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Iterative Subregion Correction Preconditioners with Adaptive Tolerance for Problems with Geometrically Localized Stiffness

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Communications on Applied Mathematics and Computation 2024年第2期6卷 811-836页

作者： Michael Franco per-olof persson Will Pazner Department of Mathematics University of CaliforniaBerkeleyBerkeleyCA 94720-3840USA Fariborz Maseeh Department of Mathematics and Statistics Portland State UniversityPortlandOR 97201USA

We present a class of preconditioners for the linear systems resulting from a finite element or discontinuous Galerkin discretizations of advection-dominated *** preconditioners are designed to treat the case of geometrically localized stiffness,where the convergence rates of iterative methods are degraded in a localized subregion of the *** convergence may be caused by a number of factors,including the mesh size,anisotropy,highly variable coefficients,and more challenging *** approach taken in this work is to correct well-known preconditioners such as the block Jacobi and the block incomplete LU(ILU)with an adaptive inner subregion *** goal of these preconditioners is to reduce the number of costly global iterations by accelerating the convergence in the stiff region by iterating on the less expensive reduced *** tolerance for the inner iteration is adaptively chosen to minimize subregion-local work while guaranteeing global convergence *** present analysis showing that the convergence of these preconditioners,even when combined with an adaptively selected tolerance,is independent of discretization parameters(e.g.,the mesh size and diffusion coefficient)in the *** demonstrate significant performance improvements over black-box preconditioners when applied to several model convection-diffusion ***,we present performance results of several variations of iterative subregion correction preconditioners applied to the Reynolds number 2.25×10^(6)fluid flow over the NACA 0012 airfoil,as well as massively separated flow at 30°angle of attack.

关键词： Subregion correction Nested Krylov Geometrically localized stiffness

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Why People Live in Flood-Prone Areas in Akuressa, Sri Lanka

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International Journal of Disaster Risk Science 2018年第2期9卷 143-156页

作者： Johan Askman olof Nilsson per Becker Division of Risk Management and Societal Safety Lund University

To investigate why people live in areas at high risk of floods, a qualitative case study was carried out in the areas around Akuressa, in southwest Sri Lanka. Data collection consisted mainly of semistructured interviews with local residents and government officials. The purpose was to study why people live in areas at high risk of floods, by looking beyond the purely physical aspects of living with hazards and exploring the underlying social factors. Four main factors were identified: an overall good living situation; a sense of place; difficulties relocating; and being well-adapted to the situation. The analysis also examined whether government officials shared the views of local residents. The findings highlighted both areas of consensus and discrepancies related to risk awareness, and the efficiency of risk reduction measures that had been implemented by the government. The case study identified and explored underlying social factors, such as risk normalization, risk trade-offs, and push-and-pull processes, which seem to influence the decision to live in a high-risk area.

关键词： Flood risk Risk awareness Risk perception Sri Lanka

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Constrained optimal steady-state control for isolated traffic intersections

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Control Theory and Technology 2014年第1期12卷 84-94页

作者： Jack HADDAD David MAHALEL Ilya IOSLOVICH per-olof GUTMAN Technion Sustainable Mobility and Robust Transportation (T-SMART) Laboratory Technion - Israel Institute of Technology Haifa 32000 Israel

The steady-state or cyclic control problem for a simplified isolated traffic intersection is considered. The optimization problem for the green-red switching sequence is formulated with the help of a discrete-event max-plus model. Two steady-state control problems are formulated： optimal steady-state with green duration constraints, and optimal steady-state control with lost time. In the case when the criterion is a strictly increasing, linear function of the queue lengths, the steady-state control problems can be solved analytically. The structure of constrained optimal steady-state traffic control is revealed, and the effect of the lost time on the optimal solution is illustrated.

关键词： Steady-state control Discrete-event models Isolated traffic intersections

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Colorless-to-colorful switching of electrochromic MXene by reversible ion insertion

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Nano Research 2022年第4期15卷 3587-3593页

作者： Jianxia Jiang Leiqiang Qin Joseph Halim per O.Å.persson Lintao Hou Johanna Rosen Guangzhou Key Laboratory of Vacuum Coating Technologies and New Energy Materials Physics DepartmentJinan UniversityGuangzhou 510632China Department of Physics Chemistry and Biology(IFM)Linköping UniversityLinköping SE-58183Sweden

