碳达峰-碳中和战略中的关键力学问题

<正>气候变化是人类面临的全球性问题.随着温室气体排放的急剧增长,地球上的生命系统面临严峻挑战.基于推动可持续发展的内在需求与构建人类命运共同体的责任担当,我国2020年提出力争2030年前实现碳达峰、2060年前实现碳中和的目标.碳达峰-碳中和战略已成为我国中长期发展的重要框架.为了反映我国在该领域与力学相关研究的最新进展,《力学学报》组织了“碳达峰-碳中和战略中的关键力学问题”专刊.专刊收录了清洁能源开发利用、非常规能源开发利用、能源低碳化利用、低碳建筑与储能技术、地质系统固碳、相关力学基础理论与方法等方向17篇研究或综述论文,供读者参考.     

氢进万家专题序(Ⅰ)——氢进万家，助力“双碳”目标实现，服务生态文明建设

<正>全球气候变化是当今世界可持续发展面临的巨大而严峻的挑战,建设生态文明社会,实现碳中和是应对挑战的重要手段。我国关于“双碳（碳达峰和碳中和）”战略目标的庄严承诺,正是作为一个负责任大国的使命与担当。氢能作为潜力巨大的清洁能源载体,是我国能源结构由高碳到低碳转型并最终实现碳中和战略目标的重要选择,甚至是实现碳中和的终极方案。目前,我国氢能产业正步入发展快车道,城镇地区用氢需求将不断提升,如何实现氢能的规模化、经济性和安全输运是制约“氢进万家”的关键问题。     

天然气随动掺氢技术研究进展

氢气是一种零排放的二次能源,是实现“双碳”目标的重要能源之一。采用在役天然气管道或管网输送掺氢天然气,是实现氢气大规模输送的有效方式。精确控制进入输送系统的掺氢比例对系统安全运行具有重要意义。本文介绍了电气式和机械式随动掺氢系统的结构与原理;分析了红外吸收型、热传导型、半导体型浓度传感器和相应的综合测量系统在掺氢比动态调整中的应用;重点评述了目前3个重要在役天然气掺氢示范项目中随动掺氢系统的组成和运行结果;基于工程实践经验展望了天然气掺氢技术的发展趋势。     

流体力学实践教学改革网络体系的构建

 根据流体力学课程的性质、特点,结合自身现场工作及教学体会,构建了流体力学课程教学改革网络体系. 既实现了丰富、指导课堂教学和实践教学的近期目标,又加速了让学生终身学习的长远目标的实现. 研究对于推动教学改革进程、探索学分制下的专业基础课教学模式有一定的借鉴意义.     

用于高温重载的碳轴承

一、前言 碳轴承具有自润滑性、抗化学性、耐高温性、尺寸稳定性和高承载能力等优点,因而可简化轴承系统的设计。这种轴承可用于一般轴承难以胜任的许多场合。碳轴承的性能还在不断改善,现已有含各种添加剂、浸渍剂和使碳自身发生化学转变等多种新的品种。采用碳轴承,由于不要供油系统、油封或脂封和定期润滑,还可减轻设备重量、缩小设备体积,所以在经济上对制造厂家或用户都是有利的。碳轴承原材料价格便宜,来源充足,尽管这类轴承的加工费用约占轴承总成本的90％,但选用碳轴承仍比其它轴承要便宜些。     

碳纤维在海洋结构与装备中的应用与挑战

碳纤维具有轻质、高强、耐腐蚀、抗疲劳等优异的性能,在工业生产中具有广泛的应用.传统的海洋结构与装备材料以钢材为主,但是随着海洋油气资源向深水的发展,以及清洁海洋能源的开发,碳纤维在海洋结构与装备中的应用也占据了一席之地.本文主要介绍了碳纤维在海洋管缆、系泊系统、耐压结构、风机叶片、储氢罐以及结构修复中的应用及相关的一些...     

