Abstract
The questions of how the bulk of the Universe’s visible mass emerges and how it is manifest in the existence and properties of hadrons are profound, and probe the heart of strongly ...interacting matter. Paradoxically, the lightest pseudoscalar mesons appear to be key to a further understanding of the emergent mass and structure mechanisms. These mesons, namely, the pion and kaon, are the Nambu–Goldstone boson modes of quantum chromodynamics (QCD). Unravelling their partonic structure and the interplay between emergent and Higgs-boson mass mechanisms is a common goal of three interdependent approaches—continuum QCD phenomenology, lattice-regularised QCD, and the global analysis of parton distributions—linked to experimental measurements of hadron structure. Experimentally, the anticipated electron–ion collider will enable a revolution in our ability to study pion and kaon structures, accessed by scattering from the ‘meson cloud’ of the proton through the Sullivan process. With the goal of enabling a suite of measurements that can address these questions, we examine key reactions that identify the critical detector-system requirements needed to map tagged pion and kaon cross-sections over a wide range of kinematics. The excellent prospects for extracting pion structural, functional, and form-factor data are outlined, and similar prospects for kaon structures are discussed in the context of a worldwide programme. The successful completion of the programme outlined herein will deliver deep, far-reaching insights into the emergence of pions and kaons, their properties, and their role as QCD’s Goldstone boson modes.
The effect of textured surfaces in hydrodynamic bearings is assessed using a mass-conserving numerical analysis that allows for arbitrary geometry and multiple regions of cavitation. The texture ...investigated consists of regularly spaced rectangular pockets through an (infinitely) long linearly convergent or parallel bearing. This arrangement leads to nine independent non-dimensional parameters including operating conditions. The effectiveness of texture at improving load support and reducing friction over a corresponding plain bearing is described in relation to these parameters and the important interaction between parameters is highlighted. The beneficial or detrimental effect of texture is explained in terms of the fundamental mechanisms of hydrodynamic pressure generation including inlet suction.
► We determine nine parameters which describe a model long textured slider bearing. ► The way in which the parameters alter the effectiveness of texture is investigated. ► Parameters interact strongly; this may lead to reversal of performance. ► Cavitation alters the response to parameter changes in a critical, non-smooth way.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The influence of EIVC (early inlet valve closure) on emissions, fuel economy and exhaust gas temperature of a turbocharged, 4 cylinder common rail direct injection diesel engine has been investigated ...and compared with the influence of deactivating two cylinders. IVC (inlet valve closing) timings were set at up to 60 CA (crank angle) degrees earlier than the production setting of 37° ABDC for the engine. At the earliest timing, effective compression ratio was reduced from 15.2:1 to 13.7:1. The effects on emissions were significant only for EIVC settings at least 40 CA degrees earlier than the production setting, and were sensitive to engine load. At 2 bar BMEP (brake mean effective pressure) and fixed levels of NOx, soot emissions were reduced but CO (carbon monoxide) and HC (hydrocarbon) increased unless fuel rail pressure was reduced. With increasing load, soot reduction diminished and was negligible at 6 bar BMEP; CO and HC emissions deteriorated further. At all conditions, EIVC raised exhaust gas temperature by >50 °C; the effect on fuel economy was negligible or a fuel economy penalty. Comparisons indicate cylinder deactivation is the more effective strategy for reducing engine-out emissions of HC and CO and raising exhaust gas temperature under light load operating conditions.
