Intrinsic Oxygen Vacancy and Extrinsic Aluminium Dopant Interplay: A Route to the Restoration of Defective TiO2_2

Density functional theory (DFT) and DFT corrected for on-site Coulomb interactions (DFT+U) calculations are presented on Aluminium doping in bulk TiO$_2$ and the anatase (101) surface. Particular attention is paid to the mobility of oxygen vacancies throughout the doped TiO$_2$ lattice, as a means by which charge compensation of trivalent dopants can occur. The effect that Al doping of TiO$_2$ electrodes has in dye sensitised solar cells is explained as a result of this mobility and charge compensation. Substitutional defects in which one Al3+ replaces one Ti4+ are found to introduce valence band holes, while intrinsic oxygen vacancies are found to introduce states in the band-gap. Coupling two of these substitutional defects with an oxygen vacancy results in exothermic defect formation which maintain charge neutrality. Nudged elastic band calculations have been performed to investigate the formation of these clustered defects in the (101) surface by oxygen vacancy diffusion, with the resulting potential energy surface suggesting energetic gains with small diffusion barriers. Efficiency in- creases observed in dye sensitised solar cells as a result of aluminium doping of TiO$_2$ electrodes are investigated by adsorbing the tetrahydroquinoline C2-1 chromophore on the defective surfaces. Adsorption on the clustered extrinsic Al3+ and intrinsic oxygen vacancy defects are found to behave as if adsorbed on a clean surface, with vacancy states not present, while adsorption on the oxygen vacancy results in a down shift of the dye localised states within the band-gap and defect states being present below the conduction band edge. Aluminium doping therefore acts as a benign dopant for 'cleaning' TiO$_2$ through oxygen vacancy diffusion.Comment: 32 pages, 15 figures, accepted for publication by J. Phys. Chem.

Linear Scaling Density Matrix Real Time TDDFT: Propagator Unitarity \& Matrix Truncation

Real time, density matrix based, time dependent density functional theory proceeds through the propagation of the density matrix, as opposed to the Kohn-Sham orbitals. It is possible to reduce the computational workload by imposing spatial cut-off radii on sparse matrices, and the propagation of the density matrix in this manner provides direct access to the optical response of very large systems, which would be otherwise impractical to obtain using the standard formulations of TDDFT. Following a brief summary of our implementation, along with several benchmark tests illustrating the validity of the method, we present an exploration of the factors affecting the accuracy of the approach. In particular we investigate the effect of basis set size and matrix truncation, the key approximation used in achieving linear scaling, on the propagator unitarity and optical spectra. Finally we illustrate that, with an appropriate density matrix truncation range applied, the computational load scales linearly with the system size and discuss the limitations of the approach.Comment: Accepted for publication in J. Chem. Phy

DSSC Anchoring Groups: A Surface Dependent Decision

Electrodes in dye sensitised solar cells (DSSCs) are typically nanocrystalline anatase TiO2 with a majority (101) surface exposed. Generally the sensitising dye employs a carboxylic anchoring moiety through which it adheres to the TiO2 surface. Recent interest in exploiting the properties of differing TiO2 electrode morphologies, such as rutile nanorods exposing the (110) surface and anatase electrodes with high percentages of the (001) surface exposed, begs the question of whether this anchoring strategy is best, irrespective of the majority surface exposed. Here we address this question by presenting density functional theory calculations contrasting the binding properties of two promising anchoring groups, phosphonic acid and boronic acid, to that of carboxylic acid. Anchor-electrode interactions are studied for the pro- totypical anatase (101) surface, along with the anatase (001) and rutile (110) surfaces. Finally the effect of using these alternative anchoring groups to bind a typical coumarin dye (NKX- 2311) to these TiO2 substrates is examined. Significant differences in the binding properties are found depending on both the anchor and surface, illustrating that the choice of anchor is necessarily dependent upon the surface exposed in the electrode. In particular the boronic acid is found to show the potential to be an excellent anchor choice for electrodes exposing the anatase (001) surface.Comment: 44 pages, 15 figures, accepted by J. Phys.:Condens. Matter. Coordinates for structures available via figshar

The Difficulty of Forecasting Ambient Air Quality: A Weak Link in Pollution Control

This article examines one important component of the problem of implementing the federal government\u27s Clean Air policy, namely, the difficulty of quantifying the relationship between emissions to the atmosphere and ambient air quality. Short-, middle-, and long-term control strategies are discussed with an emphasis on the information needed for their effective assessment and implementation. The requirement thus identified is compared with the information provided by air pollution models; it is shown that at their present stage of development, even the most sophisticated diffusion models are of limited usefulness in implementing current air pollution legislation. In view of the high cost of pollution control, further investment in model development is thought justifiable, though there are significant problems to be overcome. It is suggested that for the time being, panels of experts might be used to making air quality forecasts

