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A major challenge in forest management is to balance the competing interests of different users. The conservation of biological diversity is an important goal when managing forests in an ecologically sustainable way, but this overlooks aspects of sustainability in terms of urban development and other land use. This research examines physical and biological processes leading to changes in the spatial and temporal land cover on the Curonian Spit, in Lithuania, pre- and post-1990 when the political situation changed heralding new practices. Specifically, the levels of cover categorised as vegetation, sand, forest, urban and grassland are determined using remote sensing images over the period 1989–2017. An assessment of the accuracy of the analysis, when compared with Google Earth, other images and in situ data, produces a high level of confidence in the results. The analysis indicates that the overall forest cover initially decreased until 2009, but since then it has increased by over 1% per year. No urban growth is observed. These and other results are displayed graphically. The forestation of moving dunes, the human impact on the area and changes in the environment are all discussed. The results demonstrate how remote sensing and GIS methods can be used as an important tool for planners, dispensing with the need for costly field trips.

Social media posts incorporate real-time information that has, elsewhere, been exploited to predict social trends. This paper considers whether such information can be useful in relation to crime and fear of crime. A large number of tweets were collected from the 18 largest Spanish-speaking countries in Latin America, over a period of 70 days. These tweets are then classified as being crime-related or not and additional information is extracted, including the type of crime and where possible, any geo-location at a city level. From the analysis of collected data, it is established that around 15 out of every 1000 tweets have text related to a crime, or fear of crime. The frequency of tweets related to crime is then compared against the number of murders, the murder rate, or the level of fear of crime as recorded in surveys. Results show that, like mass media, such as newspapers, social media suffer from a strong bias towards violent or sexual crimes. Furthermore, social media messages are not highly correlated with crime. Thus, social media is shown not to be highly useful for detecting trends in crime itself, but what they do demonstrate is rather a reflection of the level of the fear of crime.

A torsion vibration isolator with quasi-zero stiffness (QZS) is proposed to attenuate the transmission of torsional vibration along a shaft system, which also plays a role of coupling between shafts. A pre-compressed cam–roller mechanism is designed to provide torsional negative stiffness that counteracts with the positive torsion stiffness of the vulcanized rubber between shafts. With the design parameters are set to satisfy a unique condition, the stiffness of the isolator delivers a QZS property about the equilibrium position. A nonlinear mathematical model is developed and its dynamic characteristics are further analyzed by using the Harmonic Balance method. A typical folded resonance curve occurs when the vibration amplitude is plotted as the excitation frequency is varied, illustrating a jump phenomenon in the response. The efficiency of vibration attenuation is estimated under a designed torque load, showing that the torsion QZS vibration isolator outperforms the corresponding linear counterpart, especial in low frequency ranges. Furthermore, the torque transmissibility of the QZS isolator is also studied to demonstrate the performance of the QZS isolator when the actual torque deviates from the design load.

This article points out a number of key failures of existing practice for building design and then promotes a new approach based upon advances made in the modelling of complex systems and systems engineering. This new approach involves the identification of building functions and modelling techniques to evaluate the performance of a building with respect to a range of criteria in different domains (e.g. spatial, structural, social, environmental, cognitive, organizational, and operational). A systems approach to building design has received limited acceptance to date but can be used to highlight inherent hierarchies and interdependencies between building subsystems, which have traditionally been viewed as being independent. There is currently little agreement as to how the design of different building subsystems should be best integrated in order to satisfy a large range of diverse building functions. Treating the building as a complex system, whereby the interaction of entities produces emergent behaviou...

We present a so-called zero-crossing identification method that can crack the security shell of the chaotic encryption method [Chaos, Solitons & Fractals 19 (2004) 919] with periodic modulation. By collecting a special set of truncated data from the zero-crossing incidents of the modulated signal, we can detect the modulating function from chaotic signal. Furthermore we extend the technique to extract modulating function from noise and discuss the potential applications of this method in engineering.

