The effects of hydrogen sulfide on the polymer electrolyte membrane fuel cell anode catalyst: H(2)S-Pt/C interaction products

The performance of a polymer electrolyte membrane fuel cell (PEMFC) operating on a simulated hydrocarbon reformate is described. The anode feed stream consisted of 80% H(2),similar to 20% N(2), and 8 ppm hydrogen sulfide (H(2)S). Cell performance losses are calculated by evaluating cell potential reduction due to H(2)S contamination through lifetime tests. It is found that potential, or power, loss under this condition is a result of platinum surface contamination with elemental sulfur. Electrochemical mass spectroscopy (EMS) and electrochemical techniques are employed, in order to show that elemental sulfur is adsorbed onto platinum, and that sulfur dioxide is one of the oxidation products. Moreover, it is demonstrated that a possible approach for mitigating H(2)S poisoning on the PEMFC anode catalyst is to inject low levels of air into the H(2)S-contaminated anode feeding stream. (C) 2011 Elsevier B.V. All rights reserved.

In Bio-Fuel We Trust

In bio-fuel we trust. Or do we? In this chapter, ethnographic material from Sweden is used to discuss ways sin which trust may influence the choice of bio-fuel for heating purposes. The meaning and substance of trust or distrust, as well as the very conditions for trust, are elaborated on in relation to solar and bio-pellet systems, district heating with bio-fuel, and traditional fireplaces. An important conclusion of this chapter is that the degree to which people perceive others as being like themselves or not tends to be decisive for whether these others are to be trusted, and therefore worth listening to. The context and situation in which a certain heating system is being chosen does not only involve trust in individuals, however, but in companies and the authorities, as well as in the arterfacts themselves. An example is given on how distrust of district heating companies led house owners to reject an offer of district heating despite the comfort and environmental benefit this could have provided. it is shown how this distrust might be resolved by making the rhythm of households and sitrict heating companies more in step with one another. The strong emotional attachment to and deep-felt trust in the traditional fireplace is also analysed, and a question is put forward as to whether these feelings could be transferred to modern bio-pellet stoves. Finally, our great and assured trust in bio-fuel as a main solution to global climate change is shortly commented upon and partly questioned.

Managing Dual Enrollment Programs: Review of Program Models, Operations, and Outcomes

Universities that offer dual enrollment programs for high school students must manage increasing student demand in the face of changing state legislation. This brief examines how institutions finance their dual enrollment programs, and how they ensure academic rigor as their programs continue to grow. The report also considers how dual enrollment programs ensure that students can transfer credits, and what strategies they use to encourage DE students to matriculate as undergraduates.

Fuel ethanol price drivers in the Atlantic basin : Brazil & the U.S. traders perspectives

Como a oportunidade de exportação de etanol combustível é muito recente, o agronegócio carece de literatura para formação de gestores e estrategistas. Este trabalho tem como objetivo descrever o mecanismo de formação de preços de etanol tanto no Brasil como nos Estados Unidos da America. Decupei as variáveis que impactam na formação de preços, custo de produção de etanol de cana-de-açúcar, custo da logística e desidratação no Caribe, custo do etanol de milho e fiz algumas análises de cenários de formação de preços das principais variáveis e consegui organizar este conhecimento em um gráfico que contém no eixo superior preço do etanol hidratado na usina no Brasil e no eixo inferior o preço do bushel de milho em Chicago cujas interceções nas retas da taxa do dólar e do preço do gás natural, fornecem no eixo Y o preço do produto no porto de Nova York, ficando uma visualização simples das possibilidades da janela de exportação. A metodologia permite assumir diferentes cenários de oferta, demanda e preços e estabelecer diferentes estratégias de comercialização.

