Roof falls and accumulation of dangerous gasses are the most common hazards in any underground coal mine. Different mechanisms can jeopardize the stability of the roof in underground excavations and successful roof control can only be obtained if the failure mechanism is identified and understood properly. The presence of discontinuities, the inherent variability of the rock mass and discontinuity properties, and the uncertainties associated with directions and magnitudes of the in-situ stress makes the rock engineering problems challenging. The numerical modeling can assist the ground control engineers in designing and evaluating the stability of the underground excavations. If extensive geological and geotechnical data are available, then detailed predictions of deformation, stress and stability can be accomplished by performing numerical modeling. If not, still the numerical modeling can be used to perform parametric studies to gain insight into the possible ranges of responses of a system due to likely ranges of various parameters. The parametric studies can help to identify the key parameters and their impact on stability of underground excavations. The priorities of the material testing and site investigation can be set based on the selected key parameters from parametric studies. An underground coal mine in western Pennsylvania is selected as a case study mine to investigate the underlying causes of roof falls at this mine. The immediate roof at the case study mine consists of laminated silty shale, shale, or sandstone that changes from area to area, and the floor is shale or soft fireclay. This study was mainly focused in the stability analysis of the roofs with the laminated silty shale rock type, where the majority of roof falls had taken place in the roof with this type of roof material. Extensive laboratory tests were performed on the core samples obtained from the case study mine to estimate the intact rock and discontinuity properties of the materials that occur in large extent at the selected interest area of the case study mine. In this research, the three-dimensional distinct element method was used to investigate the stability of the roof in an underground room-and-pillar coal mine. The implemented technique was able to accurately capture the failure of the major discontinuities and rock masses which consist of intact rock and minor discontinuities. In order to accurately replicate the post failure behavior of the rock layers in the immediate roof area, the strain-softening material constitutive law was applied to this region. Extensive numerical parametric studies were conducted to investigate the effect of different parameters such as the variation of immediate roof rock mass strength properties, variation of discontinuity mechanical properties, orientations and magnitudes of the horizontal in-situ stresses, and the size of pillars and excavations on stability of the excavations. The distribution of post failure cohesion along with other measures such as accumulated plastic shear strain, distribution of Z-displacements at the roofline, failure state (joint slip and tensile failure) and displacement (normal and shear displacements) of discontinuities were used to accurately assess the roof stability in this case study. The research conducted in this dissertation showed that the bedding planes play an important role on the behavior of roof in underground excavations. Therefore, an appropriate numerical modeling technique which incorporates the effect of discontinuities should be employed to simulate the realistic behavior of the discontinuous rock masses such as the layered materials in roof strata of the underground coal mines. The three-dimensional distinct element method used in this research showed the clear superiority of this technique over the continuum based methods.

Conventional stereoscopic displays present a pair of stereoscopic images on a single and fixed image plane decoupled with the vergence and accommodation responses of the viewer. In consequence, these displays lack the capability of correctly rendering focus cues (i.e. accommodation and retinal blur) and may induce the discrepancy between accommodation and convergence. A number of visual artifacts associated with incorrect focus cues in stereoscopic displays have been reported, limiting the applicability of these displays for demanding applications and daily usage.In this dissertation, methods and apparatus for generating addressable focus cues in conventional stereoscopic displays are proposed. Focus cues can be addressed throughout a volumetric space, either through dynamically varying the focal distance of a display enabled by an active optical element or by multiplexing a stack of 2-D image planes. Optimal depth-weighted fusing functions are developed to fuse a number of discrete image planes into a seamless volumetric space with continuous and near-correct focus cues similar to the real world counterparts.The optical design, driving methodology, and prototype implementation of the addressable focus displays are presented and discussed. Experimental results demonstrate continuously addressable focus cues from infinity to as close as the near eye distance. Experiments to further evaluate the depth perception in the display prototype are conducted. Preliminary results suggest that the perceived distance and accommodative response of the viewer match with the addressable accommodation cues rendered by the display, approximating the real-world viewing condition.

