bluuebunny/crossref_metadata_2025_split huggingface dataset:
Elementary processes of soil–water interaction and thresholds in soil surface dynamics: a review
Authors: Greene Richard S. B. , Hairsine Peter B. 
Published: August 2004

AbstractElementary processes of soil–water interaction and the thresholds to these processes are important to understand as they control a range of phenomena that occur at the soil surface. In particular processes involved with wetting by rainfall that lead to particle breakdown are critical. This breakdown causes soil detachment and crust formation, which are both key elements in erosion.This paper reviews the range of approaches that have been taken in describing the processes associated with the wetting of a soil surface by rainfall. It assembles the studies that emphasize soil physics, soil chemistry, and erosion mechanics in a framework to enable a balanced consideration of important processes and management strategies to control erosion for a particular situation. In particular it discusses the factors associated with the two basic processes of soil structural breakdown, i.e. slaking and dispersion, and how these processes are critical in particle detachment, transport and surface crust formation. Besides the balance between the exchangeable cation composition and electrolyte concentration (measured as the sodium adsorption ratio (SAR) and total cation concentration (TCC) respectively) of the soil, the importance of energy input and soil organic matter content in controlling clay dispersion is emphasized.Based on the balance between these factors, the soil can be in one of three different regions, i.e. a dispersed region, a ﬂocculated region and one where the resilience of the soil is variable. The implications of each of these regions to soil erosion management are brieﬂy outlined, as are the critical roles that soil cover levels and organic matter have in controlling erosion. Finally, the relationship between various laboratory measures of aggregate stability, and corresponding ﬁeld erosion characteristics, is discussed. Copyright © 2004 John Wiley & Sons, Ltd.
A framework relating soil surface condition to infiltration and sediment and nutrient mobilization in grazed rangelands of northeastern Queensland, Australia
Authors: Roth Christian H. 
Published: August 2004

AbstractThe effect of grazing‐induced variation in soil surface condition on inﬁltration and runoff composition was studied at the small patch scale using a rainfall simulator. A range of sites was selected to represent soil surface conditions typical of the more widely distributed rangeland soils in northeastern Queensland. A simple soil surface condition classiﬁcation scheme relates ground cover and a few easily recognizable surface features to mean inﬁltration, sediment and nutrient concentration data. Earthworm activity was identiﬁed as being a signiﬁcant factor in recovery of soil hydrological function. A broader framework is proposed that encapsulates past, current and future trends in soil surface condition in relation to landscape hydrological response and that provides a basis for future research. Copyright © 2004 John Wiley & Sons, Ltd.
Management of soil surface characteristics for soil and water conservation: the case of a silty loam region (Pays de Caux, France)
Authors: Martin P. , Joannon A. , Souchère V. , Papy F. 
Published: August 2004

AbstractThis paper explores, from an agronomic viewpoint, the way soil surface characteristics may be managed for soil and water conservation purposes in a silty loam soil context (Pays de Caux, France). We ﬁrst consider the tools used to characterize the impact of farming practices on soil surface characteristics and, as a result, on runoff and erosion processes. The way farming practices modify soil surface characteristics must be considered at various spatial scales, from the metric pattern produced by farm machinery, to the network of ﬁeld boundaries, headlands and dead furrows at the small‐watershed scale. Various time scales (yearly, daily) must also be taken into account. We then describe how a range of agricultural techniques that may reduce runoff risk on farmland can be found. In particular, we show how to analyse the farmers' leeway for adopting more opportune cultivation techniques specifying the impact of these techniques on plant growth or on work organization. But other factors such as social factors (farmers' network) also interfere and should be taken into account in soil and water protection programmes. Copyright © 2004 John Wiley & Sons, Ltd.
Size fractions resulting from an aggregate stability test, interrill detachment and transport
Authors: Leguédois Sophie , Bissonnais Yves Le 
Published: August 2004

