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Entwicklung eines Berechnungsverfahrens zur Ermittlung der Kapazität in lichtsignalgeregelten Zufahrten mit zusätzlichen Aufstellstreifen bei gleichzeitiger Freigabezeit
Get PDFIm Rahmen der Dissertation ist ein analytisches Berechnungsverfahren zur Ermittlung der Kapazität in lichtsignalgeregelten Zufahrten mit zusätzlichen Aufstellstreifen bei gleichzeitiger Freigabezeit entwickelt worden, dass sich durch folgende Eigenschaften auszeichnet:
a) einfaches Berechnungsverfahren – Ansatz eines einfachen linearen Berechnungsansatzes, der auf den Grundzusammenhängen des Verkehrsablaufs in lichtsignalgeregelten Zufahrten aufbaut,
b) breites Anwendungsgebiet – Berechnungsverfahren kann in Zufahrten mit bis zu zwei zusätzlichen Aufstellstreifen angewendet werden,
c) hohe Genauigkeit – Im Rahmen eines direkten Vergleichs konnte u. a.
gezeigt werden, dass mit dem hergeleiteten analytischen Berechnungsverfahren genauere Kapazitätswerte ermittelt werden können, als mit dem Berechnungsverfahren nach HBS 2015
Entwicklung und Untersuchung von alternativen Dicalciumsilicat-Bindern auf der Basis von alpha-C2SH
Get PDFUm den Klimawandel zu begrenzen, müssen die CO2-Emissionen drastisch gesenkt werden [100]. Bis 2050 soll bei der Herstellung von Zement eine Einsparung um 51–60 % auf 0,425–0,350 tCO2/tZement erfolgen [7]. Um dieses Ziel zu erreichen, sind alternative Bindemittelkonzepte notwendig [70].
Diese Arbeit widmet sich alternativen, hochreaktiven Dicalciumsilicat-Bindemitteln, die durch die thermische Aktivierung von α-Dicalcium-Silicat-Hydrat (α-C2SH) erzeugt werden. Das α-C2SH ist eine kristalline C S H-Phase, die im hydrothermalen Prozess, beispielsweise aus Branntkalk und Quarz, herstellbar ist. Die thermische Aktivierung kann bei sehr niedrigen Temperaturen erfolgen (>420 °C) und führt zu einem Multiphasen-C2S-Binder. Als besonders reaktive Bestandteile können x-C2S und röntgenamorphe Anteile enthalten sein. Weiterhin können β C2S, γ C2S und Dellait (Ca6(SiO4)(Si2O7)(OH)2) entstehen.
Im Rahmen der Arbeit wird zunächst der Stand des Wissens zur Polymorphie und Hydratation von C2S zusammengefasst. Es werden bekannte C2S-basierte Bindemittelkonzepte vorgestellt und bewertet.
Die Herstellung von C2S-Bindern wird experimentell im Labormaßstab untersucht. Dabei kommen unterschiedliche Autoklaven und ein Muffelofen zum Einsatz. Die Herstellungsparameter werden hinsichtlich Phasenbestand und Reaktivität optimiert. Die Bindemittel werden durch quantitative Röntgen-Phasenanalyse (QXRD), Rasterelektronenmikroskopie (REM), N2-Adsorption (BET-Methode), Heliumpycnometer, Thermoanalyse (TGA/DSC) und 29Si-MAS- sowie 29Si-1H-CP/MAS-NMR-Spektroskopie charakterisiert. Das Hydratationsverhalten der Bindemittel wird vorrangig mithilfe von Wärmeflusskalorimetrie untersucht. Weiterhin werden in situ und ex situ XRD-, TGA/DSC- und REM-Untersuchungen durchgeführt. Anhand von zwei Bindemitteln wird die Fähigkeit zur Erzielung hoher Festigkeiten demonstriert. Abschließend erfolgt eine Abschätzung zu Energiebedarf und CO2-Emissionen für die Herstellung der untersuchten C2S-Binder.
