11,469 research outputs found
Method and means for helium/hydrogen ratio measurement by alpha scattering
An apparatus for determining helium to hydrogen ratios in a gaseous sample is presented. The sample is bombarded with alpha particles created by a self contained radioactive source and scattering products falling within a predetermined forward scattering angular range impact a detector assembly. Two detectors are mounted in tandem, the first completely blocking the second with respect to incident scattering products. Alpha particle/hydrogen or alpha particle/helium collisions are identified by whether scattering product impacts occur simultaneously in both detectors or only in the first detector. Relative magnitudes of the two pulses can be used to further discriminate against other effects such as noise and cosmic ray events
Testing for Hypothetical Bias in Contingent Valuation Using a Latent Choice Multinomial Logit Model
The most persistently troubling empirical result in the contingent valuation method literature is the tendency for hypothetical willingness to pay to overestimate real willingness to pay. We suggest a new approach to test and correct for hypothetical bias using a latent choice multinomial logit (LCMNL) model. To develop this model, we extend Dempster, Laird, and Rubin’s (1977) work on the EM algorithm to the estimation of a multinomial logit model with missing information on categorical membership. Using data on both the quality of water in the Catawba River in North Carolina and the preservation of Saginaw wetlands in Michigan, we find two types of “yes” responders in both data sets. We suggest that one set of yes responses are yea-sayers who suffer from hypothetical bias and answer yes to the hypothetical question but would not pay the bid amount if it were real. The second group does not suffer from hypothetical bias and would pay the bid amount if it were real.C25, P230, Q51
Silicon-on-ceramic process: Silicon sheet growth and device development for the large-area silicon sheet task of the low-cost solar array project
The technical feasibility of producing solar cell quality sheet silicon to meet the DOE 1986 cost goal of 70 cents/watt was investigated. The silicon on ceramic approach is to coat a low cost ceramic substrate with large grain polycrystalline silicon by unidirectional solidification of molten silicon. Results and accomplishments are summarized
Identification and interpretation of patterns in rocket engine data
A prototype software system was constructed to detect anomalous Space Shuttle Main Engine (SSME) behavior in the early stages of fault development significantly earlier than the indication provided by either redline detection mechanism or human expert analysis. The major task of the research project is to analyze ground test data, to identify patterns associated with the anomalous engine behavior, and to develop a pattern identification and detection system on the basis of this analysis. A prototype expert system which was developed on both PC and Symbolics 3670 lisp machine for detecting anomalies in turbopump vibration data was checked with data from ground tests 902-473, 902-501, 902-519, and 904-097 of the Space Shuttle Main Engine. The neural networks method was also applied to supplement the statistical method utilized in the prototype system to investigate the feasibility in detecting anomalies in turbopump vibration of SSME. In most cases the anomalies detected by the expert system agree with those reported by NASA. On the neural networks approach, the results are given the successful detection rate higher than 95 percent to identify either normal or abnormal running condition based on the experimental data as well as numerical simulation
A Qualitative Study on Cancer Care Burden: Experiences of Iranian Family Caregivers.
The aim of this study was to explore the experiences of Iranian family caregivers with regard to the burden of caregiving. This is in the context of illuminating and identifying the experiences of family members from different contextual perspectives. In this qualitative study, purposive sampling was conducted in 2016. Data were collected using semistructured interviews and were analyzed using content analysis. Data analysis identified 4 categories and 8 subcategories: (1) burnout (physical problems and psychoemotional stress), (2) role conflict (balancing caring roles and family responsibilities; failure in professional or educational roles), (3) health system tensions (inadequate support from health professionals; ignorance of family members in health structure), and (4) social challenges of cancer (economic burden; taboo of cancer). In conclusion, nurses need to provide individualized support and counseling that address the sources of burden. This highlights the benefit of training health care professionals to provide culturally sensitive support based on family caregivers' needs and circumstances
Deepwater overflow through Luzon Strait
Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 111 (2006): C01002, doi:10.1029/2005JC003139.This study examines water property distributions in the deep South China Sea and
adjoining Pacific Ocean using all available hydrographic data. Our analysis reveals that
below about 1500 m there is a persistent baroclinic pressure gradient driving flow from the
Pacific into the South China Sea through Luzon Strait. Applying hydraulic theory with
assumptions of zero potential vorticity and flat bottom to the Luzon Strait yields a transport
estimate of 2.5 Sv (1 Sv=106 m3 s-1). Some implications of this result include: (i) a
residence time of less than 30 years in the deep South China Sea, (ii) a mean diapycnal
diffusivity as large as 10-3 m2 s-1, and (iii) an abyssal upwelling rate of about 3Ă—10-6 m s-1.
These quantities are consistent with residence times based on oxygen consumption rates.
The fact that all of the inflowing water must warm up before leaving the basin implies that
this marginal sea contributes to the water mass transformations that drive the meridional
overturning circulation in the North Pacific. Density distributions within the South China
Sea basin suggest a cyclonic deep boundary current system, as might be expected for an
overflow-driven abyssal circulation.This study was supported by National Science Foundation (NSF)
through Grant OCE00-95906 and by Japan Marine Science and Technology Center through
its sponsorship of the International Pacific Research center (IPRRC). Support is also from
NSF grant OCE-0325102
Tangled Nature: A model of emergent structure and temporal mode among co-evolving agents
Understanding systems level behaviour of many interacting agents is
challenging in various ways, here we'll focus on the how the interaction
between components can lead to hierarchical structures with different types of
dynamics, or causations, at different levels. We use the Tangled Nature model
to discuss the co-evolutionary aspects connecting the microscopic level of the
individual to the macroscopic systems level. At the microscopic level the
individual agent may undergo evolutionary changes due to mutations of
strategies. The micro-dynamics always run at a constant rate. Nevertheless, the
system's level dynamics exhibit a completely different type of intermittent
abrupt dynamics where major upheavals keep throwing the system between
meta-stable configurations. These dramatic transitions are described by a
log-Poisson time statistics. The long time effect is a collectively adapted of
the ecological network. We discuss the ecological and macroevolutionary
consequences of the adaptive dynamics and briefly describe work using the
Tangled Nature framework to analyse problems in economics, sociology,
innovation and sustainabilityComment: Invited contribution to Focus on Complexity in European Journal of
Physics. 25 page, 1 figur
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