360 research outputs found
Dynamic analysis of Cyber-Physical Systems
No full textWith the recent advances in communication and computation technologies, integration of software into the sensing, actuation, and control is common. This has lead to a new branch of study called Cyber-Physical Systems (CPS). Avionics, automotives, power grid, medical devices, and robotics are a few examples of such systems. As these systems are part of critical infrastructure, it is very important to ensure that these systems function reliably without any failures. While testing improves confidence in these systems, it does not establish the absence of scenarios where the system fails. The focus of this thesis is on formal verification techniques for cyber-physical systems that prove the absence of errors in a given system. In particular, this thesis focuses on {\em dynamic analysis} techniques that bridge the gap between testing and verification.
This thesis uses the framework of hybrid input output automata for modeling CPS. Formal verification of hybrid automata is undecidable in general.
Because of the undecidability result, no algorithm is guaranteed to terminate for all models.
This thesis focuses on developing heuristics for verification that exploit sample executions of the system. Moreover, the goal of the dynamic analysis techniques proposed in this thesis is to ensure that the techniques are sound, i.e., they always return the right answer, and they are relatively complete, i.e., the techniques terminate when the system satisfies certain special conditions. For undecidable problems, such theoretical guarantees are the strongest that can be expected out of any automatic procedure. This thesis focuses on safety properties, which require that nothing bad happens. In particular we consider invariant and temporal precedence properties; temporal precedence properties ensure that the temporal ordering of certain events in every execution satisfy a given specification.
This thesis introduces the notion of a discrepancy function that aids in dynamic analysis of CPS. Informally, these discrepancy functions capture the convergence or divergence of continuous behaviors in CPS systems. In control theory, several proof certificates such as contraction metric and incremental stability have been proposed to capture the convergence and divergence of solutions of ordinary differential equations. This thesis establishes that discrepancy functions generalize such proof certificates. Further, this thesis also proposes a new technique to compute discrepancy functions for continuous systems with linear ODEs from sample executions.
One of the main contributions of this thesis is a technique to compute an over-approximation of the set of reachable states using sample executions and discrepancy functions. Using the reachability computation technique, this thesis proposes a safety verification algorithm which is proved to be sound and relatively complete. This technique is implemented in a tool called, Compare-Execute-Check-Engine (C2E2) and experimental results show that it is scalable.
To demonstrate the applicability of the algorithms presented, two challenging case studies are analyzed as a part of this thesis. The first case study is about an alerting mechanism in parallel aircraft landing. For performing this case study, the dynamic analysis presented for invariant verification is extended to handle temporal properties. The second case study is about verifying key specification of powertrain control system. New algorithms for computing discrepancy function were implemented in C2E2 for performing this case study. Both these case studies demonstrate that dynamic analysis technique gives promising results and can be applied to realistic CPS.
