有向图上基于层次树索引的最大cycle truss社区搜索

社区搜索旨在从信息网络中找出包含用户查询顶点的高内聚连通子图,cycle truss是一种基于cycle三角形的社区搜索模型,而现有的基于索引的cycle truss社区搜索方法存在索引空间大、搜索效率低、社区内聚性低的缺点。为了解决这一问题,提出一种基于层次树索引的最大cycle truss社区搜索方法。首先,提出了k-cycle truss分解算法,并引入了两个重要的概念:cycle三角连通与k-层次等价。基于k-层次等价设计了层次树索引TreeCIndex与表结构索引SuperTable,在此基础上,并基于这两个新的索引,提出了两个高效的cycle truss社区搜索算法。在4个真实数据集上与已有的基于TrussIndex与EquiTruss的社区搜索算法进行了比较,实验结果表明,TreeCIndex与SuperTable比TrussIndex与EquiTruss节省至少41.5%的空间,索引构建的时间节省8.2%至98.3%,且搜索最大cycle truss社区的效率分别高出了一个和两个数量级。

Spatially-graded 3D-printed viscoelastic truss metamaterials for impact trajectory control and energy absorption

This study demonstrates that two-and three-dimensional spatially graded,truss-based polymeric-material metamaterials can be designed for beneficial impact mitigation and energy absorption capabilities.Through a combination of numerical and experimental techniques,we highlight the broad property space of periodic viscoelastic trusses,realized using 3D printing via selective laser sintering.Extending beyond periodic designs,we investigate the impact response of spatially variant viscoelastic lattices in both two and three dimensions.Our result reveal that introducing spatial variations in lattice topology allows for redirecting of the impact trajectory,opening new opportunities for engineering and tailoring lightweight materials with target impact functionality.This is achieved through the combined selection of base material and metamaterial design.

Control and vibration analyses of a sandwich doubly curved micro-composite shell with honeycomb,truss,and corrugated cores based on the fourth-order shear deformation theory

Curved shells are increasingly utilized in applied engineering due to their shared characteristics with other sandwich structures,flexibility,and attractive appearance.However,the inability of controlling and regulating vibrations and destroying them afterward is a challenge to scientists.In this paper,the curve shell equations and a linear quadratic regulator are adopted for the state feedback design to manage the structure vibrations in state space forms.A five-layer sandwich doubly curved micro-composite shell,comprising two piezoelectric layers for the sensor and actuator,is modeled by the fourth-order shear deformation theory.The core(honeycomb,truss,and corrugated)is analyzed for the bearing of transverse shear forces.The results show that the honeycomb core has a greater effect on the vibrations.When the parameters related to the core and the weight percentage of graphene increase,the frequency increases.The uniform distribution of graphene platelets results in the lowest natural frequency while the natural frequency increases.Furthermore,without taking into account the piezoelectric layers,the third-order shear deformation theory(TSDT)and fourth-order shear deformation theory(FOSDT)align closely.However,when the piezoelectric layers are incorporated,these two theories diverge significantly,with the frequencies in the FOSDT being lower than those in the TSDT.

Minimizing Weight by Optimizing Different Truss Parts Using Finite Element Analysis

This paper presents a study of minimizing weight by optimizing different truss parts using finite element analysis and comparing Warren trusses with other trusses. The aim of the optimization is to find a light design. Existing structural steel trusses were initially optimized for minimum weight and constrained with allowable stresses and deflections. Applicable Eurocode 3 design conditions are presented, which provide the constraints for the problem. Steel truss is a preferred solution in large-span roof structures due to its good attributes, such as being lightweight and durable. Existing structural steel trusses were initially optimized for minimum weight and constrained with allowable stresses and deflections. Constant spans of the trusses have been considered, and each truss has been subjected to the same types of load cases. The top chord member load has been kept constant in each truss at 2 kN/m. Two sets of load conditions are taken as the self-weight of the truss and the snow load, but the structure is calculated by the load combination. The structural steel trusses were optimized using the design optimization tool as a first-order optimization method in RFEM, and it was extended to compare the most suitable truss geometry for the minimum weight. Finally, it is concluded that the Warren truss has a higher stiffness-to-weight ratio than other trusses after optimization. The goal of this study was to analyze all trusses and ensure that the structural stress is less than the allowable stress and that the deflection is less than the allowable deflection. The span and height are constant in all cases because they have no impact on the weight increase;only the position of the rods and cross-section size affect the building’s ability to withstand loads and weight increases. In this paper, a finite element analysis (FEA)-based optimization technique is proposed for the optimization of a light design that is constrained by allowable stresses and deflections. For this purpose, there have been studies on sizing optimization to minimize the mass of different steel truss roof system types both in the past and today. For this purpose, weight design and analysis of the optimum weight are carried out on ten different structural systems.

