Microstructure and mechanical properties of Cr doped WCoB based cermets by spark plasma sintering and first principle calculation

WCoB based cermet is a potential hard alloy to replace WC-Co cermets with high hardness and corrosion resistance. WCoB based cermets with different Cr doping contents were fabricated by spark plasma sintering in liquid phase sintering stage. The densification behavior, phase composition, microstructure and mechanical properties of Cr doped WCoB cermets were investigated by XRD, EDS and SEM. Due to the lower density of Cr,the density of WCoB cermets decreased with the increasing of Cr doping content. The phase composition consisted of Cr doped WCoB, unreacted W, Co–Cr binary binder phase. When the doping content exceeded11.736 wt%, the Cr enrichment zones appeared, which was harmful to the TRS. The increasing of Cr doping content contributed to the increase of unreacted W phases content and the formation of pores. The maximum value of Vickers hardness was 1751 Hv0.5 at 9.356 wt% Cr doping content. The variation trend was explained by first principle calculation, which is consistent with Hv-Zhou hardness model.     

玻璃粉表面改性及其对水泥浆水化硬化作用

利用增钙、机械粉磨等手段对玻璃粉进行局部活化,采用SEM、XRD等测试方法研究了改性玻璃粉水泥浆水化产物和微观结构,并讨论了改性玻璃粉在水泥浆水化硬化过程的作用。研究表明:氧化钙的掺入提高了复合体系液相的碱度,从而加快了水泥水化反应生成更多水化产物;掺入氧化钙的玻璃粉水泥浆微观结构更为密实,28 d龄期时水化产物间的孔隙远远小于3 d,水化产物发育更好,硬化浆体的强度大幅提高。当CaO掺量过大(6%)时,生成过多的氢氧化钙晶体引起膨胀开裂,对玻璃粉水泥浆的强度发展产生不利影响。     

黄土隧道软弱土层施工技术

本文以天平铁路上赵家隧道、毛家磨隧道为例,根据黄土隧道易软化、强度低等特点,提出了黄土隧道软弱层施工方法,对施工类似工程提供了技术参考。     

Effect of poly(vinyl pyrrolidone ) on the morph ology and physical properties of poly(vinyl alcohol) /sodium montmorill onite nanocompos ite films

Nanocomposites of poly(vinyl alcohol)(PVA),poly(vinyl pyrrolidone)(PVP) and sodium montmorillonite(Na~+MMT) were prepared by solution mixing and then cast into films.X-ray diffraction analysis and images of transmission electron microscopy establish the formation of PVA/Na~+MMT intercalated nanocomposite.Exfoliated and highly intercalated PVA/PVP/Na~+MMT nanocomposite formed in the presence of PVP.Inclusion of PVP in PVA/Na~+MMT matrix enhances the hydrogen bonding interactions between PVA and Na~+MMT and thus increases the mechanical properties and thermal stability of PVA/PVP/Na~+MMT nanocomposites compared to PVA/Na~+MMT nanocomposite.The interactions between PVA,PVP and Na~+MMT were established by the Fourier transform infrared spectroscopy.The moisture absorption tendency of both the PVA and PVA/PVP films reduced after the incorporation of Na~+MMT at 75%constant relative humidity.Differential scanning calorimetry studies show that the presence of PVP and Na~+MMT both are responsible for reducing the heat of fusion,and crystallinity of PVA.The flow behavior of the PVA,PVA/PVP and its nanocomposite solutions has been also studied.Water vapor permeability of PVA/PVP/Na~+MMT composite films decreased in the presence of nanoclay due to increasing tortuous paths for diffusion.     

Ti – Cu– Zr–Fe– Nb ultrafine structur e-dendrite composites with good mechanical properties and biocompat ibility

Ti-Cu-Zr-Fe-Nb ultrafine structure-dendrite composites were designed by inducing Nb and more Ti to a Ti-Cu-Zr-Fe glass-forming alloy composition and prepared by copper mold casting.The composite alloys consist of β-Ti dendrites and ultrafine-structured CuTi₂ and CuTi phases as well as a trace amount of glassy phase.The volume fraction of β-Ti dendrites increases with the increase in content of Nb which acted as the β-Ti phase stabilizer in the alloys.The composites exhibit high compressive yield strength exceeding1200 MPa,maximum strength around 1800 MPa and low Young’s modulus around 48 GPa.The plasticity of the alloys is strongly influenced by the volume fraction and morphology of the dendritic β-Ti phase,and the compressive plastic strain was enlarged from 5.9%for the 4 at%Nb alloy to 9.2%for the 8 at%Nb alloy.The preliminary cell culture experiment indicated good biocompatibility of the composite alloys free from highly toxic elements Ni and Be.These Ti-based composite alloys are promising to have potential structural and biomedical applications due to the combination of good mechanical properties and biocompatibility.     