隧洞式内衬储气库极限储存压力解析解

隧洞式内衬储气库是一种新型能源储存方法,有助于平衡供需,推动国家由化石能源向绿色能源的持续过渡,有利于国家“碳中和、碳达峰”目标的实现.本文采用极限平衡方法和弹塑性分析方法推导隧洞式内衬储气库极限储存压力的解析解.在极限平衡方法中,考虑上覆围岩自重、破裂面受力和极限储存压力,选用刚性锥模型,推导了上限压力表达式;在弹塑性分析方法中,根据围岩中应力分布规律和剪切、抗拉强度,推导获得了弹塑性条件下上限与下限压力表达式.最终综合考虑两方法求得的结果,确定极限储存压力解析解.结果表明:极限平衡方法求得上限压力与埋深呈二次函数关系,且随着侧压力系数的增大而增大;弹塑性分析方法确定的上限压力和下限压力与埋深呈线性关系,下限压力随着侧压力系数的增大而减小,且Ⅰ级围岩条件下的内衬储气库不用考虑下限压力.在侧压力系数λ=1.2时上限压力最大,因此应尽量在侧压力系数为1.2的围岩条件下修建隧洞式储气库.最后根据典型工况下上限和下限压力曲线给出内衬洞室推荐压力范围.     

基于自然增长的细胞群粘附数值模拟

细胞群通过表面的粘附分子不断聚集的过程称为细胞群粘附, 是生物学许多研究领域(早期的胚胎发育、组织的新陈代谢以及肿瘤生长等)的基础. 考虑细胞群的自由运动和细胞群互相之间的粘附力作用, 并引入Logistic模型来描述细胞群自身的自然增长, 从宏观的角度研究细胞群粘附现象, 构建出一个细胞群粘附模型; 其数值模拟结果与实验结果较吻合, 能定性地对不同种类细胞群粘附的最终形态做出预判.      

振动能量采集与振动控制序

<正>振动是自然界中常见的现象,振动超过一定限度时,会对人体、设备和设施造成损伤.研究人员一般从两个方面处理振动:一方面采用振动控制技术,包括吸振、隔振、减振等,降低从振动源传输到主体的振动能量;另一方面采用能量采集技术,将振动能量转换为电能,并储存起来为低功耗电子设备供电,即能量的重新分配与利用.振动能量采集与振动控制具有相通的力学原理与方法.近年来研究者们对振动能量采集与振动控制进行了深入研究,实现自供能传感、重大装备减振降噪、自反馈振动控制等,促进我国高端智能化装备研制,助力国家“双碳”目标实现.     

一种未知环境下移动机器人自主导航方法

为提高未知环境下移动机器人自主导航性能,提出了一种未知环境下目标驱动的自主导航方法。不依赖实时更新的地图信息,移动机器人直接从激光雷达读数中构建候选目标点,并根据机器人自身位置和终点位置从候选目标点中选择最优点作为局部目标点。改进的基于深度强化学习的局部规划器从输入信息中直接输出动作信号,实现端到端的控制,使得移动机器人能够快速、安全地到达局部目标点,直至到达终点。实验表明,所提导航方法能够在未知复杂的环境下,可靠且高效地完成导航任务。与最近边界导航方法相比,平均路径长度减少了6.63%,平均运行时间缩短了19.11%,具有成功率高、路径短、速度快等优点。     

Effect of Unreinforced Masonry Infill on Floor Amplification and Other Parameters in Frame-Wall Buildings

Frame-shear wall buildings or dual systems are a common form of reinforced concrete building structures. In such systems, shear walls form the primary lateral load-resisting elements intended to carry about 75% of lateral loads. The beam-column frame elements carry the vertical loads and the balance amount of lateral loads. Unreinforced masonry infill panels are common in frame-wall buildings which are incorporated to serve functional purposes. Infill panels are generally not modeled while designing the buildings. However, the influence of infill on the behavior of the building is considerable. In the present study, the response parameters in terms of average floor spectra and roof displacements have been studied in dual system buildings designed as per Unified Performance-Based Design (UPBD) method, with and without masonry infill struts. The UPBD method satisfies both target design drift and performance level simultaneously. Floor spectra are useful in the design of Operational and Functional Components (OFCs) in buildings which are mounted on floors. For the design of OFCs, parameters such as Floor Amplification factor (FAF), Component Amplification Factor (CAF), and Total Amplification Factor (TAF) are important and have been studied here. Frame-wall buildings with two plans and various heights with and without infill struts have been considered for specified target drift and performance levels. It has been observed that floor response diminishes with the incorporation of infill struts. Some important conclusions have been drawn on FEMA provisions.     

