The Rayleigh-Taylor instability (RTI) is one of the primary hydrodynamic instabilities that acts as a disputer to achieving high yield inertial confinement fusion (ICF). The potential for RTI to grow on the interior surface of ICF capsules, caused by deceleration during the implosion, further emphasises the need to better understand the seed mechanisms for RTI and possible mitigation methods for damping the instability growth. Reducing the growth of RTI during deceleration could preserve the spherical symmetry of ICF implosions and reduce the amount of mix between the solid capsule liner and fuel hot-spot. Additionally, it has been shown that magnetic fields do damp RTI growth, and the presence of a magnetic field lowers the threshold for achieving fusion and increases the yield. Understanding the seed mechanisms of the RTI, especially on the interior surface of ICF capsules, further allows for better understanding of the morphology of the RTI growth dur- ing deceleration. Classically RTI has been studied using single or multi-mode sinusoidal perturbations, which result in bubble and spike morphology. However in addition to si- nusoidal perturbations, single-feature perturbation, such as voids or divots, can seed RTI. This form of RTI is considered the thin-layer RTI, where the perturbation's wavelength is longer than the dense layer's thickness. This specific RTI evolution results in a morphology consisting of a single central spike and arms that extend horizontally away from the spike and eventually fall back towards the interface. Thin-layer RTI is important to explore dur- ing deceleration due to the presence of the fill-tubes in ICF capsules causing holes in the shell. Creating experimental platforms for current laser configurations on Omega and the Na- tional Ignition Facility (NIF) is necessary to study deceleration-stage RTI experimentally and validate computational modeling. A comprehensive exploration of potential experimen- tal designs on Omega, Omega-EP, and NIF are explored to identify a platform with which deceleration-stage RTI can be studied with and without the presence of an externally applied magnetic field. Additionally, the design of a novel experimental platform for Omega-EP to study thin-layer RTI during deceleration with and without an externally applied magnetic field is presented, along with data collected during the first experiments performed utilizing the platform. Lastly, a first of it's kind RTI platform for NIF is fielded and the results are presented, including an exploration of the possible impacts high-intensity-laser generated hot-electrons can have on experimental targets. The results of these experimental platforms are used to benchmark computational models, and demonstrate the potential for magnetized RTI to be studied comprehensively in future experiments. / Doctor of Philosophy / The potential of controlled sustained nuclear fusions as a viable energy source has rapidly become a reality in recent years. Monumental progress has been made in the pursuit of con- trolled fusion, including the repeated achievement of fusion ignition at the National Ignition Facility (NIF), meaning there was successful production of more energy from the fusion reac- tion than laser energy used to trigger the reaction. However, in order for fusion to become a truly viable energy source improvements in capsule design and the mitigation of disruptions, like hydrodynamic instabilities, must be explored to produce higher energy yields. The Rayleigh-Taylor instability (RTI) is one of the most detrimental hydrodynamic insta- bilities in inertial confinement fusion (ICF). RTI occurs when a lighter fluid, like the fuel used in fusion reactions, supports a heavier fluid, the ICF capsule itself, under the influence of gravity. An ICF capsule is imploded, induced by the driving mechanism, such as a laser, but once the driver stops the capsule will begin to decelerate. During this deceleration stage, the interior surface of the ICF capsule in susceptible to RTI growth causing the cold capsule material to mix with the hot fusion fuel. This mixing reduces the fuel's ability to reach the necessary temperatures and densities need to achieve ignition and produce high energy yields. As a result, it is crucial to better understand the defects that cause RTI to grow and explore methods that could damp the RTI growth and preserve the integrity of the implosion and fusion fuel. The work presented here focuses on exploring both the seed mechanisms for RTI and miti- gation strategies. Specifically, using an externally applied magnetic field has been shown to damp RTI growth and in know to lower the threshold of the conditions needed to achieve ignition. A study of possible experimental setups at both the Omega laser and NIF is ex- plored in order to identify a design with which the damping effects of an externally applied magnetic field on deceleration-stage RTI can be studied experimentally. From this design study platforms for the Omega-EP and NIF were conceptualized and ultimately fielded. The results from these novel experiments are presented, along with an exploration of pos- sible effects on RTI unexpected preheating of the experimental targets. Additionally, an exploration of the seed mechanisms of RTI is presented with a look at the classic sinusoidal perturbation as well as using a divot to seeded thin-layer RTI, which evolves with a spike and arm morphology rather than the classical bubble and spike. The experimental results from Omega-EP using a divot as the perturbation are presented. Novel results of varying RTI platforms and their potential for further development provide crucial insight into the possible presence of deceleration-stage RTI in ICF capsules and can be iterated on in the future to further explore RTI evolution and damping methods.

No description available.

