Copper-based powder metallurgy friction materials are widely used in high-speed train braking systems owing to their favorable friction performance and excellent thermal conductivity. However, under high-speed and high-energy braking conditions, their friction stability and wear resistance tend to deteriorate. In this study, copper-based powder metallurgy friction materials were synergistically modified using sepiolite and ZrO2-Y2O3 composite ceramics. Using a C/C-SiC counterpart, the effects of tailored ZrO2/Y2O3 ratios on mechanical, thermal, and tribological properties were systematically investigated. The mechanical and tribological properties exhibit a pronounced dependence on the ZrO2/Y2O3 ratio, increasing initially and then decreasing with increasing ZrO2 content. Among all compositions, the sample with a ZrO2/Y2O3 ratio of 5:3 shows a relatively high and stable friction coefficient and a low wear rate at 6000rpm. Microstructural and worn surface analyses indicate that appropriately proportioned ZrO2-Y2O3 ceramic particles enhance the load-bearing capacity, while sepiolite undergoes structural degradation and phase transformation during sliding, generating SiO2 and MgSiO3 derivative phases that actively participate in tribo-layer formation. The resulting composite tribo-layer, composed of metallic oxides, ceramic particles, and sepiolite-derived phases, plays a key role in improving friction stability and reducing wear. These results demonstrate that sepiolite-assisted composite ceramic modification provides an effective approach for tailoring the tribo-layer structure and enhancing the tribological performance of copper-based powder metallurgy friction materials under high-speed braking conditions.

To address the severe high-temperature corrosion and slagging behavior during straw incineration, CoNiCrAlY coatings were prepared on NM450HIT and P91 steel substrates via high-velocity-oxy-fuel (HVOF). The hightemperature oxidation behavior of the coatings was systematically studied by comparing their performance in static air and simulated straw-ash environments. The results show that the CoNiCrAlY coatings exhibit excellent oxidation resistance at 600-700 degrees C, primarily consisting of gamma solid-solution, Al2O3, and minor YAlO3. When the temperatures are above 800 degrees C, the oxide layer becomes porous and loose, while Cl- and K2CO3 from the straw ash promote the formation of low-melting-point eutectics, accelerating crack initiation and coating degradation. The steel substrate also significantly influences coating stability. Volume expansion associated with martensitic transformation in NM450HIT steel accelerates coating cracking, whereas the pearlite-ferrite structure of P91 steel provides better stability at high temperatures. This study provides theoretical guidance for the selection and design of protective coatings for critical components in straw-incineration equipment.

The rapid expansion of the new energy industry has substantially increased the demand for lithium resources, highlighting the need of alternative supply pathways. As a potential lithium-containing mineral, petalite remains insufficient understood in terms of its high-temperature phase transformation behavior and lithium extraction potential. In this study, the kinetic parameters and transformation mechanism of petalite were investigated through TG-DSC combined with the Ozawa-Flynn-Wall, Kissinger, and Coats-Redfern methods, together with an evaluation of its lithium recovery feasibility. Starting at around 1000 °C, petalite gradually transformed into β-spodumene and SiO2, with the main phase transition occurring between 1050 and 1100 °C and nearing completion above 1150 °C. Meanwhile, β-spodumene became the dominant phase and crack formation progressively developed, facilitating subsequent lithium release. The transformation followed the Avrami-Erofeev (A1/2) model, with an apparent activation energy of 284.23–311.29 kJ·mol−1 under different methods, providing key parameters for process design and scale-up. Moreover, the lithium leaching efficiency exceeded 90% under sulfation roasting and water leaching condition. Overall, this study provides a feasible and scalable pathway for the development and utilization of petalite resources, contributing to diversified lithium supply and improved resource sustainability.

In this study, graphene/copper-coated graphite reinforced copper-based composites were fabricated via powder metallurgy, and then paired with C/C-SiC discs to form friction couples. Partial graphite was replaced with copper-coated graphite, while a small amount of graphene was incorporated. By adjusting the mass ratio of graphene to copper-coated graphite, the effects of this ratio on the properties, micromorphology, and friction-wear mechanism of the copper-based composites were systematically investigated. The results indicated that when the mass ratio of graphene to copper-coated graphite was 0:14, the composite exhibited the optimal comprehensive mechanical and thermal properties. During medium and high-speed braking, the lubricating film formed by the synergistic effect of graphene and copper-coated graphite contributed to enhancing friction stability; the optimal comprehensive friction performance of the composite was achieved when the mass ratio of graphene to copper-coated graphite was 1:13. With the increase in the mass ratio of graphene to copper-coated graphite, the wear mechanism underwent a transformation from abrasive wear and slight adhesive wear, to abrasive wear and adhesive wear, then to abrasive wear and fatigue wear, and finally to abrasive wear and severe fatigue wear. In addition, all samples were accompanied by a certain degree of oxidative wear during the friction process.

