Liveness Verification Research Articles

Fatigue research of metro car body based on operational loads

PurposeThe principle of infinite life design currently directs fatigue resistance strategies for metro car bodies. However, this principle might not fully account for the dynamic influence of operational loads and the inevitable presence of defects. This study aims to integrate methods of service life estimation and residual life assessment, which are based on operational loads, into the existing infinite life verification framework to further ensure the operational safety of subway trains.Design/methodology/approachOperational loads and fatigue loading spectra were determined through the field test. The material test was conducted to investigate characteristics of the fracture toughness and the crack growth rate. The fatigue strength of the metro car body was first verified using the finite element method and Moore–Kommers–Japer diagrams. The service life was then estimated by applying the Miner rule and high-cycle fatigue curves in a modified form of the Basquin equation. Finally, the residual life was assessed utilizing a fracture assessment diagram and a fitted curve of crack growth rate adhered to the Paris formula.FindingsNeither the maximum utilization factor nor the cumulative damage exceeds the threshold value of 1.0, the metro car body could meet the design life requirement of 30 years or 6.6 million km. However, three out of five fatigue key points were significantly influenced by the operational loads, which indicates that a single fatigue strength verification cannot achieve the infinite life design objective of the metro car body. For a projected design life of 30 years, the tolerance depth is 12.2 mm, which can underscore a relatively robust damage tolerance capability.Originality/valueThe influence of operational loads on fatigue life was presented by the discrepancy analysis between fatigue strength verification results and service life estimation results. The fracture properties of butt-welded joints were tested and used for the damage tolerance assessment. The damage tolerance life can be effectively related by a newly developed equation in this study. It can be a valuable tool to provide the theoretical guidance and technical support for the structural improvements and maintenance decisions of the metro car body.

Live Verification in an Interactive Proof Assistant

Live Verification in an Interactive Proof Assistant

Liveness and deadlock-freeness verification and enforcement in bounded Petri nets using basis reachability graphs

This paper studies the verification and enforcement of deadlock-freeness and liveness in partially controllable Petri nets. First, we introduce a particular type of basis reachability graphs called conflict-free-control-explicit basis reachability graphs (CFCE-BRGs), in which the firings of all structurally conflicting transitions and all controllable ones are explicitly encoded. We propose two sufficient and necessary conditions for verifying deadlock-freeness and liveness of a Petri net; both can be verified by inspecting a CFCE-BRG using graph theory. Moreover, we develop two maximally permissive deadlock-freeness and liveness enforcing supervisors based on the trimming of CFCE-BRGs. The developed approaches are applicable to arbitrary bounded Petri nets, without an exhaustive reachability space enumeration.

Study on the Effects of Thermal Shaping for 316L Heat Exchange System of Submersible Vehicle on Fatigue Life

In this paper present the effects of 316L steel in the environment of repeated heat load, and the impact of the thermal load on fatigue life. Using thermal fatigue experiments and ABAQUS software, rain flow counting method is used to simplify the strain cycle spectrum of stress load. The Coffin-Manson nonlinear empirical equation was established based on thermal fatigue experiments, and the fatigue life estimation was completed in accordance with the Miner damage accumulation rule and FE-SAFE fatigue software. The test rods were respectively placed at room temperature and heated at 250°C for water cooling for tensile testing. Fatigue tests were performed with 5 strain parameters (0.8%, 0.7%, 0.6%, 0.5% and 0.4%). ABAQUS and FE-SAFE software used to study 316L testing rod fatigue life verification analysis. A composite heat exchange system model made of 316L was designed for the case study. It is found that the fatigue life after heating is reduced by 35% to 12% from the experimental results and numerical simulation calculation. Therefore, when the 316L steel is subjected to thermal fatigue, the fatigue life will be reduced. The research results can provide a reference for the design of heat exchangers using 316 steel in various fields.

Secure Face and Liveness Detection with Criminal Identification for Security Systems

The advancement of computer vision, machine learning, and image processing techniques has opened new avenues for enhancing security systems. In this research work focuses on developing a robust and secure framework for face and liveness detection with criminal identification, specifically designed for security systems. Machine learning algorithms and image processing techniques are employed for accurate face detection and liveness verification. Advanced facial recognition methods are utilized for criminal identification. The framework incorporates ML technology to ensure data integrity and identification techniques for security system. Experimental evaluations demonstrate the system's effectiveness in detecting faces, verifying liveness, and identifying potential criminals. The proposed framework has the potential to enhance security systems, providing reliable and secure face and liveness detection for improved safety and security.
 The accuracy of the algorithm is 94.30 percent. The accuracy of the model is satisfactory even after the results are acquired by combining our rules inwritten by humans with conventional machine learning classification algorithms. Still, there is scope for improving and accurately classifying the attack precisely.

