Wind energy is one of the most promising renewable energy sources, straight-bladed vertical axis wind turbine(S-VAWT) appears to be particularly promising for the shortage of fossil fuel reserves owing to its distinct...Wind energy is one of the most promising renewable energy sources, straight-bladed vertical axis wind turbine(S-VAWT) appears to be particularly promising for the shortage of fossil fuel reserves owing to its distinct advantages, but suffers from poor self-starting and low power coefficient. Variable-pitch method was recognized as an attractive solution to performance improvement, thus majority efforts had been devoted into blade pitch angle effect on aerodynamic performance. Taken into account the local flow field of S-VAWT, mathematical model was built to analyze the relationship between power outputs and pitch angle. Numerical simulations on static and dynamic performances of blade were carried out and optimized pitch angle along the rotor were presented. Comparative analyses of fixed pitch and variable-pitch S-VAWT were conducted, and a considerable improvement of the performance was obtained by the optimized blade pitch angle, in particular, a relative increase of the power coefficient by more than 19.3%. It is further demonstrated that the self-starting is greatly improved with the optimized blade pitch angle.展开更多
Introduction: Lumbar disc herniation (LDH) refers to the rupture of the fibrous annulus of the intervertebral discs. Lumbar curvature may lead to the occurrence of lumbar disc degeneration. Fear of movement may worsen...Introduction: Lumbar disc herniation (LDH) refers to the rupture of the fibrous annulus of the intervertebral discs. Lumbar curvature may lead to the occurrence of lumbar disc degeneration. Fear of movement may worsen their disc herniation and cause further pain and injury. LDH conditions impact the individuals’ quality of life, to explore the relationship between lumbar curve, muscle strength, fear of movement and functional disability among patients with LDH. Methods: An electronic search was conducted on PubMed, Medline, Science Direct, Springerlink, Google Scholar and a hand search from reference lists was reviewed. Publications were included in human studies, patients 25 - 85 years of age, original studies and published in English language journals from January 2002 to December 2023. Result: In total, 64 articles were researched through the online search engines, and 9 papers were found through manual searches of reference lists. As a result, a total of 11 articles were included for the purpose of this review. The comprehensive analysis revealed the presence of eight cross-sectional studies, two retrospective studies and one experimental study. A minimum of 25 participants and a maximum of 360 participants were included. Ten studies included both genders, only one studies included healthy adults and patients with LDH but these studies didn’t mention gender. Results showed that the factors influencing LDH can be categorized into non-modifiable factors, such as gender, age, height or others. Modifiable factors included increased BMI, DM, smoking, alcohol, employment status, lifestyle and health problems or psychology. Conclusion: Females with greater VASC may be at risk of LDH. The lumbar extensor muscles indicated a localized disc herniation or nerve root pathology in patients with LDH. The fear of movement may lead to psychological consequences and reduce functional disability among patients with LDH.展开更多
With the growing demand for energy saving,emission reduction,and green metallurgy,we had designed a new C-H2 smelting reduction reactor.In order to solve the key problem that the heat transfer efficiency from high tem...With the growing demand for energy saving,emission reduction,and green metallurgy,we had designed a new C-H2 smelting reduction reactor.In order to solve the key problem that the heat transfer efficiency from high temperature oxidation zone in upper region to low temperature reduction zone in lower region is low in traditional metallurgical reduction reactor,a water simulation was adopted to optimize the mean residence time and to improve the transmission efficiency within the reactor.According to the modified Froude similarity,a water model experimental reactor with a ratio of 1:1 to the prototype was constructed.In the prototype,the feed port was used to feed preheated ore and flux.In order to simulate the effect of different feeding positions of the tracer on the mixing behavior in the molten pool,four points of tracer feeding position were arranged for a systematic study.At the same time,based on double-row side nozzle with thick slag layer in a C-H2 smelting reduction reactor,nine influencing factors,including relative angle between upper and lower side nozzles,were studied.The experimental results showed that the tracer feeding position had a great influence on the mean residence time,and the relative angle also had a great influence on tracer feeding position.Finally,through comprehensive analysis,the optimal condition parameters were obtained under different tracer feeding positions.These results provide valuable help for the design and optimization of the C-H2 smelting reduction reactor.展开更多
A novel coupled multi-active-region large optical cavity structure cascaded by a tunnel junction is proposed to solve the problems of facet catastrophic optical damage （COD） and the large vertical divergence caused ...A novel coupled multi-active-region large optical cavity structure cascaded by a tunnel junction is proposed to solve the problems of facet catastrophic optical damage （COD） and the large vertical divergence caused by the thin emitting area in conventional laser diodes. For a laser with three active regions, a slope efficiency as high as 1.49 W/A, a vertical divergence angle of 17.4~, and a threshold current density of 271 A/cm~ are achieved. By optimizing the structural parameters, the beam quMity is greatly improved, and the level of the COD power increases by more than two times compared with that of the conventional laser.展开更多
基金Project(HEUCF110707)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(E201216)supported by Heilongjiang Natural Science Fund,China
文摘Wind energy is one of the most promising renewable energy sources, straight-bladed vertical axis wind turbine(S-VAWT) appears to be particularly promising for the shortage of fossil fuel reserves owing to its distinct advantages, but suffers from poor self-starting and low power coefficient. Variable-pitch method was recognized as an attractive solution to performance improvement, thus majority efforts had been devoted into blade pitch angle effect on aerodynamic performance. Taken into account the local flow field of S-VAWT, mathematical model was built to analyze the relationship between power outputs and pitch angle. Numerical simulations on static and dynamic performances of blade were carried out and optimized pitch angle along the rotor were presented. Comparative analyses of fixed pitch and variable-pitch S-VAWT were conducted, and a considerable improvement of the performance was obtained by the optimized blade pitch angle, in particular, a relative increase of the power coefficient by more than 19.3%. It is further demonstrated that the self-starting is greatly improved with the optimized blade pitch angle.
