4,057 research outputs found

    Quantifying Spatiotemporal Chaos in Rayleigh-B\'enard Convection

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    Using large-scale parallel numerical simulations we explore spatiotemporal chaos in Rayleigh-B\'enard convection in a cylindrical domain with experimentally relevant boundary conditions. We use the variation of the spectrum of Lyapunov exponents and the leading order Lyapunov vector with system parameters to quantify states of high-dimensional chaos in fluid convection. We explore the relationship between the time dynamics of the spectrum of Lyapunov exponents and the pattern dynamics. For chaotic dynamics we find that all of the Lyapunov exponents are positively correlated with the leading order Lyapunov exponent and we quantify the details of their response to the dynamics of defects. The leading order Lyapunov vector is used to identify topological features of the fluid patterns that contribute significantly to the chaotic dynamics. Our results show a transition from boundary dominated dynamics to bulk dominated dynamics as the system size is increased. The spectrum of Lyapunov exponents is used to compute the variation of the fractal dimension with system parameters to quantify how the underlying high-dimensional strange attractor accommodates a range of different chaotic dynamics

    A review sustainable development strategies sturgeon in the Caspian Sea

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    The project of fishery regional development studies in North Alborz was conducted to establish regional development program in North Alborz Area (Provinces of Gilan, Mazandaran & Golestan). The research had several phases and was done on a survey and library-based study. Using SWOT analysis method to analyze current situation of sturgeon fisheries and aquaculture is investigated and internal and external environmental factors of shilat activities are considered. We used Quantitative Strategic Planning Matrix (QSPM) for priority setting of strategies. In current paper as a part of project’s outcomes, all activities of fisheries and aquaculture environment were considered, then, the strengths, weaknesses, opportunities and treats of internal and external environment are analyzed. At the end, a considerable number of tables and matrixes were prepared and four types of strategies including 20 strategies for sturgeon aquaculture and 17 strategies for sturgeon fisheries were carried out

    Broad Faculty Participation in Course-Level Evaluation of Student Outcomes Supporting Continuous Improvement of an Undergraduate Engineering Program

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    This paper describes a strategy of requiring all undergraduate engineering courses provide some quantitative assessment of student outcomes (SO) which is used in the overall continuous improvement process for the program. A wide range of learning activities are documented in the process and with more faculty participation being engaged in program accreditation. Except for senior design, courses, all courses have no more than two SO to limit the assessment workload on faculty and increase the quality of the data from each course. Pre-semester workshops help faculty plan learning activities so data collection is manageable and not concentrated at the end of the semester. Best practice activities are shared to encourage faculty to think beyond the use of the final exam or design project to assess SOs in their courses

    PID Controller Tuning Using Bode's Integrals

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    A new method for PID controller tuning based on Bode's integrals is proposed. It is shown that the derivatives of amplitude and phase of a plant model with respect to frequency can be approximated by Bode's integrals without any model of the plant. This information can be used to design a PID controller for slope adjustment of the Nyquist diagram and improve the closed-loop performance. Besides, the derivatives can be also employed to estimate the gradient and the Hessian of a frequency criterion in an iterative PID controller tuning method. The frequency criterion is defined as the sum of squared errors between the desired and measured gain margin, phase margin and crossover frequency. The method benefits from specific feedback relay tests to determine the gain margin, the phase margin and the crossover frequency of the closed-loop system. Simulation examples and experimental results illustrate the effectiveness and the simplicity of the proposed method to design and tune the PID controllers

    Correlation-Based Tuning of a Restricted-Complexity Controller for an Active Suspension System

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    A correlation-based controller tuning method is proposed for the ``Design and optimization of restricted-complexity controllers'' benchmark problem. The approach originally proposed for model following is extended to solve the disturbance rejection problem. The idea is to tune the controller parameters such that the closed-loop output be uncorrelated with the disturbance signal. Since perfect decorrelation between the closed-loop output and the disturbance signal is not attainable in the restricted-complexity controller design, the cross correlation between these two signals is minimized iteratively using the stochastic approximation method. Since control specifications can normally be expressed in terms of constraints on the sensitivity functions, a frequency-domain analysis of the criterion is performed. Straightforward implementation of the proposed approach on the active suspension system of the Automatic Control Laboratory of Grenoble (LAG) provides a 2nd-order controller that meets the control specifications very well

    Applying bim to built heritage with complex shapes: The ice house of filarete's ospedale maggiore in milan, Italy

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    This paper presents the development of a BIM model for a stratified historic structure characterized by a complex geometry: Filarete's Ospedale Maggiore ice house, one of the few remaining historic ice houses in Milan (Fig. 1). Filarete, a well-known Renaissance architect and theorist, planned the hospital in the 15th century, but the ice house was built two centuries later with a double-storey irregular octagonal brick structure, half under and half above ground, that enclosed another circular structure called the ice room. The purpose of the double-walled structure was to store ice in the middle and store and preserve perishable food and medicine at the outer side of the ice room. During World War II, major portions of the hospital and the above-ground section of the ice house was bombed and heavily damaged. Later, in 1962, the hospital was restored and rehabilitated into a university, with the plan to conceal the ice house's remaining structure in the courtyard, which ultimately was excavated and incorporated into a new library for the university. A team of engineers, architects, and students from Politecnico di Milano and Carleton University conducted two heritage recording surveys in 2015 and 2016 to fully document the existing condition of the ice house, resulting in an inclusive laser scanner and photogrammetric point cloud dataset. The point cloud data was consolidated and imported into two leading parametric modelling software, Autodesk Revit© and Graphisoft ArchiCAD©, with the goal to develop two BIMs in parallel in order to study and compare the software BIM workflow, parametric capabilities, attributes to capture the complex geometry with high accuracy, and the duration for parametric modelling. The comparison study of the two software revealed their workflow limitations, leading to integration of the BIM generative process with other pure modelling software such as Rhinoceros©. The integrative BIM process led to the production of a comprehensive BIM model that documented related historic data and the existing physical state of the ice house, to be used as a baseline for preventive maintenance, monitoring, and future conservation projects
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