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Damping cells for the higher order modes are necessary for the S-band linear collider to minimize BBU (Beam-Break-Up). The construction of the damper cells has to take into account the different field geometries of the higher order modes. So two different types of dampers have been designed: a wall slotted an an iris slotted cell. In order to optimize the two types of damping cells with respect to damping strength, impedance matching between coupling system and waveguide dampers and between damping cell and undamped cells and the tuning system, damping cells of both types have been built and examinated.
To reach high luminosities in future linear colliders short range wakes havea to be controlled in the range of X-band frequencies or higher. Rectangular irises can be used to introduce strong focusing quadrupole-like rf-fields. Even circular irises in iris-loaded accelarator structures have the capability of focusing if the particle velocity differs from phase velocity. Theoretical investigations concerning the focusing strength to be expected are presented. Their applicability for linear colliders is discussed.
A new method of measuring quality factors in cavities is presented. This method is well suited to measure quality factors in undamped cavities as well as in heavily damped cavities, and in addition this method provides a possibility of separating modes and measuring quality factors especially in cases of overlapping modes. Measurements have been carried out on HOM-damped cavities for the DESY/THD linear collider project. Results are presented.
Due to the additional need of very short bunches for the FEL operation with the TESLA-machine strong wakefield effects are expected. One third of the total wakefield energy per bunch is radiated into the frequency region above the energy gap of Cooper pairs in superconducting niobium. The energy of the cooper pairs in superconducting niobium at 2 K corresponds to a frequency of 700 GHz. An analytical and experimental estimation for the overall energy loss of the FEL bunch above energy gap is presented. The analytical method is based on a study from R. B. Palmer [1]. The results of the wakefield estimations are used to calculate possible quality factor reduction of the TESLA cavities during FEL operation. Results are presented.
While science claims to be universal, the notion of universality actually covers two very different facets: on the one hand, it refers to the universal value of the epistemological claims of science while, on the other hand, it addresses the issue of how fully the process of scientific communication is presently globalized. How the issue of open access crosses that of the globalization of scientific communication will be the theme of this presentation. The conclusion will be that, without open access, the globalization of scientific communication will lead to increased knowledge and digital divisions.
In this increasingly complex world of learned information delivery and discovery - is it possible that the "free lunch" the Publishing world worries about could come true? Although Open Access and Institutional Repositories have not (yet) created the "scorched earth" effect many were predicting, they are slowly and inevitably gaining momentum. Broader access to top-level information via Google (and others) does indeed appear to be "good enough" for many in their search for content. But you rarely get food for free in a good quality restaurant. You pay for the selection, preparation, speed and expertise of the delivery. At the soup kitchen the food can often be filling - but the queue will be long, the wait even longer and there is no chance of silver service or à la carte. If you are unfortunate enough to have little choice then this may be a great solution. Others will be willing to pay for a more satisfactory meal. As in all aspects of life, diversification and specialisation are fundamental forces. The publishing community in the years to come will continue to develop its offerings for a variety of needs that require more than just broth. To stretch the analogy, the ongoing presence of tap water in our lives has done little to halt the extraordinary rise of bottled water as part of our staple diet. Business reality will continue to settle these types of debate; my bet is that the commercial publishers see a role as providing information that commands an intrinsic value proposition to enough customers to remain economically viable for some time to come. Inspired by the comments and ideas expounded by Dr. James O'Donnell of Georgetown University on the liblicense listserv on 20th July this year, this paper will look to expand on the analogy and identify the good, the bad - but importantly the difference in information quality and access that will result in the radically changed (but still co-existent) information landscape of tomorrow.
The economical and organizational debates about open access have mostly been concerned with journals. This is not surprising since the open access movement can be seen largely as a response to the serials crisis. Recently the open access debate has been extended to include access to government produced data in different forms. In this presentation I'll critically look at some economic and organizational issues pertaining to the open access provision of bibliographical data.
