Spectral properties of photon pairs generated by spontaneous four wave mixing in inhomogeneous photonic crystal fibers

The photonic crystal fiber (PCF) is one of the excellent media for generating photon pairs via spontaneous four wave mixing. Here we study how the inhomogeneity of PCFs affect the spectral properties of photon pairs from both the theoretical and experimental aspects. The theoretical model shows that the photon pairs born in different place of the inhomogeneous PCF are coherently superposed, and a modulation in the broadened spectrum of phase matching function will appear, which prevents the realization of spectral factorable photon pairs. In particular, the inhomogeneity induced modulation can be examined by measuring the spectrum of individual signal or idler field when the asymmetric group velocity matching is approximately fulfilled. Our experiments are performed by tailoring the spectrum of pulsed pump to satisfy the specified phase matching condition. The observed spectra of individual signal photons, which are produced from different segments of the 1.9 m inhomogeneous PCF, agree with the theoretical predictions. The investigations are not only useful for fiber based quantum state engineering, but also provide a dependable method to test the homogeneity of PCF.Comment: to appear in Phys. Rev.

Tire pyrolysis char: Processes, properties, upgrading and applications

Waste tires are solid wastes with large annual output and with the potential for great harm to the environment. The pyrolysis of waste tires can recycle energy and produce reusable products. Although there are many reviews in the literature in regard to the pyrolysis characteristics of waste tires, no one paper focuses on reviewing and summarizing the tire char. This paper critically appraises the achievements of earlier reports and literature and assesses the current state-of-the-art for the production and application of tire char from waste tires. Initially, the thermal decomposition behavior of different tire rubbers is discussed and compared where it is shown that the different components of waste tire rubber have different thermal degradation characteristics. The influencing factors on the yield and quality of tire char are discussed and assessed in terms of different pyrolysis reactors and technologies, tire type and composition, and a range of pyrolysis process conditions. The composition of the waste tire and pyrolysis conditions are the main factors affecting the distribution of pyrolysis products. Pyrolysis technology and reactor equipment also have an effect on the distribution of pyrolysis products. The physical and chemical structural characteristics of tire char are critically reviewed in detail, including a comparison of the fundamental differences with commercial carbon black and modified tire char (physical activation and chemical activation). Finally, high-value application fields and developmental prospects of tire char are summarized. Through extensive literature review, a novel development was that tire char could be used as a source of gra-phene. The economic analysis of the various tire char applications should be one of the main research directions in the future. The keynote of this review is to promote intensification of waste tire recycling and treatment so that more tire char can be obtained from waste tire pyrolysis and thereby be reused in different applications to obtain more value.This project has received funding from the Science and Technology Exchange Project of China Ministry of Science and Technology (2021- 12-2) and Education Cooperation Project between China and Central Eastern European Countries (2021086) and Shaanxi Provincial Natural Science Foundation Research Program Shaanxi Coal Joint Funding (2019JLZ-12)

Oily sludge catalytic pyrolysis combined with fine particle removal using a Ni-ceramic membrane

Pyrolysis is one of the effective technology for oily sludge treatment and energy recovery. However, pyrolysis of oily sludge generates solid particles which are taken away from the reactor by gas, causing blockage in downstream equipment and reducing the quality of pyrolysis oil and gas. A study on the clean catalytic pyrolysis of oily sludge was carried out, by incorporating a ceramic membrane with or without Ni inside the pyrolysis reactor. It aims to investigate the effect of ceramic membrane on oily sludge pyrolysis and particulate removal. The yield of the pyrolysis gas produced from the reaction with Ni-ceramic membrane is 31.46 L/kg, while the recovery rate of pyrolysis oil is 48.21%. On the contrary, the yield of the pyrolysis gas produced from the reaction with blank ceramic membrane is 17.92 L/kg, while the recovery rate of pyrolysis oil is 62.63%. The particulate matter content in gas without and with Ni-ceramic membrane are 2.74 and 0.07 mg/L. The particulate matter content in oil without and with Ni-ceramic membrane are 3708.9 and 156.7 mg/L, respectively. Results indicated that the Ni catalyst loading on the ceramic membrane could improve the yield of the pyrolysis gas and remove the fine particles effectively. In addition, a long-time catalytic pyrolysis experiment was carried out, with the feeding speed of 4.17 g/min and the reaction temperature of 500 °C. It was found from the set conditions that the Ni-ceramic membrane could be used continuously for 420 min

Biomass-based carbon materials for CO2 capture:A review

Carbon capture and sequestration technologies are essential to reduce CO2 emissions which are responsible for global warming. Carbon-based materials can play an important role in the reduction of CO2 emissions. These materials are normally produced from biomass through technologies such as pyrolysis and hydrothermal carbonization. The type of biomass feedstock and biomass conversion conditions can significantly affect the textual properties and surface chemistry of the carbon materials. Various modification methods such as material activation or N-doping can improve the properties of carbon materials to obtain better CO2 capture effects. This review summarizes recently reported research in the areas of using biomass-based materials for CO2 capture. The technologies of biomass conversion to carbon materials and modification of the carbon materials are critically analyzed. Meanwhile, the mechanisms of the CO2 capture process and research of different modification carbon materials for CO2 capture are also discussed. Finally, potential future research directions are suggested to promote carbon capture using biomass-based materials

