- 标题
- 摘要
- 关键词
- 实验方案
- 产品
过滤筛选
- 2019
- 2017
- Phased-array
- Ultrasound-guided high-intensity focused ultrasound (USgHIFU)
- Targeting accuracy
- Calibration
- cryostat
- low intensity low temperature
- space solar cells
- LILT
- solar cell characterization
- FSO Communication System
- Optoelectronic Information Science and Engineering
- Electrical Engineering and Automation
- Galgotias College of Engineering and Technology
- Shanghai Jiao Tong University
- Fraunhofer Institute for Solar Energy Systems ISE
-
Susceptibility of LED street lamps to voltage dips
摘要： There is an ongoing transition from high-pressure sodium lamps to LED street lamps that offer higher efficiency, cost saving and better photometric performance. This transition could lead to unintended consequences such as light flicker and extinguishing in street lighting applications when they are exposed to voltage dips. The goal of this paper is to analyse the light intensity variation of various street lamps when they are exposed to voltage dips. Several performance metrics for quantifying immunity of lamps have been proposed. Values for these metrics are obtained by applying artificial voltage dips to lamps. For voltage dips with residual voltage above 38%, lamps are immune in terms of a short-term light flicker metric. For residual voltage above 25%, light intensity reduces but without extinguishing. Compared to an incandescent lamp and high-pressure sodium lamp, LED street lamps exhibit longer zero-light intensity duration. Most of the studied LED street lamps exhibit uncoordinated light intensity drops, longer or shifted, with respect to the applied voltage dip. Individual characteristics of LED street lamps require testing before installation to prevent unexpected consequences. Recommendations are given for standardisation committees to implement an assessment method for lighting equipment.
关键词： voltage dips,LED street lamps,light intensity variation,immunity,performance metrics
更新于2025-09-23 15:19:57
-
Data-Sets for Indoor Photovoltaic Behavior in Low Lighting Conditions
摘要： Analysis of voltage–current behavior of photovoltaic modules is a critical part of their modeling. Parameter identification of these models demands data from them, measured in realistic environments. In spite of advancement in modeling methodologies under solar lighting, few analyses have been focused on indoor photovoltaics. Lack of accurate and reproducible data as a major challenge in this field is addressed here. A high accuracy measurement setup for evaluation and analysis of indoor photovoltaic modules is explained. By use of this system, different modules are measured under diverse environmental conditions. These measurements are structured in data-sets that can be used for either analysis of physical environment effects and modeling or development of specific parameter identification methods in low light intensity conditions.
关键词： photovoltaic,energy harvesting,light measurement,low light intensity,indoor lighting
更新于2025-09-23 15:19:57
-
Cavitation inception pressure and bubble cloud formation due to the backscattering of high-intensity focused ultrasound from a laser-induced bubble
摘要： Cavitation bubble cloud formation due to the backscattering of high-intensity focused ultrasound (HIFU) from a laser-induced bubble in various water temperatures and dissolved oxygen (DO) has been investigated. A laser-induced bubble generated near the geometrical focus of HIFU is utilized to yield intense negative pressure by the backscattering. Optical observation with a high-speed video camera and pressure measurement with a fiber-optic probe hydrophone are conducted simultaneously to understand the forming process of a bubble cloud and corresponding pressure field by the backscattering. Optical observation shows that a bubble cloud grows stepwise forming multiple layers composed of tiny cavitation bubbles, and the cavitation inception position is consistent with the local minimum pressure position simulated with the ghost fluid method. The bubble cloud grows larger in the opposite direction of HIFU propagation, and the absolute value of the cavitation inception pressure decreases with an increase in water temperature. The linear correlation between cavitation inception pressure and water temperature agrees with that given by Vlaisavljevich, Xu, Maxwell, Mancia, Zhang, Lin, Duryea, Sukovich, Hall, Johnsen, and Cain [IEEE Trans. Ultrason. Ferroelectr. Freq. Control 63, 1064–1077 (2016)]. However DO has minor dependence on the cavitation inception pressure when DO is degassed sufficiently. Furthermore, the gas nucleus size that might exist in the experiment has been estimated by using bubble dynamics.
