Arithmetic Mean Size Research Articles

Evaluation of the effects of homogenizing matrix block sizes on the simulation of naturally fractured reservoirs

A vast amount of recoverable oil is buried in naturally fractured reservoirs. Due to the heterogeneous nature of matrix and fracture systems, there are many complexities in the simulation and production of these kinds of reservoirs. Fractures in naturally fractured reservoirs may be caused by various natural factors such as tectonic forces. Fracture distribution does not have a systematic pattern in naturally fractured reservoirs, and fractures are scattered across the formation. For the sake of simplicity, uneven distribution of fractures is not completely considered within practical reservoir simulation methodologies such as the commonly used dual-porosity approach. Using the dual-porosity methods, naturally fractured reservoirs are divided into simulation cells consisting of several matrix blocks. Against the nature of naturally fractured reservoirs, in the dual-porosity method, the fractures are often uniformly spread throughout the entire reservoir, and the sizes of matrix blocks inside the simulation cells are considered equal. For many years the assumption of homogenized matrix blocks in simulation cells has been used in the industry without proper evaluation of its effect on simulation results. This work examines the assumption of uniform matrix block size on the simulation results of naturally fractured reservoirs. An approach was proposed to create a simulation cell with randomly distributed matrix blocks to mimic the actual condition of naturally fractured reservoirs. Furthermore, realistic simulation approaches were utilized to investigate the oil recovery factor of different non-homogenized simulation cells during gravity drainage and imbibition processes. Also, the recovery factor performances of non-homogenized simulation cells were compared with simulation cells with uniform matrix block sizes created with different homogenization methods. An examination of the results revealed that a significant amount of inaccuracy in the simulation results could be caused by homogenization. Moreover, two types of homogenization approaches were used. In the first approach, a simulation cell with homogenized matrix block sizes based on the arithmetic mean of variable size matrix blocks was built. Homogenized matrix blocks in the second approach were built according to the arithmetic mean size of matrix blocks in different x, y, z directions. The first homogenization method resulted in less error compared to the second one. As compared with the gas invaded zone, simulation results of the water invaded zone are more error-prone. The findings of this work can help for better understanding the homogenization effect and prove that disregarding the heterogeneity of matrix blocks may lead to severe errors in the simulation results of naturally fractured reservoirs. The outcome also highlights the need for a more precise modeling and simulation approach for naturally fractured reservoirs.

Prediction of coke AMS through data mining: a practical approach

ABSTRACT The appropriate specification of size analysis of blast furnace coke remains debatable even today. But operators prefer consistent quality and the right size of coke for the smooth operation of the blast furnace. The arithmetic mean size (AMS) of coke and its distribution inside the blast furnace are essential for maintaining the efficient operation of the blast furnace. The coke AMS is significantly affecting the blast furnace permeability, not a small extent. Therefore, the proper sizing of coke inside the blast furnace can contribute to the increase in production of a blast furnace with the optimal coke rates. However, limited methods that incorporate process parameters and blend properties in the prediction of coke AMS exists. The present work focuses on the assessing of coke AMS using an algorithm on plant process data like parent coal characteristics, carbonization, and operational conditions that can influence coke properties like the mean size of the coke. This work using classification and regression tree (CART) and random forest algorithms provide the basis to futuristic prediction model using process and coal blend parameters.

Phosphorus removal from model wastewater using lanthanum hydroxide microcapsules with poly(vinyl chloride) shells

In this study, lanthanum hydroxide microcapsules with 20 wt% of poly(vinyl chloride) shells were prepared by encapsulation as a means of removing phosphorus from wastewater. Scanning electron microscopy observations showed that the microcapsules were highly porous and lanthanum hydroxide particles were densely located on the pore walls. The phosphorus adsorption and desorption properties of microcapsules were investigated using model wastewater with a phosphorus concentration of 1 mg-P/dm3. The maximum phosphorus uptake of the microcapsules with arithmetic mean size of 0.38 mm was 92 mg-P/g in a batch experiment, corresponding to the phosphorus uptake of 115 mg-P per gram of lanthanum hydroxide in the microcapsule, which was almost the same as the maximum phosphorus adsorption capacity (118 mg-P/g) of lanthanum hydroxide powder used for the encapsulation. The phosphorus in phosphorus-loaded microcapsules can be effectively desorbed using 3 mol/dm3 sodium hydroxide and the regenerated microcapsules can be repeatedly used without degrading the phosphorus adsorptivity. A fixed-bed column study showed that the microcapsules can effectively remove phosphorus from model wastewater to less than 0.1 mg-P/dm3 until 11,000 times the bed volume, even in the third adsorption–desorption cycle.

