Bias–Variance Analysis for Controlling Adaptive Surface Meshes

This paper presents a statistical methodology for exerting control over adaptive surface meshes. The goal is to develop an adaptive mesh which uses split and merge operations to control the distribution of planar or quadric surface patches. The novelty of the work reported in this paper is to focus on the variance–bias tradeoff that exists between the size of the fitted patches and their associated parameter variances. In particular, we provide an analysis which shows that there is an optimal patch area. This area offers the best compromise between the noise-variance, which decreases with increasing area, and the model-bias, which increases in a polynomial manner with area. The computed optimal areas of the local surface patches are used to exert control over the facets of the adaptive mesh. We use a series of split and merge operations to distribute the faces of the mesh so that each resembles as closely as possible its optimal area. In this way the mesh automatically selects its own density by adjusting the number of control-points or nodes. We provide experiments on both real and synthetic data. This experimentation demonstrates that our mesh is capable of efficiently representing high curvature surface detail.     

Route instructions in map-based human–human and human–computer dialogue: A comparative analysis

When conveying information about spatial situations and goals, speakers adapt flexibly to their addressee in order to reach the communicative goal efficiently and effortlessly. Our aim is to equip a dialogue system with the abilities required for such a natural, adaptive dialogue. In this paper we investigate the strategies people use to convey route information in relation to a map by presenting two parallel studies involving human–human and human–computer interaction. We compare the instructions given to a human interaction partner with those given to a dialogue system which reacts by basic verbal responses and dynamic visualization of the route in the map. The language produced by human route givers is analyzed with respect to a range of communicative as well as cognitively crucial features, particularly perspective choice and references to locations across levels of granularity. Results reveal that speakers produce systematically different instructions with respect to these features, depending on the nature of the interaction partner, human or dialogue system. Our further analysis of clarification and reference resolution strategies produced by human route followers provides insights into dialogue strategies that future systems should be equipped with.     

Fuzzy min–max neural networks: a bibliometric and social network analysis

Neural Computing and Applications - The amount of digital data in the universe is growing at an exponential rate with the rapid development of digital information, and this reveals new machine...     

Human–Computer input and output techniques: an analysis of current research and promising applications

Personal computing applications are constantly increasing their potential power, thanks to steadily growing hardware capabilities and large diffusion of high-quality multimedia output devices. At the same time, mobile communication tools are becoming an integral part of our everyday life, with new advanced functionalities offered at an unrestrainable pace. Although the way we interact with information machines is substantially the same since 20 years—based on keyboard, mouse and window metaphor—other communication modalities are possible, and shortly may become popular as additional interaction methods. Given the paramount importance of the “interface” in present computer applications, no alternative should be ignored, as it could greatly improve the quality of both interaction processes and user cognitive performance. Without pretending to foresee the future, in this paper we provide an overview of the main current technologies which can enable potential novel interfaces, discussing their features, strengths, weaknesses and promising applications.     

Stochastic modeling and analysis of road–tramway intersections

In the last decades, the socio-demographic evolution of the population has substantially changed mobility demand, posing new challenges in minimizing urban congestion and reducing environmental impact. In this scenario, understanding how different modes of transport can efficiently share (partially or totally) a common infrastructure is crucial for urban development. To this aim, we present a stochastic model-based analysis of critical intersections shared by tram traffic and private traffic, combining a microscopic model of the former with a macroscopic model of the latter. Advanced simulation tools are typically used for such kind of analyses, by playing various traffic scenarios. However, simulation is not an exhaustive approach, and some critical, possibly rare, event may be ignored. For this reason, our aim is instead to adopt suitable analytical solution techniques and tools that can support instead a complete, exhaustive analysis, so being able to take into account rare events as well. Transient analysis of the overall traffic model using the method of stochastic state classes is adopted to support the evaluation of relevant performance measures, namely the probability of traffic congestion over time and the average number of private vehicles in the queue over time. A sensitivity analysis is performed with respect to multiple parameters, notably including the arrival rate of private vehicles, the frequency of tram rides, and the time needed to recover from traffic congestion.

     

Pulmonary crackle detection using time–frequency and time–scale analysis

Pulmonary crackles are used as indicators for the diagnosis of different pulmonary disorders in auscultation. Crackles are very common adventitious transient sounds. From the characteristics of crackles such as timing and number of occurrences, the type and the severity of the pulmonary diseases may be assessed. In this study, a method is proposed for crackle detection. In this method, various feature sets are extracted using time–frequency and time–scale analysis from pulmonary signals. In order to understand the effect of using different window and wavelet types in time–frequency and time–scale analysis in detecting crackles, different windows and wavelets are tested such as Gaussian, Blackman, Hanning, Hamming, Bartlett, Triangular and Rectangular windows for time–frequency analysis and Morlet, Mexican Hat and Paul wavelets for time–scale analysis. The extracted feature sets, both individually and as an ensemble of networks, are fed into three different machine learning algorithms: Support Vector Machines, k-Nearest Neighbor and Multilayer Perceptron. Moreover, in order to improve the success of the model, prior to the time–frequency/scale analysis, frequency bands containing no-crackle information are removed using dual-tree complex wavelet transform, which is a shift invariant transform with limited redundancy compared to the conventional discrete wavelet transform. The comparative results of individual feature sets and ensemble of sets, which are extracted using different window and wavelet types, for both pre-processed and non-pre-processed data with different machine learning algorithms, are extensively evaluated and compared.     

