腐蚀管道剩余寿命的性能衰减模型研究   总被引：4，自引：0，他引：4  

姜如桦  张鹏  陈莉琼  侯向秦 《油气储运》2001,20(11):13-16

管道在长期的运行过程中，由于介质和土壤的腐蚀性，管材的微塑性变形、结构转变和渗氢等。不仅会使管道出现各种腐蚀损伤，而且还存在着老化效应和氢化作用，导致管材的脆变并改变材料的塑性，使机械性质参数发生衰退，从管材性能衰减和腐蚀损伤角度研究了管道的剩余寿命，提出了根据结构承载能力的极限值确定塑性变形时工作寿命的方法，为了确定剩余使用寿命，对剪切损伤率和屈服性能比等概念进行定义，在掌握管材金属剪切损害率和屈服性能比的时间特性基础上，建立了剩余寿命计算模型。并给出了算例。  相似文献   

钢筋混凝土结构锈蚀损伤定位     

吴瑾  程吉昕  陆明生 《勤云标准版测试》2004,(4)

对钢筋混凝土结构锈蚀损伤定位进行了研究,以频率变化平方比作为锈蚀损伤参数,从理论上证明该参数是锈蚀损伤位置的函数。锈蚀钢筋混凝土结构试验结果表明预测的损伤位置和实际的损伤位置较一致,模态参数用于检测混凝土结构构件中的损伤,为大型结构的鉴定和评估提供了新的途径。  相似文献   

药物防治蝇害的研究进展     

严凤  何国声 《中国兽医寄生虫病》2004,12(1):37-40

蝇害已经成为危害规模化畜禽养殖的重要问题。文章回顾了防治蝇害的三代杀虫剂的发展过程和存在的问题 ;展望了作为新一代环境友好防治蝇害药物的昆虫生长调节剂的开发前景。  相似文献   

Variation in the level of grain defect light flecks and spots on cattle hides.     

O Nafstad  H Gr?nst?l 《Acta veterinaria Scandinavica》2001,42(1):91-98

The occurrence of hide damage light flecks and spots was determined on tanned hides from 28 herds during a period of 8 to 12 months. Light flecks and spots are described as small areas of grain loss up to 3 mm in diameter that are seen on dyed crust cattle leather. Damage was found on 75.8% of all hides. The neck and shoulders were the anatomical region with the highest prevalence of damage. Sixty-eight per cent of all hides had light flecks and spots in this region. The forelimbs and dewlap were the anatomical region with the second highest occurrence with a prevalence of 39.1%. This distribution corresponded to the known distribution of lice in cattle. No significant differences were observed in age, sex, prevalence of lice in the herd assessed in March or infestations with different lice species. The frequency of light flecks and spots varied significantly during the year. The frequency was highest in the late winter and early spring, decreased significantly during the summer and was lowest in the autumn. This variation supported the importance of lice in the development of light flecks and spots and suggested a relatively long healing period for the damages induced by lice.  相似文献   

The effect of eradication of lice on the occurrence of the grain defect light flecks and spots on cattle hides.     

O Nafstad  H Gr?nst?l 《Acta veterinaria Scandinavica》2001,42(1):99-106

The influence of an eradication programme for lice on the prevalence of light flecks and spots on cattle hides was studied in 33 dairy cattle herds during a period of two and a half years. Lice were eradicated from the main group of herds after 9 to 12 months and the quality of the hides before and after treatment was compared. Hides from slaughtered animals were collected during the study period, tanned and examined with special emphasis on the occurrence of the grain damage light flecks and spots. The prevalence of hides without light flecks and spots increased from 24.2% before treatment to 61.6% after treatment. The prevalence of hides free from the damage increased significantly in all examined anatomical regions. The improvement in hide quality was most marked in the shoulders and neck region which corresponded to the major predilection site of cattle lice. The prevalence of hides with light flecks and spots started to decrease in the first period (2-40 days) after eradication. The changes after treatment suggested that most healing process took place over a period of about 4 months. The eradication programme eliminated the seasonal variation in the prevalence of light flecks and spots which was present before treatment.  相似文献   

2004年冬成都市外来园林植物冻害调查及建议   总被引：7，自引：0，他引：7  

何飞  何亚平  费世民  王乐辉  陈秀明 《西南园艺》2005,33(6):19-22

作者2005年春调查了成都市外来园林植物冻害情况,发现：（1）外来园林植物受冻害影响较为普遍,41种植物在不同程度上受害;（2）冻害影响存在区域差异,郊区冻害比城区严重.分析了冻害原因,并对园林植物引种提出建议.  相似文献   

Fractional excretion of electrolytes in volume‐responsive and intrinsic acute kidney injury in dogs: Diagnostic and prognostic implications          下载免费PDF全文

Roberta Troìa  Marta Gruarin  Chiara Grisetti  Federica Serafini  Luca Magna  Erika Monari  Massimo Giunti  Francesco Dondi 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2018,32(4):1372-1382

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A comparison of two sources of methionine supplemented at different levels on heat shock protein 70 expression and oxidative stress product of Peking ducks subjected to heat stress          下载免费PDF全文

L. Guo  R. Li  Y. F. Zhang  T. Y. Qin  Q. S. Li  X. X. Li  Z. L. Qi 《Journal of animal physiology and animal nutrition》2018,102(1):e147-e154

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Polyphenols in Eucalyptus leaves improved the egg and meat qualities and protected against ethanol‐induced oxidative damage in laying hens          下载免费PDF全文

W. Li  J. Miao  N. Chen  X. Shao  Y. Cao 《Journal of animal physiology and animal nutrition》2018,102(1):214-223

Polyphenols in Eucalyptus leaves (PE) were value resources due to various pharmacological activities, but data on the effect on laying hens are very scare. This study was conducted to determine the effect of PE on the laying performance, egg traits, meat quality, antioxidant status and liver tissues of laying hens. One hundred and twenty 256‐day‐old Yueqinhuang laying hens were randomly assigned to four treatment groups (different levels of PE at 0, 0.5, 0.8 and 1.2 g/kg diet) for 63 days with 15 replicates per group. Addition of 0.8 g/kg PE not only improved the egg trait by increasing the eggshell thickness and decreasing MDA production and cholesterol content in the egg yolk, but also significantly enhanced meat quality of hens, as suggested by the increase pH_45 min (p < .01) and a* value, and decrease drip loss rate (p < .01). Meanwhile, under acute ethanol‐induced oxidative damage condition, supplementation of 0.8 g/kg PE enhanced the serum antioxidant status by increasing enzymatic activities (GSH‐PX, T‐SOD, T‐AOC), inhibited oxidative damage and provided protective effect to liver tissue. In conclusion, addition of 0.8 g/kg PE not only improved the egg traits and meat quality without obvious adverse effects, but also increased the serum antioxidant status of the hens and protected their liver tissue from ethanol‐induced oxidative damage. This study indicated that PE could be utilized as an effective feed additive for laying hens to improve health performance and egg traits.  相似文献   

危害沙棘的围连环夜蛾生物学特性及防治     

崔峻桥 《国际沙棘研究与开发》2011,9(4):33-35

围连环夜蛾在我国多有分布，但看见其幼虫的还是很少，因资料中寄主不祥，笔者经室内外观察。发现其危害多种植物的叶片，更喜欢危害沙棘树的叶片，笔者经2a的室内外观察得知。其生物学特性在辽宁西部每年1代，以蛹越夏及冬。对沙棘树危害较重，对栽植的大果沙棘危害尤为严重，在5a生的沙棘树上有100多头幼虫危害，成虫善飞翔。  相似文献