Characterization Of Internal Structure Research Articles

Fire-resistant and mechanically-robust phosphorus-doped MoS2/epoxy composite as barrier of the thermal runaway propagation of lithium-ion batteries

Thermal runaway propagation (TRP) is an utmost safety issue in battery modules owing to its derivative accidents of fire or explosion. This study develops a novel flame-retardant epoxy resin (EP) board to prevent the battery TRP. The phosphorus doped MoS2 nanowires (PR-MoS2) is designed and incorporated into EP matrix to acquire EP/3.0 PR-MoS2 composite. The composite shows 159.4 % increase in char yield, 56.7 % decrease in peak heat release rate, 56.6 % reduction in peak CO production rate. By using EP/PR-MoS2-3 (EP/3.0 PR-MoS2 composite with thickness of 3 mm) between 103450-pouch cells, TRP can be effectively stopped. Meanwhile, the temperature of surviving battery remains below 100 °C. Of note, the minimum changes in internal crystal structure, chemical composition and electrochemical characteristics are discerned for the surviving battery. This research will offer inspirations for the design of TRP suppression materials, guaranteeing the safety the battery.

Optimisation of properties of Ti3SiC2 reinforced copper matrix composites

Cu-Ti3SiC2 composites were prepared by solid-liquid mixing, mechanical alloying and discharge plasma sintering. The composites' internal structure and performance characteristics were characterized using OM, SEM, XRD, TEM, conductivity and mechanical tests. The interaction of Ti3SiC2 with the Cu matrix was systematically investigated. The formation of Cu5Si, Cu15Si4 and TiC particles was found to optimize the bonding of Ti3SiC2 with the copper matrix. Also, the effect of different Ti3SiC2 contents (0.5, 1, 2 and 3wt%) on the materials' internal structure and performance parameters was investigated. The results showed that the samples of Cu-1 wt% Ti3SiC2 exhibit excellent overall performance. It achieved a yield strength of 270.4MPa, a tensile strength of 295.2MPa, an elongation rate of 23.8%, an electrical conductivity of 85.8% (IACS), a coefficient of friction of 0.465, and a wear rate of 7.8×10-5 mm3N-1m-1.

Enhancement Petrophysical Properties of Carbonate Reservoirs Using Plasma Channel Technology, Case Study: Yamama Formation, South of Iraq

Carbonate reservoirs are significant hydrocarbon productions, but their complex and heterogeneous nature often poses challenges in maximizing oil and gas recovery. Traditional methods for enhancing petrophysical properties have shown limited success in carbonate formations. However, new advancements in Plasma Channel Technology have shown promising results in improving the reservoir's petrophysical properties. The application of Plasma Channel Technology is considered as a novel approach to enhance the petrophysical properties of carbonate reservoirs. Plasma channel technology involves the controlled application of high-voltage electrical discharges to create conductive channels (new porosity) within the reservoir units. These channels serve as preferential pathways for fluid flow (permeability) and facilitate enhanced oil and gas recovery. The main objective of this study is to show the key aspects of the enhancement of the Yamama reservoir properties using Plasma Channel Technology minimizes the need for chemical additives to reduce operational costs and environmental impact. Therefore, Yamama Formation is studied in two oil wells Snd-1 and Snd-2, six core samples from reservoir units within the Yamama succession were studied to determine porosity using a Scanning Electron Microscope which provides valuable insights into their internal structure and porosity characteristics in these samples. A comparison had been done between porosities within rock samples before and after application of Plasma channel technology, where the porosity was ranging from micropores (10 nm) to mesopores (10-50 nm) in some samples before voltage electrical discharges, while it reached mesopores (20-50 nm) to macropores (more than 500 nm) after voltage electrical discharges.These pores have been increased in size if there was higher voltage which means enhancement in the petrophysical properties in the reservoir.