A case study on parametric verification of failure detectors

Partial synchrony is a model of computation in many distributed algorithms and modern blockchains. These algorithms are typically parameterized in the number of participants, and their correctness requires the existence of bounds on message delays and on the relative speed of processes after reaching Global Stabilization Time. These characteristics make partially synchronous algorithms parameterized in the number of processes, and parametric in time bounds, which render automated verification of partially synchronous algorithms challenging. In this paper, we present a case study on formal verification of both safety and liveness of the Chandra and Toueg failure detector that is based on partial synchrony. To this end, we first introduce and formalize the class of symmetric point-to-point algorithms that contains the failure detector. Second, we show that these symmetric point-to-point algorithms have a cutoff, and the cutoff results hold in three models of computation: synchrony, asynchrony, and partial synchrony. As a result, one can verify them by model checking small instances, but the verification problem stays parametric in time. Next, we specify the failure detector and the partial synchrony assumptions in three frameworks: TLA+, IVy, and counter automata. Importantly, we tune our modeling to use the strength of each method: (1) We are using counters to encode message buffers with counter automata, (2) we are using first-order relations to encode message buffers in IVy, and (3) we are using both approaches in TLA+. By running the tools for TLA+ and counter automata, we demonstrate safety for fixed time bounds. By running IVy, we prove safety for arbitrary time bounds. Moreover, we show how to verify liveness of the failure detector by reducing the verification problem to safety verification. Thus, both properties are verified by developing inductive invariants with IVy.

Design of HERMES: a mobile autonomous surveillance robot for security patrol

The HERMES autonomous surveillance robot platform is a low-cost outdoor autonomous surveillance vehicle. It is designed to autonomously patrol outdoor areas performing surveillance and providing automated alerts of detected vehicles and people. The design and testing of this system are covered in this paper. The design philosophy focused on the use of off-the-shelf components wherever possible with the base of the robot being a modified electric quadbike. The testing has verified that the surveillance robot can perform real-time person and vehicle detection, video streaming, manual and autonomous navigation on a low-cost platform. The development of the robot platform is continuing with the current focus being on the improvement of the autonomous navigation, ingress protection (IP) rating and verification of the battery life.

자동차 전자제어장치의 열 피로를 고려한 가속수명시험법 개발에 관한 연구

The automotive electronic control unit outputs control signals using electrical signals of various input sensors installed in the vehicle to control the state of the engine, automatic transmission, and electric power steering (EPS). These units are installed inside the vehicle or engine room, and the temperature rises and falls by several tens of degrees due to the heat of the engine and the self-heating of the electronic control unit. Therefore, it was exposed to a thermal fatigue environment due to the difference in the coefficient of thermal expansion between the components, which caused frequent component damage. Solder cracks due to thermal fatigue in electronic control units are a key failure mode. However, because of its great heat capacity, the electronic control unit for automobiles took a long time to attain the desired temperature of high or low, and as a result, the 1,000-cycle test for thermal fatigue life verification required 3,167 hours (or 4.4 months). Therefore, in this study, the thermal shock cycle test time for the verification of the thermal fatigue life of electronic control units for automobiles was reduced by dividing it into two types.

General Decidability Results for Asynchronous Shared-Memory Programs: Higher-Order and Beyond

The model of asynchronous programming arises in many contexts, from low-level systems software to high-level web programming. We take a language-theoretic perspective and show general decidability and undecidability results for asynchronous programs that capture all known results as well as show decidability of new and important classes. As a main consequence, we show decidability of safety, termination and boundedness verification for higher-order asynchronous programs -- such as OCaml programs using Lwt -- and undecidability of liveness verification already for order-2 asynchronous programs. We show that under mild assumptions, surprisingly, safety and termination verification of asynchronous programs with handlers from a language class are decidable iff emptiness is decidable for the underlying language class. Moreover, we show that configuration reachability and liveness (fair termination) verification are equivalent, and decidability of these problems implies decidability of the well-known "equal-letters" problem on languages. Our results close the decidability frontier for asynchronous programs.

