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Background and aims – Diospyros (Ebenaceae), a large genus with a mostly tropical distribution, includes 736 species worldwide, 104 of which occur in continental Africa. During recent field work in west-central Gabon, two new species of Diospyros were collected. They are described and illustrated here, and compared with their most similar relatives. Preliminary conservation status assessments are also provided. Methods – Normal practices of herbarium taxonomy were applied to study all available herbarium material, mainly from BR, BRLU, LBV, MO, P and WAG. The conservation status of both species was evaluated following the IUCN Red List Categories and Criteria. Key results – Diospyros cleistantha O.Lachenaud & G.E.Schatz occurs in the Atlantic regions of Cameroon, Equatorial Guinea and Gabon; it belongs to D. sect. Calvitiella and closely resembles D. zenkeri and D. iturensis. Diospyros subargentea O.Lachenaud, Dauby & G.E.Schatz is endemic to west-central Gabon; it belongs to D. sect. Noltia and most closely resembles D. soyauxii. The conservation status of the two species is assessed as Endangered and Vulnerable, respectively., SCOPUS: ar.j, info:eu-repo/semantics/published

Background and aims – Annonaceae are an important family in tropical rain forests of Africa. Here, we present a revision of the west-central African genus Piptostigma of the tribe Piptostigmateae. Previous molecular phylogenetic analyses of Piptostigmateae have revealed that the genus as currently circumscribed is paraphyletic. The aims of the article are: (1) to clarify the generic delimitation of the genus Piptostigma, especially in relation to its current polyphyletic delimitation; (2) to provide a new updated key to the genera of tribe Piptostigmateae; and (3) to provide for the first time in over 100 years a complete taxonomic revision of genera Brieya and Piptostigma. Material and methods – Normal practices of herbarium taxonomy were used for the morphological study of about 200 specimens from B, BR, BRLU, G, HBG, K, L, LBV, LISC, MO, P, U, US, WAG, YA and Z. We sequenced three plastid regions for 32 samples representing 26 ingroup (Piptostigmateae) and six outgroup species in order to explore the paraphyly of Piptostisma. The open source software QGis was used to generate the distribution maps of the species and their conservation status was obtained using the IUCN categories and criteria. Key results – Molecular and morphological evidence support the reinstatement of the genus Brieya De Wild. Three keys are presented, one to the genera of Piptostigmateae and the two others to the species of Brieya and Piptostigma. A total of thirteen species are described for Piptostigma and two for the genus Brieya. Four new species are presented for the genus Piptostigma: P. macrophyllum, P. mayndongtsaeanum, P. goslineanum and P. submontanum., SCOPUS: ar.j, info:eu-repo/semantics/published

This study was conducted to investigate the magnetic-field effect on the two-dimensional buoyancy-driven natural convection inside a grooved rectangular enclosure subjected to isothermal boundary conditions. The magnetohydrodynamic (MHD) equations, under Boussinesq approximation, are numerically solved using the finite volume method. Numerical simulations have been performed to investigate the free convective heat transfer induced by a temperature difference between the bottom hot wall and the upper cold flat wall. The numerical results, for wide range of Hartmann and Rayleigh numbers and for both horizontal and vertical magnetic field directions, are discussed in terms of velocity, temperature field, streamlines, isotherms, Nusselt numbers and reduction heat transfer ratio. The results highlighted the enclosure's performance condition and revealed that the heat and fluid flow fields are affected by the Rayleigh number and the magnetic field strength and direction. It is observed that increasing the Hartmann number damps the fluid flow, reduces the convection currents, decreases the average Nusselt number at the cold surface and has tendency to delay the transition to convection regime and lengthening the conduction zone. However, the use of magnetic field reduces heat exchange up to 30% with an optimal Rayleigh (Raopt) for each Hartmann number., SCOPUS: ar.j, info:eu-repo/semantics/published

Plasma catalysis is gaining increasing interest for CO2 conversion, but the interaction between the plasma and catalyst is still poorly understood. This is caused by limited systematic materials research, since most works combine a plasma with commercial supported catalysts and packings. In the present paper, we study the influence of specific material and reactor properties, as well as reactor/bead configuration, on the conversion and energy efficiency of CO2 dissociation in a packed bed dielectric barrier discharge (DBD) reactor. Of the various packing materials investigated, BaTiO3 yields the highest conversion and energy efficiency, i.e. 25% and 4.5%. Our results show that, when evaluating the influence of catalysts, the impact of the packing (support) material itself cannot be neglected, since it can largely affect the conversion and energy efficiency. This shows the large potential for further improvement of packed bed plasma reactors for CO2 conversion and other chemical conversion reactions by adjusting both packing (support) properties and catalytically active sites. Moreover, we clearly prove that comparison of results obtained in different reactor setups should be done with care, since there is a large effect of the reactor setup and reactor/bead configuration., SCOPUS: ar.j, info:eu-repo/semantics/published

We consider the dynamics of an axisymmetric, partially wetting droplet of a one-component volatile liquid. The droplet is supported on a smooth superheated substrate and evaporates into a pure vapour atmosphere. In this process, we take the liquid properties to be constant and assume that the vapour phase has poor thermal conductivity and small dynamic viscosity so that we may decouple its dynamics from the dynamics of the liquid phase. This leads to a so-called 'one-sided' lubrication-type model for the evolution of the droplet thickness, which accounts for the effects of evaporation, capillarity, gravity, slip and kinetic resistance to evaporation. By asymptotically matching the flow near the contact line region and the bulk of the droplet in the limit of a small slip length and commensurably small evaporation and kinetic resistance effects, we obtain coupled evolution equations for the droplet radius and volume. The predictions of our asymptotic analysis, which also include an estimate of the evaporation time, are found to be in excellent agreement with numerical simulations of the governing lubrication model for a broad range of parameter regimes., SCOPUS: ar.j, info:eu-repo/semantics/published

