A Bayesian approach for non-homogeneous gamma degradation processes

A Bayesian approach based on the Markov Chain Monte Carlo technique is proposed for the non-homogeneous gamma process with power-law shape function. Vague and informative priors, formalized on some quantities having a “physical” meaning, are provided. Point and interval estimation of process parameters and some functions thereof are developed, as well as prediction on some observable quantities that are useful in defining the maintenance strategy is proposed. Some useful approximations are derived for the conditional and unconditional mean and median of the residual life to reduce computational time. Finally, the proposed approach is applied to a real dataset.     

Prescribing the Families Own Dysfunctional Rules as a Therapeutic Strategy*

The use of paradox-strategy in therapy is motivated by the fact that many families request help but at the same time seem to reject all offers of help. The therapist may be drawn into a game in which every effort on his part to act as an agent of change is nullified by the family group. In systemic terms these contradictory attitudes derive from the dynamic equilibrium existing between the tendency toward change, which is implicit in the request for help at one level, and the tendency toward homeostasis which at another level imposes the repetition of the family's habitual rules of interaction. The coexistence of these forces can entangle the therapist in the family's paradoxical logic of “help me to change, but without changing anything.” By accepting the contradiction facing him and by “uniting” himself with this within the family, the therapist puts himself into a position opposite to that which the family expects. His response to the family's paradoxical request is a paradox, or counterparadox, because it creates the contradictory communication typical of rigid family systems. By prescribing its own dysfunctional rules to the family, the therapist can stimulate the tendencies toward change present in the family system.     

A non linear wavelet based estimator for long memory processes

Two wavelet based estimators are considered in this paper for the two parameters that characterize long range dependence processes. The first one is linear and is based on the statistical properties of the coefficients of a discrete wavelet transform of long range dependence processes. The estimator consists in measuring the slope (related to the long memory parameter) and the intercept (related to the variance of the process) of a linear regression after a discrete wavelet transform is performed (Veitch and Abry, 1999). In this paper its properties are reviewed, and analytic evidence is produced that the linear estimator is applicable only when the second parameter is unknown. To overcome this limitation a non linear wavelet based estimator - that takes into account that the intercept depends on the long memory parameter - is proposed here for the cases in which the second parameter is known or the only parameter of interest is the long memory parameter. Under the same hypothesis assumed for the linear estimator, the non linear estimator is shown to be asymptotically more efficient for the long memory parameter. Numerical simulations show that, even for small data sets, the bias is very small and the variance close to optimal. An application to ATM based Internet traffic is presented.Financial support from the Italian Ministry of University and Scientific Research (MIUR), also in the context of the COFIN 2002 ALINWEB (Algorithms for the Internet and the Web) Project, is gratefully acknowledged.     

Modelling the quality of work in the Italian social co-operatives combining NPCA-RSM and SEM-GME approaches

The objective of this paper is to describe and analyse with appropriate statistical models the links between work quality latent factors. Due to the complexity of the task, the analysis is carried out through a two-step approach:

• In the first step, we construct some multidimensional measures of the subjective quality of work, using nonlinear principal component analysis (NPCA) and Rasch analysis with the Rating Scale Model (NPCA-RSM);

• In the second step, we adopt a Structural Equation Model based on generalized maximum entropy (SEM-GME) to integrate the measures achieved with the previous step and to evaluate the relationships between the subjective work quality latent factors.

Therefore, the novel aspects of this paper are the following: (i) The integration between the NPCA-RSM and SEM-GME, which allows reduction of the variables analysed and evaluation of the measurement errors; (ii) The formalization of a Job Satisfaction Model for the study of the relationships between the subjective work quality latent factors in the Italian social services sector.     

