1,859 research outputs found
Geothermal reservoir simulation
The prediction of long-term geothermal reservoir performance and the environmental impact of exploiting this resource are two important problems associated with the utilization of geothermal energy for power production. Our research effort addresses these problems through numerical simulation. Computer codes based on the solution of partial-differential equations using finite-element techniques are being prepared to simulate multiphase energy transport, energy transport in fractured porous reservoirs, well bore phenomena, and subsidence
Scharp on inconsistent concepts and their engineered replacements, or: Can we mend these broken things?
Kevin Scharp’s influential work on the alethic paradoxes combines an extensively developed inconsistency theory with a substantial conceptual engineering project. I argue that Scharp’s inconsistency theory is in tension with his conceptual engineering project: the inconsistency theory includes an account of concepts that implies that the conceptual engineering project will fail. I recommend that Scharp revises his account of concepts, and show how doing so allows him to resolve the tension. The discussion is important for ongoing work on conceptual engineering. Firstly, it is important to get clear on whether Scharp’s conceptual engineering project is—or could be—successful. Secondly, the issues discussed herein may generalise to other conceptual engineering projects, such as explication and ameliorative projects. In particular, the discussion has implications for how conceptual engineers can think about concepts and their relation to how we use words
How to find an attractive solution to the liar paradox
The general thesis of this paper is that metasemantic theories can play a central role in determining the correct solution to the liar paradox. I argue for the thesis by providing a specific example. I show how Lewis’s reference-magnetic metasemantic theory may decide between two of the most influential solutions to the liar paradox: Kripke’s minimal fixed point theory of truth and Gupta and Belnap’s revision theory of truth. In particular, I suggest that Lewis’s metasemantic theory favours Kripke’s solution to the paradox over Gupta and Belnap’s. I then sketch how other standard criteria for assessing solutions to the liar paradox, such as whether a solution faces a so-called revenge paradox, fit into this picture. While the discussion of the specific example is itself important, the underlying lesson is that we have an unused strategy for resolving one of the hardest problems in philosophy
Impact of lightning-NO on eastern United States photochemistry during the summer of 2006 as determined using the CMAQ model
A lightning-nitrogen oxide (NO) algorithm is implemented in the Community Multiscale Air Quality Model (CMAQ) and used to evaluate the impact of lightning-NO emissions (LNO<sub>x</sub>) on tropospheric photochemistry over the United States during the summer of 2006. <br><br> For a 500 mole per flash lightning-NO source, the mean summertime tropospheric NO<sub>2</sub> column agrees with satellite-retrieved columns to within −5 to +13%. Temporal fluctuations in the column are moderately well simulated; however, the addition of LNO<sub>x</sub> does not lead to a better simulation of day-to-day variability. The contribution of lightning-NO to the model column ranges from &sim;10% in the northern US to >45% in the south-central and southeastern US. Lightning-NO adds up to 20 ppbv to upper tropospheric model ozone and 1.5–4.5 ppbv to 8-h maximum surface layer ozone, although, on average, the contribution of LNO<sub>x</sub> to model surface ozone is 1–2 ppbv less on poor air quality days. LNO<sub>x</sub> increases wet deposition of oxidized nitrogen by 43% and total deposition of nitrogen by 10%. This additional deposition reduces the mean magnitude of the CMAQ low-bias in nitrate wet deposition with respect to National Atmospheric Deposition monitors to near zero. <br><br> Differences in urban/rural biases between model and satellite-retrieved NO<sub>2</sub> columns were examined to identify possible problems in model chemistry and/or transport. CMAQ columns were too large over urban areas. Biases at other locations were minor after accounting for the impacts of lightning-NO emissions and the averaging kernel on model columns. <br><br> In order to obtain an upper bound on the contribution of uncertainties in NO<sub>y</sub> chemistry to upper tropospheric NO<sub>x</sub> low biases, sensitivity calculations with updated chemistry were run for the time period of the Intercontinental Chemical Transport Experiment (INTEX-A) field campaign (summer 2004). After adjusting for possible interferences in NO<sub>2</sub> measurements and averaging over the entire campaign, these updates reduced 7–9 km biases from 32 to 17% and 9–12 km biases from 57 to 46%. While these changes lead to better agreement, a considerable unexplained NO<sub>2</sub> low-bias remains in the uppermost troposphere
House screening for malaria control: views and experiences of participants in the RooPfs trial
