Showing papers by "Northeastern University (China) published in 2005"

A fractional order PID tuning algorithm for a class of fractional order plants

Abstract: Fractional order dynamic model could model various real materials more adequately than integer order ones and provide a more adequate description of many actual dynamical processes. Fractional order controller is naturally suitable for these fractional order models. In this paper, a fractional order PID controller design method is proposed for a class of fractional order system models. Better performance using fractional order PID controllers can be achieved and is demonstrated through two examples with a comparison to the classical integer order PID controllers for controlling fractional order systems.

An application of swarm optimization to nonlinear programming

Abstract: Particle swarm optimization (PSO) is an optimization technique based on population, which has similarities to other evolutionary algorithms. It is initialized with a population of random solutions and searches for optima by updating generations. Particle swarm optimization has become the hotspot of evolutionary computation because of its excellent performance and simple implementation. After introducing the basic principle of the PSO, a particle swarm optimization algorithm embedded with constraint fitness priority-based ranking method is proposed in this paper to solve nonlinear programming problem. By designing the fitness function and constraints-handling method, the proposed PSO can evolve with a dynamic neighborhood and varied inertia weighted value to find the global optimum. The results from this preliminary investigation are quite promising and show that this algorithm is reliable and applicable to almost all of the problems in multiple-dimensional, nonlinear and complex constrained programming. It is proved to be efficient and robust by testing some example and benchmarks of the constrained nonlinear programming problems.

A self-learning call admission control scheme for CDMA cellular networks

Abstract: In the present paper, a call admission control scheme that can learn from the network environment and user behavior is developed for code division multiple access (CDMA) cellular networks that handle both voice and data services. The idea is built upon a novel learning control architecture with only a single module instead of two or three modules in adaptive critic designs (ACDs). The use of adaptive critic approach for call admission control in wireless cellular networks is new. The call admission controller can perform learning in real-time as well as in offline environments and the controller improves its performance as it gains more experience. Another important contribution in the present work is the choice of utility function for the present self-learning control approach which makes the present learning process much more efficient than existing learning control methods. The performance of our algorithm will be shown through computer simulation and compared with existing algorithms.

Dissipativity Theory for Switched Systems

Abstract: A frame work of dissipativity theory for switched systems using multiple storage functions and multiple supply rates is set up. The exchange of "energy" between the activated subsystem and an inactivated subsystem is characterized by cross supply rates. Stability is reached when all supply rates are non-positive, as long as the total exchanged energy between the activated subsystem and any inactivated subsystems is finite. Passivity and L 2 -gain are addressed. For both cases, asymptotic stability is guaranteed under certain "negative" output feedback. Feedback invariance of passivity and a small-gain theorem are also given.

Three‐dimensional immersed finite element methods for electric field simulation in composite materials

Abstract: This paper presents two immersed finite element (IFE) methods for solving the elliptic interface problem arising from electric field simulation in composite materials. The meshes used in these IFE methods can be independent of the interface geometry and position; therefore, if desired, a structured mesh such as a Cartesian mesh can be used in an IFE method to simulate 3-D electric field in a domain with non-trivial interfaces separating different materials. Numerical examples are provided to demonstrate that the accuracies of these IFE methods are comparable to the standard linear finite element method with unstructured body-fit mesh. Copyright © 2005 John Wiley & Sons, Ltd.

Two-dimensional dynamic PCA for batch process monitoring

Abstract: Batch processes play an important role in many industriesfor flexible manufacturing of high value-added products. On-line monitoring of batch processes is of critical importance inensuring operation safety and quality consistency. Multivariatestatistical methods for continuous processes, such as principalcomponent analysis (PCA) and partial least square (PLS), havebeen extended to batch process monitoring with some suc-cesses, for example, multiway PCA/PLS,

Fuzzy expected value modelling approach for determining target values of engineering characteristics in QFD

Abstract: Quality function deployment (QFD) is a planning and problem-solving tool that is renowned for translating customer requirements into the technical attributes of a product. To deal with the imprecise elements in the development process, fuzzy set theory is incorporated into QFD methodology. A novel fuzzy expected value operator approach is proposed in this paper to model the QFD process in a fuzzy environment, and two fuzzy expected value models are established to determine the target values of engineering characteristics in handling different practical design scenarios. Analogous to stochastic programming, the underlying philosophy in the proposed approach is based on selecting the decision with maximum expected returns. Furthermore, the proposed approach considers not only the inherent fuzziness in the relationships between customer requirements and engineering characteristics, but also the correlation among engineering characteristics. These two kinds of fuzzy relationships are aggregated to give the fu...

