ANALYSIS OF MARKOV CHAIN MONTE CARLO METHODS IN MULTI-INDENTURE INVENTORY OPTIMIZATION

U.S. Navy aircraft are required to meet minimum operational availability targets, while minimizing spare parts procurement costs. The current optimization model written by Salmeron and Buss, uses marginal analysis, as described by Sherbrooke, to determine optimal sparing policies for this highly complex multi-indenture model. The literature lacks alternative optimization methodologies for such a problem, so we propose an alternative approach utilizing simulated annealing (SA), a Markov Chain Monte Carlo algorithm. We present three SA approaches tested in three case studies of varying size and complexity. Our initial findings show that in very simple problems, SA is easily capable of outperforming marginal analysis; however, problems with more complexity have large optimality gaps. This is likely because the SA Markov chain is unable to effectively explore the multi-indenture structure of the problem. We implement a method to account for this structure that intelligently builds initial feasible solutions using an epsilon-greedy approach to marginal analysis. This approach produces better results than NAVARM in more than half of the trials on problems of moderate complexity. We also implement a novel method for calculating operational availability that may allow full scale problems to be optimized more efficiently.NAVSUP WSSLieutenant Commander, United States NavyApproved for public release. Distribution is unlimited

BOLTED CONNECTIONS FOR EASILY REPAIRABLE SEISMIC RESISTANT STEEL STRUCTURES

Recent years have brought significant advances in the design capabilities and construction practices of steel structures. These were partially caused by technological development and a direct effect of the research community efforts towards the mitigation of the earthquake induced damage. Making the traditional structural systems more resilient is one of the directions taken but, more and more, solutions with reduced post-earthquake repair costs are preferred. Steel structures are particularly malleable in the modern spirit of integrating devices which render the structure as “low-damage” or “easily repairable”. The recent earthquakes of Japan and New Zealand have demonstrated the feasibility and the advantages of such structural typologies. The current work presents an investigation on two steel structural solutions, including thus both moment resisting and braced frames, which have the potential of being easily used in practice, with minimal alteration of the design and erection procedures and improved post-earthquake economic benefits. The thesis focuses on (i) bolted connections of detachable short links for eccentrically braced frame and second, and (ii) on bolted friction connections for moment resisting frames. The main objective is to facilitate the application of these structural solutions in practice by enhancing the knowledge of their relevant bolted connection design and behavior

Reliability monitoring techniques applied to a hot strip steel mill

Reliability engineering techniques have been used in the manufacturing environment for many years. However the reliability analysis of repairable systems is not so widely practised in the steel manufacturing environment. Many different analysis methods have been proposed for the modelling of repairable systems, most of these have had limited application in the manufacturing environment. The current reliability analysis techniques are predominantly used by engineers to construct a “snapshot” in time of a manufacturing system’s reliability status. There are no readily identifiable applications of reliability modelling techniques being applied to repairable systems over a long time period within the manufacturing environment The aim of this work is to construct a method which can analyse and monitor the reliability status of multiple repairable systems within the steel plant over an extended operating period. The developed analysis method is predominantly automated and is facilitated by applying standard reliability analysis techniques to all of the repairable systems failure data sets under review. This Thesis illuminates the methodology used to fulfil the remit of this research by the following sequential steps: Developing a new methodology for the application of reliability analysis techniques to repairable systems within a steel manufacturing facility Utilised an innovative step of combining three reliability analysis methods as complimentary activities Constructed an automated reliability analysis model which fulfils the project remit. In addition the model is capable of the long term monitoring of repairable system reliability The new reliability analysis method has been delivered to Tata Steel and is installed in the Port Talbot Technology Group with a direct link to the Hot Strip Mill (HSM) monitoring database. This reliability analysis method has been tested with four years operational data from the Hot Strip Mill manufacturing area and the analysis has shown that changes and trends in all systems reliability status can be easily identified.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Extended Fault Trees Analysis supported by Stochastic Petri Nets

This work presents several extensions to the Fault Tree [90] formalism used to build models oriented to the Dependability [103] analysis of systems. In this way, we increment the modelling capacity of Fault Trees which turn from simple combinatorial models to an high level language to represent more complicated aspects of the behaviour and of the failure mode of systems. Together with the extensions to the Fault Tree formalism, this work proposes solution methods for extended Fault Trees in order to cope with the new modelling facilities. These methods are mainly based on the use of Stochastic Petri Nets. Some of the formalisms described in this work are already present in the literature; for them we propose alternative solution methods with respect to the existing ones. Other formalisms are instead part of the original contribution of this work

