Microscopic Morphological Changes Research Articles

Multi-ion erosion test and molecular dynamics simulation of carbon nanotube concrete under stray current and salt brine environment

This study considers the superior mechanical properties of carbon nanotube concrete (CNC) and conducts corrosion tests over varying durations to investigate key aspects such as corrosion depth, strength loss, ion migration patterns, and microscopic morphological changes in CNC under the influence of stray current in a salt brine environment. Through compressive strength test, chloride ion color test, ion content titration test, microscopic detection test and molecular dynamics simulation, the results show that in an environment where multiple erosive ions coexist, sulfate ions are the most erosive ions to CNC, and are easily combined with calcium ions. The electric field speeds up the transmission of ions, especially chloride ions. Carbon nanotube has a certain adsorption effect on sulfate ions. The main corrosion products are ettringite, gypsum and magnesium hydroxide. Among them, ettringite and gypsum mainly cause expansion and corrosion.

Research and Development of Self-Waterproofing Concrete for Tunnel Lining Structure and Its Impermeability and Crack Resistance Characteristics.

This research paper systematically investigates the combined influence of fly ash, cementitious capillary crystalline waterproofing (CCCW) materials, and polypropylene fibers on the mechanical properties and impermeability of concrete through comprehensive orthogonal tests. Microscopic morphological changes in the concrete induced by different composite materials are examined via scanning electron microscopy (SEM) and X-ray diffraction (XRD) testing. The objective is to facilitate a beneficial synergetic interaction among these materials to develop highly permeable, crack-resistant concrete. Key findings of this study are: (1) The study unveils the impact of the concentration of three additive materials on the concrete's compressive strength, tensile strength, and penetration height, thereby outlining their significant influence on the mechanical properties and impermeability of the concrete; (2) An integrated scoring method determined the optimal composite dosage of three materials: 15% fly ash, 2% CCCW, and polypropylene fibers at 1.5 kg/m3. This combination increased the concrete's compressive strength by 12.5%, tensile strength by 48.4%, and decreased the average permeability height by 63.6%; (3) The collective introduction of these three materials notably augments the hydration reaction of the cement, resulting in denser concrete microstructure, enhanced bonding between fibers and matrix, and improved concrete strength and durability.

Study on the Combined Behaviour of Montmorillonite and Carbonate Mineralizing Bacteria on Lead Retention and Fixation

Heavy metal pollution management is a global environmental problem that poses a great threat to the ecological environment. Adsorption and biomineralization are considered to be the two most promising heavy metal pollution remediation techniques among the numerous available ones. In this work, a combined heavy metal removal system was constructed employing the adsorption of montmorillonite and the mineralization of carbonate mineralizing bacteria to expand their application potential for controlling heavy metal water pollution. Analysis of changes in pH, CO32− concentration, Pb2+ concentration in the liquid phase, and changes in microscopic morphology, mineral phase, and functional group on sedimentary minerals was done to study the retention and fixation behaviour of montmorillonite and carbonate mineralizing bacteria on Pb2+. The results show that the liquid phase pH may be slightly altered by the ions dissolved in montmorillonite. Based on the conditions of montmorillonite and carbonate mineralizing bacteria functioning separately, the elimination of Pb2+ may reach 35.31% and 45.75%, respectively. However, when montmorillonite is combined with carbonate mineralizing bacteria, which is the heavy metal removal system constructed in this study, montmorillonite can buffer part of the Pb2+ rapidly and reduce its biotoxicity. Subsequently, these buffered Pb2+ are gradually desorbed by carbonate mineralizing bacteria and removed by the effect of mineralized deposition. Results from SEM, FTIR, and XRD indicate that Pb2+ is primarily removed from the liquid phase as rod-shaped PbCO3. It is worth noting that this process is able to significantly increase the removal of Pb2+ up to 90.06%. In addition, the presence of carbonate mineralizing bacteria can increase montmorillonite’s desorption rate to over 81%, greatly enhancing its capacity for reuse. Therefore, our research work contributes to expanding the potential of montmorillonite and carbonate mineralizing bacteria in the treatment of heavy metal-polluted waters.

