Mechanism of K/Ni Etching for Biochar-H_(2)O Gasification

Biomass-H_(2)O gasification is a complex thermochemical reaction,including three processes of volatile removal:homogeneous/heterogeneous reforming,biochar gasification and etching.The rate-determining step is biochar-H_(2)O gasification and etching so the DFT is carried out to see the catalytic role of different metal elements(K/Ni)in the zigzag biochar model.The calculation results show that the gasification of biochar-H_(2)O needs to go through four processes:dissociative adsorption of water,hydrogen transfer(hydrogen desorption,hydrogen atom transfer),carbon dissolution and CO desorption.The energy barrier indicated that the most significant step in reducing the activation energy of K is reflected in the hydrogen transfer step,which is reduced from 374.14 kJ/mol to 152.41 kJ/mol;the catalytic effect of Ni is mainly reflected in the carbon dissolution step,which is reduced from 122.34 kJ/mol to 84.8 kJ/mol.The existence of K causes the edge to have a stronger attraction to H and does not destroy theπbonds of biochar molecules.The destruction ofπbonds is mainly due to the role of H free radicals,while the destruction ofπbonds will lead to easier C-C bond rupture.Ni shows a strong attraction to O in OH,which forms strong Ni-O chemical bonds.Ni can also destroy the aromatic structure directly,making the gasification easier to happen.This study explored the catalytic mechanism of K/Ni on the biochar-H_(2)O gasification at the molecular level and looked forward to the potential synergy of K/Ni,laying a foundation for experimental research and catalyst design.

The First Isolation of a Cyanophage-Synechococcus System from the East China Sea

A cyanophage strain and its host Synechococcus were isolated from the East China Sea. The host Synechococcus sp. S J01 was characterized by its 16S rRNA, ITS, andpsbA gene sequences as well as by its morphological appearance and pigmentation. The cyanophage, strain S-SJ2, was able to cause a lytic infection of the coastal Synechococcus. TEM of negative-stained specimens showed that the phage isolate has an isometric head with a diameter of 68 nm and a long tail with a length of 280 nm. The cyanophage-Synechococcus system from the East China Sea shares many properties with other marine cyanophage-Synechocoecus systems worldwide.

30-W supercontinuum generation based on ZBLAN fiber in an all-fiber configuration

We report an all-fiberized 30-W supercontinuum(SC) generation in a piece of ZrF4-BaF2-LaF3-AlF3-NaF(ZBLAN) fiber. The pump source is a thulium-doped fiber amplifier(TDFA) with broadband output spectrum spanning the 1.9 to 2.6 μm region. The used ZBLAN fiber has a core diameter of 10 μm, and was directly fusion-spliced to the pigtail of the TDFA without using a traditional mode field adapter(MFA) or a piece of transition fiber. Such a low-loss and robust fusion splice joint, together with a robust AlF3-fiber-based endcap,enables efficient and high-power SC generation in the ZBLAN fiber. An SC with an average power up to 30.0 W and a spectral coverage of 1.9–3.35 μm with 20-dB bandwidth of 1.92–3.20 μm was obtained. Moreover, an SC with a broader spectrum was achieved by raising the pump pulse peak power(via reducing the duty ratio of the pump laser pulse). An SC with an output power of 27.4 W and a spectral coverage of 1.9–3.63 μm(with 20-dB bandwidth of 1.92–3.47 μm) was obtained, as well as an SC with output power of 24.8 W and a spectral coverage of 1.9–3.70 μm(with 20-dB bandwidth of 1.93–3.56 μm). The power conversion efficiency was measured as>69%. To the best of the authors’ knowledge, this research demonstrates the record output power of SC lasers based on ZBLAN fibers, paving the way for broadband and efficient multi-tens-of-watts SC generation in softglass fibers.

Dynamic Response of Phragmites australis and Suaeda salsa to Climate Change in the Liaohe Delta Wetland

