世界各国草地资源管理体制及其对我国的启示   总被引：2，自引：0，他引：2  

唐海萍  陈姣  房飞 《国土资源情报》2014,(10):9-17

草地在世界各大洲均有分布,世界各国对草地资源的管理有着不同的体制与策略.本文梳理了各大洲主要国家的草地资源管理体制,分析了草地资源管理历史进程与趋势,总结了各国草地资源管理的优势和可资借鉴之处.结合我国草地资源管理中存在的问题,建议我国要在国家层面重视草地资源的管理,建立专门行政部门管理全国60忆亩草地,建立健全现有的草地资源管理体制,同时建立草原质量的监测数据网络,并加强对草地利用的监管力度.  相似文献   

Improvement of groundwater resources potential by artificial recharge technique: A case study of Charf El Akab aquifer in the Tangier region,Morocco     

SADIKI Moulay Lhassan  EL MANSOURI Bouabid  BENSEDDIK Badr  CHAO Jamal  KILI Malika  EL MEZOUARY Lhoussaine 《地下水科学与工程》2014,7(3):224-236

In arid and semi-arid zones, water is the most vulnerable resource to climate change. In fact, various techniques such as artificial recharge are adopted to restore aquifers and to ensure aquifer sustainability in relation to the accelerated pace of exploitation. Morocco is a Mediterranean country highly vulnerable to climate change, many of its main aquifers are subjected to excessive drawdowns. This technique is practiced to increase potentiality of these aquifers. In the Northwestern area of Morocco, the significant development experienced by Tangier City in the industrial, tourism, and commercial sectors will lead to increased water requirements-up to 5 067 L/s (159.8 mm3) by 2030. However, the Charf El Akab aquifer system, subject to artificial recharge, is the only groundwater resource of Tangier region; hence, a rational management context is needed to ensure aquifer sustainability, and optimized exploitation under the background of differing constraints, such as increased water requirements, and climate change impacts. This work aims to respond, for the first time, to the Charf El Akab aquifer overexploitation problem, and to evaluate the future scenarios of its exploitation in the event of failure of one of the superficial resources. This work also presents a synthesized hydrodynamic modeling based on the results of the numerical simulations carried out using Feflow software for 2004 (date of cessation of injections) and 2011 (date of resumption of these facilities), making it possible to evaluate the impact of the artificial recharge on the piezometric level of the aquifer on a spatiotemporal scale. Finally, the exploitation scenarios have shown that the aquifer of Charf El Akab will not adequatly provide for the region's water requirements on the future horizon, entailing an optimal management of water resources in the region and an intentionally increased recharge rate.  相似文献   

α-1,4-葡聚糖裂解酶的动力学性质研究   总被引：1，自引：0，他引：1  

Sun Xue 《中国海洋大学学报(自然科学版)》2000,30(Z1):230-236

红藻中的α-1,4-葡聚糖裂解酶是红藻淀粉的降解酶,除了 红藻淀粉外,它还可以作用于多种底物。文中分别以PNPG和可溶性淀粉作底物,以龙须菜的 几个品系作为材料,研究了该酶促反应的动力学方面的性质。以 PNPG作为底物,该酶在60m in内酶促反应速度与保温时间成线性关系;在野生型龙须菜品系中该酶的最适反应温度是50 ℃,在两种突变型品系中是40℃;最适pH范围在4.4～5.5;底物浓度是4mmol/L时达到最大反 应速度;葡萄糖对该酶促反应有明显的抑制作用。以可溶性淀粉作为底物,在反应60 min内 酶反应速度与保温时间成线性关系;最适反应温度为50℃;最适pH范围在5.0～5.8;底物浓 度是8mg/mL时达到最大反应速度;葡萄糖对可溶性淀粉的抑制作用比对PNPG的弱。  相似文献   

SECOND-ORDER SOLUTION FOR THE ZONAL PROBLEM OF SATELLITE THEORY     

Sławomir Breiter 《Celestial Mechanics and Dynamical Astronomy》1997,67(3):237-249

The analytical solution for the perturbations of an artificial satellite due to the zonal part of the geopotential is presented. The Hamiltonian is fully normalized up to the second order by a single averaging transformation and the generating function is given explicitly. The formulas allow an arbitrarily high degree of geopotential harmonics to be included. The transformation from mean to osculating variables or vice versa is performed by means of a numerical method proposed by the author in a previous paper (Breiter,1997): periodic perturbations are computed by means of a Runge-Kutta method of order 2 instead of being explicitly derived from a generator. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

The effects of temperature and substrate on ontogenetic behavior of bastard halibut, Paralichthys olivaceus (T. et S.)     

