Variations In Moisture Content Research Articles

Variation in Soil Moisture Content and Soil Organic Carbon in Different Agroforestry Practices in Moshi Rural District, Northern Tanzania

Agroforestry has been widely practiced in the northern highlands of Tanzania because of its prominent effects in reducing soil losses, maintaining soil moisture contents (SMCs), and improving land-use efficiency and farmer’s livelihood. We tested the hypothesis that variations of soil moisture contents in 0-20 cm and 20-40 cm depths from various agroforestry Practices differ significantly in intensified small-scale agroforestry systems. The relationship between SMCs and soil organic carbon was also evaluated. Soil samples were collected from 10 x 10 m2 plot in three points along the diagonal of the quadrat using soil auger. SMCs were determined by gravimetric method and expressed as SMC%. SOC was determined by Walkley and Black method and expressed as SOC %. The variation in SMCs% among the different agroforestry Practices were statistically determined by ANOVA in R software while the correlation between SMCs and SOC were statistically determined by Pearson product-moment analysis. Variation of SMCs was statistically insignificant (p>0.05) among surveyed sites. SMCs increased significantly (p<0.05) with increasing soil depth from 0-40 cm depth in all agroforestry Practices except in the mixed intercropping agroforestry practice (MAP). At 0-20 cm and 20-40 cm, SMCs differed significantly among agroforestry Practices (P = 0.071) and (P = 0.003), respectively. Coffee Intercropping Agroforestry Practice (CIAP) had higher (P<0.05) SMCs at 0-20 cm depth compared to BAP and MWPAP. But, at 20-40 cm depth, soil moisture contents in CIAP differed significantly (P<0.05) with SMCs all AFPs. SMCs showed a positively significant (P<0.05) relationship with SOC within 0-20 cm and 20-40 cm depths. The current study confirms that different agroforestry practices have different influence on the amount and vertical distribution of soil moisture. Therefore, management practices in agroforestry systems should aim to encourage the use of practices which ensure a stable amount of moisture contents in the soil

Segmentation uncertainty of vegetated porous media propagates during X-ray CT image-based analysis

Abstract Background and Aims Phase segmentation is a crucial step in X-ray computed tomography (CT) for image-based analysis (CT-IBA) to derive soil and root information. How segmentation uncertainty (SU) affects CT-IBA of vegetated soil has never been explored. Methods We proposed a new framework enabled by machine learning to measure SU and its propagation from the first to the second-order parameters derived from CT-IBA. Vegetated glass beads of varying moisture contents and plant species were CT scanned. Segmented images were used to determine volumetric fractions and morphological properties of each phase for determining the absolute permeability (K). Results Although the root phase is susceptible to SU, its influence on CT-IBA is minimal when the root content is low. However, its SU was magnified when the water phase is present. The grain phase has a lower SU susceptibility, but due to its large volumetric content, the IBA can be affected significantly. Fine roots were found to exhibit higher SU than coarse roots, indicating that root architecture has an effect on the segmentation of the root phase, and thus higher-order properties like K. Conclusion Segmentation of the grain phase is sensitive to SU. A small SU will lead to a remarkably erroneous estimation of pore morphological properties and K. To reduce SU, we suggest reducing the water content to a discontinuous state of a cohesionless vegetated porous media specimen before sending it for CT scanning and IBA. However, caution should be taken when fine roots were dried and experienced excessive shrinkage.

Exploring the effect of clothing moisture content on heat and moisture transfer from the human body using a sweating thermal manikin

Evaporative heat loss is an important component of the human body's energy balance and several developed thermal comfort models are available to assess heat and mass transfer during human sweating. However, the impact of sweat-soaked clothing due to human perspiration on heat and moisture transfer from the body remains understudied. In this study, the thermal and moisture properties of typical summer clothing were evaluated and moisture adsorption and desorption curves were obtained. The heat losses of the human body in different sweating states were compared using a sweating thermal manikin. It was found that the clothing moisture content and the clothing coverage ratio had a significant effect on the human body heat loss. As the sweating rate increases, additional resistances of the sweat moisture transfer will be added in the sweat-soaked clothing, which would adversely affect the skin temperature. The results show that the total thermal resistance of fully wetted clothing decreased by an average of almost 30% compared to dry clothing ensembles. To account for such differences, the clothing thermal and evaporative resistance, along with the temperature and vapor pressure at varying moisture contents were evaluated and predicted with empirical equations. This enables integrating a dynamic heat and moisture transfer model for the sweat-soaked clothing into a prevailing thermo-physiological model. Accounting for real clothing physical parameters is vital when evaluating thermal comfort in hot and humid weather conditions.

