Search Results (41)

Excavation unloading in deep rock masses involves a transition from symmetric states of energy storage to asymmetric energy dissipation, in which variations in intermediate principal stress (${\sigma }_2$) play a critical role. To investigate these symmetry-breaking mechanisms, controlled-rate true triaxial unloading experiments were performed on sandstone using a miniature creep-coupled testing system. During unloading of ${\sigma }_3$ at 0.1–0.3 MPa/s, the evolution of elastic, dissipated, and plastic energies was quantitatively evaluated. The results reveal pronounced asymmetric energy responses governed by both ${\sigma }_2$ and the unloading rate. Dissipated energy dominates the entire unloading process, while elastic energy exhibits a non-monotonic trend with increasing ${\sigma }_2$—first rising due to enhanced confinement and then decreasing as premature failure occurs. Higher unloading rates significantly accelerate total, elastic, and dissipated energy conversion and intensify post-peak brittleness. A new metric, plastically released energy, is proposed to quantify the asymmetric energy release from peak to residual state after failure. Its dependence on ${\sigma }_2$ is strongly non-monotonic, increasing under moderate ${\sigma }_2$ but decreasing when ${\sigma }_2$ is sufficiently high to trigger failure during unloading. This behavior captures the essential symmetry-breaking transition between elastic energy accumulation and irreversible plastic dissipation. These findings demonstrate that true triaxial unloading induces energy evolution patterns far from symmetry, controlled jointly by ${\sigma }_2$ and unloading kinetics. The established correlations between ${\sigma }_2$, unloading rate, and plastically released energy enrich the theoretical framework of energy-based symmetry in rock mechanics and offer insights for evaluating excavation-induced instability in deep underground engineering. Full article

Cadmium (Cd) is a persistent toxic metal that bioaccumulates in human tissues and may disrupt redox and endocrine pathways, yet the metabolic mechanisms linking Cd exposure to both endothelial and prostate dysfunctions remain insufficiently defined. This study investigated whether chronic occupational Cd exposure alters methylated arginine metabolism and prostate-specific antigen (PSA) levels, indicating a shared toxicometabolic axis. A total of 150 male workers were enrolled, including 75 metallurgical employees with documented Cd exposure and 75 matched controls. All participants were non-smokers, eliminating confounding from tobacco-related oxidative or endocrine effects. Urinary Cd concentrations were quantified using Inductively Coupled Plasma–Mass Spectrometry (ICP–MS), and serum asymmetric dimethylarginine (ADMA), symmetric dimethylarginine (SDMA), L-arginine, citrulline, and PSA were measured by Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS) and electrochemiluminescence. The use of Inductively Coupled Plasma–Mass Spectrometry for cadmium quantification and LC-MS/MS for methylated arginine profiling provided high analytical specificity and sensitivity, strengthening the validity of biomarker measurements. Correlation and multivariable analyses adjusted for age and body mass index. Cd-exposed workers demonstrated significantly elevated urinary Cd, PSA, ADMA, and SDMA levels, alongside reduced arginine/ADMA ratios, consistent with impaired nitric oxide bioavailability. Urinary Cd strongly correlated with PSA and ADMA levels. These findings indicate that Cd may disrupt the nitric oxide pathway and elevates PSA, supporting a mechanistic link between vascular and prostate stress. Combined ADMA, SDMA, and PSA profiling may serve as an early biomarker panel for Cd-related metabolic injury in occupational settings. Full article

