Ground Components Research Articles

Grind-hardening of steel surfaces: a focused review

Surface hardening of steel components using grinding-induced heat seems to be a cost-effective technique for production. This paper provides a review focusing on the research effort on grind-hardening in the author's Laboratory for Precision and Nano-processing Technologies. The discussion includes the mechanisms of heating and cooling, microstructural changes in workpiece materials, surface integrity generation and wear and fatigue behaviour of ground components.

Relative spectral mixture analysis — A multitemporal index of total vegetation cover

A new multitemporal technique is presented that allows monitoring of vegetation dynamics in coarse multispectral remote sensing data. This technique, relative spectral mixture analysis (RSMA), provides information about the amount of green vegetation (GV), nonphotosynthetic vegetation (NPV) plus litter, and snow relative to a reference time. The RSMA indices of specific ground components are defined so that they are positive when the fractional cover of a ground component is greater than that at the reference time and negative when the fractional cover is less than that at the reference time. The rationale for the new technique and its mathematical underpinnings are discussed. Example RSMA timeseries from the southern–central United States are presented based on four years of MODIS MOD43 nadir BRDF adjusted reflectance (NBAR) data. This timeseries shows that the RSMA GV index, X GV, is robust in the presence of snow. Spectral simulations show that X GV is also robust with different soil backgrounds. The RSMA index of NPV/litter cover, X NPV/litter, provides information about the dynamics of the nonphotosynthetic portion of organic matter at or above the surface. The RSMA index of total vegetation plus litter, X TV, provides information about the dynamics of the non-soil/non-snow portion of ground cover. Because it mirrors the bare ground cover, X TV may be particularly useful in remote sensing applications aimed at the study of soil erosion.

Effects of the vertical component of ground shaking on earthquake-induced landslide displacements using generalized Newmark analysis

The popular Newmark method calculates the cumulative permanent displacement of a landslide having a known critical acceleration as it is subjected to the effects of an earthquake acceleration time-history. For an infinite slope, this method considers ground acceleration as parallel to the slope and downslope which results in two important limitations: (1) vertical downslope acceleration only is considered; (2) the ratio of vertical to horizontal acceleration only depends on the inclination of the slope surface. In the model developed herein, the ground acceleration is not parallel to the slope; the ratio of vertical to horizontal acceleration, called the vertical accelerometric parameter, depends on the seismic situation of the slope (magnitude, earthquake source distance, style of faulting), and the vertical acceleration acts alternately upslope and downslope. Application of the principles of classical mechanics leads to the pseudo-static factor of safety and hence to the seismic horizontal critical acceleration of a potential landslide, which depends not only on its static factor of safety (geometry, geotechnical properties, and hydrogeologic conditions) but also on its seismic situation. It is shown that Newmark's model is in fact a particular case of the general model and, in most cases, the seismic horizontal critical acceleration results from vertical upslope acceleration and is lower than Newmark's critical acceleration. As a consequence, the displacements D resulting from the model developed herein will be greater than the displacements D N calculated from Newmark's approach. For some potential landslides, the difference ( D − D N) is considerable and results in significant consequences in the seismic stability analysis of the affected slopes, which justifies the importance of the effects of vertical ground shaking.

Recovery from equipment failures in ATC: Determination of contextual factors

Human reliability assessment (HRA) currently uses various approaches to determine and quantify human error. These approaches are increasingly being employed in various safety-critical domains, such as air traffic management and its ground component air traffic control. HRA research over the years has shown the important role of the context in which human errors take place. Recent techniques now put more emphasis on the definition of key contextual factors and their impact on the reliability of human performance. This paper presents a review of the current understanding of contextual factors in various industries. It uses this together with results from controller interviews to identify the contextual factors relevant to controller recovery from equipment failures in air traffic control. These factors should be used in conjunction with an appropriate method to analyse the performance of a controller during the process of recovery from failures.

