Positive Realization Research Articles

Effect of cross-correlated hydraulic conductivity and compression index on nonlinear consolidation in randomly heterogeneous highly compressible aquitards

The problem of land subsidence due to groundwater pumping in highly compressible, randomly heterogenous aquitards with stress-dependent parameters is analyzed through one-dimensional Monte Carlo numerical simulations of nonlinear groundwater flow and consolidation. The natural logarithm of hydraulic conductivity (Y) and compression index (Cc) are considered spatially cross-correlated random variables. A stochastic simulation method based on a bivariate normal copula was applied to generate positive, negative, and uncorrelated realizations of the two random variables. The results show that when Y and Cc are correlated random parameters, the ensemble average total settlement is consistently larger (between 13% and 40% for the synthetic cases tested) than the total settlement obtained when the parameters are deterministic (perfectly known). In addition, the results of negative and no correlation between Y and Cc are similar in terms of the ensemble average and variance of total settlement, while positive correlation leads to larger values of total settlement and its variance. The stochastic approach employed here allows incorporating the uncertainty in the parameters in the simulation of the subsidence process, which is relevant for geotechnical engineering, design of structures and groundwater management.

ПРОУЧВАНЕ НА ФАМИЛНАТА МОТИВАЦИЯ ЗА УЧИЛИЩНО ОБУЧЕНИЕ

Preparation for school is a form of implementation of the principle of continuity in the educational system and a meaningful process for the implementation of the current tasks of child development. Its result expression is the readiness for school education, which is a set of personal qualities, knowledge, skills and ways of acting, necessary for the educational process at school and for the new social position of the student. The priorities in children’s readiness for school education are related to a determining degree with the preschool education system and the family as the main factors for its positive realization. The mission of the family constellation as a socializing factor and educational subject is reflected in the „Law on Preschool and School Education“, where parents are defined as participants in the educational process who have rights and obligations in the context of stimulating educational achievements and positive personal development of children. Therefore, the study of the vision of family motivation for schooling is of topical importance, because it forms to a determining degree the attitude of preschool children towards the educational system. The subject of presentation and analysis are the orientations of parents with children of preschool age towards the phenomena of „readiness“ and „preparation“ for school as representations of the relevance of education, children’s motivation for school and student’s motivation.

A new method for computation of positive realizations of fractional linear continuous-time systems

A new method for computation of positive realizations of fractional linear continuous-time systems

International Education and the Crises of Cosmopolitanism and Global Citizenship

Globalisation has not only given rise to unprecedented dimensions of mobility of people and ideas across national borders, but it has also enhanced the activities involved in international education (IE) and inevitably drawn attention to the growing levels of cultural diversity and the necessity for cultural exchange among the ‘global communities’. Arguably, these phenomena have equally given rise to the possibilities of both cultural exchange and conflicts of interest in what constitutes an effective IE. Besides, recent phenomenal development in digital technologies has enabled people across vast far afield to be in close relations with one another; thus, opening new vistas to an effectively transnational world that could be aptly regarded as a global village. Parts of the fundamental concepts of IE which have agitated the minds of several international scholars are cosmopolitanism and global citizenship (GC). As part of the tenets of GC and cosmopolitanism, it is expected that people are treated equally and that preference should not be given to any particular cultural, political, linguistic, or national group, most especially at the expense of others. Meanwhile, there are scholarly arguments that global education has a fundamental role to play in preparing students for a world that is increasingly interconnected and interdependent. Several advocacies in the light of cosmopolitanism and GC in the context of IE have been principally brought to the fore by several scholars not only as moral frameworks resonant with educators’ efforts to cultivate people’s openness to new ideas but also as a mutual understanding through respectful dialogue, as well as the awareness of the peculiarities within the cultural values of the others. Meanwhile, there have been stridently diverse arguments from several scholars that the contemporary global practices in IE do not reflect the tenets as well as _modus operandi_ as espoused by the concepts of cosmopolitanism and or GC. It was equally argued that there exist varying levels of disequilibria in the contemporary IE, and this has made the cultural realities inherent in the ‘others’ to be disparagingly relegated. Imperatively, in recent times, there have been several calls from scholars advocating the critical incorporation of cosmopolitan dynamics and realities in approaches to IE (to reflect some of the basic hallmarks and or tenets of GC). Although the positive realisation of these attempts or calls is still at the developing stage in educational practices, recent works in other disciplines promise to forward such a critical agenda. It is, therefore, against this background that both the extant and current literature is critically and scholarly engaged to interrogate the concepts of cosmopolitanism and GC in the context of IE. At the same time, the treatise is principally divided into four (4) sections which include: conceptual clarifications of the terms: international education (IE), global citizenship, and cosmopolitanism; a critical analysis of Western, Asian (Chinese) and African perspectives on cosmopolitanism and global citizenship as well as crises of global citizenship and cosmopolitanism in the light of IE. However, the paper gives a conclusion and puts forth recommendations.

