An investigation of the hysteresis of vortex breakdown over pitching-up deltawings is presented. Based on experiments, there are two main reasons which can be usedto explain the hysteresis of vortex breakdown. One is ...An investigation of the hysteresis of vortex breakdown over pitching-up deltawings is presented. Based on experiments, there are two main reasons which can be usedto explain the hysteresis of vortex breakdown. One is the time or phase lag due to the ini-tial suPerPOsition of linearized small disturbance, which enlarges the range of the incidenceof keeping attached flow and postpones the initial incidence of vortex breakdown. Theother is the reduction of adverse pressure gradient due to the periphery centrifugal instabil-ity after the concentrated vortex has come into being, which is the key reason of hystere-sis of vortex breakdown- The structure of vortex over a pitching up delta wing can be di-vided into three layers, which is not a significant a1teration compared with that of vortexover a static delta wing.展开更多
In a previous study, we used natural butterfly wings as a cell growth matrix for tissue engineering materials and found that the surface of different butterfly wings had different ultramicrostructures, which can affec...In a previous study, we used natural butterfly wings as a cell growth matrix for tissue engineering materials and found that the surface of different butterfly wings had different ultramicrostructures, which can affect the qualitative growth of cells and regulate cell growth, metabolism, and gene expression. However, the biocompatibility and biosafety of butterfly wings must be studied. In this study, we found that Sprague-Dawley rat dorsal root ganglion neurons could grow along the structural stripes of butterfly wings, and Schwann cells could normally attach to and proliferate on different species of butterfly wings. The biocompatibility and biosafety of butterfly wings were further examined through subcutaneous implantation in Sprague-Dawley rats, intraperitoneal injection in Institute of Cancer Research mice, intradermal injection in rabbits, and external application to guinea pigs. Our results showed that butterfly wings did not induce toxicity, and all examined animals exhibited normal behaviors and no symptoms, such as erythema or edema. These findings suggested that butterfly wings possess excellent biocompatibility and biosafety and can be used as a type of tissue engineering material. This study was approved by the Experimental Animal Ethics Committee of Jiangsu Province of China(approval No. 20190303-18) on March 3, 2019.展开更多
During a dive peregrine falcons can reach velocities of more than 320 km/h and makes themselves the fastest animals in the world. The aerodynamic mechanisms involved are not fully understood yet and the search for a c...During a dive peregrine falcons can reach velocities of more than 320 km/h and makes themselves the fastest animals in the world. The aerodynamic mechanisms involved are not fully understood yet and the search for a conclusive answer to this fact motivates the three-dimensional (3-D) flow study. Especially the cupped wing configuration which is a unique feature of the wing shape in falcon peregrine dive is our focus herein. In particular, the flow in the gap between the main body and the cupped wing is studied to understand how this flow interacts with the body and to what extend it affects the integral forces of lift and drag. Characteristic shapes of the wings while diving are studied with regard to their aerodynamics using computational fluid dynamics (CFD). The results of the numerical simulations via ICEM CFD and OpenFOAM show predominant flow structures around the body surface and in the wake of the falcon model such as a pair of body vortices and tip vortices. The drag for the cupped wing profile is reduced in relation to the configuration of opened wings (without cupped-like profile) while lift is increased. The purpose of this study is primarily the basic research of the aerodynamic mechanisms during the falcon’s diving flight. The results could be important for maintaining good maneuverability at high speeds in the aviation sector.展开更多
Excessive vibration of aircraft wings during flight is harmful and may cause propagation of existing cracks in the material, leading to catastrophic failures as a result of material fatigue. This study investigates th...Excessive vibration of aircraft wings during flight is harmful and may cause propagation of existing cracks in the material, leading to catastrophic failures as a result of material fatigue. This study investigates the variations of modal characteristics of aircraft wings with respect to changes in the structural configurations. We develop parametric Computer-Aided Design (CAD) models to capture new design intend on the aircraft wing architectures. Subsequent Finite Element Analysis (FEA) based vibration analysis is performed to study the effects of architecture changes on the wing’s natural frequencies and mode shapes. It is concluded that the spar placement and the number of ribs have significant influence on the wing’s natural vibration properties. Integrating CAD modelling and FEA vibration analysis enables designers to develop alternative wing architectures to implement design requirements in the preliminary design stage.展开更多
