检索结果-南通市图书馆

On the analytical solution of transient friction in channel flows

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics and Mechanics(English Edition) 2024年第8期45卷 1447-1466页

作者： f.J.GARCíA-GARCíA p.fARI?AS-ALVARI?O Department of Naval & Industrial Engineering Polytechnic School of EngineeringUniversity of A Coru?a Campus Industrial de Ferrol Integraciones Técnicas de Seguridad S.A. Pol.Ind.Espíritu Santo

The transient friction in channel mean flows is the sum of two contributions,i.e., the underlying laminar flow(ULf) and the purely turbulent component(pTC), and the contributions are analyzed separately by theoretical experiments. It is found that,the transient friction may be higher or remarkably lower than that in equal-Reynolds number steady-state flows. The universal time constant for plane-parallel laminar flows is reported, and the role of the time constant in a turbulent mean flow is examined. It is shown that the time constant is related to the turbulence's frozen time. finally, a study of the logarithmic layer during the transient flow is accomplished, which shows that the logarithmic layer is destroyed.

关键词： 76D05 76D06 76f55 O361 transient flow transient friction unsteady channel flow

Heterogeneity of mature oligodendrocytes in the central nervous system

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Neural Regeneration Research 2025年第5期20卷 1336-1349页

作者： Chao Weng Adam M.R.Groh Moein Yaqubi Qiao-Ling Cui Jo Anne stratton G.R.Wayne Moore Jack p.Antel Neuroimmunology Unit Montreal Neurological Institute-HospitalDepartment of Neurology and NeurosurgeryMcGill UniversityMontrealQCCanada Department of Neurology Renmin Hospital of Wuhan UniversityWuhanHubei ProvinceChina

Mature oligodendrocytes form myelin sheaths that are crucial for the insulation of axons and efficient signal transmission in the central nervous *** evidence has challenged the classical view of the functionally static mature oligodendrocyte and revealed a gamut of dynamic functions such as the ability to modulate neuronal circuitry and provide metabolic support to *** the recognition of potential heterogeneity in mature oligodendrocyte function,a comprehensive summary of mature oligodendrocyte diversity is *** delve into early 20th-century studies by Robertson and Río-Hortega that laid the foundation for the modern identification of regional and morphological heterogeneity in mature ***,recent morphologic and functional studies call into question the long-assumed homogeneity of mature oligodendrocyte function through the identification of distinct subtypes with varying myelination ***,modern molecular investigations,employing techniques such as single cell/nucleus RNA sequencing,consistently unveil at least six mature oligodendrocyte subpopulations in the human central nervous system that are highly transcriptomically diverse and vary with central nervous system *** and disease related mature oligodendrocyte variation denotes the impact of pathological conditions such as multiple sclerosis,Alzheimer's disease,and psychiatric ***,caution is warranted when subclassifying mature oligodendrocytes because of the simplification needed to make conclusions about cell identity from temporally confined *** studies leveraging advanced techniques like spatial transcriptomics and single-cell proteomics promise a more nuanced understanding of mature oligodendrocyte *** research avenues that precisely evaluate mature oligodendrocyte heterogeneity with care to understand the mitigating influence of species,sex,central nervous system region,age,and disease,

关键词： aging central nervous system diseases electron microscopy heterogeneity immunohistochemistry myelin sheath natural history neuroglia oligodendroglia single-cell gene expression analysis

Collisionless shock acceleration of protons in a plasma slab produced in a gas jet by the collision of two laser-driven hydrodynamic shockwaves

在线全文

学校读者我要写书评

暂无评论

Matter and Radiation at Extremes 2024年第2期9卷 12-25页

作者： J.-R.Marquès L.Lancia p.Loiseau p.forestier-Colleoni M.Tarisien E.Atukpor V.Bagnoud C.Brabetz f.Consoli J.Domange f.Hannachi p.Nicolaï M.Salvadori B.Zielbauer LULI CNRSÉcole PolytechniqueCEASorbonne UniversitéInstitut Polytechnique de Paris91128 Palaiseau CedexFrance CEA DAMDIF91297 Arpajon CedexFrance Universitéparis-Saclay CEALMCE91680 Bruyères-le-ChatelFrance CENBG CNRS-IN2P3Universitéde Bordeaux33175 Gradignan CedexFrance GSI Helmholtzzentrum für Schwerionenforschung GmbH Planckstraße 164291 DarmstadtGermany University of Darmstadt Schloßgartenstr.764289 DarmstadtGermany ENEA fusion and Technologies for Nuclear Safety Department C.R.FrascatiVia Enrico Fermi 45FrascatiRomeItaly CELIA Universitéde Bordeaux–CNRS–CEA33405 TalenceFrance Universitéparis-Saclay CEALIDYL91191 Gif-sur-YvetteFrance

