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Surgical management of peritonitis secondary to acute superior mesenteric artery occlusion

World journal of Gastroenterology 2014年第29期20卷 9936-9941页

作者： stefan Acosta Vascular Centre Malm?Sk?ne University Hospital

Diagnosis of acute arterial mesenteric ischemia in the early stages is now possible using modern computed tomography with intravenous contrast enhancement and imaging in the arterial and/or portal *** patients have acute superior mesenteric artery(SMA)occlusion,and a large proportion of these patients will develop peritonitis prior to mesenteric revascularization,and explorative laparotomy will therefore be necessary to evaluate the extent and severity of intestinal ischemia,and to perform bowel *** establishment of a hybrid operating room in vascular units in hospitals is most important to be able to perform successful intestinal *** review outlines current frontline surgical strategies to improve survival and minimize bowel morbidity in patients with peritonitis secondary to acute SMA *** laparotomy needs to be performed *** treatment is based upon intestinal revascularization followed by bowel *** no vascular imaging has been carried out,SMA angiography is *** case of embolic occlusion of the SMA,open embolectomy is performed followed by *** case of thrombotic occlusion,the occlusive lesion can be recanalized retrograde from an exposed SMA,the guidewire snared from either the femoral or brachial artery,and stented with standard devices from these access *** resections and sometimes gall bladder removal due to transmural infarctions are performed at initial laparotomy,leaving definitive bowel reconstructions to a planned second look laparotomy,according to the principles of damage control *** with peritonitis secondary to acute SMA occlusion should be managed by both the general and vascular surgeon,and a hybrid revascularization approach is of utmost importance to improve outcomes.

关键词： Acute mesenteric ischemia Peritonitis Explorative laparotomy Endovascular treatment Hybrid revascularization Superior mesenteric artery occlusion

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Photovoltaic yield prediction using an irradiance forecast model based on multiple neural networks

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journal of Modern Power Systems and Clean Energy 2018年第2期6卷 255-267页

作者： Saad Parvaiz DURRANI stefan BALLUFF Lukas WURZER stefan KRAUTER Paderborn University Bosch Thermotechnik GmbH

In order to develop predictive control algorithms for efficient energy management and monitoring for residential grid connected photovoltaic systems, accurate and reliable photovoltaic(PV) power forecasts are required.A PV yield prediction system is presented based on an irradiance forecast model and a PV model. The PV power forecast is obtained from the irradiance forecast using the PV model. The proposed irradiance forecast model is based on multiple feed-forward neural networks. The global horizontal irradiance forecast has a mean absolute percentage error of 3.4% on a sunny day and 23% on a cloudy day for Stuttgart. PV power forecasts based on the neural network irradiance forecast have performed much better than the PV power persistence forecast model.

关键词： Grid connected photovoltaic(GCPV) Photovoltaic(PV) PV power prediction Irradiance forecast Neural network(NN)

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Galerkin Spectral Method Applied to the Chemical Master Equation

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Communications in Computational Physics 2009年第5期5卷 871-896页

作者： stefan Engblom Department of Information Technology Uppsala UniversityP.O.Box 337SE-75105 UppsalaSweden

Stochastic well-stirred chemically reacting systems can be accurately modeled by a continuous-time *** corresponding master equation evolves the system’s probability density function in time but can only rarely be explicitly *** investigate a numerical solution strategy in the form of a spectral method with an inherent natural adaptivity and a very favorable choice of basis *** results related to convergence have been developed previously and are briefly summarized while implementation issues,including how to adapt the basis functions to follow the solution they represent,are covered in more detail *** method is first applied to a model problem where the convergence can easily be *** we take on two more realistic systems from molecular biology where stochastic descriptions are often necessary to explain experimental *** conclusion is that,for sufficient accuracy demands and not too high dimensionality,the method indeed provides an alternative to other methods.

关键词： Master equation spectral-Galerkin method high dimensional problem moving basis chemical reactions

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Role of Omicron variant of SARS-CoV-2 in children in Germany

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World journal of Pediatrics 2022年第4期18卷 283-284页

作者： stefan Bittmann Department of Pediatrics Medical and Finance Center EpePed Mind Institute(PMI)Hindenburgring 448599 GronauGermany

A new variant of SARS-CoV-2,B.1.1.529 was first reported by the South African Department of Health on Nov 24,*** new variant was named as B.1.1.529 Omicron and was classified as a variant of concern(VOC)by the World Health Organization(WHO)on Nov 26,2021[1-13],Phylogenetic studies showed that Omicron arose independently of the currently dominant delta *** has an unusually high number of approximately 30 changes of amino acids in the spike protein compared with the original SARS-CoV-2,including those with known phenotypic impact(increase in transmission,immune evasion,and transmissibility),but significances of many mutations are still unclear[4-7].

