Closed-loop Verification of Medical Devices With Model Abstraction and Refinement

The design and implementation of software for medical devices is challenging due to the closed-loop interaction with the patient, which is a stochastic physical environment. The safety-critical nature and the lack of existing industry standards for verification, make this an ideal domain for exploring applications of formal modeling and closed-loop analysis. The biggest challenge is that the environment model(s) have to be both complex enough to express the physiological requirements, and general enough to cover all possible inputs to the device. In this effort, we use a dual chamber implantable pacemaker as a case study to demonstrate verification of software specifications of medical devices as timed-automata models in UPPAAL. The pacemaker model is based on the specifications and algorithm descriptions from Boston Scientific. The heart is modeled using timed automata based on the physiology of heart. The model is gradually abstracted with timed simulation to preserve properties. A manual Counter-Example-Guided Abstraction and Refinement (CEGAR) framework has been adapted to refine the heart model when spurious counter-examples are found. To demonstrate the closed-loop nature of the problem and heart model refinement, we investigated two clinical cases of Pacemaker Mediated Tachycardia and verified their corresponding correction algorithms in the pacemaker. Along with our tools for code generation from UPPAAL models, this effort enables model-driven design and certification of software for medical devices

NOODLE++: a 3 Dimensional Net-based Object-orientated Development Model

HKU CS Tech Report TR-95-04Object-oriented analysis and design methodologies are considered as the most popular software development methods for the 1990s. A common drawback, however, is that they have been developed informally. There is no theoretical framework enabling us to define precisely the object-oriented concepts involved, to solve concurrency problems, and to verify the correctness of the implementation. We propose a 3-dimensional net structure behind object-oriented software development. This structure consolidates the concepts of classes, inheritance, overloading and message passing through a single model. Inheritance and overloading can be unified with message passing in a 3-dimensional representation, but are physically differentiable by occupying the vertical and horizontal planes,respectively, of the model. Furthermore, the formal model can be mapped to various object-oriented analysis and design notations. The theoretical framework can thus be adopted for systems validation and verification for existing methodologies. The liveness and consistencies of objects can be verified, and inheritance and interaction coupling can be identified and checked.preprintThis research is supported in part by a grant of the Research Grants Council

Rapid State Space Modeling Tool for Rectangular Wing Aeroservoelastic Studies

This paper introduces a modeling and simulation tool for aeroservoelastic analysis of rectangular wings with trailing-edge control surfaces. The inputs to the code are planform design parameters such as wing span, aspect ratio, and number of control surfaces. Using this information, the generalized forces are computed using the doublet-lattice method. Using Roger's approximation, a rational function approximation is computed. The output, computed in a few seconds, is a state space aeroservoelastic model which can be used for analysis and control design. The tool is fully parameterized with default information so there is little required interaction with the model developer. All parameters can be easily modified if desired. The focus of this paper is on tool presentation, verification, and validation. These processes are carried out in stages throughout the paper. The rational function approximation is verified against computed generalized forces for a plate model. A model composed of finite element plates is compared to a modal analysis from commercial software and an independently conducted experimental ground vibration test analysis. Aeroservoelastic analysis is the ultimate goal of this tool, therefore, the flutter speed and frequency for a clamped plate are computed using damping-versus-velocity and frequency-versus-velocity analysis. The computational results are compared to a previously published computational analysis and wind-tunnel results for the same structure. A case study of a generic wing model with a single control surface is presented. Verification of the state space model is presented in comparison to damping-versus-velocity and frequency-versus-velocity analysis, including the analysis of the model in response to a 1-cos gust

Rapid State Space Modeling Tool for Rectangular Wing Aeroservoelastic Studies

This report introduces a modeling and simulation tool for aeroservoelastic analysis of rectangular wings with trailing-edge control surfaces. The inputs to the code are planform design parameters such as wing span, aspect ratio, and number of control surfaces. Using this information, the generalized forces are computed using the doublet-lattice method. Using Roger's approximation, a rational function approximation is computed. The output, computed in a few seconds, is a state space aeroservoelastic model which can be used for analysis and control design. The tool is fully parameterized with default information so there is little required interaction with the model developer. All parameters can be easily modified if desired. The focus of this report is on tool presentation, verification, and validation. These processes are carried out in stages throughout the report. The rational function approximation is verified against computed generalized forces for a plate model. A model composed of finite element plates is compared to a modal analysis from commercial software and an independently conducted experimental ground vibration test analysis. Aeroservoelastic analysis is the ultimate goal of this tool, therefore, the flutter speed and frequency for a clamped plate are computed using damping-versus-velocity and frequency-versus-velocity analysis. The computational results are compared to a previously published computational analysis and wind-tunnel results for the same structure. A case study of a generic wing model with a single control surface is presented. Verification of the state space model is presented in comparison to damping-versus-velocity and frequency-versus-velocity analysis, including the analysis of the model in response to a 1-cos gust