Simulation Study on Heat and Moisture Transfer in Cross‐Flow Drying Aeration of Bulk Corn in a Cone‐Bottom Silo Using Natural and Low‐Temperature Air

ABSTRACTUsing variable temperature and relative humidity of natural air based on local climatic conditions for natural drying aeration of grain is an energy‐saving and efficient method. The study of heat and moisture transfer within grain piles during natural air and low‐temperature air drying aeration of bulk corn in low‐humidity areas, which can provide theoretical support for selecting efficient and low‐consumption grain drying processes and practical applications. In this study, the mathematical model of the coupled heat and moisture transfer dynamics in the dry silo was verified using experimental datum of grain storage drying aeration experiment, and the relative error was less than 5% between the simulated and the experimental datum. Based on this validated model, the temperature and moisture content variations of in‐silo bulk corn drying were simulated by computational fluid dynamics (CFD) numerical simulation techniques. The simulations included continuous drying aeration with daily average, hourly average temperature and relative humidity of the local natural air, and low‐temperature air drying aeration with heated up to 3°C over the ambient temperature, as well as intermittent drying aeration. Drying effectiveness and economic efficiency were also analyzed and evaluated. The costs for continuous drying aeration with hourly average of natural air and low‐temperature, intermittent drying aeration with hourly average of natural air are 0.032, 0.042, and 0.016 CNY/kg, respectively. Compared to traditional high‐temperature hot air drying, the costs of these methods were reduced by 0.048, 0.038, and 0.064 CNY/kg, respectively.

Effect of Progressive Wetting on Permanent Deformation of Fouled Ballast under Cyclic Loading

Climate change in recent decades has increased the frequency and intensity of extreme rainfall events, causing varied moisture contents in the ballasted track, which greatly challenges railway operation and track maintenance. Currently, most research about permanent deformation of fouled ballast are under dry condition or with a moisture content in the individual tested sample, which could not fully represent varied moisture conditions in the field induced by varying rainfall intensities. In this paper, permanent deformation of field-sourced fouled ballast under progressive wetting condition was investigated using large-scale triaxial cyclic tests. The results indicate that, with progressively rising water contents (0% to 12%), the fouled ballast sample maintained their stability; however, the rate of permanent strain increases to a peak value before experiencing a slight decline, aligning with classified shakedown ranges. This observed phenomenon can be attributed to the interplay between wetting, densification, and interlocking under conditions of cyclic loading and progressive wetting, an aspect that existing research have not elaborated. To encapsulate the identified deformation characteristics, this study proposes and validates a new predictive model for the permanent deformation of fouled ballast, demonstrating high prediction accuracy for fouled ballast with varying water contents.

Predicting wood moisture classes by sound frequency spectra and Explainable Machine Learning during milling

ABSTRACT Varying moisture content in wood lead to problems in the automatic selection of optimised machining parameters. Therefore, production in the wood sector can be improved by the automatic identification of moisture classes during machining. In this work, wood milling was monitored by a novel optical microphone to detect differences in wood moisture classes. A full factorial randomised design was executed along with four moisture classes (dried, conditioned, wet and frozen) and two cutting speeds as independent variables. The measured signals were segmented by extracting information from each cut and were transformed to the frequency domain. A supervised univariate feature ranking based on χ ²-tests was applied to select the most important frequencies. Machine Learning was applied to the selected spectral data to classify the cutting speeds and moisture classes. After testing several classification models, ensemble models with regression-tree learners were the best-performing model type achieved an average validation accuracy of 97.2%. The model explanation was done by Local Interpretable Model-Agnostic Explanation based on regression trees as a simple model, where the frequencies that are responsible for the separation of the data could be identified and were used for retraining the model, achieving a validation accuracy of 90.5%.

