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Ripple-based matrix modeling and cross-coupling effect analysis of double-input DC-DC Boost converters

Science China(Technological Sciences) 2022年第8期65卷 1878-1890页

作者： ZhanG Hao ren han YI ChuanZhi DONG DaChu State Key Lab of Electrical Insulation&Power Equipment School of Electrical EngineeringXi’an Jiaotong UniversityXi’an 710049China Bosch Automotive Product(Suzhou)Co.Ltd Suzhou 215000China hangzhou Power Supply Company of State Grid Zhejiang Electric Power Co.Ltd Hangzhou 310000China

This paper deals with the modeling and cross-coupling effect analysis in double-input Boost converters with multiplex current control. A ripple-based multiplex current controlled matrix model is proposed to restore the system's high-frequency domain dynamics information and resolve the coexistence problem of the sample-and-hold effect in multiplex current controllers, which significantly improves the resolution of the conventional average model. Based on the proposed model, both sub-harmonic and low-frequency oscillations are identified in terms of stability analysis, and the inherent mechanism of these complicated nonlinear dynamic behavior is revealed, which not only illustrates the origin of the oscillations but also points out the dominant factors in diverse types of instability situation. Besides, cross-coupling effect analysis is performed to study the interaction between the input ports with the help of the Gershgorin band, and the mechanism of the special unbalanced oscillation phenomenon is revealed. Furthermore, the sensitivity analysis approach is used to identify the key parameters with respect to the cross-coupling effect, which provides more design-oriented knowledge for practical engineering. In addition, the benefits of the proposed model are further illustrated through a comparative analysis. Finally, these theoretical results are verified by experimental ones. These results are beneficial to the improvement of performance as well as the understanding of the cross-coupling effect of multi-input converters.

关键词： ripple-based matrix model cross-coupling effect multiplex current control multi-input converter Gershgorin band

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TSR: algorithm of image hole-filling based on three-step repairing

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The Journal of China Universities of Posts and Telecommunications 2022年第5期29卷 83-91页

作者： Li Fucheng Deng Junyong Zhu Yun Luo Jiaying ren han School of Electronic Engineering Xi'an University of Posts and TelecommunicationsXi'an 710121China

In order to solve the hole-filling mismatch problem in virtual view synthesis, a three-step repairing(TSR) algorithm was proposed. Firstly, the image with marked holes is decomposed by the non-subsampled shear wave transform(NSST), which will generate high-/low-frequency sub-images with different resolutions. Then the improved Criminisi algorithm was used to repair the texture information in the high-frequency sub-images, while the improved curvature driven diffusion(CDD) algorithm was used to repair the low-frequency sub-images with the image structure information. Finally, the repaired parts of high-frequency and low-frequency sub-images are synthesized to obtain the final image through inverse NSST. Experiments show that the peak signal-to-noise ratio(PSNR) of the TSR algorithm is improved by an average of 2-3 dB and 1-2 dB compared with the Criminisi algorithm and the nearest neighbor interpolation(NNI) algorithm, respectively.

关键词： virtual view point synthesis hole-filling three-step repairing(TSR) Criminisi algorithm curvature driven diffusions(CDD)algorithm

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Numerical simulation for the initial state of avalanche in polydisperse particle systems

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Chinese Physics B 2024年第2期33卷 405-412页

作者：韩韧李亭迟志鹏杨晖李然 School of Optical-Electrical and Computer Engineering University of Shanghai for Science and TechnologyShanghai 200093China

Numerical simulation is employed to investigate the initial state of avalanche in polydisperse particle systems.Nucleation and propagation processes are illustrated for pentadisperse and triadisperse particle systems,respectively.In these processes,particles involved in the avalanche grow slowly in the early stage and explosively in the later stage,which is clearly different from the continuous and steady growth trend in the monodisperse system.By examining the avalanche propagation,the number growth of particles involved in the avalanche and the slope of the number growth,the initial state can be divided into three stages:T1(nucleation stage),T2(propagation stage),T3(overall avalanche stage).We focus on the characteristics of the avalanche in the T2 stage,and find that propagation distances increase almost linearly in both axial and radial directions in polydisperse systems.We also consider the distribution characteristics of the average coordination number and average velocity for the moving particles.The results support that the polydisperse particle systems are more stable in the T2 stage.

