Dry Tests Research Articles

Application of in-situ EIS to Galvanic Corrosion of Aluminum Alloy Coupled with High-Tensile Steel

Toward multi-materials for the weight reduction of automobile bodies, the light materials have been used in the automotive industry. However, it may pose serious issues for degradation due to the galvanic corrosion. In this study, an in-situ electrochemical impedance spectroscopy (in-situ EIS) 1-4 was applied to the evaluation of galvanic corrosion of aluminum alloy coupled with high-tensile steel. This method allows for the simultaneous measurement of impedance spectra of aluminum alloy and high-tensile steel.An electrochemical measurement was performed by a three-electrode system. The working electrode (WE) was an aluminum alloy plate, the counter electrode (CE) was a high-tensile steel plate. The reference electrode (RE) was a saturated KCl-Ag/AgCl (SSE), which was set near the WE and CE. To simulate the galvanic corrosion environment of automotive materials, the aluminum alloy plate and high-tensile steel plate are set face-to-face. The distance of both electrodes was about 100 μm. The 3D impedance measurement was carried out for 2 weeks. In this measurement, the potential difference between the WE and the CE was set to 0 V to simulate galvanic corrosion 5. The frequency range was 10 kHz to 0.1 Hz at 5 frequencies per decade and AC potential amplitude was 10 mV. The electrochemical cell was placed in the temperature and humidity chamber for the wet and dry cyclic corrosion test.The in-situ EIS was successfully carried out during the wet and dry cyclic corrosion test in the temperature and humidity chamber. The three-electrode system enables the simultaneous measurement of impedance of aluminum alloy plate - high-tensile steel plate (WE-CE), aluminum alloy plate (WE), and high-tensile steel (CE). In the wet condition, the capacitive loop and part of large loop in the high and low frequency ranges were observed in the instantaneous impedance of the aluminum alloy plate-high tensile strength plate (WE-CE) determined from 3D impedance 1-4 at arbitrary time. In this case, the instantaneous impedance of the aluminum alloy plate (WE) and high-tensile steel plate (CE) described the capacitive loop and part of large loop on the Nyquist diagram respectively. It was confirmed that the capacitive loop and part of large loop in the high and low frequency ranges observed in the instantaneous impedance of the aluminum alloy - high tensile strength (WE-CE) were related to the aluminum alloy plate (WE) and high tensile strength plate (CE), respectively. The galvanic corrosion behavior during the wet and dry cyclic corrosion test was investigated by evaluating the charge transfer resistance estimated from the instantaneous impedance of the aluminum alloy plate (WE) and high-tensile steel plate (CE) to discuss the time variation of the charge transfer resistance.

Effects of Mg2Si Addition on the Pitting Corrosion Resistance of AA7075 Prepared by Spark Plasma Sintering

AA7075 containing Mg2Si was fabricated by Spark plasma sintering (SPS). Gas-atomized AA7075 powders and Mg2Si powders were mixed and sintering was performed at 773 K for 15 min. After sintering, hot-forging was conducted at 773 K, and heat-treatment was conducted at 688 K for 2 h. The specimens were polished with a diamond paste down to 0.25 µm.The surface of specimens was observed using an optical microscope and a field emission scanning electron microscope (FE-SEM) equipped with energy dispersive X-ray spectroscopy system (EDS). Electrochemical measurements were performed in 0.1 M NaCl at pH 6.0 adjusted with NaOH. With the exception of the electrode area, the surfaces of specimens were coated with an epoxy resin. The size of the exposed electrode area was ca. 5 mm × 5 mm. Dip and dry tests were conducted to evaluate the corrosion resistance of the specimens. The specimens were dipped in 0.1 M NaCl (pH 6.0) for 20 min and dried at 298 K and 50%RH for 60 min. In addition, the effect of Mg2Si on pH of 0.1 M NaCl was investigated. The variation of pH due to addition of Mg2Si to 1 L of 0.1 M NaCl at pH 6.0 was measured.The open circuit potential of Mg2Si-containing AA7075 decreased significantly after immersion compared to AA7075. In 20 cycles of dip and dry, mass loss was reduced by Mg2Si addition. Oxide films containing Al were formed on the Mg2Si-containing AA7075; however, Mg was not detected from the films. When Mg2Si was added to 1 L of 0.1 M NaCl, the pH increased significantly. The increase in pH on the specimen surface is thought to contribute to improvement of the pitting corrosion resistance.

