- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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Laser-Induced Wettability Gradient Surface of the Aluminum Matrix Used for Directional Transportation and Collection of Underwater Bubbles
摘要： The control of underwater bubble behavior on a solid surface has great research significance. However, the control of the spontaneous directional transport and collection of numerous underwater bubbles remains a challenge. A new technique of a metal mesh with superhydrophobic/hydrophobic properties is demonstrated here, which creates a wettability gradient coupled with a microporous array by means of pulsed fiber laser ablation and chemical modification of the aluminum sheet. The resultant wettability surface effectively achieved the spontaneous movement of bubbles along the directional wettability gradient (superaerophobicity to aerophilicity) and through the metal mesh (aerophilicity to superaerophilicity) in the direction of decreasing free energy. Theoretical analysis accounted first for the spontaneous sliding of bubbles on the wettability gradient surface as a result of the action of an unbalanced surface tension force and second for the spontaneous transition of bubbles from the aerophilic to superaerophilic side as a result of the combined action of Laplace pressure and buoyancy. A device with the capability of directional transportation and collection of underwater bubbles was designed based on the samples with a wettability gradient and a superhydrophobic/hydrophobic microporous array as the core components. The potential application is laser ablation of wettability gradient surfaces and metal mesh with superhydrophobic/hydrophobic properties for directional transportation and collection of underwater bubbles.
关键词： wettability gradient,collection,directional transportation,underwater bubbles,laser ablation
更新于2025-09-23 15:19:57
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[IEEE 2019 6th International Conference on Systems and Informatics (ICSAI) - Shanghai, China (2019.11.2-2019.11.4)] 2019 6th International Conference on Systems and Informatics (ICSAI) - Laser Strip Center Extraction Methodology for the Detection of Weld Seam
摘要： Envelope representations such as the auditory or traditional spectrogram can be defined by the set of envelopes from the outputs of a filterbank. Common envelope extraction methods discard information regarding the fast fluctuations, or phase, of the signal. Thus, it is difficult to invert, or reconstruct a time-domain signal from, an arbitrary envelope representation. To address this problem, a general optimization approach in the time domain is proposed here, which iteratively minimizes the distance between a target envelope representation and that of a reconstructed time-domain signal. Two implementations of this framework are presented for auditory spectrograms, where the filterbank is based on the behavior of the basilar membrane and envelope extraction is modeled on the response of inner hair cells. One implementation is direct while the other is a two-stage approach that is computationally simpler. While both can accurately invert an auditory spectrogram, the two-stage approach performs better on time-domain metrics. The same framework is applied to traditional spectrograms based on the magnitude of the short-time Fourier transform. Inspired by human perception of loudness, a modification to the framework is proposed, which leads to a more accurate inversion of traditional spectrograms.
关键词： Spectrogram inversion,gradient methods,short-time Fourier transform,auditory spectrogram
更新于2025-09-23 15:19:57
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Mechanical response of a Laser Cladding repaired structure: localization of plastic strain due to microstructure gradient
摘要： Laser Cladding is an additive manufacturing technology enabling to repair complex metallic components by removing the worn region and reconstructing locally the initial geometry. The aim of this work is to study the mechanical response of Inconel 718 repaired thin walls. More precisely, we perform an EBSD imaging and in-situ SEM tensile tests on specimen whose gauge section contains the interface between base material and repaired area. We observe the multiaxial strain patterns until failure at the grain level using a Digital Image Correlation method and superpose this pattern with the microstructure gradient induced by repair. The observations highlight a strain localization phenomenon in repaired structures mainly due to grain size effect.
关键词： SEM tensile tests,Laser Cladding,Inconel 718,strain localization,EBSD,microstructure gradient,Digital Image Correlation
更新于2025-09-23 15:19:57
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Blood-based FTIR-ATR spectroscopy coupled with extreme gradient boosting for the diagnosis of type 2 diabetes
摘要： Timely diagnosis of type 2 diabetes and early intervention and treatment of it are important for controlling metabolic disorders, delaying and reducing complications, reducing mortality, and improving quality of life. Type 2 diabetes was diagnosed by Fourier transform mid-infrared (FTIR) attenuated total reflection (ATR) spectroscopy in combination with extreme gradient boosting (XGBoost). Whole blood FTIR-ATR spectra of 51 clinically diagnosed type 2 diabetes and 55 healthy volunteers were collected. For the complex composition of whole blood and much spectral noise, Savitzky–Golay smoothing was first applied to the FTIR-ATR spectrum. Then PCA was used to eliminate redundant data and got the best number of principle components. Finally, the XGBoost algorithm was used to discriminate the type 2 diabetes from healthy volunteers and the grid search algorithm was used to optimize the relevant parameters of the XGBoost model to improve the robustness and generalization ability of the model. The sensitivity of the optimal XGBoost model was 95.23% (20/21), the specificity was 96.00% (24/25), and the accuracy was 95.65% (44/46). The experimental results show that FTIR-ATR spectroscopy combined with XGBoost algorithm can diagnose type 2 diabetes quickly and accurately without reagents.