Die Ergebnisse zeigen, dass für eine hohe Reaktivität der Binder eine niedrige Brenntemperatur und ein geringer Wasserdampfpartialdruck während der thermischen Aktivierung entscheidend sind. Weiterhin muss das hydrothermal hergestellte α-C2SH eine möglichst hohe spezifische Oberfläche aufweisen. Diese Parameter beeinflussen den Phasenbestand und die phasenspezifische Reaktivität. Brenntemperaturen von ca. 420–500 °C führen zu hochreaktiven Bindern, die im Rahmen dieser Arbeit als Niedertemperatur-C2S-Binder bezeichnet werden. Temperaturen von ca. 600–800 °C führen zu Bindern mit geringerer Reaktivität, die im Rahmen dieser Arbeit als Hochtemperatur-C2S bezeichnet werden. Höhere Brenntemperaturen (1000 °C) führen zu Bindemitteln, die innerhalb der ersten drei Tage keine hydraulische Aktivität zeigen.
Die untersuchten Bindemittel können sehr hohe Reaktionsgeschwindigkeiten erreichen. Die Wärmeflusskalorimetrie deutet bei einigen Bindemitteln einen nahezu vollständigen Umsatz innerhalb von drei Tagen an. Durch XRD wurde für einen Binder der vollständige Verbrauch von x-C2S innerhalb von drei Tagen nachgewiesen. Für einen mittels in-situ-XRD und Wärmeflusskalorimetrie untersuchten Binder wurde gezeigt, dass die Phasen vorrangig in der Reihenfolge röntgenamorph > x-C2S > β-C2S > γ-C2S hydratisieren. Hydratationsprodukte sind nadelige C S H-Phasen und Portlandit.
Die Herstellung durch thermische Aktivierung von α-C2SH führt zu tafeligen Bindemittelpartikeln, die teilweise Zwickelräume und Poren zwischen den einzelnen Partikeln einschließen. Um eine verarbeitbare Bindemittelpaste zu erzeugen, sind daher sehr hohe Wasser/Bindemittel-Werte (z. B. 1,4) erforderlich. Der Wasseranspruch kann durch Mahlung etwa auf das Niveau von Zement gesenkt werden.
Die Druckfestigkeitsentwicklung wurde an zwei Niedertemperatur-C2S-Kompositbindern mit 40 % Kalksteinmehl bzw. 40 % Hüttensand untersucht. Aufgrund von theoretischen Betrachtungen zur Porosität in Abhängigkeit des w/b-Wertes wurde dieser auf 0,3 festgelegt. Durch Zugabe von PCE-Fließmittel wurde ein verarbeitbarer Mörtel erhalten. Die Festigkeitsentwicklung ist sehr schnell. Der Kalksteinmehl-Binder erreichte nach zwei Tagen 46 N/mm². Bis Tag 28 trat keine weitere Festigkeitssteigerung ein. Der Hüttensand-Binder erreichte nach zwei Tagen 62 N/mm². Durch die Hüttensandreaktion stieg die Festigkeit bis auf 85 N/mm² nach 28 Tagen an.
Für den Herstellungsprozess von Niedertemperatur-C2S-Binder wurden Energieverbräuche und CO2-Emissionen abgeschätzt. Es deutet sich an, dass, bezogen auf die Bindemittelmenge, keine wesentlichen Einsparungen im Vergleich zur Portlandzementherstellung möglich sind. Für die tatsächlichen Emissionen muss jedoch zusätzlich die Leistungsfähigkeit der Bindemittel berücksichtigt werden. Die Leistungsfähigkeit kann als erforderliche Bindemittelmenge betrachtet werden, die je m³ Beton eingesetzt werden muss, um bestimmte Festigkeits-, Dauerhaftigkeits- und Verarbeitungseigenschaften zu erreichen.
Aus verschiedenen Veröffentlichungen [94, 201, 206] wurde die These abgeleitet, dass die Leistungsfähigkeit eines Bindemittels maßgeblich von der C-S-H-Menge bestimmt wird, die während der Hydratation gebildet wird. Daher wird für NT-C2S-Binder eine außergewöhnlich hohe Leistungsfähigkeit erwartet.
