84 research outputs found
Examination of the estimation of relative permeability for unsaturated soils
No full textThe unsaturated permeability function is an important soil property function used in the numerical modeling of saturated-unsaturated soil systems. The permeability function is generally predicted by integrating along the soil-water characteristic curve (SWCC) starting at saturated soil conditions. The integration is based on a particular integral formula. The Fredlund-Xing-Huang permeability function is a flexible integration techniques used for calculating the unsaturated permeability function. The original permeability theory published by Fredlund et al., (1994) specified that the air-entry value, ψaev (AEV), be used as the lower limit of the integration when calculating the permeability function. However, since there was no analytical procedure available for the calculation of the air-entry value on the SWCC, it became common practice to start the integration procedure from a value near zero. The assumption was made that the error associated with starting the integration from an arbitrary low value was minimal. While this might be the case in some situations, the error can be quite substantial in other situations. This paper undertakes a study of the effect of the lower limit of integration on the calculation of the permeability function. Comparisons are made between starting the integration from various values below the AEV and starting the integration from the calculated air-entry value, ψaev. A mathematical algorithm is also proposed for the calculation of the AEV for integration purposes. The results show that the relative coefficient of permeability can be significantly under-estimated when the lower limit of integration is smaller than the AEV. The recommendation is that the AEV always be used as the lower limit of integration in the Fredlund-Xing-Huang permeability equation.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author
On the Use of Fredlund Gas/Fluid Compressibility Relationship to Model Medium-Dense Gassy Sand Behavior
No full textThis paper presents the influence of gas bubbles trapped in the soil mass on the stress-strain-strength response of medium-dense sands. A hypoplastic constitutive sand model enhanced with the intergranular strain concept was coupled with the Fredlund gas/fluid compressibility relationship to capture gassy soil behavior. Boundary value element representations in a finite element platform of oedometer and saturated drained and undrained triaxial compression tests are performed for the calibration of soil parameters. For the numerical simulation of gassy soil behavior, pore fluid compressibility is modified to account for the presence of free gas in the pore fluid. The gassy soil mechanical response is studied by using only one set of parameters determined from the saturated soil response. The testing bed for this evaluation is a laboratory experimental program conducted on sands retrieved from the Oakridge Sanitary Landfill located in South Carolina, USA. The hypoplasticity sand model specialized with the Fredlund relationship reproduces reasonably well the stress-strain-strength response of these sands for a wide range of loading conditions and at a reasonable level of testing for the calibration of constitutive parameters. It is found that a slight reduction in the degree of saturation significantly decreased the undrained shear strength of the soil and caused changes in volume (i.e., drained-like behavior).The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author
Is trust in SEM an intergenerational trait? : A study of sponsored links and generational attitudes towards them
No full textTitle: Is trust in SEM an intergenerational trait? Date: 2018-05-22 Level: Bachelor Thesis in International Marketing Author: Jesper Fredlund 930427 & Timmy Biedron 961128 Supervisor: Henrietta Nilson Problem formulation: How do age correlate with trust and attitude towards SEM on Google in Sweden? Purpose: The purpose of this study is to see if the Swedish Digital Natives are more likely to be trusting search engine marketing, as opposed to the older generations of Digital Immigrants, and by doing this gaining a better understanding of the attitudes towards search engines and search enginemarketing in Sweden. Theoretical framework: The theoretical framework of this paper consists of theories about BannerBlindness, Text Blindness, EHS Theory, Search Engine Marketing, Sponsored Links, Organic Links,Generations. Methodology: This is a quantitative study with 429 respondents in an online survey. It contains Swedish users of search engines divided into groups of those born before 1980 and those born after. Empirical findings: Our study found out that Digital Natives are slightly more likely to favour Search Engine Marketing than Digital Immigrants are. Conclusion: No matter the target of your Search Engine Marketing campaign you should approach itcautiously, since both Digital Natives and Digital Immigrants have been shown to hold a negative bias against these campaigns over organic links. Keywords: SEM, SEA, Search Engines, Search Behaviour, Organic links, Sponsored links
Calculation of the Fire Resistance of Wood Based Boards and Wall Constructions
No full textThe project is a part of the research programme "Timber constructions and fire" and has been financed by funds from the Swedish Fire Research Board. The aim of the project is to illustrate the possibility of calculating the fire resistance of building panels and wall constructions. The work has been planned in consultation with the steering group "Timber construction and fire" of the Swedish Fire Research Board. The calculations in this work are based on the model developed by the author and presented in [l]. The simulations comprise a total of 23 different calculation cases. The calculations have been compared with experimenrally determined fire resistances in most of the cases. In two cases the influence of a varied opening factor for a fire compartment type A is studied. This document refers to research grants 814-89-1 and 814-89-2 from the Swedish Fire Research Board within the limits of the special programme "Timber constructions and Fire" to the author's company Bedec Engineering. The special programme is a collaboration between the Swedish Fire Research Board, the Swedish Council for Building Research, the Swedish National Board for Technical Development and the Swedish Institute for Wood Technology Research. The author wishes to thank Marianne Abrahamsson who typed the final version of the manuscript and Lewis J Gruber for correction of the English language
Leftist, Jewish, and Canadian Identities Voiced in the Repertoire of the Toronto Jewish Folk Choir, 1939-1959
No full textThis article focuses on a twenty-year period of the Toronto Jewish Folk Choir, during which the ensemble was conducted by Emil Gartner. Considering historical contexts, including political pressures and social frameworks, the author shows how repertoire choices were linked to overlapping patterns of identity, notably the choir as a voice for progressive political ideas, as a Jewish community group, and as a player in the emerging multicultural Canadian fabric
