@phdthesis{Kavrakov, author = {Kavrakov, Igor}, title = {Synergistic Framework for Analysis and Model Assessment in Bridge Aerodynamics and Aeroelasticity}, publisher = {Bauhaus-Universit{\"a}tsverlag}, address = {Weimar}, isbn = {978-3-95773-284-2}, doi = {10.25643/bauhaus-universitaet.4109}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20200316-41099}, school = {Bauhaus-Universit{\"a}t Weimar}, pages = {314}, abstract = {Wind-induced vibrations often represent a major design criterion for long-span bridges. This work deals with the assessment and development of models for aerodynamic and aeroelastic analyses of long-span bridges. Computational Fluid Dynamics (CFD) and semi-analytical aerodynamic models are employed to compute the bridge response due to both turbulent and laminar free-stream. For the assessment of these models, a comparative methodology is developed that consists of two steps, a qualitative and a quantitative one. The first, qualitative, step involves an extension of an existing approach based on Category Theory and its application to the field of bridge aerodynamics. Initially, the approach is extended to consider model comparability and completeness. Then, the complexity of the CFD and twelve semi-analytical models are evaluated based on their mathematical constructions, yielding a diagrammatic representation of model quality. In the second, quantitative, step of the comparative methodology, the discrepancy of a system response quantity for time-dependent aerodynamic models is quantified using comparison metrics for time-histories. Nine metrics are established on a uniform basis to quantify the discrepancies in local and global signal features that are of interest in bridge aerodynamics. These signal features involve quantities such as phase, time-varying frequency and magnitude content, probability density, non-stationarity, and nonlinearity. The two-dimensional (2D) Vortex Particle Method is used for the discretization of the Navier-Stokes equations including a Pseudo-three dimensional (Pseudo-3D) extension within an existing CFD solver. The Pseudo-3D Vortex Method considers the 3D structural behavior for aeroelastic analyses by positioning 2D fluid strips along a line-like structure. A novel turbulent Pseudo-3D Vortex Method is developed by combining the laminar Pseudo-3D VPM and a previously developed 2D method for the generation of free-stream turbulence. Using analytical derivations, it is shown that the fluid velocity correlation is maintained between the CFD strips. Furthermore, a new method is presented for the determination of the complex aerodynamic admittance under deterministic sinusoidal gusts using the Vortex Particle Method. The sinusoidal gusts are simulated by modeling the wakes of flapping airfoils in the CFD domain with inflow vortex particles. Positioning a section downstream yields sinusoidal forces that are used for determining all six components of the complex aerodynamic admittance. A closed-form analytical relation is derived, based on an existing analytical model. With this relation, the inflow particles' strength can be related with the target gust amplitudes a priori. The developed methodologies are combined in a synergistic framework, which is applied to both fundamental examples and practical case studies. Where possible, the results are verified and validated. The outcome of this work is intended to shed some light on the complex wind-bridge interaction and suggest appropriate modeling strategies for an enhanced design.}, subject = {Br{\"u}cke}, language = {en} } @article{KapsSchuchStaeblein, author = {Kaps, Christian and Schuch, Kai and St{\"a}blein, Stefan}, title = {Silicate coatings for concrete components with waterglass systems by means of neutral salt initiation}, doi = {10.25643/bauhaus-universitaet.2588}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20160601-25888}, pages = {1 -- 14}, abstract = {The objective of the investigations was the proof of the use of the neutral salt initiation as a construction material in the protecting silicate coating of concrete components, e.g. factory finished parts or reinforced concrete construction parts, by means of waterglass fused silica suspensions}, subject = {Silicate}, language = {en} } @phdthesis{Jenabidehkordi, author = {Jenabidehkordi, Ali}, title = {An Efficient Adaptive PD Formulation for Complex Microstructures}, doi = {10.25643/bauhaus-universitaet.4742}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20221124-47422}, school = {Bauhaus-Universit{\"a}t Weimar}, pages = {118}, abstract = {The computational costs of newly developed numerical simulation play a critical role in their acceptance within both academic use and industrial employment. Normally, the refinement of a method in the area of interest reduces the computational cost. This is unfortunately not true for most nonlocal simulation, since refinement typically increases the size of the material point neighborhood. Reducing the discretization size while keep- ing the neighborhood size will often require extra consideration. Peridy- namic (PD) is a newly developed numerical method with nonlocal nature. Its straightforward integral form equation of motion allows simulating dy- namic problems without any extra consideration required. The formation of crack and its propagation is known as natural to peridynamic. This means that discontinuity is a result of the simulation and does not demand any post-processing. As with other nonlocal methods, PD is considered an expensive method. The refinement of the nodal spacing while keeping the neighborhood size (i.e., horizon radius) constant, emerges to several nonphysical phenomena. This research aims to reduce the peridynamic computational and imple- mentation costs. A novel refinement approach is introduced. The pro- posed approach takes advantage of the PD flexibility in choosing the shape of the horizon by introducing multiple domains (with no intersections) to the nodes of the refinement zone. It will be shown that no ghost forces will be created when changing the horizon sizes in both subdomains. The approach is applied to both bond-based and state-based peridynamic and verified for a simple wave propagation refinement problem illustrating the efficiency of the method. Further development of the method for higher dimensions proves to have a direct relationship with the mesh sensitivity of the PD. A method for solving the mesh sensitivity of the PD is intro- duced. The application of the method will be examined by solving a crack propagation problem similar to those reported in the literature. New software architecture is proposed considering both academic and in- dustrial use. The available simulation tools for employing PD will be collected, and their advantages and drawbacks will be addressed. The challenges of implementing any node base nonlocal methods while max- imizing the software flexibility to further development and modification will be discussed and addressed. A software named Relation-Based Sim- ulator (RBS) is developed for examining the proposed architecture. The exceptional capabilities of RBS will be explored by simulating three dis- tinguished models. RBS is available publicly and open to further develop- ment. The industrial acceptance of the RBS will be tested by targeting its performance on one Mac and two Linux distributions.}, subject = {Peridynamik}, language = {en} } @phdthesis{Jenabidehkordi, author = {Jenabidehkordi, Ali}, title = {An efficient adaptive PD formulation for complex microstructures}, doi = {10.25643/bauhaus-universitaet.4738}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20221116-47389}, school = {Bauhaus-Universit{\"a}t Weimar}, pages = {118}, abstract = {The computational costs of newly developed numerical simulation play a critical role in their acceptance within both academic use and industrial employment. Normally, the refinement of a method in the area of interest reduces the computational cost. This is unfortunately not true for most nonlocal simulation, since refinement typically increases the size of the material point neighborhood. Reducing the discretization size while keep- ing the neighborhood size will often require extra consideration. Peridynamic (PD) is a newly developed numerical method with nonlocal nature. Its straightforward integral form equation of motion allows simulating dynamic problems without any extra consideration required. The formation of crack and its propagation is known as natural to peridynamic. This means that discontinuity is a result of the simulation and does not demand any post-processing. As with other nonlocal methods, PD is considered an expensive method. The refinement of the nodal spacing while keeping the neighborhood size (i.e., horizon radius) constant, emerges to several nonphysical phenomena. This research aims to reduce the peridynamic computational and imple- mentation costs. A novel refinement approach is introduced. The pro- posed approach takes advantage of the PD flexibility in choosing the shape of the horizon by introducing multiple domains (with no intersections) to the nodes of the refinement zone. It will be shown that no ghost forces will be created when changing the horizon sizes in both subdomains. The approach is applied to both bond-based and state-based peridynamic and verified for a simple wave propagation refinement problem illustrating the efficiency of the method. Further development of the method for higher dimensions proves to have a direct relationship with the mesh sensitivity of the PD. A method for solving the mesh sensitivity of the PD is intro- duced. The application of the method will be examined by solving a crack propagation problem similar to those reported in the literature. New software architecture is proposed considering both academic and in- dustrial use. The available simulation tools for employing PD will be collected, and their advantages and drawbacks will be addressed. The challenges of implementing any node base nonlocal methods while max- imizing the software flexibility to further development and modification will be discussed and addressed. A software named Relation-Based Sim- ulator (RBS) is developed for examining the proposed architecture. The exceptional capabilities of RBS will be explored by simulating three distinguished models. RBS is available publicly and open to further develop- ment. The industrial acceptance of the RBS will be tested by targeting its performance on one Mac and two Linux distributions.