Unit Impulse Response Research Articles

Stability analysis in state space for non-driven MEMS gyro

The non-driven MEMS gyro is a new kind of micromechanical vibratory gyro, which has no a driving structure itself. The gyro is installed on a rotating aircraft and utilizes the spinning of the carrier to obtain an angular momentum. When the carrier produces a transverse rotation, a periodic Coriolis force acts on the sensitive mass of the MEMS gyro to sense the transverse input angular velocity of the rotating carrier. In applications, we found that the MEMS gyro is subjected to a high shock when the carrier begins to launch. If the sensitive mass cannot return to balance, the gyro will not work properly. So the stability of the gyro is the key issue on whether it can properly work. In this paper, we have analyzed the stability of the MEMS gyro in details by using Lyapunov stability principle for the first time. Firstly, based on the designed structural principle of the MEMS gyro, by using Euler dynamic equation of a rigid body rotating around a fixed point, we have described the angular vibration of the sensitive mass of the gyro and obtained its motion equation. The motion is the second order system. Then, we have chosen an appropriate state vector and established a state space model in state space for describing the motion of the sensitive mass. In order to research the stability of the designed MEMS gyro by using Lyapunov stability principle, a Lyapunov function needs to be found. Therefore, we have built a quadratic function and proved that its Lyapunov matrix equation has a solution. The matrix solution is symmetric and positive definite. Thus, the found quadratic function is a Lyapunov function. According to Lyapunov stability principle, the designed MEMS gyro is asymptotically stable. Next, utilizing numerical calculation, we have done the simulation of the unit-impulse response. The response curve has shown that the system of the designed MEMS gyro can come back to the balance after 160 ms. Finally, for further verification, the MEMS gyro is fixed on the shock table to test. The shock wave is a half-sine with the strength of 60 g and the impulse width of 80 ms. The tested result has demonstrated that the output signal of the designed MEMS gyro can again come back to zero state position after 150 ms under shock disturbance.

On the influence of far-field model reduction techniques using a coupled FEM-SBFEM approach in time domain

To analyse soil-structure-interaction problems, often unbounded domain has to be taken into account. Since the finite element method (FEM) does not provide open boundary itself the scaled boundary finite element method (SBFEM) which fulfils the radiation condition for wave propagation to infinity is used. The coupling of FEM and SBFEM in time domain is very time and memory consuming, due to the almost fully populated acceleration unit-impulse matrices and the convolution integral, which has to be solved at every time step. This paper studies ways to overcome this drawback and describes the influence of different model reduction techniques: like extrapolated acceleration unit-impulse response matrices, geometric far-field decoupling and sub-structured far-fields which can be applied to the far-field and also their combination. The different techniques for a FEM-SBFEM coupling in time domain are evaluated in terms of accuracy and computational effort.

Non-stationary vibration feature extraction method based on sparse decomposition and order tracking for gearbox fault diagnosis

Vibration signals of gearboxes working under time-varying conditions are non-stationary, which causes difficulties to the fault diagnosis. Based on the techniques of signal sparse decomposition and order tracking, a novel method is proposed to extract fault features from non-stationary vibration signals of gearboxes. The method contains two key procedures, the quasi-steady component separation in angle domain and the impact resonance component extraction in time domain. The sparse dictionary including quasi-steady sub-dictionary and impact sub-dictionary is specifically designed according to the time-frequency characteristics of steady-type fault and impact-type fault. The former sub-dictionary consists of cosine functions and is based on the order spectrum information of angle domain signal. The latter sub-dictionary consists of the unit impulse response of multiple-degree-of-freedom vibration system whose modal parameters are self-adaptively recognized by the method of correlation filtering. An improved matching pursuit algorithm on segmental signal is designed to solve sparse coefficients and reconstruct steady-type fault components and impact-type fault components. The simulation analyses show that the proposed method is capable to process the signal with 30% speed fluctuation and −1.5 dB signal-to-noise ratio (SNR), in which the SNR of impact-type fault components is as low as −14.6 dB. The effectiveness is further verified by experimental tests on a fixed-shaft gearbox and a planetary gearbox.

