Global ETD Search

201	Повышение технико-эксплуатационных показателей и дорожной безопасности автомобильных поездов путем модернизации опорно-поворотных устройств : магистерская диссертация / Improving technical and operational performance and road safety of road trains by upgrading the pivoting devices Желев, Д. Й., Zhelev, D. I. January 2019 (has links) В магистерской диссертации определены закономерности изменения тягово-эксплуатационных свойств и конструктивной безопасности автопоезда при модернизации тягово-сцепного устройства, уточнены методики определения параметров опорно-поворотного устройства с наклонной поворотной платформой, предложены конструкции тягово-сцепных устройств и представлены результаты испытаний масштабной модели автопоезда на ленточной конвейерной дорожке. / This master thesis the regularities of the change of traction and the performance and structural safety of the trains when upgrading trailer hitch, refined methods of determining the parameters of support-rotating device with a tilted turntable and the proposed design of the hitch and the results of tests of scale model train on a conveyor track. АВТОПОЕЗД РАДИУС ПОВОРОТАЯ МАНЕВРЕННОСТЬ НАКЛОН ОСИ ШКВОРНЯ СТАБИЛИЗАЦИЯ КОЛЕС MASTER'S THESIS TRAILER HITCH TRAILER IMPROVING AERODYNAMICS TURNING RADIUS MANOEUVRABILITY DRAWBAR TRAILER THE TILT AXIS OF THE PIVOT THE TIME OF STABILIZATION WHEELS
202	Belief-aided Robust Control for Remote Electrical Tilt Optimization Jönsson, Jack January 2021 (has links) Remote Electrical Tilt (RET) is a method for configuring antenna downtilt in base stations to optimize mobile network performance. Reinforcement Learning (RL) is an approach to automating the process by letting an agent learn an optimal control strategy and adapt to the dynamic environment. Applying RL in real world comes with challenges, for the RET problem there are performance requirements and partial observability of the system through exogenous factors inducing noise in observations. This thesis proposes a solution method through modeling the problem by a Partially Observable Markov Decision Process (POMDP). The set of hidden states are modeled as a high- level representation of situations requiring one of the possible actions uptilt, downtilt, no change. From this model, a Bayesian Neural Network (BNN) is trained to predict an observation model, relating observed Key Performance Indicators (KPIs) to the hidden states. The observation model is used for estimating belief state probabilities of each hidden state, from which decision of control action is made through a restrictive threshold policy. Experiments comparing the method to a baseline Deep Q- network (DQN) agent shows the method able to reach the same average performance increase as the baseline while outperforming the baseline in two metrics important for robust and safe control behaviour, the worst- case minimum reward increase and the average reward increase per number of tilt actions. / Fjärrstyrning av Elektrisk Lutning (FEL) är en metod för att reglera lutningen av antenner i basstationer för att optimera presentandan i ett mobilnätverk. Förstärkande Inlärning (FI) används som metod för att automatisera processen genom att låta en agent lära sig en optimal strategi för reglering och anpassa sig till den dynamiska miljön. Att tillämpa FI i ett verkligt scenario innebär utmaningar, för FEL specifikt finns det krav på en viss nivå av prestanda samt endast en delvis observerbarhet av systemet på grund av externa faktorer som orsakar brus i observationerna. I detta arbete föreslås en metod för att hantera detta genom att modellera problemet som en Delvis Observerbar Markovprocess (DOM). De dolda tillstånden modelleras för att representera situationer där var och en av de möjliga aktionerna behövs, det vill säga att luta antennen upp, ner eller inte ändra på lutningen. Utifrån denna modellering så tränas ett Bayesiskt Neuralt Nätverk (BNN) för att estimera en observationsmodel som kopplar observerade nyckeltal till de dolda tillstånden. Denna observationsmodel används för att estimera sannolikheten att vardera dolt tillstånd är det rätta. Utifrån dessa sannolikheter så görs valet av aktion genom ett tröskelvärde på sannolikheterna. Genom experiment som jämför metoden med en standardimplementering av en agent baserad på ett Djupt Qnätverk (DQN) visas att metoden har samma prestation när det kommer till en medelnivå på prestandaökning i nätverket. Metoden överträffar dock standardmetoden i två andra mätvärden som är viktiga ur aspekten säker och robust reglering, minimumvärdet på prestandaökningen samt medelökningen av prestandan per antal up- och nerlutningar som används. Mobile Network Optimization Remote Electrical Tilt Robust Control Reinforcement Learning Belief State Estimation Bayesian Neural Network Optimering av Mobilnätverk Fjärrstyrning av Elektrisk Lutning Robust Reglering Delvis Observerbar Markovprocess Tillståndsestimering Bayesiskt Neuralt Nätverk Elektroteknik och elektronik
