Production scheduling in SMT electronic boards assembly

This paper tackles the problem of scheduling in the assembly of SMT electronic boards. In particular, it focuses on a new scheduling method developed within the framework of an industry-university joint research project. The scheduling system aims at minimizing the makespan; this goal is achieved by reducing setup times and idle times of the machines. As an example, the outcome of a test carried out on a production mix made up of 10 board types is presented and analyzed in a summarized form.     

Dynamics of Mixed Coalitions Under Social Cohesion Constraints

ABSTRACT

Parameters for the birth and death diffusion life table model subject to downward jumps randomly occurring at a constant rate are estimated. The jump magnitudes have a beta distribution with support [0, l_x ], where l_x is the total number of survivors prior to the jump. The estimation method is maximum likelihood. The Cramer–Rao Lower bound and the asymptotic distribution for the MLE are derived. The model is applied to the U.S. men′s population from 1900 to 1999.     

ON THE PREFERENCES OF PRINCIPALS AND AGENTS

One of the reasons why market economies are able to thrive is that they exploit the willingness of entrepreneurs to take risks that laborers might prefer to avoid. Markets work because they remunerate good judgment and punish mistakes. Indeed, modern contract theory is based on the assumption that principals are less risk averse than agents. We investigate if the risk preferences of entrepreneurs are different from those of laborers by implementing experiments with a random sample of the population in a fast‐growing, small‐manufacturing, economic cluster. As assumed by theory, we find that entrepreneurs are more likely to take risks than hired managers. These results are robust to the inclusion of a series of controls. This lends support to the idea that risk preferences is an important determinant of selection into occupations. Finally, our lotteries are good predictors of financial decisions, thus giving support to the external validity of our risk measures and experimental methods (JEL C93, D81, D86).     

Regression models for binary longitudinal responses

Some conditional models to deal with binary longitudinal responses are proposed, extending random effects models to include serial dependence of Markovian form, and hence allowing for quite general association structures between repeated observations recorded on the same individual. The presence of both these components implies a form of dependence between them, and so a complicated expression for the resulting likelihood. To handle this problem, we introduce, as a first instance, what Follmann and Wu (1995) called, in a different setting, an approximate conditional model, which represents an optimal choice for the general framework of categorical longitudinal responses. Then we define two more formally correct models for the binary case, with no assumption about the distribution of the random effect. All of the discussed models are estimated by means of an EM algorithm for nonparametric maximum likelihood. The algorithm, an adaptation of that used by Aitkin (1996) for the analysis of overdispersed generalized linear models, is initially derived as a form of Gaussian quadrature, and then extended to a completely unknown mixing distribution. A large scale simulation work is described to explore the behaviour of the proposed approaches in a number of different situations.     

Simpson's Paradox in Survival Models

Abstract.  In the context of survival analysis it is possible that increasing the value of a covariate X has a beneficial effect on a failure time, but this effect is reversed when conditioning on any possible value of another covariate Y . When studying causal effects and influence of covariates on a failure time, this state of affairs appears paradoxical and raises questions about the real effect of X . Situations of this kind may be seen as a version of Simpson's paradox. In this paper, we study this phenomenon in terms of the linear transformation model. The introduction of a time variable makes the paradox more interesting and intricate: it may hold conditionally on a certain survival time, i.e. on an event of the type { T > t } for some but not all t , and it may hold only for some range of survival times.     

Blurred discourses: how market isomorphism constrains and enables collective action in civil society

Abstract Civil society – both national and transnational – is produced through the activities and discourses of a plurality of social actors, including political parties, NGOs and (new) social movements, media organizations, third sector organizations, market firms, and professional and trade associations. To understand the current dynamics of civil society, we need to combine the concept of the plurality with the investigation of a second phenomenon: namely, that in our globalized landscape master ideas and patterns of practices travel and materialize not only across national borders but also across different spheres of institutional life. In opposition to mainstream diffusionist explanations of the travel of ideas, we use Latour and Callon's translation model as a theoretical tool for reading an ‘exemplary’ case study taken from a broader Italian research programme. In particular, our aim is to provide some insights about how the current emphasis on economic performance and managerialization is translated into organizational processes of everyday activity regarding one of the most traditional collective actors of civil society, the third sector organization. The case considered here is a cooperative, whose origins are rooted in an encounter with Africa, and which is now engaged in a fair trade network. Specifically, we depict the complex system of meaning and practices that characterize this field when economic categories and priorities (for example rationalization, calculative action and efficiency) meet and blend with more conventional and expected logics of action (for example solidarity, emancipation and expressive behaviour) that are embedded within it.     

LOST IN THE MAIL: A FIELD EXPERIMENT ON CRIME

Stealing, shirking, and opportunistic behavior in general can create barriers to the development of markets. The costs associated with such behavior are shared by both firms and individuals and can be large enough to even prevent the initiation of trade. Measurement of these costs is difficult because information is not available for transactions that fail to occur. We use a field experiment to identify opportunistic crime in a task that is important and relevant for trade: the delivery of mail. We subtly manipulate the content and information available in mail sent to households across neighborhoods that vary by income, and detected high levels of shirking and stealing. Eighteen percent of the mail never arrived at its destination, and significantly more was lost if there was even a slight hint of something additional inside the envelope. Our results demonstrate the importance of transaction costs created by crime and that not all populations are equally affected. Middle‐income neighborhoods suffer the most. (JEL C93, K42, H41, L87, O21)     

A Problem of Dimensionality in Normal Mixture Analysis

Suppose the p -variate random vector W , partitioned into q variables W₁ and p - q variables W₂, follows a multivariate normal mixture distribution. If the investigator is mainly interested in estimation of the parameters of the distribution of W₁, there are two possibilities: (1) use only the data on W₁ for estimation, and (2) estimate the parameters of the p -variate mixture distribution, and then extract the estimates of the marginal distribution of W₁. In this article we study the choice between these two possibilities mainly for the case of two mixture components with identical covariance matrices. We find the asymptotic distribution of the linear discriminant function coefficients using the work of Efron (1975 ) and O'Neill (1978 ), and give a Wald–test for redundancy of W₂. A simulation study gives further insights into conditions under which W₂ should be used in the analysis: in summary, the inclusion of W₂ seems justified if Δ 2.1, the Mahalanobis distance between the two component distributions based on the conditional distribution of W₂ given W₁, is at least 2.     

Engineering education on production management. Different levels and degrees in five European countries: a comparison

The paper summarizes the results of the work-session ‘Education on Production Management’, organized during the Workshop and Summer School ‘Advanced Topics in Production Systems Design and Management’, held in Varenna (Lecco, Italy), from 1–4 June 1994. The organization of studies in the production management field in Denmark, France, Germany, Italy and Norway is outlined. A comparison between them shows a range of different solutions that must be understood to reach the goal of an effective exchange of production management people throughout the European Community.