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Investigation of high-compactness and high-efficiency TPMS precoolers for precooled aero-engine

ENERGY 2025年 319卷

作者： Huang, W. S. Ning, H. Y. Tang, G. H. Xi An Jiao Tong Univ Sch Future Technol Xian 710049 Peoples R China Xi An Jiao Tong Univ Sch Energy & Power Engn Key Lab Thermo Fluid Sci & Engn MOE Xian 710049 Peoples R China

The precooler is the core functional component of the precooled air-breathing engines, which requires high power-to-weight ratio and robustness. However, the conventional compact tubular precooler suffers from low reliability, poor manufacturability and uneven flow distribution. The present study proposes a novel precooler based on triply periodic minimal surface (TPMS) in polar coordinate form. Firstly, the linear approximation method is introduced and regression models are established by response surface methodology (RSM) to determine the geometry parameters of polar TPMS. Then, the accuracy of the numerical method for TPMS is validated by experimental tests and new correlations for thermal and hydraulic performances of TPMS precooler are fitted. Subsequently, the segmental thermal design method and multi-objective genetic algorithm are combined for the multi-objective optimization of the precooler. Finally, the superior optimization objective combination selected by the decision-making method is compared with the conventional compact tubular precooler. The results indicate that the optimized TPMS precooler volume is reduced by 27.8%, with 23.8% increase in power-to- weight ratio. Additionally, the TPMS precooler fabricated by additive manufacturing can exhibit high reliability. The present methods for the novel TPMS precooler are also straightforward for high efficient and high compact heat exchangers in other fields under harsh thermal environment.

关键词： Triply periodic minimal surface linear approximation method Segmental design method Parameter analysis Response surface method Multi-objective genetic algorithm

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Resilience assessment for natural gas systems and electrical power systems without complete integration

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IET GENERATION TRANSMISSION & DISTRIBUTION 2022年第24期16卷 4893-4913页

作者： Xie, Haipeng Fu, Wei Jiang, Lizhou Bie, Zhaohong Xi An Jiao Tong Univ State Key Lab Elect Insulat & Power Equipment 28 Xianning West Rd Xian 710049 Shaanxi Peoples R China

Considering the limited information sharing between natural gas systems (NGS) and electrical power systems (EPS), this paper proposes a distributed resilience assessment method for NGS and EPS. First, a coordinated restoration framework is presented for incompletely integrated energy systems, and the collaborative benefit redistribution mechanism is proposed to motivate the participation of the cooperative restoration. Then fragility and recovery models for NGS and EPS components are developed, involving the impact of wind and rainfall during typhoons. An emergency load shedding model considering the conditional value at risk under typhoons is built, where the dynamic constraints of gas storage in NGS's pipelines is considered, and a linear approximation method is adopted to make the solution feasible. The modified alternating direction method of multipliers algorithm is used to solve the problem, and herein the self-adaptive penalty factor is leveraged to boost the efficiency. Based on the valley-shaped resilience model, the concept of skewness and kurtosis are introduced to give risk-adverse metrics more systematically to the impact of extreme events. The proposed model and algorithm are validated by case studies. Except for the performance exploration, the weakness and enhancement suggestions are also concluded from the case analysis.

关键词： valley-shaped resilience model natural gas collaborative benefit redistribution mechanism distributed resilience assessment method electrical power systems natural gas systems incompletely integrated energy systems gas storage EPS linear approximation method fragility risk management typhoons coordinated restoration framework NGS's pipelines load shedding information sharing recovery models modified alternating direction method complete integration

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Modeling and simulation for V-shaped stacked graphene nanosheet FETs (GNFETs) for high frequency applications

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e-Prime - Advances in Electrical Engineering, Electronics and Energy 2025年 12卷

作者： Kumar, S. Raj Electronics Engineering (VLSI) Department Velammal College of Engineering and Technology Madurai India

