No description available.

No description available.

The construction of a field emission ion source and its adaptation to a mass spectrometer is described. The problems involved and the advantages of such an ion source are discussed. / Thesis / Master of Science (MS)

Note:

This thesis addresses the problem of extracting heat from sealed electronic enclosures. Typical industry practice is to use various air-to-air and air-to-liquid heat exchangers. These techniques are known to require costly custom designs. This thesis points out how one can apply heat pipe technology in the form of a vapor chamber to solve this type of problem. The details on the design and testing of two prototype vapor chambers are cited. Included in the text are typical industrial applications that require sealed enclosures to protect their associated electronic control hardware. Also mentioned is some historical background on heat pipes.

The evolution of bats is characterized by a combination of two key innovations - powered flight and biosonar - that are unique among mammals. Bats still outperform engineered systems in both capabilities by a large margin. Bat biosonar stands out for its ability to encode and extract sensory information using various mechanisms such as adaptive beam width control, dynamic sound emission and reception, as well as cognitive processes. Due to the highly integrated and sophisticated design of their active sonar system, bats can survive in complex and dense environments using just a few simple smart acoustic elements. On the sound emission side, significant features that distinguish bats from the current man-made sonar system are the time-variant shapes of the noseleaves. Noseleaves are baffles that surround the nostrils in bats with nasal pulse emission such as horseshoe bats and can undergo non-rigid deformations large enough to affect their acoustic properties significantly. Behavioral studies have shown that these movements are not random byproducts, but are due to specific muscular action. To understand the underlying physical and engineering principles of the dynamic sensing in horseshoe bats, two experimental prototypes ,i.e. intact noseleaf and simplified noseleaf, have been used. We have integrated techniques of data acquisition, instrument control, additive manufacturing, signal processing, airborne acoustics, 3D modeling and image processing to facilitate this research. 3D models of horseshoe bat noseleaves were obtained by tomographic imaging, reconstructed, and modified in the digital domain to meet the needs of additive manufacturing prototype. Nostrils and anterior leaf were abstracted as an elliptical outlet and a concave baffle in the other prototype. As a reference, a circular outlet and a straight baffle designed. A data acquisition and instrument control system has been developed and integrated with transducers to characterize the dynamic emission system acoustically as well as actuators for recreating the dynamics of the horseshoe bat noseleaf. A conical horn and tube waveguide was designed to couple the loudspeaker to the outlet of bat noseleaf and simplified baffles. A pan-tilt was used to characterize the acoustic properties of the deforming prototypes over direction. By using those techniques, the dynamic effect of the noseleaf was reproduced and characterized. It was suggested that the lancet rotation induced both beam-gain and beamwidth changes. Narrow outlet produced an isotropic beampattern and concave baffle had a significant time-variant and frequency-variant effect with just a small displacement. All those results cast light on the possible functions of the biological morphology and provided new thoughts on the engineering device's design. / Ph. D.

Thesis (PhD (Physics))--University of Stellenbosch, 2006. / This thesis is devoted to a study of the 93Nb( p r ,3He) and 59Co( p r ,3He) reactions at incident energies of 100 MeV, 130 MeV and 160 MeV. Double differential cross sections and analysing power distributions were measured from a threshold of ~30 MeV up to the kinematic maximum and at scattering angles between 15º and 120º. The experimental data were compared with theoretical calculations done by combining a statistical multistep theory with a deuteron pickup mechanism in the final stage. The contribution of the first three steps towards the total double differential cross section and analysing power was assessed. The theory described the experimental double differential cross section and analysing power data reasonably well over all incident and scattered energies and for both target nuclei. As the incident energy was increased, the characteristics of the reaction mechanism also remained consistent. Thus the results supported the underlying multistep-pickup theory. The two target nuclei demonstrated similar responses, suggesting these two share the same basic reaction mechanism. The total double differential cross section for the reaction dropped with an increase in incident energy. At a fixed emission energy, near the maximum allowed value, the slope of the double differential cross section increased with an increase in incident energy, resulting in the dominance of forward peaked reactions at higher incident energies. The sensitivity of analysing power to the multistep part of the reaction was valuable to the study. Forward-peaked contributions that were associated with single step direct reactions resulted in large analysing power values at small scattering angles, and values dropped to around zero at large angles. The analysing power also appeared to decrease to values approximating zero as the incident energy was increased to 160 MeV. Furthermore, this study also confirmed the dominance of higher step mechanisms at high excitation energies, irrespective of incident energy. In general the results were in agreement with the predicted properties of the assumed reaction mechanism at all incident and emission energies, which inspires confidence that the theoretical interpretation is likely to be correct.

