On-orbit spacecraft face many threats,such as collisions with debris or other spacecraft.Therefore,perception of the surrounding space environment is vitally important for on-orbit spacecraft.Spacecraft require a dyna...On-orbit spacecraft face many threats,such as collisions with debris or other spacecraft.Therefore,perception of the surrounding space environment is vitally important for on-orbit spacecraft.Spacecraft require a dynamic attitude tracking ability with high precision for such missions.This paper aims to address the above problem using an improved backstepping controller.The tracking mission is divided into two phases:coarse alignment and fine alignment.In the first phase,a traditional saturation controller is utilized to limit the maximum attitude angular velocity according to the actuator’s ability.For the second phase,the proposed backstepping controller with different virtual control inputs is applied to track the moving target.To fulfill the high precision attitude tracking requirements,a hybrid attitude control actuator consisting of a Control Moment Gyro(CMG)and Reaction Wheel(RW)is constructed,which can simultaneously avoid the CMG singularity and RW saturation through the use of an angular momentum optimal management strategy,such as null motion.Finally,five simulation scenarios were carried out to demonstrate the effectiveness of the proposed control strategy and hybrid actuator.展开更多
Rainfall samples were collected from three observation sites in Guilin from 2013 to 2017, and the chemical composition characteristics of precipitation and the contribution made by different ion sources were analyzed ...Rainfall samples were collected from three observation sites in Guilin from 2013 to 2017, and the chemical composition characteristics of precipitation and the contribution made by different ion sources were analyzed when atmospheric pollutants levels were reduced. The results showed that acid gas emissions and atmospheric pollutant concentrations continued to decline during the study period. However, the change in the volume-weighted mean p H at the three sites suggested that acid rain pollution was not alleviated and began to deteriorate after 2015. The continuing downward trend for alkaline neutralizing ions(Ca^(2+), NH_4^+) in precipitation indicated that the reduction in alkaline neutralizing substances in the atmosphere was an important factor that led to the deterioration in acid rain across Guilin. The principal component analysis and spearman correlation analysis indicated five sources of ions in precipitation. Quantitative assessment of these five sources indicated that fossil fuel combustion contributed the most ions concentration in precipitation at the three sites, followed by agriculture, terrestrial(crustal) sources, marine sources, and biomass burning. Long-distance airflow might affect the acidity, the electrical conductivity(EC), and ion concentrations in precipitation across Guilin. The airflow trajectory from the west and southeast directions corresponded to higher acidity and ion concentrations. According to the current air pollution control strategy planned by Guilin, reducing atmospheric coarse particles and NH_3 at the same time may potentially lead to further deteriorations in acid rain contents. Therefore, Guilin needs to develop more reasonable pollution prevention measures that synergistically control atmospheric pollutants and acid rain pollution.展开更多
The 12-molybdosphoric acid mixed with titania （MPA-TiO2） was found to be a novel and efficient catalyst for the synthesis of diphenyl carbonate （DPC） via transesterification of dimethyl carbonate （DMC） and pheno...The 12-molybdosphoric acid mixed with titania （MPA-TiO2） was found to be a novel and efficient catalyst for the synthesis of diphenyl carbonate （DPC） via transesterification of dimethyl carbonate （DMC） and phenol. The X-ray diffraction （XRD） and infrared （IR） techniques were employed to characterize the prepared catalysts. The effect of the weight ratio of the 12-molybdosphoric acid to titania on the transesterification was investigated. A 13.1% yield of DPC and an 11.6% yield of methyl phenyl carbonate （MPC） were obtained over MPA-TiO2 with the weight ratio of MPA to TiO2 as 5：1.展开更多
Control Moment Gyroscope（CMG） is an effective candidate for agile satellites and large spacecraft attitude control because of its powerful torque amplification capability. The most serious situation, however, in usi...Control Moment Gyroscope（CMG） is an effective candidate for agile satellites and large spacecraft attitude control because of its powerful torque amplification capability. The most serious situation, however, in using CMG is the inherent geometric singularity problem, where there＇s no torque output along a particular direction. Space expansion method has been proposed in this work for the singularity analysis. Based on inverse mapping transformation, an expanded Jacobian matrix which is a full rank square matrix is obtained. The singular angle sets of the 3-parallel cluster and pyramid cluster are distinguished using space expansion method. An effective hybrid steering strategy, able to deal with the elliptic singularity, is further proposed. Simulation results demonstrate the excellent performance of the proposed steering logic compared to the generalized singular robust logic and pseudo inverse logic in terms of energy consumption and torque error.展开更多
Agile attitude maneuver is a basic requirement for next generation imaging spacecraft and Control Moment Gyroscope (CMG) is an effective candidate for large space station and agile spacecraft attitude control because ...Agile attitude maneuver is a basic requirement for next generation imaging spacecraft and Control Moment Gyroscope (CMG) is an effective candidate for large space station and agile spacecraft attitude control because of its torque amplification capability. This paper provides a thorough survey of Single Gimbal Control Moment Gyroscope (SGCMG) in terms of configuration,evaluation,modeling,singularity analysis and steering logic,etc. For specific space missions,CMGs are logically mounted into different particular arrays which can be chosen by the proposed evaluation methods. From the dynamic model we find a tough inverse mapping problem which suffers the inherent geometric singularity. Different techniques and theories then are applied for singularity analysis and CMG steering logics design. The pyramid CMG cluster and singular robust logics are proven to be able to enhance the agility of spacecraft. Above work forms a systematic framework of SGCMG for agile spacecraft control with lots of illustrative examples,tables and figures,and will evoke further investigation for future missions.展开更多