AbstractAggregate stability is a soil characteristic often linked with soil erodibility, but this relationship is generally empirical. The aggregate size distribution is a recognized factor inﬂuencing crust characteristics and transport during interrill erosion events. This parameter was used in this work in order to improve the understanding of the relationship between aggregate stability and erodibility. A second aspect of this study was to investigate the size selectivity of interrill erosion processes, i.e. breakdown, detachment by splash and transport by overland ﬂow. This experimental work was based on rainfall simulations and aggregate stability tests which were performed using two different soils: a clay loam slightly sensitive to erosion, and a more susceptible silt loam. Size distributions of soil fragments either produced by aggregate stability tests or detached by splash or transported by runoff were measured by both wet sieving and laser diffraction sizer analysis. The clay loam is particularly stable and has coarse breakdown products with mean weight diameters larger than 1400 µm. Aggregate breakdown is more efﬁcient for the silt loam and leads to ﬁner soil fragments with mean weight diameters between 229 and 380 mm. For the more stable soil, the clay loam, splash rate and sediment concentration are respectively two and six times lower and less time variable than for the silt loam. For the two soils, detachment by splash and short distance transport are size‐selective interrill erosion processes. This selectivity leads to the enrichment of silt and clay fractions of the eroded aggregates in comparison with the breakdown products. The low erodibility of the more stable soil is in accordance with results of aggregate stability tests. Copyright © 2004 John Wiley & Sons, Ltd.
Dynamic evolution of the unsaturated hydraulic conductivity of a developing crust
Authors: Issa O. Malam , Cousin I. , Bissonnais Y. Le , Quétin P. 
Published: August 2004

AbstractUnderstanding the evolution of hydraulic parameters during the different stages of crust formation is necessary to predict inﬁltration in crusted soil. However, only a few studies have focused on the dynamics of parameters that control inﬁltration through a developing crust. This study reports the results of laboratory experiments carried out with a speciﬁc device, the drip inﬁltrometer, which enables a crust to form at the surface, and the evolution of the pressure head and the hydraulic conductivity of the soil horizon underneath the crust to be followed simultaneously. Two soils of different susceptibility to crusting were used in the experiments: a silt loam and a silty clay loam of the Bassin de Paris (France). The results show matric potential in the unsaturated range developing below the surface from the early stage of crust formation. The values of matric potential show an increasing trend from the early stage of crust formation and at the late stage respectively for the silt loam and the silty clay loam soils. The hydraulic conductivity of the sub‐crust shows signiﬁcant changes from the early stage for the silt loam soil, but only at the ﬁnal stages for the silty clay loam. The initial value of the hydraulic conductivity of the sub‐crust drops by more than 50 per cent for silt loam compared to about 35 per cent for silty clay loam. The decrease of hydraulic conductivity beneath the surface crust is related to the changes in the soil matrix, induced by the migration of particles detached from aggregate breakdown. The different stages of crust formation were characterized by the variation of the unsaturated conductance of the soil crusted layer, calculated from the relationship between the ﬂux density through the crust and the sub‐crust pressure head. The results revealed rapid sealing at the surface of the silty loam soil, whereas sealing occurs gradually at the surface of the silty clay loam. The difference in the susceptibility to crusting and the difference in moisture characteristics between the two soils are probably the causes of the contrast in temporal variation of the sub‐crust matric potential. Copyright © 2004 John Wiley & Sons, Ltd.
Effectiveness of vegetation barriers for marly sediment trapping
Authors: Rey F. 
Published: August 2004

