Using Text Similarity to Detect Social Interactions not Captured by Formal Reply Mechanisms

In modeling social interaction online, it is important to understand when people are reacting to each other. Many systems have explicit indicators of replies, such as threading in discussion forums or replies and retweets in Twitter. However, it is likely these explicit indicators capture only part of people's reactions to each other, thus, computational social science approaches that use them to infer relationships or influence are likely to miss the mark. This paper explores the problem of detecting non-explicit responses, presenting a new approach that uses tf-idf similarity between a user's own tweets and recent tweets by people they follow. Based on a month's worth of posting data from 449 ego networks in Twitter, this method demonstrates that it is likely that at least 11% of reactions are not captured by the explicit reply and retweet mechanisms. Further, these uncaptured reactions are not evenly distributed between users: some users, who create replies and retweets without using the official interface mechanisms, are much more responsive to followees than they appear. This suggests that detecting non-explicit responses is an important consideration in mitigating biases and building more accurate models when using these markers to study social interaction and information diffusion.Comment: A final version of this work was published in the 2015 IEEE 11th International Conference on e-Science (e-Science

The Ohlson Model of Evaluation of Companies:Tutorial for Use

The article analyzes the structuring and applicability of the Ohlson Model (OM). The methodology used considered: (i) exploratory research as to the objectives of the study; (ii) bibliographical research as to the procedures applied; and (iii) qualitative research as to the addressing of the problem. The review of the literature covered both the origin (discount of dividends, evaluation by the residual profit etc) and the underlying theory of the model. In relation to the internal consistency of the OM, the structuring of the linear informational dynamics was discussed (DIL) and the formula of evaluation as well as the establishing of the entries demanded (parameters and variables). An example was also developed that illustrates the interaction between the coefficients, variables and parameters of the Ohlson modeling. The example permitted the exploration of fundamental concepts and premises for the operating of the Ohlson model, underlying the equations of the DIL (self-regressive models, parameters of persistence etc), to the behavior of the profits (persistence and ability to forecast), to the scenario of evaluation and to some aspects of the accounts model (role of the net worth etc). The study concluded that: (1) there is no consensus in the academic literature about the appropriate method of measuring the parameters of persistence; (2) there are propositions for perfecting the original conception of the OM by means of extensions to the model; (3) the Ohlson model propitiated a series of contributions in the academic literature about capital markets.evaluation of companies, Ohlson Model.

Development of an Electronic System for Field-Scale Geomorphometric Measurements

Terrain attributes are among the most studied soil characteristics. Although important, in only a few areas are topographic features mapped at the field-scale level. These features play an important role in assessing the crop production potential and erosion susceptibility of agricultural fields. Therefore high-resolution mapping of terrain attributes are vital to a better management of production fields. Today, terrain attributes are derived from elevation measurement.A more direct form of measurement was developed by Rowe and Spencer (1976), pitch and roll angles were used to derive slope gradient and vehicle attitude. Yang (1997) related vehicle attitude to slope aspect. The existing mathematical models are difficult to implement with today’s low-cost micro-controllers because of existing trigonometric functions. Research conducted at the Biosystems Department of The University of Tennessee focused on the simplification of existing models and on the development of an electronic system to test two sensing techniques in dual-axial rotational measurement of a roving vehicle: a clinometer and an accelerometer. Tests were conducted in a field with a widely varying topography located on the Blount Experiment Research Unit, by mounting the electronic monitoring system on an ATV. Elevation data measured with a RTK-GPS were used to generate an accurate elevation map. Terrain attributes were calculated in 3 spatial resolutions: 4, 16, and 100 m2.Simplification of the mathematical models relating pitch and roll angles to terrain attributes is possible because of the existing limitations on slope gradient of arable lands. Results obtained during field tests show that slope measurement accuracy varied according to spatial resolutions. The density of points used in the calculation of the terrain attributes also contributes to measurement accuracy. In general, mean absolute error (MAE) were less than 1° for both sensors in all resolutions tested. Data collected from pitch and roll sensors can also be used to detect field elevation changes.In conclusion, it is possible to rely on measurements of vehicle axial rotation for the computation of field-scale terrain attributes. The sensing techniques tested were successfully used in these measurements. The application of simplified models to derive terrain measurements is possible due to the existing slope gradient limitation of arable lands. It is possible to describe terrain attributes in a scale similar to order I soil maps using the proposed electronic system and models. The system can also be used to pinpoint locations of elevation differences in the field