Electrochromic(EC)materials that change color with voltage have been widely studied for use in dynamic ***,colorless-to-colorful switching with high contrast ratio is generically unattainable,especially for colorless-to-black electrochromic materials with an ultrahigh contrast ratio over the entire visible *** this work,we developed Nb_(1.33)C MXene-based dynamic windows with colorless-to-black switching of up to 75%reversible change in transmittance from 300 to 1,500 *** exploring the electrochromic effects of different electrolytes through in situ optical changes and electrochemical quartz crystal microbalance(EQCM),it is found that electrochromic behavior is greatly influenced by the extent of reversible Li^(+)insertion/deinsertion between the two-dimensional Nb_(1.33)C MXene *** addition,a colorless-to-black EC device based on Nb_(1.33)C with an overall integrated contrast ratio over 80%was successfully constructed by a solution-processable spin coating *** work enables a simple route to fabricate MXene-based high-performance electrochromic smart windows,which is important for further expanding the application of MXenes to optoelectronic and photonic applications.

关键词： MXenes electrochromic materials colorless-to-black switching high contrast ratio reversible Li^(+)insertion

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Fluorescence of Single Conjugated Chains of MEH-PPV Dispersed in Polymer Matrix: What Do We See in the Microscope?

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Chinese Journal of Chemistry 2023年第19期41卷 2536-2544页

作者： Mingyi Xie Marina V.Kuzimenkova per-olof Larsson Yuxi Tian Ivan G.Scheblykin Key Laboratory of Mesoscopic Chemistry of MOE School of Chemistry and Chemical EngineeringNanjing UniversityNanjingJiangsu210023 China Chemical Physics and NanoLund Lund UniversityPO Box 124SE-22100 LundSweden Pure and Applied Biochemistry Lund UniversityPO Box 124SE-22100 LundSweden

It has been a mystery that the detected fluorescence intensity of single MEH-PPV molecules is much lower than expected based on their chain *** this review,after re-evaluating of the literature data in the light of new specially designed experiments,we present a comprehensive explanation of this issue:The actual size of MEH-PPV molecules at single molecule level is much smaller than expected due to de-aggregation and chain scission,while static quenching("dark matter")also exists for large molecules,further reducing their brightness.

关键词： MEH-PPV Single molecule spectroscopy Brightness Fluorescence Molecular weight anrohonci

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MXene-based symmetric supercapacitors with high voltage and high energy density

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Materials Reports(Energy) 2022年第1期2卷 105-111页

作者： Wei Zheng Joseph Halim per O.Å.persson Johanna Rosen Michel W.Barsoum Department of Physics Chemistry and Biology(IFM)Linkoping University58183LinkopingSweden Department of Materials Science and Engineering Drexel University19104PhiladelphiaPAUSA

MXene-based aqueous symmetric supercapacitors(SSCs)are attractive due to their good rate performances and green ***,it remains a challenge to reach voltages much over 1.2 V,which significantly diminishes their energy ***,we report on Mo_(1.33)CTz MXene-based SSCs possessing high voltages in a 19.5 M LiCl *** from the vacancy-rich structure and high stable potential window of Mo_(1.33)CTz,the obtained SSCs deliver a maximum energy density of>38.2 mWh cm^(-3) at a power density of 196.6 mW cm^(-3) under an operating voltage of 1.4 V,along with excellent rate performance and impressive cycling *** highly concentrated LiCl electrolyte is also applicable to Ti_(3)C_(2)Tz,the most widely studied MXene,achieving a maximum energy density of>41.3 mWh cm^(-3) at a power density of 165.2 mW cm^(-3) with an operating voltage of 1.8 *** drop in energy density with increasing power in the Ti_(3)C_(2)Tz cells was steeper than for the Mo-based *** work provides a roadmap to develop superior SSCs with high voltages and high energy densities.

关键词： MXene Symmetric supercapacitor High voltage High energy density Highly concentrated electrolyte

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Direct generation of linearly polarized photon emission with designated orientations from site-controlled InGaN quantum dots

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Light(Science & Applications) 2014年第1期3卷 323-329页

作者： Anders Lundskog Chih-Wei Hsu K Fredrik Karlsson Supaluck Amloy Daniel Nilsson Urban Forsberg per olof Holtz Erik Janzen Department of Physics Chemistry and Biology(IFM) Linkoping UniversitySE-58183 LinkopingSweden Department of Physics Faculty of ScienceThaksin UniversityPhattalung 93110Thailand

Semiconductor quantum dots(QDs)have been demonstrated viable for efficient light emission applications,in particular for the emission of single photons on ***,the preparation of QDs emitting photons with predefined and deterministic polarization vectors has proven *** to linearly polarized photons is essential for various *** this report,a novel concept to directly generate linearly-polarized photons is *** concept is based on InGaN QDs grown on top of elongated GaN hexagonal pyramids,by which the predefined elongation determines the polarization vectors of the emitted photons from the *** growth scheme should allow fabrication of ultracompact arrays of photon emitters,with a controlled polarization direction for each individual emitter.

