In the present work, a series of Pt-based catalysts, alloyed with a second metal, i.e., Re, Sn, Er, La, and Y, and supported on activated carbon, ordered mesoporous carbon, N-doped mesoporous carbon or reduced graphen...In the present work, a series of Pt-based catalysts, alloyed with a second metal, i.e., Re, Sn, Er, La, and Y, and supported on activated carbon, ordered mesoporous carbon, N-doped mesoporous carbon or reduced graphene oxide(rGO), have been developed for selective hydrogenation of cinnamaldehyde to cinnamylalcohol. Re and rGO were proved to be the most favorable metal dopant and catalyst support, respectively. Pt_(50) Re_(50)/rGO showed the highest cinnamylalcohol selectivity of 89% with 94% conversion of cinnamaldehyde at the reaction conditions of 120 °C, 2.0 MPaH_2 and 4 h.展开更多
Based on the fire and meteorological data of forest and grassland in Inner Mongolia in recent 30 years,a forest and grassland fire risk grade forecast model is established,and a refined forest and grassland fire risk ...Based on the fire and meteorological data of forest and grassland in Inner Mongolia in recent 30 years,a forest and grassland fire risk grade forecast model is established,and a refined forest and grassland fire risk level forecast system based on smart grid is developed. The results show that predictors are determined about forest and grassland fire risk grade,such as precipitation,minimum relative humidity,maximum temperature,maximum wind speed,number of sunny or rainy days,and forest and grassland combustible stock. According to fire risk division conclusion,forest and grassland areas are divided into 5 forecast areas. By using discriminant analysis and weighted factor overlay method,an elaborate fire risk grade forecast model is established in different forecast areas of Inner Mongolia forest and grassland. By using smart grid forecast field data,an elaborate fire risk grade forecasting system is established for making fire risk grade forecast during 24,48 and 72 h.展开更多
With the rapid development of the social economy,people are paying more and more attention to environmental issues.If society wants sustainable development,it must put energy conservation and emission reduction on the...With the rapid development of the social economy,people are paying more and more attention to environmental issues.If society wants sustainable development,it must put energy conservation and emission reduction on the agenda.At this stage,China has vigorously promoted energy conservation and emission reduction,and all walks of life have gradually embarked on the green road of energy conservation.In recent years,energy saving measures has been widely used in China's oilfield electrical engineering.The author explores and analyzes the basic principles of energy saving measures applied in oilfield electrical engineering,and proposes an effective way to apply energy saving measures in oilfield electrical engineering,hoping to contribute to the energy saving effect of oilfield electrical engineering.展开更多
Porous carbon-based materials are promised to be lightweight dielectric microwave absorbents.Deeply understanding the influence of graphitization grade and porous structure on the dielectric parameters is urgently req...Porous carbon-based materials are promised to be lightweight dielectric microwave absorbents.Deeply understanding the influence of graphitization grade and porous structure on the dielectric parameters is urgently required.Herein,utilizing the low boiling point of Zn,porous N-doped carbon was fabricated by carbonization of ZIF-8(Zn)at different temperature,and the microwave absorption performance was investigated.The porous N-doped carbon inherits the high porosity of ZIF-8 precursor.By increasing the carbonization temperature,the contents of Zn and N elements are decreased;the graphitization degree is improved;however,the specific surface area and porosity are increased first and then decreased.When the carbonization temperature is 1000°C,the porous N-doped carbon behaves enhanced microwave absorption.With an ultrathin thickness of 1.29 mm,the ideal RL reaches-50.57 dB at 16.95 GHz and the effective absorption bandwidth is 4.17 GHz.The mechanism of boosted microwave absorption is ascribed to the competition of graphitization and porosity as well as N dopants,resulting in high dielectric loss capacity and good impedance matching.The porous structure can prolong the pathways and raise the contact opportunity between microwaves and porous carbon,causing multiple scattering,interface polarization,and improved impedance matching.Besides,the N dopants can induce electron polarization and defect polarization.These results give a new insight to construct lightweight carbon-based microwave absorbents by regulating the graphitization and porosity.展开更多
Background Geese are among the most important poultry species in the world.The current generally accepted hypothesis is that the European domestic geese originated from greylag geese(Anser anser),and Chinese domestic ...Background Geese are among the most important poultry species in the world.The current generally accepted hypothesis is that the European domestic geese originated from greylag geese(Anser anser),and Chinese domestic geese have two origins,most of which originated from swan geese(Anser cygnoides),and the Yili goose originated from greylag geese.To explain the origin and demographic history of geese,we selected 14 goose breeds from Europe and China and wild populations of swan and greylag geese,and whole genome sequencing data were obtained for 74 samples.Results Population structure analysis and phylogenetic trees showed that the wild ancestor of Chinese domestic geese,except for Yili,is the swan geese,and the wild ancestor of Chinese Yili and European domestic geese is greylag geese.Analysis of the demographic history suggests that the domestication of Chinese geese occurred~3499 years ago and that of the European geese occurred~7552 years ago.Furthermore,gene flow was observed between domestic geese and their wild ancestors.Analysis of introgression showed that Yili geese had been introgressed by Chinese domestic geese,and the body size of Yili geese may be influenced by introgression events of some growthrelated genes,including IGF-1.Conclusions Our study provides evidence for the origin of geese at the genome-wide level and advances the understanding of the history of goose domestication and the traits affected by introgression events.展开更多