Reliability monitoring techniques applied to a hot strip steel mill

Reliability engineering techniques have been used in the manufacturing environment for many years. However the reliability analysis of repairable systems is not so widely practised in the steel manufacturing environment. Many different analysis methods have been proposed for the modelling of repairable systems, most of these have had limited application in the manufacturing environment. The current reliability analysis techniques are predominantly used by engineers to construct a “snapshot” in time of a manufacturing system’s reliability status. There are no readily identifiable applications of reliability modelling techniques being applied to repairable systems over a long time period within the manufacturing environment The aim of this work is to construct a method which can analyse and monitor the reliability status of multiple repairable systems within the steel plant over an extended operating period. The developed analysis method is predominantly automated and is facilitated by applying standard reliability analysis techniques to all of the repairable systems failure data sets under review. This Thesis illuminates the methodology used to fulfil the remit of this research by the following sequential steps: Developing a new methodology for the application of reliability analysis techniques to repairable systems within a steel manufacturing facility Utilised an innovative step of combining three reliability analysis methods as complimentary activities Constructed an automated reliability analysis model which fulfils the project remit. In addition the model is capable of the long term monitoring of repairable system reliability The new reliability analysis method has been delivered to Tata Steel and is installed in the Port Talbot Technology Group with a direct link to the Hot Strip Mill (HSM) monitoring database. This reliability analysis method has been tested with four years operational data from the Hot Strip Mill manufacturing area and the analysis has shown that changes and trends in all systems reliability status can be easily identified

Alternative techniques and approaches for improving the seismic performance of masonry infills

This doctoral dissertation aims to report on the research work carried out in the field of alternative techniques and approaches for improving the seismic performance of masonry infills. An aspect often overlooked in the design and/or verification of Reinforced Concrete (RC) frame buildings it is the one related to the so-called "non-structural" elements, that are elements without a main structural function, but capable of causing damage to things and people during the seismic action. A typical example of non-structural elements are the external infills of RC frame buildings, which often have masses and stiffnesses able to significantly modify the behavior and response of the structure during the seismic action. Typically, the UnReinforced Masonry (URM) infill walls are made of single or double facing hollow bricks placed inside the meshes of RC frames. The main damage mechanisms observed in URM infill walls during seismic events include in the plane (IP) or out of the plane (OOP) damage mechanisms, both characterized by degradation of strength, stiffness and low energy dissipation. In this doctoral dissertation, the analysis of the influence of the in-plane and out-of-plane behavior of UnReinforced Masonry infill walls on global seismic performances of different RC frame buildings is presented. The research mainly focuses on: i) numerical investigation of the in- plane / out-of-plane interaction in order to evaluate its entity and severity pointing out the correct description of the damage scenarios; ii) identification of alternative intervention solutions, aimed at mitigating the phenomenon of overturning of the infill panels; iii) estimate of the expected economic losses. Rough cost-benefit analyses have been carried out in order to compare the sustainability of alternative seismic rehabilitation techniques, thus providing a rational base and objective criteria that can be used in the design and/or preliminary screening phase by insurance companies, to reduce the seismic risk and the impact of earthquakes on a community

Choose-Your-Own Adventure: A Lightweight, High-Performance Approach To Defect And Variation Mitigation In Reconfigurable Logic

For field-programmable gate arrays (FPGAs), fine-grained pre-computed alternative configurations, combined with simple test-based selection, produce limited per-chip specialization to counter yield loss, increased delay, and increased energy costs that come from fabrication defects and variation. This lightweight approach achieves much of the benefit of knowledge-based full specialization while reducing to practical, palatable levels the computational, testing, and load-time costs that obstruct the application of the knowledge-based approach. In practice this may more than double the power-limited computational capabilities of dies fabricated with 22nm technologies. Contributions of this work: • Choose-Your-own-Adventure (CYA), a novel, lightweight, scalable methodology to achieve defect and variation mitigation • Implementation of CYA, including preparatory components (generation of diverse alternative paths) and FPGA load-time components • Detailed performance characterization of CYA – Comparison to conventional loading and dynamic frequency and voltage scaling (DFVS) – Limit studies to characterize the quality of the CYA implementation and identify potential areas for further optimizatio

