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Nickel-base superalloys display cuboidal precipitates aligned along the cubic directions, which are the elastic soft directions. At high precipitate volume fraction, the microstructure is often described as a regular array of precipitates organized on a simple cubic macro-lattice. In the present work, we use a stability analysis and 3D phase field simulations to show that such a regular array is in fact unstable whatever the volume fraction of precipitates. The two main instability modes are the longitudinal [100] mode and the transverse [110] mode along the [ 1 1 ¯ 0 ] eigenvector. We argue that these instabilities lead to formation of configurational defects closely related to experimentally observed branches and herringbone patterns. The roles of elastic anisotropy and elastic homogeneity are also discussed.

With the rapid development of inverter-based generators (IGs), power grid is faced with critical frequency stability challenges because the existing IGs have no inertia. To equip IGs with inertial response, researchers have proposed several virtual inertia control methods, which can be classified into two categories: virtual synchronous generator (VSG) control and droop control based on rate of change of frequency (ROCOF-droop control). In this paper, the comparison between both virtual inertia control methods is conducted from three perspectives: mathematical model, output characteristic and small-signal stability. State-space models are firstly built to analyze the control mechanism of VSG control and ROCOF-droop control methods. Simulation and eigenvalue analysis are conducted to study the transient responses and oscillation characteristics of both methods, which is helpful to understand the advantages and limitations of existing virtual inertia control methods. Finally, the obtained theoretical results are validated through realtime laboratory (RT-LAB) hardware-in-loop simulation platform.

In recent years, the virtual synchronous generator (VSG) concept has been widely studied to integrate renewable energy sources. However, instability occurs due to the implementation of the dc-link voltage controllers under the weak grid, and its mechanism remains unclear, which is investigated in this article. At first, the wideband dq-frame impedance models of the VSGs with the dc-link voltage controllers for two cases are established. Then, the stability analyses of the VSGs are compared based on these impedance models. It is revealed that the interaction dynamics between the dc-link voltage loop and the active loop lead to the negative resistor behavior of the q-q channel impedances for both VSGs, which induces the emerging oscillations of the system in a weak grid. Besides, as a useful design guideline, the parameter design of the VSGs is proposed to enhance the system stability. Finally, the experimental results obtained from a 100-kW prototype system show good agreement with simulated results, validating the impedance models and theoretical analysis.

Instabile Felsb��schungen und die daraus resultierenden Sturzprozesse stellen eine Bedrohung f��r angrenzende Siedlungsr��ume und Infrastruktur dar. Die M��glichkeit der Beurteilung des Verschiebungsverhaltens und der Stabilit��t von Felsb��schungen ist f��r die Einsch��tzung der von den Felsw��nden ausgehenden Gefahr und f��r die Festlegung von Grenzwerten f��r Warnsysteme von gro��er Bedeutung. In Kooperation mit der Wildbach- und Lawinenverbauung Tirol untersucht die vorliegende Diplomarbeit die Einsatzm��glichkeiten und Grenzen von Synthetic Rock Mass (SRM) Modellen zur Beschreibung des Verschiebungsverhaltens und zur