略谈旧机动车价格评估体系设计方法

当前汽车市场逐渐成熟,建立科学的旧机动车交易平台非常重要。本文在分析传统的旧机动车价格评估方法局限性的基础上,应用主成分分析方法提出了影响旧机动车评估的4个关键因素。本文建立了旧机动车价格评估体系模型,设计了各影响因素的处理方法,为旧机动车交易平台的建设提供了理论依据和科学方法。     

粉煤灰混凝土的抗压强度试验

粉煤灰混凝土中的粉煤灰含量应包括粉煤灰取代水泥含量和粉煤灰超量含量,而水泥含量应理解为实际水泥含量和粉煤灰取代水泥含量.粉煤灰含量的多少直接影响到其抗压强度性能,因此设计了不同配合比的粉煤灰混凝土进行抗压强度比较试验.试验结果表明,粉煤灰取代水泥含量的增加使得抗压强度降低,而抗压强度峰值的应变显著增加,弹性模量降低,塑性性能提高.     

基于主成分法优化的轨道交通通勤出行方式选择研究

轨道交通一方面能够促进经济社会发展,改善投资环境,提高市民生活质量,缓解交通拥挤,但同时也需要大量的建造、运行、维护费用,到目前为止只有香港、大阪等少数几个地区能够回收运营成本.在这种情况下有必要针对轨道交通沿线居民的通勤出行,了解居民出行方式的机制,以便有关单位或机构采取相应的措施提高轨道交通的乘坐率.文中根据非集计建模的流程,以实际调查数据为基础,建立了多项Logit模型,并对其进行了相关的参数检验和解释.为了减小影响因素相关性带来的交互作用,采用了主成分分析法对变量进行筛选,通过模型参数检验的同时,模型检验中的命中率有所提高.      

基于BP网络的空中交通管制运行品质评价

为改善空中交通管制运行品质综合评价方法,建立了包括空中交通流密度、运行安全性能、运行效率性能及管制员工作负荷的通用评价指标体系;基于BP(back propagation)网络模型给出了运行品质分类评价的人工智能方法.针对成都终端管制区域平行双跑道隔离运行模式,采集60个典型样本进行网络训练测试,确立了拓扑结构为12-7-5型的BP网络模型,并应用于对40个检验样本的分类评价.经与主成分分析法比对,2种综合评价方法所得出的评价结果基本一致.      

终端区空中交通管制运行品质综合评价

为定量评价繁忙终端区空中交通管制运行品质,以成都终端区为研究对象,针对单跑道终端区,建立了包括管制业务量、安全性能、效率性能、工作负荷及交通拥挤度的管制运行品质定量评价指标体系.根据专家意见选取20个相对独立的指标,给出了基于主成分分析法的综合评价方法.采集覆盖一周每日繁忙时段10:00～22:00的84个样本,得到各时段的管制运行品质综合评价结果.经K-均值聚类分析及实际运行表明,本文方法可行,评价结果与实际情况相符.评价结论为终端区的运行策略优化提供了依据.     

Recycling of aluminum from fibre metal laminates

Recycling of aluminum alloy scrap obtained from delaminated fibre metal laminates (FMLs) was studied through high temperature refining in the presence of a salt flux. The aluminum alloy scrap contains approximately mass fraction w(Cu) = 4.4%, w(Mg) = 1.1% and w(Mn) = 0.6% (2024 aluminum alloy). The main objective of this research is to obtain a high metal yield, while maintaining its original alloy compositions. The work focuses on the metal yield and quality of recycled Al alloy under different refining conditions. The NaCl-KCl salt system was selected as the major components of flux in the Al alloy recycling. Two different flux compositions were employed at NaCl to KCl mass ratios of 44:56 and 70:30 respectively, based on either the eutectic composition, or the European preference. Different additives were introduced into the NaCl-KCl system to study the effect of flux component on recycling result. Although burning and oxidation loss of the alloying elements during re-melting and refining take place as the drawbacks of conventional refining process, the problems can be solved to a large extent by using an appropriate salt flux. Experimental results indicate that Mg in the alloy gets lost when adding cryolite in the NaCl-KCl salt system, though the metal yield can reach as high as 98%. However, by adding w(MgF₂) = 5% into the NaCl-KCl salt system (instead of using cryolite) all alloying elements were well controlled to its original composition with a metal yield of almost 98%.     

Durability of concrete made with manganese slag as supplementary cementitious materials

This paper discusses mineral composition and pore microstructure characteristics of water-cooled manganese slag and its effects on durability of concrete. The Mn slag has an alveolate pore structure, and the ground Mn slag is characterized by multiangular shape which consists of α′-C₂S, C₃MS₂, CaO·MnO·2SiO₂ and C₂AS. Experimental results show that the Mn slag has potential hydraulic reactivity. Concrete made with Mn slag as supplementary cementitious materials (SCMs) exhibits very low strength loss and weight loss in the synthetic seawater corrosion and freezing-thawing cycle tests. The research provides useful reference for knowing about Mn slag and for applying Mn slag to improve the durability of concrete.     

受力方式对活性粉末混凝土中钢筋黏结性能的影响

采用拔出和梁式两种试验方法,对比分析了在不同受力状态下变形钢筋与活性粉末混凝土之间的黏结性能.研究表明：两种受力方式下的试件均有活性粉末混凝土劈裂、钢筋拔出与活性粉末混凝土劈裂共同发生、钢筋拔出3种破坏形式;钢筋在活性粉末混凝土中的黏结应力-滑移曲线都可分为4个阶段,但不同受力方式下每阶段特征略有差异;两种受力方式下,黏结强度都随钢纤维掺量的增加而增大,当钢纤维掺量由0%增加到2.0%时,拔出试验的黏结强度增长28.25%,而梁式试验的黏结强度增幅达到58.61%;当活性粉末混凝土中不掺加钢纤维时,梁式试验的黏结强度要小于拔出试验,但掺加钢纤维后,要大于拔出试验.     

基于主成分分析的城市物流发展评价

分析了城市物流的内涵,结合以往研究提出研究城市物流评价体系必须考虑它与物流辐射区经济发展的关系,深入分析了城市物流发展水平的影响因素．在此基础上,建立了科学的城市物流发展评价体系,并构建了城市物流发展水平评价的主成分分析模型．以大连、天津、上海为例进行了实证研究,验证了城市物流发展水平评价体系的有效性．