Adaptive Importance Sampling for Performance Evaluation and Parameter Optimization of Communication Systems

We present new adaptive importance sampling techniques based on stochastic Newton recursions. Their applicability to the performance evaluation of communication systems is studied. Besides bit-error rate (BER) estimation, the techniques are used for system parameter optimization. Two system models that are analytically tractable are employed to demonstrate the validity of the techniques. As an application to situations that are analytically intractable and numerically intensive, the influence of crosstalk in a wavelength-division multiplexing (WDM) crossconnect is assessed. In order to consider a realistic system model, optimal setting of thresholds in the detector is carried out while estimating error rate performances. Resulting BER estimates indicate that the tolerable crosstalk levels are significantly higher than predicted in the literature. This finding has a strong impact on the design of WDM networks. Power penalties induced by the addition of channels can also be accurately predicted in short run-time

Denudation and geomorphic change in the Anthropocene; a global overview

The effects of human activity on geomorphic processes, particularly those related to denudation/sedimentation, are investigated by reviewing case studies and global assessments covering the past few centuries. Evidence we have assembled from different parts of the world, as well as from the literature, show that certain geomorphic processes are experiencing an acceleration, especially since the mid-twentieth century. This suggests that a global geomorphic change is taking place, largely caused by anthropogenic landscape changes

Denudation and geomorphic change in the Anthropocene; a global overview

The effects of human activity on geomorphic processes, particularly those related to denudation/sedimentation, are investigated by reviewing case studies and global assessments covering the past few centuries. Evidence we have assembled from different parts of the world, as well as from the literature, show that certain geomorphic processes are experiencing an acceleration, especially since the mid-twentieth century. This suggests that a global geomorphic change is taking place, largely caused by anthropogenic landscape changes. Direct human-driven denudation (through activities involving excavation, transport, and accumulation of geological materials) has increased by a factor of 30 between 1950 and 2015, representing a ten-fold increase of per capita effect. Direct plus indirectly human-induced denudation (triggered by land surface alteration) is presently at least one order of magnitude greater than denudation due to purely natural processes. The activity of slope movements, which represent an important contribution to denudation, sediment generation and landscape evolution, also shows a clear intensification. Frequency of hazardous events and disasters related to slope movements (an indirect measure of process frequency) in specific regions, as well as at continental and global levels, has grown considerably, in particular after the mid-twentieth century. Intense rainstorm events are often related to slope movement occurrence, but the general increasing trend observed is not satisfactorily explained by climate. Sedimentation has augmented considerably in most regions and all kinds of sedimentation environments. Although the link between denudation and sedimentation is not direct and unequivocal, it is safe to assume that if sedimentation rates increase in different regions during a given period, denudation must have increased too, even though their magnitudes could be different. This augmentation, particularly marked from the second half of the last century onwards, appears to be determined mainly by land surface changes, in conjunction with climate change. The changes observed suggest: a) there is evidence at a global scale of a growing response of geomorphic systems to socio-economic drivers, being Gross Domestic Product density, a good indicator of the human potential to cause such impacts; b) Land use/cover changes enhance effects of climate change on global denudation/sedimentation and landslide/flood frequency, and appear to be a stronger controlling factor; c) Our findings point to the existence of a global geomorphic change. This manifestation of global change is especially evident since the ?great geomorphic acceleration? that began in the middle of the 20th century, and constitutes one of the characteristics of the proposed Anthropocene.This work was supported, at different stages, by projects: FEDER, AEI, CGL2017-82703-R (Ministerio de Ciencia e Investigacion, Spain) and PICT2011-1685; MTM2014-56235-C2-2215 (Ministerio de Ciencia, Tecnología e Innovacion, Argentina). We also thank Dr. Anthony R. Berger for critical review and writing assistance

Landslide Risk Assessment by Using a New Combination Model Based on a Fuzzy Inference System Method

Landslides are one of the most dangerous phenomena that pose widespread damage to property and human lives. Over the recent decades, a large number of models have been developed for landslide risk assessment to prevent the natural hazards. These models provide a systematic approach to assess the risk value of a typical landslide. However, often models only utilize the numerical data to formulate a problem of landslide risk assessment and neglect the valuable information provided by experts’ opinion. This leads to an inherent uncertainty in the process of modelling. On the other hand, fuzzy inference systems are among the most powerful techniques in handling the inherent uncertainty. This paper develops a powerful model based on fuzzy inference system that uses both numerical data and subjective information to formulate the landslide risk more reliable and accurate. The results show that the proposed model is capable of assessing the landslide risk index. Likewise, the performance of the proposed model is better in comparison with that of the conventional techniques

Prediction rate functions of landslide susceptibility applied in the Iberian Peninsula

Prediction rate functions of landslide susceptibility applied in the Iberian Peninsula A. G. Fabbri1, F. F. Chung2, P. Napolitano3, J. Remondo4 & J. L. Zezere5 1ITC, 7500 AA Enschede, & SPINlab, Vrije Universiteit, I081 HV Amsterdam, The Netherlands 2 Geological Survey of Canada, Ottawa KIA OE8, Canada 3ACTA, Via D. Fontana 40, 80128 Napoli, Italy 4DICITIMAC, Universidad de Cantabria, 39005 Santander, Spain 5 Centro de Estudos Geograficos, Universidade de Lisboa, I699 Lisboa, Portugal Abstract The prediction models of landslide susceptibility that we have developed, generate not only predicted hazard maps but also prediction-rate curves, which allow us to estimate the probabilities of the occurrences of future landslides from the hazard maps. For a risk-analysis estimating the \“economic” values of the population, properties, economic activities, etc., the estimates of the probabilities are absolutely critical statistics. To use the hazard maps for risk analysis, we must be able to estimate the probability of occurrence of a future landslide at each hazard level in the maps. Without the estimates of such probabilities, the hazard maps can provide only indicators of landslide hazard, but they cannot be directly useful for a decision process. With those probabilities, however, decision makers can quantitatively assess the economic sterilization due to the possible damage under the assumptions of appropriate scenarios. Hence, they can take a learned and informed decision. Predictions are based on \“Favourability Functions” that integrate the spatial relationships between the distribution of trigger zones of specific dynamic types of landslides and the surrounding mapping units and contour intervals. The latter two represent the spatial support to estimate the likelihood of further failures.info:eu-repo/semantics/publishedVersio

Performance Evaluation and Parameter Optimization of Wavelength Division Multiplexing Networks with Importance Sampling Techniques

In this paper new adaptive importance sampling techniques are applied to the performance evaluation and parameter optimization of wavelength division multiplexing (WDM) network impaired by crosstalk in an optical cross-connect. Worst-case analysis is carried out including all the beat noise terms originated by in-band crosstalk. Both input signal hypotheses are considered. The accurate bit-error-rate estimates, which are obtained in short run-times, indicate that the influence of crosstalk is much lower than that predicted by previous analyses. This finding has a strong impact on the design of WDM networks. Besides, a method is used to optimize the detection threshold, which turns out to improve the system performance significantly. The presented techniques also allow us to determine the power penalty due to the introduction of additional WDM channel