Second-order Transfer Research Articles

Integral-Square-Error Based Normalized Relative Gain Array for the Input-Output Pairing and Equivalent Transfer Function Design of MIMO Processes

Input-output pairing effectively minimizes the loop interaction in MIMO processes and avoids integral instability. In this article, a modified Relative Normalized Gain Array is proposed for the Input-Output Pairing and design of the First-order and Second-order Equivalent Transfer function. The proposed modified Relative Gain Array (mRNGA) matrix is derived by Normalizing the Relative Gain Array matrix with a normalization factor, which is calculated by minimizing the Integral Square Error of the given MIMO process. After that, the first order and second order Equivalent Transfer function is design by the derived mRNGA matrix, which offers an improved estimation of the Effective open-loop transfer function of the given MIMO process. The proposed method is corroborated with the help of the Input-Output pairing examples up to the 5 × 5 MIMO processes and three ETF design example.

Performance of DC SQUID Second-Order Axial Gradiometer Response to Radio Frequency Interference

A low-Tc dc SQUID placed in a superconducting and magnetic shield is insensitive to magnetic interference, but not completely immune to the effects of radio frequency interference (RFI). Here, we investigated the effect of two orthogonal RF fields on the second-order axial gradiometer's transfer characteristics and noise characteristics. RF field induced phase shift of the V – $\Phi$ curve. The modulated spikes of RF field on the V – $\Phi$ curve and noise spectrum became significant with the RF field increasing. The white noise of the system increased to 12.5 $fT/\sqrt{\text{Hz}}$ with +10 dB axial RF field, nearly one and a half times of 8.5 $fT/\sqrt{\text{Hz}}$ without RFI. The working point jumping occurred under the radial RF field of +5 and +10 dB, and the white noise increased to 17.2 and 165.8 $fT\sqrt{\text{Hz}}$ , respectively. The reason of work point drift related to the magnetic flux coupling between the SQUID and pickup coil needs further studies.

Design and implementation of second-order microwave integrator

ABSTRACTIn this paper, a new design methodology is developed for the implementation of a second-order microwave integrator on microstrip circuit. Firstly, an existing digital first-order integrator with best magnitude and phase performance is adopted as a prototype to give digital second-order integrator transfer function. Then, by using the autoregressive process and a least mean square based error function, coefficients of the formulated second-order digital integrator are transformed into the impedance values of transmission line elements. Different sets of impedance values are obtained through the optimization process, and design with a highly accurate frequency response having maximum relative error value not more than 7.2% over the angular frequency range 0.18pi to 0.94pi is selected for implementation purpose. RT/Duroid 5880 is used to fabricate the proposed second-order microwave integrator design. Measured results for transmission coefficient S21(f) are found to follow theoretical values over the frequency range of 1.8 GHz to 8.6 GHz.

Kinetics of the outer-sphere oxidation of thiourea by heteropoly-α2-17-tungsto-1-vanadodiphosphate anion

Kinetics of the oxidation of thiourea (tu) by heteropoly-α2-17-tungsto-1-vanadodiphosphate anion, α2-[P2VVW17O62]7−, have been studied spectrophotometrically in aqueous acidic medium at 25 °C. At low pH (2.4–3.0), the neutral form of tu is the only reactive species. At higher pH (4.2–4.9), both neutral and deprotonated forms of tu participate in the reaction. The observed mixed-order kinetics suggest two parallel reactions: one in which the order in [tu] is unity, and a second in which it is two. In both cases, the order in [α2-[P2VVW17O62]7−] is unity. Based on the kinetic studies, a mechanism is proposed, in which a second-order proton-coupled electron transfer involving NH2CSNH2 and α2-[P2VVW17O62]7− proceeds through a sequential electron transfer, followed by proton transfer such that the reaction is an “activation-controlled” outer-sphere electron transfer process. By applying the Marcus equation, the self-exchange rate constants for the couples $${\text{NH}}_{2} {\text{CSNH}}_{2}^{ \cdot + }$$ /NH2CSNH2 and α2-[P2VVW17O62]7−/α2-[P2VIVW17O62]8− were evaluated.

