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- 摘要
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- 实验方案
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Multi‐Resonance Induced Thermally Activated Delayed Fluorophores for Narrowband Green OLEDs
摘要： With the increment of data scale, distributed machine learning has received more and more attention. However, as the data grows, the dimension of the dataset will increase rapidly, which leads to the increment of the communication traffic in the distributed computing cluster and decreases the performance of the distributed algorithms. This paper proposes a message filtering strategy based on asynchronous alternating direction method of multipliers (ADMM), which can effectively reduce the communication time of the algorithm while ensuring the convergence of the algorithm. In this paper, a soft threshold filtering strategy based on L1 regularization is proposed to filter the parameter of master node, and a gradient truncation filtering strategy is proposed to filter the parameter of slave node. Besides, we update the algorithm asynchronously to reduce the waiting time of the master node. Experiments on large-scale sparse data show that our algorithm can effectively reduce the traffic of messages and make the algorithm reach convergence in a shorter time.
关键词： gradient truncation,distributed machine learning,message filtering,asynchronous update,ADMM,L1 regularization
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Curve Correction of the Energy Yield by Flexible Photovoltaics for VIPV and BIPV Applications Using a Simple Correction Factor
摘要： High-power grinding mills are used in the cement and mining industries to crush clinker or copper ore and grind these materials to fine powder. The multi-megawatt speed-controlled mill drives operate at a very low angular speed. Synchronous motors with a high number of pole pairs are used as the prime movers. They are traditionally fed by load-commutated thyristorized cycloconverters. These are prone to failure modes that can lead to excessive torque pulsations and high overcurrents. The huge stator, which was built as a separate ring-shaped structure around the tubular mill, may then get mechanically displaced, and the operation of the plant is interrupted. A novel and reliable direct drive uses a voltage source inverter that operates at the unity power factor for increased efficiency. Synchronous optimal pulsewidth modulation ensures a low harmonic current distortion and reduced switching losses at a very low switching frequency. The optimization of the pulse patterns takes the anisotropic magnetic properties of a separately excited synchronous motor into account. The implementation in a 23-MW semiautonomous grinding mill installed in a Zambian copper mine is intended.
关键词： Alternators,ball milling,pulse width modulation inverters,gradient methods,software algorithms,variable speed drives,Fourier transform
更新于2025-09-19 17:13:59
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Observation of water droplets oscillation due to laser induced Marangoni convection
摘要： In this paper, using experimental characterizations, we explore the motion of water droplets suspended in mineral oil under exposure of a focused continuous wave (CW) fiber laser beam. The laser beam exposure heats the surrounding oil medium as well. The temperature gradient generates thermocapillary (or Marangoni) convection flows. This approach uses infrared laser-induced thermocapillary-driven flow for manipulation of droplets in the range of 10 to 30 μm in diameter. The droplets are trapped in the convection flow and travel with thermocapillary convection flow (depending on the droplet sizes) along the streamline with high speed. This motion is observed at a certain critical power of the laser. The behavior of a droplet in response to thermally induced convection can be considered. we also examined the oscillatory behavior of the droplet on the xy plane. As expected, oscillation frequency/amplitude are linearly correlated to the droplet size.
