Filtration Time Research Articles

Study on the extension mechanism of hydraulic fractures in bedding coal

This study is aimed at investigating the formation process and extension mechanism of hydraulic fractures (HFs) in bedding coal. To achieve this aim, a numerical model of hydraulic fracturing of bedding coal was established based on the cohesive element. Furthermore, the influences of stress field, bedding dip angle and fracturing fluid displacement on the extension law of HFs in bedding coal were studied, and the formation process and extension mechanism of HFs in bedding coal were analyzed. The following beneficial results were obtained. HFs prefer penetrating the bedding plane when extending towards it at a large angle, while they tend to extend along the bedding plane when the angle is small. Under certain stress field conditions, during hydraulic fracturing, changing the extension direction of original HFs enables HFs to develop into a complex fracture network under the combined effect of bedding structure and stress field. Meanwhile, altering injection displacement can enlarge the extension range of HFs on the bedding plane. The principle can be explained as follows: under the action of continuous unstable pressure waves caused by fluctuant injection displacement, coal is likely to undergo fatigue damage, which further promotes the generation of micro cracks within coal and facilitates the opening and extension of HFs. The pore pressure near HFs increases linearly with the rise of fluid pressure in HFs, decreases linearly with the growth of distance from HFs, and is inversely proportional to the square root of the fracturing fluid’s filtration time. After HFs penetrate the bedding plane, coal is prone to shear failure and further generates secondary fractures under the filtration effect of fracturing fluid. Under the joint effect of fracturing parameters such as bedding, ground stress and displacement, main HFs and secondary HFs can intersect to form a complex fracture network when penetrating the bedding plane.

Separation of milk fat using silicon carbide support ceramic membranes with different pore sizes

The effect of pore size and type of material on the separation of fat from raw milk using hydrophilic silicon carbide (SiC) support ceramic membranes has not previously been reported in literature. The separation performance of the fat globules (MFGs) showed 98% for SiC 0.5 μm, 92% for SiC 1.4 μm, 90% fat for ZrO2-SiC 0.06 μm, while the permeate had a fat % ranging from 0.1 to 0.6% (w/w). The MFGs were kept highly intact with well distributed proteins and phospholipids in the MFG membrane. The total filtration time at 50 °C to reach maximum VCR was 134 min for ZrO2 (VCR 3), 148 min for SiC 0.5 μm and 16 min for SiC 1.4 μm (VCR4). Further, all membranes showed a fully recoverable water permeability indicating no irreversible fouling. Industrial relevanceMicrofiltration may be an alternative process to fat separation from raw milk. In this study, for the first time was demonstrated that effective milk fat separation, and retentate and permeate streams with variable characteristics, in terms of composition and integrity of the milk fat globules can be obtained by using silicon carbide support membranes with different sizes and materials. The results obtained, provide new insights for industrial use of membrane technology to separate milk.

Stability analysis of rainfall-induced landslide considering air resistance delay effect and lateral seepage

Accumulation landslides are prone to occur during the continuous infiltration of heavy rainfall, which seriously threatens the lives and property safety of local residents. In this paper, based on the Green-Ampt (GA) infiltration model, a new slope rainfall infiltration function is derived by combining the effect of air resistance and lateral seepage of saturated zone. Considering that when the soil layer continues to infiltrate after the saturation zone is formed, the air involvement cannot be discharged in time, which delays the infiltration process. Therefore, the influence of air resistance factor in soil pores is added. According to the infiltration characteristics of finite long slope, the lateral seepage of saturated zone is introduced, which makes up for the deficiency that GA model is only applicable to infinite long slope. Finally, based on the seepage characteristics of the previous analysis, the overall shear strength criterion is used to evaluate the stability of the slope. The results show that the safety factor decreases slowly with the increase of size and is inversely correlated with the slope angle and initial moisture content. The time of infiltration at the same depth increases with the increase of size and slope angle, and is inversely correlated with the initial moisture content, but is less affected by rainfall intensity. By comparing with the results of experimental data and other methods, the results of the proposed method are more consistent with the experimental results than other methods.

