bluuebunny/crossref_metadata_2025_split huggingface dataset:
Some ideas for QFT research
Authors: Horowitz Isaac 
Published: May 2003

AbstractFeedback theory is much less popular now than 5 years ago. However, there is little question that the problem of achieving desired system tolerances from uncertain plants, at minimum cost of feedback, will remain an important, enduring one for many future generations. Although much progress has been made, it is minuscule in comparison with the extent of the problem. The purpose here is to suggest some significant QFT research problems, some tantalizingly on the boundary of the unknown. There have been in the past many suggestions for improvements in feedback synthesis. Most e.g. the Smith Regulator (Int. J. Control 1983;38:977) have been illusory, because they were formulated in a qualitative context, without the disciplines of quantitative uncertainty and performance specifications, degrees of freedom, sensor noise, plant modification, etc. Without such disciplines, it is impossible to properly evaluate competing techniques. The reader is referred to the 1991 Survey paper for some background, Horowitz (Int. J. Control 1991;53(2):255). Copyright © 2003 John Wiley & Sons, Ltd.
Some peculiarities of load sharing control
Authors: Eitelberg Eduard 
Published: May 2003

AbstractIn the recently published book, ‘Load Sharing Control’ (Eitelberg, 1999), a frequency domain, loop‐by‐loop load sharing control system design methodology was developed and demonstrated with engineering examples. A number of new concepts were introduced in order to characterize some peculiarities that are not relevant in single‐loop control systems, or have been overlooked in the general multivariable control system theory. Some of these concepts and peculiarities are introduced and explained in this paper with a minimum of technical detail. Copyright © 2003 John Wiley & Sons, Ltd.
Control of the Aero‐Electric Power Station—an exciting QFT application for the 21st century
Authors: Gutman Per‐Olof , Horesh Eran , Guetta Rami , Borshchevsky Michael 
Published: May 2003

AbstractThe Aero‐Electric Power Station is the ultimate solar power station, utilizing the dry, hot air of Earth's desert zones. By spraying water at the top of e.g. a 1200 m tall chimney with a diameter of 400 m, the air is cooled by evaporation and flows downwards through turbines at the bottom, generating 380 MW of net electric power. The Aero‐Electric Power Station is still in the planning stage, and this paper belongs to a long series of feasibility studies.The current ‘truth’ model of the Aero‐Electric Power Station is a one‐dimensional partial differential equation model. The external slowly changing weather, defined as the mean air pressures, temperatures and humidity at the top and bottom of the tower, determines the optimal operating point, i.e. the optimal water spray flow and turbine velocity that give the largest net power. The gross power produced by the turbine is partly delivered to the grid and partly to pump sea water to spray water reservoirs. The reservoirs make it possible to use the pumping power and the spray flow rate as control.Wind changes cause significant deviations from the mean external air pressures, requiring closed loop regulation to keep the rotor velocity constant. The Aero‐Electric Power Station may be modelled as an uncertain, unstable irrational transfer function, with two disturbances (external air pressure deviations at top and bottom), two control variables (turbine power and spray flow), and one output (rotor velocity), without a cascaded structure, giving rise to a robust load sharing control problem.A robust linear feedback regulator is designed by QFT, in such a way that the load of regulation is shared between the two control inputs. A closed loop step response simulation for one operating condition, using the ‘truth’ model, demonstrates the design. Copyright © 2003 John Wiley & Sons, Ltd.
Pre‐filter design for tracking error specifications in QFT
Authors: Boje Edward 
Published: May 2003

AbstractThis note shows how the pre‐filter may be designed in quantitative feedback design of single‐input, single‐output systems with tracking error specifications (Eitelberg, Automatica, 2000; 36(2):319). The method uses gain and phase information for the pre‐filter design. The design is conveniently performed on the log polar complex plane using standard CAD tools. Copyright © 2003 John Wiley & Sons, Ltd.
Simultaneous meeting of robust control specifications in QFT
Authors: Gil‐Martínez M. , García‐Sanz M. 
Published: May 2003

