Optimal and suboptimal smoothing algorithms for identification of time-varying systems with randomly drifting parameters

Noncausal estimation algorithms, which involve smoothing, can be used for off-line identification of nonstationary systems. Since smoothing is based on both past and future data, it offers increased accuracy compared to causal (tracking) estimation schemes, incorporating past data only. It is shown that efficient smoothing variants of the popular exponentially weighted least squares and Kalman filter-based parameter trackers can be obtained by means of backward-time filtering of the estimates yielded by both algorithms. When system parameters drift according to the random walk model and the adaptation gain is sufficiently small, the properly tuned two-stage Kalman filtering/smoothing algorithm, derived in the paper, achieves the Cramér-Rao type lower smoothing bound, i.e. it is the optimal noncausal estimation scheme. Under the same circumstances performance of the modified exponentially weighted least-squares algorithm is often only slightly inferior to that of the Kalman filter-based smoother.     

Comparison of the distribution and degradation of plastic debris along shorelines of the Great Lakes,North America

The distribution patterns, compositions and textures of plastic debris along the Lake Erie and St. Clair shorelines were studied in order to determine the roles of potential source locations, surface currents, and shoreline types in the accumulation of plastic litter. The results were compared with those previously determined from Lake Huron, where abundant plastic pellets characterize the southeastern shoreline. Lake Erie and St. Clair shorelines contained some pellets, but were mainly characterized by plastic fragments and intact products, respectively. The potential sources for the pellets include spillage within factories or during transport and off-loading; whereas intact products were derived from urban waste. Once entering the lake environment, low density floating polymers such as polyethylene and polypropylene were degraded by UVB radiation at either the water surface or once deposited on shorelines. Mechanical degradation by wave action and/or sand abrasion fragmented intact products into cm-size particles. Certain textures identified on the surfaces of plastic particles could be related to the nature of the depositional environment. Plastics sampled from infrequently visited muddy, organic-rich shorelines were characterized by more adhering particles and less mechanical pits than those from sandy shorelines. In terms of relative distribution, the Lake St. Clair shoreline contained the least amount of plastic debris of the three lakes. This is a function of the breakwaters and retaining walls built along Lake St. Clair, which replace natural sandy or muddy sinks for floating polymers. This study represents the first detailed record of plastics distribution along multiple, but related fresh water shorelines.     

Forward tracking of complex trajectories with non-Standard N-Trailers of non-minimum-phase kinematics avoiding a jackknife effect

It is a common conviction that forward motion control of tractor-trailer vehicles is a substantially simpler problem relative to reversing with trailers. This opinion may be misleading when considering the N-trailer vehicles moving forward with positive hitching offsets when a guidance point is located on a trailer. Due to the non-minimum-phase nature of vehicle kinematics, closing a feedback from a trailer posture can lead to the jackknife effect in this case. So far, there has been no solution to this problem for the N-trailers admitting trajectories of a varying curvature. To fill this gap, we propose a scalable and modular control strategy applicable to the N-trailer vehicles equipped solely with off-axle interconnections. The concept relies on a transformation of the control problem posed for the non-minimum-phase kinematics into a corresponding problem formulated for a virtual vehicle of minimum-phase kinematics, which can be solved by using the recently proposed cascade-like controller.     

Studies of the Kinetics of Lithium Grease Microstructure Regeneration by Means of Dynamic Oscillatory Rheological Tests and FTIR–ATR Spectroscopy

As part of this research, the kinetics of soap grease thickener microstructure regeneration during 24-h relaxation after 1-h shearing were studied. A lubricating grease, based on mineral oil ORLEN OIL SN-400, containing associated molecules of lithium 12-hydroxystearate was subjected to analysis. Rheological dynamic oscillatory and FTIR–ATR (Fourier Transform Infrared Attenuated Total Reflectance) spectroscopy were used to study the kinetics of thickener microstructure regeneration. Changes in the values of storage modulus G′ and loss modulus G″ of the investigated grease during its relaxation in the linear viscoelastic range were examined. In addition, the mechanical stability of the thickener microstructure at a variable oscillation frequency was tested, and changes in the cohesive energy of the grease versus the latter’s relaxation time were assessed. FTIR–ATR spectroscopy was used to study the physicochemical interactions between the associated molecules of lithium 12-hydroxystearate. Infrared bands were assigned to the vibrations of the particular functional groups of the grease components, and the spectral parameters in the absorption spectra in the range of 700–3,700 cm^?1 were examined. The studies carried out using the two investigative methods have revealed that the intensity of thickener microstructure regeneration was the highest in the first hour of grease relaxation after shearing. In this time interval, the largest changes in the vibrations of the main functional groups of the grease components were observed. In the next hours, the kinetics of thickener microstructure regeneration were substantially lower.     

