With the rapid development of information technology,the utilization of building information modeling(BIM)is increasingly prevalent in the construction industry.In order to cultivate BIM application-oriented talents c...With the rapid development of information technology,the utilization of building information modeling(BIM)is increasingly prevalent in the construction industry.In order to cultivate BIM application-oriented talents capable of effectively addressing industry development demands,this study proposes a reform plan for BIM courses that integrates post,course,competition,and certificate.The reform plan implements the teaching methods of post-course integration,competition-based teaching integration,and course certificate integration in the BIM course.It also carries out curriculum reform from four aspects:curriculum system,teaching mode,teaching content,and assessment method.Reform should be implemented to enhance students’professional and practical skills,thereby enabling them to secure improved employment opportunities and prospects for career development.展开更多
A total of 710 patients with first-ever ischemic stroke were consecutively recruited between January 2003 and December 2004 from five community hospitals/stations in five districts of Beijing, China. As of December 31...A total of 710 patients with first-ever ischemic stroke were consecutively recruited between January 2003 and December 2004 from five community hospitals/stations in five districts of Beijing, China. As of December 31, 2008, a total of 2 477 person-years were followed-up. During the five-year follow-ups, 117 adverse events occurred, including all-cause death and acute cardiovascular events (recurrent stroke, acute myocardial infarction, and sudden death). The five-year cumulative mortality rate was 2.18/100 person-years (54 cases), with 3.88/100 person-years (96 cases) of acute cardiovascular events and 3.02/100 person-years (75 cases) of recurrent stroke. Multiple factor analyses using the Cox proportional hazards ratio models showed that age, diabetes, and dependence of activities of daily living were independent predictors for death, acute cardiovascular disease events, or recurrent stroke. The results demonstrated that recurrent stroke was a major vascular disease that affected the prognosis of mild or moderate stroke patients. Secondary prevention of stroke patients should include active management of vascular risk factors and rehabilitation.展开更多
In order to improve the performance of the rotary engine,this paper has designed a new type of dual-pit rotary engine combustion chamber structure,and compares the combustion and emission characteristics with the rota...In order to improve the performance of the rotary engine,this paper has designed a new type of dual-pit rotary engine combustion chamber structure,and compares the combustion and emission characteristics with the rotary engine with a traditional combustion chamber.The existence of the dual-pit combustion chamber strengthens the overall vortex intensity in the cylinder,effectively promotes the mixing process of fuel and air in the cylinder,the maximum combustion pressure in the cylinder increased by 8.6%,significantly increases the diffusion combustion speed,and significantly improves the dynamic performance of the rotary engine.On this basis,the effects of fuel injection timing parameters on fuel distribution,combustion and emission characteristics were studied.Fuel distribution is more even and dispersed during injection in the later stage of compression.When the fuel injection timing was 105°BTDC in the middle of the compression phase,the matching effect of fuel distribution law and ignition scheme was the best.When the injection timing was 75°BTDC and 85°BTDC in the late compression stage,the mass fraction of NOx remained at a low level.The correlation between soot generation and the change of fuel injection timing was weak.When the injection time was 85°BTDC,the soot generation remained at a relatively high level.展开更多
The Hessian matrix has a wide range of applications in image processing,such as edge detection,feature point detection,etc.This paper proposes an image enhancement algorithm based on the Hessian matrix.First,the Hessi...The Hessian matrix has a wide range of applications in image processing,such as edge detection,feature point detection,etc.This paper proposes an image enhancement algorithm based on the Hessian matrix.First,the Hessian matrix is obtained by convolving the derivative of the Gaussian function.Then use the Hessian matrix to enhance the linear structure in the image.Experimental results show that the method proposed in this paper has strong robustness and accuracy.展开更多
