scholarly journals ANALYSIS OF AN ANTI-PARALLEL MEMRISTOR CIRCUIT

Author(s):  
Valeri Mladenov ◽  
Stoyan Kirilov

The basic purpose of the present paper is to propose an extended investigation and computer analysis of an anti-parallel memristor circuit with two equivalent memristor elements with different initial values of the state variables using a modified Boundary Condition Memristor (BCM) Model and the finite differences method. The memristor circuit is investigated for sinusoidal supply current at different magnitudes – for soft-switching and hard-switching modes, respectively. The influence of the initial values of the state variables on the circuit’s behaviour is presented as well. The equivalent i-v and memristance-flux and the other important relationshipsof the memristor circuit are also analyzed.

Author(s):  
Mohamed Arbi Khlifi ◽  
Habib Rehaoulia

Purpose – When magnetic saturation in ac machines is evolved, the theory of main flux saturation in d-q axes remains the best. Because of its simplicity, it is the most used in either motoring or generating mode for synchronous or asynchronous machines. Although, it is considered as a global way of introducing the iron saturation, compared to other methods, today, its fidelity has no contest in predicting complex ac machine operations. For this purpose, the aims of this paper consists of modeling these machines whatever the state-space variables values are taking into account the magnetic saturation. Two unified procedures are proposed. The first one deals with a common approach to establishing a complete and detailed model synthesis in d-q axes. The second also presents a unified approach to introducing magnetic saturation of the iron core in the characteristic equations. The analysis takes the salient pole synchronous machine as a general case of study. Then the approaches are extended to undamped and smooth air gap synchronous machines as well as induction machines. The paper aims to discuss these issues. Design/methodology/approach – The present paper, which is a first part of a work under study dealing with a unified method to derive multiple models of saturated ac machines, is intended to the description of an alternative method and its application for induction and synchronous machines. It mainly consists of the following parts: first, after writing the stator and rotor space vector d-q equations, the number of possible models is immediately discussed. By considering the currents and fluxes as state-space variables, 14 models are obtained for AC induction machine (IM and SM). They are classified into three families, current (three), flux (three) and mixed models (eight). Second, in order to easily introduce the magnetic saturation in the 14 developed models, a method is presented. It consists of just elaborating the model with the winding currents as state variables, then deriving all the other models from it. Third, to emphasize the influence of the presence of magnetic saturation, in each model, each inductance along the d and q axes is written with a fundamental expression which exists with or without saturation and an additional one due purely to saturation. Hence the additional terms can be studied and quantified in an easy way or simply removed when linear case is assumed. Fourth, adopting such strategy to write the different coefficients of the models had led to the definition of common saturation factors. In turn, the definition of common saturation factors had allowed the definition of different groups of models within each family. Fifth, an alternative to evaluate the static and dynamic saturation coefficients is also proposed. It is shown that by proper fitting of the experimental magnetizing curve, all saturation coefficients can be written only in terms of which is simply the magnitudes ratio of the magnetizing flux and current. Sixth, although the theory of the main flux saturation is now admitted, an investigation was carried out on a self-excited induction generator and the build-up of voltage and current phases of a standalone alternator, to prove the equivalence between the all developed models. Findings – The number of models based on the state-space variables choice, of a saturated ac machine, is reviewed. A simple method consisting of elaborating just the winding currents model, with magnetic saturation and deriving all the other models from it, is presented. In this study special interest was particularly focussed on either novel models or existing models cited in the literature but cannot be obtained by other approaches. In all cases, if the differential equations of the machine are formulated in terms of a set of variables other than the winding currents, a noticeable reduction in the size of equations may be obtained and consequently less time computing. The approach seems to be able to derive any possible model whatever the state-space variables and the type of the ac machine and hence can be classified as a general approach. Practical implications – The experiments of synchronous and induction machine transients prove the validity of the method. Originality/value – By suitable choice of state-space characteristic vectors among the fluxes and the currents, a synthesis of AC machine models in d-q axes is established. To introduce magnetic saturation in each model, an approach-based uniquely on the elaboration of the winding currents model is exposed and applied. In addition, the analysis gives a detailed classification of all found models taking into account the state variables nature as well as the cross-coupling coefficient considered as a saturation factor. The study is completed with a simple alternative to evaluate all saturation factors by just calculating the static magnetizing inductance.


Symmetry ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 513
Author(s):  
Alejandro Rincón ◽  
Gloria Yaneth Florez ◽  
Gerard Olivar

In several open and closed-loop systems, the trajectories converge to a region instead of an equilibrium point. Identifying the convergence region and proving the asymptotic convergence upon arbitrarily large initial values of the state variables are regarded as important issues. In this work, the convergence of the trajectories of a biological process is determined and proved via truncated functions and Barbalat’s Lemma, while a simple and systematic procedure is provided. The state variables of the process asymptotically converge to a compact set instead of an equilibrium point, with asymmetrical bounds of the compact sets. This convergence is rigorously proved by using asymmetric forms with vertex truncation for each state variable and the Barbalat’s lemma. This includes the definition of the truncated V i functions and the arrangement of its time derivative in terms of truncated functions. The proposed truncated function is different from the common one as it accounts for the model nonlinearities and the asymmetry of the vanishment region. The convergence analysis is valid for arbitrarily large initial values of the state variables, and arbitrarily large size of the convergence regions. The positive invariant nature of the convergence regions is proved. Simulations confirm the findings.


