Exact,almost and optimal input decoupled (delayed) observers

The core of this paper deals with the construction of input-decoupled observers which seek asymptotic estimation of a desired output variable (a linear combination of state and input) of a time-invariant either continuous- or discrete-time system driven by unknown inputs and disturbances. Exact, almost, optimal (suboptimal) and constrained optimal estimation or filtering problems are formulated and studied. All the problems defined and studied here are inherently interconnected, and have a strong common thread of estimation and filtering in the face of the unknown input and external disturbance signals. They are interconnected from a variety of angles, e.g. they are motivated by one another, methods of obtaining the solvability conditions and their methods of solution rely on one another, etc. Thus, a hierarchy of problems and their solutions is built on top of one another. Some of the problems studied here are known in the literature but not in as general a form as is given here, while a majority of the problems studied here are new. A classical variation of all the above problems is also studied here by introducing an l-step delay in estimating the desired output from the measured output. The underlying philosophy throughout this work has been to study most if not all of the facets of estimation and filtering in one stretch under a single folder. Our study of all the above problems has been guided by three important perspectives: (1) obtaining the solvability conditions, both necessary and sufficient; (2) obtaining optimal performance whenever it applies; and (3) developing sound methodologies to design and construct appropriate observers or filters.     

Regulated state synchronization of homogeneous multiagent systems with partial‐state coupling via low‐gain adaptive protocol

This paper studies regulated state synchronization for continuous‐time homogeneous multiagent systems with weakly unstable agents where the reference trajectory is given by a so‐called exosystem. The agents share part of their state over a communication network. We assume that the communication topology is completely unknown and directed. An algebraic Riccati equation–based low‐gain adaptive nonlinear dynamic protocol design is presented to achieve the regulated state synchronizations. Utilizing the adaptive control, our nonlinear dynamic protocol is universal and does not depend on any information about the communication topology or the number of agents.     

Verhalten austenitischer Manganstähle in Meerwasser

Auslagerungsversuche mit verschiedenen geschweißten und verspannten Proben aus den chromhaltigen austenitischen Manganstählen X 40 MnCrN 19 und X 12 MnCr 18 12 sowie dem chromfreien Stahl X 50 Mn 20 in Meerwasser der Nord- und Ostsee. Makroskopische und mikroskopische Beurteilung der Proben nach sechs Wochen, einem halben Jahr, einem Jahr und zwei Jahren hinsichtlich Beständigkeit gegen unterschiedliche Korrosionserscheinungen, besonders hinsichtlich transkristalliner Spannungsrißkorrosion.     

Sudden cardiac death: a retrospective and prospective study

Since the inception of mobile coronary care units (MCCU), patients with sudden cardiac death (SCD) saved by advanced emergency medical technicians (EMT-A) can be studied retrospectively and prospectively. Forty-eight cases of SCD found in ventricular fibrillation (VF) were successfully resuscitated. Only 32% had a myocardial infarction. Most survivors were New York Heart Association (NYHA) class I or II. All class IV survivors with severe congestive heart failure died within 45 days. All class II survivors had angina as the limiting factor. Of all patients with VF, 23% survived. Eighty percent of survivors were class I or II and have resumed previous lifestyles. No clear cut symptom complex was identified. Rescue response time was generally less than five minutes. Intracardiac medications were administered without complications. Empirical administration of sodium bicarbonate correlated poorly with arterial blood gas determinations.     

AES investigation of the stainless steel surface oxidized in plasma

Auger electron spectroscopy (AES) depth profiling was used to study the oxidation phenomena of AISI316L stainless steel during treatment with oxygen plasma. Samples were exposed to low-pressure RF plasma with a high dissociation degree, so that the flux of oxygen atoms onto the sample surface exceeded 10²⁴ m⁻² s⁻¹. A set of samples was oxidized 4 min at different temperatures up to 1300 K during plasma treatment. AES measurements showed that the oxide film thickness increased with the increasing temperature. The thickness of the oxide film on the samples oxidized in plasma at 300 K was nearly the same as for the untreated sample. The thickness of the oxide film of the samples which were oxidized at 1000 K was about 170 nm and it consisted of iron oxide. The thickest oxide film of about 350 nm was found on the samples heated in oxygen plasma to 1300 K. Depth profiling showed the uppermost layer of manganese oxide, followed by a mixture of chromium oxide and iron oxide. The scanning electron microscope analyses showed a dramatic increase of the surface roughness.     

Is the analysis of molecular electronic structure of corrosion inhibitors sufficient to predict the trend of their inhibition performance

The often used approach in the corrosion inhibition studies employing quantum chemical calculations that relies on the correlation between molecular electronic structure parameters and inhibition effectiveness is critically examined. It is shown that the inhibition performance of three selected triazole-based corrosion inhibitors for copper - 3-amino-1,2,4-triazole (ATA), benzotriazole (BTAH), and 1-hydroxybenzotriazole (BTAOH) - cannot be explained on this basis in a sound manner. As the effectiveness of inhibitors is due to several phenomena, the outcome depends on the interplay between them and although molecular electronic parameters may provide many necessary elements, the involved effects can be estimated only approximately which may not always suffice. This supports the proposition that in general molecular electronic properties cannot be directly related to inhibition effectiveness - the actual relation is more involved - thus emphasizing the importance of a rigorous modeling of the inhibitor-surface interaction in the corrosion inhibition studies.     

Numerical and Experimental Performance Evaluation of the 3-Stage FROSTY Supercooled Cloud Collector

An evaluation of the collection characteristics of a new multistage cascade inertial impactor designed for size-resolved cloud drop collection has been performed. The FROSTY supercooled cloud collector is intended for the collection of supercooled cloud drops in a winter environment in three independent size fractions with stage 50% cut diameters of 15 θ m, 10 θ m, and 4 θ m. Two approaches were selected for the evaluation of the collector. Numerical simulations provided a visualization of the airflow patterns and drop trajectories through the collector while experimental laboratory calibration provided a quantitative analysis of true collection performance. For each of these methods, 50% cut diameters, efficiency curves, and wall losses for each stage of the collector were determined. Collection characteristics were determined experimentally by introducing fluorescein-tagged monodisperse drops into the collector and analyzing collection patterns by fluorescence. The experimental measurements at laboratory conditions indicated 50% cut diameters of 19.0, 11.5, and 5.0 θ m for the three stages. Adjusted for operation at collector design conditions, the 50% cut diameters were 17.0, 10.5, and 4.5 θ m. Numerical modeling of the airflow patterns and drop trajectories through the collector was performed with the commercially available Computational Fluid Dynamics (CFD) software package FLUENT. Trajectory simulations based on the average continuous phase (air) velocity field as well as trajectory simulations which included the effects of statistically derived turbulent velocity fluctuations on drop motion were performed. Comparisons between the numerical and experimental work indicated that the inclusion of turbulent fluctuation effects on drop motion provided much better agreement with experimental observations than trajectories based solely on average flow field velocities. However, the use of continuous phase velocity fluctuations also produced unrealistic losses to wall surfaces for small drop sizes. Despite this shortcoming, numerically derived 50% cut diameters and overall collection efficiency curve shapes for drop trajectories including turbulent velocity fluctuations agreed reasonably well with experimental observations.     

An Adaptive Estimator of the Autocorrelation Coefficient in Regression Models with Autoregressive Errors

In this paper an adaptive estimator of the autocorrelation coefficient is constructed in regression models whose error variables follow a stationary autoregressive process of order 1. Examples of nonparametric, additive and semiparametric regression models are discussed.