Effects of the conversion of natural tropical rainforest to monoculture rubber plantations on soil hydrological processes

Abstract Rubber plantations have increased significantly under unprecedented economic growth in tropical areas, which leads to soil degradation and thereby alters soil hydrological processes. However, our understanding of how forest conversion affects soil hydrological processes remains unclear. Here, we collected soil samples from secondary forests (SF) and rubber plantations (RP) to determine the soil hydrological characteristics. We found the topsoil (0–20 cm) water retention in SF was higher than that of RP but displayed the contrast pattern in a deeper soil layer (20–60 cm). Meanwhile, the soil infiltration rates among the two vegetation types decreased significantly with infiltration time, with higher stable soil infiltration rates in SF than those in RP. Moreover, soil properties were also impacted by the forest conversion, such as the topsoil capillary porosity (CP) and total porosity (TP) in SF were higher than those of RP but contrasted in a deep soil layer. In comparison, the topsoil bulk density (BD) in SF was lower than that of RP, but contrasted in the deep soil layer and reached a significant level in the 0–10 and 40–50 cm (P < 0.05). Overall, the soil water retention was mainly determined by the CP, which could explain 31.56% of the total variance in soil water retention, followed by TP (26.57%) and soil BD (26.47%), whereas soil texture exerts a weak effect on soil water retention. Therefore, we can conclude that the conversion of tropical rainforest into rubber plantations may accelerate soil erosion owing to its lower topsoil water retention and soil infiltration rates.

Calcareous termite mounds in South Africa are ancient carbon reservoirs

Ecosystems that offer carbon sequestration by leaching bicarbonate to groundwater are valuable natural capital. One region that may offer this service is the west coast of South Africa. Over 20 % is covered by soil mounds (“heuweltjies”) up to 40 m diameter, 2 m high, inhabited by the southern harvester termite Microhodotermes viator and enriched in soil organic and inorganic carbon and soluble minerals. We aimed to generate radiogenic and stable isotope data for soils and groundwater in a region where these data are absent, to 1) verify the atmosphere-soil-groundwater link, and 2) resolve the timing and pattern of calcite dissolution and water infiltration in the landscape. Results show that soil and groundwater sulfate have the same marine aerosol source. Episodic calcite dissolution in mound centers, which increased during periods of global cooling, has been set against background input of marine aerosols since before the Last Glacial according to radiocarbon (14C) ages. Our data push back soil organic carbon 14C ages of inhabited termite mounds to 13-19 ka (kiloannum, thousand years before present), nest carbonate 14C ages to 33 ka, and mound soil carbonate 14C ages to 34 ka, making these the oldest active termite features ever dated. These ages are consistent with soil organic carbon and carbonate 14C ages of regional, non-mound, coastal petrocalcic horizons formed by accumulation of carbonate leached from their overlying aeolian dune fields. Harvesting activities of termites inject younger organic material around nests >1 m deep, leading to continuous renewal of important soil carbon reservoirs at depth. Termite bioturbation increases the system's ability to dissolve carbonate. The central, bioturbated part of the mounds have greater infiltration depths and greater calcite dissolution, whereas surrounding soils experienced more surface runoff. Calcareous termite mounds offer a mechanism to sequester CO2 through dissolution and leaching of soil carbonate-bicarbonate to groundwater.

Optimal filter materials for protist quantification via droplet digital PCR

The use of droplet digital polymerase chain reaction (ddPCR) has greatly improved the quantification of harmful protists, outperforming traditional methods like quantitative PCR. Notably, ddPCR provides enhanced consistency and reproducibility at it resists PCR inhibitors commonly found in environmental DNA samples. This study aimed to determine the most effective filter material for ddPCR protocols by assessing the reproducibility of species-specific gene copy numbers and filtration time across six filter types: cellulose acetate (CA), mixed cellulose ester (MCE), nylon (NY), polycarbonate (PC), polyethersulfone (PES), and polyvinylidene fluoride (PVDF). The study used two species of Chattonella marina complexes as a case study. Filtration rates were slower for NY, PC, and PVDF filters. Moreover, MCE, NY, PES, and PVDF yielded lower DNA amounts than other filters. Importantly, the CA filter exhibited the lowest variance (38–39%) and the highest determination coefficients (R2 = 0.92–0.96), indicating superior performance. These findings suggest that the CA filter is the most suitable for ddPCR quantification of marine protists, offering quick filtration and reliable reproducibility.