ZnGeP_(2)[ZGP] crystals have attracted tremendous attention for their applications as frequency conversion devices.Nevertheless,the existence of native point defects,including at the surface and in the bulk,lowers the...ZnGeP_(2)[ZGP] crystals have attracted tremendous attention for their applications as frequency conversion devices.Nevertheless,the existence of native point defects,including at the surface and in the bulk,lowers their laser-induced damage threshold by increasing their absorption and forming starting points of the damage,limiting their applications.Here,native point defects in a ZGP crystal are fully studied by the combination of high angle annular dark-field scanning transmission electron microscopy[HAADF-STEM] and optical measurements.The atomic structures of the native point defects of the Zn vacancy,P vacancy,and Ge-Zn antisite were directly obtained through an HAADF-STEM,and proved by photoluminescence[PL] spectra at 77 K.The carrier dynamics of these defects are further studied by ultrafast pump-probe spectroscopy,and the decay lifetimes of 180.49,346.73,and 322.82 ps are attributed to the donor V_(p)^(+)→valence band maximum[VBM] recombination,donor Ge^(+)_(Zn)→VBM recombination,and donor–acceptor pair recombination of V_(p)^(+)→V^(-)_(Zn),respectively,which further confirms the assignment of the electron transitions.The diagrams for the energy bands and excited electron dynamics are established based on these ultrahigh spatial and temporal results.Our work is helpful for understanding the interaction mechanism between a ZGP crystal and ultrafast laser,doing good to the ZGP crystal growth and device fabrication.展开更多
Microbial contributions to natural soil suppressiveness have been reported for a range of plant pathogens and cropping systems.To disentangle the mechanisms underlying suppression of banana Panama disease caused by Fu...Microbial contributions to natural soil suppressiveness have been reported for a range of plant pathogens and cropping systems.To disentangle the mechanisms underlying suppression of banana Panama disease caused by Fusarium oxysporum f.sp.cubense tropical race 4(Foc4),we used amplicon sequencing to analyze the composition of the soil microbiome from six separate locations,each comprised of paired orchards,one potentially suppressive and one conducive to the disease.Functional potentials of the microbiomes from one site were further examined by shotgun metagenomic sequencing after soil suppressiveness was confrmed by greenhouse experiments.Potential key antagonists involved in disease suppression were also isolated,and their activities were validated by a combination of microcosm and pot experiments.We found that potentially suppressive soils shared a common core community with relatively low levels of F.oxysporum and relatively high proportions of Myxococcales,Pseudomonadales,and Xanthomonadales,with five genera,Anaeromyxobacter,Kofleria,Plesiocystis,Pseudomonas,and Rhodanobacter being significantly enriched.Further,Pseudomonas was identified as a potential key taxon linked to pathogen suppression.Metagenomic analysis showed that,compared to the conducive soil,the microbiome in the disease suppressive soil displayed a significantly greater incidence of genes related to quorum sensing,biofilm formation,and synthesis of antimicrobial compounds potentially active against Foc4.We also recovered a higher frequency of antagonistic Pseudomonas isolates from disease suppressive experimental field sites,and their protective effects against banana Fusarium wilt disease were demonstrated under greenhouse conditions.Despite differences in location and soil conditions,separately located suppressive soils shared common characteristics,including enrichment of Myxococcales,Pseudomonadales,and Xanthomonadales,and enrichment of specific Pseudomonas populations with antagonistic activity against the pathogen.Moreover,changes in functional capacity toward an increase in quorum sensing,biofilm formation,and antimicrobial compound synthesizing involve in disease suppression.展开更多
Perinereis aibuhitensis was used to assess adverse biological effects caused by acute and chronic Pb2+exposure in artificial seawater under controlled laboratory conditions. In 96-hr acute toxicity experiments,the mor...Perinereis aibuhitensis was used to assess adverse biological effects caused by acute and chronic Pb2+exposure in artificial seawater under controlled laboratory conditions. In 96-hr acute toxicity experiments,the morphological changes showed a positive time/dose-dependent tendency,and the 96-hr LC50 value of Pb2+was 686.41 mg/L. The responses of enzymatic and non-enzymatic antioxidants in tissues including catalase(CAT),peroxidase(POD),superoxide dismutase(SOD),glutathione peroxidase(GSH-PX),malondialdehyde(MDA) and the content of total soluble protein(TSP),were investigated on days 1,4,7 and 10 after Pb2+exposure under chronic toxicity testing. Results showed that the activation of the antioxidant system in P. aibuhitensis depended on the Pb2+concentration and the duration of exposure time.Specifically,POD and SOD activities were induced on the first day of the exposure and decreased to the control level on day 10 after exposure. Therefore,these two indexes could be used to indicate oxidative stress associated with P. aibuhitensis exposure to Pb2+.展开更多
