Introduction: Voluntary assault and injuries are acts that damage the physical and psychological integrity of a human being. WHO in its global report on violence and health estimates that in 2000, 1.6 million people w...Introduction: Voluntary assault and injuries are acts that damage the physical and psychological integrity of a human being. WHO in its global report on violence and health estimates that in 2000, 1.6 million people worldwide died as a result of self-harm, interpersonal or collective violence, resulting in an overall rate adjusted by age of 28.8 per 100,000 population. Because of the seriousness of this phenomenon and the heavy socio-economic and health consequences that they generate, it seemed important to us to undertake this study, which aimed to study the deliberate injuries in the emergency unite of the Gabriel Touré Teaching Hospital in Bamako. Material and methods: This was a descriptive and cross-sectional study with a prospective study from September 1st, 2016 to August 31st, 12 months, covering 295 patients, including any patient received for voluntary injury consultation with a workable medical record and/or a full investigation record with or without requisition. Our data were collected on individual survey cards and subsequently analyzed with Word, Excel, IBM SPSS Statistics 22 software. Results: The majority of victims of assault and bodily injury were male with 83.1%;with a sex ratio of 4.9, the 18 to 28 age group was the most concerned with 163 cases of the 295 cases in our study, 55.2%. The extremes were 6 and 100 years old with an ectype at 11.08. The most affected ethnic group was Bambara with 38.6% (n = 114) followed by Fulani with 15.6% (n = 46). Students were the most affected at 24.7% (n = 73), followed by traders at 10%. The victims coming from outside Bamako are the most predominant with 22.4% (n = 66) followed by those of commune IV of Bamako 15.6% (n = 46). In 92.2% of the cases the mechanism was direct with n = 272. Of the lesions recorded in our study, wounds came first with 53.2% of cases. Radiography was the most used imaging at 44.7% (n = 89) followed by computed tomography at 34.7% (n = 69). The hemoperitoneum objectified by abdominal ultrasound represented 29.3% (n = 12). Fractures embarrure associated with bruising-hemorrhagic bruises were the most predominant with 13.4% (n = 10) objectified by brain scan. Conclusion: We note that the phenomenon of violence has reached worrying proportions, especially among young adults, particularly among students and is observed in all so-cio-professional layers. The polymorphism of these injuries caused by the predominant use of knives must draw the attention of our authorities to take measures to reduce these aggressions.展开更多
Images provided by the author unless otherwise stated■This summer the first major U.S.solo exhibition by leading Taiwan Residents artist Chen Chieh-jen took place at Manhattan's Asia Society.The exhibition 'C...Images provided by the author unless otherwise stated■This summer the first major U.S.solo exhibition by leading Taiwan Residents artist Chen Chieh-jen took place at Manhattan's Asia Society.The exhibition 'Condensation' united five silent films that address a variety of social topics into a cohesive unit. The films reflect the mind of someone who came to artistic maturity during a rapidly changing political environment in Taiwan.展开更多
OVER 2,000 years ago,the bronze craftsmen in today’s Datong City,Shanxi Province,had already mastered the superb skills of copper production.Datong bronze-making craft was included in China’s state-level intangible ...OVER 2,000 years ago,the bronze craftsmen in today’s Datong City,Shanxi Province,had already mastered the superb skills of copper production.Datong bronze-making craft was included in China’s state-level intangible cultural heritage list in 2014.The craftsmanship which has been passed down through the millennia still shines brightly today after countless hammer blows and engravings.展开更多
Although poly(lactic acid)(PLA)is a good environmentally-friendly bio-degradable polymer which is used to substitute traditional petrochemical-based polymer packaging films,the barrier properties of PLA films are stil...Although poly(lactic acid)(PLA)is a good environmentally-friendly bio-degradable polymer which is used to substitute traditional petrochemical-based polymer packaging films,the barrier properties of PLA films are still insufficient for high-barrier packaging applications.In this study,oxygen scavenger hydroxyl-terminated polybutadiene(HTPB)and cobalt salt catalyst were incorporated into the PLA/poly(butylene adipate-co-terephthalate)(PLA/PBAT),followed by melting extrusion and three-layer co-extrusion blown film process to prepare the composite films.The oxygen permeability coefficient of the composite film combined with 6 wt%oxygen scavenger and 0.4 wt%catalyst was decreased significantly from 377.00 cc·mil·m^(-2)·day^(-1)·0.1 MPa^(-1) to 0.98 cc·mil·m^(-2)·day^(-1)·0.1 MPa^(-1),showing a remarkable enhancement of 384.69 times compared with the PLA/PBAT composite film.Meanwhile,the degradation behavior of the composite film was also accelerated,exhibiting a mass loss of nearly 60%of the original mass after seven days of degradation in an alkaline environment,whereas PLA/PBAT composite film only showed a mass loss of 32%.This work has successfully prepared PLA/PBAT composite films with simultaneously improved oxygen barrier property and degradation behavior,which has great potential for high-demanding green chemistry packaging industries,including food,agricultural,and military packaging.展开更多
