1,720,982 research outputs found
Advertising in a vaccination campaign: A variable time control problem
No full textThe best way to prevent a highly contagious infection such as measles is active immunization with a suitable vaccine. Unfortunately, in the last 10 years in EU there has been a decrease in vaccinations, so that their coverage goes under the minimum level to obtain herd immunity. This is a sanitary emergency and it is connected with the “urban myth” that serious adverse neurological disorders should be attributed to vaccination. Anti-vaccination groups spread this “urban myth” by word-of-mouth communication. We model the evolution of the number of unvaccinated people assuming that a policy-maker can control this dynamics through advertising. The idea of connecting dynamic advertising models and vaccination campaign is recent and it represents some aspects of the issue that have never been explored before. From a mathematical point of view we study a variable final time optimal control problem in which the policy-maker wants to minimize the costs in order to obtain herd immunity in due time. We find the optimal solution and we obtain some prescriptions for the policy-maker
A dynamic advertising model in a vaccination campaign
No full textVaccines save thousands of lives every year, but many people remain unvaccinated because serious adverse neurological disorders are wrongly attributed to vaccination. The “urban myth” of a relevant vaccine-associated risk is sustained by anti-vaccination groups and it is spread by word-of-mouth communication. We face the problem of increasing the vaccination coverage using an approach which draws some elements from the theory of dynamic advertising models. We propose a dynamic model for the evolution of the number of unvaccinated people and assume that a policy-maker can control this dynamics through advertising. From a mathematical point of view, we state and analyze an optimal control problem with a pure state constraint. We find the unique optimal solution, which minimizes a cost functional, but may fail to be satisfactory from the different viewpoint of moving towards eradication of the disease. Our analysis suggests that we modify the problem statement in order to consider explicitly the goal of reducing the number of unvaccinated people, to a level which guarantees the herd immunity. Hence we introduce an upper bound to the final number of unvaccinated people. From the solutions to the two problems we obtain some prescriptions for the policy-maker
Decisions on production and quality
No full textQuality plays a central role in Operations Management as it is a relevant issue on which the customers of an organization focus their judgment. In a short-term production model, we can assume that quality is constant. Then, we treat the optimal choices of production rate and quality level as an optimal control problem with a parameter. Starting from a production planning model by Kamien and Schwartz, we introduce quality as a decision variable. In the solution, we observe that the optimal quality level and production rate are independent of each other. Next, we modify the model assuming that the ordered quantity is not exogenous, but is determined through optimization, when the market-clearing price depends on both quality and quantity. We get a more interesting solution in which optimal production and optimal quality are interdependent, in a way that is not straightforward. We characterize and discuss the optimal solutions to these problems using the necessary and sufficient conditions for optimal processes with parameters. This shows once again that the sufficient conditions for this kind of problem are too restrictive and introducing a more effective kind of sufficient conditions is still an open question
Optimal investment in age-structured goodwill
No full textSegmentation is a core strategy in modern marketing and age-specific segmentation, which is based on the age of the consumers, is very common in practice. A characteristic of age-specific segmentation is the change of the segments composition during time, which may be studied only using dynamic advertising models. Here, we assume that a firm wants to promote and sell a single product in an age segmented market and we model the awareness of this product using an infinite dimensional Nerlove- Arrow goodwill as a state variable. Assuming an infinite time horizon, we use some dynamic programming techniques to solve the problem and to characterize both the optimal advertising effort and the optimal goodwill path in the long run. An interesting feature of the optimal advertising effort is an anticipation effect with respect to the segments considered in the target market due to the time evolution of the segmentation
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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