Development of a high‐pressure infiltration process for phenol–formaldehyde matrix composites

AbstractPhenol–formaldehyde (phenolic) thermosets are known for excellent heat and chemical resistance, high flame retardance, and good mechanical performance. However, phenolics are also known for their high brittleness, and tendency to form voids, due to a condensation reaction forming water during curing. These voids can decrease the mechanical performance of the resultant phenolic composite and introduce undesirable performance characteristics. This work aims to develop a technique that uses high‐pressure infiltration to obtain dense phenolic matrix composites, with commercially available resin and fiber reinforcement. The high‐pressure system developed in this work is compared to a conventional low‐pressure resin infusion technique, and the porosity after each infusion is analyzed. A model of the low‐ and high‐pressure systems was developed, and the predicted time of infiltration was compared to the experimental results. The high‐pressure system had 97% less open porosity after infusion than the low‐pressure technique, suggesting that it can produce a higher‐quality and better‐performing phenolic composite than conventional techniques. Also, the mechanical test performed indicates improved performance for the high‐pressure injection with a 30.73% increase in ultimate tensile strength in comparison to low pressure, indicating better mechanical performance. © 2024 Society of Industrial Chemistry.

Effect of cetyltrimethylammonium bromide on flocculation and filtration of bentonite suspensions

Separation of bentonite from wastewater is challenging because bentonite, is highly dispersible in water. Using cationic polymer flocculants has a high flocculation effect on bentonite. However, the flocculation mechanism is unclear. In this study, flocculation, filtration, and bentonite adsorption behavior are investigated using cetyltrimethylammonium bromide (CTAB) as cationic small molecule; subsequently, the flocculation mechanism of bentonite is explored. The flocculation effect increases and the filtration time is reduced with increasing CTAB concentration. In particular, when more than 1500 ppm of CTAB is used, the filtration time is reduced to 2–3 min. Bentonite forms secondary flocculates after the formation of primary flocculates with increasing CTAB concentration. Additionally, the adsorption behavior reveals that CTAB is inserted between the layers, and it is excessively adsorbed on the bentonite surface. The increase CTAB concentration was effective in improving the shortening the filtration time owing to the formation of large bentonite flocculates.

Rapid, contamination-less, and efficient environmental DNA filtration system

Due to the sporadic distribution and trace amount of environmental DNA (eDNA) in deep-sea water, in the context of biodiversity monitoring, large volumes of filtration and multiple filtration replicates are required for eDNA metabarcoding. To address issues tied to the use of multiple filtration devices and large filtration volumes (e.g., contamination, time consumption, etc.), we have developed two systems for simple, rapid, and contamination-less filtration simultaneously that allow for the processing of multiple sample replicates from large volumes of water. First, the water from a Niskin bottle was filtered directly using a solenoid pump. Second, the pumped deep-sea water, using the siphon effect, was directly filtered by a filtration device driven by water pressure. This system can process 24 replicates simultaneously without the need for expensive equipment and active driving force. Compared with conventional filtering methods, e.g., peristaltic pumps, the proposed systems reduce filtration time, minimizing contamination, and enabling the simultaneous acquisition of multiple replicates. Overall, the systems presented here provide an effective approach for eDNA metabarcoding analysis, particularly for the filtration of large volumes of water containing small amounts of eDNA, such as deep-sea water.•The present systems reduce filtration time and contamination without water having to be transferred.•Simultaneous multiple replicates improve the efficiency and reliability of biodiversity assessments.

