Browsing by Subject "coverage"
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Item COST-CUTTING AT THE HOUSTON CHRONICLE: WHAT IMPACT HAS DECLINING CIRCULATION HAD UPON CRIME COVERAGE?(2012-04-19) Smith, Kese; Olson, Beth; Vardeman, Jennifer; Curtis, RussellThis study investigated the effect declining circulation at the Houston Chronicle had upon local news coverage- especially crime coverage. In 1995, it became the sole daily metro newspaper in Houston. In the ensuing years it has seen a steady erosion of paid circulation and its publishers responded, as have many newspapers in the United States, by making a series of cost-cutting moves including closing news bureaus and laying off long-time editorial staff. Story content for the years 1996 (the first full year in which the Houston Chronicle became the sole daily) and 2006, 2007, 2008 and 2009 was examined using content analysis. Particular attention was paid to crime stories as the crime beat is an entry-level reporter position, one which pays less and requires less experience than other specialized beats. Cultivation theory postulates an increase in crime coverage, which is cheap and plentiful, can lead the public to view the world as a more dangerous place than statistics indicate. Two constructed weeks per year were examined. Layoffs at the Houston Chronicle coincided with a 40 percent decrease in local stories. During that same period, stories produced by wire services or other newspapers increased, indicating they replaced some, but not all, of the shortage of local stories. Crime stories accounted for a greater percentage of local stories, although not significantly. They were eight percent of local stories in 1996 rising to a high of 10 percent in 2009. However crime stories became significantly longer over that same v period of time, suggesting crime became a greater staple in filling the newspaper's newshole. Consistent with other literature, violent crime accounted for the clear majority of all crimes reported. Crime stories were also individually coded to determine to what extent details were included which would allow a reader to determine the randomness of the crime and be extension his/her own possible risk. Such variables did not go down as expected, and in some years were even higher than in 1996. This study suggests the Houston Chronicle has responded to declining circulation by cutting staff and local content. Crime coverage has helped fill the remaining local content, but not to the extent expected. Moreover, details which allow readers to gauge their personal risk were present in greater amounts than anticipated.Item Deployment and coverage maintenance in mobile sensor networks(2009-05-15) Lee, JaeyongDeployment of mobile nodes in a region of interest is a critical issue in building a mobile sensor network because it affects cost and detection capabilities of the system. The deployment of mobile sensors in essence is the movement of sensors from an initial position to a final optimal location. Considerable attention has recently been given to this deployment issue. Many of the distributed deployment schemes use the potential field method. In most cases, the negative gradient of the potential function becomes the feedback control input to a node. This assumes that the potential function is differentiable over the entire region. This assumption is valid primarily when the topology of the network is fixed. In this research, we analyze the stability of a network that uses piecewise smooth potential functions. A gravitation-like force is proposed to deploy a group of agents and to form a certain configuration. We use a nonsmooth version of the Lyapunov stability theory and LaSalle?s invariance principle to show asymptotic stability of the network which is governed by discontinuous dynamics. We propose a hierarchical structure using potential fields for mobile sensor network deployment. A group of mobile nodes first form a cluster using a potential field method and then cluster heads are used to establish a hexagonal structure that employs a higher level potential field. We consider specifically the problem of deploying a mobile sensor network so that a certain area coverage is realized and maintained. And we propose an algorithm for main taining the desired coverage that assumes the availability of a stochastic sensor model. The model reflects the decline of the sensor accuracy as the distance increases from the sensor. It is further assumed that each node?s sensor has a different sensing range to represent sensor performance deterioration due to power decay. The network deployment scheme combines artificial forces with individual sensor ranges. The validity and the effectiveness of the proposed algorithm are compared to the conventional methods in simulations. Simulation results confirm the effectiveness of the proposed algorithms with respect to a defined performance metric.Item Robotic Searching for Stationary, Unknown and Transient Radio Sources(2012-07-16) Kim, Chang YoungSearching for objects in physical space is one of the most important tasks for humans. Mobile sensor networks can be great tools for the task. Transient targets refer to a class of objects which are not identifiable unless momentary sensing and signaling conditions are satisfied. The transient property is often introduced by target attributes, privacy concerns, environment constraints, and sensing limitations. Transient target localization problems are challenging because the transient property is often coupled with factors such as sensing range limits, various coverage functions, constrained mobility, signal correspondence, limited number of searchers, and a vast searching region. To tackle these challenge tasks, we gradually increase complexity of the transient target localization problem such as Single Robot Single Target (SRST), Multiple Robots Single Target (MRST), Single Robot Multiple Targets (SRMT) and Multiple Robots Multiple Targets (MRMT). We propose the expected searching time (EST) as a primary metric to assess the searching ability of a single robot and the spatiotemporal probability occupancy grid (SPOG) method that captures transient characteristics of multiple targets and tracks the spatiotemporal posterior probability distribution of the target transmissions. Besides, we introduce a team of multiple robots and develop a sensor fusion model using the signal strength ratio from the paired robots in centralized and decentralized manners. We have implemented and validated the algorithms under a hardware-driven simulation and physical experiments.