Franco Ruzzenenti

Reciprocity of weighted networks

In directed networks, reciprocal links have dramatic effects on dynamical processes, network growth, and higher-order structures such as motifs and communities. While the reciprocity of binary networks has been extensively studied, that of weighted networks is still poorly understood, implying an ever-increasing gap between the availability of weighted network data and our understanding of their dyadic properties. Here we introduce a general approach to the reciprocity of weighted networks, and define quantities and null models that consistently capture empirical reciprocity patterns at different structural levels. We show that, counter-intuitively, previous reciprocity measures based on the similarity of mutual weights are uninformative. By contrast, our measures allow to consistently classify different weighted networks according to their reciprocity, track the evolution of a networks reciprocity over time, identify patterns at the level of dyads and vertices, and distinguish the effects of flux (im)balances or other (a)symmetries from a true tendency towards (anti-)reciprocation.

Complex Networks and Symmetry II: Reciprocity and Evolution of World Trade

We exploit the symmetry concepts developed in the companion review of this article to introduce a stochastic version of link reversal symmetry, which leads to an improved understanding of the reciprocity of directed networks. We apply our formalism to the international trade network and show that a strong embedding in economic space determines particular symmetries of the network, while the observed evolution of reciprocity is consistent with a symmetry breaking taking place in production space. Our results show that networks can be strongly affected by symmetry-breaking phenomena occurring in embedding spaces, and that stochastic network symmetries can successfully suggest, or rule out, possible underlying mechanisms.

Complex Networks and Symmetry I: A Review

In this review we establish various connections between complex networks and symmetry. While special types of symmetries (e.g., automorphisms) are studied in detail within discrete mathematics for particular classes of deterministic graphs, the analysis of more general symmetries in real complex networks is far less developed. We argue that real networks, as any entity characterized by imperfections or errors, necessarily require a stochastic notion of invariance. We therefore propose a definition of stochastic symmetry based on graph ensembles and use it to review the main results of network theory from an unusual perspective. The results discussed here and in a companion paper show that stochastic symmetry highlights the most informative topological properties of real networks, even in noisy situations unaccessible to exact techniques.

Spatial effects in real networks: Measures, null models, and applications

Spatially embedded networks are shaped by a combination of purely topological (space-independent) and space-dependent formation rules. While it is quite easy to artificially generate networks where the relative importance of these two factors can be varied arbitrarily, it is much more difficult to disentangle these two architectural effects in real networks. Here we propose a solution to this problem, by introducing global and local measures of spatial effects that, through a comparison with adequate null models, effectively filter out the spurious contribution of nonspatial constraints. Our filtering allows us to consistently compare different embedded networks or different historical snapshots of the same network. As a challenging application we analyze the World Trade Web, whose topology is known to depend on geographic distances but is also strongly determined by nonspatial constraints (degree sequence or gross domestic product). Remarkably, we are able to detect weak but significant spatial effects both locally and globally in the network, showing that our method succeeds in retrieving spatial information even when nonspatial factors dominate. We finally relate our results to the economic literature on gravity models and trade globalization.

Detecting spatial homogeneity in the world trade web with Detrended Fluctuation Analysis

In a spatially embedded network, that is a network where nodes can be uniquely determined in a system of coordinates, links’ weights might be affected by metric distances coupling every pair of nodes (dyads). In order to assess to what extent metric distances affect relationships (link’s weights) in a spatially embedded network, we propose a methodology based on DFA (Detrended Fluctuation Analysis). DFA is a well developed methodology to evaluate autocorrelations and estimate long-range behavior in time series. We argue it can be further extended to spatially ordered series in order to assess autocorrelations in values. A scaling exponent of 0.5 (uncorrelated data) would thereby signal a perfect homogeneous space embedding the network. We apply the proposed methodology to the World Trade Web (WTW) during the years 1949–2000 and we find, in some contrast with predictions of gravity models, a declining influence of distances on trading relationships.

The Role of Distances in the World Trade Web

In the economic literature, geographic distances are considered fundamental factors to be included in any theoretical model whose aim is the quantification of the trade between countries. Quantitatively, distances enter into the so-called gravity models that successfully predict the weight of non-zero trade flows. However, it has been recently shown that gravity models fail to reproduce the binary topology of the World Trade Web. In this paper a different approach is presented: the formalism of exponential random graphs is used and the distances are treated as constraints, to be imposed on a previously chosen ensemble of graphs. Then, the information encoded in the geographical distances is used to explain the binary structure of the World Trade Web, by testing it on the degree-degree correlations and the reciprocity structure. This leads to the definition of a novel null model that combines spatial and non-spatial effects. The effectiveness of spatial constraints is compared to that of nonspatial ones by means of the Akaike Information Criterion and the Bayesian Information Criterion. Even if it is commonly believed that the World Trade Web is strongly dependent on the distances, what emerges from our analysis is that distances do not play a crucial role in shaping the World Trade Web binary structure and that the information encoded into the reciprocity is far more useful in explaining the observed patterns.

