Moving from Data-Constrained to Data-Enabled Research: Experiences and Challenges in Collecting, Validating and Analyzing Large-Scale e-Commerce Data

Widespread e-commerce activity on the Internet has led to new opportunities to collect vast amounts of micro-level market and nonmarket data. In this paper we share our experiences in collecting, validating, storing and analyzing large Internet-based data sets in the area of online auctions, music file sharing and online retailer pricing. We demonstrate how such data can advance knowledge by facilitating sharper and more extensive tests of existing theories and by offering observational underpinnings for the development of new theories. Just as experimental economics pushed the frontiers of economic thought by enabling the testing of numerous theories of economic behavior in the environment of a controlled laboratory, we believe that observing, often over extended periods of time, real-world agents participating in market and nonmarket activity on the Internet can lead us to develop and test a variety of new theories. Internet data gathering is not controlled experimentation. We cannot randomly assign participants to treatments or determine event orderings. Internet data gathering does offer potentially large data sets with repeated observation of individual choices and action. In addition, the automated data collection holds promise for greatly reduced cost per observation. Our methods rely on technological advances in automated data collection agents. Significant challenges remain in developing appropriate sampling techniques integrating data from heterogeneous sources in a variety of formats, constructing generalizable processes and understanding legal constraints. Despite these challenges, the early evidence from those who have harvested and analyzed large amounts of e-commerce data points toward a significant leap in our ability to understand the functioning of electronic commerce.Comment: Published at http://dx.doi.org/10.1214/088342306000000231 in the Statistical Science (http://www.imstat.org/sts/) by the Institute of Mathematical Statistics (http://www.imstat.org

Tactical behaviour in professional soccer:the secret of successful attacks

Soccer seems simple: "you just have to score one more goal than your opponent" (Johan Cruyf). The reality is a game of complex interactions between 22 players and a ball. Teammates have to coordinate their actions in space and time while continuously adapting to the opponent and the conditions of play: something we came to know as tactics. Until recently tactics were mainly analyzed by video-analysts who manually annotated interesting moments within a game to subsequently make qualitative assessments together with the coaching staff. Due to recent technological developments and scientific advancements a whole new era of tactical analysis opened up as during most professional games position tracking data of all players, referees and the ball is automatically collected nowadays. This results in datasets of millions of datapoints per match, that with the help of state of the art techniques from computer science and data science can be used for in depth analysis of tactical patterns. Building on the aforementioned developments, this thesis presents a body of research that aims to use data and state of the art techniques to gain in-depth insights in tactics, and to develop new analytical techniques for understanding determinants of success in attacking play. The result is a new methodology to identify key contributors and team-specific blue-prints for succes, and offers a new perspective on performance analysis in professional soccer

Fast rotating stars resulting from binary evolution will often appear to be single

Rapidly rotating stars are readily produced in binary systems. An accreting star in a binary system can be spun up by mass accretion and quickly approach the break-up limit. Mergers between two stars in a binary are expected to result in massive, fast rotating stars. These rapid rotators may appear as Be or Oe stars or at low metallicity they may be progenitors of long gamma-ray bursts. Given the high frequency of massive stars in close binaries it seems likely that a large fraction of rapidly rotating stars result from binary interaction. It is not straightforward to distinguish a a fast rotator that was born as a rapidly rotating single star from a fast rotator that resulted from some kind of binary interaction. Rapidly rotating stars resulting from binary interaction will often appear to be single because the companion tends to be a low mass, low luminosity star in a wide orbit. Alternatively, they became single stars after a merger or disruption of the binary system during the supernova explosion of the primary. The absence of evidence for a companion does not guarantee that the system did not experience binary interaction in the past. If binary interaction is one of the main causes of high stellar rotation rates, the binary fraction is expected to be smaller among fast rotators. How this prediction depend on uncertainties in the physics of the binary interactions requires further investigation.Comment: 2 pages, 1 figure, to be published in the proceedings of IAU 272 "Active OB stars: structure, evolution, mass loss and critical limit", Paris 19-23 July 201

Multi-bit sigma-delta modulators with enhanced dynamic-range using non-linear DAC for hearing aids

15th IEEE International Conference on Electronics, Circuits and Systems, MaltaThis paper presents the possibility of employing nonlinear low-resolution DACs in the feedback paths of multi-bit second-order Sigma-Delta modulators. The proposed technique is particularly attractive in applications such as hearing aids, requiring a very large dynamic range and medium signal-tonoise-plus-distortion-ratio. As demonstrated through simulated results in which noise and mismatch effects are included, for the same over-sampling ratio, improvements in the order of 6-to-9 dB in the dynamic range can be achieved when comparing with the same topology employing linear-DACs