Control of chemical and microbial pollutants in liquid-solid phases of sewer pipes by Fe(II)-activated persulfate: Performance and mechanism of simultaneous removal

Most of the problems such as odor and corrosion in sewage systems originate from the biochemical reactions of liquid and solid phases in the pipes. Suppressing the activity of microorganisms and biofilms in the sewers is conducive to maintaining the proper operation of the sewer system. This study verified the removal of microorganisms and sulfides from wastewater and the inhibition of biofilm activity by peroxodisulfate (PDS) with the activation of ferrous ions (Fe(II)). Fe(II)/PDS can achieve efficient microbial inactivation within a reaction time of 20 min after a single dosing (Up to 95% removal of planktonic bacteria in the liquid phase), and the sulfide reduction can be maintained for more than 5 days, providing the possibility of intermittent dosing. The sulfide concentration can be maintained below 4 mg/L by intermittent dosing (average dosing interval is 10 days) during the long-term operation of the reactor. Dissolved organic matter (DOM) changes in sewage predict biofilm destruction. Changes in the biofilm microscopic morphology, extracellular polymer substances (EPS) fraction, biofilm functional groups, and microbial community revealed the effects of Fe(II)/PDS on the solid–liquid phase material fraction and biofilm structure of the sewage pipeline. The mechanism of biofilm disruption was analyzed based on the identification of strongly oxidizing active species in the Fe(II)/PDS system. This study shows that it is feasible to develop an efficient and cost-effective sulfide and microbial control strategy using Fe(II) with PDS in sewage systems.

An Innovative Process for the Direct Recovery of Lead from Waste Lead Paste

A new process was proposed to recover high-purity lead by direct electrolysis in a sulfuric acid electrolyte without changing the composition of the cathode products. Compacting the waste lead paste products from suspension electrolysis significantly enhanced the conductivity of the cathode products. The dynamic reduction mechanism and microscopic morphological changes of the cathode product during compaction electrolysis was investigated. Compared with the direct compaction process (3.71 W·h/g), the electrolysis using precursors (1.91 W·h/g) could significantly reduce energy consumption, and the recovery of metallic lead reached 97. 12%. Meanwhile, suspension electrolysis was favorable for producing the active intermediate BS(PbO) (PbSO4), and the electrolyte could be recovered to collect H2SO4 during the entire electrolysis process. This innovative technology may provide an efficient, convenient, environmentally friendly and low-cost process for recovering metallic Pb from waste Pb paste.

Leonurine inhibits ferroptosis in renal tubular epithelial cells by activating p62/Nrf2/HO-1 signaling pathway

To investigate the protective effect and the potential mechanism of leonurine(Leo) against erastin-induced ferroptosis in human renal tubular epithelial cells(HK-2 cells), an in vitro erastin-induced ferroptosis model was constructed to detect the cell viability as well as the expressions of ferroptosis-related indexes and signaling pathway-related proteins. HK-2 cells were cultured in vitro, and the effects of Leo on the viability of HK-2 cells at 10, 20, 40, 60, 80 and 100 μmol·L~(-1) were examined by CCK-8 assay to determine the safe dose range of Leo administration. A ferroptosis cell model was induced by erastin, a common ferroptosis inducer, and the appropriate concentrations were screened. CCK-8 assay was used to detect the effects of Leo(20, 40, 80 μmol·L~(-1)) and positive drug ferrostatin-1(Fer-1, 1, 2 μmol·L~(-1)) on the viability of ferroptosis model cells, and the changes of cell morphology were observed by phase contrast microscopy. Then, the optimal concentration of Leo was obtained by Western blot for nuclear factor erythroid 2-related factor 2(Nrf2) activation, and transmission electron microscope was further used to detect the characteristic microscopic morphological changes during ferroptosis. Flow cytometry was performed to detect reactive oxygen species(ROS), and the level of glutathione(GSH) was measured using a GSH assay kit. The expressions of glutathione peroxidase 4(GPX4), p62, and heme oxygenase 1(HO-1) in each group were quantified by Western blot. RESULTS:: showed that Leo had no side effects on the viability of normal HK-2 cells in the concentration range of 10-100 μmol·L~(-1). The viability of HK-2 cells decreased as the concentration of erastin increased, and 5 μmol·L~(-1) erastin significantly induced ferroptosis in the cells. Compared with the model group, Leo dose-dependently increased cell via-bility and improved cell morphology, and 80 μmol·L~(-1) Leo promoted the translocation of Nrf2 from the cytoplasm to the nucleus. Further studies revealed that Leo remarkably alleviated the characteristic microstructural damage of ferroptosis cells caused by erastin, inhibited the release of intracellular ROS, elevated GSH and GPX4, promoted the nuclear translocation of Nrf2, and significantly upregulated the expression of p62 and HO-1 proteins. In conclusion, Leo exerted a protective effect on erastin-induced ferroptosis in HK-2 cells, which might be associated with its anti-oxidative stress by activating p62/Nrf2/HO-1 signaling pathway.

