| 1. |
- Riley, M A, et al.
(författare)
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Beyond band termination in Er-157 and the search for wobbling excitations in strongly deformed Hf-174
- 2005
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Ingår i: Journal of Physics G: Nuclear and Particle Physics. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 31:10, s. 1735-1740
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Tidskriftsartikel (refereegranskat)abstract
- High-spin terminating bands in heavy nuclei were first identified in nuclei around Er-158(90). While examples of special terminating states have been identified in a number of erbium isotopes, almost nothing is known about the states lying beyond band termination. In the present work the high-spin structure of Er-157 has been studied using the Gammasphere spectrometer. The subject of triaxial superdeformation and 'wobbling' modes in Lu nuclei has rightly attracted a great deal of attention. Very recently, four strongly or superdeformed (SD) sequences have been observed in Hf-174 and ultimate cranker calculations predict, such structures may have significant triaxial deformation. We have performed two experiments in an attempt to verify the possible triaxial nature of these bands. A lifetime measurement was performed to confirm the large (and similar) deformation of the bands. In addition, a high-statistics, thin-target experiment was run to search for linking transitions between the SD bands and possible wobbling modes.
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| 2. |
- Riley, M. A., et al.
(författare)
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Observation of states beyond band termination in Er-156,Er-157,Er-158 and strongly deformed structures in Hf-173,Hf-174,Hf-175
- 2006
-
Ingår i: Physica Scripta. - 0031-8949. ; T125, s. 123-126
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Tidskriftsartikel (refereegranskat)abstract
- High-spin terminating bands in heavy nuclei were first identified in nuclei around Er-158(90). While examples of terminating states have been identified in a number of erbium isotopes, almost nothing is known about the states lying beyond band termination. In the present work, the high-spin structure of Er-156,Er-157,Er-158 has been studied using the Gammasphere spectrometer. The subject of triaxial superdeformation and 'wobbling' modes in Lu nuclei has rightly attracted a great deal of attention. Very recently four strongly or superdeformed (SD) sequences have been observed in Hf-174, and cranking calculations using the Ultimate Cranker code predict that such structures may have significant triaxial deformation. We have performed two experiments in an attempt to verify the possible triaxial nature of these bands. A lifetime measurement was performed to confirm the large (and similar) deformation of the bands. In addition, a high-statistics, thin-target experiment took place to search for linking transitions between the SD bands, possible wobbling modes, and new SD band structures.
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| 3. |
- Hartley, D. J., et al.
(författare)
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Wobbling mode in Ta-167
- 2009
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 80:4
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Tidskriftsartikel (refereegranskat)abstract
- The collective wobbling mode, the strongest signature for the rotation of a triaxial nucleus, has previously been seen only in a few Lu isotopes in spite of extensive searches in nearby isotopes. A sequence of transitions in the N = 94 Ta-167 nucleus exhibiting features similar to those attributed to the wobbling bands in the Lu nuclei has now been found. This band feeds into the pi i(13/2) band at a relative energy similar to that seen in the established wobbling bands and its dynamic moment of inertia and alignment properties are nearly identical to the i(13/2) structure over a significant frequency range. Given these characteristics, it is likely that the wobbling mode has been observed for the first time in a nucleus other than Lu, making this collective motion a more general phenomenon.
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| 4. |
- Qadri, F., et al.
(författare)
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Enterotoxigenic Escherichia coli and Vibrio cholerae diarrhea, Bangladesh, 2004
- 2005
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Ingår i: Emerg Infect Dis. ; 11:7, s. 1104-7
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Tidskriftsartikel (refereegranskat)abstract
- Flooding in Dhaka in July 2004 caused epidemics of diarrhea. Enterotoxigenic Escherichia coli (ETEC) was almost as prevalent as Vibrio cholerae O1 in diarrheal stools. ETEC that produced heat-stable enterotoxin alone was most prevalent, and 78% of strains had colonization factors. Like V. cholerae O1, ETEC can cause epidemic diarrhea.
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| 5. |
- Al-Khatib, A, et al.
(författare)
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Transition to non-collective states at high spin in Xe-124
- 2008
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Ingår i: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001. ; 36:1, s. 21-29
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Tidskriftsartikel (refereegranskat)abstract
- Excited states in Xe-124 were populated in the reaction Se-82(Ca-48, 6n) Xe-124 and gamma-ray coincidence relationships were measured with the Gammasphere spectrometer. Two new bands are observed and several of the previously known bands are extended in the high-as well as in the low-spin region. Two irregular high-spin structures are also added. The irregularities are a fingerprint of a transition from collective to non-collective behaviour. Configuration assignments to the new structures are proposed on the basis of systematics and by comparing experimental properties with calculations within the framework of the cranking model.
