Average Bulk Density Research Articles

Synthesis of ultra high molecular weight polyethylene: A differentiate material for specialty applications

Tailoring the synthesis of a suitable Ziegler-Natta (ZN) catalyst coupled with optimized polymerization conditions using a suitable activator holds the key for an array of differentiated polymers with diverse and unique properties. Ultra high molecular weight polyethylene (UHMWPE) is one such polymer which we have synthesized using TiCl4 anchored on MgCl2 as the support and activated using AlRR′2 (where R, R′ = iso-prenyl or isobutyl) under specific conditions. Here in we have accomplished a process for synthesizing UHMWPE in hydrocarbon as the medium with molecular weights ranging from 5 to 10 million g/mole. The differentiated polymers exhibited the desired properties such as particle size distribution (PSD), average particle size (APS), bulk density (BD) and molecular weight (MW) with controlled amount of fine and coarse particles. Scanning electron micrographs (SEM) reflected the material to have uniform particle size distribution with a spherical morphology. The extent of entanglement was determined from thermal studies and it was found to be highly entangled.

Recent sedimentation patterns and facies distribution on the Poverty Shelf, New Zealand

Modern sediment dispersal and accumulation on the Poverty Shelf off the Waipaoa River, New Zealand, is investigated using X-radiographic, radio-isotopic and physical property analyses of nearly 200 box and Kasten cores collected in January 2005 aboard the R/V Kilo Moana. The high-yield, small mountainous Waipaoa River empties onto a tectonically active, narrow margin and represents an important analog for shelf sedimentation in similar environments worldwide. X-radiographs and bulk-density measurements from a multi-sensor core logger show three distinct facies on the shelf where physical and/or biological factors dominate strata formation. Spatial distribution of these facies delineates a radial pattern with distance from the river mouth, from areas dominated by stratified layers on the inner shelf to mottled muds on the outer shelf, demonstrating a continuum of controls from wave reworking to episodic and extreme wet event sedimentation, despite a tectonic framework that supports rapid accumulation in two recently identified shelf depocenters. Analysis of short-lived 7Be ( t 1/2 = 53 days) reveals a broad spatial distribution across- and along-shelf in surface sediments, suggesting rapid transport from the Waipaoa source. However, beryllium-7 inventories are consistent with centennial-scale trends observed by other researchers using longer-lived 210Pb analyses, with highest inventories in the shelf depocenters. Box core bulk-density analyses show lower than average bulk densities within these depocenters, and higher than average bulk densities on the inner shelf and between the depocenters. These observations confirm rapid deposition of low-density muds in the depocenters, with higher bulk-density, possibly physically reworked sediments, remaining off the mouth of Poverty Bay and between the depocenters. Based on this single observational period, there appears to be no fundamental difference between seasonal and longer-term accumulation patterns on the Poverty Shelf.

Effect of Particle Size and Soil Compaction on Gas Transport Parameters in Variably Saturated, Sandy Soils

The soil gas diffusion coefficient (Dp) and air permeability (ka) and their dependency on soil air content (ε) control gas diffusion and advection in soils. This study investigated the effects of average particle size (D50) and dry bulk density (ρb) on Dp and ka for six sandy soils under variably saturated conditions. Data showed that particle size markedly affects the effective diameter of the drained pores active in leading gas through the sample at −100 cm H2O of soil water matric potential (calculated from Dp and ka) as well as the average pore diameter at half saturation (calculated from the water retention curve), both exhibiting similar and exponential relationships with D50 Under variably saturated conditions, higher Dp and ka in coarser sand (larger D50) were observed due to rapid gas diffusion and advection through the less tortuous large‐pore networks. In addition, soil compaction (larger ρb) simultaneously caused reduced water blockage effects and a reduction of large‐pore space, resulting in higher Dp(ε) but lower ka(ε). Two recent models for Dp(ε) and ka(ε) were evaluated: the water‐induced linear reduction (WLR) model for Dp, and the reference‐point power law (RPL) model for ka, with reference point ka set at −100 cm H2O. The performance of both models for the sandy soils (particle size range 0.02–0.9 mm) was improved if the pore connectivity–tortuosity factor and water blockage factors were assumed to be functions of D50 and ρb Water blockage factors, N for the WLR Dp(ε) model and M for the RPL ka(ε) model, showed a strong nonlinear relationship (R2 = 0.95) that seems promising for predicting Dp(ε) from the more easily measureable ka(ε).

