Review on the proceeding of automatic seedlings classification by computer vision

The classification of seedlings is important to ensure the viability of seedlings after transplantation and is acknowledged as a key factor in forestation and environmental improvement. Based on numerous papers on automatic seedling classification (ASC), the seedling grading theory, traditional grading methods, the background and the proceeding of ASC techniques are described. The automation of the measurement of seedling morphological characteristics by photoelectric meters and computer vision is studied, and the automatic methods of the current grading systems are described respectively. And the further researches on ASC by computer vision are proposed.

Robust adaptive dynamic surface control for nonlinear uncertain systems

We propose a new method for robust adaptive backstepping control of nonlinear systems with parametric uncertainties and disturbances in the strict feedback form. The method is called dynamic surface control. Traditional backstepping algorithms require repeated differentiations of the modelled nonlinearities. The addition of n first order low pass filters allows the algorithm to be implemented without differentiating any model nonlinearities, thus ending the complexity arising due to the 'explosion of terms' that makes other methods difficult to implement in practice. The combined robust adaptive backstepping/first order filter system is proved to be semiglobally asymptotically stable for sufficiently fast filters by a singular perturbation approach. The simulation results demonstrate the feasibility and effectiveness of the controller designed by the method.

Simulated and experimental investigation on discontinuous dynamic recrystallization of a near-α TA15 titanium alloy during isothermal hot compression in βsingle-phase field

A cellular automaton（CA） modeling of discontinuous dynamic recrystallization（DDRX） of a near-α Ti-6Al-2Zr-1Mo-1V（TA15） isothermally compressed in the β single phase field was presented.In the CA model,nucleation of the β-DDRX and the growth of recrystallized grains（re-grains） were considered and visibly simulated by the CA model.The driving force of re-grain growth was provided by dislocation density accumulating around the grain boundaries.To verify the CA model,the predicted flow stress by the CA model was compared with the experimental data.The comparison showed that the average relative errors were10.2%,10.1%and 6%,respectively,at 1.0,0.1 and 0.01 s^-1 of 1020 ℃,and were 10.2%,11.35%and 7.5%,respectively,at 1.0,0.1and 0.01 s^-1 of 1050 ℃.The CA model was further applied to predicting the average growth rate,average re-grain size and recrystallization kinetics.The simulated results showed that the average growth rate increases with the increasing strain rate or temperature,while the re-grain size increases with the decreasing strain rate;the volume fraction of recrystallization decreases with the increasing strain rate or decreasing temperature.

Connections on Phase Space of AutonomousMechanical Systems with Constraints

The covariance of a dynamical flow with respect of a connection on tangent burdle is put forward The connection of an autonomous constrained mechanical system is found whose geodesic equations are equations of motion of the systems The connection is determined by dynamical functions and constraints of the system of the system and is reduced to the usual dynarmical connection of the dynamical flow is second drder homogmogeneous one.

Discussion on Action and Potential of Fenlong Megascience in the Symbiosis between Human and Nature

The fourth new farming model Fenlong is identified as megascience for the first time. Fenlong can be directly applied to farming of farmland, remoulding of mortar black soil and saline alkali land and development of degraded grassland. Deep loosening can create huge soil reservoirs, reduce fertilization, promote indi- rectly the improvement of river water fisheries and water sources and the upgrading of shaping and hydropower industry, thus making a new round of mobilization and pooling of natural resources. As a result, the nature is able to produce good food needed by human, the spatial dimension of the land is increased, the natural pre- cipitation storage is increased, the flood and drought disasters are reduced, the eco-environment is improved, and the economic benefits are increased. Fenlong is not restricted to global application by ecological region and crop variety and is not subject to the time-space constraints for a hundred thousand years. On the basis of utilizing the heaven and earth resources, it brings about a huge effect of mega- science. Compare with traditional farming, the depth under the mode of Fenlong is increased by 2-3 times, the contents of nutrient, water, oxygen and microorganism in the soil are increased by 10%-200%, the content of pale salt is increased by 20%-40%, the temperature is increased by 2-4 ~C, and the photosynthetic efficiency of crops is improved by 10%. Under the cultivation mode of Fenlong, the yield of crop applied with no fertilizers is increased by more than 10%, crop yield is still in- creased by more than 5% when the application amount of chemical fertilizer is re- duced by 10%-20%. Under the farming mode of Fenlong combined with no in- crease in fertilization, the crop yield, crop quality, farming efficiency, natural precipi- tation storage and air humidity are increased by 10%-50%, 5%, 15%, 100% and 5%, respectively, and the emissions of methane and other gases are reduced by more than 5%. Even in mortar black soil, saline alkali land and degraded grassland, the yield is still increased by 15%-50%. These improvement effects can last for many years, helping achieve the real harmonious coexistence between human and nature.

