| 46181. |
- Malusek, Alexandr, et al.
(författare)
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CTmod : Mathematical Foundations
- 2007
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- CTmod is a set of C++ class libraries primarily designed for the simulation of energy imparted to a CT-scanner detector array using the Monte Carlo method. This report describes mathematical methods and formulas that are used in the code. It is a supplement to the article “CTmod - a toolkit for Monte Carlo simulation of projections including scatter in computed tomography” by A. Malusek, M. Sandborg, and G. Alm Carlsson. In this report, random variables are denoted by a hat. For instance ˆx is a random variable and x is its sample. Points in space are denoted by bold capital letters, e.g. P. Directions are denoted by bold small letters, e.g. u. Inconsistencies in the current notation will be corrected in the next update of this report.
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| 46182. |
- Malusek, Alexandr, et al.
(författare)
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Validation of the CTmod toolkit
- 2007
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report is a supplement to the article “CTmod—a toolkit for Monte Carlo simulation of projections including scatter in computed tomography” by A. Malusek, M. Sandborg, and G. Alm Carlsson. It describes methods that were used to validate the CTmod toolkit. Here, we adopt the terminology used in and: Verification is a process of determining whether or not the software is coded correctly and conforms to the specified requirements. Validation is a process of evaluating software to ensure compliance with physical applicability to the process being modelled. Validation of a code would consist of comparing it with known analytical solutions or against an already validated computer code, or could include benchmarking the code against relevant experimental data. CTmod is a toolkit implemented as a C++ class libray. A user is supposed to write a main program which uses classes from the toolkit. The main program is then compiled to create an executable. In this report, we tested two executables (ctmod1 and ctmod2) created this way. In chapter 2, scatter-to-primary ratios of air collision kerma calculated using ctmod1 are compared to data published in literature. In chapter 3, primary and scatter projections calculated using ctmod2 are compared to data calculated using the MCNP5 code. Though not related to the validation, we also report speeds of ctmod1 and ctmod2 as these were often requested from us.
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| 46183. |
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| 46184. |
- Malyarenko, Anatoliy, 1957-
(författare)
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Abelian and Tauberian theorems for random fields on two-point homogeneous spaces
- 2003
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- We consider centred mean-square continuous random fields for which the incremental variance between two points depends only on the distance between these points. The relations between the asymptotic behaviour of the incremental variance near zero and the asymptotic behaviour of the spectral measure of the field near infinity are investigated. We prove several Abelian and Tauberian theorems in terms of slowly varying functions.
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| 46185. |
- Malyarenko, Anatoliy
(författare)
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Functional limit theorems for multiparameter fractional Brownian motion
- 2004
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- We prove a general functional limit theorem for mul-tiparameter fractional Brownian motion. The functional law ofthe iterated logarithm, functional L ́evy’s modulus of continuityand many other results are its particular cases. Applications toapproximation theory are discussed.
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| 46186. |
- Malyarenko, Anatoliy, 1957-
(författare)
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Moduli of continuity and fast points for Gaussian isotropic random fields
- 2002
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- We consider a class of Gaussian isotropic random fields related to multi-parameter fractional Brownian motion. We calculate both the local and global moduli of continuity as well as the Hausdorff and packing dimensions of the exceptional random sets of fast points for that fields.
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| 46187. |
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| 46188. |
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| 46189. |
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Management of Large Rivers to Secure Functions of Coastal Ecosystems : Seminar organized by the Swedish Agency for Marine and Water Management at World Water Week 2015 in Stockholm
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Human activities upstream in rivers have negative environmental impact on coastal aquatic ecosystems of which millions of people in the developing world are dependent on for their livelihoods. Some of the main problems have been identified as hydropower development, sediment extraction and pollution with impacts on ecosystem functions and services. In order to address the environmental challenges it is important to identify critical flows in the source to sea continuum. The degradation of ecosystems in the continuum illustrates the lack of understanding of these flows that are connecting the systems. In addition the linkages in existing management systems on land, in the coastal zone and in the oceans, which are often handled separately, needs to be further understood. Hence it is crucial that existing management tools are developed into integrated management approaches, such as management based on a source to sea approach to address these linkages and to resolve the environmental challenges in aquatic ecosystems. The land-river-coasts linkages are also important in order to enable the realization of the implementation of several of the Global Goals for Sustainable Development. Availability of clean freshwater and protection of aquatic ecosystems will be two of the most important issues to improve living conditions for the poor riverine and coastal communities. Linking goal 6 and 14 and their targets and indicators is therefore essential to ensure livelihoods of poor communities that depend on the natural resources from the aquatic ecosystems. Furthermore, the implementation of the Global Goals for Sustainable Development and targets will require concerted and coordinated actions at all levels and between all sectors. Active engagement of all stakeholders, effective dialogue, including poor communities, civil society and the private sector are also important conditions. The integration between the management systems of large rivers with their estuarine and coastal areas is a challenge and the future development will require new methodologies and innovative institutional arrangements. Hence, the application of a source to sea management approach is essential in order to secure a sustainable development.
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| 46190. |
- Manak, Vita, et al.
(författare)
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Biodiversity and ecosystem service contributions of trees : a review for environmental risk assessments of non-native plant pests in Sweden
- 2024
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Plant pests, particularly non-native species, can have a profound impact on their host plants. Trees are the foundation of forest ecosystems and serve as important structures in agricultural landscapes and urban areas. In Sweden, forests cover around 70 % of Sweden’s land area and serve as an important national resource for the economy and for biodiversity. Consequently, introductions of non-native tree pests can cause significant economic and environmental damage.Pest risk analysis (PRA) provides the foundation and scientific evidence to inform decisions to mitigate and manage the introduction of non-native plant pests into new areas. PRA involves structured and standardized procedures to assess the risks posed by non-native pests to a country or territory. There are general guidelines on the assessment of impact, including economic, environmental, and social aspects, as well as both direct and indirect effects.Regarding environmental impacts, two major constituents of a natural ecosystem are highlighted in environmental impact assessments of plant pest invasions; biodiversity and ecosystem services. However, there is no consensus of how environmental assessments in PRAs should be performed, and different methods are used in different assessments schemes. Overall, within pest risk assessments, there is a need for a more comprehensive understanding of the environmental consequences of plant pest invasions.The aim of this review is to summarize the main values provided by trees and compile the available information on the biodiversity and the ecosystem services to which trees contribute. All major tree species and genera found across various landscapes in Sweden were included in the report, including forests, agricultural land, and urban environments.In terms of biodiversity, we define values at risk based on the number of native species associated with individual tree species. We also identify valuable habitats where trees play an important structural role, such as old-growth forests, protected forest areas, and habitat types as defined in the Habitat Directive. Concerning ecosystem services, we summarize the contributions of trees within ecosystems identified as important for providing these services. These ecosystem services primarily cover provisioning, regulating, and cultural services. The contribution of trees for these services are described across various ecosystems, including forests, agro-ecosystems, semi-natural grasslands and urban areas. When possible, we present case studies that investigate the effects and magnitude of impacts that tree pests and pathogens have on biodiversity and the provisioning of ecosystem services. These examples, along with the reviews of the main ecosystem services provided by trees, aims to provide guidance for estimating risks in the context of pest risk assessments.
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