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The influence of the wake of a flapping wing on the production of aerodynamic forces

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Acta Mechanica Sinica 2005年第5期21卷 411-418页

作者： Jianghao wu mao Sun Ministry-of-Education Key Laboratory of Fluid Mechanics Institute of Fluid Mechanics Beihang University Beijing 100083 China

The effect of the wake of previous strokes on the aerodynamic forces of a flapping model insect wing is studied using the method of computational fluid dynamics. The wake effect is isolated by comparing the forces and flows of the starting stroke （when the wake has not developed） with those of a later stroke （when the wake has developed）. The following has been shown. （1） The wake effect may increase or decrease the lift and drag at the beginning of a half-stroke （downstroke or upstroke）, depending on the wing kinematics at stroke reversal. The reason for this is that at the beginning of the half-stroke, the wing “impinges” on the spanwise vorticity generated by the wing during stroke reversal and the distribution of the vorticity is sensitive to the wing kinematics at stroke reversal. （2） The wake effect decreases the lift and increases the drag in the rest part of the half-stroke. This is because the wing moves in a downwash field induced by previous half-stroke＇s starting vortex, tip vortices and attached leading edge vortex （these vortices form a downwash producing vortex ring）. （3） The wake effect decreases the mean lift by 6%-18% （depending on wing kinematics at stroke reversal） and slightly increases the mean drag. Therefore, it is detrimental to the aerodynamic performance of the flapping wing.

关键词： Insect. Flapping. Unsteady aerodynamics.Wing/wake interaction. CFD analysis

NEW DESIGN METHOD FOR HYPOID GEARS

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Chinese Journal of Mechanical Engineering 2005年第3期18卷 325-328页

作者： Su Zhijiang wu Xutang mao Shimin School of Mechanical Engineering Xi＇an Jiaotong University Xi＇an 710049 China

A digital model is presented for the purpose of design, manufacture and measurement of hypoid gear, based on the non-uniform rational B-spline surface （NURBS） method. The digital model and the function-oriented active design technique are combined to form a new design method for hypoid gears. The method is well adaptable to CNC bevel gear cutting machines and CNC-controlled gear inspection machines, and can be used to create the initial machine tool cutting location data or program measurement path. The presented example verifies the method is correct.

关键词： Hypoid gear Digital design Non-uniform rational B-spline surface (NURBS) Function-oriented active design

Electromagnetic and Microwave Absorbing Properties of Co-Substituted Nickel-Zinc Ferrite

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Journal of Rare Earths 2004年第Z2期22卷 167-169页

作者： wu Laying mao Changhui Yang Zhimin Su Lanying Research Center of Energy Materials & Technology General Research Institute for Non-Ferrous MetalsBeijing 100088China Research Center of Energy Materials & TechnologyGeneral Research Institute for Non-Ferrous MetalsBeijing 100088China Research Center of Energy Materials & TechnologyGeneral Research Institute for Non-Ferrous MetalsBeijing 100088China Research Center of Energy Materials & TechnologyGeneral Research Institute for Non-Ferrous MetalsBeijing 100088China

Co-substituted Ni-Zn ferrite was prepared by a chemical codeposition. The electromagnetic properties, zero reflection conditions and simulated reflection losses of the samples were investigated. As a result, it is found that with Co contents rising, the saturation magnetization (Ms) shows a tendency of decrease, while coercivity (Hc) varies clearly. In addition, Ni-Zn ferrite with different cobalt content can meet zero reflection conditions. And the reflection loss calculation indicates that with the increase of cobalt contents, the reflection loss peak moves to high frequenc; moreover, to increase Co content more than 0.15, and the absorption intensity as well as the absorbing band of microwave absorber are enhanced obviously.

关键词： Co-substituted Ni-Zn ferrite zero reflection conditions magnetic properties

Retrieval of urban slow deformation using the multi-baseline DInSAR technique

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Chinese Science Bulletin 2008年第23期53卷 3705-3714页

作者： wu mao ZHANG Hong WANG Chao TANG YiXian wu HongAn The State Key Laboratory of Remote Sensing Science Sponsored Jointly by the Institute of Remote Sensing Applications of Chinese Academy of Sciences and Beijing Normal University Beijing 100101 China Center for Earth Observation and Digital Earth Chinese Academy of Sciences Beijing 100086 China Graduate University of Chinese Academy of Sciences Beijing 100049 China

The investigation of slow displacement in urban areas using the multi-baseline DInSAR technique has been a hot research topic in the field of DInSAR. The basic flow of this technique includes several steps such as the combination of interferometric image pairs, generation of differential interferograms, selection of high coherent points, generation of the Delaunay triangular network, calculation and integration of increments in network, unwrapping and calibration of the residual phase, and the estimation of both atmospheric and nonlinear displacement phase. Among these steps, the calculation of increments is the key to retrieve linear displacement, while unwrapping and calibration of the residual phase are the keys to retrieve nonlinear displacement. In order to improve the performance of these two steps, this paper proposes a modified model coherence function for increments estimation, and a triangular "circle" algorithm to deal with phase unwrapping and calibration. Based on the above algorithms, the subsidence of Suzhou City is investigated using 24 ERS scenes from February 1993 to December 2000. The results show that the linear subsidence velocity of the most urban area is about -20 to -30 mm/a during the time, with a yearly decrease in velocity. The displacement seems to be stable after 2000. Leveling data validate our results and demonstrate the reliability of the algorithm.

