Degree Of Simplification Research Articles

EFFECT OF PIPES NETWORKS SIMPLIFICATION ON WATER HAMMER PHENOMENON

Simplification is an important design step of water supply and irrigation pipes networks. It is recognized by making the original network easier to be understood and analyzed. Water hammer in water-supply networks may give rise to high and low pressures, due to the superposition of reflected pressure waves. The effect of pipes networks’ simplification on water hammer phenomenon is investigated. This study uses a simple two loops pipes network composed of 12 high density polyethylenes (HDPE) pipes with different diameters, thicknesses, and roughness coefficients representing of a general parallel/series system. The network is fed from a boundary head reservoir and loaded by either distributed or concentrated boundary water demands. According to both hydraulic and hydraulic plus water quality equivalence, three levels of simplifications on the original network are performed. Also, the effect of water demands’ concentration on the transient flow is checked. The transient flow in the network is initialized by either concentrated or distributed boundary water demands which are suddenly shut-off or released. Water hammer and mass oscillation (WHAMO) software which uses the implicit finite difference scheme for solving the momentum and continuity equations at unsteady-state case is used in the simulation. All scenarios produced results showed that both hydraulic equivalence and demands’ concentration simplifications increase the transient pressure and flow rate in the simplified network compared with the original one. However, hydraulic plus water quality equivalence simplification results in an adverse effect. It was found that, as the degree of simplification increases the transient pressure head and flow rate of the simplified network deviate more from those of the original network. Therefore, simplifications of the distribution networks should be done with very careful caution.

Long-term deflections of reinforced concrete elements: accuracy analysis of predictions by different methods

Long-term deflection response of reinforced concrete flexural members is influenced by the interaction of complex physical phenomena, such as concrete creep, shrinkage and cracking, which makes their prediction difficult. A number of approaches are proposed by design codes with different degrees of simplification and accuracy. This paper statistically investigates accuracy of long-term deflection predictions made by some of the most widely used design codes (Eurocode 2, ACI 318, ACI 435, and the new Russian code SP 52-101) and a numerical technique proposed by the authors. The accuracy is analyzed using test data of 322 reinforced concrete members from 27 test programs reported in the literature. The predictions of each technique are discussed, and a comparative analysis is made showing the influence of different parameters, such as sustained loading duration, compressive strength of concrete, loading intensity and reinforcement ratio, on the prediction accuracy.

A Lippmann–Schwinger approach for the determination of photoionization and photodetachment cross sections based on a partial wave Green's function expansion and configuration interaction wave functions

A computational approach is presented for determining partial differential cross sections for molecular photodetachment and photoionization. The approach, which extends a recent treatment of negative ion photodetachment, uses multireference configuration interaction wave functions to describe both the target or residual molecule and its interaction with the scattered electron and can treat states of the residual molecule which can be described adiabatically or are non-adiabatically coupled by conical intersections. Antisymmetry is taken into account in an approximate manner and a Lippmann–Schwinger equation is used to treat the interaction of the ionized/detached electron with the residual molecule. A partial wave expansion of the requisite Green's functions enables a unified treatment of photoionization and photodetachment and achieves computational efficiencies. A matrix representation of the quantities appearing in the iterated solution to the Lippmann–Schwinger equation using the radial Green's function permits the iterated solution to be summed eliminating potential convergence issues. Two methods for determining the radial Green's functions are presented. In the standard approach the Green's function is determined using the regular and irregular solutions to the corresponding homogeneous equation. The numerical issues associated with this well-studied form of the Green's function are non-trivial. An alternative approach is introduced which uses the complex scaling technique to construct the relevant matrix elements of the Green's function. The degree of simplification achieved in this way is significant.

Absence of internal tidal beams due to non-uniform stratification

A linear internal-tide generation model is applied to the Faeroe–Shetland Channel, using observed profiles of stratification. Several degrees of simplification are considered: 1) uniform, i.e. constant N; 2) vertically varying N (z); 3) the full N(x, z) and associated geostrophic background flows. It is shown that clearly identifiable internal tidal beams and internal-wave attractors occur in the first case, but not in the other cases where the pattern is patchy due to internal reflections from the strong inhomogeneities in the medium. Given the general occurrence of pycnoclines and geostrophic background flows in the ocean, it is argued that this internal scattering can be expected to be a widespread phenomenon.