Hepatitis C virus point-of-care microelimination approach in a vulnerable population in the South of Spain.

Since the introduction of direct-acting antivirals, thousands of chronic hepatitis C patients have been successfully treated. However, vulnerable populations have a higher prevalence of hepatitis C virus (HCV) infection and face barriers that impede their access to antivirals. We carried out an HCV microelimination program focused on vulnerable population groups in Malaga. People in drug addiction treatment centers and homeless shelters in Malaga who participated in the program between October 2020 and October 2021 were included. After providing participants with educational information on HCV, a dry drop test (DDT) was used to collect blood for subsequent screening for HCV infection. The participants who were diagnosed with HCV infection were scheduled for comprehensive healthcare assessments, including blood tests, ultrasonography, elastography, and the prescription of antivirals, all conducted in a single hospital visit. Sustained viral response (SVR) was analysed 12 weeks after end of treatment. Of the 417 persons invited to participate, 271 (65%) agreed to participate in the program. These participants were screened for HCV infection and 28 of them were diagnosed with HCV infection (10%). These hepatitis C-infected patients had a mean age of 53 ± 9 years; 86% were males and 93% were or had been drug users. Among 23 patients with HCV infection, HCV genotype 1a predominated (74%). Medical exams showed that 19% (4/21) had advanced fibrosis (F3-4), and 5% (1/21) had portal hypertension. Finally, 23 infected patients received treatment with glecaprevir/pibrentasvir or sofosbuvir/velpatasvir and SVR was confirmed in 22 patients (96%). Drug users and homeless people have a higher prevalence of HCV infection than the general population. The microelimination program with educational activity and screening tools achieved a high participation rate, easy healthcare access, and a high rate of SVR despite the SARS-CoV-2 pandemic.

Fluidization‐bed drying and microwave radiation effects on drying rate, fatty acid, protein, and germination of flaxseed

AbstractFlaxseeds are known for their invaluable omega‐3 fatty acids and proteins. Flaxseeds need to be dried to 10%w.b. moisture for safe long‐term storability. Traditional drying ruptures the nutritional properties, therefore, this study analyzed the effect of fluidized‐bed and microwave drying on the fatty acid and protein constituency of flaxseed. The drying air temperatures in the fluidized‐bed drying tests were 40, 50 and 60°C. Three microwave power densities were selected 0.3, 0.6 and 1 W g−1. Results showed a minor effect on fatty acids whereas a significant effect on protein content with both the drying methods. A protein reduction of 7, 21, and 23% was observed for drying air temperatures of 40, 50, and 60°C, respectively. For the microwave tests, 39, 58, and 63% protein reductions for 0.3, 0.6 and 1 W g−1 power densities were observed, respectively. The fatty acids showed a maximum increase of 0.85% for fluidized bed drying and 1.23% for microwave.Practical applicationsThis study contributes a step‐forward knowledge toward adoption of microwave technology in flaxseed oil extraction industry. Previous pilot‐scale studies solely on microwave utilization have shown limited scale‐up due to its high infrastructure cost associated with emitting high‐power densities. However, if explored with a combination approach along with fluidized bed (40°C at 0.3 W g−1) to assist in early removal of surface moisture from flaxseed, it could be a potential platform to increase the productivity in parallel to matching the associated overall cost. A proper cost analysis could be a future aspect of this study.

Effect of Different Passivation Treatments on Alkali Zn-Ni Coatings: Corrosion Resistance and Adhesion Performance of Geomet 321 and ML Black Coatings

