bluuebunny/crossref_metadata_2025 huggingface dataset:
A model reference quantitative feedback design theory with application to turbomachinery
Authors: Yau Chin‐Horng , Gallagher Joseph E. , Nwokah Osita D. I.
Published: July 2007

A new decentralized robust control design framework, model reference quantitative feedback design (MRQFD), is developed for the design of the MIMO parametric uncertain control systems. An internal model reference loop is proposed to obtain the achievement of generalized diagonal dominance (GDD) and the reduction of uncertainty in the resultant compensated internal loop system. Based on nonnegative matrix theory, a useful design guide is derived to achieve the GDD condition for the internal model reference loop. Then a sensitivity‐based quantitative feedback design (QFD) method is developed and used to solve the resulting series of single‐loop QFD problems. The MIMO quantitative specifications are guaranteed to be satisfied by the proposed design framework for largely uncertain systems. A successful application to the design of a robust multivariable controller for the Allison PD‐514 aircraft turbine engine is presented to demonstrate the effectiveness of the methodology developed here.
OptimalH∞general distance problem with degree constraint
Authors: Kavranogtlu Davut , Bettayeb Maamar
Published: July 2007

In this paper the optimalH∞, general distance problem, for continuous‐time systems, with a prescribed degree on the solution is studied. The approach is based on designing the Hankel singular values using an imbedding idea. The problem is first imbedded into another problem with desirable characteristics on the Hankel singular values, then the solution to the original problem is retracted via a compression. The result is applicable to both the one‐block and the four‐block problems. A special case is given for illustration.
Semi‐global stabilization of minimum phase nonlinear systems in special normal form via linear high‐and‐low‐gain state feedback
Authors: Lin Zongli , Saberi Ali
Published: July 2007

We provide an alternative solution to the problem of semi‐global stabilization of a class of minimum phase nonlinear systems which is considered in Reference 17. Our method yields a stabilizinglinearstate feedback law in contrast to anonlinearstate feedback law proposed in Reference 17. We eliminate the peaking phenomenon by inducing a specific time‐scale structure in the linear part of the closed‐loop system. This time‐scale structure consists of a very slow and a very fast time scale. The crucial component in our method is the relation between the slow and the fast time scales. Our proposed linear state feedback control law has asingletunable gain parameter that allows for local asymptotic stability and regulation to the origin for any initial condition in somea priorigiven (arbitrarily large) bounded set.
Fixed‐orderH∞compensator design
Authors: Yeh Hsi‐Han , Hsu Chin S. , Banda Siva S.
Published: July 2007

A method is presented for the construction of fixed‐order compensators to provideH∞norm constraint for linear control systems with exogenous disturbances. The method is based on the celebrated bounded‐real lemma that predicates theH∞norm constraint via a Riccati inequality. The synthesis of fixed‐order controllers whose dimensions are less than the order of a given plant, is demonstrated by a set of sufficient conditions along with a numerical algorithm.
Approximate output tracking for nonlinear non‐minimum phase systems with an application to flight control
Authors: Benvenuti L. , di Benedetto M. D. , Grizzle J. W.
Published: July 2007

An unstable zero‐dynamics is a known obstruction to inducing exact asymptotic tracking for an open set of output trajectories with internal stability. This paper proposes a procedure for achieving approximate tracking for a nonlinear system whose linearization possesses real right‐half plane zeros. The method is guaranteed to remove the right‐half plane zeros while the other zeros remain in their previous location; moreover, it provides information on the class of signals for which good approximate tracking can be obtained. With other methods, the right‐half plane zeros are eliminated but the final location of the remaining zeros is not known a priori. The design procedure is illustrated on a trajectory control problem of an aircraft in rapid manoeuvres. Simulations illustrate the computations involved and show that precise lateral and longitudinal manoeuvres can be performed, even in the presence of uncertainties.
A linear matrix inequality approach toH∞control
Authors: Gahinet Pascal , Apkarian Pierre
Published: July 2007

The continuous‐ and discrete‐timeH∞control problems are solved via elementary manipulations on linear matrix inequalities (LMI). Two interesting new features emerge through this approach: solvability conditions valid for both regular and singular problems, and an LMI‐based parametrization of allH∞‐suboptimal controllers, including reduced‐order controllers.

The solvability conditions involve Riccati inequalities rather than the usual indefinite Riccati equations. Alternatively, these conditions can be expressed as a system of three LMIs. Efficient convex optimization techniques are available to solve this system. Moreover, its solutions parametrize the set ofH∞controllers and bear important connections with the controller order and the closed‐loop Lyapunov functions.

