Variation Of Relative Density Research Articles

Experimental investigation of the conditions at which the collapse line coincides with the critical state line

The conditions at which the collapse line coincides with the critical state line were investigated by means of a new ring shear device. Natural and artificially constituted sands were tested in undrained conditions to evaluate their responses to variations in relative density. The collapse and critical state lines merged in specimens at the critical density in which the shear resistance and pore pressure briefly reached a condition of zero rate of change and remained momentarily constant and equal. At a given normal stress, the friction angle at the phase transformation was equal to the friction angle at the steady state in specimens at the critical density. At densities below the critical density, the specimens exhibited purely contractive behaviour; above the critical density, the specimens’ behaviour was defined by three distinct stages of deformation of phase transformation, peak and steady states. A comparison of the friction angle at the phase transformation, steady state and threshold state in all of the soils revealed only slight differences.

Relative density of host-seeking ticks in different habitat types of south-western Slovakia.

Ixodes ricinus is a vector of microbial pathogens of medical and veterinary importance in Europe. Recently, increasing abundance of ticks has been observed in urban and suburban areas. The aim of this study was to investigate the tick species composition and examine correlations between local environmental variables and the relative density of host-seeking I. ricinus in two habitat types. Questing ticks were collected along six 100m(2) transects in urban/suburban locations of Bratislava town, and in a non-fragmented deciduous forest in the Small Carpathians Mountains (south-western Slovakia) during 2011-2013. In total, 6015 I. ricinus were collected (3435 and 2580 in the urban/suburban and natural habitat, respectively), out of which over 80% were nymphs. Haemaphysalis concinna comprised 1.3% of the tick collections. Peak I. ricinus nymph and adult host-seeking activities were registered in April-June. Spatial and temporal variation in tick relative density and differences in the subadult/adult ratio were observed between habitats and between locations within the same habitat type. The relative density of questing I. ricinus nymphs correlated negatively with altitude, geographical aspect and saturation deficit in a 64-day period comprising the 8-day period including the date of tick sampling and previous 56days. No significant correlation was found between roe deer density and questing nymph density. The study revealed the presence of abundant I. ricinus populations in green areas of Bratislava, suggesting a risk of exposure of town dwellers and domestic and companion animals to potentially infected ticks.

Effect of Ga3+ substitution on the microwave dielectric properties of 0.67CaTiO3–0.33LaAlO3 ceramics

0.67CaTiO3–0.33La(Al1−xGax)O3 (0≤x≤0.4) (CTLAG) ceramics with pure perovskite structure were prepared by a conventional two-step solid-state reaction process. The effect of Ga3+ substitution for Al3+ on the microwave dielectric properties of the ceramics was subsequently investigated. As Ga content increased, the ionic polarizability increased and led to an increase of the dielectric constant (εr). Meanwhile, both the tolerance factor (t) of CTLAG ceramics and A-site bond valence were considered to have effect on the temperature coefficient of the resonant frequency (τf) with the increase of Ga content. Results also showed that the quality factor (Q×f ) varied with increasing Ga3+ content because of not only intrinsic factor but also extrinsic factors such as the bimodal grain size distribution, the variation of relative density, and the packing fraction. Excellent microwave dielectric properties with εr≈45.81, Q×f≈34,152GHz, and τf≈3.09ppm/°C were achieved for 0.67CaTiO3–0.33La(Al0.9Ga0.1)O3 ceramics sintered at 1420°C for 4h.

Near-infrared extinction with discretised stellar colours

Several methods exist to convert near-infrared (NIR) stellar observations into extinction maps. We present a new method based on NIR multiband observations. The method uses a discretised version of the distribution of intrinsic stellar colours. A number of variations of the basic method are tested, and the results are compared to NICER calculations. When photometric errors are large, the results are close to those of NICER method but some advantages can be seen when the distribution of intrinsic colours cannot be described well with a single covariance matrix. A priori information about relative column density variations at sub-beam scales can result in a significant increase in accuracy. The results may be further improved by considering the magnitude dependence of the intrinsic colours. Thus, the new methods are useful mostly when photometric errors are small, the distribution of intrinsic colours is well known, or one has prior knowledge of the small-scale structures.