AbstractVegetation barriers can be effective in trapping eroded sediment, but little knowledge exists on the characteristics of vegetation barriers efﬁcient in trapping all sediments from an eroded zone upslope. The objective of this study is to quantify the effectiveness of vegetation barriers for marly sediment trapping. Relationships between eroded zones and vegetation barriers – composed of low vegetation, that is to say herbaceous and under‐shrub layers – located downslope and sufﬁcient to stop all the sediments eroded above, have been studied in the Brusquet experimental marly catchment in the French southern Alps. Forty plots with surface areas less than 500 m2 were studied. The eroded zones and the vegetation barriers were characterized by their surface areas, between which an average linear relationship exists. Results also showed that, for a marly plot with a given surface area, a downslope vegetation barrier covering only 20 per cent of this plot can be sufﬁcient to trap all the sediments eroded above it. Copyright © 2004 John Wiley & Sons, Ltd.
Variations in soil dispersivity across a gully head displaying shallow sub‐surface pipes, and the role of shallow pipes in rill initiation
Authors: Faulkner Hazel , Alexander Roy , Teeuw Richard , Zukowskyj Paul 
Published: August 2004

AbstractA small bifurcating gully head displaying shallow pipe development was surveyed to explore how far three‐dimensional patterns of geochemistry and sediment size can be related to hydraulic gradients in the local marl bedrock (Almería, SE Spain).The crust, sub‐crust and parent materials were sampled every 20 cm across a 2 m by 3 m grid, and then analysed for dispersive and granulometric characteristics. Spatial patterns of sodium adsoption ratio (SAR) for each layer were plotted separately. In‐situ material at depths of 5–10 cm was only weakly dispersive, and the thin (0–2 cm depth) crust is also found to be mostly non‐dispersive, paralleling ﬁndings from other ﬁeld sites in Almería. However, the ‘signature’ relating SAR to electrical conductivity for each layer shows that in places the immediate sub‐crust layer (2–5 cm) is highly dispersive. The pattern is not random; rather the SAR of this sub‐crust layer follows inferred hydraulic gradients, the dispersive ‘hot spots’ being located in the most incised part of the small gully, exacerbating the erodibility of that position.Patterns of sediment particle size and sorting do not correlate with inferred hydraulic gradients but surface material is slightly siltier than the sub‐crust. Clay fraction increased with depth, and SAR is shown to have a weak inverse relationship to particle size. This association between SAR and the increased clay fractions in the lower layers supports the inference that massive pipe enlargement in the Messinian‐Rich Unit is suppressed by sub‐surface swelling. Since a reduction in inﬁltration capacity (fc) with depth can be inferred from these results, inﬁltrating water must be deﬂected into the already vulnerable sub‐crust layer during rainfall events, explaining the development of shallow pipe forms at preferential depths.It is concluded that calcium replaces sodium in the crust during leaching, leaving a calcic crust, and a sub‐crust that is sodic and prone to subsequent pipe enlargement. Rill morphology in these materials also suggests that rills develop from these pipes when pipe roofs collapse (i.e. rill discontinuity; bridges; steep headwalls; and rills with excessively high depth‐to‐width ratios). Copyright © 2004 John Wiley & Sons, Ltd.
Graphical models for coded data transmission over inter‐symbol interference channels
Authors: Tüchler Michael , Koetter Ralf , Singer Andrew C. 
Published: August 2004

AbstractWe derive graphical models for coded data transmission over channels introducing inter‐symbol interference. These models are factor graph descriptions of the transmitter section of the communication system, which serve at the same time as a framework to define the corresponding receiver. The graph structure governs the complexity and nature (e.g. non‐iterative, iterative) of the receiver algorithm. A particular graph yields several algorithms optimizing various cost functions depending on the choice of messages communicated along the edges of the graph. We study these different outcomes of message passing and how the corresponding receiver algorithms are related to existing ones. We also devise strategies to find suitable graphs for communication problems of interest. Copyright © 2004 AEI
On computing the syndrome polynomial in Reed–Solomon decoder
Authors: Costa Elena , Fedorenko Sergei Valentinovich , Trifonov Peter Vladimirovich 
Published: August 2004