In keeping with the views of its guru, Stephen Harnard, the open access movement is only prepared to discuss the two models of the "green road" and the "golden road" as sole alternatives for the future of scientific publishing. The "golden road" is put forward as the royal road for solving the journals crisis. However, no one has drawn attention to the fact that the golden road represents a purely socialist solution to a free-market problem and thus continues the "samizdat" tradition of underground literature in the former Eastern bloc. The present paper reveals the alarmingly low level at which the open access movement intends to publish top-class results from science and research, and the low degree of professionalism with which they are satisfied.
Der Vortrag wurde am 5th Frankfurt Scientific Symposium gehalten (22-23 Oktober 2005). Die Betrachtung des Videos ist (leider) nur mit den Browsern Internet Explorer ab 5.0, Netscape Navigator ab 7.0 oder Internet Explorer ab 5.2.2 für MaC möglich (s. Dokument 1.html). Die gesamten Tagungsbeiträge sind unter http://publikationen.ub.uni-frankfurt.de/volltexte/2005/1992/ abrufbar.
Course management software : supporting the university’s teaching with technology initiatives
(2004)
An increasingly important element of the teaching with technology activities at Northwestern University is the course management system, a web-based class communication and administration environment. The usage growth of the system is substantial and amplifies the need for integration with other web services and resources. Integration is particularly material in area of library services. This presentation contains a case study of Northwestern University's implementation of its course management system software and highlights examples of how the system is being used to enhance the teaching and learning. A description of the integration efforts with library resources is provided. The goal of the presentation is to equip librarians with the basic knowledge required to engage with their colleagues in conversations surrounding the nature of integration of these systems within the teaching and learning landscapes of their home institutions.
The key hypothesis is that the IT industry lure us into the IT world with a promise to solve our information problems. Do we sign the contract, we will recognise that the IT industry can´t keep the promise. One reason: they themselves lost sight over there own game. Therefore they have to invent new tools continiously. LIS professionals should not leave the field IT professionals. LIS professional should rather put stress on to reveal the difference in the value chain between data – information – knowledge. Information and knowledge is brainware and not produced by hard and software in the sense of IT philosophy. Against the background of the language game of Jean-François Lyotard, the author explains the information and knowledge society as language game invented by the IT industry. Furthermore his beliefs of postmodernen LIS professionals and the consequences involved for LIS traning will be presented.
US investors hold much less foreign stocks than mean/variance analysis applied to historical data predicts. In this article, we investigate whether this home bias can be explained by Bayesian approaches to international asset allocation. In contrast to mean/variance analysis, Bayesian approaches employ different techniques for obtaining the set of expected returns. They shrink sample means towards a reference point that is inferred from economic theory. We also show that one of the Bayesian approaches leads to the same implications for asset allocation as mean-variance/tracking error criterion. In both cases, the optimal portfolio is a combination the market portfolio and the mean/variance efficient portfolio with the highest Sharpe ratio.
Applying the Bayesian approaches to the subject of international diversification, we find that substantial home bias can be explained when a US investor has a strong belief in the global mean/variance efficiency of the US market portfolio and when he has a high regret aversion falling behind the US market portfolio. We also find that the current level of home bias can justified whenever regret aversion is significantly higher than risk aversion.
Finally, we compare the Bayesian approaches to mean/variance analysis in an empirical out-ofsample study. The Bayesian approaches prove to be superior to mean/variance optimized portfolios in terms of higher risk-adjusted performance and lower turnover. However, they not systematically outperform the US market portfolio or the minimum-variance portfolio.
