scholarly journals Innovative Acoustic Treatments of Nacelle Intakes Based on Optimised Metamaterials

Aerospace ◽  
2021 ◽  
Vol 8 (10) ◽  
pp. 296
Author(s):  
Giorgio Palma ◽  
Lorenzo Burghignoli ◽  
Francesco Centracchio ◽  
Umberto Iemma
Keyword(s):  
Numerical Results ◽  
Design Parameters ◽  
Axially Symmetric ◽  
Continuous Development ◽  
Azimuthal Mode ◽  
Phase Gradient ◽  
Blade Passage ◽  
Noise Radiation ◽  
Simulation Based ◽  
Potential Benefits

Modern turbofans with high bypass ratios, low blade passage frequencies and short nacelles require continuous development of acoustic linings to achieve the noise reductions expected by the international aviation authorities. Metamaterials and metafluids have been recently proposed as promising technologies for designing innovative acoustic treatments dedicated to reducing aeronautic turbofan noise emissions. In this work, a phase-gradient metasurface treatment is investigated as a way to tackle the noise radiation from an axially symmetric nacelle. This paper aims to study the potential benefits of the mentioned technology, and is not an attempt to design a complete new liner or nacelle. The metasurface is modelled through an equivalent metafluid, and a simulation-based optimisation is used in defining the design parameters. The tonal contribution of the blade passage frequency is considered, and the numerical results with the metafluid optimised on one azimuthal mode at a time show a significant effect in terms of acoustic levels and directivity over an arc of virtual receivers.

Feasibility Study of Designing a Three Legged Walking Robot: Tribot

1991 ◽  
Author(s):  
Yueh-Jaw Lin ◽  
Aaron Tegland
Keyword(s):  
Feasibility Study ◽  
Legged Robots ◽  
Walking Robots ◽  
Design Parameters ◽  
Optimized Design ◽  
Motion Simulation ◽  
Walking Robot ◽  
Design Considerations ◽  
Simulation Based ◽  
Weight Distributions

Abstract In recent years, walking robot research has become an important robotic research topic because walking robots possess mobility, as oppose to stationary robots. However, current walking robot research has only concentrated on even numbered legged robots. Walking robots with odd numbered legs are still lack of attention. This paper presents the study on an odd numbered legged (three-legged) walking robot — Tribot. The feasibility of three-legged walking is first investigated using computer simulation based on a scaled down tribot model. The computer display of motion simulation shows that a walking robot with three legs is feasible with a periodic gait. During the course of the feasibility study, the general design of the three-legged robot is also analyzed for various weights, weight distributions, and link lengths. In addition, the optimized design parameters and limitations are found for certain knee arrangements. These design considerations and feasibility study using computer display can serve as a general guideline for designing odd numbered legged robots.

scholarly journals A simulation-based approach to improve decoded neurofeedback performance

2018 ◽  
Author(s):  
Ethan Oblak ◽  
James Sulzer ◽  
Jarrod Lewis-Peacock
Keyword(s):  
Real Time ◽  
Brain Activity ◽  
Processing Parameters ◽  
Orientation Tuning ◽  
Design Parameters ◽  
Visual Orientation ◽  
Brain Functions ◽  
Simulation Based ◽  
Using Data ◽  
The Right