This study aims to improve the corrosion properties of (AISI 1040) materials used in the automotive industry. For this purpose, two different coating techniques were applied to the same surface. As part of the research, different passivation processes (transparent, blue, yellow, and black) were applied to alkaline Zn-Ni coatings. Geomet 321 and Geomet ML Black coatings were deposited on the passivation layer to form a double-layer coating. In order to investigate the adhesion and corrosion effects of these coatings, a dry adhesion test, a water test, a humidity test, and a salt spray test were carried out, and cross-cut adhesion tests were carried out after each corrosion test. After all these tests, rust formation was analysed by visual analysis, and atomic weight percentages and coating thicknesses were examined by X-ray. The transparent passivation after the Zn-Ni coating fully satisfied both adhesion and corrosion protection requirements for 321 and ML Black coatings. No red rust formation was observed on the coating samples after the test; only partial white rust formation was observed, and no peeling of the coating layer was detected in the adhesion tests. As a result, the optimum result of the passivation processes used for Geomet 321+ML Black coatings applied after the Zn-Ni + passivation process was obtained with transparent passivated Zn-Ni coatings. Even after 1200 hours, no red rust was observed in passivated Zn-Ni coating+ Geomet 321+ Geomet ML Black.

Correlation and Path Coefficient Studies of Three Line Rice Hybrids

Thirty-one three-line rice hybrids and three commercial checks were used in the current study for correlation and path coefficient analysis. In Kharif 2021, the experiment was carried out at the TCA Hybrid Rice field in Dholi, Pusa, Bihar, India. The experimental design adopted was a Randomized Complete Block Design (RBD) with three replications that included 18 quantitative attributes. Plant height, number of tillers per plant, number of panicles per plant, leaf length, leaf area, kernel length, kernel width, root fresh weight, root dry weight, spikelet fertility, and test weight showed a positive significant correlation with grain yield per plant. Hence, selection for any one of these characteristics would ultimately bring improvement in grain yield. The traits number of tillers per plant, plant height, root fresh weight, leaf length, no. of panicles per plant, leaf width, kernel length, and root volume revealed a significant direct impact on grain yield per plant. Thus, breeding for these characteristics could end up resulting in a higher grain yield.

Laboratory investigation of osmotic tensiometers filled with cross-linked polyacrylamide

Soil suction measurement is required for the analysis of slope stability and soil-structure interactions related to unsaturated soils below transportation infrastructures. Osmotic tensiometers (OT) can measure soil suction higher than 1000 kPa but suffer from the pressure decay problem. The OT filled with cross-linked polyacrylamide can maintain a stable pressure for a long time but the research on this type of OT is quite limited. In this study, the behaviors of OTs filled with synthesized non-ionic cross-linked polyacrylamide were investigated experimentally and explained in accordance with Flory-Huggins polymer theories. A generalized calibration equation was proposed to reduce the pressure fluctuation of OT caused by temperature. The pressure variations of two OTs were observed for more than 100 days and several cycles of drying tests were conducted. The results show that the pressure of the OT recovered after it was dried in the air for tens of minutes. In contrast, a slight pressure decay appeared when the OT was dried in the air for several days. However, as more cycles of drying tests were conducted, the pressure decay caused by the drying tests gradually became negligible. The relationship between the pressure of the OT at the end of observation and the volume fraction of the polyacrylamide inside the chamber of the OT was established by considering the confinement effect on the polyacrylamide hydrogel inside the OT. Finally, it is proved that salt solutions will not affect the pressure variation of OT filled with cross-linked polyacrylamide so the OT measures the matric suction of the soil.

Replacing Toxic Hard Chrome Coatings: Exploring the Tribocorrosion Behaviour of Electroless Nickel-Boron Coatings

Electroless nickel-boron coatings present outstanding properties such as high hardness, excellent wear resistance and uniform coating, and thus they are considered to be alternative to toxic hard chrome coatings. However, they contain lead that is toxic and used as stabilizer in the plating bath. This study aims to investigate the tribocorrosion behaviour of lead-free electroless nickel-boron coatings. In the present research, several tests were carried out to investigate the behaviour of these coatings under both dry and tribocorrosion reciprocating sliding wear against alumina balls, at room temperature. The open circuit potential (OCP) method was used to determine the degradation mechanism of the coatings. The results of the tribocorrosion and dry wear tests showed that the performance of coatings was very different from each other. A steady state for the coefficient of friction (COF) is achieved during the tribocorrosion test, whereas the constant production of debris and their presence in the contact implied an increase in COF with distance during the dry wear test. The wear mechanisms of these coatings also presented variations in these tests. It was found that the wear area calculated from tribocorrosion is lower (56 µm2) than the one from dry sliding test (86 µm2).

