Search Results (72)

The development of deep coalbed methane (buried depth > 2000 m) in the Yan’an block of Ordos Basin is limited by low permeability, the pore structure of the coal reservoir, and the gas–water occurrence relationship. It is urgent to clarify the key control mechanism of pore structure on gas migration. In this study, based on high-pressure mercury intrusion (pore size > 50 nm), low-temperature N₂/CO₂ adsorption (0.38–50 nm), low-field nuclear magnetic resonance technology, fractal theory and Pearson correlation coefficient analysis, quantitative characterization of multi-scale pore–fluid system was carried out. The results show that the multi-scale pore network in the study area jointly regulates the occurrence and migration process of deep coalbed methane in Yan’an through the ternary hierarchical gas control mechanism of ‘micropore adsorption dominant, mesopore diffusion connection and macroporous seepage bottleneck’. The fractal dimensions of micropores and seepage are between 2.17–2.29 and 2.46–2.58, respectively. The shape of micropores is relatively regular, the complexity of micropore structure is low, and the confined space is mainly slit-like or ink bottle-like. The pore-throat network structure is relatively homogeneous, the difference in pore throat size is reduced, and the seepage pore shape is simple. The bimodal structure of low-field nuclear magnetic resonance shows that the bound fluid is related to the development of micropores, and the fluid mobility mainly depends on the seepage pores. Pearson’s correlation coefficient showed that the specific surface area of micropores was strongly positively correlated with methane adsorption capacity, and the nanoscale pore-size dominated gas occurrence through van der Waals force physical adsorption. The specific surface area of mesopores is significantly positively correlated with the tortuosity. The roughness and branch structure of the inner surface of the channel lead to the extension of the migration path and the inhibition of methane diffusion efficiency. Seepage porosity is linearly correlated with gas permeability, and the scale of connected seepage pores dominates the seepage capacity of reservoirs. This study reveals the pore structure and ternary grading synergistic gas control mechanism of deep coal reservoirs in the Yan’an Block, which provides a theoretical basis for the development of deep coalbed methane. Full article

In order to reveal the heat transfer mechanism of CO₂ injection and extraction in the fracture network of geothermal reservoir rock, based on the assumption of a dual-media model and considering the characteristics of the rock matrix and the fracture network, the changes in the physical properties of the heat transfer fluid, and the effects of multi-field coupling, a coupled thermo–hydro–mechanical (THM) model of CO₂ injection and extraction heat transfer was established. A numerical simulation study was carried out to investigate the evolution of injection and extraction temperature and heat extraction performance under the influence of different factors in the randomly distributed fracture network of the reservoir rock, which has a horizontal slit and a high-angle slit, with CO₂ as the heat transfer fluid. The results show that the heat exchange efficiency of reservoir fracture is higher than that of rock matrix; compared with water, the CO₂ heat extraction rate is low, and the temperature drop in production wells is small, which is favorable to the long-term exploitation of geothermal reservoirs. if the horizontal distance between the production wells and the injection wells is far and the fracture connectivity is good, the heat exchange is strong and the heat extraction rate is higher; increasing the CO₂ injection rate will increase the range of the low-temperature area, reduce the temperature of the production wells, and increase the heat extraction rate in a short period of time; and the heat extraction rate will increase in the later stages. The increase in CO₂ injection rate will rapidly increase the range of the low-temperature area in a short time, decrease the temperature of the production well and increase the heat extraction rate, and then the growth of the heat extraction rate tends to stabilize in the later stages; the width ratio of horizontal fracture and high-angle fracture affects the direction of heat exchange, the temperature of production well and the heat extraction rate, and the influence is more significant when the width ratio is greater than 1; the temperature of the production well decreases fastest, the increase in the heat extraction rate is largest, and the effects on the temperature of the production well and the heat extraction rate are insignificant when it is close to the production well. The increase in the heat extraction rate is slower when close to the injection well. Full article