Thermodynamics of Systems with Different Geometric Constraints and Intermolecular Correlations

Four types of systems with different degrees of geometric constraint and intermolecular correlations were studied to determine the differences in their thermodynamics. The average configurational internal energies of these systems were calculated using Monte Carlo simulations, and the results are compared at the same temperatures and constant average bulk density. From the energy profiles for the four systems, the effects of geometry and intermolecular correlations on the systems' phase behavior are discussed. It was observed that indirect intermolecular correlations, rather than geometric constraints, are the key to achieving a first-order phase transition.

Characterization and Estimation of Hydraulic Properties in an Alluvial Gravel Vadose Zone

Understanding the physical and hydraulic properties of the vadose zone is important for modeling land use effects on groundwater quality. This study used a variety of characterization methods to derive conceptual understanding and estimates of hydraulic properties of a coarse alluvial gravel vadose zone in New Zealand. Sandy gravel (SG) material constituted approximately 90% of the vadose zone, with the remainder comprising sand lenses and open‐framework gravels. The gravel content of the SG material was approximately 70% (v/v) (range 68–73%). The water content of the bulk SG material (43 samples) ranged from 3.5 to 13.9%. The average bulk density of the SG material was 2.20 g/cm3 (range 2.00–2.33 g/cm3) giving an average calculated porosity of 17%. The average porosity of the open‐framework gravels was 34% and these gravels were often coated with 2‐ to 3‐mm‐thick deposits of amorphous Fe and Mn oxides. Neutron probe (NP) depth profiles indicated unsteady conditions, with variable water contents with depth and time reflecting the vertical heterogeneity and the variably saturated state of the vadose zone. Time series NP data to 3 m indicated water content in the alluvial gravels responded quickly to soil drainage events, and saturation variability was greater in the sand lenses and the SG material immediately underlying. When compared with derived water retention curves, variability in the water content equated to significant fluctuation in unsaturated hydraulic conductivity (Kunsat). Tension infiltrometer measurements were variable but were within the range of the Kunsat estimates from site‐average particle size distribution data. The gravel‐transformed, texture‐based models used to estimate saturated water content values in this study appeared to underestimate the measured values.

Two-dimensional discrete element modeling of a spherical steel media in a vibrating bed

A discrete element model was developed to model granular flow in different vibratory beds and the results are compared with experimental measurements of bulk flow velocity and bed expansion. The sensitivity of the model predictions to the contact parameters was considered and the parameters were optimized with respect to the experimental results. The difference between the model predictions of the bulk flow velocity and the measurements was less than 10% at four locations in media beds of two depths. The average bulk density of the vibrating beds was also predicted to be within 10% of the measured values.

Preparation of boron carbide–aluminum composites by non-aqueous gelcasting

Gelcasting is an attractive forming process to fabricate ceramic parts with near-net-shape. In the present work, non-aqueous gelcasting of boron carbide (B 4C)–aluminum (Al) composites was studied. A stable B 4C–Al slurry with solids loading up to 55 vol.% for gelcasting was prepared. The slurry was solidified in situ to green body with the mean value of relative density of 64% and flexural strength of 21 MPa. The SEM images showed that powders in green body compact closely by the connection of polymer networks. B 4C–Al samples were also obtained by the process of gelcasting and sintering at 1300 °C for 1 h in 0.1 MPa Ar atmosphere. The average bulk density of sintered body was 2.05 g cm −3.