The tensile fracture response of Metal injection moulding (MIM) Ti- 6Al-4V was not governed solely by pores or strength, but by the combined regulation of local plastic coordination and damage-network connectivity by residual impurities introduced during debinding. This study designed four Polyoxymethylene-based Ti- 6Al-4V feedstock systems and systematically investigated the variation in residual carbon/oxygen (C/O) under different thermal debinding heating rates, as well as their effects on the microstructure, mechanical properties, wear response, and tensile fracture behavior. Combined with fracture analysis and polycrystalline-multiparticlemultisized molecular dynamics models, the tensile fracture mechanism of MIM Ti- 6Al-4V was comprehensively investigated. The results indicated that the characteristics of the binder components had a significant effect on the residual C/O contents after debinding. Sliding wear was governed by C/O dependent hardness, densification, and debris evolution. Additionally, tensile fracture was essentially governed by the evolution of the highstrain network formed by pores, grain boundaries, and their coupled regions into either a plastically coordinated network or a fracture-precursor network. In the low C/O system, a plastically coordinated zone supported by strain redistribution and deformation substructure evolution could form before crack propagation, thereby relieving the stress concentration near pores and grain boundaries and delaying damage coalescence. Conversely, high C/O suppressed the establishment of the plastically coordinated zone, making the high-strain regions more likely to develop into a rapidly propagating damage network along pores, grain boundaries, or intragranular slip bands, ultimately leading to quasi-cleavage fracture. This study provides new mechanistic insights into lowimpurity processing and performance optimization of MIM Ti- 6Al-4V.

This study explores simple pretreatments, including ball milling and heat treatment, to enhance interdiffusion bonding between Cu and Ti3SiC2 in Cu-metal matrix composites (CMMC), thereby improving their mechanical, thermal, and tribological properties. The results reveal that the Cu-Ti3SiC2 interdiffusion reaction can already take place at 500 degrees C after high-energy ball milling, owing to the enhanced surface activation. The reaction product Cu3Si contributes to strengthening the mechanical properties of CMMC by impeding crack propagation, although it compromises thermal conductivity because of its much lower intrinsic thermal conductivity compared with Cu and Ti3SiC2. Moreover, high-energy ball milling significantly refined the particle size of pure Ti3SiC2 and damaged its layered structure due to the absence of Cu buffering during milling. While this behavior benefited mechanical performance, it diminished the solid lubrication capability of Ti3SiC2. Among all tested conditions, the CMMC sample fabricated from Cu-Ti3SiC2 powders subjected to high-energy ball milling followed by heat treatment at 700 degrees C exhibited the highest coefficient of friction (COF) and the most stable friction stability coefficient (SC) under high-speed braking. This improvement is attributed to enhanced interdiffusion bonding between Cu and Ti3SiC2, while the reaction product Cu3Si further promoted the formation of friction film. The dominant wear mechanisms were identified as abrasive wear and oxidative wear.

This work revealed the friction reduction and wear mechanism of Si-DLC film in humid environment under varying loads and temperatures, utilizing reactive force field molecular dynamics (ReaxFF MD). The results show that Si-OH groups generated by the tribochemical reaction can promote water-lubricated film formed, which significantly reducing the friction force of the tribosystem. Under low loads, Si-DLC film undergo chemical oxidation wear, where the bonds between Si atoms tend to fracture first, while the C and Si atoms are bridged first by O atoms through oxidation and ultimately bridge bonds fractured to realize wear. Increasing load, the chemical wear is transformed into mechanical wear with high wear. Additionally, high temperature reduces the friction force of the tribosystem by increasing the low-shear strength structure of Si-DLC film, but this causes high wear of Si-DLC film.

