With the growing integration of distributed energy resources(DERs),flexible loads,and other emerging technologies,there are increasing complexities and uncertainties for modern power and energy systems.This brings gre...With the growing integration of distributed energy resources(DERs),flexible loads,and other emerging technologies,there are increasing complexities and uncertainties for modern power and energy systems.This brings great challenges to the operation and control.Besides,with the deployment of advanced sensor and smart meters,a large number of data are generated,which brings opportunities for novel data-driven methods to deal with complicated operation and control issues.Among them,reinforcement learning(RL)is one of the most widely promoted methods for control and optimization problems.This paper provides a comprehensive literature review of RL in terms of basic ideas,various types of algorithms,and their applications in power and energy systems.The challenges and further works are also discussed.展开更多
Dear Editor Wheat powdery mildew, caused by Blumeria graminis f. sp. tritici （Bgt）, is a destructive disease of wheat throughout the world. One of the most important environmental-friendly and economical methods to ...Dear Editor Wheat powdery mildew, caused by Blumeria graminis f. sp. tritici （Bgt）, is a destructive disease of wheat throughout the world. One of the most important environmental-friendly and economical methods to reduce wheat loss caused by Bgt is to develop highly resistant varieties （Kuraparthy et al., 2007）. Pm21 from the wild species Haynaldia villosa （also known as Dasypyrum villosum） confers high resistance to Bgt in wheat throughout all growth stages. It has now become one of the most highly effective genetic loci introgressed into wheat from wild species, and the commercial varieties harboring Pm21 have been widely used in wheat production with more than 4 million hectares in China.展开更多
The quality control processes for herbal medicines have been problematic. Flavonoids are the major active components of Huangqin Tang(HQT, a traditional Chinese medicine formula). In this study, we used a combinative ...The quality control processes for herbal medicines have been problematic. Flavonoids are the major active components of Huangqin Tang(HQT, a traditional Chinese medicine formula). In this study, we used a combinative method approach consisting of chromatographic fingerprinting(high performance liquid chromatography; HPLC), quantitative methods and a pharmacodynamic evaluation model to analyze the flavonoids of HQT obtained from different sources. Ten batches of HQT were analyzed by the HPLC fingerprinting method and 26 common peaks were detected, of which 23 peaks corresponded with the chemical profile of HQT. In addition, 11 major compounds were identified by LC–MS analysis(liquid chromatography–tandem mass spectrometer; LC–MS^n) and quantified by the HPLC quantitative method approach. The studied10 batches of HQT were found to be homogeneous in their composition with a similarity between 0.990 and1.000. The distribution of the 11 identified compounds was found to be very similar among the batches. Only slight pharmacodynamic differences were detected between the different batches, confirming the homogeneity of HQT. The results of this study prove that the combination of chromatographic fingerprinting and quantitative analysis can be readily used for comprehensive quality control of herbal medicines.展开更多
The development of the phytoplankton community was studied in the Jiaozhou Bay during the spring to neap tide in August2001, through three cruises and a 15 d continuous observation. This investigation indicates that d...The development of the phytoplankton community was studied in the Jiaozhou Bay during the spring to neap tide in August2001, through three cruises and a 15 d continuous observation. This investigation indicates that diatom cell abundance increasedsharply following the end of a spring tide, from 9 cells/cm3 to a peak of 94 cells/cm3. The dominant species composition andabundance show a quick species sequence from spring to neap tide, and the dominant species at the start phase is Skeletomenacostatum, then changes to Chaetoceros curvisetus, finally it changes to Eucampia zodiacus. Silicate concentration increasesduring spring tide, as a result of nutrient replenishment from the watersediment interface, its initial average concentration inneap tide is 1.39 mmol/dm3 and reached the peak average concentration of 8.40 mmol/dm3 in spring tide. But the nitrogenconcentration dropped due to dilution by the low nitrogen seawater from the Huanghai Sea, its initial average concentration inneap tide is 67 mmol/dm3 and decreased to the average concentration of 54 mmol/dm3 in spring tide. The degree of siliconlimitation was decreased and phytoplankton, especially diatoms, responds immediately after nutrient replenishment in thewater column. Skeletonmea costatum, as one of the dominant species in the Jiaozhou Bay, shows a quicker response tonutrient availability than Eucampia zodiacus and Chaetoceros curvisetus. It is proposed that dominant species compositionand water column stability synchronously determine the development of phytoplankton summer blooms in the Jiaozhou bay.展开更多
In underwater optical wireless communication(UOWC),a channel is characterized by abundant scattering/absorption effects and optical turbulence.Most previous studies on UOWC have been limited to scattering/absorption e...In underwater optical wireless communication(UOWC),a channel is characterized by abundant scattering/absorption effects and optical turbulence.Most previous studies on UOWC have been limited to scattering/absorption effects.However,experiments in the literature indicate that underwater optical turbulence(UOT)can cause severe degradation of UOWC performance.In this paper,we characterize an UOWC channel with both scattering/absorption and UOT taken into consideration,and a spatial diversity receiver scheme,say a singleinput–multiple-output(SIMO) scheme,based on a light-emitting-diode(LED) source and multiple detectors is proposed to mitigate deep fading.The Monte Carlo based statistical simulation method is introduced to evaluate the bit-error-rate performance of the system.It is shown that spatial diversity can effectively reduce channel fading and remarkably extend communication range.展开更多
The effects of Mo on the microstructure and mechanical properties of Ti（C,N）-based cermets with low Ni have been studied systematically. Different contents of Mo （4-12 wt.%） were added into Tl（C,N）-based cermets...The effects of Mo on the microstructure and mechanical properties of Ti（C,N）-based cermets with low Ni have been studied systematically. Different contents of Mo （4-12 wt.%） were added into Tl（C,N）-based cermets. Specimens were fabricated by conventional powder metallurgy and vacuum sintered at temperatures of 1440, 1450, and 1460℃ individually. The microstructure and fracture morphology were investigated by scanning electron microscope, and the mechanical properties such as transverse strength and hardness were measured. The results show that the microstructure is uniform and the thickness of rim phase is moderate when the content of Mo is 8 wt.%; the mechanical properties of the specimens sintered at 1450℃ are better than those sintered at 1440 and 1460℃. The integrated properties of transverse strength and hardness are the best when the content of Mo is 8 wt.% and the sintering temperature is 1450℃.展开更多
