Relative Density Research Papers - Academia.edu (original) (raw)

The possibility of producing titanium alloy Ti ? 6Al ? 4V with minimal residual porosity from mixtures of elemental powders by the method of pressing and sintering without hot deformation during or after sintering was investigated. Various powder mixtures based on titanium and titanium hydride with alloying additions of either elemental powders having different particle sizes, or master alloys, were studied. It was shown that the synthesis of Ti ? 6Al ? 4V from mixtures of titanium hydride and master alloys is optimal with respect to the attainment of high relative density. In this case the sintered material has density up to 99%, homogeneous microstructure with relatively small (100-120 µm) ß-phase grains, and a low concentration of impurities, in particular oxygen, which provide a high level of mechanical properties s(ten = 970 MPa, d = 6%).

- by O. Ivasishin
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- Powder Metallurgy, Titanium, Relative Density, Particle Size
- by Sofiane Guessasma and +1
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- Materials Engineering, Mechanical Engineering, Finite Element, Genetic Algorithm
- by Marti Anderson
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- Marine Biology, Biological Sciences, Environmental Sciences, Underwater

The effects of plantain starch obtained from the unripe fruit of the plantMusa paradisiaca L. (Musaceae) on the mechanical and disintegration properties of paracetamol tablets have been investigated in comparison with the effects of corn starch BP using a 23 factorial experimental design. The individual and combined effects of nature of starch binder (N), concentration of starch binder (C), and the relative density of tablet (RD) on the tensile strength (TS), brittle fracture index (BFI), and disintegration time (DT) of the tablets were investigated. The ranking of the individual effects on TS was RD>C≫N, on BFI was C≫RD>N and on DT was N>C>RD. The ranking for the interaction effects on TS and DT was N-C≫N-RD>C-RD, while that on BFI was N-C≫C-RD>N-RD. Changing nature of starch from a “low” (plantain starch) to a “high” (corn starch) level, increasing the concentration of starch binding agent from 2.5% to 10.0% wt/wt, and increasing relative density of the tablet from 0.80 to 0.90, led to increase in the values of TS and DT, but a decrease in BFI. Thus, tablets containing plantain starch had lower tensile strength and disintegration time values than those containing corn starch, but showed better ability to reduce the lamination and capping tendency in paracetamol tablet formulation. The interaction between N and C was significantly (P<.001) higher than those between N and RD and between C and RD. There is therefore the need to carefully choose the nature (N) and concentration (C) of starch used as binding agent in tablet formulations to obtain tablets of desired bond strength and disintegration properties. Furthermore, plantain starch could be useful as an alternative binding agent to cornstarch, especially where faster disintegration is required and the problems of lamination and capping are of particular concern.

- by Oluwatoyin Odeku
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- Starch, Experimental Design, Musa, Solubility
- by Anders Kiessling
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- Water quality, Aquaculture, FISH, Temperature

We studied seasonal variation in population attributes of arbuscular mycorrhizal (AM) fungi over 2 years in four sites of temperate grasslands of the Argentinean Flooding Pampas. The sites represent a wide range of soil conditions, hydrologic gradients, and floristic composition. Lotus glaber, a perennial herbaceous legume naturalised in the Flooding Pampas, was dominant at the four plant community sites. Its roots were highly colonised by AM fungi. Temporal variations in spore density, spore type, AM root colonisation, floristic composition and soil chemical characteristics occurred in each site and were different among sites. The duration of flooding had no effect on spore density but depressed AM root colonisation. Eleven different types of spores were recognized and four were identified. Two species dominated at the four sites: Glomus fasciculatum and Glomus intraradices. Spore density was highest in summer (dry season) and lowest in winter (wet season) with intermediate values in autumn and spring. Colonisation of L. glaber roots was highest in summer or spring and lowest in winter or autumn. The relative density of G. fasciculatum and G. intraradices versus Glomus sp. and Acaulospora sp. had distinctive seasonal peaks. These seasonal peaks occurred at all four sites, suggesting differences among AM fungus species with respect to the seasonality of sporulation. Spore density and AM root colonisation when measured at any one time were poorly related to each other. However, spore density was significantly correlated with root colonisation 3 months before, suggesting that high colonisation in one season precedes high sporulation in the next season.

