This thesis tests the validity of three theories purporting to explain the attrition of stop outs -- why students interrupt their studies with the intent to return to school. Data were gathered at two schools, Portland State University and Reed College. Two theories, those of social class and involvement, were tested at each school as contending explanations of attrition by path analysis of parsimonious models derived by factor analysis. These theories were found to explain little of the variance of attendance pattern (less than 4.3 percent) at either school. No particular lines of causation could be demonstrated at either school. The third theory, that of career planning, asserts that students interrupt their studies to re-evaluate their course of action upon recognizing that chances of employment in their field are not good. This proposition was supported by the data at Portland State University.

This thesis recounts the history of the Portland Learning Community, an experimental institution of higher education founded in 1970 by a group consisting mostly of former faculty and students at Reed College. The Learning Community was funded by the Carnegie Corporation and affiliated with Antioch College.

This study was concerned with development of chromatographic methods suitable for determination of plant sugars. The resultant methodology was applied to the comprehensive study of plant carbohydrates as they vary during plant growth. Plant cell walls were isolated with boiling water followed by delignification with acid chlorite. The soluble portions were hydrolyzed with 2N sulfuric acid and the total sugars and individual monosaccharides were quantified using gas chromatography and colorimetry. The insoluble residues were hydrolyzed with 72% sulfuric acid followed by dilution with water to 2N and further hydrolysis. The effects of duration of delignification and acid hydrolysis were interpreted in terms of carbohydrate yield monitored colorimetrically and with gas chromatography. The rapid derivation of sugars was perfected using N-methyl-imidazole as an acetylation catalyst. This catalyst was also employed for the derivatization of lactonized aldonic acids, enabling the gas chromatographic quantitation of uronic acids. The growth of reed canarygrass was interpreted with empirical and non-empirical methodology. the empirical procedures provided little insightinto plant cell wall composition. The non-empirical methodology which included DMSO extraction and gas-liquid chromatography revealed the possible presence of a branched galactoarabinoxylan and a linear arabinoxylan in reed canarygrass hemicellulose. The presence of β-glucan was also confirmed using selective enzymatic hydrolysis. As the plants matured, the proportion of linear xylan increased. The occurence of galactose, mannose, fucose and rhamnose in cell wall extracts may be the result of acid catalyzed degradations and transformations of other cell wall sugars. The results revealed the value of chromatography as it is applied to interpretation of plant growth and composition. Gas-liquid chromatography was proposed as a tool for the evaluation of forage digestibility and forage quality.

Dans cette thèse, nous étudions les codes de Reed-Muller qui constituent une des familles de codes correcteurs les plus étudiées, et les plus utilisées dans la transmission des communications numériques. Grâce à leur rapidité d'encodage et de décodage, ils furent notamment utilisés pour les transmissions satellitaires. Ils ont également un lien très fort avec les notions de fonctions booléennes. L'étude de ces dernières constitue le coeur de la réalisation et de la sécurité des systèmes de chiffrement à clé secrète, tant par blocs que par flot. Depuis l'introduction de ces codes, de très nombreux algorithmes de décodage virent le jour, et aujourd'hui encore étudier leur structure afin de construire des algorithmes de décodage constitue un fructueux domaine de recherche. Ces algorithmes de décodage peuvent être utilisés dans l'étude de la structure de systèmes de chiffrement à clé secrète. Nous exposons un point de vue unificateur à l'ensemble des algorithmes de décodage des codes de Reed-Muller, ce point de vue étant celui de la dérivée discrète. Nous exposons un algorithme performant pour le décodage des codes d'ordre deux, que nous analysons ensuite. Nous discutons les résultats de simulations des algorithmes étudiés pour les petites et moyennes longueurs de code. Ces résultats montrent que l'algorithme proposé décode beaucoup plus loin en pratique que les autres algorithmes.

Constructed wetlands are largely used for water treatment both in agricultural land and for treating water from municipal and industrial waste. These wetlands need to be managed in order to work properly. How to deal with the large amount of vegetation harvested in the wetlands has withdrawn a great concern. The application of using wetland biomass as the co-substrates in anaerobic digestion was studied in this project. Plant materials, mostly Phragmites australis (common reed) from three different wetlands were used as raw material to produce biogas. The methane production using reed material harvested from municipal wastewater, industrial wastewater and an agricultural wetland are 66, 106, 144 ml/g VS respectively, which were lower than the suggested number 180ml/g VS. The gas potential remains a lot to be improved such as harvesting at summer to reduce the lignin content and changing the co-digestion mixing level to adjust to the optimal C/N ratio. Chemical analyses were performed concerning the gas yield and the residue quality. The digested residues showed a low concentration of cadmium, providing a non-toxic possibility to be spread on farm land as fertilizers, and closing the nutrient circle from land into water and back to land again. Pretreatments in the biogas process are usually focusing on the reduction of the lignocellulosic content in the raw material. Assessment of costs and benefits is needed for using wetland reed in the biogas production and applying any pretreatment methods.

