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Sequential ensemble optimization based on general surrogate model prediction variance and its application on engine acceleration schedule design

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Chinese Journal of Aeronautics 2021年第8期34卷 16-33页

作者： Yifan YE Zhanxue WANG xiaobo zhang Shannxi Key Laboratory of Internal Aerodynamic in Aero-Engine School of Power and EnergyNorthwestern Polytechnical UniversityXi'an 710072China

The Efficient Global Optimization(EGO)algorithm has been widely used in the numerical design optimization of engineering ***,the need for an uncertainty estimator limits the selection of a surrogate *** this paper,a Sequential Ensemble Optimization(SEO)algorithm based on the ensemble model is *** the proposed algorithm,there is no limitation on the selection of an individual surrogate ***,the SEO is built based on the EGO by extending the EGO algorithm so that it can be used in combination with the ensemble ***,a new uncertainty estimator for any surrogate model named the General Uncertainty Estimator(GUE)is *** performance of the proposed SEO algorithm is verified by the simulations using ten well-known mathematical functions with varying *** results show that the proposed SEO algorithm performs better than the traditional EGO algorithm in terms of both the final optimization results and the convergence ***,the proposed algorithm is applied to the global optimization control for turbo-fan engine acceleration schedule design.

关键词： Cross-validation Efficient global optimization Engine acceleration schedule design Ensemble of surrogate models Gas turbine engine Optimization methods Surrogate-based optimization

Effects of Nd on microstructure and mechanical properties of as-cast Mg-12Gd-2Zn-xNd-0.4Zr alloys with stacking faults

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International Journal of Minerals,Metallurgy and Materials 2022年第8期29卷 1570-1577页

作者： Lixin Hong Rongxiang Wang xiaobo zhang School of Materials Science and Engineering Nanjing Institute of TechnologyNanjing 211167China Jiangsu Key Laboratory of Advanced Structural Materials and Application Technology Nanjing 211167China

In order to study the effects of Nd addition on microstructure and mechanical properties of Mg-Gd-Zn-Zr alloys,the microstruc-ture and mechanical properties of the as-cast Mg-12Gd-2Zn-xNd-0.4Zr(x=0,0.5wt%,and 1wt%)alloys were investigated by using optical microscope,scanning electron microscope,X-ray diffractometer,nano indentation tester,microhardness tester,and tensile testing *** results show that the microstructures mainly consist ofα-Mg matrix,eutectic phase,and stacking *** addition of Nd plays a significant role in grain refinement and uniform *** tensile yield strength and microhardness increase but the compression yield strength decreases with increasing Nd addition,leading to weakening tension-compression yield asymmetry in reverse of the Mg-12Gd-2Zn-xNd-0.4Zr *** highest ultimate tensile strength(194 MPa)and ultimate compression strength(397 MPa)are obtained with 1wt%Nd addition of the alloy.

关键词： magnesium alloy neodymium microstructure stacking fault mechanical properties

Development of Geothermal Resources in China: A Review

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Journal of Earth Science 2018年第2期29卷 452-467页

作者： xiaobo zhang Qinhong Hu School of Environmental Studies State Key Laboratory of Biogeology and Environmental Geology China University of Geosciences Department of Earth and Environmental Sciences University of Texas at Arlington

Geothermal resources in China are distributed throughout the country, with hydrother- real systems of high temperature in the Tibet Autonomous Region, Yunnan Province and Taiwan Island and hydrothermal systems of low-medium temperature mainly in various sedimentary basins. Devel- opment and exploration of geothermal energy in China are below expectations. The purpose of this study is to comparatively review the characteristics （geology, hydrogeology, hydrochemistry and geo- physical data） of typical hydrothermal fields/areas and suggest development and utilization approaches in the future. Hydrothermal systems formed by mountain Hfting contain a considerable amount of en- ergy for geothermal power generation, especially in the Tibet Autonomous Region, Yunnan Province and Taiwan Island. However, geothermal water in the Tatun geothermal field has high TDS （total dis- solved solids）, an issue that requires more research to resolve this problem for power generation. The large storage of geothermal resources has been investigated in Meso-Cenozoic sedimentary basins; it is basically used for heating, bathing or greenhouse plantation. Moreover, hydrothermal resources of low-medium temperature can also be used in binary power plants. Although the enhanced geothermal systems （EGS） in China are promising, the resources have not yet been commercially exploited, because the emerging technologies （hydraulic fracturing） and concerns over environmental impacts （induced miero-seismicity） lead to slow development. On the contrary, shallow geothermal energy has been di- rectly utilized mainly for heating and cooling buildings. Cities like Beijing, Tianjin and Shenyang have established a series of ground-source heat-pump systems, which has led to a massive reduction of CO2 emission of 19.87×10^6 t.

