KeywordsTruss Spar,Conceptual Design,Structural Design,Multidisciplinary Design Optimization,Collaborative Optimization,Adaptive Response Surface Method,Variable-Complexity Method
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&&&&&&&&为适应我国国民经济发展和人民生活快速增长的需求,国家已计划在油气资源丰富的南海深水海域进行海洋油气勘探开发。然而,我国现有海洋生产平台的作业深度通常在500米以内,远远不能满足对于南海等深水海域油气开发的迫切需求。当今世界范围内用于深水油气开发的平台类型主要包括浮式生产储油系统、半潜式平台、张力腿平台以及Spar平台。针对Spar平台功能性强、稳定性好、性价比高和安全性好等优势,我国已在Spar平台方面投入了多年的研究,具有良好的技术储备。因此,Spar平台无疑将成为我国今后南海等深水海域油气勘探开发装备中的重点选择之一。目前,国内船舶设计单位在包括Spar平台在内的新型海洋平台的设计研究方面,特别是最重要的概念设计方面,与国外先进企业相比存在着差距,加之Spar平台设计技术具有垄断性,我国研发Spar平台将面临很多困难。为了加快我国深海平台尤其是Spar平台的研发步伐,尽快突破Spar平台的设计技术瓶颈,我们应当在Spar平台概念设计的方法与理念上有所创新。本文首先依据现有的海洋平台设计方法,探索性地进行桁架式Spar平台的概念设计和结构设计研究。现有的海洋平台设计理念是建立在改良母型平台基础上的串行设计方法,存在过多依赖设计专家经验和母型平台、设计成本高、概念设计结果无法充分反映平台整体性能等不足。由于Spar平台系统是具有高复杂度的工程系统,其设计过程需要涉及到的多个学科,包括水动力学,结构力学、工程应用和可靠性等,这些学科之间既相互联系、相互作用,也存在着相互冲突,使得桁架式Spar平台的概念设计呈现典型的“多学科”特点。现有的海洋平台设计模式很难真正从系统的角度出发,充分考虑设计变量及各性能间的相互影响,得到的设计结果往往只是满足设计要求的方案,并非真正的系统最优设计方案。此外,船舶与海洋平台的设计发展必将走向数字化和虚拟化,如果在设计的初始阶段,就可以通过高度的系统集成,整体的把握各个方面的性能,无疑会给决策者带来巨大的帮助。而现有的海洋平台设计方法很难实现这一目标。要加快深海资源的开发,必须创新地提出新的设计理念和设计方法。在上述背景下,本文作为上海市科委重大基础研究课题“深海单柱式平台关键动力特性的理论与实验研究”的一部分,引入在航空航天领域获得巨大成功的、用于解决复杂系统设计与优化问题的多学科设计优化方法(Multidisciplinary Design Optimization,简称MDO),探索其在Spar平台概念设计中的应用可行性。论文主要的研究过程分为四个阶段:第一阶段:课题相关研究领域的综述针对现有海洋平台设计方法存在的问题,阐述了多学科设计优化在海洋平台概念设计中应用的意义。综述了多学科设计优化的发展概况和主要技术,重点介绍了多学科设计优化技术的核心技术——多学科优化算法,并对几种主要的多级优化算法,从来源和目的、近似模型、分解技术、收敛性和工程性等五个方面进行了比较。在此基础上,根据船舶与海洋平台的设计特点,指出基于近似模型的协同优化算法和BLISS 2000算法是比较适合进行船舶和海洋平台多学科设计优化的多学科优化算法。第二阶段:现有桁架式Spar平台的概念设计和结构设计方法首先根据现有的海洋平台设计方法,探索性地开展了Spar平台概念设计研究。Spar平台的概念设计涉及到两方面的问题:一是设计方法、流程以及结构物的形式;二是水动力性能。与船舶以及其它海洋平台设计相类似,Spar平台的概念设计思想依然是一个不断调整完善的过程。本文归纳了桁架式Spar平台概念设计的基本流程,并结合具体设计要求,给出了桁架式Spar平台的设计实例,完成了包括甲板布置、重量控制、主尺度的确定、稳性校核和初步的水动力分析。在概念设计基础上,进行了桁架式Spar平台的结构设计,主要工作包括:⑴归纳了桁架式Spar平台各部分结构的设计思想,根据平台结构布置特点和载荷分配情况,完成了平台结构的设计;⑵根据设计波方法,选定了两个典型波浪工况,采用三维势流理论,得到桁架式Spar平台的波浪诱导载荷,完成该桁架式Spar平台的总体结构强度分析。⑶分别对在硬舱底部采用双层底结构和单层底结构两种结构形式对于底部甲板的影响进行了计算,结果表明双层底结构可以大幅降低硬舱底部甲板应力。由概念设计和结构设计得到的桁架式Spar平台将作为基准平台,与多学科设计优化结果进行比较。第三阶段:多学科设计优化在桁架式Spar平台概念设计中的应用成功应用多学科设计优化技术的关键是建立一个合理的多学科设计优化模型。为此,首先归纳了桁架式Spar平台的主要设计参数,包括平台主尺度参数、平台作业能力参数、经济性和可靠性参数。由于本文是针对Spar平台的概念设计进行优化,因而选择主尺度参数作为优化的设计变量。然后,根据均匀设计方法,对各设计变量划分水平和建立试验方案。在建立桁架式Spar平台多学科设计优化框架时,如果在优化框架内的学科过多,常常会导致优化难以收敛;而如果所涉及的学科过少,又无法充分反应平台的特性,也就失去了多学科设计优化的意义。因此,本文提出了一种“折衷”的多学科建模方法,将影响Spar平台性能的学科划分为三个模块,即优化模块、约束模块和检验模块,对于分属不同模块的学科采用不同的方法处理。其中,优化模块中的学科是业主和设计人员最关注的,其设计结果体现一个设计方案的质量,在多学科优化设计中,通常作为优化目标处理。约束模块中的学科是实现平台功能的前提条件,以约束条件的形式出现在优化模型中,参与到优化循环过程。一般,仅选择一个学科中关键性的参数作为比较不同设计方案的指标;检验模块中的学科不参与优化循环过程,是对优化设计方案的全面、准确的校核。文中,壳体结构重量作为优化模块的优化目标;平台垂荡运动和纵摇运动的短期预报值作为水动力学科的约束目标,平台在风暴状态下的完整稳性衡准数作为稳性学科的约束目标,平台在静水力和波频载荷作用下的硬舱底部甲板与桁架结合处的主应力作为结构学科的约束目标。为建立桁架式Spar平台的多学科设计优化模型,根据试验设计的安排,对各试验方案分别进行了水动力分析、稳性分析和结构强度分析。最后,介绍了作为检验模块的平台/锚泊系统耦合时域动力分析的方法和检验准则。在此基础上,根据第一阶段中对于几种多学科设计优化算法比较的结果,选择基于近似模型的协同优化方法作为多学科设计优化算法,建立了桁架式Spar平台概念设计的协同优化数学模型,并进行了多学科优化分析。第四阶段:桁架式Spar平台多学科优化模型的改进和优化尽管近似模型可以大幅提高计算效率,然而其精度存在问题。因此,为提高多学科设计结果的可应用性,分别采用了两种改进方法:(1)响应面更新策略——提出了响应面更新技术及实施程序,完成了基于响应面更新的桁架式Spar平台概念设计的协同优化过程。对各设计变量更新的历程和结果进行了初步的讨论。通过与基准平台的对比表明:优化设计方案的结构重量大幅降低,垂荡、稳性、强度等性能参数也有所提高,只有纵摇性能略微下降。