bluuebunny/crossref_metadata_2025_split huggingface dataset:
X‐Ray Spectra and Electronic Structure of the Compounds in the ZrCoSi System
Authors: Shcherba I. D. , Antonov V. M. , Gorelenko Yu. K. , Plotnikov M. O. , Margolych I. I. , Stadnyk Yu. V. , Yatsyk B. M. 
Published: July 2007

AbstractX‐ray spectral studies were used to establish the electronic structure of the ternary compounds from the ZrCoSi system. X‐ray emission spectra of the components of ZrCo2Si2, ZrCoSi, ZrCo5Si3, and Zr6Co16Si7 compounds were presented on a unique energy scale. The partial and total densities of electronic states were calculated by the half‐relativistic LMTO method for the ZrCo2Si2 compound. Agreement between calculated and experimental X‐ray emission bands was observed for the components of the ZrCo2Si2 compound.
A Nonlocal Pseudopotential Calculation of the Thermopower of Liquid Metals
Authors: Akinlade O. 
Published: July 2007

AbstractAn accurate pseudopotential has been used to calculate the thermopower of some simple liquid metals using a formula that incorporates the nonlocality of the potential. Firstly, we investigate the role of the structure factor in thermopower calculations and find it very significant and secondly we infer that refinements in the pseudopotential theory and thus the expression for thermopower incorporated into our calculations does not have a remarkable effect on computed thermopower values when compared with experiment.
D‐Wave Superconductivity Induced Renormalization of Phonons in Strongly Interacting Fermion Systems
Authors: Mierzejewski M. , Zieliński J. , Entel P. 
Published: July 2007

AbstractWe have calculated changes in the phonon self‐energy originating from d‐wave superconductivity in the two‐dimensional Hubbard model (U → ∞ limit). Strong local correlations have been incorporated within the mean‐field approximation for auxiliary boson fields. Due to the presence of correlated quasiparticles at the Fermi surface, changes in phonon‐energy shifts and linewidths strongly depend on the concentration of holes. In particular, pronounced effects have been derived for low frequency q = 0 phonons at low doping, where superconductivity starts to set in.
Band‐Edge Photoluminescence at Room Temperature from ZnGeP2 and AgGaSe2
Authors: Petcu M. C. , Giles N. C. , Schunemann P. G. , Pollak T. M. 
Published: July 2007

AbstractPhotoluminescence near the band edge has been observed at room temperature from bulk single crystals of ZnGeP2 and AgGaSe2. Both of these materials are ternary chalcopyrite semiconductors, but they have quite different edgerelated emission behavior. The emission from ZnGeP2 is observed to peak near 2.35eV and is dominated by transitions from the upper Γ7 conduction band to the upper Γ6 valence band. The lack of emission at 1.99eV from the lowest Γ6 conduction band in ZnGeP2 indicates a Γ6 conduction‐band‐energy minimum at the high‐symmetry point T (T1 + T2 band), rather than at Γ(k = 0). In contrast, AgGaSe2 is a direct‐band‐gap semiconductor and exhibits k = 0 radiative recombination at 1.793 eV. Based on the power dependence of the PL emis‐ sion intensity, this 1.793 eV band is shown to be excitonic in nature, thus giving a room‐temperature band‐gap energy near 1.814 eV for AgGaSe2.
Optical Reflectivity and Transmissivity of Misfit Layer Compounds (MS)nTS2 (T  Ta, Nb; M  Pb, Sm, Tb; 1.08 < n < 1.23)
Authors: Rüscher C. H. 
Published: July 2007

