26 research outputs found
Legislation and Administration: Administrative Law -- ICC to Pass on Motor Carrier Use of Piggybacking -- Extent of Initial Movement Authority of Automobile Haulers
Get PDFImproving the Mathematical Model of the Tacoma Narrows Bridge
Get PDFIn this paper, we investigate the mathematical model for the torsional rotation of the Tacoma Narrows Bridge derived by P.J. McKenna. Through modifying this model and programming various cases of these modifications using Matlab, we explore how the Tacoma Narrows Bridge would respond to different loading conditions that may have occurred the day the bridge collapsed. From this we are able to gain a better understanding of how the bridge actually behaved prior to its collapse, and can see possible reasons for the ultimate collaps
Development of Optimization Models for the Set Behavior and Compressive Strength of Sodium Activated Geopolymer Pastes
Get PDFAs large countries such as China begin to industrialize and concerns about global warming continue to grow, there is an increasing need for more environmentally friendly building materials. One promising material known as a geopolymer can be used as a portland cement replacement and in this capacity emits around 67% less carbon dioxide. In addition to potentially reducing carbon emissions, geopolymers can be synthesized with many industrial waste products such as fly ash.
Although the benefits of geopolymers are substantial, there are a few difficulties with designing geopolymer mixes which have hindered widespread commercialization of the material. One such difficulty is the high variability of the materials used for their synthesis. In addition to this, interrelationships between mix design variables and how these interrelationships impact the set behavior and compressive strength are not well understood. A third complicating factor with designing geopolymer mixes is that the role of calcium in these systems is not well understood.
In order to overcome these barriers, this study developed predictive optimization models through the use of genetic programming with experimentally collected set times and compressive strengths of several geopolymer paste mixes. The developed set behavior models were shown to predict the correct set behavior from the mix design over 85% of the time. The strength optimization model was shown to be capable of predicting compressive strengths of geopolymer pastes from their mix design to within about 1 ksi of their actual strength. In addition to this the optimization models give valuable insight into the key factors influencing strength development as well as the key factors responsible for flash set and long set behaviors in geopolymer pastes.
A method for designing geopolymer paste mixes was developed from the generated optimization models. This design method provides an invaluable tool for use in future geopolymer research as well as commercial development of geopolymer products
Legislation and Administration: Administrative Law -- ICC to Pass on Motor Carrier Use of Piggybacking -- Extent of Initial Movement Authority of Automobile Haulers
Get PDFFetal intestinal fibroblasts respond to insulin-like growth factor (IGF)-II better than adult intestinal fibroblasts
Get PDFBACKGROUND: We compared IGF responses of fetal and adult intestinal fibroblasts to identify a developmental difference in the IGF-axis. Intestinal fibroblasts were isolated from maternal and fetal jejunum. Media was conditioned at confluence and one week afterwards. The proliferative response at confluence to 5 nM IGF-I or -II was compared. RESULTS: There were no significant differences in IGFBP expression at confluence. Post-confluence, fetal fibroblasts had no significant changes in IGFBP-2 and IGFBP-3 expression. Post-confluent maternal fibroblasts had increased IGFBP-3 levels that were significant compared to the fetal fibroblasts. IGF-I increased in post-confluent fetal fibroblasts, while in maternal fibroblasts it decreased (p < 0.001). IGF-II secretion decreased significantly in post-confluent maternal fibroblasts (p < 0.05). Maternal fibroblasts proliferated more with IGF-I than IGF-II (p < 0.001). Fetal fibroblasts responded to IGF-II slightly better than IGF-I and significantly greater than maternal cells (p < 0.001). CONCLUSION: Fetal intestinal fibroblasts respond to IGF-II with greater proliferation and do not have the increased IGFBPs seen post-confluence in adult intestinal fibroblasts