Improving the validation of finite element models with quantitative full-field strain comparisons

The techniques used to validate finite element (FE) models against experimental results have changed little during the last decades, even though the traditional approach of using single point measurements from strain gauges has major limitations: the strain distribution across the surface is not captured and the accurate determination of strain gauge positions on the model surface is difficult if the 3D surface topography of the bone surface is not measured. The full-field strain measurement technique of digital speckle pattern interferometry (DSPI) can overcome these problems, but the potential of this technique has not yet been fully exploited in validation studies. Here we explore new ways of quantifying and visualising the variation in strain magnitudes and orientations within and between repeated DSPI measurements as well as between the DSPI measurements and FEA results. We show that our approach provides a much more comprehensive and accurate validation than traditional methods. The measurement repeatability and the correspondence between measured and predicted strains vary to a great degree within and between measurement areas. The two models used in this study predict the measured strain directions and magnitudes surprisingly well considering that homogeneous and isotropic mechanical properties were assigned to the models. However, the full-field comparisons also reveal some discrepancies between measured and predicted strains that are most probably caused by inaccuracies in the models' geometries and the degree of simplification of the modelled material properties.

SIMULATION OF FLOW OF FIRE GASES IN A VENTILATION NETWORK OF A MINE WITH A APPLICATION OF MATHEMATICAL MODELS OF A DIFFERENT COMPLEXITY IMPLEMENTED IN THE VENTGRAPH SOFTWARE

The state of the flow of air in a network of headings may be determined based on the measurements or can be compared using model or simulation tests based on submitted mathematical models, which are constructed at various degrees of simplification. For forecasting the process of the ventilation of a network of mine headings, the simulation method is particularly useful, for it enables the forecasting of numerous disturbances of air flow, such as for example a subterranean fire [2], the sudden breakout of gases and rocks [1], the influx of methane that is caused by a rock mass crump [3], as well as for assessing the inertisation of the atmosphere of gobs [4, 5]. The above-mentioned issues are resolved by means of the numerical method based on the system of VENTGRAPH computer programmes, which enable the forecasting of ventilation processes under normal conditions and in emergency situations, such as a fire, and are characterised by considerable calculation possibilities, and ease of programme usage as well as interpretation of the results of the calculations [6].

Remarks on Oldroyd-B and related complex fluid models

We prove global existence and uniqueness of solutions of Oldroyd-B systems with relatively small data in R d , in a large functional setting (C � L 1 ). This is a stability result, solutions select an equilibrium and converge exponentially to it. Large spatial derivatives of the initial density and stress are allowed, provided the L 1 norm of the density and stress are small enough. We prove global regularity for large data for a model in which the potential responds to high rates of strain in the fluid. We also prove global existence for a class of large data for a didactic scalar model which attempts to capture in the simplest way the essence of the dissipative nature of the coupling to fluid. This latter model has an unexpected cone invariance in function space that is crucial for the global existence. 1. Introduction The complex fluids models we consider treat the interaction of a normal fluid (incompressible in our case) with insoluble matter suspended in it. Models have been devised to deal with microscopic elastic thread-like objects such as polymers ((12), (26)). The complicated hydrodynamic interactions are simplified using the separation of scales, replacing the many degrees of freedom due to them by few representative ones. In the models we consider here, an end-to-end vector in R 3 (m in this paper) represents the orientation of the polymer and it is the sole variable retained to describe the microscopic object. The models that are most studied with this degree of simplification include the kinetic description of the Oldroyd B model, the FENE model and variants. The probability distribution of the vectors m depends on time and physical space, and it is assumed to be absolutely continuous with respect to the usual Lebesgue measure dm, so the chance of finding m at time t and location x 2 R 3 in the volume element dm is f(x;m;t)dm. The aim is to describe the evolution of f in space and time. When the polymer concentration is so dilute that the polymers do not interact, and when the fluid is smooth, then the equation of f is a linear Fokker-Planck equation. The effect of the fluid can be understood perturbatively: because the objects suspended are assumed to have faster time scales and shorter length scales than the scales on which solvent varies, it is then justified to treat the fluid as varying little as far as the microscopic suspended objects are concerned. This macro-micro interaction can be rationally discussed, and leads to a kinetic description of the particles, given a fluid flow. On the other hand, the collective effect that the particles have on the flow itself is a macroscopic effect of microscopic insertions: a micro- macro interaction. These interactions are much more mysterious. There have been attempts to produce systematic upscalings based on non-equilibrium thermodynamics formalisms ((2), (13)). When the microscopic insertions have a larger number of degrees of freedom, m 2 M, where M is a Riemannian manifold representing a finite number of degrees of freedom with constrains, then the kinetic equation is a Smoluchowski equation on the manifold. The upscaling principle advocated by one of us ((5), (6)) is easiest formulated as the requirement that the sum of the energy of the fluid