AbstractThe room temperature transmission and reflection behaviour of misfit layer compounds (MLCs) (MS)nTS2 (TNb, Ta; MPb, Sm, Tb) were investigated in the spectral range between 1000 and 20000 cm−1 for incident light normal to the layered structure (k ⊥ (001)). A characteristic near infrared transmission window (TW) is observed between the Drude free carrier threshold (4000 cm−1 < ω0 < 6000 cm−1) and the onset of stronger interband transitions (above 13000 cm−1). Evaluations of the absorption profiles show an interband absorption superimposed on the free carrier absorption in the TW which are related to transitions involving states in the conduction band (or conduction bands). Values of ω0 are found to be slightly smaller for E ∥ b compared to E ∥ a (parallel to the incommensurate direction) polarized spectra for all compounds under study. This effect is interpreted in terms of slightly smaller effective masses for the optical conductivity for the E ∥ a components. The temperature dependence (213 to 423 K) of the free carrier reflectivity for (PbS)1.13TaS2 shows a linear increase of the damping parameter with temperature both for E ∥ a and E ∥ b. This is suggested to be due to ordinary electron‐phonon scattering of the free carriers. Reflection spectra for E ∥ c indicate ω0 values of about 1500 cm−1 for (SmS)1.19TaS2 ((TbS)1.21NbS2) and below 1300 cm−1 for (PbS)1.13TaS2 ((PbS)1.21NbS2).
Defect profiles in semiconductor structures
Authors: Coleman P. G. 
Published: July 2007

AbstractVariable‐energy positron annihilation spectroscopy (VEPAS) has found applications in structural and electronic analysis of thin films and near‐surface layers, nanoporous materials, ion implantation, silicon photonics, and vacancy engineering. In all this applied work it is essential that VEPAS is treated as a normal member of the arsenal of spectroscopies available to the semiconductor research community. Examples are presented of how useful insights into current problems in semiconductor physics and technology have been gained by combinations of VEPAS and other techniques such as secondary ion mass spectrometry, transmission electron microscopy, electrical characterization, and optical techniques such as photoluminescence and optically‐detected magnetic resonance. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Positron annihilation spectroscopy in the study of quasicrystals and their related materials
Authors: Sato K. , Murakami H. , Kanazawa I. , Kobayashi Y. 
Published: July 2007

AbstractRecent advances in the study of quasicrystals (QC's) and their related materials (crystalline approximants) by using positron annihilation spectroscopy are reviewed. We describe how a series of positron annihilation spectroscopy has been applied for the studies of aperiodic QC's. Positron lifetime measurements revealed the presence of high concentration of structural vacancies giving rise to saturation trapping for QC's and approximants studied. Chemical environments around the structural vacancies were successfully clarified by coincident Doppler broadening measurements. In addition, the concentrations of structural vacancies were estimated by analyzing the positron diffusion data obtained by a slow positron beam under the saturation trapping condition. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Positron annihilation characteristics in UO2: for lattice and vacancy defects induced by electron irradiation
Authors: Barthe M.‐F. , Labrim H. , Gentils A. , Desgardin P. , Corbel C. , Esnouf S. , Piron J. P. 
Published: July 2007

AbstractIn this work both 22Na based positron lifetime spectroscopy (PALS) and slow positron beam based Doppler annihilation‐ray broadening spectrometry (SPBDB) have been used to characterize respectively the bulk and the first micron under the surface of sintered UO2 disks that have been polished and annealed at high temperature (1700 °C/24 h/ArH2). Results show the presence of negative ions that are tentatively identified to negatively charged oxygen atoms located in interstitial sites. The positron annihilation characteristics in the UO2 lattice have been determined and are equal to SL(UO2) = 0.371(5), WL(UO2) = 0.078(7), τL(UO2) = 169 ± 1 ps. Such disks have been irradiated at room temperature with electrons and α particles at different fluences. After irradiation SPBDB and PALS measurements show the formation of U‐related vacancy defects after a 2.5 MeV electrons irradiation whereas no defects are detected for an irradiation at 1 MeV. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Positron studies of surfaces, structure and electronic properties of nanocrystals
Authors: Eijt S. W. H. , Barbiellini B. , Houtepen A. J. , Vanmaekelbergh D. , Mijnarends P. E. , Bansil A. 
Published: July 2007

AbstractA brief review is given of recent positron studies of metal and semiconductor nanocrystals. The prospects offered by positron annihilation as a sensitive method to access nanocrystal (NC) properties are described and compared with other experimental methods. The tunability of the electronic structure of nanocrystals underlies their great potential for application in many areas. Owing to their large surface‐to‐volume ratio, the surfaces and interfaces of NCs play a crucial role in determining their properties. Here we focus on positron 2D angular correlation of annihilation radiation (2D‐ACAR) and (two‐detector) Doppler studies for investigating surfaces and electronic properties of CdSe NCs. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Future directions of positron annihilation spectroscopy in low‐k dielectric films
Authors: Gidley D. W. , Vallery R. S. , Liu M. , Peng H.‐G. 
Published: July 2007