Formal verification of persistence and liveness in the trust-based blockchain crowdsourcing consensus protocol

Crowdsourcing is a potential computing paradigm that exploits collective human intelligence to solve complex tasks, but it suffers from various safety and security problems. Blockchain has emerged as a promising technology to address most of the security issues, however, it is challenging to find an appropriate and trusted blockchain-based consensus protocol for crowdsourcing services. This work proposes a novel Trust-based Blockchain Crowdsourcing consensus protocol that selects a leader and validators based on various trust factors. The proposed protocol addresses a major issue of ensuring correctness associated with the safety and security-critical systems which has a vital importance because failure of such systems may lead to adverse consequences. Mainly it is focused on persistence and liveness properties preventing invalid block insertion and consensus delay attacks. Model checking technique is utilized because of its effectiveness and automatic nature to perform formal verification. The proposed protocol is specified using Communicating Sequential Programs, and the persistence and liveness properties are specified through Linear Temporal Logic. The model verification is performed by giving the formal model and the properties as input to the Process Analysis Toolkit which checks for the satisfaction or violation of the properties.

Statistical Assessment of Low-Cycle Fatigue Durability

This article presents an experimental–analytical statistical study of low-cycle fatigue to crack initiation and complete failure. The application of statistical and probability methods provides for the possibility of improving the characteristics related to the structural life and the justification for the respective values of cyclic loads in the design stage. Most studies investigating statistical descriptions of crack initiation or complete failure do not analyse the distribution of the characteristics, correlation relationships, and statistical parameters of low-cycle fatigue. Low-cycle failure may be quasistatic or (due to the fatigue) transient. Materials with contrasting cyclic properties were selected for the investigation: cyclically softening alloyed steel 15Cr2MoVA; cyclically stable structural steel C45; cyclically hardening aluminium alloy D16T1. All samples were produced in a single batch of each respective material to reduce the distribution of data. The lowest values of the variation coefficient of one of the key statistical indicators were obtained using the log-normal distribution, which is superior to the normal or Weibull distribution. Statistical analysis of the durability parameters showed that the distribution was smaller than the parameters of the distribution of the deformation diagram. The results obtained in the study enable the verification of durability and life of the structural elements of in-service facilities subjected to elastoplastic loading by assessing the distribution of characteristics of crack initiation and failure and low-cycle strain parameters as well as the permissible distribution limits.

Theoretical prediction and aging experimental verification of the service life of vacuum insulation panels

Vacuum insulated panels (VIPs) are a new type of high-efficiency insulation material with the advantages of energy saving and environmental protection, especially carbon neutral. The excellent thermal performance makes it shine in the carbon reduction market. In the construction field, the service life is an important issue in the application of VIPs. This study uses experimental methods and theoretical mathematical models based on current research to investigate the effects of accelerated aging tests of temperature, humidity, size and alternating high and low temperatures on the service life and thermal conductivity of VIPs. The objective is to validate the existing theoretical aging model of VIPs. First, the experimental setup and protocol are described. Then, the work reports the experimental results of thermal conductivity of 12 VIPs under pristine and accelerated laboratory conditions. The results show that the thermal conductivity of VIPs is low when the humidity is 30%RH to 50%RH, and high when the temperature is 97 °C. The larger the size, the smaller the thermal conductivity. And the thicker the thickness, the greater the thermal conductivity. The thermal conductivity of the insulation panel is very sensitive. This work investigates the service life of vacuum insulation panels under different harsh conditions and contributes to the promotion of vacuum insulation panels in the Chinese construction market. • Thermal conductivity of vacuum insulation panels is measured using the hot plate protection method. • The effects of temperature, humidity, high and low-temperature alternations, and size on the thermal conductivity are illustrated. • Comparison of the measured values with the calculated values validates the existing aging model. • Estimating the service life of vacuum insulation panels.