Thanks to such connections, the LMI‐based characterization ofH∞controllers opens new perspectives for the refinement ofH∞design. Applications to cancellation‐free design and controller order reduction are discussed and illustrated by examples.
Optimal solutions to a two‐block ℋ︁∞problem
Authors: Meinsma Gjerrit
Published: July 2007

In this paper a generator of all optimal solutions to two‐block ℋ︁∞problems is derived. The derivation is in frequency domain and hinges on geometrical arguments. The results involve noncanonical Wiener‐Hopf factorization of rational matrices.
Robust control of multi‐robot systems: The generalized energy accumulation approach
Authors: Song Y. D. , Anderson J. N. , Lai H. Y.
Published: July 2007

This paper is concerned with the control problem of a multi‐robot system handling a common payload with unknown mass properties. Force constraints at the grasp points are considered. Robust control schemes are proposed to cope with the model uncertainty and achieve asymptotic path tracking. To deal with the force constraints, a strategy for optimally sharing the task is suggested. This strategy basically consists of two steps. The first is to detect the roots that need help and the second to arrange for help. It is shown that the overall system is robust to uncertain payload parameters, and satisfies the force constraints.
Design of minimax robust LQG controllers under parameter and noise uncertainties
Authors: Chen Wen‐Hua
Published: July 2007

The problem of design of minimax robust LQG controllers for linear systems with parameter and noise uncertainties is considered in this paper. Necessary and sufficient conditions for converting this problem to a two‐person, zero‐sum continuous game problem are presented. A simple procedure for design of a suboptimal minimax robust LQG controller, i.e., the LQG controller for least‐favourable model, is proposed. Necessary and sufficient conditions for the existence of a saddle point are established. Under these conditions, the controller obtained is exactly the minimax LQG controller. When there does not exist a saddle point, the worst‐case error between the controller obtained and the minimax robust LQG controllers under described uncertainties is bounded.
New filters for internal model control design
Authors: Campi Marco , Lee Wee Sit , Anderson Brian D. O.
Published: July 2007

In this paper we study the design of a new two‐degree‐of‐freedom filter for the internal model control (IMC) method. The new filter alleviates some disadvantages of the standard IMC filter when the IMC method is applied to unstable plants that do not have non‐minimum‐phase zeros. We show that by employing the new filter, the resulting system has a flatter frequency response, better stability robustness, and little overshoot in the step response. Furthermore, one of its design parameters can be related directly to the closed‐loop bandwidth and the other parameter can be used to control the recovery time after an overshoot has occurred in the step response. These features are important in the application of the IMC method to a new approach of adaptive robust control. Examples are given in the paper to illustrate the new filter design.
Quadratic stabilization and tracking results applied to the benchmark problem
Authors: Dolphus R. M. , Schmitendorf W. E.
Published: July 2007

Recent results regarding quadratic stabilization and disturbance attenuation are applied to the benchmark problem. We investigate the minimum achievable levels of disturbance attenuation for different disturbance inputs and controlled outputs. We then develop a feedforward tracking controller design which tracks step inputs while maintaining the disturbance attenuation properties of the regulator.
A gradient flow approach to the robust pole‐placement problem
Authors: Lam James , Van Wei‐Yong
Published: July 2007

This paper provides a computational procedure for a type of robust pole‐placement problem. By exploiting the differentiability nature of the objective function based on the Frobenius norm condition number, the minimization problem is formulated in terms of a gradient flow to which standard ODE numerical routines can be applied. It is shown that a minimum point exists for the objective function. The algorithm is efficient and faces no singularity problem with the resulting eigenvector matrix. A numerical example is used to illustrate the technique and comparison with other methods is made.
RobustH∞tracking: A game theory approach
Authors: de Souza C. E. , Shaked U. , Fu M.
Published: July 2007

This paper investigates the problem of finite‐time‐horizon robustH∞tracking, for linear continuous time‐varying systems, from the game theory point of view. Three tracking problems are considered, depending on whether the reference signal to be tracked is perfectly known in advance, measured on line, or previewed in a fixed interval of time ahead. No aprioriknowledge of a dynamic model for the reference signal is assumed, and the parameters of the system are not completely known. A game is defined where, given the specific information on the tracking signal, the controller plays against nature that can choose any initial condition, any bounded energy disturbance input and measurement noise, and any set of parameters in a prescribed bounded region. A standard quadratic pay‐off function is defined where the energy of the tracking error signal is weighted against the energy of the disturbance, the noise signal, and the Euclidean norm of the initial condition.

Conditions for the existence of a saddle‐point equilibrium in this zero‐sum game are not easy to find. We, therefore, augment the state‐space description of the system to convert the parameter uncertainty into exogenous bounded energy signals. An augmented game is then defined on the new perfectly known system, and it is shown that its saddle‐point equilibrium solution, if it exists, guarantees a prescribedH∞‐norm performance of the tracker, in the original system, for all possible parameters.

Necessary and sufficient conditions for the existence of a saddle‐point solution to the augmented game are determined.H∞‐tracking controllers, which guarantee the prescribed performance level for all possible parameters, are derived for both the state and the output feedback cases.
Control of wheeled mobile robots not satisfying ideal velocity constraints: A singular perturbation approach
Authors: D'andréa‐novel B. , Campion G. , Bastin G.
Published: July 2007

We propose in this paper a singular perturbation formulation for mechanical systems not exactly satisfying velocity constraints. We particularize to ‘wheeled mobile robots’ which do not satisfy ideal pure rolling and nonslipping constraints. We study the robustness of static‐state linearizing feedback laws which have been obtained to solve a point tracking problem in the ideal case when constraints were satisfied.
Energy methods for stability of bilinear systems with oscillatory inputs
Authors: Baillieul J.
Published: July 2007