Sexual Behavior With Noncommercial Partners: A Concurrent Partnership Study Among Middle-Aged Female Sex Workers in China

Female sex workers (FSWs) often engage in concurrent partnerships, meaning they have multiple sexual relationships at the same time. The objective of this study was to investigate sexual concurrency and its associations with condom use and syphilitic infections among FSWs over age 35. Respondent-driven sampling was used to recruit 1,245 FSWs in Nanning, Hefei, and Qingdao, China. FSWs were asked to report whether they had concurrent partners in the past six months. Concurrency was defined as engagement in sex with commercial clients and (1) husbands and boyfriends (n = 167); (2) husbands only (n = 301); or (3) boyfriends only (n = 469). FSWs with only commercial clients were used as the comparison group (n = 308). Across all groups, the percentage of FSWs with prevalent and active syphilis ranged from 19.6% to 25.6% and 9.1% to 11.5%, respectively. Condom use was low with noncommercial sexual partners and was more likely to be used when FSWs’ boyfriends had other partners. Three components of the theory of planned behavior were significantly associated with consistent condom use. Concurrent relationships may lead to increased transmission of syphilis at the workplace and family levels. Effective interventions should target concurrency with both commercial and noncommercial partners.     

A two-phase optimization method for a multiobjective vehicle relocation problem in electric carsharing systems

A spanning subgraph F of a graph G is called an even factor of G if each vertex of F has even degree at least 2 in F. It was conjectured that if a graph G has an even factor, then it has an even factor F with \(|E(F)|\ge {4\over 7}(|E(G)| + 1)+ {2\over 7}|V_2(G)|\), where \(V_2(G)\) is the set of vertices of degree 2 in G. We note that the conjecture is false if G is a triangle. In this paper, we confirm the conjecture for all graphs on at least 4 vertices, and moreover, we prove that if \(|E(H)|\le {4\over 7}(|E(G)| + 1)+ {2\over 7}|V_2(G)|\) for every even factor H of G, then every maximum even factor of G is a 2-factor consisting of even circuits.     

Labour Mobility in Italy: An Empirical Investigation

ABSTRACT: In this paper the author presents a model of unemployment inflows and outflows for the Italian labour market. The flows that the author attempts to estimate are the unemployment inflows and outflows from and to employment. The aggregate estimation suggests that a crucial role is played by the aggregate demand and wage variables, and by the structural change variable. The paper also presents intersectoral estimations of SURE, which take into consideration the flows between Industry and Services. The results are along the lines of those obtained at the aggregate level. An important factor which should be underlined, however, is the asymmetric pattern of the wage variable in the industrial and services sector.     

Female Immigrant Entrepreneurs: More Than a Family Strategy

This article explores the issue of immigrant women entrepreneurship. It focuses on the emergence of new points of view on self‐employed migrant women and in particular their search for independence. With the support of qualitative research carried on in Italy, it will set out a typology of motivations and strategies to become self‐employed in which, besides a “family strategy” and an “independency strategy”, a “mixed network strategy” also emerges. This last focuses on the role of mixed networks (with other foreigners and/or natives) not only in business management but also in the promotion of transnational social activities. Policies that support associations, creating opportunities for gathering and exchanging with local residents and improving the presence of immigrant women in local institutions, could have the side‐effect of increasing participation by immigrant women in self‐employment, not for lack of alternatives but as a path towards self‐fulfilment and empowerment.     

Impact of performance indicators on organisations: a proposal for an evaluation model

This work aims at giving some guidelines to assess the impact of performance indicators on organisations. Performance measurement systems are usually introduced into organisations in order to monitor goal achievement, to allocate resources and to implement a strategy. However, the implementation of performance indicators may generate an alteration in the rational behaviour of the monitored structure. The risk of this impact is always present, and must be considered very carefully in order to preserve the organisation from a counter-productive effect. In the present analytical work, a reference model is proposed as a first step. This model considers all the organisational dimensions on which an indicator may exert its influence. The method makes use of the four Kaplan and Norton’s balanced scorecard perspectives in order to identify the dimensions on which an indicator may exert its impact. Previous works reported in scientific literature do not provide operational models for impact analysis, whereas, the proposed model is linked to an operative procedure in order to support management to make this analysis. The aim is to make the impact analysis less complex by structuring it in a sequence of predefined steps. The proposal is supported by some practical examples.