An adaptive and efficient dimension reduction model for multivariate wireless sensor networks applications

Wireless sensor networks (WSNs) applications are growing rapidly in various fields such as environmental monitoring, health care management, and industry control. However, WSN's are characterized by constrained resources especially; energy which shortens their lifespan. One of the most important factors that cause a rapid drain of energy is radio communication of multivariate data between nodes and base station. Besides, the dynamic changes of environmental variables pose a need for an adaptive solution that cope with these changes over the time. In this paper, a new adaptive and efficient dimension reduction model (APCADR) is proposed for hierarchical sensor networks based on the candid covariance-free incremental PCA (CCIPCA). The performance of the model is evaluated using three real sensor networks datasets collected at Intel Berkeley Research Lab (IBRL), Great St. Bernard (GSB) area, and Lausanne Urban Canopy Experiments (LUCE). Experimental results show 33.33% and 50% reduction of multivariate data in dynamic and static environments, respectively. Results also show that 97–99% of original data is successfully approximated at cluster heads in both environment types. A comparison with the multivariate linear regression model (MLR) and simple linear regression model (SLR) shows the advantage of the proposed model in terms of efficiency, approximation accuracy, and adaptability with dynamic environmental changes.     

2. Numerical Simulations of Water Flow and Solute Transport Applied to Acid Sulfate Soils

Field investigations of Rassam et al. in 2001 have highlighted the effects of infiltration, drainage, and evapotranspiration on the dynamics of water flow and solute transport in acid sulfate (AS) soils. In this work, HYDRUS-2D is adopted as the modeling tool to elucidate the trends observed in that field experiment. Hypothetical simulations have shown that the relative contribution of drains to lowering the water table is significant only when closely spaced drains are installed in coarse textured soils, evapotranspiration being the main driving force in all other cases. AS soils reaction products that are close to a drain are readily transportable during infiltration and early drainage, but those produced farther away from it near the midpoint between drains are only slowly transported during a prolonged drainage process. Simulating the field trial of Rassam et al. has shown that drain depth and evapotranspiration significantly affect solute fluxes exported to the ecosystem. Managing AS soils should target minimal drain depth and density. Partial or full lining of the drains should be considered as a management option for ameliorating the environmental hazards of AS soils.     

Mechanical performance and dimensional stability of nano-silver impregnated densified spruce wood

The aim of this study was to investigate the effect of nano-silver treatment on some physical and mechanical properties of compressed low density wood species. Wood specimens were prepared from spruce (Picea abies), impregnated with water or nano-silver solution by empty cell process and compressed through radial direction in a hot press. The results showed that by nano-silver treatment, the spring back, bending strength (modulus of rupture) and impact load resistance were improved significantly. The best results for spring-back (0.04%) were seen in the nano-silver impregnated specimens that were compressed at 150°C for 4 hours. The modulus of rupture (MOR), modulus of elasticity (MOE) and impact load resistance in nano-silver impregnated densified specimens were gained for 53%, 41.2% and 175.7%, respectively (in comparison with controls). The maximum amounts of impact load resistance belonged to the nano-silver impregnated specimens which were compressed at press conditions of 150°C for 4 hours, showing the high ability of these specimens against high impact loads such as earthquake loads. An upcoming research (consisting of durability tests) will be done for evaluating the suitability of nano-silver impregnated densified spruce wood for exterior uses.     

1. Field and Laboratory Studies of Acid Sulfate Soils

Drains are introduced into acid sulfate (AS) soils grown to sugar cane to prevent waterlogging and drain runoff water. Drains have the potential to promote deleterious reactions and facilitate the transport of the resulting reaction products into the ecosystem. A field experiment was carried out to investigate the hydrology of an AS soil field and monitor the quality of its drainage water. Results have shown that in such low-conductivity soils, a steep water-table draw-down occurs close to the drain. Farther away from the drain, water-table dynamics are predominantly driven by evapotranspiration. The concentration of sulfate ions in the drainage water showed a steep decline during infiltration followed by a moderate surge during drainage. A laboratory leaching column experiment has revealed an increasing sulfate concentration away from the drain. The column experiment confirmed earlier findings of Rassam and Cook, who conducted hypothetical numerical simulations and showed that solutes from low-conductivity AS soils are mainly leached from soils located close to the drain.     

Bearing Capacity of Desiccated Tailings

The development of matric suctions in soils contributes to their shear strength, resulting in an enhanced factor of safety against bearing-capacity failure. In this paper, matric suction profiles of desiccated mine tailings are predicted from a steady-state solution for evaporative conditions, and from an isothermal mathematical model that simulates liquid and vapor water flow through soils. The shear-strength envelope with respect to matric suction is established by testing reconstituted tailings samples in a modified triaxial cell, in which matric suction can be controlled. The contribution of matric suction to the shear strength is interpreted as an additional apparent cohesion for use in bearing-capacity calculations. Because of the nonlinearity of the shear-strength profile, a numerical method of analysis is adopted to predict the ultimate bearing capacity of the desiccated tailings. A subsequent decrease in bearing capacity following 2D water infiltration into a partially capped tailings deposit and accompanying suction loss is investigated.     

Engineering properties of gold tailings

ABSTRACT

A comprehensive laboratory testing program has been conducted to establish the engineering properties of gold tailings from Kidston Gold Mines in North Queensland, Australia. The engineering properties of the tailings have been categorised into textural, hydraulic, and mechanical properties. The textural properties include the particle size distribution and the specific gravity. The hydraulic properties include the water characteristic curve, and the saturated and unsaturated hydraulic conductivity. Various models that describe the tailings water characteristic curve and hydraulic conductivity function have been presented. The mechanical properties include the bulk modulus, Poisson's ratio, the friction angle, the dilation angle, and the unsaturated shear strength parameters. The engineering properties of the tailings are vital to the management of the tailings both during the mine's operation, and long after its de-commissioning.