Self-thinning quantifies the reduction in tree numbers due to density-dependent mortality. Maximum size-density relationships (MSDRs) are a component of self-thinning that describe the maximum tree density per unit area obtainable for a given average tree size, often quadratic mean diameter (D). An MSDR species boundary line has been defined as a static upper limit of maximum tree density -- D relationships that applies to all stands of a certain species within a particular geographical area. MSDR dynamic thinning lines have been defined as the maximum tree density obtainable within an individual stand for a particular D which have been shown to vary relative to planting density. Results from this study show that differences in boundary levels of individual stands cause the MSDR species boundary line slope estimate to be sensitive to the range of planting densities within the model fitting dataset. Thus, a second MSDR species boundary line was defined whose slope is the average slope of all MSDR dynamic thinning lines. Mixed-models are presented as a statistical method to obtain an estimate of the population average MSDR dynamic thinning line slope. A common problem when modeling self-thinning is to determine what observations are within generally accepted stages of stand development. Segmented regression is presented as a statistical and less subjective method to determine what observations are within various stages of stand development. Estimates of D and trees per acre (N) where MSDR dynamic thinning lines begin and end on the logarithmic scale were used as response variables and predicted as a function of planting density. Predictions of MSDR dynamic thinning line beginning and ending D and N are used in an alternative MSDR dynamic thinning line slope estimation method. These models show that the maximum value of Reineke's Stand Density Index (SDI) varies relative to planting density. By relating planting density specific Zone of Imminent Competition Mortality boundaries to a MSDR species boundary line, self-thinning was found not to begin at a constant relative SDI. Thus, planting density specific Density Management Diagrams (DMD) showed that self-thinning began at 40 to 72% for planting densities of 605 and 2722 seedlings per acre, respectively. / Ph. D.

No description available.

The effects of polyethylene, (PE), type, compatibilizer type and organoclay type on the morphology, rheological, thermal, and mechanical properties of ternary low density polyethylene (LDPE), high density polyethylene (HDPE), and linear low density polyethylene (LLDPE), matrix nanocomposites were investigated in this study. Ethylene &ndash / Methyl acrylate &ndash / Glycidyl methacrylate terpolymer (E-MAGMA) and Ethylene &ndash / Butyl acrylate- Maleic anhydrate terpolymer (E-BA-MAH) were used as the compatibilizers. The organoclays selected for the study were Cloisite 30B and Nanofil 8. Nanocomposites were prepared by means of melt blending via co-rotating twin screw extrusion process. Extruded samples were injection molded to be used for material characterization tests. Optimum amounts of ingredients of ternary nanocomposites were determined based on to the mechanical test results of binary blends of PE/Compatibilizer and binary nanocomposites of PE/Organoclay. Based on the tensile test results, the optimum contents of compatibilizer and organoclay were determined as 5 wt % and 2 wt %, respectively. XRD and TEM analysis results indicated that intercalated and partially exfoliated structures were obtained in the ternary nanocomposites. In these nanocomposites E-MA-GMA compatibilizer produced higher d-spacing in comparison to E-BA-MAH, owing to its higher reactivity. HDPE exhibited the highest basal spacing among all the nanocomposite types with E-MA-GMA/30B system. Considering the polymer type, better dispersion was achieved in the order of LDPE&lt / LLDPE&lt / HDPE, owing to the linearity of HDPE, and short branches of LLDPE. MFI values were decreased by the addition of compatibilizer and organoclay to the matrix polymers. Compatibilizers imparted the effect of sticking the polymer blends on the walls of test apparatus, and addition of organoclay showed the filler effect and increased the viscosity. DSC analysis showed that addition of compatibilizer or organoclay did not significantly affect the melting behavior of the nanocomposites. Degree of crystallinity of polyethylene matrices decreased with organoclay addition. Nanoscale organoclays prevented the alignment of polyethylene chains and reduced the degree of crystallinity. Ternary nanocomposites had improved tensile properties. Effect of compatibilizer on property enhancement was observed in mechanical results. Tensile strength and Young&rsquo / s modulus of nanocomposites increased significantly in the presence of compatibilizers.

International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Calculating the power spectral density (PSD) at the transducer or data acquisition system offers advantages in a network-based telemetry system. The PSD is provided in real time to the users. The conversion to PSD can either be lossless (allowing a complete reconstruction of the transducer signal) or lossy (providing data compression). Post-processing can convert the PSD back to time histories if desired. A complete reconstruction of the signal is possible, including knowledge of the signal level between the sample periods. Properly implemented, this method of data collection provides a sharp anti-aliasing filter with minimal added cost. Currently no standards exist for generating PSDs on the vehicle. New standards could help telemetry system designers understand the benefits and limitations calculating the power spectral density in a network-based telemetry system.

Denna rapport baseras på experimentella försök där det undersökts hur pelletdensiteten påverkar utsläpp av kolmonoxid (CO) och stoft vid småskalig förbränning. I en testpanna med ansluten pelletsbrännare testades tre densiteter: låg, mellan och hög. Testerna uppdelades i tre faser i form av uppstart, kontinuerlig drift och släckning. Tre repetitioner gjordes på varje fas och för varje bränsle med undantag av släckning där endast en mätning per bränsle gjordes. Resultatet visade generellt en tydlig skillnad i CO-emission. Oberoende av densitet var CO-emissionerna mycket större vid uppstart och släckning än vid kontinuerlig drift. Avseende densitet gavs ett entydigt resultat där den lägsta pelletdensiteten gav högre stoftemissioner under alla driftsförhållanden. Skillnaden mellan de två pelletssorterna av högre densitet är däremot inte signifikant. För CO-emissioner sågs vid uppstartsfasen en tydlig trend mellan minskad pelletdensitet och ökade CO-emissioner. Vid kontinuerlig drift sågs emellertid det omvända: hög densitet gav högre CO-emissioner, varvid mellandensiteten gav något lägre CO-emissioner och låg densitet gav lägst CO-emissioner. Om skillnaden är uteslutande beroende på pelletdensiteten är svårt att säga. Ytterligare försök rekommenderas för att avgöra den exakta inverkan av pelletarnas densitet.

No description available.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Medicine / Master / Master of Philosophy