Analytische Bestimmung einer Datenallokation für Parallele Data Warehouses

Die stark wachsende Bedeutung der Analyse von Data Warehouse-Inhalten und bequemere Anfrageschnittstellen für Endbenutzer erhöhen das Aufkommen an OLAP-Queries signifikant. Bei der Reduktion des Arbeitsumfanges und dem Erreichen kurzer Antwortzeiten für diese komplexen Anfragen ist neben der Nutzung von Verarbeitungs- und I/O-Parallelität eine adäquate Datenallokation der Schlüssel zu guter Leistungsfähigkeit. Allerdings ist die Bestimmung einer geeigneten Fragmentierung und Allokation für große Datenmengen, wie sie z.B. in Form von Faktentabellen oder Indexstrukturen in relationalen Sternschemas vorliegen, ein schwieriges Problem. Hierfür existiert heutzutage praktisch keine Werkzeugunterstützung. Wir präsentieren daher einen Ansatz zur analytischen Bestimmung einer passenden multi-dimensionalen, hierarchischen Datenallokation. Unser Ansatz dürfte recht einfach in ein Werkzeug zur automatischen Unterstützung des Allokationsproblems integriert werden können

Inhomogeneous lens stuctures for integrated optics

The thesis is concerned with the design, analysis, fabrication am evaluation of integrated optic lenses which are inhomogeneous either in physical shape or in refractive index profile. The thesis has nine chapters. Chapter one, the introduction, illustrates the importance of these lenses within the domain of integrated optiCS, where the complicated mathematical functions required to describe the lens profiles are most easily realised. Connections are made between the study of these lenses and the exciting new field of optical computing. A special class of non-uniform lenses which are conceptually perfect optical instruments forms the main area of interest in the present study. Historically, the development of these lenses has followed two distinct lines, related to two possible methods of physically obtaining the required variation in path of light rays passing through the lens. In one method the optical path is made to vary directly, whilst the other method involves controlling the fi'lysical path, and thus the optical path, through the principle of equivalence. The dual development has been continued in the field of integrated optiCS, where lenses based on direct control of the optical path are termed variable-index lenses and those based on physical path control are termed geodesic lenses. The perfect variable-index lens studied in this work was the well-known Luneburg lens. Perfect geodesic lens designs have also been published. The design formulae for both types of lens are presented in chapter two. A simpler lens, of spherical geometry, is also presented which is easily analyzed and characterised and which serves as an archetypal model against which the performance of the more sophisticated lenses can be assessed. Chapter three investigates the problems involved in modelling fabrication conditions in a thermal-evaporation-invacuum environment so that lens profiles can actually be constructed. Chapter four goes into methods of tracing rays through these lenses in some detail. Ray-tracing has long been the classical tool of optical designers, providing a useful guide to optical performance. Ray methods, which effectively provide image error evaluations, are not entirely-appropriate for those lenses which are conceptually perfect within the geometrical optics approximation. Diffraction effects prevent the lenses from attaining true perfection. In such cases the wave-field produced by the lenses in the image space is the important quantity. In chapter five, the beam-propagation method (BPM) is used to study diffraction arrl associated effects in inhomogeneous lenses. '!he method allows the propagation of complicated waveshapes in lnhomogeneous media, normally a difficult task. Furthermore, anlsotropic effects and the interaction between acoustic waves aoo optical waves can be studied with the method. Negative focal shifts are reported which are not predicted by geometrical optics or the usual approximate diffraction theories. The fabrication of lenses is considered in chapter six. Planar waveguide measurements car r ied out on the var ious materials used in the study are presented. A major problem in the fabrication of geodesic lenses, that of obtaining a uniform wavegulde layer over the complete lens area, is dealt with in some detail in chapter seven. In chapter eight, extensive tests on the experimental performance of several lenses are reported. Near diffraction-limited performance is reported for geodesic lenses. More limited performance figures are obtained for Luneburg lenses though the possibility of high performance is lndicated if profile resolution can be improved. The themes of the thesls are pulled together for discussion in chapter nine and conclusions are drawn as to the relative merits of the various lenses. Possible means of improving fabrication procedures, thus driving lenses closer to ultimate resolution limits, are presented. The greatest problem faced is that of scatter ing in the waveguide, which appears to be accentuated as the waveguide traverses the lens surface. If the scattering problem can be successfully dealt with it is concluded that integrated optical lenses could be important and viable components in addresslng the problem of fast, high-throughput data processing

