Liveness Verification Research Articles

Life Prediction and Verification under Multiaxial Fatigue Loading

The strain change characteristics of multiaxial fatigue are analyzed under the condition of the combined tension and torsion loading for thin-tube specimen. Based on the principle of multiaxial critical plane approach, a multiaxial fatigue damage parameter is established, which takes account of the effect of not only the maximum shear strain amplitude and normal strain amplitude on the critical plane but also the parameter of non-proportionality. The non-proportionality is the function of loading parameters which is closely contact with the strain change characteristics of multiaxial fatigue and it can indicate the whole material damage. The experiments under the tension-torsion proportional and non-proportional loading were conducted to verify the multiaxial fatigue life model proposed in this paper. The life prediction has a good correlation with the experimental results.

Negative illness perceptions associated with low mental and physical health status in general hospital outpatients in China

In western countries, negative illness perceptions are associated with poor health status and affect health outcomes in primary care populations. The aim of this study is to examine the relationship between illness perception and mental and physical health status in general hospital outpatients in China. This multicentre, cross-sectional study analysed a total of 281 consecutive patients from four general hospital outpatient departments of internal medicine and traditional Chinese medicine in Beijing and Kunming. The patients answered questionnaires concerning illness perception (Brief-IPQ), somatic symptom severity (Patient Health Questionnaire-15), illness behaviour (Scale for the Assessment of Illness Behaviour), emotional distress (Hospital Anxiety and Depression Scale) and health-related quality of life (Twelve-Item Short Form Health Survey). Negative illness perception, especially negative emotional reactions, perceived illness consequences, encumbering illness concerns, and strong illness identity were significantly associated with high emotional distress, impairing illness consequences, and a low mental and physical quality of life. Using a multiple linear regression model, five strongest correlates of negative illness perception were high anxiety, seeking diagnosis verification, low mental and physical quality of life and high somatic symptom severity. The variance explained by this model was 35%. Chinese general hospital outpatients showed associations between negative illness perceptions and poor mental and physical health status that were similar to those of primary care patients in western countries. The main difference was that no association with perceived illness control was found in Chinese patients. Chinese physicians should be sensitised to their patients’ negative illness perceptions and should focus on helping patients cope with uncertainty and anxiety by providing an understandable illness model and increasing control beliefs.

Providing multimodal biometric authentication using five competent traits

Recognition accuracy of a single biometric authentication system is often much limited; hence, a multimodal biometric approach for identity verification is proposed. A new way of person authentication based on five-competent traits, namely, iris, ear, palm print, fingerprint and retina, is proposed in this paper. Each metric is analysed individually to get the matching scores from the corresponding feature sets. These scores are then combined using weighted sum fusion rule. In order to provide liveness verification for our authentication system, we employ the retinal blood vessel pattern recognition. To validate our approach, several experiments were conducted on the images obtained from five different datasets. The experimental results reveal that this multimodal biometric verification system is much more reliable and precise than the single biometric approaches.

Verification of Safety and Liveness Properties of Metric Transition Systems

We consider verification problems for transition systems enriched with a metric structure. We believe that these metric transition systems are particularly suitable for the analysis of cyber-physical systems in which metrics can be naturally defined on the numerical variables of the embedded software and on the continuous states of the physical environment. We consider verification of bounded and unbounded safety properties, as well as bounded liveness properties. The transition systems we consider are nondeterministic, finitely branching, and with a finite set of initial states. Therefore, bounded safety/liveness properties can always be verified by exhaustive exploration of the system trajectories. However, this approach may be intractable in practice, as the number of trajectories usually grows exponentially with respect to the considered bound. Furthermore, since the system we consider can have an infinite set of states, exhaustive exploration cannot be used for unbounded safety verification. For bounded safety properties, we propose an algorithm which combines exploration of the system trajectories and state space reduction using merging based on a bisimulation metric. The main novelty compared to an algorithm presented recently by Lerda et al. [2008] consists in introducing a tuning parameter that improves the performance drastically. We also establish a procedure that allows us to prove unbounded safety from the result of the bounded safety algorithm via a refinement step. We then adapt the algorithm to handle bounded liveness verification. Finally, the effectiveness of the approach is demonstrated by applying it to the analysis of implementations of an embedded control loop.