Synoptic meteorology is a branch of meteorology that uses synoptic weather observations and charts for the diagnosis,study,and forecasting of weather.Weather refers to the specific state of the atmosphere near the Ea...Synoptic meteorology is a branch of meteorology that uses synoptic weather observations and charts for the diagnosis,study,and forecasting of weather.Weather refers to the specific state of the atmosphere near the Earth’s surface during a short period of time.The spatial distribution of meteorological elements in the atmosphere can be represented by a variety of transient weather phenomena,which are caused by weather systems of different spatial and temporal scales.Weather is closely related to people’s life,and its development and evolution have always been the focus of atmospheric scientific research and operation.The development of synoptic meteorology is closely related to the development of observation systems,dynamical theories and numerical models.In China,observation networks have been built since the early 1950 s.Up to now,a comprehensive meteorological observation systembased on ground,air and space has been established.In particular,the development of a new generation of dense radar networks,the development of the Fengyun satellite series and the implementation of a series of large field experiments have brought our understanding of weather from large-scale environment to thermal dynamics,cloud microphysical structure and evolution characteristics of meso and micro-scale weather systems.The development of observation has also promoted the development of theory,numerical model and simulation.In the early days,China mainly used foreign numerical models.Lately,China has developed numerical model systems with independent intellectual property rights.Based on the results of high-resolution numerical simulations,in-depth understanding of the initiation and evolution mechanism and predictability of weather at different scales has been obtained.Synoptic meteorology has gradually changed from an initially independent development to a multidisciplinary approach,and the interaction between weather and the change of climate and environment has become a hot and frontier topic in atmospheric science.This paper reviews the important scientific and technological achievements made in China over the past 70 years in the fields of synoptic meteorology based on the literatures in China and abroad,from six aspects respectively including atmospheric dynamics,synoptic-scale weather,typhoon and tropical weather,severe convective weather,numerical weather prediction and data assimilation,weather and climate,atmospheric physics and atmospheric environment.展开更多
This paper describes experimental research into the initiation and propagation of rotating detonation for liquid Nitrogen TetrOxide(NTO) and liquid MonoMethylHydrazine(MMH).An annular rocket-type combustor without noz...This paper describes experimental research into the initiation and propagation of rotating detonation for liquid Nitrogen TetrOxide(NTO) and liquid MonoMethylHydrazine(MMH).An annular rocket-type combustor without nozzle was designed to investigate detonation combustion. The propellants were injected through unlike impingement injectors. The combustion flame fronts and pressure waves were detected using optical diagnostics and dynamic pressure sensors,respectively. The propagation of rotating detonation was established spontaneously by increasing the mass flow rate of propellants. The velocity of propagation of the flame fronts and pressure waves was nearly equal and reaches supersonic speed. Two different detonation combustion patterns are present, single wave mode and double waves mode. And in double waves mode, the two detonation waves are always counter-rotating. The possibility of rotating detonation initiation in a combustor with nozzle was also checked. Stable rotating detonation can be initialized and sustained at similar operating conditions.展开更多
In this paper,a new fast and efficient algorithm,Chebyshev super spectral viscosity(SSV)method,is introduced to solve the water hammer equations.Compared with standard spectral method,the method's advantage essent...In this paper,a new fast and efficient algorithm,Chebyshev super spectral viscosity(SSV)method,is introduced to solve the water hammer equations.Compared with standard spectral method,the method's advantage essentially consists in adding a super spectral viscosity to the equations for the high wave numbers of the numerical solution.It can stabilize the numerical oscillation(Gibbs phenomenon)and improve the computational efficiency while discontinuities appear in the solution.Results obtained from the Chebyshev super spectral viscosity method exhibit greater consistency with conventional water hammer calculations.It shows that this new numerical method offers an altemative way to investigate the behavior of the water hammer in propellant pipelines.展开更多