Medizinische Volumenvisualisierung ist ein wertvolles Werkzeug zur Betrachtung von Volumen- daten in der medizinischen Praxis und Lehre. Eine interaktive, stereoskopische und kollaborative Darstellung in Echtzeit ist notwendig, um die Daten vollständig und im Detail verstehen zu können. Solche Visualisierung von hochauflösenden Daten ist jedoch wegen hoher Hardware- Anforderungen fast nur an speziellen Visualisierungssystemen möglich. Remote-Visualisierung wird verwendet, um solche Visualisierung peripher nutzen zu können. Dies benötigt jedoch fast immer komplexe Software-Deployments, wodurch eine universelle ad-hoc Nutzbarkeit erschwert wird. Aus diesem Sachverhalt ergibt sich folgende Hypothese: Ein hoch performantes Remote- Visualisierungssystem, welches für Stereoskopie und einfache Benutzbarkeit spezialisiert ist, kann für interaktive, stereoskopische und kollaborative medizinische Volumenvisualisierung genutzt werden. Die neueste Literatur über Remote-Visualisierung beschreibt Anwendungen, welche nur reine Webbrowser benötigen. Allerdings wird bei diesen kein besonderer Schwerpunkt auf die perfor- mante Nutzbarkeit von jedem Teilnehmer gesetzt, noch die notwendige Funktion bereitgestellt, um mehrere stereoskopische Präsentationssysteme zu bedienen. Durch die Bekanntheit von Web- browsern, deren einfach Nutzbarkeit und weite Verbreitung hat sich folgende spezifische Frage ergeben: Können wir ein System entwickeln, welches alle Aspekte unterstützt, aber nur einen reinen Webbrowser ohne zusätzliche Software als Client benötigt? Ein Proof of Concept wurde durchgeführt um die Hypothese zu verifizieren. Dazu gehörte eine Prototyp-Entwicklung, deren praktische Anwendung, deren Performanzmessung und -vergleich. Der resultierende Prototyp (CoWebViz) ist eines der ersten Webbrowser basierten Systeme, welches flüssige und interaktive Remote-Visualisierung in Realzeit und ohne zusätzliche Soft- ware ermöglicht. Tests und Vergleiche zeigen, dass der Ansatz eine bessere Performanz hat als andere ähnliche getestete Systeme. Die simultane Nutzung verschiedener stereoskopischer Präsen- tationssysteme mit so einem einfachen Remote-Visualisierungssystem ist zur Zeit einzigartig. Die Nutzung für die normalerweise sehr ressourcen-intensive stereoskopische und kollaborative Anatomieausbildung, gemeinsam mit interkontinentalen Teilnehmern, zeigt die Machbarkeit und den vereinfachenden Charakter des Ansatzes. Die Machbarkeit des Ansatzes wurde auch durch die erfolgreiche Nutzung für andere Anwendungsfälle gezeigt, wie z.B. im Grid-computing und in der Chirurgie.

Objective of the research. The improvement of a methodology of a city’s 3-dimensional geoinformation system development, updating and registration of changes by applying geodetic and photogrammetric measurements.

This thesis employs computational and experimental methods to explore hotspot cooling and high heat flux removal from a 3-D stacked chip using thermoelectric and microfluidic devices. Stacked chips are expected to improve microelectronics performance, but present severe thermal management challenges. The thesis provides an assessment of both thermoelectric and microfluidic technologies and provides guidance for their implementation in the 3-D stacked chips. A detailed 3-D thermal model of a stacked electronic package with two dies and four ultrathin integrated TECs is developed to investigate the efficacy of TECs in hotspot cooling for 3-D technology. The numerical analysis suggests that TECs can be used for on demand cooling of hotspots in 3-D stacked chip architecture. A strong vertical coupling is observed between the top and bottom TECs and it is found that the bottom TECs can detrimentally heat the top hotspots. As a result, TECs need to be carefully placed inside the package to avoid such undesired heating. Thermal contact resistances between dies, inside the TEC module, and between the TEC and heat spreader are shown to significantly affect TEC performance. TECs are most effective for cooling localized hotspots, but microchannels are advantageous for cooling large background heat fluxes. In the present work, the results of heat transfer and pressure drop experiments in the microchannels with water as the working fluid are presented and compared to the previous microchannel experiments and CFD simulations. Heat removal rates of greater than 100 W/cm2 are demonstrated with these microchannels, with a pressure drop of 75 kPa or less. A novel empirical correlation modeling method is proposed, which uses finite element modeling to model conduction in the channel walls and substrate, coupled with an empirical correlation to determine the convection coefficient. This empirical correlation modeling method is compared to resistor network and CFD modeling. The proposed modeling method produced more accurate results than resistor network modeling, while solving 60% faster than a conjugate heat transfer model using CFD. The results of this work demonstrate that microchannels have the ability to remove high heat fluxes from microelectronic packages using water as a working fluid. Additionally, TECs can locally cool hotspots, but must be carefully placed to avoid undesired heating. Future work should focus on overcoming practical challenges including fabrication, cost, and reliability which are preventing these technologies from being fully leveraged.

In modern microprocessors, thermal management has become one of the main hurdles in continued performance enhancement. Cooling schemes utilizing single phase microfluidics have been investigated extensively for enhanced heat dissipation from microprocessors. However, two-phase fluidic cooling devices are becoming a promising approach, and are less understood. This study aims to examine two-phase flow and heat transfer within a pin-fin enhanced micro-gap. The pin-fin array covered an area of 1cm x 1cm and had a pin diameter, height and pitch of 150μm, 200μm and 225μm, respectively, (aspect ratio of 1.33). This study covers both uniformly and partially heated scenarios. The working fluid used was R245fa. The average heat transfer coefficient and high speed flow visualization results indicated a rapid transition to the annular flow regime with a strong dependence on heat flux. Also, unique, conically-shaped two-phase wakes were observed, demonstrating the lateral spreading capability of the pin-fin array geometry.

Recently three-dimensional graphics is being applied in many fields. It is used in geodesy, topography and architecture as well. There are a lot of programs for the work with 2D and 3D graphics in the world. Most of them are related by CAD name. It could be mentioned such production of graphic software „giants“ like Autodesk (AutoCAD, Map 3D ) or Graphisoft (ArchiCAD). The aim of our work is the program which main function is the generation of three-dimensional city. Obviously this could be done using programs mentioned above, but the assimilation of such program needs much time and money. Therefore, if we need only to generate 3D city, our program is suitable for this. Our program quickly retrieves topographic data of the city and generates its 3D view. The program is not overloaded with unnecessary functions. It makes the program easy to understand and assimilate for the user who has minimal knowledge in design and modelling.

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