Activity of bimetallic PdIn/CeO₂ catalysts tuned by thermal reduction for improving methanol synthesis via CO₂ hydrogenation

Synergistic Pd–In2O3 catalysts are promising candidates for producing methanol via CO2 hydrogenation, and the metal phases in them can be tuned by thermal reduction treatment affecting the catalytic activity significantly. This work presents a comprehensive investigation to gain an insight into the effect of thermal reduction temperature on the variation and interaction of Pd and In2O3 phases supported on CeO2 (viz., PdIn/CeO2) and their correlations with CO2 hydrogenation toward methanol synthesis. The findings show that Pd/In-rich PdIn alloys and In2O3 with relatively strong interaction are key phases (by reducing the PdIn/CeO2 at 300°C) for promoting methanol formation, leading to a high selectivity to methanol at 78.9% and space–time yield (STY) of 3.6 gCH3OH gPdIn−1 h−1. A further increase in reduction temperature (from 300 to 500°C) promoted the formation of homogenized PdIn intermetallic alloys with significantly poor ability for H2 dissociation and CO2 activation, and hence poor methanol yield

Biomass volatiles reforming by integrated pyrolysis and plasma-catalysis system for H2 production: Understanding roles of temperature and catalyst

Biomass utilization is considered a carbon–neutral way to simultaneously tackle the energy crisis and environmental contamination. Challenges still exist to hinder its application, such as low products yield, tar blockage, harsh condition and inferior stability. This paper aims to study whether the newly developed integrated pyrolysis and plasma-catalysis system can be applied into practice of H2 production from real biomass volatiles, and to understand roles of temperature and catalyst. The experiments were performed in a two-stage reactor embedded with a coaxial dielectric barrier discharge plasma zone. Impacts of operating conditions (i.e. discharge power, steam input, heat supply and catalyst packing) on H2 production were investigated. The results show that proper input of discharge power and steam can promote H2 production. Heating supply is recognized as two different effects on plasma-only and plasma-catalysis systems, since reaction temperature elevation acts as inhibitor to plasma characters and cut down the contribution of plasma reforming. After packing bimetallic Ni-Fe/γ-Al2O3 catalyst into plasma, optimal 47.65 mmol/g of H2 can be attained at reforming temperature of 500 ℃, with synergy effects observed. Plasma-catalysis system also outperformed in tar cracking, tar elimination and stability test, attributed to plasma assistance. This work provides an alternative to construct a new plasma-catalysis process for H2 production from biomass volatiles or to couple plasma technology with existing biomass conversion industries for preferable energy and fuel production, highlighting its promising commercialization prospects

Enhanced hydrogen production using a tandem biomass pyrolysis and plasma reforming process

Converting biomass into energy and fuels is considered a promising strategy for replacing the exhaustible fossil fuels. In this study, we report on a tandem process that combines cellulose pyrolysis and plasma-assisted reforming for H-2 production. The hybrid pyrolysis/plasma reforming process was carried out in a two-stage reaction system incorporating a coaxial dielectric barrier discharge (DBD) plasma reactor. The effects of discharge power, steam, reforming temperature, and catalyst on the reaction performance were investigated. The results show that low temperatures are preferred in the non-catalytic plasma reforming process, whereas high temperatures are desired to achieve a high H-2 yield and a high H-2 selectivity in the plasma-catalytic reforming system. The synergistic effect of plasma catalysis was dominant in the plasma-catalytic reforming process at 250 degrees C. In contrast, the catalyst, rather than the plasma, played a dominant role in the plasma-catalytic reforming at higher temperatures (550 degrees C). Using Ni-Co/Al(2)O3 at a reforming temperature of 550 degrees C, a high H-2 yield of 26.6 mmol/g was attainted, which was more than 8 times and about 100% greater than that obtained using plasma alone and catalyst alone, respectively. This work highlights the potential of non-thermal plasmas in lowtemperature biomass conversion.European Union [823745]; Science and Technology Ex-change Project of the Chinese Ministry of Science and Technology [2021-12-2]; Education Cooperation Project between China and Central Eastern European Countries [2021086]; British Council Newton Fund Institutional Links Grant [623389161]; Scientific and Technological Research Council of Turkey (TUBITAK) [219M123]; Chinese Scholarship Council; University of LiverpoolThis project has received the funding from the European Union's Horizon 2020 Research and Innovation Programme under the Marie Sklodowska Curie Grant Agreement (No. 823745) . C. Quan and N. Gao gratefully acknowledge funding from the Science and Technology Ex-change Project of the Chinese Ministry of Science and Technology (No. 2021-12-2) and the Education Cooperation Project between China and Central Eastern European Countries (No. 2021086) . X. Tu gratefully acknowledges the British Council Newton Fund Institutional Links Grant (No. 623389161) . J. Yanik gratefully acknowledges funding from the Scientific and Technological Research Council of Turkey (TUBITAK Project Contract no. 219M123) . W. Wang thanks the University of Liverpool and the Chinese Scholarship Council for funding this PhD

