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North American elk (Cervus elaphus L., 1758) are an important component of Canada's natural ecosystems. Overhunting and habitat decline in the 19th century led to the near eradication of Rocky Mountain elk (Cervus elaphus nelsoni Bailey, 1935) and Manitoban elk (Cervus elaphus manitobensis Millais, 1915) within Alberta. Though elk populations have been restored within provincial and national parks, it is unknown to what degree historic population declines affected overall genetic diversity and population structuring of the two subspecies. This study targeted 551 bp of mitochondrial D-loop DNA from 50 elk remains recovered from 16 archaeological sites (2260 BCE (before common era) to 1920 CE (common era)) to examine the former genetic diversity and population structure of Alberta's historic elk populations. Comparisons of ancient and modern haplotype and nucleotide diversity suggest that historic population declines reduced the mitochondrial diversity of Manitoban elk, while translocation of animals from Yellowstone National Park in the early 20th century served to maintain the diversity of Rocky Mountain populations. Gene flowbetween the two subspecies was significantly higher in the past than today, suggesting that the two subspecies previously formed a continuous population. These data on precontact genetic diversity and gene flow in Alberta elk provide essential baseline data integral for elk management and conservation in the province. Key words: archaeology, ancient DNA analysis, Alberta, conservation, gene flow, North American elk, Cervus elaphus, subspecies. Les wapitis (Cervus elaphus L., 1758) nord-americains constituent un important element des ecosystemes naturels du Canada. La chasse excessive et la perte d'habitats au 19e siecle ont entraine la quasi-disparition du wapiti des montagnes Rocheuses (Cervus elaphus nelsoni Bailey, 1935) et du wapiti du Manitoba (Cervus elaphus manitobensis Millais, 1915) en Alberta. Si les populations de wapitis ont ete retablies a l'interieur des parcs provinciaux et nationaux, l'ampleur de l'impact des diminutions historiques des populations sur la diversite genetique globale et la structure des populations des deux sous-especes n'est pas connue. L'etude a cible 551 pb de la boucle D de l'ADN mitochondrial des restes de 50 wapitis preleves de 16 sites archeologiques (de 2260 avant notre ere a 1920 de notre ere) afin d'examiner la diversite genetique et la structure passees des populations historiques de wapitis de l'Alberta. Des comparaisons de la diversite des haplotypes et des nucleotides anciens et modernes donnent a penser que les diminutions historiques des populations ont entraine une reduction de la diversite mitochondriale du wapiti du Manitoba, alors que la translocation d'animaux du parc national de Yellowstone au debut du 20e siecle a permis de maintenir la diversite des populations de wapitis des montagnes Rocheuses. Le flux genetique entre les deux sous-especes etait considerablement plus grand dans le passe qu'il ne l'est aujourd'hui, ce qui porte a croire que les deux sous-especes formaient auparavant une population continue. Ces donnees sur la diversite et le flux genetiques preeuropeens chez les wapitis de l'Alberta constituent un cadre de reference essentiel pour la gestion et la conservation du wapiti dans cette province. [Traduit par la Redaction] Mots-cles : archeologie, analyse d'ADN ancien, Alberta, conservation, flux genetique, wapiti nord-americain, Cervus elaphus, sous-espece., Introduction The North American elk (Cervus elaphus L., 1758) has recently rebounded from significant population decline. Though elk were hunted by North America's aboriginal people for millennia, habitat disruption and [...]

The variation of die bearing length is a primary way to control the metal flow in hot square die extrusion. Finite element computations are carried out to assess the influences of die bearing on metal flow and state variables. The finite element analysis is presented based on the arbitrary Lagrangian-Eulerian (ALE) description for a rigid-viscoplastic material. Since the thermal state greatly affects the product quality, temperature distribution is also analyzed. In order to estimate the varied lengths of die bearing, a numerical scheme is suggested and demonstrated through the simulation of an industrial example with varied die bearing. The computational results for extrusion with varied die bearing are compared with those from the simulation for extrusion with constant die bearing.