All Texas school districts were examined to determine the relationship of district size and diversity to the accountability ratings of selected Texas school districts and the implications of including all data in the accountability rating system. Eight large districts and 12 small districts were matched demographically utilizing data from the 2003-2004 school year. Information from the Texas Education Agency was accessed over 2003-2004 and 2004-2005. The ratings were found to be lowered from Recognized to Academically Acceptable with the inclusion of these groups 6 out of 20 times. These findings indicate that the Texas accountability system, in its current structure, excludes certain students based upon race and economic status and is not in compliance with what the law intended. This study should be replicated on a larger scale to assess its validity for a larger sample of small districts. Equity among states should be examined to provide information for a nationwide accountability system.

Geckos can freely climb on walls and ceilings against their body weight at speed of over 1ms-1. Switching between attachment and detachment seem simple and easy for geckos, without considering the surface to be dry or wet, smooth or rough, dirty or clean. In addition, gecko can shed dirt particles during use, keeping the adhesive pads clean. Mimicking this biological system can lead to a new class of dry adhesives for various applications. However, gecko’s unique dry self-cleaning mechanism remains unknown, which impedes the development of self-cleaning dry adhesives. In this dissertation we provide new evidence and self-cleaning mechanism to explain how gecko shed particles and keep its sticky feet clean. First we studied the dynamic enhancement observed between micro-sized particles and substrate under dry and wet conditions. The adhesion force of soft (polystyrene) and hard (SiO2 and Al2O3) micro-particles on soft (polystyrene) and hard (fused silica and sapphire) substrates was measured using an atomic force microscope (AFM) with retraction (z-piezo) speed ranging over 4 orders of magnitude. The adhesion is strongly enhanced by the dynamic effect. When the retraction speeds varies from 0.02 µm/s to 156 µm/s, the adhesion force increases by 10% ~ 50% in dry nitrogen while …

Asymmetric polymeric materials can be formed by either top-down or bottom-up methods. Bottom-up methods involve assembling the atoms and molecules to form small nanostructures by carefully controlled synthesis, which results in a reduction of some of the top-down limitations. In this dissertation, thermal, tribological and antireflective properties of polymeric materials have been enhanced by introducing structural asymmetry. The overall performance of commercial polymeric coatings, e.g. epoxy and polyvinyl chloride, has been improved by conducting the blending methods, specifically, chemical modification (α,ω-dihydroxydimethyl(methyl-vinyl)oligoorganosiloxane), cross-linking (triallyl isocyanurate), and antioxidant (tris(nonylphenyl) phosphite) incorporation. The nonequilibrium polymeric structures (moth-eye and square array) have been developed for the ultrahigh molecular weight block copolymers via the short-term solvent vapor annealing self-assembly. The large domain size of the moth eye structure allows for improvement of the light transmittance particularly in the visible and near infrared ranges, while the square arrangement of the block copolymer opens the possibility of magnetic data storage application by the large magnetic nanoparticles' embedment or masking of the superconductors.

Shape memory alloys (SMAs) represent a revolutionary class of active materials that can spontaneously generate strain based on an environmental input, such as temperature or stress. SMAs can provide potential solutions to many of today's engineering problems due to their compact form, high energy densities, and multifunctional capabilities. While many applications in the biomedical, aerospace, automotive, and defense industries have already been investigated and realized for nickel-titanium (NiTi) based SMAs, the effects of controlling and designing the microstructure through processing (i.e. extreme cold working) have not been well understood. Current Ni-Ti based SMAs could be improved upon by increasing their work output, improving dimensional stability, preventing accidental actuation, and reducing strain localization. Additionally, there is a strong need to increase the transformation temperature above 115 °C, the current limit for NiTi and is especially important for aerospace applications. Previous research has shown that the addition on ternary elements such as Au, Hf, Pd, Pt, and Zr to NiTi can greatly increase these transformation temperatures. However, there are several limiting factors with these ternary additions such as increased cost, especially with Au, Pd, and Pt, as well as, difficulty in conventionally processing these alloys. Therefore, the main objectives of this research …

The utilization of biodegradable polymers is critical for developing “cradle to cradle” mindset with ecological, social and economic consequences. Poly(hydroxy butyrate-co-valerate) (PHBV) shows significant potential for many applications with a polypropylene equivalent mechanical performance. However, it has limitations including high crystallinity, brittleness, small processing window, etc. which need to be overcome before converting them into useful products. Further the development of biodegradable strain sensing polymer sensors for structural health monitoring has been a growing need. In this dissertation I utilize carbon nanotubes as a self sensing dispersed nanofiller. The impact of its addition on PHBV and a blend of PHBV with poly(butylene adipate-co-terephthalate) (PBAT) polymer was examined. Nanocomposites and blends of PHBV, PBAT, and MWCNTs were prepared by melt-blending. The effect of MWCNTs on PHBV crystallinity, crystalline phase, quasi-static and dynamic mechanical property was studied concurrently with piezoresistive response. In PHBV/PBAT blends a rare phenomenon of melting point elevation by the addition of low melting point PBAT was observed. The blends of these two semicrystalline aliphatic and aromatic polyesters were investigated by using differential scanning calorimetry, small angle X-ray scattering, dynamic mechanical analysis, surface energy measurement by contact angle method, polarized optical and scanning electron microscopy, and rheology. The study …