On The Relationship Between Energy Efficiency And Complexity: Insight On The Causality Chain

The relationship between the energy effi ciency, energy density and complexity level of the system is here addressed from both thermodynamic and evolutionary perspectives. A case study from economic systems is presented to show that, contrary to widespread opinion, energy effi ciency is responsible for energy growth and the complexity leap. This article further examines to what extent complexity, on a historical time scale, may evolve to counterbalance conservative effects brought about by energy effi ciency. We analyze structural complexity growth by four different paradigms. An evolutionary pattern is then proposed that may encompass the broad dynamics underlying complexity growth. This evolutionary pattern rests on the hypothesis that thermodynamic evolutionary systems are featured from an ever growing infl ux of energy driven into the system by self-catalytic processes, which must fi nd its way through the constrains of the system. The system initially disposes of the energy by expanding, in extent and in number of components, up to saturation due to inner or outer constraints. The two counteractive forces, constraints and growing energy fl ux, expose the systems to new gradients. Every new gradient upon the system represents a symmetry rupture in components’ space. By exploring a new gradient, the system imposes further restrictions on its components and increases its overall degree of freedom.Computerized gait analysis using fuzzy logic has become an integral part of the treatment decision-making process. The integration of kinetic data, more specifically power joints in combination with fuzzy logic, is a relatively new addition to the other types of data including temporal and stride parameters. The power joints of the human leg are an important contribution to the understanding of the cause of certain gait abnormalities. This utility is not only limited to the surgical decision-making process in persons with spastic diplegia and myelomingocele but it can also be used in the rehabilitation decision-making process. The modelling of power joints and fuzzy logic applications in medicine will provide the reader with a detailed introduction to a new method of analysis of the human gait.In this article we rely on constructal theory to show that the hierarchy of universities is rigid, and that the explanation lies in the nature of education (science, news, information) as a natural fl ow system that bathes the globe most effectively. The article begins with two observations: (i) the rankings of the best engineering universities in the USA closely mirror the rankings of the universities that have the most names of researchers on the list of the most highly cited authors; and (ii) the log‐log plot of the number of highly cited authors of one school versus the rank of that school is nearly a straight line with slope between ‐1/2 and ‐1. The straight line is the same as the distribution of city sizes versus city rank throughout the history of Europe. From this follows the argument that the hierarchy of universities is tied to geography, to how each nodule of knowledge generation serves the area allocated to it. Education fl ows from point to area. The compounding of areas to cover the landscape is the origin of the hierarchical and stable arrangement of universities. The rank of a university is closely related to the visibility of its producers of ideas. The tapestry of a university on the landscape is predicted. All universities grow and improve in time (like all the river channels during the rain), but their hierarchy remains the same.The thermodynamic effect of a density gradient in a colder fluid as a result of a hotter plate located below it is something that is well known. However, its use as a flow field indicator using a light coil shaped body is a recent application developed by the author of this paper. The paper contributes to bring ahead this concept by a parametrical experimental analysis aimed at assessing the relationship among three of the parameters that mainly influence the whole process: the angular velocity of the coil as a dependent variable; the number of turns in the coil as the first independent variable and the weight of the coil as the second independent variable. A suitable apparatus was realized. The tests performed showed that, apart from a very few cases, an increase in the number of turns produces an increase in the angular velocity of the coil. A particular behaviour is observed for the weight of the coil: an increase in weight augments the angular velocity for small values, while for larger values the trend is opposite. Some considerations about the rotational stability can explain the entire concept, although further research will help deepen our knowledge of the process for wider parametrical ranges.Natural organisms often have multiple functions and multi-optimisation in a single component or mechanism. In addition, natural organisms are highly integrated assemblies. In contrast, human design has traditionally avoided multi-functioning in single components because of the difficulties this presents in the design process. Only in recent years has there been a trend towards multi-functioning in engineering components. The advantage of multi-functioning is that extremely high levels of performance can be achieved. This paper gives examples of multi-functioning and multi-optimisation in a bird flight feather and a bird display feather. In each case, the advantages of multi-functioning are explained and analogies with man-made design are given.A biomimetic study of the bombardier beetle’s explosive discharge apparatus was undertaken using numerical (CFD) modelling, first, of the beetle’s combustion chamber, and then of a scaled-up combustion chamber with a view to its application to devices such as gas turbine relighters. The new findings about the existence of a pressure release valve at the beetle’s combustion chamber exit yield a clearer understanding of the physics of the beetle’s mass ejection mechanism. The scaled-up chamber (about 1 cm in length) is modelled by considering the chamber to be filled with liquid hexane which then undergoes vapour explosion through a pressure release valve at the exit. The