Cluster in the Auroral Acceleration Region

Science.gov (United States)

Pickett, Jolene S.; Fazakerley, Andrew N.; Marklund, Gorun; Dandouras, Iannis; Christopher, Ivar W.; Kistler, Lynn; Lucek, Elizabeth; Masson, Arnaud; Taylor, Matthew G.; Mutel, Robert L.;

Sensitivity of mountain ecosystems to human-accelerated soil erosion. Contrasting geomorphic response between tropical and semi-arid ecosystems.

Science.gov (United States)

Vanacker, Veerle; Bellin, Nicolas; Schoonejans, Jerome; Molina, Armando; Kubik, Peter W.

2014-05-01

Tropical Andes where the share of natural erosion in the modern erosion rate is minimal for most disturbed sites. When pooling pre- and post-disturbance erosion data from both sites, it becomes evident that the human acceleration of erosion is significantly related to vegetation disturbance. It may therefore be expected that the potential for erosion regulation is larger in well-vegetated ecosystem where strong differences may exist in vegetation cover between human disturbed and undisturbed or restored sites.

Effects of laser-polarization and wiggler magnetic fields on electron acceleration in laser-cluster interaction

Science.gov (United States)

Singh Ghotra, Harjit; Kant, Niti

2018-06-01

We examine the electron dynamics during laser-cluster interaction. In addition to the electrostatic field of an individual cluster and laser field, we consider an external transverse wiggler magnetic field, which plays a pivotal role in enhancing the electron acceleration. Single-particle simulation has been presented with a short pulse linearly polarized as well as circularly polarized laser pulses for electron acceleration in a cluster. The persisting Coulomb field allows the electron to absorb energy from the laser field. The stochastically heated electron finds a weak electric field at the edge of the cluster from where it is ejected. The wiggler magnetic field connects the regions of the stochastically heated, ejected electron from the cluster and high energy gain by the electron from the laser field outside the cluster. This increases the field strength and hence supports the electron to meet the phase of the laser field for enhanced acceleration. A long duration resonance appears with an optimized magnetic wiggler field of about 3.4 kG. Hence, the relativistic energy gain by the electron is enhanced up to a few 100 MeV with an intense short pulse laser with an intensity of about 1019 W cm‑2 in the presence of a wiggler magnetic field.

Electron acceleration via high contrast laser interacting with submicron clusters

International Nuclear Information System (INIS)

Zhang Lu; Chen Liming; Wang Weiming; Yan Wenchao; Yuan Dawei; Mao Jingyi; Wang Zhaohua; Liu Cheng; Shen Zhongwei; Li Yutong; Dong Quanli; Lu Xin; Ma Jinglong; Wei Zhiyi; Faenov, Anatoly; Pikuz, Tatiana; Li Dazhang; Sheng Zhengming; Zhang Jie

2012-01-01

We experimentally investigated electron acceleration from submicron size argon clusters-gas target irradiated by a 100 fs, 10 TW laser pulses having a high-contrast. Electron beams are observed in the longitudinal and transverse directions to the laser propagation. The measured energy of the longitudinal electron reaches 600 MeV and the charge of the electron beam in the transverse direction is more than 3 nC. A two-dimensional particle-in-cell simulation of the interaction has been performed and it shows an enhancement of electron charge by using the cluster-gas target.

Measurement of surface roughness changes of unpolished and polished enamel following erosion.

Directory of Open Access Journals (Sweden)

Francesca Mullan

Full Text Available To determine if Sa roughness data from measuring one central location of unpolished and polished enamel were representative of the overall surfaces before and after erosion.Twenty human enamel sections (4x4 mm were embedded in bis-acryl composite and randomised to either a native or polishing enamel preparation protocol. Enamel samples were subjected to an acid challenge (15 minutes 100 mL orange juice, pH 3.2, titratable acidity 41.3mmol OH/L, 62.5 rpm agitation, repeated for three cycles. Median (IQR surface roughness [Sa] was measured at baseline and after erosion from both a centralised cluster and four peripheral clusters. Within each cluster, five smaller areas (0.04 mm2 provided the Sa roughness data.For both unpolished and polished enamel samples there were no significant differences between measuring one central cluster or four peripheral clusters, before and after erosion. For unpolished enamel the single central cluster had a median (IQR Sa roughness of 1.45 (2.58 μm and the four peripheral clusters had a median (IQR of 1.32 (4.86 μm before erosion; after erosion there were statistically significant reductions to 0.38 (0.35 μm and 0.34 (0.49 μm respectively (p<0.0001. Polished enamel had a median (IQR Sa roughness 0.04 (0.17 μm for the single central cluster and 0.05 (0.15 μm for the four peripheral clusters which statistically significantly increased after erosion to 0.27 (0.08 μm for both (p<0.0001.Measuring one central cluster of unpolished and polished enamel was representative of the overall enamel surface roughness, before and after erosion.

Semiparametric Bayesian analysis of accelerated failure time models with cluster structures.

Science.gov (United States)

Li, Zhaonan; Xu, Xinyi; Shen, Junshan

2017-11-10

In this paper, we develop a Bayesian semiparametric accelerated failure time model for survival data with cluster structures. Our model allows distributional heterogeneity across clusters and accommodates their relationships through a density ratio approach. Moreover, a nonparametric mixture of Dirichlet processes prior is placed on the baseline distribution to yield full distributional flexibility. We illustrate through simulations that our model can greatly improve estimation accuracy by effectively pooling information from multiple clusters, while taking into account the heterogeneity in their random error distributions. We also demonstrate the implementation of our method using analysis of Mayo Clinic Trial in Primary Biliary Cirrhosis. Copyright © 2017 John Wiley & Sons, Ltd.

Accelerated Simplified Swarm Optimization with Exploitation Search Scheme for Data Clustering.

Directory of Open Access Journals (Sweden)

Wei-Chang Yeh

Full Text Available Data clustering is commonly employed in many disciplines. The aim of clustering is to partition a set of data into clusters, in which objects within the same cluster are similar and dissimilar to other objects that belong to different clusters. Over the past decade, the evolutionary algorithm has been commonly used to solve clustering problems. This study presents a novel algorithm based on simplified swarm optimization, an emerging population-based stochastic optimization approach with the advantages of simplicity, efficiency, and flexibility. This approach combines variable vibrating search (VVS and rapid centralized strategy (RCS in dealing with clustering problem. VVS is an exploitation search scheme that can refine the quality of solutions by searching the extreme points nearby the global best position. RCS is developed to accelerate the convergence rate of the algorithm by using the arithmetic average. To empirically evaluate the performance of the proposed algorithm, experiments are examined using 12 benchmark datasets, and corresponding results are compared with recent works. Results of statistical analysis indicate that the proposed algorithm is competitive in terms of the quality of solutions.

Accelerated rain erosion of wind turbine blade coatings

DEFF Research Database (Denmark)

Zhang, Shizhong

. There are four chapters in the thesis. In chapter 1, a literature survey provides background information to the field. Topics discussed are the global wind energy development, possible wind turbine constructions, blade structures and materials, blade coatings, and liquid erosion mechanisms. In chapter 2......During operation, the fast-moving blades of wind turbines are exposed to continuous impacts with rain droplets, hail, insects, or solid particles. This can lead to erosion of the blades, whereby the electrical efficiency is compromised and expensive repairs may be required. One possible solution...

Altitude Distribution of the Auroral Acceleration Potential Determined from Cluster Satellite Data at Different Heights

International Nuclear Information System (INIS)

Marklund, Goeran T.; Sadeghi, Soheil; Karlsson, Tomas; Lindqvist, Per-Arne; Nilsson, Hans; Forsyth, Colin; Fazakerley, Andrew; Lucek, Elizabeth A.; Pickett, Jolene

2011-01-01

Aurora, commonly seen in the polar sky, is a ubiquitous phenomenon occurring on Earth and other solar system planets. The colorful emissions are caused by electron beams hitting the upper atmosphere, after being accelerated by quasistatic electric fields at 1-2 R E altitudes, or by wave electric fields. Although aurora was studied by many past satellite missions, Cluster is the first to explore the auroral acceleration region with multiprobes. Here, Cluster data are used to determine the acceleration potential above the aurora and to address its stability in space and time. The derived potential comprises two upper, broad U-shaped potentials and a narrower S-shaped potential below, and is stable on a 5 min time scale. The scale size of the electric field relative to that of the current is shown to depend strongly on altitude within the acceleration region. To reveal these features was possible only by combining data from the two satellites.

Forest road erosion control using multiobjective optimization

Science.gov (United States)

Matthew Thompson; John Sessions; Kevin Boston; Arne Skaugset; David Tomberlin

2010-01-01

Forest roads are associated with accelerated erosion and can be a major source of sediment delivery to streams, which can degrade aquatic habitat. Controlling road-related erosion therefore remains an important issue for forest stewardship. Managers are faced with the task to develop efficient road management strategies to achieve conflicting environmental and economic...

Mapping monthly rainfall erosivity in Europe

DEFF Research Database (Denmark)

Ballabio, C; Meusburger, K; Klik, A

2017-01-01

to Eastern Europe. The maps also show a clear delineation of areas with different erosivity seasonal patterns, whose spatial outline was evidenced by cluster analysis. The monthly erosivity maps can be used to develop composite indicators that map both intra-annual variability and concentration of erosive...... and seasonal R-factor maps and assess rainfall erosivity both spatially and temporally. During winter months, significant rainfall erosivity is present only in part of the Mediterranean countries. A sudden increase of erosivity occurs in major part of European Union (except Mediterranean basin, western part...... selected among various statistical models to perform the spatial interpolation due to its excellent performance, ability to model non-linearity and interpretability. The monthly prediction is an order more difficult than the annual one as it is limited by the number of covariates and, for consistency...

77 FR 41457 - Aging Management Associated With Wall Thinning Due to Erosion Mechanisms

Science.gov (United States)

2012-07-13

... Corrosion,'' based on the staff's review of several license renewal applications' flow-accelerated corrosion... address emergent issues not covered in license renewal guidance documents, such as the GALL Report and SRP... erosion mechanisms; (b) revise the definition of ``flow-accelerated corrosion'' and ``erosion'' to align...

Effects of Alfvénic Drift on Diffusive Shock Acceleration at Weak Cluster Shocks

Science.gov (United States)

Kang, Hyesung; Ryu, Dongsu

2018-03-01

Non-detection of γ-ray emission from galaxy clusters has challenged diffusive shock acceleration (DSA) of cosmic-ray (CR) protons at weak collisionless shocks that are expected to form in the intracluster medium. As an effort to address this problem, we here explore possible roles of Alfvén waves self-excited via resonant streaming instability during the CR acceleration at parallel shocks. The mean drift of Alfvén waves may either increase or decrease the scattering center compression ratio, depending on the postshock cross-helicity, leading to either flatter or steeper CR spectra. We first examine such effects at planar shocks, based on the transport of Alfvén waves in the small amplitude limit. For the shock parameters relevant to cluster shocks, Alfvénic drift flattens the CR spectrum slightly, resulting in a small increase of the CR acceleration efficiency, η. We then consider two additional, physically motivated cases: (1) postshock waves are isotropized via MHD and plasma processes across the shock transition, and (2) postshock waves contain only forward waves propagating along with the flow due to a possible gradient of CR pressure behind the shock. In these cases, Alfvénic drift could reduce η by as much as a factor of five for weak cluster shocks. For the canonical parameters adopted here, we suggest η ∼ 10‑4–10‑2 for shocks with sonic Mach number M s ≈ 2–3. The possible reduction of η may help ease the tension between non-detection of γ-rays from galaxy clusters and DSA predictions.

Molecular ion acceleration using tandem accelerator

Energy Technology Data Exchange (ETDEWEB)

Saito, Yuichi; Mizuhashi, Kiyoshi; Tajima, Satoshi [Japan Atomic Energy Research Inst., Takasaki, Gunma (Japan). Takasaki Radiation Chemistry Research Establishment

1996-12-01

In TIARA compound beam radiation system, cluster beams have been produced using 3 MV tandem accelerator (9SDH-2) to supply them to various radiation on injection experiments. Till now, productions of C{sub 2-8}, Si{sub 2-4} and O{sub 2} and their accelerations up to 6 MeV have been succeeded. This study aimed at production and acceleration of B{sub 2-4} and LiF. Anion clusters were produced using the conventional ion source of cesium sputter type. The proportions of atoms, molecules and clusters elicited from the ion source were varied depending on the material`s properties and the operating conditions of ion source such as sample temperature, sputter voltage and the shape of sample. The anion clusters were accelerated toward the high voltage terminal in the center of tandem accelerator, leading to cations through losing their electrons by the collision to N{sub 2} gas in a charge conversion cell at the terminal. Positively charged cluster ions could be obtained by modulating the pressure of N{sub 2} gas. Thus, B{sub 2} (64 nA), B{sub 3} (4.4 nA) and B{sub 4} (2.7 nA) have been produced and their maximum survival probabilities were higher than those of carbon or silicon clusters. In addition, the relationship between beam current and gas pressure was investigated for Bn (n = 2-4) and LiF. (M.N.)

Erosion--corrosion

International Nuclear Information System (INIS)

Vyas, B.

1978-01-01

The deterioration of materials by corrosion or erosion by itself presents a formidable problem and for this reason investigators have studied these two phenomena independently. In fact, there are very few systematic studies on E-C and the majority of references mention it only in passing. In most real systems, however, the two destructive processes take place simultaneously, hence the purpose of this review is to present the various interactions between the chemical and mechanical agents leading to accelerated degradation of the material. The papers cited in the review are those that lead to a better understanding of the process involved in the accelerated rate of material loss under E-C conditions

THE USE OF BIOTEXTILES TO RECUPERATE DEGRADADED AREAS BY EROSION

OpenAIRE

Marcia Silva Furtado; Neilianne de Fátima Costa Lima; Ulisses Denache Vieira Souza; Jane Karina Silva Mendonça; Antônio Teixeira Guerra; Antonio Cordeiro Feitosa

2005-01-01

The erosion is a process that results from the conjunct action of many natural agents over the grounds. However, this process can be accelerated, mainly by the action of the human being that has caused numerous degrading actions of the environment, depending on the level of intensity and from the characteristic of his intervention. Among the ways of degradation it is possible to stand out accelerated erosive processes, like ravines and gullies.These processes can be mitigated with the use of ...

Simulation and analysis of collapsing vapor-bubble clusters with special emphasis on potentially erosive impact loads at walls

Science.gov (United States)

Ogloblina, Daria; Schmidt, Steffen J.; Adams, Nikolaus A.

2018-06-01

Cavitation is a process where a liquid evaporates due to a pressure drop and re-condenses violently. Noise, material erosion and altered system dynamics characterize for such a process for which shock waves, rarefaction waves and vapor generation are typical phenomena. The current paper presents novel results for collapsing vapour-bubble clusters in a liquid environment close to a wall obtained by computational fluid mechanics (CFD) simulations. The driving pressure initially is 10 MPa in the liquid. Computations are carried out by using a fully compressible single-fluid flow model in combination with a conservative finite volume method (FVM). The investigated bubble clusters (referred to as "clouds") differ by their initial vapor volume fractions, initial stand-off distances to the wall and by initial bubble radii. The effects of collapse focusing due to bubble-bubble interaction are analysed by investigating the intensities and positions of individual bubble collapses, as well as by the resulting shock-induced pressure field at the wall. Stronger interaction of the bubbles leads to an intensification of the collapse strength for individual bubbles, collapse focusing towards the center of the cloud and enhanced re-evaporation. The obtained results reveal collapse features which are common for all cases, as well as case-specific differences during collapse-rebound cycles. Simultaneous measurements of maximum pressures at the wall and within the flow field and of the vapor volume evolution show that not only the primary collapse but also subsequent collapses are potentially relevant for erosion.

Dense Fe cluster-assembled films by energetic cluster deposition

International Nuclear Information System (INIS)

Peng, D.L.; Yamada, H.; Hihara, T.; Uchida, T.; Sumiyama, K.

2004-01-01

High-density Fe cluster-assembled films were produced at room temperature by an energetic cluster deposition. Though cluster-assemblies are usually sooty and porous, the present Fe cluster-assembled films are lustrous and dense, revealing a soft magnetic behavior. Size-monodispersed Fe clusters with the mean cluster size d=9 nm were synthesized using a plasma-gas-condensation technique. Ionized clusters are accelerated electrically and deposited onto the substrate together with neutral clusters from the same cluster source. Packing fraction and saturation magnetic flux density increase rapidly and magnetic coercivity decreases remarkably with increasing acceleration voltage. The Fe cluster-assembled film obtained at the acceleration voltage of -20 kV has a packing fraction of 0.86±0.03, saturation magnetic flux density of 1.78±0.05 Wb/m 2 , and coercivity value smaller than 80 A/m. The resistivity at room temperature is ten times larger than that of bulk Fe metal

Multi-scale wind erosion monitoring and assessment for US rangelands

Science.gov (United States)

Wind erosion is a major resource concern for rangeland managers. Although wind erosion is a naturally occurring process in many drylands, land use activities, and land management in particular, can accelerate wind-driven soil loss – impacting ecosystem dynamics and agricultural production, air quali...

Synergistic erosion/corrosion of superalloys in PFB coal combustor effluent

Science.gov (United States)

Benford, S. M.; Zellars, G. R.; Lowell, C. E.

1981-01-01

Two Ni-based superalloys were exposed to the high velocity effluent of a pressurized fluidized bed coal combustor. Targets were 15 cm diameter rotors operating at 40,000 rpm and small flat plate specimens. Above an erosion rate threshold, the targets were eroded to bare metal. The presence of accelerated oxidation at lower erosion rates suggests erosion/corrosion synergism. Various mechanisms which may contribute to the observed oxide growth enhancement include erosive removal of protective oxide layers, oxide and subsurface cracking, and chemical interaction with sulfur in the gas and deposits through damaged surface layers.

Estimating two indirect logging costs caused by accelerated erosion.

Science.gov (United States)

Glen O. Klock

1976-01-01

In forest areas where high soil erosion potential exists, a comparative yarding cost estimate, including the indirect costs determined by methods proposed here, shows that the total cost of using "advanced" logging methods may be less than that of "traditional" systems.

Human-induced C erosion and burial across spatial and temporal scales. (Invited)

Science.gov (United States)

van oost, K.

2013-12-01

Anthropogenic land cover change and soil erosion are tightly coupled: accelerated erosion and deposition of soil are inevitable consequences of the removal of vegetative cover and increased exposure of the soil surface to erosion. A significant portion of the earth surface has now been disturbed and this has locally accelerated erosion 10- to 100-fold. Although there is now growing awareness that the erosion-induced C flux may be an important factor determining global and regional net terrestrial ecosystem C balances, the significance of this disturbance for the past, present and future C cycle remains uncertain. In this paper, we argue that the significance for both past and present C budgets remains poorly quantified due to uncertainty about the contribution of biotic versus erosion-induced C fluxes because of their intrinsically different space and time scales. Carbon erosion research in agro-ecosystems has traditionally focused on short-term processes, i.e. single events to a few decades and longer-term observations of C and sediment dynamics are therefore rare. Likewise, C cycling is typically studied at the profile-scale while erosion processes operate over various spatial scales and whole-watershed approaches are therefore needed. We address this issue here by synthesizing 3 case studies where we report results of a measurement campaign to characterize the erosional control on vertical carbon fluxes from degraded land. First, using signatures in soil sedimentary archives, we integrate the effects of accelerated C erosion across point, hillslope and catchment scale for a temperate river catchment over the period of agriculture to demonstrate that accounting for the non-steady-state C dynamics in geomorphic active systems is pertinent to understand both past and future anthropogenic global change. Secondly, we report year-round soil respiration measurements with high temporal resolution along an erosion gradient on cultivated sloping land in the Chinese Loess

Predicting soil erosion risk at the Alqueva dam watershed

OpenAIRE

Ferreira, Vera; Panagopoulos, Thomas

2012-01-01

Soil erosion is serious economic and environmental concern. Assessing soil erosion risk in the Alqueva dam watershed is urgently needed to conserve soil and water resources and prevent the accelerated dam siltation, taking into account the possible land-use changes, due to tourism development, intensification of irrigated farming and biomass production, as well as climate change. A comprehensive methodology that integrates Revised Universal Soil Loss Equation (RUSLE) model and Geographic Info...

Amplified Erosion above Waterfalls and Oversteepened Bedrock Reaches

Science.gov (United States)

Haviv, I.; Enzel, Y.; Whipple, K. X.; Zilberman, E.; Stone, J.; Matmon, A.; Fifield, K. L.

2005-12-01

Although waterfalls are abundant along steep bedrock channels, none of the conventional erosion laws can predict incision at the lip of a waterfall where flow is non-uniform and bed slope can be vertical. Considering the expected increase in flow velocity and shear stress at the lip of a vertical waterfall we determine erosion amplification at a waterfall lip as: Elip/Enormal= (1+0.4/Fr2)3n, where Fr is the Froude number and n ranges between 0.5-1.7. This amplification expression suggests that erosion at the lip could be as much as 2-5 times higher than normally expected in a setting with identical hydraulic geometry. It also demonstrates that a freefall is expected to amplify upstream incision rates even when the flow approaching the waterfall is highly supercritical. Utilizing this erosion amplification expression in numerical simulations in conjunction with a standard detachment-limited incision model we demonstrate its impact on reach-scale morphology above waterfalls. These simulations indicate that amplified erosion at the lip of a waterfall can trigger the formation of an oversteepened reach whose length is longer than the flow acceleration zone, provided incision velocity (Vi) at the edge of the flow acceleration zone is higher than the retreat velocity of the waterfall face. Such an oversteepened reach is expected to be more pronounced when Vi increases with increasing slope. The simulations also suggest that oversteepening can eventually lead to quasi steady-state gradients upstream from a waterfall provided Vi decreases with increasing slope. Flow acceleration above waterfalls can thus account, at least partially, for oversteepened bedrock reaches that are prevalent above waterfalls. Such reaches have been reported for the escarpments of southeast Australia, western Dead Sea, and at Niagara Falls. Using the cosmogenic isotope 36Cl we demonstrate that Vi upstream of a waterfall at the Dead Sea western escarpment is high enough for freefall

Simulating soil erosion risk for Pan-European land use and climate scenarios

NARCIS (Netherlands)

Mantel, S.; Kirby, M.; Daroussin, J.; Jones, R.J.A.

2003-01-01

Soil is a vital resource with multiple functions and with high regional and internal variability. Accelerated soil erosion is a cause for decline in soil quality and is increasingly being recognized as a serious environmental problem. Soil erosion is a function of factors such as: land use and

Understanding the radio spectral indices of galaxy cluster relics by superdiffusive shock acceleration

Science.gov (United States)

Zimbardo, Gaetano; Perri, Silvia

2018-06-01

Galaxy cluster merger shocks are the likely source of relativistic electrons, but many observations do not fit into the standard acceleration models. In particular, there is a long-standing discrepancy between the radio derived Mach numbers M_radio and the Mach numbers derived from X-ray measurements, M_X. Here, we show how superdiffusive electron transport and superdiffusive shock acceleration (SSA) can help to solve this problem. We present a heuristic derivation of the superlinear time growth of the mean square displacement of particles, ⟨Δx2⟩∝tβ, and of the particle energy spectral index in the framework of SSA. The resulting expression for the radio spectral index α is then used to determine the superdiffusive exponent β from the observed values of α and of the compression ratio for a number of radio relics. Therefore, the fact that M_radio>M_X can be explained by SSA without the need to make assumptions on the energy spectrum of the seed electrons to be re-accelerated. We also consider the acceleration times obtained in the diffusive case, based both on the Bohm diffusion coefficient and on the quasilinear diffusion coefficient. While in the latter case the acceleration time is consistent with the estimated electron energy loss time, the former case it is much shorter.

Saliva in relation to dental erosion before and after radiotherapy

DEFF Research Database (Denmark)

Jensdottir, Thorbjorg; von Buchwald, Christian; Nauntofte, Birgitte

2013-01-01

Abstract Objective. Low saliva flow and abnormal saliva composition are common conditions after radiotherapy for oral cavity and pharyngeal cancer. Both conditions increase the susceptibility to dental caries and erosion, which may be further accelerated by changes in food preferences. The aim...... of this study was to determine changes in saliva flow and susceptibility to erosive challenges in pharyngeal cancer patients before and after radiotherapy to the head and neck. Materials and methods: The erosive potential of sucking acidic candies with and without calcium was determined in nine patients (50...

Mapping monthly rainfall erosivity in Europe.

Science.gov (United States)

Ballabio, Cristiano; Borrelli, Pasquale; Spinoni, Jonathan; Meusburger, Katrin; Michaelides, Silas; Beguería, Santiago; Klik, Andreas; Petan, Sašo; Janeček, Miloslav; Olsen, Preben; Aalto, Juha; Lakatos, Mónika; Rymszewicz, Anna; Dumitrescu, Alexandru; Tadić, Melita Perčec; Diodato, Nazzareno; Kostalova, Julia; Rousseva, Svetla; Banasik, Kazimierz; Alewell, Christine; Panagos, Panos

2017-02-01

Rainfall erosivity as a dynamic factor of soil loss by water erosion is modelled intra-annually for the first time at European scale. The development of Rainfall Erosivity Database at European Scale (REDES) and its 2015 update with the extension to monthly component allowed to develop monthly and seasonal R-factor maps and assess rainfall erosivity both spatially and temporally. During winter months, significant rainfall erosivity is present only in part of the Mediterranean countries. A sudden increase of erosivity occurs in major part of European Union (except Mediterranean basin, western part of Britain and Ireland) in May and the highest values are registered during summer months. Starting from September, R-factor has a decreasing trend. The mean rainfall erosivity in summer is almost 4 times higher (315MJmmha -1 h -1 ) compared to winter (87MJmmha -1 h -1 ). The Cubist model has been selected among various statistical models to perform the spatial interpolation due to its excellent performance, ability to model non-linearity and interpretability. The monthly prediction is an order more difficult than the annual one as it is limited by the number of covariates and, for consistency, the sum of all months has to be close to annual erosivity. The performance of the Cubist models proved to be generally high, resulting in R 2 values between 0.40 and 0.64 in cross-validation. The obtained months show an increasing trend of erosivity occurring from winter to summer starting from western to Eastern Europe. The maps also show a clear delineation of areas with different erosivity seasonal patterns, whose spatial outline was evidenced by cluster analysis. The monthly erosivity maps can be used to develop composite indicators that map both intra-annual variability and concentration of erosive events. Consequently, spatio-temporal mapping of rainfall erosivity permits to identify the months and the areas with highest risk of soil loss where conservation measures should be

Soil erosion and its control in Chile - An overview

International Nuclear Information System (INIS)

Ellies, A.

2000-01-01

Accelerate erosion in Chile is a consequence from land use that degrade soil such as compaction, loss of organic matter and soil structure. The erosion is favored by the very hilly landscape of the country that increases erosivity index and the high erodibility given by an elevated annual rate of rainfall with irregular distribution. Several experiences have demonstrated that adequate crop management and crop rotations can minimize erosion. The most effective control is achieved conserving and improving soil structure with management systems that include regular use of soil-improving crops, return of crop residues and tillage practices, thus avoiding unnecessary breakdown soil or compacted soil structure. Conservation tillage increased organic matter levels improving stabile soil structure, aeration and infiltration. (author) [es

Weighing galaxy clusters with gas. II. On the origin of hydrostatic mass bias in ΛCDM galaxy clusters

International Nuclear Information System (INIS)

Nelson, Kaylea; Nagai, Daisuke; Yu, Liang; Lau, Erwin T.; Rudd, Douglas H.

2014-01-01

The use of galaxy clusters as cosmological probes hinges on our ability to measure their masses accurately and with high precision. Hydrostatic mass is one of the most common methods for estimating the masses of individual galaxy clusters, which suffer from biases due to departures from hydrostatic equilibrium. Using a large, mass-limited sample of massive galaxy clusters from a high-resolution hydrodynamical cosmological simulation, in this work we show that in addition to turbulent and bulk gas velocities, acceleration of gas introduces biases in the hydrostatic mass estimate of galaxy clusters. In unrelaxed clusters, the acceleration bias is comparable to the bias due to non-thermal pressure associated with merger-induced turbulent and bulk gas motions. In relaxed clusters, the mean mass bias due to acceleration is small (≲ 3%), but the scatter in the mass bias can be reduced by accounting for gas acceleration. Additionally, this acceleration bias is greater in the outskirts of higher redshift clusters where mergers are more frequent and clusters are accreting more rapidly. Since gas acceleration cannot be observed directly, it introduces an irreducible bias for hydrostatic mass estimates. This acceleration bias places limits on how well we can recover cluster masses from future X-ray and microwave observations. We discuss implications for cluster mass estimates based on X-ray, Sunyaev-Zel'dovich effect, and gravitational lensing observations and their impact on cluster cosmology.

Legacy of human-induced C erosion and burial on soil-atmosphere C exchange.

Science.gov (United States)

Van Oost, Kristof; Verstraeten, Gert; Doetterl, Sebastian; Notebaert, Bastiaan; Wiaux, François; Broothaerts, Nils; Six, Johan

2012-11-20

Carbon exchange associated with accelerated erosion following land cover change is an important component of the global C cycle. In current assessments, however, this component is not accounted for. Here, we integrate the effects of accelerated C erosion across point, hillslope, and catchment scale for the 780-km(2) Dijle River catchment over the period 4000 B.C. to A.D. 2000 to demonstrate that accelerated erosion results in a net C sink. We found this long-term C sink to be equivalent to 43% of the eroded C and to have offset 39% (17-66%) of the C emissions due to anthropogenic land cover change since the advent of agriculture. Nevertheless, the erosion-induced C sink strength is limited by a significant loss of buried C in terrestrial depositional stores, which lagged the burial. The time lag between burial and subsequent loss at this study site implies that the C buried in eroded terrestrial deposits during the agricultural expansion of the last 150 y cannot be assumed to be inert to further destabilization, and indeed might become a significant C source. Our analysis exemplifies that accounting for the non-steady-state C dynamics in geomorphic active systems is pertinent to understanding both past and future anthropogenic global change.

Legacy of human-induced C erosion and burial on soil–atmosphere C exchange

Science.gov (United States)

Van Oost, Kristof; Verstraeten, Gert; Doetterl, Sebastian; Notebaert, Bastiaan; Wiaux, François; Broothaerts, Nils; Six, Johan

2012-01-01

Carbon exchange associated with accelerated erosion following land cover change is an important component of the global C cycle. In current assessments, however, this component is not accounted for. Here, we integrate the effects of accelerated C erosion across point, hillslope, and catchment scale for the 780-km2 Dijle River catchment over the period 4000 B.C. to A.D. 2000 to demonstrate that accelerated erosion results in a net C sink. We found this long-term C sink to be equivalent to 43% of the eroded C and to have offset 39% (17–66%) of the C emissions due to anthropogenic land cover change since the advent of agriculture. Nevertheless, the erosion-induced C sink strength is limited by a significant loss of buried C in terrestrial depositional stores, which lagged the burial. The time lag between burial and subsequent loss at this study site implies that the C buried in eroded terrestrial deposits during the agricultural expansion of the last 150 y cannot be assumed to be inert to further destabilization, and indeed might become a significant C source. Our analysis exemplifies that accounting for the non–steady-state C dynamics in geomorphic active systems is pertinent to understanding both past and future anthropogenic global change. PMID:23134723

Accelerator Service

International Nuclear Information System (INIS)

Champelovier, Y.; Ferrari, M.; Gardon, A.; Hadinger, G.; Martin, J.; Plantier, A.

1998-01-01

Since the cessation of the operation of hydrogen cluster accelerator in July 1996, four electrostatic accelerators were in operation and used by the peri-nuclear teams working in multidisciplinary collaborations. These are the 4 MV Van de Graaff accelerator, 2,5 MV Van de Graaff accelerator, 400 kV ion implanter as well as the 120 kV isotope separator

Consideration of some fundamental erosion processes encountered in hypervelocity electromagnetic propulsion

International Nuclear Information System (INIS)

Buckingham, A.C.; Hawke, R.S.

1982-01-01

Experimental and theoretical research has been conducted jointly at the Livermore and Los Alamos National laboratories on dc electromagnetic railgun Lorentz accelerators. Pellets weighing a few grams to tens of grams have been launched at velocities up to better than 11 km/s. The research is addressed to attaining repeated launches of samples at hypervelocity in target impact experiments. In these experiments, shock-induced pressures in the tens of megabars range are obtained for high pressure equation-of-state research. Primary energy sources of the order of several hundred kJ to a MJ and induction currents of the order of 1 or more MA are necessary for these launches. Erosion and deformation of the conductor rails and the accelerated sample material are continuing problems. The heating, stress, and erosion resulting from simultaneous imposition of rail induction current, dense plasma (armature) interaction, current distribution, magnetic field stresses and projectile/rail contact friction are examined. It is found that while frictional heating and consequent sliding contact erosion are minor contributors to the overall erosion process, the same cannot be said for plasma impingement, penetration, and almost simultaneous induction current (Joule) heating

Viewpoint: Sustainability of piñon-juniper ecosystems - A unifying perspective of soil erosion thresholds

Science.gov (United States)

Davenport, David W.; Breshears, D.D.; Wilcox, B.P.; Allen, Craig D.

1998-01-01

Many pinon-juniper ecosystem in the western U.S. are subject to accelerated erosion while others are undergoing little or no erosion. Controversy has developed over whether invading or encroaching pinon and juniper species are inherently harmful to rangeland ecosystems. We developed a conceptual model of soil erosion in pinon-jumper ecosystems that is consistent with both sides of the controversy and suggests that the diverse perspectives on this issue arise from threshold effects operating under very different site conditions. Soil erosion rate can be viewed as a function of (1) site erosion potential (SEP), determined by climate, geomorphology and soil erodibility; and (2) ground cover. Site erosion potential and cove act synergistically to determine soil erosion rates, as evident even from simple USLE predictions of erosion. In pinon-juniper ecosystem with high SEP, the erosion rate is highly sensitive to ground cover and can cross a threshold so that erosion increases dramatically in response to a small decrease in cover. The sensitivity of erosion rate to SEP and cover can be visualized as a cusp catastrophe surface on which changes may occur rapidly and irreversibly. The mechanisms associated with a rapid shift from low to high erosion rate can be illustrated using percolation theory to incorporate spatial, temporal, and scale-dependent patterns of water storage capacity on a hillslope. Percolation theory demonstrates how hillslope runoff can undergo a threshold response to a minor change in storage capacity. Our conceptual model suggests that pinion and juniper contribute to accelerated erosion only under a limited range of site conditions which, however, may exist over large areas.

