Connectivity In Scenarios Research Articles

Choosing between Gaussian and MPS simulation: the role of data information content\u2014a case study using uncertain interpretation data points

Integration of geophysical data with information such as from boreholes and expert domain knowledge is often performed as cognitive or explicit geological modeling when generating deterministic geological models of the subsurface. However, such cognitive geological models lack the ability to express the uncertainty of layer boundaries. To remedy the shortcomings of this strategy we propose a novel stochastic methodology combining the efforts of probabilistic data integration and cognitive modeling. We treat geological interpretation points from the cognitive model as uncertain “soft” data. These data are then combined with analogous geology in a probabilistic model. We test two ways of combining and sampling from such a probabilistic model. Firstly, a high-entropy setup based on Gaussian distributions simulation. Secondly, lower entropy (and conceivable more realistic) geological solutions are obtained from multiple-point geostatistics (MPS). We apply both ways of solving the problem at a study site near Horsens, Denmark, where airborne transient electromagnetic measurements, seismic data, and borehole information are available and interpreted in cognitive modeling. We explain the complete framework for integrating the uncertain interpretations in geostatistical simulation. Results show that both the Gaussian simulation and multiple-point geostatistical approach allows satisfactory simulations of uncertain geological interpretations and are consistent with prior geological knowledge. Our results suggest that the number of uncertain data points and their information content play a pivotal role in selecting the most appropriate simulation method for the given framework. MPS simulations allow connectivity in scenarios with few data points due to the low entropy of the model. When the number of soft data increases, Gaussian simulation is less prone to produce simulation artifacts, faster to apply, and could be considered preferential to using MPS simulation.

Implementing the connectivity of natural areas in cities as an indicator in the City Biodiversity Index (CBI)

The City Biodiversity Index (CBI), or Singapore Index on Cities’ Biodiversity, serves as a tool to monitor biodiversity in cities and was endorsed by the Convention on Biological Diversity in 2009. Indicator 2 of the CBI measures the connectivity of natural areas in cities. We propose an improved and straightforward method for measuring connectivity based on the effective mesh size metric to replace the previous method used in the CBI. The previous version did not account for intra-patch (within-patch) connectivity nor for major barriers. Our evaluation of the new version of Indicator 2 through its application to Montréal and Lisbon confirmed its reliability. In Montréal, natural areas have a total connectivity value of 581.7ha, the majority of which exists between, rather than within, patches of natural area. Smaller patches (<15ha) contribute significantly to overall connectivity, which may have implications for future conservation efforts. In Lisbon, connectivity (342ha) is concentrated within patches. We also applied the improved Indicator 2 to a case study in southwestern Montréal, where a greenway network (“green infrastructure”) has been proposed by a local community organization. We assessed the contribution of Meadowbrook Golf Course to connectivity in scenarios of the proposed greenway network and the effect that residential development would have. Not only would this development eliminate the golf course’s current contribution to connectivity, but also its much greater potential contribution to connectivity in future scenarios. Restoring and establishing additional natural areas would significantly increase connectivity in the network. Our results demonstrate that the improved version of Indicator 2 is a suitable method in the CBI. It is equally useful for identifying options to increase the connectivity of natural areas within cities in the future and for determining the impacts of urban development on connectivity. More advanced methods for quantifying connectivity exist and may also be included in Part I of the CBI. However, they are often challenging to use and this frequently discourages city planners from including any indicator of connectivity in their biodiversity monitoring. The connectivity metric presented here overcomes this problem through its practicality in a wide range of planning structures while still generating meaningful results which may then inspire city planners to move towards using more advanced methods of measuring connectivity. We dedicate this paper to the memory of Bernice Goldsmith (1934–2014).

Blockage and directivity in 60 GHz wireless personal area networks: from cross-layer model to multihop MAC design

We present a cross-layer modeling and design approach for multigigabit indoor wireless personal area networks (WPANs) utilizing the unlicensed millimeter (mm) wave spectrum in the 60 GHz band. Our approach accounts for the following two characteristics that sharply distinguish mm wave networking from that at lower carrier frequencies. First, mm wave links are inherently directional: directivity is required to overcome the higher path loss at smaller wavelengths, and it is feasible with compact, low-cost circuit board antenna arrays. Second, indoor mm wave links are highly susceptible to blockage because of the limited ability to diffract around obstacles such as the human body and furniture. We develop a diffraction-based model to determine network link connectivity as a function of the locations of stationary and moving obstacles. For a centralized WPAN controlled by an access point, it is shown that multihop communication, with the introduction of a small number of relay nodes, is effective in maintaining network connectivity in scenarios where single-hop communication would suffer unacceptable outages. The proposed multihop MAC protocol accounts for the fact that every link in the WPAN is highly directional, and is shown, using packet level simulations, to maintain high network utilization with low overhead.