ejection of vaporised fuel at high exit velocities has a number of applications, including gas turbine igniters.In reality, values of a specimen (its strength, etc.) have certain probability distributions. Deterministic values in reality are also uncertain and have error margins. Thus, averages and standard deviations are used for estimates in engineering and nature, and major factors in estimations are based on the nominal value and the upper and lower allowed (survival, design, standards) limits. Observations beyond those limits indicate mostly a failure. However, probability distributions in nature and engineering show a relatively long “tail” beyond the limits of several standard deviations. The values of deviations from the mean (or target) can be very large, which can endanger the whole specimen. The phenomena at the “tail” domain (and not in the domain up to the limits) are the main reason for the fact that larger specimens are generally more vulnerable than smaller ones, having the same mean and probability distribution. The present paper extends this concept to relevant phenomena in nature and in technology.Fractional calculus provides novel mathematical tools for modeling physical and biological processes. The bioheat equation is often used as a first order model of heat transfer in biological systems. In this paper we describe the formulation of the bioheat transfer in one dimension in terms of the fractional order differentiation with respect to time. The solution to the resulting fractional order partial differential equation reflects the interaction of the system with the dynamics of its response to the pulsed surface or volume heating and cooling. The resulting expression for the heat flux in terms of the fractional order is used to derive an expression for the depth of thermal penetration. This depth of thermal penetration, expressed as a function of time, is optimized using constructal theory, which in turn leads to the determination of the optimal time of pulsating (on‐off) heating and cooling. The advantage of using the fractional heat flux expression is demonstrated by comparing the results with that of optimization of the integer heat flux expression, which yields an ideal unrealistic condition of equal time periods for optimal cooling and heating. An example from cryogenic spray cooling of a peripheral tissue region during laser surgery is used to illustrate the utility of combining the methods of fractional calculus and constructal theory. This combined approach is useful to develop an approximate solution to complex biomedical problems that involve pulsating behavior and rhythmicity.In the vertebral body (VB), the load carrying and transmitting function is primarily performed by the cortical VB. Hence, we have modelled the cortical VB as a hyperboloid shell whose geometry and composition are made up of its generators. This paper analyses the forces in the VB generators due to compression, bending and torsional loadings. The unique feature of the hyperboloid geometry is that all the loadings are transmitted as axial forces in the generators. This makes the VB a high-strength structure. Furthermore, because the cortical VB material is primarily made up of its generators (through which all the loadings are transmitted axially), it also makes the VB an intrinsically lightweight structure. We then analyse for the optimal hyperboloid shape and geometry by minimizing the sum of the forces in the hyperboloid VB generators with respect to the hyperboloid shape parameter (angle β between pairs of generators). The value of β is determined to be 26.5 ◦ , which closely matches with the in vivo geometry of the VB based on its magnetic resonance imaging scan. In other words, for the hyperboloid shape parameter β = 26.5 ◦ , the VB generators’ forces are minimal so as to enable it to bear maximal amounts of loadings. In this way, we have demonstrated that the VB is an intrinsically, functionally optimal structure.The climatic characteristics in different regions of Iran have created architectural design problems. It is advantageous to look at various architectural solutions to such problems. In the hot-dry climate of the indigenous settlements of Iran, particularly interesting design solutions are found. Most solutions, such as high thermal capacity construction materials, compact structure of cities, narrow winding passageways, thick walls, courtyards, internal vegetation, arched roofed chambers, highly elevated wind towers and big water reservoirs, are in conformity with nature and environment. The role of architectural elements is to make use of natural forces such as light, heat, wind and water in design. In this paper, the effects of climatic factors on urban and architectural forms in the hot-dry regions of Iran, climatic design problems and architectural solutions are explained.This paper introduces a novel approach for evaluating fabric sensory responses. First, the problems in existing techniques are analyzed, and by comparing with successful cases in assessing human feeling towards cold/warmth and human color sense, a more scientific scheme based on the computer pattern recognition technique is exhibited and the details of the measurements, data processing and calculation of the ultimate parameters are introduced. The actual prototype of the instrument and related details are also provided. Finally, it is shown that the technique can also be utilized to evaluate some visual attributes such as drape and wrinkle recovery.A method based on the design rules of nature, which has been used previously for the reduction of notch stresses, is used here for the removal of underloaded parts in a mechanical component. A major advantage is that neither fi nite element analysis nor complex mathematics is necessary for this graphic method of shape optimization, which is demonstrated here using three examples.This paper presents an experimental study of constructal tree shaped networks, to optimize the fl uid networks based on minimization of pumping power. We take a fresh look at the generation of architectures for fl uid fl ow and instead of minimizing the global fl ow resistance we focus on minimization of pumping power. Nonsymmetric (9 outlets) and dendritic (24 outlets) architectures were investigated for both laminar