Energy Considerations in Blockchain-Enabled Applications

Blockchain-powered smart systems deployed in different industrial applications promise operational efficiencies and improved yields, while mitigating significant cybersecurity risks pertaining to the main application. Associated tradeoffs between availability and security arise at implementation, however, triggered by the additional resources (e.g., memory, computation) required by each blockchain-enabled host. This thesis applies an energy-reducing algorithmic engineering technique for Merkle Tree root and Proof of Work calculations, two principal elements of blockchain computations, as a means to preserve the promised security benefits but with less compromise to system availability. Using pyRAPL, a python library to measure computational energy, we experiment with both the standard and energy-reduced implementations of the Merkle Tree for different input sizes (in bytes) and of the Proof of Work for different difficulty levels. Our results show up to 98\% reduction in energy consumption is possible within the blockchain\u27s Merkle Tree construction module, such reductions typically increasing with larger input sizes. For Proof-of-Work calculations, our results show an average energy reduction of 20\% across typical difficulty levels. The proposed energy-reducing technique is potentially applicable to other key elements of blockchain computations, potentially affording even greener blockchain-powered systems than implied by only the Merkle Tree and Proof of Work results obtained thus far

Energy-efficient HMAC for wireless communications

This thesis introduces the Farming Lightweight Protocol (FLP) optimized for energy-restricted environments that depend upon secure communication, such as multi-robot information gathering systems within the vision of ``smart\u27\u27 agriculture. FLP uses a hash-based message authentication code (HMAC) to achieve data integrity. HMAC implementations, resting upon repeated use of the SHA256 hashing operator, impose additional resource requirements and thus also impact system availability. We address this particular integrity/availability trade-off by proposing an energy-saving algorithmic engineering method on the internal SHA256 hashing operator. The energy-efficient hash is designed to maintain the original security benefits yet reduce the negative effects on system availability. A simulation environment was created to represent several FLPs of practical character, each utilizing HMAC in a consistent manner assuming inputs of configurable size. We then conducted simulation experiments to test our energy-saving algorithmic engineering method for HMAC computations. Using the RAPL API from Intel, we measured computational energy for each input size and FLP protocol variant under study. Our results show that our method reduces energy usage by 11% on average, while maintaining the core capabilities of the FLP protocol without compromising security performance

Synthesis of type A zeolites from natural kaolinite for their application in CO2 capture processes

Climate change is the greatest environmental threat of the 21st century, with major economic, social and environmental consequences. The level of carbon dioxide (CO2) emissions has increased by 31%, therefore, both governments and the scientific community are taking steps to mitigate emissions into the atmosphere. The most economically sustainable method is the use of low cost adsorbents that perform a selective adsorption of CO2 with respect to other inert gases such as N2. Clay minerals are highly available materials on the planet, are a low cost raw material and have great versatility for various processes in the field of adsorption and catalysis. The present work describes the synthesis of type A zeolite from a hydrothermal process in basic medium using metacaolinite as a starting material. Several parameters such as temperature and time were modified to evaluate the relationship between the formation conditions of the zeolite and its CO2 adsorption capacity. Synthesized catalysts were characterized by X-ray diffraction (XRD), N2 adsorption-desorption at -196 ºC, nuclear magnetic resonance of solids (NMR) and infrared spectroscopy (IR). In addition, the absorption capacity of CO2 with type A zeolites has been evaluated, and all the results were compared with the commercial zeolites. With respect to the results obtained, it can be said that the bands obtained by IR for the synthesized Zeolites are similar to those of the commercial Zeolite. On the other hand, the NMR results show that the synthesized and commercial zeolite present the same chemical environment. Finally, the textural parameters corroborate that in all cases the surface area is low from 12 m2g-1 for kaolinite to 7 m2g-1 for commercial zeolite AUniversidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Nanocátalysts for oxygen removal from biomass derived biofuel

The use of bio-energy as a renewable alternative to fossil fuels is nowadays attracting more and more attention. Bio-fuel from biomass seems to be a potential energy substitute for fossil fuels since it is a renewable resource that could contribute to sustainable development and global environmental preservation and it appears to have significant economic potential. Liquid fuels can be obtained from fast pyrolysis of lignocellulosic biomass, where fast pyrolysis is a promising route because the process takes place at moderate temperatures, in absence of air and with a short hot vapor residence time. However, these liquid fuels have poor quality due to their low volatility, high viscosity, low heating value, a high oxygen content and poor chemical stability. This high oxygen is due to the presence of oxygen-containing compounds such as alcohols, aldehydes, ketones, furans and phenols. In this sense, catalytic hydrodeoxygenation (HDO) is one the most efficient processes to remove oxygen from these liquid fuels. In this context, the catalyst design is of upmost importance to achieve a high degree of deoxygenation, and bifunctional catalysts are required to achieve high degrees of activity. Noble metal and non-noble metal based catalysts will be evaluated in HDO of model molecules in order to get further insight about the important role of the active phase. Transition metal phosphides have shown excellent catalytic performances due to their good hydrogen transfer properties that diminishes the amount of metal exposed, avoiding, as much as possible, the deactivation, and modifies the electronic density of the catalyst leading to solids that favors the HDO. In addition these phosphides show bifunctional catalytic properties (metallic sites for hydrogenation and acid sites for cracking, methyl transfer reaction, dehydration and isomerization).Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

CO2 interactions with porous carbons: Is the surface stable at ambient conditions?

