Dissertationen zum Thema „Complex engineered system“

Articular cartilage represents a primary target for tissue engineering strategies as it does not functionally regenerate within the joint. Many tissue engineering approaches have focused on the in vitro generation of neo-cartilage using chondrocyte-seeded scaffolds. Several studies have reported the morphological appearance of native cartilage, although its functional competence has not been demonstrated. Accordingly, mechanical conditioning has often been introduced to enhance biosynthetic activity of chondrocytes within 3D constructs. However although this strategy has significantly up-regulated proteoglycan synthesis, its effects on the synthesis of the other major solid constituent, type II collagen, has been modest. Analyses of normal joint activities reveal that cartilage is subjected to shear superimposed on uniaxial compression. This complex mechanical state has motivated the design of a biaxial loading system intended for use in vitro to stimulated bovine chondrocytes seeded in agarose constructs. This necessitated the redesign of the construct from cylindrical morphology to accommodate shear loading. The experimental approach was complemented with the development of computational models, which permitted prediction of both cell distortion under biaxial loading regimens and nutrient diffusion within the 3D constructs. An initial study established the profile of proteoglycan and collagen synthesis in free swelling cultures up to day 12. The introduction of dynamic compression (15% strain, 1 Hz for 48 h) enhanced proteoglycan synthesis significantly. In addition, when dynamic shear (10%, 1 Hz) was superimposed on dynamic compression, total collagen synthesis was also up-regulated, within 3 days of culture, without compromising proteoglycan synthesis. Histological analysis revealed marked collagen deposition around individual chondrocytes. However, a significant proportion (50%) of collagen was released into the culture medium, suggesting that it was not fully processed. The overall biosynthetic activity was enhanced more when the biaxial stimulation was applied in a continuous mode as opposed to intermittent loading. The present work offers the potential for a more effective preconditioning of cell-seeded constructs with functional integrity intended for use to resolve defects in joint cartilage.

Thesis (S.M.)--Massachusetts Institute of Technology, Computation for Design and Optimization Program, 2009.<br>"September 2009." Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 150-157).<br>This thesis develops a framework for constructing an Evolutionary Design Model (EDM) that would enhance the design of complex systems through an efficient process. The framework proposed is generic and suggests a group of systematic methodologies that eventually lead to a fully realized and integrated design model. Within this model, complexities of the design are handled and the uncertainties of the design evolution are managed. Using the framework, vast design spaces can be searched while solutions are intelligently modified, their performance evaluated, and their results aggregated into a compatible set for design decisions. The EDM is composed of several design states as well as design evolving processes. A design state describes a design at a particular point in time and maps the system's object to the system's requirements and identifies its relation to the context in which the system will operate. A design evolving process involves many sub-processes which include formulation, decomposition, modeling, and integration. These sub-processes are not always carried out in a sequential manner, but rather a continuous move back and forth to previous and subsequent stages is expected. The resulting design model is described as an evolutionary model that moves a system's design from simple abstract states to more complex and detailed states throughout its evolution.<br>(cont.) The framework utilizes system modeling methodologies that include both logical and mathematical modeling methods. The type of model used within the EDM's evolving processes is highly dependent on and driven by design needs of each process. As the design progresses a shift from logical models to mathematical models occurs within the EDM. Finally, a partial EDM is implemented within the context of a computational design system for Masdar city to demonstrate the application of the proposed framework.<br>By Anas Alfaris.<br>S.M.