Investigation of the Impact of Moisture in Various States on the Adsorption of CH4, N2, and CO2 by Coal.

To investigate the impact of moisture in various states on the adsorption of CH4, N2, and CO2 by coal, this study conducted isothermal adsorption experiments on dry coal for moisture and on coal with varying moisture content for CH4, N2, and CO2. The results revealed that coal moisture adsorption progresses through four stages: monolayer adsorption, multilayer adsorption, cluster formation, and condensation into free moisture filling pores. The presence of moisture in coal varies across these stages, with its impact on CH4, N2, and CO2 adsorption decreasing as moisture content increases. As the moisture content rises, the adsorption constants (a and b values) progressively decline and eventually level off. Based on differences in coal moisture states, delineated by a relative humidity of 0.50 (corresponding to a moisture content of 2.39% in experimental samples), adsorption potential theory identified low moisture content stages where the monolayer and multilayer adsorption potentials for moisture (E1 = 4.99 kJ/mol, E2 = 39.71 kJ/mol) exceeded those for CH4, N2, and CO2, suggesting competitive adsorption effects. In the high-water content stage, the mesoporous structural fractal dimension D2 of the coal samples was found to be 2.77, nearly reaching 3, as determined through liquid nitrogen adsorption experiments and fractal dimension theory. This suggests that the intricate pore structure leads to water condensation, free water formation, and pore blockage, making it the primary factor influencing the adsorption of CH4, N2, and CO2 in coals, which is inherently linked to the characteristics of coal.

Emission Factors for Biochar Production from Various Biomass Types in Flame Curtain Kilns

Simple and low-cost flame curtain (“Kon-Tiki”) kilns are currently the preferred biochar technology for smallholder farmers in the tropics. While gas and aerosol emissions have been documented for woody feedstocks (twigs and leaves) with varying moisture contents, there is a lack of data on emissions from other types of feedstocks. This study aims to document the gas and aerosol emissions for common non-woody feedstocks and to compare emissions from finely grained, high-lignin feedstock (coffee husk) with those from coarser, low-lignin feedstocks (maize cobs, grass, sesame stems). Throughout each pyrolysis cycle, all carbon-containing gases and NOx were monitored using hand-held sensitive instruments equipped with internal pumps. Carbon balances were used to establish emission factors in grams per kilogram of biochar. The resulting methane emissions were nearly zero (<5.5 g/kg biochar) for the pyrolysis of three dry (~10% moisture) maize cobs, grass, and a 1:1 mixture of grass and woody twigs. For sesame stems, methane was detected in only two distinct spikes during the pyrolysis cycle. Carbon monoxide (CO) and aerosol (Total Suspended Particles, TSP) emissions were recorded at levels similar to earlier data for dry twigs, while nitrogen oxide (NOx) emissions were negligible. In contrast, the pyrolysis of finely grained coffee husks generated significant methane and aerosol emissions, indicating that technologies other than flame curtain kilns are more suitable for finely grained feedstocks. The emission results from this study suggest that certification of biochar made from dry maize, sesame, and grass biomass using low-tech pyrolysis should be encouraged. Meanwhile, more advanced systems with syngas combustion are needed to sufficiently reduce CO, CH4, and aerosol emissions for the pyrolysis of finely grained biomasses such as rice, coffee, and nut husks. The reported data should aid overarching life-cycle analyses of the integration of biochar practice in climate-smart agriculture and facilitate carbon credit certification for tropical smallholders.