Photoreforming hydrogen evolution(Pr-HE)of a water-pollutant system could simultaneously achieve efficient hydrogen production and pollutant degradation.It provides a new way to solve energy and environmental issues,b...Photoreforming hydrogen evolution(Pr-HE)of a water-pollutant system could simultaneously achieve efficient hydrogen production and pollutant degradation.It provides a new way to solve energy and environmental issues,but the poor internal charge separation still limits its performance.This work designed hetero-Janus nanofibers(HJNFs)with ordered electric field distribution and separated redox surfaces to promote Pr-HE of the water-pollutant system.Taking ZnO/NiO heterojunction as an example,the hetero-Janus structures were prepared via"Dual-channel"electrospinning and further confirmed by the element morphology analysis and asymmetric distribution of the XPS spectra.The theoretical simulation showed that Janus structures could effectively inhibit the electron trap and hole trap generation,then accelerate the directional carrier migration to the surface.Experimental investigations also confirmed that Janus structures could effectively suppress internal exciton luminescence and accelerate surface charge transfer.The Pr-HE amount and the corresponding propranolol(PRO)degradation rate of HJNFs were 7.9 and 1.5 times higher than hetero-mixed nanofibers(HMNFs).The enhancement factor of Pr-HE in water-PRO to pure water was about 3.1,but nearly zero for HMNFs.This prominent synergistic effect was due to the enhancement of charge separation and the inhibition of cascade side reaction from hetero-Janus structures.Furthermore,the synchronous Pr-HE and degradation reactions were significantly promoted by selective introducing Ag nanoparticles in one side of the HJNFs for enlarging the interfacial Fermi energy level difference.The hetero-Janus strategy offers a new perspective on designing efficient photoreforming photocatalysts for energy and environment applications.展开更多
Flowering time is an indicator of adaptation in maize and a key trait for selection in breeding.The genetic basis of flowering time in maize,especially in response to plant density,remains unclear.The objective of thi...Flowering time is an indicator of adaptation in maize and a key trait for selection in breeding.The genetic basis of flowering time in maize,especially in response to plant density,remains unclear.The objective of this study was to identify maize quantitative trait loci(QTL)associated with flowering time-related traits that are stably expressed under several plant densities and show additive effects that vary with plant density.Three hundred recombinant inbred lines(RIL)derived from a cross between Ye 478 and Qi 319,together with their parents,were planted at three plant densities(90,000,120,000,and 150,000 plants ha^(-1))in four environments.The five traits investigated were days to tasseling(DTT),days to silking(DTS),days to pollen shed(DTP),interval between anthesis and silking(ASI),and interval between tasseling and anthesis(TAI).A high-resolution bin map was used for QTL mapping.In the RIL population,the DTT,DTS,and DTP values increased with plant density,whereas the ASI and TAI values showed negligible response to plant density.A total of 72 QTL were identified for flowering time-related traits,including 15 stably expressed across environments.Maize flowering time under different densities seems to be regulated by complex pathways rather than by several major genes or an independent pathway.The effects of some stable QTL,especially qDTT8-1 and qDTT10-4,varied with plant density.Fine mapping and cloning of these QTL will shed light on the mechanism of flowering time and assist in breeding earlymaturing maize inbred lines and hybrids.展开更多
Based on a comprehensive and systematic analysis of the temporal and spatial distribution,periodic changes,and influencing factors of forest fires in Inner Mongolia,through fixed-point observations and experiments on ...Based on a comprehensive and systematic analysis of the temporal and spatial distribution,periodic changes,and influencing factors of forest fires in Inner Mongolia,through fixed-point observations and experiments on the ground,forest combustibles are divided into the ground litter layer,ground standing litter,and living plants.The combustibles are divided into various grades according to their load,dryness and combustibility.By determining the influencing factors of each combustible grade,a forecast model of the combustibility grade of combustibles is established.The forecast model has been widely used in the mid-and long-term forecast model of fire danger grade,and the accuracy rate of the fall area forecast through back-generation fitting verification is above 88.43%.展开更多
Software-defined networks (SDN) have been widely used in Cloud Data Centers in recent years. With the development of cloud technologies, different organizations need to share network resources to achieve common busine...Software-defined networks (SDN) have been widely used in Cloud Data Centers in recent years. With the development of cloud technologies, different organizations need to share network resources to achieve common business goals, which requires distributed SDN controllers to collaboratively manage cloud networks and realize cross-domain routing. However, existing distributed controller cooperative routing schemes require a third-party trust center to establish trusted relationships for controllers. Since both trust centers and certified entities are vulnerable to various attacks and security risks, the existing works cannot effectively ensure cross-domain routing is credible. To address this problem, Blockchain is employed to establish trusted relationships between distributed controllers, then a cross-domain routing mechanism was devised based on the trusted relationships. Security analysis and experiments indicate that the proposed scheme can establish trust relationships and provide credible cross-domain routing cooperation for distributed SDN controllers. Besides, the required overhead of storage and bandwidth are very limited, which implies good practicability.展开更多
Wireless body area networks(WBANs)guarantee timely data processing and secure information preservation within the range of the wireless access network,which is in urgent need of a new type of security technology.Howev...Wireless body area networks(WBANs)guarantee timely data processing and secure information preservation within the range of the wireless access network,which is in urgent need of a new type of security technology.However,with the speedy development of hardware,the existing security schemes can no longer meet the new requirements of anonymity and lightweight.New solutions that do not require complex calculations,such as certificateless cryptography,attract great attention from researchers.To resolve these difficulties,Wang et al.designed a new authentication architecture for the WBANs environment,which was claimed to be secure and efficient.However,in this paper,we will show that this scheme is prone to ephemeral key leakage attacks.Further,based on this authentication scheme,an anonymous certificateless scheme is proposed for lightweight devices.Meanwhile,user anonymity is fully protected.The proposed scheme is proved to be secure under a specific security model.In addition,we assess the security attributes our scheme meets through BAN logic and Scyther tool.The comparisons of time consumption and communication cost are given at the end of the paper,to demonstrate that our scheme performs prior to several previous schemes.展开更多