Effect of organic and inorganic farming conditions on seed storage proteins in soybean based cropping system

A field experiment was conducted during rainy (kharif) and winter (rabi) seasons of 2011-13 to evaluate the effect of application of farmyard manure (FYM), recommended doses of fertilizers (RDF) and their combination on storage protein quality of soybean [Glycine max (L.) Merr.], chickpea (Cicer arietinum L.) and wheat (Triticum aestivum L.) in soybean based cropping system in Punjab. Densitometric analysis of chromatograms revealed significant variations in relative densities of ?' subunit of ?-conglycinin protein in soybean in year 2011 and ? subunit of legumins in chickpea among different treatments whereas other subunits of glycinin and ?-conglycinin in soybean and legumins and vicillins in chickpea did not vary significantly. Maximum value of 11S/7S ratio was observed in treatment with FYM @ 10t ha-1 and FYM @ 10t ha-1+100% RDF in soybean seeds in year 2011 and 2012 respectively and with RDF in chickpea. In wheat, the relative quantity of 55.7, 48.8 and between 11-13 kDa bands increased significantly in combined treatment of organic or inorganic fertilizer than their individual treatments, whereas relative quantity of 40.7 kDa band was significantly low in FYM @10t ha-1 +100% RDF treatment as compared to other treatments. Combined treatments of organic and inorganic fertilizer resulted in presence of additional bands corresponding to 61.4 and 22.5 kDa and disappearance of subunit band corresponding to 16.4 kDa in wheat grains. It is concluded that combined organic and inorganic treatments did not change major storage protein fractions and can be used to improve fertilizer management practices.

Phenotypic Selection Exerted by a Seed Predator Is Replicated in Space and Time and among Prey Species.

Although consistent phenotypic selection arising from biotic interactions is thought to be the primary cause of adaptive diversification, studies documenting such selection are relatively few. Here we analyze 12 episodes of phenotypic selection exerted by a predispersal seed predator, the red crossbill (Loxia curvirostra complex), on five species of pines (Pinus). We find that even though the intensity of selection for some traits increased with the strength of the interaction (i.e., proportion of seeds eaten), the relative strength of selection exerted by crossbills on cone and seed traits is replicated across space and time and among species. Such selection (1) can account for repeated patterns of conifer cone evolution and escalation in seed defenses with time and (2) suggests that variation in selection is less the result of variation intrinsic to pairwise biotic interactions than, for example, variation in relative densities of the interacting species, community context, and abiotic factors.

Assessing the wood quality of interior spruce (Picea glauca × P. engelmannii): variation in strength, relative density, microfibril angle, and fiber length

Abstract A dynamic interrelationship exists among wood density and fiber traits (tracheid length and microfibril angel, MFA) and the ultimate wood strength properties. Moreover, many of the basic fundamental wood attributes are heavily influenced by crown size and architecture. In an attempt to examine this interplay, we thoroughly characterized 60 interior spruce (Picea glauca × P. engelmannii) trees sampled in three age classes from four sites in central British Columbia. Breast height discs were taken, and relative wood density was measured along two radii. Tracheid length was assessed on isolated 5 years increments from pith to bark at breast height for each tree, as was MFA. Segmented regression was used to identify the “juvenile to mature wood” transition point, which revealed transition ages of 9.4 and 15.1 years for wood density and MFA, respectively, while fiber length continued to elongate until near 60 years of age. The flexural properties, modulus of elasticity (MoE) and modulus of rupture (MoR), were also quantified in the 60 individuals and found to be best predicted by V FV, a measure of tree vigor, and not the basic wood attributes. These findings imply that long crowns carrying large amounts of foliage, V FV, negatively impact wood strength in interior spruce.

Comparative analysis of microsatellites in chloroplast genomes of lower and higher plants

Microsatellites, or simple sequence repeats (SSRs), contain repetitive DNA sequence where tandem repeats of one to six base pairs are present number of times. Chloroplast genome sequences have been shown to possess extensive variations in the length, number and distributionof SSRs. However, a comparative analysis of chloroplast microsatellites is not available. Considering their potential importance in generating genomic diversity, we have systematically analysed the abundance and distribution of simple and compound microsatellites in 164 sequenced chloroplast genomes from wide range of plants. The key findings of these studies are (1) a large number of mononucleotide repeats as compared to SSR(2-6)(di-, tri-, tetra-, penta-, hexanucleotide repeats) are present in all chloroplast genomes investigated, (2) lower plants such as algae show wide variation in relative abundance, density and distribution of microsatellite repeats as compared to flowering plants, (3) longer SSRs are excluded from coding regions of most chloroplast genomes, (4) GC content has a weak influence on number, relative abundance and relative density of mononucleotide as well as SSR(2-6). However, GC content strongly showed negative correlation with relative density (R (2)=0.5, P<0.05) and relative abundance (R (2)=0.6, P<0.05) of cSSRs. In summary, our comparative studies of chloroplast genomes illustrate the variable distribution of microsatellites and revealed that chloroplast genome of smaller plants possesses relatively more genomic diversity compared to higher plants.

