TY - JOUR AU - Al-Lami, Abbas J.S. AU - Kenig, Eugeny Y. ID - 51122 JF - Case Studies in Thermal Engineering KW - Fluid Flow and Transfer Processes KW - Engineering (miscellaneous) SN - 2214-157X TI - New pressure drop and heat transfer correlations for turbulent forced convection in internally channeled tube heat exchanger ducts ER - TY - JOUR AB - The production of hydrogen and the utilization of biomass for sustainable concepts of energy conversion and storage require gas sensors that discriminate between hydrogen (H2) and carbon monoxide (CO). Mesoporous copper–ceria (Cu–CeO2) materials with large specific surface areas and uniform porosity are prepared by nanocasting, and their textural properties are characterized by N2 physisorption, powder XRD, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The oxidation states of copper (Cu+, Cu2+) and cerium (Ce3+, Ce4+) are investigated by XPS. The materials are used as resistive gas sensors for H2 and CO. The sensors show a stronger response to CO than to H2 and low cross-sensitivity to humidity. Copper turns out to be a necessary component; copper-free ceria materials prepared by the same method show only poor sensing performance. By measuring both gases (CO and H2) simultaneously, it is shown that this behavior can be utilized for selective sensing of CO in the presence of H2. AU - Baier, Dominik AU - Priamushko, Tatiana AU - Weinberger, Christian AU - Kleitz, Freddy AU - Tiemann, Michael ID - 43457 IS - 4 JF - ACS Sensors KW - Fluid Flow and Transfer Processes KW - Process Chemistry and Technology KW - Instrumentation KW - Bioengineering SN - 2379-3694 TI - Selective Discrimination between CO and H2 with Copper–Ceria-Resistive Gas Sensors VL - 8 ER - TY - JOUR AB - In this study, quasi-unidirectional continuous fiber reinforced thermoplastics (CFRTs) are joined with metal sheets via cold formed cylindrical, elliptical and polygonal pin structures which are directly pressed into the CFRT component after local infrared heating. In comparison to already available studies, the unique novelty is the use of non-rotational symmetric pin structures for the CFRT/metal hybrid joining. Thus, a variation in the fiber orientation in the CFRT component as well as a variation in the non-rotational symmetric pins’ orientation in relation to the sample orientation is conducted. The created samples are consequently mechanically tested via single lap shear experiments in a quasi-static state. Finally, the failure behavior of the single lap shear samples is investigated with the help of microscopic images and detailed photographs. In the single lap shear tests, it could be shown that non-rotational symmetric pin structures lead to an increase in maximum testing forces of up to 74% when compared to cylindrical pins. However, when normalized to the pin foot print related joint strength, only one polygonal pin variation showed increased joint strength in comparison to cylindrical pin structures. The investigation of the failure behavior showed two distinct failure modes. The first failure mode was failure of the CFRT component due to an exceedance of the maximum bearing strength of the pin-hole leading to significant damage in the CFRT component. The second failure mode was pin-deflection due to the applied testing load and a subsequent pin extraction from the CFRT component resulting in significantly less visible damage in the CFRT component. Generally, CFRT failure is more likely with a fiber orientation of 0° in relation to the load direction while pin extraction typically occurs with a fiber orientation of 90°. It is assumed that for future investigations, pin structures with an undercutting shape that creates an interlocking joint could counteract the tendency for pin-extraction and consequently lead to increased maximum joint strengths. AU - Popp, Julian AU - Römisch, David AU - Merklein, Marion AU - Drummer, Dietmar ID - 34223 IS - 10 JF - Applied Sciences KW - Fluid Flow and Transfer Processes KW - Computer Science Applications KW - Process Chemistry and Technology KW - General Engineering KW - Instrumentation KW - General Materials Science SN - 2076-3417 TI - Joining of CFRT/Steel Hybrid Parts via Direct Pressing of Cold Formed Non-Rotational Symmetric Pin Structures