ABSTRACT Structural evolution and its effect on optical absorption/emission behavior of derivative of PPVs upon isothermal heat treatment at elevated temperatures were studied by means of a combination of polarized light microscopy, x-ray diffraction, transmission electron microscopy, ultraviolet-visible spectroscopy, and photoluminescence spectroscopy. The main physical picture drawn from results of this study over a series of PPVs with flexible side-chains may be summarized as the following: (1) They are generally liquid-crystalline in nature, typically biaxially nematic in optical texture but morphologically characterized as of lamellar or hexagonal columnar structure. This is consistent with the nematogenic nature one would expect from the rigid backbone as well as the smectogenic nature one would expect from the aliphatic side-chains. (2) The aggregates formed in solutions and the supramolecular assemblies formed in the bulk state are structurally similar (in terms of the similar level of conjugation), and hence possibly of the same thermodynamic origin. This surfactant-like self-ordering behavior is consistent with the tendency towards segregation between the aromatic, rigid backbone and the aliphatic, flexible side-chains. (3) The collapse of these conjugated polymers with flexible side-chains into aggregates appears to be a general phenomenon upon slow to moderate solvent removal and not limited to the present case of poor solvency power. This is consistent with the strong tendency toward phase separation in rigid rod solutions delineated by Flory some 30 years ago. (4) All the above observations may be explained in terms of lyotropic or thermotropic self-assembly of hairy-rod chains into coiled helical conformation with ellipsoidal cross section for the conjugated backbone as shown schematically in Figure 4-42 and 4-43. The flexible side-chains generally tend to fill the space within the ellipsoidal cylindrical structure. As the side-chain length is increased, the increased Van der Waals attraction among side-chains results in more extended period of helical twist or more straighten backbone conformation, rendering preference of lamellar structure over hexagonal helical structure. (5) As a consequence, supramolecular aggregation is basically enhanced by increased side-chain length or backbone rigidity. This in turn results in more extended conjugation length or more fully developed

Recently developed mathematical tools for the modelling of contact problems on thin film structures are adapted to allow the investigation of arbitrarily mixed purely isotropic and transversally isotropic laminate structures. The new tool is applied to model a variety of load problems resulting in the failure of windsurfing boards consisting of a relatively thin laminate shell and a soft polymer foam core. It is shown that local impact and distributed bending loads due to “bad landing” after high jumps or contact with parts of the sailing gear (the so called rig) especially the front part of the boom are leading to the most critical stress distributions resulting in failure. So most of the investigated boards were damaged because the rider (windsurfer) landed flat and thus produced a sudden impact force under his feet (impact defect). Other overloading occurred due to overturning of so called loop movements or the landing of the board exactly on respectively between two waves and this way producing high bending moments. Some of those typical loads are analysed in detail and the stresses occurring in the complex structure of the windsurfing boards are evaluated.

The Adequate Yearly Progress (AYP) Model has been used to make many high-stakes decisions concerning schools, though it does not provide a complete assessment of student academic achievement and school effectiveness. To provide a clearer perspective, many states have implemented various Growth and Value Added Models, in addition to AYP. The purpose of this study was to examine two Value Added Model specifications, the Gain Score Model and the Layered Effects Model, to understand similarities and differences in school effect results. Specifically, this study correlated value added school effect estimates, which were derived from two model specifications and two outcome measures (mathematics and reading test scores). Existing data were obtained from a moderately large and rural school district in Florida. The outcome measures of 7,899 unique students were examined using the Gain Score Model and the Layered Effects Model to estimate school effects. Those school effect estimates were then used to calculate and examine the relationship between school rankings. Overall, the findings in this study indicated that the school effect estimates and school rankings were more sensitive to outcome measures than they were to model specifications. The mathematics and reading correlations from the Gain Score Model for school effects and school rankings were low (indicating high sensitivity), when advancing from Grades 4 to 5, and were moderate in other grades. The mathematics and reading correlations from the Layered Effects Model were low at Grade 5 for school effects and school rankings, as were the correlations at Grade 7 for the school rankings. In the other grades, correlations were moderate to high (indicating lower sensitivity). Correlations between the Gain Score Model and the Layered Effects Model from mathematics were high in each grade for both school effects and school rankings. Reading correlations were also high for each of the grades. These results were similar to the findings of previous school effects research and added to the limited body of literature. Depending upon the outcome measure used, school effects and rankings can vary significantly when using Value Added Models. These models have become a popular component in educational accountability systems, yet there is no one perfect model. If used, these models should be used cautiously, in addition to other accountability approaches.