Hyperspectral payloads with high spatial and spectral resolution, combined with a wide field of view, are crucial for tackling the complexity of coastal and estuarine water ecosystems, enabling effective monitoring of water quality and ecological conditions. This study introduces a modular spectrometer design utilizing multiple sub-modules in an extended slit configuration. The system delivers a spectral resolution of 5 nm (400–1000 nm) and 10 nm (1000–2500 nm), a spatial resolution of 20 m, and a swath width of 80 km. Smile and keystone distortions are maintained below 1/5 of a pixel. Using Modran to simulate solar irradiance, the SNR of different targets under typical background conditions is calculated. Compared to conventional designs, the proposed modular approach provides compactness and high fidelity, effectively addressing size and optical aberration challenges. The simulation results confirm the system’s robustness, setting a benchmark for next-generation coast observation missions, particularly in coastal monitoring, underwater exploration, and dynamic environmental change tracking. Full article

Deep coal mining is essential for energy use and sustainable development. In a situation where coal–rock–gas dynamic disasters are prone to occur in coal seam variation areas affected by different degrees of roof angle during deep coal seam mining, a disaster energy equation considering the influence of roof elastic energy is established, and the disaster energy criterion considering the influence of roof elastic energy is derived and introduced into COMSOL6.1 software for numerical simulation. The results show that, compared with the simple change of coal thickness and coal strength, the stress concentration degree of a thick coal belt with small structure is higher, and the maximum horizontal stress can reach 47.6 MPa. There is a short rise area of gas pressure in front of the working face, and the maximum gas pressure reaches 0.82 MPa. The plastic deformation of the coal body in a small-structure thick coal belt is the largest, and the maximum value is 18.04 m³. The simulated elastic energy of rock mass is about one third of that of coal mass, and the influence of the elastic energy of roof rock on a disaster cannot be ignored. When the coal seam is excavated from thin to thick with a small-structural thick coal belt, the peak value of the energy criterion in front of the excavation face is the largest, and the maximum value is 1.42, indicating that a dynamic disaster can occur and the harm degree will be the greatest. It is easy to cause a coal and gas outburst accident when the excavation face enters a soft coal seam from a hard coal seam and a small-structural thick coal belt from a thin coal belt. Practice shows that holistic prevention and control measures based on high-pressure water jet slit drilling technology make it possible to increase the average pure volume of gas extracted from the drilled holes by 4.5 times, and the stress peak is shifted to the deeper part of the coal wall. At the same time, the use of encrypted drilling in local small tectonic thick coal zones can effectively attenuate the concentrated stress in the coal seam and reduce the expansion energy of gas. This study enriches our understanding of the mechanism of coal–rock–gas dynamic disaster, provides methods and a basis for the prevention and control of dynamic disaster in deep coal seam variation areas, and promotes the sustainable development of energy. Full article

Background/Objectives: Spatial fractionation of proton fields as sub-millimeter beamlets to treat cancer has shown better sparing of healthy tissue whilst maintaining the same tumor control. It is critical to ensure primary standard dosimetry is accurate and ready to support the modality’s clinical implementation. Methods: This work provided a proof-of-concept, using the National Physical Laboratory’s Primary Standard Proton Calorimeter (PSPC) to measure average absorbed dose-to-water in a pMBRT field. A 100 MeV mono-energetic field and a 2 cm wide SOBP were produced with a spot-scanned proton beam incident on a collimator comprising 15 slits of 400 µm width, each 5 cm long and separated by a center-to-center distance of 4 mm. Results: The results showed the uncertainty on the absorbed dose-to-water in the mono-energetic beam was dominated by contributions of 1.4% and 1.1% ($k$ = 1) for the NPL PSPC and PTW Roos chambers, respectively, originating from the achievable positioning accuracy of the devices. In comparison, the uncertainty due to positioning in the SOBP for both the NPL PSPC and PTW Roos chambers were 0.4%. Conclusions: These results highlight that it may be more accurate and reliable to perform reference dosimetry measuring the Dose-Area Product or in an SOBP for spatially fractionated fields. Full article

