490 research outputs found

    Experimental Study on the Mechanisms of Soil Water-Solute- Heat Transport and Nutrient Loss Control

    Get PDF
    The release and migration of nutrients, pesticides, and other chemicals in the runoff from agricultural lands is not only an economic loss but a threat to the quality of our surface and groundwater. In contrast to pollution from point sources, pollution from non-point sources is often low in intensity but high in volume. The development of a physically based model to simulate the transport of soil solutes would provide a better understanding of transport mechanisms and assist in the development of effective methods to control the loss of nutrients from soils and the pollution of waterways. As a result, numerous studies have been conducted in this area. But due to the soil genesis and human activity, the process is very complex, which can have a great impact on soil water movement, solute transport, as well as nutrient loss. In this study, we determined water movement and solute and heat transport through columns of disturbed soil samples. We also carried out simulated rainfall experiments on an artificial slope to study the nutrient loss

    Investigation and protection of fishery resources in the middle of Bohai Sea

    Get PDF
    In May and October 2017, 12 stations were set up in the Central Bohai Sea for fishery resources investigation. The results show that there are many dominant species in this area, and the inshore fishery resources are higher than those in the open sea because of the abundant nutrients from land, the high density of zooplankton and the food of swimming animals. In order to effectively protect the fishery resources in the Central Bohai Sea, this paper puts forward some suggestions, such as strengthening the protection propaganda, scientific and reasonable fishing, and strengthening the management of marine environment

    GEOMETRIC ANALYSIS TOOLS FOR MESH SEGMENTATION

    Get PDF
    Surface segmentation, a process which divides a surface into parts, is the basis for many surface manipulation applications which include model metamorphosis, model simplifica- tion, model retrieval, model alignment and texture mapping. This dissertation discusses novel methods for geometric surface analysis and segmentation and applications for these methods. Novel work within this dissertation includes a new 3D mesh segmentation algo- rithm which is referred to as the ridge-walking algorithm. The main benefit of this algo- rithm is that it can dynamically change the criteria it uses to identify surface parts which allows the algorithm to be adjusted to suit different types of surfaces and different segmen- tation goals. The dynamic segmentation behavior allows users to extract three different types of surface regions: (1) regions delineated by convex ridges, (2) regions delineated by concave valleys, and (3) regions delineated by both concave and convex curves. The ridge walking algorithm is quantitatively evaluated by comparing it with competing algo- rithms and human-generated segmentations. The evaluation is accompanied with a detailed geometrical analysis of a select subset of segmentation results to facilitate a better under- standing of the strengths and weaknesses of this algorithm. The ridge walking algorithm is applied to three domain-specific segmentation prob- lems. The first application uses this algorithm to partition bone fragment surfaces into three semantic parts: (1) the fracture surface, (2) the periosteal surface and (3) the articular surface. Segmentation of bone fragments is an important computational step necessary in developing quantitative methods for bone fracture analysis and for creating computational tools for virtual fracture reconstruction. The second application modifies the 3D ridge walking algorithm so that it can be applied to 2D images. In this case, the 2D image is modeled as a Monge patch and principal curvatures of the intensity surface are computed iv for each image pixel. These principal curvatures are then used by ridge walking algorithm to segment the image into meaningful parts. The third application uses the ridge walking algorithm to facilitate analysis of virtual 3D terrain models. Specifically, the algorithm is integrated as a part of a larger software system designed to enable users to browse, visualize and analyze 3D geometric data generated by NASA’s Mars Exploratory Rovers Spirit and Opportunity. In this context, the ridge walking algorithm is used to identify surface features such as rocks in the terrain models

    rac-3,9-Bis(3-chloro­phen­yl)-2,4,8,10-tetra­oxaspiro­[5.5]undeca­ne

    Get PDF
    In the title compound, C19H18Cl2O4, the two non-planar six-membered heterocycles passing through the spiro-C atom both adopt chair conformations, and the dihedral angle between the two benzene rings is 7.2 (1)°. In the crystal, the enanti­omers with R and S configurations are generated by the symmetry elements of the centrosymmetric space group, forming a racemic crystal. Inter­molecular C—H⋯π and weak C—H⋯O inter­actions link the mol­ecules in the crystal structure

    Comparative analysis of meat quality of Laiwu black, Minxinan black and Hyla rabbits

    Get PDF
    The meat rabbit industry in China relies on foreign breeds and synthetic lines; the development of superior domestic breeds has not yet been fully realised. We compared the meat quality of two Chinese local breeds of black rabbits (Laiwu black and Minxinan black) and Hyla commercial rabbits, to provide a reference for the utilisation of meat rabbit breeds. In the present study, 35 d old Laiwu black rabbits, Minxinan black rabbits, and Hyla rabbits (20 rabbits each) were selected and reared under identical feeding and management conditions for 7 weeks, after which 10 randomly selected rabbits from each group were slaughtered for the analysis of meat quality. The a∗ (redness) value of the two local breeds was significantly higher than that of Hyla rabbits (p&lt;0.01). The shearing force and drip loss of Laiwu black rabbits were significantly lower than those of the other groups (p&lt;0.05). The two local breeds exhibited significantly higher myoglobin levels than Hyla rabbits (p&lt;0.01), while melanin was highest in the meat of Minxinan black rabbits. The essential amino acids (valine, isoleucine, leucine and lysine) were significantly lower in Minxinan black rabbits than in the other groups (p&lt;0.05). Aldehyde (heptanal, octanal) contents in Minxinan black meat were significantly higher than those of the other groups (p&lt;0.01); however, nucleotide (guanine, adenine) contents were significantly lower (p&lt;0.01). Unsaturated fatty acids (oleic, linoleic, α-linolenic) were significantly higher in the meat of Laiwu black rabbits than in those of the other groups (p&lt;0.05). Both Laiwu black and Minxinan black rabbits have certain advantages in terms of nutritional indicators while also having good meat colour and flavour. The results of this study provide a theoretical reference for the research and development of meat rabbit breeds.</p
    • …
    corecore