The research described in this dissertation undertakes a computational study of wave motion due to ground excitation in layered soil media. Adjustments of soil properties consistent with the level of deformation is applied using an equivalent linear approach. The finite element method provides the basis of the numerical procedure for soil-structure system response calculation in conjunction with a first-order perturbation scheme. Available experimental data are employed for shear-modulus and damping adjustments. The findings of the research are expected to lead to efficient calculation of structural response to earthquake ground motion. / text

Technology trends toward lower power, higher speed and higher density devices have pushed the package performance to its limits. The high frequency effects e.g., crosstalk and signal distortion, may cause high bit error rates or malfunctioning of the circuit. Therefore, the successful release of a new product requires constant attention to the high frequency effects through the whole design process. Full-wave electromagnetic tools must be used for this purpose. Unfortunately, currently available full-wave tools require excessive computational resources to simulate large-scale interconnect structures.A prototype version of the Full-Wave Layered-Interconnect Simulator (UA-FWLIS), which employs the Method of Moments (MoM) technique, was developed in response to this design need. Instead of using standard numerical integration techniques, the MoM reaction elements were analytically evaluated, thereby greatly improving the computational efficiency of the simulator. However, the expansion and testing functions that are employed in the prototype simulator involve filamentary functions across the wire. Thus, many problems cannot be handled correctly. Therefore, a fundamental extension is made in this dissertation to incorporate rectangular-based, finite-width expansion and testing functions into the simulator. The critical mathematical issues and theoretical issues that were met during the extension are straightened out. The breakthroughs that were accomplished in this dissertation lay the foundation for future extensions. A new bend-cell expansion function is also introduced, thus allowing the simulator to handle bends on the interconnects with fewer unknowns. In addition, the Incomplete Lipschitz-Hankel integrals, which are used in the analytical solution, are studied. Two new series expansions were also developed to improve the computational efficiency and accuracy.