关键词：基线 DInSAR 地表面变形遥感技术

Preparation,crystallization,and wetting of ZnO-Al_2O_3-B_2O_3-SiO_2 glass-ceramics for sealing to Kovar

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International Journal of Minerals,Metallurgy and Materials 2009年第5期16卷 586-591页

作者： mao wu Xin-bo He Zhuo-shen Shen Xuan-hui Qu School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China

A novel type of ZnO-Al2O3-B2O3-SiO2 glass-ceramics sealing to Kovar in electronic packaging was developed, whose thermal expansion coefficient and electrical resistance are 5.2× 10^-6/℃ and over 1×10^13 Ω·cm, respectively. The major crystalline phases in the glass-ceramic seals were ZnAl2O4, ZnB2O4, and NaSiAl2O4. The dielectric resistance of the glass-ceramic could be remarkably enhanced through the control of alkali metal ions into crystal lattices. It was found that crystallization happened first on the surface of the sample, leaving the amorphous phase in the inner, which made the glass suitable for sealing. The glass-ceramic showed better wetting on the Kovar surface, and sealing atmosphere and temperature had great effect on the wetting angle. Strong interracial bonding was obtained, which was mainly attributed to the interracial reaction between SiO2 and FeO or Fe3O4.

关键词： electronic packaging materials glass-ceramic crystallization wetting sealing

Experimental investigation on the time-delay signature of chaotic output from a 1550 nm VCSEL subject to FBG feedback

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Photonics Research 2017年第1期5卷 6-10页

作者： Zhu-Qiang Zhong Zheng-mao wu Guang-Qiong Xia School of Physical Science and Technology Southwest University

The time-delay signature(TDS) of chaos output in a 1550 nm vertical-cavity surface-emitting laser(VCSEL) subject to fiber Bragg grating(FBG) feedback is investigated experimentally. Autocorrelation function(ACF) and mutual information(MI) are used for quantitatively identifying the TDS of chaos. For various bias currents, the TDS evolution with the feedback strength is different, as the FBG provides wavelength-selective feedback. Furthermore,based on the TDS map of the FBG feedback VCSEL(FBGF-VCSEL) in the parameter space of feedback strength and bias current, the optimal TDS suppression regions, where the dominant polarization mode of FBGF-VCSEL locates at the edge of the main lobe of FBG reflection spectrum, have been determined. Finally, for comparative purpose,the TDS of chaos in mirror feedback VCSEL(MF-VCSEL) also has been presented, and the results show that an FBGF-VCSEL possesses better TDS suppression performance than an MF-VCSEL.

关键词： VCSEL Experimental investigation on the time-delay signature of chaotic output from a 1550 nm VCSEL subject to FBG feedback FBG time

Iterative physical optics method based on efficient occlusion judgment with bounding volume hierarchy technology

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Journal of Electronic Science and Technology 2024年第1期22卷 1-12页

作者： Yang Su Yu-mao wu Jun Hu Key Laboratory for Information Science of Electromagnetic Waves(MoE) School of Information Science and TechnologyFudan UniversityShanghai200433China School of Electronic Science and Engineering University of Electronic Science and Technology of ChinaChengdu611731China

This paper builds a binary tree for the target based on the bounding volume hierarchy technology,thereby achieving strict acceleration of the shadow judgment process and reducing the computational complexity from the original O(N^(3))to O(N^(2)logN).Numerical results show that the proposed method is more efficient than the traditional *** is verified in multiple examples that the proposed method can complete the convergence of the ***,the proposed method avoids the error of judging the lit-shadow relationship based on the normal vector,which is beneficial to current iteration and *** with the brute force method,the current method can improve the simulation efficiency by 2 orders of *** proposed method is more suitable for scattering problems in electrically large cavities and complex scenarios.

关键词： Bounding volume hierarchy Cavity scattering Iterative physical optics(IPO)

Fabrication of micro-fine high Nb-containing TiAl alloyed powders by fluidized bed jet milling

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Rare Metals 2012年第1期31卷 1-6页

作者： Lu, Xin Zhu, Langping Liu, Chengcheng Zhang, Lin wu, mao Qu, Xuanhui State Key Laboratory for Advanced Meials and Materials School of Materials Science and Engineeing University of Science and Technology Beijing Beijing 100083 China

A fluidized bed jet milling process was used to make micro-fine high Nb-containing TiAl alloyed powders from the chippings obtained by crushing the Ti-45Al-8.5Nb-(W,B,Y) *** influences of classifier frequency on powder characteristics were *** results show that the powders with controlled average particle size can be prepared on a large *** powders with different sizes are all dominated by γ with aminor amount of α*** particle size significantly decreases with the classifier frequency *** a classifier frequency higher than 38 Hz,the average particle size of the ground powders is lower than 25μ*** powders are composed of two differ-ent sizes of particles:shaped particles and some clastic particles,and both particle sizes meet the log-normal *** the classifier frequency increasing,the both sizes decrease;meanwhile,the proportion of the clastic particles gradually increases,and the size distribution span value of the ground powders increases correspondingly.

