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Characterizing the influence of stress-induced microcracks on the laboratory strength and fracture development in brittle rocks using a finite-discrete element method-micro discrete fracture network FDEM-μDFN approach

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Journal of Rock Mechanics and Geotechnical Engineering 2015年第6期7卷 609-625页

作者： Pooya Hamdi Doug Stead davide Elmo Simon Fraser University 8888 University Drive NBK Institute of Mining Engineering University of British Columbia

Heterogeneity is an inherent component of rock and may be present in different forms including mineralheterogeneity, geometrical heterogeneity, weak grain boundaries and micro-defects. Microcracks areusually observed in crystalline rocks in two forms： natural and stress-induced; the amount of stressinducedmicrocracking increases with depth and in-situ stress. Laboratory results indicate that thephysical properties of rocks such as strength, deformability, P-wave velocity and permeability areinfluenced by increase in microcrack intensity. In this study, the finite-discrete element method （FDEM）is used to model microcrack heterogeneity by introducing into a model sample sets of microcracks usingthe proposed micro discrete fracture network （mDFN） approach. The characteristics of the microcracksrequired to create mDFN models are obtained through image analyses of thin sections of Lac du Bonnetgranite adopted from published literature. A suite of two-dimensional laboratory tests including uniaxial,triaxial compression and Brazilian tests is simulated and the results are compared with laboratory *** FDEM-mDFN models indicate that micro-heterogeneity has a profound influence on both the mechanicalbehavior and resultant fracture pattern. An increase in the microcrack intensity leads to areduction in the strength of the sample and changes the character of the rock strength envelope. Spallingand axial splitting dominate the failure mode at low confinement while shear failure is the dominantfailure mode at high confinement. Numerical results from simulated compression tests show thatmicrocracking reduces the cohesive component of strength alone, and the frictional strength componentremains unaffected. Results from simulated Brazilian tests show that the tensile strength is influenced bythe presence of microcracks, with a reduction in tensile strength as microcrack intensity increases. Theimportance of microcrack heterogeneity in reproducing a bi-linear or S-shape failure

关键词： Finite-discrete element method(FDEM) Micro discrete fracture network(μDFN) Brittle fracture

Velocity profiles description and shape factors inclusion in a hyperbolic,one-dimensional,transient two-fluid model for stratified and slug flow simulations in pipes

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Petroleum 2019年第2期5卷 191-198页

作者： Arianna Bonzanini davide Picchi Marco Ferrari Pietro Poesio Dipartimento di Ingegneria Meccanica ed Industriale Universita degli Studi di BresciaVia Branze3825123BresciaItaly Energy Resources Engineering Stanford UniversityStanford94305CAUnited States Department of Mathematics Politecnico di Milanop.zza Leonardo da Vinci3220133MilanItaly

In a previous work it has been shown that a one-dimensional,hyperbolic,transient five equations twofluid model is able to numerically describe stratified,wavy,and slug flow in horizontal and nearhorizontal *** statistical characteristics can be numerically predicted with results in good agreement with experimental data and well-known empirical *** this model some approximated and simplified assumptions are adopted to describe shear stresses at wall and at phase *** this paper,we focus on the possibility to account for the cross sectional flow by inserting shape factors into the momentum balance equations of the aforementioned *** profiles are obtained by a pre-integrated model and they are computed at each time step and at each computational *** that the velocity profiles are known,the obtained shape factors are inserted in the numerical *** this way it is possible to recover part of the information lost due to the one-dimensional flow *** profiles computed in stratified conditions are compared against experimental profiles measured by PIV technique;a method to compute the velocity profile during slug initiation and growth has been developed and the computed velocity distribution in the liquid phase was compared against the one-seventh power law.