Analysis of hydrogen production potential from waste plastics by pyrolysis and in line oxidative steam reforming

[EN] A study was carried out on the valorization of different waste plastics (HDPE, PP, PS and PE), their mixtures and biomass/HDPE mixtures by means of pyrolysis and in line oxidative steam reforming. A thermodynamic equilibrium simulation was used for determining steam reforming data, whereas previous experimental results were considered for setting the pyrolysis volatile stream composition. The adequacy of this simulation tool was validated using experimental results obtained in the pyrolysis and in line steam reforming of different plastics. The effect the most relevant process conditions, i.e., temperature, steam/plastic ratio and equivalence ratio, have on H-2 production and reaction enthalpy was evaluated. Moreover, the most suitable conditions for the oxidative steam reforming of plastics of different nature and their mixtures were determined. The results obtained are evidence of the potential interest of this novel valorization route, as H-2 productions of up to 25 wt% were obtained operating under autothermal conditions.This work was carried out with the financial support from Spain's ministries of Science, Innovation and Universities (RTI2018-098283-JI00 (MCIU/AEI/FEDER, UE)) and Science and Innovation (PID2019-107357RB-I00 (MCI/AEI/FEDER, UE)), the European Union's Horizon 2020 research and innovation programme under the Marie SklodowskaCurie grant agreement No. 823745, and the Basque Government (IT1218-19 and KK-2020/00107)

Optimizing drip fertigation at different periods to improve yield, volatile compounds and cup quality of Arabica coffee

How to improve and regulate coffee bean yield and quality through split fertilization in the whole life cycle of coffee is still unclear and deserves further study. A field experiment of 5-year-old Arabica coffee trees was conducted for 2 consecutive years from 2020 to 2022. The fertilizer (750 kg ha-1 year-1, N-P2O5-K2O:20%-20%-20%) was split in three times at early flowering (FL), the berry expansion (BE), and the berry ripening (BR). Taking equal fertilization throughout the growth cycle (FL250BE250BR250) as the control check, variable fertilizations including FL150BE250BR350, FL150BE350BR250, FL250BE150BR350, FL250BE350BR150, FL350BE150BR250, and FL350BE250BR150. Leaf net photosynthetic rate (Anet), stomatal conductance (gs), transpiration rate (Tr), leaf water use efficiency (LWUE), carboxylation efficiency (CE), partial factor productivity of fertilizer (PFP), bean yield, crop water use efficiency (WUE), bean nutrients, volatile compounds and cup quality, and the correlation of nutrients with volatile compounds and cup quality was evaluated. FL350BE250BR150 had the maximum Anet and gs, followed by FL250BE350BR150. The highest dry bean yield and WUE were obtained from FL250BE350BR150, which increased by 8.86% and 8.47% compared with FL250BE250BR250 in two-year average. The ash, total sugar, fat, protein, caffeine and chlorogenic acid in FL250BE350BR150 were 6.47%, 9.48%, 3.60%, 14.02%, 4.85% and 15.42% higher than FL250BE250BR250. Cluster analysis indicated FL150BE350BR250, FL250BE350BR150, FL350BE150BR250 and FL350BE250BR150 under medium roasted degree increased pyrazines, esters, ketones and furans, FL150BE350BR250 and FL250BE350BR150 under dark roasted degree increased ketones and furans. The aroma, flavor, acidity and overall score of medium roasted coffee were higher than dark roasted coffee, while the body score of dark roasted coffee was higher than medium roasted coffee. The nutrient contents were correlated with the volatile compounds and cup quality. TOPSIS indicated that FL250BE350BR150 was the optimal fertilization mode in the xerothermic regions. The obtained optimum fertilization mode can provide a scientific basis for coffee fertilization optimization and management

Evaluating how lodging affects maize yield estimation based on UAV observations

Timely and accurate pre-harvest estimates of maize yield are vital for agricultural management. Although many remote sensing approaches have been developed to estimate maize yields, few have been tested under lodging conditions. Thus, the feasibility of existing approaches under lodging conditions and the influence of lodging on maize yield estimates both remain unclear. To address this situation, this study develops a lodging index to quantify the degree of lodging. The index is based on RGB and multispectral images obtained from a low-altitude unmanned aerial vehicle and proves to be an important predictor variable in a random forest regression (RFR) model for accurately estimating maize yield after lodging. The results show that (1) the lodging index accurately describes the degree of lodging of each maize plot, (2) the yield-estimation model that incorporates the lodging index provides slightly more accurate yield estimates than without the lodging index at three important growth stages of maize (tasseling, milking, denting), and (3) the RFR model with lodging index applied at the denting (R5) stage yields the best performance of the three growth stages, with R2 = 0.859, a root mean square error (RMSE) of 1086.412 kg/ha, and a relative RMSE of 13.1%. This study thus provides valuable insight into the precise estimation of crop yield and demonstra\tes that incorporating a lodging stress-related variable into the model leads to accurate and robust estimates of crop grain yield