Volcanoes with crater lakes and/or extensive hydrothermal systems pose significant challenges with respect to monitoring and forecasting eruptions, but they also provide new opportunities to enhance our understanding of magmatic-hydrothermal processes. Their lakes and hydrothermal systems serve as reservoirs for magmatic heat and fluid emissions, filtering and delaying the surface expressions of magmatic unrest and eruption, yet they also enable sampling and monitoring of geochemical tracers. Here, we describe the outcomes of a highly focused international experimental campaign and workshop carried out at Kawah Ijen volcano, Indonesia, in September 2014, designed to answer fundamental questions about how to improve monitoring and eruption forecasting at wet volcanoes., SCOPUS: ar.k, info:eu-repo/semantics/published

In a previous study, thepotential of damping suspensionbridges with active stay cables has been evaluated on a numerical modelof a suspension bridge, and demonstrated experimentally on a laboratory mockup. In this paper, we extend our study to explore two different configurations of the active stay-cables: One classical configuration, corresponding to attaching the active stay-cables between the top of the pylons and the deck(configuration I) and, another configuration, consisting of attaching the stay-cables between the base of the pylonsand the catenary (configuration II). The analysis confirmed thatboth configurations are effective with a slight superiority of the second configuration. The study is conducted numerically and experimentally on a suspensionbridge mock-up, by considering two types of active stay-cables. The experimental results confirmed the numerical predictions, and demonstrated the effectiveness of the second configuration., SCOPUS: ar.j, info:eu-repo/semantics/published

When a liquid drop is placed on a highly superheated surface, it can be levitated by its own vapour. This remarkable phenomenon is referred to as the Leidenfrost effect. The thermally insulating vapour film results in a severe reduction of the heat transfer rate compared to experiments at lower surface temperatures, where the drop is in direct contact with the solid surface. A commonly made assumption is that this solid surface is isothermal, which is at least questionable for materials of low thermal conductivity, resulting in an overestimation of the surface temperature and heat transfer for such systems. Here we aim to obtain more quantitative insight into how surface cooling affects the Leidenfrost effect. We develop a technique based on Mach-Zehnder interferometry to investigate the surface cooling of a quartz plate by a Leidenfrost drop. The three-dimensional plate temperature field is reconstructed from interferometric data by an Abel inversion method using a basis function expansion of the underlying temperature field. By this method we are able to quantitatively measure the local cooling inside the plate, which can be as strong as 80 K. We develop a numerical model which shows good agreement with experiments and enables extending the analysis beyond the experimental parameter space. Based on the numerical and experimental results we quantify the effect of surface cooling on the Leidenfrost phenomenon. By focusing on the role of the solid surface we provide new insights into the Leidenfrost effect and demonstrate how to adjust current models to account for non-isothermal solids and use previously obtained isothermal scaling laws for the neck thickness and evaporation rate., SCOPUS: ar.j, info:eu-repo/semantics/published

The magmatic-hydrothermal system of Kawah Ijen volcano is one of the most exotic on Earth, featuring the largest acidic lake on the planet, a hyper-acidic river and a passively degassing silicic dome. While previous studies have mostly described this unique system from a geochemical perspective, to date there has been no comprehensive geophysical investigation of the system. In our study, we surveyed the lake using a thermocouple, a thermal camera, an echo sounder and CO2 sensors. Furthermore, we gained insights into the hydrogeological structures by combining self-potential surveys with ground and water temperatures. Our results show that the hydrothermal system is self-sealed within the upper edifice and releases pressurized gas only through the active crater. We also show that the extensive hydrological system is formed by not one but three aquifers: a south aquifer that seems to be completely isolated, a west aquifer that sustains the acidic upper springs, and an east aquifer that is the main source of fresh water for the lake. In contrast with previous research, we emphasize the heterogeneity of the acidic lake, illustrated by intense subaqueous degassing. These findings provide new insights into this unique, hazardous hydrothermal system, which may eventually improve the existing monitoring system., SCOPUS: ar.k, info:eu-repo/semantics/published

This paper considers the quadratic stabilization of a class of uncertain linear time-varying (LTV) continuous-time plants. The state-space representation of each plant is based on the physically meaningful assumption of a dynamical matrix containing uncertain elements whose time trajectories are sufficiently smooth to be well described by interval polynomial functions with arbitrarily time varying coefficients. At some isolated time instants, the parameters trajectories can exhibit some first-kind discontinuities due for example to sharply varying operating conditions. Using a parameter independent Lyapunov function, a quadratically stabilizing dynamic output controller is directly obtained by the solution of some LMIs. A salient feature of the paper is that, unlike all the other existing methods, quadratic stabilization can be achieved over possibly arbitrarily large uncertain domains of parameters. Copyright © 2016 John Wiley & Sons, Ltd., SCOPUS: ar.j, info:eu-repo/semantics/published

This paper examines data mining approaches to classify the state of road surfaces by simple sensors such as acceleration sensors and gyroscopes. The work aims for classification of road material and the recognition of irregularities such as potholes or railroad crossings. The sensor information therefore is transformed into frequency-based features, which are automatically rated and discussed. The best features are used to design classification routines. All routines are finally implemented into an open-source MATLAB-toolbox visualizing classifier results upon road maps, enabling the user to manually validate the results. All results are discussed using an extensive exemplary data-set., SCOPUS: ar.j, info:eu-repo/semantics/published