Chunguang oilfield is a new focus of the exploration in Junnggar Basin with the heavy crude oil distributing in Jurassic, Cretaceous and Tertiary strata. Based on the analysis of the geochemistry and fluid inclusion i...Chunguang oilfield is a new focus of the exploration in Junnggar Basin with the heavy crude oil distributing in Jurassic, Cretaceous and Tertiary strata. Based on the analysis of the geochemistry and fluid inclusion in the reservoirs, the source, accumulated period and process of the heavy crude oil reservoir has been investigated. The results indicate that the heavy crude oil can be divided into three types based on the degradation and sources. The heavy crude oil was mainly derived from the Permian source rocks, and latterly mixed by the heavy crude oil generated by the Jurassic source rocks. The accumulated period of the heavy crude oil has two stages. One was ranged from Cretaceous to Paleogene and the heavy crude oil was sourced from Permian source rocks of the Shawan depression and latterly mixed by the heavy crude oil generated by the Jurassic source rocks. The second period was from Neogene to present and the heavy crude oil was mainly derived from the Jurassic source rocks. Combined with the geological evolution, the heavy crude oil accumulated process has been recovered.展开更多
In order to compare the effects of Bassini and tension-free mesh hernioplasty,a total of 552 patients with inguinal hernia who were subjected to surgical treatment in our hospital were randomly divided into the follow...In order to compare the effects of Bassini and tension-free mesh hernioplasty,a total of 552 patients with inguinal hernia who were subjected to surgical treatment in our hospital were randomly divided into the following two groups:the Bassini group(n=269)and the tension-free mesh group(n=283).The recurrence rates,pain,dis-comfort,and other complications were recorded,and the causes of the complications were explored.The recurrence rate in the Bassini group was 8.9%(24/269),significantly higher than that in the tension-free repair group(2.8%,8/283).In addition,the recurrence rates in the Bassini and tension-free groups before 2004 were 12.6%and 5.6%,respectively,which were markedly higher than the rates after 2004(5.3%and 0.7%,respectively).The rate of post-operative discomfort and pain within thefirst three months was higher in the Bassini group compared to the tension-free group(25.7%vs 18.5%,respectively).However,there was no difference after three months in the rate of post-operative discomfort and pain,incidence of infection,or scrotal edema between the two groups.The average hospital stay in the Bassini group was longer than that in the tension-free repair group(7.6�1.2 vs 4.5�2.2 days,respectively),but the cost was lower(4518.0�510 vs 6221.3�578 yuan,respectively).Thus,tension-free mesh hernioplasty is indicated for most inguinal hernia patients due to the low recurrence rate,rapid recovery time,and treatment success,but the traditional Bassini procedure has lower cost and other beneficial effects and is still suitable for some patients.展开更多
1T-polytype tantalum disulfide(1T-TaS_(2)),an emerging strongly correlated material,features a narrow bandgap of 0.2 e V,bridging the gap between zero-bandgap graphene and large-bandgap 2D nonlinear optical(NLO)materi...1T-polytype tantalum disulfide(1T-TaS_(2)),an emerging strongly correlated material,features a narrow bandgap of 0.2 e V,bridging the gap between zero-bandgap graphene and large-bandgap 2D nonlinear optical(NLO)materials.Combined with its intense light absorption,high carrier concentration,and high mobility,1T-TaS_(2) shows considerable potential for applications in broadband optoelectronic devices.However,its NLO characteristics and related applications have rarely been explored.Here,1T-TaS_(2) nanosheets are prepared by chemical vapor deposition.The ultrafast carrier dynamics in the 400–1100 nm range and broadband NLO performance in the 515–2500 nm range are systematically studied using femtosecond lasers.An obvious saturable absorption phenomenon is observed in the visible to IR range.The nonlinear absorption coefficient is measured to be-22.60±0.52 cm MW-1under 1030 nm,which is larger than that of other typical 2D saturable absorber(SA)materials(graphene,black phosphorus,and MoS_(2))under similar experimental conditions.Based on these findings,using 1T-TaS_(2) as a new SA,passively Q-switched laser operations are successfully performed at 1.06,1.34,and 1.94μm.The results highlight the promise of 1T-TaS_(2) for broadband optical modulators and provide a potential candidate material system for mid-IR nonlinear optical applications.展开更多
文摘With the rapid development of information technology,the utilization of building information modeling(BIM)is increasingly prevalent in the construction industry.In order to cultivate BIM application-oriented talents capable of effectively addressing industry development demands,this study proposes a reform plan for BIM courses that integrates post,course,competition,and certificate.The reform plan implements the teaching methods of post-course integration,competition-based teaching integration,and course certificate integration in the BIM course.It also carries out curriculum reform from four aspects:curriculum system,teaching mode,teaching content,and assessment method.Reform should be implemented to enhance students’professional and practical skills,thereby enabling them to secure improved employment opportunities and prospects for career development.