•Data taken from a 4 cylinder, 2.2l TDI, at NOx levels around 1 g/kWh and light loads.•Both EIVC (early inlet valve closing) and cylinder disablement penalize fuel economy.•CO and HC are reduced by cylinder disablement and raised by EIVC.•Soot is reduced by EIVC and raised at loads >3 bar BMEP by cylinder disablement.•Cylinder disablement increases exhaust gas temperature more than EIVC.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
X-ray absorption spectroscopy (XAS) was used to characterize vanadium (V) and chromium (Cr) environments in low activity nuclear waste (LAW) glasses synthesized under a variety of redox conditions. V
...2O
5 was added to the melt to improve sulfur incorporation from the waste; however, at sufficiently high concentrations, V increased melt foaming, which lowered melt processing rates. Foaming may be reduced by varying the redox conditions of the melt, while small amounts of Cr are added to reduce melter refractory corrosion. Three parent glasses were studied, where CO–CO
2 mixtures were bubbled through the corresponding melt for increasing time intervals so that a series of redox-adjusted-glasses was synthesized from each parent glass. XAS data indicated that V and Cr behaviors are significantly different in these glasses with respect to the cumulative gas bubbling times: V
4+/V
total ranges from 8 to 35%, while Cr
3+/Cr
total can range from 15 to 100% and even to population distributions including Cr
2+. As Na-content decreased, V, and especially, Cr became more reduced, when comparing equivalent glasses within a series. The Na-poor glass series show possible redox coupling between V and Cr, where V
4+ populations increase after initial bubbling, but as bubbling time increases, V
4+ populations drop to near the level of the parent glass, while Cr becomes more reduced to the point of having increasing Cr
2+ populations.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Sulfur can be the waste-loading limiting constituent for vitrification of sulfur-bearing radioactive wastes due to low solubility in silicate melts. Methods to improve sulfur loading would benefit ...from improved understanding of the structural aspects of sulfur incorporation in borosilicate and other glasses. To this end, sulfur XANES spectra were collected for eight crystalline standards and twenty-four glasses, including borosilicate, phosphate, and borate compositions. Spectra for the standards show a systematic energy shift of the sulfur K-edge from 2469 to 2482 eV, as sulfur valence increases from 2− (in sulfides) to 6+ (in sulfates). Most crucible glasses investigated have simple edges near 2482 eV that indicate sulfur in the form of sulfate only. Other glasses, some synthesized under reducing conditions, have complicated edges, indicating sulfate, sulfite, and more reduced species that may include S, S–S doublets, or short polysulfide chains. Sulfide species (S
2−) were not dominant in any of the samples over the range of redox conditions investigated. These results indicate that sulfur incorporation is considerably more complex than would be suggested by the conventional interpretation of the redox-dependence of sulfur solubility, which considers only sulfate and sulfide species. Raman data indicate that several of the glasses investigated are not homogeneous with regard to all sulfur species.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
An experimental investigation has been carried out to compare the indicated performance and heat release characteristics of
a Dl diesel engine at compression ratios of 18.4:1 and 15.4:1. The ...compression ratio was changed by modifying the piston bowl
volume; the bore and stroke were unchanged, and the swept volume was nominally 500cc. The engine is a single cylinder variant
of modern design which meets Euro 4 emissions requirements. Work output and heat release characteristics for the two compression
ratios have been compared at an engine speed of 300 rev/min and test temperatures of 10, −10 and −20° C. A more limited comparison
has also been made for higher speeds representative of cold idle at one test temperature (−20°C). The reduction in compression
ratio generally produces an increase in peak specific indicated work output at low speeds; this is attributable to a reduction
in blowby and heat transfer losses and lower peak rates of heat release increasing cumulative burn. High compression however
extends the range of injection timings where useful work output can be generated. The coefficient of variation of work output
increases with increasing engine speed and decreasing loading, especially at low compression ratio, giving rise to potentially
poor idling quality.
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BFBNIB, NUK, PNG, UL, UM, UPUK
Abstract
The work reported in this paper details an experimental study of the effects of cooling system hardware changes on diesel engine emissions and fuel economy. Experiments were performed under ...both steady state and transient conditions and complemented by statistical assessments. Techniques for assessing the thermal integrity of the engine as a consequence of such changes are also presented. An experimental design was constructed to investigate the effect of water pump throttling, coolant flow control through the oil cooler, and the adoption of a pressure resistive thermostat (PRT). Use of these thermal controls offers a useful trade-off between NO
x
and fuel economy, with a saving of around 3 per cent in b.s.f.c. for a 10 per cent NO
x
penalty at low load, where NO
x
output is less of a concern. However, these benefits were not observed during drive cycle testing.
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