In this work multi-modal systems subject to impact are considered. Using energy balance techniques for an arbitrary contact interval the effects of modal vibration can be included. The energy balance is used to obtain a relationship between the coefficient of restitution and the modal energy during the contact period. This allows the effects of impact induced vibration to be considered. The subsequent analytical relationships demonstrate that increasing contact duration and excitation of higher modes can reduce the effective value of the coefficient of restitution. It is also shown how this approach can be related to work on energetically consistent impacts.

The dynamics of a vibro-impacting cantilever beam experiment using an impact load cell is considered. The signal recorded from the cell produces spike train -type data. The issues related to the analysis of such data are discussed; particularly the sampling rate and threshold values. For vibro-impact motion of the beam, the duration of impacts is investigated by using a time of contact measure. The implications are discussed for vibro-impact systems mathematically modelled by using instantaneous impact assumptions (coefficient of restitution). Using the load cell to measure impact forces for the beam system is also considered. Then a delay reconstruction of the dynamics of the system by using interspike intervals is considered. It is demonstrated how this process is effected by the influence of noise and the data-acquision process using numerical simulations of the experimental data. It is shown how simple periodic motions can be identified by using a probability density approach and possible future research is highlighted.

The study of dynamical systems is of significant practical importance. We investigate here the concept of the safe basin and the use of the amplitude/frequency of forcing parameters plane which can be applied to a wide range of dynamical systems including control applications. A computer aided study of the performance of such systems using Matlab/Simulink with a Watcom C/C++ compiler is illustrated. The technique is easy to use and is only limited by the properties of the Matlab/Simulink programme in which the system is simulated. The behaviour of a pressure transducer is used as a simple example; as a further example the stab ility and robustness of a practical control strategy, designed to control chaotic behaviour, has also been investigated.

A computer based technique has been developed to test the performance of complex nonlinear systems, using Matlab/Simulink™ and C/C++. In this approach a dynamic system, represented by its mathematical model, is stimulated by a sequence of sinusoidal signals and the system stability is observed by a stability diagram. Furthermore the technique is developed to test the degree of accuracy and sensitivity of transducers. Such devices are complicated nonlinear, closed-loop, systems in their own right. In this paper the long term stability of a typical pressure transducer model with hard and soft spring effects is examined. The range of use is determined by a shaded stability diagram. In addition performance of a micromachined, silicon, accelerometer is examined. Important properties of the accelerometer such as the degree of accuracy and sensitivity are considered

Results of a numerical investigation are presented of the behaviour of a mathematical model which approximates the response of a thin metal strip, or beam, held vertically and clamped at its base, which is driven to impact against a motion limiting constraint. Previous theoretical analyses, in conjunction with numerical studies, have highlighted the complicated dynamics that the system exhibits following a single or series of grazing bifurcations. Under certain conditions subharmonic solutions and chaotic impacting motions are unavoidable. These solutions, which involve several impacts per orbital period introducing relatively large impact velocities, have been viewed experimentally. Meanwhile research into the control of chaos, in which unstable orbits embedded within chaotic motions are stabilized, has advanced over recent years. New control methods have been developed and experimentally implemented. The present work brings these two fields together for the first time. Numerical evidence is given for the use of control to eliminate complicated motions by tracking lower periodic solutions. The stabilized motions near the grazing incidence have lower impact velocities than the naturally existing stable solutions leading to a significant reduction of the impact force which may have significant engineering relevance.

Wave induced set-up is a process that leads to increased water levels in coastal regions. When coupled with storm conditions, wave set-up – or, for brevity, set-up – can significantly increase the risk of flooding or structural damage and therefore is of particular importance when considering coastal management or issues related to the planning of nearshore infrastructures. Here, we investigate the effects of set-up in the coastal region of the Gulf of Finland in the Baltic Sea, close to Tallinn, Estonia, although the results will have wider relevance for many other areas. Due to a lack of continuous wave data we employ modelling to provide input data using a calculation scheme based on a high-resolution (470 m) spectral wave model WAM to replicate spatial patterns of wave properties based on high-quality, instrument-measured wind data from the neighbourhood of the study site. The results indicate that for the specific geometry of coastline under consideration, there is a variation in set-up which is strongly affected by wind direction. The maximum set-up values are up to 70–80 cm in selected locations. This is more than 50% of the all-time maximum water level and thus may serve as a substantial source of marine hazard for several low-lying regions around the city. Wind directions during storms have changed in recent years and, with climate variability potentially increasing, these results will encourage further tests which may be used in a policy setting regarding defences or other structures in and around coastlines. In particular, with urban development now taking place in many coastal regions (including the one within this study) these results have implications for local planners. They may also be incorporated into new storm warning systems.