There is more wind with less turbulence offshore compared with an onshore case,which drives the development of the offshore wind farm worldwide.Since a huge amount of money is required for constructing an offshore win...There is more wind with less turbulence offshore compared with an onshore case,which drives the development of the offshore wind farm worldwide.Since a huge amount of money is required for constructing an offshore wind farm,many types of research have been done on the optimization of the offshore wind farm with the purpose of either minimizing the cost of energy or maximizing the total energy production.There are several factors that have an impact on the performance of the wind farm,mainly the energy production of wind farm which is highly decided bythe wind condition of construction area and micro-siting of wind turbines(WTs),as well as the initial investment which is influenced by both the placement of WTs and the electrical system design,especially the scheme of cable connection layout.In this paper,a review of the state-of-the-art researches related to the wind farm layout optimization as well as electrical system design including cable connection scheme optimization is presented.The most significant factors that should be considered in the optimization work of the offshore wind farm is highlighted after reviewing the latest works,and the future needs are specified.展开更多
Previous studies have reported that, before or after occurrences of strong earthquakes, some low earth orbit satellites recorded ionospheric disturbances, including electromagnetic emissions and plasma fluctuations ov...Previous studies have reported that, before or after occurrences of strong earthquakes, some low earth orbit satellites recorded ionospheric disturbances, including electromagnetic emissions and plasma fluctuations over the epicenter region or its conjugate point.Theoretically speaking, due to some electromagnetic coupling effect, electromagnetic emissions from the earthquake preparation zone could propagate from the lithosphere to the atmosphere, and could reach the ionosphere, even up to the inner magnetosphere. This paper introduces the electric field detector(EFD) onboard the ZhangHeng-1 satellite(ZH-1). The EFD is designed to measure electric field fluctuations within the broad frequency range of DC to 3.5 MHz, divided into 4 channels: ULF(DC–16 Hz), ELF(6 Hz–2.2 kHz), VLF(1.8 kHz–20 kHz) and HF(18 kHz–3.5 MHz). The sampling rates of the channels are 125 Hz, 5 kHz, 50 kHz and 10 MHz, respectively. The EFD includes4 spherical probes mounted on a over 4.5 m boom and an electronic box inside the satellite module. The resolution of the EFD is 1μV·m-1·Hz-1/2 at frequencies from DC to 16 Hz, and the sensitivity is 0.1 μV·m-1·Hz-1/2 at frequencies from 6 Hz to 2.2 kHz, 0.05 μV·m-1·Hz-1/2 in the band 1.8 kHz to 20 kHz, and 0.1μV·m-1·Hz-1/2 from 20 kHz to 3.5 MHz. The dynamic range from DC to 20 kHz is over 120 dB, and over96 dB from 20 kHz to 3.5 MHz. The EFD has two observation modes: survey mode and burst mode. The survey mode concentrates primarily on electric field power density values; the burst mode provides high sampling rate waveform data. The detailed configuration of the EFD onboard the ZH-1 is also introduced in this paper. During the six months' orbit test phase, the EFD recorded a number of natural electromagnetic emissions. Preliminary analysis of these data suggests that the EFD performs well onboard the ZH-1 and is meeting the requirements of the scientific objectives of ZH-1.展开更多
Van der Waals(vdW)heterostructures based on transition metal dichalcogenides(TMDs)generally possess a type-II band alignment that facilitates the formation of interlayer excitons between constituent monolayers.Manipul...Van der Waals(vdW)heterostructures based on transition metal dichalcogenides(TMDs)generally possess a type-II band alignment that facilitates the formation of interlayer excitons between constituent monolayers.Manipulation of the interlayer excitons in TMD vdW heterostructures holds great promise for the development of excitonic integrated circuits that serve as the counterpart of electronic integrated circuits,which allows the photons and excitons to transform into each other and thus bridges optical communication and signal processing at the integrated circuit.As a consequence,numerous studies have been carried out to obtain deep insight into the physical properties of interlayer excitons,including revealing their ultrafast formation,long population recombination lifetimes,and intriguing spin-valley dynamics.These outstanding properties ensure interlayer excitons with good transport characteristics,and may pave the way for their potential applications in efficient excitonic devices based on TMD vdW heterostructures.At present,a systematic and comprehensive overview of interlayer exciton formation,relaxation,transport,and potential applications is still lacking.In this review,we give a comprehensive description and discussion of these frontier topics for interlayer excitons in TMD vdW heterostructures to provide valuable guidance for researchers in this field.展开更多
Iron-based oxygen reduction reaction(ORR)catalysts have been the focus of research,and iron sources play an important role for the preparation of efficient ORR catalysts.Here,we successfully use LiFePO4 as ideal sourc...Iron-based oxygen reduction reaction(ORR)catalysts have been the focus of research,and iron sources play an important role for the preparation of efficient ORR catalysts.Here,we successfully use LiFePO4 as ideal sources of Fe and P to construct the heteroatom doped Fe-based carbon materials.The obtained Fe-N-P co-doped coral-like carbon nanotube arrays encapsulated Fe2P catalyst(C-ZIF/LFP)shows very high half-wave potential of 0.88 V in alkaline electrolytes toward ORR,superior to Pt/C(0.85 V),and also presents a high half-wave potential of 0.74 V in acidic electrolytes,comparable to Pt/C(0.8 V).When further applied into a home-made Zn-air battery as cathode,a peak power density of 140 mW·cm^-2 is reached,exceeds commercial Pt/C(110 mW·cm^-2).Besides,it also presents exceptional durability and methanol resistance compared with Pt/C.Noticeably,the preparation method of such a high-performance catalyst is simple and easy to optimize,suitable for the large-scale production.What’s more,it opens up a more sustainable development scenario to reduce the hazardous wastes such as LiFePO4 by directly using them for preparing high-performance ORR catalysts.展开更多
