15,260 research outputs found
Laboratory requirements for in-situ and remote sensing of suspended material
Recommendations for laboratory and in-situ measurements required for remote sensing of suspended material are presented. This study investigates the properties of the suspended materials, factors influencing the upwelling radiance, and the various types of remote sensing techniques. Calibration and correlation procedures are given to obtain the accuracy necessary to quantify the suspended materials by remote sensing. In addition, the report presents a survey of the national need for sediment data, the agencies that deal with and require the data of suspended sediment, and a summary of some recent findings of sediment measurements
Laboratory requirements for in-situ and remote sensing of suspended material
Recommendations for laboratory and in-situ measurements required for remote sensing of suspended material are presented. This study investigates the properties of the suspended materials, factors influencing the upwelling radiance, and the various types of remote sensing techniques. Calibration and correlation procedures are given to obtain the accuracy necessary to quantify the suspended materials by remote sensing. In addition, the report presents a survey of the national need for sediment data, the agencies that deal with and require the data of suspended sediment, and a summary of some recent findings of sediment measurements
Criteria for the use of regression analysis for remote sensing of sediment and pollutants
Data analysis procedures for quantification of water quality parameters that are already identified and are known to exist within the water body are considered. The liner multiple-regression technique was examined as a procedure for defining and calibrating data analysis algorithms for such instruments as spectrometers and multispectral scanners
Hydrography and Hydrodynamics of Virgina Estuaries XV: Mathematical Model Studies of Water Quality of the Nansemond Estuary
In Summer, 1974, an intensive field survey was conducted in the Nansemond River estuary from Suffolk to Pig Point. Temporal and spatial distributions of the parameters dissolved oxygen, salinity and temperature were obtained from the survey. Additional slack water runs were conducted in 1974 and 1975. The hydrographic and water quality data, combined with measured bathymetric profiles, were used to construct, calibrate and verify a one-dimensional, time-dependent mathematical model. Modeling of the Nansemond River estuary is part of the continuing program of the Cooperative State Agencies (Virginia State Water Control Board and the Virginia Institute of Marine Science) to develop water quality models of Virginia\u27s estuaries. The Nansemond River is located 14.5 kilometers (9 statute miles) from the mouth of the James River. The river receives industrial and domestic wastes from packing plants, sewage treatment plants, and housing developments. In the river reach around Suffolk, low values of dissolved oxygen (less than 4 mg/1) have been observed. The implicit numerical mathematical model predicts the intra-tidal distribution of dissolved oxygen, biochemical oxygen demand, and salinity. The model accurately predicts the region of low dissolved oxygen
Temperature evolution of magnetic structure of HoFeO by single crystal neutron diffraction
We have investigated the temperature evolution of the magnetic structures of
HoFeO by single crystal neutron diffraction. The three different magnetic
structures found as a function of temperature for \hfo\ are described by the
magnetic groups Pbn, Pbn and Pbn and are stable in the
temperature ranges 600-55~K, 55-37~K and 35~K respectively. In
all three the fundamental coupling between the Fe sub-lattices remains the same
and only their orientation and the degree of canting away from the ideal axial
direction varies. The magnetic polarisation of the Ho sub-lattices in these two
higher temperature regions, in which the major components of the Fe moment lie
along and , is very small. The canting of the moments from the axial
directions is attributed to the antisymmetric interactions allowed by the
crystal symmetry. They include contributions from single ion anisotropy as well
as the Dzyaloshinski antisymmetric exchange. In the low temperature phase two
further structural transitions are apparent in which the spontaneous
magnetisation changes sign with respect to the underlying antiferromagnetic
configuration. In this temperature range the antisymmetric exchange energy
varies rapidly as the the Ho sub-lattices begin to order. So long as the
ordered Ho moments are small the antisymmetric exchange is due only to Fe-Fe
interactions, but as the degree of Ho order increases the Fe-Ho interactions
take over whilst at the lowest temperatures, when the Ho moments approach
saturation the Ho-Ho interactions dominate. The reversals of the spontaneous
magnetisation found in this study suggest that in \hfo\ the sums of the Fe-Fe
and Ho-Ho antisymmetric interactions have the same sign as one another, but
that of the Ho-Fe terms is opposite
Suppression of core polarization in halo nuclei
We present a microscopic study of halo nuclei, starting from the Paris and
Bonn potentials and employing a two-frequency shell model approach. It is found
that the core-polarization effect is dramatically suppressed in such nuclei.