- by Viviana Escudero
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- Microbiology, Soil, Plant Biology, Argentina

Empirical equations for estimating bubblepoint pressure, oil FVF at bubblepoint pressure, and total FVF for Middle East crude oils were derived as a function of reservoir temperature, total surface gas relative density, solution GOR, and stock-tank oil relative density. These empirical equations should be valid for all types of oil and gas mixtures with properties falling within the range of

- by M. Al-marhoun
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- Oil and gas, Middle East, Petroleum Technology, Fossil Fuels
- by Bradley Cardinale
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- Ecology, Trophic Cascade, Population Density, Relative Density
- by Humberto Riella
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- Materials Engineering, Microstructure, Nuclear Materials, Mixing
- by Katja Lindenberg
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- Statistical Physics, Random Walk, Mathematical Sciences, Physical sciences
- by José Ignacio Velasco
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- Comparative Analysis, IT Value, Thermal Conductivity, Relative Density
- by Louis Winnubst
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- Engineering, Materials Chemistry, Materials, CHEMICAL SCIENCES

One key strategy for increasing the application potential for biodegradable plastics lies in improving the physical and mechanical characteristics, which can be attained by inducing a cellular morphology in the pure polymer with the aid of a blowing agent, as well as by blending two or more polymers with the desirable properties. This paper examines the effect that blending two biodegradable polymers has on the thermal properties and morphology of the resultant foams blown with carbon dioxide (CO2). Polylactic acid (PLA), polyhydroxybutyrate-co-valerate (PHBV) and blends of both were foamed and characterized in terms of thermal characteristics, relative density, cell size, and foam morphology. The results indicate that although PLA and PHBV are immiscible, the presence of small quantities of PHBV (25 wt%) could lead to low density foams with finer, more uniform cells. Furthermore, the crystallinity of PHBV was found to be unaffected by the presence of PLA in the composite, which supports the immiscibility of PLA and PHBV.

- by Fereydoon Family and +1
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- Mathematical Physics, Quantum Physics, Scattering Theory, Relative Density
- by Narguess Nemati
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- Powder Metallurgy, Metal matrix composite, Mechanical Alloying, Materials Design

We present here both linear regressions and multivariate analyses correlating three global neuropsychological tests with a number of structural and neurochemical measurements performed on a prospective series of 15 patients with Alzheimer's disease and 9 neuropathologically normal subjects. The statistical data show only weak correlations between psychometric indices and plaques and tangles, but the density of neocortical synapses measured by a new immunocytochemical/densitometric technique reveals very powerful correlations with all three psychological assays. Multivariate analysis by stepwise regression produced a model including midfrontal and inferior parietal synapse density, plus inferior parietal plaque counts with a correlation coefficient of 0.96 for Mattis's Dementia Rating Scale. Plaque density contributed only 26% of that strength.

- by Robert Hill
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- Pathology, Neurology, Psychometrics, Multivariate Analysis

A comprehensive compositional and characterization study was carried out on five seed oils from varieties of the melons Citrullus lanatus and C. colocynth in order to evaluate their suitability for large-scale exploitation as edible vegetable oils. The oils were extracted by Soxhlet with a 3:1 mixture of n-hexane/2-propanol with yields that ranged from 24.8 to 30.0% (wt/wt). The refractive indices and relative densities of the oils fell within the narrow ranges of 1.465–1.469 and 0.874–0.954 g/cm3, respectively. Saponification values ranged between 182.1 and 193.8 mg KOH/g, whilst iodine values (IV) ranged from 95.8 to 124.0 (Wijs). The ranges of the values for free fatty acid (AV), 1.2–4.0 mg KOH/g, peroxide (PV), 1.1–10.9 meq/kg and p-anisidine (p-AV), 0.2–9.0, indicated that secondary oxidation products were barely present. GC analysis gave total unsaturation contents of 67.93–82.36%, with linoleic acid (18:2) being the dominant fatty acid (55.21–66.85%). The GC results agreed closely with those from proton NMR analysis of the fatty acid classes. The physicochemical and compositional properties determined in this study show that the qualities of the test Cucurbitacea seed oils are highly comparable to those of soybean, sunflower and groundnut seed oils. Therefore, the test melon seed oils could be developed into commercial products to serve as alternate vegetable oils in Southern and West Africa, the regions where these melons grow.

- by samuel yeboah
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- Chemical Engineering, West Africa, Soybean, Vegetable oil
- by MAJID MORADI
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- Civil Engineering, Ocean Engineering, Numerical Analysis, Gravity
- by Tahar Laoui
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- Engineering, Heat Transfer, Heat and Mass Transfer, Mathematical Sciences
- by Anubhav Jain
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- Engineering, Materials Science, CHEMICAL SCIENCES, Relative Density