AbstractPositronium Annihilation Lifetime Spectroscopy (PALS) has become recognized in the microelectronics industry as one of only several methods capable of quantitatively characterizing engineered nanopores in next‐generation (k < 2.2) interlayer dielectric (ILD) thin films. Successes and shortcomings of PALS to date will be assessed and compared with other methods of porosimetry such as ellipsometric and X‐ray porosimetries (EP and XRP). A major theme in future low‐k research focuses on the ability to integrate porous ILD's into chip fabrication; the vulnerability of porous dielectrics to etching, ashing, and chemical‐mechanical polishing in process integration is delaying the introduction of ultra‐low‐k films. As device size approaches 45 nm the need to probe very small (sub‐nanometer), semi‐isolated pores beneath thin diffusion barriers is even more challenging. Depth‐profiled PALS with its ability to determine a quantitative pore interconnection length and easily resolve 0.3 nm pores beneath diffusion barriers or in trench‐patterned dielectrics should have a bright future in porous ILD research. The ability of PALS (and PAS in general) to deduce evolution and growth of pores with porosity should find broad applicability in the emerging field of high performance materials with strategically engineered nanopores. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of baicalin and wogonin on mucin release from cultured airway epithelial cells
Authors: Heo Ho Jin , Lee Hyun Jae , Kim Young Sik , Kang Sam Sik , Son Kun Ho , Seok Jeong Ho , Seo Un Kyo , Lee Choong Jae 
Published: July 2007

AbstractScutellaria baicalensis Georgi has been used for the treatment of diverse chronic inflammatory diseases including respiratory disease in oriental medicine and its major components – baicalin, baicalein and wogonin – were reported to have various biological effects. This study investigated whether baicalin, baicalein and wogonin affect basal and ATP‐induced mucin release from cultured airway epithelial cells. Confluent primary hamster tracheal surface epithelial (HTSE) cells were metabolically radiolabeled using 3H‐glucosamine for 24 h and chased for 30 min in the presence of varying concentrations of each agent to assess the effects on 3H‐mucin release. The results were as follows: (1) Baicalein did not affect both basal and ATP‐induced mucin release significantly. (2) Baicalin and wogonin increased basal mucin release at the highest concentrations (10−3 m). (3) However, baicalin and wogonin significantly inhibited ATP‐induced mucin release. It is concluded that baicalin and wogonin can slightly increase basal mucin release whereas they can inhibit ATP‐induced mucin release, by directly acting on airway mucin‐secreting cells. It is suggested that baicalin and wogonin be further investigated for the possible use as mucoregulators during the treatment of chronic airway diseases. Copyright © 2007 John Wiley & Sons, Ltd.
Construction of switching sequences for reachability realization of switched impulsive control systems
Authors: Ji Zhijian , Feng Gang , Guo Xiaoxia 
Published: July 2007

AbstractThis paper studies the construction of switching sequences for reachability realization of switched impulsive control systems. An approach is proposed to design switching sequences so that the reachable subspace of switched impulsive control systems is expressed in terms of the reachable state sets of the designed switching sequences. For a class of switched impulsive control systems, it is proved that a single switching sequence can be designed with its reachable state set coinciding with the reachable subspace. Periodic switching sequences are also constructed in this paper for the reachability realization problem. The results present a new way to exploit the switching mechanism to achieve the reachability and controllability of switched impulsive control systems. Copyright © 2007 John Wiley & Sons, Ltd.
Robust stability—degree assignment and its applications to the control of flexible structures
Authors: Kimura Hidenori , Oike Taro , Miura Atsuyoshi , Akai Kenji , Kida Takashi 
Published: July 2007

