CASE STUDIES FROM DIFFERENT TYPES OF HEAT EXCHANGERS TO PLATE AND SHELL HEAT EXCHANGER: A REVIEW

A Plate and Shell Heat Exchanger (PSHE) is manufactured with round welded plates in its core. These plates are designed to withstand high pressures and temperatures. Failures in this kind of heat exchanger were registered in a short operating period. To obtain the failure modes present in this equipment and a theoretical framework concerning this field of study, a research methodology was proposed (Systematic Literature Review – SLR) and a theoretical survey was carried out focusing in the 316L stainless steel and titanium grade 1 for its use in the Brazilian offshore industry. Seeing that the whole PSHE structure is welded, it is necessary to account for the strain caused by severe expansion processes in heat exchanger joints. This regarding, the laser welding process was investigated because of its narrow melting zone. It is believed that it was possible to clarify which failure modes are related to corrosive processes or stress concentration highlighting the structural and mechanical characterization models employed. Considering that the research field is relatively new, it was feasible to establish a theoretical basis of solutions applicable to PSHE, such as the use of more recessive material, reduce the corrosiveness of the operating medium, and reduce external sources of tension. Also, new content was assembled to assess the future decision-making process, regarding the design or maintenance of welded plate exchangers

Improving light harvesting in polymer photodetector devices through nanoindented metal mask films

To enhance light harvesting in organic photovoltaic devices, we propose the incorporation of a metal (aluminum) mask film in the system’s usual layout. We fabricate devices in a sandwich geometry, where the mask (nanoindented with a periodic array of holes of sizes d and spacing s) is added between the transparent electrode and the active layer formed by a blend of the semiconducting polymer P3HT and substituted fullerene. Its function is to promote trapping of the incident light into the device’s cavity (the region corresponding to the active layer). For d, we set a value that allows light diffraction through the holes in the relevant absorption range of the polymer. To optimize the mask structure, we consider a very simple model to determine the s leading to trapped fields that are relatively intense and homogeneous within the device. From measurements of the action spectra, we show that, indeed, such architecture can considerably improve the resulting photocurrent efficiencies—one order of magnitude in the best situation studied.

Return of the Great Spaghetti Monster : Learnings from a Twelve-Year Adventure in Web Software Development

The widespread adoption of the World Wide Web has fundamentally changed the landscape of software development. Only ten years ago, very few developers would write software for the Web, let alone consider using JavaScript or other web technologies for writing any serious software applications. In this paper, we reflect upon a twelve-year adventure in web development that began with the development of the Lively Kernel system at Sun Microsystems Labs in 2006. Back then, we also published some papers that identified important challenges in web-based software development based on established software engineering principles. We will revisit our earlier findings and compare the state of the art in web development today to our earlier learnings, followed by some reflections and suggestions for the road forward.Peer reviewe

Depth-Sensing Indentation on REBa2Cu3O(7-\delta) Single Crystals obtained from Xenotime Mineral

A natural mixture of heavy rare earths oxides extracted from xenotime mineral have been used to prepare large single crystals of high-temperature REBa2Cu3O(7-\delta) superconductor grown using the CuO-BaO self-flux method. Its mechanical properties along the ab-plane were characterized using instrumented indentation. Hardness and elastic modulus were obtained by the Oliver and Pharr method and corresponds to 7.4 \pm 0.2 GPa and in range 135-175 GPa at small depths, respectively. Increasing the load promotes the nucleation of lateral cracks that causes a decrease in hardness and the measured elastic modulus by instrumented indentation at higher loads. The indentation fracture toughness was estimated by measuring the radial crack length from cube-corner indentations at various loads and was 0.8 \pm 0.2 MPa.m1/2. The observed slip systems of REBa2Cu3O(7-\delta) single crystals were [100](001) and [010](001), the same as for YBa2Cu3O(7-\delta) single crystals. The initial stages of deformation and fracture in the indentation process were investigated. The hardness and elastic modulus were not strongly modified by the crystallographic orientation in the ab-plane. This was interpreted in terms of the resolved shear stresses in the active slip systems. Evidence of cracking along the {100} and {110} planes on the ab-plane was observed. As a conclusion, the mechanical properties of REBa2Cu3O(7-\delta) single crystals prepared from xenotime are equivalent to those of YBa2Cu3O(7-\delta) single crystals produced by conventional rare earths oxides.Comment: The paper will appear in Volume 42 (2012) of the Brazilian Journal of Physic