The EcoR124INT restriction-modification (R-M) system contains the genes HsdS3, HsdM and HsdR. S3 encodes the N-terminal domain of the wild-type S subunit and has been shown to dimerise in solution (Smith et al., 1998). Following purification of the subunits of the EcoR124INT R-M system, complexes of the methyltransferase S3/M and restriction endonuclease S3/M/R were formed and shown to have activity in vitro, methylating and hydrolysing a symmetrical DNA recognition sequence, respectively. The DNA mimic OCR (overcome classical restriction) protein inhibited the methyltransferase activity in vitro, with maximum inhibition at a 1: 2 molar ratio of (S3/M)2 to an ocr dimer. Dynamic light scattering (DLS), sedimentation equilibrium (SE) and sedimentation velocity (SV) experiments showed S3 to exist as a dimer and S11 (the central conserved domain of S) to exist as a tetramer in solution. M was found to be dimeric in solution, whilst the R protein was monomeric. A complex of S3/M was found to have a stoichiometry (S3/M)2 and a complex of S3/M/R had a stoichiometry of S3/M/R1, even when a 2: 1 molar ratio of R to S3/M, was added. Small angle neutron scattering (SANS) experiments provided values for the radius of gyration (Rg), which for S3 was comparable to that calculated for the recently published crystal structure of the S subunit from Methanococcus jannaschii (Kim et al., 2005). These experiments also showed a decrease in the Dmax in the presence of the 30 bp DNA recognition sequence from 200A to 140A, suggesting a similar conformational change in the positioning of the subunits as has been detected for the wild-type M. EcoR124I and a related type 1 1/2 system AhdI. This change following DNA binding was also observed by SV experiments. Furthermore ab initio modelling from the SANS data has provided a low-resolution structure for the EcoR124INT MTase and its complex with DNA.

<p>Traditional, corporate-level risk mitigation procedures and management-led performance improvement efforts tend to ignore the relationship dynamics of Architect-Engineer design teams, and instead focus on the credentials and abilities of the individual designers, the contractual framework surrounding the individual projects, and the process for inspecting and controlling the quality of the team&rsquo;s output, the design. Management may tacitly acknowledge the complex nature of the design process, but the notion of design teams as complex systems, or more precisely, Complex Adaptive Systems (CAS), with their inherently unpredictable behaviors, is not typically considered. </p><p> The research herein analyzed the team dynamics of 113 Architect-Engineer design projects to determine if teams that leveraged or embraced (deliberately or unknowingly) the <i>self-organizing</i> and <i>sense-making </i> properties of CAS, to include improvisation, an emphasis on intra- and cross-boundary communication, broad participation in decision-making, autonomy in managing resources, and deliberate use of conflict and uncertainty to alter standard behavior patterns, delivered more successful projects than teams whose leadership attempted (again, deliberately or unknowingly) to <i> overcome</i> those same CAS properties with detailed design or quality control (QC) procedures, a strong organizational identity that informed behavior, concentrated decision-making authority with a focus on efficiency of effort, and swift resolution of conflict. The parameters for measuring project success included adherence to schedule, project profitability, design errors, contractual disputes or litigation, and customer satisfaction. </p><p> An analysis of the data utilizing non-parametric analytical tools, to include Mann-Whitney Rank Sum analysis, calculation of Kendall&rsquo;s tau-b, and ordinal logistic regression, reveals that while encouraging a design team to improvise can improve project outcomes, fostering or allowing self-organization in general is not associated with improved project performance. On the other hand, an environment that promotes team members&rsquo; sense-making abilities (although the use of conflict or noise as tools to promote adaptive thinking remains problematic) leads to improvements in project success factors. Finally, the results suggest that Architect-Engineer design team management is not a linear enterprise, and that in determining project success, the relationships between design team members may be as important as the technical competency of the designers and the design or quality control procedures they follow. </p>

Yes<br>Diagnostics and prognostics have significant roles in the reliability enhancement of systems and are focused topics of active research. Engineered systems are becoming more complex and are subjected to miscellaneous failure modes that impact adversely their performability. This everincreasing complexity makes fault diagnostics and prognostics challenging for the system-level functions. A significant number of successes have been achieved and acknowledged in some review papers; however, these reviews rarely focused on the application of complex engineered systems nor provided a systematic review of diverse techniques and approaches to address the related challenges. To bridge the gap, this paper firstly presents a review to systematically cover the general concepts and recent development of various diagnostics and prognostics approaches, along with their strengths and shortcomings for the application of diverse engineered systems. Afterward, given the characteristics of complex systems, the applicability of different techniques and methods that are capable to address the features of complex systems are reviewed and discussed, and some of the recent achievements in the literature are introduced. Finally, the unaddressed challenges are discussed by taking into account the characteristics of automotive systems as an example of complex systems. In addition, future development and potential research trends are offered to address those challenges. Consequently, this review provides a systematic view of the state of the art and case studies with a reference value for scholars and practitioners.<br>The full-text of this article will be released for public view at the end of the publisher embargo on 10 July 2022.

