Hybrid molecular-continuum fluid dynamics

We describe recent developments in the hybrid atomistic/continuum modelling of dense fluids. We discuss the general implementation of mass, momentum and energy transfers between a region described by molecular dynamics and a neighbouring domain described by the Navier-Stokes equations for unsteady continuum fluid flow.     

Rapid implementation of material models within finite element analysis

This paper presents a simple procedure for obtaining a numerical approximation to the consistent tangent matrix, together with a straightforward implicit (Euler backward) integration algorithm. The combined algorithm is used to incorporate four models into the commercial finite element package ABAQUS/Standard; illustrating how it can be used to rapidly implement material models within finite element analysis. The models have been chosen, not only because they help to illuminate the structure of the algorithm, but also because they illustrate its wide ranging applicability and permit the procedure to be tested against analytical results and an existing, well established, model.     

Latent Markov models: a review of a general framework for the analysis of longitudinal data with covariates

We provide a comprehensive overview of latent Markov (LM) models for the analysis of longitudinal categorical data. We illustrate the general version of the LM model which includes individual covariates, and several constrained versions. Constraints make the model more parsimonious and allow us to consider and test hypotheses of interest. These constraints may be put on the conditional distribution of the response variables given the latent process (measurement model) or on the distribution of the latent process (latent model). We also illustrate in detail maximum likelihood estimation through the Expectation–Maximization algorithm, which may be efficiently implemented by recursions taken from the hidden Markov literature. We outline methods for obtaining standard errors for the parameter estimates. We also illustrate methods for selecting the number of states and for path prediction. Finally, we mention issues related to Bayesian inference of LM models. Possibilities for further developments are given among the concluding remarks.     

Comments on: Latent Markov models: a review of a general framework for the analysis of longitudinal data with covariates

Bartolucci et al. (Test, 2014) provide a nice showcase of the flexibility of latent Markov models for longitudinal data. Indeed, their list of applications is impressive and includes a wide variety of models, with covariates to model transitions between latent states and direct effects on the observations, such that the model becomes a latent Markov regression model, and models for multivariate data, to mention but a few. Bartolucci et al. also briefly discuss the relationship between latent Markov models and hidden Markov models. These models share their basic assumptions, but were developed with different objectives in mind: the latent Markov model is aimed at longitudinal data, whereas the hidden Markov model is aimed at modeling time-series data. As a result of this difference in focus, different estimation and inference methods have been developed, which each have their strengths and weaknesses. Surprisingly, the literatures on latent and hidden Markov models have remained largely separate. We believe that a marriage between these literatures can provide even greater flexibility to this modeling framework than each of them can muster separately.     

Development, implementation and quality assurance of biokinetic models within CONRAD

The work of the Task Group 5.2 'Research Studies on Biokinetic Models' of the CONRAD project is presented. New biokinetic models have been implemented by several European institutions. Quality assurance procedures included intercomparison of the results as well as quality assurance of model formulation. Additionally, the use of the models was examined leading to proposals of tuning parameters. Stable isotope studies were evaluated with respect to their implications to the new models, and new biokinetic models were proposed on the basis of their results. Furthermore, the development of a biokinetic model describing the effects of decorporation of actinides by diethylenetriaminepentaacetic acid treatment was initiated.     

The PDE framework Peano applied to fluid dynamics: an efficient implementation of a parallel multiscale fluid dynamics solver on octree-like adaptive Cartesian grids

This paper presents the general purpose framework Peano for the solution of partial differential equations (PDE) on adaptive Cartesian grids. The strict structuredness and inherent multilevel property of these grids allows for very low memory requirements, efficient (in terms of hardware performance) implementations of parallel multigrid solvers on dynamically adaptive grids, and arbitrary spatial dimensions. This combination of advantages distinguishes Peano from other PDE frameworks. We describe shortly the underlying octree-like grid type and its most important properties. The main part of the paper shows the framework concept of Peano and the implementation of a Navier–Stokes solver as one of the main currently implemented application examples. Various results ranging from hardware and numerical performance to concrete application scenarios close the contribution.     

