Complete Size Distribution Research Articles

Dissolution zone model of the oxide structure in additively manufactured dispersion-strengthened alloys

The structural evolution of oxides in dispersion-strengthened superalloys during laser-powder bed fusion is considered in detail. Alloy chemistry and process parameter effects on oxide structure are assessed through a parameter study on the model alloy Ni-20Cr, doped with varying concentrations of Y2O3 and Al. Small angle neutron scattering measurements of the complete dispersoid size distribution show the dispersoid size increases with higher laser power, slower scan speed, and increasing Al and Y2O3 content. Complementary electron microscopy measurements reveal reactions between Y2O3 and Al, even in nanoscale dispersoids, and the presence of micron-scale oxide slag inclusions in select specimens. A scaling analysis of mass and momentum transport within the melt pool, presented here, establishes that diffusional structural evolution mechanisms dominate for nanoscale dispersoids, while fluid forces and advection become significant for larger slag inclusions. These findings are developed into a theory of dispersoid structural evolution, integrating quantitative models of diffusional processes – dispersoid dissolution, nucleation, growth, coarsening – with a reduced order model of time-temperature trajectories of fluid parcels within the melt pool. Calculations of the dispersoid size in single-pass melting reveal a zone in the center of the melt track in which the oxide feedstock fully dissolves. Within this zone the final Y2O3 size is independent of feedstock size and determined by nucleation and growth kinetics. If the dissolution zones of adjacent melt tracks overlap sufficiently with each other to dissolve large oxides, formed during printing or present in the powder feedstock, then the dispersoid structure throughout the build volume is homogeneous and matches that from a single pass within the dissolution zone. Gaps between adjacent dissolution zones result in oxide accumulation into larger slag inclusions. Predictions of final dispersoid size and slag formation using this dissolution zone model match the present experimental data and explain process-structure linkages speculated in the open literature.

Assimilating Size Diversity: Population Balance Equations Applied to the Modeling of Microplastic Transport.

Modeling of microplastic (MP) transport in the aquatic environment is complicated by the diverse properties of the plastic particles. Traditional modeling methods such as Lagrangian particle tracking and Eulerian discrete class (DC) methods have limitations as they are not best placed to account for the diverse characteristics of individual particles, namely, size, density, and shape, which are crucial for determining the transport of MPs. In this work, we address the issue of particle size diversity by using the population balance equations (PBE) method. In addition to the advection-diffusion terms, the PBE transport equation involves a deposition sink term. Seven size classes of MPs are modeled in the DC method, which is compared to the PBE method. The evolution of particle size distribution is compared between the two methods using a simplified test case of a schematized estuary with tidal forcing and river discharge. This work successfully demonstrates the applicability and appropriateness of the PBE model in modeling the transport of MPs to track the dynamic and complete size distribution at a reduced computational cost in comparison to the DC model. With the PBE method, it is possible to address other diversities of the MPs such as the shape and density.

Distribution Nudibranch and Carnivorous Fish in The North Bali Sea

The presence or absence of certain types of carnivorous coralfish in a coral reef ecosystem accurately indicates the health of a coral reef ecosystem and the organisms associated with it; one of them is the nudibranch. This research aims to determine whether the presence of carnivorous fish in coral reef ecosystems affects the quality of the nudibranch life cycle and the distribution size in terms of predation. Nine carnivorous fish species were found at the three research stations, the largest group being triggerfish and grouper found in Lovina Reef and Menjangan island. Observed from the size distribution of nudibranchs, the presence of nudibranchs in the three research locations shows sizes ranging from small to large, namely from the Phyllididae nudibranch group. The dead body of the nudibranch was found in Tulamben reef, but it could not be confirmed whether the nudibranch was preyed by carnivorous fish. Carnivorous fish are not predators and do not affect the life cycle of nudibranchs observed from the complete size distribution of nudibranchs from small to large. Nudibranch predators cannot digest nudibranch bodies because their bodies are venomous; they use them as self-defense against the predators. Nudibranchia are not always found when preyed on by fish.