Our study investigated the effect of utiliz</span></span><span><span><span style="font-family:;" "="">ing</span></span></span><span><sp...Our study investigated the effect of utiliz</span></span><span><span><span style="font-family:;" "="">ing</span></span></span><span><span><span style="font-family:;" "=""> chicken</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">wings and dehydrated shellfish to produce chicken nuggets rich in protein, minerals and vitamins.</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">The proximate composition, nutritional value, physical and sensorial properties were evaluated. The different</span></span></span><span><span><span style="font-family:;" "="">ly</span></span></span><span><span><span style="font-family:;" "=""> prepared chicken nuggets </span></span></span><span><span><span style="font-family:;" "="">were </span></span></span><span><span><span style="font-family:;" "="">supplemented with dehydrated shellfish CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">0%, CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">2%, CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">4% and CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">6%. There was </span></span></span><span><span><span style="font-family:;" "="">a </span></span></span><span><span><span style="font-family:;" "="">significantly reduction </span></span></span><span><span><span style="font-family:;" "="">in </span></span></span><span><span><span style="font-family:;" "="">moisture and </span></span></span><span><span><span style="font-family:;" "="">an </span></span></span><span><span><span style="font-family:;" "="">increasing in protein content (<i>P</i> < 0.05) in all Chicken Nuggets (CN) in comparison to the control. Fat content was significantly higher in CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">0% than CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">2%, CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">4% and CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">6%. Ash content was increasing with added dehydrated shellfish, while </span></span></span><span><span><span style="font-family:;" "="">the </span></span></span><span><span><span style="font-family:;" "="">reduction in carbohydrates and total calories of the different chicken nuggets were noticed with </span></span></span><span><span><span style="font-family:;" "="">the </span></span></span><span><span><span style="font-family:;" "="">significant gradual rise in pH values, TBA values showed no significant difference (<i>P</i> < 0.05) between chicken nuggets. Results showed that using dehydrated shellfish in preparing chicken nuggets caused a marked rise in its content of Ca, Fe, Na, K, Zn, Mg and Mn levels, CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">0% had the lowest concentration of all minerals, and had lower value</span></span></span><span><span><span style="font-family:;" "="">s</span></span></span><span><span><span style="font-family:;" "=""> of vitamins A, E and D but CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">6% had higher value</span></span></span><span><span><span style="font-family:;" "="">s</span></span></span><span><span><span style="font-family:;" "=""> of vitamins A, E and D. Control Nuggets (CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">0%) had the lowest value of yellowness and highest value of lightness but CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">6% had </span></span></span><span><span><span style="font-family:;" "="">the </span></span></span><span><span><span style="font-family:;" "="">highest value of yellowness and, </span></span></span><span><span><span style="font-family:;" "="">the </span></span></span><span><span><span style="font-family:;" "="">lowest value of lightness. </span></span></span><span><span><span style="font-family:;" "="">The </span></span></span><span><span><span style="font-family:;" "="">redness had </span></span></span><span><span><span style="font-family:;" "="">a </span></span></span><span><span><span style="font-family:;" "="">slightly reduction. All samples showed slight changes in</span></span></span><span><span><span style="font-family:;" "=""> hardness, cohesiveness, springiness, gumminess and chewiness were noticed. </span></span></span><span><span><span style="font-family:;" "="">An </span></span></span><span><span><span style="font-family:;" "="">increase in WHC, pick-up, and cooking loss of chicken nuggets with dehydrated shellfish was noticed. Panelists accepted all prepared chicken nuggets and the chicken nuggets CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">4% had </span></span></span><span><span><span style="font-family:;" "="">the </span></span></span><span><span><span style="font-family:;" "="">highest score compared with other chicken nuggets prepared.展开更多
