黄土耕作坡面溅蚀过程中微地形响应特征   总被引：4，自引：0，他引：4  

塔娜  王健  张慧荟  田龙  张青峰 《水土保持通报》2016,36(1):110-114

[目的]探究60mm/h雨强下不同耕作坡面在溅蚀阶段的微地形变化特征,为黄土坡地水土保持耕作方式布设提供科学依据。[方法]在室内人工模拟降雨试验的基础上,采用激光扫描量测方法分别获取溅蚀前后4种不同耕作方式(人工锄耕、人工掏挖、等高耕作、耙磨整平)黄土坡面微地形相对高程,并对能反映微地形变化的高精度M-ΔDEM进行了分析。[结果]不同耕作措施下坡面微地形均具有较弱的空间变异,其空间分异主要受耕作措施的影响;降雨对微地形具有一定的夷平效应,且不同耕作坡面在1~1.3m尺度范围内均表现出侵蚀平衡现象;不同耕作微地形对溅蚀均具有阻滞作用,其中人工掏挖和等高耕作具有较强的水土保持作用。[结论]微地形水系分维能较好地反映复杂的微地形特征,而坡面耕作方式是溅蚀过程中微地形时空变异分布状况的控制性因子。  相似文献   

大型灯泡贯流式泵站振动研究概述     

王新  李同春  塔娜 《中国农村水利水电》2009,(2):83-85

机组和泵房的振动是泵站运行中最为常见的问题,直接影响泵站的安全可靠运行。对大型灯泡贯流式泵站振动研究现状和抗振安全评价计算分析方法作了详细的介绍,对研究机组振动诱发泵房振动的共振校核法、拟静力法、谐响应求解法和瞬态动力时程法等进行了阐述,并对这几种方法进行了分析比较,就其存在的问题作了总结概述。  相似文献   

Prey preferences of notonectids towards larval mosquitoes across prey ontogeny and search area     

Arpita Dalal  Ross N Cuthbert  Jaimie TA Dick  Susmita Gupta 《Pest management science》2020,76(2):609-616

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工厂化水产养殖水质监测系统   总被引：1，自引：0，他引：1  

肖瑞超  位耀光  他旭翔  张龙 《水产学杂志》2017,(5):51-56

工厂化水产养殖的密度高、风险大,养殖对象对pH、溶解氧、温度、氨氮、亚硝酸盐等水质参数的变化敏感,受影响严重,监测水质参数极为重要。本文针对工厂化水产养殖水质监测特点和需求,研发了工厂化水产养殖水质监测系统。分析研究pH、溶解氧、温度、亚硝酸盐等水质参数的阈值,设计水质监测数据无线采集节点和基于Zigbee的无线监测网络,建立水质监测系统软件平台。结果表明,该系统能够实现工厂化水产养殖水质实时监测,保证生产安全,提高水产养殖生产效率。  相似文献   

Toxicity of aqueous aluminium to the ectoparasitic monogenean Gyrodactylus salaris     

Arnulf Soleng  Antonio B.S. Polo  Tor A. Bakke 《Aquaculture (Amsterdam, Netherlands)》2005,250(3-4):616-620

Both laboratory and field experiments have demonstrated that aqueous aluminium can act as a paraciticide to the monogenean Gyrodactylus salaris Malmberg, 1957 infecting freshwater salmonids. However, the reproductive conditions of gyrodactylids surviving to cessation of an aluminium exposure is unknown. Therefore, Atlantic salmon (Salmo salar L.) parr infected with G. salaris was experimentally exposed to elevated concentrations of aqueous aluminium for more than 1 month. During this period, the infection increased the first week before it peaked and started to steadily decline approaching elimination. When almost all parasite specimens were eliminated, the water quality was adjusted to normal aluminium-poor freshwater. During the next 3 weeks, the surviving G. salaris were shown to clearly resume their reproduction. The experiment demonstrates the potential of the gyrodactylids to reproduce after cessation of an aluminium exposure. Thus, the as-yet unknown mechanism behind the toxic effects of aluminium on G. salaris survival and reproduction might to some extent be reversible. The present study gives further support for this metal as a parasiticide to G. salaris but demonstrates at the same time that in order to eliminate the parasites totally, the aluminium treatment must eradicate all G. salaris from the skin of the infected hosts. Furthermore, the potential development of resistance to aluminium should also be studied.  相似文献   

Evaluation of the effect of commercially available plant and animal protein sources in diets for Atlantic salmon (Salmo salar L.): digestive and metabolic investigations     

Mali Hartviksen  Anne Marie Bakke  José G. Vecino  Einar Ringø  Åshild Krogdahl 《Fish physiology and biochemistry》2014,40(5):1621-1637

