Enhanced Sulfur Tolerance of Ceria-Promoted NO x Storage Reduction (NSR) Catalysts: Sulfur Uptake, Thermal Regeneration and Reduction with H2(g)

SO _x uptake, thermal regeneration and the reduction of SO _x via H₂(g) over ceria-promoted NSR catalysts were investigated. Sulfur poisoning and desulfation pathways of the complex BaO/Pt/CeO₂/Al₂O₃ NSR system was investigated using a systematic approach where the functional sub-components such as Al₂O₃, CeO₂/Al₂O₃, BaO/Al₂O₃, BaO/CeO₂/Al₂O₃, and BaO/Pt/Al₂O₃ were studied in a comparative fashion. Incorporation of ceria significantly increases the S-uptake of Al₂O₃ and BaO/Al₂O₃ under both moderate and extreme S-poisoning conditions. Under moderate S-poisoning conditions, Pt sites seem to be the critical species for SO _x oxidation and SO _x storage, where BaO/Pt/Al₂O₃ and BaO/Pt/CeO₂/Al₂O₃ catalysts reveal a comparable extent of sulfation. After extreme S-poisoning due to the deactivation of most of the Pt sites, ceria domains are the main SO _x storage sites on the BaO/Pt/CeO₂/Al₂O₃ surface. Thus, under these conditions, BaO/Pt/CeO₂/Al₂O₃ surface stores more sulfur than that of BaO/Pt/Al₂O₃. BaO/Pt/CeO₂/Al₂O₃ reveals a significantly improved thermal regeneration behavior in vacuum with respect to the conventional BaO/Pt/Al₂O₃ catalyst. Ceria promotion remarkably enhances the SO _x reduction with H₂(g).     

High‐Efficiency PbS Quantum‐Dot Solar Cells with Greatly Simplified Fabrication Processing via “Solvent‐Curing”

PbS quantum‐dot (QD) solar cells are promising candidates for low‐cost solution‐processed photovoltaics. However, the device fabrication usually requires ten more times film deposition and rinsing steps, which is not ideal for scalable manufacturing. Here, a greatly simplified deposition processing is demonstrated by replacing methanol with acetonitrile (ACN) as the rinsing solvent. It is discovered that ACN can effectively “cure” the film cracks generated from the volume loss during the solid‐state ligand‐exchange process, which enables the deposition of thick and dense films with much fewer deposition steps. Meanwhile, due to the aprotic nature of ACN, fewer trap states can be introduced during the rinsing process. As a result, with only three deposition steps for the active layer, a CPVT‐certified 11.21% power conversion efficiency is obtained, which is the highest efficiency ever reported for PbS QD solar cells employing a solid‐state ligand‐exchange process. More importantly, the simple film‐deposition processing provides an opportunity for the future application of QDs in low‐cost printing of optoelectronic devices.     

Strongly Coupled 2D Transition Metal Chalcogenide-MXene-Carbonaceous Nanoribbon Heterostructures with Ultrafast Ion Transport for Boosting Sodium/Potassium Ions Storage

Combining with the advantages of two-dimensional(2D)nanomaterials,MXenes have shown great potential in next gener-ation rechargeable batteries.Similar with othe...     

Ignition temperature of coal. 2. Binary coal mixtures

The ignition temperature of binary coal mixtures is determined. The mixtures contain coal of different metamorphic development, in various proportions. Systematic deviation of the actual ignition temperature from the values calculated on the basis of the sum rule is observed; the actual ignition temperature is lower. Statistical analysis shows that these deviations are significantly nonrandom. A formula is derived for predicting the ignition temperature of 50 : 50 binary mixtures on the basis of the ignition temperatures of their components. It appears that, in the mixtures, the component with the lower ignition temperature is ignited first. The energy liberated is consumed in the ignition of the less flammable component. That results in ignition of the mixture as a whole.     

Rapid hardening cement-gypsum composites for shotcreting on the base of bulgarian raw materials Part II. Structural Investigations, Tests in Production Conditions, conclusions

The results obtained by X-ray, calorimetric and electron microscopy investigations are discussed. The hydration process and structure formation of the proposed rapid hardening composites for shotcreting on the basis of combined binders is outlined. The relation between the strength and deformability indices and the structural characteristics is analyzed. The results obtained from these tests carried out in production conditions -- widening of the tunnel -- are also analyzed. Conclusions about the application for shotcreting of the offered composites are drawn.     

Chaotic time series prediction with employment of ant colony optimization

In this study, the novel method to predict chaotic time series is proposed. The method employs the ant colony optimization paradigm to analyze topological structure of the attractor behind the given time series and to single out the typical sequences corresponding to the different part of the attractor. The typical sequences are used to predict the time series values. The method was applied to time series generated by the Lorenz system, the Mackey–Glass equation, and weather time series as well. The method is able to provide robust prognosis to the periods comparable with the horizon of prediction.     

High Doping Density Schottky Diodes in the 3MM Wavelength Cryogenic Heterodyne Receiver

The paper describes a 3mm cryogenic mixer receiver using high doping density (“room-temperature”) Schottky diodes. The measured equivalent noise temperature T_eq of the diodes is 109 K at 20 K, which is much higher than the T_eq of the low doping density (“cryogenic”) diodes. In spite of this, the double-sideband (DSB) noise temperature of the cryogenic receiver developed is 55 K at 110 GHz, owing to the low conversion loss of the mixer and ultra-low noise of the PHEMT IF amplifier. This is the lowest noise temperature ever reported for a Schottky diode mixer receiver. The results obtained are useful for the development of submm receivers in which high doping density Schottky diodes are used.     

The H2 role in the synergistic phenomenon in selective NO x reduction by propane over a mechanical mixture of oxide catalysts

The synergistic phenomenon observed in NO _x selective reduction by propane over the mechanical mixture of commercial NTK and Ni-Cr-oxide catalysts is explained by the distinctions in the reaction mechanism over the individual mixture components. Hydrogen formed over Ni-Cr-oxide catalyst in propane oxidation significantly increases the rate of interaction between surface nitrate and acetate complexes. Besides, there is an additional input made by the route of NO _x reduction over NTK in the presence of H₂.