关键词： high Nb-containing TiAl alloys powder preparation fluidized bed jet milling powder characteristics classifier frequency

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温肾通督方促进小鼠脊髓损伤的修复

中国组织工程研究 2025年第6期29卷 1118-1126页

作者：赵瑞华陈思娴郭杨石磊吴承杰吴毛杨光露张昊恒马勇南京中医药大学中医学院·中西医结合学院江苏省南京市210023 南京中医药大学骨伤修复与重建新技术实验室江苏省南京市210023 南京中医药大学无锡附属医院江苏省中医退行性骨关节病临床医学创新中心江苏省无锡市214071

背景:前期研究证实,温肾通督方可通过抑制脾脏B细胞焦亡、促进微血管内皮细胞吞噬髓鞘碎片、影响小胶质细胞迁移和浸润、促进受损神经元恢复、降低脊髓损伤后神经元凋亡等促进脊髓损伤恢复,但其机制尚不明确。目的:探讨温肾通督方对脊... 详细信息

背景:前期研究证实,温肾通督方可通过抑制脾脏B细胞焦亡、促进微血管内皮细胞吞噬髓鞘碎片、影响小胶质细胞迁移和浸润、促进受损神经元恢复、降低脊髓损伤后神经元凋亡等促进脊髓损伤恢复,但其机制尚不明确。目的:探讨温肾通督方对脊髓损伤小鼠髓系细胞触发受体2(triggering receptor expressed on myeloid cells 2,TREM2)及PI3K/Akt信号通路的影响。方法:取36只C57BL/6小鼠,采用随机数字表法分为假手术组、模型组、温肾通督方组,每组12只。模型组与温肾通督方组采用改良Allen’s法制备小鼠T10脊髓损伤模型,造模后第1天,温肾通督方组灌胃给予温肾通督方,假手术组、模型组灌胃给予生理盐水,每天1次,连续给药28 d。给药期间,通过BMS评分和斜板实验评价各组小鼠运动功能;造模后第7,28天,采用苏木精-伊红染色观察各组小鼠脊髓组织病理变化,免疫荧光染色双标法检测脊髓组织离子化钙结合适配分子1(ionized calcium binding adaptor molecule 1,IBA1)、TREM2蛋白表达,Western blot检测脊髓组织TREM2、PI3K、p-PI3K、Akt、p-Akt、Bcl2、Bax、Caspase3蛋白表达。结果与结论:①BMS评分和斜板实验结果表明,脊髓损伤造模后小鼠后肢运动功能下降,而经过温肾通督方治疗后,脊髓损伤小鼠后肢运动功能明显提升。②苏木精-伊红染色结果显示,与模型组比较,温肾通督方小鼠脊髓组织病理结构明显改善,表现为背侧白质和神经元萎缩程度、细胞质空泡化降低及炎性细胞浸润减少等。③免疫荧光染色结果显示,造模后第7天,模型组IBA1、TREM2蛋白表达均低于假手术组(P<0.05),温肾通督方组IBA1、TREM2蛋白表达均高于模型组(P<0.05);造模后第28天,模型组TREM2蛋白表达低于假手术组(P<0.05),温肾通督方组小鼠脊髓组织中的TREM2蛋白表达高于模型组(P<0.05)。④Western blot检测结果表明,造模后第7天,与假手术组相比,模型组TREM2、Akt蛋白表达及Bcl2/Bax比值降低(P<0.05),p-Akt、Bax蛋白表达及p-Akt/Akt比值升高(P<0.05);与模型组相比,温肾通督方组TREM2、PI3K、p-PI3K、Akt、p-Akt、Bcl2蛋白表达及p-PI3K/PI3K、p-Akt/Ak、Bcl2/Bax比值升高(P<0.05),Bax、Caspase3蛋白表达降低(P<0.05)。造模后第28天,与假手术组相比,模型组TREM2、PI3K、p-PI3K、Akt、p-Akt、Bcl2蛋白表达及Bcl2/Bax比值降低(P<0.05),Bax蛋白表达升高(P<0.05);与模型组相比,温肾通督方组TREM2、PI3K、Akt、p-Akt、Bcl2蛋白表达及Bcl2/Bax比值升高(P<0.05),Bax蛋白表达降低(P<0.05)。⑤结果表明,温肾通督方可能通过上调小胶质细胞TREM2激活PI3K/Akt信号通路,抑制神经元凋亡发挥神经保护作用,进而促进脊髓损伤的修复。

关键词：脊髓损伤温肾通督方小胶质细胞髓系细胞触发受体2 PI3K/Akt信号通路