刘栋  线薇薇  朱鑫华 《中国海洋湖沼学报》2005,23(1)

1 INTRODUCTION Scientific management of aquacultural andnatural populations studies on the early life historyof flatfishes in the aspects of their metamorphosisand benthic settlement accompanying pronouncedtransitions in morphology, behavior and habitatecology have received much attention (Youson,1988). Accumulated data showed that temperatureand substrate played a main role in the recruitmentsuccess of flatfish during their early development(Rijnsdorp et al., 1995, Gibson and Robb, 2000…  相似文献   

四川旱涝震灾害的人工神经网络外推预测     

李祚泳  邓新民  黄志英 《成都信息工程学院学报》1997,(2)

选取旱、涝、震灾害之间的一步转移概率作为Ｂ－Ｐ人工神经网络训练样本的输入信息，建立了四川旱、涝、震的人工神经网络灾型预测模型。Ｂ－Ｐ网络模型应用于实例预测结果与用主分量分析法的趋势预测结果精度接近。  相似文献   

Geopotential from space techniques     

P. Exertier 《Celestial Mechanics and Dynamical Astronomy》1993,57(1-2):137-153

The monitoring of the perturbed motion of artificial satellites since the 1960's has provided a valuable resource for improved activities in geodesy. These observations and the improved geodetic techniques they fostered have provided an unparalleled means for studying both the gravity field and the Earth's shape. In this paper, we will review the various determinations of the Earth's gravity field produced at many research centers over the years from space techniques. The specific methods which have been used to measure our planet, such as satellite altimetry and satellite orbital perturbation analyses (over short and long periods of time), will be compared.  相似文献   

企鹅珍珠贝人工苗生长的初步观察   总被引：3，自引：0，他引：3  

梁飞龙  毛勇  余祥勇 《广东海洋大学学报》2001,21(1):6-9

为了解企鹅珍珠贝生长规律，观察了壳高2.5～5.0mm的出池幼苗，按月测量其生长参数和成活率，以及环境因子。结果表明，企鹅珍珠贝生长最快的月份为7～11月和次年4～6月，壳长，壳高和壳宽月均增加量分别为3.8～13.0mm、4.7～11.2mm、2.3～3.8mm，月成活率97.8%～98.6%。企鹅珍珠贝生长最慢月份是11月至次年3月。  相似文献   

Neural network prediction of nitrate in groundwater of Harran Plain, Turkey   总被引：2，自引：0，他引：2  

M. Irfan Yesilnacar  Erkan Sahinkaya  Muhsin Naz  Bestamin Ozkaya 《Environmental Geology》2008,56(1):19-25

Monitoring groundwater quality by cost-effective techniques is important as the aquifers are vulnerable to contamination from the uncontrolled discharge of sewage, agricultural and industrial activities. Faulty planning and mismanagement of irrigation schemes are the principle reasons of groundwater quality deterioration. This study presents an artificial neural network (ANN) model predicting concentration of nitrate, the most common pollutant in shallow aquifers, in groundwater of Harran Plain. The samples from 24 observation wells were monthly analysed for 1 year. Nitrate was found in almost all groundwater samples to be significantly above the maximum allowable concentration of 50 mg/L, probably due to the excessive use of artificial fertilizers in intensive agricultural activities. Easily measurable parameters such as temperature, electrical conductivity, groundwater level and pH were used as input parameters in the ANN-based nitrate prediction. The best back-propagation (BP) algorithm and neuron numbers were determined for optimization of the model architecture. The Levenberg–Marquardt algorithm was selected as the best of 12 BP algorithms and optimal neuron number was determined as 25. The model tracked the experimental data very closely (R = 0.93). Hence, it is possible to manage groundwater resources in a more cost-effective and easier way with the proposed model application.  相似文献   

Spatial Variability of Rock Depth in Bangalore Using Geostatistical, Neural Network and Support Vector Machine Models     

T. G. Sitharam  Pijush Samui  P. Anbazhagan 《Geotechnical and Geological Engineering》2008,26(5):503-517

Geospatial technology is increasing in demand for many applications in geosciences. Spatial variability of the bed/hard rock is vital for many applications in geotechnical and earthquake engineering problems such as design of deep foundations, site amplification, ground response studies, liquefaction, microzonation etc. In this paper, reduced level of rock at Bangalore, India is arrived from the 652 boreholes data in the area covering 220 km². In the context of prediction of reduced level of rock in the subsurface of Bangalore and to study the spatial variability of the rock depth, Geostatistical model based on Ordinary Kriging technique, Artificial Neural Network (ANN) and Support Vector Machine (SVM) models have been developed. In Ordinary Kriging, the knowledge of the semi-variogram of the reduced level of rock from 652 points in Bangalore is used to predict the reduced level of rock at any point in the subsurface of the Bangalore, where field measurements are not available. A new type of cross-validation analysis developed proves the robustness of the Ordinary Kriging model. ANN model based on multi layer perceptrons (MLPs) that are trained with Levenberg–Marquardt backpropagation algorithm has been adopted to train the model with 90% of the data available. The SVM is a novel type of learning machine based on statistical learning theory, uses regression technique by introducing loss function has been used to predict the reduced level of rock from a large set of data. In this study, a comparative study of three numerical models to predict reduced level of rock has been presented and discussed.  相似文献