港工自密实混凝土流变特性研究

屈服应力和塑性黏度是表征新拌自密实混凝土流变特性的两项基本参数,使用ConTec Viscometer流变仪对各组新拌混凝土的屈服应力和塑性黏度进行测试,探讨了不同矿物掺合料对流变参数和坍落扩展度的影响规律,得到了流变参数与坍落扩展度之间的对应关系,为进一步开展港工自密实混凝土设计和施工等相关领域的研究提供依据。     

掺磁选尾渣自密实混凝土工作性能试验研究

为研究掺磁选尾渣自密实混凝土的工作性能,采用坍落扩展度、T500、J环、离析率等试验方法,研究了磁选尾渣掺量、砂浆稠度和减水剂用量等因素对拌合物工作性能的影响规律,试验结果表明:将磁选尾渣作为原料配制自密实混凝土是可行的,未经筛分处理的磁选尾渣可以制备出满足工作性能要求的自密实混凝土;为使混凝土的工作性能最优,聚羧酸减水剂的掺量宜为0. 3%;当砂浆稠度V_s/V_m为0. 45时,新拌混凝土的工作性能达到最优;当磁选尾渣掺量在50%以内时,拌合物具有良好的工作性能.     

微珠对新型板式轨道用自密实混凝土工作性能的影响

通过混凝土扩展度、坍落度、扩展时间T_(500)、水泥净浆黏度等试验方法,研究微珠对CRTSⅢ型板自密实混凝土工作性的作用机理。结果表明,适宜的微珠掺量能够显著改善混凝土工作性,当微珠掺量为1. 5%时混凝土工作性最佳,T_(500)从14 s降低到5 s,J环的障碍高差BJ值从30 mm降低到17 mm。水泥净浆黏度试验及混凝土工作性试验结果表明,微珠的作用机理是通过降低混凝土黏度从而降低T_(500)的值,但微珠会提高混凝土的屈服应力,不利于混凝土扩展度的提高,因而本文对CRTSⅢ型板自密实混凝土的配制及选材具有理论指导的意义。     

海工高性能混凝土粘性简易测试方法与合理粘性形成条件

在分析了传统的坍落度表征海工高性能混凝土的工作性能不足的基础上。本文阐述了海工高性能混凝土粘性测试的简易方法，提出了将坍落度与坍落扩展度比值作为判定混凝土粘性的方法。分析了影响海工高性能混凝土的粘性的因素，并由此得出了合理粘性形成条件。     

花岗岩机制砂石粉对C80高强高性能混凝土性能的影响及机理研究*

为推动海工机制砂高强高性能混凝土技术的发展,系统研究花岗岩石粉对C80高强高性能混凝土工作性、力学性能、抗氯离子渗透性等性能的影响,分析石粉对混凝土性能的影响机理。研究结果表明：当机制砂石粉含量为4.5%～6.5%时,制备的C80高强高性能混凝土的工作性良好,石粉含量对新拌混凝土的屈服应力、塑性黏度等流变性能的影响不显著;随着石粉含量的增加,高强高性能混凝土力学性能先增加后降低,抗氯离子渗透性、干燥收缩呈现不断增大的趋势,但当石粉含量不超过6.5%时,对混凝土抗氯离子渗透性、干燥收缩影响幅度不明显;机制砂中适量的石粉降低了混凝土浆体孔隙率、优化了孔结构分布,有利于提高混凝土力学性能和耐久性,但石粉含量超过6.5%时,石粉对混凝土砂浆的孔结构、胶凝材料水化进程具有不利影响;C80高强高性能混凝土用机制砂石粉的含量宜控制在4.5%～6.5%。     