TEMPORAL VARIATION IN CERATIUM SPP. ABUNDANCE RECORDED IN JAKARTA BAY

Ceratium is non-toxic dinoflagellate which has been regarded as the most common bloom-forming species in the coastal waters around the world. Eventhough research and monitoring on phytoplankton In Jakarta Bay have been conducted for long enough, no specific attention has been given to Ceratium community. Therefore, a research was set up in order to understand the dynamic of Ceratium population and its regulating factors. A serial sampling was conducted in 10 stations during 2009 and 2010. Phytoplankton was sampled in horizontal towing using Kitahara plankton net (80 μm mesh size, 0.5 m mouth diameter and 1m length). Phytoplankton enumeration and identification were done by applying Fraction Method on Sedgewick Rafter Counting Chamber (SRCC). The result showed clear temporal variations in Ceratium absolute density, relative density, relative frequency and importance value. When phytoplankton bloomed in August 2009, no Ceratium bloom observed. High density of Ceratium was observed in November 2009 and May 2010, but it contributed relatively small proportion to phytoplankton as a whole (relative density &lt;1%). Due to its low density and relatively limited distribution in Jakarta Bay, Ceratium may demonstrate limited ecological role to the phytoplankton community.

Convection structure in the solar photosphere at granulation and mesogranulation scales

Vertical structure of the solar photospheric convection is investigated using the profiles of neutral iron line λ ≈ 639.3 nm measured in a non-pertubed region near the center of the solar disk. The observations were carried out using German Vacuum Tower Telescope (Canary Islands, Spain). They are characterized by a high spatial resolution. Spatial-temporal variations of the kinematic and ther-modynamic parameters were reproduced by solving the nonequilibrium inverse radiative transfer problem. The wave motions were eliminated using the k — ω filtration. Spatial variations of temperature, vertical velocity, density, and gas pressure in convective cells are analyzed on the scales of granules (0.5–5 Mm) and mesogranules (5–12 Mm), respectively, at various heights in the solar photosphere (h = −25–500 km). When moving to the upper photosphere layers, the convective structure undergoes the following changes: at heights h = 200–250 km, the temperature inversion occurs, as well as some-times the inversion of convective velocities; at heights h = 50–100 km, the inversion of relative density variations takes place, the relative variations in density and pressure inside convective cells increase with height and become positive in ascending flows and negative in descending flows.

Nanomaterials induced plasma spectroscopy

LIBS of nanosecond pulsed Nd: YAG laser (1064 nm) produced plasma from a set of nanomaterial and bulk targets (ZnO, Fe3O4, Ag2O, TiO2, SiO2 and Al2O3) is investigated at laser fluencies in the range 86 J/cm2 to 2.5 J/cm2. The optical emission spectra is recorded at the gate and time delay of 1 ps after the onset of the plasma in air having a constant spot size of 0.9 mm. Nanoparticle targets revealed salient enhanced spectral emission compared to their bulky counterparts. Atomic spectral lines average and integral radiance tend to decrease exponentially with laser fluence. Yet, plasma parameters measurements indicated unnoticeable variation of relative electron density and temperature. Therefore, self-absorption corrected enhanced spectral emission was plausibly attributed solely to variation in the inherent nanoparticle relative concentrations. Viable explanations were elaborated based on changes in the intrinsic physical properties of the nanomaterial under high power laser irradiation.

A study of direct forging process for powder superalloys

Powder metallurgy (PM) processing of nickel-based superalloys has been used for a wide range of near net-shape fine grained products. In this paper a novel forming process, i.e. direct forging of unconsolidated powder superalloys is proposed. In this process, encapsulated and vacuumed powder particles are heated up to a forming temperature and forged directly at high speed to the final shape, by using a high forming load. Experiments of direct powder forging have been conducted on an upsetting tool-set. Microstructure, relative density and hardness of the formed specimen have been investigated. A finite element model of the direct powder forging process has been established in DEFORM and validated by the comparisons of experimental with simulation results of load variation with stroke as well as relative density distribution. The stress state and the relative density variation have been obtained from FE simulation. The correlation between the stress and consolidation condition has been rationalised. The developed FE model can provide a guide to design the geometry and thickness of preform for direct powder forging.

