Results 1 - 10 of 346
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[en] Polyacrylamide (PAM)/reduced graphene oxide (rGO) nanocomposite (PAM/rGO) with rGO nanosheets as cross-linkers were synthesized via electropolymerizing acrylamide in an aqueous suspension of GO containing sodium nitrate and potassium persulfate. The PAM/rGO was characterized with X-ray diffraction (XRD), Fourier transfer infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). XRD patterns of the PAM/rGO indicated that rGO was fully exfoliated into individual sheets in the polymer matrix. SEM study exhibits the highly uniform coverage of PAM/rGO membrane on the GCE and its fibrous nanostructure. The electrochemical characteristics of the PAM/rGO modified glassy carbon electrode (GCE) were investigated with cyclic voltammetry (CV), suggesting the extraordinary electrocatalytic effect of PAM/rGO/GCE towards the electro-oxidation of UA and DA. The PAM/rGO/GCE behaved linearly to DA and UA in the concentration range of 3 × 10"−"7 to 5 × 10"−"5 M and 1 × 10"−"6 to 5 × 10"−"5 M with a detection limit of 1 × 10"−"7 M and 5 × 10"−"7 M, respectively. The proposed method was successfully utilized for simultaneous determination of UA and DA in real samples
[en] In this paper, a subcritical water oxidation (SBWO) process was monitored using self-modeling curve resolution (SMCR) of in situ UV-Vis measurements to estimate time-dependant composition profiles of reactants, intermediates and products. A small laboratory scale reactor with UV-Vis fiber-optic probes and a flow cell was used to demonstrate the usefulness of SMCR for monitoring the destruction of model compounds phenol, benzoic acid, and aniline in a dilute aqueous solutions. Hydrogen peroxide was used as the oxidizing reagent at moderate temperature (150-250 deg. C) and pressure (60-90 atm) in a single phase. By use of in situ monitoring, reaction times were easily determined and conditions for efficient oxidations were easily diagnosed without the need for time consuming off-line reference measurements. For selected runs, the destruction of the model compound was confirmed by gas chromatography and chemical oxygen demand (COD) measurements. Suspected intermediate oxidation products were easily detected by the use of UV-Vis spectrometry and self-modeling curve resolution, but could not be detected by gas chromatography
[en] A novel solid-state electrochemiluminescence (ECL) quenching sensor based on the luminescent composite nanofibers for detection of aniline has been developed. The gold nanoparticles (AuNPs) and Ruthenium (II) tris-(bipyridine) (Ru(bpy)32+) doped nylon 6 (PA6) luminescent composite nanofibers (Ru–AuNPs–PA6) were successfully deposited to the bare glassy carbon (GC) electrode by a one-step electrospinning technique. The Ru–AuNPs–PA6 nanofibers maintained the photoelectric properties of the Ru(bpy)32+ ions completely and exhibited excellent ECL behaviors. A high quenching effect on the ECL signal of the Ru–AuNPs–PA6/C2O42− system was obtained with the presence of low concentration aniline compounds. The potential of analytical application was explored by use of the inhibited ECL. The quenching efficiencies of the five kinds of aniline compounds were compared by monitoring the aniline-dependent ECL intensity change. The magnitude of quenching depended linearly upon the concentration of aniline in the investigated concentration range of 10–10 µM. The detection limit for aniline is 5.0 nM, which is comparable or better than that in the reported assays. The solid-state ECL quenching sensor exhibited high sensitivity and good stability. This study may provide new insight into the design of advanced electrospun nanofibers-based ECL sensors for detection and analysis of a variety of active molecules. - Highlights: • The Ru–AuNPs–PA6 nanofibers were first prepared by one-step electrospinning technique. • The Ru–AuNPs–PA6 nanofibers exhibited excellent ECL behaviors on GC electrodes. • It is the first solid-state ECL sensor based on nanofibers for aniline detection. • The quenching efficiencies of the five kinds of aniline compounds were compared. • The strategy could be extended to develop various nanofibers-based ECL sensors
[en] Highlights: • The co-combustion characteristic parameters were studied. • The co-combustion of oil shale and semi-coke could be expressed roughly by the addition of individual components. • Activation energy was calculated by Coats-Redfern, distributed activation energy model and Flynn-Wall-Ozawa methods. - Abstract: In the present work, thermogravimetric analysis was employed to investigate co-combustion behaviors of Fushun low calorific oil shale and its semi-coke. The synergy effect was estimated by using the interaction coefficient and the relative error of mean square root. In addition, activation energy was also calculated by means of Coats-Redfern, distributed activation energy model and Flynn-Wall-Ozawa methods. Results indicated that with the increase of oil shale mass fraction and oxygen concentration, combustion characteristics of the samples were improved. And some little interaction did occur during the co-combustion process, but it was relatively slight. Consequently, the co-combustion of oil shale and semi-coke still could be expressed roughly by the addition of individual components of the mixtures. Furthermore, activation energy of the samples decreased slowly at the initial stage attributed to the minerals’ catalytic effects, and in the final stage, it jumped to a high value, suggesting that the burnout of the samples was difficult. Besides, the mix proportion of oil shale which was added to stabilize the combustion in the circulating fluidized bed was also theoretically calculated.
