Optimal input design for hydrodynamic derivatives estimation of nonlinear dynamic model of AUV

Input design has a dominant role in developing the dynamic model of an autonomous underwater vehicle (AUV) through system identification. Optimal input design is the process of generating informative inputs that can be used to provide a good-quality dynamic model of AUV. In this paper, amplitude-modulated pseudo-random binary signal (APRBS) inputs are optimally designed in order to estimate the hydrodynamic derivatives of an AUV’s nonlinear dynamic model. The input controls are designed so as to minimize uncertainty in estimating hydrodynamic derivatives. The employed approach can design multiple inputs and apply constraints on an AUV system’s inputs and outputs. The genetic algorithm is utilized to solve the constraint optimization problem. The presented algorithm is used for designing the input signals of Hydrolab300 AUV, and the estimation obtained by these inputs is compared with that of zigzag maneuver. According to the results, the designed APRBS inputs improve the uncertainties that exist in estimating hydrodynamic derivatives better than zigzag inputs.     

The Stationary Nonlinear Boltzmann Equation in a Couette Setting with Multiple, Isolated L q -solutions and Hydrodynamic Limits

This paper studies the stationary nonlinear Boltzmann equation for hard forces, in a Couette setting between two coaxial, rotating cylinders with given indata of Maxwellian type on the cylinders. A priori estimates are obtained mainly in L², leading to multiple, isolated solutions together with a hydrodynamic limit control, based on asymptotic expansions together with a rest term.     

Computational NQR study of a boron nitride nanocone

Abstract  

The electronic structure of a boron nitride nanocone with 240° disclination, and some properties that derive from this structure, were studied by density-functional theory calculations. In the considered model there are only hexagonal rings, with the apex and mouth of the nanocone saturated by hydrogen atoms. The model was optimized, and then the nuclear quadrupole resonance parameters were calculated at the sites of ¹¹B and ¹⁴N nuclei. The results revealed that the nuclei in the boron nitride nanocone are divided into layers with similar electronic properties. The nuclei at the apex and mouth are very important for the electronic behavior of the nanocone, with ¹¹B playing the major role.     

Structural characterization and mechanical properties of electrospun silk fibroin nanofiber mats

The regenerated silk fibroin dissolved in formic acid was electrospun into nanofiber mats. Structural characteristics of the spun as received and methanol and ethanol treated fibers were examined using the Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction. Mechanical properties and air permeability of the electrospun mats were also studied. IR spectroscopy and X-ray diffractometry showed random coil conformation and amorphous structure for as-spun fibers while typical FTIR spectra and X-ray diffractograms of β-sheet crystalline structure were recorded for the methanol and ethanol treated fibers. The mechanical properties of the mats were found to be dependent on fiber diameter. The mats containing fibers with smaller diameter had higher tensile strength but lower breaking strain. Methanol and ethanol treatment enhanced tensile strengths of the mats at the expenses of their breaking strain. Air permeability and pore size of the mats are strongly associated with diameter of the electrospun fibers.     

Numerical solution of stochastic differential equations by second order Runge–Kutta methods

In this paper we propose the numerical solutions of stochastic initial value problems via random Runge–Kutta methods of the second order and mean square convergence of these methods is proved. A random mean value theorem is required and established. The concept of mean square modulus of continuity is also introduced. Expectation and variance of the approximating process are computed. Numerical examples show that the approximate solutions have a good degree of accuracy.     

Naphthalimide based disperse dyes for nylon 6 and polyester (pet) fibers: Synthesis and evaluation of technical properties in the presence of urea

Technical properties of two naphthalimide based disperse dyes on nylon 6 and polyester fibers were investigated in the presence of urea.The two naphthalimide based disperse dyes were synthesized.The dyes were purified and then fully characterized using ~1H-NMR,FTIR and melting point analysis.Dispersion of the dyes was prepared in water and applied on nylon 6 and PET fibers.The dyes offered good build-up properties on the substrates.In order to increase dye adsorption of the substrates,urea was added into...     

Quantum conductance investigation on carbon nanotube–based antibiotic sensor

Journal of Solid State Electrochemistry - Nanostructured carbon material (NSCM) based chemiresistive sensors are popular for sensing different analytes because of their high sensitivity, low cost,...     

Elongated Bacterial Pili as a Versatile Alignment Medium for NMR Spectroscopy

In NMR spectroscopy, residual dipolar couplings (RDCs) have emerged as one of the most exquisite probes of biological structure and dynamics. The measurement of RDCs relies on the partial alignment of the molecule of interest, for example by using a liquid crystal as a solvent. Here, we establish bacterial type 1 pili as an alternative liquid-crystalline alignment medium for the measurement of RDCs. To achieve alignment at pilus concentrations that allow for efficient NMR sample preparation, we elongated wild-type pili by recombinant overproduction of the main structural pilus subunit. Building on the extraordinary stability of type 1 pili against spontaneous dissociation and unfolding, we show that the medium is compatible with challenging experimental conditions such as high temperature, the presence of detergents, organic solvents or very acidic pH, setting it apart from most established alignment media. Using human ubiquitin, HIV-1 TAR RNA and camphor as spectroscopic probes, we demonstrate the applicability of the medium for the determination of RDCs of proteins, nucleic acids and small molecules. Our results show that type 1 pili represent a very useful alternative to existing alignment media and may readily assist the characterization of molecular structure and dynamics by NMR.