203	Vysokovklopn lopata devn tÄpky / High tipping shovel for the wood chips ulk, Petr January 2021 (has links) High tipping shovel, wood chips, quick coupler, shovel, high tipping shovel frame, Volvo L60H loader, wheel loader accessories, linear hydraulic motor
204	Mesure du tilt atmosphérique à partir de sa variation chromatique pour l'étoile laser polychromatique Vaillant, Jérôme 03 October 2002 (has links) (PDF) L'utilisation de grands télescopes rend de plus en plus nécessaire l'emploi de l'optique adaptative qui permet de corriger l'effet de la turbulence atmosphérique. Toutefois cette technique est limitée par le nombre de sources de référence. L'étoile laser permet de pallier ce manque en créant artificiellement une source lumineuse, que l'on peut placer à volonté sur la voûte céleste, au-dessus des couches turbulentes. Or, par cette technique, on ne mesure que les déformations des images mais pas leur déplacement qui est pourtant l'effet le plus important. L'étoile laser polychromatique propose de le corriger également, à partir de la différence chromatique du tilt atmosphérique. Cette mesure différentielle nécessite une grande précision et sa faisabilité n'avait pas encore été démontrée. Pour cela, j'ai conçu et réalisé une expérience dénommée MaTilD (Manipulation de Tilt Différentiel). Le signal à mesurer étant très faible, j'ai développé deux traitements distincts : i) l'estimation des angles d'arrivée par mesure du centre de gravité des images, ii) l'estimation du tilt de la surface d'onde par ajustement d'un modèle sur les images. Le premier traitement m'a permis de mettre en évidence l'existence du chromatisme du tilt. Mais la précision obtenue est inférieure à ce que prédit l'étude théorique que j'en ai faite. Le but du second algorithme est donc d'améliorer cette précision en s'affranchissant d'une partie des limitations de la mesure du centre de gravité : fenêtrage, chevauchement des images, sensibilité élevée au bruit, ... On est alors dans le cadre général de la minimisation de fonctions non-linéaires dans un espace multidimensionnel (typiquement plusieurs dizaines de paramètres). J'ai contribué au développement et aux tests d'une méthode permettant de réduire significativement le nombre de dimensions de cet espace. Étoile laser indétermination du tilt traitment d'image reconstruction de surface d'onde
205	OPTIMIZING PORT GEOMETRY AND EXHAUST LEAD ANGLE IN OPPOSED PISTON ENGINES Beau McAllister Burbrink (11792630) 20 December 2021 (has links) <div>A growing global population and improved standard of living in developing countries have resulted in an unprecedented increase in energy demand over the past several decades. While renewable energy sources are increasing, a huge portion of energy is still converted into useful work using heat engines. The combustion process in diesel and petrol engines releases carbon dioxide and other greenhouse gases as an unwanted side-effect of the energy conversion process. By improving the efficiency of internal combustion engines, more chemical energy stored in petroleum resources can be realized as useful work and, therefore, reduce global emissions of greenhouse gases. This research focused on improving the thermal efficiency of opposed-piston engines, which, unlike traditional reciprocating engines, do not use a cylinder head. The cylinder head is a major source of heat loss in reciprocating engines. Therefore, the opposed-piston engine has the potential to improve overall engine efficiency relative to inline or V-configuration engines.