Concurrency bugs in multithreaded software: modeling and analysis using Petri nets

In this paper, we apply discrete-event system techniques to model and analyze the execution of concurrent software. The problem of interest is deadlock avoidance in shared-memory multithreaded programs. We employ Petri nets to systematically model multithreaded programs with lock acquisition and release operations. We define a new class of Petri nets, called Gadara nets, that arises from this modeling process. We investigate a set of important properties of Gadara nets, such as liveness, reversibility, and linear separability. We propose efficient algorithms for the verification of liveness of Gadara nets, and report experimental results on their performance. We also present modeling examples of real-world programs. The results in this paper lay the foundations for the development of effective control synthesis algorithms for Gadara nets.

Algorithmic verification of asynchronous programs

Asynchronous programming is a ubiquitous systems programming idiom for managing concurrent interactions with the environment. In this style, instead of waiting for time-consuming operations to complete, the programmer makes a non-blocking call to the operation and posts a callback task to a task buffer that is executed later when the time-consuming operation completes. A cooperative scheduler mediates the interaction by picking and executing callback tasks from the task buffer to completion (and these callbacks can post further callbacks to be executed later). Writing correct asynchronous programs is hard because the use of callbacks, while efficient, obscures program control flow. We provide a formal model underlying asynchronous programs and study verification problems for this model. We show that the safety verification problem for finite-data asynchronous programs is expspace-complete. We show that liveness verification for finite-data asynchronous programs is decidable and polynomial-time equivalent to Petri net reachability. Decidability is not obvious, since even if the data is finite-state, asynchronous programs constitute infinite-state transition systems: both the program stack for an executing task and the task buffer of pending calls to tasks can be potentially unbounded. Our main technical constructions are polynomial-time, semantics-preserving reductions from asynchronous programs to Petri nets and back. The first reduction allows the use of algorithmic techniques on Petri nets for the verification of asynchronous programs, and the second allows lower bounds on Petri nets to apply also to asynchronous programs. We also study several extensions to the basic models of asynchronous programs that are inspired by additional capabilities provided by implementations of asynchronous libraries and classify the decidability and undecidability of verification questions on these extensions.

A robust person authentication system based on score level fusion of left and right irises and retinal features

The recognition accuracy of a single biometric authentication system is often much reduced due to the environment, user mode and physiological defects. So a multimodal biometric approach for identity verification using two competent traits, iris and retina is proposed. This multimodal approach diminishes the drawback of single biometric system and improves the performance of an authentication system. Iris and Retina biometric recognition offers a highly reliable solution to person authentication. Iris recognition system is composed of segmentation, normalization, feature encoding and matching. Instead of using the entire iris code, only the bits that are consistent in the iris code called the Best bits are considered in the feature matching process. This reduces the computational time and storage requirements of iris code. To enhance the performance of recognition, the iris recognition process is applied to left and right irises separately and the corresponding distance scores are generated for each iris of a person. These scores are combined using the weighted sum fusion rule which further increases the recognition rate. In order to provide liveness verification for our authentication system, we also employed retinal blood vessel pattern recognition. This ensures the presence of only alive persons eliminating the possible spoofing attack. It is composed of segmentation, enhancement, feature encoding and matching. The scores from iris and retina recognition are then combined using weighted sum fusion rule, which further increases the recognition rate. To validate our approach, experiments were conducted on the iris and retina images obtained from CASIA and VARIA datasets respectively. A multimodal biometric database was constructed and then 1500 inter, intra image comparisons were made using the two datasets. The experimental results reveal that our multimodal biometric authentication system is much more reliable and precise than the single biometric approaches.

Life verification of large capacity Yardney Li-ion cells and batteries in support of NASA missions

Lithium-ion batteries have been used on a number of NASA missions and have been base-lined for use on a number of up-coming aerospace applications. The Li-ion cells and batteries that have been developed together with Yardney Technical Products are especially attractive due to their high specific energy and energy density, good performance over a wide operating temperature range, as well as their good calendar and cycle life performance. However, given that the Li-ion technology is relatively new to the aerospace community and that mature, large capacity prototype cells have continued to evolve over the last 10 years, real-time performance test data is especially valuable in demonstrating the capabilities over a number of environmental and application specific conditions. For this reason, we have focused on performing a number of generic and mission specific performance life tests to establish the viability of the technology to meet current and future applications. In this work, we will describe the results of a number of generic cycle life tests, including 100% depth-of-discharge (DOD) cycling at various temperatures, partial DOD cycling simulating planetary orbiters and low earth orbit (LEO) satellite conditions, as well as partial DOD mission specific testing. We will also describe the results obtained from a number of calendar life tests where the cells were stored under different conditions, such as at different temperatures and different storage modes (i.e. open circuit voltage (OCV) conditions and storage under trickle charge conditions). Methods to quantify the capacity degradation and impedance growth of the batteries when subjected to different electrical and environmental conditions will be discussed, as well as, possible degradation mechanisms that can lead to reduced lifetime. Copyright © 2009 John Wiley & Sons, Ltd.

