Transactions of Nanjing University of Aeronautics & Astronautics
Volume 33,Issue 3,2016 Table of Contents
2016, 33(3):243-251.
Abstract:
The relationship between stiffness distribution and aeroelastic performance for a beam-frame model and a 3-D model is investigated based on aeroelastic optimization of global stiffness design for high-aspect-ratio wings. The sensitivity information of wing spanwise stiffness distribution with respect to the twist angle at wing tip, the vertical displacement at wing tip, and the flutter speed are obtained using a sensitivity method for both models. Then the relationship between stiffness distribution and aeroelastic performance is summarized to guide the design procedure. By using the genetic/sensitivity-based hybrid algorithm, an optimal solution satisfying the strength, aeroelastic and manufacturing constraints is obtained. It is found that the summarized guidance is well consistent with the optimal solution, thus providing a valuable design advice with efficiency. The study also shows that the aeroelastic-optimization-based global stiffness design procedure can obtain the optimal solution under multiple constraints with high efficiency and precision, thereby having a strong application value in engineering.
The relationship between stiffness distribution and aeroelastic performance for a beam-frame model and a 3-D model is investigated based on aeroelastic optimization of global stiffness design for high-aspect-ratio wings. The sensitivity information of wing spanwise stiffness distribution with respect to the twist angle at wing tip, the vertical displacement at wing tip, and the flutter speed are obtained using a sensitivity method for both models. Then the relationship between stiffness distribution and aeroelastic performance is summarized to guide the design procedure. By using the genetic/sensitivity-based hybrid algorithm, an optimal solution satisfying the strength, aeroelastic and manufacturing constraints is obtained. It is found that the summarized guidance is well consistent with the optimal solution, thus providing a valuable design advice with efficiency. The study also shows that the aeroelastic-optimization-based global stiffness design procedure can obtain the optimal solution under multiple constraints with high efficiency and precision, thereby having a strong application value in engineering.
2016, 33(3):252-259.
Abstract:
The issue whether transition from laminar flow to turbulent flow on a flat plate should be characterized as a vorticity redistribution process or a vorticity increasing process is investigated by a high-order direct numerical simulation on a flat plate boundary layer. The local vorticity can either increase or decrease due to tilting and stretching of vortex filaments according to the vorticity transport equation while the total vorticity cannot be changed in a boundary layer flow in conforming to the F?ppl theorem of total vorticity conservation. This seemingly contradictory problem can be well resolved by the introduction of a new term: volume vorticity of a vorticity tube, defined as vorticity flux timed by the vorticity tube length. It has been shown that, although vorticity flux must keep conserved, the total volume vorticity is significantly increased during boundary layer transition according to our direct numerical simulation (DNS) computation, which directly results from the lengthening (stretching and tilting) of vortex filaments. Therefore, the flow transition is a process with appreciable increase of volume vorticity, and cannot be only viewed as a vorticity redistribution process.
The issue whether transition from laminar flow to turbulent flow on a flat plate should be characterized as a vorticity redistribution process or a vorticity increasing process is investigated by a high-order direct numerical simulation on a flat plate boundary layer. The local vorticity can either increase or decrease due to tilting and stretching of vortex filaments according to the vorticity transport equation while the total vorticity cannot be changed in a boundary layer flow in conforming to the F?ppl theorem of total vorticity conservation. This seemingly contradictory problem can be well resolved by the introduction of a new term: volume vorticity of a vorticity tube, defined as vorticity flux timed by the vorticity tube length. It has been shown that, although vorticity flux must keep conserved, the total volume vorticity is significantly increased during boundary layer transition according to our direct numerical simulation (DNS) computation, which directly results from the lengthening (stretching and tilting) of vortex filaments. Therefore, the flow transition is a process with appreciable increase of volume vorticity, and cannot be only viewed as a vorticity redistribution process.
2016, 33(3):260-273.