Tunable electromagnetically induced transparency in a composite superconducting system

We theoretically propose an efficient method to realize electromagnetically induced transparency (EIT) in the microwave regime through a coupled system consisting of a flux qubit and a superconducting LC resonator. Driven by two appropriate microwave fields, the system will be trapped in the dark states. In our proposal, the control field of EIT is played by a second-order transfer rather than by a direct strong-pump field. In particular, we obtained conditions for electromagnetically induced transparency and Autler–Townes splitting in this composite system. Both theoretical and numerical results show that this EIT system benefits from the relatively long coherent time of the resonator. Since this whole system is artificial and tunable, our scheme may have potential applications in various domains.

First-Order and Second-Order Meshless Formulations of the Radiative Transfer Equation: A Comparative Study

In this article we compare the first- and second-order formulations of the radiative transfer equation (RTE) by using a diffuse approximation meshless (DAM) method. These formulations include the first-order radiative transfer equation (FORTE), the second-order radiative transfer equation (SORTE), and the even parity method. All of them are solved without upwinding treatment. In order to investigate the accuracy and cost, different radiative transfer problems in complex 2-D and 3-D geometries are considered. Prediction results obtained by the proposed methods are compared with other references in order to illustrate the performance of different formulations and of the meshless method.

Optimisation of wavelengths selection used for the multi-spectral temperature measurement by ordinary least squares method of surfaces exhibiting non-uniform emissivity

In this paper, a method based on the ordinary least squares method for optimising the wavelength selection used for the multi-spectral temperature measurement of surfaces exhibiting non-uniform temperature-depending emissivity is presented. The goal consists of minimising the standard deviation of the estimated temperature (optimal design experiment). Two methods for wavelengths selection are presented – sequential and global with or without constraints – on the spectral range. Then, the estimated temperature results obtained by two different models taking into account a second-order polynomial transfer function including the emissivity and for different number of parameters and wavelengths are compared. The first model is based on Wien’s approximation and fluxes ratio (as done in the bicolour temperature technique) and the other is based on the fluxes (Planck’s law but without fluxes ratio). Different selection criteria are presented. These points are treated from theoretical, numerical and experimental points of view.

Robust digital control of a DC–DC buck converter with low frequency samplings

A robust DC---DC converter which can covers extensive load change and also input voltage changes with one controller is needed. Then the demand to suppress output voltage change becomes still severer. We propose an approximate 2-degree-of-freedom (2DOF) digital controller which realized start-up response and dynamic load response independently. The controller makes a control bandwidth wider, and at the same time makes variations of the output voltage small at sudden changes of a load and an input voltage. In this paper, a new approximate 2DOF digital control system with additional zeros is proposed. Using the additional zeros, the second-order differential transfer characteristics between equivalent disturbances and a output voltage are realized. Therefore, the new controller makes variations of the output voltage smaller and the sudden changes of the load and the input voltage. This controller is actually implement on a DSP and is connected to the DC---DC converter. Experimental results demonstrate that this type of digital controller can satisfy given severe specifications with low frequency sampling.

Dynamics Simulation of Beam-Carried Cranes Based on Virtual Prototyping

Firstly this paper introduces the flexibility theory of virtual prototyping. Secondly a virtual prototype of rigid-flexible coupling model for beam-carried cranes is built, based on collaborative simulation platform by using the software of UG, ADAMS and ANSYS. Finally the response curves of the displacement for the girder’s centroid with step load and different frequency sine load were analyzed by virtual prototyping simulation. And the corresponding second-order system transfer function is given through the system identification. The result of simulation provided some theory basis for the structure design and optimization of beam-carried cranes.

Improved Iterative Convergence of the Finite-Element Method in the Solution of the Second-Order Radiative Transfer Equation by Modified Diffusion Synthetic Acceleration

A modified diffusion synthetic acceleration model is developed to improve the convergence of the second-order radiative transfer equation (SORTE). The model considers the influence of a diffusely reflecting boundary and adopts the P1 diffusion approximation to rectify the scattering source term of the SORTE and the reflecting term of the boundary condition. It can remarkably reduce the computational time in the solution of the SORTE, especially when the participating medium with intensive diffusely reflecting walls is simulated. The accuracy of the model is verified by comparing the results with those of the Monte Carlo method and the finite-element method without any accelerative technique. The effects of the emissivity of walls, the optical thickness, and the scattering albedo on the convergence are also investigated. The results indicate that the accuracy of the proposed model is reliable and its accelerative effect is significant for optically thick and scattering-dominated media with intensive diffusely reflecting walls.

