检索结果-南通市图书馆

Scaling granular material with polygonal particles in discrete element modeling

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Particuology 2023年第4期75卷 151-164页

作者： Alireza Ahmadi stefan Larsson Carl Wersall KTH Royal Institute of Technology Division of Soil and Rock MechanicsBrinellvagen 2310044StockholmSweden

Despite advancements in computational resources,the discrete element method(DEM)still requires considerable computational time to solve detailed problems,especially when it comes to the large-scale *** addition to the geometry scale of the problem,the particle shape has a dramatic effect on the computational cost of ***,many studies have been performed with simplified spherical particles or *** scaling is an approach to increase the particle size to reduce the number of particles in the *** several particle scaling methods have been introduced,there are still some disagreements regarding their applicability to certain aspects of *** this study,the effect of particle scalping on the shear behavior of granular material is *** granular particles were scanned and imported as polygonal particles in the direct shear *** effect of particle size distri-bution,particle angularity,and the amount of scalping were *** results show that particle scalping can simulate the correct shear behavior of the model with significant improvement in computational ***,the accuracy of the scalping method depends on the particle angularity and particle size range.

关键词： Particle scaling Direct shear test Discrete element method PFC Polygonal shape Granular material

Urbanization between compactness and dispersion:designing a spatial model for measuring 2D binary settlement landscape configurations

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

International Journal of Digital Earth 2019年第6期12卷 679-698页

作者： Hannes Taubenbock Michael Wurm Christian GeiB stefan Dech stefan Siedentop German Aerospace Center(DLR) German Remote Sensing Data Center(DFD)OberpfaffenhofenGermany ILS-Research Institute for Regional and Urban Development DortmundGermany

Measuring spatial patterns is a crucial task in spatial *** indicators have been developed to measure patterns in a quantitative ***,most comparative studies rely on relative comparisons,limiting their explanatory power to specific case *** by advancements in earth observation providing unprecedented resolutions of settlement patterns,this paper suggests a measurement technique for spatial patterns to overcome the limits of relative *** design a model spanning a feature space based on two metrics-largest patch index and number of *** feature space is defined as‘dispersion index’and covers the entire spectrum of possible two-dimensional binary(settlement)*** model configuration allows for an unambiguous ranking of each possible pattern with respect to spatial *** spatial resolutions of input data as well as selected areas of interest influence measurement results,we test dependencies within the ***,common other spatial metrics are selected for testing whether they allow unambiguous *** scenarios,we apply the model to artificially generated patterns representing all possible configurations as well as to real-world settlement classifications differing in growth dynamics and patterns.

关键词： Land cover spatial patterns landscape metrics dispersion index sensitivity analysis urban settlements remote sensing comparative spatial analysis

A review on the aging phenomena of organic components and their mass transfer through the NAPL interfacial phase

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal Of Geochemistry 2013年第3期32卷 252-260页

作者： LIU Lihua stefan Haderlein Key Laboratory of Renewable Energy and Gas Hydrate Guangzhou Institute of Energy Conversion Chinese Academy of Sciences Eberhard-Karls-University of Tuebingen Center for Applied Geoscience (ZAG)

It occurs worldwide that the organic components of non-aqueous phase liquid (NAPL) enter the porous medium and become the source of contaminants in the subsurface. The transport of the organic components through NAPL interphase into the aqueous phase and the subsurface determines the extent of contamination, the persistence of residual NAPL phases and the techniques of remediation. During the transport process the NAPL interphase may experience "aging", a physical and chemical change when NAPL is exposed to aqueous and or gaseous phases. This aging process alters vice versa the mass transfer behaviour of the organic contaminants in the porous medium.

关键词：老化现象有机组成传质界面相部分和非水相液体评论污染物源

Carbon Footprint of Transitional Shelters

在线全文

学校读者我要写书评

暂无评论

International Journal of Disaster Risk Science 2015年第3期6卷 226-237页

作者： Matti Kuittinen stefan Winter Department of Architecture School of Arts Design and Architecture Aalto University Faculty of Civil Geo and Environmental EngineeringTechnische Universitt München

Extreme weather events, sea level rise, and political disputes linked to climate change are driving masses to leave their homes. Their transitional settlements should be produced in a manner that causes minimum greenhouse gas(GHG) emissions to prevent any further acceleration of climate change and the humanitarian crises it causes. This article presents a study of the carbon footprint and primary energy demand of the construction materials of eight different transitional shelters. The lowest carbon footprints were found from shelter models made from bamboo or timber. The highest emissions were caused by shelters that have either a short service life or that are made from metal-intensive structures. The choice of cladding materials was surprisingly important. The findings were further compared to the overall impacts of each construction project, to national per capita GHG emissions,and to construction costs. Some shelter projects had notable total energy consumption even compared to the annual energy use of industrialized countries. The study concludes that construction materials have an important impact on the carbon footprint of shelters. Comparisons should however be made only between similar functional units. Furthermore, benchmark values and more background data are urgently needed in order to give humanitarian nongovernmental organizations tools for lowering the carbon footprint of their construction operations.

关键词： Carbon footprint Humanitarian construction Lifecycle assessment Primary energy

Predictions of the P1 approximation for radiative heat transfer in heterogeneous granular media

在线全文

学校读者我要写书评

暂无评论

Particuology 2023年第11期82卷 25-47页

作者： Jelena Macak Christoph Goniva stefan Radl DCS Computing GmbH 4020LinzAustria Graz University of Technology Institute of Process and Particle Engineering8010GrazAustria

The P1 approximation is a computationally efficient model for thermal ***,we present a P1 formulation in the context of the combined computational fluid dynamics and discrete element method(CFD-DEM),including closures for dependent scattering and *** available analytical and semi-analytical solutions,we find agreement for steady-state and transient quantities in sizedisperse *** flux is identified as the most sensitive quantity to predict,displaying unphysical spatial *** oscillations are due to a temperature slip at the locations of abrupt change in solid *** propose two techniques that mitigate this effect:smoothing of the radiative properties,and ***,using up to a million times enlarged particles,we demonstrate practically limitless compatibility with ***,we compare predictions made with our code to experimental data for a pebble bed under vacuum conditions,and in presence of *** find that a carefully calibrated simulation can replicate trends observed in experiments,with relative temperature error of less than 10%.