Fractal features of sandy soil particle-size distributions during the rangeland desertification process on the eastern Qinghai-Tibet Plateau

Fractal theory has been frequently applied to quantify soil particle-size distributions (PSDs) and evaluate soil degradation. Eolian desertification occurring on the eastern Qinghai-Tibet Plateau is threatening the ecological environment. It is essential to investigate the desertification process by adopting the concept of space as a substitute for time. Here, the fractal features of soil PSDs and their relationships with selected soil properties and wind erosion and deposition were studied. The tested soil samples were collected from rangelands with four different degrees of desertification (light, medium, severe, and extremely severe). Soil particle sizes were measured by a laser diffraction particle-size analyzer. Soil moisture and soil bulk density were determined by the soil weight difference before and after oven-drying for 8 h. Soil organic carbon was determined by the K2Cr2O7-H2SO4 oxidation method and soil total nitrogen was analyzed using the Kjeldahl digestion procedure. Wind tunnel experiments were conducted to simulate wind erosion and deposition during the desertification process. Values of the fractal dimension of soil PSDs were calculated using the volume-based fractal model. ANOVA with an LSD test and Pearson correlation analysis were used to analyze whether different parameters used in the fractal model influenced the results of the fractal dimensions and were reasonable to be applied. Different parameters, including the arithmetic mean size and the upper sieve size of two successive sieve sizes, values of Rmin, and the number of data points used in the fractal model, rarely influenced the results of the fractal dimensions (p > 0.05). The D values showed a significantly positive correlation with the clay and silt contents and a strong negative correlation with the sand contents. Along the degrees of desertification from light to extremely severe, the contents of clay, silt, and very fine sand decreased while the fine sand contents increased, and the D values decreased accordingly. Rangelands with heavier desertification and lower D values were more easily exposed to wind erosion, relating to the further loss of soil organic carbon, soil total nitrogen, and soil moisture and increased soil bulk density. The soil depth could affect soil PSDs and the selected soil properties of rangelands under light and medium degrees of desertification but rarely influenced those of severely and extremely severely desertified lands. Different parameters, including the arithmetic mean size, the upper sieve size, values of Rmin, and the number of data points used in the fractal model, had no impacts on the results of the fractal dimensions, and were reasonable to be applied. We suggest the fractal dimension as an effective indicator to evaluate soil environment changes induced by desertification.

Pressure drop model of high-concentration graded particle transport in pipelines

The existing formulas for calculating the pipeline transport resistances of granular materials are mostly based on the experimental data for single-sized or regularly graded particles. Consequently, it is necessary to simplify the in-situ distribution using an equivalent size, such as the median particle size (d50), arithmetic mean size (dm), or harmonic average size (dk), in the sediment transport resistance calculations. This simplification completely ignores the effect of particle gradation on the pressure drop, particularly in the case of multi-size, high-concentration particle transport. Therefore, the mechanism and degree of influence of the particle size variation in different flow conditions on the pipeline resistance was investigated in this study. The interaction between the differently sized particles in the graded slurry was also examined. Furthermore, a new model called the Shanghai Jiao Tong University high-concentration multi-sized slurry pressure drop (SJTU-HMSPD), which is based on the particle size distribution and multi-regime slurry resistance in pipeline transport throughout the flow velocity range, was developed and is presented in this paper. The SJTU-HMSPD is more suitable for calculating the pipeline transport resistances of complex graded slurries, and the calculation results agree well with the experimental data. All the input data are available in practice making the model very convenient.

