In terms of multiple temporal and spatial scales, massive data from experiments, flow field measurements, and high-fidelity numerical simulations have greatly promoted the rapid development of fluid mechanics. Machine...In terms of multiple temporal and spatial scales, massive data from experiments, flow field measurements, and high-fidelity numerical simulations have greatly promoted the rapid development of fluid mechanics. Machine Learning(ML) provides a wealth of analysis methods to extract potential information from a large amount of data for in-depth understanding of the underlying flow mechanism or for further applications. Furthermore, machine learning algorithms can enhance flow information and automatically perform tasks that involve active flow control and optimization. This article provides an overview of the past history, current development, and promising prospects of machine learning in the field of fluid mechanics. In addition, to facilitate understanding, this article outlines the basic principles of machine learning methods and their applications in engineering practice, turbulence models, flow field representation problems, and active flow control. In short, machine learning provides a powerful and more intelligent data processing architecture, and may greatly enrich the existing research methods and industrial applications of fluid mechanics.展开更多
Since the carbohydrate content affects pear flavor during the process of growth, it is necessary to determine the sugar components that accumulate in the fruit. We analyzed the fruit carbohydrate content, and the gene...Since the carbohydrate content affects pear flavor during the process of growth, it is necessary to determine the sugar components that accumulate in the fruit. We analyzed the fruit carbohydrate content, and the gene expression and activity ofacid invertase(AI), neutral invertase(NI), sucrose synthase(SS), and sucrose phosphate synthase(SPS) during the development of "Huangguan" and "Yali" pears. The results demonstrate that during development, the fruit sugar metabolism of the "Huangguan" pear follows a typical sorbitol–starch-soluble sugars middle model, whereas the "Yali" pear fruit follows a typical sorbitol–sucrose–starch-soluble sugars middle model. In the "Huangguan" pear, we found the AI and NI gene expressions, as well as AI( P < 0.05) and NI( P < 0.01) enzyme activities, to be positively correlated, whereas we found the NI gene expression and NI enzyme activity of "Yali" pear to be negatively correlated( P < 0.01). We observed the high levels oflate-stage AI and early-stage SS during development to roughly correspond with the gene expression found in the late and early stages, respectively, suggesting their potential regulatory roles in "Huangguan" pear fruit development. Our results indicate that the primary function of SPS during the early developmental stage is to accumulate sucrose, whereas the primary function of AI is to promote hexose accumulation during the late developmental stage ofmature "Yali" pear fruit.展开更多
Accurate measurements of physical parameters in a scramjet isolator are very important to promote the design and optimization of the isolator and even the scramjet.In a ground experiment,limited by the inherent charac...Accurate measurements of physical parameters in a scramjet isolator are very important to promote the design and optimization of the isolator and even the scramjet.In a ground experiment,limited by the inherent characteristics of measurement technology and equipment,it is a big challenge to obtain the velocity field inside an isolator.In this study,a deep learning approach was introduced to combine data obtained from ground experiments and numerical simulations,and a velocity field prediction model was developed for obtaining the velocity field inside an isolator based on experimental Schlieren images.The velocity field prediction model was designed with convolutional neural networks as the main structure.Ground experiments of a scramjet isolator under continuous Mach number variation were carried out,and Schlieren images of the flow field inside the isolator were collected.Numerical simulations of the isolator were also carried out,and the velocity fields inside the isolator under various Mach numbers were obtained.The velocity field prediction model was trained using flow field datasets containing experimental Schlieren images and velocity field,and the mapping relationship between the experimental Schlieren images and the predicted velocity field was successfully established.展开更多
Background Promoting the synchronization of glucose and amino acid release in the digestive tract of pigs could effectively improve dietary nitrogen utilization.The rational allocation of dietary starch sources and th...Background Promoting the synchronization of glucose and amino acid release in the digestive tract of pigs could effectively improve dietary nitrogen utilization.The rational allocation of dietary starch sources and the exploration of appropriate dietary glucose release kinetics may promote the dynamic balance of dietary glucose and amino acid supplies.However,research on the effects of diets with different glucose release kinetic profiles on amino acid absorption and portal amino acid appearance in piglets is limited.This study aimed to investigate the effects of the kinetic pattern of dietary glucose release on nitrogen utilization,the portal amino acid profile,and nutrient transporter expression in intestinal enterocytes in piglets.Methods Sixty-four barrows(15.00±1.12 kg)were randomly allotted to 4 groups and fed diets formulated with starch from corn,corn/barley,corn/sorghum,or corn/cassava combinations(diets were coded A,B,C,or D respectively).Protein retention,the concentrations of portal amino acid and glucose,and the relative expression of amino acid and glucose transporter m RNAs were investigated.In vitro digestion was used to compare the dietary glucose release profiles.Results Four piglet diets with different glucose release kinetics were constructed by adjusting starch sources.The in vivo appearance dynamics of portal glucose were consistent with those of in vitro dietary glucose release kinetics.Total nitrogen excretion was reduced in the piglets in group