High-performance multiphoton-pumped lasers based on cesium lead halide perovskite nanostructures are promising for nonlinear optics and practical frequency upconversion devices in integrated photonics. However, the pe...High-performance multiphoton-pumped lasers based on cesium lead halide perovskite nanostructures are promising for nonlinear optics and practical frequency upconversion devices in integrated photonics. However, the performance of such lasers is highly dependent on the quality of the material and cavity, which makes their fabrication challenging. Herein, we demonstrate that cesium lead halide perovskite triangular nanorods fabricated via vapor methods can serve as gain media and effective cavities for multiphoton-pumped lasers. We observed blue-shifts of the lasing modes in the excitation fluence-dependent lasing spectra at increased excitation powers, which fits well with the dynamics of Burstein-Moss shifts caused by the band filling effect. Moreover, efficient multiphoton lasing in CsPbBr3 nanorods can be realized in a wide excitation wavelength range （700-1,400 nm）. The dynamics of multiphoton lasing were investigated by time-resolved photoluminescence spectroscopy, which indicated that an electron-hole plasma is responsible for the multiphoton-pumped lasing. This work could lead to new opportunities and applications for cesium lead halide perovskite nanostructures in frequency upconversion lasing devices and optical interconnect systems.展开更多
To realize a hyperconnected smart society with high productivity,advances in flexible sensing technology are highly needed.Nowadays,flexible sensing technology has witnessed improvements in both the hardware performan...To realize a hyperconnected smart society with high productivity,advances in flexible sensing technology are highly needed.Nowadays,flexible sensing technology has witnessed improvements in both the hardware performances of sensor devices and the data processing capabilities of the device’s software.Significant research efforts have been devoted to improving materials,sensing mechanism,and configurations of flexible sensing systems in a quest to fulfill the requirements of future technology.Meanwhile,advanced data analysis methods are being developed to extract useful information from increasingly complicated data collected by a single sensor or network of sensors.Machine learning(ML)as an important branch of artificial intelligence can efficiently handle such complex data,which can be multi-dimensional and multi-faceted,thus providing a powerful tool for easy interpretation of sensing data.In this review,the fundamental working mechanisms and common types of flexible mechanical sensors are firstly presented.Then how ML-assisted data interpretation improves the applications of flexible mechanical sensors and other closely-related sensors in various areas is elaborated,which includes health monitoring,human-machine interfaces,object/surface recognition,pressure prediction,and human posture/motion identification.Finally,the advantages,challenges,and future perspectives associated with the fusion of flexible mechanical sensing technology and ML algorithms are discussed.These will give significant insights to enable the advancement of next-generation artificial flexible mechanical sensing.展开更多
The influence of raw powder particle size on the properties and microstructures of Ti (C, N)-based cermets has been studied. The conclusions are as follows: The microstructures of cermets were composed of two kinds of...The influence of raw powder particle size on the properties and microstructures of Ti (C, N)-based cermets has been studied. The conclusions are as follows: The microstructures of cermets were composed of two kinds of grains, the one with black cores surrounded by obvious rim structures, and the other whose cores were white with unconspicuous rim structures and adhesive phase. In the cermet made from fine powders, the amount of grains with white cores was much more than that in cermet made from coarse powders. In addition, their properties were also much better.展开更多
Light plays a critical role in plant growth and development,but the mechanisms through which light regulates fruit ripening and nutritional quality in horticultural crops remain largely unknown.Here,we found that ELON...Light plays a critical role in plant growth and development,but the mechanisms through which light regulates fruit ripening and nutritional quality in horticultural crops remain largely unknown.Here,we found that ELONGATED HYPOCOTYL 5(HY5),a master regulator in the light signaling pathway,is required for normal fruit ripening in tomato(Solanum lycopersicum).Loss of function of tomato HY5(SlHY5)impairs pigment accumulation and ethylene biosynthesis.Transcriptome profiling identified 2948 differentially expressed genes,which included 1424 downregulated and 1524 upregulated genes,in the Slhy5 mutants.In addition,genes involved in carotenoid and anthocyanin biosynthesis and ethylene signaling were revealed as direct targets of SlHY5 by chromatin immunoprecipitation.Surprisingly,the expression of a large proportion of genes encoding ribosomal proteins was downregulated in the Slhy5 mutants,and this downregulation pattern was accompanied by a decrease in the abundance of ribosomal proteins.Further analysis demonstrated that SlHY5 affected the translation efficiency of numerous ripening-related genes.These data indicate that SlHY5 regulates fruit ripening both at the transcriptional level by targeting specific molecular pathways and at the translational level by affecting the protein translation machinery.Our findings unravel the regulatory mechanisms of SlHY5 in controlling fruit ripening and nutritional quality and uncover the multifaceted regulation of gene expression by transcription factors.展开更多
The effect of surface roughness on the boundary development and loss behavior of turbine blades is investigated with different Reynolds numbers in this paper.The result shows that the velocity profile in boundary laye...The effect of surface roughness on the boundary development and loss behavior of turbine blades is investigated with different Reynolds numbers in this paper.The result shows that the velocity profile in boundary layer is plumper on rough surface than on smooth blade.The aerodynamic loss is lowered at low Reynolds number,but becomes significantly large at high Reynolds number.The total pressure loss coefficient of cascade can reach a top increase of 129%for rougher blades comparing with smooth blades at Re=300000.展开更多