Beurteilung der Stabilit��t von Felsb��schungen.F��r die Untersuchung wurde die Felswand in Vals (Tirol) herangezogen, bei der sicham 24.12.2017 ein Felssturz mit einem Abbruchvolumen von circa 117.000 m3 ereignete. Ziel des Projekts war es das in situ vorliegende Trennfl��chengef��ge mittels eines Discrete Fracture Networks (DFN) detailgetreu abzubilden und in Kombination mit der Diskreten Elemente-Software 3DEC (Itasca Consulting Group) ein realit��tsnahes Gebirgsmodell (SRM-Modell) zur R��ckrechnung des Versagens der Felswand aufzubauen. Dazu wurden Modellrechnungen mit und ohne Ber��cksichtigung der beobachteten keilbildenden Versagensfl��chen aufgebaut. Eine R��ckrechnung des Versagens ohne Ber��cksichtigung der beobachteten Versagensfl��chen stellte sich als schwierig heraus, da ein solches Modell sehr hohe Rechenzeiten erfordert und auf diese Weise die f��r die R��ckrechnung erforderlichen Parametervariationen nicht realisierbar waren. Die R��ckrechnungen unter Ber��cksichtigung der Versagensfl��chen zeigen eine starke Abh��ngigkeit der Modellparameter von der beim DFN ber��cksichtigten Kluftdichte. Die Laborparameter k��nnen also nicht direkt ��bernommen werden, sondern sind lediglich Startwerte f��r die Ermittlung des Grenzgleichgewichts.SRM Modelle sind ein vielversprechender Ansatz, doch aufgrund der Limitierungen infolge der zeitaufwendigen Berechnungen muss derzeit die Kluftdichte noch stark vereinfacht werden.Die im Labor ermittelten Materialparameter sind nicht direkt anwendbar. Dadurch ben��tigenauch SRM-Modelle aufwendige R��ckrechnungen bzw. Parameterstudien zur Bestimmung der Modellparameter., Instable rock slopes and the resulting fall processes are a threat for adjacent settlement areasand infrastructure. The possibility of assessing the displacement behaviour and stability of rock slopes is of great importance for the risk evaluation of rock slopes and for the definition ofl imit values for warning systems.In cooperation with the torrent and avalanche control, present diploma thesis investigatesthe application possibilities and limits of Synthetic Rock Mass (SRM) models to describe the displacement behaviour and to assess the stability of rock slopes. A rock slope in Vals (Tyrol) was investigated, where on 24. December 2017 a rock fall with a source volume of approximately 117.000 m3 occured. The aim of the project was to reconstruct the in situ joint network via a Discrete Fracture Network (DFN) and to build a realistic Synthetic Rock Mass model using the Discrete Element Software 3DEC (Itasca Consulting Group) in order to analyze the initial state of failure of the rock slope. For this purpose model calculations with and without the failure planes (slidingsurface of the observed wedge failure) were set up.The simulation of the failure mechanism without consideration of the observed failure planes turned out to be difficult, due to high computing times. Therefore a back analysis to determine and verify material properties could not be realized. The outcome of the back analysis with the failure planes indicate a strong dependence of the model parameters on the fracture intensity of the DFN. Therefore, the laboratory parameters cannot be transfered directly, but are only starting values for the determination of the limit equilibrium. SRM models are a promising approach but due the limitations resulting from time consuming calculation processes the fracture intensity of the DFN needs to be significantly simplified. Material parameters obtained from laboratory testing are not directly applicable. This means that SRM models also require extensive back analysis or parameter studies to determine the model parameters.

