Building an Online Learning and Research Environment to Enhance Use of Geospatial Data

Geospatial data availability, interoperability, and integration remain a problem today. Current spatial data infrastructures (SDIs) are of limited use particularly to non-expert user communities. GeoBrain, a NASA funded project, has aimed to address those challenges, facilitate easy use of geospatial data and overcome some limitations of current SDIs through building a data-intensive, Service-oriented Architecture (SOA) based online learning and research environment. By adopting the latest developing Web services and knowledge management technologies, this online environment enables easy, open, seamless, and on-demand discovery, access, retrieval, visualization and analysis of distributed geospatial data, information, services, and models from any computer connected to the Internet. Such an online environment is able to serve the different needs of global Earth sciences research and higher education communities, bridge gaps between data user needs and provider capabilities, and greatly enhance use of geospatial data

A Comparison of Satellite Data-Based Drought Indicators in Detecting the 2012 Drought in the Southeastern US

The drought of 2012 in the North America devastated agricultural crops and pastures, further damaging agriculture and livestock industries and leading to great losses in the economy. The drought maps of the United States Drought Monitor (USDM) and various drought monitoring techniques based on the data collected by the satellites orbiting in space such as the Gravity Recovery and Climate Experiment (GRACE) and the Moderate Resolution Imaging Spectroradiometer (MODIS) are inter-compared during the 2012 drought conditions in the southeastern United States. The results indicated that spatial extent of drought reported by USDM were in general agreement with those reported by the MODIS-based drought maps. GRACE-based drought maps suggested that the southeastern US experienced widespread decline in surface and root-zone soil moisture and groundwater resources. Disagreements among all drought indicators were observed over irrigated areas, especially in Lower Mississippi region where agriculture is mainly irrigated. Besides, we demonstrated that time lag of vegetation response to changes in soil moisture and groundwater partly contributed to these disagreements, as well

Structural and Acoustic Responses of a Submerged Stiffened Conical Shell

This paper studies the vibrational behavior and far-field sound radiation of a submerged stiffened conical shell at low frequencies. The solution for the dynamic response of the conical shell is presented in the form of a power series. A smeared approach is used to model the ring stiffeners. Fluid loading is taken into account by dividing the conical shell into narrow strips which are considered to be local cylindrical shells. The far-field sound pressure is solved by the Element Radiation Superposition Method. Excitations in two directions are considered to simulate the loading on the surface of the conical shell. These excitations are applied along the generator and normal to the surface of the conical shell. The contributions from the individual circumferential modes on the structural responses of the conical shell are studied. The effects of the external fluid loading and stiffeners are discussed. The results from the analytical models are validated by numerical results from a fully coupled finite element/boundary element model

A Marine Object Detection Algorithm Based on SSD and Feature Enhancement

Autonomous detection and fishing by underwater robots will be the main way to obtain aquatic products in the future; sea urchins are the main research object of aquatic product detection. When the classical Single-Shot MultiBox Detector (SSD) algorithm is applied to the detection of sea urchins, it also has disadvantages of being inaccurate to small targets and insensitive to the direction of the sea urchin. Based on the classic SSD algorithm, this paper proposes a feature-enhanced sea urchin detection algorithm. Firstly, according to the spiny-edge characteristics of a sea urchin, a multidirectional edge detection algorithm is proposed to enhance the feature, which is taken as the 4th channel of image and the original 3 channels of underwater image together as the input for the further deep learning. Then, in order to improve the shortcomings of SSD algorithm’s poor ability to detect small targets, resnet 50 is used as the basic framework of the network, and the idea of feature cross-level fusion is adopted to improve the feature expression ability and strengthen semantic information. The open data set provided by the National Natural Science Foundation of China underwater Robot Competition will be used as the test set and training set. Under the same training and test conditions, the AP value of the algorithm in this paper reaches 81.0%, 7.6% higher than the classic SSD algorithm, and the confidence of small target analysis is also improved. Experimental results show that the algorithm in this paper can effectively improve the accuracy of sea urchin detection

