A Branch and Bound algorithm for general mixed-integer quadratic programs based on quadratic convex relaxation

Let \((MQP)\) be a general mixed-integer quadratic program that consists of minimizing a quadratic function \(f(x) = x^TQx +c^Tx\) subject to linear constraints. Our approach to solve \((MQP)\) is first to consider an equivalent general mixed-integer quadratic problem. This equivalent problem has additional variables \(y_{ij}\) , additional quadratic constraints \(y_{ij}=x_ix_j\) , a convex objective function, and a set of valid inequalities. Contrarily to the reformulation proposed in Billionnet et al. (Math Program 131(1):381–401, 2012), the equivalent problem cannot be directly solved by a standard solver. Here, we propose a new Branch and Bound process based on the relaxation of the non-convex constraints \(y_{ij}=x_ix_j\) to solve \((MQP)\) . Computational experiences are carried out on pure- and mixed-integer quadratic instances. The results show that the solution time of most of the considered instances with up to 60 variables is improved by our Branch and Bound algorithm in comparison with the approach of Billionnet et al. (2012) and with the general mixed-integer nonlinear solver BARON (Sahinidis and Tawarmalani, Global optimization of mixed-integer nonlinear programs, user’s manual, 2010).     

Cooperation among competitors as status-seeking behavior: Network ties and status differentiation

Status-based affiliation represents a valuable resource in economic exchange. However, affiliation strategies introduce a status ordering paradox: whereas higher status actors seek to maintain status hierarchies, lower status actors strive to affiliate with more prestigious actors. In this paper, using original data on the network of social and professional ties among 72 hotel managers clustered in an Italian hotel district, we develop a theory of status-seeking behavior that involves the exchange of status for valued resources.     

The management of firms’ alliance network positioning: Implications for innovation

In spite of the frequent calls for a much more integrated approach, the field of management still faces the ever continuing challenges in attempting to bridge the gap between academic research and managerial actions and practices. The field of strategic alliances and firms’ networks are those among which research and practice are more diverging. Trying to cover this separation, the article presents an empirical research on automotive industry that investigates the effects on innovation performance of the position that firms occupy in the network of alliances. The hypothesis that guides this research is that innovation is generated not only from the resources that a company is able to develop internally, but also through access to resources and capabilities owned by the external companies and organizations that the firm itself is tied to through alliances and cooperation agreements. Beyond this broad argument, the paper links tightly research and practice showing way and how the quality of access to resources owned by partners is influenced by the position occupied in the network of alliances and not only by the existence of single collaborative ties. Assuming a managerial approach which relies on the milestones of network research, different types of positioning in the network of alliances are discussed and tested on their impact on innovation.     

Comparing professional identities, attitudes, and views in public communication: A study of Chilean journalists and public relations practitioners

Public relations (PR) practitioners’ and journalists’ professional views and attitudes toward each other have been a subject of academic inquiry during the past decades; however, much of this research has focused on Europe and North America. In other regions of the world, for example in Latin America, historical developments and social understandings have led to slightly different conceptualizations of PR and journalism. Using Chile as a case study, this paper reports the results of an examination of Chilean journalists’ and PR practitioners’ professional conceptions. While both groups tend to have somewhat similar views of media relations and see themselves as part of the same profession, there are also important differences which are most likely based on professional socialization processes rather than educational backgrounds or sociodemographic and work related variables. Implications for contextually grounded approaches to the study of PR and journalism are highlighted.     

Gender differences in disability-free life expectancy for selected risk factors and chronic conditions in Canada

This article shows how mortality and morbidity patterns differ for women and men 45 years of age and older. The impact on disability-free life expectancy was calculated for selected risk factors and chronic conditions: low income, low education, abnormal body mass index, lack of physical activity, smoking, cancer, diabetes, and arthritis. For each factor, the expected number of years free of disability was calculated for men and women using multi-state life tables. In terms of disability-free life expectancy, the greatest impacts on affected women were for diabetes (14.1 years), arthritis (8.8 years), and physical inactivity (6.0 years), while for affected men, the greatest impacts were for diabetes (10.5 years), smoking (6.9 years), arthritis (6.5 years), and cancer (6.4 years). The implications of these results are discussed from the perspective of developing programs designed to improve population health status.     

