Analysis of explicit and implicit discrete-time equivalent-control based sliding mode controllers

Different time-discretization methods for equivalent-control based sliding mode control (ECB-SMC) are presented. A new discrete-time sliding mode control scheme is proposed for linear time-invariant (LTI) systems. It is error-free in the discretization of the equivalent part of the control input. Results from simulations using the various discretized SMC schemes are shown, with and without perturbations. They illustrate the different behaviours that can be observed. Stability results for the proposed scheme are derived

Negotiating the Political Ecology of Aboriginal Resource Management: How Mi'kmaq Manage Their Moose and Lobster Harvest in Unama'ki, Nova Scotia, Canada

Since the Supreme Court of Canada affirmed the fishing and hunting rights of the Mi'kmaq nation in 1985 and 1990, the government has failed to accommodate these in appropriate and effective resource management frameworks. In Unama'ki/Cape Breton Island, Nova Scotia, the subsistence harvest of lobster and moose by Mi'kmaq has therefore caused cross-cultural conflict and ecological concerns. Since 2006, the Lobster Management Plan (Unama'kik Jakejue'ka'timk) and the Moose Management Plan are being developed under Mi'kmaq leadership to manage the Mi'kmaq harvest communally. These innovative management initiatives will serve as case studies for this thesis to explore how Mi'kmaq negotiate the political ecology of co-management in Nova Scotia and effectively assert Mi'kmaq rights to resource harvest and selfgovernance. Most notably, the management plans employ cultural principles of sustainability and pro-active approaches to cross-cultural communication. This research shows how Mi'kmaq communities have developed resource management capacities and frameworks that can also inspire the self-government aspirations of other aboriginal nations in Canada. Mi'kmaq strategies and experience suggests that aboriginal leadership and cultural principles are integral to the meaningful implementation of aboriginal resource rights. Semi-structured interviews with Mi'kmaq and governmental resource managers illustrated diverse discourses of aboriginal resource rights, ecological knowledge and sustainability. Aiming to represent research insights appropriately, this thesis follows the decolonization agenda of aboriginal methodologies and features reflective discussions of the author's positionality within the Mi'kmaq research community. This also allows for a review of how the author came to terms with conflicting discourses and aboriginal ontologies of ecological knowledge, as well as the requirements for decolonizing research. Supporting reflective insights, a framework of anthropological political ecology and poststructuralist arguments for ontological diversity explain the validity of aboriginal perspectives on ecological knowledge and resource rights, which is the premise of decolonization paradigms. A review of engaging with aboriginal culture both in theory and practice concludes that the practical experience is essential for an appreciation of aboriginal perspectives and thus integral to cross-cultural communication and co-management relationships

Inference of the Distribution of Selection Coefficients for New Nonsynonymous Mutations Using Large Samples.

The distribution of fitness effects (DFE) has considerable importance in population genetics. To date, estimates of the DFE come from studies using a small number of individuals. Thus, estimates of the proportion of moderately to strongly deleterious new mutations may be unreliable because such variants are unlikely to be segregating in the data. Additionally, the true functional form of the DFE is unknown, and estimates of the DFE differ significantly between studies. Here we present a flexible and computationally tractable method, called Fit∂a∂i, to estimate the DFE of new mutations using the site frequency spectrum from a large number of individuals. We apply our approach to the frequency spectrum of 1300 Europeans from the Exome Sequencing Project ESP6400 data set, 1298 Danes from the LuCamp data set, and 432 Europeans from the 1000 Genomes Project to estimate the DFE of deleterious nonsynonymous mutations. We infer significantly fewer (0.38-0.84 fold) strongly deleterious mutations with selection coefficient |s| > 0.01 and more (1.24-1.43 fold) weakly deleterious mutations with selection coefficient |s| < 0.001 compared to previous estimates. Furthermore, a DFE that is a mixture distribution of a point mass at neutrality plus a gamma distribution fits better than a gamma distribution in two of the three data sets. Our results suggest that nearly neutral forces play a larger role in human evolution than previously thought

Strategies to mitigate greenhouse gas and nitrogen emissions in Swiss agriculture: the application of an integrated sector model

Environmental impacts of agricultural production, such as greenhouse gas (GHG) and nitrogen emissions, are of major concern for scientists and policy makers throughout the world. Global agricultural activities account for about 60% of nitrous oxide and about 50% of methane emissions. From a global perspective, methane and nitrous oxide constitute crucial GHGs. They contribute substantially to climate change due to their high potential for effecting global warming compared to carbon dioxide. Emissions of these gases depend on the extent of agricultural production and applied technologies. Therefore, analysis of potential mitigation opportunities is challenging and requires an integrated approach in order to link agricultural economic perspectives to environmental aspects. In view of this, a mathematical programming model has been developed which enables assessment of cost-effective strategies for mitigating GHG and nitrogen emissions in the agricultural sector in Switzerland. This model is applied to improve understanding of the agricultural sector and its behavior with changing conditions in technology and policy. The presented recursive-dynamic model mimics the structure and inter- dependencies of Swiss agriculture and links that framework to core sources of GHG and nitrogen emissions. Calculated results for evaluation and application indicate that employed flexibility constraints provide a feasible approach to sufficiently validate the described model. Recursive-dynamic elements additionally enable adequate modeling of both an endogenous development of livestock dynamics and investments in buildings and machinery, also taking sunk costs into account. The presented findings reveal that the specified model approach is suitable to accurately estimate agricultural structure, GHG and nitrogen emissions within a tolerable range. The model performance can therefore be described as sufficiently robust and satisfactory. Thus, the model described here appropriately models strategies for GHG and nitrogen abatement in Swiss agriculture. The results indicate that there are limits to the ability of Swiss agriculture to contribute substantially to the mitigation of GHG and nitrogen emissions. There is only a limited level of mitigation available through technical approaches, and these approaches have high cost.resource use, environmental economics, greenhouse gas emission, nitrogen emission, integrated modeling