AbstractSimultaneous meeting of different‐nature feedback control specifications requires special attention, particularly in the presence of uncertainties. This paper introduces some ideas to obtain a feasible set of QFT bounds, analysing the compatibility of the desired control specifications and the model uncertainty. It studies general robust feedback requirements and their mapping on QFT bounds through quadratic inequalities. Analysing them, it is possible to infer the bound typology with dependence on the model of each particular specification and the uncertainty size. Two bound typologies (amongst three categories: upper, outer and lower bounds) are possible for each type of control objective. On this basis, some general hints are established to guarantee compatible bounds at each frequency, before designing the controller. Copyright © 2003 John Wiley & Sons, Ltd.
Construction of linear time‐invariant equivalent plants for nonlinear continuous‐time and sampled‐data systems
Authors: Nataraj P. S. V. , Kotecha K. 
Published: May 2003

AbstractIn this paper, a technique is presented for constructing the so‐called linear time‐invariant equivalent (LTIE) plants used in the nonlinear quantitative feed back theory (QFT) approach. The proposed technique is applicable equally well to both continuous‐time and sampled‐data nonlinear plants described by nonlinear integro‐differential equation and nonlinear autoregressive moving average with exogenous inputs (NARMAX) models, respectively. The technique uses inclusion function and interval integration tools of interval analysis. A nonlinear chemical reactor example is used to illustrate the procedure for both nonlinear continuous‐time and sampled‐data systems, and found to yield satisfactory results in both cases. Copyright © 2003 John Wiley & Sons, Ltd.
QFT control design for an approximately linearized pneumatic positioning system
Authors: Xiang Fulin , Wikander Jan 
Published: May 2003

AbstractA block‐oriented approximate feedback linearization for control of a pneumatic cylinder positioning system is introduced and a rather detailed discussion is presented on the uncertain linearization residual characterization. It is shown that making use of the characterized gain–phase information of the linearized system leads to a more reasonable trade‐off between performance and stability in the QFT control design and thus results in high control performance. Simulation and experimental results are shown. Copyright © 2003 John Wiley & Sons, Ltd.
Fracture‐induced reconstruction of a chalcopyrite (CuFeS2) surface
Authors: Klauber Craig 
Published: May 2003

AbstractTwo factors contributing to the high binding energy asymmetry of the S 2p XPS peak for virginal chalcopyrite (CuFeS2) surfaces have been identified. The Cu, Fe and S 2p spectra of freshly fractured surfaces of chalcopyrite have been found to display a loss feature at ∼2.6 eV that is attributed to an interband transition S 3p → Fe 3d, from occupied S levels to unoccupied Fe levels. For leached chalcopyrite systems, intensity on that side of the S 2p peak sometimes has been interpreted erroneously in terms of oxidized species such as polysulphides. A second prominent S 2p component has been determined at a binding energy of 161.9 eV and identified as the sulphide dimer S22−. With supporting evidence, a simultaneous surface reconstruction and redox reaction model has been developed for the fracturing of chalcopyrite, leading to an exposed surface phase of about two layers thick with a 50% pyritic content. The pyritic nature of the fractured chalcopyrite surface has implications for understanding the leaching chemistry of chalcopyrite. Copyright © 2003 John Wiley & Sons, Ltd.
Dielectric and mechanical properties of anodic films in the Ta–Ti system
Authors: Mato S. , Alcalá G. , Skeldon P. , Thompson G. E. , Mann A. B. , Masheder D. , Habazaki H. , Shimizu K. 
Published: May 2003

AbstractAnodic oxidation at high efficiency of sputtering‐deposited Ta–Ti alloys containing 0.6–40 at.% Ti is shown to result in amorphous films comprising a relatively thin outer layer of TiO2‐based material and an inner layer consisting of units of TiO2 and Ta2O5. The two layers develop due to the faster migration of Ti4+ ions in the inner layer relative to that of Ta5+ ions. The formation ratios for the various films are in the approximate range 1.6–1.9 nm V−1. The dielectric constants of the films are ∼28, which is a similar value to that of anodic tantala. Nanoindentation revealed that the elastic modulus and hardness of the films are essentially independent of film composition, with average values of 134 and 5.3 GPa, respectively. Copyright © 2003 John Wiley & Sons, Ltd.
Grain boundary diffusion coefficients in gold–nickel thin films
Authors: Abdul‐Lettif Ahmed M. 
Published: May 2003