THE MATRYOSHKA RUN. II. TIME-DEPENDENT TURBULENCE STATISTICS, STOCHASTIC PARTICLE ACCELERATION, AND MICROPHYSICS IMPACT IN A MASSIVE GALAXY CLUSTER

International Nuclear Information System (INIS)

Miniati, Francesco

2015-01-01

We use the Matryoshka run to study the time-dependent statistics of structure-formation-driven turbulence in the intracluster medium of a 10 15 M ☉ galaxy cluster. We investigate the turbulent cascade in the inner megaparsec for both compressional and incompressible velocity components. The flow maintains approximate conditions of fully developed turbulence, with departures thereof settling in about an eddy-turnover time. Turbulent velocity dispersion remains above 700 km s –1 even at low mass accretion rate, with the fraction of compressional energy between 10% and 40%. The normalization and the slope of the compressional turbulence are susceptible to large variations on short timescales, unlike the incompressible counterpart. A major merger occurs around redshift z ≅ 0 and is accompanied by a long period of enhanced turbulence, ascribed to temporal clustering of mass accretion related to spatial clustering of matter. We test models of stochastic acceleration by compressional modes for the origin of diffuse radio emission in galaxy clusters. The turbulence simulation model constrains an important unknown of this complex problem and brings forth its dependence on the elusive microphysics of the intracluster plasma. In particular, the specifics of the plasma collisionality and the dissipation physics of weak shocks affect the cascade of compressional modes with strong impact on the acceleration rates. In this context radio halos emerge as complex phenomena in which a hierarchy of processes acting on progressively smaller scales are at work. Stochastic acceleration by compressional modes implies statistical correlation of radio power and spectral index with merging cores distance, both testable in principle with radio surveys

Excess erosion and deposition in the catchments of Kamenichka and Radanjska river, Republic of Macedonia

Directory of Open Access Journals (Sweden)

Milevski Ivica

2009-01-01

Full Text Available One of the greatest environmental problems in the Republic of Macedonia is accelerated soil erosion caused by high human impact during last centuries on to the susceptible landscape. Natural factors itself are very suitable for development of such erosion: from mostly erodible rocks and soils on the mountainous slopes around the depressions, to the generally continental, semi-arid climate and slight vegetation cover. Because of that, there are sites with severe erosion and deposition like those in the catchments of Kamenichka River and Radanjska River, two torrential tributaries of Bregalnica. In these catchments there are varieties of erosion-related landforms: rills, gullies, badlands, landslides, as well as valley-type alluvial fans and huge alluvial plains. Such devastating accelerated erosion and deposition largely transformed original landscape, and represent significant environmental, social, and economic problem in local areas. Because of that, some measures of protection and conservation were taken from 1950-ties in both catchments. But it is obvious that the final effect of these measures is far of enough, so new efforts must be implemented to revitalizing these abandoned lands.

Short communication: Massive erosion in monsoonal central India linked to late Holocene land cover degradation

Directory of Open Access Journals (Sweden)

L. Giosan

2017-12-01

Full Text Available Soil erosion plays a crucial role in transferring sediment and carbon from land to sea, yet little is known about the rhythm and rates of soil erosion prior to the most recent few centuries. Here we reconstruct a Holocene erosional history from central India, as integrated by the Godavari River in a sediment core from the Bay of Bengal. We quantify terrigenous fluxes, fingerprint sources for the lithogenic fraction and assess the age of the exported terrigenous carbon. Taken together, our data show that the monsoon decline in the late Holocene significantly increased soil erosion and the age of exported organic carbon. This acceleration of natural erosion was later exacerbated by the Neolithic adoption and Iron Age extensification of agriculture on the Deccan Plateau. Despite a constantly elevated sea level since the middle Holocene, this erosion acceleration led to a rapid growth of the continental margin. We conclude that in monsoon conditions aridity boosts rather than suppresses sediment and carbon export, acting as a monsoon erosional pump modulated by land cover conditions.

Short communication: Massive erosion in monsoonal central India linked to late Holocene land cover degradation

Science.gov (United States)

Giosan, Liviu; Ponton, Camilo; Usman, Muhammed; Blusztajn, Jerzy; Fuller, Dorian Q.; Galy, Valier; Haghipour, Negar; Johnson, Joel E.; McIntyre, Cameron; Wacker, Lukas; Eglinton, Timothy I.

2017-12-01

Soil erosion plays a crucial role in transferring sediment and carbon from land to sea, yet little is known about the rhythm and rates of soil erosion prior to the most recent few centuries. Here we reconstruct a Holocene erosional history from central India, as integrated by the Godavari River in a sediment core from the Bay of Bengal. We quantify terrigenous fluxes, fingerprint sources for the lithogenic fraction and assess the age of the exported terrigenous carbon. Taken together, our data show that the monsoon decline in the late Holocene significantly increased soil erosion and the age of exported organic carbon. This acceleration of natural erosion was later exacerbated by the Neolithic adoption and Iron Age extensification of agriculture on the Deccan Plateau. Despite a constantly elevated sea level since the middle Holocene, this erosion acceleration led to a rapid growth of the continental margin. We conclude that in monsoon conditions aridity boosts rather than suppresses sediment and carbon export, acting as a monsoon erosional pump modulated by land cover conditions.

Active Anti-erosion Protection Strategy in Tamarisk (Tamarix aphylla)

Science.gov (United States)

Han, Zhiwu; Yin, Wei; Zhang, Junqiu; Niu, Shichao; Ren, Luquan

2013-12-01

Plants have numerous active protection strategies for adapting to complex and severe environments. These strategies provide endless inspiration for extending the service life of materials and machines. Tamarisk (Tamarix aphylla), a tree that thrives in raging sandstorm regions, has adapted to blustery conditions by evolving extremely effective and robust erosion resistant characteristics. However, the relationships among its surface cracks, internal histology and biomechanics, such as cracks, rings, cells, elasticity modulus and growth stress, which account for its erosion resistance, remain unclear. This present study reveals that the directionally eccentric growth rings of tamarisk, which are attributed to reduced stress and accelerated cell division, promote the formation of surface cracks. The windward rings are more extensive than the leeward side rings. The windward surfaces are more prone to cracks, which improves erosion resistance. Our data provide insight into the active protection strategy of the tamarisk against wind-sand erosion.

Soil erosion and causative factors at Vandenberg Air Force Base, California

Science.gov (United States)

Butterworth, Joel B.

1988-01-01

Areas of significant soil erosion and unvegetated road cuts were identified and mapped for Vandenberg Air Force Base. One hundred forty-two eroded areas (most greater than 1.2 ha) and 51 road cuts were identified from recent color infrared aerial photography and ground truthed to determine the severity and causes of erosion. Comparison of the present eroded condition of soils (as shown in the 1986 photography) with that in historical aerial photography indicates that most erosion on the base took place prior to 1928. However, at several sites accelerated rates of erosion and sedimentation may be occurring as soils and parent materials are eroded vertically. The most conspicuous erosion is in the northern part of the base, where severe gully, sheet, and mass movement erosion have occurred in soils and in various sedimentary rocks. Past cultivation practices, compounded by highly erodible soils prone to subsurface piping, are probably the main causes. Improper range management practices following cultivation may have also increased runoff and erosion. Aerial photography from 1986 shows that no appreciable headward erosion or gully sidewall collapse have occurred in this area since 1928.

Electromagnetic acceleration studies with augmented rails

International Nuclear Information System (INIS)

Maruo, T.; Fujioka, K.; Nagaoka, K.; Okamoto, A.; Ikuta, K.; Nemoto, K.

1991-01-01

A comparative study of electromagnetic acceleration in the rail-type accelerators with two kinds of rail geometry was carried out experimentally. The accelerators were energized by 200kJ capacitor bank and the weight of loaded projectiles was about 1.3 grams with 10mm x 10mm square bore. The attained velocity was 4.3km/s in the augmented accelerator, while it was 3.8km/s in the classical device. In this paper these differences in attained velocity are briefly discussed. A theoretical understanding of the rail erosion is also described

Dental erosion in 12-year-old school children living in Jakarta

Science.gov (United States)

Septalita, A.; Bahar, A.; Agustanti, A.; Rahardjo, A.; Maharani, D. A.; Rosalien, R.

2017-08-01

This study assesses the dental erosion status of 12-year-old Indonesian children and studies the determinants of dental erosion of these children. The survey was performed in 2016 with ethics approval. A multistage cluster proportional to size random sampling method was adopted to select 12-year-old children in 24 primary schools in Jakarta. The parents were asked to complete a self-administered questionnaire concerning their children’s diet and oral health habits. The children were examined by a single calibrated examiner. Detection of dental erosion followed basic erosive wear examination (BEWE) criteria. A total of 487 children participated in the survey. Most children (88%) had at least some signs of erosion (BEWE > 0), with dentin being involved in 50% of the cases (BEWE = 2). Dental erosion was significantly related to gender, the frequencies of citric tea consumption, parent’s dental knowledge, father’s education, and dental caries (OR = 3.148). The 12-year-old Indonesian school children who lived in Jakarta had signs of erosion, although severe erosion was not found. Screening programs should be provided to identify risk groups so early preventive measures can be taken.

Assessment of soil erosion sensitivity and post-timber-harvesting erosion response in a mountain environment of Central Italy

Science.gov (United States)

Borrelli, Pasquale; Schütt, Brigitta

2014-01-01

This study aimed to assess the effects of forest management on the occurrence of accelerated soil erosion by water. The study site is located in a mountainous area of the Italian Central Apennines. Here, forest harvesting is a widespread forestry activity and is mainly performed on the moderate to steep slopes of the highlands. Through modeling operations based on data on soil properties and direct monitoring of changes in the post-forest-harvesting soil surface level at the hillslope scale, we show that the observed site became prone to soil erosion after human intervention. Indeed, the measured mean soil erosion rate of 49 t ha- 1 yr- 1 for the harvested watershed is about 21 times higher than the rate measured in its neighboring undisturbed forested watershed (2.3 t ha- 1 yr- 1). The erosive response is greatly aggravated by exposing the just-harvested forest, with very limited herbaceous plant cover, to the aggressive attack of the heaviest annual rainfall without adopting any conservation practices. The erosivity of the storms during the first four months of field measurements was 1571 MJ mm h- 1 ha- 1 in total (i.e., from September to December 2008). At the end of the experiment (16 months), 18.8%, 26.1% and 55.1% of the erosion monitoring sites in the harvested watershed recorded variations equal or greater than 0-5, 5-10 and > 10 mm, respectively. This study also provides a quantification of Italian forestland surfaces with the same pedo-lithological characteristics exploited for wood supply. Within a period of ten years (2002-2011), about 9891 ha of coppice forest changes were identified and their potential soil erosion rates modeled.

Soil Erosion and Agricultural Sustainability

Science.gov (United States)

Montgomery, D. R.

2009-04-01

Data drawn from a global compilation of studies support the long articulated contention that erosion rates from conventionally plowed agricultural fields greatly exceed rates of soil production, erosion under native vegetation, and long-term geological erosion. Whereas data compiled from around the world show that soil erosion under conventional agriculture exceeds both rates of soil production and geological erosion rates by up to several orders of magnitude, similar global distributions of soil production and geological erosion rates suggest an approximate balance. Net soil erosion rates in conventionally plowed fields on the order of 1 mm/yr can erode typical hillslope soil profiles over centuries to millennia, time-scales comparable to the longevity of major civilizations. Well-documented episodes of soil loss associated with agricultural activities date back to the introduction of erosive agricultural methods in regions around the world, and stratigraphic records of accelerated anthropogenic soil erosion have been recovered from lake, fluvial, and colluvial stratigraphy, as well as truncation of soil stratigraphy (such as truncated A horizons). A broad convergence in the results from studies based on various approaches employed to study ancient soil loss and rates of downstream sedimentation implies that widespread soil loss has accompanied human agricultural intensification in examples drawn from around the world. While a broad range of factors, including climate variability and society-specific social and economic contexts — such as wars or colonial relationships — all naturally influence the longevity of human societies, the ongoing loss of topsoil inferred from studies of soil erosion rates in conventional agricultural systems has obvious long-term implications for agricultural sustainability. Consequently, modern agriculture — and therefore global society — faces a fundamental question over the upcoming centuries. Can an agricultural system

Implementing new code requirements for erosion-corrosion

International Nuclear Information System (INIS)

Deardorff, A.F.

1992-01-01

In late 1986, severe erosion-corrosion wall thinning led to complete severance of a condensate line at the Surry nuclear plant in the United States. This prompted the acceleration of a number of industry programmes to understand the cause of the faster-than-expected wall thinning, and to provide guidelines for identification, inspection and evaluation of potentially affected piping systems. (author)

Runoff erosion

OpenAIRE

Evelpidou, Niki (Ed.); Cordier, Stephane (Ed.); Merino, Agustin (Ed.); Figueiredo, Tomás de (Ed.); Centeri, Csaba (Ed.)

2013-01-01

Table of Contents PART I – THEORY OF RUNOFF EROSION CHAPTER 1 - RUNOFF EROSION – THE MECHANISMS CHAPTER 2 - LARGE SCALE APPROACHES OF RUNOFF EROSION CHAPTER 3 - MEASURING PRESENT RUNOFF EROSION CHAPTER 4 - MODELLING RUNOFF EROSION CHAPTER 5 - RUNOFF EROSION AND HUMAN SOCIETIES: THE INFLUENCE OF LAND USE AND MANAGEMENT PRACTICES ON SOIL EROSION PART II - CASE STUDIES CASE STUDIES – INTRODUCTION: RUNOFF EROSION IN MEDITERRANEAN AREA CASE STUDY 1: Soil Erosion Risk...

Prevalence of dental erosion in 12-year-old schoolchildren of Lucknow city

Directory of Open Access Journals (Sweden)

Pooja Sinha

2016-01-01

Full Text Available Introduction: Dental erosion is tooth surface loss caused by chemical processes without bacterial involvement, which can affect children because of various dietary and other lifestyle factors. Aims: The aim of this study was to assess the prevalence of dental erosion in 12-year-old schoolchildren in Lucknow city. Materials and Methods: A total of 212 schoolchildren were selected through multistage cluster random sampling method. A pretested self-administered pro forma was used to record demographic data, medical history, and dietary habits. The clinical examination was done to evaluate dental erosion of children using dental erosion index by O'Sullivan. Descriptive analytical tests were used including distribution of erosion, its extent and severity. The findings were compared across the study participants using Chi-square test. Results: The overall prevalence of dental erosion was 34.12% with no significant sex difference. Dental erosion was significantly related to the frequency of consumption of fruit juices (67.07% followed by carbonated drinks (64.47%. In most of the cases, more than half of their surfaces were diagnosed as affected by erosion (26.25% central incisors, 4.83% lateral incisors. Conclusions: Dental erosion among the study group was found to be 34.12%, providing evidence that dental erosion is becoming a significant problem in Lucknow schoolchildren.

High natural erosion rates are the backdrop for enhanced anthropogenic soil erosion in the Middle Hills of Nepal

Science.gov (United States)

West, A. J.; Arnold, M.; Aumaître, G.; Bourlès, D. L.; Keddadouche, K.; Bickle, M.; Ojha, T.

2014-08-01

Although agriculturally accelerated soil erosion is implicated in the unsustainable environmental degradation of mountain environments, such as in the Himalaya, the effects of land use can be difficult to quantify in many mountain settings because of the high and variable natural background rates of erosion. In this study, we present new long-term denudation rates, derived from cosmogenic 10Be analysis of quartz in river sediment from the Likhu Khola, a small agricultural river basin in the Middle Hills of central Nepal. Calculated long-term denudation rates, which reflect background natural erosion processes over 1000+ years prior to agricultural intensification, are similar to present-day sediment yields and to soil loss rates from terraces that are well-maintained. Similarity in short- and long-term catchment-wide erosion rates for the Likhu is consistent with data from elsewhere in the Nepal Middle Hills, but contrasts with the very large increases in short-term erosion rates seen in agricultural catchments in other steep mountain settings. Our results suggest that the large sediment fluxes exported from the Likhu and other Middle Hills rivers in the Himalaya are derived in large part from natural processes, rather than from soil erosion as a result of agricultural activity. Because of the high natural background rates, simple comparison of short- and long-term rates may not reveal unsustainable soil degradation, particularly if much of the catchment-scale erosion flux derives from mass wasting. Correcting for the mass wasting contribution in the Likhu implies minimum catchment-averaged soil production rates of ~0.25-0.35 mm yr-1. The deficit between these production rates and soil losses suggests that terraced agriculture in the Likhu may not be associated with a large systematic soil deficit, at least when terraces are well maintained, but that poorly managed terraces, forest and scrubland may lead to rapid depletion of soil resources.

Cluster analysis of accelerated molecular dynamics simulations: A case study of the decahedron to icosahedron transition in Pt nanoparticles

Science.gov (United States)

Huang, Rao; Lo, Li-Ta; Wen, Yuhua; Voter, Arthur F.; Perez, Danny

2017-10-01

Modern molecular-dynamics-based techniques are extremely powerful to investigate the dynamical evolution of materials. With the increase in sophistication of the simulation techniques and the ubiquity of massively parallel computing platforms, atomistic simulations now generate very large amounts of data, which have to be carefully analyzed in order to reveal key features of the underlying trajectories, including the nature and characteristics of the relevant reaction pathways. We show that clustering algorithms, such as the Perron Cluster Cluster Analysis, can provide reduced representations that greatly facilitate the interpretation of complex trajectories. To illustrate this point, clustering tools are used to identify the key kinetic steps in complex accelerated molecular dynamics trajectories exhibiting shape fluctuations in Pt nanoclusters. This analysis provides an easily interpretable coarse representation of the reaction pathways in terms of a handful of clusters, in contrast to the raw trajectory that contains thousands of unique states and tens of thousands of transitions.

Recent acceleration of Sea level rise in Mauritius and Rodrigues ...

African Journals Online (AJOL)

Physical evidence and anecdotes indicate that coastal erosion has also increased in the region. However, no long term series of reliable data on coastal ero- sion is available to determine if there is any linkage between the recent accelerated SLR and the observed increase in coastal erosion in Mauritius and Rodrigues.

Effect of carbides on erosion resistance of 23-8-N steel

Indian Academy of Sciences (India)

8-N nitronic steel, carbides present in the form of bands are observed to accelerate the erosion rate. Coarse ... lar carbides, precipitating at random boundaries, were more likely to ... 23-8-N nitronic steel is basically austenitic stainless steel.

Oxidative stress-induced telomeric erosion as a mechanism underlying airborne particulate matter-related cardiovascular disease

Directory of Open Access Journals (Sweden)

Grahame Thomas J

2012-06-01

Full Text Available Abstract Particulate matter (PM pollution is responsible for hundreds of thousands of deaths worldwide, the majority due to cardiovascular disease (CVD. While many potential pathophysiological mechanisms have been proposed, there is not yet a consensus as to which are most important in causing pollution-related morbidity/mortality. Nor is there consensus regarding which specific types of PM are most likely to affect public health in this regard. One toxicological mechanism linking exposure to airborne PM with CVD outcomes is oxidative stress, a contributor to the development of CVD risk factors including atherosclerosis. Recent work suggests that accelerated shortening of telomeres and, thus, early senescence of cells may be an important pathway by which oxidative stress may accelerate biological aging and the resultant development of age-related morbidity. This pathway may explain a significant proportion of PM-related adverse health outcomes, since shortened telomeres accelerate the progression of many diseases. There is limited but consistent evidence that vehicular emissions produce oxidative stress in humans. Given that oxidative stress is associated with accelerated erosion of telomeres, and that shortened telomeres are linked with acceleration of biological ageing and greater incidence of various age-related pathology, including CVD, it is hypothesized that associations noted between certain pollution types and sources and oxidative stress may reflect a mechanism by which these pollutants result in CVD-related morbidity and mortality, namely accelerated aging via enhanced erosion of telomeres. This paper reviews the literature providing links among oxidative stress, accelerated erosion of telomeres, CVD, and specific sources and types of air pollutants. If certain PM species/sources might be responsible for adverse health outcomes via the proposed mechanism, perhaps the pathway to reducing mortality/morbidity from PM would become clearer

Erosive Wear Characterization of Materials for Lunar Construction

Science.gov (United States)

Mpagazehe, Jeremiah N.; Street, Kenneth W., Jr.; Delgado, Irebert R.; Higgs, C. Fred, III

2012-01-01

NASA s Apollo missions revealed that exhaust from the retrorockets of landing spacecraft may act to significantly accelerate lunar dust on the surface of the Moon. A recent study by Immer et al. (C. Immer, P.T. Metzger, P.E. Hintze, A. Nick, and R. Horan, Apollo 12 Lunar Module exhaust plume impingement on Lunar Surveyor III, Icarus, Vol. 211, pp. 1089-1102, 2011) investigated coupons returned to Earth from the Surveyor III lunar probe which were subjected to lunar dust impingement by the Apollo 12 Lunar Module landing. Their study revealed that even with indirect impingement, the spacecraft sustained erosive damage from the fast-moving lunar dust particles. In this work, results are presented from a series of erosive wear experiments performed on 6061 Aluminum using the JSC-1AF lunar dust simulant. Optical profilometry was used to investigate the surface after the erosion process. It was found that even short durations of lunar dust simulant impacting at low velocities produced substantial changes in the surface.

Detection of soil erosion within pinyon-juniper woodlands using Thematic Mapper (TM) data

Science.gov (United States)

Price, Kevin P.

1993-01-01

Multispectral measurements collected by Landsat Thematic Mapper (TM) were correlated with field measurements, direct soil loss estimates, and Universal Soil Loss Equation (USLE) estimates to determine the sensitivity of TM data to varying degrees of soil erosion in pinyon-juniper woodland in central Utah. TM data were also evaluated as a predictor of the USLE Crop Management C factor for pinyon-juniper woodlands. TM spectral data were consistently better predictors of soil erosion factors than any combination of field factors. TM data were more sensitive to vegetation variations than the USLE C factor. USLE estimates showed low annual rates of erosion which varied little among the study sites. Direct measurements of rate of soil loss using the SEDIMENT (Soil Erosion DIrect measureMENT) technique, indicated high and varying rates of soil loss among the sites since tree establishment. Erosion estimates from the USLE and SEDIMENT methods suggest that erosion rates have been severe in the past, but because significant amounts of soil have already been eroded, and the surface is now armored by rock debris, present erosion rates are lower. Indicators of accelerated erosion were still present on all sites, however, suggesting that the USLE underestimated erosion within the study area.

Influence of plasma pressure gradient on melt layer macroscopic erosion of metal targets in disruption simulation experiments

Energy Technology Data Exchange (ETDEWEB)

Tereshin, V.I.; Garkusha, I.E. E-mail: garkusha@ipp.kharkov.ua; Bandura, A.N.; Byrka, O.V.; Chebotarev, V.V.; Makhlaj, V.A.; Solyakov, D.G.; Wuerz, H

2003-03-01

Melt layer erosion of metal targets under pulsed high heat loads is discussed. Tungsten, copper, aluminum, and titanium targets were exposed to perpendicular and inclined plasma impact in the quasi-steady-state plasma accelerator QSPA Kh-50. Melt layer motion results in erosion crater formation with rather large mountains of the resolidified material at the crater edge. It is shown that macroscopic motion of the melt layer and surface cracking are the main factors responsible for tungsten erosion.

Influence of plasma pressure gradient on melt layer macroscopic erosion of metal targets in disruption simulation experiments

International Nuclear Information System (INIS)

Tereshin, V.I.; Garkusha, I.E.; Bandura, A.N.; Byrka, O.V.; Chebotarev, V.V.; Makhlaj, V.A.; Solyakov, D.G.; Wuerz, H.

2003-01-01

Melt layer erosion of metal targets under pulsed high heat loads is discussed. Tungsten, copper, aluminum, and titanium targets were exposed to perpendicular and inclined plasma impact in the quasi-steady-state plasma accelerator QSPA Kh-50. Melt layer motion results in erosion crater formation with rather large mountains of the resolidified material at the crater edge. It is shown that macroscopic motion of the melt layer and surface cracking are the main factors responsible for tungsten erosion

Wind erosion potential after land application of biosolids

Science.gov (United States)

PI, H.; Sharratt, B. S.; Schillinger, W. F.; Bary, A.; Cogger, C.

2017-12-01

The world population is currently 7.6 billion and, along with continued population growth, comes the challenge of disposing of wastewater and sewage sludge (biosolids). Applying biosolids to agricultural land to replace synthetic fertilizers represents a relatively safe method to recycle or sustainably use biosolids. While land application of biosolids is recognized as a sustainable management practice for enhancing soil health, no studies have determined the effects of biosolids on soil wind erosion. Wind erosion potential of a silt loam was assessed using a portable wind tunnel after applying synthetic and biosolid fertilizer to conventional and conservation tillage practices during the summer fallow phase of a winter wheat-summer fallow rotation in 2015 and 2016 in east-central Washington. Little difference in soil loss was observed between biosolid and synthetic fertilizer treatments, but this result appeared to be dependent on susceptibility of the soil to erosion. Regression analysis between soil loss from fertilizer or tillage treatments indicated that soil loss was lower from biosolid versus synthetic fertilizer and conservation versus conventional tillage at high erosion rates. This suggests that biosolids may reduce wind erosion under highly erodible conditions. Meanwhile, heavy metal concentrations in the windblown sediment were similar for the biosolid and synthetic fertilizer treatments whereas metal loss in windblown sediment was 10% lower from biosolid than synthetic fertilizer. Our results indicate that land application of biosolids did not accelerate the loss of metals or nutrients from soils during high winds. KeywordsLand application of biosolids; wind erosion; wind tunnel; sustainable agriculture

Introduction to littoral erosion problem in Uraba (Arboletes-Turbo area) Colombian Caribbean Coast

International Nuclear Information System (INIS)

Correa; Ivan D; Vernette, Georges

2004-01-01

Shoreline retreat has been the net dominant historical trend along the 145 km-length littoral between Arboletes and Turbo (southern Caribbean of Colombia). For the last four decades, there were identified in this littoral shoreline retreat of about 50-100 m in several places (Uveros, Damaquiel, Zapata, Turbo) and a maximum of 1.6 km in the Punta Rey-Arboletes area, where land losses were of 4.5 km 2 , at exceptional rates of 40 rn/year. The synthesis of the available information suggest that the general susceptibility to erosion between Arboletes and turbo could be related primarily to relative sea level rise, associated to tectonic movements as well as to the effects of mud diapirism and hydroisostacy. In the more critical areas (Arboletes, Turbo), the natural erosive trends were accelerated by anthropic actions, including river diversion (Turbo), beach mining and inadequate (or total absence) practices for controlling residual and natural waters. Up to august 2000, there were invested about $ Col 10.000 billions in 155 engineering defenses (groins, sea walls and rip-rap which totalize 6.2 km of total length and a volume of materials of 37.000 m 3 ). With few exceptions, groins have not been successful and are now part of the problem, accelerating shore erosion along the adjacent sectors. In the short term, the littoral erosion between Arboletes and turbo is caused both by marine and by sub aerial factors. it is facilitated by the poor lithological strengths of cliffs and marine terraces, mainly composed of highly fractured and weathered claystones and mudstones (with stratification and weakness planes dipping toward sea) and non-consolidated, easily liquefacted, fine sediments; both conditions facilitate the occurrence of rocks falls, slides and mud flows that result in high figures of cliff retreat (3 to 4 m), specially during the first 15 days of the summer-winter transition (April) and in high waves periods. The case of the littoral erosion between Arboletes

Using REE tracers to measure sheet erosion changing to rill erosion

International Nuclear Information System (INIS)

Liu Puling; Xue Yazhou; Song Wei; Wang Mingyi; Ju Tongjun

2004-01-01

Rare Earth Elements (REE) tracer method was used to study sheet erosion changing to rill erosion on slope land. By placing different rare earth elements of different soil depth across a slope in an indoor plot, two simulated rainfalls were applied to study the change of erosion type and the rill erosion process. The results indicate that the main erosion type is sheet erosion at the beginning of the rainfalls, and serious erosion happens after rill erosion appears. Accumulated sheet and rill erosion amounts increase with the rainfalls time. The percentage of sheet erosion amount decreases and rill erosion percentage increases with time. At the end of the rainfalls, the total rill erosion amounts are 4-5 times more than sheet erosion. In this paper, a new REE tracer method was used to quantitatively distinguish sheet and rill erosion amounts. The new REE tracer method should be useful to future studying of erosion processes on slope lands. (authors)

Technology development by the U.S. industry to resolve erosion-corrosion

International Nuclear Information System (INIS)

Chexal, B.; Dietrich, N.; Horowitz, J.; Layman, W.; Randall, G.; Shevde, V.

1990-01-01

Erosion-corrosion is a flow-accelerated corrosion process that leads to wall thinning (metal loss) of steel piping exposed to flowing water or wet steam. The rate of metal loss depends on a complex interplay of several parameters. These parameters include water chemistry, material composition, and hydrodynamics. Erosion-corrosion of plant piping can lead to costly outages and repairs, and can raise concerns about plant reliability and safety. Pipe wall degradation rates as high as 1.5 mm/year have occurred, resulting in pipe ruptures at both fossil and nuclear plants. The Nuclear Management and Resource Council (NUMARC) and EPRI have developed inspection planning methods and tools to help utilities identify areas of piping that might undergo erosion-corrosion. These tools provide utilities with the ability to predict wall thinning and to assess various remedial options. This allows utilities to plan and perform inspections, and to correct problems found during inspection. The U.S. electric power industry has developed the knowledge and the tools needed to protect against erosion-corrosion, and utilities have implemented erosion-corrosion monitoring programs. This paper describes EPRI's technical developments that support the utilities in determining where to inspect for erosion-corrosion. 15 refs, 7 figs

The Arctic Coastal Erosion Problem

Energy Technology Data Exchange (ETDEWEB)

Frederick, Jennifer M. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Thomas, Matthew Anthony [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Bull, Diana L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Jones, Craig A. [Integral Consulting Inc., San Francisco, CA (United States); Roberts, Jesse D. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2016-09-01

Permafrost-dominated coastlines in the Arctic are rapidly disappearing. Arctic coastal erosion rates in the United States have doubled since the middle of the twentieth century and appear to be accelerating. Positive erosion trends have been observed for highly-variable geomorphic conditions across the entire Arctic, suggesting a major (human-timescale) shift in coastal landscape evolution. Unfortunately, irreversible coastal land loss in this region poses a threat to native, industrial, scientific, and military communities. The Arctic coastline is vast, spanning more than 100,000 km across eight nations, ten percent of which is overseen by the United States. Much of area is inaccessible by all-season roads. People and infrastructure, therefore, are commonly located near the coast. The impact of the Arctic coastal erosion problem is widespread. Homes are being lost. Residents are being dispersed and their villages relocated. Shoreline fuel storage and delivery systems are at greater risk. The U.S. Department of Energy (DOE) and Sandia National Laboratories (SNL) operate research facilities along some of the most rapidly eroding sections of coast in the world. The U.S. Department of Defense (DOD) is struggling to fortify coastal radar sites, operated to ensure national sovereignty in the air, against the erosion problem. Rapid alterations to the Arctic coastline are facilitated by oceanographic and geomorphic perturbations associated with climate change. Sea ice extent is declining, sea level is rising, sea water temperature is increasing, and permafrost state is changing. The polar orientation of the Arctic exacerbates the magnitude and rate of the environmental forcings that facilitate coastal land area loss. The fundamental mechanics of these processes are understood; their non-linear combination poses an extreme hazard. Tools to accurately predict Arctic coastal erosion do not exist. To obtain an accurate predictive model, a coupling of the influences of

Erosion-corrosion synergistics in the low erosion regime

International Nuclear Information System (INIS)

Corey, R.G.; Sethi, V.K.

1986-01-01

Many engineering alloys display good high temperature corrosion resistance. However, when they are used in corrosive environments where they are subjected to erosion also, the corrosion resistance has been adversely affected. The phenomenon known as erosion-corrosion is complex and requires detailed investigation of how the erosion and corrosion kinetics interact and compete. At the Kentucky Center for Energy Research Laboratory, an erosion-corrosion tester was used to perform erosion-oxidation tests on 2 1/4 Cr-1 Mo steel at 500-600 0 C using alumina abrasive at low velocities. The erosion-oxidation rate data and morphology of exposed surfaces are consistent with oxide chipping and fracturing being the mode of material loss

Development of a high velocity rain erosion test method

Energy Technology Data Exchange (ETDEWEB)

Chung, Dong Teak; Jin, Doo Han [Korea University of Technology and Education, Cheonan (Korea, Republic of); Kang, Hyung [Agency for Defense Development, Daejeon (Korea, Republic of)

2009-07-01

The nose of a missile, flying through raining region with a supersonic speed, is subjected to the rain erosion because the nose is made of a brittle ceramic material. A simple yet very effective rain erosion test method is developed. The sabot assembly similar to the hypodermic syringe carries specific amount of water is launched by a low pressure air gun. After the stopper stop the sabot assembly by impact, the steel plunger continues moving toward to squeeze the silicon rubber in front. The pressurized silicon rubber then is squeezed through the orifice in front of the sabot at high velocity, thus, accelerates the water droplet to higher velocity. The droplet velocity up to 800m/s is successfully attained using a low pressure air gun. The ceramic specimen assembly is placed in front of the high speed water droplet and the rain erosion damage on the surface of the specimen is observed.

Assessment of mercury erosion by surface water in Wanshan mercury mining area.

Science.gov (United States)

Dai, ZhiHui; Feng, Xinbin; Zhang, Chao; Shang, Lihai; Qiu, Guangle

2013-08-01

Soil erosion is a main cause of land degradation, and in its accelerated form is also one of the most serious ecological environmental problems. Moreover, there are few studies on migration of mercury (Hg) induced by soil erosion in seriously Hg-polluted districts. This paper selected Wanshan Hg mining area, SW China as the study area. Revised universal soil loss equation (RUSLE) and Geographic information system (GIS) methods were applied to calculate soil and Hg erosion and to classify soil erosion intensity. Our results show that the soil erosion rate can reach up to 600,884tkm(-2)yr(-1). Surfaces associated with very slight and extremely severe erosion include 76.6% of the entire land in Wanshan. Furthermore, the cumulative erosion rates in the area impacted by extremely severe erosion make up 90.5% of the total. On an annual basis, Hg surface erosion load was predicted to be 505kgyr(-1) and the corresponding mean migration flux of Hg was estimated to be 3.02kgkm(-2)yr(-1). The erosion loads of Hg resulting from farmland and meadow soil were 175 and 319kgyr(-1) respectively, which were enhanced compared to other landscape types due to the fact that they are generally located in the steep zones associated with significant reclamation. Contributing to establish a mass balance of Hg in Wanshan Hg mining area, this study supplies a dependable scientific basis for controlling soil and water erosion in the local ecosystems. Land use change is the most effective way for reducing Hg erosion load in Wanshan mining area. Copyright © 2013 Elsevier Inc. All rights reserved.

Hillslope-channel coupling in a steep Hawaiian catchment accelerates erosion rates over 100-fold

Science.gov (United States)

Stock, J. D.; Hanshaw, M. N.; Rosener, M.; Schmidt, K. M.; Brooks, B. A.; Tribble, G.; Jacobi, J.