Analysis of influence mechanism of CO2-water coupling fracturing sandstone

The existence of hard rock layers has a serious impact on coal seam mining, in order to explore the acidification and crushing mechanism of hard sandstone rock layers, this paper adopts the self-developed CO2-water-rock coupling test device to carry out the testing of mechanical properties and internal structural characteristics of rock samples before and after the coupling action of the three sandstones, and analyzes the influencing factors of sandstone CO2 coupling crushing. The study shows that: the lower the temperature of CO2-water-rock coupling, the higher the pore pressure, the higher the volume fraction of CO2 in the coupling fracturing fluid, and the longer the coupling time, the greater the decrease in the mechanical strength of the rock samples, and the more complicated the splitting damage pattern is, and the CO2-water-rock coupling makes the pore and fracture volume fraction and fractal dimension of three kinds of sandstone samples increase to varying degrees, whereas the volume fraction of minerals and the fractal dimension decrease, and the CO2-water-rock coupling results in a decrease in the volume fraction of minerals and fractal dimension, and a decrease in the volume fraction of minerals and fractal dimension. The pore volume fraction and fractal dimension of the three sandstone samples increased to different degrees, while the mineral volume fraction and fractal dimension decreased, and the pore volume fraction and fractal dimension of the three sandstone samples decreased. The damage pattern of sandstone samples after coupling is affected by both chemical and mechanical damages. When using coupling fracturing fluid with 8 % CO2, the degree of mineral dissolution and dissolution is the largest, and the dissolution effect is larger than the precipitation effect, which has the most significant effect on the morphology type and connectivity of microscopic pore cracks, and the study in this paper has certain theoretical and practical value for the chemical softening of sandstone.

Effects of interface-engineering on the internal structure and reflective characteristics of Cr/Sc multilayer mirrors

Record reflectivity’s of REXP=23.8% at 3.14 nm and RCALC=30.8% at 3.12 nm have been obtained for Cr/Sc mirrors. Such increases in reflection are the result of decreases in mixing of the system layers with each other due to the use of interface-engineering methods – passivation of the already deposited Cr layer with nitrogen before deposition of the subsequent Sc layer. However, it has been found that adding additional B4C layers to such a system leads to a decrease in reflectivity.

Reflection and transmission of ultrasonic waves in a layered structure with a functionally graded porous piezoelectric base

The phenomenon of reflection and transmission of waves offers valuable insights into the internal composition and structural characteristics of materials. This study investigates the reflection and transmission of waves in functionally graded porous piezoelectric materials. These materials, distinguished by their customised electromechanical attributes and gradual property variations, present a promising avenue for optimizing performance across diverse applications, including ultrasonics. The reflection and transmission of ultrasonic waves in a novel structure, consisting of a fluid half-space (FHS) positioned above n porous piezoelectric layers, situated on top of a functionally graded porous piezoelectric half-space (FGPPHS) is studied in this paper. The material properties of FGPPHS are considered to vary along the vertical direction and and resulting equations are solved analytically and numerically. The transfer matrix method is employed to analytically determine the energy ratios and amplitude ratios for reflected and transmitted waves. Numerical computations are performed to study the impacts of frequency, gradation, angle of incidence, and porosity on the energy ratios. Furthermore, the influence of stacking of the number of porous piezoelectric layers above FGPPHS, and the choice of materials (Barium Titanate (BaTiO 3), PZT − 5H, PZT − 7H) in layers and half-space, on the energy ratios are studied. The absolute value of acoustic impedance is plotted for various angles of incidence and porosities. From the graph, it is found that the acoustic impedance can be controlled by adjusting porosity in the structure. This will be helpful in minimizing the energy loss at ceramic-medium interface and improving the mismatch of acoustic impedances at the interfaces of medical ultrasonic imaging devices or underwater sonar detectors, and NDE applications. Further, because of lower acoustic impedance, lower density and stiffness of porous piezoelectric materials, the outcomes of this study will be helpful in designing SAW devices.