yes<br>This paper presents a methodology for fault detection, fault prediction and fault isolation based on the integration of hidden Markov modelling (HMM) and Bayesian networks (BN). This addresses the nonlinear and non-Gaussian data characteristics to support fault detection and prediction, within an explainable hybrid framework that captures causality in the complex engineered system. The proposed methodology is based on the analysis of the pattern of similarity in the log-likelihood (LL) sequences against the training data for the mixture of Gaussians HMM (MoG-HMM). The BN model identifies the root cause of detected/predicted faults, using the information propagated from the HMM model as empirical evidence. The feasibility and effectiveness of the presented approach are discussed in conjunction with the application to a real-world case study of an automotive exhaust gas Aftertreatment system. The paper details the implementation of the methodology to this case study, with data available from real-world usage of the system. The results show that the proposed methodology identifies the fault faster and attributes the fault to the correct root cause. While the proposed methodology is illustrated with an automotive case study, its applicability is much wider to the fault detection and prediction problem of any similar complex engineered system.<br>The full text will be available at the end of the publisher's embargo: 28th May 2023

abstract: The main objective of this research is to develop an integrated method to study emergent behavior and consequences of evolution and adaptation in engineered complex adaptive systems (ECASs). A multi-layer conceptual framework and modeling approach including behavioral and structural aspects is provided to describe the structure of a class of engineered complex systems and predict their future adaptive patterns. The approach allows the examination of complexity in the structure and the behavior of components as a result of their connections and in relation to their environment. This research describes and uses the major differences of natural complex adaptive systems (CASs) with artificial/engineered CASs to build a framework and platform for ECAS. While this framework focuses on the critical factors of an engineered system, it also enables one to synthetically employ engineering and mathematical models to analyze and measure complexity in such systems. In this way concepts of complex systems science are adapted to management science and system of systems engineering. In particular an integrated consumer-based optimization and agent-based modeling (ABM) platform is presented that enables managers to predict and partially control patterns of behaviors in ECASs. Demonstrated on the U.S. electricity markets, ABM is integrated with normative and subjective decision behavior recommended by the U.S. Department of Energy (DOE) and Federal Energy Regulatory Commission (FERC). The approach integrates social networks, social science, complexity theory, and diffusion theory. Furthermore, it has unique and significant contribution in exploring and representing concrete managerial insights for ECASs and offering new optimized actions and modeling paradigms in agent-based simulation.<br>Dissertation/Thesis<br>Ph.D. Industrial Engineering 2013

As the complexity of systems increases, so does what can go wrong with them. For example, the United States Air Force selected McDonnell Douglas’ design for the F-15 Eagle fighter aircraft in 1967 and the aircraft’s first test flight was in 1972, 5 years later. In contrast, the US military selected Lockheed Martin as one of two companies to develop the F-35 Lightning II in 1997 and its first flight was in 2006, 9 years later, and the first production aircraft had its first flight in 2011, 14 years after the selection. This complex program’s problems have been well-documented by the U.S. Government Accountability Office (GAO) and have contributed to the project’s long lead time and skyrocketing budget. GAO reports on other military projects reveal that problems the F-35 project has experienced are shared among all of these projects. In this dissertation I posit that similar problems plague all complex systems engineering projects and that a combination of these problems may lead to negative consequences, such as budget and schedule exceedances, quality concerns, not achieving mission objectives, as well as accidents resulting in loss of human life.<div><br></div><div>Accidents, or unexpected events resulting in loss, have been well-studied over time and we currently have sophisticated theories that help explain how they occur. The leading theory is that most accidents are a result of an accumulation of “mundane” errors at an organization, and that these errors are similar across industries. However, these mundane errors, such as failing to follow procedures and poorly training personnel, occur in all companies, such as companies that design and manufacture military aircraft. My theory is that these mundane errors accumulate in all organizations and result in many different kinds of systems engineering failures, including failures traditionally referred to as “accidents” that result in loss of life, as well as other types of failures which I refer to as “project failures”.<br></div><div><br></div><div>What can be learned from these systems engineering failures? In this dissertation, I begin by mining publicly-available reports to determine whether seemingly dissimilar failures, accidents and project failures, share common causes. I then explain the similarities and dissimilarities between these causes and provide examples from the failures I studied. To help provide systems engineers with actionable advice on these common causes, I describe how I linked the causes to recommendations from accident reports in a cause-recommendation network. I then discuss the results of interviews I held with systems engineers to determine whether the problems I identified in past failures occur in similar ways to the problems they have encountered on their projects. I also discuss the criticisms these systems engineers have about systems engineering education based on the tasks their newly-hired systems engineers struggle with. I explain how I used what I learned about problems in systems engineering that lead to failures to develop survey questions designed to gauge whether systems engineering education at Purdue prepares students to identify and fix these problems. Then, to help systems engineers learn from the data I collected and solve the problems they encounter on their projects, I describe how I built an interactive, web-based tool that presents expert advice on systems engineering failures. I finally explain the results from feedback I received from experts and novices in systems engineering to determine whether this tool could be useful for engineers in this context.<br></div>

