Mitigating Overexposure in Viral Marketing

In traditional models for word-of-mouth recommendations and viral marketing, the objective function has generally been based on reaching as many people as possible. However, a number of studies have shown that the indiscriminate spread of a product by word-of-mouth can result in overexposure, reaching people who evaluate it negatively. This can lead to an effect in which the over-promotion of a product can produce negative reputational effects, by reaching a part of the audience that is not receptive to it. How should one make use of social influence when there is a risk of overexposure? In this paper, we develop and analyze a theoretical model for this process; we show how it captures a number of the qualitative phenomena associated with overexposure, and for the main formulation of our model, we provide a polynomial-time algorithm to find the optimal marketing strategy. We also present simulations of the model on real network topologies, quantifying the extent to which our optimal strategies outperform natural baselinesComment: In AAAI-1

Optimal random search for a single hidden target

A single target is hidden at a location chosen from a predetermined probability distribution. Then, a searcher must find a second probability distribution from which random search points are sampled such that the target is found in the minimum number of trials. Here it will be shown that if the searcher must get very close to the target to find it, then the best search distribution is proportional to the square root of the target distribution. For a Gaussian target distribution, the optimum search distribution is approximately a Gaussian with a standard deviation that varies inversely with how close the searcher must be to the target to find it. For a network, where the searcher randomly samples nodes and looks for the fixed target along edges, the optimum is to either sample a node with probability proportional to the square root of the out degree plus one or not at all.Comment: 13 pages, 5 figure

Local Search in Unstructured Networks

We review a number of message-passing algorithms that can be used to search through power-law networks. Most of these algorithms are meant to be improvements for peer-to-peer file sharing systems, and some may also shed some light on how unstructured social networks with certain topologies might function relatively efficiently with local information. Like the networks that they are designed for, these algorithms are completely decentralized, and they exploit the power-law link distribution in the node degree. We demonstrate that some of these search algorithms can work well on real Gnutella networks, scale sub-linearly with the number of nodes, and may help reduce the network search traffic that tends to cripple such networks.Comment: v2 includes minor revisions: corrections to Fig. 8's caption and references. 23 pages, 10 figures, a review of local search strategies in unstructured networks, a contribution to `Handbook of Graphs and Networks: From the Genome to the Internet', eds. S. Bornholdt and H.G. Schuster (Wiley-VCH, Berlin, 2002), to be publishe

Do air support surfaces reduce development of pressure ulcers?

Abstract Background, significance, purpose: Around 2.5 million patients are affected by pressure ulcers each year, and 60,000 patients die as a result of a pressure ulcer each year. Hospital stays resulting from a pressure ulcer has an annual potential cost of $700,000. The time for a pressure injury to occur is from two to six hours. The present study will experimentally investigate if air support surfaces will reduce the development of pressure ulcers among patients admitted to Wellstar Cobb hospital. Brief literature review: A study in Baltimore, Maryland, was conducted to determine if manually repositioning patients prevented the formation of pressure ulcers. The study required additional studies to determine efficacy; however, the study found that patients were repositioned at least two hours on only 53% of the days. The low level of repositioning was consistent with several other studies. Reasons for not regularly repositioning was due to the lack of time and lack of staff. Based on the before-mentioned statistics, repositioning patients every two hours is not solely sufficient in preventing pressure injuries. Methods: Patients with no pressure injuries will be placed on an air support surface, such as a Waffle overlay, and monitored every two hours, where the sacrum and both heels will be assessed for potential skin breakdown. Evaluation: A pre- and post-pressure rate will be captured by utilizing a pressure mapping tool. The amount of pressure decrease or increase will determine if the study was successful. Keywords: Hospital, at-risk population, bedbound, air support surfaces, pressure ulce

Information Flow in Social Groups

We present a study of information flow that takes into account the observation that an item relevant to one person is more likely to be of interest to individuals in the same social circle than those outside of it. This is due to the fact that the similarity of node attributes in social networks decreases as a function of the graph distance. An epidemic model on a scale-free network with this property has a finite threshold, implying that the spread of information is limited. We tested our predictions by measuring the spread of messages in an organization and also by numerical experiments that take into consideration the organizational distance among individuals

CFD and Heat Transfer Models of Baking Bread in a Tunnel Oven

The importance of efficiency in food processing cannot be overemphasized. It is important for an organization to remain consumer- and business-oriented in an increasingly competitive global market. This means producing goods that are popular, of high quality and low cost for the consumer. This research involves studying existing methods of baking bread in a common type of industrial oven - the single level bread baking tunnel oven. Simulations of the oven operating conditions and the conditions of the food moving through the oven are performed and analyzed using COMSOL, an engineering modeling, design and simulation software. The simulation results are compared with results obtained using MATLAB (a high-level programming language), theoretical analyses and/or results from literature. The most important results from this research are the attainment of the temperature distribution and moisture content of the bread, and the temperature and velocity flow fields within the oven. More specifically, similar values for the temperature rise of a 0.1 m by 0.1 m by 1 m model dough/bread were attained for analytical results, MATLAB, COMSOL (using a volumetric heat source), and COMSOL (using heat fluxes from analytical calculation) these values are 41.1 K, 39.90 K, 41.45 K, and 41.46 K, respectively. Similarly, the temperature rise of the dough/bread from a 2-D COMSOL model (using appropriate inputs for this and all models in this research) is found to be 25.39 K, which has a percent difference of - 44.4 from the MATLAB result of 39.90 K. The moisture loss of the bread via analytical (and MATLAB) calculation is found to be 0.0423 kg water lost per hour, which is within the literature values of 0.030 and 0.25488 kg water lost per hour. The velocity flow fields within the (open) oven for the dimensional free (natural) convection COMSOL simulation show a qualitatively correct rising of the air due to the buoyancy forces imposed by the heating elements. The flow fields within the (closed) oven for the nondimensional free co