Using the Model Coupling Toolkit to couple earth system models

Continued advances in computational resources are providing the opportunity to operate more sophisticated numerical models. Additionally, there is an increasing demand for multidisciplinary studies that include interactions between different physical processes. Therefore there is a strong desire to develop coupled modeling systems that utilize existing models and allow efficient data exchange and model control. The basic system would entail model “1” running on “M” processors and model “2” running on “N” processors, with efficient exchange of model fields at predetermined synchronization intervals. Here we demonstrate two coupled systems: the coupling of the ocean circulation model Regional Ocean Modeling System (ROMS) to the surface wave model Simulating WAves Nearshore (SWAN), and the coupling of ROMS to the atmospheric model Coupled Ocean Atmosphere Prediction System (COAMPS). Both coupled systems use the Model Coupling Toolkit (MCT) as a mechanism for operation control and inter-model distributed memory transfer of model variables. In this paper we describe requirements and other options for model coupling, explain the MCT library, ROMS, SWAN and COAMPS models, methods for grid decomposition and sparse matrix interpolation, and provide an example from each coupled system. Methods presented in this paper are clearly applicable for coupling of other types of models.     

关于液滴撞击弹性固体变形预测仿真

在液滴撞击弹性固体问题中,由于流固两相的动力学特性复杂且传统网格法求解困难,研究中通常将固体结构视为刚性壁面,不考虑固体在冲击下的变形情况及变形对液滴的影响,导致数值仿真精度较低。根据光滑粒子动力学(Smoothed Particle Hydrodynamics,SPH)方法的基本原理和理论,采用连续介质力学的控制方程,引入非牛顿流体和弹性固体所遵循的本构关系,分析流固两相的相互作用,提出一种流固边界的耦合处理算法,建立流固耦合动力学模型,对非牛顿液滴撞击弹性固体的动态过程进行数值仿真。仿真结果表明,上述数值方法能够精细地预测出撞击过程中非牛顿液滴的形态变化和弹性固体结构的微变形情况,并探讨了具有不同弹性模量的固体在液滴撞击下的可变形性及对液滴的影响。     

基于递推PLS的自适应钢温软测量模型

针对轧钢加热炉系统具有多变量、非线性、大滞后、交叉耦合等特点,难以预估钢坯出口温度的难题,以块式递推偏最小二乘算法为基础,结合移动窗口和遗忘因子法,建立了出炉钢坯温度和过程变量之间的预测模型.在某钢厂的实际应用表明,该钢温软测量模型具有较好的自适应能力,能提前15 min预测钢坯出口温度,且预测误差满足工业应用的精度要求.     

A study of capillary flow from a pendant droplet

Surface tension driven capillary flow from a pendant droplet into a horizontal glass capillary is investigated in this paper. Effect of the droplet surface on dynamic behavior of such capillary flow is examined and compared with surface tension driven capillary flow from an infinite reservoir. In the experiment, capillaries of 300–700 μm in diameter were used with glycerol–DI water mixture solutions having viscosities ranging from 80 to 934 mPa s. It is observed that compared to the capillary flow from an infinite reservoir, the capillary flow from a droplet exhibits higher rates of meniscus displacement. This is due to an additional driving force resulted from change in droplet surface area (or curvature). The two main parameters influencing the flow are the dimensionless droplet geometry parameter (k) and the dynamic contact angle (θ _D). The molecular kinetics theory of Blake and De Coninck’s model [Adv Colloid Interface Sci 96(1–3):21–36, 2002] is used to interpret the dynamic contact angle. This theory considers a molecular friction coefficient (ζ) at the liquid front flowing over a solid surface. Moreover, three models are proposed to describe the shape of the pendant droplet during capillary action. It is found that the egg-shaped model provides a more realistic model to compute the shape of the pendant droplet deformed during the capillary action. Thus the predictions by the egg-shaped model are in good agreement with the experimental data.     