Macroscopic materials are heterogeneous,multi-elementary,and complex.No material is homogeneous or isotropic at a certain small scale.Parts of the material that differ from one another can be termed"natural chips...Macroscopic materials are heterogeneous,multi-elementary,and complex.No material is homogeneous or isotropic at a certain small scale.Parts of the material that differ from one another can be termed"natural chips."At different spots on the material,the composition,structure,and properties vary slightly,and the combination of these slight differences establishes the overall material performance.This article presents a state-of-the-art review of research and applications of high-throughput statistical spatialmapping characterization technology based on the intrinsic heterogeneity within materials.Highthroughput statistical spatial-mapping uses a series of rapid characterization techniques for analysis from the macroscopic to the microscopic scale.Datasets of composition,structure,and properties at each location are obtained rapidly for practical sample sizes.Accurate positional coordinate information and references to a point-to-point correspondence are used to set up a database that contains spatialmapping lattices.Based on material research and development design requirements,dataset spatialmapping within required target intervals is selected from the database.Statistical analysis can be used to select a suitable design that better meets the targeted requirements.After repeated verification,genetic units that reflect the material properties are determined.By optimizing process parameters,the assembly of these genetic unit(s)is verified at the mesoscale,and quantitative correlations are established between the microscale,mesoscale,macroscale,practical sample,across-the-scale span composition,structure,and properties.The high-throughput statistical spatial-mapping characterization technology has been applied to numerous material systems,such as steels,superalloys,galvanization,and ferrosilicon alloys.This approach has guided the composition and the process optimization of various materials.展开更多
Based on water samples collected and observations of currents, tidal levels as well as turbidities taken, respectively over a period of 15 and 7 d, in southwestern Jiaozhou Bay on August, 2001, it was found that: ( i ...Based on water samples collected and observations of currents, tidal levels as well as turbidities taken, respectively over a period of 15 and 7 d, in southwestern Jiaozhou Bay on August, 2001, it was found that: ( i ) the average content of non mineral component amounted to 87% of the suspended sediment matter (SPM) in Jiaozhou Bay,much higher than in estuaries and bays where turbidity is high and mineral particulates dominates; (ii) in contrast to high turbid bays, SPM was generally coarser than bed deposits and in upper water column than in lower water column in Jiaozhou Bay; (iii) in fair weathers, suspended sediment concentration (SPC) varied regularly within tidal cycles and neap-spring cycles, but the regularity was deformed in storms; and (iv) SPC was controlled by settling/resuspension near the bed and by advection at the surface at the study site with a depth of 20 m, suggesting weak vertical exchanges. It was concluded that SPM property of a low turbid bay is sensitive to pollution, and that the maintenance of low turbidity in the bay depends on less SPM supply, low waves and currents, and controlling on discharge of particulate pollutants.展开更多
Firm joins were obtained between Ti（C,N）-based cermet and steel with Ag-Cu-Zn-Ni filler metal by vacuum brazing. The effects of technological parameters such as brazing temperature, holding time, and filler thicknes...Firm joins were obtained between Ti（C,N）-based cermet and steel with Ag-Cu-Zn-Ni filler metal by vacuum brazing. The effects of technological parameters such as brazing temperature, holding time, and filler thickness on the shear strength of the joints were investigated. The microstructure of welded area and the reaction products of the filler metal were examined by scanning electron microscopy （SEM）, metallographic microscope （OM）, energy-dispersive X-ray analysis （EDS）, and X-ray diffraction （XRD）. The brazing temperature of 870℃, holding time of 15 min, and filler thickness of 0.4 mm are a set of optimum technological parameters, under which the maximum shear strength of the joints, 176.5 MPa, is achieved. The results of microstructure show that the wettability of the filler metal on Ti（C,N）-based cermet and steel is well. A mutual solution layer and a diffusion layer exist between the welding base materials and the filler metal.展开更多
Nickel-rich layered oxides have drawn sustainable attentions for lithium ion batteries owing to their higher theoretical capacities and lower cost.However,nickel-rich layered oxides also have exposed several defects f...Nickel-rich layered oxides have drawn sustainable attentions for lithium ion batteries owing to their higher theoretical capacities and lower cost.However,nickel-rich layered oxides also have exposed several defects for commercial application,such as uncontrollable ordered layered structure,which leads to higher energy barrier for Li+diffusion.In addition,suffering from structural mutability,the bulk nickelrich cathode materials likely trigger overall volumetric variation and intergranular cracks,thus obstructing the lithium ion diffusion path and shortening the service life of the whole device.Herein,we report wellordered layered Li Ni0.8Co0.1Mn0.1O2 submicron spheroidal particles via an optimized co-precipitation and investigated as LIBs cathodes for high-performance lithium storage.The as-fabricated Li Ni0.8Co0.1Mn0.1O2 delivers high initial capacity of 228 mAh g–1,remarkable energy density of 866 Wh kg–1,rapid Li ion diffusion coefficient(10–9cm2s–1)and low voltage decay.The remarkable electrochemical performance should be ascribed to the well-ordered layered structure and uniform submicron spheroidal particles,which enhance the structural stability and ameliorate strain relaxation via reducing the parcel size and shortening Li-ion diffusion distance.This work anticipatorily provides an inspiration to better design particle morphology for structural stability and rate capability in electrochemistry energy storage devices.展开更多
As the main limiting step of overall water splitting,oxygen evolution reaction(OER)is urgent to be enhanced by developing efficient catalysts to promote the process of electrolytic water.Based on theoretical analysis,...As the main limiting step of overall water splitting,oxygen evolution reaction(OER)is urgent to be enhanced by developing efficient catalysts to promote the process of electrolytic water.Based on theoretical analysis,the Ni-metal-organic framework(Ni-MOF)and NiFe-layered double hydroxide(NiFe-LDH)(NiFe-LDH/MOF)heterostructure can optimize the energy barrier of the OER process and decrease the adsorption energy of oxygen-containing intermediates,effectively accelerating the OER kinetics.Accordingly,layered NiFe-LDH/MOF heterostructures are in situ constructed through a facile two-step reaction process,with substantial oxygen defects and lattice defects that further improve the catalytic performance.As a result,only 208 and 275 mV OER overpotentials are needed for NiFe-LDH/MOF to drive the current densities of 20 and 100 mA·cm^(-2)in 1 M KOH solutions,and even maintain catalytic stability of 100 h at 20 mA·cm^(-2).When applied to seawater oxidation,only 235 and 307 mV OER overpotentials are required to achieve the current densities of 20 and 100 mA·cm^(-2),respectively,with almost no attenuation for 100 h stability test at 20 mA·cm^(-2),all better than commercial RuO_(2).This work provides the theoretical and experimental basis and a new idea for efficiently driving fresh water and seawater cracking by heterostructure and defect coupling design toward catalysts.展开更多
基金supported by the Sichuan Science and Technology Program(Sichuan Distinguished Young Scholars)(No.2020JDJQ0037).