Optimization of chemotherapy and immunotherapy: In silico analysis using pharmacokinetic–pharmacodynamic and tumor growth models

Chemotherapy is one of the most prominent cancer treatment modalities. However, it is not always a comprehensive solution for tumor regression. This led to the advent of novel strategies to combine chemotherapy with other emerging therapies to treat cancer patients keeping side effects to a minimum. In this work, the focus is on the optimization of chemotherapy using doxorubicin and its combination with adoptive-cell-transfer therapy which is one of the schemes of immunotherapy. The key challenge in the combination therapy is to find the sequence, timing and the dosage of therapies for a given patient. In this regard, an in silico pharmacokinetic/pharmacodynamic model describing the interaction between tumor cells, immune cells and doxorubicin is used to formulate a multi-objective optimization problem by considering clinically relevant objectives and constraints. Then, the multi-objective optimization problem is solved using genetic algorithm and the results obtained for the different cases are compared to discover a therapeutically efficacious treatment regimen. And the metrics used to compare different cases are final tumor size and tumor relapse time. The comparison between chemotherapy alone and its combination with immunotherapy shows that combination therapy is effective in controlling the tumor growth.     

Discrete Helmholtz–Hodge Decomposition on Polyhedral Meshes Using Compatible Discrete Operators

This article provides a methodology to perform discrete Helmholtz–Hodge decomposition on three-dimensional polyhedral meshes using structure-preserving schemes: the Compatible Discrete Operator schemes. We propose to extract the decomposition components independently with one equation to solve per component or potential. The key of the method is the choice of a discrete Hodge operator that makes a compromise between convergence rate and computational cost. Numerical experiments are performed to evaluate the convergence rate and the computational cost on various polyhedral meshes, in particular, on the FVCA benchmark meshes. We also investigate some linear solver capabilities to solve our equations. The main contribution of this paper is the application of the CDO schemes to the Hodge decomposition and the required solvers.     

High Order Numerical Discretization for Hamilton–Jacobi Equations on Triangular Meshes

In this paper we construct several numerical approximations for first order Hamilton–Jacobi equations on triangular meshes. We show that, thanks to a filtering procedure, the high order versions are non-oscillatory in the sense of satisfying the maximum principle. The methods are based on the first order Lax–Friedrichs scheme [2] which is improved here adjusting the dissipation term. The resulting first order scheme is -monotonic (we explain the expression in the paper) and converges to the viscosity solution as for the L -norm. The first high order method is directly inspired by the ENO philosophy in the sense where we use the monotonic Lax–Friedrichs Hamiltonian to reconstruct our numerical solutions. The second high order method combines a spatial high order discretization with the classical high order Runge–Kutta algorithm for the time discretization. Numerical experiments are performed for general Hamiltonians and L ¹, L ² and L -errors with convergence rates calculated in one and two space dimensions show the k-th order rate when piecewise polynomial of degree k functions are used, measured in L ¹-norm.     

Anisotropic Meshes and Stabilization Parameter Design of Linear SUPG Method for 2D Convection-Dominated Convection–Diffusion Equations

We propose a numerical strategy to generate a sequence of anisotropic meshes and select appropriate stabilization parameters simultaneously for linear SUPG method solving two dimensional convection-dominated convection–diffusion equations. Since the discretization error in a suitable norm can be bounded by the sum of interpolation error and its variants in different norms, we replace them by some terms which contain the Hessian matrix of the true solution, convective field, and the geometric properties such as directed edges and the area of triangles. Based on this observation, the shape, size and equidistribution requirements are used to derive corresponding metric tensor and stabilization parameters. Numerical results are provided to validate the stability and efficiency of the proposed numerical strategy.     

Thermal analysis and microstructure of the as-cast Ag–Bi–Cu alloys

The Ag–Bi–Cu system is one of the ternary alloy systems that until now is not fully experimentally studied. The literature survey indicated that the experimental data on this system are scarce. In this study the DTA method was employed to study phase transitions with temperature in Ag–Bi–Cu alloys. The measurements were performed on samples of constant silver to bismuth mole fraction ratio 4:1, 1:1, 1:4, respectively, and varying copper content. Selected as-cast samples were subjected to SEM-EDS analysis of the microstructure. The results obtained are discussed with phase transition temperatures calculated based on the data of binaries from the literature.     