The Swedish new variant of chlamydia trachomatis: genome sequence, morphology, cell tropism and phenotypic characterization
No full textChlamydia trachomatis is a major cause of bacterial sexually transmitted infections worldwide. In 2006, a new variant of C. trachomatis (nvCT), carrying a 377 bp deletion within the plasmid, was reported in Sweden. This deletion included the targets used by the commercial diagnostic systems from Roche and Abbott. The nvCT is clonal (serovar/genovar E) and it spread rapidly in Sweden, undiagnosed by these systems. The degree of spread may also indicate an increased biological fitness of nvCT. The aims of this study were to describe the genome of nvCT, to compare the nvCT genome to all available C. trachomatis genome sequences and to investigate the biological properties of nvCT. An early nvCT isolate (Sweden2) was analysed by genome sequencing, growth kinetics, microscopy, cell tropism assay and antimicrobial susceptibility testing. It was compared with relevant C. trachomatis isolates, including a similar serovar E C. trachomatis wild-type strain that circulated in Sweden prior to the initially undetected expansion of nvCT. The nvCT genome does not contain any major genetic polymorphisms - the genes for central metabolism, development cycle and virulence are conserved - or phenotypic characteristics that indicate any altered biological fitness. This is supported by the observations that the nvCT and wild-type C. trachomatis infections are very similar in terms of epidemiological distribution, and that differences in clinical signs are only described, in one study, in women. In conclusion, the nvCT does not appear to have any altered biological fitness. Therefore, the rapid transmission of nvCT in Sweden was due to the strong diagnostic selective advantage and its introduction into a high-frequency transmitting population
Calculation of the Fire Resistance of Wood Based Boards and Wall Constructions [Elektronisk resurs]
No full textThe project is a part of the research programme "Timber constructions and fire" and has been financed by funds from the Swedish Fire Research Board. The aim of the project is to illustrate the possibility of calculating the fire resistance of building panels and wall constructions. The work has been planned in consultation with the steering group "Timber construction and fire" of the Swedish Fire Research Board. The calculations in this work are based on the model developed by the author and presented in [l]. The simulations comprise a total of 23 different calculation cases. The calculations have been compared with experimenrally determined fire resistances in most of the cases. In two cases the influence of a varied opening factor for a fire compartment type A is studied. This document refers to research grants 814-89-1 and 814-89-2 from the Swedish Fire Research Board within the limits of the special programme "Timber constructions and Fire" to the author's company Bedec Engineering. The special programme is a collaboration between the Swedish Fire Research Board, the Swedish Council for Building Research, the Swedish National Board for Technical Development and the Swedish Institute for Wood Technology Research. The author wishes to thank Marianne Abrahamsson who typed the final version of the manuscript and Lewis J Gruber for correction of the English language
Use of a genetic algorithm to perform reliability analysis of unsaturated soil slopes
No full textRainfall induced landslides are a major cause of disturbance to transport networks in many parts of the world. In slopes where the water table is some depth below the ground surface, negative pore water pressure (suctions) develop in the near surface soils which contribute significantly to their overall stability. However, these suctions are transient and reduce as water percolates into the slope (and a wetting front develops) during periods of heavy or prolonged rainfall.
In this paper the development of a model for determining the reliability of a slope in which the soil properties are considered as random variables is presented. By transforming the variables into polar coordinates the complexities associated with defining the limit state function, which have affected many previous attempts at probabilistic analysis of slopes, can be overcome. The minimisation problem is solved in a powerful and efficient Genetic Algorithm environment.Other funderIarnród Éirean
Whole-genome analysis of diverse Chlamydia trachomatis strains identifies phylogenetic relationships masked by current clinical typing
No full textChlamydia trachomatis is responsible for both trachoma and sexually transmitted infections, causing substantial morbidity and economic cost globally. Despite this, our knowledge of its population and evolutionary genetics is limited. Here we present a detailed phylogeny based on whole-genome sequencing of representative strains of C. trachomatis from both trachoma and lymphogranuloma venereum (LGV) biovars from temporally and geographically diverse sources. Our analysis shows that predicting phylogenetic structure using ompA, which is traditionally used to classify Chlamydia, is misleading because extensive recombination in this region masks any true relationships present. We show that in many instances, ompA is a chimera that can be exchanged in part or as a whole both within and between biovars. We also provide evidence for exchange of, and recombination within, the cryptic plasmid, which is another key diagnostic target. We used our phylogenetic framework to show how genetic exchange has manifested itself in ocular, urogenital and LGV C. trachomatis strains, including the epidemic LGV serotype L2b
State of Practice for use of the Soil-Water Characteristic Curve in Geotechnical Engineering
No full textRoutine geotechnical engineering practice has witnessed a significant increase in the usage of unsaturated soil mechanics principles. The laboratory measurement of the soil-water characteristic curve, SWCC, for a soil has been labelled as a primary reason for the improved understanding of unsaturated soil behaviour. Laboratory measurement of the â shrinkage curveâ , has yielded further insight into the estimation of unsaturated soil property functions, USPF. The USPFs provide the necessary information for the simultaneous numerical modeling of the saturated and unsaturated portions of the soil profile. This paper presents a state-of-practice summary of the engineering protocols that have emerged amidst the numerous research studies reported over the past couple of decades. It also introduces issues related to hysteresis associated with the soil-water characteristic curve and suggests a pathway forward.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author
- …