Purpose In the JUNO,the LS serves as the medium for detecting neutrinos.When purifying the LS using HPN,it is essential to ensure low background levels of radioactive krypton and argon in the HPN Methods Using the low...Purpose In the JUNO,the LS serves as the medium for detecting neutrinos.When purifying the LS using HPN,it is essential to ensure low background levels of radioactive krypton and argon in the HPN Methods Using the low-temperature physical adsorption properties of activated carbon to adsorb and separate radioactive gases such as radon,krypton,and argon from nitrogen in a liquid nitrogen environment.Results Our results indicated that the Kr concentration in the HPN purified by HP activated carbon is 6.84μBq/m,and the Ar concentration is 3.6μBq/m for overground HPN,while the Kr concentration is 31.4μBq/m for underground HPN.The^(85)Kr concentration in the nitrogen purified by coconut shell activated carbon is 0.46μBq/m.Conclusions After adsorption with activated carbon,the content of^(39)Kr and Ar in HPN is lower than the 50μBq/m required by JUNO.This work validates that the^(85)Kr and^(39)Ar concentrations in HPN is fit the JUNO requirement.展开更多
Because of its closeness to users,fog computing responds faster than cloud computing.Thus,it has been deployed to various applications,such as healthcare system.Recently,to ensure the secure communication of the fog-b...Because of its closeness to users,fog computing responds faster than cloud computing.Thus,it has been deployed to various applications,such as healthcare system.Recently,to ensure the secure communication of the fog-based healthcare system,Jia et al.proposed an authenticated key agreement scheme.Moreover,in view of the high computation cost existing in Jia et al.’s scheme,Ma et al.presented an efficient one using elliptic curve cryptography.In this paper,we observe that both the two schemes may potentially risk ephemeral key compromise attacks and need improving.Therefore,to overcome this potential risk,we propose a new authenticated scheme based on Jia et al.’s scheme using elliptic curve computational Diffie-Hellman hypothesis and hash functions.Additionally,we provide provable security under the adopted adversarial model and ProVerif simulation,and also analyze the performance in terms of computation and communication costs by comparisons.The analysis results show that the improved scheme resists the common attacks,reduces computation overhead,and has a certain significance.展开更多
Metal-organic frameworks(MOFs)derived magnetic carbon-based nanocomposites have drawn widespread attentions due to the well distributed nanocrystals in carbon matrix.Dynamically observing the formation process is urge...Metal-organic frameworks(MOFs)derived magnetic carbon-based nanocomposites have drawn widespread attentions due to the well distributed nanocrystals in carbon matrix.Dynamically observing the formation process is urgently needed.Herein,taking zeolitic imidazolate framework(ZIF)-67 as an example,the pyrolysis process is investigated by in-situ transmission electron microscopy(TEM)assisted with ex-situ characterizations.Co nanocrystals are evenly distributed in carbon at the initial stage of carbonization.By increasing pyrolysis temperature,the nanocrystals grow bigger and migrate to carbon surface.The carbon texture transfers from amorphous to crystalline at 600°C,and thoroughly converts at 800°C.In-situ heating TEM shows that more tiny Co nanocrystals move out from the carbon texture by increasing temperature from 700 to 800°C.At 1,000°C,some escaped tiny Co nanocrystals are volatilized and disappeared.The residual escaped Co nanocrystals catalyze the formation of carbon nanotubes(CNTs).Due to the synergistic effect between Co and carbon as well as porous structure,the nanocomposites show high-efficient microwave absorption performance,which can be tuned by pyrolysis temperature,heating rate,and mass fraction.When the mass fraction is 30 wt.%,the nanocomposites obtained at 600 or 700°C display remarkable microwave absorption with optimal reflection loss(RL)smaller than−70 dB and effective absorption band larger than 4.9 GHz.Combining the in-situ and ex-situ techniques,some key findings were observed:(1)graphitization of carbon;(2)volatilization of Co nanocrystals;(3)formation process of CNTs by Co catalyst.These findings are helpful to understand the formation of MOFs derived carbon-based composites and expand their practical applications,especially for microwave absorption.展开更多
The quantum multimode of correlated fields is essential for future quantum-correlated imaging.Here we investigate multimode properties theoretically and experimentally for the parametric amplified multiwave mixing pro...The quantum multimode of correlated fields is essential for future quantum-correlated imaging.Here we investigate multimode properties theoretically and experimentally for the parametric amplified multiwave mixing process.The multimode behavior of the signals in our system stems from spatial phase mismatching caused by frequency resonant linewidth.In the spatial domain,we observe the emission rings with an uneven distribution of photon intensity in the parametric amplified four-wave mixing process,suggesting different spatial modes.The symmetrical distribution of spatial spots indicates the spatial correlation between the Stokes and anti-Stokes signals.While in the frequency domain,the multimode character is reflected as multiple peaks splitting in the signals'spectrum.A novelty in our experiment,the number of multimodes both in the spatial and frequency domains can be controlled by dressing lasers by modifying the nonlinear susceptibility.Finally,we extend the multimode properties to the multiwave mixing process.The results can be applied in quantum imaging.展开更多
