Achieving high conversion of syngas to aromatics

Realizing high CO conversion and high aromatics selectivity simultaneously in syngas-to-aromatics(STA)reaction is still challenging.Herein,we report a 57.5%CO conversion along with 74%aromatics selectivity over a composite catalyst consisting of Fe/ZnCr_(2)O_(4)(Fe modified ZnCr_(2)O_(4)spinel)oxide and H-ZSM-5 zeolite.Impregnation of only 3 wt%of Fe onto ZnCr_(2)O_(4)can remarkably increase CO conversion without sacrificing the aromatics selectivity.Oxygen vacancy concentration is improved after impregnating Fe.The highly dispersed iron carbide species is formed during the reaction over Fe/ZnCr_(2)O_(4)spinel oxide.The synergistic effect of oxygen vacancy and iron carbide results in a rapid formation of abundant oxygenated intermediate species,which can be continuously transformed to aromatics in H-ZSM-5.This study provides a new insight into the design of highly efficient catalyst for syngas conversion.

Highly Efficient Power Conversion from Salinity Gradients with Ion-Selective Polymeric Nanopores

A polymeric nanopore membrane with selective ionic transport has been proposed as a potential device to convert the chemical potential energy in salinity gradients to electrical power. However, its energy conversion efficiency and power density are often limited due to the challenge in reliably controlling the size of the nanopores with the conventional chemical etching method. Here we report that without chemical etching, polyimide （PI） membranes irradiated with GeV heavy ions have negatively charged nanopores, showing nearly perfect selectivity for cations over anions, and they can generate electrical power from salinity gradients. We further demonstrate that the power generation efficiency of the PI membrane approaches the theoretical limit, and the maximum power density reaches 130m W/m2 with a modified etching method, outperforming the previous energy conversion device that was made of polymeric nanopore membranes.

Highly efficient conversion from classical guided waves to topological chiral edge states

Electromagnetic topological chiral edge states mimicking the quantum Hall effect have attracted a great deal of attention due to their unique features of free backscattering and immunity against sharp bends and defects.However,the matching techniques between classical waveguides and the topological one-way waveguide deserve more attention for real-world applications.In this paper,a highly efficient conversion structure between a classical rectangular waveguide and a topological one-way waveguide is proposed and demonstrated at the microwave frequency,which efficiently converts classical guided waves to topological one-way edge states.A tapered transition is designed to match both the momentum and impedance of the classical guided waves and the topological one-way edge states.With the conversion structure,the waves generated by a point excitation source can be coupled to the topological one-way waveguide with very high coupling efficiency,which can ensure high transmission of the whole system(i.e.,from the source and the receiver).Simulation and measurement results demonstrate the proposed method.This investigation is beneficial to the applications of topological one-way waveguides and opens up a new avenue for advanced topological and classical integrated functional devices and systems.

Tunable circularly-polarized turnstile-junction mode converter for high-power microwave applications

Frequency tunability has become a subject of concern in the field of high-power microwave（HPM） source research.However, little information about the corresponding mode converter is available. A tunable circularly-polarized turnstilejunction mode converter（TCTMC） for high-power microwave applications is presented in this paper. The input coaxial TEM mode is transformed into TE（10） mode with different phase delays in four rectangular waveguides and then converted into a circularly-polarized TE（11） circular waveguide mode. Besides, the rods are added to reduce or even eliminate the reflection. The innovations in this study are as follows. The tunning mechanism is added to the mode converter, which can change the effective length of rectangular waveguide and the distance between the rods installed upstream and the closest edge of the rectangular waveguide, thus improving the conversion efficiency and bandwidth. The conversion efficiency of TCTMC can reach above 98% over the frequency range of 1.42 GHz–2.29 GHz, and the frequency tunning bandwidth is about 47%. Significantly, TCTMC can obtain continuous high conversion efficiency of different frequency points with the change of tuning mechanism.

Frequency Tunability and Slow-Wave Characteristics of a High-Efficiency Ridged MILO

A high-efficiency ridged magnetically insulated transmission line oscillator (RMILO) is proposed and investigated theoretically and numerically in this paper. In the RMILO, ridge-disk vanes are introduced to enhance the power efficiency. Theoretical investigation shows that the ridge-disk can enhance the coupling impedance of the slow-wave structure (SWS), and so enhance the power efficiency. Moreover, the ridge has a weak influence on frequency, so, it influences little on the tunability of the MILO. In simulation, when the applied voltage is increased to 807 kV, the RMILO can get the 3 dB tunable frequency range with 7.6 - 13.9 GHz and the 3 dB tuning bandwidth with 58.6% which has an increase of 27.6% compared with the conventional MILO. So, the tuning performance of the RMILO is more superior. Besides, the RMILO gets the maximum output power of 7.1 GW, the corresponding power efficiency is 22.6% and the frequency is 1.400 GHz. Furthermore, when the applied voltage is increased to 807 kV, high-power microwave with a power of 13.5 GW, frequency of 1.400 GHz, and ef?ciency of 24.5% is generated, which has an increase of 20.2% compared with the conventional MILO. The simulation results con?rm the ones predicted by theoretical analysis.