In the current globalization debate the law appears to be entangled in economic and political developments which move into a new dimension of depoliticization, de-centralization and de-individualization. For all the correct observations in detail, though, this debate is bringing about a drastic (polit)economic reduction of the role of law in the globalization process that I wish to challenge in this paper. Here one has to take on Wallerstein’s misconception of “worldwide economies” according to which the formation of the global society is seen as a basically economic process. Autonomous globalization processes in other social spheres running parallel to economic globalization need to be taken seriously. In protest against such (polit)economic reductionism several strands of the debate, among them the neo-institutionalist theory of “global culture”, post-modern concepts of global legal pluralism, systems theory studies of differentiated global society and various versions of “global civil society” have shaped a concept of a polycentric globalization. From these angles the remarkable multiplicity of the world society, in which tendencies to re-politicization, re-regionalization and re-individualization are becoming visible at the same time, becomes evident. I shall contrast two current theses on the globalization of law with two less current counter-theses: First thesis: globalization is relevant for law because the emergence of global markets undermines the control potential of national policy, and therefore also the chances of legal regulation. First counter-thesis: globalization produces a set of problems intrinsic to law itself, consisting in a change to the dominant lawmaking processes. Second thesis: globalization means that the law institutionalizes the worldwide shift in power from governmental actors to economic actors. Second counter-thesis: globalization means that the law has a chance of contributing to a dual constitution of autonomous sectors of world society.
The hadronic final state of central Pb+Pb collisions at 20, 30, 40, 80, and 158 AGeV has been measured by the CERN NA49 collaboration. The mean transverse mass of pions and kaons at midrapidity stays nearly constant in this energy range, whereas at lower energies, at the AGS, a steep increase with beam energy was measured. Compared to p+p collisions as well as to model calculations, anomalies in the energy dependence of pion and kaon production at lower SPS energies are observed. These findings can be explained, assuming that the energy density reached in central A+A collisions at lower SPS energies is sufficient to transform the hot and dense nuclear matter into a deconfined phase.
Vor gut einem Jahr ist im Archiv für die civilistische Praxis ein Aufsatz erschienen, in welchem ich mich mit den Perspektiven des Verbrauchervertragsrechts nach der Schuldrechtsreform auseinandergesetzt habe. Der leicht provozierende Unterton der dort vorgetragenen Kritik hat nun nicht nur – wie beabsichtigt – den einen oder anderen Leser zum Lachen verführt, sondern offensichtlich auch Irritationen bezüglich der Richtung hervorgerufen, in die der Verbraucherschutzzug in Zukunft fahren soll: zurück in die Siebziger Jahre und – nach erneutem Schlagen vergangener Schlachten – ins bürgerliche Formalrecht des 19. Jahrhundert? Oder was soll mit dem Stichwort "Prozedurales Verbrauchervertragsrecht" gemeint sein? Ich möchte an dieser Stelle einen Präzisierungsversuch unternehmen.
We present a detailed study of chemical freeze-out in nucleus-nucleus collisions at beam energies of 11.6, 30, 40, 80 and 158A GeV. By analyzing hadronic multiplicities within the statistical hadronization approach, we have studied the chemical equilibration of the system as a function of center of mass energy and of the parameters of the source. Additionally, we have tested and compared different versions of the statistical model, with special emphasis on possible explanations of the observed strangeness hadronic phase space under-saturation.
Fluctuations and NA49
(2005)
The knowledge of the build up time of space charge compensation (SCC) and the investigation of the compensation process is of main interest for low energy beam transport of pulsed high perveance ion beams under space charge compensated conditions. To investigate experimentally the rise of compensation an LEBT system consisting of a pulsed ion source, two solenoids and a drift tube as diagnostic section has been set up. The beam potential has been measured time resolved by a residual gas ion energy analyser (RGA). A numerical simulation for the calculation of self-consistent equilibrium states of the beam plasma has been developed to determine plasma parameters which are difficult measure directly. The results of the simulation has been compared with the measured data to investigate the behavior of the compensation electrons as a function of time. The acquired data shows that the theoretical rise time of space charge compensation is by a factor of two shorter than the build up time determined experimentally. In view of description the process of SCC an interpretation of the gained results is given.
