Wind-powered membrane desalination of brackish water

This thesis presents a detailed investigation of the technical feasibility, challenges and performance issues associated with the direct-connection of a wind turbine to a membrane (wind-membrane) system for treating brackish water in remote communities. The direct-connection of these two technologies negates the reliance on energy storage in batteries, which are traditionally used, but result in reduced system efficiency and increased life-cycle costs. Furthermore, the lack of knowledge of the safe operating window in which transient operation of membrane systems is beneficial or tolerable can be addressed. The impact of wind speed fluctuations on the performance of the wind-membrane system (using a BW30-4040 membrane and feed waters of 2750 and 5500 mg/L NaCl) showed that the performance deteriorated most under fluctuations at low average wind speeds with high turbulence intensity and long periods of oscillation. Therefore, the main challenge of operating with renewable energy is not the size of the fluctuations, but the effect of the power switching off. Further examination of the impact of wind intermittency (over one hour intervals with intermittent periods from 0.5 – 3 min) showed that the increase in permeate concentration was highest at off-times < 60 s, highlighting the potential for improved performance using short-term energy buffering. The safe operating window and the key constraints to safe operation were determined for several membranes and feed water concentrations to establish the optimum operating strategy for the wind-membrane system. Supercapacitors were used to expand the safe operating window by providing energy during periods of intermittency and enhancing the power quality delivered to the membrane system by absorbing wind fluctuations. When tested over 24 hours using real wind speed data (average 6 m/s), the wind-membrane system produced 0.78 m3 of water with an average permeate concentration of 240 mg/L NaCl and average specific energy consumption (SEC) of 5.2 kWh/m3. With the addition of supercapacitor storage, the system performance improved significantly with 0.93 m3 of water produced with an average permeate concentration of 170 mg/L NaCl and SEC of 3.2 kWh/m3

Molecular Structure of XeF6. II. Internal Motion and Mean Geometry Deduced by Electron Diffraction

The distribution of internuclear distances in gaseous XeF6 exhibits unusually diffuse XeF6 bonded and F–F geminal nonbonded peaks, the latter of which is severely skewed. The distribution proves the molecule cannot be a regular octahedron vibrating in independent normal modes. The instantaneous molecular configurations encountered by the incident electrons are predominantly in the broad vicinity of C3υC3υ structures conveniently described as distorted octahedra in which the xenon lone pair avoids the bonding pairs. In these distorted structures the XeF bond lengths are distributed over a range of approximately 0.08 Å with the longer bonds tending to be those adjacent to the avoided region of the coordination sphere. Fluorines suffer angular displacements from octahedral sites which range up to 5° or 10° in the vicinity of the avoided region.Alternative interpretations of the diffraction data are developed in detail, ranging from models of statically deformed molecules to those of dynamically inverting molecules. In all cases it is necessary to assume that t1ut1u bending amplitudes are enormous and correlated in a certain way with substantial t2gt2g deformations. Notwith‐standing the small fraction of time that XeF. spends near OhOh symmetry, it is possible to construct a molecular potential‐energy function more or less compatiable with the diffraction data in which the minimum energy occurs at OhOh symmerty. The most notable feature of this model is the almost vanishing restoring force for small t1ut1u bending distortions. Indeed, the mean curvature of the potential surface for this model corresponds to a υ4υ4 force constant F44F44 of 10−2 mdyn/Å or less. Various rapidly inverting non‐OhOh structures embodying particular combinations of t2gt2g and t1ut1u deformations from OhOh symmetry give slightly better radial distribution functions, however. In the region of molecular configuration where the gas molecules spend most of their time, the form of the potential‐energy function required to represent the data does not distinguish between a Jahn–Teller first‐order term or a cubic V445V445 term as the agent responsible for introducing the t2gt2g deformation. The Jahn–Teller term is consistent with Goodman's interpretation of the molecule. On the other hand, the cubic term is found to be exactly analogous to that for other molecules with stereochemically active lone pairs (e.g., SF4, ClF3). Therefore, the question as to why the XeF6 molecule is distorted remains open. The reported absence of any observable gas‐phase paramagnetism weighs against the Jahn–Teller interpretation.The qualitative success but quantitative failure of the valence‐shell–electron‐pair‐repulsion theory is discussed and the relevance of the “pseudo‐Jahn–Teller” formalism of Longuet‐Higgins et al. is pointed out. Brief comparisons are made with isoelectronic ions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70641/2/JCPSA6-48-6-2466-1.pd

Effects of Electron Correlation in X‐Ray and Electron Diffraction. IV. Approximate Treatment for Many‐Electron Atoms

A simple scheme is proposed for predicting effects of electron correlation on intra‐atomic electron—electron radial distribution functions and on intensities of x rays scattered by gas atoms. It makes use of a relationship connecting the Coulomb hole function for an electron pair with the corresponding correlation energy. The method is applied to the beryllium atom in its ground state. Results compare favorably with results calculated directly from correlated and Hartree—Fock wavefunctions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71228/2/JCPSA6-45-12-4700-1.pd

Capturing the holistic profile of high performance Olympic weightlifting development

Recent expertise development studies have used retrospective recall methods to explore developmental biographies and/or practice histories of current or past athletes. This methodological approach limits the generalizability and trustworthiness of findings. As such, a gap exists for research exploring key multidisciplinary features in athlete development using prospective longitudinal research designs. The present research aimed to holistically model the development of talent in Olympic Weightlifting using such a design. We observed the holistic profiles of 29 junior weightlifting athletes longitudinally over a 10-month period, and subsequently classified six of the 23 athletes as high performing based on their performances in competitions up to 12 months following the study. This holistic profile was based on a framework of expertise development themes: (1) demographics and family sport participation, (2) anthropometrics and physiological factors, (3) psychosocial profiling, (4) sport participation history, and (5) weightlifting specific practice activities. A summary model was produced which selected a critical set of nine features that classified group membership with 91% average accuracy. Odds ratio calculations uncovered discriminating features in the holistic profiles of performance groups, from which empirically derived logical statements could inform the description of high-performance attainment

Testing anxiety's effect on movement planning and correction: Online upper-limb corrections are not completely automatic

Via three experiments, we investigated heightened anxiety's effect on the offline planning and online correction of upper-limb target-directed aiming movements. In Experiment 1, the majority of task trials allowed for the voluntary distribution of offline planning and online correction to achieve task success, while a subset of cursor jump trials necessitated the use of online correction to achieve task success. Experiments 2 and 3 replicated and elaborated Experiment 1 by assessing movement-specific reinvestment propensity and manipulating the self-control resources of participants. This allowed more detailed inference of cognitive resource utilisation to tease apart the effects of conscious processing and distraction-based anxiety mechanisms. For the first time, we demonstrate that: anxiety-induced online-to-offline motor control shifts can be overridden when the need for online correction is necessitated (i.e., in jump trials); anxiety-induced online-to-offline shifts seem to be positively predicted by conscious processing propensity; and optimal spatial efficacy of limb information-based online correction seems to require cognitive resources. We conclude that long-standing definitions of limb information-based online correction require revision, and that both conscious processing and distraction theories appear to play a role in determining the control strategies of anxiety induced upper limb target directed aiming movements