关键词： avalanche initial state polydisperse particle systems propagation

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Micro/nano structured oleophobic agent improving the wellbore stability of shale gas wells

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Petroleum Exploration and Development 2022年第6期49卷 1452-1462页

作者： GENG Yuan SUN Jinsheng CHENG Rongchao QU Yuanzhi ZhanG Zhilei WANG Jianhua WANG ren YAN Zhiyuan ren han WANG Jianlong CNPC Engineering Technology R&D Co.Ltd. Beijing 102206China School of Petroleum Engineering China University of Petroleum(East China)Qingdao 266580China

Through embedding modified nano-silica particles on the surface of polystyrene using the method of Pickering emulsion polymerization,a kind of nano/micro oleophobic agent named OL-1 was developed.The effects of OL-1 on the rock surface properties and its performance in inhibiting the oil phase imbibition into the rock were explored.The performance and mechanisms of OL-1 in improving the wellbore stability of shale gas wells were evaluated and analyzed.OL-1 could absorb on the surface of the shale core to form a membrane with a micro-nano two-stage roughness,making the surface energy of the core decrease to 0.13 mN/m and the contact angle of the white oil on the core surface increase from 16.39°to 153.03°.Compared with the untreated capillary tube,when immersed into 3#white oil,the capillary tube treated by OL-1 had a reversal of capillary pressure from 273.76 Pa to-297.71 Pa,and the oil imbibition height inside the capillary tube decreased from 31 mm above the external liquid level to 33 mm below the external liquid level.The amount of oil invading into the rock core modified by OL-1 decreased by 64.29%compared with the untreated one.The shale core immersed into the oil-based drilling fluids with 1%OL-1 had a porosity reduction rate of only 4.5%.Compared with the core immersed in the drilling fluids without OL-1,the inherent force of the core treated by 1%OL-1 increased by 24.9%,demonstrating that OL-1 could effectively improve the rock mechanical stability by inhibiting oil phase imbibition.

关键词： shale wellbore stability oil-based drilling fluids oleophobic agent micro-nano composites wettability reversal

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最省刻度尺设计的组合差集递推算法

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浙江大学学报（理学版） 2024年第2期51卷 178-185页

作者：唐保祥任韩天水师范学院数学与统计学院甘肃天水741001 华东师范大学数学科学学院上海200062

在长度为n(n≥2为正整数)的直尺上最少刻多少个刻度就能度量1到n的所有长度,这便是至今未解决的最省刻度尺问题。阐明了最省刻度尺与极小优美图之间的关系,给出了计算最省刻度尺的所有最省刻度值的组合差集递推算法,得到长度为3~40的最... 详细信息

在长度为n(n≥2为正整数)的直尺上最少刻多少个刻度就能度量1到n的所有长度,这便是至今未解决的最省刻度尺问题。阐明了最省刻度尺与极小优美图之间的关系,给出了计算最省刻度尺的所有最省刻度值的组合差集递推算法,得到长度为3~40的最省刻度尺的所有最省刻度值,同时,结合图论模型,给出了长度为41~82的最省刻度尺的最省刻度值。

关键词：最省刻度尺优美标号极小优美图优美标号算法组合差集递推算法

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基于最省刻度尺构造极小优美图的图论方法

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厦门大学学报（自然科学版） 2024年第2期63卷 339-344页

作者：唐保祥任韩天水师范学院数学与统计学院甘肃天水741001 华东师范大学数学科学学院上海430072

[目的]利用最省刻度尺的已有研究成果研究极小优美图的构造方法.[方法]对任意正整数n≥2,在长度是n的无刻度直尺上最少刻多少个刻度,就能度量1-n的所有长度,这就是最省刻度的尺子问题.给定正整数n,存在m个整数组成的集合{a_(i)},满足0=a... 详细信息

[目的]利用最省刻度尺的已有研究成果研究极小优美图的构造方法.[方法]对任意正整数n≥2,在长度是n的无刻度直尺上最少刻多少个刻度,就能度量1-n的所有长度,这就是最省刻度的尺子问题.给定正整数n,存在m个整数组成的集合{a_(i)},满足0=a_(1)

关键词：最省刻度尺优美图联图极小优美图优美标号

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融合类增强与多尺度自适应的小样本学习方法

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数据采集与处理 2024年第3期39卷 689-698页

作者：董驰静张孙杰任涵上海理工大学光电信息与计算机工程学院上海200093

为了解决小样本学习存在特征信息提取不足、难以准确地捕获局部明显特征信息的问题,提出了一种融合类增强与多尺度自适应的小样本学习方法。首先在特征的层面上对图像进行类增强,通过将特征图的每次激活与其邻域相关联来编码丰富的语义... 详细信息

为了解决小样本学习存在特征信息提取不足、难以准确地捕获局部明显特征信息的问题,提出了一种融合类增强与多尺度自适应的小样本学习方法。首先在特征的层面上对图像进行类增强,通过将特征图的每次激活与其邻域相关联来编码丰富的语义结构,使提取后的类内特征明显,更利于当前的分类任务。其次通过多尺度特征生成来提取不同尺度上图像特征的低层表示。最后对每个尺度上的语义相关矩阵进行权重分配与相似元素最大化计算查询图像与各支持集类别图像之间的语义相似度,多尺度信息进行融合后,对目标图像进行分类。在5-way 1-shot和5-way 5-shot设置中,该方法在miniImageNet数据集上的均值平均精度(mean Average precision,mAP)分别为56.83%和75.76%,在常用细粒度图像数据集Stanford Cars和CUB-200-2011分类基准上分别达到了79.33%和93.92%、66.33%和85.78%,均优于现有方法的最好结果。

