浮箱履带式行走装置性能的分析探讨

章从地面力学的观点出发，通过对在松软地面上浮箱履行走装置的研究，探讨该装置的附着性能及一些参数对附着性能的影响，并对各种阻力进行分析研究，以寻求提高这种行走装置性能的途径。     

Improvement of flame spraying PEEK coating characteristics using lasers

Flame spraying is frequently used for PEEK coatings elaboration on metallic surfaces. However, this process has a certain number of limitations particularly considering the quality of the coatings like high porosity or low interfacial adherence. For that reason a thermal post-processing is often necessary. From all of the processes which can be used (flame, oven, etc.), laser can be an interesting technology. Then, the aim of this study is to analyse the dependence of the morphological structure (compactness) and the adherence of the flame sprayed PEEK coatings to the stainless steel (304L) and aluminium alloy (AA2017) substrates on laser parameters. Moreover, the influence of the laser beam wavelength (by using a Nd:YAG, CO₂ or diode lasers) on compactness of the coating was analysed. Whatever the laser used, it consists to estimate the most optimized parameters to achieve melting without burning the PEEK material.     

Utility of the RT3 triaxial accelerometer in free living: An investigation of adherence and data loss

There is strong evidence for the protective effects of physical activity on chronic health problems. Activity monitors can objectively measure free living occupational and leisure time physical activity. Utility is an important consideration when determining the most appropriate monitor for specific populations and environments. Hours of activity data collected, the reasons for activity hours not being recorded, and how these two factors might change over time when using an activity monitor in free living are rarely reported. This study investigated user perceptions, adherence to minimal wear time and loss of data when using the RT3 activity monitor in 21 healthy adults, in a variety of occupations, over three (7 day) repeated weeks of measurement in free living. An activity diary verified each day of monitoring and a utility questionnaire explored participant perceptions on the usability of the RT3. The RT3 was worn for an average of 14 h daily with 90% of participants having complete data sets. In total 6535.8 and 6092.5 h of activity data were collected from the activity diary and the RT3 respectively. An estimated 443.3 h (6.7%) of activity data were not recorded by the RT3. Data loss was primarily due to battery malfunction (45.2%). Non-adherence to wear time accounted for 169.5 h (38.2%) of data loss, of which 14 h were due to occupational factors. The RT3 demonstrates good utility for free living activity measurement, however, technical issues and strategies to manage participant adherence require consideration with longitudinal and repeated measures studies.     

Isolation of red wine components with anti-adhesion and anti-biofilm activity against Streptococcus mutans

Red wine is a widely consumed beverage with multiple beneficial effects on human health. In the present paper, the anticaries properties of red wine were studied in vitro and ex vivo. Our in vitro findings shows that dealcoholised red wine, besides exerting antibacterial activity, strongly interferes with Streptococcus mutans adhesion to saliva-coated hydroxyapatite (sHA) beads, promotes its detachment from sHA, and powerfully inhibits in vitro biofilm formation. The main components responsible for such activities were found to be proanthocyanidins. The ability of red wine to inhibit ex vivoS. mutans biofilm formation on the occlusal surface of natural human teeth also was demonstrated.     

A comprehensive assessment of supported titania photocatalysts in a fluidized bed photoreactor: Photocatalytic activity and adherence stability

Titania (TiO₂) was immobilized onto hydroxylated glass beads (HGB) via the thermal bonding and sol–gel coating methods. The photocatalytic activity and adherence stability of the prepared supported photocatalysts were studied in a fluidized bed photoreactor. P25 thermally bonded HGB was found to be more active than sol–gel coated HGB prepared with the same immobilization conditions, while both of them exhibited poor adherence stability, i.e., large amounts of immobilized TiO₂ detached from HGB during the degradation. The adherence stability was improved with limited extents by increasing the calcination temperature or reducing the coverage of TiO₂ on HGB, but either of these approaches resulted in lower activity. The poor adherence stability was ascribed to the fluid shear force and particle friction in fluidized bed, as well as the insufficient bonding between TiO₂ and HGB in terms of the bonding mechanism.

Hydroxylated quartz sands (HQS) and silica gel beads (SGB) were further studied and used as supports. Results have shown that the adherence stability was significantly improved with SGB but only slightly improved with HQS. Characterizations results showed that a coarser surface and more surface Si–OH groups could improve the adherence stability of supported TiO₂ photocatalysts.     