Straw pellets are widely promoted and expected to be a cleaner alternative fuel to unprocessed crop residues and rawcoal in rural China.However,the effectiveness of these dissemination programs is not well evaluated.I...Straw pellets are widely promoted and expected to be a cleaner alternative fuel to unprocessed crop residues and rawcoal in rural China.However,the effectiveness of these dissemination programs is not well evaluated.In this field study,emission characteristics of burning strawpellets,rawcoal,and unprocessed corn cobs in heating stoveswere investigated in a pilot village in Northeast China.Emission measurements covering the whole combustion cycle(ignition,flaming,and smoldering phases)shows the promotion of improved heating stoves and straw pellets could reduce pollutant emissions(e.g.,SO_(2) and CO),but increase NO_(X) and PM_(2.5) emissions compared to the initial stove-fuel use pattern in the studied area.There is a significant variance in emission characteristics between different combustion phases.The normalized emission concentrations of the different stove-fuel combinations were higher than the limits in the Chinese national standard for heating stoves,indicating that the standard is not met for real-world emissions.Coal consumption was lower than official data.Household surveys were conducted to identify the barriers to fuel and stove access associated with existing promotion strategies,management,and policies.The pilot program was of the typical“subsidy-and-policy-dependence”pattern and was unlikely to be implemented on a large scale.Technological innovation,operational optimization,and proper policies considering the local socioeconomic factors are needed to sustain the promotion of biomass straw pellets and stoves.展开更多
Compared with the traditional power grid,smart grid involves many advanced technologies and applications.However,due to the rapid development of various network technologies,smart grid is facing the challenges of bala...Compared with the traditional power grid,smart grid involves many advanced technologies and applications.However,due to the rapid development of various network technologies,smart grid is facing the challenges of balancing privacy,security,efficiency,and functionality.In the proposed scheme,we design a privacy protection scheme for outsourcing smart grid aided by fog computing,which supports fine-grained privacy-protected data aggregation based on user characteristics.The fog server matches the encrypted characteristics in the received message with the encrypted aggregation rules issued by the service provider.Therefore,the service provider can get more fine-grained analysis data based on user characteristics.Different from the existing outsourcing smart grid schemes,the proposed scheme can achieve real-time pricing on the premise of protecting user privacy and achieving system fault tolerance.Finally,experiment analyses demonstrate that the proposed scheme has less computation overhead and lower transmission delay than existing schemes.展开更多
Quantum microwave photonics(QMWP)is an innovative approach that combines energy-time entangled biphoton sources as the optical carrier with time-correlated single-photon detection for highspeed radio frequency(RF)sign...Quantum microwave photonics(QMWP)is an innovative approach that combines energy-time entangled biphoton sources as the optical carrier with time-correlated single-photon detection for highspeed radio frequency(RF)signal recovery.This groundbreaking method offers unique advantages,such as nonlocal RF signal encoding and robust resistance to dispersion-induced frequency fading.We explore the versatility of processing the quantum microwave photonic signal by utilizing coincidence window selection on the biphoton coincidence distribution.The demonstration includes finely tunable RF phase shifting,flexible multitap transversal filtering(with up to 14 taps),and photonically implemented RF mixing,leveraging the nonlocal RF mapping characteristic of QMWP.These accomplishments significantly enhance the capability of microwave photonic systems in processing ultraweak signals,opening up new possibilities for various applications.展开更多
Theβ-lactam antibiotic resistance caused by NDM-1 has become a major crisis of global public health.We have previously screened out(-)-epicatechin gallate(ECG)as a potent NDM-1 inhibitor.We further discussed its inhi...Theβ-lactam antibiotic resistance caused by NDM-1 has become a major crisis of global public health.We have previously screened out(-)-epicatechin gallate(ECG)as a potent NDM-1 inhibitor.We further discussed its inhibitory effect and action mode in the present study.According to our results,ECG reversibly inactivated NDM-1 in a non-competitive mode,with an IC50 value of 4.48μM.ECG effectively recovered the activity of severalβ-lactam antibiotics against resistant strain harboring blaNDM-1.Especially,the effects on carbapenems were worth mentioning.The zinc supplement assay indicated a zinc-related mechanism of ECG.Different from traditional chelating agents,it showed low toxicity both in vivo and in vitro.In a word,our findings provided a promising NDM-1 inhibitor,ECG,which was able to assist carbapenems against NDM-1-producing strain.展开更多
Activated carbon (AC)-supported copper or zinc made from ion exchange resin (IRCu-C and IRZn-C) have an increased metal load of 557.3 mg·g^-1 and 502.8 mg·g^-1 compared to those prepared by the tradition...Activated carbon (AC)-supported copper or zinc made from ion exchange resin (IRCu-C and IRZn-C) have an increased metal load of 557.3 mg·g^-1 and 502.8 mg·g^-1 compared to those prepared by the traditional method involving impregnation with AC and copper (II) citrate or zinc citrate solution (LaCu-C and LaZn-C) of 12.9 mg·g^-1 and 46.0 mg·g^-1 respectively. When applied to decompose 2,2',4,4',5,5'-hexachlorobiphenyl at 250 ℃, IRCu-C achieved higher activity of 99.0% decomposition efficiency than LaCu-C of 84.7%, IRZn-C of 90.5% and LaZn-C of 62.7%. When the reaction temperature rose to 350 ℃, all the four kinds of reactants can decompose PCB- 153 with efficiency above 90%. Further, X-ray photoelec- tron spectroscopy characterization of IRCu-C before and after the reaction indicated transformation of 19.1% of Cu atoms into Cu^2+, illustrating that Cu is the active ingredient or electron donor promoting the decomposition of PCB- 153. The mechanism underlying this process differs from a traditional H donor. However, there is no significant change on the surface of IRZn-C before and after the reaction, suggesting that Zn acts as catalyst during the process of PCB-153 decomposition.展开更多
基金Supported by the National Natural Science Foundation of China(21476211)the Zhejiang Provincial Natural Science Foundation of China(LY16B060004 and LY18B060016)
文摘In the present work, a series of Pt-based catalysts, alloyed with a second metal, i.e., Re, Sn, Er, La, and Y, and supported on activated carbon, ordered mesoporous carbon, N-doped mesoporous carbon or reduced graphene oxide(rGO), have been developed for selective hydrogenation of cinnamaldehyde to cinnamylalcohol. Re and rGO were proved to be the most favorable metal dopant and catalyst support, respectively. Pt_(50) Re_(50)/rGO showed the highest cinnamylalcohol selectivity of 89% with 94% conversion of cinnamaldehyde at the reaction conditions of 120 °C, 2.0 MPaH_2 and 4 h.