Taylor vortex-based protein crystal nucleation enhancement and growth evaluation in batchwise and slug flow crystallizers

The utilisation of nucleation seeds, coupling nucleation and growth during crystallization and realistic continuum are currently relatively robust, reliable and scalable methods for protein crystallization optimization. Here, we design a segmented crystallization method, in which combines the characteristics of the Taylor vortex enhanced lysozyme nucleation stage. Different crystallizer are used for the growth segment so that the nucleation segment and the growth segment are organically combined during lysozyme crystallization. During the crystal growth stage, the crystallization properties of the Couette-Taylor (CT) crystallizer, mixing Tank (MT) crystallizer and tubular crystallizer were evaluated. The experimental results emphasize the importance of shear rate, temperature, and fluid velocity in the design of segment crystallization methods to obtain products with complete crystal morphology and uniform size distribution. This strategy successfully expanded the lysozyme crystallization from the original 10 mL scale to 200 mL, realized the continuous process, and providing a promising strategy for the design and operation of continuous SFC to produce high value protein crystals in the future.

Drop Size Distributions as a Function of Dispersed Phase Viscosity: Experiments and Modeling

AbstractDetailed measurements of dynamic and steady‐state drop size distributions were performed in liquid‐liquid systems with water and different silicone oils using an in situ endoscope technique in a discontinuously operated stirred tank. The oils used as the dispersed phase vary in dynamic viscosity, while density and interfacial tension are nearly constant. The performance of a population balance model for partially mobile interfaces and its ability to predict steady‐state and dynamic Sauter mean diameters and the complete drop size distributions as a function of dispersed phase viscosity and different process parameters are evaluated. Furthermore, the impact of different daughter drop size distribution shapes on simulation results is quantified.

Pollutant characteristics and size distribution of trace elements during stormwater runoff events

Priority trace elements As, Cu, Cr, Ni, Pb, and Zn are largely present in urban stormwaters and should be controlled due to their impact on water bodies. As it has been observed that there are numerous limitations in the purification performance of roadway stormwater runoff treatment systems, the particulate size distribution of trace elements was studied extensively to assess the colloidal fractions present in stormwater runoff of a high-traffic roadway site (100 000 vehicles/day). Besides the evaluation of the total Event Mean Concentrations (EMCs) and dissolved concentrations, a complete fractionation scheme of low settling phase of runoff water (<30 µm) was applied to a series of rain events, considering 8 µm and 5 kDa, as relevant cut-offs between particulate/colloidal elements, and colloidal/truly dissolved elements. The intra-event size distribution was also considered to assess the first-flush effect and the variation of the physical speciation. The high-level traffic associated with climatic conditions (rainfall depth) are responsible for very high EMCs for Zn and Cu, together with a significant exceedance of the European environmental water standards (<0.45 µm concentrations). Ni, Cr and Pb are mainly present as particulate and colloidal metals. Therefore, considering a more complete size distribution is relevant for these elements. For As, Cu and Zn, the conventional fractionation at 0.45 µm seems to be sufficient to evaluate the highly mobile fraction. The results also indicate that, while the main particulate load may be collected within the early volumes of the rainfall events (about 30%), the variability of rain intensity during long events induces changes in particulate and colloidal metals in the runoff. The treatment of runoff must then be considered as a whole in view of the variability of trace metal size distribution. This suggests that urban stormwater runoff treatment systems which employ only the settleable fraction are not sufficient to limit the chemical and ecological risks to receiving water bodies.