Using ANSYS Workbench Computer Environment in Turbomachinery Design Process

The main focus of designing turbomachinery is to analyze and optimize the aerodynamic efficiency and structural integrity of the machine. The preferred way to perform aerodynamic and structural analysis is to connect the analyses and shorten the analysis time as much as possible. ANSYS, Inc. provides a comprehensive approach to model fluid structure interaction phenomenon in turbomachinery within the ANSYS Workbench environment. This environment combines a number of software components that conduct blade design, fluid dynamic and structural analyses, and pre- and post-processing including mesh generation and overall performance estimation. The focus of this study is to apply the ANSYS Workbench environment to two turbomachinery applications: a low speed fan design and a propeller design for high altitude flight. The entire process is successfully implemented for the low speed fan analysis and provides verification that the ANSYS Workbench environment works properly, with CFD predictions obtained within 1% of the previous research. On the other hand, the environment fails for the high altitude propeller blade analysis because the blade creation program in ANSYS Workbench does not support creating highly twisted propeller blades, and some essential design information is missing from the blade design source. Overall, it appears that the ANSYS Workbench environment is a highly useful tool for connecting CFD and structural analysis in the turbomachinery design process

Performance Based Seismic Design of Lateral Force Resisting System

Das seitliche Kraftwiderstandssystem, in diesem Fall Stahlbetonkernwände eines 10-stöckigen Gebäudes, das aus Schwerkraftstützen und Scherwänden besteht, wurde linear (unter der Annahme eines linearen elastischen Materialverhaltens von Beton) und nichtlinear gerissen (unter Berücksichtigung des Materialverhaltens von Beton) unter seismische Belastung analysiert. Erst wurde die grundlegenden Methode der äquivalenten Seitenkraft zur Schätzung der seismischen Belastungen benutzt, später wurde die aktuelle Methode The Performance Based Seismic Design verwendet, bei der reale seismische Aufzeichnungen verwendet werden und die Beschleunigungen mithilfe der Software ETABS auf das Gebäude angewendet werden. Nach dem Anwenden der Beschleunigungen wurden die maximal resultierenden Kräfte und Verformungen bewertet. Das Gebäude wurde dann für die maximal resultierenden Kräfte ausgelegt.Der Inhalt des Hauptberichts ist: - Allgemeine Beschreibung des Gebäudes, seismische Standortinformationen, Standortantwortspektren, Belastung und seismische Kräfte einschließlich Analyse des modalen Antwortspektrums. - Lineares Design des Modells für Schwerkraft und seismische Belastungen, P-M-Wechselwirkungsdiagramme für den U-Querschnitt aus Stahlbeton, Entwurf einer Längs- und Schubbewehrung der Scherwände und des Koppelbalkens. - Zwei Varianten des nichtlinearen Modells, bei denen die Kernwand (Scherwände) gemäß jeder Variante entworfen wird, wobei der Einfluss des Dämpfungsmodells auf das nichtlineare dynamische Verhalten sowie der Einfluss des Kopplungsstrahlmodells auf das nichtlineare dynamische Verhalten untersucht werden. - Entwurfsüberprüfung, erst mit der Definition der Leistungsobjekte und Modell für die Zeitverlaufsanalyse. Es wurden zwei Leistungsziele untersucht: Vollbetriebs- und Lebenssicherheitsprüfungen. - In zwei Fällen wurde eine zusätzliche Studie zur Reaktion von nicht strukturellen Elementen aufgrund seismischer Belastung durchgeführt: Überprüfung des Vollbetriebs und der Lebenssicherheit. - Die Durchsetzungszeichnungen wurden fertiggestellt und dem Bericht beigefügt. Schlussfolgerung und Empfehlungen waren am Ende des Berichts. Dies ist wichtig für die Gesellschaft, da die verwendete Methode für die seismische Planung jedes Gebäudes verwendet werden kann. Es könnte ein Holzbau oder ein Mauerwerk sein. Die Gestaltung eines Mauerwerksgehäuses wird Gegenstand eines zukünftigen Forschungsprojekts sein. Allgemeine Ziele: Lineare und nichtlineare seismische Bemessung von Stahlbetongebäuden unter Verwendung der 'seismischen Bemessung der Leistungsgrundlagen:Acknowledgement 4 PART I: General Information, Site and Loading 5 1. General Information About the Building 5 1.1. Specified Material Properties: 6 1.2. Site Information: 6 1.3. Geometry (Figure I.1): 7 2. Site Seismicity and Design Coefficients 7 2.1. USGS Results 7 2.2. Site Response Spectra 8 2.3. Design Coefficients And Factors For Seismic Force-Resisting Systems 8 3. Loading 9 3.1. Determination Of Seismic Forces 9 3.2. Modal Response Spectrum Analysis 9 3.3. Seismic Load Effects And Combinations 11 PART II: Core Wall Design - Linear Model 12 4. Model of ETABS 12 4.1. Geometry 12 4.2. Gravity Loads 13 4.3. Seismic Loads 15 4.4. Tabulated Selected Results From ETABS Analysis 16 5. P-M Interaction Diagrams 17 5.1. N-S Direction 17 5.2. E-W Direction 19 6. Lateral Force Resisting System, Linear 20 6.1. Longitudinal Reinforcement 20 6.2. Shear Reinforcement 22 6.3. Boundary Elements 24 6.3.1. Transverse Reinforcement Of Boundary Elements 26 6.4. Coupling Beams 27 7. Detailing 30 PART III: Site Response Spectra and Input Ground Motions 31 8. Performance Levels 31 8.1. ASCE 7-16 Target Spectra 31 8.2. Site Response Spectra 34 8.2.1. Ground Motion Conditioning 34 8.2.2. Amplitude Scaling 37 8.2.3. Pseudo Acceleration and Displacement Response Spectra 38 PART IV: Non-Linear Model 40 9. Variant 1 of Non-Linear Model 40 9.1. Complete Core Wall Design for Combined Axial-Flexure 40 9.2. Modal Analysis 43 9.3. Influence of the Damping Model on the Nonlinear Dynamic Response 49 10. Variant 2 