356 research outputs found
Efficiency of ETV diagrams as diagnostic tools for long-term period variations. II. Non-conservative mass transfer, and gravitational radiation
The credibility of an eclipse timing variation (ETV) diagram analysis is
investigated for various manifestations of the mass transfer and gravitational
radiation processes in binary systems. The monotonicity of the period
variations and the morphology of the respective ETV diagrams are thoroughly
explored in both the direct impact and the accretion disk mode of mass
transfer, accompanied by different types of mass and angular momentum losses
(through a hot-spot emission from the gainer and via the L2/L3 points). Mass
transfer rates comparable to or greater than 10^{-8} M_sun/yr are measurable
for typical noise levels of the ETV diagrams, regardless of whether the process
is conservative. However, the presence of a transient disk around the more
massive component defines a critical mass ratio q_cr ~ 0.83 above which the
period turns out to decrease when still in the conservative regime, rendering
the measurability of the anticipated variations a much more complicated task.
The effects of gravitational radiation proved to be rather undetectable, except
for systems with physical characteristics that only refer to cataclysmic
variables. Unlike the hot-spot effects, the Lagrangian points L2 and L3 support
very efficient routes of strong angular momentum loss. It is further shown that
escape of mass via the L3 point - when the donor is the less massive component
- safely provides critical mass ratios above which the period is expected to
decrease, no matter how intense the process is.Comment: 13 pages, 6 figures, 10 tables, published in A&
A Finite Difference method for the Wide-Angle `Parabolic' equation in a waveguide with downsloping bottom
We consider the third-order wide-angle `parabolic' equation of underwater
acoustics in a cylindrically symmetric fluid medium over a bottom of
range-dependent bathymetry. It is known that the initial-boundary-value problem
for this equation may not be well posed in the case of (smooth) bottom profiles
of arbitrary shape if it is just posed e.g. with a homogeneous Dirichlet bottom
boundary condition. In this paper we concentrate on downsloping bottom profiles
and propose an additional boundary condition that yields a well posed problem,
in fact making it -conservative in the case of appropriate real
parameters. We solve the problem numerically by a Crank-Nicolson-type finite
difference scheme, which is proved to be unconditionally stable and
second-order accurate, and simulates accurately realistic underwater acoustic
problems.Comment: 2 figure
Crank-Nicolson finite element discretizations for a 2D linear Schrödinger-type equation posed in a noncylindrical domain
Seminar Report: Innovating International Business Courts, 10 July 2018, Erasmus University Rotterd
Jetting behavior in drop-on-demand printing: Laboratory experiments and numerical simulations
The formation and evolution of micron-sized droplets of a Newtonian liquid generated on demand in an industrial inkjet printhead are studied experimentally and simulated numerically. The shapes and positions of droplets during droplet formation are observed using a high-speed camera and compared with their numerically obtained analogs. Both the experiments and the simulations use practical length scales for inkjet printing. The results show how fluid properties, specifically viscosity and surface tension, affect the drop formation, ligament length, and breakoff time. We identify the parameter space of fluid properties for producing single drops at a prescribed speed and show this is not simply a restriction on the Ohnesorge number, but that there is an additional restriction on the Reynolds number that is distinct from the Reynolds number limit associated with the prevention of splashing. This phase diagram provides more precise guidance on the space of fluid parameters for jetting single droplets in drop-on-demand inkjet printers
A randomized controlled trial of training in Motivational Interviewing for child protection.
There has been interest in developing more evidence-based approaches to child and family social work in the UK in recent years. This study examines the impact of a skills development package of training and supervision in Motivational Interviewing (MI) on the skills of social workers and the engagement of parents through a randomized controlled trial.
All workers in one local authority were randomly assigned to receive the package (n = 28) or control (n = 33). Families were then randomized to trained (n = 67) or untrained (n = 98) workers. Family meetings with the worker shortly after allocation were evaluated for MI skill. Research interviews gathered data including the WAI. Follow-up interviews 20 weeks later repeated the WAI, and other outcome measures including Goal Attainment Scaling (GAS) and rating of family life.
Between group analysis found statistically significant difference in MI skills, though these were not substantial (2.49 in control, 2.91 MI trained, p = .049). There was no statistically significant difference between groups in any other outcome measures.
The package of training and supervision did not create sufficient increase in MI skills to influence engagement or outcomes. Implications for understanding the relationship between skills, engagement and organizational change are discussed
Continuous anaerobic digestion of swine manure: ADM1-based modelling and effect of addition of swine manure fibers pretreated with aqueous ammonia soaking
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