Multi-frictional disks are employed to transmit the torque in speeding wetclutch, and the oil thickness within frictional disks could be adjusted for practical outputspeeding. As oil combined with alpha-hydrocarbon or...Multi-frictional disks are employed to transmit the torque in speeding wetclutch, and the oil thickness within frictional disks could be adjusted for practical outputspeeding. As oil combined with alpha-hydrocarbon or polyester is getting widely used as lubricantand the speeding wet clutch works within hydrodynamic lubrication, mixture lubrication, boundarylubrication and contact situation, established the thermal analysis model for investigating thebehavior of frictional disks in speeding wet clutch, which covers the power-law fluid model,Patir-Cheng average flow model, GT asperity contact model, oil film inertia and heat effects, meanenergy equation, and heat conduction equation. The formulas in the model are deduced. The numeralcalculation and analysis for hydrodynamic lubrication and mixture lubrication are executed.Relationships and variations among transmitting torque, mean push pressure, output speed, and loadare presented. Thermal effect should be considered during the hydrodynamic lubrication and largertransmitting torque makes earlier entrance to mixture lubrication.展开更多
China is the main silk producer in the world, whose RSS (Raw Silk Standard)is widely approved in international trade. After entering WTO, China needs to revise the RSSaccording to the changes of silk industry and deve...China is the main silk producer in the world, whose RSS (Raw Silk Standard)is widely approved in international trade. After entering WTO, China needs to revise the RSSaccording to the changes of silk industry and develop advanced electronic testing system and improvetesting means, so as to promote the internationlization of the RSS. 1. The international standingof Chinese silk The silk consisting of 18 amino acids has the similar protein structure to people'sskin. It is enjoyed by most people for it' s comfortable, magnificent and noble features and ispraised to be the second skin for its unique effects on health and adjusting the body water. In the21st century, silk is the main international fashion as the representative of green products.展开更多
In recent years, the subcontracting production for foreign trade of the Xi’an Aviation Engine Company (XAEC), a foreign trade production base of China, has achieved rapid development. In 1994, the company’s export e...In recent years, the subcontracting production for foreign trade of the Xi’an Aviation Engine Company (XAEC), a foreign trade production base of China, has achieved rapid development. In 1994, the company’s export earnings from foreign trade made a breakthrough at US$11 million, and it was commended by the State Economic展开更多
To introduce foreign capital for the municipal highway construction is a great measure to meet the development of the socialist market economy and to reform the investment system for the municipal highway construction...To introduce foreign capital for the municipal highway construction is a great measure to meet the development of the socialist market economy and to reform the investment system for the municipal highway construction. The aim of the reform lies in taking the construction and management of the municipal highway facilities as an industry to operate, widening the investment channel of the municipal highway construction and gradually forming a benign cycle of investment-construc-展开更多
According to customs statistics, China’s exports of machinery and electric products in 1996 were worth US$ 48.21 billion, an increase of 9.9 percent over the preceding year, and 8.4 percent higher than the growth rat...According to customs statistics, China’s exports of machinery and electric products in 1996 were worth US$ 48.21 billion, an increase of 9.9 percent over the preceding year, and 8.4 percent higher than the growth rate of the nation’s total exports. The proportion of machinery and electric product exports in the nation’s total foreign trade volume\ increased from 29.5 percent in 1995 to 31.9 percent in 1996, a growth at 2.4 percent.展开更多
Housing isone of the necessities of humansfor existence and development.The Chinese government hasalways attached great importanceto housing construction;especially in recent years,thepriority development of housingco...Housing isone of the necessities of humansfor existence and development.The Chinese government hasalways attached great importanceto housing construction;especially in recent years,thepriority development of housingconstruction has been seen inthe real estate and propertiesindustry.Hou Jie,Minister ofConstruction,not long ago wrotean article summarizing theachievements made in this sectorand drawing a blueprint forspeedup of housing constructionand the improvement of livingconditions in the future.It willprovide a vast vista for thedevelopment of China’s buildingindustry and its internationalcooperation.展开更多