城市地质图的特点·编图原则·方法

论述了城市地质图的主要特点、编图原则和方法, 其主要内容概括如下: (1)编制城市地质图的重要意义首先在于为不断完善和适应城市建设和发展的需要, 更好地使地质工作为城市建设总体规划和政府决策服务, 同时为具体工程设计和施工提供基础资料。其次为合理地开发利用城市土地资源、保护城市地质环境提供科学依据。(2)城市地质图是一个具有以专业地质规划目标与工程地质要求、城市发展总体效益评估为内容的系列图件, 是一个分别具有适应于地质专业人员、城市规划设计工程师和政府决策管理官员需要的多功能特点的系统性图件。(3)城市地质图编制原则, 第一在于客观性; 第二为评价性; 第三为预测性; 第四为实用性。前三项是前提和基础, 后者为目的。力求做到内容准确、明晰可读、易懂, 紧紧围绕城市规划设计和政府决策对地质技术的要求进行。(4)城市地质图包容了基础地质图类、分析评价图类、效益决策评估类三个等级的功能各异的图件, 在制图方法和程式上体现了图件的等级—内容—性质—用途的统一、技术性与管理决策的统一。     

Ice slurry based thermal storage in multifunctional buildings

 Ice slurry based thermal storage plays an important role in reshaping patterns of electricity use for space cooling and heating. It offers inherent advantages in energy efficiency, operating savings, load follow-up and flexible installation over conventional thermal storage technologies. This paper provides discussions on the generation mechanism and performance of ice slurry, as well as the operation principle of the ice slurry based thermal storage system. Details of the system design, control strategy and operation performance are given through a case study on a recent installation in Herbis Osaka, the largest simple building complex in Japan. An evaluation of different installations with ice slurry thermal storage reveals that it is a rewarding technology that provides significant operating savings for the building air-conditioning and improves energy utilization efficiency in modern society. Received on 23 March 2001     

Analysis of tornado and near-ground turbulence using a hybrid meteorological model/engineering LES method

A new hybrid meteorological model/engineering LES method was used to analyze a tornado and near-ground turbulence under realistic conditions. The hybrid method estimates high frequency turbulence regeneration in an actual severe storm that has complex thermal conditions in order to alleviate the problem of high frequency component dissipation in meteorological models and generate appropriate field data to investigate near-ground flow and wind loading on buildings. The high frequency regeneration method was validated in the convective boundary layer and the energy spectrum of the velocity field was successfully extended to higher frequency region in good agreement with −5/3 Kolmogorov law.Multi-scale simulations of a tornado were conducted based on meteorological model outputs with three different terrain conditions, including an actual urban building geometry and terrain, and the changes in the main tornado vortex and the interactions with near-ground turbulent field were examined. On roughened surfaces with uniform blocks and buildings, the main tornado vortex was connected to near-ground vertical vortices arising due to the urban geometry. The structure was significantly deformed, splitting into numerous finer vortices below several times the building height. These near-ground vortices create localized sharp pressure drop patterns and also affect the movement of the tornado. These effects of low pressure on buildings were quantitatively analyzed.     

纵观国际核聚变进展探讨中国核聚变发展的道路

纵观了国际核聚变发展的历史过程,认为托卡马克要成为工程可靠、经济上有竞争能力的一代商用能源,尚有待时日．但作为聚变中子源驱动次临界装置（聚变－裂变混合堆）可解决上述在聚变商用化以前大规模发展核裂变能的四个重要问题（生产核燃料、处理核废料、生产氛及处理军用钚）;保持技术发展的连续性．这种系统由于是次临界的,因而是被动的固有安全的,而且可做到深燃耗或高效率,可以成为我国大规模、可持续发展核能的重要方式,也是推动永久清洁能源─—聚变能发展的重要台阶．本文对国民经济发展过程中的能源需求作了预测,分析了国内外核聚变研究成果现状和发展趋势,对中国的聚变能源战略和历史机遇（经济、技术体系、地位）作了讨论,介绍了聚变－裂变混合堆并提出了发展聚变－裂变混合堆的总体设想、研究内容和预期目标．      