and turbulent fl ow regimes. A signifi cant reduction in pumping power and volume is observed, compared to conventional fl ow. These results emphasize the robustness of tree networks for fl uid fl ow.Mangrove forests are ecologically and economically important and frequently dominating protected coastal areas in the tropics and subtropics at suitable intertidal zones and are often subjected to disturbances that disrupt the structure of an ecosystem, that change resource availability and that create patterns in vegetation by producing a mosaic of seral stages that ecologists have long recognised as important to landscape-level patch mosaics. Several good reasons justify the need for pursuing a predictive understanding of the ecology of mangrove species competition including the role of disturbance events and the aftermath. A predictive understanding can challenge our assumptions concerning the factors that control plant distribution and abundance and provide techniques for predicting rates of species change ranges in response to disturbances. The aim of this study was to evaluate and predict the impact of canopy disturbances on Gazi Bay mangrove forests and the subsequent vegetation patterns both spatially and temporally. The use of a simple 1D cellular automaton provided a detailed and nearly comprehensive parameterisation of the model by forest structure parameters belonging to the standard measurements of mangrove fi eld surveys. In the study presented, the fi eld data were obtained for disturbance impacts at various spatial scales considering not only the spatial extent of the disturbance but also its particular location. For this, multiple sampling transects were selected a priori, based on the vegetation patterns observed on Quickbird satellite image (2002) of Gazi, to refl ect major ecological zones and vegetation transitions in space. Earlier fi eld studies already revealed different population trajectories in some cases for the same pairwise species interactions, which are consistent with the hypothesis that different scales of disturbances may affect succession trends. Simulation experiments supported these fi ndings by demonstrating that varying disturbance impacts determine coexistence or mutual exclusion of the interacting species and occasionally leading to equilibrium shifts to alternative states. We suggest the consideration of simulation experiments as a good proxy for predicting mangrove species dynamics not neglecting the need of further evaluation based on the transient ecodynamics.“Empire building” is a phenomenon that dominates today’s research landscape. Large groups, national priorities and research centers dwarf the spontaneous individual investigators. Administrators and the thirst for higher rankings encourage this trend. Yet, the individuals do not disappear. This paper explains why. It attributes the emergence of the large group to the pursuit of greater visibility for the institution as a whole. The visibility (V) is modeled as a product of the production (P) of ideas in the institution, and the support (S) that the institution secures for the production of ideas. The coalescence of some investigators into a large group tends to increase S and decrease P. On the other hand, an increase in the number of individual investigators has the opposite effect. From this trade-off emerge the main and well-known features of contemporary research organization: the proportionality between the size of the large group and the size of the entire institution, the strong relationship between the visibility of an institution and its size, and the fact that large groups occurred fi rst in the largest and most research-intensive institutions. The paper also shows that as the incentives for large-group research become stronger, smaller and smaller institutions fi nd it benefi cial to abandon the individual investigator mode and seek a balance between research empires and individual investigators. The individual researcher will not disappear.An oscillating aero-wing operating in pitch and plunge in the quasi-steady domain for lift and thrust generation is presented and analyzed. The model may serve as a reference of comparison for sustained forward propulsion of birds, insects and micro air vehicles. It turns out that the propulsive efficiency of the aero-wing cannot be maximized with respect to the Strouhal number since this number is fixed by the drag-to-lift requirements of an overall system. This is in contrast to the liftless propulsion by a hydro-wing in water. The remaining criteria for aero-propulsion are the minimization of the drag-to-lift ratios of the aero-wing and of the overall flight system. Some other current issues of aero-propulsion are discussed for model support and refinement.Experimental investigations were conducted to characterize the thermal insulation properties of different natural low-cost materials (coconut fi bers and groundnut shell). A steady state method was used to measure the thermal conductivity by holding the sample between two concentric spheres with heat transferred mainly by conduction from the inner sphere (heat source) through the testing material. For comparison, the same experimental procedure was done for a standard and man-made insulation material, aluminum silicate fi ber. The results showed that for all the materials, the thermal conductivity increases with temperature; and the rates of increase are very similar. Also, two experimental samples were made to measure the moisture transport of the two natural materials: one with groundnut shell (composed of void space and grain) and the other sample with coconut fi bers (composed of void space and fi bers). The percentage of water accumulation due to vapor absorption was calculated for each layer after a pre-set time of experiment (1 h, 2 h, ...). A numerical investigation was performed to simulate the transfer process with a general and sound model, and to present the basic features of the transfer process.Synthetic and biological fl exoelectric membranes are actuators that bend under the action of external electric fi elds, a phenomenon of interest to the development of emerging adaptive materials as well as biological mechano-transduction. This paper presents an actuator model of fl exoelectric membranes based on a Helmholtz