Auf Basis der Leistungsfähigkeitsthese verringern sich die abgeschätzten CO2-Emissionen von NT-C2S-Bindern, sodass gegenüber Portlandzement ein mögliches Einsparpotenzial von 42 % ermittelt wurde
On the fracture toughness of polymeric nanocomposites: Comprehensive stochastic and numerical studies
Get PDFPolymeric nanocomposites (PNCs) are considered for numerous nanotechnology such as: nano-biotechnology, nano-systems, nanoelectronics, and nano-structured materials. Commonly , they are formed by polymer (epoxy) matrix reinforced with a nanosized filler. The addition of rigid nanofillers to the epoxy matrix has offered great improvements in the fracture toughness without sacrificing other important thermo-mechanical properties. The physics of the fracture in PNCs is rather complicated and is influenced by different parameters. The presence of uncertainty in the predicted output is expected as a result of stochastic variance in the factors affecting the fracture mechanism. Consequently, evaluating the improved fracture toughness in PNCs is a challenging problem.
Artificial neural network (ANN) and adaptive neuro-fuzzy inference system (ANFIS) have been employed to predict the fracture energy of polymer/particle nanocomposites. The ANN and ANFIS models were constructed, trained, and tested based on a collection of 115 experimental datasets gathered from the literature. The performance evaluation indices of the developed ANN and ANFIS showed relatively small error, with high coefficients of determination (R2), and low root mean square error and mean absolute percentage error.
In the framework for uncertainty quantification of PNCs, a sensitivity analysis (SA) has been conducted to examine the influence of uncertain input parameters on the fracture toughness of polymer/clay nanocomposites (PNCs). The phase-field approach is employed to predict the macroscopic properties of the composite considering six uncertain input parameters. The efficiency, robustness, and repeatability are compared and evaluated comprehensively for five different SA methods.
The Bayesian method is applied to develop a methodology in order to evaluate the performance of different analytical models used in predicting the fracture toughness of polymeric particles nanocomposites. The developed method have considered the model and parameters uncertainties based on different reference data (experimental measurements) gained from the literature. Three analytical models differing in theory and assumptions were examined. The coefficients of variation of the model predictions to the measurements are calculated using the approximated optimal parameter sets. Then, the model selection probability is obtained with respect to the different reference data.
Stochastic finite element modeling is implemented to predict the fracture toughness of polymer/particle nanocomposites. For this purpose, 2D finite element model containing an epoxy matrix and rigid nanoparticles surrounded by an interphase zone is generated. The crack propagation is simulated by the cohesive segments method and phantom nodes. Considering the uncertainties in the input parameters, a polynomial chaos expansion (PCE) surrogate model is construed followed by a sensitivity analysis
Determination of Bonding Failures in Transparent Materials with Non-Destructive Methods – Evaluation of Climatically Stressed Glued and Laminated Glass Compounds
Get PDFAs part of an international research project – funded by the European Union – capillary glasses for facades are being developed exploiting storage energy by means of fluids flowing through the capillaries. To meet highest visual demands, acrylate adhesives and EVA films are tested as possible bonding materials for the glass setup. Especially non-destructive methods (visual analysis, analysis of birefringent properties and computed tomographic data) are applied to evaluate failure patterns as well as the long-term behavior considering climatic influences. The experimental investigations are presented after different loading periods, providing information of failure developments. In addition, detailed information and scientific findings on the application of computed tomographic analyses are presented
Nanomechanical Resonators Based on Quasi-two-dimensional Materials
Get PDFAdvances in nanotechnology lead to the development of nano-electro-mechanical systems (NEMS) such as nanomechanical resonators with ultra-high resonant frequencies. The ultra-high-frequency resonators have recently received significant attention for wide-ranging applications such as molecular separation, molecular transportation, ultra-high sensitive sensing, high-frequency signal processing, and biological imaging. It is well known that for micrometer length scale, first-principles technique, the most accurate approach, poses serious limitations for comparisons with experimental studies. For such larger size, classical molecular dynamics (MD) simulations are desirable, which require interatomic potentials. Additionally, a mesoscale method such as the coarse-grained (CG) method is another useful method to support simulations for even larger system sizes.
