Two-level Mapping Based Cache Index Selection for Packet Forwarding Engines

Packet forwarding is a memory-intensive application requiring multiple accesses through a trie structure. The efficiency of a cache for this application critically depends on the placement function to reduce conflict misses. Traditional placement functions use a one-level mapping that naively partitions trie-nodes into cache sets. However, as a significant percentage of trie nodes are not useful, these schemes suffer from a non-uniform distribution of useful nodes to sets. This in turn results in increased conflict misses. Newer organizations such as variable associativity caches achieve flexibility in placement at the expense of increased hit-latency. This makes them unsuitable for L1 caches.We propose a novel two-level mapping framework that retains the hit-latency of one-level mapping yet incurs fewer conflict misses. This is achieved by introducing a secondlevel mapping which reorganizes the nodes in the naive initial partitions into refined partitions with near-uniform distribution of nodes. Further as this remapping is accomplished by simply adapting the index bits to a given routing table the hit-latency is not affected. We propose three new schemes which result in up to 16% reduction in the number of misses and 13% speedup in memory access time. In comparison, an XOR-based placement scheme known to perform extremely well for general purpose architectures, can obtain up to 2% speedup in memory access time.

Spatio-temporal landscape modelling for natural hazard vulnerability analysis in select watersheds of Central Western Ghats

Natural hazards such as landslides are triggered by numerous factors such as ground movements, rock falls, slope failure, debris flows, slope instability, etc. Changes in slope stability happen due to human intervention, anthropogenic activities, change in soil structure, loss or absence of vegetation (changes in land cover), etc. Loss of vegetation happens when the forest is fragmented due to anthropogenic activities. Hence land cover mapping with forest fragmentation can provide vital information for visualising the regions that require immediate attention from slope stability aspects. The main objective of this paper is to understand the rate of change in forest landscape from 1973 to 2004 through multi-sensor remote sensing data analysis. The forest fragmentation index presented here is based on temporal land use information and forest fragmentation model, in which the forest pixels are classified as patch, transitional, edge, perforated, and interior, that give a measure of forest continuity. The analysis carried out for five prominent watersheds of Uttara Kannada district– Aganashini, Bedthi, Kali, Sharavathi and Venkatpura revealed that interior forest is continuously decreasing while patch, transitional, edge and perforated forest show increasing trend. The effect of forest fragmentation on landslide occurrence was visualised by overlaying the landslide occurrence points on classified image and forest fragmentation map. The increasing patch and transitional forest on hill slopes are the areas prone to landslides, evident from the field verification, indicating that deforestation is a major triggering factor for landslides. This emphasises the need for immediate conservation measures for sustainable management of the landscape. Quantifying and describing land use - land cover change and fragmentation is crucial for assessing the effect of land management policies and environmental protection decisions.

Stability numbers for an unsupported vertical circular excavation in c-phi soil

By using an axisymmetric lower bound finite element limit analysis formulation, the stability numbers (gamma H/C) for an unsupported vertical circular excavation in a cohesive-frictional soil have been generated. The numerical results are obtained for values of normalized excavation height (H/b) and friction angle (phi) greater than those considered previously in the literature. The results compare well with those available in literature. The stability numbers presented in this note would be beneficial from a design point of view. (C) 2011 Elsevier Ltd. All rights reserved.

Soil and Groundwater Pollution from Agricultural Activities

This book introduces the major agricultural activities in India and their impact on soil and groundwater. It lists the basic aspects of agricultural activities and introduces soil properties, classification and processes, and groundwater characteristics, movement, and recharge aspects. It further discusses soil and groundwater pollution from various sources, impacts of irrigation, drainage, fertilizer, and pesticide. Finally, the book dwells upon conservation and management of groundwater and soil.

Seismic reliability assessment of internal stability of reinforced soil walls using the pseudo-dynamic method

The study focuses on probabilistic assessment of the internal seismic stability of reinforced soil structures (RSS) subjected to earthquake loading in the framework of the pseudo-dynamic method. In the literature, the pseudo-static approach has been used to compute reliability indices against the tension and pullout failure modes, and the real dynamic nature of earthquake accelerations cannot be considered. The work presented in this paper makes use of the horizontal and vertical sinusoidal accelerations, amplification of vibrations, shear wave and primary wave velocities and time period. This approach is applied to quantify the influence of the backfill properties, geosynthetic reinforcement and characteristics of earthquake ground motions on reliability indices in relation to the tension and pullout failure modes. Seismic reliability indices at different levels of geosynthetic layers are determined for different magnitudes of seismic acceleration, soil amplification, shear wave and primary wave velocities. The results are compared with the pseudo-static method, and the significance of the present methodology for designing reinforced soil structures is discussed.

