The role of aerial algae in the formation of the landscape of the Yunnan Stone Forest,Yunnan Province, China

~~The role of aerial algae in the formation of the landscape of the Yunnan Stone Forest,Yunnan Province, China~~     

Mechanisms Controlling Turbulence Development Across A Forest Edge

In this paper we discuss the development of turbulence back from the transition fromopen moorland to a forest. Data from a field study and a wind-tunnel experiment arepresented. These show that the variance in the streamwise velocity begins to adjust tothe new surface between 2 to 4 tree heights downwind of the transition. This is soonerthan either the vertical velocity variance or the shear stress, both of which begin to adjust in a zone 3 to 5 tree heights downwind of the edge. Key terms in the prognostic equations for streamwise and vertical velocity variance are evaluated in order to explain these differences. The flow distortion caused by the forest edge, which extends to 4 tree heights downwind of the forest edge, is shown to be crucial in the delayed turbulence development. Initially the shear production term, which is the dominant source for the streamwise velocity variance, is counteracted by a sink in the vertical advection term. After the flow levels out the pressure redistribution (return-to-isotropy) term becomes the main sink of streamwisevelocity variance and feeds energy into the vertical velocity component. Therefore, thedevelopment of the vertical velocity variance and shear stress cannot begin until afterdevelopment of an increase in the streamwise velocity variance. Results are comparedwith other experiments, including the flow across shelterbelts, and large-eddy simulations of forest flow.     

Polymetamorphism of the Variscan Basement of the Moldanubian Black Forest （Germany） Documented in Zircon and Garnet Minerals from Gneisses

High-grade metamorphic Variscan basement is exposed in the Moldanubian zone of the Black Forest (BF), being the internal zone of the European Variscan belt. Zircon grains from K-rich felsic orthogneisses and an anatectic paragneiss in the Moldanubian Black Forest demonstrate a multi-stage crystallization at ～ 600 Ma, ～ 480 Ma, ～ 400 - 380 Ma, and ～350 Ma. The last three stages of crystallization probably represent metamorphic overprint during pre-Variscan and Variscan metamorphism.Using stepwise leaching procedures, garnet minerals from felsic orthogneisses as well as paragneisses in the Moldanubian Black Forest yielded Early Carboniferous Sm-Nd ages (～ 330- 340 Ma), which are consistent with the well-constrained Variscan HT metamorphic event,and Early Palaeozoic ( ～480 Ma) to Devonian ( ～400 - 370 Ma) Pb-Pb ages. The coincidence of growth time for zircon and garnet minerals at Early Palaeozoic is interpreted as dating a metamorphic event. These garnet data demonstrate that the Moldanubian BF basement underwent at least two metamorphic events during the Early Palaeozoic and Early Carboniferous.During the Variscan HT metamorphism, the Sm-Nd system of garnet was disturbed, but not the U-Pb system, implying the peak metamorphic temperature was lower than ～800℃.     

软硬相间岩层底板变形研究

引入损伤变量ω理论,分析水平状软硬相间岩层在竖向应力下的应力-应变关系：再引用弹性模量E和岩层厚度L两个变形参数建立软硬相间岩层底板变形参数方程,得出竖向应力随着底板深度的增加而减小的规律：运用数值模拟软件,建立煤层开采模型,模拟软硬相间岩层底板在采动作用下的变形过程。通过数值分析底板在采动作用下的应力-应变关系和位移特征,发现竖向应力作用下软岩受到的水平应力比硬岩大,竖向应变也比硬岩大,而竖向应力和水平应变变化不大,认为在采动影响下软硬相间岩层底板中的软岩具有吸收更多的应变能来保护软岩下硬岩的变形特点。     

Dynamics of evapotranspiration from a riparian pond complex in the Western Boreal Forest,Alberta, Canada

The relative contributions to total actual evapotranspiration (AET) from pond and riparian areas in a pond‐wetland complex in the Western Boreal Plain (WBP) of northern Alberta are measured using the Bowen ratio energy balance technique. Measurements show that a pond typical of the WBP evaporates at a rate more than twice that of the adjacent riparian peatland. Relating the actual to potential evapotranspiration over both surfaces yields Priestley–Taylor α coefficients of 0·69 and 1·11 for the peatland and pond respectively. Further results demonstrate that the sheltering and turbulent influences of the adjacent forested areas must be considered in the processes governing the permanence of WBP ponds. That is, forestry practices may inadvertently enhance the evaporative losses from the ponds, over and above the controls exerted by the regional climate. Copyright © 2006 John Wiley & Sons, Ltd.     