To optimize the location optimization of the coalbed methane (CBM) extraction target area in abandoned mines, based on the background of the Songzao mining area in Chongqing, theoretical analysis and numerical simulation research methods were comprehensively used to systematically evaluate the potential of residual CBM resources in the goaf of the Songzao mining area. The stress-fracture evolution law and permeability enhancement characteristics of overlying strata under repeated mining of inclined multi-coal seams were deeply revealed, and the location optimization of the residual CBM extraction borehole target area was carried out. The results show that the amount of CBM resources in Songzao Coal Mine is 5.248 × 10⁷ m³, accounting for 26.57% of the total resources, which is suitable for the extraction of CBM left in goaf. The maximum height of the overburden fracture zone caused by repeated mining of K2b, K1, and K3b coal seams in Songzao Coal Mine is 72.3 m, which is basically consistent with the results of the numerical simulation (69.76 m). The fracture development of overlying strata is in the distribution form of a symmetrical trapezoid and inclined asymmetrical trapezoid, and its development height increases with an increase in coal seam mining times, and finally forms a three-dimensional ‘O’-ring fracture area, which provides a channel and enrichment area for the effective migration of CBM. The significant permeability-increasing zone of overburden rock is stable in the range of 10~40 m above the roof of the K3b coal seam and is nearly trapezoidal. According to the calculation of the height prediction model of the fracture zone in the abandoned goaf, the fracture height of the long-term compaction of the Songzao Coal Mine is reduced to 63.74 m. Based on the stress-fracture evolution characteristics of the overburden rock, combined with the permeability-increasing characteristics of the overburden rock and the migration law of the remaining CBM, it is determined that the preferred position of the remaining CBM extraction target area of the Songzao Coal Mine should be in the upper corner of the fracture development area within the range of 10~32.47 m above the K36 coal seam. Full article

The measurement accuracy and equipment stability of superposition-type force sensors are primarily influenced by the layout and number of individual force sensors. Analyzing this impact effect through experimental testing for each configuration would consume significant manpower, material resources, and financial costs. To efficiently analyze the influence of the number of paralleled individual sensors and their layout within a superposition-type force measurement instrument on overall device stability and force measurement accuracy, this paper employs SolidWorks to establish models of force instruments based on common superposition schemes. Subsequently, ANSYS is utilized to perform finite element analysis on models of different schemes, obtaining corresponding data on total deformation, stress, and simulated force values. The analysis results indicate that a relatively sparse sensor layout with symmetric arrangement around the center point of the base plate enhances overall stability, and the force measurement error can be controlled within several ten-thousandths. Furthermore, the more stable and higher-accuracy schemes identified through simulation analysis were compared with practical experimental results to analyze theoretical versus actual errors. The test results showed that when the three single force sensors are placed in a “Pin font” shape, the sum of the forces measured by each individual sensor differs from the sum of the forces measured by the superimposed sensors by only a few ten-thousandths, which is within the acceptable range. Full article

Suspension structures, known for their excellent properties, have been widely used to cover medium and large spans. Their efficiency lies in their ability to primarily withstand permanent and variable loads through tension. Consequently, suspension roof structures typically adopt a parabolic shape, which remains in equilibrium under symmetric loads. However, when subjected to asymmetric loads, such structures experience significant kinematic displacements. To reduce these displacements, suspension systems with bending stiffness, commonly referred to as “rigid” cables, are employed. Such elements increase the sustainability of the suspension system compared with conventional spiral ropes. Although previous studies have analyzed the behavior of such systems under symmetric loads, this article examines the performance of an innovative cable–strut system composed of straight “rigid” elements under asymmetric loads. The behavior of three different types of suspension structures under asymmetric loads is analyzed. A non-linear analysis of forces and displacements is conducted in this system, assessing the impact of bending stiffness on the structural response. The results indicate that the proposed two-level suspension system performs more effectively under asymmetric loads than both conventional parabolic suspension structures and suspension systems comprising two straight “rigid” elements. It was found that the total forces and stresses in the “rigid” upper chord elements of the two-level system are the lowest among all the systems considered. Therefore, this system is particularly suitable for covering medium- and large-span roofs, especially when subjected to relatively large asymmetric loads. Full article

Triple glazing has garnered widespread attention as a key solution that balances sound insulation, building energy efficiency, and thickness-related cost-effectiveness. This study evaluated the acoustic performance of triple glazing, focusing on how cavity and glass thickness combinations performed under a fixed total thickness. Laboratory measurements were first conducted, which revealed that asymmetric triple glazing performed better for sound insulation than symmetric combinations. Based on this, 28 triple glazing combinations with a total thickness of 42 mm were selected to build finite element models, including window frames. These models were used to calculate the sound transmission loss curves, the weighted sound reduction index, and the distributions of structural stress and the displacement amplitude. The best sound insulation performance was achieved when the glass panes had unequal thicknesses, with the thickest pane positioned on the outermost layer (either on the source or the receiver side). The weighted sound reduction index $R_{\mathrm{w}}$ increased by 6 dB, and the combined value of $R_{\mathrm{w}}$ and the traffic noise spectrum correction ($R_{\mathrm{w}}$ + $C_{\mathrm{tr}}$) improved by up to 11 dB. The optimal combination was 8-12A-6-12A-4, and $R_{\mathrm{w}}$ reached 44 dB. Combinations with the thickest pane in the middle layer or with equal pane thicknesses exhibited a worse sound insulation performance. Variations in the cavity thickness had a smaller effect on sound insulation than changes in the glass’s thickness. A reasonable combination of glass thicknesses in triple glazing effectively reduced the displacement amplitude and improved the sound insulation performance. Full article

