Search

Lassalle, G., Lobry, J., Le Loc'h, F., Mackinson, S., Sanchez, F., Tomczak, M. T., and Niquil, N. 2013. Ecosystem status and functioning: searching for rules of thumb using an intersite comparison of food-web models of Northeast Atlantic continental shelves. – ICES Journal of Marine Science, 70:135–149. This work aimed to provide a better understanding of how the structure and function of marine ecosystems and trophic control mechanisms influence their response to perturbations. Comparative analysis of Ecopath models of four Northeast Atlantic ecosystems was used to search for rules of thumb defining the similarities and differences between them. Ecosystem indicators, related to the ecology of species interactions, were derived from these models and compared. Two main questions were addressed. (i) What are the main energy pathways and mechanisms of control? (ii) Do these ecosystems exhibit the widespread and potentially stabilizing food-web structure such that top predators couple distinct energy pathways? A strong bentho-pelagic coupling operated over the Bay of Biscay Shelf, while energy reached higher trophic levels mostly through pelagic compartments, in northern areas. Zooplankton was demonstrated to be trophically important in all ecosystems, acting as a regulator of the abundance of small pelagic fish. A latitudinal pattern in flow control was highlighted by this analysis, with a significant contribution of top-down effect at higher latitudes. This top-down control of the Baltic Sea, combined with the fact that this ecosystem did not exhibit the potentially stabilizing two-channel structure, suggested a non-stable environment.

cited By (since 1996)0; International audience; The computational problem of emergy within a general system of interconnected processes at steady state is a subject of interest in literature today. When there is no co-product the proposed method coincides with the Track Summing Method of Tennenbaum which was developed precisely for interconnected networks with feedbacks and splits of emergy. As the underlying algebraic structure of the Tennenbaum's method is the linear algebra, it is not well-suited to account for the co-product problem which induces the idempotent operator max. Thus, authors have chosen another underlying algebraic structure which is the idempotent semiring structure (i.e. a semiring equipped with an idempotent addition). This method is divided into two parts. The first part is the emergy flow enumeration, where paths from an emergy source to the input of a given process are enumerated avoiding double counting of emergy assignation. This part is a path-finding problem which is a slight modification of gerbier of null square approach to find elementary/simple paths in a graph. The second part evaluates the emergy flowing between two components of the system. It is a quantitative part in which the problem of avoiding double counting split and co-product flows are dealt with by introducing a way to mark splits and co-products flows. The method is partially parallelizable. However, the method enumerates paths on a graph thus, in worst cases, its complexity is not polynomial. This paper provides a rigorous framework based on an axiomatic basis to conduct the emergy evaluation of an emergy graph. © 2012 ISEIS All rights reserved.

The field of multi agen systems’ (MAS) organizational design deals with providing methods for building organizational architecture of MAS organizations. Herein, an active graph grammar (AGG) formalism, inspired by current research in graph and active database theory is introduced and applied to modeling MAS organizational structure. By defining organizational units in a recursive way, it is shown that labeled graphs and hypergraphs can be used to model various levels of organizational structure. The newly developed method is graphical, event-driven and applicable in a distributed MAS environment.

[Departement_IRSTEA]Territoires [TR1_IRSTEA]SEDYVIN; International audience; Graph-based analysis is a promising approach for analyzing the functional and structural connectivity of landscapes. In human-shaped landscapes, species have become vulnerable to land degradation and connectivity loss between habitat patches. Movement across the landscape is a key process for species survival that needs to be further investigated for heterogeneous human-dominated landscapes. The common frog (Rana temporaria) was used as a case study to explore and provide a graph connectivity analysis framework that integrates habitat suitability and dispersal responses to landscape permeability. The main habitat patches influencing habitat availability and connectivity were highlighted by using the software Conefor Sensinode 2. 2. One of the main advantages of the presented graph-theoretical approach is its ability to provide a large choice of variables to be used based on the study's assumptions and knowledge about target species. Based on dispersal simulation modelling in potential suitable habitat corridors, three distinct patterns of nodes connections of differing importance were revealed. These patterns are locally influenced by anthropogenic barriers, landscape permeability, and habitat suitability. And they are affected by different suitability and availability gradients to maximize the best possible settlement by the common frog within a terrestrial habitat continuum. The study determined the key role of landscape-based approaches for identifying the "availability-suitability-connectivity" patterns from a local to regional approach to provide an operational tool for landscape planning.