文摘With the growing integration of distributed energy resources(DERs),flexible loads,and other emerging technologies,there are increasing complexities and uncertainties for modern power and energy systems.This brings great challenges to the operation and control.Besides,with the deployment of advanced sensor and smart meters,a large number of data are generated,which brings opportunities for novel data-driven methods to deal with complicated operation and control issues.Among them,reinforcement learning(RL)is one of the most widely promoted methods for control and optimization problems.This paper provides a comprehensive literature review of RL in terms of basic ideas,various types of algorithms,and their applications in power and energy systems.The challenges and further works are also discussed.
基金This work was supported by the Important National Science and Technology Specific Projects of Transgenic Research （Grant No. 2018ZX0800963B）, the Natural Science Foundation of China （Grant No. 31671685, 31771779）, the Fundamental Research Funds for the National Central Universities （Grant No. KYZ201601）, the Czech Science Foundation （Grant No. P501/12/G090）, and the Ministry of Education, Youth and Sports of the Czech Republic （Grant No. LO1204 from the National Program of Sustainability I）.
文摘Dear Editor Wheat powdery mildew, caused by Blumeria graminis f. sp. tritici （Bgt）, is a destructive disease of wheat throughout the world. One of the most important environmental-friendly and economical methods to reduce wheat loss caused by Bgt is to develop highly resistant varieties （Kuraparthy et al., 2007）. Pm21 from the wild species Haynaldia villosa （also known as Dasypyrum villosum） confers high resistance to Bgt in wheat throughout all growth stages. It has now become one of the most highly effective genetic loci introgressed into wheat from wild species, and the commercial varieties harboring Pm21 have been widely used in wheat production with more than 4 million hectares in China.
基金financially supported by the National Natural Science Foundation of China (Nos. 81273662 and 81473592)the Operational Expenses for Basic Research of China Academy of Chinese Medical Sciences (No. ZZ2014020)
文摘The quality control processes for herbal medicines have been problematic. Flavonoids are the major active components of Huangqin Tang(HQT, a traditional Chinese medicine formula). In this study, we used a combinative method approach consisting of chromatographic fingerprinting(high performance liquid chromatography; HPLC), quantitative methods and a pharmacodynamic evaluation model to analyze the flavonoids of HQT obtained from different sources. Ten batches of HQT were analyzed by the HPLC fingerprinting method and 26 common peaks were detected, of which 23 peaks corresponded with the chemical profile of HQT. In addition, 11 major compounds were identified by LC–MS analysis(liquid chromatography–tandem mass spectrometer; LC–MS^n) and quantified by the HPLC quantitative method approach. The studied10 batches of HQT were found to be homogeneous in their composition with a similarity between 0.990 and1.000. The distribution of the 11 identified compounds was found to be very similar among the batches. Only slight pharmacodynamic differences were detected between the different batches, confirming the homogeneity of HQT. The results of this study prove that the combination of chromatographic fingerprinting and quantitative analysis can be readily used for comprehensive quality control of herbal medicines.
基金This study was supported by the National Natural Science Foundation of China under contract Nos 40036010,40206020 and 40306025.
文摘The development of the phytoplankton community was studied in the Jiaozhou Bay during the spring to neap tide in August2001, through three cruises and a 15 d continuous observation. This investigation indicates that diatom cell abundance increasedsharply following the end of a spring tide, from 9 cells/cm3 to a peak of 94 cells/cm3. The dominant species composition andabundance show a quick species sequence from spring to neap tide, and the dominant species at the start phase is Skeletomenacostatum, then changes to Chaetoceros curvisetus, finally it changes to Eucampia zodiacus. Silicate concentration increasesduring spring tide, as a result of nutrient replenishment from the watersediment interface, its initial average concentration inneap tide is 1.39 mmol/dm3 and reached the peak average concentration of 8.40 mmol/dm3 in spring tide. But the nitrogenconcentration dropped due to dilution by the low nitrogen seawater from the Huanghai Sea, its initial average concentration inneap tide is 67 mmol/dm3 and decreased to the average concentration of 54 mmol/dm3 in spring tide. The degree of siliconlimitation was decreased and phytoplankton, especially diatoms, responds immediately after nutrient replenishment in thewater column. Skeletonmea costatum, as one of the dominant species in the Jiaozhou Bay, shows a quicker response tonutrient availability than Eucampia zodiacus and Chaetoceros curvisetus. It is proposed that dominant species compositionand water column stability synchronously determine the development of phytoplankton summer blooms in the Jiaozhou bay.
基金supported by the National Key Basic Research Program of China (Grant No.2013CB329201)the National Natural Science Foundation of China (Grant Nos.61171066 and 61471332)the State Key Laboratory of Robotics
文摘In underwater optical wireless communication(UOWC),a channel is characterized by abundant scattering/absorption effects and optical turbulence.Most previous studies on UOWC have been limited to scattering/absorption effects.However,experiments in the literature indicate that underwater optical turbulence(UOT)can cause severe degradation of UOWC performance.In this paper,we characterize an UOWC channel with both scattering/absorption and UOT taken into consideration,and a spatial diversity receiver scheme,say a singleinput–multiple-output(SIMO) scheme,based on a light-emitting-diode(LED) source and multiple detectors is proposed to mitigate deep fading.The Monte Carlo based statistical simulation method is introduced to evaluate the bit-error-rate performance of the system.It is shown that spatial diversity can effectively reduce channel fading and remarkably extend communication range.
基金This work was financially supported by the National Natural Science Foundation of China (No. 50074017) the Natural Science Foundation of Hubei Province, China (No. 2003ABA092).
文摘The effects of Mo on the microstructure and mechanical properties of Ti（C,N）-based cermets with low Ni have been studied systematically. Different contents of Mo （4-12 wt.%） were added into Tl（C,N）-based cermets. Specimens were fabricated by conventional powder metallurgy and vacuum sintered at temperatures of 1440, 1450, and 1460℃ individually. The microstructure and fracture morphology were investigated by scanning electron microscope, and the mechanical properties such as transverse strength and hardness were measured. The results show that the microstructure is uniform and the thickness of rim phase is moderate when the content of Mo is 8 wt.%; the mechanical properties of the specimens sintered at 1450℃ are better than those sintered at 1440 and 1460℃. The integrated properties of transverse strength and hardness are the best when the content of Mo is 8 wt.% and the sintering temperature is 1450℃.
