Effect of boundary element details on the seismic deformation capacity of structural walls

The objective of this study is to investigate the effect of boundary element details of structural walls on their deformation capacities. Structural walls considered in this study have different sectional shapes and/or transverse reinforcement content at the boundaries of the walls (called boundary element details hereafter). Four full‐scale wall specimens (3000mm (h_w)×1500mm (l_w)×200mm (T)) were fabricated and tested. Three specimens are rectangular in section and the other specimen has a barbell‐shaped cross‐section (a wall with boundary columns). The rectangular wall specimens are reinforced according to the common practice used for reinforced concrete residence buildings in Korea and Chile. In this study, the primary variable for these rectangular specimens is the content of transverse reinforcement to confine the boundary elements of a wall. The barbell‐shaped specimen was designed in compliance with ACI 318‐95. The response of the barbell‐shaped specimen is compared with those of other rectangular specimens. The effective aspect ratio of the specimens is set to two in this study. Based on the experimental results, it is found that the deformation capacities of walls, which are represented by displacement ductility, drift ratio and energy dissipation capacities, are affected by the boundary element details. Copyright © 2002 John Wiley & Sons, Ltd.     

A Numerical Study Of Nocturnal Wavelike Motion In Forests

In this paper, we use a two-dimensional eddy-resolved model to investigate the instability of a parallel shear flow in a stably stratified boundary layer whose lower domain is occupied by a canopy. The results support our contention that wave motion in the canopy is initiated by shear in an air layer near the treetops. Significant modification by the wave motion of the mean velocity and temperature fields is found even before the wave reaches saturation. The wave fluxes of momentum and heat are not constant with height. Downwind tilting braids are found at the finite amplitude stage of the wave growth and could persist after wave breaking; these downwind tilting structures are believed to be the same as the temperature microfronts reported in the literature. We also present an analysis of the velocity and temperature fields of an observed wave event in the time-height domain and show that the simulation has captured the broad features of the observation.     

Geologic,geomorphic, and meteorological aspects of debris flows triggered by Hurricanes Frances and Ivan during September 2004 in the Southern Appalachian Mountains of Macon County,North Carolina (southeastern USA)

In September 2004, rain from the remnants of Hurricanes Frances and Ivan triggered at least 155 landslides in the Blue Ridge Mountains of North Carolina. At least 33 debris flows occurred in Macon County, causing 5 deaths, destroying 16 homes, and damaging infrastructure. We mapped debris flows and debris deposits using a light-detecting and ranging digital elevation model, remote imagery and field studies integrated in a geographic information system. Evidence of past debris flows was found at all recent debris flow sites. Orographic rainfall enhancement along topographic escarpments influenced debris flow frequency at higher elevations. A possible trigger for the Wayah and fatal Peeks Creek debris flows was a spiral rain band within Ivan that moved across the area with short duration rainfall rates of 150–230 mm/h. Intersecting bedrock structures in polydeformed metamorphic rock influence the formation of catchments within structural–geomorphic domains where debris flows originate.     

Socio-spatial polarization and the (re-)distribution of deprived groups in world cities: A case study of Hong Kong

This paper draws on theoretical discussions of world cities to analyze socio-spatial polarization and (re-)distribution of deprived groups in Hong Kong in the 2000s. Intensifying global economic restructuring processes have induced socio-economic polarization, thereby producing deprived groups although the spatial outcomes may depend on the city-specific context. When local policies do not counteract the polarization trend, a spatial manifestation of widening socio-economic gaps can be expected. Intensified pro-growth policies adopted since Hong Kong’s return to Chinese rule in 1997 and during its economic recession in the early 2000s have worsened the impact of globalization-induced socio-economic and spatial restructuring. Census data from 2001 and 2011 show increasingly differentiated socio-economic profiles at the district level. The analysis offered in this study also points to a decreased socially mixed society in 2011 when the deprived groups lived in districts with less presence of the advantaged population.     

Determination of ductility factor considering different hysteretic models

In current seismic design procedures, base shear is calculated by the elastic strength demand divided by the strength reduction factor. This factor is well known as the response modification factor, R, which accounts for ductility, overstrength, redundancy, and damping of a structural system. In this study, the R factor accounting for ductility is called the ‘ductility factor’, R_μ. The R_μ factor is defined as the ratio of elastic strength demand imposed on the SDOF system to inelastic strength demand for a given ductility ratio. The R_μ factor allows a system to behave inelastically within the target ductility ratio during the design level earthquake ground motion. The objective of this study is to determine the ductility factor considering different hysteretic models. It usually requires large computational efforts to determine the R_μ factor. In order to reduce the computational efforts, the R_μ factor is prepared as a functional form in this study. For this purpose, statistical studies are carried out using forty different earthquake ground motions recorded at a stiff soil site. The R_μ factor is assumed to be a function of the characteristic parameters of each hysteretic model, target ductility ratio and structural period. The effects of each hysteretic model to the R_μ factor are also discussed. Copyright © 1999 John Wiley & Sons, Ltd.     

