| 1. |
- Appelgren, Patrik, et al.
(author)
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Disruption mechanisms in electrified solid copper jets
- 2011
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In: Journal of applied mechanics. - : ASME International. - 0021-8936 .- 1528-9036. ; 78:2
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Journal article (peer-reviewed)abstract
- Interaction between a solid copper jet and an electric current pulse is a complex process that has been experimentally studied by letting a jet created by a shaped charge device pass through an electrode configuration consisting of two aluminum plates with a separation distance of 150 mm. When the jet bridged the electrodes, which are connected to a charged pulsed power supply, current pulses with amplitude up to 250 kA were passed through the jet. By using flash X-ray diagnostics, the disruption of the electrified jets could be studied. In this paper, the disruption of the electrified jets is discussed and compared with disruption phenomena observed in electrically exploded metal rods in a static setup. Necks are naturally formed along a stretching jet, and in the experiments with current interaction these necks explode electrically. In the static experiments, the metal rods have small notches distributed along the rod to resemble the necks of the jet. When two neighboring necks or notches explode, the shock of the explosion compresses the intermediate jet or rod segment axially and the material is forced out radially. The disruption phenomena in the jet and rod experiments are similar with rapid expansion of the metal at explosion and at comparable velocities.
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| 2. |
- Appelgren, Patrik, et al.
(author)
-
Experimental Study of Electromagnetic Effects on Solid Copper Jets
- 2010
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In: Journal of applied mechanics. - : ASME International. - 0021-8936 .- 1528-9036. ; 77:1, s. 011010-
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Journal article (peer-reviewed)abstract
- In this paper we present a study of the interaction between all electric current pulse and a solid copper jet. Experiments were performed using a dedicated pulsed power supply delivering a current pulse of such amplitude, rise little, and duration that the jet is efficiently affected. The copper jet was created by using a shaped charge warhead. All electrode configuration consisting of two aluminum plates with a separation distance of 150 mm was used. The discharge current pulse and the voltages at the capacitors and at the electrodes were measured to obtain data oil energy deposition in and the resistance of the jet and electrode contact region. X-ray diagnostics were used to radiograph the jet, and by analyzing the radiograph, the degree of disruption of the electrified jet could be obtained. It was found that a current pulse with an amplitude of 200-250 kA and a rise time of 16 mu s could strongly enhance the natural fragmentation of the jet. In this case, the initial electric energy was 100 kJ and about 90% of the electric energy was deposited in the jet and electrodes. At the exit of the electrode region, the jet fragments formed rings with a radial velocity of up to 200 m/s, depending oil the initial electric energy in the pulsed power supply. [DOI: 10.1115/1.3172251]
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| 3. |
- Appelgren, Patrik, et al.
(author)
-
Interaction between solid copper jets and powerful electrical current pulses
- 2011
-
In: Journal of applied mechanics. - : ASME International. - 0021-8936 .- 1528-9036. ; 78:2
-
Journal article (peer-reviewed)abstract
- The interaction between a solid copper jet and an electric current pulse is studied. Copper jets that were created by a shaped-charge device were passed through an electrode configuration consisting of two aluminum plates with a separation distance of 150 mm. The electrodes were connected to a pulsed-power supply delivering a current pulse with amplitudes up to 250 kA. The current and voltages were measured, providing data on energy deposition in the jet and electrode contact region, and flash X-ray diagnostics were used to depict the jet during and after electrification. The shape of, and the velocity distributions along, the jet has been used to estimate the correlation between the jet mass flow through the electrodes and the electrical energy deposition. On average, 2.8 kJ/g was deposited in the jet and electrode region, which is sufficient to bring the jet up to the boiling point. A model based on the assumption of a homogenous current flow through the jet between the electrodes underestimates the energy deposition and the jet resistance by a factor 5 compared with the experiments, indicating a more complex current flow through the jet. The experimental results indicate the following mechanism for the enhancement of jet breakup. When electrified, the natural-formed necks in the jet are subjected to a higher current density compared with other parts of the jet. The higher current density results in a stronger heating and a stronger magnetic pinch force. Eventually, the jet material in the neck is evaporated and explodes electrically, resulting in a radial ejection of vaporized jet material.
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| 4. |
- Buhrman, Monica, 1974-, et al.
(author)
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Guided internet-delivered acceptance and commitment therapy for chronic pain patients: A randomized controlled trial
- 2013
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In: Behaviour Research and Therapy. - : Elsevier. - 0005-7967 .- 1873-622X. ; 51:6, s. 307-315
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Journal article (peer-reviewed)abstract
- Acceptance and commitment therapy (ACT) interventions for persons with chronic pain have recently received empirical support. ACT focuses on reducing the disabling influences of pain through targeting ineffective control strategies and teaches people to stay in contact with unpleasant emotions, sensations, and thoughts. The aim of the present study was to investigate the effect of a guided internet-delivered ACT intervention for persons with chronic pain. A total of 76 patients with chronic pain were included in the study and randomized to either treatment for 7 weeks or to a control group that participated in a moderated online discussion forum. Intent-to-treat analyses showed significant increases regarding activity engagement and pain willingness. Measurements were provided with the primary outcome variable Chronic Pain Acceptance Questionnaire which was in favour of the treatment group. Reductions were found on other measures of pain-related distress, anxiety and depressive symptoms. A six month follow-up showed maintenance of improvements. We conclude that an acceptance based internet-delivered treatment can be effective for persons with chronic pain.
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