文摘There is more wind with less turbulence offshore compared with an onshore case,which drives the development of the offshore wind farm worldwide.Since a huge amount of money is required for constructing an offshore wind farm,many types of research have been done on the optimization of the offshore wind farm with the purpose of either minimizing the cost of energy or maximizing the total energy production.There are several factors that have an impact on the performance of the wind farm,mainly the energy production of wind farm which is highly decided bythe wind condition of construction area and micro-siting of wind turbines(WTs),as well as the initial investment which is influenced by both the placement of WTs and the electrical system design,especially the scheme of cable connection layout.In this paper,a review of the state-of-the-art researches related to the wind farm layout optimization as well as electrical system design including cable connection scheme optimization is presented.The most significant factors that should be considered in the optimization work of the offshore wind farm is highlighted after reviewing the latest works,and the future needs are specified.
基金supported by the civil space research project (ZH-1 data validation: Ionospheric observatory theory)NFSC grants 41574139 and 41874174
文摘Previous studies have reported that, before or after occurrences of strong earthquakes, some low earth orbit satellites recorded ionospheric disturbances, including electromagnetic emissions and plasma fluctuations over the epicenter region or its conjugate point.Theoretically speaking, due to some electromagnetic coupling effect, electromagnetic emissions from the earthquake preparation zone could propagate from the lithosphere to the atmosphere, and could reach the ionosphere, even up to the inner magnetosphere. This paper introduces the electric field detector(EFD) onboard the ZhangHeng-1 satellite(ZH-1). The EFD is designed to measure electric field fluctuations within the broad frequency range of DC to 3.5 MHz, divided into 4 channels: ULF(DC–16 Hz), ELF(6 Hz–2.2 kHz), VLF(1.8 kHz–20 kHz) and HF(18 kHz–3.5 MHz). The sampling rates of the channels are 125 Hz, 5 kHz, 50 kHz and 10 MHz, respectively. The EFD includes4 spherical probes mounted on a over 4.5 m boom and an electronic box inside the satellite module. The resolution of the EFD is 1μV·m-1·Hz-1/2 at frequencies from DC to 16 Hz, and the sensitivity is 0.1 μV·m-1·Hz-1/2 at frequencies from 6 Hz to 2.2 kHz, 0.05 μV·m-1·Hz-1/2 in the band 1.8 kHz to 20 kHz, and 0.1μV·m-1·Hz-1/2 from 20 kHz to 3.5 MHz. The dynamic range from DC to 20 kHz is over 120 dB, and over96 dB from 20 kHz to 3.5 MHz. The EFD has two observation modes: survey mode and burst mode. The survey mode concentrates primarily on electric field power density values; the burst mode provides high sampling rate waveform data. The detailed configuration of the EFD onboard the ZH-1 is also introduced in this paper. During the six months' orbit test phase, the EFD recorded a number of natural electromagnetic emissions. Preliminary analysis of these data suggests that the EFD performs well onboard the ZH-1 and is meeting the requirements of the scientific objectives of ZH-1.
基金The authors are grateful to the National Natural Science Foundation of China(Nos.52072117,21703059,51972105,51525202,61635001,and 61905071)the Joint Funds of the National Natural Science Foundation of China(No.U19A2090)+2 种基金the Key Program of the Hunan Provincial Science and Technology Department(No.2019XK2001)the International Science and Technology Innovation Cooperation Base of Hunan Province(2018WK4004)the Open Project Program of Wuhan National Laboratory for Optoelectronics(No.2020WNLOKF002).
文摘Van der Waals(vdW)heterostructures based on transition metal dichalcogenides(TMDs)generally possess a type-II band alignment that facilitates the formation of interlayer excitons between constituent monolayers.Manipulation of the interlayer excitons in TMD vdW heterostructures holds great promise for the development of excitonic integrated circuits that serve as the counterpart of electronic integrated circuits,which allows the photons and excitons to transform into each other and thus bridges optical communication and signal processing at the integrated circuit.As a consequence,numerous studies have been carried out to obtain deep insight into the physical properties of interlayer excitons,including revealing their ultrafast formation,long population recombination lifetimes,and intriguing spin-valley dynamics.These outstanding properties ensure interlayer excitons with good transport characteristics,and may pave the way for their potential applications in efficient excitonic devices based on TMD vdW heterostructures.At present,a systematic and comprehensive overview of interlayer exciton formation,relaxation,transport,and potential applications is still lacking.In this review,we give a comprehensive description and discussion of these frontier topics for interlayer excitons in TMD vdW heterostructures to provide valuable guidance for researchers in this field.
基金This work was financially supported by the National Key Research and Development Program of China(No.2016YFA0202603)the National Natural Science Foundation of China(No.51672204).
文摘Iron-based oxygen reduction reaction(ORR)catalysts have been the focus of research,and iron sources play an important role for the preparation of efficient ORR catalysts.Here,we successfully use LiFePO4 as ideal sources of Fe and P to construct the heteroatom doped Fe-based carbon materials.The obtained Fe-N-P co-doped coral-like carbon nanotube arrays encapsulated Fe2P catalyst(C-ZIF/LFP)shows very high half-wave potential of 0.88 V in alkaline electrolytes toward ORR,superior to Pt/C(0.85 V),and also presents a high half-wave potential of 0.74 V in acidic electrolytes,comparable to Pt/C(0.8 V).When further applied into a home-made Zn-air battery as cathode,a peak power density of 140 mW·cm^-2 is reached,exceeds commercial Pt/C(110 mW·cm^-2).Besides,it also presents exceptional durability and methanol resistance compared with Pt/C.Noticeably,the preparation method of such a high-performance catalyst is simple and easy to optimize,suitable for the large-scale production.What’s more,it opens up a more sustainable development scenario to reduce the hazardous wastes such as LiFePO4 by directly using them for preparing high-performance ORR catalysts.
