Land-cover and land-use change in a Mediterranean landscape: A spatial analysis of driving forces integrating biophysical and human factors

This article develops a spatial analysis applied to examine the main driving forces of land-cover and land-use (LCLU) change in a Mediterranean region. Three different tools have been used in order to differentiate LCLU changes, driving forces and landscape dynamics. LCLU changes have been quantified with remote sensing techniques, driving forces have been analysed with multiple logistic regressions combining biophysical and human variables, whereas landscape dynamics have been quantified using different metrics. Results show the intensification of subsidised herbaceous crops on the coastal agricultural plain, the abandonment of olive trees and vineyards in the transitional area and forest restoration in the mountainous subregion.     

An adaptive approach to selecting a flow‐partition exponent for a multiple‐flow‐direction algorithm

Most multiple‐flow‐direction algorithms (MFDs) use a flow‐partition coefficient (exponent) to determine the fractions draining to all downslope neighbours. The commonly used MFD often employs a fixed exponent over an entire watershed. The fixed coefficient strategy cannot effectively model the impact of local terrain conditions on the dispersion of local flow. This paper addresses this problem based on the idea that dispersion of local flow varies over space due to the spatial variation of local terrain conditions. Thus, the flow‐partition exponent of an MFD should also vary over space. We present an adaptive approach for determining the flow‐partition exponent based on local topographic attribute which controls local flow partitioning. In our approach, the influence of local terrain on flow partition is modelled by a flow‐partition function which is based on local maximum downslope gradient (we refer to this approach as MFD based on maximum downslope gradient, MFD‐md for short). With this new approach, a steep terrain which induces a convergent flow condition can be modelled using a large value for the flow‐partition exponent. Similarly, a gentle terrain can be modelled using a small value for the flow‐partition exponent. MFD‐md is quantitatively evaluated using four types of mathematical surfaces and their theoretical ‘true’ value of Specific Catchment Area (SCA). The Root Mean Square Error (RMSE) shows that the error of SCA computed by MFD‐md is lower than that of SCA computed by the widely used SFD and MFD algorithms. Application of the new approach using a real DEM of a watershed in Northeast China shows that the flow accumulation computed by MFD‐md is better adapted to terrain conditions based on visual judgement.     

A modified stochastic neighbor embedding for multi-feature dimension reduction of remote sensing images

In automated remote sensing based image analysis, it is important to consider the multiple features of a certain pixel, such as the spectral signature, morphological property, and shape feature, in both the spatial and spectral domains, to improve the classification accuracy. Therefore, it is essential to consider the complementary properties of the different features and combine them in order to obtain an accurate classification rate. In this paper, we introduce a modified stochastic neighbor embedding (MSNE) algorithm for multiple features dimension reduction (DR) under a probability preserving projection framework. For each feature, a probability distribution is constructed based on t-distributed stochastic neighbor embedding (t-SNE), and we then alternately solve t-SNE and learn the optimal combination coefficients for different features in the proposed multiple features DR optimization. Compared with conventional remote sensing image DR strategies, the suggested algorithm utilizes both the spatial and spectral features of a pixel to achieve a physically meaningful low-dimensional feature representation for the subsequent classification, by automatically learning a combination coefficient for each feature. The classification results using hyperspectral remote sensing images (HSI) show that MSNE can effectively improve RS image classification performance.     

河流相储层特征及识别:一个老河口油田的实例分析(英文)

河流相储层是一种重要的储层类型,寻找河道砂体是油气勘探的一项重要工作。但是河道变迁比较频繁,叠置比较严重,加之地震资料本身信噪比和分辨率的限制,河流相储层的精细描述至今仍存在一定的困难。本文以胜利油田老河口三维工区为例,首先研究了本区河流相储层的基本特征,发现该类储层剖面上呈强相位、切片上连续性好和频谱上呈低频特征;通过颜色处理和地震精细解释,发现本区河流相储层存在类串珠状特征,为了验证这一观测结果,我们用正演模拟分析了其形成机理,为在类似工区识别此类古河道找到了新的途径;应用多属性融合和RGB显示技术,河道下切特征更加明显,很好地彰显了河道结构特征,提高了河道识别能力;最后,我们研究并开发了多子波检测技术,检测出更多河流相弱反射信息。     

Analyzing spatial ecological data using linear regression and wavelet analysis

Spatial (two-dimensional) distributions in ecology are often influenced by spatial autocorrelation. In standard regression models, however, observations are assumed to be statistically independent. In this paper we present an alternative to other methods that allow for autocorrelation. We show that the theory of wavelets provides an efficient method to remove autocorrelations in regression models using data sampled on a regular grid. Wavelets are particularly suitable for data analysis without any prior knowledge of the underlying correlation structure. We illustrate our new method, called wavelet-revised model, by applying it to multiple regression for both normal linear models and logistic regression. Results are presented for computationally simulated data and real ecological data (distribution of species richness and distribution of the plant species Dianthus carthusianorum throughout Germany). These results are compared to those of generalized linear models and models based on generalized estimating equations. We recommend wavelet-revised models, in particular, as a method for logistic regression using large datasets.     

