Recent Advances in Interface Modification of Cu/graphite Composites and Layered Ternary Carbides of Modified Layer Candidate

We review the fundamental properties and significant issues related to Cu/graphite composites.In particular,recent research on the interfacial modification of Cu/graphite composites is addressed,including the metal-modified layer,carbide-modified layer,and combined modified layer.Additionally,we propose the use of ternary layered carbide as an interface modification layer for Cu/graphite composites.

Effect of Sintering Temperature and Hydrophobic Treatment on the Microstructure and Properties of Copper-Graphite Composites

Copper-graphite composites were prepared by spark plasma sintering(SPS)using coppercoated graphite powder.Hydrophobic surfaces were successfully constructed by chemical etching and surface treatment.The density,metallographic structure,microstructure,Shore hardness,resistivity,water contact angle,and friction/wear properties of the composites were investigated using the Archimedes drainage method,a metallographic microscope,a scanning electron microscope,a hardness tester,a resistometer,a surface science tester,and a friction tester.The results showed that the relative density and Shore hardness of the copper-graphite composites increased slightly from 90.04%and 56 HSD to 92.66%and 59 HSD,respectively,when the sintering temperature increased from 700 to 900℃.The copper and graphite phases in the copper-graphite composites were uniformly distributed with a continuous and network-like structure at various sintering temperatures.The interface between the copper and graphite was in good condition,without any obvious cracks or voids.The optimum process for hydrophobic surface construction included etching with a 1 mol/L K_(2)Cr_(2)O_(7)-H_(2)SO_(4)solution for 1 min,and soaking in a 0.09 mol/L cetylbenzene sulfonic acid alcohol solution for 1 h.The contact angle of the copper-graphite composite reached 130°.Hydrophobic treatment was beneficial for reducing the friction coefficient(from 0.18-0.19 to 0.13-0.15)and the wear rate(from 4.1-6.2×10^(-3)to 1.1-2.1×10^(-3)mm^(3)/(N·m)),demonstrating obvious antifriction and wear-resisting properties.The resistivities of the hydrophobic-treated samples increased slightly,from(4-8)×10^(-7)Ω·m to(5-15)×10^(-7)Ω·m,meeting the resistivity requirements of copper-graphite composite pantograph sliders and current receiver sliders in actual working conditions.

民族村寨旅游引导乡村振兴的路径研究

民族村寨旅游作为民族地区实现乡村振兴战略的重要抓手,在带动相关产业发展、吸纳村民就业、帮助村民脱贫致富、保护民族村寨生态环境等方面都发挥着积极作用。然而民族村寨旅游发展实践中也面临着旅游基础设施落后、民族文化特色逐渐消逝等一系列亟待解决的问题。在分析民族村寨旅游引导乡村振兴作用机理的基础上,针对民族村寨旅游发展面临的困境,探究民族村寨旅游引导乡村振兴的可行路径是十分必要的。

基于激光雷达的轮腿式机器人爬楼可通过性研究

基于现阶段移动侦察机器人的应用场景多处于城市环境的背景下,综合轮式速度快、腿式越障能力强的特点,设计了一款用于攀爬楼梯的轮腿式移动机器人。提出了轮腿式机器人攀爬楼梯的控制策略,并通过对比实验验证了轮腿式机器人在攀爬楼梯方面具有明显的优势,同时针对移动机器人在未知环境下无法对楼梯可通过性进行判断的问题,通过分析激光雷达扫描楼梯图像,建立线性回归模型得到楼梯的坡度,这为机器人在实际工程应用中路径规划提供了基础。

核电汽轮机高压缸表面换热系数修正计算

准确的换热系数计算公式是数值分析汽轮机高压缸温度分布、应力及汽密性的基础。目前国内外关于核电汽轮机高压缸换热系数的研究较少,汽缸表面换热系数一直没有统一的公式。本文选用并修正了高压缸内表面换热系数计算公式,对比高压缸壁面温度的计算值和实际监测数据,得到了适用于核电汽轮高压缸的换热系数模型,求解了汽缸温度分布,并对高压缸的应力及中分面汽密性进行了分析。结果表明:该模型具有较高的计算精度,最大误差为4.3%;停机过程中高压缸各表面换热以强迫对流为主,高压缸进汽及排汽处缸表面的换热系数量级在1 000~2 000 W/(m^2·K);停机过程中高压缸内外壁最大温差为29.9℃。

主蒸汽管道恒力弹簧吊架应力分析与疲劳寿命预估

为研究轴向位移和偏转角度对恒力弹簧吊架受力的影响,采用有限元方法对主蒸汽管道的吊架建立模型,并对应力集中位置进行了疲劳寿命预估。结果表明:吊架应力集中主要发生在管夹下端螺栓、环形耳子处螺栓、吊杆、管道与管夹接触区域;轴向位移对环形耳子螺栓的疲劳寿命影响最大,偏转角度对管道与管夹接触区域的疲劳寿命影响最大。

