Research report (Texas Tech University. Center for Multidisciplinary Research in Transportation)

Report discussing the primary objective of this research project, whcih was to develop rational guidelines on the use of dowel bars in longitudinal construction joints (LCJs) for better-performing concrete pavements without potential longitudinal cracking problems

Technical report (Texas Tech University. Center for Multidisciplinary Research in Transportation)

This report explains why a mechanistic-empirical (ME) based pavement design method will allow Texas Department of Transportation (TxDOT) to optimize pavement structures to best utilize the limited financial resources available

Clinical validity of two different grading systems for lumbar central canal stenosis: Schizas and Lee classification systems.

OBJECTIVE:To assess the learnability of two magnetic resonance imaging (MRI) grading systems for lumbar central canal stenosis based on inter-observer agreement and test-retest reliability of doctors with no prior knowledge of the two systems. MATERIALS AND METHODS:Two clinical fellows, one novice radiology resident, one neurosurgeon, and one orthopedic surgeon, who were unaware of the two qualitative MRI grading systems prior to this study, acquainted themselves with the teaching files. All five observers independently assessed the LCCS grade of 70 patients using T2-weighted axial magnetic resonance images at the L2-3, L3-4, L3-4, and L5-S1 disc levels. Analysis was performed twice at an interval of two months. RESULTS:The inter-observer agreement among all five readers was excellent and test-retest reliability was moderate to excellent for both the Schizas and Lee systems. Positive percentage agreements were found to be over 0.8 in almost all observers with relatively narrow 95% confidence limits. CONCLUSION:Both Schizas and Lee MRI grading systems for LCCS are reliable grading systems, and can be used as a learnable method for both clinicians and radiologists

Fabrication of a Completely Transparent and Highly Flexible ITO Nanoparticle Electrode at Room Temperature

We report the fabrication of a highly flexible indium tin oxide (ITO) electrode that is completely transparent to light in the visible spectrum. The electrode was fabricated via the formation of a novel ITO nanoarray structure, consisting of discrete globular ITO nanoparticles superimposed on an agglomerated ITO layer, on a heat-sensitive polymer substrate. The ITO nanoarray spontaneously assembled on the surface of the polymer substrate by a simple sputter coating at room temperature, without nanolithographic or solution-based assembly processes being required. The ITO nanoarray exhibited a resistivity of approximately 2.3 × 10^–3 Ω cm and a specular transmission of about 99% at 550 nm, surpassing all previously reported values of these parameters in the case of transparent porous ITO electrodes synthesized via solution-based processes at elevated temperatures. This novel nanoarray structure and its fabrication methodology can be used for coating large-area transparent electrodes on heat-sensitive polymer substrates, a goal unrealizable through currently available solution-based fabrication methods

Guidelines for Partial Depth Repair in Continuously Reinforced Concrete Pavement

0-5549-P1Over the years, the Texas Department of Transportation (TxDOT) has improved design and construction practices of Continuously Reinforced Concrete Pavement (CRCP), which has resulted in good overall performance of CRCP in Texas. At the same time, the improved design and construction practices changed the type of distresses in CRCP. Typical punchout distresses that were once prevalent and required full-depth repairs, have become rare; rather, a substantial portion of distresses observed in CRCP built with the improved design and construction practices are partial depth distress (PDD). In PDD, the distress is confined to the top half of the slab, above longitudinal steel. The concrete below the longitudinal steel, or the approximate bottom half of the slab, remains in sound condition. In CRCP, good load transfer at transverse cracks is provided by an adequate amount of longitudinal steel and aggregate interlock, which is responsible for good performance of CRCP in Texas. On the other hand, if load transfer is degraded or lost at transverse cracks or any transverse joints (construction joints or repair joints), CRCP performance could be severely compromised. In repairing PDD, it is strongly advisable to keep the continuity of the longitudinal steel so that a high level of load transfer is maintained at the transverse repair joints. Full-depth repair (FDR) requires cutting of longitudinal steel at the transverse repair joints and it\u2019s difficult to restore the continuity of longitudinal steel and load transfer capability at transverse repair joints. Accordingly, partial-depth repair (PDR) should be used for the repair of PDD, because it will keep the continuity of longitudinal steel, provide a high level of load transfer at transverse repair joints, and is more cost-effective than FDR. This document provides guidelines for the evaluation of CRCP distress to determine whether a distress is PDD, and for the proper repair procedures including repair material selection. This document does not address the repair of CPCD (Concrete Pavement Contraction Design)

Preparation of Flexible Organic Solar Cells with Highly Conductive and Transparent Metal-Oxide Multilayer Electrodes Based on Silver Oxide

We report that significantly more transparent yet comparably conductive AgO_<i>x</i> films, when compared to Ag films, are synthesized by the inclusion of a remarkably small amount of oxygen (i.e., 2 or 3 atom %) in thin Ag films. An 8 nm thick AgO_<i>x</i> (O/Ag = 2.4 atom %) film embedded between 30 nm thick ITO films (ITO/AgO_<i>x</i>/ITO) achieves a transmittance improvement of 30% when compared to a conventional ITO/Ag/ITO electrode with the same configuration by retaining the sheet resistance in the range of 10–20 Ω sq^–1. The high transmittance provides an excellent opportunity to improve the power-conversion efficiency of organic solar cells (OSCs) by successfully matching the transmittance spectral range of the electrode to the optimal absorption region of low band gap photoactive polymers, which is highly limited in OSCs utilizing conventional ITO/Ag/ITO electrodes. An improvement of the power-conversion efficiency from 4.72 to 5.88% is achieved from highly flexible organic solar cells (OSCs) fabricated on poly­(ethylene terephthalate) polymer substrates by replacing the conventional ITO/Ag/ITO electrode with the ITO/AgO_<i>x</i>/ITO electrode. This novel transparent electrode can facilitate a cost-effective, high-throughput, room-temperature fabrication solution for producing large-area flexible OSCs on heat-sensitive polymer substrates with excellent power-conversion efficiencies