Characterization of string cavitation in large-scale Diesel nozzles with tapered holes

The cavitation structures formed inside enlarged transparent replicas of tapered Diesel valve covered orifice nozzles have been characterized using high speed imaging visualization. Cavitation images obtained at fixed needle lift and flow rate conditions have revealed that although the conical shape of the converging tapered holes suppresses the formation of geometric cavitation, forming at the entry to the cylindrical injection hole, string cavitation has been found to prevail, particularly at low needle lifts. Computational fluid dynamics simulations have shown that cavitation strings appear in areas where large-scale vortices develop. The vortical structures are mainly formed upstream of the injection holes due to the nonuniform flow distribution and persist also inside them. Cavitation strings have been frequently observed to link adjacent holes while inspection of identical real-size injectors has revealed cavitation erosion sites in the area of string cavitation development. Image postprocessing has allowed estimation of their frequency of appearance, lifetime, and size along the injection hole length, as function of cavitation and Reynolds numbers and needle lif

Direct Band Gap Gallium Antimony Phosphide (GaSb\u3csub\u3ex\u3c/sub\u3eP\u3csub\u3e1-x\u3c/sub\u3e) Alloys

Here, we report direct band gap transition for Gallium Phosphide (GaP) when alloyed with just 1–2 at% antimony (Sb) utilizing both density functional theory based computations and experiments. First principles density functional theory calculations of GaSbxP1−x alloys in a 216 atom supercell configuration indicate that an indirect to direct band gap transition occurs at x = 0.0092 or higher Sb incorporation into GaSbxP1−x. Furthermore, these calculations indicate band edge straddling of the hydrogen evolution and oxygen evolution reactions for compositions ranging from x = 0.0092 Sb up to at least x = 0.065 Sb making it a candidate for use in a Schottky type photoelectrochemical water splitting device. GaSbxP1−x nanowires were synthesized by reactive transport utilizing a microwave plasma discharge with average compositions ranging from x = 0.06 to x = 0.12 Sb and direct band gaps between 2.21 eV and 1.33 eV. Photoelectrochemical experiments show that the material is photoactive with p-type conductivity. This study brings attention to a relatively uninvestigated, tunable band gap semiconductor system with tremendous potential in many fields

Cyprus' image—a sun and sea destination—as a detrimental factor to seasonal fluctuations. Exploration into motivational factors for holidaying in Cyprus

Cyprus is established as a summer destination. To aid the destination in developing its winter season as well, this research uses a qualitative inductive approach to explore the tourists’ current image of the island and their motivations of visiting it. The research indicates that the current image, which essentially portrays Cyprus as a sun-and-sea destination is thought to dissuade tourists from perceiving the island as a year-round destination. Nonetheless, increasing the pull factors of the destination through the development of unique special interest products can help in extending the tourism season as well as broaden its narrow image

On the formation of string cavitation inside fuel injectors

The formation of vortex or ‘string’ cavitation has been visualised in the flow upstream of the injection hole inlet of an automotive-sized optical diesel fuel injector nozzle operating at pressures up to 2,000 bar. Three different nozzle geometries and three-dimensional flow simulations have been employed to describe how, for two adjacent nozzle holes, their relative positions influenced the formation and hole-to-hole interaction of the observed string cavitation vortices. Each hole was shown to contain two counter-rotating vortices: the first extending upstream on axis with the nozzle hole into the nozzle sac volume and the second forming a single ‘bridging’ string linked to the adjacent hole. Steady-state and transient fuel injection conditions were shown to produce significantly different nozzle-flow characteristics with regard to the formation and interaction of these vortices in the geometries tested, with good agreement between the experimental and simulation results being achieved. The study further confirms that the visualised vortices do not cavitate themselves but act as carriers of gas-phase components within the injector flow

Interaction Between Superconducting and Ferromagnetic Order Parameters in Graphite-Sulfur Composites

The superconductivity of graphite-sulfur composites is highly anisotropic and associated with the graphite planes. The superconducting state coexists with the ferromagnetism of pure graphite, and a continuous crossover from superconducting to ferromagnetic-like behavior could be achieved by increasing the magnetic field or the temperature. The angular dependence of the magnetic moment m(alpha) provides evidence for an interaction between the ferromagnetic and the superconducting order parameters.Comment: 11 pages, 4 figures, to be published in Phys. Rev.

