Multi-Fidelity Kriging-Based Optimization of Engine Subsystem Models With Medial Meshes

2018 ◽  
Author(s):  
Hau Kit Yong ◽  
Leran Wang ◽  
David J. J. Toal ◽  
Andy J. Keane ◽  
Felix Stanley
Keyword(s):  
Optimum Design ◽  
Computational Cost ◽  
Optimization Approach ◽  
Engine Model ◽  
Solid Models ◽  
Medial Surfaces ◽  
First Time ◽  
Kriging Approach ◽  
Modelling Approach

Engine subsystem models are not commonly used in design optimization studies as it is computationally expensive to solve these models for a large number of iterations. To reduce the computational cost of such optimizations, a novel multi-fidelity Kriging-based optimization approach is proposed that uses shell FEMs to provide a low-fidelity response and solid FEMs to provide a high-fidelity response. This marks the first time that shell and solid models are used together in a multi-fidelity surrogate modelling approach. The shell FEMs are generated from medial surfaces that are extracted from solid component geometries in a semi-automatic manner. This approach is applied to a case study for optimizing the intercasing subsystem from the CRESCENDO whole engine model. The results show that the optimum design found by the multi-fidelity Kriging approach was on par with the optimum design found by a single-fidelity Kriging approach using only solid FEMs which is more than twice as expensive to run. The shell and solid FEMs were also shown to be well-correlated such that optimization studies employing only the shell FEMs by themselves could generate designs that are feasible with respect to the design constraints imposed on the solid model.

Two-part modelling approach for ship engine simulations

2015 ◽  
Author(s):  
M. Godjevac ◽  
P. de Vos ◽  
H. Zhou ◽  
C. Thiem
Keyword(s):  
Mean Value ◽  
Propulsion System ◽  
Component Model ◽  
First Principle ◽  
Transient Conditions ◽  
Ship Propulsion ◽  
Engine Model ◽  
Component Models ◽  
Modelling Approach

When simulating a ship propulsion system, it is often required to evaluate various characteristics of a ship propulsion system and the selected modelling approach changes according to the goal of the simulation. For example, data-based models are sufficient for simulations of steady state conditions while first principle models are more suitable for transient conditions. Additionally, it is often necessary to compare different propulsion configurations. For component models, this might require different modelling approaches to describe various performances and/or different sets of parameters used to describe different propulsion configurations. Even though there are various databases of ship component models, none of them allows the user to change the modelling approach or pre-set values of parameters used to describe the component models. In order to allow the changing of the modelling approach together with the parameters of the component models, a novel two-part modelling approach is proposed in this paper. The proposed approach separates the component model into two parts: process and parametric part. By adjusting the process part of the component model, the modelling approach can easily be changed. And by adjusting the parametric part of the component model, it is possible to adjust the component’s characteristics and accommodate different configurations. In this investigation, a mean value first principle diesel engine model has been selected as a case study to demonstrate the flexibility of the proposed approach. As shown in the paper, the proposed approach allows the user to combine the benefits of a first principle model with the accuracy of the data based models. Additionally, the functional mock-up interface (FMI) standard has been used in the investigation to show that the proposed approach can be used in different software environments.

scholarly journals Antenna array synthesis using a newly evolved optimization approach: Strawberry algorithm

2019 ◽  
Vol 70 (4) ◽  
pp. 317-322 ◽  
Author(s):  
Konidala R. Subhashini
Keyword(s):  
Antenna Array ◽  
Optimization Technique ◽  
Beam Width ◽  
Side Lobe ◽  
Side Lobe Level ◽  
Optimization Approach ◽  
Circular Array ◽  
First Time ◽  
Antenna Array Synthesis

Abstract An attempt has been made for the first time to apply this proposed Strawberry optimization technique to antenna array synthesis problem. The case study cited here refer to linear and circular array configurations. The design constraints are limited to minimizing the side lobe level and restricting the first null beam width, which play significant roles in antenna array performances. The key parameters which greatly influence in achieving the said objectives are either placement of antenna elements or amplitudes of excitations of these elements or both. And the recently reported meta heuristic nature inspired optimization algorithms have addressed to these problems quite effectively and the exciting result obtained using the said approach has undoubtedly proved the strawberry algorithm as a potential contender in the optimization domain.