The dilution is an event that have a high influence on the microstructure and, consequently, in the properties of weld claddings. The present study evaluated the effect of dilution level on the microstructure of the fusion zone of alloy Inconel 686 weld claddings. The claddings were welded by the TIG cold wire feed process. The dilution was calculated from the geometric characteristics and based on chemical composition of the materials obtained by energy dispersive X-ray spectroscopy and optical emission spectroscopy. The microstructure of all claddings were composed by a γ-FCC matrix with some minor precipitates. These particles are called in literature as topologically closed-packed phases (TCP). These precipitates assumed several morphological aspects, being the shapeless morphology observed in more frequency in all claddings evaluated, independent of dilution level. A phase with lamellar morphology, which growth establishing an orientation relationship with the γ-FCC matrix solidification direction, was observed only in claddings with a low dilution level. In addition, a shapeless phase with a fine precipitation aggregated was observed in claddings with a high dilution level., SCOPUS: ar.j, info:eu-repo/semantics/published

Mechanical properties of metastable β-Ti alloys are highly dependent on the final microstructure, which is controlled by the thermomechanical processing. These alloys are used for biomedical applications and require a high mechanical strength as well as a low Young’s modulus to avoid stress shielding. Previous work on the development of cold swaged Ti-10Mo-20Nb alloy showed that the best compromise strength and Young’s modulus was obtained when the forming is followed by an aging heat treatment at 500 °C. In this work, Ti-10Mo-20Nb alloy was hot swaged and aged at 500 °C for 10 min, 4h and 24h. The microstructure was analyzed by X-ray diffraction, optical microscopy and transmission electron microscopy. Mechanical characterization was based on Vickers microhardness tests and Young’s modulus measurements. Aging at 500°C for 10 min after hot swaging resulted in a nearly 100% β phase microstructure while aging at 500°C for 4h or 24h led to a bimodal microstructure consisting on α precipitates dispersed in the β matrix. The higher hardness to Young’s modulus ratio was obtained for the sample aged at 500 °C for 4h. This value was higher than those obtained for the Ti-6Al-4V alloy and commercially pure Ti., SCOPUS: cp.k, info:eu-repo/semantics/published

The paper first reviews the theory of active tendon control with decentralized Integral Force Feedback (IFF) and collocated displacement actuator and force sensor; a formal proof of the formula giving the maximum achievable damping is provided for the first time. Next, the potential of the control strategy for the control of suspension bridges with active stay cables is evaluated on a numerical model of an existing footbridge; several configurations are investigated where the active cables connect the pylon to the deck or the deck to the catenary. The analysis confirms that it is possible to provide a set of targeted modes with a considerable amount of damping, reaching ξ = 15% .Finally, the control strategy is demonstrated experimentally on a laboratory mock-up equipped with four control stay cables equipped with piezoelectric actuators. The experimental results confirm the excellent performance and robustness of the control system and the very good agreement with the predictions., SCOPUS: ar.j, info:eu-repo/semantics/published

We describe a novel application of graphene-based materials to enhance heat transport in sintered metal wicks, which are the core components for Loop Heat Pipe (LHP) evaporators. Standard metal wicks limit the applicability of LHP to about 8-10 m of transport length and around few meters of gravitational head. This is due to the typical average pore size (about 1 μm) in the sintered metal wicks made of nickel or titanium, which are the most commonly used materials. The idea of the present work is to bond a layer of graphene on top of the wick facing the vapor side of the LHP evaporator. The much smaller pore sizes of graphene (around tens of nanometers) would produce a significant increase in capillary force, while at the same time minimising the pressure drop due to its microscopic thickness (few microns). The wicking height (i.e. capillary rise of a liquid inside a pore) measurements demonstrate that there is an improvement of at least more than 3.5 times when the graphene coating is used, compared to the standard nickel sintered powder wick. This means that the heat transfer of a graphene LHP could work in a spatial range in excess of 28-35 m, which would allow breakthrough applications such as anti-icing of aircraft wings and propellers, as well as wind turbines that cannot be addressed by standard LHP technology., SCOPUS: ar.j, info:eu-repo/semantics/published

Electron Beam Melting (EBM), a powder bed additive layer manufacturing process, was used to produce Ti-6Al-4V specimens, whose microstructure, texture, and tensile properties were fully characterized. The microstructure, analyzed by optical microscopy, SEM/EBSD and X-ray diffraction, consists in fine α lamellae. Numerical reconstruction of the parent β phase highlighted the columnar morphology of the prior β grains, growing along the build direction upon solidification of the melt pool. The presence of grain boundary αGB along the boundaries of these prior β grains is indicative of the diffusive nature of the β→α phase transformation. Texture analysis of the reconstructed high temperature β phase revealed a strong <001> pole in the build direction. For mechanical characterization, tensile specimens were produced using two different build themes and along several build orientations, revealing that vertically built specimens exhibit a lower yield strength than those built horizontally. The effect of post processing, either mechanical or thermal, was extensively investigated. The influence of surface finish on tensile properties was clearly highlighted. Indeed, mechanical polishing induced an increase in ductility - due to the removal of critical surface defects - as well as a significant increase of the apparent yield strength - caused by the removal of a ~150μm rough surface layer that can be considered as mechanically inefficient and not supporting any tensile load. Thermal post-treatments were performed on electron beam melted specimens, revealing that subtransus treatments induce very moderate microstructural changes, whereas supertransus treatments generate a considerably different type of microstructure, due to the fast β grain growth occurring above the transus. The heat treatments investigated in this work had a relatively moderate impact on the mechanical properties of the parts., SCOPUS: ar.j, info:eu-repo/semantics/published