Blowing snow events in Antarctica play an important role in the climate system,affecting the mass balance of the ice sheet and the radiative effects of the atmosphere.Due to the harsh weather conditions in Antarctica,...Blowing snow events in Antarctica play an important role in the climate system,affecting the mass balance of the ice sheet and the radiative effects of the atmosphere.Due to the harsh weather conditions in Antarctica,ground-based detection data is deficient,making it difficult to accurately obtain both the frequency of blowing snow and the evolution of the height of the blowing snow layer.In this study,we introduce a new method based on the raw signal from the C12 ceilometer to separate clear-sky,cloud,snowfall,and blowing snow conditions within a height of 500 meters above the surface of Zhongshan Station.Research has shown that more than 80%of the blowing snow at Zhongshan Station is affected by cyclonic systems,and less than 20%of the blowing snow is affected by katabatic winds.Further,Antarctic blowing snow is closely related to snowfall.When there is heavy snowfall(even a blizzard),a smaller wind speed can lead to the formation of a deep blowing snow layer within an hour after snowfall.However,as time increases,the threshold wind speed required to generate blowing snow significantly increases,and the thickness of the blowing snow layer becomes shallower.展开更多
The top-bottom combined blowing converter mainly adopts the blowing method of top-blowing oxygen and bottom-blowing nitrogen.In the production process,there are some disadvantages,such as a significant temperature dif...The top-bottom combined blowing converter mainly adopts the blowing method of top-blowing oxygen and bottom-blowing nitrogen.In the production process,there are some disadvantages,such as a significant temperature difference between the top and bottom of the molten pool,inadequate gas permeability of bottom blowing,and low decarburization efficiency.Therefore,we propose a novel bottom-blowing gas doped oxygen process to enhance the smelting conditions in the converter.The 500 kg medium frequency induction furnace with top and bottom-blowing function was used to explore the influence of the proportion of bottom-blowing gas doped oxygen on the smelting effect in different smelting cycles.Subsequently,industrial experimental verification was carried out on a 60 t converter.The results of intermediate frequency furnace experiments demonstrate that the bottom-blowing gas doped oxygen process exhibits a superior heating rate and decarburization efficiency during the initial and final stages of blowing compared to pure N2 used for bottom-blowing.Simultaneously,the dephosphorization efficiency exhibited an initial increase followed by a subsequent decrease as the bottom-blowing oxygen content increased.The industrial test of 60 t converter validates the findings above.Moreover,when the oxygen content in bottom-blowing gas is 5%,the average blowing time reduces by 54 s,and the minimum endpoint carbon-oxygen equilibrium reaches 0.00219 under this condition.The results demonstrate that the appropriate amount of oxygen doped in bottom-blowing gas can effectively enhance the metallurgical conditions of the converter and improve production efficiency.展开更多
The turbulent characteristics of the top-blown Laval nozzle and the influence of pressure and Mach number were studied through numerical simulation.With 2.72%error between the results and the empirical formula,the res...The turbulent characteristics of the top-blown Laval nozzle and the influence of pressure and Mach number were studied through numerical simulation.With 2.72%error between the results and the empirical formula,the results are reliable.Nozzle fluid is influenced by pipe structure,causing pressure and density to drop as speed increases.Differences in pressure and velocity between the jet and surrounding gas lead to jet velocity attenuation,flow expansion,deflection,and eddy currents.The optimal top blowing pressure is 0.6 MPa,and the center velocity and width of the jet are 345 m/s and 0.124 m,respectively,at 20De(De is the nozzle exit diameter).It achieves a maximum jet velocity of 456 m/s.The optimal nozzle Mach number is 1.75,with a maximum jet velocity of 451 m/s.At 20D_(e),the jet center velocity is 338 m/s,with a width of 0.12 m.展开更多
In this paper,a class of semilinear parabolic equations with cross coupling of power and exponential functions and large initial values are studied.By constructing and solving ordinary differential equations,the upper...In this paper,a class of semilinear parabolic equations with cross coupling of power and exponential functions and large initial values are studied.By constructing and solving ordinary differential equations,the upper and lower bounds on the solution life span of the equations areobtained.展开更多
Under the background of the strategic goal of"double carbon,"the carbon reduction and consumption reduction of the iron and steel industry,especially in the ironmaking process,need to be further improved.The...Under the background of the strategic goal of"double carbon,"the carbon reduction and consumption reduction of the iron and steel industry,especially in the ironmaking process,need to be further improved.The raceway of tuyere provides the chemical environment,fuel and power source for blast furnace smelting.The research on the characteristics of its action mode and mechanism is of great significance to clarify the way of reducing carbon and consumption of blast furnace.In general,the formation mechanism,energy distribution,research progress,extended resource injection and directional regulation are studied and expounded.The research results of various scholars on the characteristics of the raceway show that the raceway is a complex process including multiphase turbulent flow,heat,momentum,mass and homogeneous and heterogeneous chemical reactions.With the development of multi-source fuel injection technology,the complexity of problem research is more obvious.Therefore,the collection of multi-factor,multi-directional and multi-process characteristic information in the raceway can provide guarantee for the stability,smooth operation,high yield,carbon reduction and consumption reduction of blast furnace and provide new ideas for the green and low-carbon development of iron and steel industry.展开更多