基金Acknowledgements All authors are grateful to the National Natural Science Foundation of China （Nos. 51525202, 61574054, 61505051 and 61474040）, the Hunan province science and technology plan （Nos. 2014FJ2001 and 2014TT1004）, the Aid program for Science and Technology Innovative Research Team in Higher Educational Institutions of Hunan Province, and the Fundamental Research Funds for the Central Universities.
文摘High-performance multiphoton-pumped lasers based on cesium lead halide perovskite nanostructures are promising for nonlinear optics and practical frequency upconversion devices in integrated photonics. However, the performance of such lasers is highly dependent on the quality of the material and cavity, which makes their fabrication challenging. Herein, we demonstrate that cesium lead halide perovskite triangular nanorods fabricated via vapor methods can serve as gain media and effective cavities for multiphoton-pumped lasers. We observed blue-shifts of the lasing modes in the excitation fluence-dependent lasing spectra at increased excitation powers, which fits well with the dynamics of Burstein-Moss shifts caused by the band filling effect. Moreover, efficient multiphoton lasing in CsPbBr3 nanorods can be realized in a wide excitation wavelength range （700-1,400 nm）. The dynamics of multiphoton lasing were investigated by time-resolved photoluminescence spectroscopy, which indicated that an electron-hole plasma is responsible for the multiphoton-pumped lasing. This work could lead to new opportunities and applications for cesium lead halide perovskite nanostructures in frequency upconversion lasing devices and optical interconnect systems.
基金support from National Natural Science Foundation of China(Nos.62274140,61904141,52173234)the State Key Laboratory of Mechanics and Control of Mechanical Structures(Nanjing University of Aeronautics and Astronautics)(Grant No.MCMS-E-0422G03)the Shenzhen-Hong Kong-Macao Technology Research Program(Type C,202011033000145,SGDX2020110309300301).
文摘To realize a hyperconnected smart society with high productivity,advances in flexible sensing technology are highly needed.Nowadays,flexible sensing technology has witnessed improvements in both the hardware performances of sensor devices and the data processing capabilities of the device’s software.Significant research efforts have been devoted to improving materials,sensing mechanism,and configurations of flexible sensing systems in a quest to fulfill the requirements of future technology.Meanwhile,advanced data analysis methods are being developed to extract useful information from increasingly complicated data collected by a single sensor or network of sensors.Machine learning(ML)as an important branch of artificial intelligence can efficiently handle such complex data,which can be multi-dimensional and multi-faceted,thus providing a powerful tool for easy interpretation of sensing data.In this review,the fundamental working mechanisms and common types of flexible mechanical sensors are firstly presented.Then how ML-assisted data interpretation improves the applications of flexible mechanical sensors and other closely-related sensors in various areas is elaborated,which includes health monitoring,human-machine interfaces,object/surface recognition,pressure prediction,and human posture/motion identification.Finally,the advantages,challenges,and future perspectives associated with the fusion of flexible mechanical sensing technology and ML algorithms are discussed.These will give significant insights to enable the advancement of next-generation artificial flexible mechanical sensing.
基金the National Natural Science Foundation of China, the Doctoral EducationFoundation of China, the State Key Laboratory of Powde
文摘The influence of raw powder particle size on the properties and microstructures of Ti (C, N)-based cermets has been studied. The conclusions are as follows: The microstructures of cermets were composed of two kinds of grains, the one with black cores surrounded by obvious rim structures, and the other whose cores were white with unconspicuous rim structures and adhesive phase. In the cermet made from fine powders, the amount of grains with white cores was much more than that in cermet made from coarse powders. In addition, their properties were also much better.
基金the National Natural Science Foundation of China(grant Nos.31801601,31925035,and 31871855)the China Postdoctoral Science Foundation(2018T110153)the Youth Innovation Promotion Association CAS(2019083).
文摘Light plays a critical role in plant growth and development,but the mechanisms through which light regulates fruit ripening and nutritional quality in horticultural crops remain largely unknown.Here,we found that ELONGATED HYPOCOTYL 5(HY5),a master regulator in the light signaling pathway,is required for normal fruit ripening in tomato(Solanum lycopersicum).Loss of function of tomato HY5(SlHY5)impairs pigment accumulation and ethylene biosynthesis.Transcriptome profiling identified 2948 differentially expressed genes,which included 1424 downregulated and 1524 upregulated genes,in the Slhy5 mutants.In addition,genes involved in carotenoid and anthocyanin biosynthesis and ethylene signaling were revealed as direct targets of SlHY5 by chromatin immunoprecipitation.Surprisingly,the expression of a large proportion of genes encoding ribosomal proteins was downregulated in the Slhy5 mutants,and this downregulation pattern was accompanied by a decrease in the abundance of ribosomal proteins.Further analysis demonstrated that SlHY5 affected the translation efficiency of numerous ripening-related genes.These data indicate that SlHY5 regulates fruit ripening both at the transcriptional level by targeting specific molecular pathways and at the translational level by affecting the protein translation machinery.Our findings unravel the regulatory mechanisms of SlHY5 in controlling fruit ripening and nutritional quality and uncover the multifaceted regulation of gene expression by transcription factors.
文摘The effect of surface roughness on the boundary development and loss behavior of turbine blades is investigated with different Reynolds numbers in this paper.The result shows that the velocity profile in boundary layer is plumper on rough surface than on smooth blade.The aerodynamic loss is lowered at low Reynolds number,but becomes significantly large at high Reynolds number.The total pressure loss coefficient of cascade can reach a top increase of 129%for rougher blades comparing with smooth blades at Re=300000.
基金This research was supported by the National Key Research and Development Program of China(2016YFB0700300).The authors acknowledge helpful discussions with Profs.Hong Wang,Xiaodong Xiang,and Liang Jiang.We thank Laura Kuhar,Ph.D.from Liwen Bianji,Edanz Group China(www.liwenbianji.cn/ac),for editing the English text of a draft of this manuscript.
