A backoff strategy for model‐based experiment design under parametric uncertainty

Model‐based experiment design techniques are an effective tool for the rapid development and assessment of dynamic deterministic models, yielding the most informative process data to be used for the estimation of the process model parameters. A particular advantage of the model‐based approach is that it permits the definition of a set of constraints on the experiment design variables and on the predicted responses. However, uncertainty in the model parameters can lead the constrained design procedure to predict experiments that turn out to be, in practice, suboptimal, thus decreasing the effectiveness of the experiment design session. Additionally, in the presence of parametric mismatch, the feasibility constraints may well turn out to be violated when that optimally designed experiment is performed, leading in the best case to less informative data sets or, in the worst case, to an infeasible or unsafe experiment. In this article, a general methodology is proposed to formulate and solve the experiment design problem by explicitly taking into account the presence of parametric uncertainty, so as to ensure both feasibility and optimality of the planned experiment. A prediction of the system responses for the given parameter distribution is used to evaluate and update suitable backoffs from the nominal constraints, which are used in the design session to keep the system within a feasible region with specified probability. This approach is particularly useful when designing optimal experiments starting from limited preliminary knowledge of the parameter set, with great improvement in terms of design efficiency and flexibility of the overall iterative model development scheme. The effectiveness of the proposed methodology is demonstrated and discussed by simulation through two illustrative case studies concerning the parameter identification of physiological models related to diabetes and cancer care. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

Source–receptor relationships for heavy metals in the European atmosphere

Atmospheric concentrations of heavy metals (HMs), in particular As, Cd, Cu, Pb and Zn, were studied in an effort to contribute to the understanding of European source-receptor relationships. A comparison was made between the ambient concentrations measured at 11 background aerosol monitoring stations (in Denmark, the Czech Republic, Finland, Norway and Sweden) and the corresponding HM concentrations estimated by the Heavy Metals Eulerian Transport (HMET) meteorological dispersion model. The collected samples were analysed with Particle Induced X-ray Emission analysis (PIXE) except the Finnish samples which were analysed with Inductively Coupled Plasma – Mass Spectrometry (ICP-MS). The available data covers the period 1985–1994. The comparison showed that the European emissions of As, Cd and Pb seem to be fairly well estimated. On the other hand, the European Zn emissions are underestimated by a factor of 3 or more, while the Cu emissions appear to be slightly overestimated. The HMET dispersion model also made it possible to select occasions for which the sampling sites had a substantial contribution of HM from the highly polluted “Black Triangle” region (on the borders between the Czech Republic, Poland and Germany). The time evolution of the sources of HMs within this source region could be studied by applying various statistical receptor models on the extensive data set from two Danish stations, Keldsnor and Tange, covering the period 1985–1994. Four source types were clearly discerned throughout the 10 year time period. These sources were: soil dust; sea spray; general combustion and oil combustion. The strong time-dependence observed for the contribution from the Black Triangle region emphasizes the importance of keeping the emission inventories continuously updated if HMs deposition calculations and HMs emissions reduction protocols are to be based on dispersion modelling approaches.     

Tolerance modelling of vibrations of thin functionally graded plates

A problem of a modelling of vibrations of thin plates with a functionally graded macrostructure and a tolerance-periodic microstructure in planes parallel to the plate midplane is analysed. The proposed model, based on the Kirchhoff plate theory assumptions and additional hypothesis of the tolerance averaging technique [Wo?niak et al., editors. Thermomechanics of heterogeneous solids and structures. Tolerance averaging approach. ?ód?, University Press, Technical University of ?ód?; 2008], describes the effect of the microstructure size on dynamic behaviour of the plate. In this paper, as an example there are analysed free vibration frequencies of a functionally graded plate band. These frequencies are obtained in the framework of two proposed models—the tolerance model and the asymptotic model, using the known Ritz method.     

Modelling opinion formation driven communities in social networks

In a previous paper we proposed a model to study the dynamics of opinion formation in human societies by a co-evolution process involving two distinct time scales of fast transaction and slower network evolution dynamics. In the transaction dynamics we take into account short range interactions as discussions between individuals and long range interactions to describe the attitude to the overall mood of society. The latter is handled by a uniformly distributed parameter α, assigned randomly to each individual, as quenched personal bias. The network evolution dynamics is realised by rewiring the societal network due to state variable changes as a result of transaction dynamics. The main consequence of this complex dynamics is that communities emerge in the social network for a range of values in the ratio between time scales. In this paper we focus our attention on the attitude parameter α and its influence on the conformation of opinion and the size of the resulting communities. We present numerical studies and extract interesting features of the model that can be interpreted in terms of social behaviour.     

