用开挖料加工混凝土骨料工艺研究与实践

为满足溪洛渡水电站混凝土骨料中针片状含量低于规范允许值5%的要求,对开挖利用料加工高品质混凝土骨料工艺进行了研究,骨料加工采取4段破碎整形工艺,很好地解决了开挖利用料特大石缺少、对骨料中针片状含量要求低等问题。工艺研究与生产实践表明,采用骨料破碎及整形工艺有效降低了骨料针片状的含量,提高了特大石的获得率,为其他类似工程开挖利用料的应用提供了很好的借鉴作用。     

人工大理岩骨料应用几个关键问题与对策分析

国内某大型水电工程的混凝土骨料母岩为洞挖大理岩渣料,应用中面临岩性较脆、料源均一性欠佳、毛料含水率大、粗骨料裹粉严重且级配较差、干法生产的人工砂石粉含量超标严重等诸多问题。大理岩人工骨料大规模用于大型水电工程,并采用干式制砂系统,在国内尚属首次。根据工程建设中长期的跟踪检测数据,针对上述问题进行了深入剖析,提出了增加缓降装置和二次筛分及水洗装置、采用胶带运输、调整主筛分车间筛网、筛除毛料中大于20 mm的颗粒、调整风选车间参数等相应对策。在取得较好的技术效果的同时,为类似工程的进一步大范围应用积累了经验。     

多维数据的复杂查询聚集算法研究

对空间多维数据的复杂查询是多维数据研究的重点和难点,目前研究的结论相对较少。在传统算法的基础上,进行了几个方面的改进：按分组属性值进行数据分块;对分组数据进行有效的排序;在聚集函数的应用上进行优化。模拟数据的试验表明：改进算法较大地提高了查询效率。     

Formulation to obtain the most reliable aggregate mix with quantity and other constraints

The aggregate batch mixing problem determines the proportion (or relative masses) in which aggregate batches with different gradations are to be blended so as to achieve a target mix with a given gradation. As shown in previous studies, the gradation of a batch is not homogeneous and should be considered stochastic. Also, when batches are blended in the field there are random variations in the masses or proportions of individual batches in the mix. Assuming batch gradation and blend masses as stochastic implies that the notion of a mix (blend) satisfying the gradation of a target mix becomes stochastic. In such a framework, every mix has a reliability with which it satisfies the definition of the target mix. In addition, a mix is also required to satisfy various restrictions. This article presents an optimization formulation to determine the most reliable mix while satisfying restrictions on available quantity, budget, etc.     

ACL在聚合端口上应用研究

访问控制列表在网络安全中是一种重要的手段。文章通过对其研究,提出了在聚合端口上应用ACL的方法,该方法可以大大减少网络管理人员配置ACL的复杂性。结合该方法,给出了一个网络安全模型的实例,通过端口聚合方案和制定安全策略,实现网络性能的优化和保护网络的目的。     

路网数据流的预测聚集查询新方法研究

时空数据流的聚集查询技术已经成为数据库领域的研究热点。到目前为止,还没有一种有效的全时态聚集索引适用于非欧氏空间的路网数据流聚集查询。实现路网数据流的全时态聚集查询,必须解决:(1)路网的非欧氏空间特性问题;(2)路网上移动对象的重复计数、非均匀分布以及预测聚集问题。Sketch RR-tree解决了非欧氏空间特性和重复计数问题;为解决非均匀分布问题,借鉴草图划分思想,提出动态草图索引结构DynSketch:采用AMH智能划分Sketch RR-tree,使每个划分区域内车辆均匀分布,以提高聚集查询质量;同时,基于DynSketch,结合ES预测模型,提出了路网数据流的预测聚集查询算法。     

改进的签名长度固定的无证书聚合签名

现有的具有固定签名长度的无证书聚合签名(certificateless aggregate signatures, CLAS)方案要么存在安全缺陷,要么通信开销较大。提出一种改进的CLAS方案,由聚合人选择整数域上的随机参数替代状态信息,并且广播给所有签名者。在随机预言模型下,改进方案被规约为多项式时间敌手求解CDH(computational Diffie- Hellman)难题,具有可证明安全性。对比分析表明,改进CLAS方案的状态信息协商阶段仅需要1次广播通信,通信开销更低,易于实现。改进方案可用于在资源受限的网络环境下构建多对一的认证方案。     

重质油中的分子聚集结构及其对重质油稳定性的影响

重质油组分分子的聚集是重质油最显著的特征之一,重质油的高粘特性和相态稳定性均与此聚集行为有紧密的联系.为克服实验研究获得重质油微观聚集结构的困难,本文采用Zhang等人针对重质油体系改进的耗散粒子动力学(DPD)方法,研究重质油的分子聚集结构及其对重质油稳定性的影响.根据重质油组分的结构特征,可将重质油表达为其他轻组分...     

Properties of concrete incorporating fine recycled aggregate

The properties of concrete containing fine recycled aggregate are investigated. Recycled aggregate consisted of crushed concrete (CC) or crushed brick (CB) with particles less than 5 mm in diameter. The free water/cement ratio was kept constant for all mixes. The fine aggregate in concrete was replaced with 0%, 25%, 50% and 100% CC or CB. Generally, there is strength reduction of 15-30% for concrete containing CC. However, concrete incorporating up to 50% CB exhibits similar long-term strength to that of the control. Even at 100% replacement of fine aggregate with CB, the reduction in strength is only 10%. Beyond 28 days of curing, the rate of strength development in concrete containing either CC or CB is higher than that of the control indicating further cementing action in the presence of fine recycled aggregate. More shrinkage and expansion occur in concrete containing CC or CB.