关键词： Dissolved oxygen,Water temperature,Bubble cloud formation,Cavitation inception pressure,Laser-induced bubble,High-intensity focused ultrasound,Cavitation
更新于2025-09-23 15:19:57
-
In-Situ LED-Based Observation of Snow Surface and Depth Transects
摘要： As part of a new snowpack monitoring framework, this study evaluated the feasibility of using an LED LIDAR (Leddar) time of ?ight sensor for snowpack depth measurement. The Leddar sensor has two additional features over simple sonic ranging sensors: (i) the return signal is divided into 16 segments across a 48° ?eld of view, each recording individual distance-to-target (DTT) measurements; (ii) an index of re?ectance or intensity signal is recorded for each segment. These two features provide information describing snowpack morphology and surface condition. The accuracy of Leddar sensor DTT measurements for snow depth monitoring was found to be < 20 mm, which was better than the 50 mm quoted by the manufacturer, and the precision was < 5 mm. Leddar and independent sonic ranger snow depth measurement showed strong linear agreement (r2 = 0.98). There was also a strong linear relationship (r2 = 0.98) between Leddar and manual ?eld snow depth measurements. The intensity signal response was found to correlate with snow surface albedo and inversely with air temperature (r = 0.77 and ?0.77, respectively).
关键词： snowpack depth,LED LIDAR,intensity,LIDAR,Leddar,sonic ranging device
更新于2025-09-23 15:19:57
-
Ionization and acceleration of multiply charged gold ions in solid film irradiated by high intensity laser
摘要： In this paper, we present the mechanisms of ionization of a thin gold ?lm irradiated by a high-intensity, short-pulse laser in the range of I ? 1020(cid:2)22 W=cm2 and the associated acceleration of multiply charged gold ions. A numerical one-dimensional simulation using an extended particle-in-cell code, which includes atomic and collisional relaxation processes, indicates that two types of acceleration, hole-boring radiation pressure acceleration (RPA) and target normal sheath acceleration (TNSA), contribute to the generation of highly charged ions with kinetic energies on the order of 10 MeV/u. In each acceleration, a longitudinal electrostatic ?eld excited by different mechanisms dominantly ionizes atoms to higher charge states and accelerates them to the vacuum region from the rear surface, which is opposite the front surface irradiated by the laser ?eld. The ?eld ionization process dominantly ionizes high energy ions to the high charge state, while a large number of ions with energy <1 MeV=u are ionized by an electron impact ionization process. In TNSA, a multiply charged ion generated at the rear surface is accelerated to the maximum energy although the ion with the highest charge state is generated at the front surface in RPA. However, the existence of contamination, such as water vapor, suppresses the ion energy of TNSA to less than that of RPA since the sheath ?eld readily accelerates the protons and oxygen prior to the acceleration of the gold ions. Our derived theoretical scaling describes the maximum ion energy for each charge state in the cases with and without contamination using the relationship between the longitudinal electrostatic ?eld pro?le near the rear surface and the classical tunnel ?eld ionization model.
关键词： acceleration,multiply charged gold ions,RPA,TNSA,high-intensity laser,ionization,solid film
更新于2025-09-23 15:19:57
-
Exploring phase contrast imaging with a laser-based K?± x-ray source up to relativistic laser intensity
摘要： this study explores the ability of a hard Kα x-ray source (17.48 keV) produced by a 10 TW class laser system operated at high temporal contrast ratio and high repetition rate for phase contrast imaging. For demonstration, a parametric study based on a known object (PET films) shows clear evidence of feasibility of phase contrast imaging over a large range of laser intensity on target (from ~1017 W/cm2 to 7.0 × 1018 W/cm2). To highlight this result, a comparison of raw phase contrast and retrieved phase images of a biological object (a wasp) is done at different laser intensities below the relativistic intensity regime and up to 1.3 × 1019 W/cm2. this brings out attractive imaging strategies by selecting suitable laser intensity for optimizing either high spatial resolution and high quality of image or short acquisition time.