A large body of recent literature has been devoted to the topic of motions of mechanical systems forced by oscillatory inputs (see, for example, References 7, 12, 15, 17 and 29). A common feature in most of this work (with Reference 7 being the exception) is that the results apply principally to kinematic problems, and the equations of motion do not involve drift terms. The main object of study in this paper is the class of bilinear control systems with oscillatory (periodic) inputs. We shall show that included in this class are models of mechanical system dynamics which are obtained through a process of reduction and linearization about operating points. In particular, we study the stability of such systems under high‐frequency, periodic forcing. Theaveraged potentialis defined for linearizations of the systems on the (reduced) configuration space, and it is shown that stable motions of the forced system are associated with minimum values of this quantity. We use both classical averaging theory as well as a novel geometric argument to provide parallel but independent assessments of the use of theaveraged potentialin carrying out a stability analysis. A salient feature of the geometric approach is that we are able to justify the use of an energy‐like quantity to determine Lyapunov stability in conservative mechanical systems. This makes contact with a growing body of literature on the use of energy methods for stability and control design (e.g. References 7, 8, 18, 24, 26 and 27). We briefly describe the connection with previous work on the averaged potential.
On passivity‐based output feedback global stabilization of euler‐lagrange systems
Authors: Ortega Romeo , Loria Antonio , Kelly Rafael , Praly Laurent
Published: July 2007

It is well known that in systems described by Euler‐Lagrange equations the stability of the equilibria is determined by the potential energy function. Further, these equilibria are asymptotically stable if suitable damping is present in the system. These properties motivated the development of a passivity‐based controller design methodology which aims at modifying the potential energy of the closed loop and the addition of the required dissipation. To achieve the latter objective measurement of the generalized velocities is typically required. Our main contribution in this paper is the proof that damping injection without velocity measurement is possible via the inclusion of a dynamic extension provided the system satisfies a dissipation propggation condition. This allows us to determine a class of Euler‐Lagrange systems that can be globally asymptotically stabilized with dynamic output feedback. We illustrate this result with the problem of set‐point control of elastic joints robots. Our research contributes, if modestly, to the development of a theory for stabilization of nonlinear systems with physical structures which effectively exploits its energy dissipation properties.
Classical framework for nonholonomic mechanical control systems
Authors: Steigenberger Joachim
Published: July 2007

With this paper we recall some of the formal framework developed in classical analytical mechanics with emphasis on constrained systems. It can be used in describing nonholonomic control systems and serve as a starting point for further differential‐geometric investigations.
The multi‐steeringN‐trailer system: A case study of goursat normal forms and prolongations
Authors: Tilbury D. , Sastry S.
Published: July 2007

In this paper, wheeled mobile robots towing trailers are used as examples of systems which can be converted into extended Goursat normal form. For some configurations of this class of systems, a prolongation of the Pfaffian system is necessary before the Goursat form can be achieved. The advantage of the Goursat form is that once the kinetic constraints are in this normal form, the point‐to‐point path planning problem can be solved in a straightforward way.
On the continuity and incremental‐gain properties of certain saturated linear feedback loops
Authors: Chitour Yacine , Liu Wensheng , Sontag Eduardo
Published: July 2007

This paper discusses various continuity and incremental‐gain properties for neutrally stable linear systems under linear feedback subject to actuator saturation. The results complement our previous ones, which applied to the same class of problems and provided finite‐gain stability.
Robust control of constrained systems via convex optimization
Authors: Sznaier Mario , Blanchini Franco
Published: July 2007

A successful controller design paradigm must take into account both model uncertainty and design specifications. Model uncertainty can be successfully addressed using ℋ︁∞robust control theory. However, this framework cannot directly accommodate the realistic case where in addition to robustness considerations the system is subject to both time‐ and frequency‐domain specifications, such as bounds on the control action. In this paper we propose a design procedure, based upon the use of convex optimization, that takes explicitly into account both time‐ and frequency‐domain specifications. The main result of the paper is a new framework to address problems having both control and output constraints and model uncertainty. Additionally, the paper serves as a brief tutorial on the issues involved in addressing design problems with multiple design specifications via convex optimization.
Constrained stabilization of discrete‐time systems
Authors: Zheng Alex , Balakrishnan Ragu , Morari Manfred
Published: July 2007

Based on the growth rate of the set of states reachable with unit‐energy inputs, we show that a discretetime controllable linear system is globally controllable to the origin with constrained inputs if and only if all of its eigenvalues lie in the closed unit disk. These results imply that the constrained Infinite‐Horizon Model Predictive Control algorithm is stabilizing for a sufficiently large number of control moves if and only if the controlled system is stabilizable and all its eigenvalues lie in the closed unit disk.

In the second part of the paper, we propose an implementable Model Predictive Control algorithm and show that with this scheme a discrete‐time linear system withnpoles on the unit disk (with any multiplicity) can be globally stabilized if the number of control moves is larger thann. For pure integrator systems, this condition is also necessary. Moreover, we show that global asymptotic stability is preserved for any asymptotically constant disturbance entering at the plant input.
Discrete‐time reference governors and the nonlinear control of systems with state and control constraints
Authors: Gilbert Elmer G. , Kolmanovsky Ilya , Tan Kok Tin
Published: July 2007

Discrete‐time, linear control systems with specified pointwise‐in‐time constraints, such as those imposed by actuator saturation, are considered. The constraints are enforced by the addition of a nonlinear ‘reference governor’ that attenuates, when necessary, the input commands. Because the constraints are satisfied, the control system remains linear and undesirable response effects such as instability due to saturation are avoided. The nonlinear action of the reference governor is defined in terms of a finitely determined maximal output admissible set and can be implemented on‐line for systems of moderately high order. The main result is global in nature: if the input command converges to a statically admissible input and the initial state of the system belongs to the maximal output admissible set, the eventual action of the reference governor is a unit delay.
New algebraic criteria for absolute stability of nonlinear systems
Authors: Hsiao Feng‐Hsiag , Hsieh Jer‐Guang , Chang Jaion‐Shea
Published: July 2007

