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AbstractAs an important part of the ITER gas injection system, the fusion power shutdown system delivers large quantities of gas into the vacuum vessel to stop the fusion power in an emergency case. Two identical but independent units are designed for mutual redundancy. Each unit includes an injection pipeline and a unit that contains a gas reservoir, solenoid valve, pneumatic isolation valve, and pressure switches. Among these components, the working gas reservoir parameters are investigated by experiments based on the required total gas quantity of at least 3000 Pa m3neon or mixtures of neon and hydrogen injected within 3 s. The working gas is released utilizing a pneumatically actuated valve that is not affected by the strong stray magnetic field of about 0.205 T. The associated solenoid valve is equipped with magnetic shielding that is designed by a magnetostatic analysis. These components lie on the same plane in the unit to maximize the maintainability. Furthermore, the structure integrity of the unit and its support frame is validated by a preliminary structural analysis.

AbstractThe ITER gas injection system delivers gases from the tritium plant to the vacuum vessel, fueling pellet injection system, and neutral beam for plasma operation and fusion power shutdown. In this system, the gas fueling (GF) gas valve box (GVB) is an indispensable part that mainly provides functions of gas throughput control and measurement of gas pressure, flow rate, and temperature. The preliminary structure design is largely driven by the requirements of magnetic field compatibility and limited integration space. A strong magnetic field of over 0.2 T exists around the GVB locations, so a magnetic shielding design is required to ensure the normal function of susceptible components. Instead of the previous overall shielding, a local magnetic shielding has been developed by a validated analysis method. As a result, the total weight of the shield has been reduced from over 7000 kg to about 200 kg. Furthermore, considering the limited space reservation, a highly compact flat layout for the GF GVB has been developed to ensure enough maintenance space in front of it. In addition, other requirements such as structure integrity under various load combinations, leak detectability, in situ maintainability, etc., have all been taken into account.

316LN is a type of austenitic stainless steel whose grain refinement only depends on hot deformation. The true stress–strain curves of 316LN were obtained by means of hot compression experiments conducted at a temperature range of 900–1200°C and at a strain rate range of 0·001–10 s-1. The influence of deformation parameters on the microstructure of 316LN was analysed. Both the constitutive equation for 316LN and the model of grain size after dynamic recrystallisation were established, and the effect of different deformation conditions on the microstructure was analysed. The results show that the suitable working region is the one with a relatively higher deformation temperature and a lower strain rate, in which the dynamic recrystallisation is finely conducted. Moreover, the working region that should be avoided during hot deformation was indicated.

Novel worm-like Ag/ZnO core–shell heterostructural composites were fabricated using a two-step chemical method. As-prepared silver nanowires were soaked in a solution of zinc acetate and triethanolamine to form worm-like Ag/ZnO core–shell composites under ultrasonic irradiation. Samples were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), photoluminescence spectroscopy, and UV–vis spectrophotometer. The results show that the core–shell composites are composed of single-crystal Ag nanowires serving as the core, on which dense ZnO particles grow as the shell. The surface plasmon absorption band of Ag/ZnO composites is distinctly broadened and red shifted to monometallic Ag nanowires. The PL intensity of Ag/ZnO heterostructural composites varies and has the minimum intensity for the sample prepared with Ag of 2.8 atom %. Moreover, photocatalytic tests show that the Ag/ZnO composites exhibit higher photocatalytic activity compared to pure ZnO particles.

The effects of neodymium rich rare earth elements [RE(Nd)] on microstructure and mechanical properties of as cast AZ31 magnesium alloy were investigated. The microstructures of as cast AZ31–xRE(Nd) alloys display a dendrite configuration, and the secondary dendrite spacing of the a-Mg phase was decreased with the increasing Nd content. The addition of RE(Nd) resulted in the formation of Al2Nd and Mg12Nd phases. Mechanical properties were improved significantly due to grain refinement and precipitation of intermetallic phases. When the amount of RE is 1·0 wt-%,The as cast AZ31 alloy reached its maximum tensile strength of 249 MPa at room temperature, yield strength of 169 MPa and elongation of 9·0%.

The internal thermally coupled air separation column (ITCASC) is a frontier of air separation energy savings research. The first principles model of the ITCASC is proposed and is based on the material balance, energy balance, and the related thermal coupling relationship which can be used for further control and design studies. The related solution procedures are given. Detailed behavior analyses are carried out. The research results reveal that the ITCASC process has the perfect separation effect and exhibits different behaviors compared to the conventional air separation column (CASC). The optimization model and the related operation optimization are further explored to gain insight on the energy saving potential of the ITCASC process. Optimization research results show that the ITCASC has about 47 % energy saving potential compared to the CASC process.