[en] Temperature variation caused by climate change, seasonal variation and geographic locations affects the physicochemical compositions of chromophoric dissolved organic matter (CDOM), resulting in difference in the fates of CDOM-related environmental pollutants. Exploration into the thermal induced structural transition of CDOM can help to better understand their environmental impacts, but information on this aspect is still lacking. Through integrating fluorescence excitation–emission matrix coupled parallel factor analysis with synchronous fluorescence two-dimensional correlation spectroscopy, this study provides an in–depth insight into the temperature–dependent conformational transitions of CDOM and their impact on its hydrophobic interaction with persistent organic pollutants (with phenanthrene as an example) in water. The fluorescence components in CDOM change linearly to water temperature with different extents and different temperature regions. The thermal induced transition priority in CDOM is protein-like component → fulvic-like component → humic-like component. Furthermore, the impact of thermal–induced conformational transition of CDOM on its hydrophobic interaction with phenanthrene is observed and explored. The fluorescence–based analytic results reveal that the conjugation degree of the aromatic groups in the fulvic– and humic–like substances, and the unfolding of the secondary structure in the protein–like substances with aromatic structure, contribute to the conformation variation. This integrated approach jointly enhances the characterization of temperature–dependent conformational variation of CDOM, and provides a promising way to elucidate the environmental behaviours of CDOM. - Highlights: • Thermal-induced structural transition of CDOM was explored. • EEM-PARAFAC and 2DCOS analysis jointly characterized the transition process. • Temperature-dependent hydrophobic interaction of CDOM with PAH was demonstrated. • The integrated approach can help to elucidate the environmental behaviours of CDOM. - Insight into the temperature-dependent conformational transitions of chromophoric DOMs and their impact on their interaction with PoPs is provided.
[en] Reactor pressure vessel (RPV) is an important equipment of the main coolant loop pressure boundary, sealing analysis is very important in its design process, because it has high temperature, high pressure, and high-level radioactive characteristics. In order to verify the seal performance of Hong Yan He power project's RPV sealing structure, the sealing capacity of it has been analyzed, under normal and upset condition, based on 3D elastoplastic method of ANSYS software, calculated results show that the RPV meets the sealing criteria under normal and upset condition. (authors)
[en] Commercial CFD code CFX 12.0 was used as an approach to investigate the flow and convective heat transfer phenomena of a typical 7-pin fuel bundle with wrapped-wire. The pressure drop coefficient and Nusselt number under different Re were obtained, and the simulation results are in good agreement with empirical correlations. The transverse flow effects in three kinds of typical subchannels were investigated, and its features were analyzed. The results show that the corner channel's transverse flow intensity varies heavily along the axial direction. and the transverse flow intensities in three typical subchannels show periodic feature. The local Nusselt number distribution on three cross sections of the central rod surface was also analyzed. The results show that the minimum local Nusselt number occurs close to the contact location of wire and rod, which means that the convective heat transfer condition is the worst in such area, and the special attention in accident analysis is deserved. (authors)
[en] After 50 years of research on controlled thermonuclear fusion, a new stage will be reached in 2003, when a site for the International Thermonuclear Experimental Reactor project will be chosen to start the construction. Scientists hope that this project could herald a new era in which the energy problem will be solved completely. The great progress made on the HT-7 superconducting tokamak in China has provided positive and powerful support for fusion research. The HT-7 is one of the only two superconducting tokamaks in the world that can carry out minute-scale high temperature plasma research, and has achieved a duration of 63.95s for the hot plasma discharge. This is a major step towards real steady-state operation of the tokamak configuration. We present an overview of the latest progress on the tokamak experiments in the Institute of Plasma Physics, Chinese Academy of Sciences
[en] The thermal-hydraulic behavior of triangular arranged fuel bundle with wrapped wire spacer of fuel assembly for sodium-cooled fast reactor was investigated by employing CFD code CFX, and the results were compared with subchannel analysis code SuperEnergy. Fuel bundles composed of 7, 19, 37 and 61 fuel rods were analyzed separately. The axial velocity, cross flow mixing effect, and temperature rise along axial direction for different subchannels of the fuel bundle were discussed, and the effect of wrapped wire spacer was carefully investigated. The results show that the wrapped wire spacer plays an important role on the cross flow effect and axial velocity distribution as well as the temperature rise in different subchannels. Moreover, with the increase of fuel rods, the flow in fuel bundle becomes more complicated, and the non-uniformity of the axial flow also shows a tendency to enhance. (authors)
[en] Dielectric resonance of InSb pure crystal is found at 35.07 MHz at room temperature, while the free-electron conductivity remains constant at 339Ωsup(-1) cmsup(-1). The imaginary part of the complex dielectric function at resonance is about 2.7.104 at 300 K and increases to 5.6 .104 at 360 K. The resonance frequency found by the present experiment is close to that found by using the r.f. bylk size effect method, which is different from the present r.f. wave penetration method