A new method that uses time-domain response data under random loading is proposed for detecting damage to the structural elements of offshore platforms. In our study, a time series model with a fitting order was first...A new method that uses time-domain response data under random loading is proposed for detecting damage to the structural elements of offshore platforms. In our study, a time series model with a fitting order was first constructed using the time-domain of noise data. A sensitivity matrix consisting of the first differential of the autoregressive coefficients of the time series models with respect to the stiffness of structural elements was then obtained based on time-domain response data. Locations and severity of damage may then be estimated by solving the damage vector whose components express the degrees of damage to the structural elements. A unique aspect of this detection method is that it requires acceleration history data from only one or a few sensors. This makes it feasible for a limited array of sensors to obtain sufficient data. The efficiency and reliability of the proposed method was demonstrated by applying it to a simplified offshore platform with damage to one element. Numerical simulations show that the use of a few sensors’ acceleration history data, when compared with recorded levels of noise, is capable of detecting damage efficiently. An increase in the number of sensors helps improve the diagnosis success rate.展开更多
The Donnell theory of shell was applied to describe shell motion. The inner and outer shells were stiffened by transverse components. Using deformation harmonious conditions of the interface, the effects of stiffeners...The Donnell theory of shell was applied to describe shell motion. The inner and outer shells were stiffened by transverse components. Using deformation harmonious conditions of the interface, the effects of stiffeners were treated as reverse forces and moments on the double cylindrical shell. In the acoustic field produced by vibration and sound radiation of the double shell, the structure dynamic equation, Helmholtz equation in the fluid field and the continuity conditions of the surface of fluid-structure compose the vibration equation coupled by the sound-fluid-structure. The extract of acoustic pressure comes down to the extract of coupling vibration equation. The near field acoustic pressure can be solved directly by complicated calculational methods.展开更多
Wireless sensor networks(WSNs)are characterized by heterogeneous traffic types(audio,video,data)and diverse application traffic requirements.This paper introduces three traffic classes following the defined model of h...Wireless sensor networks(WSNs)are characterized by heterogeneous traffic types(audio,video,data)and diverse application traffic requirements.This paper introduces three traffic classes following the defined model of heterogeneous traffic differentiation in WSNs.The requirements for each class regarding sensitivity to QoS(Quality of Service)parameters,such as loss,delay,and jitter,are described.These classes encompass real-time and delay-tolerant traffic.Given that QoS evaluation is a multi-criteria decision-making problem,we employed the AHP(Analytical Hierarchy Process)method for multi-criteria optimization.As a result of this approach,we derived weight values for different traffic classes based on key QoS factors and requirements.These weights are assigned to individual traffic classes to determine transmission priority.This study provides a thorough comparative analysis of the proposed model against existing methods,demonstrating its superior performance across various traffic scenarios and its implications for future WSN applications.The results highlight the model’s adaptability and robustness in optimizing network resources under varying conditions,offering insights into practical deployments in real-world scenarios.Additionally,the paper includes an analysis of energy consumption,underscoring the trade-offs between QoS performance and energy efficiency.This study presents the development of a differentiated services model for heterogeneous traffic in wireless sensor networks,considering the appropriate QoS framework supported by experimental analyses.展开更多
Dynamic response of beam-like structures to moving vehicles has been extensively studied. However, the study on dynamic response of plates to moving vehicles has so far received but scant attention. A plate-vehicle st...Dynamic response of beam-like structures to moving vehicles has been extensively studied. However, the study on dynamic response of plates to moving vehicles has so far received but scant attention. A plate-vehicle strip for simulating the interaction between a rectangular plate and moving vehicles was described. For the portion of strips that are in direct contact with the moving vehicles, the plate-vehicle strips were employed. Conventional plate finite strips were used to model the portion of strips that are not directly under the action of moving vehicles. In the analysis, each moving vehicle is idealized as a one-foot dynamic system with tire unsprung mass and sprund mass interconnected by a spring and a dashpot. The numerical results obtained from the proposed method agree well with available results.展开更多
Redesign of motorized and non-motorized transport in cities and sustainable mobility possibilities and utilization of already occupied areas for motorized and non-motorized transport in cities. Reserved area for publi...Redesign of motorized and non-motorized transport in cities and sustainable mobility possibilities and utilization of already occupied areas for motorized and non-motorized transport in cities. Reserved area for public transport may be the redesign much more to take advantage of without taking up new space in cities. Redesigned solutions shown in the work of public mass transport and the redesign of non-motorized transport, bicycle and pedestrian paths point to the improved use and safety of movement of passengers, cyclists and pedestrians. This paper presents five redesigned concept designs as improving existing forms of transport and movement of cyclists and pedestrians in cities. Redesigned conceptual designs of motorized and non-motorized transport in cities should serve as ideas for the growing problems of urban development in the segment of insufficient surface for pedestrians and cyclists, as well as sustainable mobility transport people in the city.展开更多