This study addresses the thermal decay of the coefficient of friction (COF) in Cu-based friction materials when paired with carbon fiber-reinforced carbon and silicon carbide composites (C/C-SiC) under high-speed braking conditions. Cu-based composites were reinforced with a ternary ceramic system consisting of SiC, B4C, and large-particle Al2O3 to enhance mechanical, thermal, and tribological performance. The sample with an Al2O3/SiC ratio of 3:5 demonstrated the highest compressive strength and superior surface hardness, likely due to the combined reinforcing effects of large-particle Al2O3 and the "Orowan strengthening" mechanism of SiC. Additionally, this sample demonstrated excellent overall friction performance, with an average COF exceeding 0.3 and a stable friction coefficient approaching 0.8. The enhanced performance is mainly driven by the frictional force generated by Al2O3, while SiC plays a key role in developing a denser and uniform Si-rich friction film on the surface. The friction film primarily consisted of graphite, fine SiC debris, and some metal oxides. Notably, the sample caused an exceptionally low level of damage to the brake disc. This reduced damage is attributed to the formation of a metal transfer film on the disc surface, which underwent fatigue delamination during severe wear, leading to the formation of a thin transitional carbon layer at elevated temperatures.

Existing studies have shown that bonding a ±45° biaxial GFRP under CFRP laminate can significantly improve the load-carrying capacity and ultimate deformation of CFRP–concrete bonded joints. In such a bonding configuration, the GFRP interlayer is wider than the CFRP laminate so that the interfacial stress can be redistributed to achieve a higher fracture work; however, the effect of the bonding sequence,—specifically, the position of the GFRP layer—on the bond behavior is not yet clear. In this study, considering the same CFRP and GFRP usage, three types of CFRP–concrete bonded joints with CFRP bonded under, above, and between GFRP layers were prepared and tested under single-shear loading. Digital image correlation (DIC) was used to measure the deformation of the bonded joints during the test. Afterward, the failure mode, load–displacement behavior, and principal strain distribution were analyzed. The experimental results show that the dominant failure mode is the combined cohesion failure mode within the concrete and GFRP delamination, which is not affected by the bonding sequence. Compared to conventional CFRP–concrete bonded joints, bonding the CFRP laminate above, under, and between the GFRP layers achieved a 157.6%, 175.0%, and 177.2% increase in load-carrying capacity, respectively. Accordingly, the ultimate deformation also recorded an 83.0%, 103.6%, and 86.3% increase. However, the bonding sequence showed a slight influence on the initial stiffness of the load–displacement curve with a maximum difference of 16.1%, taking the minimum as a reference, which could be attributed to the differences in the strength and stiffness between the CFRP–concrete and CFRP–GFRP–concrete interfaces.

Zirconia toughened alumina (ZTA)/high chromium cast iron (HCCI) architectural composites are widely used in many fields, and several factors can affect their wear resistance. The objective of this study was to examine the three-body abrasive wear characteristics of an irregularly shaped ZTA/HCCI composite in comparison with conventional HCCI and crushing ZTA/HCCI composites. Irregularly shaped ZTA was prepared in this study, and ZTA/HCCI composites were fabricated with different ZTA shapes. The mass loss rates of crushed and irregularly shaped ZTA/HCCI composites were observed 0.29 % and 0.26 %, respectively, when subjected to the three-body abrasive wear process. These results indicated the improved wear resistance of the ZTA/HCCI composite. Because the irregularly shaped ZTA ceramic particles did not have sharp edges, which suppressed the tendency for stress concentration, the internal stress was significantly reduced. Therefore, the likelihood of crack formation was substantially reduced, reducing the probability of failure and increasing the wear resistance. In this study, this approach provided a new idea to enhance the wear resistance.

To address the issues of short tool life and frequent failures of agricultural soil-engaging components due to poor wear resistance and low impact toughness, this study successfully developed WC10Co4Cr wear-resistant coatings on 65Mn and 60Si2Mn steel substrates before and after heat treatment using high-velocity oxygen fuel (HVOF) spraying technology. The microstructure and phase composition of the coatings were analyzed using SEM, EDS, XRD, and XPS. The microhardness and wear resistance of the coatings were evaluated using a hardness tester, friction wear testing machine, and wet rubber wheel testing machine. The wear resistance and mechanisms of the coatings were also analyzed and summarized. The prepared coatings, with a thickness of approximately 0.25 mm, exhibited low porosity, high microhardness, and excellent wear resistance, achieving a microhardness of up to 1203 HV0.5. The coatings adhered well to the substrates. Reciprocating friction test results showed a slow increase in the coefficient of friction over wear time. The wet rubber wheel friction test, simulating soil conditions, indicated that the wear mass of samples with WC10Co4Cr coatings decreased by >90 % compared to uncoated samples. Additionally, the WC10Co4Cr wear-resistant coating was applied to rotary tiller blades and field-tested. Results showed a 63 % reduction in wear for the coated blades, demonstrating the coating's excellent combined wear and impact resistance. The WC10Co4Cr coatings prepared on heat-treated substrates showed lower porosity and superior wear resistance, with a bonding strength of up to 78.5 MPa on heat-treated 60Si2Mn. These findings provide valuable insights for enhancing the performance of agricultural soil-engaging components such as rotary tiller blades, plowshares, and subsoilers.