关键词：小样本学习类增强多尺度特征生成自适应任务注意

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Exponentially many maximum genus embeddings and genus embeddings for complete graphs

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Science China Mathematics 2008年第11期51卷 2013-2019页

作者： ren han BAI Yun Department of Mathematics East China Normal UniversityShanghai 200062China

There are many results on the maximum genus, among which most are written for the existence of values of such embeddings, and few attention has been paid to the estimation of such embeddings and their applications. In this paper we study the number of maximum genus embeddings for a graph and find an exponential lower bound for such numbers. Our results show that in gen-eral case, a simple connected graph has exponentially many distinct maximum genus embeddings. In particular, a connected cubic graph G of order n always has at least 2~1/2m+n+ α2 distinct maximum genus embeddings, where α and m denote, respectively, the number of inner vertices and odd compo-nents of an optimal tree T . What surprise us most is that such two extremal embeddings (i.e., the maximum genus embeddings and the genus embeddings) are sometimes closely related with each other. In fact, as applications, we show that for a suffcient large natural number n, there are at least C2 n4 dmeapneyn dgienngu os ne mthbee vdadliuneg soffonrocf ormespidleutee 1g2r.a pThh eKsen rwesiuthlt sn i m≡p r4o,v 7e, 1th0e ( mbooudn1d2)s, owbthaeirnee dC b iys Ka ocroznhsikta anncde Voss and the methods used here are much simpler and straight.

关键词： maximum genus embedding optimal tree current graph

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Fundamental cycles and graph embeddings

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Science China Mathematics 2009年第9期52卷 1920-1926页

作者： ren han ZHAO HongTao LI HaoLing Department of Mathematics East China Normal UniversityShanghai 200062China

In this paper, we investigate fundamental cycles in a graph G and their relations with graph embeddings. We show that a graph G may be embedded in an orientable surface with genus at least g if and only if for any spanning tree T , there exists a sequence of fundamental cycles C1, C2, . . . , C2g with C2i-1 ∩ C2i≠ф for 1≤ i ≤g. In particular, among β(G) fundamental cycles of any spanning tree T of a graph G, there are exactly 2γM (G) cycles C1, C2, . . . , C2γM (G) such that C2i-1 ∩ C2i≠ф for 1 ≤i≤γM (G), where β(G) and γM (G) are the Betti number and the maximum genus of G, respectively. This implies that it is possible to construct an orientable embedding with large genus of a graph G from an arbitrary spanning tree T (which may have very large number of odd components in G\E(T )). This is different from the earlier work of Xuong and Liu, where spanning trees with small odd components are needed. In fact, this makes a common generalization of Xuong, Liu and Fu et al. Furthermore, we show that (1) this result is useful for locating the maximum genus of a graph having a specific edge-cut. Some known results for embedded graphs are also concluded; (2) the maximum genus problem may be reduced to the maximum matching problem. Based on this result and the algorithm of Micali-Vazirani, we present a new efficient algorithm to determine the maximum genus of a graph in O((β(G)) 25 ) steps. Our method is straight and quite different from the algorithm of Furst, Gross and McGeoch which depends on a result of Giles where matroid parity method is needed.

关键词： fundamental cycle maximum genus upper-embedded

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Shape of free-fall arch in quasi-2D silo

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Particuology 2021年第2期19卷 62-69页

作者： Qi Wang Quan Chen Ran Li Gang Zheng ren han Hui Yang School of Optical-Electrical and Computer Engineering University of Shanghai for Science and TechnologyShanghai 200093China School of Medical Instrument and Food Engineering University of Shanghai for Science and TechnologyShanghai 200093China

In this study,the optical flow method is used to measure the velocity distribution of a granular flow in a rectangular quasi-two-dimensional silo.Using the velocity gradient,a free-fall arch(FFA)is obtained and its geometric characteristics are calculated.A parabola-shaped FFA structure is discovered above the orifice in the steady flow state.The shape of the FFA affects the flow rate through the orifice.Furthermore,as jamming begins to occur,the geometry of the FFA disappears gradually from both sides and then from the middle;finally,the FFA disappears completely in the state of jamming.As the boundary between finite-stress and stress-free regions,the FFA facilitates further studies regarding the discontinuity of the stress area above the orifice.

关键词： Granular flow Optical flow method Velocity field Free-fall arch Flow rate Jamming

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