}, subject = {Peridynamik}, language = {en} } @phdthesis{Jaouadi, author = {Jaouadi, Zouhour}, title = {Pareto and Reliability-Oriented Aeroelastic Shape Optimization of Bridge Decks}, doi = {10.25643/bauhaus-universitaet.4935}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20230303-49352}, school = {Bauhaus-Universit{\"a}t Weimar}, pages = {167}, abstract = {Due to the development of new technologies and materials, optimized bridge design has recently gained more attention. The aim is to reduce the bridge components materials and the CO2 emission from the cement manufacturing process. Thus, most long-span bridges are designed to be with high flexibility, low structural damping, and longer and slender spans. Such designs lead, however, to aeroelastic challenges. Moreover, the consideration of both the structural and aeroelastic behavior in bridges leads to contradictory solutions as the structural constraints lead to deck prototypes with high depth which provide high inertia to material volume ratios. On the other hand, considering solely the aerodynamic requirements, slender airfoil-shaped bridge box girders are recommended since they prevent vortex shedding and exhibit minimum drag. Within this framework comes this study which provides approaches to find optimal bridge deck cross-sections while considering the aerodynamic effects. Shape optimization of deck cross-section is usually formulated to minimize the amount of material by finding adequate parameters such as the depth, the height, and the thickness and while ensuring the overall stability of the structure by the application of some constraints. Codes and studies have been implemented to analyze the wind phenomena and the structural responses towards bridge deck cross-sections where simplifications have been adopted due to the complexity and the uniqueness of such components besides the difficulty of obtaining a final model of the aerodynamic behavior. In this thesis, two main perspectives have been studied; the first is fully deterministic and presents a novel framework on generating optimal aerodynamic shapes for streamlined and trapezoidal cross-sections based on the meta-modeling approach. Single and multi-objective optimizations were both carried out and a Pareto Front is generated. The performance of the optimal designs is checked afterwards. In the second part, a new strategy based on Reliability-Based Design Optimization (RBDO) to mitigate the vortex-induced vibration (VIV) on the Trans-Tokyo Bay bridge is proposed. Small changes in the leading and trailing edges are presented and uncertainties are considered in the structural system. Probabilistic constraints based on polynomial regression are evaluated and the problem is solved while applying the Reliability Index Approach (RIA) and the Performance Measure Approach (PMA). The results obtained in the first part showed that the aspect ratio has a significant effect on the aerodynamic behavior where deeper cross-sections have lower resistance against flutter and should be avoided. In the second part, the adopted RBDO approach succeeded to mitigate the VIV, and it is proven that designs with narrow or prolonged bottom-base length and featuring an abrupt surface change in the leading and trailing edges can lead to high vertical vibration amplitude. It is expected that this research will help engineers with the selections of the adequate deck cross-section layout, and encourage researchers to apply concepts of optimization regarding this field and develop the presented approaches for further studies.}, subject = {Gestaltoptimierung}, language = {en} } @phdthesis{Hommel, author = {Hommel, Angela}, title = {Diskret holomorphe Funktionen und deren Bedeutung bei der L{\"o}sung von Differenzengleichungen}, doi = {10.25643/bauhaus-universitaet.3784}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20180827-37846}, school = {Bauhaus-Universit{\"a}t Weimar}, abstract = {Auf der Grundlage diskreter Cauchy-Riemann Operatoren werden diskret holomorphe Funktionen definiert und detailliert studiert. Darauf aufbauend wird die L{\"o}sung von Differenzengleichungen mit Hilfe der diskret holomorphen Funktionen beschrieben.}, subject = {Differenzengleichung}, language = {de} } @masterthesis{Hoinkis, type = {Bachelor Thesis}, author = {Hoinkis, Jule Hannah}, title = {Hitze in der Stadt Jena}, doi = {10.25643/bauhaus-universitaet.4632}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20220414-46323}, school = {Bauhaus-Universit{\"a}t Weimar}, abstract = {Die vorliegende Arbeit befasst sich mit den spezifischen Faktoren und Wechselwirkungen des st{\"a}dtischen Klimas und Strategien zur Pr{\"a}vention und Kompensation lokaler Klimaver{\"a}nderungen. Problematische Merkmale des Stadtklimas werden sich infolge des Klimawandels st{\"a}rker auspr{\"a}gen. Insbesondere die Hitzebelastung wird zunehmen und die Lebensbedingungen in der Stadt negativ beeinflussen. Infolge h{\"o}herer Temperaturen in St{\"a}dten und einer h{\"o}heren Temperaturdifferenz zum Umland ver{\"a}ndern sich Windstr{\"o}me und die Wasserbilanz. Es sind Strategien notwendig, um den Schadstoffausstoß, die Fl{\"a}cheninanspruchnahme, die Abfallproduktion und den Wasser-, Energie- und Ressourcenverbrauch zu verringern, um sowohl langfristig den Klimawandel als auch dessen bereits unvermeidbaren Auswirkungen auf St{\"a}dte zu begrenzen. Beispielhaft untersucht die Arbeit das Stadtklima, dessen zuk{\"u}nftige Ver{\"a}nderungen infolge des Klimawandels, bauliche Maßnahmen und Anpassungsstrategien der Stadt Jena. Jena ist die zweitgr{\"o}ßte Stadt im Bundesland Th{\"u}ringen und geh{\"o}rt heute zu den w{\"a}rmsten und trockensten Großst{\"a}dten Deutschlands. Die Ergebnisse der Arbeit werden anschließend anhand eines st{\"a}dtebaulichen Konzepts und Entwurfs angewendet. Das Bachstraßenareal liegt in der Innenstadt, dem am st{\"a}rksten von Hitze betroffenen Stadtteil. Als ehemaliger Hauptstandort des Jenaer Universit{\"a}tsklinikums, soll es zu einem nachhaltigen Wissenschaftscampus der Lebenswissenschaften umgebaut werden, wobei ein Großteil der denkmalgesch{\"u}tzten, ehemaligen Klinikgeb{\"a}ude erhalten bleibt. Der Fokus liegt dabei auf der Umsetzung der zuvor formulierten, nachhaltigen Strategien zur Verbesserung des lokalen Stadtklimas und einer Abschw{\"a}chung der Auswirkungen des Klimawandels auf den besonders stark betroffenen Innenstadtbereich Jenas.}, subject = {Hitze}, language = {de} } @phdthesis{Hatahet, author = {Hatahet, Tareq}, title = {On the Analysis of the Disproportionate Structural Collapse in RC Buildings}, doi = {10.25643/bauhaus-universitaet.3740}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20180329-37405}, school = {Bauhaus-Universit{\"a}t Weimar}, pages = {243}, abstract = {Increasing structural robustness is the goal which is of interest for structural engineering community. The partial collapse of RC buildings is subject of this dissertation. Understanding the robustness of RC buildings will guide the development of safer structures against abnormal loading scenarios such as; explosions, earthquakes, fine, and/or long-term accumulation effects leading to deterioration or fatigue. Any of these may result in local immediate structural damage, that can propagate to the rest of the structure causing what is known by the disproportionate collapse. This work handels collapse propagation through various analytical approaches which simplifies the mechanical description of damaged reinfoced concrete structures due to extreme acidental event.}, subject = {Beton}, language = {en} } @misc{Habtemariam, type = {Master Thesis}, author = {Habtemariam, Abinet Kifle}, title = {Numerical Demolition Analysis of a Slender Guyed Antenna Mast}, doi = {10.25643/bauhaus-universitaet.4460}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20210723-44609}, school = {Bauhaus-Universit{\"a}t Weimar}, pages = {75}, abstract = {The main purpose of the thesis is to ensure the safe demolition of old guyed antenna masts that are located in different parts of Germany. The major problem in demolition of this masts is the falling down of the masts in unexpected direction because of buckling problem. The objective of this thesis is development of a numerical models using finite element method (FEM) and assuring a controlled collapse by coming up with different time setups for the detonation of explosives which are responsible for cutting down the cables. The result of this thesis will avoid unexpected outcomes during the demolition processes and prevent risk of collapsing of the mast over near by structures.