Stability Of Filter Research Articles

LC filter design for on-grid and off-grid distributed generating units

This paper deals with the design procedure of an LC-based output filter for three-phase inverters to be used in both off-grid and on-grid scenarios. The aim of this procedure is to provide guidelines and component selection criteria for reducing the inverter output switching ripple in order to limit the interaction with the control algorithm and to increase the filter stability. A suitable combination of resistive and reactive components is used to realize the complete filter structure. The proposed procedure is applied to the design of the output power filter for a 40-kVA three-phase inverter.

Characteristics of titanium dioxide microdispersions with different photo-activity suitable for sunscreen formulations

The aim of the study was the comparison of photo-activity of three types of titanium dioxide (TiO2) micro-dispersions intended for use as UV filters for cosmetic sunscreen products. The dispersions were also investigated with regard to their influence on the stability of photo-protective systems in cosmetic emulsions, their skin penetration/absorption and their photo-toxicity for humans and skin bacterial flora. All the tested micro-dispersions of rutile TiO2 type (agglomerates with diameter 120–150nm), with primary particle size lower than 100nm, demonstrated no phototoxic effect and insignificant antimicrobial behaviour. On the other hand, TiO2 with insufficient deactivation of photo-activity had significant negative impact on the stability of other organic UV filters and therefore on the stability of declared UV protective factors (SPF, UVA-PF). The study demonstrated that the level of deactivation of TiO2 is one of the highly important factors for evaluation of UV filters used as sunscreens.

Distributed Kalman consensus filter with intermittent observations

We consider the problem of distributed state estimation for linear time-varying systems with intermittent observations. An optimal Kalman consensus filter has been developed by minimizing the mean-squared estimation error for each node. To derive a scalable algorithm for the covariance matrices update, a suboptimal filter is proposed by omitting the edge covariance matrices among nodes. By using the Lyapunov-based approach, a sufficient condition is presented for ensuring the stochastic stability of the suboptimal filter. Two numerical examples are provided to verify the effectiveness of the proposed filter.

The Effect of D2O on the Inactivation Kinetics and Recovery from Slow Inactivation of Shaker-IR K+ Channels

In the absence of N-type inactivation Shaker potassium channels display slow (C-type) inactivation which is stabilized by a multipoint hydrogen-bond network behind at the selectivity filter in eukaryotic KV channels. The selectivity filter is sterically locked in the inactive conformation by buried water molecules which prevent recovery from inactivation. To further test the critical role of these, structural water” molecules in the conformational stability of the selectivity filter we studied the effects of substituting water for heavy water (deuterium oxide, D2O in the solutions) on various gating transitions in Shaker-IR channels having the following mutations and allowing slow inactivation at various rates: T449A, T449A/I470A and T449K/I470C. All channels were transiently expressed in tsA_201 cells and ionic currents were recorded in excised inside-out patches. 2.0-s-long depolarizing pulses from a holding potential of −120 mV to +50 mV were applied to measure the current through the channels. The extracellular application of D2O dramatically slowed entry into the inactivated state, the inactivation time constats were τi,D2O = 189±48 ms (n=5) (T449A, τi,H2O = 72±13 (n=5)), τi,D2O = 418±63 ms (n=4) (T449A/I470A, τi,H2O = 247±90 (n=5)), τi,D2O = 60±21 ms (n=6) (T449K/I470C, τi,H2O = 31±15 ms (n=10)), respectively. In contrast, applying D2O from the intracellular side did not change the inactivation kinetics. The kinetics of recovery from slow inactivation was also slowed down in the D2O environment. Our macroscopic current measurements confirm that water molecules may have access to the region behind the selctivity filter only from the external solution and the binding of these ‘hidden’ molecules slows the development of inactivation and that of the recovery process.

On Stability of Tunable Linear Time-Varying Band-Pass Filters

Tunable linear time-varying filters are widely used in many adaptive and signal processing applications. In this paper we consider a problem of stability analysis of tunable time-varying band-pass filters and prove that for a certain realization of these filters stability is ensured under assumption that tuning signal, namely a central frequency of the filter, is bounded and strictly above zero. An illustrative example of measurement noise attenuation is also given.

Fault estimation for discrete time LPV systems under noisy scheduling measurements

Developed in the paper, is a systematic design framework for parameter-dependent fault diagnosis, with noise corrupted measurements of the scheduling parameter. A stochastic fault estimation filter design method is addressed for a class of discrete-time Linear Parameter Varying (LPV) systems. First, the average valued filter stability is ensured by means of a quadratic dissipativity condition. Apart stability, within the same mean square framework a robust performance objective is defined. Conditions to satisfy robust stability requirements are translated to an optimization problem subject to Bilinear Matrix Inequality (BMI) constraints. A comparative numerical example is given to illustrate and validate the proposed methodology.