MoleView: An Attribute and Structure-Based Semantic Lens for Large Element-Based Plots

We present MoleView, a novel technique for interactive exploration of multivariate relational data. Given a spatial embedding of the data, in terms of a scatter plot or graph layout, we propose a semantic lens which selects a specific spatial and attribute-related data range. The lens keeps the selected data in focus unchanged and continuously deforms the data out of the selection range in order to maintain the context around the focus. Specific deformations include distance-based repulsion of scatter plot points, deforming straight-line node-link graph drawings, and as varying the simplification degree of bundled edge graph layouts. Using a brushing-based technique, we further show the applicability of our semantic lens for scenarios requiring a complex selection of the zones of interest. Our technique is simple to implement and provides real-time performance on large datasets. We demonstrate our technique with actual data from air and road traffic control, medical imaging, and software comprehension applications.

A method for generating high-yield enriched neuronal cultures from P19 embryonal carcinoma cells

P19 embryonal carcinoma (EC) cells are an invaluable tool for approximating the mechanisms that govern neuronal differentiation but with an enormous degree of simplification and have primarily been used to model the early stages of neurogenesis. However, they are often cultured under conditions that promote unrestricted non-neuronal growth that compromises neuronal viability. In this study we report an improved method to differentiate P19 EC cells that gives rise to high yields of functionally and morphologically mature neurons while significantly reducing the over-growth of non-neuronal cells in the cultures. In this protocol, P19 EC cells are induced in Minimum Essential Medium alpha supplemented with all-trans retinoic acid (RA) and 2.5% serum, and cultured as a monolayer. After RA-induction, cells are cultured on Matrigel coated-plates using defined media comprised of Neurobasal-A medium temporally supplemented with N2 and then B-27 for the remaining culture period. By treating the culture with Cytosine β-d-arabinofuranoside and 2′-Deoxycytidine for five days, the cultures are reliably promoted toward the neuronal differentiation vs non-neuronal differentiation, this accounting for a progressive neuronal enrichment of the cultures reaching 56% after 20 days of culture. P19-derived neural progenitor cells progressively expressed neuronal markers such as NeuN, Calretinin, Calbindin and Synapsin I in close resemblance to that occurring in vivo in the central nervous system (CNS). Furthermore, RA-induced P19 EC cells progressively acquired functional neuronal traits and after approximately 3 weeks in culture revealed mature neurophysiological properties, characteristics of CNS neurons. This protocol allows for a more specific assessment of the neuronal differentiation processes in vitro.

Simplifying a hydrological ensemble prediction system with a backward greedy selection of members – Part 1: Optimization criteria

Abstract. Hydrological Ensemble Prediction Systems (HEPS), obtained by forcing rainfall-runoff models with Meteorological Ensemble Prediction Systems (MEPS), have been recognized as useful approaches to quantify uncertainties of hydrological forecasting systems. This task is complex both in terms of the coupling of information and computational time, which may create an operational barrier. The main objective of the current work is to assess the degree of simplification (reduction of the number of hydrological members) that can be achieved with a HEPS configured using 16 lumped hydrological models driven by the 50 weather ensemble forecasts from the European Centre for Medium-range Weather Forecasts (ECMWF). Here, Backward Greedy Selection (BGS) is proposed to assess the weight that each model must represent within a subset that offers similar or better performance than a reference set of 800 hydrological members. These hydrological models' weights represent the participation of each hydrological model within a simplified HEPS which would issue real-time forecasts in a relatively short computational time. The methodology uses a variation of the k-fold cross-validation, allowing an optimal use of the information, and employs a multi-criterion framework that represents the combination of resolution, reliability, consistency, and diversity. Results show that the degree of reduction of members can be established in terms of maximum number of members required (complexity of the HEPS) or the maximization of the relationship between the different scores (performance).

A composite computational model of liver glucose homeostasis. I. Building the composite model

A computational model of the glucagon/insulin-driven liver glucohomeostasis function, focusing on the buffering of glucose into glycogen, has been developed. The model exemplifies an 'engineering' approach to modelling in systems biology, and was produced by linking together seven component models of separate aspects of the physiology. The component models use a variety of modelling paradigms and degrees of simplification. Model parameters were determined by an iterative hybrid of fitting to high-scale physiological data, and determination from small-scale in vitro experiments or molecular biological techniques. The component models were not originally designed for inclusion within such a composite model, but were integrated, with modification, using our published modelling software and computational frameworks. This approach facilitates the development of large and complex composite models, although, inevitably, some compromises must be made when composing the individual models. Composite models of this form have not previously been demonstrated.