}, subject = {Abbruch}, language = {en} } @phdthesis{Habtemariam, author = {Habtemariam, Abinet Kifle}, title = {Generalized Beam Theory for the analysis of thin-walled circular pipe members}, doi = {10.25643/bauhaus-universitaet.4572}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20220127-45723}, school = {Bauhaus-Universit{\"a}t Weimar}, pages = {188}, abstract = {The detailed structural analysis of thin-walled circular pipe members often requires the use of a shell or solid-based finite element method. Although these methods provide a very good approximation of the deformations, they require a higher degree of discretization which causes high computational costs. On the other hand, the analysis of thin-walled circular pipe members based on classical beam theories is easy to implement and needs much less computation time, however, they are limited in their ability to approximate the deformations as they cannot consider the deformation of the cross-section. This dissertation focuses on the study of the Generalized Beam Theory (GBT) which is both accurate and efficient in analyzing thin-walled members. This theory is based on the separation of variables in which the displacement field is expressed as a combination of predetermined deformation modes related to the cross-section, and unknown amplitude functions defined on the beam's longitudinal axis. Although the GBT was initially developed for long straight members, through the consideration of complementary deformation modes, which amend the null transverse and shear membrane strain assumptions of the classical GBT, problems involving short members, pipe bends, and geometrical nonlinearity can also be analyzed using GBT. In this dissertation, the GBT formulation for the analysis of these problems is developed and the application and capabilities of the method are illustrated using several numerical examples. Furthermore, the displacement and stress field results of these examples are verified using an equivalent refined shell-based finite element model. The developed static and dynamic GBT formulations for curved thin-walled circular pipes are based on the linear kinematic description of the curved shell theory. In these formulations, the complex problem in pipe bends due to the strong coupling effect of the longitudinal bending, warping and the cross-sectional ovalization is handled precisely through the derivation of the coupling tensors between the considered GBT deformation modes. Similarly, the geometrically nonlinear GBT analysis is formulated for thin-walled circular pipes based on the nonlinear membrane kinematic equations. Here, the initial linear and quadratic stress and displacement tangent stiffness matrices are built using the third and fourth-order GBT deformation mode coupling tensors. Longitudinally, the formulation of the coupled GBT element stiffness and mass matrices are presented using a beam-based finite element formulation. Furthermore, the formulated GBT elements are tested for shear and membrane locking problems and the limitations of the formulations regarding the membrane locking problem are discussed.}, subject = {Finite-Elemente-Methode}, language = {en} } @phdthesis{Goswami, author = {Goswami, Somdatta}, title = {Phase field modeling of fracture with isogeometric analysis and machine learning methods}, doi = {10.25643/bauhaus-universitaet.4384}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20210304-43841}, school = {Bauhaus-Universit{\"a}t Weimar}, pages = {168}, abstract = {This thesis presents the advances and applications of phase field modeling in fracture analysis. In this approach, the sharp crack surface topology in a solid is approximated by a diffusive crack zone governed by a scalar auxiliary variable. The uniqueness of phase field modeling is that the crack paths are automatically determined as part of the solution and no interface tracking is required. The damage parameter varies continuously over the domain. But this flexibility comes with associated difficulties: (1) a very fine spatial discretization is required to represent sharp local gradients correctly; (2) fine discretization results in high computational cost; (3) computation of higher-order derivatives for improved convergence rates and (4) curse of dimensionality in conventional numerical integration techniques. As a consequence, the practical applicability of phase field models is severely limited. The research presented in this thesis addresses the difficulties of the conventional numerical integration techniques for phase field modeling in quasi-static brittle fracture analysis. The first method relies on polynomial splines over hierarchical T-meshes (PHT-splines) in the framework of isogeometric analysis (IGA). An adaptive h-refinement scheme is developed based on the variational energy formulation of phase field modeling. The fourth-order phase field model provides increased regularity in the exact solution of the phase field equation and improved convergence rates for numerical solutions on a coarser discretization, compared to the second-order model. However, second-order derivatives of the phase field are required in the fourth-order model. Hence, at least a minimum of C1 continuous basis functions are essential, which is achieved using hierarchical cubic B-splines in IGA. PHT-splines enable the refinement to remain local at singularities and high gradients, consequently reducing the computational cost greatly. Unfortunately, when modeling complex geometries, multiple parameter spaces (patches) are joined together to describe the physical domain and there is typically a loss of continuity at the patch boundaries. This decrease of smoothness is dictated by the geometry description, where C0 parameterizations are normally used to deal with kinks and corners in the domain. Hence, the application of the fourth-order model is severely restricted. To overcome the high computational cost for the second-order model, we develop a dual-mesh adaptive h-refinement approach. This approach uses a coarser discretization for the elastic field and a finer discretization for the phase field. Independent refinement strategies have been used for each field. The next contribution is based on physics informed deep neural networks. The network is trained based on the minimization of the variational energy of the system described by general non-linear partial differential equations while respecting any given law of physics, hence the name physics informed neural network (PINN). The developed approach needs only a set of points to define the geometry, contrary to the conventional mesh-based discretization techniques. The concept of `transfer learning' is integrated with the developed PINN approach to improve the computational efficiency of the network at each displacement step. This approach allows a numerically stable crack growth even with larger displacement steps. An adaptive h-refinement scheme based on the generation of more quadrature points in the damage zone is developed in this framework. For all the developed methods, displacement-controlled loading is considered. The accuracy and the efficiency of both methods are studied numerically showing that the developed methods are powerful and computationally efficient tools for accurately predicting fractures.}, subject = {Phasenfeldmodell}, language = {en} } @article{GhazvineiDarvishiMosavietal., author = {Ghazvinei, Pezhman Taherei and Darvishi, Hossein Hassanpour and Mosavi, Amir and Yusof, Khamaruzaman bin Wan and Alizamir, Meysam and Shamshirband, Shahaboddin and Chau, Kwok-Wing}, title = {Sugarcane growth prediction based on meteorological parameters using extreme learning machine and artificial neural network}, series = {Engineering Applications of Computational Fluid Mechanics}, volume = {2018}, journal = {Engineering Applications of Computational Fluid Mechanics}, number = {12,1}, publisher = {Taylor \& Francis}, doi = {10.1080/19942060.2018.1526119}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20181017-38129}, pages = {738 -- 749}, abstract = {Management strategies for sustainable sugarcane production need to deal with the increasing complexity and variability of the whole sugar system. Moreover, they need to accommodate the multiple goals of different industry sectors and the wider community. Traditional disciplinary approaches are unable to provide integrated management solutions, and an approach based on whole systems analysis is essential to bring about beneficial change to industry and the community. The application of this approach to water management, environmental management and cane supply management is outlined, where the literature indicates that the application of extreme learning machine (ELM) has never been explored in this realm. Consequently, the leading objective of the current research was set to filling this gap by applying ELM to launch swift and accurate model for crop production data-driven. The key learning has been the need for innovation both in the technical aspects of system function underpinned by modelling of sugarcane growth. Therefore, the current study is an attempt to establish an integrate model using ELM to predict the concluding growth amount of sugarcane. Prediction results were evaluated and further compared with artificial neural network (ANN) and genetic programming models. Accuracy of the ELM model is calculated using the statistics indicators of Root Means Square Error (RMSE), Pearson Coefficient (r), and Coefficient of Determination (R2) with promising results of 0.8, 0.47, and 0.89, respectively. The results also show better generalization ability in addition to faster learning curve. Thus, proficiency of the ELM for supplementary work on advancement of prediction model for sugarcane growth was approved with promising results.