关键词： Convection,Fiber laser,Marangoni force,Manipulation,Oscillation frequency,Thermocapillary,Temperature gradient
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Inverse Design of Orbital Angular Momentum Mode Demultiplexer by Combining Wavefront Matching Method and Gradient Descent Algorithm
摘要： The spatial mode demultiplexer is a critical component in the mode division multiplexing communication system, which requires the merits of power-efficiency and low-crosstalk. It has been demonstrated that any unitary transform of spatial modes can be implemented by passing through a succession of phase masks with free-space propagation in between, and the key is to inversely design the phase distribution of each phase mask. One inverse approach is based on wavefront matching method, which is employed in the technique termed multi-plane light conversion (MPLC). This approach enables an efficient optimization of overlap integrals between the obtained modes and the desired modes. However, this method does not have an objective function, meaning that it is incapable of implementing specific optimization. Another approach is based on the gradient descent algorithm, which is flexible in choosing objective functions, while the performance in maximizing overlap integrals is less desirable when compared with wavefront matching method. In this work, we design an efficient orbital angular momentum (OAM) demultiplexer inversely by combining the wavefront matching method and the gradient descent algorithm. Firstly, we employ the wavefront matching method to optimize all the phase masks until convergence. Then, by setting adjacent crosstalk as a part of the objective function, we apply the gradient descent algorithm to further optimize the mode demultiplexing performance. Since the objective function is already close to the local minimum, the subsequent gradient descent process will converge in a few iterations. To confirm this idea, we demonstrate the mode transformation from OAM modes with azimuthal topological charge from l = -3 to l = 3 to displaced Gaussian modes. The configuration including the input and output modes as well as the number and positions of the phase masks are determined with reference to the spiral transformation scheme. By the combinational use of aforementioned methods, we design an OAM demultiplexer that can sort 7 pure vortex modes with 3 phase masks. The designed phase profiles present a similarity to those implemented in spiral transformation, especially for the third phase mask resembling to an elliptical lens. The maximum insertion loss and crosstalk of the device are -0.2 dB and -21.1 dB, with a 5.6-dB improvement in maximum crosstalk resulting from the further gradient descent optimization after wavefront matching.
关键词： Gradient Descent Algorithm,Mode Demultiplexer,Inverse Design,Wavefront Matching Method,Orbital Angular Momentum
更新于2025-09-16 10:30:52
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High-Gradient Cherenkov Radiation Based on a New Dielectric-Loaded Waveguide
摘要： A new type of dielectric-loaded waveguide, the high-gradient dielectric-loaded waveguide (HG-DLW), where the Cherenkov radiation with a high gradient can be excited by relativistic electron, is proposed in this paper. Based on the simulation results, the process of the high-gradient Cherenkov radiation excited in the proposed structure is studied in details, and the amplitude of wakefields excited in proposed structure can be enhanced by over six times compared with that from ordinary dielectric-loaded waveguides.
关键词： Cherenkov radiation,high-gradient field,dielectric-loaded waveguide
更新于2025-09-16 10:30:52
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Investigation of Aluminum Composite Produced by Laser-Assisted Cold Spray Additive Manufacturing
摘要： The relevance of the work is due to the need in the modern world to obtain products with gradient properties for aerospace and medical applications. The method of laser-assisted cold spraying allows obtaining composite materials by additive technology. As a result of this work, a layer of material was constructed from a mechanical mixture of aluminum Al powder with corundum powder Al2O3, then the structure and properties of the material obtained were studied, and zones of gradient transition were identified.
关键词： powder metallurgy,additive technologies,laser-assisted cold spray,gradient materials,functional materials,microstructure
更新于2025-09-16 10:30:52
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Across‐vendor standardization of semi‐LASER for single‐voxel MRS at 3T
摘要： The semi-adiabatic localization by adiabatic selective refocusing (sLASER) sequence provides single-shot full intensity signal with clean localization and minimal chemical shift displacement error and was recommended by the international MRS Consensus Group as the preferred localization sequence at high- and ultra-high fields. Across-vendor standardization of the sLASER sequence at 3 tesla has been challenging due to the B1 requirements of the adiabatic inversion pulses and maximum B1 limitations on some platforms. The aims of this study were to design a short-echo sLASER sequence that can be executed within a B1 limit of 15 μT by taking advantage of gradient-modulated RF pulses, to implement it on three major platforms and to evaluate the between-vendor reproducibility of its perfomance with phantoms and in vivo. In addition, voxel-based first and second order B0 shimming and voxel-based B1 adjustments of RF pulses were implemented on all platforms. Amongst the gradient-modulated pulses considered (GOIA, FOCI and BASSI), GOIA-WURST was identified as the optimal refocusing pulse that provides good voxel selection within a maximum B1 of 15 μT based on localization efficiency, contamination error and ripple artifacts of the inversion profile. An sLASER sequence (30 ms echo time) that incorporates VAPOR water suppression and 3D outer volume suppression was implemented with identical parameters (RF pulse type and duration, spoiler gradients and inter-pulse delays) on GE, Philips and Siemens and generated identical spectra on the GE ‘Braino’ phantom between vendors. High-quality spectra were consistently obtained in multiple regions (cerebellar white matter, hippocampus, pons, posterior cingulate cortex and putamen) in the human brain across vendors (5 subjects scanned per vendor per region; mean signal-to-noise ratio > 33; mean water linewidth between 6.5 Hz to 11.4 Hz). The harmonized sLASER protocol is expected to produce high reproducibility of MRS across sites thereby allowing large multi-site studies with clinical cohorts.
