Dyakonov-Shur instability in plasmonic ?eld-e?ect transistors by optimizing the boundary conditions, controlling the plasma velocity, and making it possible to drive periodic plasmonic structures wirelessly, thus avoiding the contact problems.
关键词： THz plasmonic,hydrodynamic model,plasmonic stubs,Dyakonov-Shur instability,ballistic nanostructures
更新于2025-09-09 09:28:46
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Application of kinetic flux vector splitting scheme for solving viscous quantum hydrodynamical model of semiconductor devices
摘要： In this article, one-dimensional viscous quantum hydrodynamical model of semiconductor devices is numerically investigated. The model treats the propagation of electrons in a semiconductor device as the flow of a charged compressible fluid. It plays an important role in predicting the behavior of electron flow in semiconductor devices. The nonlinear viscous quantum hydrodynamic models contain Euler-type equations for density and current, viscous and quantum correction terms, and a Poisson equation for electrostatic potential. Due to high nonlinearity of model equations, numerical solution techniques are applied to obtain their solutions. The proposed numerical scheme is a splitting scheme based on the kinetic flux-vector splitting (KFVS) method for the hyperbolic step, and a semi-implicit Runge-Kutta method for the relaxation step. The KFVS method is based on the direct splitting of macroscopic flux functions of the system on the cell interfaces. The second order accuracy of the scheme is achieved by using MUSCL-type initial reconstruction and Runge-Kutta time stepping method. Several case studies are considered. For validation, the results of current scheme are compared with those obtained from the splitting scheme based on the NT central scheme. The effects of various parameters such as device length, viscosities, different doping and voltage are analyzed. The accuracy, efficiency and simplicity of the proposed KFVS scheme validates its generic applicability to the given model equations.
关键词： Numerical simulation,Kinetic flux-vector splitting scheme,Semiconductor devices,Viscous quantum hydrodynamic model
更新于2025-09-04 15:30:14
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Investigation of moments-based transport models applied to plasma waves and the Dyakonov–Shur instability
摘要： Transport models based on balance equations with different degrees of numerical complexity can be derived from the Boltzmann transport equation (BTE). In this paper two different drift-diffusion models based on the first two moments of the BTE as well as two hydrodynamic models based on four moments are derived and analyzed for their accuracy in the THz frequency range with emphasis on the generation of plasma waves. To this end, they are compared to the BTE in the small-signal regime under homogeneous bulk conditions where harmonic waves were assumed, which reveals that the hydrodynamic models provide a higher accuracy. It is also shown that the anisotropy of the distribution function must be taken into account in the closure relations. This leads to convective derivatives in the balance equations, which are very difficult to treat by numerical means in the case of semiconductor devices and are neglected in commercial TCAD suites. But without them a meaningful simulation of the Dyakonov–Shur plasma instability will not be possible.
关键词： Boltzmann transport equation,THz,drift-diffusion,plasma instability,hydrodynamic
更新于2025-09-04 15:30:14