波罗的海干散货运价指数时间序列建模

讨论了运用时间序列建模方法对近两年的波罗的海干散货运价指数进行分析的问题。文章首先对原始数据进行分析处理,得到若干个ARIMA模型。在这些模型中,采用残差检验和AIC、BIC指标的比较,选取最佳方案,最终得到一个比较理性的模型。     

Heterogeneous archaeal communities in the particle-rich environment of an arctic shelf ecosystem

We evaluated the phylogenetic diversity of particle-associated and free-living archaeal assemblages from the Mackenzie River and Beaufort Sea in the western Canadian Arctic. The physico-chemical characteristics of the water separated the sampling sites into three groups: riverine, coastal and marine water, which had strikingly different archaeal communities. The riverine water was characterised by the presence of Euryarchaeota mainly belonging to the LDS and RC-V clusters. The coastal water was also dominated by Euryarchaeota but they were mostly affiliated to Group II.a. The marine waters contained most exclusively Crenarchaeota belonging to the Marine Group I.1a. The results suggest that Euryarchaeota in the coastal surface layer are associated with particle-rich waters, while Crenarchaeota are more characteristic of Arctic Ocean waters that have been less influenced by riverine inputs. The particle-associated communities were similar to the free-living ones at the riverine and marine sites but differed from each other at the coastal site in terms of the presence or absence of some taxonomic groups in one of the fractions, or differences in the proportion of the phylogenetic groups. However, there was no specific archaeal group that was exclusively restricted to the free-living or particle fraction, and the diversity of the particle-associated archaeal assemblages did not significantly differ from the diversity of the free-living communities.     

跨度62.8m钢桁梁浮拖架设技术

通过对跨度为62 8m钢桁梁浮拖架设的尝试,对浮拖架设中的浮拖船结构和组装、浮拖法施工步骤、膺架搭设、牵引和走行设备布置、浮拖稳定性检算、挂杆E3A3加固等主要技术环节进行了总结,并对牵引设备的选用、浮拖支承点位置选择等有关方面提出建议。     

水灰比对机场水泥道面强度的影响分析

通过对比同一坏境下不同水灰比混凝土试样的弯拉强度和劈裂强度,研究了水灰比对机场水泥道面强度的影响。结果表明:混凝土水灰比为0.35~0.55时,试样的劈裂强度出现显著的峰值,当水灰比为0.46左右时,试样的劈裂强度达到最佳,当水灰比大于或小于0.46时,试样的劈裂强度会出现明显的下降;当混凝土水灰比为0.35~0.55时,随水灰比增大,试样的弯拉强度不断减小,无峰值。采用二次多项式对混凝土试样的水灰比-弯拉强度、水灰比-劈裂强度进行拟合,得到的关系式可为国内通用机场飞行区水泥道面建设提供建议和指导。     

梁式转换层在高层建筑中的设计与研究

高层建筑中应用最多的梁式转换层的主要受力构件转换大梁的设计至关重要.本文将转换大梁按其承托的不同上部结构形式分为Ⅰ,Ⅱ两类,探讨了转换大梁各自的受力特点,分析了影响转换大梁受力的各种因素,并给出了设计建议,供设计者参考.     

地铁盾构下穿浅基础太平北路石拱桥施工技术

盾构在市区交通流量繁忙地段穿越浅基础石拱桥,经分析需要对石拱桥进行加固才能满足盾构顺利通过,在传统加固桥梁过程中地面道路不具备交通导改条件(分流通过桥梁车辆),进而影响对桥梁加固,通过对桥梁进行增加内拱圆箱加固及优化盾构掘进参数,确保盾构掘进施工质量和管片施工质量,在满足桥梁安全情况下保证盾构顺利通过了石拱桥,并节约了施工成本。     

基坑开挖对邻近地铁车站安全影响的三维有限元分析——以西朗公交枢纽站为例

随着城市地铁工程的快速发展,地铁周边建筑物基坑的施工必然会对邻近的地铁车站产生一定的影响,特别是超近距离的基坑施工;因此必须进行更为可靠的安全评估。借助有限元分析软件MIDAS/GTS,考虑边界条件、土层参数等工况条件,建立了基坑开挖的三维有限元模型。先计算出基坑开挖前地铁结构的初始应力状态,再计算出由于基坑施工引起的位移、内力等的变化,根据该变化值来判断基坑施工对地铁结构的影响。同时,为满足超近距离安全评估可靠性较高的要求,提出运用Plaxis有限元模型进行复核,为超近距离地铁车站的深基坑施工安全评估提供了操作可行的方法。     

夏季洒水降温减缓沥青混凝土路面车辙发展的研究

夏季高温是沥青路面产生车辙的主要因素。洒水养护因实施简易、可操作性强、养护费用低、性价比高的优势成为路面养护较常用的一种措施。分析了洒水降温的原理,通过埋设温度传感器,研究了沥青混凝土路面不同深度的温度变化规律,从而明确了洒水对路面的降温效果,并与微表处养护进行了经济效益对比分析,为洒水养护的应用提供了理论支撑。     

无碴轨道桥上无缝线路纵向力研究

由于中德两国桥上无缝线路纵向力计算中的线路纵向阻力取值差异较大,首先利用MATLAB软件编制桥上无缝线路纵向力计算程序,分别采用德铁规范的线路纵向阻力模型和中国线路阻力模型,结合实际工点进行计算,对比分析桥上无缝线路纵向力计算结果,建议我国桥上无碴轨道铺设小阻力扣件。     

An econometric analysis of deficiencies noted in port state control inspections

The factors to consider in selecting which vessels to board for port state control (PSC) inspections are crucial. This paper tries to identify these factors using 4080 reported PSC inspections from the Swedish Maritime Administration for the period 1996-2001. It relies on count data models and compares results from the Poisson, negative binomial, random effect and random parameters models. The results suggest that three factors are the main determinants of the number of reported deficiencies: the age at inspection, the flag of registry and the type of ships. Conversely, the year when the inspection occurs does not seem to be a significant factor. Estimations also stress that the relationship between the age at inspection and the number of deficiencies detected is not similar for different vessel types. For instance, the number of deficiencies detected decreases for chemical carriers and Ro-Ro passenger vessels older than 25 and 22 years old, while for instance the effect is rather small for tanker and bulk carriers and only occurs when vessels are older than 35 years.