Price discovery in dual-class shares across multiple markets

We extend the standard price discovery analysis to estimate the information share of dual-class shares across domestic and foreign markets. By examining both common and preferred shares, we aim to extract information not only about the fundamental value of the rm, but also about the dual-class premium. In particular, our interest lies on the price discovery mechanism regulating the prices of common and preferred shares in the BM&FBovespa as well as the prices of their ADR counterparts in the NYSE and in the Arca platform. However, in the presence of contemporaneous correlation between the innovations, the standard information share measure depends heavily on the ordering we attribute to prices in the system. To remain agnostic about which are the leading share class and market, one could for instance compute some weighted average information share across all possible orderings. This is extremely inconvenient given that we are dealing with 2 share prices in Brazil, 4 share prices in the US, plus the exchange rate (and hence over 5,000 permutations!). We thus develop a novel methodology to carry out price discovery analyses that does not impose any ex-ante assumption about which share class or trading platform conveys more information about shocks in the fundamental price. As such, our procedure yields a single measure of information share, which is invariant to the ordering of the variables in the system. Simulations of a simple market microstructure model show that our information share estimator works pretty well in practice. We then employ transactions data to study price discovery in two dual-class Brazilian stocks and their ADRs. We uncover two interesting ndings. First, the foreign market is at least as informative as the home market. Second, shocks in the dual-class premium entail a permanent e ect in normal times, but transitory in periods of nancial distress. We argue that the latter is consistent with the expropriation of preferred shareholders as a class.

Impacto da emissão dual-class na estrutura de capital

A tese propõe que empresas que emitem apenas ações com direitos de voto utilizam mais capitais de terceiros do que empresas que emitem tanto ações votantes quanto não votantes. No desenvolvimento do trabalho, foi demonstrada a relevância de relacionar endividamento ao fato de uma empresa emitir ou não ações sem direito a voto, considerando as principais teorias de estrutura de capital e a realidade brasileira. Como os modelos teóricos que explicam o nível de endividamento das empresas ainda carecem de capacidade explicativa, a busca por novos determinantes está presente na literatura de estrutura de capital. A ocorrência da emissão de ações em classes diferenciadas (dual-class) como fator impactante no nível de endividamento foi analisada sob três prismas: de mercado, dos setores e das empresas que unificaram suas ações. Pelas três investigações ficou evidenciada a perspectiva de que o endividamento seja menor nos casos de emissão de ações preferenciais, considerando o ambiente de negociação e regulamentação do Brasil. A aceitação da tese tem reflexos teóricos na identificação de um fator que deve ser levado em consideração nos modelos de estrutura de capital, bem como suscita a importância de gestores, investidores e credores reconhecerem que o fato de uma empresa ser dual-class impacta não apenas na sua estrutura de controle, mas principalmente em sua estrutura de capital. Entre as considerações da aceitação da tese, estaria o reconhecimento de que empresas que ingressam no Novo Mercado na prática estão, no longo prazo, trocando o uso de ações preferenciais como forma de financiamento pela emissão de dívida.

Dual resource transfers and interruption in external debt service

Externai debt service requires a dual resource transfer. Trade surpluses have to be generated in order to make foreign exchange revenues available for debt repayment. In addition, with developing countries' externai debt being largely a public liability, debt service requires that resources can be effectively transferred from the private to the public sector. This paper derives a statistical model for dealing with dual constraints in the presence of binary dependent variables and applies it to the dual resource transfer problem. The results from the estimation of the model for a sample of 31 middle-income developing countries in the period of 1980 to 1990, strongly support the hypothesis that both externai and fiscal constraints are important in explaining externai debt service disruptions.

