Solar-thermal driven drying technologies for large-scale industrial applications: State of the art,gaps, and opportunities

Research and Innovation (R&I) on Large-scale Industrial Solar-thermal driven Drying technologies (LISDs) is one of the strategies required to transition to a low-carbon energy future. The objective for this work is to guide future R&I on LISDs by defining the state of the art, gaps, and opportunities. To provide a high-level perspective on the current state of solar drying research, results are presented from an analysis of the content relevant to LISDs found in 45 solar drying Review Articles published in journals over the past 25 years. A conclusion is that most of the existing solar drying research is not focused on LISDs. To build-on these existing 45 solar drying Review Articles, results are presented from an analysis of 30 Original Research Articles with significant content relevant to LISDs published over the past 5 years. A gap is identified in coupling existing or slightly modified solar thermal collectors with existing or slightly modified industrial drying technologies to create indirect LISDs. To facilitate formulating new coupling strategies, the drying characteristics most relevant to this coupling are described and four fundamental classes of industrial dryer technologies are defined based on the underlying heat transfer mechanism, which then impacts the appropriate collector choice. At their most fundamental level, many of the technologies needed to couple solar collectors and industrial dryers to create novel indirect LISDs are not unique to indirect LISDs, but rather can be generalized across a wide range of Solar Heat for Industrial Processes (SHIP) applications, and integration issues are discussed at a more fundamental SHIP level. The technical and economic characteristics of 19 existing LISDs installations throughout the world are presented, and potential and emerging areas discussed.     

Development of a Surface‐Active Coating for Promoted Gas Hydrate Formation

This work deals with the influences of surface‐active coatings made by silanization with an increasing hydrophobicity on methane hydrate formation in view of induction times, gas uptake, and rate of gas consumption. Hydrate formation was performed in a stirred pressure autoclave under stationary and transient conditions in presence of different coatings made from diverse silanes. With increasing carbon chain length of the silanes, promoting effects were observed while using stationary formation conditions.     

Organic Photovoltaic Sensors for Photocapacitive Stimulation of Voltage‐Gated Ion Channels in Neuroblastoma Cells

Organic semiconductors are emerging as promising candidates for novel electrically self‐sufficient photovoltaic prosthetics for neurostimulation, especially for restoration of light sensitivity in degenerate retina. Considering future applications, it is essential to gain fundamental insight into the signaling mechanisms at the organic photosensor–electrolyte–neuron interface. Particularly, targeting voltage‐gated ion channels by a pure photocapacitive stimulation is a preferred therapeutic approach as it avoids redox reactions involved in Faradaic charge injection. The present study investigates whether single neuroblastoma (N2A) cells, grown on a photosensor based on a small molecular squaraine:fullerene photoactive layer blend, optionally covered with silicon dioxide, can be activated by photocapacitive stimulation. Indeed, upon pulsed illumination, a rapid transient photocurrent strongly depolarizes the membrane potential and subsequently activates fast‐responding voltage‐gated sodium channels. The dielectric top coating on the organic layer ensures sufficient capacitive charge injection efficiency while maintaining the rapid response of the device. Due to the high irradiance level required for photocapacitive stimulation, another slower, independent, and unintended, nonelectrical signaling pathway is identified. This activates voltage‐gated potassium channels, presumably by photothermal effects. The present study provides the basis for further improvements on standalone photovoltaic neurostimulating platforms based on organic photoactive layers.     

V-FPGAs: Increasing Performance with Manual Placement,Timing Extraction and Extended Timing Modeling

Journal of Signal Processing Systems - Virtual FPGAs (V-FPGAs) are used as vendor-independent virtualization layers, to retrofit features which are not available on the host FPGA and to prototype...     

Chloride-induced steel corrosion in alkali-activated fly ash mortar: Increased propensity for corrosion initiation at defects

Chloride contents at the steel–mortar interface that initiate steel corrosion were determined for carbon steel in alkali-activated fly ash mortar for three different exposure conditions: exposure to 1 M NaCl solution; leaching in deionized water and then exposure to 1 M NaCl solution; and leaching in deionized water, aging in air at 20°C and natural CO₂ concentration, and then exposure to 1 M NaCl solution. For comparison, a Portland cement mortar, exposed to 1 M NaCl solution, was studied. The median values of the corrosion-initiating chloride contents (average over the full length of the rebar) in the alkali-activated fly ash mortar varied between 0.35 and 1.05 wt% Cl with respect to binder, consistently lower than what was obtained for the Portland cement mortar, but with no clear trend regarding the exposure conditions. For most of the alkali-activated fly ash mortar specimens, preferential corrosion at the connection between the working electrode and the external measurement setup was observed, while preferential corrosion did not occur for the Portland cement mortar. Scanning electron microscopy and auxiliary experiments in synthetic solutions indicated that this behavior was caused by inhomogeneities at the steel–mortar interface in the alkali-activated mortar, likely due to its peculiar rheological properties in the fresh state.     