In estimating how economic growth depends on various inputs, economists commonly use long periods of data encompassing both main extremes to fluctuations in the economy: recession and expansion. Here we focus on recession years because during expansion even countries with bad economic policies may experience large growth. Specifically, we study how growth depends on the proportion of public-sector workforce, p and competitiveness, quantified by the Global Competitiveness Index, GCI. For the 2008-2011 economic downturn and for 57 countries, we find that the growth rate of GDP per capita, g, decreases with p, and increases with ΔGCI. Further, more competitive countries attract more foreign direct investments per capita, I, than less competitive countries, where I is proportional to GCI(α). We propose a production function, divided into the private and public sectors, where GDP depends on market capitalization, the public (private)-sector workforce, and competitiveness level, used to quantify the public sector efficiency.

Society’s increasing interactions with technology are creating extensive “digital traces” of our collective human behavior. These new data sources are fuelling the rapid development of the new field of computational social science. To investigate user attention to the Hurricane Sandy disaster in 2012, we analyze data from Flickr, a popular website for sharing personal photographs. In this case study, we find that the number of photos taken and subsequently uploaded to Flickr with titles, descriptions or tags related to Hurricane Sandy bears a striking correlation to the atmospheric pressure in the US state New Jersey during this period. Appropriate leverage of such information could be useful to policy makers and others charged with emergency crisis management.

This paper presents a nonlinear magnetic low-frequency vibration isolator designed with the characteristic of quasi-zero stiffness (QZS). An approximate expression of the magnet repulsive force is proposed and a unique analytical relationship between the stiffness of vertical spring and initial gap settings of the magnet springs is derived for the QZS system. Based on the harmonic balance (HB) method, the force transmissibility is formulated and the jumping frequencies, effect of excitation force and damping ratio are discussed for characteristic analysis. An experimental prototype is developed and tested. The performance of the QZS system is verified through a series of experimental studies showing that the new model greatly outperforms standard linear isolation systems especially in low-frequency domain. The tuning techniques for adapting to the change of loading mass and adjusting the QZS property in practice are also addressed.

In an earlier work a deterministic model, FIRE-SPRINT A1, which predicts the conditions for fire spread in a tunnel, has been presented. The model, based on the concepts of non-linear dynamics, may be used to predict the conditions for spread from one vehicle to another in a tunnel fire. A few illustrative simulations were given. In this communication the results of further simulations are presented; in particular, bifurcation following has been conducted for the case of fire spread from one heavy goods vehicle to another in a rail tunnel. These demonstrate further how the model may be used to identify those geometrical and thermo-physical conditions which give rise to instability and a jump. In principle, such a model may be used as an aid to design and operation for a tunnel.

A nonlinear model for simulating the heave-roll motions of ships in following waves is presented. The parametric excitation is modeled by a Hill's type equation, instead of the conventional Mathieu's equation. The model includes not only the linear but also the quadratic coupling term. Instability conditions for parametrically excited rolling motions are derived using the harmonic balance method. The results are verified by numerical analyses. The effects of including the quadratic coupling term on the instability conditions and nonlinear responses are studied. The complex dynamic behaviour of the coupled system in the various instability regions is also investigated. Bifurcations of the flip, fold and pitchfork types are observed in the Poincare mapping of the numerically simulated responses. Chaotic motions leading to boundary crises and inevitable capsize are also reported.

