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Performance analysis and flow mechanism of channel wing considering propeller slipstream

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Chinese Journal of Aeronautics 2023年第11期36卷 165-184页

作者： Xiaoxuan MENG Ziyi XU min chang Junqiang BAI School of Aeronautics Northwestern Polytechnical UniversityXi’an 710072China Unmanned System Research Institute Northwestern Polytechnical UniversityXi’an 710072China Shenzhen Research Institude of Northwestern Polytechnical University Shenzhen 518057China

The development of the Urban Air Mobility concept has proposed stringent requirements for the fixed-wing vehicle’s Short/Vertical Take-Off and Landing(S/VTOL)*** its lift-enhancing impact,the channel wing,can improve aircraft low-speed performance and Short Take-Off and Landing(STOL)*** is critical for the performance analysis and flow mechanism study of a channel wing that considers the influence of propeller slipstream to guide the design of S/VTOL *** law and mechanism for the effect of the enclosing angle of the arc wing,the phase angle of the propeller,the tip clearance,the rotational speed and the chordwise position of the propeller on the channel wing are explored utilizing the quasi-steady multi reference frame method.A channel wing with a larger enclosing angle has a better ability to enhance lift and reduce drag using propeller *** effect of propeller phase angle on channel wing aerodynamic forces is periodic and *** propeller rotational speed is helpful to enhance lift and resist flow separation for channel *** can reduce drag for tractor configuration but increase drag for pusher ***,the nose-down pitching moment of a channel wing will grow dramatically,making longitudinal trimming in aircraft layout design challenging.

关键词： Channel wing Computational fluid dynamics Flow interactions Mechanisms Slipstream effect

Dynamic recrystallization behaviour of H13-mod steel

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Journal of Iron and Steel Research International 2020年第9期27卷 1073-1086页

作者： chang-min Li Yuan-biao Tan Fei Zhao College of Materials and Metallurgy Guizhou UniversityGuiyang 550025GuizhouChina

H13-mod steel developed after optimizing the composition and heat treatment process exhibits good hardness and impact toughness and can be used as a shield machine *** on the Avrami equation,the dynamic recrystallization(DRX)behaviour of H13-mod steel during hot compression was studied in the temperature of 900-1150°C and strain rate ranges of 0.01-10 s^-1.A DRX model and finite element software were used to study DRX behaviour of H13-mod *** DRX was found at both low and high strain *** backscatter diffraction and optical microscopy analyses found different DRX nucleation mechanisms at low and high strain rates under different *** a low strain rate,the nucleation was dominated by the strain-induced grain boundary migration,whereas the subgrain coalescence mechanism was dominant at a high strain ***,dynamic recovery occurred in both *** addition,it was easier to obtain small and uniform equiaxed grains at high strain rates than at low strain rates.

关键词： H13-mod steel Dynamic recrystallization Dynamic recrystallization volume fraction model Finite element simulation Nucleation mechanism

Cuticle and skin cell walls have common and unique roles in grape berry splitting

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Horticulture Research 2021年第1期8卷 2428-2438页

作者： Ben-min chang Markus Keller Department of Horticulture Irrigated Agriculture Research and Extension CenterWashington State UniversityProsserWAUSA

The skin protects a fruit from environmental stresses and supports the fruit’s *** of the skin leads to fruit splitting and may compromise commercial production for fruit *** mechanical properties of the cuticle and skin cell walls might influence the splitting susceptibility of fleshy *** shell theory and fracture mechanics were utilized in this study to target the potential factors contributing to splitting *** study analyzed the structure of the cuticle and epidermis in ripening grape berries and examined the temporal dynamics of berry *** waxes were partially removed,and skin cell walls were manipulated using wall stiffening and loosening solutions that altered reactions involving hydrogen peroxide.A more than twofold difference in cuticle thickness among grape cultivars did not account for their differences in splitting ***,while removing predominantly epicuticular wax did not alter the berries’splitting resistance,their surface appearance and increasing yield strength following partial wax removal support the notion that cuticular waxes contribute to berry mechanical *** berries in H 2 O 2-based cell wall loosening solutions increased the splitting probability and accelerated berry splitting,whereas cell wall stiffening solutions decreased the splitting probability and delayed berry *** results showed that both cuticle and skin cell walls contribute to the mechanical properties of grape berries and to their splitting *** results also suggest that the two current explanations for fruit splitting,the critical turgor model and the zipper model,should be viewed as complementary rather than incompatible.

