Energy efficient engine high-pressure turbine single crystal vane and blade fabrication technology report

The objective of the High-Pressure Turbine Fabrication Program was to demonstrate the application and feasibility of Pratt & Whitney Aircraft-developed two-piece, single crystal casting and bonding technology on the turbine blade and vane configurations required for the high-pressure turbine in the Energy Efficient Engine. During the first phase of the program, casting feasibility was demonstrated. Several blade and vane halves were made for the bonding trials, plus solid blades and vanes were successfully cast for materials evaluation tests. Specimens exhibited the required microstructure and chemical composition. Bonding feasibility was demonstrated in the second phase of the effort. Bonding yields of 75 percent for the vane and 30 percent for the blade were achieved, and methods for improving these yield percentages were identified. A bond process was established for PWA 1480 single crystal material which incorporated a transient liquid phase interlayer. Bond properties were substantiated and sensitivities determined. Tooling die materials were identified, and an advanced differential thermal expansion tooling concept was incorporated into the bond process

Advanced oxygen-hydrocarbon rocket engine study

The advantages and disadvantages, system performance and operating limits, engine parametric data, and technology requirements for candidate high pressure LO2/Hydrocarbon engine systems are summarized. These summaries of parametric analysis and design provide a consistent engine system data base. Power balance data were generated for the eleven engine cycles. Engine cycle rating parameters were established and the desired condition and the effect of the parameter on the engine and/or vehicle are described

Effective-Hamiltonian parameters for \emph{ab initio} energy-level calculations of SrCl2_{2}:Yb2+^{2+} and CsCaBr3_{3}:Yb2+^{2+}

Calculated energy levels from recent \emph{ab initio} studies of the electronic structure of SrCl$_{2}$:Yb$^{2+}$ and CsCaBr$_{3}$:Yb$^{2+}$ are fitted with a semi-empirical "crystal-field" Hamiltonian, which acts within the model space $4f^{14} + 4f^{13}5d + 4f^{13}6s$. Parameters are obtained for the minima of the potential-energy curves for each energy level and also for a range of anion-cation separations. The parameters are compared with published results parameters fitted to experimental data and to atomic calculations. The states with significant $4f^{13}6s$ character give a good approximation of the impurity-trapped exciton states that appear in the \emph{ab initio} calculations.Comment: Minor revisio

Access to sustainable lifestyles: disability and environmental citizenship

Reducing environmental impacts at the level of the individual or household is a key feature of sustainability debates, and there is interest in transitions toward more sustainable lifestyles. The implications of this for disability equality, however, have not yet been fully explored. This thesis examines disabled people’s experiences regarding sustainable lifestyles and uses these to bring a disability studies perspective to various sustainability literatures, such as environmental citizenship, which have so far neglected disability issues. Policy discourses around sustainability and disability equality are also explored and their implications examined. Methods included qualitative interviews and focus groups with disabled participants living in one local authority area, enabling participants’ experiences to be situated in the context of local sustainability- and disability-focused strategies. The findings indicate significantly more complex and diverse engagements with sustainable lifestyles than has been shown in previous research. Although many participants’ experiences could be conceptualised as issues of environmental (in)justice, they tended to favour perspectives based on responsibility rather than rights. Many participants could be identified as environmental citizens, demonstrating that disabled people can play an active role in environmental protection. Taking a social practice approach to the data also indicates a potentially valuable way to more fully conceptualise accessibility in relation to sustainable lifestyles. This research has important implications for transitions towards sustainable lifestyles. Current policy contexts are significantly constrained by the wider neoliberal economic context, so change may need to begin outside the policy arena – such as the environmental movement. The movement itself, however, also needs to incorporate disability equality as a concern. Disability equality can be conceptualised as a feature of sustainability, meaning sustainability will not be achieved without the inclusion of disabled people. Considering environmentalism as facilitated by external factors rather than internal values may be a potential way forward

Spatial analysis of plague in California: niche modeling predictions of the current distribution and potential response to climate change

