某X65钢级输气管道环焊缝泄漏失效分析

针对某X65输气管道环焊缝泄漏失效问题，通过无损探伤、硬度试验、金相组织分析、扫描电镜分析等方法，对钢管环焊缝进行了分析研究。分析结果显示，焊接接头组织未见明显异常，但裂纹附近存在疏松组织，该疏松组织主要元素为铁和氧，以及少量铝、硅、钙、硫元素。研究表明，该疏松组织为焊接时未清理干净的焊渣，在外力和内压作用下，夹渣处裂纹相互贯穿形成穿透性裂纹，裂纹由内表面向外表面扩展，导致焊缝产生开裂而发生泄漏。     

全自动焊含缺陷环焊缝管段承载能力研究

为了研究全自动焊在役管线的真实承压能力，通过水压爆破试验对全自动焊含缺陷环焊缝在役管段的承载能力进行研究。研究结果表明，全自动焊焊接工艺下环焊缝缺陷主要是未熔合缺陷，且3种含未熔合缺陷管段起爆点、爆破压力、撕裂方向大致相同；含3种未熔合缺陷环焊缝管段的真实爆破压力均大于爆破压力的理论计算值，远远满足现场运行所需要的承载能力；含缺陷环焊缝的存在并没有对在役管段的整体承载能力造成影响；管段的承载能力主要取决于母材自身的材料性能。     

基于应变设计的高强钢管道环缝焊接技术

在复杂地形地貌、地震断裂带和海洋环境等情况下的管道敷设通常采用基于应变的设计方法，这对管道环焊缝的性能提出了特殊的要求。为了掌握基于应变设计条件下高强度管道的环缝焊接技术，设计了FeNi合金焊丝，制定了焊接工艺，进行了环缝焊接试验，并对焊缝金属的力学性能进行了检测。结果表明，所焊环焊缝的性能满足基于应变设计的X80高强钢管道环焊缝的强度与韧性要求，焊缝强韧匹配度较好，且具有大的缺陷容限和高的抗大应变能力。     

回转窑大齿圈的安装与找正

根据回转窑大齿圈结构特点 ,阐述了回转窑大修中两个半齿圈组装、校正及与筒体的安装、找正方法 ,提出了其重要工艺施工过程中的注意事项     

Short communication: Verifying Holstein heifer heart girth to body weight prediction equations

The estimation of Holstein heifer body weight (BW) from heart girth measurements is needed, as many farms do not have animal scales to make the management decisions that require BW. The correlation between heart girth and BW is known to vary with differing animal conformation. The previous equation to correlate the 2 measures for Holstein dairy heifers was done 25 yr ago. Data were derived from 6 US experiment stations that are part of Regional Research Project NC-2042: Management Systems to Improve the Economic and Environmental Sustainability of Dairy Enterprises. After deriving a new equation from a data set of observations and using a second validation data set, it was determined that the equation developed in 1992 was still valid and further equation development was not needed at this time.     

Efficient algorithm for calculating short cycles in Tanner graph based on matrix computation

Loop distribution of Tanner graph affects the BER performance of low-density parity-check codes(LDPC) decoding.To count short cycles in the Tanner graph efficiently,a side by side recursion algorithm based on matrix computation was proposed.Firstly,5 basic graph structures were defined to realize recursive calculate in the implementation process.Compared with previous works,the algorithm provided many methods for counting the same length of cycles.The same result confirmed the correctness of the algorithm.The new algorithm could not only calculate the total number of cycles,but also gave the number each edge participating in fixed-length cycles.Its complexity was proportional to the product of D and square of N,where D was the average degree of variable nodes,and N denoted the code length.For LDPC codes,D was far less than N.For most of the LDPC codes,the calculation for numbers of cycle-length g、g+2、g+4 was only several seconds.     

Investigation of the impact toughness of self-shielded flux-cored wire girth welds for X80 pipelines

Self-shielded flux-cored wire is a convenient and efficient consumable for pipeline field girth welding because of its self-protection characteristic and high deposition rate,especially for remote construction sites in rugged terrain. From the perspective of pipeline safety,the impact toughness of the girth welds is an important factor in pipeline integrity,which determines the crack arrest behavior in the girth welds. Therefore,improving the girth weld impact toughness is of primary importance in the field of pipeline girth welding. Three self-shielded flux-cored wires comprising different chemical composition systems have been applied to large diameter X80 UOE( U-ing-O-ingExpanding) pipeline semi-automatic girth welding,and the impact toughness of the welds has been evaluated by girth weld chemical composition analysis and microstructural analysis using scanning electron microscopy( SEM) and energy dispersive spectrometry( EDS) to investigate pipeline girth weld impact toughness and find ways to improve it.This helps in determining the main factors that influence girth weld impact toughness. Pipeline girth weld impact toughness is mainly determined by the final microstructure produced in the solid-state phase transition. In the as-weld state,acicular ferrite( AF) and fine bainite( FB) are a benefit to the impact toughness. For multilayer semiautomatic self-shielded flux-cored wire welding,the normalizing and tempering function of the latter beads to the initial beads plays an important role in the transition of girth weld microstructure,which affects the impact toughness. The original AF and FB and the corresponding heat treatment microstructure of the fine and uniform block ferrite and pearlite result in very good impact toughness. The following two mechanisms are found to promote the production of AF and FB in the girth weld. First,elements promoting the broadening of the austenitic region,such as Ni,C,Cu,and Mn,induce low temperature phase transitions and restrain the opposing function of Al,which is a benefit to the production of AF and FB. Second,dispersed high-melting-point inclusions,especially Al2O3,induce the nucleated production of AF. The advantageous function of inclusions is determined by their shape,distribution,and dimension. Dispersed spherical inclusions of small dimension are a benefit to the production of AF,and result in good impact toughness.     

储罐倒装施工内外横缝两用埋弧自动横焊机的设计及焊接工艺

在发展大型储罐倒装法施工技术的过程中,因国内外没有能够焊接储罐内环缝的自动焊机,通过不断探索,自行设计了储罐倒装施工内外横缝两用埋弧自动横焊机,制定了先焊接外环缝,在下落液压缸和胀圈后,再焊接内环缝的施工工艺,在国内外首次实现了储罐内环缝埋弧自动焊接,为大型储罐倒装法施工技术的发展提供了有力的保障.     

一类环长至少为10的准循环LDPC码

为扩展性能优良、易于工程实现的LDPC码的构造方法,提出了一类环长至少为10的准循环低密度奇偶校验(quasi-cyclic low-density parity-check, QC-LDPC)码的构造方法。该方法首先基于基矩阵和 准则[11]构造出环长至少为10的校验矩阵;然后,利用掩蔽矩阵对得到的校验矩阵进行变换;最终,构造出满秩的准循环LDPC码。理论分析和仿真结果表明,该类QC-LDPC码字构造灵活,在AWGN信道下具有优异的性能。