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VARIATIONAL DISCRETIZATION OF A CONTROL-CONSTRAINED PARABOLIC BANG-BANG OPTIMAL CONTROL PROBLEM

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Journal of Computational Mathematics 2020年第1期38卷 14-40页

作者： nikolaus von Daniels Michael Hinze Schwerpunkt Optimierung und Approximation Universitat HamburgBundesstrase 5520146 HamburgGermany

We consider a control-constrained parabolic optimal control problem without Tikhonov term in the tracking *** the numerical treatment,we use variational discretization of its Tikhonov regularization:For the state and the adjoint equation,we apply Petrov-Galerkin schemes in time and usual conforming finite elements in *** prove a-priori estimates for the error between the discretized regularized problem and the limit *** these estimates are not robust if the regularization parameter tends to zero,we establish robust estimates,which--depending on the problem's regularity——enhance the previous *** the special case of bang-bang solutions,these estimates are further improved.A numerical example confirms our analytical findings.

关键词： Optimal control Heat equation Control constraints Finite elements A-priori error estimates Bang-bang controls

Sediment generation and soil mound denudation in areas of high-density tree throw along a river valley in the Jura Mountains, Switzerland

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Journal of Mountain Science 2021年第2期18卷 377-391页

作者： Philip GREENWOOD Jan BAUER nikolaus J KUHN Physical Geography&Environmental Change Research Group Department of Environmental SciencesUniversity of BaselKlingelbergstrasse 27Basel-4056Switzerland

A preliminary field-based investigation was undertaken in a small(<10 km^(2))river valley located in the mountainous Jura region of northwest *** aims of the work were to assess sediment generation and annual sediment transport rates by tree throw on forested hillslopes,and to document surface hydrology characteristics on four fresh soil mounds associated with recent tree throws over a 24-day monitoring *** the soil mounds,average sediment recovery ranged from 7.7-28.2 g(dry weight),equivalent to a suspended sediment concentration of 145.2-327.8 g L^(-1),and runoff coefficients ranged from 1.0%-4.2%.Based on a soil bulk density value of 1,044 kg m^(-3),upslope runoff generation areas were denuded by an average 0.14 mm by the end of the 24-day monitoring period,representing an erosion rate equivalent to 2.1 mm yr^(-1).A ca.50 cm high soil mound could therefore feasibly persist for around 200-250 *** tree throw work,the dimensions of 215 individual tree throws were measured and their locations mapped in 12 separate locations along the river valley representing a cumulative area equivalent to 5.3 ha(***,43 per ha).Tree throws generated a total of 20.1 m^(3) of fine-sediment(<2 mm diameter),or the equivalent of 3.8×10^(-4) m^(3) m^(-2).The process of tree throw was originally attributed to two extreme weather events that occurred in west and central Europe in late December *** the 18-year period since both storms,this represents an annual sediment transport rate of 2.7×10^(-5) m^(3) m^(-1) yr^(-1).Exploring the relationship with wind on fall direction,65.5%of tree throws(143)generally fell in a downslope direction irrespective of hillslope aspect on which they were *** infers that individual storms may not have been responsible for the majority of tree throws,but instead,could be associated with root *** the high density of tree throws and their relative maturity(average age 41 years),we hypothesise that once tr

关键词： Tree throw Hillslope processes Sediment generation mechanism Sediment transport rate Soil mound Ibach river valley

Adaptive progressive download based on the MPEG-4 file format

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2006年第Z1期7卷 106-111页

作者： FRBER nikolaus DHLA Stefan ISSING Jochen Multimedia Transport Dept.Audio Fraunhofer Institute for Integrated Circuits IISErlangen 91058Germany

In this paper we describe how progressive download and adaptive streaming can be combined into a simple and efficient streaming framework. Based on the MPEG-4 file format (MP4) we use HTTP for transport and argue that these two components are sufficient for specifying an open streaming architecture. The client selects appropriate chunks from the MP4 file to be transferred based on (1) the header information (i.e. the 'moov' box) in the first part of the file and (2) his observation of network throughput. The framework is completely client driven which allows for better server scalability and reduces signalling overhead. We discuss architecture and implementation issues such as complexity, interoperability and scalability and compare to 3GPP PSS Re1-6 adaptive streaming when appropriate. Measurements from a simple MP4/HTTP streaming client are presented showing that appropriate chunks are selected such that increased reliability is achieved.