TAPInspector: Safety and Liveness Verification of Concurrent Trigger-Action IoT Systems

Trigger-action programming (TAP) is a popular end-user programming framework that can simplify the Internet of Things (IoT) automation with simple trigger-action rules. However, it also introduces new security and safety threats. A lot of advanced techniques have been proposed to address this problem. Rigorously reasoning about the security of a TAP-based IoT system requires a well-defined model and verification method both against rule semantics and physical-world features, e.g., concurrency, rule latency, extended action, tardy attributes, and connection-based rule interactions, which has been missing until now. By analyzing these features, we find 9 new types of rule interaction vulnerabilities and validate them on two commercial IoT platforms. We then present TAPInspector, a novel system to detect these interaction vulnerabilities in concurrent TAP-based IoT systems. It automatically extracts TAP rules from IoT apps, translates them into a hybrid model by model slicing and state compression, and performs semantic analysis and model checking with various safety and liveness properties. Our experiments corroborate that TAPInspector is practical: it identifies 533 violations related to rule interaction from 1108 real-world market IoT apps and is at least 60000 times faster than the baseline without optimization.

Liveness in broadcast networks

We study liveness and model checking problems for broadcast networks, a system model of identical clients communicating via message passing. The first problem that we consider is Liveness Verification. It asks whether there is a computation such that one clients visits a final state infinitely often. The complexity of the problem has been open. It was shown to be texttt {P}-hard but in texttt {EXPSPACE}. We close the gap by a polynomial-time algorithm. The latter relies on a characterization of live computations in terms of paths in a suitable graph, combined with a fixed-point iteration to efficiently check the existence of such paths. The second problem is Fair Liveness Verification. It asks for a computation where all participating clients visit a final state infinitely often. We adjust the algorithm to also solve fair liveness in polynomial time. Both problems can be instrumented to answer model checking questions for broadcast networks against linear time temporal logic specifications. The first problem in this context is Fair Model Checking. It demands that for all computations of a broadcast network, all participating clients satisfy the specification. We solve the problem via the Vardi–Wolper construction and a reduction to Liveness Verification. The second problem is Sparse Model Checking. It asks whether each computation has a participating client that satisfies the specification. We reduce the problem to Fair Liveness Verification.

Admission test analysis of pre-service math-science teacher based on its related factors

The admission test of pre-service teachers uses a knowledge test that has not explored the non-cognitive factors. This study is focused on considering the basic abilities, logical thinking abilities, gender, level of cognitive development and the type of pre-service teacher programme. Moreover, other factors, such as motivation, role of life experiences and verification of logical thinking test result (TOLT), were also contemplated. This study applied TOLT to 281 pre-service math–science teachers from four different programmes. This study also developed a multiple mini interview modification with expert screening methods that have validity, reliability and homogeneity parameters based on Aiken's criteria. Our study provides an alternative to reformulate the selection test that combines paper-based tests with interviews as an admission test for pre-service teacher candidates. Our results also illustrate how gender and cognitive development affect the basic abilities based on their programme. Furthermore, admission tests should have balanced cognitive and non-cognitive factors.
 
 Keywords: admission test; content-knowledge ability; level of cognitive development; logical thinking (TOLT); multiple-mini interview (MMI); teacher education.

A Secure Live Signature Verification with Aho-Corasick Histogram Algorithm for Mobile Smart Pad

There is a long history of using handwritten signatures to verify or authenticate a “signer” of the signed document. With the development of Internet technology, many tasks can be accomplished through the document management system, such as the applications of digital contracts or important documents, and more secure signature verification is demanded. Thus, the live handwriting signatures are attracting more interest for biological human identification. In this paper, we propose a handwriting signature verification algorithm by using four live waveform elements as the verification features. A new Aho-Corasick Histogram mechanism is proposed to perform this live signature verification. The benefit of the ACH algorithm is mainly its ability to convert time-series waveforms into time-series short patterns and then perform a statistical counting on the AC machine to measure the similarity. Since AC is a linearly time complexity algorithm, our ACH method can own a deterministic processing time. According to our experiment result, the proposed algorithm has satisfying performance in terms of speed and accuracy with an average of 91% accuracy.