淤泥固化土高浓度非牛顿浆体的输送特性

疏浚工程固化处理后的淤泥属于高浓度非牛顿浆体。通过淤泥固化土的流动度试验,采用H-B流变模型进行流动度二维瞬态数值模拟,确定其屈服应力值。采用水固比为0.8、0.9和1.0的淤泥固化土,在管道管径为150、200和250 mm,流速为1.5、2.5和3.5 m/s的工况条件下,分析其水力输送特性,并拟合水力损失计算公式。结果表明,流速、黏度和管径对水力损失均有比较明显的影响,水力损失随流速和黏度的增加而增加,随管径的增加而减小。     

混凝土掺和料对混凝土强度增长的影响

混凝土掺合料是为了改善混凝土性能,节约用水,调节混凝土强度等级,在混凝土拌合时掺入天然的或人工的能改善混凝土性能的粉状矿物质。本文结合盐城港射阳港区通用码头三期工程混凝土配合比设计及混凝土强度实际增长情况,探究混凝土掺和料对混凝土强度增长的影响情况。结果表明,单惨粉煤灰对混凝土抗压强度的贡影响随其养护龄期的增加而增大,早期强度增长较慢。为尽快提高混凝土早期强度,可在混凝土中惨入高活性掺和料。     

泥粉对砂岩机制砂MB值及砂浆性能的影响

研究不同岩石特性、泥粉含量和最大粒径对机制砂MB值的影响,分析MB值对砂浆流动度、力学性能及孔结构的影响规律。结果表明:砂岩机制砂MB值随泥粉含量的增加线性增大,随机制砂最大粒径的减小而呈对数增大,细粉料颗粒是影响MB值的重要原因,而矿石岩性对MB值的影响并不显著;砂浆的流动度、力学性能随MB值的增大而不断降低,尤其当MB值大于1.5时对砂浆的工作性和力学性能影响更为显著。另外,随机制砂MB值的增加,砂浆的孔隙率和平均孔径不断增大,有害孔数量增多,而凝胶孔等无害孔数量降低,使得孔结构劣化。建议现场生产过程中机制砂MB值控制在不大于1.5。     

润滑脂在圆管内流动速度及粘度分布规律

润滑脂在管内流动的速度、粘度是影响润滑脂输送的重要因素,深入研究不同温度、流变指数、屈服应力对润滑脂在输送过程中的速度分布、粘度分布具有重要意义.文中首先采用旋转流变仪对润滑脂的流变行为进行实验研究,得到润滑脂的本构方程;然后基于Herschel-Bulkley模型,运用CFD对润滑脂的流动进行数值模拟.结果表明:温度和剪切速率对润滑脂的流变行为均存在较大影响,在低温下,润滑脂存在较大的屈服应力,且润滑脂输送性能较差;随着温度的升高,其流速增大,润滑脂表现出更好的流动性,且在管内中心,粘度分布均呈峰形;随着屈服应力增加,流速降低,粘度增加,当屈服应力从1 200 Pa升高到1 500 Pa时,流核区速度降低了65%,且中心处粘度升高了24%;流性指数对润滑脂在管内的粘度分布影响较小,而对速度分布影响较大,随着流性指数增大,润滑脂速度明显降低,当流性指数从0.19增加到0.79时,流核区速度降低了69%,而粘度分布基本保持一致.     

港工自密实自养护抗裂型耐久混凝土关键技术

对港工混凝土及自密实混凝土的研究现状进行了调研分析,开展了港工自密实耐久混凝土配合比系列优化试验,以及港工自密实混凝土自养护抗裂性能试验.明确了适合于港工条件自密实高耐久混凝土的水胶比、掺合料方案等重要参数,提出了相应的配制技术,并提出了抗裂的自养护方案.结合依托工程特点开展了现场应用研究工作,研究成果进一步拓展应用于海底隧道、跨海桥梁等大型涉海工程中,获得了成功.     