free energy that incorporates tension, bending, and torsion as well as polarization and dielectric energies. The electro-elastic components of the membrane tension, moment tensor and tensor are derived and used to construct an actuator model that includes dissipation due to viscous fl uids in contact with the membrane. The actuator model is expressed by a balance between the externally imposed electric forces, the viscous dissipation of the contacting fl uid phases, and the elastic storage of the membrane. The nonlinearity is shown to originate in the viscous dissipation. The model is analyzed for externally imposed oscillating electric fi elds. The Deborah number De given by the ratio of driving frequency and the resonant frequency is shown to control the viscoelastic response. The key fi ndings are: (i) for De � 1 the response is purely elastic and the electric energy is stored in the elastic deformations of the membrane; (ii) at larger De, the response is anharmonic and viscoelastic; (iii) due to the nature of the viscous nonlinearity only even harmonics are generated in the response; and (iv) secondary resonant frequencies appear at lower driving frequencies. These fi nding contribute towards the emerging understanding of fl in biological membranes, pioneered by Petrov and co-workers (Petrov, A.G., The Lyotropic State of Matter, Gordon and Breach Science Publishers: Amsterdam, 1999).Shape factors have been used to calculate the shape effi ciency of palm leaf petiole sections in order to understand how palms compensate for the torsional and bending forces they are subjected to by their environment. The part of the palm leaf that is similar in form to the leaf stalk (petiole) in dicot leaves will be referred to as a petiole in this paper, whilst recognising that it is probably not an exact homologue. Wind and rain on the blade generate combined fl exural and torsion loads on the petiole and a question arises as to how the section properties of the petiole deal with this loading. By isolating the shape from the size of the sections through the use of shape factors, the effects of the petiole section shape can be analysed on its own. Thus microstructural and material factors become a separate issue and will be discussed in a later paper. Cross section profi les from seven palm petioles are modelled, independent of their sizes, in order to calculate and plot the fl exural and torsional coupling effi ciencies for comparison with other plants and typical engineering cross sections.The intervertebral disc (IVD) acts as a shock-absorbing unit and effectively contains its lateral and axial deformations while providing the necessary flexibility to the spine. These attributes are due to the stress-stiffening material (elastic modulus) property of the annulus, caused by the pressure developed in the nucleus pulposus (NP). Hence, one of the biomechanical roles of the NP in the IVD is to stress the annulus while the IVD is loaded. In this paper, a closed-form solution of the IVD (with NP, i.e. a healthy IVD, and without NP, i.e. a nucleotomized IVD) under compressive loading is developed. Based on the analysis, it is observed that the deformations of the IVD do not increase in proportion to the load. Rather, the rate of increase in deformation decreases as the load increases. This is a key optimal feature because it means that deformations are contained and therefore stability is maintained. Further, it is shown that the nucleotomized IVD deforms more than the healthy IVD. This means that the nucleotomized IVD will have higher chances of collapse than the healthy IVD for the same level of loading. This result is a contra-indication for nucleotomy. Our proposal is to place a biocompatible gel-filled balloon to simulate the beneficial effects of the NP.The complexity we observe in life forms, in their development and in biological evolution, is the result of the temporal and spatial constraints of a long evolutionary history made up of relations accumulating in time. This work assumes that space and time belong to different logical types: the fi rst being reversible and conservative and the second irreversible and evolutionary. Time and space are reciprocally irreducible quantities. We refer to the thermodynamics of the Nobel laureate in Chemistry, Ilya Prigogine, to perform a new point of view of life, in terms of evolutionary thermodynamics.Design prototypes for the physical and social worlds are found in nature in the domains of fl ora, fauna and the human body. However, in designing and developing structures and systems, learning from the common creative principles in nature is probably more important than borrowing formal patterns and models. Physical structures and systems in development are designed and modifi ed in response to needs that arise at various interfaces concerning societies and individuals. Principles, learned from nature, and adopted as approaches to structural and behavior aspects of design can assist in resolving successfully intrinsic and extrinsic interface problems of interactions in space and time. The signifi cance of the principles of heterogeneity, complexity, adaptability and integration grows with ever-deepening exploration of nature. Their manifestations are found in an endless variety of forms and relationships in the universe. The lessons derived from nature contribute to a general philosophy of engineering design and justify solutions toward innovations and sustainable existence.Human-induced soil erosion and drastic change in land use practices have adversely infl uenced the land degradation and surface runoff response in upper Njoro River catchment. The drainage area is approximately 127 km 2 . Due to human activities, the land has been exposed to accelerated erosion and low land productivity, water scarcity, decline in ground water recharge, siltation of Lake Nakuru and other sediment sinks. This study was conducted to establish event-based risk areas for prioritized conservation within the catchment. Spatially distributed soil erosion map was created as a ratio of sediment yield to sediment delivery ratio (SDR). Modifi ed Universal Soil Loss Equation (MUSLE) integrated within a Geographical Information Systems environment was used to create the sediment yield map. Spatial data layers for the MUSLE