检索结果-南通市图书馆

风机技术 2020年第6期62卷 7-17页

作者： luca d'agostino department of Civil&Industrial Engineering Pisa University8 Via Gerolamo Caruso

The article illustrates the application of Bayesian estimation to the identification of flow instabilities,with special reference to rotating cavitation,in a three-bladed axial inducer using the unsteady pressure readings of a single transducer mounted on the casing just behind the leading edges of the impeller *** typical trapezoidal pressure distribution in the blade channels is parametrized and modulated in time and space for theoretically reproducing the expected pressure generated by known forms of cavitation instabilities(cavitation auto-oscillations and higher-order surge cavitation modes,n-lobed subsynchronous/synchronous/super-synchronous rotating cavitation).The Fourier spectra of the theoretical pressure so obtained in the rotating frame are transformed in the stationary frame,frequency broadened to better approximate the experimental results,and parametrically fitted by maximum likelihood estimation to the measured auto-correlation *** form of instability generates a characteristic distribution of sidebands in addition to its fundamental *** identification makes use of this information for effective detection and characterization of multiple simultaneous flow instabilities with intensities spanning over about 20 db down to about 4 db signal-to-noise *** same information also allows for effectively bypassing the aliasing limitations of traditional cross-correlation methods in the discrimination of multiple-lobed azimuthal instabilities from the measurements returned by arrays of equally spaced *** method returns both the estimates of the model parameters and their standard deviations,providing the information needed for the assessment of the statistical significance of the *** proposed approach represents therefore a promising tool for experimental research on flow instabilities in high-performance turbopumps.

关键词： Rocket Propulsion Liquid Propellant Rocket Engines Turbomachinery Turbopumps Turbopump Cavitation Instabilities Parametric Identification

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

火箭发动机导流器和涡轮泵中空化不稳定性和转子动力学载荷（英文）

引用

风机技术 2018年第3期60卷 45-61页

作者： luca d’agostino Civil and Industrial Engineering department University of Pisa

After a brief review of flow-induced instabilities in turbopumps for liquid propellant feed systems of modern rocket engines, some recent results of the work carried out by the author and his collaborators to elucidate the role of cavitation on the development of unsteady flow phenomena and rotordynamic impeller forces in these machines are illustrated. Specifically, the results are presented of a series of tests conducted in water in the Cavitating Pump Rotordynamic Test Facility(CPRTF) under similarity conditions on a threebladed, tapered-hub, high-head *** flow instabilities detected in these machines include axial cavitation surge oscillations, backflow oscillations, non-synchronous and synchronous(alternating blade) rotating cavitation, higher-order surge and higher-order rotating cavitation, depending on the operational conditions of the machine. The occurrence of these instabilities under the relevant operational conditions is critically *** characterization of the rotordynamic forces acting on the whirling impellers of the above machines under different load and cavitation conditions is also illustrated and discussed. The results have been obtained in the CPRTF by means of a novel experimental technique that allows for the continuous measurement of the rotordynamic force spectra as functions of the whirl ratio. Comparison with simultaneous high-speed movies of the inducer inlet flow highlights the relationship between the cavitation dynamics in the inducer backflow and the spectral behavior of the rotordynamic force as functions of the whirl ratio.

关键词： Turbomachines Turbopumps Aerospace Propulsion Rocket Propulsion Liquid Propellant Rocket Engines Liquid Propellant Feed Turbopumps Two-Phase Flows Cavitation Inducers Unsteady Turbopump and Inducer Hydrodynamics Flow Instabilities Rotordynamics Rotordynamic Fluid Forces Cavitation-Induced Flow Instabilities

来源：

同方期刊数据库评论

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

混流空间诱导轮的性能快速交互设计（英文）

引用

风机技术 2019年第3期61卷 1-13,I0006页

作者： luca d’agostino Civil and Industrial Engineering department University of Pisa

本文介绍了一种空间推进用混流锥形轮毂诱导轮初步设计和空化性能预测降阶模型的开发与实验验证。该模型通过将二维轴向涡度修正施加到充分导向轴对称流(其轴向速度沿径向均匀分布)上,来描述叶片流道中的三维不可压缩、无粘性、无旋流... 详细信息