Consequently the effective interaction for halo nucleons is almost entirely
given by the bare G-matrix alone, which presently can be evaluated with a high
degree of accuracy. The experimental pairing energies between the two halo
neutrons in He and Li nuclei are satisfactorily reproduced by our
calculation. It is suggested that the fundamental nucleon-nucleon interaction
can be probed in a clearer and more direct way in halo nuclei than in ordinary
nuclei.Comment: 11 pages, RevTex, 2 postscript figures; major revisions, matches
version to appear in Phys. Rev. Letter
Transcritical flow of a stratified fluid over topography: analysis of the forced Gardner equation
Transcritical flow of a stratified fluid past a broad localised topographic
obstacle is studied analytically in the framework of the forced extended
Korteweg--de Vries (eKdV), or Gardner, equation. We consider both possible
signs for the cubic nonlinear term in the Gardner equation corresponding to
different fluid density stratification profiles. We identify the range of the
input parameters: the oncoming flow speed (the Froude number) and the
topographic amplitude, for which the obstacle supports a stationary localised
hydraulic transition from the subcritical flow upstream to the supercritical
flow downstream. Such a localised transcritical flow is resolved back into the
equilibrium flow state away from the obstacle with the aid of unsteady coherent
nonlinear wave structures propagating upstream and downstream. Along with the
regular, cnoidal undular bores occurring in the analogous problem for the
single-layer flow modeled by the forced KdV equation, the transcritical
internal wave flows support a diverse family of upstream and downstream wave
structures, including solibores, rarefaction waves, reversed and trigonometric
undular bores, which we describe using the recent development of the nonlinear
modulation theory for the (unforced) Gardner equation. The predictions of the
developed analytic construction are confirmed by direct numerical simulations
of the forced Gardner equation for a broad range of input parameters.Comment: 34 pages, 24 figure
Comparison of Exact and perturbative Results for Two Metrics
We compare the exact and perturbative results in two metrics and show that
the spurious effects due to the perturbation method do not survive for
physically relevant quantities such as the vacuum expectation value of the
stress-energy tensor.Comment: 12 page
Attentive Neural Architecture Incorporating Song Features For Music Recommendation
Recommender Systems are an integral part of music sharing platforms. Often
the aim of these systems is to increase the time, the user spends on the
platform and hence having a high commercial value. The systems which aim at
increasing the average time a user spends on the platform often need to
recommend songs which the user might want to listen to next at each point in
time. This is different from recommendation systems which try to predict the
item which might be of interest to the user at some point in the user lifetime
but not necessarily in the very near future. Prediction of the next song the
user might like requires some kind of modeling of the user interests at the
given point of time. Attentive neural networks have been exploiting the
sequence in which the items were selected by the user to model the implicit
short-term interests of the user for the task of next item prediction, however
we feel that the features of the songs occurring in the sequence could also
convey some important information about the short-term user interest which only
the items cannot. In this direction, we propose a novel attentive neural
architecture which in addition to the sequence of items selected by the user,
uses the features of these items to better learn the user short-term
preferences and recommend the next song to the user.Comment: Accepted as a paper at the 12th ACM Conference on Recommender Systems
(RecSys 18
Safety-Aware Apprenticeship Learning
Apprenticeship learning (AL) is a kind of Learning from Demonstration
techniques where the reward function of a Markov Decision Process (MDP) is
unknown to the learning agent and the agent has to derive a good policy by
observing an expert's demonstrations. In this paper, we study the problem of
how to make AL algorithms inherently safe while still meeting its learning
objective. We consider a setting where the unknown reward function is assumed
to be a linear combination of a set of state features, and the safety property
is specified in Probabilistic Computation Tree Logic (PCTL). By embedding
probabilistic model checking inside AL, we propose a novel
counterexample-guided approach that can ensure safety while retaining
performance of the learnt policy. We demonstrate the effectiveness of our
approach on several challenging AL scenarios where safety is essential.Comment: Accepted by International Conference on Computer Aided Verification
(CAV) 201
- …