Theoretical Analysis of Landfill Gas Migration in Capillary Barrier Covers Considering Effects of Waste Temperature

The high-temperature and high-humidity conditions arising from the biochemical degradation of landfill waste result in significant temperature gradients within the landfill cover. The effects of waste temperature on landfill gas transport and microbial aerobic methane oxidation are not fully understood. In this study, a fully coupled theoretical model was developed to simulate the interactions of moisture, heat, and gas transport within a capillary barrier cover. A series of parametric studies were carried out to investigate the influence of the combined effects of temperature gradient, initial soil moisture content, and landfill gas generation rate on methane transport, oxidation, and emissions. The simulated results indicated that increasing waste temperature intensified the temperature gradient, leading to higher surface evaporation rates and variations in methane oxidation efficiencies. Additionally, variations in initial soil moisture content and landfill gas generation rates were found to significantly impact gas migration and methane oxidation in the cover. This study demonstrates the critical role of waste temperature in landfill gas migration within landfill cover systems, providing technical methodologies for the optimized design of soil cover systems.

Study of microwave hardwood board modification and drying: experiments and technical-economic assessment

The very low permeability of many hardwood species causes problems during lumber drying. These include very long drying times, drying defects, large material losses after drying, high energy consumption, and expensive drying processes. Jarrah (Eucalyptus marginata) is a species which very difficult to dry. Microwave (MW) wood modification and MW drying can provide an increase in wood permeability and solve some hardwood drying problems. Two 60 kW MW conveyor plants at frequencies 2.45 and 0.922 GHz were used for experiments. The study of MW Jarrah (29x87mm) board drying after pre-drying MW modification showed that it is possible to dry boards in the moisture content range from 70 to 10% during 147-159 hours (6 -7 days) using the cycle method of MW power application. Such intensive MW drying does not bring perceptible damage to the wood and provides low variability of moisture content in the board cross sections. The shorter drying times reduce associated capital, space, energy and labor costs whilst the reduction in drying defects can increase yields. A short time of MW drying provides an opportunity to develop conveyor systems for hardwood sawn timber drying. Economic assessment of MW Jarrah board drying showed that a specific drying cost ranges from US$ 50 to $277/m3 at electricity prices from US$0.08 to $0.32/kWh. The electricity costs form the largest share in total specific drying costs - 44 to 82%. Jarrah boards are expensive product and MW drying costs can be acceptable for industry taking into consideration savings provided by fast drying and wood loss reduction.

Rapid calibration method for discrete element simulation parameters of columnar granular organic fertilizer with variable moisture content

The variable moisture content of granular organic fertilizers leads to poor applicability of discrete element simulation parameters, making quick calibration of these parameters a challenge. Therefore, a method was proposed to quickly calibrate columnar granular organic fertilizers' DEM parameters with varying moisture content. Initially, a method for measuring the angle of repose of irregular piles formed by columnar granular organic fertilizers was proposed. Then, a prediction model between moisture content (7.8 % to 18.5 %) and DEM parameters was developed using the Plackett-Burman test, the Steepest Ascent test, and the Box-Behnken test. Experimental results show that the proposed method for measuring the angle of repose has an average relative error of 2.88 %, which is lower than the conventional angle of repose measurement method. The simulation angles of repose predicted by the proposed DEM parameter model had an average relative error of 4.28 %, indicating that the model is stable and reliable.

Enhancing horticultural harvest efficiency: The role of moisture content in ultrasonic cutting of tomato stems

Ultrasonic vibration has notable benefits in the harvesting and processing of tomato stems, particularly in reducing cutting force and minimizing moisture loss. Given the anisotropic nature of biological materials, the moisture content of tomato stems significantly impacts their physical properties. This study investigates the influence of varying moisture content on temperature and cutting force during the ultrasonic cutting of tomato stems. Initially, the moisture content of tomato stems at different maturity stages was measured using a water activity meter. Mechanical properties were characterized using a universal testing machine, and thermal properties were analyzed with a differential scanning calorimeter (DSC). Regression models were established to correlate moisture content with these material properties. Additionally, a three-dimensional microscopic model of stem skeletons, interfaces, and fiber bundles was created to simulate the fracture mechanisms during ultrasonic cutting under different moisture levels. Single-factor and response surface optimization experiments were conducted using a custom experimental setup under varying maturity stages, excitation frequencies, and voltage variations. Results showed that after 24 h, the peak temperatures for tomato stems at different maturity stages were 97.84 °C, 80.59 °C, and 74.15 °C, with corresponding cutting forces of 0.492 N, 0.544 N, and 0.998 N, respectively. The discrepancy between experimental results and simulation data was within 10 %. Higher moisture content was found to enhance the thermal conductivity of fiber materials, aiding in the fracture of fiber bundles, thus reducing cutting time and force. This study provides a theoretical foundation for the application of ultrasonic technology in the efficient harvesting and processing of industrial crops, with significant implications for horticultural crop treatment and processing.

