Control of the Modified Chaotic Chua’s Circuit Using Threshold Method

В роботi представлена модифiкована хаотична схема Чуа, яка реалiзує хаотичну поведiнку. Приведена система диференцiйних рiвнянь, що описує дану схему при певних значеннях системних параметрiв та початкових умов, генерує хаотичний атрактор. Ця схема має простий нелiнiйний елемент, спроектований так, щоб мати кусково-лiнiйну характеристику, тобто комбiнацiю операцiйного пiдсилювача з двома дiодами, що ввiмкненi назустрiч один одному. Для реалiзацiї нелiнiйностi, для двох дiодiв не потрiбно окремого джерела живлення, достатньо лише одного двополярного живлення для операцiйного пiдсилювача. Приведено схему для дослiдження нелiнiйного елементу та результати комп’ютерного моделювання, тобто вольт-амперну характеристику (ВАХ) при певних значеннях номiналiв компонентiв схеми. Ця модифiкована схема Чуа, яка генерує хаотичний та контрольований атрактор з фiксованим перiодом, може використовуватися в сучасних системах передавання та приймання iнформацiї. Управлiння хаотичними коливаннями є досить важливим процесом в радiотехнiцi та телекомунiкацiях. Число видiлених окремих перiодичних (контрольованих) атракторiв може використовуватися як ключi для маскування iнформацiйного носiя. За допомогою програмного середовища MultiSim проведено схемотехнiчний аналiз i представлено результати моделювання нелiнiйного елемента та модифiкованої хаотичної схеми Чуа. Дослiджена поведiнка системи за допомогою чисельного моделювання, використовуючи вiдомi iнструменти нелiнiйної теорiї, такi як хаотичний атрактор i часовi розподiли хаотичних координат. Приведено опис порогового методу для здiйснення управлiння хаотичними коливаннями та представлено результати практичного застосування даного методу до модифiкованої хаотичної схеми Чуа. Практичними результатами є видiленi 2- та 3-перiоднi контрольованi орбiти iз хаотичного атрактора.Introduction. General scientific fields where can be used circuits that realize chaotic behavior and generate chaotic oscillations are presented.Methods for control of chaotic oscillations are also presented. For modelling, analysis and demonstrate results was selected MultiSim software environment. Modelling and Analysis of Non-Linear Element. This modified Chua’s circuit has a simple non-linear element, designed to have a piecewise-linear characteristic, that is, a combination of an opamp with two diodes that are mutually inline. For realization of nonlinearity, for two diodes do not need a separate power source, only one bipolar power source for the opamp is enough. The scheme for modelling of the nonlinear element and the results of computer simulation, i.e. the volt-ampere characteristic (VAC) at certain values of the components of the scheme’s nominal values, is presented. This modified Chua’s circuit, which generates a chaotic and controlled attractor with a fixed period, can be used in modern transmission and reception systems of information. Modeling and Analysis of the Modified Chaotic Chua’s Generator. System’s behavior is investigated through numerical simulations, by using well known tools of nonlinear theory, such as chaotic attractor and time distributions of the chaotic coordinates. Threshold Method for Control of Chaotic Oscillations. System of equations that realize chaotic oscillations of Chua’s circuit is presented. Using threshold method was practical realization of the control of chaotic attractor. This modified Chua’scircuit that generate a chaotic and controlled attractor with a fixed period can be used in modern systemstransmitting and receiving information. Number of periodic (controlled) attractor can be used as a keys formasking of information carrier. Conclusions. For the first time was used threshold method forcontrol of chaotic oscillations for modified Chua’schaotic generator. This modified Chua’s circuit thatgenerate a chaotic and controlled attractor with afixed period can be used in modern systems transmittingand receiving information. Number of periodic(controlled) attractor can be used as a keys for maskingof information carrier.В работе представлена модифицированная хаотичная схема Чуа, которая реализует хаотическое поведение. Эта схема имеет простой нелинейный элемент, спроектированный так, чтобы иметь кусочно-линейную характеристику. Эта модифицированная схема Чуа, которая генерирует хаотический и контролируемый аттрактор с фиксированным периодом, может использоваться в современных системах передачи и получения информации. Количество периодических (контролируемых) аттракторов может использоваться как ключи для маскировки информационного носителя. С помощью программной среды MultiSim проведен схемотехнический анализ и представлены результаты моделирования нелинейного элемента и модифицированной хаотической схемы Чуа. Исследовано поведение системы с помощью численного моделирования, используя известные инструменты нелинейной теории, такие как хаотичный аттрактор и временные распределения хаотических координат. Приведено описание порогового метода для осуществления управления хаотическими колебаниями и представлены результаты практического применения данного метода к модифицированной хаотической схеме Чуа. Практическими результатами являются выделенные 2- и 3-периодные контролируемые орбиты с хаотического аттрактора

Climate adaptation for airports by climate change risk indicators (CCRI)

The study is to develop a Climate Change Risk Indicator (CCRI) framework for airport adaptation to climate change. This paper firstly describes the results of a literature review of the studies by international and professional bodies on climate change adaptation for transportation systems, with a focus on the aviation sector. Secondly, a Fuzzy Evidential Reasoning (FER) method is employed to develop a new CCRI framework to evaluate the climate risks of airports. Finally, six airports in the United Kingdom (UK) are selected as the real cases to demonstrate the feasibility of using the proposed CCRI framework

Climate change adaptation for seaports by Climate Change Risk Indicators (CCRI)

