Detection of the eroding surface in the EDM process based on the current signal in the gap

To achieve high removal rate and low electrode wear in sinking electrical discharge machining process (EDM), rough machining parameters have to be selected according to the size of the eroding surface. In general, the size of the eroding surface varies according to the depth of the machining. Thus, it has to be determined on-line. This paper shows that the electric current signal in the gap depends on the size of the eroding surface. The significance of the process attributes of the electric current signal is established by inductive machine learning and the general decision rules are derived. The size of the eroding surface can be detected on-line by monitoring and evaluating the electric current signal in the gap.     

Multi-layer models of friction between solids

Recent simulations of processes in surface layers of rubbing solids have shown the formation of a boundary layer, called quasi-fluid layer. To better understand the physical nature of the quasi-fluid layer, we investigate the processes occurring in the surface layer of rubbing solids in the frame of a simple multi-layer model, which also leads to the formation of a quasi-fluid layer. The multi-layer model can further be used to investigate how the friction force is determined by the material and loading parameters. It has been shown that the friction force and the thickness of the quasi-fluid layer depend on sliding velocity, the viscosity of the material and on a microscopic parameter (layer thickness). Subsequently, two different ways of extending the discussed model are proposed aiming at a model that can also predict the influence of normal pressure and surface topography on the friction force and on the formation of the quasi-fluid layer.     

Dynamic analysis of charge transport in fluidized bed electrodes: Impedance techniques for electroactive beds

Impedance techniques are used to investigate the average dynamic behaviour of a fluidized bed of gold-coated beads in potassium ferri-ferrocyanide/NaOH solution. A transmission line is used as a model. The main features of the fluidized bed are correctly interpreted, especially the capacitive high frequency impedance related to the intermittent contacts between the particles. The use of a nonuniform transmission line is attempted in order to study the influence of a distance dependent charge transfer mechanism in the bulk of the fluidized bed.     

Microvascular growth, development, and remodeling in the embryonic avian kidney: the interplay between sprouting and intussusceptive angiogenic mechanisms

Embryonic development is associated with extensive vascular growth and remodeling. We used immunohistochemical, light and electron microscopical techniques, as well as vascular casting methods to study the developing chick embryo kidney with special attention to the interplay between sprouting and intussusceptive vascular growth modes. During inauguration at embryonic day 5 (E5), the early mesonephros was characterised by extensive microvascular sprouting. By E7, the vascular growth mode switched to intussusception, which contributed to rapid kidney vasculature growth up to E11, when the first obvious signs of vascular degeneration were evident. The metanephros underwent similar phases of vascular development inaugurating at E8 with numerous capillary sprouts and changing at E13 to intussusceptive growth, which was responsible for vascular amplification and remodeling. A phenomenal finding was that future renal lobules arose as large glomerular tufts, supplied by large vessels, which were split into smaller intralobular feeding and draining vessels with subsequent formation of solitary glomeruli. This glomerular duplication was achieved by intussusception, i.e., by formation of pillars in rows and their successive merging to delineate the vascular entities. Ultimately, the maturation of the vasculature was achieved by intussusceptive pruning and branching remodeling. An interesting finding was that strong VEGF expression was associated with the sprouting phase of angiogenesis while bFGF was upregulated during the phase of intussusceptive microvascular growth. We conclude that microvascular growth and remodeling in avian kidney follows an adroitly crafted pattern, which entails a precise spaciotemporal interplay between sprouting and intussusceptive angiogenic growth modes supported partly by VEGF and bFGF.     

Methodology to assess groundwater pollution conditions (current and pre-disposition) in the São Carlos and Ribeirão Preto regions,Brazil

The goal of the study was to establish a methodology for territorial zoning based on predicted groundwater pollution. The 31 attributes identified were divided into six different environmental components associated with the transport of contaminants to the geological medium. Two indices were obtained: the pre-disposition index (PI), and the potential pollution intensity index (PPII). The paper reports an assessment of the potential pollution of the groundwater in the sandstones of the Botucatu and Pirambóia Formations, Sao Paulo, Brazil. The region was divided into 447 units according to the type of land use, size of watershed and degree of lithological homogeneity. The units were assessed for potential pollution in the pre-disposition condition (based on geological/geotechnical data) and the complete condition (geological/geotechnical and situation specific data) using the analytical hierarchical process method. A high degree of pollution potential was established for 35 of the units in the complete condition and 157 units in the pre-disposition condition. The study has highlighted areas where attention to pollution control should be focused.      

Environmental assessment of an uncontrolled sanitary landfill,Pocos de Caldas,Brazil

There are more than 20,000 uncontrolled sanitary landfill areas in Brazil. The paper reports an integrated study undertaken to develop an environmental assessment of the uncontrolled sanitary landfill area of the city of Po?os de Caldas, State of Minas Gerais, Brazil. A number of remedial alternatives were evaluated. The USGS modular 3D finite difference groundwater flow model (Modflow) and Modular 3D Finite Difference Mass Transport Model (MT3D) software were used to simulate groundwater flow and contaminant transport modelling, as well as to predict changes due to the proposed remediation measures. The remedial alternatives considered for normal conditions from 20 to 40 year periods were waste removal, vertical cut-off barriers, extraction wells and top capping. The results indicated that extraction wells and waste removal are the best alternatives because they significantly reduce both the extension and levels of the contamination plume even after 5 years. The extraction well proved a less expensive remedial alternative than waste removal.      

Adsorption of Thin Liquid Helium Films on Cs Measured via Photoelectron Tunneling

The alkali metals Cs and Rb are the only surfaces which are not wetted by superfluid ⁴ He below a certain temperature. In our experiments, using the photoelectron tunneling method, we can highly resolve the growth of the non-wetting thin-film state of ⁴ He on a quench-condensed Cs surface. It turns out that far from coexistence there is little adsorption of helium. In contrast, close to coexistence a rapid growth up to two monolayers of helium is observed, but the surface is still non-wet under the usual convention.