Corrosion behavior of steel reinforcement in concrete exposed to composite chloride–sulfate environment

The corrosion of steel reinforcement in concrete is the most significant durability problem encountered in reinforced concrete structures. The concomitant presence of sulfate ions may affect chloride induced corrosion of steel reinforcement in concrete. In this paper the outcome of a comprehensive experimental investigation is presented wherein corrosion performance of steel reinforcement in concrete exposed to composite solutions of chloride and sulfate ions has been evaluated. In this investigation, concrete specimens with a centrally embedded steel bar have been prepared from two types of cement namely ordinary Portland cement (OPC) and Portland pozzolana cement (PPC), four w/c ratios and one type of steel reinforcement. The reinforced concrete specimens have been exposed to composite solutions of chloride and sulfate ions of different concentrations. Further in order to evaluate the effect of cation type associated with sulfate ions on corrosion parameters, sodium sulfate and magnesium sulfate were used individually with sodium chloride in the preparation of composite solutions. After exposure, the different corrosion parameters namely half-cell potential, relative resistivity and corrosion current density have been measured. From the results, it was observed that the specimens made with PPC exhibited higher values of relative resistivity and lower values of corrosion density as compared to those made with OPC in all the composite solutions. Further opposite behavior was observed between composite solutions of sodium chloride with magnesium sulfate and sodium chloride with sodium sulfate in terms of variations in relative resistivity and corrosion current density for both OPC and PPC. In addition on the basis of results of analysis of variance, the effect of different parameters on relative resistivity and corrosion current density in composite solutions of sodium chloride and magnesium sulfate and that in composite solutions of sodium chloride and sodium sulfate has also been evaluated.

Hydrogen permeation and chemical stability of In-doped SrCe0.95Tm0.05O3−δ membranes

A series of SrCe0.95−xInxTm0.05O3−δ (x=0.00, 0.05, 0.10, 0.15, 0.20) samples were prepared by the sol–gel technique using ethylenediaminetetraacetic acid and citric acid as the complexing agents. The X-ray diffraction (XRD) measurements were carried out to study the formation of SrCe0.75In0.20Tm0.05O3−δ oxide. The results indicate that In can dissolve in the orthorhombic lattice of strontium cerate to form a solid solution at 1300°C. The effects of In doping on the sinterability, chemical stability and hydrogen permeation flux of SrCe0.95Tm0.05O3−δ oxides were investigated by a variety of characterization methods. According to the results of XRD and scanning electron microscopy (SEM), increasing In content in the oxides causes lattice constriction and promotes grain growth during sintering process at 1300°C. The relative density and morphology variation of the sintered membranes reveals that In doping improves the sintering activity of SrCe0.95Tm0.05O3−δ membrane. The stability test shows that the stability of strontium cerate against CO2 increases with the increasing In content. Hydrogen permeation through the SrCe0.95−xInxTm0.05O3−δ membranes was carried out between 700 and 900°C using 40% H2/He mixture as feed gas and Ar as sweep gas, respectively. The H2 permeation flux decreases with the increase of the In content. Activation energies of SrCe0.95Tm0.05O3−δ, SrCe0.85In0.10Tm0.05O3−δ and SrCe0.75In0.20Tm0.05O3−δ are 36.61, 52.25 and 73.06kJ/mol, respectively.

A climatology of medium‐scale gravity wave activity in the midlatitude/low‐latitude daytime upper thermosphere as observed by CHAMP

AbstractWe report on a detailed global climatology of medium‐scale (150–600 km) thermospheric gravity wave (GW) activity using mass density observations onboard the CHAMP satellite from 2001 to 2010. Our study focuses mainly on daytime (09–18 h in local time) and midlatitude/low‐latitude upper thermosphere between 300 km and 400 km altitudes. Midlatitude GW activity is strongest in the winter hemisphere. GW activity during June solstice adjacent to the Andes and Antarctic Peninsula is stronger than in any other season or location. GW activity in the low‐latitude summer hemisphere is stronger above continents than above oceans: especially during December solstice and equinoxes. In terms of relative density variation, GW activity is stronger during solar minimum than solar maximum. These results agree well with the characteristics of stratospheric GWs, implying that the CHAMP GWs are mainly caused by GWs from tropospheric/stratospheric processes. Using mesosphere/lower thermosphere wind observations at a Korean Antarctic station, we investigated at which altitudes the upper thermospheric GW climatology becomes visible. While the correlation is insignificant at z=82–88 km, it becomes significant for most cases at z=90–98 km, suggesting that the upper thermospheric GW climatology may start to emerge at z≥90 km.