This paper presents a comprehensive model for the inertia force field acting on a moving connecting rod. The derived formulas enable the accurate calculation of resultant inertia forces and their distribution on individual components for finite element analysis (FEA). The method applies to symmetrical and complex-shaped connecting rods, addressing challenges in modeling forces for asymmetrical designs. This work advances the precision of stress and vibration modeling in connecting rods, crucial for tribology and reliability studies. By improving the understanding of wear and failure mechanisms in reciprocating systems, it supports design optimization. The article presents the application of the proposed computational methods using three materials typically used for connecting rod construction: 42CrMo4, aluminum 2618, and Ti6Al4V. The presented results demonstrate how the material selection influences the total inertia force and the resulting stresses within the material. The numerical results are presented based on simulations conducted for two connecting rods of different sizes, operating at extremely different rotational speeds. The conducted analyses show that in the examined cases, rotational speed is the key factor influencing inertia stresses. The implementation, based on Open Source tools, allows a numerical analysis of inertia forces and stresses, with all the methods and models available in an open repository. Full article

We study the Stueckelberg field in de Sitter space, which is a massive vector field with the gauge fixing (GF) term ${\displaystyle \frac{1}{2\zeta }}{({A^{\mu }}_{;\mu })}^2$. We obtain the vacuum stress tensor, which consists of the transverse, longitudinal, temporal, and GF parts, and each contains various UV divergences. By the minimal subtraction rule, we regularize each part of the stress tensor to its pertinent adiabatic order. The transverse stress tensor is regularized to the 0th adiabatic order, while the longitudinal, temporal, and GF stress tensors are regularized to the 2nd adiabatic order. The resulting total regularized vacuum stress tensor is convergent and maximally symmetric, has a positive energy density, and respects the covariant conservation, and thus, it can be identified as the cosmological constant that drives the de Sitter inflation. Under the Lorenz condition ${A^{\mu }}_{;\mu }=0$, the regularized Stueckelberg stress tensor reduces to the regularized Proca stress tensor that contains only the transverse and longitudinal modes. In the massless limit, the regularized Stueckelberg stress tensor becomes zero, and is the same as that of the Maxwell field with the GF term, and no trace anomaly exists. If the order of adiabatic regularization were lower than our prescription, some divergences would remain. If the order were higher, say, under the conventional 4th-order regularization, more terms than necessary would be subtracted off, leading to an unphysical negative energy density and the trace anomaly simultaneously. Full article

In the context of the automotive industry, this paper proposes an enhancement of the numerical simulation using FEM and performing material choosing with the Ashby method for automotive brake discs, using the symmetric shape of the disc. Automotive braking involves the dissipation of kinetic energy through heat generation due to friction, a physical phenomenon that alters the mechanical properties of brake discs. This prompts automotive development engineers to investigate new materials capable of absorbing heat while maintaining their mechanical properties. A thermomechanical study of a ventilated front brake disc has successfully demonstrated a good performance of cast iron because the equivalent stress is significantly lower than the elastic limit, with a margin of approximately 73 MPa. Compared to validated results extracted from the state of the art, the adopted methodology gives more realistic results with minimum CPU requirements, where the total time of calculation is around 40 min. More than that, the results are suitable to be used for studying durability and other properties like mechanical impact and fatigue. Full article

