Search

The objective of this research is to evaluate how the physical properties and thickness of asphalt pavements influence behaviors of ultra thin whitetopping (UTW). The results of the three-dimensional finite-element method reveal that properties of asphalt and concrete layers, bonding between the two layers, and temperature strongly affect the distress of UTW. Based on results of FEM analysis, a wheel tracking device called the 'heart wheel load simulator (HWLS)' was developed and used to perform an experiment to observe behavior variation in accordance with asphalt and concrete layer thicknesses as well as temperature. The results of HWLS simulation show that the effect of temperature is not significant and the increase of the tensile strain with the increase of a load is relatively small for a 100 mm concrete layer, as compared to a 50 mm concrete layer. In addition, for a 50 mm concrete layer with a less than 150 mm asphalt layer, the increased ratio of the tensile strain at the bottom of the concrete slab is significantly higher. Therefore, this research recommends that an at least 150 mm asphalt layer after milling be required in order to apply UTW safely. DOI: 10.1061/(ASCE)0733-947X(2006) (880) CE Database subject headings: Rehabilitation; Asphalt pavements; Simulation.

Intramolecular cyclization of 1,1‐diisopropyl‐ or diphenyl‐bis(phenylethynyl)‐silanes (2a and 2b) followed by bromination or trimethylsilylation were carried out to yield 1,1‐diisopropyl‐ or ‐diphenyl‐3,4‐diphenyl‐2,5‐dibromo‐siloles (3a and 3b) and 1,1‐diisoproyl‐ or ‐diphenyl‐3,4‐diphenyl‐2,5‐bis(trimethylsilyl)‐siloles (4a and 4b), respectively. The structures of 3a,b and 4a,b were confirmed using 1H, 13C, and 29Si NMR as well as FTIR spectroscopy. The absorption bands of the siloles 3a,b and 4a,b in THF were measured at 303–325 nm with the molar absorptivities of 1.85 × 103 ~ 2.18 × 103 cm−1·M−1. The excitation bands were measured at 347–376 nm and the emission peaks were measured at 409–445 nm. Cyclic voltammograms of 3a and 3b indicated oxidation peaks at 0.90 and 0.80 V and reduction peaks at −1.20 and −1.20 V, respectively. The cyclic voltammograms of 4a and 4b indicated two oxidation peaks between −0.05 and −0.95 V and two reduction peaks between −0.10 and −0.93 V, respectively. Compound 4a exhibits a better long cycle performance by almost 1000 cycles as compared that of 3a and 4b. The rate performance test of the anodes Li‐3a and Li‐4a exhibited better performance properties at various C rate than Li‐4b. According to discharge–charge curves, 4a shows one plateau at approximately 0.58 V of the first discharge curve and the initial discharge specific capacity of 972 mAh/g. The electrochemical impedance spectroscopy of 4a indicates low charge transfer resistance, good conductivity of the electrolyte, and fast chemical adsorption/desorption rate of electrolyte ions on electrode surface, due to the electronic structure of 4a. [ABSTRACT FROM AUTHOR]

In South Korea, the performance of continuously reinforced concrete pavement (CRCP) has been better than that of jointed concrete pavement (JCP). However, most of the Portland cement concrete (PCC) pavements in South Korea have been JCP, primarily due to the difficulty in providing extra space along the edge of the pavement needed for concrete delivery in CRCP construction. In a tube-feeding method (TFM), concrete can be supplied from the front of a paver, which could facilitate CRCP construction without extra space needed. In the present study, efforts were made to improve the capability of TFM in placing longitudinal steel at correct elevations, which resulted in the development of tube feeding equipment (TFE). Field testing results showed that the key to ensuring steel placement at correct elevations was to keep longitudinal steel in adequate tension. The distance from the back of the tubes and the front of the mould, up to 1500 mm, did not have substantial effects on the steel settlement. To evaluate the viability of CRCP construction with TFE, a 400 m long CRCP section with 300 mm slab thickness and 8.2-m width was constructed and performance monitored. [ABSTRACT FROM AUTHOR]

Byline: Do Hyun Ahn, Jae Kyeong Kim, Il Young Choi, Yoon Ho Cho With the advance of e-commerce, the importance of recommender systems grows larger than before. Collaborative filtering is the most successful recommendation method, but its widespread use has exposed some problems such as sparsity and scalability. To overcome such limitations, this paper proposes hybrid recommendation methodologies based on web usage mining and dimensionality reduction techniques to enhance the recommendation quality and performance of current collaborative filtering-based recommender systems. Web usage mining populates the rating database by tracking customers' shopping behaviours on the web, thereby leading to better quality recommendations. The product taxonomy and SVD (Singular Value Decomposition) are used to improve the performance of searching for nearest neighbours through dimensionality reduction of the rating database. Experiments on real e-commerce data show that the proposed methodologies provide higher quality recommendations and better performance than existing collaborative filtering methodologies.

Abstract: We report the ionic conductivity studies of three different Ruddlesden‐Popper layered perovskite (RP‐LP) materials (Li2SrTa2O7, Li2SrNb2O7, and Li2CaTa2O7) in composites with poly (ethylene oxide) (PEO). For the first time, the lithium‐ion conduction pathway in the RP‐LP materials, of n=2 in AnA′BnO3n+1 general crystal structure, have been studied by using bond valence sum mapping. The results show a two‐dimensional lithium‐ion pathway. The temperature dependence of the conductivity is modelled by using a Vogel−Tamman−Fulcher (VTF)‐type relationship for PEO RP‐LP and pure PEO samples. The PEO RP‐LP composites deliver ionic conductivities in the range of 3.32 to 4.09×10−06 σ cm−2 at 80 °C, and their corresponding activation energies range from 6.37 to 7.01 kJ mol−1 at the calculated temperature slope range of 50 to 80 °C. They also deliver appreciable lithium transference numbers in the range of 0.20 to 0.58 at 30 °C and an excellent wide potential window stability of 4 V. [ABSTRACT FROM AUTHOR]