27 research outputs found

    The Mechanism of Alternating Current Corrosion of API Grade X65 Pipeline Steel

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    In the present work, corrosion rates of API grade X65 pipeline steel in sodium chloride solutions with and without alternating currents (AC) at different direct current (DC) potentials were measured using weight loss analysis. The results show that the effect of AC is most pronounced near the open-circuit potential; at more positive potentials, the rates approach those of the ohmic drop/mass transport-limited DC rates. Correspondingly, at negative potentials the rates decrease. Surprisingly, it was found that at all potentials, the AC corrosion rate was equal to the average AC current in the system. The data generated from weight loss experiments were compared with the results from a model for AC corrosion that was developed using a modified Butler-Volmer approach. The model considers the anodic and cathodic Tafel slopes, diffusion limited oxygen transport, interfacial capacitance, and solution resistance. Both experimental and model results showed the importance of the interfacial capacitance on the rate of AC corrosion, especially at a frequency of 60 Hz. The models were also used to explain the observation that the AC corrosion rate was equal to the average AC current in the system

    Avaliação nutricional da silagem de grãos úmidos de milho com diferentes teores de óleo para leitões na fase de creche Nutritional evaluation of high moisture corn silage with different oil contents for piglets in nursery phase

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    Utilizaram-se 60 leitões mestiços (Large White x Landrace), desmamados com peso inicial médio de 7,9kg, no experimento de desempenho e 20 leitões mestiços, com peso inicial médio de 16,8kg, no experimento de digestibilidade para avaliar a silagem de grãos úmidos de milho com diferentes teores de óleo. O delineamento experimental foi o de blocos ao acaso em ambos os experimentos avaliou-se o valor nutricional das silagens e dos milhos secos com teor normal (4,3%EE na MS) ou elevado de óleo (5,66%EE na MS). Não houve efeito dos tratamentos sobre o consumo diário de ração e no ganho de peso diário nos períodos de 0 a 9 e 0 a 31 dias. Os leitões apresentaram melhor conversão alimentar em ambos os períodos estudados, quando receberam silagem e no período de 0 a 9 dias, quando foram alimentados com milho com teor mais alto de óleo. As frações digestível e metabolizável da energia foram influenciadas pelo processamento, sendo que a ensilagem proporcionou melhor aproveitamento da energia, independentemente do teor de óleo presente nos grãos.<br>Sixty crossbred weaned pigs (Large White x Landrace) average initial body weight of 7.9kg and 20 crossbred pigs average initial body weight of 16.8kg were used in the performance and digestibility experiments, respectively, to evaluate high-moisture corn silage with different oil contents. The nutritional value of high-moisture corn silage and dry corn with normal (4.3% EE in DM) or higher (5.66% EE in DM) oil contents were analyzed. The treatments had no effect on either average daily feed intake (ADFI) or average daily gain (ADG) from 0 to 9 and 0 to 31 days. The piglets had higher feed/weight gain in both periods when fed silage and in the period from 0 to 9 days when fed higher oil content corn. In the digestibility experiment only the digestible and metabolizable fractions of energy were affected by the processing method and the silage provided higher energy utilization regardless of the oil content in the grains
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