Grinding-hardening with liquid nitrogen: Mechanisms and technology

This paper studies an innovative development of a steel grinding–hardening technology using an inert cryogen—liquid nitrogen. It was found that phase transformations took place during grinding with the application of liquid nitrogen and resulted in hardened surface layer in a ground component. The layer had a fine laths martensite structure which gave rise to a remarkably high hardness. It was also shown that the treatment can produce superior surface integrity, with compressive surface residual stresses and without surface oxidation. Due to the inert nature of the liquid nitrogen, the grinding process becomes environmentally conscious.

Effects of the cryogenic cooling on the fatigue strength of the AISI 304 stainless steel ground components

For environmental considerations, the substitution of the conventionally used oil-based grinding fluids has nowadays become strongly recommended. Although several alternatives have been proposed, cryogenic cooling by liquid nitrogen is the non-polluting coolant that has been given relatively more attention because of its very low temperature. In this investigation, in order to contribute to developing this promising cooling mode, its beneficial effects on the ground surface integrity of the AISI 304 stainless steel and their consequences on the fatigue lifetime are explored. Results of this investigation show that grinding under cryogenic cooling mode generates surfaces with lower roughness, less defects, higher work hardening and less tensile residual stresses than those obtained on surfaces ground under oil-based grinding fluid. These surface enhancements result into substantial improvements in the fatigue behaviour of components ground under this cooling mode. An increasing rate of almost 15% of the endurance limit at 2 × 10 6 cycles could be realized. SEM analyses of the fatigue fracture surfaces have shown that the fatigue cracks observed on the specimens ground under cryogenic cooling are shorter (i.e., 30–50 μm) than those generated under oil-based cooling mode (i.e., 150–200 μm). The realized improvements in the surface integrity and in the fatigue behaviour are thought to be related to the reduction of the grinding zone temperature observed under cryogenic cooling, as no significant differences between the grinding force components for both cooling modes have been observed.

Text binarization in color documents

This article presents a new method for the binarization of color document images. Initially, the colors of the document image are reduced to a small number using a new color reduction tech- nique. Specifically, this technique estimates the dominant colors and then assigns the original image colors to them in order that the back- ground and text components to become uniform. Each dominant color defines a color plane in which the connected components (CCs) are extracted. Next, in each color plane a CC filtering procedure is applied which is followed by a grouping procedure. At the end of this stage, blocks of CCs are constructed which are next redefined by obtaining the direction of connection (DOC) property for each CC. Using the DOC property, the blocks of CCs are classified as text or nontext. The identified text blocks are binarized properly using suita- ble binarization techniques, considering the rest of the pixels as background. The final result is a binary image which contains always black characters in white background independently of the original colors of each text block. The proposed document binarization approach can also be used for binarization of noisy color (or gray- scale) document images. Several experiments that confirm the effec- tiveness of the proposed technique are presented. V C 2007 Wiley

The measurement of grinding temperatures at high specific material removal rates

Developments in measuring surface temperatures during grinding at high specific material removal rates using PVD low melting point coatings are reported. This paper considers the use of this type of coating to determine the finished surface temperature and the thermal gradient below the workpiece surface under aggressive grinding conditions. Theoretical surface temperatures derived from mathematical modelling are compared to those measured by the PVD coating technique. Theoretical temperatures showed good correlation to the measured temperatures. Metallographic examination including Vickers microhardness testing was used to validate the measured thermal gradients and depth of phase transformations. The effect of the heating rate due to the grinding conditions was shown to have a significant influence on the A3 austenitic transition temperature. The technique of using low melting point PVD coatings is shown to offer a robust measurement technique for the determination of the finished surface temperature of a ground component, within aggressive environments and at high specific material removal rates.