Stall flutter poses great challenges to flight safety.To alleviate this problem,a steady blowing control considering the perturbation and wake-induced vibration at a large angle of attack is developed in this paper,wh...Stall flutter poses great challenges to flight safety.To alleviate this problem,a steady blowing control considering the perturbation and wake-induced vibration at a large angle of attack is developed in this paper,where two blowings are configured on upper and lower tail surfaces to suppress the stall flutter.The stall flutter with one-degree-of-freedom is first evaluated by numerical simulation.The equation of motion for stall flutter is solved by the Newmark-β method.Then,the stall flutter responses for five blowing speeds,i.e.,0,4,12,20,and 28 m/s under the airspeed range of 3–9 m/s,are studied in detail.The stall flutter suppression mechanism can be summarized as follows:a large blowing speed can inject energy into the boundary layer and enhance the high-pressure zone,which delays the flow separation on the suction surface.In this way,the formation of the leading-edge separation vortex is suppressed.Thus,the dynamic stall vortex is weakened and accelerates shedding.In addition,the driving moment is reduced,which leads to a decrement in the stall flutter amplitude.When the blowing speed is 28 m/s(stall flutter amplitude=0.1357 rad),compared with uncontrolled case(stall flutter amplitude=0.6002 rad),the amplitude can decrease by 77.39%,which demonstrates the effectiveness of the proposed steady blowing based active control strategy.展开更多
Sea ice and snow are the most sensitive and important crucial components of the global climate system,affecting the global climate by modulating the energy exchange between the ocean and the atmosphere.The sea near Zh...Sea ice and snow are the most sensitive and important crucial components of the global climate system,affecting the global climate by modulating the energy exchange between the ocean and the atmosphere.The sea near Zhongshan Station in Antarctica is covered by landfast sea ice,with snow depth influenced by both thermal factors and wind.This region frequently experiences katabatic winds and cyclones from the westerlies,leading to frequent snow blowing events that redistribute the snow and affects its depth,subsequently impacting the thermodynamic growth of sea ice.This study utilized the one-dimensional thermodynamic model ICEPACK to simulate landfast sea ice thickness and snow depth near Zhongshan Station in 2016.Two parameterization schemes for snow blowing,the Bulk scheme,and the ITDrdg(ITD/ridges)scheme are evaluated for their impact on snow depth.The results show that simulations using snow blowing schemes more closely align with observed results,with the ITDrdg scheme providing more accurate simulations,evidenced by root mean square errors of less than 10 cm for both snow depth and sea ice thickness.Snow blowing also impacts the thermodynamic growth of sea ice,particularly bottom growth.The sea ice bottom increases by 9.0 cm using the ITDrdg scheme compared to simulations without the snow blowing,accounting for 12.5%of total sea ice bottom growth.Furthermore,snow blowing process also influences snow ice formation,highlighting its primary role in affecting snow depth.Continued field observations of snow blowing are necessary to evaluate and improve parameterization schemes.展开更多
In this paper,we consider the initial boundary value problem for the 2-D hyperbolic viscous Cahn-Hilliard equation.Firstly,we prove the existence and uniqueness of the local solution by the Galerkin method and contrac...In this paper,we consider the initial boundary value problem for the 2-D hyperbolic viscous Cahn-Hilliard equation.Firstly,we prove the existence and uniqueness of the local solution by the Galerkin method and contraction mapping principle.Then,using the potential well theory,we study the global well-posedness of the solution with initial data at different levels of initial energy,i.e.,subcritical initial energy,critical initial energy and arbitrary positive initial energy.For subcritical initial energy,we prove the global existence,asymptotic behavior and finite time blowup of the solution.Moreover,we extend these results to the critical initial energy using the scaling technique.For arbitrary positive initial energy,including the sup-critical initial energy,we obtain the sufficient conditions for finite time blow-up of the solution.As a further study for estimating the blowup time,we give a unified expression of the lower bound of blowup time for all three initial energy levels and estimate the upper bound of blowup time for subcritical and critical initial energy.展开更多