The irregular joint network unique to columnar joints separates the rock mass into several irregular polygonal prisms. Similar physical model specimens of columnar jointed rock mass (CJRM) were fabricated using a rock-like material. The effect of the irregularity of the joint network was considered in the horizontal plane, and the effect of the dip angle of the joint network was considered in the vertical plane. The strength and deformation moduli of the specimen were investigated using uniaxial compression tests. A total of four failure modes of regular columnar jointed rock mass (RCJRM) and irregular columnar jointed rock mass (ICJRM) were identified through the tests. The peak stress of the irregular columnar jointed rock mass specimen is reduced by 56.65%. The strength and deformation moduli of RCJRM were greater than those of ICJRM, while the anisotropic characteristics of ICJRM were stronger. The failure mode of CJRM was determined by the dip angle. With the increase in the dip angle, the strength and deformation moduli of irregular columnar jointed rock mass are a symmetrical “V” type distribution, 45° corresponds to the minimum strength, and 30° obtains the minimum deformation modulus. With the increase in the irregularity coefficient, the strength and deformation moduli of CJRM decreased first and then increased gradually. When the irregularity coefficient is 0.1, the linear deformation modulus reaches the minimum value. When the irregularity coefficient is 0.7, the median deformation modulus reaches the minimum value. The fitting function proposed in the form of the cosine function managed to predict the strength value of CJRM and showed the strength of the anisotropic characteristics caused by the change in the dip angle. Compared with the existing physical model test results, it is determined that the strength of the specimen is positively correlated with the addition amount of rock-like material and the loading rate, and negatively correlated with the water consumption. Full article

Background: Abdominal aortic aneurysms and peripheral artery disease pose significant health risks, ranking third after heart attacks and cerebral strokes. Surgical interventions often involve temporary aortic clamping, leading to ischemia–reperfusion injury and tissue damage. Colchicine and mesenchymal stem cells have shown promise, individually, in mitigating ischemia–reperfusion injury, but their combined effects remain understudied. Methods: This study utilized 42 male Wistar rats, divided into six groups: Control, Sham, Ischemia–Reperfusion, Colchicine, Mesenchymal stem cell, and Mix (colchicine and mesenchymal stem cell). The ischemia–reperfusion model involved clamping the abdominal aorta for 60 min, followed by 120 min of reperfusion. Colchicine and mesenchymal stem cell treatments were administered as pre- and post-ischemia interventions, respectively. Mesenchymal stem cells were cultured, characterized by flow cytometry, and verified for specific surface antigens. Blood and tissue samples were analyzed for oxidative stress markers, nitric oxide metabolites, and apoptosis using TUNEL. Results: There were significant differences between the groups in terms of the serum total antioxidant capacity (p < 0.001) and inflammation markers (ischemia-modified albumin, p = 0.020). The combined therapy group (Mix) exhibited the lowest inflammation levels. Arginine levels also showed significant variation (p = 0.028), confirming the ischemia–reperfusion injury model. In muscle tissues, the total antioxidant capacity (p = 0.022), symmetric dimethylarginine, and citrulline levels (p < 0.05) indicated nitric oxide metabolism. Apoptosis was notably high in the ischemia–reperfusion injury group as anticipated. It appeared to be reduced by colchicine, mesenchymal stem cells, and their combination, with the most significant decrease observed in the Mix group (p < 0.001). Conclusions: This study highlights the potential of using combined colchicine and mesenchymal stem cell therapy to reduce muscle damage caused by ischemia–reperfusion injury. Further research is needed to understand the underlying mechanisms and confirm the clinical significance of this approach in treating extremity ischemia–reperfusion injuries. Full article

Asymmetric studies can indicate disturbances in the developmental process. Fluctuating asymmetry (FA) is considered an indicator of stress. The Sanmartinero (SM) creole bovine is native to the department of Meta (Colombian Orinoquia) and its adaptation process has allowed it to live in extreme tropical environments. The aim of this cross-sectional and descriptive study was to present the current state of the knowledge of asymmetries in some cephalic characters of the SM creole bovine. A total of 94 animals were studied (18 uncastrated males and 76 females) from three different farms, with an age range of 0.5–10 years. For each animal, two measurements of the ear (width and length) and two measurements of the horn (perimeter and length) were obtained in vivo. The degree of asymmetry was calculated as (R − L)/(R + L). Bilateral differences pointed towards a fluctuating asymmetry (e.g., a random variation in the trait that is expected to be perfectly symmetrical) biased towards right for ear width and horn perimeter, and towards left for ear and horn length. Since the development of these structures—ears and horns—is under the control of the same set of genes, the fluctuating asymmetry could constitute a reflection of a normal condition. Full article