Duration of the processing cycle is related to the wide range of problems and requires knowledge of the set of variables: the order processing, the spatial arrangement of equipment and schedule of production quantity. The planning of production cycle includes a number of interdependent variables which includes all activities: technological and transport operations. With graphical depiction of the production cycle it is possible to simulate the material flow in production systems, and the value of this way of planning is most obvious in cases of multi products production systems.

Many optimization problems are characterized by the flexibility to establish utility between the objective functions. The experimental strategy plays an important role in generating these objective functions, in addition, it has been conveniently applied to reduce quality costs and in the continuous improvement of the quality of processes and products. It is common to find many industrial applications with several responses whose purpose is to achieve the overall quality of a product, so it is necessary to simultaneously optimize the responses of interest. In essence, the problem of optimization of several responses involves selecting a set of independent variables such conditions or that result in a product or service appropriate. That is, it is desired to select the levels of the independent variables that optimize all the answers at the same time., Muchos problemas de optimización son caracterizados por la flexibilidad para establecer la utilidad entre las funciones objetivo. La estrategia experimental desempeña un papel importante para generar estas funciones objetivo, además, ésta se ha aplicado de manera conveniente para disminuir costos de calidad y en la mejora continua de la calidad de procesos y productos. Es frecuente encontrar muchas aplicaciones industriales con varias respuestas cuya finalidad es alcanzar la calidad global de un producto, por lo que es necesario optimizar de manera simultánea las respuestas de interés. En esencia, el problema de optimización de varias respuestas involucra la selección de un conjunto de condiciones o variables independientes tales que den como resultado un producto o servicio adecuado. Es decir, se desea seleccionar los niveles de las variables independientes que optimicen todas las respuestas a la vez.

In this article we consider the problem of testing for parameter changes in ARIMA models based on the cusum test. The proposed test procedure is applicable to testing for the change from stationary models to non stationary models, and vice versa. The idea is to transform the time series via differencing to make the whole time series as a combination of stationary subseries. For this task, we propose a graphical method to identify the right order of differencing. Then the cusum test statistic proposed by Lee et al. (2003) is constructed based the differenced time series. Simulation study and real data analysis are provided for illustration.

The methods of ventilation meshes solving are described in details and possibilities for their application are analysed. The numerical method is programmed for digital computer.

In this study, a graphical method is presented to detect sigmoidal binding of in vivo data at low nonsaturating doses. The method can also be applied when the overall binding includes nonspecific binding. Irrespective of the mathematical expression describing the saturation curve, it is shown that a sigmoid curve, in contrast to a nonsigmoid, can be converted into a peak-shaped curve by normalizing the ordinate values with the corresponding value of the abscissa. Computer simulations of in vivo ligand binding demonstrate this principle for in vivo data plots. Experimental results are described to illustrate this approach based on in vivo binding of the neuroleptic drug N-methylspiperone in the rat brain. It is concluded that the method is in particular useful for in vivo applications, e.g., positron emission tomography (PET) studies in human, because low doses are required, and specifically bound, nonspecifically bound, and unbound ligand do not need to be determined separately.

To implement for large inventory systems becomes rather cumbersome because each item requires managements of order cycle and quantity. The inventory control problem is greatly simplified as only a few groups rather than many items will have to be controlled. This method is the ABC analysis. A.K. Chakaravarty have showed that the optimal groups possess the property of consecutiveness that they are composed of items ordered by the product of their demand rate and holding cost rate (PDHC). The grouping scheme can thus be viewed as a simple process of dividing the items into optimal ranges of the PDHC values. Further the order cycle grouping is shown to be, usually, superior to the order quantity grouping scheme. This paper discusses the analytic properties of the problem of grouping that is modelled as a dynamic programming. Further the graphical method of the order cycle grouping is shown with the numerical method. Also, the economical consideration of almost optimal groups which is based on the principle of dividing the items into convinient ranges of their usage cost rates, is given and we have compared our method with ABC analysis.