High perveance negative ion beams with low emittance are essential for several next generation particle accelerators (i. g. spallation sources like ESS [1] and SNS [2]). The extraction and transport of these beams have intrinsic difficulties different from positive ion beams. Limitation of beam current and emittance growth have to be avoided. To fulfill the requirements of those projects a detailed knowledge of the physics of beam formation the interaction of the H- with the residual gas and transport is substantial. A compact cesium free H- volume source delivering a low energy high perveance beam (6.5 keV, 2.3 mA, perveance K= 0.0034) has been built to study the fundamental physics of beam transport and will be integrated into the existing LEBT section in the near future. First measurements of the interaction between the ion beam and the residual gas will be presented together with the experimental set up and preliminary results.
Low energy beam transport (LEBT) for a future heavy ion driven inertial fusion (HIDIF [1]) facility is a crucial point using a Bi+ beam of 40 mA at 156 keV. High space charge forces (generalised perveance K=3.6*10-3) restrict the use of electrostatic focussing systems. On the other hand magnetic lenses using space charge compensation suffer from the low particle velocity. Additionally the emittance requirements are very high in order to avoid particle losses in the linac and at ring injection [2]. urthermore source noise and rise time of space charge compensation [3] might enhance particle losses and emittance. Gabor lenses [4] using a continuous space charge cloud for focussing could be a serious alternative to conventional LEBT systems. They combine strong cylinder symmetric focussing with partly space charge compensation and low emittance growth due to lower non linear fields. A high tolerance against source noise and current fluctuations and reduced investment costs are other possible advantages. The proof of principle has already been shown [5, 6]. To broaden the experiences an experimental program was started. Therefrom the first experimental results using a double Gabor lens (DGPL, see fig. 1 ) LEBT system for transporting an high perveance Xe+ beam will be presented and the results of numerical simulations will be shown.
The determination of the beam emittance using conventional destructive methods suffers from two main disadvantages. The interaction between the ion beam and the measurement device produces a high amount of secondary particles. Those particles interact with the beam and can change the transport properties of the accelerator. Particularly in the low energy section of high current accelerators like proposed for IFMIF, heavy ion inertial fusion devices (HIDIF) and spallation sources (ESS, SNS) the power deposited on the emittance measurement device can lead to extensive heat on the detector itself and can destruct or at least dejust the device (slit or grit for example). CCD camera measurements of the incident light emitted from interaction of beam ions with residual gas are commonly used for determination of the beam emittance. Fast data acquisition and high time resolution are additional features of such a method. Therefore a matrix formalism is used to derive the emittance from the measured profile of the beam [1,2] which does not take space charge effects and emittance growth into account. A new method to derive the phase space distribution of the beam from a single CCD camera image using statistical numerical methods will be presented together with measurements. The results will be compared with measurements gained from a conventional Allison type (slit-slit) emittance measurement device.
Vortrag gehalten an der Tagung "The XVI International Conference on Ultrarelativistic Nucleus-Nucleus Collisions, organized by SUBATECH Laboratory", in Nantes, France, 18-24 Juli 2002.
The experiment NA49 at the CERN SPS is a large acceptance detector for charmed hadrons. The identification of neutral strange hadrons Lambda and AntiLambda is based on the measurement of their charged decay particles and the reconstruciton of the decay vertex. The charged particles were measured with the 4 time projection chambers (TPC), two of them are situated inside 2 large dipole magnets, the two others are downstream of the magnet. Lambda and AntiLambda baryons have been measured in central Pb+Pb collisions at 40, 80 and 160 GeV/nucleon over a wide range in rapidity (1 - 5) and transverse momentum (0 - 3 GeV/c). Particle yields and spectra will be shown for the different energies. The results will be put into the existing systematics of Lambda-production as a function of beam energy.