关键词： Multi-phase pipeline transport Oil&gas Hyperbolic two-fluid model Velocity profiles Shape factors

Pediatric liver transplantation

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World Journal of Gastroenterology 2009年第6期15卷 648-674页

作者： Marco Spada Silvia Riva Giuseppe Maggiore davide Cintorino Bruno Gridelli Istituto Mediterraneo peri Trapiantie Terapie ad alta specializzazione-IsMeTT University of Pittsburgh Medical Center90127 PalermoItaly Department of Reproductive Medicine and Child Development University of Pisa56100 PisaItaly

In previous decades,pediatric liver transplantation has become a state-of-the-art operation with excellent success and limited *** and patient survival have continued to improve as a result of improvements in medical,surgical and anesthetic management,organ availability,immunosuppression,and identification and treatment of postoperative *** utilization of split-liver grafts and living-related donors has provided more organs for pediatric *** immunosuppression regimens,including induction therapy,have had a significant impact on graft and patient *** developments of pediatric liver transplantation will deal with long-term followup,with prevention of immunosuppression-related complications and promotion of as normal growth as *** review describes the state-of-the-art in pediatric liver transplantation.

关键词： Pediatric liver transplantation Indications Surgical techniques Complications

Exergy Analysis of Organic Rankine Cycles with Zeotropic Working Fluids

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Fluid Dynamics & Materials Processing 2023年第3期19卷 593-601页

作者： Antonio Mariani davide Laiso Biagio Morrone Andrea Unich Department of Engineering DI Universitàdella Campania“Luigi Vanvitelli”Aversa(CE)Caserta81031Italy

Waste heat recovery is one of the possible solutions to improve the efficiency of internal combustion *** of wasting the exhaust stream of an energy conversion system into the environment,its residual energy content can be usefully recovered,for example in Organic Rankine Cycles(ORC).This technology has been largely consolidated in stationary power plants but not yet for mobile applications,such as road transport,due to the limitations in the layout and to the constraints on the size and weight of the ORC *** ORC system installed on the exhaust line of a bus powered by a natural gas spark ignition engine has been *** thermal power available at engine exhaust has been evaluated by measuring gas temperature and mass flow rate during real driving *** waste thermal power has been considered as heat input for the ORC plant simulation.A detailed heat exchanger model has been developed because it is a crucial component for the ORC *** exergy analysis of the ORC was performed comparing different working fluids:R601,R1233zd(E)and two zeotropic blends of the two organic pure *** model allowed the evaluation of the ORC produced energy over the driving cycle and the potential benefit on the engine efficiency.

关键词： Organic Rankine Cycle zeotropic mixtures exergy analysis waste heat recovery engine efficiency internal combustion engine

Alternative stable states in mountain forest ecosystems： the case of European larch(Larix decidua) forests in the western Alps

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Journal of Mountain Science 2017年第5期14卷 811-822页

作者： Jose V.MORIS Giorgio VACCHIANO davide ASCOLI Renzo MOTTA University of Turin DISAFALargo Paolo Braccini 210095 Grugliasco(TO)Italy

European larch(Larix decidua) forests of the western Alps form extensivecultural landscapes whose resilience to global changes is currently unknown. Resilience describes the capacity of ecological systems to maintain the same state, i.e., the same function, processes, structure, and composition despite disturbances, environmental changes and internal fluctuations. Our aim is to explore the resilience of larch forests to changes in climate and land use in the western Italian *** do so, we examined whether larch forests can be described as an alternative stable state in mountain forest ecosystems. We used tree basal area data obtained from field forest inventories in combination with topography, forest structure, land use, and climate information. We applied three different probabilistic methods: frequency distributions, logistic regressions, and potential analyses to infer the resilience of larch forests relative to that of other forest *** found patters indicative of alternative stable states: bimodality in the frequency distribution of the percent of larch basal area, and the presence of an unstable state, i.e., mixed larch forests, in the potential analyses. We also found:(1) high frequency ofpurelarchforestsathighelevation,(2)the probability of pure larch forests increased mostly with elevation, and(3) pure larch forests were a stable state in the upper montane and subalpine *** study shows that the resilience of larch forests may increase with elevation, most likely due to the altitudinal effect on climate. Under the same climate conditions, land use seems to be the main factor governing the dominance of larch forests. In fact, subalpine larch forests may be more resilient, and natural succession after land abandonment, e.g., towards Pinuscembra forests, seems slower than in montane larch forests. In contrast, in the upper montane belt only intense land use regimes characterized by open canopies and forest grazing may maintain larch *** con

