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Generation of millijoule-level sub-5 fs violet laser pulses

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High Power laser Science and Engineering 2024年第2期12卷 33-40页

作者： Xinhua Xie Yi Hung Yunpei Deng Adrian l.Cavalieri Andrius Baltuška steven l.johnson SwissFEl Paul Scherrer InstituteVilligen PSISwitzerland Photonics Institute Technische Universität WienViennaAustria Institute of Applied Physics University of BernBernSwitzerland Institute for Quantum Electronics Physics DepartmentETH ZurichZurichSwitzerland

We demonstrate the generation,spectral broadening and post-compression of second harmonic pulses using a thin beta barium borate(BBO)crystal on a fused-silica substrate as the nonlinear interaction *** combining second harmonic generation in the BBO crystal with self-phase modulation in the fused-silica substrate,we efficiently generate millijoule-level broadband violet pulses from a single optical *** second harmonic spectrum covers a range from long wave ultraviolet(down to 310 nm)to visible(up to 550 nm)with a bandwidth of 65 ***,we compress the second harmonic beam to a duration of 4.8 fs with a pulse energy of 0.64 mJ(5 fs with a pulse energy of 1.05 mJ)using chirped *** all-solid free-space apparatus is compact,robust and pulse energy scalable,making it highly advantageous for generating intense second harmonic pulses from near-infrared femtosecond lasers in the sub-5 fs regime.

关键词： post-compression second harmonic generation self-phase modulation supercontinuum generation

Applying machine learning to study fluid mechanics

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Acta Mechanica Sinica 2021年第12期37卷 1718-1726页

作者： steven l.Brunton Department of Mechanical Engineering University of WashingtonSeattleWA 98195USA

This paper provides a short overview of how to use machine learning to build data-driven models in fluid *** process of machine learning is broken down into five stages:(1)formulating a problem to model,(2)collecting and curating training data to inform the model,(3)choosing an architecture with which to represent themodel,(4)designing a loss function to assess the performance of the model,and(5)selecting and implementing an optimization algorithm to train the *** each stage,we discuss how prior physical knowledge may be embedding into the process,with specific examples from the field of fluid mechanics.

关键词： Machine learning Fluid mechanics Physics-informed machine learning Neural networks Deep learning

Active learning of deep surrogates for PDEs:application to metasurface design

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npj Computational Materials 2020年第1期6卷 312-318页

作者： Raphaël Pestourie Youssef Mroueh Thanh V.Nguyen Payel Das steven G.johnson Department of Mathematics Massachusetts Institute of Technology77 Massachusetts AveCambridgeMA 02139USA IBM Research AI IBM Thomas J Watson Research CenterYorktown HeightsYorktownNY 10598USA MIT-IBM Watson AI lab CambridgeMA 02139USA Iowa State University AmesIA 50011USA

Surrogate models for partial differential equations are widely used in the design of metamaterials to rapidly evaluate the behavior of composable ***,the training cost of accurate surrogates by machine learning can rapidly increase with the number of *** photonic-device models,we find that this training becomes especially challenging as design regions grow larger than the optical *** present an active-learning algorithm that reduces the number of simulations required by more than an order of magnitude for an NN surrogate model of optical-surface components compared to uniform random *** show that the surrogate evaluation is over two orders of magnitude faster than a direct solve,and we demonstrate how this can be exploited to accelerate large-scale engineering optimization.

关键词： optimization surrogate faster

Common-path interferometric label-free protein sensing with resonant dielectric nanostructures

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light(Science & Applications) 2020年第1期9卷 1086-1094页

作者： Isabel Barth Donato Conteduca Christopher Reardon steven johnson Thomas F.Krauss Department of Physics University of YorkYO105DD YorkUK Department of Electronic Engineering University of YorkYO105DD YorkUK

Research toward photonic biosensors for point-of-care applications and personalized medicine is driven by the need for high-sensitivity,low-cost,and reliable *** the most sensitive modalities,interferometry offers particularly high performance,but typically lacks the required operational simplicity and ***,we introduce a common-path interferometric sensor based on guided-mode resonances to combine high performance with inherent *** sensor exploits the simultaneous excitation of two orthogonally polarized modes,and detects the relative phase change caused by biomolecular binding on the sensor *** wide dynamic range of the sensor,which is essential for fabrication and angle tolerance,as well as versatility,is controlled by integrating multiple,tuned structures in the field of *** approach circumvents the trade-off between sensitivity and dynamic range,typical of other phase-sensitive modalities,without increasing *** sensor enables the challenging label-free detection of procalcitonin,a small protein(13 kDa)and biomarker for infection,at the clinically relevant concentration of 1 pg ml^(−1),with a signal-to-noise ratio of *** result indicates the utility for an exemplary application in antibiotic guidance,and opens possibilities for detecting further clinically or environmentally relevant small molecules with an intrinsically simple and robust sensing modality.

关键词： dielectric integrating simplicity

FRACTAl NATURE OF lIGHT SCATTERING IN TISSUES

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Journal of Innovative Optical Health Sciences 2011年第1期4卷 1-7页

作者： steven l.JACQUES Dermatology and Biomedical Engineering Oregon Health and Science University 3303 SW Bond Ave Portland OR97239USA

light scattering by a tissue has a wavelength dependence that depends on the size distribution of scatterers in the *** measuring the wavelength dependence of scattering,one can deduce changes in the nanoscale architecture of cells and *** report discusses the connection between nanoscale architecture and measurable light *** significance of this work is to develop label-free optical imaging that describes tissue structure,to complement the absorption,fluorescence,and Raman scattering spectra that describe the chemical constituents of a tissue.