A novel time-domain linear ringdown method based on vector fitting for estimating electromechanical modes

This paper proposes a novel method, called Ringdown Time-Domain Vector Fitting (RTD-VF), for estimating electromechanical modes in interconnected power systems. Such a method authentically extends, to the context of ringdown analysis, the well known Time-Domain Vector Fitting (TD-VF) method, which has already been successfully applied within other power systems areas. The proposed method is based on a state-space discretization framework which enables ringdown events to be effectively estimated when described as artificial unit impulse responses. Moreover, RTD-VF completely avoids the necessity to perform discrete Fourier transforms (DFTs) of ringdown data sequences. Three case studies are used to validate the proposed method. One of the examples considers a synthetic test signal, whereas the other two case studies consider actual ringdown data sets extracted from the North American Eastern Interconnection (NAEI) system and from the Brazilian Interconnected Power (BIP) system.

Determinants of Credit and Financing Risk: Evidence of Dual Banking System in Indonesia

Given the fact that banking is the backbone of the Indonesian economy with a dual banking system. This paper seeks determinants of default rate in Indonesia. Various techniques of econometric tools such as unit root, co-integration test and Impulse Response Function (IRF) utilized. Bank capital has similar influence on the own credit or financing risks. Overall economic performance has a different result to the risk. Among the recommendations are for the government to maintain economic performance to keep default rate as low as possible. Financing Deposit Ratio-based Reserve Requirement policy (which is adopted only in Indonesia) imposed by the central bank seems to be effective in developing the real sector and should adopt in conventional banks. DOI: 10.15408/aiq.v10i1.5903

Graphical User Interface Design of FIR Filter

FIR digital filter is a stable linear phase filter. Relying on the powerful computing power of MATLAB software and its GUI platform, this graduation project has completed the GUI design and implementation of FIR digital filter through programming. Through the FIR filter to achieve the program, you can design and implement a variety of amplitude characteristics of the FIR digital filter, according to the user input filter design indicators, select the corresponding filter design method (window function, frequency sampling method) to design the corresponding filter. According to the different amplitude characteristics, the parameters of the filter design parameters will change accordingly; when the Kaiser window design filter is selected, the user is allowed to input the stopband attenuation of the filter; when using the frequency sampling method to design the filter, the user must input the filter length and the transition zone sample value; when the parameter is entered incorrectly, the system will prompt for an error message. GUI can also provide intuitive filter amplitude characteristics, phase characteristics and the unit impulse response graphics to help users to confirm whether the design of the filter meets the design specifications; by setting the global shortcut keys, the user after all parameters and options is confirmed by the Shortcut keys to achieve the rapid implementation of filter design.

Determinants of Credit and Financing Risk: Evidence of Dual Banking System in Indonesia

Given the fact that banking is the backbone of the Indonesian economy with a dual banking system. This paper seeks determinants of default rate in Indonesia. Various techniques of econometric tools such as unit root, co-integration test and Impulse Response Function (IRF) utilized. Bank capital has similar influence on the own credit or financing risks. Overall economic performance has a different result to the risk. Among the recommendations are for the government to maintain economic performance to keep default rate as low as possible. Financing Deposit Ratio-based Reserve Requirement policy (which is adopted only in Indonesia) imposed by the central bank seems to be effective in developing the real sector and should adopt in conventional banks. DOI: 10.15408/aiq.v10i1.5903

Response covariance-based sensor placement for structural damage detection

One important function of a structural health monitoring system is to detect structural damage in a structure. However, this is a very challenging task since the measurement is often incomplete in a civil structure due to a limited number of sensors. This paper presents a response covariance-based sensor placement method for structural damage detection with two objective functions for optimisation. The relationship between the covariance of acceleration responses and the covariance of unit impulse responses of a structure subjected to multiple white noise excitations is first derived. The response covariance-based damage detection method is then presented. Two objective functions based on the response covariance sensitivity and the response independence are, respectively, formulated and finally integrated into a single objective function for optimal sensor placement. Numerical studies are conducted to investigate the feasibility and effectiveness of the proposed method via a three-dimensional frame structure. Numerical results show that the proposed method with the backward sequential sensor placement algorithm is effective for damage detection.