Furthermore, quasi-two-dimensional (Q2D) materials have attracted intensive research interest due to their many novel properties over the past decades. However, the energy dissipation mechanisms of nanomechanical resonators based on several Q2D materials are still unknown. In this work, the addressed main issues include the development of the CG models for molybdenum disulphide (MoS2), investigation of the mechanism effects on black phosphorus (BP) nanoresonators and the application of graphene nanoresonators. The primary coverage and results of the dissertation are as follows:
Method development. Firstly, a two-dimensional (2D) CG model for single layer MoS2 (SLMoS2) is analytically developed. The Stillinger-Weber (SW) potential for this 2D CG model is further parametrized, in which all SW geometrical parameters are determined analytically according to the equilibrium condition for each individual potential term, while the SW energy parameters are derived analytically based on the valence force field model. Next, the 2D CG model is further simplified to one-dimensional (1D) CG model, which describes the 2D SLMoS2 structure using a 1D chain model. This 1D CG model is applied to investigate the relaxed configuration and the resonant oscillation of the folded SLMoS2. Owning to the simplicity nature of the 1D CG model, the relaxed configuration of the folded SLMoS2 is determined analytically, and the resonant oscillation frequency is derived analytically. Considering the increasing interest in studying the properties of other 2D layered materials, and in particular those in the semiconducting transition metal dichalcogenide class like MoS2, the CG models proposed in current work provide valuable simulation approaches.
Mechanism understanding. Two energy dissipation mechanisms of BP nanoresonators are focused exclusively, i.e. mechanical strain effects and defect effects (including vacancy and oxidation). Vacancy defect is intrinsic damping factor for the quality (Q)-factor, while mechanical strain and oxidation are extrinsic damping factors. Intrinsic dissipation (induced by thermal vibrations) in BP resonators (BPRs) is firstly investigated. Specifically, classical MD simulations are performed to examine the temperature dependence for the Q-factor of the single layer BPR (SLBPR) along the armchair and zigzag directions, where two-step fitting procedure is used to extract the frequency and Q-factor from the kinetic energy time history. The Q-factors of BPRs are evaluated through comparison with those of graphene and MoS2 nanoresonators. Next, effects of mechanical strain, vacancy and oxidation on BP nanoresonators are investigated in turn. Considering the increasing interest in studying the properties of BP, and in particular the lack of theoretical study for the BPRs, the results in current work provide a useful reference.