Agile manufacturing: Enablers and an implementation framework

Tougher competitive situations have led to increasing attention being paid to customer satisfaction, of which timely and customized services are the key concepts. As the product life cycle becomes shortened, high product quality becomes necessary for survival. Markets become highly diversified and global, and continuous and unexpected change become the key factors for success. The need for a method of rapidly and cost-effectively developing products, production facilities and supporting software, including design, process planning and shop floor control system has led to the concept of agile manufacturing. Agile manufacturing can be defined as the capability to survive and prosper in a competitive environment of continuous and unpredictable change by reacting quickly and effectively to changing markets, driven by customer-designed products and services. This article details the key concepts and enablers of agile manufacturing. The key enablers of agile manufacturing include: (i) virtual enterprise formation tools/metrics; (ii) physically distributed manufacturing architecture and teams; (iii) rapid partnership formation tools/metrics; (iv) concurrent engineering; (v) integrated product/production/business information system; (vi) rapid prototyping tools; and (vii) electronic commerce. A conceptual framework for the development of an agile manufacturing system and future research directions are presented in this paper. This framework takes into account the customization and system integration with the help of business process redesign, legal issues, concurrent engineering, computer-integrated manufacturing, cost management, total quality management and information technology.     

Assessment of future snowfall regimes within the Italian Alps using general circulation models

General Circulation Models GCMs are widely adopted tools to achieve future climate projections. However, one needs to assess their accuracy, which is only possible by comparison of GCMs’ control runs against past observed data. Here, we investigate the accuracy of two GCMs models delivering snowfall that are included within the IPCC panel's inventory (HadCM3, CCSM3), by comparison against a comprehensive ground data base (ca. 400 daily snow gauging stations) located in the Italian Alps, during 1990-2009. The GCMs simulations are objectively compared to snowfall volume by regionally evaluated statistical indicators. The CCSM3 model provides slightly better results than the HadCM3, possibly in view of its finer computational grid, but yet the performance of both models is rather poor. We evaluate the bias between models and observations, and we use it as a bulk correction for the GCMs' snowfall simulations for the purpose of future snowfall projection. We carry out stationarity analysis via linear regression and Mann Kendall tests upon the observed and simulated snowfall volumes for the control run period, providing contrasting results. We then use the bias adjusted GCMs output for future snowfall projections from the IPCC-A2 scenario. The two analyzed models provide contrasting results about projected snowfall during the 21st century (until 2099). Our approach provides a first order assessment of the expected accuracy of GCM models in depicting past and future snowfall upon the (Italian) Alps. Overall, given the poor depiction of snowfall by the GCMs here tested, we suggest that care should be taken when using their outputs for predictive purposes.     

Hybrid BWM-ELECTRE-based decision framework for effective offshore outsourcing adoption: a case study

The present study seeks to develop a decision framework of enabler to help managers in offshore outsourcing adoption by focusing on the relevant enablers and their intensities. A hybrid Best Worst Method (BWM) – ELimination and Choice Expressing REality approach is used to test the applicability of developed offshore outsourcing focused enabler’s across four automotive business organisations in India and the adoption score of framework among case organisations is evaluated too. The intensity of offshore outsourcing focused enablers is analysed through BWM and the ranking of organisations and adoption index scores are computed through ELimination and Choice Expressing REality method. The developed framework possesses high adoption rate in offshore outsourcing initiatives across the case organisations. Findings of the study reveal that among the main enablers; managerial and strategic enabler holds the highest weight followed by technological enablers and organisational enablers. This study further presents the sensitivity analysis to check the robustness of developed framework by conducting experiments in different conditions. This research work will facilitate managers and professionals involved in practising offshore outscoring initiatives and results in higher cost advantages on labour and raw material, increased economies of scale, and higher sustainable business development.     

Incorporating individual health-protective decisions into disease transmission models: a mathematical framework

It is anticipated that the next generation of computational epidemic models will simulate both infectious disease transmission and dynamic human behaviour change. Individual agents within a simulation will not only infect one another, but will also have situational awareness and a decision algorithm that enables them to modify their behaviour. This paper develops such a model of behavioural response, presenting a mathematical interpretation of a well-known psychological model of individual decision making, the health belief model, suitable for incorporation within an agent-based disease-transmission model. We formalize the health belief model and demonstrate its application in modelling the prevalence of facemask use observed over the course of the 2003 Hong Kong SARS epidemic, a well-documented example of behaviour change in response to a disease outbreak.     

A general framework for describing diversity within systems and similarity between systems with applications in informetrics

Building on the ideas of Stirling (J R Soc Interface, 4(15), 707?C719, 2007) and Rafols and Meyer (Scientometrics, 82(2), 263?C287, 2010), we borrow models of genetic distance based on gene diversity and propose a general conceptual framework to investigate the diversity within and among systems and the similarity between systems. This framework can be used to reveal the relationship of systems weighted by the similarity of the corresponding categories. Application of the framework to scientometrics is explored to evaluate the balance of national disciplinary structures, and the homogeneity of disciplinary structures between countries.     