of Non-Linear Model 57 10.1. Influence of the Coupling Beam Model on the Nonlinear Dynamic Response 57 10.2. Estimated Roof Displacement 68 PART V: Design Verification 70 11. General 70 11.1. Performance Objectives 70 11.2. Model For Time-History Analyses 71 11.3. Performance Level Verification 71 11.4. Fully Operational Performance Level Verification 71 11.5. Life Safety Performance Level Verification 78 PART VI: Capacity Design of Force Controlled Elements and Regions and Design of Acceleration-Sensitive Nonstructural Elements 87 12. General 87 12.1. Design Verification 87 12.1.1. Full Occupancy Case 87 12.1.2. Life Safety Case 91 12.1.3. Observations on Plots 93 12.2. Acceleration response spectra at roof level 94 12.2.1. Observations on Plots 95 12.3. Core Wall 97 12.4. Design Detail Comparison 103 12.5. Detailed Drawing 103 12.6. Diaphragm 104 12.7. Fire Sprinkler System 117 12.8. Overhanging Projector 119 PART VII: Conclusion 122Lateral Force Resisting System, in this case reinforced concrete core walls of a 10 story building consists of gravity columns and shear walls, has been analyzed in linear (assuming linear elastic material behavior of concrete) and nonlinear cracked (considering plastic material behavior of concrete) case, for seismic loading. Starting with the basic method of equivalent lateral force to estimate the seismic loads, then using the up to date method, The Performance Based Seismic Design, which uses real seismic records and apply the accelerations on the building using the software ETABS. After applying the accelerations, maximum resulted forces and deformations have been evaluated. The building then have been designed for the maximum resulted forces. The contents of the main report are: - General description of the building, site seismic information, site response spectra, loading and seismic forces including modal response spectrum analysis. - Linear design of the model for gravity and seismic loads, P-M interaction diagrams developed for U cross section from reinforced concrete, designing longitudinal and shear reinforcement of the shear walls and coupling beam. - Two variants of Nonlinear model, designing the core wall (shear walls) according to each variant, studying the influence of damping model on the nonlinear dynamic response, as well as the influence of the coupling beam model on the nonlinear dynamic response. - Design verification, starting with defining the performance objects, and model for time history analysis. Two performance objectives have been studied: Fully operational and Life safety level verifications. - Additional study was performed for the response of non-structural elements due to seismic loading in two cases: Fully operational and Life safety level verifications. - Reinforcement Drawings have been finalized and attached to the report. - Conclusion and recommendations was at the end of the report. It is important for the society, because the used method could be used for the seismic design of any building. It could be wood building or masonry building. Designing a masonry building case will be the subject of future research project. Overall objectives: Linear and Nonlinear seismic design of reinforced concrete building using the performance bases seismic design.:Acknowledgement 4 PART I: General Information, Site and Loading 5 1. General Information About the Building 5 1.1. Specified Material Properties: 6 1.2. Site Information: 6 1.3. Geometry (Figure I.1): 7 2. Site Seismicity and Design Coefficients 7 2.1. USGS Results 7 2.2. Site Response Spectra 8 2.3. Design Coefficients And Factors For Seismic Force-Resisting Systems 8 3. Loading 9 3.1. Determination Of Seismic Forces 9 3.2. Modal Response Spectrum Analysis 9 3.3. Seismic Load Effects And Combinations 11 PART II: Core Wall Design - Linear Model 12 4. Model of ETABS 12 4.1. Geometry 12 4.2. Gravity Loads 13 4.3. Seismic Loads 15 4.4. Tabulated Selected Results From ETABS Analysis 16 5. P-M Interaction Diagrams 17 5.1. N-S Direction 17 5.2. E-W Direction 19 6. Lateral Force Resisting System, Linear 20 6.1. Longitudinal Reinforcement 20 6.2. Shear Reinforcement 22 6.3. Boundary Elements 24 6.3.1. Transverse Reinforcement Of Boundary Elements 26 6.4. Coupling Beams 27 7. Detailing 30 PART III: Site Response Spectra and Input Ground Motions 31 8. Performance Levels 31 8.1. ASCE 7-16 Target Spectra 31 8.2. Site Response Spectra 34 8.2.1. Ground Motion Conditioning 34 8.2.2. Amplitude Scaling 37 8.2.3. Pseudo Acceleration and Displacement Response Spectra 38 PART IV: Non-Linear Model 40 9. Variant 1 of Non-Linear Model 40 9.1. Complete Core Wall Design for Combined Axial-Flexure 40 9.2. Modal Analysis 43 9.3. Influence of the Damping Model on the Nonlinear Dynamic Response 49 10. Variant 2 of Non-Linear Model 57 10.1. Influence of the Coupling Beam Model on the Nonlinear Dynamic Response 57 10.2. Estimated Roof Displacement 68 PART V: Design Verification 70 11. General 70 11.1. Performance Objectives 70 11.2. Model For Time-History Analyses 71 11.3. Performance Level Verification 71 11.4. Fully Operational Performance Level Verification 71 11.5. Life Safety Performance Level Verification 78 PART VI: Capacity Design of Force Controlled Elements and Regions and Design of Acceleration-Sensitive Nonstructural Elements 87 12. General 87 12.1. Design Verification 87 12.1.1. Full Occupancy Case 87 12.1.2. Life Safety Case 91 12.1.3. Observations on Plots 93 12.2. Acceleration response spectra at roof level 94 12.2.1. Observations on Plots 95 12.3. Core Wall 97 12.4. Design Detail Comparison 103 12.5. Detailed Drawing 103 12.6. Diaphragm 104 12.7. Fire Sprinkler System 117 12.8. Overhanging Projector 119 PART VII: Conclusion 12