In this paper, new and simple algebraic criteria are derived via elementary proofs to provide easy sufficient conditions for the standard absolute stability problems of nonlinear systems, i.e. Lur'e problems. These criteria are equivalent to the famous graphical circle criteria and Popov criterion. By means of the Sturm theorem and the Euclidean division algorithm, a Routh‐Hurwitz‐like Sturm criterion is obtained. No graphical technique is needed. Only basic numerical manipulations are involved in the new criteria.
Loop recovery via ℋ︁∞‐modified complementary sensitivity recovery for non‐minimum phase plants
Authors: Saeki Masami
Published: July 2007

In order to recovery robust stability of a desirable state feedback system by output feedback, the desirable complementary function is approximated by a modified complementary function of the output feedback system by solving an ℋ︁∞ norm‐minimization problem. The modified complementary function is obtained by getting rid of non‐minimum phase factors from the complementary function. Numerical examples show the superiority of this method to LQG/LTR method and other methods.
Loop transfer recovery design via new observer‐based and css architecture‐based controllers
Authors: Chen Ben M. , Chen Ya‐Ling
Published: July 2007

Two new controller structures, namely the continuous‐time current‐type observer and current‐type CSS (Chen‐Saberi‐Sannuti) architecture‐based controllers, are considered in this paper for loop transfer recovery design for general non‐strictly proper non‐minimum phase systems. The proposed observer is structurally analogous to the current estimator of discrete‐time systems, while the proposed CSS architecture falls into the category of the controller structures developed recently by Chen, Saberi and Sannuti. The properties of these new structures are characterized. In particular, sets of necessary and sufficient conditions under which a target loop transfer function can be either exactly and/or asymptotically recovered by the abovementioned controllers are obtained. More importantly, the new current‐type observer balances the observer structures for continuous‐time and discrete‐time linear systems.
Robust stability analysis of systems with real parametric uncertainty: A global optimization approach
Authors: Psarris Polycarpos , Floudas Christodoulos A.
Published: July 2007

This paper presents an optimization framework for the robustness analysis of linear and nonlinear systems with real parameter uncertainty. For linear systems, a nonlinear programming formulation for the exact calculation of the stability margin is presented. The potential of decomposition‐based global optimization methods for the solution of this nonconvex problem is discussed. Next the concept of the stability margin is extended to a class of nonlinear systems. A nonlinear stability margin and a uniqueness margin are defined to address the effect of parametric uncertainty on the stability of a particular steady state, as well as on the number of steady states of the system. This analysis allows for the derivation of necessary and sufficient conditions for robust stability and robust uniqueness of the steady state of the system in the presence of parametric uncertainty.
A global stabilization theorem for planar nonlinear systems
Authors: Tsinias J.
Published: July 2007

We provide sufficient conditions for global stabilization of planar nonlinear systems by means of static and dynamic feedback laws. The results of the paper extend previous work on the same problem. Our approach uses some ideas from a recent paper of the author based on the well‐known Artstein theorem on stabilization as well as a recent result of Coron and Praly.
A new H∞ design methodology for the control of flexible structures: Application to a sight system
Authors: Coustal P. , Delebecque F. , Nikoukhah R.
Published: July 2007

We present an Hscr;∞ controller design methodology for flexible systems. We illustrate our approach using an example drawn from an industrial application. The proposed method avoids undesirable (lightly damped) pole‐zero cancellations and yields a low‐order controller, using a new formulation of the standard problem.
A comparison of bootstrap methods and an adjusted bootstrap approach for estimating the prediction error in microarray classification
Authors: Jiang Wenyu , Simon Richard
Published: July 2007

This paper first provides a critical review on some existing methods for estimating the prediction error in classifying microarray data where the number of genes greatly exceeds the number of specimens. Special attention is given to the bootstrap‐related methods. When the sample sizenis small, we find that all the reviewed methods suffer from either substantial bias or variability. We introduce a repeated leave‐one‐out bootstrap (RLOOB) method that predicts for each specimen in the sample using bootstrap learning sets of sizeln. We then propose an adjusted bootstrap (ABS) method that fits a learning curve to the RLOOB estimates calculated with different bootstrap learning set sizes. The ABS method is robust across the situations we investigate and provides a slightly conservative estimate for the prediction error. Even with small samples, it does not suffer from large upward bias as the leave‐one‐out bootstrap and the 0.632+ bootstrap, and it does not suffer from large variability as the leave‐one‐out cross‐validation in microarray applications. Copyright © 2007 John Wiley & Sons, Ltd.
Geographic‐based ecological correlation studies using supplemental case–control data
Authors: Haneuse S. , Wakefield J.
Published: July 2007