An axiomatic approach to existence and liveness for differential equations

This article presents an axiomatic approach for deductiveverification of existence and liveness for ordinary differentialequations (ODEs) with differential dynamic logic (dL). The approachyields proofs that the solution of a given ODE exists long enough toreach a given target region without leaving a given evolutiondomain. Numerous subtleties complicate the generalization ofdiscrete liveness verification techniques, such as loop variants, tothe continuous setting. For example, ODE solutions may blow up infinite time or their progress towards the goal may converge to zero.These subtleties are handled in dL by successively refining ODEliveness properties using ODE invariance properties which have acomplete axiomatization. This approach is widely applicable: severalliveness arguments from the literature are surveyed and derived asspecial instances of axiomatic refinement in dL. These derivationsalso correct several soundness errors in the surveyed literature,which further highlights the subtlety of ODE liveness reasoning andthe utility of an axiomatic approach. An important special case ofthis approach deduces (global) existence properties of ODEs, whichare a fundamental part of every ODE liveness argument. Thus, allgeneralizations of existence properties and their proofs immediatelylead to corresponding generalizations of ODE liveness arguments.Overall, the resulting library of common refinement steps enablesboth the sound development and justification of new ODE existenceand of liveness proof rules from dL axioms. These insights are putinto practice through an implementation of ODE liveness proofs inthe KeYmaera X theorem prover for hybrid systems.

Analysis and Experimental Study on Friction and Wear Characteristics of Super High-Speed Mechanical Seal

Mechanical seal is the core component of the servo system. It’s sealing, reliability and wear resistance depend not only on the structural design of the seal, but also on the matching of friction pair materials on the end face of the seal. On the basis of the feasibility study of ion implantation on the surface of the seal ring, a comprehensive test scheme is proposed to verify the friction and wear characteristics of the seal pair. By selecting typical graphite and rotating metal ring pairs to test and test under dry grinding conditions, changing the linear velocity and the end face specific pressure, the friction and wear characteristics of paired friction pairs are compared and analyzed by using friction and wear testing machine, the influence of load and rotational speed on the pair friction coefficient of sealing pair is systematically studied, and the sealing tribological characteristics are revealed. This paper introduces mechanical-seal work reliability of temperature stress and system test performace based seal pair, the application of these plans will provide a reasonable and efficient technical way for the verification of life and reliability test of ultra-high speed mechanical seal.

Statistical n-Best AFD-Based Sparse Representation for ECG Biometric Identification

Electrocardiogram (ECG) biometric recognition as a personal identification method is receiving more and more attention because it can support live verification results. Compared with other biometric-based methods, it can provide higher security performance. The difficulty of the problem lies in how to stably extract ECG signal features and achieve real-time verification. In this study, a new type of sparse representation learning framework called statistical $n$ -best adaptive Fourier decomposition (SAFD) originated by Qian is adopted in ECG biometric identification. Adaptive Fourier decomposition (AFD) is a recently developed combination of transform-based signal decomposition and sparse representation method, which can adaptively select the atoms from a redundant dictionary through orthogonal processing. The advantage of the AFD-type methods is that each atom in the dictionary has a precise mathematical formula with good analytic properties. This characteristic is significantly distinguished it from other existing sparse representations, where the atoms learned are usually matrix data and cannot be described mathematically. The proposed SAFD extends the existing $n$ -best AFD from processing single signal to multi-signals and implements the $n$ -best AFD in the stochastic Hardy space. Therefore, the small number of learned atoms by SAFD is sufficient to capture internal structure and robustness of the signal and generate a discriminative representation that reflects the time–frequency characteristics of signals. It is very suitable for non-stationary signals like ECG. The proof of convergence of the algorithm is presented. Extensive experiments are conducted on five public databases collected in different realistic conditions, and an average identification accuracy of 98.0% is achieved. In addition, less than 1 ms for one matching process makes it possible to be implemented in real time. Experimental results demonstrate that the proposed method can achieve superior performance compared to other state-of-the-art ECG biometric identification methods.

Stress/strain state for critical components of a jet engine aeronautical compressor

In order to prevent in-flight fatigue failure, a numerical analysis of in service-operative cases is an useful approach for preliminary evaluation of most stressed and critical zones in components of aeronautical engine. The zero-stage compressor rotor disk and blades represent one of the most critical part of aircraft turbojet. This paper presents a verification FEM analysis of this component. An accurate 3D scanning was performed to reconstruct both blade and disk real geometry and the detailed point cloud was obtained and opportunely elaborated by using specific software to generate CAD sections and volumes given in input to finite element analysis. The stress field due to different operating conditions is studied for a suitable evaluation of the most stressed and critical areas where a failure may occur, particularly near the rotor connection under contact conditions. FEM and flight data analysis are finally used for a subsequent fatigue life verification, based on classical Palmgren Miner’ rule. The suggested procedure for verification of engine aeronautical component is here optimized for maintenance program improvements.