VL - 12 ER - TY - CONF AB - The spinning process is a flexible incremental forming process for the manufacturing of axially-symmetric sheet metal or tubular components with functionally graded properties. It is characterized by the utilization of universal tooling geometries and quite low forming forces. The process has a high potential to reduce material waste, to extend the forming limits and to achieve more complex geometries as well as favorable part properties [1]. Current research work at the Chair of Forming Technology (LUF) is focused on innovative flow-turning processes that have a high potential for producing flat components with excellent geometrical and mechanical properties while keeping process times short [2]. In combination with process-integrated local heat treatment, the new spinning process is predestined for the efficient forming of ultra-high-strength steel or tailored materials. Due to the desired field of food industry only food-safe materials such as special stainless steels are being investigated. This paper presents an innovative machine layout as well as an adequate process design for the production of high-performance circular knives with optimized mechanical hardness. In this context, particular attention is paid to various areas of temperature control as well as process-related challenges during the process. AU - Engemann, David AU - Homberg, Werner ID - 30292 KW - Cutting blades KW - Flow-forming KW - Incremental forming KW - Hot Forming KW - High strength steels TI - Hot Spinning of Cutting Blades for Food Industry ER - TY - JOUR AB - Crack growth in structures depends on the cyclic loads applied on it, such as mechanical, thermal and contact, as well as residual stresses, etc. To provide an accurate simulation of crack growth in structures, it is of high importance to integrate all kinds of loading situations in the simulations. Adapcrack3D is a simulation program that can accurately predict the propagation of cracks in real structures. However, until now, this three-dimensional program has only considered mechanical loads and static thermal loads. Therefore, the features of Adapcrack3D have been extended by including contact loading in crack growth simulations. The numerical simulation of crack propagation with Adapcrack3D is generally carried out using FE models of structures provided by the user. For simulating models with contact loading situations, Adapcrack3D has been updated to work with FE models containing multiple parts and necessary features such as coupling and surface interactions. Because Adapcrack3D uses the submodel technique for fracture mechanical evaluations, the architecture of the submodel is also modified to simulate models with contact definitions between the crack surfaces. This paper discusses the newly implemented attribute of the program with the help of illustrative examples. The results confirm that the contact simulation in Adapcrack3D is a major step in improving the functionality of the program. AU - Joy, Tintu David AU - Weiß, Deborah AU - Schramm, Britta AU - Kullmer, Gunter ID - 34224 IS - 15 JF - Applied Sciences KW - Fluid Flow and Transfer Processes KW - Computer Science Applications KW - Process Chemistry and Technology KW - General Engineering KW - Instrumentation KW - General Materials Science SN - 2076-3417 TI - Further Development of 3D Crack Growth Simulation Program to Include Contact Loading Situations VL - 12 ER - TY - JOUR AU - Ahmadov, A. I. AU - Nagiyev, Sh. M. AU - Aydin, C. AU - Tarverdiyeva, V. A. AU - Orujova, M. Sh. AU - Badalov, S. V. ID - 44041 IS - 9 JF - The European Physical Journal Plus KW - General Physics and Astronomy KW - Fluid Flow and Transfer Processes SN - 2190-5444 TI - Bound state solutions of Dirac equation: spin and pseudo-spin symmetry in the presence of the combined Manning–Rosen and Yukawa tensor potentials VL - 137 ER - TY - JOUR AB - Requirement changes and cascading effects of change propagation are major sources of inefficiencies in product development and increase the risk of project failure. Proactive change management of requirement changes yields the potential to handle such changes efficiently. A systematic approach is required for proactive change management to assess and reduce the