In the present study, the influence of active cooling on hypersonic boundary-layer transition at different Mach numbers, from 7 up to 10, is investigated. The analyses are carried out on a $$7^\circ$$ half-angle, blunted cone with different nose radii and various gas injection mass flow rates. In all cases, low mass fluxes, which do not inducing visible shocks in the schlieren images, are applied. As injection gas nitrogen is used. At the considered free stream conditions, second modes are the dominant boundary-layer instabilities, which are consequently the focus of this study. The stability analyses are performed by means of the stability code NOLOT, NOnLOcal Transition analysis, of the German Aerospace Center (DLR). The influence of different mass injections on the frequencies and growth rates of the second modes is analyzed in detail. The effect on the transition onset locations is discussed. The numerical predictions are compared with experimental results. The experimental data referred to in the present study were obtained in the DLR High Enthalpy Shock Tunnel Gottingen.

In multiphase alloys, internal elastic fields often arise as a result of a coherently adjusted misfit between the lattices of coexisting phases. Given their long-range and usually anisotropic nature, the interaction of these fields is known to significantly alter the kinetics of diffusion-controlled phase transformations, as well as influence the shapes and spatial arrangement of the misfitting precipitates. In the microstructure of single-crystal nickel-base superalloys, obtained by precipitation of the L12-ordered γ’ phase in the FCC γ matrix, elasticity leads to the formation of nearly periodic alignments of the cuboidal γ’ precipitates. However, the γ/γ’ microstructure systematically displays defects in the precipitate alignment: branches, macro-dislocations and chevron patterns. We first address the question of the origin of these alignment defects. Stability analyses of the periodic arrangement of elastically interacting precipitates are carried out. Contrary to the expected stability, the semi-analytical calculations revealed the periodic distribution of cubic γ‘ precipitates to be unstable against specific perturbation modes. The main instabilities are the [100] longitudinal mode and the [110] transverse mode, and their instability range is analyzed with respect to the elastic anisotropy. The consequences of these unstable modes are investigated using a classic phase field method, by modeling the evolution of periodic microstructures undergoing small initial perturbations. We show the expression of the instabilities mainly proceeds by the evolution of the precipitate shapes, and leads to the formation of patterns which were related to experimental microstructures. Specifically, the [110] transverse instability is responsible for the formation of chevron patterns. The effects of the volume fraction and of an inhomogeneity on the C’ shear modulus on the stability of the arrangement are studied, and we show the role they play in the partial stabilization of the periodic distribution, though the [100] longitudinal mode always remains unstable. In phase field calculations carried out in previous studies, the dynamics of alignment defects are analyzed by means of topological parameters derived from pattern formation theory. During annealing, branches and macro-dislocations were observed to migrate in the microstructure according to climbing and gliding mechanisms. We then use a new formulation of phase field models, intrinsically discrete, in which the interfaces are resolved with essentially one grid point with no pinning on the grid and an accurate rotational invariance. This approach, known as the Sharp Phase Field Method (S-PFM), is implemented on a FCC grid and accounts for the four translational variants of the γ’ precipitates. We show that the S-PFM allows for the modeling of large-scale microstructures, with several thousand precipitates both in two and three dimensions, and provides access to statistical information on the microstructure evolution and on the the dynamics of alignment defects. We finally discuss the perspective of modeling the evolution of the γ/γ’ microstructure at the macroscale by means of a description of the defect dynamics in the precipitate alignments.; Dans les alliages multiphasés, la cohérence des interfaces entre des phases en désaccord paramétrique génère des champs élastiques internes à longue distance et généralement anisotropes. L'interaction de ces champs affecte fortement la cinétique des transformations de phase diffusives, et influence la forme et l'arrangement spatial des précipités. Dans la microstructure des superalliages monocristallins à base de nickel, obtenue par précipitation de la phase γ’ ordonnée L12 dans la matrice CFC γ, l'élasticité conduit à la formation d'alignements quasi-périodiques des précipités γ’ cuboïdaux. La microstructure γ/ γ’ possède cependant des défauts systématiques d'alignement des précipités: des branches, des macro-dislocations et des motifs en chevrons. Nous nous intéressons à l'origine de ces défauts d'alignement. Nous conduisons des analyses de stabilité de l'arrangement périodique de précipités en interactions élastiques. Contrairement à la stabilité attendue, les calculs semi-analytiques ont révélé l'instabilité de la distribution périodique de précipités γ’ cubiques, vis-à-vis de certains modes de perturbation. Les principales instabilités sont le mode longitudinal [100] et le mode transverse [110], et leur domaine d'instabilité est analysé vis-à-vis de l'anisotropie élastique. Le développement de ces modes instables est étudié par une méthode de champ de phase classique, en simulant l'évolution de microstructures périodiques soumises à des légères perturbations initiales. Nous montrons que l'expression des instabilités d'arrangement procède essentiellement par l'évolution de la forme des précipités, et conduit à la formation de motifs qui ont pu être reliés à des microstructures expérimentales. En particulier, le mode transverse [110] conduit à la formation de motifs en chevrons. Nous étudions l'influence du taux de phase γ’ et de l'inhomogénéité du module élastique C’, et nous montrons le rôle qu'ils jouent dans la stabilisation de l'arrangement périodique. Dans des simulations réalisées dans des études antérieures, la dynamique des défauts est analysée au moyen de paramètres topologiques issus de la phénoménologie des structures hors-équilibre. Au cours d'un recuit isotherme, nous observons que les branches et les macro-dislocations migrent dans la microstructure selon des mécanismes de montée et de glissement. Nous utilisons ensuite une nouvelle formulation des modèles de champ de phase, intrinsèquement discrète, dans laquelle les interfaces sont résolues essentiellement avec un pas de grille sans friction de réseau et avec une invariance par rotation précise. Cette approche, appelée Sharp Phase Field Method (S-PFM), est implémentée sur une grille CFC, et avec une description des quatre variants de translation des précipités γ’. Nous montrons que la S-PFM permet la modélisation de microstructures à grande échelle, avec plusieurs milliers de précipités à deux et trois dimensions, et donne ainsi accès à des informations statistiques sur l'évolution de la microstructure et sur la dynamique des défauts d'alignement. Nous discutons finalement la perspective de modéliser l'évolution de la microstructure γ/γ’ à une échelle supérieure par une description de la dynamique des défauts d'alignement des précipités.