2009-12-01

In tropical watersheds, hillslope changes are producing increasing amounts of fine sediment that can be quickly carried to reefs by channels. Suspended sediment concentrations off the reefs of Molokai, Hawaii, chronically exceed a toxic level of 10 mg/L, threatening reef ecosystems. We hypothesize that historic conversion of watersheds from soil creep to overland flow erosion increased both magnitude and frequency of sediment flooding adjacent reefs. We combined surficial and ecological mapping, hillslope and stream gages, and novel sensors to locate, quantify and model the generation of fine sediments polluting the Molokai reef. Ecological and geomorphic mapping from LiDAR and multi-spectral imagery located a subset of overland flow areas with vegetation cover below a threshold value preventing erosion. Here, feral goat grazing exposed cohesive volcanic soils whose low matrix hydraulic conductivities (1-20 mm/hour) promote Horton overland flow erosion. We instrumented steep, barren hillslopes with soil moisture sensors, overland flow meters, Parshall flumes, ISCO sediment samplers, and a rain gage and conducted repeat Tripod LiDAR and infiltration tests. To characterize soil resistance here and elsewhere to overland flow erosion, we deployed a Cohesive Strength Meter (CSM) to simulate the stresses of flowing water. At the 13.5 km 2 watershed mouth we used a USGS stream gage and ISCO sediment sampler to estimate total load. Over 2 years, storms triggered overland flow during rainfall intensities above 10-15 mm/hr. Overland flow meters indicate such flows can be up to 3 cm deep, with a tendency to deepen downslope. CSM tests indicate that these depths are insufficient to erode soils where vegetation is dense, but far above threshold values of 2-3 mm depth for bare soil erosion. Sediment ratings curves for both hillslope and downstream catchment gages show strong clock-wise hysteresis during the first intense storms in the Fall, becoming linear later in the rainy

Effects of uranium development on erosion and associated sedimentation in southern San Juan Basin, New Mexico

Science.gov (United States)

Cooley, Maurice E.

1979-01-01

A reconnaissance was made of some of the effects of uranium development on erosion and associated sedimentation in the southern San Juan Basin, where uranium development is concentrated. In general, the effects of exploration on erosion are minor, although erosion may be accelerated by the building of access roads, by activities at the drilling sites, and by close concentration of drilling sites. Areas where the greatest effects on erosion and sedimentation from mining and milling operations have occurred are: (1) in the immediate vicinity of mines and mills, (2) near waste piles, and (3) in stream channels where modifications, such as changes in depth have been caused by discharge of excess mine and mill water. Collapse of tailings piles could result in localized but excessive erosion and sedimentation.

Cavitation erosion prediction on Francis turbines

Energy Technology Data Exchange (ETDEWEB)

Bourdon, P.; Farhat, M.; Simoneau, R.; Lavigne, P. [Hydro-Quebec, Montreal, PQ (Canada); Pereira, F.; Dupont, P.; Avellan, F.; Caron, J.F. [IMHEF/EPFL, (France); Dorey, J.M.; Archer, A. [Electricite de France (EDF), 92 - Clamart (France). Dir. des Etudes et Recherches; and others

1997-12-31

On-board aggressiveness measurement methods were tested on a severely eroded prototype blade of a 266 MW Francis turbine: pressure, pit counting, DECER electrochemical and vibration measurements. The test program provided understanding of the heterogeneous erosion distribution of the prototype blades and quantitative data for comparison in subsequent tests on the model of the machine. Model tests and flow analysis were also performed, to detect cavitation on a Francis turbine model. The results are compared to those obtained on the prototype measurements. The model used for that study is built on the basis of a geometrical recovery of one of the most eroded blade of the prototype. Different methods were investigated to predict cavitation erosion on Francis turbines from model. They are based on measurement of pitting, pressure fluctuations and acceleration. The methods proposed are suitable to measure cavitation aggressiveness on model and on prototype, and that the level on the model is several orders of magnitude smaller than on the prototype. (author) 18 refs.

THE EVALUATION OF SOIL EROSION OFF-SITES EFFECTS IN LARGE BASINS: THE STUDYCASE OF LERMA-CHAPALA WATERSHED, MEXICO

OpenAIRE

Helena Cotler A.; Susana Gutierrez D.; Carlos Enriquez G.; Arturo Garrido P.

2005-01-01

One of the primary global concerns during the new millennium is the assessment of the impact of accelerated soil erosion on the economy and the environment (Pimentel et al. 1995; Lal, 1995). Erosion damages the site on which it occurs and also has undesirable effects off-site in the larger environment. Erosion moves sediments and nutrients out of the land, creating the two most widespread water pollution problems in the rivers, lakes and dams. The nutrients impact water quality largely throug...

The influence of frequently consumed beverages and snacks on dental erosion among preschool children in Saudi Arabia.

Science.gov (United States)

Al-Dlaigan, Yousef H; Al-Meedania, Laila A; Anil, Sukumaran

2017-12-11

To determine the prevalence of dental erosion and its association to commonly used beverages and snacks among 3 to 5 year old preschool children in Riyadh, Saudi Arabia. Three hundred eighty-eight preschool children between 3 and 5 years old were selected from 10 different schools using a cluster random sample selection; there were 184 (47%) boys and 204 (53%) girls. The surfaces of each tooth were examined for erosion, and the level of tooth wear was recorded. Data on the frequently used beverages and snacks were obtained by questionnaires completed by the parents of the preschool children. Among the 388 children examined, 47% exhibited low erosion, 10% exhibited moderate erosion and 4% exhibited severe erosion. There was no statistically significant difference between boys and girls in terms of the prevalence of erosion. Sixty percent of the children regularly consumed juice drinks. Among daily consumers, 84% of children showed erosion prevalence with strongly significant association (p erosion (p dental erosion and the frequency of citrus and carbonated juice consumed by the preschool children in Saudi Arabia.

First high energy hydrogen cluster beams

International Nuclear Information System (INIS)

Gaillard, M.J.; Genre, R.; Hadinger, G.; Martin, J.

1993-03-01

The hydrogen cluster accelerator of the Institut de Physique Nucleaire de Lyon (IPN Lyon) has been upgraded by adding a Variable Energy Post-accelerator of RFQ type (VERFQ). This operation has been performed in the frame of a collaboration between KfK Karlsruhe, IAP Frankfurt and IPN Lyon. The facility has been designed to deliver beams of mass selected Hn + clusters, n chosen between 3 and 49, in the energy range 65-100 keV/u. For the first time, hydrogen clusters have been accelerated at energies as high as 2 MeV. This facility opens new fields for experiments which will greatly benefit from a velocity range never available until now for such exotic projectiles. (author) 13 refs.; 1 fig

Detection of soil erosion within pinyon-juniper woodlands using Thematic Mapper (TM) satellite data

Science.gov (United States)

Price, Kevin P.; Ridd, Merrill K.

1991-01-01

The sensitivity of Landsat TM data for detecting soil erosion within pinyon-juniper woodlands, and the potential of the spectral data for assigning the universal soil loss equation (USLE) crop managemnent (C) factor to varying cover types within the woodlands are assessed. Results show greatly accelerated rates of soil erosion on pinyon-juniper sites. Percent cover by pinyon-juniper, total soil-loss, and total nonliving ground cover accounted for nearly 70 percent of the variability in TM channels 2, 3, 4, and 5. TM spectral data were consistently better predictors of soil erosion than the biotic and abiotic field variables. Satellite data were more sensitive to vegetation variation than the USLE C factor, and USLE was found to be a poor predictor of soil loss on pinyon-juniper sites. A new string-to-ground soil erosion prediction technique is introduced.

Soil erosion in Iran: Issues and solutions

Science.gov (United States)

Hamidreza Sadeghi, Seyed; Cerdà, Artemi

2015-04-01

Iran currently faces many soil erosion-related problems (see citations below). These issues are resulted from some inherent characteristic and anthropogenic triggering forces. Nowadays, the latter plays more important rule to accelerate the erosion with further emphasis on soil erosion-prone arid and semi arid regions of the country. This contribution attempts to identify and describe the existing main reasons behind accelerated soil erosion in Iran. Appropriate solutions viz. structural and non-structural approaches will be then advised to combat or minimise the problems. Iran can be used as a pilot research site to understand the soil erosion processes in semiarid, arid and mountainous terrain and our research will review the scientific literature and will give an insight of the soil erosion rates in the main factors of the soil erosion in Iran. Key words: Anthropogenic Erosion, Land Degradation; Sediment Management; Sediment Problems Acknowledgements The research projects GL2008-02879/BTE, LEDDRA 243857 and PREVENTING AND REMEDIATING DEGRADATION OF SOILS IN EUROPE THROUGH LAND CARE (RECARE)FP7-ENV-2013- supported this research. References Aghili Nategh, N., Hemmat, A., & Sadeghi, M. (2014). Assessing confined and semi-confined compression curves of highly calcareous remolded soil amended with farmyard manure. Journal of Terramechanics, 53, 75-82. Arekhi, S., Bolourani, A. D., Shabani, A., Fathizad, H., Ahamdy-Asbchin, S. 2012. Mapping Soil Erosion and Sediment Yield Susceptibility using RUSLE, Remote Sensing and GIS (Case study: Cham Gardalan Watershed, Iran). Advances in Environmental Biology, 6(1), 109-124. Arekhi, S., Shabani, A., Rostamizad, G. 2012. Application of the modified universal soil loss equation (MUSLE) in prediction of sediment yield (Case study: Kengir Watershed, Iran). Arabian Journal of Geosciences, 5(6), 1259-1267.Sadeghi, S. H., Moosavi, V., Karami, A., Behnia, N. 2012. Soil erosion assessment and prioritization of affecting factors at plot

A terminological matter: paragenesis, antigravitative erosion or antigravitational erosion ?

Directory of Open Access Journals (Sweden)

Pasini G.

2009-07-01

Full Text Available In the speleological literature three terms are utilized to designate the “ascending erosion”: paragenesis (= paragénésis, coined in1968, antigravitative erosion (= erosione antigravitativa, coined in 1966 and antigravitational erosion (wrong English translation ofthe Italian term erosione antigravitativa, utilized later on. The term paragenesis should be abandoned because of the priority of theterm erosione antigravitativa - on the ground of the “law of priority” – and because of its ambiguous etimology. On the other hand,the term antigravitational erosion should be forsaken in favour of the term antigravitative erosion, given the meaning that the termsgravitation and gravity have in Physics. Therefore, to designate the phenomenon of the “ascending erosion” there would be nothingleft but the term antigravitative erosion.The antigravitative erosion process and its recognizability are illustrated.Examples of caves with evident antigravitative erosion phenomena, developed in different karstifiable rocks and in several partsof the world, are given.It is recalled that the antigravitative erosion is a phenomenon well-known since 1942 and widely proven and supported, and that it isrelatively easy – in many cases - to recognize the antigravitative origin of karstic passages.It is stressed that the antigravitative erosion is an important phenomenon, exclusive of the karstic caves and unique in nature.

Modeling the fluid/soil interface erosion in the Hole Erosion Test

Directory of Open Access Journals (Sweden)

Kissi B.

2012-07-01

Full Text Available Soil erosion is a complex phenomenon which yields at its final stage to insidious fluid leakages under the hydraulic infrastructures known as piping and which are the main cause of their rupture. The Hole Erosion Test is commonly used to quantify the rate of piping erosion. In this work, The Hole Erosion Test is modelled by using Fluent software package. The aim is to predict the erosion rate of soil during the hole erosion test. The renormalization group theory – based k–ε turbulence model equations are used. This modelling makes it possible describing the effect of the clay concentration in flowing water on erosion. Unlike the usual one dimensional models, the proposed modelling shows that erosion is not uniform erosion along the hole length. In particular, the concentration of clay is found to increase noticeably the erosion rate.

Electric potential structures of auroral acceleration region border from multi-spacecraft Cluster data

Science.gov (United States)

Sadeghi, S.; Emami, M. R.

2018-04-01

This paper studies an auroral event using data from three spacecraft of the Cluster mission, one inside and two at the poleward edge of the bottom of the Auroral Acceleration Region (AAR). The study reveals the three-dimensional profile of the region's poleward boundary, showing spatial segmentation of the electric potential structures and their decay in time. It also depicts localized magnetic field variations and field-aligned currents that appear to have remained stable for at least 80 s. Such observations became possible due to the fortuitous motion of the three spacecraft nearly parallel to each other and tangential to the AAR edge, so that the differences and variations can be seen when the spacecraft enter and exit the segmentations, hence revealing their position with respect to the AAR.

Coastal erosion and accretion in Pak Phanang, Thailand by GIS analysis of maps and satellite imagery

Directory of Open Access Journals (Sweden)

Sayedur Rahman Chowdhury

2013-12-01

Full Text Available Coastal erosion and accretion in Pak Phanang of southern Thailand between 1973 and 2003 was measured using multi-temporal topographic maps and Landsat satellite imageries. Within a GIS environment landward and seaward movements of shoreline was estimated by a transect-based analysis, and amounts of land accretion and erosion were estimated by a parcel-based geoprocessing. The whole longitudinal extent of the 58 kilometer coast was classified based on the erosion and accretion trends during this period using agglomerative hierarchical clustering approach. Erosion and accretion were found variable over time and space, and periodic reversal of status was also noticed in many places. Estimates of erosion were evaluated against field-survey based data, and found reasonably accurate where the rates were relatively great. Smoothing of shoreline datasets was found desirable as its impacts on the estimates remained within tolerable limits.

Thermal erosion of a permafrost coastline: Improving process-based models using time-lapse photography

Science.gov (United States)

Wobus, C.; Anderson, R.; Overeem, I.; Matell, N.; Clow, G.; Urban, F.

2011-01-01

Coastal erosion rates locally exceeding 30 m y-1 have been documented along Alaska's Beaufort Sea coastline, and a number of studies suggest that these erosion rates have accelerated as a result of climate change. However, a lack of direct observational evidence has limited our progress in quantifying the specific processes that connect climate change to coastal erosion rates in the Arctic. In particular, while longer ice-free periods are likely to lead to both warmer surface waters and longer fetch, the relative roles of thermal and mechanical (wave) erosion in driving coastal retreat have not been comprehensively quantified. We focus on a permafrost coastline in the northern National Petroleum Reserve-Alaska (NPR-A), where coastal erosion rates have averaged 10-15 m y-1 over two years of direct monitoring. We take advantage of these extraordinary rates of coastal erosion to observe and quantify coastal erosion directly via time-lapse photography in combination with meteorological observations. Our observations indicate that the erosion of these bluffs is largely thermally driven, but that surface winds play a crucial role in exposing the frozen bluffs to the radiatively warmed seawater that drives melting of interstitial ice. To first order, erosion in this setting can be modeled using formulations developed to describe iceberg deterioration in the open ocean. These simple models provide a conceptual framework for evaluating how climate-induced changes in thermal and wave energy might influence future erosion rates in this setting.

Real-Tme Boron Nitride Erosion Measurements of the HiVHAc Thruster via Cavity Ring-Down Spectroscopy

Science.gov (United States)

Lee, Brian C.; Yalin, Azer P.; Gallimore, Alec; Huang, Wensheng; Kamhawi, Hani

2013-01-01

Cavity ring-down spectroscopy was used to make real-time erosion measurements from the NASA High Voltage Hall Accelerator thruster. The optical sensor uses 250 nm light to measure absorption of atomic boron in the plume of an operating Hall thruster. Theerosion rate of the High Voltage Hall Accelerator thruster was measured for discharge voltages ranging from 330 to 600 V and discharge powers ranging from 1 to 3 kW. Boron densities as high as 6.5 x 10(exp 15) per cubic meter were found within the channel. Using a very simple boronvelocity model, approximate volumetric erosion rates between 5.0 x 10(exp -12) and 8.2 x 10(exp -12) cubic meter per second were found.

Testing of Composite Fan Vanes With Erosion-Resistant Coating Accelerated

Science.gov (United States)

Bowman, Cheryl L.; Sutter, James K.; Otten, Kim D.; Samorezov, Sergey; Perusek, Gail P.

2004-01-01

The high-cycle fatigue of composite stator vanes provided an accelerated life-state prior to insertion in a test stand engine. The accelerated testing was performed in the Structural Dynamics Laboratory at the NASA Glenn Research Center under the guidance of Structural Mechanics and Dynamics Branch personnel. Previous research on fixturing and test procedures developed at Glenn determined that engine vibratory conditions could be simulated for polymer matrix composite vanes by using the excitation of a combined slip table and electrodynamic shaker in Glenn's Structural Dynamics Laboratory. Bench-top testing gave researchers the confidence to test the coated vanes in a full-scale engine test.

Numerical modelling of concentrated leak erosion during Hole Erosion Tests

OpenAIRE

Mercier, F.; Bonelli, S.; Golay, F.; Anselmet, F.; Philippe, P.; Borghi, R.

2015-01-01

This study focuses on the numerical modelling of concentrated leak erosion of a cohesive soil by a turbulent flow in axisymmetrical geometry, with application to the Hole Erosion Test (HET). The numerical model is based on adaptive remeshing of the water/soil interface to ensure accurate description of the mechanical phenomena occurring near the soil/water interface. The erosion law governing the interface motion is based on two erosion parameters: the critical shear stress and the erosion co...

Soil Erosion Analysis in a Small Forested Catchment Supported by ArcGIS Model Builder

Directory of Open Access Journals (Sweden)

CSÁFORDI, Péter

2012-01-01

Full Text Available To implement the analysis of soil erosion with the USLE in a GIS environment, a new workflow has been developed with the ArcGIS Model Builder. The aim of this four-part framework is to accelerate data processing and to ensure comparability of soil erosion risk maps. The first submodel generates the stream network with connected catchments, computes slope conditions and the LS factor in USLE based on the DEM. The second submodel integrates stream lines, roads, catchment boundaries, land cover, land use, and soil maps. This combined dataset is the basis for the preparation of other USLE-factors. The third submodel estimates soil loss, and creates zonal statistics of soil erosion. The fourth submodel classifies soil loss into categories enabling the comparison of modelled and observed soil erosion. The framework was applied in a small forested catchment in Hungary. Although there is significant deviation between the erosion of different land covers, the predicted specific soil loss does not increase above the tolerance limit in any area unit. The predicted surface soil erosion in forest subcompartments mostly depends on the slope conditions.

High natural erosion rates are the backdrop for present-day soil erosion in the agricultural Middle Hills of Nepal

Science.gov (United States)

West, A. J.; Arnold, M.; AumaItre, G.; Bourles, D. L.; Keddadouche, K.; Bickle, M.; Ojha, T.

2015-07-01

Although agriculturally accelerated soil erosion is implicated in the unsustainable environmental degradation of mountain environments, such as in the Himalaya, the effects of land use can be challenging to quantify in many mountain settings because of the high and variable natural background rates of erosion. In this study, we present new long-term denudation rates, derived from cosmogenic 10Be analysis of quartz in river sediment from the Likhu Khola, a small agricultural river basin in the Middle Hills of central Nepal. Calculated long-term denudation rates, which reflect background natural erosion processes over 1000+ years prior to agricultural intensification, are similar to present-day sediment yields and to soil loss rates from terraces that are well maintained. Similarity in short- and long-term catchment-wide erosion rates for the Likhu is consistent with data from elsewhere in the Nepal Middle Hills but contrasts with the very large increases in short-term erosion rates seen in agricultural catchments in other steep mountain settings. Our results suggest that the large sediment fluxes exported from the Likhu and other Middle Hills rivers in the Himalaya are derived in large part from natural processes, rather than from soil erosion as a result of agricultural activity. Catchment-scale erosional fluxes may be similar over short and long timescales if both are dominated by mass wasting sources such as gullies, landslides, and debris flows (e.g., as is evident in the landslide-dominated Khudi Khola of the Nepal High Himalaya, based on compiled data). As a consequence, simple comparison of catchment-scale fluxes will not necessarily pinpoint land use effects on soils where these are only a small part of the total erosion budget, unless rates of mass wasting are also considered. Estimates of the mass wasting contribution to erosion in the Likhu imply catchment-averaged soil production rates on the order of ~ 0.25-0.35 mm yr-1, though rates of mass wasting are

Bibliometria, história e geografia da pesquisa brasileira em erosão acelerada do solo Bibliometrics, history and geography of Brazilian research on accelerated soil erosion

Directory of Open Access Journals (Sweden)

Alberto Giaroli de Oliveira Pereira Barretto

2008-12-01

Full Text Available Há poucos estudos sobre a história da ciência do solo e, no Brasil, essa matéria ainda não recebeu maior atenção por parte de sua comunidade científica. Este trabalho focaliza a formação histórica da pesquisa brasileira em erosão acelerada do solo a partir de uma análise bibliométrica e geográfica, com base numa ampla compilação de artigos científicos publicados sobre o tema por autores vinculados a instituições brasileiras. A metodologia envolveu o armazenamento, em um banco de dados dimensional, estruturado especificamente para esse objetivo, de informações espaciais e bibliométricas. Indicadores quantitativos foram calculados, e a geografia da pesquisa foi mapeada por meio de consultas SQL e ferramentas de geoprocessamento. Os resultados apontaram para gênese recente da pesquisa brasileira em erosão acelerada do solo e centralização da produção científica e formação de linhas em instituições e autores do Sul e Sudeste do Brasil. Ainda, a análise dos dados temáticos indicou predominância do enfoque da erosão a partir de uma perspectiva agrícola e grande ênfase na pesquisa dos fatores do modelo USLE de estimativa de erosão.Soil science history studies are rare and the Brazilian scientific community has not given substantial attention to this subject yet. The present study focused on the formation of research on accelerated soil erosion in the Brazil from a bibliometric perspective. A comprehensive database of published scientific papers was organized in a relational database and analyzed by SQL queries and GIS tools. These data were used to calculate quantitative indicators and spatial distribution patterns. Results indicate a recent development of research on accelerated soil erosion in Brazil by few institutions and authors in the South and Southeast regions. Moreover, a thematic analysis indicated the agricultural perspective as the main focus of erosion studies, with a great emphasis on the USLE

The interaction of super-intense ultra-short laser pulse and micro-clusters with large atomic clusters

International Nuclear Information System (INIS)

Miao Jingwei; Yang Chaowen; An Zhu; Yuan Xuedong; Sun Weiguo; Luo Xiaobing; Wang Hu; Bai Lixing; Shi Miangong; Miao Lei; Zhen Zhijian; Gu Yuqin; Liu Hongjie; Zhu Zhouseng; Sun Liwei; Liao Xuehua

2007-01-01

The fusion mechanism of large deuterium clusters (100-1000 Atoms/per cluster) in super-intense ultra-short laser pulse field, Coulomb explosions of micro-cluster in solids, gases and Large-size clusters have been studied using the interaction of a high-intensity femtosecond laser pulses with large deuterium clusters, collision of high-quality beam of micro-cluster from 2.5 MV van de Graaff accelerator with solids, gases and large clusters. The experimental advance of the project is reported. (authors)

Dependence of polar effect on parameters of coaxial plasma-erosive switches

International Nuclear Information System (INIS)

Bystritskij, V.M.; Ivanov, I.B.; Krasik, Ya.E.; Ryzhakin, N.N.; Sinebryukhov, A.A.; Tolmacheva, V.G.

1988-01-01

The results of experimental investigations and numerical simulation of the polar effect in a coaxial plasma-erosive switch (PES) established in a circuit of a strong-current nanosecond accelerator are presented. PES characteristics (energy losses, impedance, rate of its increase, etc.) are investigated depending on mutual direction of accelerator current and plasma flow as well as on the cathode radius in the PES region. It is experimentally shown that the magnetic fields near the cathode determined by this electrode radius influences mainly on PES characteristics. Mutual direction of accelerator current and plasma flow is the second significance factor influencing on PES characteristics. The optimal mode of PES operation is realized when providing the less with respect to the positive electrode, cathode radius and coinciding in direction accelerator current and plasma flow. Numerical simulation of dynamic processes in coaxial PES for different ratios of cathode and anode radii and mutual directions of accelerator current and plasma flow gives qualitative agreement with the experimental results

Cluster forcing

DEFF Research Database (Denmark)

Christensen, Thomas Budde

The cluster theory attributed to Michael Porter has significantly influenced industrial policies in countries across Europe and North America since the beginning of the 1990s. Institutions such as the EU, OECD and the World Bank and governments in countries such as the UK, France, The Netherlands...... or management. Both the Accelerate Wales and the Accelerate Cluster programmes target this issue by trying to establish networks between companies that can be used to supply knowledge from research institutions to manufacturing companies. The paper concludes that public sector interventions can make...... businesses. The universities were not considered by the participating companies to be important parts of the local business environment and inputs from universities did not appear to be an important source to access knowledge about new product development or new techniques in production, distribution...

Technical note on local adaptations to soil erosion and low soil ...

African Journals Online (AJOL)

This study explored the local adaptations to soil erosion and low soil water status in the semi arid Tharaka area in Kenya. Personal interviews and non-participant observations were used to solicit information from 137 small-scale farmers. A workshop was held in each of the three village clusters at the beginning and at the ...

Study on pipe wastage mechanism by liquid droplet impingement erosion

International Nuclear Information System (INIS)

Higashi, Yuma; Narabayashi, Tadashi; Shimazu, Yoichiro; Tsuji, Masashi; Ohmori, Shuichi; Mori, Michitsugu; Tezuka, Kenichi

2009-01-01

Evaluation of wastage speed for nuclear power plant maintains plant reliability and power up rating is important. There are two main cause of wastage flow accelerated corrosion (FAC) and mechanical erosion. This study is to develop evaluating the wastage speed by liquid droplet impingement erosion (LDIE). LDIE often occurs at downstream of corner of pipe or orifice. In this study, the liquid drop impinging tests were conducted with the test pieces mounted on a high speed rotating disk that cross thin water down jet and produced LDIE phenomena. The amount of the wastage by LDIE was evaluated by changing the rotational speed, the impingement frequency, and test piece materials. In addition, the generation mechanism of erosion was investigated by observing the surface of the test piece with a microscope. There is a method of evaluating by the mass difference before and after experiments. But this method is not correct because error becomes larger for mass measurement in the experiment, for the lost mass by LDIE is very little amount. Therefore, the method was developed to measure the volume in the erosion part. In this method, depth of LDIE was measured by the accuracy of ±0.01μm; therefore accurate measurement of the wastage can be improved. (author)

Contrasting Modern and 10Be- derived erosion rates for the Southern Betic Cordillera, Spain

Science.gov (United States)

Bellin, N.; Vanacker, V.; Kubik, P.

2012-04-01

In Europe, Southeast Spain was identified as one of the regions with major treat of desertification in the context of future land use and climate change. During the last years, significant progress has been made to understand spatial patterns of modern erosion rates in these semi-arid degraded environments. Numerous European projects have contributed to the collection of modern erosion data at different spatial scales for Southeast Spain. However, these data are rarely analysed in the context of long-term changes in vegetation, climate and human occupation. In this paper, we present Modern and Holocene denudation rates for small river basins (1 to 10 km2) located in the Spanish Betic Cordillera. Long-term erosion data were derived from cosmogenic nuclide analyses of river-borne sediment. Modern erosion data were quantified through analysis of sediment deposition volumes behind check dams, and represent average erosion rates over the last 10 to 40 years. Modern erosion rates are surprisingly low (mean erosion rate = 0.048 mm y-1; n=36). They indicate that the steep, sparsely vegetated hillslopes in the Betic Cordillera cannot directly be associated with high erosion rates. 10Be -derived erosion rates integrate over the last 37500 to 3500 years, and are roughly of the same magnitude. They range from 0.013 to 0.243 mm y-1 (mean denudation rate = 0.062 mm y-1 ± 0.054; n=20). Our data suggest that the modern erosion rates are similar to the long-term erosion rates in this area. This result is in contrast with the numerous reports on human-accelerated modern erosion rates for Southeast Spain. Interestingly, our new data on long-term erosion rates show a clear spatial pattern, with higher erosion rates in the Sierra Cabrera and lower erosion rates in Sierra de las Estancias, and Sierra Torrecilla. Preliminary geomorphometric analyses suggest that the spatial variation that we observe in long-term erosion rates is related to the gradient in uplift rates of the Betic

Mercury erosion experiments for spallation target system

International Nuclear Information System (INIS)

Kinoshita, Hidetaka; Kaminaga, Masanori; Haga, Katsuhiro; Hino, Ryutaro

2003-01-01

The Japan Atomic Energy Research Institute (JAERI) and the High Energy Accelerator Research Organization (KEK) are promoting a plan to construct the spallation neutron source at the Tokai Research Establishment, JAERI, under the High-Intensity Proton Accelerator Project (J-PARC). A mercury circulation system has been designed so as to supply mercury to the target stably under the rated flow rate of 41 m 3 /hr. Then, it was necessary to confirm a mercury pump performance from the viewpoint of making the mercury circulation system feasible, and more, to investigate erosion rate under the mercury flow as well as an amount of mercury remained on the surface after drain from the viewpoints of mechanical strength relating to the lifetime and remote handling of mercury components. The mercury pump performance was tested under the mercury flow conditions by using an experimental gear pump, which had almost the same structure as a practical mercury pump to be expected in the mercury circulation system, and the erosion rates in a mercury pipeline as well as the amount of mercury remained on the surface were also investigated. The discharged flow rates of the experimental gear pump increased linearly with the rotation speed, so that the gear pump would work as the flow meter. Erosion rates obtained under the mercury velocity less than 1.6 m/s was found to be so small that decrease of pipeline wall thickness would be 390 μm after 30-year operation under the rated mercury velocity of 0.7 m/s. For the amount of remaining mercury on the pipeline, remaining rates of weight and volume were estimated at 50.7 g/m 2 and 3.74 Hg-cm 3 /m 2 , respectively. Applying these remaining rates of weight and volume to the mercury target, the remaining mercury was estimated at about 106.5 g and 7.9 cm 3 . Radioactivity of this remaining mercury volume was found to be three-order lower than that of the target casing. (author)

Effects of oil on the rate and trajectory of Louisiana marsh shoreline erosion

International Nuclear Information System (INIS)

McClenachan, Giovanna; Eugene Turner, R; Tweel, Andrew W

2013-01-01

Oil can have long-term detrimental effects on marsh plant health, both above- and belowground. However, there are few data available that quantify the accelerated rate of erosion that oil may cause to marshes and the trajectory of change. Between November 2010 and August 2012, we collected data on shoreline erosion, soil strength, per cent cover of Spartina alterniflora, and marsh edge overhang at 30 closely spaced low oil and high oil sites in Bay Batiste, Louisiana. Surface oil samples were taken one meter into the marsh in February 2011. All high oiled sites in Bay Batiste were contaminated with Macondo 252 oil (oil from the Deepwater Horizon oil spill, 20 April–15 July 2010). The results suggest that there is a threshold where soil parameters change dramatically with a relatively small increase in oil concentration in the soil. Heavy oiling weakens the soil, creating a deeper undercut of the upper 50 cm of the marsh edge, and causing an accelerated rate of erosion that cascades along the shoreline. Our results demonstrate that it could take at least 2 yr to document the effects heavy oiling has had on the marsh shoreline. The presence of aboveground vegetation alone may not be an appropriate indicator of recovery. (letter)

Managing dental erosion.

Science.gov (United States)

Curtis, Donald A; Jayanetti, Jay; Chu, Raymond; Staninec, Michal

2012-01-01

The clinical signs of dental erosion are initially subtle, yet often progress because the patient remains asymptomatic, unaware and uninformed. Erosion typically works synergistically with abrasion and attrition to cause loss of tooth structure, making diagnosis and management complex. The purpose of this article is to outline clinical examples of patients with dental erosion that highlight the strategy of early identification, patient education and conservative restorative management. Dental erosion is defined as the pathologic chronic loss of dental hard tissues as a result of the chemical influence of exogenous or endogenous acids without bacterial involvement. Like caries or periodontal disease, erosion has a multifactorial etiology and requires a thorough history and examination for diagnosis. It also requires patient understanding and compliance for improved outcomes. Erosion can affect the loss of tooth structure in isolation of other cofactors, but most often works in synergy with abrasion and attrition in the loss of tooth structure (Table 1). Although erosion is thought to be an underlying etiology of dentin sensitivity, erosion and loss of tooth structure often occurs with few symptoms. The purpose of this article is threefold: first, to outline existing barriers that may limit early management of dental erosion. Second, to review the clinical assessment required to establish a diagnosis of erosion. And third, to outline clinical examples that review options to restore lost tooth structure. The authors have included illustrations they hope will be used to improve patient understanding and motivation in the early management of dental erosion.

Climate-sensitive feedbacks between hillslope processes and fluvial erosion in sediment-driven incision models

Science.gov (United States)

Skov, Daniel S.; Egholm, David L.

2016-04-01

Surface erosion and sediment production seem to have accelerated globally as climate cooled in the Late Cenozoic, [Molnar, P. 2004, Herman et al 2013]. Glaciers emerged in many high mountain ranges during the Quaternary, and glaciation therefore represents a likely explanation for faster erosion in such places. Still, observations and measurements point to increases in erosion rates also in landscapes where erosion is driven mainly by fluvial processes [Lease and Ehlers (2013), Reusser (2004)]. Flume experiments and fieldwork have shown that rates of incision are to a large degree controlled by the sediment load of streams [e.g. Sklar and Dietrich (2001), Beer and Turowski (2015)]. This realization led to the formulation of sediment-flux dependent incision models [Sklar and Dietrich (2004)]. The sediment-flux dependence links incision in the channels to hillslope processes that supply sediment to the channels. The rates of weathering and soil transport on the hillslopes are processes that are likely to respond to changing temperatures, e.g. because of vegetation changes or the occurrence of frost. In this study, we perform computational landscape evolution experiments, where the coupling between fluvial incision and hillslope processes is accounted for by coupling a sediment-flux-dependent model for fluvial incision to a climate-dependent model for weathering and hillslope sediment transport. The computational experiments first of all demonstrate a strong positive feedback between channel and hillslope processes. In general, faster weathering leads to higher rates of channel incision, which further increases the weathering rates, mainly because of hillslope steepening. Slower weathering leads to the opposite result. The experiments also demonstrate, however, that the feedbacks vary significantly between different parts of a drainage network. For example, increasing hillslope sediment production may accelerate incision in the upper parts of the catchment, while at

Comparison of erosion and erosion control works in Macedonia, Serbia and Bulgaria

Directory of Open Access Journals (Sweden)

Ivan Blinkov

2013-12-01

Natural conditions in the Balkan countries contribute to the appearance of various erosion forms and the intensity of the erosion processes. Over the history of these countries, people who settled this region used the available natural resources to fill their needs (tree cutting, incorrect plugging, overgrazing, which contributed to soil erosion. Organized erosion control works in the Balkans started in the beginning of the 20th century (1905 in Bulgaria. The highest intensity of erosion control works were carried out during the period 1945 – 1990. Various erosion control works were launched. Bulgaria had a large anti-erosion afforestation, almost 1 million ha. Bulgaria's ecological river restoration approach has been in use for almost 50 years. Serbia contributed significant erosion and torrent control works on hilly agricultural areas. Specific screen barrages and afforestation on extremely dry areas are characteristic in Macedonia. A common characteristic for all countries is a high decrease in erosion control works in the last 20 years.

Erosion-corrosion

International Nuclear Information System (INIS)

Aghili, B.