Characteristics and Nitrogen Value of Stratified Bedded Pack Dairy Manure

Compost dairy barns are relatively new, and this manure, which we refer to as stratified bedded pack (SBP) dairy manure, has neither been characterized in detail nor defined in terms of its N supply. We measured physical characteristics, nutrient concentration, N mineralization, and N supply to corn (Zea mays L.) of SBP dairy manure from eight Minnesota farms. Concentrations of N, P, and K were generally higher than standard book values for solid dairy manure, were lower for P and K than typical solid dairy composts, and were highly variable within and among buildings. Average bulk density of SBP dairy manure was 58.2 lb/ft³. All SBP dairy manures produced nitrate during a 4-month-long incubation in soil, but the four with highest C:N ratios (19 to 21) immobilized N for 30 to 60 days. Infield fertilizer N equivalents to corn ranged from 1.4 to 12.1 lb/ton for quickly incorporated manure, but only -0.3 to 5.3 lb/ton when incorporation was delayed until spring. Guidelines for solid dairy manure were not reliable for predicting N availability from SBP dairy manure. Until validated prediction equations are available, we recommend farmers apply moderate rates of SBP dairy manure, incorporate it immediately to improve N supply, apply a basal rate of fertilizer N near planting time, and sidedress fertilizer N based on recommended soil or plant analysis for their region.

Characterization of medical waste from hospitals in Tabriz, Iran

Medical waste has not received enough attention in recent decades in Iran, as is the case in most economically developing countries. Medical waste is still handled and disposed of together with domestic waste, creating great health risks to health-care stuff, municipal workers, the public, and the environment. A fundamental prerequisite for the successful implementation of any medical waste management plan is the availability of sufficient and accurate information about the quantities and composition of the waste generated. The objectives of this study were to determine the quantity, generation rate, quality, and composition of medial waste generated in the major city northwest of Iran in Tabriz. Among the 25 active hospitals in the city, 10 hospitals of different size, specializations, and categories (i.e., governmental, educational, university, private, non-governmental organization (NGO), and military) were selected to participate in the survey. Each hospital was analyzed for a week to capture the daily variations of quantity and quality. The results indicated that the average (weighted mean) of total medical waste, hazardous–infectious waste, and general waste generation rates in Tabriz city is 3.48, 1.039 and, 2.439 kg/bed-day, respectively. In the hospital waste studied, 70.11% consisted of general waste, 29.44% of hazardous–infectious waste, and 0.45% of sharps waste (total hazardous–infectious waste 29.89%). Of the maximum average daily medical waste, hazardous–infectious waste, and general waste were associated with N.G.O and private hospitals, respectively. The average composition of hazardous–infectious waste was determined to be 35.72% plastics, 20.84% textiles, 16.70% liquids, 11.36% paper/cardboard, 7.17% glass, 1.35% sharps, and 6.86% others. The average composition of general waste was determined to be 46.87% food waste, 16.40% plastics, 13.33% paper/cardboard, 7.65% liquids, 6.05% textiles, 2.60% glass, 0.92% metals, and 6.18% others. The average bulk densities of total medical waste, hazardous–infectious waste, and general waste were determined to be 99.58, 96.16 and 101.26 kg/m 3, respectively. Significant differences were observed between the medical waste characteristics of the hospitals studied here and those reported in other studies. In conclusion, the characteristics of generated medical waste, current environmental problems and strict budgets necessitate that the implementation of efficient management, training, and segregation program be top priorities if we are to minimize the treatment and disposal costs and reduce the risks of hazardous–infectious waste in Tabriz city.

Effects of NiO addition on the structural, microstructural and electromagnetic properties of manganese–zinc ferrite

Structural, microstructural and electromagnetic properties of NiO doped manganese–zinc (MnZn) ferrites prepared by a solid-state reaction method have been investigated. The continuous doping of NiO resulted in an increase in lattice constant ( a), porosity ( P) and electrical resistivity ( ρ), a decrease in average grain size ( D) and bulk density ( d b), while no obvious change in X-ray density ( d X). Hysteresis loss ( P h) increased monotonically with increasing NiO, and its variation could be explained by the relation: P h ∝ 1 / μ i 3 , where μ i was initial permeability. Eddy current loss ( P e) first reduced before achieving its minimum, and then rose gradually. The variation of P e was inconsistent with the classical expression, P e,cl ∝ D 2/ ρ, where D and ρ were average grain size and resistivity, respectively, and the excess loss ( P e,exc) could contribute to the P e. Residual loss ( P r) reduced slowly due to D’s decrease and f r’s increase which were caused by the increase in NiO, where f r was resonance frequency. Finally, the sample doped with 0.10 wt% NiO showed the lowest losses of 207 kW m −3 at 100 °C, 1 MHz and 30 mT.

