管道三通塑性极限压力及其影响因素分析

基于极限分析的观点,得到了两个适于工程上采用的焊制三通塑性极限压力估算式,并结合试验数据进行了验证和影响因素分析。结果表明,基于相贯性屈服和等面积补强得到的估算公式是可用的,其中相贯线屈服分析得到的公式最精确,具有推广价值,主管厚径比对三通塑性承载能力有加强作用,而管径比对极限压力的影响规律有待进一步研究。     

环氧煤沥青涂料用缓蚀剂的研制

在环氧煤沥青的底漆和面漆中分别加入自选合成的胺类缓蚀剂Ｒ、Ｙ和Ｚ后,采用交流阻抗和盐雾试验等方法进行了测试。测试结果表明,覆盖层的耐蚀性能大为提高,覆盖层针孔电阻Ｒｆｐ的阻值提高２￣３个数量级,覆盖层的物理机械性能不受影响。     

基于Attention_DenseCNN的水稻问答系统问句分类

为了解决“中国农技推广APP”问答社区中水稻提问数据快速自动分类的问题,提出一种基于Attention_DenseCNN的水稻文本分类方法。根据水稻文本具备的特征,采用Word2vec方法对文本数据进行处理与分析,并结合农业分词词典对文本数据进行向量化处理,采用Word2vec方法能够有效地解决文本的高维性和稀疏性问题。对卷积神经网络（CNN）上下游卷积块之间建立一条稠密的链接,并结合注意力机制（Attention）,使文本中的关键词特征得以充分体现,使文本分类模型具有更好的文本特征提取精度,从而提高了分类精确率。试验表明：基于Attention_DenseCNN的水稻问句分类模型可以提高文本特征的利用率、减少特征丢失,能够快速、准确地对水稻问句文本进行自动分类,其分类精确率及F1值分别为95.6%和94.9%,与其他7种神经网络问句分类方法相比,分类效果明显提升。     

地面式明钢管温度作用机理与取消伸缩节研究

以某水电站地面式明钢管为例,建立了水电站钢管结构整体有限元模型,考虑了均匀温度作用和非均匀温度作用对明钢管受力变形的影响,论证了地面式明钢管取消伸缩节的可行性.结果表明:取消伸缩节后钢管的Mises应力远小于钢材允许应力值,虽然上平段钢管产生了较大的轴向应力,但不会引起钢管屈曲失稳,因此从结构强度和稳定性多方面都表明地...     

Development Trend of Computer Network

At present, the computer network is the most quickly developing technology, so following the direction of this technology development is quite necessary. This paper introduces mainly four aspects of present network development, that is: connection technology, connecting device, high-speed transmission and network utility. Then, a few hot-topics were discussed as well.     

The Finite Element Method for Frame Structure with Fuzzy Elastic Connections

The connections of frame structure elements at a node are ofen an elastic connection between hinged and rigid.In this paper,the stiffness matrix and the loading transfer matrix of frame element with turn elastic connections is deduced,the cross shear effect has been taken into consideration simultaneously.The stiffness matrices of some bar elements,such as both ends of the bar are hinged or rigid and one end is hinged but the other is rigid,are special cases of the stiffness matrices presented in this paper.After pointing out that the elastic coefficient at a node of a bar element with elastic joint is really a fuzzy quantity,the fuzzy stiffness matrix of the bar element is obtained,and a solution to structural fuzzy finite element equilibrium equations is presented.The fuzzy solution obtained from above is not only containing the solution of ordinary finite element method but also providing some additional informations with practical value.[WT5HZ]     

钢筋钢纤维混凝土轴心受拉构件抗裂度的计算方法

根据４０根钢筋钢纤维混凝土轴拉构件及对比试件的试验结果,分析了钢纤维掺量对构件初裂荷载的影响,推导出构件抗裂度的计算公式,并用本次试验结果对公式进行了验证。所给公式模型清晰,计算简便,可供工程设计参考。     

草鱼7个插入/缺失型突变多态性及与幼鱼生长性状关联分析

对草鱼生长性状进行数量性状基因座(quantitative trait locus,QTL)定位过程中,在15号连锁群中定位到一个与体质量相关的QTL,本研究根据已有的草鱼遗传连锁图谱和基因组序列,拟用短片段重复序列(short tandem repeat,STR)分型技术对该连锁群的3个scaffolds中插入/缺失型突变位点进行筛选,以降低分型成本,同时将筛选出的7个多态性位点与草鱼幼鱼生长性状进行关联分析。结果显示,(1)草鱼3个scaffolds中44个插入/缺失型突变位点中有17个简单重复序列(又称微卫星,simple sequence repeats,SSRs),2个位点引物设计不成功,设计的25对引物中仅22对扩增和分型成功;(2) 22个位点中仅有7对引物在4个亲本中存在多态性,直接测序结果发现,STR分型技术不仅可准确对插入/缺失型突变位点进行分型,同时可降低分型成本;(3)将7个插入/缺失型突变位点与323尾选育F2草鱼的生长性状进行关联分析发现,除了位点ID-10H和ID-41F以外,其余5个位点都与草鱼幼鱼的一个或多个生长性状显著相关,其中ID-6H与幼鱼肥满度性状显著相关,位点ID-11F、ID-15F、ID-32F和ID-39F分别与草鱼幼鱼体质量、体长、体宽和体高性状显著相关,可将以上5个与草鱼幼鱼生长性状相关的突变位点用于草鱼生长性状QTL加密和分子标记辅助育种。     

Organic sulfur forms in mineral top soils of the Marsh in Schleswig‐Holstein,Northern Germany

Little is known about the nature of organic sulfur (S) in soils of the Marsh in Schleswig‐Holstein, Northern Germany. In addition to total and inorganic S, we determined two organic S fractions (ester sulfate‐sulfur and carbon‐bonded sulfur) in 14 aerated mineral top horizons of two salt marshes and ten dyked polder soils of different age. All soils developed from marine sediments. Total S concen‐trations ranged from 153 to 950 mg kg^—1. Organic S was the main S constituent (range from 53 to 99% with a median of 97%). Higher inorganic S levels were found only in the salt marshes due to soluble sulfate (15 to 47%). The younger marsh soils (salt marshes and soils of a polder dyked in 1978) had unique high S contents of 0.9 to 2.4% in their organic matter, whereas the S contents of the organic matter in older marsh soils were at only 0.6%. This S‐rich organic matter is a heritage of a former anoxic marine environment. In most horizons the carbon‐bonded S was the dominant sulfur form. However, both carbon‐bonded S and ester sulfate‐S did not relate to soil age. This limits the benefit of the wet chemical fractionation procedure used for studying the fate of organic S in marsh soils.     

排水沟塘分布特性及与农田水力联系对水质净化能力的影响

湿地是一种能够有效治理农业非点源污染的生态设施;在一些无法建设人工湿地的地区,现存的排水沟塘系统具有类似湿地的水质净化效果。为研究排水沟塘的分布以及其与农田水力联系对其水质净化能力的影响,该文以扬州市江都区昭关灌区为例,首先通过实地调查,明确研究区不同形式沟塘的分布规律,确定沟塘与农田逐级详细水力联系,然后建立理论分析模型,分别计算考虑与不考虑水力联系2种情况下,沟塘的污染物去除能力。结果表明,考虑水力联系后,污染物去除能力为不考虑水力联系的70%~84%;水质净化作用主要集中在一些面积较大的支沟和池塘。从农田排水的角度考虑,尺寸较大沟塘会出现一定的水力冗余,但是从水质改善的角度看,则有必要保留。研究区可通过较为简单的工程措施来优化水力联系,提高其污染物的去除能力。