The underlying mechanism of variety–water–nitrogen–stubble damage interactions on yield formation in ratoon rice with low stubble height under mechanized harvesting

Agronomic measures are the key to promote the sustainable development of ratoon rice by reducing the damage from mechanical crushing to the residual stubble of the main crop, thereby mitigating the impact on axillary bud sprouting and yield formation in ratoon rice. This study used widely recommended conventional rice Jiafuzhan and hybrid rice Yongyou 2640 as the test materials to conduct a four-factor block design field experiment in a greenhouse of the experimental farm of Fujian Agricultural and Forestry University, China from 2018 to 2019.The treatments included fertilization and no fertilization, alternate wetting and drying irrigation and continuous water flooding irrigation, and plots with and without artificial crushing damage on the rice stubble. At the same time, a 13C stable isotope in-situ detection technology was used to fertilize the pot experiment. The results showed significant interactions among varieties, water management, nitrogen application and stubble status.Relative to the long-term water flooding treatment, the treatment with sequential application of nitrogen fertilizer coupled with moderate field drought for root-vigor and tiller promotion before and after harvesting of the main crop, significantly improved the effective tillers from low position nodes. This in turn increased the effective panicles per plant and grains per panicle by reducing the influence of artificial crushing damage on rice stubble and achieving a high yield of the regenerated rice. Furthermore, the partitioning of 13C assimilates to the residual stubble and its axillary buds were significantly improved at the mature stage of the main crop, while the translocation rate to roots and rhizosphere soil was reduced at the later growth stage of ratooning season rice. This was triggered by the metabolism of hormones and polyamines at the stem base regulated by the interaction of water and fertilizer at this time. We therefore suggest that to achieve a high yield of ratoon rice with low stubble height under mechanized harvesting, the timely application of nitrogen fertilizer is fundamental,coupled with moderate field drying for root-vigor preservation and tiller promotion before and after the mechanical harvesting of the main crop.

Catalytic effect in lithium metal batteries: From heterogeneous catalyst to homogenous catalyst

Lithium metal batteries are regarded as prominent contenders to address the pressing needs owing to the high theoretical capacity.Toward the broader implementation,the primary obstacle lies in the intricate multi-electron,multi-step redox reaction associated with sluggish conversion kinetics,subsequently giving rise to a cascade of parasitic issues.In order to smooth reaction kinetics,catalysts are widely introduced to accelerate reaction rate via modulating the energy barrier.Over past decades,a large amount of research has been devoted to the catalyst design and catalytic mechanism exploration,and thus the great progress in electrochemical performance has been realized.Therefore,it is necessary to make a comprehensive review toward key progress in catalyst design and future development pathway.In this review,the basic mechanism of lithium metal batteries is provided along with corresponding advantages and existing challenges detailly described.The main catalysts employed to accelerate cathode reaction with emphasis on their catalytic mechanism are summarized as well.Finally,the rational design and innovative direction toward efficient catalysts are suggested for future application in metal-sulfur/gas battery and beyond.This review is expected to drive and benefit future research on rational catalyst design with multi-parameter synergistic impacts on the activity and stability of next-generation metal battery,thus opening new avenue for sustainable solution to climate change,energy and environmental issues,and the potential industrial economy.

某船舵桨装置安装

结合实船安装过程中精确度校装控制遇到的难点,制定船舶整体推进舵桨装置安装的改进和解决方案,确保舵桨装置安装过程顺利,为今后同类型推进舵桨装置的安装提供依据。

The magnetic field design of a solenoid for the cold-cathode Penning ion source of a miniature neutron tube

A high-yield and beam-stable neutron tube can be applied in many fields.It is of great significance to the optimal external magnetic field intensity of the cold-cathode Penning ion source(PIS)and precisely controls the movement of deuterium(D),tritium(T)ions and electrons in the source of the neutron tubes.A cold-cathode PIS is designed based on the solenoidal magnetic field to obtain better uniformity of the magnetic field and higher yield of the neutron tube.The degree of magnetic field uniformity among the magnetic block,double magnetic rings and solenoidal ion sources is compared using finite element simulation methods.Using drift diffusion approximation and a magnetic field coupling method,the plasma distribution of hydrogen and the relationship between plasma density and magnetic field intensity at 0.06 Pa pressure and a solenoid magnetic field are obtained.The results show that the solenoidal ion source has the most uniform magnetic field distribution.The optimum magnetic field strength of about 0.1 T is obtained in the ion source at an excitation voltage of 1 V.The maximum average number density of monatomic hydrogen ions(H+)is 1×108 m−3,and an ion-beam current of about 14.51μA is formed under the−5000 V extraction field.The study of the solenoidal magnetic field contributes to the understanding of the particle dynamics within the PIS and provides a reference for the further improvement of the source performance of the neutron tube in the future.