Broadband frequency-dependent amplification of seismic waves across Bucharest, Romania

The determination of seismic amplitude amplification is a fundamental contribution to seismic hazard assessment. While often only high-frequency amplitude variations (>1 Hz) are taken into account, we analyse broadband waveforms from 0.14 to 8.6 Hz using a temporary network of 32 stations in and around the earthquake-prone city of Bucharest. Spectral amplitudes are calculated with an adaptive multiple-taper approach. Across our network (aperture 25 km × 25 km), we find a systematic northwest/southeast-oriented structural influence on teleseismic P-wave amplitudes from 0.14 to 0.86 Hz that can be explained by constructive interference in the dipping Cenozoic sedimentary layers. For higher frequencies (1.4–8.75 Hz), more local site effects prevail and can be correlated partly among neighbouring stations. The transition between systematic and localised amplitude variations occurs at about 1 Hz.     

Wave forces on, and water-surface fluctuations around a vertical cylinder encircled by a perforated square caisson

The wave forces and moments on and the water surface fluctuations around a vertical circular cylinder encircled by a perforated square caisson were experimentally investigated. The porosity of the outer square caisson was varied from 4.24 to 14.58%. The in-line wave forces on the inner vertical cylinder are influenced by changing the porosity of the outer caisson, whereas the variations in the water surface fluctuations are less influenced in this porosity range. The in-line moment on the vertical cylinder is relatively less sensitive when the porosity is increased from 4.24 to 8.75%, but varies substantially when it is increased from 8.75 to 14.58%. The force and moment ratio (i.e. the ratio of the force or moment on the vertical cylinder, when it is encircled by the perforated caisson to the force or moment on the cylinder without any protection around it) reduces with increased wave height, H, and wave length, L, whereas the wave height ratio (ratio of the wave height at a point in the vicinity of the structure to the incident wave height) is less sensitive for the varying H and L. A new non-dimensional parameter, p^1.5 (D/L)/(H/d), is introduced to predict the in-line force and moment on the inner vertical cylinder, where d is local water depth, D is the diameter of the inner cylinder and p is the porosity of the outer caisson in percentage. Simple predictive equations for forces, moments and water surface fluctuations are provided.     

南海北部第四系厚度分布图的编制与简要说明

收集南海北部大量多道地震和钻井资料,编制了该区域首幅第四系厚度分布图。第四系等厚线总体呈NEE向,特别是珠江口外大陆架最明显,莺歌海、琼东南呈NW-EW-NE向弧形,珠江口大陆架南部存在次一级NW向等厚线。第四系等厚线分布形态明显受到断裂构造控制。     

Radiative Exchange in an Urban Street Canyon

The influence of building geometry on the radiation terms ofthe surface energy balance is a principal reason for surfacetemperature differences between rural and urban areas.Methods exist to calculate the radiation balance in an urban area,but their validity across the range of urban geometries andmaterials has not been carefully considered.Here the exchange of diffuse radiation in an urban street canyon isinvestigated using a method incorporating all reflections of radiation.This exact solution is compared to two commonly used approximationsthat retain either no reflections, or just one reflection of radiation.The area-averaged net radiative flux density from the facets of the canyondecreases in magnitude monotonically as the canyon aspect ratio increases.The two approximate solutions possess unphysical differences from thismonotonic decrease for high canyon aspect ratios or low materialemissivities/high material albedos.The errors of the two approximate solutions are small for near blackbodymaterials and small canyon aspect ratios but can be an order ofmagnitude for intermediate material properties and deep street canyons.Urban street canyon models need to consider at least one reflectionof radiation and multiple reflections are desirable for full applicability.     

Testing for sufficient signal resetting during sediment transport using a polymineral multiple-signal luminescence approach

We present a multiple luminescence signal measurement procedure that simultaneously measures six different luminescence signals from a single polymineral aliquot (i.e. multiple-signal, short MS-SAR approach). The six signals show different bleaching rates in bleaching experiments, ranging from rapid bleaching for the quartz dominated blue stimulated luminescence signal (measured at 125 °C, BSL-125), to the slow-bleaching polymineral thermoluminescence signal. The bleaching rate of the infrared stimulated luminescence (IRSL) measured at room temperature (IR-25) and elevated temperature post-IR IRSL (pIRIR-90, pIRIR-155, pIRIR-225) signals decrease with increasing measurement temperature. Owing to these different bleaching rates, the MS-SAR approach allows inference of the degree of bleaching, and thereby information on the transport history of sediments. We test this approach by applying the MS-SAR to four coastal samples from a well-monitored sand-nourishment site at the Dutch coast. Our results show that the proposed MS-SAR approach can be utilised to construct bleaching plateaus which provide an independent and time-effective measure of the degree of poor bleaching in a sediment sample based on the measurement of only a few large aliquots. We propose that the MS-SAR protocol can be used to profile the age, luminescence properties and degree of bleaching of minimal prepared polymineral. This pre-profiling will allow the selection of suitable samples for full luminescence dating analysis in a target-orientated and time-effective manner.