Efficient System Analysis Research Articles

Building functional networks for complex response analysis in systems of coupled nonlinear oscillators

Some aspects of engineering dynamics, such as nonlinearities and transient motion of many interconnected parts, remain difficult to handle today. To comply with increasing demands on resilience and safety, the dynamics of large machines need to be better understood. Complex network methods, already present in many scientific disciplines, provide a tool set complementary to conventional methods of system analysis. This work aims at providing a new, function-based view on mechanical systems by generating functional networks. To this end, a network algorithm is applied to sets of cyclically coupled Duffing oscillators as a common example of a complex nonlinear mechanical system. In the functional network, each node represents an oscillator while the direction of the network edges represents a functional coupling. Results show that the network method is capable of identifying dynamical transitions and synchronization between components, as well as determining the number of different states present within a system. Additionally, the time evolution of the component interactions, especially in response to a disturbance, is studied via a sliding-window approach. The results of this analysis might hopefully open new ways for a more efficient system analysis through optional sensor placement, and for effective countermeasures against unwanted dynamics through improved analysis of transient dynamics.

Impacts of Nodal Demand Allocations on Transient-Based Skeletonization of Water Distribution Systems

AbstractUrban water distribution systems (WDSs) are often skeletonized to enable efficient system analysis and management. While different methods are available to account for transient dynamics wi...

Model development for the separation of a strongly adsorbing gas mixture on a semi-pilot scale adsorber

A detailed model is developed for the separation of strongly adsorbing gas mixtures at semi-pilot scale. It assumes a non-isothermal compressible transport-diffusion mechanism in the adsorber and dispersed compressible flow in the periphery, respectively. A methodology is proposed for efficient system analysis and parameter determination, leading to high model accuracy. The separation of N2 and CO2 on the carbon molecular sieve CMS-H2 55/2 serves as example problem. Based on experimental equilibrium data for different temperatures, the applicability of different adsorption isotherm models is investigated for the single components. Isosteric heats of adsorption and their dependency on adsorbate loadings are determined by an analysis using the virial isotherm. A single reference experiment – an adsorption-desorption breakthrough for a diluted gas mixture – allows estimating heat and mass transfer coefficients and investigating the role of competitive adsorption and heat effects. The final model accurately predicts compositions, temperatures, and flow rates for a complete set of adsorption and desorption experiments in a broad range of conditions.

Model-based Reasoning Approach for Automated Failure Analysis: An Industrial Gas Turbine Application


 
 
 Keeping up with the technological advances, turbo- machinery industry aspires to integrate manufacturing, servicing and maintenance of their plants. Typically, these objectives may be accomplished by adoption of condition monitoring services and diagnostic solutions, resulting in improved plant operations, lower maintenance cost, and impart safety and reliability. Specifically, failure analysis, within systematic diagnostics, is a fundamental feature of design and maintenance phase, as it allows fault identification, and its causes and effects that propagate at different system levels. With the large number of subsystems and process flows, failure analysis for industrial gas turbines is non-trivial, and requires expertise of system mechanics, aerodynamics, thermodynamics, etc. Consequently, in order to realize an efficient system analysis, we device an automated model-based approach to failure analysis for industrial gas turbine applications. This paper presents context-independent qualitative models of key turbine components, which are most error-prone, together with their potential failure mode descriptions, and their impact at different system levels. Using an existing reasoning engine, we present behavior models and results for two most vulnerable turbine subsystems i.e. Lubrication Oil System and the Core Gas Turbine Engine. Finally, we evaluate the practical use-cases of this model-based solution implemented for diagnostic services at Siemens AG.
 
 

Environment generation for validating event-driven software using model checking

Event-driven systems maintain an ongoing dialog with their environment. Examples include: distributed programs, where each process reacts to received messages by performing computation and sending messages to peers; graphical user interfaces (GUI), where the interface software and the underlying application react to user inputs and web-based applications, where presentation, business logic and storage tier functionality react to user inputs and response from other web-based services. Such applications are difficult to test because the set of possible interaction sequences between the system and its environment can be very large and governed by complex constraints. The exhaustive nature of software model checking techniques offers hope for effectively validating such systems, however, they only work for closed systems. Previously, the authors developed the Bandera Environment Generator, which given an open system, called a unit under analysis, closes it with a model of its environment. The authors' previous work on environment generation has focused on developing broadly applicable mechanisms for modelling environment behaviour. The generality of this approach often makes it difficult to produce environment models that enable precise and efficient system analysis. The authors' experience shows that by exploiting information about the application domain, generated environments can be made both more precise and more efficient for model checking. This study presents the concept of domain-specific environment generation, details techniques for customising environment generation for the domain of event-driven software, and assesses those techniques on the domains of GUI and web-based applications.

Modeling of a Disk Drive's Front-End Channel Path

A system approach for designing the channel path of disk drives is required for achieving high data rates and maintaining data integrity. The channel path includes electronics, electrical interconnects, and the read/write heads. The signal transfer through electrical interconnects is affected by its physical components that create the losses and the termination effects. From electromagnetic analysis or measurements, s-parameters are obtained for analyzing signal transfer and crosstalk. Using these s-parameters, chain type matrices can be created to apply an efficient system analysis of the signal transfer. This type of system analysis can be used to produce frequency and time domain response of the complete channel path: read/write transducers, suspension interconnect, read/write IC, flex interconnect, and channel IC

Low peak factor waveforms for efficient system analysis using a fast Fourier transform

Low peak factor waveforms [M. R. Schroeder, Number Theory in Science and Communication (Springer, New York, 1984)] can be designed so that multiple harmonics in the waveform appear to have the ideal spectrum of a true Fourier transform when the waveform is analyzed using a fast Fourier transform (FFT). If the harmonics in the waveform are restricted to those having an integral number of cycles in the FFT data record length, there is no leakage, and the magnitudes and phases of the Fourier coefficients are identical to those of the harmonics in the waveform. Low peak factor waveforms drastically reduce peak power requirements. For example, the peak power requirement for a waveform having 63 harmonics can be reduced by a factor of about 30. Waveforms can be designed having harmonics with constant, octave, and close approximations to one‐third octave frequency differences. This approach can provide an efficient alternative to other methods in current use for measuring system transfer functions. [Work supported in part by the National Research Council of Canada and the Lanikai Foundation.]