By incorporating the dual ceramic elements TiB2/B4C, we investigated their impact on the mechanical properties, thermal properties, and friction performance of copper-based powder metallurgy materials, and elucidated the friction wear mechanism. Additionally, machine learning algorithms were employed to predict the friction coefficient and stability coefficient. The conclusions are as follows:With the increase in the TiB2/B4C ratio, the trend of mechanical properties initially increases and then decreases, with the optimum ratio being 5:3 for TiB2 and B4C, exhibiting superior mechanical properties. Moreover, B4C enhances the thermal conductivity of copper-based friction materials more effectively than TiB2. In terms of overall friction performance, the ratio of TiB2 to B4C at 5:3 yields better frictional properties. The primary components of the friction surface friction film are CuO, Cu2O, Fe2O3, and B2O3, transitioning from a ceramic film to a metallic film as the TiB2/B4C ratio increases. The friction wear mechanism shifts from abrasive wear to severe fatigue wear as the TiB2/B4C ratio increases, accompanied by oxidative wear. Furthermore, an AdaBoost algorithm model was developed to effectively predict the friction coefficient and stability coefficient, with accuracies of 0.9993 and 0.8739, respectively.

Objective:To investigate the urinary virology and clinical characteristics of female overactive bladder (OAB) patients.Methods:Catheterized urine samples were collected from 55 women with OAB and 18 control individuals between January 2021 and August 2021. Inclusion criteria were: female with age>18, diagnosed as OAB, OABSS total score≥3 and item Urgency score≥2, informed consent signed. Exclusion criteria were: Urine culture positive, urinary catheter indwelling status, antibiotic usage in recent 30 days, other disease leading to OAB-like symptoms, pelvic organ prolapse and current pregnancy, immunosuppressive therapy or status. Clinical characteristic and history were collected. OAB symptoms were assessed via both OABSS (overactive bladder symptom score) and OAB-V8 (8-item overactive bladder questionnaire). The urine specimens were analyzed using mNGS for identifying viral infections. The correlation between the disease and JC virus infection was analyzed by t test, chi-square test, binary logistic regression analysis and Spearman correlation matrix, and the Nomogram map for predicting the risk of viral infection was constructed. Results:In total, 55 women with OAB and 18 healthy controls were recruited in the study. There are significant difference in terms of UTI history, pelvic surgery history and the habit of holding urine [60.0%(n=33)to 16.7%(n=3), P=0.002; 43.6%(n=24)to 0.0%(n=0), P<0.01; 36.4%( n=20)to 5.6%( n=1), P=0.015]. Based on mNGS results, OAB patients were identified with more positive viral infection [47.3%(n=26)to 33.3%(n=6)] and more JC virus infection. In the OAB group, subtype 7B of JCV ( n=8) was identified, while in the control group, subtype 7A(n=2) was identified. Pairwise Spearman correlation analysis indicated high correlations between viral infection and OABSS ( r=0.58), age and pausimenia ( r=0.68), hypertension and age ( r=0.53), respectively. Estimates from binary logistic regression model indicated risk factors for virus infection in OAB patients including age ( OR=1.99, 95% CI 0.02-2.61), holding urine habit( OR=2.16, 95% CI 0.18-3.85) and pelvic surgery ( OR=2.53, 95% CI 0.54-4.27). Conclusions:Urinary viral infections appear to be associated with more severe OAB symptoms and JC virus may be a potential therapeutic target for OAB.

Objective:To analyze the current status of referral of stroke inpatients and explore the characteristics of the referral network in Changsha, for the reference to improve and promote the hierarchical medical system of stroke.Methods:Data of the inpatient medical record of stroke patients and the annual reports of medical institutions in Changsha in 2018 were collected from the health statistics network direct reporting system of Health Commission of Hunan province, for analysis of the referrals of inpatients in different medical institutions. Social network analysis was adopted to analyze the density, centrality and K-core of the referral network of stroke inpatients.Results:A total of 82 medical institutions for stroke inpatients were included with 2 859 referrals of patients. Most of the referrals were made between tertiary hospitals(1 515), especially within hospitals of a stroke alliance(1 123). The density of referral network was 0.613.Tertiary hospitals were in the center of the network, the entry points of secondary hospitals were in the center of the network and primary medical institutions were located at peripheral positions. Most of the tertiary hospitals in the 15-core(14, 72.68%), 12 of them were the units of Hunan Stroke Alliance.Conclusions:Tertiary hospitals played an important role in the region, secondary hospitals were able to receive patients referred by tertiary hospitals, but few patients were transferred to primary care institutions; The primary medical institutions failed to play due roles in the referral network. The establishment of stroke alliances could promote the cooperation of hospitals in the alliance, but the division of labor and cooperation among different levels of medical institutions in the region needed to be further optimized.