证明了协同优化方法在桁架式Spar平台概念设计中应用的可行性以及多学科设计优化技术的优越性。通过百年一遇海况的时域耦合分析,验证了优化结果的合理性。(2)可变复杂度方法——由于近似模型与真实模型间存在着差距,而响应面更新策略只是提高了响应面模型的精度,并没有体现真实模型的结果。因此,使用可变复杂度方法对第三阶段协同优化的结果进行修正。针对可变复杂度方法需要大量初始计算以保证计算精度的缺点,结合上述两种改进方法的各自特点,提出了基于响应面更新的可变复杂度方法。研究表明:基于响应面更新的可变复杂度方法可以在较少初始样本计算的情况下,获得精度高的结果,这大大节省了初始计算的时间。综上,论文在以下四个方面,做出了创新性的研究成果:(1)提出了一套完整的桁架式Spar平台的概念设计方法和流程。开展了甲板布置、主尺度设计、稳性和水动力性能初步分析等概念设计工作。在此基础上,进行了桁架式Spar平台的结构设计,并应用设计波法对平台主要结构进行了强度校核。(2)将多学科设计优化技术应用到桁架式Spar平台的概念设计中,通过对由现有设计方法和多学科设计优化方法得到的方案的对比,证明了多学科设计优化技术在桁架式Spar平台设计领域的适用性和优越性。(3)提出将Spar平台设计中所涉及的学科进行分模块处理的多学科建模方法,即分为优化模块、约束模块和检验模块,针对分属不同模块的学科采用不同方法处理。不仅简化了多学科设计优化的计算流程,降低了优化收敛的难度,而且也可以保证模型的合理性和工程适用性。(4)针对多学科设计优化中采用近似模型所存在的精度问题,分别采用了响应面更新策略和可变复杂度方法,来改进近似模型的精度和提高优化结果的可靠性。在此基础上,提出了基于响应面更新的可变复杂度方法,通过响应面的逐步更新提高精度,通过可变复杂度方法,减小近似模型与高精度模型间的差距。本文四个阶段的研究成果和主要创新点,是对现行Spar平台概念设计方法的革新。将多学科设计优化方法更好地应用于Spar平台设计,进而促进海洋平台设计的数字化和虚拟化发展,对推动包括Spar平台在内的新型平台的自主研制与应用均具有一定的意义。
&&&&To meet the demand of national economic development and people’s fast-growing living condition, China has planned projects of exploiting oil and gas reserves in the South China Sea. However, the manufacturing capability of offshore production platforms in China is still below 500 meters water depth, far from the exploration requirement in South China Sea. Nowadays, the mainstream platforms used in deep water around the world include Floating Production Storage and Offloading System, Semi-submersible, Tension Leg Platform and Spar platform. Among them, Spar platforms have advantages in aspects of functionality, stability, cost-efficiency and safety. Besides, China has dedicated many years’study on Spar platform and has rich technical reserves. In such circumstances, Spar platform will become one of the major equipment for the gas and oil exploration for our country in the deep water, including South China Sea.Presently, Chinese design capability is lagged behind the foreign design enterprises on the design of advanced ocean engineering units, especially in the conceptual design stage. In addition, the technical monopoly brings difficulties for us to develop Spar platforms. To speed up the pace of research on Spar platforms, and to break through the technical bottleneck, we should make innovation in both concept and method for the conceptual design of Spar platform.Firstly, this thesis carries out a Truss Spar conceptual design and structural design task based on the current design method of offshore platforms. The current design method prevailing in China is the series process, based on the purpose to improve the parent unit. This design process has the shortcomings of relying too much on the parent unit and high design cost. Even worse, the results of conceptual design can hardly present the overall performances. The design of Spar platforms is a complex engineering problem involving many disciplines, such as hydrodynamics, structures, reliability, etc. These disciplines are both mutual interaction and contradictions, so the overall conceptual design of Spar platform is a typical Multidisciplinary Design Optimization (MDO) problem. However, the