1999-05-01

A literature study on erosion-corrosion of pipings in the nuclear industry was performed. Occurred incidents are reviewed, and the mechanism driving the erosion-corrosion is described. Factors that influence the effect in negative or positive direction are treated, as well as programs for control and inspection. Finally, examples of failures from databases on erosion-corrosion are given in an attachment

Plasma-based and novel accelerators

International Nuclear Information System (INIS)

Sugihara, Ryo; Nishida, Yasushi

1992-05-01

This publication is a collection of papers presented at Workshop on Plasma-Based and Novel Accelerators held at National Institute for Fusion Science, Nagoya, on December 19-20, 1991. Plasma-based accelerators are attracting considerable attention in these days a new, exciting field of plasma applications. The study gives rise to and spurs study of other unique accelerators like laser-based accelerators. The talks in the Workshop encompassed beat-wave accelerator (BWA), plasma wake field accelerator (PWFA), V p x B accelerator, laser-based accelerators and some novel methods of acceleration. They also covered the topics such as FEL, cluster acceleration and plasma lens. Small scale experiments as those in universities have exhibited brilliant results while larger scale experiments like BWA in Institute of Laser Engineering, Osaka University, and PWFA in KEK start showing significant results as well. (J.P.N.)

The Impact of Sea Ice Loss on Wave Dynamics and Coastal Erosion Along the Arctic Coast

Science.gov (United States)

Overeem, I.; Anderson, R. S.; Wobus, C. W.; Matell, N.; Urban, F. E.; Clow, G. D.; Stanton, T. P.

2010-12-01

The extent of Arctic sea ice has been shrinking rapidly over the past few decades, and attendant acceleration of erosion is now occurring along the Arctic coast. This both brings coastal infrastructure into harm’s way and promotes a complex response of the adjacent landscape to global change. We quantify the effects of declining sea ice extent on coastal erosion rates along a 75-km stretch of coastal permafrost bluffs adjacent to the Beaufort Sea, Alaska, where present-day erosion rates are among the highest in the world at ~14 m yr-1. Our own observations reinforce those of others, and suggest that the rate-limiting process is thermal erosion at the base of the several-meter tall bluffs. Here we focus on the interaction between the nearshore sea ice concentration, the location of the sea ice margin, and the fetch-limited, shallow water wave field, since these parameters ultimately control both sea surface temperatures and the height to which these waters can bathe the frozen bluffs. Thirty years of daily or bi-daily passive microwave data from Nimbus-7 SMMR and DMSP SSM/I satellites reveal that the nearshore open water season lengthened ~54 days over 1979-2009. The open water season, centered in August, expands more rapidly into the fall (September and October~0.92 day yr-1) than into the early summer (July~0.71 days yr-1). Average fetch, defined for our purposes as the distance from the sea ice margin to the coast over which the wind is blowing, increased by a factor 1.7 over the same time-span. Given these time series, we modeled daily nearshore wave heights during the open water season for each year, which we integrated to provide a quantitative metric for the annual exposure of the coastal bluffs to thermal erosion. This “annual wave exposure” increased by 250% during 1979-2009. In the same interval, coastal erosion rates reconstructed from satellite and aerial photo records show less acceleration. We attribute this to a disproportionate extension of the

Manufacturing issues which affect coating erosion performance in wind turbine blades

Science.gov (United States)

Cortés, E.; Sánchez, F.; Domenech, L.; Olivares, A.; Young, T. M.; O'Carroll, A.; Chinesta, F.

2017-10-01

Erosion damage, caused by repeated rain droplet impact on the leading edges of wind turbine blades, is a major cause for cost concern. Resin Infusion (RI) is used in wind energy blades where low weight and high mechanical performance materials are demanded. The surface coating plays a crucial role in the manufacturing and performance response. The Leading Edge coating is usually moulded, painted or sprayed onto the blade surface so adequate adhesion in the layers' characterization through the thickness is required for mechanical performance and durability reasons. In the current work, an investigation has been directed into the resulting rain erosion durability of the coating was undertaken through a combination of mass loss testing measurements with manufacturing processing parameter variations. The adhesion and erosion is affected by the shock wave caused by the collapsing water droplet on impact. The stress waves are transmitted to the substrate, so microestructural discontinuities in coating layers and interfaces play a key role on its degradation. Standard industrial systems are based on a multilayer system, with a high number of interfaces that tend to accelerate erosion by delamination. Analytical and numerical models are commonly used to relate lifetime prediction and to identify suitable coating and composite substrate combinations and their potential stress reduction on the interface. In this research, the input parameters for the appropriate definition of the Cohesive Zone Modelling (CZM) of the coating-substrate interface are outlined by means of Pull off testing and Peeling testing results. It allowed one to optimize manufacturing and coating process for blades into a knowledge-based guidance for leading edge coating material development. It was achieved by investigating the erosion degradation process using both numerical and laboratory techniques (Pull off, Peeling and Rain Erosion Testing in a whirling arm rain erosion test facility).

Linking rapid erosion of the Mekong River delta to human activities.

Science.gov (United States)

Anthony, Edward J; Brunier, Guillaume; Besset, Manon; Goichot, Marc; Dussouillez, Philippe; Nguyen, Van Lap

2015-10-08

As international concern for the survival of deltas grows, the Mekong River delta, the world's third largest delta, densely populated, considered as Southeast Asia's most important food basket, and rich in biodiversity at the world scale, is also increasingly affected by human activities and exposed to subsidence and coastal erosion. Several dams have been constructed upstream of the delta and many more are now planned. We quantify from high-resolution SPOT 5 satellite images large-scale shoreline erosion and land loss between 2003 and 2012 that now affect over 50% of the once strongly advancing >600 km-long delta shoreline. Erosion, with no identified change in the river's discharge and in wave and wind conditions over this recent period, is consistent with: (1) a reported significant decrease in coastal surface suspended sediment from the Mekong that may be linked to dam retention of its sediment, (2) large-scale commercial sand mining in the river and delta channels, and (3) subsidence due to groundwater extraction. Shoreline erosion is already responsible for displacement of coastal populations. It is an additional hazard to the integrity of this Asian mega delta now considered particularly vulnerable to accelerated subsidence and sea-level rise, and will be exacerbated by future hydropower dams.

Plasma heating by cluster injection: basic features and expected behaviour

International Nuclear Information System (INIS)

Bottiglioni, F.; Coutant, J.; Fois, M.; CEA Centre d'Etudes Nucleaires de Fontenay-aux-Roses, 92

1976-01-01

Each main component of an injection line (beam source, cluster ionizer, accelerating tube) is briefly discussed together with the behavior of clusters interacting with a plasma. Outlines of the experiment of cluster injection into TFR, in progress at Fontenay-aux-Roses are presented and discussed all along the paper. It is shown that high current densities at rather low energy per atom can be obtained by accelerated cluster beams. In present size toroidal devices, both ion temperature and density can be increased simultaneously without heating electrons. This feature could be attractive as long as tokamak losses are dominated by electrons. The extrapolation of the ionizers under construction does not seem to present much difficulty; on the contrary, the accelerating tube could be the most serious problem to solve. (40 references)

Characteristics of pulsed runoff-erosion events under typical rainstorms in a small watershed on the Loess Plateau of China.

Science.gov (United States)

Wu, Lei; Jiang, Jun; Li, Gou-Xia; Ma, Xiao-Yi

2018-02-27

The pulsed events of rainstorm erosion on the Loess Plateau are well-known, but little information is available concerning the characteristics of superficial soil erosion processes caused by heavy rainstorms at the watershed scale. This study statistically evaluated characteristics of pulsed runoff-erosion events based on 17 observed rainstorms from 1997-2010 in a small loess watershed on the Loess Plateau of China. Results show that: 1) Rainfall is the fundamental driving force of soil erosion on hillslopes, but the correlations of rainfall-runoff and rainfall-sediment in different rainstorms are often scattered due to infiltration-excess runoff and soil conservation measures. 2) Relationships between runoff and sediment for each rainstorm event can be regressed by linear, power, logarithmic and exponential functions. Cluster Analysis is helpful in classifying runoff-erosion events and formulating soil conservation strategies for rainstorm erosion. 3) Response characteristics of sediment yield are different in different levels of pulsed runoff-erosion events. Affected by rainfall intensity and duration, large changes may occur in the interactions between flow and sediment for different flood events. Results provide new insights into runoff-erosion processes and will assist soil conservation planning in the loess hilly region.

Lifespan of mountain ranges scaled by feedbacks between landsliding and erosion by rivers.

Science.gov (United States)

Egholm, David L; Knudsen, Mads F; Sandiford, Mike

2013-06-27

An important challenge in geomorphology is the reconciliation of the high fluvial incision rates observed in tectonically active mountain ranges with the long-term preservation of significant mountain-range relief in ancient, tectonically inactive orogenic belts. River bedrock erosion and sediment transport are widely recognized to be the principal controls on the lifespan of mountain ranges. But the factors controlling the rate of erosion and the reasons why they seem to vary significantly as a function of tectonic activity remain controversial. Here we use computational simulations to show that the key to understanding variations in the rate of erosion between tectonically active and inactive mountain ranges may relate to a bidirectional coupling between bedrock river incision and landslides. Whereas fluvial incision steepens surrounding hillslopes and increases landslide frequency, landsliding affects fluvial erosion rates in two fundamentally distinct ways. On the one hand, large landslides overwhelm the river transport capacity and cause upstream build up of sediment that protects the river bed from further erosion. On the other hand, in delivering abrasive agents to the streams, landslides help accelerate fluvial erosion. Our models illustrate how this coupling has fundamentally different implications for rates of fluvial incision in active and inactive mountain ranges. The coupling therefore provides a plausible physical explanation for the preservation of significant mountain-range relief in old orogenic belts, up to several hundred million years after tectonic activity has effectively ceased.

Modeling erosion of unsaturated compacted bentonite by groundwater flow; pinhole erosion test case

International Nuclear Information System (INIS)

Laurila, T.; Sane, P.; Olin, M.; Koskinen, K.

2012-01-01

Document available in extended abstract form only. Erosion of compacted clay material by water flow is a critical factor affecting the performance of radioactive waste confinement. Our emphasis in this work is the buffer of KBS-3V concept, proposed to be compacted MX-80 bentonite. Unsaturated erosion occurs during the saturation phase of the EBS, and the main quantity of interest is the total buffer mass carried away by a groundwater flow that induces erosion by forming piping channels near the buffer/rock interface. The purpose of this work is to provide modeling tools to support erosion experiments. Role of modeling is first to interpret experimental observations in terms of processes, and to estimate robustness of experimental results. Secondly, we seek to scale up results from the laboratory scale, particularly to time scales longer than those experimentally accessible. We have performed modeling and data analysis pertaining to tests of unsaturated clay erosion. Pinhole experiments were used to study this erosion case. The main differences to well-understood pinhole erosion tests are that the material is strongly swelling and that the water flow is not determined by the pressure head but by the total flux. Groundwater flow in the buffer is determined by the flux because pressure losses occur overwhelmingly in the surrounding rock, not in the piping channel. We formulate a simple model that links an effective solid diffusivity -based swelling model to erosion by flow on the solid/liquid interface. The swelling model is similar in concept to that developed at KTH, but simpler. Erosion in the model is caused by laminar flow in the pinhole, and happens in a narrow region at the solid/liquid interface where velocity and solid volume fraction overlap. The erosion model can be mapped to erosion by wall shear, and can thus be considered as extension of that classic erosion model. The main quantity defining the behavior of clay erosion in the model is the ratio of

Erosion products of ITER divertor materials under plasma disruption simulation

Energy Technology Data Exchange (ETDEWEB)

Guseva, M.I.; Gureev, V.M.; Kolbasov, B.N.; Korshunov, S.N.; Martynenko, Yu.V. E-mail: martyn@nfi.kiae.ru; Stolyarova, V.G.; Strunnikov, V.M.; Vasiliev, V.I

2003-09-01

Candidate ITER divertor armor materials: carbon-fiber-composite and four tungsten grades/alloys as well as mixed re-deposited W+Be and W+C layers were exposed in electrodynamic plasma accelerator MKT which provided a pulsed deuterium plasma flux simulating plasma disruptions with maximum ion energy of 1-2 keV, an energy density of 300 kJ/m{sup 2} per shot and a pulse duration of {approx}60 {mu}s. The number of pulses was from 2 to 10. The resultant erosion products were collected on a basalt filter and Si-collectors and studied in terms of morphology and size distribution using both scanning and transmission electron microscopy. Metal erosion products usually occurred in the form of spherical droplets, sometimes flakes. Their size distribution depended on the positioning of the collector. Simultaneously irradiated W, CFC and mixed W+Be targets appeared to have undergone a greater erosion than the same targets irradiated individually. Particles sized from 0.01 to 30 {mu}m were found on collectors and on a molten W-surface. A model of droplet emission and behavior in shielding plasma is provided.

Electromagnetic forming - a potentially viable technique for accelerator technology

International Nuclear Information System (INIS)

Rajawat, R.K.; Desai, S.V.; Kulkarni, M.R.; Dolly Rani; Nagesh, K.V.; Sethi, R.C.

2003-01-01

Modern day accelerator development encompasses a myriad technologies required for their diverse needs. Whereas RF, high voltage, vacuum, cryogenics etc., technologies meet their functional requirements, high finish lapping processes, ceramic-metal joining, oven brazing, spark erosion or wire cutting etc., are a must to meet their fabrication requirements. Electromagnetic (EM) forming technique falls in the latter category and is developed as a special technology. It is currently catering to the development as a nuclear reactor technology, but has the potential to meet accelerator requirements too. This paper highlights the general principle of its working, simple design guidelines, advantages, and suggests some specific areas where this could benefit accelerator technologies

Rainfall Erosivity in Europe

DEFF Research Database (Denmark)

Panagos, Panos; Ballabio, Cristiano; Borrelli, Pasquale

2015-01-01

Rainfall is one the main drivers of soil erosion. The erosive force of rainfall is expressed as rainfall erosivity. Rainfall erosivity considers the rainfall amount and intensity, and is most commonly expressed as the Rfactor in the USLE model and its revised version, RUSLE. At national...... and continental levels, the scarce availability of data obliges soil erosion modellers to estimate this factor based on rainfall data with only low temporal resolution (daily, monthly, annual averages). The purpose of this study is to assess rainfall erosivity in Europe in the form of the RUSLE R-factor, based...

The effectiveness of aerial hydromulch as an erosion control treatment in burned chaparral watersheds

Science.gov (United States)

Pete Wohlgemuth; Jan Beyers; Pete Robichaud

2011-01-01

High severity wildfire can make watersheds susceptible to accelerated erosion, which impedes resource recovery and threatens life, property, and infrastructure in downstream human communities. Land managers often use mitigation measures on the burned hillside slopes to reduce postfire sediment fluxes. Hydromulch, a slurry of paper or wood fiber that dries to a...

Estimating surface soil erosion losses and mapping erosion risk for Yusufeli micro-catchment (Artvin

Directory of Open Access Journals (Sweden)

Mustafa Tüfekçioğlu

2016-10-01

Full Text Available Sheet erosion, one of the most important types of water erosion, takes place on the top soil as tiny soil layer movement that affects lake and stream ecosystem. This type of erosion is very important because the productive soil layer on the top soil can be lost in a very short period of time. The goal of this study was to quantify the amount of surface (sheet and rill soil erosion, and to identify areas under high erosion risk within the study area at Yusufeli province in Artvin by using RUSLE erosion methodology. As a result of the study it was found that the average annual potential soil loss by surface erosion was 3.6 ton ha-1yr-1. Additionally, the maps produced and conclusions reached by the study revealed that the areas of high erosion risk were identified spatially and measures to control erosion on some of these high risk areas can be possible with appropriate erosion control techniques.

THE USE OF BIOTEXTILES TO RECUPERATE DEGRADADED AREAS BY EROSION

Directory of Open Access Journals (Sweden)

Marcia Silva Furtado

2005-05-01

Full Text Available The erosion is a process that results from the conjunct action of many natural agents over the grounds. However, this process can be accelerated, mainly by the action of the human being that has caused numerous degrading actions of the environment, depending on the level of intensity and from the characteristic of his intervention. Among the ways of degradation it is possible to stand out accelerated erosive processes, like ravines and gullies.These processes can be mitigated with the use of several technical and material alternatives, being necessary specific knowledge for the right choice, in each case.In São Luís, a research project started since 2002 and thanks this project, it was indentified and monitorated several erosive processes with high degree of evolution, like gullies in Salina, Sacavém, Araçagi, Castelão, Bequimão, Coeduc, Santa Eulália site, among others.After these phases of the recognition and monitoration, the efforts for recuperation of the degraded areas have been developed with the use of bioengineering techniques. Such initiatives have been applied in different situations, with positive results for being an alternative which makes use of biodegradable materials such as vegetal fibers, wooden stakes, rigid iron-like structures, besides vegetation to make the soil more stable, lowering the costs and providing improvement to the environmental balance. Firstly, biodegradable screens, made of buriti, carnaúba, tucum, babaçu and marajá palm will be installed, as a matter of an experiment, at Sacavém’s gully, in São Luís – Maranhão State.The choice of the gullies in Sacavém occured because the necessity of the area, once this area offers serious risks to the population around, but later the project is going to contemplate the other monitored areas.

The comparison of various approach to evaluation erosion risks and design control erosion measures

Science.gov (United States)

Kapicka, Jiri

2015-04-01

In the present is in the Czech Republic one methodology how to compute and compare erosion risks. This methodology contain also method to design erosion control measures. The base of this methodology is Universal Soil Loss Equation (USLE) and their result long-term average annual rate of erosion (G). This methodology is used for landscape planners. Data and statistics from database of erosion events in the Czech Republic shows that many troubles and damages are from local episodes of erosion events. An extent of these events and theirs impact are conditional to local precipitation events, current plant phase and soil conditions. These erosion events can do troubles and damages on agriculture land, municipally property and hydro components and even in a location is from point of view long-term average annual rate of erosion in good conditions. Other way how to compute and compare erosion risks is episodes approach. In this paper is presented the compare of various approach to compute erosion risks. The comparison was computed to locality from database of erosion events on agricultural land in the Czech Republic where have been records two erosion events. The study area is a simple agriculture land without any barriers that can have high influence to water flow and soil sediment transport. The computation of erosion risks (for all methodology) was based on laboratory analysis of soil samples which was sampled on study area. Results of the methodology USLE, MUSLE and results from mathematical model Erosion 3D have been compared. Variances of the results in space distribution of the places with highest soil erosion where compared and discussed. Other part presents variances of design control erosion measures where their design was done on based different methodology. The results shows variance of computed erosion risks which was done by different methodology. These variances can start discussion about different approach how compute and evaluate erosion risks in areas

Large-Scale Multi-Dimensional Document Clustering on GPU Clusters

Energy Technology Data Exchange (ETDEWEB)

Cui, Xiaohui [ORNL; Mueller, Frank [North Carolina State University; Zhang, Yongpeng [ORNL; Potok, Thomas E [ORNL

2010-01-01

Document clustering plays an important role in data mining systems. Recently, a flocking-based document clustering algorithm has been proposed to solve the problem through simulation resembling the flocking behavior of birds in nature. This method is superior to other clustering algorithms, including k-means, in the sense that the outcome is not sensitive to the initial state. One limitation of this approach is that the algorithmic complexity is inherently quadratic in the number of documents. As a result, execution time becomes a bottleneck with large number of documents. In this paper, we assess the benefits of exploiting the computational power of Beowulf-like clusters equipped with contemporary Graphics Processing Units (GPUs) as a means to significantly reduce the runtime of flocking-based document clustering. Our framework scales up to over one million documents processed simultaneously in a sixteennode GPU cluster. Results are also compared to a four-node cluster with higher-end GPUs. On these clusters, we observe 30X-50X speedups, which demonstrates the potential of GPU clusters to efficiently solve massive data mining problems. Such speedups combined with the scalability potential and accelerator-based parallelization are unique in the domain of document-based data mining, to the best of our knowledge.

The application of high-speed photography and spectrography for investigations of erosive pulsed plasma streams

International Nuclear Information System (INIS)

Kiselevskiy, L.I.; Minko, L.Ja.

The extensive information of pulsed plasma dynamic processes related to formation and interaction of plasma streams with a surrounding medium and obstacles is obtained with the help of high-speed photo and spectrography. The wave structure of pulsed supersonic under-expanded erosive plasma jets is studied. Some physical processes which are due to interactions of laser radiation with the laser-produced erosive plasma and of this plasma with a surrounding medium are investigated. The wide possibilities of frame photography of spectra quantitative spectroscopic investigations of fast-proceeding plasma processes are shown on the basis of joint use of high-speed photographic apparatus (type SFR) and standard spectrographs. The radial distribution of charged-particle concentrations at separate moments of time is obtained from the broadening of spectral lines at the brightness of the continuous spectrum of an erosive plasma jet from a pulsed accelerator

Improving Erosion Resistance of Plasma-Sprayed Ceramic Coatings by Elevating the Deposition Temperature Based on the Critical Bonding Temperature

Science.gov (United States)

Yao, Shu-Wei; Yang, Guan-Jun; Li, Cheng-Xin; Li, Chang-Jiu

2018-01-01

Interlamellar bonding within plasma-sprayed coatings is one of the most important factors dominating the properties and performance of coatings. The interface bonding between lamellae significantly influences the erosion behavior of plasma-sprayed ceramic coatings. In this study, TiO2 and Al2O3 coatings with different microstructures were deposited at different deposition temperatures based on the critical bonding temperature concept. The erosion behavior of ceramic coatings was investigated. It was revealed that the coatings prepared at room temperature exhibit a typical lamellar structure with numerous unbonded interfaces, whereas the coatings deposited at the temperature above the critical bonding temperature present a dense structure with well-bonded interfaces. The erosion rate decreases sharply with the improvement of interlamellar bonding when the deposition temperature increases to the critical bonding temperature. In addition, the erosion mechanisms of ceramic coatings were examined. The unbonded interfaces in the conventional coatings act as pre-cracks accelerating the erosion of coatings. Thus, controlling interlamellar bonding formation based on the critical bonding temperature is an effective approach to improve the erosion resistance of plasma-sprayed ceramic coatings.

Watershed sediment losses to lakes accelerating despite agricultural soil conservation efforts.

Science.gov (United States)

Heathcote, Adam J; Filstrup, Christopher T; Downing, John A

2013-01-01

Agricultural soil loss and deposition in aquatic ecosystems is a problem that impairs water quality worldwide and is costly to agriculture and food supplies. In the US, for example, billions of dollars have subsidized soil and water conservation practices in agricultural landscapes over the past decades. We used paleolimnological methods to reconstruct trends in sedimentation related to human-induced landscape change in 32 lakes in the intensively agricultural region of the Midwestern United States. Despite erosion control efforts, we found accelerating increases in sediment deposition from erosion; median erosion loss since 1800 has been 15.4 tons ha(-1). Sediment deposition from erosion increased >6-fold, from 149 g m(-2) yr(-1) in 1850 to 986 g m(-2) yr(-1) by 2010. Average time to accumulate one mm of sediment decreased from 631 days before European settlement (ca. 1850) to 59 days mm(-1) at present. Most of this sediment was deposited in the last 50 years and is related to agricultural intensification rather than land clearance or predominance of agricultural lands. In the face of these intensive agricultural practices, traditional soil conservation programs have not decelerated downstream losses. Despite large erosion control subsidies, erosion and declining water quality continue, thus new approaches are needed to mitigate erosion and water degradation.

Acceleration of O+ from the cusp to the plasma sheet

Science.gov (United States)

Liao, J.; Kistler, L. M.; Mouikis, C. G.; Klecker, B.; Dandouras, I.

2015-02-01

Heavy ions from the ionosphere that are accelerated in the cusp/cleft have been identified as a direct source for the hot plasma in the plasma sheet. However, the details of the acceleration and transport that transforms the originally cold ions into the hot plasma sheet population are not fully understood. The polar orbit of the Cluster satellites covers the main transport path of the O+ from the cusp to the plasma sheet, so Cluster is ideal for tracking its velocity changes. However, because the cusp outflow is dispersed according to its velocity as it is transported to the tail, due to the velocity filter effect, the observed changes in beam velocity over the Cluster orbit may simply be the result of the spacecraft accessing different spatial regions and not necessarily evidence of acceleration. Using the Cluster Ion Spectrometry/Composition Distribution Function instrument onboard Cluster, we compare the distribution function of streaming O+ in the tail lobes with the initial distribution function observed over the cusp and reveal that the observations of energetic streaming O+ in the lobes around -20 RE are predominantly due to the velocity filter effect during nonstorm times. During storm times, the cusp distribution is further accelerated. In the plasma sheet boundary layer, however, the average O+ distribution function is above the upper range of the outflow distributions at the same velocity during both storm and nonstorm times, indicating that acceleration has taken place. Some of the velocity increase is in the direction perpendicular to the magnetic field, indicating that the E × B velocity is enhanced. However, there is also an increase in the parallel direction, which could be due to nonadiabatic acceleration at the boundary or wave heating.

Predicting of soil erosion with regarding to rainfall erosivity and soil erodibility

Science.gov (United States)

Suif, Zuliziana; Razak, Mohd Amirun Anis Ab; Ahmad, Nordila

2018-02-01

The soil along the hill and slope are wearing away due to erosion and it can take place due to occurrence of weak and heavy rainfall. The aim of this study is to predict the soil erosion degree in Universiti Pertahanan Nasional Malaysia (UPNM) area focused on two major factor which is soil erodibility and rainfall erosivity. Soil erodibility is the possibilities of soil to detach and carried away during rainfall and runoff. The "ROM" scale was used in this study to determine the degree of soil erodibility, namely low, moderate, high, and very high. As for rainfall erosivity, the erosive power caused by rainfall that cause soil loss. A daily rainfall data collected from January to April was analyzed by using ROSE index classification to identify the potential risk of soil erosion. The result shows that the soil erodibilty are moderate at MTD`s hill, high at behind of block Lestari and Landslide MTD hill, and critical at behind the mess cadet. While, the highest rainfall erosivity was recorded in March and April. Overall, this study would benefit the organization greatly in saving cost in landslide protection as relevant authorities can take early measures repairing the most affected area of soil erosion.

Mesh erosion after abdominal sacrocolpopexy.

Science.gov (United States)

Kohli, N; Walsh, P M; Roat, T W; Karram, M M

1998-12-01

To report our experience with erosion of permanent suture or mesh material after abdominal sacrocolpopexy. A retrospective chart review was performed to identify patients who underwent sacrocolpopexy by the same surgeon over 8 years. Demographic data, operative notes, hospital records, and office charts were reviewed after sacrocolpopexy. Patients with erosion of either suture or mesh were treated initially with conservative therapy followed by surgical intervention as required. Fifty-seven patients underwent sacrocolpopexy using synthetic mesh during the study period. The mean (range) postoperative follow-up was 19.9 (1.3-50) months. Seven patients (12%) had erosions after abdominal sacrocolpopexy with two suture erosions and five mesh erosions. Patients with suture erosion were asymptomatic compared with patients with mesh erosion, who presented with vaginal bleeding or discharge. The mean (+/-standard deviation) time to erosion was 14.0+/-7.7 (range 4-24) months. Both patients with suture erosion were treated conservatively with estrogen cream. All five patients with mesh erosion required transvaginal removal of the mesh. Mesh erosion can follow abdominal sacrocolpopexy over a long time, and usually presents as vaginal bleeding or discharge. Although patients with suture erosion can be managed successfully with conservative treatment, patients with mesh erosion require surgical intervention. Transvaginal removal of the mesh with vaginal advancement appears to be an effective treatment in patients failing conservative management.

Susceptibility of bovine dental enamel with initial erosion lesion to new erosive challenges.

Science.gov (United States)

Oliveira, Gabriela Cristina de; Tereza, Guida Paola Genovez; Boteon, Ana Paula; Ferrairo, Brunna Mota; Gonçalves, Priscilla Santana Pinto; Silva, Thiago Cruvinel da; Honório, Heitor Marques; Rios, Daniela

2017-01-01

This in vitro study evaluated the impact of initial erosion on the susceptibility of enamel to further erosive challenge. Thirty bovine enamel blocks were selected by surface hardness and randomized into two groups (n = 15): GC- group composed by enamel blocks without erosion lesion and GT- group composed by enamel blocks with initial erosion lesion. The baseline profile of each block was determined using the profilometer. The initial erosion was produced by immersing the blocks into HCl 0.01 M, pH 2.3 for 30 seconds, under stirring. The erosive cycling consisted of blocks immersion in hydrochloric acid (0.01 M, pH 2.3) for 2 minutes, followed by immersion in artificial saliva for 120 minutes. This procedure was repeated 4 times a day for 5 days, and the blocks were kept in artificial saliva overnight. After erosive cycling, final profile measurement was performed. Profilometry measured the enamel loss by the superposition of initial and final profiles. Data were analyzed by t-test (perosion on bovine dental enamel does not enhance its susceptibility to new erosive challenges.

Susceptibility of bovine dental enamel with initial erosion lesion to new erosive challenges.

Directory of Open Access Journals (Sweden)

Gabriela Cristina de Oliveira

Full Text Available This in vitro study evaluated the impact of initial erosion on the susceptibility of enamel to further erosive challenge. Thirty bovine enamel blocks were selected by surface hardness and randomized into two groups (n = 15: GC- group composed by enamel blocks without erosion lesion and GT- group composed by enamel blocks with initial erosion lesion. The baseline profile of each block was determined using the profilometer. The initial erosion was produced by immersing the blocks into HCl 0.01 M, pH 2.3 for 30 seconds, under stirring. The erosive cycling consisted of blocks immersion in hydrochloric acid (0.01 M, pH 2.3 for 2 minutes, followed by immersion in artificial saliva for 120 minutes. This procedure was repeated 4 times a day for 5 days, and the blocks were kept in artificial saliva overnight. After erosive cycling, final profile measurement was performed. Profilometry measured the enamel loss by the superposition of initial and final profiles. Data were analyzed by t-test (p<0.05. The result showed no statistically significant difference between groups (GS = 14.60±2.86 and GE = .14.69±2.21 μm. The presence of initial erosion on bovine dental enamel does not enhance its susceptibility to new erosive challenges.

Soil physical properties affecting soil erosion in tropical soils

International Nuclear Information System (INIS)

Lobo Lujan, D.

2004-01-01

The total vegetated land area of the earth is about 11,500 hectare. Of this, about 12% is in South America. Of this, about 14% is degraded area. Water erosion, chemical degradation, wind erosion, and physical degradation have been reported as main types of degradation. In South America water erosion is a major process for soil degradation. Nevertheless, water erosion can be a consequence of degradation of the soil structure, especially the functional attributes of soil pores to transmit and retain water, and to facilitate root growth. Climate, soil and topographic characteristics determine runoff and erosion potential from agricultural lands. The main factors causing soil erosion can be divided into three groups: Energy factors: rainfall erosivity, runoff volume, wind strength, relief, slope angle, slope length; Protection factors: population density, plant cover, amenity value (pressure for use) and land management; and resistance factors: soil erodibility, infiltration capacity and soil management. The degree of soil erosion in a particular climatic zone, with particular soils, land use and socioeconomic conditions, will always result from a combination of the above mentioned factors. It is not easy to isolate a single factor. However, the soil physical properties that determine the soil erosion process, because the deterioration of soil physical properties is manifested through interrelated problems of surface sealing, crusting, soil compaction, poor drainage, impeded root growth, excessive runoff and accelerated erosion. When an unprotected soil surface is exposed to the direct impact of raindrops it can produce different responses: Production of smaller aggregates, dispersed particles, particles in suspension and translocation and deposition of particles. When this has occurred, the material is reorganized at the location into a surface seal. Aggregate breakdown under rainfall depends on soil strength and a certain threshold kinetic energy is needed to start

Cause Analysis of Flow Accelerated Corrosion and Erosion-Corrosion Cases in Korea Nuclear Power Plants

Energy Technology Data Exchange (ETDEWEB)

Lee, Y. S.; Lee, S. H. [Korea Hydro and Nuclear Power Co., Ltd., Gyeongju (Korea, Republic of); Hwang, K. M. [KEPCO Engineering and Construction Company, Gimcheon (Korea, Republic of)

2016-08-15

Significant piping wall thinning caused by Flow-Accelerated Corrosion (FAC) and Erosion-Corrosion (EC) continues to occur, even after the Mihama Power Station unit 3 secondary pipe rupture in 2004, in which workers were seriously injured or died. Nuclear power plants in many countries have experienced FAC and EC-related cases in steam cycle piping systems. Korea has also experienced piping wall thinning cases including thinning in the downstream straight pipe of a check valve in a feedwater pump line, the downstream elbow of a control valve in a feedwater flow control line, and failure of the straight pipe downstream of an orifice in an auxiliary steam return line. Cause analyses were performed by reviewing thickness data using Ultrasonic Techniques (UT) and, Scanning Electron Microscope (SEM) images for the failed pipe, and numerical simulation results for FAC and EC cases in Korea Nuclear Power Plants. It was concluded that the main cause of wall thinning for the downstream pipe of a check valve is FAC caused by water vortex flow due to the internal flow shape of a check valve, the main cause of wall thinning for the downstream elbow of a control valve is FAC caused by a thickness difference with the upstream pipe, and the main cause of wall thinning for the downstream pipe of an orifice is FAC and EC caused by liquid droplets and vortex flow. In order to investigate more cases, additional analyses were performed with the review of a lot of thickness data for inspected pipes. The results showed that pipe wall thinning was also affected by the operating condition of upstream equipment. Management of FAC and EC based on these cases will focus on the downstream piping of abnormal or unusual operated equipment.

Dental erosion among children aged 3-6 years and its associated indicators.

Science.gov (United States)

Tao, Dan-Ying; Hao, Gu; Lu, Hai-Xia; Tian, Yu; Feng, Xi-Ping

2015-01-01

To analyze the status quo of dental erosion in 3- to 6-year-old children in Shanghai. A stratified, cluster, multistage random sampling methods was applied to 3- to 6-year-old children in Shanghai in 2012. Both questionnaire and clinical oral examination were performed in the survey. The questionnaire included general information, such as age, gender, parental education, dietary habit, oral health behavior, general medical health, and socioeconomic status. The clinical examination focused on the eroded tooth surface and dental erosion extent. SPSS v19.0 software package was utilized for statistical analysis. A total of 1,837 children aged 3-6 years were randomly selected in Shanghai. The overall dental erosion prevalence was 15.1 percent. Among different age groups, a relatively high prevalence of 17.1 percent was found in the 4-year-old group, and a relatively low prevalence of 12.0 percent was observed in the 3-year-old group. Surprisingly, there was no significant difference among the four age groups. The occurrence of dental erosion was influenced by habits of vinegar/coffee/tea consumption, mother's educational background, birthplace, and regurgitation (P dental erosion prevalence in 3- to 6-year-old children in Shanghai appears to be close to that of other Chinese provinces as well as that observed in most of surveys carried out in different parts of the world. Efforts should be made to raise public awareness about the disease. Moreover, further studies targeted to explore the relationship between dental erosion and risk factors are needed. It is also necessary to establish a unified diagnostic standard for future epidemiological investigations. © 2015 American Association of Public Health Dentistry.

On the geoethical implications of wind erosion

Science.gov (United States)

Károly, Tatárvári

2016-04-01

precipitation changes, this also increases the occurrence of bush-fires, and the growing extent of uncovered soil surface shall intensify wind erosion as well accelerating the negative effects described above. Who will be held responsible for this? Who should bear the larger cost of production in agriculture that is caused by the cost of research necessary to uncover the methods of prevention of irreversible damages caused in nature and environment? Because the field of research requires an interdisciplinary approach, research and innovation requires huge funds, the different approaches to the problem in every single field, and different reasoning methods represent a hurdle as well. In search for possible solutions it is necessary that political decision-makers adopt regulations which have solid scientific fundamentals, and also the cooperation of mankind active in science and economy is crucial. This is the only way of finding sustainable and long term solutions to the problem.

