Multiwalled carbon nanotube (MWCNT)/CdS core/shell heterostructures have been successfully synthesized via a simple solution-phase method. The thickness of CdS shells can be facilely tuned by either the reaction temperature or time. The CdS nanoparticles are first formed directly on the surface of MWCNT, and then a uniform CdS sheath is yielded via orientated aggregation processes. The present work provides a simple route to obtain MWCNT-based core/shell heterostructures and thus is of wide interest for the studies of nanomaterials and nanodevices. 相似文献
Reconfigurable multi-channel optical power splitter is proposed and its optical properties are calculated. The device can dynamically reconfigure the number of splitting channels by providing programmed refractive index modulations on a multimode interference (MMI) waveguide. A reconfigurable 3-channel optical power splitter is designed to work as 1 × 1, 1 × 2 or 1 × 3 optical power splitter depending on the state of the heat electrodes using thermo-optic modulation, and the input light can be distributed to three output channels with sequential orders. The device can work in the whole C-band (1530-1565 nm) with extinction ratio better than −29.0 dB, excess loss better than −0.45 dB, imbalance better than 0.08 dB and polarization dependent loss (PDL) better than 0.14 dB. The design conception is scalable to a multi-channel splitting-on-demand optical power splitter which can divide input light to 1, 2, …, N output channels equally by using the 3-channel reconfigurable optical power splitter as a building block. 相似文献
This paper presents the experimental study and numerical simulation of two-dimensional two-phase flow in horizontal heated
tube bundles. In the experiments, two advanced measuring systems with a single-fibre optical probe and a tri-fibre-optical-probe
were developed to measure respectively the local void fraction and vapor bubble velocities among the heated tube bundles.
In accordance with the internal circulation characteristics of two-phase flow in the tube bundles, a mathematical model of
two-dimensional two-phase low Reynolds number turbulent flow based on the modified drift flux model and the numerical simulation
method to analyze the two-phase flow structures have been developed. The modified drift flux model in which both the acceleration
by gravity and the acceleration of the average volumetric flow are taken into account for the calculation of the drift velocities
enables its application to the analysis of multi-dimensional two-phase flow. In the analysis the distributions of the vapor-phase
velocity, liquid-phase velocity and void fraction were numerically obtained by using the modified drift flux model and conventional
drift flux model respectively and compared with the experimental results. The numerical analysis results by using the modified
drift flux model agree reasonably well with the experimental investigation. It is confirmed that the modified drift flux model
has the capability of correctly simulating the two-dimensional two-phase flow.
Received on 3 September 1998 相似文献
The highly efficient asymmetric total synthesis of indole alkaloid, (−)-corynantheidol, containing a 2,4,5-trisubstituted piperidine core, was achieved using a new version of the one-pot azaelectrocyclization reaction. The formal synthesis of (−)-corynantheidine was also achieved using the common synthetic intermediate for these corynantheines. 相似文献
A method for growing polymers directly from the surface of graphene oxide is demonstrated. The technique involves the covalent attachment of an initiator followed by the polymerization of styrene, methyl methacrylate, or butyl acrylate using atom transfer radical polymerization (ATRP). The resulting materials were characterized using a range of techniques and were found to significantly improve the solubility properties of graphene oxide. The surface‐grown polymers were saponified from the surface and also characterized. Based on these results, the ATRP reactions were determined to proceed in a controlled manner and were found to leave the structure of the graphene oxide largely intact.
Cerium oxide (CeO2) nanoparticles display excellent antioxidant properties by scavenging free radicals. However, some studies have indicated that they can cause an adverse response by generating reactive oxygen species (ROS). Hence, it is important to clarify the factors that affect the oxidant/antioxidant activities of CeO2 nanoparticles. In this work, we report the effects of different buffer anions on the antioxidant activity of CeO2 nanoparticles. Considering the main anions present in the body, Tris‐HCl, sulfate, and phosphate buffer solutions have been used to evaluate the antioxidant activity of CeO2 nanoparticles by studying their DNA protective effect. The results show that CeO2 nanoparticles can protect DNA from damage in Tris‐HCl and sulfate systems, but not in phosphate buffer solution (PBS) systems. The mechanism of action has been explored: cerium phosphate is formed on the surface of the nanoparticles, which interferes with the redox cycling between Ce3+ and Ce4+. As a result, the antioxidant activity of CeO2 nanoparticles is greatly affected by the external environment, especially the anions. These results may provide guidance for the further practical application of CeO2 nanoparticles. 相似文献
Electrical double-laye r capacitors are widely concerned fo r their high power density,long cycling life and high cycling efficiency.However,their wide application is limited by their low energy density.In this study,we propose a simple yet environmental friendly method to synthesize cobalt and nitrogen atoms co-doped porous carbon(CoAT-NC) material.Cobalt atoms connected with primarily pyridinic nitrogen atoms can be uniformly dispersed in the amorphous carbon matrix,which is benefit for improving electrical conductivity and density of states of the carbon material.Therefore,an enhanced perfo rmance is expected when CoAT-NC is served as electrode in a supercapacitor device.CoAT-NC displays a good gravimetric capacitance of 160 F/g at 0.5 A/g combing with outstanding capacitance retention of 90% at an extremely high current density of 100 A/g in acid electrolyte.Furthermore,a good energy density of30 Wh/kg can be obtained in the organic electrolyte. 相似文献