High-speed railways have the merits of high speed, high transport capacity, low consumption of energy, less pollution, less occupation of land, and greater safety. The development of high-speed railways is suitable fo...High-speed railways have the merits of high speed, high transport capacity, low consumption of energy, less pollution, less occupation of land, and greater safety. The development of high-speed railways is suitable for the national conditions in China.The authors suggest that, with the Hu-Ning (Shanghai-Nanjing) section of the Jing-Hu (Beijing-Shanghai) Railway as the starting point, a high-speed dedicated passenger railway line be built to realize the separate transportation of passengers and goods, thus easing the strain on transport in East China, accumulating experience for the future development of high-speed railways, and bringing along the development of high and new technology industries.展开更多
This paper discusses the urgency to further develop China’s space technological industry;analyzes the gaps between China and other advanced countries in space industry,including technological level,development scale,...This paper discusses the urgency to further develop China’s space technological industry;analyzes the gaps between China and other advanced countries in space industry,including technological level,development scale,application scope and investment;describes the current severe situation that the China’s space industry is faced with and proposes the overall objective,guiding principles and major tasks of China’s space technological sector in the Ninth-Five Year Plan and the coming decade.Finally,it proposes some policies and effective measures to speed up the development of China’s space industry to meet the challenge in the 21st century.展开更多
Speeding in a work zone needs to be tackled effectively to enhance work zone safety. This study evaluates the influence of three different work zone signs—speed photo enforced signs, dynamic speed display signs and r...Speeding in a work zone needs to be tackled effectively to enhance work zone safety. This study evaluates the influence of three different work zone signs—speed photo enforced signs, dynamic speed display signs and reduced speed limit signs—on driver speeding behavior using a medium-fidelity driving simulator. The speed photo enforced and reduced speed limit signs were placed at intervals before the start of the work zone and in the work zone. A virtual work zone network was built to replicate the Baltimore–Washington Parkway(MD-295). A total of 66 participants from different socioeconomic backgrounds participated in 264 driving simulation sessions. The speeds were measured over four phases: initial speed area, sign visible area, sign readable area and post sign area. An analysis of variance and post hoc analysis showed that the speed photo enforced sign was the most effective of the three signs. The second speed photo enforced sign within the work zone was more effective at reducing speed than the sign before the start of the work zone, especially in the post sign area. It was observed that female participants tend to slow down more when encountering a speed photo enforcement sign.展开更多
The present research aimed to identify critical factors that affect speeding behavior.For that purpose,high-resolution smartphone data collected from a naturalistic driving experiment of 88 drivers were utilized,augme...The present research aimed to identify critical factors that affect speeding behavior.For that purpose,high-resolution smartphone data collected from a naturalistic driving experiment of 88 drivers were utilized,augmented with data from self-reported questionnaires.Using risk exposure and driving behavior indicators calculated from smartphone sensor data,as well as demographic characteristics and self-reported driving performance,statistical analysis was carried out for modelling the percentage of driving time over the speed limit,namely by means of generalized linear mixed-effects models.More precisely,an overall model was developed for all road environments,and additional separate models were developed for driving on urban and rural roads.The results from the interpretation of the estimated parameters of the models can be summarized as follows:the parameters of trip distance and mobile phone use while driving have been determined as statistically significant and positively correlated with the percentage of speeding time during a driver's trip.In the same context,male drivers and drivers in the age group of18-34 also increase the percentages of speeding instances while driving.Regarding driving behavior as stated on the questionnaire,it seems that low frequencies of self-declared speeding(never or rarely)are statistically significant and negatively correlated with the percentage of speeding time.It is expected that this research can provide considerable gains to society,since the stakeholders including policy makers and industry could rely on the results and recommendations regarding risk factors that appear to be critical for safe driving.展开更多