A heteroclinic tangency marking the initial change in secondary Birkhoff signature is identified as a good indicator of the chaotic escape from a symmetric potential well under parametric excitation as it occurs shortly after the symmetry breaking bifurcation which precedes the final event. This is compared to the criterion for asymmetric potential wells, and the lack of any change in primary Birkhoff signature highlights the differences in the two cases.

A non-linear model of fire in a tunnel, FIRE-SPRINT A1, is presented. It predicts the conditions for fire spread from one object to another within a tunnel which has longitudinal ventilation. It does this by identfying unstable states within the system and associating instability with the onset of fire spread. The particular case of spread from an initial fire to a heavy goods vehicle (HGV) within the Channel Tunnel is considered as an illustration. Thereby the thermo-physical and geometrical conditions leading to such a jump may be elucidated.

We introduce a future orientation index to quantify the degree to which Internet users worldwide seek more information about years in the future than years in the past. We analyse Google logs and find a striking correlation between the country's GDP and the predisposition of its inhabitants to look forward., Scientific Reports, 2, ISSN:2045-2322

The European Physical Journal Special Topics, 214 (1), ISSN:1951-6355, ISSN:1951-6401

Society depends decisively on the availability of infrastructure systems such as energy, telecommunication, transportation, banking and finance, health care and governmental and public administration. Even selective damages of one of these infrastructures may result in disruptions of governmental, industrial or public functions. Vulnerability of infrastructures therefore provides spectacular leverage for natural disasters as well as criminal and terrorist actions. Threats and risks are part of the technological, economical, and societal development. This article focuses on the development and characterization of an integrative risk-management which, from the perspective of “resilient systems”, can be seen as an innovative and pro-active crisis management approach dealing with the increasing amount of complexity in societies in a comprehensive, agile and adaptive way.

This paper considers the behaviour of a two degree-of-freedom autonomous system with static and dynamic friction consisting of two blocks linked by springs on a moving belt. This system is the simplest model which has been used to simulate the dynamics of seismic faults. The friction force is assumed to be a decreasing function of the relative sliding velocity. The motion of the blocks is composed of a uniform stick motion, during which the divergence of the system is zero, and an accelerated slip motion, during which the divergence is positive. The mathematical model by definition concentrates the dissipation on the point where the slip motion ceases. It is assumed that slip occurs only in one direction. A three-dimensional Poincare map and a scalar single variable map are discussed which characterize the dynamics of the system in a simple way. The one-dimensional map can be used to diagnose the chaotic behaviour of the full system, and quantities, similar to Lyapunov exponents, can be easily calculated which provide information regarding the system-sensitive dependence on initial conditions. The system dynamics illustrate the idea of studying the earthquake generation mechanism as a chaotic phenomenon.

This paper examines the dynamical behavior of fire growth within a building or more simply a compartment. Simplified equations are derived to study the development of a fire. The transient fire growth is modelled using concepts of nonlinear dynamical systems theory, and the effect of ventilation is considered. Emphasis is placed on qualitative behavior with a view to understanding the phenomena involved in fire growth, with specific attention focused on highly dangerous flashover conditions.

A comparison between experimental data and both the qualitative and quantitative nonlinear behavior predicted by a fire growth model is made for a model compartment (0·4 m cube). The predictions are in relatively good agreement with the data, and are consistent with the expected nonlinear behaviour and in particular the occurrence of flashover jumps.

Flashover is a phenomenon whereby a room fire undergoes a rapid increase in size and intensity. Such a transition is suggestive of a nonlinear process. We therefore seek to apply modern geometrical and computational techniques of nonlinear dynamics to a simplified model of fire growth to investigate flashover and other instabilities occuring in compartment fires. We present here a simplified model of fire growth in a compartment and conduct a preliminary analysis of the dynamics exhibited, in terms of both transient simulations and quasi-steady evolution manifolds, for variations in controlling parameters.