关键词： Resilience Ecosystem bistability Elevation Land use Natural succession Pinuscembra European larch

Snow gliding and loading under two different forest stands: a case study in the north-western Italian Alps

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Journal of Forestry Research 2013年第4期24卷 633-642页

作者： davide Viglietti Margherita Maggioni Enrico Bruno Ermanno Zanini Michele Freppaz University of Torino-Dipartimento di Scienze Agrarie Forestalie Alimentari and NatRisk-LNSA Via L.

The presence of a thick snowpack could interfere with forest stability, especially on steep slopes with potential damages for young and old stands. The study of snow gliding in forests is rather complex be- cause this phenomenon could be influenced not only by forest features, but also by snow/soil interface characteristics, site morphology, meteoro- logical conditions and snow physical properties. Our starting hypothesis is that different forest stands have an influence on the snowpack evolu- tion and on the temperature and moisture at the snow/soil interface, which subsequently could affect snow gliding processes and snow forces. The aim of this work is therefore to analyse the snowpack evolution and snow gliding movements under different forest covers, in order to deter- mine the snow forces acting on single trees.

关键词： snow/soil interface temperature water content snow forces trees

Time sensitive networking security:issues of precision time protocol and its implementation

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Cybersecurity 2023年第4期6卷 1-13页

作者： davide Berardi Nils OTippenhauer Andrea Melis Marco Prandini Franco Callegati Alma Mater Studiorum-Universitàdegli studi di Bologna BolognaItaly CISPA Helmholtz Center for Information Security SaarbrückenGermany

Time Sensitive Networking(TSN)will be an integral component of industrial *** synchronization in TSN is provided by the IEEE-1588,Precision Time Protocol(PTP)*** standard,dating back to 2008,marginally addresses security aspects,notably not encompassing the frames designed for management purposes(Type Length Values or TLVs).In this work we show that the TLVs can be abused by an attacker to reconfigure,manipulate,or shut down time *** effects of such an attack can be serious,ranging from interruption of operations to actual unintended behavior of industrial devices,possibly resulting in physical damages or even harm to *** paper analyzes the root causes of this vulnerability,and provides concrete examples of attacks leveraging it to de-synchronize the clocks,showing that they can succeed with limited resources,realistically available to a malicious actor.

关键词： Time synchronization Time sensitive networking Precision time protocol Cybersecurity attacks

Long-term mechanical behavior and characteristics of cemented tailings backfill through impact loading

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International Journal of Minerals,Metallurgy and Materials 2020年第2期27卷 140-151页

作者： Yu-ye Tan Elmo davide Yu-cheng Zhou Wei-dong Song Xiang Meng Key Laboratory of High-Efficient Mining and Safety of Metal Mines(Ministry of Education of China) University of Science and Technology BeijingBeijing 100083China School of Civil and Resources Engineering University of Science and Technology BeijingBeijing 100083China Norman B.Keevil Institute of Mining Engineering Applied Science SchoolUniversity of British ColumbiaVancouverBC Canada V6T 1Z4

Cemented tailings backfill(CTB)structures are important components of underground mine *** is important to investigate the characteristics and dynamic behavior of CTB materials because they are susceptible to disturbance by dynamic loading,such as excavation and *** this study,the authors present the results of a series of Split-Hopkinson pressure bar(SHPB)single and cyclic impact loading tests on CTB specimens to investigate the long-term dynamic mechanical properties of *** stress-strain relationship,dynamic strength,and dynamic failure characteristics of CTB specimens are analyzed and discussed to provide valuable conclusions that will improve our knowledge of CTB long-term mechanical behavior and *** instance,the dynamic peak stress under cyclic impact loading is approximately twice that under single impact loading,and the CTB specimens are less prone to fracture when cyclically *** findings and conclusions can provide a new set of references for the stability analysis of CTB materials and help guide mine designers in reducing the amount of binding agents and the associated mining cost.