Effects of tillage systems on soil organic carbon dynamics, structural stability and crop yields in irrigated wheat (Triticum aestivum L.)–cotton (Gossypium hirsutum L.) rotation in semi-arid Zimbabwe

In southern Africa, tillage research has focused on rainfed smallholder cropping systems, while literature on high-input irrigated cropping systems is limited. We evaluated the effects of conventional (CT), minimum (MT) and no-till (NT) tillage systems on soil organic carbon (SOC), bulk density, water-stable aggregates (WSA), mean weighted diameter (MWD) and crop yields in an irrigated wheat-cotton rotation. Soil data were mon- itored in the first and final year, while yields were monitored seasonally. Average bulk densities (1.5-1.7 Mg m -3 ) were similar among tillage systems, but often exceeded the critical limit (1.60 Mg m -3 )

(42355) Typhon–Echidna: Scheduling observations for binary orbit determination

Abstract We describe a strategy for scheduling astrometric observations to minimize the number required to determine the mutual orbits of binary transneptunian systems. The method is illustrated by application to Hubble Space Telescope observations of (42355) Typhon–Echidna, revealing that Typhon and Echidna orbit one another with a period of 18.971 ± 0.006 days and a semimajor axis of 1628 ± 29 km , implying a system mass of ( 9.49 ± 0.52 ) × 10 17 kg . The eccentricity of the orbit is 0.526 ± 0.015 . Combined with a radiometric size determined from Spitzer Space Telescope data and the assumption that Typhon and Echidna both have the same albedo, we estimate that their radii are 76 −16 +14 and 42 −9 +8 km , respectively. These numbers give an average bulk density of only 0.44 −0.17 +0.44 g cm −3 , consistent with very low bulk densities recently reported for two other small transneptunian binaries.

Influence of Two Ground-Based Skidding Systems on Soil Compaction Under Different Slope and Gradient Conditions

Forest soils are sensitive to compaction by forest machinery. Forest operations such as harvesting and skidding have a high potential for soil compaction. This study was carried out in the Hyrcanian hardwood forests of Iran to measure the changes in bulk density (ρb) in the top 10 cm of soil following machine and animal skidding. The density change or compaction was induced by (i) a rubber-tired skidder in three skid trails: flat skid trail (STF), skid trail with transversal slope (STTS), and skid trail with longitudinal gradient (STLG) and (ii) a mule in two animal trails: flat animal trail (ATF) and animal trail with transversal slope (ATTS). Soil cores were collected pre- and post-skidding at random locations along the upslope and downslope tracks of each skid trail to determine bulk density and moisture content of the soil. Average soil bulk density in the tracks of machine skid trails was significantly greater than the soil density outside the tracks, but the increase in bulk density was not significant on the animal trails. An increase in soil density was considered significant if p < 0.05. A highly significant increase in soil bulk density (p < 0.01) occurred with machine skidding after the first 12 skidding cycles on the STF before stabilizing. In comparison, on STLG and STTS the increase of bulk density was greatest after the first six skidding cycles. Additional cycles did not cause a significant increase in soil density. While the number of skidding cycles to reach the steady compaction state varied between flat trails and those with a slope, the severity of compaction was the same between them. Concentrating machine operations will minimize the areal extent of compaction and the use of mules could further reduce the impact of the extraction of short logs.