}, subject = {K{\"u}nstliche Intelligenz}, language = {en} } @article{FathiSajadzadehMohammadiSheshkaletal., author = {Fathi, Sadegh and Sajadzadeh, Hassan and Mohammadi Sheshkal, Faezeh and Aram, Farshid and Pinter, Gergo and Felde, Imre and Mosavi, Amir}, title = {The Role of Urban Morphology Design on Enhancing Physical Activity and Public Health}, series = {International Journal of Environmental Research and Public Health}, volume = {2020}, journal = {International Journal of Environmental Research and Public Health}, number = {Volume 17, Issue 7, 2359}, publisher = {MDPI}, address = {Basel}, doi = {10.3390/ijerph17072359}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20200402-41225}, pages = {29}, abstract = {Along with environmental pollution, urban planning has been connected to public health. The research indicates that the quality of built environments plays an important role in reducing mental disorders and overall health. The structure and shape of the city are considered as one of the factors influencing happiness and health in urban communities and the type of the daily activities of citizens. The aim of this study was to promote physical activity in the main structure of the city via urban design in a way that the main form and morphology of the city can encourage citizens to move around and have physical activity within the city. Functional, physical, cultural-social, and perceptual-visual features are regarded as the most important and effective criteria in increasing physical activities in urban spaces, based on literature review. The environmental quality of urban spaces and their role in the physical activities of citizens in urban spaces were assessed by using the questionnaire tool and analytical network process (ANP) of structural equation modeling. Further, the space syntax method was utilized to evaluate the role of the spatial integration of urban spaces on improving physical activities. Based on the results, consideration of functional diversity, spatial flexibility and integration, security, and the aesthetic and visual quality of urban spaces plays an important role in improving the physical health of citizens in urban spaces. Further, more physical activities, including motivation for walking and the sense of public health and happiness, were observed in the streets having higher linkage and space syntax indexes with their surrounding texture.}, subject = {Morphologie}, language = {en} } @article{FaizollahzadehArdabiliNajafiAlizamiretal., author = {Faizollahzadeh Ardabili, Sina and Najafi, Bahman and Alizamir, Meysam and Mosavi, Amir and Shamshirband, Shahaboddin and Rabczuk, Timon}, title = {Using SVM-RSM and ELM-RSM Approaches for Optimizing the Production Process of Methyl and Ethyl Esters}, series = {Energies}, journal = {Energies}, number = {11, 2889}, publisher = {MDPI}, address = {Basel}, doi = {10.3390/en11112889}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20181025-38170}, pages = {1 -- 20}, abstract = {The production of a desired product needs an effective use of the experimental model. The present study proposes an extreme learning machine (ELM) and a support vector machine (SVM) integrated with the response surface methodology (RSM) to solve the complexity in optimization and prediction of the ethyl ester and methyl ester production process. The novel hybrid models of ELM-RSM and ELM-SVM are further used as a case study to estimate the yield of methyl and ethyl esters through a trans-esterification process from waste cooking oil (WCO) based on American Society for Testing and Materials (ASTM) standards. The results of the prediction phase were also compared with artificial neural networks (ANNs) and adaptive neuro-fuzzy inference system (ANFIS), which were recently developed by the second author of this study. Based on the results, an ELM with a correlation coefficient of 0.9815 and 0.9863 for methyl and ethyl esters, respectively, had a high estimation capability compared with that for SVM, ANNs, and ANFIS. Accordingly, the maximum production yield was obtained in the case of using ELM-RSM of 96.86\% for ethyl ester at a temperature of 68.48 °C, a catalyst value of 1.15 wt. \%, mixing intensity of 650.07 rpm, and an alcohol to oil molar ratio (A/O) of 5.77; for methyl ester, the production yield was 98.46\% at a temperature of 67.62 °C, a catalyst value of 1.1 wt. \%, mixing intensity of 709.42 rpm, and an A/O of 6.09. Therefore, ELM-RSM increased the production yield by 3.6\% for ethyl ester and 3.1\% for methyl ester, compared with those for the experimental data.}, subject = {Biodiesel}, language = {en} } @phdthesis{Ehrhardt, author = {Ehrhardt, Dirk}, title = {ZUM EINFLUSS DER NACHBEHANDLUNG AUF DIE GEF{\"U}GEAUSBILDUNG UND DEN FROST-TAUMITTELWIDERSTAND DER BETONRANDZONE}, doi = {10.25643/bauhaus-universitaet.3688}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20171120-36889}, school = {Bauhaus-Universit{\"a}t Weimar}, pages = {235}, abstract = {Die Festigkeitsentwicklung des Zementbetons basiert auf der chemischen Reaktion des Zementes mit dem Anmachwasser. Durch Nachbehandlungsmaßnahmen muss daf{\"u}r gesorgt werden, dass dem Zement gen{\"u}gend Wasser f{\"u}r seine Reaktion zur Verf{\"u}gung steht, da sonst ein Beton mit minderer Qualit{\"a}t entsteht. Die vorliegende Arbeit behandelt die grunds{\"a}tzlichen Fragen der Betonnachbehandlung bei Anwendung von Straßenbetonen. Im Speziellen wird die Frage des erforderlichen Nachbehandlungsbedarfs von h{\"u}ttensandhaltigen Kompositzementen betrachtet. Die Wirkung der Nachbehandlung wird anhand des erreichten Frost-Tausalz-Widerstandes und der Gef{\"u}geausbildung in der unmittelbaren Betonrandzone bewertet. Der Fokus der Untersuchungen lag auf abgezogenen Betonoberfl{\"a}chen. Es wurde ein Modell zur Austrocknung des jungen Betons erarbeitet. Es konnte gezeigt werden, dass in einer fr{\"u}hen Austrocknung (Kapillarphase) keine kritische Austrocknung der Betonrandzone einsetzt, sondern der Beton ann{\"a}hrend gleichm{\"a}ßig {\"u}ber die H{\"o}he austrocknet. Es wurde ein Nomogramm entwickelt, mit dem die Dauer der Kapillarphase in Abh{\"a}ngigkeit der Witterung f{\"u}r Straßenbetone abgesch{\"a}tzt werden kann. Eine kritische Austrocknung der wichtigen Randzone setzt nach Ende der Kapillarphase ein. F{\"u}r Betone unter Verwendung von Zementen mit langsamer Festigkeitsentwicklung ist die Austrocknung der Randzone nach Ende der Kapillarphase besonders ausgepr{\"a}gt. Im Ergebnis zeigen diese Betone dann einen geringen Frost-Tausalz-Widerstand. Mit Zementen, die eine 2d-Zementdruckfestigkeit ≥ 23,0 N/mm² aufweisen, wurde unabh{\"a}ngig von der Zementart (CEM I oder CEM II/B-S) auch dann ein hoher Frost-Tausalz-Widerstand erreicht, wenn keine oder eine schlechtere Nachbehandlung angewendet wurde. F{\"u}r die Praxis ergibt sich damit eine einfache M{\"o}glichkeit der Vorauswahl von geeigneten Zementen f{\"u}r den Verkehrsfl{\"a}chenbau. Betone, die unter Verwendung von Zementen mit langsamere Festigkeitsentwicklung hergestellt werden, erreichen einen hohen Frost-Tausalz-Widerstand nur mit einer geeigneten Nachbehandlung. Die Anwendung von fl{\"u}ssigen Nachbehandlungsmitteln (NBM gem{\"a}ß TL NBM-StB) erreicht eine {\"a}hnliche Wirksamkeit wie eine 5 t{\"a}gige Feuchtnachbehandlung. Voraussetzung f{\"u}r die Wirksamkeit der NBM ist, dass sie auf eine Betonoberfl{\"a}che ohne sichtbaren Feuchtigkeitsfilm (feuchter Glanz) aufgespr{\"u}ht werden. Besonders wichtig ist die Beachtung des richtigen Auftragszeitpunktes bei k{\"u}hler Witterung, da hier aufgrund der verlangsamten Zementreaktion der Beton l{\"a}nger Anmachwasser abst{\"o}ßt. Ein zu fr{\"u}her Auftrag des Nachbehandlungsmittels f{\"u}hrt zu einer Verschlechterung der Qualit{\"a}t der Betonrandzone. Durch Bereitstellung hydratationsabh{\"a}ngiger Transportkenngr{\"o}ßen (Feuchtetransport im Beton) konnten numerische Berechnungen zum Zusammenspiel zwischen der Austrocknung, der Nachbehandlung und der Gef{\"u}geentwicklung durchgef{\"u}hrt werden. Mit dem erstellten Berechnungsmodell wurden Parameterstudien durchgef{\"u}hrt. Die Berechnungen best{\"a}tigen die wesentlichen Erkenntnisse der Laboruntersuchungen. Dar{\"u}ber hinaus l{\"a}sst sich mit dem Berechnungsmodell zeigen, dass gerade bei langsam reagierenden Zementen und k{\"u}hler Witterung ohne eine Nachbehandlung eine sehr d{\"u}nne Randzone (ca. 500 µm - 1000 µm) mit stark erh{\"o}hter Kapillarporosit{\"a}t entsteht.}, subject = {Beton}, language = {de} } @article{Dressel, author = {Dressel, Dennys}, title = {Reaktivit{\"a}t von H{\"u}ttensand : Thermodynamische Grundlagen und Anwendung}, doi = {10.25643/bauhaus-universitaet.2677}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20160829-26778}, pages = {178}, abstract = {Die thermodynamischen Grundlagen der Hydratation von H{\"u}ttensand als Hauptbestandteil von Zementen werden erforscht. Hierbei werden thermodynamische Bildungs- und Reaktionsdaten experimentell bestimmt und berechnet. Dar{\"u}ber hinaus wird der Prozess der Feststoffaufl{\"o}sung von H{\"u}ttensand in w{\"a}ssrigen L{\"o}sungen untersucht. L{\"o}sungs- und F{\"a}llungsprozesse werden unter verschiedenen Konditionen gemessen, ausgewertet und diskutiert. Die Ergebnisse werden im weiteren Verlauf zur Bestimmung der Hydratationsgrades in Pasten sowie zum besseren Verst{\"a}ndnis in der Wechselwirkung zwischen H{\"u}ttensanden und Mahlhilfsstoffen genutzt und angewandt.