2016 ◽  
Vol 6 (2) ◽  
pp. 118-135
Author(s):  
Lucia Della Torre

Not very long ago, scholars saw it fit to name a new and quite widespread phenomenon they had observed developing over the years as the “judicialization” of politics, meaning by it the expanding control of the judiciary at the expenses of the other powers of the State. Things seem yet to have begun to change, especially in Migration Law. Generally quite a marginal branch of the State's corpus iuris, this latter has already lent itself to different forms of experimentations which then, spilling over into other legislative disciplines, end up by becoming the new general rule. The new interaction between the judiciary and the executive in this specific field as it is unfolding in such countries as the UK and Switzerland may prove to be yet another example of these dynamics.


2019 ◽  
Vol 34 (2) ◽  
Author(s):  
Sipho Stephen Nkosi

The note is about the appeal lodged by the late Mrs Winnie Madikizela-Mandela to the SCA against the decision of the Eastern Cape High Court, Mthatha, dismissing her application for review in 2014. In that application, she sought to have reviewed the decision of the Minister of Land Affairs, to transfer the now extended and renovated Qunu property to Mr Mandela and to register it in his name. Because her application was out of time, she also applied for condonation of her delay in making the application. The court a quo dismissed both applications with costs, holding that there had been an undue delay on her part. Mrs Mandela then approached the Supreme Court of Appeal, for special leave to appeal the decision of the court a quo. Two questions fell for decision by the SCA: whether there was an unreasonable and undue delay on Mrs Mandela’s part in instituting review proceedings; and whether the order for costs was appropriate in the circumstances of the case. The SCA held that there was indeed an unreasonable delay (of seventeen years). Shongwe AP (with Swain, Mathopo JJA, Mokgothloa and Rodgers AJJA concurring) held that the fact that there had been an undue delay does not necessarily mean that an order for costs should, of necessity, particularly where, as in this case, the other litigant is the state. It is the writer’s view that two other ancillary points needed to be raised by counsel and pronounced on by the Court: (a) the lawfulness and regularity of the transfer of the Qunu property to Mr Mandela; and (b) Mrs Mandela’s status as a customary-law widow—in relation to Mr Mandela.


2017 ◽  
Vol 1 (1) ◽  
pp. 90
Author(s):  
Dian Septiandani ◽  
Abd. Shomad

Zakat is one of principal worship requiring every individual (<em>mukallaf</em>) with considerable property to spend some of the wealth for zakat under several conditions applied within. On the other hand, tax is an obligation assigned to taxpayers and should be deposited into the state based on policies applied, with no direct return as reward, for financing the national general expense. In their development, both zakat and tax had quite attention from Islamic economic thought. Nevertheless, we, at first, wanted to identify the principles of zakat and tax at the time of Rasulullah SAW. Therefore, this study referred to normative research. The primary data was collected through library/document research and the secondary one was collected through literature review by inventorying and collecting textbooks and other documents related to the studied issue.


Author(s):  
Anatolii Petrovich Mykolaiets

It is noted that from the standpoint of sociology, “management — a function of organized systems of various nature — (technical, biological, social), which ensures the preservation of their structure, maintaining a certain state or transfer to another state, in accordance with the objective laws of the existence of this system, which implemented by a program or deliberately set aside”. Management is carried out through the influence of one subsystem-controlling, on the other-controlled, on the processes taking place in it with the help of information signals or administrative actions. It is proved that self-government allows all members of society or a separate association to fully express their will and interests, overcome alienation, effectively combat bureaucracy, and promote public self-realization of the individual. At the same time, wide direct participation in the management of insufficiently competent participants who are not responsible for their decisions, contradicts the social division of labor, reduces the effectiveness of management, complicates the rationalization of production. This can lead to the dominance of short-term interests over promising interests. Therefore, it is always important for society to find the optimal measure of a combination of self-management and professional management. It is determined that social representation acts, on the one hand, as the most important intermediary between the state and the population, the protection of social interests in a politically heterogeneous environment. On the other hand, it ensures the operation of a mechanism for correcting the political system, which makes it possible to correct previously adopted decisions in a legitimate way, without resorting to violence. It is proved that the system of social representation influences the most important political relations, promotes social integration, that is, the inclusion of various social groups and public associations in the political system. It is proposed to use the term “self-government” in relation to several levels of people’s association: the whole community — public self-government or self-government of the people, to individual regions or communities — local, to production management — production self-government. Traditionally, self-government is seen as an alternative to public administration. Ideology and practice of selfgovernment originate from the primitive, communal-tribal democracy. It is established that, in practice, centralization has become a “natural form of government”. In its pure form, centralization does not recognize the autonomy of places and even local life. It is characteristic of authoritarian regimes, but it is also widely used by democratic regimes, where they believe that political freedoms should be fixed only at the national level. It is determined that since the state has achieved certain sizes, it is impossible to abandon the admission of the existence of local authorities. Thus, deconcentration appears as one of the forms of centralization and as a cure for the excesses of the latter. Deconcentration assumes the presence of local bodies, which depend on the government functionally and in the order of subordination of their officials. The dependency of officials means that the leadership of local authorities is appointed by the central government and may be displaced.