Islamic and Jewish Religious Feminists Tackle Islamic and Jewish Oral Law: Maintenance and Rebellion of Wives

2017 ◽  
Vol 11 (1) ◽  
pp. 35-63
Author(s):  
Ruth Roded
Keyword(s):  
State Policy ◽  
Political System ◽  
Daily Life ◽  
The State ◽  
The Political ◽  
Jewish Law ◽  
Modern Times ◽  
Parallel Case ◽  
First Time

Beginning in the early 1970s, Jewish and Muslim feminists, tackled “oral law”—Mishna and Talmud, in Judaism, and the parallel Hadith and Fiqh in Islam, and several analogous methodologies were devised. A parallel case study of maintenance and rebellion of wives —mezonoteha, moredet al ba?ala; nafaqa al-mar?a and nush?z—in classical Jewish and Islamic oral law demonstrates similarities in content and discourse. Differences between the two, however, were found in the application of oral law to daily life, as reflected in “responsa”—piskei halacha and fatwas. In modern times, as the state became more involved in regulating maintenance and disobedience, and Jewish law was backed for the first time in history by a state, state policy and implementation were influenced by the political system and socioeconomic circumstances of the country. Despite their similar origin in oral law, maintenance and rebellion have divergent relevance to modern Jews and Muslims.

Investigation of a New Approach to Predict Water Quality Extremes with a Case Study of Chemical Determinands in Stream Water

1991 ◽  
Vol 24 (6) ◽  
pp. 25-33
Author(s):  
A. J. Jakeman ◽  
P. G. Whitehead ◽  
A. Robson ◽  
J. A. Taylor ◽  
J. Bai
Keyword(s):  
Water Quality ◽  
Stream Water ◽  
Probability Distributions ◽  
Management Strategies ◽  
Hybrid Modelling ◽  
Trend Model ◽  
Environmental Extremes ◽  
Modelling Approach

The paper illustrates analysis of the assumptions of the statistical component of a hybrid modelling approach for predicting environmental extremes. This shows how to assess the applicability of the approach to water quality problems. The analysis involves data on stream acidity from the Birkenes catchment in Norway. The modelling approach is hybrid in that it uses: (1) a deterministic or process-based description to simulate (non-stationary) long term trend values of environmental variables, and (2) probability distributions which are superimposed on the trend values to characterise the frequency of shorter term concentrations. This permits assessment of management strategies and of sensitivity to climate variables by adjusting the values of major forcing variables in the trend model. Knowledge of the variability about the trend is provided by: (a) identification of an appropriate parametric form of the probability density function (pdf) of the environmental attribute (e.g. stream acidity variables) whose extremes are of interest, and (b) estimation of pdf parameters using the output of the trend model.

scholarly journals Cobalt-based magnetic Weyl semimetals with high-thermodynamic stabilities

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Wei Luo ◽  
Yuma Nakamura ◽  
Jinseon Park ◽  
Mina Yoon
Keyword(s):  
Tight Binding ◽  
Three Dimensional ◽  
Interlayer Coupling ◽  
First Principles Calculation ◽  
Optimization Approach ◽  
Binding Model ◽  
Nodal Lines ◽  
Weyl Semimetal ◽  
Topological Quantum ◽  
First Time

AbstractRecent experiments identified Co3Sn2S2 as the first magnetic Weyl semimetal (MWSM). Using first-principles calculation with a global optimization approach, we explore the structural stabilities and topological electronic properties of cobalt (Co)-based shandite and alloys, Co3MM’X2 (M/M’ = Ge, Sn, Pb, X = S, Se, Te), and identify stable structures with different Weyl phases. Using a tight-binding model, for the first time, we reveal that the physical origin of the nodal lines of a Co-based shandite structure is the interlayer coupling between Co atoms in different Kagome layers, while the number of Weyl points and their types are mainly governed by the interaction between Co and the metal atoms, Sn, Ge, and Pb. The Co3SnPbS2 alloy exhibits two distinguished topological phases, depending on the relative positions of the Sn and Pb atoms: a three-dimensional quantum anomalous Hall metal, and a MWSM phase with anomalous Hall conductivity (~1290 Ω−1 cm−1) that is larger than that of Co2Sn2S2. Our work reveals the physical mechanism of the origination of Weyl fermions in Co-based shandite structures and proposes topological quantum states with high thermal stability.

