Reaching phase free adaptive fuzzy synergetic power system stabilizer

In this paper, an adaptive fuzzy power system stabilizer is developed based on robust synergetic control theory and terminal attractor techniques. The main contribution consists in making the dynamic system insensitive to parameters variation. This aim is achieved using a new synergetic controller design such that power system states start, evolve and remain on a designer chosen attractor toward the equilibrium point therefore avoiding transient mode. Rendering the design more robust, fuzzy logic systems are used to approximate the unknown power system dynamic functions without calling upon usual model linearization and simplifications. Based on an indirect adaptive scheme and Lyapunov theory, adaptation laws are developed to make the controller handle parameters variations due to the different operating conditions occurring on the power system and to guarantee stability. The performance of the proposed stabilizer is evaluated for a single machine infinite bus system and for a multi machine power system under different type of disturbances. Simulation results show the effectiveness and robustness of the proposed stabilizer in damping power system oscillations under various disturbances and better overall performance than classical PSS and some other types of power stabilizers.     

碳酸化塔CO2浓度的软测量

通过联碱碳酸化塔中与CO2浓度相关且可在线实时检测的参数,如进气量、温度、压力等,构造出CO2浓度的多元一次回归模型。并根据自适应辩识原理,对变量形式进行变换,导出可变窗口自适应辩识方法,建立了联碱碳酸化塔中CO2浓度估计器,利用该估计器的模型参数和可在线实时检测的相关参数,以及在线估计算法,使得联碱碳酸化塔中CO2浓度在线检测成为可能。     

Characterizing asbestos fiber comminution resulting from preparation of environmental samples

The evaluation of asbestos fibers by transmission electron microscopy requires that particulate be deposited on a filter and that the filter be prepared for analysis in a manner that retains the spatial characteristics of the particulate as it was deposited. Occasionally, the samples are prepared by redistributing the particulate onto a second filter. While numerous reports have described the effect of the redistribution of the particulate in terms of the number of particles or the resulting size of particles, no study has attempted to model the effect of redistribution. The effect of this redistribution on particle size is evaluated here and is described using standard comminution models. The proposed model is shown to reasonably fit the observed data.     

New approaches for household energy conservation—In search of personal household energy budgets and energy reduction options

Large-scale energy reduction campaigns focusing on households generally have two shortcomings. First, an energy reduction campaign is either personalized but time intensive or time extensive but generalized. Second, because only the direct energy requirements are addressed, only 50% of the total household energy requirement is subject to reduction. The other 50%, the indirect energy requirement, is much more difficult to calculate and address and therefore not subject to reduction.

In this paper, we describe a web-based tool that has the potential to overcome both of these shortcomings. The tool addresses direct as well as indirect energy requirements. By means of a simple expert system participants obtain personalized reduction options and feedback on the energy reduced. The tool was tested in Groningen (the Netherlands) with a sample of 300 households, resulting in a direct energy reduction of about 8.5% compared to a control group. The reduction in indirect energy was not statistically significant.     

Influence of arm soft tissue on non-invasive blood pressure measurements: An experimental and mathematical study

We investigated the possible influence of arm soft tissue on the accuracy of blood pressure measurements performed with indirect techniques. To this end we measured arterial pressure repeatedly on 36 patients by means of an automatic procedure based on the Riva-Rocci method and controlled by a personal computer. Measurement results point out that, in about 1/3 of patients, squeezing of arm tissue by repeated cuff pressure measurements can cause a significant decrease (0.66–1.33 kPa, i.e. 5–10 mmHg) in the estimated systolic and diastolic pressure values. This phenomenon may be ascribed to alterations in the elastic properties of arm tissue.

Mathematical analyses, performed with a finite element model of the upper arm, show that pressure transmission across the arm can be significantly affected by the elastic parameters of the soft tissue, especially by a decrease in tissue compressibility. Decreasing the Poisson ratio from 0.45 to 0.3, in fact, causes a fall in pressure transmission as high as 1–2 kPa (7.5–15 mmHg).

In order to achieve individual identification of the elastic parameters of arm tissue, we developed an original non-invasive experimental procedure, based on two contiguous cuffs placed around the same upper arm and separately inflated. The possibility of achieving a unique theoretical identificability of the elastic parameters with this procedure is demonstrated.     

Influence functions of the displacement discontinuity method for anisotropic bodies

In this study, the boundary element equations are obtained from the influence functions of a displacement discontinuity in an anisotropic elastic medium. For this purpose, Kelvin fundamental solutions for anisotropic media on infinite and semi-infinite planes are used to form dipoles from singular loads. Various combinations of these dipoles are used to obtain the influence functions of the displacement discontinuity. Boundary element equations are then derived analytically by the integration of these influence functions on a constant element which results in a linear system for unknown displacement discontinuities. The boundary integrals are calculated in closed form over constant elements. The obtained formulation is applied to a number of classical engineering problems.Tel.: +90-212-285-65-85, 90-212-285-37-07     

(Al_xGa_(1-x)As)_m/(GaAs)_m(001)超晶格的能带结构与合金组分x间的关系

采用紧束缚的重整化方法研究了(Al_xGa_(1-x)As)_m/(GaAs)_m(001)超晶格的电子能带结构与合金组分x及层厚间的变化关系。给出了临界组分x_o与层厚m间的变化关系图。并以二次函数形式给出了直接能隙和间接能隙与合金组分x间的变化关系。最后,也用Kronig—Penney模型对超晶格的电子能带结构进行了计算,并与紧束缚的计算结果进行了比较。     

Approximate weight function technique using single-layer potential for a cracked circular disc

An efficient weight function technique using the indirect boundary integral method was presented for cracked circular discs. The crack opening displacement field was presented by a single layer whose kernel was a modified form of the fundamental solution in elastostatics. The application of a single-layer potential to the weight function method leads to a unique closed-form SIF (stress intensity factor) solution. The solution can be applied to a cracked circular discs with or without an internal hole or opening. For these crack geometries over a wide range of crack ratios, the SIF solution can be applied without any modification.

The calculation procedure of SIFs for the various cracked circular discs using only one analytical solution is very simple and straightforward. The information necessary in the analysis includes only two or three reference load cases. In most cases the SIF solution using two reference SIFs gives reasonably accurate results while the SIF solution with three reference load cases may be used to improve the solution accuracy of the crack configurations, with an internal opening or hole, compared with the solutions of the available literature.     

Evaluation on the impacts of the implementation of civil building energy efficiency standards on Chinese economic system and environment

In this paper, in contrast to the usual rough estimation, we present a model to simulate and evaluate the direct, indirect economic and environmental impacts of the implementation of building energy efficiency standards on Chinese economic system and environment by 12 indicators in two scenarios. Four indicators are used to evaluate the direct economic impact degree, five indicators are used to evaluate the direct environmental impact degree, three indicators are used to evaluate the indirect economic impact degree of 34 sectors and the whole Chinese economic system. This research makes it possible to link developments in the implementation of building energy efficiency standards with environmental and economic structure change. The most important finding is that the implementation of building energy efficiency standards can reduce a large amount of pollutants emissions and increase the GDP at the same time.     

矿井通风阻力测定数据平差处理方法及应用

本文论述了矿井通风阻力测定数据平差处理的两种方法：条件平差和间接平差，并基于通风网络和平差理论编制了相应的通风阻力测量数据平差软件，最后以西石门铁矿中区通风阻力实测数据为例，验证了该种分析方法的可靠性和及实用性。