Risk seeking with diminishing marginal utility in a non-expected utility model

The present work takes place in the framework of a non-expected utility model under risk: the RDEU theory (Rank Dependent Expected Utility, first initiated by Quiggin under the denomination of Anticipated Utility), where the decision maker's behavior is characterized by two functionsu andf. Our first result gives a condition under which the functionu characterizes the decision maker's attitude towards wealth. Then, defining a decision maker as risk averter (respectively risk seeker) when he always prefers to any random variable its expected value (weak definition of risk aversion), the second result states that a decision maker who has an increasing marginal utility of wealth (a convex functionu) can be risk averse, if his functionf issufficiently below his functionu, hence if he is sufficientlypessimistic. Obviously, he can also be risk seeking with a diminishing marginal utility of wealth. This result is noteworthy because with a stronger definition of risk aversion/risk seeking, based on mean-preserving spreads, Chew, Karni, and Safra have shown that the only way to be risk averse (in their sense) in RDEU theory is to have, simultaneously, a concave functionu and a convex functionf.     

Shall we keep the highly skilled at home? The optimal income tax perspective

We examine how allowing individuals to emigrate to pay lower taxes abroad changes the optimal non-linear income tax scheme in a Mirrleesian economy. An individual emigrates if his domestic utility is less than his utility abroad net of migration costs, utilities and costs both depending on productivity. Three average social criteria are distinguished—national, citizen and resident—according to the agents whose welfare matters. A curse of the middle-skilled occurs in the first-best, and it may be optimal to let some highly skilled leave the country under the resident criterion. In the second-best, under the Citizen and Resident criteria, preventing emigration of the highly skilled is not necessarily optimal because the interaction between the incentive-compatibility and participations constraints may cause countervailing incentives. In important cases, a Rawlsian policymaker should decrease top marginal tax rates to keep everyone at home.     

Recognizing experiential knowledge in the process of qualification of peer helpers: an analysis of an educational program for service users in France

ABSTRACT

This article analyzes an innovative training program enabling the qualification of peer carers, working within the sector of ‘social inclusion’. Since the French national debate on social work conducted within the ‘Estates General’ of 2015, peer workers have become key players in training programs in virtue of their experiential knowledge and their understanding of issues related to the process of social exclusion. This article addresses the role of peer helpers’ experiential knowledge in the training process. Because of their ‘experiential’ and ‘empirical’ knowledge about questions linked to the process of exclusion, peer helpers have become key players in social work teams and within social institutions, thus contributing to new methods of socio-educational intervention. What impact will this recognition of peer helpers’ and service users’ experiential knowledge have on education in social work? This article gives an account of an 8-month training program for peer helpers examined on the methodological level through a process of Participant observation, and based on data from comprehensive interviews carried out with a panel of peer helpers.     

On the Use of Paradox for Generating Theoretical Contributions in Management and Organization Research

Although research relating to paradox has burgeoned throughout the past decades, how paradox has been used in generating theoretical contributions remains largely tacit. Hinging on the systematic analysis of 476 publications, this literature review uncovers how scholars have leveraged paradox in demarcating theoretical contributions in the area of management and organization research. First, scholars can make use of paradox as a means to theorize, adding to the core conceptual conversation on paradox. Second, scholars can make use of paradox as a means to understand or advance insight on particular phenomena, drawing from paradox's conceptual knowledge to push forth discussions or debates in other strands of the management and organization field. Finally, scholars can make use of paradox as a way to verbalize something puzzling or surprising, supporting how readers are to appreciate or make sense of theoretical contributions advanced. Denoting approaches identified as highly complementary, this paper offers explicit handholds for academics to develop theoretical contributions through paradox, supporting the consolidation and further elevation of scholarly impact for the paradox community as such.