Browsing by Issue Date, starting with "2009-05"
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- Estratégia competitiva: Michael Porter 30 anos depoisPublication . Schneider, Aline Botelho; Carneiro, Marcelo Lopes; Serra, Fernando A. Ribeiro; Ferreira, Manuel PortugalOs estudos de estratégia têm sido muito influenciados pelos trabalhos de Michael Porter, em todas as suas fases, como as cinco forças, as estratégias genéricas, a cadeia de valor e as vantagens competitivas das nações. Neste artigo, analisou-se a influência de Porter nos trabalhos brasileiros em estratégia, a partir dos trabalhos selecionados e apresentados no EnANPAD. No levantamento para a análise dos artigos, considerando 10 anos de EnANPAD (1997-2006), foram selecionados 46 artigos. A identificação e seleção dos artigos envolveram os seguintes critérios: busca complementar por palavra-chave Porter na base de dados do EnANPAD; avaliação dos títulos e resumos dos artigos apresentados na área de estratégia entre 1997 e 2006, bem como na íntegra quando necessário. Procedeu-se também à análise das referências utilizadas nos artigos e o posicionamento dos autores em relação às tipologias de Porter. Como resultado, verificou-se que Michael Porter é um autor com grande influência nas pesquisas acadêmicas de estratégia. Seus estudos mais utilizados são os da análise da indústria e das estratégias genéricas, e também se verificou que a maioria dos estudos analisados é favorável aos seus conceitos, mesmo existindo pesquisas contrárias.
- Dimensional Templates in Data Warehouses: Automating the Multidimensional Design of Data Warehouse PrototypesPublication . Oliveira, Rui; Rodrigues, Fátima; Martins, Paulo; Moura, João PauloPrototypes are valuable tools in Data Warehouse (DW) projects. DW prototypes can help end-users to get an accurate preview of a future DW system, along with its advantages and constraints. However, DW prototypes have considerably smaller development time windows when compared to complete DW projects. This puts additional pressure on the achievement of the expected prototypes' high quality standards, especially at the highly time consuming multidimensional design: in it, a thin margin for harmful unreflected decisions exists. Some devised methods for automating DW multidimensional design can be used to accelerate this stage, yet they are more suitable to DW full projects rather than to prototypes, due to the effort, cost and expertise they require. This paper proposes the semi-automation of DW multidimensional designs using templates. We believe this approach better fits the development speed and cost constraints of DW prototyping since templates are pre-built highly adaptable and highly reusable solutions.
- An application of the student relationship management conceptPublication . Piedade, Maria Beatriz; Santos, Maribel Yasmina; Guerra da Piedade, Maria BeatrizIt is largely accepted that a way to promote the students’ success is by implementing processes that allow the students closely monitoring, the evaluation of their success and the approximation to their day-by-day activities. However, the implementation of these processes does not take place in many Higher Education Institutions due to the lack of appropriates institutional practices and an adequate technological infrastructure able to support these practices. In order to overcome these conceptual and technological limitations, this paper presents the Student Relationship Management System (SRM System). The SRM System supports the SRM concept and the SRM practice, also here presented, and it is implemented using the technological infrastructure that supports the Business Intelligence (BI) systems. The SRM system was used in an application case (in a real context) to obtain knowledge about the students and their academic behaviour. Such information is fundamental to support the decision-making associated with the teaching learning process. All the obtained results are also presented and analysed in this paper.
- The HADES RPC inner TOF wallPublication . Belver, D.; Blanco, A.; Cabanelas, P.; Carolino, N.; Castro, E.; Diaz, J.; Fonte, P.; Garzón, J.A.; Gonzalez-Diaz, D.; Gil, A.; Koenig, W.; Lopes, L.; Mangiarotti, A.; Oliveira, O.; Pereira, A.; Silva, C.; Sousa, C.C.; Zapata, M.The upgraded HADES inner TOF Wall will cover a total area of 8 m2 with 1116 variable-geometry 4-gap, symmetric, timing RPCs, readout by 2232 time and charge channels. Each RPC is individually shielded for robust multi-hit performance and optimum use of the readout channels (crosstalk minimization). The double layer configuration provides a useful degree of redundancy for very accurate timing of a large fraction of all particles crossing the detector. In this paper we describe the concept of the detector, its inner structure and the multi-hit performance.
- Modelling transport phenomena and chemical reactions in automotive three-way catalytic convertersPublication . Santos, H.; Costa, M.; Santos, HelderThis study concentrates on the external and internal mass transfer with multiple reactions in the catalytic layer of a three-way catalyst (TWC). A single channel model accounting for the species diffusion inside the washcoat using the effectiveness factor was developed. Validation and calibration of the model was achieved by comparing predictions against experimental data obtained previously by the same authors. The model was then applied to study the importance of both turbulent monolith structures and controlled washcoat structures on TWC conversions. The numerical results show that: (i) increasing the transport coefficients using turbulent monolith structures can produce either positive or negative effects on the TWC conversions; (ii) overall, the net effect of increasing the transport coefficients on the TWC conversions is positive; (iii) at high inlet gas temperatures and high space velocities the turbulent monolith structures present important improvements in the TWC conversions; (iv) the TWC conversions can be significantly improved enhancing the transport properties of the porous washcoat structure; (v) enhancements in the transport properties of the washcoat structure have deeper impacts on the TWC conversions than improvements in the monolith channel structure.