Protection from erosion following wildfire

Science.gov (United States)

Peter R. Robichaud; William J. Elliot

2006-01-01

Erosion in the first year after a wildfire can be up to three orders of magnitude greater than the erosion from undisturbed forests. To mitigate potential postfire erosion, various erosion control treatments are applied on highly erodible areas with downstream resources in need of protection. Because postfire erosion rates generally decline by an order of magnitude for...

Erosivity, surface runoff, and soil erosion estimation using GIS-coupled runoff-erosion model in the Mamuaba catchment, Brazil.

Science.gov (United States)

Marques da Silva, Richarde; Guimarães Santos, Celso Augusto; Carneiro de Lima Silva, Valeriano; Pereira e Silva, Leonardo

2013-11-01

This study evaluates erosivity, surface runoff generation, and soil erosion rates for Mamuaba catchment, sub-catchment of Gramame River basin (Brazil) by using the ArcView Soil and Water Assessment Tool (AvSWAT) model. Calibration and validation of the model was performed on monthly basis, and it could simulate surface runoff and soil erosion to a good level of accuracy. Daily rainfall data between 1969 and 1989 from six rain gauges were used, and the monthly rainfall erosivity of each station was computed for all the studied years. In order to evaluate the calibration and validation of the model, monthly runoff data between January 1978 and April 1982 from one runoff gauge were used as well. The estimated soil loss rates were also realistic when compared to what can be observed in the field and to results from previous studies around of catchment. The long-term average soil loss was estimated at 9.4 t ha(-1) year(-1); most of the area of the catchment (60%) was predicted to suffer from a low- to moderate-erosion risk (soil erosion was estimated to exceed > 12 t ha(-1) year(-1). Expectedly, estimated soil loss was significantly correlated with measured rainfall and simulated surface runoff. Based on the estimated soil loss rates, the catchment was divided into four priority categories (low, moderate, high and very high) for conservation intervention. The study demonstrates that the AvSWAT model provides a useful tool for soil erosion assessment from catchments and facilitates the planning for a sustainable land management in northeastern Brazil.

Rainfall erosivity and sediment load over the Poyang Lake Basin under variable climate and human activities since the 1960s

Science.gov (United States)

Gu, Chaojun; Mu, Xingmin; Gao, Peng; Zhao, Guangju; Sun, Wenyi; Yu, Qiang

2018-03-01

Accelerated soil erosion exerts adverse effects on water and soil resources. Rainfall erosivity reflects soil erosion potential driven by rainfall, which is essential for soil erosive risk assessment. This study investigated the spatiotemporal variation of rainfall erosivity and its impacts on sediment load over the largest freshwater lake basin of China (the Poyang Lake Basin, abbreviate to PYLB). The spatiotemporal variations of rainfall erosivity from 1961 to 2014 based on 57 meteorological stations were detected using the Mann-Kendall test, linear regression, and kriging interpolation method. The sequential t test analysis of regime shift (STARS) was employed to identify the abrupt changes of sediment load, and the modified double mass curve was used to assess the impacts of rainfall erosivity variability on sediment load. It was found that there was significant increase (P change-points were identified in both 1985 and 2003. It was found that take annual rainfall erosivity as the explanatory variables of the double mass curves is more reasonable than annual rainfall and erosive rainfall. The estimation via the modified double mass curve demonstrated that compared with the period before change-point (1961-1984), the changes of rainfall erosivity increased 8.0 and 2.1% of sediment load during 1985-2002 and 2003-2014, respectively. Human activities decreased 50.2 and 69.7% of sediment load during the last two periods, which indicated effects of human activities on sediment load change was much larger than that of rainfall erosivity variability in the PYLB.

Intermittent thermal plasma acceleration linked to sporadic motions of the magnetopause, first Cluster results

Directory of Open Access Journals (Sweden)

J.-A. Sauvaud

Full Text Available This paper presents the first observations with Cluster of a very dense population of thermal ionospheric ions (H⁺, He⁺, O⁺ locally "accelerated" perpendicularly to the local magnetic field in a region adjacent to the magnetopause and on its magnetospheric side. The observation periods follow a long period of very weak magnetic activity. Recurrent motions of the magnetopause are, in the presented cases, unexpectedly associated with the appearance inside closed field lines of recurrent energy structures of ionospheric ions with energies in the 5 eV to  ~1000 eV range. The heaviest ions were detected with the highest energies. Here, the ion behaviour is interpreted as resulting from local electric field enhancements/decreases which adiabatically enhance/lower the bulk energy of a local dense thermal ion population. This drift effect, which is directly linked to magnetopause motions caused by pressure changes, allows for the thermal ions to overcome the satellite potential and be detected by the suprathermal CIS Cluster experiment. When fast flowing, i.e. when detectable, the density (~ 1 cm^-3 of these ions from a terrestrial origin is (in the cases presented here largely higher than the local density of ions from magnetospheric/plasma sheet origin which poses again the question of the relative importance of solar and ionospheric sources for the magnetospheric plasma even during very quiet magnetic conditions.

Key words. Ionosphere (planetary ionosphere; plasma convection Magnetospheric physics (magnetopause, cusp and boundary layers

Giant Radio Halos in Galaxy Clusters as Probes of Particle ...

Indian Academy of Sciences (India)

2016-01-27

Jan 27, 2016 ... Giant radio halos in galaxy clusters probe mechanisms of particle acceleration connected with cluster merger events. Shocks and turbulence are driven in the inter-galactic medium (IGM) during clusters mergers and may have a deep impact on the non-thermal properties of galaxy clusters. Models of ...

Mapping erosion from space

NARCIS (Netherlands)

Vrieling, A.

2007-01-01

Soil erosion by water is the most important land degradation problem worldwide. Spatial information on erosion is required for defining effective soil and water conservation strategies. Satellite remote sensing can provide relevant input to regional erosion assessment. This thesis comprises a review

Effects of Topography and Surface Soil Cover on Erosion for Mining Reclamation: The Experimental Spoil Heap at El Machorro Mine (Central Spain)

OpenAIRE

Martín Moreno, Cristina; Martín Duque, J. F.; Nicolau, J. M.; Hernando, N.; Sanz, M. A.; Sánchez Castillo, L.

2013-01-01

Mining reclamation tries to reduce environmental impacts, including accelerated runoff, erosion and sediment load in the nearby fluvial networks and their ecosystems. This study compares the effects of topography and surface soil cover on erosion on man-made slopes coming from surface mining reclamation in Central Spain. Two topographic profiles, linear and concave, with two surface soil covers, subsoil and topsoil, were monitored for two hydrologic years. Sediment load, rill development and ...

Mechanical weathering and rock erosion by climate-dependent subcritical cracking

Science.gov (United States)

Eppes, Martha-Cary; Keanini, Russell

2017-06-01

This work constructs a fracture mechanics framework for conceptualizing mechanical rock breakdown and consequent regolith production and erosion on the surface of Earth and other terrestrial bodies. Here our analysis of fracture mechanics literature explicitly establishes for the first time that all mechanical weathering in most rock types likely progresses by climate-dependent subcritical cracking under virtually all Earth surface and near-surface environmental conditions. We substantiate and quantify this finding through development of physically based subcritical cracking and rock erosion models founded in well-vetted fracture mechanics and mechanical weathering, theory, and observation. The models show that subcritical cracking can culminate in significant rock fracture and erosion under commonly experienced environmental stress magnitudes that are significantly lower than rock critical strength. Our calculations also indicate that climate strongly influences subcritical cracking—and thus rock weathering rates—irrespective of the source of the stress (e.g., freezing, thermal cycling, and unloading). The climate dependence of subcritical cracking rates is due to the chemophysical processes acting to break bonds at crack tips experiencing these low stresses. We find that for any stress or combination of stresses lower than a rock's critical strength, linear increases in humidity lead to exponential acceleration of subcritical cracking and associated rock erosion. Our modeling also shows that these rates are sensitive to numerous other environment, rock, and mineral properties that are currently not well characterized. We propose that confining pressure from overlying soil or rock may serve to suppress subcritical cracking in near-surface environments. These results are applicable to all weathering processes.

Synergia CUDA: GPU-accelerated accelerator modeling package

International Nuclear Information System (INIS)

Lu, Q; Amundson, J

2014-01-01

Synergia is a parallel, 3-dimensional space-charge particle-in-cell accelerator modeling code. We present our work porting the purely MPI-based version of the code to a hybrid of CPU and GPU computing kernels. The hybrid code uses the CUDA platform in the same framework as the pure MPI solution. We have implemented a lock-free collaborative charge-deposition algorithm for the GPU, as well as other optimizations, including local communication avoidance for GPUs, a customized FFT, and fine-tuned memory access patterns. On a small GPU cluster (up to 4 Tesla C1070 GPUs), our benchmarks exhibit both superior peak performance and better scaling than a CPU cluster with 16 nodes and 128 cores. We also compare the code performance on different GPU architectures, including C1070 Tesla and K20 Kepler.

Flow Accelerated Erosion-Corrosion (FAC) considerations for secondary side piping in the AP1000{sup R} nuclear power plant design

Energy Technology Data Exchange (ETDEWEB)

Vanderhoff, J. F.; Rao, G. V. [Westinghouse Electric Company LLC, 1000 Westinghouse Drive, Cranberry Township, PA 16066 (United States); Stein, A. [Shaw Power Nuclear, 1000 Technology Center Drive, Stoughton, MA 02072 (United States)

2012-07-01

The issue of Flow Accelerated Erosion-Corrosion (FAC) in power plant piping is a known phenomenon that has resulted in material replacements and plant accidents in operating power plants. Therefore, it is important for FAC resistance to be considered in the design of new nuclear power plants. This paper describes the design considerations related to FAC that were used to develop a safe and robust AP1000{sup R} plant secondary side piping design. The primary FAC influencing factors include: - Fluid Temperature - Pipe Geometry/layout - Fluid Chemistry - Fluid Velocity - Pipe Material Composition - Moisture Content (in steam lines) Due to the unknowns related to the relative impact of the influencing factors and the complexities of the interactions between these factors, it is difficult to accurately predict the expected wear rate in a given piping segment in a new plant. This paper provides: - a description of FAC and the factors that influence the FAC degradation rate, - an assessment of the level of FAC resistance of AP1000{sup R} secondary side system piping, - an explanation of options to increase FAC resistance and associated benefits/cost, - discussion of development of a tool for predicting FAC degradation rate in new nuclear power plants. (authors)

Galactic cluster winds in presence of a dark energy

Science.gov (United States)

Bisnovatyi-Kogan, G. S.; Merafina, M.

2013-10-01

We obtain a solution for the hydrodynamic outflow of the polytropic gas from the gravitating centre, in the presence of the uniform dark energy (DE). The antigravity of DE is enlightening the outflow and makes the outflow possible at smaller initial temperature, at the same density. The main property of the wind in the presence of DE is its unlimited acceleration after passing the critical point. In application of this solution to the winds from galaxy clusters, we suggest that collision of the strongly accelerated wind with another galaxy cluster, or with another galactic cluster wind, could lead to the formation of a highest energy cosmic rays.

Long-Term Analysis for Harvest Erosion Caused by Sugar Beet Production in Turkey

Directory of Open Access Journals (Sweden)

Selen DEVİREN SAYGIN

2018-02-01

Full Text Available The sustainability of soil resources is under significant threat due to the accelerated anthropogenic pressures at the historical expansion of human population. In this context, soil erosion is defined as a limiting factor for human interests in terms of ecosystem services. As an erosion type, harvest erosion occurs by harvesting of the taproot and tuberous root plants such as sugar beet (Beta vulgaris L., potato (Solanum tuberosum L., carrot (Daucus carota L. and chicory (Cichorium intybus L., has begun to take attention in recent years. The objective of this study was to estimate soil loss due to harvest erosion and to economically analyze the transport of plant nutrients between 1999 and 2016 from sugar beet growing areas in Turkey. For this aim, the compiled data of 25 different sugar factories throughout Turkey were obtained from Türkşeker and soil loss estimations were performed and economically analyzed. According to the results, average soil loss rate was calculated as 3.41 Mg ha-1y-1 for the studied period (1999-2016. That means annually an average of 716983 Mg soil removed from the Türkşeker sugar beet production areas. This result indicated that harvest erosion represents only 0.9% of soil lost by water erosion in Turkey. But, if tolerable soil loss value considered as “1 Mg ha-1 y-1”, calculated soil loss values are above this critical value for all the factories. In addition, economic assessments of soil losses showed that costs are to be more than US $10 000 annually on the 60% of the factories due to removal of plant nutrients with harvest process. And, annually US $419 433 investment must be made to recover all these losses. Conclusively, harvest erosion as an ignored erosion type must be emphasized to the economic sustainability of natural resources in fragile ecosystems such as our country.

Caries and dental erosion: are Soroti children and adolescents at risk from increased soft-drink availability in Uganda?

Science.gov (United States)

Cheng, Jordan; Campbell, Karen

2016-12-01

An initial field study to investigate dental caries and dental erosion in children and adolescents in the community of Soroti, Uganda. A stratified two-stage cluster sample of 84 children (ages 8-10) and adolescents (ages 16-19) were recruited. A survey was undertaken to assess the state of determinants of oral health, oral hygiene practices, and soft-drink and sweetened-tea consumption. Intra-oral photographs were taken and reviewed to measure Decayed, Missing, and Filled Teeth (DMFT) and dental erosion. A significant difference was observed in DMFT between children and adolescents (3.7 ± 2.7 versus 2.1 ± 2.4 p=.02). A trend of lower erosion scores was seen in children compared to adolescents. Greater frequency of sweetened-tea consumption over soft-drinks was noted in both groups. This study did not reveal any relationship between different levels of cariogenic beverage consumption and DMFT or dental erosion in this sample group.

Erosive gastritis

International Nuclear Information System (INIS)

Mohammed, S.H.; Conrad, C.; Kjoergaad, J.

1982-01-01

Erosive gastritis is a well-defined radiologic and endoscopic entity. It is one of the common causes of upper gastrointestinal bleeding, yet it is seldom diagnosed and often confused with a number of other diseases. This communication re-emphasizes the characteristic endoscopic and radiologic features of erosive gastritis and its differential diagnosis. Two representative cases are reported. (orig.)

Erosive gastritis

Energy Technology Data Exchange (ETDEWEB)

Mohammed, S.H.; Conrad, C.; Kjoergaad, J.

1982-08-01

Erosive gastritis is a well-defined radiologic and endoscopic entity. It is one of the common causes of upper gastrointestinal bleeding, yet it is seldom diagnosed and often confused with a number of other diseases. This communication re-emphasizes the characteristic endoscopic and radiologic features of erosive gastritis and its differential diagnosis. Two representative cases are reported.

Non-thermal electron acceleration in low Mach number collisionless shocks. II. Firehose-mediated Fermi acceleration and its dependence on pre-shock conditions

Energy Technology Data Exchange (ETDEWEB)

Guo, Xinyi; Narayan, Ramesh [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Sironi, Lorenzo [NASA Einstein Postdoctoral Fellow. (United States)

2014-12-10

Electron acceleration to non-thermal energies is known to occur in low Mach number (M{sub s} ≲ 5) shocks in galaxy clusters and solar flares, but the electron acceleration mechanism remains poorly understood. Using two-dimensional (2D) particle-in-cell (PIC) plasma simulations, we showed in Paper I that electrons are efficiently accelerated in low Mach number (M{sub s} = 3) quasi-perpendicular shocks via a Fermi-like process. The electrons bounce between the upstream region and the shock front, with each reflection at the shock resulting in energy gain via shock drift acceleration. The upstream scattering is provided by oblique magnetic waves that are self-generated by the electrons escaping ahead of the shock. In the present work, we employ additional 2D PIC simulations to address the nature of the upstream oblique waves. We find that the waves are generated by the shock-reflected electrons via the firehose instability, which is driven by an anisotropy in the electron velocity distribution. We systematically explore how the efficiency of wave generation and of electron acceleration depend on the magnetic field obliquity, the flow magnetization (or equivalently, the plasma beta), and the upstream electron temperature. We find that the mechanism works for shocks with high plasma beta (≳ 20) at nearly all magnetic field obliquities, and for electron temperatures in the range relevant for galaxy clusters. Our findings offer a natural solution to the conflict between the bright radio synchrotron emission observed from the outskirts of galaxy clusters and the low electron acceleration efficiency usually expected in low Mach number shocks.

Assessing storm erosion hazards

NARCIS (Netherlands)

Ranasinghe, Ranasinghe W M R J B; Callaghan, D.; Ciavola, Paolo; Coco, Giovanni

2017-01-01

The storm erosion hazard on coasts is usually expressed as an erosion volume and/or associated episodic coastline retreat. The accurate assessment of present-day and future storm erosion volumes is a key task for coastal zone managers, planners and engineers. There are four main approaches that can

Measurement of erosion: Is it possible?

NARCIS (Netherlands)

Stroosnijder, L.

2005-01-01

Reasons for erosion measurements are: (1) to determine the environmental impact of erosion and conservation practices, (2) scientific erosion research; (3) development and evaluation of erosion control technology; (4) development of erosion prediction technology and (5) allocation of conservation

Mapping Soil Erosion Factors and Potential Erosion Risk for the National Park "Central Balkan"

Science.gov (United States)

Ilieva, Diliana; Malinov, Ilia

2014-05-01

Soil erosion is widely recognised environmental problem. The report aims at presenting the main results from assessment and mapping of the factors of sheet water erosion and the potential erosion risk on the territory of National Park "Central Balkan". For this purpose, the Universal Soil Loss Equation (USLE) was used for predicting soil loss from erosion. The influence of topography (LS-factor) and soil erodibility (K-factor) was assessed using small-scale topographic and soil maps. Rainfall erosivity (R-factor) was calculated from data of rainfalls with amounts exceeding 9.5 mm from 14 hydro-meteorological stations. The values of the erosion factors (R, K and LS) were presented for the areas of forest, sub-alpine and alpine zones. Using the methods of GIS, maps were plotted presenting the area distribution among the classes of the soil erosion factors and the potential risk in the respective zones. The results can be used for making accurate decisions for soil conservation and sustainable land management in the park.

How development and disturbance of biological soil crust do affect runoff and erosion in drylands?

Energy Technology Data Exchange (ETDEWEB)

Chamizo, S.; Canton, Y.; Afana, A.; Lazaro, R.; Domingo, F.; Sole-Benet, A.

2009-07-01

Deserts and semiarid ecosystems (shrub lands and grasslands) are the largest terrestrial biome, covering more than 40% of the Earth's terrestrial surface and Biological Soil Crusts (BSCs) are the predominant surface type in most of those ecosystems covering up to 70% of its surface. BSCs have been demonstrated to be very vulnerable to disturbance due to human activities and their loss has been implicated as a factor leading to accelerate soil erosion and other forms of land degradation. Incorporation of the response of different type of soil crusts and the effects of the their disturbance is likely to improve the prediction of runoff and water erosion models in arid and semi-arid catchments. The aim of this work is to analyse the influence of crust disturbance on infiltration and erosion. Extreme rainfall simulations at micro plots scale were performed in two semiarid ecosystems with different lithology and conditions of occurrence of BSCs: El Cautivo and Amoladeras. (Author) 10 refs.

How development and disturbance of biological soil crust do affect runoff and erosion in drylands?

International Nuclear Information System (INIS)

Chamizo, S.; Canton, Y.; Afana, A.; Lazaro, R.; Domingo, F.; Sole-Benet, A.

2009-01-01

Deserts and semiarid ecosystems (shrub lands and grasslands) are the largest terrestrial biome, covering more than 40% of the Earth's terrestrial surface and Biological Soil Crusts (BSCs) are the predominant surface type in most of those ecosystems covering up to 70% of its surface. BSCs have been demonstrated to be very vulnerable to disturbance due to human activities and their loss has been implicated as a factor leading to accelerate soil erosion and other forms of land degradation. Incorporation of the response of different type of soil crusts and the effects of the their disturbance is likely to improve the prediction of runoff and water erosion models in arid and semi-arid catchments. The aim of this work is to analyse the influence of crust disturbance on infiltration and erosion. Extreme rainfall simulations at micro plots scale were performed in two semiarid ecosystems with different lithology and conditions of occurrence of BSCs: El Cautivo and Amoladeras. (Author) 10 refs.

The influence of rill density on soil erosion against USLE-soil erosion methode

OpenAIRE

Rizalihadi, A.M.; Faimah, B.E.; Nazia, C.L.

2013-01-01

Land and water is one of the major natural resource which has an important role for human life. Exploitation of land in catchment areas that not correspond to its carrying capacity will cause damage. One of the effect is increassing the soil erosion. Continuous erosion will also lead to increased sediment transport in rivers that disrupt the ship navigation on estuary due sediment accumulation. At present, soil erosion is estimated using USLE method, which is only limited to the erosion in th...

Dynamical processes in space: Cluster results

Directory of Open Access Journals (Sweden)

C. P. Escoubet

2013-06-01

Full Text Available After 12 years of operations, the Cluster mission continues to successfully fulfil its scientific objectives. The main goal of the Cluster mission, comprised of four identical spacecraft, is to study in three dimensions small-scale plasma structures in key plasma regions of the Earth's environment: solar wind and bow shock, magnetopause, polar cusps, magnetotail, plasmasphere and auroral zone. During the course of the mission, the relative distance between the four spacecraft has been varied from 20 km to 36 000 km to study the scientific regions of interest at different scales. Since summer 2005, new multi-scale constellations have been implemented, wherein three spacecraft (C1, C2, C3 are separated by 10 000 km, while the fourth one (C4 is at a variable distance ranging between 20 km and 10 000 km from C3. Recent observations were conducted in the auroral acceleration region with the spacecraft separated by 1000s km. We present highlights of the results obtained during the last 12 years on collisionless shocks, magnetopause waves, magnetotail dynamics, plasmaspheric structures, and the auroral acceleration region. In addition, we highlight Cluster results on understanding the impact of Coronal Mass Ejections (CME on the Earth environment. We will also present Cluster data accessibility through the Cluster Science Data System (CSDS, and the Cluster Active Archive (CAA, which was implemented to provide a permanent and public archive of high resolution Cluster data from all instruments.

Saliva and dental erosion.

Science.gov (United States)

Buzalaf, Marília Afonso Rabelo; Hannas, Angélicas Reis; Kato, Melissa Thiemi

2012-01-01

Dental erosion is a multifactorial condition. The consideration of chemical, biological and behavioral factors is fundamental for its prevention and therapy. Among the biological factors, saliva is one of the most important parameters in the protection against erosive wear. This review discusses the role of salivary factors on the development of dental erosion. A search was undertaken on MeDLINe website for papers from 1969 to 2010. The keywords used in the research were "saliva", "acquired pellicle", "salivary flow", "salivary buffering capacity" and "dental erosion". Inclusion of studies, data extraction and quality assessment were undertaken independently and in duplicate by two members of the review team. Disagreements were solved by discussion and consensus or by a third party. Several characteristics and properties of saliva play an important role in dental erosion. Salivary clearance gradually eliminates the acids through swallowing and saliva presents buffering capacity causing neutralization and buffering of dietary acids. Salivary flow allows dilution of the acids. In addition, saliva is supersaturated with respect to tooth mineral, providing calcium, phosphate and fluoride necessary for remineralization after an erosive challenge. Furthermore, many proteins present in saliva and acquired pellicle play an important role in dental erosion. Saliva is the most important biological factor affecting the progression of dental erosion. Knowledge of its components and properties involved in this protective role can drive the development of preventive measures targeting to enhance its known beneficial effects.

Saliva and dental erosion

Directory of Open Access Journals (Sweden)

Marília Afonso Rabelo Buzalaf

2012-10-01

Full Text Available Dental erosion is a multifactorial condition. The consideration of chemical, biological and behavioral factors is fundamental for its prevention and therapy. Among the biological factors, saliva is one of the most important parameters in the protection against erosive wear. Objective: This review discusses the role of salivary factors on the development of dental erosion. Material and Methods: A search was undertaken on MeDLINe website for papers from 1969 to 2010. The keywords used in the research were "saliva", "acquired pellicle", "salivary flow", "salivary buffering capacity" and "dental erosion". Inclusion of studies, data extraction and quality assessment were undertaken independently and in duplicate by two members of the review team. Disagreements were solved by discussion and consensus or by a third party. Results: Several characteristics and properties of saliva play an important role in dental erosion. Salivary clearance gradually eliminates the acids through swallowing and saliva presents buffering capacity causing neutralization and buffering of dietary acids. Salivary flow allows dilution of the acids. In addition, saliva is supersaturated with respect to tooth mineral, providing calcium, phosphate and fluoride necessary for remineralization after an erosive challenge. Furthermore, many proteins present in saliva and acquired pellicle play an important role in dental erosion. Conclusions: Saliva is the most important biological factor affecting the progression of dental erosion. Knowledge of its components and properties involved in this protective role can drive the development of preventive measures targeting to enhance its known beneficial effects.

Auto consolidated cohesive sediments erosion; Erosion des sediments cohesifs en autoconsolidation

Energy Technology Data Exchange (ETDEWEB)

Ternat, F

2007-02-15

Pollutants and suspended matters of a river can accumulate into the sedimentary column. Once deposited, they are submitted to self-weight consolidation processes, ageing and burying, leading to an increase of their erosion resistance. Pollutant fluxes can be related to sedimentary fluxes, determined by threshold laws. In this work, an erosion threshold model is suggested by introducing a cohesion force into the usual force balance. A model of cohesion is developed on the basis of interactions between argillaceous cohesive particles (clays), particularly the Van der Waals force, whose parameterization is ensured by means of granulometry and porosity. Artificial erosion experiments were performed in a recirculating erosion flume with natural cored sediments where critical shear stress measurements were performed. Other analyses provided granulometry and porosity. The results obtained constitute a good database for the literature. The model is then applied to the experimental conditions and gives good agreement with measurements. An example of the accounting for self-weight consolidation processes is finally suggested, before finishing on a Mohr like diagram dedicated to soft cohesive sediment erosion. (author)

High-performance dynamic quantum clustering on graphics processors

Energy Technology Data Exchange (ETDEWEB)

Wittek, Peter, E-mail: peterwittek@acm.org [Swedish School of Library and Information Science, University of Boras, Boras (Sweden)

2013-01-15

Clustering methods in machine learning may benefit from borrowing metaphors from physics. Dynamic quantum clustering associates a Gaussian wave packet with the multidimensional data points and regards them as eigenfunctions of the Schroedinger equation. The clustering structure emerges by letting the system evolve and the visual nature of the algorithm has been shown to be useful in a range of applications. Furthermore, the method only uses matrix operations, which readily lend themselves to parallelization. In this paper, we develop an implementation on graphics hardware and investigate how this approach can accelerate the computations. We achieve a speedup of up to two magnitudes over a multicore CPU implementation, which proves that quantum-like methods and acceleration by graphics processing units have a great relevance to machine learning.

Flow accelerated corrosion and erosion-corrosion of RAFM steel in liquid breeders

International Nuclear Information System (INIS)

Kondo, Masatoshi; Muroga, Takeo; Sagara, Akio

2010-11-01

Corrosion experiments for RAFM, JLF-1 steel (Fe-9Cr-2w-0.1C) in 3types of flowing liquid breeders (i.e. Li, Pb-17Li and Flinak) were performed at the same conditions, and the compatibility was compared with each other. The weight loss of the specimens in the fluids was evaluated by the corrosion model based on mass transfer. The model can be applied to different test systems with different quantity of liquid breeders and different surface area of the systems. The flow enhanced the dissolution of element of the steel in the fluids. The mechanism of an erosion-corrosion in the liquid breeders was the peeling off of the corroded steel surface by the flow. (author)

Rainfall erosivity in Europe.

Science.gov (United States)

Panagos, Panos; Ballabio, Cristiano; Borrelli, Pasquale; Meusburger, Katrin; Klik, Andreas; Rousseva, Svetla; Tadić, Melita Perčec; Michaelides, Silas; Hrabalíková, Michaela; Olsen, Preben; Aalto, Juha; Lakatos, Mónika; Rymszewicz, Anna; Dumitrescu, Alexandru; Beguería, Santiago; Alewell, Christine

2015-04-01

Rainfall is one the main drivers of soil erosion. The erosive force of rainfall is expressed as rainfall erosivity. Rainfall erosivity considers the rainfall amount and intensity, and is most commonly expressed as the R-factor in the USLE model and its revised version, RUSLE. At national and continental levels, the scarce availability of data obliges soil erosion modellers to estimate this factor based on rainfall data with only low temporal resolution (daily, monthly, annual averages). The purpose of this study is to assess rainfall erosivity in Europe in the form of the RUSLE R-factor, based on the best available datasets. Data have been collected from 1541 precipitation stations in all European Union (EU) Member States and Switzerland, with temporal resolutions of 5 to 60 min. The R-factor values calculated from precipitation data of different temporal resolutions were normalised to R-factor values with temporal resolutions of 30 min using linear regression functions. Precipitation time series ranged from a minimum of 5 years to a maximum of 40 years. The average time series per precipitation station is around 17.1 years, the most datasets including the first decade of the 21st century. Gaussian Process Regression (GPR) has been used to interpolate the R-factor station values to a European rainfall erosivity map at 1 km resolution. The covariates used for the R-factor interpolation were climatic data (total precipitation, seasonal precipitation, precipitation of driest/wettest months, average temperature), elevation and latitude/longitude. The mean R-factor for the EU plus Switzerland is 722 MJ mm ha(-1) h(-1) yr(-1), with the highest values (>1000 MJ mm ha(-1) h(-1) yr(-1)) in the Mediterranean and alpine regions and the lowest (<500 MJ mm ha(-1) h(-1) yr(-1)) in the Nordic countries. The erosivity density (erosivity normalised to annual precipitation amounts) was also the highest in Mediterranean regions which implies high risk for erosive events and floods

Immunohistochemical Study of p53 Expression in Patients with Erosive and Non-Erosive Oral Lichen Planus

Science.gov (United States)

Shiva, Atena; Zamanian, Ali; Arab, Shahin; Boloki, Mahsa

2018-01-01

Statement of the Problem: Oral lichen planus is a common mucocutaneous lesion with a chronic inflammatory process mediated by immune factors while a few cases of the disease become malignant. Purpose: This study aimed to determine the frequency of p53 marker as a tumor suppressor in patients with erosive and non-erosive oral lichen planus (OLP) by using immunohistochemical methods. Materials and Method: This descriptive cross-sectional study investigated the p53 expression in 16 erosive OLP, 16 non-erosive OLP samples, and 8 samples of normal oral mucosa through immunohistochemistry. The percentage of stained cells in basal and suprabasal layers, and inflammatory infiltrate were graded according to the degree of staining; if 0%, 50% of the cells were stained, they were considered as (-), (+), (++), (+++) and (++++), respectively. The obtained data was statistically analyzed and compared by using Chi square and Fisher’s exact test. Results: The mean percentage of p53 positive cells in erosive OLP (34.5±14.2) was considerably higher than that in non-erosive OLP (23.8±10.4) and normal mucosa (17.5±17). There was a significant difference among the three groups of erosive, non-erosive and control in terms of staining intensity. No significant difference existed between the patients’ age and sex in the two OLP groups. Conclusion: The increased incidence of p53 from normal mucosa to erosive OLP indicated the difference between biological behavior of erosive and non-erosive OLP. It can be claimed that the erosive OLP has great premalignant potential compared with the non-erosive one.

Continuing studies of plasma erosion switches for power conditioning on multiterawatt pulsed power accelerators

International Nuclear Information System (INIS)

Stringfield, R.; Gilman, C.; James, G.; Peters, T.; Sincerny, P.; Wong, S.

1983-01-01

Recent PITHON experiments with plasma erosion switches (PES) have extended the range of operation of the switches by about 50 percent, in terms of closed time and charge passing through the switch. The quantity of charge passed through the switch has been increased to as much as 35 mC. Currents as large as 1 MA and voltages as great as 1.8 MV have been switched off to be diverted to a downstream load. The impedance of the erosion switch can be described as having three stages: 1) essentially zero impedance, 2) a transitional opening phase, and 3) an impedance which is very large (greater than 5 Ω) in comparison with the subohm downstream load. Current diagnostics, consisting of Rogowski coils and segmented shunts, have been successfully developed to monitor the current which propagates to the load region. These monitors have measured rise times as short as 38 ns and slew rates as great as 10 14 A/s at the load. With wire array loads, the pulse conditioning of the switch has been observed to reduce the magnitude of the current losses in the feed which are present when no switch is used. Correlations have been made between the switch closed time, voltage, current, and power with the feed inductance and the generator power injected into the magnetic insulated transmission line (MITL)

Divergent taxonomic and functional responses of microbial communities to field simulation of aeolian soil erosion and deposition.

Science.gov (United States)

Ma, Xingyu; Zhao, Cancan; Gao, Ying; Liu, Bin; Wang, Tengxu; Yuan, Tong; Hale, Lauren; Nostrand, Joy D Van; Wan, Shiqiang; Zhou, Jizhong; Yang, Yunfeng

2017-08-01

Aeolian soil erosion and deposition have worldwide impacts on agriculture, air quality and public health. However, ecosystem responses to soil erosion and deposition remain largely unclear in regard to microorganisms, which are the crucial drivers of biogeochemical cycles. Using integrated metagenomics technologies, we analysed microbial communities subjected to simulated soil erosion and deposition in a semiarid grassland of Inner Mongolia, China. As expected, soil total organic carbon and plant coverage were decreased by soil erosion, and soil dissolved organic carbon (DOC) was increased by soil deposition, demonstrating that field simulation was reliable. Soil microbial communities were altered (p soil erosion and deposition, with dramatic increase in Cyanobacteria related to increased stability in soil aggregates. amyA genes encoding α-amylases were specifically increased (p = .01) by soil deposition and positively correlated (p = .02) to DOC, which likely explained changes in DOC. Surprisingly, most of microbial functional genes associated with carbon, nitrogen, phosphorus and potassium cycling were decreased or unaltered by both erosion and deposition, probably arising from acceleration of organic matter mineralization. These divergent responses support the necessity to include microbial components in evaluating ecological consequences. Furthermore, Mantel tests showed strong, significant correlations between soil nutrients and functional structure but not taxonomic structure, demonstrating close relevance of microbial function traits to nutrient cycling. © 2017 John Wiley & Sons Ltd.

Effects of pH-Induced Changes in Soil Physical Characteristics on the Development of Soil Water Erosion

Directory of Open Access Journals (Sweden)

Shinji Matsumoto

2018-04-01

Full Text Available Soil water erosion is frequently reported as serious problem in soils in Southeast Asia with tropical climates, and the variations in pH affect the development of the erosion. This study investigated the effects of changes in pH on soil water erosion based on changes in the physical properties of the simulated soils with pH adjusted from 2.0 to 10.0 through artificial rainfall tests. The zeta potential was entirely shifted to positive direction at each pH condition due to Al, Ca, and Mg. In the pH range of 6.0 to 2.0, the aggregation of soil particles resulting from the release of Al3+ from clay minerals and/or molecular attraction between soil particles caused the plastic index (IP of the soil to decrease. The decrease in IP led to the development of soil water erosion at the pH range. When the pH exceeded 6.0, the repulsive force generated by the negative charges on soil particles decreased IP, resulting in accelerated erosion by water. The results suggest that changes in pH causes physical properties of the soil to change through changes of the zeta potential in the clayey soil rich in Al, Ca, and Mg, leading to the development of soil water erosion.