How to trust size distributions obtained by single particle inductively coupled plasma mass spectrometry analysis

Single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) is a technique widely used to obtain direct information about the number concentration and the size distribution of nanoparticles in liquid suspensions. However, its methods still lack clear quality control strategies to confirm the validity of the information derived from them. Only the detection of the complete size distribution of the nanoparticles in a sample over the size critical value ensures obtaining unbiased quantitative information, otherwise information should be restricted to report the presence of nanoparticles over a certain size and number concentration since their actual total number concentration is underestimated and the size overestimated. Under the latter conditions, data processing produces histograms showing the tails of the incomplete size distributions, although apparently, complete distributions can also be obtained when particle events are recorded as peaks, as reported here for the first time. The occurrence of these misleading situations must be critically evaluated for each SP-ICP-MS analysis. An approach, based on estimation of size critical values and successive dilutions, is proposed for the assessment of the validity of the quantitative information obtained, together with specific criteria for reconsidering the information that can be derived from those measurements. The approach was verified with different case studies and applied to the analysis of complex nanomaterials, confirming the validity of the reported information by comparison with other techniques. A calculation tool is also included to facilitate the estimation of size critical values under experimental conditions.Graphical abstract

Quantification of Pore Size and Movable Fluid Distribution in Zhangjiatan Shale of the Ordos Basin, China

The Triassic Zhangjiatan shale in the Ordos basin, recognized as one of most promising shale oil and gas resources in China, is one example of medium-low-maturity lacustrine shale reservoirs wherein the pore network has been proven to be different from those of both conventional and high-maturity marine shale reservoirs. Here, we examine the quantitative characterization of pore size and movable fluid distribution of the Zhangjiatan shale reservoir. Eight shale core plugs were measured in a series of nuclear magnetic resonance (NMR) experiments to determine the pore structure and pore fluid transport during the processes of centrifuging and heating. The complete pore size distribution was obtained from the T 2 spectrum by integrating NMR, high-pressure mercury intrusion, and nitrogen gas adsorption. The results show that the movable fluid saturation of Zhangjiatan shale is 19.47–33.02% and the capillary-bound fluid saturation is 14.53–27.62%, whereas the unrecoverable fluid saturation was 43.51–65.26%. The movable fluids are mainly detected in macropores and mesopores with a minimum pore size of 50.5–121.2 nm, while capillary-bound fluids are mainly found in small pores and some mesopores with a minimum size of 25.8–67.5 nm. Almost all unrecoverable fluids are in micropores and small pores. In contrast to high-maturity shale reservoirs, the Zhangjiatan shale shows a poor correlation between total organic carbon content and unrecoverable fluid saturation but a good correlation between clay minerals and unrecoverable fluid saturation, showing that most micropores are associated with clay minerals and the organic matter pores are less developed. This study provides an accurate determination of the pore size distribution and pore fluid typing of Zhangjiatan shale, which is of great significance for the development of high-quality but medium-low-maturity shale reservoirs in China.

Exploitation of striped snakehead (Channa striata) in Sempor Reservoir, Central Java, Indonesia: A proposed conservation strategy

Abstract. Setyaningrum N, Lestari W, Krismono, Nuryanto A. 2022. Exploitation of striped snakehead (Channa striata) in Sempor Reservoir, Central Java, Indonesia: A proposed conservation strategy. Biodiversitas 23: 3584-3592. Striped snakehead (Channa striata) has important economic value in freshwater systems, including Sempor Reservoir in Indonesia, where increases in catch sizes have resulted in a declining population. In this study, we determined its population size based on abundance and distribution of length and assessed the rate of exploitation based on estimated growth and mortality rates to determine a conservation strategy in Sempor Reservoir. The study was undertaken from March to October 2020. The method used was a purposive random sampling survey. Fish samples were taken from five stations with different land uses. The estimated growth, mortality, and exploitation rates were analyzed by Pauly's model using FISAT II. Channa striata abundance data were analyzed using a Kruskal-Wallis test. The results showed that the highest abundance of C. striata at the KW station was almost three times higher than at the BK station. The average size of the gonads at first maturity was 277.4 mm in females and 284 mm in males. The estimated growth parameters indicated an asymptotic length (L?) of 409.5 mm. An exploitation rate of 0.74 was classified as overfishing. The proposed conservation strategy is to limit the number of catches by as much as 44% and prohibit the catching of individuals with a length of 230-349 mm. Kedungwringin Station was defined as a reference area with the largest abundance and complete size distribution, namely, the pre-reproduction, reproduction, and post-reproduction stages. Bangkong Station was defined as a spawning ground because there were many fish in the reproductive stage and Sempor River Station was the nursery ground with mostly juvenile fish. These two sites must be protected for sustainable striped snakehead populations in the river and reservoir.

