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Solving non-monotone equilibrium problems via a direct-type approach

JOURNAL OF GLOBAL OPTIMIZATION 2022年第4期83卷 699-725页

作者： Lucidi, Stefano Passacantando, Mauro Rinaldi, Francesco Sapienza Univ Rome Dept Comp Control & Management Engn Antonio Ruber Via Ariosto 25 I-00185 Rome Italy Univ Pisa Dept Comp Sci Largo B Pontecorvo 3 I-56127 Pisa Italy Univ Padua Dept Math Tullio Levi Civita Via Trieste 63 I-35121 Padua Italy

A global optimization approach for solving non-monotone equilibrium problems (EPs) is proposed. The class of (regularized) gap functions is used to reformulate any EP as a constrained global optimization program and some bounds on the Lipschitz constant of such functions are provided. The proposed global optimization approach is a combination of an improved version of the direct algorithm, which exploits local bounds of the Lipschitz constant of the objective function, with local minimizations. Unlike most existing solution methods for EPs, no monotonicity-type condition is assumed in this paper. Preliminary numerical results on several classes of EPs show the effectiveness of the approach.

关键词： Equilibrium problem Gap function Global optimization direct algorithm

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Multiple spheres detection problem-Center based clustering approach

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PATTERN RECOGNITION LETTERS 2023年 176卷 34-41页

作者： Sabo, Kristian Scitovski, Rudolf Ungar, Sime Univ Osijek Dept Math Trg Lj Gaja 6 Osijek 31000 Croatia Univ Zagreb Dept Math Bijenicka 30 Zagreb 10000 Croatia

In this paper, we propose an adaptation of the well-known k-means algorithm for solving the multiple spheres detection problem when data points are homogeneously scattered around several spheres. We call this adaptation the k-closest spheres algorithm. In order to choose good initial spheres, we use a few iterations of the global optimizing algorithm direct, resulting in the high efficiency of the proposed k-closest spheres algorithm. We present illustrative examples for the case of non-intersecting and for the case of intersecting spheres. We also show a real-world application in analyzing earthquake depths.

关键词： Multiple spheres detection k-means algorithm k-closest spheres algorithm direct algorithm

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A Regression Tree as Acquisition Function for Low-Dimensional Optimisation 16th

A Regression Tree as Acquisition Function for Low-Dimensiona...

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16th Mexican Conference on Pattern Recognition (MCPR)

作者： de Paz, Erick G. G. Vaquera Huerta, Humberto Albores Velasco, Francisco Javier Bauer Mengelberg, John R. Romero Padilla, Juan Manuel Colegio Postgrad Texcoco 56230 Mexico Mexico Univ Autonoma Tlaxcala Apizaco 90341 Tlaxcala Mexico

ISBN: (纸本)9783031628351;9783031628368

direct-type optimisation algorithms recursively explore the domain of an objective function by means of a hierarchical partition. In this context, a regression tree can be estimated with the exploration data and be used to quickly reach the optimum. This regression tree allows to apply Bayesian optimisation techniques instead of the poorly adaptive rules applied within the original direct algorithm. Although based on a probabilistic framework, this approach can perform a deterministic search, a remarkable attribute of direct-type algorithms. This method based on a machine learning algorithm and Bayesian inference is compared with several R libraries for optimisation, including the original direct algorithm and three representative evolutionary algorithms. For a collection of well-known benchmark functions, the proposal is statistically more reliable and robust than direct with respect of dimensionality, but not enough to beat the evolutionary alternatives.

关键词： Regression Tree direct algorithm Bayesian Optimisation

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Fuel Efficiency Optimization of Input-Split Hybrid Electric Vehicle using direct algorithm 9

Fuel Efficiency Optimization of Input-Split Hybrid Electric ...

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9th Int Conf Ind Information Syst (ICIIS2014)

作者： Panday, Aishwarya Bansal, Hari Om Birla Inst Technol & Sci Dept Elect & Elect Engn Pilani Rajasthan India

ISBN: (纸本)9781479964994

For cleaner and greener future, Hybrid vehicle has been accepted as best practical applications for transportation. The presence of two power sources, i.e. engine and battery in hybrid electric vehicles makes it necessary to intelligently split the power for lesser fuel consumption. An intelligent power management strategy is developed to fulfil on road power demand with good fuel economy. This article uses direct method to control toggling between the engine and battery to reduce the overall liquid fuel consumption. The battery charge is utilized effectively without deteriorating its health. The control strategy is based on the optimization of vital parameters such as state of charge in the battery, engine idle speed, engine on duration and power demand. Numerous simulations are executed on the advanced vehicle simulator (ADVISOR) to authenticate the feasibility of the proposed controller.

关键词： Hybrid electric vehicle power -split configuration direct algorithm State of charge Fuel economy energy optimization

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LFM Signal Parameters Estimation using an Improved direct algorithm 4

LFM Signal Parameters Estimation using an Improved DIRECT Al...