This paper addresses a virtual prototyping and testing method intended for electromechanical components in the context of the electric vehicle market. The focus point is the battery energy consumption when simulating different reference driving cycles and monitoring the electric machine performance parameters. The author adopted a Model-based (MBD) design approach distinguished by Model-in-the-loop (MiL) simulation and Hardware-in-the-loop (HiL) testing. This is constructed through a process of co-simulation between a MATLAB/Simulink electric drive indirect field oriented control (IFOC) model and an AMESim forward-facing electric vehicle model for the offline case and real-time file generation between the same software environments plus the Triphase interface that commands the mechanical coupled induction machines on the test-bench done in the online case. The vehicle model takes into account the signal received from the driver model and commands the vehicle control unit (VCU) in a way that permits energy consumption management through the use of regenerative braking. An estimation of the DC current at the level of the battery terminals and an efficiency map of the real induction machine were needed to achieve the battery energy consumption results. Finally, the energy consumption in Wh/km is obtained by dividing the consumed battery energy by the distance traveled by the vehicle. By monitoring the speed, torque and energy consumption in the offline and online tests we remarked the similarity between the different variables and we can determine which drive cycle is more energy demanding., SCOPUS: ar.j, info:eu-repo/semantics/published

The present work attempts to characterize the accelerometric environment of the DSC-DCMIX1 thermodiffusion experiment carried out in the International Space Station, from November 7th 2011 until January 16th 2012. Quasi-steady and vibrational/transient data coming from MAMS and SAMS2 sensors have been downloaded from the database of the PIMS NASA website. To be as exhaustive as possible, simultaneous digital signals coming from different SAMS2 sensors located in the Destiny and Columbus modules have also been considered. In order to detect orbital adjustments, dockings, undockings, as well as, quiescent periods, when the experiment runs were active, we have used the quasi-steady eight hours averaged (XA, YA and ZA) acceleration functions as well as the eight hours RMS ones. To determine the spectral contents of the different signals the Thomson multitaper and Welch methods have been used. On the other hand, to suppress the high levels of noise always existing in the raw SAMS2 signals, denoising techniques have been preferred for comparative reboostings considerations. Finally, the RMS values for specific 1/3 octave frequency bands showed that the International Space Station vibratory limit requirements have not been totally accomplished during both quiescent periods and strong disturbances, specially in the low frequency range., SCOPUS: ar.j, info:eu-repo/semantics/published

In this paper, I apply the recent nonparametric multi-sector production-frontier methodology of Walheer (), tailored to analyse the economic growth and convergence of countries taking the sector heterogeneity and interdependence into account, to the European countries from 1995 to 2014. Thanks to a simple rewriting of his initial model, I also provide results at the sector level, which was not possible with the initial version of the methodology. My results confirm the non-neutrality of technological change and highlight that human capital accumulation plays the biggest role in the increase of labour productivity. Technological change and capital accumulation also play an important, if smaller, role in the increase of output-labour productivity. My results also confirm the presence of heterogeneity between sectors in Europe, which supports the use of multi-sector analysis. Finally, my results confirm the presence of two groups, in terms of labour productivity, within the European counties: Eastern and Central European countries and the EU12. These two groups diverge over time. The results are not affected by robustness checks., SCOPUS: ar.j, FLWIN, info:eu-repo/semantics/published

Five models describing heat transfer during evaporation of the water sprayed over the forest to stop fires and to cool down the pyrolysis of the bio- top layer are established and investigated by a parametric approach. It aims to improve the understanding of the behavior and the properties of the forest combustible material (FCM). A mathematical description of FCM surfaces (needles of pine and fir-tree, leaves of birch) is established. The characteristic time td to cool down the FCM layer below the temperature of the onset of the pyrolysis is the important parameter investigated in the present work. The effective conditions were determined allowing to reach the shortest td time and the lowest consumption of e.g. water to be dropped., SCOPUS: ar.j, SCOPUS: ar.j, SCOPUS: ar.j, info:eu-repo/semantics/published

Cd1-xZnxS thin films have been studied extensively as window layers for solar cell applications. However, a mismatch between the Cd1-xZnxS and copper-indium-gallium-selenide absorber layers increases with Zn film concentration, which reduces the device eficiency. In this work, Cd1-xZnxS thin films with low Zn concentrations were analyzed. The effect of the addition of different molar Zn concentrations to the reaction mixture on the growth mechanism of Cd1-xZnxS thin films and the influence of these mechanisms on structural, optical and morphological properties of the films has been studied. Cd1-xZnxS thin films were synthesized by chemical bath deposition using an ammonia-free alkaline solution. Microstructural analysis by X-ray diffraction showed that all deposited films grew with hexagonal structure and crystallite sizes decreased as the Zn concentration in the film increased. Optical measurements indicated a high optical transmission between 75% and 90% for wavelengths above the absorption edge. Band gap value increased from 2.48 eV to 2.62 eV, and the refractive index values for Cd1-xZnxS thin films decreased as the Zn increased. These changes in films and properties are related to a modification in growth mechanism of the Cd1-xZnxS thin films, with the influence of Zn(OH)2 formation being more important as Zn in solution increases., SCOPUS: ar.j, info:eu-repo/semantics/published

A major drawback of metal additive manufacturing is the surface roughness of the manufactured components. This is even more critical when complex lattice structures are considered. An octet-truss lattice structure was fabricated by Electron Beam Melting. A chemical post-treatment was applied in order to improve the surface quality. The morphology of individual struts was characterized experimentally by high resolution X-ray tomography after different chemical etching times. The chemical etching treatment was found to be beneficial as it decreases significantly the occurrence of surface defects. The evolution of the elastic mechanical properties with the etching time was determined by FFT computations directly applied to the 3D volume of the struts. A cellular automaton based model was also developed in order to predict the morphological evolution of the as-built strut during etching. The model enables to predict the kinetics of dissolution as well as the evolution of the surface defects and the elastic mechanical properties of the samples. It also enables to determine the required etching time to firstly remove powder particles stuck to the surface and secondly to reduce the plate-pile like defect occurrence., SCOPUS: ar.j, info:eu-repo/semantics/published

