Pumice flotation time: how does the infiltration of water progress inside pumice?

A theoretical and experimental study of the acoustic properties of porous materials containing dead-end (or partially opened) porosity was recently proposed by Dupont, Leclaire, Sicot, Gong, and Panneton [J. Appl. Phys. 110, 094903 (2011)]. The present article provides a description of partially opened porosity systems and their numerous potential applications in the general context of the study of porous materials, the classical models describing them, and the characterization techniques. It is shown that the dead-end pore effect can be treated independently and that the description of this effect can be associated with any acoustic model of porous media. Different theoretical developments describing the dead-end porosity effect are proposed. In particular, a model involving the average effective length of the dead-end pores is presented. It is also shown that if the dead-end effect can be treated separately, the transfer matrix method is particularly well suited for the description of single or multilayer systems with dead-end porosity.

Long-term tillage impact on soil hydraulic properties

Relative flow porosity is defined as the fraction of the void volume in a porous medium through which fluid can flow under a macroscopic pressure gradient. In saturated paper, much of the void volume is occupied by water that cannot flow due to chemical or physical absorption and mechanical obstruction (isolated or dead-end pores). In partially saturated paper, surface tension effects further hinder fluid flow through the sheet. In this paper, we discuss various methods for examining relative flow porosity and present results of new experimental techniques based on in-plane flow measurements. The experimental approach involves radially injecting known volumes of aqueous, non-absorbing dye into the center of a compressed, saturated sheet restrained by solid surfaces. The volume of the sheet occupied by the dye is measured, as is the total porosity of the sheet. The ratio of injected dye volume to pore volume within the dyed region is an estimate of effective porosity. We show that in unrefined, filler-free paper, effective porosity values are on the order of 40% or more. The relative porosity may be as high as 90% of the extra fiber pore volume. Data for both initially dry and initially saturated sheets are presented. A geometric theory exists to predict relative porosity in fibrous structures, but we find that this model predicts values for relative porosity much lower than we observe here. Using simple measures of the volume occupied by the swollen-fibers in a compressed mat, we find that most(on the order of 90%) of the extra fiber pores pace is available to flow.

A simple method to count total faecal Capillaria worm eggs in racing pigeons (Columba livia)

The article presents the results of tests of porosity of the Upper-Silesian Coal Basin (USCB) hard coals. The porosity was determined for various lithotypes of hard coal, collected in different areas of the Upper-Silesian Coal Basin. Samples of hard coal were collected in 60 seams of 16 coal mines, from the depth of approximately between 350 and 1200 m. There are also presented differences in values of open porosity of coal depending on the depth of occurrence, as well as chronostratigraphic and tectonic correlation of a seam. Uniaxial compression strength of the tested coals falls in the strength class from very low to very high (from 8.1 to 51.5 MPa), open porosity is 0.68–12.5% and total porosity is 3.29–17.45%. With an increase in depth, in general, open porosity of coals decreases. There is an apparent decrease in open porosity correlated with the age of hard coals. It was observed that the lower and upper limits of open porosity ranges of variability shift towards lower values the older the coals are, from the Łaziskie Beds to the Jaklowieckie Beds. The older the coals the greater the average drop in the share of open porosity in total porosity from 60% for the youngest coals to merely several per cent for the oldest ones. The highest values of total porosity (over 10%) were observed in the youngest coals (Cracow sandstone series and siltstone series). Older coals reached more diversified values of total porosity (3.29–17.45%). Based on the conducted tests, zones correlated with tectonics of the basin and with deposition of lithostratigraphic beds of specific age, where values of porosity of hard coals differ, were determined in the area of the USCB. However, in spite of their correlation to a structural unit, the coals demonstrated a decrease in open porosity with an increase in their geologic age. Thus, there is an apparent influence of the deposition depth of coal within a given structural unit on open porosity following the age of coal, i.e. correlation to an older and older chronostratigraphic unit. Porosity tests of hard coal are published in scientific journals yet, most often, there is no information on the type of porosity. Such detailed characteristics of open porosity for coal of the Upper Silesian Coal Basin, as in the article, have not been prepared yet, making our research novel. Such broad tests of porosity of hard coals, correlated with their strength and referring to the deposition depth of seams as well as a correlation to lithostratigraphic units within individual structural units in the USCB, had not been conducted yet. We believe it is a sufficient argument to start detailed research into the open porosity of hard coals. The results of the tests are important from both the research and practical points of view. Knowledge of coal porosity is indispensable in solving many engineering problems of geological engineering, mining geomechanics and mining e.g.: assessing behaviour of coal when it is mined and processed, assessing the possibility of capturing methane, which makes up over 90% of natural gas, from coal in the areas of methane-rich deposits; the possibility of storing various substances in abandoned hard coal mining areas (e.g. CO2 storage within the structure of coal), assessing risk of occurrence of certain natural hazards resulting from mining deposits (e.g. coal and rocks outburst hazard), as well as assessing the possibility of applying unconventional methods of mining hard coal deposits (e.g. underground coal gasification).