A comprehensive structural and electrochemical study on the performance of Mn-phosphate layers

Several manganese phosphating routes, including the influence of immersion time (15 min. and 30 min.), addition of accelerators (Ni(NO3)2, 2 g/l), modification in the activation stage (increased concentration in the activator), and ultrasonic stirring, were used to obtain films with a variety of characteristics. This research uses the following common analytical methods for the phosphate characterisation: scanning electron microscopy (SEM) and electrochemical techniques (potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS). Thus, modifications in the coating mass, covering efficiency, surface appearance, and chemical composition/structure could be determined. This study showed that accelerators induced the formation of thicker layers (up to 125 % bigger), whereas ultrasonic stirring assisted with reducing the crystal sizes and developing denser films (up to 50 % reduction in the icorr values). The dry frictional tests showed that the wear behaviour depended on the phosphate thickness, crystal density, and film tortuosity. A fine-grained structure or a thick film contributed to an improved wear performance (near 80 % reduction in the coefficient of friction), but grains that are too fine along with an intricate structure worsened the behaviour under frictional forces.

Multi-functionalized MCNs effectively improve the interfacial compatibility of mixed matrix membranes and enhance CO2 separation performance

Traditional two-dimensional (2D) membrane fillers are prone to interfacial defects such as agglomeration and phase separation in the membrane, limiting the separation performance of membrane. In this paper, microporous carbon nanoplates (MCNs) with controllable microporous structures were functionalized with two different amine carriers of low molecular weight polyethyleneimine (PEI) and 3-aminopropyl triethoxysilane (APTES) to prepare multi-functionalized microporous carbon nanoplates (MfMCNs). It is worth noting that with the success of composite functionalization, the filling content of mixed matrix membranes is also high to a certain extent. To a certain extent, it has been demonstrated that interfacial compatibility between the polymer and the fillers has been improved. It was confirmed by characterization technology that the morphology of the fillers had not been changed, but the pore size of MfMCNs was declined to 0.53–0.55 nm because part of the amino carrier was immersed in the pore structure of MfMCNs. The gas permeability tests under dry gas and wet gas conditions show that the improvement of phase interface by MfMCNs is significant. Under the condition of a dry gas test, the CO2/N2 selectivity of MfMCNs/Pebax-1.0 wt% MMMs is 76.3, which is 27 % higher than that of MCNs/Pebax-1.0 wt% MMMs. Under the moisture condition, the permeability and selectivity of MfMCNs/Pebax-1.0 wt% MMMs CO2 are 287.72 Barrer and 79.1 separately. Compared with Pebax membrane, the permeability of CO2 (176.6 Barrer) was rose by 62.9 %, and the selectivity of CO2 (59.1) was rose by 33.84 %. Significantly, the best MMMs separation performance exceeds upper limit of Robeson. This provides a powerful strategy to strengthen the compatibility between inorganic materials and polymers and strengthen the performance of MMMs in CO2 gas capture.

Research on the mechanism of the two-dimensional ultrasonic surface burnishing process to enhance the wear resistance for aluminum alloy

The gradient nanostructure is machined on the aluminum (Al) alloy by the two-dimensional ultrasonic surface burnishing process (2D-USBP). The mechanism of why the gradient nanostructure enhances wear resistance is investigated. The mechanical properties and microstructure characterization for the gradient nanostructure are performed by operating a nanoindenter, transmission electron microscopy (TEM), and electron backscattered diffraction (EBSD). Dry wear tests are performed on the samples before and after machining to evaluate the wear resistance and mechanisms. The effect of the gradient nanostructure on the wear resistance is explored by developing the crystal plasticity (CP) finite element and molecular dynamics (MD) models. The characterization results show that the 2D-USBP sample prepared a gradient structure of ∼600 µm thick on the aluminum surface, increasing the surface hardness from 1.13 to 1.71 GPa and reducing the elastic modulus from 78.84 to 70.14 GPa. The optimization of the surface microstructure and the increase of the mechanical properties effectively enhance the wear resistance of the sample, with 41.20%, 39.07%, and 54.58% of the wear scar areas for the 2D-USBP treated samples to the original samples under 5, 10, and 15 N loads, respectively. The gradient nanostructure hinders the slip of dislocations inside the sample during the wear process and reduces the size and scope of plastic deformation; meanwhile, the resistance to deformation, adhesion, and crack initiation and propagation of the sample surface is improved, resulting in enhanced wear resistance.