AbstractA new method of robust controller synthesis is introduced which is an extension of robust stabilization to robust stability‐degree assignment. This method guarantees a lower bound of stability degree for all uncertainties within a prescribed magnitude band.The method is applied to the control of four types of flexible structures, namely, colocated beam, non‐colocated beam, beam with moving base and large scale satellite model. Excellent performances have been obtained experimentally with respect to the response speed and the robustness.
Quadratic robust tracking control — A Polynomial Matrix Approach
Authors: Kim Jeong‐Yeol , Ko Myoung‐Sam 
Published: July 2007

AbstractA quadratic robust tracking problem is solved using a polynomial matrix approach. Because of the possibly unstable mode of the control sequence we propose a new quadratic cost function of error and control sequences to facilitate the optimization. The optimal controller makes the plant output track the reference sequence robustly and minimizes the proposed quadratic cost function. We also present the parametrized set of suboptimal controllers which yield finite costs so that there exists the central optimal controller in the set when the parameter is set to zero. The usefulness of our proposed cost function is demonstrated by simulation examples. Our design procedure has advantages over two other possible approaches: the LQ state‐space approach and the Wiener–Hopf approach which may be tried to tackle the same problem. Our approach obviates the need to construct a dynamic observer compared to the state‐space approach and it is computationally attractive compared to the Wiener–Hopf approach.
Branch and bound algorithm for computing the minimum stability degree of parameter‐dependent linear systems
Authors: Balakrishnan V. , Boyd S. , Balemi S. 
Published: July 2007

AbstractWe consider linear systems with unspecified parameters that lie between given upper and lower bounds. Except for a few special cases, the computation of many quantities of interest for such systems can be performed only through an exhaustive search in parameter space. We present a general branch and bound algorithm that implements this search in a systematic manner and apply it to computing the minimum stability degree.
Stable control of nonlinear systems using neural networks
Authors: Tzirkel‐Hancock E. , Fallside F. 
Published: July 2007

AbstractA neural‐network‐based direct control architecture is presented that achieves output tracking for a class of continuous‐time nonlinear plants, for which the nonlinearities are unknown. The controller employs neural networks to perform approximate input/output plant linearization. The network parameters are adapted according to a stability principle. The architecture is based on a modification of a method previously proposed by the authors, where the modification comprises adding a sliding control term to the controller. This modification serves two purposes: first, as suggested by Sanner and Slotine,1 sliding control compensates for plant uncertainties outside the state region where the networks are used, thus providing global stability; second, the sliding control compensates for inherent network approximation errors, hence improving tracking performance.A complete stability and tracking error convergence proof is given and the setting of the controller parameters is discussed. It is demonstrated that as a result of using sliding control, better use of the network's approximation ability can be achieved, and the asymptotic tracking error can be made dependent only on inherent network approximation errors and the frequency range of unmodelled dynamical modes. Two simulations are provided to demonstrate the features of the control method.
Coprime factorization over a class of nonlinear systems
Authors: Moore J. B. , Irlicht L. 
Published: July 2007

AbstractIn this paper, we consider the problem of generalizing elements of linear coprime factorization theory to a nonlinear context. The idea is to work with a suitably wide class of nonlinear systems to cover many practical situations, yet not cope with so broad a class as to disallow useful generalizations to the linear results. In particular, we work with nonlinear systems characterized in terms of (possibly time‐varying) state‐dependent matricesA(x),B(x),C(x),D(x) and an initial statex0. (This class clearly does contain the class of finite‐dimensional linear (time‐varying) systems.) We achieve first right coprime factorizations for idealized situations. To achieve stable left factorizations we specialize to the case where the matrices are output‐dependent. Alternatively, we work with systems, perhaps augmented by a direct feedthrough term, where the input is reconstructible from the output. For nonlinear feedback control systems, with plant and controller having stable left factorizations, then under appropriate regularity‐conditions earlier results have allowed the generation of the class of stabilizing controllers for a system in terms of an arbitrary stable system (parameter). Plant uncertainties, including unknown initial conditions are modelled by means of a Yula–Kucera‐type parametrization approach developed for nonlinear systems. Certain robust stabilization results are also shown, and simulations demonstrate the regulation of nonlinear plants using the techniques developed. All the results are presented in such a way that specialization for the case of linear systems is immediate.
Multi‐input/single‐output computer‐aided control design using the quantitative feedback theory
Authors: Chait Yossi , Yaniv Oded 
Published: July 2007