were derived from a 20-m resolution Digital Elevation Model, soil property, land use maps and climatic data of the catchment. Land use map was derived from Landsat imagery via its processing using Integrated Land and Water Information Systems software. The results show that the spatially distributed soil erosion ranged from 0.06 to 0.51 t/ha for a 43.2-mm rainfall event. Spatially distributed SDR ranged from 0.09 to 0.82, while the average SDR for the whole catchment was 0.72. These values were derived using an empirical equation. A new contribution was made by developing spatially distributed slope length factor, SDR, runoff volumes, MUSLE parameters and classifi ed erosion risk areas for prioritized catchment conservation. This means that the event-based soil erosion classifi cation can be adopted for prioritized soil and water conservation within Njoro catchment.Industrial design is an applied art where the aesthetics and the usability of products may be improved. During the 20th century, we have seen an interesting transformation in our society from hand-made consumer goods designed and made by skilled craftsmen to mass production using new materials and technologies. Design aspects specified by the industrial designer may include the object’s overall shape, the location of the details with respect to one another, colours, textures and ergonomics. Often, through the application of industrial design, a product’s appeal to the consumer is greatly improved. Industrial design consists of the ideation of a shape or configuration, or composition of a pattern or colour. An industrial design can be a twoor three-dimensional pattern used to produce an object. For many years designers were inspired by Euclidean geometry and Euclidean shapes (e.g. triangles, squares, Platonic solids and polyhedra), and it is not surprising that industrial design objects have Euclidean characteristics. The evolution of materials (e.g. steel, plastic, glass) and technologies (from hand-made products to Computerized Numeric Control) have permitted designers to overcome the limits imposed by Euclidean geometry. Thus, modern design studies apply complex shapes and fractal geometry to create new kinds of objects that have futuristic shapes. The aim of this paper is to present some examples of industrial design objects that are analysed using the complexity and the fractal geometry.In this paper, the effect of a wavy fl ow on the motion of a body in water or air is considered. Experimental results are reviewed, which show that fl ow waviness decreases the hydrodynamic or aerodynamic drag and even generates a forward thrust. The physics of this phenomenon is explained and examples of research vessels, dirigible balloons and unmanned air vehicles are given, which demonstrated the usefulness of this effect. The design of future vehicles is discussed to draw attention to the potential of wave propulsion for technical applications.Constructed wetlands are complex dynamic ecosystems. Ecosystem-level modeling of the processes that take place in a constructed wetland is a useful tool for understanding wetland function and structure and for making predictions. We present a primary productivity model for the wetland that is currently under construction in the area of Carla in central Greece, restoring one of the most important wetlands in Europe that was drained in 1962. The model includes the area’s hydrology and geomorphology and is used to explore the role of different wetland structures and functions on the dynamics of primary producers and sediments in the constructed ecosystem, in order to provide a better understanding of the processes involved and the nutrient dynamics in these processes.Insect-inspired micro air vehicles (MAVs) have been the subject of extensive research in recent years for a range of novel applications. The current generation of vehicles, however, has yet to match even a fraction of the performance of insect fl ight, in particular with respect to manoeuvrability and payload capacity. Precise reproduction of insect-like fl apping motion on the micro-vehicle scale holds signifi cant potential to address this defi ciency. The design and optimisation of this critical aspect of an insect-inspired MAV is the subject of this paper. The actuated fl apping mechanism must deliver a high power output via complex wing kinematics, which should be dynamically adjustable for controlled fl ight without the need for traditional control surfaces. This paper fi rst addresses several key fl apping MAV design criteria that greatly infl uence the power requirements and aerodynamic forces for fl ight, through an assessment of design parameters such as wing length and wingbeat frequency. Two solutions are then proposed that meet these requirements while satisfying the current limitations of miniature actuation technologies and issues related to mechanism constraint. The fi rst of these, the development of an ‘artifi cial muscle’ actuator is crucial to the feasibility of a highly adjustable, lightweight under-constrained fl apping mechanism. A prototype ‘artifi cial muscle’ based on a silicone dielectric elastomer was tested and found to produce a strain output comparable to muscle. We also report the development of an alternative fl apping mechanism solution utilising conventional rotary DC motors. The novel parallel crankrocker (PCR) mechanism produces similar wing kinematics to insects and, unlike previously developed DC motor-driven MAV fl apping mechanisms, it allows dynamically adjustable control of the wing angle of attack. Aerodynamic testing of a PCR prototype found that it produced a maximum lift force of 6.4 g per wing pair at a wingbeat frequency of 13.2 Hz. Wind tunnel testing with high-speed fl ow visualisation footage showed that the measured lift forces are augmented by a bound leading edge vortex on the downstroke, which is the mostThis paper describes an active vision system based reverse engineering approach to extract the 3D geometric information from dental cast/teeth and transfer this information into computer-aided design/computer-aided manufacture (CAM) systems to improve the accuracy of the constructed units for patient care. The benefits of our approach are a non-contact measurement, low cost, and capturing all the surface data at the same