Tagungsvorträge werden als MP3-Files zum Anhören angeboten. Das Motiv: 2003 stand der 100. Geburtstag Theodor W. Adornos auf der Tagesordnung des kulturellen und akademischen Geschehens. Adorno war sicherlich einer der wirkungsmächtigsten Philosophen und Theoretiker der Gesellschaft des 20. Jahrhunderts. Seine Schriften sind weltweit verbreitet und haben unzählige Wissenschaftler aus den verschiedensten Disziplinen anhaltend inspiriert. Wo immer man in der Welt als Frankfurter Hochschullehrer auf geistig tätige Menschen trifft, man wird auf Adorno angesprochen. Zum Schicksal eines jeden Klassikers gehört es, dass es einen Streit um das Erbe gibt und sich folglich verschiedene Strömungen auf das Vorbild beziehen. Zugleich provoziert das die unausgesetzte Debatte darum, ob das Werk nicht bereits historisch geworden sei und uns für unsere Zeit also nicht mehr viel zu sagen habe. Oder ob es klassisch: unvergänglich vergangen sei, und damit ein starker Anstoß zum Weiterdenken geblieben sei. Hinter dieser, in vielen Buchpublikationen und Feuilletons (insbesondere in der Frankfurt Allgemeinen Zeitung) geführten Debatte um die Aktualität der kritischen Theorie und des Denkens Adornos verschwindet leicht die aufmerksame Beobachtung, was denn nach Adornos Tod 1969 von seinen direkten oder mittelbaren Schülern in den Feldern geleistet worden ist, auf die insgesamt sich das Genie Adornos beziehen konnte. Es stand zu befürchten, dass das Jubiläum als Geburtstagsfeier einer Geistesgröße mit einer Fülle von Erinnerungen und Würdigungen vollzogen wird, ohne dass der doch ungleich interessanteren Frage nachgegangen würde, in welcher Hinsicht das Werk Adornos in den produktiven Arbeiten heutiger Wissenschaftler lebendig geblieben ist. Inhaltliche Akzente: Lebendigkeit bedeutet keineswegs die Fortsetzung eines orthodox verwalteten Erbes, sondern verweist notwendig auf oft eigensinnige Versuche, die Denkmittel Adornos im Sinne seiner Kritik an der Gesellschaft zu nutzen. Lebendigkeit konkretisiert sich also nicht als Traditionspflege oder als wohlfeile Revision von Positionen, über die die Zeit hinweggegangen sein soll, sondern im sachhaltigen Aufweis ihrer Aktualität durch Arbeiten, mit denen aus unterschiedlicher fachlicher Sicht kritische Theorie als fortgesetztes Arbeitsprogramm deutlich wird. Insofern diente der Kongress der systematischen Überprüfung und Dokumentation der in produktiver Forschung sich ausdrückenden Lebendigkeit der Ansätze Adornos sowie der Ausarbeitung der Aufgaben für die nähere Zukunft. Zugleich wird damit nicht weniger beansprucht als einen repräsentativen Überblick zu geben, wie es heute mit der Aufklärung selbst bestellt ist. Auf der Tagung sprachen Wissenschaftler sprechen, die in den vergangenen Jahrzehnten bewiesen haben, dass sie mit ihrem Forschungsprogramm die Diagnose der Gesellschaft, inspiriert durch jene Denkmittel, insbesondere auf unbearbeitetem Terrain fortgeführt haben und die zugleich für die Zukunft die Untersuchung von Fragen versprechen, die auf der Tagesordnung der Aufklärung stehen. Jeder Vortragende wird seine Arbeiten in den Kontext auch derjenigen stellen, die innerhalb seines Faches ebenfalls von Kritischer Theorie beeinflusst wurden. Im Vordergrund der Darstellung soll aber die eigene bislang geleistete Arbeit unter der Fragestellung der Tagung rekapituliert werden und schlaglichtartig erkennbar gemacht werden, in welchem Sinne Fragen der gegenwärtigsten Gegenwart mit den theoretischen Figuren Adornos kommunizieren.