The distribution and abundance of thirteen species of regular
sea urchin were assessed on Sosoikula and Nukubuco reefs, Fiji. Their
morphology and behavior were contrasted relative to wave activity,
water depth, substratum composition, food, and predation through all the
reefs zones. Densities and relative densities of species in each zone were
determined and their significance tested relative to the species distribution.
Results indicated species associations with different reef areas, thus
habitat preferences, which reflected species’ competitive abilities and
resource partitioning. Echinometra mathaei was the most prolific and
adaptable species, having the greatest densities in all zones. Peak mean
densities occurred in the mid back reef area on the echinoderm flat (2.64
ind. m–2), comprising 93.6% of all echinoids found. Diadema savignyi
and Diadema setosum were found at maximum densities in the boulder
zone, utilizing the narrow elevated crevice space. Both these species of
Diadema showed an increase in test diameters and spine lengths from
the reef crest to the hard coral bommies, proportional to the increase in
observed crevice size. Echinothrix diadema and Echinothrix calamaris
(brown color morph) demonstrated a similar trend, but with continued
growth-related migration to the Porites and soft coral zone. The white
color morph of E. calamaris showed no apparent association between
size distribution and crevice space. This was due to behavioral adaptations,
where both juveniles and adults aggregated together in the few
very large crevices found. Algal and seagrass species distributions
appeared to have only a moderate influence on echinoid species distributions,
as most species diets appeared broad within habitat. Predation
pressure was assessed to be relatively low, with greatest predator densities
on the fore reef (0.24 ind. m–2). Refuge quality and availability,
moderated by predation, combined with different echinoid morphologies
and behaviors, determined species distributions through the reefs varied
habitats.

- by Simon Coppard
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- Biology, Coral Reef, Indicator species, Species Distribution
- by Cameron Tropea
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- Mechanical Engineering, Chemical Engineering, Mass Transfer, Experimental Design
- by Rossella Surace
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- Powder Metallurgy, Statistical Analysis, Materials Design, Design of experiment
- by B. Choudhury
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- DISTRIBUTION, Biological Sciences, Conservation Status, Environmental Sciences
- by Sylvie Rossignol
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- Materials Engineering, Physical Chemistry, Scanning Electron Microscopy, Ph
- by sripriya R
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- Mechanical Engineering, Chemical Engineering, Mineral Processing, Magnetic separation
- by H. Dhaou and +2
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- Engineering, Heat Exchanger, Hydrogen Storage, Heat and Mass Transfer
- by Sujit Kumar Dash
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- Civil Engineering, Relative Density, Bearing Capacity
- by Andrey Ragulya and +1
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- Materials Engineering, Condensed Matter Physics, Scanning Electron Microscopy, Composite Material
- by Madhavi Latha Gali
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- Civil Engineering, Retaining Wall, Relative Density, Seismic response
- by Luis Villegas
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- Peru, Relative Density, Habitat Preference
- by Jose Riquelme
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- Relative Density, Emin, Emax

This paper presents the results from laboratory-model tests on a strip footing supported by a sand bed reinforced with a geocell mattress. The parameters varied in the testing program include pattern of geocell formation, pocket size,... more

- by Sujit Kumar Dash
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- Civil Engineering, Geotextiles, Relative Density, Bearing Capacity
- by Serena Best
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- Algorithms, Pharmaceutical Chemistry, Pharmaceutical industry, Porosity

The year-round food habits of lynx were studied using radio-telemetry and snow-tracking in the boreal forest of southeastern Norway. The main objectives of the study were to clarify the importance of domestic sheep and small prey species in the diet of lynx in an area with a very low density of roe deer. During the period 1995–1999, we found 193 scats and 358 kills made by lynx. Our results indicate that roe deer were the most common prey species (contributing to 83 and 34% of the biomass consumed in winter and summer, respectively), although a wide range of other species were also found, including mountain hares, tetranoids, red foxes, domestic sheep, wild reindeer, and even moose. Most of the diet was obtained by predation, although we did document several cases of scavenging. Roe deer were more important in the diet in winter than in summer, perhaps because they were easier to locate in winter as they clustered around feeding sites. In summer, domestic sheep and small prey increased in importance. Despite the very low density of roe deer in this study area, lynx seemed to still specialise on them, although domestic sheep did constitute a significant amount to their diet, especially for males and yearlings. However, the contribution of sheep to summer diet was far from that expected if their relative density was considered.

