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Literatura académica sobre el tema "Complex mdof structural systems"

Autor: Grafiati

Publicado: 10 de marzo de 2023

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Artículos de revistas sobre el tema "Complex mdof structural systems"

F. Masri, S., F. Tasbihgoo, J. P. Caffrey, A. W. Smyth y A. G. Chassiakos. "Data-based model-free representation of complex hysteretic MDOF systems". Structural Control and Health Monitoring 13, n.º 1 (enero de 2006): 365–87. http://dx.doi.org/10.1002/stc.147.

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Reyes-Salazar, Alfredo, Federico Valenzuela-Beltran, David de Leon-Escobedo, Eden Bojorquez-Mora y Arturo Lopez Barraza. "Combination rules and critical seismic response of steel buildings modeled as complex MDOF systems". Earthquakes and Structures 10, n.º 1 (25 de enero de 2016): 211–38. http://dx.doi.org/10.12989/eas.2016.10.1.211.

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Chen, Menghui, Xiaoshu Gao, Cheng Chen, Tong Guo y Weijie Xu. "A Comparative Study of Meta-Modeling for Response Estimation of Stochastic Nonlinear MDOF Systems Using MIMO-NARX Models". Applied Sciences 12, n.º 22 (14 de noviembre de 2022): 11553. http://dx.doi.org/10.3390/app122211553.

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Complex dynamic behavior of nonlinear structures makes it challenging for uncertainty analysis through Monte Carlo simulations (MCS). Surrogate modeling presents an efficient and accurate computational alternative for a large number of MCS. The previous study has demonstrated that the multi-input multi-output nonlinear autoregressive with exogenous input (MIMO-NARX) model provides good discrete-time representations of deterministic nonlinear multi-degree-of-freedom (MDOF) structural dynamic systems. Model order reduction (MOR) is executed to eliminate insignificant modes to reduce the computational burden due to too many degrees of freedom. In this study, the MIMO-NARX strategy is integrated with different meta-modeling techniques for uncertainty analysis. Different meta-models including Kriging, polynomial chaos expansion (PCE), and arbitrary polynomial chaos (APC) are used to surrogate the NARX coefficients for system uncertainties. A nine-DOF structure is used as an MDOF dynamic system to evaluate different meta-models for the MIMO-NARX. Good fitness of statistical responses is observed between the MCS results of the original system and all surrogated MIMO-NARX predictions. It is demonstrated that the APC-NARX model with the advantage of being data-driven is the most efficient and accurate tool for uncertainty quantification of nonlinear structural dynamics.

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McElhaney, J. M., A. Palazzolo y A. Kascak. "Modeling and Simulation Methods for MDOF Structures and Rotating Machinery With Impact Dampers". Journal of Engineering for Gas Turbines and Power 119, n.º 2 (1 de abril de 1997): 436–46. http://dx.doi.org/10.1115/1.2815594.

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Previously published work on applied impact damping typically relates to SDOF models or simple MDOF models such as the classical cantilever beam. Structural models often require an extremely large number of DOF with mode shapes that are generally very complex. Dynamics simulation of these typically becomes both complicated and time consuming. The nonlinear behavior of impact dampers further complicates such simulation in that standard linear solutions are not possible. The primary objective in this research extends previous work by applying impact dampers to MDOF structures that are modeled with general three-dimensional “beam” finite elements. Modal-based models of the MDOF systems and efficient impact damper tracking algorithms were also developed that significantly reduced CPU time for simulation. Significant among the objectives was obtaining an impact damper design for the MDOF casing structure of the Space Shuttle Main Engine (SSME), High-Pressure Oxygen Turbo-Pump (HPOTP), subject to pump rotor shaft unbalance. Impact damper performance is based on suppression of vibration at casing critical frequencies for rotor speed ranges, at rotor full speed, and very high unbalance to simulate a defect such as losing an impeller blade fragment or a cracked bearing [6]. Simulations show significant reductions in vibration at the casing critical frequencies and very high unbalance levels while little or no improvement was observed off resonance. Additionally, the previous work with an experimental rotor bearing system (RBS) and impact damper was modeled using the developed modal-based methods. Simulation of the resulting model response shows remarkable agreement with the experimental. Finally, both the RBS and the HPOTP were modeled and simulated as unstable systems with attached impact dampers. The simulations predict that the impact damper is an excellent stabilizing mechanism for a range of instability driver values. Simulation of the models in this research with the developed modal based algorithms were accomplished with excellent efficiency, and accurate results.

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Reyes-Salazar, Alfredo, Achintya Haldar, Ramon Eduardo Rodelo-López y Eden Bojórquez. "Effect of Damping and Yielding on the Seismic Response of 3D Steel Buildings with PMRF". Scientific World Journal 2014 (2014): 1–21. http://dx.doi.org/10.1155/2014/915494.

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The effect of viscous damping and yielding, on the reduction of the seismic responses of steel buildings modeled as three-dimensional (3D) complex multidegree of freedom (MDOF) systems, is studied. The reduction produced by damping may be larger or smaller than that of yielding. This reduction can significantly vary from one structural idealization to another and is smaller for global than for local response parameters, which in turn depends on the particular local response parameter. The uncertainty in the estimation is significantly larger for local response parameter and decreases as damping increases. The results show the limitations of the commonly used static equivalent lateral force procedure where local and global response parameters are reduced in the same proportion. It is concluded that estimating the effect of damping and yielding on the seismic response of steel buildings by using simplified models may be a very crude approximation. Moreover, the effect of yielding should be explicitly calculated by using complex 3D MDOF models instead of estimating it in terms of equivalent viscous damping. The findings of this paper are for the particular models used in the study. Much more research is needed to reach more general conclusions.

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Reyes-Salazar, Alfredo, Eden Bojorquez, Achintya Haldar, Arturo Lopez-Barraza y J. Luz Rivera-Salas. "Ductility Reduction Factors for Steel Buildings Modeled as 2D and 3D Structures". Applied Mechanics and Materials 595 (julio de 2014): 166–72. http://dx.doi.org/10.4028/www.scientific.net/amm.595.166.

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The global ductility parameter (μG), commonly used to represent the capacity of a structure to dissipate energy, and the associated ductility reduction factor (Rμ), are estimated for steel buildings with perimeter moment resisting frames (PMRF), which are modeled as 2D and 3D complex MDOF systems. Results indicate that the μG value of 4, commonly assumed for moment resisting steel frames, cannot be justified. A value of 3 is more reasonable. The values of μG and Rμ may be quite different for 2D and 3D structural representations or for local and global response parameters, showing the limitation of the commonly used Equivalent Lateral Force Procedure (ELFP). Thus, the ductility and ductility reduction factors obtained from simplified structural representation must be taken with caution.