It is well known that the ecological study design suffers from a variety of biases that render the interpretation of its results difficult. Despite its limitations, however, the ecological study design is still widely used in a range of disciplines. The only solution to the ecological inference problem is to supplement the aggregate data with individual‐level data and, to this end, Haneuse and Wakefield (Biometrics2007;63:128–136) recently proposed a hybrid study design in which an ecological study is supplemented with a sample of case–control data. The latter provides the basis for the control of bias, while the former may provide efficiency gains. Building on that work, we illustrate the use of the hybrid design in the context of a geographical correlation study of lung cancer mortality from the state of Ohio. Focusing on epidemiological applications, we initially provide an overview of the use of ecological studies in scientific research, highlighting the breadth of current application as well as advantages and drawbacks of the design. We consider the interplay between the two sources of information in the design: ecological and case–control, and then provide details on a Bayesian spatial random effects model in the setting of the hybrid design. Issues of specification are addressed, as well as sensitivity to modeling assumptions. Further, an interesting feature of these data is that they provide an example of how the proposed design may be used to resolve the ecological fallacy. Copyright © 2007 John Wiley & Sons, Ltd.
Aufbau und Eigenschaften verschiedener ölfreier Vakuumpumpen für den Grob‐ und Feinvakuumbereich
Authors: Hablanian Mars H.
Published: July 2007

The development of high vacuum pumps and systems during the last 35 years can be characterized by a trend of gradual elimination of liquids exposed to vacuum environment. The need for high purity vacuum process equipment precipitated the development of new pumping techniques: iongettering pumps, turbomolecular pumps and cryopumps. During the last 5 years, a number of dry coarse‐vacuum pumps have been developed. Some are entirely oilfree, some still use lubricants at the seals separating the driving mechanism from the vacuum side. This review contains general design and performance characteristics of four classes of equipment: hermetically sealed pumps using bellows to isolate the driving mechanism, a variety of multistaged positive displacement blowers, pumping trains based on turbo‐drag pumps, and multistaged reciprocal piston pumps. It is entirely practical to achieve pressure of 105 to 106 while discharging to atmosphere. Despite a complete absence of conventional lubrication in some of these pumps, periods exceeding 10000 hours without maintenance are obtained, providing a viable technology for clean vacuum systems.
Entgasen in der Kunststoffaufbereitungstechnik
Authors: Kapfer Klaus
Published: July 2007

Polymer Compounding is the link between polymer synthesis and the conversion to the final part. Besides well known processing tasks such as Melting, Mixing, Homogenisation and Pelletisation, the Devolatilisation of volatile components such as air, moisture, monomers, oligomers and solvents represents a major aspect of the compoundig technology. Increasing demands for cleaner polymer parts and requirements for less environmental impact will augment the importance of this process task in polymer compounding.
Carl Hoffmann (1844 – 1910), der Erfinder der Drehschieberpumpe
Authors: Reich G.
Published: July 2007

Der gelernte Schlosser Carl Hoffmann aus Berlin war seit 1869 bei Siemens & Halske beschäftigt zunächst als Monteur und Dreher, dann als Werkstattleiter und Konstrukteur. Nach sehr erfolgreichen Arbeiten auf dem Gebiet der Generatoren und Elektromotoren wurde er zum Oberingenieur ernannt. Er beschäftigte sich weiter mit dem Problem, rotierende Geräte so auszuführen, daß diese unmittelbar von Elektromotoren angetrieben werden konnten. Im Rahmen dieser Tätigkeit entstanden ganze Reihen von rotierenden Pumpen für Flüssigkeiten und Gase, darunter auch die – heute als Drehschieberpumpe bezeichnete – wichtigste Vakuumpumpe. Der wesentliche Fortschritt bestand darin, daß er für rotierende Vakuumpumpen ein Rückschlagventil einführte. Diese Pumpen wurden ab 1905 von den Siemens‐Schuckert Werken in Berlin‐Charlottenburg, ab 1906 von Arthur Pfeiffer in Wetzlar und ab 1908 von Leybold in Köln (als Gaedesche Kapselpumpe) hergestellt.

Daß Carl Hoffmann, der als Starkstromtechniker nie etwas mit Vakuumtechnik zu tun hatte, kaum bekannt wurde, mag daran liegen, daß angestellte Techniker nur selten publizierten.
Information on Surface Structure by Low Energy Electron Diffraction
Authors: Wedler Harald , Heinz Klaus
Published: July 2007

In den letzten Jahrzehnten ist die quantitative Bestimmung von Oberflächenstrukturen zu einem wichtigen und interessanten Gebiet der Festkörperphysik geworden. Eine der leistungsfähigsten Methoden dieser Oberflächenkristallographie ist die Beugung langsamer Elektronen (Low Energy Electron Diffraction = LEED). Mittels Analyse von LEED‐Bildern und ‐Intensitäten können Gestalt und Größe der Oberflächeneinheitszelle, der Ordnungszustand und der atomare Aufbau bestimmt werden. Hochentwickelte Videomeßtechniken erlauben eine schnelle und verläßliche Datenaufnahme. Die dynamische Analyse der Intensitäten, die die Vielfachstreuung der Elektronen berücksichtigt, liefert den strukturellen Aufbau der Oberfläche mit einer Genauigkeit von bis zu 10−12 m.
High Rate Aluminum Sputtering in Compact Disc Production
Authors: Lübbehusen Michael , Seiler Reiner , Sichmann Eggo
Published: July 2007

Eine etwa 55 nm dicke Aluminiumschicht verleiht der Compact Disc (CD) ihr typisch „silbriges”︁ Aussehen. Die Schicht dient als Reflektor für den Laserstrahl des Abspielgerätes.

