- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
ANALYSIS OF MULTIPLICATION CHARACTERISTICS OF COAXIAL WAVEGUIDE LOADED CERAMIC UNDER EXTERNAL ELECTRIC FIELD
摘要： Multipacting is electron discharge that occurs in components operating in RF high-power electromagnetic fields. In this paper, we will study a new coaxial structure with a ceramic window. A similar structure is utilized in many high power devices for power transfer. Due to the multipactor effect, it will generate huge heat and cause damage to the window, ultimately affect the performance of microwave devices. In order to suppress the surface multipactor effect and improve the transmitting power, the application of an external DC bias is analyzed and simulated. A Monte Carlo algorithm is used to track the secondary electron trajectories and study the multipactor scenario on the surface of a ceramic window in a coaxial line by using 2-D particles distribution code. Since secondary electron multiplication needs to meet specific resonance conditions, an appropriate DC bias will generate a compensating trajectory and collision, which can suppress the secondary electron avalanche. The optimal value of this external bias voltage that will avoid the multipactor phenomenon in the coaxial line will be calculated by simulation in MATLAB.
关键词： DC bias,Coaxial waveguide,Monte Carlo simulation,Ceramic window,Multipacting
更新于2025-09-23 15:19:57
-
Monte Carlo Simulation of Laser-Ablated Particle Splitting Dynamic in a Low Pressure Inert Gas
摘要： A Monte Carlo simulation method with an instantaneous density dependent mean-free-path of the ablated particles and the Ar gas is developed for investigating the transport dynamics of the laser-ablated particles in a low pressure inert gas. The ablated-particle density and velocity distributions are analyzed. The force distributions acting on the ablated particles are investigated. The in?uence of the substrate on the ablated-particle velocity distribution and the force distribution acting on the ablated particles are discussed. The Monte Carlo simulation results approximately agree with the experimental data at the pressure of 8 Pa to 17 Pa. This is helpful to investigate the gas phase nucleation and growth mechanism of nanoparticles.
关键词： Monte Carlo simulation,instantaneous mean-free-path,ablated particles,transport dynamic,low pressure
更新于2025-09-23 15:19:57
-
Plasmonic Nanoslit Arrays Fabricated by Serial Bideposition: Optical and Surface-Enhanced Raman Scattering Study
摘要： Recently, studies have been carried out to combine surface-enhanced Raman spectroscopy substrates that are based on either localized surface plasmon or surface plasmon polariton structures. By combining these two systems, the individual drawbacks of each can be overcome. However, the manufacturing methods involved so far are sophisticated, labor-intensive, expensive, and technically demanding. We propose a facile method for the fabrication of a flexible plasmonic nanoslit SERS sensor. We utilized the pattern on periodic optical disks as an inexpensive substitute for printing the periodic pattern on polydimethylsiloxane with soft imprint lithography. The Ag nanoslits were fabricated by serial bideposition using the dynamic oblique angle deposition technique. The nanoslit structures were physically and optically characterized, and the experimental results were compared to the results of the numerical simulation: Monte Carlo and finite-difference time-domain simulation. The AgNS samples showed excellent SERS performance with an enhancement factor of ～105 and a limit of detection of 5 × 10-7 g/mL for a Rhodamine 6G solution. Their biosensing capability was demonstrated by the sensing of bilirubin.
关键词： FDTD,Ag nanoslit,Monte Carlo simulation,dynamic oblique angle deposition,SERS
更新于2025-09-23 15:19:57
-
Enhancement of optical penetration depth of LED-based NIRS systems by comparing different beam profiles
摘要： Near-Infrared Spectroscopy (NIRS) is a non-invasive brain imaging technique involving the quantification of oxy and deoxy-hemoglobin concentrations resolved from the measurement of Near-Infrared (NIR) light attenuation within the tissue. Previous studies have shown that NIR light is more influenced by the optical properties of the superficial layers than those of the deeper target layers such as cortex. NIR light produced by the Laser source penetrates deeper regions of the tissue rather than the LED source although Laser needs more expensive instrumentation. In this study, we investigate the effect of Uniform and Gaussian beam profiles on the enhancement of LED light penetration depth. The latter beam profiles were generated and compared using Flat and Aspherical lenses applied to the LED sources. In order to increase the signal to noise ratio, the lenses were also applied to the light detector. For performance analysis, two experiments were carried out by scanning the intra space of a liquid phantom by static and dynamic (pulsating) absorbers. Monte Carlo simulations were also carried out to be compared with the experiment. The results showed that Gaussian beam profile and in particular, Bi-Convex lenses applied to both source and detector leads to a greater light penetration depth in the liquid phantom close to that of a Laser source.
关键词： near infrared spectroscopy,optical sensors,biomedical optic,monte carlo simulation,instrumentation
更新于2025-09-23 15:19:57
-
[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Monte Carlo Simulation of CdTe Thin Film Recrystallization Process During Chlorine Activation
摘要： In this paper we studied the grain growth and orientation change of CdTe multi-crystallize thin film during chlorine activation. A simulation of the chlorine activation process is also carried on by Monte-Carlo method combined with annealing algorithm based on thermodynamic energy criterion. Visualized pixel images of simulation are in good agreement with experimental results. Based on these results a thermodynamic energy criterion is proposed for finding non-toxic substitutes of cadmium chloride and predictions of substitutes are given.
