Topology Optimization of Sound-Absorbing Materials for Two-Dimensional Acoustic Problems Using Isogeometric Boundary Element Method

In this work,an acoustic topology optimizationmethod for structural surface design covered by porous materials is proposed.The analysis of acoustic problems is performed using the isogeometric boundary elementmethod.Taking the element density of porousmaterials as the design variable,the volume of porousmaterials as the constraint,and the minimum sound pressure or maximum scattered sound power as the design goal,the topology optimization is carried out by solid isotropic material with penalization(SIMP)method.To get a limpid 0–1 distribution,a smoothing Heaviside-like function is proposed.To obtain the gradient value of the objective function,a sensitivity analysis method based on the adjoint variable method(AVM)is proposed.To find the optimal solution,the optimization problems are solved by the method of moving asymptotes(MMA)based on gradient information.Numerical examples verify the effectiveness of the proposed topology optimization method in the optimization process of two-dimensional acoustic problems.Furthermore,the optimal distribution of sound-absorbingmaterials is highly frequency-dependent and usually needs to be performed within a frequency band.

Sintering preparation of porous sound-absorbing materials from steel slag

Porous sound-absorbing materials were prepared from steel slag using waste expanded polystyrene（EPS） particles as pore former.The influences of the experimental conditions such as fly ash content,sintering temperature,sintering time,and pore former addition on the performance of the porous sound-absorbing materials were investigated.The results show that the porosity of the specimens can reach above 50.0%;the compressive strength and average sound-adsorption coefficient of the sintered specimens are above 3.0 MPa and 0.47,respectively.The optimum preparation conditions for the steel slag porous sound-absorbing materials are as follows：mass fraction of fly ash 50%,waste EPS particles 3.6 g,sintering temperature 1100℃,and sintering time 7.5h,which are determined by considering the properties of the sound-absorbing materials,energy consumption and cost.

Parameter Study on a Composite Sound-Absorbing Structure Liner in Elevator Shafts

With the growing global environmental awareness,the development of renewable and green materials has gained increased worldwide interest to substitute conventional materials and are favorable for sustainable economic development.This paper proposed a novel eco-friendly sound absorbing structure(NSAS)liner for noise reduction in elevator shafts.The base layer integrated with the shaft walls is a damping gypsum mortarboard,and a rock wool board and a perforated cement mortarboard are used to compose the NSAS.Based on the acoustic impedance theory of porous materials and perforated panels,the sound absorption theory of the NSAS was proposed;the parameter effects of the rock wool board(flow resistivity,porosity,structure factor)and perforated panel(perforated rates,thickness,density,perforated diameter)on NSAS absorption were discussed theoretically for absorption improvement,and experiments were also conducted.Numerical results showed that the perforation rate,the thickness of the perforated plate,and the porosity,flow resistance,and volume density of the rock wool board played a key issue in the absorption performances of the NSAS.Experiments verified the accuracy of the proposed theoretical model.Wideband sound absorption performance of the NSAS at frequencies between 500–1600 Hz was achieved in both numerical analysis and experiments,and the sound absorption coefficient was improved to 0.72 around 1000 Hz after parameter adjustments.The NSAS proposed in this paper can also be made of other renewable materials with preferable structure strength and still has the potential to broaden the absorption bandwidth.It can provide a reference for controlling the elevator shaft noise.

木质材料对室内声学调控的研究进展

木材为多孔性材料,在室内空间中,使用木质材料除了具有饰面作用外,还可以有效吸收声能,控制室内混响时间,改善音质,提高语言清晰度。本文概述了木质材料的吸声和隔声性能两方面的研究现状,并对未来的研究提出了建议。在此基础之上,总结了前人在大型建筑空间、小型办公空间、家居室内空间中声环境调控的不足之处。主要有以下3点:1)研究者多选取某一特定的室内空间类型进行声环境改善,尚缺乏对不同使用功能的室内空间声环境的规律性研究,以形成较为系统的室内声环境调控体系。2)成片的家具几何结构改变室内声环境的程度有待进一步研究验证。3)对于改变空间的形状、比例、布局的方法有待进一步研究其内在规律,为设计师、建筑师和科研人员提供参考依据。未来研究重点包括:1)通过使用木质材料对空间进行合理化布局与设计;2)处理好不均匀的声频或室内声场驻波的简并现象,需合理选择吸声构件。3)建立智能化声学仿真模型。

应县木塔结构稳定性评估预问题之我见

国家重点研发计划支持项目《应县木塔结构稳定性评估与保护研究》研究指南在明确常规研究内容的同时,强调了“研究应县木塔营建历史、形制、用材原则,构件劣化特征与损伤累积效应关系”。清华大学建筑学院研究团队认为该问题正是应县木塔结构稳定性评估工作的基础性“预问题”,并就此进行延伸思考,提出此“预问题”的3个方面及解决问题的相应技术路线。

