Nodes on ropes: a comprehensive data and control flow for steering ensemble simulations

Flood disasters are the most common natural risk and tremendous efforts are spent to improve their simulation and management. However, simulation-based investigation of actions that can be taken in case of flood emergencies is rarely done. This is in part due to the lack of a comprehensive framework which integrates and facilitates these efforts. In this paper, we tackle several problems which are related to steering a flood simulation. One issue is related to uncertainty. We need to account for uncertain knowledge about the environment, such as levee-breach locations. Furthermore, the steering process has to reveal how these uncertainties in the boundary conditions affect the confidence in the simulation outcome. Another important problem is that the simulation setup is often hidden in a black-box. We expose system internals and show that simulation steering can be comprehensible at the same time. This is important because the domain expert needs to be able to modify the simulation setup in order to include local knowledge and experience. In the proposed solution, users steer parameter studies through the World Lines interface to account for input uncertainties. The transport of steering information to the underlying data-flow components is handled by a novel meta-flow. The meta-flow is an extension to a standard data-flow network, comprising additional nodes and ropes to abstract parameter control. The meta-flow has a visual representation to inform the user about which control operations happen. Finally, we present the idea to use the data-flow diagram itself for visualizing steering information and simulation results. We discuss a case-study in collaboration with a domain expert who proposes different actions to protect a virtual city from imminent flooding. The key to choosing the best response strategy is the ability to compare different regions of the parameter space while retaining an understanding of what is happening inside the data-flow system.     

World lines

In this paper we present World Lines as a novel interactive visualization that provides complete control over multiple heterogeneous simulation runs. In many application areas, decisions can only be made by exploring alternative scenarios. The goal of the suggested approach is to support users in this decision making process. In this setting, the data domain is extended to a set of alternative worlds where only one outcome will actually happen. World Lines integrate simulation, visualization and computational steering into a single unified system that is capable of dealing with the extended solution space. World Lines represent simulation runs as causally connected tracks that share a common time axis. This setup enables users to interfere and add new information quickly. A World Line is introduced as a visual combination of user events and their effects in order to present a possible future. To quickly find the most attractive outcome, we suggest World Lines as the governing component in a system of multiple linked views and a simulation component. World Lines employ linking and brushing to enable comparative visual analysis of multiple simulations in linked views. Analysis results can be mapped to various visual variables that World Lines provide in order to highlight the most compelling solutions. To demonstrate this technique we present a flooding scenario and show the usefulness of the integrated approach to support informed decision making.     

Resilience Assessment of Water Resources System

The resilience perspective, which emphasizes the integrated, systemic concept of human and nature interactions, is increasingly used as an approach for understanding the dynamic of social-ecological system. As the water resources system (WRS) is a social-ecological system, resilience thinking such as Holling??s adaptive cycle has been adopted as a fundamental unit for understanding the water resources system dynamics in this paper. In the adaptive cycle of WRS, the likelihood shift among different phases largely depends on resilience value; and a quantitative method for estimating the resilience of WRS is proposed. The method is related to the degree of change and characteristics of the WRS, and has been applied to identify the phase of WRS in every city in Zhejiang province, China. The results of resilience assessment have also been discussed in terms of adaptive cycle.     

Numerical modelling of calcination reaction mechanism for cement production

Calcination is a thermo-chemical process, widely used in the cement industry, where limestone is converted by thermal decomposition into lime CaO and carbon dioxide CO₂. The focus of this paper is on the implementation and validation of the endothermic calcination reaction mechanism of limestone in a commercial finite volume based CFD code. This code is used to simulate the turbulent flow field, the temperature field, concentrations of the reactants and products, as well as the interaction of particles with the gas phase, by solving the mathematical equations, which govern these processes. For calcination, the effects of temperature, decomposition pressure, diffusion and pore efficiency were taken into account. A simple three-dimensional geometry of a pipe reactor was used for numerical simulations. To verify the accuracy of the modelling approach, the numerical predictions were compared with experimental data, yielding satisfying results and proper trends of physical parameters influencing the process.     

