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Transient thermoelastic response in a cracked strip of functionally graded materials via generalized fractional heat conduction
摘要： This work is devoted to analyzing a thermal shock problem of an elastic strip made of functionally graded materials containing a crack parallel to the free surface based on a generalized fractional heat conduction theory. The embedded crack is assumed to be insulated. The Fourier transform and the Laplace transform are employed to solve a mixed initial-boundary value problem associated with a time-fractional partial differential equation. Temperature and thermal stresses in the Laplace transform domain are evaluated by solving a system of singular integral equations. Numerical results of the thermoelastic fields in the time domain are given by applying a numerical inversion of the Laplace transform. The temperature jump between the upper and lower crack faces and the thermal stress intensity factors at the crack tips are illustrated graphically, and phase lags of heat flux, fractional orders, and gradient index play different roles in controlling heat transfer process. A comparison of the temperature jump and thermal stress intensity factors between the non-Fourier model and classical Fourier model is made. Numerical results show that wave-like behavior and memory effects are two significant features of the fractional Cattaneo heat conduction, which does not occur for the classical Fourier heat conduction.
关键词： functionally graded materials,thermal stress,crack,time-fractional heat conduction,phase lag of heat flux
更新于2025-09-19 17:15:36
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Multi-parameter optimization of a loose focusing high flux high-harmonic beamline
摘要： We perform a multi-dimensional parameter scan in the generation of high-order harmonics, with the main purpose to find the macroscopic conditions that optimize the harmonic yield in a specific spectral domain, around 40 eV for this particular case. The scanned parameters are the laser pulse energy, gas pressure, interaction cell position relative to focus and the cell length, while the fixed parameters are chosen to model a loose focusing configuration which is used in many existing laboratories. We performed the simulations with a 3D non-adiabatic model complemented by a detailed analysis of the phase matching mechanisms involved in an efficient harmonic generation. Based on the results we identify a range of parameter combinations that lead to a high yield in the specified spectral domain. The method and results presented here can be the framework for the design and construction of high flux high-order harmonic generation beamlines.
关键词： XUV flux,high-order harmonic generation,optimization,multi-dimensional parameter scan,numerical simulation
更新于2025-09-19 17:15:36
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[IEEE 2019 Workshop on Recent Advances in Photonics (WRAP) - Guwahati, India (2019.12.13-2019.12.14)] 2019 Workshop on Recent Advances in Photonics (WRAP) - Experimental Verification of Enhanced Photoluminescence in p-doped GaAs using Fluorescence Lifetime Measurements
摘要： Recent studies indicate that pretreating microorganisms with ribosome-targeting antibiotics may promote a transition in the microbial phenotype, such as the formation of persister cells; i.e., those cells that survive antibiotic treatment by becoming metabolically dormant. In this letter, we developed the first genome-scale modeling approach to systematically investigate the influence of ribosome-targeting antibiotics on the metabolism of Pseudomonas aeruginosa. An approach for integrating gene expression data with metabolic networks was first developed to identify the metabolic reactions whose fluxes were positively correlated with gene activation levels. The fluxes of these reactions were further constrained via a flux balance analysis to mimic the inhibition of antibiotics on microbial metabolism. It was found that some of metabolic reactions with large flux change, including metabolic reactions for homoserine metabolism, the production of 2-heptyl-4-quinolone, and isocitrate lyase, were confirmed by existing experimental data for their important role in promoting persister cell formation. Metabolites with large exchange-rate change, such as acetate, agmatine, and oxoglutarate, were found important for persister cell formation in previous experiments. The predicted results on the flux change triggered by ribosome-targeting antibiotics can be used to generate hypotheses for future experimental design to combat antibiotic-resistant pathogens.
关键词： persister cells,systems biology,flux balance analysis (FBA),Computational modeling and simulations in biology
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE International Conference on Space Optical Systems and Applications (ICSOS) - Portland, OR, USA (2019.10.14-2019.10.16)] 2019 IEEE International Conference on Space Optical Systems and Applications (ICSOS) - High Power Indium Phosphide Photonic Integrated Circuit for Pulse Position Modulation Free Space Optical Communications
摘要： Detection of defects in induction machine rotor bars for disassembled motors are required to evaluate machines considered for repair as well as fulfilling incremental quality assurance checks in the manufacture of new machines. Detection of rotor bar defects prior to motor assembly are critical in increasing repair efficiency and assuring the quality of newly manufactured machines. Many methods of detecting rotor bar defects in unassembled motors lack the sensitivity to find both major and minor defects in both cast and fabricated rotors along with additional deficiencies in quantifiable test results and arc-flash safety hazards. A process of direct magnetic field analysis can examine measurements from induced currents in a rotor separated from its stator yielding a high-resolution fingerprint of a rotor’s magnetic field. This process identifies both major and minor rotor bar defects in a repeatable and quantifiable manner appropriate for numerical evaluation without arc-flash safety hazards.