Department of Chemistry, Visva-Bharati, Santiniketan 731285 Manuscript received 18 January 1977, revised 4 July 1977, accepted 21 November 1977 Proton-ligand stability constant of hippuric acid as also of glycine, α and β-alanine determined by the method of Irving-Rossotti in 50% V/V ethanol-water mixture at 30°and 0.1 ionic-strength have been reported. The log \(K_1^H\) and log \(K_2^H\) values for the three amino acids have also been reinvestigated in water medium under similar conditions.The differences of stability constant values in the mixed solvent and water are fairly positive in case of log \(K_2^H\) (for carboxylic proton) and slightly negative in case oflog \(K_1^H\) , as expected. In case of β-alanine, log \(K_2^H\) value is higher than that of the at-isomer due to the increased distance of the amino and the carboxylic groups. The pK* value for hippuric acid as computed by half-integral and graphical method has been found to be 4.3 at 30° and 0.1 ionic strength.

The chemical composition of low temperature cofired ceramics (LTCC) allows to locally embed air into sintered substrates by a selective wet chemical etch process. Therefore, LTCC substrate with areas of low permittivity can be created without material combination. The presented graphical method of material component contrast images enables the evaluation of their most important material properties which are their component distribution, their porosification gradient and their residual bearing surface. The graphical method, including focused ion beam and scanning electron microscopy analyses, is applied to different commercially available LTCC types having two porosification states each. Derived mathematical models, which are suitable for finite element method implementation, allow the characterisation of the effective permittivity reduction while keeping a maximum residual surface area for, e.g., metallisation purposes. The shape of the optimum material distribution function features an 'air pocket' of small width and a depth being dependent on the application specific operating frequency.