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4th IEEE International Conference on Information Science and Technology (ICIST)

作者： Ding, Dan Cheng, Naiping Acad Equipment Dept Opt & Elect Equipment Beijing Peoples R China

ISBN: (纸本)9781479948086

In the paper, the widely used numerical optimization method for linear frequency modulated (LFM) signal parameters estimation is modified. To this purpose, an improved Dividing RECTangles (direct) algorithm is proposed to substitute for the commonly used grid search method. The proposed global optimization algorithm can provide initial estimates for local optimization algorithms such as Newton and Simplex. Based on classical direct algorithm, the improved version, called Lipschitz constant assisted direct (L-direct) algorithm, eliminates hopeless areas, suspends unlikely areas, and concentrates on more promising areas in search space, finding the range of attraction (ROA) with lower SNR threshold or less computational burden for local optimization algorithms. The effect of the modification is validated by simulation results.

关键词： Linear frequency modulated signal direct algorithm Global optimization Local optimization

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Reformulating the direct convolution for high-performance deep learning inference on ARM processors

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JOURNAL OF SYSTEMS ARCHITECTURE 2023年第1期135卷

作者： Barrachina, Sergio Castello, Adrian Dolz, Manuel F. Low, Tze Meng Martinez, Hector Quintana-Orti, Enrique S. Sridhar, Upasana Tomas, Andres E. Univ Jaume 1 Castellon De La Plana Spain Univ Politecn Valencia Valencia Spain Carnegie Mellon Univ Pittsburgh PA 15213 USA Univ Cordoba Cordoba Spain

We present two high-performance implementations of the convolution operator via the direct algorithm that outperform the so-called lowering approach based on the im2col transform plus the gemm kernel on an ARMv8-based processor. One of our methods presents the additional advantage of zero-memory overhead while the other employs an additional yet rather moderate workspace, substantially smaller than that required by the im2col+gemm solution. In contrast with a previous implementation of a similar zero-memory overhead direct convolution, this work exhibits the key advantage of preserving the conventional NHWC data layout for the input/output activations of the convolution layers.

关键词： Convolution direct algorithm Deep learning High performance ARMv8 architecture

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A Unified Approach Toward Simulating Constant and Varying Amplitude Fatigue Failure Effects of Metals with Fast and Efficient algorithms

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Acta Mechanica Solida Sinica 2021年第1期34卷 53-64页

作者： Si-Yu Wang Lin Zhan Hui-Feng Xi Heng Xiao College of Mechanics and Construction Engineering and MOE Key Lab of Disaster Forecast and Control in Engineering Jinan UniversityGuangzhou510632China

A new finite strain elastoplastic J2-flow model is established with an explicit formulation of work-hardening and softening effects up to eventual failure,in which both a new flow rule free of yielding and an asymptotically vanishing stress limit are *** novelties of this new model are as follows:(i)Fatigue failure effects under repeated loading conditions with either constant or varying amplitudes are automatically characterized as inherent response features;(ii)neither additional damage-like variables nor failure criteria need to be involved;and(iii)both high-and low-cycle fatigue effects may be simultaneously treated.A fast and efficient algorithm of high accuracy is proposed for directly simulating high-and medium-high-cycle fatigue failure effects under repeated loading *** this goal,a direct and explicit relationship between the fatigue life and the stress amplitude is obtained by means of explicit and direct procedures of integrating the coupled elastoplastic rate equations for any given number of loading-unloading cycles with varying stress *** examples suggest that the new algorithm is much more fast and efficient than usual tedious and very time-consuming integration procedures.

关键词： Metals Finite strain Elastoplasticity Fatigue failure direct algorithm

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Assessment and optimization of a single flash geothermal system recovered by a trans-critical CO2 cycle using different scenarios

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ENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY 2024年第4期43卷 e14371-e14371页

作者： Aryanfar, Yashar Castellanos, Humberto Garcia Akhgarzarandy, Farshad Kecebas, Ali Algarni, Salem Alqahtani, Talal Irshad, Kashif Tag-Eldin, Elsayed M. Autonomous Univ Ciudad Juarez Dept Elect Engn & Computat Ciudad Juarez Chihuahua Mexico Khazar Univ Thermo Fluids Res Grp Baku Azerbaijan Tecnol Nacl Mexico IT Ciudad Juarez Engn Sci Ciudad Juarez Chihuahua Mexico Hohai Univ Coll Energy & Elect Engn Nanjing Peoples R China Mugla Sitki Kocman Univ Technol Fac Dept Energy Syst Engn Mugla Turkiye King Khalid Univ Coll Engn Mech Engn Dept Abha Saudi Arabia King Fahd Univ Petr & Minerals KFUPM Res Inst Interdisciplinary Res Ctr Sustainable Energy Syst Dhahran Saudi Arabia Future Univ Egypt Fac Engn & Technol New Cairo Egypt

In the evolving landscape of sustainable energy, optimizing geothermal power systems presents a critical challenge. This study explores the energy and exergy efficiencies of a power production system utilizing a single-flash geothermal cycle integrated with a trans-critical CO2 cycle. The study's methodology involves a detailed examination of key performance parameters-separator pressure, CO(2 )turbine intake pressure, and steam turbine output pressure. Utilizing the EES software environment, the study innovatively employs a combination of Genetic algorithm (GA), Nelder-Mead Simplex (NMS) method, and direct algorithm (DA). When using GA, NMS and DA, the system's exergy efficiency increases from 32.46% in the default operating mode to 39.21%, 36.16%, and 38.82%, respectively. One of the notable outcomes is the identification of optimal separator pressure for maximum energy efficiency. Furthermore, the study reveals that increasing the CO2 turbine's inlet pressure adversely impacts the system's efficiency. The study's results contribute significantly to the field of renewable energy, offering practical guidelines for enhancing the performance of geothermal power systems.