Microstructure,texture,and mechanical properties of the extruded Mg-2.49Nd-1.82Gd-0.2Zn-0.2Zr alloy were investigated at different extrusion temperatures(260 and 320℃),extrusion ratios(10:1,15:1,and 30:1),and extrusi...Microstructure,texture,and mechanical properties of the extruded Mg-2.49Nd-1.82Gd-0.2Zn-0.2Zr alloy were investigated at different extrusion temperatures(260 and 320℃),extrusion ratios(10:1,15:1,and 30:1),and extrusion speeds(3 and 6 mm/s).The experimental results exhibited that the grain sizes after extrusion were much finer than that of the homogenized alloy,and the second phase showed streamline distribution along the extrusion direction(ED).With extrusion temperature increased from 260 to 320℃,the microstructure,texture,and mechanical properties of alloys changed slightly.The dynamic recrystallization(DRX)degree and grain sizes enhanced as the extrusion ratio increased from 10:1 to 30:1,and the strength gradually decreased but elongation(EL)increased.With the extrusion speed increased from 3 to 6 mm/s,the grain sizes and DRX degree increased significantly,and the samples presented the typical<2111>-<1123>rare-earth(RE)textures.The alloy extruded at 260℃ with extrusion ratio of 10:1 and extrusion speed of 3 mm/s showed the tensile yield strength(TYS)of 213 MPa and EL of 30.6%.After quantitatively analyzing the contribution of strengthening mechanisms,it was found that the grain boundary strengthening and dislocation strengthening played major roles among strengthening contributions.These results provide some guidelines for enlarging the industrial application of extruded Mg-RE alloy.展开更多
The pressure wave generated by an urban-rail vehicle when passing through a tunnel affects the comfort of passengersand may even cause damage to the train and related tunnel structures.Therefore,controlling the trains...The pressure wave generated by an urban-rail vehicle when passing through a tunnel affects the comfort of passengersand may even cause damage to the train and related tunnel structures.Therefore,controlling the trainspeed in the tunnel is extremely important.In this study,this problem is investigated numerically in the frameworkof the standard k-εtwo-equation turbulence model.In particular,an eight-car urban rail train passingthrough a tunnel at different speeds(140,160,180 and 200 km/h)is considered.The results show that the maximumaerodynamic drag of the head and tail cars is most affected by the running speed.The pressure at selectedmeasuring points on the windward side of the head car is very high,and the negative pressure at the side windowof the driver’s cab of the tail car is also very large.From the head car to the tail car,the pressure at the same heightgradually decreases.The positive pressure peak at the head car and the negative pressure peak at the tail car aregreatly affected by the speed.展开更多
As the proportion of newenergy increases,the traditional cumulant method(CM)produces significant errorswhen performing probabilistic load flow(PLF)calculations with large-scale wind power integrated.Considering the wi...As the proportion of newenergy increases,the traditional cumulant method(CM)produces significant errorswhen performing probabilistic load flow(PLF)calculations with large-scale wind power integrated.Considering the wind speed correlation,a multi-scenario PLF calculation method that combines random sampling and segmented discrete wind farm power was proposed.Firstly,based on constructing discrete scenes of wind farms,the Nataf transform is used to handle the correlation between wind speeds.Then,the random sampling method determines the output probability of discrete wind power scenarios when wind speed exhibits correlation.Finally,the PLF calculation results of each scenario areweighted and superimposed following the total probability formula to obtain the final power flow calculation result.Verified in the IEEE standard node system,the absolute percent error(APE)for the mean and standard deviation(SD)of the node voltages and branch active power are all within 1%,and the average root mean square(AMSR)values of the probability curves are all less than 1%.展开更多
The challenge of aerodynamic noise is a key obstacle in the advancement of low-pressure tube ultra-high-speed maglev transportation,demanding urgent resolution.This study utilizes a broadband noise source model to per...The challenge of aerodynamic noise is a key obstacle in the advancement of low-pressure tube ultra-high-speed maglev transportation,demanding urgent resolution.This study utilizes a broadband noise source model to perform a quantitative analysis of the aerodynamic noise produced by ultra-high-speed maglev trains operating in low-pressure environments.Initially,an external flow field calculation model for the ultra-high-speed maglev train is presented.Subsequently,numerical simulations based on the broadband noise source model are used to examine the noise characteristics.The impact of the train speed and pressure level on noise generation is investigated accordingly.Subsequently,a correlation formula is derived.The results reveal that the amplitude of sound source changes in the streamlined region of the head and tail cars of the train is large,and the amplitude of changes for the middle car is smaller.The noise source strength increases with speed,with a quadrupole noise source becoming dominant when the train speed exceeds 600 km/h.At a speed of 1000 km/h,the noise source intensity from the streamlined area at the rear of the train overcomes that at the front.Furthermore,the noise source decreases as the pressure level in the tube decreases.When the pressure level drops to 0.01 atm,the quadrupole noise source intensity of a train running at 600 km/h significantly weakens and falls below that of the dipole noise source.展开更多