AbstractPolycrystalline gold–nickel thin films are deposited on silicon (111) wafers by evaporation in a vacuum of 2 × 10−6 mbar. Concentration profiles of heat‐treated specimens are obtained by Auger electron depth profiling. The heat treatments are carried out in a vacuum furnace of 4 × 10−6 mbar in the temperature interval 473–773 K. The grain boundary diffusion coefficient is determined, using a modified Wipple model, to be (3 × 10−4 cm2 s−1) exp (−0.94 eV kT−1). It is concluded that interdiffusion in the investigated system is characterized by type B kinetics, and that grain boundary diffusion plays a dominant role in the mass transport process of such films. Copyright © 2003 John Wiley & Sons, Ltd.
Experimental evidence of the reversibility of the first stage of protein adsorption at a hydrophobic quartz surface near the isoelectric point
Authors: Santos Jose H. , Matsuda Naoki , Qi Zhi‐mei , Yoshida Takamitsu , Takatsu Akiko , Kato Kenji 
Published: May 2003

AbstractThe reversibility of the first stage of adsorption of zwitterionic cytochrome c on a hydrophobic quartz surface was investigated using time‐resolved slab optical waveguide (SOWG) absorption spectroscopy. Using a novel prism‐free broadband coupling approach, absorbance data were collected successfully at a 50 ms time interval during the first few seconds after solution–surface contact. Near the isoelectric point where the cytochrome c molecules possess a net charge of zero and hence cannot be influenced by an electric field, the speed at which adsorption proceeded was found to be dependent on cytochrome c concentration as well as on surface hydrophobicity. It was also observed that the degree of protein adsorption increased as the surface hydrophobicity was increased. Within 6 s the adsorption process appeared to be reversible, as revealed by extremely low chi‐squared values when the absorbance data were fitted into the reversible Langmuir‐type kinetic model. The standard Gibbs free energy of adsorption was also calculated from the absorbance data. Copyright © 2003 John Wiley & Sons, Ltd.
Analysis of non‐woven fabric fibre using an ion and electron multibeam microanalyser
Authors: Takanashi K. , Shibata K. , Sakamoto T. , Owari M. , Nihei Y. 
Published: May 2003

AbstractNon‐woven fabric can have various functions by adding different additives to the fibre. The size of this fibre ranges from a few to a few tens of microns in diameter. In order to develop a more efficient and a longer‐life non‐woven fabric, three‐dimensional distribution of additives in the non‐woven fabric fibres is required. Owing to the spindly shape of this fibre, however, it is difficult to obtain the precise elemental distribution inside the fibre with a conventional method. Thus, a new three‐dimensional microanalysis method has been developed. One of the features of this new method is its applicability to the arbitrary‐shaped samples. According to the concept of this method, an ion and electron multibeam microanalyser has been manufactured. In this paper, the results of the application of this apparatus to the non‐woven fabric fibres are described. Focused ion beam‐induced secondary electron images and time‐of‐flight SIMS spectra and maps indicate that calcium, which is believed to have a similar distribution to Chimassorb 944 as an additive, is concentrated near the voids. Copyright © 2003 John Wiley & Sons, Ltd.
Titanium‐implanted CaTiO3 films and their changes in Hanks' solution
Authors: Asami K. , Saito K. , Ohtsu N. , Nagata S. , Hanawa T. 
Published: May 2003

AbstractTitanium‐implanted CaTiO3 film was prepared and then characterized by x‐ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectrometry (RBS) before and after immersion in Hanks' solution for 7 days. An as‐prepared specimen contained a small amount of Ar implanted during sputtering, although the pressure was as low as 10−4 Torr. Even though Ar convolution increased with an increase in the relative Ti ion dose, most of the convoluted Ar was not from the Ar gas used for Ti ion production but rather was from the Ar gas used for sputtering the CaTiO3. During Ti implantation, the CaTiO3 films were ion‐etched by Ti ions. The composition of the CaTiO3 film was not changed to any great degree by the Ti implantation, however its properties changed considerably. After immersion in Hanks' solution, the thickness of the specimen not implanted with Ti decreased the most whereas the [Ca]/[P] ratio, which was nearly unity before exposure, decreased significantly, becoming 0.23 on the Ti‐implanted specimen prepared at 200 W and 0.13 on the Ti‐implanted specimen prepared at 50 W. It was also observed by XPS that the ratio [Ca]/[P] was ∼1.9 for all Ti‐implanted specimens after immersion in Hanks' solution for 7 days. Judging from the binding energies of Ca 2p3/2 and P 2p electrons and the [Ca]/[P] ratio, it was suggested that a hydroxyapatite‐like substance had formed on the surfaces of the Ti‐implanted specimens after immersion in Hanks' solution. Copyright © 2003 John Wiley & Sons, Ltd.
Studies of photosensitive alignment layer based on ladder‐like polysilsequioxane liquid‐crystal devices using atomic force microscopy/force curve
Authors: Zhu C. F. , Shang G. Y. , Li B. S. , Wang C. , Cui L. , Xie P. , Zhang R. B. 
Published: May 2003