Corrosion Studies on Ternary Blended High Performance Self-Compacting Concretes Containing Fly Ash and Graphene Oxide

Effective utilization of industrial byproducts as mineral admixtures and filler materials in cement concrete has been a practice to develop sustainable construction materials. The use of mineral admixtures like fly ash, silica fume, ground granulated blast furnace slag etc. as a partial replacement of cements have proved to improve the performance characteristics of concrete through reduced porosity and improved mechanical characteristics through pozzolanic effect and filler effect. Moreover, extensive research in the recent period has been mainly focused to study the effect of nano-additions in concrete. The present work was focused to assess the performance of ternary blended high performance self-compacting concretes with varied quantities of graphene oxide additions. Control concrete of M60 grade was designed in correspondence to IS-10262:2019 containing fly ash, and three other concretes mixes were formulated with 0.03%, 0.06% and 0.09% addition of Graphene Oxide (By weight of total cementitious material). The specimens were cast and tested at different ages to determine rheological, mechanical and durability characteristics by evaluating slump flow, Compressive Strength, Split Tensile Strength, Absorption- Desorption characteristics, Rapid Chloride Penetration Test values and resistance to accelerated corrosion cracking. Moreover, the specimens were assessed for corrosion resistance by conducting a cyclic wet – dry test, where parameters like UPV & depth of chloride penetration in concrete were measured. Results depict the fact that addition of Graphene Oxide improves the durability characteristics to a great extent. The optimum results for most of parameters were obtained at 0.06% of Graphene Oxide addition in comparison to remaining mix proportions.

Antibacterial activity of solid surfaces is critically dependent on relative humidity, inoculum volume, and organic soiling.

Antimicrobial surface materials potentially prevent pathogen transfer from contaminated surfaces. Efficacy of such surfaces is assessed by standard methods using wet exposure conditions known to overestimate antimicrobial activity compared to dry exposure. Some dry test formats have been proposed but semi-dry exposure scenarios e.g. oral spray or water droplets exposed to ambient environment, are less studied. We aimed to determine the impact of environmental test conditions on antibacterial activity against the model species Escherichia coli and Staphylococcus aureus. Surfaces based on copper, silver, and quaternary ammonium with known or claimed antimicrobial properties were tested in conditions mimicking microdroplet spray or larger water droplets exposed to variable relative air humidity in the presence or absence of organic soiling. All the environmental parameters critically affected antibacterial activity of the tested surfaces from no effect in high-organic dry conditions to higher effect in low-organic humid conditions but not reaching the effect size demonstrated in the ISO 22169 wet format. Copper was the most efficient antibacterial surface followed by silver and quaternary ammonium based coating. Antimicrobial testing of surfaces using small droplet contamination in application-relevant conditions could therefore be considered as one of the worst-case exposure scenarios relevant to dry use surfaces.

Solar drying of agrobiomass for biopellets production

This paper presents the results of the research devoted to the determination of the conditions of solar drying of agrobiomass waste in open area in Mediterranean climate in Aydin region. The testing was undertaken in the summer season.
 Drying tests were performed for two type mixtures i.e., sewage sludge and olive mill waste (OMW30) and sewage sludge and animal waste (DMC30).
 In order to determine the optimum conditions for the process and undertake an analysis of kinetic drying of sewage sludge, a set of tests were performed under variable parameters, i.e. for various thickness of the dried mixture of materials: 5, 10 and 20 cm and with the application of various mixing intensity: no mixing, and 6 times a day.
 The conducted tests let to the determination of the time interval necessary for the drying in the conditions of summer and also the parameters, which are optimal in terms of the time needed for the solar drying process in open sun drying.

Evaluation and Test of Activity of Anti-Acne Peel-Off Mask Preparation Formulation of Brotowali Stem Extract (Tinospora crispa L.)