risk of a requirement change with appropriate effort in industrial application. Within the paper at hand, a novel method for Proactive Management of Requirement Changes (ProMaRC) is presented. It is developed in close collaboration with industry experts and evaluated based on workshops, pilot users’ feedback, three industrial case studies from the automotive industry and five development projects from research. To limit the application effort, an automated approach for dependency analysis based on the machine learning technique BERT and semi-automated assessment of change likelihood and impact using a modified PageRank algorithm is developed. Applying the method, the risks of requirement changes are assessed systematically and reduced by means of proactive change measures. Evaluation shows high performance of dependency analysis and confirms the applicability and usefulness of the method. This contribution opens up the research space of proactive risk management for requirement changes which is currently almost unexploited. It enables more efficient product development. AU - Gräßler, Iris AU - Oleff, Christian AU - Preuß, Daniel ID - 30213 IS - 4 JF - Applied Sciences KW - Fluid Flow and Transfer Processes KW - Computer Science Applications KW - Process Chemistry and Technology KW - General Engineering KW - Instrumentation KW - General Materials Science SN - 2076-3417 TI - Proactive Management of Requirement Changes in the Development of Complex Technical Systems VL - 12 ER - TY - CONF AB - Datacenter applications have different resource requirements from network and developing flow scheduling heuristics for every workload is practically infeasible. In this paper, we show that deep reinforcement learning (RL) can be used to efficiently learn flow scheduling policies for different workloads without manual feature engineering. Specifically, we present LFS, which learns to optimize a high-level performance objective, e.g., maximize the number of flow admissions while meeting the deadlines. The LFS scheduler is trained through deep RL to learn a scheduling policy on continuous online flow arrivals. The evaluation results show that the trained LFS scheduler admits 1.05x more flows than the greedy flow scheduling heuristics under varying network load. AU - Hasnain, Asif AU - Karl, Holger ID - 20125 KW - Flow scheduling KW - Deadlines KW - Reinforcement learning T2 - 2021 IEEE 18th Annual Consumer Communications & Networking Conference (CCNC) TI - Learning Flow Scheduling ER - TY - JOUR AU - Wortmann, Martin AU - Viertel, Klaus AU - Welle, Alexander AU - Keil, Waldemar AU - Frese, Natalie AU - Hachmann, Wiebke AU - Krieger, Philipp AU - Brikmann, Johannes AU - Schmidt, Claudia AU - Moritzer, Elmar AU - Hüsgen, Bruno ID - 35327 JF - International Journal of Heat and Mass Transfer KW - Fluid Flow and Transfer Processes KW - Mechanical Engineering KW - Condensed Matter Physics SN - 0017-9310 TI - Anomalous bulk diffusion of methylene diphenyl diisocyanate in silicone elastomer VL - 177 ER - TY - CONF AB - One of the main objectives of production engineering is to reproducibly manufacture (complex) defect-free parts. To achieve this, it is necessary to employ an appropriate process or tool design. While this will generally prove successful, it cannot, however, offset stochastic defects with local variations in material properties. Closed-loop process control represents a promising approach for a solution in this context. The state of the art involves using this approach to control geometric parameters such as a length. So far, no research or applications have been conducted with closed-loop control for microstructure and product properties. In the project on which this paper is based, the local martensite content of parts is to be adjusted in a highly precise and reproducible manner. The forming process employed is a special, property-controlled flow-forming process. A model-based controller is thus to generate corresponding correction values for the tool-path geometry and tool-path velocity on the basis of online martensite content measurements. For the controller model, it is planned to use a special process or microstructure (correlation) model. The planned paper not only describes the experimental setup but