Orthorhombicity mixing of s- and d- gap components in YBa2Cu3O7YBa_2Cu_3O_7 without involving the chains

Momentum decoupling develops when forward scattering dominates the pairing interaction and implies tendency for decorrelation between the physical behavior in the various regions of the Fermi surface. In this regime it is possible to obtain anisotropic s- or d-wave superconductivity even with isotropic pairing scattering. We show that in the momentum decoupling regime the distortion of the $CuO_2$ planes is enough to explain the experimental reports for s- mixing in the dominantly d-wave gap of $YBa_2Cu_3O_7$. In the case of spin fluctuations mediated pairing instead, a large part of the condensate must be located in the chains in order to understand the experiments.Comment: LATEX file and 3 Postscript figure

Vortex formation and recirculation zones in left anterior descending artery stenoses: computational fluid dynamics analysis

Flow patterns may affect the potential of thrombus formation following plaque rupture. Computational fluid dynamics (CFD) were employed to assess hemodynamic conditions, and particularly flow recirculation and vortex formation in reconstructed arterial models associated with ST-elevation myocardial infraction (STEMI) or stable coronary stenosis (SCS) in the left anterior descending coronary artery (LAD). Results indicate that in the arterial models associated with STEMI, a 50% diameter stenosis immediately before or after a bifurcation creates a recirculation zone and vortex formation at the orifice of the bifurcation branch, for most of the cardiac cycle, thus allowing the creation of stagnating flow. These flow patterns are not seen in the SCS model with an identical stenosis. Post-stenotic recirculation in the presence of a 90% stenosis was evident at both the STEMI and SCS models. The presence of 90% diameter stenosis resulted in flow reduction in the LAD of 51.5% and 35.9% in the STEMI models and 37.6% in the SCS model, for a 10 mmHg pressure drop. CFD simulations in a reconstructed model of stenotic LAD segments indicate that specific anatomic characteristics create zones of vortices and flow recirculation that promote thrombus formation and potentially myocardial infarction

Social representations and community attitudes towards spring breakers

Social representations theory has been adopted for explaining tourism impacts and local attitudes. However, its usefulness in segmenting local population in terms of their attitudes towards specific types of tourists has not been tested. This study identifies the attitudes of local people towards spring break, a North American young tourist phenomenon in the context of the Mexican beach resort of Acapulco. Although residents perceive an increase in alcohol consumption, drug use, noise and litter during the spring break season, they largely recognise economic benefits and are thus generally supportive for the phenomenon. Based on these attitudes, three clusters were identified: spring break supporters (identified by their high appreciation of spring break benefits), ambivalents (who are uncertain about both benefits and costs) and realistics (characterised by recognising both benefits and costs). The main contribution of this study lies in the confirmation of the usefulness of social representations theory in explaining residents’ attitudes towards a very specific type of tourists whose hedonist behaviours are a common characteristic

Applications of microalgal biofilms for wastewater treatment and bioenergy production

Background: Microalgae have shown clear advantages for the production of biofuels compared with energy crops. Apart from their high growth rates and substantial lipid/triacylglycerol yields, microalgae can grow in wastewaters (animal, municipal and mining wastewaters) efficiently removing their primary nutrients (C, N, and P), heavy metals and micropollutants, and they do not compete with crops for arable lands. However, fundamental barriers to the industrial application of microalgae for biofuel production still include high costs of removing the algae from the water and the water from the algae which can account for up to 30–40% of the total cost of biodiesel production. Algal biofilms are becoming increasingly popular as a strategy for the concentration of microalgae, making harvesting/dewatering easier and cheaper. Results: We have isolated and characterized a number of natural microalgal biofilms from freshwater, saline lakes and marine habitats. Structurally, these biofilms represent complex consortia of unicellular and multicellular, photosynthetic and heterotrophic inhabitants, such as cyanobacteria, microalgae, diatoms, bacteria, and fungi. Bioflm #52 was used as feedstock for bioenergy production. Dark fermentation of its biomass by Enterobacter cloacae DT-1 led to the production of 2.4 mol of H2/mol of reduced sugar. The levels and compositions of saturated, monosaturated and polyunsaturated fatty acids in Bioflm #52 were target-wise modifed through the promotion of the growth of selected individual photosynthetic inhabitants. Photosynthetic components isolated from different biofilms were used for tailoring of novel biofilms designed for (i) treatment of specifc types of wastewaters, such as reverse osmosis concentrate, (ii) compositions of total fatty acids with a new degree of unsaturation and (iii) bio-focculation and concentration of commercial microalgal cells. Treatment of different types of wastewaters with biofilms showed a reduction in the concentrations of key nutrients, such as phosphates, ammonia, nitrates, selenium and heavy metals. Conclusions: This multidisciplinary study showed the new potential of natural bioflms, their individual photosynthetic inhabitants and assembled new algal/cyanobacterial bioflms as the next generation of bioenergy feedstocks which can grow using wastewaters as a cheap source of key nutrient

Aspects of sustainability in the destination branding process: a bottom-up approach

The concept of sustainability is based on the premise that the inhabitants of a destination should be involved in the way that destination is managed and promoted. At the same time, the literature of place branding emphasizes the important role of local stakeholders in the creation of a true and reliable place brand. In fact, the process of developing a destination brand begins with the aim of shaping the identity of a destination; what the destination stands for. The sustainable dimensions of the destination branding process are explored, while focus groups and structured questionnaires are used to evaluate the usefulness of projection techniques in the process of building a brand identity. It seems that the use of the personification technique could work as an effective destination positioning exercise and as an alternative proposal to the outdated clichés used in tourism promotion