The Lifetime Prediction and Insulation Failure Mechanism of XLPE for High-Voltage Cable

The performance parameters and service life of the insulation layer of high-voltage cables are the key to ensure safe cable operation. Through extracting the mechanical parameters of high voltage cable insulation layer under different thermal aging temperatures, a normal linear regression model is established to predict the service life of high voltage cables. Meanwhile, the physicochemical characteristics such as microscopic morphology and molecular structure changes of the cable insulation layer are analyzed, the dielectric properties and breakdown field strength under ac condition are tested and the macroscopic electrical properties of the insulation layer are studied, and the insulation failure mechanism is further analyzed. The experimental results show that the elongation at break retention rate of cross-linked polyethylene (XLPE) increases slowly with the aging time, and then decreases rapidly when it reaches 50% of the initial elongation at break retention rate. The normal linear regression prediction model is established based on the Arrhenius formula, and it can be obtained the life endpoint of XLPE high voltage cable about 65 years at an operating temperature of 70 °C. Further analysis, under the action of heat and oxygen, the crystal zone structure of cable insulation is seriously damaged, and the carbonyl index is significantly increased. Accordingly, when the aging failure point is reached, the dielectric permittivity and dielectric loss of insulation are significantly increased, and the breakdown performance is significantly decreased. The work has an important guiding significance for insulation condition assessment and life prediction of high voltage cable.

Single-Cell RNA Sequencing Reveals Cellular Heterogeneity in an Acral Amelanotic Melanoma After Immunotherapy Treatment.

Anti-programmed cell death ligand-1 (anti-PD-L1) immunotherapy is often used for advanced urothelial carcinoma and melanoma, including amelanotic melanoma, a relatively rare subtype with little to no pigment in the tumor cells. However, cellular heterogeneity of amelanotic melanoma during or after anti-PD-L1 immunotherapy treatments has not been described. To investigate cellular heterogeneity in acral amelanotic melanoma after immunotherapy exposure. We evaluated subtle visual changes of the melanoma by dermoscopy and performed a pathological examination to analyze the heterogeneity of microscopic morphological and immunohistochemistry changes. The cellular transcriptional heterogeneity and corresponding biological function profiles of the melanoma were determined by single-cell RNA sequencing (scRNA-seq). The dermoscopic examination revealed black globules and scar-like depigmentation areas against a homogeneous red background. Pigmented and amelanotic melanoma cells were observed microscopically. The pigmented cells were large and contained melanin granules expressing Melan-A and HMB45; the amelanotic cells were small and did not express HMB45. Ki-67 immunohistochemical staining revealed that the pigmented melanoma cells had a higher proliferative ability than the amelanotic cells. scRNA-seq identified three cell clusters: amelanotic cell cluster 1, amelanotic cell cluster 2, and pigmented cell cluster. Furthermore, a pseudo-time trajectory analysis showed that amelanotic cell cluster 2 originated from amelanotic cell cluster 1 and transformed into the pigmented melanoma cell cluster. The expression pattern of melanin synthesis-related and lysosome-endosome-related genes in different cell clusters supported the cell cluster transformation results. Also, upregulated expression of cell cycle genes indicated that the pigmented melanoma cells had a high proliferative ability. Coexisting amelanotic and pigmented melanoma cells indicated cellular heterogeneity in an acral amelanotic melanoma from a patient who underwent immunotherapy treatment. Additionally, the pigmented melanoma cells acquired a higher proliferative ability than the amelanotic melanoma cells.