The size dependent fracture strength and fracture mechanisms of polycrystalline silicon films are investigated by analyzing a wide range of specimen lengths and widths with thicknesses equal to 240 and 40 nm. An on-chip method is used to deform the films and to determine the strength. The strength increases with decreasing external surface area. The thinnest films exhibit the lowest strength and a weaker size effect. The crack path changes from transgranular to intergranular with decreasing thickness. These results are related to differences in microstructure and surface roughness characteristics of the films as controlled by the fabrication process and thickness., SCOPUS: ar.j, info:eu-repo/semantics/published

This paper deals with mean square state estimation over sensor networks with a fixed topology. Attention is focused on designing local stationary state estimators with a general structure while accounting for the network communication topology. Two estimator design approaches are proposed. One is based on the observability Gramian, and the other on the controllability Gramian. The computation of the estimator state-space matrices is recast as off-line convex optimization problems and requires the system asymptotic stability and global knowledge of the network topology. Convergence of the estimation error variance is ensured at each network node and a guaranteed performance in the mean square sense is achieved. The proposed approaches are also extended for designing robust filters to handle polytopic-type parameter uncertainty., SCOPUS: ar.j, info:eu-repo/semantics/published

Sustainability in higher education is a growing field of reflection and practice, yet integrating sustainability and academic research (as a distinct pillar of academia – next to education, societal service and campus operations) is still considered a challenge. This study: i. Proposes a conceptualization of sustainability in academic research based on an explorative literature review; ii. Suggests a range of actions fostering sustainability in academic research based on an expert-based workshop; and iii. Critically reflects on a case study entailing a university-wide sustainability transition initiative. The proposed conceptualization of sustainability in academic research is shaped by the diversity of perspectives in the scientific literature and focuses on the degree of disciplinary integration within and outside academia. Actions to foster sustainability in academic research include actions with regard to: i. Research funding; ii. Research & career evaluation; iii. Research organization; iv. Capacity building and v. policy. The emerging range of possible actions as designed by research managers as well as the early experience of individual higher education institutions in experimenting with sustainability in academic research contribute to the translation of sustainability into a range of tangible and realistic research actions for higher education institutions., SCOPUS: ar.j, info:eu-repo/semantics/published

Well-optimized intelligent control of products and systems with a substantial energy and/or consumables demand can allow to reduce the use phase impact of these devices and systems significantly. However, depending on the usage patterns and their variability, the system efficiency and tardiness, as well as comfort-impact avoidance trade-off considerations, the effectiveness of such strategies can greatly differ. This contribution describes models for and analyses the sensitivity of the achievable impact reduction with respect to these factors, thus facilitating use phase oriented eco-design decision making. The observations are illustrated by means of a zone heating and a laser cutting machine case study., SCOPUS: ar.j, info:eu-repo/semantics/published

Previously determined degradation mechanisms of a model polymer compound, poly(vinyl acetate) (PVAc), blended with two different flame retardants, ammonium poly(phosphate) (APP) and melamine isocyanurate (MIC), were used for reaction rate parameter optimization using a kinetic modelling and simulation software. Rate parameters for all different decomposition reactions were established for inert and oxidative conditions, giving insight into all interactions between flame retardants and polymer. Analyzing kinetic data, it was found that APP catalyzes the deacetylation reaction of PVAc, independent from the mixing ratio, and has a higher catalyzing effect than oxygen. Down to ten parts APP per one hundred parts of PVAc, APP is also a very efficient crosslinker with PVAc upon decomposition. MIC on the other hand acts in two ways: as heat-sink flame retardant during deacetylation and charring of the polymer, whereas during this charring step, another part of MIC crosslinks with PVAc. Simulations using kinetic parameter sets of PVAc/MIC and PVAc/APP blends showed that MIC and APP interact independently with PVAc when both flame retardants are mixed together into PVAc. A very efficient flame retarded composite is as such obtained at low loading levels., SCOPUS: ar.j, info:eu-repo/semantics/published

NiOx thin films approximately 300 nm thick were deposited on indium tin oxide (ITO)-coated glass substrates by magnetron sputtering. Their electrochromic properties were tested in a 1 M potassium hydroxide (KOH) aqueous solution and in a 1 M lithium perchlorate dissolved in propylene carbonate (LiClO4-PC) anhydrous electrolyte, respectively. The evolution of the lattice structure, surface morphology, chemical composition, optical transmittance modulation, cyclic voltammograms, inserted and extracted charge capacities of NiOx thin films was evaluated as a function of the number of cycles. Even though the cyclic voltammograms and the charge capacity present a similar variation tendency during 1000 cycles, significant differences between cycling in 1 M KOH and 1 M LiClO4-PC were observed. In 1 M KOH, X-ray diffraction (XRD) results showed that the lattice planes (111) and (200) had a larger shift toward higher diffraction angles, and SEM images exhibited that cracks emerged more quickly from the surface of NiOx thin film during the cycling process. More importantly, the optical modulation varying from 58.5% to 32.9% presented an obvious degradation after 1000 cycles. On the contrary, in 1 M LiClO4-PC, NiOx thin films presented a better cyclic durability and a stable optical modulation approximating 41%. In a second step, an all-solid-state complementary electrochromic device with an ITO/WO3/LiClO4-PC-PMMA/NiOx/ITO structure was assembled. The device had an average optical modulation of 51.7% in the visible region and an excellent cyclic durability (over 50,000 times). In situ optical transmittance spectra showed that, in the initial cycles, the response time was 4.5 s for the coloring process and 1.7 s for the bleaching process. After 1000 cycles, both were delayed to 5.0 s and 2.9 s, respectively. In addition, open circuit memory of the device was characterized by the optical transmittance variation plotted against time after disconnection of the external circuit., SCOPUS: ar.j, info:eu-repo/semantics/published