关键词： magnetic flux,ac motors,electromagnetic measurements,induction motors,rotors,AC machines
更新于2025-09-19 17:13:59
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Gas chromatography vs. quantum cascade laser-based??N <sub/>2</sub> O flux measurements using a novel chamber design
摘要： Recent advances in laser spectrometry offer new opportunities to investigate the soil–atmosphere exchange of nitrous oxide. During two field campaigns conducted at a grassland site and a willow field, we tested the performance of a quantum cascade laser (QCL) connected to a newly developed automated chamber system against a conventional gas chromatography (GC) approach using the same chambers plus an automated gas sampling unit with septum capped vials and subsequent laboratory GC analysis. Through its high precision and time resolution, data of the QCL system were used for quantifying the commonly observed nonlinearity in concentration changes during chamber deployment, making the calculation of exchange fluxes more accurate by the application of exponential models. As expected, the curvature values in the concentration increase was higher during long (60 min) chamber closure times and under high-flux conditions (FN2O > 150 μg N m?2 h?1) than those values that were found when chambers were closed for only 10 min and/or when fluxes were in a typical range of 2 to 50 μg N m?2 h?1. Extremely low standard errors of fluxes, i.e., from ～ 0.2 to 1.7 % of the flux value, were observed regardless of linear or exponential flux calculation when using QCL data. Thus, we recommend reducing chamber closure times to a maximum of 10 min when a fast-response analyzer is available and this type of chamber system is used to keep soil disturbance low and conditions around the chamber plot as natural as possible. Further, applying linear regression to a 3 min data window with rejecting the first 2 min after closure and a sampling time of every 5 s proved to be sufficient for robust flux determination while ensuring that standard errors of N2O fluxes were still on a relatively low level. Despite low signal-to-noise ratios, GC was still found to be a useful method to determine the mean the soil–atmosphere exchange of N2O on longer timescales during specific campaigns. Intriguingly, the consistency between GC and QCL-based campaign averages was better under low than under high N2O efflux conditions, although single flux values were highly scattered during the low efflux campaign. Furthermore, the QCL technology provides a useful tool to accurately investigate the highly debated topic of diurnal courses of N2O fluxes and its controlling factors. Our new chamber design protects the measurement spot from unintended shading and minimizes disturbance of throughfall, thereby complying with high quality requirements of long-term observation studies and research infrastructures.
关键词： gas chromatography,soil–atmosphere exchange,chamber design,nitrous oxide,quantum cascade laser,flux measurements
更新于2025-09-19 17:13:59
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Enhanced growth of Nd <sup>3+</sup> :MgGdB <sub/>5</sub> O <sub/>10</sub> laser crystals with intense multi-wavelength emission characteristics
摘要： Higher quality Nd:GMB crystal was obtained using enhanced K2Mo3O10–B2O3 flux. Intense multi-wavelength emissions reveal the potential in THz technology.
关键词： K2Mo3O10–B2O3 flux,Nd:GMB crystal,multi-wavelength emissions,THz technology
更新于2025-09-19 17:13:59
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Applicability of a gas analyzer with dual quantum cascade lasers for simultaneous measurements of N2O, CH4 and CO2 fluxes from cropland using the eddy covariance technique
摘要： We evaluated the applicability of a closed-path gas analyzer with two mid-infrared quantum cascade lasers (QCLs) for simultaneous measurement of nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2) fluxes from a cropland using the eddy covariance (EC) technique. The measurements were carried out in a typical vegetable field in the subtropical China during the wintertime, when the gas fluxes are at their lowest level in the year. A new approach was proposed to optimize the determination of lag times between the wind and gas concentration data, which was proven efficient to increase the reliability of the measured fluxes when the gas exchanges are weak. The dual-QCL analyzer showed a median precision (1σ) of 0.14 nmol mol?1 for N2O, 3.3 nmol mol?1 for CH4 and 0.36 μmol mol–1 for CO2 at sampling frequency of 10 Hz under the field conditions. Such precisions are better than, or comparable with, those of other commonly used closed-path or open-path gas analyzers, which are capable of measuring only one or two of the three gases. The detection limit of the EC system for measuring half-hourly fluxes were 0.05 nmol m?2 s?1 for N2O, 1.12 nmol m?2 s?1 for CH4 and 0.14 μmol m–2 s–1 for CO2. The results showed that 100% of the N2O, 87% of the CH4 and 96% of the CO2 fluxes were larger than the above detection limits. This study suggests that the EC technique using a closed-path gas analyzer with two quantum cascade lasers is qualified for reliable and simultaneous measurements of N2O, CH4 and CO2 fluxes from a subtropical cropland throughout the year. Moreover, EC method based on this type of gas analyzer provides an additional option for long-term and simultaneous flux measurements of the three greenhouse gases in a wide range of agricultural and natural ecosystems.