A sketch-based approach to human body modelling

In this paper, we present a new approach and a novel interface, Virtual Human Sketcher (VHS), which enables those who can draw, to sketch-out various human body models. Our approach supports freehand drawing input and a “Stick Figure→Fleshing-out→Skin Mapping” modelling pipeline. Following this pipeline, a stick figure is drawn first to illustrate a figure pose, which is automatically reconstructed into 3D through a “Multi-layered Back-Front Ambiguity Clarifier”. It is then fleshed-out with freehand body contours. A “Creative Model-based Method” is developed for interpreting the body size, shape, and fat distribution of the sketched figure and transferring it into a 3D human body through graphical comparisons and generic model morphing. The generic model is encapsulated with three distinct layers: skeleton, fat tissue, and skin. It can be transformed sequentially through rigid morphing, fatness morphing, and surface matching to match the 2D figure sketch. The initial resulting 3D body model can be incrementally modified through sketching directly on the 3D model. In addition, this body surface can be mapped onto a series of posed stick figures to be interpolated as a 3D character animation. VHS has been tested by various users on Tablet PC. After minimal training, even a beginner can create plausible human bodies and animate them within minutes.     

The air traffic flow control problem as an application of network theory

In this paper the air traffic flow control is approached as a constrained optimization problem on a multicommodity network. The proposed dynamic mathematical model, by means of a suitable time discretization, has been changed into a “static” one, in order to use static network flow algorithms while taking into account the “unsteady” nature of the air traffic congestion problems.The complexity of the model requires some preliminary effort, such as the identification of some characteristic parameters of the system.In this paper, the network theory is applied to evaluate the influence of the time discretization interval on the model significancy with respect to the actual traffic situation. In particular, a computational example concerning the Rome air traffic control region is presented and the relative results are discussed.     

Development of a micrometeorological model for the estimation of methane flux from paddy fields: Validation with standard direct measurements

This work has focussed on the development of an indirect method for estimating methane fluxes from paddy fields and wetlands. A micrometeorological model, based on an analytical solution of the Eulerian advection–diffusion equation for vertical diffusion, has been used; model parameters include the location of the methane analyser and standard surface layer scaling factors. Flux chambers, which are commonly used for measuring methane fluxes from agricultural sources, are usually mechanically operated with a rated induced-draft fan and as such cannot replicate the real world atmospheric conditions. The results are not very reliable due to leakages along the piping and at fittings, especially when these chambers are used over a relatively rough surface like an agricultural field or a wetland. The results of the model have been compared with those from the direct method. The seasonal average methane flux calculated by the indirect method, for the cultivar type “Sundari”, is 7.13E+05 g/ha, while cultivar type “Shatabdi” gives a little lower value of 5.22E+05 g/ha. In case of the direct chamber method also, the seasonal average methane flux for the cultivar type “Sundari” (6.20E+05 g/ha) is more than cultivar type “Shatabdi” (4.84E+05 g/ha). When the two methods of assessment were compared, season September–December 2004 gave r² = 0.91, RMSE = 0.16 and MNB = 0.13 while we got r² = 0.94, RMSE = 1.22 and MNB = 0.06 for the season September–December 2005.In very few experiments we could cover a huge aerial plot instead of a huge number of experiments necessary for the direct chamber method.     

高空台喷雾水滴运动轨迹及流动换热规律数值研究

高空台因其结构特殊,喷雾参数测量较为困难.为探究喷雾水滴在高空台内的运动和传热规律,对喷雾水滴在高空台内的运动和沿程的传质传热过程进行了分析,采用仿真计算的方法,建立了相应的数学物理模型,发展了适用于求解高空台内喷雾水滴沿程速度、温度和粒径的计算方法,可预测水滴沿程相关参数随运动时间和路程的变化规律.通过数值计算结果表明,适当延长试验舱通道长度,可提高水滴的跟随性;气流参数对水滴运动轨迹存在一定影响;喷雾水滴运动过程中的传质传热作用对于水滴沿程粒径变化影响较为明显.研究结果为高空台进行进气结冰试验提供了理论依据.     