Particulate matter(PM)from high-temperature emissions like chemical plants,coal stoves and vehicle exhausts poses a gravel challenge to human health.To address this issue,researchers have explored vari-ous fiber filte...Particulate matter(PM)from high-temperature emissions like chemical plants,coal stoves and vehicle exhausts poses a gravel challenge to human health.To address this issue,researchers have explored vari-ous fiber filters,yet the bulk struggle to withstand high temperatures.In this study,mullite fiber sponges were developed utilizing low-cost materials and Kármán vortex solution blow spinning,using surfac-tants to improve the spinnability of the sol.Optimized sponges demonstrate ultralight(19 mg cm^(-3)),temperature-resistant reversible compressibility(50% strain)and a water contact angle of 135°.These sponges exhibited exceptional thermal insulation(thermal conductivity:0.0256 W m^(-1) K^(-1))and per-formed well in high-temperature air filtration.At 800℃,the mullite sponge with a base weight of 35 mg cm^(-2),achieved an average filtration efficiency of 98.18%and 99.57% for PM_(2.5) and PM_(2.5-10),respectively,with a quality value of 0.98 Pa^(-1) at a wind speed of 4 cm s^(-1).This low-cost mullite fiber sponge offers a promising avenue for designing high-performance filtration materials.展开更多
The unfolding global financial crisis is arousing jitters about another round of heavy blows to the world economy, which may be intensified by the possible U.S. government takeover of Citigroup Inc. and Bank of Americ...The unfolding global financial crisis is arousing jitters about another round of heavy blows to the world economy, which may be intensified by the possible U.S. government takeover of Citigroup Inc. and Bank of America Corp. lg, Chief Economist of the Asia-Pacific region for Credit Suisse First Boston (Hong Kong ) Ltd., published an article in the Securities Market Weekly, warning about five other major crashes that might dampen global economic recovery. Edited excerpts follow.展开更多
There is a beautiful city in southwestern Germany,lying on the southern bank of the Rhine River,which has flowed quietly nearby since ancient times.The city was the hometown of Johannes Gutenberg,the inventor of moder...There is a beautiful city in southwestern Germany,lying on the southern bank of the Rhine River,which has flowed quietly nearby since ancient times.The city was the hometown of Johannes Gutenberg,the inventor of modern typography,as well as of an excellent Bundesliga soccer team.It features a combination of ancient flavor and modern fashion,with not only time-honored churches展开更多
Unusual head trauma is rare with various mechanisms of occurrence. The injuries can be similar to those of road accidents but sometimes with significant complexities. The objective was to determine the frequency of th...Unusual head trauma is rare with various mechanisms of occurrence. The injuries can be similar to those of road accidents but sometimes with significant complexities. The objective was to determine the frequency of this pathology in our practice, describe the different mechanisms and report the craniocerebral lesions caused by this type of trauma. Materials and Method: This was a descriptive study with retrospective collection spread over a period of 3 years. After selecting the files, the patients and/or their companions were contacted by telephone to inquire about them and then returned to the consultation for reassessment. Disease history and information were obtained from patients’ medical records. Result: The frequency of this pathology was 1.78% and his incidence was 0.4 cases per month. The average age of the patients was 13.47 years. All the victims were male. 41.17% of patients were in school. The mechanisms of trauma were the hoof blow 47.1%, the horn blow 29.4% and the stone blow 11.7% respectively. 23.5% of patients were confused and 11.7% children were in coma. One patient presented an anisocoria. The motor deficit was present in 5 cases. CT-scan made it possible to highlight a skull depressing fracture 58.8% and confirm a craniocerebral wound in 35.3%. The average time between patient admission to hospital and completion of surgery was 24.5 hours. The surgery had consisted of the trimming of cranio-cerebral wounds, exploration, duroplasty and lifting of skull depressing fracture. After 15 months of follow-up, the evolution was favorable in 53.3%, the morbidity was 33.4% and the mortality 17.6%. Conclusion: These are rare but serious conditions because they are fatal and disabling. An early and multidisciplinary management can hope to have a good favorable.展开更多
The amount of oxygen blown into the converter is one of the key parameters for the control of the converter blowing process,which directly affects the tap-to-tap time of converter. In this study, a hybrid model based ...The amount of oxygen blown into the converter is one of the key parameters for the control of the converter blowing process,which directly affects the tap-to-tap time of converter. In this study, a hybrid model based on oxygen balance mechanism (OBM) and deep neural network (DNN) was established for predicting oxygen blowing time in converter. A three-step method was utilized in the hybrid model. First, the oxygen consumption volume was predicted by the OBM model and DNN model, respectively. Second, a more accurate oxygen consumption volume was obtained by integrating the OBM model and DNN model. Finally, the converter oxygen blowing time was calculated according to the oxygen consumption volume and the oxygen supply intensity of each heat. The proposed hybrid model was verified using the actual data collected from an integrated steel plant in China, and compared with multiple linear regression model, OBM model, and neural network model including extreme learning machine, back propagation neural network, and DNN. The test results indicate that the hybrid model with a network structure of 3 hidden layer layers, 32-16-8 neurons per hidden layer, and 0.1 learning rate has the best prediction accuracy and stronger generalization ability compared with other models. The predicted hit ratio of oxygen consumption volume within the error±300 m^(3)is 96.67%;determination coefficient (R^(2)) and root mean square error (RMSE) are0.6984 and 150.03 m^(3), respectively. The oxygen blow time prediction hit ratio within the error±0.6 min is 89.50%;R2and RMSE are0.9486 and 0.3592 min, respectively. As a result, the proposed model can effectively predict the oxygen consumption volume and oxygen blowing time in the converter.展开更多