关键词： Omi Phylogenetic children

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Modeling of aggregation kernels for fluidized beds using discrete particle model simulations

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Particuology 2014年第2期12卷 134-144页

作者： Nageswara Rao Narni Mirko Peglow Gerald Warnecke jitendra Kumar stefan Heinriche j.A.M.Kuipers Department of Mathematics Rajiv Gandhi University of Knowledge TechnologiesGachibowliHyderabad 500032India Institute for Process Engineering Otto-von-Guericke-University MagdeburgUniversitatsplatz 2D-39106 MagdeburgGermany Institute for Analysis and Numerics Otto-von-Guericke-University MagdeburgUniversitatsplatz 2D-39106 MagdeburgGermany Department of Mathematics ⅡT KharagpurIndia Institute of Solids Process Engineering and Particle TechnologyHamburg University of TechnologyHamburgGermany Eindhoven University of Technology-SMR P.O.Box 5135600 MB EindhovenThe Netherlands

Aggregation is one of the many important processes in chemical and process engineering. Several researchers have attempted to understand this complex process in fluidized beds using the macro-model of population balance equations （PBEs）. The aggregation kernel is an effective parameter in PBEs, and is defined as the product of the aggregation efficiency and collision frequency functions. Attempts to derive this kernel have taken different approaches, including theoretical, experimental, and empirical techniques. The present paper calculates the aggregation kernel using micro-model computer simulations, i.e., a discrete particle model. We simulate the micro-model without aggregation for various initial conditions, and observe that the collision frequency function is in good agreement with the shear kernel. We then simulate the micro-model with aggregation and calculate the aggregation efficiency rate.

关键词： Aggregation kernelsMulti-phase flowCollision frequency functionAggregation efficiency rateBed parameter

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MP-PIC simulation of circulating fluidized beds using an EMMS based drag model for Geldart B particles

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Particuology 2021年第6期19卷 76-90页

作者： Timo Dymala Tom Wytrwat stefan Heinrich Hamburg University of Technology Institute of Solids Process Engineering and Particle TechnologyDenickestr.1521073 HamburgGermany

In this study the multiphase particle-in-cell(MP-PIC)method is used for the simulation of two pilot-scale circulating fluidized beds(CFBs)with quartz sand belonging to Geldart’s group B as bed *** simulations were performed using a homogeneous drag model as well as a structure dependent drag model based on the energy minimization multi-scale method(EMMS).The results are compared with experimental data from literature as well as *** simulations with the EMMS based drag model show a good agreement of the time-averaged axial solids concentration,circulation rate and riser pressure ***,a lower grid sensitivity is observed compared to the homogeneous drag *** contrast to the conventional drag model a dense bottom zone is predicted by the EMMS based drag *** overprediction of the solid concentration in the dense bottom zone is presumably due to an overprediction of the cluster diameter that is calculated using an empirical cluster diameter *** shows the necessity for a new meso-scale cluster correlation for the simulation of Geldart B ***,the results of the time-averaged radial solids concentration differ from the expectations of a core-annulus flow indicating that a mesh refinement at the walls is ***,the importance of using a realistic particle size distribution is identified.

关键词： 3D-CFD simulation Circulating fluidized bed(CFB) Multiphase particle-in-cell method(MP-PIC) Energy minimizing multi-scale theory(EMMS) Validation study

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Influence of water evaporation on elastohydrodynamic lubrication with water-containing polyalkylene glycols

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Friction 2024年第10期12卷 2370-2388页

作者： stefan HOFMANN Thomas LOHNER Karsten STAHL Technical University of Munich School of Engineering and DesignDepartment of Mechanical EngineeringGear Research Center(FZG)Boltzmannstraße 1585748 Garching near MunichGermany

The reduction of frictional power losses in power transmitting gears takes a crucial role in the design of energy-and resource-efficient ***-containing lubricants like glycerol and polyalkylene glycols have shown great potential in achieving friction within the superlubricity regime with coefficients of friction lower than 0.01 under elastohydrodynamic ***,a bio-based production of the base stocks can lead to the development of green ***,one challenge associated with the application of water-containing lubricants to gearboxes is the evaporation of water and its impact on the lubricant *** this study,the influence of water evaporation on elastohydrodynamic friction and film thickness was investigated for three water-containing polyalkylene *** nominal water contents of 20 wt%and 40 wt%and two viscosities were *** results show that the friction increases continuously with higher evaporated water content,while the overall friction level remains low in nearly water-free states.A similar trend is observed for film thickness,where the strong increase in viscosity results in a notable increase in film ***,the sensitivity of friction and film thickness to water evaporation is low for small amounts of evaporated *** allows generous thresholds for permissible variations in water content.