Unlike other major crops,little research has been performed on tomato to reduce the generation time for speed breeding.We evaluated several agronomic treatments to reduce the generation time of tomato in the‘M82'...Unlike other major crops,little research has been performed on tomato to reduce the generation time for speed breeding.We evaluated several agronomic treatments to reduce the generation time of tomato in the‘M82'(determinate)and‘Moneymaker'(indeterminate)varieties and evaluated the best combination in conjunction with embryo rescue.Five container sizes with volumes of 0.2 L(XS),0.45 L(S),0.8 L(M),1.3 L(L),and6 L(XL),were evaluated in the first experiment under the autumn cycle.We found that plants grown in XL containers exhibited better development and required less time from sowing to anthesis(DSA)and from anthesis to fruit ripening(DAR).In the second experiment,using XL containers in the autumn-winter cycle,we evaluated the effects of cold priming at the cotyledonary stage,water stress,P supplementation,and K supplementation on generation time.Compared to the control,we found that cold priming significantly reduced the number of leaves,plant height to first the inflorescence,and DSA(2.7 d),whereas K supplementation reduced the DAR(8.8 d).In contrast,water stress and P supplementation did not significantly affect any of the measured traits like DAR,DSA or fruit set.To validate these data,in a third experiment with XL containers in the spring-summer cycle,the combination of cold priming and K supplementation was tested,confirming the significant effect of this combination on the reduction of generation time(2.9 d for DSA and 3.9 d for DAR)compared to the control.Embryo rescue during the cell expansion cycle(average of 22.0 d and 23.3 d after anthesis for‘M82'and‘Moneymaker',respectively)allowed the shortening of the generation time by 8.7 d in‘M82'and 11.6 d in‘Moneymaker'compared to the in planta fruit ripening.The combination of agronomic treatments with embryo rescue can effectively increase the number of generations per year from three to four for speed breeding of tomato.展开更多
In the wake of the global financial crisis, China has amazed the world with the speed of its economic recovery. But what has been even more surprising is the speed of its railway evolution.
Chinese carmakers find the way to become more technologically intensive In the classic economic model, there is land,labor and capital. Each plays a role in economic development through its supply, and development can...Chinese carmakers find the way to become more technologically intensive In the classic economic model, there is land,labor and capital. Each plays a role in economic development through its supply, and development cannot occur with-展开更多
文摘Multi-frictional disks are employed to transmit the torque in speeding wetclutch, and the oil thickness within frictional disks could be adjusted for practical outputspeeding. As oil combined with alpha-hydrocarbon or polyester is getting widely used as lubricantand the speeding wet clutch works within hydrodynamic lubrication, mixture lubrication, boundarylubrication and contact situation, established the thermal analysis model for investigating thebehavior of frictional disks in speeding wet clutch, which covers the power-law fluid model,Patir-Cheng average flow model, GT asperity contact model, oil film inertia and heat effects, meanenergy equation, and heat conduction equation. The formulas in the model are deduced. The numeralcalculation and analysis for hydrodynamic lubrication and mixture lubrication are executed.Relationships and variations among transmitting torque, mean push pressure, output speed, and loadare presented. Thermal effect should be considered during the hydrodynamic lubrication and largertransmitting torque makes earlier entrance to mixture lubrication.
文摘China is the main silk producer in the world, whose RSS (Raw Silk Standard)is widely approved in international trade. After entering WTO, China needs to revise the RSSaccording to the changes of silk industry and develop advanced electronic testing system and improvetesting means, so as to promote the internationlization of the RSS. 1. The international standingof Chinese silk The silk consisting of 18 amino acids has the similar protein structure to people'sskin. It is enjoyed by most people for it' s comfortable, magnificent and noble features and ispraised to be the second skin for its unique effects on health and adjusting the body water. In the21st century, silk is the main international fashion as the representative of green products.
