Impacts of the local land-use system in a semi-arid region of northeastern China on soil properties, crop growth, and weed communities     

T. Miyasaka  T. OkuroH. Zhao  X. ZhaoX. Zuo  K. Takeuchi 《Journal of Arid Environments》2011,75(11):1155-1163

We examined changes in soil properties, crop biomass, and weed communities in the Horqin Sandy Land of China to elucidate cropland degradation. We studied three local cropland types having periods of cultivation of up to 20 years: maize cropland on lowlands without irrigation (nonirrigated lowland), maize cropland on flat sandy lands with irrigation (irrigated flatland), and bean-centered cropland on sand dunes without irrigation (nonirrigated dunes). Soil properties and crop biomass were more degraded in nonirrigated lowland and nonirrigated dunes than in irrigated flatland. Weed communities in the nonirrigated croplands were the type that become established in drier conditions, whereas wetland weeds were more abundant on irrigated flatland. Trends of change in each indicator did not always occur in parallel and differed statistically among the cropland types. Monitoring these indicators within the context of local land-use systems can provide scientific evidence on which to base local management practices or recommendations for change.  相似文献   

Inverse calculation of in situ stress in rock mass using the Surrogate-Model Accelerated Random Search algorithm     

《Computers and Geotechnics》2014

A new approach is presented that incorporates the Surrogate Model Accelerated Random Search (SMARS) Algorithm to inversely determine the overall stress state in a rock mass based on sparse stress measurements. The SMARS algorithm relies on a random search component to maintain global search capabilities, while using the surrogate-model method to accelerate convergence to a solution estimate. Two examples sets are carried out in this presentation to display the utility of the proposed SMARS-based inverse characterization process. The first example set compares the SMARS algorithm with two other popular methods, namely a multiple linear regression analysis method and a neural network method, to estimate the in situ stress field for a simple numerically simulated test case. The results of the numerical testing verify that SMARS provides a relatively stable approach and gives rise to a relatively high accuracy and efficiency (i.e., with less computational expense) compared to the other contemporary approaches considered. Finally, an example is shown for utilizing the SMARS approach for in situ stress estimation based on an actual underground mine located in Pennsylvania. The SMARS results are shown to produce a realistic estimate of the distribution of stress within the area investigated, and overall, the approach has potential for practical use in realistic scenarios to efficiently and accurately estimate in situ stresses in rock mass.  相似文献   

Isolation and Characterization of Psychrophilic Algae in Boron Enriched Pond on Boron Deposit of Qinghai     

KONG Fanjing  ZHENG Mianping  KONG Weigang  ZHANG Xuefei 《《地质学报》英文版》2014,88(Z1):80-81

正1 Introduction Cold environments on the planet occur in the Antarctic,the Arctic and high mountains which cover with ice and snow permanently.Microorganism adapted to cold habitats has been detected,but most of them were prokaryotes.(Morgan-Kiss et al,2006;jungbut et al,2012).Research on cold-adapted microorganism has  相似文献   

结合多光谱影像降维与深度学习的城市单木树冠检测     

奚祥书  夏凯  杨垠晖  杜晓晨  冯海林 《遥感学报》2022,26(4):711-721

多光谱数据的降维处理对基于深度学习的单木树冠检测研究有重要意义,如何使用合适的降维方法以提高单木检测的精度却少有研究讨论。本文使用无人机搭载多光谱相机进行航拍作业,采集研究区内银杏树种多光谱影像。将原始多光谱影像通过特征波段选择、特征提取、波段组合的方法生成5种不同的数据集用于训练3种经典的深度学习网络FPN-Faster-R-CNN,YOLOv3,Faster R-CNN。其中由波段组合方法得到的近红外、红色、绿色波段组合在不同类型的目标检测网络中都有最好的检测结果,其中FPN-Faster-R-CNN网络对银杏树冠的检测精度最高为88.4%,由OIF指标得到的蓝色、红色、近红外波段组合信息量最高,但在所有网络中的平均检测精度最低,仅为79.3%。实验结果表明：在不同波段降维方法中,若降维后的影像中目标物体的色彩与背景差异较明显,且轮廓清晰,则深度学习网络对树冠的检测可获得较好的结果。而影像自身的信息量则对深度学习网络的树冠检测能力的提升作用有限。本研究中针对多光谱影像的降维方法分析,为基于深度学习的单木树冠检测研究提供了重要的实验参考。  相似文献   

On the assimilation of uncertain physical knowledge bases: Bayesian and non-Bayesian techniques     

George Christakos   《Advances in water resources》2002,25(8-12)

  相似文献   

树轮氢氧同位素方法在环境变迁研究中的应用   总被引：1，自引：0，他引：1  

刘广深  戚长谋 《世界地质》1997,16(3):45-51

树轮氢氧同位素方法是过去环境气候变化研究领域内的主要技术手段之一，因其时间分辨率高，反映环境参数多，准确定量的优点，近年日益受到重视。  相似文献   

Role of temporal resolution of meteorological inputs for process‐based snow modelling          下载免费PDF全文

