A cluster-based simulation of facet-based search

The recent increase of online video has challenged the research in the field of video information retrieval. Video search engines are becoming more and more interactive, helping the user to easily find what he or she is looking for. In this poster, we present a new approach of using an iterative clustering algorithm on text and visual features to simulate users creating new facets in a facet-based interface. Our experimental results prove the usefulness of such an approach

Exploiting log files in video retrieval

While research into user-centered text retrieval is based on mature evaluation methodologies, user evaluation in multimedia retrieval is still in its infancy. User evaluations can be expensive and are also often non-repeatable. An alternative way of evaluating such systems is the use of simulations. In this poster, we present an evaluation methodology which is based on exploiting log files recorded from a user-study we conducted

Simulated evaluation of faceted browsing based on feature selection

In this paper we explore the limitations of facet based browsing which uses sub-needs of an information need for querying and organising the search process in video retrieval. The underlying assumption of this approach is that the search effectiveness will be enhanced if such an approach is employed for interactive video retrieval using textual and visual features. We explore the performance bounds of a faceted system by carrying out a simulated user evaluation on TRECVid data sets, and also on the logs of a prior user experiment with the system. We first present a methodology to reduce the dimensionality of features by selecting the most important ones. Then, we discuss the simulated evaluation strategies employed in our evaluation and the effect on the use of both textual and visual features. Facets created by users are simulated by clustering video shots using textual and visual features. The experimental results of our study demonstrate that the faceted browser can potentially improve the search effectiveness

Essays on the Royal African Company and the Slave Trade

The Royal African Company of England traded European commodities, such as alcohol, cloth, and _rearms, for African goods and slaves. The Company sold stock to finance its business activities and paid local chiefs in West Africa for exclusive access to trade. Chapter 1 of the thesis studies rent-seeking associated with the slave trade in West Africa. Chapter 2 examines trade and ownership of stock by elites and non-elites. Chapter 3 analyses turning points in the number of slaves exported from Africa and its individual regions. In Chapter 1, I measure rent-seeking in the slave trade using new data from archival sources. In seventeenth-century Ghana, the Royal African Company paid African chiefs for exclusive access to trade along the caravan routes. The total value of these payments was 18 times a Company agent's salary and 145 times the annual cost of living. The Glorious Revolution in 1688 facilitated competition from other English merchants, and payments increased after this. Using an event study, I find that payments increased the most to chiefs in locations where they could stop or redirect trade coming from inland to the coast. The Company made larger payments to chiefs whose cooperation was most important in deterring other English merchants from competing with the Company. The highest-ranking chiefs received the highest value of payments per capita. European cloth was the most sought after type of payment - head chiefs used European cloth for prestige and received most of the European cloth. In Chapter 2, I examine Royal African Company stock transfers from 1672 to 1712. I highlight three new stylized facts. Firstly, neither elites nor non-elites dominated stock transfers before the book value of stock quadrupled in 1691, suggesting that the experience of the capital market was widespread among elites and non-elites. Secondly, the decreased share in stock transferred by some types of elites between 1685 and 1690 occurred against the background of political events that reduced the Company's future prospects. Thirdly, non-elites dominated the buying and selling of stock after the stock was quadrupled in 1691, suggesting that Company decisions played a major role in explaining its capital market experience. In the final chapter, Chapter 3, I determine to what extent turning points in slave exports were unique to specific regions, and to what extent they were common across all of Africa. I use the Bai and Perron (2003) structural break test to show that slave exports from all of Africa began falling in 1815. This is earlier than the traditional view in the literature that the slave trade effectively ended in the 1850s. Demand shocks, particularly the British abolition of the slave trade in 1807, are relatively important in explaining the end of the slave trade at the regional level. The downward-sloping trend of slave exports began in 1784 for the Bight of Biafra, 1808 for the Windward and Gold Coasts, and 1815 for the Bight of Benin, West Central Africa, and Southeast Africa. Supply shocks, such as wars and conflicts, are relatively important in explaining the dynamics of the slave trade in specific regions

Collider Signatures of SuperWIMP Warm Dark Matter

SuperWeakly-Interacting Massive Particles (superWIMPs) produced in the late decays of other particles are well-motivated dark matter candidates and may be favored over standard Weakly-Interacting Massive Particles (WIMPs) by small scale structure observations. Among the most promising frameworks that incorporate superWIMPs are R-parity conserving supersymmetry models in which the lightest supersymmetric particle (LSP) is the gravitino or the axino. In these well-defined particle models, astrophysical observations have direct implications for possible measurements at future colliders.Comment: Contributed to the 2005 International Linear Collider Physics and Detector Workshop and 2nd ILC Accelerator Workshop, Snowmass, Colorado, 14-27 Aug 2005. 3 pages, LaTeX, 1 figur