AbstractApplication of the cyclotomic fast Fourier transform (FFT) algorithm to the syndrome evaluation problem in classical Reed–Solomon decoders is described. A number of complexity reduction tricks is suggested. Application of the algorithm leads to significant reductions in the complexity of syndrome evaluation. Moreover, automatic generation of the program code implementing the described algorithm is possible. Copyright © 2004 AEI
Radio resource management in cellular multihop networks
Authors: Zirwas Wolfgang , Li Hui , Lott Matthias , Weckerle Martin , Schulz Egon , Lampe Mattias 
Published: August 2004

AbstractIn future mobile broadband radio systems, multihop for coverage extension is seen as a basic building block. Here, we investigate radio resource management (RRM) for multihop networks and assume that the central access point (AP) can control the whole multihop network based on channel state information (CSI) of all links. Specifically we investigate interference effects between neighboring multihop networks as well as within a single multihop network. Interference within a multihop network occurs only when the central scheduler allows simultaneous transmission at the same time and frequency, here called SIMU, on several radio links. It is shown, that SIMU can increase overall capacity of a multihop network compared to a fully orthogonal transmission, here called time division multiple access (TDMA), where only one single link is active at a time. For neighboring multihop networks it is shown that inter cell interference (ICI) may be treated as additive white Gaussian noise (AWGN) with typically only small performance degradation. Copyright © 2004 AEI
Asynchronous TDMA ad hoc networks: scheduling and performance
Authors: Salonidis Theodoros , Tassiulas Leandros 
Published: August 2004

AbstractA common assumption of time division multiple access (TDMA)‐based wireless ad hoc networks is the existence of network‐wide slot synchronization. Such a mechanism is difficult to support in practice. In asynchronous TDMA systems, each link uses a local time slot reference provided by the hardware clock tick of one of the node endpoints. Inevitably, slots are wasted when nodes switch time slot references. This restricts the rate allocations that can be supported when compared to a perfectly synchronized system. To address this practical performance issue, we first introduce a general framework for conflict‐free scheduling in asynchronous TDMA networks. We then propose scheduling algorithms that target overhead minimization while ensuring upper bounds on the generated overhead. Through extensive simulations the algorithm performances are evaluated in the context of Bluetooth, a wireless technology that operates according to the asynchronous TDMA communication paradigm. Copyright © 2003 AEI
Secure and efficient voice‐over‐IP in a cdma2000® Network
Authors: McCann Peter J. , Rance Robert , Patel Sarvar 
Published: August 2004

AbstractThis paper examines how to provide secure and efficient voice‐over‐IP service on a cdma2000 network. Various alternative solutions and their relationship to header compression techniques are discussed. We propose a new method of end‐to‐end encryption that could be used to provide privacy even when Header Removal, a cdma2000‐specific technique where IP/UDP/RTP headers are discarded before transmission over the air, is in use. The new method relies on a novel variable‐length block cipher that can be re‐used with fixed parameters across many voice frames, eliminating the requirement to carry precise cryptographic synchronization with each and every voice frame. Instead, the parameters to the block cipher are varied on an infrequent basis, and synchronization information is communicated from the encryptor to the decryptor by overwriting the occasional voice frame, with minimal impact on resulting voice quality. The method offers provable security guarantees given some assumptions about the amount of entropy contained in the encoded speech data. Copyright © 2004 AEI
Haplotype block structures show significant variation among populations
Authors: Liu Nianjun , Sawyer Sarah L. , Mukherjee Namita , Pakstis Andrew J. , Kidd Judith R. , Kidd Kenneth K. , Brookes Anthony J. , Zhao Hongyu 
Published: August 2004