Donors with repeated blood product discards for filtration problems, clots or hemolysis: Causes and follow-up.

Sanquin donor medicine department is informed when donations or their components are rejected. This can occur isolated or frequently. It is undesirable because the donations cannot be used and there may be an underlying medical cause. Based on regional approaches, a uniform procedure was developed. Information about whole blood, plasma- plateletpheresis donations from which one or more components were rejected for filtration time (>2 h), hemolysis or clots were extracted from blood bank information system. After rejection of two successive components or donations or total ≥3 the donor is contacted. Depending on the medical history and investigation by the family doctor, the donor carrier is re-evaluated. We looked for the causes of the discarded products and performed a survey among blood services regarding polices with discarded products. One or more components from 1742 of about 2.2 million successful donations (0.08%) were rejected. The highest percentage of rejection was seen in plateletpheresis (1.5%), all for clots. No underlying medical causes were found. 24 whole blood donors were found to have sickle cell trait (SCT) and were permanently deferred. The policies for follow-up after discarded products or acceptance of SCT donors vary between the 16 blood banks. Six organizations do not follow-up donors and seven accept SCT for blood or plasma donation. Informing donors with repeated discarded products avoids the non-use of donations. Causes of repeated discarded products can be found by follow-up of donors. The results of the survey indicate a large discrepancy in policies applied worldwide.

Effect of flux and shear rate on E. coli recovery in tangential flow filtration through a single hollow fiber.

Pathogenic bacteria which enter a viable but non-culturable (VBNC) state impede efforts to reach detectable concentrations required for PCR methods. This motivated a strategy for tangential flow filtration to concentrate bacteria in aqueous samples while maintaining the bacteria in a viable state, maximizing their recovery and achieving high fluxes through a single hollow fiber membrane. Filtrations were carried out for green fluorescent protein (GFP) E. coli at high shear rates (up to 27,000 sec-1) through 0.2 μm cut-off polyethersulfone (PES) microfilter membranes or 50 kDa polysulfone (PS) ultrafilter membranes. High shear minimized bacterial attachment on membrane surfaces, which would otherwise occur due to forced convection of the particles to the membrane surface at high flux conditions. Single fiber filter modules were constructed to facilitate concentration of Escherichia coli at fluxes ranging from 55 to 4500 L m-2 h-1. The effect of high shear rates on bacterial viability was found to be minimal with bacterial losses during filtration caused principally by their accumulation on the membrane surface. Recoveries of 90% were achievable at high shear rates when the average flux was ≤300 L m-2 h-1. This corresponded to a 3-h filtration time for a 225 mL sample through a single hollow fiber. Detectable bacteria concentrations of 1800 colony-forming unit (CFU)/mL were achieved for starting concentrations of 140 CFU/mL.

Nitrate dynamics in the streamwater-groundwater interaction system: Sources, fate, and controls

Nitrate (NO3−) pollution has attracted widespread attention as a threat to human health and aquatic ecosystems; however, elucidating the controlling factors behind nitrate dynamics under the context of changeable hydrological processes, particularly the interactions between streamwater and groundwater (SW-GW), presents significant challenges. A multi-tracer approach, integrating physicochemical and isotopic tracers (Cl−, δ2H-H2O, δ18O-H2O, δ15N-NO3− and δ18O-NO3−), was employed to identify the response of nitrate dynamics to SW-GW interaction in the Fen River Basin. The streamwater and groundwater NO3− concentrations varied greatly with space and time. Sewage and manure (28 %–73 %), fertilizer (14 %–36 %) and soil organic nitrogen (12 %–28 %) were the main NO3− sources in water bodies. Despite the control of land use type on streamwater nitrate dynamics in losing sections, SW-GW interactions drove NO3− dynamics in both streamwater and groundwater under most circumstances. In gaining streams, streamwater nitrate dynamics were influenced either by groundwater dilution or microbial nitrification, depending on whether groundwater discharge ratios exceeded or fell below 25 %, respectively. In losing streams, groundwater nitrate content increased with streamwater infiltration time, but the influence was mainly limited within 3 km from the river channel. This study provides a scientific basis for the effective management of water nitrate pollution at the watershed scale.

