Showing papers by "Andrew R. Gray published in 2004"

Vascular trauma in New Zealand: an 11-year review of NZVASC, the New Zealand Society of Vascular Surgeons' audit database.

Abstract: AIM: To describe vascular trauma in New Zealand: its management and early outcomes. METHODS: Patients suffering vascular trauma between January 1993 and December 2003 were analysed using data collected prospectively by the New Zealand Society of Vascular Surgeons' database (NZVASC). RESULTS: There were 549 cases of vascular trauma amongst 45,759 vascular admissions collected by the database in the 11-year period. This study confirmed the findings in international studies that younger adult males were more likely to suffer vascular trauma. Elderly patients, especially females, were most at risk of iatrogenic vascular injury, which accounted for 22% of cases in this study. Complication rates reported by rural vascular surgeons in New Zealand were comparable to results in the main centres and to international reports. CONCLUSION: While programmes to slow down and sober up road users help reduce injuries in the younger age groups, it lies in the hands of our own profession to reduce the iatrogenic injuries in the older patients. Language: en

Optimization methods for minimum power multicasting in wireless networks with sectored antennas

Abstract: In this paper the problem of minimum power multicasting in wireless networks with sectored antennas is considered. For omnidirectional antenna systems, a transmission from node i to node j will also reach all nodes which are closer to i than j. Depending on the network geometry, this strategy can be highly power efficient In ideal sectored antenna systems, however, this phenomenon is sector specific; i.e., only those nodes which are located in the same sector as j will receive the transmission implicitly. Though this might seem an apparent disadvantage, the higher gains associated with directional antennas (as opposed to omni-directional antennas) allow for reduced transmission powers without sacrificing the signal-to-interference ratio at the receiver. In this paper, we first develop a mixed integer linear programming model for optimal solution of the minimum power multicast problem with sectored antennas. Subsequently, we discuss a biologically inspired algorithm for solving the problem to near-optimality at a very reasonable computation time. Experiments on randomly generated 10, 20 and 30-node networks indicate that near-optimal solutions can be obtained using the proposed algorithm.