湿热环境下CFRP-水泥砂浆的抗弯性能

 1.Key Laboratory of Advanced Textile Materials and Manufacturing Technology;Ministry of Education;Zhejiang University of Science and Technology;Hangzhou;Zhejiang 310033;China; 2.Hangzhou College of Vacation Technology;Hangzhou;Zhejiang 310018;China     

FRP-水泥砂浆抗弯性能的研究

利用三点弯研究了水泥砂浆外贴碳纤维和芳纶纤维片材后的抗弯性能,并对2种纤维进行表面处理,探讨纤维的表面处理对FRP水泥砂浆体系抗弯性能的影响。结果表明,用等离子体分别对碳纤维和芳纶纤维进行表面处理,CFRP和AFRP水泥砂浆的最大断裂载荷都能显著提高,而且构件在受弯过程中没有发生剥离破坏,FRP被拉断,纤维高强的特点得到充分发挥。     

废纸造纸污泥灰的制备及其对水泥砂浆性能的影响

为提高废纸造纸污泥的资源化利用效率,在煅烧温度650℃的条件下制备了废纸造纸污泥灰,对掺有0、5%、10%、15%和20%污泥灰的水泥砂浆流动度、凝结时间和抗压强度进行了研究。结果表明,污泥灰的掺入会降低水泥砂浆的流动性,当污泥灰掺量从0增加到5%时,初始流动度损失约14.2%,当污泥灰掺量增加到20%时,初始流动度损失约29.6%;污泥灰的掺入会缩短水泥砂浆的凝结时间,当污泥灰掺量为15%时,凝结时间明显缩短,砂浆初凝时间缩短约53 min,终凝时间缩短约37 min;掺加污泥灰有利于提高水泥砂浆的抗压强度,当污泥灰掺量从0增加到5%时,水泥砂浆的抗压强度提升较大,其中3天抗压强度提升约12.5%,28天抗压强度提升约8.7%。     

柔软整理对大麻纤维性能的影响

 为提高大麻纤维的柔软性、可纺性能,针对不同脱胶工艺处理后的大麻纤维在分梳前进行柔软整理。分析柔软整理前后大麻纤维经分梳后的物理机械性能。结果表明：柔软整理后大麻纤维的断裂强度及断裂伸长率均有不同幅度的提高,而且当脱胶程度较低时,柔软整理后大麻纤维的断裂强度与伸长率提高幅度较大;柔软整理后的大麻纤维比整理前的抗弯刚度、摩擦因数均有不同幅度的降低,而且当脱胶程度较低时,柔软整理后大麻纤维的摩擦因数降低的幅度较小;柔软整理后,大麻纤维的回潮率比柔软前均有不同幅度的提高,脱胶程度较低时大麻纤维柔软整理的作用较明显。说明柔软整理有助于改善大麻纤维的可纺性能。     

芳纶1313混纺织物耐热性能的测试研究

芳纶混纺织物的混纺比对其耐热性能有较大的影响.通过对不同比例的芳纶1313/棉混纺织物、芳纶1313/羊毛混纺织物耐热性能的测试,研究了混纺比与织物耐热性能之间的关系,为根据耐热、阻燃的要求设计不同混纺比织物提供参考依据.     

最近的功能性纤维材料—耐热性及阻燃性

综述了从杂志及专利看最近功能性纤维材料有关耐热及阻燃性的动向,并介绍功能纤维新技术和静电纺功能纤维新技术两参考书的信息。     

最近的功能性纤维材料一耐热性及阻燃性

综述了从杂志及专利看最近功能性纤维材料有关耐热及阻燃性的动向，并介绍功能纤维新技术和静电纺功能纤维新技术两参考书的信息。     

水泥砂浆包装机中混合料在料仓内自由流动的数值模拟

为认知水泥砂浆混合物料靠重力自由流出的流动状态,对包装机出口处料仓内的水泥砂浆混合物的三维定常流场进行了数值模拟。考虑到物料在料仓内流动时是密实状态,因此简化为流体模型进行分析,同时综合考虑了混合物料所受重力和内摩擦力对流动性能的影响。模拟结果直观显示了料仓内的速度和流线等特征,研究结果对研究背压式水泥砂浆包装机的设计与改进提供了一定的理论指导。     

Outlast腈纶纤维的耐化学试剂性研究

探讨Outlast腈纶纤维的耐酸碱试剂性.将纤维在不同浓度、不同温度、不同时间的酸碱试剂下进行处理并测试其力学性能.研究结果表明:Outlast腈纶纤维有稳定的耐酸碱试剂性;浓度、温度和时间三因素都影响Outlast腈纶纤维力学性能,随着这三者量的增加纤维的断裂强力和断裂伸长均减小.     

