How Bad is Forming Your Own Opinion?

The question of how people form their opinion has fascinated economists and sociologists for quite some time. In many of the models, a group of people in a social network, each holding a numerical opinion, arrive at a shared opinion through repeated averaging with their neighbors in the network. Motivated by the observation that consensus is rarely reached in real opinion dynamics, we study a related sociological model in which individuals' intrinsic beliefs counterbalance the averaging process and yield a diversity of opinions. By interpreting the repeated averaging as best-response dynamics in an underlying game with natural payoffs, and the limit of the process as an equilibrium, we are able to study the cost of disagreement in these models relative to a social optimum. We provide a tight bound on the cost at equilibrium relative to the optimum; our analysis draws a connection between these agreement models and extremal problems that lead to generalized eigenvalues. We also consider a natural network design problem in this setting: which links can we add to the underlying network to reduce the cost of disagreement at equilibrium

Argumentation-Based Contract Monitoring in Uncertain Domains

Publisher PD

Breakdown potentials of gases under alternating voltages

This investigation was devoted to a study of the starting potentials of gases of commercial purity for frequencies less than one million cycles per second. The gases used were Hydrogen, Nitrogen, Helium, and Argon. The discharge tube was of spherical design having spherical aluminum electrodes three-fourths inch to diameter. Five gap distances were used ranging from 10 mm to 50 mm;The results of the investigation show that: (1) The effect of impurities in the gas pointed out by J. Thomson were not observed. (2) The usual straight line portion of the curves of Vs versus pressure were observed to be concave downward. An explanation for this was not obtained. A general form for the curve was shown to be: Vs=Ax1/2+Bx 3/2 where x is a number proportional to the mean free path of an electron. (3) The three stages of the discharge as observed by J. Thomson were also observed. This phenomenon occurred in all the gases at a frequency of one million cycles per second only. (4) The relations connecting the starting potential, the pressure and the gap distance for plane parallel electrodes do not hold for spherical electrodes. At the larger gap distances the variation of the starting potential with the gap distance was quite unreliable. As the gap distance became less the reliability increased, also, giving a strong indication that the conditions were rapidly approaching those of the plane parallel electrodes. (5) The slope of the log p versus log d curve is independent of frequency and also of the gas for gap distances less than approximately 32 mm. This suggests that the expressions representing the conditions in the discharge are independent of the gas and of the frequency for plane parallel electrodes

ConStance: Modeling Annotation Contexts to Improve Stance Classification

Manual annotations are a prerequisite for many applications of machine learning. However, weaknesses in the annotation process itself are easy to overlook. In particular, scholars often choose what information to give to annotators without examining these decisions empirically. For subjective tasks such as sentiment analysis, sarcasm, and stance detection, such choices can impact results. Here, for the task of political stance detection on Twitter, we show that providing too little context can result in noisy and uncertain annotations, whereas providing too strong a context may cause it to outweigh other signals. To characterize and reduce these biases, we develop ConStance, a general model for reasoning about annotations across information conditions. Given conflicting labels produced by multiple annotators seeing the same instances with different contexts, ConStance simultaneously estimates gold standard labels and also learns a classifier for new instances. We show that the classifier learned by ConStance outperforms a variety of baselines at predicting political stance, while the model's interpretable parameters shed light on the effects of each context.Comment: To appear at EMNLP 201

Patterns in three families of Neotropical forest birds: a test of the Pleistocene refugia model

Datos recientes sobre distnbución de aves en manchas remanentes de selva en el Estado de Sao Paulo, Brasil (willis. 1979), dan la oportunidad de extender a las mismas una prueba de la teoría que explica la diversificación de la biota neotropical por medio de refugios recientemente propuesta por Oren, 1981a, 1981b. El modelo predice que, a mayor superficie minima de selva que requiere un taxón determinado, menor sería el número de refugios de selva donde el taxón podría haber sobrevivido durante el Pleistoceno. Estos deberían reflejarse hoy día en el número y distribución del taxón en cuestión. Este trabajo se refiere a las familias Dendrocolaptidae, Fumariidae y Formicariidae. En todos los casos el patrón actual resulta el predicho por el modelo. Esto refuerza el cúmulo de evidencias que indica que la selva neotropical estuvo fragmentada durante los picos glaciales del Pleistoceno

Generating Information-Diverse Microwave Speckle Patterns Inside a Room at a Single Frequency With a Dynamic Metasurface Aperture

We demonstrate that dynamic metasurface apertures (DMAs) are capable of generating a multitude of highly uncorrelated speckle patterns in a typical residential environment at a single frequency. We use a DMA implemented as an electrically-large cavity excited by a single port and loaded with many individually-addressable tunable metamaterial radiators. We placed such a DMA in one corner of a plywood-walled L-shape room transmitting microwave signals at 19 GHz as we changed the tuning states of the metamaterial radiators. In another corner, in the non-line-of-sight of the DMA, we conducted a scan of the field generated by the DMA. For comparison, we also performed a similar test where the DMA was replaced by a simple dipole antenna with fixed pattern but generating a signal that spanned 19-24 GHz. Using singular value decomposition of the scanned data, we demonstrate that the DMA can generate a multitude of highly uncorrelated speckle patterns at a single frequency. In contrast, a dipole antenna with a fixed pattern can only generate such a highly uncorrelated set of patterns when operating over a large bandwidth. The experimental results of this paper suggest that DMAs can be used to capture a diversity of information at a single frequency which can be used for single frequency computational imaging systems, NLOS motion detection, gesture recognition systems, and more

Absence of differential protection from extinction in human causal learning

Elemental models of associative learning typically employ a common prediction-error term. Following a conditioning trial, they predict that the change in the strength of an association between a cue and an outcome is dependent upon how well the outcome was predicted. When multiple cues are present, they each contribute to that prediction. The same rule applies both to increases in associative strength during excitatory conditioning and the loss of associative strength during extinction. In five experiments using an allergy prediction task, we tested the involvement of a common error term in the extinction of causal learning. Two target cues were each paired with an outcome prior to undergoing extinction in compound either with a second excitatory cue or a cue that had previously undergone extinction in isolation. At test, there was no difference in the causal ratings of the two target cues. Manipulations designed to bias participants towards elemental processing of cue compounds, to promote the acquisition of inhibitory associations, or to reduce generalization decrement between training and test were each without effect. These results are not consistent with common error term models of associative learning

The Effect of Particle Strength on the Ballistic Resistance of Shear Thickening Fluids

The response of shear thickening fluids (STFs) under ballistic impact has received considerable attention due to its field-responsive nature. While efforts have primarily focused on the response of traditional ballistic fabrics impregnated with fluids, the response of pure STFs to penetration has received limited attention. In the present study, the ballistic response of pure STFs is investigated and the effect of fluid density and particle strength on ballistic performance is isolated. The loss of ballistic resistance of STFs at higher impact velocities is governed by particle strength, indicating the range of velocities over which they may provide effective armor solutions.Comment: 4 pages, 4 figure