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Valenzuela-Beltrán, Federico, Mario D. Llanes-Tizoc, Edén Bojórquez, Juan Bojórquez, Robespierre Chávez, Jesus Martin Leal-Graciano, Juan A. Serrano y Alfredo Reyes-Salazar. "Effect of the Distribution of Mass and Structural Member Discretization on the Seismic Response of Steel Buildings". Applied Sciences 12, n.º 1 (3 de enero de 2022): 433. http://dx.doi.org/10.3390/app12010433.

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The response of steel moment frames is estimated by first considering that the mass matrix is the concentrated type (ML) and then consistent type (MC). The effect of considering more than one element per beam is also evaluated. Low-, mid- and high-rise frames, modeled as complex-2D-MDOF systems, are used in the numerical study. Results indicate that if ML is used, depending upon the response parameter under consideration, the structural model, the seismic intensity and the structural location, the response can be significantly overestimated, precisely calculated, or significantly underestimated. Axial loads at columns, on an average basis, are significantly overestimated (up to 60%), while lateral drifts and flexural moments at beams are precisely calculated. Inter-story shears and flexural moments at columns, on average, are underestimated by up to 15% and 35%, respectively; however, underestimations of up to 60% can be seen for some individual strong motions. Similarly, if just one element per beam is used in the structural modeling, inter-story shears and axial loads on columns are overestimated, on average, by up to 21% and 95%, respectively, while the lateral drifts are precisely calculated. Flexural moments at columns and beams can be considerably underestimated (on average up to 14% and 35%, respectively), but underestimations larger than 50% can be seen for some individual cases. Hence, there is no error in terms of lateral drifts if ML or one element per beam is used, but significant errors can be introduced in the design due to the overestimation and underestimation of the design forces. It is strongly suggested to use MC and at least two elements per beam in the structural modeling.

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Qiang, Pei, Er Liang Chen y Xiao Dong Zhao. "Dynamic Calculation of MDOF Systems Based on GIS". Advanced Materials Research 446-449 (enero de 2012): 3019–22. http://dx.doi.org/10.4028/www.scientific.net/amr.446-449.3019.

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The paper presents an integration of a Geographic Information System (GIS) and Multiple Degree of Freedom (MDOF) model for structural dynamic calculations. The input data of MDOF is stored in the format of spatial data model in GIS with 2D and 3D with the help of Google SketchUp. The output data of MDOF can be viewed in both 2D graph and 3D visualization after simulation calculation in GIS. A case study of dynamic response of campus buildings is presented to illustrate how the GIS-coupled system has been developed. Results show that the proposed GIS-model integrated system can perform a large number of dynamic responses of MDOF affected by earthquakes, promote better earthquake resistant behavior of building structure in urban regions, and thus optimize hazard assessment, vulnerability estimation and seismic risk reduction.

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Wang, Xiaohan, Weihang Ren, Baocheng Liu y Dong Hu. "Structural Dynamics and Vibration Analysis of the MDOF Systems". Journal of Physics: Conference Series 2381, n.º 1 (1 de diciembre de 2022): 012004. http://dx.doi.org/10.1088/1742-6596/2381/1/012004.

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Abstract Because the vibration of buildings plays an important role in resisting an earthquake, we need some methods to analyze the vibration of the MDOF systems. This paper proposes a method to analyze the structural dynamics and vibration of the MDOF systems by using the “modal superposition method” and the “Duhamel integral”. We set the system consisting of mass, stiffness, and damping to correspond to actual situations. The results obtained in this research include the E.O.M: natural frequency and mode shape of the building model, which can show the resonance of the building. Based on our analysis, designers can make a more appropriate design of buildings that can reduce the mortality in the earthquake.

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Tang, Yu, Chao Luo y Bo Fu. "Choices of the Critical Frequency for φ in TL-φ Algorithms When Applied to Multi-Degree of Freedom Systems". Buildings 12, n.º 6 (20 de junio de 2022): 863. http://dx.doi.org/10.3390/buildings12060863.

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TL-φ algorithms are newly developed explicit structure-dependent integration algorithms utilized for solving the temporally discretized equations of motion. In contrast to the existing algorithms, the most significant improvement of TL-φ algorithms is in diminishing the amount of period errors by introducing a precorrection coefficient φ into the integration parameters of TL-φ algorithms, which is related to the critical frequency of a system. In the previous work, the fundamental frequency of the system is deemed to be the critical frequency, so that φ is a constant scaling corresponding to the fundamental frequency for both single-degree-of-freedom (SDOF) and multi-degree-of-freedom (MDOF) systems. However, for a MDOF system, the first mode may not contribute to the total response more than other ones under a given external excitation, calculating φ only by the fundamental frequency will underestimate the contribution of the higher-frequency modes to structural dynamics. In this paper, choices of the critical frequency for φ when applying TL-φ algorithms to MDOF systems are investigated thoroughly. By considering the initial structural properties of the system and the frequency characteristics of the external excitation simultaneously, a calculation criterion of φ for MDOF systems under specific external excitations is proposed. Four numerical examples with different initial structure properties and loading conditions are designed, and the results demonstrate that the proposed criterion can be potentially used to solve structural dynamic problems of MDOF systems with a more desirable numerical dispersion performance.

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Tesis sobre el tema "Complex mdof structural systems"

Gunay, Mehmet Selim. "An Equivalent Linearization Procedure For Seismic Response Prediction Of Mdof Systems". Phd thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/3/12609447/index.pdf.

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Nonlinear response history analysis is accepted as the most accurate analytical tool for seismic response determination. However, accurate estimation of displacement responses using conceptually simple, approximate analysis procedures is preferable, since there are shortcomings in the application of nonlinear response history analysis resulting from its complexity. An equivalent linearization procedure, which utilizes the familiar response spectrum analysis as the analysis tool and benefits from the capacity principles, is developed in this thesis study as an approximate method for predicting the inelastic seismic displacement response of MDOF systems under earthquake excitations. The procedure mainly consists of the construction of an equivalent linear system by reducing the stiffness of structural members which are expected to respond in the inelastic range. Different from similar studies in literature, equivalent damping is not explicitly employed in this study. Instead, predetermined spectral displacement demands are utilized in each mode of the equivalent linear system for the determination of global displacement demands. Response predictions of the equivalent linearization procedure are comparatively evaluated by using the benchmark nonlinear response history analysis results and other approximate methods including conventional pushover analysis and modal pushover analysis (MPA). It is observed that the proposed procedure results in similar accuracy with approximate methods which employ nonlinear analysis. Considering the conceptual simplicity of the procedure and the conventional analysis tools used in its application, presented equivalent linearization procedure can be suggested as a practically applicable method for the prediction of inelastic seismic displacement response parameters with sufficient accuracy.