文摘Macroscopic materials are heterogeneous,multi-elementary,and complex.No material is homogeneous or isotropic at a certain small scale.Parts of the material that differ from one another can be termed"natural chips."At different spots on the material,the composition,structure,and properties vary slightly,and the combination of these slight differences establishes the overall material performance.This article presents a state-of-the-art review of research and applications of high-throughput statistical spatialmapping characterization technology based on the intrinsic heterogeneity within materials.Highthroughput statistical spatial-mapping uses a series of rapid characterization techniques for analysis from the macroscopic to the microscopic scale.Datasets of composition,structure,and properties at each location are obtained rapidly for practical sample sizes.Accurate positional coordinate information and references to a point-to-point correspondence are used to set up a database that contains spatialmapping lattices.Based on material research and development design requirements,dataset spatialmapping within required target intervals is selected from the database.Statistical analysis can be used to select a suitable design that better meets the targeted requirements.After repeated verification,genetic units that reflect the material properties are determined.By optimizing process parameters,the assembly of these genetic unit(s)is verified at the mesoscale,and quantitative correlations are established between the microscale,mesoscale,macroscale,practical sample,across-the-scale span composition,structure,and properties.The high-throughput statistical spatial-mapping characterization technology has been applied to numerous material systems,such as steels,superalloys,galvanization,and ferrosilicon alloys.This approach has guided the composition and the process optimization of various materials.
文摘Based on water samples collected and observations of currents, tidal levels as well as turbidities taken, respectively over a period of 15 and 7 d, in southwestern Jiaozhou Bay on August, 2001, it was found that: ( i ) the average content of non mineral component amounted to 87% of the suspended sediment matter (SPM) in Jiaozhou Bay,much higher than in estuaries and bays where turbidity is high and mineral particulates dominates; (ii) in contrast to high turbid bays, SPM was generally coarser than bed deposits and in upper water column than in lower water column in Jiaozhou Bay; (iii) in fair weathers, suspended sediment concentration (SPC) varied regularly within tidal cycles and neap-spring cycles, but the regularity was deformed in storms; and (iv) SPC was controlled by settling/resuspension near the bed and by advection at the surface at the study site with a depth of 20 m, suggesting weak vertical exchanges. It was concluded that SPM property of a low turbid bay is sensitive to pollution, and that the maintenance of low turbidity in the bay depends on less SPM supply, low waves and currents, and controlling on discharge of particulate pollutants.
基金supported by the National Natural Science Foundation of China (No. 50074014)
文摘Firm joins were obtained between Ti（C,N）-based cermet and steel with Ag-Cu-Zn-Ni filler metal by vacuum brazing. The effects of technological parameters such as brazing temperature, holding time, and filler thickness on the shear strength of the joints were investigated. The microstructure of welded area and the reaction products of the filler metal were examined by scanning electron microscopy （SEM）, metallographic microscope （OM）, energy-dispersive X-ray analysis （EDS）, and X-ray diffraction （XRD）. The brazing temperature of 870℃, holding time of 15 min, and filler thickness of 0.4 mm are a set of optimum technological parameters, under which the maximum shear strength of the joints, 176.5 MPa, is achieved. The results of microstructure show that the wettability of the filler metal on Ti（C,N）-based cermet and steel is well. A mutual solution layer and a diffusion layer exist between the welding base materials and the filler metal.
基金supported by the National Natural Science Foundation of China (21573083)1000 Young Talent (to Deli Wang)the Innovation Research Funds of HuaZhong University of Science and Technology (2017KFYXJJ164)。
文摘Nickel-rich layered oxides have drawn sustainable attentions for lithium ion batteries owing to their higher theoretical capacities and lower cost.However,nickel-rich layered oxides also have exposed several defects for commercial application,such as uncontrollable ordered layered structure,which leads to higher energy barrier for Li+diffusion.In addition,suffering from structural mutability,the bulk nickelrich cathode materials likely trigger overall volumetric variation and intergranular cracks,thus obstructing the lithium ion diffusion path and shortening the service life of the whole device.Herein,we report wellordered layered Li Ni0.8Co0.1Mn0.1O2 submicron spheroidal particles via an optimized co-precipitation and investigated as LIBs cathodes for high-performance lithium storage.The as-fabricated Li Ni0.8Co0.1Mn0.1O2 delivers high initial capacity of 228 mAh g–1,remarkable energy density of 866 Wh kg–1,rapid Li ion diffusion coefficient(10–9cm2s–1)and low voltage decay.The remarkable electrochemical performance should be ascribed to the well-ordered layered structure and uniform submicron spheroidal particles,which enhance the structural stability and ameliorate strain relaxation via reducing the parcel size and shortening Li-ion diffusion distance.This work anticipatorily provides an inspiration to better design particle morphology for structural stability and rate capability in electrochemistry energy storage devices.
基金This work was supported by the National Natural Science Foundation of China(No.22075223)the State Key Laboratory of Advanced Technology for Materials Synthesis and Processing(Wuhan University of Technology)(No.2022-ZD-4).
文摘As the main limiting step of overall water splitting,oxygen evolution reaction(OER)is urgent to be enhanced by developing efficient catalysts to promote the process of electrolytic water.Based on theoretical analysis,the Ni-metal-organic framework(Ni-MOF)and NiFe-layered double hydroxide(NiFe-LDH)(NiFe-LDH/MOF)heterostructure can optimize the energy barrier of the OER process and decrease the adsorption energy of oxygen-containing intermediates,effectively accelerating the OER kinetics.Accordingly,layered NiFe-LDH/MOF heterostructures are in situ constructed through a facile two-step reaction process,with substantial oxygen defects and lattice defects that further improve the catalytic performance.As a result,only 208 and 275 mV OER overpotentials are needed for NiFe-LDH/MOF to drive the current densities of 20 and 100 mA·cm^(-2)in 1 M KOH solutions,and even maintain catalytic stability of 100 h at 20 mA·cm^(-2).When applied to seawater oxidation,only 235 and 307 mV OER overpotentials are required to achieve the current densities of 20 and 100 mA·cm^(-2),respectively,with almost no attenuation for 100 h stability test at 20 mA·cm^(-2),all better than commercial RuO_(2).This work provides the theoretical and experimental basis and a new idea for efficiently driving fresh water and seawater cracking by heterostructure and defect coupling design toward catalysts.