High CO methanation activity on zirconia-supported molybdenum sulfide catalyst

In this study, different methods were used to prepare MoO3/ZrO2 catalysts for sulfur resistant methanation reaction. It was found that MoO3/ZrO2 catalyst prepared by one-step co-precipitation method achieved high methanation performance. CO conversion could reach up to 90% on 25 wt% MoO3/ZrO2 catalyst, much higher than that on the conventional 25 wt% MoO3/Al2O3 catalyst. The Mo-based catalysts were characterized by XRF, XRD, Raman, BET, TEM and H2-TPR etc. It was found that MoO3 particles were highly dispersed on ZrO2 support for 25 wt% MoO3/ZrO2 catalyst prepared at 65-85℃ because of its relatively larger pore size, which contributed to a high CO conversion. Meanwhile, when MoO3 loading exceeded the monolayer coverage, the formed crystalline MoO3 and ZrM020g might block the micropores of the catalyst and make the methanation activity declined. These results are useful for preparing highly efficient catalyst for CO methanation process.

Rodlike nanomaterials from organic diradicaloid with high photothermal conversion capability for tumor treatment

Organic diradicaloids with unique open-shell structures and properties have been widely used in organic electronics and spintronics.However,their advantageous optical properties have been explored less in the biomedical field.In this work,the photothermal conversion behaviors of a boron-containing organic diradicaloid(BOD)are reported.BOD can assemble with 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-poly(ethylene glycol)to form rodlike nanoparticles(BOD NPs).These as-prepared BOD NPs exhibit high photothermal conversion capability and robust photothermal stability.Notably,they possess morphological superiority,which guarantees the effective photothermal therapy of tumors.This work thus demonstrates the promise of organic diradicaloids as efficient photothermal agents for biomedical applications.

An asymmetric broad waveguide structure for a 0.98-μm high-conversion-efficiency diode laser

A novel asymmetric broad waveguide diode laser structure was designed for high power conversion efficiency（PCE）.The internal quantum efficiency,the series resistance,and the thermal resistance were theoretically optimized.The series resistance and the thermal resistance were greatly decreased by optimizing the thickness of the P-waveguide and the P-cladding layers.The internal quantum efficiency was increased by introducing a novel strain-compensated GaAs0.9P0.1/InGaAs quantum well.Experimentally,a single 1-cm bar with 20% fill factor and 900 μm cavity length was mounted P-side down on a microchannel-cooled heatsink,and a peak PCE of 60% is obtained at 26.3-W continuous wave output power.The results prove that this novel asymmetric waveguide structure design is an efficient approach to improve the PCE.

A High Power Conversion Efficiency L-Band Erbium Doped Fiber Amplifier

By using two sections of erbium doped fiber and a fiber optical reflector, a novel, highly efficient L-band amplifier is demonstrated with significantly power-conversion-efficiency enhancement and the gain increasing of as much as 13 dB.

让语文课青春永葆

通过对当前高中语文课堂教学面临的困境的分析,力求探寻语文课堂的生命力所在。要让语文课堂青春永葆,应实施对话教学,构建和谐氛围;应精心准备教学,用魅力课堂吸引学生;注意课堂教学管理,促成教学目标的达成。

Design of a high-efficiency C-band backward wave oscillator

For practicability of the high power microwave source,a C-band backward wave oscillator（BWO） which has high conversion efficiency is designed.When the axial guiding magnetic field is 0.83 T,the electron energy and the beam current of the diode are respectively 80 keV and 2.1 kA,a microwave output power of 100 MW at 7.4 GHz microwave frequency with 65% conversion efficiency is achieved in simulation.

Kilowatt-level supercontinuum generation in a single-stage random fiber laser with a half-open cavity

The random distributed-feedback fiber laser(RFL) is a new approach to obtain a high-power stable supercontinuum(SC) source.To consider both structure simplification and high-power SC output,an innovative structure achieving a kilowatt-level SC output in a single-stage RFL with a half-open cavity is demonstrated in this paper.It consists of a fiber oscillator,a piece of long passive fiber and a broadband coupler,among which the broadband coupler acting as a feedback device is crucial in SC generation.When the system has no feedback,the backward output power is up to298 W under the pump power of 1185 W.When the feedback is introduced before the pump laser,the backward power loss can be reduced and the pump can be fully utilized,which could promote forward output power and conversion efficiency significantly.Under the maximum pump power of 1847 W,a 1300 W SC with spectrum ranging from 887 to1920 nm and SC conversion efficiency of 66% is obtained.To the best of our knowledge,it is the simplest structure used for high-power SC generation,and both the generated SC output power and the conversion efficiency are highest in the scheme of the half-opened RFL output SC.