海洋大气区预应力混凝土氯离子传输时间相似关系研究

海洋大气区预应力混凝土内氯离子在现场环境与实验室内传输的过程有所不同.为探究二者的时间相似关系,本文基于相似理论,以连云港某港区在役混凝土构件为参照物,制定室内人工气候模拟加速试验制度,并浇筑12根与现场构件材料、受力相似的试验梁进行盐雾喷淋侵蚀.通过检测现场和室内试验构件中的自由氯离子含量并计算其表观氯离子扩散系数,以时间衰减系数为工具,分析水胶比、预应力张拉水平、粉煤灰掺量对氯离子扩散的影响,得出预应力混凝土内氯离子传输的时间相似系数表达式,并利用实际工程验证该表达式的准确性,说明基于相似理论的预应力混凝土内,氯离子传输的时间相似关系可用来研究海工预应力混凝土结构耐久性寿命预测问题.     

硫酸盐环境下氯离子在预应力混凝土中的传输

合理确定氯离子扩散系数,对研究预应力混凝土在沿海及西部盐碱地区环境下的耐久性具有重要意义.基于相似理论,综合考虑毛细孔隙率、硫酸根抗压抗蚀系数、氯离子结合能力、时间依赖性常数等影响,提出氯离子在预应力混凝土受硫酸盐侵蚀下的扩散模型,并对各影响因素进行了分析.通过试验值与模型计算值的对比,发现试验值与模拟值吻合良好.研究结果表明:孔隙率、应力水平影响系数及时间依赖性常数对氯离子在预应力混凝土中的扩散性能影响较大,其次是硫酸盐抗压抗蚀系数,最后是硫酸盐影响下的氯离子结合能力.研究发现:孔隙率的减小能有效地提高预应力混凝土抗氯离子侵蚀能力.     

干湿时间比对海工混凝土结构氯盐扩散的影响研究

为了探究海洋环境干湿交替区混凝土结构中氯离子扩散规律,将干湿时间比量化,对应连云港港口泊位现场环境与结构状况设计进行干湿交替区的混凝土构件在不同干湿时间比和不同压应力水平下的室内氯盐加速侵蚀试验,以混凝土内部扩散区的氯离子扩散系数和表面氯离子浓度作为侵蚀指标,将室内加速试验与现场试验的结果对比,分析干湿时间比和应力水平对氯离子扩散的影响.结果证明室内试验取得良好的加速侵蚀效果,试验结果表明对于干湿交替区的混凝土结构,干湿时间比对氯离子扩散的影响十分显著,不同的干湿时间比甚至将氯离子扩散系数提高2倍,其影响力远高于压应力水平.     

弯曲应力作用下钢纤维混凝土氯离子侵蚀性能

研究弯曲应力作用下钢纤维混凝土的氯离子侵蚀性能,分析了钢纤维掺量、弯曲应力水平对混凝土氯离子含量、氯离子扩散系数的影响规律.结果表明,钢纤维的存在能改善弯曲应力作用下的氯离子侵蚀性能,钢纤维掺量为1.5％时,改善效果最明显.弯曲应力的存在加速了氯离子在钢纤维混凝土中的扩散速度、增大了混凝土氯离子含量,应力水平越大时影响越明显.钢纤维混凝土氯离子扩散系数与应力水平间存在指数型数学关系式,最终建立了钢纤维混凝土氯离子扩散系数随应力水平变化的数学模型.     

水灰比对混凝土氯离子扩散系数和碳化速率影响的试验研究

氯离子扩散系数和碳化速率是表征混凝土耐久性的主要指标.通过氯盐浸泡和快速碳化试验,基于试验检测和数据分析,研究了水灰比对氯离子扩散系数和碳化速率系数的影响规律.试验结果表明,水灰比越大,氯离子扩散系数越大,但水灰比过小时水灰比对扩散系数的影响程度降低;水灰比越大,混凝土碳化速度越快.碳化速率系数与水灰比成线性关系.结合试验数据并通过现有模型对比分析,给出较为合理的粉煤灰影响系数表达式和建议取值.     

剪应力作用下混凝土结构氯离子传输试验研究

实际工程中混凝土结构受到正应力和剪应力共同作用会加速耐久性劣化,但混凝土结构在剪应力作用下的氯离子侵蚀规律研究却鲜见报道.提出新的耐久性试验加载方式使混凝土小梁承受长期剪应力作用.试验研究了剪应力作用下混凝土结构氯离子侵蚀规律,结果表明,剪应力作用会使混凝土结构的氯离子渗透性增加,随着荷载水平的提高,氯离子扩散系数Di显著增大.最后,根据试验数据建立了混凝土试件在剪应力作用下氯离子扩散系数数学模型,量化分析了剪应力作用大小对混凝土氯离子扩散系数的影响.     