Cet article traite des problèmes liés à l'étude des équilibres calco-carboniques en limitant leur présentation à l'aspect purement graphique. Dans cette optique, on a développé un nouvel abaque original en choisissant comme coordonnées pH et [CO3 total].La construction d'un tel abaque ne fait appel qu'à 2 lois fondamentales, à savoir : a) la relation du produit de solubilité du carbonate calcique :Ks=Y22[Ca2+[CO2-3]Cette dernière peut, moyenant l'introduction d'une variable auxiliaire :∆=[Ca2+]-[CO3 total]se transformer en une relation équivalente plus commode pour le calcul des courbes constitutives de l'abaque.b) une deuxième relation, prenant en compte les ions H+ soit libres, soit engagés dans des combinaisons avec le groupe carbonate ou avec le solvant H2 O. Dans ce but, on introduit une concentration totale appelée acidité potentielle totale (en abrégé APT) définie de la sorte :APT=2[H2CO3]+[HCO-3]+[H2O]+[H+]En outre, on utilise une variable dérivée de APT à laquelle on a donné le nom d'acidité potentielle carbonatée et le symbole. Sa définition est la suivante :δ=2[H2CO3]+[HCO-3]Les 2 variables et APT jouissent en commun de la propriété intéressante de rester invariantes lors de la mise en équilibre de l'eau selon l'équation :CaCO3+H+⇌Ca2++HCO-3La variable peut également être considérée comme pratiquement invariante dans le domaine des eaux naturelles.Cette propriété est mise à profit pour construire 2 réseaux de courbes constitutives de l'abaque, à savoir :a) celles satisfaisant à la condition : APT=constante. Ces dernières seront appelées "courbes d'iso-aciditéb) celles répondant à la condition : ∆=constante.On les désignera sous le nom de "courbes d'iso-équilibre"L'article s'attache à décrire le mode d'utilisation de cet abaque tout en mettant en valeur sa facilité d'emploi pour l'évaluation, tant qualitative que quantitative du comportement d'une eau à l'égard du carbonate calcique.En particulier, la technique permet de visualiser les caractéristiques essentielles de l'eau telles que pH équilibrant, pH stabilisant et indice de stabilisation, caractéristiques dont la signification est précisée dans l'article.L'abaque en question, en parallèle avec un logiciel qui peut lui être associé, constitue ainsi un outil précieux tant pour caractériser une eau que pour procéder ensuite aux traitements chimiques les plus connus.Le cas du mélange d'eaux peut également être avantageusement traité par le biais de cet abaque. De nombreux exemples d'application aux traitements de l'eau sont également largement développés dans la publication. Ceux-ci devraient aider grandement ceux qui sont confrontés aux divers problèmes de l'industrie de l'eau.L'analyse graphique constitue par ailleurs une excellente introduction à la gestion informatisée plus complète de ces problèmes et dont le traitement ne pouvait trouver place dans le cadre limité de cette publication.Le lecteur désireux de poursuivre ces développements ou d'avoir accès au programme informatique complémentaire à cette étude, trouvera les indications nécessaires dans les références bibliographiques figurant en fin de l'article., Although many good methods exist for computing calcium-carbonate equilibria, we considered that it was still possible to improve the representation to the problem and for this reason we have developed a new method of calculation. In this paper we have restricted ourselves to the graphical aspect of the question, referring the reader to the original bibliography at the end of the paper and as well we have not taken into account the kinetic aspects of the reactions involving the dissolution or precipitation of CaCO3.From this perspective, an original graph has been designed choosing for co-ordinates the pH (abscissa) and [CO3 total] (ordinate). The construction of such a graph requires only two fundamental laws, i.e.1) The solubility product relationship of calcium carbonate. This relationship, with the introduction of an auxiliary variable:∆=[Ca2+] - [CO3 total]can be transformed itself into an équivalent relationship, more convenient for the computation of the various curves composing the graph.2) A second relationship, taking into account the H+-ions in their free or bound state (with the C03 group or the H20 solvent). For this purpose, one introduces a total concentration, called potential total acidity (in abbreviated form PTA), the définition of which is:PTA=2[H2CO3]+[HCO-3]+[H2O]+[H+]In addition, one uses also another variable derived from PTA to which we gave the name : carbonated potential acidity with the following definition:δ=2[H2CO3]+[HCO-3]Both variables PTA and ∆ have jointly the interesting property of remaining constant during the evolution of the water towards equilibrium according to the equation: CaCO3+H+⇌Ca2++HCO-3The variable may also be considered as practically constant in the field of natural waters. We have taken advantage of this property to build up two networks of curves that make up the overall graph, i.e., a) the curves satisfying the condition : PTA=constant (these curves are named " iso-acidity curves "), and b) the curves whose characteristics are : =constant, and which are named " iso-equilibrium curves ".The paper describes how to use the graph and brings out its ease of use for both the qualitative and quantitative prediction of the behaviour of water in contact with calcium carbonate. In particular, the graph illustrates such essential water characteristics as equilibrium pH, stabilisation pH and stabilisation index, characteristics whose meanings are defined in the paper. The graph is shown to be a useful tool for the characterisation of waters as well as for the evaluation of most chemical treatments. The case of the mixture of different waters is also treated. Numerous examples for using the graph under different circumstances are developed in the paper, which should be useful for those whose job is connected with industrial water treatment. The graphical method here described, in conjunction with an associated computer programme, also constitutes an excellent introduction to the more complete computing methods developed elsewhere but which could not be treated in the limited frame of this publication.The graph turns out to be a useful tool for the characterisation of waters as well as for the evaluation of different chemical treatments, such as softening, carbonation, decarbonation, acidification, alkalinisation, aeration, etc. The case of the mixture of different waters is also treated. Numerous examples for using the graph under different circumstances are developed. The paper shows how it is possible, on the basis of the diagram, to predict the evolution of the water when different reagents are added, when the temperature changes or when one mixes different waters. The diagram should be a useful aid for those people whose job is connected with industrial water treatment.A computing program is necessary to draw the curves, to obtain the water characteristics with a better accuracy than can be read from the graphs. This programme, named Carbeq+, is commercially available (see below for the bibliographical reference). The values necessary for the computation and the drawing of the curves are :1. temperature of analysis and temperature of computation2. pH, alkalinity, calcium concentration3. the ionic strength, which can be calculated either from the knowledge of the complete analysis of the water, or if that one is not available, by using an empirical relation based on either the conductivity or the salt content. The program computes then the equilibrium pH, the stabilisation pH and the stabilisation index and draws the graphs described in the paper. The graphical method here described, in conjunction with the associated computer programme, constitutes also an excellent introduction to the more complete computing methods developed elsewhere but which could not be treated in the limited frame of this publication. Note that the case of the influence of the gaseous carbon dioxide phase on the equilibrium is not treated in this paper, but it is taken into account in the Carbeq+ programme mentioned above.