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Rodríguez-Dávila, Héctor M. "Optimum design for feedforward structural-acoustic control of complex structural systems". Diss., Virginia Tech, 1996. http://hdl.handle.net/10919/40254.

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Thomya, Panthida. "STRUCTURAL CHARACTERIZATION OF COMPLEX POLYMER SYSTEMS BY DEGRADATION / MASS SPECTROMETRY". Akron, OH : University of Akron, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=akron1163969934.

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Thesis (Ph. D.)--University of Akron, Dept. of Chemistry, 2006.
"December, 2006." Title from electronic dissertation title page (viewed 04/24/2008). Advisor, Chrys Wesdemiotis; Committee members, Matthew P. Espe, Jun Hu, Wiley J. Youngs, Frank W. Harris; Department Chair, Kim C. Calvo; Dean of the College, Ronald F. Levant; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.

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Abat, Diren. "Harmonic Vibration Analysis Of Large Structures With Local Nonlinearity". Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/2/12610475/index.pdf.

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With the rapid development in today&rsquo
s technology, reliability and performance requirements on components of various mechanical systems, which tend to be much lighter and work under much more severe working conditions, dramatically increased. In general, analysis techniques based on simplified model of structural components with linearity assumption may provide time saving for solutions with reasonable accuracy. However, since most engineering structures are often very complex and intrinsically nonlinear, in some cases they may behave in a different manner which cannot be fully described by linear mathematical models, or linear treatments may not be applicable at all. In fact, some studies revealed that deviations in the modal properties of dynamic structures gathered from measured data are due to nonlinearities in the structure. Hence, in problems where accuracy is the primary concern, taking the nonlinear effects into account becomes inevitable. In this thesis, it is aimed to analyze the harmonic response characteristics of multi degree of freedom nonlinear structures having different type of nonlinearities. The amplitude dependencies of nonlinearities are modelled by using describing function method. To increase the accuracy of the results, effect of the higher order harmonic terms will be considered by using multi harmonic describing function theory. Mathematical formulations are embedded in a computer program developed in MATLAB®
with graphical user interface. The program gets the system matricies from the file which is obtained by using substructuring analysis in ANSYS®
, and nonlinearities in the system can easily be defined through the graphical user interface of the MATLAB®
program.

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Coccon, Marco. "Structural Reliability Analysis of Complex Systems: Applications to Offshore and Composite Structures". Doctoral thesis, Università degli studi di Padova, 2015. http://hdl.handle.net/11577/3424201.

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This thesis aims at developing new methodologies for the reliability analysis of structural systems with applications to offshore and aeronautical fields. In general, sructures of practical interest are complex redundant systems, in which more than one element is required to fail in order to have catastrophic failure. Moreover, ramdomness inherently exists in both material properties and external loads. As a result, complex structural systems are typically characterised by a huge number of possible failure sequences, of which only some are most likely to occour. Therefore, for an efficient risk analysis, only the dominant failure modes need to be considered, so as to minimise the number of failure paths as well as the computational costs associated to their enumeration and evaluation. However, although several techniques have been developed for the identification of the critical failure sequences, these methods are still either time-demanding or prone to miss potential failure modes. These challenges motivated the first part of the thesis, in which the merits of a risk assessment framework recently developed for truss and frame structures are here investigated in view of its extensive application to the offshore field. To this end, the case study of a jacket-type platform under an extreme sea state is considered. First, the dominant failure modes of the structure are rapidly identified by a multi-point parallel search employing a genetic algorithm. Then, a multi-scale system reliability analysis is performed, in which the statistical dependence among both structural elements and failure modes is fully considered through simple matrix operations. Finally, the accuracy and the efficiency of the proposed approach are successfully validated against crude Monte Carlo simulation. In the second part of the thesis, system reliability theory is applied to the uncertainty quantification of the longitudinal tensile strength of UniDirectional (UD) composites, a structural component very common in aircraft structures. Predictive models for size effects in this class of materials are paramount for scaling small-coupon experimental results to the design of large composite structures. In this respect, a Monte Carlo progressive failure analysis is proposed to calculate the strength distributions of hierarchical fibre bundles, which are formed by grouping a predefined number of smaller-order bundles into a larger-order one. The present approach is firstly validated against a recent analytical model to be later applied to more complex load-sharing configurations. The resulting distributions are finally used to analyse the damage accumulation process and the formation of clusters of broken fibres during progressive failure.
Lo scopo principale di questa tesi è lo sviluppo di nuove metodologie per determinare l’affidabilità dei sistemi strutturali con applicazioni sia in campo offshore che aeronautico. In generale, strutture di interesse pratico sono caratterizzate da un elevato grado di ridondanza, per cui il collasso globale richiede la rottura simulatanea e/o progressiva di più elementi. Inoltre, i sistemi fisici sono influenzati da diverse fonti di incertezza, quali le prorietà dei materiali e le condizioni ambientali e operative. Pertanto, il collasso strutturale può avvenire con diverse modalità (modi di guasto), di cui solo alcune possiedono una probabilità di accadimento significativa (modi di guasto dominanti). Per una valutazione efficiente del rischio risulta dunque indispensabile limitare l’analisi ai soli modi dominanti, così da ridurre il costo computazionale associato alle fasi di identificazione e di valutazione dei modi stessi. Tuttavia, nonostante in letteratura vi siano numerose soluzioni per l’analisi del rischio, tali metodi richiedono ancora tempi di calcolo notevoli e sono inclini a tralasciare potenziali modi di guasto. Queste motivazioni conducono alla prima parte delle tesi, in cui si ripropone un metodo recentemente sviluppato per l’analisi del rischio di strutture discrete (reticolari e telai) in previsione di una sua applicazione al campo offshore. A tale scopo si considera il caso di studio di una piattaforma di tipo jacket in condizioni di mare estremo. Dapprima, i modi di guasto dominanti vengono rapidamente identificati per mezzo di un algoritmo genetico. In seguito, l’affidabilità del sistema viene calcolata mediante un approccio multi-scala che fa uso di semplici operazioni matriciali, in cui la dipendenza statistica viene considerata sia tra le componenti strutturali che tra i modi di guasto dominanti. Infine, l’accuratezza e l’efficienza del metodo vengono testate con successo tramite comparazione con Monte Carlo. Nella seconda parte della tesi, la teoria dell’affidabilità dei sistemi viene applicata per la quantificazione dell’incertezza nella resistenza a trazione di compositi UniDirezionali (UD), problema di notevole interesse per l’ambito aeronautico e non solo. Infatti, il comportamento aletorio di questi materiali è fortemente influenzato da effetti di scala, che limitano la progettazione di strutture in composito di grandi dimensioni sulla base dei dati sperimentali ricavati da provini. In quest’ottica, si propone di modellare fasci di fibre secondo una legge di scala gerarchica, ossia raggruppando un numero prestabilito di fasci più piccoli in un fascio di ordine superiore. La distribuzione di resistenza di tali fasci viene quindi simulata attraverso un’analisi di collasso progressivo. Questo approccio, dapprima validato rispetto ad un modello analitico recentemente sviluppato per disposizioni semplici di fasci, viene poi esteso a configurazioni più realistiche. I risultati così ottenuti sono infine processati per l’analisi statistica del danno.

