Fatigue of teflon bladder materials

The fatigue properties of Teflon laminates employed in the fabrication of liquid propellant expulsion bladders were studied by cyclically stretching specimens to constant load in order to achieve a correlation of cycles to failure versus the maximum stress amplitude. This approach provides a useful technique for evaluating the resistance of bladder materials to fatigue failure which could be caused by vibration-induced cyclic loadings during ground testing and launch. Further, the data provides for a direct comparison of the relative fatigue properties of Teflon laminates and, in particular for those which were studied, the relative fatigue properties correlated with their ultimate breaking stresses. This observation, which suggests a simple and rapid method for evaluating relative fatigue behavior of candidate Teflon laminates, is discussed along with the effect of delamination on the fatigue properties observed for one laminate.     

滤汁上浮清净

1 引言 澄清是制糖生产过程中一个重要的工序.在经过压榨机或者渗出器提汁之后,混合汁必须进行澄清,以除去悬浮物、中和有机酸和降低蔗汁浊度.通常,这一步操作是通过添加石灰到蔗汁中并进行加热完成,而当这些澄清剂不足时,也添加一定的磷酸作为补充.     

Physical Characterization of Cigarette Smoke Aerosol Generated from a Walton Smoke Machine

Mainstream cigarette smoke generated using a Walton smoking machine and Kentucky 2R1 research cigarettes was studied. Results showed that puff volume and total particulate matter were consistent after the first puff, with average values of 35.6 cm³ and 3.37 mg, respectively. The particle size distribution, measured with a multijet cascade impactor, was not related to butt length or relative humidity (≤95%), but was strongly dependent on the aging time. Based on simple monodisperse coagulation, the mass median aerodynamic diameter was calculated to be 0.45 μm at a dilution ratio of 21.7. Using a technique based on the dimensional change of collected droplet particles at various viewing angles of a scanning electron microscope, the count median diameter was estimated to be 0.22 μm. These values were in good agreement with those reported by others. The results suggest that there is a dilution value critical to the rapid evaporation and final particle size of the cigarette smoke aerosol. Once reaching this value, further dilution has little effect on the final particle size. By using the derived mass concentration and size distribution, the particle density, number concentration, and coagulation coefficient of the cigarette smoke aerosol were estimated to be 1.12 g/cm³, 7.20 × 109 particles/cm³, and 6.64 × 10 ^?10 cm³/s respectively. Solid particles > 1 μm were found in the first few puffs. These were considered to consist of tobacco debris.     

Hygroscopic properties of magnetic recording tape

Relative humidity has been recognized as an important environmental factor in many head-tape interface phenomena such as headwear, friction, staining, and tape shed. Accordingly, the relative humidity is usually specified in many applications of tape use, especially when tape recorders are enclosed in hermetically sealed cases. Normally, the relative humidity is believed regulated by humidification of the fill gas to the specification relative humidity. However, this study demonstrates that the internal relative humidity in a sealed case is completely controlled by the time-dependence of the hygroscopic properties of the pack of magnetic recording tape. Procedures for the humidity conditioning of sealed cases must be established on the basis of the tapes' hygroscopic properties, and not on humidification of the fill gas. Without taking the tape into account, the final, stabilized, relative humidity can be significantly different from the specification requirement. Additionally, this same study finds differences in the hygroscopic properties of the same brand of tape, which apparently results from aging, and which may have significance on the long-term humidity-regulating behavior in a sealed case, and on the occurrence of head-tape interface phenomena from the long-term use of the tape. This article presents results on the basic hygroscopic properties of tape, its humidity-regulating behavior in a sealed case, and includes a theoretical commentary on the relative humidity dependence of head-wear by tape.     

The effect of visual design and placement of intra-article navigation schemes on reading comprehension and website user perceptions

Multipage articles on websites require intra-article navigation schemes and, when well designed, such navigational schemes signal the topical structure of the article’s contents. This study examines the effect of the visual design and placement of intra-article navigation schemes on website users’ reading comprehension and user experience. Using an informational medical website, four treatments of an intra-article navigation scheme were varied in their level of visual distinctness from the site’s other navigation devices and in their placement in the web page. Significant differences were found for reading comprehension and perceived knowledge gained. Reading comprehension was highest with an intra-article navigation scheme that was most visually distinct as an article table of contents and that replaced the site’s navigation on the web page layout. Paradoxically, participants’ perceptions of the amount of knowledge they gained were rated lowest for this condition. Suggestions for navigation design are presented.     

Positive Coping and Stress-Related Psychological Growth Following Lower Limb Amputation.

Objective: To present a cross-sectional qualitative exploration of how individuals cope with a lower limb amputation and to examine the influence of positive coping and stress-related psychological growth on adjustment. Participants: 12 patients with a lower limb amputation. Setting: Artificial Limb and Appliance Centre in South Wales, United Kingdom. Design: Semistructured interviews, using grounded theory for analysis. Measures: The Hospital Anxiety and Depression Scale (A. Zigmond & R. Snaith, 1983) and the Rosenberg Self-Esteem Scale (M. Rosenberg, 1965). Results: No evidence of psychological distress among participants. Qualitative analysis revealed 5 categories of coping, and a theoretical model of positive coping following lower limb amputation was generated. Conclusions: Coping strategies evolve, reflecting the changes in psychological demands postamputation. Positive coping and psychological growth facilitates psychological adjustment. Clinicians may facilitate adaptive outcomes by appreciating the positive psychology perspective. (PsycINFO Database Record (c) 2010 APA, all rights reserved)