Study on the effect of rubber content on the frost resistance of steel fiber reinforced rubber concrete

In cold areas, the steel fiber reinforced rubber concrete (SFRRC) pavement is exposed to natural environment and experiences varying degrees of damage from freezing and thawing. This can have a serious impact on the normal usage and safe operation of the pavement structure. This research examines the impact of varying rubber concentrations on multiple variables, such as the rate of mass reduction, relative dynamic modulus of elasticity, compressive strength, and thickness of the damage layer (Hf) during freeze–thaw (F-T) durability testing conducted on SFRRC. Furthermore, an analysis is conducted to determine the degradation pattern exhibited by SFRRC. The internal structure evolution and pore structure characteristics of SFRRC were examined using scanning electron microscopy and mercury intrusion porosimetry techniques, which revealed the underlying damage mechanism in SFRRC during F-T cycles. The results suggest that the addition of an appropriate amount of rubber can effectively enhance the frost resistance of SFRRC in water. A gradual improvement in the frost resistance of SFRRC is observed when increasing the rubber content from 0 to 10%. The optimal frost resistance is observed in SFRRC with 10% rubber content. However, when the rubber content reaches 15%, SFRRC exhibits significant degradation and lower level of resistance to freezing compared to SFRRC without rubber. Microcracks form within SFRRC due to the freezing–thawing forces experienced during the experiment, resulting in the development of a damage layer that extends from the surface to the interior. The compressive strength of the damaged layer significantly decreases as Hf increases. The addition of appropriate rubber in SFRRC improves its pore structure, leading to an increased proportion of harmless or less harmful pores and a reduction in average pore size, thereby significantly enhancing its frost resistance.

Experimental and numerical investigation of the effects of porous bleed systems on a model scramjet inlet under high backpressure conditions

In this study, we conducted experimental and numerical investigations to assess the effects of backpressure and configurations of porous bleeds on a scramjet inlet's performance at Mach 5. Experiments in a high-enthalpy wind tunnel, using a backpressure controller and a porous bleed with 1 mm holes and 10 mm lateral spacing, were paired with Reynolds-averaged Navier-Stokes simulations to explore the mitigation of flow separation and the prevention of inlet unstart under various backpressure conditions. The simulations provided insights into how backpressure levels and porous bleed geometries impact internal flow structures, as well as the critical backpressure ratio at which inlet unstart occurs. Additional simulations varied the bleed system's hole diameter and spacing, identifying configurations that optimize aerodynamic performance by enhancing total pressure recovery and Mach number at the isolator exit, while reducing bleed mass flow rates. The study also quantified the impact of these configurations on engine thrust, determining that certain bleed system designs significantly improve thrust by efficiently suppressing the interaction between the core flow and corner recirculation zones. This study examined the internal three-dimensional flow structure characteristics under high back pressure and provided insights into porous bleed configuration capable of efficiently suppressing inlet unstart.

Identification of Geochemical Anomalies Based on RPCA and Multifractal Theory: A Case Study of the Sidaowanzi Area, Chifeng, Inner Mongolia.

The focus of exploration geochemistry is an accurate interpretation of geochemical data and the precise extraction of anomaly information related to mineralization from complex geological information. However, geochemical data are component data and exhibit a closure effect. Thus, traditional statistical methods cannot adequately reveal and identify the distribution of deep-seated anomaly information. This paper focuses on the Sidaowanzi area in Inner Mongolia and uses multivariate component data analysis methods to process 1:50 000 soil geochemical data. Using the Exploratory Data Analysis (EDA) method, the spatial distribution and internal structure characteristics of raw, logarithmic, and isometric logarithmic ratio (ILR) transformed data were compared and, coupled with robust principal component analysis (RPCA) and elemental component biplots, the association between element combinations and mineralization indicated by these three types of data was revealed. The S-A method was used to decompose composite anomalies of the ILR transformed RPCA score data to extract the characteristics of elemental combination anomalies and background distribution, and the Fry analysis method was utilized to analyze the dominant mineralization direction within the area. The results show that (1) data transformed using the ILR eliminated the influence of the closure effect, making the data more uniform on a spatial scale and exhibiting characteristics of an approximately normal distribution. (2) The S-A method was further used to decompose the composite anomaly of the PC1 and PC2 principal component combinations. The screened-out anomaly and background fields can essentially reflect the ore-causing anomalies dominated by Au and Cu-Mo mineralization. Moreover, the extracted anomalies and background information closely align with known mineral deposits (prospects) and can effectively identify weakly retarded geochemical anomaly information. (3) Fry analysis based on geochemical anomalies indicates that the dominant mineralization directions, by an assemblage dominated by Au and Cu-Mo, predominantly occur in the NE, NW, and proximate EW orientations. The combined application of the aforementioned three methods for the quantitative analysis of geochemical data aims to explore a transferable methodological system, providing new insights and approaches for further prediction of mineralization potential.