In multiphase alloys, internal elastic fields often arise as a result of a coherently adjusted misfit between the lattices of coexisting phases. Given their long-range and usually anisotropic nature, the interaction of these fields is known to significantly alter the kinetics of diffusion-controlled phase transformations, as well as influence the shapes and spatial arrangement of the misfitting precipitates. In the microstructure of single-crystal nickel-base superalloys, obtained by precipitation of the L12-ordered γ’ phase in the FCC γ matrix, elasticity leads to the formation of nearly periodic alignments of the cuboidal γ’ precipitates. However, the γ/γ’ microstructure systematically displays defects in the precipitate alignment: branches, macro-dislocations and chevron patterns. We first address the question of the origin of these alignment defects. Stability analyses of the periodic arrangement of elastically interacting precipitates are carried out. Contrary to the expected stability, the semi-analytical calculations revealed the periodic distribution of cubic γ‘ precipitates to be unstable against specific perturbation modes. The main instabilities are the [100] longitudinal mode and the [110] transverse mode, and their instability range is analyzed with respect to the elastic anisotropy. The consequences of these unstable modes are investigated using a classic phase field method, by modeling the evolution of periodic microstructures undergoing small initial perturbations. We show the expression of the instabilities mainly proceeds by the evolution of the precipitate shapes, and leads to the formation of patterns which were related to experimental microstructures. Specifically, the [110] transverse instability is responsible for the formation of chevron patterns. The effects of the volume fraction and of an inhomogeneity on the C’ shear modulus on the stability of the arrangement are studied, and we show the role they play in the partial stabilization of the periodic distribution, though the [100] longitudinal mode always remains unstable. In phase field calculations carried out in previous studies, the dynamics of alignment defects are analyzed by means of topological parameters derived from pattern formation theory. During annealing, branches and macro-dislocations were observed to migrate in the microstructure according to climbing and gliding mechanisms. We then use a new formulation of phase field models, intrinsically discrete, in which the interfaces are resolved with essentially one grid point with no pinning on the grid and an accurate rotational invariance. This approach, known as the Sharp Phase Field Method (S-PFM), is implemented on a FCC grid and accounts for the four translational variants of the γ’ precipitates. We show that the S-PFM allows for the modeling of large-scale microstructures, with several thousand precipitates both in two and three dimensions, and provides access to statistical information on the microstructure evolution and on the the dynamics of alignment defects. We finally discuss the perspective of modeling the evolution of the γ/γ’ microstructure at the macroscale by means of a description of the defect dynamics in the precipitate alignments., Dans les alliages multiphasés, la cohérence des interfaces entre des phases en désaccord paramétrique génère des champs élastiques internes à longue distance et généralement anisotropes. L'interaction de ces champs affecte fortement la cinétique des transformations de phase diffusives, et influence la forme et l'arrangement spatial des précipités. Dans la microstructure des superalliages monocristallins à base de nickel, obtenue par précipitation de la phase γ’ ordonnée L12 dans la matrice CFC γ, l'élasticité conduit à la formation d'alignements quasi-périodiques des précipités γ’ cuboïdaux. La microstructure γ/ γ’ possède cependant des défauts systématiques d'alignement des précipités: des branches, des macro-dislocations et des motifs en chevrons. Nous nous intéressons à l'origine de ces défauts d'alignement. Nous conduisons des analyses de stabilité de l'arrangement périodique de précipités en interactions élastiques. Contrairement à la stabilité attendue, les calculs semi-analytiques ont révélé l'instabilité de la distribution périodique de précipités γ’ cubiques, vis-à-vis de certains modes de perturbation. Les principales instabilités sont le mode longitudinal [100] et le mode transverse [110], et leur domaine d'instabilité est analysé vis-à-vis de l'anisotropie élastique. Le développement de ces modes instables est étudié par une méthode de champ de phase classique, en simulant l'évolution de microstructures périodiques soumises à des légères perturbations initiales. Nous montrons que l'expression des instabilités d'arrangement procède essentiellement par l'évolution de la forme des précipités, et conduit à la formation de motifs qui ont pu être reliés à des microstructures expérimentales. En particulier, le mode transverse [110] conduit à la formation de motifs en chevrons. Nous étudions l'influence du taux de phase γ’ et de l'inhomogénéité du module élastique C’, et nous montrons le rôle qu'ils jouent dans la stabilisation de l'arrangement périodique. Dans des simulations réalisées dans des études antérieures, la dynamique des défauts est analysée au moyen de paramètres topologiques issus de la phénoménologie des structures hors-équilibre. Au cours d'un recuit isotherme, nous observons que les branches et les macro-dislocations migrent dans la microstructure selon des mécanismes de montée et de glissement. Nous utilisons ensuite une nouvelle formulation des modèles de champ de phase, intrinsèquement discrète, dans laquelle les interfaces sont résolues essentiellement avec un pas de grille sans friction de réseau et avec une invariance par rotation précise. Cette approche, appelée Sharp Phase Field Method (S-PFM), est implémentée sur une grille CFC, et avec une description des quatre variants de translation des précipités γ’. Nous montrons que la S-PFM permet la modélisation de microstructures à grande échelle, avec plusieurs milliers de précipités à deux et trois dimensions, et donne ainsi accès à des informations statistiques sur l'évolution de la microstructure et sur la dynamique des défauts d'alignement. Nous discutons finalement la perspective de modéliser l'évolution de la microstructure γ/γ’ à une échelle supérieure par une description de la dynamique des défauts d'alignement des précipités.

