1,158 research outputs found
Conclusion of Viking Lander Imaging Investigation: Picture catalog of experiment data record
The images returned by the two Viking landers during the Viking Survey Mission are presented in this report. Listing of supplemental information which describe the conditions under which the images were acquired are included. Subsets of the images are listed in a variety of sequences to aid in locating images of interest. The format and organization of the digital magnetic tape storage of the images are described. A brief description of the mission and the camera system is also included
Composite Operators in QCD
We give a formula for the derivatives of a correlation function of composite
operators with respect to the parameters (i.e., the strong fine structure
constant and the quark mass) of QCD in four-dimensional euclidean space. The
formula is given as spatial integration of the operator conjugate to a
parameter. The operator product of a composite operator and a conjugate
operator has an unintegrable part, and the formula requires divergent
subtractions. By imposing consistency conditions we derive a relation between
the anomalous dimensions of the composite operators and the unintegrable part
of the operator product coefficients.Comment: 26 page
Effective Discharge for Suspended Sediment Transport in Streams of the Saskatchewan River Basin
Effective discharge for suspended sediment load was determined for 21 sites in the Saskatchewan River basin at which sediment records range from 5 to 29 years in length. The drainage areas for these streams ranges from 10 to over 300,000 km2. The sediment discharge histograms have a variety of forms ranging from the classic unimodal form in which the peak occurs at discharges with a duration of 1â3% to those in which the effective discharge is the extreme event of record and cases in which a single effective discharge is difficult to define. The percentage duration of the effective-discharge ranges from less than 0.1% to over 15%, a greater range than previously has been reported. There is an obvious tendency for the percentage duration of the effective discharge to increase with drainage area and hence downstream through the drainage system
Spatial and Temporal Patterns of Suspended-Sediment Yield in the Saskatchewan River Basin
Long-term suspended-sediment concentration and load records are available for 23 Water Survey of Canada sediment-monitoring stations in the Saskatchewan River basin, where the drainage areas range from 10 to over 300â000âkm2. Mean annual sediment yield is greatest in the western Alberta Plains along the Oldman and Red Deer rivers (over 100âtâkmâ2âyearâ1) and tends to increase downstream along the North and South Saskatchewan rivers until major reservoirs in Saskatchewan intervene. Average sediment concentration shows a pattern of variation similar to that of yield. Temporal aspects of suspended-sediment transport vary along the drainage network. The range and skewness of the yieldâduration and concentrationâduration curves are greater in the intermediate-size basins close to the Rocky Mountains and in two small basins with Prairie sources than they are in the large Prairie streams with mountain sources and the glacier-fed upper North Saskatchewan River. Similarly, infrequent flows transport a larger proportion of the annual load in the smaller Foothills and western Plains basins than in the large Prairie streams because of differences in drainage area and discharge regime
The Delphi method: methodological issues arising from a study examining factors influencing the publication or non-publication of mental health nursing research
Purpose â The paper describes how the classic Delphi method can be adapted and structured to ensure that specific research questions are clearly addressed.
Design/methodology/approach â As part of a larger mixed method project, a modified Delphi study was undertaken to explore factors influencing publication and non-publication of mental health nursing research.
Findings - This paper reports brief findings from the Delphi study. However, its main focus is the methodological issues arising from the Delphi method.
Implications - The paper argues that the classic Delphi method can be adapted and structured to ensure that specific research questions are able to be clearly answered. The adaptations are pragmatic in approach and in keeping with the general principles underpinning the Delphi method, while successfully addressing the problems of attrition and previous criticism of homogenous panels.
Originality/value - This paper offers some practical solutions to issue arising from undertaking research using the Delphi method
Grain sorting in the morphological active layer of a braided river physical model.