A linear relationship between wave power and erosion determines salt-marsh resilience to violent storms and hurricanes

Science.gov (United States)

Leonardi, Nicoletta; Ganju, Neil K.; Fagherazzi, Sergio

2016-01-01

Salt marsh losses have been documented worldwide because of land use change, wave erosion, and sea-level rise. It is still unclear how resistant salt marshes are to extreme storms and whether they can survive multiple events without collapsing. Based on a large dataset of salt marsh lateral erosion rates collected around the world, here, we determine the general response of salt marsh boundaries to wave action under normal and extreme weather conditions. As wave energy increases, salt marsh response to wind waves remains linear, and there is not a critical threshold in wave energy above which salt marsh erosion drastically accelerates. We apply our general formulation for salt marsh erosion to historical wave climates at eight salt marsh locations affected by hurricanes in the United States. Based on the analysis of two decades of data, we find that violent storms and hurricanes contribute less than 1% to long-term salt marsh erosion rates. In contrast, moderate storms with a return period of 2.5 mo are those causing the most salt marsh deterioration. Therefore, salt marshes seem more susceptible to variations in mean wave energy rather than changes in the extremes. The intrinsic resistance of salt marshes to violent storms and their predictable erosion rates during moderate events should be taken into account by coastal managers in restoration projects and risk management plans.

A linear relationship between wave power and erosion determines salt-marsh resilience to violent storms and hurricanes.

Science.gov (United States)

Leonardi, Nicoletta; Ganju, Neil K; Fagherazzi, Sergio

2016-01-05

Salt marsh losses have been documented worldwide because of land use change, wave erosion, and sea-level rise. It is still unclear how resistant salt marshes are to extreme storms and whether they can survive multiple events without collapsing. Based on a large dataset of salt marsh lateral erosion rates collected around the world, here, we determine the general response of salt marsh boundaries to wave action under normal and extreme weather conditions. As wave energy increases, salt marsh response to wind waves remains linear, and there is not a critical threshold in wave energy above which salt marsh erosion drastically accelerates. We apply our general formulation for salt marsh erosion to historical wave climates at eight salt marsh locations affected by hurricanes in the United States. Based on the analysis of two decades of data, we find that violent storms and hurricanes contribute less than 1% to long-term salt marsh erosion rates. In contrast, moderate storms with a return period of 2.5 mo are those causing the most salt marsh deterioration. Therefore, salt marshes seem more susceptible to variations in mean wave energy rather than changes in the extremes. The intrinsic resistance of salt marshes to violent storms and their predictable erosion rates during moderate events should be taken into account by coastal managers in restoration projects and risk management plans.

An early cretaceous phase of accelerated erosion on the south-western margin of Africa: evidence from apatite fission track analysis and the offshore sedimentary record

International Nuclear Information System (INIS)

Brown, R.W.; Gleadow, A.J.W.; Rust, D.J.; Summerfield, M.A.; De Wit, M.C.J.

1990-01-01

Apatite fission track ages and confined track length distributions have been determined for rock samples from the south-western continental margin of Africa. The apatite ages fall into two groups, one having early Cretaceous ages and mean confined track lengths of ∼ 14 μm with very few short tracks, and the other having older ages with confined track length distributions containing a significant proportion of strongly annealed tracks (<10 μm). In any particular area the older apatite ages only occur above a critical threshold elevation, forming a regional pattern in the data and indicating cooling of the upper few kilometres of the crust during the early cretaceous. This episode of cooling is shown to have been the consequence of an accelerated phase of erosion associated with the early stages of rifting and break-up of Gondwana, and correlates with sedimentation patterns derived from borehole data for the adjacent offshore basin. (author)

An early cretaceous phase of accelerated erosion on the south-western margin of Africa: evidence from apatite fission track analysis and the offshore sedimentary record

Energy Technology Data Exchange (ETDEWEB)

Brown, R.W.; Gleadow, A.J.W. (La Trobe Univ., Bundoora (Australia)); Rust, D.J.; Summerfield, M.A. (Edinburgh Univ. (UK)); De Wit, M.C.J. (De Beers Consolidated Mines Ltd., Kimberley (South Africa))

1990-01-01

Apatite fission track ages and confined track length distributions have been determined for rock samples from the south-western continental margin of Africa. The apatite ages fall into two groups, one having early Cretaceous ages and mean confined track lengths of {approx} 14 {mu}m with very few short tracks, and the other having older ages with confined track length distributions containing a significant proportion of strongly annealed tracks (<10 {mu}m). In any particular area the older apatite ages only occur above a critical threshold elevation, forming a regional pattern in the data and indicating cooling of the upper few kilometres of the crust during the early cretaceous. This episode of cooling is shown to have been the consequence of an accelerated phase of erosion associated with the early stages of rifting and break-up of Gondwana, and correlates with sedimentation patterns derived from borehole data for the adjacent offshore basin. (author).

Following of erosive wash of soil in variants with different intercrops

Directory of Open Access Journals (Sweden)

Barbora Badalíková

2010-01-01

Full Text Available In a pilot experiment established in a sugar beet growing region the erosive washing away of soil was studied in the years 2006 to 2008. The area is located at an altitude of 246 m with the long-term mean precipitation of 500 mm and the mean annual temperature of 8.4 °C. The soils are classified as Chernozem, moderately heavy, loamy, with a good supply of nutrients, humus content of 2.30 % and an alkaline soil reaction. Slope gradient is 12 %, exposition is NE. To study the role of intercrops in erosion control, three variants were established after the harvest of the main crop, two variants with different intercrops and one (control with no intercrop. These were Variant 1 with Secale cereale L. var. multicaule METZG. ex ALEF., a non-freezing intercrop, Variant 2 with cluster mallow (Malva verticillata L., a freezing intercrop, and a control variant with no intercrop. In Variant 1 Secale cereale L. var. multicaule was desiccated with the herbicide Roundup in early spring. All the variants involved maize as the main crop. In variants 1 and 2, maize was sown in intercrop residues after seedbed preparation by Vario and a compactor. In Variant 3 maize was sown after conventional seedbed preparation. For assessment of soil conditions soil samples were taken to determine soil physical and chemical properties and water content in the soil. Soil loss by erosion was determined using specially-designed pockets. Erosive washing away of soil was monitored during the entire growing season of maize. The variants in which intercrops were used were found very effective in soil erosion control. In Variant 3 (control without surface crop residues, the washing away of soil was recorded with each heavy torrential rain. During the all years the total amount of soil loss by erosion in this treatment was 2.25 t . ha−1.

Rainfall erosivity map for Ghana

International Nuclear Information System (INIS)

Oduro Afriyie, K.

1995-10-01

Monthly rainfall data, spanning over a period of more than thirty years, were used to compute rainfall erosivity indices for various stations in Ghana, using the Fournier index, c, defined as p 2 /P, where p is the rainfall amount in the wettest month and P is the annual rainfall amount. Values of the rainfall erosivity indices ranged from 24.5 mm at Sunyani in the mid-portion of Ghana to 180.9 mm at Axim in the south western coastal portion. The indices were used to construct a rainfall erosivity map for the country. The map revealed that Ghana may be broadly divided into five major erosion risk zones. The middle sector of Ghana is generally in the low erosion risk zone; the northern sector is in the moderate to severe erosion risk zone, while the coastal sector is in the severe to extreme severe erosion risk zone. (author). 11 refs, 1 fig., 1 tab

Accelerating three-dimensional FDTD calculations on GPU clusters for electromagnetic field simulation.

Science.gov (United States)

Nagaoka, Tomoaki; Watanabe, Soichi

2012-01-01

Electromagnetic simulation with anatomically realistic computational human model using the finite-difference time domain (FDTD) method has recently been performed in a number of fields in biomedical engineering. To improve the method's calculation speed and realize large-scale computing with the computational human model, we adapt three-dimensional FDTD code to a multi-GPU cluster environment with Compute Unified Device Architecture and Message Passing Interface. Our multi-GPU cluster system consists of three nodes. The seven GPU boards (NVIDIA Tesla C2070) are mounted on each node. We examined the performance of the FDTD calculation on multi-GPU cluster environment. We confirmed that the FDTD calculation on the multi-GPU clusters is faster than that on a multi-GPU (a single workstation), and we also found that the GPU cluster system calculate faster than a vector supercomputer. In addition, our GPU cluster system allowed us to perform the large-scale FDTD calculation because were able to use GPU memory of over 100 GB.

Rill erosion rates in burned forests

Science.gov (United States)

Joseph W. Wagenbrenner; Peter R. Robichaud

2011-01-01

Introduction Wildfires often produce large increases in runoff and erosion rates (e.g., Moody and Martin, 2009), and land managers need to predict the frequency and magnitude of postfire erosion to determine the needs for hazard response and possible erosion mitigation to reduce the impacts of increased erosion on public safety and valued resources. The Water Erosion...

Evaluation of the serum zinc level in erosive and non-erosive oral lichen planus.

Science.gov (United States)

Gholizadeh, N; Mehdipour, M; Najafi, Sh; Bahramian, A; Garjani, Sh; Khoeini Poorfar, H

2014-06-01

Lichen planus is a chronic inflammatory immunologic-based disease involving skin and mucosa. This disease is generally divided into two categories: erosive and non-erosive. Many etiologic factors are deliberated regarding the disease; however, the disorders of immune system and the role of cytotoxic T-lymphocytes and monocytes are more highlighted. Zinc is an imperative element for the growth of epithelium and its deficiency induces the cytotoxic activity of T-helper2 cells, which seems to be associated with lichen planus. This study was aimed to evaluate the levels of serum zinc in erosive and non-erosive oral lichen planus (OLP) and to compare it with the healthy control group to find out any feasible inference. A total of 22 patients with erosive oral lichen planus, 22 patients with non erosive OLP and 44 healthy individuals as the control group were recruited in this descriptive-comparative study. All the participants were selected from the referees to the department of oral medicine, school of dentistry, Tabriz University of Medical Sciences. Serum zinc level was examined for all the individuals with liquid-stat kit (Beckman Instruments Inc.; Carlsbad, CA). Data were analyzed by adopting the ANOVA and Tukey tests, using SPSS 16 statistical software. The mean age of patients with erosive and non-erosive LP was 41.7 and 41.3 years, respectively. The mean age of the healthy control group was 34.4 years .The mean serum zinc levels in the erosive and non erosive lichen planus groups and control groups were 8.3 (1.15), 11.15 (0.92) and 15.74 (1.75) μg/dl respectively. The difference was statistically significant (poral lichen planus. This finding may probably indicate the promising role of zinc in development of oral lichen planus.

Modeling soil erosion in a watershed

OpenAIRE

Lanuza, R.

1999-01-01

Most erosion models have been developed based on a plot scale and have limited application to a watershed due to the differences in aerial scale. In order to address this limitation, a GIS-assisted methodology for modeling soil erosion was developed using PCRaster to predict the rate of soil erosion at watershed level; identify the location of erosion prone areas; and analyze the impact of landuse changes on soil erosion. The general methodology of desktop modeling or soil erosion at watershe...

[US Geological Survey research in radioactive waste disposal, fiscal year 1980:] Tectonics, seismicity, volcanism, and erosion rates in the southern Great Basin

International Nuclear Information System (INIS)

Carr, W.J.; Rogers, A.M.

1982-01-01

The objective is to assess the potential for faulting, damaging earthquakes, recurrence of volcanism, and local acceleration of erosion in parts of the southern Great Basin. The following approaches are being used: (1) investigating the rate, intensity, and distribution of faulting during approximately the last 25 m.y., with emphasis on the last 10 m.y.; (2) monitoring and interpreting present seismicity; (3) studying the history of volcanism; and (4) evaluating past rates of erosion and deposition. Progress is reported

Use of 137Cs technique for soil erosion study in the agricultural region of Casablanca in Morocco

International Nuclear Information System (INIS)

Nouira, A.; Sayouty, E.H.; Benmansour, M.

2003-01-01

Accelerated erosion and soil degradation currently cause serious problems to the Oued El Maleh basin (Morocco). Furthermore, there is still only limited information on rates of soil loss for optimising strategies for soil conservation. In the present study we have used the 137 Cs technique to assess the soil erosion rates on an agricultural land in Oued el Maleh basin near Casablanca (Morocco). A small representative agricultural field was selected to investigate the soil degradation required by soil managers in this region. The transect approach was applied for sampling to identify the spatial redistribution of 137 Cs. The spatial variability of 137 Cs inventory has provided evidence of the importance of tillage process and the human effects on the redistribution of 137 Cs. The mean 137 Cs inventory was found about 842 Bq m -2 , this value corresponds to an erosion rate of 82 tha -1 yr -1 by applying simplified mass balance model in a preliminary estimation. When data on site characteristics were available, the refined mass balance model was applied to highlight the contribution of tillage effect in soil redistribution. The erosion rate was estimated about 50 tha -1 yr -1 . The aspects related to the sampling procedures and the models for calculation of erosion rates are discussed

CAMPAIGN: an open-source library of GPU-accelerated data clustering algorithms.

Science.gov (United States)

Kohlhoff, Kai J; Sosnick, Marc H; Hsu, William T; Pande, Vijay S; Altman, Russ B

2011-08-15

Data clustering techniques are an essential component of a good data analysis toolbox. Many current bioinformatics applications are inherently compute-intense and work with very large datasets. Sequential algorithms are inadequate for providing the necessary performance. For this reason, we have created Clustering Algorithms for Massively Parallel Architectures, Including GPU Nodes (CAMPAIGN), a central resource for data clustering algorithms and tools that are implemented specifically for execution on massively parallel processing architectures. CAMPAIGN is a library of data clustering algorithms and tools, written in 'C for CUDA' for Nvidia GPUs. The library provides up to two orders of magnitude speed-up over respective CPU-based clustering algorithms and is intended as an open-source resource. New modules from the community will be accepted into the library and the layout of it is such that it can easily be extended to promising future platforms such as OpenCL. Releases of the CAMPAIGN library are freely available for download under the LGPL from https://simtk.org/home/campaign. Source code can also be obtained through anonymous subversion access as described on https://simtk.org/scm/?group_id=453. kjk33@cantab.net.

High-performance dynamic quantum clustering on graphics processors

International Nuclear Information System (INIS)

Wittek, Peter

2013-01-01

Clustering methods in machine learning may benefit from borrowing metaphors from physics. Dynamic quantum clustering associates a Gaussian wave packet with the multidimensional data points and regards them as eigenfunctions of the Schrödinger equation. The clustering structure emerges by letting the system evolve and the visual nature of the algorithm has been shown to be useful in a range of applications. Furthermore, the method only uses matrix operations, which readily lend themselves to parallelization. In this paper, we develop an implementation on graphics hardware and investigate how this approach can accelerate the computations. We achieve a speedup of up to two magnitudes over a multicore CPU implementation, which proves that quantum-like methods and acceleration by graphics processing units have a great relevance to machine learning.

SUSCEPTIBILITY AND RISKS TO WATER EROSION IN THE UPPER OF ARAGUAIA RIVER BASIN (GO/MT, BRAZIL

Directory of Open Access Journals (Sweden)

OLIVEIRA, Victoria Christina Vilela

2005-05-01

Full Text Available The soil is a very important natural resource to life in general, especially to human life, because it is the base of its activities. However, in some parts of the word it is not exposed to adequate conservational practices, which result in degradation of the quality and negative impacts on the ecosystems and biodiversity. One of this impacts concerns the water erosion, the most important cause of the accelerated loss of properties on agricultural lands by reduction of fertility, desertification and increase of recent sedimentation in the hydrical channels. The laminar erosion is a common form but no evident signs are visible, except when the roots appear on the cultures and pastures. It is caused by runoff, mainly in the tropics.Some soils have high susceptibility and risks to this form of erosion, frequently the fine sandy soils after deforestation of their original cover and replacement by intensive agricultural an pasturage activities without conservational practices.

Control of cluster ion sizes for efficient injection heating

International Nuclear Information System (INIS)

Enjoji, Hiroshi; Be, S.H.; Yano, Katsuki; Okamoto, Kosuke

1976-01-01

For heating of plasmas by injection of hydrogen cluster ions, the specific size (N/Z) approximately 10 2 molecules/charge is believed to be most desirable. A fundamental research to develop a practical method for tailoring large cluster ions into small suitable sizes has been carried out by using nitrogen cluster ions of the initial mean specific size (N/Z) 0 approximately 10 5 . The beam of neutral large clusters of total intensity 20 mAsub(eq) was led to an ionizer and then the large cluster ions are accelerated to 8.9 keV before entering the divider which disintegrates them into small fragments by multiple ionization. The mean specific size of disintegrated cluster ions (N/Z)' becomes smaller with increase in ionizing electron current of the divider. (N/Z)' becomes 10 3 approximately 10 4 at an electron current of 140 mA and an accelerating voltage of 680 V of the divider with its efficiency of 20 approximately 60%. Thus, the original large cluster ions are divided into small fragments of which the mean specific size is 1/20 approximately 1/100 of the initial value without much decrease in total intensity of the cluster ion beam

Software for virtual accelerator designing

International Nuclear Information System (INIS)

Kulabukhova, N.; Ivanov, A.; Korkhov, V.; Lazarev, A.

2012-01-01

The article discusses appropriate technologies for software implementation of the Virtual Accelerator. The Virtual Accelerator is considered as a set of services and tools enabling transparent execution of computational software for modeling beam dynamics in accelerators on distributed computing resources. Distributed storage and information processing facilities utilized by the Virtual Accelerator make use of the Service-Oriented Architecture (SOA) according to a cloud computing paradigm. Control system tool-kits (such as EPICS, TANGO), computing modules (including high-performance computing), realization of the GUI with existing frameworks and visualization of the data are discussed in the paper. The presented research consists of software analysis for realization of interaction between all levels of the Virtual Accelerator and some samples of middle-ware implementation. A set of the servers and clusters at St.-Petersburg State University form the infrastructure of the computing environment for Virtual Accelerator design. Usage of component-oriented technology for realization of Virtual Accelerator levels interaction is proposed. The article concludes with an overview and substantiation of a choice of technologies that will be used for design and implementation of the Virtual Accelerator. (authors)

Acceleration Modes and Transitions in Pulsed Plasma Accelerators

Science.gov (United States)

Polzin, Kurt A.; Greve, Christine M.

2018-01-01

accelerators was developed by Cheng, et al. The Coaxial High ENerGy (CHENG) thruster operated on the 10-microseconds timescales of pulsed plasma thrusters, but claimed high thrust density, high efficiency and low electrode erosion rates, which are more consistent with the deflagration mode of acceleration. Separate work on gas-fed pulsed plasma thrusters (PPTs) by Ziemer, et al. identified two separate regimes of performance. The regime at higher mass bits (termed Mode I in that work) possessed relatively constant thrust efficiency (ratio of jet kinetic energy to input electrical energy) as a function of mass bit. In the second regime at very low mass bits (termed Mode II), the efficiency increased with decreasing mass bit. Work by Poehlmann et al. and by Sitaraman and Raja sought to understand the performance of the CHENG thruster and the Mode I / Mode II performance in PPTs by modeling the acceleration using the Hugoniot Relation, with the detonation and deflagration modes representing two distinct sets of solutions to the relevant conservation laws. These works studied the proposal that, depending upon the values of the various controllable parameters, the accelerator would operate in either the detonation or deflagration mode. In the present work, we propose a variation on the explanation for the differences in performance between the various pulsed plasma accelerators. Instead of treating the accelerator as if it were only operating in one mode or the other during a pulse, we model the initial stage of the discharge in all cases as an accelerating current sheet (detonation mode). If the current sheet reaches the exit of the accelerator before the discharge is completed, the acceleration mode transitions to the deflagration mode type found in the quasi-steady MPD thrusters. This modeling method is used to demonstrate that standard gas-fed pulsed plasma accelerators, the CHENG thruster, and the quasi-steady MPD accelerator are variations of the same device, with the overall

Fully accelerating quantum Monte Carlo simulations of real materials on GPU clusters

Science.gov (United States)

Esler, Kenneth

2011-03-01

Quantum Monte Carlo (QMC) has proved to be an invaluable tool for predicting the properties of matter from fundamental principles, combining very high accuracy with extreme parallel scalability. By solving the many-body Schrödinger equation through a stochastic projection, it achieves greater accuracy than mean-field methods and better scaling with system size than quantum chemical methods, enabling scientific discovery across a broad spectrum of disciplines. In recent years, graphics processing units (GPUs) have provided a high-performance and low-cost new approach to scientific computing, and GPU-based supercomputers are now among the fastest in the world. The multiple forms of parallelism afforded by QMC algorithms make the method an ideal candidate for acceleration in the many-core paradigm. We present the results of porting the QMCPACK code to run on GPU clusters using the NVIDIA CUDA platform. Using mixed precision on GPUs and MPI for intercommunication, we observe typical full-application speedups of approximately 10x to 15x relative to quad-core CPUs alone, while reproducing the double-precision CPU results within statistical error. We discuss the algorithm modifications necessary to achieve good performance on this heterogeneous architecture and present the results of applying our code to molecules and bulk materials. Supported by the U.S. DOE under Contract No. DOE-DE-FG05-08OR23336 and by the NSF under No. 0904572.

Properties of an ionised-cluster beam from a vaporised-cluster ion source

International Nuclear Information System (INIS)

Takagi, T.; Yamada, I.; Sasaki, A.

1978-01-01

A new type of ion source vaporised-metal cluster ion source, has been developed for deposition and epitaxy. A cluster consisting of 10 2 to 10 3 atoms coupled loosely together is formed by adiabatic expansion ejecting the vapour of materials into a high-vacuum region through the nozzle of a heated crucible. The clusters are ionised by electron bombardment and accelerated with neutral clusters toward a substrate. In this paper, mechanisms of cluster formation experimental results of the cluster size (atoms/cluster) and its distribution, and characteristics of the cluster ion beams are reported. The size is calculated from the kinetic equation E = (1/2)mNVsub(ej) 2 , where E is the cluster beam energy, Vsub(ej) is the ejection velocity, m is the mass of atom and N is the cluster size. The energy and the velocity of the cluster are measured by an electrostatic 127 0 energy analyser and a rotating disc system, respectively. The cluster size obtained for Ag is about 5 x 10 2 to 2 x 10 3 atoms. The retarding potential method is used to confirm the results for Ag. The same dependence on cluster size for metals such as Ag, Cu and Pb has been obtained in previous experiments. In the cluster state the cluster ion beam is easily produced by electron bombardment. About 50% of ionised clusters are obtained under typical operation conditions, because of the large ionisation cross sections of the clusters. To obtain a uniform spatial distribution, the ionising electrode system is also discussed. The new techniques are termed ionised-cluster beam deposition (ICBD) and epitaxy (ICBE). (author)

Scales and erosion

Science.gov (United States)

There is a need to develop scale explicit understanding of erosion to overcome existing conceptual and methodological flaws in our modelling methods currently applied to understand the process of erosion, transport and deposition at the catchment scale. These models need to be based on a sound under...

Non-linear sputtering effects induced by MeV energy gold clusters

International Nuclear Information System (INIS)

Boussofiane-Baudin, K.; Brunelle, A.; Chaurand, P.; Della-Negra, S.; Depauw, J.; Le Beyec, Y.; Hakansson, P.

1993-09-01

Gold clusters Au n + with 1 < n ≤ 4, accelerated to MeV energies at the Orsay tandem accelerator, have been used to induce secondary ion emission from the surface of thin organic and inorganic films. A non-linear enhancement of the secondary ion yields is observed when cluster impacts are compared to single atom impacts at the same velocity. It has been shown that the collective effects propagate in the solid over a depth larger than 2000 A. The equilibrium charge state of cluster constituents after their passage through a thin carbon foil (1000 A) has been measured. The mean value for the cluster constituents is the same as for single atoms at the same velocity. (authors). 41 refs., 8 figs., 1 tab

Plasma heating by cluster injection: basic features and expected behaviour

International Nuclear Information System (INIS)

Bottiglioni, F.; Coutant, J.; Fois, M.

1976-08-01

The main components of a cluster injection line intended for plasma heating is briefly discussed, that is the beam source, the cluster ionizer and the accelerating tube, as well as the behavior of clusters interacting with a plasma. Outlines of the experiment of cluster injection into TFR, in progress at Fontenay-aux-Roses, and expected results will be presented and discussed all along the paper

Study of Car Acceleration and Deceleration Characteristics at Dangerous Route FT050

Science.gov (United States)

Omar, N.; Prasetijo, J.; Daniel, B. D.; Abdullah, M. A. E.; Ismail, I.

2018-04-01

Individual vehicle acceleration and deceleration are important to generate vehicles speed profile. This study covered acceleration and deceleration characteristics of passenger car in Federal Route FT050 Jalan Batu Pahat-Ayer Hitam that was the top ranking dangerous road. Global Positioning System was used to record 10 cars speed to develop speed profile with clustering zone. At the acceleration manoeuver, the acceleration rate becomes lower as the drivers get near to desired speed. While, at deceleration manoeuver, vehicles with high speed needs more time to stop compare to low speed vehicle. This is because, the drivers need to accelerate more from zero speed to achieve desired speed and drivers need more distance and time to stop their vehicles. However, it was found out that 30% to 50% are driving in dangerous condition that was proven in clustering acceleration and deceleration speed profile. As conclusion, this excessive drivers are the factor that creating high risk in rear-end collision that inline FT050 as dangerous road in Malaysia

Does a more sophisticated storm erosion model improve probabilistic erosion estimates?

NARCIS (Netherlands)

Ranasinghe, R.W.M.R.J.B.; Callaghan, D.; Roelvink, D.

2013-01-01

The dependency between the accuracy/uncertainty of storm erosion exceedance estimates obtained via a probabilistic model and the level of sophistication of the structural function (storm erosion model) embedded in the probabilistic model is assessed via the application of Callaghan et al.'s (2008)

Buffer erosion in dilute groundwater

International Nuclear Information System (INIS)

Schatz, T.; Kanerva, N.; Martikainen, J.; Sane, P.; Olin, M.; Seppaelae, A.; Koskinen, K.

2013-08-01

One scenario of interest for repository safety assessment involves the loss of bentonite buffer material in contact with dilute groundwater flowing through a transmissive fracture interface. In order to examine the extrusion/erosion behavior of bentonite buffer material under such circumstances, a series of experiments were performed in a flow-through, 1 mm aperture, artificial fracture system. These experiments covered a range of solution chemistry (salt concentration and composition), material composition (sodium montmorillonite and admixtures with calcium montmorillonite), and flow velocity conditions. No erosion was observed for sodium montmorillonite against solution compositions from 0.5 g/L to 10 g/L NaCl. No erosion was observed for 50/50 calcium/sodium montmorillonite against 0.5 g/L NaCl. Erosion was observed for both sodium montmorillonite and 50/50 calcium/sodium montmorillonite against solution compositions ≤ 0.25 g/L NaCl. The calculated erosion rates for the tests with the highest levels of measured erosion, i.e., the tests run under the most dilute conditions (ionic strength (IS) < ∼1 mM), were well-correlated to flow velocity, whereas the calculated erosion rates for the tests with lower levels of measured erosion, i.e., the tests run under somewhat less dilute conditions (∼1 mM < IS < ∼4 mM), were not similarly correlated indicating that material and solution composition can significantly affect erosion rates. In every experiment, both erosive and non-erosive, emplaced buffer material extruded into the fracture and was observed to be impermeable to water flowing in the fracture effectively forming an extended diffusive barrier around the intersecting fracture/buffer interface. Additionally, a model which was developed previously to predict the rate of erosion of bentonite buffer material in low ionic strength water in rock fracture environments was applied to three different cases: sodium montmorillonite expansion in a vertical tube, a

Dynamics of soil organic carbon and microbial biomass carbon in relation to water erosion and tillage erosion.

Science.gov (United States)

Xiaojun, Nie; Jianhui, Zhang; Zhengan, Su

2013-01-01

Dynamics of soil organic carbon (SOC) are associated with soil erosion, yet there is a shortage of research concerning the relationship between soil erosion, SOC, and especially microbial biomass carbon (MBC). In this paper, we selected two typical slope landscapes including gentle and steep slopes from the Sichuan Basin, China, and used the (137)Cs technique to determine the effects of water erosion and tillage erosion on the dynamics of SOC and MBC. Soil samples for the determination of (137)Cs, SOC, MBC and soil particle-size fractions were collected on two types of contrasting hillslopes. (137)Cs data revealed that soil loss occurred at upper slope positions of the two landscapes and soil accumulation at the lower slope positions. Soil erosion rates as well as distribution patterns of the erosion is the major process of soil redistribution in the gentle slope landscape, while tillage erosion acts as the dominant process of soil redistribution in the steep slope landscape. In gentle slope landscapes, both SOC and MBC contents increased downslope and these distribution patterns were closely linked to soil redistribution rates. In steep slope landscapes, only SOC contents increased downslope, dependent on soil redistribution. It is noticeable that MBC/SOC ratios were significantly lower in gentle slope landscapes than in steep slope landscapes, implying that water erosion has a negative effect on the microbial biomass compared with tillage erosion. It is suggested that MBC dynamics are closely associated with soil redistribution by water erosion but independent of that by tillage erosion, while SOC dynamics are influenced by soil redistribution by both water erosion and tillage erosion.

Effectiveness assessment of soil conservation measures in reducing soil erosion in Baiquan County of Northeastern China by using (137)Cs techniques.

Science.gov (United States)

Zhang, Qing-Wen; Li, Yong

2014-05-01

Accelerated soil erosion is considered as a major land degradation process resulting in increased sediment production and sediment-associated nutrient inputs to the rivers. Over the last decade, several soil conservation programs for erosion control have been conducted throughout Northeastern China. Reliable information on soil erosion rates is an essential prerequisite to assess the effectiveness of soil conservation measures. A study was carried out in Baiquan County of Northeastern China to assess the effectiveness of soil conservation measures in reducing soil erosion using the (137)Cs tracer technique and related techniques. This study reports the use of (137)Cs measurements to quantify medium-term soil erosion rates in traditional slope farmland, contour cropping farmland and terrace farmland in the Dingjiagou catchment and the Xingsheng catchment of Baiquan County. The (137)Cs reference inventory of 2532 ± 670 Bq m(-2) was determined. Based on the principle of the (137)Cs tracer technique, soil erosion rates were estimated. The results showed that severe erosion on traditional slope farmland is the dominant soil erosion process in the area. The terrace measure reduced soil erosion rates by 16% for the entire slope. Typical net soil erosion rates are estimated to be 28.97 Mg per hectare per year for traditional slope farmland and 25.04 Mg per hectare per year for terrace farmland in the Dingjiagou catchment. In contrast to traditional slope farmland with a soil erosion rate of 34.65 Mg per hectare per year, contour cultivation reduced the soil erosion rate by 53% resulting in a soil erosion rate of 22.58 Mg per hectare per year in the Xingsheng catchment. These results indicated that soil losses can be controlled by changing tillage practices from the traditional slope farmland cultivation to the terrace or contour cultivation.

Resonant heating of a cluster plasma by intense laser light

International Nuclear Information System (INIS)

Antonsen, Thomas M. Jr.; Taguchi, Toshihiro; Gupta, Ayush; Palastro, John; Milchberg, Howard M.

2005-01-01

Gases of atomic clusters are interaction media for laser pulse propagation with properties useful for applications such as extreme ultraviolet (EUV) and x-ray microscopy, harmonic generation, EUV lithography, and laser plasma acceleration. To understand cluster heating and expansion, a series of two- and three-dimensional electrostatic particle in cell simulations of the explosion of argon clusters of diameter in the range 20 nm-53 nm have been preformed. The studies show that heating is dominated by a nonlinear, resonant absorption process that gives rise to a size-dependent intensity threshold for strong absorption and that controls the dielectric properties of the cluster. Electrons are first accelerated out from the cluster and then driven back into it by the combined effects of the laser field and the electrostatic field produced by the laser-driven charge separation. Above the intensity threshold for strong heating there is a dramatic increase in the production of energetic particles and harmonic radiation. The dielectric properties of a gas of clusters are determined by the ensemble average cluster polarizability. Individual electrons contribute to the polarizability differently depending on whether they are in the core of the cluster or in the outer edge. Consequently, there can be large fluctuations in polarizability during the heating of a cluster

Erhversbetinget erosion?

DEFF Research Database (Denmark)

Dige, Irene; Gjørup, Hans; Nyvad, Bente

2012-01-01

Baggrund – I forbindelse med dental erosion er en grundig udredning af patienten vigtig, således at årsagen til erosionernes opståen findes, og der kan iværksættes adækvat forebyggende indsats. En sådan udredning er ikke mindst vigtig, når arbejdsmiljøet mistænkes. Patienttilfælde – En 30-årig...... arbejdsskade, men ikke anerkendt, da erosioner ikke er optaget på Arbejdsskadestyrelsens liste over erhvervssygdomme. En systematisk registrering af lignende tilfælde kunne imidlertid på sigt ændre retspraksis for fremtidige patienter med arbejdsbetinget erosion....... patient, der arbejder som pladesmed, blev henvist til Landsdels- og Videnscenter, Århus Sygehus, med henblik på udredning af patientens kraftige slid. Patienten udviste ikke-alderssvarende tandslid af emalje og dentin svarende til erosion forårsaget af syredampe i arbejdsmiljøet, muligvis forstærket af...

PARALLEL SPATIOTEMPORAL SPECTRAL CLUSTERING WITH MASSIVE TRAJECTORY DATA

Directory of Open Access Journals (Sweden)

Y. Z. Gu

2017-09-01

Full Text Available Massive trajectory data contains wealth useful information and knowledge. Spectral clustering, which has been shown to be effective in finding clusters, becomes an important clustering approaches in the trajectory data mining. However, the traditional spectral clustering lacks the temporal expansion on the algorithm and limited in its applicability to large-scale problems due to its high computational complexity. This paper presents a parallel spatiotemporal spectral clustering based on multiple acceleration solutions to make the algorithm more effective and efficient, the performance is proved due to the experiment carried out on the massive taxi trajectory dataset in Wuhan city, China.

Farmers' identification of erosion indicators and related erosion damage in the Central Highlands of Kenya

NARCIS (Netherlands)

Sterk, G.; Okoba, B.O.