文摘In recent years, the subcontracting production for foreign trade of the Xi’an Aviation Engine Company (XAEC), a foreign trade production base of China, has achieved rapid development. In 1994, the company’s export earnings from foreign trade made a breakthrough at US$11 million, and it was commended by the State Economic
文摘To introduce foreign capital for the municipal highway construction is a great measure to meet the development of the socialist market economy and to reform the investment system for the municipal highway construction. The aim of the reform lies in taking the construction and management of the municipal highway facilities as an industry to operate, widening the investment channel of the municipal highway construction and gradually forming a benign cycle of investment-construc-
文摘According to customs statistics, China’s exports of machinery and electric products in 1996 were worth US$ 48.21 billion, an increase of 9.9 percent over the preceding year, and 8.4 percent higher than the growth rate of the nation’s total exports. The proportion of machinery and electric product exports in the nation’s total foreign trade volume\ increased from 29.5 percent in 1995 to 31.9 percent in 1996, a growth at 2.4 percent.
文摘Housing isone of the necessities of humansfor existence and development.The Chinese government hasalways attached great importanceto housing construction;especially in recent years,thepriority development of housingconstruction has been seen inthe real estate and propertiesindustry.Hou Jie,Minister ofConstruction,not long ago wrotean article summarizing theachievements made in this sectorand drawing a blueprint forspeedup of housing constructionand the improvement of livingconditions in the future.It willprovide a vast vista for thedevelopment of China’s buildingindustry and its internationalcooperation.
文摘High-speed railways have the merits of high speed, high transport capacity, low consumption of energy, less pollution, less occupation of land, and greater safety. The development of high-speed railways is suitable for the national conditions in China.The authors suggest that, with the Hu-Ning (Shanghai-Nanjing) section of the Jing-Hu (Beijing-Shanghai) Railway as the starting point, a high-speed dedicated passenger railway line be built to realize the separate transportation of passengers and goods, thus easing the strain on transport in East China, accumulating experience for the future development of high-speed railways, and bringing along the development of high and new technology industries.
文摘This paper discusses the urgency to further develop China’s space technological industry;analyzes the gaps between China and other advanced countries in space industry,including technological level,development scale,application scope and investment;describes the current severe situation that the China’s space industry is faced with and proposes the overall objective,guiding principles and major tasks of China’s space technological sector in the Ninth-Five Year Plan and the coming decade.Finally,it proposes some policies and effective measures to speed up the development of China’s space industry to meet the challenge in the 21st century.
基金the Maryland State Highway Association (SHA) for its funding support throughout the study
文摘Speeding in a work zone needs to be tackled effectively to enhance work zone safety. This study evaluates the influence of three different work zone signs—speed photo enforced signs, dynamic speed display signs and reduced speed limit signs—on driver speeding behavior using a medium-fidelity driving simulator. The speed photo enforced and reduced speed limit signs were placed at intervals before the start of the work zone and in the work zone. A virtual work zone network was built to replicate the Baltimore–Washington Parkway(MD-295). A total of 66 participants from different socioeconomic backgrounds participated in 264 driving simulation sessions. The speeds were measured over four phases: initial speed area, sign visible area, sign readable area and post sign area. An analysis of variance and post hoc analysis showed that the speed photo enforced sign was the most effective of the three signs. The second speed photo enforced sign within the work zone was more effective at reducing speed than the sign before the start of the work zone, especially in the post sign area. It was observed that female participants tend to slow down more when encountering a speed photo enforcement sign.