We present a combined analytical approach and numerical study on the stability of a ring bound to an annular elastic substrate, which contains a circular cavity. The system is loaded by depressurizing the inner cavity. The ring is modeled as an Euler-Bernoulli beam and its equilibrium equations are derived from the mechanical energy which takes into account both stretching and bending contributions. The curvature of the substrate is considered explicitly to model the work done by its reaction force on the ring. We distinguish two different instabilities: periodic wrinkling of the ring or global buckling of the structure. Our model provides an expression for the critical pressure, as well as a phase diagram that rationalizes the transition between instability modes. Towards assessing the role of curvature, we compare our results for the critical stress and the wrinkling wavelength to their planar counterparts. We show that the critical stress is insensitive to the curvature of the substrate, while the wavelength is only affected due to the permissible discrete values of the azimuthal wavenumber imposed by the geometry of the problem. Throughout, we contrast our analytical predictions against finite element simulations., SCOPUS: ar.j, info:eu-repo/semantics/published

In search of a cost effective cathode material for microbial fuel cells (MFCs), graphite was chemically treated with H3PO4, HNO3, ZnCl2, urea or melamine, and the effect of chemical activations on the oxygen reduction reaction (ORR) was examined. The performance of MFCs with activated graphite as the catalyst-free cathodes was then compared to those with untreated graphite. Results suggested that H3PO4 and HNO3 activations could improved ORR, showing the highest ORR activity in graphite treated with 14.62 M H3PO4 for 12 h at 30-50 °C. MFCs with H3PO4 and HNO3 activated graphite cathodes generated maximum power densities (7.9 W/m3 and 6.5 W/m3, respectively) 2.4 and 1.8 times higher than that of the untreated control. The chemical activation process involves just a simple immersion step, and it does not require heating, electrochemical process or expensive chemicals. Therefore, it is a highly cost-effective approach to improve the performance of MFCs. We recommend an in-situ modification of graphite cathodes in scale-up MFCs with either H3PO4 or HNO3 to optimize MFCs' various industrial applications., SCOPUS: ar.j, info:eu-repo/semantics/published

Wind power technology is now a reliable electricity production system. It presents an economically attractive possible solution for the continuously increasing energy demand of Lebanon. However, the stochastic behavior of wind speed leads to significant disharmony between wind energy production and electricity demand. Hence, the prospect of creating a combined wind-hydro energy station is found to be a vital issue. This paper is an attempt to analyze the design of a pumping station and the performance of a hybrid wind-hydro power plant, in two dams in Lebanon (Quaraoun and Chabrouh), in order to choose the most suitable dam to store the energy surplus produced by wind power at night. An evaluation of the amount of water that could be pumped in both dams and the energy that could be produced from the stored electricity surplus are carried out in this paper, in order to select the most suitable dam to implement the hydro pumped storage power plant and store the electricity surplus. It is shown that the energy that could be produced in the dam of Chabrouh varies between 17 MWh and 698 MWh, while in the dam of Quaraoun is between 17 MWh and 768 MWh. An analysis of the cost of the energy produced by wind turbines per kWh and the produced water per m3 are carried out in this paper as well., SCOPUS: ar.j, info:eu-repo/semantics/published

Jatropha was identified as a potential feedstock to satisfy off-grid and on-grid energy solutions. However, the potential has been questioned due to agronomic frustrations, the lack of an organized value chain and heavy criticism on biofuels due to emissions triggered by land use change (LUC). To contribute to the realistic integration of Jatropha in rural development, this article proposes a modeling approach to probe the feasibility of Jatropha-based electrification in rural Africa and the layout of such a value chain.A multi-component modeling setup is presented, featuring a life cycle inventory, spatial modeling and the optimization model, OPTIMASS. In this modeling setup, OPTIMASS is parameterized with data regarding the global warming potential and the potential location of each operation in the value chain including cultivation sites and related LUC emissions. This enables OPTIMASS to spatially design the Jatropha-based on-grid and off-grid electrification value chain (i.e. cultivation, transport and storage, biofuel production and electricity generation) in Southern Mali with minimal GWP to reach 10% substitution of fossil fuels for Jatropha in electricity production for a current and two future electricity demand scenarios.Analysis of the optimization results demonstrates that emissions from transporting the oil are lower than LUC emissions per harvestable seed of other sites. Finally, it can be said that harnessing the entirety of the Jatropha value chain is crucial to make it GWP competitive relative to fossil fuels in which the location of plantations is crucial to attain low LUC-related emissions and viable yields., SCOPUS: ar.j, iiTSE, info:eu-repo/semantics/published

The influence of an interfacial heat release and heat consumption on nonlinear convective flows, developed under the joint action of buoyant and thermocapillary effects in a laterally heated two-layer system with periodic boundary conditions, is investigated. Regimes of traveling waves and modulated traveling waves have been obtained. It is found that rather intensive heat sinks at the interface can lead to the change of the direction of the waves' propagation., SCOPUS: ar.j, info:eu-repo/semantics/published

We have discovered a peculiar behaviour of the interface between two miscible liquids placed in a finite-size container under horizontal vibration. We provide evidence that periodic wave patterns created by the Kelvin-Helmholtz instability and Faraday waves simultaneously exist in the same system of miscible liquids. We show experimentally in reduced and normal gravity that large-scale frozen waves yield Faraday waves with a smaller wavelength on a diffusive interface. The emergence of the different scale patterns observed in the experiments is confirmed numerically and explained theoretically., SCOPUS: ar.j, info:eu-repo/semantics/published