<p>Abstract</p> <p>Background</p> <p>Plague, caused by the bacterium <it>Yersinia pestis</it>, is a public and wildlife health concern in California and the western United States. This study explores the spatial characteristics of positive plague samples in California and tests Maxent, a machine-learning method that can be used to develop niche-based models from presence-only data, for mapping the potential distribution of plague foci. Maxent models were constructed using geocoded seroprevalence data from surveillance of California ground squirrels (<it>Spermophilus beecheyi</it>) as case points and Worldclim bioclimatic data as predictor variables, and compared and validated using area under the receiver operating curve (AUC) statistics. Additionally, model results were compared to locations of positive and negative coyote (<it>Canis latrans</it>) samples, in order to determine the correlation between Maxent model predictions and areas of plague risk as determined via wild carnivore surveillance.</p> <p>Results</p> <p>Models of plague activity in California ground squirrels, based on recent climate conditions, accurately identified case locations (AUC of 0.913 to 0.948) and were significantly correlated with coyote samples. The final models were used to identify potential plague risk areas based on an ensemble of six future climate scenarios. These models suggest that by 2050, climate conditions may reduce plague risk in the southern parts of California and increase risk along the northern coast and Sierras.</p> <p>Conclusion</p> <p>Because different modeling approaches can yield substantially different results, care should be taken when interpreting future model predictions. Nonetheless, niche modeling can be a useful tool for exploring and mapping the potential response of plague activity to climate change. The final models in this study were used to identify potential plague risk areas based on an ensemble of six future climate scenarios, which can help public managers decide where to allocate surveillance resources. In addition, Maxent model results were significantly correlated with coyote samples, indicating that carnivore surveillance programs will continue to be important for tracking the response of plague to future climate conditions.</p

Transient photoluminescence enhancement as a probe of the structure of impurity-trapped excitons in CaF2_2:Yb2+^{2+}

We demonstrate a direct measurement of the energy levels of impurity-trapped excitons in CaF$_2$:Yb$^{2+}$. The radically different radiative decay rates of the lowest exciton state and higher excited states enable the generation of a transient photoluminescence enhancement measured via a two-step excitation process. We observe sharp transitions arising from changes of state of localized electrons, broad bands associated with changes of state of delocalized electrons, and broad bands arising from trap liberation.Comment: Minor corrections. arXiv admin note: text overlap with arXiv:1107.4888v

A falls prevention programme to improve quality of life, physical function and falls efficacy in older people receiving home help services: study protocol for a randomised controlled trial

BACKGROUND: Falls and fall-related injuries in older adults are associated with great burdens, both for the individuals, the health care system and the society. Previous research has shown evidence for the efficiency of exercise as falls prevention. An understudied group are older adults receiving home help services, and the effect of a falls prevention programme on health-related quality of life is unclear. The primary aim of this randomised controlled trial is to examine the effect of a falls prevention programme on quality of life, physical function and falls efficacy in older adults receiving home help services. A secondary aim is to explore the mediating factors between falls prevention and health-related quality of life. METHODS: The study is a single-blinded randomised controlled trial. Participants are older adults, aged 67 or older, receiving home help services, who are able to walk with or without walking aids, who have experienced at least one fall during the last 12 months and who have a Mini Mental State Examination of 23 or above. The intervention group receives a programme, based on the Otago Exercise Programme, lasting 12 weeks including home visits and motivational telephone calls. The control group receives usual care. The primary outcome is health-related quality of life (SF-36). Secondary outcomes are leg strength, balance, walking speed, walking habits, activities of daily living, nutritional status and falls efficacy. All measurements are performed at baseline, following intervention at 3 months and at 6 months' follow-up. Sample size, based on the primary outcome, is set to 150 participants randomised into the two arms, including an estimated 15-20% drop out. Participants are recruited from six municipalities in Norway. DISCUSSION: This trial will generate new knowledge on the effects of an exercise falls prevention programme among older fallers receiving home help services. This knowledge will be useful for clinicians, for health managers in the primary health care service and for policy makers