Laboratory studies on the mechanical properties of sulphur-based construction material at simulated Martian temperatures

Mars is the next destination for further exploration and the hypothetical establishment of humanity's frontier. However, the planet offers very harsh environmental conditions particularly the very cold temperature in the Martian environment. Knowing that the sulphur-based construction material is perceived as one of the ideal Martian construction materials based on the identified abundant source of sulphur on Mars, its behaviour when subjected to the very cold Martian temperature is yet to be fully clarified. Therefore, this study intends to investigate the behaviour of the Martian sulphur-based construction material subjected to the simulated very cold Martian temperature whilst being compared with the simulated hot Martian temperature. Two mixture compositions of 50/50 and 60/40 comprising of sulphur and Mojave Mars simulant 1 (MMS-1) respectively were fabricated in this study characterising the simulated Martian temperature. The workability at 50 % and 60 % sulphur content was initially investigated. Subsequently, the overall mechanical properties characterising the sulphur content and simulated Martian temperature were investigated via unconfined compression, three-point bending and tensile splitting tests. Necessary factors that influence the overall mechanical properties including the internal structure and microstructural characteristics were also performed via ultrasonic pulse velocity (UPV) and scanning electron microscopy (SEM) respectively. X-ray diffraction (XRD) was also conducted to identify the chemical composition of the end product. The comparisons between this study and other previous related studies within the state-of-the-art Martian sulphur-based construction materials were also outlined. Prospects for future construction on Mars are also presented. It was found that the 60 % sulphur content exhibited higher workability due to the high amount of unreactive sulphur. The 50 % sulphur content recorded the optimal overall mechanical properties under the simulated hot and very cold Martian temperatures. The simulated very cold Martian temperature triggered non-uniform interparticle distribution and larger cavities thus dramatically reducing its overall strength and triggering higher volumetric inconsistency. The very brittle nature of unreactive crystallised sulphur binder at excessive thickness particularly at 60 % sulphur content in between filler particles also triggered volumetric inconsistency which further worsened at the simulated very cold Martian temperature. The iron sulphate hydrate found was almost in agreement with the related works and another new compound, potassium calcium magnesium sulphate was identified as well. The overall mechanical properties are comparable with the other previous related studies and the residual strength when subjected to the simulated very cold Martian temperature remains adequate in the Martian environment of low gravity. The 60 % sulphur content is suggested for structural elements built internally whereas the 50 % sulphur content demonstrated a high potential in adapting to the harsh Martian environmental conditions. The findings of this study hoped to act as the initial outlook on how such Martian sulphur-based construction material would react upon fabrication on Mars.

Mn(II) Coordination Complex Loaded Hydrogel: Synthesis, Characterization, Fluorescence Properties, and Application in Treating Knee Arthritis.

Using a mixed-ligand approach, we successfully obtained two Mn(II)-based coordination compounds, namely [Mn2(L1)(TBIP)·H2O]n (1) and [Mn2(L2)(NPTA)·H2O]n (2) (where L1 and L2 are 1,4-bis(thiabenzimidazol-1-ylmethyl)benzene and 1,2-bis(thiabenzimidazol-1-ylmethyl)benzene, H2NPTA is 2-nitroterephthalic acid, and H2TBIP is 5-tert-butylisophthalic acid). Fluorescence performance testing of complexes 1 and 2 showed excellent green and blue fluorescence properties. Based on this, we further prepared HA/CMCS hydrogels using natural polysaccharides hyaluronic acid (HA) and carboxymethyl chitosan (CMCS) as raw materials and studied their internal structural characteristics using scanning electron microscopy. Using "Duhuo Jisheng Decoction" as a drug model, two metal gel scaffolds loaded with "Duhuo Jisheng Decoction" were prepared, and their potential for treating knee osteoarthritis was evaluated.

