Significant maldistribution negatively influences performance of equipment containing dense tube bundles and, moreover, it can cause a wide range of operating issues. This thesis therefore focuses on analysis of fluid flow in complete distribution systems via computational fluid dynamics (CFD). Data obtained from simulations carried out using the software ANSYS Fluent were also statistically analysed. Influence of system arrangement, tube bundle parameters and operating parameters on flow distribution non-uniformity and pressure drop was investigated. According to the results, system arrangement is the crucial differentiating parameter in terms of flow distribution as well as pressure drop. Additionally, data obtained via the classical CFD approach were compared with those yielded by a simplified CFD model for three selected distribution systems. Simplified CFD approach can - given its low computational demand - be utilised in optimization algorithms as well as in the course of the initial stage of equipment design process. Furthermore, this thesis discusses a simulation tool which is based on the simplified CFD approach. Although this tool is still being developed, the results it yields are very promising.

Flow distribution has big importance in equipment with limited tube rows because it provides correct operation and sometimes specific flow distribution for technology purposes is needed. This thesis is focusing on flow analysis in these units using computational fluid dynamics (CFD). For analysis of such systems models with varying tube rows and varying perforated segment lengths were created. Analysis showed significant impact of flow manifold layout along with tube layout and number of tubes. Simplified 1D model using static pressure regain coefficient was created which provides much shorter computational times. Comparison of 1D and CFD models was made to determine field of their usage.

Tato diplomová práce se zaměřuje na modelování proudění tekutiny v paralelních distribučních systémech, kde hraje důležitou roli rovnoměrnost distribuce tekutin. Pro tento účel je vytvořen vlastní CFD kód. Kód je napsán v programovacím jazyce Java a používá ke zlepšení výkonu knihovny třetích stran, které se vyznačují přímým přístupem ke hardwarovým a systémovým prostředkům. Kód se také vyznačuje určitými zjednodušeními, u nichž se očekává, že sníží výpočetní časy. Vliv použitých zjednodušujících opatření je vyhodnocen porovnáním výsledků simulací proudění na několika geometriích s údaji získanými z podrobných modelů CFD. Geometrie použitých svazků trubek se odlišují různými uspořádáními toku a trubek a také různým počtem trubek.

This diploma thesis deals with calculation methods of heat exchanger with cross-flow tube bundle. The first part of the thesis contains summary of generally known basic calculation relations used in calculations of heat exchangers and a detailed description of a given heat exchanger.The second part of the thesis provides a description of available calculation methods of a given aparatus required for its thermal and hydraulic calculation. The final part describes application POST in 1.0 which has been formed on the basis of these calculation methods. Using this application check calculation of exchanger with cross-flow tube bundle was carried out and gained figures compared with results gained by means of professional calculation program HTRI.

Sprinkled tube bundles with a thin liquid film flowing over them are used in various technology processes where it is necessary to separate the vapour and liquid phases quickly and efficiently. The process occurs predominantly at low temperatures with a corresponding decrease of pressure around the tube bundle. Such a technology is represented for instance by an evaporator at absorption units or an evaporator for sea water desalination. In ideal conditions water boils at the whole surface of an exchanger, but in practice it must be considered that in original spots of contact between water and the exchanger wall the water will not boil at the tubes' surface but the cooling liquid will merely be heated-up. The presented dissertation thesis focuses on this issue. The objective of the thesis was to determine the heat transfer coefficient at the surface of sprinkled tube bundles of various geometries at atmospheric pressure as well as low pressure. For this purpose experiments have been carried out at tube bundles consisting of copper tubes of 12,0 mm diameter placed horizontally one above another that were heated by water. Three types of tubes (smooth, sandblasted and grooved) of four various pitches (15,0 to 30,0 mm by 5,0 mm increments) have been tested. Simultaneously individual bundles' geometries consisted of 4, 6, 8 and 10 tubes with identical surface finish. Based on the conducted experiments the mathematical model of heat transfer that involves mainly analogy criteria has been made more accurate. A temperature field at the sprinkled tube bundle surface has been scanned by a thermographic camera during the performed experiments. Influence of geometry and tube surface finish on flow mode and consequently also on heat transfer has been assessed in accordance with the compiled methodology.

