Cluster growth in far-from-equilibrium particle models with diffusion, detachment, reattachment and deposition

Monolayer cluster growth in far-from-equilibrium systems is investigated by applying simulation and analytic techniques to minimal hard core particle (exclusion) models. The first model (I), for post-deposition coarsening dynamics, contains mechanisms of diffusion, attachment, and slow activated detachment (at rate epsilon<<1) of particles on a line. Simulation shows three successive regimes of cluster growth: fast attachment of isolated particles; detachment allowing further (epsilon t)^(1/3) coarsening of average cluster size; and t^(-1/2) approach to a saturation size going like epsilon^(-1/2). Model II generalizes the first one in having an additional mechanism of particle deposition into cluster gaps, suppressed for the smallest gaps. This model exhibits early rapid filling, leading to slowing deposition due to the increasing scarcity of deposition sites, and then continued power law (epsilon t)^(1/2) cluster size coarsening through the redistribution allowed by slow detachment. The basic (epsilon t)^(1/3) domain growth laws and epsilon^(-1/2) saturation in model I are explained by a simple scaling picture. A second, fuller approach is presented which employs a mapping of cluster configurations to a column picture and an approximate factorization of the cluster configuration probability within the resulting master equation. This allows quantitative results for the saturation of model I in excellent agreement with the simulation results. For model II, it provides a one-variable scaling function solution for the coarsening probability distribution, and in particular quantitative agreement with the cluster length scaling and its amplitude.Comment: Accepted in Phys. Rev. E; 9 pages with figure

Technology Adoption in Nonrenewable Resource Management

Nonrenewable resource scarcity has been a traditional concern when designing optimal growth models. Technological change has played an important role in those models, since its presence is assumed to mitigate the depletion effect on extraction paths over time. We formalize the general problem of a competitive nonrenewable resource extracting firm to analyze optimal extraction behavior and technology adoption when adoption is costly, both in a deterministic and a stochastic environment, when the firm either anticipates adoption or not. Based on a quadratic extraction cost function, our results do not support the traditional view according to which the firm will only incur in an adoption cost when the stock is depleted enough.nonrenewable resources; technology adoption; depletion effect; cost of adoption.

Fuzzy approach to discrete data reduction: an application in economics for assessing the skill premium

Measures of stock of skills alternative to human capital have raised fresh difficulties, especially in data managing. We propose to empirically compare the efficiency of a hierarchical cluster analysis and a fuzzy clustering in reducing discrete skill data. The outcomes of both methods are subsequently used to measure the impact of skills on earnings in addition to human capital. The proposed methodological comparison was made using an original dataset of retail bankers’ skills assessed by supervisors. Empirical evidence shows that the fuzzy approach is more efficient than the hierarchical clustering: the resulting clusters are fewer and easier to interpret. Furthermore, the earnings equation enriched with skill variables allowed us to correct the education premium, and provides information on monetary incentives related to individual skills. Our paper attempts to raise researchers’ and practitioners’ awareness of data reducing methods, and their implications for wage determinants.info:eu-repo/semantics/publishedVersio

The relevance of follow-ups in data collection for the quality assurance system of the Portuguese population and housing census

The operationalization of the Population and Housing Census in Portugal is managed by a hierarchical structure in which Statistics Portugal is at the top and local government institutions at the bottom. When the Census takes place every ten years, local governments are asked to collaborate with Statistics Portugal in the execution and monitoring of the fieldwork operations at the local level. During the Pilot Test stage of the 2011 Census, local governments were asked for additional collaboration: to answer the Perception of Risk survey, whose aim was to gather information to design a quality assurance instrument that could be used to monitor the Census operations. The response rate of the survey was desired to be 100%, however, by the deadline of data collection nearly a quarter of local governments had not responded to the survey and thus a decision was made to make a follow up mailing. In this paper, we examine whether the same conclusions could have been reached from survey without follow ups as with them and evaluate the influence of follow ups on the conception of the quality assurance instrument. Comparison of responses on a set of perception variables revealed that local governments answering previous or after the follow up did not differ. However the configuration of the quality assurance instrument changed when including follow up responses.info:eu-repo/semantics/publishedVersio

Index of satisfaction with public transport: a fuzzy clustering approach

Increasing public transport use is recognized by many countries as crucial to the pursuit of a global strategy for environmental sustainability and improving urban mobility. Understanding what users value in a public transport service is essential to carry out this strategy. Using fuzzy clustering, we developed an index that measures individual user satisfaction with the public transport service in the metropolitan area of Lisbon and subsequently identified the possible determinants of satisfaction by means of a regression tree model. The results achieved unveil a hierarchical partition of the data, highlighting the diversified level of satisfaction among public transport users that is reflected in the distribution of the index. The managerial implications of the findings for the public transport service are addressed.info:eu-repo/semantics/publishedVersio

Quality assurance in the Portuguese census: the contribution of the balanced scorecard

This article describes how the balanced scorecard methodology and associated procedures were developed and implemented as the framework for the quality assurance strategy of the fieldwork in the 2011 Portuguese Population and Housing Census. The main goal of a census operation is to provide high-quality statistical information on population, buildings, and dwellings that meet users’ needs. The most critical activity of a census is the fieldwork operation where the distribution, completion, and recollection of census questionnaires are handled. Due to the dimension, complexity, and need to guarantee the final product quality of the census 2011 operation, the balanced scorecard methodology was elected as the framework for the quality assurance strategy implementation. This was the first time such a management system was used in a census operation. In terms of academic research on census quality control, the quality focus has been on the net undercount based on post enumeration survey. On the contrary, the authors’ concern is about how to ensure quality enumeration work during the census operation. The balanced scorecard methodology allowed integrating the operational execution of goals and its control into a single census management tableaux du bord, which allowed the provision of updated information on the ongoing processes and, thus, the ability to make timely corrections for those targets that suffered deviations.info:eu-repo/semantics/acceptedVersio

Avaliação de progênies de Eucalyptus crebra no norte do Estado de Goiás.

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