Efficient and private distance approximation in the communication and streaming models

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.Includes bibliographical references (p. 109-114).This thesis studies distance approximation in two closely related models - the streaming model and the two-party communication model. In the streaming model, a massive data stream is presented in an arbitrary order to a randomized algorithm that tries to approximate certain statistics of tile data with only a few (usually one) passes over the data. For instance, the data may be a flow of packets on the internet or a set of records in a large database. The size of the data necessitates the use of extremely efficient randomized approximation algorithms. Problems of interest include approximating the number of distinct elements, approximating the surprise index of a stream, or more generally, approximating the norm of a dynamically-changing vector in which coordinates are updated multiple times in an arbitrary order. In the two-party communication model, there are two parties who wish to efficiently compute a relation of their inputs. We consider the problem of approximating Lp distances for any p > 0. It turns out that lower bounds on the communication complexity of these relations yield lower bounds on the memory required of streaming algorithms for the problems listed above. Moreover, upper bounds in the streaming model translate to constant-round protocols in the communication model with communication proportional to the memory required of the streaming algorithm. The communication model also hias its own applications, such as secure datamining, where in addition to low communication, the goal is not to allow either party to learn more about the other's input other than what follows from the output and his/her private input.(cont.) We develop new algorithms and lower bounds that resolve key open questions in both of these models. The highlights of the results are as follows. 1. We give an Q(1/E2) lower bound for approximating the number of distinct elements of a data stream in one pass to within a (1 ± c) factor with constant probability, as well as the p-th frequency moment Fp for any p Ž 0. This is tight up to very small factors, and greatly improves upon the earlier Q(1/E) lower bound for these problems. It also gives the same quadratic improvement for the communication complexity of 1-round protocols for approximating the Lp distance for any p 2 0. 2. We give a 1-pass O(ml-2/p)-space streaming algorithm for (1 ± 6)-approximating the Lp norm of an m-dimensional vector presented as a data stream for any p 2 2. This algorithm improves the previous ((m1-1/(P-')) bound, and is optimal up to polylogarithmic factors. As a special case our algorithm can be used to approximate the frequency moments Fp of a data stream with the same optimal amount of space. This resolves the main open question of the 1996 paper by Alon, Matias, and Szegedy. 3. In the two-party communication model, we give a protocol for privately approximating the Euclidean distance (L2) between two m-dimensional vectors, held by different parties, with only polylog m communication and 0(1) rounds. This tremendously improves upon the earlier protocol of Feigenbaum, Ishai, Malkin, Nissim, Strauss, and Wright, which achieved O(vm) communication for privately approximating the Hamming distance only. This thesis also contains several previously unpublished results concerning the first item above, including new lower bounds for the communication complexity of approximating the Lp distances when the vectors are uniformly distributed and the protocol is only correct for most inputs, as well as tight lower bounds for the multiround complexity for a restricted class of protocols that we call linear.by David P. Woodruff.Ph.D

An analysis of the wind-forced response of Conception Bay using a reduced-gravity numerical model

A reduced-gravity numerical model of Conception Bay, Newfoundland, with a realistic coastline and driven by local wind is developed to analyze the wind-forced response of the pycnocline. Model solutions are compared with temperature and current measurements collected from sub-surface moorings deployed at the month in the spring of 1989 and near the head in the spring of 1990. The observed temperature near the head shows similar behavior at all six moorings indicating upwelling of the pycnocline due to northeastward winds. Upwelling around the head and evidence of phase lag from one mooring to the next are consistent with Kelvin wave propagation. The model reproduces most of this variability at all six moorings including the two moorings on the eastern side of the Bay near Bell Island Tickle where Kelvin waves might be expected to be scattered by bottom topography. At the mouth, only the 2 day temperature signal at the mooring closest to the western shore is successfully reproduced by the model. The model's ability to better reproduce temperature variability at the head is explained by the increased wind-forced response at the head and the likely importance of external forcing at the mouth, either from Trinity Bay or due to eddies entering the Bay from outside. The current field at both the head and mouth is poorly reproduced by the model, probably due to the complicated vertical structure of the current. Coherence analysis of the current data shows that the horizontal scale of coherent motions is small (less than 10 km). -- In developing the model used for comparison with observations, boundary conditions that allowed an accurate solution were developed. Placing a radiation condition perpendicular to the coast "upstream" of the Bay resulted in the generation of spurious fluxes and near-inertial Kelvin waves at the boundary. These problems were eliminated by extending the coastline out to sea on the "upstream" side of the mouth and applying a condition of zero normal gradient in interface displacement on the artificial stretch of boundary. Experiments using sponge layers rather than radiation conditions on the other boundaries showed that sponging only the interface displacement and leaving the velocities undamped gives results that compare well with those obtained using radiation conditions. Sponging the velocities as well as the interface displacement led to significantly different results suggesting that applying highly viscous layers around open ocean parts of model boundaries can be counter-productive