Dynamic Response of Stepped Beams Under Impulsive Loading

Aim To analyze dynamic failure of aerospace strutures subjected lateral impulsive loading. Methods Structures were modeled as rigid-perfectly plastic free-free stepped beams. Basic equations of motion un set up for analysis. Results Final pat deformation and rigid motion solutions were determined for a uniform impulsive loading. The critical rupture conditions for a space shuttle and a missile were obtained. Conclusion Failure is possible for aerospace structures under a uniform impulsive loading, but it is mere difficult in space.

SYSTEM IDENTIFICATION OF ADAPTIVE TRUSS STRUCTURES USING PIEZOELECTRIC ACTIVE MEMBERS

Adaptive truss structures are a new kind of structures with integrated active members,whose dynamic characteristies can be beneficially modified to meet mission requirements.Active members containing actuating and sensing units are the major components of adaptive truss structures.Modeling of adaptive truss structures is a key step to analyze the structural dynamic characteristics.A new experimental modal analysis approach,in which active members are used as excitatiDn sources for modal test,has been proposed in this paper.The excitation forces generated by the active members, which are different from the excitation forces exerted on structures in the conventional modal test,are internal forces for the truss structures.The relation between internal excitation forces and external forces is revealed such that the traditional identification method can be adopted to obtain modal parameters of adaptive structures.Placement problem of the active member in adaptive truss structures is also discussed in this work. Modal test and analysis are conducted with a planar adaptive truss structure by using piezoelectric active members in order to verify the feasibility and effectiveness of the proposed method.

Optimization of deformation parameters of dynamic recrystallization for 7055 aluminum alloy by cellular automaton

In order to simulate the microstructure evolution during hot compressive deformation,models of dynamic recrystallization(DRX)by cellular automaton(CA)method for7055aluminum alloy were established.The hot compression tests were conducted toobtain material constants,and models of dislocation density,nucleation rate and recrystallized grain growth were fitted by leastsquare method.The effects of strain,strain rate,deformation temperature and initial grain size on microstructure variation werestudied.The results show that the DRX plays a vital role in grain refinement in hot deformation.Large strain,high temperature andsmall strain rate are beneficial to grain refinement.The stable size of recrystallized grain is not concerned with initial grain size,butdepends on strain rate and temperature.Kinetic characteristic of DRX process was analyzed.By comparison of simulated andexperimental flow stress–strain curves and metallographs,it is found that the established CA models can accurately predict themicrostructure evolution of7055aluminum alloy during hot compressive deformation.

Simulation and experimental study of dynamic recrystallization process during friction stir vibration welding of magnesium alloys

A two-dimensional cellular automaton(CA)model was utilized to analyze the effect of mechanical vibration on microstructure evolution of AZ91 alloy during friction stir welding(FSW).The simulated results,namely grain topology,grain size distribution,average grain size,and also the dynamic recrystallization(DRX)fraction were compared with measured data.The adequate comparability between FEM and experimental data shows that the CA method can be applied to the analysis of the microstructure progression during the friction stir welding of AZ91 alloy.It is concluded that the dislocation density during the friction stir vibration welding(FSVW)is higher than that in the FSW process and the process of nucleation and grain growth is faster for samples during FSVW compared to FSW.The grain size modification and DRX phenomenon with various vibration frequencies were also simulated in detail during FSVW.It is found that vibration makes nucleation start earlier and decreases the proportion of the incubation period and the percentage of recrystallization as vibration frequency improves.

