Energy consumption is a crucially important issue in battery-driven wireless sensor networks (WSNs). In most sensor networks, the sensors near the data collector (i.e. the sink) become drained more quickly than those elsewhere in the network since they are required to relay all of the data collected in the network to the sink. Therefore more balanced data paths to the sink should be established in order to extend the lifetime of the sensor network. Accordingly, a novel relay deployment scheme for WSNs based on the Voronoi diagram is proposed. The proposed scheme is applicable to both two-dimensional and three-dimensional network topologies and establishes effective routing paths that balance the traffic load within the sensor network and alleviate the burden on the sensors around the sink. Simulation results indicate that the number of relays deployed in the proposed scheme is similar to that deployed in the predetermined location scheme and is significantly less than that deployed in the minimum set cover scheme. Furthermore, the lifetime of the sensor network containing relay nodes deployed using the current scheme is longer than that achieved using either the predetermined location scheme or the minimum set cover scheme.
The success of many wireless sensor network (WSN) applications, such as moving target tracking or environment monitoring, is dependent upon achieving 'k-coverage' of the sensed area, that is every point in the surveillance area is monitored by at least k sensors. This study presents a novel distributed self-location estimation scheme based on a Voronoi diagram to achieve k-coverage in a WSN with mobile nodes. The simulation results show that the proposed scheme effectively to perform k-coverage within the sensing field and fast convergent to fulfil more than 88% k-coverage ratio following three movements for the minimal required sensor deployment.
Summary 1. In a cholera epidemic, a study of the therapeutic effect of sulfonamide drugs has been made in 25 adult patients treated with sulfaguanidine, 25 with sulfadiazine and 29 without sulfonamides as control. 2. One death occurred in the control group and one in the group with sulfaguanidine treatment. 3. The average duration of diarrhea is shortened and the average amount of intravenous saline given is reduced in the sulfonamide-treated group as compared with the control. The differences are statistically significant. 4. There is no significant difference between the therapeutic results produced by these two sulfonamide drugs. 5. No striking effect of the sulfonamides on the time of disappearance of cholera vibrios from the stool has been observed. 6. With the dosage used in this study, only bacteriostatic concentration of the sulfonamides has been found in the stool of the patients under treatment.
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