Simulasi Model Material Tanah Pada Bidang Gelincir Longsor Dengan Variasi Sudut Kemiringan (Studi Kasus Material Tanah di Daerah Kabupaten Gorontalo Utara)

Landslides are one of the geological disasters that often occur in Indonesia. North Gorontalo is an area where landslides occur every year. Based on data from the 2022 Badan Penanggulangan Bencana Daerah (BPBD), in the last year, there were 8 landslides. Landslides can occur due to several factors, namely; human factors and natural factors. In principle, landslides occur when the restraining force is less than the driving force. In this study a landslide simulation will be carried out using a simulation model made on a lab scale, the size of the simulation model is 40 cm x 30 cm x 25 cm. The simulation was carried out using soil samples taken at the research location. Variables that were observed during the simulation were the effect of the slope angle (o) on the exiting water (ml), the water infiltration time (t), and the effect of the slope (o) on the depth of the slip plane (cm). The soil taken from the research location will be subjected to a sieving analysis test with a hydrometer test to determine the texture class of the soil. From the soil texture test results, some of the research locations have a sand-gravel type of texture. The simulation test carried out also obtained the result that the slope of the slope greatly influences the water infiltration time with the depth of the slip plane. The greater the angle of the slope of the sled that is carried out, the results of the variable being measured will also be directly proportional.

Use of unmalted cereals with enzyme preparations in brewing

The use of unmalted grain is one of the methods for improving quality, reducing production costs, and creating new types of beer. However, the enzymatic activity of such raw materials is zero, so the use of enzyme preparations is relevant. The purpose of the study was to compare the quality indicators of 100% malt beer and beer with the replacement of malt with unmalted barley using enzymes. Methods of technical and chemical analysis were used to determine the organoleptic and physico-chemical parameters of beer. Recommendations have been developed for intensifying the preparation of wort using various types of grain raw materials – unmalted barley and rice grits with the addition of enzyme preparations from Novozymes (Denmark) at different stages of brewing were developed. When testing new enzyme preparations (β-glucanase complex, xylanase), the filtration time, wort viscosity, and the content of β-glucans and arabinoxylans decreased by about 20% compared to the control samples. The use of a new enzyme preparation resulted in better breakdown of substances, which affected the quality and duration of filtration. This leads to an improvement of wort quality, reducing the duration of the process and reducing the cost of raw materials. To ensure the required ratio of substances in the wort, it is necessary to introduce complex enzyme preparations – peptidhydrolase, α-amylase, endo-β-glucanase (Ceremis Plus). Preparations containing endo-β-glucanase (Ultraflo Max) should be used at the beginning of mashing to improve the rheological properties of the wort and reduce its viscosity, which improves the filtration process. To obtain beer with the required degree of fermentation during mashing, it is better to use new enzyme preparations (glucoamylase). The practical significance of the study lies in the use of large amounts of unmalted grain together with exoenzymes such as Ultraflo Max and Ceremis Plus, which will allow brewers to produce wort and beer of the same composition and quality as premium wort and beer, using only malt

Rainfall- and Irrigation-Induced Landslide Mechanisms in Loess Slopes: An Experimental Investigation in Lanzhou, China

To reveal the mechanism of rainfall- and irrigation-induced landslides in loess slopes within cold regions, a series of tests on loess samples subjected to different permeability durations were conducted, and the effects of rainfall on several performance indicators, including the permeability coefficient, composition, microstructure, soil–water characteristic curve, and the shear strength of the loess, were investigated. The results show that the permeability coefficient of the loess decreased by 68% after permeability testing. With increased permeability duration, there is a marked decrease in total dissolved solids, sand particles, and clay particles, contrasted with an increase in silt particles. This dynamic alters the original soil structure and impacts the soil–water characteristic curve of the loess. Additionally, rainwater infiltration heightens the effective saturation of the loess, in turn diminishing the shear strength of the loess as effective saturation increases. This reduction in shear strength is further intensified with extended infiltration time (or rainfall duration). A landslide is triggered once the shear strength diminishes to the level of the geostatic stress of the loess slope, and the influence of the rainfall-induced loss of soil shear strength should be taken into account during slope stability analysis. This study enhances the understanding of the initiation mechanisms of rainfall-induced landslides in loess slopes.