聚合物和硅粉复合修复砂浆的性能试验

针对老旧码头混凝土修复需求较大,普通砂浆的修补效果有待提高等问题,采用丙烯酸乳液(PAE)和硅粉复合配制港工修复砂浆,进行试验研究,对试验数据分析得出:聚丙烯酸乳液的黏结作用以及硅粉的火山灰效应和填充作用可以有效改善修复砂浆力学性能,显著提高黏结强度,降低干缩,提高砂浆的抗冲磨、抗渗等耐久性能,相比于其他不掺丙烯酸乳液(PAE)和硅粉的砂浆综合性能更好,可替代普通砂浆作为良好的混凝土修补材料。     

硅灰对高石粉含量机制砂制备混凝土的影响

针对天然砂日渐匮乏,而机制砂中石粉含量偏高所制备的混凝土工作性、泵送性差等问题,研究硅灰对机制砂混凝土的工作性、力学和体积稳定性的影响,并分析硅灰的作用机理。结果表明:适量硅灰可以增加混凝土工作性和稳定性,解决机制砂高石粉含量引起的混凝土黏度大和泌水问题,改善浆体微观形貌,提高混凝土力学和耐久性能,且28 d干燥收缩率400×10-6。机制砂中石粉含量为10%左右时,硅灰掺量6%~9%,制备的C50机制砂混凝土匀质性好,浆体旋转黏度约2.5 Pa·s,泌水率为0,工程应用效果良好。     

船用焚烧炉烟气排放控制技术研究

为防止船舶排放物污染海洋环境,国际海事组织不断制定新的法规以限制船舶废弃物的排放。同样,船用焚烧炉的废气排放也受到相关法规的严格限制。焚烧炉技术研究中降低废气中有害物质排放、使其符合相关规范或要求成为研究的重点。本文在分析船舶废弃物的热动力性能、燃烧过程的基础上,重点对焚烧炉烟气排放控制技术进行了分析研究,对船用焚烧炉的优化设计及其控制策略的确定有着重要的指导意义。     

斯达-斯太尔重型柴油机排烟故障检修

介绍斯达-斯太尔重型柴油机排烟的生成机理及其影响因素，结合实践维修经验，对斯达-斯太尔重型柴油机排烟故障进行了分析和诊断，通过应用这一诊断分析方法，能够更准确、更快捷地诊断和排除斯达．斯太尔重型柴油机的排烟故障。     

柴油机运转不正常时排烟颜色的分析

柴油机运转状况是否良好主要表现在:油耗和功率利用上,其宏观表现也就是排气颜色和排气温度上。介绍了柴油机运转的基本原理,叙述了柴油机运转不正常时排烟的具体表现。     

柴油机排烟烟色的判断与分析

明确了柴油机排烟烟色的概念,进一步阐述其生成机理,并对柴油机在使用过程中产生的排烟烟色及影响因素作出准确判断和分析.     

Biogenic silica cycle in surface sediments of the Greenland Sea

In contrast to several investigations of biogenic silica (BSi) content and recycling in surface sediments of the Southern Ocean, little is known about the benthic cycle of BSi in high northern latitudes. Therefore, we investigated the silicic acid concentration of pore water and BSi content of surface sediments from the Greenland Sea. Low BSi contents of less than 2% were observed. High-resolution (2–5 mm) BSi profiles and comparisons to trap studies suggest that only relatively dissolution-resistant siliceous components reach the seafloor. Pore water investigations reveal BSi fluxes of more than 300 mmol m⁻² a⁻¹ only for a few sites on the shelf. A statistically significant relationship between water depth and BSi rain rate reaching the seafloor was not observed. Sampling along a transect perpendicular to the marginal ice zone (MIZ) revealed no enhanced rain rate of BSi reaching the seafloor in the vicinity of the ice edge. Although the MIZ of the Greenland Sea is characterized by the enhanced export of biogenic particles from surface waters, this feature is not reflected in the benthic cycle of biogenic silica. The lack of such a relationship, which is in contrast to observations of shelf and continental margin sediments in the southern South Atlantic, is probably caused by the enhanced dissolution of BSi in the water column and highly dynamic ice conditions in the Greenland Sea.     