关键词： friction superlubricity aqueous lubrication elastohydrodynamic lubrication(EHL) evaporation polyalkylene glycol

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A Design Concept and Kinematic Model for a Soft Aquatic Robot with Complex Bio-mimicking Motion

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journal of Bionic Engineering 2022年第1期19卷 16-28页

作者： Shokoofeh Abbaszadeh Roberto Leidhold stefan Hoerner Institute of Electrical Power Systems Department of Electrical Engineering and Information TechnologyOtto-Von-Guericke University of MagdeburgUniversitätsplatz 239106MagdeburgGermany Institute of Fluid Dynamics and Thermodynamics Department of Process and Systems EngineeringOtto-Von-Guericke University of MagdeburgUniversitätsplatz 239106MagdeburgGermany

Fish mortality assessments for turbine passages are currently performed by live-animal testing with up to a hundred thousand fish per year in Germany.A propelled sensor device could act as a fish *** this context,the study presented here investigates the state of the art via a thorough literature review on propulsion systems for aquatic *** evaluation of propulsion performance,weight,size and complexity of the motion achievable allows for the selection of an optimal concept for such a fish mimicking device carrying the *** the second step,the design of a bioinspired soft robotic fish driven by an unconventional drive system is *** is based on piezoceramic actuators,which allow for motion with five degrees of freedom(DOF)and the creation of complex bio-mimicking body motions.A kinematic model for the motion’s characteristics is developed,to achieve accurate position feedback with the use of strain *** measurements validate the complex deformation of the body and deliver the basis for the calibration of the kinematic ***,it can be shown,that the calibrated model presented allows the tracking of the deformation of the entire body with an accuracy of 0.1 mm.

关键词： Unconventional drive system Biologically inspired robots Biomimetics Flexible robots

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Supercritical angle Raman microscopy: a surfacesensitive nanoscale technique without field enhancement

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Light(Science & Applications) 2017年第1期6卷 482-489页

作者： Diana Serrano stefan Seeger Department of Chemistry University of ZurichWintherthurerstrasse 190CH-8057 ZurichSwitzerland

Raman scattering microscopy is a versatile tool for label-free imaging and molecular fingerprint ***,we provide the first demonstration that the selective collection of scattered signals exceeding the critical angle for total internal reflection enables surface-confined spontaneous Raman investigations at nanometre *** high-axial selectivity leads to improved signal-to-background ratios,thus making this technique an excellent probe for surface-related molecular *** richness of the spectroscopic information obtained through the supercritical angle Raman(SAR)collection path was proven by comparing its output with that of a parallel far-field collection ***,we demonstrated that the proposed SAR technique is a versatile microscopy approach that can be used alone or in combination with amplified Raman modalities such as surfaceenhanced resonance Raman scattering.

关键词： near-field optics Raman scattering supercritical microscopy surface science

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Exploring Content Popularity in Information-Centric Networks

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China Communications 2015年第7期12卷 13-22页

作者： Andriana Ioannou stefan Weber School of Computer Science and Statistics Trinity College

Information-Centric Networking(ICN), an alternative architecture to the current Internet infrastructure, focuses on the distribution and retrieval of content by employing caches in a network to reduce network traffic. The employment of caches may be accomplished using graph-based and content-based criteria such as the position of a node in a network and content popularity. The contribution of this paper lies on the characterization of content popularity for on-path in-network caching. To this end, four dynamic approaches for identifying content popularity are evaluated via simulations. Content popularity may be determined per chunk or per object, calculated by the number of requests for a content against the sum of requests or the maximum number of requests. Based on the results, chunk-based approaches provide 23% more accurate content popularity calculations than object-based approaches. In addition, approaches that are based on the comparison of a content against the maximum number of requests have been shown to be more accurate than the alternatives.

关键词： network distributed architectures future internet information-centric networks caching technologies on-path caching content popularity

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