For distributed CPS implementations, where message passing, and clocks skews between agents make formal verification difficult to scale, this thesis presents a dynamic analysis algorithm for inferring global predicates. Such global predicates include assertions about the physical state and the software state of all the agents involved in distributed CPS. This algorithm is applied to coordinated robotic maneuvers for inferring safety and detecting deadlock.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2017-12-01The student, Parasara Duggirala, accepted the attached license on 2015-08-20 at 10:16.The student, Parasara Duggirala, submitted this Dissertation for approval on 2015-08-20 at 10:54.This Dissertation was approved for publication on 2015-08-21 at 13:11.DSpace SAF Submission Ingestion Package generated from Vireo submission #8666 on 2016-03-02 at 14:04:58Made available in DSpace on 2016-03-02T20:23:09Z (GMT). No. of bitstreams: 2
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Previous issue date: 2015-08-21Embargo set by: Seth Robbins for item 91306
Lift date: 2018-03-02T20:24:31Z
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Digital Dermatoglyphic Patterns of Eskimo and Amerindian Populations: Relationships between Geographic, Dermatoglyphic, Genetic, and Linguistic Distances
No full textDermatoglyphic traits have been used to assess population affinities and structure. Here, we describe the digital patterns of four Eskimo populations from Alaska: two Yupik-speaking villages from St. Lawrence Island and two Inupik groups presently residing on mainland Alaska. For a broader evolutionary perspective, these four Eskimo populations are compared to other Inuit groups, to North American Indian populations, and to Siberian aggregates. The genetic structures of 18 New and Old World populations were explored using R -matrix plots and Wright’s FST values. The relationships between dermatoglyphic, blood genetic, geographic, and linguistic distances were assessed by comparing matrices through Mantel correlations and through partial and multiple correlations. Statistically significant relationships between dermatoglyphics and genetics, genetics and geography, and geography and language were revealed. In addition, significant correlations between dermatoglyphics and geography, with linguistic variation constant, were noted for females but not for males. These results attest to the usefulness of dermatoglyphics in resolving various evolutionary questions concerning normal human variation
Effect of copper on trihalomethane formation during chlorination of water and wastewater
No full textCopper (II) increases the formation of trihalomethanes (THMs) during chlorination of humic acid and some model compounds. The ability of copper to catalyze THM formation appears to be linked to the formation of copper complexes by THM precursors. Humic substances form stable and labile complexes with transition metals. The complexation of copper with humic materials was characterized by potentiometric titrations using a cupric ion selective electrode. The results demonstrated that most of the copper was complexed by humic material at copper concentrations likely to be seen in chlorine based disinfection processes. Experiments were designed using fractional factorials to study the effect of copper on chloroform formation from humic acid and to evaluate various first-order and second-order interactions. The results were used to build second-order response surface models at different times, and non-linear models that incorporate the effect of time. The results demonstrate that there is a substantial increase in THM formation in the presence of copper (II). The results also indicate that copper (II) enhances THM formation by activating a portion of humic acid which is otherwise not a significant contributor to THM formation. The non-linear models indicated that THM formation is a stronger function of chlorine dose in the presence of copper. Experiments carried out with several model compounds showed that copper enhances the formation of trihalomethanes by activating citric acid and similar structures in humic acid. Based on a literature review, a mechanism for the formation of trihalomethanes from citric acid is proposed. Copper (II) is expected to enhance the THM formation by catalyzing the decarboxylation reactions. The effect of bromide ion in conjunction with the effect of copper was also studied. Copper (II) enhanced formation of brominated THMs in a manner similar to the enhancement of chloroform formation. The results from these studies demonstrated that copper is a significant factor in THM formation during chlorination of water and wastewater. Control of copper (II) will be important in THM control during chlorination of water and wastewater
Multi-site genetic analysis of diffusion images and voxelwise heritability analysis : a pilot project of the ENIGMA–DTI working group