Background: Diseases in humans caused by amphizoic amoebae that can result in visual impairment and even blindness, have recently been identified more frequently worldwide. Etiologically complex incidents of keratitis, including those connected with Acanthamoeba strains detected in Poland, were evaluated in this study. Methods: Corneal samples from cases resistant to antimicrobial therapy assessed for epidemiological, microbiological and parasitological aspects were investigated by phase-contrast microscope, slit lamp and by confocal microscopy. In vitro techniques were applied for detection of bacteria and fungi, and corneal isolates cultured under axenic condition using BSC medium—for detection of Acanthamoeba spp.; molecular techniques were applied for amoeba species identification. Results: Most etiologically complicated keratitis cases, detected in ~84% of incidents, was due to exposure of contact lenses to tap water or pool water; trophozoites and cysts of Acanthamoeba, concomitant bacteriae, e.g., Pseudomonas aeruginosa, fungi and microfilariae were identified in contact lens users. Conclusions: In samples from contact lens wearers where microbial keratitis is identified along with some connection with the patient’s exposure to contaminated water environments, a risk of Acanthamoeba spp. infections should be considered. Understanding the complicated relationship between Acanthamoeba spp., co-occurring pathogens including associated endosymbionts is needed. In vivo confocal microscopy and in vitro cultivation were necessary to identify potentially contagious concomitant factors affecting the complex course of the keratitis. Full article

As mature oilfields enter the high-water-cut development stage, significant amounts of residual oil remain trapped underground. To enhance the effectiveness of tertiary oil recovery, it is crucial to understand the distribution and mobilization patterns of this residual oil. In this study, polydimethylsiloxane (PDMS) was used to create a microscopic oil displacement model, which was observed and recorded using a stereomicroscope. The experimental images were extracted, analyzed, and quantitatively evaluated, categorizing the microscopic residual oil in the high-water-cut sandstone reservoirs of Dagang Oilfield into cluster-like, pore surface film-like, corner-like, and slit-like types. Polymer–surfactant composite flooding (abbreviated as SP flooding) effectively mobilized 47.16% of cluster-like residual oil and 43.74% of pore surface film-like residual oil, with some mobilization of corner-like and slit-like residual oil as well. Building on SP flooding, dual-mobility flooding further increased the mobilization of cluster-like residual oil by 12.37% and pore surface film-like residual oil by 3.52%. With the same slug size, dual-mobility flooding can reduce development costs by 16.43%. Overall, dual-mobility flooding offers better development prospects. Full article

A binary Fe₂O₃/Fe₃O₄ mixed nanocomposite was prepared by phyto-mediated avenue to be suited in the photo-Fenton photodegradation of methylene blue (MB) in the presence of H₂O₂. XRD and SEM analyses illustrated that Fe₂O₃ nanoparticles of average crystallite size 8.43 nm were successfully mixed with plate-like aggregates of Fe₃O₄ with a 15.1 nm average crystallite size. Moreover, SEM images showed a porous morphology for the binary Fe₂O₃/Fe₃O₄ mixed nanocomposite that is favorable for a photocatalyst. EDX and elemental mapping showed intense iron and oxygen peaks, confirming composite purity and symmetrical distribution. FTIR analysis displayed the distinct Fe-O assignments. Moreover, the isotherm of the developed nanocomposite showed slit-shaped pores in loose particulates within plate-like aggregates and a mesoporous pore-size distribution. Thermal gravimetric analysis (TGA) indicated the high thermal stability of the prepared Fe₂O₃/Fe₃O₄ binary nanocomposite. The optical properties illustrated a narrowing in the band gab (Eg = 2.92 eV) that enabled considerable absorption in the visible region of solar light. Suiting the developed binary Fe₂O₃/Fe₃O₄ nanocomposite in the photo-Fenton reaction along with H₂O₂ supplied higher productivity of active oxidizing species and accordingly a higher degradation efficacy of MB. The solar-driven photodegradation reactions were conducted and the estimated rate constants were 0.002, 0.0047, and 0.0143 min⁻¹ when using the Fe₂O₃/Fe₃O₄ nanocomposite, pure H₂O₂, and the Fe₂O₃/Fe₃O₄/H₂O₂ hybrid catalyst, respectively. Therefore, suiting the developed binary Fe₂O₃/Fe₃O₄ nanocomposite and H₂O₂ in photo-Fenton reaction supplied higher productivity of active oxidizing species and accordingly a higher degradation efficacy of MB. After being subjected to four photo-Fenton degradation cycles, the Fe₂O₃/Fe₃O₄ nanocomposite catalyst still functioned admirably. Further evaluation of Fe₂O₃/Fe₃O₄ nanocomposite in photocatalytic remediation of contaminated water using a mixture of MB and pyronine Y (PY) dyestuffs revealed substantial dye photodegradation efficiencies. Full article

