750 research outputs found
Einstein-de Sitter model re-examined for the newly discovered SNe Ia
Consistency of Einstein-de Sitter model with the recently observed SNe Ia by
the Hubble Space Telescope is examined. The model shows a reasonable fit to the
observation, if one takes into account the extinction of SNe light by the
intergalactic metallic dust ejected from the SNe explosions. Though the fit to
the new data is worsened considerably compared with the earlier data, it can
still be regarded acceptable. We should wait for more accurate observations at
higher redshifts (as expected from the coming space missions such as SNAP and
JWST) in order to rule out a model, which seems to explain all the other
existing observations well (some even better than the favoured CDM
model), is consistent with beautiful theoretical ideas like inflation and cold
dark matter, and is not as speculative as the models of dark energy.Comment: 14 pages including 2 figures, to appear in the Mon. Not. Roy. Astron.
So
On the detection of newly created CN radicals and comets
Laboratory investigations of CN radical formation by photodissociation of parent molecules have suggested the possibility of observing emission lines in cometary spectra from newly formed CN radicals. These laboratory studies have shown that high initial internal excitation of CN is the rule with excitation of rotational levels N up to 70. In the collisionless environment of the cometary atmosphere this initial excitation would yield a corresponding distribution for the lowest vibrational level of the ground X(2) Sigma (+) state. Our calculations show that it is feasible with present observational techniques to detect photochemically excited lines with N approx. equal to 30 in the 0-0 band of the violet system
Angular scattering from irregularly shaped particles with application to astronomy
Angular scattering from irregularly shaped particles with application to astronom
THE VALUE OF SPORT FISHING IN THE SNAKE RIVER BASIN OF CENTRAL IDAHO
The value of sportfishing in the Snake River Basin in Central Idaho was measured using a two-stage/disequilibrium travel model. The two-stage/disequilibrium model does not require monetization of recreationists? travel time as required of traditional equilibrium labor market travel cost models. The model was estimated using Poisson regression, appropriate for count data when over-dispersion is absent, and adjusted for endogenous stratification (self selection bias) . Contrary to expectations that anglers living close to the sites with low values would be over represented in the sample, the endogenous stratification adjustment caused estimated consumers surplus to decline from 35 after adjustment. The average number of sportfishing trips per year was 6.72, resulting in an average annual willingness-to-pay of $236 per year per angler.Resource /Energy Economics and Policy,
A spectroscopic study of intermediates in the condensation of refractory smokes: Matrix isolation experiments SiO
The infrared and Raman spectra of N2 matrix isolated silicon oxides are investigated. The vibrational frequencies of SiO, Si2O2, and Si3O3 were identified and assigned on the basis of normal coordinate analyses. Heating the solid to 50 K (evaporating the matrix) leaves a residue whose infrared spectrum is identical to that of a smoke condensed at ambient temperatures. Further heating of the sample to 500 K leads to significant changes in the band shapes. Investigations of the infrared spectra at several stages of the diffusion process result in the proposal of a mechanism for the transition from molecular properties to those of the residue (bulk) material, which is characterized as Si2O3
Measuring the Location Value of a Recreation Site
The demand for sport fishing on the Snake River reservoirs was estimated using the travel cost method. A short-run demand model was specified with location value for anglers who have the option to access a follow-on site if fishing conditions are poor. Willingness to pay for a fishing trip to the site was 43.48 for anglers who did. A location value of 0.78 million) if location value for anglers with a follow-on site was excluded from the benefit estimate.contingent behavior, count data, endogenous stratification, follow-on site, location value, multiple destination, option value, short-run demand, travel cost method, Resource /Energy Economics and Policy,
Methods and Implementation of Fluid-Structure Interaction Modeling into an Industry-Accepted Design Tool
Fluid-structure interaction (FSI) modeling is a method by which fluid and solid domains are coupled together to produce a single result that cannot be produced if each physical domain was evaluated individually. The work presented in this dissertation is a demonstration of the methods and implementation of FSI modeling into an industry-appropriate design tool. Through utilizing computationally inexpensive equipment and commercially available software, the studies presented in this work demonstrate the ability for FSI modeling to become a tool used broadly in industry.