Fractal analysis and control in the predator–prey model

The two-dimensional predator–prey Lotka–Volterra model is discussed from the point of fractal theory. Julia set of the discrete version of the model is introduced. Then, the linear feedback control is taken to control the Julia set. By controlling the Julia set, the attractive domain of the attractive fixed point is controlled indirectly. To associate two different Julia sets of the model with different parameters, nonlinear coupling items are designed to make one Julia set change to be another. The simulations illustrate the efficacy of these methods.     

Modelling and analysis of a rigid–compliant parallel mechanism

This paper presents a two-staged parallel mechanism composed by a rigid platform in a serial connection with a compliant platform, and concentrates on its configuration and interrelation. The analysis starts with the operator of a 3UPU configuration with a central strut being derived. Configuration and displacement formulas of the compliant platform are demonstrated, leading to the analytic equations of the relationship between the actuated angles of the operator and the position parameters of the end-effector. The numerical evaluation of workspace of the two-staged parallel mechanism is then followed.     

Cognitive–metacognitive and content-technical aspects of constructivist Internet-based learning environments: a LISREL analysis

Through a LISREL analysis, this study validated the Constructivist Internet-based Learning Environment Survey (CILES). CILES consisted of six scales, sorted by two aspects. The first aspect, the cognitive–metacognitive aspect, included the scales of student negotiation, inquiry learning, and reflective thinking, whereas the second aspect, the content-technical aspect, involved the scales of Relevance, Ease of Use, and Challenge. A LISREL structural model was also proposed to examine the relationships between students' responses across these two aspects. Survey responses gathered from 483 high school students in Taiwan were the research data for this study. The results from the LISREL confirmatory analysis showed that CILES had highly satisfactory validity and reliability to assess students' preferences for constructivist Internet-based learning environments. Moreover, the structural model indicated that the Internet learning environments that challenged students' existing concepts could facilitate their preferences for student negotiation, inquiry learning and reflective thinking activities. It is proposed that the Internet can have rich connections with numerous resources and a variety of perspectives, thus constructing appropriate learning environments to provide different kinds of challenges for learners.     

Isogeometric shell analysis: The Reissner–Mindlin shell

A Reissner–Mindlin shell formulation based on a degenerated solid is implemented for NURBS-based isogeometric analysis. The performance of the approach is examined on a set of linear elastic and nonlinear elasto-plastic benchmark examples. The analyses were performed with LS-DYNA, an industrial, general-purpose finite element code, for which a user-defined shell element capability was implemented. This new feature, to be reported on in subsequent work, allows for the use of NURBS and other non-standard discretizations in a sophisticated nonlinear analysis framework.     

Modeling,analysis and control of robot–object nonsmooth underactuated Lagrangian systems: A tutorial overview and perspectives

So-called robot–object Lagrangian systems consist of a class of nonsmooth underactuated complementarity Lagrangian systems, with a specific structure: an “object” and a “robot”. Only the robot is actuated. The object dynamics can thus be controlled only through the action of the contact Lagrange multipliers, which represent the interaction forces between the robot and the object. Juggling, walking, running, hopping machines, robotic systems that manipulate objects, tapping, pushing systems, kinematic chains with joint clearance, crawling, climbing robots, some cable-driven manipulators, and some circuits with set-valued nonsmooth components, belong this class. This article aims at presenting their main features, then many application examples which belong to the robot–object class, then reviewing the main tools and control strategies which have been proposed in the Automatic Control and in the Robotics literature. Some comments and open issues conclude the article.     

Closed-loop analysis and control of a non-inverting buck–boost converter

In this article, a cascade controller is designed and analysed for a non-inverting buck–boost converter. The fast inner current loop uses sliding mode control. The slow outer voltage loop uses the proportional–integral (PI) control. Stability analysis and selection of PI gains are based on the nonlinear closed-loop error dynamics incorporating both the inner and outer loop controllers. The closed-loop system is proven to have a nonminimum phase structure. The voltage transient due to step changes of input voltage or resistance is predictable. The operating range of the reference voltage is discussed. The controller is validated by a simulation circuit. The simulation results show that the reference output voltage is well-tracked under system uncertainties or disturbances, confirming the validity of the proposed controller.     

Robot–human rescue teams: a user requirements analysis

Time-critical operations of equipment in emergencies require efficient human–machine interaction. In order to evaluate and rank the factors affecting search and rescue activities in emergencies, a requirements analysis among this professional community has been performed. The analyses presented here focus on cooperating robot–human teams. They have been performed on the basis of questionnaires and personal interviews with professionals in search and rescue from Germany, Finland and the Czech Republic. This includes professional fire fighters, plant fire brigades (nuclear power plants, airports, chemical factories), governmental disaster relief organizations and the military. The analyses identify the end-user requirements and provide guidelines for the development of rescue systems. On this basis, a system design for human–robot teams has been derived, with particular emphasis on telerobotics interface implemenation.