关键词： HTTP-streaming Adaptive progressive download MPEG-4 file format (MP4) Moov box

Smoothed particle hydrodynamics:Methodology development and recent achievement

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Journal of Hydrodynamics 2022年第5期34卷 767-805页

作者： Chi Zhang Yu-jie Zhu Dong Wu nikolaus A.Adams Xiangyu Hu TUM School of Engineering and Design Technical University of MunichMunichGermany Xi’an Research Institute of High Technology Xi’an 710025China

Since its inception,the full Lagrangian meshless smoothed particle hydrodynamics(SPH)has experienced a tremendous enhancement in methodology and impacted a range of multi-physics applications in science and *** review presents a concise survey on latest developments and achievements of the SPH method,including:(1)Brief review of theory and fundamental with kernel corrections,(2)The Riemann-based SPH method with dissipation limiting and high-order data reconstruction by using MUSCL,WENO and MOOD schemes,(3)Particle neighbor searching with particle sorting and efficient dual-criteria time stepping schemes,(4)Total Lagrangian formulation with stablized,dynamics relaxation and hourglass control schemes,(5)Fluid-structure interaction scheme with interface treatments and multi-resolution discretizations,(6)Novel applications of particle relaxation in SPH methodology for mesh and particle *** but not least,benchmark tests for validating computational accuracy,convergence,robustness and efficiency are also supplied accordingly.

关键词： Smoothed particle hydrodynamics(SPH) Riemann-based SPH update and total Lagrangian formulations fluid-structure interaction mesh and particle generation

Synergistic optimization framework for the process synthesis and design of biorefineries

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Frontiers of Chemical Science and Engineering 2022年第2期16卷 251-273页

作者： nikolaus IVollmer Resul Al Krist V.Gernaey Gürkan Sin Process and Systems Engineering(PROSYS)Research Center Department of Chemical and Biochemical EngineeringTechnical University of Denmark2800 Kgs.LyngbyDenmark Novo Nordisk A/S 2880 BagsværdDenmark

The conceptual process design of novel bioprocesses in biorefinery setups is an important task,which remains yet challenging due to several *** propose a novel framework incorporating superstructure optimization and simulation-based optimization *** this context,several approaches for superstructure optimization based on different surrogate models can be *** means of a case study,the framework is introduced and validated,and the different superstructure optimization approaches are *** results indicate that even though surrogate-based optimization approaches alleviate the underlying computational issues,there remains a potential issue regarding their *** development of appropriate surrogate models,comprising the selection of surrogate type,sampling type,and size for training and cross-validation sets,are essential *** this aspect,satisfactory validation metrics do not ensure a successful outcome from its embedded use in an optimization ***,the framework’s synergistic effects by sequentially performing superstructure optimization to determine candidate process topologies and simulationbased optimization to consolidate the process design under uncertainty offer an alternative and promising *** findings invite for a critical assessment of surrogatebased optimization approaches and point out the necessity of benchmarking to ensure consistency and quality of optimized solutions.

关键词： biotechnology surrogate modelling superstructure optimization simulation-based optimization process design

Modifier-concept of colorectal carcinogenesis: Lipidomics as a technical tool in pathway analysis

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World Journal of Gastroenterology 2010年第15期16卷 1820-1827页

作者： nikolaus Gassler Christina Klaus Elke Kaemmerer Andrea Reinartz Institute of Pathology RWTH Aachen University Department of Pediatrics RWTH Aachen University School of Biology Parker H. Petit Institute for Bioengineering and Bioscience Georgia Institute of Technology

In the modifier concept of intestinal carcinogenesis, lipids have been established as important variables and one focus is given to long-chain fatty acids. Increased consumption of long-chain fatty acids is in discussion to modify the development of colorectal carcinoma in humans. Saturated long-chain fatty acids, in particular, are assumed to promote carcinogenesis, whereas poly-unsaturated forms are likely to act in the opposite way. At present, the molecular mechanisms behind these effects are not well understood. Recently, it has been demonstrated by lipidomics and associated molecular techniques, that activation and metabolic channeling of long-chain fatty acids are important mechanisms to modify colorectal carcinogenesis. In this Editorial, an overview about the present concept of long-chain fatty acids and its derivatives in colorectal carcinogenesis as well as technical algorithms in lipid analysis is given.

