论流水施工在公路工程中的局限性

结合工程项目实践，探讨了流水施工在公路工程应用中的局限性，分析了流水施工的影响因素，并提出了相关的应用改进措施和建议，从而达到有效提高施工作业效率的目的。     

变频器综合实践 第5讲 变频工艺控制系统的综合实践

由于变频调速具有调速范围广、调速精度高、动态响应好等优点，在许多需要精确速度控制的应用中，变频器正在发挥着提升工艺质量和生产效率的显著作用。因此，变频工艺控制在纺织、食品、饮料、包装、造纸、机床、电梯等行业的应用前景和发展潜力都不可小觑。     

Study of Cheese Associated Lactic Acid Bacteria Under Carbohydrate-Limited Conditions Using D-Stat Cultivation

The metabolic pathways alternative to glycolytic energy (ATP) during growth of starter and nonstarter lactic acid bacteria were studied simulating the depletion of carbohydrates during cheese ripening. D-stat cultivation strategy with the gradual decrease of galactose concentration in tryptone-arginine feeding medium was used. With the decrease of galactose feeding, the biomass yield calculated on carbohydrate consumption (Y_X/HEX) and acetate/lactate production ratio of all strains increased. We assume that ATP and biomass yields improved by directing the pyruvate flow from lactate to acetate and that metabolic energy could be obtained either by producing acetate from carbohydrates or from arginine metabolism in ADI-positive strains. Four LAB strains out of eight produced ornithine from arginine indicating active arginine-deiminase (ADI) pathway. These ADI-positive strains achieved 3-10 times higher Y_X/HEX than ADI-negative strains in tryptone-arginine medium. Lactobacillus plantarum also used serine as an energy source. Starters and NSLAB strains using the amino acids arginine and serine or limited amounts of carbohydrates therefore have the potential to influence flavor production in cheese more efficiently.     

角形级联型STATCOM不平衡工况下的无功功率控制策略

针对电压不对称工况下级联静止同步补偿器(STATCOM)的无功功率控制问题,提出一种适用于角形级联型STATCOM的柔性无功控制策略,通过改变正序和负序无功功率指令值的比例,能够在电压不对称工况下柔性地调节输出的正序和负序无功功率,改善公共连接点电压。结合应用于常规两电平的柔性无功控制策略与角形STATCOM电流控制指令求解方法,利用相量分解法,推导了电压不对称工况下的零序电流和相电流解析表达式,所提策略利用电压和电流瞬时值实时计算电流指令,具有较好的动态性能,同时根据推导的相电流表达式可以实时限制相电流幅值最大值,在提供无功功率的同时可以确保STATCOM运行在安全范围以内,提高了STATCOM的工程实用性。最后,仿真验证了所提方法的正确性和有效性。     

空间句法在城市规划中应用的局限性及改善和扩展途径

空间句法是一种在建筑领域认可度比较高的定量研究方法。近来得到城市规划领域关注,并广泛应用于城市规划理论和实践的探索。然而国外地理学空间分析领域对空间句法理论方法在城市规划中的应用一直存在争议。但随着近年来理论自身的不断修正和其他学科的不断扩展,增强了空间句法理论方法在城市规划应用的适应性。现着重从地理空间分析的视角讨论空间句法在城市规划中应用的局限性,同时回顾空间句法方法自身的近期发展,以及地理空间分析领域对其方法的扩充和发展。     

植物药材农药残留药典标准分析研究

该文系统研究我国药典与主要发达国家药典中涉及植物药材农药残留限量及检测技术的相关规定,探讨我国药典标准在农药残留规定方面的不足。结果表明:我国药典的农药残留限量标准缺乏针对性和实效性,应重视登记使用农药和国际关注的农药种类;检测技术则应以定性准确、灵敏度高为特点的质谱技术作为检测手段制定农药残留检测标准方法。     

论社会中心教学文化的历史、价值与局限

社会中心教学文化是以社会发展为本位而组织起来的,充分彰显教学的社会适应和社会改造功能,以培养合格公民和促进社会进步为目的而生成的一种教学生活方式。它的存在与发展有着特殊的时代背景和连续的历史脉络,它具备有利于汲取社会知识经验、维护社会稳定与发展、进行社会批判、引领社会进步、促进师生参与社会生活、使教学文化由迷失走向觉醒的价值。但也存在宣扬社会沙文主义、压抑人自由发展、忽视教学主体对社会和教育的改造、鼓吹工具理性而缺乏反思精神和人文信念、使师生沦为被动适应者的局限。因此,只有对其理性地批判继承才有助于师生过上幸福的教学生活。     

朗肯土压力局限性的有限元法分析

针对挡土墙上主动土压力计算方法中朗肯理论的局限性,运用有限元法对其进行了分析,以Mohr-Coulomb准则作为屈服准则进行计算,得出设计时如无实测资料,用有限元计算的土压力比用朗肯理论计算出的土压力更安全。     

钢筋混凝土构件正截面极限承载能力计算法

介绍了钢筋混凝土构件正截面极限承载能力的一种新型计算方法。它对大小偏心受压,根据力的平衡原理,将受压区高度或压应变用黄金分割法(优选法)进行搜索,得到数值解。这样对各种截面形状、各种受力状态,编一个程序即可解决,故方法简明实用,有利于计算机编程。这也是对经典的理论解析法的补充。     

Circular tests for HSM machine tools: Bore machining application

Today's High-Speed Machining (HSM) machine tool combines productivity and part quality. The difficulty inherent in HSM operations lies in understanding the impact of machine tool behaviour on machining time and part quality. Analysis of some of the relevant ISO standards [230. Acceptance code for machine tools. Part 4, Circular tests for numerically controlled machine-tools, April 1998, 10791. Test conditions for machining centres. Part 6, Accuracy of feeds, speeds and interpolation, September 1998, 10791. Test conditions for machining centres. Part 7, Accuracy of feeds, speeds and interpolation, September 1998] and a complementary protocol for better understanding HSM technology are presented in the first part of this paper. These ISO standards are devoted to the procedures implemented in order to study the behaviour of machine tool. As these procedures do not integrate HSM technology, the need for HSM machine tool tests becomes critical to improving the trade-off between machining time and part quality. A new protocol for analysing the HSM technology impact during circular interpolation is presented in the second part of the paper. This protocol, which allows evaluating kinematic machine tool behaviour during circular interpolation, was designed from tests without machining. These tests are discussed and their results analysed in the paper. During the circular interpolation, axis capacities (such as acceleration or Jerk) related to certain setting parameters of the numerical control unit have a significant impact on the value of the feed rate. Consequently, a kinematic model for a circular-interpolated trajectory was developed on the basis of these parameters. Moreover, the link between part accuracy and kinematic machine tool behaviour was established. The kinematic model was ultimately validated on a bore machining simulation.