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Calculation of ship motions in steep waves with restoring and Froude-Krylov forces on an adaptive panel mesh with Gauss and analytic integration methods

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Journal of Hydrodynamics 2024年第2期36卷 275-289页

作者： Malwin Wermbter Moustafa Abdel-Maksoud Institute for Fluid Dynamics and Ship Theory Hamburg University of TechnologyHamburgGermany

The impulse response method is a frequently used method to calculate ship seakeeping *** this paper,the restoring and Froude-Krylov calculation is conducted with constant evaluation of panel pressures as well as Gauss quadrature and an analytical *** applied panel grid is coarsened by an adaptive algorithm which is based on a normal vector *** comparison of methods is based on grid convergence studies which are followed by a verification of forces with computational fluid dynamics(CFD)results on the fixed duisburg test case in *** with experimental results in head,oblique and following waves show that all integration methods are *** exact integration is numerically sensitive in some *** quadrature is highly accurate;however,the additional effort is not beneficial since the geometrical accuracy has-stronger influence on the force amplitudes than the integration *** grid coarsening reduces the simulation time and is accurate up to a level,where the panel length comes close the *** added resistance at the investigated Froude number of 0.05 shows higher uncertainty levels,this applies to the results of both the numerical methods and model tests.

关键词： Ship hydrodynamics seakeeping impulse response method added resistance wave loads

Antigen presentation,autoantibody production,and therapeutic targets in autoimmune liver disease

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Cellular & Molecular Immunology 2021年第1期18卷 92-111页

作者： Andrea Kristina Horst Kingsley Gideon Kumashie Katrin Neumann Linda Diehl Gisa Tiegs Institute of Experimental Immunology and Hepatology University Medical Center Hamburg-EppendorfMartinistraBe 52D-20251 HamburgGermany hamburg Center for Translational Immunology University Medical Center Hamburg-EppendorfMartinistraBe 52D-20251 HamburgGermany

The liver is an important immunological organ that controls systemic *** liver harbors professional and unconventional antigen-presenting cells that are crucial for tolerance induction and *** the immune response in homeostasis depends on a healthy and well-toned immunological liver microenvironment,which Is maintained by the crosstalk of liver-resident antigen-presenting cells and intrahepatic and liver-infiltrating *** response to pathogens or autoantigens,tolerance is disrupted by unknown *** parenchymal and nonparenchymal cells exhibit unique antigen-presenting *** presentation of microbial and endogenous lipid-,metabolite-and peptide-derived antigens from the gut via conventional and nonconventional mechanisms can educate intrahepatic immune cells and elicit effector responses or *** of this balance results in autoimmune liver diseases,such as autoimmune hepatitis,primary biliary cholangitis,and primary sclerosing *** the exact etiologies of these autoimmune liver diseases are unknown,it is thought that the disruption of tolerance towards self-antigens and microbial metabolites and lipids,as well as alterations in bile acid composition,may result in changes in effector cell activation and polarization and may reduce or impair protective antiinflammatory regulatory T and B cell ***,the canonical and noncanonical transmission of antigens and antigen:MHC complexes via trogocytosis or extracellular vesicles between different(non)immune cells in the liver may play a role in the induction of hepatic inflammation and ***,we summarize emerging aspects of antigen presentation,autoantibody production,and the application of novel therapeutic approaches in the characterization and treatment of autoimmune liver diseases.

关键词： liver tolerance autoimmune liver disease antigen presentating cell

Advances on numerical and experimental investigation of ship roll damping

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Journal of Hydrodynamics 2023年第3期35卷 431-448页

作者： Patrick Sumislawski Moustafa Abdel-Maksoud Institute for Fluid Dynamics and Ship Theory Hamburg University of Technology (TUHH) Hamburg Germany

This paper presents recent developments towards efficient and reliable methods for roll damping estimation based on numerical simulations as well as model tests using the harmonic excited roll motion(HERM)technique.A newly designed automatic roll damping estimation procedure shows the advantage of a just-in-time post processing of experimental measurement ***-time analysis of the measured roll damping values permits a considerable shortening of the test ***,a large number of investigations can be carried out with relatively manageable effort in order to determine the roll damping behavior of different keel configurations or at operating conditions,e.g.,different sized keels or Froude *** addition,HERM measurement method is applied to investigate the memory *** this purpose,different excitation schemes are introduced and the results are ***,a study of the scale effect on the roll damping properties is conducted,in which experimental and numerical investigations are performed for two scales of a ship ***,a method is developed that significantly reduces the effort of Reynolds average Navier-Stokes(RANS)-based simulations of roll *** reduction of simulation time is achieved by introducing an artificial *** obtained results show that the developed method is very well applicable for numerical as well as in experimental *** the model tests using HERM technique,the model is free and the rudder is used to keep the straight-ahead *** analysis of the numerical and experimental results shows that the influence of the rudder induced force and moment during HERM tests is not negligible and the contribution of the rudder must be taken into account by estimating the roll ***,a new concept is developed to investigate the parametric roll behavior of ships,which allows neglecting the consideration of the complex modelling of free surface waves in the *** the RAN