Defect Inspection Technology for Steel Truss Suspension Bridges

Steel truss suspension bridges are prone to developing defects after prolonged use.These defects may include corrosion of the main cable or the steel truss.To ensure the normal and safe functioning of the suspension bridge,it is necessary to inspect for defects promptly,understand the cause of the defect,and locate it through the use of inspection technology.By promptly addressing defects,the suspension bridge’s safety can be ensured.The author has analyzed the common defects and causes of steel truss suspension bridges and proposed specific inspection technologies.This research is intended to aid in the timely discovery of steel truss suspension bridge defects.

Truss Spar平台滑移装船研究

Truss Spar平台是当今Spar平台的主流形式。由于Truss Spar平台主体结构的特殊性,致使其滑移装船工程设计具有一定的特殊性。该文依据NOBLE DENTON指导性文件,从Truss Spar结构特点出发,对与平台装船相关的船舶滑道设计、滑靴设计、系泊设计、调载方案设计、泵和拖拉设备的选型等进行了研究,提出了需要关注的关键性技术问题,为今后Truss Spar平台主体结构的滑移装船设计提供参考。

Truss Spar平台垂荡响应频域分析

利用已有水动力试验和数值模拟结果及Morison方程,简化估计了Truss Spar平台垂荡方向水动力贡献,快速有效地预报了平台极端海况下的垂荡响应。在频域内分别采用数值迭代计算和粘滞阻尼线性化方法得到了平台在不同数量垂荡板配置下的垂荡响应幅值算子。在墨西哥湾、西非和中国南海等3种不同地区极端海况以及墨西哥湾工作状态海况下计算了平台的响应极值,分析发现平台波频垂荡响应对入射波浪周期非常敏感。采用JONSWAP波能谱得到了Truss Spar平台垂荡响应谱。通过比较和参数分析,验证了平台在设计上的合理性与实际海况下良好的垂荡运动性能。

随机波浪下Truss Spar平台垂荡运动时域分析

研究Truss Spar平台在随机波浪下的垂荡运动特性。采用ITTC双参数谱,考虑绕射作用,数值计算了平台所受的随机波浪力。利用已有的水动力试验和数值模拟结果及Morison方程,估计了Truss Spar平台垂荡方向的附加质量和粘滞阻尼大小。考虑非线性阻尼和瞬时波面的影响,运用Runge-Kutta数值迭代算法,比较了不同随机波浪参数对平台运动响应的影响,特别是波浪特征周期接近垂荡固有周期时。结果表明,当波浪特征周期接近平台垂荡固有周期时,平台产生大幅垂荡运动,频域的运动分析结果比时域结果偏小。

均匀流中深水系泊Truss Spar平台涡激运动试验研究

在工程中广泛应用的Truss Spar平台自诞生之初就为涡激运动问题所困扰,对其运动特性及抑制方法的机理性研究始终都在进行。采用截断系泊系统水池模型试验对设计中的Truss Spar平台在均匀流中的涡激运动响应进行了研究,分析了有无侧板平台的运动轨迹以及不同速度及流向角来流对平台运动的平衡位置的影响。在影响平台涡激运动特性的重要因素中,选取折合速度及流向角分别加以研究,分析了幅值在锁定区间中的变化规律,验证了减涡侧板对涡激运动良好的抑制作用,并对"热点"问题进行了探讨。为进一步研究Spar平台的涡激运动特性奠定了基础。

Experimental research on ultimate bearing capacity of N-joints of grouted square steel tube trusses

