Response of extract release volume to the variations in pH and microbial load during spoilage of fish at refrigeration temperature

This report briefly describes the microbial status and storage properties of fish raised under composite fish culture in sewage fed ponds.

Preservation of Sardinella longiceps in iced and chilled seawater. Part 1 - Changes during storage with particular reference to bacterial load and nitrogenous compounds

Oil sardines in prime condition were subjected to onboard chilling. Two lots were chilled in CSW (samples C and CI), a third lot was chilled in crushed ice (sample I) and a fourth lot left not iced on deck (Sample AI). Upon landing sample AI was iced and sample CI was removed from the CSW and iced. All the four samples were kept in a chilled room for storage studies. The fish chilled and stored in CSW recorded the least, and the fish subjected to delayed icing, the highest values for all the indices of spoilage namely, free amino nitrogen, trimethylamine (TMA) and total volatile base nitrogen (TVBN). The total psychrophilic bacterial number also showed a similar trend. The organoleptic assessment of the cooked samples revealed C I, CI, AI to be the order of preference throughout the storage. This assessment was found to hold good for the rest of the parameters as well. The CSW held fishes were found to be distinctly superior to the iced ones for the first five days of storage. Such a marked prevalence in quality for five days would suffice for the fish to fetch a premium in the market over other landings of the same fish whether chilled or not chilled. Chilling on board in CSW and icing the same after landings, did not show encouraging results.

Load-displacement behavior during sharp indentation of viscous-elastic-plastic materials

A constitutive equation is developed for geometrically-similar sharp indentation of a material capable of elastic, viscous, and plastic deformation. The equation is based on a series of elements consisting of a quadratic (reversible) spring, a quadratic (time-dependent, reversible) dashpot, and a quadratic (time-independent, irreversible) slider-essentially modifying a model for an elastic-perfectly plastic material by incorporating a creeping component. Load-displacement solutions to the constitutive equation are obtained for load-controlled indentation during constant loading-rate testing. A characteristic of the responses is the appearance of a forward-displacing "nose" during unloading of load-controlled systems (e.g., magnetic-coil-driven "nanoindentation" systems). Even in the absence of this nose, and the associated initial negative unloading tangent, load-displacement traces (and hence inferred modulus and hardness values) are significantly perturbed on the addition of the viscous component. The viscous-elastic-plastic (VEP) model shows promise for obtaining material properties (elastic modulus, hardness, time-dependence) of time-dependent materials during indentation experiments.

Estimating material elasticity by spherical indentation load-relaxation tests on viscoelastic samples of finite thickness

A two-step viscoelastic spherical indentation method is proposed to compensate for 1) material relaxation and 2) sample thickness. In the first step, the indenter is moved at a constant speed and the reaction force is measured. In the second step, the indenter is held at a constant position and the relaxation response of the material is measured. Then the relaxation response is fit with a multi-exponential function which corresponds to a three-branch general Maxwell model. The relaxation modulus is derived by correcting the finite ramp time introduced in the first step. The proposed model takes into account the sample thickness, which is important for applications in which the sample thickness is less than ten times the indenter radius. The model is validated numerically by finite element simulations. Experiments are carried out on a 10% gelatin phantom and a chicken breast sample with the proposed method. The results for both the gelatin phantom and the chicken breast sample agree with the results obtained from a surface wave method. Both the finite element simulations and experimental results show improved elasticity estimations by incorporating the sample thickness into the model. The measured shear elasticities of the 10% gelatin sample are 6.79 and 6.93 kPa by the proposed finite indentation method at sample thickness of 40 and 20 mm, respectively. The elasticity of the same sample is estimated to be 6.53 kPa by the surface wave method. For the chicken breast sample, the shear elasticity is measured to be 4.51 and 5.17 kPa by the proposed indentation method at sample thickness of 40 and 20 mm, respectively. Its elasticity is measured by the surface wave method to be 4.14 kPa. © 2011 IEEE.

Mechanism of pile group settlement in liquefiable soils

This paper examines the settlement of instrumented 2 × 2 model pile groups in liquefiable soil based on the results of dynamic centrifuge tests. The piles are end-bearing in dense sand, and are instrumented such that base, shaft and total pile load components can be measured. The data suggest that the overall co-seismic group settlement is accrued from incremental settlements of the individual piles as the group rocks under the action of the kinematic and inertial lateral loads. A Newmarkian framework for describing this behaviour is presented in which permanent settlement is incremented whenever the load in any of the piles exceeds the capacity of the soil to support the pile. This bearing capacity of the piles in liquefied soil is estimated based on measured dynamic soil properties during shaking and observations of the changes in load carried by the piles. The contribution of the pile cap in reducing settlement is also discussed. © 2008 ASCE.

Hybrid model predictive control applied to switching control of burner load for a compact marine boi

This paper discusses the application of hybrid model predictive control to control switching between different burner modes in a novel compact marine boiler design. A further purpose of the present work is to point out problems with finite horizon model predictive control applied to systems for which the optimal solution is a limit cycle. Regarding the marine boiler control the aim is to find an optimal control strategy which minimizes a trade-off between deviations in boiler pressure and water level from their respective setpoints while limiting burner switches.The approach taken is based on the Mixed Logic Dynamical framework. The whole boiler systems is modelled in this framework and a model predictive controller is designed. However to facilitate on-line implementation only a small part of the search tree in the mixed integer optimization is evaluated to find out whether a switch should occur or not. The strategy is verified on a simulation model of the compact marine boiler for control of low/high burner load switches. It is shown that even though performance is adequate for some disturbance levels it becomes deteriorated when the optimal solution is a limit cycle. Copyright © 2007 International Federation of Automatic Control All Rights Reserved.