Compressive sensing reconstruction based on weighted directional total variation

Directionality of image plays a very important role in human visual system and it is important prior information of image. In this paper we propose a weighted directional total variation model to reconstruct image from its finite number of noisy compressive samples. A novel self-adaption, texture preservation method is designed to select the weight. Inspired by majorization-minimization scheme, we develop an efficient algorithm to seek the optimal solution of the proposed model by minimizing a sequence of quadratic surrogate penalties. The numerical examples are performed to compare its performance with four state-of-the-art algorithms. Experimental results clearly show that our method has better reconstruction accuracy on texture images than the existing scheme.     

Sliding mode robust fault-tolerant control for uncertain systems with time delay

Considering the modeling uncertainties and external disturbance, a kind of sliding mode robust H∞fault-tolerant control method for time delay system with actuator fault is proposed. The upper-bound of the uncertainties is considered as a known constant, while the upper-bound of the actuator fault is unknown. A sufficient condition for the existence of an integral sliding mode dynamics is given in terms of linear matrix inequality(LMI). A novel adaptive law is given to estimate the unknown upper-bound of faults. On this basis, a type of sliding mode robust H∞fault-tolerant control law is designed to guarantee the asymptotic stability and the H_∞ performance index of the system. Finally, the simulation on quad-rotor semi-physical platform demonstrates the reliability and validity of the method.     

Research on reduction of Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> by biomass sawdust

The research on biomass reduction of Fe₂O₃ was carried out by using sawdust as reductant. The direct reducing agents in the biomass magnetization process were determined by comparing various biomass pyrolysis products with the reduction degree (divalent iron content in total iron), reduction temperature range and valence change of Fe₂O₃ in the reduction process. The microstructure variation of Fe₂O₃ at different stages was also analyzed by scanning electron microscopy (SEM). Nonisothermal thermogravimetric analysis (TGA) was applied to explore the thermal reduction process. The results show that the direct reducing substances in the biomass reaction with Fe₂O₃ are H₂ and bio-oil, and the reduction process can be divided into two steps: biomass pyrolyzing to release H₂ and bio-oil, and reductive volatiles reacting with Fe₂O₃. The two steps are relatively independent. The kinetic of the reduction reaction follows a first-order reaction kinetic model, with 88.99 kJ/mol activation energy and 9.55 × 10⁸ min^?1 frequency factor.     

Investigation on maneuverability of a twin-screw ship driven by one screw

It is possible for a twin-screw ship that one screw failure occurs during navigation, and the maneuverability in this case should be noticed by ship designers and operators. It is of great significance to evaluate the related risk. Firstly, a mathematical model for the twin-screw ship maneuvering motion with one failed screw is developed based on the maneuvering model group (MMG) equations, and verified by the model test results. Secondly, the maneuvering motions of a twin-screw liquefied natural gas (LNG) ship with one free rotating failure screw or with one locked failure screw are simulated and compared by using the mathematical model. It is shown that the numerical modeling results are in agreement with the model test results. Compared with those of normal navigation, the port turning ability of the ship with one failed port screw is better, but the starboard turning ability and yaw checking ability become worse. The maneuverability of the ship with locked failure screw is better than that with free failure screw, although the ship speed drops obviously.     

Warship spare parts configuration optimization for stock control: Investigating the gap between qualitative and quantitative constraints

This paper investigates the gap between qualitative and quantitative constraints in spare parts stock control, with specific reference to warship spare parts support projects. A critical literature review of theoretical contributions about qualitative or quantitative factors for warship spare parts warehouse management is firstly provided, which allows to analyze the reasons for this qualitative-quantitative gap by addressing the limitations of spare parts models developed in the literature. Therefore a model including cloud model, marginal analysis and Lagrange multiplier method (CML) for study is proposed in this paper to bridge the gap. The model is used to solve the mix-constraints (both qualitative and quantitative constraints are considered) problem in a logic decision diagram particularly at the different decision nodes of the diagram. Finally, verifying test results show that the algorithm is feasible and its optimal support project meets the needs of engineering practices.     