Stability of rigid blocks exposed to single-pulse excitation

This paper proposes a numerical procedure that can predict the minimum duration of a rectangular, half-cycle sine wave, linearly increasing and triangular single-pulse excitation required to overturn the rigid block resting on a moving base. Since the linearization assumption in the derivation of an analytical solution, which has already been used by Housner and other researchers, cannot be valid for a block with various slenderness ratios and dimensions, a derivation of numerical solutions which would be valid for all types of block is necessary. The proposed numerical procedure takes into account the possibility of sliding and uplifting of the block from the base. The numerical algorithm for the proposed numerical procedure in a commercial code C++ is given in the “Appendix.”     

3D Visualization on mobile devices

This paper discusses current status and recent advancements of 3D graphics on mobile platforms and describes open issues concerning its usage in different applications. We have treated two particular application fields. Firstly, we deal with problems of visualization of complex data structures on mobile devices. The implementation of a 3D visualization renderer on the Symbian platform for mobile devices is written as a C++ application and based on the DieselEngine^® as a rendering engine. 3D visualization of data is generated in the form of a Virtual Reality Modelling Language (VRML) file meaning that actually any kind of 3D content written in VRML file format can be rendered on such a device. It was the result of a project the objective of which was to provide a user interface on a mobile platform displaying visualization of hierarchical Grid monitoring data. Secondly, we describe the system that brings face animation to embedded platforms. Face animation is considered to be one of the toughest tasks in computer animation today and its delivery to mobile platforms brings possibilities for development of new innovative and attractive services for the mobile market.     

Configuration and Recent Field installations of LV-Converter Based Energy Storage System

Energy storage plays an increasingly important role in modem power systems. It can add value to power systems in various aspects. This paper discusses possible energy storage system （ESS） applications and their benefits to power systems. The system configuration, converter design, and recent field installations of an LV converter based ESS are presented.     

两种瑞利衰落信道模型的研究

信道建模和仿真是研究移动无线通信中各种技术和网络规划的基础和关键.在给出的移动无线信道建模的数学参考模型基础上,分析了传统Jakes模型中存在的不足.后人因此提出了两种改进型的模型:Pop模型和Zheng模型.将两种改进型模型进行了理论上的对比,区分两者是如何分别引入随机相位来改善原有模型的,还对两种模型进行了MATLAB仿真研究,对比两种模型的性能.研究表明两种模型都能通过随机相位的引入解决Jakes模型中的稳定性问题,但是Zheng模型的性能更好且更容易实现.Zheng模型对于瑞利衰落信道的建模具有更大的价值.     

Comparison of two techniques for reliable characterization of thin metal-dielectric films

In the present study we determine the optical parameters of thin metal-dielectric films using two different characterization techniques based on nonparametric and multiple oscillator models. We consider four series of thin metal-dielectric films produced under various deposition conditions with different optical properties. We compare characterization results obtained by nonparametric and multiple oscillator techniques and demonstrate that the results are consistent. The consistency of the results proves their reliability.     

Numerical simulation of ammonia/methane/air combustion using reduced chemical kinetics models

Ammonia appears to be a potential alternative fuel that can be used as a hydrogen vector and fuel for gas turbines and internal combustion engines. Chemical mechanisms of ammonia combustion are important for the development of ammonia combustion systems, but also as a mean of investigation of harmful NOx emissions, so they can be minimized. Despite of large body of experimental and modelling work on the topic of ammonia combustion, there is still need for additional investigation of combustion kinetics.The object of this work is further numerical study of ammonia combustion chemistry under conditions resembling industrial ones. After literature review, three mechanisms of ammonia combustion that also include carbon chemistry are used for simulation of experimental premixed swirl burner with the aim of evaluating their performance. San Diego mechanism, that was also the most detailed one, proved to be the best in terms of emissions, but neither one of the models was able to accurately reproduce CO emission after equivalence ratio went beyond 0.81. It was also observed that oxygen is excessively consumed. This study contributes to the current knowledge by providing new insights in ammonia burning conditions closely resembling those in industrial applications, and consequently is expected that insights obtained will help in the design of real industrial burning systems.