}, subject = {H{\"u}ttensand}, language = {de} } @misc{CicekCancino, type = {Master Thesis}, author = {Cicek, Burhan and Cancino, Pamela}, title = {K{\"u}reken 2013. Entwerfen eines Dorfes aus Lehm}, doi = {10.25643/bauhaus-universitaet.6356}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20240507-63568}, school = {Bauhaus-Universit{\"a}t Weimar}, pages = {107}, abstract = {Die Diskussionen in der Politik und in der Gesellschaft {\"u}ber Klimawandel, globale Erw{\"a}rmung oder Nachhaltigkeit, die schon noch l{\"a}nger anh{\"a}lt, werden nie ein Ende finden, solange die Probleme, auf denen sie basiert, unl{\"o}sbar bleiben. Vorgeschlagene L{\"o}sungen werden meist nicht richtig umgesetzt. Im Zusammenhang mit dieser Problematik steigt aber das Verantwortungsgef{\"u}hl f{\"u}r bessere Zukunftsstrategien immer mehr. Die in den letzten Jahren vorgekommenen Umweltkatastrophen, wie im Golf von Mexiko (April 2010) oder im Fukushima (M{\"a}rz 2011) die noch aktuell sind, zeigen, dass der Prim{\"a}renergieeinsatz oder die Transportproblematik nicht mehr nur die Sorge der Entwicklungsl{\"a}nder, sondern auch der Industriel{\"a}nder ist. Die Bauwelt mit ihrem erheblichen Energiebedarf spielt bei der Festlegung der Zukunftsstrategien eine große Rolle. Vor allem sind die Forschungen nach umweltfreundlichen Materialien, der Recyclebarkeit der eingesetzten Baumaterialien oder dem vern{\"u}nftigen Nutzen der Naturressourcen die wichtigsten Schwerpunkte. In dieser Hinsicht bringt Lehm als Baumaterial viele Vorteile mit sich. Bei einem Artikel sagt der Lehmbauexperte Martin Rauch: "In heutiger Zeit und einem Kulturkreis, in dem Baugrund und Arbeitszeit unsere großen Kosten verursachen, findet der tradierte Lehmbau mit dem verbundenen großen Aufwand an menschlicher Arbeitszeit nur schwer seinen Platz. {\"U}ber die Art der Bauweise wird auch die Entscheidung gef{\"a}llt, wie und wo die Wertsch{\"o}pfung erfolgt und ob der Einsatz des Budgets einen gesellschaftlichen Nutzen mit sich bringt. Im Vergleich zu einem Sichtbetonhaus k{\"o}nnen bei einem Stampflehmhaus 40\% der Prim{\"a}renergie ein gespart und daf{\"u}r mehr lokale Arbeitsressourcen gebunden werden. Davon profitieren vor allem die lokalen Handwerker und mittelst{\"a}ndischen Betriebe" Anatolien ist der Ort, wo man immer noch die tiefsten Wurzeln der Baukultur menschlicher Geschichte findet. Diese Baukultur, die in den vergangenen Jahrzehnten fast verlorengegangen ist, ist die Lehmbaukultur. In dieser Hinsicht beabsichtigt dieser Entwurf die W{\"u}rde des Lehms in Anatolien wieder herzustellen und dadurch dessen Glaubw{\"u}rdigkeit zur{\"u}ckzubringen.}, subject = {Lehm}, language = {de} } @article{ChenSchwingKarlovšeketal., author = {Chen, Zhen and Schwing, Moritz and Karlovšek, Jurij and Wagner, Norman and Scheuermann, Alexander}, title = {Broadband Dielectric Measurement Methods for Soft Geomaterials: Coaxial Transmission Line Cell and Open-Ended Coaxial Probe}, series = {International Journal of Engineering and Technology}, volume = {2014}, journal = {International Journal of Engineering and Technology}, number = {volume 6, number 5}, doi = {10.7763/IJET.2014.V6.728}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20210408-43984}, pages = {373 -- 380}, abstract = {Broadband dielectric measurement methods based on vector network analyzer coupled with coaxial transmission line cell (CC) and open-ended coaxial probe (OC) are simply reviewed, by which the dielectric behaviors in the frequency range of 1 MHz to 3 GHz of two practical geomaterials are investigated. Kaolin after modified compaction with different water contents is measured by using CC. The results are consistent with previous study on standardized compacted kaolin and suggest that the dielectric properties at frequencies below 100 MHz are not only a function of water content but also functions of other soil state parameters including dry density. The hydration process of a commercial grout is monitored in real time by using OC. It is found that the time dependent dielectric properties can accurately reveal the different stages of the hydration process. These measurement results demonstrate the practicability of the introduced methods in determining dielectric properties of soft geomaterials.}, subject = {Impedanzspektroskopie}, language = {en} } @phdthesis{Chen, author = {Chen, Na}, title = {A Balance between Ideals and Reality — Establishing and Evaluating a Resilient City Indicator System for Central Chinese Cities}, doi = {10.25643/bauhaus-universitaet.4030}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20191121-40309}, school = {Bauhaus-Universit{\"a}t Weimar}, pages = {212}, abstract = {Recent years have seen a gradual shift in focus of international policies from a national and regional perspective to that of cities, a shift which is closely related to the rapid urbanization of developing countries. As revealed in the 2011 Revision of the World Urbanization Prospects published by the United Nations, 51\% of the global population (approximately 3.6 billion people) lives in cities. The report predicts that by 2050, the world's urban population will increase by 2.3 billion, making up 68\% of the population. The growth of urbanization in the next few decades is expected to primarily come from developing countries, one third of which will be in China and India. With rapid urbanization and the ongoing growth of mega cities, cities must become increasingly resilient and intelligent to cope with numerous challenges and crises like droughts and floods arising from extreme climate, destruction brought by severe natural disasters, and aggregated social contradictions resulting from economic crises. All cities face the urban development dynamics and uncertainties arising from these problems. Under such circumstances, cities are considered the critical path from crisis to prosperity, so scholars and organizations have proposed the construction of "resilient cities." On the one hand, this theory emphasizes cities' defenses and buffering capacity against disasters, crises and uncertainties, as well as recovery after destruction; on the other hand, it highlights the learning capacity of urban systems, identification of opportunities amid challenges, and maintenance of development vitality. Some scholars even believe that urban resilience is a powerful supplement to sustainable development. Hence, resilience assessment has become the latest and most important perspective for evaluating the development and crisis defense capacity of cities. Rather than a general abstract concept, urban resilience is a comprehensive measurement of a city's level of development. The dynamic development of problems is reflected through quantitative indicators and appraisal systems not only from the perspective of academic research, but also governmental policy, so as to scientifically guide development, and measure and compare cities' development levels. Although international scholars have proposed quantitative methods for urban resilience assessment, they are however insufficiently systematic and regionally adaptive for China's current urban development needs. On the basis of comparative study on European and North American resilient city theories, therefore, this paper puts forwards a theoretical framework for resilient city systems consistent with China's national conditions in light of economic development pressure, natural resource depletion, pollution, and other salient development crises in China. The key factors influencing urban resilience are taken into full consideration; expert appraisal is conducted based on the Delphi Method and the analytic hierarchy process (AHP) to design an extensible and updatable resilient city evaluation system which is sufficiently systematic, geographically adaptable, and sustainable for China's current urban development needs. Finally, Changsha is taken as the main case for empirical study on comprehensive evaluation of similar cities in Central China to improve the indicator system.}, subject = {Stadtplanung}, language = {en} } @phdthesis{Chan, author = {Chan, Chiu Ling}, title = {Smooth representation of thin shells and volume structures for isogeometric analysis}, doi = {10.25643/bauhaus-universitaet.4208}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20200812-42083}, school = {Bauhaus-Universit{\"a}t Weimar}, pages = {162}, abstract = {The purpose of this study is to develop self-contained methods for obtaining smooth meshes which are compatible with isogeometric analysis (IGA). The study contains three main parts. We start by developing a better understanding of shapes and splines through the study of an image-related problem. Then we proceed towards obtaining smooth volumetric meshes of the given voxel-based images. Finally, we treat the smoothness issue on the multi-patch domains with C1 coupling. Following are the highlights of each part. First, we present a B-spline convolution method for boundary representation of voxel-based images. We adopt the filtering technique to compute the B-spline coefficients and gradients of the images effectively. We then implement the B-spline convolution for developing a non-rigid images registration method. The proposed method is in some sense of "isoparametric", for which all the computation is done within the B-splines framework. Particularly, updating the images by using B-spline composition promote smooth transformation map between the images. We show the possible medical applications of our method by applying it for registration of brain images. Secondly, we develop a self-contained volumetric parametrization method based on the B-splines boundary representation. We aim to convert a given voxel-based data to a matching C1 representation with hierarchical cubic splines. The concept of the osculating circle is employed to enhance the geometric approximation, where it is done by a single template and linear transformations (scaling, translations, and rotations) without the need for solving an optimization problem. Moreover, we use the Laplacian smoothing and refinement techniques to avoid irregular meshes and to improve mesh quality. We show with several examples that the method is capable of handling complex 2D and 3D configurations. In particular, we parametrize the 3D Stanford bunny which contains irregular shapes and voids. Finally, we propose the B´ezier ordinates approach and splines approach for C1 coupling. In the first approach, the new basis functions are defined in terms of the B´ezier Bernstein polynomials. For the second approach, the new basis is defined as a linear combination of C0 basis functions. The methods are not limited to planar or bilinear mappings. They allow the modeling of solutions to fourth order partial differential equations (PDEs) on complex geometric domains, provided that the given patches are G1 continuous. Both methods have their advantages. In particular, the B´ezier approach offer more degree of freedoms, while the spline approach is more computationally efficient. In addition, we proposed partial degree elevation to overcome the C1-locking issue caused by the over constraining of the solution space. We demonstrate the potential of the resulting C1 basis functions for application in IGA which involve fourth order PDEs such as those appearing in Kirchhoff-Love shell models, Cahn-Hilliard phase field application, and biharmonic problems.