2016 ◽  
Vol 1 (1) ◽  
Author(s):  
D.G. Shah ◽  
D.N. Mehta ◽  
R.V. Gujar

Bryophytes are the second largest group of land plants and are also known as the amphibians of the plant kingdom. 67 species of bryophytes have been reported from select locations across the state of Gujrat. The status of family fissidentaceae which is a large moss family is being presented in this paper. Globally the family consists of 10 genera but only one genus, Fissidens Hedw. has been collected from Gujarat. Fissidens is characterized by a unique leaf structure and shows the presence of three distinct lamina, the dorsal, the ventral and the vaginant lamina. A total of 8 species of Fissidens have been reported from the state based on vegetative characters as no sporophyte stages were collected earlier. Species reported from the neighboring states also showed the absence of sporophytes. The identification of different species was difficult due to substantial overlap in vegetative characters. Hence a detailed study on the diversity of members of Fissidentaceae in Gujarat was carried out between November 2013 and February 2015. In present study 8 distinct species of Fissidens have been collected from different parts of the state. Three species Fissidens splachnobryoides Broth., Fissidens zollingerii Mont. and Fissidens curvato-involutus Dixon. have been identified while the other five are still to be identified. Fissidens zollingerii Mont. and Fissidens xiphoides M. Fleisch., which have been reported as distinct species are actually synonyms according to TROPICOS database. The presence of sexual reproductive structures and sporophytes for several Fissidens species are also being reported for the first time from the state.


2015 ◽  
Vol 4 (3) ◽  
Author(s):  
Vinay Chauhan ◽  
Sushma Kaushal

Environmental scanning yields greater anticipatory management that provides important inputs for aquitision and use of information for planning and designing organization strategies. Apart from this, effective environmental scanning activities are likely to deal with threats and grasp the opportunities to finally link with enhancing organizational effectiveness. In fact this relationship matrix has led the researchers to conduct an environmental scanning through an examination of the existing status the components of the macro-environment vis-a-vis their relationship with the organizational effectiveness. There are a number of approaches, which describe the macro-environment, of which PEST analysis is regarded as the most common approach for considering the external business environment. Thus, the present study applies PEST analysis to scan the existing business environment. Jammu and Kashmir due to its peculiar political, geographical, economic, and socio-cultural features, had led its cost mountain economy become a distinctive identity. Despite the fact that the state has rich endowments, international relations with its neighbours vis-a-vis its impact on political environment also pose developmental challenges for the business units operating in the state. This has provided valid rationale for conducting the present. The environmental scanning is done through the perception of the select entrepreneurs operating MSMEs in the state of J & K. An impact analysis of environmental factors (PEST) on the organizational effectiveness is also done in the study. The findings of the study show that the political environment of the state that is not favourable for entrepreneural development whereas the rest of the other drivers of PEST i.e. economic environment, socio-cultural environment, and technological environment show a favourable response of the entrepreneurs. In terms of cause and effect relationship, it is found that the first two drivers of the PEST i.e. political and economic dimension impacts OE positively whereas the other two dimensions namely socio-cultural and technological impacts OE negatively but it is pertinent to mention that the impact is very less and is insigninificant. The study also suggests some of strategic options for developing and creating an enabling environment for successful entrepreneurial development to achieve integrated development of the state.


Author(s):  
Clive Holes

The vocabulary of the modern Gulf Arabic dialects contains many items of ancient Mesopotamian origin; there is also evidence of early south Arabian influences. Historically, three dialect types existed in the region: Najdi, coastal (these two are ‘A dialects’), and Baḥārna (‘B’ dialects). There must long have been contact between these three, but the main interface was between the Najdi and the coastal type. The (Shīˁī) Baḥārna lived in separate settlements, pursued livelihoods specific to them, and did not marry with the other two groups. All of this preserved their dialect. This sociolinguistic division was most evident in the state of Bahrain. In recent decades, changes in employment and increased urbanization have brought about increased interdialectal contact, resulting in the loss of B dialect features and a homogenization of the A dialects to the point that one can now speak of the emergence of a Gulf koine.


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