The Temperature Field Evolution and Water Migration Law of Coal under Low-Temperature Freezing Conditions

This study examines the evolution law of the coal temperature field under low-temperature freezing conditions. The temperature inside coal samples with different water contents was measured in real-time at several measurement points in different locations inside the sample under the condition of low-temperature medium (liquid nitrogen) freezing. The temperature change curve was then used to analyse the laws of temperature propagation and the movement of the freezing front of the coal, which revealed the mechanism of internal water migration in the coal under low-temperature freezing conditions. The results indicate that the greater the water content of the coal sample, the greater the temperature propagation rate. The reasons for this are the phase change of ice and water inside the coal during the freezing process; the increase in the contact area of the ice and coal matrix caused by the volume expansion; and the joint action of the two. The process of the movement of the freezing front is due to the greater adsorption force of the ice lens than that of the coal matrix. Thus, the water molecules adsorbed in the unfrozen area of the coal matrix migrate towards the freezing front and form a new ice lens. Considering the temperature gradient and water content of the coal samples, Darcy’s permeation equation and water migration equation for the inside of the coal under freezing conditions were derived, and the segregation potential and matrix potential were analysed. The obtained theoretical and experimental results were found to be consistent. The higher the water content of the coal samples, the smaller the matrix potential for the hindrance of water migration. Furthermore, the larger the temperature gradient, the larger the segregation potential, and the faster the water migration rate.

Numerical approximation of the scattering amplitude in elasticity

We propose a numerical method to approximate the scattering amplitudes for the elasticity system with a non-constant matrix potential in dimensions $$d=2$$ d = 2 and 3. This requires to approximate first the scattering field, for some incident waves, which can be written as the solution of a suitable Lippmann-Schwinger equation. In this work we adapt the method introduced by Vainikko (Res Rep A 387:3–18, 1997) to solve such equations when considering the Lamé operator. Convergence is proved for sufficiently smooth potentials. Implementation details and numerical examples are also given.

Higher-order Darboux transformations for two-dimensional Dirac systems with diagonal matrix potential

We construct the explicit form of higher-order Darboux transformations for the two-dimensional Dirac equation with diagonal matrix potential. The matrix potential entries can depend arbitrarily on the two variables. Our construction is based on results for coupled Korteweg-de Vries equations [27].

Irrigation Regime for Protection on Root Intrusion for Subsurface Drip Irrigation

Root intrusion into emitters poses a threat to the service lives of subsurface drip irrigation systems. In an attempt to address this problem, an experiment was conducted on spring wheat grown in soil columns installed in a greenhouse to study the effects of irrigation regimes in protecting against root intrusion into emitters. Spring wheat was planted in soil columns. The specifications of the soil column were 15-cm width, 60-cm length and 100-cm depth. Drip tapes were buried manually in the center of the soil columns at a -40-cm depth. The soil matrix potential at a 20-cm depth immediately over the drip emitters was used to schedule the subsurface drip irrigation regime. Five different irrigation arrangements, with targeted soil matrix potentials of -10, -20, -30, -40 and -50 kPa, were maintained. The soil matrix potential influenced the spring wheat root distribution, emitter flow rate, root intrusion, and spring wheat yield and quality. The total root dry weight increased as the soil matrix potential decreased. Root length density at 35-45-cm increased as the soil matrix potential increased. The decrease in the emitter flow rate increased along with the soil matrix potential. All the treatments had root intrusion, but its severity was correlated with the soil matrix potential. Root intrusion first decreased as the soil matrix potential decreased but then increased as the soil matrix potential continued to decrease. The lowest root intrusion rate (22.22%), as well as the greatest relative yield and relative thousand-grain weight values, were achieved with a soil matrix potential of -40 kPa.