Indukcyjny czujnik prądu w technologii PCB

Artykuł dotyczy indukcyjnego czujnika prądu do zastosowań w licznikach energii elektrycznej. Budowa czujnika oparta jest o technologię wytwarzania obwodów drukowanych. Elementem statycznego licznika energii elektrycznej, który ma największy wpływ na dokładność pomiaru energii jest czujnik prądu. Wynika to z bardzo dużej dynamiki, jaką musi posiadać ten czujnik, a także stosunkowo szerokiego pasma sygnału mierzonego. Ponadto w licznikach wielofazowych niezbędne jest zastosowanie izolacji galwanicznej pomiędzy torami prądowymi, a układem pomiarowym. W obecnych rozwiązaniach izolację galwaniczną najczęściej realizuje się za pomocą sprzężenia magnetycznego, które jest szczególnie podatne na zakłócenia zewnętrznymi stałymi i zmiennymi polami magnetycznymi. Stosowane są także konstrukcje ze sprzężeniem optycznym, ale ze względu na koszty rozwiązanie to występuje rzadko. Konstrukcja prezentowanego czujnika prądu oparta jest na wielowarstwowym obwodzie drukowanym. Tor prądowy oraz cewki pomiarowe tego czujnika skonstruowane zostały poprzez odpowiednie poprowadzenie mozaiki ścieżek wielowarstwowego obwodu drukowanego. Zastosowanie takiej technologii pozwala na tanią i prostą produkcję czujnika, jednocześnie zapewniając dużą powtarzalność. Dzięki odpowiedniemu poprowadzeniu toru prądowego oraz cewek pomiarowych, uzyskuje się znaczną odporność na zakłócenia zewnętrznymi polami magnetycznymi stałymi i zmiennymi.The paper deals with an inductive current sensor applied to watt-hour meters. Construction of this sensor is based on multilayer PCB (printed circuit board) technology. Current sensors have the biggest influence on the electronic energy meter accuracy because they must have very good dynamics and wide bandwidth of the measured current. There is used magnetic or optical coupling in current sensing methods to achieve galvanic insulation. However, the magnetic coupling is especially susceptible to external disturbing static and alternate magnetic field. The disadvantages of the optical coupling is its high cost and complex power supply. The presented current sensor is based on multilayer PCB technology. Current path and sensing coils of this sensor are made by appropriate arrangement of multilayer PCB tracks. Applying this kind of technology allows for chip and easy sensor production, and simultaneously provides high repeatability. On the basis of simulations and investigations performed, it can be stated that this sensor technology is highly resistant to the external mag-netic static and alternate disturbance field

Mechanical and tribological properties of a sintered glass-ceramic compared to granite and porcelainized stoneware

a b s t r a c t Mechanical and tribological properties of a partially crystallized sintered glass-ceramic were compared to two commercial floor tiles: black granite and porcelainized stoneware. Mechanical properties, hardness and elastic modulus were evaluated by instrumented indentation. Friction coefficient and wear characterization were evaluated using a reciprocating ball-on-flat tribometer in two controlled environments: air with relative humidity of 53% and under running water at 23 • C. The sintered glass-ceramic and porcelainized stoneware presented similar mechanical and tribological properties. Regarding the mechanical and tribological properties, the results suggest that this glass-ceramic is suitable to be used as industrial tile