基金supported by the National Natural Science Foundation of China, No. 30671797 and 81072361
文摘A total of 710 patients with first-ever ischemic stroke were consecutively recruited between January 2003 and December 2004 from five community hospitals/stations in five districts of Beijing, China. As of December 31, 2008, a total of 2 477 person-years were followed-up. During the five-year follow-ups, 117 adverse events occurred, including all-cause death and acute cardiovascular events (recurrent stroke, acute myocardial infarction, and sudden death). The five-year cumulative mortality rate was 2.18/100 person-years (54 cases), with 3.88/100 person-years (96 cases) of acute cardiovascular events and 3.02/100 person-years (75 cases) of recurrent stroke. Multiple factor analyses using the Cox proportional hazards ratio models showed that age, diabetes, and dependence of activities of daily living were independent predictors for death, acute cardiovascular disease events, or recurrent stroke. The results demonstrated that recurrent stroke was a major vascular disease that affected the prognosis of mild or moderate stroke patients. Secondary prevention of stroke patients should include active management of vascular risk factors and rehabilitation.
基金National Natural Science Foundation of China No.51976083 and the Qing Lan Project.
文摘In order to improve the performance of the rotary engine,this paper has designed a new type of dual-pit rotary engine combustion chamber structure,and compares the combustion and emission characteristics with the rotary engine with a traditional combustion chamber.The existence of the dual-pit combustion chamber strengthens the overall vortex intensity in the cylinder,effectively promotes the mixing process of fuel and air in the cylinder,the maximum combustion pressure in the cylinder increased by 8.6%,significantly increases the diffusion combustion speed,and significantly improves the dynamic performance of the rotary engine.On this basis,the effects of fuel injection timing parameters on fuel distribution,combustion and emission characteristics were studied.Fuel distribution is more even and dispersed during injection in the later stage of compression.When the fuel injection timing was 105°BTDC in the middle of the compression phase,the matching effect of fuel distribution law and ignition scheme was the best.When the injection timing was 75°BTDC and 85°BTDC in the late compression stage,the mass fraction of NOx remained at a low level.The correlation between soot generation and the change of fuel injection timing was weak.When the injection time was 85°BTDC,the soot generation remained at a relatively high level.
基金supported by the key scientific research projects of the Hunan Provincial Department of Education (No.19A099,20A102)the Educational Reform Project of the Hunan Provincial Department of Education (No.HNJG-2021-1121)+2 种基金the Hunan First Normal University Teaching Reform Project (No.XYS21J09)Shaoyang City Science and Technology Bureau Science and Technology Research Project (No.2020GX31)Shaoyang University Cooperation Project (No.2019HX115).
文摘The Hessian matrix has a wide range of applications in image processing,such as edge detection,feature point detection,etc.This paper proposes an image enhancement algorithm based on the Hessian matrix.First,the Hessian matrix is obtained by convolving the derivative of the Gaussian function.Then use the Hessian matrix to enhance the linear structure in the image.Experimental results show that the method proposed in this paper has strong robustness and accuracy.
基金supported by the National Natural Science Foundation of China(Nos.51872198,52172151,52172002,92163207,51972229,and 51890865)the Natural Science Foundation of Tianjin(No.18JCYBJC42500)+1 种基金the National Defense Science and Technology 173 Program(No.2021-JCJQJJ-0639)the Natural Science Foundation of Heilongjiang Province(No.YQ2020B002)。
文摘ZnGeP_(2)[ZGP] crystals have attracted tremendous attention for their applications as frequency conversion devices.Nevertheless,the existence of native point defects,including at the surface and in the bulk,lowers their laser-induced damage threshold by increasing their absorption and forming starting points of the damage,limiting their applications.Here,native point defects in a ZGP crystal are fully studied by the combination of high angle annular dark-field scanning transmission electron microscopy[HAADF-STEM] and optical measurements.The atomic structures of the native point defects of the Zn vacancy,P vacancy,and Ge-Zn antisite were directly obtained through an HAADF-STEM,and proved by photoluminescence[PL] spectra at 77 K.The carrier dynamics of these defects are further studied by ultrafast pump-probe spectroscopy,and the decay lifetimes of 180.49,346.73,and 322.82 ps are attributed to the donor V_(p)^(+)→valence band maximum[VBM] recombination,donor Ge^(+)_(Zn)→VBM recombination,and donor–acceptor pair recombination of V_(p)^(+)→V^(-)_(Zn),respectively,which further confirms the assignment of the electron transitions.The diagrams for the energy bands and excited electron dynamics are established based on these ultrahigh spatial and temporal results.Our work is helpful for understanding the interaction mechanism between a ZGP crystal and ultrafast laser,doing good to the ZGP crystal growth and device fabrication.