Abstract:
Piezoelectric pump faces unprecedented challenges when higher expectation and requirements need to be met in their applications mainly to medical treatment, hygiene and public health, and preventive healthcare. Specifically, the piezoelectric pump with valve has the disadvantages of complex structure, high duty cycle of valves, and valve movement lagged behind piezoelectric ceramics oscillation. In an attempt to inhibit its shortcomings, some researchers presented novel concepts for structural design of piezoelectric pump with valve, which could become a new research focus. Among them, the investigation into various soft valves, represented by soft structure valves made of rigid materials and soft material valves made of flexible materials, has been fruitful in recent years. The integrated design of both material and structure can tackle the problems encountered in the study of piezoelectric pump with valve, thus simplifying the pump structure, reducing the duty-cycle of valves, and improving the lagging of valve motion. In addition, new inventions of pump structure have sprung up, such as the pumps containing a single-chamber with double-drive, single-chamber with single-drive in series and single-chamber with single-drive in parallel, as well as the mixed-chamber in series and parallel. After surveying the recent progresses made by dominant academia in the development of piezoelectric pump encompassing valve, with a particular emphasis on structure design of both valve and pump body, we also summarize and identify the future research directions.
Piezoelectric pump faces unprecedented challenges when higher expectation and requirements need to be met in their applications mainly to medical treatment, hygiene and public health, and preventive healthcare. Specifically, the piezoelectric pump with valve has the disadvantages of complex structure, high duty cycle of valves, and valve movement lagged behind piezoelectric ceramics oscillation. In an attempt to inhibit its shortcomings, some researchers presented novel concepts for structural design of piezoelectric pump with valve, which could become a new research focus. Among them, the investigation into various soft valves, represented by soft structure valves made of rigid materials and soft material valves made of flexible materials, has been fruitful in recent years. The integrated design of both material and structure can tackle the problems encountered in the study of piezoelectric pump with valve, thus simplifying the pump structure, reducing the duty-cycle of valves, and improving the lagging of valve motion. In addition, new inventions of pump structure have sprung up, such as the pumps containing a single-chamber with double-drive, single-chamber with single-drive in series and single-chamber with single-drive in parallel, as well as the mixed-chamber in series and parallel. After surveying the recent progresses made by dominant academia in the development of piezoelectric pump encompassing valve, with a particular emphasis on structure design of both valve and pump body, we also summarize and identify the future research directions.
2016, 33(3):274-284.
Abstract:
Based on computational fluid dynamics (CFD)/computational electromagnetics method (CEM) coupling method and surrogate model optimization techniques, an integration design method about aerodynamic/stealth characteristics of airfoil is established. The O-type body-fitted and orthogonal grid around airfoil is first generated by using the Poisson equations, in which the points per wave and the normal range satisfy the aerodynamic and electromagnetic calculation accuracy requirement. Then the aerodynamic performance of airfoil is calculated by solving the Navier-Stokes (N-S) equations with Baldwin-Lomax (B-L) turbulence model. The stealth characteristics of airfoil are simulated by using finite volume time domain (FVTD) method based on the Maxwell′s equations, Steger-Warming flux splitting and the third-order MUSCL scheme. In addition, based upon the surrogate model optimization technique with full factorial design (FFD) and radial basis function (RBF), an integration design about aerodynamic/stealth characteristics of rotor airfoil is conducted by employing the CFD/CEM coupling method. The aerodynamic/stealth characteristics of NACA series airfoils with different maximum thickness and camber combinations are discussed. Finally, by choosing suitable lift-to-drag ratio and radar cross section (RCS) amplitudes of rotor airfoil in four important scattering regions as the objective function and constraint, the compromised airfoil with high lift-to-drag ratio and low scattering characteristics is designed via systemic and comprehensive analyses.