ICOME: An Immersive Collaborative 3D Object Modelling Environment

In most existing immersive virtual environments, 3D geometry is imported from external packages. Within ICOME (an Immersive Collaborative 3D Object Modelling Environment) we focus on the immersive construction of 3D geometrical objects within the environment itself. Moreover, the framework allows multiple people to simultaneously undertake 3D modelling tasks in a collaborative way. This article describes the overall architecture, which conceptually follows a client/server approach. The various types of clients, which are implemented, are described in detail. Some illustrative 3D object modelling examples are given. Extensions to the system with regard to 3D audio are also mentioned.     

Simulation of the urban climate variations in connection with the transformations of the city of Nantes since the 17th century

The paper seeks to quantify the effect of urban politics on the microclimate of the city of Nantes (France), in particular those initiated by the sanitarians in the mid-19th century to find a remedy for the insalubrity that had been developing with urban densification since the late 17th century. Intensive historical research was first carried out in order to define and date the major transformations undergone by the city, its structure (densification, then widening of the streets, filling of water courses), the lifestyle habits (heating) or the building practices (appearance of stone and paving, higher buildings, insulation). This led to the definition of 5 characteristic states of the city, in 1680, 1756, 1835, 1880 and 1945.     

Longitudinal vibration analysis of strain gradient bars made of functionally graded materials (FGM)

Longitudinal free vibration analysis of axially functionally graded microbars is investigated on the basis of strain gradient elasticity theory. Functionally graded materials can be defined as nonhomogeneous composites which are obtained by combining of two different materials in order to obtain a new desired material. In this study, material properties of microbars are assumed to be smoothly varied along the axial direction. Rayleigh–Ritz solution technique is utilized to obtain an approximate solution to the free longitudinal vibration problem of strain gradient microbars for clamped–clamped and clamped-free boundary conditions. A parametric study is carried out to show the influences of additional material length scale parameters, material ratio, slenderness ratio and ratio of Young’s modulus on natural frequencies of axially functionally graded microbars.     

Management of stream compensation for a large conjunctive use scheme,Shropshire, UK

The Shropshire Groundwater Scheme (SGS) is the largest conjunctive use scheme in the United Kingdom. The SGS operates in drought periods, pumping water from the Permo‐Triassic Sandstone aquifer in Shropshire, England to regulate flows in the River Severn, alongside releases from conventional surface water reservoirs. This regulation protects the environment and increases the security of supply of major public water supply abstractions downstream. An important operational consideration is the impact SGS groundwater abstraction has on small streams that rise on the Shropshire Permo‐Triassic Sandstone. Compensation boreholes have been installed to maintain flows during and after the operation of the SGS. This paper shows how a groundwater model of the East Shropshire Permo‐Triassic Sandstone has been used to estimate the required level of compensation flows for recent climatic conditions to optimise the use of the SGS. The catchment wide conditions are included in this analysis by using the results of a large‐scale surface water model of the River Severn.     

Modelling of temperature and forces when orthogonally machining hardened steel

This paper initially considers heat generation in single-point metal cutting and the direct/indirect techniques employed to measure cutting temperatures. The development of analytical models of the cutting process is briefly reviewed, including more recent work involving finite element (FE) methods. Details are given of the different FE packages and formulation methods used by different researchers. Following on from this, an FE model is presented using FORGE 2® to simulate cutting forces and temperature distributions when orthogonal turning a hardened hot work die steel, AISI H13 (52HRC), with polycrystalline cubic boron nitride (PCBN) tooling. Experimental data from infrared chip surface temperature measurements and cutting force output are used to validate the model. Good correlation was obtained between experimental and modelled results for temperature; however, the FE analysis underestimated feed force results due to a lack of adequate workpiece property data and simplistic tool/chip friction assumptions.     

电炉导电横臂技术的发展趋势

对电炉关键部件—导电横臂的三种类型作了对比分析，并指出全铝合金导电横臂这一新型技术，将是国内外电炉导电横臂技术的最新发展趋势。