Disturbance rejection problem solvability: From structural approach to reliability/availability analysis

This paper examines the relationship between product architecture, supply-chain performance metrics, and supply-chain efficiency. We model the contracting relationship between a supplier and a buyer. The supplier is privately informed about the outcome of his design/production investment. The buyer both appraises the supplier's component and does further processing/component production of his own. If the final product produced by the buyer exhibits decoupling and no function sharing with respect to the components (termed separable architecture), the first-best outcome is attained if both internal and external failures are contractible. When only one type of failure can be contracted on, we derive conditions under which contracting on internal failure is superior to contracting on external failure, and vice versa. If the buyer's final product has a nonseparable architecture with respect to the components, first-best cannot be achieved even if both internal and external failures are contractible. The value of contracting on internal failure alone is unaffected by the architecture design, while that of external failure declines relative to the separable setting; the net result is often to make the former the uniformly dominant performance metric. Our results highlight the interaction between the performance metrics used for contracting within the supply chain, the architecture of the product produced by the supply chain, and the incentive efficiency of the chain.

The first part of the paper deals with the FEM computation of deformations, stresses and strain in the surrounding area of internal and external circular artificial failures with a set of given geometrical dimensions in steel pipelines. For the investigation of this problem three groups of mechanical models are applied: multilayered elastic shell, 3D elastic solid and 3D elastic-plastic solid FEM models. The aim of this analysis is to clarify the case in which the pipeline fails. When a pipe fails and needs repair or reinforcement, this is called critical case. In the second part of the paper the repaired pipes are investigated. For repairing of the internal and external failures, internal or external multilayered textile composite reinforcements are applied by winding technology. The task is to determine the width of the reinforcement and the number of layers needed for repair. The different mechanical models (multilayered elastic shell, 3D elastic solid and 3D elasto-plastic solid) are compared on the basis of numerical results. The critical cases are determined and the questions of repair are answered also numerically.

Diaphragmatic pacing for the treatment of congenital central alveolar hypoventilation syndrome

Health care decision makers often have a limited understanding of the costs associated with quality improvement efforts. However, such information is vital for managers to make appropriate operational and financial decisions to ensure high quality health care services. We used the Cost of Quality (COQ) model to estimate the cost of quality-related activities at the Makerere University-Johns Hopkins University (MU-JHU) Laboratory in Uganda. Using data collected from January 1, 2007–December 31, 2007, we allocated the direct costs associated with quality-related activities in the laboratory across COQ’s cost categories: prevention, appraisal, internal failures, and external failures. We found that approximately 94% of total COQ was spent on costs of “good quality” (prevention and appraisal), while 6% was spent on costs of “poor quality” (internal and external failures). The high percentage of COQ spent on prevention and appraisal activities is consistent with efforts to ensure high quality laboratory results. Future studies should try to link COQ to health outcomes and quantify “hidden” failure costs. This CE update introduces the Cost of Quality (COQ) model and illustrates how it can be applied to a clinical laboratory setting to help managers and executives make more informed decisions about spending on quality-related activities. We begin with an overview of the COQ concept and its 4 main cost categories, followed by an illustration of how the model can be applied in a medical laboratory setting. We then discuss some of the advantages and limitations of this methodology and provide suggestions for future research. * COQ : Cost of Quality MU-JHU : Makerere University-Johns Hopkins University IOM : Institute of Medicine P-A-F : prevention-appraisal-failure CAP : College of American Pathology PCR : polymerase chain reaction QA : quality assurance LIS : laboratory Information System EQA : External Quality Assurance CSC : Customer Service Concern PM : preventive maintenance QC : Quality Control PIR : Process Improvements Reports GLP : good laboratory practices GAAP : generally accepted accounting principles

Discusses the implementation of cost for quality programmes in non‐manufacturing functions, suggesting their necessity in enabling management to accept the true cost of not getting it right first time. Outlines methods of analyzing work, highlighting prevention, appraisal, internal failure, external failure, exceeding requirements and lost opportunities. Reviews the “no blame” philosophy, and provides examples of internal departmental failures. Explores the process of re‐education. Suggests that no matter how successful a company is, the key to success is to look for a better way of doing business.

This paper deals with the problems of constructing a compensator for linear multi-variable systems that simultaneously ensures: (I) model-following with stability and (ii) disturbance rejection. Necessary and sufficient conditions for the solvability of the problems are given by using a geometric approach. The solvability conditions are explicit and the constructive procedure for finding a solution does not require any additional conditions for the plant.

This paper concerns the disturbance rejection problem arising in the coordination control of a group of autonomous agents subject to external disturbances. The agent network is said to possess a desired level of disturbance rejection, if the H∞ norm of its transfer function matrix from the disturbance to the controlled output is satisfactorily small. Undirected graph is used to represent the information flow topology among agents. It is shown that the disturbance rejection problem of an agent network can be solved by analyzing the H∞ control problem of a set of independent systems whose dimensions are equal to that of a single node. An interesting result is that the disturbance rejection ability of the whole agent network coupled via feedback of merely relative measurements between agents will never be better than that of an isolated agent. To improve this, local feedback injections are applied to a small fraction of the agents in the network. Some criteria for possible performance improvement are derived in terms of linear matrix inequalities. Finally, extensions to the case when communication time delays exist are also discussed.

