A structural theory of mutualistic networks

2020 ◽  
pp. 93-115
Author(s):  
Jordi Bascompte ◽  
Antonio Ferrera
Keyword(s):  
Structural Stability ◽  
Network Architecture ◽  
Interaction Strength ◽  
Dynamical Stability ◽  
Theoretical Ecology ◽  
Feasibility Constraints ◽  
Living Species ◽  
Mutualistic Networks ◽  
Set Up ◽  
Parameter Values

Mutualistic interactions among free-living species have shaped much of biodiversity on Earth. Ironically, however, mutualism has not been prominently featured in theoretical ecology. Recent efforts have tried to fill this gap by assessing to what degree the structure of plant-animal mutualistic networks affects species persistence. Here, we review this growing literature emphasizing how different papers relate to each other and to what extent their conclusions depend on particular assumptions. A central concept in this effort is that of structural stability. While main approaches in theoretical ecology focus on local dynamical stability, structural stability shifts the question to how large is the range of parameter values compatible with the stable coexistence of all species. This structural approach has shown that mutualism has to be understood as a balance to competition and that network architecture should be seen as affected by both stability and feasibility constraints. Constraints on the dynamical stability of these communities set up a maximum mutualistic strength. Constraints on their feasibility tend to push interaction strength near this limit and select for a nested architecture. These results, however, assume similar interspecific competition amongst species and very small mutualistic strength. Future work should thus explore the consequences of relaxing these constraints.

scholarly journals Application of intelligent orienteering based on Internet of things

2020 ◽  
Vol 2020 (1) ◽  
Author(s):  
Donghui Zhang ◽  
Ruijie Liu
Keyword(s):  
Internet Of Things ◽  
Network Architecture ◽  
Emergency Services ◽  
Simulation Experiment ◽  
Experimental Studies ◽  
Signal Stability ◽  
Anchor Nodes ◽  
Set Up ◽  
The Relationship ◽  
The Internet Of Things

Abstract Orienteering has gradually changed from a professional sport to a civilian sport. Especially in recent years, orienteering has been widely popularized. Many colleges and universities in China have also set up this course. With the improvement of people’s living conditions, orienteering has really become a leisure sport in modern people’s life. The reduced difficulty of sports enables more people to participate, but it also exposes a series of problems. As the existing positioning technology is relatively backward, the progress in personnel tracking, emergency services, and other aspects is slow. To solve these problems, a new intelligent orienteering application system is developed based on the Internet of things. ZigBee network architecture is adopted in the system. ZigBee is the mainstream scheme in the current wireless sensor network technology, which has many advantages such as convenient carrying, low power consumption, and signal stability. Due to the complex communication environment in mobile signal, the collected information is processed by signal amplification and signal anti-interference technology. By adding anti-interference devices, video isolators and other devices, the signal is guaranteed to the maximum extent. In order to verify the actual effect of this system, through a number of experimental studies including the relationship between error and traffic radius and the relationship between coverage and the number of anchor nodes, the data shows that the scheme studied in this paper has a greater improvement in comprehensive performance than the traditional scheme, significantly improving the accuracy and coverage. Especially the coverage is close to 100% in the simulation experiment. This research has achieved good results and can be widely used in orienteering training and competition.

scholarly journals An enhanced set of displacement parameter restraints in CRYSTALS

2018 ◽  
Vol 51 (4) ◽  
pp. 1059-1068 ◽  
Author(s):  
Pascal Parois ◽  
James Arnold ◽  
Richard Cooper
Keyword(s):  
Structural Model ◽  
Rigid Bodies ◽  
Model Parameters ◽  
Coordinate Systems ◽  
Principal Axes ◽  
Anisotropic Displacement Parameters ◽  
Set Up ◽  
Meaningful Relationships ◽  
Parameter Values ◽  
Total Model

Crystallographic restraints are widely used during refinement of small-molecule and macromolecular crystal structures. They can be especially useful for introducing additional observations and information into structure refinements against low-quality or low-resolution data (e.g. data obtained at high pressure) or to retain physically meaningful parameter values in disordered or unstable refinements. However, despite the fact that the anisotropic displacement parameters (ADPs) often constitute more than half of the total model parameters determined in a structure analysis, there are relatively few useful restraints for them, examples being Hirshfeld rigid-bond restraints, direct equivalence of parameters and SHELXL RIGU-type restraints. Conversely, geometric parameters can be subject to a multitude of restraints (e.g. absolute or relative distance, angle, planarity, chiral volume, and geometric similarity). This article presents a series of new ADP restraints implemented in CRYSTALS [Parois, Cooper & Thompson (2015), Chem. Cent. J. 9, 30] to give more control over ADPs by restraining, in a variety of ways, the directions and magnitudes of the principal axes of the ellipsoids in locally defined coordinate systems. The use of these new ADPs results in more realistic models, as well as a better user experience, through restraints that are more efficient and faster to set up. The use of these restraints is recommended to preserve physically meaningful relationships between displacement parameters in a structural model for rigid bodies, rotationally disordered groups and low-completeness data.