Co-Evaluation of Plant Leaf Nutrient Concentrations and Resorption in Response to Fertilization under Different Nutrient-Limited Conditions

Plant leaf nutrient concentrations and resorption are sensitive to fertilization, yet their co-responses under different nutrient-limited conditions have not been well studied. We conducted a meta-analysis from a global dataset of 43 reports, including 130 observations of studies with plant leaf nitrogen (N) or phosphorus (P) concentrations and nitrogen resorption efficiency (NRE) or phosphorus resorption efficiency (PRE), in response to fertilization under different nutrient-limited conditions divided by the thresholds of leaf N:P ratio values of 10 and 20. The results showed that N fertilization generally increased leaf N concentration and decreased NRE, with greater magnitudes under N-limited conditions. P fertilization also generally increased leaf P concentration and decreased PRE, with greater magnitudes under P-limited conditions. N fertilization decreased leaf P concentration and increased PRE only under the N-limited condition. Under the P-limited or N and P co-limited conditions, however, N fertilization increased leaf P concentration and did not change PRE. Moreover, P fertilization did not change leaf N concentration under all nutrient-limited conditions but significantly increased NRE under the N-limited or N and P co-limited conditions. These findings suggest that plants cope with fertilization-induced N limitation vs. P limitation at the leaf level with different nutrient-use strategies

Wave Based Method for Free Vibration Analysis of Ring Stiffened Cylindrical Shell with Intermediate Large Frame Ribs

Wave based method which can be recognized as a semi-analytical and semi-numerical method is presented to analyze the free vibration characteristics of ring stiffened cylindrical shell with intermediate large frame ribs for arbitrary boundary conditions. According to the structure type and the positions of discontinuities, the model is divided into different substructures whose vibration field is expanded by wave functions which are exactly analytical solutions to the governing equations of the motions of corresponding structure type. Boundary conditions and continuity equations between different substructures are used to form the final matrix to be solved. Natural frequencies and vibration mode shapes are calculated by wave based method and the results show good agreement with finite element method for clamped-clamped, shear diaphragm – shear diaphragm and free-free boundary conditions. Free vibration characteristics of ring stiffened cylindrical shells with intermediate large frame ribs are compared with those with bulkheads and those with all ordinary ribs. Effects of the size, the number and the distribution of intermediate large frame rib are investigated. The frame rib which is large enough is playing a role as bulkhead, which can be considered imposing simply supported and clamped constraints at one end of the cabin and dividing the cylindrical shell into several cabins vibrating separately at their own natural frequencies

Co-Evaluation of Plant Leaf Nutrient Concentrations and Resorption in Response to Fertilization under Different Nutrient-Limited Conditions

Plant leaf nutrient concentrations and resorption are sensitive to fertilization, yet their co-responses under different nutrient-limited conditions have not been well studied. We conducted a meta-analysis from a global dataset of 43 reports, including 130 observations of studies with plant leaf nitrogen (N) or phosphorus (P) concentrations and nitrogen resorption efficiency (NRE) or phosphorus resorption efficiency (PRE), in response to fertilization under different nutrient-limited conditions divided by the thresholds of leaf N:P ratio values of 10 and 20. The results showed that N fertilization generally increased leaf N concentration and decreased NRE, with greater magnitudes under N-limited conditions. P fertilization also generally increased leaf P concentration and decreased PRE, with greater magnitudes under P-limited conditions. N fertilization decreased leaf P concentration and increased PRE only under the N-limited condition. Under the P-limited or N and P co-limited conditions, however, N fertilization increased leaf P concentration and did not change PRE. Moreover, P fertilization did not change leaf N concentration under all nutrient-limited conditions but significantly increased NRE under the N-limited or N and P co-limited conditions. These findings suggest that plants cope with fertilization-induced N limitation vs. P limitation at the leaf level with different nutrient-use strategies