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Al-Haddad, Tristan Farris. "PerFORMance: Integrating Structural Feedback into Design Processes for Complex Surface-Active Form". Thesis, Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-07102006-111810/.

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Rahman, Brian M. "Sensor Placement for Diagnosis of Large-Scale, Complex Systems: Advancement of Structural Methods". The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1562859497638274.

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Hoppe, Konrad. "Complex networks with node intrinsic fitness : on structural properties and contagious phenomena". Thesis, Brunel University, 2014. http://bura.brunel.ac.uk/handle/2438/10345.

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Complex networks is a vibrant research field and has received much attention over the last decade. Central to this area is the question of how networks around us are constructed. The essential notion of network research is that these systems are assembled in a decentralised way, thus no central agent is planning the network beforehand. Despite this lack of central coordination, many networks present intriguing universalities, such as broad degree distributions, in the form of power-laws. The subject of study in this thesis is a class of networks that are constructed by a node intrinsic variable, called fitness. The way these networks grow could be called a rich-get-richer mechanism. The fitter a node is, the more likely it is to acquire new connections inside the network. Several aspects that are directly connected to these networks are explored in this thesis. In the first part, the properties of growing networks that are driven by fitness are investigated and it is shown that the introduction of growth leads to a topological structure that is different from its static counterpart. In the subsequent chapter, percolation on fitness driven networks is studied. The results give insights into possible mechanisms that can stabilise systems. Furthermore, the theory can be used to identify vulnerable structures around us. In the following chapter, the world trade network is discussed. This numerical investigation highlights possible improvements to the methodology to make statistical analysis more robust. That chapter is followed by an analysis of time-varying networks. Time-varying networks represent an interesting construct that allows a formulation of stochastic processes on the same time-scale as the evolution of the network itself. This possibility is highly relevant to the investigation of epidemics, for instance. In the last chapter, a study of a system of clusters and their self-organised formation is presented.

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Goode, Natassia. "Determinants of the control of dynamic systems: The role of structural knowledge". Thesis, The University of Sydney, 2011. http://hdl.handle.net/2123/8967.

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In educational and organisational settings it has become common practice to use computer-based complex problems that represent dynamic systems for assessment and training purposes. In the interpretation of performance scores and the design of training programs, it is often assumed that the capacity to effectively control the outcomes of a dynamic system depends on the acquisition of structural knowledge. Control performance scores are generally interpreted as evidence of individual differences in the capacity to acquire and utilise structural knowledge and training programs typically try to improve learners‘ mental models of the system of interest. However, a causal relationship between the acquisition of structural knowledge and successful system control has not been established, and some findings suggest that it may be possible to control dynamic systems in the absence of structural knowledge. Therefore, the goals of this project were to determine the conditions that are required to learn how to control dynamic systems and the psychological processes that separate successful from less successful problem solvers in the performance of this task. The main emphasis of this investigation was to clarify the role of structural knowledge in the control of dynamic systems and to identify sources of individual differences in problem solvers‘ capacity to acquire such knowledge and apply it in a goal-orientated application. In a series of studies, a combined experimental and differential approach was adopted to address these goals. This consisted of the experimental manipulation of the task and structural characteristics of complex problems combined with the use of process indicators and external psychometric tests. Study 1 examined whether problem solvers need to directly interact with a dynamic system in order to acquire structural knowledge that is useful for system control. Study 2 examined whether increments in structural knowledge lead to improvements in control performance and whether dynamic systems can be successfully controlled without structural knowledge. Study 3 examined whether the relationship between structural knowledge and control performance is moderated by system complexity. Each of these studies also investigated the role of fluid intelligence in the acquisition and application of knowledge. Additional methodological contributions include the application of Cognitive Load Theory to the design of the instructions used to manipulate structural knowledge, the use of randomly generated control performance scores to evaluate the success of performance and the development of a theoretically driven operationalisation of system complexity. Across the studies, it was found that structural knowledge was a necessary condition of better than random performance and that there was a causal relationship between structural knowledge and control performance. However, the likelihood that structural knowledge would be acquired and utilised was found to be dependent on the complexity of the system. Small increments in system complexity resulted in floor effects on performance. Fluid intelligence was found to play a crucial role in the acquisition and subsequent application of knowledge. Overall, the results indicate that the complexity of the system determines the amount of knowledge that is acquired by the problem solver, which in turn, combined with their intelligence, determines the quality of their control performance.

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Hagström, Peter. "The "wired" MNC : the role of information systems for structural change in complex organizations /". Stockholm : Inst. of Intern. Business, 1991. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=002955192&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.

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Más fuentes

Libros sobre el tema "Complex mdof structural systems"

Casciati, Fabio. Fragility analysis of complex structural systems. Taunton, Somerset, England: Research Studies Press, 1991.

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Zattoni, Elena, Anna Maria Perdon y Giuseppe Conte, eds. Structural Methods in the Study of Complex Systems. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-18572-5.

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author, Mills Andrew R., Kadirkamanathan Visakan 1962 author y Clifton David A. author, eds. Equipment health monitoring in complex systems. Boston: Artech House, 2018.

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Brudastova, Olga. Stochastic response determination and spectral identification of complex dynamic structural systems. [New York, N.Y.?]: [publisher not identified], 2018.

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Geurts, Frédéric. Abstract compositional analysis of iterated relations: A structural approach to complex state transition systems. Berlin: Springer Berlin Heidelberg, 1999.

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Complex adaptive innovation systems: Relatedness and transversality in the evolving region. New York: Routledge, 2011.