AbstractAtomic force microscopy (AFM)/force curve measurements were used to study the photochemical process of UV‐treated (0, 10, 20, 30 and 60 min) organic thin films that were prepared from azobenzene and cinnamate side‐chain co‐grafted ladder‐like polysilsequioxanes (LPS). The morphological data of the thin films describe the changing process on the surface of the thin film. The statistical results of the adhesion force of the thin films further demonstrate the intermolecular characteristics of the thin films. A photosensitive thin film after UV exposure for 20 min would be a better material with a preferred orientation that can be used to make liquid‐crystal devices. Copyright © 2003 John Wiley & Sons, Ltd.
Static SIMS studies of carboxylic acids on gold and aluminium–magnesium alloy surfaces
Authors: Miller D. J. , Sun L. , Walzak M. J. , Mclntyre N. S. , Chvedov D. , Rosenfeld A. 
Published: May 2003

AbstractStatic secondary ion mass spectrometry was used to study the surface reactions and lateral distributions of fatty carboxylic acid molecules on sputter‐deposited gold and aluminium surfaces, as well as commercial aluminium–magnesium alloy surfaces, cleaned using UV/ozone. Films were prepared by spin coating dilute solutions of stearic acid and lauric acid onto the above surfaces. These carboxylic acids were shown to react with the oxide formed on the aluminium and aluminum–magnesium alloy substrates to produce a deprotonated acid anion, stabilized by the formation of a magnesium soap on the aluminium–magnesium alloy surface. Secondary ion imaging of stearic acid films revealed the formation of C‐type crystals. Copyright © 2003 John Wiley & Sons, Ltd.
Sequential segregation of Sn and Sb in a Cu(111) single crystal
Authors: Asante J. K. O. , Roos W. D. , Terblans J. J. 
Published: May 2003

AbstractThe sequential segregation of Sn and Sb to the surface of a Cu(111) single crystal was measured in the temperature range 400–1100 K by Auger electron spectroscopy. It was found that Sn with the higher diffusion coefficient first segregates to the surface and then is replaced by the slower‐segregating Sb. The results were fitted by a ternary segregation model yielding segregation energies (ΔGSn= 76.3 kJ mol−1, ΔGSb= 95.9 kJ mol−1), interaction parameters (ΩSnCu= 3.8 kJ mol−1, ΩSbCu= 16.2 kJ mol−1, ΩSnSb= −5.3 kJ mol−1) and diffusion coefficients (D0(Sn)= 1.8 × 10−5m2s−1,ESn= 173 kJ mol−1,D0(Sb)= 6.0 × 10−5m2s−1,ESb= 205 kJ mol−1) for both species. The validity of the interaction coefficients and segregation energies was verified using the Guttman equations for equilibrium segregation in ternary systems. Copyright © 2003 John Wiley & Sons, Ltd.
Surface analysis of plasma‐treated polydimethylsiloxane by x‐ray photoelectron spectroscopy and surface voltage decay
Authors: Youn Bok‐Hee , Huh Chang‐Su 
Published: May 2003

AbstractSurface states of polydimethylsiloxane (PDMS) treated by plasma were investigated by x‐ray photoelectron spectroscopy and surface voltage decay. X‐ray photoelectron spectroscopy confirmed the formation of a silica‐like (SiOx, x = 3–4) oxidative surface layer. This layer increased in thickness with increasing exposure duration of plasma. Plasma exposure lowers the surface resistivity from 1.78 × 1014 to 1.09 × 1013 Ω □−1 with increasing plasma treatment time. By measuring the decay time constant of surface voltage, the calculated surface resistivity was compared with the value measured directly by a voltage–current method; good agreement between the two methods was obtained. It was observed that plasma treatment led to a decrease in the thermal activation energy of the surface conduction from 31.0 kJ mol−1 for an untreated specimen to 21.8 kJ mol−1 for a plasma‐treated specimen for 1 h. Our results allow the examination of effects of plasma on the electrical properties of PDMS. Copyright © 2003 John Wiley & Sons, Ltd.
Physicochemical characterization of biological glass coatings
Authors: Barbotteau Y. , Irigaray J. L. , Jallot E. 
Published: May 2003