The fuzzy clustering analysis based on AFS theory

Abstract: In the framework of axiomatic fuzzy sets theory, we first study how to impersonally and automatically determine the membership functions for fuzzy sets according to original data and facts, and a new algorithmic framework of determining membership functions and their logic operations for fuzzy sets has been proposed. Then, we apply the proposed algorithmic framework to give a new clustering algorithm and show that the algorithm is feasible. A number of illustrative examples show that this approach offers a far more flexible and effective means for the intelligent systems in real-world applications. Compared with popular fuzzy clustering algorithms, such as c-means fuzzy algorithm and k-nearest-neighbor fuzzy algorithm, the new fuzzy clustering algorithm is more simple and understandable, the data types of the attributes can be various data types or subpreference relations, even descriptions of human intuition, and the distance function and the class number need not be given beforehand.

A neural network model and algorithm for the hybrid flow shop scheduling problem in a dynamic environment

Abstract: A hybrid flow shop (HFS) is a generalized flow shop with multiple machines in some stages. HFS is fairly common in flexible manufacturing and in process industry. Because manufacturing systems often operate in a stochastic and dynamic environment, dynamic hybrid flow shop scheduling is frequently encountered in practice. This paper proposes a neural network model and algorithm to solve the dynamic hybrid flow shop scheduling problem. In order to obtain training examples for the neural network, we first study, through simulation, the performance of some dispatching rules that have demonstrated effectiveness in the previous related research. The results are then transformed into training examples. The training process is optimized by the delta-bar-delta (DBD) method that can speed up training convergence. The most commonly used dispatching rules are used as benchmarks. Simulation results show that the performance of the neural network approach is much better than that of the traditional dispatching rules.

Octadecyl immobilized surface for precipitate collection with a renewable microcolumn in a lab-on-valve coupled to an electrothermal atomic absorption spectrometer for ultratrace cadmium determination.

Abstract: Octadecyl immobilized surface was, for the first time, proved to be a superb precipitate-collecting medium. Surface charge effect was assumed to dominate the adsorption of cadmium hydroxide precipitate, facilitated by electrostatic interaction between the negatively charged C18 bead surface and positively charged cadmium hydroxide clusters. Residual silanol groups on the C18-immobilized silica surface did not contribute to precipitate adsorption. A novel procedure for ultratrace cadmium preconcentration was proposed by incorporating a renewable microcolumn in a lab-on-valve system. Cd(OH)2 precipitate was adsorbed onto the C18 surface, which was afterward eluted with 20 μL of nitric acid (1%) and quantified with detection by electrothermal atomic absorption spectrometry. An enrichment factor of 28 and a limit of detection of 1.7 ng L-1, along with a sampling frequency of 13 h-1 were obtained with a sample consumption of 600 μL within the concentration range of 0.01−0.2 μg L-1, achieving a precision of 2.1...

Delay-dependent H-infinity control for linear descriptor systems with delay in state

Abstract: A delay-dependent H-infinity control for descriptor systems with a state-delay is investigated. The purpose of the problem is to design a linear memoryless state-feedback controller such that the resulting closed-loop system is regular, impulse free and stable with an H-infinity norm bound. Firstly, a delay-dependent bounded real lemma(BRL) of the time-delay descriptor systems is presented in terms of linear matrix inequalities(LMIs) by using a descriptor model transformation of the system and by taking a new Lyapunov-Krasovsii functional. The introduced functional does not require bounding for cross terms, so it has less conservation.Secondly, with the help of the obtained bounded real lemma, a sufficient condition for the existence of a new delay-dependent H-infinity state-feedback controller is shown in terms of nonlinear matrix inequalities and the solvability of the problem can be obtained by using an iterative algorithm involving convex optimization. Finally, numerical examples are given to demonstrate the effectiveness of the new method presented.