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| 6. |
- Benzerga, A. A., et al.
(författare)
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Computational methodology for modeling fracture in fiber-reinforced polymer composites
- 2009
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Ingår i: Journal of Aerospace Engineering. - 0893-1321 .- 1943-5525. ; 22:3, s. 296-303
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Tidskriftsartikel (refereegranskat)abstract
- A framework is presented for analyzing the inelastic behavior and fracture of polymer matrix composites. Physics-based viscoplastic constitutive equations are used and supplemented with a matrix cracking model and an energy-based debonding model. The capabilities of the framework are illustrated by finite-element solutions of boundary-value problems under plane strain conditions using the unit-cell concept. In the application, focus is centered on the effect of manufacturing induced voids on local modes of fracture under both tension and compression
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| 7. |
- Chowdhury, A. A., et al.
(författare)
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Causal and seasonal analysis of bulk transmission line forced outages using the MAPP outage database
- 2006
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Ingår i: 2006 International Conference on Probabilistic Methods Applied to Power Systems. - NEW YORK : IEEE. ; , s. 847-853
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper describes the Mid-Continent Area Power Pool (MAPP), transmission equipment outage data collection scheme and presents bulk transmission line average outage statistics for forced outage category for the 230 kV and above systems computed using the data for the ten-year operating period from 1991 to 2000. In addition, a causal and seasonal contribution to forced outages of bulk transmission line is analyzed that helps to identify appropriate remedial actions to improve transmission line reliability. This paper presents selected applications of transmission line forced outage statistics by different MAPP member utilities.
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| 8. |
- Chowdhury, A. A., et al.
(författare)
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Determining distribution substation transformer optimal loadings using a reliability cost-benefit approach
- 2006
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Ingår i: 2006 International Conference on Probabilistic Methods Applied to Power Systems, Vols 1 and 2. - NEW YORK : IEEE. ; , s. 1201-1209
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Konferensbidrag (refereegranskat)abstract
- This paper presents a novel reliability cost-benefit approach, taking into account customer value of reliability, to compare different transformer loading philosophies while concurrently considering varying levels of transformer emergency capability. Using this cost benefit approach, guidelines for loading existing transformers can be determined. The developed methodology can also be used to establish standard emergency rating criteria for purchasing new transformers, which will optimize reliability performance versus cost. The methodology is illustrated using practical system examples.
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| 9. |
- Chowdhury, A. A., et al.
(författare)
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Distribution system in-depth causal reliability assessment
- 2006
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Ingår i: 2006 International Conference on Probabilistic Methods Applied to Power Systems, Vols 1 and 2. - NEW YORK : IEEE. ; , s. 805-812
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Konferensbidrag (refereegranskat)abstract
- The methodology used to assess the historical reliability performance of a Canadian Utility's electric distribution system is outlined. Included is an overview of the process used to collect and organize the required interruption data as well as a description of the performance indices calculated for use in the causal assessment. The various component parts of the reliability performance assessment are described. This includes a description of indices comparison between years and to the average at different levels of the system and by outage cause and component failure. Finally, results from the 2004 reliability assessment of the utility's electric distribution system are summarized and the application of the calculated performance statistics in planning, operating and maintaining distribution systems is described.
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| 10. |
- Chowdhury, A. A., et al.
(författare)
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Monte Carlo simulation model for multi-area generation reliability evaluation
- 2006
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Ingår i: 2006 International Conference on Probabilistic Methods Applied to Power Systems, Vols 1 and 2. - NEW YORK : IEEE. ; , s. 1216-1225
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Konferensbidrag (refereegranskat)abstract
- Power system reliability assessment methods can be categorized either analytical or as Monte Carlo simulation. Analytical methods represent the power system by a mathematical model and assess the reliability performance indices from the model utilizing mathematical solutions. On the other hand, Monte Carlo simulation methods, compute the reliability indices by simulating the actual process and random behavior of the power system, and can include any system effects or system processes which may have to be approximated in analytical methods. This paper describes a Monte Carlo simulation tool, which has been developed by General Electric (GE) Company for the reliability analysis of multi-area generation systems with explicit recognition of those unit and system operating considerations, rules, and constraints that influence system reliability indices. The basic features, capabilities and applications of the Monte Carlo simulation model are illustrated using the Mid-Continent Area Power Pool (MAPP) interconnected system reserve capacity obligation (RCO) study in this paper.
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