11 research outputs found
Forest Management Zone Design with a Tabu Search Algorithm
Increased conflicts between timber production and environmental protection led some analysts to advocate land-use segregation, often referred to as forest management zoning. The objective of zoning is to create ecologically desirable non-fragmented forest reserves and group timber production areas. We formulate an integer programming model of forest zoning that explicitly addresses clustering of spatial units allocated to timber production and reserve zones while also promoting separation of these zones. A tabu search algorithm is developed, implemented and tested using a case study. The case study results indicate that up to 5% of the net financial return is sacrificed with a 'satisfactory' grouping of units within each zone. A 'good' separation between the reserves and timber production zone is achieved at the cost of further decline of the net financial return up to 11% relative to the unconstrained case.forest planning, integer programming, reserves, tabu search, timber production, zoning
Satellite downlink scheduling problem: A case study
The synthetic aperture radar (SAR) technology enables satellites to
efficiently acquire high quality images of the Earth surface. This generates
significant communication traffic from the satellite to the ground stations,
and, thus, image downlinking often becomes the bottleneck in the efficiency of
the whole system. In this paper we address the downlink scheduling problem for
Canada's Earth observing SAR satellite, RADARSAT-2. Being an applied problem,
downlink scheduling is characterised with a number of constraints that make it
difficult not only to optimise the schedule but even to produce a feasible
solution. We propose a fast schedule generation procedure that abstracts the
problem specific constraints and provides a simple interface to optimisation
algorithms. By comparing empirically several standard meta-heuristics applied
to the problem, we select the most suitable one and show that it is clearly
superior to the approach currently in use.Comment: 23 page
Waiting strategies for the dynamic pickup and delivery problem with time windows
The dynamic pickup and delivery problem with time windows arises in courier companies making same-day pickup and delivery of letters and small parcels. In this problem solution quality is affected by the way waiting time is distributed along vehicle routes. This article defines and compares four waiting strategies. An extensive empirical study is carried out on instances generated using real-life data.
Forest Management Zone Design with a Tabu Search Algorithm
Increased conflicts between timber production and environmental protection led some analysts to advocate land-use segregation, often referred to as forest management zoning. The objective of zoning is to create ecologically desirable non-fragmented forest reserves and group timber production areas. We formulate an integer programming model of forest zoning that explicitly addresses clustering of spatial units allocated to timber production and reserve zones while also promoting separation of these zones. A tabu search algorithm is developed, implemented and tested using a case study. The case study results indicate that up to 5% of the net financial return is sacrificed with a 'satisfactory' grouping of units within each zone. A 'good' separation between the reserves and timber production zone is achieved at the cost of further decline of the net financial return up to 11% relative to the unconstrained case
Age as a prognostic factor in skin melanoma
The aim of this study was to establish whether older patients with skin
melanoma (in an analyzed group of 189 patients treated at the Institute for
Oncology and Radiology of Serbia from 2004 to 2008), have worse survival
compared to younger patients. In 100 men and 89 women with an average age of
58.9 years, the following parameters were observed and statistically
analyzed in SPSS: gender, age, localization, tumor thickness, ulceration,
lymphonodal status and invasion level. In the four age subgroups -
quartiles, the best survival was shown in patients <50 years (85.7%), and
the worst in patients >70 years (76.1%). Patients without ulcerations, with
negative lymph nodes, thin melanomas and Clark levels I and II had
significantly better survival outcomes. Although the results showed no
statistical significance of age as a prognostic factor in the survival of
patients with skin melanoma, further research on a larger number of patients
is warranted