16,677 research outputs found
Introducing the concept of first and last value to aid lean design: learning from social housing projects In Chile
Value for the customer through efficient production processes is a fundamental principle of Lean. In Lean Construction, Value to customers is largely delivered through project planning and control activities only. Thus, it can be argued that Lean Construction overlooks the opportunity to address Value from the early stages of a project. Aimed at improving this, Lean Design arose as a new approach for design management promoting customer and end user involvement from the early stage of projects. However, even here environmental & social issues are postponed over individual requirements. As a result, Lean potential in general skips the opportunity to address Value from a wider perspective in which the return of Value from the construction industry to society is considered. This paper proposes dividing the wider understanding of the performance of the (global) built environment from the particular (local) project requirements calling the former First Value and the latter Last Value. The theory is triangulated through observation of how a developing country (Chile) is resolving social issues through the use of the built environment. The work described develops Lean Design Management by providing a clearer vision of Value to reduce waste and aid sustainability in the built environment
Dealing with Integer-valued Variables in Bayesian Optimization with Gaussian Processes
Bayesian optimization (BO) methods are useful for optimizing functions that
are expensive to evaluate, lack an analytical expression and whose evaluations
can be contaminated by noise. These methods rely on a probabilistic model of
the objective function, typically a Gaussian process (GP), upon which an
acquisition function is built. This function guides the optimization process
and measures the expected utility of performing an evaluation of the objective
at a new point. GPs assume continous input variables. When this is not the
case, such as when some of the input variables take integer values, one has to
introduce extra approximations. A common approach is to round the suggested
variable value to the closest integer before doing the evaluation of the
objective. We show that this can lead to problems in the optimization process
and describe a more principled approach to account for input variables that are
integer-valued. We illustrate in both synthetic and a real experiments the
utility of our approach, which significantly improves the results of standard
BO methods on problems involving integer-valued variables.Comment: 7 page
The role of rotation on Petersen Diagrams. The period ratios
The present work explores the theoretical effects of rotation in calculating
the period ratios of double-mode radial pulsating stars with special emphasis
on high-amplitude delta Scuti stars (HADS). Diagrams showing these period
ratios vs. periods of the fundamental radial mode have been employed as a good
tracer of non-solar metallicities and are known as Petersen diagrams (PD).In
this paper we consider the effect of moderate rotation on both evolutionary
models and oscillation frequencies and we show that such effects cannot be
completely neglected as it has been done until now. In particular it is found
that even for low-to-moderate rotational velocities (15-50 km/s), differences
in period ratios of some hundredths can be found. The main consequence is
therefore the confusion scenario generated when trying to fit the metallicity
of a given star using this diagram without a previous knowledge of its
rotational velocity.Comment: A&A in pres
Inconsistencies in the application of harmonic analysis to pulsating stars
Using ultra-precise data from space instrumentation we found that the
underlying functions of stellar light curves from some AF pul- sating stars are
non-analytic, and consequently their Fourier expansion is not guaranteed. This
result demonstrates that periodograms do not provide a mathematically
consistent estimator of the frequency content for this kind of variable stars.
More importantly, this constitutes the first counterexample against the current
paradigm which considers that any physical process is described by a contin-
uous (band-limited) function that is infinitely differentiable.Comment: 9 pages, 8 figure
Verifying black hole orbits with gravitational spectroscopy
Gravitational waves from test masses bound to geodesic orbits of rotating
black holes are simulated, using Teukolsky's black hole perturbation formalism,
for about ten thousand generic orbital configurations. Each binary radiates
power exclusively in modes with frequencies that are
integer-linear-combinations of the orbit's three fundamental frequencies. The
following general spectral properties are found with a survey of orbits: (i)
99% of the radiated power is typically carried by a few hundred modes, and at
most by about a thousand modes, (ii) the dominant frequencies can be grouped
into a small number of families defined by fixing two of the three integer
frequency multipliers, and (iii) the specifics of these trends can be
qualitatively inferred from the geometry of the orbit under consideration.
Detections using triperiodic analytic templates modeled on these general
properties would constitute a verification of radiation from an adiabatic
sequence of black hole orbits and would recover the evolution of the
fundamental orbital frequencies. In an analogy with ordinary spectroscopy, this
would compare to observing the Bohr model's atomic hydrogen spectrum without
being able to rule out alternative atomic theories or nuclei. The suitability
of such a detection technique is demonstrated using snapshots computed at
12-hour intervals throughout the last three years before merger of a kludged
inspiral. Because of circularization, the number of excited modes decreases as
the binary evolves. A hypothetical detection algorithm that tracks mode
families dominating the first 12 hours of the inspiral would capture 98% of the
total power over the remaining three years.Comment: 18 pages, expanded section on detection algorithms and made minor
edits. Final published versio
Symmetries in Fluctuations Far from Equilibrium
Fluctuations arise universally in Nature as a reflection of the discrete
microscopic world at the macroscopic level. Despite their apparent noisy
origin, fluctuations encode fundamental aspects of the physics of the system at
hand, crucial to understand irreversibility and nonequilibrium behavior. In
order to sustain a given fluctuation, a system traverses a precise optimal path
in phase space. Here we show that by demanding invariance of optimal paths
under symmetry transformations, new and general fluctuation relations valid
arbitrarily far from equilibrium are unveiled. This opens an unexplored route
toward a deeper understanding of nonequilibrium physics by bringing symmetry
principles to the realm of fluctuations. We illustrate this concept studying
symmetries of the current distribution out of equilibrium. In particular we
derive an isometric fluctuation relation which links in a strikingly simple
manner the probabilities of any pair of isometric current fluctuations. This
relation, which results from the time-reversibility of the dynamics, includes
as a particular instance the Gallavotti-Cohen fluctuation theorem in this
context but adds a completely new perspective on the high level of symmetry
imposed by time-reversibility on the statistics of nonequilibrium fluctuations.
The new symmetry implies remarkable hierarchies of equations for the current
cumulants and the nonlinear response coefficients, going far beyond Onsager's
reciprocity relations and Green-Kubo formulae. We confirm the validity of the
new symmetry relation in extensive numerical simulations, and suggest that the
idea of symmetry in fluctuations as invariance of optimal paths has
far-reaching consequences in diverse fields.Comment: 8 pages, 4 figure
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