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A new control problem of roll-pitch seeker about the disturbance coupling is investigated in this work. Previous control strategies of roll-pitch seeker rarely considered the effects of the dynamic coupling disturbances from the missile angular motion, and because of the polar coordinate structure, the disturbance rejection strategies of yaw-pitch seeker cannot be utilized directly on roll-pitch seeker. Thus this article presents a new control strategy to improve the disturbance rejection ability of roll-pitch seeker. To analyze the disturbance coupling problem, the roll-pitch seeker model is derived with consideration of the missile body angular motion and torque disturbances. The motion equation of roll-pitch seeker shows that part of the dynamic coupling disturbance can be eliminated by certain choices of inertial parameters. The rest of disturbance is reduced by the stabilization loops using a differentiator-based disturbance compensation controller. Particularly, a missile body angular acceleration estimation method is designed for the compensator based on an adaptive differentiator. In addition, comparisons with other control strategies are carried out via numerical simulations, and the results confirm the effectiveness of the proposed method.

Highlights • A diffusive predator-prey system with time-delay and competitive interference is considered. • Time delay induced instability and Hopf bifurcation at coexisting equilibrium are obtained. • The direction of the Hopf bifurcation and stability of the bifurcating periodic solutions are determined. Abstract In this paper, we studied a diffusive predator-prey model with competitive interference and Crowley-Martin type functional response. The conditions for local stability of coexisting equilibrium are given by analyzing the eigenvalue spectrum. By using delay as bifurcation parameter, conditions for occurrence of Hopf bifurcation are also given. The property of bifurcating period solutions is investigated by calculating the normal form. Some numerical simulations are performed to support our theoretical result. Our conclusions show that diffusion and delay are two factors that should be considered in establishing the predator-prey model, since they can induce spatially bifurcating period solutions. [ABSTRACT FROM AUTHOR]

Abstract: The failure rate of the mixture of two normal distributions in an unequal variance case may have four changes in monotonicity. This work analyzes the conditions for which the four changes occur and others for which increasing failure rate and modified bathtub shape can be shown. [Copyright &y& Elsevier]

The absorption spectra of the praseodymium complex with 1-cyclopropyl-6-fluoro-1,4-dihydro-7-(4-ethyl-1-piperazinyl)-4-oxo-3-quinoline carboxylic acid hydrochloride (NNFX) has been studied by normal and derivative spectrophotometry. The complex showed maximum absorption at 350 nm at pH 6.0. The stoichiometry of the Pr-NNFX complex was calculated by the molar ratio and continuous variation methods. The ratio of Pr to NNFX was 1:3. The absorption bands of the 4f electron transitions of the praseodymium complex with NNFX are enhanced markedly, especially the wavelength at 481 nm. Using the third-derivative spectrum, the calibration graph is linear over the range 2.5 × 10–5–3.5 × 10–4mol dm–3for praseodymium. The detection limits (signal-to-noise ratio of 2) is 1.4 × 10–6mol dm–3. The relative standard deviation is 1.2% for 7.0 × 10–5mol dm–3of praseodymium. A method for the direct determination of praseodymium in rare earth mixtures with good accuracy and selectivity is described.

Through first-principles calculations, the photovoltaic properties of Cs2PdI6were investigated and found that (i) Cs2PdI6has a quasi-direct band gap nature, and strong p-d coupling of lower conduction bands is responsible for light electrons; (ii) dominant Pdiand Iidefects would be produced at a deep level in the band gap which acts as charge trapping states. Thus, should be passivated by suitable external doping, if Cs2PdI6works as a solar cell absorber; (iii) The Cs2Pd(I1-xBrx)6alloy is highly miscible. Tunable band gap depending on composition xhas a non-linear bowing behavior occurring a lowest band gap at composition Cs2Pd(I0.7Br0.3)6.