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- Henningsson, Mathias, et al.
(författare)
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A column generation approach for a ring network design problem
- 2003
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- When designing a telecommunication network, one often wish to include some kind of survivability requirement, for example that there should be at least two paths between every pair of nodes in the network. A design model who fulfills this requirement is a network build up with rings. The network design problem is to choose links from a given network, and compose them into a number of rings. The rings are connected to each other at certain transit nodes. The number of possible rings is enormous, and each possible ring is associated with a certain fixed cost. A ring has a fixed capacity, however, we model it as a linear cost depending on the traffic using the ring and the length of the ring. We describe the problem, and model it is a set covering model, where a column describes how a specific ring is used. Even with a small set of rings, number of possible columns in the model is large. Therefore, a column generation approach is used to solve the set covering model with a given set of rings. An important part of the problem is to generate new rings, were the dual solution from the set covering model gives rewards on the nodes, representing a nodes’ wish to be included in a new ring. The ring generation problem is a modification of a traveling salesman subtour problem. New rings are generated using a heuristic. We present some computational results for a real data network and a number of random generated networks.
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- Henningsson, Mathias, 1970-, et al.
(författare)
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A ring network design problem and heuristics for generating a set of feasible rings
- 2003
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- We discuss the problem of designing a telecommunication network with the survivability requirement that the network should be composed of connected rings of links. The work design problem is then to choose links from a given network, and compose them into a number of rings. Furthermore, the rings should be connected at certain transit nodes. The traffic between rings may pass through other rings. Each ring is associated with a certain fixed cost depending on the length of the ring. We describe the problem, modeled as a linear integer programming problem. We find a feasible solution to the problem by first find good rings in the network using two heuristics, and then solve the optimization model using only these rings. Finally, we give some computational results for different networks.
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- Henningsson, Mathias, 1970-, et al.
(författare)
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A ring network design problem solved by a ring generation and allocation approach
- 2003
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The development of optical fibers in telecommunications has lead large changes in the field. When design a telecommunication network, capacity nowadays is cheap, and the minimal cost design tends to be a tree. Since such a design is very vulnerable for link or node failures, one often wish to include some kind of survivability requirement, for example that the network should be two-edge-connected or two-node-connected. Another form of design model is to prescribe that the network should be composed of connected rings of links. The network design problem is then to choose links from a give network, and compose them into a number of rings. Furthermore, the rings should be connected at certain transit nodes. Each possible ring is associated with a certain fixed cost, and all links in a certain ring are given the same capacity. Traffic between rings may pass through other rings, which is an important element of the problem. Finally, reserve capacity allocation according to certain principles is included. We describe the problem, modeled as a linear integer programming problem, and discuss different formulations and different solution methods. As the problem is quite difficult, we focus on heuristic solution methods, including elements of column generation and Lagrangean relaxation.
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| 6. |
- Henningsson, Mathias, et al.
(författare)
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Ring network design by Lagrangean based column generation
- 2002
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Ingår i: Telecommunications Systems. - 1018-4864 .- 1572-9451. ; 21:2-4, s. 301-318
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Tidskriftsartikel (refereegranskat)abstract
- We discuss the problem of designing a telecommunication network with the survivability requirement that the network should be composed of connected rings of links. The network design problem is then to choose links from a given network, and compose them into a number of rings. Furthermore, the rings should be connected at certain transit nodes. The traffic between rings may pass through other rings. Each ring is associated with a certain fixed cost depending on the length of the ring. We describe the problem, modeled as a linear integer programming problem, and a heuristic solution method, based on column generation and Lagrangean relaxation.
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- Holmberg, Johan, et al.
