Optimal linear combination of Poisson variables for multivariate statistical process control

In this paper we analyze the monitoring of p Poisson quality characteristics simultaneously, developing a new multivariate control chart based on the linear combination of the Poisson variables, the LCP control chart. The optimization of the coefficients of this linear combination (and control limit) for minimizing the out-of-control ARL is constrained by the desired in-control ARL. In order to facilitate the use of this new control chart the optimization is carried out employing user-friendly Windows© software, which also makes a comparison of performance between this chart and other schemes based on monitoring a set of Poisson variables; namely a control chart on the sum of the variables (MP chart), a control chart on their maximum (MX chart) and an optimized set of univariate Poisson charts (Multiple scheme). The LCP control chart shows very good performance. First, the desired in-control ARL (ARL₀) is perfectly matched because the linear combination of Poisson variables is not constrained to integer values, which is an advantage over the rest of charts, which cannot in general match the required ARL₀ value. Second, in the vast majority of cases this scheme signals process shifts faster than the rest of the charts.     

基于伪谱展开的抛物型系统镇定与边界观测研究(英文)

模型截断设计方法在无限维系统控制中得到广泛的应用,但是其自身存在信息丢失的缺陷而限制了控制器对高频扰动抑制的性能.本文研究具有内部和Neumann边界控制的抛物型系统,其中系统采用边界测量.内部控制采用比例反馈形式,其中反馈增益核由Sturm-Liouville系统稳定性分析来待定;类似地,边界反馈的设计也采用待定反馈增益核的方式,最终对描述系统稳定性的Sturm-Liouville系统采用伪谱方法进行求解.数字仿真结果表明了该方法的有效性.     

Influence of the filler CaCO3 on the cure kinetic of the epoxy network diglycidyl ether of bisphenol a (BADGE n = 0) with isophorone diamine

The influence of the presence of CaCO₃ on the cure reaction of the epoxy network diglycidyl ether of bisphenol A with isophorone diamine has been studied. The total enthalpy of reaction, the glass transition temperature and the partial enthalpies at different isothermal temperatures have been determined using differential scanning calorimetry (DSC) in dynamic and isothermal mode. A kinetic model accounting the influence of the diffusion of the reactive groups at high conversions was used. All the kinetic parameters have been compared with those of the system without filler (CaCO₃). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Impact of human activity on NO soil fluxes

Changes in land use driven by the increasing demand of food are affecting the fluxes of trace gases to the atmosphere. The more important human activities that affect NO soil fluxes are: deforestation, intensification of agricultural practices, and biomass burning. In this review emphasis is given to identifying the physicochemical and biological processes involved in the changes, and no attempt to quantify their contribution to global or regional NO budgets is made.Conversion of tropical forest to pasture is occurring very rapidly. An increase of the NO emission is observed immediately after deforestation (1–5 years) followed by a significant decrease (below forest levels) in old pastures and secondary successional forests. It seems that deforested tropical areas produce, in the long term, less NO than primary forests. The observed changes are not completely understood, but are most likely driven by the availability of exchangeable nitrogen and the bacteria' population.Soil plowing and fertilization are important factors that affect NO fluxes in agricultural soils. Plowing increases soil porosity and aeration, as well increasing the surface area that is exposed to the atmosphere. These physical changes increase the production of soil nitrate, and the escape efficiency of NO from the soil, enhancing NO fluxes. The emission of NO from fertilized soils depends on many variables: type of fertilizer (i.e. ammonium, nitrate), the structure of the soil microbial community (e.g., populations of nitrifiers and denitrifiers), meteorogical conditions (e.g. soil moisture and temperature), and soil management (e.g. plowing). A combination of these factors should explain the large range reported for the fraction of N-fertilizer that is emitted as NO to the atmosphere. Measurements made in diverse ecosystems show that vegetation burning enhances NO soil emissions. However, it seems that different processes, which are not well understood, occur at the various sites; e.g., in the tropical savannah, enhanced emissions, from dry soils, are observed immediately after burning, whereas in Californian chaparral burned dry soils emit on average less than the unburned plots, and the fluxes only increase after soil wetting. Changes in the physical conditions of the soil surface and N availability are the most likely factors that explain the increased fluxes.     