B,while apparent nitrogen digestibility and nitrogen retention increased(P<0.05).Regardless of the time(2 h or 4 h after morning feeding),the portal total free amino acids content and contents of some individual amino acids(Thr,Glu,Gly,Ala,and Ile)of the piglets in group B were significantly higher than those in groups A,C,and D(P<0.05).Cluster analysis showed that different glucose release kinetic patterns resulted in different portal amino acid patterns in piglets,which decreased gradually with the extension of feeding time.The portal His/Phe,Pro/Glu,Leu/Val,Lys/Met,Tyr/Ile and Ala/Gly appeared higher similarity among the diet treatments.In the anterior jejunum,the glucose transporter SGLT1 was significantly positively correlated with the amino acid transporters B0AT1,EAAC1,and CAT1.Conclusions Rational allocation of starch resources could regulate dietary glucose release kinetics.In the present study,group B(corn/barley)diet exhibited a better glucose release kinetic pattern than the other groups,which could affect the portal amino acid contents and patterns by regulating the expression of amino acid transporters in the small intestine,thereby promoting nitrogen deposition in the body,and improving the utilization efficiency of dietary nitrogen.展开更多
In this paper, a new physically based constitutive model is developed for hexagonal close-packed metals, especially the Ti-6Al-4V alloy, subjected to high strain rate and different temperatures based on the microscopi...In this paper, a new physically based constitutive model is developed for hexagonal close-packed metals, especially the Ti-6Al-4V alloy, subjected to high strain rate and different temperatures based on the microscopic mechanism of plastic deformation and the theory of thermally activated dislocation motion. A global analysis of constitutive parameters based on the Latin Hypercube Sampling method and the Spearman＇s rank correlation method is adopted in order to improve the identification efficiency of parameters. Then, an optimal solution of constitutive parameters as a whole is obtained by using a global genetic algorithm composed of an improved niche genetic algorithm, a global peak determination strategy and the local accurate search techniques. It is concluded that the proposed constitutive modal can accurately describe the Ti-6Al-4V alloy＇s dynamic behavior because the prediction results of the model are in good agreement with the experimental data.展开更多
When a gas-liquid two-phase flow(GLTPF)enters a parallel separator through a T-junction,it generally splits unevenly.This phenomenon can seriously affect the operation efficiency and safety of the equipment located do...When a gas-liquid two-phase flow(GLTPF)enters a parallel separator through a T-junction,it generally splits unevenly.This phenomenon can seriously affect the operation efficiency and safety of the equipment located downstream.In order to investigate these aspects and,more specifically,the so-called bias phenomenon(all gas and liquid flowing to one pipe,while the other pipe is a liquid column that fluctuates up and down),laboratory experiments were carried out by using a T-junction connected to two parallel vertical pipes.Moreover,a GLTPF prediction model based on the principle of minimum potential energy was introduced.The research results indicate that this model can accurately predict the GLTPF state in parallel risers.The boundary of the slug flow and the churn flow in the opposite pipe can be predicted.Overall,according to the results,the pressure drop curves of the two-phase flow in the parallel risers are basically the same when there is no bias phenomenon,but the pressure drop in the parallel riser displays a large deviation when there is a slug flow-churn flow.Only when the parallel riser is in a state of asymmetric flow and one of the risers produces churn flow,the two-phase flow is prone to produce the bias phenomenon.展开更多
In this study, the environmental indicators （including temperature, light, air relative humidity and CO2 concentration） of facility watermelon in Beijing area were monitored with US350 environmental sensor during th...In this study, the environmental indicators （including temperature, light, air relative humidity and CO2 concentration） of facility watermelon in Beijing area were monitored with US350 environmental sensor during the whole growth period. The results showed that in the solar greenhouses in Beijing area, the average air temperature was in the range of 10.67-29.95 ℃ during the whole growth period of watermelon, the average soil temperature ranged from 16.92 to 35.10 ℃, the average light intensity changed from 268.37 to 13 842.60 Ix, the average air relative humidity ranged from 52.40% to 94.26%, and the average CO2 concentration was in the range of 455-631 ml/m3; and in the spring greenhouses in Beijing area, the variation range of average air temperature was 14.05-29.84 ℃ during the whole growth period of watermelon, the average soil temperature ranged from 17.47 to 28.12 ℃, the average light intensity was in the range of 55.80-12 858.64 Ix, the average soil moisture content ranged from 18.19%-34.56%, the variation range of average air relative humidity was 20.72%-96.26%, and the average CO2 concentra- tion was in the range of 351-544 ml/m3,展开更多
Aiming at the problems of low standardization, unstable quality and low commodity rate of facility watermelon cultivation technology in Beijing, to meet the demand for high-quality and standardized supply capacity of ...Aiming at the problems of low standardization, unstable quality and low commodity rate of facility watermelon cultivation technology in Beijing, to meet the demand for high-quality and standardized supply capacity of the watermelon industry, the technical regulations for facility watermelon production in Beijing area were formulated, mainly including the environmental conditions of the producing area, cultivation techniques, pest control and harvesting. This regulation can provide a reference for the standardization of facility watermelon production.展开更多
