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Shock effects on the upper limit of the collision weld process window

2001年

作者： Gary L.Musser William F. Burger blake E. Peterson

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Advances in Manufacturing 2024年第2期12卷 365-378页

作者： blake Barnett Anupam Vivek Glenn Daehn Department of Materials Science and Engineering The Ohio State UniversityColumbusOH43210USA Army Research Directorate Army Research LaboratoryDEVCOMAberdeen Proving GroundHarfordMD21005USA

The maximum flyer impact velocity based on a dynamic solidification cracking mechanism is proposed to describe the upper limit of collision welding process ***,the upper limit of the weld window is governed by the evolution of dynamic stresses and temperatures at the weld *** formulations for the upper limit of the collision weld window assume that both the flyer and target are made of the same material and approximate stress propagation velocities using the acoustic velocity or the shear wave velocity of the weld ***,collision welding fundamentally depends on the impacts that generate shockwaves in weld members,which can dominate the stress propagation velocities in thin weld ***,this study proposes an alternative weld window upper limit that approximates stress propagation using shock velocities calculated from modified 1-D Rankine-Hugoniot *** shock upper limit is validated against the experimental and simulation data in the collision welding literature,and offers a design tool to rapidly predict more accurate optimal collision weld process limits for similar and dissimilar weld couples compared to existing models without the cost or complexity of high-fidelity simulations.

关键词： Collision welding Solid-state welding Shock impact Weld process modelling Explosive bonding Laser impulse welding(LIW)

LINEAR WAVES THAT EXPRESS THE SIMPLEST POSSIBLE PERIODIC STRUCTURE OF THE COMPRESSIBLE EULER EQUATIONS

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Acta Mathematica Scientia 2009年第6期29卷 1749-1766页

作者： blake Temple Robin Young Department of Mathematics University of California Davis CA 95616 USA Department of Mathematics and Statistics University of Massachusetts Amherst MA 01003 USA

In this paper we show how the simplest wave structure that balances compression and rarefaction in the nonlinear compressible Euler equations can be represented in a solution of the linearized compressible Euler equations. Such waves are exact solutions of the equations obtained by linearizing the compressible Euler equations about the periodic extension of two constant states separated by entropy jumps. Conditions on the states and the periods are derived which allow for the existence of solutions in the Fourier 1-mode. In [3, 4, 5] it is shown that these are the simplest linearized waves such that, for almost every period, they are isolated in the kernel of the linearized operator that imposes periodicity, and such that they perturb to nearby nonlinear solutions of the compressible Euler equations that balance compression and rarefaction along characteristics in the formal sense described in [3]. Their fundamental nature thus makes them of interest in their own right.

关键词： compressible Euler periodic solutions conservation laws

EXISTENCE AND STABILITY OF VISCOUS SHOCK PROFILES FOR 2-D ISENTROPIC MHD WITH INFINITE ELECTRICAL RESISTIVITY

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Acta Mathematica Scientia 2010年第2期30卷 447-498页

作者： blake Barker Olivier Lafitte Kevin Zumbrun Department of Mathematics Indiana University LAGA Institut GalileeUniversite Paris 1393 430 Villetaneuse and CEA SaclayDM2S/DIR91 191 Gif sur Yvette CedexFrance

For the two-dimensional Navier-Stokes equations of isentropic magnetohydrodynamics （MHD） with γ-law gas equation of state, γ≥ 1, and infinite electrical resistivity, we carry out a global analysis categorizing all possible viscous shock profiles. Precisely, we show that the phase portrait of the traveling-wave ODE generically consists of either two rest points connected by a viscous Lax profile, or else four rest points, two saddles and two nodes. In the latter configuration, which rest points are connected by profiles depends on the ratio of viscosities, and can involve Lax, overcompressive, or undercompressive shock profiles. Considered as three-dimensional solutions, undercompressive shocks axe Lax-type （Alfven） waves. For the monatomic and diatomic cases γ= 5/3 and γ=7/5, with standard viscosity ratio for a nonmagnetic gas, we find numerically that the the nodes are connected by a family of overcompressive profiles bounded by Lax profiles connecting saddles to nodes, with no undercompressive shocks occurring. We carry out a systematic numerical Evans function analysis indicating that all of these two-dimensional shock pro- files are linearly and nonlinearly stable, both with respect to two- and three-dimensional perturbations. For the same gas constants, but different viscosity ratios, we investigate also cases for which undercompressive shocks appear; these are seen numerically to be stable as well, both with respect to two-dimensional and （in the neutral sense of convergence to nearby Riemann solutions） three-dimensional perturbations.