Improved Frame Error Concealment Algorithm Based on Transform- Domain Mobile Audio Codec

In this paper, we propose an improved frame error concealment algorithm for TCX-based audio coders in order to improve the quality of decoded audio at the receiver. Conventional TCX-based frame error concealment algorithms in the AMR-WB+ audio codec are usually unable to adaptively adjust gain control according to changes in the magnitude of the correct frame before lost frames. Thus, we propose a new gain control approach based on stability of LPC filter, and the stream data need to contain the line spectrum frequency data and utilize different continuous attenuation factor formula based on different categories of lost frames. The proposed frame error concealment algorithm is designed for TCX-based audio codec. We make the performance comparison between the proposed method and the original algorithm currently employed in AMR-WB+ audio codec through the objective evaluation test and subjective evaluation test. The results prove that our algorithm can achieve better audio recovery quality than original frame error concealment algorithm employed in AMR-WB+ speech codec.

Stability of the filter with Poisson observations

The short interest rate process is modeled by a diffusion process \(X(t)\). With the counting process observations, a filtering problem is formulated and its exponential stability is derived when the process \(X(t)\) is asymptotically stationary.

Degradation in chlorinated water of the UV filter 4-tert-butyl-4′-methoxydibenzoylmethane present in commercial sunscreens

4-tert-Butyl-4′-methoxydibenzoylmethane (BMDM) is a widely used ultraviolet A filter. In this work, we have studied the effect of chlorine and dissolved organic matter (DOM) concentrations on the stability of UV filter (BMDM) present in two commercial sunscreen cream formulations in water. An experimental design was used to assess the effect of the two experimental factors on the degradation of BMDM. Higher concentrations of chlorine lead to higher degradation percentages of BMDM and higher concentrations of DOM inhibit its degradation. Moreover, a mono and a dichloro derivate of BMDM were identified as by-products.

Design of Mobile Communication Non Intersymbol Interference System Based on Calman Filter and PID Control

In the digital baseband transmission system, the intersymbol interference is one of the main factors affecting the performance. Therefore, how to overcome its influence, making the system error rate reduction must study and solve the problems in the digital baseband system. This paper designs a new mobile communication non intersymbol interference filtering system based on MATLAB numerical simulation, the system is the integration of the Calman filter theory, and combining the genetic algorithm and PID control algorithm to achieve the rapidity and stability of the system filter. The filter design and validation simulation can be seen that the filter can effectively eliminate the measurement and observation error in the mobile communication process, to avoid the signal fluctuation caused by intersymbol interference. Through the system response curve, it can be seen that the system does not appear overshoot, fast convergence speed, and good response stability will provide the technical reference for the research of mobile communication system.

Thermo-mechanical characterization of optical thin films filters deposited onto shape memory alloy micro-actuators

Different optical thin films filters have been deposited by plasma techniques onto shape memory alloy micro-actuators controlled by the heating of laser irradiations. Thermomechanical cycles have been performed to investigate the stability of these optical filters. Excellent properties have been obtained with amorphous hydrogenated silicon/silica and amorphous hydrogenated silicon/plasma polymerized methacrylic acid-based filters; no degradation was observed after up to 50 000 cycles. Other silver/plasma polymerized methacrylic acid-based filters, which have a better selectivity and permit the use of more laser sources of different wavelengths for optical actuation, showed lower stability. The optical-filtering properties are lost during the thermomechanical cycles, due to a rearrangement of the silver atoms with heating. Thus, there is a trade-off between wavelength selectivity and the stability of the structures used for the optical control of the micro-actuators.

Conditional ergodicity in infinite dimension

The goal of this paper is to develop a general method to establish conditional ergodicity of infinite-dimensional Markov chains. Given a Markov chain in a product space, we aim to understand the ergodic properties of its conditional distributions given one of the components. Such questions play a fundamental role in the ergodic theory of nonlinear filters. In the setting of Harris chains, conditional ergodicity has been established under general nondegeneracy assumptions. Unfortunately, Markov chains in infinite-dimensional state spaces are rarely amenable to the classical theory of Harris chains due to the singularity of their transition probabilities, while topological and functional methods that have been developed in the ergodic theory of infinite-dimensional Markov chains are not well suited to the investigation of conditional distributions. We must therefore develop new measure-theoretic tools in the ergodic theory of Markov chains that enable the investigation of conditional ergodicity for infinite dimensional or weak-* ergodic processes. To this end, we first develop local counterparts of zero-two laws that arise in the theory of Harris chains. These results give rise to ergodic theorems for Markov chains that admit asymptotic couplings or that are locally mixing in the sense of H. F\"{o}llmer, and to a non-Markovian ergodic theorem for stationary absolutely regular sequences. We proceed to show that local ergodicity is inherited by conditioning on a nondegenerate observation process. This is used to prove stability and unique ergodicity of the nonlinear filter. Finally, we show that our abstract results can be applied to infinite-dimensional Markov processes that arise in several settings, including dissipative stochastic partial differential equations, stochastic spin systems and stochastic differential delay equations.