班组精细化星级质量管控模式的研究与应用

主要从班组精细化星级质量管控模式的研究与应用的角度,介绍如何通过加强班组管理,提升班组自主质量管理水平,解决人员流动快导致的施工质量不稳定,生产效率低等问题,实现提质增效的目的。

A bifunctional and recyclable catalyst:Amine and ionic liquid grafting on MOFs for the one-pot synthesis of N-aryl oxazolidin-2-ones

A bifunctional heterogeneous catalyst was designed and synthesized,denoted DMEDA/IL–NH2-MIL-101.The structure and physical-chemical characterization of DMEDA/IL–NH2-MIL-101 and its precursors were characterized by SEM,N2 adsorption-desorption,XPS,FT-IR,PXRD,elemental analysis,and TGA techniques.The date showed that the two catalytic components of N,N-dimethylethylenediamine(DMEDA)and 1-butyl-3-methylimidazolium bromide(BmimBr)were chemically immobilized in NH2-MIL-101 nanocages.The amine of DMEDA was grafted onto carrier NH2-MIL-101 by N–Cr coordinate covalent bonds and the ionic liquid of BmimBr(IL(Br-))was anchored in the NH2-MIL-101 nanocages by'ship-in-a-bottle'method,in which the amidogen of NH2-MIL-101 condensed with N,N-carbonyldiimidazole(CDI)firstly,and then alkylated with 1-bromo butane.This novel heterogeneous catalyst with two different active sites can efficiently catalyze the synthesis of N-aryl oxazolidin-2-ones from carbon dioxide(CO2),epoxides,and anilines in one-pot under mild solvent-free conditions.It not only showed good stability and recoverability after five cycles but also exhibited shape selectivity for the substrate due to the synergic catalysis of amine,ionic liquid,and NH2-MIL-101.This novel bifunctional material is a promising solid catalyst for the green synthesis of N-aryl oxazolidin-2-ones.

A Bifunctional Brønsted Acidic Deep Eutectic Solvent to Dissolve and Catalyze the Depolymerization of Alkali Lignin

Lignin is an abundant renewable macromolecular material in nature,and degradation of lignin to improve its hydroxyl content is the key to its efficient use.Alkali lignin(AL)was treated with Brønsted acidic deep eutectic solvent(DES)based on choline chloride and p-toluenesulfonic acid at mild reaction temperature,the structure of the lignin before and after degradation,as well as the composition of small molecules of lignin were analyzed in order to investigate the chemical structure changes of lignin with DES treatment,and the degradation mechanism of lignin in this acidic DES was elucidated in this work.FTIR and NMR analyses demonstrated the selective cleavage of the lignin ether linkages in the degradation process,which was in line with the increased content of phenolic hydroxyl species.XPS revealed that the O/C atomic ratio of the regenerated lignin was lower than that of the AL sample,revealing that the lignin underwent decarbonylation during the DES treatment.Regenerated lignin with low molecular weight and narrow polydispersity index was obtained,and the average molecular weight(Mw)decreased from 17680 g/mol to 2792 g/mol(130°C,3 h)according to GPC analysis.The lignin-degraded products were mainly G-type phenolics and ketones,and small number of aldehydes were also generated,the possible degradation pathway of lignin in this acidic DES was proposed.