A new 2D analytical model for the V-shaped Stacked Graphene Nanosheet Field Effect Transistor (GNFETs) is developed in this study. Using suitable boundary conditions, the linear approximation method (LAM) is used to determine the 2D Poisson equation for the first time. To assess the performance of the device, the exact analytical equations for the variables drain current, transconductance, threshold voltage, electric field, and channel potential are derived. The device operates at cryogenic temperatures as a result of the high electron fluxes into the channel caused by the effect of the Nanosheet channel contact with the gate. It offers a significant scaling of device with a large capacity for drive current. With a perpendicular layered structure, the V-shaped Nanosheet achieves low threshold voltage and high transconductance. When TCAD simulation software and analytical model results are compared, a good degree of agreement is obtained. © 2025 The Author(s)

关键词： Drain current Graphene nanosheet linear approximation method Threshold voltage Transconductance

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A multi-period bi-level model for a competitive food supply chain with sustainability considerations

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JOURNAL OF CLEANER PRODUCTION 2021年 325卷 129260-129260页

作者： Manteghi, Yashar Arkat, Jamal Mahmoodi, Anwar Farvaresh, Hamid Univ Kurdistan Dept Ind Engn Sanandaj Iran

The use of food additives and greenhouse gas (GHG) emissions are major factors that affect consumer health, which cannot be ensured, therefore, unless the food supply chain is controlled. This paper presents a bi-level optimization approach to address competition between the members of a food supply chain, including two suppliers and one manufacturer. The manufacturer seeks to determine prices, production, and investment in reducing GHG emissions to maximize profits at the upper level. A multi-period model is presented, in which the manufacturer seeks to reduce production costs by maintaining inventory and, of course, accepting the risk of waste. At the lower level, the suppliers compete to determine the price of raw materials and the amount of additives to maximize their profits. Two linear approximation methods are proposed to linearize the nonlinear model. According to the results, the lowest relative gaps obtained from solving the model for two numerical examples using the second linear approximation method are lower than those obtained by the first method. A sensitivity analysis of the effective parameters demonstrates that an increase in the dependence of demand on price leads to a 30% decrease in the profit of the entire supply chain. The manufacturer faces an average 3% drop in demand with an increase of 4%-7% in the rate of production waste. An 18% increase in the cost of GHG emission reduction leads to a 5% decrease in total supply chain profit. Hence, the increase in the cost of reducing GHG emissions is not economical and environment-friendly for the supply chain members. A budget increase is appropriate in terms of the economic and environmental goals, but its impact on the manufacturer's decision variables varies by period.

关键词： Food supply chain Greenhouse gas emissions Bi-level programming Supply chain sustainability linear approximation method

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Projection of the diameter structure in Eucalyptus grandis x urophylla stands submitted to thinnings in Bahia State

SCIENTIA FORESTALIS

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SCIENTIA FORESTALIS 2020年第128期48卷

作者： de Souza, Emilio Goncalves Nogueira, Gilciano Saraiva Leite, Helio Garcia Romarco de Oliveira, Marcio Leles Barbosa, Gabriela Paranhos Lopes, Efigenio Teixeira Univ Fed Vales Jequitinhonha & Mucuri UFVJM Diamantina MG Brazil Univ Fed Vicosa UFV Vicosa MG Brazil

This study aimed to compare two diameter distribution models in Eucalyptus grandis x Eucalyptus urophylla submitted to thinning;and evaluate the influence of two adjustment methods of probability density functions on the quality of the diameter structure projections. The data used in this study came from an experiment on thinning of eucalyptus clones, located in the northeast region of the state of Bahia. The measurements were made at the ages 27, 40, 50, 58, 61, 76, 87, 101, 112, 122, 137, 147, 158 and 165 months, with thinnings carried out at 58 and 142 months. Two diameter distribution models were used to prognosticate the diametric structures of the stands, starting from an observed distribution at ages 27 (before first thinning), 61 (after first thinning) and 147 (after second thinning) months. Three systems were obtained according to the adjusting method of the Weibull function: System 1, using the linear approximation;Systems 2 and 3, using the maximum likelihood. The goodness of fit of prognosticated structures in relation to those observed was verified by the Kolmogorov-Smirnov test at 5% of significance. System 2 was the most suitable for practical applications for thinning in eucalypts. The maximum likelihood method should preferably be used when compared to linear approximation, ensuring a better quality in the prognoses of the diameter distribution.