current design method can not consider the mutual influence among these disciplines sufficiently, so it often leads to a suboptimal design instead of optimal design. Besides, the trend for ships and offshore platforms design is moving toward digitalization and virtualization, which will be beneficial for designers to acquire comprehensive information about the system to design in the early stage. Such trend demands the design method be able to highly integrate all the relevant disciplines. Obviously, it can hardly be realized by current method. To speed up the development of deep sea resources exploration, some breakthrough and innovation for the concept and method of design is in urgent need.In such a situation, as a part of the project supported by the Science and Technology Commission of Shanghai Municipality, this thesis introduces Multidisciplinary Design Optimization, emerged from aeronautics and astronautics fields for complex engineering integrated optimization problems, and explores feasibility and applicability of MDO method to the conceptual design of Truss Spars. The thesis mainly consists of four parts.Part I: Review about the related research areaThe significance of applying MDO techniques in the Truss Spar conceptual design is stated. The definition, development and main research contents of MDO are reviewed. Four mainstream MDO algorithms are elaborated and compared in categories including origin and purpose, approximation models, decomposition, convergence and engineering applicability. Two algorithms– collaborative optimization based on approximation models and BLISS 2000 are regarded as suitable methods to apply MDO techniques in the design of ships and offshore platforms.Part II: Study on the current conceptual design method and structural design method of Truss SparThe current Truss Spar conceptual design method is explored. Two aspects are involved during the conceptual design: one deals with the design method and process, and the other concerns the hydrodynamic behavior. The conceptual design process of Spar platform can be described as an interactive flow. A Truss Spar conceptual design process including general arrangement, weight control and selection of main particulars is conducted. The stability and hydrodynamic performances for the Truss Spar are accessed. Based on the results of conceptual design, the structural design is conducted including:(1) The design method for each part of Spar platforms is concluded and the structural scantling process is accomplished based on the main particulars, general arrangement a (2) The global strength analysis based on design wave methodology is accomplished. Two critical load criteria are selected and wave-induced load is obtained based on 3-D potential theory.