3 resultados para ácaros

em Biblioteca de Teses e Dissertações da USP


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Early project termination is one of the most difficult decisions to be made by Research and Development managers. While there is the risk of terminating good projects, there is also the opposite risk of not terminating bad projects and overspend resources in unproductive research. Criteria used for identifying these projects are common subject of research in Business Administration. In addition, companies might take important lessons from its interrupted projects that could improve their overall portfolio technical and commercial success. Finally, the set and weight of criteria, as well as the procedures companies use for achieve learning from cancelled projects may vary depending on the project type. This research intends to contribute to the understanding of policies applied to projects that were once considered attractive, but by some reason is not appreciated anymore. The research addressed the question: How companies deal with projects that become unattractive? More specifically, this research tried to answer the following questions: (1) Are projects killed or (otherwise) they die naturally by lack of resources? (2) What criteria are used to terminate projects during development? (3) How companies learn from the terminated projects to improve the overall portfolio performance? (4) Are the criteria and learning procedures different for different types of projects? In order to answer these questions, we performed a multiple case study with four companies that are reference in business administration and innovation: (1) Oxiteno, considered the base case, (2) Natura, the literal replication, (3) Mahle and (4) AES, the theoretical replications. The case studies were performed using a semi-structured protocol for interviews, which were recorded and analyzed for comparison. We found that the criteria companies use for selecting projects for termination are very similar to those anticipated by the literature, except for a criteria related to compliance. We have evidences to confirm that the set of criteria is not altered when dealing with different project types, however the weight they are applied indeed varies. We also found that learning with cancelled projects is yet very incipient, with very few structured formal procedures being described for capturing learning with early-terminated projects. However, we could observe that these procedures are more common when dealing with projects labeled as innovative, risky, big and costly, while those smaller and cheaper derivative projects aren\'t subject of a complete investigation on the learning they brought to the company. For these, the most common learning route is the informal, where the project team learns and passes the knowledge though interpersonal information exchange. We explain that as a matter of cost versus benefit of spending time to deeply investigate projects with little potential to bring new knowledge to the project team and the organization

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The cohort Astigmatina is divided in two major groups: Psoroptidia, composed mainly by feather and fur mites, and Non-psoroptidia, a dominant component of the acarofauna in ephemeral habitats. In these environments Astigmatina usually are saprophages or feed on fungi or bacteria. Astigmatina protonymphs undergo a complete reorganization of the body structure leading to the production of heteromorphic deutonymphs, generally specialized for dispersion through phoresy using arthropods and vertebrates as phoronts. Although most Astigmatina occur in natural environments, some species live in anthropic environments, such as food deposits, where some of them became pests; some Astigmatina infest subterraneous plant organs. Despite their economic and ecological importance, studies on the diversity and taxonomy of Astigmatina in Brazil have been rare over the last decades. The general objective of this thesis was to collaborate to the knowledge of the diversity and to evaluate the potential practical uses of these mites in Brazil. For this, new genera and species were described, method for rearing dust mites was studied and the efficiency of Astigmatina as prey for edaphic predators was evaluated. A new species of Thyreophagus (Astigmatina: Acaridae) was described based on specimens collected in Brazil, the association of three other species of this genus with stored food was reviewed and a key to all species of this genus was prepared. The genus Neotropacarus (Astigmatina: Acaridae), commonly found on plant leaves, was reviewed with the redescription of two species and description of new species collected in Brazil and from the Philippines. Two new genera and seven new species of Acaridae associated with the bee family Apidae was described and a key to Acaridae genera in subfamily Horstiinae was prepared. Several species of Astigmatina were evaluated as prey for predatory mites Stratiolaelaps scimitus (Womersley) (Mesostigmata: Laelapidae) and Protogamasellopsis zaheri Abo-Shnaf, Castilho and Moraes (Mesostigmata: Rhodacaridae), which oviposited on all evaluated astigmatids, with Tyrophagus putrescentiae (Schrank) and Aleuroglyphus ovatus (Tropeau) (Acaridae) being the most suitable prey. Seven foods and two development period, 30 and 60 days, after the introduction of 400 females of two important dust mite species, Blomia tropicalis van Bronswijk, de Cock e Oshima and Dermatophagoides pteronyssinus (Trouessart) were evaluate. With the most suitable foods, the population growth were higher than 20.2 and 15.3 for B. tropicalis and D. pteronyssinus, respectively.

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Um dos grandes desafios enfrentados pelos fabricantes de turbinas hidráulicas é prevenir o aparecimento de vibrações induzidas pelo escoamento nas travessas do pré-distribuidor e pás do rotor. Considerando apenas as travessas, e atribuídos a tais vibrações, foram relatados 28 casos de trincas ou ruídos anormais nas últimas décadas, que acarretaram enormes prejuízos associados a reparos, atrasos e perda de geração. O estado da arte na prevenção destes problemas baseia-se na utilização de sofisticados, e caros, programas comerciais de dinâmica dos fluidos computacional para o cálculo transiente do fenômeno. Este trabalho faz uma ampla revisão bibliográfica e levantamento de eventos de trincas ou ruídos ocorridos em travessas nos últimos 50 anos. Propõe, então, um enfoque alternativo, baseado exclusivamente em ferramentas de código aberto. A partir de hipóteses simplificadoras devidamente justificadas, o problema é formulado matematicamente de forma bidimensional, no plano da seção transversal da travessa, levando em conta a interação fluido-estrutura. Nesta estratégia, as equações de Navier-Stokes são resolvidas pelo método dos elementos finitos por meio da biblioteca gratuita oomph-lib. Um código especial em C++ é desenvolvido para o problema de interação fluido-estrutura, no qual o fenômeno de turbulência é levado em consideração por meio de um algoritmo baseado no modelo de Baldwin-Lomax. O método proposto é validado por meio da comparação dos resultados obtidos com referências e medições disponíveis na literatura, que tratam de problemas de barras retangulares suportadas elasticamente. O trabalho finaliza com a aplicação do método a um estudo de caso envolvendo uma travessa particular.