In any case, it shows that over thousands of hundreds of years, the inseparable connection between human beings and the sea has been generating enormous curiosity, yearning, romances and ardors. Even for someone who w...In any case, it shows that over thousands of hundreds of years, the inseparable connection between human beings and the sea has been generating enormous curiosity, yearning, romances and ardors. Even for someone who was brought展开更多
Air Algerie’s Beijing route shows great promise as Africa’s aviation industry seeks to make global gains UPON entering the office of Samy Boutemadja, Chief Representative of Air Algerie in China, the decor may make ...Air Algerie’s Beijing route shows great promise as Africa’s aviation industry seeks to make global gains UPON entering the office of Samy Boutemadja, Chief Representative of Air Algerie in China, the decor may make visitors think they have stepped into the North African nation.Boutemadjia, in his 40s,looks shy and reserved,but when it comes to Algeria,a top Mediterranean destination,he becomes a good conversationalist.展开更多
Winged animals such as insects are capable of flying and surviving in an unsteady and unpredictable aerial environment.They generate and control aerodynamic forces by flapping their flexible wings.While the dynamic sh...Winged animals such as insects are capable of flying and surviving in an unsteady and unpredictable aerial environment.They generate and control aerodynamic forces by flapping their flexible wings.While the dynamic shape changes of their flapping wings are known to enhance the efficiency of their flight,they can also affect the stability of a flapping wing flyer under unpredictable disturbances by responding to the sudden changes of aerodynamic forces on the wing.In order to test the hypothesis,the gust response of flexible flapping wings is investigated numerically with a specific focus on the passive maintenance of aerodynamic forces by the wing flexibility.The computational model is based on a dynamic flight simulator that can incorporate the realistic morphology,the kinematics,the structural dynamics,the aerodynamics and the fluid-structure interactions of a hovering hawkmoth.The longitudinal gusts are imposed against the tethered model of a hovering hawkmoth with flexible flapping wings.It is found that the aerodynamic forces on the flapping wings are affected by the gust,because of the increase or decrease in relative wingtip velocity or kinematic angle of attack.The passive shape change of flexible wings can,however,reduce the changes in the magnitude and direction of aerodynamic forces by the gusts from various directions,except for the downward gust.Such adaptive response of the flexible structure to stabilise the attitude can be classified into the mechanical feedback,which works passively with minimal delay,and is of great importance to the design of bio-inspired flapping wings for micro-air vehicles.展开更多
文摘An investigation of the hysteresis of vortex breakdown over pitching-up deltawings is presented. Based on experiments, there are two main reasons which can be usedto explain the hysteresis of vortex breakdown. One is the time or phase lag due to the ini-tial suPerPOsition of linearized small disturbance, which enlarges the range of the incidenceof keeping attached flow and postpones the initial incidence of vortex breakdown. Theother is the reduction of adverse pressure gradient due to the periphery centrifugal instabil-ity after the concentrated vortex has come into being, which is the key reason of hystere-sis of vortex breakdown- The structure of vortex over a pitching up delta wing can be di-vided into three layers, which is not a significant a1teration compared with that of vortexover a static delta wing.
基金supported by the National Natural Science Foundation of China,No. 31971276the Natural Science Foundation of Jiangsu Higher Education Institutions of China (Major Program),No. 19KJA320005 (both to JHH)。
文摘In a previous study, we used natural butterfly wings as a cell growth matrix for tissue engineering materials and found that the surface of different butterfly wings had different ultramicrostructures, which can affect the qualitative growth of cells and regulate cell growth, metabolism, and gene expression. However, the biocompatibility and biosafety of butterfly wings must be studied. In this study, we found that Sprague-Dawley rat dorsal root ganglion neurons could grow along the structural stripes of butterfly wings, and Schwann cells could normally attach to and proliferate on different species of butterfly wings. The biocompatibility and biosafety of butterfly wings were further examined through subcutaneous implantation in Sprague-Dawley rats, intraperitoneal injection in Institute of Cancer Research mice, intradermal injection in rabbits, and external application to guinea pigs. Our results showed that butterfly wings did not induce toxicity, and all examined animals exhibited normal behaviors and no symptoms, such as erythema or edema. These findings suggested that butterfly wings possess excellent biocompatibility and biosafety and can be used as a type of tissue engineering material. This study was approved by the Experimental Animal Ethics Committee of Jiangsu Province of China(approval No. 20190303-18) on March 3, 2019.