To demonstrate this capability, the cases studied purposely include substantial complexity to demonstrate the stability techniques required for modeling the inherent instabilities of FSI models that contain three-dimensional geometries, nonlinear materials, thin-walled geometries, steep gradients, and transient behavior. The work also modeled scenarios that predict system failure and optimal design to extend service lifetime, thereby expanding upon current FSI literature. Four independent studies were performed, evaluating three separate modes of failure in FSI models, to demonstrate that FSI modeling is a viable design tool for widespread industry use.
The first study validates FSI modeling techniques by comparing the results of a thin-walled FSI geometry model under hydrostatic forces with existing experimental data.
The second study explored a parametric study that evaluated the factors influencing an FSI model containing a highly complex thermal-fluid fatigue model. This model involved dynamically changing temperature loads resulting in significant thermal expansion that led to material yielding and dynamic fatigue life.
The third study evaluated a thermal-fluid conjugate heat transfer problem. The model was tuned, validated, and optimized for lifetime, and the validation of the system was performed using experimental data.
The final study modeled the highly complex fluid and solid phenomena involved in a peristaltic pump where the goal was to demonstrate that the lifetime performance of the tubing could be altered by changing the geometry, material properties, and operating temperature. The model in this final study combined all the methods and techniques from the three earlier studies and applied them to a thin-walled tube geometry with nonlinear and temperature-dependent material properties to create large solid deformation and fluid motion
ISSUES IN NONMARKET VALUATION AND POLICY APPLICATION: A RETROSPECTIVE GLANCE
While issues in estimating nonmarket values continue to cause concern, resource economists have more reason now than ever before to be optimistic. More progress toward improved measurement has been made in the past six years than in the previous quarter century since development of the contingent valuation and travel cost methods. The new challenge is to learn how to adjust past studies to estimate nonmarket values for future policy analysis. The process involves developing an understanding of the important variables that explain the observed difference in estimates. This paper illustrates how the results thus far could be adjusted to develop some tentative estimates of the recreation-use value of Forest Service resources.Research Methods/ Statistical Methods, Resource /Energy Economics and Policy,
IDENTIFIKASI SENYAWA BIOAKTIF EKSTRAK ETANOL DAN METANOL JAHE MERAH (Zingiber officinale var.Rubrum) DENGAN MENGGUNAKAN GAS CHROMATOGRAPHY-MASS SPECTROMETER
Dalam penelitian ini kami melaporkan hasil kandungan senyawa bioaktif Zingiber officinale var. Rubrum yang telah dievaluasi menggunakan Shimadzu GCMS-QP2010 Ultra. Ekstra jahe merah 250 g dilarutkan dengan pelarut etanol dan methanol 96% sebanyak 400ml hasil ekstrak jahe merah difilter dengan menggunakan kertas saring whatman no 1 sesudah itu didiamkan selama 4 jam. Maserat dipisahkan dan diuapkan melalui evaporasi selama 1 jam pada temperature 60\degc. Untuk metode analisis GC-MS ekstra jahe merah dilakukan dengan suhu oven sebesar 100.0\degc dengan mode injeksi split pada suhu injeksi temperatur 300.00\degc. Dari hasil percobaan methanol menggunakan GC-MS maka diperoleh senyawa benzene (24.07%), senyawa zingiberene (34.69%), senyawa farnesene (5.94%), senyawa \beta-Bisabolene (14.73%), dan senyawa terakhir yaitu senyawa \beta-Sesquiphellandrene (20.57%). Sedangkan pada pelaurut etanol terdapat senyawa Benzene (26.35%), senyawa Zingiberene (37.68%), senyawa \beta-BisaboleneCyclohexene (16.13%), senyawa \beta-Sesquiphellandrene (19.84%). Hasil GC-MS kandungan bioaktif dengan menggunakan perbandingan pada pelarut etanol dan methanol maka terdapat kandungan senyawa tertinggi dari kedua pelarut yaitu, senyawa zingiberene dengan waktu retensi 9.675 pada pelarut methanol dan waktu retensi 9.677 pada pelarut etanol
The study of comets, part 2
Flyby missions and systematic observations of comets are projected for studying comet nuclei and cometary dust tail structures
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