基金supported by the National Natural Science Foundation of China(31972509,42090065,and 42107142)the Guidance Foundation of the Sanya Institute of Nanjing Agricultural University(NAUSY-MS1O).
文摘Microbial contributions to natural soil suppressiveness have been reported for a range of plant pathogens and cropping systems.To disentangle the mechanisms underlying suppression of banana Panama disease caused by Fusarium oxysporum f.sp.cubense tropical race 4(Foc4),we used amplicon sequencing to analyze the composition of the soil microbiome from six separate locations,each comprised of paired orchards,one potentially suppressive and one conducive to the disease.Functional potentials of the microbiomes from one site were further examined by shotgun metagenomic sequencing after soil suppressiveness was confrmed by greenhouse experiments.Potential key antagonists involved in disease suppression were also isolated,and their activities were validated by a combination of microcosm and pot experiments.We found that potentially suppressive soils shared a common core community with relatively low levels of F.oxysporum and relatively high proportions of Myxococcales,Pseudomonadales,and Xanthomonadales,with five genera,Anaeromyxobacter,Kofleria,Plesiocystis,Pseudomonas,and Rhodanobacter being significantly enriched.Further,Pseudomonas was identified as a potential key taxon linked to pathogen suppression.Metagenomic analysis showed that,compared to the conducive soil,the microbiome in the disease suppressive soil displayed a significantly greater incidence of genes related to quorum sensing,biofilm formation,and synthesis of antimicrobial compounds potentially active against Foc4.We also recovered a higher frequency of antagonistic Pseudomonas isolates from disease suppressive experimental field sites,and their protective effects against banana Fusarium wilt disease were demonstrated under greenhouse conditions.Despite differences in location and soil conditions,separately located suppressive soils shared common characteristics,including enrichment of Myxococcales,Pseudomonadales,and Xanthomonadales,and enrichment of specific Pseudomonas populations with antagonistic activity against the pathogen.Moreover,changes in functional capacity toward an increase in quorum sensing,biofilm formation,and antimicrobial compound synthesizing involve in disease suppression.
基金Acknowledgements All authors are grateful to the National Natural Science Foundation of China （Nos. 51525202, 61574054, 61505051 and 61474040）, the Hunan province science and technology plan （Nos. 2014FJ2001 and 2014TT1004）, the Aid program for Science and Technology Innovative Research Team in Higher Educational Institutions of Hunan Province, and the Fundamental Research Funds for the Central Universities.
基金supported by the National Natural Science Foundation of China (No.41206102,31070458)the National Marine Public Welfare Research Project (No.201005007,201305009)
文摘Perinereis aibuhitensis was used to assess adverse biological effects caused by acute and chronic Pb2+exposure in artificial seawater under controlled laboratory conditions. In 96-hr acute toxicity experiments,the morphological changes showed a positive time/dose-dependent tendency,and the 96-hr LC50 value of Pb2+was 686.41 mg/L. The responses of enzymatic and non-enzymatic antioxidants in tissues including catalase(CAT),peroxidase(POD),superoxide dismutase(SOD),glutathione peroxidase(GSH-PX),malondialdehyde(MDA) and the content of total soluble protein(TSP),were investigated on days 1,4,7 and 10 after Pb2+exposure under chronic toxicity testing. Results showed that the activation of the antioxidant system in P. aibuhitensis depended on the Pb2+concentration and the duration of exposure time.Specifically,POD and SOD activities were induced on the first day of the exposure and decreased to the control level on day 10 after exposure. Therefore,these two indexes could be used to indicate oxidative stress associated with P. aibuhitensis exposure to Pb2+.
