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Nitrogen-doped porous carbon (NPC) was prepared by directly carbonizing zeolite ZSM-39 containing a structure-directing agent, tetramethylammonium chloride (TMACl), which also acted as a source of C and N for NPC. The cage-like pore of zeolite ZSM-39 acted as an ideal space for immobilizing the C and N species. The obtained NPCs have a high N content up to 18.14%. The quaternary N of template TMACl was transformed into pyridinic and pyrrolic/pyridonic N during the carbonization. NPCs were suitable for selective adsorption of CO2 because of their unique ultra-micropores and abundant basic sites. The adsorption selectivity of CO2 over N2 was more than 12.1 (molar ratio). The CO2 adsorption capacity of the unit surface area for a NPC-723 sample was calculated as 26.6 μmol m−2 at 0.93 bar and 273 K, which is one of the highest values among carbon adsorbents. Its excellent selectivity makes the NPC a good candidate for separating low concentrations of CO2 in the purification of gas mixtures.

Despite an increased interest in sustainable energy conversion systems, there have been limited studies investigating the electrocatalytic reaction mechanism of methanol oxidation on Ni-based amorphous materials in alkaline media. A thorough understanding of such mechanisms would aid in the development of amorphous catalytic materials for methanol oxidation reactions. In the present work, amorphous Ni-B and Ni-B-Co nanoparticles were prepared by a simple chemical reduction, and their electrocatalytic properties were investigated by cyclic voltammetry measurements. The diffusion coefficients (D0) for Ni-B, Ni-B-Co0.02, Ni-B-Co0.05, and Ni-B-Co0.1 nanoparticles were calculated to be 1.28 &times, 10&minus, 9, 2.35 &times, 9, 4.48 &times, 9 and 2.67 &times, 9 cm2 s&minus, 1, respectively. The reaction order of methanol in the studied transformation was approximately 0.5 for all studied catalysts, whereas the reaction order of the hydroxide ion was nearly 1. The activation energy (Ea) values of the reaction were also calculated for the Ni-B and Ni-B-Co nanoparticle systems. Based on our kinetic studies, a mechanism for the methanol oxidation reaction was proposed which involved formation of an electrocatalytic layer on the surface of amorphous Ni&ndash, B and Ni-B-Co nanoparticles. And methanol and hydroxide ions could diffuse freely through this three-dimensional porous conductive layer.

The performance of atmospheric pressure dielectric barrier discharge (DBD) driven by dual-frequency sources of 200 kHz/13.56 MHz has been investigated numerically here in a one-dimensional fluid model. By varying the ratio of dual frequency excitation amplitudes, strong nonlinear coupling in the discharge is observed, with the electron density rising significantly due to the synergistic effect governing the ionization process. Moreover, it is shown that the phase shift between the dual frequencies also has an influence on the electron temperature and density. As to different high frequency components, the modulation of the electron temperature and density induced by the phase-shift also varies significantly. Those results then demonstrated the possibility of applying amplitude and/or phase modulations in a wide operation window to optimize the plasma parameters in dual-frequency DBDs with fixed frequencies.The performance of atmospheric pressure dielectric barrier discharge (DBD) driven by dual-frequency sources of 200 kHz/13.56 MHz has been investigated numerically here in a one-dimensional fluid model. By varying the ratio of dual frequency excitation amplitudes, strong nonlinear coupling in the discharge is observed, with the electron density rising significantly due to the synergistic effect governing the ionization process. Moreover, it is shown that the phase shift between the dual frequencies also has an influence on the electron temperature and density. As to different high frequency components, the modulation of the electron temperature and density induced by the phase-shift also varies significantly. Those results then demonstrated the possibility of applying amplitude and/or phase modulations in a wide operation window to optimize the plasma parameters in dual-frequency DBDs with fixed frequencies.