关键词： walls splitting Cut

Devonian reef development and strata-bound ore deposits in South China

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Journal of Palaeogeography 2021年第4期10卷 571-583页

作者： chang-min Yu Yue Li Kun Liang Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and Paleoenvironment Chinese Academy of SciencesNanjing 210008Jiangsu ProvinceChina State Key Laboratory of Palaeobiology and Stratigraphy Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and PaleoenvironmentChinese Academy of SciencesNanjing 210008Jiangsu ProvinceChina

This study focuses on the close association between Devonian reefs and the strata-bound ore deposits in South *** the first time,the development of Devonian reefs was subdivided into three stages,respectively as the initial,succeeding and peak stages,and its evolution model is *** Dachang,Nandan county,Guangxi Zhuang Autonomous Region(Guangxi for short),a large-scale strata-bound ore deposit formed in a Devonian reef,which was affected by marine volcanic activities and Mesozoic magmatic *** reef-building reached its peak stage at the Givetian,indicating a large-scale build-up of reef and inter-reef *** central-eastern Hunan Province,the strata-bound ore deposits belong to low-temperature ore-types without later magmatic intrusions or volcanic *** Hunan Province as well as many other localities in South China,the Givetian reefs played important roles in mobilizing ore-forming materials from the surrounding pre-Devonian rocks,providing spaces and passages for transporting hydrothermal fluid,and progressing mineralization and accumulation of ore-forming materials.

关键词： Strata-bound ore deposit Reef Inter-reef depression South China

Effect of Hot Deformation on Formation and Growth of Thermal Fatigue Crackin Chromium Wear Resistant Cast Iron

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Journal of Iron and Steel Research International 2006年第1期13卷 36-39页

作者： chang Li-min LIU Jian-hua Analysis and Measure Center Jilin Normal University Siping 136000 Jilin China Key Laboratory of Metastable Materials Science and Technology Yanshan University Qinhuangdao 066004 Hebei China

The formation and growth of thermal fatigue crack in chromium wear resistant cast iron was investigated, and the effect of hot deformation on the crack was analyzed by means of optical microscope and scanning electron microscope and high frequency induction thermal fatigue tester. The results show that eutectic carbide is the main location and passage for initiation and extension of thermal fatigue cracks, hot deformation can improve the eutectic carbiders morphology and distribution, inhibit the generation and propagation of thermal fatigue cracks. In the experiment, the propagation rate of thermal fatigue crack reduces with the quantity of hot deformation increasing, which was analyzed in the point view of the activation energy of crack propagation.

关键词： hot deformation chromium wear resistant cast iron thermal fatigue crack

Influence of X-ray Powder Diffraction Instrument Error on Crystalline Structure Analysis

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Chinese Journal of Structural Chemistry 2005年第6期24卷 691-695页

作者： HUANGQing-ming YUJian-chang WANGYun-min WUWan-Guo InstrumentationAnalysisandMeasurementCenterofFuzhouUniversity FuzhouFujiang350002China

Standard mica was used to correct the X-ray powder diffraction instrument error and mathematic methods were employed to find the correction equation. By analyzing mullite sample and comparing the corrected and uncorrected analysis results we found the former is obviously more reasonable. So the conclusion is that the X-ray powder diffraction instrument error greatly affects the crystalline structure analysis, and the above method is convenient and effective for the correction of instrument error.