本文介绍了一种空间推进用混流锥形轮毂诱导轮初步设计和空化性能预测降阶模型的开发与实验验证。该模型通过将二维轴向涡度修正施加到充分导向轴对称流(其轴向速度沿径向均匀分布)上,来描述叶片流道中的三维不可压缩、无粘性、无旋流动。在不忽略径向流动的情况下适当地再定义了叶片的扩压系数,可以控制叶片的负载,并在设计流量系数下预估边界层阻塞和叶片粘性损失,为匹配轮毂型线与叶距角的轴向变化提供一个简单的判据。采用卡特法则计算诱导轮尾缘处的流量偏差。利用质量守恒定律、角动量守恒定律和欧拉方程,推导出了一个简化的二阶边值问题,其数值解定义了诱导轮出口的远场轴对称流速。对攻角、机匣和叶顶间隙损失进行适当的半经验修正,进而得到空化性能。该模型已被证实与在空化泵转子动力学试验装置中测试的两个空间诱导轮的几何和空化特性十分接近,与文献中提到的许多锥形轮毂诱导轮也十分相似。

关键词：交互设计性能预测诱导轮流空间角动量守恒定律叶片流道降阶模型轴向速度

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Application of flame-formed carbon nanoparticle films for ethanol sensing Author links open overlay panel

引用

Particuology 2024年第8期91卷 202-210页

作者： Pegah darvehi luca Basta Mario Commodo Patrizia Minutolo Andrea d'Anna Istituto di Scienze e Tecnologie per l’Energia e la MobilitàSostenibili Consiglio Nazionale delle RicercheP.le Tecchio 8080125NapoliItaly dipartimento di Ingegneria Chimica dei Materiali e della Produzione IndustrialeUniversitàdegli Studi di Napoli Federico IIP.le Tecchio 8080125NapoliItaly

Carbon nanoparticles(CNPs)have received considerable attention due to their exceptional qualities and *** unique physical and chemical characteristics make them extremely intriguing as materials for numerous high-potential applications,such as electronics and gas *** study focused on producing carbon-based nanomaterial devices by deposition of flame-formed carbon nanoparticles on a suitable substrate and investigating their gas-sensing *** were produced in a fuel-rich laminar premixed ethylene/air flame and the collected CNP film was morphologically and electrically *** electrical conductivity of the film was investigated as a function of ethanol concentration and amount of deposited ***,CNP films exhibited high sensitivity to ambient ethanol gas concentrations,and rapid recovery times at room temperature,and showed a sensitivity increasing with the amount of deposited material and the surface *** findings demonstrate the high potential of combustion-generated CNPs as building materials for low-cost and portable ethanol sensors.

关键词： Flame synthesis Carbon nanoparticles Soot Nanostructured thin film Optical and electrical characterization Atomic force microscopy Sensors

来源：

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

Interpreting siliciclastic sedimentation in the upper Paleozoic Mulargia-Escalaplano Basin(Sardinia, Italy):influence of tectonics on provenance

引用

Journal of Palaeogeography 2024年第1期13卷 18-34页

作者： luca G.Costamagna Sara Criniti dipartimento di Scienze Chimiche e Geologiche Citadella UniversitariaBlocco A09042 Monserrato CAItaly dipartimento di Ingegneria dell'Ambiente Universita della Calabria87036 Arcavacata di Rende CSItaly

Late to post-Variscan molassic basins of Late Pennsylvanian-Permian age are exposed in Sardinia(Italy). Here, the compositional and stratigraphic evolution of the Mulargia-Escalaplano sedimentary basin(central Sardinia) has been investigated to highlight how the tectono-magmatic processes have influenced the sedimentation. Ruditic and arenitic samples were collected along well-characterized stratigraphic sections to provide a new insight into the impact of the tectono-magmatic processes on siliciclastic sedimentation. As a result, the conglomerates are mainly clast-supported, petromictic, and thus immature, with no defined maturity trend upwards. Nevertheless, pebble composition changes in times from Variscan basement pebble-rich to volcanic rock-rich, as a consequence of the basin widening and the dismantling and reworking of the coeval volcanic activity. The sandstone composition clearly changes from quartzolithic to feldspatholithic upwards, as a response to the same change of feeding and reworking of the volcanic rocks. Occasionally, interbedded quartzolithic arenites suggest exceptional floods carrying debris from the far borders of the basin. Also, the immature sandstone composition has been interpreted as being controlled by a continuous supply of fresh debris and to a rapid burial rate. In addition, the disappearance of metaradiolarite(lydite AA) Paleozoic grains in the sandstone mineral suite could represent a distinctive marker of a progressive unroofing of the Variscan chain and a clastic supply from deeper tectonic units.