For the first time a cyclone evaporator has been designed and tested with perfectly wetting liquids in two separate experiments on condensation, at variable gravity conditions during parabolic flights. Two liquids (FC-72 and HFE-7100), with surface tension coefficient of 12-15 mN/m, were used in the experiments. The concept of the liquid retention by the centrifugal force and the specific design of the walls were validated in the first series of experiments in isothermal conditions. The liquid behaviour inside the experimental cell in weightlessness is reported and discussed for the variable liquid volume (100-200 ml) inside the cell and the rotating velocity of the magnetic stirrer inside the evaporator (0-900 rpm). The data obtained during the isothermal case were used to improve the design of the evaporation cell for the non-isothermal case, tested during a second parabolic flight campaign. In this second experiment, both the power (1.8-16 W) and rotational velocity of the magnetic stirrer (0-250 rpm) were varied. For a fluid charge of 100 ml the same fluid never left the evaporator in all tests performed with rotation of the magnetic stirrer. The vapour pressure in the cell increased during microgravity period. It was found that the stabilization of vapour pressure after transition to microgravity decreases with an increase in the rotational speed of the magnetic stirrer. We conclude that the cyclone evaporator is also an ideal candidate for those systems that have to work in microgravity and rely on pool boiling, because the cyclone chops large bubbles that would otherwise occupy the whole evaporator space and reduce the heat-transfer rate., SCOPUS: ar.j, info:eu-repo/semantics/published

This paper presents structural optimization of piezoelectric modal sensors and actuators for plate structures. Unlike for beam structures, the design of constant thickness, distributed modal transducers for plate structures is not straightforward. In this work the design problem for plate structures is tackled as a (multi-material) structural optimization problem where the optimal distribution of the piezoelectric material as well as its polarization profile have to be found. For the solution a parametric level set method is proposed. This allows simultaneous shape and topology optimization. In contrast to most conventional level set approaches we choose a parametric level set method that does not involve the direct solution of the Hamilton-Jacobi equation using numerical methods such as the finite difference method. The optimization problem is directly posed in terms of the parameters of the parameterization and is solved with an evolutionary algorithm., SCOPUS: ar.j, info:eu-repo/semantics/published

In this article, a unified framework is introduced for robust structural topology optimization for 2D and 3D continuum and truss problems. The uncertain material parameters are modelled using a spatially correlated random field which is discretized using the Karhunen-Loève expansion. The spectral stochastic finite element method is used, with a polynomial chaos expansion to propagate uncertainties in the material characteristics to the response quantities. In continuum structures, either 2D or 3D random fields are modelled across the structural domain, while representation of the material uncertainties in linear truss elements is achieved by expanding 1D random fields along the length of the elements. Several examples demonstrate the method on both 2D and 3D continuum and truss structures, showing that this common framework provides an interesting insight into robustness versus optimality for the test problems considered., SCOPUS: ar.j, info:eu-repo/semantics/published

β-metastable titanium alloys with high strength to Young's modulus ratio have been developed by different authors aiming their use as biomaterials for hard tissue replacement. However, it is not easy to combine low elastic modulus with high mechanical strength. In this work, a β-Ti alloy (Ti-10Mo-20Nb) was produced by arc-melting, then homogenized, cold swaged and aged in order to obtain fine α-Ti precipitates in a β-Ti matrix. The microstructures were characterized by transmission electron microscopy and X-ray diffraction. Mechanical properties characterization was based on Vickers microhardness tests and Young's modulus measurements. The cold swaged material subjected to an ageing treatment at 500 °C for 4 h showed the highest hardness/Young's modulus ratio, associated to very fine α phase precipitates in a β-Ti matrix., SCOPUS: cp.j, info:eu-repo/semantics/published

Beta titanium alloys were developed for biomedical applications due to the combination of its mechanical properties including low elasticity modulus, high strength, fatigue resistance, good ductility and with excellent corrosion resistance. With this perspective a metastable beta titanium alloy Ti-12Mo-13Nb was developed with the replacement of both vanadium and aluminum from the traditional alloy Ti-6Al-4V. This paper presents the microstructure, mechanical properties of the Ti-12Mo-13Nb hot swaged and aged at 500 °C for 24 h under high vacuum and then water quenched. The alloy structure was characterized by X-ray diffraction and transmission electron microscopy. Tensile tests were carried out at room temperature. The results show a microstructure consisting of a fine dispersed α phase in a β matrix and good mechanical properties including low elastic modulus. The results indicate that Ti-12Mo-13Nb alloy can be a promising alternative for biomedical application., SCOPUS: cp.j, info:eu-repo/semantics/published

Atmospheric flow simulations in engineering practice - such as simulations of pollutant dispersion, wind load on buildings, wind climate of urban areas - are fairly sensitive to the inlet boundary conditions. The objective of the present paper is to introduce suitable profiles for velocity and turbulent quantities, which do not only fit the measured vertical distributions, but also guarantee the overall consistency of the turbulence model. If the latter aspect is not verified, the inlet profiles deteriorate rapidly within the computational domain, leading to unrealistic wind profiles in the area of interest.Considering that, in general, the atmospheric boundary layer profiles might not satisfy the equations describing an unperturbed atmospheric boundary layer, turbulence models need to be corrected to guarantee the overall consistency of the approach. Former studies have addressed such a problem via the introduction of source terms in the transport equations of kinetic energy and turbulent dissipation rate, to guarantee consistency between the turbulence model and inlet profiles. In the present study, the formulation is further extended to improve the numerical stability of the approach as well as the realistic character of the produced profiles., SCOPUS: ar.j, info:eu-repo/semantics/published