(författare)
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Phobic postural vertigo: body sway during vibratory proprioceptive stimulation
- 2003
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Ingår i: NeuroReport. - : Ovid Technologies (Wolters Kluwer Health). - 1473-558X .- 0959-4965. ; 14:7, s. 1007-1011
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Tidskriftsartikel (refereegranskat)abstract
- Phobic postural vertigo patients might rely more on proprioceptive than visual cues to regulate stance. We tested 14 phobic postural vertigo patients and 24 healthy subjects with posturography during quiet stance and periods of vibratory proprioceptive calf muscle stimulation, both with eyes open and closed. During quiet stance phobic postural vertigo patients showed higher torque variance than healthy subjects, especially above 0.1 Hz. Vibratory proprioceptive stimulation increased the differences between healthy subjects and phobic postural vertigo patients. The patients were less able to use vision to counteract vibration-induced movements. Phobic postural vertigo patients are more sensitive to proprioceptive disturbances than healthy subjects are, and less apt to use visual information to control upright stance. This might be part of an anxious mode of balance control.
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- Holmberg, Mikael, 1950
(författare)
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Out-of-hospital cardiac arrest patients treated by emergency medical systems in Sweden 1990-1995
- 2000
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Between Jan 1990 and May 1995 the Swedish Cardiac Arrest Registry collected and analysed 14,065 standardised reports on cardiac arrests. The reports emanated from approximately half of Sweden's ambulance districts, which cover five of Sweden's 8.7 million inhabitants. From 1983 to 1995 approximately 15-20% of the inhabitants had been trained in CPR.Method: A prospective, observational study of cardiac arrests reported to the Swedish Cardiac Arrest Registry. Results: Resuscitation was attempted in 10,966 cases. The median age was 70 years. In 70% the arrest was witnessed, and in 43% patients had ventricular fibril--lation (VF). The incidence of VF at the time of cardiac arrest was estimated to be 80% in the cases with probable heart disease. In 1,692 cases (15.4 %) the patient was admitted alive in hospital and 544 patients (5.0 %) were alive after one month. Survival to one month in the subgroup with VF was 9.5 % and 1.6% for patients with non-shockable rhythm. The survivors were analysed in relation to time to defibrillation and we found a strong correlation between a short time and increased survival. Bystander cardiopulmonary resuscitation (B-CPR) was initiated in 36% of the cases. In 56% of these cases, the bystanders were lay persons and in 28% they were medical personnel. Most of the arrests took place at home (65%) and only 23% of these patients were given B-CPR in contrast to cardiac arrest in other places where 53% were given CPR. Survival to one month was significantly higher in all cases that received B-CPR (8.2% vs. 2.5%). The odds ratio for survival to one month with B-CPR was in a logistic regression analysis 2.5 (95% CI 1.9-3.1). Factors that were associated with the effect of B-CPR were the interval between the collapse and the start of B-CPR, the completeness of B-CPR, whether or not the bystander was a layperson, the interval between collapse and the arrival of the ambulance, age and the place of arrest. Adrenalin was given in 42% and 48% were intubated. Among patients given adrenalin 3.4% were alive after one month and among patients who were intubated 3.6% were alive after one month. In a multivariate analysis treatment with adrenalin and intubation were both independently associated with predictors of a lower chance of survival.Conclusion: In a survey in Sweden of out-of-hospital cardiac arrests the overall sur-vival was low (5.0%). Survival for the patients with VF was 9.5%. Initial incidence of VF was estimated to be 80% in patients with probable heart disease. Survival decreased with increasing time to defibrillation. Bystander-CPR increased survival two to three times. Intubation and adrenalin were not associated with an increased survival.
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- Jansson, Per, et al.
(författare)
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Liquid-tin-jet laser-plasma extreme ultraviolet generation
- 2004
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 84:13, s. 2556-2258
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate the applicability of liquid-metal jets in vacuum as regenerative targets for laser-plasma generation of extreme ultraviolet (EUV) and soft x-ray radiation. This extends the operation of liquid jet laser-plasma,sources to high-temperature, high-Z, high-density, low-vapor-pressure materials with new spectral signatures. The system is demonstrated using tin (Sn) as the target due to its strong emission around lambdaapproximate to13 nm, which makes the material suitable for EUV lithography. We show a conversion efficiency of 2.5% into (2% BW x 2pi x sr) and report quantitative measurements of the ionic/atomic as well as particulate debris emission.
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