关键词： Petrography Stratigraphy Provenance Molassic basins Sardinia

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Well-Posedness of Stochastic Continuity Equations on Riemannian Manifolds

引用

Chinese Annals of Mathematics,Series B 2024年第1期45卷 81-122页

作者： luca GALIMBERTI Kenneth H.KARLSEN department of Mathematical Sciences NTNU Norwegian University of Science and TechnologyN-7491 TrondheimNorway department of mathematics University of OsloP.O.Box 1053BlindernN-0316 OsloNorway

The authors analyze continuity equations with Stratonovich stochasticity,■ρ+divh[ρo(u(t,x)+∑_(i=1)^(N)a_(i)(x)w_(i)(t))]=0defined on a smooth closed Riemannian manifold M with metric *** velocity field u is perturbed by Gaussian noise terms Wi(t),:WN(t)driven by smooth spatially dependent vector fields a1(x),...,aN(x)on *** velocity u belongs to L_(t)^(1)W_(x)^(1,2)with divh u bounded in Lf,for p>d+2,where d is the dimension of M(they do not assume div_(h) u∈L_(t,x)^(∞)).For carefully chosen noise vector fields ai(and the number N of them),they show that the initial-value problem is well-posed in the class of weak L^(2) solutions,although the problem can be ill-posed in the deterministic case because of concentration *** proof of this“regularization by noise”result is based on a L^(2) estimate,which is obtained by a duality method,and a weak compactness argument.

关键词： Stochastic continuity equation Riemannian manifold Hyperbolic equa-tion Non-smooth velocity field Weak solution Existence Uniqueness

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Corneal collagen cross-linking in patients with keratoconus from the dresden protocol to customized solutions:theoretical basis

引用

International Journal of Ophthalmology(English edition) 2024年第5期17卷 951-962页

作者： Ciro Caruso luca d’Andrea Mario Troisi Michele Rinaldi Raffaele Piscopo Salvatore Troisi Ciro Costagliola Corneal Transplant Center Pellegrini HospitalVia Portamedina alla Pignasecca 41Napoli 80127Italy Eye Clinic Department of NeurosciencesReproductive and Odontostomatological SciencesUniversity of Naples Federico IINaples 80131Italy Public Health department University of Naples Federico IINaples 80131Italy Salerno Hospital University Ophthalmologic UnitBaronissiCampania 84131Italy

Keratoconus is an ectatic condition characterized by gradual corneal thinning,corneal protrusion,progressive irregular astigmatism,corneal fibrosis,and visual *** therapeutic options regarding improvement of visual function include glasses or soft contact lenses correction for initial stages,gas-permeable rigid contact lenses,scleral lenses,implantation of intrastromal corneal ring or corneal transplants for most advanced *** keratoconus cases showing disease progression corneal collagen crosslinking(CXL)has been proven to be an effective,minimally invasive and safe *** consists of a photochemical reaction of corneal collagen by riboflavin stimulation with ultraviolet A radiation,resulting in stromal crosslinks *** aim of this review is to carry out an examination of CXL methods based on theoretical basis and mathematical models,from the original dresden protocol to the most recent developments in the technique,reporting the changes proposed in the last 15y and examining the advantages and disadvantages of the various treatment ***,the limits of non-standardized methods and the perspectives offered by a customization of the treatment are highlighted.

关键词： corneal collagen cross linking keratoconus custom fast protocol dresden protocol lambert-beer law Bunsen-roscoe law

来源：

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

Topological optimization of ballistic protective structures through genetic algorithms in a vulnerability-driven environment

引用

defence Technology（防务技术） 2024年第10期40卷 125-137页

作者： Salvatore Annunziata luca Lomazzi Marco Giglio Andrea Manes Politecnico di Milano Department of Mechanical EngineeringVia Giuseppe La Masa120156Italy

