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沼气生态农业模式综合评价 总被引:5,自引:4,他引:5
为了对沼气生态农业模式结构、功能和效益进行综合定量评价,该研究结合沼气生态农业模式自身的结构和功能特点,以生态农业模式评价指标体系为基础,选择了17个指标构建了沼气生态农业模式综合评价指标体系,应用层次均权法确定了沼气生态农业模式综合评价各指标的权重,在此基础上,运用综合指数法构建了沼气生态农业模式综合评价模型。并以宝鸡市2个典型沼气生态农业模式(陇县“沼气池—厕所—畜舍—菜(果、粮)”庭院生态农业模式和千阳县“桑—蚕—双孢蘑菇—畜舍—沼气池”生态农业模式)的研究数据对模型进行了验证,评价结果与实际情况吻合,表明该研究所提出的评价指标体系和模型具有适用性。 相似文献
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Gamal O. El Naggar George John Mahmoud A. Rezk Waheed Elwan Mohammed Yehia 《Aquaculture (Amsterdam, Netherlands)》2006,261(3):904-907
The development of a reliable methodology for spawning of African catfish, Clarias gariepinus without the use of hormone injections would greatly improve the prospects of aquaculture in Africa. Earlier work has shown that it is possible to produce C. gariepinus fingerlings by subjecting the broodfish to a physical stress of reduced water depth and/or increased temperature. The hypothesis that C. gariepinus could be induced to spawn through a combined physical stress of lowered water level and increased stocking density was tested in concrete tanks. Three water levels (25, 50 and 75 cm) and three stocking densities (2, 4 and 6 pairs of broodfish at a 1:1 sex ratio in each hapa) were tested. Water depth in the tanks and brood fish density in the hapas affected spawning success. The percentage of spawning females was significantly higher when broodfish were stocked at 2 and 4 pairs in each hapa at water levels of 25 cm or 50 cm. There was no significant difference in spawning response between the 25 and 50 cm depths while a significant difference was seen between the 75 cm and both 25 and 50 cm depths. The results indicate optimum levels and densities for enhancing spawning success in C. gariepinus. 相似文献
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要提高认识,产政策,加强领导,认真实施,花大力气加快方格蔟推广步伐,进一步提高我省蚕茧质量。 相似文献
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Based on the experimental study of two prestressed frames in redistribution of Internal force, it can be concluded that the dominating influence factors on moment modulation are the relative height of equivalent compression zone, the secondary moment, the ratio of beam rigidity to column and development of cracks in the top of columns.The secondary moment is very important in modulation of frames. Especially, the secondary moment will governing the modulation when the relative height of equivalent compression zone is large enough. 相似文献
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Impacts of chlorpyriphos (2, 4, 6 ppm) on the profiles of antioxidant (catalase) and anaerobic (lactate dehydrogenase) enzymes and other macromolecular contents (DNA, RNA, protein) of various tissues of the freshwater fish, Heteropneustes fossilis were studied. Chlorpyriphos significantly decreased the specific activity of catalase (CAT) and lactate dehydrogenase (LDH) in the brain, liver, gill and skeletal muscle of the fish. The reduction in specific activity might be due to the binding of chlorpyriphos or its metabolites with the enzyme molecules or affecting the synthesis and/or degradation of the enzymes. Like enzymes, the DNA, RNA and protein contents decreased in the brain, liver, gill and skeletal muscle of the fish as a function of increase in chlorpyriphos concentrations (2-6 ppm). The chlorpyriphos-induced reduction in these biochemical constituents might be because of alteration in their turnover (synthesis/degradation) in different tissues. The maximum effects on CAT, LDH, DNA, RNA and protein were obtained in response to 6 ppm chlorpyriphos. The present findings suggest chlorpyriphos concentration related impairment in antioxidative, anaerobic and protein synthesizing capacity of the fish. Therefore, the use of higher concentrations of chlorpyriphos should be avoided to protect the health of economically important freshwater food fish. 相似文献
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提出了一种计算A形排架杆件轴力的通用公式,应用此公式可避免求解各结点的静力平衡方程组,直接计算任意杆件的轴力. 相似文献
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Shay Allred Wenjie Shao Jacob H. Jones M. Wes Schilling Beth H. Baker Peter J. Allen 《Aquaculture Research》2020,51(5):1854-1866
Catfish Ictalurus spp. are subjected to stressful conditions during harvest, which may be linked to fillet coloration and quality. Poor water quality in ponds, socks or hauling tanks, as well as handling stress, have been suggested to cause red fillets in catfish; however, chronic exposure has not resulted in red fillets. Short‐term occurrences of extreme poor water quality, particularly low dissolved oxygen, high carbon dioxide and high temperature, may occur in ponds or during harvest. Therefore, market‐sized Channel Catfish Ictalurus punctatus were acutely exposed (12 hr) to one of the three water quality treatments while confined during a simulated socking procedure and evaluated for stress responses by means of change in blood parameters and fillet quality. In fish subjected to the extreme treatment, hematocrit, plasma cortisol, glucose and lactate levels increased, with 22% mortality, indicating highly stressful conditions. In fish subjected to moderate and typical (control) treatments, cortisol increased but a lack of change or decrease in glucose and lactate indicated minimal anaerobic metabolism. Only one red fillet was produced by the extreme treatment and two by the typical treatment; therefore, the results suggest red fillets are not a product of poor water quality compounded by handling during harvest. 相似文献