Influência da cristalização na dureza, módulo de elasticidade e tenacidade à fratura por indentação em vitrocerâmicas de dissilicato de lítio (Li2 O.2SiO2 )

Resumo O efeito da cristalização sobre as propriedades mecânicas (dureza, módulo de elasticidade e tenacidade à fratura por indentação) do vitrocerâmico dissilicato de lítio Li2O.2SiO2 foi investigado pela técnica de indentação (indentação instrumentada, microdurezas Vickers e Knoop). Os tratamentos térmicos para cristalização foram realizados em duas etapas: nucleação em 475 °C por 2, 5 e 10 h, e crescimento de cristais em 563 °C por 0,5, 1, 2, 3 e 24 h. Foram determinadas as frações cristalizadas, que foram correlacionadas com a dureza, o módulo de elasticidade e a tenacidade à fratura por indentação. Os testes de microdureza foram realizados utilizando-se penetradores Vickers e Knoop. O módulo de elasticidade das regiões amorfas e cristalinas foi medido por testes de indentação instrumentada com um indentador Berkovich, realizado em cada fase separadamente. A modificação da morfologia das trincas geradas por indentação com pontas piramidais foi avaliada para amostras com diferentes frações cristalinas utilizando microscopia óptica. Foi discutida a alteração dos padrões de trincas, para diferentes graus de cristalização, na forma de determinação da tenacidade à fratura por indentação. Os maiores valores de dureza e tenacidade foram obtidos em amostras com 100% de fração cristalina, sendo que maiores tempos de nucleação de cristais levaram a melhores valores nas propriedades mecânicas investigadas. Os valores obtidos para amostras 100% de fração cristalina foram: tenacidade à fratura por indentação de 1,8 MPa.m1/2, microdureza Knoop de 7,2 GPa e módulo de elasticidade de 155 GPa

Mechanical and tribological properties of a sintered glass-ceramic compared to granite and porcelainized stoneware

Mechanical and tribological properties of a partially crystallized sintered glass-ceramic were compared to two commercial floor tiles: black granite and porcelainized stoneware. Mechanical properties, hardness and elastic modulus were evaluated by instrumented indentation. Friction coefficient and wear characterization were evaluated using a reciprocating ball-on-flat tribometer in two controlled environments: air with relative humidity of 53% and under running water at 23 degrees C. The sintered glass-ceramic and porcelainized stoneware presented similar mechanical and tribological properties. Regarding the mechanical and tribological properties, the results suggest that this glass-ceramic is suitable to be used as industrial tile. (C) 2011 Elsevier B.V. All rights reserved.CNPqCAPESFAPESP[2007/08179-9

Designing a MOOC as an Agent-Platform Aggregating Heterogeneous Virtual Learning Environments

With the emergence of cloud technologies on the one hand and social networks on the other hand, the possibilities for e-learning have been considerably enhanced in the latest years. Virtual Learning Environments (VLE) can now indeed contain a huge amount of learning resources; in parallel large user communities are available in social networks. Nevertheless, these systems remain different but, by using these heterogeneous software environments together, the possibilities for interaction could be multiplied. That is why, this paper suggests building a Massive Open Online Course (MOOC) environment through a Multi-Agent System (MAS) working as a virtual abstraction layer over heterogeneous software platforms. The idea is to aggregate different traditional VLE to dispose of the learning objects they own as well as other platforms like social networks to furnish an easy access to the MOOC of their large user communities. The MAS design and implementation has been architectured around a real-life organizational pattern – the joint venture – allowing us to deal with the complexity of heterogeneous software environments in the fashion that real-life companies join governance and management. Communication scenarios issued from a field analysis are pointed out in the paper; these are supported by the MOOC platform in the native environment as well as in Facebook. The proposal is indeed validated through the development of a prototype using Facebook as a case study for third-party platform interfacing. We finally highlight the benefits for the user experience