2006-01-01

Most soil and water conservation planning approaches rely on empirical assessment methods and hardly consider farmers' knowledge of soil erosion processes. Farmers' knowledge of on-site erosion indicators could be useful in assessing the site-specific erosion risk before planning any conservation

Indium tin oxide surface smoothing by gas cluster ion beam

CERN Document Server

Song, J H; Choi, W K

2002-01-01

CO sub 2 cluster ions are irradiated at the acceleration voltage of 25 kV to remove hillocks on indium tin oxide (ITO) surfaces and thus to attain highly smooth surfaces. CO sub 2 monomer ions are also bombarded on the ITO surfaces at the same acceleration voltage to compare sputtering phenomena. From the atomic force microscope results, the irradiation of monomer ions makes the hillocks sharper and the surfaces rougher from 1.31 to 1.6 nm in roughness. On the other hand, the irradiation of CO sub 2 cluster ions reduces the height of hillocks and planarize the ITO surfaces as smooth as 0.92 nm in roughness. This discrepancy could be explained by large lateral sputtering yield of the cluster ions and re-deposition of sputtered particles by the impact of the cluster ions on surfaces.

Multi-temporal Soil Erosion Modelling over the Mt Kenya Region with Multi-Sensor Earth Observation Data

Science.gov (United States)

Symeonakis, Elias; Higginbottom, Thomas

2015-04-01

Accelerated soil erosion is the principal cause of soil degradation across the world. In Africa, it is seen as a serious problem creating negative impacts on agricultural production, infrastructure and water quality. Regarding the Mt Kenya region, specifically, soil erosion is a serious threat mainly due to unplanned and unsustainable practices linked to tourism, agriculture and rapid population growth. The soil types roughly correspond with different altitudinal zones and are generally very fertile due to their volcanic origin. Some of them have been created by eroding glaciers while others are due to millions of years of fluvial erosion. The soils on the mountain are easily eroded once exposed: when vegetation is removed, the soil quickly erodes down to bedrock by either animals or humans, as tourists erode paths and local people clear large swaths of forested land for agriculture, mostly illegally. It is imperative, therefore, that a soil erosion monitoring system for the Mt Kenya region is in place in order to understand the magnitude of, and be able to respond to, the increasing number of demands on this renewable resource. In this paper, we employ a simple regional-scale soil erosion modelling framework based on the Thornes model and suggest an operational methodology for quantifying and monitoring water runoff and soil erosion using multi-sensor and multi-temporal remote sensing data in a GIS framework. We compare the estimates of this study with general data on the severity of soil erosion over Kenya and with measured rates of soil loss at different locations over the area of study. The results show that the measured and estimated rates of erosion are generally similar and within the same order of magnitude. They also show that, over the last years, erosion rates are increasing in large parts of the region at an alarming rate, and that mitigation measures are needed to reverse the negative effects of uncontrolled socio-economic practices.

Tritium depth profiling in carbon by accelerator mass spectrometry

International Nuclear Information System (INIS)

Friedrich, M.; Pilz, W.; Sun, G.; Behrisch, R.; Garcia-Rosales, C.; Bekris, N.; Penzhorn, R.-D.

2000-01-01

Tritium depth profiling measurements by accelerator mass spectrometry have been performed at the facility installed at the Rossendorf 3 MV Tandetron. In order to achieve a uniform erosion at the target surface inside a commercial Cs ion sputtering source and to avoid edge effects, the samples were mechanically scanned and the signals were recorded only during sputtering at the centre of the sputtered area. The sputtered negative ions were mass analysed by the injection magnet of the Tandetron. Hydrogen and deuterium profiles were measured with the Faraday cup between the injection magnet and the accelerator, while the tritium was counted after the accelerator with semiconductor detectors. Depth profiles have been measured for carbon samples which had been exposed to the plasma at the first wall of the Garching fusion experiment ASDEX-Upgrade and from the European fusion experiment JET, Culham, UK

Matahina Dam : lessons learned from an earthquake-related internal erosion incident at the Matahina Dam, New Zealand

Energy Technology Data Exchange (ETDEWEB)

Gillon, M. [Damwatch Services Ltd., Wellington (New Zealand)

2009-07-01

This case history discussed internal erosion damage and crest subsidence caused by an earthquake at the Matahina Dam in New Zealand. The study showed that cracking and internal erosion was initiated during the 1967 reservoir filling operation. Located in an area of active volcanism and faulting, the dam is located on a river with extensive erosion through an ignimbrite flow. The dam's core is founded on compact Tertiary age sediments overlain by sand and gravel deposits beneath the shoulders of the dam. The earthquake caused a rupture along an unidentified fault trace 12 km from the dam. The horizontal base acceleration recorded at the dam was 3.25 m/s. Transverse cracking was observed at each abutment, and deformations were observed in the rockfill. An investigation program was conducted to determine the dam's integrity. Piezometer measurements showed widespread fluctuations. It was concluded that the lack of an effective filter was a significant design omission. 12 refs., 12 figs.

THE EVALUATION OF SOIL EROSION OFF-SITES EFFECTS IN LARGE BASINS: THE STUDYCASE OF LERMA-CHAPALA WATERSHED, MEXICO

Directory of Open Access Journals (Sweden)

Helena Cotler A.

2005-05-01

Full Text Available One of the primary global concerns during the new millennium is the assessment of the impact of accelerated soil erosion on the economy and the environment (Pimentel et al. 1995; Lal, 1995. Erosion damages the site on which it occurs and also has undesirable effects off-site in the larger environment. Erosion moves sediments and nutrients out of the land, creating the two most widespread water pollution problems in the rivers, lakes and dams. The nutrients impact water quality largely through the process of eutrophication caused by an excessive content of nitrogen and phosphorus. In addition to the nutrients presence, sediment and runoff may also carry toxic metals and organic compounds, such as pesticides (Brady and Weil, 1999; Lal, 1994; de Graaf, 2000; Renschler and Harbor, 2002. The sediment itself is a major pollutant causative agent, causing a wide range of environmental damages. The sedimentation of dams and canals, reduces their lifetime and efficiency, promoting a high restoration cost to the downstream users and affecting thenational budget. In this sense, sedimentation knowledge is an important tool to guide spatial planning efficiently. Despite more than six decades of research, sedimentation is still probably the most serious technical problem faced by the dam industry (Mc Cully, 2001. Many studies estimate present-day fluvial sediment and solute loads including both natural and accelerated soil erosion (Douglas, 1990. However, as Douglas mentioned (op.cit many do not include all the erosion caused by human activity, because the eroded sediment is redeposited after a short movement downslope. Many soil particles are detached and carried downslope only to be held and trapped by a plant, tree or other obstacle a little further downslope. The sediment reaching the valley floor may not be completely removed by the river, but may be redistributed as alluvial floodplain deposits. The sediment transported downstream may be redeposited

Enzyme clustering accelerates processing of intermediates through metabolic channeling

Science.gov (United States)

Castellana, Michele; Wilson, Maxwell Z.; Xu, Yifan; Joshi, Preeti; Cristea, Ileana M.; Rabinowitz, Joshua D.; Gitai, Zemer; Wingreen, Ned S.

2015-01-01

We present a quantitative model to demonstrate that coclustering multiple enzymes into compact agglomerates accelerates the processing of intermediates, yielding the same efficiency benefits as direct channeling, a well-known mechanism in which enzymes are funneled between enzyme active sites through a physical tunnel. The model predicts the separation and size of coclusters that maximize metabolic efficiency, and this prediction is in agreement with previously reported spacings between coclusters in mammalian cells. For direct validation, we study a metabolic branch point in Escherichia coli and experimentally confirm the model prediction that enzyme agglomerates can accelerate the processing of a shared intermediate by one branch, and thus regulate steady-state flux division. Our studies establish a quantitative framework to understand coclustering-mediated metabolic channeling and its application to both efficiency improvement and metabolic regulation. PMID:25262299

Chaos theory perspective for industry clusters development

Science.gov (United States)

Yu, Haiying; Jiang, Minghui; Li, Chengzhang

2016-03-01

Industry clusters have outperformed in economic development in most developing countries. The contributions of industrial clusters have been recognized as promotion of regional business and the alleviation of economic and social costs. It is no doubt globalization is rendering clusters in accelerating the competitiveness of economic activities. In accordance, many ideas and concepts involve in illustrating evolution tendency, stimulating the clusters development, meanwhile, avoiding industrial clusters recession. The term chaos theory is introduced to explain inherent relationship of features within industry clusters. A preferred life cycle approach is proposed for industrial cluster recessive theory analysis. Lyapunov exponents and Wolf model are presented for chaotic identification and examination. A case study of Tianjin, China has verified the model effectiveness. The investigations indicate that the approaches outperform in explaining chaos properties in industrial clusters, which demonstrates industrial clusters evolution, solves empirical issues and generates corresponding strategies.

Real-time boronization in PBX-M using erosion of solid boronized targets

International Nuclear Information System (INIS)

Kugel, H.W.; Timberlake, J.; Bell, R.; LeBlanc, B.; Okabayashi, M.; Paul, S.; Tighe, W.; Hirooka, Y.

1994-11-01

Thirty one real-time boronizations were applied to PBX-M using the plasma erosion of solid target probes. More than 17 g of boron were deposited in PBX-M using this technique. The probes were positioned at the edge plasma to optimize vaporization and minimize spallation. Auger depth profile analysis of poloidal and toroidal deposition sample coupon arrays indicate that boron was transported by the plasma around the torus and deep into the divertors. During discharges with continuous real-time boronization, low-Z and high-Z impurities decreased rapidly as plasma surfaces were covered during the first 20-30 discharges. After boronization, a short-term improvement in plasma conditions persisted prior to significant boron erosion from plasma surfaces, and a longer term, but less significant improvement persisted as boron farther from the edge continued gettering. Real-time solid target boronization has been found to be very effective for accelerating conditioning to new regimes and maintaining high performance plasma conditions

The FAST (FRC Acceleration Space Thruster) Experiment

Science.gov (United States)

Martin, Adam; Eskridge, R.; Lee, M.; Richeson, J.; Smith, J.; Thio, Y. C. F.; Slough, J.; Rodgers, Stephen L. (Technical Monitor)

2001-01-01

The Field Reverse Configuration (FRC) is a magnetized plasmoid that has been developed for use in magnetic confinement fusion. Several of its properties suggest that it may also be useful as a thruster for in-space propulsion. The FRC is a compact toroid that has only poloidal field, and is characterized by a high plasma beta = (P)/(B (sup 2) /2Mu0), the ratio of plasma pressure to magnetic field pressure, so that it makes efficient use of magnetic field to confine a plasma. In an FRC thruster, plasmoids would be repetitively formed and accelerated to high velocity; velocities of = 250 km/s (Isp = 25,000s) have already been achieved in fusion experiments. The FRC is inductively formed and accelerated, and so is not subject to the problem of electrode erosion. As the plasmoid may be accelerated over an extended length, it can in principle be made very efficient. And the achievable jet powers should be scalable to the MW range. A 10 kW thruster experiment - FAST (FRC Acceleration Space Thruster) has just started at the Marshall Space Flight Center. The design of FAST and the status of construction and operation will be presented.

Divertor erosion in DIII-D

International Nuclear Information System (INIS)

Whyte, D.G.; Bastasz, R.; Wampler, W.R.; Brooks, J.N.; West, W.P.; Wong, C.P.C.

1998-05-01

Net erosion rates of carbon target plates have been measured in situ for the DIII-D lower divertor. The principal method of obtaining this data is the DiMES sample probe. Recent experiments have focused on erosion at the outer strike-point of two divertor plasma conditions: (1) attached (Te > 40 eV) ELMing plasmas and (2) detached (Te 10 cm/year, even with incident heat flux 2 . In this case, measurements and modeling agree for both gross and net carbon erosion, showing the near-surface transport and redeposition of the carbon is well understood and that effective sputtering yields are > 10%. In ELM-free discharges, this erosion rate can account for the rate of carbon accumulation in the core plasma. Divertor plasma detachment eliminates physical sputtering, while spectroscopically measured chemical erosion yields are also found to be low (Y(C/D + ) ≤ 2.0 x 10 -3 ). This leads to suppression of net erosion at the outer strike-point, which becomes a region of net redeposition (∼ 4 cm/year). The private flux wall is measured to be a region of net redeposition with dense, high neutral pressure, attached divertor plasmas. Leading edges intercepting parallel heat flux (∼ 50 MW/m 2 ) have very high net erosion rates (∼ 10 microm/s) at the OSP of an attached plasma. Leading edge erosion, and subsequent carbon redeposition, caused by tile gaps can account for half of the deuterium codeposition in the DIII-D divertor

Molybdenum erosion measurements in Alcator C-Mod

Energy Technology Data Exchange (ETDEWEB)

Wampler, W.R. [Sandia National Labs., Albuquerque, NM (United States); LaBombard, B.; Lipshultz, B.; Pappas, D.; Pitcher, C.S. [Massachusetts Inst. of Tech., Cambridge, MA (United States); McCracken, G.M. [JET Joint Undertaking, Abingdon (United Kingdom)

1998-05-01

Erosion of molybdenum was measured on a set of 21 tiles after a run campaign of 1,090 shots in the Alcator C-Mod tokamak. The net erosion of molybdenum, was determined from changes in the depth of a thin chromium marker layer measured by Rutherford backscattering. Net Mo erosion was found to be approximately 150 nm near the outer divertor strike point, and much less everywhere else. Gross erosion rates by sputtering were estimated using ion energies and fluxes obtained from Langmuir probe measurements of edge-plasma conditions. Predicted net erosion using calculated gross erosion with prompt redeposition and measured net erosion agree within a factor of 3. Sputtering by boron and molybdenum impurities dominates erosion.

HIGH TEMPERATURE EROSION WEAR OF CERMET PARTICLES REINFORCED SELF-FLUXING ALLOY MATRIX HVOF SPRAYED COATINGS

Directory of Open Access Journals (Sweden)

Andrei Surzhenkov

2015-09-01

Full Text Available In the present paper, the resistance of high velocity oxy-fuel (HVOF sprayed TiC-NiMo and Cr3C2-Ni cermet particles reinforced NiCrSiB self-fluxing alloy matrix coatings to high temperature erosion wear is studied. Microstructure of the coatings was examined by SEM, phase composition was determined by XRD. A four-channel centrifugal particle accelerator was applied to study the high temperature erosion wear of the coatings. The impact angles were 30 and 90 degrees, initial particle velocity was 50 m/s, temperature of the test - 650 degrees. Volume wear of the coatings was calculated and compared to the respective values of the reference materials. Wear mechanisms were studied by SEM.DOI: http://dx.doi.org/10.5755/j01.ms.21.3.7617

Sea level driven marsh expansion in a coupled model of marsh erosion and migration

Science.gov (United States)

Kirwan, Matthew L.; Walters, David C.; Reay, William G.; Carr, Joel

2016-01-01

Coastal wetlands are among the most valuable ecosystems on Earth, where ecosystem services such as flood protection depend nonlinearly on wetland size and are threatened by sea level rise and coastal development. Here we propose a simple model of marsh migration into adjacent uplands and couple it with existing models of seaward edge erosion and vertical soil accretion to explore how ecosystem connectivity influences marsh size and response to sea level rise. We find that marsh loss is nearly inevitable where topographic and anthropogenic barriers limit migration. Where unconstrained by barriers, however, rates of marsh migration are much more sensitive to accelerated sea level rise than rates of edge erosion. This behavior suggests a counterintuitive, natural tendency for marsh expansion with sea level rise and emphasizes the disparity between coastal response to climate change with and without human intervention.

The Monitoring Erosion of Agricultural Land and spatial database of erosion events

Science.gov (United States)

Kapicka, Jiri; Zizala, Daniel

2013-04-01

In 2011 originated in The Czech Republic The Monitoring Erosion of Agricultural Land as joint project of State Land Office (SLO) and Research Institute for Soil and Water Conservation (RISWC). The aim of the project is collecting and record keeping information about erosion events on agricultural land and their evaluation. The main idea is a creation of a spatial database that will be source of data and information for evaluation and modeling erosion process, for proposal of preventive measures and measures to reduce negative impacts of erosion events. A subject of monitoring is the manifestations of water erosion, wind erosion and slope deformation in which cause damaged agriculture land. A website, available on http://me.vumop.cz, is used as a tool for keeping and browsing information about monitored events. SLO employees carry out record keeping. RISWC is specialist institute in the Monitoring Erosion of Agricultural Land that performs keeping the spatial database, running the website, managing the record keeping of events, analysis the cause of origins events and statistical evaluations of keeping events and proposed measures. Records are inserted into the database using the user interface of the website which has map server as a component. Website is based on database technology PostgreSQL with superstructure PostGIS and MapServer UMN. Each record is in the database spatial localized by a drawing and it contains description information about character of event (data, situation description etc.) then there are recorded information about land cover and about grown crops. A part of database is photodocumentation which is taken in field reconnaissance which is performed within two days after notify of event. Another part of database are information about precipitations from accessible precipitation gauges. Website allows to do simple spatial analysis as are area calculation, slope calculation, percentage representation of GAEC etc.. Database structure was designed

Spatial and temporal diversification of crops dynamics in soil erosion modelling. A case study in the arable land of the upper Enziwigger River, Switzerland.

Science.gov (United States)

Borrelli, Pasquale; Meusburger, Katrin; Panagos, Panos; Ballabio, Cristiano; Alewell, Christine

2017-04-01

Accelerated soil erosion by water is a widespread phenomenon that affects several Mediterranean and Alpine landscapes causing on-site and off-site environmental impacts. Recognized in the EU Thematic Strategy for Soil Protection as one of the major threats to European soils (COM(2006)231), accelerated soil erosion is a major concern in landscape management and conservation planning (UN SDG 2.4). Agriculture and associated land-use change is the primary cause of accelerated soil erosion. This, because the soil displacement by water erosion mainly occurs when bare-sloped soil surfaces are exposed to the effect of rainfall and overland flow. The Revised Universal Soil Loss Equation (RUSLE) and other RUSLE-based models (which account for more than 90% of current worldwide modelling applications) describe the effect of the vegetation in the so called cover and management factor (C). The C-factor is generally the most challenging modelling component to compute over large study sites. To run a GIS-based RUSLE modelling for a study site greater than few hectares, the use of a simplified approach to assess the C-factor is inevitably necessary. In most of the cases, the C-factor values are assigned to the different land-use classes according to i) the C-values proposed in the literature, and ii) through land-use classifications based on vegetation indices (VI). In previous national (Land Use Policy, 50, 408-421, 2016) and pan-European (Environmental Science & Policy, 54, 438-447, 2015) studies, we computed regional C-values through weighted average operations combining crop statistics with remote sensing and GIS modelling techniques. Here, we present the preliminary results of an object-oriented change detection approach that we are testing to acquire spatial as well temporal crops dynamics at field-scale level in complex agricultural systems.

Cluster plasma and its dispersion relation

International Nuclear Information System (INIS)

Tajima, T.; Downer, M.C.; Kishimoto, Y.

1998-01-01

It is shown that unlike a gas plasma or an electron plasma in a metal, an ionized cluster material (open-quotes cluster plasmaclose quotes) permits propagation below the plasma cut-off of electromagnetic (EM) waves whose phase velocity is close to but below the speed of light. Its unique properties allow a variety of applications, including direct acceleration of particles with its EM fields and the phase matching of waves of high harmonic generation (HHG)

Gastric Mucosal Erosions - Radiologic evaluation -

International Nuclear Information System (INIS)

Kim, Seung Hyup

1985-01-01

70 cases of gastric mucosal erosions were diagnosed by double contrast upper gastrointestinal examinations and endoscopic findings. Analyzing the radiologic findings of these 70 cases of gastric mucosal erosions, the following results were obtained. 1. Among the total 70 cases, 65 cases were typical varioliform erosions showing central depressions and surrounding mucosal elevations. Remaining 5 cases were erosions of acute phase having multiple irregular depressions without surrounding elevations. 2. The gastric antrum was involved alone or in part in all cases. Duodenal bulb was involved with gastric antrum in 4 cases. 3. The majority of the cases had multiple erosions. There were only 2 cases of single erosion. 4. In 65 cases of varioliform erosions; 1) The diameter of the surrounding elevations varied from 3 to 20 mm with the majority (47 cases) between 6 and 10 mm. 2) In general, the surrounding elevations with sharp margin on double contrast films were also clearly demonstrated on compression films but those with faint margin were not. 3) The size of the central barium collections varied from pinpoint to 10 mm with the majority under 5 mm. The shape of the central barium collections in majority of the cases were round with a few cases of linear, triangular or star-shape. 5. In 5 cases of acute phase erosions; 1) All the 5 cases were females. 2) On double contrast radiography, all the cases showed multiple irregular depressed lesions without surrounding elevations. 3) 1 case had the history of hematemesis. 4) In 1 case, there was marked radiological improvement on follow-up study of 2 months interval. 6. In 23 cases, there were coexistent diseases with gastric mucosal erosions. These were 13 cases of duodenal bulb ulcers,7 cases of benign gastric ulcers and 3 others

Quantitative remote sensing study indicates doubling of coastal erosion rate in past 50 yr along a segment of the Arctic coast of Alaska

Science.gov (United States)

Mars, J.C.; Houseknecht, D.W.

2007-01-01

A new quantitative coastal land gained-and-lost method uses image analysis of topographic maps and Landsat thematic mapper short-wave infrared data to document accelerated coastal land loss and thermokarst lake expansion and drainage. The data span 1955-2005 along the Beaufort Sea coast north of Teshekpuk Lake in the National Petroleum Reserve in Alaska. Some areas have undergone as much as 0.9 km of coastal erosion in the past 50 yr. Land loss attributed to coastal erosion more than doubled, from 0.48 km2 yr-1 during 1955-1985 to 1.08 km2 yr-1 during 1985-2005. Coastal erosion has breached thermokarst lakes, causing initial draining of the lakes followed by marine floodng. Although inland thermokarst lakes show some uniform expansion, lakes breached by coastal erosion display lake expansion several orders of magnitude greater than inland lakes. ?? 2007 The Geological Society of America.

Numerically Modeling the Erosion of Lunar Soil by Rocket Exhaust Plumes

Science.gov (United States)

2008-01-01

In preparation for the Apollo program, Leonard Roberts of the NASA Langley Research Center developed a remarkable analytical theory that predicts the blowing of lunar soil and dust beneath a rocket exhaust plume. Roberts assumed that the erosion rate was determined by the excess shear stress in the gas (the amount of shear stress greater than what causes grains to roll). The acceleration of particles to their final velocity in the gas consumes a portion of the shear stress. The erosion rate continues to increase until the excess shear stress is exactly consumed, thus determining the erosion rate. Roberts calculated the largest and smallest particles that could be eroded based on forces at the particle scale, but the erosion rate equation assumed that only one particle size existed in the soil. He assumed that particle ejection angles were determined entirely by the shape of the terrain, which acts like a ballistic ramp, with the particle aerodynamics being negligible. The predicted erosion rate and the upper limit of particle size appeared to be within an order of magnitude of small-scale terrestrial experiments but could not be tested more quantitatively at the time. The lower limit of particle size and the predictions of ejection angle were not tested. We observed in the Apollo landing videos that the ejection angles of particles streaming out from individual craters were time-varying and correlated to the Lunar Module thrust, thus implying that particle aerodynamics dominate. We modified Roberts theory in two ways. First, we used ad hoc the ejection angles measured in the Apollo landing videos, in lieu of developing a more sophisticated method. Second, we integrated Roberts equations over the lunar-particle size distribution and obtained a compact expression that could be implemented in a numerical code. We also added a material damage model that predicts the number and size of divots which the impinging particles will cause in hardware surrounding the landing

Acceleration of Magnetospheric Relativistic Electrons by Ultra-Low Frequency Waves: A Comparison between Two Cases Observed by Cluster and LANL Satellites

Science.gov (United States)

Shao, X.; Fung, S. F.; Tan, L. C.; Sharma, A. S.

2010-01-01

Understanding the origin and acceleration of magnetospheric relativistic electrons (MREs) in the Earth's radiation belt during geomagnetic storms is an important subject and yet one of outstanding questions in space physics. It has been statistically suggested that during geomagnetic storms, ultra-low-frequency (ULF) Pc-5 wave activities in the magnetosphere are correlated with order of magnitude increase of MRE fluxes in the outer radiation belt. Yet, physical and observational understandings of resonant interactions between ULF waves and MREs remain minimum. In this paper, we show two events during storms on September 25, 2001 and November 25, 2001, the solar wind speeds in both cases were > 500 km/s while Cluster observations indicate presence of strong ULF waves in the magnetosphere at noon and dusk, respectively, during a approx. 3-hour period. MRE observations by the Los Alamos (LANL) spacecraft show a quadrupling of 1.1-1.5 MeV electron fluxes in the September 25, 2001 event, but only a negligible increase in the November 2.5, 2001 event. We present a detailed comparison between these two events. Our results suggest that the effectiveness of MRE acceleration during the September 25, 2001 event can be attributed to the compressional wave mode with strong ULF wave activities and the physical origin of MRE acceleration depends more on the distribution of toroidal and poloidal ULF waves in the outer radiation belt.

Current and future assessments of soil erosion by water on the Tibetan Plateau based on RUSLE and CMIP5 climate models.

Science.gov (United States)

Teng, Hongfen; Liang, Zongzheng; Chen, Songchao; Liu, Yong; Viscarra Rossel, Raphael A; Chappell, Adrian; Yu, Wu; Shi, Zhou

2018-04-18

Soil erosion by water is accelerated by a warming climate and negatively impacts water security and ecological conservation. The Tibetan Plateau (TP) has experienced warming at a rate approximately twice that observed globally, and heavy precipitation events lead to an increased risk of erosion. In this study, we assessed current erosion on the TP and predicted potential soil erosion by water in 2050. The study was conducted in three steps. During the first step, we used the Revised Universal Soil Equation (RUSLE), publicly available data, and the most recent earth observations to derive estimates of annual erosion from 2002 to 2016 on the TP at 1-km resolution. During the second step, we used a multiple linear regression (MLR) model and a set of climatic covariates to predict rainfall erosivity on the TP in 2050. The MLR was used to establish the relationship between current rainfall erosivity data and a set of current climatic and other covariates. The coefficients of the MLR were generalised with climate covariates for 2050 derived from the fifth phase of the Coupled Model Intercomparison Project (CMIP5) models to estimate rainfall erosivity in 2050. During the third step, soil erosion by water in 2050 was predicted using rainfall erosivity in 2050 and other erosion factors. The results show that the mean annual soil erosion rate on the TP under current conditions is 2.76tha -1 y -1 , which is equivalent to an annual soil loss of 559.59×10 6 t. Our 2050 projections suggested that erosion on the TP will increase to 3.17tha -1 y -1 and 3.91tha -1 y -1 under conditions represented by RCP2.6 and RCP8.5, respectively. The current assessment and future prediction of soil erosion by water on the TP should be valuable for environment protection and soil conservation in this unique region and elsewhere. Copyright © 2018 Elsevier B.V. All rights reserved.

Coastal Erosion Control Methods

Science.gov (United States)

Greene, V.

2016-12-01

Coastal erosion is bad because the ecosystem there will be washed away and the animals could drown or be displaced and have to adapt to a new ecosystem that they are not prepared for. I'm interested in this problem because if there aren't beaches when I grow up I won't be able to do the things I would really like to do. I would like to be a marine biologist. Secondly, I don't want to see beach houses washed away. I would like to see people live in harmony with their environment. So, to study ways in which to preserve beaches I will make and use models that test different erosion controls. Two different ideas for erosion control I tested are using seaweed or a rock berm. I think the rock berm will work better than the model of seaweed because the seaweed is under water and the waves can carry the sand over the seaweed, and the rock berm will work better because the rocks will help break the waves up before they reach the shore and the waves can not carry the sand over the rocks that are above the water. To investigate this I got a container to use to model the Gulf of Mexico coastline. I performed several test runs using sand and water in the container to mimic the beach and waves from the Gulf of Mexico hitting the shoreline. I did three trials for the control (no erosion control), seaweed and a rock berm. Rock berms are a border of a raised area of rock. The model for seaweed that I used was plastic shopping bags cut into strips and glued to the bottom of my container to mimic seaweed. My results were that the control had the most erosion which ranged from 2.75 - 3 inches over 3 trials. The seaweed was a little better than the control but was very variable and ranged from 1.5 - 3 inches over 3 trials. The rock berm worked the best out of all at controlling erosion with erosion ranging from 1.5 - 2 inches. My hypothesis was correct because the rock berm did best to control erosion compared to the control which had no erosion control and the model with seaweed.

Monthly Rainfall Erosivity Assessment for Switzerland

Science.gov (United States)

Schmidt, Simon; Meusburger, Katrin; Alewell, Christine

2016-04-01

Water erosion is crucially controlled by rainfall erosivity, which is quantified out of the kinetic energy of raindrop impact and associated surface runoff. Rainfall erosivity is often expressed as the R-factor in soil erosion risk models like the Universal Soil Loss Equation (USLE) and its revised version (RUSLE). Just like precipitation, the rainfall erosivity of Switzerland has a characteristic seasonal dynamic throughout the year. This inter-annual variability is to be assessed by a monthly and seasonal modelling approach. We used a network of 86 precipitation gauging stations with a 10-minute temporal resolution to calculate long-term average monthly R-factors. Stepwise regression and Monte Carlo Cross Validation (MCCV) was used to select spatial covariates to explain the spatial pattern of R-factor for each month across Switzerland. The regionalized monthly R-factor is mapped by its individual regression equation and the ordinary kriging interpolation of its residuals (Regression-Kriging). As covariates, a variety of precipitation indicator data has been included like snow height, a combination of hourly gauging measurements and radar observations (CombiPrecip), mean monthly alpine precipitation (EURO4M-APGD) and monthly precipitation sums (Rhires). Topographic parameters were also significant explanatory variables for single months. The comparison of all 12 monthly rainfall erosivity maps showed seasonality with highest rainfall erosivity in summer (June, July, and August) and lowest rainfall erosivity in winter months. Besides the inter-annual temporal regime, a seasonal spatial variability was detectable. Spatial maps of monthly rainfall erosivity are presented for the first time for Switzerland. The assessment of the spatial and temporal dynamic behaviour of the R-factor is valuable for the identification of more susceptible seasons and regions as well as for the application of selective erosion control measures. A combination with monthly vegetation

Applicability of 239Pu as a tracer for soil erosion in the wet-dry tropics of northern Australia

Science.gov (United States)

Lal, R.; Tims, S. G.; Fifield, L. K.; Wasson, R. J.; Howe, D.

2013-01-01

The technique of accelerator mass spectroscopy (AMS) has been employed to determine modern soil loss rates through the analysis of 239Pu profiles in soil cores from the Daly basin in Northern Territory, Australia. In areas in which soil conservation banks were not present or were only added recently (banks in other parts of the catchment. High intensity seasonal rainfall combined with reduction in land cover due to grazing and episodic bush fires are primary factors influencing erosion although other impacts on the landscape such as tillage generated runoff and land clearing seem to be responsible for accelerated sediment production.

Report on the study of erosion and H-recycle/inventory of carbon/graphite

International Nuclear Information System (INIS)

Haasz, A.A.; Davis, J.W.

1990-04-01

This study investigated the erosion and hydrogen retention capacity of graphite under plasma exposure by performing controlled plasma simulation experiments using a low-energy high-flux mass analyzed ion accelerator. The authors studied radiation-enhanced sublimation (RES) of graphite, the effect of ion angle of incidence on physical sputtering, the effect of oxygen on hydrocarbon formation during O 2 /H 2 impact, chemical erosion of boron carbide, and the effect of thermal atoms on self-sputtering of graphite. The flux dependence of RES is nearly linear (power of .91) for the extended flux range of 10 13 - 10 17 H + /cm 2 s. Physical sputtering yields were enhanced for off-normal angles of incidence, especially for highly-oriented polished surfaces. Oxygen did not appear to have an effect on the hydrocarbon formation rate; however, some erosion through CO formation was observed. Although large transients were observed in hydrocarbon production in B 4 C, steady-state levels were typically about two orders of magnitude below the erosion rate of graphite. To investigate carbon self-sputtering, thermal H 0 atoms were added to impacting C + ions, simulating a condition existing in the tokamak plasma edge. This led to a synergistic enhancement of the chemical erosion process. For C + /H+0 flux ratios of less than about 10 -1 the chemical erosion yield exceeds unity. Work on hydrogen retention concentrated on the study of H + trapping in different types of graphites as a function of flux and fluence of incident H + . The amount of H trapped in the near-surface region of graphite reaches a saturation level, a function of graphite temperature and impacting H + energy. The amount of H trapped in graphite beyond the ion range was found to increase with increasing fluence and varied for different graphites tested. It seems that hydrogen diffuses through grain boundaries and open porosity in the material until trapped by available carbon bonds

How does soil erosion influence the terrestrial carbon cycle and the impacts of land use and land cover change?

Science.gov (United States)

Naipal, V.; Wang, Y.; Ciais, P.; Guenet, B.; Lauerwald, R.

2017-12-01

The onset of agriculture has accelerated soil erosion rates significantly, mobilizing vast quantities of soil organic carbon (SOC) globally. Studies show that at timescales of decennia to millennia this mobilized SOC can significantly alter previously estimated carbon emissions from land use and land cover change (LULCC). However, a full understanding of the impact of soil erosion on land-atmosphere carbon exchange is still missing. The aim of our study is to better constrain the terrestrial carbon fluxes by developing methods, which are compatible with earth system models (ESMs), and explicitly represent the links between soil erosion and carbon dynamics. For this we use an emulator that represents the carbon cycle of ORCHIDEE, which is the land component of the IPSL ESM, in combination with an adjusted version of the Revised Universal Soil Loss Equation (RUSLE) model. We applied this modeling framework at the global scale to evaluate how soil erosion influenced the terrestrial carbon cycle in the presence of elevated CO2, regional climate change and land use change. Here, we focus on the effects of soil detachment by erosion only and do not consider sediment transport and deposition. We found that including soil erosion in the SOC dynamics-scheme resulted in two times more SOC being lost during the historical period (1850-2005 AD). LULCC is the main contributor to this SOC loss, whose impact on the SOC stocks is significantly amplified by erosion. Regionally, the influence of soil erosion varies significantly, depending on the magnitude of the perturbations to the carbon cycle and the effects of LULCC and climate change on soil erosion rates. We conclude that it is necessary to include soil erosion in assessments of LULCC, and to explicitly consider the effects of elevated CO2 and climate change on the carbon cycle and on soil erosion, for better quantification of past, present, and future LULCC carbon emissions.

Accelerating Information Retrieval from Profile Hidden Markov Model Databases.

Science.gov (United States)

Tamimi, Ahmad; Ashhab, Yaqoub; Tamimi, Hashem

2016-01-01

Profile Hidden Markov Model (Profile-HMM) is an efficient statistical approach to represent protein families. Currently, several databases maintain valuable protein sequence information as profile-HMMs. There is an increasing interest to improve the efficiency of searching Profile-HMM databases to detect sequence-profile or profile-profile homology. However, most efforts to enhance searching efficiency have been focusing on improving the alignment algorithms. Although the performance of these algorithms is fairly acceptable, the growing size of these databases, as well as the increasing demand for using batch query searching approach, are strong motivations that call for further enhancement of information retrieval from profile-HMM databases. This work presents a heuristic method to accelerate the current profile-HMM homology searching approaches. The method works by cluster-based remodeling of the database to reduce the search space, rather than focusing on the alignment algorithms. Using different clustering techniques, 4284 TIGRFAMs profiles were clustered based on their similarities. A representative for each cluster was assigned. To enhance sensitivity, we proposed an extended step that allows overlapping among clusters. A validation benchmark of 6000 randomly selected protein sequences was used to query the clustered profiles. To evaluate the efficiency of our approach, speed and recall values were measured and compared with the sequential search approach. Using hierarchical, k-means, and connected component clustering techniques followed by the extended overlapping step, we obtained an average reduction in time of 41%, and an average recall of 96%. Our results demonstrate that representation of profile-HMMs using a clustering-based approach can significantly accelerate data retrieval from profile-HMM databases.