AbstractThe neural correlates of specific brain functions such as visual orientation tuning and individual finger movements can be revealed using multivoxel pattern analysis (MVPA) of fMRI data. Neurofeedback based on these distributed patterns of brain activity presents a unique ability for precise neuromodulation. Recent applications of this technique, known as decoded neurofeedback, have manipulated fear conditioning, visual perception, confidence judgements and facial preference. However, there has yet to be an empirical justification of the timing and data processing parameters of these experiments. Suboptimal parameter settings could impact the efficacy of neurofeedback learning and contribute to the ‘non-responder’ effect. The goal of this study was to investigate how design parameters of decoded neurofeedback experiments affect decoding accuracy and neurofeedback performance. Subjects participated in three fMRI sessions: two ‘finger localizer’ sessions to identify the fMRI patterns associated with each of the four fingers of the right hand, and one ‘finger finding’ neurofeedback session to assess neurofeedback performance. Using only the localizer data, we show that real-time decoding can be degraded by poor experiment timing or ROI selection. To set key parameters for the neurofeedback session, we used offline simulations of decoded neurofeedback using data from the localizer sessions to predict neurofeedback performance. We show that these predictions align with real neurofeedback performance at the group level and can also explain individual differences in neurofeedback success. Overall, this work demonstrates the usefulness of offline simulation to improve the success of real-time decoded neurofeedback experiments.

scholarly journals Efficient and flexible simulation-based sample size determination for clinical trials with multiple design parameters

2020 ◽  
pp. 096228022097579
Author(s):  
Duncan T Wilson ◽  
Richard Hooper ◽  
Julia Brown ◽  
Amanda J Farrin ◽  
Rebecca EA Walwyn
Keyword(s):  
Sample Size ◽  
Computer Experiments ◽  
Small Sample ◽  
Sample Size Determination ◽  
Design Parameters ◽  
Size Determination ◽  
Parametric Regression ◽  
Software Packages ◽  
Primary Endpoints ◽  
Simulation Based

Simulation offers a simple and flexible way to estimate the power of a clinical trial when analytic formulae are not available. The computational burden of using simulation has, however, restricted its application to only the simplest of sample size determination problems, often minimising a single parameter (the overall sample size) subject to power being above a target level. We describe a general framework for solving simulation-based sample size determination problems with several design parameters over which to optimise and several conflicting criteria to be minimised. The method is based on an established global optimisation algorithm widely used in the design and analysis of computer experiments, using a non-parametric regression model as an approximation of the true underlying power function. The method is flexible, can be used for almost any problem for which power can be estimated using simulation, and can be implemented using existing statistical software packages. We illustrate its application to a sample size determination problem involving complex clustering structures, two primary endpoints and small sample considerations.

Characteristics of a Self-Lubricated Stepped Thrust Pad of Infinite Width With Compressible Lubricant

1959 ◽  
Vol 81 (2) ◽  
pp. 135-145 ◽  
Author(s):  
Kikuo C. Kochi
Keyword(s):  
Optimum Design ◽  
Practical Interest ◽  
Numerical Data ◽  
Numerical Results ◽  
Design Parameters ◽  
Analytic Expressions ◽  
Thrust Pad ◽  
Compressible Lubricant

Harrison’s equation for the pressure in a gas-lubricated bearing of infinite width is solved for a thrust pad with stepped configuration. Analytic expressions for the pressure and load are developed. Numerical results are presented graphically. The analytic expressions together with the numerical data permit most of those characteristics of the stepped pad of practical interest to be completely determinable. Determination of optimum design parameters is given by a pair of graphs.

Friction-Induced Dynamics of Axially-Moving Media in Contact With an Actively-Positioned Surface

2008 ◽  
Author(s):  
V. Kartik ◽  
Evangelos Eleftheriou
Keyword(s):  
Data Storage ◽  
Surface Friction ◽  
Design Parameters ◽  
Moving Medium ◽  
Critical Design ◽  
Flexible Material ◽  
Potential Benefits ◽  
Axially Moving ◽  
The Stability ◽  
Moving Media

The dynamics of an axially-moving flexible medium are examined in the context of an application where the medium is partially supported by a frictional surface, that actively-orients itself relative to the direction of transport. The stability and motion of the medium are of interest in a magnetic tape data storage application where the orientation of a sensing surface is continuously altered in order to ‘follow’ the medium’s motion. Moving media that are in contact with such guiding surfaces experience friction excitations induced by the relative motion in addition to what is observed with a stationary guiding surface. Friction-induced bending moments, as well as tension fluctuation beyond the permissible limits for the flexible material can erode the potential benefits of such active positioning. This paper describes some of these dynamic phenomena using the simplified example of a planar guiding surface whose orientation is dynamically altered relative to the moving medium. A physical model for the friction-induced excitation of the moving medium is developed, and the dynamics are analyzed for their effect on critical design parameters such as the achievable bandwidth of the active control algorithm, as well as with respect to constraints on the geometry and positioning of the guiding surface.