基金Supported by Scientific and Technological Project of Inner Mongolia Autonomous Region (2020GG0016)。
文摘Based on the fire and meteorological data of forest and grassland in Inner Mongolia in recent 30 years,a forest and grassland fire risk grade forecast model is established,and a refined forest and grassland fire risk level forecast system based on smart grid is developed. The results show that predictors are determined about forest and grassland fire risk grade,such as precipitation,minimum relative humidity,maximum temperature,maximum wind speed,number of sunny or rainy days,and forest and grassland combustible stock. According to fire risk division conclusion,forest and grassland areas are divided into 5 forecast areas. By using discriminant analysis and weighted factor overlay method,an elaborate fire risk grade forecast model is established in different forecast areas of Inner Mongolia forest and grassland. By using smart grid forecast field data,an elaborate fire risk grade forecasting system is established for making fire risk grade forecast during 24,48 and 72 h.
文摘With the rapid development of the social economy,people are paying more and more attention to environmental issues.If society wants sustainable development,it must put energy conservation and emission reduction on the agenda.At this stage,China has vigorously promoted energy conservation and emission reduction,and all walks of life have gradually embarked on the green road of energy conservation.In recent years,energy saving measures has been widely used in China's oilfield electrical engineering.The author explores and analyzes the basic principles of energy saving measures applied in oilfield electrical engineering,and proposes an effective way to apply energy saving measures in oilfield electrical engineering,hoping to contribute to the energy saving effect of oilfield electrical engineering.
基金financially supported by National Natural Science Foundation of China(Nos.51572218 and 11504293)Natural Science Foundation of Shaanxi Province(No.2019JM-138)+1 种基金Natural Science Foundation from Department of Science and Technology of Shaanxi Province(Nos.2021JQ-431,2021JM-304,and 2021JQ-427)Scientific Research Program Funded by Shaanxi Provincial Education Department(No.20JK0946)。
文摘Porous carbon-based materials are promised to be lightweight dielectric microwave absorbents.Deeply understanding the influence of graphitization grade and porous structure on the dielectric parameters is urgently required.Herein,utilizing the low boiling point of Zn,porous N-doped carbon was fabricated by carbonization of ZIF-8(Zn)at different temperature,and the microwave absorption performance was investigated.The porous N-doped carbon inherits the high porosity of ZIF-8 precursor.By increasing the carbonization temperature,the contents of Zn and N elements are decreased;the graphitization degree is improved;however,the specific surface area and porosity are increased first and then decreased.When the carbonization temperature is 1000°C,the porous N-doped carbon behaves enhanced microwave absorption.With an ultrathin thickness of 1.29 mm,the ideal RL reaches-50.57 dB at 16.95 GHz and the effective absorption bandwidth is 4.17 GHz.The mechanism of boosted microwave absorption is ascribed to the competition of graphitization and porosity as well as N dopants,resulting in high dielectric loss capacity and good impedance matching.The porous structure can prolong the pathways and raise the contact opportunity between microwaves and porous carbon,causing multiple scattering,interface polarization,and improved impedance matching.Besides,the N dopants can induce electron polarization and defect polarization.These results give a new insight to construct lightweight carbon-based microwave absorbents by regulating the graphitization and porosity.
基金funded by the Open Project of Xinjiang Production&Construction Corps Key Laboratory of Protection and Utilization of Biological Resources in Tarim Basinthe National Nature Science Foundation of China (grant numbers:BRZD2104 and 31960648)the Joint Plan of Liaoning Province in the field of Livelihood Science and Technology (Rural Revitalization Science and Technology Support)。
文摘Background Geese are among the most important poultry species in the world.The current generally accepted hypothesis is that the European domestic geese originated from greylag geese(Anser anser),and Chinese domestic geese have two origins,most of which originated from swan geese(Anser cygnoides),and the Yili goose originated from greylag geese.To explain the origin and demographic history of geese,we selected 14 goose breeds from Europe and China and wild populations of swan and greylag geese,and whole genome sequencing data were obtained for 74 samples.Results Population structure analysis and phylogenetic trees showed that the wild ancestor of Chinese domestic geese,except for Yili,is the swan geese,and the wild ancestor of Chinese Yili and European domestic geese is greylag geese.Analysis of the demographic history suggests that the domestication of Chinese geese occurred~3499 years ago and that of the European geese occurred~7552 years ago.Furthermore,gene flow was observed between domestic geese and their wild ancestors.Analysis of introgression showed that Yili geese had been introgressed by Chinese domestic geese,and the body size of Yili geese may be influenced by introgression events of some growthrelated genes,including IGF-1.Conclusions Our study provides evidence for the origin of geese at the genome-wide level and advances the understanding of the history of goose domestication and the traits affected by introgression events.
基金supported by the National Natural Science Foundation of China(Nos.52072064,51972051,62171115,and 51732003)the 111 Project(No.B13013).