also presents results of initial experimental investigations for subsequent use in the closed-loop control of α’-martensite content during flow-forming. AU - Arian, Bahman AU - Homberg, Werner AU - Riepold, Markus AU - Trächtler, Ansgar AU - Rozo Vasquez, Julian AU - Walther, Frank ID - 23465 KW - Flow-forming KW - Spinning KW - Process Strategy KW - Martensite Content KW - Property Control KW - Micromagnetic Measurement KW - Metastable Austenitic Stainless Steel SN - 978-2-87019-302-0 TI - Forming of metastable austenitic stainless steel tubes with axially graded martensite content by flow-forming ER - TY - CONF AB - Even though the spectrum of parts is expected to shift over the long term as a result of increasing e-mobility, there is still an extremely high demand for complex components made of high-strength materials which can only be produced by hydroforming technologies. The innovative combination of hydroforming processes with other forming processes, as well as the improvement of the processes themselves, offers considerable potential for improvement. A number of promising ways of improving the hydroforming process chain are therefore the subject of this contribution. The focus of the article is on possible approaches for combining (incremental) pre- and post-forming operations, which can permit considerable improvements in both quality and features at a reduced cost. Furthermore, a novel combination of quasi-static and high-speed forming processes is presented, leading to an improved overall forming process (with a high application potential) for the production of complex parts. AU - Wiens, Eugen AU - Djakow, Eugen AU - Homberg, Werner ID - 21447 KW - Hydroforming KW - Incremental Forming KW - Internal Flow-turning KW - High-speed Forming T2 - Nebu/Nehy 2020 TI - Some ideas for the further development of hydroforming process chains ER - TY - CONF AB - Consider mitigating the effects of denial of service or of malicious traffic in networks by deleting edges. Edge deletion reduces the DoS or the number of the malicious flows, but it also inadvertently removes some of the desired flows. To model this important problem, we formulate two problems: (1) remove all the undesirable flows while minimizing the damage to the desirable ones and (2) balance removing the undesirable flows and not removing too many of the desirable flows. We prove these problems are equivalent to important theoretical problems, thereby being important not only practically but also theoretically, and very hard to approximate in a general network. We employ reductions to nonetheless approximate the problem and also provide a greedy approximation. When the network is a tree, the problems are still MAX SNP-hard, but we provide a greedy-based 2l-approximation algorithm, where l is the longest desirable flow. We also provide an algorithm, approximating the first and the second problem within {\$}{\$}2 {\backslash}sqrt{\{} 2{\backslash}left| E {\backslash}right| {\}}{\$}{\$}and {\$}{\$}2 {\backslash}sqrt{\{}2 ({\backslash}left| E {\backslash}right| + {\backslash}left| {\backslash}text {\{}undesirable flows{\}} {\backslash}right| ){\}}{\$}{\$}, respectively, where E is the set of the edges of the network. We also provide a fixed-parameter tractable (FPT) algorithm. Finally, if the tree has a root such that every flow in the tree flows on the path from the root to a leaf, we solve the problem exactly using dynamic programming. AU - Polevoy, Gleb AU - Trajanovski, Stojan AU - Grosso, Paola AU - de Laat, Cees ED - Kim, Donghyun ED - Uma, R. N. ED - Zelikovsky, Alexander ID - 17651 KW - flow KW - Red-Blue Set Cover KW - Positive-Negative Partial Set Cover KW - approximation KW - tree KW - MAX SNP-hard KW - root KW - leaf KW - dynamic programming KW - FPT SN - 978-3-030-04651-4 T2 - Combinatorial Optimization and Applications TI - Removing Undesirable Flows by Edge Deletion ER - TY - CONF AB - Ein wichtiges Element der Digitalen Transformation ist die Digitalisierung der Prozesse in Unternehmen. Eine Herausforderung besteht hierbei in der systematischen Erkennung von Digitalisierungspotenzialen in Prozessen. Bestehende Ansätze benötigen Experten, welche Potenziale über ihre Erfahrung oder zeitaufwendig mithilfe von Musterkatalogen identifizieren. In