文摘During a dive peregrine falcons can reach velocities of more than 320 km/h and makes themselves the fastest animals in the world. The aerodynamic mechanisms involved are not fully understood yet and the search for a conclusive answer to this fact motivates the three-dimensional (3-D) flow study. Especially the cupped wing configuration which is a unique feature of the wing shape in falcon peregrine dive is our focus herein. In particular, the flow in the gap between the main body and the cupped wing is studied to understand how this flow interacts with the body and to what extend it affects the integral forces of lift and drag. Characteristic shapes of the wings while diving are studied with regard to their aerodynamics using computational fluid dynamics (CFD). The results of the numerical simulations via ICEM CFD and OpenFOAM show predominant flow structures around the body surface and in the wake of the falcon model such as a pair of body vortices and tip vortices. The drag for the cupped wing profile is reduced in relation to the configuration of opened wings (without cupped-like profile) while lift is increased. The purpose of this study is primarily the basic research of the aerodynamic mechanisms during the falcon’s diving flight. The results could be important for maintaining good maneuverability at high speeds in the aviation sector.
文摘Excessive vibration of aircraft wings during flight is harmful and may cause propagation of existing cracks in the material, leading to catastrophic failures as a result of material fatigue. This study investigates the variations of modal characteristics of aircraft wings with respect to changes in the structural configurations. We develop parametric Computer-Aided Design (CAD) models to capture new design intend on the aircraft wing architectures. Subsequent Finite Element Analysis (FEA) based vibration analysis is performed to study the effects of architecture changes on the wing’s natural frequencies and mode shapes. It is concluded that the spar placement and the number of ribs have significant influence on the wing’s natural vibration properties. Integrating CAD modelling and FEA vibration analysis enables designers to develop alternative wing architectures to implement design requirements in the preliminary design stage.
文摘Our study investigated the effect of utiliz</span></span><span><span><span style="font-family:;" "="">ing</span></span></span><span><span><span style="font-family:;" "=""> chicken</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">wings and dehydrated shellfish to produce chicken nuggets rich in protein, minerals and vitamins.</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">The proximate composition, nutritional value, physical and sensorial properties were evaluated. The different</span></span></span><span><span><span style="font-family:;" "="">ly</span></span></span><span><span><span style="font-family:;" "=""> prepared chicken nuggets </span></span></span><span><span><span style="font-family:;" "="">were </span></span></span><span><span><span style="font-family:;" "="">supplemented with dehydrated shellfish CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">0%, CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">2%, CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">4% and CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">6%. There was </span></span></span><span><span><span style="font-family:;" "="">a </span></span></span><span><span><span style="font-family:;" "="">significantly reduction </span></span></span><span><span><span style="font-family:;" "="">in </span></span></span><span><span><span style="font-family:;" "="">moisture and </span></span></span><span><span><span style="font-family:;" "="">an </span></span></span><span><span><span style="font-family:;" "="">increasing in protein content (<i>P</i> < 0.05) in all Chicken Nuggets (CN) in comparison to the control. Fat content was significantly higher in CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">0% than CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">2%, CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">4% and CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">6%. Ash content was increasing with added dehydrated shellfish, while </span></span></span><span><span><span style="font-family:;" "="">the </span></span></span><span><span><span style="font-family:;" "="">reduction in carbohydrates and total calories of the different chicken nuggets were noticed with </span></span></span><span><span><span style="font-family:;" "="">the </span></span></span><span><span><span style="font-family:;" "="">significant