Infiltration into water repellent soils has been widely observed, quantified and documented. The modelling of water infiltration into water repellent soils is more rarely taken into account explicitly. In this study, we modelled water infiltration into water repellent soils considering explicitly the contact angle, with the geometrical pore model proposed and validated previously. The applied microscopical approach showed good agreement with macroscopical models and with experimental data. We firstly investigated the case of contact angles lower than 90°, for the cylindrical pore and pearl necklace (PN) models. The cumulative infiltrations were numerically generated versus contact angle and for different pore radii. Then, the modelled infiltration curves were fitted to the two-terms Philip equation and parameters S and A were evaluated versus contact angle. As predicted sorptivity S decreased with increasing contact angle, and the constant infiltration rate A increased with contact angle for both models. Then, the modelled data were fitted to the numerical solution of the Richards equation to derive the equivalent hydraulic parameters assuming van Genuchten model. The results showed that the contact angle decreased the saturated hydraulic conductivity and increased the parameter α. Lastly, our model was used to investigate strong water repellency with contact angles higher than 90°. Cumulative infiltration and related Philip parameters, S and A, were evaluated versus water pressure head at surface h0 and contact angles (between 90° and 96°). Our model may be used to predict water infiltration into water repellent soils for both moderate and strong water repellency, including fingering features

Shale reservoirs contain predominantly micro and mesopores (<50 nm), within which gas is stored as free or adsorbed gas. Due to the ultra-small pore size, multiple transport mechanisms coexist in shale reservoirs, including gas slippage, Knudsen diffusion of free gas and surface diffusion of adsorbed gas. In this work, we propose a new transport model, valid for all ranges of Knudsen number, which combines all transport mechanisms with different weighting coefficients. To quantify the effects of influence factors, we introduce the compressibility factor for real gas effect and effective pore radius for gas adsorption and stress dependence. The model is proven to be more accurate than existing models since the deviation of the analytical solution of our model (3%) from published molecular simulation data is lower than that of existing models (10~20%). Based on this model, we compare (1) the contribution of each transport mechanism to gas transport in pores of different radii, (2) shale permeability measured in laboratory and at reservoir conditions, and (3) permeability of nanopores and natural fractures. It is found that gas transport is dominated by gas slippage and surface diffusion when the pore radius is over 10 nm and below 5 nm, respectively. Knudsen diffusion only becomes significant when the pore radius is between 2 and 25 nm and pore pressure is below 1000 psi. Furthermore, laboratory measurements usually over-estimate shale permeability. We also propose a promising enhanced gas recovery method, which is to open and prop up closed natural fractures using micro size proppants.

The article presents an analysis of the effectiveness of selected machine learning methods: Random Forest (RF), Extreme Gradient Boosting (XGB), and Support Vector Machine (SVM) in the classification of land use and cover in satellite images. Several variants of each algorithm were tested, adopting different parameters typical for each of them. Each variant was classified multiple (20) times, using training samples of different sizes: from 100 pixels to 200,000 pixels. The tests were conducted independently on 3 Sentinel-2 satellite images, identifying 5 basic land cover classes: built-up areas, soil, forest, water, and low vegetation. Typical metrics were used for the accuracy assessment: Cohen’s kappa coefficient, overall accuracy (for whole images), as well as F-1 score, precision, and recall (for individual classes). The results obtained for different images were consistent and clearly indicated an increase in classification accuracy with the increase in the size of the training sample. They also showed that among the tested algorithms, the XGB algorithm is the most sensitive to the size of the training sample, while the least sensitive is SVM, which achieved relatively good results even when using training samples of the smallest sizes. At the same time, it was pointed out that while in the case of RF and XGB algorithms the differences between the tested variants were slight, the effectiveness of SVM was very much dependent on the gamma parameter – with too high values of this parameter, the model showed a tendency to overfit, which did not allow for satisfactory results.