Laser-directed energy deposition(LDED)technology has demonstrated great potential for the rapid and integrated fabrication of nickel-based superalloy components.The plastic deformation-assisted method is crucial for a...Laser-directed energy deposition(LDED)technology has demonstrated great potential for the rapid and integrated fabrication of nickel-based superalloy components.The plastic deformation-assisted method is crucial for achieving grain refinement and microstructural homogeneity in LDED-fabricated superalloys.However,existing methods suffer from uniformity constraints owing to their high deformation resistance,which significantly limits their application in load-bearing components.To address these issues,a synchronous-hot-forging-assisted(SHFA)LDED additive manufacturing method was proposed,and its effects on the macroscopic morphology,microstructure,and mechanical properties of GH4169 nickel-based alloy specimens were systematically compared.The results demonstrated up to 30.1%average plastic deformation in hot-forging components while maintaining good surface flatness.The synergistic effect of dislocation accumulation and dynamic recrystallization during hot forging enables dramatic grain refinement,reducing the average grain size by 89.1%(from 168.5μm to 18.4μm)while weakening texture intensity from 15.31 to 2.15,ultimately promoting equiaxed grain formation.The pores of hot-forging components changed from fine round to flat,the porosity decreased from 0.264%to 0.089%,and the densification level was significantly improved.With the increase in the synchronous hot-forging force,the average ultimate tensile strength of hot-forging components can reach 1175.1 MPa,while the anisotropy difference is gradually weakened.The SHFA-LDED process not only achieves excellent grain refinement and microstructure homogenization but also enhances mechanical properties,providing a new technical path for the additive manufacturing of high-performance nickel-based superalloy components.展开更多
Meiosis,a critical process for sexual reproduction,requires precise regulation to ensure the correct progression of meiotic stages.In yeast and animals,errors in meiotic recombination and homologous chromosomes synaps...Meiosis,a critical process for sexual reproduction,requires precise regulation to ensure the correct progression of meiotic stages.In yeast and animals,errors in meiotic recombination and homologous chromosomes synapsis bring a surveillance mechanism named pachytene checkpoint to prevent pachytene exit.However,most plant mutants with defects in meiotic prophase I continue cell cycle progression,which hindered the characterization of factors controlling the prophase I to metaphase I transition.Here,we characterized a male-sterile mutant in maize,prolonged prophase1(pp1),which exhibited pachytene and diakinesis arrest in male meiosis,and abnormal chromatin condensation.Using mapbased cloning,the PP1 gene was isolated as a PHD family transcription factor,and its transcripts of PP1 were preferentially accumulated in tapetum and male germline cells during microsporogenesis.Transcriptomic analysis of the pp1 mutant revealed downregulation of genes associated with chromatin assembly,cell cycle,and male meiosis,correlating with observed meiotic arrest and chromatin condensation defects.These findings highlight the role of PP1 in maize microsporogenesis,and providing more insights into the mechanisms regulating the meiotic progression in maize.展开更多
In the present work, the governing equations based on theory of irreversible thermodynamics is deduced by introducing two internal variables to characterize the phase transformation and finite plastic deformation evol...In the present work, the governing equations based on theory of irreversible thermodynamics is deduced by introducing two internal variables to characterize the phase transformation and finite plastic deformation evolution for NiTi shape memory alloy. Thus a three-dimensional dynamic constitutive model is established by summarizing the governing equations for phase transformation and plastic deformation under high strain rate loading conditions. By adopting a stress compensation algorithm to update the stress tensor, the phenomenologicalbased constitutive model is embedded into ABAQUS finite element software as user material subroutine with FORTRAN code. Thus the numerical simulation of dynamic responses of NiTi alloy is successfully implemented. The numerical simulation results are in good agreement with the experimental data, validating the feasibility of this proposed model. Comparison between the simulation results and the experimental data indicates that the proposed model can well describe not only the different deformation stages of NiTi alloy but also its constitutive behavior subjected to different high strain rates.展开更多
The high sensitivity of room-temperature gas sensors is the key to innovation in the areas of environment,energy conservation and safety.However,metal-oxide-based sensors generally operate at high temperatures.Herein,...The high sensitivity of room-temperature gas sensors is the key to innovation in the areas of environment,energy conservation and safety.However,metal-oxide-based sensors generally operate at high temperatures.Herein,we designed three ZrO_(2)-based sensors and explored their NO_(2)sensing properties at room temperature.ZrO_(2)with three different morphologies and microstructure were synthesized by simple hydrothermal methods.The microstructures of sensing materials are expected to significantly affect gas sensing properties.The rod-shaped ZrO_(2)(ZrO_(2)-R)displayed the advantages such as higher crystallinity,larger pore size,narrower band gap and more chemisorbed adsorbed oxygen,compared to hollow sphere-shaped ZrO_(2)(ZrO_(2)-HS),stellate-shaped ZrO_(2)(ZrO_(2)–S).The ZrO_(2)-R sensor showed the highest response towards 30 ppm NO_(2)(423.8%)at room temperature,and a quite high sensitivity of 198.0%for detecting 5 ppm NO_(2).Although ZrO_(2)-HS and ZrO_(2)–S sensors exhibited lower response towards 30 ppm NO_(2)(232.9%and 245.1%),the response time and recovery time of these two sensors are 5 s/19 s and 4 s/3 s,respectively.This work can provide a new strategy for the development of roomtemperature metal-oxide-based sensors.展开更多
