Search

Based on observation data and temperature diffusion experiment of soluble hazardous chemicals, propylene oxide was taken as a typical hazardous chemical to simulate diffusion after leakage in conditions of variable locations, source intensities, and tides in the Daya Bay by FVCOM model. The results show no unsafe concentration (0.02 mg/L) area after 24 hours for leakage of 100 tons occurring in channel and anchorage, and over 3 km2 unsafe area for the same amount of leakage occurring in port. There are more than 5 km2 and 10 km2 unsafe areas after 24 hours in all locations for 500 t and 1000 t leakage, respectively. Maximum diffusion distance and range increase with increasing diffusion space and current velocity, while the dilution effect becomes stronger, which results in maximum diffusion distance and range in channel, followed by anchorage and port, and reversed maximum concentration distribution. Current velocity acts more as a disincentive within 1 hour and an incentive for diffusion after 1 hour. Diffusion simulation of typical hazardous chemicals will provide technical supports to improve ability of handling environmental emergency in the Daya Bay.

To study the effects of the different electrodes on the charge transport mechanism in XLPE, the conductive currents of cross-linked polyethylene (XLPE) with Al electrode and semi-conductive screen have been compared. And the currents of the two kinds of samples at low electric field, which are tested after not injecting and injecting space charge. The transportation mechanism of XLPE with Al electrode under high voltage is proved to not obey the Ohm's law, but also not obey the space charge limited-current (SCLC) mechanism. The transportation mechanism of XLPE with semi-conductive current is proved to obey SCLC. The charge transport mechanism traditional criterion of XLPE is not very precise. So the study of high voltage direct current (HVDC) in laboratory should take the electrode materials of testing samples into consideration, and the results of the samples with the different electrodes should be analyzed and compared.

Vertically aligned single-walled carbon nanotubes (VA-SWCNTs) have been fabricated on carbon nanocones (CNCs) in a gravity-assisted chemical vapour deposition (CVD) process. The CNCs with nanoscale Co particles at the top were first grown on the Co/Si(100) substrate biased at 350?V in a plasma enhanced chemical vapour deposition process. The CNCs typically are ~200?nm in height, and their diameters are ~100?nm near the bottom and ~10?nm at the top. The nanoscale Co particles ~10?nm in diameter act as catalysts which favour the growth of VA-SWCNTs out of CNCs at 850??C in the gravity-assisted CVD process. The average length and the growth time of VA-SWCNTs are ~150?nm and 1.5?min, equivalent to a growth rate of ~6??m?h?1. The diameters of VA-SWCNTs are estimated to be 1.2?2.1?nm. When VA-SWCNTs are fabricated on CNCs, the turn-on voltage is reduced from 3.9 to 0.7?V??m?1 and the emission current density at the electric field of 5?V??m?1 is enhanced by a factor of more than 200. The composite VA-SWCNT/CNC structure is potentially an excellent field emitter. The emission stability of the VA-SWCNT/CNC field emitter is discussed.

This paper researches the theory of geometric error evaluation and its application. On the basis of the geometric model of error evaluation, the features of the geometric error enclosure evaluation are analyzed, and the paper has founded the linear programming model of minimum zone association, maximum inscribed association and minimum circumscribed association. By taking the minimum conditions criterion and the theory on minimizing the extremal difference function as rules of geometric error evaluation, a correctional simplex method for direct solution of the programming model is proposed, and also the process is given. Furthermore, the method is verified by giving an example of the cylindricity error evaluation and comparing the experiment results with the ones obtained from other common methods. In addition, this designed method is also used to other geometric error evaluation in practice. The theoretical analysis and experimental results indicate that, the proposed correctional simplex method does provide well accuracy on geometric error evaluation. The outstanding advantages conclude not only high efficiency and stability but also good universality and practicality.