Based on computational fluid dynamics (CFD)/computational electromagnetics method (CEM) coupling method and surrogate model optimization techniques, an integration design method about aerodynamic/stealth characteristics of airfoil is established. The O-type body-fitted and orthogonal grid around airfoil is first generated by using the Poisson equations, in which the points per wave and the normal range satisfy the aerodynamic and electromagnetic calculation accuracy requirement. Then the aerodynamic performance of airfoil is calculated by solving the Navier-Stokes (N-S) equations with Baldwin-Lomax (B-L) turbulence model. The stealth characteristics of airfoil are simulated by using finite volume time domain (FVTD) method based on the Maxwell′s equations, Steger-Warming flux splitting and the third-order MUSCL scheme. In addition, based upon the surrogate model optimization technique with full factorial design (FFD) and radial basis function (RBF), an integration design about aerodynamic/stealth characteristics of rotor airfoil is conducted by employing the CFD/CEM coupling method. The aerodynamic/stealth characteristics of NACA series airfoils with different maximum thickness and camber combinations are discussed. Finally, by choosing suitable lift-to-drag ratio and radar cross section (RCS) amplitudes of rotor airfoil in four important scattering regions as the objective function and constraint, the compromised airfoil with high lift-to-drag ratio and low scattering characteristics is designed via systemic and comprehensive analyses.
2016, 33(3):285-293.
Abstract:
The aerodynamic and aeroacoustic characteristics of a scissor tail-rotor in a forward flight are numerically calculated. A novel computational fluid dynamics (CFD) model based on Navier-Stokes (N-S) equations is presented to simulate the unsteady flowfield and the aerodynamic characteristics of a scissor tail-rotor in the forward flight. Then the Farassat Formulation 1A derived from the FW-H equation is coupled into the CFD model in order to compute the aeroacoustic characteristics of the scissor tail-rotor. In addition, two different scissor tail-rotor configurations, i.e., the L- and U-configuration, are analyzed in details and compared with a conventional one. The influence of scissor angles on the aerodynamic and aeroacoustic characteristics of the scissor tail-rotor is also investigated. The simulation results demonstrate that the flowfield, aerodynamic force and aeroacoustic characteristics of a scissor tail-rotor are significantly different from the conventional one, and the aerodynamic interaction decreases with the increase of scissor angle, which leads to a reduction of amplitude variation of the tail-rotor thrust in the forward flight. The scissor angle has an important effect on the aerodynamics and aeroacoustics of the scissor tail-rotor.
The aerodynamic and aeroacoustic characteristics of a scissor tail-rotor in a forward flight are numerically calculated. A novel computational fluid dynamics (CFD) model based on Navier-Stokes (N-S) equations is presented to simulate the unsteady flowfield and the aerodynamic characteristics of a scissor tail-rotor in the forward flight. Then the Farassat Formulation 1A derived from the FW-H equation is coupled into the CFD model in order to compute the aeroacoustic characteristics of the scissor tail-rotor. In addition, two different scissor tail-rotor configurations, i.e., the L- and U-configuration, are analyzed in details and compared with a conventional one. The influence of scissor angles on the aerodynamic and aeroacoustic characteristics of the scissor tail-rotor is also investigated. The simulation results demonstrate that the flowfield, aerodynamic force and aeroacoustic characteristics of a scissor tail-rotor are significantly different from the conventional one, and the aerodynamic interaction decreases with the increase of scissor angle, which leads to a reduction of amplitude variation of the tail-rotor thrust in the forward flight. The scissor angle has an important effect on the aerodynamics and aeroacoustics of the scissor tail-rotor.
2016, 33(3):294-300.
Abstract:
An asymmetric actuated 3-PPPS parallel mechanism was analyzed in its application to an aircraft wing adjustment process. The posture alignment precision at the wing ends was enhanced with a kinematic calibration method. A constraint equation was built based on a constraint condition that distances among spherical joints of the mechanism were constant, and further eight groups of analytic forward solutions of all poses of the mechanism were solved. An inverse equation of the posture alignment displacements of aircraft wing parts was built based on space vector chains, and a mapping equation of the pose and geometric errors of the posture alignment mechanism containing 39 error sources was derived by differentiating the kinematic equation of the mechanism. After kinematic calibration experiments, the maximum position error of the posture alignment platform dropped from 2.67 mm to 0.82 mm, the maximum angle error decreased from 0.481° to 0.167°, and the posture alignment precision of the aircraft wing end was improved.
