牙鲆幼鱼对n-3高度不饱和脂肪酸的吸收及与生长关系的初步研究   总被引：9，自引：1，他引：8  

刘洪杰  毛兴华 《海洋与湖沼》1999,30(3):238-244

于1996年9-10月在中国水产科学研究院黄海水产研究所小麦岛实验基地,采用人工投喂的方法,给牙鲆幼鱼投喂含不同含量n-3高度不饱和脂肪酸（n-3HUFA）的人工饵料,研究牙鲆幼鱼对饵料中n-3HUFA的消化、吸收以及n-3HUFA的含量与日增重率、饵料效率的关系。结果表明,在饵料中添加0.60％—2.40％的n-3HUFA可有效提高牙鲆幼鱼的日增重率和饵料效率;肝脏中n-3HUFA的含量与饵料中n-3HUFA（尤其是DHA）的含量成正比;牙鲆幼鱼对饵料中n-3HUFA的表观消化吸收率随其含量的增加呈下降趋势。  相似文献   

Analytical‐numerical solution for stress distribution around tunnel reinforced by radial fully grouted rockbolts          下载免费PDF全文

Masoud Ranjbarnia  Pierpaolo Oreste  Ahmad Fahimifar  Amir Arya 《国际地质力学数值与分析法杂志》2016,40(13):1844-1862

This paper presents an analytical‐numerical approach to obtain the distribution of stresses and deformations around a reinforced tunnel. The increase in the radial stress of the reinforced tunnel, based on the performance of a bolt, is modeled by a function, which its maximum value is in the vicinity of the bolt periphery and it exponentially decreases in the far distance from the bolt. On the basis of this approach, the shear stiffness between the bolt and the rock mass and the shear stress distribution around the bolt within the rock mass are also analytically obtained. The results are compared with those obtained by the assumption of ‘uniform increase of radial stress’ method, which is made by the previous studies. The analyses show when the bolts' spacing is large, the safety factor must be increased if the ‘uniform increase of radial stress’ method is used for the design. Finally, a procedure is introduced to calculate the non‐equal deformation of the rock mass between the bolts at any radius that can be useful to compute the bending moment in shotcrete layer in New Austrian Tunnelling Method (NATM) approach. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Analysis of effects of operating parameters on rate of penetration in drilling process with air down-the-hole hammer     

HO Yinchol  PAK Kumdol  PENG Jianming  RI Jaemyong  KIM Yongnam  CHOE Cholho 《世界地质(英文版)》2021,24(1):64-70

Air down-the-hole(DTH)hammer drilling has long been recognized to have the potential of drilling faster than conventional rotary drill,especially in some hard rocks such as granite,sandstone,limestone,dolomite,etc.with the same weight on bit(WOB)and rotations per minute(RPM).So,it has been widely used in many drilling fields including mineral resource exploration drilling,oil and gas drilling and geothermal drilling.In order to reduce drilling cost by selecting optimal drilling parameters,rate of penetration(ROP)should be estimated accurately and the effects of different factors on ROP should be analyzed.In this research,ANN model with several multi-layer perception back propagation(BP)networks for predicting ROP of air DTH hammer drilling was developed using controllable parameters such as impact energy,impact frequency,WOB,RPM and bit operating time for the formations with a certain drillability index of rock.Several BP neural networks with the different neurons in hidden layers were developed and compared for selecting optimal architecture of ANN.The effects of the drilling parameters such as impact energy,impacting frequency,WOB,RPM and bit operating time on the ROP of air DTH hammer drilling were investigated by trained ANN.From the analyses,the optimum range of drilling parameters for providing high ROP were determined and analyzed for a formation with a certain drillability index of rock.The methodology proposed in this study can be used in many mathematical problems for optimization of drilling process with air DTH hammer.  相似文献   

Special Lateral Increase in a Permian Rugose Coral Kepingophyllum aksuence Wu et Chow     

ZHANG Feng  WANG Xiangdong 《《地质学报》英文版》2011,85(2):465-470

Well-preserved specimens of Kepingophyllum aksuence Wu et Chow were collected from Early Permian strata in western Tarim Basin, Xinjiang. More than 100 serial thin sections were made for this study. Kepingophyllum aksuence displays a unique increase pattern. The bud appears in lonsdaleoid dissepiments between the corallites where the wall of parent corallite disappears and the area becomes aphroid. This increase pattern is different from other lateral increases of most colonial rugose corals, and therefore has taxonomic significance to differentiate Kepingophyllidae from other compound rugose corals. It is also discussed that Kepingophyllum aksuence has a high “reproductive integration”, which means a rapid growth of buds during the offsetting process. Kepingophyllum was possibly originated from Ivanovia and was also a probable ancestor of Wentzellophyllum, which is supported here by more or less the similarity of the blastogeny in different stages of three taxa.  相似文献   

Photosynthesis,growth and survival of the Mediterranean seagrass Posidonia oceanica in response to simulated salinity increases in a laboratory mesocosm system     

Lázaro Marín-Guirao  José M. Sandoval-Gil  Juan M. Ruíz  José L. Sánchez-Lizaso 《Estuarine, Coastal and Shelf Science》2011