基金supported by the National Natural Science Foundation of China (Grant No. 41425018)the National Key Research and Development Program of China (Grant No. 2017YFC1501601)+3 种基金the National Natural Science Foundation of China (Grant No. 41675045)the National Key Research and Development Program of China (Grant No. 2017YFC1501904)the National Natural Science Foundation of China (Grant Nos. 41875066, 41675108 & 41875051)the Special Program on the Monitoring, Warning and Prevention of Major Natural Disasters (Grant No. 2018YFC1506702)
文摘Synoptic meteorology is a branch of meteorology that uses synoptic weather observations and charts for the diagnosis,study,and forecasting of weather.Weather refers to the specific state of the atmosphere near the Earth’s surface during a short period of time.The spatial distribution of meteorological elements in the atmosphere can be represented by a variety of transient weather phenomena,which are caused by weather systems of different spatial and temporal scales.Weather is closely related to people’s life,and its development and evolution have always been the focus of atmospheric scientific research and operation.The development of synoptic meteorology is closely related to the development of observation systems,dynamical theories and numerical models.In China,observation networks have been built since the early 1950 s.Up to now,a comprehensive meteorological observation systembased on ground,air and space has been established.In particular,the development of a new generation of dense radar networks,the development of the Fengyun satellite series and the implementation of a series of large field experiments have brought our understanding of weather from large-scale environment to thermal dynamics,cloud microphysical structure and evolution characteristics of meso and micro-scale weather systems.The development of observation has also promoted the development of theory,numerical model and simulation.In the early days,China mainly used foreign numerical models.Lately,China has developed numerical model systems with independent intellectual property rights.Based on the results of high-resolution numerical simulations,in-depth understanding of the initiation and evolution mechanism and predictability of weather at different scales has been obtained.Synoptic meteorology has gradually changed from an initially independent development to a multidisciplinary approach,and the interaction between weather and the change of climate and environment has become a hot and frontier topic in atmospheric science.This paper reviews the important scientific and technological achievements made in China over the past 70 years in the fields of synoptic meteorology based on the literatures in China and abroad,from six aspects respectively including atmospheric dynamics,synoptic-scale weather,typhoon and tropical weather,severe convective weather,numerical weather prediction and data assimilation,weather and climate,atmospheric physics and atmospheric environment.
文摘This paper describes experimental research into the initiation and propagation of rotating detonation for liquid Nitrogen TetrOxide(NTO) and liquid MonoMethylHydrazine(MMH).An annular rocket-type combustor without nozzle was designed to investigate detonation combustion. The propellants were injected through unlike impingement injectors. The combustion flame fronts and pressure waves were detected using optical diagnostics and dynamic pressure sensors,respectively. The propagation of rotating detonation was established spontaneously by increasing the mass flow rate of propellants. The velocity of propagation of the flame fronts and pressure waves was nearly equal and reaches supersonic speed. Two different detonation combustion patterns are present, single wave mode and double waves mode. And in double waves mode, the two detonation waves are always counter-rotating. The possibility of rotating detonation initiation in a combustor with nozzle was also checked. Stable rotating detonation can be initialized and sustained at similar operating conditions.
基金This work was supported by Public Science and Technology Research Funds Projects of Ocean （Grant No. 201505022）, the National Natural Science Foundation of China NSFC-Shandong Joint Fund （U1406402-5）, the National Natural Science Foundation of China （Grant No. 81671828）, and the Taishan Scholar Program of China.
文摘In this paper,a new fast and efficient algorithm,Chebyshev super spectral viscosity(SSV)method,is introduced to solve the water hammer equations.Compared with standard spectral method,the method's advantage essentially consists in adding a super spectral viscosity to the equations for the high wave numbers of the numerical solution.It can stabilize the numerical oscillation(Gibbs phenomenon)and improve the computational efficiency while discontinuities appear in the solution.Results obtained from the Chebyshev super spectral viscosity method exhibit greater consistency with conventional water hammer calculations.It shows that this new numerical method offers an altemative way to investigate the behavior of the water hammer in propellant pipelines.
