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A novel type of bioreactor was successfully developed for the production of taxol and its precursors by culturing cells of Taxus cuspidata (Japanese yew) on a pilot-scale. Rapidly growing cell lines were selected from callus cultures derived from immature embryos of yew. The cells were inoculated in 20-l capacity bioreactors of different types to test the growth performance. The models of small-scale bioreactors incorporated in this study included a balloon-type bubble bioreactor (BTBB), a bubble-column bioreactor (BCB), a BCB with a split-plate internal loop, a BCB with a concentric draught-tube internal loop, a BCB with a fluidized bed bioreactor, and two different models of stirred tank reactors. Among the reactors, BTBB appeared to be the most efficient in promoting cell growth. The doubling time of cell growth in BTBB was 12 days with a 30% inoculation cell density. The optimum time for medium replacement or feeding was 12-15 days after inoculation as determined by monitoring both the levels of sugars and medium conductivity. When yew tree cells were grown in different sizes (100-500-l) of BTBBs, more than 70% cell viability was recorded at the time of harvest. The growth pattern of the cells in the pilot-scale BTBB appeared to be the same as that of cells in the 20-l bioreactors. Approximately 3 mg/l of taxol and 74 mg/l total taxanes were obtained after 27 days of culture.

Flexure-based compliant mechanisms have been used in ultra-precision stages, stages for nano-imprint machines, AFM scanners, and MEMS structures, etc. In this paper, a mathematical static model for flexure-based compliant mechanism driven by piezo stacks is derived. The force vector generated from piezo stacks was linearized in terms of displacement and applied voltage vectors. Then, the piezo force vector was substituted into the static model of a compliant mechanism. Finally, the force and the displacement vectors of input bodies, and the block force and the displacement vectors of output bodies were derived. The derived mathematical model was verified by FEM analyses and experiments. The derived mathematical model can well describe the static performance of a flexure-based compliant mechanism driven by piezo stacks.

This paper presents an optimal design of a compliant mechanism with circular notch flexure hinges as well as a performance evaluation of a two-axes ultra-precision stage using the compliant mechanism. The compliant mechanism consists of two double-symmetric four-link mechanisms for two translational motions. As the circular notch flexure hinge can produce rotation as well as axial translation via its deformation, the double symmetric four-link mechanism can translate along one direction in a small range. In the optimal design, a composite global design index based on Min-Max principle is applied for the design of the compliant mechanism with circular notch flexure hinges owing to its simplicity and compactness. The designed compliant mechanism, piezoelectric elements for actuation, and capacitance-type displacement sensors for position measurement are assembled into an ultra-precision stage. The experimental results show that the stage implemented by the compliant mechanism will be applicable to two-axes ultra-precision positioning systems such as the fine positioning table of coarse-fine positioning systems, ultra-precision machining centres, wafer stages, and scanners for atomic force microscopy (AFM).

This paper presents a novel equation of motion for flexure hinge-based mechanisms. The conventional equation of motion presented in previous work does not adequately describe the behaviours of rigid bodies for the following reasons: firstly, rotational directions for a transformed stiffness lack consistency at the two ends of a flexure hinge; secondly, the length of the flexure hinge is not considered in the equation. The equation of motion proposed in this study solves these problems. Modal analyses are carried out using the proposed equation of motion, the conventional equation of motion found in previous work, and a finite element method. The results show that the proposed equation of motion describes the behaviours of the rigid bodies better than the conventional equation of motion does.

1 We studied the effects of extremely low frequency (ELF, 60 Hz) magnetic fields (MFs) on pain thresholds using the hot plate test. The implication of opioid and benzodiazepine system in the MFs-induced alteration of pain thresholds was also studied. 2 There was an increase at night time and a decrease at daytime of pain thresholds in normal mice. Exposure of MFs (24 h, 20 gauss (G)) inhibited the increase of pain thresholds at night time and even produced hyperalgesia at daytime. 3 The increase of pain thresholds induced by melatonin at daytime was inhibited by exposure to MFs (24 h, 20 G) or opioid antagonist naloxone. The MFs and naloxone synergically inhibited hypoalgesia produced by melatonin. The hyperalgesia at daytime after MFs exposure was potentiated by the benzodiazepine agonist, diazepam, and inhibited by the benzodiazepine antagonist, flumazenil. There was no significant difference in all rotarod performance we tested. 4 From these results, it is suggested that exposure to MFs inhibits the increase of pain thresholds at night time and produces hyperalgesia at daytime with the involvement of opioid and benzodiazepine systems.

Flow characteristics of a circulating gas–solid fluidized-bed heat exchanger with multiple vertical pipes were studied. The glass beads were circulated inside the vertical pipes of the heat exchanger with fluidizing air. The pressure drop and the circulation rate of solid particles were measured. In addition, one-dimensional velocity distribution of solid particles and the pressure distribution inside the vertical pipe were analysed. The prediction on the pressure drop with the circulation of solid particles was proved to be reasonably accurate by comparing with the measured results. © 1998 John Wiley & Sons, Ltd.

Turbo‐fans for a FFU unit should be aerodynamically designed to provide the FFU system with the given flow‐rate at the lowest rotational‐speed by considering the interaction effect with the FFU casing. In this study, slim and highly efficient turbo‐fans are designed to satisfy the given performance at the specific speed by using the hybrid‐stacking method of an inducer and a 2D‐bladed turbo fan. The mean‐line analysis, cascade theory, and CFD technique are all together applied to control the passage areas on the meridional plane from the inlet to the exit of the blade. Furthermore, the torque control algorithm is adopted to improve the performances within the constraints by the motor rpm‐torque characteristics, and the resulting measured performances of mock‐up fans are discussed.