(3) The impact on bottom deck strength for two structural configurations– double bottom and single bottom is studied. The result shows the double bottom can reduces the stress of bottom deck of hard tank in great extent.The Spar designed by current conceptual design method and structural design method is treated as baseline Spar for further comparison with the result of MDO.Part III: Application of MDO on the Truss Spar conceptual designThe design parameters in the design of Spar platform, including main particulars, operation parameters, economics and reliability, are elaborated. Because the thesis focuses on the conceptual design, the main particulars are selected as design variables. Then the varying level of design variables are arranged by the theory of Design of Experiment (DOE) and corresponding design plans are determined by uniform design table.One of the most significant factors for a successful application of MDO is to obtain a reasonable MDO model. A comprehensive MDO model, which includes every discipline related to Truss Spar, will make the optimization process d On the contrary, if only a few disciplines are included, the result of MDO can hardly represent the whole system and be impractical for engineering. To solve this contradiction, an innovative multidisciplinary modeling method is proposed. The disciplines related to Spar platform are divided into three modules: optimization module, constraint module and inspection module. Each module is treated as a different role during the optimization.The optimization module is the main focus for platform owners and designers, and treated as optimization object function. The disciplines of constraint module are the characteristics of Spar platforms. These characteristics are precondition for the realization of platform functions, and treated as constraints in the optimization process. Only a few critical objectives for each discipline are selected and integrated in the optimization model. The inspection module is not involved in the optimization process and is used to provide a comprehensive assessment of the optimized design for checking.In the thesis, the hull weight is treated as optimization object. The short term predictions of heave motion and pitch motion are selected as constraint objects for hydr the intact stability coefficient is selected as the constraint object for
the von Mises stress of the connection zone of hard tank bottom deck with truss is selected as the constraint object for structure discipline. A hull/mooring coupled analysis in time domain is utilized as the method of inspection module. To set up the MDO model for Truss Spar, numerous hydrodynamic analyses, stability analyses and structural strength analyses are conducted for all design plans defined by DOE.The Collaborative Optimization (CO) based on response surface method is selected as the MDO algorithm and the CO model for Truss Spar conceptual design is established for the first time. Then the CO optimization process is executed and an optimal design is achieved.Part IV: The improvements of the Collaborative Optimization modelAlthough the approximation models can greatly improve the computational efficiency, the accuracy of the models may be not eligible. To enhance the accuracy of the approximation models and consequent optimization quality, two methods are used:(1) Adaptive response surface method (ARSM)– The concept and procedure of ARSM is proposed. The