Transmittance predictions for transparent alumina ceramics based on the complete grain size distribution or a single mean grain size replacing the whole distribution

A simple method, based on the equivalent composite model or the dense polycrystalline model, is proposed for predicting the in-line transmittance in ceramics with a grain size distribution of birefringent crystallites. It is shown that the transmittance predictions based on the Rayleigh-Gans approximation are indistinguishable from those based on Mie theory, so that the latter can be replaced by the former. Based on normal distributions of different position and width it is shown that size distributions with smaller mean sizes lead to higher transmittance, whereas the effect of the distribution width on the transmittance is comparatively weak (with the narrowest distribution being the most favorable for high transmittance). The key result of this paper is the fact that for the distributions investigated (normal and log-normal) the transmittance prediction based the whole grain size distribution can be replaced by a transmittance prediction based on the geometric mean of the intensity-weighted distribution.

Spatially-resolved characterization of oil-in-water emulsion sprays

When an oil-in-water emulsion is utilized for application in a flat-fan spray, micrometer-sized oil droplets are thought to facilitate hole formation on the spray lamella, leading to an earlier breakup of the spray sheet and an increase in resulting droplet sizes. However, prior work has largely focused on changes to the mean or median droplet size, and has not examined the influence of oil-in-water emulsions on the complete droplet size distribution, as well as other droplet properties such as droplet shape and droplet velocity distributions in flat fan sprays. This study concerns the effects of pressure, spatial location, and application of oil emulsions on the resulting droplet size, eccentricity, as well as velocity distributions, all of which are crucial information in determining the dispersion dynamics of the droplets during the spray applications. Experiments were conducted with a TP6515 nozzle, with the abovementioned droplets information measured using digital inline holography (DIH). Results show that the DIH-inferred volumetric droplet size distributions (VDSD) span widely from sub-100 μm to over 2 mm in size. The application of an oil-in-water emulsion results largely in suppression of smaller droplets, while the VDSD is relatively insensitive to increasing the oil volume fraction beyond a critical level. DIH results are consistent with the observation that smaller ligaments are observed only in the breakup regions for the single-phase water sprays, which break up more violently and earlier than larger ligaments. It is these smaller ligaments that are suppressed in the oil-in-water emulsion, which yield sub-millimeter droplets, some with sizes approaching sub-100 μm dimensions, corresponding to driftable sizes in agricultural settings. Interestingly, the application of oil-in-water emulsion generally decreases the eccentricity more significantly at the center than at the edge of the spray fan. We attribute this decrease to the increase in lamella sheet thickness and thus decrease in characteristic shrinkage rates, consistent with observations of high speed shadowgraphs. In all instances, oil-in-water emulsion droplets have higher velocities than equivalent sized water droplets. We attribute this to the earlier action of the spray breakup process in the oil-in-water emulsion, reduced surface energy generation during breakup (larger droplets), and reduced energy dissipation during breakup with oil-in-water emulsions, leading to increased translational energy after the breakup process. Therefore, it appears that oil-in-water emulsion application simultaneously suppresses small droplet formation and increases droplet velocity, and hence spray penetration in agricultural application.

