Surrogate modeling of a 3D scramjet-powered hypersonic vehicle based on screening method IFFD

2016 ◽  
Vol 231 (2) ◽  
pp. 265-278 ◽  
Author(s):  
Chen Boyi ◽  
Liu Yanbin ◽  
Shen Haidong ◽  
Lu Yuping
Keyword(s):  
Vehicle Dynamics ◽  
Screening Method ◽  
Kriging Model ◽  
Surrogate Models ◽  
Hypersonic Vehicle ◽  
Fractional Factorial ◽  
Gap Metric ◽  
Alternative Approach ◽  
Pitch Moment ◽  
The Difference

The emphasis of this paper lies in the development of an efficient approach to reproduce the behaviors of the scramjet-powered hypersonic system with high fidelity. The modeling of the dual-mode scramjet powered hypersonic vehicle dynamics with shock interaction, Ram-to-Scram transition, and finite rate chemistry reaction is firstly introduced. The structure of surrogate model is identified with the implement of iterative fractional factorial design (IFFD). In order to declare the reliability of the surrogate models, ν-gap metric is applied to distinguish the difference among these surrogate models in terms of closed-loop performance. The results show that the influence of Mach number on the aerodynamics should not be overlooked, and the effect of propulsion system to the aerodynamic pitch moment is dramatic. Further, the partial Kriging model appears to have the closest plants throughout the flight envelope compared with the full Kriging model and polynomials model. Nevertheless, considering the briefness of analytical expression, the polynomials model may be an alternative approach for design-oriented modeling.

Kriging Modeling for Engine Mount Optimization in Motorcycles

2009 ◽  
Author(s):  
Sudhir Kaul ◽  
Anoop K. Dhingra
Keyword(s):  
Correlation Function ◽  
Theoretical Model ◽  
Optimization Problem ◽  
Design Space ◽  
Substantial Reduction ◽  
Kriging Model ◽  
Surrogate Models ◽  
Fractional Factorial ◽  
Engine Mount ◽  
Selection Of

This paper addresses two critical aspects associated with the successful use of a Kriging model for solving the engine mount optimization problem. The two aspects are the selection of an appropriate correlation function and the use of a suitable governing design for sampling within the design space. The selection of a correlation function is critical in building a Kriging model since the function should accurately represent the behavior of the response over the entire design space. Whereas the Gaussian correlation function is most commonly used for building Kriging models, it is generally suitable for only those processes or systems which have a relatively smooth response within the entire design space. The correlation functions that have been evaluated in this paper for building the Kriging models for solving the engine mount optimization problem are as follows: Exponential, Linear Spline, Matern’s 3/2, Matern’s 5/2 and Gaussian. Three types of experimental designs – Fractional Factorial, D-optimal and Latin Hypercube, have been used to select the sampling points for making simulation runs in order to build the Kriging models. A theoretical model that represents the dynamics of the engine mount system in a motorcycle application has been used to build all the surrogate models. The Kriging models are then used to solve the engine mount optimization problem for enhanced vibration isolation with mount stiffness, mount orientation and mount location as the design variables. The optimization results of the Kriging models are compared to the results of the theoretical model. It is found that the D-optimal design in conjunction with Matern’s 3/2 correlation function provides the best results. This can be attributed to the high irregularity of the response function in the design space, especially due to the influence of orientation variables. The use of the surrogate Kriging model simplifies the governing model and leads to a substantial reduction in computational effort for solving the optimization problem. Based on the results, it can be concluded that the Kriging modeling technique can be successfully used to build surrogate models for the engine mount problem for design iterations as well as for design optimization if the correlation function and the governing design are judiciously chosen.

scholarly journals OPTIONS WRITTEN ON STOCKS WITH KNOWN DIVIDENDS

2004 ◽  
Vol 07 (07) ◽  
pp. 901-907
Author(s):  
ERIK EKSTRÖM ◽  
JOHAN TYSK
Keyword(s):  
Stock Price ◽  
Option Price ◽  
Option Prices ◽  
Strike Price ◽  
Call Options ◽  
Alternative Approach ◽  
Black Scholes ◽  
Market Practice ◽  
The Difference ◽  
Risk Free Rate