The present study investigated the effect of various alternative diet ingredients partially replacing fishmeal (FM) on digestive and metabolic parameters in Atlantic salmon (Salmo salar L.) post-smolts (initial body mass 305 ± 69 g) following 12 weeks of feeding. Experimental diets containing 20 % extracted sunflower (ESF), pea protein concentrate (PPC), soy protein concentrate (SPC), feather meal (FeM) and poultry by-product (PBY) were compared to a reference diet containing FM as the main protein source. For the different intestinal compartments trypsin, lipase, bile salts, dry matter and chyme-associated leucine aminopeptidase (LAP) were measured from the content and LAP was measured in the tissue. Selected metabolites were measured in plasma samples. In general, use of plant proteins resulted in low C-LAP activity, low plasma cholesterol and high plasma magnesium. The plasma levels of cholesterol and Mg reflecting were most likely reflections of the composition of the diet, while the LAP activity in chyme may indicate lower epithelial cell turnover. Other responses varied depending on the plant protein source. Results from the animal protein substitution also varied both between diets and compartments; however, both materials increased lipase activity in DI. FeM resulted in a significant increase in both total and specific LAP activities suggesting an attempt to increase the digestive capacity in response to low digestibility of the diet while PBY showed very little difference from the FM-fed control fish. The present trial indicates that 20 % PPC, SPC and PBY can partially replace FM in diets for Atlantic salmon. The qualities of ESF and FeM used in this trial show little promise as FM replacement at 20 % inclusion level.  相似文献   

几种甘蓝型油菜幼苗抗旱性特征的比较研究     

关周博  田建华  胡银岗  李少钦  董育红  郑磊  韦世豪  塔娜  王学芳  张文学  李殿荣 《上海交通大学学报(农业科学版)》2014,21(5):46-51

以EV1、EV2、EV3、EV4、EV5、EV66个抗旱性不同的油菜品种为试验材料,通过不同浓度PEG-6000渗透溶液模拟干旱胁迫处理,研究油菜幼苗的抗旱指数、根长、苗高和根冠比等性状变化,探索在大田环境条件下的苗期生长特征。结果表明,水分胁迫下EV2的抗旱指数最大,EV6的抗旱指数最小;不同浓度PEG胁迫下,各品种差异显著, EV1、EV2、和EV3的根长、苗高和根冠比较大,而EV5和EV6的表现较差。在大田油菜五叶期时,EV2的冠层覆盖面积最大,与其它品种之间存在极显著性差异;总生物量以EV2、EV3和EV1较大,根系干重以EV2较大,而且三者之间存在显著相关性;与抗旱指数进行通径分析,冠层覆盖面积对抗旱性的直接通径系数最大,达到0.5975。冠层覆盖面积的大小反映了早期活力的强弱,早期活力强,相应的品种抗旱指数高,抗旱性强。  相似文献   

Agglomeration and Competition among Chinese Cities: An Investigation of Taiwanese High‐Tech Foreign Direct Investment     

KENG‐HSIANG CHENG  YU‐CHING CHIAO  HSIN‐YU SHIH  TAI‐YU LEE  TA‐SHUN CHO 《Growth and change》2011,42(4):517-548

The purpose of this study was to investigate how Taiwanese high‐tech firms' foreign direct investment (FDI) leads to agglomeration and competition among cities in China. By using social network analysis to analyze 1,111 subsidiaries affiliated with 270 multinational corporations (MNCs) during the years between 1988 and 2006 in 30 major Chinese cities, this study finds that: 1) agglomeration in Chinese cities falls into three primary categories: the hub cluster, the communication‐extended cluster, and the computer‐extended cluster. Among the aforementioned clusters, the hub cluster is the most critical in terms of firm location, and therefore is often a high‐priority investment site for Taiwanese high‐tech firms. 2) Chinese cities fall into four primary groups, or “blocks”: the core block, the coast block, the inland block, and the periphery block; these groups were determined by applying a structural equivalence analysis of which members of each type are in competition with one another. By linking the findings of the urban network characteristics to Chinese regional economic policies, this study provides guidance to aid executives in determining the optimal location for future FDI. Implications and suggestions for host country governments in terms of firms' investment strategies are also discussed.  相似文献   

Metabolism of 2-chloro-4-cyclopropylamino-6-isopropylamino-s-triazine (cyprazine) in the rat.     

G L Larsen  J E Bakke 《Journal of agricultural and food chemistry》1975,23(3):388-392

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An Investigation of Ovine Pneumonia in Four Herds from Central Norway: I. Prevalence of Pneumonia and Microbiological Findings     

Trude Bakke  Svein Nstvold 《Acta veterinaria Scandinavica》1982,23(2):248

In a study of 4 sheep herds, 1 apparently healthy and 3 having respiratory problems, lesions typical of subacute or chronic pneumonia were found in 3–36 % of slaughtered lambs. Occurrence appeared to be related to certain environmental factors such as pasture, whereas moderate lungworm invasion was not found to contribute to subacute or chronic pneumonia. Relation between pneumonia and low carcass weight was established only in 1 herd.Lungs were subjected to microbiological examination. Mycoplasma ovipneumoniae was isolated from both normal and pneumonic lungs from all 4 herds. The prevalence was far higher in pneumonic (98 %) than in normal ones (28 %). Bacteria, mostly Pasteurella haemolytica, were also found in both pneumonic (49 %) and normal (18 %) lungs from all 4 herds. These results confirm the conclusions of a previous study that M. ovipneumoniae is of etiological significance in subacute or chronic pneumonia, whereas bacteria mainly occur as secondary invaders. M. ovipneumoniae appears, however, only to be a potential pathogen. Examinations for Mycoplasma arginini and virus were negative and these agents are considered to be of less significance in subacute or chronic pneumonia under Norwegian conditions.  相似文献