Having a BLAST: Searchable transcriptome resources for the gilthead sea bream and the European sea bass

The gilthead sea bream (Sparus aurata) and the European sea bass (Dicentrarchus labrax) are the most important aquaculture species in the Mediterranean Sea and since the last decade it has been seen an exponential increase in their available molecular resources. In order to improve accessibility to transcriptome resources, Expressed Sequence Tags (ESTs), mRNA sequences and raw read sequences were assembled and deposited in BLAST queryable databases. The publicly available sea bream and sea bass sequences (6.4 and 247.5 million) generated 45,094 and 68,117 assembled sequences, with, respectively, arithmetic mean size of 998 and 2125bp and N50 of 1302 and 2966bp. The assemblies will be regularly updated and new analytical tools added to the web server at http://sea.ccmar.ualg.pt.

Non-parametric analysis of the rest-frame UV sizes and morphological disturbance amongstL*galaxies at 4 <z< 8

We present the results of a study investigating the sizes and morphologies of redshift 4 < z < 8 galaxies in the CANDELS GOODS-S, HUDF and HUDF parallel fields. Based on non-parametric measurements and incorporating a careful treatment of measurement biases, we quantify the typical size of galaxies at each redshift as the peak of the log-normal size distribution, rather than the arithmetic mean size. Parameterizing the evolution of galaxy half-light radius as $r_{50} \propto (1+z)^n$, we find $n = -0.20 \pm 0.26$ at bright UV-luminosities ($0.3L_{*(z=3)} < L < L_*$) and $n = -0.47 \pm 0.62$ at faint luminosities ($0.12L_* < L < 0.3L_*$). Furthermore, simulations based on artificially redshifting our z~4 galaxy sample show that we cannot reject the null hypothesis of no size evolution. We show that this result is caused by a combination of the size-dependent completeness of high-redshift galaxy samples and the underestimation of the sizes of the largest galaxies at a given epoch. To explore the evolution of galaxy morphology we first compare asymmetry measurements to those from a large sample of simulated single S\'ersic profiles, in order to robustly categorise galaxies as either `smooth' or `disturbed'. Comparing the disturbed fraction amongst bright ($M_{UV} \leq -20$) galaxies at each redshift to that obtained by artificially redshifting our z~4 galaxy sample, while carefully matching the size and UV-luminosity distributions, we find no clear evidence for evolution in galaxy morphology over the redshift interval 4 < z < 8. Therefore, based on our results, a bright ($M_{UV} \leq -20$) galaxy at z~6 is no more likely to be measured as `disturbed' than a comparable galaxy at z~4, given the current observational constraints.

Structurization and phase formation in the course of preparing nanocomposite TiN–Ni ion-plasma vacuum–arc coatings and their thermal stability

Structure and phase formation in the course of fabricating composite ion–plasma vacuum-arc nanocrystalline TiN–Ni coatings are investigated in a broad range of nickel concentrations (from 0 to 26 at %). It is established that the introduction of Ni into the coating composition refines the nitride phase crystallites. The arithmetic mean size of TiN grains decreases from 100–120 to 15–18 nm upon varying the Ni concentration from 0 to 12 at % and normal particle-size distribution. The further increase in the Ni content is accompanied by the transition to the polymodal particle distribution with an increase in their arithmetic mean diameter to 27 nm for the third mode. Nickel in coatings at a concentration of 12–13 at % Ni is in the X-ray amorphous state. As the concentration increases above 13 at %, the TiNi intermetallic compound is formed in the composition of coatings. This phenomenon in turn causes the appearance of porosity in the structure of the deposited layer. The blocking role of nickel simultaneously weakens with the formation of the intermetallic compound, which manifests itself in the growth of separate TiN grains to 30–35 nm. The TiN–Ni coatings are characterized by the thermal stability of the structure and composition upon heating to 800°C.