文摘Photoreforming hydrogen evolution(Pr-HE)of a water-pollutant system could simultaneously achieve efficient hydrogen production and pollutant degradation.It provides a new way to solve energy and environmental issues,but the poor internal charge separation still limits its performance.This work designed hetero-Janus nanofibers(HJNFs)with ordered electric field distribution and separated redox surfaces to promote Pr-HE of the water-pollutant system.Taking ZnO/NiO heterojunction as an example,the hetero-Janus structures were prepared via"Dual-channel"electrospinning and further confirmed by the element morphology analysis and asymmetric distribution of the XPS spectra.The theoretical simulation showed that Janus structures could effectively inhibit the electron trap and hole trap generation,then accelerate the directional carrier migration to the surface.Experimental investigations also confirmed that Janus structures could effectively suppress internal exciton luminescence and accelerate surface charge transfer.The Pr-HE amount and the corresponding propranolol(PRO)degradation rate of HJNFs were 7.9 and 1.5 times higher than hetero-mixed nanofibers(HMNFs).The enhancement factor of Pr-HE in water-PRO to pure water was about 3.1,but nearly zero for HMNFs.This prominent synergistic effect was due to the enhancement of charge separation and the inhibition of cascade side reaction from hetero-Janus structures.Furthermore,the synchronous Pr-HE and degradation reactions were significantly promoted by selective introducing Ag nanoparticles in one side of the HJNFs for enlarging the interfacial Fermi energy level difference.The hetero-Janus strategy offers a new perspective on designing efficient photoreforming photocatalysts for energy and environment applications.
基金This study was supported by Hebei Province Special Postdoctoral Financial Assistance(B2017003030)the Youth Innovation Fund of the Institute of Cereal and Oil Crops,Hebei Academy of Agriculture and Forestry Sciences(LYS2017001)the Hebei Financial Special Project:Construction of Talents Team for Agricultural Science Technical Innovation,and the China Agriculture Research System(CARS-02).
文摘Flowering time is an indicator of adaptation in maize and a key trait for selection in breeding.The genetic basis of flowering time in maize,especially in response to plant density,remains unclear.The objective of this study was to identify maize quantitative trait loci(QTL)associated with flowering time-related traits that are stably expressed under several plant densities and show additive effects that vary with plant density.Three hundred recombinant inbred lines(RIL)derived from a cross between Ye 478 and Qi 319,together with their parents,were planted at three plant densities(90,000,120,000,and 150,000 plants ha^(-1))in four environments.The five traits investigated were days to tasseling(DTT),days to silking(DTS),days to pollen shed(DTP),interval between anthesis and silking(ASI),and interval between tasseling and anthesis(TAI).A high-resolution bin map was used for QTL mapping.In the RIL population,the DTT,DTS,and DTP values increased with plant density,whereas the ASI and TAI values showed negligible response to plant density.A total of 72 QTL were identified for flowering time-related traits,including 15 stably expressed across environments.Maize flowering time under different densities seems to be regulated by complex pathways rather than by several major genes or an independent pathway.The effects of some stable QTL,especially qDTT8-1 and qDTT10-4,varied with plant density.Fine mapping and cloning of these QTL will shed light on the mechanism of flowering time and assist in breeding earlymaturing maize inbred lines and hybrids.
基金Supported by Scientific and Technological Project of Inner Mongolia Autonomous Region(2020GG0016).
文摘Based on a comprehensive and systematic analysis of the temporal and spatial distribution,periodic changes,and influencing factors of forest fires in Inner Mongolia,through fixed-point observations and experiments on the ground,forest combustibles are divided into the ground litter layer,ground standing litter,and living plants.The combustibles are divided into various grades according to their load,dryness and combustibility.By determining the influencing factors of each combustible grade,a forecast model of the combustibility grade of combustibles is established.The forecast model has been widely used in the mid-and long-term forecast model of fire danger grade,and the accuracy rate of the fall area forecast through back-generation fitting verification is above 88.43%.
基金National Natural Science Foundation of China (Grant Nos. U1708262, U1736203, 61772173, 61672413)ational Key R&D Program of China (2017YFB0801805)he Fundamental Research Funds for the Central Universities and the Innovation Fund of Xidian University.
文摘Software-defined networks (SDN) have been widely used in Cloud Data Centers in recent years. With the development of cloud technologies, different organizations need to share network resources to achieve common business goals, which requires distributed SDN controllers to collaboratively manage cloud networks and realize cross-domain routing. However, existing distributed controller cooperative routing schemes require a third-party trust center to establish trusted relationships for controllers. Since both trust centers and certified entities are vulnerable to various attacks and security risks, the existing works cannot effectively ensure cross-domain routing is credible. To address this problem, Blockchain is employed to establish trusted relationships between distributed controllers, then a cross-domain routing mechanism was devised based on the trusted relationships. Security analysis and experiments indicate that the proposed scheme can establish trust relationships and provide credible cross-domain routing cooperation for distributed SDN controllers. Besides, the required overhead of storage and bandwidth are very limited, which implies good practicability.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.61872449,62172433,62072093,62125205)the Science Foundation for the Excellent Youth Scholars of Henan Province(No.222300420099).
文摘Wireless body area networks(WBANs)guarantee timely data processing and secure information preservation within the range of the wireless access network,which is in urgent need of a new type of security technology.However,with the speedy development of hardware,the existing security schemes can no longer meet the new requirements of anonymity and lightweight.New solutions that do not require complex calculations,such as certificateless cryptography,attract great attention from researchers.To resolve these difficulties,Wang et al.designed a new authentication architecture for the WBANs environment,which was claimed to be secure and efficient.However,in this paper,we will show that this scheme is prone to ephemeral key leakage attacks.Further,based on this authentication scheme,an anonymous certificateless scheme is proposed for lightweight devices.Meanwhile,user anonymity is fully protected.The proposed scheme is proved to be secure under a specific security model.In addition,we assess the security attributes our scheme meets through BAN logic and Scyther tool.The comparisons of time consumption and communication cost are given at the end of the paper,to demonstrate that our scheme performs prior to several previous schemes.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA10010500).
