3,709 research outputs found
Alliance capability as a mediator between experience and alliance performance: An empirical investigation into the alliance capability development process.
An (in)efficiency based measurement of economic resilience
The ecosystem and the economic subsystem are interlinked. In fact, it is the overconsumption of scarce resources or the overproduction of bad outputs at economic system level that causes a great part of the imbalances at the ecosystem level. Some imbalances do not originate at the economic system level, but are due to external factors. Given the possibility of external shocks, respecting static sustainability thresholds is not a guarantee for system sustainability. In a dynamic setting, the concept of resilience is therefore helpful. In this paper we show how this concept can complement the traditional efficiency approach to come to a sustainable value creating economic system.Resource /Energy Economics and Policy,
Initial spreading of low-viscosity drops on partially wetting surfaces
Liquid drops start spreading directly after brought into contact with a
partial wetting substrate. Although this phenomenon involves a three-phase
contact line, the spreading motion is very fast. We study the initial spreading
dynamics of low-viscosity drops, using two complementary methods: Molecular
Dynamics simulations and high-speed imaging. We access previously unexplored
length- and time-scales, and provide a detailed picture on how the initial
contact between the liquid drop and the solid is established. Both methods
unambiguously point towards a spreading regime that is independent of
wettability, with the contact radius growing as the square root of time
The Knysna Elephants: A Relict Population
Population estimate for the Knysna elephants in 1876 was 500-600. By 1910 there were 40 elephants, by 1920 18, in 1970 between 11 and 13, and in 1981 this number further declined to 3: a mature bull, a cow and a calf. Poaching and human encroachment into elephant habitat are believed to be the major contributing factors for this decimation
Bubble formation during the collision of a sessile drop with a meniscus
The impact of a sessile droplet with a moving meniscus, as encountered in
processes such as dip-coating, generically leads to the entrapment of small air
bubbles. Here we experimentally study this process of bubble formation by
looking through the liquid using high-speed imaging. Our central finding is
that the size of the entrapped bubble crucially depends on the location where
coalescence between the drop and the moving meniscus is initiated: (i) at a
finite height above the substrate, or (ii) exactly at the contact line. In the
first case, we typically find bubble sizes of the order of a few microns,
independent of the size and speed of the impacting drop. By contrast, the
bubbles that are formed when coalescence starts at the contact line become
increasingly large, as the size or the velocity of the impacting drop is
increased. We show how these observations can be explained from a balance
between the lubrication pressure in the air layer and the capillary pressure of
the drop
On the smoothness of nonlinear system identification
We shed new light on the \textit{smoothness} of optimization problems arising
in prediction error parameter estimation of linear and nonlinear systems. We
show that for regions of the parameter space where the model is not
contractive, the Lipschitz constant and -smoothness of the objective
function might blow up exponentially with the simulation length, making it hard
to numerically find minima within those regions or, even, to escape from them.
In addition to providing theoretical understanding of this problem, this paper
also proposes the use of multiple shooting as a viable solution. The proposed
method minimizes the error between a prediction model and the observed values.
Rather than running the prediction model over the entire dataset, multiple
shooting splits the data into smaller subsets and runs the prediction model
over each subset, making the simulation length a design parameter and making it
possible to solve problems that would be infeasible using a standard approach.
The equivalence to the original problem is obtained by including constraints in
the optimization. The new method is illustrated by estimating the parameters of
nonlinear systems with chaotic or unstable behavior, as well as neural
networks. We also present a comparative analysis of the proposed method with
multi-step-ahead prediction error minimization
Two candidate brown dwarf companions around core helium-burning stars
Hot subdwarf stars of spectral type B (sdBs) are evolved, core helium-burning
objects. The formation of those objects is puzzling, because the progenitor
star has to lose almost its entire hydrogen envelope in the red-giant phase.
Binary interactions have been invoked, but single sdBs exist as well. We report
the discovery of two close hot subdwarf binaries with small radial velocity
amplitudes. Follow-up photometry revealed reflection effects originating from
cool irradiated companions, but no eclipses. The lower mass limits for the
companions of CPD-64481 () and PHL\,457
() are significantly below the stellar mass limit. Hence
they could be brown dwarfs unless the inclination is unfavourable. Two very
similar systems have already been reported. The probability that none of them
is a brown dwarf is very small, 0.02%. Hence we provide further evidence that
substellar companions with masses that low are able to eject a common envelope
and form an sdB star. Furthermore, we find that the properties of the observed
sample of hot subdwarfs in reflection effect binaries is consistent with a
scenario where single sdBs can still be formed via common envelope events, but
their low-mass substellar companions do not survive.Comment: accepted to A&
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