Rapid and Sensitive Determination of Trace Chloride Ion in Drinks Using Resonance Light Scattering Technique

A resonance light scattering (RLS) technique to determine chloride ions in drinks was developed. Chloride ions were found to bind Ag+ forming AgCl aggregates that produced intense resonance scattering light. Effects of factors such as acidity, ionic strength, and coexistent interferents on the RLS of AgCl aggregates were investigated. The pH of solution almost did not affect the production of RLS and few foreign species interfered with the detection of chloride ions. The resonance scattering light intensity at the maximum peak of 571 nm was linear to the concentration of chloride ions in the range of 1.42–8.52 ng mL−1 with a detection limit of 0.71 ng mL−1. To determine the feasibility of the proposed method, some samples of water and drinks were analyzed. The attained results were in agreement with that of ion-selective electrode method. Good recovery results were also obtained with the range of 94.08–105.63%. The sensitivity and selectivity of the RLS method are high enough to determine trace amounts of chloride ions without any significant interference from high concentration of other components such as common anions and cations

GA-Based Model Predictive Control of Semi-Active Landing Gear

AbstractSemi-active landing gear can provide good performance of both landing impact and taxi situation, and has the ability for adapting to various ground conditions and operational conditions. A kind of Nonlinear Model Predictive Control algorithm (NMPC) for semi-active landing gears is developed in this paper. The NMPC algorithm uses Genetic Algorithm (GA) as the optimization technique and chooses damping performance of landing gear at touch down to be the optimization object. The valve's rate and magnitude limitations are also considered in the controller's design. A simulation model is built for the semi-active landing gear's damping process at touchdown. Drop tests are carried out on an experimental passive landing gear systerm to validate the parameters of the simulation model. The result of numerical simulation shows that the isolation of impact load at touchdown can be significantly improved compared to other control algorithms. The strongly nonlinear dynamics of semi-active landing gear coupled with control valve's rate and magnitude limitations are handled well with the proposed controller

Terephthalic acid–2,2′-dimethyl-1,1′-(butane-1,4-di­yl)dibenzimidazole (2/3)

In the crystal structure of the title compound, 2C8H6O4·3C20H22N4, there are three independent 2,2′-dimethyl-1,1′-(butane-1,4-di­yl)dibenzimidazole mol­ecules, each of which lies on an inversion centre. The terephthalic acid mol­ecules are linked to adjacent 2,2′-dimethyl-1,1′-(butane-1,4-di­yl)dibenzimidazole mol­ecules via O—H⋯N hydrogen bonds

Finding the spectral radius of a nonnegative irreducible symmetric tensor via DC programming

The Perron-Frobenius theorem says that the spectral radius of an irreducible nonnegative tensor is the unique positive eigenvalue corresponding to a positive eigenvector. With this in mind, the purpose of this paper is to find the spectral radius and its corresponding positive eigenvector of an irreducible nonnegative symmetric tensor. By transferring the eigenvalue problem into an equivalent problem of minimizing a concave function on a closed convex set, which is typically a DC (difference of convex functions) programming, we derive a simpler and cheaper iterative method. The proposed method is well-defined. Furthermore, we show that both sequences of the eigenvalue estimates and the eigenvector evaluations generated by the method $Q$-linearly converge to the spectral radius and its corresponding eigenvector, respectively. To accelerate the method, we introduce a line search technique. The improved method retains the same convergence property as the original version. Preliminary numerical results show that the improved method performs quite well