Exact solution of free vibration of adjacent buildings interconnected by visco-elastic dampers

With consideration of a high-rise coupled building system, a flexible beams-based analytical model is setup to characterize the dynamic behavior of the system. The general motion equation for the two beams interconnected by multiple viscous/visco-elastic dampers is rewritten into a non-dimensional form to identify the minimal set of parameters governing the dynamic characteristics. The corresponding exact solution suitable for arbitrary boundary conditions is presented. Furthermore, the methodology for computing the coefficients of the modal shape function is proposed. As an example, the explicit expression of the modal shape function is derived, provided only one damper is adopted to connect the adjacent buildings. Finally, to validate the proposed methodologies, three case studies are performed, in which the existence of the overdamping and the optimal damping coefficient are revealed. In the case of using one damper in connecting two similar buildings, the estimating equations for the first modal damping ratio are formulated.     

Progress of passive daytime radiative cooling technologies towards commercial applications

Global warming has become one of the major environmental problems facing mankind in the 21st century. The existing refrigeration technology of buildings, like air conditioning, consumes a lot of energy. Passive daytime radiative cooling technology works without consuming energy, nor emitting carbon dioxide and other greenhouse gases. This review summarizes the development of daytime passive radiative cooling technology from the basic principles, structure and materials of radiative coolers; analyses and evaluates the various existing radiative coolers. The core of radiative cooling lies in the combination of multi-scale micro/nano structures. The cooler reflects sunlight thus preventing the building from being heated up; while allows the building to radiate its own heat out thus being cooled down; meanwhile maintains the temperature difference by the heat insulation effect of the porous structure in the film. The common challenges and potential solutions for the commercialization of radiative cooling technologies are analyzed, which may promote the applications of the technology in the near future.     

爆破振动速度预测安全保证系数的确定

基于爆破振动速度预测公式回归分析的基本原理,提出根据建筑物不同安全等级应选择一定的可靠性指标,并推导了预测爆破振动速度公式中所含安全保证系数的计算过程。为简化计算过程,又进一步提出了基于监测数据量、回归分析相关系数以及可靠性指标的关于安全保证系数计算的经验公式。经过大量监测数据验证了该经验公式的计算精度和可靠性均能满足工程实际需要,从而修正了萨氏公式预测精确度不够的缺陷,可为重要建筑物周边的安全爆破设计提供参考。     

Evaluation of the Filtered Noise Turbulent Inflow Generation Method

Flows around buildings and in urban areas have the ability to exchange mass and momentum through mixing layers. The complex dynamical phenomena arising in mixing layers can be studied using Large Eddy Simulation (LES). As mixing layers depend on the turbulence conditions upstream of the buildings or urban areas, appropriate turbulent inlet conditions have to be provided to a simulation. Due to the high efficiency and level of control, the filtered noise inflow method was selected. The control over the Reynolds stresses as well as nine length scales make this method suitable to replicate conditions measured in experiments. In this paper, a formal method to obtain the filter coefficients is presented. This is achieved by relating the spatial filtering to a Finite Impulse Response (FIR) filter and the temporal filtering to an Autoregressive (AR) model. Three closed-form solutions for the spatial filter coefficients are presented having a Gaussian, double-exponential and exponential correlation function. By means of an LES simulation of a turbulent wall-bounded flow, the input-output behaviour is investigated. It was found that a combination of a Gaussian filter with length scales that increase with increasing wall distance result in the fastest downstream development of the artificial turbulence and the smallest loss of turbulent kinetic energy.     

我国高层建筑设计计算的回顾及存在的问题

本文综述了近４０年来国内高层建筑结构设计计算的进展．回顾了以手算为基础的各种算法；以杆件为单元的矩阵位移法；以解析、半解析方法为基础的常微分方程求解器方法；多种单元组合的有限元方法；结构的动力特性及动力时程分析；高层建筑ＣＡＤ研究；高层建筑结构力学分析中急待解决的专门问题等．此外对高层建筑力学分析近期进一步研究的课题作了展望．