An asymmetric actuated 3-PPPS parallel mechanism was analyzed in its application to an aircraft wing adjustment process. The posture alignment precision at the wing ends was enhanced with a kinematic calibration method. A constraint equation was built based on a constraint condition that distances among spherical joints of the mechanism were constant, and further eight groups of analytic forward solutions of all poses of the mechanism were solved. An inverse equation of the posture alignment displacements of aircraft wing parts was built based on space vector chains, and a mapping equation of the pose and geometric errors of the posture alignment mechanism containing 39 error sources was derived by differentiating the kinematic equation of the mechanism. After kinematic calibration experiments, the maximum position error of the posture alignment platform dropped from 2.67 mm to 0.82 mm, the maximum angle error decreased from 0.481° to 0.167°, and the posture alignment precision of the aircraft wing end was improved.
2016, 33(3):301-309.
Abstract:
A bionic shoulder joint with three degree-of-freedom (DOF) driven by pneumatic muscle actuator is proposed and its corresponding kinematic model is established. The bionic shoulder is optimized by particle swam optimization (PSO) with the fitness standards that the requirements of rotation indexes are met and the fluctuation of motion is kept in the lowest resolution in a pneumatic muscle actuator range. Simulation considering rotation indexes only (first simulation) is compared with the one considering both rotation indexes and motion resolution (second simulation) subsequently.Mounting position of the pneumatic muscle actuators in bionic shoulder is optimized after initializing the same condition in simulations. Results show that the fluctuations of parameters are consistent, and the parameters of the first simulation have good convergence than those of the second one. With the increase of stretch rate of the pneumatic muscle actuator, the needed length of fixed link in the center of static platform decreases in optimization.
A bionic shoulder joint with three degree-of-freedom (DOF) driven by pneumatic muscle actuator is proposed and its corresponding kinematic model is established. The bionic shoulder is optimized by particle swam optimization (PSO) with the fitness standards that the requirements of rotation indexes are met and the fluctuation of motion is kept in the lowest resolution in a pneumatic muscle actuator range. Simulation considering rotation indexes only (first simulation) is compared with the one considering both rotation indexes and motion resolution (second simulation) subsequently.Mounting position of the pneumatic muscle actuators in bionic shoulder is optimized after initializing the same condition in simulations. Results show that the fluctuations of parameters are consistent, and the parameters of the first simulation have good convergence than those of the second one. With the increase of stretch rate of the pneumatic muscle actuator, the needed length of fixed link in the center of static platform decreases in optimization.
2016, 33(3):310-318.
Abstract:
A robust attitude control methodology is proposed for satellite system with double rotary payloads. The dynamic model is built by the Newton-Euler method and then the dynamic interconnection between satellite′s main body and payloads is described precisely. A nonlinear disturbance observer is designed for satellite′s main body to estimate disturbance torque acted by motion of payloads. Meanwhile, the adaptive fast nonsingular terminal sliding-mode attitude stabilization controller is proposed for satellite′s main body to quicken convergence speed of state variables. Similarly, the adaptive fast nonsingular terminal sliding-mode attitude maneuver controller is designed for each payload to weaken the disturbance effect of motion of satellite′s main body. Simulation results verify the effectiveness of the proposed method.
A robust attitude control methodology is proposed for satellite system with double rotary payloads. The dynamic model is built by the Newton-Euler method and then the dynamic interconnection between satellite′s main body and payloads is described precisely. A nonlinear disturbance observer is designed for satellite′s main body to estimate disturbance torque acted by motion of payloads. Meanwhile, the adaptive fast nonsingular terminal sliding-mode attitude stabilization controller is proposed for satellite′s main body to quicken convergence speed of state variables. Similarly, the adaptive fast nonsingular terminal sliding-mode attitude maneuver controller is designed for each payload to weaken the disturbance effect of motion of satellite′s main body. Simulation results verify the effectiveness of the proposed method.
2016, 33(3):319-328.
Abstract:
A robust fault-tolerant control scheme is proposed for the longitudinal dynamics of an aircraft with input saturation, using the anti-windup method and the fault detection observer technology. To estimate the system fault, a detection observer is designed for the longitudinal dynamics, and a fault-tolerant control law is developed to compensate for the fault effects of the longitudinal dynamics. Then, an anti-windup compensator is augmented into the fault-tolerant control law to eliminate the effect of input saturation. Using linear matrix inequality (LMI) technology, the detection observer based fault-tolerant controller is designed to ensure the stability of the closed-loop system and the convergence of the detection observer. Finally, the developed robust fault-tolerant control scheme is applied to the longitudinal model of an aircraft and simulation results are presented to illustrate the effectiveness of the proposed control scheme.