BAS: A Case Study for Modeling and Verification in Trustable Model Driven Development

Multi-view modeling and separation of concerns are widely used to decrease the design complexity of the large-scale software system. To ensure the correctness and consistency of multi-view requirement models, the formal verification technology should be applied to the model-driven development process. However, there still lacks unified theory foundation and tool supports for the rigorous modeling approach. To solve these problems, we implemented an integrated modeling and verification environment tMDA (Trustable MDA) based on the theory of UTP. In tMDA, developers model system requirements with UML static and dynamic models and verify the correctness and consistency of different models. A multidimensional model is proposed, which supports the consistency verification, liveness and safety property verification, OCL constraints and LTL formula verification. A Bank ATM System (BAS) is introduced to demonstrate how to utilize tMDA for design and verification.

Accelerated Thermo-Mechanical Fatigue Life of Pb-Free Solder Joints for PZT Ceramic Resonator

In this study, we optimized Pb-free Sn/Ni plating thickness and conditions were optimized to counteract the environmental regulations, such as RoHS and ELV(End-of Life Vehicles). The B life verification method was also suggested to have been successful when used with the accelerated life test(ALT) for assessing Pb-free solder joint life of piezoelectric (PZT) ceramic resonator. In order to evaluate the solder joint life, a modified Norris-Landzberg equation and a Coffin-Manson equation were utilized. Test vehicles that were composed of 2520 PZT ceramic resonator on FR-4 PCB with Sn-3.0Ag-0.5Cu for ALT were manufactured as well. Thermal shock test was conducted with 1,500 cycles from (-40 ± 2) C to (120 ± 2) C, and 30 minutes dwell time at each temperature, respectively. It was discovered that the thermal shock test is a very useful method in introducing the CTE mismatch caused by thermo-mechanical stress at the solder joints. The resonance frequency of test components was measured and observed the microsection views were also observed to confirm the crack generation of the solder joints.

Automatic verification of safety and liveness for pipelined machines using WEB refinement

We show how to automatically verify that complex pipelined machine models satisfy the same safety and liveness properties as their instruction-set architecture (ISA) models by using well-founded equivalence bisimulation (WEB) refinement. We show how to reduce WEB-refinement proof obligations to formulas expressible in the decidable logic of counter arithmetic with lambda expressions and uninterpreted functions (CLU). This allows us to automate the verification of the pipelined machine models by using the UCLID decision procedure to transform CLU formulas to Boolean satisfiability problems. To relate pipelined machine states to ISA states, we use the commitment and flushing refinement maps. We evaluate our work using 17 pipelined machine models that contain various features, including deep pipelines, precise exceptions, branch prediction, interrupts, and instruction queues. Our experimental results show that the overhead of proving liveness, obtained by comparing the cost of proving both safety and liveness with the cost of only proving safety, is about 17%, but depends on the refinement map used; for example, the liveness overhead is 23% when flushing is used and is negligible when commitment is used.

Proving non-termination

The search for proof and the search for counterexamples (bugs) are complementary activities that need to be pursued concurrently in order to maximize the practical success rate of verification tools.While this is well-understood in safety verification, the current focus of liveness verification has been almost exclusively on the search for termination proofs. A counterexample to termination is an infinite programexecution. In this paper, we propose a method to search for such counterexamples. The search proceeds in two phases. We first dynamically enumerate lasso-shaped candidate paths for counterexamples, and then statically prove their feasibility. We illustrate the utility of our nontermination prover, called TNT, on several nontrivial examples, some of which require bit-level reasoning about integer representations.

Re-assessment of the fatigue life for a riser steel pipe in an offshore loading buoy

A substantial remaining fatigue life of a riser steel pipe has been verified before re-installing it in another loading buoy. The analysis involves S-N predictions, evaluation of inspection results, fracture mechanics modelling, and stochastic modelling of the fatigue process. Recent rules and regulations give useful guidelines for deterministic fatigue life verification for items used beyond the original target service life. Through a reliability analysis, the actual probability of failure during the life extension can be revealed and an efficient inspection strategy can be determined.