A Temporal Logic for Proving Properties of Topologically General Executions

We present a generalization of the temporal propositional logic of linear time which is useful for stating and proving properties of the generic execution sequence of a parallel program or a non-deterministic program. The formal system we present is exactly that same as the third of three logics presented by Lehmann and Shelah (Information and Control53, 165–198 (1982)), but we give it a different semantics. The models are tree models of arbitrary size similar to those used in branching time temporal logic. The formulation we use allows us to state properties of the “co-meagre” family of paths, where the term “co-meagre” refers to a set whose complement is of the first category in Baire's classification looking at the set of paths in the model as a metric space. Our system is decidable, sound, and, complete for models of arbitrary size, but it has the finite model property; namely, every sentence having a model has a finite model.     

On the controllability of linear juggling mechanical systems

This paper deals with the controllability of a class of nonsmooth complementarity mechanical systems. Due to their particular structure they can be decomposed into an “object” and a “robot”, consequently they are named juggling systems. It is shown that the accessibility of the “object” can be characterized by nonlinear constrained equations, or generalized equations. Examples are presented, including a simple model of backlash. The main focus of the work is about linear jugglers.     

A variational approach to the contact angle dynamics of spreading droplets

The modeling and the numerical representation of the contact line between a two-phase interface and a solid surface are still open problems from the physical, mathematical and numerical point of view. This paper deals with the numerical simulation of the spreading of a single droplet impacting over horizontal dry surfaces. A new variational approach to study the droplet spreading is presented by coupling an interface front-tracking algorithm to the single-fluid finite element formulation of the incompressible Navier-Stokes equations which are solved on a fixed mesh. Standard no-slip boundary conditions near the contact line lead to a singular behavior that in the variational approach is removed by introducing a generalized boundary condition which is the sum of a dissipation term and the dynamical contact angle law. By changing the intensity of the dissipation a large number of boundary conditions around the contact point are modeled, ranging from no-slip to free-slip. Since the impact is over horizontal surfaces, axisymmetric solutions are investigated with high mesh resolutions. A very precise implementation of the capillary force with a volumetric extension of the curvature has been adopted. We have considered a Lagrangian front-tracking method to advect the interface. The marker representing the contact point is simply advected by the computed velocity at the boundary without the need to extrapolate the vector field from the interior and to enforce locally mass-conservation. The model has been tested for the impact and the spreading of a droplet on solid substrates with a different wettability at low Reynolds numbers where the inertial, the viscous and the surface tension forces are all important. A number of droplet impacts with different outcomes, ranging from simple deposition to partial and complete rebound, have been reproduced. However, our simulations indicate that the formulas suggested in the literature for the dynamical contact angle should be modified to simulate a broad class of experiments.     

Extracting a polyhedron from a single-view sketch: Topological construction of a wireframe sketch with minimal hidden elements

An essential prerequisite to construct a manifold trihedral polyhedron from a given natural (or partial-view) sketch is solution of the “wireframe sketch from a single natural sketch (WSS)” problem, which is the subject of this paper. Published solutions view WSS as an “image-processing”/“computer vision” problem where emphasis is placed on analyzing the given input (natural sketch) using various heuristics. This paper proposes a new WSS method based on robust tools from graph theory, solid modeling and Euclidean geometry. Focus is placed on producing a minimal wireframe sketch that corresponds to a topologically correct polyhedron.     

Analysis of MIMD congestion control algorithm for high speed networks

Proposals to improve the performance of TCP in high speed networks have been recently put forward. Examples of such proposals include High Speed TCP, Scalable TCP, and FAST. In contrast to the additive increase multiplicative decrease algorithm used in the standard TCP, Scalable TCP uses a multiplicative increase multiplicative decrease (MIMD) algorithm for the window size evolution. In this paper, we present a mathematical analysis of the MIMD congestion control algorithm in the presence of random losses. Random losses are typical to wireless networks but can also be used to model losses in wireline networks with a high bandwidth-delay product. Our approach is based on showing that the logarithm of the window size evolution has the same behaviour as the workload process in a standard G/G/1 queue. The Laplace–Stieltjes transform of the equivalent queue is then shown to directly provide the throughput of the congestion control algorithm and the higher moments of the window size. Using ns-2 simulations, we validate our findings using Scalable TCP.     