In the giga-Hz (GHz) regime, not only does an advanced electromagnetic platform need a stealth function to shield itself from radar detection, similar to the “invisible” cloak in the visible light regime, but also an enhanced transmission function to communicate with others. To satisfy the seemingly contradictory requirements, we here propose a multi-functional mode of plasma cloaking, invisible to radar detection but signal-enhanced in communication bands. Such a synergistic effect is achieved by combining a “detour” layer of cloaking and an enhancement layer of communication. Thus, with such a design we can successfully apply an ideal “cloak” to the low frequency detecting regime (in the P-band) and improve signal transmission capabilities in a higher frequency communication regime (in the L-band) at the same time. Furthermore, the tunability and limitations of the multi-functional system are discussed, and the principles of designing inner and outer plasma layers are acquired.

Natural gas is becoming an important fuel source for China, which is also expected to remain so in the future. In this article, chronological data of natural gas are summarized through the descriptive statistics methodology. The status quo and development trend of natural gas resources in China are analyzed as well, with the result showing that the productions and imports of natural gas are increasing rapidly. Meanwhile, China has formed a multigas source supply pattern, including domestic gas, imported liquefied natural gas, and pipeline gas. Then, the current situation and main problems of gas-fired generation are analyzed. The finding shows that the economic competitiveness of the gas-fired generation and the supply mode of natural gas are the main barriers in promoting the development of gas-fired generation. Moreover, the technical analysis on three different types of gas-fired power generation is provided. In China, combined cycle gas-fired power stations and single cycle gas-fired power stations are good choices for the 12th Five-Year period, and the large-scale natural gas distributed energy combined cooling, heat, and power is more applicable for the 13th Five-Year period. Finally, three suggestions are proposed for guiding the rational use of natural gas resources and promoting the development of gas-fired power generation in China. © 2015 American Institute of Chemical Engineers Environ Prog, 2015

Dielectric barrier discharges (DBD) as a common method to generate plasmas with high density, low gas temperature, and abundant active particle under atmospheric pressure have been widely investigated in the past decades. Among these researches, the investigation on plasma parameters modulation represents a novel and budding focus. According to our previous works of DBD driven by dual-frequency, it has been demonstrated to provide a possible approach of controlling both averaged electron density and gas temperature independently based on the nonlinear frequency coupling effect. In this work, we used one-dimensional fluid model with semi-kinetic method, systemically studied the nonlinear behavior of the dual radio-frequency driven DBD. In term of the results of effective electron energy distribution function (EEDF) and electron impact ionization rate, it is found that the variations of power density and phase relationship provide separate control over the electron density, mean electron energy and gas temperature. Moreover, mode transitions are discussed in this paper. It is shown that there exist three kinds of discharge modes, which are governed by the nonlinear dynamics in the plasma sheath. Among which, the ionization in α mode is determined by the nonlinear coupling electron heating and local momentary charge density. While in γ mode, the ionization is caused mainly by the electron avalanches. In summary, the dual radio-frequency applied in DBD system is found to generate a nonlinear synergistic effect between two frequencies, which can provide a possible approach to enhance control over the plasma parameters.

The Ni/Pt core-shell nanoparticles with different shell thicknesses were prepared by composite coating of colloid particles and then characterized by HRTEM, EDS, XPS and XRD. Electrochemical properties for the oxygen electro-reduction reaction and methanol electro-oxidation were measured by potentiodynamic and cyclic voltammetry. The experimental results show that Ni/Pt core-shell nanoparticles are spherical and the mean particle size of Ni1-Pt0.067 is about 7 nm with shell thickness of 1 nm. Compared with Pt/C, Ni/Pt core-shell nanoparticels possess higher activity. Ni1-Pt0.067/C has the highest catalytic activity in these prepared catalysts with different thickness, and its peak current density can reach 143.06 mA/mg in 0.5 mol/L H2SO4 solution, 1.4 times of that of Pt/C for O2 electro-reduction reaction. Peak current density of Ni1-Pt0.067/C for methanol electro-oxidation reaches 538.3 mA/mg in 0.5 mol/L H2SO4+1.0 mol/L CH3OH solution, which is 5.2 times of that of Pt/C. Based on 1 mg Pt, the specific mass activity of Ni1-Pt0.067/C is 30-fold higher than that of Pt/C nanoparticles.

