考虑场地各向异性的结构输入地震反应谱调整

为了预测地震动特性,同时考虑场地土动力特性各向异性及其对结构输入地震动的影响,基于地震各向异性理论,提出了场地动力特性各向异性的概念,研究了场地动力特性各向异性的微动测试分析方法.考虑地震动的各向异性特征,分析了地震动各向异性对结构地震动力响应的影响,以及结构分析中现有的地震时程选择和调整中存在的问题,提出了基于场地微动测试确定场地动力特性及其各向异性的输入地震动调整新思想.     

场地微动各向异性观测实例及其分布

在试验观测的基础上 ,本文首次提出了场地微动各向异性的概念 ,并从弹性波理论出发 ,对各向异性场地微动进行了研究 ,分析了场地微动各向异性的机制。这对于深入研究各向异性场地条件下场地动力特性、预测地震动特性、结构抗震研究具有非常重要的意义。     

各向异性场地微动数值模拟研究

场地微动的理论研究和工程应用均基于各向同性介质模型,这与实际情况不符.首次提出了各向异性介质中场地微动的概念,从弹性波理论出发,对各向异性场地微动进行了模拟研究,得出了一些有益结论.这对深入研究各向异性场地条件下场地动力特性、地震动特性预测、结构抗震研究具有非常重要的意义.     

基于Nakamura的各种场地类型转换方法研究

本文结合国外强震观测记录,通过不同场地分类条件的研究,提出了一种基于Nakamura方法的各种场地类型标准间的转换方法。该方法的使用有助于提高观测数据的应用价值,同时也为我国许多未能进行钻孔确定场地类型的强震观测台站进行场地分类提供了依据。     

湿地公园的场地规划与设计

综合运用场地设计理论,从生态系统的完整性要求出发,在大尺度场地规上来确定湿地公园的范围和大小,利用生态主导因素来确定中尺度的公园功能分区从使用者的感知上来考虑,在小尺度角度上设计景观(点)的位置、大小和边界。     

基于扎根理论的我国污染场地治理修复的投融资影响因素分析

针对我国污染场地治理修复的投融资问题,采用扎根理论,对专家建议及文献资料等进行了编码分析,并建立了影响因素作用机制模型。研究结果表明：污染场地治理修复的投融资受外部政策环境、市场环境、场地条件、社会环境以及内部治理修复主体的决策能力、技术能力、管理能力的共同作用。其中政策环境与市场环境为主要影响因素。通过影响因素作用机制模型,提出了应出台有利政策,驱动激活市场新活力;建立多元化生态补偿机制,激励投融资;加强修复技术创新,完善修复效果评估体系;高度重视社会认知引导,信息公开透明;加强监督管理,提升决策能力5点对策建议,以利于开展我国污染场地治理修复的投融资工作。     

场地污染土壤调查及评估分析

指出了近年来国家提出的“可持续发展战略”、“绿水青山就是金山银山理念”、“城市文明建设”等政策观念,要求企业在追求经济效益的同时,不能忽视环境保护问题,特别是企业搬离工业场地后,应当对场地的污染情况负责,以保证场地的二次开发使用。基于此,针对场地污染中的土壤污染情况调查、风险评估方案进行了梳理,并以实际污染场地为实例进行了探讨。     

低影响开发理念下我国场地景观优化设计研究进展

低影响开发是以可持续水循环为核心的现代雨洪管理理念,越来越多地应用于场地景观优化设计中。基于我国低影响开发理念研究动态和场地景观优化实践,从景观雨水设施、场地雨洪调控能力影响因素、雨水设施量化、相关设计规范标准及规划设计方法等进行了总结,为优化场地景观设计提供参考。     

简析场地设计在园林景观中的应用——以西南交通大学镜湖片区为例

从场地在园林设计中作用出发,以西南交大九里校区镜湖片区为例,对此区域的环境、园林设计进行了解读,指出了该区域设计的长处与不足,最后得出结论:场地是有性格的,它的性格来源于活动在这片土地上的自然与人文.     