Application. A novel application for graphene nanoresonators, using them to self-assemble small nanostructures such as water chains, is proposed. All of the underlying physics enabling this phenomenon is elucidated. In particular, by drawing inspiration from macroscale self-assembly using the higher order resonant modes of Chladni plates, classical MD simulations are used to investigate the self-assembly of water molecules using
graphene nanoresonators. An analytic formula for the critical resonant frequency based on the interaction between water molecules and graphene is provided. Furthermore, the properties of the water chains assembled by the graphene nanoresonators are studied
A Hybrid Clustering and Classification Technique for Forecasting Short-Term Energy Consumption
Get PDFElectrical energy distributor companies in Iran have to announce their energy demand at least three 3-day ahead of the market opening. Therefore, an accurate load estimation is highly crucial. This research invoked methodology based on CRISP data mining and used SVM, ANN, and CBA-ANN-SVM (a novel hybrid model of clustering with both widely used ANN and SVM) to predict short-term electrical energy demand of Bandarabbas. In previous studies, researchers introduced few effective parameters with no reasonable error about Bandarabbas power consumption. In this research we tried to recognize all efficient parameters and with the use of CBA-ANN-SVM model, the rate of error has been minimized. After consulting with experts in the field of power consumption and plotting daily power consumption for each week, this research showed that official holidays and weekends have impact on the power consumption. When the weather gets warmer, the consumption of electrical energy increases due to turning on electrical air conditioner. Also, con-sumption patterns in warm and cold months are different. Analyzing power consumption of the same month for different years had shown high similarity in power consumption patterns. Factors with high impact on power consumption were identified and statistical methods were utilized to prove their impacts. Using SVM, ANN and CBA-ANN-SVM, the model was built. Sine the proposed method (CBA-ANN-SVM) has low MAPE 5 1.474 (4 clusters) and MAPE 5 1.297 (3 clusters) in comparison with SVM (MAPE 5 2.015) and ANN (MAPE 5 1.790), this model was selected as the final model. The final model has the benefits from both models and the benefits of clustering. Clustering algorithm with discovering data structure, divides data into several clusters based on similarities and differences between them. Because data inside each cluster are more similar than entire data, modeling in each cluster will present better results. For future research, we suggest using fuzzy methods and genetic algorithm or a hybrid of both to forecast each cluster. It is also possible to use fuzzy methods or genetic algorithms or a hybrid of both without using clustering. It is issued that such models will produce better and more accurate results.
This paper presents a hybrid approach to predict the electric energy usage of weather-sensitive loads. The presented methodutilizes the clustering paradigm along with ANN and SVMapproaches for accurate short-term prediction of electric energyusage, using weather data. Since the methodology beinginvoked in this research is based on CRISP data mining, datapreparation has received a gr eat deal of attention in thisresear ch. Once data pre-processing was done, the underlyingpattern of electric energy consumption was extracted by themeans of machine learning methods to precisely forecast short-term energy consumption. The proposed approach (CBA-ANN-SVM) was applied to real load data and resulting higher accu-racy comparing to the existing models.
2018 American Institute of Chemical Engineers Environ Prog, 2018
https://doi.org/10.1002/ep.1293
Damage Localization of Mechanical Structures by Subspace Identification and Krein Space Based H-infinity Estimation
Get PDFThis dissertation is devoted to the theoretical development and experimental laboratory verification of a new damage localization method: The state projection estimation error (SP2E). This method is based on the subspace identification of mechanical structures, Krein space based H-infinity estimation and oblique projections. To explain method SP2E, several theories are discussed and laboratory experiments have been conducted and analysed.
A fundamental approach of structural dynamics is outlined first by explaining mechanical systems based on first principles. Following that, a fundamentally different approach, subspace identification, is comprehensively explained. While both theories, first principle and subspace identification based mechanical systems, may be seen as widespread methods, barely known and new techniques follow up. Therefore, the indefinite quadratic estimation theory is explained. Based on a Popov function approach, this leads to the Krein space based H-infinity theory. Subsequently, a new method for damage identification, namely SP2E, is proposed. Here, the introduction of a difference process, the analysis by its average process power and the application of oblique projections is discussed in depth.