<div>The security, resilience and sustainability of water supply in urban areas are of major concern in cities around the world. Their dynamics and long-term trajectories result from external change processes, as well as adaptive and maladaptive management practices aiming to secure urban livelihoods. This dissertation examines the dynamics of urban water systems from a social-ecological-technical systems perspective, in which infrastructure and institutions mediate the human-water-ecosystem relationship. </div><div><br></div><div>The three concepts of security, resilience and sustainability are often used interchangeably, making the achievement of goals addressing such challenges somewhat elusive. This becomes evident in the international policy arena, with the UN Sustainable Development Goals being the most prominent example, in which aspirations for achieving the different goals for different sectors lead to conflicting objectives. Similarly, the scientific literature remains inconclusive on characterizations and quantifiable metrics. These and other urban water challenges facing the global urban community are discussed, and research questions and objectives are introduced in Section 1. </div><div><br></div><div>In Section 2, I suggest distinct definitions of urban water security, resilience and sustainability: Security refers to the state of system functioning regarding water services; resilience refers to ability to absorb shocks, to adapt and transform, and therefore describes the dynamic, short- to medium-term system behavior in response to shocks and disturbances; sustainability aims to balance the needs in terms of ecology and society (humans and the economic systems they build) of today without compromising the ability to meet the needs of future generations. Therefore, sustainability refers to current and long-term impacts on nature and society of maintaining system functions, and therefore affects system trajectories. I suggest that sustainability should include not only local effects, but consider impacts across scales and sectors. I propose methods for the quantification of urban water security, resilience and sustainability, an approach for modeling dynamic water system behavior, as well as an integrated framework combining the three dimensions for a holistic assessment of urban water supply systems. The framework integrates natural, human and engineered system components (“Capital Portfolio Approach”) and is applied to a range of case study cities selected from a broad range of hydro-climatic and socio-economic regions on four continents. Data on urban water infrastructure and services were collected from utilities in two cities (Amman, Jordan; Ulaanbaatar, Mongolia), key stakeholder interviews and a household survey conducted in Amman. Publicly available, empirical utility data and globally accessible datasets were used to support these and additional case studies. </div><div><br></div><div>The data show that community adaptation significantly contributes to urban water security and resilience, but the ability to adapt is highly heterogeneous across and within cities, leading to large inequality of water security. In cities with high levels of water security and resilience, adaptive capacity remains latent (inactive), while water-insecure cities rely on community adaptation for the self-provision of services. The framework is applied for assessing individual urban water systems, as well as for cross-city comparison for different types of cities. Results show that cities fall along a continuous gradient, ranging from water insecure and non-resilient cities with inadequate service provision prone to failure in response to extant shock regimes, to water secure and resilient systems with high levels of services and immediate recovery after shocks. Although limited by diverse constraints, the analyses show that urban water security and resilience tend to co-evolve, whereas sustainability, which considers local and global sustainable management, shows highly variable results across cities. I propose that the management of urban water systems should maintain a balance of security, resilience and sustainability.