Models of approximation in databases

Partial information in databases can arise when information from several databases is combined. Even if each database is complete for some “world”, the combined databases will not be, and answers to queries against such combined databases can only be approximated. In this paper we describe various situations in which a precise answer cannot be obtained for a query asked against multiple databases. Based on an analysis of these situations, we propose a classification of constructs that can be used to model approximations.

The main goal of the paper is to study several formal models of approximations and their semantics. In particular, we obtain universality properties for these models of approximations. Universality properties suggest syntax for languages with approximations based on the operations which are naturally associated with them. We prove universality properties for most of the approximation constructs. Then we design languages built around datatypes given by the approximation constructs. A straightforward approach results in languages that have a number of limitations. In an attempt to overcome those limitations, we explain how all the languages can be embedded into a language for conjunctive and disjunctive sets from Libkin and Wong (1996) and demonstrate its usefulness in querying independent databases. We also discuss the semantics of approximation constructs and the relationship between them.     

Dissipative control systems synthesis with full state feedback

In this paper we present a general framework for synthesizing state feedback controllers to achieve any desired closed loop dissipative behavior. Special cases include positive real andH _∞ controller synthesis. We show that the solution to this dissipative controller synthesis problem is equivalent to the existence of a solution to a partial differential inequality (nonlinear systems case) or an algebraic Riccati inequality (linear systems case). Stability results can be obtained under appropriate detectability assumptions, and a generalization of the strict bounded real lemma is given. We also present an application of the results to a robust stabilization problem. This work was supported by the Cooperative Research Centre for Robert and Adaptive Systems (CRASys), Australia.     

GIS局部放电信号的联合时频分析

该文通过EMIP—ATP仿真软件，模拟计算了GIS局部放电信号在一个线路间档上的传播情况，为实际GIS局部放电的检测和定位提供了一个理论依据。并把联合时频分析方法应用到GIS局部放电信号的分析与处理上，取得了良好的效果。     

基于数学形态滤波器抑制局部放电窄带周期性干扰的研究

变压器局部放电在线检测的关键技术之一是有效抑制现场强烈的电磁干扰。文中引入非线性数学形态学变换，基于最小均方(LMS)算法构造了一种结构元素自适应的形态开、闭组合形态滤波器，很好地解决了局部放电在线检测的窄带周期性干扰问题。仿真表明该方法对窄带周期性干扰的噪声抑制比(NNR)大于60dB，而现场实际测量的噪声抑制比超过20dB。数学形态滤波器为电力变压器局部放电在线检测提供了一种新的干扰抑制方法。     

Further oscillation criteria for delay partial difference equations

This paper is concerned with the partial difference equation A_m+1,n+A_m,n+1−A_m,n+p_m,nA_m−k,n−l=0,m,n=0,1,2,…,, where k and l are two positive integers, {p_m,n} is a real double sequence. Some new oscillation criteria for this equation are obtained.     

Integrated condition monitoring and control of fed-batch fermentation processes

This paper investigates the benefits that the partial least squares (PLS) modelling approach offers engineers involved in the operation of fed-batch fermentation processes. It is shown that models developed using PLS can be used to provide accurate inference of quality variables that are difficult to measure on-line, such as biomass concentration. It is further shown that this model can be used to provide fault detection and isolation capabilities and that it can be integrated within a standard model predictive control framework to regulate the growth of biomass within the fermenter. This model predictive controller is shown to provide its own monitoring capabilities that can be used to identify faults within the process and also within the controller itself. Finally it is demonstrated that the performance of the controller can be maintained in the presence of fault conditions within the process.     

