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[en] Highlights: •A novel high temperature solar thermal energy storage system is presented. •The system employs a molten metal oxide for energy storage. •The system can achieve a high energy density of 5 GJ/m3. •Oxygen can be also produced as a valuable by-product. -- Abstract: A novel cycle, the chemical looping of molten copper oxide, is proposed with the thermodynamic potential to achieve sensible, latent and thermochemical heat storage with an energy density of approximately 5.0 GJ/m3, which is approximately 6 times more than the 0.83 GJ/m3 of molten salt. This cycle avoids the technical challenges associated with the application of solid materials (especially multivalent metals) for thermochemical energy storage such as attrition, agglomeration, particle breakage and structural change in successive reduction and oxidation reactions, although it brings alternative challenges associated with the handling of molten metal oxides. A process path for the concept is proposed based on data from the literature for the equilibrium composition of copper and oxygen at different temperatures and gas phase pressures. The process has been modelled with codes developed in MATLAB. The calculations estimate that from the total input concentrated solar thermal energy into the system, about 73% can be absorbed, while the rest is lost through re-radiation heat loss. Furthermore, it is estimated that of the absorbed heat, approximately 95% is stored, while the rest leaves the system as high temperature gas. The calculations also predict that approximately 20% of the inlet solar thermal energy is partitioned as the chemical storage, which is also employed for oxygen production. Also reported is the sensitivity to the effects of key operating parameters.
[en] Highlights: • SAPG with concentrating and non-concentrating collectors has been compared. • Non-concentrating collectors could be superior to concentrating collectors in SAPG. • Using non-concentrating collectors is more effective in low latitude. - Abstract: The preheating of the feedwater in a Regenerative Rankine Cycle power plant with solar thermal energy, termed Solar Aided Power Generation, is an efficient method to use low to medium temperature solar thermal energy. Here, we compared the use of medium temperature (200–300 °C) energy from concentrating solar collectors (e.g. parabolic trough collectors) to displace the extraction steam to high temperature/pressure feedwater heaters with that from low temperature (100–200 °C) non-concentrating solar collectors (e.g. evacuated tube collectors) to displace the extraction steam to low temperature/pressure feedwater heaters of the power plant. In this paper, the in terms of net land based solar to power efficiency and annual solar power output per collector capital cost of a Solar Aided Power Generation using concentrating and non-concentrating solar collectors has been comparted using the annual hourly solar radiation data in three locations (Singapore; Multan, Pakistan and St. Petersburg, Russia). It was found that such a power system using non-concentrating solar collectors is superior to concentrating collectors in terms of net land based solar to power efficiency. In some low latitude locations e.g. Singapore, using non-concentrating solar collectors even have advantages of lower solar power output per collector capital cost over using the concentrating solar collectors in an SAPG plant.
[en] We estimate the long-duration gamma-ray burst (LGRB) progenitor rate using our recent work on the effects of environmental metallically on LGRB formation in concert with supernovae (SNe) statistics via an approach patterned loosely off the Drake equation. Beginning with the cosmic star formation history, we consider the expected number of broad-line Type Ic events (the SNe type associated with LGRBs) that are in low-metallicity host environments adjusted by the contribution of high-metallicity host environments at a much reduced rate. We then compare this estimate to the observed LGRB rate corrected for instrumental selection effects to provide a combined estimate of the efficiency fraction of these progenitors to produce LGRBs and the fraction of which are beamed in our direction. From this we estimate that an aligned LGRB occurs for approximately every 4000 ± 2000 low-metallically broad-lined SNe Ic. Therefore, if one assumes a semi-nominal beaming factor of 100, then only about one such supernova out of 40 produce an LGRB. Finally, we propose an off-axis LGRB search strategy of targeting only broad-line Type Ic events that occur in low-metallicity hosts for radio observation.
[en] Tarsal coalitions are relatively rare diagnoses affecting adolescent patients that typically present with progressive foot pain. Cubed-navicula r coalition, a type of tarsal coalition, is extremely rare with less than 10 reported cases to date. Most prevailing theories reported have described this specific type of coalition as asymptomatic except at specific moments of stress and exercise. The purpose in presenting this case is to demonstrate that cubed-navicula r coalition can be associated with chronic unremitting pain, as in our patient. We present a case of cubed-navicula r fibrocartilaginous coalition in an adolescent patient presenting with chronic foot pain. Furthermore, from an imaging standpoint, radiographic findings are often subtle and radiologists cannot rely on indirect signs such as talar beak in clinching the diagnosis of cubed-navicula r coalition. Instead, abnormal articulation between the cubed and navicula r must be sought
[en] Discrete dislocation dynamics simulations have been generally limited to modeling systems described by isotropic elasticity. Effects of anisotropy on dislocation interactions, which can be quite large, have generally been ignored because of the computational expense involved when including anisotropic elasticity. We present a different formalism of dislocation dynamics in which the dislocations are represented by the deformation tensor, which is a direct measure of the slip in the lattice caused by the dislocations and can be considered as an eigenstrain. The stresses arising from the dislocations are calculated with a fast Fourier transform (FFT) method, from which the forces are determined and the equations of motion are solved. Use of the FFTs means that the stress field is only available at the grid points, which requires some adjustments/regularizations to be made to the representation of the dislocations and the calculation of the force on individual segments, as is discussed hereinafter. A notable advantage of this approach is that there is no computational penalty for including anisotropic elasticity. We review the method and apply it in a simple dislocation dynamics calculation. (paper)
[en] Palladium (Pd) is considered as a possible candidate as catalyst for proton exchange membrane fuel cells (PEMFCs) due to its high activity and affordable price compared to platinum (Pt). However, the stability of Pd is known to be limited, yet still not fully understood. In this work, Pd dissolution is studied in acidic media using an online inductively coupled plasma mass spectrometry (ICP-MS) in combination with an electrochemical scanning flow cell (SFC). Crucial parameters influencing dissolution like potential scan rate, upper potential limit (UPL) and electrolyte composition are studied on a bulk polycrystalline Pd (poly-Pd). Furthermore, a comparison with a supported high-surface area catalyst is carried out for its potential use in industrial applications. For this aim, a carbon supported Pd nanocatalyst (Pd/C) is synthesized and its performance is compared with that of bulk poly-Pd. Our results evidence that the transient dissolution is promoted by three main contributions (one anodic and two cathodic). At potentials below 1.5 VRHE the anodic dissolution is the dominating mechanism, whereas at higher potentials the cathodic mechanisms prevail. On the basis of the obtained results, a model is thereafter proposed to explain the transient Pd dissolution.