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Structures, Congress '86 (1986 New Orleans La ). Recent applications in computational mechanics: Proceedings of 2 sessions at Structures Congress '86. New York, N.Y: The Society, 1986.

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1959-, Pierre Christophe, Perkins N. C, American Society of Mechanical Engineers. Design Engineering Division. y Conference on Mechanical Vibration and Noise (14th : 1993 : Albuquerque, N.M.), eds. Structural dynamics of large scale and complex systems: Presented at the 1993 ASME Design Technical Conferences, 14th Biennial Conference on Mechanical Vibration and Noise, Albuquerque, New Mexico, September 19-22, 1993. New York: American Society of Mechanical Engineers, 1993.

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1959-, Pierre Christophe, Perkins N. C, American Society of Mechanical Engineers. Design Engineering Division. y Conference on Mechanical Vibration and Noise. (14th : 1993 : Albuquerque, N.M.), eds. Structural dynamics of large scale and complex systems: Presented at the 1993 ASME design technical conferences, 14th Biennial Conference on Mechanical Vibration and Noise, Albuquerque, New Mexico, September 19-22, 1993. New York: American Society of Mechanical Engineers, 1993.

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Ivanov, Anatoliy. Flexible modular assembly lines on a single structural basis. ru: INFRA-M Academic Publishing LLC., 2022. http://dx.doi.org/10.12737/1196558.

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The textbook discusses topical issues of automating the assembly of an extensive range of machine and instrument-making products based on highly efficient robotic reconfigurable systems of a new generation built on a single structural basis. The possibility of fast organization of automated assembly of new types of products, which is provided by the presence of a flexible basic set as part of the complex (line), is shown. A complete set of original technical means for basic and service operations of assembly and control of products is described. Analytical conditions of automatic assembly are given, and recommendations on optimization of design solutions and modeling of projected assembly systems are given. It is intended for students studying under the bachelor's degree programs, certified specialists and masters, teachers of technical universities, as well as designers, technologists and scientists dealing with the problem of complex assembly automation.

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Capítulos de libros sobre el tema "Complex mdof structural systems"

Pradlwarter, H. J., G. I. Schuëller y P. G. Melnik-Melnikov. "Advances in Reliability Estimation of MDOF-Systems". En Probabilistic Structural Mechanics: Advances in Structural Reliability Methods, 432–41. Berlin, Heidelberg: Springer Berlin Heidelberg, 1994. http://dx.doi.org/10.1007/978-3-642-85092-9_27.

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Di Paola, M., G. Falsone, G. Muscolino y G. Ricciardi. "Modal Analysis for Random Response of MDOF Systems". En Stochastic Structural Dynamics 1, 63–81. Berlin, Heidelberg: Springer Berlin Heidelberg, 1991. http://dx.doi.org/10.1007/978-3-642-84531-4_4.

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Sporns, Olaf y Giulio Tononi. "Structural Determinants of Functional Brain Dynamics". En Understanding Complex Systems, 117–47. Berlin, Heidelberg: Springer Berlin Heidelberg, 2007. http://dx.doi.org/10.1007/978-3-540-71512-2_4.

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Belov, Mikhail V. y Dmitry A. Novikov. "Structural Models of Complex Activity". En Studies in Systems, Decision and Control, 61–83. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-48610-5_3.

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Gürdal, Zafer y Ramzi Zakhama. "Cellular Automata for Simultaneous Analysis and Optimal Structural Topology Design". En Understanding Complex Systems, 333–53. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-12203-3_14.

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Paus, Tomáš. "Maturation of Structural and Functional Connectivity in the Human Brain". En Understanding Complex Systems, 463–75. Berlin, Heidelberg: Springer Berlin Heidelberg, 2007. http://dx.doi.org/10.1007/978-3-540-71512-2_16.

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Arenas, Alex y Filippo Radicchi. "A Tipping Point in the Structural Formation of Interconnected Networks". En Understanding Complex Systems, 1–15. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-23947-7_1.

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Li, Xiang, Peng Yao y Yujian Pan. "Towards Structural Controllability of Temporal Complex Networks". En Complex Systems and Networks, 341–71. Berlin, Heidelberg: Springer Berlin Heidelberg, 2015. http://dx.doi.org/10.1007/978-3-662-47824-0_13.

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de Lim, Alexsandro Souza y José Roberto de Paula. "Mectron’s Innovation Management: Structural and Behavioral Analysis". En Complex Systems Concurrent Engineering, 701–8. London: Springer London, 2007. http://dx.doi.org/10.1007/978-1-84628-976-7_77.

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Gegov, Alexander. "Structural Properties of Basic Operations". En Fuzzy Networks for Complex Systems, 51–108. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-15600-7_5.

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Actas de conferencias sobre el tema "Complex mdof structural systems"

McElhaney, John M., A. Palazzolo y A. Kascak. "Modeling and Simulation Methods for MDOF Structures and Rotating Machinery With Impact Dampers". En ASME 1995 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1995. http://dx.doi.org/10.1115/95-gt-397.

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Previously published work on applied impact damping typically relates to SDOF models or simple MDOF models such as the classical cantilever beam. Structural models often require an extremely large number of DOF with mode shapes that are generally very complex. Dynamics simulation of these typically becomes both complicated and time consuming as well. The non-linear behavior of impact dampers further complicates such simulation in that standard linear solutions are not possible. The primary objective in this research extends previous work by applying impact dampers to MDOF structures that are modeled with general 3-D ‘beam’ finite elements. Modal based models of the MDOF systems and efficient impact damper tracking algorithms were also developed which significantly reduced CPU time for simulation. Significant among the objectives was obtaining an impact damper design for the MDOF casing structure of the Space Shuttle Main Engine (SSME), High Pressure Oxygen Turbo-Pump (HPOTP), subject to pump rotor shaft unbalance. Impact damper performance is based on suppression of vibration at casing critical frequencies for rotor speed ranges, at rotor full speed, and very high unbalance to simulate a defect such as loosing an impeller blade fragment or a cracked bearing[6]. Simulations show significant reductions in vibration at the casing critical frequencies and very high unbalance levels while little or no improvement was observed off resonance. Additionally, the previous work with an experimental rotor bearing system (RBS) and impact damper was modeled using the developed modal based methods. Simulation of the resulting model response shows remarkable agreement with the experimental. Finally, both the RBS and the HPOTP were modeled and simulated as unstable systems with attached impact dampers. The simulations predict that the impact damper is an excellent stabilizing mechanism for a range of instability driver values. Simulation of the models in this research with the developed modal based algorithms were accomplished with excellent efficiency, and accurate results.