文摘Introduction: Voluntary assault and injuries are acts that damage the physical and psychological integrity of a human being. WHO in its global report on violence and health estimates that in 2000, 1.6 million people worldwide died as a result of self-harm, interpersonal or collective violence, resulting in an overall rate adjusted by age of 28.8 per 100,000 population. Because of the seriousness of this phenomenon and the heavy socio-economic and health consequences that they generate, it seemed important to us to undertake this study, which aimed to study the deliberate injuries in the emergency unite of the Gabriel Touré Teaching Hospital in Bamako. Material and methods: This was a descriptive and cross-sectional study with a prospective study from September 1st, 2016 to August 31st, 12 months, covering 295 patients, including any patient received for voluntary injury consultation with a workable medical record and/or a full investigation record with or without requisition. Our data were collected on individual survey cards and subsequently analyzed with Word, Excel, IBM SPSS Statistics 22 software. Results: The majority of victims of assault and bodily injury were male with 83.1%;with a sex ratio of 4.9, the 18 to 28 age group was the most concerned with 163 cases of the 295 cases in our study, 55.2%. The extremes were 6 and 100 years old with an ectype at 11.08. The most affected ethnic group was Bambara with 38.6% (n = 114) followed by Fulani with 15.6% (n = 46). Students were the most affected at 24.7% (n = 73), followed by traders at 10%. The victims coming from outside Bamako are the most predominant with 22.4% (n = 66) followed by those of commune IV of Bamako 15.6% (n = 46). In 92.2% of the cases the mechanism was direct with n = 272. Of the lesions recorded in our study, wounds came first with 53.2% of cases. Radiography was the most used imaging at 44.7% (n = 89) followed by computed tomography at 34.7% (n = 69). The hemoperitoneum objectified by abdominal ultrasound represented 29.3% (n = 12). Fractures embarrure associated with bruising-hemorrhagic bruises were the most predominant with 13.4% (n = 10) objectified by brain scan. Conclusion: We note that the phenomenon of violence has reached worrying proportions, especially among young adults, particularly among students and is observed in all so-cio-professional layers. The polymorphism of these injuries caused by the predominant use of knives must draw the attention of our authorities to take measures to reduce these aggressions.
文摘Images provided by the author unless otherwise stated■This summer the first major U.S.solo exhibition by leading Taiwan Residents artist Chen Chieh-jen took place at Manhattan's Asia Society.The exhibition 'Condensation' united five silent films that address a variety of social topics into a cohesive unit. The films reflect the mind of someone who came to artistic maturity during a rapidly changing political environment in Taiwan.
文摘OVER 2,000 years ago,the bronze craftsmen in today’s Datong City,Shanxi Province,had already mastered the superb skills of copper production.Datong bronze-making craft was included in China’s state-level intangible cultural heritage list in 2014.The craftsmanship which has been passed down through the millennia still shines brightly today after countless hammer blows and engravings.
基金financial support of this work by the National Natural Science Foundation of China(Nos.22378332,52003219)the Open Fund of Zhejiang Key Laboratory of Flexible Electronics(No.2022FE008)+1 种基金the Natural Science Foundation of Ningbo(NO.2022J058)Ministry of Industry and Information Technology high quality development project(TC220A04A-206).
文摘Although poly(lactic acid)(PLA)is a good environmentally-friendly bio-degradable polymer which is used to substitute traditional petrochemical-based polymer packaging films,the barrier properties of PLA films are still insufficient for high-barrier packaging applications.In this study,oxygen scavenger hydroxyl-terminated polybutadiene(HTPB)and cobalt salt catalyst were incorporated into the PLA/poly(butylene adipate-co-terephthalate)(PLA/PBAT),followed by melting extrusion and three-layer co-extrusion blown film process to prepare the composite films.The oxygen permeability coefficient of the composite film combined with 6 wt%oxygen scavenger and 0.4 wt%catalyst was decreased significantly from 377.00 cc·mil·m^(-2)·day^(-1)·0.1 MPa^(-1) to 0.98 cc·mil·m^(-2)·day^(-1)·0.1 MPa^(-1),showing a remarkable enhancement of 384.69 times compared with the PLA/PBAT composite film.Meanwhile,the degradation behavior of the composite film was also accelerated,exhibiting a mass loss of nearly 60%of the original mass after seven days of degradation in an alkaline environment,whereas PLA/PBAT composite film only showed a mass loss of 32%.This work has successfully prepared PLA/PBAT composite films with simultaneously improved oxygen barrier property and degradation behavior,which has great potential for high-demanding green chemistry packaging industries,including food,agricultural,and military packaging.