Self-operation and low-carbon scheduling optimization of solar thermal power plants with thermal storage systems

Photo thermal power generation, as a renewable energy technology, has broad development prospects. However, the operation and scheduling of photo thermal power plants rarely consider their internal structure and energy flow characteristics. Therefore, this study explains the structure of a solar thermal power plant with a thermal storage system and analyzes its main energy flow modes to establish a self-operation and low-carbon scheduling optimization model for the solar thermal power plant. The simulation results of the example showed that for the self-operating model oriented towards power generation planning and peak valley electricity prices, the existence of a thermal storage system could improve the power generation capacity and revenue of the photovoltaic power plant. For example, when the capacity of the thermal storage system was greater than 6 h, the penalty for insufficient power generation in the simulation result was 0 $, and the maximum increase in revenue reached 84.9% as the capacity of the thermal storage system increased. In addition, when the capacity of the thermal storage system increased from 0 to 8 h, the comprehensive operating cost decreased from 1635.2 k $ to 1224.6 k $, and the carbon emissions decreased from 26.4 × 103 ton to 22.1 × 103 ton. Compared with the existing literature, this study provides a more comprehensive and systematic solution through detailed energy flow analysis and optimization model. The research has practical and far-reaching significance for promoting the development of clean energy technology, improving the sustainable utilization of renewable energy, and optimizing the overall performance of the energy system.

Allergenicity Modulation of Casein with the Modifications of Linearization, Cross-Linking, and Glycation via the Regulation of Th1/Th2 Homeostasis.

Casein (CN) is the primary allergenic protein in cow's milk, contributing to the worldwide escalating prevalence of food allergies. However, there remains limited knowledge regarding the effect of structural modifications on CN allergenicity. Herein, we prepared three modified CNs (mCN), including sodium dodecyl sulfate and dithiothreitol-induced linear CN (LCN), transglutaminase-cross-linked CN (TCN), and glucose-glycated CN (GCN). The electrophoresis results indicated widespread protein aggregation among mCN, causing variations in their molecular weights. The unique internal and external structural characteristics of mCN were substantiated by disparities in surface microstructure, alterations in the secondary structure, variations in free amino acid contents, and modifications in functional molecular groups. Despite the lower digestibility of TCN and GCN compared to LCN, they significantly suppressed IL-8 production in Caco-2 cells without significantly promoting their proliferation. Moreover, GCN showed the weakest capacity to induce LAD2 cell degranulation. Despite the therapeutic effect of TCN, GCN-treated mice displayed the most prominent attenuation of allergic reactions and a remarkably restored Th1/Th2 imbalance, while LCN administration resulted in severe allergic phenotypes and endotypes in both cellular and murine models. This study highlighted the detrimental effect of linear modifications and underscored the significance of glycation in relation to CN allergenicity.

Crystallization processes of quartz in a granitic magma: Implications for the magma chamber processes of Okueyama granite, Kyushu, Japan

Cathodoluminescence (CL) characterization combined with titanium concentration of quartz crystals in granite is a prevalent tool for elucidating the crystal growth of quartz in granitic magmas. The CL pattern yields to the internal structure, and the titanium concentration allows crystallization temperature determination based on TitaniQ geothermometry. Using two approaches, 1) observations of quartz crystals using thin sections and 2) observations based on multiple sections of separated quartz, we identified the overall characteristics of quartz crystals within a magma chamber and the 3D internal structure and growth characteristics of quartz grains. Thin section observations allow for the characterization of quartz containing zircon inclusions, indicating that zircon crystallization was followed by quartz crystallization; therefore, the onset of quartz crystallization occurred later than the onset of zircon crystallization in the cooling magma chamber. Such petrological restrictions permit allow for suitable geothermometer use and appropriate TiO2 activity estimation, and thus, accurate quartz crystallization temperature determination. Observations using multiple sections of separated quartz crystals provide 3D internal structures and true onset parts within the grains. Progressive variation in local activities of TiO2 in the concentration boundary layer at the growing quartz crystal interface in the magma chamber can be evaluated using a combination of the crystallization temperature and variations in titanium concentration within the grain, yielding a sequential crystallization model of oscillatory zoning quartz with local activities of TiO2 in the cooling magma chamber. The difference in CL characteristics and crystallization temperature among the lithofacies in granite contributes to clarifying the spatiotemporal magma chamber processes.