Microstructure of rapidly solidified Cu–25 wt.% Cr alloys

Abstract: Rapid solidification of Cu–25 wt.% Cr alloys was carried out by melt spinning at three wheel speeds 4, 12 and 36 m/s. The microstructure of the ribbons was investigated by scanning electron microscopy (SEM). It was found that the ribbons generally have a microstructure consisting of a fine dispersion of a Cr-rich phase in a Cu-rich matrix, and that the morphology and size of the Cr-rich phase vary with the wheel speed. For lower wheel speeds, the Cr-rich phase shows dual morphologies, dendrites and spheroids. The Cr-rich dendrites are all distributed around the Cr-rich spheroids, and have a larger amount on the free surface than on the wheel surface. The Cr-rich spheroids show a wide distribution of size, and have a larger mean size on the free surface than on the wheel surface. In the ribbons of the lowest wheel speed, small Cr-rich spheroids tend to gather around those big ones forming spheroid clusters. For the highest wheel speed, the Cr-rich phase shows one morphology, spheroids, and a reduced size. The results were discussed with respect to the formation of the Cr-rich spheroids during rapid solidification.

The constituents in Al–10Zn–2.5Mg–2.5Cu aluminum alloy

Abstract: The constituents in Al–10Zn–2.5Mg–2.5Cu aluminum alloy and their morphology and distribution pattern in the subsequent working process were investigated by SEM, energy spectrum microanalysis and X-ray diffraction. Constituents in the alloy consisted of Al7Cu2Fe and Al14Mg33Zn37Cu13 of the same crystal structure with Mg32(AlZn)49. The compositions of alloy elements in Al14Mg33Zn37Cu13 all had a broad range. During the extrusion of alloy ingot, Al7Cu2Fe crushed obviously and distributed along the extrusion direction, Al14Mg33Zn37Cu13 crushed slightly. But Al14Mg33Zn37Cu13 in the extrusion rod with heat treatment was easy to break during the tensile test and became the source of the crack.

Multi-model direct adaptive decoupling control with application to the wind tunnel system.

Abstract: In this paper, a new multi-model direct adaptive decoupling controller is presented for multivariable processes, which includes multiple fixed optimal controllers, one free-running adaptive controller, and one re-initialized adaptive controller. The fixed controllers provide initial control to the process if its model lies in the corresponding region. For each controller selected, the re-initialized adaptive controller uses the values of this particular controller to improve the adaptation speed. This controller may replace the fixed controller at a later stage according to the switching criterion which is to select the best one among all controllers. A free-running adaptive controller is also added to guarantee the overall system stability. Different from the multiple models adaptive control structure proposed in Narendra, Balakrish-nan, and Ciliz [Adaptation and learning using multiple models, switching, and tuning. IEEE Control Syst. Mag. 15 , 37–51 (1995)], the method not only is applicable to the multi-input multi-output processes but also identifies the decoupling controller parameters directly, which reduces both the computational burden and the chances of a singular matrix during the process of determining controller parameters. Several examples for a wind tunnel process are given to demonstrate the effectiveness and practicality of the proposed method.

Estimation of maximum inclusion size and fatigue strength in high-strength ADF1 steel

Abstract: There are two statistic methods, statistics of extreme values (SEV) and generalized Pareto distribution (GPD), which estimate the size of maximum inclusion in high-strength steel. The characteristic size of the maximum inclusion was evaluated by above two methods in different volumes of ADF1 steel, and the fatigue strength was estimated according to the characteristic size of inclusion in different volumes of ADF1 steel and compared with the experimental results. (c) 2004 Elsevier B.V. All rights reserved.