Reducing the vulnerability of a platform,i.e.,the risk of being affected by hostile objects,is of paramount importance in the design process of vehicles,especially aircraft.A simple and effective way to decrease vulnerability is to introduce protective structures to intercept and possibly stop ***,this type of solution can lead to a significant increase in weight,affecting the performance of the *** this reason,it is crucial to study possible solutions that allow reducing the vulnerability of the aircraft while containing the increase in structural *** possible strategy is to optimize the topology of protective solutions to find the optimal balance between vulnerability and the weight of the added *** the many optimization techniques available in the literature for this purpose,multiobjective genetic algorithms stand out as promising *** this context,this work proposes the use of a in-house software for vulnerability calculation to guide the process of topology optimization through multi-objective genetic algorithms,aiming to simultaneously minimize the weight of protective structures and *** addition to the use of the in-house software,which itself represents a novelty in the field of topology optimization of structures,the method incorporates a custom mutation function within the genetic algorithm,specifically developed using a graph-based approach to ensure the continuity of the generated *** tool developed for this work is capable of generating protections with optimized layouts considering two different types of impacting objects,namely bullets and fragments from detonating *** software outputs a set of non-dominated solutions describing different topologies that the user can choose from.

关键词： Topological optimization Protective structure Genetic algorithm Survivability Vulnerability

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

High-speed tracked vehicle model order reduction for static and dynamic simulations

引用

defence Technology（防务技术） 2024年第8期38卷 89-110页

作者： luca dimauro Simone Venturini Antonio Tota Enrico Galvagno Mauro Velardocchia department of Mechanical and Aerospace Engineering Politecnico di TorinoCorso Duca degli Abruzzi2410129TorinoItaly

In this paper, a model order reduction strategy is adopted for the static and dynamic behaviour simulation of a high-speed tracked vehicle. The total number of degree of freedom of the structure is condensed through a selection of interface degrees of freedom and significant global mode shapes, for an approximated description of vehicle dynamic behaviour. The methodology is implemented in a customised open-source software to reduce the computational efforts. The modelled tracked vehicle includes the sprung mass, the unsprung masses, connected by means of torsional bars, and all the track assemblies, composing the track chain. The proposed research activity presents a comprehensive investigation of the influence of the track chain, combined with longitudinal vehicle speed, on statics and vehicle dynamics, focusing on vertical dynamics. The vehicle response has been investigated both in frequency and time domain. In this last case road-wheel displacements are assumed as inputs for the model, under different working conditions, hence considering several road profiles with different amplitudes and characteristic excitation frequencies. Simulation results have proven a high fidelity in model order reduction approach and a significant contribution of the track chain in the global dynamic behaviour of the tracked vehicle.

关键词： Tracked vehicle dynamics Rubber characteristics Component mode synthesis Modal analysis Open-source

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

development of deep-learning-based autonomous agents for low-speed maneuvering in Unity

Journal of Intelligent and Connected Vehicles

引用

Journal of Intelligent and Connected Vehicles 2024年第3期7卷 229-244页

作者： Riccardo Berta luca Lazzaroni Alessio Capello Marianna Cossu luca Forneris Alessandro Pighetti Francesco Bellotti Electrical Electronics and Telecommunication Engineering and Naval Architecture Department(DITEN)University of GenoaGenoa 16145Italy

This study provides a systematic analysis of the resource-consuming training of deep reinforcement-learning (dRL) agents for simulated low-speed automated driving (Ad). In Unity, this study established two case studies: garage parking and navigating an obstacle-dense area. Our analysis involves training a path-planning agent with real-time-only sensor information. This study addresses research questions insufficiently covered in the literature, exploring curriculum learning (CL), agent generalization (knowledge transfer), computation distribution (CPU vs. GPU), and mapless navigation. CL proved necessary for the garage scenario and beneficial for obstacle avoidance. It involved adjustments at different stages, including terminal conditions, environment complexity, and reward function hyperparameters, guided by their evolution in multiple training attempts. Fine-tuning the simulation tick and decision period parameters was crucial for effective training. The abstraction of high-level concepts (e.g., obstacle avoidance) necessitates training the agent in sufficiently complex environments in terms of the number of obstacles. While blogs and forums discuss training machine learning models in Unity, a lack of scientific articles on dRL agents for Ad persists. However, since agent development requires considerable training time and difficult procedures, there is a growing need to support such research through scientific means. In addition to our findings, we contribute to the R&d community by providing our environment with open sources.

关键词： automated driving autonomous agents deep reinforcement learning curriculum learning modeling and simulation

来源：

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

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：