Microstructural characterization and mechanical behaviour of laser powder Bed Fusion stainless steel 316L

Laser Powder Bed Fusion (L-PBF) is a highly precise and customizable additive manufacturing (AM) technique that uses a high-energy laser to selectively melt and fuse powdered material into a three-dimensional object. However, depending on the process parameters, the final components may have potential flaws that can affect their quality and mechanical properties, due to porosity, melting and incomplete fusion of powder particles; and because the process involves local heating and sometimes uneven heat transfer, the processed components may warp or crack due to residual stresses or thermal gradients. The manufacturing process itself reflects in the final component structure having a detrimental effect on the strength, durability, fatigue resistance, and corrosion.In this work, static tensile and fatigue tests were performed on traditional and L-PBF manufactured AISI 316L stainless steel specimens. The energetic release has been evaluated with an infrared camera during the static and fatigue tests aiming to identify material thermal response to the loading and to predict the failure in rapid way adopting Thermographic Methods. Differences were observed comparing the fatigue data of the L-PBF processed specimens with the traditional material. However, analysis of internal structure, porosity, and surface characteristics of the AM material in combination with fractographic analysis helped to explain the differences in the fatigue life. The observed energy release, different for both material types, was discussed based on the structural characteristics. The results show that the crack originates from a defect on the surface or just below the surface, with a transgranular propagation.

Analysis of internal flow characteristics of a multistage pump during start-up

In order to study the transient characteristics during the startup process of a multi-stage pump, the Flowmaster software was used to obtain the rotating speed and flow characteristic curves of the pump under different valve openings, and analyze its internal flow and structural characteristics based on numerical simulation. The study results indicate that the time required for the flow to reach a steady state lags significantly behind the time required for the rotational speed to reach a stable state during the initial stage of pump start-up. By comparing the pressure distributions of a multistage pump under quasi-steady state and transient conditions, it can be seen that the internal flow field evolution of the pump under transient condition during the startup process lagged behind that under quasi-steady state condition, which makes using quasi-steady state laws were not suitable for describing the changes in transient flow field. The deformation law of the first-stage impeller under stable and start-up conditions was similar. The impact of increased flow rate on deformation was relatively weak and the difference in deformation values under different flow rates was relatively small under transient condition.

Polishing-induced material attrition in surface-texturing AlN using a nanoscale polishing tool: An atomic-scale understanding

This study examines the alterations in the material properties and the effectiveness of the nano-polishing process applied to the surface of AlN substrate material through molecular dynamics simulations. Various controlled parameters at the outset of the polishing process, including polishing depth, polishing speed, and surface texture, exert both positive and negative influences on substrate characteristics, such as polishing force, friction coefficient, atomic phase transformation, subsurface damage layer (SDL), von Mises stress, temperature, dislocation characteristics, surface topography, atom removal, and root-mean-square (RMS). The results depicted that great polishing depth and slow polishing velocity have adverse effects on the internal structure of the material, leading to the creation of a substantial SDL and a dense network of dislocation formation. Conversely, increased material polishing velocity results in elevated von Mises stress and high generated temperatures. When combined with the initial surface structure conditions of the material, this mitigates detrimental effects on the internal structural characteristics while facilitating the phase transformation process and enhancing atom removal efficiency. The calculated RMS results of the substrate demonstrate that adjustments in polishing speed yield a higher improvement in surface roughness compared to alterations in polishing depth and surface texture. Therefore, a comprehensive understanding of the impact of initial conditions in the polishing process, as well as the atomic-level surface structure of the substrate, aids in selecting the most appropriate polishing conditions to produce the highest-quality products.