The paper proposes an approximate solution to the classical (parabolic) multidimensional 2D and 3D heat conduction equation for a 5 × 5 cm aluminium plate and a 5 × 5 × 5 cm aluminum cube. An approximat...The paper proposes an approximate solution to the classical (parabolic) multidimensional 2D and 3D heat conduction equation for a 5 × 5 cm aluminium plate and a 5 × 5 × 5 cm aluminum cube. An approximate solution of the generalized (hyperbolic) 2D and 3D equation for the considered plate and cube is also proposed. Approximate solutions were obtained by applying calculus of variations and Euler-Lagrange equations. In order to verify the correctness of the proposed approximate solutions, they were compared with the exact solutions of parabolic and hyperbolic equations. The paper also presents the research on the influence of time parameters τ as well as the relaxation times τ ∗ to the variation of the profile of the temperature field for the considered aluminum plate and cube.展开更多
It is known that Fourier’s heat equation, which is parabolic, implies an infinite velocity propagation, or, in other words, that the mechanism of heat conduction is established instantaneously under all conditions. T...It is known that Fourier’s heat equation, which is parabolic, implies an infinite velocity propagation, or, in other words, that the mechanism of heat conduction is established instantaneously under all conditions. This is unacceptable on physical grounds in spite of the fact that Fourier’s law agrees well with experiment. However, discrepancies are likely to occur when extremely short distances or extremely short time intervals are considered, as they must in some modern problems of aero-thermodynamics. Cattaneo and independently Vernotte proved that such process can be described by Heaviside’s telegraph equation. This paper shows that this fact can be derived using calculus of variations, by application of the Euler-Lagrange equation. So, we proved that the equation of heat conduction with finite velocity propagation of the thermal disturbance can be obtained as a solution to one variational problem.展开更多
The paper researches the effect of temperature on ammonia synthesis. The ammonia synthesis reaction N2(g)+3H2(g)=2NH3(g)is exothermic with a negative entropy change. ΔG0condition is fulfilled at lower temperatures up...The paper researches the effect of temperature on ammonia synthesis. The ammonia synthesis reaction N2(g)+3H2(g)=2NH3(g)is exothermic with a negative entropy change. ΔG0condition is fulfilled at lower temperatures up to 464 K. It is a constant equilibrium of the ammonia synthesis reaction K′p≫1at lower temperatures, which means that the NH3(g)) synthesis reaction is shifted in the direction of NH3(g) formation (higher production of ammonia). The downside of lowering the temperature is that more ammonia is obtained, but the reaction rate slows down. Above 464K, the free enthalpy of the NH3(g) synthesis reaction is greater than zero, so the reaction enters thermodynamically unfavorable conditions. By increasing the reaction temperature, the ammonia yield NH3(g) decreases in the equilibrium mixture. At 400 K, it is 0.5128 kmol/kmol (51.28%) and at 900 K, the synthesis process NH3(g) is practically complete.展开更多
基金the National Natural Science Foundation of China under Grant No. 50479050
文摘A new method that uses time-domain response data under random loading is proposed for detecting damage to the structural elements of offshore platforms. In our study, a time series model with a fitting order was first constructed using the time-domain of noise data. A sensitivity matrix consisting of the first differential of the autoregressive coefficients of the time series models with respect to the stiffness of structural elements was then obtained based on time-domain response data. Locations and severity of damage may then be estimated by solving the damage vector whose components express the degrees of damage to the structural elements. A unique aspect of this detection method is that it requires acceleration history data from only one or a few sensors. This makes it feasible for a limited array of sensors to obtain sufficient data. The efficiency and reliability of the proposed method was demonstrated by applying it to a simplified offshore platform with damage to one element. Numerical simulations show that the use of a few sensors’ acceleration history data, when compared with recorded levels of noise, is capable of detecting damage efficiently. An increase in the number of sensors helps improve the diagnosis success rate.
文摘The Donnell theory of shell was applied to describe shell motion. The inner and outer shells were stiffened by transverse components. Using deformation harmonious conditions of the interface, the effects of stiffeners were treated as reverse forces and moments on the double cylindrical shell. In the acoustic field produced by vibration and sound radiation of the double shell, the structure dynamic equation, Helmholtz equation in the fluid field and the continuity conditions of the surface of fluid-structure compose the vibration equation coupled by the sound-fluid-structure. The extract of acoustic pressure comes down to the extract of coupling vibration equation. The near field acoustic pressure can be solved directly by complicated calculational methods.
