Statistical Modelling of Information Sharing: Community, Membership and Content

File-sharing systems, like many online and traditional information sharing communities (e.g. newsgroups, BBS, forums, interest clubs), are dynamical systems in nature. As peers get in and out of the system, the information content made available by the prevailing membership varies continually in amount as well as composition, which in turn affects all peers' join/leave decisions. As a result, the dynamics of membership and information content are strongly coupled, suggesting interesting issues about growth, sustenance and stability. In this paper, we propose to study such communities with a simple statistical model of an information sharing club. Carrying their private payloads of information goods as potential supply to the club, peers join or leave on the basis of whether the information they demand is currently available. Information goods are chunked and typed, as in a file sharing system where peers contribute different files, or a forum where messages are grouped by topics or threads. Peers' demand and supply are then characterized by statistical distributions over the type domain. This model reveals interesting critical behaviour with multiple equilibria. A sharp growth threshold is derived: the club may grow towards a sustainable equilibrium only if the value of an order parameter is above the threshold, or shrink to emptiness otherwise. The order parameter is composite and comprises the peer population size, the level of their contributed supply, the club's efficiency in information search, the spread of supply and demand over the type domain, as well as the goodness of match between them.Comment: accepted in International Symposium on Computer Performance, Modeling, Measurements and Evaluation, Juan-les-Pins, France, October-200

STARLINK: IMPACTS ON THE U.S. CORN MARKET AND WORLD TRADE

StarLink disrupted the U.S. corn market during the marketing year of 2000/01 as a result of inadvertent commingling. The potential volume of marketed StarLink-commingled corn from the 2000 crop located in areas near wet and dry millers prior to October 1, 2000, is estimated at 124 million bushels. Price differentials between StarLink-free and StarLink-commingled corn existed during the early stage of the incident, but eroded quickly. While StarLink has had a negative impact on U.S. corn exports, most of the reduction in exports to Japan and South Korea during November 2000 and March 2002 is due to Japan's increased purchases from South Africa, China's decision to continue to subsidize exports, increased competition from the large back-to-back crops in Argentina, and a record Brazilian crop.Crop Production/Industries, Research and Development/Tech Change/Emerging Technologies,

THE DISTRIBUTION OF BENEFITS RESULTING FROM BIOTECHNOLOGY ADOPTION

The purposes of this study are two-fold: (1) to estimate the size of total benefits arising from the adoption of agricultural biotechnology, and (2) to measure the distribution of total benefits among key stakeholders along the production and marketing chain, including U.S. farmers, gene developers, germplasm suppliers, U.S. consumers, and the producers and consumers in the rest of the world. This study focuses on the benefits that resulted from the adoption of herbicide-tolerant soybeans as well as insect-resistant (Bt) and herbicide-tolerant cotton in 1997. In this analysis, various data sources are examined for measuring the farm-level effects of adopting biotechnology and the resulting benefit estimates are compared. The size and distribution of the benefits arising from the adoption of biotech crops vary significantly, depending on the farm-level effects obtained from the various data sources and the supply and demand elasticity assumptions for the domestic and world markets. Estimates of the benefits derived from farm-level impacts that isolate the effects biotechnology appear to be the most plauible. This study does not lend support to the popular belief that U.S. farmers received at least one-half, or as much as two-thirds, of the total benefits realized from the adoption of biotechnology. In contrast, the results of this study indicate that in 1997, U.S. farmers realized considerably less than half of the total benefits. The bulk of the benefits appear to have gone to the gene supplier, seed companies, U.S. consumers, and the rest of the world.Research and Development/Tech Change/Emerging Technologies,

Stereospecific synthesis of the aglycone of pseudopterosin E

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Using LIP to Gloss Over Faces in Single-Stage Face Detection Networks

This work shows that it is possible to fool/attack recent state-of-the-art face detectors which are based on the single-stage networks. Successfully attacking face detectors could be a serious malware vulnerability when deploying a smart surveillance system utilizing face detectors. We show that existing adversarial perturbation methods are not effective to perform such an attack, especially when there are multiple faces in the input image. This is because the adversarial perturbation specifically generated for one face may disrupt the adversarial perturbation for another face. In this paper, we call this problem the Instance Perturbation Interference (IPI) problem. This IPI problem is addressed by studying the relationship between the deep neural network receptive field and the adversarial perturbation. As such, we propose the Localized Instance Perturbation (LIP) that uses adversarial perturbation constrained to the Effective Receptive Field (ERF) of a target to perform the attack. Experiment results show the LIP method massively outperforms existing adversarial perturbation generation methods -- often by a factor of 2 to 10.Comment: to appear ECCV 2018 (accepted version