关于船舶木甲板制作安装工艺及质量控制

木甲板作为主流的高档装饰材料,在国外民用高档豪华邮轮、木质帆船、游艇上已大量应用。目前由于国内邮轮、帆船发展起步较晚,在国内邮轮、帆船上较少采用,从而造成相关工艺的缺失和不足。但此次在国内某首制帆船的实际建造过程中相关工艺已大量应用,而随着民用航运的飞速发展,高标准装修材料上船已是大势所趋。因此,有必要制定一套标准工艺来填补该类型船舶建造领域的空白,提高木甲板的安装质量和精度,为木甲板的质量控制提供工艺支持。

常用渗透标准对工件表面要求的简析和验证

解析非荧光溶剂去除型渗透检测,对比NB/T 47013.5-2015《承压设备无损检测第5部分:渗透检测》[1]、CB/T3958-2004《船舶钢焊缝磁粉检测、渗透检测工艺和质量分级》[2]和DNVGL-CG-0051《DNV规范》[3]标准对检测表面要求有相当大的工性,但是也存在一定的差异,并通过具体试验验证,直观反映差异性对渗透检测效果的影响,为检测人员提供参考。

Simultaneously tuning structural defects and crystal phase in accordion-like Ti_(x)O_(2x−1)derived from Ti_(3)C_(2)T_(x)MXene for enhanced electromagnetic attenuation

Single Ti_(3)C_(2)T_(x)MXene(MTO)materials are not suitable for electromagnetic(EM)wave absorption due to their high conductivity and impedance mismatch.To address this issue,we ingeniously took advantage of easily oxidized characteristics of Ti_(3)C_(2)T_(x)MXene to establish structural defects and multiphase engineering in accordion-like TixO_(2x−1)derived from Ti_(3)C_(2)T_(x)MXene by a high-temperature hydrogen reduction process for the first time.Phase evolution sequences are revealed to be Ti_(3)C_(2)T_(x)MXene/anatase TiO_(2)→Ti_(3)C_(2)T_(x)MXene/rutile TiO_(2)→TixO_(2x−1)(1≤x≤4)during a hydrogen reduction reaction.Benefiting from conductance loss caused by hole motion under the action of an external electric field and heterointerfaces caused by interfacial polarization,the impedance match and EM attenuation capability of accordion-like TixO_(2x−1)absorbers derived from Ti_(3)C_(2)T_(x)MXene are superior to that of pristine Ti_(3)C_(2)T_(x)MXene/TiO_(2)materials.Additionally,simulated whole radar cross section(RCS)plots in different incident angular of the Ti_(3)C_(2)T_(x)MXene/rutile TiO_(2)product are lower than−20 dBm^(2),and the minimum RCS value can reach−43 dBm^(2),implying a great potential for practical applications in the EM wave absorption.Moreover,the relationship among charges,defects,interfaces,and EM performances in the accordion-like TixO_(2x−1)materials is systematically clarified by the energy band theory,which is suitable for the research of other MXene-derived semiconductor absorbing composites.

Controllable synthesis of mesoporous carbon hollow microsphere twined by CNT for enhanced microwave absorption performance

The low dielectric loss of mesoporous carbon hollow microsphere(PCHM)requires high filler loading(higher than 20 wt%)when it is used as microwave absorbers.In order to decrease the filler loading of PCHM,a new strategy for synergistic increase of polarization and conductive loss was developed by twining PCHM with carbon nanotube(CNT)according to theoretic calculation.By the optimization of CNT content,the minimum reflection coefficient was -34.6 dB with a filler loading of only 10 wt%,which was much lower than -2.1 dB of PCHM.In addition,the effective absorption bandwidth was 3.6 GHz at X band with a thickness of 2.8 mm.The enhanced microwave absorption performance can be ascribed to the unique combination of hollow PCHM and one-dimensional CNT with higher graphitization degree,leading to increase of conductivity and heterogeneous interfaces.As a result,the conductive loss increased from 0.12 to 2.27 and polarization loss increased from 0.15 to 0.67,achieving the balance between attenuation ability and impedance match.

Ultra-light, high flexible and efficient CNTs/Ti3C2-sodium alginate foam for electromagnetic absorption application

Ultra-light carboxylic functionalized multi-walled carbon nanotubes(CNTs-COOH) and Ti3C2 MXene hybrids modified sodium alginate(CNTs/Ti3C2-SA) based composite foams were prepared through ice-templated freeze-drying method. The microstructure of the synthesized CNTs/Ti3C2 hybrids and CNTs/Ti3C2-SA foams is characterized by the presence of CNTs inserted between MXene layers which prevents their restacking. The resultant CNTs/Ti3C2 hybrids exhibit a unique sandwich-like hierarchical structure. Scanning electron microscopy(SEM) images show that the CNTs/Ti3C2-SA foam exhibits a heterogeneous anisotropic microstructure and CNTs/Ti3C2 hybrids are homogeneously dispersed in the skeleton of the porous foam. In case that the content of the hybrids amounts 40 mg/cm^3, the CNTs/Ti3C2-SA foam possesses excellent electromagnetic(EM) absorption performance with a minimum reflection coefficient(RCmin) as low as-40.0 dB. In case of a sample thickness of 3.95 mm, the RCminreaches-24.4 dB and the effective absorption bandwidth covers the whole X band from 8.2 to 12.4 GHz. A control test shows that, with the same absorbent content, the CNTs/Ti3C2-SA foam exhibits a far better EM performance than that of CNT-free Ti3C2-SA foam.