Optimal response under partial plant shutdown with discontinuous dynamic models

This work describes mathematical formulations for modeling aspects of partial shutdowns in multiunit plants. The specific type of partial shutdown considered is one that permits the decoupling of affected units from the rest of the plant, thus enabling continued plant operation, albeit in a more limited fashion. Parsimonious and computationally efficient mixed-integer formulations are presented for specific discontinuous phenomena that arise in partial shutdown modeling, such as shutdown thresholds, induced shutdowns, discontinuous costs, and minimum shutdown durations. It is demonstrated that induced shutdowns (secondary shutdowns triggered by the original shutdown) can be correctly penalized in the objective by capturing the shutdown's true discontinuous economic cost. The computed optimal solution is implemented in closed-loop by employing a multitiered model predictive shutdown controller, in which a discrete-time mixed-integer dynamic optimization (MIDO) problem is embedded. Both objectives of maximizing economics and minimizing restoration (shutdown recovery) time are considered.     

Simflowny: A general-purpose platform for the management of physical models and simulation problems

Simflowny is a software platform which aims to formalize the main elements of a simulation flow. It allows users to manage (i) formal representations of physical models based on Initial Value Problems (hyperbolic, parabolic and mixed-type partial differential equations), (ii) simulation problems based on such models, and (iii) discretization schemes to translate the problem to a finite mesh. Additionally, Simflowny generates automatically code for general-purpose simulation frameworks. This paper first presents an introductory example of such problems. Then, formal representations are explained. Afterwards, it summarizes the platform’s architecture. Finally, validation results are provided.     

Individual-based multi-objective optimal structured treatment interruption for HIV infection

In this paper, based on the measurable quantities from an individual patient that has infection to human immunodeficiency virus (HIV) and his/her condition is near to acquired immune deficiency syndrome (AIDS), individual-based multi-objective optimal treatments have been proposed. Firstly, the most effective parameters of the patient in computing Long-term non-progressor (LTNP) equilibrium are derived using global sensitivity analysis (GSA). To accomplish GSA effectively, Latin hypercube sampling (LHS) and partial rank correlation coefficients (PRCC) are utilized to rank each of the parameters based on each state of the 5-dimensional model. Then, these results are used by Dempster–Shafer (D–S) evidence theory (DSET) to rank the most effective parameters comprehensively. Now, these effective identified parameters are estimated using extended Kalman filter (EKF), which its covariance matrices are optimized based on particle swarm optimization (PSO) algorithm. Thus, the proposed methodology gives a calibrated model corresponding to the individual patient. Based on this calibrated model, the LTNP equilibrium related to the individual patient is derived. Using the derived individual-based LTNP equilibrium optimal structured treatment interruption (STI) strategies are extracted by defining suitable multi-objective optimization problem and solving it through using non-dominated sorting genetic algorithm-II (NSGA-II). The results demonstrate that the proposed optimal treatments are able to effectively reach LTNP equilibrium with using the minimum and maximum drug usage of 3.6% and 35.1% of full drug usage treatment. Meanwhile, the different optimal treatments give the decision-makers enough flexibility to choose the suitable treatment based on existing facilities and necessities.     

Effective suppression of deactivation by utilizing Ni-doped ordered mesoporous alumina-supported catalysts for the production of hydrogen and CO gas mixture from methane

Several different kinds of ordered mesoporous alumina (OMA)-supported and Ni-doped OMA-supported Ni catalysts have been prepared for catalytic partial oxidation of methane (CPOM) to produce hydrogen and CO gas mixture. The Ni metal was incorporated in various ways of the impregnation, the doping, and the partial doping followed by impregnation. The prepared OMA-supported catalysts showed a wormhole-like, pseudo-hexagonal structure. By incorporating Ni in the OMA matrix during synthesis of supports, the resulting catalysts showed better-distributed and less-sintered nanocrystals even after CPOM at elevated temperature for over 100 h. By employing the partial doping of Ni followed by impregnation of Ni, the prepared CPOM catalyst was found more productive due to the well-distributed and well-anchored Ni nanocrystals inside the OMA matrix and the confined ordered mesopores as well. Through the test under non-stoichiometric feed ratio, the catalyst prepared only by impregnation was found vulnerable to carbon deposition and deactivated more rapidly. Even worse, the formation rate of carbon deposition was so fast that the test could not be conducted due to the increased pressure difference. In contrast, the highly distributed Ni nanocrystals partially or fully utilizing doping were found to have stronger resistance to carbon deposition.