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Krüger, Thomas D., Sauro Liberatore, Eric Knopf y Alastair Clark. "Consideration of Complex Support Structure Dynamics in Rotordynamic Assessments". En ASME Turbo Expo 2013: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/gt2013-95196.

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In rotordynamic analyses, support structures are commonly represented by lumped mass systems (single-degree-of-freedom, SDOF). This representation is easy to implement using standard rotordynamic tools. However, in reality the dynamic behaviour of the support structure (e.g. pedestals, casings, foundations) are in general much more complex. Only a multi-degree-of-freedom (MDOF) representation provides modelling close to reality. For many applications the dynamic behaviour of the support structure significantly influences the rotordynamic characteristics of the shaft train and therefore needs to be included in the assessment. Due to this impact, a good quality of the dynamic model used for the support structure is imperative. Regarding the rotor itself, the modelling is well understood and the prediction quality is excellent, not least due to the jointless welded rotor design. Numerous theoretical approaches exist for considering the complex dynamic behaviour of the support structure, all coming along with both drawbacks and opportunities. By discussing the characteristics of established approaches for modelling the support structure, the paper particularly presents an advanced theoretical approach based on a state-space representation using modal parameters. A case study of a real shaft train is shown, including a comparison of achieved results using the SDOF and the presented MDOF approach. By validating with experimental results, the excellent prediction quality of the MDOF approach is confirmed. The implementation of this approach enabled to further improve the reliability and the efficiency, which means high accuracy combined with low computation time, in performing rotordynamic assessments.

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Casciati, Fabio, Lucia Faravelli, Roberto Rossi y Guido Torelli. "Fuzzy chip control of MDOF structural systems". En 1999 European Control Conference (ECC). IEEE, 1999. http://dx.doi.org/10.23919/ecc.1999.7099787.

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Shen, Xiuli y Dan Long. "Research on Multidisciplinary Design Optimization of Aeroengine Turbine Flow Path in the Preliminary Design Phase". En ASME Turbo Expo 2014: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-25858.

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The design of an aero-engine is traditionally divided into three levels: conceptual design, preliminary design and detailed design. This three-step design process is inherently iterative, which can slow the design process and overall productivity. Additionally, as an integrated systems engineering analysis, aero-engine design involves multiple-disciplines. The complex coupled-relationship among multiple-disciplines and multiple-components gives rise to severe conflict with performance requirements when designing, especially when it comes to high-performance aero-engine. Traditionally, designers need to empirically balance all kinds of requirements, which lead to a longer design cycle. So it is necessary to apply Multidisciplinary Design Optimization (MDO) to organize and manage the process of design system which sufficiently utilizes the effect of interaction of multidisciplines for the optimal solution. The MDO of a turbine flow path is one of the key multidisciplinary optimization technologies in aeroengine overall design. The problem studied and presented in this paper consists in optimizing a turbine modeled by a multidisciplinary system of two coupled disciplines: turbine aerodynamics and structural strength, with temperature limited by the materials. In the present work, three modules are established to conduct the MDO research of turbine flow path: flow path design, turbine strength calculation and MDO. The aeroengine turbine flow path, including high and low pressure turbine flow path, is designed in the first module, with its efficiency estimated. In the second module, turbine rotors consisting of blades, discs and the low spool shaft are parametric modeled so as to analyze the structural aspects of turbine rotors, such as weight and stresses. MDO is conducted using multi-island genetic algorithm optimization (MIGA) optimization algorithm provided in iSIGHT software. Fully Integrated Optimization (FIO) strategy is studied to deal with the multidisciplinary analysis. The complex coupling relations between aerodynamic performance and turbine strength are analyzed to establish turbine multidisciplinary optimization system. The optimal values of loading coefficient, rotational speed, bore diameter of rotor discs defined by the shaft size, and other independent design variables are obtained in order to achieve minimum weight of turbine rotors while simultaneously meeting the strength and aerodynamics efficiency requirements. This method presented in this paper can greatly shorten turbine design cycle, improve aeroengine design ability, and is prospective to be widely applied to engineering field.

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Kougioumtzoglou, I. A., Fan Kong, P. D. Spanos y J. Li. "Harmonic Wavelets-Based Response Power Spectrum Determination of MDOF Nonlinear Structural Systems". En Second International Conference on Vulnerability and Risk Analysis and Management (ICVRAM) and the Sixth International Symposium on Uncertainty, Modeling, and Analysis (ISUMA). Reston, VA: American Society of Civil Engineers, 2014. http://dx.doi.org/10.1061/9780784413609.163.

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Ikushima, Akira J. "Structural Relaxations in Silica Glass". En SLOW DYNAMICS IN COMPLEX SYSTEMS: 3rd International Symposium on Slow Dynamics in Complex Systems. AIP, 2004. http://dx.doi.org/10.1063/1.1764226.

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Hernandez-Garcia, Miguel R., Sami F. Masri y Roger Ghanem. "An Experimental Study of Change Detection in Uncertain Chain-Like Systems". En ASME 2008 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. ASMEDC, 2008. http://dx.doi.org/10.1115/smasis2008-469.

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In this study, a decentralized time-domain identification technique for chain-like MDOF systems is used in conjunction with a probabilistic framework to obtain a stochastic representation of estimated changes in stiffness-like and damping-like structural coefficients in a laboratory three-story building structure that had been tested at the Los Alamos National Laboratory.

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Elseifi, Mohamed. "Discrete Wavelet Transforms for Damage Identification in MDOF Structural Systems with Breakable Springs". En 51st AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference
18th AIAA/ASME/AHS Adaptive Structures Conference
12th. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2010. http://dx.doi.org/10.2514/6.2010-3109.

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Morishita, Tetsuya, Michio Tokuyama, Irwin Oppenheim y Hideya Nishiyama. "Structural Heterogeneity and Non-Exponential Relaxation in Supercooled Liquid Silicon". En COMPLEX SYSTEMS: 5th International Workshop on Complex Systems. AIP, 2008. http://dx.doi.org/10.1063/1.2897909.

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Kardes, Hakan y Mehmet Hadi Gunes. "Structural Graph Indexing for Mining Complex Networks". En 2010 30th International Conference on Distributed Computing Systems Workshops (ICDCS Workshops). IEEE, 2010. http://dx.doi.org/10.1109/icdcsw.2010.42.