Because of its unique geographical location and ecological function, the Liaohe Delta Wetland is important in maintaining regional ecological balance and security. Monitoring and evaluating changes in the wetland are therefore of great importance. We used medium-and high-resolution satellite data, meteorological station data, and site measurement data to analyze changes in the area and spatial distribution of Phragmites australis and Suaeda salsa in the Liaohe Delta Wetland from 1998 to 2017, as well as their growth response to the climate change. The results showed that during 1998–2017, the areas of both P. australis and S. salsa wetlands alternated through periods of decreasing,increasing, and then decreasing trends. The annual change in the area and spatial distribution range of S. salsa fluctuated more than that of P. australis. The annual variation of normalized difference vegetation index(NDVI) in P. australis wetland showed an upward trend from 1998 to 2017. The area of P. australis cover that was improved, unchanged, and decreased accounted for 81.8%, 12.3%, and 5.9%, respectively, of the total area;evaporation and wind speed were the main meteorological factors affecting the NDVI;and contribution rates of the climate change and human activities to the NDVI were 73.2% and 26.8%, respectively. The area with vegetation cover being mainly S.salsa that was improved, unchanged, and decreased accounted for 63.3%, 18.3%, and 18.4%, respectively, of the total area;and no meteorological factors significantly affected the NDVI of S. salsa in the region. The interaction between vegetation growth and meteorological factors may help to explain the increasing trend in vegetation cover.The improvement in wetland vegetation also led to carbon sequestration and an increase in sequestration capacity.

Spectrally flat supercontinuum generation in a holmium-doped ZBLAN fiber with record power ratio beyond 3μm

A spectrally flat mid-infrared supercontinuum(MIR-SC) spanning 2.8–3.9 μm with a maximum output power of 411 mW was generated in a holmium-doped ZBLAN fiber amplifier(HDZFA). A broadband fiber-based SC covering the 2.4–3.2 μm region was designed to seed the amplifier. Benefiting from the broadband seed laser,the obtained SC had a high spectral flatness of 3 dB over the range of 2.93–3.70 μm(770 nm). A spectral integral showed that the SC power beyond 3 μm was 372 mW, i.e., a power ratio of 90.6% of the total power. This paper,to the best of our knowledge, not only demonstrates the first spectrally flat MIR-SC directly generated in fluoride fiber amplifiers, but also reports the highest power ratio beyond 3 μm obtained in rare-earth-doped fluoride fiber until now.

Generation rate scaling: the quality factor optimization of microring resonators for photon-pair sources

To achieve photon-pair generation scaling, we optimize the quality factor of microring resonators for efficient continuous-wave-pumped spontaneous four-wave mixing. Numerical studies indicate that a high intrinsic quality factor makes high pair rate and pair brightness possible, in which the maximums take place under overcoupling and critical-coupling conditions, respectively. We fabricate six all-pass-type microring resonator samples on a silicon-on-insulator chip involving gap width as the only degree of freedom. The signal count rate, pair brightness,and coincidence rate of all the samples are characterized, which are then compared with the modified simulations by taking the detector saturation and nonlinear loss into account. Being experimentally validated for the first time to the best of our knowledge, this work explicitly demonstrates that reducing the round-trip loss in a ring cavity and designing the corresponding optimized gap width are more effective to generate high-rate or high-brightness photon pairs than the conventional strategy of simply increasing the quality factor.

Transport of a volatile contaminant in a free-surface wetland flow

Presented in this paper is an analytical study of a pulsed volatile contaminant emission into a free-surface wetland flow. A simplified model is given for contaminant transport under the combined action of advection, mass dispersion, apparent reaction, and volatilization at the free water surface. The effect of periodic apparent reaction on contaminant transport is separated from the hydraulic effect via an extended transformation, with a limiting case covering the known transformation for constant apparent reaction rate. The analytical solutions of zeroth and first order concentration moments are rigorously derived and illustrated. It was found that the amount of contaminant decreases from the bottom bed to the free-surface under volatilization, and the total amount of contaminant decays with time. It was also found that the moving speed of the mass center of the whole contaminant cloud increases, as the ratio of volatilization coefficient to vertical effective mass dispersivity increases.

The influence of the corporate social responsibility disclosures on consumer brand attitudes under the impact of CO VID-19

This study focuses on the use of we-media by small-and medium-sized enterprises(SMEs)to disclose internal corporate social responsibility(ICSR)under the impact of the 2019 novel coronavirus disease(COVID-19).Study 1 interprets the catalyst effect of COVID-19 on the externalization of SMEs'ICSR.The fuzzy grading evaluation method is initially verified.Under the impact of COVID-19,SMEs fulfilling their ICSR can enhance consumer brand attitudes.Study 2 uses a structural equation model and empirical analysis of 946 effective samples and finds that consumers perceive the self-sacrifice of corporations during the coronavirus disease period.SMEs can fulfill their ICSR to enhance the internal explanation mechanism of consumer brand attitudes and the moderating role of enterprise losses.