热带岛礁某二级医院常见病特征分析

背景热带岛礁特殊气候与当地常见病的发生相关,热带常见病特征的研究报道较少。目的回顾性分析热带岛礁某二级医院门诊就诊情况,探讨与大陆常见疾病谱的差异性,为热带岛礁常见病精准化防治提供参考。方法按照国际疾病分类(International Classification of Diseases,ICD)-10标准,统计分析热带岛礁某二级医院2016年1月-2019年12月门诊病历中62870例次诊断信息。结果就诊人群18~30岁年龄段占比最高(60.15%),男性(95.83%)占比远高于女性(4.17%)。按人体系统分,排名前5位的是肌肉骨骼系统和结缔组织疾病(19.15%)、呼吸系统疾病(17.57%)、消化系统疾病(15.50%)、皮肤和皮下组织疾病(10.24%)、损伤和中毒(8.13%)。按疾病类型分,排名前5位的是上呼吸道感染(9.81%)、腰痛(5.64%)、意外事故(5.58%)、皮炎(2.96%)、陈旧性肌肉劳损(2.08%)。结论热带岛礁常见疾病中上呼吸道感染是主要疾病类型,病原体不明确,存在流感暴发风险,应提高检测能力,予以针对性防控;同时应提高肌肉骨骼系统疾病和皮肤、皮下组织疾病的防治。

山区公路隧道拱顶沉降回归模型的比选

以西沟垭隧道工程为背景,对采用新奥法施工的隧道拱顶沉降监测数据进行分析研究,并进行奇异值检验与处理。分别用幂函数、指数函数、对数函数和双曲线函数建立4种拱顶沉降回归模型,得到4种函数模型的表达式并进行了相关系数r、标准差σ、回归平方和U以及F检验等相关参数的对比分析。将回归模型回归曲线与工程实测曲线进行拟合对比分析,认为对数函数模型为该隧道拱顶沉降分析评价的最佳回归模型。研究结果可为该隧道工程的施工提供科学分析与指导,研究过程同时对类似工况下的其他山区公路隧道工程拱顶沉降分析评价具有借鉴意义。

Optimization of Quenching Process for ZTAP/ High Chromium Cast Iron Composites

In order to solve the problem of cracking of ZTAP(Zirconia toughened alumina ceramic particles)reinforced HCCI(high chromium cast iron)matrix composites,the quenching process was optimized.ZTAP reinforced HCCI matrix composites were prepared by infiltration method with gravity sand casting.The thermal expansion curves of HCCI and the composites were measured at different cooling rates by Glebble-3500.The microstructure of the HCCI matrix and the composites were characterized by X-ray diffraction,light microscopy,SEM,ESD,and EPMA.The tested mechanical properties include Rockwell hardness and impact toughness.The deformation differences of HCCI and the composite at different cooling rates were obtained according to the test results of thermal expansion coefficient curve and changes in microstructure and mechanical properties,and air cooling was the most favorable for the composites to have good hardness and not easy to crack.The cooling rate during air cooling is approximately equal to 21℃/s in this work.When the quenching process was air cooling,the impact toughness and hardness of the composites are 3.7 J/cm^(2) and 61.8 HRC,respectively,and the deformation difference between the composites and HCCI was 20μm at 300℃.

送粉式激光增材和铣削减材复合制造316L不锈钢的表面质量及力学性能

为了研究送粉式激光增材和铣削减材复合制造零件的表面质量及力学性能,以316L不锈钢粉末为原料,通过"增材-减材-增材-减材"交替循环的方式进行样件的制造,并对其表面粗糙度、显微硬度和力学性能进行分析测试。结果表明:送粉式激光增材和铣削减材复合制造样件的表面粗糙度随着铣削速度的增大而下降,随着每齿进给量的增加而增大;送粉式激光增材和铣削减材复合制造样件的表面粗糙度较传统工艺生产的基板试样更低,显微硬度较增材制造样件和锻造件更高,抗拉强度和屈服强度比增材制造样件分别提高了5%和60.5%,但断后伸长率却有所降低。送粉式激光增材和铣削减材复合制造技术能够制造出具有高表面质量和优良力学性能的零件,可直接应用于316L不锈钢轮胎模具等零件的制造。该技术充分融合了增材制造的高材料利用率、高自由度以及减材制造的高精度、高表面质量优势,可以获得结构复杂、形状精度和表面质量高的零件。

321例下咽癌患者临床特征及两种治疗方式疗效分析

目的:分析下咽鳞状细胞癌的临床特点、治疗效果及预后影响因素。方法:采用寿命表计算321例下咽鳞状细胞癌患者的总生存率,Kaplan-Meier法进行生存分析,组间差异采用Log-rank法检验,交叉表格法比较两种治疗方式的保喉率。Cox回归模型分析预后的独立影响因素。结果:321例患者中,采用手术+术后综合治疗197例,非手术综合治疗124例。全部患者1年、3年、5年总生存率分别为75.87%、49.39%和41.38%,中位生存时间为37.65个月。非手术综合治疗保喉率(41.94%)与手术+术后综合治疗保喉率(11.17%)比较,差异有统计学意义(P<0.01)。单因素分析显示肿瘤临床分期、T分期、N分期、M分期、治疗方式对患者生存预后的影响具有统计学意义。Cox回归模型多因素分析显示生存率的独立影响因素为肿瘤T分期、N分期和治疗方式。结论:下咽癌仍是疗效较差的头颈部恶性肿瘤,具有恶性程度高、早期不易发现、易复发及转移、治疗创伤大等特点,治疗前应全面检查,明确肿瘤分期,选择合理的治疗方案,手术+术后综合治疗仍是中晚期下咽癌的主要治疗方式。