time. Our system involves the development of a vision rig prototype accommodating up to three charged couple device cameras, image processing, and shape recovery from a series of convex profile (2D) images of complex objects morphology (e.g. incisor or sunflower seed). The rig is designed using engineering design methods such as a concept selection matrix and a weighted objectives evaluation chart. The rig concept design is based on the human/stereo vision principles in computer vision. The occluding boundary technique and its derived method, the slicing method, are described and employed by the vision system to generate (3D) models of two typical teeth using a dental cast. Comparison of the vision system and the Renishaw Triclone dental system is demonstrated on these two models with one of them being manufactured using CAM technology. The results have shown that our vision system is capable of supporting the advanced reverse design applications in restorative dentistry. It is concluded that the new system could encode the shape of small complex objects and the device could be useful in the characterization of natural materials as a basis for biology-based design.This paper reports on a piece of research which attempts to take 32 different images of landforms and to show how different classes of people perceive or “value” the scenic beauty of these landforms. This is an interesting question and one which bears research. In this case the term “scenic beauty” refers to the public preference of various forms of the earths relief. It is a figure which, even though it depends on various subjective factors, aims to quantify the general preference of the public for various landforms. A questionnaire survey takes place in order to investigate the public preference, using a sample of 221 persons in the area of Athens and Piraeus, and the city suburbs. This area concentrates a very large proportion of Greeces population and can ensure variety in terms of social and demographic status of the sampled population. The means used to demonstrate the various forms of relief are 32 digital relief images, created with the use of an algorithm developed for this purpose. The representative selection of the sample of digital images took place after the classification of the forms of relief in Lefka Ori mountain range in Crete. The questionnaire included 11 questions describing the person questioned in relation to the environment he/she has experienced or knows and his/her contact with the countryside. Each question corresponded to a factor (e.g. age, sex, education, income etc.) that had been generalised in categories. Following this, a primary statistical analysis of variance was carried out for each of the factors examined and some preliminary results are reported. Little research in this specific area has been done and it is interesting to explore further the way people with different social backgrounds react or perceive the various landforms.The electro-osmotically driven flow near an earthworm’s body surface is a basic electrokinetic phenomenon that takes place when the earthworm moves in moist soil. The flow in a micro thin layer of water is formed in the vicinity of the earthworm’s body surface as a result of the electric double layer interaction. Such a micro scale electro-osmotically driven flow plays the role of lubrication between the earthworm’s body surface and the surrounding medium of moist soil and reduces the surface adhesion. The examples of bionic design in engineering inspired by such natural phenomena of the earthworm in soil are reported.The petiole is a plant organ that connects the stem to the blade of a leaf. The petiole is made up of a fi brous biomaterial that consists of three integrated tissues. Each of these specializes in different functions, but they work together to provide basic needs, such as nutrient transport, food storage and plant support. From a structural viewpoint, the petiole resembles a cantilever that should resist wind torsion and gravity bending forces acting on the leaf blade. It has a solid cross-section with a grooved fl attened asymmetric shape with size decreasing lengthwise. As all plant organs, the petiole morphology is developed by adaptive growth, which is the plant response to environmental stimuli. Thus, the petiole grows a shape that best optimizes the use of vital resources. This paper focuses on the structural effi ciency of the shape petiole and it examines the capability of the petiole in reducing the wind drag without sagging under gravity forces. Continuum mechanics and dimensionless factors are used to model the twist-to-bend ratio. Twenty specimens of Polygonaceae Rheum rhabarbarum plants were investigated. The results are visualized on maps that contrast the petiole shape properties to those of ideal cross-sections.It is increasingly recognized that growing demands for diverse, multifunctional and quality recreation landscapes have placed a high pressure on the natural resources and its management. This fact coupled with the current common way of perceiving landscape as something separate from us, with several functions for society and individuals – in spite of something that changes automatically according to cultural, economic and social changes, enhances the necessity for developing new approaches and methodologies that effectively apply sustainable principles to landscape monitoring, planning and management. For this reason, adequate information about the existing landscape and about the nature of places that it is desirable to make cannot be the result of superfi cial approaches based exclusively on designers and planners’ ideas. Even if planning and monitoring programs frequently use remote sensing data and focus only on changes in land cover and land use in relation to values such as biodiversity, land capability and recreation, they often neglect landscape aesthetics, cultural heritage and public will. To show that it is possible to combine all these factors in a specifi c approach, this paper presents a specifi c study of the estuarine landscape of the Arade River in Algarve, Portugal, based on a methodology that incorporates SWOT (strengths, weaknesses, opportunities and threats) analysis and aesthetic, cultural, biophysical and social factors in landscape assessment.