关键词： direct algorithm genetic algorithm Nelder-Mead simplex optimization single flash geothermal trans-critical CO2 cycle

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Discrete sizing optimization method based on dividing rectangles algorithm and local response surface for steel frame structures

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JOURNAL OF BUILDING ENGINEERING 2023年 79卷

作者： Wan, Yinyuan Hu, Bo Yang, Ye Jin, Fengling Zhou, Jianlu Gao, Boqing Zhejiang Univ Coll Civil Engn & Architecture Hangzhou 310058 Peoples R China Zhejiang Univ Ctr Balance Architecture Hangzhou 310058 Peoples R China Zhejiang Nan Cheng Yue Jing Architecture & Urban P Hangzhou Peoples R China

It has always been the goal of structural engineers to construct safe and stable buildings using the least amount of materials. Utilizing a quick and effective way to optimize the cross-section size is crucial because conventional building design methods are impacted by the designers' knowledge, and it is challenging to prevent material waste. Due to its implicit optimization function, discrete design variables, and expensive individual evaluation, sizing optimization of high-rise buildings is very challenging to achieve. In order to effectively handle this optimization problem, a two-stage discrete sizing optimization method for high-rise buildings based on the DIviding RECTangles (direct) algorithm and local response surface is proposed in this paper. The optimization method suggested in this research consists of two key stages: the global search stage and the local search stage. In the global search stage, the entire design domain is divided using a modified direct algorithm to swiftly identify potentially optimal subregions that may contain the best points. In the local search stage, the local response surface model is constructed to approximate the objective and constraint functions using the sampling points from the previous stage, and the discrete optimal solution is rapidly found through mathematical iterative solving. A sizing optimization calculation program for high-rise buildings was developed in Microsoft Visual Studio 2015 on the basis of C++ to achieve automatic optimization. The new method was applied to optimize three high-rise steel frame buildings with different heights and plan shapes. The results showed that the material cost could be successfully saved compared with the conventional design, and the over-limit constraints could be adjusted automatically, which demonstrated the viability and efficacy of the two-stage optimization method.

关键词： High-rise buildings Component size optimization Discrete optimization direct algorithm Response surface

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Modelling, Analysis and Entropy Generation Minimization of Al2O3-Ethylene Glycol Nanofluid Convective Flow inside a Tube

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ENERGIES 2022年第9期15卷 3073页

作者： Mukherjee, Sayantan Aljuwayhel, Nawaf F. Bal, Sasmita Mishra, Purna Chandra Ali, Naser KIIT Deemed Univ Sch Mech Engn Kalinga Inst Ind Technol Thermal Engn Res Lab TRL Bhubaneswar 751024 Orissa India Kuwait Univ Coll Engn & Petr Mech Engn Dept POB 5969 Safat 13060 Kuwait Alliance Univ Alliance Coll Engn & Design Dept Mech Engn Bengaluru 562106 KA India Kuwait Inst Sci Res Nanotechnol & Adv Mat Program Energy & Bldg Res Ctr POB 24885 Kuwait 13109 Kuwait

Entropy generation is always a matter of concern in a heat transfer system. It denotes the amount of energy lost as a result of irreversibility. As a result, it must be reduced. The present work considers an investigation on the turbulent forced convective heat transfer and entropy generation of Al2O3-Ethylene glycol (EG) nanofluid inside a circular tube subjected to constant wall temperature. The study is focused on the development of an analytical framework by using mathematical models to simulate the characteristics of nanofluids in the as-mentioned thermal system. The simulated result is validated using published data. Further, Genetic algorithm (GA) and direct algorithm are implemented to determine the optimal condition which yields minimum entropy generation. According to the findings, heat transfer increases at a direct proportion to the mass flow, Reynolds number (Re), and volume concentration of nanoparticles. Furthermore, as Re increases, particle concentration should be decreased in order to reduce total entropy generation (TEG) and to improve heat transfer rate of any given particle size. A minimal concentration of nanoparticles is required to reduce TEG when Re is maintained constant. The highest increase in TEG with nanofluids was 2.93 times that of basefluid. The optimum condition for minimum entropy generation is Re = 4000, nanoparticle size = 65 nm, volume concentration = 0.2% and mass flow rate = 0.54 kg/s.

关键词： nanofluid entropy generation optimization genetic algorithm direct algorithm

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