Automatic tuning of the window size in the Box Car Back Slope data compression algorithm

In spite of the fact that there exist newer data compression algorithms with better compression ratios, the Box Car Back Slope (BCBS) algorithm is still offered by vendors of data acquisition systems and remains in use in many process industries. The assumption behind the BCBS algorithm is that the recorded process variable can be approximated by a piece-wise linear function, whereby variable values within a threshold window around the line segments are not stored. The window size is a critical parameter which should be selected such that a desired compromise between the data compression ratio and the approximation error is achieved. Based on a criterion function reflecting such a compromise, an automatic, recursive algorithm for tuning the BCBS threshold window size is presented in this paper. The algorithm has been used successfully to tune the window size for hundreds of process variables at the carton board manufacturing plant of Assi–Domän Frövi, Sweden.     

A Partial Order Approach to Branching Time Logic Model Checking

Partial order techniques enable reducing the size of the state space used for model checking, thus alleviating the “state space explosion” problem. These reductions are based on selecting a subset of the enabled operations from each program state. So far, these methods have been studied, implemented, and demonstrated for assertional languages that model the executions of a program as computation sequences, in particular the linear temporal logic. The present paper shows, for the first time, how this approach can be applied to languages that model the behavior of a program as a tree. We study here partial order reductions for branching temporal logics, e.g., the logics CTL and CTL* (with the next time operator removed) and process algebra logics such as Hennesy–Milner logic (withτactions). Conditions on the selection of subset of successors from each state during the state-space construction, which guarantee reduction that preserves CTL* properties, are given. The experimental results provided show that the reduction is substantial.     

Incorporating citizens' views in local policy decision making processes

Local policy issues usually exhibit a high degree of complexity and uncertainty and are often characterized as “ill-structured” problems. Problem Structuring Methods (PSMs) rely on stakeholder representation and workshop format procedures to support policy making processes. We consider public participation as a way to reduce uncertainty and to improve the democratic legitimacy of those processes, and we propose a new model for e-participation (information and communication technology supported public participation), employing collaborative writing processes to produce agreed documents. These documents may then be used as formal input into the policy making process, thereby incorporating the citizens' views on those issues. A public participation support system has been developed according to this model.     

Information - organization - decision: Some strange loops

Acceptance of the theoretical foundations of Management Information Systems (MIS) has remained surprisingly high in the past twenty years, whereas information processing technologies have been improving at an incredible rate. This stability appears to be because the MIS model is based on the cybernetic model of organizations. We see, however, a conceptual crisis due in the development of more and more complex information systems and increased questioning of the deficiencies of organizational models based on cybernetic theory. This is particularly highlighted by the problems encountered in introducing the “bounded rationality paradigm” of H.A. Simon into the model.In this paper, we propose a new model that should be better adapted to contempory technology. This model allows both order and disorder to be included, while incorporating the concept of “organizational memory,” to improve the representation of a complex organizational information system with an action and process aspect.     

NEGO — Group decision support system

There are two major frameworks for decision making: maximizing and satisficing. A combination of both may be used to describe group decision making (GDM). In the satisficing approach, decision makers (DMs) formulate aspiriation levels or demands which take the form of constraints. Choosing from among different decisions, DMs take into account their preferences or wants, which take the form of objective functions.GDM is divided into two stages: first, each DM makes a decision, and second, DMs negotiate so as to achieve a compromise decision. Negotiating is an iterative process. Negotiations are completed when all demands have been met.The group decision support system “NEGO” assists DMs in finding a compromise. It has been used for solving a GDM problem at the corporate level and is currently utilized in management courses.