关键词： Colorectal neoplasms Carcinogenesis Long-chain fatty acids Acyl-CoA Lipidomics

Interventional strategies in infected necrotizing pancreatitis:Indications,timing,and outcomes

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World Journal of Gastroenterology 2022年第27期28卷 3383-3397页

作者： Birte Purschke Louisa Bolm Max nikolaus Meyer Hiroki Sato Department of Gastrointestinal Surgery Massachusetts General HospitalBostonMA 02114United States Department of Radiation Oncology Massachusetts General HospitalBostonMA 02114United States Department of Medicine Asahikawa Medical UniversityAsahikawa 0788510HokkaidoJapan Department of Gastroenterology Asahikawa Kosei HospitalAsahikawa 0788211HokkaidoJapan

Acute pancreatitis(AP)is one of the most common gastrointestinal diseases and remains a life-threatening *** AP resolves to restitutio ad integrum in approximately 80%of patients,it can progress to necrotizing pancreatitis(NP).NP is associated with superinfection in a third of patients,leading to an increase in mortality rate of up to 40%.Accurate and early diagnosis of NP and associated complications,as well as state-of-the-art therapy are essential to improve patient *** emerging role of endoscopy and recent trials on multidisciplinary management of NP established the“step-up approach”.This approach starts with endoscopic interventions and can be escalated to other interventional and ultimately surgical procedures if *** showed that this approach decreases the incidence of new multiple-organ failure as well as the risk of interventional ***,the optimal interventional sequence and timing of interventional procedures remain *** review aims to summarize the indications,timing,and treatment outcomes for infected NP and to provide guidance on multidisciplinary decision-making.

关键词： Pancreatitis Acute necrotizing pancreatitis Necrosis Superinfection Endoscopy Surgery

Social interactivity in pigeon courtship behavior

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Current Zoology 2017年第1期63卷 85-95页

作者： Emma L.R. WARE Daniel R. SAUNDERS nikolaus F, TROJE Department of Psychology Queen's University Kingston Ontario K7L 3N6 Canada Centre for Neuroscience Studies Queen's University Kingston Ontario K7L 3N6 Canada Wellesley Institute Toronto Ontario M4V 3B Canada Centre for Brain/Mind Sciences University of Trento Trento Italy Department of Biology Queen's University Kingston K7L 3N6 Canada

A closed-loop teleprompter system was used to isolate and manipulate social interactivity in thenatural courtship interactions of pigeons Columbia livia. In Experiment 1, a live face-to-face real-time interaction between 2 courting pigeons （Live） was compared to a played back version of thevideo stimulus recorded during the pairs Live interaction. We found that pigeons were behavinginteractively; their behavior depended on the relationships between their own signals and those oftheir partner. In Experiment 2, we tested whether social interactivity relies on spatial cues presentin the facing direction of a partner＇s display. By moving the teleprompter camera 90~ away from itsoriginal location, the partner＇s display was manipulated to appear as if it is directed 90~ away fromthe subject. We found no effect of spatial offset on the pigeon＇s behavioral response. In Experiment3, 3 time delays, 1 s, 3s, and 9s, a Live condition, and a playback condition were chosen to investi-gate the importance of temporal contiguity in social interactivity. Furthermore, both opposite-sex（courtship） and same-sex （rivalry） pairs were studied to investigate whether social-context affectssocial interactivity sensitivity. Our results showed that pigeon courtship behavior is sensitive totemporal contiguity. Behavior declined in the 9 s and Playback conditions as compared to Live con-dition and the shorter time delays. For males only, courtship behavior also increased in the 3-sdelay condition. The effect of social interactivity and time delay was not observed in rivalry inter-actions, suggesting that social interactivity may be specific to courtship.

关键词： courtship behavior, pigeons, social interactivity, spatial offset, time delay, video playback.

Intestinal acyl-CoA synthetase 5: Activation of long chain fatty acids and behind

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World Journal of Gastroenterology 2013年第42期19卷 7369-7373页

作者： Christina Klaus Min Kyung Jeon Elke Kaemmerer nikolaus Gassler Institute of Pathology RWTH Aachen University52074 AachenGermany

The intestinal mucosa is characterized by a high complexity in terms of structure and functions and allows for a controlled demarcation towards the gut *** the one hand it is responsible for pulping and selective absorption of alimentary substances ensuring the immunological tolerance,on the other hand it prevents the penetration of micro-organisms as well as bacterial *** continuous regeneration of surface epithelia along the crypt-villus-axis in the small intestine is crucial to assuring these various *** core phenomena of intestinal epithelia regeneration comprise cell proliferation,migration,differentiation,and *** partly contrarily oriented processes are molecularly balanced through numerous interacting signaling pathways like Wnt/β-catenin,Notch and Hedgehog,and regulated by various modifying *** of these modifiers is acyl-CoA synthetase 5(ACSL5).It plays a key role in de novo lipid synthesis,fatty acid degradation and membrane modifications,and regulates several intestinal processes,primarily through different variants of protein lipidation,e.g.,***5 was shown to interact with proapoptotic molecules,and besides seems to inhibit proliferation along the *** of its proapoptotic and antiproliferative characteristics it could be of significant relevance for intestinal homeostasis,cellular disorder and tumor development.

关键词： Acyl-CoA synthetase Apoptosis Carcinogenesis Colorectal cancer Intestinal homeostasis