社会转型视野中的湖南木帆船运输业探析(1949—1952)

1949—1952年是国民经济恢复时期,社会急剧变革,各行业在新民主主义经济秩序下重建和发展。木帆船运输市场得以重建,成为当时重要的运输力量。以湖南为例,新中国成立后,木帆船运输业逐渐恢复,建立了新民主主义的运输市场秩序;降低运价,加强管理,在城乡物资交流中发挥着民船联运的优势,大运输体系建立起来;土产、矿产和粮食得以外运,工业品和食盐输往农村,农村初级市场末端得以拓展,新商业路线得到开辟,在国家工程建设中发挥着重要作用。

生物基阻燃剂对木家具水性漆性能影响及调控

以薄木材料为基材,通过以薄木表面生物基阻燃剂的载药量、涂刷材料、涂层顺序为条件,研究不同涂饰方式处理后木质家具材料阻燃性能和装饰效果。植酸基阻燃剂处理后木质家具材料表面不能用水性涂料进行涂饰。生物基阻燃剂涂刷薄木之后,再涂刷水性涂料会降低生物基阻燃的阻燃效果。当生物基阻燃剂的载药量大于25%时,薄木的阻燃效果良好。植酸基阻燃剂覆膜保护后涂刷于薄木表面对水性漆涂饰后薄木的装饰效果影响不大;在薄木涂刷生物基阻燃剂后,再对其涂刷聚乙烯醇溶液,最后进行水性漆涂饰,该方式的装饰效果良好,且获得的薄木氧指数接近30。结果表明:覆膜保护涂饰方式工艺简单且对环境友好,所得薄木装饰效果和阻燃性良好,生物基阻燃最佳载药量为28%。在实际生产中,可根据实际情况利用该涂饰工艺对木质家具材料进行处理。

CLT发展现状与展望

在“双碳”和生态文明背景下,木质建筑材料作为一类环保型建材,具有绿色可再生、低碳、可持续发展的优势,是实现我国“双碳”目标的重要助力。本文介绍了一种典型的木结构建筑材料——正交胶合木的特点和发展现状,讨论了目前存在的问题,并对正交胶合木的未来发展进行了展望。

传统木结构建筑材料的循环利用研究与实践

针对现有中国传统木结构建筑的修缮过程中未充分利用其所使用的石料、土料及木料可重复使用的问题,基于建筑材料利用层次理论中“3Rs”模式,提出传统木结构建筑材料的循环利用的原则,形成传统木结构建筑材料循环利用的模式。并进一步在实际传统木结构建筑修缮中积极推进这一模式,为传统木结构建筑材料的循环利用模式的构建提供一些思路和方向。

Wooden Structures within the Context of Parametric Design: Pavilions and Seatings in Urban Landscape

Today,on the one hand,while the traditional design process continues,on the other hand,digital design systems along with advances in computer technologies continue to present designers with new and effective ideas.Parametric design is preferred by designers for its relationality,contributing toward versatility,ensuring flexibility,simplifying diversification,and for presenting programmatic solutions.As is seen in a number of areas,we have also begun to encounter the use of parametric designs produced with parametric design systems and wooden materials in urban landscaping.The purpose of this study is to examine the upper cover application and seating elements generated by taking advantage of parametric designs from wooden construction materials in urban landscaping areas,and examine the impact of wooden material characteristics while generating behavior and parametric structures of technologies.After researching parametric design and wooden material concepts,an attempt was made to reach conclusions through analyses conducted by examining parametric wooden designed pavilion and seating element specimens applied in various regions of the world.

论中国传统木构建筑现代传承之困

木构是中国传统建筑最突出的特征。近几十年里,历史发展的诸多影响因素,使得传统木构建筑的营建无法有效承续,对其传承价值产生误判与漠视,导致中国传统建筑精神与智慧无法对应当下,更遑论引领未来。文章认为,中国传统木构建筑在当下面临之传承困境主要有理念之困、结构之困、材料之困、人才之困四个方面。通过揭示中国传统建筑走入困局的历史原因及传承发展的现实遭遇,现行建筑设计规范对木构建造的诸多限制,本土建材的现代化研究缺乏,以及传统木结构无法得到有效计算等问题,明确传统木构建筑在当代传承的发展障碍及其原因。并提出从观念上摆脱对传统木构认识的形式误区,建立基于传统木构自身营建规律的知识体系。从传统出发,或能寻求突破,摆脱困局。

无醛阻燃人造板的研究现状及发展趋势

木质材料因具有重量轻、强重比高、弹性好等优点被广泛应用于各个领域,但其可燃的特性限制了在某些方面的应用。阐述了现阶段木材阻燃剂种类及应用研究现状,包括卤系阻燃剂、磷氮系阻燃剂、无机阻燃剂,并对其阻燃机理及应用优缺点进行了对比。此外,重点对无醛阻燃人造板的研究现状进行了阐述,综述了近几年无醛阻燃人造板的研究进展,并对未来无醛阻燃人造板的发展方向进行了深入探讨。