海工混凝土表面氯离子浓度时间相似关系研究

根据相似理论,以混凝土表面氯离子浓度时变性为纽带,建立现场环境和人工模拟加速侵蚀环境下混凝土构件的时间相似关系.分别对海工混凝土构件和试验构件做取粉试验,通过RCT法检测构件中自由氯离子含量并计算表面氯离子浓度值,分析表面氯离子浓度的时变模型.最终提出时间相似系数表达式并计算得到时间相似系数,为服役中的混凝土结构寿命预测奠定基础.     

碳化和应力作用对混凝土抗氯离子渗透性能的影响

碳化、氯离子侵蚀、应力三者共同作用对沿海地区混凝土结构耐久性具有重要影响.以C25级普通混凝土为研究对象,针对应力、碳化和氯盐三因素共同作用,借助室内试验手段,对混凝土试样进行加载及快速碳化试验,研究了碳化和应力作用下混凝土中的氯离子迁移规律.研究表明:碳化龄期短的混凝土试件,氯离子扩散系数会有很大程度的下降,随着碳化时间的增加下降速度不断减缓;碳化龄期较长的混凝土试件,氯离子扩散系数会略有升高.随压应力的增大,混凝土碳化深度逐渐减小,氯离子扩散系数也逐渐减小.     

氯离子侵蚀下受弯梁耐久性可靠度评估

以弯矩与抗弯承载力之比作为荷载水平指标,对氯离子在混凝土受弯梁中的扩散行为进行研究,建立荷载水平与氯离子扩散系数的函数关系,进而提出考虑荷载作用下钢筋表面氯离子浓度达到临界值的极限状态方程及相应耐久性可靠度计算方法.结合算例,对浪溅区混凝土梁构件在不同荷载水平下的耐久性可靠指标进行计算.结果表明:荷载水平对耐久性可靠指标β的影响较为显著,不考虑荷载作用时结构的耐久性可靠指标比考虑荷载作用时耐久性可靠指标偏高100%以上.从确保服役混凝土梁构件达到预期耐久性要求出发,建议对应浪溅区设计使用年限分别为30年、50年以及100年梁构件,相应的最小保护层厚度应分别取为60 mm,65 mm和75 mm,相应的最大水灰比限值均建议取为0.36.     

荷载裂缝和养护龄期对混凝土内氯离子传输影响研究

为了分析实际荷载和氯盐侵蚀环境共同作用下开裂混凝土结构的耐久性能,通过弯曲开裂和预压开裂两种方式制备出两类开裂混凝土构件,采用RCM试验法研究了开裂混凝土构件中氯离子的传输特性,并深入分析了荷载裂缝和养护龄期对氯离子传输过程的影响.研究结果表明,裂缝的存在加剧了氯离子在裂缝位置及其周围10 mm范围混凝土内的传输进程,且裂缝对氯离子传输的影响范围随着裂缝宽度的增大而增大;从受弯开裂构件中得到的弯曲开裂试件,当最大裂缝宽度小于0.3 mm时仍可采用RCM法进行传输性能分析,而预压开裂试件的裂缝宽度大于0.12 mm时,已不宜采用RCM法进行分析;随着养护龄期的增加,预压开裂混凝土试件的氯离子传输能力在裂缝周围略有降低,在离裂缝距离超过10 mm后,氯离子传输能力降低明显.综合现有研究结果得出,利用裂缝宽度w的二次多项式函数表征两类开裂混凝土构件的氯离子扩散系数劣化特性是可行的.     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Methyl 2,4,6-decatrienoates Attract Stink Bugs and Tachinid Parasitoids

Halyomorpha halys (Stål) (Pentatomidae), called the brown marmorated stink bug (BMSB), is a newly invasive species in the eastern USA that is rapidly spreading from the original point of establishment in Allentown, PA. In its native range, the BMSB is reportedly attracted to methyl (E,E,Z)-2,4,6-decatrienoate, the male-produced pheromone of another pentatomid common in eastern Asia, Plautia stali Scott. In North America, Thyanta spp. are the only pentatomids known to produce methyl 2,4,6-decatrienoate [the (E,Z,Z)-isomer] as part of their pheromones. Methyl 2,4,6-decatrienoates were field-tested in Maryland to monitor the spread of the BMSB and to explore the possibility that Thyanta spp. are an alternate host for parasitic tachinid flies that use stink bug pheromones as host-finding kairomones. Here we report the first captures of adult and nymph BMSBs in traps baited with methyl (E,E,Z)-2,4,6-decatrienoate in central Maryland and present data verifying that the tachinid, Euclytia flava (Townsend), exploits methyl (E,Z,Z)-2,4,6-decatrienoate as a kairomone. We also report the unexpected finding that various isomers of methyl 2,4,6-decatrienoate attract Acrosternum hilare (Say), although this bug apparently does not produce methyl decatrienoates. Other stink bugs and tachinids native to North America were also attracted to methyl 2,4,6-decatrienoates. These data indicate there are Heteroptera in North America in addition to Thyanta spp. that probably use methyl 2,4,6-decatrienoates as pheromones. The evidence that some pentatomids exploit the pheromones of other true bugs as kairomones to find food or to congregate as a passive defense against tachinid parasitism is discussed.     