Tiriamojo darbo objektas: Stabatiškės aikštelė. Tiriamojo darbo tikslas: išanalizuoti esamą Stabatiškės aikštelės situaciją ir parinkti galimus sausinimo sistemos techninius sprendinius. Tiriamojo darbo uždaviniai: 1. Išanalizuoti kalvotų žemių sausinimo ypatumus ir drėgmės pertekliaus priežastis; 2. Išanalizuoti Stabatiškės aikštelės gamtines sąlygas, numatyti bei parinkti tinkamas sausinimo priemones; 3. Įvertinti Stabatiškės aikštelės topografines, geologines bei hidrogeologines sąlygas; 4. Parinkti galimas sausinimo schemas ir apibūdinti atskirus jų elementus. Tiriamojo darbo metodika: tyrimams panaudoti geologinių, hidrologinių ir hidrogeologinių tyrimų duomenys, jie apibendrinti, susisteminti ir išanalizuoti. Atsižvelgiant į ilgaamžiškumo faktorių, pasiūlyti sausinimo sistemos techniniai sprendiniai. Tiriamojo darbo rezultatai: • atlikus Stabatiškės aikštelės tyrimų analizę, buvo nustatytos pagrindinės priežastys, kodėl teritorijoje toks drėgmės perteklius; • pagal turimus duomenis parinkta optimaliausia sausinimo priemonių sistema; • nustatyta jog teritorija geografiniu, geologiniu ir geotechniniu požiūriu tinkama žemo aktyvumo radioaktyviųjų atliekų saugyklos statybai; • atviri melioraciniai grioviai bei daugiasluoksnis drenažas, tinkamiausias būdas kontroliuoti perteklinį vandenį Stabatiškės aikštelėje. Išvados: Pagrindinis veiksnys lemiantis parinktą sausinimo sistemos tipą yra teritorijos paskirtis. Žinant saugyklos eksploatavimo trukmę (300 metų), reikia... [toliau žr. visą tekstą] / The subject of the research work: Stabatiske site. The aim of the study: analyze current situation of the Stabatiske site and choose drainage potential technical solutions. The specific aims of this study: 1. Analise the hilly land drainage characteristics and causes of excess moisture; 2. Analise Stabatiske site natural conditions and provide adequate drainage measures; 3. Evaluate Stabatiske site topography, geological and hydro-geological conditions; 4. Select the possible drainage schemes, and describe their individual elements. The methodology of the study: for research was using geological, hydrological and hydro-geological data which was summarized, analyzed and structured. To take account of long-lived factor was offer drainage system technical solutions. Results: • Carried out Stabatiske site research and analysis was identified the main reasons why the territory is in the excess moisture; • According to available data was choose optimal drainage system; • Established the geographic, geological and geotechnical point of view appropriate low-level radioactive waste storage facility construction; • Open reclamation ditches and multi-drainage, is the best way to control excess water in Stabatiske site. Conclusions: The main factor determining the selected type of drainage system is designed area. Knowing the storage lifetime (300 years), need for know suitable drainage complex for that period. Knowing the local water regime and soil composition, the best option to... [to full text]

Trijų sudėčių sluoksniuoti dvigubi hidroksidai (SDH) Mg/Al, Co/Mg/Al ir Ni/Mg/Al susintetinti bendro nusodinimo esant mažoms koncentracijoms metodu. Šie SDH buvo termiškai suskaidyti, ir gautieji mišrūs metalų oksidai reformuoti vandenyje ir pirmą kartą magnio nitrato tirpale. Naudojant XRF ir TG duomenis pasiūlytos susintetintų bendro nusodinimo metodu SDH formulės. XRD analizės rezultatai parodė, kad SDH ir mišrių metalų oksidų faziniai kitimai reformavimo metu priklauso nuo proceso temperatūros ir terpės prigimties. Co ir Ni turinčių SDH mėginių sluoksninės struktūros atstatymas kambario temperatūros vandenyje vyksta nepilnai, tačiau pakėlus temperatūrą iki 80 °C pašalinės oksidų fazės reformuotuose pavyzdžiuose nebelieka. Kai SDH atstatymui buvo naudojamas magnio nitrato tirpalas, katijonų sudėtis pakito dėl padidėjusio sluoksninėje struktūroje magnio kiekio. Ryškus temperatūros ir vandeninės terpės poveikis stebimas ne tik reformavimui, bet ir gautų SDH kristalitų dydžiams. Iškaitinus SDH gautų oksidų morfologija priklauso nuo jų sudėtyje esančio pereinamojo metalo ir reformavimui naudoto tirpalo prigimties. Praktiniai panaudojimai reformuotų SDH tirti NOx pašalinimo reakcijose ir gazifikacijos metu gaunamų dujų valyme. / Three layered double hydroxides Mg/Al, Co/Mg/Al and Ni/Mg/Al were successfully synthesized by the low supersaturation method, thermally decomposed and derived mixed metal oxides reformed to layered structures in water and for first time to our knowledge in magnesium nitrate media. XRD measurements provided direct evidence for phase transformation processes during calcination and reformation of layered structure at different temperatures. From XRF and TG analyses data the formulas of synthesized LDH were proposed. Incomplete regeneration of Co and Ni containing LDH samples at room temperature in aqueous media has been observed. However, with increasing temperature up to 80 °C the reconstitution process of LDH proceeds fully. Changes of cations composition after reformation could be explained by the increase of magnesium content when the reconstitution in magnesium nitrate solution followed. The hydration causes the formation of LDH with higher crystallite size in comparison with the LDH samples reformed in magnesium nitrate media. In most of the cases, with increasing the temperature of reconstitution media to 80ºC the crystallite size also increased. Reformation media had a considerable influence to the morphology of mixed metal oxides. Moreover, the effects for nickel or cobalt containing samples were found to be different. Catalysts prepared from LDH containing cobalt were tested in the removal of NOx and nickel containing LDH were tested in gasification gas cleaning.