Controlador em modo dual adaptativo robusto - DMARC

The so-called Dual Mode Adaptive Robust Control (DMARC) is proposed. The DMARC is a control strategy which interpolates the Model Reference Adaptive Control (MRAC) and the Variable Structure Model Reference Adaptive Control (VS-MRAC). The main idea is to incorporate the transient performance advantages of the VS-MRAC controller with the smoothness control signal in steady-state of the MRAC controller. Two basic algorithms are developed for the DMARC controller. In the first algorithm the controller's adjustment is made, in real time, through the variation of a parameter in the adaptation law. In the second algorithm the control law is generated, using fuzzy logic with Takagi-Sugeno s model, to obtain a combination of the MRAC and VS-MRAC control laws. In both cases, the combined control structure is shown to be robust to the parametric uncertainties and external disturbances, with a fast transient performance, practically without oscillations, and a smoothness steady-state control signal

Uma abordagem indireta para o Controlador em Modo Dual Adaptativo Robusto

In this work is proposed an indirect approach to the DualMode Adaptive Robust Controller (DMARC), combining the typicals transient and robustness properties of Variable Structure Systems, more specifically of Variable Structure Model Reference Adaptive Controller (VS-MRAC), with a smooth control signal in steady-state, typical of conventional Adaptive Controllers, as Model Reference Adaptive Controller (MRAC). The goal is to provide a more intuitive controller design, based on physical plant parameters, as resistances, inertia moments, capacitances, etc. Furthermore, with the objective to follow the evolutionary line of direct controllers, it will be proposed an indirect version for the Binary Model Reference Adaptive Controller (B-MRAC), that was the first controller attemptting to act as MRAC as well as VS-MRAC, depending on a pre-defined fixed parameter

A influência das injunções de orientação relativa na calibração de um sistema dual de câmeras digitais

Image acquisition systems based on multi-head arrangement of digital frame cameras, such as the commercial systems DMC, UltraCam, besides others, are attractive alternatives enabling larger imaging area when compared to a single frame camera. Considering that in these systems, cameras are tightly attached to an external mount, it is assumed that relative position and orientation between cameras are stable during image acquisition and, consequently, these constraint can be included in the calibration step. This constraint is acceptable because estimates of the relative orientation (RO) parameters between cameras, from previously estimated exterior orientation parameters, present higher and significant deviations than the expected physical variations, due to error propagation. In order to solve this problem, this work presents an approach based on simultaneous calibration of two or more cameras using constraints that state that the relative rotation matrix and the distance between the cameras head are stable. Experiments with images acquired by an arrangement of two Hasselblad H2D cameras were accomplished, without and with the mentioned constraints. The experiments showed that the calibration process with RO constraints allows better results than the approach based on single camera calibration, provided that the estimation has included only images with good target distribution.

Briquetting of charcoal from sugar-cane bagasse fly ash (scbfa) as an alternative fuel

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Um método primal-dual aplicado na resolução do problema de fluxo de potência ótimo

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A modified Primal-Dual Logarithmic-Barrier Method for solving the Optimal Power Flow problem with discrete and continuous control variables

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Predictor-Corrector Primal-Dual Interior Point Method for Solving Economic Dispatch Problems: A Postoptimization Analysis

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Analysis of a molten carbonate fuel cell: cogeneration to produce electricity and cold water

The fuel cell is an emerging cogeneration technology that has been applied successfully in Japan, the USA and some countries in the European Union. This system performs direct conversion of the chemical energy of the oxidation of hydrogen from fuel with atmospheric oxygen into direct current electricity and waste heat via an electrochemical process relying on the use of different electrolytes (phosphoric acid, molten carbonate and solid oxide, depending on operating temperature). This technology permits the recovery of waste heat, available from 200 degreesC up to 1000 degreesC depending on the electrolyte technology, which can be used in the production of steam, hot or cold water, or hot or cold air, depending on the associated recuperation equipment. In this paper, an energy, exergy and economic analysis of a fuel cell cogeneration system (FCCS) is presented. The FCCS is applied in a segment of the tertiary sector to show that it is a feasible alternative for rational decentralized energy production under Brazilian conditions. The technoeconomic analysis shows a global efficiency or fuel utilization efficiency of 86%. Analysis shows that the exergy losses in the fuel cell unit and the absorption refrigeration system are significant. Furthermore, the payback period estimated is about 3 and 5 years for investments in fuel cells of 1000 and 1500 US$/kW, respectively. (C) 2001 Elsevier B.V. Ltd. All rights reserved.