Research on Deterioration Mechanism and High-Precision Modelling of the Core Loss for Amorphous Alloys after Wire-Cut Electric Discharge Machining

Amorphous alloys (AAs) have the advantage of low core loss. Thus, they can be used in high-speed motor applications. However, compared with the nominal performances, the performance of the wire-cut electric discharge machine (W-EDM)-processed AA iron core changes significantly, which limits its popularization. This paper focuses on the performance degradation mechanism of the AA ribbon caused by W-EDM and establishes a modified core loss model after machining. First, a 308 × 15 mm ribbon-shaped AA sample machined by W-EDM was prepared. The characterization and analysis of the magnetic properties, phase, magnetic domain, nano-indentation, micro-morphology, and composition were carried out. In this paper, by analysing the variation in the magnetic domain distribution based on domain width and nano-mechanical properties, it is proposed that the performance degradation range of AA ribbons processed by W-EDM is within 1 mm from the edge. By comparing the microscopic morphology and chemical composition changes in the affected and the unaffected area, this paper presents a mechanism for the property deterioration of W-EDM-processed AA ribbons based on electrochemical corrosion. Finally, a modified loss model for W-EDM-processed AAs is established based on the division of the affected area. This model can significantly improve the accuracy of core loss estimation in the medium- and high-frequency bands commonly used in high-speed motors.

Chemical Structure and Microscopic Morphology Changes of Dyed Wood Holocellulose Exposed to UV Irradiation

Dyed wood is prone to photoaging when exposed to UV irradiation which decreases its decorative effect and service life. Holocellulose, as the main component of dyed wood, has a photodegradation behavior which is still unclear. To investigate the effect of UV irradiation on chemical structure and microscopic morphology changes of dyed wood holocellulose, Maple birch (Betulacostata Trautv) dyed wood and holocellulose were exposed to UV accelerated aging treatment; the photoresponsivity includes crystallization, chemical structure, thermal stability, and microstructure were studied. Results showed that UV radiation has no significant effect on the lattice structure of dyed wood fibers. The wood crystal zone diffraction 2θ and layer spacing was basically unchanged. With the UV radiation time extension, the relative crystallinity of dyed wood and holocellulose showed a trend of increasing first and then decreasing, but the overall change was not significant. The relative crystallinity change range of the dyed wood was not more than 3%, and the dyed holocellulose was not more than 5%. UV radiation caused the molecular chain chemical bond in the non-crystalline region of dyed holocellulose to break, the fiber underwent photooxidation degradation, and the surface photoetching feature was prominent. Wood fiber morphology was damaged and destroyed, finally leading to the degradation and corrosion of the dyed wood. Studying the photodegradation of holocellulose is helpful to understand the photochromic mechanism of dyed wood, and, further, to improve its weather resistance.

Aging diagnosis-oriented three-scale impedance model of lithium-ion battery inspired by and reflecting morphological evolution

Numerous mutually coupled factors contribute to the aging of lithium-ion battery (LIB). Inspired by the observation of microscopic morphological changes and their mechanistic analysis, this paper considers the evolving agglomerate fracture and growing SEI film as the main driving forces, and the aging of LIB and consequential impedance changes are represented with the fracture expansion of secondary particle and thickness growth of SEI layer, leading to a full-cell impedance model suitable for describing aging behavior of LIB, which is capable of effectively approximating the electrochemical impedance spectrum (EIS) throughout the usable life. By analyzing the identified parameters with regard to the state of health (SOH), the fracture depth of cathode agglomerate and the thickness of anode SEI film exhibit trends consistent with the morphological development on electrode materials and the deduction of multi-physical mechanisms, and such strong correlation is conveniently used to estimate the SOH of LIB. A large number of qualitative studies are emerging regarding the aging of LIB, and this paper aims to supplement research on the aging modeling and diagnosis of SOH in the frequency-domain by unifying the cause and effect from a quantitative perspective.

Mechanism of Lead-zinc Enrichment and Resistance of Spent Mushroom Compost to Lead-Zinc Slag in Koelreuteria paniculata