Data⁃Based Feedback Relearning Algorithm for Robust Control of SGCMG Gimbal Servo System with Multi⁃source Disturbance

Single gimbal control moment gyroscope(SGCMG)with high precision and fast response is an important attitude control system for high precision docking,rapid maneuvering navigation and guidance system in the aerospace field.In this paper,considering the influence of multi-source disturbance,a data-based feedback relearning(FR)algorithm is designed for the robust control of SGCMG gimbal servo system.Based on adaptive dynamic programming and least-square principle,the FR algorithm is used to obtain the servo control strategy by collecting the online operation data of SGCMG system.This is a model-free learning strategy in which no prior knowledge of the SGCMG model is required.Then,combining the reinforcement learning mechanism,the servo control strategy is interacted with system dynamic of SGCMG.The adaptive evaluation and improvement of servo control strategy against the multi-source disturbance are realized.Meanwhile,a data redistribution method based on experience replay is designed to reduce data correlation to improve algorithm stability and data utilization efficiency.Finally,by comparing with other methods on the simulation model of SGCMG,the effectiveness of the proposed servo control strategy is verified.

Self-diffractionin Porous Silicon/PMMA-DR1 Composite Fil ms

Two-layer structure consisting of PS/PMMA-DR1 composite film planar waveguide layer on porous silicon cladding layer was fabricated in our experiment. The induced grating based on the third nonlinear optical properties was formed by interaction of two Nd∶YAG laser beams at 1064nm in the porous silicon/PMMA-DR1 waveguide. The diffraction efficiency of the first order diffracted light is measured to be about 0.2% of the total output.

Research on transformation from UML statechart to interface automata

This paper studies the problem of deriving an interface automata model from UML statechart, in which, interface automata is a formaliged model for describing component behavior in an open system, but there is no universal criterion for deriving behavior from component to construct the model. UML is a widely used modeling standard, yet it is very difficult to apply it to system verification and testing directly for its imprecise semantics. After analyzing the expression ability of the two models, several transforma- tion rules are defined and each step of transformation is described in detail, after that, the approach is illustrated with an example. The paper provides a method for acquiring interface automata and lays the foundation for related research.

Global Robust and Adaptive Output Feedback Dynamic Positioning of Surface Ships

A constructive method was presented to design a global robust and adaptive output feedback controller for dynamic positioning of surface ships under environmental disturbances induced by waves, wind, and ocean currents. The ship's parameters were not required to be known. An adaptive observer was first designed to estimate the ship's velocities and parameters. The ship position measurements were also passed through the adaptive observer to reduce high frequency measurement noise from entering the control system. Using these estimate signals, the control was then designed based on Lyapunov's direct method to force the ship's position and orientation to globally asymptotically converge to desired values. Simulation results illustrate the effectiveness of the proposed control system. In conclusion, the paper presented a new method to design an effective control system for dynamic positioning of surface ships.

Study on Characteristic of Electric Power Assist Steering System

A pinion-type electric power steering (EPS) equipped on a sedan is reached in this paper. A three-freedom dynamic model of this system is created. The variables affecting assist character is analyzed. The formulas of simpled steering resistance force and the relationship between assist gain and vehicle speed are presented for the first time. Assist character is found based on the parameters of a sedan at last. This assist character is fit for the control rule of the EPS system through analyzing this character. The assist character figure offers reference for system design and control. Furthermore, this research method has generality for assist character of different kinds of vehicles.

Fabric and Programming of Photoautotrophic Micro-propagation System Controlled by Dynamic Parameters

According to theory of photoautotrophic micro-propagation, and principle and technology of environmental engineering, an automatic control and regulation under photoautotrophic micro-propagation by plants was designed, which can be used for planting condition optimization of photoautotrophic micro-propagation and qualified industrialized production of seedlings.