Finally, the new method is verified in laboratory experiments. Therefore, the identification of a laboratory structure at Leipzig University of Applied Sciences is elaborated. Then structural alterations are experimentally applied, which were localized by SP2E afterwards. In the end four experimental sensitivity studies are shown and discussed. For each measurement series the structural alteration was increased, which was successfully tracked by SP2E. The experimental results are plausible and in accordance with the developed theories. By repeating these experiments, the applicability of SP2E for damage localization is experimentally proven
An Intelligent Artificial Neural Network-Response Surface Methodology Method for Accessing the Optimum Biodiesel and Diesel Fuel Blending Conditions in a Diesel Engine from the Viewpoint of Exergy and Energy Analysis
Get PDFBiodiesel, as the main alternative fuel to diesel fuel which is produced from renewable and available resources, improves the engine emissions during combustion in diesel engines. In this study, the biodiesel is produced initially from waste cooking oil (WCO). The fuel samples are applied in a diesel engine and the engine performance has been considered from the viewpoint of exergy and energy approaches. Engine tests are performed at a constant 1500 rpm speed with various loads and fuel samples. The obtained experimental data are also applied to develop an artificial neural network (ANN) model. Response surface methodology (RSM) is employed to optimize the exergy and energy efficiencies. Based on the results of the energy analysis, optimal engine performance is obtained at 80% of full load in presence of B10 and B20 fuels. However, based on the exergy analysis results, optimal engine performance is obtained at 80% of full load in presence of B90 and B100 fuels. The optimum values of exergy and energy efficiencies are in the range of 25–30% of full load, which is the same as the calculated range obtained from mathematical modeling
Spatial Retrieval of Broadband Dielectric Spectra
No full textA broadband soil dielectric spectra retrieval approach ( 1 MHz– 2 GHz) has been implemented for a layered half space. The inversion kernel consists of a two-port transmission line forward model in the frequency domain and a constitutive material equation based on a power law soil mixture rule (Complex Refractive Index Model - CRIM). The spatially-distributed retrieval of broadband dielectric spectra was achieved with a global optimization approach based on a Shuffled Complex Evolution (SCE) algorithm using the full set of the scattering parameters. For each layer, the broadband dielectric spectra were retrieved with the corresponding parameters thickness, porosity, water saturation and electrical conductivity of the aqueous pore solution. For the validation of the approach, a coaxial transmission line cell measured with a network analyzer was used. The possibilities and limitations of the inverse parameter estimation were numerically analyzed in four scenarios. Expected and retrieved layer thicknesses, soil properties and broadband dielectric spectra in each scenario were in reasonable agreement. Hence, the model is suitable for an estimation of in-homogeneous material parameter distributions. Moreover, the proposed frequency domain approach allows an automatic adaptation of layer number and thickness or regular grids in time and/or space
Konfektionierung eines Calciumsulfat-Bindemittelsystems zur Herstellung volumenstabiler Fließestrichmörtel
Get PDFBei einem marktüblichen Calciumsulfat-Fließestrich wurden in der Praxis schädigende Volu-menexpansionen festgestellt. Diese sind ein Resultat aus dem Zusammenwirken des einge-setzten Bindemittel-Compounds und einer kritischen Gesteinskörnung.
Das Ziel dieser Arbeit ist es, ein Calciumsulfat-Bindemittelsystem zu konfektionieren, welches in der Lage ist, die im Mörtel festgestellten Volumenexpansionen zu unterbinden. Es sollen verschiedene Bindemittel- und Additivzusammensetzungen untersucht werden, welche in Verbindung mit der kritischen Gesteinskörnung die Herstellung eines volumenstabilen Fließestrichs ermöglichen. Dazu soll folgende Fragestellung beantwortet werden: Welche Ursachen hat die Volumenzunahme und wie ist diese zu minimieren bzw. unterbinden?
Dabei werden unterschiedliche Bindemittelrezepturen aus α-Halbhydrat, Thermoanhydrit und Naturanhydrit, sowie verschiedene Additivzusammensetzungen hergestellt und untersucht.
Durch Längenänderungsmessungen in der Schwindrinne werden die Einflüsse der Binde-mittel, der Additivzusammensetzungen und der Wasser/Bindemittel-Werte auf das Län-genänderungsverhalten untersucht. Mittels Variation der einzelnen Compound-Bestandteile kann festgestellt werden, dass der Stabilisierer die Längenänderung negativ beeinflusst. Dieser bindet freies Wasser, welches für eine Reaktion zwischen Bindemittel und Gesteins-körnung im plastischen Zustand nicht mehr zur Verfügung steht. Diese Reaktion kann folglich erst im erhärteten Zustand ablaufen und verursacht die schädigende Volumenexpansion.
Abschließend wurde ein Bindemittel-Compound konfektioniert, welcher ohne Zusatz von Stabilisierern in Zusammenhang mit der kritischen Gesteinskörnung volumenstabil ist und keine Schäden auslöst