氮气弹簧液压卡盘的设计与分析

通过分析坑道钻机中常见胶筒卡盘和碟簧卡盘的不足之处,设计出一种氮气弹簧液压卡盘．通过理论计算及结构分析,利用ADAMS仿真软件对氮气弹簧液压卡盘进行了运动学及动力学仿真,并对卡瓦和钻杆出现磨损时卡盘夹紧力的变化进行了分析．仿真结果表明此卡盘结构合理,性能良好,工作可靠性高．     

Analysis and improvement of an authentication protocol for the multi-server architecture

Cryptanalysis of Li et al.'s authentication protocol shows that it is vulnerable to masquerade attack, session key disclosure attack and forge smart card attack. To overcome these security flaws, an improved protocol is presented. This protocol proves secure against some possible attacks. Besides, the improved scheme maintains the features of identity anonymity, concise registration, simple operation, and so on.     

Heat treatment temperature effect on the microstructure and optical properties of Dy2(WO4)3 powders

Dy₂(WO₄)₃ powders were synthesized through liquid-phase reaction. The structure transformation of Dy₂(WO₄)₃ powders were analyzed by differential scanning calorimetry (DSC), X-ray diffractometer (XRD) and Fourier transform infrared spectroscopy (FTIR). The optical absorption and photoluminescence properties were characterized by UV-vis-infra diffuse reflectance spectra and fluorescence spectra. The Dy₂(WO₄)₃ host could absorb deep UV light and transfer the energy of UV light to Dy³⁺ ions, which convert the high-energy UV light to blue light (482 nm, ⁴ F _9/2→⁶ H _15/2) and yellow light (547 nm, ⁴ F _9/2→⁶ H _13/2). The Dy₂(WO₄)₃ powders could also absorb near UV light and exhibit blue and yellow emissions near 482 and 547 nm, respectively. Heat treating promoted the crystallization and regulated the micro-structure of Dy₂(WO₄)₃ hosts. The bands of W-O_d anti-symmetric stretching vibration exhibited red shift with the increasing of sintering temperature. The W-O_b-W groups tended to combine with each other to form W-O_c-W groups after heat treating. These regulation of micro-structure had influence on the luminescent color of Dy₂(WO₄)₃. The samples could emit yellow-green, white-yellow and white light under the excitation of 350 nm after being treated at 600, 800 and 1 000 °C, respectively. The prepared Dy₂(WO₄)₃ powders have potential to act as UV absorber for solar cell to improve the conversion efficiency and also exhibit potential for white light LED.     

Fabrication and thermal insulating properties of ATO/PVB nanocomposites for energy saving glass

The pechini method was used to synthesize antimony-doped tin oxide (ATO) nanoparticles, and the subsequent solution co-blend was employed to fabricate ATO/PVB nanocomposites. Uv-Vis-NIR spectra show that the addition of ATO nano particles can significantly enhance the thermal insulating efficiency of ATO/PVB nanocomposites. With the increase of ATO content, the thermal insulating efficiency is increased. Uv is almost fully absorbed by all ATO/PVB nanocomposites. Vis transmittance-haze spectra reveal that ATO/PVB nanocomposites exhibit higher Vis transmittance of over 72.7% and lower haze of below 2% when ATO content is in the range of 0.1 wt%–0.5 wt%. The thermal insulating tests indicate that in comparison with the pure PVB film, nanocomposite films with 0.1 wt%–0.5 wt% ATO can reduce temperature of 1–3 °C, suggesting that this novel nanocomposite can be used for energy-saving glass.     

Enhanced adsorption of Pb(II) ions from aqueous solution by persimmon tannin-activated carbon composites

The modification of activated carbon with persimmon tannin and its application for the removal of Pb(II) ions were carried out by batch method. The effects of solution pH, contact time, temperature and initial concentration on the immobilization of persimmon tannin were studied. The experimental results showed that the experimental data of persimmon tannin and Pb(II) fitted better by Langmuir adsorption isotherm model and pseudo-second order model. The adsorption capacities of adsorbents for persimmon tannin and Pb(II) were calculated from the Langmuir isotherm model, and found to be 42.97 and 12.40 mg/g at optimum pH, respectively. It was noted that the adsorbent exhibited the best adsorption property for Pb(II) when 1.0 g activated carbon was modified by 17.32 mg persimmon tannin. The modified activated carbon is more effective than the plain activated carbon, and it is expected to be an economic and effective adsorbent for the disposal of wastewater containing Pb(II) ions.     

附加几何条件所得到的平面时差定位解析方程

传统的平面时差定位问题需要求解非线性方程组,且得不到解析解。该文的分析表明对于平面任意布置的3站时差定位系统,因存有两个独立的三角形,故利用余弦定理可得到两个独立的平面几何方程,一旦作为附加的几何条件与时差定位方程联解,即可获得任意平面布站时的时差定位解析方程。     

我国食品法律法规标准体系的建设与完善对策

对我国食品安全背景进行了认真分析,系统地阐述了我国64年来食品安全法律、法规、标准体系的5个发展过程,论述了食品安全立法繁荣的原因,分析了存在的问题,提出了完善我国食品安全法律法规标准体系10个方面的对策建议.     

饮食文化旅游产品开发体系探析

饮食文化旅游资源具有区域历史性、人文艺术性、参与体验性等特征,能满足旅游者对于异质文化的体验需求,具有很好的开发前景。饮食文化旅游产品形式表现为商业产品、景观产品、社会经济类产品,其开发体系可从产品生产、人文历史和经济区域三个方面构建,开发过程从初级阶段的特色餐饮旅游产品、中级阶段的愿景与文化展示,到高级阶段的产业经济与饮食文化现象整合三个阶段逐步推进。     

荷移分光光度法测定多杀菌素

建立一个新方法测定多杀菌素发酵液中多杀菌素含量.用分光光度法研究多杀菌素与碘在乙醇中的荷移反应,形成的络合物中多杀菌素与碘分子的摩尔比是2:3,生成的络合物在290 nm和360 nm处有2个吸收峰,表观摩尔吸光系数分别是3.89×103和2.35×103L/( mol·cm),当多杀菌素浓度为200 mg/L时,相对标准偏差(RSD)为0.712％(n=9).利用本法测定多杀菌素发酵液中有效成分多杀菌素的含量,并与文献报道的高效液相色谱法进行比较,两者结果基本一致,回收率为98.2％.     

校友会在高职院校学生顶岗实习中的作用探析

校友会可以在高职院校学生顶岗实习中发挥重要的作用.但是,在学生顶岗实习实际工作中,校友会作用的发挥存在着如工作不利,对实习学生缺少了解及实习管理精力不足等问题.提出了发挥校友会作用的具体对策,即加强毕业生跟踪调查和联系;加强学校与校友之间的相互促进;定期选派专职教师到校友企业挂职等.