Dynamic imaging of metallic contamination plume based on self-potential data

A dynamic imaging method for monitoring self-potential data was proposed.Based on the Darcy’s law and Archie’sformulas,a dynamic model was built as a state model to simulate the transportation of metallic ions in porous medium,and theNernst equation was used to calculate the redox potential of metallic ions for observation modeling.Then,the state model andobservation model form an extended Kalman filter cycle to perform dynamic imaging.The noise added synthetic data imaging testshows that the extended Kalman filter can effectively fuse the model evolution and observed self-potential data.The further sandboxmonitoring experiment also demonstrates that the self-potential can be used to monitor the activities of metallic ions and exactlyretrieve the dynamic process of metallic contamination.

Cellular automaton simulation of dynamic recrystallization behavior in V-10Cr-5Ti alloy under hot deformation conditions

The deformation behavior of V-10Cr-5Ti alloy was studied on the Gleeble-1500 thermomechanical simulator at the temperatures of 950-1350℃, and the strain rates of 0.01-10 s^-1. Based on the Arrhenius model, dislocation density model, nucleation model and grain growth model, a numerical cellular automaton (CA) model coupling simulation of hot deformation is established to simulate and characterize the microstructural evolution during DRX. The results show that the flow stress is fairly sensitive to the strain rate and deformation temperature. The error between the predicted stress by the Arrhenius model and the actual measured value is less than 8%. The initial average grain size calculated by the CA model is 86.25 μm, which is close to the experimental result (85.63 μm). The simulations show that the effect of initial grain size on the dynamic recrystallization microstructure evolution is not significant, while increasing the strain rate or reducing the temperature can refine the recrystallized grains.

Lateral static and dynamic characteristics of thin-walled box girder

To analyze the static and dynamic behaviors of the thin-walled box girder in its lateral webs in consideration of shear lag effect and shear deformation, an approach based on the minimum potential principle is introduced in this paper. Both static and dynamic response equations as well as the corresponding natural boundary conditions of the box girder are deduced. Meanwhile, three generalized displacement functions： w （x） , U（x） and O（x） are employed and their differences in the calculus of variation are quantitatively investigated. The comparison of finite shell element results with analytical results of calculation examples validates the feasibility of the proposed approach.

Adaptive Parameter Selection for Total Variation Image Deconvolution

In this paper,we propose a discrepancy rule-based method to automatically choose the regularization parameters for total variation image restoration problems. The regularization parameters are adjusted dynamically in each iteration.Numerical results are shown to illustrate the performance of the proposed method.

Maneuver and vibration reduction of flexible spacecraft using sliding mode/command shaping technique

A generalized scheme based on the sliding mode and component synthesis vibration suppression (CSVS) method has been proposed for the rotational maneuver and vibration suppression of an orbiting spacecraft with flexible appendages. The proposed control design process is twofold: design of the attitude controller followed by the design of a flexible vibration attenuator. The attitude controller using only the attitude and the rate information for the flexible spacecraft (FS) is designed to serve two purposes: it forces the attitude motion onto a pre-selected sliding surface and then guides it to the state space origin. The shaped command input controller based on the CSVS method is designed for the reduction of the flexible mode vibration, which only requires information about the natural frequency and damping of the closed system. This information is used to discretize the input so that minimum energy is injected via the controller to the flexible modes of the spacecraft. Additionally, to extend the CSVS method to the system with the on-off actuators, the pulse-width pulse-frequency (PWPF) modulation is introduced to control the thruster firing and integrated with the CSVS method. PWPF modulation is a control method that provides pseudo-linear operation for an on-off thruster. The proposed control strategy has been implemented on a FS, which is a hub with symmetric cantilever flexible beam appendages and can undergo a single axis rotation. The results have been proven the potential of this technique to control FS.