A bi‐criterion optimization approach for the design and planning of hydrogen supply chains for vehicle use

In this article, we address the design of hydrogen supply chains for vehicle use with economic and environmental concerns. Given a set of available technologies to produce, store, and deliver hydrogen, the problem consists of determining the optimal design of the production‐distribution network capable of satisfying a predefined hydrogen demand. The design task is formulated as a bi‐criterion mixed‐integer linear programming (MILP) problem, which simultaneously accounts for the minimization of cost and environmental impact. The environmental impact is measured through the contribution to climate change made by the hydrogen network operation. The emissions considered in the analysis are those associated with the entire life cycle of the process, and are quantified according to the principles of Life Cycle Assessment (LCA). To expedite the search of the Pareto solutions of the problem, we introduce a bi‐level algorithm that exploits its specific structure. A case study that addresses the optimal design of the hydrogen infrastructure needed to fulfill the expected hydrogen demand in Great Britain is introduced to illustrate the capabilities of the proposed approach. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

A Solvent‐Free Dispersion Method for the Preparation of PET/MWCNT Composites

A simple, easily accessible solvent‐free method for the dispersion of MWCNTs into PET is proposed, based on the preparation of a microparticulate polymer/nanotube masterbatch via cryogenic impact‐milling and its subsequent melt blending with the bulk polymer. Thermal and mechanical properties of nanocomposites prepared using this method were evaluated as a function of nanotube concentration. Thermal stability was improved, and superior crystallization behavior of PET in the nanocomposites was observed. Significant improvements of around 25% in tensile strength and tensile modulus of the nanocomposites was achieved using this strategy, with only 0.25 wt.‐% MWCNT, compared to previous literature data where 1 wt.‐% MWCNT was employed.

     

Gene Therapy in HIV‐Infected Cells to Decrease Viral Impact by Using an Alternative Delivery Method

The ability of dendrimer 2G‐[Si{O(CH₂)₂N(Me)₂⁺(CH₂)₂NMe₃⁺(I^?)₂}]₈ (NN16) to transfect a wide range of cell types, as well as the possible biomedical application in direct or indirect inhibition of HIV replication, was investigated. Cells implicated in HIV infection such as primary peripheral blood mononuclear cells (PBMC) and immortalized suspension cells (lymphocytes), primary macrophages and dendritic cells, and immortalized adherent cells (astrocytes and trophoblasts) were analyzed. Dendrimer toxicity was evaluated by mitochondrial activity, cell membrane rupture, release of lactate dehydrogenase, erythrocyte hemolysis, and the effect on global gene expression profiles using whole‐genome human microarrays. Cellular uptake of genetic material was determined using flow cytometry and confocal microscopy. Transfection efficiency and gene knockdown was investigated using dendrimer‐delivered antisense oligonucleotides and small interfering RNA (siRNA). Very little cytotoxicity was detected in a variety of cells relevant to HIV infection and erythrocytes after NN16 dendrimer treatment. Imaging of cellular uptake showed high transfection efficiency of genetic material in all cells tested. Interestingly, NN16 further enhanced the reduction of HIV protein 24 antigen release by antisense oligonucleotides due to improved transfection efficiency. Finally, the dendrimer complexed with siRNA exhibited therapeutic potential by specifically inhibiting cyclooxygenase‐2 gene expression in HIV‐infected nervous system cells. NN16 dendrimers demonstrated the ability to transfect genetic material into a vast array of cells relevant to HIV pathology, combining high efficacy with low toxicity. These results suggest that NN16 dendrimers have the potential to be used as a versatile non‐viral vector for gene therapy against HIV infection.     

High-Impact PLA in Compatibilized PLA/PCL Blends: Optimization of Blend Composition and Type and Content of Compatibilizer

In this work, the effectiveness of seven commercial compatibilizers is tested in polylactide (PLA)/poly(ε-caprolactone) (PCL) blends with different compositions to obtain a high-impact PLA. None of the compatibilizers is effective for 90/10 and 80/20 PLA/PCL compositions, as no improvement of the impact strength is observed. For the 70/30 composition, compatibilizers having glycidyl methacrylate (GMA) and acrylate groups in their structure are proved the most effective, as the morphological change towards co-continuity induced by them leads to significant impact strength improvements (of ≈345% and 90% with respect to the neat PLA and the noncompatibilized PLA/PCL 70/30 blend, respectively). The 70/30 PLA/PCL composition, as it shows the best balance of properties, and the best compatibilizer (ElvaloyPTW) are chosen to carry out the optimization of the compatibilizer content. It is found that adding 6 phr to the blend results in highly toughened and ductile blends while maintaining a high modulus and yield strength values. Larger compatibilizer contents lead to even higher impact strength values, but the low-strain mechanical properties are notably reduced. Thus, in this work, a simple and easily scalable method to produce high-impact PLA is shown, as it implies the compounding of three commercially available components without involving any toxic solvents.     