Deconvolution-based real-time neutron flux reconstruction for Self-Powered Neutron Detector

Self-Powered Neutron Detector (SPND) is useful for in-core neutron flux measurement in nuclear reactors due to its tiny size, simple structure, ruggedness and self-powered feature. One type of SPNDs with delayed current from instable intermediate nuclides cannot directly represent the real-time in-core neutron flux Φ(t) by their current I(t), which should be avoided during reactor control and protection. In this paper, we proposed a deconvolution-based method to reconstruct real-time neutron flux for SPND. Following the establishment of dynamic model, the unit-impulse response function h(t) was easily obtained when neutron flux was unit-impulse. Then, the iterative compensation relations were established for delay compensation according to the convolution relationship I(t) = Φ(t) * h(t). In the meanwhile, determination methods for initial values were also proposed and the compensation performance for jump neutron flux was demonstrated to be only 0.3 s. Furthermore, the dependences on initial conditions and sampling time interval were studied systematically, indicating our method is effective and robust. Finally, our method has been compared with a typical compensation method and validated with measured current, showing its advantages. This method is very attractive due to its obvious simplicity, high intuitiveness and general applicability.

Transient response of vibration systems with viscous-hysteretic mixed damping using Hilbert transform and effective eigenvalues

This paper presents the time response of a mixed vibration system with the viscous damping and the hysteretic damping. There are two ways to derive the time response of such a vibration system. One is an analytical method, using the contour integral of complex functions to compute the inverse Fourier transforms. The other is an approximate method in which the analytic functions derived by Hilbert transform are expressed in the state space representation, and only the effective eigenvalues are used to efficiently compute the transient response. The unit impulse responses of the two methods are compared and the change in the damping properties which depend on the viscous and hysteretic damping values is investigated. The results showed that the damping properties of a mixed damping vibration system do not present themselves as a linear combination of damping properties.

A New Integer Order Approximation Table for Fractional Order Derivative Operators

There is considerable interest in the study of fractional order calculus in recent years because real world can be modelled better by fractional order differential equation. However, computing analytical time responses such as unit impulse and step responses is still a difficult problem in fractional order systems. Therefore, advanced integer order approximation table which gives satisfying results is very important for simulation and realization. In this paper, an integer order approximation table is presented for fractional order derivative operators (sa) where α ϵ R and 0 < α < 1 using exact time response functions computed with inverse Laplace transform solution technique. Thus, the time responses computed using the given table are almost the same with exact solution. The results are also compared with some well-known integer order approximation methods such as Oustaloup and Matsuda. It has been shown in numerical examples that the proposed method is very successful in comparison to Oustaloup’s and Matsuda’s methods.

Froude-Krylov forces from exact pressure integrations on adaptive panel meshes in a time domain partially nonlinear model for ship motions

A partially nonlinear time domain model for predicting ship motions is presented with Froude-Krylov forces being calculated on the exact instantaneous wet part of the floating body. An adaptive mesh technique following a quad-tree subdivision and cutting scheme is applied, in order to track the free-surface of the undisturbed wave, and its intersection with the hull, to generate instantaneous wet meshes. Analytical exact pressure integration expressions are evaluated on the, thus formed, wet panel mesh, regarding the undisturbed wave and hydrostatic pressures, which allow for considerably coarse meshes without any loss of accuracy. Diffraction and radiation forces are kept linear with the latter being introduced using linear unit impulse response functions. The body is impeded from drifting by artificial kinematic restrains in non-restoring modes.Roll decay motions of a military vessel's hull, and under head, beam and quartering waves are numerically predicted and compared with published experimental ones, for zero advance speed. The capabilities and limitations of the proposed method, taking into account the specific simulation setup applied, are addressed. An overall agreement with the experiments is witnessed, with the method showing a considerable improvement of numerical predictions of the ship motions in beam and quartering waves in comparison with those by a linear method.