A single particle aerosol mass spectrometer was deployed to measure the changes of single particle species and sizes during March 2015 in Weizhou Island of the Beibu Gulf, Guangxi province, South China. In this campai...A single particle aerosol mass spectrometer was deployed to measure the changes of single particle species and sizes during March 2015 in Weizhou Island of the Beibu Gulf, Guangxi province, South China. In this campaign, a total of 3,100,597 particles were sized, and 25.8%particles with both positive and negative mass spectrum were collected and 24.8%characterized in combination with the ART-2 a neural network algorithm. The distribution of sized particles was mainly in from 520 to 600 nm, and the diameters ranging from 340 to1000 nm accounted for above 90%. Eight types of particles were classified： Elemental Carbon containing（EC）, Organic Carbon containing（OC）, EC and OC combined containing particles,Na containing particles, K containing particles（K）, Levoglucosan containing particles,mineral containing particles, and Heavy Metal containing particles（HM）. EC, OC and K were the major containing particles, which accounted for 84.3% in the eight types particles. The relative ratio and size distribution of the three types were EC（48.1%, 620 nm）, OC（12.7%,440 nm）, and K（23.5%, 600 nm）, respectively. The three types of particles were a bit increasing ratios compared with those in clean periods during haze pollution periods.Combined with the back-trajectory results from the Hysplit-4 model and local pollution sources revealed that the ambient air quality on the Weizhou Island may be influenced by biomass burning in the Indochina Peninsula（biomass burning in the Indochina Peninsula）from the transportation on higher level atmospheric layer and by mainland of south China located northeast of Weizhou Island on the ground.展开更多
Time-resolved single-particle measurements were conducted during Chinese New Year in Nanning, China. Firework displays resulted in a burst of SO2, coarse mode, and accumulation mode （100-500 nm） particles. Through s...Time-resolved single-particle measurements were conducted during Chinese New Year in Nanning, China. Firework displays resulted in a burst of SO2, coarse mode, and accumulation mode （100-500 nm） particles. Through single particle mass spectrometry analysis, five different types of particles （fireworks-metal, ash, dust, organic carbon-sulfate （OC-sulfate）, biomass burning） with different size distributions were identified as primary emissions from firework displays. The fireworks-related particles accounted for more than 70% of the total analyzed particles during severe firework detonations. The formation of secondary particulate sulfate and nitrate during firework events was investigated on single particle level. An increase of sulfite peak （80SO3） followed by an increase of sulfate peaks （97HSO7＋96SO7） in the mass spectra during firework displays indicated the aqueous uptake and oxidation of SO2 on particles. High concentration of gaseous SO2, high relative humidity and high particle loading likely promoted SO2 oxidation. Secondary nitrate formed through gas-phase oxidation of NO2 to nitric acid, followed by the condensation into particles as ammonium nitrate. This study shows that under worm, humid conditions, both primary and secondary aerosols contribute to the particulate air pollution during firework displays.展开更多
Aiming at the safety problem of the stage separation of parallel reusable high-speed air vehicles,this paper studies the unsteady test method and focuses on deriving a similarity law of parallel stage separation free-...Aiming at the safety problem of the stage separation of parallel reusable high-speed air vehicles,this paper studies the unsteady test method and focuses on deriving a similarity law of parallel stage separation free-flight wind tunnel tests.The new similarity law considers the influences of aerodynamic force and gravity on the motions of the two stages,as well as the influence of aerodynamic interference between the two stages on each other’s motion.From the perspective of multiangle physical equations,the conditions to ensure that the two-stage separation trajectory of a wind tunnel test is similar to that of a real air vehicle are derived innovatively,so as to ensure the authenticity and credibility of wind tunnel test results.The similarity law is verified by an HIFiRE-5 air vehicle,and the separation trajectories of wind tunnel tests and the real air vehicle are obtained by numerical simulation.The research shows that the similarity law derived in this paper can ensure that wind tunnel free-flight tests have the ability to predict the two-stage separation characteristics of real parallel vehicles.By analyzing the separation trajectory curve of the typical state,it is found that the new method can ensure that the trajectory error of a wind tunnel test does not exceed 1%,which indicates that this method is credible.The establishment of the new method lays the foundation for subsequent wind tunnel tests and provides support for research on the safety of the stage separation of parallel reusable air vehicles.展开更多
The LGS1(Large grain size 1)gene,also known as GS2/GL2/Os GRF4,is involved in regulating grain size and quality in rice,but the mechanism governing grain size has not been elucidated.We performed transcriptomic,proteo...The LGS1(Large grain size 1)gene,also known as GS2/GL2/Os GRF4,is involved in regulating grain size and quality in rice,but the mechanism governing grain size has not been elucidated.We performed transcriptomic,proteomic,and phosphoproteomic analyses of young rice panicles in Samba(a wild-type cultivar with extra-small grain)and NIL-LGS1(a nearly isogenic line of LGS1 with large grain in the Samba genetic background)at three developmental stages(4–6)to identify internal dynamic functional networks determining grain size that are mediated by LGS1.Differentially expressed proteins formed seven highly functionally correlated clusters.The concordant regulation of multiple functional clusters may be key features of the development of grain length in rice.In stage 5,16 and 24 phosphorylated proteins were significantly up-regulated and down-regulated,and dynamic phosphorylation events may play accessory roles in determining rice grain size by participating in protein–protein interaction networks.Transcriptomic analysis in stage 5 showed that differentially expressed alternative splicing events and dynamic gene regulatory networks based on 39 transcription factors and their highly correlated target genes might contribute to rice grain development.Integrative multilevel omics analysis suggested that the regulatory network at the transcriptional and posttranscriptional levels could be directly manifested at the translational level,and this analysis also suggested a regulatory mechanism,regulation of protein translation levels,in the biological process that extends from transcript to protein to the development of grain.Functional analysis suggested that biological processes including MAPK signaling,calcium signaling,cell proliferation,cell wall,energy metabolism,hormone pathway,and ubiquitin-proteasome pathway might be involved in LGS1-mediated regulation of grain length.Thus,LGS1-mediated regulation of grain size is affected by dynamic transcriptional,posttranscriptional,translational and posttranslational changes.展开更多
