303 research outputs found
Updated west african rainbelt indices, 1919-1989
No full textTropical West African rainfall data at a one-degree latitude interval within the range 4°N-19°N, averaged over the longitude band of 5°W-5°E, are updated through 1990 by using monthly station rainfall data for the July-September period derived from the Global Historical Climatology Network (GHCN) data base. Making use of the latitudinal rainfall data, the West African rainbelt indices are calculated, (i.e., the latitude of its center of gravity and the total rainfall that occurs over the entire rainbelt zone). The century's worst Sahelian drought for the early 1980s is primarily associated with weakened convection over the entire West African rainbelt zone. During this period, the southward retreat of the rainbelt plays a secondary role in the drought conditions. The rainbelt behavior as related to the Sahelian droughts confirms the previous results of Shinoda (1990a). The slight increase in Sahelian rainfall for 1988-1989 is associated with the near-normal position and total rainfall of the rainbelt
Sample Complexity of Learning Multi-value Opinions in Social Networks
No full textWe consider how many users we need to query in order to estimate the extent to which multi-value opinions (information) have propagated in a social network. For example, if the launch date of a new product has changed many times, the company might want to know to which people the most current information has reached. In the propagation model we consider, the social network is represented as a directed graph, and an agent (node) updates its state if it receives a stronger opinion (updated information) and then forwards the opinion in accordance with the direction of its edges. Previous work evaluated opinion propagation in a social network by using the probably approximately correct (PAC) learning framework and considered only binary opinions. In general, PAC learnability, i.e., the finiteness of the number of samples needed, is not guaranteed when generalizing from a binary-value model to a multi-value model. We show that the PAC learnability of multi-value opinions propagating in a social network. We first prove that the number of samples needed in a multi-opinion model is sufficient for (k−1)log(k−1) times the number of samples needed in a binary-opinion model, when k (≥3) is the number of opinions. We next prove that the upper and lower bounds on the number of samples needed to learn a multi-opinion model can be determined from the Natarajan dimension, which is a generalization of the Vapnik-Chervonenkis dimension
Mid-Air Ultrasonic Stimulations of the Palm - The Influence of Frequency and Stimulus Duration on Perceived Intensity
No full textIt is known that the duration of a short stimulus affects the perceived intensity of both visual, auditory, and, vibrotactile events, but it is still unclear whether such a relationship also exists for mid-air ultrasonic inputs to the hand. Here we investigate this issue and show how the perceived intensity of focused ultrasonic stimulations of the palm is indeed systematically related to stimulus duration - a relationship that is, however, independent of modulation frequency. This is an important finding for the overall goal of providing perceptually stronger inputs and enlarging the repertoire of realistic mid-air haptic experiences.Human Information Communication Desig
INFLUENCES OF PROTEOLYTIC ENZYMES ON PAROTIN VI. ISOLATION AND PROPERTIES OF A BIOLOGICALLY ACTIVE PROTEIN “PAROTIN-T. A” FROM THE PAROTIN-DIGEST BY TRYPSIN
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Single-delete Nim
No full textThe classic game of Nim has been well-known for many years, inspiring numerous variations. One such variant is Delete Nim, where players take turns eliminating one pile of stones and splitting the remaining pile into two smaller piles. In this paper we generalize the game to include the case of n piles. On each turn, a player eliminates one pile and splits one of the remaining piles into two smaller piles. We specifically analyze the case where n=4, deriving the conditions for a winning strategy.17 page
Annual Rainfall Variability and its Interhemispheric Coherence in the Semi-Arid Region of Tropical Africa : Data Updated to 1987
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