Finite-time Consensus of Leader-following Multi-agent Systems with Multiple Time Delays over Time-varying Topology

This paper studies the finite-time consensus of leader-following multi-agent systems with multiple time delays over time-varying topology. The finite-time     

Effect of target peak power density on the phase formation,microstructure evolution,and mechanical properties of Cr2AlC MAX-phase coatings

The applicability of Cr₂AlC MAX-phases as protective coatings in energy conversion or aerospace applications requires a dense, single-phase structure. Therefore, we study the effect of target power density and substrate bias on phase formation, microstructure evolution, and mechanical properties of Cr₂AlC coatings utilizing direct current (DCMS) and high-power pulsed magnetron sputtering (HPPMS). Generally, HPPMS results in coatings with superior density and hence larger elastic moduli compared to DCMS, indicating that ion bombardment by ionized film-forming species is beneficial. However, decreasing the substrate bias to ?200 V for DCMS and ?100 V for HPPMS favors the ion bombardment induced formation of the disordered (Cr,Al)₂C_x solid solution. It is evident that there is an optimum moderate ion energy for the formation of dense Cr₂AlC coatings. Too low energy results in the formation of under-dense coatings. Too high energy yields the formation of (Cr,Al)₂C_x in addition to Cr₂AlC.     

Mechanical reliability of Ce0.8Gd0.2O2−δ-FeCo2O4 dual phase membranes synthesized by one-step solid-state reaction

Ce_0.8Gd_0.2O_2−δ-FeCo₂O₄ composites are attractive candidate materials for high-purity oxygen generation providing robust chemical stability. Aiming for future industrial applications, a feasible solid-state reaction process with one thermal processing step was used to synthesize 50 wt% Ce_0.8Gd_0.2O_2−δ:50 wt% FeCo₂O₄ and 85 wt% Ce_0.8Gd_0.2O_2−δ:15 wt% FeCo₂O₄ composites. Mechanical reliabilities of the sintered membranes were assessed based on the characterized mechanical properties and subcritical crack growth behavior. In general, the fracture strengths of as-sintered membranes were reduced by tensile residual stresses and microcracks. In particular, the enhanced subcritical crack growth behavior, which leads to limited stress tolerance and high failure probability after a 10-year operation, was evaluated in more detail. Further materials and processing improvements are needed to eliminate the tensile stress and microcracks to warrant a long-term reliable operation of the composites.     

ZnO-based single crystal-polycrystal structures for piezotronic applications

Electrostatic potential barriers at doped ZnO-ZnO interfaces can be modified by stress-induced polarization charges. This concept was enhanced by preparing ZnO-based single crystal-polycrystal-single crystal structures by diffusion bonding. Increasing time for epitaxial solid-state transformation results in structures with a decreasing thickness of residual polycrystalline material in between two well-oriented single crystals. Microstructural and electrical analysis quantifies the influence of high-temperature treatment during epitaxial growth on the stress sensitivity of the prepared structures. The orientation of the single crystals is defined to maximize the interaction between stress-induced polarization charges and the potential barriers at doped ZnO-ZnO interfaces. With decreasing thickness of residual polycrystalline material, the percentage of grain boundaries with favorably aligned polarization vectors is increased resulting in a higher stress sensitivity. This effect is compensated by an adverse effect of the high-temperature treatment on the initial potential barrier height. Hence, a maximum in stress sensitivity can be observed for intermediate times of epitaxial growth. The prepared structures close the gap between the varistor piezotronics based on bulk ceramics with random orientation of the polarization vector and the bicrystal piezotronics with perfect orientation of the polarization vector, demonstrating the capability of microstructural engineering for varistor-based piezotronic devices.     

Kinetics of the glass transition of styrene-butadiene-rubber: Dielectric spectroscopy and fast differential scanning calorimetry

The glass transition is relevant for performance definition in rubber products. For extrapolation to high-frequency behavior, time–temperature superposition is usually assumed, although most complex rubber compounds might be outside of its area of validity. Fast differential scanning calorimetry (FDSC) with cooling rates up to 1500 K/s and broadband dielectric spectroscopy (BDS) with frequencies up to 20 MHz are applied here to directly access both kinetics and dynamics of glass formation in a wide frequency range. For the first-time, the relation between the thermal vitrification and the dielectric relaxation is studied on vulcanized styrene-butadiene rubber, showing that both cooling rate and frequency dependence of its glass transition can be described by one single Vogel-Fulcher-Tammann-Hesse equation. The results indicate the validity of the Frenkel-Kobeko-Reiner equation. Another focus is the sample preparation of vulcanized elastomers for FDSC and BDS as well as the temperature calibration below 0°C.