Development of a small air vehicle based on aerodynamic model analysis in the tunnel tests

Tunnel tests play critical role to aerodynamics analysis, but few work has been done in this area for developing small air vehicles. This paper presents development of an electrically powered small air vehicle prototype based on aerodynamic analysis in wind tunnel and water tunnel tests. Firstly, two airframe models in triangle and square wing planforms, each with a wingspan of 100 mm, are analyzed with a small-scale low speed wind tunnel. The purpose of the wind tunnel test is to examine the practical characteristics such as lift and drag coefficients. The test in a water tunnel is further carried out to investigate the relationship between the vortex aerofoil design and turbulences created. In both wind tunnel and water tunnel tests, the airframe models, apparatus and the methodology are discussed, and the testing results show that the triangle wing aerofoil appears greater maximum lift coefficient and little occurrence of vortex and turbulences. Secondly, based on the verified wing planform in the tunnel tests, a small air vehicle prototype was designed and fabricated. The ground and onboard subsystems or components, such as flight control unit, vision system, and propulsion system etc., are studied. The materials and fabrication processes are also presented in the paper. Finally, the developed air vehicle prototype is successfully tested in the real flight.

Biomass production and C-sequestration of Gmelina arborea in plantation and agroforestry system in India

Tree based land use systems make a valuable contribution to sequester carbon and improve productivity and nutrient cycling within the systems. This study was conducted to determine biomass production, C-sequestration and nitrogen allocation in Gmelina arborea planted as sole and agrisilviculture system on abandoned agricultural land. At 5 years, total stand biomass in agrisilviculture system was 14.1 Mg ha−1. Plantations had 35% higher biomass than agrisilviculture system. At 5 years, leaves, stem, branches and roots contributed 4.1, 65.2, 10.0 and 20.7%, respectively to total standing biomass (17.9 Mg ha−1). Over the 5 years of study, trees had 3.5 Mg ha−1 more C and 36 kg ha−1 more N in plantation than agrisilviculture system. Biomass and C storage followed differential allocation. Relatively more C was allocated in above ground components in plantations compared to agrisilviculture system. C:N ratios for tree components were higher in stem wood (135–142) followed by roots (134–139), branches (123–128) and leaves (20–21). In agrisilviculture system crops recommended are: soybean and cowpea in rainy season; wheat and mustard in winter season. After 5 years, soil organic C increased by 51.2 and 15.1% and N by 38.4 and 9.3% in plantation and agrisilviculture system, respectively. Total C storage in abandoned agricultural land before planting was 26.3 Mg ha−1, which increased to 33.7 and 45.8 Mg ha−1 after 5 years in plantation and agrisilviculture system, respectively. Net C storage (soil + tree) was 7.4 Mg ha−1 in agrisilviculture system compared to 19.5 Mg ha−1 in G. arborea monoculture stands. The studies suggest that competitive interactions played a significant role in agrisilviculture system. Plantations were more efficient in accreting C than agrisilviculture system on abandoned agricultural land.

High-performance grinding—A review

Presented paper deals with the contemporary aspects of grinding with regards to enhanced productivity and precision demands. High-performance grinding is essential to achieve high dimensional accuracy and surface integrity of ground components at optimum cost efficiency. The objectives of this paper refer to a review of state of the art technology of high-performance grinding at increased wheel speeds with highly efficient abrasives. The review relies on notable academic publications and recent conference proceedings.

The effects of dynamic characteristics on the surface texture in mirror grinding

In order to make clear the effects of mirror grinding conditions on the ground surfaces in the surface mirror grinding of sintered carbide adopting an in-process electrolytic dressing method, experiments are conducted to measure the vibration signals of the workpiece during grinding and the profile of the ground surface. It is found that components with low frequency vibration signals have a very close relation to the undulation of a ground surface and components with high frequencies to the surface roughness .