Leader-Based Consensus in Directed Networks of Homogeneous Positive Agents With Multiple Inputs

Abstract In this paper, the non-zero finite positive state consensus problem of leader-following multi-agent systems (MASs) connected over a directed network is investigated. The multi-agent network consists of homogeneous linear time-invariant (LTI) positive agents whose minimal positive state-space realization is assumed to be known. In this paper, a state-feedback hierarchical control protocol is proposed where the local controller synthesizes a singular, Lyapunov stable, and Metzler system matrix with a simple dominant eigenvalue at origin. The obtained consensus vector is the positive eigenvector associated with the zero eigenvalue of the synthesized system matrix. The controller gain matrices are obtained by solving a set of necessary and sufficient conditions derived in linear programing framework. A numerical example is given to elucidate the usefulness of the proposed results.

Minimal positive realizations for linear systems with two-different-pole transfer functions

The minimal positive realization problem for linear systems is to find positive systems with a state space of minimal dimensions while keeping their transfer functions unchanged. Here the necessary and sufficient condition is established for the linear systems with third-order two-different-pole transfer functions to have a three-dimensional minimal positive realization by developing a new approach. The approach is to identify a canonical form of positive realizations with the help of polyhedral cone theory, and the identification consists of a sequential edge transformations with some invariant feature. The analyses are then successfully extended to the linear systems with general nth-order two-different-pole transfer functions. At the same time, the approach can also be used to generate infinitely many distinct minimal positive realizations for some linear systems.

Internally Hankel $k$-Positive Systems

There has been an increased interest in the variation diminishing properties of controlled linear time-invariant (LTI) systems and time-varying linear systems without inputs. In controlled LTI systems, these properties have recently been studied from the external perspective of $k$-positive Hankel operators. Such systems have Hankel operators that diminish the number of sign changes (the variation) from past input to future output if the input variation is at most $k-1$. For $k=1$, this coincides with the classical class of externally positive systems. For linear systems without inputs, the focus has been on the internal perspective of $k$-positive state-transition matrices, which diminish the variation of the initial system state. In the LTI case and for $k=1$, this corresponds to the classical class of (unforced) positive systems. This paper bridges the gap between the internal and external perspectives of $k$-positivity by analyzing internally Hankel $k$-positive systems, which we define as state-space LTI systems where controllability and observability operators as well as the state-transition matrix are $k$-positive. We show that the existing notions of external Hankel and internal $k$-positivity are subsumed under internal Hankel $k$-positivity, and we derive tractable conditions for verifying this property in the form of internal positivity of the first $k$ compound systems. As such, this class provides new means to verify external Hankel $k$-positivity, and lays the foundation for future investigations of variation diminishing controlled linear systems. As an application, we use our framework to derive new bounds for the number of over- and undershoots in the step responses of LTI systems. Since our characterization defines a new positive realization problem, we also discuss geometric conditions for the existence of minimal internally Hankel $k$-positive realizations.

Minimal positive realizations: A survey

This survey aims to present a comprehensive and systematic synthesis of concepts and results on the minimal state space realization problem for positive, linear, time-invariant systems. Positive systems are systems for which the state and the output are always non-negative for any non-negative initial state and input. They are used to model phenomena in which the variables must take non-negative values due to the nature of the underlying physical system. Restricting the state–space realization to positive systems makes the problem extremely different and much more difficult than that for ordinary systems. Indeed, a minimal positive realization may have a dimension even much greater than the order of the transfer function it realizes. Although the problem of finding a finite-dimensional positive state–space realization of a given transfer function has been solved, the characterization of minimality for positive systems is still an open problem. This survey introduces the reader to different aspects of the problem and presents the mathematical approaches used to tackle it as well as some relevant related problems. Moreover, some partial results are presented. Finally, a comprehensive bibliography on positive systems, organized by topics, is provided.