In this work involving an atmospheric dielectric barrier discharge system, the feasibility of independence control of key plasma parameters through strategic modulation of applied dual-frequency excitation sources is demonstrated. In this paper, a one-dimensional fluid model with semi-kinetic method has been used to investigate the discharge properties of atmospheric dielectric barrier discharge by using 200 kHz/13.56 MHz excitations. Bearing good consistency and coherence with experimental results, the electrical characteristics and typical electron dynamics are studied numerically. It is revealed that the application of the high frequency excitation can restrain the increment of the low frequency current component and is effective in preventing the discharge from transitioning to a filamentary mode. This method then suggests and enables possible approaches to obtain discharges with good stability in described DBD systems.

The dielectric barrier discharge (DBD) is a promising technology to generate high density and uniform cold plasmas in atmospheric pressure gases. The effective independent tuning of key plasma parameters is quite important for both application-focused and fundamental studies. In this paper, based on a one-dimensional fluid model with semi-kinetics treatment, numerical studies of ionization asymmetry effects on the properties modulation of atmospheric DBD sustained by tailored voltage waveforms are reported. The driving voltage waveform is characterized by an asymmetric-slope fundamental sinusoidal radio frequency signal superimposing one or more harmonics, and the effects of the number of harmonics, phase shift, as well as the fluctuation of harmonics on the sheath dynamics, impact ionization of electrons and key plasma parameters are investigated. The results have shown that the electron density can exhibit a substantial increase due to the effective electron heating by a spatially asymmetric sheath structure. The strategic modulation of harmonics number and phase shift is capable of raising the electron density significantly (e.g., nearly three times in this case), but without a significant increase in the gas temperature. Moreover, by tailoring the fluctuation of harmonics with a steeper slope, a more profound efficiency in electron impact ionization can be achieved, and thus enhancing the electron density effectively. This method then enables a novel alternative approach to realize the independent control of the key plasma parameters under atmospheric pressure.

Plasma ionization, excitation, mode transitions and associated electron heating mechanisms in atmospheric pressure dielectric barrier discharges (DBD) driven by dual radio frequency sources are investigated in this paper. The electrons are found to be heated mainly by the high frequency component in the plasma bulk when discharged in α mode. On the contrary, the low frequency component is primarily responsible for heating in the sheath which is caused by intense motion in the sheath. It was also found that variation of the lower frequency component ratio could effectively modulate the electron energy distribution as determined from time averaged EEDF. The results above have demonstrated that the independent control of plasma parameters via non-linear synergistic effect between the dual frequency sources can be achieved through reasonable selection of processing parameters.

The Pt-Ru-Ho/C catalysts for methanol electro-oxidation have been prepared by pulse electro-deposition method. The activities of catalysts were characterized by cyclic voltammetry (CV) and electrochemical impedance spectrum (EIS). The microstructure and composition of the catalysts were characterized by XRD, EDS and XPS. The results show that Pt-based alloy nano-particles supported on carbon black consist of Pt, Ru, Ho elements, and the particle size and the specific surface of catalysts are about 3.5 nm and 73.3 m2·g−1, respectively. The electro-catalytic activity of Pt-Ru/C can markedly be improved by doping with Ho. The optimum mole fraction in Pt-Ru-Ho alloy nano-particle is nPt:nRu:nRu=1:1:0.2. Tafel constant a for Pt-Ru-Ho0.2/C is lower than that of Pt-Ru/C. The reaction order and the active energy of the methanol electro-oxidation are 0.17 and 28.4 kJ·mol−1, respectively.

Based on the test data, survey data and the real-time monitoring data, this paper makes the Tangjiao #1 cohesive landslide in Three Gorges Area to be the research object, analyzing and studying the impact of reservoir water level fluctuation rates on stability of typical cohesive colluvial landslide with the help of the SEEP/W and SLOPE/W of Geoscience software GeoStudio. The results show that the impact of changing reservoir level on reservoir landslide stability is controlled by a variety of factors, including the hydrodynamic pressure, hydrostatic pressure, and uplift force, physical and mechanical properties (c, φ value change) and the stability trend depends on the dominant factor(s).