Phytoremediation is an ecological technique for tailing area restoration; adding substrate modifiers can reduce the stress of heavy metals on plants and enhance the restoration efficiency. The woody plant Koelreuteria paniculata was used as a test plant and potted in 100% tailings (S), 90% tailings+5% mushroom residue (SMC)+5% CaCO3 (MS), and natural red soil (RS). The effects of physiological responses and tolerance enrichment effects on Pb and Zn tolerance in K. paniculata under different treatments were investigated to compare the growth morphology, microscopic morphological changes, and microbial diversity changes in each substrate of K. paniculata seedlings. The results showed that compared with the control group S, the MS treatment group could significantly improve the structure and fertility of the tailing substrates; significantly enhance the relevant physiological indicators such as biomass, plant height, and chlorophyll content of K. paniculate; and increase the accumulated heavy metal content in K. paniculata. In the treatment group, the overall physiological indexes of MS compared to RS biomass and plant height were promoted, and the total root length increased up to 69.3%, whereas the average root diameter of RS in the treatment group decreased 118.7% compared to that in the control group S. The MS treatment group showed a 266.67% increase in Pb and Zn residue state, a significant decrease in the weak acid extractable state and oxide-bound state compared to that in the control group S. The heavy metals were less active for plant migration. Furthermore, most of the heavy metals were trapped in the roots of K. paniculata, and the changes in its root conformation indicated its strong adaptability in the face of high Pb stress. Transmission electron microscopy (TEM) analysis showed that the higher concentration of heavy metals in the S control damaged the cell wall structure and caused toxic effects on plant cells. The addition of the modifier effectively alleviated the effects of heavy metal stress on various tissues of K. paniculata, affected the structure of microbial communities, significantly increased microbial richness and diversity, and enhanced the adaptability of K. paniculata to heavy metals and phytoremediation ability.

Aging and tribological behavior of styrene butadiene rubber conveyor belts under combined seawater dry-wet conditions

In this study, the aging and tribological behaviors of styrene butadiene rubber (SBR) conveyor belts exposed to seawater dry–wet cycles were investigated. Using hardness as a measure of the aging performance, the worst seawater dry-wet (W-SDW ) cycle conditions were selected using an orthogonal design method, the study was conducted based on such conditions. The changes in SBR surface properties and tribological properties with aging time before and after aging and the degree were investigated by using a hardness tester, SEM, EDS, etc. The performance degradation, microscopic morphological changes of wear surface, and evolutionary behavior of wear mechanism of styrene-butadiene rubber conveyor belt after aging by dry and wet cycles of seawater were discussed. The results show that the most severe combination of wet-dry cycles of seawater for the aging of SBR conveyor belts comprised a soak temperature of 45 °C, soak time of 12 h, drying temperature of 100 °C, and drying time of 9 h. The total surface discoloration of the conveyor belt increases as the number of W-SDW cycles increases, along with the hardness. The friction coefficient of the belt increases with increasing load and decreases with the increasing number of W-SDW cycles. The mass loss increases gradually with the number of W-SDW cycles and load. The wear mechanism gradually changes from fatigue wear to the damage mechanism of coexistence of adhesive wear and fatigue.

Study on Thermo-oxidative Aging Mechanism of Air Spring Rubber Cord Composites

To study the thermo-oxidative aging mechanism of air spring rubber cord composites, observe the changes in surface micro-morphology, study the thermo-oxidative aging mechanism of air spring rubber cord composites, observe the changes in surface micro-morphology, infrared spectrum, quality, hardness, and mechanical properties during the process of thermo-oxidative aging, and analyze the aging mechanism. The results show that the micro-morphological changes of the rubber surface of the rubber cord composites go through two stages: at 0-72 h, the rubber surface The results show that the micro-morphological changes of the rubber surface of the rubber cord composites go through two stages: at 0-72 h, the rubber surface develops from no cracks to a large number of cracks; at 96-336 h, the rubber surface changes from a cracked state. The size of the crack on the rubber surface affects the rate of change of IRHD hardness. The larger the crack, the greater the hardness growth rate, otherwise the opposite. In the aging process, the rubber is in a state of dynamic development. The increase of cross-linking density causes changes in microscopic The increase of cross-linking density causes changes in microscopic morphology and accessible volume, which affects the IRHD hardness. The aging mechanism is more complicated. Material failure is dominated by the failure of the rubber matrix.

