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This paper presents a study on bioinspired closed-loop Central Pattern Generator (CPG) based control of a robot fish for obstacle avoidance and direction tracking. The biomimetic robot fish is made of a rigid head with a pair of pectoral fins, a wire-driven active body covered with soft skin, and a compliant tail. The CPG model consists of four input parameters: the flapping amplitude, the flapping angular velocity, the flapping offset, and the time ratio between the beat phase and the restore phase in flapping. The robot fish is equipped with three infrared sensors mounted on the left, front and right of the robot fish, as well as an inertial measurement unit, from which the surrounding obstacles and moving direction can be sensed. Based on these sensor signals, the closed-loop CPG-based control can drive the robot fish to avoid obstacles and to track designated directions. Four sets of experiments are presented, including avoiding a static obstacle, avoiding a moving obstacle, tracking a designated direction and tracking a designated direction with an obstacle in the path. The experiment results indicated that the presented control strategy worked well and the robot fish can accomplish the obstacle avoidance and direction tracking effectively.

Fish has attracted the attentions of researchers because of its excellent swimming performance in water, and biomimetic robot fish was then developed. For robot fish, it is quite significant to perceive its surroundings and then take actions automatically due to the unexpected obstacles. In this paper, a wire-driven robot fish, which can detect obstacles, is designed. We adopt Central Pattern Generator (CPG) for motion control of the robot fish which is capable for smooth transitions among different swimming modes. Moreover, an obstacle avoidance control strategy based on a rule base and a closed loop control structure based on PID algorithm are proposed, which can improve the robot fish’s perception and reaction abilities to the surrounding environment. Finally, experiments are carried out to examine the feasibility of the proposed control strategy.

To immobilize Pseudomonas delafieldii R-8 cells in magnetic polyvinyl alcohol (PVA) beads for biodesulfurization.Magnetic PVA beads were prepared by a freezing-thawing technique under liquid nitrogen. The beads have distinct super-paramagnetic properties and their saturation magnetization is 8.02 emu g(-1). The desulfurization rate of the immobilized cells could reach 40.2 mmol kg(-1) h(-1). Desulfurization patterns of dibenzothiophene in model oil with the immobilized and free cells were represented by the Michaelis-Menten equation. The Michaelis constant for both immobilized and free cells was 1.3 mmol l(-1).The cells immobilized in magnetic PVA beads could be stably stored and be repeatedly used over 12 times for biodesulfurization. The immobilized cells could be easily separated by magnetic field.Magnetic PVA beads are easy to prepare. The immobilization process in the paper is to increase the efficiency of cells and to decrease the cost of operations.

The desulfurization kinetics of Nocardia globerula R-9 was investigated initially in a model system consisting of dibenzothiophene (DBT) dissolved in dodecane. The ability to desulfurize straight-run diesel oil by resting cells of this strain was also evaluated. The course of desulfurization of DBT in dodecane could be represented by the Michaelis-Menten equation. The desulfurization of DBT and 4,6-dimethyl dibenzothiophene (4,6-DMDBT) in a mixture of the two proceeded simultaneously without preference for either of them. The sulfur content of the straight-run diesel oil could be reduced from 1807 to 741 mg dm(-3) by treatment with resting cells of this strain, at a mean rate of 5.1 mmol sulfur kg(-1) h(-1). This showed that Nocardia globerula R-9 could be a potential bacterium for reducing the sulfur content of petroleum products. (C) 2003 Society of Chemical Industry.

This paper reports our investigations on the secondary structure of lysozyme in aqueous solution with D2O and comparing systems emulsified with ionic and non-ionic amphiphiles, respectively. The opposite effect of concentration of surfactants on the lysozyme aqueous system was studied and the activity of lysozyme by the turbidimetric assay with different kinds of surfactant was compared. The effect of different surfactants on emulsification volume formed was observed and discussed. The different interactive patterns between lysozyme and ionic and non-ionic surfactants, such as sodium dodecyl sulfate (SDS), cetyl trimethyl ammonium bromide (CTAB) and Triton-X100 (Isooctoylphenoxypolyethoxy ethanol), respectively, was studied with FTIR. A simple relationship between the secondary structure and denaturation of protein is given for the emulsification of lysozyme in aqueous solutions. It is important for understanding the stabilization and avoiding the emulsions in the extraction process that the interactions between the proteins and surfactants which leads to the formation of such complexes are characterized. The utility of surfactants as a de-emulsifying agent for the commercial process to extract penicillin G from the filtrate of fermentation broth was consistent with these results. (C) 1998 Elsevier Science S.A. All rights reserved.

The desulfurization of dibenzothiophene (DBT), 4,6-dimethyldibenzothiophene (4,6-DMDBT) and their mixture by lyophilized cells ofPseudomonas delafieldii R-8 was studied in the presence of dodecane. The desulfurization rate for 4,6-DMDBT was found to be about 40% in comparison with that for DBT. The desulfurization process for DBT and 4,6-DMDBT proceeded simultaneously without preference for either one. The desulfurization rate for each compound was decreased when they were mixed together. The extent of desulfurization of 4,6-DMDBT was increased with the increase of cell concentration and the decrease of the volume ratio of oil-to-water used. The specific desulfurization rate for 4,6-DMDBT could be reached to 10.4 mmol sulfur kg−1 (cell) h−1 [approximately 0.33 mg sulfur g−1 (cell) h−1].Pseudomonas delafieldii R-8 showed high desulfurization capability for straight-run diesel oil (containing 1,807 mg/L of sulfur). About 1,000 mg/L of sulfur in diesel oil was removed by resting cells of this strain in 24 h of reaction. The specific desulfurization rate was 8.75 mmol sulfur kg−1 (cell) h−1.

Sulphuric acid is the reagent often used for the leaching of solid materials such as ores and concentrates and iron is usually present in the leach solution as an impurity. The most difficult problem associated with the solvents that have been studied for iron removal in sulphate solution is the stripping of iron from the organic phase. Several mixed solvent systems for iron removal were developed in this work. These solvents have the common feature that iron extracted into the organic phase can be stripped with dilute sulphuric acid. The extraction and stripping for some of the mixed solvent systems have been studied and a mechanism is proposed.

The kinetics of base catalyzed racemization of ibuprofen enantiomers has been studied in DMSO-water mixed medium. The dynamic equilibrium rate of keto-enol tautomerism leading to racemization of ibuprofen enantiomers, is proportional to the concentrations of base catalyst and substrate. A kinetic model capable of predicting the time course of racemization, under different base and substrate concentrations, is established and experimentally verified.