A robust fault-tolerant control scheme is proposed for the longitudinal dynamics of an aircraft with input saturation, using the anti-windup method and the fault detection observer technology. To estimate the system fault, a detection observer is designed for the longitudinal dynamics, and a fault-tolerant control law is developed to compensate for the fault effects of the longitudinal dynamics. Then, an anti-windup compensator is augmented into the fault-tolerant control law to eliminate the effect of input saturation. Using linear matrix inequality (LMI) technology, the detection observer based fault-tolerant controller is designed to ensure the stability of the closed-loop system and the convergence of the detection observer. Finally, the developed robust fault-tolerant control scheme is applied to the longitudinal model of an aircraft and simulation results are presented to illustrate the effectiveness of the proposed control scheme.
2016, 33(3):329-338.
Abstract:
Digital images are frequently contaminated by impulse noise (IN) during acquisition and transmission.The removal of this noise from images is essential for their further processing. In this paper, a two-staged nonlinear filtering algorithm is proposed for removing random-valued impulse noise (RVIN) from digital images. Noisy pixels are identified and corrected in two cascaded stages. The statistics of two subsets of nearest neighbors are employed as the criterion for detecting noisy pixels in the first stage, while directional differences are adopted as the detector criterion in the second stage. The respective adaptive median values are taken as the replacement values for noisy pixels in each stage. The performance of the proposed method was compared with that of several existing methods. The experimental results show that the performance of the suggested algorithm is superior to those of the compared methods in terms of noise removal, edge preservation, and processing time.
Digital images are frequently contaminated by impulse noise (IN) during acquisition and transmission.The removal of this noise from images is essential for their further processing. In this paper, a two-staged nonlinear filtering algorithm is proposed for removing random-valued impulse noise (RVIN) from digital images. Noisy pixels are identified and corrected in two cascaded stages. The statistics of two subsets of nearest neighbors are employed as the criterion for detecting noisy pixels in the first stage, while directional differences are adopted as the detector criterion in the second stage. The respective adaptive median values are taken as the replacement values for noisy pixels in each stage. The performance of the proposed method was compared with that of several existing methods. The experimental results show that the performance of the suggested algorithm is superior to those of the compared methods in terms of noise removal, edge preservation, and processing time.
2016, 33(3):339-361.
Abstract:
RNA-sequencing (RNA-seq), based on next-generation sequencing technologies, has rapidly become a standard and popular technology for transcriptome analysis. However, serious challenges still exist in analyzing and interpreting the RNA-seq data. With the development of high-throughput sequencing technology, the sequencing depth of RNA-seq data increases explosively. The intricate biological process of transcriptome is more complicated and diversified beyond our imagination. Moreover, most of the remaining organisms still have no available reference genome or have only incomplete genome annotations. Therefore, a large number of bioinformatics methods for various transcriptomics studies are proposed to effectively settle these challenges. This review comprehensively summarizes the various studies in RNA-seq data analysis and their corresponding analysis methods, including genome annotation, quality control and pre-processing of reads, read alignment,transcriptome assembly, gene and isoform expression quantification, differential expression analysis, data visualization and other analyses.
RNA-sequencing (RNA-seq), based on next-generation sequencing technologies, has rapidly become a standard and popular technology for transcriptome analysis. However, serious challenges still exist in analyzing and interpreting the RNA-seq data. With the development of high-throughput sequencing technology, the sequencing depth of RNA-seq data increases explosively. The intricate biological process of transcriptome is more complicated and diversified beyond our imagination. Moreover, most of the remaining organisms still have no available reference genome or have only incomplete genome annotations. Therefore, a large number of bioinformatics methods for various transcriptomics studies are proposed to effectively settle these challenges. This review comprehensively summarizes the various studies in RNA-seq data analysis and their corresponding analysis methods, including genome annotation, quality control and pre-processing of reads, read alignment,transcriptome assembly, gene and isoform expression quantification, differential expression analysis, data visualization and other analyses.