Propagation of a cohesive crack crossing a reinforcement layer

This paper analyzes the propagation of a cohesive crack through a reinforcement layer and gives a solution that can be used for any specimen and loading condition. Here it faces the case of a reinforced prismatic beam loaded at three points. Reinforcement is represented by means of a free-slip bar bridging the cracked section, anchored at both sides of the crack at a certain distance that is called the effective slip length. This length is obtained by making the free-slip bar mechanically equivalent to the actual adherent reinforcement. With this model, the crack development depends on three parameters (apart from those that represent the specimen geometry): the size of the specimen, the cover thickness of the layer and the reinforcement strength. The latter depends on the reinforcement ratio and its adherence to the matrix while the reinforcement is in the elastic regime; otherwise, on the reinforcement ratio and its yielding strength. The thickness of the reinforcement cover influences the first stages of the development of the cohesive crack, and thus it also affects the value of the load peak. The computed load-displacement curves display a noticeable size effect, as real cohesive materials do. Finally, the model is able to fit the available experimental results, and accurately reproduces the influence of size, amount of reinforcement and adherence variations in the tests.     

Surface treatment effects on ceramic matrix composites: Case of a thermal sprayed alumina coating on SiC composites

High-temperature-resistant ceramics are already used for many industrial applications. In response to the growing demand, the need for further research considering the final application and the global behaviour of the material is becoming increasingly apparent. In general, it is possible to comply with many specifications, just by treating the surface of the ceramics. For instance, it is possible to achieve an adequate mechanical strength by depositing a protective layer with different structure and/or chemical composition. Regardless to the specification, the adhesion coating/substrate is the most crucial property to be considered. Conventionally, surface degreasing (applying solvents to remove organic impurities) and grit blasting (corundum) are carried out as a two steps pretreatment prior to the thermal-spraying operation to guarantee a mechanical anchorage of the molten particles to the substrate. However, some substrates are grit-blasting sensitive and therefore, alternative treatments should be considered. In these cases, the adherence of the coating must be attained by others means, either from a chemical point of view by modifying the surface wettability, or from a photonic one.Within this context, this study aims to explore the surface modifications induced on SiC composites (Ceramic Matrix Composites, CMC) before plasma spraying of alumina coatings. The effect of two different pre-treatments, deposition of a silicon bonding layer and short-pulse laser treatment (Nd:YAG), on the coating-substrate interface is investigated. A better chemical affinity between the alumina coating and the silicon carbide CMC has been observed with the silicon bond coating. On the other hand, a mixture of chemical and mechanical interaction induced by a cone-like structure occurs when treating the SiC CMC surface by laser prior thermal-spraying.     

Corrosion and adherence properties of cement clinker on porous periclase-spinel refractory aggregates with varying spinel content

The corrosion and adherence properties of cement clinker on porous periclase-spinel refractory aggregates with varying spinel content were examined using a static crucible test and a sandwich test, respectively. The reaction characteristics of porous periclase-spinel aggregates and cement clinker and the effects of spinel content on the adherence property were investigated through scanning electron microscope (SEM), energy dispersive spectrometer (EDS), and FactSage^® thermo-chemical software. It was observed that the spinel content and pore characteristics strongly affected the corrosion results and thus affected the adherence ability of cement clinker on porous periclase-spinel aggregates. With an increase in the spinel content, the amount of glass phase formed from the reaction of the refractory and cement clinker increases because the rate of the spinel dissolution into the cement clinker is higher than that of periclase. The glass phase acts as a bridge between the cement clinker and the aggregate to enhance the adherence property, which depends on the amount, area distribution and viscosity of the glass phase and its penetration in aggregates. When the spinel content is 15–40 wt%, the refractory aggregate not only has a high cement clinker resistance but also a high adherence property. Once the spinel content exceeds 50 wt%, the skeletal structure of the aggregate will be destroyed, which will lead to a substantial decline in the cement clinker resistance.     

水性UV光油附着性能的研究

附着力是水性UV光油非常重要的性能,直接影响了光油的涂布质量和后续加工工序的进行。采用不同的预聚物及单体制备水性UV光油样品,通过一系列实验研究,探讨了体积收缩性及润湿性对水性UV光油附着力的影响。实验结果表明,体积收缩性对光油的附着力有明显的影响,体积收缩率越小,光油对基材的附着力越好;单体官能度越高,体积收缩越大;润湿是水性UV光油能附着在基材上的必要条件,对附着力没有直接的影响。