Positive consensus of multi-agent systems with hierarchical control protocol

In this paper, the positive state consensus problem of a network of homogeneous LTI positive agents is presented. A hierarchical control protocol is applied to achieve finite positive state consensus over directed networks. The minimal state-space realization considered for the interconnected positive agents is not restricted to be (internally) positive state-space realization, which is in contrast to the existing literature. A set of sufficient conditions is derived in linear programming framework which is solved to find controller gain matrices involved in the consensus protocol. Also, in this paper, an observer-based hierarchical control protocol has been derived to achieve finite positive state consensus. Numerical examples are given to demonstrate the usefulness of the proposed results.

Cadeias de Markov em estratégia de negociação de ações em alta frequência

The price prediction problem for any given stock has been an object of study, deepening and evolution within the past few decades, to achieve the basic goal of positive financial realizations with the smaller risk possible. A known risk minimization strategy is a high frequency trading regime, taking benefit from minor price variations, and achieving small profits multiple times a day. By the hypothesis and the interpretation that prices variations behavior as a Random Walk, it is possible to characterize a Markov (stochastic) process with states and transition probabilities known, allowing to describe price variations through time. Therefore, this study aims to estimate the financial outcome using Markov chains for automated decision making in a high frequency trading strategy, and then comparing the computed results with stock’s valuation (or devaluation) within the same analyzed period.

Reiki - nova paradigma postojanja

Reiki represents a self-help technique that explains how we can balance our own inner energy in relation to the outer energy of the universe around us, because it is the basis of peace and tranquility that bring positive realization to life. Reiki is a natural self-help technique where a person helps himself using his own energy and the energy that surrounds him. This phenomenon has been understood and accepted since time immemorial by man in all traditions and cultures where man has dealt with his personal healing, philosophy of life and his own place in nature. When Reiki originated cannot be claimed with certainty. The first traces of this technique are recorded in ancient Lotus Sutras written more than 5,000 years ago. After centuries of oblivion, the first to restore this philosophy was a Japanese, Mikao Usui. This high-frequency phenomenon was ascertained in the nineteenth century in Japan.

A new method for computation of positive realizations of linear discrete-time systems

A new method for computation of positive realizations of given transfer matrices of linear discrete-time linear systems is proposed. Sufficient conditions for the existence of positive realizations of transfer matrices are given. A procedure for computation of the positive realizations is proposed and illustrated by an example.

Definition of the concept of “patriotism” in the historical, cultural and educational space of the city

There are five natural beginnings of life created by the hand of God: personality; family; nation (homeland), the kingdom of heaven and the church. In this article, we will try to consider only one aspect of responsibility of a man associated with the formation of national identity. Today, patriotism becomes the idea that can turn from an intangible force into a material one if it is mastered by the people and for many it will become an internal conviction and installation. Today, patriotism has become one of the most controversial topics in Russia. The range of opinions is quite large: from discrediting patriotism as an analogue of destruction and conflict, to calls of the first persons of the state to the unity of the Russian people on the basis of the integration of patriotism with internationalism. Patriotism helps to unite society, reveals to many people the meaning of their own life, raises their understanding and responsibility for the framework of corporatism and social class differences. Patriotism is increasingly recognized by the population as the protection of national interests, the implementation of social justice, as a positive and constructive realization of human rights. It becomes the main task in the programs of patriotic education of the young people. It acts both as an element of worldview and attitude to one’s country, and other peoples and as an educational component of pedagogic system especially in the historical, cultural and educational space of the city.

On Second-Order Cone Positive Systems

Internal positivity offers a computationally cheap certificate for external (input-output) positivity of a linear time-invariant system. However, the drawback with this certificate lies in its realization dependency. Firstly, computing such a realization requires to find a polyhedral cone with a potentially high number of extremal generators that lifts the dimension of the state-space representation, significantly. Secondly, not all externally positive systems posses an internally positive realization. Thirdly, in many typical applications such as controller design, system identification and model order reduction, internal positivity is not preserved. To overcome these drawbacks, we present a tractable sufficient certificate of external positivity based on second-order cones. This certificate does not require any special state-space realization: if it succeeds with a possibly non-minimal realization, then it will do so with any minimal realization. While there exist systems where this certificate is also necessary, we also demonstrate how to construct systems, where both second-order and polyhedral cones as well as other certificates fail. Nonetheless, in contrast to other realization independent certificates, the present one appears to be favourable in terms of applicability and conservatism. Three applications are representatively discussed to underline its potential. We show how the certificate can be used to find externally positive approximations of nearly externally positive systems and demonstrated that this may help to reduce system identification errors. The same algorithm is used then to design state-feedback controllers that provide closed-loop external positivity, a common approach to avoid over- and undershooting of the step response. Lastly, we present modifications to generalized balanced truncation such that external positivity is preserved where our certificate applies.

