The IEEE 802.15.4 specification has enabled lowpower, low-cost wireless sensor networks (WSNs) capable of robust and reliable communication.

Abstract-We consider the problem of deploying wireless sensors in a three dimensional space to achieve a desired degree of coverage, while minimizing the number of sensors placed. Typical sensor deployment scenarios impose constraints on possible locations of the sensors, and on the desired coverage, but currently there is no unified way to handle these constraints in optimizing the number of sensors placed. We present a novel approach called discretization which allows us to cast the sensor deployment problem as a discrete optimization problem, and hence apply well-understood and flexible discrete optimization techniques for sensor deployment. Our results show that this approach yields solutions that nearly minimize the number of sensors used, while providing a high degree of coverage. Further, unlike typical approaches to sensor deployment, where 3D coverage is significantly more complex than 2D coverage, discretization is equally easy to apply for 2D as well as 3D coverage.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractStatoil is a Norwegian based oil and gas company with a daily oil and gas production of 1.1 million boe, operations in 30 countries and about 24.000 employees. Statoil is the world's 3rd largest net seller of crude oil, and supplies two-thirds of all Norwegian gas to the European market. As part of an improvement campaign with focus on increased production and reduced maintenance and operational costs, Statoil is working with initiatives related to turnaround strategies and execution of maintenance that requires shutdown. One of these initiatives is called RAPID, which stands for "Remove Activities, Prolong Interval and Decrease duration". The project was released to challenge existing procedure and mindset to handle turnarounds and shutdowns recognising that turnarounds are the largest single contributor to reduced production in Statoil. Turnarounds with production shutdown are conducted on a regular basis, with a typical duration of 15 days and with a 1-3 yrs. frequency for offshore facilities and 4-8 yrs. for land based facilities. It is a long-term objective to reduced lost production due to turnarounds by increased use of condition monitoring, new procedures for hot work, safety integrity verification, opportunity maintenance and improved planning. This paper describes the RAPID-project and its applied methodologies.