Efficient and convenient treatment of industrial dyeing wastewater is of great significance to guarantee human and animal health.This work presented the enhanced catalytic activity at pH 3.0 of laccase immobilized on ...Efficient and convenient treatment of industrial dyeing wastewater is of great significance to guarantee human and animal health.This work presented the enhanced catalytic activity at pH 3.0 of laccase immobilized on amino-functionalized ZnFe_(2)O_(4) nanoparticles(ZnFe_(2)O_(4)-laccase)and its application for the degradation of textile dyes.Due to the existence of a large number of oxygen vacancies on the surface of the ZnFe_(2)O_(4) nanoparticles,negative ions accumulated on the magnetic carriers,which resulted in a harsh optimal pH value of the ZnFe_(2)O_(4)-laccase.Laccase activity assays revealed that the ZnFe_(2)O_(4)-laccase possessed superior pH and thermal stabilities,excellent reusability,and noticeable organic solvent tolerance.Meanwhile,the ZnFe_(2)O_(4) laccase presented efficient and sustainable degradation of high concentrations of textile dyes.The initial decoloration efficiencies of malachite green(MG),brilliant green(BG),azophloxine,crystal violet(CV),reactive blue 19(RB19),and procion red MX-5B were approximately 99.1%,95.0%,93.3%,87.4%,86.1%,and 85.3%,respectively.After 10 consecutive reuses,the degradation rates of the textile dyes still maintained about 98.2%,92.5%,83.2%,81.5%,79.8%and 65.9%,respectively.The excellent dye degradation properties indicate that the ZnFe_(2)O_(4)-laccase has a technical application in high concentrations of dyestuff treatment.展开更多
On-orbit servicing, such as spacecraft maintenance, on-orbit assembly, refueling, and de-orbiting, can reduce the cost of space missions, improve the performance of spacecraft, and extend its life span. The relative s...On-orbit servicing, such as spacecraft maintenance, on-orbit assembly, refueling, and de-orbiting, can reduce the cost of space missions, improve the performance of spacecraft, and extend its life span. The relative state between the servicing and target spacecraft is vital for on-orbit servicing missions, especially the final approaching stage. The major challenge of this stage is that the observed features of the target are incomplete or are constantly changing due to the short distance and limited Field of View (FOV) of camera. Different from cooperative spacecraft, non-cooperative target does not have artificial feature markers. Therefore, contour features, including triangle supports of solar array, docking ring, and corner points of the spacecraft body, are used as the measuring features. To overcome the drawback of FOV limitation and imaging ambiguity of the camera, a "selfie stick" structure and a self-calibration strategy were implemented, ensuring that part of the contour features could be observed precisely when the two spacecraft approached each other. The observed features were constantly changing as the relative distance shortened. It was difficult to build a unified measurement model for different types of features, including points, line segments, and circle. Therefore, dual quaternion was implemented to model the relative dynamics and measuring features. With the consideration of state uncertainty of the target, a fuzzy adaptive strong tracking filter( FASTF) combining fuzzy logic adaptive controller (FLAC) with strong tracking filter(STF) was designed to robustly estimate the relative states between the servicing spacecraft and the target. Finally, the effectiveness of the strategy was verified by mathematical simulation. The achievement of this research provides a theoretical and technical foundation for future on-orbit servicing missions.展开更多
[Objective]The research aimed to study rapid dechlodnation kinetics of 1,4-dichlorobenzene （1,4-DCB） by microwave-assisted Raney Ni -AI alloy catalyst. [ Method] Microwave-assisted Raney Ni -AI alloy catalyst was us...[Objective]The research aimed to study rapid dechlodnation kinetics of 1,4-dichlorobenzene （1,4-DCB） by microwave-assisted Raney Ni -AI alloy catalyst. [ Method] Microwave-assisted Raney Ni -AI alloy catalyst was used for dechlorination of chlorobenzene （CB） and 1,4-DCB to analyze dechlorination kinetics of 1,4-DCB. [ Result] Reductive dechlorination reaction of 1,4-DCB by microwave-assisted Raney Ni- AI alloy catalyst was in accordance of the two-order reaction kinetics. Reaction rate constants of 1,4-DCB dechlorination at 35 and 50 ℃ were 0.037 6 and 0.151 mol/（ L . min）, and the activation energy was 76.66 kJ/mol. By microwave-assisted Raney Ni - AI alloy catalyst, dechlorination rate of 1,4- DCB reached 90% at 10 rain and 35 ℃. Moreover, two chlorine atoms were removed simultaneously, reaching the target of efficient dechlorination. [ Condusion] Oechlodnation of polychlodnated organic compounds by microwave-assisted Raney Ni- AI alloy catalyst obtained good effect .展开更多
Rubidium-Sr isotope is one of the most widely used radiogenic isotopic systems in planetary geochronology and geochemistry for tracing and dating igneous processes or events.This utility stems from the distinct geoche...Rubidium-Sr isotope is one of the most widely used radiogenic isotopic systems in planetary geochronology and geochemistry for tracing and dating igneous processes or events.This utility stems from the distinct geochemical properties of Rb and Sr,which drive substantial Rb/Sr fractionation during planetary differentiation,resulting in a large variation of ^(87)Sr/^(86)Sramong different reservoirs.展开更多