Micro-morphological analysis of the effect of sampling by the volumetric ring method on soil structure

This report investigates the effect of sampling by the volumetric ring method on pore size number and shape distributions. Soil porosity was analyzed using the micromorphological image analysis technique, which helped to explain soil structure changes near the border of samples collected in cylinders and provided detailed information about pore shape, number, and size distribution variations along the samples. Compaction due to sampling affects mainly large irregular and rounded pores of the soils utilized in this study. When evaluating inaccuracies in density measurements due to the compacted regions caused by the sampling device the average soil bulk density for each soil resulted in the ranges of 1.72 ± 0.05 g.cm −3 for Geric Ferralsol soil, 1.66 ± 0.03 g.cm −3 for Eutric Nitosol soil and 1.33 ± 0.05 g.cm −3 for Rhodic Ferralsol soil, respectively. When calculating the average soil bulk density over smaller regions, e.g. in the center of each sample (area of 17.14 mm 2 ) results reduced to 1.64 ± 0.05 g.cm −3 with Geric Ferralsol soil, 1.56 ± 0.03 g.cm −3 with Eutric Nitosol soil and 1.29 ± 0.10 g.cm −3 with Rhodic Ferralsol soil, respectively. These results clearly indicate the effect of sampling by the volumetric ring method. The use of image analysis was essential to explain compaction differences close to the border of the samples collected using cylinders (volumetric ring method) and provided detailed information about pore shape and size distribution variations within soil samples. The results are useful as indicators of the consequences of sampling on the quality of soil samples.

The Correlation between Bulk Density and Shock Resistance of Waterlogged Archaeological Wood using the Pilodyn

The correlation (R2 = 0.87) between bulk density and the shock resistance of homogeneously and heterogeneously degraded waterlogged archaeological wood, with densities ranging from 100 to 700 kg·m-3, was determined using the Pilodyn wood tester. The results showed that the energy required to fracture a given mass of wood substance was constant (R2 = 0.83) and independent of wood species. However, measurements in the three main orientations (longitudinal, radial and tangential) showed a significant variation and therefore further measurements were preferentially taken in the radial axis. A model to enable the determination of the average bulk density of waterlogged wood from the depth of penetration of the Pilodyn showed that the average bulk density of homogeneously and heterogeneously degraded waterlogged wood could be determined with an average accuracy of ± 9%. A high correlation coefficient (R2 = 0.995) for measurements taken in water and air enable the Pilodyn to assess waterlogged wood under water as well as in air.

The texture of condensed CO 2 on the martian polar caps

The widespread deposition of CO 2 ice on the martian polar caps in winter is readily visible from Earth and has been extensively studied from orbit. As the surface cools during polar night, CO 2 condenses directly out of the atmosphere at a rate that establishes equilibrium between radiative loss and latent heat of condensation. Since radiative loss is strongly geometry-dependent, the CO 2 frost will grow most rapidly on exposed surfaces and more slowly in depressions. Positive feedback will cause a dramatic enhancement of the relief of the underlying topography and a corresponding reduction in the average bulk density. The resulting surface will be highly textured and riddled with perforations.

Soil bulk density as a factor of the microrelief formation in semideserts of the north Caspian region

Relative elevations of different elements of the microtopography and the soil bulk density values within the 2-m-deep layer have been measured at the same points, and the relationship between these characteristics has been analyzed. It is shown that the heights (depths) of the elements of the microtopography calculated from the data on the soil bulk density agree with their actual heights (depths). The range of calculated heights (depths) is almost equal to the actual range (34 and 40 cm, respectively). A regression analysis shows that there is a close correlation between the factual heights (depths) of microhighs and microlows and the soil bulk density values (r = 0.957). The regression curve showing the dependence of the factual heights of the elements of the microtopography on the soil bulk density is very close to the regression curve showing the same dependence for the calculated heights. A change in the average bulk density of the of the 2-m-thick soil layer by 0.10 g/cm3 is accompanied by a change in the factual and calculated height of the soil surface by 12 cm. It is argued that the dynamics of the surface microtopography in the study area are controlled by changes in the soil bulk density.