Software components and formal methods from a computational viewpoint

Software components and the methodology of component-based development offer a promising approach to master the design complexity of huge software products because they separate the concerns of software architecture from individual component behavior and allow for reusability of components. In combination with formal methods, the specification of a formal component model of the later software product or system allows for establishing and verifying important system properties in an automatic and convenient way, which positively contributes to the overall correctness of the system. Here, we study such a combined approach. As similar approaches, we also face the so-called state space explosion problem which makes property verification computationally hard. In order to cope with this problem, we derive techniques that are guaranteed to work in polynomial time in the size of the specification of the system under analysis, i.e., we put an emphasis on the computational viewpoint of verification. As a consequence, we consider interesting subclasses of component-based systems that are amenable to such analysis. We are particularly interested in ideas that exploit the compositionality of the component model and refrain from understanding a system as a monolithic block. The assumptions that accompany the set of systems that are verifiable with our techniques can be interpreted as general design rules that forbid to build systems at will in order to gain efficient verification techniques. The compositional nature of software components thereby offers development strategies that lead to systems that are correct by construction. Moreover, this nature also facilitates compositional reduction techniques that allow to reduce a given model to the core that is relevant for verification. We consider properties specified in Computation Tree Logic and put an emphasis on the property of deadlock-freedom. We use the framework of interaction systems as the formal component model, but our results carry over to other formal models for component-based development. We include several examples and evaluate some ideas with respect to experiments with a prototype implementation