diesem Artikel werden verschiedene Digitalisierungspotenziale klassifiziert und Muster für ein zukünftiges musterbasiertes Analyseverfahren zur automatisierten Identifikation von Digitalisierungspotenzialen in BPMN-Diagrammen beschrieben. Im Vergleich zu bestehenden Ansätzen erlaubt es Experten die Identifizierung von Digitalisierungspotenzialen effizienter und effektiver durchzuführen. AU - Rittmeier, Florian AU - Engels, Gregor AU - Teetz, Alexander ID - 2332 KW - Digitalisierungspotenziale KW - BPI KW - Digitale Transformation KW - Information Flow-Modellierung KW - Patterns KW - Requirements Engineering T2 - Joint Proceedings of the Workshops at Modellierung 2018 co-located with Modellierung 2018, Braunschweig, Germany, February 21, 2018. TI - Digitalisierungspotenziale in Geschäftsprozessen effizient und effektiv erkennen (Effective and Efficient Identification of Digitalization Potentials in Business Processes) VL - 2060 ER - TY - JOUR AB - There are many hard conjectures in graph theory, like Tutte's 5-flow conjecture, and the 5-cycle double cover conjecture, which would be true in general if they would be true for cubic graphs. Since most of them are trivially true for 3-edge-colorable cubic graphs, cubic graphs which are not 3-edge-colorable, often called snarks, play a key role in this context. Here, we survey parameters measuring how far apart a non 3-edge-colorable graph is from being 3-edge-colorable. We study their interrelation and prove some new results. Besides getting new insight into the structure of snarks, we show that such measures give partial results with respect to these important conjectures. The paper closes with a list of open problems and conjectures. AU - Fiol, M. A. AU - Mazzuoccolo, Guiseppe AU - Steffen, Eckhard ID - 10129 IS - 4 JF - The Electronic Journal of Combinatorics KW - Cubic graph KW - Tait coloring KW - Snark KW - Boole coloring KW - Berge's conjecture KW - Tutte's 5-flow conjecture TI - Measures of Edge-Uncolorability of Cubic Graphs VL - 25 ER - TY - CONF AU - Polevoy, Gleb AU - Trajanovski, Stojan AU - Grosso, Paola AU - de Laat, Cees ID - 17652 KW - flow KW - filter KW - MMSA KW - set cover KW - approximation KW - local ratio algorithm SN - 978-3-319-71150-8 T2 - Combinatorial Optimization and Applications: 11th International Conference, COCOA 2017, Shanghai, China, December 16-18, 2017, Proceedings, Part I TI - Filtering Undesirable Flows in Networks ER - TY - JOUR AB - Banks face a 'behavioralization' of their balance sheets since deposit funding increasingly consists of non-maturing deposits with uncertain cash flows exposing banks to asset liability (ALM) risk. Thus, this study examines the behavior of banks’ retail customers regarding non-maturing deposits. Our unique sample comprises the contract and cash flow data for 2.2 million individual contracts from 1991 to 2010. We find that contractual rewards, i.e., qualified interest payments, and government subsidies, effectively stabilize saving behavior and thus bank funding. The probability of an early deposit withdrawal decreases by approximately 40%, and cash flow volatility drops by about 25%. Our findings provide important insights for banks using pricing incentives to steer desired saving patterns for their non-maturing deposit portfolios. Finally, these results are informative regarding the bank liquidity regulations (Basel III) concerning the stability of deposits and the minimum requirements for risk management (European Commission DIRECTIVE 2006/48/EC). AU - Schlueter, Tobias AU - Sievers, Sönke AU - Hartmann-Wendels, Thomas ID - 4873 JF - Journal of Banking & Finance (VHB-JOURQUAL 3 Ranking A) KW - retail saving behavior KW - non-maturing deposits KW - deposit funding KW - contractual rewards KW - interest rate bonus KW - saving persistence KW - cash flow volatility TI - Bank funding stability, pricing strategies and the guidance of depositors VL - 51 ER - TY - JOUR AB - In this paper, we define and study a new problem, referred to as the Dependent Unsplittable Flow Problem (D-UFP). We present and discuss this problem in the context of large-scale powerful (radar/camera) sensor networks, but we believe it has important applications on the admission of large flows in other networks as