Management: A continuing bibliography with indexes

This bibliography lists 551 reports, articles, and other documents introduced into NASA scientific and technical information system in 1980

The role of muscle in Spondyloarthritis

A espondiloartrite axial (axSpA) é uma doença reumática inflamatória, caracterizada principalmente pelo envolvimento da coluna e articulações sacroilíacas, e geralmente apresenta-se como dor crónica nas costas e rigidez. À medida que a doença progride, a mobilidade da coluna vertebral e a função física são prejudicadas podendo afetar as atividades da vida diária. A genética e os fatores ambientais (microbiota e microtrauma) são as causas conhecidas da suscetibilidade e progressão da doença. Esta tese teve como objetivo melhorar o nosso conhecimento atual da fisiopatologia da axSpA, caracterizando as propriedades musculares axiais e periféricas e identificando biomarcadores genéticos e proteicos que possam explicar tais propriedades. Realizamos um estudo transversal com 54 participantes: 27 pacientes com axSpA e 27 controles saudáveis (HC), pareados por idade, sexo e nível de atividade física. Dados epidemiológicos, clínicos e de caracterização muscular (propriedades físicas musculares, força, massa e desempenho) foram registados e comparados entre pacientes com axSpA e HC. Foi ainda colhido sangue periférico para abordagens ómicas. A transcriptómica e a proteómica foram realizadas por sequenciação de RNA e tecnologias de espectrometria de massa, respectivamente. Os nossos resultados indicam que pacientes com axSpA (idade média de 36,5 (DP 7,5) anos, 67% do sexo masculino e duração média da doença de 6,5 (3,2) anos) não apresentaram diferença significativa na rigidez muscular segmentar em comparação com os HC, apesar de apresentarem uma discreta menor rigidez lombar. Pacientes com axSpA, comparados com os HC, apresentaram menor força total, bem como menor força nos membros superiores e inferiores, independentemente das propriedades físicas dos músculos. Os pacientes também apresentaram velocidades de marcha significativamente menores do que o HC. As características da marcha podem representar um potencial biomarcador em pacientes com axSpA. A análise de enriquecimento de genes expressos diferencialmente permitiu revelar vias metabólicas significativas (como sinalização de IL6 e vias do sistema imunológico) com papel patológico para esse grupo de pacientes. Salienta-se ainda que níveis séricos aumentados de várias citocinas pró-inflamatórias em pacientes com axSpA foram observados em correlação adequada com os parâmetros de atividade da doença. Além disso, foram identificados genes expressos diferencialmente associados ao músculo (como NACA, FRG1 e ARPC5L) desempenham papeis no desenvolvimento de miotubos e montagem de actina, afetando eventualmente a força muscular em pacientes com axSpA. Finalmente, a integração dos resultados da transcriptómica e da proteómica mostra que a análise dos genes e proteínas diferencialmente expressos permite obter uma clara discriminação entre pacientes com axSpA e HCs, possibilitando ainda avançar no diagnóstico, prognóstico e eventuais opções terapêuticas para esse grupo de pacientes. Globalmente, os resultados aqui obtidos permitem oferecer algumas possibilidades interessantes para explicar o papel do músculo na patogénese da axSpA.Axial spondylarthritis (axSpA) is an inflammatory rheumatic disease, characterized primarily by the involvement of the spine and sacroiliac joints, and usually presenting as chronic back pain and stiffness. As the disease progresses, impaired spinal mobility and physical function may impact activities of daily living. Genetics and environmental factors (microbiota and microtrauma) are the known causes of disease susceptibility and progression. This thesis aimed to improve our current knowledge of axSpA physiopathology by characterizing axial and peripheral muscle properties and identifying genetic and protein biomarkers that might explain such properties. We performed a cross-sectional study on 54 participants: 27 patients with axSpA and 27 healthy controls (HC), matched by age, gender, and level of physical activity. Epidemiological, clinical, and muscle characterization (muscle physical properties, strength, mass, and performance) data were registered and compared between patients with axSpA and HC. Peripheral blood was collected for omics approaches. Transcriptomics and proteomics were performed by RNA-sequencing, RT q-PCR, and mass spectrometry technologies, respectively. Our results indicate patients with axSpA (mean age 36.5 (SD 7.5) years, 67% males, and mean disease duration of 6.5 (3.2) years) had no significant difference in segmental muscle stiffness compared with the HC, despite showing a slight numerically higher lower lumbar stiffness. Patients with axSpA, compared to the HC, had lower total strength as well as lower strength in the upper and lower limbs, independently of muscle physical properties. Patients also had significantly lower gait speeds than the HC. Gait characteristics may represent a potential biomarker in patients with axSpA. Enrichment analysis of differentially expressed genes reveals significant pathways (such as IL6 signaling and immune system pathways) with a pathological role for this group of patients. Notably, increased serum levels of various pro-inflammatory cytokines in patients with axSpA have been observed in proper correlation with disease activity parameters. Moreover, differentially muscle-associated expressed genes (such as NACA, FRG1, and ARPC5L) play roles in the development of myotubes and actin assembly, eventually affecting muscle strength in patients with axSpA. Worth of note, the integration of transcriptomic’s and proteomic’s results shows number of genes and proteins causes a clear discrimination between patients with axSpA and HCs that may advance diagnosis, prognosis, and therapeutic options for this group of patients. This work, taken together, provides some interesting possibilities to explain the role of muscle in the pathogenesis of axSpA