No full textThe ENIGMA (Enhancing NeuroImaging Genetics through Meta-Analysis) Consortium was set up to analyze brain measures and genotypes from multiple sites across the world to improve the power to detect genetic variants that influence the brain. Diffusion tensor imaging (DTI) yields quantitative measures sensitive to brain development and degeneration, and some common genetic variants may be associated with white matter integrity or connectivity. DTI measures, such as the fractional anisotropy (FA) of water diffusion, may be useful for identifying genetic variants that influence brain microstructure. However, genome-wide association studies (GWAS) require large populations to obtain sufficient power to detect and replicate significant effects, motivating a multi-site consortium effort. As part of an ENIGMA–DTI working group, we analyzed high-resolution FA images from multiple imaging sites across North America, Australia, and Europe, to address the challenge of harmonizing imaging data collected at multiple sites. Four hundred images of healthy adults aged 18–85 from four sites were used to create a template and corresponding skeletonized FA image as a common reference space. Using twin and pedigree samples of different ethnicities, we used our common template to evaluate the heritability of tract-derived FA measures. We show that our template is reliable for integrating multiple datasets by combining results through meta-analysis and unifying the data through exploratory mega-analyses. Our results may help prioritize regions of the FA map that are consistently influenced by additive genetic factors for future genetic discovery studies. Protocols and templates are publicly available at (http://enigma.loni.ucla.edu/ongoing/dti-working-group/)
Simulation-based Testing of the Traffic Rules Requirements for Autonomous Vehicles at Intersections
No full textTo successfully integrate autonomous vehicles as a mode of transportation, we must test these systems against their end-to-end requirements. When AVs and humans (pedestrians, bicyclists, human-driven vehicles) share the road, they must follow the same traffic rules. Using the common traffic rules (written for human drivers) as an engineering requirement poses a challenge due to the ambiguity of the natural language. On the other hand, an AV is fundamentally different from a human, and a simple road test is not sufficient to assess an AV's compliance and skills. This calls for automated, systematic and scalable testing techniques. The focus of this dissertation is on simulation-based testing of the traffic-rules requirements. This dissertation develops techniques for systematic exploration of the test-case space of autonomous vehicles based on two crucial concepts: complexity and coverage. Here, these concepts are formalized with respect to the traffic rules requirements. The efficiency of finding bugs is improved by incrementally increasing the complexity of a test-case, namely making it harder for an AV to pass a test-case. On the other hand, the diversity of a test-suite is improved by guiding the test-case generation towards increasing the coverage of a test-suite. The framework for formalization of the traffic rules is made more amenable to vetting by the authorities and regulators by narrowing the gap between human intuition and machine language. This is achieved by formalizing traffic rules in first-order logic (FOL) which allows modeling objects and predicates.Doctor of Philosoph
Population Genetics and Structure of Buryats from the Lake Baikal Region of Siberia
No full textGenetic polymorphisms of blood groups, serum proteins, red cell enzymes, PTC tasting, and cerumen types are reported for five Mongoloid populations of Buryats from the Lake Baikal region of Siberia (Russia). These groups are characterized by relatively high frequencies of alleles ABO*B, RH*D, cerumen D, GC*1F, ACP1*B, ESD*2, and PGD*C. Significant genetic heterogeneity between populations was demonstrated for the loci RH, MN, cerumen, PGD, ABO, GC, GLO, TF, and PGM1. Genetic distance analyses using five loci revealed a lower level of genetic microdifferentiation within the Buryat populations compared with other native Siberian groups. The distribution of gene markers in Buryats is similar to that found in neighboring Central Asian groups, such as the Yakuts and the Mongols. Intrapopulational analyses of the five Buryat subdivisions, based on R matrix and rii indicate that one of the subdivisions is reproductively more isolated than the others and that two of the communities have received considerable gene flow. A nonlinear relationship was demonstrated between geographic and genetic distances of Buryat population subdivisions
Letting Go as an Aspect of Rumination and Its Relationship to Mindfulness, Dysphoria, Anxiety, and Eudemonic Well-Being
No full textBackground: We examined how a newly proposed facet of rumination, that is, the (in)ability to let go, might relate to other aspects of rumination and to psychological outcomes. Methods: In two independent samples (n = 423 and 329, resp.) of college students, we measured a broad set of rumination and rumination-related measures, letting go, anxiety and dysphoria; in the second sample, we also collected data on mindfulness, self-compassion and eudemonic well-being. Results: Factor analysis of rumination and rumination-related measures yielded three factors: (a) negative intrusive thought; (b) reflectiveness; and (c) the inability to let go. Repetitive intrusive thought and the ability to let go were significant (and thus partially independent) predictors for the three outcomes of anxiety, dysphoria, and wellbeing. The inability to let go and repetitive intrusive thought significantly mediated between mindfulness and all three outcomes. Conclusions: The findings suggest that letting go is a potentially interesting aspect of rumination not fully captured in the traditional concept of rumination and its standard measures
Active circuits for ultra-high efficiency micropower generators using nickel-63 radioisotope
No full textEnergy efficient bridge management policies for inter piconet communication in Bluetooth scatternets
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