Peritoneal metastasis is life threatening and is the result of an extensive communication between disseminated cancer cells, mesothelial cells and cancer-associated fibroblasts (CAF). CAFs secrete extracellular matrix (ECM) proteins creating a receptive environment for peritoneal implantation. Considering cancer as an ecosystem may provide opportunities to exploit CAFs to create biomimetic traps to deceive and redirect cancer cells. We have designed microparticles (MP) containing a CAF-derived ECM-surface that is intended to compete with natural niches. CAFs were encapsulated in alginate/gelatine beads (500-750μm in diameter) functionalised with a polyelectrolyte coating (MP[CAF]). The encapsulated CAFs remain viable and metabolically active (≥35 days), when permanently encapsulated. CAF-derived ECM proteins are retained by the non-biodegradable coating. Adhesion experiments mimicking the environment of the peritoneal cavity show the selective capture of floating cancer cells from different tumor origins by MP[CAF] compared to control MP. MP[CAF] are distributed throughout the abdominal cavity without attachment to intestinal organs and without signs of inflammatory reaction. Intraperitoneal delivery of MP[CAF] and sequential removal redirects cancer cell adhesion from the surgical wound to the MP[CAF], delays peritoneal metastasis formation and prolongs animal survival. Our experiments suggest the use of a biomimetic trap based on tumor-environment interactions to delay peritoneal metastasis., SCOPUS: ar.j, info:eu-repo/semantics/published

It is well established that 718 superalloy exhibits brittle intergranular cracking when deformed under tension at temperatures above 600°C. This embrittlement effect is related with grain boundary penetration by oxygen (Oxygen Assisted Intergranular Cracking - OAIC). Simultaneously, impacting on its mechanical properties, the precipitation of coherent γ′ and γ″ phases occur above 650°C and Dynamic Strain Aging (DSA) occurs in the temperature range between 200 and 800°C. Although literature indicates that OAIC is the mechanism that controls mechanical properties at high temperatures, its interactions with DSA and precipitation are still under discussion. The objective of this work is to investigate the interactions between the embrittlement phenomena (OAIC and DSA) and the hardening mechanism of γ′ and γ″ precipitation on the mechanical properties of an annealed 718 superalloy. Tensile tests were performed at a strain rate of 3.2 × 10-4 s-1 under secondary vacuum, in temperatures ranging from 200 to 800°C. Fracture surfaces were observed by scanning electron microscopy (SEM) and precipitation by transmission electron microscopy (TEM). The effect of DSA and precipitation on the strength and of OAIC on the ductility was verified., SCOPUS: ar.j, info:eu-repo/semantics/published

Water splitting using sunlight is an important process for future energy supplies. TiO2 is widely used as photoanode, but has a limited light absorption range. Here, ternary Ti-Mo-Ni mixed oxide nanotube arrays were fabricated via electrochemical anodization of Ti-Mo-Ni alloy in formamide-ethylene glycol-based electrolytes, to extend the absorption range into visible light. The electrolyte composition and anodization time were found crucial in controlling the structural features of the nanotubes. By tuning these parameters, arrays of thin walled (∼9 nm) and ∼8 μm long nanotubes were obtained. In photoelectrochemical water splitting, the mixed oxides showed incident photon conversion efficiency (IPCE) up to 65% for wavelengths from 300 nm to 450 nm. This enhancement in the IPCE of the mixed oxide nanotubes, compared with pure titania, can be related to synergistic effects of Mo and Ni oxides as well as to the unique structural properties of the fabricated mixed oxide nanotubes., SCOPUS: ar.j, info:eu-repo/semantics/published

The origin of the extragalactic γ-ray background (EGB) has been debated for some time. The EGB comprises the γ-ray emission from resolved and unresolved extragalactic sources, such as blazars, star-forming galaxies, and radio galaxies, as well as radiation from truly diffuse processes. This Letter focuses on the blazar source class, the most numerous detected population, and presents an updated luminosity function and spectral energy distribution model consistent with the blazar observations performed by the Fermi-Large Area Telescope (LAT). We show that blazars account for 50% of the EGB photons (>0.1 GeV), and that Fermi-LAT has already resolved ∼70% of this contribution. Blazars, and in particular hard-spectrum sources such as BL Lacs, are responsible for most of the EGB emission above 100 GeV. We find that the extragalactic background light, which attenuates blazars' high-energy emission, is responsible for the high-energy cutoff observed in the EGB spectrum. Finally, we show that blazars, star-forming galaxies, and radio galaxies can naturally account for the amplitude and spectral shape of the background in the 0.1-820 GeV range, leaving only modest room for other contributions. This allows us to set competitive constraints on the dark matter annihilation cross section., SCOPUS: ar.j, info:eu-repo/semantics/published

Flameless combustion is able to provide high combustion efficiency with low NOx and soot emissions. The present work aims at investigating the role of closure sub-models for the modelling of a flameless furnace, as well as the main NO formation paths. Among the different turbulence models that were tested, modified k-εprovides the best agreement with the experimental data, especially for temperature measurements. Reynolds stress model leads to smaller deviation for radial velocity predictions. Since in flameless combustion regime the turbulence-chemistry interaction as well as the kinetic mechanism play a fundamental role, the Eddy Dissipation Concept (EDC), coupled with four different kinetic schemes (JL, KEE58, GRI 2.11 and GRI 3.0) was considered. The GRI 2.11 and KEE58 mechanisms perform better, thus confirming the necessity of turbulence/chemistry interaction models accounting for finite-rate chemistry when flameless combustion is studied. As far as NO emissions are concerned, the N2O intermediate NO mechanism is found to play a major role, while thermal NO formation mechanism is not as relevant as in traditional combustion regime. An assessment of the uncertainty related to the choice of boundary conditions as well as to the choice of the parameters of the physical models is also performed. Finally the operation characteristics (such as the recirculation rate and the location of the reaction zone) of the furnace are evaluated., SCOPUS: ar.j, info:eu-repo/semantics/published

The present study deals with the microstructure and mechanical properties of intercritically rolled TRIP-assisted multiphase steels. It is shown that the occurrence of the TRIP effect in a recovered ferritic matrix brings about an improved strength-ductility balance with respect to a fully recrystallised ferrite matrix. On the other hand, the intercritical deformation does not influence the austenite transformation rate during straining at room temperature. The improvement of the mechanical properties results from the interactions between the transformation strain and the recovered ferrite., SCOPUS: ar.j, info:eu-repo/semantics/published