基于灰预测模型的自密实混凝土收缩徐变研究

对自密实混凝土试件进行为期120d持续加载徐变试验,分别将其中一组试件进行密封处理,同期进行收缩对比试验,由此可测得自密实混凝土干燥徐变度、基本徐变度、干燥收缩和自生收缩发展曲线：在短期收缩徐变变形数据分析基础上采用基于灰色系统理论的预测模型对自密实混凝土收缩徐变发展进行预测;结果表明,模型预测结果与试验结果吻合较好,该方法可以运用于自密实混凝土收缩徐变变形预测,可以给自密实混凝土工程实践提供一定的参考和指导。     

单片机的炭素焙烧窑多点温度监测系统

介绍以MCS-51单片机为核心,利用K型热电偶作温度传感器,用MAX6675热电偶温度数字传感器进行温度采集,对炭素焙烧窑中64点温度测量的系统。此系统通过485总线通信,将数据传输给工控机(IPC)。     

干拌自密实混凝土变形性能试验研究

研究了干拌自密实混凝土的弹性模量、横向变形系数以及峰值应变,分析了干拌自密实混凝土变形性能的特点,并根据统计分析给出了弹性模量的回归公式,试验结果表明,加水量对干拌自密实混凝土的弹性模量影响较大,横向变形系数与普通混凝土及高强混凝土均有较大差别,随着粗骨料含量的增加,干拌自密实混凝土的峰值应变减小.     

基于义类同现频率的汉语语义排歧方法

义类标注是信息检索和自然语言处理中的一个重要问题,但依靠人工对义类进行标注不仅是一个十分烦琐的工作,而且很难把握标准,对义类代自动标注的研究就显得尤为迫切,而要实现自动标注,必须解决多义词排歧这一重要问题,在地《现代汉语词典》的义类标注过程中,文中通过统计相邻词语义类组合串的出现频率构造了一个同现频率矩阵集,这一同现频率矩阵集充分利用了义类体系的层次结构,极大地减少了数据稀疏和数据冗余,在此基础上     

Textural pattern classification for oral squamous cell carcinoma

Despite being an area of cancer with highest worldwide incidence, oral cancer yet remains to be widely researched. Studies on computer‐aided analysis of pathological slides of oral cancer contribute a lot to the diagnosis and treatment of the disease. Some researches in this direction have been carried out on oral submucous fibrosis. In this work an approach for analysing abnormality based on textural features present in squamous cell carcinoma histological slides have been considered. Histogram and grey‐level co‐occurrence matrix approaches for extraction of textural features from biopsy images with normal and malignant cells are used here. Further, we have used linear support vector machine classifier for automated diagnosis of the oral cancer, which gives 100% accuracy.     

硫化氢罐开裂失效分析

硫化氢罐发生开裂,对该罐开裂原因进行了失效分析。该罐存在三种开裂：容器内硫化氢产生氢原子向钢中扩散并聚集形成氢鼓泡;不同层面上的相邻氢鼓泡裂纹在内压下相互连接,形成氢致开裂;在内压下鼓泡位置产生拉应力,在拉应力和湿硫化氢环境下发生应力腐蚀开裂。介绍了检验方法和通过改善材料和防腐工艺避免开裂方法。     

Behavior of 316L stainless steel containing corrosion pits under cyclic loading

The environmental performance of 316L grade stainless steel, in the form of tensile specimens containing a single corrosion pit with various aspect ratios, under cyclic loading in aerated chloride solutions is investigated in this study. Results from environmental tests were compared and contrasted with those obtained using finite element analysis (FEA). Fractography of the failed specimens obtained from experiments revealed that fatigue crack initiation took place at the base of the shallow pit. The crack initiation shifted towards the shoulder and the mouth of the pit for pits of increasing depth. This process is well predicted by FEA, as the strain contour maps show that strain is the highest around the centric strip of the pit. However, for shallow pits, local strain is uniformly distributed around that strip but begins to concentrate more towards the shoulder and the mouth region for increasingly deep pits.     

频繁碱洗对不锈钢及钛材设备的影响

Pd/C催化剂对PTA生产中加氢精制起了至关重要的作用。介绍了加氢反应器选材、催化剂失活及其再生碱洗的生产情况。并分析了高温碱洗对加氢反应器碱脆与后续不锈钢设备氯脆的影响。提出了防止应力腐蚀破裂的措施,包括提高催化剂质量、减少碱洗频次、改进碱洗工艺、同时优化加氢工艺、控制进料浆料质量分数,以提高催化剂使用寿命。采用优等品NaOH,消除设备残余应力,加强设备定期检测等也是有效的。对钛设备高温碱洗会发生氢脆也作了分析。     

Influence of clays on the shrinkage and cracking tendency of SCC

The influence of different types of clay on the shrinkage and cracking tendency of fly ash modified self-consolidating concrete (SCCF) for the application of slipform paving were investigated in this study. The mortar phase of each mix was tested for autogenous shrinkage, total free shrinkage under drying and restrained shrinkage cracking. The mechanical properties (flexural strength, compressive strength, and modulus) were studied to supplement the results of the shrinkage and cracking tests. The plain SCCF mix was compared against the clay-modified SCCF mixes, as well as conventional SCC and slipform concrete (SFC) mixes. The results showed that the very early-age autogenous shrinkage of SCCF mortar was increased by the addition of clays due to adsorption effects. The effects of the clays on total shrinkage under long-term drying were found to depend mainly on the pozzolanic reactivity, but these effects were very slight at low dosages of about 1% by mass of binder. The early-age cracking tendency was aggravated by the clays composed of purified magnesium alumino silicate and metakaolin, but little influenced by the clay composed of kaolinite, illite and silica. Overall, the SCC mixture modified with both fly ash and a small amount of clay showed comparable shrinkage and early-age cracking performances as conventional SFC.     

Numerical analysis of residual stress distribution generated by welding after surface machining based on hardness variation in surface machined layer due to welding thermal cycle

Recently, stress corrosion cracking (SCC) has been observed near the welded zone of the primary loop recirculation pipes made of low-carbon austenitic stainless steel type 316L in boiling water reactors. SCC is initiated by superposition effect of three factors. They are material, environmental and mechanical factors. For non-sensitized material such as type 316L, residual stress as a mechanical factor of SCC is comparatively important. In the joining processes of pipes, butt welding is conducted after surface machining. Surface machining is performed in order to match the inside diameter and smooth surface finish of pipes. Residual stress is generated by both processes. Moreover, residual stress distribution generated by surface machining is varied by subsequent welding processes, and it has the maximum residual stress around 900 MPa near the weld metal. The variation of metallographic structure, such as recovery and recrystallization, in the surface machined layer due to the welding thermal cycle is an important factor for this residual stress distribution. In this study, thermal ageing tests were performed in order to evaluate hardness variation due to the thermal cycle in the surface machined layer. Results of thermal ageing tests were applied to the finite-element method as the additivity rule of the hardness variation. Varied hardness was converted into equivalent plastic strain. Then, thermo-elastic-plastic analysis was performed under residual stress fields generated by surface machining. As a result, analytical results of surface residual stress distribution generated by bead-on-plate welding after surface machining show good agreement with measured results by the X-ray diffraction method. The maximum residual stress near the weld metal is generated by the same mechanism as in the both-ends-fixed bar model in the surface machined layer that has high yield stress.