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Elasticity and viscosity of carrot root tissue at different rate of deformation

100%

Golacki K., Stankiewicz A., Stropek Z.

Polish Journal of Food and Nutrition Sciences

2007

tom 57

nr 2[A]

63-66

Viscosity of foods and their mechanical properties are essential for modeling the mechanical behaviour of foods during deformation and flow. The rheological models are used for engineering calculations, e.g., during design of food processing machines, pumping systems, packaging machines, etc. Although the classical linear rheology is a rate-independent theory, the mechanical properties of the viscoelastic plant materials depend on a deformation rate. The influence of a deformation rate on mechanical properties of biological viscoelastic materials needs to be documented and it is the aim of this paper. It is proved, based on the Maxwell model, that the modulus of elasticity and the viscosity ratio are decreasing functions of the rate of deformation. Next, the modulus of elasticity and the viscosity ratio of the carrot cylindrical samples are determined using discrete-time measurements of the reaction force obtained in the compression and relaxation tests at a wide range of preliminary deformation rates, i.e. from 1.67×10–4 m·s-1 to 1.5 m·s-1. The relaxation data were processed using a four-element Maxwell model and the changes in viscoelastic constants were determined as a function of the deformation rate. The stress relaxation both in the state of uniaxial stress as well as in the state of uniaxial strain is considered. The experimental results are in good agreement with theoretical analysis for the biological material considered. The results motivate hypothesis that the number of microcrackings increases along with the deformation rate and indicate the irreversible character of the changes that proceed in plant materials under loading.

Effects of temperature on survival, deformations rate and selected parameters of newly hatched larvae of three rheophilic cyprinids (genus Leuciscus)

80%

Kupren K., Mamcarz A., Kucharczyk D.

Polish Journal of Natural Sciences

2010

tom 25

nr 3

Experiments were conducted to determine full range of tolerated and optimal water condition for eggs incubation of three species from genus Leuciscus i.e: dace Leuciscus leuciscus (L.), ide Leuciscus idus (L.), and chub Leuciscus cephalus (L.). Spawners were caught from rivers of the northern (Pasleka River drainage) and central (Pilica River drainage) parts of Poland. Fertilized eggs were incubated under controlled conditions at ten different constant temperatures ranging from 4.5 to 29.0℃. The optimal temperature ranges for the incubation of dace, ide and chub eggs were 7.5 to 12.3℃; 15.7℃ and 19.0 to 23.0℃, respectively (considering hatching percentage, incidence of abnormalities and size of hatched larvae), which are close to the water temperature during spawning season. This study also reveals that embryos of studied species can adapt to increasing water temperature due to global warming up to 23.0℃ (dace and ide) and 27.5℃ (chub). Besides, some inter-population differences in the response to temperature were observed.

Ograniczanie wyników

1 Polish Journal of Food and Nutrition Sciences

1 Polish Journal of Natural Sciences

1 Golacki K.

1 Kucharczyk D.

1 Kupren K.

1 Mamcarz A.

1 Stankiewicz A.

1 Stropek Z.

1 2010

1 2007

Wyniki wyszukiwania

Elasticity and viscosity of carrot root tissue at different rate of deformation

Effects of temperature on survival, deformations rate and selected parameters of newly hatched larvae of three rheophilic cyprinids (genus Leuciscus)