The content of unfrozen water in the freezing process of coal body affects the microscopic pore structure and macroscopic mechanical properties of coal body and determines the permeability-enhancement effect of coal seam and the extraction efficiency of coal mine gas. To investigate the evolution mechanism of unfrozen water content in the melting process of lignite, this paper takes the melting process of lignite liquid nitrogen after freezing for 150 min as the research object and quantifies the spatial change process of unfrozen water distribution based on two-dimensional nuclear magnetic resonance technology. Through the accurate interpretation of the superimposed signals of different fluids, the 2D NMR technique can more easily obtain the spatial distribution of different fluids and even the specific content of fluids in different pores in coals. The results show that at −196 °C, the unfrozen water mainly existed in the small coal pore and the small ice pore in the large pore. As the temperature rose, the pores melted, and free water began to be produced. The mathematical model analysis shows that there was intermolecular potential energy between fluid molecules and the coal pore wall, and the pore wall exerted a part of pressure on its internal fluid, and the pressure affected the melting point of pore ice with pore diameter and melting temperature, resulting in the difference of unfrozen water content. Full article

Traditional research on apparent permeability in shale reservoirs has mainly focussed on effects such as poromechanics and porosity-assisted adsorption layers. However, for a more realistic representation of field conditions, a comprehensive multi-scale and multi-flowing mechanism model, considering the fracturing process, has not been thoroughly explored. To address this research gap, this study introduces an innovative workflow for dynamic permeability assessment. Initially, an accurate description of the pore size distribution (PSD) within three major mineral types in shale is developed using focussed ion beam-scanning electron microscopy (FIB-SEM) and nuclear magnetic resonance (NMR) data. Subsequently, an apparent permeability model is established by combining the PSD data, leading to the derivation of dynamic permeability. Finally, the PSD-related dynamic permeability model is refined by incorporating the effects of imbibition resulting from the fracturing process preceding shale gas production. The developed dynamic permeability model varies with pore and fracture pressures in the shale reservoir. The fracturing process induces water blockage, water-film formation, and water-bridging phenomena in shale, requiring additional pressure inputs to counteract capillary effects in hydrophilic minerals in shale, But also increases the overall permeability from increasing permeability at larger scale pores. Unlike traditional reservoirs, the production process commences when the fracture is depleted to 1–2 MPa exceeds the pore pressure, facilitated by the high concentration of hydrophobic organic matter pores in shale, this phenomenon explains the gas production at the intial production stage. The reduction in adsorption-layer thickness resulting from fracturing impacts permeability on a nano-scale by diminishing surface diffusion and the corresponding slip flow of gas. this phenomenon increases viscous-flow permeability from enlarged flow spacing, but the increased viscous flow does not fully offset the reduction caused by adsorbed-gas diffusion and slip flow. In addition to the phenomena arising from various field conditions, PSD in shale emerges as a crucial factor in determining dynamic permeability. Furthermore, considering the same PSD in shale, under identical pore spacing, the shape factor of slit-like clay minerals significantly influences overall permeability characteristics, much more slit-shaped pores(higher shape factor) reduce the overall permeability. The dynamic permeability-assisted embedded discrete fracture model (EDFM) showed higher accuracy in predicting shale gas production compared to the original model. Full article