关键词： Roll damping harmonic excited roll motion rudder HERM experimental fluid dynamics(EFD) CFD

Local Entropy Production in Turbulent Shear Flows:A Tool for Evaluating Heat Transfer Performance

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Journal of Thermal Science 2006年第2期15卷 159-167页

作者： H. HERWIG F. KOCK hamburg university of Technology 21073 hamburg Germany. BMW 80788 Munich Germany

Performance evaluation of heat transfer devices can be based on the overall entropy production in these devices. In our study we therefore provide equations for the systematic and detailed determination of local entropy production due to dissipation of mechanical energy and due to heat conduction, both in turbulent flows. After turbulence modeling has been incorporated for the fluctuating parts the overall entropy production can be determined by integration with respect to the whole flow domain. Since, however, entropy production rates show very steep gradients close to the wall, numerical solutions are far more effective with wall functions for the entropy production terms. These wall functions are mandatory when high Reynolds number turbulence models are used. For turbulent flow in a pipe with an inserted twisted tape as heat transfer promoter it is shown that based on the overall entropy production rate a clear statement from a thermodynamic point of view is possible. For a certain range of twist strength there is a decrease in overall entropy production compared to the case without insert. Also, the optimum twist strength can be determined. This information is unavailable when only pressure drop and heat transfer data are given.

关键词： entropy production turbulent heat transfer wall functions

Haemorrhage after thrombectomy with adjuvant thrombolysis in unknown onset stroke depends on high early lesion water uptake

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Stroke & Vascular Neurology 2024年第4期9卷 390-398页

作者： Gabriel Broocks Lukas Meyer Uta Hanning Tobias Djamsched Faizy Matthias Bechstein Helge Kniep Noel Van Horn Gerhard Schön Ewgenia Barow Götz Thomalla Jens Fiehler Andre Kemmling Department of Diagnostic and Interventional Neuroradiology University Medical Center Hamburg-EppendorfHamburgGermany Department of Medical Biometry and Epidemiology University Medical Center Hamburg EppendorfHamburgGermany Department of Neurology University Medical Center Hamburg-EppendorfHamburgGermany Department of Neuroradiology University MarburgMarburgGermany

Background and purpose In wake-up stroke,CT-based quantitative net water uptake(NWU)might serve as an alternative tool to MRI to guide intravenous thrombolysis with alteplase(IVT).An important complication after IVT is symptomatic intracerebral haemorrhage(sICH).As NWU directly implies ischaemic lesion progression,reflecting blood-brain barrier injury,we hypothesised that NWU predicts sICH in patients who had a ischaemic stroke undergoing thrombectomy with unknown *** Consecutive analysis of all patients who had unknown onset anterior circulation ischaemic stroke who underwent CT at baseline and endovascular treatment between December 2016 and October *** NWU was assessed on baseline *** primary endpoint was *** association of NWU and other baseline parameters to sICH was investigated using inverse-probability weighting(IPW)*** A total of 88 patients were included,of which 46 patients(52.3%)received *** median NWU was 10.7%(IQR:5.1–17.7).The proportion of patients with any haemorrhage and sICH were 35.2%and 13.6%.NWU at baseline was significantly higher in patients with sICH(19.1%vs 9.6%,p<0.0001)and the median Alberta Stroke Program Early CT Score(ASPECTS)was lower(5 vs 8,p<0.0001).Following IPW,there was no association between IVT and sICH in unadjusted ***,after adjusting for ASPECTS and NWU,there was a significant association between IVT administration and sICH(14.6%,95%CI:3.3%to 25.6%,p<0.01).Conclusion In patients with ischaemic stroke with unknown onset,the combination of high NWU with IVT is directly linked to higher rates of *** ASPECTS for evaluating the extent of the early infarct lesion,quantitative NWU could be used as an imaging biomarker to assess the degree of blood-brain barrier damage in order to predict the risk of sICH in patients with wake up stroke.

关键词： throm thrombolysis high

PE/CaCO_3-nanocomposites synthesized by in-situ polymerization

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Journal of Zhejiang university-Science A(Applied Physics & Engineering) 2007年第7期8卷 987-990页

作者： SCHARLACH Katrin KAMINSKY Walter Department of Chemistry University of Hamburg Bundesstr. 45 Hamburg 20146 Germany

Polyethylene-nanocomposites with CaCO3-weight fractions from 0 to 15 wt.% were prepared by in-situ polymerization with Me2Si（Ind）2ZrC12/MAO metallocene catalysts. A high activity especially in the presence of TIBA was observed. The morphology was investigated by using raster electron microscopy （REM） showing that the CaCO3-nanoparticles are uniformly distributed. The melting temperatures and the crystallization temperatures are not much influenced by increasing filler content.