Grain protein content(GPC)is an indicator of cereal nutritional quality.Identification of genes involved in the regulation of GPC provides targets for molecular breeding for crop protein quality.We characterized a mai...Grain protein content(GPC)is an indicator of cereal nutritional quality.Identification of genes involved in the regulation of GPC provides targets for molecular breeding for crop protein quality.We characterized a maize gene encoding the putative amino acid transporter ZmAAP6,a gene expressed mainly in immature seeds,especially in the basal endosperm transfer layer.Total protein and zein contents were decreased in ZmAAP6 null mutants and increased in ZmAAP6 overexpression(OE)lines,consistent with their changed in the size of protein bodies.Metabolic and transcriptomic analysis supported the regulatory role of ZmAAP6 in amino acid transportation.These results suggest that ZmAAP6 functions as a positive regulator of GPC in maize,shedding new light on the genetic basis of GPC regulation.展开更多
The problem of contingency return from the low lunar orbit is studied.A novel twomaneuver indirect return strategy is proposed.By effectively using the Earth’s gravity to change the orbital plane of the transfer orbi...The problem of contingency return from the low lunar orbit is studied.A novel twomaneuver indirect return strategy is proposed.By effectively using the Earth’s gravity to change the orbital plane of the transfer orbit,the second maneuver in the well-known three-maneuver return strategy can be removed,so the total delta-v is reduced.Compared with the singlemaneuver direct return,our strategy has the advantage in that the re-entry epoch for the minimum delta-v cost can be advanced in time,with a minimum delta-v value similar to that of the direct return.The most obvious difference between our strategy and the traditional single-or multiplemaneuver strategies is that the complete transfer orbit is a patch between a two-body conic orbit and a three-body orbit instead of two conic orbits.Our strategy can serve as a useful option for contingency return from a low lunar orbit,especially when the delta-v constraint is stringent for a direct return and the contingency epoch is far away from the return window.展开更多
Rhododendron is famous for its high ornamental value.However,the genus is taxonomically difficult and the relationships within Rhododendron remain unresolved.In addition,the origin of key morphological characters with...Rhododendron is famous for its high ornamental value.However,the genus is taxonomically difficult and the relationships within Rhododendron remain unresolved.In addition,the origin of key morphological characters with high horticulture value need to be explored.Both problems largely hinder utilization of germplasm resources.Most studies attempted to disentangle the phylogeny of Rhododendron,but only used a few genomic markers and lacked large-scale sampling,resulting in low clade support and contradictory phylogenetic signals.Here,we used restriction-site associated DNA sequencing(RAD-seq)data and morphological traits for 144 species of Rhododendron,representing all subgenera and most sections and subsections of this species-rich genus,to decipher its intricate evolutionary history and reconstruct ancestral state.Our results revealed high resolutions at subgenera and section levels of Rhododendron based on RAD-seq data.Both optimal phylogenetic tree and split tree recovered five lineages among Rhododendron.Subg.Therorhodion(cladeⅠ)formed the basal lineage.Subg.Tsutsusi and Azaleastrum formed cladeⅡand had sister relationships.CladeⅢincluded all scaly rhododendron species.Subg.Pentanthera(cladeⅣ)formed a sister group to Subg.Hymenanthes(cladeⅤ).The results of ancestral state reconstruction showed that Rhododendron ancestor was a deciduous woody plant with terminal inflorescence,ten stamens,leaf blade without scales and broadly funnelform corolla with pink or purple color.This study shows significant distinguishability to resolve the evolutionary history of Rhododendron based on high clade support of phylogenetic tree constructed by RAD-seq data.It also provides an example to resolve discordant signals in phylogenetic trees and demonstrates the application feasibility of RAD-seq with large amounts of missing data in deciphering intricate evolutionary relationships.Additionally,the reconstructed ancestral state of six important characters provides insights into the innovation of key characters in Rhododendron.展开更多
In order to screen out the small watermelon varieties with red flesh suitable for soilless cultivation and to meet people's requirements of high-quality watermelons,comparative tests were conducted on 6 small wate...In order to screen out the small watermelon varieties with red flesh suitable for soilless cultivation and to meet people's requirements of high-quality watermelons,comparative tests were conducted on 6 small watermelon varieties with red flesh under soilless culture conditions in 2018.Based on the data of field traits,yield traits,quality traits and commercial traits,the integrated results showed that ‘Chuanqi 2’ had good quality and high yield,and the overall performance was the best.展开更多
基金supported by the National Natural Science Foundation of China(No.11972139)。
文摘In terms of multiple temporal and spatial scales, massive data from experiments, flow field measurements, and high-fidelity numerical simulations have greatly promoted the rapid development of fluid mechanics. Machine Learning(ML) provides a wealth of analysis methods to extract potential information from a large amount of data for in-depth understanding of the underlying flow mechanism or for further applications. Furthermore, machine learning algorithms can enhance flow information and automatically perform tasks that involve active flow control and optimization. This article provides an overview of the past history, current development, and promising prospects of machine learning in the field of fluid mechanics. In addition, to facilitate understanding, this article outlines the basic principles of machine learning methods and their applications in engineering practice, turbulence models, flow field representation problems, and active flow control. In short, machine learning provides a powerful and more intelligent data processing architecture, and may greatly enrich the existing research methods and industrial applications of fluid mechanics.