- by reidar andersen
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- Zoology, Capreolus capreolus, Roe Deer, Boreal Forest

Seed oils from six legume cultivars of Phaseolus vulgaris, grown in the Kingdom of Lesotho, were extracted and their physicochemical properties and FA compositions were determined in order to compare their dietary lipids with those in P. vulgaris cultivars grown in other parts of the world. The oil content of the beans was very low, ranging from 1.5 to 2.0% (w/w). The acid values ranged from 11.0 to 19.2 mg KOH/g, whereas a combination of the PV and the p-anisidine values in Holm's equation gave oxidation values that ranged from 11.0 to 15.0. Thus, considerable enzymatic hydrolysis and oxidation had taken place in the beans during storage. Iodine values ranged from 80.5 to 92.3 (Wijs method), indicating moderate unsaturation in the oils. However, capillary GC analysis, supported by proton NMR analysis of the FAME, gave a total unsaturation range from 79.67 to 84.24%. The dominant FA were α-linolenic acid (36.47–48.81%) and linoleic acid (20.96–36.10%), with appreciable amounts of palmitic acid (14.33–18.23%). This FA composition pattern is quite similar to the FA distribution reported for low oil-bearing legume seeds. Thus, notwithstanding the different climatic and soil conditions, the general properties of lipids in the southern African legume cultivars were quite similar to those of lipids in P. vulgaris cultivars grown in other parts of the world. The high content of α-linolenic acid in the cultivars of P. vulgaris could very likely play a beneficial role in reducing the risk of coronary heart disease among the large populations consuming them in the southern African region.

- by samuel yeboah
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- Chemical Engineering, Southern Africa,  Enzymatic hydrolysis, Relative Density
- by Osman Uyanık and +2
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- Materials Engineering, Mechanical Engineering, Seismic Waves, Relative Density
- by Marcos A L Nobre and +1
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- Engineering, Microstructure, Manufacturing, Impedance Spectroscopy

The study presented here investigates the effect of density in cementitious mortar on its mechanical properties under quasi-static loading. The reduction in density was achieved through the addition of expanded perlite as a lightweight aggregate into cement paste by volume replacement of cement in the ratio from 0 to 8. This yielded a range of densities between 1000 and 2000 kg/m3. The compressive and flexural response of these mixes were determined for geometrically scaled specimens to study the size effect. Some mixes were reinforced with polymer microfibres and the Mode I fracture toughness parameters were evaluated through flexural testing of notched beams. When compared with a reference Portland cement paste, the compressive strength and elastic modulus scaled as the cube of the density, while the fracture toughness varied linearly with it. The study shows that the specimen size effect on compressive and flexural strength decreases with a drop in the density of the mix and also with fibre reinforcement. On the other hand, the specimen size effect on the critical crack mouth opening displacement was more pronounced at lower densities.

- by J.Y. Cavaillé
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- Engineering, Electron Microscopy, Viscoelasticity, Modeling
- by Prabir Kumar Basudhar
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- Civil Engineering, Homogenization, Experimental Study, Relative Density
- by Nader Hataf
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- Civil Engineering, Experimental Study, Relative Density, Bearing Capacity

The theoretical maximum specific gravity (Gmm) is a parameter required for the calculation of the aggregate effective specific gravity, asphalt absortion, effective asphalt content and air voids content (Vv), within the design of a hot mix asphalt. From the Gmm and the bulk specific gravities of the aggregates and the compacted mixture, one can determine the volumetric characteristics and the

- by Kamilla Vasconcelos
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- Relative Density, Specific Gravity, Tensile Strength, Hot Mix Asphalt

In this review I will describe the importance of seed banks and thepopulation dynamics of seeds on the distribution of species in salinehabitats. The main questions being examined in this review include: 1.Does the seed bank represent the flora of the entire salinity gradient or isit restricted to the species in each zonal community? 2. Is the size andspecies composition of the persistent seed bank regulated by the degree ofsalt stress in habitats along an environmental gradient? 3. Does thepopulation dynamics of seeds influence the temporal and spatial distributionof plant species in saline habitats? Seed banks may be transient orpersistent depending upon the physiological responses of species and thesoil environment in which the seeds are found. The formation of zonalcommunities in salt marsh environments is affected by changes in soilsalinity and flooding along an elevational gradient. Population dynamics ofseeds have been found to determine the spatial and temporal distributionof species along salinity gradients. The flora and relative density of speciesof zonal communities are significantly dependent upon the stress toleranceof species at different stages of development and the presence of transientor persistent seed banks. The occurrence of a seed bank is related to thesalinity tolerance of species at the germination stage of development, aseeds ability to tolerate hypersaline conditions and flooding, and whetheror not species are able to maintain a persistent seed bank until hypersalineconditions are alleviated.

- by Rain Loveless
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- Biological Sciences, Environmental Sciences, Seed bank, Physiological Response
- by Jamel Bouaziz
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- Materials Engineering, Condensed Matter Physics, Diffusion, Grain Growth
- by Wen ZHU
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- Materials Engineering, Condensed Matter Physics, Microstructure, Density