Water utilities in Japan face a number of challenges, including declining water demand due to a shrinking population, shrinking workforce, and aging water supply facilities. Widespread use of smart water meters is crucial for solving these problems. The widespread use of smart water meters is expected to bring many benefits such as reduced labor by automating meter reading, early identification of leaks, and visualization of pipeline data to strengthen the infrastructure of water services, business continuity, and customer service, as detailed data can be obtained using wireless communication. Demonstration tests are actively conducted in Japan; however, many problems have been reported with cast iron meter boxes blocking radio waves. To address the issue, a low-cost slit structure for cast iron meter boxes is investigated in this study. The results confirm that the L-shaped tapered slit array structure with a cavity, which can be fabricated in a cast iron integral structure, satisfies the design loads required for road installation. The proposed slit structure achieved gain characteristics from −3.32 to more than 9.54 dBi in the 800 to 920 MHz band. The gain characteristics of conventional cast iron meter boxes range from −15 to −20 dBi, and the gain has been significantly improved. Antennas with a gain of −2.0 to +1.5 dB (0.8 to 2.5 GHz) were used for the transmitter antenna, which was found to have a higher gain than the transmit antenna in the 800 to 880 MHz frequency band. In the 1.5 to 2.0 GHz band, a high peak gain of 4.25 dBi was achieved at 1660 MHz, with no null and the lowest gain confirmed that this is an improvement of more than 10 dBi over conventional products. Full article

Ammonia (NH₃) emissions affect the environment, the climate, and human health and originate mainly from agricultural sources like urea fertilizers. Such losses from urea fertilizer can be avoided by different application techniques like incorporation. However, the knowledge of the effect of these techniques on NH₃ emissions is very limited and ambiguous since incorporation can also promote nitrous oxide (N₂O) emissions. Three different principles of fertilizer incorporation methods were compared in three different soils (sandy, loamy, and clayey) at two moisture levels of 70% and 30% water-holding capacity (WHC), shallow mixing at 2 cm, injection with the slit technique at 5 cm, and deep complete incorporation at 5 cm simulating plow incorporation. The laboratory study was conducted with open dynamic incubation chambers where NH₃ emissions were monitored with washing bottles while N₂O emissions were studied with gas chromatographic (GC) measurements. The highest cumulative NH₃ emissions occurred at low soil moisture levels in sandy soil (34% of the N applied). A maximum reduction in emissions by 87% was achieved with slit injection and 82% with deep injection compared to standard surface application. The reduction effect was positively related to increasing clay content. N₂O emissions were delayed and highest from sandy soil. Overall, all urea incorporation techniques showed great potential for mitigating NH₃ emissions on the clayey soil; for sandy and drier soils, only deeper or closed slot injection were consistently effective. However, connected to the surface incorporation at the higher moisture level, a relevant increase in N₂O emissions compared to surface application was observed. Therefore, an increase in N₂O emissions by urea incorporation may rule out specific incorporation techniques for NH₃ emissions reduction from field-applied urea. In agricultural practice, a lower reduction in NH₃ by fertilizer incorporation can be assumed in sandy soils or under dry soil conditions, as well as a more challenging technical implementation. Full article