Nano-SiO2 and PVA Fiber Synergistically Strengthened Concrete to Optimize the Antifreeze, Antipermeability, and Anticorrosion Performance of Roads

As a modified material, nano-SiO2 can be compounded with many high molecular polymer resins to improve the performance of the polymer and be used as a concrete filler. PVA is a kind of synthetic fiber made of high-quality polyvinyl alcohol with a high degree of polymerization and processed by specific advanced technology. This research mainly discusses the optimization of the antifreeze, antipermeability, and anticorrosion performance of the concrete reinforced by nano-SiO2 and PVA fiber synergistically. In this paper, nanosilica PVA fiber-modified concrete was synthesized. Through compressive strength test, split tensile strength test, rapid freeze-thaw test, and microstructure test (X-ray diffraction and scanning electron microscope), this paper also analyzed the modification effect of PVA fiber concrete in different blends and the corresponding mechanism of nanoparticles. The instrument model of the scanning electron microscope used is S-4700; the manufacturer is Hitachi, a Japanese company; and the test voltage is 20 kV. Before the test, the hydrogel was placed in a freeze-drying oven at −40°C for 48 hours to remove water. Then, we put the sample in liquid nitrogen and break. The morphology of the cross-section was observed by SEM, and the microscopic morphology changes brought by different amounts of MTMS to the hydrogel were analyzed. After the test piece is immersed in water to reach a saturated state, we check the appearance size of the test piece, wipe the surface of the test piece clean with a rag, weigh the unfreeze-thaw test piece, then measure the ultrasonic wave speed of the test piece with a nondestructive testing instrument, and do good record. After every 25 freeze-thaw cycles, we measure the mass and relative dynamic elastic modulus of each group of specimens, make corresponding records, then put them into the freeze-thaw box, and add clean water as the freeze-thaw medium to continue the test. The average initial crack load of the three specimens of W W3 is increased by 52% compared with that of the specimens of W W1, and the load of W W4 is increased by 77%. This research helps promote the application of concrete on roads.

Mobility control capability of a modified chitosan hyperbranched polymer in porous media

AbstractThe residual resistance factor (RRF) is an important parameter expressing the mobility control capability of the polymer, and it is related to the polymer molecular structure. This study investigated the ability of three polymers with different molecular structures to establish RRF in a one‐dimensional sand pack model at different permeabilities. In addition, the static adsorption capacity of the three polymers on the rock surface was investigated, and the mechanism of the polymer retention in porous media was explored by changing the wettability of the rock surface. Furthermore, the microscopic morphological changes of the polymers before and after passing through the porous media were observed by environmental scanning electron microscopy. Finally, nuclear magnetic resonance core flooding experiments were used to investigate the oil displacement characteristics of the three polymers in the core. T Results show that the ability of the three polymers to establish RRF gradually decreases with the increase in permeability. Still, the modified chitosan hyperbranched polymer (HPDACS) has the best ability to establish RRF in porous media with the largest static adsorption equilibrium amount of 1249 μg/g. Mechanical capture is the dominant mechanism for HPDACS to establish retention in porous media. In addition, HPDACS has a better ability to enhance recovery. It can improve oil recovery by 20.43%, which is higher than that by dendritic polymer HPDA at 16.34% and partially hydrolyzed polyacrylamide at 10.07%. HPDACS can establish a larger resistance in the macropores of the core. Thus, the remaining oil is better driven in the medium and small pores. This finding indicates that HPDACS has excellent potential for oil displacement.

Mechanical and micro-structural damage mechanisms of coal samples treated with dry–wet cycles

The construction of mine goafs as an underground reservoir to store and utilise mine water can effectively alleviate the contradiction between coal and water in the arid mining areas in western China. Understanding the effects of water on the mechanical properties and micro-structure of coal is essential for the stability design of coal pillar dams subjected to repeated water erosion. In this study, ultrasonic, X-ray diffraction, scanning electron microscopy (SEM), nuclear magnetic resonance (NMR), and uniaxial compression tests were conducted on coal samples with zero to five dry–wet cycles to investigate the changes in water absorption characteristics, pore structure, microscopic morphology, and mechanical properties as the number of dry–wet cycles, n, increased. Moreover, the connection of the pore structure and microscopic morphology with the mechanical damage was established. The results showed that the peak stress and elastic modulus were negative exponential functions of n. As n increased, the moisture content saturation and homogeneity of the coal sample increased, the number of pores increased, and tiny pores within the coal converted to medium-to-large pores. Further, the peak stress had a good negative linear fit to the porosity and internal damage defined by the integrated area of the T2 curve. According to the SEM test results, the coal underwent five stages during a dry–wet cycle: uniform and dense original structure, particle aggregation, pore development, fracture sprouting, and overall structural fragmentation, with a gradual decrease in structural integrity. The damage variable, D, was defined by the fractal dimension, F, of the SEM images, enabling the quantitative characterisation of the coal microscopic damage during the dry–wet cycle; moreover, D/F was an exponential function of n. Finally, the damage mechanism of coal samples was interpreted from both macroscopic (i.e. NMR) and microscopic (i.e. SEM) perspectives, and they showed good agreement. Our results could provide a reference for the long-term stability assessment and design of coal pillar dams.