Effect of moisture content on pyrolysis product yield from lignite and lignite-peanut shell mixtures using slow pyrolysis

ABSTRACT The conversion of biomass-coal mixtures into energy using thermal conversion systems offers a more environmentally sustainable alternative to conventional coal consumption. A reactor with an internal compartment is proposed to improve the pyrolysis performance of lignite coal and mixtures of lignite coal with peanut shells. The study investigates lignite coal with varying moisture contents and peanut shell proportions (0%, 10%, 25%, and 50%) at a temperature of 500°C, using a heating rate of 0.1°C/s. The results indicated that dry mixtures demonstrated higher overall productivity compared to wet mixtures, particularly in terms of charcoal production. The weight of charcoal increased by 4.83%, 4.71%, 4.02%, and 2.61% across the mixtures. The total conversion rates for dry mixtures were 24.59%, 29.27%, 34.36%, and 40.44%, while for wet mixtures, the conversion rates were 29.42%, 33.98%, 38.38%, and 43.05%, respectively. The results revealed that moisture content during pyrolysis significantly influenced the productivity of lignite and lignite-peanut shell mixtures. The conversion rates in dry mixtures were lower compared to those in wet mixtures. The novelty of this work lies in its pioneering investigation of the impact of moisture on the slow pyrolysis of Turkish lignite mixed with peanut shells. It offers novel insights into optimizing the thermal conversion process for these materials by uniquely examining the effects of moisture on productivity and conversion rates.

Harvesting location influences the physicochemical properties, microbiological quality and sensory attributes of honey produced by an Afrotropical stingless bee, Axestotrigona ferruginea

This study investigated the physicochemical properties, sugar profiles, microbiological quality and sensory attributes of the honey produced by an Afrotropical stingless bee, Axestotrigona ferruginea, collected from two locations in Tanzania; Kibiti, representing the coastal mangrove ecosystem, and Siha, representing the northern highland’s Afromontane region. Honey samples from the two locations showed significant variations in moisture content, pH, free acidity, color, 5-hydroxymethylfurfural, total yeast and mold counts, and sensory properties (p < 0.05). However, there was no difference in the sugar profiles of the studied honey samples (p > 0.05). Overall, all honey samples met the East African quality standards for stingless bee honey, except for reducing sugars content. Additionally, all honey samples had acceptable microbial counts, indicating good quality. These findings provide valuable insights into the quality and sensory diversity of stingless bee honey, which can positively influence its acceptability and marketability.

Sensibility Analysis of Traditional Span Frame

ABSTRACT Traditional timber frames may have a complex mechanical behavior regarding to today engineer skills and design standards. For an identical rebuilding as required for the Notre-Dame de Paris Cathedral, accurate modeling must be performed to assess modern reliability. Identical rebuilt means same green oak material, same geometry and timber connections. In the context of the rebuilt of the Notre-Dame carpentry, a part of the timber frame based on the original schemes of the nave extracted from historical graphic document was reproduced. A full-scale replica was erected in order to perform mechanical tests. Through an in-situ monitoring, this structure represents a case study in order to provide data relative to the kinetics of displacements. This investigation allows to evaluate the global behavior of the structure. Based on the finite element method (F.E.M), a dedicated model is used to analyze the sensitivity of the material properties, the beam geometry and the wood-to-wood connections in order to design the testing carried out on the wooden structure. From these full-scale tests, we determine the real stiffness of the carpentry. Then, a retro-analysis was proposed to evaluate the axial stiffness of connections according to the corresponding finite element model, by fitting data to reproduce the real displacements. The study reveals that this property is substantial to describe the global behavior. Furthermore, we carried out in the laboratory an experimental campaign consisting in characterizing traditional joints. The goal was to estimate their stiffness and their specific failure modes by using image correlation. Concomitantly, numerical simulations were developed in order to investigate the dependence of the stiffness according to moisture content variation of oak species. The global research supplies useful tools and results, which may be able to improve the understanding of the mechanical performance of traditional structures and provide valuable information for design purposes.