well. In order to optimize the selection of flows transmitted to the gateway, D-UFP takes into account possible dependencies between flows. We show that D-UFP is more difficult than NP-hard problems for which no good approximation is known. Then, we address two special cases of this problem: the case where all the sensors have a shared channel and the case where the sensors form a mesh and route to the gateway over a spanning tree. AU - Cohen, R. AU - Nudelman, I. AU - Polevoy, Gleb ID - 17663 IS - 5 JF - Networking, IEEE/ACM Transactions on KW - Approximation algorithms KW - Approximation methods KW - Bandwidth KW - Logic gates KW - Radar KW - Vectors KW - Wireless sensor networks KW - Dependent flow scheduling KW - sensor networks SN - 1063-6692 TI - On the Admission of Dependent Flows in Powerful Sensor Networks VL - 21 ER - TY - JOUR AB - Standard equity valuation approaches (i.e., DDM, RIM, and DCF model) are derived under the assumption of ideal conditions, such as infinite payoffs and clean surplus accounting. Because these conditions are hardly ever met, we extend the standard approaches, based on the fundamental principle of financial statement articulation. The extended models are then tested empirically by employing two sets of forecasts: (1) analyst forecasts provided by Value Line and (2) forecasts generated by cross-sectional regression models. The main result is that our extended models yield considerably smaller valuation errors. Moreover, by construction, identical value estimates are obtained across the extended models. By reestablishing empirical equivalence under non-ideal conditions, our approach provides a benchmark that enables us to quantify the errors resulting from individual deviations from ideal conditions, and thus, to analyze the robustness of the standard approaches. Finally, by providing a level playing field for the different valuation approaches, our findings have implications for other empirical settings, for example, estimating the implied cost of capital. AU - Heinrichs, Nicolas AU - Hess, Dieter AU - Homburg, Carsten AU - Lorenz, Michael AU - Sievers, Sönke ID - 5113 IS - 1 JF - Contemporary Accounting Research (VHB-JOURQUAL 3 Ranking A) KW - Dividend Discount Model KW - Residual Income KW - Discounted Cash Flow KW - Dirty Surplus KW - Terminal Value KW - Valuation Error TI - Extended dividend, cash flow, and residual income valuation models: Accounting for deviations from ideal conditions VL - 30 ER - TY - CONF AU - Anwer, Jahanzeb AU - Meisner, Sebastian AU - Platzner, Marco ID - 10620 KW - fault tolerant computing KW - field programmable gate arrays KW - logic design KW - reliability KW - BYU-LANL tool KW - DRM tool flow KW - FPGA based hardware designs KW - avionic application KW - device technologies KW - dynamic reliability management KW - fault-tolerant operation KW - hardware designs KW - reconfiguring reliability levels KW - space applications KW - Field programmable gate arrays KW - Hardware KW - Redundancy KW - Reliability engineering KW - Runtime KW - Tunneling magnetoresistance T2 - Reconfigurable Computing and FPGAs (ReConFig), 2013 International Conference on TI - Dynamic reliability management: Reconfiguring reliability-levels of hardware designs at runtime ER - TY - CONF AB - The main obstacle for the wide acceptance of UML and SysML in the design of electronic systems is due to a major gap in the design flow between UML-based modeling and SystemC-based verification. To overcome this gap, we present an approach developed in the SATURN project which introduces UML profiles for the co-modeling of SystemC and C with code generation support in the context of the SysML tool suite ARTiSAN Studio®. We finally discuss the evaluation of the approach by two case studies. AU - Müller, Wolfgang AU - He, Da AU - Mischkalla, Fabian AU - Wegele, Arthur AU - Larkham, Adrian AU - Whiston, Paul AU - Penil, Pablo AU - Villar, Eugenio AU - Mitas, Nikolaos AU - Kritharidis, Dimitros AU - Azcarate, Florent AU - Carballeda, Manuel ID - 37050 KW - Communicate Sequential Process Virtual Platform Smart Camera Synchronous Data Flow Artisan Studio T2 - Proceedings of the IEEE Computer Society Annual Symposium on VLSI TI - The SATURN Approach to SysML-based HW/SW Codesign ER -