scholarly journals MODELO MATEMÁTICO DEL ECOSISTEMA DE LA CIÉNAGA GRANDE DE SANTA MARTA

2016 ◽  
Vol 32 ◽  
Author(s):  
Yuri S. Tuchkovenko ◽  
Luis Alfredo Calero
Keyword(s):  
Mathematical Model ◽  
Organic Matter ◽  
Spatial Distribution ◽  
Dissolved Oxygen ◽  
Coastal Lagoon ◽  
Two Dimensional ◽  
Balance Equations ◽  
Dead Organic Matter ◽  
Shallow Reservoir ◽  
Nitrite Nitrate

The structure of the chemical – biological block of two-dimensional mathematical model of ecosystem and shallow reservoir and his methods of calibration is described in detail. The model includes the balance equations for the following components of ecosystem: phytoplankton, bacteria, zooplankton, dead (organic) matter, phosphate, ammonium, nitrite, nitrate and dissolved oxygen. Results of calculations of spatial distribution of several components of the ecosystem for the Ciénaga Grande de Santa Marta coastal lagoon (Colombia) in various seasons of year are given.

scholarly journals Effects of Physicochemical Variables of Superficial Waters on the Abundance of the North African Freshwater Crab Potamon algeriense (Bott, 1967)

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Soufiane Fadlaoui ◽  
Ouahid El Asri ◽  
Mustapha Bouterfas ◽  
Mohammed Melhaoui
Keyword(s):  
Organic Matter ◽  
Dissolved Oxygen ◽  
Water Temperature ◽  
Suspended Matter ◽  
Mountain Stream ◽  
Freshwater Crab ◽  
Physicochemical Variables ◽  
The North ◽  
Global Quality ◽  
Nitrite Nitrate

The large number of pollutants discharged into the aquatic environment may influence the physicochemical and biological qualities of the aquatic ecosystem. This study discloses the global quality of the surface waters and the effect of physicochemical variables on the abundance of the African freshwater crab Potamon algeriense inhabiting Zegzel watercourse, a mountain stream in the northeast of Morocco. Physicochemical variables including streamflow, water temperature, pH, dissolved oxygen, suspended matter, chloride, calcium, magnesium, ammonia, nitrite, nitrate, orthophosphate, and organic matter were evaluated monthly for one year (October 2017–September 2018). The evaluation of the physicochemical quality showed that the waters of all the stations studied are between the excellent and good quality classes concerning all the physicochemical variables and highlights also two variations with a tendency towards degradation, one spatial from upstream to downstream and the other seasonal from the wet to the dry period. The abundance of crabs was recorded to exhibit a positive correlation with dissolved oxygen, calcium (N = 44) (p < 0.01), and magnesium. However, a negative correlation has been noticed for streamflow (N = 1) (p < 0.01), water temperature, pH, suspended matter, chloride, ammonia, nitrite, nitrate, orthophosphate, and organic matter. The results obtained reveal that besides the biotic variables, the distribution of P. algeriense also depends on these specific environmental variables.

Assessing the impact of soil erosion on plant vigor (NDVI) and the spatial patterns of soil-bound Cu, Zn and B micro- and N, P macronutrients in a sloping vineyard (Tokaj, Hungary)

2021 ◽  
Author(s):  
Izabella Babcsányi ◽  
Ferenc Kovács ◽  
Szabolcs Juhász ◽  
Péter Balling ◽  
Nhung Pham Thi Ha ◽  
...  
Keyword(s):  
Organic Matter ◽  
Spatial Distribution ◽  
Soil Erosion ◽  
Soil Loss ◽  
Vegetation Indices ◽  
Moderate Degree ◽  
Nutrient Contents ◽  
Plant Vigor ◽  
Nitrate N ◽  
Nitrite Nitrate