基金supported by the National Natural Science Foundation of China(No.41202105)the Open Research Foundation of Key Laboratory of Tectonics and Petroleum Resources Ministry of Education,China University of Geoscience(Wuhan)(No.TPR-2010-20)
文摘Chunguang oilfield is a new focus of the exploration in Junnggar Basin with the heavy crude oil distributing in Jurassic, Cretaceous and Tertiary strata. Based on the analysis of the geochemistry and fluid inclusion in the reservoirs, the source, accumulated period and process of the heavy crude oil reservoir has been investigated. The results indicate that the heavy crude oil can be divided into three types based on the degradation and sources. The heavy crude oil was mainly derived from the Permian source rocks, and latterly mixed by the heavy crude oil generated by the Jurassic source rocks. The accumulated period of the heavy crude oil has two stages. One was ranged from Cretaceous to Paleogene and the heavy crude oil was sourced from Permian source rocks of the Shawan depression and latterly mixed by the heavy crude oil generated by the Jurassic source rocks. The second period was from Neogene to present and the heavy crude oil was mainly derived from the Jurassic source rocks. Combined with the geological evolution, the heavy crude oil accumulated process has been recovered.
文摘In order to compare the effects of Bassini and tension-free mesh hernioplasty,a total of 552 patients with inguinal hernia who were subjected to surgical treatment in our hospital were randomly divided into the following two groups:the Bassini group(n=269)and the tension-free mesh group(n=283).The recurrence rates,pain,dis-comfort,and other complications were recorded,and the causes of the complications were explored.The recurrence rate in the Bassini group was 8.9%(24/269),significantly higher than that in the tension-free repair group(2.8%,8/283).In addition,the recurrence rates in the Bassini and tension-free groups before 2004 were 12.6%and 5.6%,respectively,which were markedly higher than the rates after 2004(5.3%and 0.7%,respectively).The rate of post-operative discomfort and pain within thefirst three months was higher in the Bassini group compared to the tension-free group(25.7%vs 18.5%,respectively).However,there was no difference after three months in the rate of post-operative discomfort and pain,incidence of infection,or scrotal edema between the two groups.The average hospital stay in the Bassini group was longer than that in the tension-free repair group(7.6�1.2 vs 4.5�2.2 days,respectively),but the cost was lower(4518.0�510 vs 6221.3�578 yuan,respectively).Thus,tension-free mesh hernioplasty is indicated for most inguinal hernia patients due to the low recurrence rate,rapid recovery time,and treatment success,but the traditional Bassini procedure has lower cost and other beneficial effects and is still suitable for some patients.
基金National Key Research and Development Program of China(2018YFE0115900)National Natural Science Foundation of China(11874369,51802218,51972229,52002271)+3 种基金China Postdoctoral Science Foundation(2021M703326)CAS Special Research Assistant ProjectKey Foreign Cooperation Projects of the Bureau of International Cooperation of the Chinese Academy of Sciences(181231KYSB20210001)National Defense Science and Technology 173 Program(2021-JCJQ-JJ-0639)。
文摘1T-polytype tantalum disulfide(1T-TaS_(2)),an emerging strongly correlated material,features a narrow bandgap of 0.2 e V,bridging the gap between zero-bandgap graphene and large-bandgap 2D nonlinear optical(NLO)materials.Combined with its intense light absorption,high carrier concentration,and high mobility,1T-TaS_(2) shows considerable potential for applications in broadband optoelectronic devices.However,its NLO characteristics and related applications have rarely been explored.Here,1T-TaS_(2) nanosheets are prepared by chemical vapor deposition.The ultrafast carrier dynamics in the 400–1100 nm range and broadband NLO performance in the 515–2500 nm range are systematically studied using femtosecond lasers.An obvious saturable absorption phenomenon is observed in the visible to IR range.The nonlinear absorption coefficient is measured to be-22.60±0.52 cm MW-1under 1030 nm,which is larger than that of other typical 2D saturable absorber(SA)materials(graphene,black phosphorus,and MoS_(2))under similar experimental conditions.Based on these findings,using 1T-TaS_(2) as a new SA,passively Q-switched laser operations are successfully performed at 1.06,1.34,and 1.94μm.The results highlight the promise of 1T-TaS_(2) for broadband optical modulators and provide a potential candidate material system for mid-IR nonlinear optical applications.