基金supported by the National Key Research and Development Program of China(Grant No.2021YFC2802501)the National Natural Science Foundation of China(Grant Nos.41875025,62105367,42175154,42305084)+1 种基金the Hunan Provincial Natural Science Foundation of China(Grant Nos.2021JJ10047,2020JJ4662)the Research Project of National University of Defense Technology(Grant No.202401-YJRC-XX-030)。
文摘Blowing snow events in Antarctica play an important role in the climate system,affecting the mass balance of the ice sheet and the radiative effects of the atmosphere.Due to the harsh weather conditions in Antarctica,ground-based detection data is deficient,making it difficult to accurately obtain both the frequency of blowing snow and the evolution of the height of the blowing snow layer.In this study,we introduce a new method based on the raw signal from the C12 ceilometer to separate clear-sky,cloud,snowfall,and blowing snow conditions within a height of 500 meters above the surface of Zhongshan Station.Research has shown that more than 80%of the blowing snow at Zhongshan Station is affected by cyclonic systems,and less than 20%of the blowing snow is affected by katabatic winds.Further,Antarctic blowing snow is closely related to snowfall.When there is heavy snowfall(even a blizzard),a smaller wind speed can lead to the formation of a deep blowing snow layer within an hour after snowfall.However,as time increases,the threshold wind speed required to generate blowing snow significantly increases,and the thickness of the blowing snow layer becomes shallower.
基金supported by the National Natural Science Foundation of China(No.U21A20317)the National Key Research and Development Program of China(No.2017YFB0304201).
文摘The top-bottom combined blowing converter mainly adopts the blowing method of top-blowing oxygen and bottom-blowing nitrogen.In the production process,there are some disadvantages,such as a significant temperature difference between the top and bottom of the molten pool,inadequate gas permeability of bottom blowing,and low decarburization efficiency.Therefore,we propose a novel bottom-blowing gas doped oxygen process to enhance the smelting conditions in the converter.The 500 kg medium frequency induction furnace with top and bottom-blowing function was used to explore the influence of the proportion of bottom-blowing gas doped oxygen on the smelting effect in different smelting cycles.Subsequently,industrial experimental verification was carried out on a 60 t converter.The results of intermediate frequency furnace experiments demonstrate that the bottom-blowing gas doped oxygen process exhibits a superior heating rate and decarburization efficiency during the initial and final stages of blowing compared to pure N2 used for bottom-blowing.Simultaneously,the dephosphorization efficiency exhibited an initial increase followed by a subsequent decrease as the bottom-blowing oxygen content increased.The industrial test of 60 t converter validates the findings above.Moreover,when the oxygen content in bottom-blowing gas is 5%,the average blowing time reduces by 54 s,and the minimum endpoint carbon-oxygen equilibrium reaches 0.00219 under this condition.The results demonstrate that the appropriate amount of oxygen doped in bottom-blowing gas can effectively enhance the metallurgical conditions of the converter and improve production efficiency.
基金supported by the National Key Research and Development Project of China(No.2022YFC3902001)the National Natural Science Foundation of China(No.52004340)the Guangxi Innovation-driven Development Project,China(Nos.Gui 2021AA12006 and 2021AB26024)。
文摘The turbulent characteristics of the top-blown Laval nozzle and the influence of pressure and Mach number were studied through numerical simulation.With 2.72%error between the results and the empirical formula,the results are reliable.Nozzle fluid is influenced by pipe structure,causing pressure and density to drop as speed increases.Differences in pressure and velocity between the jet and surrounding gas lead to jet velocity attenuation,flow expansion,deflection,and eddy currents.The optimal top blowing pressure is 0.6 MPa,and the center velocity and width of the jet are 345 m/s and 0.124 m,respectively,at 20De(De is the nozzle exit diameter).It achieves a maximum jet velocity of 456 m/s.The optimal nozzle Mach number is 1.75,with a maximum jet velocity of 451 m/s.At 20D_(e),the jet center velocity is 338 m/s,with a width of 0.12 m.
基金Supported by Key Project Funding for Shaanxi Higher Education Teaching Reform Research (23BZ078)Shaanxi Provincial Education Science Planning Project (SGH24Y2782)+4 种基金Shaanxi Provincial Social Science Foundation Program(2024D008)Key Projects of the Second Huang Yanpei Vocational Education Thought Research Planning Project (ZJS2024ZN026)Shaanxi Higher Education Society Key Projects(XGHZ2301)2024 Annual Planning Project of the China Association for Non-Government Education (School Development Category)(CANFZG24095)the Youth Innovation Team of Shaanxi Universities。
文摘In this paper,a class of semilinear parabolic equations with cross coupling of power and exponential functions and large initial values are studied.By constructing and solving ordinary differential equations,the upper and lower bounds on the solution life span of the equations areobtained.
基金financially supported by the Major Science and Technology-Special Plan“Unveiling and Leading”Project of Shanxi Province(No.202201050201011)National Natural Science Foundation of China(No.52274316)+4 种基金China Baowu Low-Carbon Metallurgy Innovation Foundation(No.BWLCF202116)National Key R&D Program of China(No.2022YFE0208100)Major Science and Technology Project of Xinjiang(No.2022A01003)Major Science and Technology Projects of Anhui Province(No.202210700037)Special Funding for Science and Technology of China Minmetals Corporation(No.2021ZXD01).