There are two common methods for pricing European call options on a stock with known dividends. The market practice is to use the Black–Scholes formula with the stock price reduced by the present value of the dividends. An alternative approach is to increase the strike price with the dividends compounded to expiry at the risk-free rate. These methods correspond to different stock price models and thus in general give different option prices. In the present paper we generalize these methods to time- and level-dependent volatilities and to arbitrary contract functions. We show, for convex contract functions and under very general conditions on the volatility, that the method which is market practice gives the lower option price. For call options and some other common contracts we find bounds for the difference between the two prices in the case of constant volatility.

Stochastic Bayesian optimization for predicting borderline knock

2021 ◽  
pp. 146808742110652
Author(s):  
Jian Tang ◽  
Anuj Pal ◽  
Wen Dai ◽  
Chad Archer ◽  
James Yi ◽  
...  
Keyword(s):  
Fuel Economy ◽  
Learning Algorithm ◽  
Feedforward Control ◽  
Model Development ◽  
Kriging Model ◽  
Optimization Method ◽  
Surrogate Models ◽  
Bayesian Optimization ◽  
Control Parameters ◽  
Operation Conditions

Engine knock is an undesirable combustion that could damage the engine mechanically. On the other hand, it is often desired to operate the engine close to its borderline knock limit to optimize combustion efficiency. Traditionally, borderline knock limit is detected by sweeping tests of related control parameters for the worst knock, which is expensive and time consuming, and also, the detected borderline knock limit is often used as a feedforward control without considering its stochastic characteristics without compensating current engine operational condition and type of fuel used. In this paper, stochastic Bayesian optimization method is used to obtain a tradeoff between stochastic knock intensity and fuel economy. The log-nominal distribution of knock intensity signal is converted to Gaussian one using a proposed map to satisfy the assumption for Kriging model development. Both deterministic and stochastic Kriging surrogate models are developed based on test data using the Bayesian iterative optimization process. This study focuses on optimizing two competing objectives, knock intensity and indicated specific fuel consumption using two control parameters: spark and intake valve timings. Test results at two different operation conditions show that the proposed learning algorithm not only reduces required time and cost for predicting knock borderline but also provides control parameters, based on trained surrogate models and the corresponding Pareto front, with the best fuel economy possible.

scholarly journals ASAMS: An Adaptive Sequential Sampling and Automatic Model Selection for Artificial Intelligence Surrogate Modeling

Sensors ◽  
2020 ◽  
Vol 20 (18) ◽  
pp. 5332
Author(s):  
Carlos A. Duchanoy ◽  
Hiram Calvo ◽  
Marco A. Moreno-Armendáriz
Keyword(s):  
Artificial Intelligence ◽  
Model Selection ◽  
Adaptive Sampling ◽  
Search Algorithm ◽  
Sequential Sampling ◽  
Surrogate Modeling ◽  
Kriging Model ◽  
Surrogate Models ◽  
Physical Experiments ◽  
Leave One Out

Surrogate Modeling (SM) is often used to reduce the computational burden of time-consuming system simulations. However, continuous advances in Artificial Intelligence (AI) and the spread of embedded sensors have led to the creation of Digital Twins (DT), Design Mining (DM), and Soft Sensors (SS). These methodologies represent a new challenge for the generation of surrogate models since they require the implementation of elaborated artificial intelligence algorithms and minimize the number of physical experiments measured. To reduce the assessment of a physical system, several existing adaptive sequential sampling methodologies have been developed; however, they are limited in most part to the Kriging models and Kriging-model-based Monte Carlo Simulation. In this paper, we integrate a distinct adaptive sampling methodology to an automated machine learning methodology (AutoML) to help in the process of model selection while minimizing the system evaluation and maximizing the system performance for surrogate models based on artificial intelligence algorithms. In each iteration, this framework uses a grid search algorithm to determine the best candidate models and perform a leave-one-out cross-validation to calculate the performance of each sampled point. A Voronoi diagram is applied to partition the sampling region into some local cells, and the Voronoi vertexes are considered as new candidate points. The performance of the sample points is used to estimate the accuracy of the model for a set of candidate points to select those that will improve more the model’s accuracy. Then, the number of candidate models is reduced. Finally, the performance of the framework is tested using two examples to demonstrate the applicability of the proposed method.