Prediction of sediment yield by coupling Kalman filter with instantaneous unit sediment graph

An instantaneous unit sediment graph (IUSG) model in conjunction with Kalman filter was investigated for prediction of sediment yield from an upland watershed in Northwestern Mississippi. The state vector of the watershed sediment yield system was constituted by the IUSG and then the sediment yield was estimated by the IUSG model using Kalman filter. The initial values of the state vector were assumed as the average of the IUSG values and the initial sediment yield estimated from the average IUSG. The IUSG model using Kalman filter with a recursive algorithm accurately predicted sediment yield from watershed W‐5, Mississippi. The filter allowed the IUSG to vary in time, increased the accuracy of the IUSG model, and reduced physical uncertainty of the sediment yield process in the watershed. Copyright © 1999 John Wiley & Sons, Ltd.     

KPAR:一个数值模糊的光学量

光合有效辐射(PAR)的漫衰减系数KPAR是水环境研究中经常使用的一个光学量.水体的漫衰减系数与波长紧密相关,随着水体深度的不断增加,PAR频谱收缩到具有更小衰减系数的波长处,对上层水体或者混合均匀的水体而言,此时的KPAR与水深关系极为密切.为了更为准确的描述PAR剖面,获取更可靠的光学衰减参数,强调了KPAR数值的模糊性,倡导正确表达KPAR的垂直变化.     

3D joint inversion of magnetotelluric and airborne tipper data: a case study from the Morrison porphyry Cu–Au–Mo deposit,British Columbia,Canada

Z‐axis tipper electromagnetic and broadband magnetotelluric data were used to determine three‐dimensional electrical resistivity models of the Morrison porphyry Cu–Au–Mo deposit in British Columbia. Z‐axis tipper electromagnetic data are collected with a helicopter, thus allowing rapid surveys with uniform spatial sampling. Ground‐based magnetotelluric surveys can achieve a greater exploration depth than Z‐axis tipper electromagnetic surveys, but data collection is slower and can be limited by difficult terrain. The airborne Z‐axis tipper electromagnetic tipper data and the ground magnetotelluric tipper data show good agreement at the Morrison deposit despite differences in the data collection method, spatial sampling, and collection date. Resistivity models derived from individual inversions of the Z‐axis tipper electromagnetic tipper data and magnetotelluric impedance data contain some similar features, but the Z‐axis tipper electromagnetic model appears to lack resolution below a depth of 1 km, and the magnetotelluric model suffers from non‐uniform and relatively sparse spatial sampling. The joint Z‐axis tipper electromagnetic inversion solves these issues by combining the dense spatial sampling of the airborne Z‐axis tipper electromagnetic technique and the deeper penetration of the lower frequency magnetotelluric data. The resulting joint resistivity model correlates well with the known geology and distribution of alteration at the Morrison deposit. Higher resistivity is associated with the potassic alteration zone and volcanic country rocks, whereas areas of lower resistivity agree with known faults and sedimentary units. The pyrite halo and ≥0.3% Cu zone have the moderate resistivity that is expected of disseminated sulphides. The joint Z‐axis tipper electromagnetic inversion provides an improved resistivity model by enhancing the lateral and depth resolution of resistivity features compared with the individual Z‐axis tipper electromagnetic and magnetotelluric inversions. This case study shows that a joint Z‐axis tipper electromagnetic–magnetotelluric approach effectively images the interpreted mineralised zone at the Morrison deposit and could be beneficial in exploration for disseminated sulphides at other porphyry deposits.     

Climate change and plague history in Europe

Previous research that reported the linkage between climate change and plague activity primarily refers to the immediate effect of short-term climatic variation. Yet, decades of discussion about the climate-plague association cannot determine the precise role of climate in shaping plague dynamics. One reason for this discrepancy originates from the narrow selection of spatio-temporal settings for comprehensive analysis of the correlation, leading to a limited consideration of the complexity of possible dynamics. By analyzing a 414-year long record of plague outbreak in pre-industrial Europe and the corresponding climatic data in multi-scale, we find little evidence to support climate-plague correlation in (1) both climatic variations and large-scale climatic phenomena, (2) both country scale and continental scale, (3) annual to inter-annual scale, and (4) both linear and non-linear analytic approaches. The null-result should not be viewed as a general rejection of other recent findings related to climate-plague association; nevertheless, it suggests that a wider consideration of scales, sensitivity checks and consideration of contexts should be included in explaining and predicting plague transmission under contemporary global climate conditions.