2005～2006年国外塑料工业进展

收集了2005年7月～2006年6月国外塑料工业的相关资料，介绍了2005—2006年国外塑料工业的发展情况。提供了世界塑料产量、消费量及全球各类树脂生产量以及各国塑料制品的进出口情况。作为对比，介绍了中国塑料的生产情况。按通用热塑性树脂（聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂）、工程塑料（聚酰胺、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚）、通用热固性树脂（酚醛、聚氨酯、不饱和树脂、环氧树脂）、特种工程塑料（聚苯硫醚、液晶聚合物、聚醚醚酮）的品种顺序，对树脂的产量、消费量、供需状况及合成工艺、产品开发、树脂品种的延伸及应用的扩展作了详细的介绍。     

2007～2008年世界塑料工业进展

收集了2007年7月～2008年6月世界塑料工业的相关资料,介绍了2007～2008年国外塑料工业的发展情况,提供了世界塑料产量、消费量及全球各类树脂的需求量及产能情况.按通用热塑性树脂(聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂)、工程塑料(尼龙、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚)、特种工程塑料(聚苯·硫醚、液晶聚合物、聚醚醚酮)、通用热固性树脂(酚醛、聚氨酯、不饱和聚酯树脂、环氧树脂)不同品种的顺序,对树脂的产量、消费量、供需状况及合成工艺、产品应用开发、树脂品种的延伸及应用的进一步扩展等技术作了详细介绍.     

Inorganic/organic nanocomposite coatings: The next step in coating performance

Inorganic/organic hybrid materials have considerable promise and are beginning to become a major area of research for many coating usages, including abrasion and corrosion resistance. Our primary approach is to prepare the inorganic phase in situ within the film formation process of the organic phase. The inorganic phase is introduced via sol-gel chemistry into a thermosetting organic phase. By this method, the size, periodicity, spatial positioning, and density of the inorganic phase can be controlled. An important aspect of the inorganic/organic hybrid materials is the coupling agent. The initial task of the coupling agent is to provide uniform mixing of the oligomeric organic phase with the sol-gel precursors, which are otherwise immiscible. UV-curable inorganic/organic hybrid systems have the advantages of a rapid cure and the ability to be used on heat sensitive substrates such as molded plastics. Also, it is possible to have better control of the growth of the inorganic phase using UV curing. It is our ultimate goal to completely separate the curing of inorganic and organic phases to gain complete control over the morphology, and hence optimization of “all” the coating properties. Thus far, it has been found that concomitant UV curing of the inorganic and organic phases using titanium sol-gel precursors afforded nanocomposite coatings which completely block the substrate from UV light while maintaining a transparent to visible light. Also, it has been found that the morphology of the inorganic phase is highly dependent on the concentration and reactivity of the coupling agent. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004, in Chicago, IL.     

Ethanol and (−)-α-Pinene: Attractant Kairomones for Some Large Wood-Boring Beetles in Southeastern USA

Ethanol and α-pinene were tested as attractants for large wood-boring pine beetles in Alabama, Florida, Georgia, North Carolina, and South Carolina in 2002–2004. Multiple-funnel traps baited with (−)-α-pinene (released at about 2 g/d at 25–28°C) were attractive to the following Cerambycidae: Acanthocinus nodosus, A. obsoletus, Arhopalus rusticus nubilus, Asemum striatum, Monochamus titillator, Prionus pocularis, Xylotrechus integer, and X. sagittatus sagittatus. Buprestis lineata (Buprestidae), Alaus myops (Elateridae), and Hylobius pales and Pachylobius picivorus (Curculionidae) were also attracted to traps baited with (−)-α-pinene. In many locations, ethanol synergized attraction of the cerambycids Acanthocinus nodosus, A. obsoletus, Arhopalus r. nubilus, Monochamus titillator, and Xylotrechus s. sagittatus (but not Asemum striatum, Prionus pocularis, or Xylotrechus integer) to traps baited with (−)-α-pinene. Similarly, attraction of Alaus myops, Hylobius pales, and Pachylobius picivorus (but not Buprestis lineata) to traps baited with (−)-α-pinene was synergized by ethanol. These results provide support for the use of traps baited with ethanol and (−)-α-pinene to detect and monitor common large wood-boring beetles from the southeastern region of the USA at ports-of-entry in other countries, as well as forested areas in the USA.