scholarly journals Influence of Potato Crisps Processing Parameters on Acrylamide Formation and Bioaccesibility

Molecules ◽  
2019 ◽  
Vol 24 (21) ◽  
pp. 3827 ◽  
Author(s):  
Martinez ◽  
Rodriguez ◽  
Mondragon ◽  
Lorenzo ◽  
Santos
Keyword(s):  
Fractional Factorial Design ◽  
Processing Parameters ◽  
Storage Conditions ◽  
Fractional Factorial ◽  
Slice Thickness ◽  
Frying Time ◽  
Intestinal Phase ◽  
Textural Parameters ◽  
Effects Of Temperature ◽  
The Difference

A fractional factorial design was used to evaluate the effects of temperature, frying time, blanching treatment and the thickness of potato slices on acrylamide content in crisps. The design was used on freshly harvested and four-month stored potatoes. The critical factors found were temperature and frying time, and the interaction between blanching treatment and slice thickness. Once frying conditions were selected, an acrylamide content of 725 and 1030 mg kg−1 was found for non-stored and 4-month stored tubers, with adequate textural parameters in both cases. The difference in concentration is related to storage conditions, which must be controlled in order to control acrylamide levels. Bioaccesibility studies demonstrated that acrylamide concentration remained at 70%, and reductions took place mainly at the intestinal phase, as a result of reaction with nucleophilic compounds.

scholarly journals An alternative approach to avoid overfitting for surrogate models

2011 ◽  
Author(s):  
Huu Minh Nguyen ◽  
Ivo Couckuyt ◽  
Luc Knockaert ◽  
Tom Dhaene ◽  
Dirk Gorissen ◽  
...  
Keyword(s):  
Surrogate Models ◽  
Alternative Approach

Rawls, Brandt, and the Definition of Rational Desires

1978 ◽  
Vol 8 (2) ◽  
pp. 329-340 ◽  
Author(s):  
Robert K. Shope
Keyword(s):  
John Rawls ◽  
Social Scientists ◽  
Subjunctive Conditionals ◽  
Alternative Approach ◽  
The Difference ◽  
Definition Of ◽  
Manifest Rationality

Philosophers, psychiatrists, and social scientists would welcome clarification of the distinction between rational and irrational desires. It may be proper to say that rational desires are those which manifest rationality (or which at least do not conflict with its manifestations). But since this seems a rather unilluminating characterization, philosophers sometimes offer definitions of what constitute such manifestations of rationality. I shall consider definitions provided by John Rawls and Richard Brandt. Their definitions are unsatisfactory mainly because they include subjunctive conditionals. An alternative approach, which avoids conditionals, is attractive. But it encounters so many additional problems that I shall conclude that we are not now in a position to define rationality in this area and must treat it as a state or disposition which to date has only been partially characterized. Thus, if we want a definition of the difference between rational and irrational desires, we must at present settle for the rather unexciting one mentioned above.

Shape Optimization of Turbomachinery Blade Using Multiple Surrogate Models

2006 ◽  
Author(s):  
Abdus Samad ◽  
Kwang-Yong Kim ◽  
Tushar Goel ◽  
Raphael T. Haftka ◽  
Wei Shyy
Keyword(s):  
Shape Optimization ◽  
Cost Benefit Analysis ◽  
Weighted Average ◽  
Cost Benefit ◽  
Network Models ◽  
Surrogate Models ◽  
Fractional Factorial ◽  
Neural Network Models ◽  
Optimal Point ◽  
Multiple Surrogate Models

