Combined Effect of Loading and Cold Temperature on the Stiffness of Glass Fiber Composites

Because of the short construction season and cold winters in Alaska, the prestressed concrete decked bulb-tee bridge system is very popular. However, the concrete deck is an integral part of the bridge superstructure and cannot be easily replaced when it deteriorates. Obviously, there is merit in combining durable “premanufactured” fiber-reinforced polymer (FRP) composite deck with stiffer prestressed concrete girders in cold regions. However, the effects of long-term exposure to extreme temperature variations and various moisture conditions typical of cold regions on the performance of FRP composite materials are not fully understood. This paper summarizes the combined effect of low-temperature and deformation strain levels on the longitudinal modulus of glass fiber-reinforced polymer (GFRP) samples. The modulus of elasticity of GFRP laminate coupons was tested at various temperatures down to ?31 °F (?35°C) by temporarily subjecting the samples to three strain levels of 1,000, 2,000, or 3,000 microstrains. Both biaxial and uniaxial samples subjected to a deformation of 1,000 microstrains showed an increase in stiffness when tested at increasingly colder temperatures, and no noticeable change in stiffness was seen when the samples were retested after being equilibrated to room temperature. However, samples subjected to a predetermined elevated strain level did show significant stiffness degradation after room temperature equilibration. The degree of degradation was noticeably larger for samples subjected to the low temperatures than for control samples that were subjected to the equivalent number of cycles at room temperature. It was also noted that the degradation due to load cycles or temperature coupled with load cycles was noticeably less for uniaxial samples than for biaxial samples.     

Modeling Impacts of Thaw Lakes to Ground Thermal Regime in Northern Alaska

In northern Alaska, the ground is largely underlain by permafrost. Many engineering problems in this region can be attributed to the variations of ground thermal regime. Engineering projects such as construction of gas pipelines must be based on a good understanding of ground thermal regime and its interaction with seasonal climate changes. Numerical modeling is used to simulate a multimedia system with transient heat transfer in this research. The system includes a snow cover on the top, a shallow lake in the middle, and soils beneath the lake. The finite-element method is used for the spatial domain solution, and the finite-difference method is used for the temporal domain solution. The model is applied to three sites in northern Alaska for a nine-month period during the winter of 1995–1996. The result reveals the impacts of thaw lake on the ground thermal regime, the formation of the talik, as well as the formation of ice in the lake. The model is verified against field observations. The difference between the simulated and observed ice thickness is less than 3%.     

On the asymmetric effects of oil price changes on Alaska oil tax revenue

Alaska depends on oil tax revenue for more than 90% of the state budget. In this article, we apply the nonlinear autoregressive distributed lag (ARDL) approach of to test whether the effect of changes in oil prices on Alaska’s oil reven ues is symmetric or asymmetric. The results show that oil prices have an asymmetric effect on Alaska’s oil revenues in the long run, though not in the short run. Additionally, declines in oil prices have a more substantial long-run effect than increases in oil prices.     

Effects of adding fish gelatin on Alaska pollock surimi gels

Fish gelatin is a food additive obtained after hydrolysis of collagen from fish skin. The importance of fish gelatin as a food additive is increasing due to its increased commercial availability. Surimi is washed minced fish meat used as the raw material for seafood analogs like crabmeat substitutes. The most important attributes of surimi are gelling and whiteness. The objective of this work was to determine the effect of using fish gelatin as an additive in surimi to improve the mechanical and functional properties of gels. Surimi gels were prepared by mixing grade A or FA surimi (Alaska pollock) with salt (20 g/kg w/w) and commercial fish gelatin at 0 (control), 5, 7.5, 10, or 15 g/kg (w/w) previously dissolved in water (200 mL/kg surimi). The solubilized paste was incubated at 40 °C for 30 min followed by cooking at 90 °C for 15 min. Changes in mechanical properties (torsion test), a functional property (expressible water content) and color attributes of surimi gels were measured. Grade FA surimi gels containing 7.5–15 g/kg of fish gelatin showed an improved expressible moisture. However, gelatin added at 15 g/kg showed a disruptive effect detrimental to the mechanical properties. Color parameters were modified slightly. Whiteness attribute as affected by increasing the fish gelatin was instrumentally detected but not observed by sensory panelists. Gelatin did not change the overall color attributes and all gels remained in the grayish region. These results indicated that fish gelatin did not have an advantage for using as a functional additive in Alaska pollock surimi grades A or FA. However, it can be used at up to 10 g/kg without a negative effect on the mechanical properties.     

The development of imitation crab stick containing chicken breast surimi

Imitation crab stick samples were made from Alaska pollack with Golden treadfin bream surimi (C), Alaska pollack with Golden treadfin bream surimi and spent laying hens breast surimi (T1), Alaska pollack with spent laying hens breast surimi (T2), and Alaska pollack with Golden treadfin bream with mechanically deboning chicken meat (MDCM) (T3). Crude protein was significantly lower in T2 and T3 compared with C and T1. However, crude fat and carbohydrate were not significantly different among the samples during storage periods. pH steadily increased until 2 weeks of storage thereafter pH was decreased in all samples. Lightness (L^∗) and whiteness (W) were significantly lower in T3 than those of other samples. In fatty acid composition, the amount of polyunsaturated fatty acids such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) was higher than other fatty acids in all samples at 0 week of storage period. TBARS (thiobarbituric acid reactive substances) value was highest in control sample compared with other samples. In sensory evaluation, color was the highest in C than other samples, whereas T3 was lowest in color than those of other samples. Overall acceptability was significantly highest in T1 compared with other samples during the storage periods.