Utilization of silica fume in concrete: Review of hardened properties

Several types of industrial byproducts are generated. With increased environmental awareness and its potential hazardous effects, utilization of industrial byproducts has become an attractive alternative to disposal. One such by-product is silica fume (SF), which is a byproduct of the smelting process in the silicon and ferrosilicon industry. Silica fume is very effective in the design and development of high strength high performance concrete.This paper covers the physical, chemical properties of silica fume, and its reaction mechanism. It deals with the effect of silica fume on the workability, porosity, compressive strength, splitting tensile strength, flexural strength, creep and shrinkage of concrete.     

消防射水对火灾后高性能混凝土剩余抗压强度的影响

对火灾后消防射水对高性能混凝土(HPC)剩余抗压强度的影响进行了研究。分析了在不同温度、不同冷却方式条件下,C40HPC剩余抗压强度的变化规律,并利用ORIGIN 7.5软件,拟合了高温作用后HPC剩余抗压强度与温度之间的关系。研究表明:消防射水对高温作用后的HPC的剩余抗压强度的影响很大,射水冷却后的HPC剩余抗压强度明显低于自然冷却后的剩余抗压强度;随着破坏温度的升高,经消防射水冷却的HPC剩余抗压强度呈衰减状态。最后,建立了自然冷却及消防射水冷却条件下,C40HPC剩余强度与火场温度之间的二元回归曲线公式。     

Using Ecological Function to Develop Recovery Criteria for Depleted Species: Sea Otters and Kelp Forests in the Aleutian Archipelago

Abstract: Recovery criteria for depleted species or populations normally are based on demographic measures, the goal being to maintain enough individuals over a sufficiently large area to assure a socially tolerable risk of future extinction. Such demographically based recovery criteria may be insufficient to restore the functional roles of strongly interacting species. We explored the idea of developing a recovery criterion for sea otters (Enhydra lutris) in the Aleutian archipelago on the basis of their keystone role in kelp forest ecosystems. We surveyed sea otters and rocky reef habitats at 34 island‐time combinations. The system nearly always existed in either a kelp‐dominated or deforested phase state, which was predictable from sea otter density. We used a resampling analysis of these data to show that the phase state at any particular island can be determined at 95% probability of correct classification with information from as few as six sites. When sea otter population status (and thus the phase state of the kelp forest) was allowed to vary randomly among islands, just 15 islands had to be sampled to estimate the true proportion that were kelp dominated (within 10%) with 90% confidence. We conclude that kelp forest phase state is a more appropriate, sensitive, and cost‐effective measure of sea otter recovery than the more traditional demographically based metrics, and we suggest that similar approaches have broad potential utility in establishing recovery criteria for depleted populations of other functionally important species.     

车辆间碰撞交通事故计算机辅助鉴定技术综述

在分析车辆间事故过程的基础上,论述车辆间碰撞交通事故计算机辅助鉴定技术的基本原理,回顾碰撞前后阶段的HVOSM,PHASE4,SIMON等事故再现轨迹模型,概要地阐述CRASH类、动量模型类逆向计算系统以及二维、三维正向模拟类软件的计算原理,并进行分析和评述。研究认为,我国车辆间碰撞交通事故鉴定应将逆向计算与正向模拟相结合,建议通过研究交通事故现场勘查技术和建立车辆、轮胎、路面摩擦特性等基础数据库来提高逆向计算系统初始数据的准确性,从而提高交通事故鉴定的精度。     

中国液态生物质燃料的潜力测算

中国液态生物质燃料潜力测算为下一步开发提供依据.该文对我国发展液态生物质燃料原料的分布进行整合,从宜能荒地测算、高浓度酒精降度模拟和餐饮地沟油估算等方面,对生产燃料乙醇和生物柴油的原料潜力进行梳理.利用覆盖甜高粱、木薯、甘薯、食用酒精、麻疯树、黄连木和餐饮地沟油等原料来源的数据,测算了我国液态生物质燃料的潜力产量,发现:到2030年,我国燃料乙醇生产潜力将达到5 500万t左右,生物柴油生产潜力将达到3 200万t左右,将能有效保证我国经济增长对能源的需求和缓解化石能源对外依存度过离的能源安全威胁.同时,应该在生物质燃料产业化的关键技术研究上寻求突破,并配套以政府部门的补贴政策,提升我国生物质燃料产业化初期的综合实力.     

固化剂对矿用充填泡沫固化行为的影响

为提高泡沫的充填堵漏风效果,选取有机强酸A,有机磺酸B,无机强酸C等3种固化剂,通过测定泡沫的发泡时间、发泡温度、承压强度和氧指数等参数,分析不同组合固化剂对矿用充填泡沫固化行为的影响。结果表明:乳化时间、起泡时间和表干时间随固化剂用量的增加而明显缩短;泡沫的发泡倍数和发泡温度随固化剂用量的增加而增加;单独使用有机强酸A或有机磺酸B时,泡沫都存在不同程度的收缩,当添加较高量的无机强酸C时,泡沫的尺寸稳定性变好。当复合固化剂有机强酸A用量∶有机磺酸B用量∶无机强酸C用量=1.2∶1∶1时,泡沫的固化效果最优。     

C、D、M_f值综合异常交汇区在华北及其西部地区中强震前的中期异常变化

在华北及其西部地区用描述地震分布时、空、强基本特点的空间集中度C、地震危险度D、地震强度因子Mf 进行交汇寻找综合异常区预测未来中强震 ,预测震中位置在 1 5°半径之内。以实例显示综合异常区存在的稳定性和对未来较强地震的可预测性 ,并对比分析了大华北地区不同区域的应用效果 ,认为其差异是由资料详尽程度决定的。     

灾害熵：概念引入及应用案例

某一区域的灾害风险反映珠不确定性。据此,本文采用信息熵的理论与方法,引入了区域灾害熵和区域灾害加权熵概念,并给出了相应的计算公式。选取山东省作为应用案例研究的区域,利用了１９４９￣１９９４年旱灾、洪涝灾害受灾面积资料计算了旱灾、洪涝灾害的区域熵和区域灾害加权熵。研究结果表明,区域灾害加权熵可以作为表征区域灾害风险整体水平的一个综合指标。本文给出了区域灾害熵计算方法简便易行。     

Characterization of eco-cement paste produced from waste sludges

In this study, marble sludge, sewage sludge, drinking water treatment plant sludge, and basic oxygen furnace sludge were used as replacements for limestone, sand, clay, and iron slag, respectively, as the raw materials for the production of cement in order to produce eco-cement. It was found that it is feasible to use marble sludge to replace up to 50% of the limestone and also that other materials can serve as total replacements for the raw materials typically used in the production of cement. The major components of Portland cement were all found in eco-cement clinkers. The eco-cement was confirmed to produce calcium hydroxide and calcium silicate hydrates during the hydration process, increasing densification with the curing age. The compressive strength (S_c) and microstructural evaluations conducted at 28 d revealed the usefulness of eco-cement. It was observed that the S_c data correlated linearly with the pore volume (P) data at 28 d. The proposed model equation could be represented as S_c = 178-461P (correlation coefficient, R² = 0.96). Two parameters, the large capillary pore volume and the medium capillary pore volume, were evaluated using multiple regression analysis.