The Savi’s Warbler (Locustella luscinioides) is a recently established bird species in a few reedy shallow lakes of southern Sweden and has only been found nesting for the last twenty years. Little is known about the species' habitat preferences, breeding biology and demands for specific territory structures at breeding sites in Sweden. Knowledge of a newly established species’ habitat requirements is essential to maintain a viable population and design action plans. This study, the first of its kind in Sweden, examined the vegetation structures in occupied territories of Savi’s Warblers at Lake Tåkern, the country's stronghold for the species. The species was found to be associated with the outer edge zones and fragmented areas of reed (Phragmites australis). Occupied territories differed from randomly chosen unoccupied (control) territories by having a thicker layer of reed litter, and on average more bushes of Willow (Salix spp.) present. Reed density and reed height did not differ from areas that lacked Savi’s Warblers. Territorial and displaying males were concentrated in two edge areas with a mosaic of reed islets where the territories remained relatively close together.

Lookup-table (LUT)-based method is a common approach used in all kinds of research topics. In this dissertation, we present several new designs for table-based function evaluation and table-based error correcting coding. In Chapter 3, a new function evaluation method, called two-level approximation, is presented where piecewise degree-one polynomials are used for initial approximation in the first level, followed by the refined approximation for the shared normalized difference functions in the second level. In Chapter 4, we present a new non-uniform segmentation method that searches for the optimal segmentation scheme with the different design goals of minimizing either ROM, total area, or delay. In Chapter 5, a new design methodology for table-based function evaluation is presented. Unlike previous approaches that usually determine the bit widths by assigning allowable errors for individual hardware components, the total error budget of our new design is considered jointly in order to optimized the bit widths of all the hardware components, leading to significant improvements in both area and delay. Finally, in Chapter 6, the similar table-based concept is used in the design of error correcting encoder using the modified polynomial of the Lagrange interpolation formula, resulting in smaller critical path delay and lower power consumption.

With the approach of the era of digital TV system around the world, how to grasp the design techniques of the receiver of the DVB-T has become a very important topic. The goal of this thesis is to pursue a highly optimized VLSI architecture compatible to the channel decoding standard of the DVB-T protocol. The channel decoding scheme adopted in DVB-T is based on the concatenated code; which is comprised of an inner Viterbi decoder, outer Reed-Solomon decoder and inner and outer de-interleaver modules. These modules all require a significant amount of data storage space, therefore the main feature of the proposed channel decoder architectures is to realize the data storage based on RAM instead of registers. This approach can lead to the reduction of silicon area and the dynamic power dissipation compared with the shift register based architecture. In order to achieve this, in the design of Viterbi module, the popular register-exchange and trace-back techniques used for the detection of the survivor path has been combined for the survivor memory management unit. As for the design of Reed-Solomon decoder, it is designed based on the modified inverse-free Berlekamp-Massey algorithm. A novel finite field constant multiplier architecture has been proposed which can reduce the required gate count of the multipliers by 20%. For outer convolutional deinterleaver, a specific address generator has been designed such that the data deinterleaver path can be merged and implemented as two memory blocks. For inner symbol deinterleaver, a lookahead technique has been applied to the design of address generator and deinterleaver memory has been reduced by a half compared with those in the literature. These four modules have been verified and integrated as robust channel decoder silicon IP. The related models used for IP integration and verification have also been provided. The prototyping on the FPGA has been tested to satisfy the requirement of the spec.

Enhanced heat transfer in electronic hardware by direct, small-scale actuation is investigated experimentally in two test bed configurations. The first configuration exploits the unsteady motions induced by a vibrating reed embedded within a heated duct (in contact with hardware that needs cooling) to enhance forced convection transport heat from the duct surfaces. The flow within the duct is either exclusively driven by the reed or, for higher heat flux, is augmented by an induced core flow. The time harmonic motion of the reed results in the regular shedding of vortical structures that interact with the inner surfaces in the absence and presence of a core flow. The second configuration focuses on the effects of small scale motions induced by a synthetic jet on heat transfer within an advanced heat sink. The synthetic jets emanate directly through the base of the heat sink and induce a recirculating flow between the fins, resulting in a lower thermal resistance than what is typically achieved with traditional fans. The unsteady flow characteristics in both configurations are investigated using particle image velocimetry (PIV). Of particular interest are the effects of small-scale motions and enhanced mixing on heat transfer compared to conventional time-invariant flows at similar or higher Reynolds numbers.

Thesis (M.E.S.)--The Evergreen State College, 2006. / Title from title screen (viewed 3/11/2010). Includes bibliographical references (leaves 41-53).