12 Model Updating for High Speed Aircraft in Thermal Environment Using Adaptive Weighted-Sum Methods
2016, 33(3):362-369.
Abstract:
Model updating for aircraft in a high temperature environment (HTE) is proposed based on the hierarchical method. With this method, the problem can be decomposed into temperature field updating and dynamic structural updating. In order to improve the estimation accuracy, the model updating problem is turned into a multi-objective optimization problem by constructing the objective function which combined with residues of modal frequency and effective modal mass. Then the metamodeling, support vector regression (SVR) is introduced to improve the optimization efficiency, and the solution can be determined by adaptive weighted-sum method (AWS). Finally, the proposed method is tested on a finite element (FE) model of a reentry vehicle model. The results show that the multi-objective model updating method in HTE can identify the input parameters of the temperature field and structure with good accuracy．
Model updating for aircraft in a high temperature environment (HTE) is proposed based on the hierarchical method. With this method, the problem can be decomposed into temperature field updating and dynamic structural updating. In order to improve the estimation accuracy, the model updating problem is turned into a multi-objective optimization problem by constructing the objective function which combined with residues of modal frequency and effective modal mass. Then the metamodeling, support vector regression (SVR) is introduced to improve the optimization efficiency, and the solution can be determined by adaptive weighted-sum method (AWS). Finally, the proposed method is tested on a finite element (FE) model of a reentry vehicle model. The results show that the multi-objective model updating method in HTE can identify the input parameters of the temperature field and structure with good accuracy．
2016, 33(3):370-374.
Abstract:
A dynamometer was designed and manufactured to measure the joining force in the linear friction welding process. The error percentages of the dynamometer in the upset (x) and vibration (y) directions were 0.9% and 0.75%, respectively. The cross-sensitivity range of the dynamometer was 1.2%—3.3% in the two directions. The precision level satisfies the requirements of the dynamometer test. The joining force of the TC17 and TC11 heterogeneous titanium alloys in the linear friction welding process was used to test the manufactured dynamometer. The test results showed that the upset force was large, but the vibration force showed a smaller change in TC11 during the linear friction welding process. In addition, the upset and vibration forces of the linear friction welding were greater with a short welding time than those with a long welding time.
A dynamometer was designed and manufactured to measure the joining force in the linear friction welding process. The error percentages of the dynamometer in the upset (x) and vibration (y) directions were 0.9% and 0.75%, respectively. The cross-sensitivity range of the dynamometer was 1.2%—3.3% in the two directions. The precision level satisfies the requirements of the dynamometer test. The joining force of the TC17 and TC11 heterogeneous titanium alloys in the linear friction welding process was used to test the manufactured dynamometer. The test results showed that the upset force was large, but the vibration force showed a smaller change in TC11 during the linear friction welding process. In addition, the upset and vibration forces of the linear friction welding were greater with a short welding time than those with a long welding time.
2016, 33(3):375-385.
Abstract:
As an efficient cooling method for high heat flux field, spray cooling has a great application potential on aircraft directed energy weapon cooling. Based on previous research results, an experimental system of open-loop spray cooling was established, and the potassium chloride aqueous solutions and ethylene glycol aqueous solutions with different mass fractions were applied to investigate the influence of different additives on spray cooling system performance. Besides, theoretical analysis was conducted according to the droplet breakage principle and the characteristic parameters of fluid mechanics. The results indicate that heat transfer can be enhanced by adding potassium chloride up to a certain concentration and then decrease with higher concentration. Heat transfer is deteriorated with the increase of ethylene glycol concentration. Both of the two additives can reduce the freezing point of the system, and ethylene glycol is preferred to improve the application range of the system in consideration of the corrosion of salt solution.