Diatom stratigraphy and long-term dissolved silica concentrations in the Baltic Sea

In many parts of the world coastal waters with anthropogenic eutrophication have experienced a gradual depletion of dissolved silica (DSi) stocks. This could put pressure on spring bloom diatom populations, e.g. by limiting the intensity of blooms or by causing shifts in species composition. In addition, eutrophication driven enhanced diatom growth is responsible for the redistribution of DSi from the water phase to the sediments, and changes in the growth conditions may be reflected in the sediment diatom stratigraphy.To test for changes in diatom communities we have analyzed four sediment cores from the Baltic Sea covering approximately the last 100 years. The sediment cores originate from the western Gulf of Finland, the Kattegat, the Baltic Proper and the Gulf of Riga. Three out of the four cores reveal only minor changes in composition of diatom assemblages, while the Gulf of Riga core contains major changes, occurring after the second World War. This area is set apart from the other Baltic Sea basins by a high frequency of low after spring bloom DSi concentrations (< 2 µmol L^− 1) during a relatively well defined time period from 1991–1998. In 1991 to 1993 a rapid decline of DSi spring concentrations and winter stocks (down to 5 µmol L^− 1) in the Gulf was preceded by exceptionally intense diatom spring blooms dominated by the heavily silicified species Thalassiosira baltica (1991–1992; up to 5.5 mg ww L^− 1). T. baltica has been the principal spring bloom diatom in the Gulf of Riga since records began in 1975. DSi consumption and biomass yield experiments with cultured T. baltica suggest that intense blooms can potentially exhaust the DSi stock of the water column and exceed the annual Si dissolution in the Gulf of Riga. The phytoplankton time series reveals another exceptional T. baltica bloom period in 1981–1983 (up to 8 mg L^− 1), which, however, took place before the regular DSi measurements. These periods may be reflected in the conspicuous accumulation of T. baltica frustules in the sediment core corresponding to ca. 1975–1985.     

Modelling the silica pump in the Permanently Open Ocean Zone of the Southern Ocean

A coupled 1D physical–biogeochemical model has been built to simulate the cycles of silicon and of nitrogen in the Indian sector of the Permanently Open Ocean Zone of the Southern Ocean. Based on a simplified trophic network, that includes two size classes of phytoplankton and of zooplankton, and a microbial loop, it has been calibrated by reference to surface physical, chemical and biological data sets collected at the KERFIX time-series station (50°40′S–68°25′E). The model correctly reproduces the high nutrient low chlorophyll features typical of the studied area. In a region where the spring–summer mixed layer depth is usually deeper than 60 m, the maximum of chlorophyll never exceeds 1.5 mg m⁻³, and the annual primary production is only 68 g C m⁻² year⁻¹. In the surface layer nitrate is never exhausted (range 27–23.5 mmoles m⁻³) while silicic acid shows strong seasonal variations (range 5–20 mmoles m⁻³). On an annual basis 71% of the primary production sustained by nanophytoplankton is grazed by microzooplankton. Compared to North Atlantic, siliceous microphytoplankton is mainly prevented from blooming because of an unfavourable spring–summer light-mixing regime. Silicic acid limitation (high half saturation constant for Si uptake: 8 mmoles m⁻³) also plays a major role on diatom growth. Mesozooplankton grazing pressure excerpts its influence especially in late spring. The model illustrates the efficiency of the silica pump in the Southern Ocean: up to 63% of the biogenic silica that has been synthetized in the photic layer is exported towards the deep ocean, while only 11% of the particulate organic nitrogen escapes recycling in the surface layer.     

虚拟样机技术在气垫船推进系统特性研究中的应用

由于气垫船的结构特点,传统的研究方法不适于气垫船推进系统特性研究.本文将现代虚拟样机技术引入气垫船推进系统特性研究中,对气垫船船体和轴系建模及船体-推进系统的耦合方法进行了比较研究.并应用本文提出研究方法,对某型气垫船推进轴系进行了动态支承力的仿真研究.