基金funded as a key project in the National Science and Technology Pillar Program during the 11th 5-Year Plans (No.2006BAD22B01)supported by the National Natural Science Foundation of China (No.31171769)the Special Fund for Agro-Scientific Research in the Public Interest (No.201303075)
文摘Since the carbohydrate content affects pear flavor during the process of growth, it is necessary to determine the sugar components that accumulate in the fruit. We analyzed the fruit carbohydrate content, and the gene expression and activity ofacid invertase(AI), neutral invertase(NI), sucrose synthase(SS), and sucrose phosphate synthase(SPS) during the development of "Huangguan" and "Yali" pears. The results demonstrate that during development, the fruit sugar metabolism of the "Huangguan" pear follows a typical sorbitol–starch-soluble sugars middle model, whereas the "Yali" pear fruit follows a typical sorbitol–sucrose–starch-soluble sugars middle model. In the "Huangguan" pear, we found the AI and NI gene expressions, as well as AI( P < 0.05) and NI( P < 0.01) enzyme activities, to be positively correlated, whereas we found the NI gene expression and NI enzyme activity of "Yali" pear to be negatively correlated( P < 0.01). We observed the high levels oflate-stage AI and early-stage SS during development to roughly correspond with the gene expression found in the late and early stages, respectively, suggesting their potential regulatory roles in "Huangguan" pear fruit development. Our results indicate that the primary function of SPS during the early developmental stage is to accumulate sucrose, whereas the primary function of AI is to promote hexose accumulation during the late developmental stage ofmature "Yali" pear fruit.
基金supported by the National Natural Science Foundation of China(No.52125603).
文摘Accurate measurements of physical parameters in a scramjet isolator are very important to promote the design and optimization of the isolator and even the scramjet.In a ground experiment,limited by the inherent characteristics of measurement technology and equipment,it is a big challenge to obtain the velocity field inside an isolator.In this study,a deep learning approach was introduced to combine data obtained from ground experiments and numerical simulations,and a velocity field prediction model was developed for obtaining the velocity field inside an isolator based on experimental Schlieren images.The velocity field prediction model was designed with convolutional neural networks as the main structure.Ground experiments of a scramjet isolator under continuous Mach number variation were carried out,and Schlieren images of the flow field inside the isolator were collected.Numerical simulations of the isolator were also carried out,and the velocity fields inside the isolator under various Mach numbers were obtained.The velocity field prediction model was trained using flow field datasets containing experimental Schlieren images and velocity field,and the mapping relationship between the experimental Schlieren images and the predicted velocity field was successfully established.
基金partially supported by the National Key Research and Development Program of China(2021YFD1300201)Jilin Province Key Research and Development Program of China(20220202044NC)。
文摘Background Promoting the synchronization of glucose and amino acid release in the digestive tract of pigs could effectively improve dietary nitrogen utilization.The rational allocation of dietary starch sources and the exploration of appropriate dietary glucose release kinetics may promote the dynamic balance of dietary glucose and amino acid supplies.However,research on the effects of diets with different glucose release kinetic profiles on amino acid absorption and portal amino acid appearance in piglets is limited.This study aimed to investigate the effects of the kinetic pattern of dietary glucose release on nitrogen utilization,the portal amino acid profile,and nutrient transporter expression in intestinal enterocytes in piglets.Methods Sixty-four barrows(15.00±1.12 kg)were randomly allotted to 4 groups and fed diets formulated with starch from corn,corn/barley,corn/sorghum,or corn/cassava combinations(diets were coded A,B,C,or D respectively).Protein retention,the concentrations of portal amino acid and glucose,and the relative expression of amino acid and glucose transporter m RNAs were investigated.In vitro digestion was used to compare the dietary glucose release profiles.Results Four piglet diets with different glucose release kinetics were constructed by adjusting starch sources.The in vivo appearance dynamics of portal glucose were consistent with those of in vitro dietary glucose release kinetics.Total nitrogen excretion was reduced in the piglets in group B,while apparent nitrogen digestibility and nitrogen retention increased(P<0.05).Regardless of the time(2 h or 4 h after morning feeding),the portal total free amino acids content and contents of some individual amino acids(Thr,Glu,Gly,Ala,and Ile)of the piglets in group B were significantly higher than those in groups A,C,and D(P<0.05).Cluster analysis showed that different glucose release kinetic patterns resulted in different portal amino acid patterns in piglets,which decreased gradually with the extension of feeding time.The portal His/Phe,Pro/Glu,Leu/Val,Lys/Met,Tyr/Ile and Ala/Gly appeared higher similarity among the diet treatments.In the anterior jejunum,the glucose transporter SGLT1 was significantly positively correlated with the amino acid transporters B0AT1,EAAC1,and CAT1.Conclusions Rational allocation of starch resources could regulate dietary glucose release kinetics.In the present study,group B(corn/barley)diet exhibited a better glucose release kinetic pattern than the other groups,which could affect the portal amino acid contents and patterns by regulating the expression of amino acid transporters in the small intestine,thereby promoting nitrogen deposition in the body,and improving the utilization efficiency of dietary nitrogen.