Mohammad M. Sohrabi  Daniele Tonina  Rohan Benjankar  Mukesh Kumar  Patrick Kormos  Danny Marks 《水文研究》2018,32(19):2976-2989

Accurate snow accumulation and melt simulations are crucial for understanding and predicting hydrological dynamics in mountainous settings. As snow models require temporally varying meteorological inputs, time resolution of these inputs is likely to play an important role on the model accuracy. Because meteorological data at a fine temporal resolution (~1 hr) are generally not available in many snow‐dominated settings, it is important to evaluate the role of meteorological inputs temporal resolution on the performance of process‐based snow models. The objective of this work is to assess the loss in model accuracy with temporal resolution of meteorological inputs, for a range of climatic conditions and topographic elevations. To this end, a process‐based snow model was run using 1‐, 3‐, and 6‐hourly inputs for wet, average, and dry years over Boise River Basin (6,963 km²), which spans rain dominated (≤1,400 m), rain–snow transition (>1,400 and ≤1,900 m), snow dominated below tree line (>1,900 and ≤2,400 m), and above tree line (>2,400 m) elevations. The results show that sensitivity of the model accuracy to the inputs time step generally decreases with increasing elevation from rain dominated to snow dominated above tree line. Using longer than hourly inputs causes substantial underestimation of snow cover area (SCA) and snow water equivalent (SWE) in rain‐dominated and rain–snow transition elevations, due to the precipitation phase mischaracterization. In snow‐dominated elevations, the melt rate is underestimated due to errors in estimation of net snow cover energy input. In addition, the errors in SCA and SWE estimates generally decrease toward years with low snow mass, that is, dry years. The results indicate significant increases in errors in estimates of SCA and SWE as the temporal resolution of meteorological inputs becomes coarser than an hour. However, use of 3‐hourly inputs can provide accurate estimates at snow‐dominated elevations. The study underscores the need to record meteorological variables at an hourly time step for accurate process‐based snow modelling.  相似文献   

Risk and decision making analyses and applications to the petroleum exploration — A certain PSC area     

Mingyin Zhang  Xiaokang Fu  Shibin He 《Natural Resources Research》1997,6(4):281-284

Risk is a critical factor that an investor must take into account, regardless of where money is invested. Before making important decisions in petroleum exploration, it is standard practice to calculate the expected monetary value for each given prospect. Because of the large uncertainty inherent in decisions that involve large sums of money, the investor needs to exercise prudence. This paper describes an application of calculating the expected monetary value in a mature producing area in the Malacca Strait PSC Contract Area, Indonesia.  相似文献   

空间数据挖掘技术在土地定级估价中应用   总被引：9，自引：0，他引：9  

贾泽露  刘耀林  张彤 《地球科学与环境学报》2005,27(3):72-77

介绍了空间数据挖掘技术和决策树算法。通过对其研究，将可视化空间数据挖掘技术应用于土地定级估价，并介绍了基于Visual C^＋＋ 6．0和ESRI公司的MapObiect 2．0组件技术设计和开发了一个可视化交互空间数据挖掘土地定级估价原型系统。系统采用决策树方法作为数据挖掘方法的基本算法，采用训练与学习相结合实现土地定级估价。阐述了基于决策树空间数据挖掘土地定级估价的系统模型，系统总体框架、主要模块、系统界面及系统实现定级估价的工作流程。该方法是对土地定级估价方法的一种新的探索，是对土地信息系统开发的一种新的尝试，也是土地信息系统智能化发展的一个方向。  相似文献   

Construction of Porphyra yezoensis Pure Line from Protoplasts and Its 18S rDNA Sequence Determination     

LIU Hongquan )  )  YU Wengong )  *  DAI Jixun )  GONG Qianhong )  SHI Xiaochong )  YANG Kunfeng ) ) Institute of Marine Drugs  Foods  Ocean University of China  Qingdao  P..R.China ) College of Marine Life Sciences  Ocean University of China  Qingdao  P..R.China 《中国海洋大学学报(英文版)》2004,3(1)

1　Introduction　PorphyraisthemainobjectforalgafarmingandplaysaveryimportantroleinChinesemarineindus tries.Recently ,therehasbeenagreatlossinPor phyracultivationduetothedegenerationoftheculti var,sothereisanincreasingdemandforgoodPor phyracultivars .Theprerequisiteofthetraditionalbreed ingandbioengineeringresearchofPorphyraistheconstructionofpurelines .Traditionally ,theclassifi cationofPorphyrawasaccordingtotheirmorphologi calcharacteristics .However ,mostmorphologicalfea turesofPorphyraar…  相似文献