</div><div><br></div><div>The focus in Section 3 is on intra-city patterns and mechanisms, which contribute to urban water security, resilience and sustainability. In spite of engineering design and planning, and against common expectations, intra-city patterns emerge from self-organizing processes similar to those found in nature. These are related to growth processes following the principle of preferential attachment and functional efficiency considerations, which lead to Pareto power-law probability distributions characteristic of scale-free-like structures. Results presented here show that such structures are also present in urban water distribution and sanitary sewer networks, and how deviation from such specific patterns can result in vulnerability towards cascading failures. In addition, unbounded growth, unmanaged demand and unregulated water markets can lead to large inequality, which increases failure vulnerability. </div><div><br></div><div>The introduction of infrastructure and institutions for providing urban water services intercedes and mediates the human-water relationship. Complexity of infrastructural and institutional setups, growth patterns, management strategies and practices result in different levels of disconnects between citizens and the ecosystems providing freshwater resources. “Invisibility” of services to citizens results from maximized water system performance. It can lead to a lack of awareness about the effort and underlying infrastructure and institutions that operate for delivering services. Data for the seven cities illustrate different portfolios of complexity, invisibility and disconnection. Empirical data gathered in a household survey and key stakeholder interviews in Amman reveals that a misalignment of stakeholder perceptions resulting from the lack of information flow between citizens and urban managers can be misguiding and can constrain the decision-making space. Unsustainable practices are fostered by invisibility and disconnection and exacerbate the threats to urban water security and resilience. Such challenges are investigated in the context of urban water system traps: the poverty and the rigidity trap. Results indicate that urban water poverty is associated with local unsustainability, while rigidity traps combined with urban demand growth gravitate towards global unsustainability. </div><div><br></div><div>Returning to the city-level in Section 4, I investigate urban water system evolution. The question how the trajectories of urban water security, resilience and sustainability can be managed is examined using insights from hydrological and social-ecological systems research. I propose an “Urban Budyko Landscape”, which compares urban water supply systems to hydrological catchments and highlights the different roles of supply- and demand-management of water and water-related urban services. A global assessment of 38 cities around the world puts the seven case studies in perspective, emphasizing the relevance of the proposed framework and the representative, archetypal character of the selected case studies. </div><div><br></div><div>Furthermore, I examine how managing for the different dimensions of the CPA (capital availability, robustness, risk and sustainable management) determines the trajectories of urban water systems. This is done by integrating the CPA with the components of social-ecological system resilience, which explain how control of the different components determines the movement of systems through states of security and resilience in a stability landscape. Finally, potential feedbacks resulting from the global environment are investigated with respect to the role that globally sustainable local and regional water management can play in determining the trajectories of urban water systems. These assessments demonstrate how the impact of supply-oriented strategies reach beyond local, regional and into global boundaries for meeting a growing urban demand, and come at the cost of global sustainability and communities elsewhere.</div><div><br></div><div>Despite stark differences between individual cities and large heterogeneities within cities, convergent trends and patterns emerge across systems and are revealed through application of the proposed concepts and frameworks. The implications of these findings are discussed in Section 5, and are summarized here as follows: </div><div>1) The management of urban water systems needs to move beyond the security and resilience paradigms, which focus on current system functioning and short-term behavior. Sustaining a growing global, urban population will require addressing the long-term, cross-scale and inter-sector impacts of achieving and maintaining urban water security and resilience. </div><div>2) Emergent spatial patterns are driven by optimization for the objective functions. Avoiding traps, cascading failure, extreme inequality and maintaining global urban livability requires a balance of supply- and demand-management, consideration of system complexity, size and reach (i.e., footprint), as well as internal structures and management strategies (connectedness and modularity).</div><div>3) Urban water security and resilience are threatened by long-term decline, which necessitates the transformation to urban sustainability. The key to sustainability lies in experimentation, modularization and the incorporation of interdependencies across scales, systems and sectors.</div><div><br></div>