Açık ocak basamaklarında şev duraysızlığı oluşması sonucu meydana gelen kaymalar yaşam kaybı yanında ekonomik kayıplara ve ocak geometrisinin bozulması gibi sonuçlara neden olabilmektedir. Bu tür olayların önüne geçilmesi için alınması gereken tedbirlerin başında emniyetli jeoteknik tasarımlar, desteklemeler, kaya düşme önleme sistemleri ve şevlerde oluşan deformasyonların değişiminin izlenmesi gelmektedir. Bu çalışma, günümüzde halen Yatağan Termik AŞ bünyesine olan ancak ölçümlerin yapıldığı yıl olan 2011’de Türkiye Kömür İşletmeleri Güney Ege Linyitleri İşletmesi’ne (TKİ-GELİ) bağlı olan Yatağan–Eskihisar linyit açık ocağında gerçekleştirilmiştir. Ocakta yapılan incelemeler ve ön değerlendirmeler neticesinde ocağın batı tarafındaki şevlerde şev duraysızlığı olasılığı bulunan alanlar tespit edilmiştir. Bu alanlarda karşılaşılan ve tehlike yaratacağından kuşkulanılan şevdeki hareketi izlemek amacıyla tespit edilen çekme çatlağındaki deformasyon değişimlerinin izlenmesine karar verilmiştir. Bu kapsamda sahada belirlenen bu sorunlu bölgelerde izleme çalışmaları yapılmasına karar verilmiştir. Ocakta dekapaj ve kömür üretimi sonrası batı şevlerinde oluşan gerilim çatlakları ve buna bağlı gelişen şev duraysızlığı olasılığı nedeniyle ölçüm istasyonları kurularak, jeodezik ölçüm yöntemleriyle 216 günlük bir süreçte belirli aralıklarla şev hareketliliği izlenmiştir. Elde edilen veriler sonucunda şevdeki deformasyon hareketliliği değerlendirilmiş ve hareketin orta hızlı bir eğilimde devam ettiği belirlenmiştir. Bu hareketliliğe bağlı bir matematiksel eşitlik geliştirilmiştir. Geliştirilen model sonuçları ile gerçek veriler arasında yüksek korelasyon mevcuttur. Bu model ile şevde gelecekte oluşabilecek deformasyon miktarları ve hızlarını tahmin etme ihtimali oluşabilecektir., Slope sliding and landslides occurring on the open pit benches can lead to consequences such as the loss of life as well as the economic loss and deterioration of the stove geometry. Safe geotechnical designs, supports, rock fall prevention systems and monitoring the deformations occurring on the slopes are among the most familiar precautions which must be taken to prevent these consequences. This study is performed in Muğla Province Yatağan District Eskihisar lignite open pit mine which was in the management of TKİ-GELİ (Turkish Coal Enterprises-South Aegean Lignite Management) in 2011. As a result of investigations and preliminary assessments at the mine regions which have instability problems were identified at the western side of the mine. Then, it is decided to monitor these regions which could have instability problems. Measurement stations were set up on the tension cracks which are the signs of a probable instability problem at the western slopes and slope movements were monitored periodically for 216 days by geodetic measurement methods. As a result of the obtained data deformation movements were evaluated and it was determined that the movement was continuing in a moderate velocity trend. A mathematical model was developed related to these movements. It was seen that there is a good correlation between the results of the model and the in-situ data. It will be possible to predict future deformation rates and velocities on the slopes of this location with this model., DOI: 10.15317/Scitech.2017.93 URL: http://sujest.selcuk.edu.tr/sumbtd/article/view/430

Driver assistance systems support drivers in operating vehicles in a safe, comfortable and efficient way, and thus may induce changes in traffic flow characteristics. This paper puts forward a receding horizon control framework to model driver assistance and cooperative systems. The accelerations of automated vehicles are controlled to optimise a cost function, assuming other vehicles driving at stationary conditions over a prediction horizon. The flexibility of the framework is demonstrated with controller design of Adaptive Cruise Control (ACC) and Cooperative ACC (C-ACC) systems. The proposed ACC and C-ACC model characteristics are investigated analytically, with focus on equilibrium solutions and stability properties. The proposed ACC model produces plausible human car-following behaviour and is unconditionally locally stable. By careful tuning of parameters, the ACC model generates similar stability characteristics as human driver models. The proposed C-ACC model results in convective downstream and absolute string instability, but not convective upstream string instability observed in human-driven traffic and in the ACC model. The control framework and analytical results provide insights into the influences of ACC and C-ACC systems on traffic flow operations., Comment: Submitted to Transportation Research Part C: Emerging Technologies

En éste artículo se analizan diferentes mecanismos de rotura típicamente asociados a taludes de muro, con el objetivo de poder evaluar su estabilidad, mediante el código numérico UDEC (Código de Elementos Distintos Universal). Se analizan, también, mediante métodos de equilibrio límite (MEL), comparándose los resultados obtenidos por ambos métodos, a fin de determinar la validez del código UDEC como herramienta de análisis de la estabilidad de taludes de muro. Se incluye además, el análisis de dos casos reales, en los que la rotura del talud se produjo por mecanismos complejos.