As an efficient cooling method for high heat flux field, spray cooling has a great application potential on aircraft directed energy weapon cooling. Based on previous research results, an experimental system of open-loop spray cooling was established, and the potassium chloride aqueous solutions and ethylene glycol aqueous solutions with different mass fractions were applied to investigate the influence of different additives on spray cooling system performance. Besides, theoretical analysis was conducted according to the droplet breakage principle and the characteristic parameters of fluid mechanics. The results indicate that heat transfer can be enhanced by adding potassium chloride up to a certain concentration and then decrease with higher concentration. Heat transfer is deteriorated with the increase of ethylene glycol concentration. Both of the two additives can reduce the freezing point of the system, and ethylene glycol is preferred to improve the application range of the system in consideration of the corrosion of salt solution.
2016, 33(3):386-394.
Abstract:
Long-term and stable wireless sensor network (WSN) node′s operation should be included in large-scale unattended industrial production. Here a kind of WSN node applied to multiple large-scale industrial productions is designed by analyzing WSN technologies and its multiple applications, and studying the node′s practical operating environment. A new method for applying image-recognition technology realized initially by using plenty of expensive sensors is proposed to analyze video data. When the node is applied in such situations as unattended operation and field monitoring, solar power generator is adopted to provide energy for the node system by charging a battery. The communication between WSN and background monitoring center is realized by GPRS module, and the operation of node is managed by transplanting μC/OS-Ⅱ into the ARM7 kernel microprocessor. The results show that the WSN node designed in this paper can be applied to control information transmission of wild and unattended large-scale industrial applications with stable and reliable performance.
Long-term and stable wireless sensor network (WSN) node′s operation should be included in large-scale unattended industrial production. Here a kind of WSN node applied to multiple large-scale industrial productions is designed by analyzing WSN technologies and its multiple applications, and studying the node′s practical operating environment. A new method for applying image-recognition technology realized initially by using plenty of expensive sensors is proposed to analyze video data. When the node is applied in such situations as unattended operation and field monitoring, solar power generator is adopted to provide energy for the node system by charging a battery. The communication between WSN and background monitoring center is realized by GPRS module, and the operation of node is managed by transplanting μC/OS-Ⅱ into the ARM7 kernel microprocessor. The results show that the WSN node designed in this paper can be applied to control information transmission of wild and unattended large-scale industrial applications with stable and reliable performance.
2016, 33(3):395-402.
Abstract:
The performance of concrete beams repaired with epoxy mortar was investigated by constructing twelve beam specimens. All the beam specimens were subjected to a constant current for accelerated corrosion. Six specimens were corroded without subsequent reparation as a control group, and the other six beam specimens were corroded and repaired utilizing epoxy mortar. All specimens were tested to failure. During test process, we focused on the failure pattern of beam specimens, structural cracks, mid-deflections, bearing capacity, and probed into the influence of corrosion degree and repair of epoxy mortar on the performance of beam specimens. It was observed that corrosion-repaired beams in the loading test were in a bending failure pattern. It is obvious that cracking loads and bending stiffness of repaired beams and corrosion-repaired beams were larger than those of unrepaired beams and secondly-corroded beams. When the mass loss of main steel bars was smaller than 10%, the bearing capacity of the repaired beams was similar to that of the unrepaired beams. When the mass loss of main steel bars was larger than 10%, the bearing capacity of the repaired beams increased significantly compared with that of the unrepaired beams.
The performance of concrete beams repaired with epoxy mortar was investigated by constructing twelve beam specimens. All the beam specimens were subjected to a constant current for accelerated corrosion. Six specimens were corroded without subsequent reparation as a control group, and the other six beam specimens were corroded and repaired utilizing epoxy mortar. All specimens were tested to failure. During test process, we focused on the failure pattern of beam specimens, structural cracks, mid-deflections, bearing capacity, and probed into the influence of corrosion degree and repair of epoxy mortar on the performance of beam specimens. It was observed that corrosion-repaired beams in the loading test were in a bending failure pattern. It is obvious that cracking loads and bending stiffness of repaired beams and corrosion-repaired beams were larger than those of unrepaired beams and secondly-corroded beams. When the mass loss of main steel bars was smaller than 10%, the bearing capacity of the repaired beams was similar to that of the unrepaired beams. When the mass loss of main steel bars was larger than 10%, the bearing capacity of the repaired beams increased significantly compared with that of the unrepaired beams.
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