关键词： stability of viscous shock waves Evans function magnetohydrodynamics

Assessment of buckling-restrained braced frame reliability using an experimental limit-state model and stochastic dynamic analysis

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Earthquake Engineering and Engineering Vibration 2009年第3期8卷 373-385页

作者： blake M.Andrews Junho Song Larry A.Fahnestock Wiss JanneyElstner AssociatesIncNorthbrookIllinoisUSA Department of Civil and Environmental Engineering University of Illinois at Urbana-ChampaignUrbanaIllinoisUSA

Buckling-restrained braces （BRBs） have recently become popular in the United States for use as primary members of seismic lateral-force-resisting systems. A BRB is a steel brace that does not buckle in compression but instead yields in both tension and compression. Although design guidelines for BRB applications have been developed, systematic procedures for assessing performance and quantifying reliability are still needed. This paper presents an analytical framework for assessing buckling-restrained braced frame （BRBF） reliability when subjected to seismic loads. This framework efficiently quantifies the risk of BRB failure due to low-cycle fatigue fracture of the BRB core. The procedure includes a series of components that：（1） quantify BRB demand in terms of BRB core deformation histories generated through stochastic dynamic analyses; （2） quantify the limit-state of a BRB in terms of its remaining cumulative plastic ductility capacity based on an experimental database; and （3） evaluate the probability of BRB failure, given the quantified demand and capacity, through structural reliability analyses. Parametric studies were conducted to investigate the effects of the seismic load, and characteristics of the BRB and BRBF on the probability of brace failure. In addition, fragility curves （i.e., conditional probabilities of brace failure given ground shaking intensity parameters） were created by the proposed framework. While the framework presented in this paper is applied to the assessment of BRBFs, the modular nature of the framework components allows for application to other structural components and systems.

关键词： risk and reliability analysis buckling-restrained brace stochastic dynamic analysis first-order reliability method cumulative plastic ductility capacity

On the exoneration of Dr. William H. Stewart: debunking an urban legend

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Infectious Diseases of Poverty 2013年第1期2卷 17-21页

作者： Brad Spellberg Bonnie Taylor-blake Los Angeles Biomedical Research Institute at Harbor-University of California at Los Angeles(UCLA)Medical Center TorranceCAUSA The David Geffen School of Medicine at UCLA Los AngelesCAUSA University of North Carolina School of Medicine Chapel Hill WilmingtonNCUSA

Background:It is one of the most infamous quotes in the history of biomedicine:“It is time to close the book on infectious diseases,and declare the war against pestilence won.”Long attributed to the United States Surgeon General,*** ***(1965-1969),the statement is frequently used as a foil by scientific and lay authors to underscore the ever-increasing problems of antibiotic-resistant and emerging ***,the primary source for the quote has never been ***:We undertook a comprehensive search of multiple databases encompassing medical literature,news articles,and congressional records to attempt to identify sources for the ***:No source of the quote was ***,a trail of source documents was identified that clearly serves as the basis for subsequent,incorrect attribution of the quote to *** multiple source documents,*** made statements to the opposite effect,clearly recognizing that infectious diseases had not been *** urban legend was created by a combination of lack of primary witnesses to the originating speech,misunderstanding of points made by *** in the speech,and increasing societal concern about emerging and re-emerging infectious ***:Attribution to *** of a belief that it was time to close the book on infectious diseases is an urban legend;he never made any such *** other verifiable sources,however,confirm that other people in academia adopted this *** should no longer be cited in this regard,and should be replaced with verifiable sources.

关键词： William H.Stewart Urban legend History of antibiotics Antibiotic development Antibiotic crisis Public policy

Perspective on oligomeric products from lignin depolymerization:their generation,identification,and further valorization

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Industrial Chemistry & Materials

Industrial Chemistry & Materials 2023年第2期1卷 207-223页

作者： Yinglei Han blake A.Simmons Seema Singh Deconstruction Division Joint Bioenergy Institute5885 Hollis StreetEmeryvilleCA 94608USA Department of Bioresource and Environmental Security Sandia National Laboratories7011 East AvenueLivermoreCA 94551USA Biological Systems and Engineering Division Lawrence Berkeley National Laboratory1 Cyclotron RoadBerkeleyCA 94720USA

The present contribution emphasizes the formation of oligomeric products in various depolymerization approaches of lignin,namely reductive catalytic fractionation,oxidative catalytic fractionation,and *** possible routes to form such oligomers in these depolymerization processes are summarized and compared from various studies conducted on model ***,the main identification techniques for characterizing oligomeric products are *** focus is given to 2D-HSQC-NMR,GPC,Maldi-TOF-MS and FT-ICR-MS,which represent the state-of-art characterization of *** attention was paid to the transferability of these techniques for depolymerized oligomeric ***,both the existing and expected potential lignin valorization routes are discussed for these oligomers,and technical hurdles and recommendations are provided in an attempt to catalyze the development of new discoveries and enabling technologies.