关键词： biological imaging,laser intensity,phase contrast imaging,high repetition rate,Kα x-ray source
更新于2025-09-23 15:19:57
-
Generation of gamma radiation by a subterawatt ultrashort laser pulse: optimisation of preplasma and pulse duration
摘要： We report an experimental and numerical study of the acceleration of electrons in a plasma interacting with a subterawatt laser pulse (intensity of ~3 × 10^18 W cm^–2 at a pulse duration of 50 fs). A preplasma layer on the surface of a molybdenum target is formed by an additional laser pulse with a duration of 8 ns and an intensity of ~2 × 10^12 W cm^–2. It is shown that an increase in the laser pulse duration to 1700 fs at a constant energy (and a proportional decrease in intensity) leads to an increase in the yield of bremsstrahlung γ-radiation by more than an order of magnitude when the nanosecond pulse is ahead of the femtosecond one by 15 – 25 ns. Interferometry data and results of diagnostics of optical and γ-radiation of a plasma demonstrate that the collisional ionisation of atoms by electrons oscillating in the field of such a laser pulse plays an essential role in the formation of electron density profile. The sensitivity of the described effect to the level of amplified spontaneous emission is determined, despite the nanosecond pulse impact. Numerical simulations show that at a large pulse duration, the acceleration of electrons is stipulated by the beaking of plasma waves excited during stimulated Raman scattering of laser radiation.
关键词： preplasma,subrelativistic intensity,amplified spontaneous emission,laser plasma,contrast,electron acceleration,collisional ionisation
更新于2025-09-23 15:19:57
-
Three-player polaritons: nonadiabatic fingerprints in an entangled atom-molecule-photon system
摘要： A quantum system composed of a molecule and an atomic ensemble, con?ned in a microscopic cavity, is investigated theoretically. The indirect coupling between atoms and the molecule, realized by their interaction with the cavity radiation mode, leads to a coherent mixing of atomic and molecular states. It is shown for the Na2 molecule that by changing the cavity wavelength and the molecular states, and at strong enough cavity ?eld strengths hybrid atom-molecule-photon polaritons are formed. Moreover, an unforeseen intensity borrowing e?ect, which can be seen as a strong nonadiabatic ?ngerprint, is identi?ed in the atomic transition peak, originating from the contamination of the atomic excited state with excited molecular rovibronic states.
关键词： nonadiabatic,entangled atom-molecule-photon system,intensity borrowing effect,polaritons,cavity quantum electrodynamics
更新于2025-09-23 15:19:57
-
Structural Modification of Graphene on Copper Substrates Irradiated by Nanosecond High-Intensity Ion Beams
摘要： Interaction of a nanosecond high-intensity pulsed ion beam with thin graphene films on copper substrates is analyzed. Methods of Raman spectroscopy are used to investigate the degree of graphene degradation depending on the integral implanted dose. The role of the substrate in the structural degradation of graphene irradiated by charged particle beams is demonstrated using the software package SRIM, intended for modeling radiative defect cascades under irradiation by charged particle beams, and the data on radiation resistance of graphene available in the literature.
关键词： graphene,electromagnetic radiation,high-intensity ion beams
更新于2025-09-23 15:19:57
-
Intensity-Based Nonoverlapping Area Registration Supporting “Drop-Outs” in Terms of Model-Based Radiostereometric Analysis
摘要： A model-based radiostereometric analysis (MBRSA) is a method for precise measurement of prosthesis migration, which does not require marking the implant with tantalum beads. Instead, the prosthesis pose is typically recovered using a feature-based 2D-3D registration of its virtual model into a stereo pair of radiographs. In this study, we evaluate a novel intensity-based formulation of previously published nonoverlapping area (NOA) approach. The registration is capable of performing with both binary radiographic segmentations and nonsegmented X-ray images. In contrast with the feature-based version, it is capable of dealing with unreliable parts of prosthesis. As the straightforward formulation allows efficient acceleration using modern graphics adapters, it is possible to involve precise high-poly virtual models. Moreover, in case of binary segmentations, the nonoverlapping area is simply interpretable and useful for indicating the accuracy of the registration outcome. In silico and phantom evaluations were performed using a cementless Zweymüller femoral stem and its reverse engineered (RE) model. For initial pose estimates with difference from the ground-truth limited to ±4 mm and ±4°, respectively, the mean absolute translational error was not higher than 0.042 ± 0.035 mm. The error in rotation around the proximodistal axis was 0.181 ± 0.265°, and the error for the remaining axes was not higher than 0.035 ± 0.037°.
关键词： radiostereometric analysis,nonoverlapping area,drop-outs,2D-3D registration,intensity-based registration
更新于2025-09-19 17:15:36