谈谈阳台种兰的场地问题

种兰是一种高雅的艺术享受,可以丰富精神生活,有益身心健康。我怀着“养兰而养于兰”的心情,自一九八六年起,在六楼向北四平方米的阳台种了150多盆中国兰花。经过不断学习和总结经验,现在所种兰花生长也算不错。基本上没有病虫害,叶面很少黑点,开花也较多。有人说:“兰花虽好,但很难种”。其实不然,只要认识兰花的生长习性,知其对阳光、通风、温度、湿度、水分、肥料等的要求,创造一个适合的场地,就不难把兰花种好。下面仅就个人体会,谈谈怎样在阳台创造一个适合兰花生长的场地问题。兰花原是生长在阴凉湿润、空气流通的山谷中。在阳台种兰首先要改造周围环境,创造一个与山谷类似、能适应兰花生长的特殊场地。一、要适当采光。阳光是否适当,关系着兰花生长的壮弱。兰花虽是阴生植物,但也需要适当阳光才能进行光合作用,制造养分,强根健叶,促进发芽开花,抗卸病虫害。没有阳光,虽不枯死,也会影响发芽开花。但兰花不能让阳光曝晒,尤其是墨兰最怕强光。     

Acoustoelastic birefringence effect in wood II: influence of texture anisotropy on the polarization direction of shear wave in wood

Ultrasonic shear waves were propagated through the breadth direction of a wood beam which was subjected to a bending load such that it was in a plane-stress state. The oscillation direction of the shear waves with respect to the wood beam axis was varied by rotating an ultrasonic sensor, and the relationship between the shear wave velocity and the oscillation direction was examined. The results indicate that when the oscillation direction of the shear wave corresponds to the tangential direction of the wood beam, the shear wave velocity decreases sharply and the relationship between shear wave velocity and rotation angle tends to become discontinuous. When the oscillation of the shear waves occurs in the anisotropic direction of the wood beam instead of in the direction of principal stress, the shear wave velocity exhibits a peak value. In addition, the polarization direction was found to correspond to the direction of anisotropy of the wood beam according to the theory of acoustoelastic birefringence with respect to plane stress. This indicates that when the acoustoelastic birefringence method is applied to stress measurement of wood, it is appropriate to align the oscillation direction of the shear wave with the principal axial direction of anisotropy in order to carry out ultrasonic measurement.     

Propagation behavior of acoustic wave in wood

We used acoustic tests on a quarter-sawn poplar timbers to study the effects of wood anisotropy and cavity defects on acoustic wave velocity and travel path, and we investigated acoustic wave propagation behavior in wood. The timber specimens were first tested in unmodified condition and then tested after introduction of cavity defects of varying sizes to quantify the transmitting time of acoustic waves in laboratory conditions. Two-dimensional acoustic wave contour maps on the radial section of specimens were then simulated and analyzed based on the experimental data. We tested the relationship between wood grain and acoustic wave velocity as waves passed in various directions through wood. Wood anisotropy has significant effects on both velocity and travel path of acoustic waves, and the velocity of waves passing longitudinally through timbers exceeded the radial velocity. Moreover, cavity defects altered acoustic wave time contours on radial sections of timbers. Acous-tic wave transits from an excitation point to the region behind a cavity in defective wood more slowly than in intact wood.     

Acoustoelastic birefringence effect in wood I: effect of applied stresses on the velocities of ultrasonic shear waves propagating transversely to the stress direction

The velocity changes of ultrasonic shear waves propagating transversely to the applied stress direction in wood were investigated. The wave oscillation directions were parallel and normal to the uniaxially applied stress direction. The velocities of the shear waves for both oscillations decreased as the compressive load increased, and increased as the tensile load increased. The velocity of the normally oscillated shear wave showed smaller change against the stress applied than that of the parallel oscillated wave. The initial birefringence due to the orthotropy of wood was observed without any stress. Velocity changes in the two principally oscillated shear waves were proportional to the stress within the stress range tested. The acoustoelastic birefringence effect was obtained from the velocity difference between the two shear waves. The relative difference between the two velocities (called acoustic anisotropy) was given as a function of the applied stress. The acoustoelastic birefringence constants were obtained from the relationships between the acoustic anisotropy and the applied stress.     

Transverse swelling behavior of hinoki (Chamaecyparis obtusa) revealed by the replica method

Transverse swelling and its anisotropy in hinoki (Chamaecyparis obtusa) in several kinds of organic liquids and in water were investigated by means the replica method. There was more cross-sectional swelling of cell walls and cell wall thickness in earlywood than in latewood. Marked swelling toward cell lumens was observed in wood swollen in liquids that had higher swelling potentials than water. This suggests that the swelling of cell walls in these liquids is much greater than the external swelling. Feret's diameters of the cell lumens were reduced by swelling in all the observed cases except in the tangential direction of earlywood, suggesting that cell walls swell to a much less extent in width than in thickness. Deformation of cell shapes caused by the tensile force from the latewood were observed in the earlywood and in the transitional region from earlywood to latewood. When swollen in water, transverse swelling anisotropy caused only by the swelling in cell wall thickness were calculated to be 1.2 for the whole region over an annual ring and 1.4 for the earlywood. These values could not account for the external swelling anisotropy of 2.1. Considering obvious deformations of cell shapes in the earlywood and in the transitional region, we conclude that the interaction between earlywood and latewood is one of the prime factors contributing to the transverse swelling anisotropy of coniferous wood.Part of this report was presented at the 48th Annual Meeting of the Japan Wood Research Society, Nagoya, April 1998     

