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Grain Refinement of Primary Si in Hypereutectic Al-Si Alloys Using P-based Master Alloys

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Grain Refinement of Primary Si in Hypereutectic Al-Si Alloys...

作者： benson Kihono Njuguna 大连理工大学

学位级别：硕士

过共晶铝硅合金因具有低的热膨胀系数和高的高温力学性能等优点被广泛应用于汽车、航空航天等领域,然而合金中粗大的初晶硅相易形成裂纹源并导致断裂,严重影响了合金的力学性能。磷变质处理是减小初晶硅尺寸、改善其形貌的重要方法,常... 详细信息

过共晶铝硅合金因具有低的热膨胀系数和高的高温力学性能等优点被广泛应用于汽车、航空航天等领域,然而合金中粗大的初晶硅相易形成裂纹源并导致断裂,严重影响了合金的力学性能。磷变质处理是减小初晶硅尺寸、改善其形貌的重要方法,常见的含磷变质剂有Al-P、Al-Si-P、Cu-P等中间合金。本文以过共晶Al-24Si（质量百分数,下同）合金为研究对象,采用金相显微镜（OM,Optical Microscope）、场发射扫描电镜（FESEM,Field Emission Scanning Electron Microscope）、X射线衍射仪（X-Ray Diffraction）等分析手段研究了Si-3P、Al-10Si-2Fe-3P和Si-25Mn-10P中间合金的微观组织及其对初晶硅的晶粒细化作用。分别在810℃、820℃和840℃条件下向Al-24Si合金熔体中添加三种中间合金,并对比分析不同保温时间（30min、60min、90min）下Al-24Si合金的微观组织及初晶硅的尺寸,从而获得中间合金及工艺参数对初晶硅细化作用的影响。本文取得的主要研究结果为:（1）Si-3P、Si-25Mn-10P和Al-10Si-2Fe-3P中间合金中的磷化物分别为SiP、MnP和AlP,三种中间合金均为过共晶Al-24Si合金的有效晶粒细化剂,经过细化处理后合金中初晶硅的尺寸由花瓣状变为细小块状。保温时间为30min时,中间合金的晶粒细化效果最优,随保温时间的延长,其晶粒细化效果逐渐衰退。（2）经过Si-25Mn-10P中间合金细化后的初晶硅的平均尺寸可达到18μm,其晶粒细化效果明显优于Si-3P和Al-10Si-2Fe-3P中间合金,这可能是由中间合金存在高活性的MnP相导致的。此外,提高熔炼温度有利于提升Si-25Mn-10P中间合金的晶粒细化效果。

关键词：铝硅合金初晶硅晶粒细化中间合金 AlP

ON THE MODIFIED NONLINEAR SCHRDINGER EQUATION IN THE SEMICLASSICAL LIMIT:SUPERSONIC,SUBSONIC,AND TRANSSONIC BEHAVIOR

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Acta Mathematica Scientia 2011年第6期31卷 2343-2377页

作者： Jeffery C. DiFranco Peter D. Miller benson K. Muite Department of Mathematics Seattle University Department of Mathematics University of Michigan

The purpose of this paper is to present a comparison between the modified nonlinear SchrSdinger （MNLS） equation and the focusing and defocusing variants of the （unmodified） nonlinear SchrSdinger （NLS） equation in the semiclassical limit. We describe aspects of the limiting dynamics and discuss how the nature of the dynamics is evident theoretically through inverse-scattering and noncommutative steepest descent methods. The main message is that, depending on initial data, the MNLS equation can behave either like the defocusing NLS equation, like the focusing NLS equation （in both cases the analogy is asymptotically accurate in the semiclassical limit when the NLS equation is posed with appropriately modified initial data）, or like an interesting mixture of the two. In the latter case, we identify a feature of the dynamics analogous to a sonic line in gas dynamics, a free boundary separating subsonic flow from supersonic flow.

关键词： semiclassical limits dispersionless limits modulational instability focusing,defocusing, and modified nonlinear SchrSdinger equations

Neoadjuvant treatment of rectal cancer:where are we now?

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Gastroenterology Report 2016年第3期4卷 206-209,I0002页

作者： Aparna Kalyan Shaina Rozelle Al benson III Developmental Therapeutics Program of Division of Hematology&Oncology Robert H.Lurie Comprehensive Cancer Center of Northwestern UniversityChicagoIL USA Division of Hematology&Oncology Robert H.Lurie Comprehensive Cancer Center of Northwestern UniversityChicagoIL USA

Introduction Colorectal cancer is the third leading cause of cancer-related mortality in the United States[1].Of this group of patients,approximately 39000 cases of rectal cancer were reported in the US in 20151].Treatment of rectal cancer truly requires combinatorial therapy with surgery,chemotherapy and radiation(RT),which now comprise the cornerstone of treatment for rectal cancer.