scholarly journals Axial Compressor Mean-Line Analysis: Choking Modelling and Fully-Coupled Integration in Engine Performance Simulations

2021 ◽  
Vol 6 (1) ◽  
pp. 4
Author(s):  
Ioannis Kolias ◽  
Alexios Alexiou ◽  
Nikolaos Aretakis ◽  
Konstantinos Mathioudakis
Keyword(s):  
Axial Compressor ◽  
Engine Performance ◽  
Engine Model ◽  
Multi Stage ◽  
Transient Simulations ◽  
Full Knowledge ◽  
Compressor Performance ◽  
First Time ◽  
Performance Calculation ◽  
Fully Coupled

A mean-line compressor performance calculation method is presented that covers the entire operating range, including the choked region of the map. It can be directly integrated into overall engine performance models, as it is developed in the same simulation environment. The code materializing the model can inherit the same interfaces, fluid models, and solvers, as the engine cycle model, allowing consistent, transparent, and robust simulations. In order to deal with convergence problems when the compressor operates close to or within the choked operation region, an approach to model choking conditions at blade row and overall compressor level is proposed. The choked portion of the compressor characteristics map is thus numerically established, allowing full knowledge and handling of inter-stage flow conditions. Such choking modelling capabilities are illustrated, for the first time in the open literature, for the case of multi-stage compressors. Integration capabilities of the 1D code within an overall engine model are demonstrated through steady state and transient simulations of a contemporary turbofan layout. Advantages offered by this approach are discussed, while comparison of using alternative approaches for representing compressor performance in overall engine models is discussed.

scholarly journals Toward Decentralised Sanitary Sewage Collection Systems: A Multiobjective Approach for Cost-Effective and Resilient Designs

Water ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 1886
Author(s):  
Arezoo Zahediasl ◽  
Amin E. Bakhshipour ◽  
Ulrich Dittmer ◽  
Ali Haghighi
Keyword(s):  
Treatment Plant ◽  
Drainage System ◽  
Cost Effective ◽  
Optimization Approach ◽  
Hydraulic Design ◽  
Multiobjective Approach ◽  
Layout Generation ◽  
Plant Allocation ◽  
Problem Solving Process

In recent years, the concept of a centralized drainage system that connect an entire city to one single treatment plant is increasingly being questioned in terms of the costs, reliability, and environmental impacts. This study introduces an optimization approach based on decentralization in order to develop a cost-effective and sustainable sewage collection system. For this purpose, a new algorithm based on the growing spanning tree algorithm is developed for decentralized layout generation and treatment plant allocation. The trade-off between construction and operation costs, resilience, and the degree of centralization is a multiobjective problem that consists of two subproblems: the layout of the networks and the hydraulic design. The innovative characteristics of the proposed framework are that layout and hydraulic designs are solved simultaneously, three objectives are optimized together, and the entire problem solving process is self-adaptive. The model is then applied to a real case study. The results show that finding an optimum degree of centralization could reduce not only the network’s costs by 17.3%, but could also increase its structural resilience significantly compared to fully centralized networks.

scholarly journals Erratum: Gravrok, J., et al. Beyond the Benefits of Assistance Dogs: Exploring Challenges Experienced by First-Time Handlers. Animals 2019, 9, 203

Animals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 237
Author(s):  
Jennifer Gravrok ◽  
Dan Bendrups ◽  
Tiffani Howell ◽  
Pauleen Bennett
Keyword(s):  
Assistance Dogs ◽  
First Time

The authors wish to make the following corrections [1]:In Table 1, under case study 4, the code was originally labeled as H8, P8 and ADI 8; these labels should be H4, P4 and ADI 4, respectively [...]

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