A qualitative study of barriers and facilitators for health behavior change in low-income men with prostate cancer.

Low-income prostate cancer survivors, who typically have worse outcomes and greater all-cause mortality, often have poor health-promoting behaviors. Our objective was to assess perceived facilitators of and barriers to healthy behavior change by interviewing low-income men with prostate cancer who received no-cost treatment through a state-funded program. Between September 2021 and April 2022, we conducted semi-structured interviews with 19 men (ages 60-75). Purposive sampling was utilized from participants of a cohort of men with prostate cancer from low-income backgrounds. Interviews were recorded, transcribed, and then coded by the authors to generate salient themes via thematic analysis. We found internal characteristics and structural characteristics that functioned independently and in concert to promote and/or hinder healthy behavior change. Internal characteristics such as motivations (prostate cancer diagnosis, self-perceptions, support system, and preferences) and determination, defined as level of motivation, drove behavior actualization. Structural characteristics that influenced behavior change included resources (access to food and opportunities for exercise) and social support. These outcomes suggest that motivation and determination can serve as protective facilitators encouraging healthy behaviors despite structural barriers low-income prostate cancer survivors may face. However, motivations challenged by financial constraints were not sufficient to guide healthy behavior change. With this in mind, we recommend that interventions promoting healthy behavior change among this population should focus on identifying and strengthening internal assets such as motivations, self-perceptions, preferences, and support systems.

Study on the Dynamic Properties of Concrete under Freeze-Thaw Cycles and CT Fine View Damage

In order to study the dynamic mechanical properties of concrete under freeze-thaw cycles, uniaxial impact compression tests were conducted on concrete specimens with different number of freeze-thaw cycles (0, 25, 50, 75, and 100) using a 50 mm diameter split Hopkinson pressure bar (SHPB) test device at an impact air pressure of 0.4 MPa and combined with a CT scanning system to analyze the internal fissures of concrete specimens before and after freeze-thaw cycles. The results showed the following. (1) The concrete specimens were divided into linear elastic stage, plastic stage, and damage stage under the freeze-thaw cycle, and the macroscopic mechanical parameters of the specimens were weakened with the increase of the number of freeze-thaw cycles. (2) Freeze-thaw intensified the expansion and penetration of the internal fracture of the specimens, and the CT scan results showed that the internal fracture parameters of the concrete specimens were increased with the increase of the number of freeze-thaw cycles, and the structural characteristics of the internal fracture show gradually complex expansion and evolution characteristics. (3) The degree of damage was defined at the fine level, which increased with the number of freeze-thaw cycles, establishing an intrinsic link between the fine deterioration of concrete specimens and the loss of macroscopic parameters under freeze-thaw cycles. The results are of great significance to further elucidate the internal structural characteristics of concrete material damage under freeze-thaw conditions and to reveal the damage deterioration mechanism.

Material Characteristics of Lime Plaster in Goguryeo Mural Tombs (I): Focusing on Lime Plaster Excavated from Anak Tomb No.3

Physical and chemical investigations were conducted on lime sample from Anak Tomb No.3 to determine the properties of the plaster material. The morphological and physical characteristics of the specimens were analyzed using both a microscope and a polarizing microscope. The constituent materials were identified through X-ray diffraction and scanning electron microscope-energy dispersive spectrometer, and the qualities of the mixed material were established through thermal analysis. Additionally, micro-computed tomography was used to non-destructively confirm the internal structure and density characteristics. The lime sample was recognized as a lime plaster material with two unique layers. Each layer shows variations in material properties. It is speculated that this lime specimen was used to finish the edges of the authentic wall within Anak Tomb No.3. Through the synthesis of various morphological attributes and physical properties; the whiteness, durability, thinness, and repetition of the layers, as well as smoothness of the lime plaster used for Anak Tomb No. 3 indicate that a high level of lime wall plastering technique was used in Goguryeo Tomb. It was possible to evaluate the refined level of lime wall manufacturing technology in the Goguryeo era.