This paper describes the development of a method for predicting the recovery of the seabed after the extraction by dredging of marine aggregates for commercial purposes. The model is based on a rule-based cellular automata technique rather than conventional process-based methods, and has been developed from an earlier model of dunes and aeolian sand transport. Preliminary results reproduce realistic bedforms under initial conditions and demonstrate the backfilling of a trench left after dredging is complete. Seabed biological systems have been characterized and rules developed to drive the model that describes their response to and interactions with physical and hydrodynamic conditions perturbed by the dredging process. © 2007 World Scientific Publishing Co. Pte. Ltd.

In this paper the application of the computer based approach originally developed at UCL, Thompson & Soliman (1990), for the determination of stability of marine structures is applied to the investigation of performance of a typical digital accelerometer structure. One of the features of this work is that large amounts of data have to be processed. This is achieved by use of parameter plane, Poincare sectioning and safe basin techniques in software designed specifically for the purpose of advanced transducer analysis. Results are presented with practical comparisons of different transducer and modulator structures types of stability compensation. Examples of the potential uses for these techniques are discussed and software demonstrated. >

Work based upon the application of computer techniques for the study of safe basins of stability and Poincare sections for such devices has been extended to investigate the performance of high order models and also the relation to their forced performance. This paper combines a standard approach with methods based on ideas stimulated by chaotic solution. The effects of integrator leak, saturation, and nonlinear compensation techniques are also investigated with a view to chaotic behavior. Work previously due to Feely & Chua has also been extended to include higher order models.

As part of decision-making with regard to fire risk, mathematical models of fire growth are starting to be developed and used. in order to further this effort, work is under way to try to understand the nonlinear behaviour of fire in a compartment and the instabilities which may exist. in particular, the conditions for the existence of a mathematical jump may be interpreted as a ‘flashover’; a potentially disastrous event in which a small, localized, fire comes to involve the whole of a compartment.

An approach towards the classification of the stability of a ship is presented. This concept is based on the evaluation of the basin of transient attraction of the response of a ship in roll The determination of these basins allows us to summarise the global transient behaviour of the ship. A sudden erosion of these basins implies a loss of engineering integrity of the system, which can often happen at a wave height that is considerably smaller than that predicted by a steady state analysis. The analysis can be used to investigate the transient behaviour of a ship and can lead to guidelines which can be incorporated in ship hull design.

A zonal formulation has been used to construct a non-linear model with a single state-variable corresponding to temperature. The governing equatisu are shown to be equivalent to a system with a swallowtail catastrophe. Using the model, conoitions may be identified which produce a jump and such a jump in the model's behaviour is being associated with one kind of flashover jump, i.e. that in which a fuel-controlled state becomes unstable. Thereby, the conditions for a flashover jump may be elucidated.

When monitoring the wave-driven motions of a compliant offshore facility, be it an articulated mooring tower or a vessel, the engineer would like to be able to predict, in real time, any incipient jump to resonance that might be imminent due to the slowly evolving sea-state. We explore in this paper a study of some new possible prediction techniques for both a jump to a main fundamental resonance leading to capsize and a flip bifurcation to a subharmonic resonance. Stroboscopic Poincare´ mapping techniques based on discrete time sampling are used to give information about the approach to instability. The first application of these techniques is in the prediction of the jump in resonance and consequent capsize at a cyclic fold in the roll response of a vessel in regular beam seas. Secondly, the techniques are shown to work extremely well in a variety of computational situations when applied to the simulation of an articulated mooring tower during the approach to the potentially dangerous oscillations produced by the onset of subharmonic resonance at a flip bifurcation, in both regular and irregular ocean waves.

The motion of a moored semi-submersible is modelled using a semi-empirical nonlinear ordinary differential equation. Time domain simulations, guided by the qualitative theory of dynamical systems, illustrate the extremely complex nature of typical responses in regular seas. The importance of nonlinearities is emphasised together with the implications for floating structures in general.

This paper describes a combined numerical and geometric approach to study the dynamic behavior of a moored semi-submersible based on solutions of the nonlinear differential equation used to model the system. Complex features including competing steady states, subharmonic resonances and chaos are shown to be typical responses in regular seas. A qualitative overview is used to classify the computer data generated from direct time simulation with the aim of illustrating the inadequacies and limitations of a linear or a purely analytical approach.