Structural Evolution and Medium Range Order in Permanently Densified VitreousSiO2

Positron annihilation lifetime spectroscopy is employed to measure the size of the interstitial void spaces characterizing the structure of a set of permanently densified SiO2 glasses. The average volume of the voids is markedly affected by the densification process and linearly shrinks by almost an order of magnitude after a relative density variation of 22%. In addition, x-ray diffraction shows that this change of density does not modify appreciably the short range order, which remains organized in SiO4 tetrahedra. These results strongly suggest a porous medium description for v-SiO2 glasses where the compressibility and the medium range order are dominated by the density variation of the voids volume up to densities close to that of α-quartz.

Effects of punches with embossed features on compaction behaviour

This work investigated the modifications of compaction behaviour that resulted from using punches with one or two embossed (i.e. raised) ridges across their contact faces, to produce debossed furrows on otherwise flat-faced cylindrical specimens. Single-sided uniaxial compaction of spheronised microcrystalline cellulose was used to prepare specimens of different thickness and density. Based on methods developed previously, small-angle X-ray scattering (SAXS) was used to map local density variations, compressive stress, strain and strain direction over diametral sections from the specimens. The results revealed zones of relatively high compaction below the debossed furrows, with lower compaction along the flanks. High compressive stresses (up to eight times the average peak punch pressure) were indicated just below the furrows, which decreased exponentially with increasing distance below the furrows. Extrapolation towards the surface suggested that even higher stress occurred where the powder was in direct contact with the embossed ridges on the punches. It is suggested that the significant variations in relative density, stress, strain and principal strain direction observed around the debossed features could contribute towards the pressing faults that are sometimes encountered during commercial tabletting. The high stresses may also cause crystallographic changes in susceptible materials. Moreover, although the present work was performed using a pharmaceutical material, it seems likely that similar effects would also arise where powder compaction is used to produce metallic or ceramic items with complex shape.

Stochastic roots of growth phenomena

We show that the Gompertz equation describes the evolution in time of the median of a geometric stochastic process. Therefore, we induce that the process itself generates the growth. This result allows us further to exploit a stochastic variational principle to take account of self-regulation of growth through feedback of relative density variations. The conceptually well defined framework so introduced shows its usefulness by suggesting a form of control of growth by exploiting external actions.

Annihilation Radiation Gauge for Relative Density and Multiphase Fluid Monitoring

The knowledge of the multi-phase flow parameters are important for the petroleum industry, specifically during the transport in pipelines and network related to exploitation's wells. Crude oil flow is studied by Monte Carlo simulation and experimentally to determine transient liquid phase in a laboratory system. Relative density and fluid phase time variation is monitored employing a fast nuclear data acquisition setup that includes two large volume BaF2 scintillator detectors coupled to an electronic chain and data display in a LabView® environment. Fluid parameters are determined by the difference in count rate of coincidence pulses. The operational characteristics of the equipment indicate that 2 % deviation in the CCR corresponds to a variation, on average, of 20 % in the fraction of liquid of the multiphase fluid.

Exploring high frequency densitometry calibration functions for different tree species

Wood density is a trait of paramount importance for the assessment of wood quality, in dendroclimatology and in attempts to enhance biomass and carbon estimations. X-ray densitometry is the established but costly and time consuming method for high resolution measurements of wood density. An inexpensive and rapid alternative is high frequency (HF) densitometry, which until now has only been yielding relative density variation profiles that were not calibrated to true volumetric mass density. This study examines the potential of calibration functions for density values obtained from HF scanning and compares the results to volumetrically determined true wood density and density derived from optical image analysis. We found that mean HF values of 112 stem discs of different tree species were highly correlated (R2 of 0.9) to the samples’ true densities. Species specific calibration functions performed significantly better than a pooled model, whereas grouping according to basic wood anatomical types did not improve the model significantly. Prediction errors for species specific calibration functions were reasonably low (S(Yˆi)<5%). High resolution radial density profiles for 10 wood pieces of Norway spruce (Picea abies) obtained from HF densitometry calibrated with the species specific calibration function were highly correlated to density profiles obtained from optical image analysis of thin sections of the same samples. The mean densities obtained from the two different methods did not differ significantly. Thus it could be shown that values from HF densitometry can be calibrated to true density and therefore produce comparable density chronologies and be used as a proxy to predict wood quality parameters as well as for assessment of biomass.