Les systèmes d'aide à la conduite et les travaux concernant le véhicule autonome ont atteint une certaine maturité durant ces dernières aimées grâce à l'utilisation de technologies avancées. Une étape fondamentale pour ces systèmes porte sur l'estimation du mouvement et de la structure de l'environnement (Structure From Motion) pour accomplir plusieurs tâches, notamment la détection d'obstacles et de marquage routier, la localisation et la cartographie. Pour estimer leurs mouvements, de tels systèmes utilisent des capteurs relativement chers. Pour être commercialisés à grande échelle, il est alors nécessaire de développer des applications avec des dispositifs bas coûts. Dans cette optique, les systèmes de vision se révèlent une bonne alternative. Une nouvelle méthode basée sur des approches 2D/2D à partir d'un réseau de caméras asynchrones est présentée afin d'obtenir le déplacement et la structure 3D à l'échelle absolue en prenant soin d'estimer les facteurs d'échelle. La méthode proposée, appelée méthode des triangles, se base sur l'utilisation de trois images formant un triangle : deux images provenant de la même caméra et une image provenant d'une caméra voisine. L'algorithme admet trois hypothèses: les caméras partagent des champs de vue communs (deux à deux), la trajectoire entre deux images consécutives provenant d'une même caméra est approximée par un segment linéaire et les caméras sont calibrées. La connaissance de la calibration extrinsèque entre deux caméras combinée avec l'hypothèse de mouvement rectiligne du système, permet d'estimer les facteurs d'échelle absolue. La méthode proposée est précise et robuste pour les trajectoires rectilignes et présente des résultats satisfaisants pour les virages. Pour affiner l'estimation initiale, certaines erreurs dues aux imprécisions dans l'estimation des facteurs d'échelle sont améliorées par une méthode d'optimisation : un ajustement de faisceaux local appliqué uniquement sur les facteurs d'échelle absolue et sur les points 3D. L'approche présentée est validée sur des séquences de scènes routières réelles et évaluée par rapport à la vérité terrain obtenue par un GPS différentiel. Une application fondamentale dans les domaines d'aide à la conduite et de la conduite automatisée est la détection de la route et d'obstacles. Pour un système asynchrone, une première approche pour traiter cette application est présentée en se basant sur des cartes de disparité éparses. / Driver assistance systems and autonomous vehicles have reached a certain maturity in recent years through the use of advanced technologies. A fundamental step for these systems is the motion and the structure estimation (Structure From Motion) that accomplish several tasks, including the detection of obstacles and road marking, localisation and mapping. To estimate their movements, such systems use relatively expensive sensors. In order to market such systems on a large scale, it is necessary to develop applications with low cost devices. In this context, vision systems is a good alternative. A new method based on 2D/2D approaches from an asynchronous multi-camera network is presented to obtain the motion and the 3D structure at the absolute scale, focusing on estimating the scale factors. The proposed method, called Triangle Method, is based on the use of three images forming a. triangle shape: two images from the same camera and an image from a neighboring camera. The algorithrn has three assumptions: the cameras share common fields of view (two by two), the path between two consecutive images from a single camera is approximated by a line segment, and the cameras are calibrated. The extrinsic calibration between two cameras combined with the assumption of rectilinear motion of the system allows to estimate the absolute scale factors. The proposed method is accurate and robust for straight trajectories and present satisfactory results for curve trajectories. To refine the initial estimation, some en-ors due to the inaccuracies of the scale estimation are improved by an optimization method: a local bundle adjustment applied only on the absolute scale factors and the 3D points. The presented approach is validated on sequences of real road scenes, and evaluated with respect to the ground truth obtained through a differential GPS. Finally, another fundamental application in the fields of driver assistance and automated driving is road and obstacles detection. A method is presented for an asynchronous system based on sparse disparity maps

This diploma thesis deals with the new trends in the monetization of the video gaming industry with emphasis on crowdfunding, free-to-play model, selling games by "pay what you want" bundles and sales on Steam and other digital distribution stores. The purpose of this diploma thesis is to describe how the players on personal computers react to these trends in the Czech Republic. First, the situation in Czech gaming industry and the situation of players in the Czech Republic is described. Then, the new trends are analyzed thoroughly using foreign researches. The practical part analyses the effects of the new trends on Czech players with the results of an online questionnaire. First, the methodology is presented and subsequently the collected data is analyzed. Gradually, the thesis are answering the three research questions which are clarifying various aspects of how the Czech players respond to the new trends in the video gaming industry monetization. Powered by TCPDF (www.tcpdf.org)