Computationally Efficient Algorithm for Solving Population Balances with Size-Dependent Growth, Nucleation, and Growth-Dissolution Cycles

A computationally efficient algorithm for solving population balance equations (PBEs) for describing the evolution of crystal size distribution (CSD) in seeded batch crystallization processes is developed. The algorithm is particularly suitable for solving problems with size-dependent growth and dissolution kinetics where temperature cycling is applied to modify the CSD. It is much faster than the quadrature method of moments (QMOM) which has been widely applied to solve this type of problem and has the added benefit that it provides the complete crystal size distribution rather than only the moments. These features make it especially well suited for solving problems in optimization and determination of feasible regions, where many batch simulations are required. The algorithm is applied to determine attainable regions for seed-grown product crystals (characterized by the mean and variance of the seed-grown product CSD) and analyze the trade-off between the objectives of minimizing batch time and nucleated crystal volume in a batch crystallization process with temperature cycling. Two main conclusions are drawn from the results. First, the attainable region expands with an increasing number of growth-dissolution cycles as expected, but the extent of the increase or decrease in the attainable variance depends on the sensitivity of the growth and dissolution rates to the crystal size. Second, the trade-off between the abovementioned objectives subject to constraints on the seed-grown crystal mean size and variance is significant and an outcome representing a good compromise can be achieved by specifying proper supersaturation and undersaturation set points.

Baltic Sea Spray Emissions: In Situ Eddy Covariance Fluxes vs. Simulated Tank Sea Spray

We present the first ever evaluation of sea spray aerosol eddy covariance (EC) fluxes at near coastal conditions and with limited fetch, and the first over water with brackish water (on average 7 ppt). The measurements were made on the island of Garpen in the Baltic Sea (56°23′ N, 16°06′ E) in September 2005. We found that wind speed is a major factor that is driving an exponential increase in sea spray sea salt emissions, comparable to previous studies over waters with higher salinity. We were able to show that the inclusion of a thermodenuder in the EC system allowed for the parallel measurements of the dry unheated aerosol flux (representing both organic and sea salt sea spray emissions) and the heated (300 °C) non-volatile sea salt emissions. This study’s experimental approach also included measurements of the artificial sea spray formed in a tank in locally sampled water at the same location as the EC fluxes. We attempted to use the EC aerosol flux measurements to scale the tank measurements to aerosol emissions in order to derive a complete size distribution for the sea spray emission fluxes below the size range (0.3–2 µm dry diameter) of the optical particle counters (OPCs) in the EC system, covering in total 0.01 µm to 2 µm diameter. In the wind directions with long fetches (corresponding to conditions similar to open sea), we were able to distinguish between the aerosol emission fluxes of dry aerosol and heated non-volatile (sea salt only) in the smallest size bins of the OPC, and could therefore indirectly estimate the organic sea spray fraction. In agreement with several previous ambient and tank experiments deriving the size resolved chemical mass concentration of sea salt and water-insoluble organic sea spray, our EC fluxes showed that sea sprays were dominated by sea salt at sizes ≥1 µm diameter, and by organics at the smallest OPC sizes. Since we used direct measures of the sea spray emission fluxes, we confirmed previous suggestions that this size distribution of sea salt and organics is a signature of sea spray aerosols. We were able to show that two sea salt source parameterizations (Mårtensson et al. (2003) and Salter et al. (2015)) agreed fairly well with our observed heated EC aerosol emission fluxes, as long as their predicted emissions were modified for the actual salinity by shifting the particle diameters proportionally to the cubic rote of the salinity. If, in addition, we added organics to the parameterized sea spray following the mono-layer model by Ellison et al. (1999), the combined sea spray parameterizations for sea salt and organics fell reasonably close to the observed fluxes for diameters &gt; 0.15 µm, while one of them overpredicted the sea spray emissions below this size. The organic mono-layer model by Ellison et al. appeared to be able to explain most of the differences we observed between the aerosol emission fluxes with and without the thermodenuder.

Connecting Longitudinal and Transverse Relaxation Rates in Live-Cell NMR.

