A review of techniques for parameter sensitivity analysis of environmental models

Mathematical models are utilized to approximate various highly complex engineering, physical, environmental, social, and economic phenomena. Model parameters exerting the most influence on model results are identified through a ‘sensitivity analysis’. A comprehensive review is presented of more than a dozen sensitivity analysis methods. This review is intended for those not intimately familiar with statistics or the techniques utilized for sensitivity analysis of computer models. The most fundamental of sensitivity techniques utilizes partial differentiation whereas the simplest approach requires varying parameter values one-at-a-time. Correlation analysis is used to determine relationships between independent and dependent variables. Regression analysis provides the most comprehensive sensitivity measure and is commonly utilized to build response surfaces that approximate complex models.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42691/1/10661_2004_Article_BF00547132.pd

Quality of poultry litter submitted to different treatments in five consecutive flocks Qualidade da cama de frango submetida a diferentes tratamentos em cinco lotes consecutivos

It was evaluated the effects of poultry litter treatment on moisture content, pH, density and volatilized ammonia for five consecutive flocks of broiler chicken breeding. It was used 640 birds per flock as a complete randomized design with eight treatments and four replicates. The treatments were the following: 1 non-treated litter; 2 litter submitted to in-house composting; 3 litter treated with aluminum sulfate; 4 litter submitted to gypsum; 5 litter treated with quicklime; 6 litter treated with dolomitic limestone; 7 litter treated with zeolite and 8 litter treated with charcoal. Chopped elephant-grass hay was used as poultry litter in all flocks. Fermentation in the shed increased moisture content of the litters in the second and first flocks on 21 and 42 days of breeding, respectively. There was no difference on density among treatments. Aluminum sulfate reduced pH of the litters in all flocks at 21 days of breding. On 42 days of breeding, pH of the litters was reduced in the litters with aluminum sulfate and gypsum in the first, second and forth flocks. On 21 days, aluminum sulfate reduced the volatilized ammonia in the first, third and forth flocks, and on 42 days, there was a reduction of volatilized ammonia in the litters with aluminum sulfate in the forth flock. Aluminum sulfate can improve quality of poultry litter of chopped elephant-grass hay by reducing pH and ammonia volatilization.<br>Foram avaliados os efeitos do tratamento da cama de frango sobre o teor de umidade, o pH, a densidade e a amônia volatilizada durante cinco lotes consecutivos de criação de frangos de corte. Foram utilizadas 640 aves por lote em delineamento inteiramente casualizado com oito tratamentos e quatro repetições. Os tratamentos foram: 1 cama não-tratada; 2 cama submetida à compostagem dentro do galpão; 3 cama tratada com sulfato de alumínio; 4 cama tratada com gesso agrícola; 5 cama tratada com cal virgem; 6 cama tratada com calcário dolomítico; 7 cama tratada com zeolita; e 8 cama tratada com carvão vegetal. O feno de capim-elefante picado foi utilizado como cama de frango em todos os lotes. A fermentação no galpão aumentou o teor de umidade das camas no segundo e primeiro lotes aos 21 e 42 dias de criação, respectivamente. Não houve diferença na densidade entre os tratamentos. O sulfato de alumínio reduziu o pH das camas em todos os lotes aos 21 dias de criação. Aos 42 dias, o pH das camas foi reduzido nas camas contendo sulfato de alumínio e gesso agrícola no primeiro, segundo e quarto lotes. Aos 21 dias, o sulfato de alumínio reduziu a amônia volatilizada no primeiro, terceiro e quarto lotes e, aos 42 dias, houve redução da amônia volatilizada das camas contendo sulfato de alumínio no quarto lote. O sulfato de alumínio pode melhorar a qualidade da cama de frango de feno de capim-elefante picado, por reduzir o pH e a volatilização de amônia