中国古代隔声技术初探

本文以现代声学知识讨论了方以智等人记载的“瓮墙”隔声原理;并进一步分析了《续汉书·律历志》“候气之法”中的“律室”的隔声性能,认为似乎可与现代隔音室相媲美,堪称中国古代高级隔音室.     

FTIR Measurement of Cellulose Microfibril Angle in Historic Scots Pine Wood and Its Use to Detect Fungal Decay

Microfibril angle (MFA) – the orientation of cellulose fibres in the S2 layer of the secondary cell wall – is a key determinant of the stiffness and strength of timber. The microfibril angle depends on the way in which the timber was grown and its position within the tree. Microfibril angle can be measured by X-ray diffraction and other methods, but the methods in current use are slow or require advanced instrumentation. The aim of this study was to explore the use of polarised Fourier transform infrared (FTIR) microscopy as a relatively fast and inexpensive method for measuring MFA in historic Scots pine (Pinus sylvestris L.). The FTIR measurements were calibrated against X-ray measurements of MFA in modern Scots pine. We observed a wide range in MFA values and a radial pattern of MFA similar to modern Scots pine in undecayed Scots pine heartwood from sixteenth and seventeenth century beams in Scottish secular buildings. The density of the heartwood was also similar to modern plantation-grown Scots pine despite the much slower growth rate recorded in the ring widths of the historic timber. The sapwood, which had been attacked by both insect pests and fungi, showed an erratic reduction in density and a large increase in MFA compared to the modern material. The increased sapwood MFA was attributed to selective destruction of the S2 layer of the wood cell walls by fungal decay. Using MFA measurements in conjunction with density offers the possibility to estimate the mechanical properties of sound historic pine timber, to detect fungal decay more sensitively than by density alone, and to distinguish between pest and fungal attack in a way that relates directly to the remaining mechanical performance of the timber.     

Preventive Conservation Applied to Wallpaintings in a Desert Environment in Mexico

ABSTRACT

The church of San Diego de Alcalá, located in Pitiquito, Sonora , in Mexico, lies on a missionary road founded by the Jesuit Eusebio F. Kino, which, with the expulsion of the Jesuit order in 1767, passed into the care of the Franciscans. It contains wallpaintings which presented deterioration problems whose cause was not easy to determine, since the damage appeared to be inconsistent with the techniques used and the environmental conditions. With an interdisciplinary team, a methodology was designed for a combined study of the environment of the church and its wallpaintings. Thermal imaging of the exterior and interior walls indicated that the building was made up of different materials, and the junctions between them explained the different deterioration pathologies between one zone and another. Hydrological maps for groundwater in the locality were studied, to elucidate the presence of water in a desert zone; abundant sources of water in the subsoil were identified, which, because of overexploitation of the land, have been diminishing over time. This allowed the elaboration of a plan for site management, through the identification of those deterioration factors that can be mitigated by simple maintenance actions that are inherent to the environment and the materials, which enabled a scheduled maintenance scheme to be implemented. This improved the condition of the building and its wallpaintings, while reducing the resource invested to achieve this goal.     

机场航站楼桩基基础施工技术探讨

桩基基础施工技术种类繁多,常见的木桩、钢桩、钢筋混凝土桩等。在机场航站楼施工中绝大部分为钢筋混凝土桩,结合贵州省贵阳市龙洞堡国际机场1号航站楼扩建工程2标段实际情况,分别从桩基人工开挖,机械开挖等方面对机场航站楼桩基基础施工技术探讨。研究表明:机场航站楼桩基础施工技术,施工更加稳定,安全性高,施工工期更加容易掌控,值得大范围推广应用。     

建筑砖砌体裂缝原因及防治探析

建筑砖砌体裂缝不仅种类繁多,形态各异,而且较普遍。轻微者影响建筑物美观,造成渗漏水;严重者降低建筑结构的承载力、刚度、稳定和整体性、耐久性,甚至还会导致整体倒塌的重大质量事故。分析了常见建筑砖砌体裂缝产生的原因,并提出了相应的防治措施。     

美国证券法上“中国墙”制度的实证研究

“中国墙”作为西方主要国家金融证券业中普遍实行的一种信息隔离制度,对证券经营机构从事内幕交易的防范,已经有了较为成熟的实践。阐述了“中国墙”的涵义、该制度在美国的案例以及在中国出现的类似情况,对其进行评价并且揭示其意义。     

Numerical prediction of statistical masonry wall fragment distribution induced by blast loading

The hazard caused by the fragments of damaged structures is usually significant in acci-dental explosions or hostile blast events.A reliable and efficient method to estimate probable fragment size,velocity and launch distance will be useful to assess and design countermeasures to mitigate the possible fragment hazards.This paper presents a numerical method for predicting the size and launch distance of the fragments caused by explosive damage of masonry wall.Numerical simulations with different scaled distances are carried out,and the statistical distribution functions of the fragment size and launch distance in terms of the scaled distance are derived.     

“墙壁法”在网球教学中的应用

采用文献资料、专家访谈、归纳总结等研究方法对网球教学中利用墙壁进行各种技术的教学研究,旨在扩宽网球课的教学方法和手段,同时也有利于学生课余的网球练习,促进网球运动在校园的进一步开展。     

西部地区文献信息资源共建共享网络安全保障体系研究

本文从安全保障体系入手,从主动防御和被动防御两个大的方面,从联网设备安全,系统运行安全和数据存储安全的角度全面论述文献安全保障体系,强调西部地区要搞好区域性文献保障体系。