DESIGN AND STABILITY ANALYSIS OF MIXED-MODE FILTERS CONTAINING ONLY GROUNDED CAPACITORS

In this paper, three dual-mode (mixed-mode) analog filters using only grounded capacitors and two to three second-generation current conveyors (CCIIs) are presented. The first proposed filter can provide a transimpedance-mode (TIM) second-order filter transfer function (TF), and is free from passive component matching constraints, which is advantageous in integrated circuit (IC) design. Other two mixed-mode filters having the property of tunability are derived from the first proposed filter. However, the developed filters in this work, like other active filters, suffer from nonidealities such as nonideal gain and parasitic impedance effects which increase the order of the filter TFs; accordingly, stability problem may arise. In this study, stability analysis using gain and phase margins is accomplished. To explain the claimed ideas, several computer simulations and an experimental test are performed.

Comparative Study on Accuracy and Solution Cost of the First/Second-Order Radiative Transfer Equations Using the Meshless Method

The direct collocation meshless (DCM) method is applied to solve and evaluate the performance of the second-order radiative transfer equation (SORTE) proposed by Zhao and Liu (Numer. Heat Transfer B, vol. 51, pp. 391–409, 2007). The SORTE transforms the original first-order radiative transfer equation (FORTE) into a form similar to a diffusion equation, so no additional artificial diffusion or upwinding treatment is needed in the numerical discretization for stabilization. In order to investigate the accuracy and cost of the direct collocation meshless method based on the SORTE, two typical radiative transfer problems are considered. These cases are also solved by the DCM approach and the least-squares collocation meshless (LSCM) approach based on the FORTE. Numerical results show that the DCM approach based on the SORTE is more accurate and stable than the DCM approach and the LSCM approach based on the FORTE. The convergence rate of the SORTE-based methods with increase of collocation point number is faster than that of the FORTE-based methods. For obtaining the same target accuracy, the DCM approach based on the SORTE is more efficient than the other two meshless methods based on the FORTE. In addition, the DCM approach based on the SORTE also exhibits higher accuracy in solving radiative transfer problems with complex geometries or discontinuous temperature distributions along the boundary.

Calculation of Total Integrated Noise in Analog Circuits

Electronic noise is a significant and fundamental issue in the design of analog circuits. In the widely used class of switched-capacitor circuits, the noise metric of interest is the so-called total integrated noise. Closed-form expressions for this quantity are unavailable in literature for all but the simplest circuit configurations that involve first- and second-order noise transfer functions. The lack of these expressions has prevented design automation and performance optimization without relying on repetitive simulations. In this paper we provide a general formula for calculating the total integrated noise in arbitrary circuits. The results are applied to two popular operational transconductance amplifier (OTA) circuits; a two-stage Miller-compensated architecture and a two-stage cascode-compensated topology. Simulations show that the calculated noise for these circuits is in close agreement with SPICE simulations.

Finite-Volume Solution of the Second-Order Radiative Transfer Equation: Accuracy and Solution Cost

The finite-volume method is applied to the second-order radiative transfer equation, proposed by Zhao and Liu, to study its accuracy and solution cost for two simple two-dimensional problems. The second-order equation leads to results that are accurate and bounded, but the iterative solution of the equations is expensive, especially for weakly participating media. The high cost is due mainly to the elliptic character of the second-order equation and the lack of diagonal dominance of the algebraic equations.

A Symmetric-Impulse Approximation Applied to the Faddeev Theory on the Charge Transfer Amplitude

Off-the-shell anomalous factors of the two-body Coulomb transition matrices appear in the integral form of the Faddeev second-order nuclear-electronic amplitude, for proton-hydrogen charge transfer scattering in a typical nlm → n′l′m′ transition. A symmetric-impulse approximation (SIA) is applied to eliminate these factors and an induction method is proposed to analytically calculate the remaining integrals. The nuclear-electronic amplitude is derived for the general case, and for totally symmetric collisions, in terms of generalized hypergeometric functions of two variables, F4, and of one variable, 3F2, respectively. The angular distribution of the second-order nuclear-electronic charge transfer amplitude shows the Thomas mechanism as a peak or a hump for symmetric and asymmetric collisions. There also exists a peak in the forward angular distribution of the second-order nuclear-electronic amplitude, which partly cancels the kinematic peak in the angular distribution of the charge transfer differential cross sections.