A Low-Voltage CMOS Buffer for RF Applications Based on a Fully-Differential Voltage-Combiner

Part 20: Electronics: RF ApplicationsInternational audienceThis paper presents a new CMOS buffer circuit topology for radio-frequency (RF) applications based on a fully-differential voltage-combiner circuit, capable of operating at low-voltage. The proposed circuit uses a combination of common-source (CS) and common-drain (CD) devices. The simulation results show good levels of linearity and bandwidth. To improve total harmonic distortion (THD) a source degeneration technique is used. The proposed circuit has been designed in a 130nm logic CMOS technology and it achieves a simulated gain of 1.54 dB, a bandwidth of 1.14 GHz for a total power dissipation of 13.34 mW, when driving an RF active probe (with 0.8 pF in parallel with 200 kΩ)

FLUID MECHANICS ANALYSIS IN VOLLEYBALL SERVICES

The service is considered the first attack action in volleyball games. Erratic behavior also appears along the trajectory, hindering reception. We suspect that these effects can be related to the ‘drag crisis’ phenomenon described in fluid mechanics. Thus, we decided to quantify the trajectories of four types of services (underhand, floater, floater with jump, overhand with jump). Altogether, twenty-six real trajectories of service balls were recorded and 3D reconstructed with the DVIDEOW system. Polynomials of the 4th degree of time were adjusted to the coordinates of each trajectory, obtaining the speed and acceleration of the balls. We compared, in the horizontal and vertical planes, the real trajectories with simulated ones in which the ball was submitted to the same initial conditions but without any aerodynamic drag forces. We calculated the Reynolds Number (Re), the drag coefficient (CD) and the drag force (FD), applying the model presented at the XVI ISB Congress (Deprá et al., 1997). We observed that all services are placed in the region of the so-called drag crisis (1.105 < Re < 3.105) and present great variations of drag coefficient (Fig. 1). We also observed that the four types of services analyzed can be ordered in an increasing sequence of Reynolds numbers. The first three types presented a decreasing sequence of median values of CD, accompanying the CD(Re) literature curve (line in Fig. 1). Even so, we observed the growth of the drag force (FD) as a function of Re (Fig. 2). Comparing the magnitude of the two forces that act on the ball, we estimated that in the case of the overhand service with jump the drag force becomes up to 1.4 times larger than the weight force (mg = 2.55 N). All these kind of quantification may also be used to compare characteristics of different players

Predicting match outcome in professional Dutch football using tactical performance metrics computed from position tracking data

Quality as well as quantity of tracking data have rapidly increased over the recent years, and multiple leagues have programs for league-wide collection of tracking data. Tracking data enables in-depth performance analysis, especially with regard to tactics. This already resulted in the development of several Key Performance Indicators (KPI’s) related to scoring opportunities, outplaying defenders, numerical balance and territorial advantage. Although some of these KPI’s have gained popularity in the analytics community, little research has been conducted to support the link with performance. Therefore, we aim to study the relationship between match outcome and tactical KPI’s derived from tracking data. Our dataset contains tracking data of all players and the ball, and match outcome, for 118 Dutch premier league matches. Using tracking data, we identified 72.989 passes. For every pass-reception window we computed KPI’s related to numerical superiority, outplayed defenders, territorial gains and scoring opportunities using position data. This individual data was then aggregated over a full match. We then split the dataset in a train and test set, and predicted match outcome using different combinations of features in a logistic regression model. KPI’s related to a combination of off-the-ball features seemed to be the best predictor of match outcome (accuracy of 64.0% and a log loss of 0.67), followed by KPI’s related to the creation of scoring opportunities (accuracy of 58% and a log loss of 0.69). This indicates that although most (commercially) available KPI’s are based on ball-events, the most important information seems to be in off-the-ball activity. We have demonstrated that tactical KPI’s computed from tracking data are relatively good predictors of match outcome. As off-the-ball activity seems to be the main predictor of match outcome, tracking data seems to provide much more insight than notational analysis

The State of Utah v. Joseph C. Valdez : Brief of Appellee

APPEAL FROM THE THIRD CIRCUIT COURT IN AND FOR TOOELE COUNTY, THE HONORABLE EDWARD A. WATSON PRESIDIN

Determinação de níveis economicos de NPK na cultura da alface em Macapá.

A produção de alface no Amapá e insuficiente para atender a demanda local, aliado a esse fato, o abastecimento através de outros centros produtores e dificultado pela perecibilidade do produto e pelo isolamento geografico do estado. Com essa preocupação, diversos genotipos de alface foram avaliados, ja possuindo-se no momento, resultados para sua recomendação aos agricultores.bitstream/item/74279/1/AP-1998-niveis-economicos-npk.pd