</div><div><br></div>The objective of this research project was to further improve the design of opposed-piston engines by using computational fluid dynamics (CFD) modeling to optimize the engine geometry. The CFD method investigated the effect of intake port geometry and exhaust piston lead angle on the scavenging process and in-cylinder turbulence. After the CFD data was analyzed, scavenging efficiency was found insensitive to transfer port geometry and exhaust piston lead angle with a maximum change of 0.61%. Trapping efficiency was altered exclusively by exhaust piston lead angle and changed from 18% to 26% as the lead angle was increased. The in-cylinder turbulence parameters of the engine (normalized swirl circulation, normalized tumble circulation, and normalized TKE) experienced more complex relationships. All turbulence parameters were sensitive to changing transfer port geometry and exhaust piston lead angle. Some examples of trends seen during the analysis include: an increase in normalized swirl circulation from 0.01 to 4.45 due to changes in swirl angle, a change in normalized tumble circulation from -28.52 to 21.11 as swirl angle increased, and an increase in normalized tumble circulation from 14.20 to 33.68 as exhaust piston lead angle was increased. Based on the present work, an optimum configuration was identified for a swirl angle of 15°, a tilt angle of 10°, and an exhaust piston lead angle of 20°. Future work includes expanding the numerical model’s domain to support a complete cylinder-port configuration, adding combustion products to the diffusivity equation in the UDF, and running additional test cases to describe the entire input space for the sensitivity analysis.<br> Mechanical Engineering Applied Physics Computational Physics Mechanics Thermodynamics Computational Fluid Dynamics Computational Heat Transfer Fluidisation and Fluid Mechanics Heat and Mass Transfer Operations Fluid Physics Internal combustion engines (ICEs) Opposed-piston engines Opposed piston engines CFD Computational fluid dynamics analysis Scavenging efficiency Trapping efficiency Delivery ratio Swirl circulation Turbulent kinetic energy Exhaust piston lead angle Tilt angle Swirl angle Port geometry CO2 production
206	Vyhodnocení rychlosti šíření tlakové vlny v lidském těle / Evaluation of pulse wave velocity in the human body Mezuláníková, Radka January 2013 (has links) This Mater's thesis deals with the evaluation of pulse wave velocity using multi-channel whole-body impedance cardiography. Data were taken from the group of healthy volunteers whose impedance changes were measured during rest, respiratory maneuvers, tilt and stress exercise. The result of this measurement are values of peaks of pulse wave time shifts towards R-wave. The velocity values towards the thorax electrodes were recalculated on the basis of knowledge about the pulse wave time shifts and the distances from the heart to the scanned locations, which were measured using the arterial segment's lengths.
207	Řešení stability prutových konstrukcí / Stability solution of framed structures Baxant, Radek January 2015 (has links) This diploma thesis deals with the subject of slenderness bars’ stability assessment, especially in the steel structures. Before the assessment of bars in the frame constructions, we search for the influence of the computational model’s settings on the final result. The initial geometrical imperfections are examined on the model of Euler’s bar. The influence of the rigidity of girders on the poles’ buckling length is examined on the basic frame construction. The buckling lengths are assessed in the comparison with the figures we got from the statistical tables and the computational software. The influence of construction’s initial tilt and its replacement by the system of outer forces is examined on the frame structure. Three-hinged frame structure with variable cross-section member is designed then and the influence of non-linear calculations on the inner forces is studied. In the complex frame assessment, the influence of the number of parts of variable cross-section member on the bars’ buckling length is examined.
208	Analýza silového zatížení řezného nástroje při pětiosém frézování / Cutting force analysis when 5-axis milling Dvořáček, Jan January 2009 (has links) The diploma thesis is focused on machining using the ball-end shank mill. Content of the preliminary part of the work is a shank mill characteristic and a consequent part shows a splitting of ball-end milling cutters, its application, the cutting tool geometry and a characteristic signs of machining. The cutting force model of the ball-end mill is presented as well. A part of proposed model is the conversion of the resultant force too. Practical part is aimed at cutting force analysis of the ball-end mill and the main purpose of this part is a quantification of the cutting force for different work piece tilt angles while milling is performed.
