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排序方式: 共有705条查询结果,搜索用时 15 毫秒
1.
Currently, very few aquaculture operations are employing airlift pump technology for water recirculation, aeration, and waste removal. This is likely due to the poor design and lower efficiency of traditional airlift design, the limited amount of research effort that has been invested in improving performance capabilities of air lift pumps and the general lack of awareness of the industry about the inherent advantages of airlift systems. A new efficient airlift pump is hydrodynamically designed by incorporating the Volume of Fluid (VOF) multi-phase model along with the K-ε turbulence model utilizing Computational Fluid Dynamics (CFD) tools. The pump is designed to offer a substantial reduction in total energy usage as well as an improved quality of the culture products in order to make it attractive to aquaculture industry. In this study, both numerical and experimental investigations were carried out for airlift systems operating under two different submergence ratios of 50% and 90% in a lab setting using 2.54 cm diameter pumps. Also, the performance of a large-scale pumps of 10.16 cm diameters were also tested in an aquaculture raceway to determine its effect on the operation. The numerical results were found to be in agreement with the experiments within ±20% which is considered very reasonable for multiphase flow analysis. The present study was found to present a great tool for modelling the airlift pump performance, and potentially proposing new designs. 相似文献
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蒸压加气混凝土是一种新型的节能、环保墙体材料 ,它在基本建设中运用具有良好的综合经济效益和社会效益。这里以加气混凝土在建筑中的应用实例 ,从材料、施工、抹灰及存在的问题等方面论述了它的运用情况 ,可供有关设计和施工人员参考。 相似文献
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M. Kreuzer S. Müller L. Mazzolini R. E. Messikommer I. D. M. Gangnat 《British poultry science》2020,61(1):33-42
ABSTRACT1. Although fattening dual-purpose types or male layer hybrid chickens appears more ethical than the common practice of culling day-old male layer chicks, the lower feed efficiency of these birds raises concerns. Replacing feed ingredients that compete with food production by those of lower value for human nutrition would be beneficial.2. Lohmann Dual (LD), a modern dual-purpose type, Lohmann Brown (LB), a male layer hybrid, and Hubbard JA 957 (HU), a slow-growing broiler type, were fattened for nine weeks on two diets (control or ?20% crude protein; n = 6 × 12 birds). Growth, carcass and meat quality were analysed.3. Growth performance of HU exceeded that of LD and especially of LB. The growth depression caused by the low-protein diet fed to LD (?7%) was only half of that found in HU (?13%). The LD fed the control diet had the same feed efficiency as the HU fed the low-protein diet. Even the LB had a lower performance and feed efficiency with the low-protein diet in growth. There was a gradient in carcass properties (weight, dressing percentage, breast meat yield, breast proportion and breast angle) from HU to LD to LB, with some additional adverse effects of the low-protein diet especially in HU. There were some breed differences in fatty acid profile in the intramuscular fat.4. In conclusion, the dual-purpose type used complied with regulations for Swiss organic poultry systems in terms of growth rate and was found to respond less when fed a low-protein diet than the slow-growing broiler type. The LB males were inferior in all growth and carcass quality traits. Future studies need to determine the exact protein and amino acid requirements of dual-purpose and layer hybrid chickens and the economic feasibility of the systems, especially for organic farming. 相似文献
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马力 《湖南农业大学学报(自然科学版)》2011,37(5):479-483
采用三速和单速循环风机,研究密集烤房不同循环风机对烤烟色素及感官质量的影响.结果表明:采用三速循环风机烤后烟叶的叶绿素a、叶绿素b含量分别为5.10、167.74 μg/g,分别为单速循环风机的72.11%和93.30%;叶黄素、β-胡萝卜素、类胡萝卜素含量分别为0.84、155.56、156.40 μg/g,分别为单... 相似文献
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介绍了电控LPG-柴油双燃料内燃机供给系统的设计,柴油分别采用机械泵和电磁铁执行器供给,LPG采用电控顺序喷射方式供给。同时对控制系统进行了硬件和软件设计,对软件的功能进行详细的说明,最后对双燃料内燃机进行标定试验,论证了柴油的电控喷射对降低烟度排放的影响。 相似文献
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美国青蛙膨气病病原菌的分离鉴定及药敏试验 总被引:1,自引:0,他引:1
经对膨气病病原菌的分离鉴定,嗜水气单胞菌与假单胞菌属细菌是致病菌。药敏试验结果:庆大霉素,氯霉素对致病菌有较强的杀灭作用,中草药黄连,黄岑也有一定的抑制作用,该病发生与环境条件密切相关,保持良好的养殖水质环境是预防该病的最好方法。 相似文献
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不同能源类型密集烤房烘烤效果对比研究 总被引:7,自引:0,他引:7
[目的]探讨不同能源类型密集烤房的烘烤效果.[方法]2014年在云南大理进行了不同能源密集式烤房烘烤效果对比研究,通过试验分析了不同能源类型密集烤房在烘烤成本、经济效益及烤房温度控制等方面的烘烤效果.[结果]研究表明,最优处理为T2处理(25 kW内除湿热泵+20 kW电发热管辅助供热烤房),相比对照1 kg干烟可以减少烘烤成本1.28元,提高均价1.54元,中上等烟比例也有所提高,且烤房温度控制精准性好,其次是生物质燃烧机烤房和甲醇燃烧机烤房,但结合烤房的实际应用性,当前生物质燃烧机烤房最具推广价值.[结论]研究可为今后新能源烤房的开发与应用奠定基础. 相似文献