Liu, X.-G. and J. Sandkühler.Characterization of long-term potentiation of C-fiber–evoked potentials in spinal dorsal horn of adult rat: essential role of NK1 and NK2 receptors. J. Neurophysiol.78: 1973–1982, 1997. Impulses in afferent C fibers, e.g., during peripheral trauma, may induce plastic changes in the spinal dorsal horn that are believed to contribute to some forms of hyperalgesia. The nature of lasting changes in spinal nociception are still not well understood. Here we characterized the long-term potentiation (LTP) of spinal field potentials with a negative focus in superficial spinal dorsal horn evoked by supramaximal electrical stimulation of the sciatic nerve in urethan-anesthetized adult rats. The field potentials studied in this work had high thresholds (≥7 V, 0.5 ms), long latencies (90–130 ms), and long chronaxy (1.1 ms) and were not abolished by muscle relaxation and spinalization. Thus they were evoked by afferent C fibers. In response to 1-Hz stimulation of afferent C fibers, amplitudes of C-fiber–evoked field potentials remained constant, whereas number of action potentials of some dorsal horn neurons increased progressively (wind-up). In all 25 rats tested, high-frequency, high-intensity stimulation (100 Hz, 30–40 V, 0.5 ms, 400 pulses given in 4 trains of 1-s duration at 10-s intervals) always induced LTP (to ∼200% of control), which consistently lasted until the end of recording periods (4–9 h). This tetanic stimulation also significantly decreased mean threshold of C-fiber–evoked field potentials. The C-fiber volley, which was recorded simultaneously in sural nerve, was, however, not affected by the same tetanic stimulation. High-frequency, low-intensity stimulation (100 Hz, 3 V, 0.5 ms) never induced LTP in six rats tested. At an intermediate frequency, high-intensity stimulation (20 Hz, 40 V, 0.5 ms, 400 pulses given in 4 trains of 5 s at 10-s intervals) induced LTP in four out of six rats, which lasted until end of recording periods (3–6 h). In the remaining two rats, no LTP was induced. Low-frequency, high-intensity stimulation (2 Hz, 30–40 V, 0.5 ms, 400 pulses) induced LTP that lasted for 2–8 h in four out of five rats. Intravenous application of neurokinin 1 (NK1) or neurokinin 2 (NK2) receptor antagonist RP 67580 (2 mg/kg, n= 5) or SR 48968 (0.3 mg/kg, n= 5) 30 min before high-frequency, high-intensity stimulation blocked the induction of LTP in all rats tested. In contrast, the same dose of their inactive enantiomers RP 68651 (n= 5) or SR 48965 (n= 5) did not affect the induction of LTP. Spinal superfusion with RP 67580 (1 μM) from 30 min before to 30 min after high-frequency, high-intensity stimulation blocked induction of LTP in all five rats tested. Spinal application of SR 48968 (10 nM) prevented LTP in five out of seven rats. However, when spinal superfusions with RP 67580 (1 μM, n= 3) or SR 48968 (10 nM, n= 3) were started 1 h after high-frequency, high-intensity stimulation, established LTP was not affected. Thus the activation of neurokinin receptors is necessary for the induction but not for the maintenance of LTP of C-fiber–evoked field potentials in spinal dorsal horn. This model may be useful to study plastic changes in spinal cord induced by peripheral C-fiber stimulation. The LTP of C-fiber–evoked field potentials may be a mechanism underlying some forms of hyperalgesia.

It has been suggested that the expression of c-fos and other immediate early genes in spinal dorsal horn neurons would trigger changes in the phenotype of nociceptive neurons which may lead to long-term changes in spinal nociception. To test this hypothesis, we have used a minimally invasive intrathecal stimulation and injection technique which can be applied to adult Sprague-Dawley rats under brief ether anesthesia to induce massive c-fos expression in spinal neurons without affecting peripheral nociceptors. Electrical intrathecal stimulation (0.5 ms pulses, 15 V, 3 Hz for 15 min) or intrathecal injection ofN-methyl-d-aspartate (25 nmol) produced massive c-Fos immunoreactivity in neurons throughout the sacral spinal cord and the dorsal horn of the lumber spinal cord. Immunoreactivity declined to control values at mid-thoracic levels. To assess effects of these intrathecal stimuli on nociception, hot-plate and tail-flick latencies and mechanical thresholds of hindlimb withdrawal reflexes were measured once every day for 14 days before and up to 14 days after conditioning stimulation. Spontaneous locomotion of each animal was video-taped daily for 5 min and analysed off-line. On the day of the intrathecal stimulation the tests were performed 1 h before and also 6 h after conditioning stimulation. Thermal and mechanical nociceptive thresholds were temporarily enhanced 6 h after intrathecal stimulation but they were not different from controls one to 14 days later.

Ti, Ni, activated carbon, and Mo powders were used as raw materials to prepare a composite TiC cermet in this study. The powders were mixed and prepared through high-energy ball milling and then sintered in a spark plasma sintering (SPS) system. Results revealed that ball milling time affected the raw materials. After ball milling was performed for 10 h, Ti and C particles reacted and generated TiC, meanwhile, the solid Mo solutionized in TiC and formed (Ti,Mo)C lumps. XRD results showed that the product of (Ti,Mo)C cermet with high hardness can be prepared at a low sintering temperature of 1150 degC. The microstructure of composite TiC cermet was different from the traditional core-ring structure. In particular, the developed microstructure comprises a (Ti,Mo)C-Ni dark-gray phase at the center surrounded by (Ti,Mo)C light-gray phase and dispersed Mo white phase.

Sympathetic‐sensory coupling after L5 spinal nerve lesion in the rat and its relation to changes in dorsal root ganglion blood flow. (Christian‐Albrechts‐Universität, Kiel, Germany) Pain2000;87:335–345.