关键词： instrument error structure analysis polycrystalline diffraction

Aerodynamic performance of a low-Reynolds UAV with leading-edge protuberances inspired by humpback whale flippers

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Chinese Journal of Aeronautics 2021年第5期34卷 415-424页

作者： Yang ZHANG Xu ZHANG Yi LI min chang Jiakuan XU State Key Laboratory for Strength and Vibration of Mechanical Structures Xi'an Jiaotong UniversityXi'an 710049China School of Aeronautics Northwestern Polytechnical UniversityXi'an 710072China Unmanned System Research Institute Northwestern Poly technical UniversityXi'an 710072China

The aerodynamic forces and flowfield on a delta-wing Unmanned Aerial Vehicle(UAV)with specific airfoil are studied *** leading-edge protuberances inspired from the flippers of the humpback whale is introduced in present work to watch its effect on stall delaying and drag *** installing factors,which are amplitude and wavelength of the protuberances,are considered to study the interaction of leading-edge variation and de-tached *** changes in both amplitude and wavelength are investigated ***,the modified models have larger stall angle of attack than that of the baseline model;the difference exists in the attainable lift coefficient and drag reduction.

关键词： Flippers Flow control Humpback whale RANS Stall delay UAV

Aerodynamic Performance of Three Flapping Wings with Unequal Spacing in Tandem Formation

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Journal of Bionic Engineering 2024年第4期21卷 1662-1676页

作者： min chang Ziyi Xu Zengshuang Chen Li Li Xueguang Meng Unmanned System Research Institute National Key Laboratory of Unmanned Aerial Vehicle TechnologyNorthwestern Polytechnical UniversityXi’an710072People’s Republic of China State Key Laboratory for Strength and Vibration of Mechanical Structures School of Aerospace EngineeringXi’an Jiaotong UniversityXi’an710049People’s Republic of China Xi’an Aeronautics Computing Technique Research Institute Aviation Industry Corporation of ChinaXi’an710076People’s Republic of China

To better understand the aerodynamic reasons for highly organized movements of flying organisms,the three-flapping wing system in tandem formation was studied numerically in this *** from previous relevant studies on the multiple flapping wings that are equally spaced,this study emphasizes the impact of unequal spacing between individuals on the aerodynamics of each individual wing as well as the whole *** is found that swapping the distance between the first and second wing with the distance between the second wing and the rearmost wing does not affect the overall aerodynamic performance,but significantly changes the distribution of aerodynamic benefits across each *** the whole flapping cycle,three effects are at *** narrow channel effect and the downwash effect can promote and weaken the wing lift,respectively,while the wake capture effect can boost the *** also shows that these effects could be manipulated by changing the spacing between adjacent *** findings provide a novel way for flow control in tandem formation flight and are also inspiring for designing the formation flight of bionic aircraft.

关键词： Three flapping wings Unequal spacing Aerodynamic performance Tandem formation

minimally invasive surgery for submucosal(subepithelial) tumors of the stomach

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World Journal of Gastroenterology 2014年第36期20卷 13035-13043页

作者： chang min Lee Hyung-Ho Kim Department of Surgery Seoul National University Bundang Hospital Seongnam 463-707 South Korea Colledge of Medicine Seoul National University Seoul 110-799 South Korea

minimally invasive surgery has become common in the surgical resection of gastrointestinal submucosal tumors(SMTs). The purpose of this article is to review recent trends in minimally invasive surgery for gastric SMTs. Although laparoscopic resection has been main stream of minimally invasive surgery for gastrointestinal SMTs, recent advances in endoscopic procedures now provide various treatment modalities for gastric SMTs. Moreover, investigators have developed several hybrid techniques that include the advantages of both laparoscopic and endoscopic procedure. In addition, several types of reduced port surgeries, modification of conventional laparoscopic procedures, have been recently applied to the surgical resection of SMTs. Meanwhile, robotic surgery for SMTs requires further evidence and improvement.

关键词： minimally invasive Surgery Submucosal tumor Gastrointestinal tract