The Neglect of Socioeconomic Research by US Energy and Environmental Agencies

The published research plans of the US Environmental Protection Agency (EPA) and the US Energy Research and Development Administration (ERDA) have each been criticized by the Office of Technology Assessment for focusing largely on the development of technological “hardware” and giving little attention to socioeconomic research (broadly defined). This paper first examines socioeconomic research areas that EPA might be expected to cover and shows that its plans for doing so are inadequate. The paper then identifies gaps in ERDA\u27s coverage of socioeconomic research that remain unfilled even in the agency\u27s updated plan. Several reasons for this neglect of socioeconomic research are hypothesized, namely: the dominance of research management by scientists and technologists; the apparent irrelevance and/or lack of success of socioeconomic research performed in the past; the greater political acceptability of technological compared with non-technological approaches to pollution control: the public\u27s apparent faith in our ability to develop technological solutions to energy and environmental problems; and the compatibility of new technology development with economic growth. Following a discussion of these reasons, it is concluded that senior management positions in both agencies must no longer be monopolized by those with solely scientific and technical backgrounds; instead, managers should be appointed who not only have appropriate social science or professional qualifications but are also able to communicate to their colleagues, to lawmakers, and to the public at large, the importance of having a balanced research program with both technological and socioeconomic components

Distribution and Ecology of Cavernicolous Coleoptera in Bat Cave, Carter County, Kentucky

A thesis presented to the faculty of the School of Sciences and Mathematics at Morehead State University in partial fulfillment of the requirements for the Degree of Master of Science by David Bruce Conn on April 28, 1980

Carter County - Carter Caves

A term paper on Carter Caves State Park written by David Bruce Conn in 1981

The Relationship Between Prior Experiences in Mathematics and Pharmacy School Success

Objective. To assess students’ pre-pharmacy math experiences, confidence in math ability, and relationship between experiences, confidence, and grades in math-based pharmacy courses. Methods. A cross-sectional survey of first year to third year pharmacy students was conducted. Students reported type of pre-pharmacy math courses taken, when they were taken [high school (HS) vs. college] and year of HS and college graduation. Students rated their confidence in math ability using the previously validated 11-item Fogerty Math Confidence Scale (Cronbach alpha=0.92). Math grade point average (GPA), Pharmacy College Admission Test quantitative (PCAT quant) scores, and grades (calculations and kinetics) were obtained from transcripts and school records. Spearman correlation and multivariate linear regression were used to compare math experiences, confidence, and grades. Results. There were 198 students who reported taking math courses 7.1 years since HS graduation and 2.9 years since their last schooling prior to pharmacy school. Students who took math courses with more time since HS/last schooling had lower calculations and kinetics grades. Students reporting having taken more HS math courses had better calculations grades. Students with higher math GPA, and PCAT quant scores also had higher calculations and kinetics grades. Greater confidence in math ability was associated with higher calculations grades. In multivariate regressions, PCAT quant scores and years since HS independently predicted calculations grades, and PCAT quant scores independently predicted kinetics grades. Conclusion. The number of pre-pharmacy math courses and time elapsed since they were taken are important factors to consider when predicting a pharmacy student’s success in math-based pharmacy school courses

Bi-directional coordination of plug-in electric vehicles with economic model predictive control

© 2017 by the authors. Licensee MDPI, Basel, Switzerland. The emergence of plug-in electric vehicles (PEVs) is unveiling new opportunities to de-carbonise the vehicle parcs and promote sustainability in different parts of the globe. As battery technologies and PEV efficiency continue to improve, the use of electric cars as distributed energy resources is fast becoming a reality. While the distribution network operators (DNOs) strive to ensure grid balancing and reliability, the PEV owners primarily aim at maximising their economic benefits. However, given that the PEV batteries have limited capacities and the distribution network is constrained, smart techniques are required to coordinate the charging/discharging of the PEVs. Using the economic model predictive control (EMPC) technique, this paper proposes a decentralised optimisation algorithm for PEVs during the grid-To-vehicle (G2V) and vehicle-To-grid (V2G) operations. To capture the operational dynamics of the batteries, it considers the state-of-charge (SoC) at a given time as a discrete state space and investigates PEVs performance in V2G and G2V operations. In particular, this study exploits the variability in the energy tariff across different periods of the day to schedule V2G/G2V cycles using real data from the university's PEV infrastructure. The results show that by charging/discharging the vehicles during optimal time partitions, prosumers can take advantage of the price elasticity of supply to achieve net savings of about 63%