关键词： Fourier transform mid-infrared attenuated total reflection spectroscopy,whole blood,extreme gradient boosting,type 2 diabetes
更新于2025-09-23 15:19:57
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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
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A 3D Mask Presentation Attack Detection Method Based on Polarization Medium Wave Infrared Imaging
摘要： Facial recognition systems are often spoofed by presentation attack instruments (PAI), especially by the use of three-dimensional (3D) face masks. However, nonuniform illumination conditions and significant differences in facial appearance will lead to the performance degradation of existing presentation attack detection (PAD) methods. Based on conventional thermal infrared imaging, a PAD method based on the medium wave infrared (MWIR) polarization characteristics of the surface material is proposed in this paper for countering a flexible 3D silicone mask presentation attack. A polarization MWIR imaging system for face spoofing detection is designed and built, taking advantage of the fact that polarization-based MWIR imaging is not restricted by external light sources (including visible light and near-infrared light sources) in spite of facial appearance. A sample database of real face images and 3D face mask images is constructed, and the gradient amplitude feature extraction method, based on MWIR polarization facial images, is designed to better distinguish the skin of a real face from the material used to make a 3D mask. Experimental results show that, compared with conventional thermal infrared imaging, polarization-based MWIR imaging is more suitable for the PAD method of 3D silicone masks and shows a certain robustness in the change of facial temperature.
关键词： presentation attack detection,polarization medium wave infrared imaging,three-dimensional silicone mask,gradient amplitude feature
更新于2025-09-23 15:19:57
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[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) - Triple-wide-band Linear to Circular Polarization Converters Using Bi-layered Metasurfaces
摘要： Conventional EM optimization aims to use fewest possible fine model evaluations to increase the speed of optimization. In this work, we propose to use a large number of fine model evaluations to achieve an overall speedup. A large number of fine model evaluations allows us to build a surrogate model valid in a large neighborhood. In the proposed technique, these valid surrogate models are used to achieve large and effective optimization updates, thereby resulting in fewer iterations of the optimization process. Valid surrogate models uses many fine model evaluations which are realized in parallel using hybrid distributed shared memory computing platforms. Parallel computation of large number of fine model evaluations reduces the major computational time required for constructing a surrogate model. Furthermore, we exploit trust region algorithms to guarantee convergence and to re-define the fine model evaluation range in each iteration of the proposed optimization algorithm. The proposed technique aims to increase the speed of gradient based EM optimization when no coarse model (e.g., empirical or equivalent circuits) is available. Three typical examples are used to illustrate the proposed technique.
关键词： parallel computation,electromagnetic (EM) optimization,Antennas,surrogate model,passive microwave circuits,trust region,gradient based optimization
更新于2025-09-23 15:19:57
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Solidification Effect on the Microstructure and Mechanism of Laser Solid Forming Produced Flame-Resistant Ti-35V-15Cr Alloy
摘要： The block and thin-wall Ti-35V-15Cr samples were built by laser solid forming (LSF). The extremely sensitive thermal behavior condition in LSF results in significantly different microstructure. The microstructure of LSF-produced block sample mainly consists of epitaxial columnar dendritic grains, while that of the thin-wall sample is mainly composed of near-equiaxed grains together with sub-grains formed in the near-equiaxed grains.
关键词： sub-grains,Laser solid forming,temperature gradient,Ti-35V-15Cr,thermal cycling
更新于2025-09-23 15:19:57
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Laser Technology to Guide Rainfall to a Particular Region
摘要： Rain bearing clouds can be effectively guided to a specific region during monsoon or other seasons so that rainfall shall be equitably distributed without creating drought situations. Lasers sent into the lower troposphere region with intensities sufficient to create a temperature gradient and thereby creating a low pressure area in a specific region can invite rain bearing clouds to a region opposite to where heat is generated by laser effect, so as to bring convective rainfall during a season.
关键词： Troposphere,Laser effect,Low pressure,Convective rainfall,Equitably,Temperature gradient
更新于2025-09-23 15:19:57
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Chemoa?? and magnetotaxis of selfa??propelled light emitting chemoa??electronic swimmers
摘要： Miniaturized autonomous chemo-electronic swimmers, based on the coupling of spontaneous oxidation and reduction reactions at the two poles of light emitting diodes (LEDs), are presented as chemotactic and magnetotactic devices. In homogeneous aqueous media, random motion caused by a bubble-induced propulsion mechanism, is observed. However, in an inhomogeneous environment, the self-propelled devices exhibit positive chemotactic behavior, propelling themselves along a pH or ionic strength gradient (?pH, ?I, respectively) in order to reach a thermodynamically higher active state. In addition, the intrinsic permanent magnetic moment of the LED allows self-orientation in the terrestrial magnetic field or following other external magnetic perturbations, which enables a directional motion control coupled with light emission. The interplay between chemotaxis and magnetotaxis allows fine-tuning the dynamic behavior of these swimmers.
关键词： electronic swimmers,magnetotaxis,pH gradient,Chemotaxis,light emission
更新于2025-09-23 15:19:57