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吸力式筒形基础沉贯过程的大变形有限元模拟

岩土力学 2015年第12期36卷 3615-3624页

作者：吕阳王胤杨庆大连理工大学海岸和近海工程国家重点实验室辽宁大连116023

吸力式筒形基础在海洋工程中已获得越来越广泛地应用,其安装过程的数值模拟对指导工程实践具有重要意义。在大型通用有限元软件ABAQUS平台上建立了二维轴对称模型,基于AlE(任意拉格朗日-欧拉法)技术模拟了黏土中吸力筒的大变形沉贯过程... 详细信息

吸力式筒形基础在海洋工程中已获得越来越广泛地应用,其安装过程的数值模拟对指导工程实践具有重要意义。在大型通用有限元软件ABAQUS平台上建立了二维轴对称模型,基于AlE(任意拉格朗日-欧拉法)技术模拟了黏土中吸力筒的大变形沉贯过程。模拟过程利用了子程序VUFIElD控制土体的不排水抗剪强度和弹性模量随土体深度变化。参照离心机试验及理论计算,对模型进行验证。利用已验证模型分析不同吸力下沉贯阻力、土塞高度,并讨论了筒壁摩擦特性。数值计算结果表明,AlE技术能有效地模拟吸力筒贯入过程,避免网格畸变。贯入方式对贯入阻力影响很大,吸力式贯入阻力明显低于压力式贯入阻力。进一步研究发现,随着最终吸力值的增大,沉贯阻力会显著降低,土塞高度会显著提高。对内壁摩擦特性的研究表明,内壁摩擦阻力是导致沉贯阻力改变的主要因素,并且相比吸力式贯入方式,筒壁摩擦特性会对压力式贯入造成更大的影响。

关键词：筒形基础吸力式沉贯大变形有限元 AlE技术

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土体软化条件下条形基础地基承载力数值模拟

岩土工程学报 2019年第A2期41卷 9-12页

作者：吕玺琳薛大为同济大学岩土及地下工程教育部重点实验室上海200092 同济大学地下建筑与工程系上海200092

为克服材料软化导致的有限元网格敏感性难题,提出了一个压力相关隐式梯度塑性模型来模拟土体软化条件下条形基础地基承载力。通过引入微应变作为附加运动学变量,推导了包含高阶广义应力的微力平衡和经典动量方程,并基于热力学第二定律,... 详细信息

为克服材料软化导致的有限元网格敏感性难题,提出了一个压力相关隐式梯度塑性模型来模拟土体软化条件下条形基础地基承载力。通过引入微应变作为附加运动学变量,推导了包含高阶广义应力的微力平衡和经典动量方程,并基于热力学第二定律,将附加的微力平衡转化为宏观等效塑性应变与微应变耦合的Helmholtz方程。进一步建立能耦合位移和微变量的有限元算法,并通过软化材料双轴压缩试验模拟,验证了该算法在应变局部化数值模拟中的适用性。将建立的方法用于条形基础地基承载力特性模拟,并通过与理想弹塑性模型计算结果对比表明,土体软化将导致地基承载能力降低,破坏模式表现为失稳区域变小且塑性应变幅值增大。

关键词：隐式梯度模型应变软化剪切带地基承载力网格敏感性

“Acute postoperative open abdominal wall”: Nosological concept and treatment implications

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World Journal of Gastrointestinal Surgery 2013年第12期5卷 314-320页

作者： Manuel lópez-Cano José A Pereira Manuel Armengol-Carrasco Abdominal Wall Surgery Unit Department of General Surgery Hospital Universitari Vall d’Hebrón Universitat Autònoma de Barcelona Department of General and Digestive Surgery Parc de Salut Mar Universitat Autònoma de Barcelona Department of Health and Experimental Sciences Universitat Pompeu Fabra

The so-called 'burst abdomen' has been described for many years and is a well-known clinical condition, whereas the concept of the 'open abdomen' is relatively new. In clinical practice, both nosological entities are characterized by a complex spectrum of symptoms apparently disconnected, which in many cases poses a great challenge for surgical repair. In order to assess the management of these disorders in a more comprehensive and integral fashion, the concept of 'acute postoperative open abdominal wall'(acute POAW) is presented, which in turn can be divided into 'intentional' or planned acute POAW and 'unintentional' or unplanned POAW. The understanding of the acute POAW as a single clinical process not only allows a better optimization of the ther-apeutic approach in the surgical repair of abdominal wallrelated disorders, but also the stratification and collection of data in different patient subsets, favoring a better knowledge of the wide spectrum of conditions involved in the surgical reconstruction of the abdominal wall.