Heute können diese Schichten in Single Disc Coatern in nur 1,1 s durch einen DC‐Magnetron Sputterprozeß aufgebracht werden, obwohl das Polycarbonat, aus dem die CD im wesentlichen besteht, nur beschränkt temperaturbelastbar ist.

Forderungen der Industrie nach Produktivität, Zuverlässigkeit, geringem Energieverbrauch, hoher Targetausnutzung und stets gleichbleibender Schichtqualität stellen besondere Anforderungen an das Design von Sputterquellen.
Integration von Mikromechanik und Elektronik
Authors: Biebl Markus
Published: July 2007

Die Oberflächen‐Mikromechanik erlaubt die Herstellung komplexer mechanischer Strukturen mit Dimensionen im Mikrometer‐ Bereich. In diesem Artikel werden zunächst die Grundzüge der Technologie der Oberflächen‐Mikromechanik dargestellt. Die Adhäsion der Strukturen wird als Beispiel für zu lösende Probleme bei der Herstellung mikromechanischer Systeme aufgezeigt. Mikromechanischer Resonatoren als Teststrukturen zur Bestimmung mechanischer Parameter werden vorgestellt. Schließlich wird auf die kostengünstige monolithische Integration mit CMOS‐Elektronik eingegangen.
Trockene Vakuumpumpe – sichere und kostensparende Vakuumerzeugung
Authors: Mohrdieck E.
Published: July 2007

Es wird eine neuartige „Trockenlaufende Vakuumpumpe”︁ vorgestellt: Diese isochor arbeitende Verdrängermaschine mit einem berührungslos schnellrotierenden Schraubenspindelpaar wird in vertikaler Bauweise betrieben. Diese Pumpe ist durch die elektronische Motorpaar‐Synchronisation der erste intelligente „Trockenläufer”︁. Mittels Drehzahl‐Variation sowie verschiedener Rotorparameter kann ein umfangreiches Saugvermögenskennfeld abgedeckt werden. Mit den Möglichkeiten des elektronisch geregelten Rotoreinzelantriebes erreicht die Pumpe durch Eigendiagnose und umfassende Selbstüberwachung ein Höchstmaß an Zuverlässigkeit, um den unerwarteten Betriebsausfall weitestgehend zu vermeiden. Die auftretenden Gas‐ und Oberflächentemperaturen können über innovative Kühlungsmechanismen innerhalb applikationsspezifischer Grenzwerte gehalten werden. Des weiteren wird durch eine anwendungsbezogene umfangreiche Werkstoffauswahl und den Wegfall der bekannten Verschleißteile eine bisher nicht gekannte Standzeit und Zuverlässigkeit erreichbar.
The Disappearing Anode Myth
Authors: Sellers Jeff C.
Published: July 2007

The goal of this paper was to simply demystify the disappearing anode problem. Three key concepts for anode control were presented. First, anode / cathode area ratio, second, magnetron ejection angle and, lastly, the concept of aspect ratio / acceptance angle were introduced. Examples of the application of these principles were demonstrated. Finally, tradeoffs associated with dual magnetron sputtering and DC pulsed deposition were discussed.
Vakuumwaagen – Teil 2: Mikrowaagen
Authors: Robens Erich , Gast Theodor , Jenemann Hans R.
Published: July 2007

Für Sorptionsmessungen und thermogravimetrische Untersuchungen wurden Vakuum‐ Balkenwaagen mit einer Auflösung bis herab zum Nanogrammbereich entwickelt. In korrosiver Atmosphäre oder unter sehr reinen Bedingungen ist die magnetische Schwebewaage vorteilhafter. Der von der Waage getrennte Probenraum enthält nur die Probe auf der Waagschale in stabiler Position an einem Permanentmagneten hängend, der in einigem Abstand von einem geregelten Magneten schwebt. Die Federwaage bietet für solche Aufgaben eine billigere Alternative, falls geringere Anforderungen an die relative Empfindlichkeit gestellt werden. Schwingsysteme, insbesondere Quarzschwinger werden zur Überwachung von Aufdampfprozessen benutzt. Solche oszillierenden Sensoren benötigen kein Gravitationsfeld und sind deshalb in der Raumfahrt anwendbar.
Massenflußreglung in modernen Vakuumprozessen
Authors: Hofmann Peter
Published: July 2007

Viele moderne Vakuumprozesse benötigen eine Stoffzufuhr von flüssigen/festen Materialien mit niedrigsten Dampfdrücken. Thermische Massenflußregler (MFC) werden im allgemeinen eingesetzt, um geregelt Dämpfe und Gase in Prozesse einzuleiten. Jedoch beschränkt sich deren Einsatzgebiet auf Applikationen, in denen hohe Dampfdrücke oder Gasdrücke einen ausreichenden Stofftransport gewährleisten. Um dennoch definiert und reproduzierbar Materialien mit geringen Dampfdrücken in Vakuumprozesse zu befördern, kommen Techniken wie druckgestützte MFC's oder ein Transport über die flüssige Phase zum Einsatz. Eine detaillierte Diskussion dieser Technologien, mit entsprechenden Anwendungsbeispielen findet sich im Folgenden.
Inner division and uncertain contours: William James and the politics of the modern self
Authors: BORDOGNA FRANCESCA
Published: July 2007

