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Electrically pumped metallic and plasmonic nanolasers

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Chinese Physics B 2018年第11期27卷 158-166页

作者： martin T Hill School of Electrical Electronic and Computer Engineering The University of Western Australia

In recent years, there have been a significant number of demonstrations of small metallic and plasmonic lasers. The vast majority of these demonstrations have been for optically pumped devices. Electrically pumped devices are advantageous for applications and could demonstrate concepts not amenable for optical pumping. However, there have been relatively few demonstrations of electrically pumped small metal cavity lasers. This lack of results is due to the following reasons： there are limited types of electrically pumped gain media available; there is a significantly greater level of complexity required in the fabrication of electrically pumped devices; finally, the required components for electrical pumping restrict cavity design options and furthermore make it intrinsically more difficult to achieve lasing. This review looks at the motivation for electrically pumped nanolasers, the key issues that need addressing for them to be realized, the results that have been achieved so far including devices where lasing has not been achieved, and potential new directions that could be pursued.

关键词： semiconductor lasers laser diode microcavity and microdisk laser integrated optics

Lattice-Boltzmann simulations for analysing the detachment of micron-sized spherical particles from surfaces with large-scale roughness structures

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Particuology 2022年第2期20卷 47-59页

作者： Yan Cui martin Sommerfeld School of Mechanical Science and Engineering Huazhong University of Science and TechnologyWuhan 430074HubeiChina Multiphase Flow Systems Institute of Process EngineeringOtto-von-Guericke-University MagdeburgHoher Weg 7bD-06120 Halle(Saale)Germany

Fully resolved numerical simulations of a micron-sized spherical particle residing on a surface with large-scale roughness are performed by using the Lattice-Boltzmann *** aim is to investigate the influence of surface roughness on the detachment of fine drug particles from larger carrier particles for transporting fine drug particles in a DPI(dry powder inhaler).Often the carrier surface is modified by mechanical treatments for modifying the surface roughness in order to reduce the adhesion force of drug ***,drug particle removal from the carrier surface is equivalent to the detachment of a sphere from a rough plane *** a sphere with a diameter of 5μm at a particle Reynolds number of 1.0,3.5 and 10 are *** surface roughness is described as regularly spaced semi-cylindrical asperities(with the axes oriented normal to the flow direction)on a smooth *** influence of asperity distance and size ratio(*** radius of the semi-cylinder to the particle radius,Rc/Rd)on particle adhesion and detachment are *** asperity distance is varied in the range 1.2

关键词： Lattice-Boltzmann method Fully-resolved simulations Particle detachment Surface roughness Semi-cylindrical asperities Particle detachment model

Turbulence model performance for ventilation components pressure losses

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Building Simulation 2022年第3期15卷 389-399页

作者： Karsten Tawackolian martin Kriegel Hermann-Rietschel-Institut EnergyComfort&Health in BuildingsTU BerlinGermany

This study looks to find a suitable turbulence model for calculating pressure losses of ventilation *** building ventilation,the most relevant Reynolds number range is between 3×10^(4) and 6×10^(5),depending on the duct dimensions and airflow *** loss coefficients can increase considerably for some components at Reynolds numbers below 2×10^(5).An initial survey of popular turbulence models was conducted for a selected test case of a bend with such a strong Reynolds number *** of the turbulence models failed in reproducing this dependence and predicted curve progressions that were too flat and only applicable for higher Reynolds *** effects near walls played an important role in the present *** turbulence modelling,near-wall damping functions are used to account for this influence.A model that implements near-wall modelling is the lag elliptic blending k-ε*** model gave reasonable predictions for pressure loss coefficients at lower Reynolds *** example is the low Reynolds number k-εturbulence model of Wilcox(LRN).The modification uses damping functions and was initially developed for simulating profiles such as aircraft *** has not been widely used for internal flows such as air duct *** on selected reference cases,the three closure coefficients of the LRN model were adapted in this work to simulate ventilation *** predictions were obtained with new coefficients(LRNM model).This underlined that low Reynolds number effects are relevant in ventilation ductworks and give first insights for suitable turbulence models for this *** the lag elliptic blending model and the modified LRNM model predicted the pressure losses relatively well for the test case where the other tested models failed.

关键词： HVAC ductwork CFD simulation turbulence model model calibration

Invariant observer design of attitude and heading reference system

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Control Theory and Technology 2019年第3期17卷 228-240页

作者： martin BARCZYK Department of Mechanical Engineering University of Alberta Edmonton AB T6G 1H9 Canada

An attitude and heading reference system (AHRS) is a nonlinear state estimator unit for computing orientation in 3D space. This paper designs an AH RS using three approaches: an in variant observer, an invaria nt exte nded Kalman filter (IEKF), and a conventional extended Kalman filter (EKF). The three designs are validated in experiment versus a ground truth, dem on strati ng the practical interest of the invariant observer methodology and the advantage of the IEKF over the EKF under model uncertainty.