Mangroves as a coastal protection from waves in the Tong King delta,Vietnam

The wave reduction (wave period; 5–8 sec.) was investigated in amangrove reforestation area (Kandelia candel) close toaquaculture ponds in the Tong King delta, Vietnam.On one site where only young mangrove trees grew, the wavereduction due to the drag force on the trees was hardlyeffective. On the other site where mangrove trees weresufficiently tall, the rate of wave reduction per 100 m was aslarge as 20%. Due to the high density of vegetation distributedthroughout the whole water depth, the effect of wave reductionwas large even when the water depth increased. These resultsdemonstrate the usefulness of mangrove reforestation for coastalprotection.     

Transverse shrinkage anisotropy of coniferous wood investigated by the power spectrum analysis

The transverse shrinkage behavior of early wood and late wood tracheids of radiata pine (Pinus radiata D. Don) was investigated by the power spectrum analysis. The representative cell model shapes before and after shrinkage constructed by the analysis revealed that the early wood tracheid showed anisotropic shrinkage, although the late wood tracheid showed almost isotropic shrinkage. To link the macroscopic shrinkage of coniferous wood with the results obtained by the power spectrum analysis, a two-layer model composed of early wood and late wood was adopted, and the relation between shrinkage anisotropy and late wood fraction was predicted. The results suggested that the shrinkage anisotropy depended significantly on the mechanical interaction between early and late wood.Part of this report was presented at the 46th Annual Meeting of the Japan Wood Research Society at Kumamoto, April 1996     

Determining Young’s modulus of timber on the basis of a strength database and stress wave propagation velocity I: an estimation method for Young’s modulus employing Monte Carlo simulation

In this article, we report on an estimation method for Young’s modulus that entails measuring only the stress wave propagation velocity of timber built into structures such as wooden buildings. Methods of estimating Young’s modulus that use the stress wave propagation velocity and characteristic frequency of timber in conjunction with timber density have long been used. In this article, we propose a method of easily and accurately estimating Young’s modulus from the stress wave propagation velocity without knowing the timber density. This method is based on a database of wood strength performance and density accumulated from a variety of research data and the method estimates Young’s modulus by a simulation method. We compared the Young’s moduli estimated by this method with those obtained by the bending test and by the measurement of the stress wave propagation velocity and density, and found similar results. This coincidence suggests that the method of estimating Young’s modulus presented in this article is valid. For example, the method is effective for convenient evaluation on site when determining whether a wooden building’s structural components should be reused or replaced when repairing or remodeling a building.     

Site quality assessment of a Pinus radiata plantation in Victoria,Australia, using LiDAR technology

The aim of site quality assessment of Pinus radiata plantations is to determine the quality and productivity of the growing stock at different sites. It provides a useful indication of the site productivity to assist in the allocation of optimum thinning and fertiliser regimes and the scheduling of silvicultural operations. The predominant stand height (PDH) at a specific reference age, also known as site index (SI), is often used for site quality assessment of Pinus radiata plantations in Australia, as it is closely correlated with site productivity. However, measuring PDH in the field can be a time- and resource-consuming task. This paper proposes the use of light detection and ranging (LiDAR) data to estimate PDH for assessing the site quality of Pinus radiata. LiDAR provides highly accurate digital elevation and surface data that can be used to build a canopy height model (CHM). In this study, the state-of-the-art image segmentation technique, marker-controlled watershed segmentation, was employed for identifying locations of individual trees and estimating their heights from a CHM. Using an empirically derived SI equation, PDHs with reference age 11 years (SI₁₁) were estimated from the tallest trees identified in each forest stand, and were then used to determine the site quality class for each stand. The comparison of LiDAR-derived tree heights with field measurements produced an RMSE value of 0.42 m. The maximum horizontal distance between the field-measured locations of individual trees and the LiDAR-detected locations of their treetops was 1.87 m. Site quality classification was conducted in terms of 0.05 ha gridded plots, which revealed more detailed spatial variations of site quality across the study area than classification based on management plots. The study demonstrated that LiDAR provides an effective and accurate method for site quality classification of Pinus radiata.