疲劳失效是金属构件的主要失效方式之一,该文针对金属疲劳裂纹扩展过程中的不确定性,以"首次达到给定裂纹长度a的时间t(a)"为随机描述量,采用比例型Paris公式描述裂纹的平均扩展路径,建立基于逆高斯过程的单样本疲劳裂纹扩展随机模型和考虑样本异质性的裂纹扩展随机效应模型,分别采用最大似然估计法(MLE)和最大期望算法(EM)推导了单样本模型和随机效应模型的参数估计公式.最后,利用提出的裂纹扩展随机模型拟合了68个铝合金板的疲劳裂纹数据,对结果进行了拟合优度分析.结果表明:该文提出的疲劳裂纹扩展随机模型能够有效地分析和解释金属疲劳裂纹扩展过程中的不确定性.

In this paper, the effect of Zn-vacancy defect on adsorption of HS on smithsonite (101) surface was studied by density-functional theory (DFT). The results showed that Zn-vacancy defect made the peaks of the VB and VT defect surfaces both move to left, and the peaks of them around the Fermi energy both decreased. Hence, the reactivity of VB and VT defect surfaces were both lower than that of the perfect smithsonite surface. The presence of Zn-vacancy on the smithsonite surface not only inhibited the adsorption of HS on the site of Zn-vacancy (VT-V and VB-V) but also depressed its adsorption on the Zn site nearby the Zn-vacancy (VT-BZn and VB-TZn). When HS was on the VT-BZn site on the smithsonite surface, the adsorption site of HS was the bridge between S atom the two Zn atoms, and when on the VT-V and VB-TZn sites, the adsorption site of HS was the Zn atom on the smithsonite surface. While on the VB-V site, the adsorption site of HS was the C atom on the smithsonite surface, and the bonding of S‒C was formed. Meanwhile, electron transfers among the bonding atoms on smithsonite surface were observed. The results can provide insights into the sulphidization of smithsonite containing defects.

During flotation, fine gangue minerals can enter the concentrate through mechanical entrainment, which seriously affects the quality of concentrate. In this work, the effect of sodium carboxymethyl cellulose (CMC) on the flotation performance of zoisite, a silicate mineral, was studied. The role of CMC in reducing zoisite entrainment was investigated by dynamic foaming tests, surface tension measurements, rheology measurements, sedimentation tests, and optical microscopy experiments. The flotation results showed that zoisite mainly entered the concentrate by entrainment; the addition of low dosages of CMC decreased zoisite entrainment and efficiently separated cassiterite from zoisite; moreover, the concentrate grade and recovery of SnO2 increased by 1.27 % and 5.63 %, respectively, by using CMC in closed-circuit flotation tests. Dynamic foaming studies on the two-phase and three-phase foam/froth revealed that the presence of CMC decreased the froth ability and froth stability, and greatly altered the three-phase froth structure. Basically, the bubbles in the foam were larger after adding CMC. For the two-phase foam, the change of foam property had little to do with surface activity and bulk viscosity. For the three-phase froth, the froth property was strongly affected by the interaction of CMC and zoisite. The results of the sedimentation test and microscopy experiment demonstrated that CMC can cause zoisite to flocculate and enlarge the particle size, which was the main reason for the decrease of froth stability and entrainment. This study indicates that the side effects of depressants should not be overlooked when discussing the role of depressants in flotation.

针对红水河特大桥贵州岸钢梁顶推施工过程中临时墩位置和主梁顶推节段长度的优化,为使主梁在顶推过程中弯矩最小且梁体的安装累积误差最小,应选取最优的临时墩位置和主梁顶推节段长度.通过构造评价函数,将多目标优化转化为单目标优化,并采用综合权重法对各目标函数的权重进行分配,以确定最优的一组临时墩位置.在此基础上,构建数学模型,得到最优的一组主梁顶推节段长度为(10.8+26.2+50+50+50+50)m,优化后的安装误差比原设计方案减小43.5％.通过MIDAS/Civil建立有限元模型模拟,最不利工况的计算结果表明:优化后因安装误差引起的最大应力比原设计方案减少42.9％,优化效果显著,说明本文方法行之有效.