The traffic engineering community currently faces the advent of a new generation of Intelligent Transportation Systems (ITS), known as cooperative systems. More specifically, the recent developments of connected and autonomous vehicles, i.e. cooperative vehicles, are expected to cause a societal shift, changing the way people commute on a daily basis and relate to transport in general. The research presented in this dissertation is motivated by the need for proper understanding of the possible inputs of cooperative vehicles in a traffic stream. Beyond legal aspects regarding the introduction of such vehicles and considerations on standardization and harmonization of the communication norms, the research focuses on the use of communication for highway traffic flow homogenization. In particular, the selected approach for the introduction of cooperation inherits from the theory of traffic flow and the recent developments of microscopic traffic models. Cooperation can first be introduced as a form of multi-anticipation, which can either come from drivers' behaviors or from communication. A mathematical framework for investigating the impact of perturbations into a steady-state traffic is proposed for the class of time continuous car-following models. Linear stability analyses are refined for forward and backward multi-anticipation, exploring the underlying importance of considering upstream information. The linear stability analyses for all wavelengths can be deepened by the mean of the graphical root locus analysis, which enables comparisons and design of strategies of cooperation. The positive influence of bilateral cooperation and of added linear control terms are highlighted. Weakly non-linear analyses are also performed, and the equations of solitary waves appearing at the frontier of the instability domain are obtained. A simple condition over the partial derivatives of the dynamical system is found to determine the acceleration regime of the leading edge of the travelling wave. Following these analytical results, one aim is to simulate a realistic traffic thereby reproducing the driving behavior variability. A Next Generation Simulation trajectory dataset is used to calibrate three continuous car-following models. A methodology involving data filtering, robust calibration, parameters estimation and sampling of realistic parameters is detailed, and allows realistic traffic with stop-and-go waves appearances to be replicated. Based on these simulated trajectories, previous analytical results are confirmed, and the growing perturbations are removed for various coverage rates of cooperative vehicles and adequately tuned cooperative strategies. Finally the issue of information reliability is assessed for a mixed fleet of cooperative and non-cooperative vehicles. The modeling choice consists in building a three layers multi-agent framework that enables the following properties to be defined: the physical behavior of vehicles, the communication possibilities, and the trust each vehicle -or agent- has in another vehicle information or in itself. The investigation of trust and communication rules allow the model to deal with high rates of disturbed cooperative vehicles sensors and to learn in real time the quality of the sent and received information. It is demonstrated that appropriate communication and trust rules sensibly increase the robustness of the network to perturbations coming from exchanges of unreliable information.

The Grohovo Landslide is a reactivated complex landslide in the outback of the City of Rijeka, Croatia. Several historical episodes of landslide movements and consequences demonstrate the needs for a landslide forecasting and an early warning system in order to reduce related hazard and risk and to protect human lives. The part of the Rječina River Valley between the Valići Reservoir and the Pašac Bridge is the most unstable part of the City of Rijeka area, with a highest hazard of possible sliding. Numerous historical descriptions, figures and maps describing landslides were found in the Croatian State Archive in Rijeka. An early warning system for possible landslide occurrence and assessment of landslide risk in the Rječina River Valley should be established based on possibility of prediction of instabilities appearances in the zones where the monitoring equipment is installed. Prediction of possible movements would be carried out on the basis of the results of 2D or 3D landslide stability analyses of wider landslide area in combination with the results of existing monitoring data. Critical limit values must be also defined for indicating of new sliding appearance and starting up the alarm. The 3D landslide stability analyses enable indication of possible hazard and risk for further landslide occurrences under unfavorable hydrological conditions in the most unstable part of the Rječina River Valley. The 3D stability analyses were carried out using landslide simulation model software LS-Rapid. LS-Rapid software could integrate the initiation of the landslide process triggered by rainfalls and the development of sliding due to strength reduction and the entrainment of deposits in the run out path. Stability analyses are based on strength parameters obtained by laboratory test on soil samples taken from the zones in which should be developed sliding surfaces. Soil testing were conducted on representative samples in a portable ring shear apparatus ICL- 1 designed for testing the residual shear resistance mobilized along the sliding surface at large shear displacements under static and/or dynamic local conditions. The results of the ring shear tests are necessary to enable input data for analyses of the development and propagation of the sliding mass in LS-Rapid software. In this paper will be presented deterministic 3D stability analyses using LS- Rapid software applied on the wider zone of the Grohovo Landslide at the north-eastern slope of the Rječina River Valley. The results of these analyses enabled prediction of possible sliding zones so as critical groundwater conditions (expressed by saturation ratio) those will cause sliding. Critical groundwater conditions could be connected with precipitation values, run off coefficients and infiltration ratios and these correlations will be used as an indicator of possible sliding in an early warning system. The most important indicators for alarm decision should be measured values on installed monitoring equipment in the moment when measured values reach proposed critical values.