Background: Facial skin care for acne treatment is better formulated in topical form, this is due to the duration of the active substances that interact with the skin. One dosage form is a peel-off mask with active substances brotowali stems which contain flavanoids, tannins, alkaloids as antibacterial causes acne. Objective: Analyzing the effect of variations in the concentration of brotowali stem extract (Tinospora crispa L.) on physicochemical evaluation and antibacterial activity of optimal anti-acne peel-off mask preparation formulations Methods: The research method used is True Experimental with a posttest only control group design research design. Make peel-off mask formulations with variations in extract concentrations of 20%, 30%, and 40%. The evaluation then includes organoleptis, homogeneity, dispersion, adhesion, dry time, pH, viscosity, and antibacterial activity tests, statistically analyzed using One Way ANOVA Results: Qualify in the organoleptis test is formula II (30%) and III (40%), the dispersion test is formula I (20%) and II (30%) with a p-value of 0.022, the adhesion test of all formulations with a p-value of 0.014, the dry time test of all formulations with a p-value of 0.000, the pH test is formula I (20%) with a p-value of 0.000, the viscosity test is formula II (30%) with a p-value of 0.000. The diameter of the formula's third inhibitory zone against propionibacterium acnes was 8.61mm ± 0.19 respectively; 14.31mm ± 3.88, and 15.54mm ± 4.80 with a p-value of 0.012 Conclusion: Variations on concentration of brotowali stem extract have an influence on physicochemical evaluation and antibacterial activity, the most optimal formulation is formulation II (30%)

Revealing the impact of isolated pores on the properties of foam cement using hollow microspheres

Since foam concrete inevitably leads to foam bursting and merging during the molding process, the relationship between specific pore connectivity and pore diameter distribution on foam concrete properties is still difficult to characterize exactly. This study intentionally introduced hollow microspheres of three sizes (40 µm, 60 µm, and 80 µm) into foam concrete to control the number and diameter of isolated pores. The influence of isolated porosity and pore diameter distribution on the properties of foam concrete were evaluated by dry density, mechanical property and thermal conductivity. Meanwhile, the SEM and X-CT technologies were employed to assess the pore structure of the sample, and the measured thermal conductivity was compared with the theoretical thermal conductivity calculated by the formula based on the isolated porosity. Finally, the correlation between isolated pores and heat transfer paths were analyzed by the calculated tortuosity. The results of the dry density and mechanical tests indicated that the dry density tended to be lower with the increase of isolated pores’ diameter, which 80 µm hollow microspheres resulted in a notable reduction in the dry density within the three size groups, whereas 28 days compressive strength trended oppositely. The 40 µm hollow microsphere specimen with a dry density of 400 kg/m3 exhibited the better mechanical property among three groups, which was 1.82 MPa, due to the uniform distribution within the matrix, preventing fusion between foams. Specifically, the trend of the theoretical value calculated by the formula was consistent with that of the measured value, proving that the decrease in thermal conductivity of sample can be attributed to the increase of isolated porosity. The lowest thermal conductivity and highest tortuosity were achieved by specimens mixed with 80 µm hollow microspheres at the dry density of 300 kg/m3, which were 0.07045 W/(m·K) and 2.015, respectively, demonstrating that specimens mixed with 80 µm hollow microspheres exhibited a more complex heat transfer path than the other two groups.

Improvement of the post-analytical phase by means of an algorithm based autoverification

Abstract Objectives Autoverification (AV) is releasing laboratory results using predefined rules. AV standardizes the verification of laboratory results, improves turnaround time (TAT), detects errors in the total test process, and enables effective use of laboratory staff. In this study, we aimed to evaluate the outcomes of implementing the AV in a tertiary hospital. Methods The study was performed in Gazi University Health Research and Application Hospital, Core Biochemistry Laboratory, between August 2017 and October 2019. Step by step, AV algorithms were designed and implemented via middleware for 29 clinical biochemistry tests. A comprehensive validation was performed before the AV system was run. Initially, AV system was tested with datasets and simulated patients (dry testing). Next, samples that may violate AV rules were tested anonymously with no-named trial barcodes (wet testing). Finally, validation of the system was performed with real patients, while the AV was running in the background but not active (i.e., while the manual verification was still going on). After all these steps were successful, the system was started. Results In the daytime, AV rates were ≥75 % for 23 of 29 tests. In night-shift, AV rates were ≥70 % for 16 of 25 tests. Report-based performance was found 26 % for daytime. TAT in the daytime decreased after AV implementation. Conclusions Although this is the first time we have implemented the AV, a significant percentage of the tests have been verified. However, approaches that will increase the percentage of report-based verification will enhance the efficiency of autoverification.

