Simple laser vision sensor calibration for surface profiling applications

Due to the relatively large structures in the Oil and Gas industry, original equipment manufacturers (OEMs) have been implementing custom-designed laser vision sensor (LVS) surface profiling systems as part of quality control in their manufacturing processes. The rough manufacturing environment and the continuous movement and misalignment of these custom-designed tools adversely affect the accuracy of laser-based vision surface profiling applications. Accordingly, Oil and Gas businesses have been raising the demand from the OEMs to implement practical and robust LVS calibration techniques prior to running any visual inspections. This effort introduces an LVS calibration technique representing a simplified version of two known calibration techniques, which are commonly implemented to obtain a calibrated LVS system for surface profiling applications. Both calibration techniques are implemented virtually and experimentally to scan simulated and three-dimensional (3D) printed features of known profiles, respectively. Scanned data is transformed from the camera frame to points in the world coordinate system and compared with the input profiles to validate the introduced calibration technique capability against the more complex approach and preliminarily assess the measurement technique for weld profiling applications. Moreover, the sensitivity to stand-off distances is analyzed to illustrate the practicality of the presented technique.     

Nonlinear FCS-MPC strategy of NPC/H-5 L inverter based on satisfactory optimization algorithm

In the design of the cost function in the nonlinear finite control set model predictive control (FCS-MPC) system, the traditional method based on weighting factors demonstrates some limitations, such as the weighting factors adjusting and heavy predictive calculation due to the increased number of voltage vectors applied in controlling multilevel converters. This paper proposes a simplified FCS-MPC method based on common mode voltage satisfactory optimization, which could considerably reduce the predictive calculation by the optimized switch combination and simplify the cost function design. Moreover, satisfactory optimization is adopted to achieve the accuracy control of common-mode voltage amplitude without adjusting process of weighting factors. The simulation and experimental results verify the feasibility of this control strategy.     

Extraordinary acoustic transmission,symmetry, blaschke products and resonators

The phenomenon of extraordinary acoustic transmission ( eat) in a resonator, which has recently been investigated experimentally, is studied theoretically. It is shown that the combination of a single propagating mode and a symmetry orthogonal to the direction of propagation for a resonator leads to eat. This is accomplished by decomposing the problem using symmetry, the Blaschke product and the properties of functions of a single complex variable which have modulus one on the real axis. The conditions of a resonator requires that the solution has singularities in the analytic extension to complex frequencies (resonances) and it is precisely near these resonances that we observe eat. The condition of a Blaschke product requires that there is a zero at the complex conjugate of the singularity and eat occurs when the solution on the real axis passes between these complex conjugate pairs of poles and zeros. A detailed numerical study of the problem is conducted and we show that once the single mode of propagation or the symmetry is broken then eat (at least perfect transmission) no longer holds generally.     

Structural,magnetic and optical properties of vanadium doped zinc oxide: Systematic first-principles investigations

The electronic structural, magnetic and optical properties of pure and V-doped ZnO are investigated by first-principles calculations based on the density functional theory. With the introduction of V atoms, the spin-splitting near the Fermi level leads to a net magnetic moment of the system. A significant possibility of room temperature ferromagnetism (RTFM) originated from the Ruderman–Kittel–Kassuya–Yosida (RKKY) exchange is predicted. Oxygen vacancy is positive to enhance the ferromagnetism while zinc vacancy is negative. With respect to the optical properties, the presence of V atoms was found to have an obvious influence on the transmittivity, especially in the low energy region. A slight V-doping can keep a high optical transmission and smoothly modulate the optical bandgap.     

A fast wavelet block Jacobi method

In this paper, we develop a fast block Jacobi method for linear systems based on discrete wavelet transform (DWT). Traditional wavelet-based methods for linear systems do not fully utilize the sparsity and the multi-level block structure of the transformed matrix after DWT. For the sake of numerical efficiency, we truncate the transformed matrix to be a sparse matrix by letting the small values be zero. To combine the advantages of the direct method and the iterative method, we solve the sub-systems appropriately based on the multi-level block structure of the transformed matrix after DWT. Numerical examples show that the proposed method is very numerically effective.     

Versatile wideband balanced detector for quantum optical homodyne tomography

We present a comprehensive theory and an easy to follow method for the design and construction of a wideband homodyne detector for time-domain quantum measurements. We show how one can evaluate the performance of a detector in a specific time-domain experiment based on the electronic spectral characteristic of that detector. We then present and characterize a high-performance detector constructed using inexpensive, commercially available components such as low-noise high-speed operational amplifiers and high-bandwidth photodiodes. Our detector shows linear behavior up to a level of over 13 dB clearance between shot noise and electronic noise, in the range from DC to 100 MHz. The detector can be used for measuring quantum optical field quadratures both in the continuous-wave and pulsed regimes with standard commercial mode-locked lasers.     

Convergence and permanence of a delayed Nicholson’s Blowflies model with feedback control

In this paper, we study a generalized Nicholson??s Blowflies model with feedback control and multiple time-varying delays. Under proper conditions, we employ a novel proof to establish some criteria to guarantee the global exponential convergence and permanence of this model. Moreover, we give two examples to illustrate our main results.     

Localization of diffusion sources in complex networks with sparse observations

Locating sources in a large network is of paramount importance to reduce the spreading of disruptive behavior. Based on the backward diffusion-based method and integer programming, we propose an efficient approach to locate sources in complex networks with limited observers. The results on model networks and empirical networks demonstrate that, for a certain fraction of observers, the accuracy of our method for source localization will improve as the increase of network size. Besides, compared with the previous method (the maximum–minimum method), the performance of our method is much better with a small fraction of observers, especially in heterogeneous networks. Furthermore, our method is more robust against noise environments and strategies of choosing observers.     

Co1−xFe2+xO4 (x = 0.1, 0.2) anode materials for rechargeable lithium-ion batteries

A cobalt-poor or iron rich bicomponent mixture of Co_0.9Fe_2.1O₄/Fe₂O₃ and Co_0.8Fe_2.2O₄/Fe₂O₃ anode materials have been successfully prepared using simple, cost-effective, and scalable urea-assisted auto-combustion synthesis. The threshold limit of lower cobalt stoichiometry in CoFe₂O₄ that leads to impressive electrochemical performance was identified. The electrochemical performance shows that the Co_0.9Fe_2.1O₄/Fe₂O₃ electrode exhibits high capacity and rate capability in comparison to a Co_0.8Fe_2.2O₄/Fe₂O₃ electrode, and the obtained data is comparable with that reported for cobalt-rich CoFe₂O₄. The better rate performance of the Co_0.9Fe_2.1O₄/Fe₂O₃ electrode is ascribed to its unique stoichiometry, which intimately prefers the combination of Fe₂O₃ with Co_1−xFe_2+xO₄ and the high electrical conductivity. Further, the high reversible capacity in Co_0.9Fe_2.1O₄/Fe₂O₃ and Co_0.8Fe_2.2O₄/Fe₂O₃ electrodes is most likely attributed to the synergistic electrochemical activity of both the nanostructured materials (Co_1−xFe_2+xO₄ and Fe₂O₃), reaching beyond the well-established mechanisms of charge storage in these two phases.