Dams are designed and assessed based on traditional factor of safety methodology. Several drawbacks of this approach exist; for example varying failure probability for structures where the factor of safety is the same. This traditional factor of safety methodology imposes conservative assumptions in terms of both design and analysis. A probability-based analysis has been suggested to account for the omission of uncertainties and provide a less conservative analysis (Westberg & Johansson, 2014). Through the stability analyses of three existing dam structures, a minimum level of reliability or maximum failure probability may be calculated with the ultimate goal of defining a target safety index (β-target) for buttress and gravity dams. These analyses shall in turn contribute to the formulation of a probability-based guideline for the design and assessment of Swedish concrete dams. This probability-based guideline shall be known as the ‘Probabilistic Model Code for Concrete Dams.’ The calculations carried out in this study adhere to the methodologies and specifications set out in the preliminary draft of the Probabilistic Model Code for Concrete Dams. These methodologies encompass analyses within two dominating failure modes for concrete dams; sliding stability and overturning stability. Various load combinations have been modelled for each dam structure to account for the probabilistic failure of each dam under commonly occurring circumstances. A parametric study has been carried out in order to provide insight into the contribution that existing rock bolts provide to the stability of each dam. Furthermore, a study has been carried out into the existence of a persistent rock joint or failure plane in the rock foundation and the effects its presence would have on the sliding stability of a dam. Finally a discussion had been carried out in order to provide suggestions into the formulation of a target safety index through the data envisaged by our analyses for the design and assessment of Swedish concrete dams.

Driver assistance systems support drivers in operating vehicles in a safe, comfortable and efficient way, and thus may induce changes in traffic flow characteristics. This paper puts forward a receding horizon control framework to model driver assistance and cooperative systems. The accelerations of automated vehicles are controlled to optimise a cost function, assuming other vehicles driving at stationary conditions over a prediction horizon. The flexibility of the framework is demonstrated with controller design of Adaptive Cruise Control (ACC) and Cooperative ACC (C-ACC) systems. The proposed ACC and C-ACC model characteristics are investigated analytically, with focus on equilibrium solutions and stability properties. The proposed ACC model produces plausible human car-following behaviour and is unconditionally locally stable. By careful tuning of parameters, the ACC model generates similar stability charac- teristics as human driver models. The proposed C-ACC model results in convective downstream and absolute string instability, but not convective upstream string instability observed in human-driven traffic and in the ACC model. The control framework and analytical results provide insights into the influences of ACC and C-ACC systems on traffic flow operations.

This paper reports in situ test results and monitoring performed to characterise the development of a gravitational phenomenon. Analysis made it possible to create a 3D subsoil model to identify the main preferential paths of groundwater seepage, the boundaries of the subsidence area and the relationships between rainfall and displacements. The results of seepage and stability analyses highlight some aspects that characterise the kinematical mechanism of the slope. Displacements show a constant increase over time independently from the pluviometric regime. Stratigraphic sections and geophysical investigations highlight that the subsidence basin was formed just above a morphological bedrock depression and was filled with weathered gypseous arenite and sandy silt. The slow and constant sinking of the cover may be ascribed to the progressive collapse of the voids created through karstification within the gypseous rock mass and which attract loose material from above causing vertical and horizontal movements.

URL: http://sujest.selcuk.edu.tr/sumbtd/article/view/230, Açık ocak madencilik çalışmaları esnasında oluşturulan şevlerde oluşabilecek şev duraysızlıkları sonucu meydana gelen kaymalar ve heyelanlar yaşam kayıplarına, yaralanmalara ve ekonomik kayıplara neden olabilmektedir. Bu tür kayıpların önüne geçebilmek için çeşitli yollar mevcuttur. Bunlar emniyetli jeoteknik tasarımlar, desteklemeler, kaya düşme önleme sistemleri ve şevlerin önceden uyarı için izlenmesi olarak sıralanabilir. Bu çalışmanın amacı Konya’nın Ilgın ilçesinde bulunan TKİ-GLİ Ilgın linyit açık ocağında dekapaj ve kömür üretimi sonrası batı şevlerinde oluşan gerilim çatlaklarının hareketlerinin kurulan istasyonlar yardımı ile belirli aralıklarla ölçülerek şev hareketliliğinin izlenmesi, bu ölçümlerden elde edilen verilerin matematiksel modellenmesi ve elde edilen bu verilerin gerçek veriler ile karşılaştırılmasıdır. Bu kapsamda sahada 55 gün boyunca şev hareketliliği izlenmiş ve elde edilen deformasyon verileri modellenmiştir., Landslides which occur as a result of slope failures during open pit mining operations can cause loss of life, injuries and economic losses. In order to prevent these losses some solutions are available such as reliable geotechnical designs, slope supports, rock fall protection systems and monitoring slopes for early warning. Purpose of this study is measuring the movements of the tension cracks after overburden removal and coal production by the help of established stations at regular intervals, mathematical modeling of these data and comparing with field data at the western slopes of TKI-GLI open pit lignite mine in the district of Konya-Ilgın. Consequently slope movements were monitored for 55 days and obtained deformation data were modeled.