The human sense of hearing is characterized by its exquisite sensitivity, sharp frequency selectivity, and wide dynamic range. These features depend on an active process that in the inner ear boosts vibrations evoked by auditory stimuli. Spontaneous otoacoustic emissions constitute a demonstrative manifestation of this physiologically vulnerable mechanism. In the cochlea, sensory hair bundles transduce sound-induced vibrations into neural signals. Hair bundles can power mechanical movements of their tip, oscillate spontaneously, and operate as tuned nonlinear amplifiers of weak periodic stimuli. Active hair-bundle motility constitutes a promising candidate with respect to the biophysical implementation of the active process underlying human hearing. The responsiveness of isolated hair bundles, however, is seriously hampered by intrinsic fluctuations. In this thesis, we present theoretical and experimental results concerning the noise-imposed limitations of nonlinear amplification by active sensory hair bundles. We analyze the effect of noise within the framework of a stochastic description of hair-bundle dynamics and relate our findings to generic aspects of the stochastic dynamics of oscillatory systems. Hair bundles in vivo are often elastically coupled by overlying gelatinous membranes. In addition to theoretical results concerning the dynamics of elastically coupled hair bundles, we report on an experimental study. We have interfaced dynamic force clamp performed on a hair bundle from the sacculus of the bullfrog with real-time stochastic simulations of hair-bundle dynamics. By means of this setup, we could couple a hair bundle to two virtual neighbors, called cyber clones. Our theoretical and experimental work shows that elastic coupling leads to an effective noise reduction. Coupled hair bundles exhibit an increased coherence of spontaneous oscillations and an enhanced amplification gain. We therefore argue that elastic coupling by overlying membranes constitutes a morphological specialization for reducing the detrimental effect of intrinsic fluctuations.

No description available.

<p>Unmanned aerial vehicles (UAVs) equipped with imaging systems and integrated global navigation satellite system/inertial navigation system (GNSS/INS) are used for a variety of applications. Disaster relief, infrastructure monitoring, precision agriculture, and ecological forestry growth monitoring are among some of the applications that utilize UAV imaging systems. For most applications, accurate 3D spatial information from the UAV imaging system is required. Deriving reliable 3D coordinates is conditioned on accurate geometric calibration. Geometric calibration entails both spatial and temporal calibration. Spatial calibration consists of obtaining accurate internal characteristics of the imaging sensor as well as estimating the mounting parameters between the imaging and the GNSS/INS units. Temporal calibration ensures that there is little to no time delay between the image timestamps and corresponding GNSS/INS position and orientation timestamps. Manual and automated spatial calibration have been successfully accomplished on a variety of platforms and sensors including UAVs equipped with frame and push-broom line cameras. However, manual and automated temporal calibration has not been demonstrated on both frame and line camera systems without the use of ground control points (GCPs). This research focuses on manual and automated spatial and temporal system calibration for UAVs equipped with GNSS/INS frame and line camera systems. For frame cameras, the research introduces two approaches (direct and indirect) to correct for time delay between GNSS/INS recorded event markers and actual time of image exposures. To ensure the best estimates of system parameters without the use of ground control points, an optimal flight configuration for system calibration while estimating time delay is rigorously derived. For line camera systems, this research presents the direct approach to estimate system calibration parameters including time delay during the bundle block adjustment. The optimal flight configuration is also rigorously derived for line camera systems and the bias impact analysis is concluded. This shows that the indirect approach is not a feasible solution for push-broom line cameras onboard UAVs due to the limited ability of line cameras to decouple system parameters and is confirmed with experimental results. Lastly, this research demonstrates that for frame and line camera systems, the direct approach can be fully-automated by incorporating structure from motion (SfM) based tie point features. Methods for feature detection and matching for frame and line camera systems are presented. This research also presents the necessary changes in the bundle adjustment with self-calibration to successfully incorporate a large amount of automatically-derived tie points. For frame cameras, the results show that the direct and indirect approach is capable of estimating and correcting this time delay. When a time delay exists and the direct or indirect approach is applied, horizontal accuracy of 1–3 times the ground sampling distance (GSD) can be achieved without the use of any ground control points (GCPs). For line camera systems, the direct results show that when a time delay exists and spatial and temporal calibration is performed, vertical and horizontal accuracy are approximately that of the ground sample distance (GSD) of the sensor. Furthermore, when a large artificial time delay is introduced for line camera systems, the direct approach still achieves accuracy less than the GSD of the system and performs 2.5-8 times better in the horizontal components and up to 18 times better in the vertical component than when temporal calibration is not performed. Lastly, the results show that automated tie points can be successfully extracted for frame and line camera systems and that those tie point features can be incorporated into a fully-automated bundle adjustment with self-calibration including time delay estimation. The results show that this fully-automated calibration accurately estimates system parameters and demonstrates absolute accuracy similar to that of manually-measured tie/checkpoints without the use of GCPs.</p>