文摘Purpose In the JUNO,the LS serves as the medium for detecting neutrinos.When purifying the LS using HPN,it is essential to ensure low background levels of radioactive krypton and argon in the HPN Methods Using the low-temperature physical adsorption properties of activated carbon to adsorb and separate radioactive gases such as radon,krypton,and argon from nitrogen in a liquid nitrogen environment.Results Our results indicated that the Kr concentration in the HPN purified by HP activated carbon is 6.84μBq/m,and the Ar concentration is 3.6μBq/m for overground HPN,while the Kr concentration is 31.4μBq/m for underground HPN.The^(85)Kr concentration in the nitrogen purified by coconut shell activated carbon is 0.46μBq/m.Conclusions After adsorption with activated carbon,the content of^(39)Kr and Ar in HPN is lower than the 50μBq/m required by JUNO.This work validates that the^(85)Kr and^(39)Ar concentrations in HPN is fit the JUNO requirement.
基金supported by the National Natural Science Foundation of China(Grant Nos.Ui708262,U1736203,61872449).
文摘Because of its closeness to users,fog computing responds faster than cloud computing.Thus,it has been deployed to various applications,such as healthcare system.Recently,to ensure the secure communication of the fog-based healthcare system,Jia et al.proposed an authenticated key agreement scheme.Moreover,in view of the high computation cost existing in Jia et al.’s scheme,Ma et al.presented an efficient one using elliptic curve cryptography.In this paper,we observe that both the two schemes may potentially risk ephemeral key compromise attacks and need improving.Therefore,to overcome this potential risk,we propose a new authenticated scheme based on Jia et al.’s scheme using elliptic curve computational Diffie-Hellman hypothesis and hash functions.Additionally,we provide provable security under the adopted adversarial model and ProVerif simulation,and also analyze the performance in terms of computation and communication costs by comparisons.The analysis results show that the improved scheme resists the common attacks,reduces computation overhead,and has a certain significance.
基金the National Natural Science Foundation of China(Nos.51572218,11504293,51771085,and 51801087)the Natural Science Foundation of Shaanxi Province(No.2019JM-138)+2 种基金the Natural Science Foundation from Department of Science and Technology of Shaanxi Province(Nos.2021JQ-431,2021JM-304,and 2021JQ-427)the Scientific Research Program Funded by Shaanxi Provincial Education Department(No.20JK0946)the Key Project of Research and Development of Shaanxi Province(No.2018ZDCXL-GY-08-05).
文摘Metal-organic frameworks(MOFs)derived magnetic carbon-based nanocomposites have drawn widespread attentions due to the well distributed nanocrystals in carbon matrix.Dynamically observing the formation process is urgently needed.Herein,taking zeolitic imidazolate framework(ZIF)-67 as an example,the pyrolysis process is investigated by in-situ transmission electron microscopy(TEM)assisted with ex-situ characterizations.Co nanocrystals are evenly distributed in carbon at the initial stage of carbonization.By increasing pyrolysis temperature,the nanocrystals grow bigger and migrate to carbon surface.The carbon texture transfers from amorphous to crystalline at 600°C,and thoroughly converts at 800°C.In-situ heating TEM shows that more tiny Co nanocrystals move out from the carbon texture by increasing temperature from 700 to 800°C.At 1,000°C,some escaped tiny Co nanocrystals are volatilized and disappeared.The residual escaped Co nanocrystals catalyze the formation of carbon nanotubes(CNTs).Due to the synergistic effect between Co and carbon as well as porous structure,the nanocomposites show high-efficient microwave absorption performance,which can be tuned by pyrolysis temperature,heating rate,and mass fraction.When the mass fraction is 30 wt.%,the nanocomposites obtained at 600 or 700°C display remarkable microwave absorption with optimal reflection loss(RL)smaller than−70 dB and effective absorption band larger than 4.9 GHz.Combining the in-situ and ex-situ techniques,some key findings were observed:(1)graphitization of carbon;(2)volatilization of Co nanocrystals;(3)formation process of CNTs by Co catalyst.These findings are helpful to understand the formation of MOFs derived carbon-based composites and expand their practical applications,especially for microwave absorption.
基金National Key RD Program of China(2017YFA0303700,2018YFA0307500)National Natural Science Foundation of China(11604256,11804267,61605154,61975159,11904279)
文摘The quantum multimode of correlated fields is essential for future quantum-correlated imaging.Here we investigate multimode properties theoretically and experimentally for the parametric amplified multiwave mixing process.The multimode behavior of the signals in our system stems from spatial phase mismatching caused by frequency resonant linewidth.In the spatial domain,we observe the emission rings with an uneven distribution of photon intensity in the parametric amplified four-wave mixing process,suggesting different spatial modes.The symmetrical distribution of spatial spots indicates the spatial correlation between the Stokes and anti-Stokes signals.While in the frequency domain,the multimode character is reflected as multiple peaks splitting in the signals'spectrum.A novelty in our experiment,the number of multimodes both in the spatial and frequency domains can be controlled by dressing lasers by modifying the nonlinear susceptibility.Finally,we extend the multimode properties to the multiwave mixing process.The results can be applied in quantum imaging.
基金supported by the Ministry of Science and Technology of China(No.2017YFC0211400)and the China Office of Clean Air Asia.