Driver assistance systems support drivers in operating vehicles in a safe, comfortable and efficient way, and thus may induce changes in traffic flow characteristics. This paper put forward a receding horizon control framework to model driver assistance systems. The accelerations of automated vehicles are determined to optimise a cost function, assuming other vehicles driving at stationary conditions over a prediction horizon. The flexibility of the framework is demonstrated with controller design of Adaptive Cruise Control (ACC)systems. The proposed ACC model characteristics are investigated analytically, with focus on equilibrium solutions and stability properties. The proposed ACC model is unconditionally locally stable. By careful tuning of parameters, the ACC model generates similar stability characteristics as human driver models.

Safety of dams can be evaluated based on the risk analysis methodologies that accounts for estimation of the risks associated to the dam-reservoir system. For this purpose it is important to estimate the probability of load events and probability of failure for several failure modes. The following thesis emphasises on estimation of the probability of one specific failure mode, i.e. “sliding failure” for a concrete gravity dam. The main idea behind this thesis was to analyse the estimation of the probability of sliding failure of an existing dam by obtaining the relationships among the different load events, factors of safety associated to those events and the probability of failure estimated using numerical simulation techniques together with different reliability methods. The analysed dam is taken from theme C of the eleventh ICOLD Benchmark workshop on numerical analysis of dams. The thesis covers the methodology for estimating the probability of failure of a given concrete gravity dam with five water levels, considering the sliding failure mode along the dam-foundation interface along with the estimation of factors of safety for each water level and with two different drainage conditions. First order second moment Taylor’s Series Approximation is being used as Level 2 reliability method and Monte Carlo simulation as Level 3 reliability method to estimate the probability of failure against sliding of the dam. Conclusions are drawn in the end by comparing the results obtained from factor of safety estimation and probability of failure for each water level and drainage condition, followed by suggestions for further research in the context of sliding stability of concrete dams.

The paper deals with design and practice of reinforced earth walls (REWs) in karst region at the highway Split-Ploče. It is discussed that REWs are suitable type of retaining structure in karst, because, besides satisfying the criteria for serviceability and stability, they comply with karst environment visually, as they recall to traditional means of building of retaining constructions in the area which are dry-stone-walls. REWs also serve for protection of environment, because they may play roll as storage for a great amount of crushed stone that is produced by cutting way through rocks. On the other hand, crushed stone is very suitable for REWs because of its high frictional resistance characteristics. In the paper, shortly is presented a stability calculation for REWs Strikići, the highest from until now built REW along the Split – Ploče highway. Discussed is also, due to ground rock characteristics, a possibility for building RE walls of extreme dimensions.

Many authors have been proposed several correlation equations between geomechanical classifications and strength parameters. However, these correlation equations have been based in rock masses with different characteristics when compared to Brazilian rock masses. This paper aims to study the applicability of the geomechanical classifications to obtain strength parameters of three Brazilian rock masses. Four classification systems have been used; the Rock Mass Rating (RMR), the Rock Mass Quality (Q), the Geological Strength Index (GSI) and the Rock Mass Index (RMi). A strong rock mass and two soft rock masses with different degrees of weathering located in the cities of Ouro Preto and Mariana, Brazil; were selected for the study. Correlation equations were used to estimate the strength properties of these rock masses. However, such correlations do not always provide compatible results with the rock mass behavior. For the calibration of the strength values obtained through the use of classification systems, ​​stability analyses of failures in these rock masses have been done. After calibration of these parameters, the applicability of the various correlation equations found in the literature have been discussed. According to the results presented in this paper, some of these equations are not suitable for the studied rock masses.

Driver assistance systems support drivers in operating vehicles in a safe, comfortable and efficient way, and thus may induce changes in traffic flow characteristics. This paper put forward a receding horizon control framework to model driver assistance systems. The accelerations of automated vehicles are determined to optimise a cost function, assuming other vehicles driving at stationary conditions over a prediction horizon. The flexibility of the framework is demonstrated with controller design of Adaptive Cruise Control (ACC)systems. The proposed ACC model characteristics are investigated analytically, with focus on equilibrium solutions and stability properties. The proposed ACC model is unconditionally locally stable. By careful tuning of parameters, the ACC model generates similar stability characteristics as human driver models.