Stability of the Non-abelian X-ray Transform in Dimension $$\ge 3$$

Non-abelian X-ray tomography seeks to recover a matrix potential $$\Phi :M\rightarrow {\mathbb {C}}^{m\times m}$$ Φ : M → C m × m in a domain M from measurements of its so-called scattering data $$C_\Phi $$ C Φ at $$\partial M$$ ∂ M . For $$\dim M\ge 3$$ dim M ≥ 3 (and under appropriate convexity and regularity conditions), injectivity of the forward map $$\Phi \mapsto C_\Phi $$ Φ ↦ C Φ was established in (Paternain et al. in Am J Math 141(6):1707–1750, 2019). The present article extends this result by proving a Hölder-type stability estimate. As an application, a statistical consistency result for $$\dim M =2$$ dim M = 2 (Monard et al. in Commun Pure Appl Math, 2019) is generalised to higher dimensions. The injectivity proof in (Paternain et al. in Am J Math 141(6):1707–1750, 2019) relies on a novel method by Uhlmann and Vasy (Invent Math 205(1):83–120, 2016), which first establishes injectivity in a shallow layer below $$\partial M$$ ∂ M and then globalises this by a layer stripping argument. The main technical contribution of this paper is a more quantitative version of these arguments, in particular, proving uniform bounds on layer depth and stability constants.

Role of soil microstructure on the emission of N2O in intact small soil columns

<p>N<sub>2</sub>O emission in soils is a consequence of the activity of nitrifying and denitrifying microorganisms and potentially abiotic processes. However, the <span>large</span> microscale variability of the soil characteristics that influence these processes and in particular the location of anoxic microsites, limits prediction efforts. Better understanding of denitrification activity on microscopic scales is required to improve predictions of N<sub>2</sub>O emissions.</p><p>This study explored the role of soil microstructure on N<sub>2</sub>O emission. To fulfill this objective we sampled 24 soil columns (5 cm diameter, 6 cm height) in the surface layer of a same plot in a cultivated soil (Luvisol, La Cage, Versailles, France). The soil samples were saturated with a solution of ammonium nitrate (NH<sub>4</sub>NO<sub>3</sub>), and equilibrated at a matrix potential of -32 cm (pF 1.5). The emitted fluxes of N<sub>2</sub>O were measured during 7 days. At the end of the experiment, the soil columns were scanned in a X-ray micro tomograph, at the University of Poitiers. A 32 µm voxel resolution was achieved for the 3D reconstructed images.</p><p>In order to reduce noise and segment the 3D images, the same protocol was implemented for all columns. The reduction of noise consisted of passing a non-local mean filter, a non-sharp mask and a radial correction. Such combination of steps succeeded in removing both ring artifacts and the radial dependence of the voxel values. Due to the variety of material densities in the soil, a local segmentation based on the watershed method was implemented to classify the soil <span>constituents</span> in four <span>classes (based on its density value)</span>: air, water and organic matter (OM), soil matrix and minerals. This method is good for detecting thin pores and avoids missclassification of voxels undergoing partial volume effect, which can lead to false organic coatings around macropores.</p><p>The soil columns exhibited a large variability of accumulated N<sub>2</sub>O after 7 days (from 107 to 1940 <span>µgN kg</span><sup><span>-1</span></sup><span> d.w. soil</span>). The size of OM clusters varied between a couple and up to t<span>housands</span> of voxels. No correlation was found between the emission of N<sub>2</sub>O and the porosity, nor between the N<sub>2</sub>O emission and the connectivity of the air phase. Based on the <span>premise</span> that the less accessible is the oxygen to the OM, the bigger should be the N<sub>2</sub>O emission of the soil column, we proposed and computed a microscopic spatial descriptor, I<sub>gd</sub>, based on the notion of the geodesic distance between <span>clusters</span> of OM and air for each soil column 3D image. We expect to find a correlation between I<sub>gd</sub> and the <span>N</span><sub><span>2</span></sub><span>O emission.</span></p>

Biogeosystem Technique methodology as a new chemical soil-biological engineering foundation for the safe expanded technological development in the Noosphere