A safety assessment framework for Automatic Dependent Surveillance Broadcast (ADS-B) and its potential impact on aviation safety

The limitations of the current civil aviation surveillance systems include a lack of coverage in some areas and low performance in terms of accuracy, integrity, continuity and availability particularly in high density traffic areas including airports, with a negative impact on capacity and safety. Automatic Dependent Surveillance Broadcast (ADS-B) technology has been proposed to address these limitations by enabling improved situational awareness for all stakeholders and enhanced airborne and ground surveillance, resulting in increased safety and capacity. In particular, its scalability and adaptability should facilitate its use in general aviation and in ground vehicles. This should, in principle, provide affordable, effective surveillance of all air and ground traffic, even on airport taxiways and runways, and in airspace where radar is ineffective or unavailable. The success of the progressive implementation of ADS-B has led to numerous programmes for its introduction in other parts of the World where the operational environment is considerably different from that of Australia. However, a number of critical issues must be addressed in order to benefit from ADS-B, including the development and execution of a safety case that addresses both its introduction into legacy and new systems’ operational concepts, the latter including the Single European Sky (SES) / Single European Sky ATM Research (SESAR) and the US’ Next Generation Air Transportation System (NexGEN). This requires amongst others, a good understanding of the limitations of existing surveillance systems, ADS-B architecture and system failures and its interfaces to the existing and future ATM systems. Research on ADS-B to date has not addressed in detail the important questions of limitations of existing systems and ADS-B failure modes including their characterisation, modelling and assessment of impact. The latter is particularly important due to the sole dependency of ADS-B on GNSS for information on aircraft state and its reliance on communication technologies such as Mode-S Extended Squitter, VHF Data Link Mode-4 (VDLM4) or Universal Access Transceiver (UAT), to broadcast the surveillance information to ground-based air traffic control (ATC) and other ADS-B equipped aircraft within a specified range, all of which increase complexity and the potential for failures. This thesis proposes a novel framework for the assessment of the ADS-B system performance to meet the level of safety required for ground and airborne surveillance operations. The framework integrates various methods for ADS-B performance assessment in terms of accuracy, integrity, continuity, availability and latency, and reliability assessment using probabilistic safety assessment methods; customized failure mode identification approach and fault tree analysis. Based on the framework, the thesis develops a failure mode register for ADS-B, identifies and quantifies the impact of a number of potential hazards for the ADS-B. Furthermore, this thesis identifies various anomalies in the onboard GNSS system that feeds aircraft navigation information into the ADS-B system. Finally, the thesis maps the ADS-B data availability and the quantified system performance to the envisioned airborne surveillance application’s requirements. The mapping exercise indicates that, the quantified ADS-B accuracy is sufficient for all applications while ADS-B integrity is insufficient to support the most stringent application: Airborne Separation (ASEP). In addition, some of the required performance parameters are unavailable from aircraft certified to DO-260 standard. Therefore, all aircraft must be certified to DO-260B standard to support the applications and perform continuous monitoring, to ensure consistency in the system performance of each aircraft.Open Acces