Characterization of the porosity distribution in the upper part of the karst Biscayne aquifer using common offset ground penetrating radar, Everglades National Park, Florida

Water infiltration into soil is one of the basic factors for estimating irrigation intensity according to the plants' requirements; this is aimed at avoiding problems of surface run-off and degradation. The purpose of the present investigation was to determine the spatial variation of infiltration and its relationship to some physical properties of soil by means of geostatistical techniques in Typic Plinthaquult soils having average texture and flat relief. A 113-point mesh was designed, having a regular distance of 10 m between points, samples being taken from 0 to 0.20 meters depth. Sand, silt and clay content, bulk density, macroporosity, microporosity and total porosity were determined. Infiltration tests were carried out in the field by means of a 15 cm diameter ring. Descriptive statistics and geostatistics were used for analysing the data. Infiltration, silt and microporosity data did not fit a normal distribution curve. Infiltration had high variability, having an average 36.03 mm h-1. Total porosity was 56.73%, this being the only property that did not show spatial dependency. The smallest ranges were observed for bulk density, macroporosity and microporosity, having values of less than 40 m. The smallest degrees of spatial dependence were observed for infiltration, silt and clay, evidence also being shown of the influence of silt and clay on infiltration rate. Contour maps were constructed; fitting them to the semivariogram models, together with studying the correlations, led to establishing relationships between the properties.

TIXIER, M.P., MEMBER AIME, SCHLUMBERGER WELL SURVEYING CORP., HOUSTON, TEX. Abstract The logging services most favored by the oil and gas industry are reviewed, and their characteristics and uses are discussed. Log evaluation is especially efficient when all the zones are investigated in such a way that the interesting levels stand out. Simple techniques that allow visual detection of oil and gas saturation are of great value, and are featured in the text. The selection of logging services must be governed by hole conditions and type of formations encountered. For each group, examples are shown which illustrate the preferred tools and techniques. Comments are made on various philosophies that are relevant to the problems. Conceptions that have existed in the past, as well as in the present thinking, and future trends are discussed. Introduction Modern well logging uses tools and techniques that were unknown a few years ago. Changes have been brought about not only by the discovery of new tools, but also by the ever-changing needs of the industry. This paper presents a resume of modern logging methods and of the information and utility they afford. A good set of logs permits correlation, assures depth control, defines the thickness of possible pays, and identifies zones for testing and further evaluation. To evaluate a zone, several quantities must be obtained: the effective and total porosity, the fractional water saturation, and evidence of permeability. Porosity is derived in a more-or-less direct manner by measuring the formation transit time (with a Sonic, or acoustic velocity, log), the formation density (with a Formation Density log), or the amount of hydrogen in the formation (with a Neutron log). Porosity may also be derived, indirectly, from a knowledge of F, the formation resistivity factor. The value of F is obtained from the responses of various resistivity devices that are chosen according to hole and invasion conditions. The empirical relation by which the porosity ( ) is derived from F is of the form .................(1) where a and m are based upon experience. Conversely, the value of F can be obtained from a knowledge of the porosity. The determination of water saturation Sw uses Archie's relation, ..............(2) The resistivity of the formation water, Rw, may be known from measured samples, or it can be found from the SP curve. Rw may also be found from a study of porosity and resistivity values in clean water-bearing formations. The true resistivity Rt is preferably obtained from a focused log, such as a deep-investigation Induction log or a Laterolog. A value of 2.0 is normally assigned to the n exponent in Eq. 2.Evidence of permeability is best shown by the Microlog, since it locates mud cakes deposited during filtration into permeable zones. A hole caliper survey can also detect the mud cake in many cases. Furthermore, conclusions as to permeability can often be made as a result of detailed log analysis. Hole conditions, as well as formation characteristics, have a great influence on the selection of logs. Thus, it is essential to group together the various conditions that dictate specific logs which are combined into a proper logging program. Most logs in wide usage today are made with essentially focused devices. Logging programs in water-base muds will be discussed under two main categories, according to the resistivity contrast between formations and mud. Some special logging techniques will also be examined, and future improvements will be discussed. The most important part of log evaluation is to so interpret the different levels that the interesting ones clearly stand out. To that end, a simple analysis that gives a visual evidence of hydrocarbon saturation is greatly preferred by the majority of people using well logs. Low Resistivity Contrast Logging Programs This section applies to the logging of most sands and sandstones and to some carbonate formations of relatively high porosity in relatively fresh muds. The resistivities of such formations generally are not very great, and the resistivity contrast between formations and mud (the ratio of Rt to Rm) generally will not exceed 200. JPT P. 1327^