We have recently proposed a new technique of plasma tailoring by laser-driven hydrodynamic shockwaves generated on both sides of a gas jet[Marquès et al.,*** 28,023103(2021)].In a continuation of this numerical work,we study experimentally the influence of the tailoring on proton acceleration driven by a high-intensity picosecond laser in three cases:without tailoring,by tailoring only the entrance side of the picosecond laser,and by tailoring both sides of the gas *** tailoring,the acceleration is transverse to the laser axis,with a low-energy exponential spectrum,produced by Coulomb *** the front side of the gas jet is tailored,a forward acceleration appears,which is significantly enhanced when both the front and back sides of the plasma are *** forward acceleration produces higher-energy protons,with a peaked spectrum,and is in good agreement with the mechanism of collisionless shock acceleration(CSA).The spatiotemporal evolution of the plasma profile is characterized by optical shadowgraphy of a probe *** refraction and absorption of this beam are simulated by post-processing 3D hydrodynamic simulations of the plasma *** with the experimental results allows estimation of the thickness and near-critical density of the plasma slab produced by tailoring both sides of the gas *** parameters are in good agreement with those required for CSA.

关键词： acceleration hydrodynamic collision

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

可供选择的炉气氛

铸锻热（热处理实践） 1992年第1期 18-24页

作者： p.f.stratton 杨礼萍英国氧气公司

1简介自热处理一开始,就产生了用于保护工件或与工件反应的气氛,最初这种气氛只简单地为加热工件所需的燃烧产物,但很快就引用了固体“气氛发生器”如木炭或铸铁的铁屑。

关键词：化学热处理氮基气氛应用

Artificial ground freezing of underground mines in cold regions using thermosyphons with air insulation

在线全文

学校读者我要写书评

暂无评论

International Journal of Mining Science and Technology 2024年第5期34卷 643-654页

作者： Ahmad f.Zueter Mohammad Zolfagharroshan Navid Bahrani Agus p.Sasmito Department of Civil and Resource Engineering Dalhousie UniversityHalifax B3H4R2Canada Department of Mining Engineering McGill UniversityMontreal H3A0E8Canada

Current practice of underground artificial ground freezing(AGf)typically involves huge refrigeration systems of large economic and environmental *** this study,a novel AGf technique is proposed deploying available cold wind in cold *** is achieved by a static heat transfer device called thermosyphon equipped with an air insulation layer.A refrigeration unit can be optionally integrated to meet additional cooling *** introduction of air insulation isolates the thermosyphon from ground zones where freezing is not needed,resulting in:(1)steering the cooling resources(cold wind or refrigeration)towards zones of interest;and(2)minimizing refrigeration *** design is demonstrated using well-validated mathematical models from our previous work based on two-phase enthalpy method of the ground coupled with a thermal resistance network for the *** Canadian mines are considered:the Cigar Lake Mine and the Giant *** results show that our proposed design can speed the freezing time by 30%at the Giant Mine and by two months at the Cigar Lake ***,a cooling load of 2.4 GWh can be saved at the Cigar Lake ***,this study provides mining practitioners with sustainable solutions of underground AGf.

关键词： Artificial ground freezing Underground mining Sustainable mining Thermosyphon Air insulation Cold regions

在线全文

学校读者我要写书评

暂无评论

非深冷法制氮在炉气氛中的应用

热处理 1990年第3期50卷 40-44,47页

作者： p. f. stratton 朱秉慧

引言许多年来,在热处理炉中已经应用了专门生产的气氛以保护或与所处理的材料发生反应。早期,这种气氛由现场发生器通过燃烧天然气以及分解氨来提供的,在六十年代末或七十年代初时。

关键词：深冷热处理炉变压吸附活性气体渗碳气氛连续作业炉金属热处理保护气氛净化气脱碳退火

在线全文

学校读者我要写书评

暂无评论

非深冷制氮在氮基气氛热处理中的应用

铸锻热（热处理实践） 1991年第2期 50-56页

作者： p. f. stratton 叶伟江 BOC有限公司

一、绪言直至最近,氮基热处理气氛系统采用的是高纯氮气,它是在深冷过程中通过空气分馏来制取的。现在,利用变压吸附(pSA)技术的发生器可以在现场制取一种纯度比较低的替代型氮气源。这种氮气由于含少量的残余氧,因此并不能在所有热处... 详细信息