Preparation of monodispersed PMMA particles and composite particles containing pigment green 36 by dispersion polymerization

Monodispersed PMMA (polymethyl methacrylate) particles were prepared via a dispersion polymerization process using methanol as the dispersive medium, azobisisobutyronitrile (AIBN) as initiator, and polyvinylpyrrolidone (PVP) as steric stabilizer. This study applied the Taguchi experimental design to determine an optimized formulation for preparing monodispersed PMMA particles at a stabilizer molecular weight of 360kDa, a concentration of 8.0wt.%, a monomer concentration of 5.0wt.%, and an initiator concentration of 0.05wt.%. The addition of water to the dispersive medium alters the dispersive medium solvency, causing a reduction in size of the monodispersed particles, which could be as small as 0.40μm diameter under our experimental conditions. We used pure methanol as dispersive medium, and successfully prepared spherical monodispersed composite particles containing pigment green 36 and PMMA by dispersion polymerization in the presence of pigment green 36. The experimental results show that the arithmetic mean size of composite particles decreased, and pigment content in composite particles increased after increasing the amount of pigment in the polymerization process.

Precipitation kinetics of PMMA sub-micrometric particles with a supercritical assisted-atomization process

Sub-micrometric particles of PMMA were successfully prepared via a supercritical assisted-atomization (SAA) process using acetone as a solvent and supercritical carbon dioxide as a spraying medium. The effects of several key factors on the particle size were investigated. These factors included the concentration of polymer solution, temperature in saturator and volumetric flow rate ratio of carbon dioxide to polymer solution. The shape of the polymer's primary particles is spherical with the arithmetic mean size ranging from 82 nm to 176 nm and the mass-weighted mean size ranging from 127 nm to 300 nm. As evidenced from the experimental results, the lower concentrations of polymer solution, optimized volumetric flow rate ratios, and higher temperatures in saturator can effectively reduce the mean particle size. The precipitation kinetic parameters were determined from the particle size distributions with the aid of the population balance theory. This study found the primary nucleation to be dominant in the precipitation and diffusion may govern particle growth.

On Sizing and Counting of Microbubbles Using Optical Microscopy

Intra- and interobserver (n = 3) variability of sizing and counting microbubbles using optical microscopy (OM) was assessed. The system was calibrated using standardised mono-disperse and poly-disperse microspheres. Results of the calibration show intraobserver variations of number count (C) = 13.0% and arithmetic mean size (MS) = 0.2%, and interobserver variations of C = 18.4% and MS = 0.6%, for the mono-disperse microspheres. For the poly-disperse microspheres, intraobserver variations were: C = 6.9% and MS = 0.8%, and interobserver: C = 10.5% and MS = 0.3%. For SonoVue™ the intraobserver variations were: C = 23.3% and MS = 8.0%, and interobserver C = 6.8% and MS = 3.8%. The results suggest that the higher values of the intraobserver variation for SonoVue™ arise from the natural decay of microbubbles over time. This article presents a detailed protocol and outlines potential pitfalls in our approach. These results are in general agreement with those previously reported and compare well with known size distributions. (E-mail: c.sennoga@imperial.ac.uk)

Influence of cohesion on the incipient motion condition of sediment mixtures

Previous investigations on initiation of motion and erosion of cohesive sediment mixtures have not included gravel within the mixtures. Experimental results on the incipient motion characteristics of cohesive sediment mixtures containing gravel are presented in this paper. The sediment used consisted of fine gravel mixed with clay in proportions varying from 10% to 50% by weight, and fine gravel with fine sand mixed in equal proportion, with clay proportions again varying from 10% to 50% by weight. The stages of the incipient condition of motion were visually identified. Three modes of initiation of motion of cohesive sediment mixtures were noticed, namely, pothole erosion, line erosion, and mass erosion. The modes of initiation of motion changed mainly with clay percentages in the mixture, its antecedent moisture characteristics, and the applied shear stress. Analysis of the experimental data from the present study and the literature revealed that depending upon the flow and sediment characteristics, the critical shear stress of the incipient motion condition in cohesive sediment mixtures can be up to 50 times larger than the critical shear stress of cohesionless sediments having similar arithmetic mean size as the cohesive sediments. On the basis of dimensional considerations, a relationship is proposed for the determination of critical shear stress of the incipient motion condition in cohesive sediment mixtures also containing gravel. The variables, namely, clay percentage, void ratio, and unconfined compressive strength of the sediment bed, are noticed to be the main parameters controlling the incipient motion condition of the cohesive sediments. In the absence of cohesion, the proposed relationship reduces to the critical shear stress for the incipient motion condition of the cohesionless sediment mixture having the same arithmetic mean size. The condition for the threshold of erosion of cohesive sediment mixtures by the flow is thus parameterized in the present study.

