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- Al-Askary, Omar, et al.
(författare)
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Adaptive coding for OFDM based systems using generalized concatenated codes
- 2005
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Ingår i: VTC2005-SPRING: 2005 IEEE 61ST VEHICULAR TECHNOLOGY CONFERENCE, VOLS 1-5, PROCEEDINGS. - 0780388879 ; , s. 649-653
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Konferensbidrag (refereegranskat)abstract
- Orthogonal Frequency Division Multiplexing (OFDM) is considered to be a promising candidate for future high-speed wireless communication systems. In this paper we present an adaptive coding scheme for OFDM based systems using generalized concatenated codes. We study the performance of HIPERLAN/2 after encoding with the proposed coding scheme and compare it to the standard convolutional coding scheme currently used. The criteria of our study is the optimization of the throughput. Through the adaptive scheme, we propose a modulation selection based on the average quality of the channel, and a code assigning method for the different sub-channels, that adapts to the channel conditions. We argue that the proposed scheme protects the information better than the ones in the conventional systems, since the latter do not take advantage of the individual sub-channel condition. Our simulations show that lower packet error rate can be accomplished for even higher throughput.
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| 2. |
- Al-Askary, Omar, et al.
(författare)
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Rate adaptive generalized concatenated codes for wireless communication
- 2005
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Ingår i: Proceedings of the INMIC 2005. - 9780780394292 ; , s. 137-142
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Konferensbidrag (refereegranskat)abstract
- This paper presents the construction and performance of rate adaptive generalized concatenated codes (GCCs) (sic) on linear block codes over Rayleigh fading Multi Input (sic) Output (MIMO) communication channels with N transmit (sic) N receive antennas. The code design criteria is chosen (sic) that it tries to follow the Shannon capacity of the MIMO (sic). It is envisaged that such codes provide a superior performance over systems that use Maximum Ratio Combining (sic) while maintaining the encoder/decoder complexity within acceptable level of practical usage. Furthermore it is expected (sic) these codes will provide good performance without an interver/deinterleaver because of their good burst error correction (sic).
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| 4. |
- Amir, Omar A., et al.
(författare)
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Feeding ecology of the Indo-Pacific bottlenose dolphin (Tursiops aduncus) incidentally caught in the gillnet fisheriesoff Zanzibar, Tanzania
- 2005
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Ingår i: Estuarine, Coastal and Shelf Science. - : Elsevier BV. - 0272-7714 .- 1096-0015. ; 63:3, s. 429-437
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Tidskriftsartikel (refereegranskat)abstract
- The stomach contents of 26 Indo-Pacific bottlenose dolphins (Tursiops aduncus) incidentally caught in gillnet fisheries aroundUnguja Island (Zanzibar) between February 2000 and August 2002 were examined. The relative importance of each prey species wasassessed through indices of relative importance. In total, 1403 prey items comprising 50 species of bony fish and three species ofsquid were identified from food remains. Five species of fish, Uroconger lepturus, Synaphobranchus kaupii, Apogon apogonides,Lethrinus crocineus, Lutjanus fulvus, and three species of squid, Sepioteuthis lessoniana, Sepia latimanus and Loligo duvauceli, werethe most important prey species. Based on an index that included frequency of occurrence, percentage by number and by weight,Uroconger lepturus proved to be the most important prey species of mature dolphins whereas Apogon apogonides was the preferredprey of immature dolphins. These results indicate that Indo-Pacific bottlenose dolphins off the coast of Zanzibar forage ona relatively large number of prey species, but that only a few small- and medium-sized neritic fish and cephalopods contributesubstantially to the diet. Further, the ecology and behavior of the preferred fish prey species indicate that the dolphins forage overreef or soft bottom substrata and near the shore.
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| 5. |
- Amir, Omar A., et al.
(författare)
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The occurrence and distribution of dolphins in Zanzibar, Tanzania, with comments on the differences between two species of Tursiops
- 2005
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Ingår i: Western Indian Ocean Journal of Marine Science. - 0856-860X .- 2683-6416. ; 4:1, s. 85-93
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Tidskriftsartikel (refereegranskat)abstract
- Incidental catches (bycatch) in gillnet fisheries off Zanzibar (Unguja Island), as asource of mortality among several species of dolphins, were reported in a questionnaire surveyconducted in 1999. As a follow-up to that survey, from January 2000 to August 2003, wemonitored the incidental catches of dolphins collected from 12 fish landing sites. Six species ofdolphins were recorded from 143 specimens retrieved from bycatches in drift- and bottom setgillnets. Of these, 68 (48%) were Indo-Pacific bottlenose dolphins (Tursiops aduncus), 44 (31%) spinner dolphins (Stenella longirostris), 12 (8%) Risso’s dolphins (Grampus griseus), 11 (8%) Indo-Pacific humpback dolphins (Sousa chinensis), 6 (4%) Pan-tropical spotted dolphins(Stenella attenuata) and 2 (1%) common bottlenose dolphins (Tursiops truncatus). Most of thebycatches (71%) were in nets set off the north coast of Unguja Island. In this paper, bycatchrecords are examined to describe the occurrence and distribution of dolphin species in UngujaIsland coastal waters. The relatively large numbers of bycatch dolphins recorded indicate thatbycatch may be a potential threat to local populations that need to be addressed in futureconservation and management efforts in the region.
