Life cycle assessment of the biofuel production from lignocellulosic biomass in a hydrothermal liquefaction - aqueous phase reforming integrated biorefinery

The use of biofuels in the transport sector is one of the strategies for its decarbonization. Here, the LCA meth-odology was used for the first time to assess the environmental impacts of a biorefinery where hydrothermal liquefaction (HTL) and aqueous phase reforming (APR) were integrated. This novel coupling was proposed to valorize the carbon loss in the HTL-derived aqueous phase, while simultaneously reducing the external H2 de-mand during biocrude upgrading. Corn stover (residue) and lignin-rich stream (waste) were evaluated as possible lignocellulosic feedstocks. The global warming potential (GWP) was 56.1 and 58.4 g CO2 eq/MJbiofuel, respec-tively. Most of the GWP was attributable to the electrolysis step in the lignin-rich stream case and to the thermal duty and platinum use in the corn stover case. Other impact categories were investigated, and an uncertainty analysis was also carried out. A sensitivity analysis on biogenic carbon, electricity/thermal energy source and alternative hydrogen supply was conducted to estimate their influence on the GWP. Finally, the two scenarios were compared with the environmental impact of fossil-and other biomass-derived fuels, also considering fuel utilization. HTL-APR allowed a 37% reduction compared to fossil diesel, further reduced to 80% with the lignin -rich stream when green energy was used

Aqueous phase reforming of pilot-scale Fischer-Tropsch water effluent for sustainable hydrogen production

Fischer-Tropsch (FT) synthesis produces an aqueous stream containing light oxygenates as major by-product. The low carbon concentration of the organics makes its thermal recovery unprofitable. Thus, novel processes are needed to utilize this waste carbon content. In this work, the aqueous phase reforming of the wastewater obtained from a 15 kWth Fischer-Tropsch plant was explored as a promising process to produce hydrogen at mild temperatures. The FT product water was firstly characterized and afterward subjected to the reforming at different reaction temperatures and time, using a platinum catalyst supported on activated carbon. It was observed that, besides activity, the selectivity towards hydrogen was favored at higher temperatures; equally, increasing the reaction time allowed to obtain the total conversion of most molecules found in the solution, without decreasing the selectivity and reaching a plateau at 4 hours in the hydrogen productivity. In order to get more insights into the reaction mechanism and product distribution derived from the APR of FT product water, several tests were performed with single compounds, finding characteristic features. The importance of the position of the hydroxyl group in the molecule structure was highlighted, with secondary alcohols more prone to dehydrogenation pathways compared to primary alcohols. Moreover, no interference among the substrates was reported despite the mixture is constituted by several molecules: in fact, the results obtained with the real FT product water were analogous to the linear combination of the single compound tests. Finally, the reuse of the catalyst showed no appreciable deactivation phenomena

Althusser e Pêcheux: um encontro paradoxal

Este artigo busca refl etir em torno da produção intelectual dos filósofos Louis Althusser e Michel Pêcheux, com base em uma análise de seus textos escritos no início dos anos 1980, que circularam através de diferentes modalidades tais como: conferências, publicações, entrevistas, edições em outras línguas, tendo sido somente publicados em língua Francesa, entretanto, a partir dos anos 1990

Position and Stiffness Control of One DoF Revolute Joint Using a Biphasic Media Variable Stiffness Actuator

At this time, several industrial processes and service tasks need safe interactions between humans and robots. This safety can be achieved using compliance design and control of mechanisms. This paper presents a compliant revolute joint mechanism using a variable stiffness actuator. The method for adapting the stiffness in the actuator includes a member onfigured to transmit motion that is connected to a fluidic circuit, into which a biphasic control fluid circulates. Actuator's stiffness is controlled by changing pressure of control fluid into distribution lines. The used control fluid is biphasic, composed of separated gas and liquid fractions with predefined ratio. A mathematical model of the actuator is presented, a modelbased control method is implemented to track the desired position and stiffness, and equations relating to the dynamics of the mechanism are provided. Results from force loaded and unloaded simulations and experiments with a physical prototype are discussed

Point of view : the blind spot of the theories of polyphony

Neste artigo vamos discutir algumas questões sobre a subjetividade e a polifonia nos estudos enunciativos da linguagem. Para isso, percorremos um certo caminho, apresentando como Anscombre e Ducrot trazem o conceito da polifonia para os estudos linguísticos e a reconfiguração dada a este conceito por Carel e Ducrot. Após, mostraremos como a questão do ponto de vista vem sendo tratada em estudos desenvolvidos no Brasil, a partir do funcionamento do agenciamento enunciativo proposto por Guimarães.PALAVRAS-CHAVE: Polifonia. Subjetividade. Enunciação. ABSTRACTIn this article, we discuss some issues about the subjectivity and polyphony studies set out from the language. At first, introducing the concept of polyphony that Anscombre and Paige established in their linguistic studies and the reconfiguration of this concept by Carel and Duprot. Secondly, we discussed how the point of view is treated in studies developed in Brazil, from the operation enunciative forwarding information proposed by Guimaraes. KEYWORDS: Polyphony. Subjectivity. enunciationIn this article, we discuss some issues about the subjectivity and polyphony studies set out from the language. At first, introducing the concept of polyphony that Anscombre and Paige established in their linguistic studies and the reconfiguration of this concept by Carel and Duprot. Secondly, we discussed how the point of view is treated in studies developed in Brazil, from the operation enunciative forwarding information proposed by Guimaraes. KEYWORDS: Polyphony. Subjectivity. enunciatio

Modeling of a Cable-Based Revolute Joint Using Biphasic Media Variable Stiffness Actuation

In recent times, safe interactions between humans and robots are required for innumerable tasks and environments. This safety can be achieved using compliance design and control of mechanisms. Cable-driven mechanisms are used when applications need to have light structures, meaning that their actuators must be relocated to ground and forces are transferred along tensioned cables. This paper presents a compliant cable-driven revolute joint using biphasic media variable stiffness actuators. Actuator's stiffness is controlled by changing pressure of control fluid into distribution lines. The used control fluid is biphasic, composed of separated gas and liquid fractions with predefined ratio. The mathematical model of the actuator is presented along with its position and stiffness model-based control, then, equations relating to the dynamics of the mechanism are provided with a joint stiffness and orientation controller. Results from simulations are discussed