This article revisits the question of the social valence of William James's account of the self. As biographers have long noted, James worried much about the crisis of the autonomous, unitary and well-bounded self. This article suggests that, despite his anxieties, James perceived that those features of the self opened up new possibilities both for the individual and for society. By locating the Jamesian self in the context of period techniques for the cultivation of the self, religious and occult practices, and mystical-cum-political discourse, I argue that for James the crisis of the modern self represented a means both of rooting individuals firmly in the community and of endowing them with a form of agency stronger than those promised by traditional doctrines of the simple, self-directed and well-bounded self. Thus, I argue, James's conception of the self and the techniques of the self that he advocated were part and parcel of an attempt to rethink the relationship between individual and community and to promote a new type of society, one composed of spontaneous pluralistic, open and intimate communities.
Isoflavones from soya foods are more bioavailable in children than adults
Authors: Halm Brunhild M. , Ashburn Leslie A. , Franke Adrian A.
Published: July 2007

The purpose of the present study was to determine whether children experience a higher systemic exposure to isoflavonoids when consuming a body weight-adjusted dose of soya compared with adults. Forty study participants were recruited from a local Waldorf school, including twenty-one children and nineteen adults. Participants collected a baseline urine sample and ate immediately thereafter a body weight-adjusted dose of soya nuts (15 g/54·4 kg equivalent to 0·615 (sd0·036) mg total isoflavones/kg) followed by a 12 h urine collection. Nineteen children and eighteen adults completed the protocol correctly (fourteen child–parent pairs). Children, compared with adults, showed a statistically significant (P < 0·05 by unpairedttest) higher urinary isoflavone excretion rate for daidzein (+39 %), genistein (+44 %), all non-metabolites (daidzein + genistein + glycitein; +41 %) and total isoflavonoids (+32 %). Isoflavones are more bioavailable in childrenv.adults. Urine is an excellent medium to determine systemic isoflavone exposure in children due to its non-invasiveness and high compliance, in particular when collected overnight; it also allows evaluation of completeness of specimen collection.
Sternotomy for substernal goitre: an otolaryngologist's perspective
Authors: Burns P , Doody J , Timon C
Published: July 2007

Introduction:

Large substernal goitres present a challenge to the otolaryngologist due to their size and location. Predicting which patients will require sternotomy can enable planning of surgery in a specialist centre, with the assistance of a thoracic surgeon. Our aim for this study was to establish clinical and radiological predictors which would aid the otolaryngologist in the pre-operative planning of such cases.

Methods:

A retrospective medical record review was conducted for all patients undergoing thyroidectomy for substernal goitre who required sternotomy in our institution over a 10-year period.

Results:

During the study period, 140 patients with substernal goitres underwent thyroidectomy. Three patients (2 per cent) required sternotomy. These cases are described.

Conclusions:

Radiological evidence of extension of a substernal goitre to the aortic knuckle, or loss of tissue planes on computed tomography, should raise suspicion that the patient may require sternotomy for safe delivery of the gland. The otolaryngologist should plan surgery for these patients in a specialist centre, with the help of a thoracic surgeon.
A full digital, high definition video system (1080i) for laryngoscopy and stroboscopy
Authors: Tsunoda A , Hatanaka A , Tsunoda R , Kishimoto S , Tsunoda K
Published: July 2007

Objective:

This study aimed to estimate the effectiveness of a full digital, high definition video system for laryngeal observations.

Methods:

A newly available, full digital, high definition video camera and high definition video monitor were used. With an endoscopic adaptor and rigid telescope, laryngoscopy and stroboscopy were performed on patients with various kinds of laryngeal lesions.

Results:

All laryngeal lesions were observed and recorded by the full digital, high definition video camera without incident. The image quality for laryngoscopy and stroboscopy was far superior to that of a conventional video system, including video-endoscopy. Even tiny structures or lesions could clearly be visualised on the monitor. The still image obtained from the full digital, high definition video camera was 1920 × 1080 pixels and was comparable to that obtained from a still camera.

Conclusions:

Full digital, high definition video cameras are now commonplace products and can easily be applied to patients with laryngeal disorders. They provide superior laryngeal images, compared with conventional video systems. Furthermore, high definition video systems are cheaper than proprietary medical video systems. We consider our system to represent an accessible technique of gaining superior laryngeal observation in otolaryngological clinics.
Patterns of subjective memory impairment in the elderly: association with memory performance
Authors: JESSEN FRANK , WIESE BIRGITT , CVETANOVSKA GABRIELA , FUCHS ANGELA , KADUSZKIEWICZ HANNA , KÖLSCH HEIKE , LUCK TOBIAS , MÖSCH EDELGARD , PENTZEK MICHAEL , RIEDEL-HELLER STEFFI G. , WERLE JOCHEN , WEYERER SIEGFRIED , ZIMMERMANN THOMAS , MAIER WOLFGANG , BICKEL HORST
Published: July 2007

Background

The association of subjective memory impairment (SMI) with cognitive performance in healthy elderly subjects is poor because of confounds such as depression. However, SMI is also a predictor for future dementia. Thus, there is a need to identify subtypes of SMI that are particularly related to inferior memory performance and may represent at-risk stages for cognitive decline.

Method

A total of 2389 unimpaired subjects were recruited from the German Study on Ageing, Cognition and Dementia in Primary Care Patients (AgeCoDe), as part of the German Competence Network on Dementia. Clusters of SMI according to patterns of response to SMI questions were identified. Gender, age, depressive symptoms, apolipoprotein E (apoE) genotype, delayed recall and verbal fluency were included in a Classification and Regression Tree (CART) analysis to identify discriminators between the clusters.

