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A 9-week feeding trial was conducted to determine the effect of dietary vitamin E levels (0, 100, 200 and 1000 mg kg diet) on the growth performance and hematological indices in rainbow trout (Oncorhynchus mykiss) fingerlings (initial weight of 2.1 ± 0.1). Results indicated significant effect (p<0.05) of vitamin E levels on the fish growth performance. In terms of hematological indicators, vitamin E levels significantly affected the hematocrit, hemoglobin, red blood cell (RBC) count, monocyte and eosinophil in rainbow trout. However, it did not change MCHC, lymphocyte and MCH values.

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In this paper, an optimal active controller is designed to prevent the shimmy vibrations in aircraft nose landing gear. The controller is designed according to the linearized system while the input is implemented on the real non-linear plant. Shimmy vibration is the lateral and torsional vibrations in the wheel that causes instability in high speed performances. Thus, control and suppressing of this vibration is extremely important. In this paper, using the nonlinear dynamics of the nose landing gear system, the equivalent linearized system is extracted and then its related linearized state space is derived. Stability, controllability and observability of the system are investigated based on the linearized model of the system and damping the shimmy vibrations is performed with the least consumption of energy using Linear Quadratic Regulator (LQR). To estimate the states of the system which are not measurable using ordinary sensors, an observer is designed and implemented using separation principal. To verify the performance of the proposed controller, vibration response of the open loop system is compared with the closed loop response of the designed optimal controller. Considerable improvement can be seen in the performance of the closed loop system since not only the vibrations are effectively damped but also the consumption of energy is minimized. Finally, digital control system is extended in order to implement the proposed controller on the discretized model of the system and the effect of sampling rate on the accuracy of the system is studied.

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Foam fractionation or foam floatation technology has been introduced to remove fine particles in the Recirculation Aquaculture System (RAS). The main objective of this study was to assess the effect of a dissolved air flotation reactor on foam floatation efficiency in a conventional RAS. In this study, two different types of air bubble producers were tested for 30 days: dissolved air flotation reactor was compared to a commercialized air bubble producer in a skimming column. Nitrogen concentrations and particles removal rates were measured every other day during the study. The results showed that average rates of ammonia and nitrite concentration were lower in the system equipped with air flotation skimmer compared to those in the air bubble system (0.39 and 0.35 versus 3.45 and 0.65 mg L^-1, respectively; P< 0.05). However, nitrate concentration was not influenced by the foam floatation systems (P> 0.05). Nitrogen concentrations were almost similar in the two treatments up to day 15 of the study and then showed higher values for the air bubble system.Total particle collection was significantly higher in the systems containing air flotation skimmer (296.1 versus 276.4; P< 0.05), though daily collected particle was almost similar in both systems at the end of the study. In conclusion, dissolved air flotation skimmer was able to remove a larger portion of particles rendering improvement of water quality in RAS.

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