A physical scale model of a gravel-bed braided river was used to measure vertical grain size sorting in the morphological active layer aggregated over the width of the river. This vertical sorting is important for analyzing braided river sedimentology, for numerical modeling of braided river morphodynamics, and for measuring and predicting bedload transport rate. We define the morphological active layer as the bed material between the maximum and minimum bed elevations at a point over extended time periods sufficient for braiding processes to rework the river bed. The vertical extent of the active layer was measured using 40 hourly high-resolution DEMs (digital elevation models) of the model river bed. An image texture algorithm was used to map bed material grain size of each DEM. Analysis of the 40 DEMs and texture maps provides data on the geometry of the morphological active layer and variation in grain size in three dimensions. By normalizing active layer thickness and dividing into 10 sublayers, we show that all grain sizes occur with almost equal frequency in all sublayers. Occurrence of patches and strings of coarser (or finer) material relates to preservation of particular morpho-textural features within the active layer. For numerical modeling and bedload prediction, a morphological active layer that is fully mixed with respect to grain size is a reliable approximation
Bed Particle Displacements and Morphological Development in a Wandering Gravel-Bed River
Bed particles were tracked using passive integrated transponder tags in a wandering reach of the San Juan River, British Columbia, Canada, to assess particle movement around three major bars in the river. In-channel topographic changes were monitored through repeat LiDAR surveys during this period and used in concert with the tracer data set to assess the relationship between particle displacements and changes in channel morphology, specifically, the development and re-working of bars. This has direct implications for virtual velocity and morphologic based estimates of bedload flux, which rely on accurate estimates of the variability and magnitude of particle path lengths over time. Tracers were deployed in the river at three separate locations in the Fall of 2015, 2016, 2017, and 2018, with recovery surveys conducted during the summer low-flow season the year after tracer deployment and multiple mobilizing events. Tracers exhibited path length distributions reflective of both morphologic controls and year to year differences related to the annual flow regime. Annual tracer transport was restricted primarily to less than one riffle-pool-bar unit, even during years with a greater number of peak floods and duration of competent flow. Tracer deposition and burial was focused along bar margins, particularly at or downstream of the bar apex, reflecting the downstream migration and lateral bar accretion observed on Digital Elevation Models of difference. This highlights the fundamental importance of bar development and re-working underpinning bedload transport processes in bar-dominated channels
The Thermal Stability of Mass-Loaded Flows
We present a linear stability analysis of a flow undergoing
conductively-driven mass-loading from embedded clouds. We find that
mass-loading damps isobaric and isentropic perturbations, and in this regard is
similar to the effect of thermal conduction, but is much more pronounced where
many embedded clumps exist. The stabilizing influence of mass-loading is
wavelength independent against isobaric (condensing) perturbations, but
wavelength dependent against isentropic (wave-like) perturbations. We derive
equations for the degree of mass-loading needed to stabilize such
perturbations. We have also made 1D numerical simulations of a mass-loaded
radiative shock and demonstrated the damping of the overstability when
mass-loading is rapid enough.Comment: 4 pages, 1 figure, to be published in A&
An Approach for Developing National Guidelines for Postsecondary Support Services Programs
This paper presents a case for developing standards for specialized support programs serving deaf students in postsecondary institutions. A step-by-step plan for producing standards for the evaluation, development, and accreditation of these programs is outlined. Criteria for forming flexible standards which (1) account for variations in program size and type and (2) enhance support services which make postsecondary education more accessible for deaf students are clarified. The importance of teamwork between postsecondary specialists and generalists to link standards for special service programs to the process of accrediting regular institutions of higher education is emphasized. An example of accrediting a special college for deaf students is discussed. Results from a process of setting priorities for future actions in developing program standards which emerged from a professional conference are reported. Expected benefits of these standards to enhancing program quality are described
Dust in Interstellar Clouds, Evolved Stars and Supernovae
Outflows of pre-main-sequence stars drive shocks into molecular material
within 0.01 - 1 pc of the young stars. The shock-heated gas emits infrared,
millimeter and submillimeter lines of many species including. Dust grains are
important charge carriers and play a large role in coupling the magnetic field
and flow of neutral gas. Some effects of the dust on the dynamics of oblique
shocks began to emerge in the 1990s. However, detailed models of these shocks
are required for the calculation of the grain sputtering contribution to gas
phase abundances of species producing observed emissions. We are developing
such models. Some of the molecular species introduced into the gas phase by
sputtering in shocks or by thermally driven desorption in hot cores form on
grain surfaces. Recently laboratory studies have begun to contribute to the
understanding of surface reactions and thermally driven desorption important
for the chemistry of star forming clouds. Dusty plasmas are prevalent in many
evolved stars just as well as in star forming regions. Radiation pressure on
dust plays a significant role in mass loss from some post-main-sequence stars.
The mechanisms leading to the formation of carbonaceous dust in the stellar
outflows are similar to those important for soot formation in flames. However,
nucleation in oxygen-rich outflows is less well understood and remains a
challenging research area. Dust is observed in supernova ejecta that have not
passed through the reverse shocks that develop in the interaction of ejecta
with ambient media. Dust is detected in high redshift galaxies that are
sufficiently young that the only stars that could have produced the dust were
so massive that they became supernovae. Consequently, the issue of the survival
of dust in strong supernova shocks is of considerable interest.Comment: 4 pages, to be published in the proceedings of Fifth International
Conference on Physics of Dusty Plasma
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