Search results for "PROB"
showing 10 items of 8859 documents
Resident and transient dynamics, site fidelity and survival in wintering Blackcaps Sylvia atricapilla: evidence from capture-recapture analyses
2007
In their winter quarters, migrant birds may either remain within a small area (resident strategy) or move frequently over a large area looking for locally abundant food (transient strategy). It has been suggested that both strategies could simultaneously occur in the same population. We used time-since-marking capture‐recapture models to infer the coexistence of these two behavioural strategies (transient and resident) among wintering Blackcaps Sylvia atricapilla using weekly recapture data over a 7-year period. A related question is whether Blackcaps, if surviving to the next winter, always return to the same wintering area, so we also used this approach to analyse winter site fidelity and…
Family networks and refugees’ health conditions. A picture from Italian informal settlements
2021
While the relationships between social networks and health are widely acknowledged in the literature, few of these studies have covered the population of refugees living in makeshift camps. In our analysis of a nationally representative Italian survey of individuals living in informal settlements, we find that many had weak family relations: only 10 per cent had one or more family members in their settlement. The paper analyses the effects of individual social network on two measures of health, and finds that the refugees’ health conditions were associated with both their personal characteristics and the characteristics of the settlement. The results show that more than 50 per cent of these…
A Study of the Health of Seafaring Workers of Valencia, Spain
1997
Under the auspices of the Service of Maritime Health of the Marine Social Institute of Valencia, Spain, the health status of seafaring workers from Valencia was evaluated. An epidemiologic study was carried out based on 707 pre-embarkation health examinations, collecting information about the health problems of these workers and their associated risk factors. The data were analyzed to estimate population frequencies and the corresponding 95% confidence intervals. Significance among groups was calculated by the chi-square test (p0.05). Relative risks were calculated in comparisons of the seafaring workers with the general population of Valencia. High incidences of ophthalmologic disorders we…
The use of Markovian metapopulation models: Reducing the dimensionality of transition matrices by self-organizing Kohonen networks
2006
Abstract Markovian population models are used in conservation biology to find an accurate estimate of a population's extinction probability. Such models require handling of large transition matrices and calculations are thus extremely time-consuming when large populations have to be studied. To accomplish these problems, some authors have suggested to group together several states/sizes of the population. Unfortunately, this so-called binning frequently results in errors in estimates obtained. The main problem with binning is that it assumes that grouped states behave nearly identical with respect to the underlying stochastic population process and that so far binning methods implicitly vio…
Scatter search for an uncapacitated p-hub median problem
2015
Scatter search is a population-based method that has been shown to yield high-quality outcomes for combinatorial optimization problems. It uses strategies for combining solution vectors that have proved effective in a variety of problem settings. In this paper, we present a scatter search implementation for an NP -hard variant of the classic p-hub median problem. Specifically, we tackle the uncapacitated r-allocation p-hub median problem, which consists of minimizing the cost of transporting the traffics between nodes of a network through special facilities that act as transshipment points. This problem has a significant number of applications in practice, such as the design of transportati…
A hybrid evolution strategy for the open vehicle routing problem
2010
This paper presents a hybrid evolution strategy (ES) for solving the open vehicle routing problem (OVRP), which is a well-known combinatorial optimization problem that addresses the service of a set of customers using a homogeneous fleet of non-depot returning capacitated vehicles. The objective is to minimize the fleet size and the distance traveled. The proposed solution method manipulates a population of @m individuals using a (@m+@l)-ES; at each generation, a new intermediate population of @l offspring is produced via mutation, using arcs extracted from parent individuals. The selection and combination of arcs is dictated by a vector of strategy parameters. A multi-parent recombination …
A two-point boundary value formulation of a mean-field crowd-averse game
2014
Abstract We consider a population of “crowd-averse” dynamic agents controlling their states towards regions of low density. This represents a typical dissensus behavior in opinion dynamics. Assuming a quadratic density distribution, we first introduce a mean-field game formulation of the problem, and then we turn the game into a two-point boundary value problem. Such a result has a value in that it turns a set of coupled partial differential equations into ordinary differential equations.
Estimating Polling Accuracy in Multiparty Elections Using Surveybias
2016
Any rigorous discussion of bias in opinion surveys requires a scalar measure of survey accuracy. Martin, Traugott, and Kennedy (2005, Public Opinion Quarterly 69: 342-369) propose such a measure A for the two-party case, and Arzheimer and Evans (2014, Political Analysis 22: 31-44) demonstrate how measures A'i, B, and Bw for the more common multiparty case can be derived. We describe the commands surveybias, surveybiasi, and surveybiasseries, which enable the fast computation of these binomial and multinomial measures of bias in opinion surveys. While the examples are based on pre-election surveys, the methodology applies to any multinomial variable whose true distribution in the population…
Memetic Compact Differential Evolution for Cartesian Robot Control
2010
This article deals with optimization problems to be solved in the absence of a full power computer device. The goal is to solve a complex optimization problem by using a control card related to portable devices, e.g. for the control of commercial robots. In order to handle this class of optimization problems, a novel Memetic Computing approach is presented. The proposed algorithm employs a Differential Evolution framework which instead of processing an actual population of candidate solutions, makes use of a statistical representation of the population which evolves over time. In addition, the framework uses a stochastic local search algorithm which attempts to enhance the performance of th…
A Discrete-Time Hazard Model for Loans: Some Evidence from Italian Banking System
2012
Problem statement: The probability of default, PD, is a crucial probl em for banks. In the last years international accords (Basel, Basel 2 an d Basel 3) have incentived banks to adopt objective s systems to evaluating and monitoring risk of defaul t in order to predict PD for new loans based on borrower's characteristics. The aim of this study i s to introduce a discrete survival model to study t he risk of default and to propose the empirical eviden ce by the Italian banking system. Approach: Survival analysis is used if we are interested in w hether and when an event occurs. In this context th e event occurrence represents a borrower's transition from one state, loan in bonis that is not…