5,377 research outputs found
The limits of spatial resolution achievable using a 30kHz multibeam sonar: model predictions and field results
A Simrad EM300 multibeam sonar was used to attempt to resolve small (-5m high) targets in 450m of water. The targets had previously been surveyed using a deeply towed 59 kHz sidescan sonar. Using multisector active yaw, pitch and roll compensation, together with dynamically altering angular sectors, the sonar is capable of maintaining sounding densities of as tight as 10m spacing in these water depths. This is significantly smaller than the largest dimension of the projected beam footprints (1 6-64m). The observed data suggest that the targets are intermittently resolved. The field results compare well to the output of a numerical model which reproduces the imaging geometry. Possible variations in the imaging geometry are implemented in the model, comparing equiangular and equidistant beam spacings, differing angular sectors and all the different combinations of transmit and receive beam widths that are available for this model of sonar. While amplitude detection is significantly aliased by targets smaller than the across track beam footprint, under conditions where the signal to noise ratio is favorable, phase detection can be used to reduce the minimum size of target observed to about the scale of the across track beam width. Thus having the beam spacing at the scale is justifiable. The phase distortion due to smaller targets, however, is generally averaged out
Inception and evolution of financial reporting in the Protestant Episcopal Church in the United States of America
This research documents the emergence of accounting procedures and concepts in a centrally controlled not-for-profit organization during a period of change and consolidation. The evolution of accounting as prescribed by the General Canons is identified and its implementation throughout the church conferences is examined
Measurement Error in Research on Human Resources and Firm Performance: Additional Data and Suggestions for Future Research
Gerhart and colleagues and Huselid and Becker recently debated the presence and implications of measurement error in measures of human resource practices. This paper presents data from three more studies, one of large organizations from different industries at the corporate level, one from commercial banks, and the other of autonomous business units at the level of the job. Results of all three studies provide additional evidence that single respondent measures of HR practices contain large amounts of measurement error. Implications for future research are discussed
Bistability in a simple fluid network due to viscosity contrast
We study the existence of multiple equilibrium states in a simple fluid
network using Newtonian fluids and laminar flow. We demonstrate theoretically
the presence of hysteresis and bistability, and we confirm these predictions in
an experiment using two miscible fluids of different viscosity--sucrose
solution and water. Possible applications include bloodflow, microfluidics, and
other network flows governed by similar principles
Estimates for measures of sections of convex bodies
A estimate in the hyperplane problem with arbitrary measures has
recently been proved in \cite{K3}. In this note we present analogs of this
result for sections of lower dimensions and in the complex case. We deduce
these inequalities from stability in comparison problems for different
generalizations of intersection bodies
How to validate machine-learned interatomic potentials
Machine learning (ML) approaches enable large-scale atomistic simulations
with near-quantum-mechanical accuracy. With the growing availability of these
methods there arises a need for careful validation, particularly for physically
agnostic models - that is, for potentials which extract the nature of atomic
interactions from reference data. Here, we review the basic principles behind
ML potentials and their validation for atomic-scale materials modeling. We
discuss best practice in defining error metrics based on numerical performance
as well as physically guided validation. We give specific recommendations that
we hope will be useful for the wider community, including those researchers who
intend to use ML potentials for materials "off the shelf"
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