关键词： geothermal energy potential exploitation and utilization China.

Stress corrosion cracking of magnesium alloys:A review

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Journal of Magnesium and Alloys 2023年第6期11卷 1906-1930页

作者： Jiahao Jiang Xue Geng xiaobo zhang School of Materials Science and Engineering Nanjing Institute of TechnologyNanjing 211167China Jiangsu Key Laboratory of Advanced Structural Materials and Application Technology Nanjing 211167China

Magnesium(Mg)alloys have been widely used in automobile,aviation,computer,and other fields due to their lightweight,high specific strength and stiffness,low pollution,and good electromagnetic shielding ***,the chemical stability of Mg alloys is poor,especially in the corrosive medium environment with high stress corrosion sensitivity,which causes sudden damage to structural components and restricts their application *** recent years,owing to the increasing failure rate of engineering structures caused by stress corrosion of Mg alloys,it has become necessary to understand and pay more attention to the stress corrosion cracking(SCC)behavior of Mg *** this paper,the SCC mechanisms and test methods of Mg alloys have been *** recent research progress on SCC of Mg alloys has been reviewed from the aspects of alloying,preparation process,surface modification,corrosive medium,and strain *** importantly,future research trends in the field of SCC of Mg alloys have also been proposed.

关键词： Magnesium alloys Stress corrosion cracking Alloying Preparation process Corrosion media Surface treatment

Recent developments on corrosion behaviors of Mg alloys with stacking fault or long period stacking ordered structures

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Journal of Magnesium and Alloys 2021年第4期9卷 1124-1148页

作者： Yujin Nie Jianwei Dai Xuan Li xiaobo zhang School of Materials Science and Engineering Nanjing Institute of TechnologyNanjing 211167China Jiangsu Key Laboratory of Advanced Structural Materials and Application Technology Nanjing 211167China

Corrosion is one of the most drawbacks which restricts the wide applications of Mg *** the last decade,the corrosion behaviors of Mg alloys with stacking fault(SF)and/or long period stacking ordered(LPSO)structures have obtained increasing ***,the corrosion mechanism of the SF–or LPSO–containing Mg alloys has not been well illustrated and even reverse results have been *** this paper,we have reviewed recent reports on corrosion behaviors of SF–or LPSO–containing Mg alloys to better clarify and understand the significance and ***,some deficiencies are presented and advises are proposed for the development of corrosion resistant Mg alloys with SF or LPSO structures.

关键词： Magnesium alloys Corrosion behavior Stacking fault Long period stacking ordered

Effects of Load on Dry Sliding Wear Behavior of Mg–Gd–Zn–Zr Alloys

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Journal of Materials Science & Technology 2017年第7期33卷 645-651页

作者： Jie zhang xiaobo zhang Qinghua Liu Shujie Yang zhangzhong Wang School of Materials Science and Engineering Nanjing Institute of TechnologYNanjing 211167China Jiangsu-Key Laboratory of Advanced Structural Materials and APplication Technology Nanjing 211167China

Dry sliding wear tests on as-cast and T6-treated Mg-3Gd-1Zn-0.4Zr（wt%, GZ31K） and Mg-6Gd-1Zn-0.4Zr（wt%, GZ61K） alloys were performed using a ball-on-disk configuration at room temperature. Friction coefficient and wear rate of the alloys were measured under three different applied loads（50 N, 100 N, and 200 N, respectively）. Worn surface morphologies were analyzed using a scanning electron microscope（SEM） coupled with an energy dispersive spectrometer（EDS）. It is found that the friction coefficient of the alloys decreases with increasing load, except the as-cast GZ61 K. The wear rates of the as-cast Mg-Gd-Zn-Zr alloys increase with the increase of the load. However, the wear rates of the T6-treated Mg-Gd-Zn-Zr alloys first increase because of the participation of a large amount of needle-like precipitates, but then decline due to obvious work hardening. The wear mechanisms of abrasion, plastic deformation, oxidation, adhesion and delamination are detected. Abrasion dominates the wear mechanism under the low load; whereas, adhesion is the main wear mechanism under intermediate load, and plastic deformation has great effect on the wear rate under high applied load.