Numerical modeling of drying from saturated to unsaturated conditions with two-phase partitioning boundaries at the medium surface and interface-dependent phase change

To accurately predict the drying of a porous medium from saturated to unsaturated conditions over time, this paper proposes two-phase partitioning boundaries for liquid water evaporation and water vapor transport at the medium surface. A non-isothermal two-phase (liquid water and gas mixtures), two-component (dry air and water vapor) transport model with nonequilibrium and interface-dependent phase change is then developed. The governing equations are then numerical solved using COMSOL Multiphysics software and applied to describe a series of laboratory soil drying tests as examples. The performance of the proposed boundaries at the surface is illustrated by comparison with other three common used boundaries. The results show that a specific flux of vapor at the surface with a zero flux of liquid water cannot be adopted to describe the drying process of initially saturated media due to the lack of interconnected gas-filled pores. The merged liquid-vapor boundary applied in the Darcy–Richards model significantly prolongs the constant rate stage when the liquid water evaporation is dominant. Then, the effects of air/gas–water interfacial area and water retention parameters on the drying process are investigated. A faster reduction in the air–water relative interfacial area at the medium surface will shorten the drying process with earlier dominance of the vapor transport. An increased entry capillary pressure and a decreased pore size distribution index for the water retention curve will result in slower drying, more loss by vapor transport and a more homogeneous distribution of pore water respect to depth. The current study can promote the understanding of the evolution of drying mechanisms of a porous medium from saturated to unsaturated conditions.

A cyclic (intermittent) drying schedule for Macassar ebony—the prevention of collapse deformation and the utilization of mechano-sorptive creep gradient

Ebony wood is often defective, showing severe cracks and deformations during manufacturing processes, and requires ample times for drying. The continuous drying has been proved to result in enormous collapses during the entire drying stage. In order to control the extent of collapses and further prevent these defects, a low temperature pre-freezing procedure was projected and followed by a cyclic drying program. This cyclic (intermittent) drying schedule was proposed based upon a so-called “mechano-sorptive creep gradient” (MSCG) strategy and elaborated by a “corresponding temperature differentia” (CTD) concept. The MSCG and CTD variables provided the theoretical explanation and the operational instruction to the cyclic drying test, respectively. The overall evolutions of collapse and transversal shrinkage of the ebony lumber boards were quantitatively investigated during the entire period of a cyclic drying process. Furthermore, the relationships between collapse and moisture content as well as cross section orientation were determined quantitatively. Under this specified pre-freezing plus cyclic drying method, the averaged collapse deformations were significantly decreased, with the maximum collapse variables accounting for 20 ∼ 30% of those under continuous cases, fully achieving the collapse controlling objective.

Macroscopic and Microscopic Characteristics of Strength Degradation of Silty Soil Improved by Regenerated Polyester Fibers under Dry-Wet Cycling.

The structural stability of silt foundations, particularly sensitive to moisture content, can be severely compromised by recurring wetting and drying processes. This not only threatens the foundational integrity but also raises grave concerns about the long-term safety of major civil engineering endeavors. Addressing this critical issue, our study delves into the transformative effects of reclaimed polyester fiber on subgrade silt exposed to such environmental stressors. Through rigorous wet-dry cycle tests on this enhanced soil, we evaluate shifts in shear strength across varying confining pressures. We also dissect the interplay between average pore diameter, particle distribution, and morphology in influencing the soil's microstructural responses to these cycles. A detailed analysis traces the structural damage timeline in the treated soil, elucidating the intertwined micro-macro dynamics driving strength reduction. Key discoveries indicate a notably non-linear trajectory of shear strength degradation, marked by distinct phases of rapid, subdued, and stabilized strength attrition. Alterations within the micropores induce a rise in both their count and size, ultimately diminishing the total volume proportion of the reinforced soil. Intriguingly, particle distribution is directly tied to the wet-dry cycle frequency, while the fractal dimension of soil particles consistently wanes. This research identifies cement hydrolysis and pore expansion as the dominant culprits behind the observed macroscopic strength degradation due to incessant wet-dry cycles. These revelations hold profound implications for risk management and infrastructural strategizing in areas dominated by silt foundations.