Anodic composite deposition is demonstrated to be a unique method for fabricating a ternary ruthenium dioxide/reduced graphene oxide/carbon nanotube (RuO2 xH2O/rGO/CNT, denoted as RGC) nanocomposite onto Ti as an advanced electrode material for supercapacitors. The rGO/CNT composite in RGCs acts as a conductive backbone to facilitate the electron transport between current collector and RuO2 xH2O nanoparticles (NPs), revealed by the high total specific capacitance (C(S,T) = 808 F g(-1)) of RGC without annealing. The contact resistance among RuO2 xH2O NPs is improved by low-temperature annealing at 150 °C (RGC-150), which renders slight sintering and enhances the specific capacitance of RuO2 xH2O to achieve 1200 F g(-1). The desirable nanocomposite microstructure of RGC-150 builds up the smooth pathways of both protons and electrons to access the active oxy-ruthenium species. This nanocomposite exhibits an extremely high C(S,T) of 973 F g(-1) at 25 mV s(-1) (much higher than 435 F g(-1) of an annealed RuO2 xH2O deposit) and good capacitance retention (60.5% with scan rate varying from 5 to 500 mV s(-1)), revealing an advanced electrode material for high-performance supercapacitors.

A monolithic integrated photoreceiver constructed of a ZnS MSM photodiode and an InGaP/GaAs HBT utilizing the pattern-oxide growth technique is demonstrated. The XRD and PL analyses of the as-grown ZnS epilayers exhibit good quality. The optical and electrical performance of the ZnS MSM photodiode, InGaP/GaAs HBT and integrated photoreceiver is estimated. Photocurrent induced from the ZnS MSM photodiode is amplified linearly by a common-emitter preamplifier based on an InGaP/GaAs HBT. The current amplification ratio and the voltage amplification sensitivity of the integrated photoreceiver are 18.2 and −8.7 mV µW−1, respectively. The ZnS-based integrated photoreceiver carried out successfully on a GaAs substrate indicates the potential of the pattern-oxide growth technique in the development for the II–VI WBG-based short wavelength integrated devices.

Diamond nanotips were synthesized on diamond/Si substrates by using a microwave plasma-enhanced chemical vapor deposition process. The diamond nanotips are ~1??m in height and the diameter at the bottom of a nanotip is ~200?nm. The as-grown diamond nanotips exhibit excellent field emission characteristics after treating with nitrogen plasma immersion ion implantation (PIII) for 10?min. A low turn-on field of 3?V??m?1 and a high current density of 4?mA?cm?2 at 9?V??m?1 are achieved. The morphologies of diamond nanotips are unchanged after the nitrogen PIII treatment. The diamond quality reduces with treatment time. The sp3 bonds in diamond can be broken by the nitrogen ions accelerated by the pulse voltage of ?25?kV, which results in G peak broadening in Raman spectra. Several nanoscale amorphous regions are generated in a crystalline diamond nanotip, observed by the high resolution transmission electron microscope. The improvement of field emission properties is correlated to the amorphous regions and possible implantation-induced atomic defects.

Carbon nanosheets were synthesized on pyramidal Si(100) substrates without any catalyst in a microwave plasma-enhanced chemical vapour deposition process. The average length and the growth time of carbon nanosheets were measured to be ~300 nm and 10 min, equivalent to a growth rate of ~30 nm min−1. By replacing flat Si(100) with pyramidal Si(100) as the substrate, the field emission performance of carbon nanosheets was greatly improved. A low turn-on field of 3.2 V µm−1 and a high current density of 2.5 mA cm−2 at 7.0 V µm−1, close to those of carbon nanotube emitters, were achieved. The improvement in field emission was attributed primarily to the pyramidal shape.

The qualities of freestanding single-walled carbon nanotubes (SWCNTs) grown on Co/Si(100) in the gravity-assisted chemical vapour deposition (CVD) process have been investigated. Vertically oriented SWCNTs of high quality appear at a growth time of less than 3 min, verified by the clear radial breathing mode (RBM) in the Raman spectra and by the high resolution images taken by a transmission electron microscope (TEM). At a growth time of 3 min, vertical and looped SWCNTs co-appear on the substrate. A SWCNT longer than ~1 µm tends to bend into a semicircular loop. At a longer growth time such as 20 min, the coating of amorphous carbon (a-C) on the SWCNT becomes dominant, which is attributed to catalytic poisoning. A relatively long SWCNT (~10–40 µm) surrounded with a thick a-C layer is the final structure. The bending stiffness of the a-C tube is estimated ~15 times larger than that of the SWCNT, which helps to keep the a-C/SWCNT composite structure in a nearly vertical shape. A mechanism has been proposed to explain the coating of a-C on SWCNTs.