collaborative optimization based on ARSM for Truss Spar conceptual design is accomplished and an optimal design solution, which satisfied all the constraints, is obtained. A discussion on the adaptive history for each design variables is made. The optimized results are compared with the baseline Spar. The comparison shows that the optimized solution by MDO achieves a lighter platform, and that the performances of heave response motion, stability coefficient and strength of the bottom deck are much improved. The only performance degradation for the optimized solution is the pitch motion, while the change is not significant. Finally, the time domain analysis based on 100-year storm of Gulf of Mexico is conducted and the results prove that the optimized design solution by MDO is feasible.(2) Variable-complexity method (VCM)– Although ARSM can effectively improve the accuracy of approximation models, it fails to diminish the difference between approximation models and physical models. VCM is adapted to correct results of CO in part II by using the results of high-fidelity analysis tool.However, VCM generally requires large number of calculations for initial sampling points to ensure precision. To overcome such a deficiency, an improved VCM method based on ARSM is proposed. The application results show that the improved VCM strategy can attain high accuracy with a small number of initial sampling. In summary, four innovative accomplishments have been made in the thesis.(1) A complete conceptual design process for Truss Spar is proposed and structural design is conducted. Design wave methodology is used to check the structural strength of the platform.(2) MDO techniques are applied in Truss Spar conceptual design. The optimized design results by MDO show superiority in performances contrasting to the ones by the current design method. The feasibility of applying MDO techniques in the Spar platform is verified.(3) An innovative multidisciplinary modeling method is proposed. The related disciplines for Spar platform are divided into three modules: optimization module, constraint module and inspection module. Each module is treated as different role during the optimization. Such modeling method decreases the convergence difficulty of optimization and relieves the computational burden. The rationality of the MDO model is also guaranteed.(4) Adaptive response surface method and variable-complexity method are adopted to improve the accuracy of approximation models. An improved VCM method based on ARSM is proposed. The method shows advantages in both improving the accuracy of approximation models and diminishing the difference between approximation models and physical models.The accomplishment of this thesis is an innovation to the current conceptual design method. A successful application of MDO in Truss Spar conceptual design will promote the development of digitalization and virtualization for offshore platforms, make a contribution to the independent research and application of offshore platforms, Spar platform included, in deep sea areas in China.
