Analysis Of Spatial Diversity Research Articles

Seasonal and spatial occurrence of plankton and environmental variables in Ogun coastal water on the Bight of Benin

The influence of environmental variables on the seasonal and spatial distribution of plankton was studied for 24 months between February 2015 and January 2017 in the marine coastal water of Ogun State, Nigeria. The coastline was stratified into three sampling stations, and surface water samples were collected monthly per station for physico-chemical and plankton analyses. Mean values of physico-chemical parameters were: temperature (28.60±0.27°C), salinity (29.25±0.45‰), pH (7.38±0.07), electrical conductivity (42.13±0.33μS/l), total dissolved solids (29.59±0.30mg/l), dissolved oxygen (6.48±0.07mg/l), phosphate (1.36×10-2±0.39mg/l) and nitrate (2.25×10-2±0.65mg/l). The dominant phytoplankton and zooplankton groups were Diatomaceae (42.06%) and Calanoids (25.42%), respectively. Spatial diversity analysis of plankton in the study area showed that the highest (19, 35) species richness and abundance (5703, 12,452) for phytoplankton and zooplankton, respectively occurred in Site 3. Seasonal species richness of phytoplankton and zooplankton was higher in the wet (27, 40) than the dry (23, 38) season. Canonical correspondence analysis explained 77.8% of the influence of environmental variables on plankton distribution. Water temperature, dissolved oxygen, salinity, phosphate, pH, TDS and nitrate were the most marked factors that affected the distribution and abundance of plankton.

Analysis of Spatial Diversity in Both Transmitter and Receiver on Low-Height Links at Forests

This work focuses on radio wave propagation within forested environments, at 5.8 GHz. Concretely, we explore the advantages of implementing spatial diversity in reception or even in both ends for improving the strength of the received signal in such environments, which could be useful in applications such as vehicle-to-infrastructure, vehicle-to-vehicle, or emergency communications. Measurements gathered at both evergreen and deciduous forests sustain the thesis. Once processed, the results support the proposal of implementing a spatial diversity technique in reception or in both ends using a 2 × 4 (or 2 × 2) scheme in order to improve the connectivity at 5.8 GHz band within forests. In fact, we estimated a gain due to spatial diversity in reception of 5 dB and 2 dB at evergreen and deciduous forests, respectively, and 16 dB or 5 dB when implementing at both ends.

English

Analysis of spatial diversity, temporal diversity and coefficient of parentage (COP) were carried out along with measurements of agronomic and morphological traits to explain on-farm diversity of modern varieties or landraces of wheat (Triticum aestivum L. and Triticum durum L.) grown by farmers in Ethiopia. Farm level surveys showed low spatial diversity of wheat where only a few dominant varieties appeared to occupy a large proportion of wheat area. The five top wheat varieties were grown by 56% of the sample farmers and these varieties were planted on 80% of the total wheat area. The weighted average age of wheat varieties was high with an average of 13.8 years for bread wheat showing low temporal diversity or varietal replacement by farmers. The COP analysis showed that average and weighted diversity of bread wheat was 0.76 and 0.66, respectively variance component analysis showed significant variations for agronomic characters such as plant height, grain yield, and yield components (kernels spike-1, thousand seed weight) among modern varieties and/or landraces. The principal component analysis explained better the variation among varieties and landraces. Cluster analysis based on agro-morphological traits grouped modern varieties and landraces into separate clusters. The present study describes the diversity of wheat crop available on the farm using different indicators. The variation among modern varieties and landraces offered opportunities for using genotypes with desired agronomic characters in plant breeding to develop varieties suitable for different agro-ecological zones in the country.   Key words: Ethiopia, wheat, genetic diversity, spatial diversity, temporal diversity, coefficient of parentage, landraces. &nbsp

A family of spatial biodiversity measures based on graphs

While much research in ecology has focused on spatially explicit modelling as well as on measures of biodiversity, the concept of spatial (or local) biodiversity has been discussed very little. This paper generalises existing measures of spatial biodiversity and introduces a family of spatial biodiversity measures by flexibly defining the notion of the individuals’ neighbourhood within the framework of graphs associated to a spatial point pattern. We consider two non-independent aspects of spatial biodiversity, scattering, i.e. the spatial arrangement of the individuals in the study area and exposure, the local diversity in an individual’s neighbourhood. A simulation study reveals that measures based on the most commonly used neighbourhood defined by the geometric graph do not distinguish well between scattering and exposure. This problem is much less pronounced when other graphs are used. In an analysis of the spatial diversity in a rainforest, the results based on the geometric graph have been shown to spuriously indicate a decrease in spatial biodiversity when no such trend was detected by the other types of neighbourhoods. We also show that the choice of neighbourhood markedly impacts on the classification of species according to how strongly and in what way different species spatially structure species diversity. Clearly, in an analysis of spatial or local diversity an appropriate choice of local neighbourhood is crucial in particular in terms of the biological interpretation of the results. Due to its general definition, the approach discussed here offers the necessary flexibility that allows suitable and varying neighbourhood structures to be chosen.

A New Statistical Channel Model for Hybrid-Diversity MIMO Systems

Based on analysis of spatial-diversity and polarization-diversity MIMO systems, a new modeling method, which utilizes the covariance matrix and the power matrix to build a general-purpose statistical MIMO channel model, is proposed. The new model is able to represent the characteristic of hybrid diversity, which integrates both spatial diversity and polarization diversity, and can be applied to MIMO systems with various diversity types. A comparison between the simulation results and measurements shows the validity of the proposed model as well as its advantage over an existing model.

Spatial diversity analysis for digital TV systems

Spatial diversity for digital TV systems has been studied using the results of a measurement campaign of the radio channel complex frequency response for two different situations: an outdoor-indoor channel and an indoor-indoor channel. It is shown that the actual improvement of spatial diversity is not only the mean level increase, but the reduction of both the level crossing rate (LCR) and the average fade duration (AFD). The mean level gain is in the range 1.2-3 dB for the indoor-indoor channel and within 1.4-2.9 dB for the outdoor-indoor channel and the LCR/AFD improvement is between 9.5 and 15 dB for both environments. To explain the behavior of the diversity system, high resolution angle of arrival and delay information was obtained. It is concluded that it is the interference of the direct propagation path with the main reflections that causes the received field to follow a standing wave pattern and shapes the spatial diversity gain behavior.