The complex phenomenon of indentation deformation is studied using finite element analysis for both homogeneous and layered materials. For the homogeneous materials, the elastic-plastic deformation at large indentation depth is studied. The variation of the load-displacement curves as well as the variation of the energy ratio with the applied indentation depth for different strain hardening indices is presented. The power law relation between the indentation load and depth for shallow indentation becomes invalid for deep indentation. The ratio of plastic energy to total mechanical work is a linear function of the ratio of residual indentation depth and maximum indentation depth. For the layered materials (film-substrate systems), the elastic deformation under an indenter is studied. Various material parameters are investigated, including film thickness and modulus. A generalized power law equation is presented for characterizing the indentation load-displacement responses of film-substrate structures.

Thermally stimulated current measurements are carried out on as-grown TlGaS2, TlGaSe2 and TlInS2 layered single crystals with the current owing perpendiclar to the c-axis in the wide temperature range of 10-300 K with various heating rates. Experimental evidence is found for the presence of three, two and one trapping centers for TlGaS2 , TlGaSe2 and TlInS2 crystals with activation energies 6, 12 and 26 / 98 and 130 / 12 meV respectively. We have determined the trap parameters using varous methods of analyis, and these agree well with each other. The retrapping process is negligible for these levels, as confirmed by good agreement between the experimental results and theoretical predictions of the model that assumes slow retrapping. Also the calculated values of the capture cross sections, attempt to escape frequencies and the concentration of the traps are reported.

ABSTRACT PRODUCTION AND CHARACTERIZATION OF RESOL TYPE PHENOLIC RESIN / LAYERED SILICATE NANOCOMPOSITES TaSan, Cemal Cem M.S., Department of Metallurgical and Materials Engineering Supervisor: Assoc.Prof. Cevdet Kaynak April 2005 133 Pages Polymer / layered silicate (P/LS) nanocomposites belong to one of the most promising group of materials of the past few decades and most probably for the near future. Combining two of the most widely studied topics of material science: composite materials and nanotechnology / P/LS research have drawn great attention starting with the pioneering works of Toyota Research Group in 1980&rsquo / s. The research is now being carried out world wide / since the excellent properties of these new materials, which is achieved by using very low amounts of a cheap reinforcement material (clay), increases the interest on these materials everyday after. In this present study, the object was to investigate the production parameters of phenol formaldehyde based layered silicate nanocomposites. For this purpose, 14 different specimen groups were produced / using two different resol type phenolic resins (PF76 and PF76TD) as the matrix / and 9 different montmorillonite clays (Rheospan, Resadiye, Cloisite Na+, 10A, 15A, 20A, 25A, 30B, 94A) as the reinforcement phase. Initially the curing schedules for the available resins were experimentally determined. Then, a short and effective mixing procedure for the thermosetting resin and the montmorillonite clay was developed. The effects of several processing parameters / such as clay type, clay source, clay content, clay modification, resin type, resin cure type, cure cycle and mixing cycle were determined by X-ray Diffraction, Scanning Electron Microscopy and Mechanical Tests. Then, Transmission Electron Microscopy was used to investigate the level of intercalation and/or exfoliation of the layered silicates. Finally, Differential Scanning Calorimetry was also carried out to analyse thermal properties of the specimens. It was concluded that, a partially intercalated and/or exfoliated structure could be obtained in resol type phenolic resin based systems at very low clay contents (such as 0,5%) leading to remarkable increases in mechanical properties (e.g. 66% increase in fracture toughness).