Reliability improvement of gas discharge tube by suppressing the formation of short-circuit pathways

After cumulative discharge of gas discharge tube (GDT), it is easy to form a short circuit pathway between the two electrodes, which increases the failure risk and causes severe influences on the protected object. To reduce the failure risk of GDT and improve cumulative discharge times before failure, this work aims to suppress the formation of two short-circuit pathways by optimizing the tube wall structure, the electrode materials and the electrode structure. A total of five improved GDT samples are designed by focusing on the insulation resistance change that occurs after the improvement; then, by combining these designs with the microscopic morphology changes inside the cavity and the differences in deposition composition, the reasons for the differences in the GDT failure risk are also analyzed. The experimental results show that compared with GDT of traditional structure and material, the method of adding grooves at both ends of the tube wall can effectively block the deposition pathway of the tube wall, and the cumulative discharge time before device failure is increased by 149%. On this basis, when the iron-nickel electrode is replaced with a tungsten-copper electrode, the difference in the electrode’s surface splash characteristics further extends the discharge time before failure by 183%. In addition, when compared with the traditional electrode structure, the method of adding an annular structure at the electrode edge to block the splashing pathway for the particles on the electrode surface shows no positive effect, and the cumulative discharge time before the failure of the two structures is reduced by 22.8% and 49.7%, respectively. Among these improved structures, the samples with grooves at both ends of the tube wall and tungsten-copper as their electrode material have the lowest failure risk.

Application of Mesoscale Simulation to Explore the pH Response of Eudragit S100 Used as the Novel Colon-Targeted Powder of Pulsatilla Saponin D

As a pH-sensitive nanomaterial, Eudragit S100 has good colon targeting. However, little research has been carried out on its mesoscopic scale. In this paper, the self-assembly behavior of Pulsatilla saponins D (PSD) and Eudragit S100, as well as the loading and release mechanism of PSD, was investigated via computer simulations. The effects of the self-assembly characteristics of PSD and Eudragit S100 in the dry powder state on the drug-carrier ratio were explored by the coarse-grained molecular dynamics (CGMD) method. According to the pH-responsive feature of Eudragit S100, the drug protection under gastric pH conditions and release in colonic pH conditions were simulated through the dissipative particle dynamics (DPD) method, which has provided insights into the microscopic morphological changes in the pH-sensitive drug delivery systems.

Study on shear performance of cotton straw fiber reinforced mud soil under freeze-thaw cycle

To explore the shear properties in cotton straw fiber-reinforced mud soil under freeze-thaw(F-T) cycles, direct shear tests are carried out on soil samples after different F-T times to obtain the influence of fiber content and F-T times to the shear strength of cotton straw fiber-reinforced soil. Then combined with scanning electron microscopy(SEM) to observe the microstructure of fiber and reinforced soil. Results indicate that the shear strength and cohesion of mud soil can be significantly improved by the addition of cotton straw fibers compared with plain soil, and the shear strength and cohesion of reinforced soil are higher than the plain soil during the same F-T times. Among three fiber contents of 0%, 0.2% and 0.4%, the shear strength and cohesion of 0.2% fiber-reinforced soil are higher than those of plain soil and 0.4% reinforced soil. After F-T cycles, the cohesion of soil decreases, among which the decrease is larger for 1 and 3 F-T times, and then the decrease of cohesion will be slowed down gradually, and when the number of F-T times reaches 10, the cohesion becomes stable. The internal friction angle for reinforced soil is higher than the plain soil, and it decreases first, then rises and finally decreases under the effect of F-T cycles, but in general, the changes are not large. The SEM observation shows that the microscopic morphological changes of the fibers themselves are small under the influence of F-T cycles, but the reinforced soil structure is destroyed, the pores and cracks become more, by which the connection between the fibers and soil particles decreases, resulting in a decline in the soil’s shear strength.