Soil aggressivity consideration for laying petroleum pipelines

The magnitude and volume of transportation of petroleum products (both crude and finished products) has necessitated constructing dedicated pipelines from the refineries to the various consumer centers. The present status and scenario of pipeline transportation has been briefly described. Published literatures covering geotechnical engineering aspects, especially corrosion studies for pipelines are scanty. Available literature has been summarized. Main topic includes soil resistivity survey, classification based on resistivity and various parameters of chemical analysis. Detailed analysis has been carried out from the data generated through field investigation and laboratory tests on soil samples obtained from different locations along the two selected pipeline route where they are to be constructed. Typical data has been analysed for aggressivity. Summary of aggressivity analysis has been presented for the two field cases and modification has been suggested for existing practice.

Tensile force distribution along the reinforcement for reinforced soil foundations

In a reinforced soil bed system reinforcement layer is usually placed with or without end anchorage. Since soil is weak in tension reinforcement develop tension under the applied load or the displacement of the footing. This tensile force is distributed along the length of the reinforcement subjected to the end condition. The reinforccement tension helps in distributing the load over a wider area, and becomes more effective at large induced settlements. As a result, vertical componenent of tensile force generated becomes effective in reducing applied load. However, very few studies to quantify the tensile force along the reinforcement have been reported in the literature. In this paper an attempt has been made to obtain the true nature of tensile force distribution along the reinforcement. For a reinforced soil bed below a strip footing this paper brings out induced tensile force distribution along the reinforcement at different load levels and for different types of reinforcements.

Analysis of residual tropical cemented soil behaviour

In -situ soils in gee-material spectrum might arise due to sedimentation or could be non-sedimentary residual formations. The inherent nature and diversity of geological processes involved in the soil formation stage itself are responsible for a wide variability in the in-situ state of the soil. In this paper the possibility of analyses to arrive at engineering parameters of residual soils with varied degrees of residual or acquired cementation by the use of physical and in-situ parameters normally determined in routine investigations, are examined. An Intrinsic State Line,(ISL), with reference to an intrinsic state parameter (e/e(L)) and its variation with effective stress for reconstituted clays has been developed for residual tropical soils of non-sedimentary origin. In relation to the Intrinsic State Line (ISL), the undisturbed state, e, the potential parameter, e(L), along with the overburden pressure data has been analyzed to identify the dominance of cementation or stress history or both in controlling the compressibility and strength behaviour of natural residual soil. The location of yield stress point in relation to the ISL, pre-, and post- yield stress, compression indices along the e- log sigma(v) path provide a simple means to the analysis of the compressibility characteristics of cemented soils for analysis.

Vertical uplift capacity of a group of two coaxial anchors in a general c-phi soil

The vertical uplift resistance of a group of two horizontal coaxial strip anchors, embedded in a general c-phi soil (where c is the unit cohesion and phi is the soil friction angle), has been determined by using the lower bound finite element limit analysis. The variation of uplift factors F-c and F-gamma, due to the components of soil cohesion and unit weight, respectively, with changes in depth (H)/width (B) has been established for different values of vertical spacing (S)/B. As compared to a single isolated anchor, the group of two anchors provides a significantly greater magnitude of F-c for phi <= 20 degrees and with H/B >= 3. The magnitude of F-c becomes almost maximum when S/B is kept closer to 0.5H/B. On the other hand, with the same H/B, as compared to a single anchor, hardly any increase in F-gamma occurs for a group of two anchors.

Hierarchical Clustering Algorithm for Land Cover Mapping Using Satellite Images

This paper presents hierarchical clustering algorithms for land cover mapping problem using multi-spectral satellite images. In unsupervised techniques, the automatic generation of number of clusters and its centers for a huge database is not exploited to their full potential. Hence, a hierarchical clustering algorithm that uses splitting and merging techniques is proposed. Initially, the splitting method is used to search for the best possible number of clusters and its centers using Mean Shift Clustering (MSC), Niche Particle Swarm Optimization (NPSO) and Glowworm Swarm Optimization (GSO). Using these clusters and its centers, the merging method is used to group the data points based on a parametric method (k-means algorithm). A performance comparison of the proposed hierarchical clustering algorithms (MSC, NPSO and GSO) is presented using two typical multi-spectral satellite images - Landsat 7 thematic mapper and QuickBird. From the results obtained, we conclude that the proposed GSO based hierarchical clustering algorithm is more accurate and robust.