On the analysis of heterogeneous fluids with jumps in the viscosity using a discontinuous pressure field

Heterogeneous incompressible fluid flows with jumps in the viscous properties are solved with the particle finite element method using continuous and discontinuous pressure fields. We show the importance of using discontinuous pressure fields to avoid errors in the incompressibility condition near the interface.     

A finite point method for incompressible flow problems

A stabilized finite point method (FPM) for the meshless analysis of incompressible fluid flow problems is presented. The stabilization approach is based in the finite increment calculus (FIC) procedure developed by O?ate [14]. An enhanced fractional step procedure allowing the semi-implicit numerical solution of incompressible fluids using the FPM is described. Examples of application of the stabilized FPM to the solution of two incompressible flow problems are presented. Received: 30 June 1999 / Accepted: 21 September 1999     

The Fuzzy Project Scheduling Problem with Minimal Generalized Precedence Relations

In scheduling, estimations are affected by the imprecision of limited information on future events, and the reduction in the number and level of detail of activities. Overlapping of processes and activities requires the study of their continuity, along with analysis of the risks associated with imprecision. In this line, this article proposes a fuzzy heuristic model for the Project Scheduling Problem with flows and minimal feeding, time and work Generalized Precedence Relations with a realistic approach to overlapping, in which the continuity of processes and activities is allowed in a discretionary way. This fuzzy algorithm handles the balance of process flows, and computes the optimal fragmentation of tasks, avoiding the interruption of the critical path and reverse criticality. The goodness of this approach is tested on several problems found in the literature; furthermore, an example of a 15‐story building was used to compare the better performance of the algorithm implemented in Visual Basic for Applications (Excel) over that same example input in Primavera© P6 Professional V8.2.0, using five different scenarios.     

Anisotropic thermal conductivity of silicon nitride ceramics containing carbon nanostructures

Silicon nitride (Si₃N₄) composites containing carbon nanotubes (CNTs) or graphene nanoplateles (GNPs) are of great relevance in the electronic and aerospace industries where the search for new materials with enhanced and anisotropic thermal conductivity to work in harsh environments is a strategic guideline. Here we study thermal conduction in Si₃N₄ composites with different amounts of carbon nanostructures. The effects of the nanostructure orientation respect the heat flux, the testing temperature and the α/β Si₃N₄ phase ratio are analyzed. The addition of CNTs and GNPs leads to an anisotropic thermal response, decreasing the through-thickness thermal conductivity of the Si₃N₄ composites and raising the in-plane thermal conductivity, especially for GNPs that enhance it up to twice that of the monolithic Si₃N₄. This effect is related to the preferred orientation of the nanostructures that gives a less resistive network in the in-plane direction and the intrinsic anisotropy of their thermal conductivity.     

A facile single-step procedure for the synthesis of luminescent Ln3+:YVO4 (Ln = Eu or Er + Yb)-silica nanocomposites

A simple and single-step method for the production of Ln-doped YVO₄ nanocrystals and their simultaneous encapsulation in a silica network based on the pyrolysis of liquid aerosols at 800 °C is reported. The procedure is illustrated for Yb,Er:YVO₄-silica nanocomposites consisting of spherical particles, which present up-converted green luminescence after IR excitation whose efficiency increased on annealing up to 1000 °C due to the release of impurities (adsorbed water, and residual anions). XPS spectroscopy and TEM observations revealed that the surface of the composite particles was enriched in silica, which would facilitate their functionalisation required to use them in biological applications. The procedure can also be used to prepare other rare earth doped systems as illustrated for the case of Eu-doped YVO₄/silica having down-converted red luminescence.