162 research outputs found

    Model-based phase velocity and attenuation estimation in wideband ultrasonic measurement systems

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    Effect of the exhaust gas side fouling on the performance of a plate and shell type heat exchanger

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    fi=vertaisarvioimaton|en=nonPeerReviewed

    Different methods to improve the exhaust gas temperature in modern stage V 0ff-road diesel engine over transient emission cycles

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    This paper presents several methods to improve the exhaust gas temperature of a modern diesel engine. A high exhaust gas temperature is needed to improve the after-treatment system efficiency and particulate filter regeneration in low engine loads. This study is based on experimental measurements of two Stage 5 level off-road diesel engines. The effect of the different heating methods determined over steady state runs and emission and performance are presented with standard emission transient test procedure (NRTC). In the first step of the study, an intake air restriction and an exhaust gas restriction method are compared. The intake restriction produces better fuel economy over the measuring cycle. However, with the exhaust restriction, higher exhaust gas temperature can be achieved in low engine loads. In the second phase of study, the intake air restriction method was implemented in the research engine. In addition, active waste gate controlling, and injection retardation methods were taken in use for heating purposes. The engine performance was determined with normal calibration and with high exhaust temperature calibration. The differences to the exhaust temperature, engine performance and emission were presented in transient emission cycle NRTC.fi=vertaisarvioitu|en=peerReviewed

    First encounters in the north : cultural diversity and gene flow in Early Mesolithic Scandinavia

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    Population genetic studies often overlook the evidence for variability and change in past material culture. Here, the authors use a Mesolithic example to demonstrate the importance of integrating archaeological evidence into the interpretation of the Scandinavian hunter-gatherer genetic group. Genetic studies conclude that this group resulted from two singleevent dispersals into Scandinavia before 7500 BC. Archaeological evidence, however, shows at least six immigration events pre-dating the earliest DNA, and that the first incoming groups arrived in Scandinavia before 9000 BC. The findings underline the importance of conducting careful archaeological analysis of prehistoric human dispersal in tandem with the study of ancient population genomics.Population genetic studies often overlook the evidence for variability and change in past material culture. Here, the authors use a Mesolithic example to demonstrate the importance of integrating archaeological evidence into the interpretation of the Scandinavian hunter-gatherer genetic group. Genetic studies conclude that this group resulted from two single-event dispersals into Scandinavia before 7500 BC. Archaeological evidence, however, shows at least six immigration events pre-dating the earliest DNA, and that the first incoming groups arrived in Scandinavia before 9000 BC. The findings underline the importance of conducting careful archaeological analysis of prehistoric human dispersal in tandem with the study of ancient population genomics.Peer reviewe
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