The study is to provide a Climate Change Risk Indicators (CCRI) framework for climate adaptation for seaports, to link research to policy-making process on such a demanding topic. This paper first provides a literature review with international bodies and technical bodies on climate change adaptation for seaports. Second, a Fuzzy Evidential Reasoning (FER) model is employed to evaluate the climate risks in seaports. Third, six seaports in United Kingdom (UK) are selected for examples to demonstrate the use of CCRI. Finally, a comparative analysis of Yangtze River Delta and the United Kingdom (UK) in climates and seaport industries is done to visualize the possibilities in implementing the frameworks

Review on Seaport and Airport Adaptation to Climate Change: A Case on Sea Level Rise and Flooding

Seaports and airports are the critical nodes of international supply chains and thus stand on the edge of social and economic disasters. They are often affected by extreme and rough weather. Comparing all climate threats, sea level rise (SLR) and storming and flooding currently present, according to the relevant literature, the most severe impact in ports and airports. This paper aims to provide a comprehensive review of seaport and airport adaptation to climate change with a focus on SLR and flooding. We have summarized all related research papers and divided them into different types and described the trend of studies. After that, the study involves a comparison to analyze the synergy between previous studies in seaports and airports and provides insights for further studies to emphasize the needs and opportunities for the collaborative work that can complement the adaptation planning of and ensure the resilience of seaports and airports

Concentric double hollow grid cathode discharges

A new cathode system, consisting of two concentric spherical hollow grids with two aligned orifices, is investigated by space-resolved Langmuir probe measurements and non-linear dynamics analysis. Negative biases of this spherical hollow grids arrangement lead to the formation of two complex space charge structures in the regions of the orifices. The overall dynamics of the current-voltage characteristic (I–V characteristic) of each discharge is characterized by strong oscillatory behaviour with various waveforms correlated with jumps in the static I–V characteristics. Space-resolved measurements through the two aligned orifices of the two grids show a peak increase of the electron temperature and particle density in the regions of the two space-charge structures. The effects of the biases and Ar pressure on the overall spatial distribution of all plasma parameters are investigated. Two important working points of the concentric double hollow grid cathode discharges are revealed which could make this configuration suitable as an electron source

Impact analysis of climate change on rail systems for adaptation planning: A UK case

Climate change poses critical challenges for rail infrastructure and operations. However, the systematic analysis of climate risks and the associated costs of tackling them, particularly from a quantitative perspective, is still at an embryonic phase due to the kaleidoscopic nature of climate change impacts and lack of precise climatic data. To cope with such challenges, an advanced Fuzzy Bayesian Reasoning (FBR) model is applied in this paper to understand climate threats of the railway system. This model ranks climate risks under high uncertainty in data and comprehensively evaluates these risks by taking account of infrastructure resilience and specific aspects of severity of consequence. Through conducting a nationwide survey on the British railway system, it dissects the status quo of primary climate risks. The survey implies that the top potential climate threats are heavy precipitation and floods. The primary risks caused by the climate threats are bridges collapsing and bridge foundation damage due to flooding and landslips. The findings can aid transport planners to prioritise climate risks and develop rational adaptation measures and strategies

Prioritizing Vehicle Cleanliness (PVC) using Key Green Performance Indicators (KGPI)

Climate catastrophes (e.g. hurricane, flooding and heat waves) are generating increasing impact on port operations and hence configuration of shipping networks. This paper formulates the routing problem to optimise the resilience of shipping networks, by taking into account the disruptions due to climate risks to port operations. It first describes a literature review with the emphasis on environmental sustainability, port disruptions due to climate extremes and routing optimisation in shipping operations. Second, a centrality assessment of port cities by a novel multi-centrality-based indicator is implemented. Third, a climate resilience model is developed by incorporating the port disruption days by climate risks into shipping route optimisation. Its main contribution is constructing a novel methodology to connect climate risk indices, centrality assessment, and shipping routing to observe the changes of global shipping network by climate change impacts

Empirical evaluation of microtremor H/V spectral ratio

The objective of this work is to perform a purely empirical assessment of the actual capabilities of the horizontal-to-vertical (H/V) spectral ratio technique to provide reliable and relevant information concerning site conditions and/or site amplification. This objective has been tackled through the homogeneous (re)processing of a large volume of earthquakes and ambient noise data recorded by different research teams in more than 200 sites located mainly in Europe, but also in the Caribbean and in Tehran. The original recordings were first gathered in a specific database with information on both the sites and recorded events. Then, for all sites close to an instrumented reference, average site-to-reference spectral ratios (“spectral ratio method” (SSR)) were derived in a homogeneous way (window selection, smoothing, signal-to-noise ratio threshold, averaging), as well as H/V ratios (“HVSRE–RF”) on earthquake recordings. H/V ratios were also obtained from noise recordings at each site (either specific measurements, or extracted from pre- or post-event noise windows). The spectral curves resulting from these three techniques were estimated reliable for a subset of 104 sites, and were thus compared in terms of fundamental frequency, amplitude and amplification bandwidth, exhibiting agreements and disagreements, for which interpretations are looked for in relation with characteristics of site conditions. The first important result consists in the very good agreement between fundamental frequencies obtained with either technique, observed for 81% of the analyzed sites. A significant part of the disagreements correspond to thick, low frequency, continental sites where natural noise level is often very low and H/V noise ratios do not exhibit any clear peak. The second important result is the absence of correlation between H/V peak amplitude and the actual site amplification measured on site-to-reference spectral ratios. There are, however, two statistically significant results about the amplitude of the H/V curve: the peak amplitude may be considered as a lower bound estimate of the actual amplification indicated by SSR (it is smaller for 79% of the 104 investigated sites), and, from another point of view, the difference in amplitude exhibits a questioning correlation with the geometrical characteristics of the sediment/basement interface: large SSR/HV differences might thus help to detect the existence of significant 2D or 3D effects.Published75-1084.1. Metodologie sismologiche per l'ingegneria sismicaJCR Journalreserve

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