Background The housing stock of rural sub-Saharan Africa is changing rapidly. With millions of new homes required over the coming decades, there is an opportunity to protect residents by screening homes from malaria mosquitoes. This study, undertaken in the Upper River Region of The Gambia, explores local perceptions of what a good house should provide for its inhabitants and responses to living in a house that has been modified as part of a randomized control trial designed to assess whether improved housing provided additional protection against clinical malaria in children (the RooPfs trial). Methods This descriptive, exploratory study was undertaken over 22 months using mixed-methods (informal conversations, observations, focus group discussions, photovoice, and a questionnaire survey) in a parallel convergent design. Analysis was conducted across the data sets using a framework approach. Following coding, the textual data were charted by a priori and emerging themes. These themes were compared with the quantitative survey results. The nature and range of views about housing and the RooPfs study modifications and the relationships among them were identified and described. Results The data were derived from a total of 35 sets of observations and informal conversations in 10 villages, 12 discussions with the photovoice photographers, 26 focus group discussions (across 13 villages) and 391 completed questionnaires. The study participants described a ‘good house’ as one with a corrugate-metal roof, cement walls (preferably cement block, but mud block covered with cement plaster was also an acceptable and cheaper substitute) and well-fitting doors. These features align with local perceptions of a modern house that provides social status and protection from physical harms. The RooPfs modifications were largely appreciated, although poor workmanship caused concerns that houses had become insecure. However, the long-term trusting relationship with the implementing institution and the actions taken to rectify problems provided reassurance and enhanced acceptability. Conclusion In developing housing to address population needs in Africa, attention should be paid to local perceptions of what is required to make a house secure for its inhabitants, as well as providing a healthy environment
Evidence-based vector control? Improving the quality of vector control trials.
Vector-borne diseases (VBDs) such as malaria, dengue, and leishmaniasis cause a high level of morbidity and mortality. Although vector control tools can play a major role in controlling and eliminating these diseases, in many cases the evidence base for assessing the efficacy of vector control interventions is limited or not available. Studies assessing the efficacy of vector control interventions are often poorly conducted, which limits the return on investment of research funding. Here we outline the principal design features of Phase III vector control field studies, highlight major failings and strengths of published studies, and provide guidance on improving the design and conduct of vector control studies. We hope that this critical assessment will increase the impetus for more carefully considered and rigorous design of vector control studies
Evidence of high bed net usage from a list randomization experiments in rural Gambia.
Label: BACKGROUND NlmCategory: BACKGROUND content:
Recording behaviours that have the potential to impact health
can be doubly challenging if the behaviour takes place in
private spaces that cannot be observed directly, and where
respondents answer what they think the recorder may want to
hear. Sleeping under a long-lasting insecticidal net (LLIN) is
an important intervention for malaria prevention, yet it is
difficult to gauge the extent to which coverage (how many nets
are in the community) differs from usage (how many people
actually sleep under a net). List randomization, a novel method
which partially obscures respondents' answers to sensitive
questions, was employed to estimate LLIN usage in The Gambia. -
Label: METHODS NlmCategory: METHODS content: "802
heads-of-household from 15 villages were recruited into a
randomized controlled trial assessing the effect of a housing
intervention on malaria. These houses were randomly assigned to
a housing intervention versus control, with stratification by
village so as to ensure balance between arms. From these, 125
households (63 intervention, 52 control) were randomly selected
for participation in the list randomization experiment, along
with 68 households from the same villages but which were not
part of the housing improvement study, resulting in a total of
196 households for the list randomization experiment.
Approximately half (n\xE2\x80\x89=\xE2\x80\x8997) of the 196
study participants were randomly assigned to the control group
and received a four-question list about non-sensitive
behaviours; the intervention group
(n\xE2\x80\x89=\xE2\x80\x8999) received the same list, with the
addition of one question on a sensitive behaviour: whether or
not they had used a bed net the previous night. Participants
were read the list of questions and then said how many of the
statements were true. Bed net usage was estimated by calculating
the difference in means between the number of affirmative
responses between the two groups." - Label: RESULTS NlmCategory:
RESULTS content: The mean number of affirmative responses in the
control group was 2.60 of four statements (95% confidence
interval, 95% CI 2.50-2.70), compared with 3.68 (95% CI
3.59-3.78) in the intervention group. Such difference (1.08; 95%
CI 94.9-100%) suggests near universal bed net usage. - Label:
CONCLUSIONS NlmCategory: CONCLUSIONS content: Bed net usage by
household heads in these rural villages was found to be high.
Though not entirely unexpected given other studies' estimates of
high bed net usage in the area, the list randomization method
should be further validated in an area with lower coverage
- …