关键词： Monte-Carlo simulation,CdCl2,CdTe,Cl treatment
更新于2025-09-23 15:19:57
-
[IEEE 2019 25th International Workshop on Thermal Investigations of ICs and Systems (THERMINIC) - Lecco, Italy (2019.9.25-2019.9.27)] 2019 25th International Workshop on Thermal Investigations of ICs and Systems (THERMINIC) - Assessment of the validity of multi-domain LED model parameters in a broad current and temperature range
摘要： In this paper, a power switched, baseband modulation technique for visible light communications (VLC) is proposed and a theoretical model is constructed. It is shown that this technique, called single edge position modulation (SEPM), offers the unique performance characteristic that the communication properties reliability and power and spectral efficiency are invariable over a wide range of dimming levels. It is demonstrated that dimming robustness is obtained by increasing the number of bits per symbol. SEPM is compared with contemporary used baseband power switched modulation techniques for VLC that support dimming. The number of bits per symbol can be chosen to make a compromise between the dimming range over which reliability robustness is obtained on one hand, and the level of power and spectral efficiency on the other hand.
关键词： Modulation,visible light communications,reliability,Monte Carlo simulation,synchronization
更新于2025-09-23 15:19:57
-
[IEEE 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - Xiamen, China (2019.12.17-2019.12.20)] 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - A 220 GHz GaN HEMT Power Amplifier
摘要： Evolutions of Geant4 code have affected the simulation of electron backscattering with respect to previously published results. Their effects are quantified by analyzing the compatibility of the simulated electron backscattering fraction with a large collection of experimental data for a wide set of physics configuration options available in Geant4. Special emphasis is placed on two electron scattering implementations first released in Geant4 version 10.2: the Goudsmit-Saunderson multiple scattering model and a single Coulomb scattering model based on Mott cross section calculation. The new Goudsmit-Saunderson multiple scattering model appears to perform equally or less accurately than the model implemented in previous Geant4 versions, depending on the electron energy. The new Coulomb scattering model was flawed from a physics point of view, but computationally fast in Geant4 version 10.2; the physics correction released in Geant4 version 10.2p01 severely degrades its computational performance. Problems observed in electron backscattering simulation in previous publications have been addressed by evolutions in the Geant4 geometry domain.
关键词： Electrons,Monte Carlo,simulation,Geant4
更新于2025-09-23 15:19:57
-
Remote Spatio-Temporal Focusing over Multimode Fiber Enabled by Single-Ended Channel Estimation
摘要： Interest in deep probabilistic graphical models has increased in recent years, due to their state-of-the-art performance on many machine learning applications. Such models are typically trained with the stochastic gradient method, which can take a significant number of iterations to converge. Since the computational cost of gradient estimation is prohibitive even for modestly sized models, training becomes slow and practically usable models are kept small. In this paper we propose a new, largely tuning-free algorithm to address this problem. Our approach derives novel majorization bounds based on the Schatten- norm. Intriguingly, the minimizers of these bounds can be interpreted as gradient methods in a non-Euclidean space. We thus propose using a stochastic gradient method in non-Euclidean space. We both provide simple conditions under which our algorithm is guaranteed to converge, and demonstrate empirically that our algorithm leads to dramatically faster training and improved predictive ability compared to stochastic gradient descent for both directed and undirected graphical models.
关键词： Monte Carlo simulation methods,graphical models,Boltzmann distributions,Gradient methods,maximum likelihood estimation
更新于2025-09-23 15:19:57
-
High-speed light source depth estimation using spatially-resolved diffuse imaging
摘要： We describe a system for high-speed depth estimation of a light source embedded in a scattering medium. A polynomial model estimates source depth from the spatially-resolved, diffuse reflectance profile measured with a fibre optic probe on the surface of a scattering medium. A dataset of Monte Carlo reflectance profiles is generated over a range of typical optical properties and the model is fit to the simulated reflectance at four detector locations. The model accounts for a source depth up to 15 mm. Cross-validation using the Monte Carlo dataset produced a root mean square error of 0.12 mm. Experimental reflectance data is acquired with the detector probe, which consists of four optical fibres mounted in a black acetal plastic disk. The optical fibres are coupled into avalanche photodiodes for high-speed acquisition of the reflectance profile. When applied to measurements from a tissue-mimicking phantom with an embedded light source, the polynomial model generates depth estimates within 2 mm of the true depth, up to a source depth of 15 mm.
关键词： source location,Monte Carlo simulation,tissue optics,turbid media,diffuse reflectance
更新于2025-09-19 17:15:36
-
[IEEE 2019 Compound Semiconductor Week (CSW) - Nara, Japan (2019.5.19-2019.5.23)] 2019 Compound Semiconductor Week (CSW) - Photonic-crystal Lasers with Extremely Short Embedded Active-regions
摘要： Evolutions of Geant4 code have affected the simulation of electron backscattering with respect to previously published results. Their effects are quantified by analyzing the compatibility of the simulated electron backscattering fraction with a large collection of experimental data for a wide set of physics configuration options available in Geant4. Special emphasis is placed on two electron scattering implementations first released in Geant4 version 10.2: the Goudsmit-Saunderson multiple scattering model and a single Coulomb scattering model based on Mott cross section calculation. The new Goudsmit-Saunderson multiple scattering model appears to perform equally or less accurately than the model implemented in previous Geant4 versions, depending on the electron energy. The new Coulomb scattering model was flawed from a physics point of view, but computationally fast in Geant4 version 10.2; the physics correction released in Geant4 version 10.2p01 severely degrades its computational performance. Problems observed in electron backscattering simulation in previous publications have been addressed by evolutions in the Geant4 geometry domain.
关键词： Electrons,Monte Carlo,simulation,Geant4
更新于2025-09-19 17:13:59