Synergy of Lip-Motion and Acoustic Features in Biometric Speech and Speaker Recognition

This paper presents the scheme and evaluation of a robust audio-visual digit-and-speaker-recognition system using lip motion and speech biometrics. Moreover, a liveness verification barrier based on a person's lip movement is added to the system to guard against advanced spoofing attempts such as replayed videos. The acoustic and visual features are integrated at the feature level and evaluated first by a support vector machine for digit and speaker identification and, then, by a Gaussian mixture model for speaker verification. Based on ap300 different personal identities, this paper represents, to our knowledge, the first extensive study investigating the added value of lip motion features for speaker and speech-recognition applications. Digit recognition and person-identification and verification experiments are conducted on the publicly available XM2VTS database showing favorable results (speaker verification is 98 percent, speaker identification is 100 percent, and digit identification is 83 percent to 100 percent).

The vulnerability of nursing workers to tuberculosis in a teaching hospital

This study aimed to identify aspects that potentially increase the vulnerability of nursing workers to tuberculosis, through the verification of personal life, work and disease knowledge indexes. The sample is composed of 81 nursing workers involved with assistance in the night and day shifts at USP Teaching Hospital, who answered a questionnaire about life and work habits. The sample aggregated the indexes that increase vulnerability to tuberculosis: long professional experience in hospitals and work load longer than 12 hours. Data show that nursing auxiliaries and workers from the night shift in general have a higher number of vulnerability indexes.

On-line self-checking of replication consistency for autonomic computing

In this paper we are concerned with the live verification of the consistency of a replicated system, an issue that has not been addressed by the research community so far. We consider the problem of how to enable the system to detect automatically and in production whether the invariants defining the correctness of object replication are violated. This feature could greatly improve the dependability of distributed applications and is necessary for constructing self-managing and self-healing replicated systems. We focus on systems that enforce strongly consistent replication: all replicas of each object must be kept "continuously" in-sync. This replication strategy is appropriate for application domains where correctness guarantees in spite of failures are more important than performance and scalability. We present the design and implementation of a replicated web service capable of self-checking whether all replicas are indeed kept in sync. This check occurs on-line, transparently to clients. We also discuss the performance cost of self-checking in our prototype.

Application of the Battery Technology Life Verification Test Manual to the Gen 2 GDR Ce

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Turning of hardened steel with interrupted and semi-interrupted cutting

This work studies the hardened steel turning with interrupted surfaces. Most of the works in this area is focused on continuous surfaces, rarely dealing with interrupted surfaces, so common in real workpieces. Among the tools used for turning hardened steels, CBN is outstanding. There is a tougher CBN grade, supposedly more suitable for turning interrupted surfaces and a thermal and chemical more stable CBN grade, supposedly suitable for continuous cutting. However a question remains: which class is most suitable for the turning of semi-interrupted surfaces? This work tries to answer this question. Aiming at this goal, several hardened steel turning experiments were carried out with three kinds of workpiece surfaces – continuous, interrupted and semi-interrupted – using the two grades of CBN tools cited above. Besides the verification of tool life, a detailed study about the occurrence which caused the end of tool life for all kinds of cutting was also carried out. The main conclusion points out that the low CBN content tool is more suitable for continuous and semi-interrupted surfaces. When cutting interrupted surfaces, the high CBN content tool presented a slightly longer life.

Counterexamples to “Liveness-Enforcing Supervision of Bounded Ordinary Petri Nets Using Partial-Order Methods”

This note shows by means of simple counterexamples that some key results presented by He and Lemmon in the above paper (Automat. Contr., vol. 47, pp. 1042-1055, July 2002) on the liveness verification and enforcing of Petri nets using unfolding are incorrect. As a result, the applicability of unfolding for Petri net supervision is still an open issue.

Presburger liveness verification of discrete timed automata

Using an automata-theoretic approach, we investigate the decidability of liveness properties (called Presburger liveness properties) for timed automata when Presburger formulas on configurations are allowed. While the general problem of checking a temporal logic such as TPTL augmented with Presburger clock constraints is undecidable, we show that there are various classes of Presburger liveness properties which are decidable for discrete timed automata. For instance, it is decidable, given a discrete timed automaton A and a Presburger property P, whether there exists an ω-path of A where P holds infinitely often. We also show that other classes of Presburger liveness properties are indeed undecidable for discrete timed automata, e.g., whether P holds infinitely often for eachω-path of A. These results might give insights into the corresponding problems for timed automata over dense domains, and help in the definition of a fragment of linear temporal logic, augmented with Presburger conditions on configurations, which is decidable for model checking timed automata.