Civilising Globalisation. Human Rights and the Global Economy. By DAVID KINLEY

Most of those who work in human rights-related fields ask themselves the question, at some point, about the interdependence between human rights and economic welfare. With a certain degree of simplification, one could argue that human rights concerns are often brought to international fora by developed Western countries, with the major violators of human rights being poorer developing countries. However, it still remains unclear whether economic well-being brings a stronger human rights-based approach to governance or whether there might be a more nuanced interrelationship which is subject to a much broader array of variables. These questions become even more complicated at the international level when developed and developing states attempt to establish common rules for economic and social cooperation and regulation within intergovernmental organizations, and more complex still when transnational corporations (TNC) attempt to intervene and advance human rights standards in developing states. Civilising Globalisation is an attempt to expand upon the link between human rights and the global economy. Arguments are often put forward by leaders of authoritarian regimes that these two areas should be kept separate, and that economic cooperation should not be conditioned on adherence to human rights standards. However, David Kinley illustrates the unbreakable link between international human rights and all pillars of the global economy. While he observes some well-known controversies between human rights and economics, namely the attitude of some ‘capitalist’ lawyers that human rights, including workers’ rights, constitute an obstacle to economic growth, the author maintains that all freedoms are interconnected and strengthen one another. The author explores different aspects of the interaction between human rights and economics—socio-political, legal and institutional.

A multi-scale coastal vulnerability index: A tool for coastal managers?

Coastal hazard management involves the assessment of vulnerability in natural and human environments. Indices incorporating a diversity of indicators have therefore been used extensively to provide spatial analyses of the degree of vulnerability. Such indices are typically applied at global and national scales, and they involve varying degrees of simplification and aggregation of information. The degree of simplification that is desirable depends on the management scale, and higher resolution is required at the local compared to the global scale. To investigate the implications of spatial scale in depicting coastal hazard risk, coastal vulnerability indices were developed at national (Northern Ireland), local authority and site levels. Variables were separated into three sub-indices: a coastal characteristics sub-index concerned with the resilience and susceptibility of the coast to erosion, a coastal forcing sub-index to characterize the forcing variables contributing to wave-induced erosion and a socio-economic sub-index to assess the infrastructure potentially at risk. The three sub-indices were merged to calculate the overall index, which is portrayed in the form of colour-coded vulnerability maps. While a common tripartite index could be employed at national, regional and local scales, the nature of the data used to quantify many of the variables varies according to the scale of management. Some important local variations in vulnerability are masked by simplifications at the national scale. For some variables more detailed information is available as the spatial resolution of the study increases, while others become obsolete as data are of insufficient resolution to differentiate real variability at more detailed scales. The results highlight the importance of spatial scale in developing indices of vulnerability: while a common index architecture can be applied, the selection of variables must take account of the scale at which the hazard is to be assessed. It is likely that limits on index development will also be imposed by data availability at various scales.

INDICES OF DEVELOPMENT AND THEIR PRACTICAL APPLICATION

This research work was devoted to the development of indices of social, economic and political growth, to the practical application of these indices, and to their real-world verification with actual data. The study identified the advantages and disadvantages of the application of different indices to the assessment of growth. For example, one group of indices can be calculated, with some degree of simplification, for a fairly long time-period (half a century). Another group of indices that target the full consideration of growth includes indices that consist of a number of individual indicators though calculated for a relatively short time-period (e.g., one year only). The authors introduced specific indices of economic and social growth of countries and regions that were applied to the assessment of the social, economic, and political development of the world’s countries. The assessment was verified using actual data on the countries’ development.

Simplified models of a single-phase power electronic inverter for railway power system stability analysis—Development and evaluation

Use of power electronic equipment has increased and introduced new dynamical phenomena in power systems. For example, new electric rail vehicles (locomotives) equipped with modern power electronic traction chains have caused situations of low-frequency power oscillations and instability in single-phase railway power supply systems. This paper presents the development and implementation of an instantaneous value model and simplified fundamental frequency (RMS) models of such an advanced electric rail vehicle in order to investigate their representation of low-frequency dynamics. The dynamical behaviour is studied by use of both time-domain simulations and linear analysis (eigenvalues) and the degree of simplifications regarding controller dynamics and power system dynamics are presented and discussed. An enhanced RMS model is tested in order to account for the impact of fast current dynamics on the low-frequency behaviour. The results show that this enhanced model is corresponding more closely to the instantaneous value model than what can be obtained by the traditional RMS simplifications and indicate that current dynamics should be included in stability studies involving power electronic inverters.