Micropillar‐based channel patterning in high‐loading graphite anodes for superior Li‐ion batteries

AbstractThis study presents a low‐cost, one‐step electrode patterning method that uses a template with micropillars to indent a hexagonal array of channels in high‐loading graphite anodes for faster electrolyte infiltration and Li‐ion transport. In contrast to prior studies on using laser micro‐machining, active material losses could be completely avoided by the proposed methodology. The process can also be made roll‐to‐roll and continuous. Furthermore, the very small volume fraction of the introduced channels (<1 wt.%) has little impact on practically attainable energy density or specific energy. Yet, thus introducing pore channels significantly reduces electrolyte infiltration time and improves rate performance.

Numerical simulation study on impact factors to dynamic filtration loss

During drilling operations, naturally, fractured formations are prone to show serious mud losses, which hinder drilling and increase nonproductive time and costs. The influencing factors of dynamic fluid loss are important for optimizing drilling parameters, reducing drilling fluid loss, and protecting oil and gas reservoirs. In this study, we simulated the dynamic filtration loss of drilling fluid during drilling under formation conditions using commercial software CMG (Computer Modelling Group). The effects of filtration time, filtrate viscosity, pressure difference, internal filter cake permeability, and external filter cake permeability on filtration loss were investigated. The simulation results showed that the permeability of the external mud cake is an important factor to control the fluid loss, and the pressure consumed by the external mud cake with low permeability can account for more than 90% of the total pressure difference. When the permeability of the external mud cake is high, the permeability of the internal mud cake also has a significant influence on the dynamic fluid loss. Under formation conditions, the dynamic fluid loss of radial fluid loss is still proportional to the filtration time and pressure difference, and inversely proportional to the filtrate viscosity of drilling fluid. Under the simulated conditions, the pressure will quickly transfer to the boundary, and the formation pressure at the same position in the formation will gradually increase, while the increase is relatively small with a constant filtration rate. The results of this paper can be used to the real site for drilling optimization. This numerical analysis method can be easily applied to filtrate loss analysis, formation damage area calculation, and other radial flow-related study.

Multiple growth of zirconolite in marble (Mogok metamorphic belt, Myanmar): evidence for episodes of fluid metasomatism and Zr–Ti–U mineralization in metacarbonate systems