Surface charge transfer doping(SCTD)is widely recognized as an effective and non-destructive method for modulating the electrical properties of atomically thin transition metal dichalcogenides(TMDs),capitalizing on th...Surface charge transfer doping(SCTD)is widely recognized as an effective and non-destructive method for modulating the electrical properties of atomically thin transition metal dichalcogenides(TMDs),capitalizing on their distinctive two-dimensional(2D)structure.Nevertheless,the challenges of achieving precise area-selective doping using conventional methods,such as dopant vaporization,have impeded the advancement of practical optoelectronic and electronic devices based on TMDs.Herein,we propose a simple and reliable area-selective SCTD strategy to facilitate transfer,doping,and encapsulation simultaneously during the polyvinyl alcohol(PVA)-assistant transfer process.The electrical performance of PVA-doped molybdenum disulfide(MoS_(2))field-effect transistor(FET)exhibited significant enhancement,with carrier concentrations reaching up to 1013 cm^(−2),on-state currents increasing to 10μA·μm^(−1),and on/off ratios attaining a remarkable value of 107.Optical photothermal infrared(O-PTIR)spectroscopy was employed to elaborate the intrinsic temperature-dependent doping mechanism.The functionalization of MoS_(2)FETs was successfully achieved by introducing a hexagonal boron nitride(hBN)capping layer to define the doping area,enabling the creation of a homojunction with a rectification ratio of 106,an inverter fabricated within a single channel,and a Schottky barrier as low as 30.17 meV at the Au/MoS_(2)interface.This area-selective SCTD strategy,enabled by the PVA-assisted transfer process,offers a reliable,efficient,and economical approach for tailoring the functionalities of TMD-based devices,demonstrating substantial potential for diverse electronic applications.展开更多
Post-harvest precooling of strawberries can reduce fruit decay and tissue damage during post-harvest storage.To determine the most suitable precooling method,cold room precooling(CRPC),cold-water precooling(CWPC),elec...Post-harvest precooling of strawberries can reduce fruit decay and tissue damage during post-harvest storage.To determine the most suitable precooling method,cold room precooling(CRPC),cold-water precooling(CWPC),electrolyzed water precooling(EWPC),fluidized-ice precooling(FIPC),forced air precooling(FAPC),and vacuum precooling(VPC)were used to precool the strawberries.After per-cooling,strawberries were stored at 4℃ cold storage for 15 d.Compared with CRPC,CWPC,EWPC,FIPC,and VPC,FAPC can rapidly reduce the temperature of strawberries while maintaining clean fruit skin,effectively inhibiting microbial growth and consequently minimizing strawberry spoilage during storage.The FAPC treatments reduced weight loss during storage,maintained color and fruit hardness,inhibited browning,decreased the total viable count,preserved soluble solid and ascorbic acid contents,inhibited the increase in MDA,increased SOD and CAT activities,and delayed POD and PPO activities.Strawberries treated with CRPC and FAPC had a shelf life of 15 d,which was 3 d longer than those treated with CWPC,EWPC,FIPC,and VPC.Therefore,FAPC treatment is the most suitable method for maintaining strawberry quality and extending its post-harvest shelf life.展开更多
In this paper,we prove the H^(2)regularity of the solution to the time-harmonic Maxwell equations with impedance boundary conditions on domains with a C^(2)boundary under minimum regularity assumptions on the source a...In this paper,we prove the H^(2)regularity of the solution to the time-harmonic Maxwell equations with impedance boundary conditions on domains with a C^(2)boundary under minimum regularity assumptions on the source and boundary functions.展开更多
Polygonatum sibiricum has long been a popular functional food in Asia,known for its anti-inflammatory properties.However,its efficacy in alleviating colitis has yet to be investigated.This study aimed to explore the t...Polygonatum sibiricum has long been a popular functional food in Asia,known for its anti-inflammatory properties.However,its efficacy in alleviating colitis has yet to be investigated.This study aimed to explore the therapeutic potential of P.sibiricum polysaccharides(PSP)in dextran sulfate sodium(DSS)-induced colitis,focusing on the related pyroptosis mechanisms.Scanning electron microscopy(SEM)analysis showed that PSP possesses a smooth surface with no pore structure and a dense,lamellar structure adorned with numerous spherical entities.PSP treatment significantly reduced colitis symptoms and decreased pro-inflammatory cytokines,likely through suppression of the Toll like receptor 4(TLR4)/nuclear factor KB(NF-KB)signaling pathway.Additionally,PSP attenuated NOD-like receptor protein 3(NLRP3)/apoptosis-associated speck-like protein containing a CARD(ASC)/Caspase-1/Gasdermin D(GSDMD)-mediated pyroptosis and mitochondria damage in the colon,while enhanced the expression of tight junction and adherens junction proteins.Microbiota sequencing showed that PSP increased the abundance of phylum Bacteroidota and genus such as g_unclassified_f_Muribaculaceae,Lactobacillus,Clostridia_UCG-014,and Lachnospiraceae_NK4A136_group,while decreased the phylum Proteobacteria and the genus Enterobacter,Escherichia-Shigella,and Blautia.In conclusion,this study demonstrates that PSP exerts the potential therapeutic role against colitis,which was mediated by the regulation of gut microbiota and the inhibition of colonic NLRP3/ASC/Caspase-1/GSDMD signaling pathway.展开更多
基金the support provided by the National Natural Science Foundation of China(No.61973153)the National Key Research and Development Plan of China(No.2016YFB0500901)the Open Fund of the National Defense Key Discipline Laboratory of Micro-Spacecraft Technology of China(No.HIT.KLOF.MST.201705)
文摘On-orbit spacecraft face many threats,such as collisions with debris or other spacecraft.Therefore,perception of the surrounding space environment is vitally important for on-orbit spacecraft.Spacecraft require a dynamic attitude tracking ability with high precision for such missions.This paper aims to address the above problem using an improved backstepping controller.The tracking mission is divided into two phases:coarse alignment and fine alignment.In the first phase,a traditional saturation controller is utilized to limit the maximum attitude angular velocity according to the actuator’s ability.For the second phase,the proposed backstepping controller with different virtual control inputs is applied to track the moving target.To fulfill the high precision attitude tracking requirements,a hybrid attitude control actuator consisting of a Control Moment Gyro(CMG)and Reaction Wheel(RW)is constructed,which can simultaneously avoid the CMG singularity and RW saturation through the use of an angular momentum optimal management strategy,such as null motion.Finally,five simulation scenarios were carried out to demonstrate the effectiveness of the proposed control strategy and hybrid actuator.
