In Pelton turbines, when the water jet emerges in the air, its velocity decreases downstream and its diameter increases to meet the continuity. In this paper, a physical parameter, the enlarging rate of jet diameter k...In Pelton turbines, when the water jet emerges in the air, its velocity decreases downstream and its diameter increases to meet the continuity. In this paper, a physical parameter, the enlarging rate of jet diameter kDi was introduced and measured experimentally. The measurement of enlarging rate was carried out in three model turbines with different distributing Y-branch and nozzle configurations under various operating conditions. The effect of jet enlarging rate on the unsteady water sheet flow in the rotating buckets has not been investigated so tar. This paper also presents the comparative numerical analysis of the flow in buckets at different enlarging rates of jet. It is shown that the effect of jet enlargement is so large that the flow pattern in the bucket is drastically changed by the latter half of the frames, The jet with large enlarging rate also introduces worse energy behavior to the hydraulic performance of the Pelton turbine. Besides, the phenomenon of jet interference was also discussed by using the results of numerical simulation for one jet. It indicates that the jet with large enlarging rate takes more risk that jet interference may damage the performance of multi-nozzle Pelton turbine.展开更多
After expatiating the guiding ideology,contents,standards and principles of eco-environment restoration based on enlarging terrace and de-farming,this paper discussed the planning method and technical flow of enlargin...After expatiating the guiding ideology,contents,standards and principles of eco-environment restoration based on enlarging terrace and de-farming,this paper discussed the planning method and technical flow of enlarging terrace and garden plot in a small catchment of loess hilly region by means of GIS spatial analysis technology,and then the planning method was applied in Yangou catchment.The result showed that it is practicabl,and the areas of newly-built terrace and garden plot in Yangou catchment are at least 295.06 and 4.61 hm2,so that the areas of basic farmland and garden plot reach 359.23 and 622.69 hm2.After the land use structure is regulated,the forest coverage is 48.87%,and the permanent vegetation coverage is about 75% in Yangou catchment,while sediment reduction benefit is above 80% in slope land.In agricultural development,Yangou catchment can yield 1 645.13 tons of food supplies,above 9 340 tons of apples,and can feed 7 500 sheep every year.展开更多
In this paper,a new type of machinery which can enlarge the stroke of air cylinder is introduced. It is very useful when the original stroke of air cylinder cannot satisfy the work requirement.According to design requ...In this paper,a new type of machinery which can enlarge the stroke of air cylinder is introduced. It is very useful when the original stroke of air cylinder cannot satisfy the work requirement.According to design requirements,its multi-objective mathematic model with constrained conditions is built. In order to solve this model, some methods are discussed and used such as penalty function method,variable metric method,Newton tangent method and bisection method. Based on the optimal result,motion curves of enlarging stroke mechanism are obtained. Results show that the motion characteristic of enlarging stroke of air cylinder mechanism is satisfying. In addition,we also consider the influence of different initial values of link length to optimal results and two important laws are got in this paper on the basis of optimal results.展开更多
In an information society,the English knowledge in capacity for college students has gradually been improved and its range is alsoenlarged.If teachers overlook summing up the knowledge which the students have gained a...In an information society,the English knowledge in capacity for college students has gradually been improved and its range is alsoenlarged.If teachers overlook summing up the knowledge which the students have gained and improving their skills in English,it will behard for students to learn English well.In educational circles people often say"teaching method isn't fixed ",but it is of the same view togive students some basic regularity,let students have enough abilities and make knowledge which the students have gained assimilate and sys-tematize etc.Facing medical college students'tasks are arduous and the students often seem at a loss.In English lessons,it is necessary forteachers to help students find out some basic laws,give students enough skills and methods,let students sum up and classify knowledge whichis scattered,disorderly,bit by bit and even fragmented.展开更多
Increasing the energy density of supercapacitor without sacrificing its high power is an everlasting pursuit in energy storage.Using ionic liquid electrolyte with high operating voltage can increase the energy density...Increasing the energy density of supercapacitor without sacrificing its high power is an everlasting pursuit in energy storage.Using ionic liquid electrolyte with high operating voltage can increase the energy density but usually at the expense of power density due to the large ion size,low ionic conductivity and high viscosity.Herein we demonstrate a simultaneous increase of the energy and power densities with ionic liquid electrolyte(EMIMBF4)mainly by enlarging the ion-transfer micropore channels of the electrode material,i.e.,the unique hierarchical carbon nanocages(hCNC).Boudouard reaction is adopted to tune the micropore size while remaining the hierarchical framework of hCNC.Meanwhile,the specific surface area,pore volume and conductivity are also increased under optimal activation temperature.Such a unique modification boosts the large-sized ion transfer,leading to the obvious decrease of equivalent series resistance and the dramatic increase of supercapacitive performance thereof.The optimized product exhibits an energy density up to 153.8 W h kg^(-1) at the power density of 1.8 kW kg^(-1),and maintains 54.0 W h kg^(-1) even at an ultrahigh power density of 480.1 kW kg^(-1).This study demonstrates an effective way to explore advanced electrode materials by the fine regulation of micropores and related properties.展开更多
文摘In Pelton turbines, when the water jet emerges in the air, its velocity decreases downstream and its diameter increases to meet the continuity. In this paper, a physical parameter, the enlarging rate of jet diameter kDi was introduced and measured experimentally. The measurement of enlarging rate was carried out in three model turbines with different distributing Y-branch and nozzle configurations under various operating conditions. The effect of jet enlarging rate on the unsteady water sheet flow in the rotating buckets has not been investigated so tar. This paper also presents the comparative numerical analysis of the flow in buckets at different enlarging rates of jet. It is shown that the effect of jet enlargement is so large that the flow pattern in the bucket is drastically changed by the latter half of the frames, The jet with large enlarging rate also introduces worse energy behavior to the hydraulic performance of the Pelton turbine. Besides, the phenomenon of jet interference was also discussed by using the results of numerical simulation for one jet. It indicates that the jet with large enlarging rate takes more risk that jet interference may damage the performance of multi-nozzle Pelton turbine.