Multiresolution in astronomical image processing: A general framework

Multiresolution transforms, including a wavelet transform, are applied simage visualization, image restoration, filtering and compression, × object detection. Variance stabilization is used, when appropriate, cater for common astronomical image noise models. We discuss idation of such methods in the case of astronomical image processing. A range of examples illustrate the effectiveness of this aproach in handling point source and extended astronomical objects.     

一种通用网络通信系统的设计与实现

在TCP／IP协议的基础上，采用合理的软件结构、算法以及对同一主机的多网卡支持，设计了一种可应用于大型分布式处理（如分布式仿真）的多机通信系统，目标是屏蔽诸如IP地址、端口号、套接字等网络通信概念，实现一种通用的进行网络通信实时可靠传输的机制，避免类似程序的重复开发，使网络通信的实现更加容易。应用结果表明，系统使用容易、通用性强，实现了对通信服务的实时传输和可靠传输的支持。     

Explicit robust schemes for implementation of a class of principal value-based constitutive models: Symbolic and numeric implementation

The issue of developing effective and robust schemes to implement a class of the Ogden-type hyperelastic constitutive models is addressed. To this end, special purpose functions (running under MACSYMA) are developed for the symbolic derivation, evaluation, and automatic FORTRAN code generation of explicit expressions for the corresponding stress function and material tangent stiffness tensors. These explicit forms are valid over the entire deformation range, since the singularities resulting from repeated principal-stretch values have been theorectically removed. The required computational algorithms are outlined, and the resulting FORTRAN computer code is presented.     

Manufacturing system development framework using a data models driven approach

We report on a data models driven approach for the development of a manufacturing system framework. Relational data schemes are used for the creation of data models. A modular approach is adopted for the creation of complex manufacturing system configurations. Each module is created by selecting the appropriate resources from the data models and is represented as a standard module template in the module library for future use. Several modules can be integrated together through an automated guided vehicles system to model a complex manufacturing system. Each module is autonomous in creating and executing its plans, but cooperative with other modules to realize the system's overall goals. For effective control of parts in the system, an event-based simulation strategy is implemented. The developed algorithm can resolve the situations arising due to any deadlock or conflict during a simulation run. System data tables are regularly updated as and when an event occurs in the system. The updated information includes machine status, part location and status, and capacity status, etc. of all parts and resources. A case study comprising eight part types with five different flow patterns in a three-module system is taken to show the effectiveness of the proposed approach.     

Evaluating adaptive smoothing models: some guidelines for implementation

A number of multiple-parameter adaptive exponential smoothing models have been proposed and demonstrated over the last two decades for short range forecasting. There have been conflicting results on their performance and no systematic study has been conducted to compare them in a controlled environment. The work reported here fills this void by testing a set of well known multiple-parameter adaptive procedures against the three-parameter Winters' model. First, sets of synthetic time series with known characteristics are used to compare performance for the different approaches using the standard deviation of forecast errors. Second, the information gathered at this point is used to predict the technique's performance on six empirical time series. And third, general guidelines are presented for model selection.     

回转形AUV水下通用对接装置的设计与实现

自主式水下机器人(autonomous underwater vehicle,AUV),尤其是回转形AUV,是海底探测、海洋地貌观察和军事海洋学研究的重要工具,但其续航能力一直是限制其完成远距离和长时间工作的关键问题。目前已研制出的水下对接装置只能与特定尺寸的水下机器人完成对接,通用性较差。为了解决不同尺寸回转形AUV的能源补充及数据上传下载的问题,介绍了目前存在的水下对接形式,并在此基础上设计了一款通用性水下对接装置。该装置采用水下灯光导引方式对AUV进行导引定位,当AUV进入对接装置后通过导流罩对AUV进行导向,最终采用丝杠滑台装置夹持固定AUV。该装置可以为不同尺寸的回转形AUV补充能源并提供数据上传下载服务,提高了AUV的续航力、数据收集能力,扩大了巡航范围。最后在水池中对该水下对接装置的灯光引导、夹持装置进行了测试,验证了该水下对接装置整体的可靠性及可行性。结果表明该装置结构简单,通用性较强,稳定可靠,对水下对接装置的总体设计具有一定的借鉴和指导意义。