AbstractMetallic implants are widely used in orthopaedic surgery but metal release has been reported by several authors. High metallic ion concentration in surrounding tissues may play a major role in therapeutic failure. We have investigated in vivo and in vitro two biological glasses (BVA and BVH) used as coatings of metal implants. Physicochemical characterization was made by several complementary methods, particularly particle induced x‐ray emission (PIXE) and energy‐dispersive x‐ray spectroscopy (EDXS) associated with electronic microscopy. Analyses clearly show the differences of behaviour between both glasses. The BVA glass is bioactive, i.e. it develops a direct chemical bond between prosthesis and bone by the formation of a calcium phosphate layer at its surface. These structural and compositional modifications are caused by hydrolysis of the glass. After its dissolution BVA glass is replaced by bone, which ensures better integration of the implant in the bone site. The BVH glass is not bioactive and is used as a cement to isolate the metal implant from the biological environment, but the coating disaggregates with implantation time and glass grains migrate through the bony lacuna network. Copyright © 2003 John Wiley & Sons, Ltd.
Hierarchical linear models for the development of growth curves: an example with body mass index in overweight/obese adults
Authors: Heo Moonseong , Faith Myles S. , Mott John W. , Gorman Bernard S. , Redden David T. , Allison David B. 
Published: May 2003

AbstractWhen data are available on multiple individuals measured at multiple time points that may vary in number or inter‐measurement interval, hierarchical linear models (HLM) may be an ideal option. The present paper offers an applied tutorial on the use of HLM for developing growth curves depicting natural changes over time. We illustrate these methods with an example of body mass index (BMI; kg/m2) among overweight and obese adults. We modelled among‐person variation in BMI growth curves as a function of subjects' baseline characteristics. Specifically, growth curves were modelled with two‐level observations, where the first level was each time point of measurement within each individual and the second level was each individual. Four longitudinal databases with measured weight and height met the inclusion criteria and were pooled for analysis: the Framingham Heart Study (FHS); the Multiple Risk Factor Intervention Trial (MRFIT); the National Health and Nutritional Examination Survey I (NHANES‐I) and its follow‐up study; and the Tecumseh Mortality Follow‐up Study (TMFS). Results indicated that significant quadratic patterns of the BMI growth trajectory depend primarily upon a combination of age and baseline BMI. Specifically, BMI tends to increase with time for younger people with relatively moderate obesity (25 BMI <30) but decrease for older people regardless of degree of obesity. The gradients of these changes are inversely related to baseline BMI and do not substantially depend on gender. Copyright © 2003 John Wiley & Sons, Ltd.
Interim analysis of continuous long‐term endpoints in clinical trials with longitudinal outcomes
Authors: Galbraith Sally , Marschner Ian C. 
Published: May 2003

AbstractThis paper discusses interim analysis for clinical trials where the primary endpoint is observed at a specific long‐term follow‐up time, but where repeated measures of the same outcome are also taken at earlier times. Methods are considered for improving the efficiency with which the long‐term treatment difference is estimated, making use of information from shorter‐term follow‐up times. This approach to interim analysis has previously been studied for binary endpoints assessed at two time points during follow‐up. Here we adapt and extend this methodology to include continuous endpoints assessed at an arbitrary number of follow‐up times, making use of methods for analysing multivariate normal data subject to monotone missingness and unstructured mean and covariance relationships. The magnitude of efficiency gains obtained by using short‐term measurements is considered, as well as how these gains depend on the number and timing of the short‐term measurements. Sequential analysis of treatment differences is discussed, including the extent to which efficiency gains translate into reductions in the expected duration of a sequentially monitored trial. The methods are illustrated on a data set involving a placebo‐controlled comparison of longitudinal cholesterol measurements. Copyright © 2003 John Wiley & Sons, Ltd.
Microarrays, pattern recognition and exploratory data analysis
Authors: Mertens Bart J. A. 
Published: May 2003

AbstractWe explore the application of principal component based approaches to pattern recognition in microarray analysis. A comparative assessment is presented, based on predictive evaluation, following a review of some key methodology. On the basis of these results, we select principal component based linear discrimination for a further in‐depth analysis. We are particularly interested in studying the use of principal component decomposition for the evaluation of the condition of estimation of the pooled covariance matrix. The results are used to give some guidance as to how principal components may be used as a data exploratory tool in the analysis of microarray data. Opportunities for further development are outlined as well as implications for wider statistical modelling of microarray data. Copyright © 2003 John Wiley & Sons, Ltd.