Biophysical characterization and management effects on semiarid rangeland observed from Landsat ETM+ data

Semiarid rangelands are very sensitive to global climatic change; studies of their biophysical attributes are crucial to understanding the dynamics of rangeland ecosystems under human disturbance. In the Santa Rita Experimental Range, AZ, the vegetation has changed considerably, and there have been many management activities applied. This study calculates seven surface variables: the enhanced vegetation index, the normalized difference vegetation index (NDVI), surface albedos (total shortwave, visible, and near-infrared), leaf area index (LAI), and the fraction of photosynthetically active radiation (FPAR) absorbed by green vegetation from the Enhanced Thematic Mapper (ETM+) data. Comparison with the Moderate Resolution Imaging Spectroradiometer vegetation index and albedo products indicates they agree well with our estimates from ETM+, while their LAI and FPAR are larger than from ETM+. Human disturbance has significantly changed the cover types and biophysical conditions. Statistical tests indicate that surface albedos increased and FPAR decreased following tree-cutting disturbances. The recovery will require more than 67 years and is about 50% complete within 40 years at the higher elevation. Grass cover, vegetation indexes, albedos, and LAI recovered from cutting faster at the higher elevation. Woody plants, vegetation indexes, and LAI have recovered to their original characteristics after 65 years at the lower elevation. More studies are needed to examine the spectral characteristics of different ground components.

A New Grinding-Hardening Technology Using an Inert Cryogen(Grinding technology)

This paper proposes an innovative development of a grinding-hardening technology using an inert cryogen-liquid nitrogen. This technology not only integrates precision surface grinding with surface hardening treatment, but at the same time, produces satisfactory surface integrity of ground components, including compressive surface residual stresses and fine microstructure with a high hardness and wear resistance. The technology is cost-effective and because of the inert nature of the cryogen, the grinding process becomes environmentally conscious.

Typological variation in encoding the manner, path, and ground components of a metaphorical motion event

The paper compares two typologically distinct languages with regard to their lexicalization patterns in encoding metaphorical motion events: (1) verb-framed (V-language, represented by Turkish), in which the preferred pattern for framing motion events is the use of a path verb with an optional manner adjunct (e.g.,enter running), and (2) satellite-framed (S-language, represented by English), in which path is lexicalized in an element associated with the verb, leaving the verb free to encode manner (e.g.,run in). The paper focuses on typological differences in encoding the manner, path, and ground components of metaphorical motion events, using data from novels written originally in English or Turkish, and further extends the applicability of the typological dichotomy to the metaphorical uses of the lexicon.

The effect of the colonisation extent of arbuscular mycorrhizal fungi on the growth of pot grownPterocarpus angolensisseedlings

Synopsis The effect of the level of arbuscular mycorrhizal fungi (AMF) colonisation on the growth of Pterocarpus angolensis was studied. Mycorrhizal infected seedlings, showing either good or poor growth, under the same environmental conditions (temperature, humidity, light level) were analyzed for above and below ground biomass and Nand P concentration. The grouping was based on the number ofleaves and seedling size. All plants had AMF infection, with poor growth plants having a 7 5% infection and good growth plants 45%. The highly infected poor growth plants had fewer leaves, smaller total leaf area and total plant mass. The below ground plant component Nand P concentration of good growth plants was higher than in poor growth plants. There was however no difference inN and P concentrations of above ground components between the two groups. No nodules were recorded for good growth plants while plants in the poor growth group had nodules. There was no difference in the specific leaf mass and shoot:root ra...

Fatigue Life Improvements of the AISI 304 Stainless Steel Ground Surfaces by Wire Brushing

The surface and subsurface integrity of metallic ground components is usually characterized by an induced tensile residual stress, which has a detrimental effect on the fatigue life of these components. In particular, it tends to accelerate the initiation and growth of the fatigue cracks. In this investigation, to deliberately generate compressive residual stresses into the ground surfaces of the AISI 304 stainless steel (SS), wire brushing was applied. It was found that under the experimental conditions selected in this investigation, while the surface roughness was slightly improved by the brushing process, the surface residual stress shifted from a tensile stress (σ‖=+450 MPa) to a compressive stress (σ‖=−435 MPa). On the other hand, the work-hardened deformation layer was almost two times deeper after wire brushing. Concerning the fatigue life, an improvement of 26% in terms of endurance limit at 2×106 cycles was realized. Scanning electron microscope (SEM) observations of the fatigue fracture location and size were carried out to explain the fatigue life improvement. It was found that the enhancement of the fatigue strength could be correlated with the distribution and location of the fatigue fracture nucleation sites. Concerning the ground surfaces, it was seen that the fatigue cracks initiated at the bottom of the grinding grooves and were particularly long (150–200 µm). However, the fatigue cracks at the brushed surfaces were shorter (20–40 µm) and appeared to initiate sideways to the plowed material caused by the wire brushing. The results of the wire-brushed surface characterization have shown that significant advantages can be realized regarding surface integrity by the application of this low-cost process compared to shot peening.