文摘Introduction: Lumbar disc herniation (LDH) refers to the rupture of the fibrous annulus of the intervertebral discs. Lumbar curvature may lead to the occurrence of lumbar disc degeneration. Fear of movement may worsen their disc herniation and cause further pain and injury. LDH conditions impact the individuals’ quality of life, to explore the relationship between lumbar curve, muscle strength, fear of movement and functional disability among patients with LDH. Methods: An electronic search was conducted on PubMed, Medline, Science Direct, Springerlink, Google Scholar and a hand search from reference lists was reviewed. Publications were included in human studies, patients 25 - 85 years of age, original studies and published in English language journals from January 2002 to December 2023. Result: In total, 64 articles were researched through the online search engines, and 9 papers were found through manual searches of reference lists. As a result, a total of 11 articles were included for the purpose of this review. The comprehensive analysis revealed the presence of eight cross-sectional studies, two retrospective studies and one experimental study. A minimum of 25 participants and a maximum of 360 participants were included. Ten studies included both genders, only one studies included healthy adults and patients with LDH but these studies didn’t mention gender. Results showed that the factors influencing LDH can be categorized into non-modifiable factors, such as gender, age, height or others. Modifiable factors included increased BMI, DM, smoking, alcohol, employment status, lifestyle and health problems or psychology. Conclusion: Females with greater VASC may be at risk of LDH. The lumbar extensor muscles indicated a localized disc herniation or nerve root pathology in patients with LDH. The fear of movement may lead to psychological consequences and reduce functional disability among patients with LDH.
基金This study was funded by the National Science and Technology Support Program(2006BAE03A12).
文摘With the growing demand for energy saving,emission reduction,and green metallurgy,we had designed a new C-H2 smelting reduction reactor.In order to solve the key problem that the heat transfer efficiency from high temperature oxidation zone in upper region to low temperature reduction zone in lower region is low in traditional metallurgical reduction reactor,a water simulation was adopted to optimize the mean residence time and to improve the transmission efficiency within the reactor.According to the modified Froude similarity,a water model experimental reactor with a ratio of 1:1 to the prototype was constructed.In the prototype,the feed port was used to feed preheated ore and flux.In order to simulate the effect of different feeding positions of the tracer on the mixing behavior in the molten pool,four points of tracer feeding position were arranged for a systematic study.At the same time,based on double-row side nozzle with thick slag layer in a C-H2 smelting reduction reactor,nine influencing factors,including relative angle between upper and lower side nozzles,were studied.The experimental results showed that the tracer feeding position had a great influence on the mean residence time,and the relative angle also had a great influence on tracer feeding position.Finally,through comprehensive analysis,the optimal condition parameters were obtained under different tracer feeding positions.These results provide valuable help for the design and optimization of the C-H2 smelting reduction reactor.
基金Project supported by the State Key Development Program for Basic Research of China (Grant No. G20000863-02)the Natural Science Foundation of Beijing, China (Grant No. 4032007)
文摘A novel coupled multi-active-region large optical cavity structure cascaded by a tunnel junction is proposed to solve the problems of facet catastrophic optical damage （COD） and the large vertical divergence caused by the thin emitting area in conventional laser diodes. For a laser with three active regions, a slope efficiency as high as 1.49 W/A, a vertical divergence angle of 17.4~, and a threshold current density of 271 A/cm~ are achieved. By optimizing the structural parameters, the beam quMity is greatly improved, and the level of the COD power increases by more than two times compared with that of the conventional laser.