<p>Nature of soil as a main Earth’s biogeochemical reactor is dramatically underestimated. This is the inappropriate result of outdated technologies of the current industrial stage of development.</p><p>There are attempts to hide the technological drawbacks under the veil of different modern terms. This, unfortunately, does not change the essence of the current aggravating conflict between biosphere and technology. This is a reluctance to abandon the nature-imitation approach to technology, including environmental, chemical, agrarian technology. The development potential of the biosphere is used now not on the full scale. There is a need now for heuristically qualified intuition to understand the nature of the niche for environmental soil engineering technology strategic development. This approach will ease the current contradiction between biosphere and technology. The global environmental challenge is a transcendental (not a direct imitation of nature) Biogeosystem Technique (BGT*) technological platform of the Noosphere.  BGT* is capable to promote a promising niche for the environmental business development and nature-similar technological management.</p><p>One time BGT* based intra-soil milling of the 20–50 cm layer provides soil stable fine multilevel aggregate system, soil biome function for up to 40 years. The BGT* based intra-soil pulse continuous-discrete watering solves the world water scarcity problem. Water consumption is 5–20 times less compared to standard irrigation. The soil solution matrix potential range is from −0.2 MPa to −0.4 MPa, plant stomatal apparatus operates in the regulation mode. Water and nutrient efficacy is high. Intra-soil recycling of the municipal, industrial, waste and gasification byproduct in the soil layer of 20–50 cm in the course of this layer milling provides safety of the environment and plant nutrition. The yield is higher for 50–80 % compared to standard technology.</p><p>BGT* gives the new transcendental prospect to stabilize the Earth’s biosphere and climate system. The possibilities to achieve a goal are as follows: soil compaction overcoming; freshwater saving and high-level soil solution equilibria control; environmentally safe waste recycling; high biogeochemical barrier for heavy metal; of atmosphere N fixation in photosynthesis; soil organic matter synthesis, better function of humic substances, polymicrobial biofilms, and plant stimulants; plant resistance to phytopathogen, phytopathological, medical and veterinary environmental safety.</p><p>BGT*chemical soil-biological engineering intensifies the nutrient turnover and fertilizers return, decreases pesticides and nutrients off-target transport. This ensures higher yield and biofuel, higher efficacy of the technology, soil-biological reversible C sequestration, productive biosphere spreading, abundance, and safety; adaptation to climate change. BGT* provides the higher recreational potential of the biosphere. BGT* implementation requires technological and regulatory breakthrough for soil-chemical technology development niche expansion non-contradicting to Nature. BGT* is a promising sphere for worldwide Noosphere ventures<strong>.</strong></p><p>The research was financially supported by the RFBR, project no. 18-29-25071, and the Ministry of Science and Higher Education of Russia, project no. 0852-2020-0029.</p>

Hydrological effects of combining Italian alder and blackberry in an agroforestry system in South Africa

<p>Water limitation provides the potential to hinder the productivity of agricultural systems especially in arid and semi-arid regions. In agroforestry systems interactions between trees and crops range from mutually beneficial to critically competing, shaping the demand for resources, such as water. In this study, we investigated the hydrological effects of an Italian Alder (Alnus cordata) windbreak on an irrigated blackberry plantation near Stellenbosch, South Africa. We determine the key components of the water budget in the system and compare them at two positions: alongside the windbreak, and amongst the crop away from the windbreak’s influence.</p><p>We measured soil water content depth profiles in the summer months, from October 2019 to March 2020, in both locations with four consecutive time domain reflectometry (TDR) tube sensors, each integrating over 20 cm depth. Potential evapotranspiration (ET) was estimated from site based meteorological observations. We surveyed and classified the local soil, and defined soil chemical and physical properties (e.g. texture, matrix potential). The windbreak structure was measured on a single tree basis (e.g. tree height, volume and biomass) using manual and terrestrial laser scanning methodologies.</p><p>The data indicate that high potential ET, caused by high summer temperatures and strong winds, dominates the water budget at the study site, exceeding the water input of the drip irrigation. We found differences in the water dynamics between the two sites, e.g. greater soil water content at greater distances from the windbreak. Possible reasons are: (1) the water demand of trees increases underground competition for water, and/or; (2) microclimatic conditions closer to the windbreak increase ET. Modelling of the windbreak influence on the ET and further analysis of water fluxes will be conducted as next steps to combine the results from the sensors and the joint field campaign.</p>