Cave-in failure is apt to occur in joints of trusses made of square hollow sections. In order to turn the failure mode into a strength failure mode of joint members, the idea is proposed that the chord of the truss is grouted to increase the cave-in beating capacity of a hollow tube chord. An experiment of eight specimens of N- joints made of grout-filled square steel tubes is performed. Based on the experimental study, the geometrical parameters of specimens are analyzed, and the effects of the confinement index ε, the spacing between the two web members g and the ratio of side length of the vertical web member to that of the chord β on the behavior of specimens are investigated through simulation analysis by simulation analyses, the mechanical properties and the failure an ANSYS program. Based on the test results and modes of this kind of joints are analyzed and the formulae to predict the ultimate bearing capacities corresponding to different failure modes are developed. The ultimate bearing capacity of compressive N-joints is calculated in accordance with the cave-in failure mode of a chord member; the ultimate bearing capacity of tension N-joints is calculated in accordance with the punchingshear failure mode; the ultimate bearing capacity of a chord member is calculated in accordance with the shear failure mode in normal sections.

Truss Spar平台涡激运动拖曳模型试验方法研究

采用拖曳水池模型试验对设计中的Truss Spar平台进行了模型试验,详细对试验内容、试验方法和布置进行了介绍,对试验数据进行了初步处理,得到了研究涡激运动的关键参数,并判断了试验数据的合理性。

一种大规模双网络中k-连通Truss子图发现算法

双网络由具有相同顶点集合但不同边集合的物理图和概念图构成,能够反映顶点间不同层面的交互关系.双网络中稠密子图发现问题旨在发现物理图中连通而概念图中稠密的子图,在协作者网络分析、社区发现和疾病功能团检测等方面具有广泛应用.但现有稠密子图模型存在以下问题:(1)基于最密集子图模型的稠密子图发现问题本质上是NP-难的,导致精确的子图发现算法在效率上存在很大问题;(2)基于k-核的模型虽然解决了效率问题,但是发现的稠密子图并不真正“稠密”.针对以上问题,本文(1)提出了k-连通truss子图(k-CT)模型.该模型更加稠密,因此允许子图间存在重叠;(2)为了发现k-连通truss子图,提出了一种高效的精确亚线性算法用于发现双网络中所有的k-CT子图;(3)基于k-CT子图,提出了最大连通truss子图(MCT)概念,对当前k-CT子图不存在任何非空(k+1)-CT子图;(4)提出了自顶向下、自底向上和二分法三种不同策略的MCT子图发现算法.大量基于真实和合成双网络数据的实验结果证明了本文提出算法的高效性和有效性.

垂荡板对Truss Spar平台垂荡性能的影响分析

为了研究垂荡板对Truss Spar平台垂荡性能的影响,在建立Truss Spar平台垂向波浪载荷计算模型的基础上,基于柯莱根-卡彭特数Kc计算了Truss Spar平台的黏性阻尼,提出了垂荡响应幅值的理论计算方法,并将理论计算结果与AQWA软件的仿真结果进行对比。分析结果表明:2种分析方法下垂荡响应幅值趋势一致,峰值较为接近,而且理论计算方法计算速度明显优于仿真分析方法;基于Kc数的垂荡响应幅值理论计算方法能快速有效地分析设有垂荡板的海洋平台的垂荡响应;黏性阻尼能够有效抑制Truss Spar平台的垂荡响应,在垂荡响应分析中不可或缺,垂荡板贡献的黏性阻尼是总黏性阻尼的主要组成部分。所得结论可为合理确定Truss Spar平台垂荡响应幅值提供参考。

VIBRATION CONTROL OF A SPACE TRUSS STRUCTURE WITH A PIEZOELECTRIC ACTIVE MEMBER

Active vibration control is an effective way of increasing robustness of the design to meet the stringent accuracy requirements for space structures. This paper presents the results of active damping realized by a piezoelectric active member to control the vibration of a four-bay four-longern aluminum truss structure with cantilever boundary. The active member, which utilizes a piezoelectric actuating unit and an integrated load cell, is designed for vibration control of the space truss structures. Active damping control is realized using direct velocity feedback around the active member. The placement of the active member as one of the most important factor of affecting the control system performance, is also investigated by modal dissipation energy ratio as indicator. The active damping effectiveness is evaluated by comparing the closed-loop response with the open loop response.