- A new biocatalyst: Penicillin G acylase immobilized in sol‐gel micro‐particles with magnetic propertiesPublication . Bernardino, Susana M. S. A.; Fernandes, Pedro; P. Fonseca, Luís; Bernardino, SusanaThe present work focuses on the development and basic characterization of a new magnetic biocatalyst, namely penicillin G acylase (PGA), immobilized in sol-gel matrices with magnetic properties, ultimately aimed for application in cephalexin (CEX) synthesis. A mechanically stable carrier, based on porous xerogels silica matrixes starting from tetramethoxysilane (TMOS), was prepared leading to micro-carriers with medium sized particles of 30 μm, as determined by scanning electron microscopy. An immobilization yield of 95-100% and a recovered activity of 50-65% at 37°C, as determined by penicillin G (PG) hydrolysis (pH STAT method), were observed. These results clearly exceed those reported in a previous work on PGA immobilization in sol-gel, where only 10% of activity was recovered. The values of activity were kept constant for 6 months. Immobilized PGA (682 U/gdry weight) retained high specific activity throughout ten consecutive runs for PG hydrolysis, suggesting adequate biocatalyst stability. The CEX synthesis was performed at 14°C, using the free and immobilized PGA in aqueous medium. Phenylglycine methyl ester was used as acyl donor at 90 mM and 7-aminodeacetoxycephalosporanic acid was the limiting substrate at 30 mM. The CEX stoichiometric yield after 1-h reaction was close to 68% (23 mM CEX/h) and 65% (19 mM CEX/h), respectively.
- Video summary generation and coding using temporal scalabilityPublication . Ferreira, Lino; Cruz, Luís; Assunção, Pedro A. AmadoIn this paper two algorithms for video summary generation and coding are proposed. Two distortion metrics used in the video summary generation algorithm are compared and an algorithm with reduced computational complexity is presented. The paper also proposes two frame structures in the temporal domain suitable for coding using temporal scalability of the H.264/SVC.
- Abscisic acid inhibits type 2C protein phosphatases via the PYR/PYL family of START proteinsPublication . Park, Sang-Youl; Fung, Pauline; Nishimura, Noriyuki; Jensen, Davin R.; Fujii, Hiroaki; Zhao, Yang; Lumba, Shelley; Santiago, Julia; Rodrigues, Américo; Chow, Tsz-fung F.; Alfred, Simon E.; Bonetta, Dario; Finkelstein, Ruth; Provart, Nicholas J.; Desveaux, Darrell; Rodriguez, Pedro L.; McCourt, Peter; Zhu, Jian-Kang; Schroeder, Julian I.; Volkman, Brian F.; Cutler, Sean R.Type 2C protein phosphatases (PP2Cs) are vitally involved in abscisic acid (ABA) signaling. Here, we show that a synthetic growth inhibitor called pyrabactin functions as a selective ABA agonist. Pyrabactin acts through PYRABACTIN RESISTANCE 1 (PYR1), the founding member of a family of START proteins called PYR/PYLs, which are necessary for both pyrabactin and ABA signaling in vivo. We show that ABA binds to PYR1, which in turn binds to and inhibits PP2Cs. We conclude that PYR/PYLs are ABA receptors functioning at the apex of a negative regulatory pathway that controls ABA signaling by inhibiting PP2Cs. Our results illustrate the power of the chemical genetic approach for sidestepping genetic redundancy.
- Evaluating the performance and intrusiveness of virtual machines for desktop grid computingPublication . Domingues, Patrício Rodrigues; Araújo, Filipe; Silva, LuísWe experimentally evaluate the performance overhead of the virtual environments VMware Player, QEMU, VirtualPC and VirtualBox on a dual-core machine. Firstly, we assess the performance of a Linux guest OS running on a virtual machine by separately benchmarking the CPU, file I/O and the network bandwidth. These values are compared to the performance achieved when applications are run on a Linux OS directly over the physical machine. Secondly, we measure the impact that a virtual machine running a volunteer @home project worker causes on a host OS. Results show that performance attainable on virtual machines depends simultaneously on the virtual machine software and on the application type, with CPU-bound applications much less impacted than IO-bound ones. Additionally, the performance impact on the host OS caused by a virtual machine using all the virtual CPU, ranges from 10% to 35%, depending on the virtual environment.
- Computation of nodal marginal prices in the presence of load and generation cost UncertaintiesPublication . Gomes, B.A.; Tomé Saraiva, João; Neves, L.M.P.Marginal prices have been recognized as the core approach to the economic evaluation of generation and transmission services in an electricity market environment. In this context, this paper presents the New Fuzzy Optimal Power Flow algorithm as a model to addresses the impact of load and generation cost uncertainties in nodal marginal prices. Since loads and generation costs are represented by fuzzy numbers, nodal marginal prices will no longer be represented by deterministic values, but rather by fuzzy membership functions reflecting the specified uncertainties. The paper also presents the algorithm used for the integration of the transmission losses effect on the results. Since the proposed algorithm uses multiparametric programming techniques, it contributes to characterize in a better way the system behavior. Finally, it includes results based on the IEEE 24 bus/38 branch test system to illustrate the proposed approach.