A compound channel’s discharge capacity and boundary shear force can be predicted as a sum of the discharge capacity of different sub-regions once the apparent shear stress of the dividing line is reasonably quantified. The apparent shear stress was usually expressed as a coefficient multiplied by the difference between two squared velocities of two adjacent regions. This study investigated the range of the coefficient values and their influencing factors. Firstly, the optimal values of the coefficient were obtained based on experimental data. Then, comparisons between the optimal values and several parameters used in quantifying the apparent shear stress were conducted. The results show that the coefficient is mainly related to a morphological parameter of the floodplain and the ratio of resistance coefficients between the floodplain and the main channel. An empirical formula to calculate the coefficient was developed and introduced to calculate the flow discharge and boundary shear stress. Experimental data, including 142 sets of test data of symmetric-floodplain cases and 104 sets of one-floodplain cases, have been used to examine the prediction accuracy of discharges and boundary shear stress. For all these tests, the ranges of water depth of the main channel and the total width of the compound cross-section are about 0.05~0.30 m and 0.3~10 m, respectively; the Q range and the range of Froude numbers of the main channel flow are about 0.0033~1.11 m³/s and 0.3~2.3, respectively. Comparison with other methods and experimental data from both rigid and erodible compound channels indicated that the proposed method not only provided acceptable accuracy for the computation of discharge capacity and boundary shear stress of compound channels in labs but also gave insights for calculating discharge capacity in natural compound channels. Full article

Background: Lichen planus (LP) is a chronic inflammatory skin disease of unelucidated etiology. LP immunopathogenesis is mainly governed by cytotoxic T lymphocytes that mediate an immune response in basal keratinocytes, which may transform into a reservoir of antigens able to initiate an autoimmune reaction. However, other pathogenic pathways complement these mechanisms. Recent studies highlight the involvement of nitrosative stress in the pathogenesis of chronic inflammatory skin diseases. Current data on its role in the pathogenesis of LP are scarce. Methods: In this article, we investigated nitrosative stress in 40 cutaneous LP (CLP) patients compared to 40 healthy subjects using serum markers including nitrosative stress markers—direct nitrite, total nitrite, nitrate and symmetric dimethylarginine (SDMA), total antioxidant status (TAS), and hsCRP, a marker of inflammation, and analyzed the relationship between nitrosative stress, antioxidant defense, and inflammation to offer new insights into the role of the NO pathway in LP pathogenesis. Results: We identified significantly higher serum levels of direct nitrite, total nitrite, nitrate, SDMA and hsCRP, and significantly lower levels of TAS in CLP patients versus controls. There were significant negative correlations between the serum levels of TAS and significantl positive correlations between the serum levels of hsCRP and the analyzed nitrosative stress markers in patients with CLP. Conclusion: Our results indicate an increased level of nitrosative stress in LP patients that correlates with a pro-inflammatory status and altered antioxidant defense. Full article

In this study, the combination of ordinary cement concrete (OCC) and shrinkage-compensating concrete (SCC) was utilized to pour super-long mass concrete. The temperature and strain of the concrete were continuously monitored and managed actively after pouring. The investigation focused on the temporal and spatial distribution patterns of the temperature field, the temperature difference between the core and surface, and the strain evolution. Based on the constructed hydration exothermic model of layered poured concrete, the effects of the SCC, molding temperature, and surface heat transfer coefficient on the temperature field were analyzed. The results show that the temperature of super-long mass concrete rises quickly but falls slowly. SCC exhibits higher total hydration heat than OCC. The temperature field is symmetric along the length but asymmetric along the thickness due to varying efficiency of heat dissipation between the upper and lower parts of the concrete. After final setting of the concrete, the strain varies opposite to the temperature and peaks at −278 με. A few short cracks are observed on the end of the upper surface. Moreover, the numerical simulation results are in good agreement with the measured results. Increasing the molding temperature and surface wind speed increases the temperature difference between the core and surface. Conversely, increasing the thickness of the insulation layer is an effective way to curtail this difference. Thermal stress analysis is carried out and shows that lowering the molding temperature of SCC and increasing the thickness of insulation material can effectively reduce thermal stress. Full article