基金Supported by National Natural Science Foundation of China(41171449)Key Project of Chinese Academy of Sciences(KZZD-EW-06-01)
文摘After expatiating the guiding ideology,contents,standards and principles of eco-environment restoration based on enlarging terrace and de-farming,this paper discussed the planning method and technical flow of enlarging terrace and garden plot in a small catchment of loess hilly region by means of GIS spatial analysis technology,and then the planning method was applied in Yangou catchment.The result showed that it is practicabl,and the areas of newly-built terrace and garden plot in Yangou catchment are at least 295.06 and 4.61 hm2,so that the areas of basic farmland and garden plot reach 359.23 and 622.69 hm2.After the land use structure is regulated,the forest coverage is 48.87%,and the permanent vegetation coverage is about 75% in Yangou catchment,while sediment reduction benefit is above 80% in slope land.In agricultural development,Yangou catchment can yield 1 645.13 tons of food supplies,above 9 340 tons of apples,and can feed 7 500 sheep every year.
基金Program for Changjiang Scholars and Innovative Research Team in University,China(No.IRT1220)Donghua University Thesis Innovation Fund,China(No.EG2014028)
文摘In this paper,a new type of machinery which can enlarge the stroke of air cylinder is introduced. It is very useful when the original stroke of air cylinder cannot satisfy the work requirement.According to design requirements,its multi-objective mathematic model with constrained conditions is built. In order to solve this model, some methods are discussed and used such as penalty function method,variable metric method,Newton tangent method and bisection method. Based on the optimal result,motion curves of enlarging stroke mechanism are obtained. Results show that the motion characteristic of enlarging stroke of air cylinder mechanism is satisfying. In addition,we also consider the influence of different initial values of link length to optimal results and two important laws are got in this paper on the basis of optimal results.
文摘In an information society,the English knowledge in capacity for college students has gradually been improved and its range is alsoenlarged.If teachers overlook summing up the knowledge which the students have gained and improving their skills in English,it will behard for students to learn English well.In educational circles people often say"teaching method isn't fixed ",but it is of the same view togive students some basic regularity,let students have enough abilities and make knowledge which the students have gained assimilate and sys-tematize etc.Facing medical college students'tasks are arduous and the students often seem at a loss.In English lessons,it is necessary forteachers to help students find out some basic laws,give students enough skills and methods,let students sum up and classify knowledge whichis scattered,disorderly,bit by bit and even fragmented.
基金supported by the National Key Research and Development Program of China (2017YFA0206500and 2018YFA0209103)the National Natural Science Foundation of China (21832003, 21773111, 21573107 and 21971061)the Fundamental Research Funds for the Central Universities (020514380126)
文摘Increasing the energy density of supercapacitor without sacrificing its high power is an everlasting pursuit in energy storage.Using ionic liquid electrolyte with high operating voltage can increase the energy density but usually at the expense of power density due to the large ion size,low ionic conductivity and high viscosity.Herein we demonstrate a simultaneous increase of the energy and power densities with ionic liquid electrolyte(EMIMBF4)mainly by enlarging the ion-transfer micropore channels of the electrode material,i.e.,the unique hierarchical carbon nanocages(hCNC).Boudouard reaction is adopted to tune the micropore size while remaining the hierarchical framework of hCNC.Meanwhile,the specific surface area,pore volume and conductivity are also increased under optimal activation temperature.Such a unique modification boosts the large-sized ion transfer,leading to the obvious decrease of equivalent series resistance and the dramatic increase of supercapacitive performance thereof.The optimized product exhibits an energy density up to 153.8 W h kg^(-1) at the power density of 1.8 kW kg^(-1),and maintains 54.0 W h kg^(-1) even at an ultrahigh power density of 480.1 kW kg^(-1).This study demonstrates an effective way to explore advanced electrode materials by the fine regulation of micropores and related properties.
