Carboxylate Adsorption on Rutile TiO2(100): Role of Coulomb Repulsion, Relaxation, and Steric Hindrance

Understanding the adsorption and photoactivity of acetic acid and trimethyl acetic acid on TiO2 surfaces is important for improving the performance of photocatalysts and dye-sensitized solar cells. Here we present a structural study of adsorption on rutile TiO2(100)-1 × 1 and -1 × 3 using Scanning Tunnelling Microscopy and Density Functional Theory calculations. Exposure of both terminations to acetic acid gives rise to a ×2 periodicity in the [001] direction (i.e., along Ti rows), with a majority ordered c(2 × 2) phase in the case of the 1 × 1 termination. The DFT calculations suggest that the preference of c(2 × 2) over the 2 × 1 periodicity found for TiO2(110)-1 × 1 can be attributed to an increase in interadsorbate Coulomb repulsion. Exposure of TiO2(100)-1 × 1 and -1 × 3 to trimethyl acetic acid gives rise to largely disordered structures due to steric effects, with quasi-order occurring in small areas and near step edges where these effects are reduced

Rare earthquake response spectra for typical site conditions in Hong Kong

Hong Kong is located in a region of low-to-moderate seismicity; the potential consequences in the event of a nearby major earthquake should not be underrated. In the past two decades, researchers have conducted many studies on this issue and it is now clear that design procedures should not be directly borrowed from other codes of practice without modifications. This paper aims at presenting the rare earthquake response spectra for typical rock and soil sites in Hong Kong, which form the basis of a seismic design procedure. The uniform hazard spectrum (UHS) for rock sites was obtained from seismic hazard assessment using probabilistic methods. Records from 16 boreholes, representing a wide range of local site conditions, were collected from different locations in Hong Kong. A site-specific response spectrum was then constructed based on the results of site response analyses. Moreover, the 16 site-specific response spectra have been grouped into four types based on the (initial) site natural periods, which allows convenient evaluation of the loading characteristics that are expected at different types of sites. Finally, the rare earthquake response spectra proposed for Hong Kong are compared with those constructed based on the Chinese code (GB) and the Eurocode (EC8).postprin

CPT-Based Liquefaction Triggering Procedure

A probabilistic cone penetration test (CPT) based liquefaction triggering procedure for cohesionless soils is derived using a maximum likelihood method with an updated case history database. The liquefaction analysis framework includes revised relationships for the magnitude scaling factor (MSF) and for estimating fines contents from CPT data when laboratory test data are not available. The updated case history database and methodology for developing the liquefaction correlation are described. Measurement and estimation uncertainties, the potential effects of false positives and false negatives in the case history database, and the effects of the choice-based sampling bias in the case history database are accounted for. Sensitivity analyses showed that the position of the most likely triggering curve and the magnitude of the total error term are reasonably well constrained by the data. The sensitivity study provides reasonable bounds on the effects of different interpretations, from which probabilistic and deterministic relationships for practice are recommended