We introduce a new method for representing and solving a general class of non-preemptive resource-constrained project scheduling problems. The new approach is to represent scheduling problems as de- scriptions (activity terms) in a language called RSV, which allows nested expressions using pll, seq, and xor. The activity-terms of RSV are similar to concepts in a description logic. The language RSV generalizes previous approaches to scheduling with variants insofar as it permits xor's not only of atomic activities but also of arbitrary activity terms. A specific semantics that assigns their set of active schedules to activity terms shows correctness of a calculus normalizing activity terms RSV similar to propositional DNF-computation. Based on RSV, this paper describes a diagram-based algorithm for the RSV-problem which uses a scan-line principle. The scan-line principle is used for determining and resolving the occurring resource conflicts and leads to a nonredundant generation of all active schedules and thus to a computation of the optimal schedule.
In the last decade, much effort went into the design of robust third-person pronominal anaphor resolution algorithms. Typical approaches are reported to achieve an accuracy of 60-85%. Recent research addresses the question of how to deal with the remaining difficult-toresolve anaphors. Lappin (2004) proposes a sequenced model of anaphor resolution according to which a cascade of processing modules employing knowledge and inferencing techniques of increasing complexity should be applied. The individual modules should only deal with and, hence, recognize the subset of anaphors for which they are competent. It will be shown that the problem of focusing on the competence cases is equivalent to the problem of giving precision precedence over recall. Three systems for high precision robust knowledge-poor anaphor resolution will be designed and compared: a ruleset-based approach, a salience threshold approach, and a machine-learning-based approach. According to corpus-based evaluation, there is no unique best approach. Which approach scores highest depends upon type of pronominal anaphor as well as upon text genre.
In the last years, much effort went into the design of robust anaphor resolution algorithms. Many algorithms are based on antecedent filtering and preference strategies that are manually designed. Along a different line of research, corpus-based approaches have been investigated that employ machine-learning techniques for deriving strategies automatically. Since the knowledge-engineering effort for designing and optimizing the strategies is reduced, the latter approaches are considered particularly attractive. Since, however, the hand-coding of robust antecedent filtering strategies such as syntactic disjoint reference and agreement in person, number, and gender constitutes a once-for-all effort, the question arises whether at all they should be derived automatically. In this paper, it is investigated what might be gained by combining the best of two worlds: designing the universally valid antecedent filtering strategies manually, in a once-for-all fashion, and deriving the (potentially genre-specific) antecedent selection strategies automatically by applying machine-learning techniques. An anaphor resolution system ROSANA-ML, which follows this paradigm, is designed and implemented. Through a series of formal evaluations, it is shown that, while exhibiting additional advantages, ROSANAML reaches a performance level that compares with the performance of its manually designed ancestor ROSANA.
Syntactic coindexing restrictions are by now known to be of central importance to practical anaphor resolution approaches. Since, in particular due to structural ambiguity, the assumption of the availability of a unique syntactic reading proves to be unrealistic, robust anaphor resolution relies on techniques to overcome this deficiency. In this paper, two approaches are presented which generalize the verification of coindexing constraints to de cient descriptions. At first, a partly heuristic method is described, which has been implemented. Secondly, a provable complete method is specified. It provides the means to exploit the results of anaphor resolution for a further structural disambiguation. By rendering possible a parallel processing model, this method exhibits, in a general sense, a higher degree of robustness. As a practically optimal solution, a combination of the two approaches is suggested.
An anaphor resolution algorithm is presented which relies on a combination of strategies for narrowing down and selecting from antecedent sets for re exive pronouns, nonre exive pronouns, and common nouns. The work focuses on syntactic restrictions which are derived from Chomsky's Binding Theory. It is discussed how these constraints can be incorporated adequately in an anaphor resolution algorithm. Moreover, by showing that pragmatic inferences may be necessary, the limits of syntactic restrictions are elucidated.