文摘Under the background of the strategic goal of"double carbon,"the carbon reduction and consumption reduction of the iron and steel industry,especially in the ironmaking process,need to be further improved.The raceway of tuyere provides the chemical environment,fuel and power source for blast furnace smelting.The research on the characteristics of its action mode and mechanism is of great significance to clarify the way of reducing carbon and consumption of blast furnace.In general,the formation mechanism,energy distribution,research progress,extended resource injection and directional regulation are studied and expounded.The research results of various scholars on the characteristics of the raceway show that the raceway is a complex process including multiphase turbulent flow,heat,momentum,mass and homogeneous and heterogeneous chemical reactions.With the development of multi-source fuel injection technology,the complexity of problem research is more obvious.Therefore,the collection of multi-factor,multi-directional and multi-process characteristic information in the raceway can provide guarantee for the stability,smooth operation,high yield,carbon reduction and consumption reduction of blast furnace and provide new ideas for the green and low-carbon development of iron and steel industry.
基金co-supported by the National Natural Science Foundation of China(Nos.52472394,52425211,52201327,52272360)。
文摘Stall flutter poses great challenges to flight safety.To alleviate this problem,a steady blowing control considering the perturbation and wake-induced vibration at a large angle of attack is developed in this paper,where two blowings are configured on upper and lower tail surfaces to suppress the stall flutter.The stall flutter with one-degree-of-freedom is first evaluated by numerical simulation.The equation of motion for stall flutter is solved by the Newmark-β method.Then,the stall flutter responses for five blowing speeds,i.e.,0,4,12,20,and 28 m/s under the airspeed range of 3–9 m/s,are studied in detail.The stall flutter suppression mechanism can be summarized as follows:a large blowing speed can inject energy into the boundary layer and enhance the high-pressure zone,which delays the flow separation on the suction surface.In this way,the formation of the leading-edge separation vortex is suppressed.Thus,the dynamic stall vortex is weakened and accelerates shedding.In addition,the driving moment is reduced,which leads to a decrement in the stall flutter amplitude.When the blowing speed is 28 m/s(stall flutter amplitude=0.1357 rad),compared with uncontrolled case(stall flutter amplitude=0.6002 rad),the amplitude can decrease by 77.39%,which demonstrates the effectiveness of the proposed steady blowing based active control strategy.
基金The National Natural Science Foundation of China under contract Nos 42306255 and 41976217the National Key R&D Program of China under contract No.2018YFA0605903。
文摘Sea ice and snow are the most sensitive and important crucial components of the global climate system,affecting the global climate by modulating the energy exchange between the ocean and the atmosphere.The sea near Zhongshan Station in Antarctica is covered by landfast sea ice,with snow depth influenced by both thermal factors and wind.This region frequently experiences katabatic winds and cyclones from the westerlies,leading to frequent snow blowing events that redistribute the snow and affects its depth,subsequently impacting the thermodynamic growth of sea ice.This study utilized the one-dimensional thermodynamic model ICEPACK to simulate landfast sea ice thickness and snow depth near Zhongshan Station in 2016.Two parameterization schemes for snow blowing,the Bulk scheme,and the ITDrdg(ITD/ridges)scheme are evaluated for their impact on snow depth.The results show that simulations using snow blowing schemes more closely align with observed results,with the ITDrdg scheme providing more accurate simulations,evidenced by root mean square errors of less than 10 cm for both snow depth and sea ice thickness.Snow blowing also impacts the thermodynamic growth of sea ice,particularly bottom growth.The sea ice bottom increases by 9.0 cm using the ITDrdg scheme compared to simulations without the snow blowing,accounting for 12.5%of total sea ice bottom growth.Furthermore,snow blowing process also influences snow ice formation,highlighting its primary role in affecting snow depth.Continued field observations of snow blowing are necessary to evaluate and improve parameterization schemes.
基金supported by the NSFC(12271122)the Fundamental Research Funds for the Central Universities.Han’s research was supported by the Fundamental Research Funds for the Central Universities(3072023GIP2401).
文摘In this paper,we consider the initial boundary value problem for the 2-D hyperbolic viscous Cahn-Hilliard equation.Firstly,we prove the existence and uniqueness of the local solution by the Galerkin method and contraction mapping principle.Then,using the potential well theory,we study the global well-posedness of the solution with initial data at different levels of initial energy,i.e.,subcritical initial energy,critical initial energy and arbitrary positive initial energy.For subcritical initial energy,we prove the global existence,asymptotic behavior and finite time blowup of the solution.Moreover,we extend these results to the critical initial energy using the scaling technique.For arbitrary positive initial energy,including the sup-critical initial energy,we obtain the sufficient conditions for finite time blow-up of the solution.As a further study for estimating the blowup time,we give a unified expression of the lower bound of blowup time for all three initial energy levels and estimate the upper bound of blowup time for subcritical and critical initial energy.
基金sponsored by the National Key R&D Program of China(No.2020YFC1910000)the National Natural Science Foundation of China(Grants No 51978153).