单蜂窝纸芯的抗弯稳定分析

针对现有蜂窝纸制品开发要求,分析了在轴向动力荷载作用下单蜂窝纸芯的抗弯特征.首先在理论分析的基础上完成单蜂窝芯的建模;其次在有限元软件进行抗压分析,发现蜂窝纸高度较低的情况下经历4个阶段:线弹性阶段、弹塑性阶段、塑性坍塌阶段、密实化阶段.但是当高度超过一定值后在塑性坍塌阶段容易产生折弯现象.同时得到蜂窝纸压缩变形过程的载荷力和剪应力变化随着压溃位移的变化曲线,该过程中载荷力和剪应力超过屈曲临界点后变化明显.最后用实验验证了载荷力的变化曲线,蜂窝纸芯内部存在空气压力以及胶水等使蜂窝纸具有更大的承载能力,导致了实验值比仿真值偏大.     

Heat resistance of Listeria monocytogenes

The heat resistance data on Listeria monocytogenes in culture media and foods are summarized. Most heat resistance data for foods have been obtained in dairy, meat, poultry, and egg products. Limited data have been published on seafood, fruits, and vegetables. The methodologies employed have evolved over time; hence data from earlier experiments are not directly comparable to more recent studies. Many factors influence the heat resistance of L. monocytogenes. Variation exists among different strains in their ability to withstand heat treatment. In addition, heat resistance is influenced by age of the culture, growth conditions, recovery media, and characteristics of foods such as salt content, a(w), acidity, and the presence of other inhibitors. Listeriae are more heat resistant than most other nonspore-forming foodborne pathogens, and thus, processing recommendations based on data from experiments with Salmonella spp. or pathogenic Escherichia coli may not be sufficient to eliminate similar numbers of L. monocytogenes. The data provided in this review may prove useful for food processors in determining appropriate times and temperatures for producing foods free of vegetative pathogens.     

黄麻纤维对砂浆早期抗裂性能的试验研究

研究黄麻纤维在纤维掺量、纤维长度及混杂纤维配合比不同的情况下分别对砂浆早期抗裂性能的影响,并与聚丙烯腈纤维作对比研究。试验结果表明：黄麻纤维能有效地增强砂浆的早期抗裂性能,并随着纤维掺量的增加、纤维长度的减小以及混杂纤维中起主要作用的黄麻纤维含量的增加而增强;黄麻纤维对砂浆早期抗裂性能的增强效果不及聚丙烯腈纤维。     

Heat resistance of juice spoilage microorganisms

The heat resistance of various yeasts (Saccharomyces cerevisiae, Rhodotorula mucilaginosa, Torulaspora delbrueckii, and Zygosaccharomyces rouxii), molds (Penicillium citrinum, Penicillium roquefortii, and Aspergillus niger), and lactic acid bacteria (Lactobacillus fermentum and Lactobacillus plantarum) obtained from spoiled acid or acidified food products was determined in 0.1 M citrate buffer at pH values of 3.0, 3.5, and 4.0. S. cerevisiae was the most heat resistant of the microorganisms in citrate buffer, and its heat resistance was further evaluated in apple, grapefruit, calcium-fortified apple, and tomato juices as well as in a juice base with high fructose corn syrup. Decimal reduction times (D-values) and changes in temperature required to change the D-value (z-values) for S. cerevisiae were higher in the juices than in citrate buffer at all pH values tested. The D57 degrees C(135 degrees F)-values varied from 9.4 min in the juice product with pH 2.8 to 32 min in a calcium-added apple juice with pH 3.9. The S. cerevisiae strain used in this study can be used in thermal-death-time experiments in acidic products to calculate process conditions and in challenge tests to validate the calculated temperatures and hold times during processing.     

