铁路桥梁施工实例及方案比较

阐述了我国铁路桥梁发展状况,论述了铁路桥梁施工技术发展的对策,着重介绍了京广线下行238号桥工程概况和307号桥换梁施工情况,对换梁方案、作业程序、换粱前准备工作以及施工技术措施等做了详细说明.     

切削用量对刀具耐用度影响的探讨

简述了切削用量对刀具耐用度的影响程度,叙述了在零件加工过程中合理的选取切削用量和合适的刀具耐用度,对于提高机械加工的效率有很大的作用.     

中央空调系统节能技术分析

近年来随着我国建筑业的发展,中央空调系统的应用日益普及。由于中央空调系统的耗能量很大,所以如何节约能源、提高效率就成为迫切需要解决的问题。本文从中央空调系统的设计、设备选配、系统调节控制及运行管理等方面提出了若干切实可行的节能措施。     

浅析数列极限的教学

数列极限的教学,从总的策略来说,应注重对这个概念内涵的揭示和描述。极限＂ε-N＂语言应根据不同的教学对象确定不同的教授方式。另外,把描述性定义过渡成＂ε-N＂定义时应深入剖析并利于接受。     

假颗粒现象及其对再生铝镁碳制品性能的影响

对用后铝镁碳砖再生颗粒料的组成和结构特点进行显微分析,并通过改变混料方式以及不同粒度再生料的加入量研究假颗粒对再生铝镁碳制品结构与性能的影响.结果表明:用后铝镁碳砖再生料中含有约40%与废砖相组成和结构相似、骨料与基质并存于同一颗粒的二次颗粒,即所谓的"假颗粒",假颗粒的组成、结构及外形的均匀程度均远不如一次骨料颗粒;混碾可使用后铝镁碳砖再生料中假颗粒发生二次破碎,且粒度越大,发生二次破碎的颗粒数量越多;假颗粒二次破碎导致再生制品的粒度组成发生改变,进而影响其密度和耐压强度.     

基于稀疏贝叶斯回归的正则化核密度估计算法

为了加快核密度估计(KDE)的计算速度,简化模型复杂度,提出了一种基于稀疏贝叶斯回归的KDE稀疏构造算法SBR-KDE.该算法将经人工加噪处理后的分布函数逼近值作为输入,获得了KDE的极为稀疏表示形式.实验结果表明:与传统KDE算法相比,在保持相当计算精度(多数情况下降低了模型误差)的情况下,文中算法的时空效率大幅度提高,而且在小样本训练集条件下得到的密度估计更光滑;独立成分分析及高斯化变换的应用使文中算法在一定程度上缓解了维数灾难.     

Missing completely of the CMB quadrupole in WMAP data

In cosmic microwave background (CMB) experiments, foreground-cleaned temperature maps are still contaminated by the residual dipole due to uncertainties of the Doppler dipole direction and microwave radiometer sidelobe. To obtain reliable CMB maps, such contamination has to be carefully removed from observed data. We have previously built a software package for map-making, residual dipole-contamination removal, and power spectrum estimation from the Wilkinson Microwave Anisotropy Probe (WMAP) raw data. This software has now been significantly improved. With the improved software, we obtain a negative result of CMB quadrupole detection with the WMAP raw data, which is 3.2±3.5 K2 from the seven-year WMAP (WMAP7) data. This result is evidently incompatible with ～1000 K2 expected from the standard cosmological model ΛCDM. The completely missing of CMB quadrupole poses a serious challenge to the standard model and sets a strong constraint on possible models of cosmology. Due to the importance of this result for understanding the origin and early evolution of our universe, the software codes we used are opened for public checking.     

高职动漫专业学生培养模式研究

动漫产业作为创意文化产业的一部分,其健康的发展离不开大量合格的动漫设计人才的培养。本文从高职教育的角度,在分析高职学生的学习习惯、高职学生对于校园文化的认同以及分层教育基础上,剖析高职高专动漫专业学生的培养模式。     

Prediction of sites under adaptive evolution in flavin-containing monooxygenases: Selection pattern revisited

Flavin-containing monooxygenase (FMO), like cytochrome P450 (CYP), is a monooxygenase that uses the reducing equivalents of NADPH to reduce one atom of molecular oxygen to water, while the other atom is used to oxidize the substrate. Recently, it was shown that some CYP isoforms have been subject to positive selection. However, it is unknown whether the highly conserved phase I detoxification enzyme, FMO, has undergone similar positive Darwinian selection. We used maximum-likelihood models of codon substitution, evolutionary fingerprinting, and cross species comparison to investigate the occurrence of adaptive evolution in FMO sequences. We used recent genomic data from a range of species, including vertebrates and invertebrates. We present the evidence for the occurrence of adaptive evolution in mammalian FMO 3, 4, 5, and fugu FMOs but not in mammalian FMO 1, FMO 2, frog FMOs, other fish FMOs and invertebrate FMOs. The sites under adaptive evolution were significantly associated with the insertion domain in mammalian FMO 5. We identified specific amino acid sites in FMOs 3–5 that are likely targets for selection based on the patterns of parallel amino acid change. The most likely role of adaptive evolution is the repair of mutations that permitted optimal NADP+ binding and improved catalytic efficiency. The occurrence of positive selection during the evolution of phase I detoxification enzymes such as FMOs 3–5 and fugu FMO suggests the occurrence of both high selection pressure acting on species within their unique habitats and significant changes in intensity and direction (forms of xenobiotics and drugs) resulting from changes in microhabitat and food.