Ultrasonication-assisted synthesis of calcium carbonate nanoparticles

Abstract: This article presents a batch carbonation method with ultrasonication to synthesize monodispersed nanoparticles of calcium carbonate (CaCO3). The synthesis processes with and without ultrasonication were compared. The results showed that the application of ultrasonication into the synthesis caused a supersaturation of Ca2+ ions in the synthesis, leading to a rapid nucleation of calcium carbonate and improved the solute transfer as well as. It was also found that the effect of ultrasonication on the grain size of the nanoparticles synthesized was related to other synthesis conditions, such as initial temperature for carbonation, mass fraction of Ca(OH)2 suspension, and CO2 flow rate. The initial temperature applied for the carbonation was increased by at least 5°C when ultrasonication was applied. The nanoparticles formed in the presence of ultrasonication became smaller with a narrower particle size distribution at 6–12 wt.% of Ca(OH)2 suspension or at 1.28 l/h of CO2 consumed by per gram of Ca(O...

Sub-Optimum H2 Rational Approximations to Fractional Order Linear Systems

Abstract: In this paper, we propose a procedure to achieve rational approximation to arbitrary fractional order linear time invariant (FO-LTI) systems with sub-optimum H2 -norm. Through illustrations, we show that the rational approximation is simple and effective. It is also demonstrated that this sub-optimum approximation method is effective in designing integer order controllers for FO-LTI systems in general form. Useful Matlab codes are also given in the appendices.Copyright © 2005 by ASME

Trends and perspectives of flow injection/sequential injection on-line sample-pretreatment schemes coupled to ETAAS

Abstract: Flow injection (FI) analysis, the first generation of this technique, became in the 1990s supplemented by its second generation, sequential injection (SI), and most recently by the third generation (ie, Lab-on-Valve) The dominant role played by FI in automatic, on-line, sample pretreatments in recent decades is amply demonstrated by the large number of publications to which it has given rise Among these, its hyphenation with electrothermal atomic absorption spectrometry (ETAAS) is one of the most attractive sub-branches because of the high sensitivity of ETAAS instruments for metal species After a decade of development, it is apparent from the literature that coupling FI sample pretreatment with ETAAS remains most dynamic in the new millenium; meanwhile, it is exciting to note that some novel trends associated with this subject have also emerged The aim of this mini-review is thus to illustrate the state-of-the-art progress in implementing miniaturized FI/SI systems for on-line separation and preconcentration of trace metals with detection by ETAAS since 2000 We also discuss future perspectives in this field

Improvement of oxidation resistance of γ-TiAl At 800 and 900 °C in air by TiAl2 coatings

Abstract: In the present work, γ-TiAl and TiAl 2 coatings with the thickness of about 20 μm were made on γ-TiAl substrates by using a close-field magnetron sputter deposition (CFMSD) technique. The coatings showed good quality with no micro-cracks being observed in the as-deposited TiAl 2 coating cross-sections. Oxidation exposure tests at 800 and 900 °C in air were carried out to assess the oxidation resistance of the coatings and the cast γ-TiAl. The γ-coating and cast TiAl showed similar oxidation performance. Both of them had suffered great oxide losses with the formation of Al 2 O 3 + TiO 2 mixtures and no Al 2 O 3 -rich layer was found in either case. By contrast, only external Al 2 O 3 layers with a θ -phase structure was formed on the TiAl 2 coatings at 800 and 900 °C, and the θ-Al 2 O 3 scales showed high protective ability with low mass-gains and good scale adherence. After the oxidation exposures, the TiAl 2 coating remained to be almost free of micro-clacks, and an inter-diffusion region of about 5 μm was observed between the TiAl 2 coating and the γ-substrate, which could act as a metallurgical bonding between the coating and substrate.

Electropolymerization of aniline in aqueous solutions at pH 2 to 12

Abstract: Electroactive polyaniline (PANI) films were made in aqueous solutions at pH 2 to 12 by means of potential cycling. The protonation degree of oligoanilines and PANI was low in solutions of high pH, resulting in high polymerization efficiency. Fewer PANI hydrolysis products were formed when electropolymerization of aniline was conducted in neutral or slightly basic solutions, providing a synthetic route for PANI with little degradation. FT-IR spectra of PANI made in solutions of different pH displayed main vibrational bands of the polymer, including the characteristic peak of protonated states of PANI. SEM images of films made in neutral or basic solutions showed three-dimensional distributions, which were very different from those made in slightly acidic solutions.