关键词： Inertial navigation state estimation Kalman filters nonlinear dynamical systems covariance matrices

A Survey of the L1 Scheme in the Discretisation of Time-Fractional Problems

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Numerical Mathematics(Theory,Methods and Applications) 2022年第4期15卷 1173-1192页

作者： martin Stynes Applied and Computational Mathematics Division Beijing Computational Science Research CenterBeijing 100193China

A survey is given of convergence results that have been proved when the L1 scheme is used to approximate the Caputo time derivative D_(t)^(α)(where 0<α<1)in initial-boundary value problems governed by D_(t)^(α)u−△u=f and similar equations,while taking into account the weak singularity that is present in typical solutions of such *** aspects of these analyses are outlined,such as global and local convergence bounds and the techniques used to derive them,fast implementation of the L1 scheme,semilinear problems,multi-term time derivatives,α-robustness,a posteriori error analysis,and two modified L1 schemes that achieve better *** fifty references are provided in the bibliography,more than half of which are from the period 2019-2022.

关键词： L1 scheme fractional derivative survey

Local symmetries of finite type hypersurfaces in C^2 Dedicated to Professor Sheng GONG on the occasion of his 75th birthday

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Science China Mathematics 2006年第11期49卷 1633-1641页

作者： KOL■ martin Depart. of Mathematical Analysis Masaryk University Janackovo Nam. 2A662 95 BrnoCzech Republic

The first part of this paper gives a complete description of local automorphism groups for Levi degenerate hypersurfaces of finite type in C2. It is also proved that, with the exception of hypersurfaces of the form v = |z|k, local automorphisms are always determined by their 1-jets. Using this result, the second part describes special normal forms which by an additional normalization eliminate the nonlinear symmetries of the model and allows to decide effectively about local equivalence of two hypersurfaces given in this normal form.

关键词： normal form finite type hypersurfaces local equivalence problem finite jet determination stability group.

Almost nonnegative curvature operator and cohomology rings

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Frontiers of Mathematics in China 2016年第5期11卷 1259-1274页

作者： martin HERRMANN Fakultat fur Mathematik Karlsruher Institut fur Technologie Kaiserstraβe 89-93 76133 Karlsruhe Germany

We give a survey of results on the construction of and obstructions to metrics of almost nonnegative curvature operator on closed manifolds and results on the cohomology rings of closed, simply-connected manifolds with a lower curvature and upper diameter bound. The latter is motivated by a question of Grove whether these condition imply finiteness of rational homotopy types. This question has answers by F. Fang-X. Rong, B. Totaro and recently A. Dessai and the present author.

关键词： Nonnegative curvature homogeneous spaces curvature operator almost nonnegative curvature

Binary operations for homotopy groups with coefficients

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Science China Mathematics 2018年第9期61卷 1543-1552页

作者： martin Arkowitz Department of Mathematics Dartmouth College

We define and study binary operations for homotopy groups with coefficients, and give conditions to prove that certain binary operations are the homomorphic image of the generalized Whitehead product. This allows carrying over properties of the generalized Whitehead product to these operations. We discuss two classes of binary operations, i.e., the Whitehead products and the torsion products. We also introduce a new class of operations called Ext operations and determine some of its properties. Then we compare the torsion product with the Whitehead product in a special case, and prove that the smash product of two Moore spaces has the homotopy type of a wedge of two Moore spaces.

关键词： homotopy groups with coefficients binary operations the generalized Whitehead product Whitehead products torsion products

Applicability of high-temperature cooling systems in different European countries from the view of the condensation risk

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Building Simulation 2021年第5期14卷 1453-1466页

作者： Vladimir Zmrhal martin Bartak Czech Technical University in Prague Faculty of Mechanical EngineeringDepartment of Environmental Engineering Technicka 416000 Prague 6Czech Republic

Due to the different approaches in determining the ventilation airflow rate per person for workspaces,where high-temperature air conditioning systems are used for air conditioning,problems with the condensation of water vapour on the cold surfaces of the system can *** article analyses the risk of condensation in various European cities using the available climatic *** with cooling ceilings and cooling beams with a ventilation device operating in parallel are taken into *** ventilation airflow rates per person were *** the example of a room equipped with high-temperature cooling,an energy simulation calculation is performed,which includes a ventilation and air-conditioning system with the possibility of capacity *** is clear from the results that the condensation of water vapour can be prevented by technical measures at the cost of reducing the cooling capacity,which can affect the achievement of the thermal comfort of those *** the end,suitable solutions are discussed,which should already be adopted at the time the device is designed so that the risk of condensation is not a major obstacle in the operation of these energy-efficient *** irreplaceable role in the operation of high-temperature cooling systems is played by a measurement and control system with a suitable algorithm to prevent condensation.

关键词： ventilation air-conditioning cooled ceilings chilled beams low energy cooling risk of condensation