Different sediment-related disasters due to torrential hazards, such as flash floods, debris flows, and landslides, can occur in an Alpine torrential catchment. When protecting infrastructure and human lives, different structural and non-structural protection measures can be used to mitigate permanent and future risks. An overview of the mitigation measures constructed near the Krvavec ski resort in northwest Slovenia (Central Europe) is presented. In May 2018, an extreme debris flood occurred in this area, causing significant economic damage. After the May 2018 event, different field investigations (i.e., geological and topographic surveys) and modeling applications (e.g., hydrological modeling, debris flow) have been conducted with the purpose of preparing the required input data for the design of protection measures against such disasters in future—due to climate change, more disasters are expected to happen in this torrential watershed. The mitigation includes the restoration of local streams, the construction of a large slit check dam for sediment retention, the construction of several smaller check dams and the construction of 16 flexible net barriers with an estimated ~8000 m³ retention volume for controlling in-channel erosion in steep torrential streams. Additionally, in order to observe and monitor potential future extreme events, an extensive monitoring system has been established in the investigated area. This monitoring system will cover measurements of flexible net corrosion, the estimation of concrete abrasion at check dams, periodical geodetic surveys using small drones (UAV), hydro-meteorological measurements using rainfall gauges and water level sensors. The recent extreme floods of August 2023 also hit this part of Slovenia, and this combination of technical countermeasures withstood the event and prevented large amounts of coarse debris from being transported to the downstream section and devastating infrastructure, as was the case in May 2018 during a less extreme event. Therefore, such mitigation measures can also be used in other torrential catchments in the Alpine environment. Full article

Grand Canonical Monte Carlo (GCMC) simulation and Molecular Dynamics (MD) simulations were used to study the effects of temperature (310 K to 400 K), pressure (≤30 MPa) and water content (0 molecule/nm³ to 9 molecule/nm³) on the adsorption and diffusion behavior of CH₄ and C₂H₆ in 3 nm kaolinite slit under supercritical conditions. The obtained adsorption capacity, isosteric adsorption heat, concentration distribution and diffusion coefficient were analyzed and compared. The simulation results show that the adsorption capacity of C₂H₆ is higher under low pressure conditions, and the adsorption capacity of CH₄ is higher under high pressure conditions due to the small molecular radius and increased adsorption space. The addition of water molecules and the increase in temperature will reduce the adsorption capacity and isosteric adsorption heat of the two gases. We analyzed the changes in Langmuir volume and Langmuir pressure of the two gases under different temperature and water content conditions. The addition of water molecules and the increase in temperature will reduce the saturation adsorption capacity (which has a greater effect on C₂H₆) and the adsorption rate of the two gases in the kaolinite slit. The water molecules occupy the adsorption site of the gas molecules (limiting the diffusion of the gas molecules), which reduces the interaction between gas molecules and the wall surface, thus altering the distribution of the two gases in the slit. The increase in temperature will accelerate the oscillation of the gas molecules, increasing diffusion, and also leads to a reduction in the peak value of the adsorption peaks of the two gases. Full article

The present study investigated some physico-chemical and microbiological traits of 20-month ripened hard cheeses produced from low-temperature high-speed centrifuged raw milk that developed a structural defect consisting of eyes or slits in the paste. Cheeses obtained using the same process and that did not develop the defect were used as controls. The colour, texture, moisture, water activity, proton molecular mobility, microstructure, extent of proteolysis, and viable microorganisms have been evaluated in all the cheese samples, and the significant differences between the defective and non-defective cheeses have been critically discussed. At a microstructural level, the defects caused fat coalescence and an unevenly organised protein matrix with small cracks in the proximity of the openings. The different fat organisation was correlated to a different transverse relaxation time of ¹H population relaxing at higher times. The textural and colour features were not different from those of the control cheeses and were comparable with those reported in the literature for other long-ripened hard cheeses. On the other hand, the defective cheeses showed a higher moisture level and lower lactobacilli and total mesophilic bacteria concentrations, but the microbial origin of the defect remains an open hypothesis that deserves further investigation. Full article