关键词： Weibull function Diameter distribution Maximum likelihood method linear approximation method

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Differential Structure of Inductive Proximity Sensor

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SENSORS 2019年第9期19卷 2210.-2210.页

作者： Guo, Yi-Xin Lai, Cong Shao, Zhi-Biao Xu, Kai-Liang Li, Ting Xi An Jiao Tong Univ Sch Elect & Informat Engn 28 Xianning West Rd Xian 710049 Shaanxi Peoples R China Xian Univ Technol Sch Automat & Informat Engn 5 South Jinhua Rd Xian 710048 Shaanxi Peoples R China

The inductive proximity sensor (IPS) is applicable to displacement measurements in the aviation field due to its non-mechanical contact, safety, and durability. IPS can increase reliability of position detection and decrease maintenance cost of the system effectively in aircraft applications. Nevertheless, the specialty in the aviation field proposes many restrictions and requirements on the application of IPS, including the temperature drift effect of the resistance component of the IPS sensing coil. Moreover, reliability requirements of aircrafts restrict the use of computational-intensive algorithms and avoid the use of process control components. Furthermore, the environment of airborne electronic equipment restricts measurements driven by large current and proposes strict requirements on emission tests of radio frequency (RF) energy. For these reasons, a differential structured IPS measurement method is proposed in this paper. This measurement method inherits the numerical separation of the resistance and inductance components of the IPS sensing coil to improve the temperature adaptation of the IPS. The computational complexity is decreased by combining the dimension-reduced look-up table method to prevent the use of process control components. The proposed differential structured IPS is equipped with a differential structure of distant and nearby sensing coils to increase the detection accuracy. The small electric current pulse excitation decreases the RF energy emission. Verification results demonstrate that the differential structured IPS realizes the numerical decoupling calculation of the vector impedance of the sensing coil by using 61 look-up table units. The measuring sensitivity increased from 135.5 least significant bits (LSB)/0.10 mm of a single-sensing-coil structured IPS to 1201.4 LSB/0.10 mm, and the linear approximation distance error decreased from 99.376 m to -3.240 m. The proposed differential structured IPS method has evident comparative adva

关键词： inductive proximity sensor displacement measurements differential structure linear approximation method look-up table airborne electronic equipment small electric current pulse

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Solution of interval reactive power optimization model through defining security limits

Solution of interval reactive power optimization model throu...

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International Conference on Power System Technology (POWERCON)

作者： Zhang, Cong Chen, Haoyong Hua, Dong Shi, Ke Liu, Yumeng Wang, Xiaojuan Li, Canbing South China Univ Technol Sch Elect Power Guangzhou 510640 Guangdong Peoples R China Asia Pacific Res Inst Smart Grid & Renewable Ener Hong Kong Peoples R China Hunan Univ Sch Elect & Informat Engn Changsha 410082 Hunan Peoples R China

ISBN: (纸本)9781538664612

The model of reactive power optimization including interval uncertainty (RPOIU) is used to make a voltage control strategy for ensuring the interval state variables (including load voltages and reactive power generation) of the power grid within their safe operating limits, under interval active power generation and power load demand input data. To solve the RPOIU model, this paper defined security limits, and then switches the RPOIU model to two deterministic reactive power optimization models, whose constraints bound limits are the security limits. By solving the deterministic models through the interior point method, a voltage control strategy is obtained as the solution of the RPOIU model. The results obtained by the proposed method are compared with the linear approximation method, which is a previously proposed effective method for solving the RPOIU model, and simulation results and analysis demonstrate the advantages, effectiveness, and good applicability of the proposed method.