Analysis of transient wave scattering and its applications to site response analysis using the scaled boundary finite-element method

In this paper, the problem of scattering and amplification of seismic waves by topographical and geological irregularities is addressed directly in the time domain through the scaled boundary finite-element method (SBFEM). The quadtree domain decomposition technique is utilized for the SBFEM discretization of the near field. The far field is rigorously modeled by the displacement unit-impulse response matrix. The computational cost of analyses is reduced through using local formulations in space and time. Considering incident fields of obliquely plane waves coming from far field, the seismic wave inputs are formulated as boundary tractions applied to the near field. Implementing all these aspects in the SBFEM, leads to an elegant technique for time-domain modeling of seismic wave propagation in heterogeneous media with topographical irregularities. Four numerical examples considering various site effects and wave patterns demonstrate the accuracy, versatility and applicability of the approach.The approach is straightforwardly applicable to nonlinear and 3D wave scattering problems with complex site effects.

Application of an NLME–Stochastic Deconvolution Approach to Level A IVIVC Modeling

Stochastic deconvolution is a parameter estimation method that calculates drug absorption using a nonlinear mixed-effects model in which the random effects associated with absorption represent a Wiener process. The present work compares (1) stochastic deconvolution and (2) numerical deconvolution, using clinical pharmacokinetic (PK) data generated for an in vitro–in vivo correlation (IVIVC) study of extended release (ER) formulations of a Biopharmaceutics Classification System class III drug substance. The preliminary analysis found that numerical and stochastic deconvolution yielded superimposable fraction absorbed (Fabs) versus time profiles when supplied with exactly the same externally determined unit impulse response parameters. In a separate analysis, a full population-PK/stochastic deconvolution was applied to the clinical PK data. Scenarios were considered in which immediate release (IR) data were either retained or excluded to inform parameter estimation. The resulting Fabs profiles were then used to model level A IVIVCs. All the considered stochastic deconvolution scenarios, and numerical deconvolution, yielded on average similar results with respect to the IVIVC validation. These results could be achieved with stochastic deconvolution without recourse to IR data. Unlike numerical deconvolution, this also implies that in crossover studies where certain individuals do not receive an IR treatment, their ER data alone can still be included as part of the IVIVC analysis.

Optimal Wavelet Selection for the Size Estimation of Manufacturing Defects of Tapered Roller Bearings with Vibration Measurement using Shannon Entropy Criteria

Fault diagnosis of bearings is essential in manufacturing to increase quality. Traditionally, fault diagnosis of tapered roller element bearings is performed by signal processing methods, which handle the nonstationary behaviour of the signal. The wavelet transform is an efficient tool for analysing the vibration signal of the bearings because it can detect the sudden changes and transient impulses in the signal caused by faults in the bearing elements. In this article, manufacturing faults on the outer ring of tapered roller bearings due to the grinding process in manufacturing are investigated. Nine different real values wavelets (Symlet-2, Symlet-5, Symlet-8, db02, db06, db10, db14, Meyer, and Morlet) are compared according to the Energy-to-Shannon-Entropy ratio criteria, and which is efficient for detecting the manufacturing faults is determined. Finally, experiments are carried out on a test rig for determining the geometrical size of the manufacturing faults with all wavelets directly from the vibration signature the result of db02, Symlet-5, and Morlet wavelets are presented. When modelling the bearing structure as an under-damped second-order mass-spring-damper mechanical system, its unit impulse response function is compared to the wavelets on the basis of their Energy-to-Shannon-Entropy ratio to determine the fault size from the vibration signal. The proposed technique has been successfully implemented for measuring defect widths. The maximum deviation in result has been found to be 4.12 % for the defect width which was verified with image analysis methods using an optical microscope and contact measurement.

Stability of initialization response of fractional oscillators

Application of fractional calculus representations, shortly termed as fractional constitute relations becomes an effective and powerful technique to characterize the rheological behavior of viscoelastic materials. Research on fractional oscillators provides a novel approach to deal with viscoelastically damped structures. This paper firstly investigates the memory effects or historical effects on dynamical responses of fractional oscillators via numerical simulations. Then the stability of initialization response is proved based on the unit impulse response function and the Lyapunov stability theorem for fractional differential equations. The main conclusion in this paper is that the stability of initialization responses of fractional oscillators is irrelevant to initial conditions or prehistory.