AbstractThe quantitative feedback theory is an engineering design technique of uncertain feedback systems having robust stability and robust performance specifications. The crux of the quantitative feedback theory is a transformation of robust stability and robust performance specifications into domains in the complex plane, referred to as bounds, where a nominal loop transmission should lie within. To date, a quantitative feedback theory design is being carried out using manual (i.e. graphical) procedures or search algorithms. This paper shows that there exists a formal map from the uncertain plant and each closed‐loop specification to these bounds. In particular, it is shown that each map has a closed form consisting of a quadratic inequality. These maps greatly simplify the computational aspects of the quantitative feedback theory in design of single‐loop feedback systems. Based on this new development, a simple‐to‐implement, efficient computer algorithm is outlined.
A weak kharitonov theorem holds if and only if the stability region and its reciprocal are convex
Authors: Rantzer Anders 
Published: July 2007

AbstractWe give necessary and sufficient conditions on the stability region for the validity of a weak version of Kharitonov's theorem, stating that stability of an ‘interval family’ of complex polynomials is implied by stability of the corner polynomials. Furthermore, we define a class of stability regions which do not satisfy the conditions, but for which the implication still holds in the case of real polynomials.
Asymptotic linearization of uncertain nonlinear systems by means of continuous control
Authors: Bartolini G. , Pydynowski P. 
Published: July 2007

AbstractIn this paper a new method for the solution of the asymptotic linearization of uncertain nonlinear systems by means of a continuous control law is presented. The main feature of this approach consists of a continuous first‐order estimator and control laws with piecewise continuous derivatives. As an important by‐product of this theory we can deal easily with the case of some uncertain systems which do not satisfy the matching condition, and with systems presenting first order unmodelled dynamics.
Robust stabilization of singularly perturbed nonlinear systems
Authors: Corless M. , Garofalo F. , Glielmo L. 
Published: July 2007

AbstractConsider a singularly perturbed nonlinear system endowed with a control input and suppose a static nonlinear feedback law is designed. We show that the operations ‘compute the reduced order system’ (i.e., let the singular perturbation parameter μ = 0) and ‘close the feedback loop’ commute, i.e. the closed loop reduced‐order system is unambiguously determined. We then show that, if the reduced order system associated with the original system is stabilizable or has uncertainties matched with the input (a condition frequently used in the design of robust controllers), then the closed loop reduced‐order system enjoys the same property. As shown by an example, this result can be used to simplify the structure of a composite controller.
Adaptive control of aircraft in windshear
Authors: Leitmann George , Pandey Sandeep , Ryan Eugene 
Published: July 2007

AbstractThe control of an aircraft encountering windshear after takeoff is treated as a problem of stabilizing the climb rate about a desired value. An adaptive strategy is developed which uses only climb rate information. Robustness vis à vis windshear structure and intensity is illustrated via simulations employing four different windshear models.
Adaptive stabilization of multi‐input nonlinear systems
Authors: Ryan E. P. 
Published: July 2007

AbstractUniversal stabilizers are presented for two classes of nonlinear systems, linear in their multiple control inputs: (I) a class of pth order controlled differential inclusions on R″ with full state available for feedback, and (II) a class of nonlinearly perturbed linear systems with restricted state availability. The stabilizers are of a discontinuous feedback form (embedded in a set‐valued map), and incorporate adaptive matrix‐valued gain functions which exploit the existence of finite spectrum‐unmixing sets associated with the systems under consideration. The analysis draws on an extension, to differential inclusions, of LaSalle's invariance principle for ordinary differential equations.
Robust absolute stability of continuous systems
Authors: Tsypkin Ya. Z. , Polyak B. T. 
Published: July 2007

AbstractThe problem of stability of continuous‐time nonlinear systems with nonparametric uncertainty of a linear part and sector uncertainty of its nonlinear part is considered. The proposed robust stability criterion is a natural extension of the circle criterion for absolute stability. The situation with the Popov criterion is also discussed; it is demonstrated to be nonrobust for perturbations of a linear part, bounded in H∞ norm.