关键词： Interval uncertainty reactive power optimization security limits interior point method linear approximation method

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Dimension-Reduced AnalogDigital Mixed Measurement method of Inductive Proximity Sensor

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SENSORS 2017年第7期17卷 1533-1533页

作者： Guo, Yi-Xin Shao, Zhi-Biao Tao, Hui-Bin Xu, Kai-Liang Li, Ting Xi An Jiao Tong Univ Sch Elect & Informat Engn 28 Xianning West Rd Xian 710049 Shaanxi Peoples R China Xi An Jiao Tong Univ Inst Robot 28 Xianning West Rd Xian 710049 Shaanxi Peoples R China Xian Univ Technol Sch Automat & Informat Engn 5 South Jinhua Rd Xian 710048 Shaanxi Peoples R China

Inductive proximity sensors (IPSs) present a unique no-contact advantage. They are widely preferred for displacement measurement in various industrial fields (e.g., aviation and aerospace), and they are improved continuously. When the inductance and resistance components of the IPS sensing core are separated, the influence of temperature drift on measurement can be eliminated. The complexity of online computation of component separation can be reduced using a two-dimensional look-up table method. However, this method exhibits disadvantages, such as large capacity of the look-up table, dependency on precision measurement of sensing core parameter, and nonlinear distribution of measurement resolution. This study aims to overcome these disadvantages by examining the nonlinear relationship between the response of the sensing core and the ambient temperature, and proposes a dimension-reduced measurement method. The proposed method extracts the characteristics of the response curves at two temperatures and calculates the characteristics of the response curves at any temperature using a linear approximation. The look-up table capacity is less than 0.37% of the two-dimensional look-up table capacity (condensed) under the same condition;dimension reduction enables the construction of a complete look-up table directly by calibration procedures and avoids precise measurement on sensing core parameters;the calibration procedures establish uniform mapping of the distribution of measurement resolution. The experiment shows that, when the measurement ranges are 0-6, 0-5, and 0-4 mm, the maximum measurement errors are 0.140, 0.065, and 0.040 mm, respectively, under temperature ranging from 20 degrees C to 110 degrees C. This study extends the measurement range from 0-5 mm to 0-7 mm and improves the measurement accuracy over 0.1 mm (50% at 5 mm) compared with the two-dimensional look-up table method. Therefore, the proposed method not only inherits the advantages of the original met

关键词： inductive proximity sensor displacement measurement dimension-reduced method characteristic of response curve linear approximation method look-up table

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Asymptotic Equalities for Best approximations for Classes of Infinitely Differentiable Functions Defined by the Modulus of Continuity

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MATHEMATICAL NOTES 2016年第5-6期99卷 901-915页

作者： Serdyuk, A. S. Sokolenko, I. V. Natl Acad Sci Ukraine Inst Math Kiev Ukraine

We obtain asymptotic estimates for best approximations by trigonometric polynomials in the metric of the space C(L-p) for classes of periodic functions expressible as convolutions of kernels Psi(beta) with Fourier coefficients decreasing to zero faster than any power sequence, and with functions phi is an element of C (phi is an element of L-p) whose moduli of continuity do not exceed the given majorant of omega(t). It is proved that, in the spaces C and L-1, for convex moduli of continuity omega(t), the obtained estimates are asymptotically sharp.

关键词： best approximation by trigonometric polynomials periodic infinitely differentiable function modulus of continuity generalized Poisson kernel linear approximation method Kolmogorov-Nikol'skii problem

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Asymptotic behavior of best approximations of classes of Poisson integrals of functions from H_ω

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JOURNAL OF approximation THEORY 2011年第11期163卷 1692-1706页

作者： Serdyuk, A. S. Sokolenko, I. V. Ukrainian Natl Acad Sci Inst Math UA-01601 Kiev 4 Ukraine

We find asymptotic formulas for the least upper bounds of approximation in the metric of the space C by using a linear method U*(n) for classes of Poisson integrals of continuous 2 pi-periodic functions in the case where their moduli of continuity do not exceed fixed convex majorants. On the basis of these results, we obtain asymptotic formulas for the best uniform approximations by trigonometric polynomials and, under some restrictions, asymptotic formulas for Kolmogorov widths of these classes in the uniform metric. (C) 2011 Elsevier Inc. All rights reserved.

关键词： Poisson integral Modulus of continuity Best approximation linear approximation method Kolmogorov-Nikol'skii problem Kolmogorov width

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