关键词： CFD-DEM Thermal radiation Coarse-graining P1 Pebble bed nuclear reactor

IMPROVING SOLVER PERFORMANCE THROUGH REDUNDANCY

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Systems Science and Systems Engineering 2016年第3期25卷 303-325页

作者： Eduardo Lalla-Ruiz stefan Voβ Department of Computer Engineering and Systems University of La Laguna Spain Institute of Information Systems (IWI) University of Hamburg Germany Eseuela de Ingenierla Industrial Pontificia Universidad Catolica de Valparaiso (PUCV) Chile

It is well known that hierarchies of mathematical programming formulatlons with different numbers of variables and constraints have a considerable impact regarding the quality of solutions obtained once these formulations are fed to a commercial solver. In addition, even if dimensions are kept the same, changes in formulations may largely influence solvability and quality of results. This becomes evident especially if redundant constraints are used. We propose a related framework for information collection based on these constraints. We exemplify by means of a well-known combinatorial optimization problem from the knapsack problem family, i.e., the multidimensional multiple-choice knapsack problem （MMKP）. This incorporates a relationship of the MMKP to some generalized set partitioning problems. Moreover, we investigate an application in maritime shipping and logistics by means of the dynamic berth allocation problem （DBAP）, where optimal solutions are reached from the root node within the solver.

关键词： Erraticism redundant constraints multidimensional multiple-choice knapsack problem,dynamic berth allocation problem

Pathological tumor response to neoadjuvant therapy in borderline resectable pancreatic cancer

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Hepatobiliary & Pancreatic Diseases International 2019年第4期18卷 305-306页

作者： stefan Heinrich General Visceral and Transplantation Surgery University Hospital of Mainz

Surgery is the standard therapy for pancreatic ductal adenocarcinoma(PDAC).After the dramatic decline of operative mortality over the past decades,the indications for pancreas resections have been continuously extended:currently resections of the portal/superior mesenteric vein are considered standard by many centers,and even arterial resections are under *** these changes,different expert groups have defined resectability criteria containing a grey zone(“borderline resectable disease”)of tumors,which may be technically resectable with appropriate surgical expertise,but resection inherits an increased risk of an R1-resection[1].

关键词： Surgery mortality operative

Risk-Layering for Indirect Effects

在线全文

学校读者我要写书评

暂无评论

International Journal of Disaster Risk Science 2021年第5期12卷 770-778页

作者： stefan Hochrainer-Stigler Karina Reiter IIASA-International Institute for Applied Systems Analysis A-2361 Laxenburg.Austria

Environmental risks are one of the greatest threats in the twenty-first *** in the last years,the cascading impacts and risks associated with such events have received great attention as economic losses and consequences have mounted in their *** concerns about these ripple effects are rising,strategies to prevent and manage indirect risks are in urgent ***,such effects are currently barely considered in most countries and can seriously threaten global agendas such as achieving the Sustainable Development Goals by 2030 or the targets set out in the Sendai Framework for Disaster Risk Reduction *** discuss how the concept of risk-layering,which,though already applied in disaster risk management,could be expanded to include indirect *** point out some of the benefits,limitations,and ways forward for using this *** do so,we first delineate the transition of the risk-layering concept,which originated from the insurance industry,from its original use to its application in a wider *** bring special focus to the application of risk-layering in disaster risk management and identify strategies that allow for the inclusion of indirect *** main suggestion is that,while a probabilistic approach is appropriate for evaluating direct risks,a focus on connectedness is appropriate for indirect risks,which still allows for an easy link to direct ***,so we argue,facilitates more comprehensive risk management systems apt to deal with the multi-dimensional challenges ahead.

关键词： Connectedness Indirect risks Natural hazards and disasters Risk-layering Risk management

Analysis of the Caratheodory's Theorem on Dynamical System Trajectories Under Numerical Uncertainty

在线全文

学校读者我要写书评

暂无评论

IEEE/CAA Journal of Automatica Sinica 2018年第4期5卷 787-793页

作者： Pavel Osinenko Grigory Devadze stefan Streif Automatic Control and System Dynamics Laboratory Technische Universitat Chemnitz09107 ChemnitzGermany IEEE

The current work proposes a new and constructive proof for the Caratheodory's theorem on existence and uniqueness of trajectories of dynamical systems. The key concern is the numerical uncertainty, i.e., the discrepancy between mathematical proofs, algorithms, and their implementations, which may affect the correct functioning of a control system. Due to growing demands on security and compliance with specifications,correctness of the control system functioning is becoming ever more important. Since in both dynamical systems and many control design approaches, one of the central notions is the system trajectory, it is important to address existence and uniqueness of system trajectories in a way which incorporates numerical uncertainty. Constructive analysis is a particular approach to formalizing numerical uncertainty and is used as the basis of the current work. The major difficulties of guaranteeing existence and uniqueness of system trajectories arise in the case of systems and controllers which possess discontinuities in time,since classical solutions to initial value problems do not *** issue is addressed in Caratheodory's theorem. A particular constructive variant of the theorem is proven which covers a large class of problems found in practice.

关键词： Constructive analysis Caratheodory’s theorem dynamical systems