Motion of slender bodies in unsteady Stokes flow

2011 ◽  
Vol 688 ◽  
pp. 66-87 ◽  
Author(s):  
Efrath Barta
Keyword(s):  
Stokes Flow ◽  
Slenderness Ratio ◽  
Creeping Flow ◽  
Slender Body Theory ◽  
Wide Range ◽  
Unsteady Stokes Flow ◽  
Slender Bodies ◽  
Set Up ◽  
Micro Organisms ◽  
Parameter Values

AbstractThe flow regime in the vicinity of oscillatory slender bodies, either an isolated one or a row of many bodies, immersed in viscous fluid (i.e. under creeping flow conditions) is studied. Applying the slender-body theory by distributing proper singularities on the bodies’ major axes yields reasonably accurate and easily computed solutions. The effect of the oscillations is revealed by comparisons with known Stokes flow solutions and is found to be most significant for motion along the normal direction. Streamline patterns associated with motion of a single body are characterized by formation and evolution of eddies. The motion of adjacent bodies results, with a reduction or an increase of the drag force exerted by each body depending on the direction of motion and the specific geometrical set-up. This dependence is demonstrated by parametric results for frequency of oscillations, number of bodies, their slenderness ratio and the spacing between them. Our method, being valid for a wide range of parameter values and for densely packed arrays of rods, enables simulation of realistic flapping of bristled wings of some tiny insects and of locomotion of flagella and ciliated micro-organisms, and might serve as an efficient tool in the design of minuscule vehicles. Its potency is demonstrated by a solution for the flapping of thrips.

Tuners review: How crucial are set-up values to find effective parameter values?

2018 ◽  
Vol 76 ◽  
pp. 108-118 ◽  
Author(s):  
Elizabeth Montero ◽  
María-Cristina Riff ◽  
Nicolás Rojas-Morales
Keyword(s):  
Effective Parameter ◽  
Set Up ◽  
Parameter Values

Trans-lithospheric diapirism documented in the Variscan Bohemian Massif – comparison with numerical models

2020 ◽  
Author(s):  
Petra Maierová ◽  
Karel Schulmann ◽  
Pavla Štípská ◽  
Taras Gerya ◽  
Ondrej Lexa
Keyword(s):  
Bohemian Massif ◽  
Numerical Models ◽  
Typical Feature ◽  
Crustal Material ◽  
Plate Interface ◽  
Peak Metamorphism ◽  
Subducting Plate ◽  
Set Up ◽  
Parameter Values ◽  
Temperature Time

<p>In the easternmost part of the European Variscan collisional belt, the Bohemian Massif, strongly metamorphosed felsic rocks crop out at several locations in a current distance of up to several hundreds of kilometers from the supposed contact of the subducting and overriding plates. These rocks were interpreted to originate from the subducting plate (now the Saxothuringian domain), which means that the orogenic root (the Moldanubian domain) consists of rocks that originate from both upper and lower plate. More specifically, the root domain is composed of (U)HP granulites and orthogneiss, garnet peridotites, eclogites and ultra-potassic plutons that alternate with the less metamorphosed rocks of the upper plate.</p><p>Such a process of subduction and emplacement of the subducted crust into the upper plate is called relamination. In order to better constrain the dynamics of relamination, we set up a numerical thermal-mechanical model and compare the modeling results with the data from the Bohemian Massif. The model simulates oceanic and continental subduction and takes into account non-linear visco-plastic rheology, percolation of fluids, melting and melt extraction. For different parameter values, the models show different styles of behavior, namely (i) exhumation of the subducted crust along the plate interface, and (ii) flow of the subducted crust beneath the upper plate and then incorporation into its crust (i.e. relamination).</p><p>In the former case, the material records heterogeneous peak metamorphism sampling the conditions along the subduction zone, and cooling during decompression. Similar features are typical for the metamorphic complex in the Saxothuringian domain of the Bohemian Massif.</p><p>In the latter case, the typical feature is the development of diapirs that grow from the subducted continental crust, pierce the overlying lithosphere and intrude into the middle crust of the upper plate. We show that growth of such trans-lithospheric diapirs results in a similar rock assemblage as observed in the orogenic root in the Bohemian Massif. The pressure-temperature-time paths obtained in the modeled diapirs mimic those of the Moldanubian granulites. The flow of crustal material through the mantle wedge results into mixing, hydration of the mantle and melting of both materials. Emplacement of the resulting melt into crust can explain formation of the Moldanubian ultra-potassic plutons.</p>

scholarly journals Multiple states for flow through a collapsible tube with discontinuities

2014 ◽  
Vol 761 ◽  
pp. 105-122 ◽  
Author(s):  
A. Siviglia ◽  
M. Toffolon
Keyword(s):  
Past History ◽  
Steady State Solution ◽  
External Pressure ◽  
The Other ◽  
Critical Conditions ◽  
Actual State ◽  
Collapsible Tube ◽  
Set Up ◽  
Parameter Values ◽  
Flow States