Best Structural Theories for Free Vibrations of Sandwich Composites via Machine Learning

2019 ◽  
Author(s):  
Marco Petrolo ◽  
Erasmo Carrera
Keyword(s):  
Degrees Of Freedom ◽  
Computational Cost ◽  
Free Vibrations ◽  
Numerical Results ◽  
Design Parameters ◽  
Sandwich Composites ◽  
Accuracy Requirement ◽  
Minimum Number ◽  
Carrera Unified Formulation ◽  
Structural Theories

Abstract This work presents a novel methodology for the development of refined structural theories for the modal analysis of sandwich composites. Such a methodology combines three well-established techniques, namely, the Carrera Unified Formulation (CUF), the Axiomatic/Asymptotic Method (AAM), and Artificial Neural Networks (NN). CUF generates structural theories and finite element arrays hierarchically. CUF provides the training set for the NN in which the structural theories are inputs and the natural frequencies targets. AAM evaluates the influence of each generalized displacement variable, and NN provides Best Theory Diagrams (BTD), i.e., curves providing the minimum number of nodal degrees of freedom required to satisfy a given accuracy requirement. The aim is to build BTD with far less computational cost than in previous works. The numerical results consider sandwich spherical shells with soft cores and different features, such as thickness and curvature to investigate their influence on the choice of generalized displacement variables. The numerical results show the importance of third-order generalized displacement variables and prove that the present framework can be of interest to evaluate the performance of any structural theory as typical design parameters change and provide guidelines to the analysts on the most convenient computational model to save computational cost without accuracy penalties.

Simulation-Based Evaluation of Advanced Traveler Information Systems

2005 ◽  
Vol 1910 (1) ◽  
pp. 90-98 ◽  
Author(s):  
Ramachandran Balakrishna ◽  
Haris N. Koutsopoulos ◽  
Moshe Ben-Akiva ◽  
Bruno M. Fernandez Ruiz ◽  
Manish Mehta
Keyword(s):  
Information Systems ◽  
Dynamic Network ◽  
Evaluation Methodology ◽  
Design Parameters ◽  
Route Guidance ◽  
Test Bed ◽  
Advanced Traveler Information Systems ◽  
Traveler Information ◽  
Traveler Information Systems ◽  
Simulation Based

Traveler information has the potential to reduce travel times and improve their reliability. Studies have verified that driver overreaction from the dissemination of information can be eliminated through prediction-based route guidance that uses short-term forecasts of network state. Critical off-line tests of advanced dynamic traffic assignment–based prediction systems have been limited, since the system being evaluated has also been used as the test bed. This paper outlines a detailed simulation-based laboratory for the objective and independent evaluation of advanced traveler information systems, a laboratory with the flexibility to analyze the impacts of various design parameters and modeling errors on the quality of the generated guidance. MITSIMLab, a system for the evaluation of advanced traffic management systems, is integrated with Dynamic Network Assignment for the Management of Information to Travelers (DynaMIT), a simulation-based decision support system designed to generate prediction-based route guidance. Evaluation criteria and requirements for the closed-loop integration of MITSIMLab and DynaMIT are discussed. Detailed case studies demonstrating the evaluation methodology and sensitivity of DynaMIT's guidance are presented.