Verification templates for the analysis of user interface software design

The paper describes templates for model-based analysis of usability and safety aspects of user interface software design. The templates crystallize general usability principles commonly addressed in user-centred safety requirements, such as the ability to undo user actions, the visibility of operational modes, and the predictability of user interface behavior. These requirements have standard forms across different application domains, and can be instantiated as properties of specific devices. The modeling and analysis process is carried out using the Prototype Verification System (PVS), and is further facilitated by structuring the specification of the device using a format that is designed to be generic across interactive systems. A concrete case study based on a commercial infusion pump is used to illustrate the approach. A detailed presentation of the automated verification process using PVS shows how failed proof attempts provide precise information about problematic user interface software features.This work has been funded by the EPSRC research grant EP/G059063/1: CHI+ MED (Computer-Human Interaction for Medical Devices). We are grateful to Harold Thimbleby's team at Swansea University, part of the CHI+ MED project, and especially Patrick Oladimeji who developed the infusion pump simulation that helped us develop the models. We also thank the anonymous reviewers for valuable feedback. Jose C. Campos and Paolo Masci were funded by project NORTE-01-0145-FEDER-000016, financed by the North Portugal Regional Operational Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, and through the European Regional Development Fund (ERDF)

Modeling and Analysis of Multicommodity Network Flows via Goal Programming

In this research we focused on the mobility system modeled by the AMC mobility planner\u27s calculator (AMPCALC). We developed AMPCALC as a user-friendly tool and allow the user to easily carry out strategic airlift, air refueling and aeromedical evacuation calculations that are covered in Air Force Pamphlet 10-1403. In this study, Excel software and its macro language, Visual Basic for Application, are our two main tools. In the methodology of the thesis we examined fundamental aspects of the mobility system in AMPCALC. We discussed formulation logic of the mobility cycle. We presented ramp use optimization and tanker optimization processes. We also conducted verification and validation of AMPCALC. Sensitivity analysis of the model includes a response surface study. To be able to investigate the main effects and interaction effects of the input factors on closure time, we performed a 26 factorial design. No linear relations are observed, but some relations between inputs and closure time are observed

Development of Finite Element Techniques to Simulate Concrete-Filled Fiber-Reinforced Polymer Tube Structures

This dissertation presents the development of finite-element (FE) techniques to simulate the behavior of concrete-filled fiber reinforced polymer (FRP) tubes (CFFTs) in support of more effective structural design and analysis methods for buried composite arch bridges (BCABs) that use CFFT arches as main structural members. The research includes three specific topics to make contributions in different aspects of the investigation of these complex structures. The first topic is the nonlinear three-dimensional FE modeling of steel-free CFFT splices. For model validation, comparisons were made between the model predictions and control beam and spliced beams with and without internal collars tested by others. The modeling was complex due to the need to capture the nonlinear constitutive response of the confined concrete, simulate concrete-FRP interaction, and explicitly incorporate the splice components. Therefore, the numerical analysis utilized the Abaqus/CAE software package with a modified damage concrete plasticity model to idealize the concretefill. The second topic of this research is the development of a computationally efficient structural FE analysis technique for the second-order inelastic behavior of these CFFT arches that includes initial arch curvature. A curved, planar, corotational, flexibility-based (FB), layered frame element is employed to handle geometric and material nonlinearities. An FRP-confined concrete stress-strain model that explicitly considers the effect of dilation of the concrete core and confinement provide by the FRP tube is implemented. Verification of the FB formulation was carried out for elastic-plastic analysis of a beam and elastic post-buckling analysis of a circular arch. The measured flexural responses of different isolated CFFT arches available in the literature were used to verify the proposed model. The model was shown to accurately predict the load-carrying capacity and ductility of the tested CFFT arches. The model captured arch collapse mechanisms arising from FRP rupture and concrete crushing at the apex of the arches. The third topic is an extension of the planar FB model to three-dimensions and incorporation of a soil-spring model to simulate soil-structure interaction using a recently developed horizontal earth pressure model. The model rigorously incorporates the interaction between axial load and bending effects in the arches and permits the examination of out-of-plane stability and arch deformations due to bridge skew. Parametric studies were conducted to assess the effect of abutment skew angle on the behavior of CFFT arch bridge components, an important practical design consideration