6 research outputs found
A linear quadratic regulator for nonlinear SIRC epidemic model
The control of an epidemic disease consists in introducing the strategies able to reduce the number of infected subjects by means of medication/quarantine actions, and the number of the subjects that could catch the disease through an informative campaign and, when available, a vaccination strategy. Some diseases, like the influenza, do not guarantee immunity; therefore, the subjects could get ill again by different strain of the same viral subtype. The epidemic model adopted in this paper introduces the cross-immune individuals; it is known in literature as SIRC model, since the classes of susceptible (S), infected (I), removed (R) and cross-immune (C) subjects are considered. Its control is herein determined in the framework of the linear quadratic regulator, by applying to the original nonlinear model the optimal control found on the linearized system. The results appear satisfactory, and the drawback of using a control law based on the linear approximation of the system is compensated by the advantages arising from such a solution: no costate equations to be solved and a solution depending on the current state evolution which allows a feedback implementation
An Improvement in a Local Observer Design for Optimal State Feedback Control: The Case Study of HIV/AIDS Diffusion
The paper addresses the problem of an observer design for a nonlinear system for which a preliminary linear
state feedback is designed but the full state is not measurable. Since a linear control assures the fulfilment of
local approximated conditions, usually a linear observer is designed in these cases to estimate the state with
estimation error locally convergent to zero. The case in which the control contains an external reference, like
in regulations problems, is studied, showing that the solution obtained working with the linear approximation
to get local solutions produces non consistent results in terms of local regions of convergence for the system
and for the observer. A solution to this problem is provided, proposing a different choice for the observer
design which allows to obtain all conditions locally satisfied on the same local region in the neighbourhood of
a new equilibrium point. The case study of an epidemic spread control is used to show the effectiveness of the
procedure. The linear control with regulation term is present in this case because the problem is reconducted to
a Linear Quadratic Regulation problem. Simulation results show the differences between the two approaches
and the effectiveness of the proposed on
Seasonality and adaptive dynamics in host-parasite systems in wildlife
I parametri ecologici sono solitamente difficili da stimare nella fauna selvatica, ma, nel caso di malattie infettive, il tasso di trasmissione del patogeno è il processo più complesso da valutare. Tra i tratti caratteristici dell’ospite la taglia corporea è sicuramente il più influente, in quanto molti parametri demografici scalano allometricamente con essa. In questo lavoro ho mostrato come le relazioni allometriche possono legare la taglia dell’ospite al tasso di trasmissione della malattia e al suo tasso netto di riproduzione. Quindi ho analizzato come le dinamiche epidemiologiche variano in funzione della taglia. Inoltre, sotto le stesse ipotesi, ho studiato l’effetto della variazione stagionale di parametri come tasso di trasmissione e natalità, sulla dinamica della malattia.
Per quanto riguarda il controllo dell’infezione, ho analizzato l’effetto di politiche di abbattimento in diverse condizioni ecologiche. In particolare, mi sono concentrato sull’efficacia del controllo in presenza di ceppi a diversa virulenza e in presenza di struttura d’età nella popolazione ospite. In entrambi i casi ho trovato che esistono determinate condizioni ecologiche per cui una politica di eradicazione della malattia basata sull’abbattimento può avere conseguenze peggiori dell’alternativa zero. Ho inoltre mostrato in quali condizioni semplici politiche di abbattimento tempo-variante possono migliorare significativamente il controllo della malattia.Ecological parameters are usually hard to estimate correctly in wild populations, but, in the case of infectious diseases, the rate of transmission of the pathogen agent is often the most complex process to evaluate. Of the many traits characterizing host species demography, body size is probably the most influential one, as many demographic parameters scale allometrically with host body size. In this work I show how the allometric relationships, usually found for demographic parameters, may link host body size with the disease transmission rate and its basic reproduction number. Then, I analysed the effect of seasonal variation in different ecological and epidemiological parameters on disease dynamics.
Under the point of view of disease control, I analysed the effectiveness of depopulation policies in different ecological conditions. In particular, I focused on control effectiveness when strains with different virulence co-circulate in the host population and when disease transmission is a function of the age/stage class of the host individuals. In both cases, I found that (under certain conditions) culling policies may perform worse, in terms of disease control, than the do-nothing alternative. I also show in which conditions simple time-variant control policies can improve disease control in wildlife
Збірник наукових праць 9-ї Міжнародної конференції з моніторингу, моделювання та управління емерджентною економікою (M3E2-MLPEED 2021). Одеса, Україна, 26-28 травня 2021 р.
Збірник наукових праць 9-ї Міжнародної конференції з моніторингу, моделювання та управління емерджентною економікою (M3E2-MLPEED 2021). Одеса, Україна, 26-28 травня 2021 р.Proceedings of the Selected and Revised Papers of 9th International Conference on Monitoring, Modeling & Management of Emergent Economy (M3E2-MLPEED 2021). Odessa, Ukraine, May 26-28, 2021
A complex systems approach to education in Switzerland
The insights gained from the study of complex systems in biological, social, and engineered systems enables us not only to observe and understand, but also to actively design systems which will be capable of successfully coping with complex and dynamically changing situations. The methods and mindset required for this approach have been applied to educational systems with their diverse levels of scale and complexity. Based on the general case made by Yaneer Bar-Yam, this paper applies the complex systems approach to the educational system in Switzerland. It confirms that the complex systems approach is valid. Indeed, many recommendations made for the general case have already been implemented in the Swiss education system. To address existing problems and difficulties, further steps are recommended. This paper contributes to the further establishment complex systems approach by shedding light on an area which concerns us all, which is a frequent topic of discussion and dispute among politicians and the public, where billions of dollars have been spent without achieving the desired results, and where it is difficult to directly derive consequences from actions taken. The analysis of the education system's different levels, their complexity and scale will clarify how such a dynamic system should be approached, and how it can be guided towards the desired performance
Factors Influencing Customer Satisfaction towards E-shopping in Malaysia
Online shopping or e-shopping has changed the world of business and quite a few people have
decided to work with these features. What their primary concerns precisely and the responses from
the globalisation are the competency of incorporation while doing their businesses. E-shopping has
also increased substantially in Malaysia in recent years. The rapid increase in the e-commerce
industry in Malaysia has created the demand to emphasize on how to increase customer satisfaction
while operating in the e-retailing environment. It is very important that customers are satisfied with
the website, or else, they would not return. Therefore, a crucial fact to look into is that companies
must ensure that their customers are satisfied with their purchases that are really essential from the ecommerce’s
point of view. With is in mind, this study aimed at investigating customer satisfaction
towards e-shopping in Malaysia. A total of 400 questionnaires were distributed among students
randomly selected from various public and private universities located within Klang valley area.
Total 369 questionnaires were returned, out of which 341 questionnaires were found usable for
further analysis. Finally, SEM was employed to test the hypotheses. This study found that customer
satisfaction towards e-shopping in Malaysia is to a great extent influenced by ease of use, trust,
design of the website, online security and e-service quality. Finally, recommendations and future
study direction is provided.
Keywords: E-shopping, Customer satisfaction, Trust, Online security, E-service quality, Malaysia