Differences In Fundamental Properties Research Articles

Understanding the ignition process and flame structure of conventional and oxygenated fuels under engine relevant conditions – An optical study

Renewably generated synthetic fuels such as poly-oxymethylene ethers (OME) have a significant potential to effectively break the soot-NOX trade-off in compression ignition engines by using exhaust gas recirculation (EGR) to maintain low nitrogen oxide (NOX) emissions while maintaining good efficiency and simultaneously contributing to circular carbon economy. However, owing to the fundamental differences in properties of OME when compared to fossil-based diesel fuels, it is critical to fully understand its ignition and combustion phenomenology to take advantage of this fuel to its utmost potential. In this context, this work outlines the results of a systematic experimental study performed in a heavy-duty, single-cylinder, optical engine probing the spatial and temporal progression of fuel decomposition and ignition behavior of OME when compared to n-dodecane, a diesel-fuel surrogate. Thermodynamic analysis and optical diagnostics techniques including simultaneous HCHO-PLIF and OH-PLIF complemented by high-speed OH* chemiluminescence were employed along with parametric sweeps of intake temperature and EGR dilution rates. OME does not exhibit any observable low temperature heat release irrespective of the ambient oxygen concentration. Differences in the observed diffusive flame structure such as longer flame lift-off length, less pronounced combustion recession, faster premixed burn at ignition (“volumetric” ignition), non-sooting behavior suggest that the inherent presence of fuel-bound oxygen in OME can skew the air-fuel ratio (AFR) distribution within the jet thereby reducing the reliance of combustion on mixing and air entrainment. This leads to rapid late-cycle oxidation leading to shorter combustion duration and favorable combustion phasing. Results also suggest that OME exhibits relatively weak negative temperature coefficient (NTC) behavior, however, the OME fuel-decomposition kinetic-pathways produce significant concentration of HCHO, which might be erroneously interpreted as a product of cool-flames.

Fundamental differences in the properties of red and blue quasars: measuring the reddening and accretion properties with X-shooter

ABSTRACT We have recently found fundamental differences in the radio properties of red quasars when compared to typical blue quasars. In this paper, we use data from the X-shooter spectrograph on the Very Large Telescope, providing spectral coverage from ∼3000–$25\,000\,$ Å, of a sample of 40 red and blue luminous quasars at 1.45 < z < 1.65 to explore the connections between the radio, emission-line, and accretion-disc properties. We fit various dust-extinction curves to the data and find that dust reddening can fully explain the observed colours for the majority of the red quasars in our sample, with moderate extinctions ranging from AV ∼ 0.06–0.7 mag. We confront our spectra with a simple thin accretion-disc model and find this can describe the continua of both the blue and red quasars, once corrected for dust extinction; we also find no significant differences in the accretion properties. We detect ionized outflows in a number of red and blue quasars, but do not find any significant evidence that they are more prevalent in the red quasar population. Overall our findings imply that the radio emission is more closely connected to circumnuclear/ISM opacity rather than accretion disc or outflow differences.

Differences in fundamental and functional properties of HPMC co-processed fillers prepared by fluid-bed coating and spray drying

This study aimed to develop novel co-processed tablet fillers based on the principle of particle engineering for direct compaction and to compare the characteristics of co-processed products obtained by fluid-bed coating and co-spray drying, respectively. Water-soluble mannitol and water-insoluble calcium carbonate were selected as representative fillers for this study. Hydroxypropyl methylcellulose (HPMC), serving as a surface property modifier, was distributed on the surface of primary filler particles via the two co-processing methods. Both fundamental and functional properties of the products were comparatively investigated. The results showed that functional properties of the fillers, like flowability, compactibility, and drug-loading capacity, were effectively improved by both co-processing methods. However, fluid-bed coating showed greater advantages over co-spray drying in some aspects, which was mainly attributed to the remarkable differences in some fundamental properties of co-processed powders, like particle size, surface topology, and particle structure. For example, the more irregular surface and porous structure induced by fluid-bed coating could contribute to better compaction properties and lower lubricant sensitivity due to the increasing contact area and mechanical interlocking between particles under pressure. More effective surface distribution of HPMC during fluid-bed coating was also a contributor. In addition, such a porous agglomerate structure could also reduce the separation of drug and excipients after mixing, resulting in the improvement in drug loading capacity and tablet uniformity. In summary, fluid-bed coating appears to be more promising for co-processing than spray drying in some aspects, and co-processed excipients produced by it have a great prospect for further investigations and development.