&&&&&&&&&&多学科设计优化在桁架式Spar平台概念设计中的应用研究摘要5-9Abstract9-13第一章 绪论18-40&&&&1.1 选题背景及意义18-20&&&&1.2 多学科设计优化综述20-36&&&&&&&&1.2.1 多学科设计优化理论的提出、发展和主要技术20-26&&&&&&&&1.2.2 多学科设计优化算法26-34&&&&&&&&&&&&1.2.2.1 并行子空间优化27-29&&&&&&&&&&&&1.2.2.2 二级系统一体化合成优化29-31&&&&&&&&&&&&1.2.2.3 协同优化31-32&&&&&&&&&&&&1.2.2.4 分级目标传递法32-34&&&&&&&&1.2.3 多学科设计优化算法的比较与选取34-36&&&&1.3 本文主要工作及创新点36-40&&&&&&&&1.3.1 主要研究内容36-37&&&&&&&&1.3.2 论文的创新点37-40第二章 桁架式 Spar 平台的概念设计40-62&&&&2.1 引言40&&&&2.2 Spar 平台发展现状和主要特点40-51&&&&&&&&2.2.1 Spar 平台的产生40-42&&&&&&&&2.2.2 Spar 平台的总体结构42-45&&&&&&&&&&&&2.2.2.1 顶部甲板模块43&&&&&&&&&&&&2.2.2.2 主体结构43-44&&&&&&&&&&&&2.2.2.3 系泊系统44-45&&&&&&&&&&&&2.2.2.4 立管系统45&&&&&&&&2.2.3 Spar 平台的发展45-49&&&&&&&&&&&&2.2.3.1 第一代Spar 平台——经典式Spar 平台45-46&&&&&&&&&&&&2.2.3.2 第二代Spar 平台——桁架式Spar 平台46-47&&&&&&&&&&&&2.2.3.3 第三代Spar 平台——多柱式Spar 平台47&&&&&&&&&&&&2.2.3.4 新概念Spar 平台——多柱桁架式Spar 平台47-49&&&&&&&&2.2.4 Spar 平台与其他深海平台的比较49-51&&&&2.3 Spar 平台概念设计流程51-60&&&&&&&&2.3.1 现有海洋平台概念设计的基本流程51-53&&&&&&&&2.3.2 设计任务要求53&&&&&&&&2.3.3 甲板总布置及主尺度设计53-58&&&&&&&&2.3.4 稳性计算58&&&&&&&&2.3.5 水动力学性能的初步分析58-60&&&&2.4 本章小结60-62第三章 桁架式 Spar 平台的结构设计62-92&&&&3.1 引言62&&&&3.2 平台结构布置62-66&&&&&&&&3.2.1 硬舱结构布置62-64&&&&&&&&3.2.2 软舱结构布置64-65&&&&&&&&3.2.3 桁架及垂荡板结构布置65-66&&&&3.3 基于规范的结构设计66-85&&&&&&&&3.3.1 硬舱结构设计66-77&&&&&&&&&&&&3.3.1.1 甲板结构设计66-67&&&&&&&&&&&&3.3.1.2 单壳舱室结构设计67-72&&&&&&&&&&&&3.3.1.3 双壳舱室结构设计72-74&&&&&&&&&&&&3.3.1.4 硬舱结构尺寸汇总74-77&&&&&&&&3.3.2 软舱结构设计77-81&&&&&&&&&&&&3.3.2.1 软舱甲板结构设计77-79&&&&&&&&&&&&3.3.2.2 软舱舱壁结构设计79-80&&&&&&&&&&&&3.3.2.3 软舱结构尺寸汇总80-81&&&&&&&&3.3.3 垂荡板及桁架结构设计81-85&&&&&&&&&&&&3.3.3.1 垂荡板板架结构设计81-82&&&&&&&&&&&&3.3.3.2 桁架结构设计82-85&&&&&&&&&&&&3.3.3.3 垂荡板及桁架结构尺寸汇总85&&&&3.4 桁架式Spar 平台的强度初步计算85-91&&&&&&&&3.4.1 强度分析方法85-86&&&&&&&&3.4.2 Spar 平台的强度初步计算86-91&&&&3.5 本章小结91-92第四章 桁架式 Spar 平台的多学科建模92-124&&&&4.1 引言92-93&&&&4.2 试验设计技术93-95&&&&4.3 桁架式Spar 平台的设计变量参数95-99&&&&&&&&4.3.1 设计变量参数的分类95-96&&&&&&&&4.3.2 设计变量的选择96-97&&&&&&&&4.3.3 均匀设计安排97-99&&&&4.4 多学科建模99-123&&&&&&&&4.4.1 优化模块101-102&&&&&&&&4.4.2 约束模块102-120&&&&&&&&&&&&4.4.2.1 水动力学科分析102-113&&&&&&&&&&&&4.4.2.2 稳性学科分析113-118&&&&&&&&&&&&4.4.2.3 结构学科分析118-120&&&&&&&&4.4.3 检验模块120-123&&&&4.5 本章小结123-124第五章 基于响应面的协同优化过程124-152&&&&5.1 引言124&&&&5.2 协同优化124-128&&&&&&&&5.2.1 协同优化的基本思想和框架结构124-126&&&&&&&&5.2.2 协同优化的数学模型126-127&&&&&&&&5.2.3 协同优化的特点127-128&&&&5.3 近似方法128-132&&&&&&&&5.3.1 响应面模型128-130&&&&&&&&5.3.2 基于响应面模型的协同优化过程130-131&&&&&&&&5.3.3 响应面模型的建立131-132&&&&5.4 基于响应面的桁架式Spar 平台协同优化过程132-139&&&&&&&&5.4.1 设计变量、系统级与子系统级划分132-135&&&&&&&&5.4.2 协同优化框架135-137&&&&&&&&5.4.3 优化求解137-139&&&&5.5 基于响应面更新策略的桁架式Spar 平台协同优化过程139-145&&&&&&&&5.5.1 响应面更新策略139-141&&&&&&&&5.5.2 优化求解141-144&&&&&&&&5.5.3 优化结果讨论144-145&&&&5.6 优化方案的验证145-150&&&&5.7 本章小结150-152第六章 基于可变复杂度方法的协同优化过程152-164&&&&6.1 引言152&&&&6.2 可变复杂度方法152-157&&&&&&&&6.2.1 可变复杂度方法介绍152-154&&&&&&&&6.2.2 基于可变复杂度方法的桁架式Spar 平台协同优化模型154-157&&&&6.3 基于响应面更新的可变复杂度方法157-163&&&&&&&&6.3.1 基于响应面更新的可变复杂度方法的提出和应用流程157-158&&&&&&&&6.3.2 优化过程及计算结果158-163&&&&6.4 本章小结163-164第七章 总结与展望164-168&&&&7.1 全文总结164-166&&&&7.2 研究展望166-168参考文献168-180附录 Spar 平台结构设计规范（结构尺寸设计部分）180-189致谢189-191攻读博士学位期间发表学术论文情况191-194上海交通大学学位论文答辩决议书194
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