烟气轮机叶片寿命的影响因素和评估方法

合理准确预测烟气轮机叶片寿命,是催化裂化装置安全运行的必要保障。文章研究了影响烟气轮机叶片疲劳寿命的因素;评述了叶片疲劳寿命评估方法;选取并介绍了适合烟气轮机叶片寿命的评估方法;阐明了目前存在有关叶片寿命的关键问题。     

雏议造价监理工程师在工程建设中的作用

分析了造价监理工程师如何在在施工前期的招投标、施工组织方案技术经济评价和工程施工阶段的签证、索赔、进度款控制等方面对造价进行合理确定和有效控制。     

A Clock Generator for High-Speed High-Resolution Pipelined A/D Converter Zhao Lei(赵磊) , Yang Yintang(杨银堂), Zhu Zhangming(朱樟明), Liu Lianxi(刘帘羲)

A clock generator circuit for a high-speed high-resolution pipelined A/D converter is presented.The circuit is realized by a delay locked loop(DLL),and a new differential structure is used to improve the precision of the charge pump.Meanwhile,a dynamic logic phase detector and a three transistor NAND logic circuit are proposed to reduce the output jitter by improving the steepness of the clock transition.The proposed circuit,designed by SM1C 0.18μm 3.3 V CMOS technology,is used as a clock generator for a 14 bit 100 MS/s pipelined ADC.The simulation results have shown that the duty cycle ranged from 10%to 90%and can be adjusted.The average duty cycle error is less than 1%.The lock-time is only 13 clock cycles.The active area is 0.05 mm2 and power consumption is less than 15 mW.     

电子电气产品如何引入生态设计

在全球环保法规以及可持续发展的要求下,我国电子电气企业为避免出口损失,亟需将生态设计引入产品的研发。该文介绍了电子电气产品引入生态设计的一般流程,并提供生态设计策略供企业参考。     

激光喷丸强化变形镁合金的疲劳寿命数值分析

以ABAQUS和MSC.fatigue软件为平台, 建立了激光喷丸强化前后试样疲劳寿命及薄弱位置预测的有限元分析模型。为研究材料强度对激光喷丸强化效果的影响, 以AZ31B和ZK60两种不同强度变形镁合金为对象, 对激光喷丸强化后的残余应力和塑性变形进行了分析, 并预测了喷丸前后的疲劳寿命, 两种材料的疲劳寿命增益分别为112.04%和181.2%。结果表明, 高强度材料激光喷丸强化效果优于低强度材料。     

基于关系代数树的查询优化方法实例分析

在数据库操作中查询操作所占比重最大,而查询操作所基于的SELECT语句在SQL语言中又是代价最大的语句。结合实际课题应用,提出了基于关系代数树结构的SQL查询优化策略。利用改进查询计划的代数定律,分析基于关系代数树的关系代数式查询优化方法、研究关系代数表达式与SQL查询的等价变换准则、分析关系代数表达式等价变换前后的查询代价;通过实验、实例以及代价估计验证了利用关系代数树改进数据库查询优化操作的优势。     

改性填料在瓦楞原纸表面施胶中的应用

将经甲壳素和有机盐改性的填料以一定比例替代原淀粉进行瓦楞原纸表面施胶,其最佳替代比例为15%,瓦楞原纸物理指标不受影响,吨纸成本下降9元。     

培养液匀浆人参发根抗氧化、抗黑色素瘤作用

以培养液匀浆人参发根为实验材料,选用Cu2＋螯合能力、多酚氧化酶活力、总抗氧化能力3 种方法对其 抗氧化能力进行测定;采用流式细胞术对黑色素瘤细胞A375凋亡、细胞周期进行测定。结果表明：随着质量浓 度的增大,培养液匀浆人参发根的Cu2＋螯合率逐渐提高,在100 mg/mL时与VC差异不显著（P＞0.05）;40、 60、80、100 mg/mL时培养液匀浆人参发根与VC的多酚氧化酶活力差异不显著（P＞0.05）;培养液匀浆人参 发根的总抗氧化能力具有质量浓度依赖性,在100 mg/mL时达到0.877 4 mmol FeSO4/g。与对照组相比培养液匀 浆人参发根组细胞凋亡显著（P＜0.05）;S、G2/M期比例升高,G0/G1期比例下降。结论：人参发根具有抗氧 化、抗黑色素瘤作用。     

Degradation of 5‐Hydroxymethylfurfural in Honey

ABSTRACT: 5‐Hydroxymethylfurfural (HMF) is the most important intermediate product of the acid‐catalyzed dehydration reaction of hexoses and/or Maillard reaction; furthermore, it is the most used index to evaluate thermal damages or ageing in food products. Usually its degradation reactions, being very slow, are neglected. This study reports the findings concerning the degradation kinetics of HMF, in honeys of different floral origin at a temperature between 25 and 50 °C. The results highlighted higher degradation rates (k_{HMFdegradation}) compared to the corresponding formation rates (k_HMFformation) in chestnut and citrus samples. Similar k‐values were found in multifloral honey. Moreover, the reaction of HMF degradation was characterized by lower activation energy (E_a) values compared to E_a formation values. The final concentration of HMF in honey, during storage at room temperature, should be ascribed to high sugar concentration. The fluctuation of HMF in honeys could depend on the equilibrium between the accumulation and the degradation processes. This can affect the validity of HMF as storage index in some honeys, above all during the analysis of those honeys whose legislation is too restrictive (citrus) or in chestnut honey analysis where it does not accumulate.     

钢包材料SM490B钢断裂及中温低周疲劳性能研究

针对新型钢包包壳材料SM490B钢，进行了室温断裂韧度、疲劳裂纹扩展速率及350℃（32作状态下，钢包包壳表面的最高温度）下的低周疲劳试验研究。结果表明，SM490B钢的强度和断裂韧度明显高于包壳曾用材料SM41A（Q235）、20g。在试验所取的应力强度因子幅值范围内，与Q235A钢和20g钢相比，SM490B钢的疲劳裂纹扩展速率较快。350℃下的低周疲劳寿命高于压力容器常用钢材16MnR钢30（1℃下的疲劳寿命。新型钢包包壳材料采用SM490B钢，可大大减少包壳开裂的可能性，提高钢包的承载能力和使用安全性，延长钢包的使用寿命。