}, subject = {Modellierung}, language = {en} } @phdthesis{Ashour, author = {Ashour, Mohammed}, title = {Electromechanics and Hydrodynamics of Single Vesicles and Vesicle Doublet Using Phase-Field Isogeometric Analysis}, doi = {10.25643/bauhaus-universitaet.6400}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20230628-64003}, school = {Bauhaus-Universit{\"a}t Weimar}, pages = {175}, abstract = {Biomembranes are selectively permeable barriers that separate the internal components of the cell from its surroundings. They have remarkable mechanical behavior which is characterized by many phenomena, but most noticeably their fluid-like in-plane behavior and solid-like out-of-plane behavior. Vesicles have been studied in the context of discrete models, such as Molecular Dynamics, Monte Carlo methods, Dissipative Particle Dynamics, and Brownian Dynamics. Those methods, however, tend to have high computational costs, which limited their uses for studying atomistic details. In order to broaden the scope of this research, we resort to the continuum models, where the atomistic details of the vesicles are neglected, and the focus shifts to the overall morphological evolution. Under the umbrella of continuum models, vesicles morphology has been studied extensively. However, most of those studies were limited to the mechanical response of vesicles by considering only the bending energy and aiming for the solution by minimizing the total energy of the system. Most of the literature is divided between two geometrical representation methods; the sharp interface methods and the diffusive interface methods. Both of those methods track the boundaries and interfaces implicitly. In this research, we focus our attention on solving two non-trivial problems. In the first one, we study a constrained Willmore problem coupled with an electrical field, and in the second one, we investigate the hydrodynamics of a vesicle doublet suspended in an external viscous fluid flow. For the first problem, we solve a constrained Willmore problem coupled with an electrical field using isogeometric analysis to study the morphological evolution of vesicles subjected to static electrical fields. The model comprises two phases, the lipid bilayer, and the electrolyte. This two-phase problem is modeled using the phase-field method, which is a subclass of the diffusive interface methods mentioned earlier. The bending, flexoelectric, and dielectric energies of the model are reformulated using the phase-field parameter. A modified Augmented-Lagrangian (ALM) approach was used to satisfy the constraints while maintaining numerical stability and a relatively large time step. This approach guarantees the satisfaction of the constraints at each time step over the entire temporal domain. In the second problem, we study the hydrodynamics of vesicle doublet suspended in an external viscous fluid flow. Vesicles in this part of the research are also modeled using the phase-field model. The bending energy and energies associated with enforcing the global volume and area are considered. In addition, the local inextensibility condition is ensured by introducing an additional equation to the system. To prevent the vesicles from numerically overlapping, we deploy an interaction energy definition to maintain a short-range repulsion between the vesicles. The fluid flow is modeled using the incompressible Navier-Stokes equations and the vesicle evolution in time is modeled using two advection equations describing the process of advecting each vesicle by the fluid flow. To overcome the velocity-pressure saddle point system, we apply the Residual-Based Variational MultiScale (RBVMS) method to the Navier-Stokes equations and solve the coupled systems using isogeometric analysis. We study vesicle doublet hydrodynamics in shear flow, planar extensional flow, and parabolic flow under various configurations and boundary conditions. The results reveal several interesting points about the electrodynamics and hydrodynamics responses of single vesicles and vesicle doublets. But first, it can be seen that isogeometric analysis as a numerical tool has the ability to model and solve 4th-order PDEs in a primal variational framework at extreme efficiency and accuracy due to the abilities embedded within the NURBS functions without the need to reduce the order of the PDE by creating an intermediate environment. Refinement whether by knot insertion, order increasing or both is far easier to obtain than traditional mesh-based methods. Given the wide variety of phenomena in natural sciences and engineering that are mathematically modeled by high-order PDEs, the isogeometric analysis is among the most robust methods to address such problems as the basis functions can easily attain high global continuity. On the applicational side, we study the vesicle morphological evolution based on the electromechanical liquid-crystal model in 3D settings. This model describing the evolution of vesicles is composed of time-dependent, highly nonlinear, high-order PDEs, which are nontrivial to solve. Solving this problem requires robust numerical methods, such as isogeometric analysis. We concluded that the vesicle tends to deform under increasing magnitudes of electric fields from the original sphere shape to an oblate-like shape. This evolution is affected by many factors and requires fine-tuning of several parameters, mainly the regularization parameter which controls the thickness of the diffusive interface width. But it is most affected by the method used for enforcing the constraints. The penalty method in presence of an electrical field tends to lock on the initial phase-field and prevent any evolution while a modified version of the ALM has proven to be sufficiently stable and accurate to let the phase-field evolve while satisfying the constraints over time at each time step. We show additionally the effect of including the flexoelectric nature of the Biomembranes in the computation and how it affects the shape evolution as well as the effect of having different conductivity ratios. All the examples were solved based on a staggered scheme, which reduces the computational cost significantly. For the second part of the research, we consider vesicle doublet suspended in a shear flow, in a planar extensional flow, and in a parabolic flow. When the vesicle doublet is suspended in a shear flow, it can either slip past each other or slide on top of each other based on the value of the vertical displacement, that is the vertical distance between the center of masses between the two vesicles, and the velocity profile applied. When the vesicle doublet is suspended in a planar extensional flow in a configuration that resembles a junction, the time in which both vesicles separate depends largely on the value of the vertical displacement after displacing as much fluid from between the two vesicles. However, when the vesicles are suspended in a tubular channel with a parabolic fluid flow, they develop a parachute-like shape upon converging towards each other before exiting the computational domain from the predetermined outlets. This shape however is affected largely by the height of the tubular channel in which the vesicle is suspended. The velocity essential boundary conditions are imposed weakly and strongly. The weak implementation of the boundary conditions was used when the velocity profile was defined on the entire boundary, while the strong implementation was used when the velocity profile was defined on a part of the boundary. The strong implementation of the essential boundary conditions was done by selectively applying it to the predetermined set of elements in a parallel-based code. This allowed us to simulate vesicle hydrodynamics in a computational domain with multiple inlets and outlets. We also investigate the hydrodynamics of oblate-like shape vesicles in a parabolic flow. This work has been done in 2D configuration because of the immense computational load resulting from a large number of degrees of freedom, but we are actively seeking to expand it to 3D settings and test a broader set of parameters and geometrical configurations.