文摘Wireless sensor networks(WSNs)are characterized by heterogeneous traffic types(audio,video,data)and diverse application traffic requirements.This paper introduces three traffic classes following the defined model of heterogeneous traffic differentiation in WSNs.The requirements for each class regarding sensitivity to QoS(Quality of Service)parameters,such as loss,delay,and jitter,are described.These classes encompass real-time and delay-tolerant traffic.Given that QoS evaluation is a multi-criteria decision-making problem,we employed the AHP(Analytical Hierarchy Process)method for multi-criteria optimization.As a result of this approach,we derived weight values for different traffic classes based on key QoS factors and requirements.These weights are assigned to individual traffic classes to determine transmission priority.This study provides a thorough comparative analysis of the proposed model against existing methods,demonstrating its superior performance across various traffic scenarios and its implications for future WSN applications.The results highlight the model’s adaptability and robustness in optimizing network resources under varying conditions,offering insights into practical deployments in real-world scenarios.Additionally,the paper includes an analysis of energy consumption,underscoring the trade-offs between QoS performance and energy efficiency.This study presents the development of a differentiated services model for heterogeneous traffic in wireless sensor networks,considering the appropriate QoS framework supported by experimental analyses.
文摘Dynamic response of beam-like structures to moving vehicles has been extensively studied. However, the study on dynamic response of plates to moving vehicles has so far received but scant attention. A plate-vehicle strip for simulating the interaction between a rectangular plate and moving vehicles was described. For the portion of strips that are in direct contact with the moving vehicles, the plate-vehicle strips were employed. Conventional plate finite strips were used to model the portion of strips that are not directly under the action of moving vehicles. In the analysis, each moving vehicle is idealized as a one-foot dynamic system with tire unsprung mass and sprund mass interconnected by a spring and a dashpot. The numerical results obtained from the proposed method agree well with available results.
文摘Redesign of motorized and non-motorized transport in cities and sustainable mobility possibilities and utilization of already occupied areas for motorized and non-motorized transport in cities. Reserved area for public transport may be the redesign much more to take advantage of without taking up new space in cities. Redesigned solutions shown in the work of public mass transport and the redesign of non-motorized transport, bicycle and pedestrian paths point to the improved use and safety of movement of passengers, cyclists and pedestrians. This paper presents five redesigned concept designs as improving existing forms of transport and movement of cyclists and pedestrians in cities. Redesigned conceptual designs of motorized and non-motorized transport in cities should serve as ideas for the growing problems of urban development in the segment of insufficient surface for pedestrians and cyclists, as well as sustainable mobility transport people in the city.
文摘The paper proposes an approximate solution to the classical (parabolic) multidimensional 2D and 3D heat conduction equation for a 5 × 5 cm aluminium plate and a 5 × 5 × 5 cm aluminum cube. An approximate solution of the generalized (hyperbolic) 2D and 3D equation for the considered plate and cube is also proposed. Approximate solutions were obtained by applying calculus of variations and Euler-Lagrange equations. In order to verify the correctness of the proposed approximate solutions, they were compared with the exact solutions of parabolic and hyperbolic equations. The paper also presents the research on the influence of time parameters τ as well as the relaxation times τ ∗ to the variation of the profile of the temperature field for the considered aluminum plate and cube.
文摘It is known that Fourier’s heat equation, which is parabolic, implies an infinite velocity propagation, or, in other words, that the mechanism of heat conduction is established instantaneously under all conditions. This is unacceptable on physical grounds in spite of the fact that Fourier’s law agrees well with experiment. However, discrepancies are likely to occur when extremely short distances or extremely short time intervals are considered, as they must in some modern problems of aero-thermodynamics. Cattaneo and independently Vernotte proved that such process can be described by Heaviside’s telegraph equation. This paper shows that this fact can be derived using calculus of variations, by application of the Euler-Lagrange equation. So, we proved that the equation of heat conduction with finite velocity propagation of the thermal disturbance can be obtained as a solution to one variational problem.
文摘The paper researches the effect of temperature on ammonia synthesis. The ammonia synthesis reaction N2(g)+3H2(g)=2NH3(g)is exothermic with a negative entropy change. ΔG0condition is fulfilled at lower temperatures up to 464 K. It is a constant equilibrium of the ammonia synthesis reaction K′p≫1at lower temperatures, which means that the NH3(g)) synthesis reaction is shifted in the direction of NH3(g) formation (higher production of ammonia). The downside of lowering the temperature is that more ammonia is obtained, but the reaction rate slows down. Above 464K, the free enthalpy of the NH3(g) synthesis reaction is greater than zero, so the reaction enters thermodynamically unfavorable conditions. By increasing the reaction temperature, the ammonia yield NH3(g) decreases in the equilibrium mixture. At 400 K, it is 0.5128 kmol/kmol (51.28%) and at 900 K, the synthesis process NH3(g) is practically complete.