Porous hybrid scaffold strategy for the realization of lightweight,highly efficient microwave absorbing materials

Exploring an advanced and efficient electromagnetic(EM) wave absorbing material by improving dielectric loss capacity and adjusting impendence matching is crucial yet challenging. Herein, the bacterial cellulose(BC) derived carbon aerogel(CA) with a robust nanofibrous network was used as a conductive loss scaffold to dissipate EM waves effectively, and the Zn O microparticles with excellent dielectric properties and low electrical conductivity were decorated on the scaffold to adjust dielectric parameters and impedance matching adequately. By using different zinc precursors, the tunable size and morphologies of Zn O crystals were obtained due to the growth rate of different crystallographic, including flowerlike, nanorod like, and cauliflower-like morphologies, which is beneficial to strong multiple reflections,intensive interfacial polarization, better impendence matching, as well as excellent maintenance of the hierarchical structure. Owing to the appropriate impendence matching and the considerable EM wave dissipation, the CA@ZnO composites achieve a superior EM absorbing performance with a broad effective absorbing bandwidth(whole X band) and a minimum reflection coefficient(-53.3 d B). This work paves a new way for developing lightweight and highly efficient EM absorbing materials comprising the carbon scaffold and semiconductor microparticles.

Effects of Power Inversion Spatial Only Adaptive Array on GNSS Receiver Measurements

The Spatial Only Processing Power Inversion(SOP-PI) algorithm is frequently used in Global Navigation Satellite System(GNSS) adaptive array receivers for interference mitigation because of its simplicity of implementation. This study investigates the effects of SOP-PI on receiver measurements for high-precision applications. Mathematical deductions show that if an array with a centro-symmetrical geometry is used, ideally,SOP-PI is naturally bias-free; however, this no longer stands when non-ideal factors, including array perturbations and finite-sample effect, are added. Simulations are performed herein to investigate how exactly the array perturbations affect the carrier phase biases, while diagonal loading and forward-backward averaging are proposed to counter the finite-sample effect. In conclusion, whether SOP-PI with a centro-symmetrical array geometry will satisfy the high precision demands mainly depends on the array perturbation degree of the element amplitude and the phase center.

Efficient Signal Separation Method Based on Antenna Arrays for GNSS Meaconing

As an effective deceptive interference technique for military navigation signals, meaconing can be divided into two main types: those that replay directly and those that replay after signal separation. The latter can add different delays to each satellite signal and mislead the victim receiver with respect to any designated position,thus has better controllability and concealment capability. A previous study showed there to be two main spatial processing techniques for separating military signals, whereby either multiple large-caliber antennas or antenna arrays are used to form multiple beams that align with all visible satellites. To ensure sufficient spatial resolution,the main lobe width of the antenna or beam must be sufficiently narrow, which requires the use of a large antenna aperture or a large number of array elements. In this paper, we propose a convenient and effective signal separation method, which is based on an antenna array with fewer elements. While the beam of the array is pointing to a specified satellite, the other satellite signals are regarded as interference and their power is suppressed to a level below the receiver's sensitivity. With this method, the number of array elements depends only on the number of visible satellites, thus greatly reducing the hardware cost and required processing capacity.

Visible-Light-Promoted Formation of C-C and C-P Bonds Derived from Evolution of Bromoalkynes under Additive-Free Conditions:Synthesis of 1,1-Dibromo-1-en-3-ynes and Alkynylphosphine Oxides

Main observation and conclusion The controllable achievement of C-C and C-P bond formations is developed via visible-light-promoted bromoalkyne dimerization or its further transformation with secondary phosphine oxides.The 1,1-dibromo-1-en-3-ynes are formed when bromoalkyne is exposed to visible-light.While alkynylphosphine oxides are generated when bromoalkynes are mixed with secondary phosphine oxides.