A multi-objective control approach for the synthesis of robust digital guidance laws

This paper proposes a new approach for the synthesis of robust digital guidance laws with the objective of achieving stable and accurate missile guidance despite parametric uncertainties in the missile flight control system dynamics, prescribed limits on missile acceleration, and digital implementation at possibly slow sampling rates. The proposed approach is characterized by two consecutive steps. Firstly, a robust continuous-time guidance law is designed using mixed H2-H∞ minimization and pole placement such that the effects of noise and parametric uncertainties are attenuated. To carry out this first step of the approach, missile flight control dynamics are modelled as second-order interval transfer functions, where bounded time-varying parameters characterize the missile flight envelope. Secondly, digital redesign of the robust continuous-time missile control system (including guidance and flight control) is performed by solving an optimal control problem. The proposed global digital redesign strategy results in robust performance for the closed-loop sampled-data missile control system for a wider range of sampling rates than those obtained with currently available approaches and can be readily implemented on commercially available software by following the step-by-step procedure described in the paper. Numerical simulations consisting of a missile pursuing a manoeuvring target, described by the so-called Singer model, demonstrate the effectiveness of the proposed approach.

Modelling the mean and turbulent structure of the summertime Arctic cloudy boundary layer

This paper addresses the problem of modelling the summertime Arctic cloudy boundary layer. Specifically we consider the problem of multi-layered clouds in the boundary layer that includes the decoupling of the turbulence between upper and lower clouds. A high-resolution one-dimensional model with second-order turbulence closure and spectral radiative transfer is used to simulate a case study that was obtained during the 1980 Arctic Stratus Experiment. The effects of radiation, large-scale vertical motion and drizzle are investigated in sensitivity studies. Results of this study show that radiative transfer is important to the maintenance of the multiple cloud layers, and suggest that weak rising vertical motion is the most favorable situation to maintain two separate cloud layers.

A control theory approach to the stability and transient analysis of the filtered-x LMS adaptive notch filter

A method is presented for analyzing the stability and transient response of the filtered-x LMS adaptive notch filter by formulating the problem in the complex weight domain and applying standard control theory. Examples are given for pure delay and second-order low-pass cancellation path transfer functions. The method is also extended to the multichannel case, where the eigenvalues of the equivalent open-loop transfer function matrix characterize the behavior. >

Kinetics, isotope effects of the reaction of 1-(4-nitrophenyl)-1-nitroalkanes with DBU in tetrahydrofuran and chlorobenzene solvents

The kinetics of the reaction of[Formula: see text](R = Me, Et, i-Pr; NPNE, NPNP, MNPNP respectively; L is H or D) with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) base in tetrahydrofuran (THF) and chlorobenzene (CB) solvents are reported. The products of these proton transfer reactions are ion pairs absorbing at λmax = 460–480 nm. The equilibrium constants in THF were [Formula: see text]and in CB [Formula: see text]for NPNE, NPNP, MNPNP respectively. The thermodynamic parameters of the reactions are also quoted. The substrate reacts with DBU in both THF and CB solvents in a normal second-order proton transfer reaction. In the case of deuteron transfer, isotopic D/H exchange is much faster than internal return. The reactions show low values of enthalpy of activation ΔH* = 14.3, 18.1, 24.2 and 13.0, 15.1, 18.6 kJmol−1 for NPNE, NPNP, and MNPNP in THF and CB respectively, and large negative entropies of activation −ΔS* = 141, 139, 146; 140, 146, 160 J mol−1 deg−1 for the same sequence of substrates and solvents. The kinetic isotope effects are large, (kH/kD)20°c = 12.2, 13.0, 10.1; 12.9, 12.0, 10.2 for the above sequence of substrates and solvents, and show no difference with changes in either steric hindrance of the C-acids or polarity of the solvents. Keywords: proton transfer, kinetic isotope effect.

Signal scaling in cascade digital filters

Scaling of filter variables is central to fixed-point implementation of digital filters. A simple method of scaling based on scaling constants of individual sections of a cascade digital filter is presented. The proposed method saves much computational labor in the implementation of higher-order digital filters. Maximal amplitude expressions of second-order filter transfer functions are also presented.