Aesculus hippocastanum L. as a Stabilizer in Hemp Seed Oil Nanoemulsions for Potential Biomedical and Food Applications

Nanoemulsion systems receive a significant amount of interest nowadays due to their promising potential in biomedicine and food technology. Using a two-step process, we produced a series of nanoemulsion systems with different concentrations of hemp seed oil (HSO) stabilized with Aesculus hippocastanum L. extract (AHE). Water and commercially-available low-concentrated hyaluronic acid (HA) were used as the liquid phase. Stability tests, including an emulsifying index (EI), and droplet size distribution tests performed by dynamic light scattering (DLS) proved the beneficial impact of AHE on the emulsion’s stability. After 7 days of storage, the EI for the water-based system was found to be around 100%, unlike the HA systems. The highest stability was achieved by an emulsion containing 5% HSO and 2 g/L AHE in water, as well as the HA solution. In order to obtain the detailed characteristics of the emulsions, UV-Vis and FTIR spectra were recorded, and the viscosity of the samples was determined. Finally, a visible microscopic analysis was used for the homogeneity evaluation of the samples, and was compared with the DLS results of the water system emulsion, which showed a desirable stability. The presented results demonstrate the possible use of oil emulsions based on a plant extract rich in saponins, such as AHE. Furthermore, it was found that the anti-inflammatory properties of AHE provide opportunities for the development of new emulsion formulations with health benefits.     

Water‐redispersible low‐Tg acrylic powders for the modification of hydraulic binder compositions

Water‐redispersible, low‐T_g acrylic polymer powders are obtained in a free‐flowing form by spray drying the structured aqueous dispersions. Powder sticking and caking phenomena are minimized thanks to the heterogeneous particle morphology achieved through a sequential polymerization technique. Redispersibility is reached by the presence of functional monomers containing acid groups, properly distributed in the polymer particles. The influence of the different synthesis parameters on the drying and redispersion processes is discussed. The acrylic powders developed here are well suited for the modification of Portland cement mortars, giving performances comparable to their corresponding “mother” latices. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1781–1787, 1999     

Modelling of the carding process for spunlace nonwovens with particular regard to selected mechanical parameters in a double-drum card. Part 2: Modelling of delay times in the longitudinal mixing process

Abstract

The production of Spunlace nonwoven fabric is a complex process and includes, among other things, several important stages, such as carding, needling and drying. One of the most important stages is the carding process, which has a significant impact on the shaping of the physico-mechanical and qualitative characteristics of the nonwoven fabric. The article presents the modelling of the carding process in a two-drum system. A mathematical model, determining the expected number of drum and carding card cycles was proposed. Based on this model, delays were determined, due to longitudinal shifts of fibre in the carding process. Numerical simulations have been made and discussed in relation to fibre collection factors, at different production speeds and the number of carding rollers in the worker-stripper system.     

Heme Oxygenase-1 Has a Greater Effect on Melanoma Stem Cell Properties Than the Expression of Melanoma-Initiating Cell Markers

Melanoma-initiating cells (MICs) contribute to the tumorigenicity and heterogeneity of melanoma. MICs are identified by surface and functional markers and have been shown to display cancer stem cell (CSC) properties. However, the existence of MICs that follow the hierarchical CSC model has been questioned by studies showing that single unselected melanoma cells are highly tumorigenic in xenotransplantation assays. Herein, we characterize cells expressing MIC markers (CD20, CD24, CD133, Sca-1, ABCB1, ABCB5, ALDH^high) in the B16-F10 murine melanoma cell line. We use flow cytometric phenotyping, single-cell sorting followed by in vitro clonogenic assays, and syngeneic in vivo serial transplantation assays to demonstrate that the expression of MIC markers does not select CSC-like cells in this cell line. Previously, our group showed that heme-degrading enzyme heme oxygenase-1 (HO-1) can be upregulated in melanoma and increase its aggressiveness. Here, we show that HO-1 activity is important for non-adherent growth of melanoma and HO-1 overexpression enhances the vasculogenic mimicry potential, which can be considered protumorigenic activity. However, HO-1 overexpression decreases clone formation in vitro and serial tumor initiation in vivo. Thus, HO-1 plays a dual role in melanoma, improving the progression of growing tumors but reducing the risk of melanoma initiation.     

Improving the average delay of sorting

In previous work we have introduced an average case measure for the time complexity of Boolean circuits. Instead of fixed circuit depth, for each input we take the minimal number of time steps necessary to perform the computation for that particular input using gates that forward their output values as soon as possible. This measure is called delay. Based on it, the complexity of a whole class of functions that can be described as prefix computations has been analysed in detail.     

Multi‐scale Finite Element Cellular Automata Simulation of Multi‐step Cold Forging Operations

The application of new materials to produce forged connecting parts is presented in this work. Particular attention is put on modern bainitic steels due to their increased ductile and strength properties, which influence the behaviour of final products under further exploitation conditions. Bainitic steels do not require a series of thermo‐mechanical operations to obtain these elevated properties, which is one of the advantages of this material. Experimental analysis and numerical simulations of steel behaviour during multi‐step cold forging operations are described in this paper. Since it is one of the possible fracture initiation mechanisms, strain localization development during cold forging is investigated in detail. Conventional constitutive models used in finite element programs have limitations in modeling stochastic and discontinuous phenomena that are responsible for strain localization. The cellular automata model is used as constitutive law in this work to overcome these difficulties and investigate material flow during multi‐stage cold forging operations. Connection of the cellular automata (CA) and finite element (FE) methods creates a so‐called multi‐scale CAFE model. The main aspects of the model are described briefly in this paper. The experimental part of this work supports the numerical investigation. Comparison of the parameters measured and predicted by the CAFE model is presented and discussed as well.