关键词： rectal cancer neoadjuvant chemoradiation 5-fluorouracil local recurrence

Endarterectomy for symptomatic non-stenotic carotids: a systematic review and descriptive analysis

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Stroke & Vascular Neurology 2022年第1期7卷 6-12页

作者： Anthony Larson Valentina Nardi Waleed Brinjikji John benson Giuseppe Lanzino Luis Savastano Department of Radiology Mayo ClinicRochesterMinnesotaUSA Neurosurgery Mayo ClinicRochesterMinnesotaUSA

Objective To systematically analyse prior reports of carotid endarterectomy(CEA)performed in cases of≤50%carotid stenosis in order to understand patient tolerance and potential *** A systematic review and descriptive analysis was performed in concordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses *** English-language search was performed of online databases using librarian-selected search *** were reviewed for relevance which included mention of carotid endarterectomy and *** or retrospective observational cohort studies that reported series of patients who underwent endarterectomy for minimal(≤50%)luminal stenosis with reported outcomes were *** Six studies(which included our institutional series)with a total of 143 patients met the inclusion *** weighted mean age at the time of CEA was 72.3 years;113(79.0%)were male.55.8%of patients with available data had recurrent ipsilateral ischaemic events despite medical *** patients out of 129 with available perioperative data(1.6%)had perioperative MRI findings of acute ischaemic stroke,both within the hemisphere contralateral to the side of *** the 138 patients with available follow-up(mean,36 months),none had recurrent ipsilateral ischaemic *** Endarterectomy for symptomatic carotid disease causing≤50%stenosis may be a potentially beneficial strategy to prevent stroke *** with robust methodology are needed to draw more definitive conclusions in terms of the safety and efficacy of endarterectomy for minimal stenosis with vulnerable features relative to intensive medical therapy.

关键词： carotid stenosis analysis

Controllable Fabrication of Spider-Web-Like Structured Anaphe Panda Regenerated Silk Nanofibers / Nets via Electrospinning / Netting

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Journal of Donghua University(English Edition) 2014年第4期31卷 497-502页

作者： DULO benson 王娜李彦 OYONDI Erick MADARA S Diana 丁彬 College of Textiles Donghua University Department of Manufacturing Industrial and Textile EngineeringMoi University State Key Laboratory for Modification of Chemical Fibers and Polymer Materials College of Materials Science and EngineeringDonghua University

An Anaphe panda silk nanofibers / nets( NFN) membrane with attractive structures consisting of common electrospun nanofibers and two-dimensional( 2D) spider-web-like structured nano-nets were successfully fabricated via electrospinning / netting technology. The unique structures of NFN membranes such as extremely small diameter( < 20 nm),high porosity,large specific surface area. and biocompatibility make this Anaphe panda silk NFN membrane a promising candidate for biomedical applications. In the present study, field emission scanning electron microscopy( FESEM) was used to investigate the influence of polymer solution and humidity on nano-nets coverage and morphology. The FE-SEM images revealed that nano-net coverage area increased with increase in concentration of solution while lowering the humidity increased the nano-nets formation. Moreover,the mechanical properties of the membrane were also tested and the result showed that the silk NFN membrane displayed a breaking stress of 3. 7 MPa and breaking strain of 13. 8%. For further structural elucidation, Fourier transform infrared spectroscopy( FT-IR) was used to analyze the structural conformation changes from random coil to β-sheet in the NFN membrane which was an important factor effecting the usability of membrane. Thus,the results above confirmed the feasibility of Anaphe panda NFN structures applicability in cell tissue culture and other biomedical applications.

关键词： Anaphe panda silk electrospinning / netting nanofibers / nets(NFN) biocompatibility

Near-infrared benzodiazoles as small molecule environmentally-sensitive fluorophores

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Frontiers of Chemical Science and Engineering 2022年第1期16卷 128-135页

作者： Fabio de Moliner Ina Biazruchka Karolina Konsewicz Sam benson Suraj Singh Jun-Seok Lee Marc Vendrell Centre for Inflammation Research Queen’s Medical Research InstituteThe University of EdinburghEdinburgh EH164TJUK Molecular Recognition Research Centre Korea Institute of Science and Technology(KIST)&Bio-Med ProgramKIST-School USTSeoul 02792Korea Department of Pharmacology Korea University College of MedicineSeoul 02841Korea

The development of fluorophores emitting in the near-infrared spectral window has gained increased attention given their suitable features for biological *** this work,we have optimised a general and straightforward synthetic approach to prepare a small library of near-infrared-emitting C-bridged nitrobenzodiazoles using commercial precursors.C-bridged benzodiazoles have low molecular weight and neutral character as important features that are not common in most nearinfrared *** have investigated their fluorescence response in the presence of a wide array of 60 different biomolecules and identified compound 3i as a potential chemosensor to discriminate between Fe2+and Fe^(3+)ions in aqueous media.