}, subject = {Isogeometrische Analyse}, language = {en} } @article{AmirinasabShamshirbandChronopoulosetal., author = {Amirinasab, Mehdi and Shamshirband, Shahaboddin and Chronopoulos, Anthony Theodore and Mosavi, Amir and Nabipour, Narjes}, title = {Energy-Efficient Method for Wireless Sensor Networks Low-Power Radio Operation in Internet of Things}, series = {electronics}, volume = {2020}, journal = {electronics}, number = {volume 9, issue 2, 320}, publisher = {MDPI}, doi = {10.3390/electronics9020320}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20200213-40954}, pages = {20}, abstract = {The radio operation in wireless sensor networks (WSN) in Internet of Things (IoT)applications is the most common source for power consumption. Consequently, recognizing and controlling the factors affecting radio operation can be valuable for managing the node power consumption. Among essential factors affecting radio operation, the time spent for checking the radio is of utmost importance for monitoring power consumption. It can lead to false WakeUp or idle listening in radio duty cycles and ContikiMAC. ContikiMAC is a low-power radio duty-cycle protocol in Contiki OS used in WakeUp mode, as a clear channel assessment (CCA) for checking radio status periodically. This paper presents a detailed analysis of radio WakeUp time factors of ContikiMAC. Furthermore, we propose a lightweight CCA (LW-CCA) as an extension to ContikiMAC to reduce the Radio Duty-Cycles in false WakeUps and idle listening though using dynamic received signal strength indicator (RSSI) status check time. The simulation results in the Cooja simulator show that LW-CCA reduces about 8\% energy consumption in nodes while maintaining up to 99\% of the packet delivery rate (PDR).}, subject = {Internet der Dinge}, language = {en} } @phdthesis{Amiri, author = {Amiri, Fatemeh}, title = {Computational modelling of fracture with local maximum entropy approximations}, doi = {10.25643/bauhaus-universitaet.2631}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20160719-26310}, school = {Bauhaus-Universit{\"a}t Weimar}, pages = {130}, abstract = {The key objective of this research is to study fracture with a meshfree method, local maximum entropy approximations, and model fracture in thin shell structures with complex geometry and topology. This topic is of high relevance for real-world applications, for example in the automotive industry and in aerospace engineering. The shell structure can be described efficiently by meshless methods which are capable of describing complex shapes as a collection of points instead of a structured mesh. In order to find the appropriate numerical method to achieve this goal, the first part of the work was development of a method based on local maximum entropy (LME) shape functions together with enrichment functions used in partition of unity methods to discretize problems in linear elastic fracture mechanics. We obtain improved accuracy relative to the standard extended finite element method (XFEM) at a comparable computational cost. In addition, we keep the advantages of the LME shape functions,such as smoothness and non-negativity. We show numerically that optimal convergence (same as in FEM) for energy norm and stress intensity factors can be obtained through the use of geometric (fixed area) enrichment with no special treatment of the nodes near the crack such as blending or shifting. As extension of this method to three dimensional problems and complex thin shell structures with arbitrary crack growth is cumbersome, we developed a phase field model for fracture using LME. Phase field models provide a powerful tool to tackle moving interface problems, and have been extensively used in physics and materials science. Phase methods are gaining popularity in a wide set of applications in applied science and engineering, recently a second order phase field approximation for brittle fracture has gathered significant interest in computational fracture such that sharp cracks discontinuities are modeled by a diffusive crack. By minimizing the system energy with respect to the mechanical displacements and the phase-field, subject to an irreversibility condition to avoid crack healing, this model can describe crack nucleation, propagation, branching and merging. One of the main advantages of the phase field modeling of fractures is the unified treatment of the interfacial tracking and mechanics, which potentially leads to simple, robust, scalable computer codes applicable to complex systems. In other words, this approximation reduces considerably the implementation complexity because the numerical tracking of the fracture is not needed, at the expense of a high computational cost. We present a fourth-order phase field model for fracture based on local maximum entropy (LME) approximations. The higher order continuity of the meshfree LME approximation allows to directly solve the fourth-order phase field equations without splitting the fourth-order differential equation into two second order differential equations. Notably, in contrast to previous discretizations that use at least a quadratic basis, only linear completeness is needed in the LME approximation. We show that the crack surface can be captured more accurately in the fourth-order model than the second-order model. Furthermore, less nodes are needed for the fourth-order model to resolve the crack path. Finally, we demonstrate the performance of the proposed meshfree fourth order phase-field formulation for 5 representative numerical examples. Computational results will be compared to analytical solutions within linear elastic fracture mechanics and experimental data for three-dimensional crack propagation. In the last part of this research, we present a phase-field model for fracture in Kirchoff-Love thin shells using the local maximum-entropy (LME) meshfree method. Since the crack is a natural outcome of the analysis it does not require an explicit representation and tracking, which is advantageous over techniques as the extended finite element method that requires tracking of the crack paths. The geometric description of the shell is based on statistical learning techniques that allow dealing with general point set surfaces avoiding a global parametrization, which can be applied to tackle surfaces of complex geometry and topology. We show the flexibility and robustness of the present methodology for two examples: plate in tension and a set of open connected pipes.}, language = {en} } @article{AlkamLahmer, author = {Alkam, Feras and Lahmer, Tom}, title = {A robust method of the status monitoring of catenary poles installed along high-speed electrified train tracks}, series = {Results in Engineering}, volume = {2021}, journal = {Results in Engineering}, number = {volume 12, article 100289}, publisher = {Elsevier}, address = {Amsterdam}, doi = {10.1016/j.rineng.2021.100289}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20211011-45212}, pages = {1 -- 8}, abstract = {Electric trains are considered one of the most eco-friendly and safest means of transportation. Catenary poles are used worldwide to support overhead power lines for electric trains. The performance of the catenary poles has an extensive influence on the integrity of the train systems and, consequently, the connected human services. It became a must nowadays to develop SHM systems that provide the instantaneous status of catenary poles in- service, making the decision-making processes to keep or repair the damaged poles more feasible. This study develops a data-driven, model-free approach for status monitoring of cantilever structures, focusing on pre-stressed, spun-cast ultrahigh-strength concrete catenary poles installed along high-speed train tracks. The pro-posed approach evaluates multiple damage features in an unfied damage index, which leads to straightforward interpretation and comparison of the output. Besides, it distinguishes between multiple damage scenarios of the poles, either the ones caused by material degradation of the concrete or by the cracks that can be propagated during the life span of the given structure. Moreover, using a logistic function to classify the integrity of structure avoids the expensive learning step in the existing damage detection approaches, namely, using the modern machine and deep learning methods. The findings of this study look very promising when applied to other types of cantilever structures, such as the poles that support the power transmission lines, antenna masts, chimneys, and wind turbines.}, subject = {Fahrleitung}, language = {en} } @phdthesis{Alkam, author = {Alkam, Feras}, title = {Vibration-based Monitoring of Concrete Catenary Poles using Bayesian Inference}, volume = {2021}, publisher = {Bauhaus-Universit{\"a}tsverlag}, address = {Weimar}, doi = {10.25643/bauhaus-universitaet.4433}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20210526-44338}, school = {Bauhaus-Universit{\"a}t Weimar}, pages = {177}, abstract = {This work presents a robust status monitoring approach for detecting damage in cantilever structures based on logistic functions. Also, a stochastic damage identification approach based on changes of eigenfrequencies is proposed. The proposed algorithms are verified using catenary poles of electrified railways track. The proposed damage features overcome the limitation of frequency-based damage identification methods available in the literature, which are valid to detect damage in structures to Level 1 only. Changes in eigenfrequencies of cantilever structures are enough to identify possible local damage at Level 3, i.e., to cover damage detection, localization, and quantification. The proposed algorithms identified the damage with relatively small errors, even at a high noise level.