关键词： MR spectroscopy,human,brain,gradient-modulated,harmonization,clinical,GOIA-WURST
更新于2025-09-16 10:30:52
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Machine learning based temperature prediction of poly( <i>N</i> -isopropylacrylamide)-capped plasmonic nanoparticle solutions
摘要： The temperature-dependent optical properties of gold nanoparticles that are capped with the thermo-sensitive polymer: ‘poly(N-isopropylacrylamide)’ (PNIPAM), have been studied extensively for several years. Also, their suitability to function as nanoscopic thermometers for bio-sensing applications has been suggested numerous times. In an attempt to establish this, many have studied the temperature-dependent optical resonance characteristics of these particles; however, developing a simple mathematical relationship between the optical measurements and the solution temperature remains an open challenge. In this paper, we attempt to systematically address this problem using machine learning techniques to quickly and accurately predict the solution-temperature, based on spectroscopic data. Our emphasis is on establishing a simple and practically useful solution to this problem. Our dataset comprises spectroscopic absorption data from both nanorods and nanobipyramids capped with PNIPAM, measured at discretely varied and pre-set temperature states. Specific regions of the spectroscopic data are selected as features for prediction using random forest (RF), gradient boosting (GB) and adaptive boosting (AB) regression techniques. Our prediction results indicate that RF and GB techniques can be used successfully to predict solution temperatures instantly to within 1 1C of accuracy.
关键词： PNIPAM,spectroscopic data,temperature prediction,adaptive boosting,machine learning,random forest,gradient boosting,gold nanoparticles
更新于2025-09-16 10:30:52
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Inverse analysis of the residual stress in laser-assisted milling
摘要： In laser-assisted milling, higher temperature in shear zone softens the material potentially resulting in a shift of mean residual stress, which significantly affects the damage tolerance and fatigue performance of product. In order to guide the selection of laser and cutting parameters based on the preferred mean residual stress, inverse analysis is conducted by predicting residual stress based on guessed process parameters, which is defined as the forward problem, and applying iterative gradient search to find process parameters for next iteration, which is defined as the inverse problem. An analytical inverse analysis is therefore proposed for the mean residual stress in laser-assisted milling. The forward problem is solved by analytical prediction of mean residual stress after laser-assisted milling. The residual stress profile is predicted through the calculation of thermal stress, by treating laser beam as heat source, and plastic stress by first assuming pure elastic stress in loading process, then obtaining true stress with kinematic hardening followed by the stress relaxation. The variance-based recursive method is applied to solve inverse problem by updating process parameters to match the measured mean residual stress. Three cutting parameters including depth of cut, feed per tooth, and cutting speed, and two laser parameters including laser-tool distance and laser power, are updated with respected to the minimization of resulting residual stress and measurement in each iteration. Experimental measurements are referred on the laser-assisted milling of Ti–6Al–4 V and Si3N4. The percentage difference between experiments and predictions is less than 5% for both materials, and the selection is completed within 50 loops.
关键词： Residual stress,Ti–6Al–4V,Si3N4,Laser-assisted milling,Inverse analysis,Iterative gradient search
更新于2025-09-16 10:30:52
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Mixed FEM for quantum nanostructured solar cells
摘要： The gradient theory of piezoelectricity is developed for 3D analyses of QDs with the functionally graded lattice mismatch between the QD and the matrix. Governing equations in the gradient theory contain higher order derivatives than in conventional approaches. Then, it is needed to apply the C1-elements for approximation of primary ?elds in the FEM. The mixed FEM with the C0 continuous interpolation and collocation approach for kinematic constraints between strains and displacements is developed. The high-density arrays of quantum dots requires to consider various sizes for the representative volume element of the nanostructured solar cell created by the QD (InAs) and matrix (GaAs).
关键词： Gradient theory,High-density arrays of quantum dots,Mixed FEM,Functionally graded lattice mismatch
更新于2025-09-16 10:30:52