Summary For technological applications it can be useful to identify some simple physical mechanisms, which, on the basis of the available
knowledge of the production process, may suggest the most appropriate approach to statistical control of the random quantities
of interest. For this purpose the notion of rupture point is introduced firstly. A rupture point is characterized bym randomly arising out of control states, assumed to be mutually exclusive and stochastically independent. Shewhart's control
charts seem to represent the natural statistical tool for controlling a rupture point; however it is shown that they are fully
justified only when the hazard rates attached to the causes of failure are constant. Otherwise, typically in the presence
of time increasing hazard rates, Shewhart's control charts should be completed by a preventive intervention rule (preventive
maintenance). In the second place, the notion of dynamic instability point is introduced, which is specifically characterized
by assuming that the random quantity of interest is ruled by a stochastic differential equation with constant coefficients.
By discretization, developed according to a possibly new approach, it is shown that the former model reduces to an equation
error model, which is among the simplest used in adaptive control, and thus particularly easy to deal with in regard to parameter
estimation and the definition of the optimum control rule. 相似文献
We study, from the standpoint of coherence, comparative probabilities on an arbitrary familyE of conditional events. Given a binary relation ·, coherence conditions on · are related to de Finetti's coherent betting system: we consider their connections to the usual properties of comparative probability and to the possibility of numerical representations of ·. In this context, the numerical reference frame is that of de Finetti's coherent subjective conditional probability, which is not introduced (as in Kolmogoroff's approach) through a ratio between probability measures.Another relevant feature of our approach is that the family & need not have any particular algebraic structure, so that the ordering can be initially given for a few conditional events of interest and then possibly extended by a step-by-step procedure, preserving coherence. 相似文献
Empirical studies have documented a decline in indicators of social participation in the last five decades. The responsibility of social disengagement has often been attributed to pervasive busyness and the increasing pressure on time. In this paper we argue that computer-mediated interaction, and particularly online networking, can help mitigate this downward trend. We develop a logical framework for assessing the role of the Internet in the evolution of social participation. We analyze an economy where agents can develop their social interactions through two main modes of participation, one encompassing both online networking and face to face interactions, and the other solely based on physical encounters. We study the interdependence between the increase in the pressure on time and the variation in the relative performance of the two strategies of participation. 相似文献
Cet article traite, en premier lieu, du problème de la définition d'une méthode d'enquête, appropriée à l'analyse et à la compréhension de la réalité sociale. Il le fait en partant de la critique du modèle cognitiviste-comportementaliste que l'on peut relier aux noms de Boudon et Weber. Les intérêts, mais aussi et surtout les carences de ce modèle sont mis en évidence. Etant donné qu'il occupe, parmi les schémas méthodologiques apprêtés à la recherche sociologique, une place d'honneur pour sa rigueur et sa fécondité analytique, ses carences soulignent avec une clarté particulière non seulement les difficultés que la pensée sociale rencontre dans le domaine de la méthode, mais aussi les conséquences négatives de celles-ci sur la scientificité de l’élaboration théorique, entendue comme la capacité à interpréter et à expliquer la réalité de référence.
La critique de l’élaboration de R. Boudon sur la méthode aide aussi à mettre en évidence, par contraste, les motifs, les caractéristiques et les potentialités de notre proposition méthodologique, qui est présentée tout de suite après. Sur la base de cette proposition, que nous appelons objectivisme social, nous avons formulé non seulement des objections au relativisme culturel de Weber et à l'anti-relativisme culturel et cognitif de R. Boudon, mais aussi à la notion de rationalité et à la théorie sur l’évolution sociale de ce dernier auteur.