基金the financial support by the National Natural Science Foundation of China Academy of Engineering Physicsthe jointly set-up"NSAF"joint fund under Contract No.U1430119
文摘In this paper, a new physically based constitutive model is developed for hexagonal close-packed metals, especially the Ti-6Al-4V alloy, subjected to high strain rate and different temperatures based on the microscopic mechanism of plastic deformation and the theory of thermally activated dislocation motion. A global analysis of constitutive parameters based on the Latin Hypercube Sampling method and the Spearman＇s rank correlation method is adopted in order to improve the identification efficiency of parameters. Then, an optimal solution of constitutive parameters as a whole is obtained by using a global genetic algorithm composed of an improved niche genetic algorithm, a global peak determination strategy and the local accurate search techniques. It is concluded that the proposed constitutive modal can accurately describe the Ti-6Al-4V alloy＇s dynamic behavior because the prediction results of the model are in good agreement with the experimental data.
基金supported by the Research Project of the Technical Inspection Center of Sinopec Shengli Oilfield Company.
文摘When a gas-liquid two-phase flow(GLTPF)enters a parallel separator through a T-junction,it generally splits unevenly.This phenomenon can seriously affect the operation efficiency and safety of the equipment located downstream.In order to investigate these aspects and,more specifically,the so-called bias phenomenon(all gas and liquid flowing to one pipe,while the other pipe is a liquid column that fluctuates up and down),laboratory experiments were carried out by using a T-junction connected to two parallel vertical pipes.Moreover,a GLTPF prediction model based on the principle of minimum potential energy was introduced.The research results indicate that this model can accurately predict the GLTPF state in parallel risers.The boundary of the slug flow and the churn flow in the opposite pipe can be predicted.Overall,according to the results,the pressure drop curves of the two-phase flow in the parallel risers are basically the same when there is no bias phenomenon,but the pressure drop in the parallel riser displays a large deviation when there is a slug flow-churn flow.Only when the parallel riser is in a state of asymmetric flow and one of the risers produces churn flow,the two-phase flow is prone to produce the bias phenomenon.
基金Supported by Industry Technology System of Watermelon and Melon in China(BAIC10-2017)
文摘In this study, the environmental indicators （including temperature, light, air relative humidity and CO2 concentration） of facility watermelon in Beijing area were monitored with US350 environmental sensor during the whole growth period. The results showed that in the solar greenhouses in Beijing area, the average air temperature was in the range of 10.67-29.95 ℃ during the whole growth period of watermelon, the average soil temperature ranged from 16.92 to 35.10 ℃, the average light intensity changed from 268.37 to 13 842.60 Ix, the average air relative humidity ranged from 52.40% to 94.26%, and the average CO2 concentration was in the range of 455-631 ml/m3; and in the spring greenhouses in Beijing area, the variation range of average air temperature was 14.05-29.84 ℃ during the whole growth period of watermelon, the average soil temperature ranged from 17.47 to 28.12 ℃, the average light intensity was in the range of 55.80-12 858.64 Ix, the average soil moisture content ranged from 18.19%-34.56%, the variation range of average air relative humidity was 20.72%-96.26%, and the average CO2 concentra- tion was in the range of 351-544 ml/m3,
基金Supported by Beijing Local Standard Revision Project(20171092)Experimental Demonstration of High-efficiency Ecological Facility Substrate Cultivation Technology of West Melon(2019036204)
文摘Aiming at the problems of low standardization, unstable quality and low commodity rate of facility watermelon cultivation technology in Beijing, to meet the demand for high-quality and standardized supply capacity of the watermelon industry, the technical regulations for facility watermelon production in Beijing area were formulated, mainly including the environmental conditions of the producing area, cultivation techniques, pest control and harvesting. This regulation can provide a reference for the standardization of facility watermelon production.
基金supported by National Natural Science Foundation of China(Grant No.52375312)National Key Research and Development Program of China(Grant No.2023YFB4605900)+3 种基金Liaoning Province Science and Technology Plan Joint Program(Grant No.2023JH2/101700299)Open Research Fund of Key Laboratory of Precision Special Machining and Micromanufacturing Technology of Ministry of Education for Dalian University of Technology(Grant No.B202305)Shenzhen National Major Science and Technology Projects(Grant No.CJGJZD20240729113704006)Shenzhen Key Technology R&D Programs(Grant No.JSGG20210420091802007).