关键词： fluorescence probes iron screening library

An examination of the population dynamics of syngnathid fishes within Tampa Bay,Florida,USA

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Current Zoology 2010年第1期56卷 118-133页

作者： Heather D.MASONJONES Emily ROSE Lori benson McRAE Danielle L.DIXSON Biology Department University of Tampa Biology Department Texas A & M University School of Marine and Tropical Biology James Cook University

Seagrass ecosystems worldwide have been declining, leading to a decrease in associated fish populations, especially those with low mobility such as syngnathids （pipefish and seahorses）. This two-year pilot study investigated seasonal patterns in density, growth, site fidelity, and population dynamics of Tampa Bay （FL） syngnathid fishes at a site adjacent to two marinas under construction. Using a modified mark-recapture technique, fish were collected periodically from three closely located sites that varied in seagrass species （Thalassia spp., Syringodium spp., and mixed-grass sites） and their distance from open water, but had consistent physical/chemical environmental characteristics. Fish were marked, photographed for body size and gender measurements, and released the same day at the capture site. Of the 5695 individuals surveyed, 49 individuals were recaptured, indicating a large, flexible population. Population density peaks were observed in July of both years, with low densities in late winter and late summer. Spatially, syngnathid densities were highest closest to the mouth of the bay and lowest near the shoreline. Seven species of syngnathid fishes were observed, and species-specific patterns of seagrass use emerged during the study. However, only two species, Syngnathus scovelli and Hippoeampus zosterae, were observed at high frequencies. For these two species, body size decreased across the study period, but while S. scovelli＇s population density decreased, H. zosterae＇s increased. Across six of the seven species, population size declined over the course of this preliminary study; however, seasonal shifts were impossible to distinguish from potential anthropogenic effects of construction [Current Zoology 56 （1）： 118-133, 2010].

关键词： Syngnathids Habitat-use Seahorse Pipefish Population density Mark-recapture

Spatiotemporal modeling of mid-infrared photoluminescence from terbium(Ⅲ) ion doped chalcogenide-selenide multimode fibers

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Journal of Rare Earths 2019年第11期37卷 1157-1163页

作者： Slawomir Sujecki Lukasz Sojka Zhuoqi Tang Dinuka Jayasuriya David Furniss Emma Barney Trevor benson Angela Seddon Telecommunications and Teleinformatics Department Wroclaw University of Science and TechnologyWroclawPoland Mid-Infrared Photonics Group George Green Institute for Electromagnetics ResearchFaculty of EngineeringThe University of NottinghamNottinghamUK

A numerical model was developed to study the time dynamics of photo luminescence emitted by Tb^3+doped multimode chalcogenide-selenide glass fibers pumped by laser light at approximately 2μ*** model consists of a set of partial differential equations(PDEs),which describe the temporal and spatial evolution of the photon density and level populations within the *** order to solve numerically the PDEs a method of lines was *** modeling parameters were extracted from measurements and from data available in the *** numerical results obtained support experimental *** particular,the developed model reproduces the discrepancies that are observed between the photoluminescence decay curves obtained from different points along the *** numerical analysis was also used to explain the source of these discrepancies.

关键词： Chalcogenide glass fiber Numerical modeling Photoluminescence Mid-infrared light Rare earths

Multi-Material ALE with AMR for Modeling Hot Plasmas and Cold Fragmenting Materials

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Plasma Science and Technology 2015年第2期17卷 117-128页

作者： Alice KONIGES Nathan MASTERS Aaron FISHER David EDER Wangyi LIU Robert ANDERSON David benson Andrea BERTOZZI Lawrence Berkeley National Laboratory Lawrence Livermore National Laboratory Jacobs School of Engineering 9500 Gilman Dr.UCSDLa JollaCA 92093USA Department of Mathematics 520 Portola PlazaUCLALos AngelesCA 90095USA

We have developed a new 3D multi-physics multi-material code, ALE-AMR, which combines Arbitrary Lagrangian Eulerian （ALE） hydrodynamics with Adaptive Mesh Refinement （AMR） to connect the continuum to the microstructural regimes. The code is unique in its ability to model hot radiating plasmas and cold fragmenting solids. New numerical techniques were developed for many of the physics packages to work efficiently on a dynamically moving and adapting mesh. We use interface reconstruction based on volume fractions of the material components within mixed zones and reconstruct interfaces as needed. This interface reconstruction model is also used for void coalescence and fragmentation. A flexible strength/failure framework allows for pluggable material models, which may require material history arrays to determine the level of accumulated damage or the evolving yield stress in J2 plasticity models. For some applications laser rays are propagating through a virtual composite mesh consisting of the finest resolution representation of the modeled space. A new 2nd order accurate diffusion solver has been implemented for the thermal conduction and radiation transport packages. One application area is the modeling of laser/target effects including debris/shrapnel generation. Other application areas include warm dense matter, EUV lithography, and material wall interactions for fusion devices.

关键词： multi-physics simulations arbitrary lagrangian eulerian hydrodynamics,adaptive mesh refinement fragmentation laser ray tracing NIF