关键词： Nitrous oxide,eddy covariance,cropland,methane,flux,quantum cascade laser,carbon dioxide
更新于2025-09-19 17:13:59
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Flexible high flux solar simulator based on optical fiber bundles
摘要： High ?ux solar simulators have been widely used in solar thermal research due to their controllable ?ux intensity. Simulators based on optical-?ber transmission have recently gained further attention because of their superior ?exibility. In this study, we developed a ?exible, high-?ux solar simulator that consists of a xenon lamp-truncated ellipsoidal mirror array, a multicomponent glass optical-?ber bundle and a secondary concentrator. The ?exibility of the ?bers allows the simulator to produce various ?ux distributions in 2D and 3D space through corresponding optical-?ber bundle arrangements. Each bundle has a diameter of 10 mm and contains 30,000 optical ?bers that can transmit the high ?ux of a xenon lamp to a target. The density of the spot can reach 500 kW/m2. The intensity of the ?ux produced is determined by the power of the lamps, and the transmission properties and temperature resistance of the ?ber bundle.
关键词： Flux,Flexible,Solar simulator,Optical ?ber
更新于2025-09-19 17:13:59
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Lumen Degradation Lifetime Prediction for High Power White LEDs based on the Gamma Process Model
摘要： Nowadays, due to the advancement of design and manufacturing technology, there are many consumer products with high reliability. Similarly, the competition in the business sector influences the product development time to become shorter and that makes it difficult for manufacturers to evaluate the reliability of current products before new products are released to the market. This phenomenon is manifested in the lighting industry, especially for the high power white light-emitting diodes (LEDs) as these products have a long lifetime and high reliability. Currently, the standard to predict the lifetime of LEDs is based on a deterministic nonlinear least squares method which has low prediction accuracy. To overcome this, degradation models are being used to study the reliability of such products, considering the uncertainties and the quality characteristics whose degradation over a period of time can be related to the product lifetime. A stochastic approach based on gamma distributed degradation (GDD) is proposed in this study to estimate the long-term lumen degradation lifetime of phosphor-converted white LEDs. An accelerated thermal degradation test was designed to gather luminous flux degradation data which was analyzed based on maximum likelihood estimation (MLE) and the method of moments (MM) to estimate the parameters for the GDD model. The MLE method has shown superiority over MM in terms of the estimation of the model parameters due to its iterative algorithm being likely to find the optimal estimation. The lifetime prediction results show that the accuracy of the proposed method is much better than the TM-21 nonlinear least squares (NLS) approach which makes it promising for future industrial applications.
关键词： Luminous flux degradation,Gamma distributed degradation (GDD),Method of moments,Light-emitting diodes (LEDs),Maximum likelihood estimation
更新于2025-09-16 10:30:52
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Nonpairwise Interactions Induced by Virtual Transitions in Four Coupled Artificial Atoms
摘要： Various protocols implementing a quantum computer are being pursued, one of which is the adiabatic quantum computer. Natural interactions in electromagnetic environments are only two-body local interactions, but the construction or simulation of higher-order couplers is indispensable for a universal adiabatic quantum computer using conventional flux qubits (no nonstoquastic interactions). Here we show that in a specific flux-qubit coupler design without ancilla qubits, four-body stoquastic interactions are induced by virtual coupler excitations. For specific parameter regimes they are the leading effect and can be tuned up to the gigahertz range.
关键词： adiabatic quantum computer,four-body interactions,quantum computer,virtual transitions,flux qubits
更新于2025-09-16 10:30:52