Technical–economic evaluation of a small-scale model plant for the manufacture of pine glue laminated timber

A small-scale glue laminated timber (GLT) model plant, capable of producing an average of 880 linear m of lamellas per day, approximately 1500 m³/year, located in Castilla y León, Spain, was technically and economically evaluated. The production of such plant is aimed at substituting imports of GLT manufactured from spruce in Central Europe. The total investment considered for this theoretical operation was 455 k€. The raw material proposed was Pinus sylvestris classified according to UNE 56544 as ME-2. The external lamellas were defined as ME-1, upgraded from ME-2 by the removal of knots and deformations, which gives an average block length of 1825 and 3800 mm for external and internal lamellas, respectively. The effective stiffness of such configuration was modeled, rendering beams that could be assigned to class resistance GL24. Production costs were 770 k€, 52% of which were timber as raw material. The volume of production is affected by the combination of products manufactured; therefore, this variable was presented as a function of economic result, defining zones of product-mix that would be economically unfeasible, feasible with reservations, and feasible. The products to be manufactured were straight beams, 6-m long, of 9 different cross-sections, varying from 80?×?120 mm² to 200?×?600 mm². Additionally, production volume, wood cost, and block length are identified as critical parameters for the sensitivity analysis of the plant. Considering a wood cost for ME-2 of 220 €/m³, the plant must operate at 70% of its capacity to be economically feasible. The economic result of the operation increases proportionally to block length. The plant generates an EBIT of 51 k€, PNV of 415 k€ (discount rate of 4%), and an IRR of 19%.

     

Expert system for the integrated management of a power utility'scommunication system

In this paper we present a rule-based expert system applied to the fault diagnosis in the communication system of a power utility. The expert system is part of the system devoted to the management of a power utility's communication system, that we called NOMOS. NOMOS manages the communication systems of Sevillana de Electricidad and Union Electrica Fenosa (two major Spanish power utilities)     

A systems view of temporary housing projects in post‐disaster reconstruction

Natural cataclysms (earthquakes, hurricanes and so forth) become natural disasters when they coincide with vulnerabilities; unfortunately, informal settlements in developing countries are only too often highly vulnerable – a reality amply and unhappily confirmed by available statistics. In this context, reconstruction projects are sandwiched between the short‐term necessity to act promptly and the long‐term requirements of sustainable community development – a situation that is currently reflected in alternative and conflicting paradigms at the policy level.

Adopting a case‐study approach, we explore the use of temporary housing within two post‐disaster environments, where the impact of different organizational designs leads to fundamentally different solutions to the short‐term housing problem.

Our research adopts a dynamic systems approach, associating strategic organizational team design with the development of tactical technical proposals. Two case studies from Turkey and Colombia show that a coherent approach to the sequential stages of providing immediate shelter, temporary housing and permanent reconstruction is not always obtained. The research results emphasize that the performance of reconstruction projects is directly linked to the design and management of the project team.     

Characterisation of glasses in the TeO2–WO3–PbO system

As potential candidates for photonic devices, non-linear materials and coatings, 22 glasses in the TeO₂–WO₃–PbO system have been formulated and prepared by conventional melting at temperatures ranging between 710 and 750 °C. The glass forming area has been determined for a wide region of the corresponding ternary diagram. Structural characterisation of the glasses was conducted through FTIR spectrometry and the variation of density values, which allowed calculation of the glass molar volume and the oxygen molar volume. UV–VIS spectra were recorded to determine optical absorption/transmission and energy gap values. Likewise, such results were correlated with the glasses composition and their ability for optical materials. DTA curves yielded data of transition temperature (T_g), onset crystallisation temperature (T_c) and the thermal stability range of glasses. Crystalline phases formed in devitrified and partially devitrified glasses were detected by X-ray diffraction. The properties and structural features of glasses were discussed in terms of their relative proportion of former/modifier oxides. The main glass former oxide is TeO₂, which arranges [TeO₄] groups with tetrahedral coordination, while PbO plays as glass modifier oxide. Tungsten oxide is incorporated as network former, alternating with TeO₂ and forming mixed linkages Te–O–W and W–O–W. WO₃ is the component that contributes most to increase the glass transition temperature, and to decrease both the oxygen molar volume and the thermal expansion coefficient.     

Bio-hydrogen production during acidogenic fermentation in a multistage stirred tank reactor

The objective of this study was to evaluate the production of hydrogen in a two-stage CSTR system – both reactors having the same volume – and compare its performance with a conventional one-stage process. The lab-scale two-stage and one-stage systems were operated at five pHs and five hydraulic retention time (HRTs). The maximum volumetric hydrogen productivity and yield obtained with the two-stage system were 5.8 mmol L⁻¹ h⁻¹ and 2.7 mol H₂ mol glucose⁻¹, respectively, at an HRT of 12 h and pH 5.5. Overall, the two-stage system showed, at steady state, a better performance that the one-stage system for all the evaluated pHs. However, a comparison between the one-stage system, operating at 6 h of HRT, and the first reactor of the two-stage system at the same HRT did not show any significant difference, highlighting the positive impact of having a two-stage process. The determination of the ratio between the experimental measured H₂ in the gas phase and the theoretical H₂ generated in the liquid phase (discrepancy factor) indicated that an important part of the hydrogen produced in the first reactor was transferred into the second reactor instead of being desorbed in the headspace. Therefore, the improving of hydrogen production in the two-stage system is rather attributed to the increased transfer of hydrogen from liquid to gas than an actual total hydrogen production increase.