Some new results on the stability of direct-form digital filters with finite wordlength nonlinearities

This paper proposes a new criterion for the input/output-to-state stability (IOSS) of interfered direct-form digital filters with finite wordlength nonlinearities based on an augmented Lyapunov function. Without external interferences, the output-to-state stability (OSS) and asymptotic stability of direct-form digital filters are guaranteed under the proposed criterion. An improved criterion is also proposed for the IOSS and OSS of interfered direct-form digital filters, with the introduction of four slack matrices. A new state-norm estimator for direct-form digital filters is constructed based on an exponential-decay IOSS criterion. The criteria presented in this paper are expressed by linear matrix inequalities (LMIs). Two numerical examples demonstrate the effectiveness of the proposed results.

Geometric changes of the inferior vena cava in trauma patients subjected to volume resuscitation.

Dynamic changes in anatomic geometry of the inferior vena cava from changes in intravascular volume may cause passive stresses on inferior vena cava filters. In this study, we aim to quantify variability in inferior vena cava dimensions and anatomic orientation to determine how intravascular volume changes may impact complications of inferior vena cava filter placement, such as migration, tilting, perforation, and thrombosis. Retrospective computed tomography measurements of major axis, minor axis, and horizontal diameters of the inferior vena cava at 1 and 5 cm below the lowest renal vein in 58 adult trauma patients in pre-resuscitative (hypovolemic) and post-resuscitative (euvolemic) states were assessed in a blinded fashion by two independent readers. Inferior vena cava perimeter, area, and volume were calculated and correlated with caval orientation. Mean volumes of the inferior vena cava segment on pre- and post-resuscitation scans were 9.0 cm(3) and 11.0 cm(3), respectively, with mean percentage increase of 48.6% (P < 0.001). At 1 cm and 5 cm below the lowest renal vein, the inferior vena cava expanded anisotropically, with the minor axis expanding by an average of 48.7% (P < 0.001) and 30.0% (P = 0.01), respectively, while the major axis changed by only 4.2% (P = 0.11) and 6.6% (P = 0.017), respectively. Cross-sectional area and perimeter at 1 cm below the lowest renal vein expanded by 61.6% (P < 0.001) and 10.7% (P < 0.01), respectively. At 5 cm below the lowest renal vein, the expansion of cross-sectional area and perimeter were 43.9% (P < 0.01) and 10.7% (P = 0.002), respectively. The major axis of the inferior vena cava was oriented in a left-anterior oblique position in all patients, averaging 20° from the horizontal plane. There was significant underestimation of inferior vena cava maximal diameter by horizontal measurement. In pre-resuscitation scans, at 1 cm and 5 cm below the lowest renal vein, the discrepancy between the horizontal and major axis diameter was 2.1 ± 1.2 mm (P < 0.001) and 1.7 ± 1.0 mm (P < 0.001), respectively, while post-resuscitation studies showed the same underestimation at 1 cm and 5 cm below the lowest renal vein to be 2.2 ± 1.2 mm (P < 0.01) and 1.9 ± 1.0 mm (P < 0.01), respectively. There is significant anisotropic variability of infrarenal inferior vena cava geometry with significantly greater expansive and compressive forces in the minor axis. There can be significant volumetric changes in the inferior vena cava with associated perimeter changes but the major axis left-anterior oblique caval configuration is always maintained. These significant dynamic forces may impact inferior vena cava filter stability after implantation. The consistent major axis left-anterior oblique obliquity may lead to underestimation of the inferior vena cava diameter used in standard anteroposterior venography, which may influence initial filter selection.

