2,721 research outputs found
Optimal search strategies of space-time coupled random walkers with finite lifetimes
We present a simple paradigm for detection of an immobile target by a
space-time coupled random walker with a finite lifetime. The motion of the
walker is characterized by linear displacements at a fixed speed and
exponentially distributed duration, interrupted by random changes in the
direction of motion and resumption of motion in the new direction with the same
speed. We call these walkers "mortal creepers". A mortal creeper may die at any
time during its motion according to an exponential decay law characterized by a
finite mean death rate . While still alive, the creeper has a finite
mean frequency of change of the direction of motion. In particular, we
consider the efficiency of the target search process, characterized by the
probability that the creeper will eventually detect the target. Analytic
results confirmed by numerical results show that there is an
-dependent optimal frequency that maximizes the
probability of eventual target detection. We work primarily in one-dimensional
() domains and examine the role of initial conditions and of finite domain
sizes. Numerical results in domains confirm the existence of an optimal
frequency of change of direction, thereby suggesting that the observed effects
are robust to changes in dimensionality. In the case, explicit
expressions for the probability of target detection in the long time limit are
given. In the case of an infinite domain, we compute the detection probability
for arbitrary times and study its early- and late-time behavior. We further
consider the survival probability of the target in the presence of many
independent creepers beginning their motion at the same location and at the
same time. We also consider a version of the standard "target problem" in which
many creepers start at random locations at the same time.Comment: 18 pages, 7 figures. The title has been changed with respect to the
one in the previous versio
Notes on Two Herbivorous Palm Weevil Species Associated with Sago Palms (Metroxylon sagu Rottb.) in the Philippines
Abstrac
Reactive dynamics on fractal sets: anomalous fluctuations and memory effects
We study the effect of fractal initial conditions in closed reactive systems
in the cases of both mobile and immobile reactants. For the reaction , in the absence of diffusion, the mean number of particles is shown to
decay exponentially to a steady state which depends on the details of the
initial conditions. The nature of this dependence is demonstrated both
analytically and numerically. In contrast, when diffusion is incorporated, it
is shown that the mean number of particles decays asymptotically as
, the memory of the initial conditions being now carried by the
dynamical power law exponent. The latter is fully determined by the fractal
dimension of the initial conditions.Comment: 7 pages, 2 figures, uses epl.cl
Supporting Analysts by Dynamic Extraction and Classification of Requirements-Related Knowledge
© 2019 IEEE. In many software development projects, analysts are required to deal with systems' requirements from unfamiliar domains. Familiarity with the domain is necessary in order to get full leverage from interaction with stakeholders and for extracting relevant information from the existing project documents. Accurate and timely extraction and classification of requirements knowledge support analysts in this challenging scenario. Our approach is to mine real-time interaction records and project documents for the relevant phrasal units about the requirements related topics being discussed during elicitation. We propose to use both generative and discriminating methods. To extract the relevant terms, we leverage the flexibility and power of Weighted Finite State Transducers (WFSTs) in dynamic modelling of natural language processing tasks. We used an extended version of Support Vector Machines (SVMs) with variable-sized feature vectors to efficiently and dynamically extract and classify requirements-related knowledge from the existing documents. To evaluate the performance of our approach intuitively and quantitatively, we used edit distance and precision/recall metrics. We show in three case studies that the snippets extracted by our method are intuitively relevant and reasonably accurate. Furthermore, we found that statistical and linguistic parameters such as smoothing methods, and words contiguity and order features can impact the performance of both extraction and classification tasks
The Single State Dominance Hypothesis and the Two-Neutrino Double Beta Decay of Mo100
The hypothesis of the single state dominance (SSD) in the calculation of the
two-neutrino double beta decay of Mo100 is tested by exact consideration of the
energy denominators of the perturbation theory. Both transitions to the ground
state as well as to the 0+ and 2+ excited states of the final nucleus Ru100 are
considered. We demonstrate, that by experimental investigation of the single
electron energy distribution and the angular correlation of the outgoing
electrons, the SSD hypothesis can be confirmed or ruled out by a precise
two-neutrino double beta decay measurement (e.g. by NEMO III collaboration).Comment: 13 pages, RevTex, 1 figur
Integrable su(3) spin chain combining different representations
The general expression for the local matrix of a quantum chain
with the site space in any representation of su(3) is obtained. This is made by
generalizing from the fundamental representation and imposing the
fulfillment of the Yang-Baxter equation. Then, a non-homogeneous spin chain
combining different representations of su(3) is solved by developing a method
inspired in the nested Bethe ansatz. The solution for the eigenvalues of the
trace of the monodromy matrix is given as two coupled Bethe equations. A
conjecture about the solution of a chain with the site states in different
representations of su(n) is presented. The thermodynamic limit of the ground
state is calculated.Comment: PlainTex harvmac, 30 pages, 7 figures, to appear in Journal of
Physics
Hormonal and emotional responses to competition using a dyadic approach: Basal testosterone predicts emotional state after a defeat
The present study analyzes the testosterone (T), cortisol (C) and emotional response in competitive interactions between dyads, as well as the relationship between basal T and the emotional response. Seventy-two men and women (36 dyads) participated in same-sex dyads in a face-to-face laboratory competition, and thirty-two men and women (16 dyads) carried out the same task in a non-competitive condition. Salivary samples (5 ml of saliva, plastic vials) were provided at three time points (baseline, task, and post-task), and subsequently T (pg/ml) and C (nmol/L) concentrations were measured using ELISA method. Participants completed self-reported measures of emotional valence, emotional arousal and perceived dominance by means of the Self-Assessment Manikin (SAM), at three time points (pre-task, task, and post-task). Two-level crossed Multilevel Models (MLM) showed a participants' stability in C (Mean ± SEM: baseline: 3.84 ± 0.28, task: 2.92 ± 0.28 and post-task: 2.62 ± 0.3), emotional valence (pre-task: 4 ± 0.06, task: 3.66 ± 0.1 and post-task: 3.84 ± 0.09), arousal (pre-task: 3.29 ± 0.09, task: 3.83 ± 0.09 and post-task: 3.38 ± 0.1) and dominance (pre-task: 3.28 ± 0.08, task: 3.4 ± 0.1 and post-task: 3.44 ± 0.09) values, which in the case of emotional valence and dominance was modulated by time-point, outcome and sex. Furthermore, analyses revealed that opponents' C, arousal and dominance values at one time-point influenced participants' values at the following time-point modulated by outcome, sex and time-point. Moreover, MLM indicated that in loser men, individuals higher in basal T (126.31 ± 6.4) displayed higher negative emotional valence after the defeat (post-task: 3.6 ± 0.21), while in women basal T (99.78 ± 12.6) was not significantly related to post competition emotional valence. These findings reinforce the importance of studying the relationship between hormonal and psychological changes in dyadic competition, and confirm that men and women differ in their psychophysiological responses to competition
Thermodynamical limit of general gl(N) spin chains: vacuum state and densities
We study the vacuum state of spin chains where each site carry an arbitrary
representation. We prove that the string hypothesis, usually used to solve the
Bethe ansatz equations, is valid for representations characterized by
rectangular Young tableaux. In these cases, we obtain the density of the center
of the strings for the vacuum. We work out different examples and, in
particular, the spin chains with periodic array of impurities.Comment: Latex file, 27 pages, 5 figures (.eps) A more detailed study of the
representations allowing string hypothesis has added. A simpler formula for
the densities is given. References added and misprint correcte
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