An upper bound on the dimension of minimal positive realizations for discrete time systems

Abstract In some applications one is interested in having a state–space realization with nonnegative matrices (positive realization) of a given transfer function and it is known that such a realization may have a dimension strictly larger than the order of the transfer function itself. Moreover, in most cases, it is desirable to have a realization with minimal dimension. Unfortunately, it is not known, to date, how to determine in general the minimum dimension of a positive realization and only lower and upper bounds to it are available. This letter provides an upper bound on the dimension of a minimal positive realization for transfer functions with simple poles. This is a considerable improvement on an earlier upper bound in which only transfer functions with real poles were considered.

The NIEP and the positive realization problem

The nonnegative inverse eigenvalue problem is the problem of determining necessary and sufficient conditions for a multiset of complex numbers to be the spectrum of a nonnegative real matrix of size equal to the cardinality of the multiset itself. The problem is longstanding and proved to be very difficult so that several variations have been defined by considering particular classes of multisets and nonnegative real matrices. In this paper, a novel variation of the problem is proposed. This variation is motivated by a practical application in the positive realization problem, that is the problem of characterizing existence and minimality of a positive state--space representation of a given transfer function.

Nanoparticles induce autophagy via mTOR pathway inhibition and reactive oxygen species generation.

Due to their unique physicochemical properties, nanoparticles (NPs) have been increasingly developed for use in various fields. However, there has been both growing negative concerns with toxicity and positive realization of opportunities in nanomedicine, coming from the growing understanding of the associations between NPs and the human body, particularly relating to their cellular autophagic effects. This review summarizes NP-induced autophagy via the modulation of the mTOR signaling pathway and other associated signals including AMPKand ERKand also demonstrates how reactive oxygen species generation greatly underlies the regulation processes. The perspectives in this review aim to contribute to NP design, particularly in consideration of nanotoxicity and the potential for the precise application of NPs in nanomedicine.

The traditional Yorùbá conception of a meaningful life

This article examines the question of the meaningfulness of life in traditional African thought with a focus on the Yorùbá. It discovers that the dominant Yorùbá conception of a meaningful life among the Yorùbá is the manifestation of some relational valuable ends: material comfort symbolised with monetary possession; a long healthy life; children; a peaceful spouse; and victory over life’s vicissitudes. The Yorùbá account considers a positive realisation of the quintuple ends as sufficient conditions of a meaningful life worth pursuing by an individual. This article argues that the Yorùbá conception of life’s meaningfulness is neither supernaturalistic nor nihilistic in motivation and orientation. Rather, it is holistic, and rationally and relationally embedded in ways that reveal the communal structure of traditional Yorùbá society. This article critically exposes the problems and limitations of such an account with some suggestions for future research in the African philosophy of life.

A direct method to obtain a realization of a polynomial matrix and its applications

In this paper we present a Silverman-Ho algorithm-based method to obtain a realization of a polynomial matrix. This method provides the final formulation of a minimal realization directly from a full rank factorization of a specific given matrix. Also, some classical problems in control theory such as model reduction in singular systems or the positive realization problem in standard systems are solved with this method.

Positive Real Properties and Physical Realizability Conditions For a Class of Linear Quantum Systems

Theoretical developments in the field of quantum optics and quantum superconducting electrical circuits involving continuous measurement based feedback control as well as coherent control are an important prerequisites for advances in the domain of quantum technology. Within these perspectives, this paper considers positive real properties for a class of quantum systems whose quantum stochastic differential equation model involves annihilation operators only and then relates them to corresponding bounded real properties and consequently to physical realizability conditions developed earlier by the authors. Based on the positive real properties of these quantum systems, it is anticipated that it is possible to use the Brune algorithm in order to find an electrical circuit that can physically implement these quantum systems. This theory, in the case of one-port circuits, may be useful for the implementation of microwave circuits related to quantum filters found in the field of quantum computing.