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This article proposes barrier Lyapunov function-based guidance strategies to achieve target interception, by a seeker-equipped interceptor having a limited field-of-view (FOV), at a prespecified impact time. A novel approach to respect the FOV constraint, using the conditions on time-to-go of the engagement, is first proposed. Guidance commands are then derived to steer the course of the interceptor in a way so as to adhere to the necessary conditions. Guidance strategy is first derived for 3-D engagements, and then, the same for planar scenarios is presented as a special case. The set of achievable impact times for given initial conditions, while satisfying FOV constraints, is first obtained, and then, a way to expand the achievable range of impact time is suggested using a two-stage approach. The behavior of lead angle is analyzed, and it is shown that guidance commands remain nonsingular and converge to zero near interception. Simulations are shown to validate the efficacy of proposed methods for various initial engagement geometries. [ABSTRACT FROM AUTHOR]

This article proposes a guidance strategy that enables the interceptor to control its impact time against stationary targets, while also meeting the field-of-view (FOV) constraints of the on-board seeker. The guidance strategy, so designed, always keeps the target within its FOV using its seeker. A barrier Lyapunov function is used to meet the FOV constraints, and an approximate expression for the interceptor's lead angle is obtained analytically. This facilitates the computation, as well as control, of impact time. The proposed guidance consists of two stages, with the former stage being deviated pursuit, while during the latter stage, the deviation angle or lead angle decreases to zero. This, in turn, ensures a zero terminal lateral acceleration. Furthermore, through a cooperative selection of tuning parameters, simultaneous interception of the target by multiple interceptors (also called salvo) can be achieved. Simulations, that are run for different engagement scenarios and with varying tuning parameters, vindicate the efficacy of the proposed strategy. [ABSTRACT FROM AUTHOR]

In this article, a nonlinear three-dimensional guidance strategy for multiple identical constant speed interceptors is proposed to capture a stationary target simultaneously. To design this proposed guidance strategy, a proportional navigation based time-to-go estimate, without any small angle assumption, is used. Based on the maximum value of time-to-go estimates of all interceptors, the range error for each interceptors is computed. Sufficiency conditions for simultaneous capture are satisfied by ensuring the range errors and their rates converge to zero for all interceptors. The proposed guidance strategy employs Lyapunov and sliding-mode control-based techniques to achieve these sufficiency conditions. Simulation studies demonstrate that this proposed strategy performs satisfactorily for various geometric engagements and in the presence of a first-order autopilot. [ABSTRACT FROM AUTHOR]

This article proposes a leader–follower cooperative salvo guidance strategy to intercept nonmaneuvering targets by exploiting the advantages of supertwisting sliding mode control. An improved estimate of time-to-go, that does not assume interceptor's small heading angle, is used in the guidance design. This allows the guidance strategy to remain effective even for large initial heading of the interceptor. Under the action of supertwisting control, the error in impact time settles precisely to zero in finite time. The proposed guidance strategy provides robustness against uncertainties and a smooth control signal, along with finite-time convergence of error. The guidance performance has been shown for one-to-one engagement, and in a cooperative framework, to achieve a salvo in a predetermined time. Numerical simulations are presented for various engagement scenarios to aid the analysis, and illustrate the efficacy of the proposed guidance scheme, even under noisy environment. [ABSTRACT FROM AUTHOR]

The efficacy of Sargassum filipendula was evaluated for removal of Pb2+, Cd2+ and Ni2+ ions. All experiments were performed in a batch system to study the effects of contact time, pH, biosorbent dose, initial metal ion concentration and temperature on the biosorption process. The optimum pH for Pb2+, Cd2+ and Ni2+ ions biosorption was found to be 5.0, 6.0 and 5.0, respectively. The equilibrium time for Pb2+ ions was 40 min and for Cd2+ and Ni2+ ions was 60 min. The equilibrium experimental data were analyzed using the six isotherm models and six kinetic models. The results were best fitted by the Bangham, pseudo-second order and pseudo-first order kinetic models for Pb2+, Cd2+ and Ni2+ ions biosorption, respectively. The biosorption isotherm was better explained by Fritz isotherm for Pb2+ ions and Redlich–Peterson isotherm for Cd2+ and Ni2+ ions biosorption. The uptake capacities of S. filipendula for Pb2+, Cd2+ and Ni2+ ions were obtained as 367.94, 103.5 and 34.3 mg/g, respectively. According to the thermodynamic parameters, the biosorption process was spontaneous, feasible and endothermic in nature. The result obtained has shown that the order of metal ion binding affinity for S. filipendula was Pb2+ > Cd2+ > Ni2+ ions. [ABSTRACT FROM AUTHOR]

The removal of Pb +2 ions by Sargassum filipendula was studied using batch process. The biosorbent characterization was carried out by FESEM-EDX and FTIR techniques. Central composite design was used to optimize Pb +2 ions biosorption process by varying four different independent process parameters (temperature, pH, biosorbent dosage, and initial concentration of Pb +2 ions). The adequacy of response surface model was checked by analysis of variance (ANOVA). The optimum process parameters for the removal of Pb +2 ions were found as temperature (34.8 °C), pH (4.99), initial concentration (152.10 mg/L) and biosorbent dosage (0.49 g/L) at which 96% of removal were achieved. The predictive capabilities of six types of kinetic models and six types of adsorption isotherm models were examined for S. filipendula . For this study, Fritz isotherm model and Bangham kinetic model were found as best fitted models for the biosorption of Pb +2 ions. Desorption studies showed that after four consecutive biosorption-desorption cycles 77.53% and 90.84% of desorption and biosorption efficiency were achieved, respectively. The studied thermodynamic parameters showed that biosorption of Pb +2 ions on S. filipendula were feasible, spontaneous, and endothermic in nature. Thus, in view of experimental observations it can be concluded that S. filipendula can be used as an efficient biosorbent for Pb +2 ions biosorption from the aqueous solution. [ABSTRACT FROM AUTHOR]