In the cytosolic environment, protein crowding and Brownian motions result in numerous transient encounters. Each such encounter event increases the apparent size of the interacting molecules, leading to slower rotational tumbling. The extent of transient protein complexes formed in live cells can conveniently be quantified by an apparent viscosity, based on NMR-detected spin-relaxation measurements, that is, the longitudinal (T1) and transverse (T2) relaxation. From combined analysis of three different proteins and surface mutations thereof, we find that T2 implies significantly higher apparent viscosity than T1. At first sight, the effect on T1 and T2 seems thus nonunifiable, consistent with previous reports on other proteins. We show here that the T1 and T2 deviation is actually not a inconsistency but an expected feature of a system with fast exchange between free monomers and transient complexes. In this case, the deviation is basically reconciled by a model with fast exchange between the free-tumbling reporter protein and a transient complex with a uniform 143 kDa partner. The analysis is then taken one step further by accounting for the fact that the cytosolic content is by no means uniform but comprises a wide range of molecular sizes. Integrating over the complete size distribution of the cytosolic interaction ensemble enables us to predict both T1 and T2 from a single binding model. The result yields a bound population for each protein variant and provides a quantification of the transient interactions. We finally extend the approach to obtain a correction term for the shape of a database-derived mass distribution of the interactome in the mammalian cytosol, in good accord with the existing data of the cellular composition.

Comparisons between Geotextile Pore Sizes Obtained from Capillary Flow And Dry Sieving Tests

Abstract In the United States of America, two standard methods of measuring the largest pore size of a geotextile have been accepted: Dry Sieving Test (ASTM D4751, Standard Test Methods for Determining Apparent Opening Size of a Geotextile) and Capillary Flow Test (ASTM D6767, Standard Test Method for Pore Size Characteristics of Geotextiles by Capillary Flow Test). Despite several drawbacks of Dry Sieving Tests, such as the amount of time required; tendency of glass beads to become trapped, including trapping of glass beads inside the geotextiles; likelihood of imprecise preparation of glass beads; and potential electrostatic effects, the largest pore size (apparent opening size [AOS], O95) results obtained from Dry Sieving Test still determines many filtration criteria. Although the Capillary Flow Test was approved in 2002, it is still not widely adopted, despite the fact that it provides the largest pore size (Bubble Point, O98) and a complete pore size distribution of a geotextile. Decades of analyses searched for a correlation between the Dry Sieving and Capillary Flow Test results; however, none of them have been widely accepted because of the limited number of geotextiles used and a lack of proper calibration. The current study investigates a possible correlation between the Dry Sieving and Capillary Flow Test results with 51 woven, nonwoven, and composite geotextiles. The Capillary Flow Porometer was calibrated using four thin metal plates with known pore openings and two membranes. This study describes the challenges experienced during the Capillary Flow Test and factors affecting the test results. One finding is that the cleaning of calibration materials and equipment with Methanol plays an important role in the Capillary Flow Test results. The use of different shape factors, contact angles, and wetting liquids in the analyses are also considered. The outliers of Capillary Flow Test results were removed from the analysis using a box plot and whisker diagram, and a good correlation between AOS and Bubble Point (R2 = 0.78) was established.

A Cosserat Breakage Mechanics model for brittle granular media

This paper introduces a Breakage Mechanics model formulated in the framework of Cosserat continuum theory. This formulation allows us to account for the interaction of grain size evolution with shear band formation in a physically motivated and thermodynamically consistent way. We provide an upscaling procedure that introduces material parameters accounting for the contribution of the Cosserat rotations, as well as the micro-inertia of the entire grain size distribution. A particular highlight of the new formulation is the capacity to describe an evolving internal Cosserat length that takes account of the complete grain size distribution and its evolution. In addition, we specify a particular model that requires no additional calibration relative to the same model in the classical continuum. We apply this model to the study of a layer sheared under constant volume which simulates the fast undrained deformation observed in seismogenic faults. Through linear stability analysis we use the model to examine the effect of grain size polydispersity on the thickness of shear bands. By implementing the model using the finite element method we provide an explanation for the geological formation of double cataclastic shear bands.