Characterization of water states and pore size distribution in Beijing poplar using nuclear magnetic resonance techniques

ABSTRACT This study employs nuclear magnetic resonance (NMR) techniques to elucidate the water states and pore size distribution within Beijing poplar (Populus beijingensis W. Y. Hsu) across various temperatures. By analyzing the variation in moisture content (MC) at different freezing temperatures, the proportion and distribution of cell wall pores were determined using the NMR Cryoporometry (NMR-C) method. The results show approximately 60% of the pores in both the heartwood (HW) and sapwood (SW) of Beijing poplar have diameters were 1.5 nm, while the proportion of pores with diameters greater than 4.6 nm was less than 10%. Moreover, the MC of both more freely bound water (C-water) and OH bound water (B-water) is observed to decrease exponentially with decreasing temperature. B-water in Beijing poplar is found to maintain a higher MC than C-water across the temperature range from −3 to −60°C, indicating greater resistance to freezing. The findings of this study contribute to a comprehensive understanding of water states in Beijing poplar. Also the pore size distribution of Beijing poplar provides reference data for the selection of wood chemical modification groups.

Optimization of Bioremediation of Crude Oil Polluted Soil through Variation in Moisture Content and Proportion of Augmenting Bacterium and Fungus

Aim: The aim of this study was to enhance bioremediation of crude-oil polluted soil through optimization procedures. Study Design: The Box-Benkhen coded values format and experimental design were used in the design of the study. Place and Duration of Study: The study was carried out in the Microbiology laboratory of the Department of Microbiology, Rivers State University, Nigeria, between February 2024 and July 2024. Methodology: Hydrocarbon utilizing bacteria (HUB) &amp; fungi (HUF) were isolated from crude-oil polluted soil, and screened for hydrocarbon degrading ability (HCDA). HUB and HUF with the highest HCDA were identified and used for bioremediation optimization experiment. In the experiment, different combination of moisture content (MC), and proportion of HUB (pHUB) &amp; HUF (pHUF) were investigated for their effect on extent of hydrocarbon reduction (EoHR). EoHR obtained from the different combinations were fitted using a generalized polynomial model so as to obtain a polynomial equation for predicting EoHR. The equation was used in generating prediction profiles from which the combined values of the 3 parameters that will lead to the highest EoHR was determined. The predicted combined values were implemented in a new setup. A control and a setup enhanced with fertilizer were also prepared. The setups were maintained for 3 weeks. On day 0, 14, and 21 samples were collected and analyzed for total hydrocarbon concentration (THC). Results: The results obtained showed that among the coded isolated HUB and HUF, HB5 and HF1 had the highest HCDA; 36.4% and 4.1% respectively, and were identified phenotypically as Klebsiella ornithinolytica and Aspergillus flavus respectively. The results of the optimization experiment and prediction profiles showed that the highest (68.6%) EoHR was achievable at MC = 20%, pHUB = 10%, and pHUF = 1%. The actual EoHR on day 21 in the optimized, enhanced optimized, and control setups were 60.3, 58.9, and 39.9% respectively. Conclusion: Bioremediation optimization studies is advantageous and should be carried out on crude-oil polluted sites before carrying out bioremediation.

A transformation and auxiliary extraction of Cr during electrokinetic removal of Cr-contaminated multilayer composite soil chamber.