This study aims to examine the effect of increased salinity on the photosynthetic activity of the Mediterranean seagrass Posidonia oceanica in a laboratory mesocosm system. To do this, large rhizome fragments were transplanted in a mesocosm laboratory system and maintained at 37 (ambient salinity, control treatment), 39, 41 and 43 (hypersaline treatments) for 47 days. Pigment content, light absorption, photosynthetic characteristics (derived from P vs. E curves and fluorescence parameters), and shoot size, growth rates and net shoot change were determined at the end of the experimental period. Both net and gross photosynthetic rates of plants under hypersaline conditions were significantly reduced, with rates some 25–33% and 13–20% lower than in control plants. The pigment content (Chla, Chlb, Chlb:Chla molar ratio, total carotenoids and carotenoids:Chla ratio), leaf absorptance and maximum quantum yield of PSII (F_v/F_m) of control plants showed little or no changes under hypersaline conditions, which suggests that alterations to the capacity of the photosynthetic apparatus to capture and process light were not responsible for the reduced photosynthetic rates. In contrast, dark respiration rates increased substantially, with mean values up to 98% higher than in control leaves. These results suggest that the respiratory demands of the osmoregulatory process are likely to be responsible for the observed decrease in photosynthetic rates, although alterations to photosynthetic carbon assimilation and reduction could also be involved. As a consequence, leaf carbon balance was considerably impaired and leaf growth rates decreased as salinity increased above the ambient (control) salinity. No significant differences were found in the percentage of net shoot change, but mean values were clearly negative at salinity levels of 41 and 43. Results presented here indicate that photosynthesis of P. oceanica is highly sensitive to hypersaline stress and that it likely account for the decline in leaf growth and shoot survival reported in this and previous studies in response to even small increments of the ambient salinity.  相似文献   

临沂市城乡建设用地增减挂钩工作问题研究及对策建议          下载免费PDF全文

杨静 《山东国土资源》2011,27(10):70-72

通过调查临沂市城乡建设用地增减挂钩工作现状,系统总结了增减挂钩在支持新农村建设、加速城镇化进程、促进集约用地、增加耕地面积等方面发挥的积极作用,指出了工作中存在资金缺口大、拆迁安置难度大、政策有待完善等问题,提出了完善工作机制、强化资金筹措、坚持让利于民、加强监管审计、加大宣传力度等对策措施。  相似文献   

岚县近54年气候变化特征分析     

张国勇  刘谋荣  杜月辉  李玉平  孙迎秀 《山西气象》2011,(2):16-18

利用吕梁高海拔山区代表站岚县气象观测站1957年-2010年的气温、年（季）降水量、年日照时数、年蒸发量等地面气象资料,应用线性趋势函数分析法进行了统计分析。结果表明：岚县年平均气温呈上升趋势,冬季增温最显著;降水量的变化总体上呈减少趋势,降水量的减少主要是夏季降水减少所引起。年日照时数有明显的下降趋势,年蒸发量则缓慢增加。  相似文献   

土地利用总体规划中农村居民点综合整治研究     

赵先勇 《现代测绘》2011,34(6)

本文阐述了土地利用总体规划中农村居民点综合整治的意义及整体思路。在对政和县农村居民点用地现状分析的基础上,结合土地利用总体规划,合理测算了到2020年政和县农村居民点潜力与整治目标,提出了不同区域农村居民点综合整治的模式以及促进农村居民点综合整治目标实施的建议。  相似文献   

应用水力空化射流技术提高灰岩地层钻速          下载免费PDF全文

鲍洪志 《探矿工程》2013,40(5):1-3

水力空化射流技术具有安全、可靠、效果好等特点,在石油钻井中得到了推广应用。针对伊朗Y油田中下部中硬灰岩地层可钻性差、机械钻速低的情况,试验应用了水力空化射流工具。研究了试验油田的地层强度及可钻性参数,优选了水力脉冲空化射流装置和下部钻具组合,优化了机械及水力参数。现场实钻资料表明,水力空化射流工具提高钻速明显,对中硬地层的灰岩具有良好的钻进效果。  相似文献   

WRF大气模式与台风经验模型在超强台风“山竹”过程重构中的比较分析     

李心雨  杨昀  李自如  王惠群  管卫兵  何杰 《海洋工程》2022,40(4):53-64,111

通过中尺度气象研究与预报模式WRF（weather research and forecasting）和两种台风经验模型重构了2018年影响我国珠江口地区的超强台风“山竹”过程中的气压和风矢量场,在台风最佳路径数据的基础上开展了方法间的比较,并与香港、澳门和深圳三个国际机场的实测数据进行了对比分析,验证了三种模拟方案模拟台风“山竹”的可靠性。利用非结构网格半隐式跨尺度海洋模式SCHISM （semi-implicit cross-scale hydroscience integrated system model）,将三种模拟气压和风场作为驱动场输入风暴潮模式中进行增水模拟试验,比较了它们在赤湾、三灶、横门和黄埔四个测站风暴潮增水中各自的效果,并进一步验证了WRF模式和两种经验模型模拟台风“山竹”的有效性。综合来看, WRF大气模式对气压、风速、风向及风暴增水模拟效果最佳,如果进一步优化该模式的各种参数化方案,可能还能提高其精度。如果不具备使用WRF大气模式的条件,台风经验1模型也是一个完全可以接受的、简单快捷的方案。  相似文献