关键词： Optical scattering fractal biomedical optics

SPECTRAl IMAGING AND ANAlYSIS TO YIElD TISSUE OPTICAl PROPERTIES

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Journal of Innovative Optical Health Sciences 2009年第2期2卷 123-129页

作者： steven l.JACQUES Departments of Dermatology and Biomedical Engineering Oregon Health&Science University PortlandOregonUSA

An introduction to the basics of spectral imaging as applied to biological tissues is *** example of a spectral image of a face is used to demonstrate the data and spectral analysis that specify the melanin content(M),blood content(B),tissue oxygen saturation(S),water content(W),fraction of scattering due to Rayleigh scattering(f)and due to Mie scattering(1−f),and the reduced scattering coefficient at 500-nm wavelength(µs 500 nm).The sensitivity of reflectance spectra to variation in the various parameters is illustrated.

关键词： Spectroscopy spectral imaging tissue optical properties optical diagnostics.

Biomimetic Composite Structural T-joints

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Journal of Bionic Engineering 2012年第3期9卷 377-384页

作者： Vimal Kumar Thummalapalli steven l. Donaldson University of Dayton 300 College Park Dayton Ohio 45469-0243 USA

Biological structural fixed joints exhibit unique attributes, including highly optimized fiber paths which minimize stress concentrations. In addition, since the joints consist of continuous, uncut fiber architectures, the joints enable the organism to transport information and chemicals from one part of the body to the other. To the contrary, sections of man-made composite material structures are often joined using bolted or bonded joints, which involve low strength and high stress concentrations. These methods are also expensive to achieve. Additional functions such as fluid transport, electrical signal delivery, and thermal conductivity across the joints typically require parasitic tubes, wires, and attachment clips. By using the biomimetic methods, we seek to overcome the limitations which are present in the conventional methods. In the present work, biomimetic co-cured composite sandwich T-joints were constructed using unidirectional glass fiber, epoxy resin, and structural foam. The joints were fabricated using the wet lay-up vacuum bag resin infusion method. Foam sandwich T-joints with multiple continuous fiber architectures and sandwich foam thickness were prepared. The designs were tested in quasi-static bending using a mechanical load frame. The significant weight savings using the biomimetic approaches is discussed, as well as a comparison of failure modes versus architecture is described.

关键词： composites T-joints biomimetic fiberglass epoxy sandwich foam

Assessing the reproductive health of men with occupational exposures

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Asian Journal of Andrology 2014年第1期16卷 23-30页

作者： steven M Schrader Katherine l Marlow Centers for Disease Control and Prevention National Institute for Occupational Safety and Health Division of Applied Research and Technology Cincinnati OH USA.

The earliest report linking environmental （occupational） exposure to adverse human male reproductive effects dates back to1775 when an English physician, Percival Pott, reported a high incidence of scrotal cancer in chimney sweeps. This observation led to safety regulations in the form of bathing requirements for these workers. The fact that male-mediated reproductive harm in humans may be a result of toxicant exposures did not become firmly established until relatively recently, when lancranjan studied lead-exposed workers in Romania in 1975, and later in 1977, when Whorton examined the effects of dibromochloropropane （DBCP） on male workers in California. Since these discoveries, several additional human reproductive toxicants have been identified through the convergence of laboratory and observational findings. Many research gaps remain, as the pool of potential human exposures with undetermined effects on male reproduction is vast. This review provides an overview of methods used to study the effects of exposures on male reproduction and their reproductive health, with a primary emphasis on the implementation and interpretation of human studies. Emphasis will be on occupational exposures, although much of the information is also useful in assessing environmental studies, occupational exposures are usually much higher and better defined.

关键词： accessory glands endocrine epidemiology semen sexual function sperm testis toxicology

High-Throughput UAV Image-Based Method Is More Precise Than Manual Rating of Herbicide Tolerance

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Plant Phenomics 2019年第1期1卷 133-141页

作者： Hema S.N.Duddu Eric N.johnson Christian *** steven J.Shirtliffe Department of Plant Sciences College of Agriculture and BioresourcesUniversity of Saskatchewan51 Campus DriveSaskatoonSKCanada

The traditional visual rating system is labor-intensive,time-consuming,and prone to human *** aerial vehicle(UAV)imagery-based vegetation indices(VI)have potential applications in high-throughput plant *** study objective is to determine if UAV imagery provides accurate and consistent estimations of crop injury from herbicide application and its potential as an alternative to visual *** study was conducted at the Kernen Crop Research Farm,University of Saskatchewan in 2016 and ***(Vicia faba l.)crop tolerance to nine herbicide tank mixtures was evaluated with 2 rates distributed in a randomized complete block design(RCBD)with 4 *** trial was imaged using a multispectral camera with a ground sample distance(GSD)of 1.2 cm,one week after the treatment *** ratings of growth reduction and physiological chlorosis were recorded simultaneously with *** optimized soil-adjusted vegetation index(OSAVI)was calculated from the thresholded *** UAV-based vegetation index(OSAVI)produced more precise results compared to visual ratings for both *** coefficient of variation(CV)of OSAVI was~1%when compared to 18-43%for the visual ***,Tukey’s honestly significance difference(HSD)test yielded a more precise mean separation for the UAV-based vegetation index than visual *** significant correlations between OSAVI and the visual ratings from the study suggest that undesirable variability associated with visual assessments can be minimized with the UAVbased ***-based imagery methods had greater precision than the visual-based ratings for crop herbicide *** methods have the potential to replace visual ratings and aid in screening crops for herbicide tolerance.

关键词： Visual precise replace