机械设计制造及自动化专业创新性应用型人才培养模式探索

机械设计制造及自动化专业具有宽口径和知识更新速度快的特点,在对该专业人才需求广泛调研的基础上,作为地方院校的德州学院尝试进行了机械设计制造及自动化专业人才培养模式的改革探索,设定了创新性、应用型人才的培养目标和层次定位,构建了模块化课程体系,对课程体系与实践教学体系进行了调整与改革,在注重理论基础知识的同时,进一步加强了学生的创新意识和实践能力的培养.     

《机械制图》整合式教学方法的研究与实践

《机械制图》是工科各专业的基础课程,但教学效果一直不好,要提高教学质量,就必须将《机械制图》课与相关专业课、制图课与相关基础课、制图课前、后内容之间的知识进行整合讲授。     

韵：宋代美学的新追求

“韵”是宋代诗歌美学的一个重要范畴,也是书画美学的一个重要范畴。“韵”和“胸次”有关,“胸次”又和圣哲之学、道义相关,与“俗”是对立的。综合宋代学者的看法,曹植、陶渊明被认为是有“韵”的诗人。“韵”是不可学的,是一种天生的灵性。范温在《潜溪诗眼》中对“韵”作了规定：有余意和美之极。从美学史的角度看,“韵”主要概括了欧阳修、梅尧臣．苏轼等诗歌美学的特征、     

Effect of tramadol on immune responses and nociceptive thresholds in a rat model of incisional pain

Objective： To evaluate the effects oftramadol on the proinflammatory responses in a rat model of incisional pain by investigating its effects on nociceptive thresholds and serum interleukin-6 （IL-6） and IL-2 levels. Methods： Forty-two male Sprague-Dawley （SD） rats scheduled for plantar incision were randomly divided into 7 groups 01=6 in each group）. Rats in Group 1 receiving general anesthesia with no incision were served as control; At 30 min before skin incision, Groups 2-5 were given 5 ml normal saline or 1, 10, and 20 mg/kg tramadol, respectively, intraperitoneally （i.p.）; Group 6 received 10 mg/kg tramadol after operation; Group 7 received 10 mg/kg tramadol before incision, followed by 200 μg/kg naloxone after operation. Mechanical allodynia was measured by electronic yon Frey filament to evaluate the nociceptive thresholds 1 h before incision, and 1 h and 2 h after operation. Serum IL-6 and IL-2 levels were measured by enzyme-linked immunosorbent assay （ELISA） 2 h after operation. Results： Mechanical thresholds decreased significantly and serum IL-6 level increased significantly after operation in Group 2 compared with control （P〈0.01）, and these changes were reversed respectively by tramadol in a dose-dependent manner （P〈0.05 and P〈0.01, respectively）. IL-2 level remained unchanged after operation in Group 2, but decreased in Group 3 （P〈0.05）, then gradually returned to the normal level in Groups 4 and 5. The intraperitoneally injected tramadol （10 and 20 mg/kg） produced a potent and dose-dependent antinocicptive effect on the lesioned paw. The antinocicptive effects of tramadol were partially an- tagonized by naloxone （200 μg/kg）, suggesting an additional non-opioid mechanism. Conclusion： The results suggest that tramadol could be a good choice for the treatment of pain under the conditions that immunosuppression may be particularly contraindicated.     

农用轮式移动机器人系统仿真研究

农用轮式移动机器人是一个复杂的机电一体化系统,在移动机器人的设计过程中,如果缺乏设计经验就需要通过系统仿真的方法来辅助移动机器人的设计.本文针对移动机器人的机械子系统和智能控制系统进行了仿真研究,减少了设计过程中的失误,缩短了设计和开发的周期.