Performances of multiple surrogate models are evaluated in a turbomachinery blade shape optimization. The basic models, i.e., Response Surface Approximation, Kriging and Radial Basis Neural Network models as well as weighted average models are tested for shape optimization. Global data based errors for each surrogates are used to calculate the weights. These weights are multiplied with the respective surrogates to get the final weighted average models. Sequential Quadratic Programming is used to search the optimal point from these constructed surrogates. Use of multiple surrogates via weighted averaged surrogates gives more robust approximation than individual surrogates. Three design variables are selected to enhance the performance of transonic axial compressor (NASA rotor 37) blade and the design points are selected using three level fractional factorial D-optimal designs. The performance of compressor is improved by optimization because of reduction of losses and movement of separation line towards down stream directions. The present approach can help address the multi-objective design on a rational basis with quantifiable cost-benefit analysis.

scholarly journals The evaluation of the reverse algorithm for syphilis screening in blood donors

2019 ◽  
Vol 27 (4) ◽  
pp. 383-388
Author(s):  
Rukiye Berkem ◽  
Ayşe Esra Karakoç
Keyword(s):  
Screening Method ◽  
Screening Strategy ◽  
Chi Square ◽  
Screening Algorithm ◽  
Traditional Algorithm ◽  
Chi Square Test ◽  
Syphilis Screening ◽  
The Difference ◽  
Anti Hiv ◽  
Hiv 1

Abstract Background: In Turkey, prior to transfusion and apheresis, it is mandatory to screen blood for HBsAg, anti-HCV, anti-HIV 1/2, and syphilis. In recent years, efforts have been made to create effective diagnostic algorithms for screening, and as a screening strategy, many countries have switched from traditional algorithms to reverse algorithms. This study was carried out to evaluate the results we obtained after changing to chemiluminescence immunoassay (CLIA) based reverse algorithm, which is more sensitive and specific than the traditional algorithm and VDRL test we currently use for syphilis screening. Methods: The screening algorithm was initiated with the treponemal CLIA method. The reactive samples were tested using a nontreponemal test VDRL and a second treponemal test TPHA. In the descriptive analyses, the averages, numbers, and percentage distributions were calculated. The group comparisons were undertaken with the chi-square test, accepting p < 0.05 as statistically significant. Results: Of the 5,053 samples that were tested with CLIA syphilis TPA assay 5,043 were negative (99.802%) and 10 were positive reactive (0.198%), and the difference between the two was statistically significant (p < 0.001). Ten samples that were recurrently reactive were analyzed by VDRL and TPHA tests simultaneously. VDRL was negative in all 10 samples, whereas TPHA was negative in one sample, but positive in nine samples at a titer of ≥1/160. Conclusion: Based on the results of this study, we decided to use the CLIA method and reverse algorithm instead of using the traditional algorithm and VDRL as the initial screening method.

Modified facelift incision for parotidectomy

1994 ◽  
Vol 108 (7) ◽  
pp. 574-578 ◽  
Author(s):  
David J. Terris ◽  
Katherine M. Tuffo ◽  
Willard E. Fee
Keyword(s):  
Patient Satisfaction ◽  
Additional Risk ◽  
Time Of Surgery ◽  
Alternative Approach ◽  
The Mean ◽  
The Difference ◽  
Good Exposure ◽  
Total Parotidectomy ◽  
Modified Facelift Incision

AbstractThe most commonly used incision for parotidectomies is the modified Blair incision. We have successfully used an alternative incision which allows good exposure, and leaves no neck scar.Between 1 March 1989 and 1 August 1991, 18 parotidectomies were performed using a modified facelift incision. Fifteen parotidectomies were done for similar indications during the same period using a modified Blair incision. The mean age in both groups of patients was 40.3 years. The pathology and incidence of complications was similar in the two groups. The difference in mean (±SD) time of surgery between the two groups was not statistically significant: 3.14 ±0.75 hours in patients with a modified facelift incision and 3.25 ±1.27 hours in patients with a modified Blair incision (p<20.1).The modified facelift incision is an alternative approach to parotidectomy for selected patients. It provides adequate exposure, even for a total parotidectomy and mastoidectomy and it results in improved patient satisfaction without additional risk of complications.

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