文摘Straw pellets are widely promoted and expected to be a cleaner alternative fuel to unprocessed crop residues and rawcoal in rural China.However,the effectiveness of these dissemination programs is not well evaluated.In this field study,emission characteristics of burning strawpellets,rawcoal,and unprocessed corn cobs in heating stoveswere investigated in a pilot village in Northeast China.Emission measurements covering the whole combustion cycle(ignition,flaming,and smoldering phases)shows the promotion of improved heating stoves and straw pellets could reduce pollutant emissions(e.g.,SO_(2) and CO),but increase NO_(X) and PM_(2.5) emissions compared to the initial stove-fuel use pattern in the studied area.There is a significant variance in emission characteristics between different combustion phases.The normalized emission concentrations of the different stove-fuel combinations were higher than the limits in the Chinese national standard for heating stoves,indicating that the standard is not met for real-world emissions.Coal consumption was lower than official data.Household surveys were conducted to identify the barriers to fuel and stove access associated with existing promotion strategies,management,and policies.The pilot program was of the typical“subsidy-and-policy-dependence”pattern and was unlikely to be implemented on a large scale.Technological innovation,operational optimization,and proper policies considering the local socioeconomic factors are needed to sustain the promotion of biomass straw pellets and stoves.
基金This work was supported in part by the National Natural Science Foundation of China(Grant Nos.62125205,62072361 and 61872449)。
文摘Compared with the traditional power grid,smart grid involves many advanced technologies and applications.However,due to the rapid development of various network technologies,smart grid is facing the challenges of balancing privacy,security,efficiency,and functionality.In the proposed scheme,we design a privacy protection scheme for outsourcing smart grid aided by fog computing,which supports fine-grained privacy-protected data aggregation based on user characteristics.The fog server matches the encrypted characteristics in the received message with the encrypted aggregation rules issued by the service provider.Therefore,the service provider can get more fine-grained analysis data based on user characteristics.Different from the existing outsourcing smart grid schemes,the proposed scheme can achieve real-time pricing on the premise of protecting user privacy and achieving system fault tolerance.Finally,experiment analyses demonstrate that the proposed scheme has less computation overhead and lower transmission delay than existing schemes.
基金supported by the National Natural Science Foundation of China(Grant Nos.12033007,61801458,12103058,12203058,12074309,and 61875205)the Youth Innovation Promotion Association,CAS(Grant Nos.2021408,2022413,and 2023425)the China Postdoctoral Science Foundation(Grant No.2022M723174).
文摘Quantum microwave photonics(QMWP)is an innovative approach that combines energy-time entangled biphoton sources as the optical carrier with time-correlated single-photon detection for highspeed radio frequency(RF)signal recovery.This groundbreaking method offers unique advantages,such as nonlocal RF signal encoding and robust resistance to dispersion-induced frequency fading.We explore the versatility of processing the quantum microwave photonic signal by utilizing coincidence window selection on the biphoton coincidence distribution.The demonstration includes finely tunable RF phase shifting,flexible multitap transversal filtering(with up to 14 taps),and photonically implemented RF mixing,leveraging the nonlocal RF mapping characteristic of QMWP.These accomplishments significantly enhance the capability of microwave photonic systems in processing ultraweak signals,opening up new possibilities for various applications.
基金Natural Sciences Foundation of China(NSFC,Grant No.81872913)National High-tech R&D Program(863 Program,Grant No.2015AA020911)。
文摘Theβ-lactam antibiotic resistance caused by NDM-1 has become a major crisis of global public health.We have previously screened out(-)-epicatechin gallate(ECG)as a potent NDM-1 inhibitor.We further discussed its inhibitory effect and action mode in the present study.According to our results,ECG reversibly inactivated NDM-1 in a non-competitive mode,with an IC50 value of 4.48μM.ECG effectively recovered the activity of severalβ-lactam antibiotics against resistant strain harboring blaNDM-1.Especially,the effects on carbapenems were worth mentioning.The zinc supplement assay indicated a zinc-related mechanism of ECG.Different from traditional chelating agents,it showed low toxicity both in vivo and in vitro.In a word,our findings provided a promising NDM-1 inhibitor,ECG,which was able to assist carbapenems against NDM-1-producing strain.
基金Acknowledgements This research was supported by the National Natural Science Foundation of China (Grant Nos. 21277010 and 51078013), Special Research Funding for Public Benefit Industries from National Ministry of Environmental Protection (No. 201209005), the National Science and Technology Support Program of China (No. 2010BAC66B04), and Key Laboratory for Advanced Technology in Environmental Protection of Jiangsu Province (No. AE201003).
文摘Activated carbon (AC)-supported copper or zinc made from ion exchange resin (IRCu-C and IRZn-C) have an increased metal load of 557.3 mg·g^-1 and 502.8 mg·g^-1 compared to those prepared by the traditional method involving impregnation with AC and copper (II) citrate or zinc citrate solution (LaCu-C and LaZn-C) of 12.9 mg·g^-1 and 46.0 mg·g^-1 respectively. When applied to decompose 2,2',4,4',5,5'-hexachlorobiphenyl at 250 ℃, IRCu-C achieved higher activity of 99.0% decomposition efficiency than LaCu-C of 84.7%, IRZn-C of 90.5% and LaZn-C of 62.7%. When the reaction temperature rose to 350 ℃, all the four kinds of reactants can decompose PCB- 153 with efficiency above 90%. Further, X-ray photoelec- tron spectroscopy characterization of IRCu-C before and after the reaction indicated transformation of 19.1% of Cu atoms into Cu^2+, illustrating that Cu is the active ingredient or electron donor promoting the decomposition of PCB- 153. The mechanism underlying this process differs from a traditional H donor. However, there is no significant change on the surface of IRZn-C before and after the reaction, suggesting that Zn acts as catalyst during the process of PCB-153 decomposition.