关键词： Nanocomposites CaCO3 Polyethylene Metallocene catalysts

Virtual reality for immersive multi-user firefighter-training scenarios

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Virtual Reality & Intelligent Hardware 2022年第5期4卷 406-417页

作者： Philipp BRAUN Michaela GRAFELMANN Felix GILL Hauke STOLZ Johannes HINCKELDEYN Ann-Kathrin LANGE hamburg university of Technology Hamburg 21073Germany

Background Virtual reality(VR)applications can be used to provide comprehensive training scenarios that are difficult or impossible to represent in physical *** includes team training for emergency services such as *** a high level of immersion is essential for achieving effective virtual *** this respect,motion-capture systems offer the possibility of creating highly immersive multi-user training experiences,including full-body *** This study presents a preliminary prototype that helps extin-guish a virtual fire on a container ship as a VR training *** prototype provides a full-body and multi-user VR experience based on the synthesis of position data provided by the motion-capture system and orientation data from the VR ***,the prototype facilitates an initial evaluation of the *** The results confirm the value of using VR for training procedures that are difficult to implement in the real ***,the results show that motion-capture-based VR technologies are particularly useful for firefighting training,in which participants can collaborate in difficult-to-access ***,this study also indicates that increasing the immersion in such training remains a *** This study presents a prototypical VR application that enables the multi-user training of maritime *** research should evaluate the initial results,provide more extensive training scenarios,and measure the training progress.

关键词： Virtual reality Multi-user Motion capture Training Firefighting

Thermal degradation and hydrolysis depolymerization of printing ink components for plastic packaging in recycling processes: a review

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Frontiers of Environmental Science & Engineering 2024年第10期18卷 139-153页

作者： Jinyang Guo Cong Luo Zhi Kai Chong Ayah Alassali Kerstin Kuchta Circular Resource Engineering and Management(CREM) Hamburg University of Technology(TUHH)21079 HamburgGermany

This review covers the decomposition mechanisms of various printing ink binder resins,with a particular focus on their behavior under extrusion conditions in the mechanical recycling process of polyolefin(PO)based plastic *** degradation and hydrolysis of the nitrocellulose(NC)-the most used binder for flexographic surface printing on single-layer flexible plastic packaging,occur concurrently during the mechanical recycling process under 160-210℃.For other printing ink binders,polyurethane(PU)noticeable degradation takes place between 200 and 300℃,mostly above 250℃.However,with the involvement of humidity,degradation by hydrolysis can start from 150℃.A similar effect is also discovered with the cellulose acetate(CA)derivatives,which are thermally stable until 300℃ and can be hydrolyzed at 100℃.The thermal stability of polyvinyl butyral(PVB)is not influenced by humidity,with thermal stability ranging from 170 to 260℃,depending on different ***(UV)-cured acrylics are thermaliy stable until 400℃.The hydrolysis degradation can take place at room ***,this review covers the thermal stability of different colorants used for printing ink application and elaborates on several thermal-stable alternatives of some common *** study further reviews how the binder resin affects the quality of recyclates,revealing it to be not only induced by the degradation of the binder resin but also by the immiscibility between the plastic and binder *** advanced recycling processes,mainly selective dissolution-precipitation and pyrolysis,the presence of binder resin and its degradation products could stll affect the quality of the *** review accentuates the imperative need for in-depth research to unravel the impact of printing ink constituents on the quality of recycled products.

关键词： Plastic recycling Flexible packaging Polymer degradation Green chemistry

Learning synergies based in-hand manipulation with reward shaping

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CAAI Transactions on Intelligence Technology 2020年第3期5卷 141-149页

作者： Zhen Deng Jian Wei Zhang TAMS Group InformaticsUniversity of HamburgHamburg D-22527Germany

In-hand manipulation is a fundamental ability for multi-fingered robotic hands that interact with their *** to the high dimensionality of robotic hands and intermittent contact dynamics,effectively programming a robotic hand for in-hand manipulations is still a challenging *** address this challenge,this work employs deep reinforcement learning(DRL)algorithm to learn in-hand manipulations for multi-fingered robotic hands.A reward-shaping method is proposed to assist the learning of in-hand *** synergy of robotic hand postures is analysed to build a low-dimensional hand posture *** additional rewards are designed based on both the analysis of hand synergies and its learning *** two additional rewards cooperating with an extrinsic reward are used to assist the in-hand manipulation *** value functions are trained jointly with respect to their reward *** they cooperate to optimise a control policy for in-hand *** reward shaping not only improves the exploration efficiency of the DRL algorithm but also provides a way to incorporate domain *** performance of the proposed learning method is evaluated with object rotation *** results demonstrated that the proposed learning method enables multi-fingered robotic hands to learn in-hand manipulation effectively.

关键词： manipulation policy jointly