209	Stavebně technologický projekt rozšíření chráněné dílny v Třinci / Construction technological expansion project of sheltered workshop in Trinec Gwóźdź, Dariusz January 2016 (has links) The subject of graduation thesis is a building-technological study of production and warehousing hall and headquarters of Ergon protected workshops in Třinec. The work is prepared on the basis of the project documentation. This consists of 8 building objects( 2 main building objects and 6 engineering objects). Building object SO 01-assembly and warehousing hall will be used for installation of assembly lines for simple mounting of imported parts and for semi automatic painting line equipment. Building object SO 02- headquarters building will be used for social activities of employees (WC. showers, social room , cloak rooms) and office premises. The main aims of graduation thesis are : project of construction site equipment including of time and economical evaluation, time schedule and financial plan for objects, study of main phases of project realisation for objects SO 01 and SO 02, project of main building machines including their radius( reach), time schedule of building object SO 02, technological prescript for steel construction preparation of object SO 01 with control and check plan.
210	Prognose und bergschadenkundliche Analyse dynamischer Bodenbewegungen durch oberflächennahen Steinkohlenbergbau in den USA Zimmermann, Karsten 28 March 2011 (has links) (PDF) Der untertägige Abbau von Steinkohle führt zu Bewegungen des überlagernden Gebirges und der Tagesoberfläche. Eine Bewegungsprognose ist im Hinblick auf entstehende Bergschäden weltweit von großer Bedeutung. In dieser Arbeit wird untersucht, ob eine Prognose von Bodenbewegungen im amerikanischen Steinkohlenbergbau mit einem in Europa bewährten Verfahren, einem dynamischen stochastischen Senkungsmodell, möglich ist. Dazu wurde eine Literaturstudie über den bisherigen Kenntnisstand in den USA durchgeführt, abbaubegleitende Bodenbewegungsmessungen aus dem Steinkohlengebiet der Appalachen ausgewertet und durch Modellrechnungen nachgebildet. Es wurde darüber hinaus untersucht, welchen Einfluss die spezifischen Abbaubedingungen und die räumliche und zeitliche Abbauführung auf die Größe und Dynamik von Bodenbewegungen haben. Die theoretischen und praktischen Untersuchungen zeigen einen deutlichen Know-how Vorsprung des europäischen Bergbaus in den Bereichen der Senkungsmodellierung und Bewertung abbauinduzierter Bodenbewegungen und belegen die Anwendbarkeit des Senkungsmodells. Es wurden wichtige Erkenntnisse gewonnen, die Möglichkeiten und Grenzen einer Optimierung des Abbauzuschnitts und der zeitlichen Abbauführung im Sinne einer bergschadensmindernden Abbauplanung aufzeigen. Die Arbeit trägt zur Verbesserung der bergmännischen und markscheiderischen Abbauplanung im Steinkohlenbergbau bei. Bergbau Bergwerk Steinkohlenbergbau Steinkohlenabbau Steinkohlenbergwerk Steinkohle Abbau Streb Strebabbau Bodenbewegung Gebirgsbewegung Deformation Senkung Schieflage Zerrung Pressung Krümmung Bergsenkung Senkungsmodell Senkungsmodellierung Prognose Modellierung Abbauplanung Planung Abbaugeschwindigkeit Bewegungsdynamik Abbaustopp Dynamik Bergschaden Bergschadenkunde Bergschadensminderung Bergschadensmindernde Appalachen USA Pennsylvania Pittsburgh Morgantown Knothe Markscheider Markscheidewesen mining mine coal hard anthracite stone longwall face surface ground movement seam deformation subsidence strata overburden rock mass subsidence slope tilt model modeling prediction planning retreat winning rate speed stop break dynamics impact damage mitigation assessment protection control engineering Appalachia Appalachian basin USA Pennsylvania Pittsburgh Morgantown Knothe Knothe’s method surveyor miner surveying ddc:620 Appalachen USA / Nordoststaaten Steinkohlenbergwerk Steinkohlenbergbau Bergschaden Bergsenkung

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