关键词： GaN InGaN photoluminescence polarized emission quantum dot

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WARA-PS:a research arena for public safety demonstrations and autonomous collaborative rescue robotics experimentation

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Autonomous Intelligent Systems 2021年第1期1卷 104-134页

作者： Olov Andersson Patrick Doherty Mårten Lager Jens-olof Lindh Linnea persson Elin A.Topp Jesper Tordenlid Bo Wahlberg Department of Computer and Information Science Linköping UniversityLinköpingSweden Saab Kockums MalmöSweden Division of Decision and Control Systems School of Electrical Engineering and Computer ScienceKTH Royal Institute of TechnologyStockholmSweden Department of Computer Science Lund UniversityLundSweden Saab Combitech AB LinköpingSweden Division of Automatic Control Department of Electrical EngineeringLinköping UniversityLinköpingSweden

A research arena(WARA-PS)for sensing,data fusion,user interaction,planning and control of collaborative autonomous aerial and surface vehicles in public safety applications is *** objective is to demonstrate scientific discoveries and to generate new directions for future research on autonomous systems for societal *** enabler is a computational infrastructure with a core system architecture for industrial and academic *** includes a control and command system together with a framework for planning and executing tasks for unmanned surface vehicles and aerial *** motivating application for the demonstration is marine search and rescue operations.A state-of-art delegation framework for the mission planning together with three specific applications is also *** first one concerns model predictive control for cooperative rendezvous of autonomous unmanned aerial and surface *** second project is about learning to make safe real-time decisions under uncertainty for autonomous vehicles,and the third one is on robust terrain-aided navigation through sensor fusion and virtual reality tele-operation to support a GPS-free positioning system in marine *** research results have been experimentally evaluated and demonstrated to industry and public sector audiences at a marine test *** would be most difficult to do experiments on this large scale without the WARA-PS research ***,these demonstrator activities have resulted in effective research dissemination with high public visibility,business impact and new research collaborations between academia and industry.

关键词： Autonomous systems Intelligent system architectures Research demonstration arena Autonomous drones Autonomous marine vessels Public safety and security Collaborative robotics

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Disentanglement of a Singlet Spin State in a Coincidence Stern-Gerlach Device

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Journal of Modern Physics 2019年第10期10卷 1247-1254页

作者： per-olof Westlund Hå kan Wennerstrô m Department of Chemistry Theoretical Chemistry Ume&aring University Ume&aring Sweden Department of Physical Chemistry Lund University Lund Sweden

We analyze the spin coincidence experiment considered by Bell in the derivation of Bells theorem. We solve the equation of motion for the spin system with a spin Hamiltonian, Hz, where the magnetic field is only in the z-direction. For the specific case of the coincidence experiment where the two magnets have the same orientation the Hamiltonian Hz commutes with the total spin Iz, which thus emerges as a constant of the motion. Bells argument is then that an observation of spin up at one magnet A necessarily implies spin down at the other B. For an isolated spin system A-B with classical translational degrees of freedom and an initial spin singlet state there is no force on the spin particles A and B. The spins are fully entangled but none of the spin particles A or B are deflected by the Stern-Gerlach magnets. This result is not compatible with Bells assumption that spin 1/2 particles are deected in a Stern-Gerlach device. Assuming a more realistic Hamiltonian Hz + Hx including a gradient in x direction the total Iz is not conserved and fully entanglement is not expected in this case. The conclusion is that Bells theorem is not applicable to spin coincidence measurement originally discussed by Bell.

关键词： Bells Theorem Disentanglement Stern-Gerlach Coincident Measurement Singlet Spin State

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The Future of Science Centres

The Future of Science Centres

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中国自然科学博物馆协会二十五周年暨国际学术报告会

作者： per-Edvin persson Finnish Science Centre

＜正＞There are more than 1500 science centres in the world, and the field is still growing. Science centres complement formal education systems and are components of life-long learning. From an exclusive hands-on approach in their exhibitions, science centres are broadening their approach to include use of different media. The field is focussing on a minds-on approach. The broadening of media includes historical artefacts, multimedia and models in the exhibition halls, as well as public programmes that include lectures, workshops, panel discussions and thematic events throughout the entire museum. Currently, the web is used for operational purposes, as a complement to the exhibitions and to web cast events that occur in the centre. There will be an increasing integration between the physical and the virtual world. The exhibitions of science centres may change over time, but for a long time to come the science museum will remain a meeting place and a place to visit. The science centre visit is a social event and it includes interaction with the real world, which cannot be achieved on the web.

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