Control strategy research of a selective catalytic reduction system for heavy-duty application

An AdBlue dosing control strategy of the selective catalytic reduction(SCR) system is developed for a heavy-duty diesel(HDD) engine. The strategy includes a raw emission prediction model, an ammonia(NH_3)coverage prediction model, a transient heat hysteresis correction algorithm, an NH_3 leakage control model for transient operation conditions, and a feedback controller(FBC). FBC has been developed by using mathematical manipulation to change output signal of sensor based on cross-sensitivity of nitrogen oxide(NO_x) sensor to NH_3.The quantification of control parameters is based on experiments and Nyquist stability criterion. FBC is enabled in most test conditions to satisfy the stability requirements. NOxconversion(DeNO_x) efficiency of SCR system is 82.4% in European steady-state cycle(ESC) test and 80.3% in European transient cycle(ETC) test, while the leakage of NH_3 is under 10-5 volume fraction in average.     

A new fractal model of elastic,elastoplastic and plastic normal contact stiffness for slow sliding interface considering dynamic friction and strain hardening

The deflection properties of elastic stage, elastoplastic stage and plastic stage of elastomer were analyzed. Taking account of the kinetic friction force in friction interface and strain hardening in slow sliding interface, the elastic, elastoplastic and plastic normal contact stiffness model for harsh surface was established, which revised the Majumdar-Bhushan fractal model and made it more perfect. In the combination of macro and micro perspective, the effects of coarse surface fractal variables, kinetic friction force in the friction interface, material characters of the friction couples on the contact status and contact property were discussed by the study of digital analysis. Results imply that the normal contact stiffness improves with the increasing real contact area and normal contact load, and reduces with the augment of kinetic friction coefficient. When the kinetic friction coefficient is smaller than 0.3, the normal contact stiffness comprises a linear decrease with the increment of kinetic friction coefficient. When the kinetic friction coefficient is bigger than 0.3, the normal contact stiffness has an exponential decrease with the increasing kinetic friction coefficient.     

Minimum resistance ship hull uncertainty optimization design based on simulation-based design method

In the ship hull optimization design based on simulation-based design (SBD) technology, low precision of the approximate model leads to an uncertainty form of optimization model. In order to enable the approximate model with finite precision to maximize the effectiveness, uncertainty optimization method is introduced here. Wave resistance coefficient approximation model, built by back propagation (BP) neural network, is represented as a form of interval. Afterwards, a minimum resistance optimization model is established with the design space constituted by principal dimensions and ship form coefficients. Double-level nested optimization architecture is proposed: for outer layer, improved particle swarm optimization (IPSO) algorithm with learning factor improvement strategy is used to generate design variables, and for inner layer, modified very fast simulated annealing (MVFSA) algorithm is used to solve the objective function interval with uncertainty region. Cases calculation proves the effectiveness and superiority of uncertainty optimization method for ship hull SBD optimization design, thus providing a good way for finding optimal designs.     

Trade-off in optimizing energy consumption and end user quality of experience in radio access network

To reduce network access latency, network traffic volume and server load, caching capacity has been proposed as a component of evolved Node B (eNodeB) in the ratio access network (RAN). These eNodeB caches reduce transport energy consumption but lead to additional energy cost by equipping every eNodeB with caching capacity. Existing researches focus on how to minimize total energy consumption, but often ignore the trade-off between energy efficiency and end user quality of experience, which may lead to undesired network performance degradation. In this paper, for the first time, we build an energy model to formulate the problem of minimizing total energy consumption at eNodeB caches by taking a trade-off between energy efficiency and end user quality of experience. Through coordinating all the eNodeB caches in the same RAN, the proposed model can take a good balance between caching energy and transport energy consumption while also guarantee end user quality of experience. The experimental results demonstrate the effectiveness of the proposed model. Compared with the existing works, our proposal significantly reduces the energy consumption by approximately 17% while keeps superior end user quality of experience performance.