木质室内装饰材料污染物及防治

阐述木质室内装饰材料在装修过程中释放的主要污染物甲醛和TVOC的特点及危害,并从装修前材料的选择、装修方案设计和装修后室内空气质量改善等方面提出降低木质室内装饰材料污染物释放量的措施,为解决环境污染问题提供借鉴。

Preparation of steel slag porous sound-absorbing material using coal powder as pore former

The aim of the study was to prepare a porous sound-absorbing material using steel slag and fly ash as the main raw material, with coal powder and sodium silicate used as a pore former and binder respectively. The influence of the experimental conditions such as the ratio of fly ash, sintering temperature, sintering time, and porosity regulation on the performance of the porous sound-absorbing material was investigated. The results showed that the specimens prepared by this method had high sound absorption performance and good mechanical properties, and the noise reduction coefficient and compressive strength could reach 0.50 and 6.5 MPa, respectively. The compressive strength increased when the dosage of fly ash and sintering temperature were raised. The noise reduction coefficient decreased with increasing ratio of fly ash and reducing pore former, and first increased and then decreased with the increase of sintering temperature and time. The optimum preparation conditions for the porous sound-absorbing material were a proportion of fly ash of 50%（wt.%）, percentage of coal powder of 30%（wt.%）, sintering temperature of 1130°C,and sintering time of 6.0 hr, which were determined by analyzing the properties of the sound-absorbing material.

木质建筑材料对室内空气化学污染的影响分析

为了解木质建筑材料对房屋室内空气质量的影响,提高室内空间环境和家具的舒适性,提高对于装修与家具材料的环保要求。介绍了建筑室内设计的概念与要求,针对实木家具设计的概念进行了阐述。分析了室内木质建筑材料的成分与污染来源,对室内木质建材的污染问题进行了实验测定,并提出了减少家具对室内环境污染的方法。研究结果表明,室内木质建材的污染源主要来源于甲醛、重金属、挥发性有机化合物、异味物质4类,季节更替对于室内污染物的散发有一定影响,提出了减少污染有效方法,为今后对木质家具与建材污染物的研究提供参考。

新型材料在古建筑木结构修复中的应用

通过分析古建筑木结构的物理和力学性能,确定木结构损坏程度,利用墩接法对木桩糟朽部分进行剔补处理,采用化学加固材料对古建筑木结构裂缝进行嵌补修复,利用碳纤维布材料对木结构的弯垂部位进行补强处理,从而完成基于新型材料的古建筑木结构修复处理。根据试验结果可以看出,新型材料应用于修复古建筑木结构后,木结构的力学性能明显优于修复前。

生命共同体的吟唱——物质生态批评视域下的林露德传记小说研究

美国华裔女作家林露德的传记小说在呈现人物人生轨迹的过程中,隐含着对非人类自然物质与人类关系的探讨,展现了其深刻的生态伦理思想。小说中所描绘的万物平等、物之治愈与万物一体的关系,彰显了作品对构建跨民族、跨物种界限的有序和谐生命共同体的呼吁。

皮革材料在木质产品中的应用研究

皮革与木材作为两种天然材料,具有不同的特点。近年来,随着消费理念的改变,皮革在木质产品中得到了广泛的应用。文章分析了当前皮革材料在木质产品中的应用现状,从材料的碰撞、色彩的平衡、结构的丰富、自然的交织四个层面总结了两者的结合应用方法,并阐述了皮革材料对木质产品美学、功能、可持续三方面的应用价值,丰富了皮革材料在产品设计领域的应用研究视野。

The Effect of Reflector with Sound-Absorbing Material on Supersonic Jet Noise

This paper describes an experimental work to investigate the effect of a reflector on supersonic jet noise radiated from a convergent-divergent nozzle with a design Mach number 2.0.In the present study,a metal reflector and reflectors made of three different sound-absorbing materials(grass wool and polyurethane foam)were employed,and the reflector size was varied.Acoustic measurement is carried out to obtain the acoustic characteristics such as frequency,amplitude of screech tone and overall sound pressure level(OASPL).A high-quality schlieren optical system is used to visualize the detailed structure of supersonic jet.The results obtained show that the acoustic characteristics of supersonic jet noise are strongly dependent upon the jet pressure ratio and the reflector size.It is also found that the reflector with sound-absorbing material reduces the screech tone amplitude by about 5-13dB and the overall sound pressure levels by about 2-5dB,compared with those of the metal reflector.

木质材料缺陷无损检测主要研究进展

从基于成像技术、信号传播速度变化、人工模拟缺陷和信号处理的木质材料缺陷无损检测以及木质材料缺陷对其力学性能的影响5个方面论述了木质材料缺陷无损检测的研究进展,简要分析了目前研究中存在的主要问题及其发展趋势。