Modeling Strategic Behavior in Human-Automation Interaction: Why an "Aid" Can (and Should) Go Unused

1993 ◽  
Vol 35 (2) ◽  
pp. 221-242 ◽  
Author(s):  
Alex Kirlik
Keyword(s):  
Sensitivity Analysis ◽  
System Performance ◽  
Strategic Behavior ◽  
Task Demands ◽  
Design Parameters ◽  
Task Context ◽  
Effective Operator ◽  
Effective Strategies ◽  
Potential Benefits ◽  
Intelligent Assistant

Task-offload aids (e.g., an autopilot, an "intelligent" assistant) can be selectively engaged by the human operator to dynamically delegate tasks to automation. Introducing such aids eliminates some task demands but creates new ones associated with programming, engaging, and disengaging the aiding device via an interface. The burdens associated with managing automation can sometimes outweigh the potential benefits of automation to improved system performance. Aid design parameters and features of the overall multitask context combine to determine whether or not a task-offload aid will effectively support the operator. A modeling and sensitivity analysis approach is presented that identifies effective strategies for human-automation interaction as a function of three task-context parameters and three aid design parameters. The analysis and modeling approaches provide resources for predicting how a well-adapted operator will use a given task-offload aid, and for specifying aid design features that ensure that automation will provide effective operator support in a multitask environment.

Mechanism Simulation Based on ADAMS and Structure Optimization for Automobile Punching Parts On-Line Detector

2011 ◽  
Vol 211-212 ◽  
pp. 619-623
Author(s):  
Xi Xin Rao ◽  
Kang He ◽  
He Sheng Liu
Keyword(s):  
Objective Function ◽  
Dynamic Performance ◽  
Mathematic Model ◽  
Design Parameters ◽  
Work Piece ◽  
Simulation And Optimization ◽  
Design Variables ◽  
Simulation Based ◽  
On Line ◽  
Line Detector

Camera Device is crucial components of Automobile punching parts on-line detector and Its dynamic characteristics has a critical influence on the accuracy of Automobile punching parts on-line detector. To reduce the relative acceleration of Camera Device to the measured part, biaxial body of Automobile Punching Parts On-line Detector was optimized. On the basis of analyzing mechanism, simplifying the prototype, determining the design variables and the objective function and the constraint condition, this paper puts forward the parameter optimization mathematic model with the minimum of the acceleration of Camera Device relative to the point on the measured work piece as objective function and completes mechanism simulation and optimization by the ADAMS software. The results show that some design parameters gets more reasonable and dynamic performance of Automobile punching parts on-line detector is better.

Optimal Design of Underwater Shells With Active Stiffeners

2001 ◽  
Author(s):  
W. Akl ◽  
M. Ruzzene ◽  
A. Baz
Keyword(s):  
Optimal Design ◽  
Low Cost ◽  
Element Model ◽  
Design Parameters ◽  
Optimization Approach ◽  
Noise Radiation ◽  
Stiffened Shells ◽  
Shell Vibration ◽  
The Cost ◽  
Controllability And Observability

Abstract The optimal design parameters of fluid-loaded shells, provided with actively controlled stiffeners, are determined using a rational multi-criteria optimization approach. The adopted approach aims at simultaneously minimizing the shell vibration, associated sound radiation, weight of the stiffening rings, the control energy, and the cost of the shell/stiffeners assembly while maximizing the controllability and observability indices. A finite element model is presented to predict the vibration and noise radiation from cylindrical shells, with active stiffeners, into the surrounding fluid domain. The production cost as well as the life cycle and maintenance costs of the stiffened shells are computed using the Parametric Review of Information for Costing and Evaluation (PRICE) model. A Pareto/min-max multi-criteria optimization approach is then utilized to select the optimal locations and dimensions of the active stiffeners. Numerical examples are presented to compare the vibration and noise radiation characteristics of me optimally designed/controlled stiffened shells with the corresponding characteristics of plain un-stiffened and uncontrolled shells. The obtained results emphasize me importance of the adopted multi-criteria optimization approach in the design of quiet, low weight and low cost underwater shells which are suitable for various critical applications.

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