Multi-resolution recognition of 3D objects based on visual resolution limits

This paper presents a multi-resolution recognition method for 3D objects, based on the human visual model. In the first part of this paper, we propose a new visual resolution limit (VRL) calculation method that considers lens size, the scale of imaging cells and the distance, orientation and velocity of the object. In addition, we simplify 3D models with a novel mesh simplification method based on edge collapse, which controls the simplification degree with VRL. After applying viewpoint space partitioning to the simplified models at different resolutions, we develop a multi-resolution aspect graph library indexed by observation distance. Finally, we propose a 3D object recognition method based on multi-resolution aspect graphs and implement a real-time gradual multi-resolution recognition system that imitates human vision. We design and execute a set of experiments based on plane, car and ship models. Our results demonstrate that our recognition method is effective.

‘Six hat supervision’: a model for the supervisor of midwives

If midwives are to recognize supervision as being a proactive supportive model, the role of the supervisor may require a degree of simplification and a new identity that can be readily recognized, understood and accessed. This article explores the use of ‘six hat supervision’ adapted from De Bono's (1990) metaphorical thinking hats as a possible solution. Each of the six hats represents a facet of the role of the supervisor and a direction of thinking, which is used proactively rather than reactively. The model's potential as a useful, supportive, visual analytical framework and deliberate supportive thinking technique is demonstrated by examining the role and responsibilities of the supervisor of midwives following a specific clinical incident. As a consequence of using ‘Six Hat Supervision’ it is anticipated that midwives will choose to seek support from supervisors who will then be well equipped to ensure that the practice of midwives is both safe and effective.

Constrained connectivity for hierarchical image partitioning and simplification

This paper introduces an image decomposition and simplification method based on the constrained connectivity paradigm. According to this paradigm, two pixels are said to be connected if they comply to a series of constraints defined in terms of simple measures such as the maximum grey level differences over well-defined pixel paths and regions. The resulting connectivity relation generates a unique partition of the image definition domain. The simplification of the image is then achieved by setting each segment of the partition to the mean value of the pixels falling within this segment. Fine to coarse partition hierarchies (and therefore images of increasing degree of simplification) are produced by varying the threshold value associated with each connectivity constraint. The paper also includes a generalisation to multichannel images, applications, a review of related image segmentation techniques, and pseudo-code for an implementation based on queue and stack data structures.

Pathway Complexity of Model Virus Capsid Assembly Systems

As computational and mathematical studies become increasingly central to studies of complicated reaction systems, it will become ever more important to identify the assumptions our models must make and determine when those assumptions are valid. Here, we examine that question with respect to viral capsid assembly by studying the ‘pathway complexity’ of model capsid assembly systems, which we informally define as the number of reaction pathways and intermediates one must consider to accurately describe a given system. We use two model types for this study: ordinary differential equation models, which allow us to precisely and deterministically compare the accuracy of capsid models under different degrees of simplification, and stochastic discrete event simulations, which allow us to sample use of reaction intermediates across a wide parameter space allowing for an extremely large number of possible reaction pathways. The models provide complementary information in support of a common conclusion that the ability of simple pathway models to adequately explain capsid assembly kinetics varies considerably across the space of biologically meaningful assembly parameters. These studies provide grounds for caution regarding our ability to reliably represent real systems with simple models and to extrapolate results from one set of assembly conditions to another. In addition, the analysis tools developed for this study are likely to have broader use in the analysis and efficient simulation of large reaction systems.

How to determine sapling buckling risk with only a few measurements

Tree buckling risk (actual height/critical buckling height) is an important biomechanical trait of plant growth strategies, and one that contributes to species coexistence. To estimate the diversity of this trait among wide samples, a method that minimizes damage to the plants is necessary. On the basis of the rarely used, complete version of Greenhill's model (1881, Proceedings of the Cambridge Philosophical Society 4(2): 65-73), we precisely measured all the necessary parameters on a sample of 236 saplings of 16 species. Then, using sensitivity (variance) analysis, regressions between successive models for risk factors and species ranks and the use of these models on samples of self- and nonself-supporting saplings, we tested different degrees of simplification up to the most simple and widely used formula that assumes that the tree is a cylindrical homogeneous pole. The size factor had the greatest effect on buckling risk, followed by the form factor and the modulus of elasticity of the wood. Therefore, estimates of buckling risk must consider not only the wood properties but especially the form factor. Finally, we proposed a simple but accurate method of assessing tree buckling risk that is applicable to a wide range of samples and that requires mostly nondestructive measurements.