New power production options for biomass and cogeneration

Power production and combined heat and power production from biomass is a form of renewable energy that has gained significance and is expected to grow steadily over the coming years. Because of fundamental differences in properties between biomass and traditional fossil fuels for power generation, biomass power plants source their fuel mostly locally and their capacity is restricted by local availability. Biomass conversion technologies can be broadly classified as thermochemical and biochemical. Thermochemical processes include combustion, gasification, and pyrolysis and are mostly suitable for dry biomass fractions. Wet biomass fractions are most commonly converted using biochemical processes, such as fermentation and anaerobic digestion. Integration with power production systems depends on the intermediate energy carrier produced (steam, gas) and is usually achieved through conventional or organic Rankine cycles or reciprocating internal combustion engines. Despite being considered as a carbon‐neutral energy source, power production from biomass can have environmental consequences, which depend on the feedstock type, conversion process, and the type of flue gas–cleaning equipment installed. WIREs Energy Environ 2015, 4:471–485. doi: 10.1002/wene.163This article is categorized under: Bioenergy > Science and Materials Bioenergy > Systems and Infrastructure Bioenergy > Climate and Environment

Seeking footprints of the primeval Universe in dwarf galaxies

AbstractWe present the star formation histories (SFHs) of four isolated dwarf galaxies, Cetus, Tucana, LGS-3, and Phoenix, as a function of galactocentric radius. Our results suggest that beyond some distance from the center, there are no significative differences in fundamental properties of these galaxies, such as the star formation rate (SFR) or age-metallicity relation (AMR). The stellar content of this region would be composed of old (≳ 10.5 Gyr) metal-poor stars only. In the innermost regions, dwarf galaxies appear to have formed stars during time intervals which duration varies from galaxy to galaxy. This extended star formation produces the dichotomy between dwarf spheroidal (dSph) and dwarf Transition (dTr) galaxy types.

Defect and surface asperity dependent yield during contact loading of an organic molecular single crystal

The onset of plastic deformation was investigated using nanoindentation in single crystals of the explosive cyclotrimethylene trinitramine (RDX). Cleavage and habit planes were tested revealing a range of yielding behaviors. Smooth habit planes of unprocessed single crystals exhibited distinct yield points near the theoretical shear strength; planes produced by cleavage yielded at lower applied stresses. Cumulative probability distributions of maximum shear stresses at yield were used to illustrate the representative yielding behavior for samples prepared by the different methods. A statistically significant difference was observed for cleavage and habit planes. This suggested that structural defects, such as dislocations from growth and sample preparation, were being probed and nanoindentation can be used to correlate the mechanical response of organic molecular crystals with defect density. This capability may help explain the observed range of measurement differences in fundamental properties in this class of materials, such as sensitivity to the initiation of detonation in explosives, and disparate tablet integrity and stability responses in polymorphs of some pharmaceutical materials.

English

Airframe applications of composite material structures have been investigated for a number of years. With the availability of advanced fibrous reinforcements of high specific strengths and moduli, airframe weight reductions of about 40 percent were frequently predicted. However, as actual development programs were completed it became apparent that weight savings from increased strength and stiffness could be easily offset by weight losses resulting from inefficient joining of these materials. Eliminating structural joints and cutouts (which are special joint cases if stressed covers are used) is impractical in present-day aircraft because of the requirements for manufacturing breaks, assembly and equipment access, and replacement of damaged structures. Optimum joint proportions have evolved from essentially invariant relationships between tension, shear, and bearing strengths (and moduli) of structural metals. Because of the fundamental differences in properties caused by the anisotropy and inhomogeneity of composites, design policies that were evolved for metal joints cannot be applied directly to composites. The basic strength and modulus relationships on which metal joint technology is based are variables in the composite structural design process. Thus, the design of optimum joints in reinforced composites must start in the selection and arrangement of the basic material constituents. The objective of this project is to create a 3D spacer fabric composite by simple hand layup technique and conduct mechanical tests on them by joining them in different methods. Thus, to find the joint that gives the highest strength. Also, to evaluate the failure modes of the specimens and predict the best joint configuration for the material under consideration. Three methods are followed for achieving viz. Mathematical method, Analytical Method and Experimental Method.