AbstractRecent studies suggest that haplotypes tend to have block‐like structures throughout the human genome. Several methods were proposed for haplotype block partitioning and for tagging single‐nucleotide polymorphism (SNP) identification. In population genetics studies, several research groups compared block structures across human populations. However, the measures used to quantify population similarity are either less than satisfactory or nonexistent. In this article, we propose several similarity measures to facilitate the comparisons of haplotype structures, namely block boundaries and tagging SNPs, across populations. With these measures, we can more objectively compare haplotype block structures and tagging SNP sets between different populations. In addition, these measures allow us to compare the results of different methods for block partition and tagging SNP identification. When we applied these measures to a real data set on chromosome 10 in 16 worldwide populations, we found that in this genome region: 1) haplotype block boundaries vary among populations, with European and some African populations showing similar boundaries but other populations showing other patterns; 2) tagging SNP sets are generally similar for populations with similar haplotype block structures but differ if the block structures differ; and 3) all but one of the block finding methods we tested yield consistent results, although variations exist regarding consistency. Our tentative results show that at least in the genome region studied, it is unlikely that a common haplotype pattern exists for all human populations: many populations, even in the same geographical region, may have different haplotype patterns. © 2004 Wiley‐Liss, Inc.
Stability of hippocampal place cell activity across the rat estrous cycle
Authors: Tropp Jennifer , Figueiredo Cristina M. , Markus Etan J. 
Published: August 2004

AbstractFindings from both in vitro and in vivo studies have shown that estrogen exerts pronounced effects on hippocampal morphology and physiology. The degree to which these molecular findings influence hippocampal processing in freely behaving animals is unclear. The present study assessed the effect of the estrous cycle on hippocampal place cells in naturally cycling rats during two behavioral states. Female Sprague‐Dawley rats were trained to alternate on a U‐shaped runway for food reinforcement. Single‐unit recordings of hippocampal CA1 cells were conducted under two conditions: (1) at rest on a holder, and (2) running on the maze. Spatial firing characteristics of the cells were examined at different stages of the estrous cycle (i.e., diestrus, proestrus, and estrus). Specifically, information was collected on (1) mean firing rates; (2) basic place field parameters; and (3) changes in the firing dynamics of these cells (e.g., burst properties). The findings showed a decrease in mean firing rate on the maze during proestrus. However, other basic measures of spatial tuning and burst properties were unchanged. The current study suggests that there is relative stability of hippocampal place cells across the estrous cycle during a well‐trained task. © 2004 Wiley‐Liss, Inc.
Experimental research on the effects of distributor configuration on flow distribution in plate‐fin heat exchangers
Authors: Zhang Zhe , Li Yanzhong , Xu Qing 
Published: August 2004

AbstractThe effects of different distributor configurations on the flow distribution in plate‐fin heat exchangers were studied. It was found that an irrational distributor configuration would lead to the flow maldistribution and a different degree of non‐uniformity of the flow distribution in the transverse and longitudinal directions. The distributor configuration and Reynolds number are the main factors affecting the flow distribution. An improved distributor configuration with a fluid complementary cavity has been brought forward. The experimental results showed that the improved distributor configuration can effectively improve the performance of flow distribution in heat exchangers. The best performance of flow distribution was obtained at h/H = 0.2. The correlations between the flow maldistribution characteristic and the flow Reynolds number for different distributor configurations were deduced according to the experimental data. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(6): 402–410, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20023
Effect of micro mass transfer through phase interface on numerical simulation of solidification process
Authors: Feng Yanhui , Zhang Xinxin 
Published: August 2004

AbstractExisting models for the solute redistribution during solidification have been reviewed. Some typical models are applied for the numerical simulation of heat and mass transfer with phase change under experimental condition of inverse casting. The results show that the effect of micro mass transfer models on the formation of the new phase cannot be omitted. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(6): 393–401, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20024
Enhanced heat transfer analysis of latent functionally thermal fluid
Authors: Bai Fengwu , Lu Wen‐Qiang 
Published: August 2004

AbstractA physical model has been developed to analyze the enhanced heat transfer process of the latent functionally thermal fluid with microencapsulated phase‐change material. The problem is solved by the combination of the finite difference method and the moving heat source method. The calculated results reveal that putting the phase‐change microcapsules into the fluids can enhance the heat transfer capabilities of the mixture. The effects of capsule radius and concentration of particles are numerically predicted. The numerical results provide the theoretical basis for the application and design of the latent functionally thermal fluid. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(6): 383–392, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20025