关键词： cyclic impact loading cemented tailings backfill dynamic mechanical properties Split–Hopkinson pressure bar dynamic peak stress

Strategies of Vertical Product Extension:Effects,Risks and Opportunities in the Luxury Automotive Market in China

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Strategies of Vertical Product Extension:Effects,Risks and O...

作者： davide SFRECOLA 复旦大学

学位级别：硕士

垂直的产品扩展策略是在市场上推出新产品。新的扩展属于相同的产品类别为核心的品牌,但在不同的质量和价格点。启动扩展在市场上是一个战略决策,通过一些新的和有吸引力的战略决策。如进军新的细分市场的不同需求驱动,满足竞争对手的... 详细信息

垂直的产品扩展策略是在市场上推出新产品。新的扩展属于相同的产品类别为核心的品牌,但在不同的质量和价格点。启动扩展在市场上是一个战略决策,通过一些新的和有吸引力的战略决策。如进军新的细分市场的不同需求驱动,满足竞争对手的产品或保持品牌的忠诚度。此类行动战略背后是强制执行的可能性,充分利用令人难以置信的大量企业内部的自身所产生的协同作用：有形资产和无形资产深深协同,追求和实现向上或向下延伸策略。上述策略代表一种普遍的做法,在市场上的学术研究主要研究了成熟市场的关联效应和风险这些行动。垂直产品扩展是一个熟悉汽车行业的战略,但它只是在最近,一直是豪华汽车制造商正试图通过这样的方法,新的细分市场渗透。本研究从一个非常重要的问题：在一个豪华车品牌在中国的产品纵向延伸的情况下会发生什么?一直在中国汽车行业在过去十年涨再涨。它一直自2009年以来,虽然单位在生产汽车,克服了美国和日本的总和。2009年本土品牌的生产占44.3%而其余的主要由国外生产商生产(大众第一,.通用汽车公司和日本OEM)通过与中国公司合资成立了自己的操作。国内市场一直占最大的一部分,最近对焦出口(主要销往新兴经济体在2012年的100万台)的销售。豪车一般都是合资公司和本土公司一起经营的,在偏好进口车的市场里豪车仍然只占很小的份量。客户对品牌的态度思考实施纵向延伸战略时需要考虑的关键。它会影响操作有助于确定客户新产品的接受程度的成功的可能性。的影响,品牌资产的稀释和蚕食的主要风险分析和连接的研究重点也尝试研究如何抓住中国市场提供的机会。调查可以了解产品的针对性和品牌相关性和他们的购买决策过程的相对重要性之间存在的关系。希思,德尔维奇奥和麦卡锡的模型是用于检查的不对称对品牌权益的影响情况下,向上或向下垂直产品延伸,从而确定变量分析,理解,如果延伸策略最适合精确的品牌。主要品牌支柱,将被视为是品牌态度(对品牌的换位思考),品牌的声望(品牌能精确的传达精英主义的感觉)的品牌信誉,品牌创新性(对创新和创造力的倾向)和品牌的专业知识(品牌协会的质量和性能) 。向上扩展和向下扩展的效果最不对称性在离开时被发现几乎没有不对称的品牌信誉,品牌的专业知识和品牌创新的支柱。更多的相关品牌在某一特定客户的感知,延长降压的影响就越大由此造成的不对称性降低。更深层次的客户的复杂性,更不对称的影响扩展***还发现,品牌信誉是最有影响力的帐户实施扩展战略时必须考虑到的因素。关于拆的考虑可以更好地了解中国汽车动态,并可能建议未来的研究领域。

关键词：战略产品延伸豪华轿车中国市场