基金co-financed by the European Union-European Regional Development Fund (ERDF)and Greek national funds through the Operational Program“Competitiveness,Entrepreneurship and Innovation” (EPAnEK)of the National Strategic Reference Framework (NSRF)-Research Funding Program:BeSmart-multi-modal driver behavior and safety support system on the basis of smartphone applications。
文摘The present research aimed to identify critical factors that affect speeding behavior.For that purpose,high-resolution smartphone data collected from a naturalistic driving experiment of 88 drivers were utilized,augmented with data from self-reported questionnaires.Using risk exposure and driving behavior indicators calculated from smartphone sensor data,as well as demographic characteristics and self-reported driving performance,statistical analysis was carried out for modelling the percentage of driving time over the speed limit,namely by means of generalized linear mixed-effects models.More precisely,an overall model was developed for all road environments,and additional separate models were developed for driving on urban and rural roads.The results from the interpretation of the estimated parameters of the models can be summarized as follows:the parameters of trip distance and mobile phone use while driving have been determined as statistically significant and positively correlated with the percentage of speeding time during a driver's trip.In the same context,male drivers and drivers in the age group of18-34 also increase the percentages of speeding instances while driving.Regarding driving behavior as stated on the questionnaire,it seems that low frequencies of self-declared speeding(never or rarely)are statistically significant and negatively correlated with the percentage of speeding time.It is expected that this research can provide considerable gains to society,since the stakeholders including policy makers and industry could rely on the results and recommendations regarding risk factors that appear to be critical for safe driving.
基金supported by the National Science and Technology Major Project,China(No.2019-VI-0004-0118)the National Natural Science Foundation of China(No.51771152)the National Key R&D Program of China(No.2018YFB1106800)。
文摘Microstructure,texture,and mechanical properties of the extruded Mg-2.49Nd-1.82Gd-0.2Zn-0.2Zr alloy were investigated at different extrusion temperatures(260 and 320℃),extrusion ratios(10:1,15:1,and 30:1),and extrusion speeds(3 and 6 mm/s).The experimental results exhibited that the grain sizes after extrusion were much finer than that of the homogenized alloy,and the second phase showed streamline distribution along the extrusion direction(ED).With extrusion temperature increased from 260 to 320℃,the microstructure,texture,and mechanical properties of alloys changed slightly.The dynamic recrystallization(DRX)degree and grain sizes enhanced as the extrusion ratio increased from 10:1 to 30:1,and the strength gradually decreased but elongation(EL)increased.With the extrusion speed increased from 3 to 6 mm/s,the grain sizes and DRX degree increased significantly,and the samples presented the typical<2111>-<1123>rare-earth(RE)textures.The alloy extruded at 260℃ with extrusion ratio of 10:1 and extrusion speed of 3 mm/s showed the tensile yield strength(TYS)of 213 MPa and EL of 30.6%.After quantitatively analyzing the contribution of strengthening mechanisms,it was found that the grain boundary strengthening and dislocation strengthening played major roles among strengthening contributions.These results provide some guidelines for enlarging the industrial application of extruded Mg-RE alloy.
基金supported by the Beijing Postdoctoral Research Foundation(No.2023-ZZ-133)Scientific Research Foundation of Beijing Infrastructure Investment Co.,Ltd.(No.2023-ZB-03)Fundamental Research Funds for the Central Universities(No.2682023ZTPY036).
文摘The pressure wave generated by an urban-rail vehicle when passing through a tunnel affects the comfort of passengersand may even cause damage to the train and related tunnel structures.Therefore,controlling the trainspeed in the tunnel is extremely important.In this study,this problem is investigated numerically in the frameworkof the standard k-εtwo-equation turbulence model.In particular,an eight-car urban rail train passingthrough a tunnel at different speeds(140,160,180 and 200 km/h)is considered.The results show that the maximumaerodynamic drag of the head and tail cars is most affected by the running speed.The pressure at selectedmeasuring points on the windward side of the head car is very high,and the negative pressure at the side windowof the driver’s cab of the tail car is also very large.From the head car to the tail car,the pressure at the same heightgradually decreases.The positive pressure peak at the head car and the negative pressure peak at the tail car aregreatly affected by the speed.
基金supported by Basic Science Research Program through the National Natural Science Foundation of China(Grant No.61867003).
文摘As the proportion of newenergy increases,the traditional cumulant method(CM)produces significant errorswhen performing probabilistic load flow(PLF)calculations with large-scale wind power integrated.Considering the wind speed correlation,a multi-scenario PLF calculation method that combines random sampling and segmented discrete wind farm power was proposed.Firstly,based on constructing discrete scenes of wind farms,the Nataf transform is used to handle the correlation between wind speeds.Then,the random sampling method determines the output probability of discrete wind power scenarios when wind speed exhibits correlation.Finally,the PLF calculation results of each scenario areweighted and superimposed following the total probability formula to obtain the final power flow calculation result.Verified in the IEEE standard node system,the absolute percent error(APE)for the mean and standard deviation(SD)of the node voltages and branch active power are all within 1%,and the average root mean square(AMSR)values of the probability curves are all less than 1%.