关键词： Lignin oligomer Reductive and oxidative depolymerization Biofuels Characterization techniques Lignin valorization.

Retrieval of dislodged AmplifEYE using balloon dilator during colonoscopy

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Gastroenterology Report 2019年第2期7卷 139-140,I0002页

作者： Jihui Li Luke blake Steven D.Wexner Department of General Surgery Paris Community HospitalParisILUSA Department of Colorectal Surgery Cleveland Clinic FloridaWestonFLUSA

AmplifEYE can increase the detection rate of adenomatous polyps and stabilize the mucosa for easy biopsy and *** it can also become a foreign body when it is dislodged during the *** report a case of dislodged AmplifE... 详细信息

关键词： colonoscopy AmplifEYE foreign-body retrieval balloon dila

Dramatic decline of observed atmospheric CO_(2) and CH_(4) during the COVID-19 lockdown over the Yangtze River Delta of China

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Journal of Environmental Sciences 2023年第2期124卷 712-722页

作者： Miao Liang Yong Zhang Qianli Ma Dajiang Yu Xiaojian Chen Jason blake Cohen Meteorological Observation Center China Meteorological AdministrationBeijing 100081China Lin’an Atmospheric Regional Background Station China Meteorological Administration(CMA)Hangzhou 311307China Longfengshan Regional Background Station China Meteorological Administration(CMA)Heilongjiang 150200China Shanxi Meteorological Information Center China Meteorological Administration(CMA)Shanxi 030000China School of Environment and Spatial Informatics China University of Mining and TechnologyXuzhou221116China

The temporal variation of greenhouse gas concentrations in China during the COVID-19 lockdown in China is analyzed in this work using high resolution measurements of near surface ΔCO_(2),ΔCH_(4) andΔCO concentrations above the background conditions at Lin’an station(LAN),a regional background station in the Yangtze River Delta *** the pre-lockdown observational period(IOP-1),bothΔCO_(2) andΔCH_(4) exhibited a significant increasing trend relative to the 2011-2019 climatological *** reduction ofΔCO_(2),ΔCH_(4) andΔCO during the lockdown observational period(IOP-2)(which also coincided with the Chinese New Year Holiday)reached up to 15.0 ppm,14.2 ppb and 146.8 ppb,respectively,and a reduction ofΔCO_(2)/ΔCO probably due to a dramatic reduction from industrial emissions.ΔCO_(2),ΔCH_(4) and ΔCO were observed to keep declining during the post-lockdown easing phase(IOP-3),which is the synthetic result of lower than normal CO_(2) emissions from rural regions around LAN coupled with strong uptake of the terrestrial ***,the trend reversed to gradual increase for all species during the later easing phase(IOP-4),with ΔCO_(2)/ΔCO constantly increasing from IOP-2 to IOP-3 and finally IOP-4,consistent with recovery in industrial emissions associated with the staged resumption of economic *** average,ΔCO_(2) declined sharply throughout the days during IOP-2 but increased gradually throughout the days during *** findings showcase the significant role of emission reduction in accounting for the dramatic changes in measured atmosphericΔCO_(2) and ΔCH_(4) associated with the COVID-19 lockdown and recovery.

关键词： Atmospheric CO_(2) Atmospheric CH_(4) COVID-19 lockdown The Yangtze river delta

Enhancement of THz generation in LiNbO_(3) waveguides via multi-bounce velocity matching

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Light(Science & Applications) 2022年第12期11卷 2994-3001页

作者： blake S.Dastrup Eric R.Sung Frank Wulf Clara Saraceno Keith A.Nelson Department of Chemistry Massachusetts Institute of TechnologyCambridgeMA 02139USA Faculty of Electrical Engineering and Information Technology Ruhr University BochumBochum 44801Germany

To realize the full promise of terahertz polaritonics(waveguide-based terahertz field generation,interaction,and readout)as a viable spectroscopy platform,much stronger terahertz fields are needed to enable nonlinear and even robust linear terahertz *** use a novel geometric approach in which the optical pump is totally internally reflected to increase the distance over which optical rectification *** matching is achieved by tuning the angle of internal *** doing this,we are able to enhance terahertz spectral amplitude by over 10x compared to conventional single-pass terahertz *** analysis of the depletion mechanisms reveals that 3-photon absorption and divergence of the pump beam are the primary limiters of further *** level of enhancement is promising for enabling routine spectroscopic measurements in an integrated fashion and is made more encouraging by the prospect of further enhancement by using longer pump wavelengths.

关键词： pump waveguide tuning