剪切流中Cell-Truss Spar平台涡激运动的CFD计算与模型试验研究

目前，Spar平台在离岸深水作业中得到越来越广泛的应用，作为影响Spar平台在某些来流条件下运动响应特性的一种重要现象，涡激运动已成为国际海洋工程界亟待研究的一个新课题。本文采用CFD计算与模型试验相结合的方法，对一座称为“Cell-Truss Spar”的新型Spar平台在剪切流作用下发生涡激运动的现象进行了研究。相对于目前已存在并应用的Spar平台，Cell-Truss Spar平台在结构形式上有其自身的特征，研究中充分考虑了这一特征，对其建立适当的CFD计算模型，得到其涡激运动的特征，模拟了锁定现象的发生过程，分析了锁定现象的发生机理和规律；同时制作了精细的物理模型，测试了一系列的剪切流表面流速，得到了Cell-Truss Spar平台涡激运动的一些关键性参数，并成功地观察到了锁定现象的发生。CFD计算与模型试验相互比较，相互验证，最后对该平台涡激运动响应的特征进行了分析和总结，为进一步的涡激运动抑制研究奠定了基础。

Truss Spar平台在船舶碰撞下的数值模拟分析

海洋平台在海上进行工程作业时除了遭受恶劣的环境载荷外,还可能与海上船舶发生碰撞。为探究Spar平台在遭受船舶碰撞后的动力响应,本文选取1座墨西哥湾的Truss Spar平台,运用有限元分析软件Ansys/Lsdyna,建立5 000吨级补给船与Truss Spar平台的有限元模型并模拟碰撞过程,得到船舶在不同速度下与Spar平台碰撞过程中的能量转化情况和船舶撞击力时程曲线,通过对结果的分析得出一般性规律和结论,为Spar平台的设计提供理论参考依据。

SYSTEM IDENTIFICATION OF ADAPTIVE TRUSS STRUCTURES USING PIEZOELECTRIC ACTIVE MEMBERS

Adaptive truss structures are a new kind of structures with integrated active members,whose dynamic characteristies can be beneficially modified to meet mission requirements.Active members containing actuating and sensing units are the major components of adaptive truss structures.Modeling of adaptive truss structures is a key step to analyze the structural dynamic characteristics.A new experimental modal analysis approach,in which active members are used as excitatiDn sources for modal test,has been proposed in this paper.The excitation forces generated by the active members, which are different from the excitation forces exerted on structures in the conventional modal test,are internal forces for the truss structures.The relation between internal excitation forces and external forces is revealed such that the traditional identification method can be adopted to obtain modal parameters of adaptive structures.Placement problem of the active member in adaptive truss structures is also discussed in this work. Modal test and analysis are conducted with a planar adaptive truss structure by using piezoelectric active members in order to verify the feasibility and effectiveness of the proposed method.

Truss Spar平台桁架管节点疲劳分析

Truss Spar平台在风、浪、流的作用下,结构受力十分复杂,准确分析其疲劳强度相当困难。通过建立Truss Spar平台三维有限元模型,利用HydroD软件进行载荷预报、波浪搜索,得到产生最大应力幅响应的最不利浪向和相位角。运用Sestra软件进行整体有限元分析,得到的结果作为桁架管节点细化模型的边界条件,再用Nastran软件进行局部分析求得节点的热点应力,修正壁厚影响。最后根据DNV规范的S-N曲线计算了管节点的疲劳寿命。

基于Wu-Ritt法的一类TRUSS问题符号解求法的设计与实现

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Truss Spar平台总体结构强度分析

在南海百年一遇海况条件下,综合考虑风、浪、流载荷的联合作用,在频域范围内计算平台的纵摇和横摇极值响应以及锚缆的张力。根据不同浪向下的结构应力谱分析确定的设计波参数,基于三维势流理论和Morison公式计算一阶波浪力,采用规范推荐的公式计算风、流载荷。在准静力条件下,根据ABS规范推荐的强度准则,针对精细化的混合有限元结构模型进行总体强度分析。