基金funded by the Talent Program(Ph.D.Fund)of Chengdu Technological University(grant number 2024RC025)the Natural Science Foundation of Sichuan Province(grant number 2022NSFSC1892)Fundamental Research Funds for the Central Universities(grant number XJ2021KJZK054).
文摘The challenge of aerodynamic noise is a key obstacle in the advancement of low-pressure tube ultra-high-speed maglev transportation,demanding urgent resolution.This study utilizes a broadband noise source model to perform a quantitative analysis of the aerodynamic noise produced by ultra-high-speed maglev trains operating in low-pressure environments.Initially,an external flow field calculation model for the ultra-high-speed maglev train is presented.Subsequently,numerical simulations based on the broadband noise source model are used to examine the noise characteristics.The impact of the train speed and pressure level on noise generation is investigated accordingly.Subsequently,a correlation formula is derived.The results reveal that the amplitude of sound source changes in the streamlined region of the head and tail cars of the train is large,and the amplitude of changes for the middle car is smaller.The noise source strength increases with speed,with a quadrupole noise source becoming dominant when the train speed exceeds 600 km/h.At a speed of 1000 km/h,the noise source intensity from the streamlined area at the rear of the train overcomes that at the front.Furthermore,the noise source decreases as the pressure level in the tube decreases.When the pressure level drops to 0.01 atm,the quadrupole noise source intensity of a train running at 600 km/h significantly weakens and falls below that of the dipole noise source.
基金funded by the European Commission H2020 Research and Innovation Programme through the HARNESSTOM innovation action(Grant No.101000716)Grant CIPROM/2021/020(project SOLECO)funded by Conselleria d’Innovació,Universitats,Ciència i Societat Digital(Generalitat Valenciana,Spain)Pietro Gramazio received a post-doctoral fellowship(Grant No.RYC2021-031999-I)funded by MCIN/AEI/10.13039/501100011033 and by“European Union NextGenerationEU/PRTR”。
文摘Unlike other major crops,little research has been performed on tomato to reduce the generation time for speed breeding.We evaluated several agronomic treatments to reduce the generation time of tomato in the‘M82'(determinate)and‘Moneymaker'(indeterminate)varieties and evaluated the best combination in conjunction with embryo rescue.Five container sizes with volumes of 0.2 L(XS),0.45 L(S),0.8 L(M),1.3 L(L),and6 L(XL),were evaluated in the first experiment under the autumn cycle.We found that plants grown in XL containers exhibited better development and required less time from sowing to anthesis(DSA)and from anthesis to fruit ripening(DAR).In the second experiment,using XL containers in the autumn-winter cycle,we evaluated the effects of cold priming at the cotyledonary stage,water stress,P supplementation,and K supplementation on generation time.Compared to the control,we found that cold priming significantly reduced the number of leaves,plant height to first the inflorescence,and DSA(2.7 d),whereas K supplementation reduced the DAR(8.8 d).In contrast,water stress and P supplementation did not significantly affect any of the measured traits like DAR,DSA or fruit set.To validate these data,in a third experiment with XL containers in the spring-summer cycle,the combination of cold priming and K supplementation was tested,confirming the significant effect of this combination on the reduction of generation time(2.9 d for DSA and 3.9 d for DAR)compared to the control.Embryo rescue during the cell expansion cycle(average of 22.0 d and 23.3 d after anthesis for‘M82'and‘Moneymaker',respectively)allowed the shortening of the generation time by 8.7 d in‘M82'and 11.6 d in‘Moneymaker'compared to the in planta fruit ripening.The combination of agronomic treatments with embryo rescue can effectively increase the number of generations per year from three to four for speed breeding of tomato.
文摘In the wake of the global financial crisis, China has amazed the world with the speed of its economic recovery. But what has been even more surprising is the speed of its railway evolution.
文摘Chinese carmakers find the way to become more technologically intensive In the classic economic model, there is land,labor and capital. Each plays a role in economic development through its supply, and development cannot occur with-