}, subject = {Parameteridentifikation}, language = {en} } @misc{Alabassy, type = {Master Thesis}, author = {Alabassy, Mohamed Said Helmy}, title = {Automated Approach for Building Information Modelling of Crack Damages via Image Segmentation and Image-based 3D Reconstruction}, doi = {10.25643/bauhaus-universitaet.6416}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20230818-64162}, school = {Bauhaus-Universit{\"a}t Weimar}, pages = {101}, abstract = {As machine vision-based inspection methods in the field of Structural Health Monitoring (SHM) continue to advance, the need for integrating resulting inspection and maintenance data into a centralised building information model for structures notably grows. Consequently, the modelling of found damages based on those images in a streamlined automated manner becomes increasingly important, not just for saving time and money spent on updating the model to include the latest information gathered through each inspection, but also to easily visualise them, provide all stakeholders involved with a comprehensive digital representation containing all the necessary information to fully understand the structure's current condition, keep track of any progressing deterioration, estimate the reduced load bearing capacity of the damaged element in the model or simulate the propagation of cracks to make well-informed decisions interactively and facilitate maintenance actions that optimally extend the service life of the structure. Though significant progress has been recently made in information modelling of damages, the current devised methods for the geometrical modelling approach are cumbersome and time consuming to implement in a full-scale model. For crack damages, an approach for a feasible automated image-based modelling is proposed utilising neural networks, classical computer vision and computational geometry techniques with the aim of creating valid shapes to be introduced into the information model, including related semantic properties and attributes from inspection data (e.g., width, depth, length, date, etc.). The creation of such models opens the door for further possible uses ranging from more accurate structural analysis possibilities to simulation of damage propagation in model elements, estimating deterioration rates and allows for better documentation, data sharing, and realistic visualisation of damages in a 3D model.}, subject = {Building Information Modeling}, language = {en} } @article{AlYasiriMutasharGuerlebecketal., author = {Al-Yasiri, Zainab Riyadh Shaker and Mutashar, Hayder Majid and G{\"u}rlebeck, Klaus and Lahmer, Tom}, title = {Damage Sensitive Signals for the Assessment of the Conditions of Wind Turbine Rotor Blades Using Electromagnetic Waves}, series = {Infrastructures}, volume = {2022}, journal = {Infrastructures}, number = {Volume 7, Issue 8 (August 2022), article 104}, editor = {Shafiullah, GM}, publisher = {MDPI}, address = {Basel}, doi = {10.3390/infrastructures7080104}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20220831-47093}, pages = {18}, abstract = {One of the most important renewable energy technologies used nowadays are wind power turbines. In this paper, we are interested in identifying the operating status of wind turbines, especially rotor blades, by means of multiphysical models. It is a state-of-the-art technology to test mechanical structures with ultrasonic-based methods. However, due to the density and the required high resolution, the testing is performed with high-frequency waves, which cannot penetrate the structure in depth. Therefore, there is a need to adopt techniques in the fields of multiphysical model-based inversion schemes or data-driven structural health monitoring. Before investing effort in the development of such approaches, further insights and approaches are necessary to make the techniques applicable to structures such as wind power plants (blades). Among the expected developments, further accelerations of the so-called "forward codes" for a more efficient implementation of the wave equation could be envisaged. Here, we employ electromagnetic waves for the early detection of cracks. Because in many practical situations, it is not possible to apply techniques from tomography (characterized by multiple sources and sensor pairs), we focus here on the question of whether the existence of cracks can be determined by using only one source for the sent waves.}, subject = {Windkraftwerk}, language = {en} } @phdthesis{AbuBakar, author = {Abu Bakar, Ilyani Akmar}, title = {Computational Analysis of Woven Fabric Composites: Single- and Multi-Objective Optimizations and Sensitivity Analysis in Meso-scale Structures}, issn = {1610-7381}, doi = {10.25643/bauhaus-universitaet.4176}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20200605-41762}, school = {Bauhaus-Universit{\"a}t Weimar}, pages = {151}, abstract = {This study permits a reliability analysis to solve the mechanical behaviour issues existing in the current structural design of fabric structures. Purely predictive material models are highly desirable to facilitate an optimized design scheme and to significantly reduce time and cost at the design stage, such as experimental characterization. The present study examined the role of three major tasks; a) single-objective optimization, b) sensitivity analyses and c) multi-objective optimization on proposed weave structures for woven fabric composites. For single-objective optimization task, the first goal is to optimize the elastic properties of proposed complex weave structure under unit cells basis based on periodic boundary conditions. We predict the geometric characteristics towards skewness of woven fabric composites via Evolutionary Algorithm (EA) and a parametric study. We also demonstrate the effect of complex weave structures on the fray tendency in woven fabric composites via tightness evaluation. We utilize a procedure which does not require a numerical averaging process for evaluating the elastic properties of woven fabric composites. The fray tendency and skewness of woven fabrics depends upon the behaviour of the floats which is related to the factor of weave. Results of this study may suggest a broader view for further research into the effects of complex weave structures or may provide an alternative to the fray and skewness problems of current weave structure in woven fabric composites. A comprehensive study is developed on the complex weave structure model which adopts the dry woven fabric of the most potential pattern in singleobjective optimization incorporating the uncertainties parameters of woven fabric composites. The comprehensive study covers the regression-based and variance-based sensitivity analyses. The second task goal is to introduce the fabric uncertainties parameters and elaborate how they can be incorporated into finite element models on macroscopic material parameters such as elastic modulus and shear modulus of dry woven fabric subjected to uni-axial and biaxial deformations. Significant correlations in the study, would indicate the need for a thorough investigation of woven fabric composites under uncertainties parameters. The study describes here could serve as an alternative to identify effective material properties without prolonged time consumption and expensive experimental tests. The last part focuses on a hierarchical stochastic multi-scale optimization approach (fine-scale and coarse-scale optimizations) under geometrical uncertainties parameters for hybrid composites considering complex weave structure. The fine-scale optimization is to determine the best lamina pattern that maximizes its macroscopic elastic properties, conducted by EA under the following uncertain mesoscopic parameters: yarn spacing, yarn height, yarn width and misalignment of yarn angle. The coarse-scale optimization has been carried out to optimize the stacking sequences of symmetric hybrid laminated composite plate with uncertain mesoscopic parameters by employing the Ant Colony Algorithm (ACO). The objective functions of the coarse-scale optimization are to minimize the cost (C) and weight (W) of the hybrid laminated composite plate considering the fundamental frequency and the buckling load factor as the design constraints. Based on the uncertainty criteria of the design parameters, the appropriate variation required for the structural design standards can be evaluated using the reliability tool, and then an optimized design decision in consideration of cost can be subsequently determined.}, subject = {Verbundwerkstoff}, language = {en} } @phdthesis{Abeltshauser, author = {Abeltshauser, Rainer}, title = {Identification and separation of physical effects of coupled systems by using defined model abstractions}, doi = {10.25643/bauhaus-universitaet.2860}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20170314-28600}, school = {Bauhaus-Universit{\"a}t Weimar}, abstract = {The thesis investigates at the computer aided simulation process for operational vibration analysis of complex coupled systems. As part of the internal methods project "Absolute Values" of the BMW Group, the thesis deals with the analysis of the structural dynamic interactions and excitation interactions. The overarching aim of the methods project is to predict the operational vibrations of engines. Simulations are usually used to analyze technical aspects (e. g. operational vibrations, strength, ...) of single components in the industrial development. The boundary conditions of submodels are mostly based on experiences. So the interactions with neighboring components and systems are neglected. To get physically more realistic results but still efficient simulations, this work wants to support the engineer during the preprocessing phase by useful criteria. At first suitable abstraction levels based on the existing literature are defined to identify structural dynamic interactions and excitation interactions of coupled systems. So it is possible to separate different effects of the coupled subsystems. On this basis, criteria are derived to assess the influence of interactions between the considered systems. These criteria can be used during the preprocessing phase and help the engineer to build up efficient models with respect to the interactions with neighboring systems. The method was developed by using several models with different complexity levels. Furthermore, the method is proved for the application in the industrial environment by using the example of a current combustion engine.}, subject = {Strukturdynamik}, language = {en} }