Infiltration of water into the soil is an important physical process affecting the fate of water under field conditions, especially the amount of subsurface recharge and surface runoff and hence the hazard of soil erosion. The study was conducted to evaluate the infiltration models of soils developed on coastal plain sands and to select a suitable models as a basis to improve the management of the soil. A total of 16 infiltration runs were made with the double ring infiltrometer. For the purpose of getting best fitting model, the results obtained from various infiltration models were compared with observed field data. The parameters considered for best fitting of model were correlation coefficient and coefficient of variability (CV). Model-predicted cumulative infiltration consistently deviated from field-measured data, that is, the models under-predicted cumulative infiltration by several orders of magnitude for Kostiakov, Green Ampt and Philip model but the model over predicted cumulative infiltration for Horton model. The results of the soil samples analysed revealed that the mean values of 707.50, 208.13 and 84.38 gkg-1 for sand, silt and clay with the textural class of sandy loam. The bulk density, particle density and total porosity had mean values of 1.84 gcm-3, 2.44 gcm-3 and 22.56%. However, there was a fairly good agreement between mean-measured cumulative infiltration (7.30 cm/hr, CV = 32.19%); Philips (1.93 cm/hr, CV = 42.49%); Kostiakov (0.13 cm/hr, CV = 30.77%); Horton (64.49 cm/hr, CV = 22.39%) and Green Ampt model (42.04 cm/hr, CV = 0.57%) respectively. The data however showed that the correlation coefficient for Kostiakov (1.00) was best fitting in predicting the field measured data and this was closely followed by Green Ampt (0.88); while Philip’s model and Horton model showed a negative correlation (r = -0.88 and r = -0.82) with the field measured data. Conservation measures involving mulching, cover cropping and afforestation are recommended to improve the soil structure and infiltration capacity.

The imaging quality of X-ray in-line outline imaging(XIOI)is mainly related to the size of samples, X-ray photon energy, X-ray scattering, distance from sample to detector Dsd and also distance from source to sample for point X-ray source and so on. To maximize the resolution of the image under the practical limitations of laboratorial equipment in distance from sample to detector and range of adjustable photon energy etc., the present paper studies the effect of the above factors on the imaging quality using numeral simulation. We obtained the relationship between imaging quality and photon energy, and not only found that there are certain X-ray photon energies which are equally well suitable for imaging but also found that we can get some high quality images for phase retrieval through which we can get the exact phase and absorption information. We have determined the precice Dsd values at which the imaging quality is the best for samples of different size, and found that Dsd is propertional to the sample size and determined the factor of proportionality. Though the diffuse scattering of X-ray reduces the contrast of images, we can still have good contrast when the variation in thickness is the order of the sample size when the scattering are only caused by the variation in thickness. So under these unfavorable conditions XIOI still performs effectively.

If we have k binomial samples of different sizes, we may sometimes be interested in the question of homogeneity, i.e. we may want to know whether the k samples all came from binomial distributions with the same parameter p. A similar question of homogeneity may arise if we have k samples from multinomial or Poisson distributions. This paper, which is the first of a series of two, treats the binomial and multinomial situations; the second paper will treat the Poisson case. Homogeneity tests already exist for the problems just mentioned, but these existing tests apparently were not constructed with any optimal power properties explicitly in mind. These papers approach the problems of homogeneity testing by attempting to construct tests having maximal power against certain reasonable alternative hypotheses. Some new tests result from this approach; these tests will be described and numerical illustrations will be presented. The traditional tests(i.e. the usual X2 tests) will also be discussed. For the binomial problem, all tests which are considered are applicable to the situation(frequently arising in genetics) in which some or all of the k sample sizes are small numbers(even as small as 2 or 3). Section 1 of this paper is concerned with testing for homogeneity for the binomial case; a number of biological applications are presented. In §3, we show briefly how the new test which is introduced in §1 may be generalized to the multinomial case. All of the more technical details have been relegated to the Mathematical Appendices, which form the last part of the paper.

Adequate statistical methods should be used to assess the compliance with the respirable dust standard accurately. The objectives of this article are to study the statistical methods that can be used in compliance hypothesis testing under the assumption that the time-weighted-average dust concentrations follow a lognormal distribution, and to analyze the testing power under different situations. Through simulation, the statistical methods are compared in terms of testing power, at different given type I errors for samples of different sizes and different geometric standard deviations. Based on the results, suggestions are given concerning the possible use of these methods. The power of a test depends on the chosen type I error, geometric standard deviation, sample size, and the ratio of the mean dust level upon which compliance is based to the respirable dust standard. The impact of each factor is studied. With samples of small size (e.g., 5), the testing powers can be high only under very specif...