The effect of the soil compaction on the contents of alfalfa root reserve nutrients in relation to the stand density and the amount of root biomass

The reserve root nutrients influence the overwintering, regrowth, yield, and persistence of alfalfa plants. The total amount of the root reserves is considered more important than their concentration. One of the factors which can affect the reserve content can be the soil compaction. The aim of this study is to clarify the effect of the soil compaction on the reserve root nutrients in relation to the stand density and the amount of the root biomass. In this experiment, the stand density ranged from 28 to 112 plants per m&lt;sup&gt;2&lt;/sup&gt;. The average soil bulk density in the uncompacted and compacted variants was found to be 1.38 and 1.52 g/cm&lt;sup&gt;3&lt;/sup&gt;, respectively. In spring and autumn periods, the root samples were taken from an area of 0.25 m&lt;sup&gt;2&lt;/sup&gt; (the depth 150 mm) in four replications. The number of plants, the root weight, and the concentrations of starch, saccharose, fructose, and crude protein were assessed in each plot. The total amount of the root reserves was calculated from the determined concentrations and the weights of roots of each sample. A higher soil compaction reduced significantly the stand density, root weight, total amount of all nutrients as well as the starch and crude protein concentrations. The concentration of the soluble non-structural saccharides was identical to or increased over that in the compacted variant. The negative significant effect of a higher soil compaction on the root weight and, consequently, on the total amount of all reserve root nutrients was explained by the changes in the stand density. When the root weight effect was excluded, the compacted variant provided a significantly lower density and crude protein amount and concentration. The significant effect of density on the reserve nutrients was explained by changes in the root weight.

The orbit, mass, size, albedo, and density of (65489) Ceto/Phorcys: A tidally-evolved binary Centaur

Hubble Space Telescope observations of Uranus- and Neptune-crossing object (65489) Ceto/Phorcys (provisionally designated 2003 FX 128) reveal it to be a close binary system. The mutual orbit has a period of 9.554 ± 0.011 days and a semimajor axis of 1840 ± 48 km . These values enable computation of a system mass of ( 5.41 ± 0.42 ) × 10 18 kg . Spitzer Space Telescope observations of thermal emission at 24 and 70 μm are combined with visible photometry to constrain the system's effective radius ( 109 −11 +10 km ) and geometric albedo ( 0.084 −0.014 +0.021 ) . We estimate the average bulk density to be 1.37 −0.32 +0.66 g cm −3 , consistent with ice plus rocky and/or carbonaceous materials. This density contrasts with lower densities recently measured with the same technique for three other comparably-sized outer Solar System binaries (617) Patroclus, (26308) 1998 SM 165, and (47171) 1999 TC 36, and is closer to the density of the saturnian irregular satellite Phoebe. The mutual orbit of Ceto and Phorcys is nearly circular, with an eccentricity ⩽0.015. This observation is consistent with calculations suggesting that the system should tidally evolve on a timescale shorter than the age of the Solar System.

Carbon Storage in the Soils of a Mesotidal Gulf of Maine Estuary

Estuaries have the highest primary productivity of all ecosystems, yet the soils in estuarine environments have been largely overlooked in C sequestration studies. This research quantified organic C stored in the top 1 m of soils from the Taunton Bay estuary in Hancock County, Maine. Taunton Bay is centrally located within Maine's Island–Bay Coastal Complex, a physiographic region that encompasses 47% of the state's coastline. Riverine inputs of sediments and sediment‐associated organic matter to this and most Maine estuaries are quite low. These estuary soils form by incremental additions of reworked glaciofluvial marine sediments and estuarine organic matter to the soil surface. The organics are protected from decomposition by anaerobic conditions. As sea level rises, the estuary area increases by inundating and submerging the soils at its edges. The average concentration of soil organic C in the top 1 m of these estuary soils is 2.4% and the average soil bulk density is 0.67 g cm−3 The organic C content is 136 Mg C ha−1, which is greater than the C content in the top 1 m of Maine's upland soils. These results suggest that systematically quantifying and dating the C in estuarine soils will provide valuable data for use in regional and global C budgets and climate models.