尿素合成塔检测技术

综述了尿素合成塔在使用过程中可能出现的腐蚀和缺陷形态,并根据失效的可能性给出了有效的检测方法,包括宏观检查、厚度检测、磁粉检测、渗透检测、硬度检测、声发射检测、金相检查和金属磁记忆检测等技术.分别介绍了这些无损检测方法的特点,以及如何在尿素合成塔检验中进行实施.     

结构系统风致疲劳寿命可靠性分析

工程结构一般是由很多构件组成的超静定结构。在风荷载作用下,一个或者几个构件发生风致疲劳破坏不一定导致结构系统失效。首先,结合风速风向联合分布等风荷载特征,给出计算结构系统风致疲劳寿命失效概率的计算流程。其次,由风洞试验结果对目前世界最高的电视塔——610m的广州新电视塔的天线结构进行风振响应分析,风振响应计算中考虑塔身结构的振动对天线结构响应的影响。最后,在以上两步分析的基础上,对该天线结构系统的风致疲劳寿命可靠性进行计算。计算结果表明:用阶段疲劳寿命分枝-约界法识别出17个主要失效模式;S-N曲线中随机变量的参数对主要失效模式的失效概率影响较大;用蒙特卡罗方法计算的100年设计寿命相应的这一实际天线结构的风致疲劳失效概率为4.2%左右。     

广州新电视塔超高异形核心筒施工技术

广州新电视塔核心筒结构具有超高、异形(椭圆形)、空间狭小、层高大、内隔结构复杂等特点,采用内置劲性柱,部分采用C80高强混凝土,使得结构模板设计和施工、设施设置、钢筋加工和绑扎、混凝土制备和泵送均面临很多挑战.通过采用弧形钢模板、整体提升钢平台;优化混凝土配合比设计后,采用两泵两布、一泵到顶等工艺和技术;对混凝土、钢筋等原材料严格控制等措施,有效地解决了上述问题.     

区域标志性建筑形象塑造的思考——以中国金融信息大厦和上海长风跨国采购中心为例

文章针对影响城市区域景观关键因素的区域标志性建筑形象设计问题,从区域标志性建筑概念界定入手,在区域标志性建筑形象的立意、调控、造型、审美四个方面,阐释塑造区域性标志建筑形象的设计要点,并以中国金融信息大厦及上海长风跨国采购中心为例进行探讨。     

基于Elman超声信号时间融合的塔机防碰撞技术

针对塔机防碰撞以缺乏灵活性和时实性的被动防御为主的现状,为实现智能化主动防碰撞的目的,通过分析障碍物轮廓与超声测距时间序列间的映射关系,以时间融合的思想引入Elman网络,并通过变形输入输出实现了单超声传感器由测距序列快速识别障碍物高精度位置信息的功能,并经试验验证可以达到预期低成本、快速度、高精度的塔机工作使用要求,也为低精度传感器获取高精度融合结果提出借鉴思路。     

Performance characteristics of a new spherical metal mesh packing

Various tests and analysis on hydrodynamics and mass transfer properties show that, the newly invented spherical metal mesh packing (SMMP) has excellent properties from three aspects: (i) high void space (∼99%) and lower material cost; (ii) high mass transfer efficiency; (iii) easy installation, good liquid distribution, and prevention of wall flow. Moreover, SMMP is a type of isotropic spherical unit with numerous hollow holes, which realizes the regularization of random packing. The results indicate the potential of developing high-efficiency and energy-saving SMMP-based equipment.     

Design von pulverförmigen und granularen Waschmitteln

In the last fifty years, powder and granular detergents have been significantly improved in performance and ecology: more concentrated (less chemicals), biodegradable surfactants, no phosphates, reduced water and energy consumption. The use of optimized enzymes and bleaching boosters enables lowered wash temperatures and the removal of natural stains. The production of solid detergents runs either in spray towers without and with compaction step, or in a non‐tower agglomeration plant. The latest generation of granulation with an integrated mill for simultaneous drying and grinding allows the production of spherical particles, which can be adjusted (small or large, heavy or light). Future formulations will enable lower washing temperatures.     

Harnstoffhydrolyse für die selektive katalytische Reduktion von NOx: Vergleich der Flüssig‐ und Gasphasenzersetzung

In order to reduce the NO_x concentration in car exhausts usually the selective catalytic reduction with ammonia is used. However, to avoid the transport of ammonia in vehicles urea is applied as NH₃ precursor. Controlled urea decomposition before the injection into the exhaust gas system itself may be accomplished by the use of a separate reactor. Urea decomposition to ammonia in the liquid phase under pressure in a heated reactor was compared to its decomposition in the gas phase. In the liquid phase, higher conversion rates relative to the reactor volume were realized than in the gas phase. Catalysts which showed high activity in the gas phase influenced the decomposition in the liquid phase only slightly.     

Maximum Spreading of Urea Water Solution during Drop Impingement

Droplet impingement of urea water solution (UWS) is a common source for liquid film and solid deposits formed in the tailpipe of diesel engines. In order to better understand and predict wetting phenomena on the tailpipe wall, this study focuses on droplet spreading dynamics of urea water solution. Impingement of single droplets is investigated under defined conditions by high‐speed imaging using shadowgraphy technique. The experimental studies are complemented by numerical simulations with a phase‐field method. Computational results are in good agreement with experimental data for the advancing phase of spreading and the maximum and terminal spreading radius, whereas for the receding phase notable differences occur. For the maximum spreading radius, an empirical correlation derived for glycerol‐water‐ethanol mixtures is found to be valid for millimeter‐sized UWS droplets as well. A numerical simulation for a much smaller droplet however indicates that this correlation is not valid for the tiny droplets of UWS sprays in technical applications.