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| 9. |
- Pettersson, Ulrika, et al.
(författare)
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Polymorphisms of the CLCN7 gene are associated with BMD in women.
- 2005
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Ingår i: Journal of Bone and Mineral Research. - 0884-0431 .- 1523-4681. ; 20:11, s. 1960-7
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Tidskriftsartikel (refereegranskat)abstract
- UNLABELLED: Here we show that a common polymorphism causing a valine to methionine amino acid substitution at codon 418 (V418M) in the CLCN7 gene is associated with femoral neck BMD in women. Our study adds to accumulating evidence that shows that common allelic variants in monogenic bone disease genes often contribute to BMD regulation in normal subjects. INTRODUCTION: The CLCN7 gene is a strong candidate for regulation of BMD, because mutations in CLCN7 cause some forms of osteopetrosis, a disease characterized by impaired osteoclast function and increased BMD. In this study, we sought to determine whether common allelic variation within CLCN7 was associated with BMD in the normal population. MATERIALS AND METHODS: We conducted mutation screening of the exons and intron-exon boundaries in CLCN7 by DNA sequencing in 50 normal subjects. We conducted an association study between common polymorphisms in CLCN7 and haplotypes defined by these polymorphisms and BMD values at the lumbar spine and femoral neck in a population-based cohort study of 1077 Scottish women 45-55 years of age. RESULTS: We identified 24 polymorphisms, but most were rare and only 4 had allele frequencies of >5%. These were a conservative single nucleotide polymorphism (SNP) in exon 1 (rs3751884), a 50-bp tandem repeat polymorphism within intron 8, and two SNPs within exon 15 (rs12926089 and rs12926669), of which one (rs12926669) predicts an amino acid change from valine to methionine at codon 418 (V418M). The exon 15 SNPs were in strong linkage disequilibrium and were both associated with femoral neck BMD (p = 0.001-0.003). None of the other polymorphisms were associated with BMD, and long-range haplotypes showed a much weaker association with BMD than the exon 15 SNPs. The V418M polymorphism was an independent predictor of femoral neck BMD on multiple regression analysis accounting for 1% of the variance in BMD at this site. CONCLUSIONS: Our study indicates that the V418M polymorphism of CLCN7 contributes to the genetic regulation of femoral neck BMD in women and adds to accumulating evidence that indicates that subtle polymorphic variation in genes that cause monogenic bone diseases also contribute to regulation of BMD in normal subjects.
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| 10. |
- Razouki, Sabah, et al.
(författare)
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Strong Correlation between the Bearing Capacity and CBR of a Gypsiferous Subgrade Soil Subjected to Long-Term Soaking
- 2005
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Konferensbidrag (refereegranskat)abstract
- Presented in this paper is a correlation between the bearing capacity of a gypsiferous subgrade soil with the corresponding CBR value. The geotechnical tests carried out on this soil indicate that the soil is sandy lean clay of CL group according to the USCS and A-6 (6) group according to AASHTO Soil Classification System. The soil contains about 33% gypsum content. For this purpose, thirty six CBR samples were prepared at optimum moisture content (of the modified AASHTO compaction test) namely 11.5% at compactive efforts of 1, 2 and 4.56 times that of the Proctor compaction (standard AASHTO). These samples were soaked for 0, 4, 7, 15, 30, and 120 days under the effect of 40 lbs (178 N) surcharge load. For each soaking period, three pairs of CBR soil samples were prepared, one for each compactive effort. The first CBR sample from each pair was used to determine the CBR value while the second CBR sample was used to obtain triaxial soil samples for unconsolidated undrained tests to arrive at the corresponding shear strength parameters. The present paper reveals that for each soaking period, there is a linear increase of the ultimate bearing capacity with increasing compactive effort, while a significant drop in the ultimate bearing capacity of the tested soil took place with increasing soaking period. The paper reveals also that there is a strong linear correlation between the estimated ultimate bearing capacity and the corresponding CBR value indicating that the Rosenak's equation correlating the bearing capacity with CBR value is very conservative.
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