Some aspects of the geomagnetic response to solar wind pressure variations: a case study at low and middle latitudes

Abstract. We examined geomagnetic field observations at low and middle latitudes in the Northern Hemisphere during a 50-min interval (12 May 1999), characterized by a complex behaviour of the solar wind dynamic pressure. For the entire interval, the aspects of the geomagnetic response can be organized into four groups of events which show common characteristics for the H and D components, respectively. The correspondence between the magnetospheric field and the ground components reveals different aspects of the geomagnetic response in different magnetic local time (MLT) sectors. For the H component, the correspondence is highly significant in the dusk and night sectors; in the dawn and prenoon sectors it shows a dramatic change across a separation line that extends approximately between (6 MLT, 35°) and (13 MLT, 60°). For the D component, the correspondence has significant values in the dawn and prenoon regions. We propose a new approach to the experimental data analysis which reveals that, at each station, the magnetospheric field has a close correspondence with the geomagnetic field projection along an axis (M1) that progressively rotates from north/south (night events) to east/west orientation (dawn events). When projected along M1, the geomagnetic signals can be interpreted in terms of a one-dimensional pattern that mostly reflects the field behaviour observed at geostationary orbit. Several features appear more evident in this perspective, and the global geomagnetic response to the SW pressure variations appears much clearer than in other representations. In particular, the MLT dependence of the geomagnetic response is much smaller than that one estimated by previous investigations. A clear latitudinal dependence emerges in the dusk sector. The occurrence of low frequency waves at ~2.8mHz can be interpreted in terms of global magnetospheric modes driven by the SW pulse. This event occurred in the recovery phase after the day the SW almost disappeared (11 May 1999): in this sense our results suggest a rapid recovery of almost typical magnetospheric conditions soon after a huge expansion. Overshoot amplitudes, greater than in other cases, are consistent with a significant reduction of the ring current.

A Quantitative and Comparative Analysis of Endmember Extraction Algorithms From Hyperspectral Data

Linear spectral unmixing is a commonly accepted approach to mixed-pixel classification in hyperspectral imagery. This approach involves two steps. First, to find spectrally unique signatures of pure ground components, usually known as endmembers, and, second, to express mixed pixels as linear combinations of endmember materials. Over the past years, several algorithms have been developed for autonomous and supervised endmember extraction from hyperspectral data. Due to a lack of commonly accepted data and quantitative approaches to substantiate new algorithms, available methods have not been rigorously compared by using a unified scheme. In this paper, we present a comparative study of standard endmember extraction algorithms using a custom-designed quantitative and comparative framework that involves both the spectral and spatial information. The algorithms considered in this study represent substantially different design choices. A database formed by simulated and real hyperspectral data collected by the Airborne Visible and Infrared Imaging Spectrometer (AVIRIS) is used to investigate the impact of noise, mixture complexity, and use of radiance/reflectance data on algorithm performance. The results obtained indicate that endmember selection and subsequent mixed-pixel interpretation by a linear mixture model are more successful when methods combining spatial and spectral information are applied.

Recomendaciones para el diseño de circuitos impresos de potencia

Commonly you can see that many of PCB designers (Printed Circuit Board) when generating a power's printed circuit, they don't consider factors like the disposition of the elements, ground's references,components DC and AC of operating signals or dimension of traces. These considerations could be entail phenomena like electromagnetic interference (EMI), instability and reduction of life's time of circuit.In the present paper are mentioned some recommendations for the right design of power's PCB