基金supported by the Special Scientific Research Business of Central-level Public Welfare Research Institutes (No. 2015-YSKY-09)the Guangxi Key Research and Development Plan for Department of Guangxi Science (No. GUIKEAB16380292)。
文摘Rainfall samples were collected from three observation sites in Guilin from 2013 to 2017, and the chemical composition characteristics of precipitation and the contribution made by different ion sources were analyzed when atmospheric pollutants levels were reduced. The results showed that acid gas emissions and atmospheric pollutant concentrations continued to decline during the study period. However, the change in the volume-weighted mean p H at the three sites suggested that acid rain pollution was not alleviated and began to deteriorate after 2015. The continuing downward trend for alkaline neutralizing ions(Ca^(2+), NH_4^+) in precipitation indicated that the reduction in alkaline neutralizing substances in the atmosphere was an important factor that led to the deterioration in acid rain across Guilin. The principal component analysis and spearman correlation analysis indicated five sources of ions in precipitation. Quantitative assessment of these five sources indicated that fossil fuel combustion contributed the most ions concentration in precipitation at the three sites, followed by agriculture, terrestrial(crustal) sources, marine sources, and biomass burning. Long-distance airflow might affect the acidity, the electrical conductivity(EC), and ion concentrations in precipitation across Guilin. The airflow trajectory from the west and southeast directions corresponded to higher acidity and ion concentrations. According to the current air pollution control strategy planned by Guilin, reducing atmospheric coarse particles and NH_3 at the same time may potentially lead to further deteriorations in acid rain contents. Therefore, Guilin needs to develop more reasonable pollution prevention measures that synergistically control atmospheric pollutants and acid rain pollution.
文摘The 12-molybdosphoric acid mixed with titania （MPA-TiO2） was found to be a novel and efficient catalyst for the synthesis of diphenyl carbonate （DPC） via transesterification of dimethyl carbonate （DMC） and phenol. The X-ray diffraction （XRD） and infrared （IR） techniques were employed to characterize the prepared catalysts. The effect of the weight ratio of the 12-molybdosphoric acid to titania on the transesterification was investigated. A 13.1% yield of DPC and an 11.6% yield of methyl phenyl carbonate （MPC） were obtained over MPA-TiO2 with the weight ratio of MPA to TiO2 as 5：1.
基金support from the National Natural Science Foundation of China (No. 61403197)the National Key Research and Development Plan of China (No. 2016YFB0500901)
文摘Control Moment Gyroscope（CMG） is an effective candidate for agile satellites and large spacecraft attitude control because of its powerful torque amplification capability. The most serious situation, however, in using CMG is the inherent geometric singularity problem, where there＇s no torque output along a particular direction. Space expansion method has been proposed in this work for the singularity analysis. Based on inverse mapping transformation, an expanded Jacobian matrix which is a full rank square matrix is obtained. The singular angle sets of the 3-parallel cluster and pyramid cluster are distinguished using space expansion method. An effective hybrid steering strategy, able to deal with the elliptic singularity, is further proposed. Simulation results demonstrate the excellent performance of the proposed steering logic compared to the generalized singular robust logic and pseudo inverse logic in terms of energy consumption and torque error.
基金Sponsored by the National Natural Science Foundation of China(Grant No.61403197)the Natural Science Foundation of Jiangsu Province(Grant No.BK20140830)the Program of Shanghai Subject Chief Scientist(Grant No.14XD1423300)
文摘Agile attitude maneuver is a basic requirement for next generation imaging spacecraft and Control Moment Gyroscope (CMG) is an effective candidate for large space station and agile spacecraft attitude control because of its torque amplification capability. This paper provides a thorough survey of Single Gimbal Control Moment Gyroscope (SGCMG) in terms of configuration,evaluation,modeling,singularity analysis and steering logic,etc. For specific space missions,CMGs are logically mounted into different particular arrays which can be chosen by the proposed evaluation methods. From the dynamic model we find a tough inverse mapping problem which suffers the inherent geometric singularity. Different techniques and theories then are applied for singularity analysis and CMG steering logics design. The pyramid CMG cluster and singular robust logics are proven to be able to enhance the agility of spacecraft. Above work forms a systematic framework of SGCMG for agile spacecraft control with lots of illustrative examples,tables and figures,and will evoke further investigation for future missions.