Interactions of CO2 with polymer derived carbon/rGO composites at ambient conditions were studied. Both, dynamic adsorption tests and equilibrium adsorption measurements were analyzed. The samples differed in the porosity, oxidation level and speciation of sulfur on the surface. Even though more CO2 was adsorbed on the oxidized sample than in the unmodified one, the surface chemistry of the latter was found as having more pronounced effect on attracting CO2 to the pore system. The results showed the marked changes in S-doped nanoporous carbon composite surface chemistry upon CO2 adsorption at ambient conditions. The changes were more pronounced for carbon with higher density of sulfur in thiophenic configurations on the surface emphasizing the role of these species in CO2 reduction. Even though CO could not be the target of our detection, identification of water, SO and SO2 as products of surface reactions supports our hypothesis that CO2 adsorption was accompanied by some extent of its reduction to CO. CO is formed in the process of electron transfer from thiophenes to CO2 in which the former are oxidized forming sulfones and sulfonic acids. Those species are likely thermodynamically unstable and decompose forming SO/SO2 and water providing additional electrons for CO2 reduction. Conductivity of carbon matrix and the local increase in this feature owing to the presence of the graphene-based phase facilitate this process. Based on the results collected, it is recommended that the stability of carbons towards carbon dioxide should be evaluated before it is used as CO2 sequestration medium

Role of Mo in catalysts based on noble metals in hydrodeoxygenation reactions

The use of bio-energy as a renewable alternative to fossil fuels is nowadays attracting more and more attention. The bio-fuel from biomass seems to be a potential energy substitute for fossil fuels since it is a renewable resource that could contribute to sustainable development and global environmental preservation and it appears to have significant economic potential1. The problem is its high oxygen content, which gives undesirable properties for combustion. To remove oxygen, catalytic hydrodeoxygenation (HDO) reactions are carried out. Monometallic Mo/Si, Pt/Si as well as bimetallic PtMo/Si catalysts were prepared and evaluated in the hydrodeoxygenation (HDO)reaction of dibenzofurane (DBF) as a model molecule in biomass derived bio-oil.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Au-Cu/SBA(Ti) based catalysts for photocatalytic applications

Comunicación a congresoIn this work, it has been synthesized several Au and Au-Cu alloy photocatalysts supported on two different mesoporous supports: a non-commercial SBA-15 and a post-synthesis TiO2 modified SBA-15 (TiSBA-15), with which a high dispersion of TiO2 species have been achieved maintaining the SBA-15 structure. In addition, it has also been obtained highly dispersed Au nanoparticles confined in SBA-15 pore channels, as can be observed in Figure 1. The photocatalysts have been preliminary tested in the preferential CO oxidation in a H2-rich stream (CO-PROX) at room temperature and atmospheric pressure under simulated solar light irradiation. In spite of the very low gold and copper loading (1.5 wt% and 0.5wt% respectively), the catalysts resulted active and selective in the low temperature photo-CO-PROX.Universidad de Málaga, Campus de Excelencia Internacional Andalucía Tec

Synthesis and characterization of silver vanadates thin films for photocatalytic applications

Silver vanadates thin films were deposited by a hybrid deposition system combining laser ablation and thermal evaporation. A high purity vanadium target was ablated using the third harmonic of a Nd:YAG laser whereas high purity silver pellets were evaporated. The as-deposited thin films were subjected to thermal treatments at 400 °C to obtain crystalline films. For films without Ag amorphous V2O5 thin films were deposited and as the Ag is incorporated in the material different silver vanadates were obtained. The effect of the silver load on the composition, structure, optical properties, surface morphology and photocatalytic response of the deposited films was studied. The film composition, determined by X-ray photoelectron spectroscopy, reveals Ag contents from 5.5 to 18.9 at.%. The crystalline phases formed were identified by micro-Raman Spectroscopy; the results indicate the formation of three silver vanadates depending on the silver content. The morphology was observed using scanning electron microscopy, the filmś surface changes from a smooth surface to belts covering the surface and finally Ag nanoparticles are observed at the higher Ag contens. Optical properties determined from UV–vis reveal the presence of the surface plasmon signal in films containing silver. The films were tested in the photocatalytic degradation of Malachite Green dye reaching maximum degradations degrees close to 53% under solar irradiation. Reactive species trapping experiments suggest that O2 − produced by the O2 reduction via the photogenerated electrons drives the photodegradation mechanismCB-168827 CB-240998 F. Gonzalez-Zavala thanks to CONACyT for the PhD and Beca Mixta grants, and also to the SIEA-UAEM for the beca movilidad para estudios avanzados 2016. E. Rodríguez-Castellón thanks to project CTQ2015-68951-C3-3-R of Ministerio de Economía y Competitividad (Spain) and FEDER funds

Synthesis of porous graphene/TiO2 by use of recycled graphite

Graphene-based nanomaterials are a kind of new technological materials with high interest for physicists, chemists and materials scientists. Graphene is a two-dimensional (2-D) sheet of carbon atoms in a hexagonal configuration with atoms bonded by sp2 bonds. These bonds and this electron configuration provides the extraordinary properties of graphene, such as very large surface area, a tunable band gap, high mechanical strength and high elasticity and thermal conductivity [1]. Graphene has also been investigated for preparation of composites with various semiconductors like TiO2, ZnO, CdS aiming at enhanced photocatalytic activity for their use for photochemical reaction as water splitting or CO2 to methanol conversion [2-3]. In this communication, the synthesis of porous graphene@TiO2 obtained from a powder graphite recycled, supplied by ECOPIBA, is presented. This graphite was exfoliated, using a nonionic surfactant (Triton X-100) and sonication. Titanium(IV) isopropoxide was used as TiO2 source. After removing the surfactant with a solution HCl/n-propanol, a porous solid is obtained with a specific area of 358 m2g-1. The solid was characterized by XRD, FTIR, XPS, EDX and TEM. Figure 1 shows the graphene 2D layer bonded with nanoparticles of TiO2. When a water suspension of this material is exposed with UV-vis radiation, water splitting reaction is carried out and H2/O2 bubbles are observed (Figure 2)Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech