1,527 research outputs found
Dynamic Package Interfaces - Extended Version
A hallmark of object-oriented programming is the ability to perform
computation through a set of interacting objects. A common manifestation of
this style is the notion of a package, which groups a set of commonly used
classes together. A challenge in using a package is to ensure that a client
follows the implicit protocol of the package when calling its methods.
Violations of the protocol can cause a runtime error or latent invariant
violations. These protocols can extend across different, potentially
unboundedly many, objects, and are specified informally in the documentation.
As a result, ensuring that a client does not violate the protocol is hard.
We introduce dynamic package interfaces (DPI), a formalism to explicitly
capture the protocol of a package. The DPI of a package is a finite set of
rules that together specify how any set of interacting objects of the package
can evolve through method calls and under what conditions an error can happen.
We have developed a dynamic tool that automatically computes an approximation
of the DPI of a package, given a set of abstraction predicates. A key property
of DPI is that the unbounded number of configurations of objects of a package
are summarized finitely in an abstract domain. This uses the observation that
many packages behave monotonically: the semantics of a method call over a
configuration does not essentially change if more objects are added to the
configuration. We have exploited monotonicity and have devised heuristics to
obtain succinct yet general DPIs. We have used our tool to compute DPIs for
several commonly used Java packages with complex protocols, such as JDBC,
HashSet, and ArrayList.Comment: The only changes compared to v1 are improvements to the Abstract and
Introductio
On the predictive power of Local Scale Invariance
Local Scale Invariance (LSI) is a theory for anisotropic critical phenomena
designed in the spirit of conformal invariance. For a given representation of
its generators it makes non-trivial predictions about the form of universal
scaling functions. In the past decade several representations have been
identified and the corresponding predictions were confirmed for various
anisotropic critical systems. Such tests are usually based on a comparison of
two-point quantities such as autocorrelation and response functions. The
present work highlights a potential problem of the theory in the sense that it
may predict any type of two-point function. More specifically, it is argued
that for a given two-point correlator it is possible to construct a
representation of the generators which exactly reproduces this particular
correlator. This observation calls for a critical examination of the predictive
content of the theory.Comment: 17 pages, 2 eps figure
Is local scale invariance a generic property of ageing phenomena ?
In contrast to recent claims by Enss, Henkel, Picone, and Schollwoeck [J.
Phys. A 37, 10479] it is shown that the critical autoresponse function of the
1+1-dimensional contact process is not in agreement with the predictions of
local scale invariance.Comment: 7 pages, 3 figures, final form, c++ source code on reques
Transfer-matrix DMRG for stochastic models: The Domany-Kinzel cellular automaton
We apply the transfer-matrix DMRG (TMRG) to a stochastic model, the
Domany-Kinzel cellular automaton, which exhibits a non-equilibrium phase
transition in the directed percolation universality class. Estimates for the
stochastic time evolution, phase boundaries and critical exponents can be
obtained with high precision. This is possible using only modest numerical
effort since the thermodynamic limit can be taken analytically in our approach.
We also point out further advantages of the TMRG over other numerical
approaches, such as classical DMRG or Monte-Carlo simulations.Comment: 9 pages, 9 figures, uses IOP styl
The Nature of the Nuclear H2O Masers of NGC 1068: Reverberation and Evidence for a Rotating Disk Geometry
We report new (1995) Very Large Array observations and (1984 - 1999)
Effelsberg 100m monitoring observations of the 22 GHz H2O maser spectrum of the
Seyfert 2 galaxy NGC 1068. The sensitive VLA observations provide a
registration of the 22 GHz continuum emission and the location of the maser
spots with an accuracy of ~ 5 mas. Within the monitoring data, we find evidence
that the nuclear masers vary coherently on time-scales of months to years, much
more rapidly than the dynamical time-scale. We argue that the nuclear masers
are responding in reverberation to a central power source, presumably the
central engine. Between October and November 1997, we detected a simultaneous
flare of the blue-shifted and red-shifted satellite maser lines. Reverberation
in a rotating disk naturally explains the simultaneous flaring. There is also
evidence that near-infrared emission from dust grains associated with the maser
disk also responds to the central engine. We present a model in which an X-ray
flare results in both the loss of maser signal in 1990 and the peak of the
near-infrared light curve in 1994. In support of a rotating disk geometry for
the nuclear masers, we find no evidence for centripetal accelerations of the
redshifted nuclear masers; the limits are +/- 0.006 km/s/year, implying that
the masers are located within 2 degrees of the kinematic line-of-nodes. We also
searched for high velocity maser emission like that observed in NGC 4258. In
both VLA and Effelsberg spectra, we detect no high velocity lines between +/-
350 km/s to +/- 850 km/s relative to systemic, arguing that masers only lie
outside a radius of ~ 0.6 pc (1.9 light years) from the central engine
(assuming a distance of 14.4 Mpc).Comment: 62 pages, 19 figure
Ageing in disordered magnets and local scale-invariance
The ageing of the bond-disordered two-dimensional Ising model quenched to
below its critical point is studied through the two-time autocorrelator and
thermoremanent magnetization (TRM). The corresponding ageing exponents are
determined. The form of the scaling function of the TRM is well described by
the theory of local scale-invariance.Comment: Latex2e, with epl macros, 7 pages, final for
Local scale invariance and strongly anisotropic equilibrium critical systems
A new set of infinitesimal transformations generalizing scale invariance for
strongly anisotropic critical systems is considered. It is shown that such a
generalization is possible if the anisotropy exponent \theta =2/N, with N=1,2,3
... Differential equations for the two-point function are derived and
explicitly solved for all values of N. Known special cases are conformal
invariance (N=2) and Schr\"odinger invariance (N=1). For N=4 and N=6, the
results contain as special cases the exactly known scaling forms obtained for
the spin-spin correlation function in the axial next nearest neighbor spherical
(ANNNS) model at its Lifshitz points of first and second order.Comment: 4 pages Revtex, no figures, with file multicol.sty, to appear in PR
Response of non-equilibrium systems with long-range initial correlations
The long-time dynamics of the -dimensional spherical model with a
non-conserved order parameter and quenched from an initial state with
long-range correlations is studied through the exact calculation of the
two-time autocorrelation and autoresponse functions. In the aging regime, these
are given in terms of non-trivial universal scaling functions of both time
variables. At criticality, five distinct types of aging are found, depending on
the form of the initial correlations, while at low temperatures only a single
type of aging exists. The autocorrelation and autoreponse exponents are shown
to be generically different and to depend on the initial conditions. The
scaling form of the two-time response functions agrees with a recent prediction
coming from local scale invariance.Comment: Latex, 18pp, 2 figures (final version
Personality Types of Master of Science in Project Management Students: A Field Study
In this research study, students enrolled in a university Master of Science in Project Management degree program were asked to respond to the Big Five personality inventory to ascertain whether their personality traits were in alignment with Big Five Leadership profile proposed by Lussier and Achua (2013) or were ranked similarly with the general population. Additionally, this study sought to explore whether university project management master degree studentsâ Big Five personalities were aligned with the suggested Big Five profile for project managers. The ranking of the Big Five leadership categories of 172 project management students was compared to rankings in previous studies. It was observed that the Big Five rankings of project management students differed in order from both the Lussier and Achua (2013) leadership profile as well as multiple studies conducted within the general population. However, the project management student rankings were consistent with recommended rankings for project managers. The findings can contribute to better understanding the traits that characterize students studying in the project management field of occupation
Project Manager Leadership Behavior: Task-Oriented Versus Relationship-Oriented
In this paper, we examined managersâ leadership behavior when working on a simulated team project regarding task-oriented versus relationship-oriented leadership behavior to effectively achieve successful project completion. Managers attending an advanced project management development program responded to the Fielder Leadership Behavior Style Self-Assessment, which is a useful framework to determine task-oriented versus relationship-oriented leadership behavioral styles. The degree of task-oriented versus relationship-oriented leadership behavior styles was assessed to determine the approach taken by the managers for achieving successful project completion. A Pearsonâs chi-square test was conducted to determine whether the observed values were significantly different from an expected value of five. The findings can contribute to better understanding the leadership styles, which characterize project management accomplishment
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