关键词： Magnesium alloys Applied load Wear and friction Wear mechanism

An efficient algorithm for calculating Profust failure probability

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Chinese Journal of Aeronautics 2019年第7期32卷 1657-1666页

作者： xiaobo zhang Zhenzhou LYU Kaixuan FENG Chunyan LING School of Aeronautics Northwestern Polytechnical University

For efficiently estimating the Profust failure probability based on probability input variables and fuzzy-state assumption, a General Performance Function(GPF) expression is established under the strict mathematical derivation for the Profust reliability model. By constructing the GPF,the calculation of the Profust failure probability can be transformed into the calculation of the traditional failure probability. Then various existing methods for the traditional failure probability can be used to estimate the Profust failure probability. Due to the high efficiency of the Adaptive Kriging(AK) model and the universality of the Monte Carlo Simulation(MCS), AK inserted MCS(abbreviated as AK-MCS) has been proven to be an efficient method for estimating the failure probability. Therefore, the AK-MCS combined with the GPF(abbreviated as AK-MCS + GPF)is proposed for estimating Profust failure probability. The proposed method greatly reduces the computational cost while ensuring the accuracy. Finally, four examples are given to validate the proposed AK-MCS + GPF. The results of the examples show the rationality and the efficiency of the proposed AK-MCS + GPF.

关键词： Failure probability Fuzzy-state assumption General performance function Kriging model Profust reliability Reliability

A survey on one-bit compressed sensing： theory and applications

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Frontiers of Computer Science 2018年第2期12卷 217-230页

作者： Zhilin LI Wenbo XU xiaobo zhang Jiaru LIN Key Lab of Universal Wireless Communications Ministry of Education Beijing University of Posts and Telecommunications Beijing 100876 China

In the past few decades, with the growing popularity of compressed sensing （CS） in the signal processing field, the quantization step in CS has received significant attention. Current research generally considers multi-bit quantization. For systems employing quantization with a sufficient number of bits, a sparse signal can be reliably recovered using various CS reconstruction algorithms. Recently, many researchers have begun studying the one- bit quantization case for CS. As an extreme case of CS, one- bit CS preserves only the sign information of measurements, which reduces storage costs and hardware complexity. By treating one-bit measurements as sign constraints, it has been shown that sparse signals can be recovered using certain reconstruction algorithms with a high probability. Based on the merits of one-bit CS, it has been widely applied to many fields, such as radar, source location, spectrum sensing, and wireless sensing network. In this paper, the characteristics of one-bit CS and related works are reviewed. First, the framework of one-bit CS is introduced. Next, we summarize existing reconstruction algorithms. Additionally, some extensions and practical applications of one-bit CS are categorized and discussed. Finally, our conclusions and the further research topics are summarized.

关键词： compressed sensing one-bit quantization sign information support consistency

Characterization of DNA polymerase δ from deep-sea hydrothermal vent shrimp Rimicaris exoculata

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Acta Oceanologica Sinica 2021年第8期40卷 168-175页

作者： Wenlin Wu Hongyun Li Tiantian Ma xiaobo zhang Fujian Province Key Laboratory for the Development of Bioactive Material from Marine Algae Quanzhou Normal UniversityQuanzhou 362000China College of Life Sciences Zhejiang UniversityHangzhou 310058China

DNA polymerase δ(Polδ)plays a crucial and versatile role in DNA replication and DNA repair *** shrimp Rimicaris exoculata is the primary megafaunal community living in hydrothermal *** this study,the Polδfrom shrimp Rimicaris exoculata was cloned,expressed and *** results showed that the Polδcatalytic subunit(POLD1),852 amino acids in length,shared high homology with crayfish Procambarus clarkii and shrimp Oratosquilla *** recombinant POLD1 expressed in Escherichia coli showed that the enzyme was active in a range of 20℃ to 40℃ with an optimum temperature at 25℃ and in a wide range of p H with an optimum at pH *** activities of POLD1 were significantly enhanced in the presence of Triton-X 100,Tween 20 and Mn^(2+).The K_(m)(dNTP)value of POLD1 was 4.7μmol/*** present study would be helpful to reveal the characterization of Polδof deep-sea vent animals.

关键词： deep-sea hydrothermal vent Rimicaris exoculata DNA polymeraseδ characterization