Rebound Effect and Structural Change

The rebound effect (RE) is an unintended increase in energy usage due to the introduction of an energy-efficient technology and the consequential lower price of the relative energy service (brief intro to the idea helpful). The RE arguably poses serious threats to the ongoing energy conservation and GHG-mitigating policies. This alarming issue is now widely recognized by the scientific community. Last year the European Commission (DG environmental unit C2) commissioned, for the first time, a study on the RE, acknowledging the need of approaching this problem and urging more research on this important topic. Current modeling methodologies of the RE are time- and space limited. In this chapter we show that there are structural changes in the economy, occurring on a long range of time and concerning the whole productive structure, that are energy demanding. We approach structural changes with network theory and statistical mechanics of networks to show to what extent they can be regarded as an increase in complexity of transport systems. We analyze these changes in the light of economic growth theory and more broadly, of growth theory of metabolic processes. We finally advanced a heuristic explanation of structural changes based on saturation and symmetry breaking.

Paper on the energy efficiency evolution in the European road freight transport sector

One of the goals of WP7 is that of analyzing the energy crisis within the global economic crisis and assess to what extent fuel prices can promote the transition towards a more sustainable and efficient energy regime. This paper addresses the European freight transport system, national and cross-boarder, and assesses the evolution of its efficiency and intensity during the period 1998-2011, when oil prices globally increased, up the hike of the 2008. It will also be investigated the rebound effect in the sector according to two different approaches: 1) a standard, econometric approach based on regressing the elasticity of energy efficiency and energy service; 2) a new methodology based on network theory and statistical mechanics. According to the econometric approach to the European freight transport sector there was a positive rebound of about 40% globally and 38% on cross-border trade, whereas there was no significant (cross-border) rebound in Europe according to the model based on network theory. Interestingly, this latter model showed that the cross-border European freight transport network is more efficient compared to other regional networks and to the world, because weights more mass than money in its exchanges.