关键词： Burst abdomen Open abdomen Evisceration Abdominal wall mesh Negative pressure wound therapy Incisional hernia Enteroatmospheric fistula

Using meshes to change the characteristics of simulated rainfall produced by spray nozzles

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International Soil and Water Conservation Research 2014年第2期2卷 67-78页

作者： Sílvia C.P.Carvalho João l.M.P.de lima M.Isabel P.de lima Department of Civil Engineering Faculty of Science and TechnologyUniversity of CoimbraCoimbraPortugal Department of Civil Engineering Campus II-University of CoimbraRua Luís Reis Santos3030-788 CoimbraPortugal

Rainfall simulators have been used for many years contributing to the understanding of soil and water conservation ***,rainfall simulators’design and operation might be rather demanding for achieving specific rainfall intensity distributions and drop characteristics and are still open for *** study explores the potential of combining spray nozzle simulators with meshes to change rainfall characteristics,namely drop properties(drop diameters and fall speeds).A rainfall simulator laboratory set-up was prepared that enabled the incorporation of different wire meshes beneath the spray *** tests conducted in this exploratory work included different types of spray nozzles,mesh materials(plastic and steel),square apertures and wire thicknesses,and positions of the meshes in relation to the *** intensity and drop size distribution and fall speed were *** showed that the meshes combined with nozzles increased the mean rainfall intensity on the 1 m^(2) control plot below the nozzle and altered the rain drops’properties,by increasing the mass-weighted mean drop diameter,for example.

关键词： Rainfall simulators Spray nozzle meshes Drop characteristics

Diversity and Influence of Environmental Factors on the Spatio-Temporal Distribution of the Ichthyofauna of Malonda lagoon (Congo Brazzaville)

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Natural Resources 2021年第5期12卷 147-163页

作者： Tenda Hélène Dembe louvinguila Armel Ibala Zamba Victor Mamonekene lérège Batiabo Mikembi Freedom Honest Poaty Ngot Joseph Goma-Tchimbakala Ecole Nationale Supérieure d’Agronomie et de Foresterie (ENSAF) Université Marien Ngouabi Brazzaville République du Congo Institut national de Recherche en Sciences Exactes Naturelles Laboratoire de l’Environnement et Océanographie Brazzaville République du Congo

This study was initiated with the aim of studying the diversity and spatio-temporal distribution of fish in the Malonda lagoon, one of the coastal ecosystems of the Base Guinea in the Republic of Congo. The fish were sampled over a period of two years in three zones each including three stations known as: Mangrove, Grass and Full water. One station upstream towards the freshwater zone, one station downstream towards the mouth and one station in the containment zone. The catches were made using monofilament gillnets of 8, 10, 20 and 30 mm mesh size. During the rainy season, 1516 specimens belonging to 29 species, 17 families and 12 orders were collected. In the dry season, 768 specimens belonging to 20 species, 11 families and 8 orders were collected. For both seasons, the family Cichlidae is the most diversified. The marine forms are the most represented compared to the continental forms. Redundancy Analysis with forward selection coupled with Monte Carlo permutation tests showed that in the rainy season four variables influenced the distribution of species (Depth: 48%, Vase: 16%, Nitrogen: 10% and Transparency: 10%);in the dry season three variables influenced the distribution of species (Vase: 38%, Nitrogen: 14% and Oxygen: 11%). Ecological indices showed that the Malonda lagoon is already undergoing either anthropic or natural impacts, its state of ecological integrity is disturbed, the values of Shannon diversity and Equitability indices are not close to maximum values. The results of this study will serve as an ecological database for the proper management of these ecosystems.

关键词： Fish Ecology Distribution Season Malonda lagoon lower Guinea

砷化镓金属—半导体场效应晶体管的二维数值分析

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西安交通大学学报 1990年第1期24卷 79-86页

作者：陈贵灿 K.l.Wang 刘之行邵志标西安交通大学电子系洛杉矶加州大学电气系西安交通大学数学系

本文叙述用有限元方法对工作在导带的 GaAs MESFET's 器件进行二维稳态模拟的程序.用三角形单元不均匀网格剖分的程序,能局部加密,优化结点编码,缩小带宽;对基本方程离散采用改进的电荷浓缩法和有限元——有限差分混合法;方程求解采用... 详细信息

本文叙述用有限元方法对工作在导带的 GaAs MESFET's 器件进行二维稳态模拟的程序.用三角形单元不均匀网格剖分的程序,能局部加密,优化结点编码,缩小带宽;对基本方程离散采用改进的电荷浓缩法和有限元——有限差分混合法;方程求解采用藕合法,偏压步长大,计算速度快.