Transmitting boundary for transient analysis of wave propagation in layered media formulated based on acceleration unit-impulse response

An efficient transmitting boundary (TB) is developed for transient analysis of scalar wave as well as vector wave motion in layered media of constant depth, it is suited for both waves propagating out to infinity and for evanescent waves. The TB is formulated based on the acceleration unit-impulse response, such that singular term does not present, which results in simplifying the solution. The scaled boundary finite element method (SBFEM) is employed for the derivation. For numerical implementation, the very efficient scheme proposed by Radmanović and Katz is applied for the solution of the acceleration unit-impulse response matrix and the evaluation of interaction forces, significant reduction of computational effort can be achieved. In comparison with the various schemes of TBs available in the literature, the proposed approach has following advantages: it is accurate, the computational cost is less and stability of the solution can be ensured. The extension to the case of orthogonal anisotropic media can be performed without extra effort.

Optimal least squares model approximation for large-scale linear discrete-time systems

A new computationally simple and precise model approximation method is described for large-scale linear discrete-time systems. By least squares matching of a suitable number of time moment proportionals and Markov parameters about [Formula: see text] of the original higher order system within the approximate model, stable denominator polynomial coefficients of the approximate model are determined. To improvise the accuracy of the approximate model, numerator polynomial coefficients are determined by minimizing the integral squared error (ISE) between the unit impulse responses of the original system and its approximate model. A matrix formula is formulated for evaluating numerator coefficients of the approximate model that leads to minimum ISE, and also for evaluating ISE. The efficacy of the proposed method is shown by illustrating three typical numerical examples employed from the literature, and the results are compared with many familiar reduction methods in terms of the ISE and relative ISE values pertaining to impulse input. Furthermore, time and frequency responses of the original system and the respective approximate model are plotted.

CO2 Emissions and Economic Growth of SAARC Countries: Evidence from a Panel VAR Analysis

The paper examined the causality in both static and dynamic framework between CO2 emissions and economic growth of SAARC countries over the period 1972-2010 using panel approach. The paper presents the facts obtained on the basis of panel unit root test, panel-co-integration test , panel VECM and Impulse Response functions (IRFs) and Variance decomposition (VDs). IRFs and VDs analysis indicate that CO2 emissions, GDP have positive impact on each other. The result from the application of VECM analysis suggests unidirectional causality running from economic growth to CO2 emissions. The result found contradicts the Environmental Kuznets Curve hypothesis.

Development and Validation of an In Vitro and In Vivo Correlation Model in NZ Rabbit for Topiramate Extended Release Capsules

The purpose of this study was to build an in vitro-in vivo correlation model for topiramate extended release capsules. Three formulations with different release rate were developed by varying the percentage of the rate controlling polymer ethylcellulose and pore former hypromellose. In vitro dissolution of all formulations was performed by united states of phaemacopiea type I apparatus using multimedia dissolution conditions such as 0.1 N hydrochloric acid pH 1.2 for initial 2 h followed by phosphate buffer pH 6.8 for the rest of 22 h. Total dissolution time was up to 24 h. In vivo pharmacokinetic profile of the immediate release suspension and different extended release formulations were investigated in rabbit model after single oral administration of topiramate at a dose of 10.33 mg/kg in vitro-in vivo correlation model was established by using two stage numerical deconvolution approaches. Unit impulse response was obtained from pharmacokinetic profile of immediate release suspension which was used as a reference formulation. A linear correlation model with a time scaling factor was found to be useful to build level A correlation. The developed in vitro-in vivo correlation model was validated as per food drug administration guideline, and the % prediction error for maximum concentration observed (Cmax) and area under the concentration time curve was within acceptable limits of below 15%. The utility of the developed model was evaluated by testing the targeted formulations. The observed % prediction error was 2.61 and -0.43 for Cmax and area under the concentration time curve, respectively suggesting the usefulness of the present in vitro-in vivo correlation model.