Heat resistance of prions and food processing

The knowledge of heat inactivation kinetics of scrapie and Creutzfeldt-Jacob Disease (CJD) prions is incomplete and fragmentary. This occurs also because the inactivation kinetics of prions is not exponential. However, by the analysis of available data, it results that usual food processing parameters are largely unable to kill prions. The required prions lethality could be reached by changing the food processing technology. The aseptic process is the most promising alternative.     

Heat resistance of fungi isolated from frozen blueberries

This study dealt with the isolation, characterization, and identification of the fungal microflora of frozen blueberries imported from Canada. The thermal inactivation rates of the rarely studied isolated heat-resistant molds, Devriesia spp. and Hamigera striata, in naturally and artificially contaminated blueberry slurries were also determined. The D-values of naturally contaminating Devriesia spp. at 70, 80, 85, and 90 degrees C were 714, 114, 44.4, and 14.1 min, respectively. The D-values of H. striata at 70, 80, 85, and 90 degrees C were 909, 286, 42.6, and 10.3 min, respectively. The z-values calculated from the thermal death time curves were 11.0 and 6.9 degrees C for Devriesia spp. and H. striata, respectively. Results also showed that in both test mold species, the naturally occurring molds had significantly higher thermal resistance than did the artificially contaminated counterparts. The results established by this study may be used by blueberry processors to prevent losses due to spoilage caused by the heat-resistant microorganisms.     

Heat resistance of thermoduric enterococci isolated from milk

Enterococci are reported to survive pasteurisation but the extent of their survival is unclear. Sixty-one thermoduric enterococci isolates were selected from laboratory pasteurised milk obtained from silos in six dairy factories. The isolates were screened to determine log(10) reductions incurred after pasteurisation (63°C/30 min) and ranked from highest to lowest log(10) reduction. Two isolates each of Enterococcus faecalis, Enterococcus faecium, Enterococcus durans and Enterococcus hirae, exhibiting the median and the greatest heat resistance, as well as E. faecalis ATCC 19433, were selected for further heat resistance determinations using an immersed coil apparatus. D values were calculated from survival curves plotted from viable counts obtained after heating isolates in Brain Heart Infusion Broth at 63, 69, 72, 75 and 78°C followed by rapid cooling. At 72°C, the temperature employed for High Temperature Short Time (HTST) pasteurisation (72°C/15s), the D values extended from 0.3 min to 5.1 min, depending on the isolate and species. These data were used to calculate z values, which ranged from 5.0 to 9.8°C. The most heat sensitive isolates were E. faecalis (z values 5.0, 5.7 and 7.5°C), while the most heat resistant isolates were E. durans (z values 8.7 and 8.8°C), E. faecium (z value 9.0°C) and E. hirae (z values 8.5 and 9.8°C). The data show that heat resistance in enterococci is highly variable.     

Heat resistance of Neosartorya fischeri in various juices

Heat resistance of Neosartorya fischeri was studied in three different juices (apple, pineapple and papaya). The optimum heat activation temperature and time for the ascospores of the N. fischeri (growth for 30 days at 30 °C) was 85 °C for 10 min. Of the three juices tested, apple juice exhibited maximum 1/k values at 80, 85 and 90 °C (208.3, 30.1 and 2.0 min, respectively). The 1/k values for papaya juice (129.9, 19.0 and 1.9 min) and pineapple juice (73.5, 13.2 and 1.5 min) decreased with acidity and °Brix/acidity (ratio) level. The Z^* values for apple, papaya and pineapple juices were 5, 5.5 and 5.9 °C, respectively. The sterilization F values (4-log reduction) for apple, pineapple and papaya juices were 56.3, 38.0 and 7.2 s, respectively. Considering the thermal treatments commercially applied to pineapple (96 °C/30 s) and apple juices (95 °C/30 s), it is concluded that such treatments will not guarantee that less than 1 ascospore in each set of 10³ packs survive. Only the treatment applied to papaya juice (100 °C/30 s) will be sufficient because the F value is less than 30 s.     

Heat resistance of Bacillus spores exposed to food processing conditions

The heat resistance of the spores of 5 Bacillus species was studied in distilled water and pasteurized skim milk. The spores were also subjected to frying and cooking conditions used in fried rice preparations. In presence of milk, the heat resistance of all the five Bacillus species was found to decrease compared to distilled water. Spores of all five Bacillus survived cooking conditions of rice. Frying and subsequent cooking conditions inactivated the spores of all five Bacillus species.