一、绪言直至最近,氮基热处理气氛系统采用的是高纯氮气,它是在深冷过程中通过空气分馏来制取的。现在,利用变压吸附(pSA)技术的发生器可以在现场制取一种纯度比较低的替代型氮气源。这种氮气由于含少量的残余氧,因此并不能在所有热处理场合使用。然而,由于经济和技术上的原因,这种气源已成功地应用于许多工艺中。本文将详细叙述这些应用的结果,并提出同样可以成功地应用这项技术的其它场合。

关键词：变压吸附氮气氮基热处理应用

Electron kinetic effects in back-stimulated Raman scattering bursts driven by broadband laser pulses

在线全文

学校读者我要写书评

暂无评论

Matter and Radiation at Extremes 2024年第4期9卷 54-67页

作者： Q.K.Liu L.Deng Q.Wang X.Zhang f.Q.Meng Y.p.Wang Y.Q.Gao H.B.Cai S.p.Zhu Graduate School China Academy of Engineering PhysicsBeijing 100088China Institute of Applied physics and Computational Mathematics Beijing 100094China School of Nuclear Science and Technology University of Science and Technology of ChinaHefei 230026China Shanghai Institute of Laser plasma Shanghai 201800China HEDpS Center for Applied Physics and TechnologyPeking UniversityBeijing 100871China School of physics Zhejiang UniversityHangzhou 310027China

We examine electron kinetic effects in broadband-laser-driven back-stimulated Raman scattering(BSRS)bursts using particle-in-cell *** bursts occur during the nonlinear stage,causing reflectivity spikes and generating large numbers of hot ***-duration simulations are performed to observe burst events,and a simplified model is developed to eliminate the interference of the broadband laser’s random intensity *** the simplified model,we isolate and characterize the spectrum of electron plasma *** spectrum changes from a sideband structure to a turbulence-like structure during the burst.A significant asymmetry in the spectrum is *** asymmetry is amplified and transferred to electron phase space by high-intensity broadband laser pulses,leading to violent vortex-merging and generation of hot *** proportion of hot electrons increases from 6.76%to 14.7%during a single violent burst *** demonstrate that kinetic effects profoundly influence the BSRS evolution driven by broadband lasers.

关键词： scattering kinetic simplified

Bulking Up the Bay-position Substituents Enables Enhanced Selectivity of C_(s)‑Symmetric Boron Subphthalocyanine−Subnaphthalocyanine Hybrids

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

precision Chemistry 2024年第4期2卷 161-181页

作者： Nina f.farac Alan J.Lough Timothy p.Bender Department of Chemical Engineering and Applied Chemistry University of TorontoTorontoOntario M5S 3E5Canada Department of Chemistry University of TorontoTorontoOntario M5S 3H6Canada Department of Materials Science and Engineering University of TorontoTorontoOntario M5S 3E4Canada Department of Mechanical and Industrial Engineering University of TorontoTorontoOntario M5S 3G8Canada

The precise synthesis of subporphyrinoid hybrids withπ-expanded topologies and unique material properties plays a promising role in the design of functional ***,selective,and controllable routes to boron subphthalocyanine−subnaphthalocyanine hybrids,Bsub(pc_(3‑p)-Nc_(p))s,are desirable for this purpose yet synthetically challenging due to random mixtures of C_(s-),C_(3v-),and,in some cases,C_(1)-symmetric compounds that form during traditional statistical mixed ***,we addressed this issue by developing a sterically driven mixed cyclotrimerization with enhanced selectivity for the targeted C_(s)-symmetric hybrid and complete suppression of sterically crowded macrocyclic *** process,coupled with a rationally designed precursor bearing bulky phenyl substituents,enabled the synthesis and characterization of bay-position phenylated ph_(2)-(R_(p))_(8)Bsub(pc_(2)-Nc_(1))hybrids with halogens(Rp=Cl or f)in their peripheral isoindole *** selectivity ranged between 59 and 72%with remarkable yields,significantly higher than that of conventional mixed *** findings were augmented by theoretical calculations on precursor Lewis basicity as guiding principles into hybrid macrocycle ***,the incorporation of unfused phenyl groups and halogen atoms into the hybrid framework resulted in fine-tuned optical,structural,electronic,and electrochemical *** straightforward approach achieved improved selectivity and controlled narrowing of the product distribution,affording the efficient synthesis of structurally sophisticated Bsub(pc_(2)-Nc_(1))*** then expands the library of 3-dimensionalπ-extended macrocycles for use in a range of applications,such as in optoelectronic devices with precisely tailored optical properties.

关键词： subphthalocyanine hybrids low-symmetry aromatic macrocycle selective cyclotrimerization sterically driven chemistry broad absorption material properties