Ocean salinity is a renewable energy source that has not been recognized and could provide an opportunity to capture significant amount of clean energy when it mixes with river water. One of the processes emerging as a sustainable method for capturing energy from seawater is reverse electrodialysis (RED), which generates power via the transport of the positive and negative ions in the water through selective ion exchange membranes (IEMs). RED power generation is relatively close to commercialization, but its application is often limited by system power efficiency in natural water conditions. Although various types of salt ions exist in environmental saline water, most efforts have been focused on sodium chloride as a single ionic source in the water and the effects of other common multivalent ions (e.g., magnesium and sulfate) on power generation remain unexplored. Moreover, the commercial feasibility of RED is highly challenged by the absence of specialized RED membranes. Currently available IEMs are not optimized for RED power conversion systems, but successful operation is highly dependent on the membranes used. Major advances in manufacturing of proper IEMs will be a critical pathway to accelerate large-scale energy conversion by RED. Therefore, this study aimed at advancing our understanding of the RED power system for efficient and stable salinity gradient energy generation. Specifically, it is comprised of three parts. First, a mathematical model is developed for three different monovalent and multivalent ion combinations to determine the effect of different ionic compositions of the feed solution on the power density. Efforts are further made to optimize the RED system with respect to improving power density by investigating the sensitivity of key response parameters such as flow rate ratios and intermembrane distance ratios. Second, novel organic-inorganic nanocomposite cation exchange membranes (CEMs) are synthesized for RED application by introducing functionalized inorganic materials into an organic polymer matrix. The effect of inorganic particle filler loading within the organic polymer matrix on physico- and electrochemical performance is investigated. The results revealed that the increase of functionalized nanoparticle loading controls the effective ion transport in the membrane structure and there exists an optimum amount of nanoparticles (i.e., charged groups), which performs the best in selectively exchanging counter-ions, while excluding co-ionic species. Third, the membrane structure modification is demonstrated to enhance ion transport while maintaining large surface-charged functional groups in the polymer matrix. We have synthesized custom nanocomposite CEMs to tailor porous membrane structures of various thicknesses, aging (evaporation) time, and inorganic nanoparticle loadings. We have further tailored the membrane structure by incorporating different inorganic particle filler sizes. These engineered design approaches are found to be highly effective in obtaining desired physico- and electrochemical properties, which allowed higher ionic current flow throughout the system. Furthermore, for the first time we showed the successful application of tailor-made nanocomposite CEMs in a RED stack and achieved superb power density, which exceeds the power output obtained with the commercially available membranes. In summary, this dissertation has advanced our understanding of salinity gradient energy generation using RED technique. Specifically, computational modeling and simulation study investigates the development and optimization approaches of the RED process for practical application of RED using natural water conditions. Furthermore, the RED membranes developed in this dissertation focuses on fabrication, characterization, and optimization of cation exchange membranes. Overall, the results of this study are anticipated to benefit the future optimization of energy-capturing mechanisms in RED and provide the better pathway for the sustainable salinity gradient power generation.

Graduate

Oblique continental collision between the Pacific and Australian Plates in the central South Island of New Zealand (between c. 44 and 46°S) results in distributed reverse faulting. Only a few of these faults have been studied in detail, highlighting a major knowledge deficit in the earthquake behaviour, magnitude potential and contribution to seismic hazard for many faults in this part of the orogen. Three reverse faults are investigated in detail in this thesis: the Moonlight Fault Zone (MFZ), the Fox Peak Fault and the Forest Creek Fault. Geochronologic approaches, including Schmidt hammer exposure-age dating, radiocarbon dating, and optically stimulated luminescence dating, are combined with paleoseismic trenching, fault surface trace mapping, analysis of GPS and LiDAR survey data, and numerical modelling to characterise the rupture behaviour of these faults. A new Schmidt hammer chronofunction based on over 7000 clast analyses is developed that relates rebound value (R-value) to age for river terraces. The rapid, inexpensive, non-destructive, and statistically valid nature of this technique makes it widely applicable for age dating here and globally. I use Schmidt hammer exposure-age dating along with other geochronologic and surveying methods to show that stranded post-last glacial lake shorelines of Lake Wakatipu are undeformed and at a uniform elevation across the MFZ. This indicates an absence of uplift across the MFZ since c. 13 ka and suggests that this fault may be inactive or subject to long periods of interseismic quiescence despite its location in the active orogen. This result also challenges the long-held hypothesis that lake shorelines throughout central NZ are tilted due to isostatic rebound. Three segments of the Fox Peak Fault are identified through field mapping and surveying. Slip rates at over 50 locations along the 36.5 km total length of the fault (c. 1.5 mm yr⁻¹ maximum) co-vary with the bounding range topography and exhibit large gradients near intersecting NW-striking faults. Four paleoseismic trenches were excavated to determine if these segment boundaries represent barriers to earthquake rupture propagation. Evidence of 3-4 earthquakes since c. 16 ka on the two end segments with overlapping age uncertainties indicates that the recurrence interval of the fault is 2000-3000 years. The most recent event (MRE) occurred at c. 2.5 ka. Large single event displacement to length ratios on these segments and a single event scarp on the central segment indicate that while the segment boundaries control on-fault slip gradients, they are not likely to impede through-going ruptures in an earthquake. This is a relatively recent development from the long-term tectonic geomorphology, which is suggestive of range growth on separate faults.

No description available.

Thesis (PhD)--University of South Australia, 2001

Aging is an inevitable trend for most of the countries. Compared to developed countries, China lacks a comprehensive social security system that provides a safety net for the welfare of the elderly in their retirement. Even more, Chinese seniors are about to suffer insufficient support from traditional means ??? family and government support. As a last resort, reverse mortgages are a good financial tool to unlock home equity and improve the living standard for elderly without them moving out. This thesis aims to assess the Chinese reverse mortgage market from different perspectives to determine whether reverse mortgages will work in Chinese market. From the demand side, the analysis shows that China???s aged population, identified as the potential consumers of reverse mortgages, has a large fraction of wealth tied up in the form of housing and is in need of a method to release their home equity to finance life after retirement. From the supply side, potential providers could also benefit from reverse mortgages despite the exposure to various risks, e.g. cross over risks. Further examination of the Chinese financial and housing markets, and mortality rate helps to build the Chinese context based on which cash flows of reverse mortgage transactions are simulated. Simulation results show that reverse mortgages are beneficial to the Chinese elderly as accessing home equity allows them to double their consumption. Based on this analysis from different angles, we conclude that reverse mortgages will work in the Chinese market.

Stuttgart, Univ., Diplomarb., 2002.

Zugl.: Heidelberg, Univ., Diplomarbeit, 2006

Thesis (Ph. D.)--West Virginia University, 2004. / Title from document title page. Document formatted into pages; contains ix, 174 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 166-170).

Zugl.: Saarbrücken, Univ., Diss., 2009