Abstract. Fluid infiltration into (meta-)carbonate rocks is an important petrologic process that induces metamorphic decarbonation and potential mineralization of metals or nonmetals. The determination of the infiltration time and the compositional features of reactive fluids is essential to understand the mechanism and process of fluid–rock interactions. Zirconolite (ideal formula: CaZrTi2O7) is an important U-bearing accessory mineral that can develop in metasomatized metacarbonate rocks. In this study, we investigate the occurrence, texture, composition, and chronology of various types of zirconolite from fluid-infiltrated reaction zones in dolomite marbles from the Mogok metamorphic belt, Myanmar. Three types of zirconolite are recognized: (1) the first type (Zrl-I) coexists with metasomatic silicate and oxide minerals (forsterite, spinel, phlogopite) and has a homogeneous composition with high contents of UO2 (21.37 wt %–22.82 wt %) and ThO2 (0.84 wt %–1.99 wt %). (2) The second type (Zrl-II) has textural characteristics similar to those of Zrl-I. However, Zrl-II shows a core–rim zonation with a slightly higher UO2 content in the rims (average of 23.5 ± 0.4 wt % (n=8)) than the cores (average of 22.1 ± 0.3 wt % (n=8)). (3) The third type (Zrl-III) typically occurs as coronas around baddeleyite and coexists with polycrystalline quartz. Zrl-III has obviously lower contents of UO2 (0.88 wt %–5.3 wt %) than those of Zrl-I and Zrl-II. All types of zirconolite have relatively low rare earth element (REE) contents (< 480 µg g−1 for ΣREE). Microtextures and compositions of the three zirconolite types, in combination with in situ zirconolite U–Pb dating using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), reveal episodic fluid infiltration and element mobilization in the dolomite marbles. The first-stage infiltration occurred at ∼ 35 Ma, leading to the formation of Mg-rich silicates and oxides and accessory minerals (Zrl-I, baddeleyite, and geikielite). The reactive fluid was characterized by high contents of Zr, Ti, U, and Th. After that, some Zrl-I grains underwent a local fluid-assisted dissolution–precipitation process, which produced a core–rim zonation (i.e., the Zrl-II type). The final stage of fluid infiltration, recorded by the growth of Zrl-III after baddeleyite, took place at ∼ 19 Ma. The infiltrating fluid of this stage had relatively lower U contents and higher SiO2 activities than the first-stage infiltrating fluid. This study illustrates that zirconolite is a powerful mineral that can record repeated episodes (ranging from 35 to 19 Ma) of fluid influx, metasomatic reactions, and Zr–Ti–U mineralization in (meta-)carbonates. This mineral not only provides key information about the timing of fluid flow but also documents the chemical variation in reactive fluids. Thus, zirconolite is expected to play a more important role in characterizing the fluid–carbonate interaction, orogenic CO2 release, and the transfer and deposition of rare metals.

THE DETERMINATION OF THE MOST OPTIMAL METHODS FOR THE IRRIGATION OF CROPS ON DIFFERENT SOIL TYPES

Climate change due to multiple pollution problems (forest clearing, overgrazing, motor vehicle emissions, construction expansion, etc.), has led to increased global average temperature and reduced rainfall. Under these conditions, the mineralization of organic matter is intensified, the activity of soil microorganisms is reduced and implicitly decreases soil trophicity. These aspects further show the need to apply irrigation in the agricultural sector, rationalysing water, managing it and recommending the best methods of water distribution, on soils with different textural classes. In this regard, research was carried out on water permeability, on soils formed in different pedo-climatic conditions. Thus, three soil profiles were opened, in the Tecuci Plain, on a typical arenosoil, in the Dobrogea Plateau, on a calcaric chernozem and in the Gavanu-Burdea Plain on a chromic luvisol. Soil profiles were characterized morphologically and physico-chemically, soil samples were collected both in natural and modified settlement (metal cylinders). The physico-chemical analyses for the three soil types were determined within INCDPA laboratories Bucharest. Based on soil samples collected in metal cylinders, water permeability was determined using the ratio between the thickness of the soil horizon and the time of water infiltration. Depending on the permeability of the soil on the three different soil types, the most suitable and economical watering methods for the current climatic conditions have been established and recommended.

Numerical mapping relationship between process parameters and mechanical properties of unidirectional carbon/carbon composites

This paper proposes an innovative algorithm derived from the isothermal chemical infiltration process to generate quasi-real microstructures of unidirectional carbon/carbon composites. This algorithm, which can predict the relationship between the composite density and infiltration time, is termed the isothermal chemical infiltration algorithm. To further evaluate the relationship between the process parameters and the mechanical properties, a mesoscale finite element model of the unidirectional carbon/carbon composite is established based on the isothermal chemical infiltration algorithm. After validation, the developed numerical model is employed to study the effects of the infiltration time, pressure, and temperature on the effective mechanical properties. The results show that the transverse modulus and tensile strength increase with an increase in the infiltration time, pressure, and temperature, with the effect of temperature being the most significant. In parallel, it is revealed that the complete failure of unidirectional carbon/carbon composites results from interfacial debonding and propagation of multiple cracks during transverse tension. The proposed model has potential applications in the process design and optimization of high-performance carbon/carbon composites.