文摘Laser-directed energy deposition(LDED)technology has demonstrated great potential for the rapid and integrated fabrication of nickel-based superalloy components.The plastic deformation-assisted method is crucial for achieving grain refinement and microstructural homogeneity in LDED-fabricated superalloys.However,existing methods suffer from uniformity constraints owing to their high deformation resistance,which significantly limits their application in load-bearing components.To address these issues,a synchronous-hot-forging-assisted(SHFA)LDED additive manufacturing method was proposed,and its effects on the macroscopic morphology,microstructure,and mechanical properties of GH4169 nickel-based alloy specimens were systematically compared.The results demonstrated up to 30.1%average plastic deformation in hot-forging components while maintaining good surface flatness.The synergistic effect of dislocation accumulation and dynamic recrystallization during hot forging enables dramatic grain refinement,reducing the average grain size by 89.1%(from 168.5μm to 18.4μm)while weakening texture intensity from 15.31 to 2.15,ultimately promoting equiaxed grain formation.The pores of hot-forging components changed from fine round to flat,the porosity decreased from 0.264%to 0.089%,and the densification level was significantly improved.With the increase in the synchronous hot-forging force,the average ultimate tensile strength of hot-forging components can reach 1175.1 MPa,while the anisotropy difference is gradually weakened.The SHFA-LDED process not only achieves excellent grain refinement and microstructure homogenization but also enhances mechanical properties,providing a new technical path for the additive manufacturing of high-performance nickel-based superalloy components.
基金supported by National Key Research and Development Program of China(2022YFF1003501)Biological BreedingMajor Projects(2023ZD04076)+1 种基金Funds from State Key Laboratory of Maize Bio-breeding(SKLMB2404,SKLMB2440)Anhui Natural Science Foundation(2308085QC92).
文摘Meiosis,a critical process for sexual reproduction,requires precise regulation to ensure the correct progression of meiotic stages.In yeast and animals,errors in meiotic recombination and homologous chromosomes synapsis bring a surveillance mechanism named pachytene checkpoint to prevent pachytene exit.However,most plant mutants with defects in meiotic prophase I continue cell cycle progression,which hindered the characterization of factors controlling the prophase I to metaphase I transition.Here,we characterized a male-sterile mutant in maize,prolonged prophase1(pp1),which exhibited pachytene and diakinesis arrest in male meiosis,and abnormal chromatin condensation.Using mapbased cloning,the PP1 gene was isolated as a PHD family transcription factor,and its transcripts of PP1 were preferentially accumulated in tapetum and male germline cells during microsporogenesis.Transcriptomic analysis of the pp1 mutant revealed downregulation of genes associated with chromatin assembly,cell cycle,and male meiosis,correlating with observed meiotic arrest and chromatin condensation defects.These findings highlight the role of PP1 in maize microsporogenesis,and providing more insights into the mechanisms regulating the meiotic progression in maize.
基金the National Natural Science Foundation of China Academy of Engineering Physics and the "NSAF” joint fund under Contract No. U1530140.
文摘In the present work, the governing equations based on theory of irreversible thermodynamics is deduced by introducing two internal variables to characterize the phase transformation and finite plastic deformation evolution for NiTi shape memory alloy. Thus a three-dimensional dynamic constitutive model is established by summarizing the governing equations for phase transformation and plastic deformation under high strain rate loading conditions. By adopting a stress compensation algorithm to update the stress tensor, the phenomenologicalbased constitutive model is embedded into ABAQUS finite element software as user material subroutine with FORTRAN code. Thus the numerical simulation of dynamic responses of NiTi alloy is successfully implemented. The numerical simulation results are in good agreement with the experimental data, validating the feasibility of this proposed model. Comparison between the simulation results and the experimental data indicates that the proposed model can well describe not only the different deformation stages of NiTi alloy but also its constitutive behavior subjected to different high strain rates.
基金supported by the Natural Science Foundation of Hebei Province(Project No.F2020202050)the National Natural Science Foundation of China(Grant No.62004059,11632004 and U1864208)+5 种基金the Key Program for International Science and Technology Cooperation Projects of the Ministry of Science and Technology of China(No.2016YFE0125900)National Science and Technology Major Project(2017-VII-0011-0106)Science and Technology Planning Project of Tianjin(20ZYJDJC00030)the Key Program of Research and Development of Hebei Province(202030507040009)the Fund for Innovative Research Groups of Natural Science Foundation of Hebei Province(A2020202002)the Key Project of Natural Science Foundation of Tianjin(S20ZDF077).
文摘The high sensitivity of room-temperature gas sensors is the key to innovation in the areas of environment,energy conservation and safety.However,metal-oxide-based sensors generally operate at high temperatures.Herein,we designed three ZrO_(2)-based sensors and explored their NO_(2)sensing properties at room temperature.ZrO_(2)with three different morphologies and microstructure were synthesized by simple hydrothermal methods.The microstructures of sensing materials are expected to significantly affect gas sensing properties.The rod-shaped ZrO_(2)(ZrO_(2)-R)displayed the advantages such as higher crystallinity,larger pore size,narrower band gap and more chemisorbed adsorbed oxygen,compared to hollow sphere-shaped ZrO_(2)(ZrO_(2)-HS),stellate-shaped ZrO_(2)(ZrO_(2)–S).The ZrO_(2)-R sensor showed the highest response towards 30 ppm NO_(2)(423.8%)at room temperature,and a quite high sensitivity of 198.0%for detecting 5 ppm NO_(2).Although ZrO_(2)-HS and ZrO_(2)–S sensors exhibited lower response towards 30 ppm NO_(2)(232.9%and 245.1%),the response time and recovery time of these two sensors are 5 s/19 s and 4 s/3 s,respectively.This work can provide a new strategy for the development of roomtemperature metal-oxide-based sensors.