NUMERICAL AND LABORATORY EXPERIMENTS ON STABILITY OF GRANULAR FILTERS IN MARINE ENVIRONMENT

Geometrically closed filters are usually applied for marine structures, because they are designed neglecting the hydraulic load and geometrically open filters cannot be reliably designed so far. There are still gaps in the knowledge concerning hydro-geotechnical processes under the influence of oscillatory flow and combined oscillatory with unidirectional flow. The focus of this work is on the contact erosion at the interface between base and overlying filter under vertical oscillatory flow. Therefore, laboratory experiments on the stability of granular filters were performed. The objectives are (i) a better understanding of hydro-geotechnical processes, (ii) the description of hydraulic gradient, pore pressure and (iii) the development of prediction formulae for the hydraulic stability of granular filter under wave loads. Preliminary results show that geometrically closed filters are not stable under oscillatory flow and the hydraulic load cannot be neglected for a reliable filter design.

Long-term stability of sequential Monte Carlo methods under verifiable conditions

This paper discusses particle filtering in general hidden Markov models (HMMs) and presents novel theoretical results on the long-term stability of bootstrap-type particle filters. More specifically, we establish that the asymptotic variance of the Monte Carlo estimates produced by the bootstrap filter is uniformly bounded in time. On the contrary to most previous results of this type, which in general presuppose that the state space of the hidden state process is compact (an assumption that is rarely satisfied in practice), our very mild assumptions are satisfied for a large class of HMMs with possibly noncompact state space. In addition, we derive a similar time uniform bound on the asymptotic $\mathsf{L}^p$ error. Importantly, our results hold for misspecified models; that is, we do not at all assume that the data entering into the particle filter originate from the model governing the dynamics of the particles or not even from an HMM.

Linear minimum mean squared estimation of measurement bias driven by structured unknown inputs

In this study, a generalised systematic bias (SB) is presented, which is represented via a dynamic model driven by structured unknown inputs (UI). The online SB estimation is implemented in two steps. In the first step, the state-free SB measurement and the UI-free SB dynamic model are derived in the case that UI-free condition holds. In the second step, the linear minimum mean squared filter is obtained via orthogonal principle, and the sufficient condition of filtering stability is presented. A simulation about target tracking is given to verify the proposed method.

Stochastic stability of center difference predictive filter

In this paper, based on Stirling’׳s polynomial interpolation formula, the Second-order Central Difference Predictive Filter (CDPF2) is proposed for nonlinear estimation. To facilitate the new method, the algorithm flow of CDPF2 is given first. Then, the theoretical deductions demonstrate that the estimated accuracy of the model error and system state for the CDPF2 is higher than that of the conventional PF. In addition, the stochastic boundedness and the error behavior of CDPF2 is analyzed for general nonlinear systems in a stochastic framework. The theoretical analysis presents that the estimation error will remain bounded and the covariance will remain stable if the system׳s initial estimation error, disturbing noise terms and model error are small enough, which is the core part of the CDPF2 theory. All of the results have been demonstrated by numerical simulations for a nonlinear example system.

Kalman Filtering Over Lossy Networks Under Switching Sensors

AbstractIn this paper, we study the mean square stability of Kalman filtering of a discrete‐time stochastic system under two periodically switching sensors. The sensor measurements are sent to a remote estimator over a lossy channel whose packet loss process is independent and identically distributed. We prove that the problem can be converted into the stability analysis of Kalman filtering using two sensors at each time, and the measurements of each sensor are transmitted to the estimator via an independent lossy channel of the same packet loss rate. Some necessary and/or sufficient conditions for stability of the estimation error covariance matrices are derived. Moreover, the effect of the sensor switching on the filter stability is revealed. Their implications and relationships with related results in the literature are discussed.

State Estimation Over a Lossy Network in Spatially Distributed Cyber-Physical Systems

In this paper, we analyze stochastic stability of Kalman filter (KF) based state estimation over a lossy network in spatially distributed cyber-physical systems. We study a practical scenario in which sensors are arbitrarily deployed over an area to jointly sense the state of underlying physical system. The sensors directly communicate observations to a central state estimation unit over a network resulting in random loss in measurements and partial observation updates in KF. We analyzed stability of state estimation process in this scenario by establishing conditions under which steady state error covariance matrix is bounded. In contrast to previous work on gathered measurement scenario with intermittent loss, we considered a dispersed measurement scenario and established bounds on critical probability of receiving measurements over individual sensor communication links. Our analysis later exploited possible existence of spatial correlation among states in the filtering process and characterized its impact on the bounds. We further extended our analysis by considering correlated loss among sensor measurements. The overall analysis quantifies the trade-off between state estimation accuracy and the quality of underlying communication network. In addition, our analysis demonstrates that by exploiting spatial correlation among states, a higher degree of information loss (or lower network quality) can be tolerated to achieve a certain estimation accuracy. Since estimation accuracy directly impacts the stability of control operation, this analysis is critical for architecture and network planing design of cyber-physical systems.