Multilayer composite soil chamber was proposed to extract the Cr of contaminated site soil and insight into transformation of Cr fractionation associated with valence states. The variations of current, soil pH and moisture content were explored, as well as the migration of Cr fractionation and redistribution of Cr. Results indicated that duration of half peak current could be used to adjust treatment time and it varied among different composite ways. Moreover, extraction efficiency of Cr in soil near cathode was relatively higher and reached 60% when citric acid was used. Citric acid could promote the transformation between different Cr fractionations or different valence states. It could also improve the desorption of Cr, and could prevent excessive fluctuations of moisture content at the same time. Cr redistributed acrossed the soil chamber after extraction. When deionized water was used, Cr(VI) significantly migrated toward anode mainly in the form of exchangeable fractionation (EXC) while Fe-Mn oxides fractionation (Fe-Mn) which may be in the form of cationic Cr(III) hydroxides migrated toward cathode. When using citric acid, fractionations that were difficult to migrate of Cr, especially for Fe-Mn in site soils could be activated and became EXC and carbonate fractionation (CAR), then migrated to the anode or cathode. The migration of exchangeable Cr(III) was dramatically enhanced. But the use of citric acid could cause Cr(VI) transformation to Cr(III) near anode. In addition, during the migration process, EXC could go back to Fe-Mn again or transform to residue fractionation (RES).

Effect of water occurrence in coal reservoirs on the production capacity of coalbed methane by using NMR simulation technology and production capacity simulation

The occurrence of gas and water is a critical factor affecting the production capacity of coalbed methane. Therefore, occurrence and dynamic interaction between gas and water in coal reservoirs need to be studied. T2 spectrum of all the samples were studied by NMR technique at 0, 5, 9, and 28 h of natural evaporation. Then, multifractal model was used to characterize water distribution heterogeneity, and a novel evaluation coefficient was proposed to characterize distribution heterogeneity of water content, the correlation among evaluation coefficient, water distribution heterogeneity and pore structure parameters was analyzed. The results are as follows. In the saturated state, the moisture distribution of three types is heterogeneous. Type A of adsorption pore-developed exhibits strong moisture variation heterogeneity of small pores, in contrast to the uniform moisture variation in large pores. Type B of fracture-developed has the highest coefficient of variation in moisture distribution. The coefficient of variation A1 for moisture content can determine the speed of moisture transport and evaporation in the pore structure. A lower A1 indicates a greater moisture transport volume and faster moisture transport rate over the same time. The coefficient of variation A2 for moisture distribution represents the heterogeneity of moisture content variation in the pore structure. That is, a smaller A2 indicates better heterogeneity in the distribution of moisture content in the pore structure. Numerical simulation indicates the average gas production and the peak gas production time increase and decrease with the initial moisture content (Sgrw) increases, respectively. These findings provide practical guidance for coalbed methane development, especially in optimizing coalbed methane production capacity prediction and improving recovery efficiency.

Multiscale modeling of microstructural and hygrothermal effects on vibrations of CNT-enhanced fiber-reinforced polymer composites

This work presents a multi-scale analytical and computational approach designed to predict the hygro-thermo-mechanical vibrational response of laminated composite structures reinforced with multi-walled carbon nanotubes (MWCNTs). Employing the modified Halpin-Tsai model, this study estimates the elastic properties of the MWCNT-enhanced epoxy matrix, incorporating the impacts of MWCNT agglomeration, orientation, waviness, and size-dependent characteristics. Additionally, the Chamis micromechanical model is utilized to ascertain the independent elastic constants of the nanocomposite lamina, considering environmental variables such as temperature and humidity. Subsequent analysis involves the determination of natural frequencies for both pristine and MWCNT-integrated laminated composite structures via the Finite Element Method (FEM), addressing various design-related parameters. This investigation further explores the macroscopic influences of MWCNT incorporation, boundary condition and layup scheme, along with the temperature, moisture content, and the nanoscopic impact of MWCNTs on the natural frequencies of laminated composite plates. The obtained results of the proposed multiscale modeling are compared with experimental and theoretical observations. It has been demonstrated that while the incorporation of carbon nanotubes (CNTs) can enhance the mechanical properties of nanocomposite laminae, the natural frequencies of these nanocomposite plates are adversely affected by variations in temperature and moisture content. Furthermore, the findings indicate that the microstructural characteristics of CNTs play a crucial role in determining the efficacy of the reinforcement phenomenon. The developed multi-scale methodological framework offers significant potential for the design and optimization of MWCNT-based composite structures across diverse industries, including automotive and aerospace sectors.