A Knowledge-based approach to understanding natural language

Understanding a natural language requires knowledge about that language as a system of representation. Further, when the task is one of understanding an extended discourse, world knowledge is also required. This thesis explores some of the issues involved in representing both kinds of knowledge, and also makes an effort to arrive at some under standing of the relationship between the two. A part of this exploration involves an examination of some natural language understanding systems which have attempted to deal with extended discourse both in the form of stories and in the form of dialogues. The systems exam ined are heavily dependent on world knowledge. Another part of this exploration is an effort to build a dialogue system based on speech acts and practical argu ments, as they are described in Recognizing Promises, Advice, Threats, and Warnings , a Masters Thesis presented to Rochester Institute of Technology, School of Computer Science and Technology, in 1986 by Kevin Donaghy. This dialogue system includes a deterministic syntactic parser, a semantic representation based on the idea of case frames, and a context interpreter that recognizes and represents groups of sentences as practical arguments. This Prolog implementation employs a frame package developed and described in A Frame Virtual Machine in C-Prolog , a Masters Thesis presented to Rochester Institute of Technology, School of Computer Science and Technology, in 1987 by LeMora Hiss. While this automated dialogue system is necessarily limited in the domain that it recognizes, the opportunity it allows to build a mechanism and a system of representation brings with it a range of issues from the syntactic, through the semantic, to the contextual and the pragmatic. Here, the focus of inquiry came to settle in the semantic representa tion, where the relationship between knowledge about language and knowledge about the world seems to be naturally resident

Comparison between explicit and implicit discrete-time implementations of sliding-mode controllers

International audienceDifferent time-discretization methods for sliding mode control (SMC) are presented. A new discrete-time sliding mode control scheme is proposed for linear time-invariant (LTI) systems. It is error-free in the discretization of the equivalent part of the control input. Results from simulations using the various discretized SMC schemes are shown, with and without perturbations. They illustrate the different behaviours that can be observed

Discrete-time twisting controller without numerical chattering: analysis and experimental results with an implicit method

International audienceIn this note, we present an implementation of the twisting controller on an electropneumatic plant for a tracking control problem. Implicit and explicit discrete-time twisting controllers are considered, and some implementation details are provided. Experimental results are provided and analyzed. They sustain the theoretical superiority of the implicitly discretized version, as shown in previous work. The main advantages of the implicit method are better tracking and drastic reduction in the input and output chattering. This is achieved without modifying the controller structure compared to its continuous-time version

Epstein-Barr Virus Transactivates the Human Endogenous Retrovirus HERV-K18 that Encodes a Superantigen

AbstractSuperantigens (SAgs) are proteins produced by pathogenic microbes to elicit potent, antigen-independent T cell responses that are believed to enhance the microbes' pathogenicity. Here we show that the human lymphotropic herpesvirus Epstein-Barr virus (EBV) transcriptionally activates the env gene of an endogenous retrovirus, HERV-K18, that possesses SAg activity. SAg activity was demonstrated by MHC class II dependent preferential activation of TCRVB13 T cells in response to murine B cells transfected with the HERV-K18 env gene. This is a unique demonstration of a pathogen inducing a host-encoded Sag and accounts for the previously described EBV associated Sag activity. The T cell activation elicited by the Sag could play a central role in EBV infection and associated diseases

Exploratory Analysis of Functional Data via Clustering and Optimal Segmentation

We propose in this paper an exploratory analysis algorithm for functional data. The method partitions a set of functions into $K$ clusters and represents each cluster by a simple prototype (e.g., piecewise constant). The total number of segments in the prototypes, $P$, is chosen by the user and optimally distributed among the clusters via two dynamic programming algorithms. The practical relevance of the method is shown on two real world datasets

Lyapunov stability and performance analysis of the implicit discrete sliding mode control

International audienceDiscrete-time sliding mode controllers with an implicit discretization of the signum function are considered.With a proper choice of the equivalent part of the control, the resulting controller is shown to be Lyapunov stable withfinite-time convergence of the sliding variable to $0$. The convergence of the control input, as the sampling period goes to $0$,to the continuous-time one is shown. The robustness with respect to matching perturbations is also investigated.The discretization performance in terms of the error order is studied for different discretizations of the equivalent part of the input.Numerical and experimental results illustrate and support the analysis