What expansion factor should be used in binned probability proportional to size sampling?

In probability proportional to size sampling, including prism cruising and other forms of point and line sampling, calculation of an exact expansion factor requires that size be recorded exactly. When sizes are binned or recorded by class, this information is lost. While several alternatives for calculating the expansion factor have been proposed, theoretical attention has been lacking. A decision-theoretic perspective helps distinguish between the alternatives and offers some support to the use of the arithmetic mean size in calculating the expansion factor, a choice which had previously come under some criticism. However, consistency arguments strongly favor estimators based on squared error loss or minimax principles. Some new alternatives are suggested when prior information about the diameter distribution in a stratum is available.

Density‐Dependent Pond Growout of Single Year‐Class Cohorts of a Freshwater Crayfish Cherux tenuimanus (Smith) to Two Years of Age

AbstractPond growout of Cherax tenuimanus to two years of age provided data for mean crayfish weight, surviving density and distribution of individual sizes at intervals and final harvest for 12 single year‐class cohorts. Final mean size (47–156 g) was most significantly related to surviving density (4.5–0.7/m2). A hyperbolic model with a harvest date variable accounted for 89% of the variation in mean weight. The biological basis of this model is that the reciprocal of density, i.e., pond area per crayfish, represents food supply for a bottom‐dwelling crayfish. By incorporating the Richards growth function, the hyperbolic model can be more realistically fitted to include the limit to potential size at very low densities. The growth‐density relationship developed after an initial period of 300 days of low growth (to ∼ 10% of final size) and high mortality. Then, mean weight increased rapidly and density stabilized. Final cumulative production (1.401–3,922 kg/ha) and harvest biomass (1,110–2,991 kg/ha) both increased linearly with density. Survival of the total amount of crayfish produced was about 75% at harvest. Although cohort size distributions were positively skewed, the arithmetic mean size employed in the model was very closely and linearly related to the geometric mean of the lognormal distribution, The causal basis and assumptions of the growthdensity model are discussed in relation to resource sharing by individuals and the disproportionate influence of size‐related dominance behaviour.

Optimal sample size for thin-section size studies

The measured two- or one-dimensional sizes on polished thin-sections are differentially biased due to: (1) the section plane does not necessarily pass through the centre of the grains; and (2) larger grains have a greater chance of inclusion (and hence of being measured) in the section plane. The required size moments in the higher three- or two-dimensional space should be computed by the Sahu probability model, which is more accurate than either the Hagerman—Krumbein or Wicksell models for bias correction. A highly significant linear regression structure between the logarithm of sample size (log N) as dependent, and sampling variance of corrected arithmetic mean size as independent variables, predicts that equivalent precision for a space reduction of one or two units, is respectively given by 13 times or 13 × 13 = 169 times more grain measurements in the lower space under the Sahu model. Thus, 260 circle diameters or 3380 intercepts are equivalent to 20 spheres, and numbers greater than these form large samples. Similarly, 3900 circle diameters or 50,700 intercepts are equivalent to 300 spheres which form a sufficient sample size. Since a very large number of counts is necessary for polished thin-section size studies, it is desirable to measure size in the lower (polished thin-section) space by automatic scanning devices.

Some Problems of Size and Sorting in Sands

AbstractFor certain unconsolidated sediments there is a linear relationship between the arithmetic mean size and the “grading factor”, and sediments with an average particle size of 0·2 mm. show the maximum degree of sorting. An hypothesis has been developed to explain this relationship in terms of the environment of deposition.