关键词：场效应晶体管肖特基势垒栅砷化镓

Evolution and advances in laparoscopic ventral and incisional hernia repair

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World Journal of Gastrointestinal Surgery 2015年第11期7卷 293-305页

作者： Alan l Vorst Christodoulos Kaoutzanis Alfredo M Carbonell Michael G Franz Department of Surgery Saint Joseph Mercy Health System Department of Surgery Greenville Health System University of South Carolina School of Medicine-Greenville

Primary ventral hernias and ventral incisional hernias have been a challenge for surgeons throughout the ages. In the current era, incisional hernias have increased in prevalence due to the very high number of laparotomies performed in the 20 th century. Even though minimally invasive surgery and hernia repair have evolved rapidly, general surgeons have yet to develop the ideal, standardized method that adequately decreases common postoperative complications, such as wound failure, hernia recurrence and pain. The evolution of laparoscopy and ventral hernia repair will be reviewed, from the rectoscopy of the 4th century to the advent of laparoscopy, from suture repair to the evolution of mesh reinforcement. The nuances of minimally invasive ventral and incisional hernia repair will be summarized, from preoperative considerations to variations in intraoperative practice. New techniques have become increasingly popular, such as primary defect closure, retrorectus mesh placement, and concomitant component separation. The advent of robotics has made some of these repairs more feasible, but only time and well-designed clinical studies will tell if this will be a durable modality for ventral and incisional hernia repair.

关键词： Evolution Advances laparoscopic ventral hernia rep

行程敏感式液阻减振器动力学特性的三维流-固耦合有限元仿真分析

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工程力学 2020年第9期37卷 217-229页

作者：徐文雪吕振华清华大学车辆与运载学院北京100084

建立了缸壁槽形行程敏感式减振器较精细的三维流-固耦合动力学仿真分析模型,利用基于AlE流-固耦合、滑移网格流-流耦合的同步化迭代流-固耦合计算方法及动网格控制方法求解减振器内部的稳态及瞬态流-固耦合动力学响应,进行了部分实验验... 详细信息

建立了缸壁槽形行程敏感式减振器较精细的三维流-固耦合动力学仿真分析模型,利用基于AlE流-固耦合、滑移网格流-流耦合的同步化迭代流-固耦合计算方法及动网格控制方法求解减振器内部的稳态及瞬态流-固耦合动力学响应,进行了部分实验验证。量化分析了缸壁槽形行程敏感式减振器的高速阻尼特性、冲击阻尼特性和活塞偏置、缸壁槽通流面积及结构变化对阻尼特性的影响,结果表明:活塞沿压缩行程方向偏置后的阻尼特性是有利的,而沿伸张行程方向偏置的状态是不利的;缸壁槽的附加泄流作用可削减减振器在地面冲击激励下阻尼力的瞬间冲击峰值;多缸壁槽形行程敏感式减振器的阻尼特性表现出单条缸壁槽作用结果的叠加效应;缸壁槽对阻尼力的减弱比例随活塞速度幅值的减小而增大;缸壁槽在高速工况下被开启及关闭的瞬态过程中伴随有阻尼力波动现象,可通过适当延长缸壁槽端部收缩段加以改善。这些分析结论对于此类液阻减振器的变阻尼特性匹配设计具有重要的价值。

关键词：流-固耦合动力学有限元仿真分析迭代耦合算法行程敏感式液阻减振器缸壁槽振动阻尼特性

基于非结构自适应网格和嵌入边界法的残差格式研究（英文）

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空气动力学学报 2016年第2期34卷 214-223页

作者： R. Abgrall H. Alcin H. Beaugendre C. Dobrzynski l. Nouveau Universitat Zürich Institut für Mathematik Winterthurstrasse 190 CH-8057 Zürich Switzerland INRIA Bordeaux Sud-Ouest F-33400 Talence France University of Bordeaux IMB UMR 5251 INRIA Bordeaux Sud-Ouest F-33400 Talence France

嵌入边界法由于在求解NS方程时能够简化网格生成问题而在计算流体领域受到越来越广泛的关注。简言之,嵌入边界法能够简化大变形和运动条件下多物理流动模拟、流固相互作用耦合问题,然而壁面边界条件的精确处理仍旧是该方法需要解决的问... 详细信息

嵌入边界法由于在求解NS方程时能够简化网格生成问题而在计算流体领域受到越来越广泛的关注。简言之,嵌入边界法能够简化大变形和运动条件下多物理流动模拟、流固相互作用耦合问题,然而壁面边界条件的精确处理仍旧是该方法需要解决的问题。在本文工作中,为考虑壁面边界条件而在NS方程中增加了补偿项,同时采用非结构网格自适应技术保持了壁面边界条件的精度。

关键词：残差格式浸入边界法补偿非结构网格网格自适应