Parameter estimation of a two-horizon soil profile by combining crop canopy and surface soil moisture observations using GLUE

Estimation of soil parameters by inverse modeling using observations on either surface soil moisture or crop variables has been successfully attempted in many studies, but difficulties to estimate root zone properties arise when heterogeneous layered soils are considered. The objective of this study was to explore the potential of combining observations on surface soil moisture and crop variables - leaf area index (LAI) and above-ground biomass for estimating soil parameters (water holding capacity and soil depth) in a two-layered soil system using inversion of the crop model STICS. This was performed using GLUE method on a synthetic data set on varying soil types and on a data set from a field experiment carried out in two maize plots in South India. The main results were (i) combination of surface soil moisture and above-ground biomass provided consistently good estimates with small uncertainity of soil properties for the two soil layers, for a wide range of soil paramater values, both in the synthetic and the field experiment, (ii) above-ground biomass was found to give relatively better estimates and lower uncertainty than LAI when combined with surface soil moisture, especially for estimation of soil depth, (iii) surface soil moisture data, either alone or combined with crop variables, provided a very good estimate of the water holding capacity of the upper soil layer with very small uncertainty whereas using the surface soil moisture alone gave very poor estimates of the soil properties of the deeper layer, and (iv) using crop variables alone (else above-ground biomass or LAI) provided reasonable estimates of the deeper layer properties depending on the soil type but provided poor estimates of the first layer properties. The robustness of combining observations of the surface soil moisture and the above-ground biomass for estimating two layer soil properties, which was demonstrated using both synthetic and field experiments in this study, needs now to be tested for a broader range of climatic conditions and crop types, to assess its potential for spatial applications. (C) 2012 Elsevier B.V. All rights reserved.

Effect of frequency on seismic response of reinforced soil slopes in shaking table tests

This paper studies the effect of frequency of base shaking on the dynamic response of unreinforced and reinforced soil slopes through a series of shaking table tests. Slopes were constructed using clayey sand and geogrids were used for reinforcing the slopes. Two different slope angles 45 degrees and 60 degrees were used in tests and the quantity and location of reinforcement is varied in different tests. Acceleration of shaking is kept constant as 0.3 g in all the tests to maximize the response and the frequency of shaking was 2 Hz, 5 Hz and 7 Hz in different tests. The slope is instrumented with ultrasonic displacement sensors and accelerometers at different elevations. The response of different slopes is compared in terms of the deformation of the slope and acceleration amplifications measured at different elevations. It is observed that the displacements at all elevations increased with increase in frequency for all slopes, whereas the effect of frequency on acceleration amplifications is not significant for reinforced slopes. Results showed that the acceleration and displacement response is not increasing proportionately with the increase in the frequency, suggesting that the role of frequency in the seismic response is very important. Reinforced slopes showed lesser displacements compared to unreinforced slopes at all frequency levels. (C) 2012 Elsevier Ltd. All rights reserved.

Quasi-based hierarchical clustering for land cover mapping using satellite images

This paper presents an improved hierarchical clustering algorithm for land cover mapping problem using quasi-random distribution. Initially, Niche Particle Swarm Optimization (NPSO) with pseudo/quasi-random distribution is used for splitting the data into number of cluster centers by satisfying Bayesian Information Criteria (BIC). Themain objective is to search and locate the best possible number of cluster and its centers. NPSO which highly depends on the initial distribution of particles in search space is not been exploited to its full potential. In this study, we have compared more uniformly distributed quasi-random with pseudo-random distribution with NPSO for splitting data set. Here to generate quasi-random distribution, Faure method has been used. Performance of previously proposed methods namely K-means, Mean Shift Clustering (MSC) and NPSO with pseudo-random is compared with the proposed approach - NPSO with quasi distribution(Faure). These algorithms are used on synthetic data set and multi-spectral satellite image (Landsat 7 thematic mapper). From the result obtained we conclude that use of quasi-random sequence with NPSO for hierarchical clustering algorithm results in a more accurate data classification.

Verification of Masonry Building Code to Flexural Behavior of Cement-Stabilized Soil Block

Most studies involving cement-stabilized soil blocks (CSSB) concern material properties, such as the characteristics of erosion and strength and how the composition of the block affects these properties. Moreover, research has been conducted on the performance of various mortars, investigating their material properties and the tensile bond strength between CSSB units and mortar. In contrast, very little is currently known about CSSB masonry structural behavior. Because structural design codes of traditional masonry buildings were well developed over the past century, many of the same principles may be applicable to CSSB masonry buildings. This paper details the topic of flexural behavior of CSSB masonry walls and whether the Masonry Standards Joint Committee (MSJC) code can be applied to this material for improved safety of such buildings. DOI: 10.1061/(ASCE)MT.1943-5533.0000566. (C) 2013 American Society of Civil Engineers.