gradual rise in pH values, TBA values showed no significant difference (<i>P</i> < 0.05) between chicken nuggets. Results showed that using dehydrated shellfish in preparing chicken nuggets caused a marked rise in its content of Ca, Fe, Na, K, Zn, Mg and Mn levels, CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">0% had the lowest concentration of all minerals, and had lower value</span></span></span><span><span><span style="font-family:;" "="">s</span></span></span><span><span><span style="font-family:;" "=""> of vitamins A, E and D but CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">6% had higher value</span></span></span><span><span><span style="font-family:;" "="">s</span></span></span><span><span><span style="font-family:;" "=""> of vitamins A, E and D. Control Nuggets (CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">0%) had the lowest value of yellowness and highest value of lightness but CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">6% had </span></span></span><span><span><span style="font-family:;" "="">the </span></span></span><span><span><span style="font-family:;" "="">highest value of yellowness and, </span></span></span><span><span><span style="font-family:;" "="">the </span></span></span><span><span><span style="font-family:;" "="">lowest value of lightness. </span></span></span><span><span><span style="font-family:;" "="">The </span></span></span><span><span><span style="font-family:;" "="">redness had </span></span></span><span><span><span style="font-family:;" "="">a </span></span></span><span><span><span style="font-family:;" "="">slightly reduction. All samples showed slight changes in</span></span></span><span><span><span style="font-family:;" "=""> hardness, cohesiveness, springiness, gumminess and chewiness were noticed. </span></span></span><span><span><span style="font-family:;" "="">An </span></span></span><span><span><span style="font-family:;" "="">increase in WHC, pick-up, and cooking loss of chicken nuggets with dehydrated shellfish was noticed. Panelists accepted all prepared chicken nuggets and the chicken nuggets CN</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">4% had </span></span></span><span><span><span style="font-family:;" "="">the </span></span></span><span><span><span style="font-family:;" "="">highest score compared with other chicken nuggets prepared.
文摘In any case, it shows that over thousands of hundreds of years, the inseparable connection between human beings and the sea has been generating enormous curiosity, yearning, romances and ardors. Even for someone who was brought
文摘Air Algerie’s Beijing route shows great promise as Africa’s aviation industry seeks to make global gains UPON entering the office of Samy Boutemadja, Chief Representative of Air Algerie in China, the decor may make visitors think they have stepped into the North African nation.Boutemadjia, in his 40s,looks shy and reserved,but when it comes to Algeria,a top Mediterranean destination,he becomes a good conversationalist.
文摘Winged animals such as insects are capable of flying and surviving in an unsteady and unpredictable aerial environment.They generate and control aerodynamic forces by flapping their flexible wings.While the dynamic shape changes of their flapping wings are known to enhance the efficiency of their flight,they can also affect the stability of a flapping wing flyer under unpredictable disturbances by responding to the sudden changes of aerodynamic forces on the wing.In order to test the hypothesis,the gust response of flexible flapping wings is investigated numerically with a specific focus on the passive maintenance of aerodynamic forces by the wing flexibility.The computational model is based on a dynamic flight simulator that can incorporate the realistic morphology,the kinematics,the structural dynamics,the aerodynamics and the fluid-structure interactions of a hovering hawkmoth.The longitudinal gusts are imposed against the tethered model of a hovering hawkmoth with flexible flapping wings.It is found that the aerodynamic forces on the flapping wings are affected by the gust,because of the increase or decrease in relative wingtip velocity or kinematic angle of attack.The passive shape change of flexible wings can,however,reduce the changes in the magnitude and direction of aerodynamic forces by the gusts from various directions,except for the downward gust.Such adaptive response of the flexible structure to stabilise the attitude can be classified into the mechanical feedback,which works passively with minimal delay,and is of great importance to the design of bio-inspired flapping wings for micro-air vehicles.
