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- Öwall, Viktor
(författare)
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Synthesis of Controllers from a Range of Controller Architectures
- 1994
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- An algorithm specific digital signal processor is a powerful alternative to a general purpose signal processor for demanding specifications such as high throughput, low power, small size, etc. These properties are achieved as the processor architecture is tailored to the algorithm as opposed to the general purpose architecture which must suit a wide range of algorithms. The increased performance is traded for reduced flexibility of the final circuit and an increased design effort. Consequently powerful CAD-tools are needed to decrease the design effort. This thesis presents COMA, a CAD-tool for synthesis of controllers suitable for a wide range of digital signal processing algorithms and application fields. COMA synthesizes a complete controller with all modules and interconnection specifications. COMA has been developed with the intention of being used by an active designer where his knowledge, skills, and experience is best utilized. An automated synthesis process can be performed but is preferably refined to a competitive solution using designer interaction before a circuit is fabricated. The main reason for designing an algorithm specific digital signal processors is the possibility to use an architecture dedicated to the algorithm. Consequently, COMA supports arbitrary datapath architectures and does not impose any restrictions. This is crucial in order to fully exploit the advantages of an algorithm specific design. Results presented in this thesis and the discussion regarding controller architectures show that different controller architectures are suitable for different algorithms and different implementation techniques of the fabricated circuit. Thus, COMA can synthesize a range of controller architectures suitable for these different needs. This approach, I believe, is unique for COMA. Standard controller architectures have been modified to suit application specific digital signal processing design and new solutions have been developed. Using COMA complex algorithm specific digital signals processors for a wide range of applications can be designed with a considerable reduction in design effort compared to a hand made design.
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- Bhandary, Sumanta, et al.
(författare)
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Quasiperiodic Van der Waals Heterostructures of Graphene and Hexagonal Boron Nitride
- 2022
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Ingår i: Physica status solidi. B, Basic research. - : John Wiley & Sons. - 0370-1972 .- 1521-3951. ; 259:2
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Tidskriftsartikel (refereegranskat)abstract
- Advancement toward opening a bandgap at the Dirac point induced by symmetry breaking paved the way to realize 2D heterostructures with graphene and hexagonal boron nitride (h-BN). An alternate arrangement of graphene and h-BN layers in a 3D stacking can tune the bandgaps of these composites depending on the position of B and N atoms with respect to C atoms of graphene. Herein, a unique possibility of arranging graphene and h-BN atomic layers in a quasiperiodic Fibonacci sequence to study the possibilities of controlling the electronic properties of these heterostructures is explored. Density functional theory calculations combined with van der Waals corrections reveal that these quasiperiodic heterostructures are more stable than normal periodic stacking of monolayers of graphene and h-BN. Moreover, for certain arrangements of atomic layers, sizeable bandgaps can be obtained.
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- Bodare, Sofia, 1984-
(författare)
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Conservation Genetics and Speciation in Asian Forest Trees
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Tropical forests are important because they are the home of millions of species at the same time as they perform ecosystem services and provide food, cash income and raw materials for the people living there. The present thesis elucidates questions relevant to the conservation of selected forest trees as it adds to the knowledge in the phylogeny, population structure, genetic diversity and adaptation in these species.We investigated the genetic diversity and speciation of four spruce species around the Qinghai-Tibetan Plateau (QTP), Western China, and one from Taiwan. Nucleotide diversity was low in P. schrenkiana and the Taiwanese P. morrisonicola but higher in P. likiangensis, P. purpurea and P. wilsonii. This can be explained by the population bottlenecks that were detected in the two former species by coalescent-based analysis. The phylogenetic relationships between the five species were difficult to interpret, possibly because other Asian spruce species might have been involved. However, all species are distinct except P. purpurea, which likely has a hybrid origin. The rate of bud set and expression of the FTL2 gene in response to photoperiod in the southernmost growing spruce species, P. morrisonicola, was studied. We found that in this species, although growing near the equator, bud set appears to be induced mainly by a shortening of photoperiod, similarly to its more northerly growing spruce relatives. In addition, seedlings originating from mother trees growing at higher elevations showed a trend towards earlier bud set than seedlings originating from mother trees at lower altitudes.We also studied the population structure and genetic diversity in the endemic white cedar (Dysoxylum malabaricum) in the Western Ghats, India. Overall, no increase in inbreeding that could be related to human activities could be detected. Populations appear to have maintained genetic diversity and gene flow in spite of forest fragmentation over the distribution range. However, there is a severe lack of juveniles and young adults in several populations that needs to be further addressed. Finally, we recommend conservation units based on population structure.
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