Application of big data analysis technique on high-velocity airblast atomization: Searching for optimum probability density function

In this paper, the droplet size distributions of high-velocity airblast atomization were analyzed. The spray measurement was performed by a Phase-Doppler anemometer at several points and different diameters across the spray for diesel oil, light heating oil, crude rapeseed oil, and water. The atomizing gauge pressure and the liquid preheating temperature varied from 0.3 to 2.4 bar and 25 to 100 °C, respectively. Approximately 400 million individual droplets were recorded; therefore, a big data evaluation technique was applied. 18 of the most commonly used probability density functions (PDF) were fitted to the histogram of each measuring point and evaluated by their relative log-likelihood. Among the three-parameter PDFs, Generalized Extreme Value and Burr PDFs provided the most desirable result to describe a complete drop size distribution. With restriction to two-parameter PDFs, the Nakagami PDF unexpectedly outperformed all the others, including Weibull (Rosin-Rammler) PDF, which is commonly used in atomization. However, if the spray is characterized by a single value, such as the Sauter Mean Diameter, i.e. an expected value-like parameter is of primary importance over the distribution, Gamma PDF is the best option, used in several papers of the atomization literature.

The Grain Size Distribution of Blasted Rock

The determination of the grain size distribution of blasted rock exceeds the capability of an analytical sieving machine which only gives reliable results within a range of 63 μm to 125 mm. Other sophisticated methods are often not available for particle size measurement in coarse-grained applications in medium scale mining. Therefore, an alternative low cost method to investigate the grain sizes of blasted rock is introduced which can cover a range from 63 μm at the lower end without an upper limit. Three different options to examine blasted dolomite grains are investigated and combined with sieve analysis to determine a complete sieving equivalent grain size distribution. Comparison with results of a technical sieving shows that this method gives a good approximation of the size distribution, improving the possibilities for design of mineral processing equipment.

A model for characterizing the continuous distribution of gas storing space in low-rank coals

The quantitative characterization of pore size distribution in low-rank coal reservoirs is significant for the determination of gas content and evaluation of coalbed methane (CBM) development potential. However, each test method can only detect the limited pore size range and the measured data cannot be used comprehensively. In this paper, a continuous distribution model of pore space was constructed for coal reservoirs based on the measured data of mercury intrusion porosimetry (MIP) and low-temperature nitrogen adsorption (LTNA) experiments. This model can overcome the above weakness and obtain the complete pore size distribution from nanopores to microfractures. Through verifying and adjusting the whole structure model, it can be used to refine the gas storage space of low-rank coals. The simulation results show that the pore size distribution differs greatly for coal samples from different regions or even from the same region, which is consistent with the general feature of strong heterogeneity of coal reservoirs in China. Even though pores smaller than 100 nm are still dominate in low-rank coal reservoir, the average volume of pores larger than 100 nm can reach 37%, which is obviously higher than that in medium-high rank coal reservoir and provides effective space for the storage of large amount of free gas. With the increase of coalification degree, the percentage of pores smaller than 100 nm presents an increasing trend.

Determination of the size distribution of non-spherical nanoparticles by electric birefringence-based methods

The in situ determination of the size distribution of dispersed non-spherical nanoparticles is an essential characterization tool for the investigation and use of colloidal suspensions. In this work, we test a size characterization method based on the measurement of the transient behaviour of the birefringence induced in the dispersions by pulsed electric fields. The specific shape of such relaxations depends on the distribution of the rotational diffusion coefficient of the suspended particles. We analyse the measured transient birefringence with three approaches: the stretched-exponential, Watson-Jennings, and multi-exponential methods. These are applied to six different types of rod-like and planar particles: PTFE rods, goethite needles, single- and double-walled carbon nanotubes, sodium montmorillonite particles and gibbsite platelets. The results are compared to electron microscopy and dynamic light scattering measurements. The methods here considered provide good or excellent results in all cases, proving that the analysis of the transient birefringence is a powerful tool to obtain complete size distributions of non-spherical particles in suspension.