AbstractWe study the occurrence of the multiple steady states that flows in a collapsible tube can develop under the effect of: (i) geometrical alterations (e.g. stenosis), (ii) variations of the mechanical properties of the tube wall, or (iii) variations of the external pressure acting on the conduit. Specifically, if the approaching flow is supercritical, two steady flow states are possible in a restricted region of the parameter space: one of these flow states is wholly supercritical while the other produces an elastic jump that is located upstream of the variation. In the latter case the flow undergoes a transition through critical conditions in the modified segment of the conduit. Both states being possible, the actual state is determined by the past history of the system, and the parameter values show a hysteretic behaviour when shifting from one state to the other. First we set up the problem in a theoretical framework assuming stationary conditions, and then we analyse the dynamics numerically in a one-dimensional framework. Theoretical considerations suggest that the existence of multiple states is associated with non-uniqueness of the steady-state solution, which is confirmed by numerical simulations of the fully unsteady problem.

Restoration of the Tsar-Bell Pedestal in the Moscow Kremlin

2010 ◽  
Vol 133-134 ◽  
pp. 1155-1159
Author(s):  
Andrew Shilin ◽  
Michail Zaitsev ◽  
Alexey Kirilenko ◽  
Leonid Fabijansky
Keyword(s):  
Cultural Heritage ◽  
Structural Stability ◽  
Structural State ◽  
Technical Information ◽  
Main Idea ◽  
Historic Buildings ◽  
Metal Elements ◽  
Set Up ◽  
Technical Solutions ◽  
Underlying Soil

The report contains brief historic and technical information about the Tsar-Bell as well as the structure of its pedestal and gives a detailed description of the instrumental inspection performed to assess structural state of the monument which included examination of the pedestal broad stone/brick masonry and metal fixing elements, check drilling and probing. The inspection results set up the basis for the restoration works. The authors describe basic technical solutions for strengthening of the pedestal foundation and underlying soil providing structural stability and protection. Some of the solutions were tried out before to strengthen foundations of old historic buildings and cultural heritage monuments. Restoration procedure of the pedestal superstructure is explained in detail including refurbishment of its metal elements, internal and external lining, special drainage systems installed under the pedestal. It must be noted that the main idea of this interesting project was to choose appropriate technical solutions and materials which allowed not only to restore the monument but also to preserve its historic appearance.

Optimization of One Legged Hopping Robot Hardware Parameters via Solidworks

2013 ◽  
Vol 393 ◽  
pp. 544-549
Author(s):  
N.H.A. Rahim ◽  
A.M. Kassim ◽  
M.F. Miskon ◽  
A.H. Azahar ◽  
H. Sakidin
Keyword(s):  
Normal Distribution ◽  
Optimum Parameter ◽  
Hopping Robot ◽  
Set Up ◽  
Spring Coefficient ◽  
Parameter Values ◽  
Best Parameters

This paper discussed about simulation of one legged hopping robot via Solidworks software in order to determine the optimum hardware parameters of the hopping robot. Simulations have been done according to different variables that have been set up earlier which are crank bar length, spring length and spring coefficient. The best parameters were chosen in terms of higher and stable hopping performance. Besides that, an experiment is done to validate the parameters from the simulation. Average hopping height is discussed and overall performances of hopping height stability are proved by the normal distribution graph. As the result, the optimum parameter values for hardware of one legged hopping robot are validated.

scholarly journals Application of Intelligent Orienteering Based on Internet of Things

2020 ◽  
Author(s):  
Donghui Zhang ◽  
Ruijie Liu
Keyword(s):  
Internet Of Things ◽  
Network Architecture ◽  
Emergency Services ◽  
Simulation Experiment ◽  
Experimental Studies ◽  
Signal Stability ◽  
Anchor Nodes ◽  
Set Up ◽  
The Relationship ◽  
The Internet Of Things

Abstract Orienteering has gradually changed from a professional sport to a civilian sport. Especially in recent years, orienteering has been widely popularized. Many colleges and universities in China have also set up this course. With the improvement of people's living conditions, orienteering has really become a leisure sport in modern people's life. The reduced difficulty of sports enables more people to participate, but it also exposes a series of problems. As the existing positioning technology is relatively backward, the progress in personnel tracking, emergency services and other aspects is slow. To solve these problems, a new intelligent Orienteering application system is developed based on the Internet of things. ZigBee network architecture is adopted in the system. ZigBee is the mainstream scheme in the current wireless sensor network technology, which has many advantages such as convenient carrying, low power consumption, and signal stability. Due to the complex communication environment in mobile signal, the collected information is processed by signal amplification and signal anti-interference technology. By adding anti-interference devices, video isolators and other devices, the signal is guaranteed to the maximum extent. In order to verify the actual effect of this system, through a number of experimental studies including the relationship between error and traffic radius and the relationship between coverage and the number of anchor nodes, the data shows that the scheme studied in this paper has a greater improvement in comprehensive performance than the traditional scheme, significantly improving the accuracy and coverage. Especially the coverage is close to 100% in the simulation experiment. This research has achieved good results and can be widely used in Orienteering Training and competition.

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