Modeling and active disturbance rejection control for sequential airdrop operations

With the assumption t at the motion acceleration of the cargo is unknown, the dynamic model that accords with the engineering practice of sequential cargo airdrop operations is derived by using the separation body method, which can describe the impact of the sequential moving cargos on the flight safety and airdrop-mission capacity. On this basis, a novel flight control method is designed based on the active disturbance rejection control (ADRC) theory. the system is decoupled and linearized through the nonlinear state error feedback; the total unknown disturbances, including unmolded dynamics and uncertainty, are estimated and compensated real-timely by the extended state observer. Moreover, with the consideration of the time-delay system, the ADRC is improved to enhance the accuracy and rapidity of the control system. Simulations are carried out under the condition that one transport aircraft performs sequential airdrop operations. The results verify that the desirable performance and robustness have been achieved and the proposed control method is quite competent for the sequential airdrop operations

Mechanical Characteristics of Precast Cracked Concrete under Freeze-Thaw-Load Action

Four types of precast double-cracked concrete specimens and non-cracked control group were prepared, and the specimens were subjected to freezing and thawing cycles and uniaxial compression tests, with a total of five freezing and thawing cycles, namely 0, 25, 50, 75 and 100, in order to analyse the fracture phenomena and mechanical properties of the specimens after freezing and thawing in uniaxial compression, and to determine the damage variables of the precast cracked concrete under the action of freezing and thawing loads on the basis of strain energy and fracture mechanics theories. The test results show that: (1) the crack aggregation mode generated by the compression damage of precast cracked specimens is mainly influenced by the crack inclination angle, when the crack inclination angle is 30°, the specimen undergoes wing tension aggregation, and when the crack inclination angle is 60°/90°, the specimen undergoes a mixed tension-shear aggregation mode; (2) After the freeze-thaw cycle test, the degree of deterioration of the prefabricated cracked specimens is significantly higher than that of the non-cracked specimens, and the loss of compressive strength and Young’s modulus of the specimens with crack inclination angle of 60° and 90° is the most severe, and the decrease of the stress-strain curve is the most obvious; (3) Based on fracture mechanics and damage-strain energy to derive the damage variables of the prefabricated cracked loaded specimens, and based on the Weibull function and the principle of equivalent effect of Lemaitre effect, the damage variables under freeze-thaw loading are also derived based on the Weibull function and Lemaitre equivalent strain principle

A visual XML query interface

As XML becomes more and more popular, easy-to-use and powerful XML query languages are in great need. Xing is a visual query and restructuring language for XML documents. The objective of this project is to develop a basic version of Xing, including a user-oriented XML query interface and a simple query translation implementation. The interface design is based on a visual document metaphor and the notion of document patterns and rules. End users do not have to be good at programming or XML syntax to use Xing. In this report, we describe the implementation for the Xing prototype, including GUI design, data structures and algorithms. We also compare the features of Xing with other XML query languages

Strong Variational Sufficiency for Nonlinear Semidefinite Programming and its Implications

Strong variational sufficiency is a newly proposed property, which turns out to be of great use in the convergence analysis of multiplier methods. However, what this property implies for non-polyhedral problems remains a puzzle. In this paper, we prove the equivalence between the strong variational sufficiency and the strong second order sufficient condition (SOSC) for nonlinear semidefinite programming (NLSDP), without requiring the uniqueness of multiplier or any other constraint qualifications. Based on this characterization, the local convergence property of the augmented Lagrangian method (ALM) for NLSDP can be established under strong SOSC in the absence of constraint qualifications. Moreover, under the strong SOSC, we can apply the semi-smooth Newton method to solve the ALM subproblems of NLSDP as the positive definiteness of the generalized Hessian of augmented Lagrangian function is satisfied.Comment: 23 page

An improved adaptive genetic algorithm for image segmentation and vision alignment used in microelectronic bonding

In order to improve the precision and efficiency of microelectronic bonding, this paper presents an improved adaptive genetic algorithm (IAGA) for the image segmentation and vision alignment of the solder joints in the microelectronic chips. The maximum between-cluster variance (OTSU) threshold segmentation method was adopted for the image segmentation of microchips, and the IAGA was introduced to the threshold segmentation considering the features of the images. The performance of the image segmentation was investigated by computational and experimental tests. The results show that the IAGA has faster convergence and better global optimality compared with standard genetic algorithm (SGA), and the quality of the segmented images becomes better by using the OTSU threshold segmentation method based on IAGA. On the basis of moment invariant approach, the microvision alignment was realized. Experiments were carried out to implement the microvision alignment of the solder joints in the microelectronic chips, and the results indicate that there are no alignment failures using the OTSU threshold segmentation method based on IAGA, which is superior to the OTSU method based on SGA in improving the precision and speed of the vision alignments