基金supported by the Innovation Funds for Scientific Research Academy of Guangxi Environmental Protection(No.HKYCX-2015-5)Guangxi key research and development plan for Department of Guangxi Science(No.GUIKEAB16380292)+1 种基金the China Ministry of Environmental Protection's Special Funds for Scientific Research on Public Welfare(No.201309016)the support from the operation and maintenance teams of the environment observation stations in Beihai
文摘A single particle aerosol mass spectrometer was deployed to measure the changes of single particle species and sizes during March 2015 in Weizhou Island of the Beibu Gulf, Guangxi province, South China. In this campaign, a total of 3,100,597 particles were sized, and 25.8%particles with both positive and negative mass spectrum were collected and 24.8%characterized in combination with the ART-2 a neural network algorithm. The distribution of sized particles was mainly in from 520 to 600 nm, and the diameters ranging from 340 to1000 nm accounted for above 90%. Eight types of particles were classified： Elemental Carbon containing（EC）, Organic Carbon containing（OC）, EC and OC combined containing particles,Na containing particles, K containing particles（K）, Levoglucosan containing particles,mineral containing particles, and Heavy Metal containing particles（HM）. EC, OC and K were the major containing particles, which accounted for 84.3% in the eight types particles. The relative ratio and size distribution of the three types were EC（48.1%, 620 nm）, OC（12.7%,440 nm）, and K（23.5%, 600 nm）, respectively. The three types of particles were a bit increasing ratios compared with those in clean periods during haze pollution periods.Combined with the back-trajectory results from the Hysplit-4 model and local pollution sources revealed that the ambient air quality on the Weizhou Island may be influenced by biomass burning in the Indochina Peninsula（biomass burning in the Indochina Peninsula）from the transportation on higher level atmospheric layer and by mainland of south China located northeast of Weizhou Island on the ground.
基金supported by the National Natural Science Foundation of China(Nos.91544224,41275126)the Ministry of Science&Technology of China(No.2012YQ220113-4)+1 种基金the Ministry of Environmental Protection of China(No.201409008)the Science&Technology Commission of Shanghai Municipality(No.14DZ1202900)
文摘Time-resolved single-particle measurements were conducted during Chinese New Year in Nanning, China. Firework displays resulted in a burst of SO2, coarse mode, and accumulation mode （100-500 nm） particles. Through single particle mass spectrometry analysis, five different types of particles （fireworks-metal, ash, dust, organic carbon-sulfate （OC-sulfate）, biomass burning） with different size distributions were identified as primary emissions from firework displays. The fireworks-related particles accounted for more than 70% of the total analyzed particles during severe firework detonations. The formation of secondary particulate sulfate and nitrate during firework events was investigated on single particle level. An increase of sulfite peak （80SO3） followed by an increase of sulfate peaks （97HSO7＋96SO7） in the mass spectra during firework displays indicated the aqueous uptake and oxidation of SO2 on particles. High concentration of gaseous SO2, high relative humidity and high particle loading likely promoted SO2 oxidation. Secondary nitrate formed through gas-phase oxidation of NO2 to nitric acid, followed by the condensation into particles as ammonium nitrate. This study shows that under worm, humid conditions, both primary and secondary aerosols contribute to the particulate air pollution during firework displays.
基金supported by the National Natural Science Foundation of China(Nos.U21B2054 and 11772317).
文摘Aiming at the safety problem of the stage separation of parallel reusable high-speed air vehicles,this paper studies the unsteady test method and focuses on deriving a similarity law of parallel stage separation free-flight wind tunnel tests.The new similarity law considers the influences of aerodynamic force and gravity on the motions of the two stages,as well as the influence of aerodynamic interference between the two stages on each other’s motion.From the perspective of multiangle physical equations,the conditions to ensure that the two-stage separation trajectory of a wind tunnel test is similar to that of a real air vehicle are derived innovatively,so as to ensure the authenticity and credibility of wind tunnel test results.The similarity law is verified by an HIFiRE-5 air vehicle,and the separation trajectories of wind tunnel tests and the real air vehicle are obtained by numerical simulation.The research shows that the similarity law derived in this paper can ensure that wind tunnel free-flight tests have the ability to predict the two-stage separation characteristics of real parallel vehicles.By analyzing the separation trajectory curve of the typical state,it is found that the new method can ensure that the trajectory error of a wind tunnel test does not exceed 1%,which indicates that this method is credible.The establishment of the new method lays the foundation for subsequent wind tunnel tests and provides support for research on the safety of the stage separation of parallel reusable air vehicles.
基金the National Key Research and Development Program of China(2017YFD0100103)the Seed Industry Innovation and Industrialization Project of Fujian Province(fjzycxny2017004,zycxny2021004)+1 种基金the Program on Technology of Fujian Province(2020NZ08016,2020N0049)the Open Program of State Key Laboratory of Rice Biology of China(170101)。
文摘The LGS1(Large grain size 1)gene,also known as GS2/GL2/Os GRF4,is involved in regulating grain size and quality in rice,but the mechanism governing grain size has not been elucidated.We performed transcriptomic,proteomic,and phosphoproteomic analyses of young rice panicles in Samba(a wild-type cultivar with extra-small grain)and NIL-LGS1(a nearly isogenic line of LGS1 with large grain in the Samba genetic background)at three developmental stages(4–6)to identify internal dynamic functional networks determining grain size that are mediated by LGS1.Differentially expressed proteins formed seven highly functionally correlated clusters.The concordant regulation of multiple functional clusters may be key features of the development of grain length in rice.In stage 5,16 and 24 phosphorylated proteins were significantly up-regulated and down-regulated,and dynamic phosphorylation events may play accessory roles in determining rice grain size by participating in protein–protein interaction networks.Transcriptomic analysis in stage 5 showed that differentially expressed alternative splicing events and dynamic gene regulatory networks based on 39 transcription factors and their highly correlated target genes might contribute to rice grain development.Integrative multilevel omics analysis suggested that the regulatory network at the transcriptional and posttranscriptional levels could be directly manifested at the translational level,and this analysis also suggested a regulatory mechanism,regulation of protein translation levels,in the biological process that extends from transcript to protein to the development of grain.Functional analysis suggested that biological processes including MAPK signaling,calcium signaling,cell proliferation,cell wall,energy metabolism,hormone pathway,and ubiquitin-proteasome pathway might be involved in LGS1-mediated regulation of grain length.Thus,LGS1-mediated regulation of grain size is affected by dynamic transcriptional,posttranscriptional,translational and posttranslational changes.
