We consider the problem of super-resolution reconstruction (SRR) in MRI. Subpixel-shifted MR images were taken in several fields of view (FOVs) to reconstruct a high-resolution image. A novel algorithm is presented. The algorithm can be applied locally and guarantees perfect reconstruction in the absence of noise. Results that demonstrate resolution improvement are given for phantom studies (mathematical model) as well as for MRI studies of a phantom carried out with a GE clinical scanner. The method raises questions that are discussed in the last section of the paper. Open questions should be answered in order to apply this method for clinical purposes.
Traditionally, the value of a product has been assessed according to the direct revenues the product creates. However, products do not exist in isolation but rather influence one another's sales. Such influence is especially evident in e-commerce environments, in which products are often presented as a collection of web pages linked by recommendation hyperlinks, creating a large-scale product network. The authors present a systematic approach to estimate products’ true value to a firm in such a product network. Their approach, which is in the spirit of the PageRank algorithm, uses available data from large-scale e-commerce sites and separates a product's value into its own intrinsic value, the value it receives from the network, and the value it contributes to the network. The authors demonstrate their approach using data collected from the product network of books on Amazon.com . Specifically, they show that the value of low sellers may be underestimated, whereas the value of best sellers may be overestimated. The authors explore the sources of this discrepancy and discuss the implications for managing products in the growing environment of product networks.
Table A1 depicts comparison statistics on the matched sample versus the treatment groups for each distance. Similarly, Table A2 depicts comparison statistics on the network-based group used as a control versus the treatment groups. The variable Total25 is used to control for Amazon's $25 shipping policy, capturing whether the sum of the price of the reviewed book and any of the books in the local network passes the $25 free shipping threshold; indegree captures the number of books directed to a focal book in the product network; local clustering measures the degree to which books in the product network tend to cluster together to create groups characterized by a their density of ties; same binding indicates whether a purchased book is of the same binding type (e.g., hardcover, paperback) as the reviewed book; sale price controls for the sales price of a purchased book; average rating captures the subjective evaluation of a book as reported by consumers; and sales rank measuring a book's demand relative to other products.
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