基金supported by the 2022 Research Program of Sanya Yazhou Bay Science and Technology City(SYND-2022-10 to Wei Huang and SYND-2022-03 to Weiwei Jin)。
文摘Grain protein content(GPC)is an indicator of cereal nutritional quality.Identification of genes involved in the regulation of GPC provides targets for molecular breeding for crop protein quality.We characterized a maize gene encoding the putative amino acid transporter ZmAAP6,a gene expressed mainly in immature seeds,especially in the basal endosperm transfer layer.Total protein and zein contents were decreased in ZmAAP6 null mutants and increased in ZmAAP6 overexpression(OE)lines,consistent with their changed in the size of protein bodies.Metabolic and transcriptomic analysis supported the regulatory role of ZmAAP6 in amino acid transportation.These results suggest that ZmAAP6 functions as a positive regulator of GPC in maize,shedding new light on the genetic basis of GPC regulation.
基金supported by the National Natural Science Foundation of China(No.12233003).
文摘The problem of contingency return from the low lunar orbit is studied.A novel twomaneuver indirect return strategy is proposed.By effectively using the Earth’s gravity to change the orbital plane of the transfer orbit,the second maneuver in the well-known three-maneuver return strategy can be removed,so the total delta-v is reduced.Compared with the singlemaneuver direct return,our strategy has the advantage in that the re-entry epoch for the minimum delta-v cost can be advanced in time,with a minimum delta-v value similar to that of the direct return.The most obvious difference between our strategy and the traditional single-or multiplemaneuver strategies is that the complete transfer orbit is a patch between a two-body conic orbit and a three-body orbit instead of two conic orbits.Our strategy can serve as a useful option for contingency return from a low lunar orbit,especially when the delta-v constraint is stringent for a direct return and the contingency epoch is far away from the return window.
基金supported by Ten Thousand Talent Program of Yunnan Province(Grant No.YNWR-QNBJ-2018-174)the Key Basic Research Program of Yunnan Province,China(Grant No.202101BC070003)+3 种基金National Natural Science Foundation of China(Grant No.31901237)Conservation Program for Plant Species with Extremely Small Populations in Yunnan Province(Grant No.2022SJ07X-03)Key Technologies Research for the Germplasmof Important Woody Flowers in Yunnan Province(Grant No.202302AE090018)Natural Science Foundation of Guizhou Province(Grant No.Qiankehejichu-ZK2021yiban 089&Qiankehejichu-ZK2023yiban 035)。
文摘Rhododendron is famous for its high ornamental value.However,the genus is taxonomically difficult and the relationships within Rhododendron remain unresolved.In addition,the origin of key morphological characters with high horticulture value need to be explored.Both problems largely hinder utilization of germplasm resources.Most studies attempted to disentangle the phylogeny of Rhododendron,but only used a few genomic markers and lacked large-scale sampling,resulting in low clade support and contradictory phylogenetic signals.Here,we used restriction-site associated DNA sequencing(RAD-seq)data and morphological traits for 144 species of Rhododendron,representing all subgenera and most sections and subsections of this species-rich genus,to decipher its intricate evolutionary history and reconstruct ancestral state.Our results revealed high resolutions at subgenera and section levels of Rhododendron based on RAD-seq data.Both optimal phylogenetic tree and split tree recovered five lineages among Rhododendron.Subg.Therorhodion(cladeⅠ)formed the basal lineage.Subg.Tsutsusi and Azaleastrum formed cladeⅡand had sister relationships.CladeⅢincluded all scaly rhododendron species.Subg.Pentanthera(cladeⅣ)formed a sister group to Subg.Hymenanthes(cladeⅤ).The results of ancestral state reconstruction showed that Rhododendron ancestor was a deciduous woody plant with terminal inflorescence,ten stamens,leaf blade without scales and broadly funnelform corolla with pink or purple color.This study shows significant distinguishability to resolve the evolutionary history of Rhododendron based on high clade support of phylogenetic tree constructed by RAD-seq data.It also provides an example to resolve discordant signals in phylogenetic trees and demonstrates the application feasibility of RAD-seq with large amounts of missing data in deciphering intricate evolutionary relationships.Additionally,the reconstructed ancestral state of six important characters provides insights into the innovation of key characters in Rhododendron.
基金Supported by the Science and Technology Project of Beijing Municipal Bureau of Agriculture in 2018
文摘In order to screen out the small watermelon varieties with red flesh suitable for soilless cultivation and to meet people's requirements of high-quality watermelons,comparative tests were conducted on 6 small watermelon varieties with red flesh under soilless culture conditions in 2018.Based on the data of field traits,yield traits,quality traits and commercial traits,the integrated results showed that ‘Chuanqi 2’ had good quality and high yield,and the overall performance was the best.