基金supported by the National Natural Science Foundation of China(21471002)Scientific Research Projects of Universities in Anhui Province(2022AH040135)+1 种基金Natural Science Research Project for Anhui Universities(KJ2021A0509)Anhui Natural Science Foundation(2208085MC83).
文摘Efficient and convenient treatment of industrial dyeing wastewater is of great significance to guarantee human and animal health.This work presented the enhanced catalytic activity at pH 3.0 of laccase immobilized on amino-functionalized ZnFe_(2)O_(4) nanoparticles(ZnFe_(2)O_(4)-laccase)and its application for the degradation of textile dyes.Due to the existence of a large number of oxygen vacancies on the surface of the ZnFe_(2)O_(4) nanoparticles,negative ions accumulated on the magnetic carriers,which resulted in a harsh optimal pH value of the ZnFe_(2)O_(4)-laccase.Laccase activity assays revealed that the ZnFe_(2)O_(4)-laccase possessed superior pH and thermal stabilities,excellent reusability,and noticeable organic solvent tolerance.Meanwhile,the ZnFe_(2)O_(4) laccase presented efficient and sustainable degradation of high concentrations of textile dyes.The initial decoloration efficiencies of malachite green(MG),brilliant green(BG),azophloxine,crystal violet(CV),reactive blue 19(RB19),and procion red MX-5B were approximately 99.1%,95.0%,93.3%,87.4%,86.1%,and 85.3%,respectively.After 10 consecutive reuses,the degradation rates of the textile dyes still maintained about 98.2%,92.5%,83.2%,81.5%,79.8%and 65.9%,respectively.The excellent dye degradation properties indicate that the ZnFe_(2)O_(4)-laccase has a technical application in high concentrations of dyestuff treatment.
基金Sponsored by the National Natural Science Foundation of China(Grant No.61973153)
文摘On-orbit servicing, such as spacecraft maintenance, on-orbit assembly, refueling, and de-orbiting, can reduce the cost of space missions, improve the performance of spacecraft, and extend its life span. The relative state between the servicing and target spacecraft is vital for on-orbit servicing missions, especially the final approaching stage. The major challenge of this stage is that the observed features of the target are incomplete or are constantly changing due to the short distance and limited Field of View (FOV) of camera. Different from cooperative spacecraft, non-cooperative target does not have artificial feature markers. Therefore, contour features, including triangle supports of solar array, docking ring, and corner points of the spacecraft body, are used as the measuring features. To overcome the drawback of FOV limitation and imaging ambiguity of the camera, a "selfie stick" structure and a self-calibration strategy were implemented, ensuring that part of the contour features could be observed precisely when the two spacecraft approached each other. The observed features were constantly changing as the relative distance shortened. It was difficult to build a unified measurement model for different types of features, including points, line segments, and circle. Therefore, dual quaternion was implemented to model the relative dynamics and measuring features. With the consideration of state uncertainty of the target, a fuzzy adaptive strong tracking filter( FASTF) combining fuzzy logic adaptive controller (FLAC) with strong tracking filter(STF) was designed to robustly estimate the relative states between the servicing spacecraft and the target. Finally, the effectiveness of the strategy was verified by mathematical simulation. The achievement of this research provides a theoretical and technical foundation for future on-orbit servicing missions.
文摘[Objective]The research aimed to study rapid dechlodnation kinetics of 1,4-dichlorobenzene （1,4-DCB） by microwave-assisted Raney Ni -AI alloy catalyst. [ Method] Microwave-assisted Raney Ni -AI alloy catalyst was used for dechlorination of chlorobenzene （CB） and 1,4-DCB to analyze dechlorination kinetics of 1,4-DCB. [ Result] Reductive dechlorination reaction of 1,4-DCB by microwave-assisted Raney Ni- AI alloy catalyst was in accordance of the two-order reaction kinetics. Reaction rate constants of 1,4-DCB dechlorination at 35 and 50 ℃ were 0.037 6 and 0.151 mol/（ L . min）, and the activation energy was 76.66 kJ/mol. By microwave-assisted Raney Ni - AI alloy catalyst, dechlorination rate of 1,4- DCB reached 90% at 10 rain and 35 ℃. Moreover, two chlorine atoms were removed simultaneously, reaching the target of efficient dechlorination. [ Condusion] Oechlodnation of polychlodnated organic compounds by microwave-assisted Raney Ni- AI alloy catalyst obtained good effect .
基金financially supported by the Chinese Academy of Sciences(XDB 1180000 and ZDBS-SSW-JSC007-11)the Lunar research program of GIGCAS(2022SZJJZD-03)+2 种基金the Guangzhou city program(2025A04J7199)the National Natural Science Foundation of China(42241104)the Technical Talent Program of CAS.