Results

We identified three clusters. Cluster 1 contained subjects without memory complaints. Cluster 2 contained subjects with general memory complaints, but mainly without memory complaints on individual tasks of daily living. Cluster 3 contained subjects with general memory complaints and complaints on individual tasks of daily living. Depressive symptoms, as the first-level discriminator, distinguished between clusters 1 and 2versuscluster 3. In subjects with only a few depressive symptoms, delayed recall discriminated between cluster 1versusclusters 2 and 3.

Conclusions

In SMI subjects with only a minor number of depressive symptoms, memory complaints are associated with delayed recall. As delayed recall is a sensitive predictor for future cognitive decline, SMI may be the first manifestation of future dementia in elderly subjects without depression.
The safe-conduct for the Abbasid ‘Abd Allāh b. ‘Alī (d. 764)
Authors: Marsham A , Robinson C. F.
Published: July 2007

In his Ta’rīkh al-Mawṣil, al-Azdī (d. 945) records the safe-conduct (amān) said to have been written for the surrender of the Abbasid ‘Abd Allāh b. ‘Alī (d. 764) to his nephew, the caliph al-Manṣūr. This text has been overlooked in discussions of early Abbasid history and in studies of the work of Ibn al-Muqaffa‘ (d. c. 756), who is widely credited with its production. This article presents an annotated translation of the amān and considers its transmission, authenticity, attribution and significance. Parallels with epigraphic, documentary and literary sources suggest that it was indeed originally composed in the early Abbasid period and that it conforms to developing conventions for amāns. Thus, it is important evidence for political theory and practice in the mid-eighth-century caliphate. Furthermore, it probably substantially reflects the agreement between the caliph and his uncle and may indeed be the work of Ibn al-Muqaffa‘.
Looking back from somewhere: reflections on what remains ‘critical’ in critical theory
Authors: KRATOCHWIL FRIEDRICH
Published: July 2007

This article revisits some of the theoretical debates within the field of IR since Ashley and Cox challenged the mainstream. But in so doing it attempts also to show that the proposed alternatives have their own blind spots that are subjected in the second part to discursive criticism. Neither Ashley’s celebration of the wisdom of old realists nor their ‘silence’ on economics, nor the notion of ‘internationalisation of the state’ and of the world order are adequate for understanding politics in the era of globalisation. Instead, a critical theory has to examine the political projects that were engendered by the Hobbesian conception of order and rationality. Highlighting the disconnect between our present political vocabularies and the actual political practices, I argue that a critical theory has not only to ‘criticise’ existing approaches but has to rethink and re-conceptualise praxis, which is ill served by the analytical tools which are imported to this field from ‘theory’.
Is critical theory always for the white West and for Western imperialism? Beyond Westphilian towards a post-racist critical IR
Authors: HOBSON JOHN M.
Published: July 2007

In appraising critical IR theory after twenty-five years, this article begins by asking whether critical theory implicitly reinforces the ‘superiority’ of Western civilisation and naturalises Western imperialism. In revealing the Eurocentrism of much of critical IR theory the article proceeds to reconstruct it by steering it in fresh non-Eurocentric directions. This is not to say that extant critical theory is moribund since it undoubtedly has much to offer. But it is to say that until the problem of Eurocentrism is exorcised from its body theoretique, critical theory inadvertently lies in danger of joining the ranks of problem-solving theories. The first two sections deconstruct the leading schools of critical IR theory – Gramscianism, postmodernism and feminism – to reveal their frequent lapsing into Eurocentrism, while the final section seeks to decolonise ‘Westphilian’ critical IR by reconstructing a ‘post-racist IR’. And this in turn leads on to the conclusion, which sketches out a post-racist emancipatory political project that can help begin the urgent task of effecting global reconciliation between East and West.
Existence of geodesics in static Lorentzian manifolds with convex boundary
Authors: Piccione P.
Published: July 2007

We study some global geometric properties of a static Lorentzian manifold Λ embedded in a differentiable manifold M, with possibly non-smooth boundary ∂Λ. We prove a variational principle for geodesics in static manifolds, and using this principle we establish the existence of geodesics that do not touch ∂Λ and that join two fixed points of Λ. The results are obtained under a suitable completeness assumption for Λ that generalizes the property of global hyperbolicity, and a weak convexity assumption on ∂Λ. Moreover, under a non-triviality assumption on the topology of Λ, we also get a multiplicity result for geodesics in Λ joining two fixed points.
C*-convex sets and completely bounded bimodule homomorphisms
Authors: Magajna B.
Published: July 2007

If A and B are C*-algebras and X is an operator A, B-bimodule, then points of X can be separated from closed A, B-absolutely convex subsets of X by completely bounded A, B-bimodule homomorphisms from X into B(K), where K is a Hilbert space and the A, B-bimodule structure on B(K) is induced by a pair of representations π : A → B(K) and σ : B → B(K). If A and B are von Neumann algebras and X is a normal (not necessarily dual) operator A, B-bimodule, those A, B-absolutely convex subsets of X are characterized which can be separated from points of X as above, but with the additional requirement that the two representations π and σ are normal. This requires a new topology on X, which has appeared also in connection with some other questions concerning operator modules.