Parallèlement, sont proposées une notion de rationalité différente et une explication alternative des processus sociaux, laquelle embrasse des aspects concernant tant l’évolution que l'organisation des sociétés humaines et qui peut être facilement étendue aussi à l'interprétation des processus historiques. 相似文献
Alien squirrels may seriously threaten native species by means of interspecific competition. In our work, we analysed whether the distribution of alien Siberian chipmunks within the Sigurtà Garden urban park (north-eastern Italy) changed after the natural spread of native Eurasian red squirrels in a 20-year period. Distribution of both squirrels was estimated through a citizen-science approach, in the first 10-year after red squirrel arrival 1 (i.e. Decade 1: 1997–2006) and in the second 10-year interval (i.e. Decade 2: 2007–2017). We compared habitat use of both species and we assessed whether a vertical segregation occurred through a dissimilarity index. Woodlands were selected by both species in both decades. Red squirrels also selected tree lines in Decade 1. A vertical segregation was apparent in Decade 1, whereas in Decade 2 both squirrel species were observed on the lowest branches or on the ground, where they are fed by humans. This was also confirmed by the habitat niche-overlap index, which increased in Decade 2. The extent of occurrence of Sciurus vulgaris increased throughout the park, whereas those of Eutamias sibiricus decreased. Differently from what is usually observed with alien squirrels, the spread of the native species appears to be halting and reversing the expansion of the non-native one. 相似文献
A reference method to estimate Feral Pigeon (C. livia) population size in urban areas is missing: results of different surveys are difficult to compare due to the wide heterogeneity of approaches. A combined technique, the Superimposed Urban Strata (SUS) method, especially designed to estimate pigeon population size in urban areas, is proposed. SUS implements methods based on stratified sampling layers: its reliability was tested with a pilot study in Padua (Italy). The survey area was split into two superimposed strata and a different survey technique was applied to each stratum. The first stratum consisted of twelve topographic sampling units, identified as critical ornithic-density loci. The second stratum was obtained by selecting 10 % of the survey area with systematic sampling. In the estimate of the population size, different detection probabilities were assigned to the two strata. The SUS method was first applied in 2007, when three-year growth projections for the C. livia population were calculated, with a density-dependent model. In 2010, the survey was repeated to countercheck previous data. Estimated C. livia population size was of 2340 ±93 units in 2007, whereas in 2010 it was of 3679 ±161 units. The 2010 estimated population size resulted in fair accordance with the three-year projections, showing less than a 4 % mismatch. SUS proved to be an adequate estimate method for urban areas: so far it has been tested only in an average Italian urban area, but it could be easily adapted to other cities by calibrating parameters linked to the peculiar urban background. 相似文献
ABSTRACTResidential care is one of the most restrictive out-of-home care settings; however, this is a temporary placement and youth eventually reintegrate into the home and community setting. Reintegration presents many challenges, and aftercare becomes critical for maintaining youth gains and promoting family stability. Aftercare programs and supports should align to individual family needs that entail understanding individual and familial characteristics. Previous studies have explored characteristics related to family functioning, mental health, behavior, and perceptions of need during reintegration; yet little is known regarding how affective characteristics (i.e., self-efficacy, empowerment) factor into reintegration, or the implications this may have for providers. The purpose of this study was to address this gap by exploring empowerment and self-efficacy in caregivers (N = 120) who had a child return home within 1 month of departing residential care. Overall, caregivers reported high levels of empowerment and self-efficacy during the initial transition period. Significant differences for empowerment and self-efficacy were present in characteristics such as race, income, number of children in the home, and free/reduced lunch status. 相似文献
Aim of this article is to address the issue of citizen participation and democratic engagement within a specific area—slum
upgrading—presenting and theoretically discussing the approach of an international network called Shack/Slum Dwellers International
(SDI), which represents member federations of urban poor and homeless groups from about 30 countries in Asia, Africa, and
Latin America. The article addresses the model of intervention embraced by the network, the activities carried out, its philosophy,
etc., mainly focusing on the way it envisions and pursues the engagement of local governments in upgrading slum dwellers living
conditions. The basic idea within SDI is that the lack of participation by the urban poor has historically been one of the
major obstacles to achieve real development: either the government or the donors’ agencies, in fact, usually treat the poor
as beneficiaries of someone else’s actions, thus undervaluing their knowledge and skills. Radically opposing this view, SDI
interprets its role not as an intermediary agency of slum dwellers in the engagement/negotiation with local governments but
rather as an “enabling tool” of direct negotiation between the urban poor and the public institutions. SDI’s most relevant
feature, in fact, is surely the genuine leading role assigned to the slum dwellers grassroots organizations. 相似文献