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Informes sobre el tema "Complex mdof structural systems"

Nechaev, V., Володимир Миколайович Соловйов y A. Nagibas. Complex economic systems structural organization modelling. Politecnico di Torino, 2006. http://dx.doi.org/10.31812/0564/1118.

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One of the well-known results of the theory of management is the fact, that multi-stage hierarchical organization of management is unstable. Hence, the ideas expressed in a number of works by Don Tapscott on advantages of network organization of businesses over vertically integrated ones is clear. While studying the basic tendencies of business organization in the conditions of globalization, computerization and internetization of the society and the results of the ﬁnancial activities of the well-known companies, the authors arrive at the conclusion, that such companies, as IBM, Boeing, Mercedes-Benz and some others companies have not been engaged in their traditional business for a long time. Their partner networks performs this function instead of them. The companies themselves perform the function of system integrators. The Tapscott’s idea ﬁnds its conﬁrmation within the framework of a new powerful direction of the development of the modern interdisciplinary science – the theory of the complex networks (CN) [2]. CN-s are multifractal objects, the loss of multifractality being the indicator of the system transition from more complex state into more simple state. We tested the multifractal properties of the data using the wavelet transform modulus maxima approach in order to analyze scaling properties of our company. Comparative analysis of the singularity spectrumf(®), namely, the diﬀerence between maximum and minimum values of ® (∆ = ®max ¡ ®min) shows that IBM company is considerably more fractal in comparison with Apple Computer. Really, for it the value of ∆ is equal to 0.3, while for the vertically integrated company Apple it only makes 0.06 – 5 times less. The comparison of other companies shows that this dependence is of general character. Taking into consideration the fact that network organization of business has become dominant in the last 5-10 years, we carried out research for the selected companies in the earliest possible period of time which was determined by the availability of data in the Internet, or by historically later beginning of stock trade of computer companies. A singularity spectrum of the ﬁrst group of companies turned out to be considerably narrower, or shifted toward the smaller values of ® in the pre-network period. The latter means that dynamic series were antipersistant. That is, these companies‘ management was rigidly controlled while the impact of market mechanisms was minimized. In the second group of companies if even the situation did changed it did not change for the better. In addition, we discuss applications to the construction of portfolios of stock that have a stable ratio of risk to return.

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Pierre, Christophe y Matthew P. Castanier. Mid-Frequency Dynamics of Complex Structural Systems: Assessing the State of the Art and Defining Future Research Directions. Fort Belvoir, VA: Defense Technical Information Center, noviembre de 2002. http://dx.doi.org/10.21236/ada409674.

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Russell, David H. Developing Ion Mobility-Mass Spectrometry for Structural Characterization of Complex Molecular Systems, Final Report/Product Number: DOE_ER-15520-3. Office of Scientific and Technical Information (OSTI), junio de 2017. http://dx.doi.org/10.2172/1430105.

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Perdigão, Rui A. P. y Julia Hall. Spatiotemporal Causality and Predictability Beyond Recurrence Collapse in Complex Coevolutionary Systems. Meteoceanics, noviembre de 2020. http://dx.doi.org/10.46337/201111.

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Causality and Predictability of Complex Systems pose fundamental challenges even under well-defined structural stochastic-dynamic conditions where the laws of motion and system symmetries are known. However, the edifice of complexity can be profoundly transformed by structural-functional coevolution and non-recurrent elusive mechanisms changing the very same invariants of motion that had been taken for granted. This leads to recurrence collapse and memory loss, precluding the ability of traditional stochastic-dynamic and information-theoretic metrics to provide reliable information about the non-recurrent emergence of fundamental new properties absent from the a priori kinematic geometric and statistical features. Unveiling causal mechanisms and eliciting system dynamic predictability under such challenging conditions is not only a fundamental problem in mathematical and statistical physics, but also one of critical importance to dynamic modelling, risk assessment and decision support e.g. regarding non-recurrent critical transitions and extreme events. In order to address these challenges, generalized metrics in non-ergodic information physics are hereby introduced for unveiling elusive dynamics, causality and predictability of complex dynamical systems undergoing far-from-equilibrium structural-functional coevolution. With these methodological developments at hand, hidden dynamic information is hereby brought out and explicitly quantified even beyond post-critical regime collapse, long after statistical information is lost. The added causal insights and operational predictive value are further highlighted by evaluating the new information metrics among statistically independent variables, where traditional techniques therefore find no information links. Notwithstanding the factorability of the distributions associated to the aforementioned independent variables, synergistic and redundant information are found to emerge from microphysical, event-scale codependencies in far-from-equilibrium nonlinear statistical mechanics. The findings are illustrated to shed light onto fundamental causal mechanisms and unveil elusive dynamic predictability of non-recurrent critical transitions and extreme events across multiscale hydro-climatic problems.

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Nagahi, Morteza, Raed Jaradat, Simon Goerger, Michael Hamilton, Randy Buchanan, Sawsan Abutabenjeh y Junfeng Ma. The impact of practitioners’ personality traits on their level of systems-thinking skills preferences. Engineer Research and Development Center (U.S.), octubre de 2022. http://dx.doi.org/10.21079/11681/45791.

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In this study, we used a structural equation modeling method to investigate the relationship between systems engineers and engineering managers’ Systems-Thinking (ST) skills preferences and their Personality Traits (PTs) in the domain of complex system problems. As organizations operate in more and more turbulent and complex environments, it has become increasingly important to assess the ST skills preferences and PTs of engineers. The current literature lacks studies related to the impact of systems engineers and engineering managers’ PTs on their ST skills preferences, and this study aims to address this gap. A total of 99 engineering managers and 104 systems engineers provided the data to test four hypotheses posed in this study. The results show that the PTs of systems engineers and engineering managers have a positive impact on their level of ST skills preferences and that the education level, the current occupation type, and the managerial experience of the systems engineers and engineering managers moderate the main relationship in the study.

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BAGIYAN, A. y A. VARTANOV. SYSTEMS ACQUISITION IN MULTILINGUAL EDUCATION: THE CASE OF AXIOLOGICALLY CHARGED LEXIS. Science and Innovation Center Publishing House, 2021. http://dx.doi.org/10.12731/2077-1770-2021-13-4-3-48-61.

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The process of mastering, systematizing and automatizing systems language skills occupies a key place in the theory and practice of teaching foreign languages and cultures. Following the main trends of modern applied linguistics in the field of multilingual research, we hypothesize the advisability of using the lexical approach in mastering the entire complex of systems skills (grammar, vocabulary, phonology, functions, discourse) in students receiving multilingual education at higher educational institutions. In order to theoretically substantiate the hypothesis, the authors carry out structural, semantic, and phonological analysis of the main lexical units (collocations). After this, linguodidactic analysis of students’ hypothetical problems and, as a result, problems related to the teaching of relevant linguistic and axiological features is carried out. At the final stage of the paper, a list of possible outcomes from the indicated linguistic and methodological problematic situations is given. This article is the first in the cycle of linguodidactic studies of the features of learning and teaching systems language skills in a multilingual educational space.

