The high-temperature phase of NdP5O14

Monoclinic neodymium-pentaphosphate NdP₅O₁₄ (space group $\text{P}\text{2}{}_1\text{c}$) suffers a reversible phase transition at 115°C. The high-temperature structure belongs to the orthorhombic space group Pncm. This phase is a new structure which has not been previously observed in the rare-earth pentaphosphates. We explain the lattice transition by a displacive transformation. A Guinier-Lenné high-temperature camera is used for the X-ray detection of this transition. With the measured θ-values we determined the lattice parameters of both structures.     

Stress intensity factors for an edge cracked circular bar in tension and bending

The variation of the stress intensity factor along the front of an edge crack in an elastic bar of circular cross-section is determined. Both straight and circular-arc crack fronts are modelled using a three-dimensional tinite element analysis of the tension and bending problems. Results are obtained for crack depth to bar diameter ratios ranging from 0.1 to 0.594, in the case of cracks with straight fronts, and from 0.175 to 0.6, in the case of cracks with curved fronts.

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Résumé On détermine la variation du facteur d'intensité de contraintes sur le front d'une fissure latérale dans un barreau élastique de section circulaire. On modélise des points de fissure droits et à arc circulaire à l'aide d'une analyse par éléments finis à trois dimensions des problèmes en traction et en flexion. Les résultats sont obtenus pour des rapports de profondeur de fissure à diamètre de barreaux compris entre 0.1 et 0.594, pour des fissures a front droit, et entre 0,175 et 0,6 dans le cas de fissures à front incurvé.

     

The design of large hot melt extruders

A method is proposed for the rational design of large single screw extruders for processing hot molten thermoplastics, which is based on a theoretical analysis of polymer flow. A typical design study for an homogenizer for low density polyethylene is examined in detail, with particular attention being paid to the effects of screw diameter, length and channel depths on melt temperatures, degree of mixing, residence time, machine cost and power consumption. Owing to the physical properties of polymer melts, heat transfer by conduction is very inefficient. Barrel cooling serves to draw power from the motor rather than heat from the polymer, and in order to achieve a given level of mixing there is a largely unavoidable increase in melt temperature.     

A two-dimensional bibliometric index reflecting both quality and quantity

Scientometrics - We propose a two-dimensional bibliometric index that strikes a balance between quantity (as measured by the number of publications of a researcher) and quality (as measured by the...     

Process selection for sanitation systems and wastewater treatment in refugee camps during disaster-relief situations

Disasters and emergency situations can disrupt the provision of clean water and hygienic sanitation, which are crucial for maintaining public health. Excreta disposal in emergencies has often been a low priority and this has led to the provision of unsuitable on‐site sanitation systems in urban areas. A decision algorithm for the selection of adequate excreta‐disposal solutions suitable for different disaster‐relief scenarios is presented. The special requirements of a wastewater treatment system for deployment during an emergency are discussed and a semi‐centralised system is recommended to serve 5000 refugees under a range of assumed loading conditions. Twenty‐three aerobic, anaerobic and natural systems are considered for secondary treatment and a process‐selection matrix is presented based around 16 evaluation criteria. A system layout is developed based around several sanitation facilities including sedimentation tanks connected to a centralised roughing trickling filter and an activated sludge unit, which provides optimal performance against the evaluation criteria. The system provides the required treatment performance in an easy‐to‐deploy, low‐cost compact installation.     

Interactions between elevated CO2 and warming could amplify DOC exports from peatland catchments

Peatlands export more dissolved organic carbon (DOC) than any other biome, contributing 20% of all terrestrial DOC exported to the oceans. Both warming and elevated atmospheric CO2 (eCO2) can increase DOC exports, but their interaction is poorly understood. Peat monoliths were, therefore, exposed to eCO2, warming and eCO2 + warming (combined). The combined treatment produced a synergistic (i.e., significant interaction) rise in DOC concentrations available for export (119% higher than the control, interaction P < 0.05) and enriched this pool with phenolic compounds (284%). We attribute this to increased plant inputs, coupled with impaired microbial degradation induced by competition with the vegetation for nutrients and inhibitory phenolics. Root biomass showed a synergistic increase (407% relative to the control, P < 0.1 only), while exudate inputs increased additively. Phenol oxidase was suppressed synergistically (58%, interaction P < 0.1 only) and beta-glucosidase (27%) additively, while microbial nutritional stress increased (51%) additively. Such results suggest intensified carbon exports from peatlands, with potentially widespread ramifications for aquatic processes in the receiving waters.     

The phenomenon of decision oscillation: A new consequence of pathology in game trees

Random minimaxing studies the consequences of using a random number for scoring the leaf nodes of a full width game tree and then computing the best move using the standard minimax procedure. Experiments in Chess showed that the strength of play increases as the depth of the lookahead is increased. Previous research by the authors provided a partial explanation of why random minimaxing can strengthen play by showing that, when one move dominates another move, then the dominating move is more likely to be chosen by minimax. This paper examines a special case of determining the move probability when domination does not occur. Specifically, we show that, under a uniform branching game tree model, whether the probability that one move is chosen rather than another depends not only on the branching factors of the moves involved, but also on whether the number of ply searched is odd or even. This is a new type of game tree pathology, where the minimax procedure will change its mind as to which move is best, independently of the true value of the game, and oscillate between moves as the depth of lookahead alternates between odd and even.