文摘Rubidium-Sr isotope is one of the most widely used radiogenic isotopic systems in planetary geochronology and geochemistry for tracing and dating igneous processes or events.This utility stems from the distinct geochemical properties of Rb and Sr,which drive substantial Rb/Sr fractionation during planetary differentiation,resulting in a large variation of ^(87)Sr/^(86)Sramong different reservoirs.
基金support from the National Natural Science Foundation of China(Nos.62104017 and 62074015)Beijing Institute of Technology Research Fund Program for Young Scholars.
文摘Surface charge transfer doping(SCTD)is widely recognized as an effective and non-destructive method for modulating the electrical properties of atomically thin transition metal dichalcogenides(TMDs),capitalizing on their distinctive two-dimensional(2D)structure.Nevertheless,the challenges of achieving precise area-selective doping using conventional methods,such as dopant vaporization,have impeded the advancement of practical optoelectronic and electronic devices based on TMDs.Herein,we propose a simple and reliable area-selective SCTD strategy to facilitate transfer,doping,and encapsulation simultaneously during the polyvinyl alcohol(PVA)-assistant transfer process.The electrical performance of PVA-doped molybdenum disulfide(MoS_(2))field-effect transistor(FET)exhibited significant enhancement,with carrier concentrations reaching up to 1013 cm^(−2),on-state currents increasing to 10μA·μm^(−1),and on/off ratios attaining a remarkable value of 107.Optical photothermal infrared(O-PTIR)spectroscopy was employed to elaborate the intrinsic temperature-dependent doping mechanism.The functionalization of MoS_(2)FETs was successfully achieved by introducing a hexagonal boron nitride(hBN)capping layer to define the doping area,enabling the creation of a homojunction with a rectification ratio of 106,an inverter fabricated within a single channel,and a Schottky barrier as low as 30.17 meV at the Au/MoS_(2)interface.This area-selective SCTD strategy,enabled by the PVA-assisted transfer process,offers a reliable,efficient,and economical approach for tailoring the functionalities of TMD-based devices,demonstrating substantial potential for diverse electronic applications.
基金supported by key projects in the field of agriculture by the Shanghai Municipal Commission of Science and Technology(No.23N31900100)the Shanghai Professional Technology Service Platform on Cold Chain Equipment Performance and Energy Saving Evaluation(No.19DZ2284000),China.
文摘Post-harvest precooling of strawberries can reduce fruit decay and tissue damage during post-harvest storage.To determine the most suitable precooling method,cold room precooling(CRPC),cold-water precooling(CWPC),electrolyzed water precooling(EWPC),fluidized-ice precooling(FIPC),forced air precooling(FAPC),and vacuum precooling(VPC)were used to precool the strawberries.After per-cooling,strawberries were stored at 4℃ cold storage for 15 d.Compared with CRPC,CWPC,EWPC,FIPC,and VPC,FAPC can rapidly reduce the temperature of strawberries while maintaining clean fruit skin,effectively inhibiting microbial growth and consequently minimizing strawberry spoilage during storage.The FAPC treatments reduced weight loss during storage,maintained color and fruit hardness,inhibited browning,decreased the total viable count,preserved soluble solid and ascorbic acid contents,inhibited the increase in MDA,increased SOD and CAT activities,and delayed POD and PPO activities.Strawberries treated with CRPC and FAPC had a shelf life of 15 d,which was 3 d longer than those treated with CWPC,EWPC,FIPC,and VPC.Therefore,FAPC treatment is the most suitable method for maintaining strawberry quality and extending its post-harvest shelf life.
基金supported in part by the National Key Technologies R&D Program of China under the Grant 2019YFA0709602the National Natural Science Foundation of China under the Grants 11831016,12288201,and 12201621.
文摘In this paper,we prove the H^(2)regularity of the solution to the time-harmonic Maxwell equations with impedance boundary conditions on domains with a C^(2)boundary under minimum regularity assumptions on the source and boundary functions.
基金supported by Xiamen Science and Technology Plan Project(3502Z20226034)Xiamen Marine and Fishery Development Special Fund(23YYZP013QCA11)Natural Science Foundation of Fujian Province(2022J01315).
文摘Polygonatum sibiricum has long been a popular functional food in Asia,known for its anti-inflammatory properties.However,its efficacy in alleviating colitis has yet to be investigated.This study aimed to explore the therapeutic potential of P.sibiricum polysaccharides(PSP)in dextran sulfate sodium(DSS)-induced colitis,focusing on the related pyroptosis mechanisms.Scanning electron microscopy(SEM)analysis showed that PSP possesses a smooth surface with no pore structure and a dense,lamellar structure adorned with numerous spherical entities.PSP treatment significantly reduced colitis symptoms and decreased pro-inflammatory cytokines,likely through suppression of the Toll like receptor 4(TLR4)/nuclear factor KB(NF-KB)signaling pathway.Additionally,PSP attenuated NOD-like receptor protein 3(NLRP3)/apoptosis-associated speck-like protein containing a CARD(ASC)/Caspase-1/Gasdermin D(GSDMD)-mediated pyroptosis and mitochondria damage in the colon,while enhanced the expression of tight junction and adherens junction proteins.Microbiota sequencing showed that PSP increased the abundance of phylum Bacteroidota and genus such as g_unclassified_f_Muribaculaceae,Lactobacillus,Clostridia_UCG-014,and Lachnospiraceae_NK4A136_group,while decreased the phylum Proteobacteria and the genus Enterobacter,Escherichia-Shigella,and Blautia.In conclusion,this study demonstrates that PSP exerts the potential therapeutic role against colitis,which was mediated by the regulation of gut microbiota and the inhibition of colonic NLRP3/ASC/Caspase-1/GSDMD signaling pathway.