Input-output decoupling and disturbance rejection problems in structural analysis

The paper is aimed to the design of a generalized class of continuous controllers for time delay systems. The proposed controllers ensure internal stability and simultaneous reference tracking and disturbance rejection. Several approximations for first order system with time delay were used. All of them can be covered by a second order transfer function. Then explicit formulas were derived for SISO systems with a feedback as well as with a feedback-feedforward structure of the controlled system. The proposed control synthesis is based on general solutions of Diophantine equations in the ring of proper and Hurwitz stable rational functions R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">PS</sub> and the Youla-Kučera parametrization of controllers is utilized. The conditions for asymptotic tracking and disturbance rejection are obtained through the divisibility conditions in the ring R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">PS</sub> . Robustness of proposed algorithms can be studied through the infinity norms (H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> ) and through the sensitivity functions of controlled systems. A scalar parameter m>0 is introduced for tuning and influencing of proposed controllers. A Matlab + Simulink program system for automatic design and simulation has been developed. The program system is suitable for a wide engineering applications without a deep insight into the control theory.

This paper deals with the problem of robust tracking and disturbance rejection for a linear time-invariant system where the uncertainty of the system is represented in a structured form and the output to be controlled may be different from the measurement output. First, the problem is considered in a rather classical setting in that the required property of tracking and disturbance rejection can be attained as long as the resulting closed-loop system remains stable. Conditions for solvability of the problem are given and two algorithms are presented for designing controllers having the robust tracking and disturbance rejection property. Second, the problem of robust output regulation with robust stability is formulated as one of finding a controller such that the resulting closed-loop system satisfies an additional requirement of robust stability and thus the output regulation property can be maintained for all perturbations of uncertain parameters within a prescribed set. A procedure based on a high gain observer approach is proposed to solve this problem.

Modified active disturbance rejection control based on gain scheduling for circulating fluidized bed units

Active disturbance rejection control of pressurizer pressure during startup process in a pressurized water reactor nuclear power plant

SUMMARY This paper investigates the problem of global disturbance rejection for switched nonlinear systems in strict-feedback form with unknown exosystem where the solvability of the disturbance rejection problem for subsystems is not assumed. First, a sufficient condition for the solvability of the global disturbance rejection problem is given. As an extension of the classic concept of internal model for non-switched systems, a new concept of switched internal model is proposed. Second, in order to solve the problem in question, a constructive adaptive control methodology is established on the basis of the multiple Lyapunov functions method, backstepping, and the changing supply functions technique. Finally, an example is provided to demonstrate the effectiveness of the proposed approach. Copyright © 2013 John Wiley & Sons, Ltd.

This paper is concerned with the problem of disturbance rejection in an adaptive controller design. A new adaptive control algorithm is derived to obtain the complete measurable disturbance rejection both in dynamic and static states for a class of non-minimum phase MIMO systems by reassigning the system zeros to the stable region

Cross-browser incompatibilities (XBIs) are defined as inconsistencies that can be observed in Web applications when they are rendered in a specific browser compared to others. These inconsistencies are associated with differences in the way each browser implements its capabilities and renders Web applications. The inconsistencies range from minor layout differences to lack of core functionalities of Web applications when rendered in specific browsers. The state of the art proposes different approaches for detecting XBIs and many of them are based on classification models, using features extracted from the document object model (DOM) structure (DOM-based approaches) and screenshots (computer vision approaches) of Web applications. To the best of our knowledge, a comparison between DOM-based and computer vision classification models has not yet been reported in the literature, and a combination between both approaches could possibly lead to increased accuracy of classification models. In this article, we extend the use of these classification models for detecting layout XBIs in responsive design Web applications, rendered on different browser viewport widths and devices (iPhone 12 mini, iPhone 12, iPhone 12 Pro Max, and Pixel XL). We investigate the use of state-of-the-art classification models (Browserbite, CrossCheck, and our previous work) for detecting layout cross-browser failures, which consist of layout XBIs that negatively affect the layout of responsive design Web applications. Furthermore, we propose an enhanced classification model that combines features from different state-of-the-art classification models (DOM based and computer vision) using feature selection. We built two datasets for evaluating the efficacy of classification models in separately detecting external and internal layout failures using data from 72 responsive design Web applications. The proposed classification model reported the highest F1-score for detecting external layout failures (0.65) and internal layout failures (0.35), and these results reported significant differences compared to Browserbite and CrossCheck classification models. Nevertheless, the experiment showed a lower accuracy in the classification of internal layout failures and suggests the use of other image similarity metrics or deep learning models for increasing the efficacy of classification models.