Southern Accent September 2003 - April 2004

Southern Adventist University\u27s newspaper, Southern Accent, for the academic year of 2003-2004.https://knowledge.e.southern.edu/southern_accent/1081/thumbnail.jp

Admission control and routing : theory and practice

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1995.Includes bibliographical references (leaves 183-190).by Rainer Gawlick.Ph.D

The Whitworthian 2004-2005

The Whitworthian student newspaper, September 2004-May 2005.https://digitalcommons.whitworth.edu/whitworthian/1088/thumbnail.jp

EZRA pound and the ideogrammic method

This work addresses the question of Pound's poetics, proceeding upon the conviction that the term "ideogrammic method", so often slighted by commentators, is to be taken seriously, and that an understanding of its nature and implications provides a sound framework for one's understanding of Pound's mature poetic practice. Part One begins by tracing the evolution of Imagism/Worticism, locating in Pound's theory and practice at that time his first adumbration of the poetic morphology which I maintain is central to the Cantos. The first four Cantos are then examined and their pattern of theophanies related to the merphology. The Malatesta Cantos are identified as the first expression of the ideogrammic method, the latter being defined as an extention into the "epic" dimension of Imagist/Vorticist principles. Part Two retreats somewhat from the detail of the Cantos to deal more speculatively with the ideogrammic method and its related ideas. In particular, through the figures of Francis Bacon, Emerson, Fenollosa and Pound himself the method is set in relation to the Adamic conception of language. Part Three begins by further enlarging the terms of the ideogrammic method to incorporate Pound's notion of the forma, and relating both method and notion to the poetic morphology. This complex of ideas is then shown in action in Cantos XXXIX and XLVII. The rhythms of the Leopoldine Cantos are examined, and a more generalizing discussion of rhythms in the Cantos as a whole follows; This is then related to the question of form in the poem. The work concludes with a detailed examination of the Pisan Cantos and Canto XC. The ideogrammic method is not a body of settled doctrine, but I believe it to be the generative locus of Pound's mature poetics. It as as such that I would recommend the concept for fresh attention

The Crisis of Chinese Rock in the mid-1990s: Weakness in Form or Weakness in Content?

Born in the political turmoil of the 1989 student movement, Chinese rock music is often understood as an ideological weapon to against the Communist principles due to its western origin. The movement pushed Chinese rock to an unprecedented height of cultural prominence in the. early 1990s. Chinese rock, however, lost this cultural prominence in the mid-1990s. The political suppression is generally regarded as the key reason causing the crisis, but the real reason is much more complicated and deep inside China's society. . The 1990s is a decade when China was profoundly transformed into a new nation in every dimension. The substantial economic growth hid other social problems, such as the unparalleled development between economy and culture. The crisis of Chinese rock is just evidence demonstrating how cultures are co-produced by multi-forces social movements rather than any single factors. Social powers and the political power are often mixed in previous studies. It is also incorrect to treat ordinary people as a passive group who actually had exerted their influences on the formation of Chinese rock in the 1990s. Qualitative data (such as the lyrics and comments) and quantitative data (such as the number ofrock album and economic figures) display why the crisis happened. The political-concentrated content and the purely artistic form are the two direct causes of the crisis, but digging deeper, social power, social classes, and cultural capital play vital roles. The immaturity of Chinese rock music itself is the direct reason, but the immaturity of China's society is the essential and primary reason for the crisis. The crisis of Chinese rock, however, does not mean its death, but a period when rockers, the music industries, the media, fans, and even the government needed to learn and accumulate adequate source and capital to develop this new culture. It cannot be an overnight task. The comeback of Chinese rock in the new millennium demonstrates that Chinese rock is a culture related to China. Its social significance and role likely differ from its western counterpart. Because China has been opened up to the outside world since 1979, the development of intercultural exchange is inevitable, which makes rock music develop in China in a together-in-difference situation