Prediction of the soil erosion in a forest and sediment yield from road network through GIS and SEDMODL

This study was conducted to classify water erosion risk for a deciduous forest and to predict the amount of sediment yield from forest road network. GIS in combination with AHP was used for determining the soil erosion risk degrees of forest. Beside, sediment yield from forest roads with gravel and asphalted surfacing was estimated using SEDMODL. Rainfall simulator was used in calibration and validation process of model. Results showed that 47.9% of forest soil is classified from moderate to very high vulnerability. 32.3% of roads were located in soil erosion risk class of very high. This class is generally found in the eastern region of forest, while areas with very low risk are found in the south western part. 14.6% of the forest roads were ranked as having very low sediment yield. Only 61 segments out of 339 segments of forest road network delivered sediment to the ravine network. The estimated annual sediment yield for all of road sections by SEDMODL and rainfall simulator were 10,935.45 and 10,509.29 g m-2, respectively. Results of the calibration and validation process showed that the variation accounted for in the predicted values by SEDMODL with the observed values under rainfall simulation was 3.90%. Best management practices （BMP） must be considered for the areas with high degrees of erosion risk.     

底板破坏深度六因素线性预测模型

针对煤矿底板破坏深度影响因素较多,难以准确地确定难题,通过分析影响底板岩体变形程度的底板岩层的抗破坏能力和作用在底板上的矿山压力两方面因素,选取采深、采高、斜长（工作面）、倾角、底板岩性组合与顶板岩性组合6个因素进行底板破坏深度研究,以某矿4602工作面为背景概化工程地质模型进行6因素5水平正交数值模拟试验。试验结果表明,（1）影响底板破坏深度的主要因素是斜长,顶板岩性组合、底板岩性组合、采深、采高依次减弱,倾角最差;（2）首次明确了顶板岩性组合是影响底板破坏深度的关键因素;（3）建立了斜长-顶底板岩性组合-采深-采高-倾角的采动底板破坏深度预测模型,计算结果较开采规程经验公式的计算结果更接近实际,精度高、误差小,基本可以满足工程使用。研究结果对底板破坏深度的研究以及工程应用具有积极的指导意义。     

Experimental evaluation of a glass curtain wall of a tall building

The seismic demand parameters including the floor acceleration amplification (FAA) factors and the interstory drift ratios (IDRs) were acquired from the floor response in time history analysis of a tall building subjected to selected ground motions. The FAA factors determined in this way are larger than those given in most current code provisions, but the obtained IDRs are close to the values given in some code provisions. Imposing a series of in‐plane pre‐deformations to two glass curtain wall (CW) specimens mounted on a shaking table, the IDRs were reproduced and the FAA factors were satisfied through applications of computed floor spectra compatible motion time histories, whose peak accelerations corresponded to the FAA factors. The CW specimens performed well during the whole experimental program with almost no change in the fundamental frequencies. No visible damage was observed in the glass panels. The maximum stresses detected in each component of the CW system were smaller than the design strengths. The obtained component acceleration amplification factor approached 3.35, which is larger than the value given in the current code provisions. In conclusion, the performance of the studied CW system is seismically safe. Copyright © 2016 John Wiley & Sons, Ltd.     

Effects of balanced impact damper in structures subjected to walking and vertical seismic excitations

This study investigates whether a balanced impact damper (BID) with a vertically suspended impact body colliding with shock absorbing rubber can suppress vibrations of a floor slab subjected to walking and vertical seismic excitations. The impact body is suspended by coil springs to sustain its deadweight and centralize it within the gap, and collides with the stopper when its amplitude exceeds the specified gap width. The stopper is covered by a shock‐absorbing rubber made of polyurethane gel. The installed BID was evaluated in a single degree‐of‐freedom model of a floor slab subjected to vertical excitations. Simulations revealed that the installed BID properly controls the vibrations. Next, the effects of the BID installed on a steel plate were investigated in shaking table tests. The BID effectively suppressed vertical vibrations of the plate subjected to sinusoidal waves, seismic motions, and walking excitations. In addition, the shaking table tests were accurately simulated by the developed mathematical model of the damper. Copyright © 2015 John Wiley & Sons, Ltd.     

Investigations on serviceability control of long-span structures under human-induced excitation

The increasing strength of new structural materials and the span of new structures,accompanied by aesthetic requirements for greater slenderness,are resulting in more applications of long-span structures.In this paper,serviceability control technology and its design theory are studied.First,a novel tuned mass damper(TMD)with controllable stiffness is developed.Second,methods for modeling human-induced loads are proposed,including standing up,walking,jumping and running,and an analysis method for long-span floor response is proposed based on a finite element model.Third,a design method for long-span floors installed with a multiple TMD(MTMD)system considering human comfort is introduced, largely based on a study of existing literature.Finally,a design,analysis and field test is conducted using several large scale buildings in China including the Beijing Olympic Park National Conference Center,Changsha New Railway Station and the Xi’an Northern Railway Station.The analytical and field test results show that the MTMD system designed using the proposed method is capable of effectively mitigating the vertical vibration of long-span floor structures.The study presented in this paper provides an important reference for the analysis of vibration serviceability of similar long-span floors and design of control system for these structures.