Tsang Wei Mong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 86-93). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgement --- p.iv / Contents --- p.v / List of Figure Captions --- p.vi / List of Table Captions --- p.vii / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.2 --- Theory of Electron Field Emission --- p.1 / Chapter 1.2.1 --- Fowler Nordheim Planar Field Emission Model for Metal --- p.2 / Chapter 1.3 --- Goal of this Project --- p.9 / Chapter Chapter 2 --- Sample Preparation and Characterization Methods / Chapter 2.1 --- Sample Preparation --- p.12 / Chapter 2.1.1 --- MEVVA Implantation System --- p.13 / Chapter 2.1.2 --- Implantation Conditions --- p.16 / Chapter 2.1.3 --- Simulation by SRIM --- p.17 / Chapter 2.2 --- Characterization Methods --- p.20 / Chapter 2.2.1 --- AFM and CAFM --- p.20 / Chapter 2.2.2 --- RBS --- p.22 / Chapter 2.2.3 --- XPS --- p.24 / Chapter 2.2.4 --- XRD --- p.27 / Chapter 2.2.5 --- TEM --- p.28 / Chapter 2.2.6 --- FE Measurement --- p.29 / Chapter Chapter 3 --- FE Properties of IBS SiC layers / Chapter 3.1 --- Introduction --- p.31 / Chapter 3.2 --- Field Enhancement Mechanisms for the IBS SiC Layers --- p.32 / Chapter 3.3 --- Embedded Conducting Grains (ECG) Model of Local Field Enhancement --- p.45 / Chapter 3.4 --- The Role of Conducting Grains in Field Enhancement --- p.48 / Chapter Chapter 4 --- FE Properties of W modified IBS SiC layer / Chapter 4.1 --- Introduction --- p.58 / Chapter 4.2 --- Experimental --- p.59 / Chapter 4.3 --- Phase and Structural Evolution of W Modified IBS SiC Layers --- p.60 / Chapter 4.3.1 --- XRD Results --- p.60 / Chapter 4.3.2 --- XPS Results --- p.64 / Chapter 4.3.3 --- TEM Results --- p.69 / Chapter 4.3.4 --- AFM Results --- p.74 / Chapter 4.4 --- Field Emission Properties --- p.76 / Chapter Chapter 5 --- Conclusion --- p.84 / Reference --- p.86 / List of Publications --- p.94 / Appendix --- p.96

No description available.

An 15 Biogas-BHKW mit und ohne Abgasreinigung (Katalysator bzw. thermische Nachverbrennung) wurden Emissionsmessungen durchgeführt, davon an drei Anlagen über einen Zeitraum von 21 Tagen. Neben der Ermittlung der Formaldehyd- und Geruchsemissionen sollten dabei auch Erkenntnisse über die Standzeit von Abgasreinigungsanlagen gewonnen werden. Die wesentlichen Ergebnisse waren: 1. Der zulässige Grenzwert für Formaldehyd (Altanlagen: 60 mg/m³, Neuanlagen: 40 mg/m³) wurde von den meisten untersuchten Anlagen eingehalten, bei einem Teil der Anlagen wurde allerdings der NOx-Grenzwert von 500 mg/m³ überschritten. 2. Mittels Katalysatoren lassen sich Formaldehydemissionen deutlich reduzieren, Methanemissionen (Schlupf) dagegen nicht. 3. Aussagen über Standzeiten von Katalysatoren sind derzeit nicht möglich. 4. Mittels thermischer Nachverbrennung sind sowohl bei Formaldehyd als auch Methan sehr niedrige Reingaswerte erreichbar, die dazu auch noch hohe Standzeiten aufweisen. 5. Ein negativer Einfluss der Abgasreinigungsanlagen auf die Geruchsemissionen war nicht festzustellen.