The development and application of a multiple wavelength illumination technique for the vision-based process monitoring of aero-structure riveting

Airframe riveting is a critical process that requires high levels of process monitoring and quality assurance due to the very high risk associated with the failure of such joints. This paper describes the development of the enabling technology developed for a machine vision-based process monitoring system. One of the key factors affecting the performance of a machine vision system is the quality of the lighting. In the application described in this paper the available lighting was severely limited by the confined space in which the system had to operate. The problem was also compounded by the reflective nature of the objects to be examined. The initial images obtained were not suitable for further processing due to the presence of significant shadows and specular reflections. A novel solution to this problem based on multiple wavelength illumination and signal processing is presented along with results from experimental trials of the approach.     

SIMULATION STUDIES OF THE REMOVAL OF WATER FROM ETHANOL BY A CATALYTIC DISTILLATION PROCESS

A new approach based on catalytic distillation (CD) technology was proposed to remove water from ethanol. Isobutylene was introduced to react with water in the CD column. The commercial software simulation tool Aspen Plus was used to investigate the effects of key design factors such as operating pressure and temperature, reactant ratios, reflux and distillate to feed ratios, number of separation and reaction stages, and feed and reaction zone location. It was found that the CD technology offers potential advantages of reduced energy consumption and reduced capital cost over traditional approaches for the removal of water from ethanol.     

Polyimide foams from powder: Experimental analysis of competitive diffusion phenomena

In the present study, various diffusive processes have been investigated during foaming of powdered precursors of polyimide. A detailed analysis of the powdered precursor's characteristics allows for an enhanced morphological understanding of the resulting microstructures and foam unit cell. Parameters that are central to the foaming process such as particle morphology, volatile concentration and sorption-desorption processes are evaluated. Isothermal and non-isothermal desorption experiments have been carried out by thermogravimetric analysis (TGA), and specific diffusive processes have been correlated to thermodynamic and kinetic transitions by means of modulated differential scanning calorimetry (MDSC) of the corresponding materials. It was found that two primary fluxes of volatiles, one out of the external surface of the particles (responsible for volatile desorption) and the other into the growing bubble (responsible for vapor supersaturation inside the bubble) compete against each other creating a competitive scenario that becomes the controlling factor for potential inflation within the precursor particles.     

Improvement of the deflocculating power of polyacrylates in ceramic slips by small additions of quaternary ammonium salts

In this work, we examine the effect of small additions of cationic quaternary ammonium salts (QAS) of different molecular weight on the rheology of an industrial ceramic suspension deflocculated with sodium polyacrylate and sodium metasilicate. The observed shear thinning behaviors obey the typical power law of fluid rheology. In order to characterize the rheological behavior of these slurries, three new parameters are introduced: a low shear rate consistency index and two transient viscosities, distant from the equilibrium, after increasing and decreasing the shear rates. These parameters vary with polyacrylate molecular weight and on additions of small quantities of QAS, which we found to be useful for decreasing the slurry viscosity.     

Grain growth kinetics in Dy-doped Bi0.5Na0.5TiO3 ceramics

Dysprosium-doped bismuth sodium titanate ceramics were prepared using the conventional mixed-oxide method. The amount of dysprosium used was varied from 0 to 2 at.%. The mixed powders were calcined at 800 °C and checked for phase purity using X-ray diffraction technique. The calcined powders were then cold-pressed into pellets and sintered at 1050 °C for the time ranging from 2 to 48 h. The ceramics were checked for phases and microstructures using an X-ray diffractometer and a scanning electron microscope, respectively. The analysis showed that undoped BNT ceramics sintered at longer time exhibited a significant grain growth with non-uniform grain size distribution and shape. The Dy-doped BNT however showed a much more limited grain growth behavior, resulting in smaller grain size and more equiaxed grain shape. It was also found that all Dy-doped BNT ceramics sintered at 48 h possessed lower porosity than those sintered for shorter time.     

Effects of strontium gallate additions on sintering behavior of gadolinia-doped ceria

The densification behavior and grain growth of Ce_0.8Gd_0.2O_1.9 ceramics were investigated with the strontium gallate concentration ranging from 0 to 5 mol%. Both the sintered density and grain size were found to increase rapidly up to 0.5 mol% Sr₂Ga₂O₅, and then to decrease with further addition. Dense Ce_0.8Gd_0.2O_1.9 ceramics with 97% of the theoretical density could be obtained for 0.5 mol% Sr₂Ga₂O₅-added specimen sintered at 1250^∘C for 5 h, whereas pure Ce_0.8Gd_0.2O_1.9 ceramics needed to be sintered at 1550^∘C in order to obtain an equivalent theoretical density. The addition of Sr₂Ga₂O₅ was found to promote the sintering properties of Gd₂O₃-doped CeO₂.     

陶艺的文化性与功能

中国古陶艺制品造型,釉色,装饰等艺术符号都与每时期的阶段性精神和物质生活相联系,但在"现代艺术"文化认识领域中,往往从理论思维角度把陶艺实用目的的物质性排斥在文化范畴之外。艺术常常强调物质的观赏性,而陶艺的实用功能就是这种文化类型的主体,陶艺的文化性和功能性,具有实用和审美文化的高度叠合,永久地承载着实用功能和精神功能两大内容。     

Effective factors on synthesis of the hematite–silica red inclusion pigment

The work focuses on the synthesis of a red ceramic pigment by inclusion of hematite in a fumed silica matrix with different specific surface areas. Iron(II) sulfate was used as hematite precursor. Mixtures of iron(II) sulfate and fumed silica with different mole ratios were heated at different temperatures from 1000 to 1300 °C for 4 h.     

钢包钢水保温覆盖剂的开发

研制了钢包钢水新型保温覆盖剂，主要成分为（%）；15-25C，20-35SiO2,10-20Al2O3,2-5Fe2O3,15-25CaO,2-5MgO，新覆盖剂铺展性与保温性能良好。经转炉钢水160t钢包生产使用，统计数据表明，镇静15min后钢水降温速度由原碳化稻壳覆盖剂1.33℃/min降低到0.93℃/min。     

Sintering studies of nano-crystalline zinc oxide

Sintering and grain growth of nano-crystalline undoped ZnO has been studied in detail over a wide range of temperature and holding time. Below 800 °C, sintering of over 70% theoretical density is not observed, irrespective of particle size. At 900 °C for 6 h, the nano-crystalline sample sinters to 99% of theoretical density whereas the density for as received sample is 93% of theoretical density. However, at 1300 °C or higher, the densification is found to be much faster and after a few hours becomes independent of holding time. Grain growth studies reveal a similar feature of attaining saturation over holding time. The average saturated grain size is found to be ∼1.5 and ∼2.2 μm at 800 and 900 °C, respectively, while at 1300 °C or higher, it is in between 12 and 13 μm.