&lt;p&gt;Soil erosion in sloping vineyards greatly influence the spatial distribution of soil nutrient contents and can affect plant nutrition and vigor. The study aimed to evaluate possible links between the grapevine (Vitis Vinifera) vigor and the erosion-impacted macro- and micronutrient contents in the topsoil. Our study combined field observations, laboratory measurements and remote sensing data.&lt;/p&gt;&lt;p&gt;The field experiment was performed in a 1.8 ha vineyard plot in Tokaj (NE Hungary) with a mean slope of 8&amp;#176; and a slope length of 270 m. The main soil type in the vineyard is Regosol developed on loess. The stock unearthing method was applied for estimating soil loss/sedimentation in the vineyard. The study plot is separated by pathways perpendicular to the south-facing main slope into four equal areas with decreasing slope steepness. A total of 42 soil samples (0-10 cm) were collected (10-12 in each area) to measure organic matter content, plant-available nitrite+nitrate-N, P&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;5&lt;/sub&gt;-P, and total contents of Cu, Zn and B micronutrients. Additionally, five subsoil samples were taken at 2 m depth for determining micronutrient accumulation in the topsoil due to vine treatments. The spatial variability of topsoil nutrient contents was assessed by interpolating the measured parameters using the inverse distance weighting method. The effects of soil erosion and spatial distribution of the nutrient contents on plant vigor were analyzed using the Normalized Difference Vegetation Index (NDVI). Sentinel-2 images with 10 m resolution were acquired on three dates in June and July 2020. In the study area, a median Cu enrichment factor (EF=topsoil/subsoil) of 2.7 can be attributed to a prevailing anthropogenic origin of the topsoil-bound Cu content. The vineyard is an organic farm, therefore Cu use (in a dose of 4 kg/ha/year) is an obvious way to protect grapevines against fungal infections. We also observed a moderate degree of Zn and B enrichment in the topsoil (EF&lt;sub&gt;Zn&lt;/sub&gt;: 1.2, EF&lt;sub&gt;B&lt;/sub&gt;: 1.4) due to vine treatments with foliar fertilizers. The element distribution maps show a fairly similar spatial pattern of Cu, available P&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;5&lt;/sub&gt;-P, and organic matter contents. Their accumulation in the footslope area with the lowest steepness can be seen. Compared with the soil loss/sedimentation map based on stock unearthing data, the Cu, P&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;5&lt;/sub&gt;-P and organic matter contents of the topsoil are lower in areas subject to more intense erosion, which may even affect the development of vines. The latter is to be examined in the light of vegetation indices (NDVI). Changes in vegetation indices along the main slope can be observed with clearly increasing NDVI values in the footslope area. Spatial changes in B, Zn and nitrite-nitrate-N contents do not show a clear relationship with the topographic patterns of the area and the resulting soil erosion losses. Besides the nutrient contents, the presumably higher soil moisture content in the footslope area may also explain the higher NDVI values.&lt;/p&gt;&lt;p&gt;&lt;sub&gt;I. B. is grateful for the support of the Premium Postdoctoral Research Program of the Hungarian Academy of Sciences. The research received funds from the OTKA 1K 116981.&lt;/sub&gt;&lt;/p&gt;

Two Dimensional Unsteady State Mathematical Model for dispersion of Chlorine in Water in a Channel

2011 ◽  
Vol 3 (8) ◽  
pp. 503-505
Author(s):  
Jaipal Jaipal ◽  
◽  
Rakesh Chandra Bhadula ◽  
V. N Kala V. N Kala
Keyword(s):  
Mathematical Model ◽  
Two Dimensional ◽  
Unsteady State

Modelling of experiments with colloidal organic matter in biofilm reactors

1994 ◽  
Vol 29 (10-11) ◽  
pp. 479-486 ◽  
Author(s):  
T. A. Larsen ◽  
P. Harremoës
Keyword(s):  
Mathematical Model ◽  
Organic Matter ◽  
Bulk Liquid ◽  
Native Starch ◽  
Trickling Filters ◽  
Biofilm Reactors ◽  
Removal Capacity

A mathematical model for the degradation of colloidal organic matter in biofilm reactors has been developed. Contradictory to existing theories, the model includes bulk liquid hydrolysis as the first important step in the degradation sequence. This leads to unexpected effects of different reactor configurations. The model was successfully verified with native starch as a model substrate. Observed differences in colloid removal capacity between trickling filters and RBC-reactors are well explained by the model.

Resource Similarity, Market Commonality, and Spatial Distribution of Hotel Competitive Sets

2021 ◽  
pp. 109634802098857
Author(s):  
Zvi Schwartz ◽  
Timothy Webb
Keyword(s):  
Mathematical Model ◽  
Spatial Distribution ◽  
Performance Evaluation ◽  
Critical Role ◽  
Principal Agent ◽  
Large Dataset ◽  
Principal Agent Theory ◽  
Agent Theory ◽  
Performance And Evaluation

Index scores and competitive sets (compsets) play a critical role in the performance and evaluation of hotels. The reliance on these metrics has drawn skepticism in recent years as competitive sets may be opportunistically chosen, creating bias in performance evaluation. Drawing from the principal–agent theory and the theory of incentives, we explore whether the distance of the competitors chosen for a hotel’s compset influences revenue per available room (RevPAR) index scores. Based on the concepts of resource similarity and market commonality, we develop a novel mathematical model through which we empirically analyze a large dataset of 10,000 compsets. We find evidence that competitor distance influences index performance and that this relationship is bidirectional. Results show that hotels that outperform the competition may use distance to inflate RevPAR indices, while those that underperform may use distance to further reduce scores. These conflicting results may be reflected from the reverse motivations of the stakeholders.

Study on Grinding Force in Two-Dimensional Ultrasonic Grinding Nano-Ceramics

2010 ◽  
Vol 42 ◽  
pp. 204-208 ◽  
Author(s):  
Xiang Dong Li ◽  
Quan Cai Wang
Keyword(s):  
Mathematical Model ◽  
Ultrasonic Vibration ◽  
Contact Time ◽  
Reaction Force ◽  
Grinding Force ◽  
Two Dimensional ◽  
Indentation Fracture ◽  
Ultrasonic Grinding ◽  
The Impact ◽  
Ultrasonic Vibration Assisted Grinding

In this paper, the characteristic of grinding force in two-dimensional ultrasonic vibration assisted grinding nano-ceramic was studied by experiment based on indentation fracture mechanics, and mathematical model of grinding force was established. The study shows that grinding force mainly result from the impact of the grains on the workpiece in ultrasonic grinding, and the pulse power is much larger than normal grinding force. The ultrasonic vibration frequency is so high and the contact time of grains with the workpiece is so short that the pulse force will be balanced by reaction force from workpiece. In grinding workpiece was loaded by the periodical stress field, which accelerates the fatigue fracture.

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