Minimal Universal Extra Dimensions

Highly degenerate spectra associated with universal extra dimensions (UED) provide an interesting phenomenology not only from the point of view of cosmology and astrophysics, but also for colliders. We study these exotic signals for the simplest case, called minimal UED, where it is natural to find slow charged particles, displaced vertices, tracks with non-vanishing impact parameters, track kinks, and even vanishing charged tracks.Comment: 6 pages, 3 figures. Contributed to XXIII International Symposium on Lepton and Photon Interactions at High Energy, Aug 13-18, 2007, Daegu, Kore

Observational evidence of the formation of cyanopolyynes in CRL618 through the polimerization of HCN

The abundance ratio of consecutive members of the cyanopolyynes family has been explored in CRL618 using data acquired in a complete line survey covering the frequency range 81-356 GHz. The Jup range explored for the different molecules is the following: 1 to 4 for HCN and HNC, 9 to 39 for HC3N, 31 to 133 for HC5N, and 72 to 85 for HC7N (not detected beyond Jup=85). The lowest vibrationally excited state of HC7N (nu_15 at 62 cm^-1) has been tentatively detected. Data analysis has been performed by extending our previous geometrical and radiative transfer model of the slowly expanding envelope (SEE) surrounding the compact central continuum source of CRL 618, that was established from the study of rotational lines in several vibrationally excited states of HC_3N. The new lines analyzed here require to model the high velocity wind (HVW) component and the colder circumstellar gas, remnant of the AGB phase of CRL618. The derived HC3N/HC5N and HC5N/HC7N abundance ratios from this set of uniformly calibrated lines are between 3 and 6 in the different regions, similar to standard values in the CSM and ISM, and consistent with previous estimates obtained from ISO observations and chemical models. However, the abundance ratios of HC3N, HC5N and HC7N with respect to HCN are at least two orders of magnitude larger than those typical for AGB C-rich stars, such as IRC+10216. This fact indicates that, in the short transition toward the Planetary Nebula phase, HCN is quickly reprocessed into longer cyanopolyyne chains. A similar behavior was previously found in this object for the polyacetylenic chains (C(2n)H2).Comment: 8 figures, accepted in ApJ main journa

Goplana Dioscoreae-Alatae Nom. Nov and Other Uredinales On Dioscoreaceae: Nomenclature and Taxonomy

Among the sixteen species of rust fungi described on Dioscoreaceae, three require replacement names. This paper re-describes and proposes Goplana dioscoreae-alatae as a replacement name for Goplana dioscoreae Cummins, nom. illegit. We also propose Uredo dioscoreae-doryphorae as a replacement name for Uredo spinulosa Y. Ono, nom. illegit.; and Aecidium tumbayensis as a replacement name for Aecidium dioscoreae J.C. Lindq., nom. illegit. We discuss nomenclatural controversies surrounding these taxa

Canonical transformations in three-dimensional phase space

Canonical transformation in a three-dimensional phase space endowed with Nambu bracket is discussed in a general framework. Definition of the canonical transformations is constructed as based on canonoid transformations. It is shown that generating functions, transformed Hamilton functions and the transformation itself for given generating functions can be determined by solving Pfaffian differential equations corresponding to that quantities. Types of the generating functions are introduced and all of them is listed. Infinitesimal canonical transformations are also discussed. Finally, we show that decomposition of canonical transformations is also possible in three-dimensional phase space as in the usual two-dimensional one.Comment: 19 pages, 1 table, no figures. Accepted for publication in Int. J. Mod. Phys.

Current-induced vortex dynamics in Josephson-junction arrays: Imaging experiments and model simulations

We study the dynamics of current-biased Josephson-junction arrays with a magnetic penetration depth smaller than the lattice spacing. We compare the dynamics imaged by low-temperature scanning electron microscopy to the vortex dynamics obtained from model calculations based on the resistively-shunted junction model, in combination with Maxwell's equations. We find three bias current regions with fundamentally different array dynamics. The first region is the subcritical region, i.e. below the array critical current I_c. The second, for currents I above I_c, is a "vortex region", in which the response is determined by the vortex degrees of freedom. In this region, the dynamics is characterized by spatial domains where vortices and antivortices move across the array in opposite directions in adjacent rows and by transverse voltage fluctuations. In the third, for still higher currents, the dynamics is dominated by coherent-phase motion, and the current-voltage characteristics are linear.Comment: 10 pages, with eps figures. To appear in Phys. Rev.