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Wozniakowska, P., D. W. Eaton, C. Deblonde, A. Mort y O. H. Ardakani. Identification of regional structural corridors in the Montney play using trend surface analysis combined with geophysical imaging. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/329795.

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Induced (anthropogenic) earthquakes are caused by reactivation of pre-existing faults due to human activities, including hydraulic fracturing and saltwater disposal. The Montney play, the pre-eminent shale gas play in Canada, contains localized regions with relatively high geological susceptibility to induced seismicity. Identification of potential seismogenic structures is hindered because published fault maps in the Montney play are often focused on small areas, leading to inconsistencies when these are compiled across the region. We have developed a regional framework based on structural corridors: complex, multi-strand faults systems. A three-step structural interpretation workflow was used, including seismic and structural interpretation along with trend surface analysis (TSA). This approach was used to identify 34 structural corridors in NE BC and NW Alberta.

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Nagahi, Morteza, Niamat Ullah Ibne Hossain, Safae El Amrani, Raed Jaradat, Laya Khademibami, Simon Goerger y Randy Buchanan. Investigating the influence of demographics and personality types on practitioners' level of systems thinking skills. Engineer Research and Development Center (U.S.), marzo de 2022. http://dx.doi.org/10.21079/11681/43622.

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Although the application of systems thinking (ST) has become essential for practitioners when dealing with turbulent and complex environments, there are limited studies available in the current literature that investigate how the ST skills of practitioners vary with regard to demographic factors and personality types (PTs). To address this gap, this article uses a structural equation modeling approach to explore the relationship be-tween practitioners’ ST skills, PT, and a set of demographic factors. The demographic factors included in the study are education level, the field of the highest degree, organizational ownership structure, job experience, and current occupation type. A total of 99 engineering managers, 104 systems engineers (SEs), and 55 practitioners with other occupations participated in this article. Results showed that the education level, the field of the highest degree, PT, organizational ownership structure, and current job experience of practitioners influenced their level of ST skills. Additionally, the current occupation type of practitioners partially affects their level of ST skills. An in-depth analysis was also conducted using multiple group analysis to show how seven ST skills of the practitioners vary across their level of education. Taken together, the findings of the study suggest that PT and a set of demographic factors influence the overall ST skill of the practitioners.

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Montville, Thomas J. y Roni Shapira. Molecular Engineering of Pediocin A to Establish Structure/Function Relationships for Mechanistic Control of Foodborne Pathogens. United States Department of Agriculture, agosto de 1993. http://dx.doi.org/10.32747/1993.7568088.bard.

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This project relates the structure of the bacteriocin molecule (which is genetically determined) to its antimicrobial function. We have sequenced the 19,542 bp pediocin plasmid pMD136 and developed a genetic transfer system for pediococci. The pediocin A operon is complex, containing putative structural, immunity, processing, and transport genes. The deduced sequence of the pediocin A molecule contains 44 amino acids and has a predicted PI of 9.45. Mechanistic studies compared the interaction of pediocin PA-1 and nisin with Listeria monocytgenes cells and model lipid systems. While significant nisin-induced intracellular ATP depletion is caused by efflux, pediocin-induced depletion is caused exclusively by hydrolysis. Liposomes derived from L. monocytogenes phospholipids were used to study the physical chemistry of pediocin and nisin interactions with lipids. Their different pH optima are the results of different specific ionizable amino acids. We generated a predicted 3-D structural model for pediocin PA-1 and used a variety of mutant pediocins to demonstrate that the "positive patch" at residues 11 and 12 (and not the YGNGV consensus sequence) is responsible for the binding step of pediocin action. This structure/function understanding gained here provides necessary prerequisites to the more efficacious use of bacteriocins to control foodborne pathogens.

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Chen, Yona, Jeffrey Buyer y Yitzhak Hadar. Microbial Activity in the Rhizosphere in Relation to the Iron Nutrition of Plants. United States Department of Agriculture, octubre de 1993. http://dx.doi.org/10.32747/1993.7613020.bard.

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Iron is the fourth most abundant element in the soil, but since it forms insoluble hydroxides at neutral and basic pH, it often falls short of meeting the basic requirements of plants and microorganisms. Most aerobic and facultative aerobic microorganisms possess a high-affinity Fe transport system in which siderophores are excreted and the consequent Fe complex is taken up via a cognate specific receptor and a transport pathway. The role of the siderophore in Fe uptake by plants and microorganisms was the focus of this study. In this research Rhizopus arrhizus was found to produce a novel siderophore named Rhizoferrin when grown under Fe deficiency. This compound was purified and its chemical structure was elucidated. Fe-Rhizoferrin was found to alleviate Fe deficiency when applied to several plants grown in nutrient solutions. It was concluded that Fe-Rhizoferrin is the most efficient Fe source for plants when compared with other among microbial siderophores known to date and its activity equals that of the most efficient synthetic commercial iron fertilizer-Fe EDDHA. Siderophores produced by several rhizosphere organisms including Rhizopus Pseudomonas were purified. Monoclonal antibodies were produced and used to develop a method for detection of the siderophores produced by plant-growth-promoting microorganisms in barley rhizosphere. The presence of an Fe-ferrichrome uptake in fluorescent Pseudomonas spp. was demonstrated, and its structural requirements were mapped in P. putida with the help of biomimetic ferrichrome analogs. Using competition experiments, it was shown that FOB, Cop B and FC share at least one common determinant in their uptake pathway. Since FC analogs did not affect FOB or Cop-mediated 55Fe uptake, it could be concluded that these siderophores make use of a different receptor(s) than FC. Therefore, recognition of Cop, FOB and FC proceeds through different receptors having different structural requirements. On the other hand, the phytosiderophores mugineic acid (MA and DMA), were utilized indirectly via ligand exchange by P. putida. Receptors from different biological systems seem to differ in their structural requirements for siderophore recognition and uptake. The design of genus- or species-specific drugs, probes or chemicals, along with an understanding of plant-microbe and microbe-microbe relationships as well as developing methods to detect siderophores using monoclonal antibodies are useful for manipulating the composition of the rhizosphere microbial population for better plant growth, Fe-nutrition and protection from diseases.

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