文摘Particulate matter(PM)from high-temperature emissions like chemical plants,coal stoves and vehicle exhausts poses a gravel challenge to human health.To address this issue,researchers have explored vari-ous fiber filters,yet the bulk struggle to withstand high temperatures.In this study,mullite fiber sponges were developed utilizing low-cost materials and Kármán vortex solution blow spinning,using surfac-tants to improve the spinnability of the sol.Optimized sponges demonstrate ultralight(19 mg cm^(-3)),temperature-resistant reversible compressibility(50% strain)and a water contact angle of 135°.These sponges exhibited exceptional thermal insulation(thermal conductivity:0.0256 W m^(-1) K^(-1))and per-formed well in high-temperature air filtration.At 800℃,the mullite sponge with a base weight of 35 mg cm^(-2),achieved an average filtration efficiency of 98.18%and 99.57% for PM_(2.5) and PM_(2.5-10),respectively,with a quality value of 0.98 Pa^(-1) at a wind speed of 4 cm s^(-1).This low-cost mullite fiber sponge offers a promising avenue for designing high-performance filtration materials.
文摘The unfolding global financial crisis is arousing jitters about another round of heavy blows to the world economy, which may be intensified by the possible U.S. government takeover of Citigroup Inc. and Bank of America Corp. lg, Chief Economist of the Asia-Pacific region for Credit Suisse First Boston (Hong Kong ) Ltd., published an article in the Securities Market Weekly, warning about five other major crashes that might dampen global economic recovery. Edited excerpts follow.
文摘There is a beautiful city in southwestern Germany,lying on the southern bank of the Rhine River,which has flowed quietly nearby since ancient times.The city was the hometown of Johannes Gutenberg,the inventor of modern typography,as well as of an excellent Bundesliga soccer team.It features a combination of ancient flavor and modern fashion,with not only time-honored churches
文摘Unusual head trauma is rare with various mechanisms of occurrence. The injuries can be similar to those of road accidents but sometimes with significant complexities. The objective was to determine the frequency of this pathology in our practice, describe the different mechanisms and report the craniocerebral lesions caused by this type of trauma. Materials and Method: This was a descriptive study with retrospective collection spread over a period of 3 years. After selecting the files, the patients and/or their companions were contacted by telephone to inquire about them and then returned to the consultation for reassessment. Disease history and information were obtained from patients’ medical records. Result: The frequency of this pathology was 1.78% and his incidence was 0.4 cases per month. The average age of the patients was 13.47 years. All the victims were male. 41.17% of patients were in school. The mechanisms of trauma were the hoof blow 47.1%, the horn blow 29.4% and the stone blow 11.7% respectively. 23.5% of patients were confused and 11.7% children were in coma. One patient presented an anisocoria. The motor deficit was present in 5 cases. CT-scan made it possible to highlight a skull depressing fracture 58.8% and confirm a craniocerebral wound in 35.3%. The average time between patient admission to hospital and completion of surgery was 24.5 hours. The surgery had consisted of the trimming of cranio-cerebral wounds, exploration, duroplasty and lifting of skull depressing fracture. After 15 months of follow-up, the evolution was favorable in 53.3%, the morbidity was 33.4% and the mortality 17.6%. Conclusion: These are rare but serious conditions because they are fatal and disabling. An early and multidisciplinary management can hope to have a good favorable.
基金financially supported by the National Natural Science Foundation of China (Nos.51974023 and52374321)the funding of State Key Laboratory of Advanced Metallurgy,University of Science and Technology Beijing,China (No.41620007)。
文摘The amount of oxygen blown into the converter is one of the key parameters for the control of the converter blowing process,which directly affects the tap-to-tap time of converter. In this study, a hybrid model based on oxygen balance mechanism (OBM) and deep neural network (DNN) was established for predicting oxygen blowing time in converter. A three-step method was utilized in the hybrid model. First, the oxygen consumption volume was predicted by the OBM model and DNN model, respectively. Second, a more accurate oxygen consumption volume was obtained by integrating the OBM model and DNN model. Finally, the converter oxygen blowing time was calculated according to the oxygen consumption volume and the oxygen supply intensity of each heat. The proposed hybrid model was verified using the actual data collected from an integrated steel plant in China, and compared with multiple linear regression model, OBM model, and neural network model including extreme learning machine, back propagation neural network, and DNN. The test results indicate that the hybrid model with a network structure of 3 hidden layer layers, 32-16-8 neurons per hidden layer, and 0.1 learning rate has the best prediction accuracy and stronger generalization ability compared with other models. The predicted hit ratio of oxygen consumption volume within the error±300 m^(3)is 96.67%;determination coefficient (R^(2)) and root mean square error (RMSE) are0.6984 and 150.03 m^(3), respectively. The oxygen blow time prediction hit ratio within the error±0.6 min is 89.50%;R2and RMSE are0.9486 and 0.3592 min, respectively. As a result, the proposed model can effectively predict the oxygen consumption volume and oxygen blowing time in the converter.