Site-specific applications of nitrogen in corn based on yield potential

Burdened by high production costs and increased environmental concerns, today\u27s farmers are looking for new technologies that can help optimize their production efficiency. Site-specific farming is a technique to describe what some are calling the next major revolution in production agriculture which has the potential to address many of these concerns. During the 1994 season, an experiment was conducted to document site-specific yield response of corn for different application rates of nitrogen fertilizer within soils with varying yield potentials. To accomplish this task, new technologies such as Global Positioning System (GPS), Geographic Information Systems (GIS), grain yield monitoring, and variable rate control were integrated into a overall system. A 22-acre no-till production corn field located in Milan, Tennessee was selected for this study. Prior to planting, an extensive soil survey was conducted and the field was classified based on varying levels of yield potential. Five different application rates of nitrogen were applied on the field using a variable rate applicator controlled by a laptop PC with control information being received in real-time from a GPS receiver and digital application map. Soil nutrient samples, leaf nitrogen samples, and plant population samples were collected through the season. The GIS software in conjunction with the GPS receiver proved to be an effective method for managing spatially related information. Results indicate that variable rate application of nitrogen based on site-specific soil types within a field has the potential to increase the production efficiency for producers

Automatic Face Recognition System Based on Local Fourier-Bessel Features

We present an automatic face verification system inspired by known properties of biological systems. In the proposed algorithm the whole image is converted from the spatial to polar frequency domain by a Fourier-Bessel Transform (FBT). Using the whole image is compared to the case where only face image regions (local analysis) are considered. The resulting representations are embedded in a dissimilarity space, where each image is represented by its distance to all the other images, and a Pseudo-Fisher discriminator is built. Verification test results on the FERET database showed that the local-based algorithm outperforms the global-FBT version. The local-FBT algorithm performed as state-of-the-art methods under different testing conditions, indicating that the proposed system is highly robust for expression, age, and illumination variations. We also evaluated the performance of the proposed system under strong occlusion conditions and found that it is highly robust for up to 50% of face occlusion. Finally, we automated completely the verification system by implementing face and eye detection algorithms. Under this condition, the local approach was only slightly superior to the global approach.Comment: 2005, Brazilian Symposium on Computer Graphics and Image Processing, 18 (SIBGRAPI

The role of epistemic communities in developing Brazilian statistics

This paper studies three moments in the emergence of Brazilian economic gauges: the first official economic indicators produced by the FGV in the 1940s, the production of competing indicators by the DIEESE from the 1950s onwards, and finally, the transference of economic statistics production to the IBGE in the 1970s. I found that epistemic communities played an important role in creating and developing Brazilian economic statistics. More interestingly, access to knowledge from outside Brazil through migrants, conferences, and technical partnerships were the main conduits for these indicators in the first place. Furthermore, understanding the reasons for the construction of Brazilian economic gauges explains the kind of relationship Brazilian society has with its statistics and the degree of independence its statistical offices enjoy.This paper studies three moments in the emergence of Brazilian economic gauges: the first official economic indicators produced by the FGV in the 1940s, the production of competing indicators by the DIEESE from the 1950s onwards, and finally, the transference of economic statistics production to the IBGE in the 1970s. I found that epistemic communities played an important role in creating and developing Brazilian economic statistics. More interestingly, access to knowledge from outside Brazil through migrants, conferences, and technical partnerships were the main conduits for these indicators in the first place. Furthermore, understanding the reasons for the construction of Brazilian economic gauges explains the kind of relationship Brazilian society has with its statistics and the degree of independence its statistical offices enjoy

Conditions for the sliding-bouncing transition for the interaction of a bubble with an inclined wall

In this study we analyze the interaction of a single rising bubble with an inclined wall. We conduct experiments considering different liquids and bubble sizes, to cover a wide range of Reynolds and Weber numbers, with wall angles from nearly horizontal to nearly vertical. For all cases, the bubble initially collides with the wall; after the initial interaction, in accord with previous studies, the bubble either steadily slides on the wall or ascends, colliding repeatedly with it. Considering a force balance for the bubble motion on the wall, we propose a set of conditions for the transition from sliding to bouncing that is validated with the present and previous data

Sliding motion of a bubble against an inclined wall from moderate to high bubble Reynolds number

The motion of a bubble sliding over an inclined wall from moderate to high bubble Reynolds number is studied experimentally for a wide range of liquid properties and bubbles sizes, considering wall inclination angles from nearly horizontal to nearly vertical. All experiments are restricted to sliding behavior, below the transition to steady bouncing motion. We study both the shape of the bubble and its drag coefficient. For small angles, the bubble shape is dominated by gravitational effects resulting in a flattened shape against the wall; for large angles, the bubble remains in constant contact with the wall but adopts a shape that is aligned perpendicularly to the wall, closer to that observed for an inertia- dominated free rising bubble. We model this transition of shape considering balances among surface tension, gravitational, and inertial forces; we observe good agreement with experiments. We found that the drag coefficient is strongly influenced by the shape that the bubble adopts as it slides over the wall. By considering the flow in the film and around the bubble, we propose a correlation to predict the drag coefficient for each regime of bubble shape. In the regime dominated by viscous effects, the drag of a single bubble is increased due to the mirror effect with the wall and by the friction in the film formed between the wall; conversely, for the case dominated by inertial effects, the drag coefficient is constant. The behavior for a single bubble is changed: no significant increase due to deformation. In both shape regimes the proposed expression agrees well with the experimental measurements