Efficient construction of two-dimensional cluster states with probabilistic quantum gates

International Nuclear Information System (INIS)

Chen Qing; Cheng Jianhua; Wang Kelin; Du Jiangfeng

2006-01-01

We propose an efficient scheme for constructing arbitrary two-dimensional (2D) cluster states using probabilistic entangling quantum gates. In our scheme, the 2D cluster state is constructed with starlike basic units generated from 1D cluster chains. By applying parallel operations, the process of generating 2D (or higher-dimensional) cluster states is significantly accelerated, which provides an efficient way to implement realistic one-way quantum computers

Mapping the particle acceleration in the cool core of the galaxy cluster RX J1720.1+2638

International Nuclear Information System (INIS)

Giacintucci, S.; Markevitch, M.; Brunetti, G.; Venturi, T.; ZuHone, J. A.; Mazzotta, P.; Bourdin, H.

2014-01-01

We present new deep, high-resolution radio images of the diffuse minihalo in the cool core of the galaxy cluster RX J1720.1+2638. The images have been obtained with the Giant Metrewave Radio Telescope at 317, 617, and 1280 MHz and with the Very Large Array at 1.5, 4.9, and 8.4 GHz, with angular resolutions ranging from 1'' to 10''. This represents the best radio spectral and imaging data set for any minihalo. Most of the radio flux of the minihalo arises from a bright central component with a maximum radius of ∼80 kpc. A fainter tail of emission extends out from the central component to form a spiral-shaped structure with a length of ∼230 kpc, seen at frequencies 1.5 GHz and below. We find indication of a possible steepening of the total radio spectrum of the minihalo at high frequencies. Furthermore, a spectral index image shows that the spectrum of the diffuse emission steepens with increasing distance along the tail. A striking spatial correlation is observed between the minihalo emission and two cold fronts visible in the Chandra X-ray image of this cool core. These cold fronts confine the minihalo, as also seen in numerical simulations of minihalo formation by sloshing-induced turbulence. All these observations favor the hypothesis that the radio-emitting electrons in cluster cool cores are produced by turbulent re-acceleration.

Divertor erosion in DIII-D

International Nuclear Information System (INIS)

Whyte, D.G.; Bastasz, R.; Wampler, W.R.; Brooks, J.N.; West, W.P.; Wong, C.P.C.; Buzhinskij, O.I.; Opimach, I.V.

1998-08-01

Net erosion rates of carbon target plates have been measured in situ for the DIII-D lower divertor. The principal method of obtaining this data is the DiMES sample probe. Recent experiments have focused on erosion at the outer strike-point (OSP) of two divertor plasma conditions: attached (T e > 40 eV) ELMing plasmas, and detached (T e 2 . In this case, measurements and modeling agree for both gross and net carbon erosion, showing the near-surface transport and redeposition of the carbon is well understood. In the attached cases, physical sputtering (with enhancement from self-sputtering and oblique incidence) is dominant, and the effective sputtering yield, Y, is greater than 10%. In ELM-free discharges, the total OSP net erosion rate is equal to the rate of carbon accumulation in the core plasma. For the detached divertor cases, the cold incident plasma eliminates physical sputtering. Attempts to measure chemically eroded hydrocarbon molecules spectroscopically indicate an upper limit of Y ≤ 0.1% for the chemical sputtering yield. Net erosion is suppressed at the outer strike-point, which becomes a region of net redeposition (∼ 4 cm/exposure-year). The private flux wall is measured to be a region of net redeposition with dense, high neutral pressure, attached divertor plasmas. Leading edges intercepting parallel heat flux (∼ 50 MW/m 2 ) have very high net erosion rates at the OSP of an attached plasma (∼ 10 microm/s > 1,000x erosion rate of aligned surfaces). Leading edge erosion, and subsequent carbon redeposition, caused by tile gaps can account for half of the deuterium codeposition in the DIII-D divertor

STUDY OF RAINFALL RATES AND EROSIVE PROCESSES AT THE URBAN AREA OF SÃO LUÍS – MA

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Antonio José Teixeira Guerra

2005-05-01

Full Text Available The study of the rain rates is here highlighted, in order to understand the mechanisms that generate the starting point of the erosive processes. The precipitation varies spatially not only in local and regional levels, due to mechanisms that generate rains, but also in short distances, due to the control of local variations, such as winds and constructions. In this way, the precipitations should be measured in different points of the study area, depending on the interest of the study and scale of analysis.The erosive process caused by rainfall covers almost the whole terrestrial surface, especially in tropical areas where the total rainfall is higher than in other regions of the planet. Besides that, the rain only falls on specific seasons in several areas, which worsens the erosion. The process tends to accelerate as the deforestation for wood exploitation and/or agricultural production takes place, once the soils become unprotected without the vegetal cover, so that the rains affect the surface of the grounds directly (GUERRA, 1999.This work presents the results of the monitoring of erosive processes along more than three years of studies at the urban area of São Luís City, relating rainfall rates to gullies evolution, an important instrument for the control and recovery of large-scale erosive processes.

X-ray diagnosis of erosive gastritis

International Nuclear Information System (INIS)

Taskov, A.; Krastin, A.

1993-01-01

A series of 602 patients are studied according to a standard protocol including double contrast examination, taking films with dosed compression and complete filling (accordingly 3+3+1 radiographs). A barium suspension at concentration 200.0 BaSO 4 in 100 ml water is used as a positive contrast medium, and effervescent powder or pills - as a negative contrast. Erosive gastritis is diagnosed in 48 patients (7.9%) of which 38 present complete erosions (79.2%), 6 (12.6%) - incomplete, and 4 (8.3%) - mixed erosions. In 35 cases (72.9%) erosions are differentiated in double-contrast films, while in 21 (43.8%) - in those with compression. The advantage of the double contrast technique consists in visualization of erosions of the body of the stomach and discovering of incomplete erosions. In 483 patients a comparative assessment is done of the X-ray and endoscopic findings. There are recorded 5 false-positive and 25 false-negative radiological results. The sensitivity of the X-ray study in terms of erosive gastritis amounts to 59.7%. 15 refs., 4 figs. (orig.)

Ultrasonic Measurement of Erosion/corrosion Rates in Industrial Piping Systems

Science.gov (United States)

Sinclair, A. N.; Safavi, V.; Honarvar, F.

2011-06-01

Industrial piping systems that carry aggressive corrosion or erosion agents may suffer from a gradual wall thickness reduction that eventually threatens pipe integrity. Thinning rates could be estimated from the very small change in wall thickness values measured by conventional ultrasound over a time span of at least a few months. However, measurements performed over shorter time spans would yield no useful information—minor signal distortions originating from grain noise and ultrasonic equipment imperfections prevent a meaningful estimate of the minuscule reduction in echo travel time. Using a Model-Based Estimation (MBE) technique, a signal processing scheme has been developed that enables the echo signals from the pipe wall to be separated from the noise. This was implemented in a laboratory experimental program, featuring accelerated erosion/corrosion on the inner wall of a test pipe. The result was a reduction in the uncertainty in the wall thinning rate by a factor of four. This improvement enables a more rapid response by system operators to a change in plant conditions that could pose a pipe integrity problem. It also enables a rapid evaluation of the effectiveness of new corrosion inhibiting agents under plant operating conditions.

EFFECTS OF SLOPE SHAPES ON SOIL EROSION

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Hüseyin ŞENSOY, Şahin PALTA

2009-01-01

Full Text Available Water is one of the most important erosive forces. A great number of factors also play a role in erosion process and slope characteristic is also one of them. The steepness and length of the slope are important factors for runoff and soil erosion. Another slope factor that has an effect on erosion is the shape of the slope. Generally, different erosion and runoff characteristics exist in different slopes which can be classified as uniform, concave, convex and complex shape. In this study, the effects of slope shape on erosion are stated and emphasized by taking similar researches into consideration.

The use of radionuclide techniques in soil erosion studies

International Nuclear Information System (INIS)

Bernard, C.; Mabit, L.

2006-01-01

Erosion is of concern since it can reduce soil productivity as a result of exportation of inorganic and organic material and nutrients out of the cultivated fields. These are the so-called 'onsite' impacts of erosion. Some of the exported materials, and the associated elements, find their way to water bodies The result is a degradation of the water quality due to suspended solids, sedimentation, eutrophication and pesticide toxicity, what is currently referred to as off-site impacts. Despite its importance, many countries lack reliable and comprehensive data on the problem, its magnitude and spatial extent. One of the reasons is that producing representative and reliable data on erosion is a long and resource intensive process.Fallout radionuclides (FRNs), such as 137 Cs, 210 Pb and 7 Be, have proven to be very powerful tracers of soil movements, that can complement interestingly more conventional approaches. Starting in the mid-1990's the IAEA has been actively involved in supporting coordinated research activities to further develop several methodological aspects related to the use of these isotopes and in the dissemination of the techniques among Member States, through the joint efforts of the Soil and Water Management and Crop Nutrition Section (SWMCN) of the Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture and the Soil Science Unit (SSU) of the FAO/IAEA Agriculture and Biotechnology Laboratory. A first Coordinated Research Project (CRP), from 1996 to 2001, helped to test and validate the basic assumptions underlying the use of FRN, to accelerate the development of conversion models used to translate FRN data into soil movements and to evaluate the effect of specific land use management on soil erosion. A second CRP, planned for 2003-2007, builds on the results of the first one to assess the efficiency of different soil conservation practices, to continue the validation of conversion models and the development of user-friendly software to

Cooking a `Sausage': the impact of merger shocks in cluster gas and galaxy evolution

Science.gov (United States)

Stroe, Andra; Sobral, David; Harwood, Jeremy; Van Weeren, Reinout J.; Rumsey, Clare; Intema, Huib; Röttgering, Huub; Brüggen, Marcus; Saunders, Richard; Hardcastle, Martin; Hoeft, Matthias

2015-01-01

Galaxy clusters mainly grow through mergers with other clusters and groups. Major mergers give rise to important astrophysical phenomena such as the segregation of dark and luminous matter and the formation of cluster-wide traveling shocks and also drive galaxy evolution. The observable effects of shock waves can be seen at radio wavelengths as relics: elongated, diffuse synchrotron emitting areas located at the periphery of merging clusters. Despite the great interest in relics, candidates with simple geometry, undisturbed morphology and high surface brightness are scarce. The `Sausage' cluster hosts an extraordinary Mpc-wide relic, which enables us to study to study particle acceleration and the effects of shocks on cluster galaxies. We use a unique combination of facilities (INT, WHT, Keck, Subaru, CFHT, GMRT, WSRT, AMI) to obtain the first cluster-wide, multi-wavelength, multi-method analysis aimed at giving a complete picture of a merging cluster with relics. Using the radio data, we derive shock properties and the magnetic field structure for the relic. Using spectral modeling, we test acceleration and electron energy-loss mechanisms and resolve the discrepancy between the Mach number calculated from the radio and X-rays. Our results indicate that particles are shock-accelerated, but turbulent re-acceleration or unusually efficient transport of particles in the downstream area and line-of-sight mixing are important effects. We demonstrate the feasibility of high-frequency observations of radio relics, by presenting a 16 GHz detection of the `Sausage' relic. The radio analysis is complemented by Hα mapping of the cluster volume, aimed at providing the first direct test as to whether the shock drives or prohibits star formation. We find numerous Hα emitting galaxies in close proximity to the radio relic which are extremely massive, metal-rich, mostly star-forming with evidence for gas mass loss though outflows. We speculate that the complex interaction

Spatial and temporal variations of wind erosion climatic erosivity in the farming-pastoral zone of Northern China

Science.gov (United States)

Yue, Shuping; Yang, Ruixin; Yan, Yechao; Yang, Zhengwei; Wang, Dandan

2018-03-01

Wind erosion climatic erosivity is an important parameter to assess the possible effects of climatic conditions on wind erosion. In this paper, the wind erosion climatic factor (C-factor), which was used to quantify the wind erosion climatic erosivity, was calculated for the period 1960-2014 based on monthly meteorological data collected from 101 stations in the farming-pastoral zone of Northern China. The Mann-Kendall (M-K) test, trend analysis, and geostatistical analysis methods were used to explore the spatial and temporal characteristics of the wind erosion climatic erosivity in this region. The result suggests that the annual C-factor, with a maximum of 76.05 in 1969 and a minimum of 26.57 in 2007, has a significant decreasing trend over the past 55 years. Strong seasonality in the C-factor was found, with the highest value in spring, which accounts for a significant proportion of the annual C-factor (41.46%). However, the coefficient of variation of the seasonal C-factor reaches a maximum in winter and a minimum in spring. The mean annual C-factor varies substantially across the region. Areas with high values of the mean annual C-factor (C ≥ 100) are located in Ulanqab and Dingxi, while areas with low values (C ≤ 10) lie in Lanzhou, Linxia, Dingxi, Xining, and Chengde. Spatial analysis on the trend of the C-factor reveals that 81% of the stations show statistically significant decreases at a 90% confidence level. An examination of the concentration ratio of the C-factor shows that the wind erosion climatic erosivity is concentrated in spring, especially in April, which makes this period particularly important for implementing soil conservation measures.

Elevated temperature erosive wear of metallic materials

International Nuclear Information System (INIS)

Roy, Manish

2006-01-01

Solid particle erosion of metals and alloys at elevated temperature is governed by the nature of the interaction between erosion and oxidation, which, in turn, is determined by the thickness, pliability, morphology, adhesion characteristics and toughness of the oxide scale. The main objective of this paper is to critically review the present state of understanding of the elevated temperature erosion behaviour of metals and alloys. First of all, the erosion testing at elevated temperature is reviewed. This is followed by discussion of the essential features of elevated temperature erosion with special emphasis on microscopic observation, giving details of the erosion-oxidation (E-O) interaction mechanisms. The E-O interaction has been elaborated in the subsequent section. The E-O interaction includes E-O maps, analysis of transition criteria from one erosion mechanism to another mechanism and quantification of enhanced oxidation kinetics during erosion. Finally, the relevant areas for future studies are indicated. (topical review)

Assessment and management of dental erosion.

Science.gov (United States)

Wang, Xiaojie; Lussi, Adrian

2010-07-01

Studies have shown a growing trend toward increasing prevalence of dental erosion, associated with the declining prevalence of caries disease in industrialized countries. Erosion is an irreversible chemical process that results in tooth substance loss and leaves teeth susceptible to damage as a result of wear over the course of an individual's lifetime. Therefore, early diagnosis and adequate prevention are essential to minimize the risk of tooth erosion. Clinical appearance is the most important sign to be used to diagnose erosion. The Basic Erosive Wear Examination (BEWE) is a simple method to fulfill this task. The determination of a variety of risk and protective factors (patient-dependent and nutrition-dependent factors) as well as their interplay are necessary to initiate preventive measures tailored to the individual. When tooth loss caused by erosive wear reaches a certain level, oral rehabilitation becomes necessary. Copyright 2010 Elsevier Inc. All rights reserved.

Soil erosion processes on sloping land using REE tracer

International Nuclear Information System (INIS)

Shen Zhenzhou; Liu Puling; Yang Mingyi; Lian Zhenlong; Ju Tongjun; Yao Wenyi; Li Mian

2007-01-01

Sheet erosion is the main performance in the slope soil erosion process at the primary stage of natural rainfall. For three times of rainfall during experiment, the ratios of sheet erosion to total erosion account for 71%, 48% and 49% respectively, which showed that the sloping erosion was still at the primary stage from sheet erosion to rill erosion. With the rainfall going, the rill erosion amount increase. It showed that soil erosion was changing from sheet erosion to rill erosion. The sources of sediment from different sections of the plot were analyzed, and the results indicated that whatever the sheet erosion changed, the ratio erosion of upper part of surface soil was always lower than 10%. Sheet erosion came mainly from the lower section of surface soil. With the ratios to the amount of total rill erosion changes, the rill erosion amount of each section regularly changes too. The general conclusion is that when the rainfall ends, relative erosion of different slope element to the foot of slope is: 1 meter away accounts for 16%, 2-4 meters away is 6% and 5-9 meters away is 3%. The ratio of rill erosion amount of these three slope element is 5:2:1, which shows the rill erosion amount are mainly from the slope element of 4 meters from the foot of slope. (authors)

Medication-related dental erosion: a review.

Science.gov (United States)

Thomas, Manuel S; Vivekananda Pai, A R; Yadav, Amit

2015-10-01

Dental erosion has become a major problem that affects the long-term health of the dentition. Among the various potential causes for erosive tooth wear, the different drugs prescribed for patients may be overlooked. Several therapeutic medications can directly or indirectly be associated with dental erosion. It is the responsibility of oral health providers to make both patients and colleagues aware of drugs that may contribute to this condition. Therefore, the purpose of this discussion is to provide an overview of the various therapeutic medications that can be related to tooth erosion. The authors also include precautionary measures-summarized as The 9 Rs-to avoid or at least reduce medication-induced erosion.

Relative contributions of wind and water erosion to total soil loss and its effect on soil properties in sloping croplands of the Chinese Loess Plateau.

Science.gov (United States)

Tuo, Dengfeng; Xu, Mingxiang; Gao, Guangyao

2018-08-15

Wind and water erosion are two dominant types of erosion that lead to soil and nutrient losses. Wind and water erosion may occur simultaneously to varying extents in semi-arid regions. The contributions of wind and water erosion to total erosion and their effects on soil quality, however, remains elusive. We used cesium-137 ( 137 Cs) inventories to estimate the total soil erosion and used the Revised Universal Soil Loss Equation (RUSLE) to quantify water erosion in sloping croplands. Wind erosion was estimated from the subtraction of the two. We also used 137 Cs inventories to calculate total soil erosion and validate the relationships of the soil quality and erosion at different slope aspects and positions. The results showed that wind erosion (1460tkm -2 a -1 ) on northwest-facing slope was responsible for approximately 39.7% of the total soil loss, and water erosion (2216tkm -2 a -1 ) accounted for approximately 60.3%. The erosion rates were 58.8% higher on northwest- than on southeast-facing slopes. Northwest-facing slopes had lower soil organic carbon, total nitrogen, clay, and silt contents than southeast-facing slopes, and thus, the 137 Cs inventories were lower, and the total soil erosions were higher on the northwest-facing slopes. The variations in soil physicochemical properties were related to total soil erosion. The lowest 137 Cs inventories and nutrient contents were recorded at the upper positions on the northwest-facing slopes due to the successive occurrence of more severe wind and water erosion at the same site. The results indicated that wind and water could accelerate the spatial variability of erosion rate and soil properties and cause serious decreases in the nutrient contents in sloping fields. Our research could help researchers develop soil strategies to reduce soil erosion according to the dominant erosion type when it occurs in a hilly agricultural area. Copyright © 2018 Elsevier B.V. All rights reserved.

Composition of enamel pellicle from dental erosion patients.

Science.gov (United States)

Carpenter, G; Cotroneo, E; Moazzez, R; Rojas-Serrano, M; Donaldson, N; Austin, R; Zaidel, L; Bartlett, D; Proctor, G

2014-01-01

Oral health is dependent upon a thin mobile film of saliva on soft and hard tissues. Salivary proteins adhere to teeth to form the acquired enamel pellicle which is believed to protect teeth from acid erosion. This study investigated whether patients suffering diet-induced dental erosion had altered enamel pellicles. Thirty patients suffering erosion were compared to healthy age-matched controls. Subjects wore a maxillary splint holding hydroxyapatite and human enamel blocks for 1 h. The acquired enamel pellicle was removed from the blocks and compared to the natural incisor pellicle. Basic Erosive Wear Examination scores confirmed that dental erosion was present in erosion patients and absent from healthy age-matched controls. Erosion patients had half the amount of proteins (BCA assay) within the acquired pellicle forming on splint blocks compared to normal controls (p erosion patients (p erosion patients and healthy controls. In summary, the formation of new acquired pellicles on surfaces was reduced in erosion patients, which may explain their greater susceptibility to acid erosion of teeth. © 2014 S. Karger AG, Basel.

Observation of energy-time dispersed ion structures in the magnetosheath by CLUSTER: possible signatures of transient acceleration processes at shock

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P. Louarn

Full Text Available We analyse energy-time dispersed ion signatures that have been observed by CLUSTER in the dayside magnetosheath. These events are characterized by sudden increases in the ion flux at energies larger than 10 keV. The high energy ions (30 keV are first detected, with the transition to the low energy ions (5 keV lasting about 100 s. These injections are often associated with transient plasma structures of a few minutes in duration, characterized by a hotter, less dense plasma and a diverted flow velocity, thus presenting similarities with "hot flow anomalies". They also involve modifications of the magnetic field direction, suggesting that the shock interacts with a solar wind discontinuity at the time of the event. The injections can originate from the magnetosphere or the shock region. Studying in detail a particular event, we discuss this last hypothesis. We show that the observed energy/time dispersion can be explained by combining a time-of-flight effect with a drift of the source of energetic particles along the shock. We propose that the acceleration results from a Fermi process linked to the interaction of the discontinuity with a quasi-perpendicular shock. This model explains the observed pitch-angle selection of the accelerated particles. The Fermi process acting on the beam of ions reflected from the shock appears to be sufficiently efficient to accelerate over short time scales (less than 30 s particles at energies above 30 keV.

Key words. Magnetospheric physics (solar-wind-magnetosphere interaction; magnetosheath – Space plasma physics (shock waves

Anthropogenic control on geomorphic process rates: can we slow down the erosion rates? (Geomorphology Outstanding Young Scientist Award & Penck Lecture)

Science.gov (United States)

Vanacker, V.

2012-04-01

The surface of the Earth is changing rapidly, largely in response to anthropogenic perturbation. Direct anthropogenic disturbance of natural environments may be much larger in many places than the (projected) indirect effects of climate change. There is now large evidence that humans have significantly altered geomorphic process rates, mainly through changes in vegetation composition, density and cover. While much attention has been given to the impact of vegetation degradation on geomorphic process rates, I suggest that the pathway of restoration is equally important to investigate. First, vegetation recovery after crop abandonment has a rapid and drastic impact on geomorphic process rates. Our data from degraded catchments in the tropical Andes show that erosion rates can be reduced by up to 100 times when increasing the protective vegetation cover. During vegetation restoration, the combined effects of the reduction in surface runoff, sediment production and hydrological connectivity are stronger than the individual effects together. Therefore, changes in erosion and sedimentation during restoration are not simply the reverse of those observed during degradation. Second, anthropogenic perturbation causes a profound but often temporary change in geomorphic process rates. Reconstruction of soil erosion rates in Spain shows us that modern erosion rates in well-vegetated areas are similar to long-term rates, despite evidence of strong pulses in historical erosion rates after vegetation clearance and agriculture. The soil vegetation system might be resilient to short pulses of accelerated erosion (and deposition), as there might exist a dynamic coupling between soil erosion and production also in degraded environments.

The water erosion processes in the retreat erosive of cliff on soft rocks in the province of Cadiz (Spain)

International Nuclear Information System (INIS)

Rendon Aragon, J. J.; Gracia Prieto, F. J.; Rio Rodriguez, L. del

2009-01-01

The littoral cliffs on soft materials of the Atlantic Cadiz coast show an important activity of the fresh water erosion processes, sometimes even more significant than the marine erosion processes. The connection of the lower cliffs with sandy beaches favours aeolian sand invasion, which fills previous rills and reduces the water erosion intensity by increasing infiltration. Cliff retreat and rill erosion measurement by using erosion sticks has shown very variables values, most of them higher than the estimated error of the employed methods. This indicates the existence of other factors influencing the distribution of water erosion processes along these cliffs, which have to be studied through different techniques. (Author) 5 refs.

Summary of the works on blistering and related erosion phenomena in JAERI

International Nuclear Information System (INIS)

Kamada, Kohji

1980-01-01

The works in JAERI on the blistering and related erosion phenomena on material surfaces have been made theoretically and experimentally. The theoretical studies were concerned with the blistering and flaking mechanisms from the standpoint of pressure driven model. A condition for blistering was introduced as a result of the theoretical work. Assuming ductile crack propagation in an ion-irradiated subsurface layer due to the presence of small spherical bubbles, blistering and flaking are reasonably discriminated on the basis of a single mechanism of gas driven model. Experimentally, the in-situ observations of blistered surfaces were carried out with a scanning electron microscope connected to a 2 MeV Van de Graaff accelerator. Targets were single crystals of Nb, Mo, Cu and Al. The flaking in pyrolytic graphite due to He + , Ne + , Ar + and N + ion bombardments, and the hole-formation in glassy carbon by Ne + ion bombardment were also studied. The theoretical explanation gave satisfactory agreements with the experimental results. The in-situ observation of blistering and subsequent exfoliation during 100 keV He + bombardment on a polycrystalline Mo surface was carried with a 400 keV Cockcroft-Walton type ion accelerator. It was found by scanning electron microscopy that the surface erosion due to blistering was effectively reduced by the multi-groove structure. The phenomena named grain ejection were found by bombardment with pulsed intense beam of 25 keV H + , as well as H 2 + , in the temperature range of 150 to 250 degree C. (Kato, T.)

Accelerating Information Retrieval from Profile Hidden Markov Model Databases.

Directory of Open Access Journals (Sweden)

Ahmad Tamimi

Full Text Available Profile Hidden Markov Model (Profile-HMM is an efficient statistical approach to represent protein families. Currently, several databases maintain valuable protein sequence information as profile-HMMs. There is an increasing interest to improve the efficiency of searching Profile-HMM databases to detect sequence-profile or profile-profile homology. However, most efforts to enhance searching efficiency have been focusing on improving the alignment algorithms. Although the performance of these algorithms is fairly acceptable, the growing size of these databases, as well as the increasing demand for using batch query searching approach, are strong motivations that call for further enhancement of information retrieval from profile-HMM databases. This work presents a heuristic method to accelerate the current profile-HMM homology searching approaches. The method works by cluster-based remodeling of the database to reduce the search space, rather than focusing on the alignment algorithms. Using different clustering techniques, 4284 TIGRFAMs profiles were clustered based on their similarities. A representative for each cluster was assigned. To enhance sensitivity, we proposed an extended step that allows overlapping among clusters. A validation benchmark of 6000 randomly selected protein sequences was used to query the clustered profiles. To evaluate the efficiency of our approach, speed and recall values were measured and compared with the sequential search approach. Using hierarchical, k-means, and connected component clustering techniques followed by the extended overlapping step, we obtained an average reduction in time of 41%, and an average recall of 96%. Our results demonstrate that representation of profile-HMMs using a clustering-based approach can significantly accelerate data retrieval from profile-HMM databases.

Erosion characteristics and horizontal variability for small erosion depths in the Sacramento-San Joaquin River Delta, California, USA

Science.gov (United States)

Schoellhamer, David H.; Manning, Andrew J.; Work, Paul A.

2017-01-01

Erodibility of cohesive sediment in the Sacramento-San Joaquin River Delta (Delta) was investigated with an erosion microcosm. Erosion depths in the Delta and in the microcosm were estimated to be about one floc diameter over a range of shear stresses and times comparable to half of a typical tidal cycle. Using the conventional assumption of horizontally homogeneous bed sediment, data from 27 of 34 microcosm experiments indicate that the erosion rate coefficient increased as eroded mass increased, contrary to theory. We believe that small erosion depths, erosion rate coefficient deviation from theory, and visual observation of horizontally varying biota and texture at the sediment surface indicate that erosion cannot solely be a function of depth but must also vary horizontally. We test this hypothesis by developing a simple numerical model that includes horizontal heterogeneity, use it to develop an artificial time series of suspended-sediment concentration (SSC) in an erosion microcosm, then analyze that time series assuming horizontal homogeneity. A shear vane was used to estimate that the horizontal standard deviation of critical shear stress was about 30% of the mean value at a site in the Delta. The numerical model of the erosion microcosm included a normal distribution of initial critical shear stress, a linear increase in critical shear stress with eroded mass, an exponential decrease of erosion rate coefficient with eroded mass, and a stepped increase in applied shear stress. The maximum SSC for each step increased gradually, thus confounding identification of a single well-defined critical shear stress as encountered with the empirical data. Analysis of the artificial SSC time series with the assumption of a homogeneous bed reproduced the original profile of critical shear stress, but the erosion rate coefficient increased with eroded mass, similar to the empirical data. Thus, the numerical experiment confirms the small-depth erosion hypothesis. A linear

Nourishment of perched sand dunes and the issue of erosion control in the Great Lakes

Science.gov (United States)

Marsh, William M.

1990-09-01

Although limited in coverage, perched sand dunes situated on high coastal bluffs are considered the most prized of Great Lakes dunes. Grand Sable Dunes on Lake Superior and Sleeping Bear Dunes on Lake Michigan are featured attractions of national lakeshores under National Park Service management. The source of sand for perched dunes is the high bluff along their lakeward edge. As onshore wind crosses the bluff, flow is accelerated upslope, resulting in greatly elevated levels of wind stress over the slope brow. On barren, sandy bluffs, wind erosion is concentrated in the brow zone, and for the Grand Sable Bluff, it averaged 1 m3/yr per linear meter along the highest sections for the period 1973 1983. This mechanism accounts for about 6,500 m3 of sand nourishment to the dunefield annually and clearly has been the predominant mechanism for the long-term development of the dunefield. However, wind erosion and dune nourishment are possible only where the bluff is denuded of plant cover by mass movements and related processes induced by wave erosion. In the Great Lakes, wave erosion and bluff retreat vary with lake levels; the nourishment of perched dunes is favored by high levels. Lake levels have been relatively high for the past 50 years, and shore erosion has become a major environmental issue leading property owners and politicians to support lake-level regulation. Trimming high water levels could reduce geomorphic activity on high bluffs and affect dune nourishment rates. Locally, nourishment also may be influenced by sediment accumulation associated with harbor protection facilities and by planting programs aimed at stabilizing dunes.

Study of alternative materials to minimize erosion in heat exchanger tubes used in thermoelectric generators

Energy Technology Data Exchange (ETDEWEB)

Arnt, A.B.C.; Paula, M.M. da S. Paula; Rocha, M.R. da; Angioletto, E.; Zanini, L.C.; Miranda, R.; Zanelatto, C.C. [Universidade do Extremo Sul Catarinense (UNESC), Criciuma, SC (Brazil)], e-mails: anb@unesc.net, mms@unesc.net, marcio2r@terra.com.br, an@unesc.net, elucaslcz@yahoo.com.br, frdgmiranda@hotmail.com, gcrisrincao20@yahoo.com.br; Felippe, L. [Universidade do Extremo Sul Catarinense (UNESC), Capivari de Baixo, SC (Brazil)], e-mail: hlfelippe@tractebelenergia.com.br

2007-07-01

The machinery used in coal thermo electrical plants usually is submitted to erosive wear. The erosive wear occurs mainly in the metallic pipe set of heat exchangers due the flow of hot gases carrying erosive particles. Jaguar Ludicrous thermo electrical complex at Capivari de Baixo city holds seven power units, where two units use approximately 20 000 ASTM A178 heat pipes. The set is submitted to a semester maintenance schedule (preventive and corrective) where the damaged pipes are changed. So, in this work a set of erosive wear accelerated tests according ASTM G76 were performed in order to develop and specify materials and methods to diminish the erosive action caused by the combustion gases over the heat pipes. Specimens were coated with WC12Co and Cr{sub 3}C{sub 2}-25NiCr alloys using the HVOF technique and the coated specimens were tested at 450 deg C, the heat pipes working temperature. Silica was used as abrasive material at 30 deg and 45 deg impact angles, simulating a harder erosive condition than the real condition. The best performance coating at laboratory scale was later used in field condition. The results showed the coated specimen performance is better than the ASTM A178 alloy. The erosion resistance of the Cr{sub 3}C{sub 2}-25NiCr and WC12Co coatings is eight times higher than the uncoated alloy, and the coatings also presented a better corrosion resistance. This feature is important, because despite the erosive action the circulating gases also present a large amount of sulfur in their composition. Sulfur at lower temperatures forms H{sub 2}SO{sub 4}, causing intense corrosion of the pipes located at the heat exchangers colder parts. Based on the results and considering the coating costs the Cr{sub 3}C{sub 2}-25NiCr alloy was selected to coat a set of pipes mounted at the region of the heat exchanger with the most intense erosive wear. At the moment these coated tubes are in field operation and under observation regarding their performance in

Wind erosion of soils burned by wildfire

Science.gov (United States)

N. S. Wagenbrenner; M. J. Germino; B. K. Lamb; R. B. Foltz; P. R. Robichaud

2011-01-01

Wind erosion and aeolian transport processes are largely unstudied in the post-wildfire environment, but recent studies have shown that wind erosion can play a major role in burned landscapes. A wind erosion monitoring system was installed immediately following a wildfire in southeastern Idaho, USA to measure wind erosion from the burned area (Figure 1). This paper...

Robotic weld overlay coatings for erosion control

Science.gov (United States)

The erosion of materials by the impact of solid particles has received increasing attention during the past twenty years. Recently, research has been initiated with the event of advanced coal conversion processes in which erosion plays an important role. The resulting damage, termed Solid Particle Erosion (SPE), is of concern primarily because of the significantly increased operating costs which result in material failures. Reduced power plant efficiency due to solid particle erosion of boiler tubes and waterfalls has led to various methods to combat SPE. One method is to apply coatings to the components subjected to erosive environments. Protective weld overlay coatings are particularly advantageous in terms of coating quality. The weld overlay coatings are essentially immune to spallation due to a strong metallurgical bond with the substrate material. By using powder mixtures, multiple alloys can be mixed in order to achieve the best performance in an erosive environment. However, a review of the literature revealed a lack of information on weld overlay coating performance in erosive environments which makes the selection of weld overlay alloys a difficult task. The objective of this project is to determine the effects of weld overlay coating composition and microstructure on erosion resistance. These results will lead to a better understanding of erosion mitigation in CFB's.

Regionalization of monthly rainfall erosivity patternsin Switzerland

Science.gov (United States)

Schmidt, Simon; Alewell, Christine; Panagos, Panos; Meusburger, Katrin

2016-10-01

One major controlling factor of water erosion is rainfall erosivity, which is quantified as the product of total storm energy and a maximum 30 min intensity (I30). Rainfall erosivity is often expressed as R-factor in soil erosion risk models like the Universal Soil Loss Equation (USLE) and its revised version (RUSLE). As rainfall erosivity is closely correlated with rainfall amount and intensity, the rainfall erosivity of Switzerland can be expected to have a regional characteristic and seasonal dynamic throughout the year. This intra-annual variability was mapped by a monthly modeling approach to assess simultaneously spatial and monthly patterns of rainfall erosivity. So far only national seasonal means and regional annual means exist for Switzerland. We used a network of 87 precipitation gauging stations with a 10 min temporal resolution to calculate long-term monthly mean R-factors. Stepwise generalized linear regression (GLM) and leave-one-out cross-validation (LOOCV) were used to select spatial covariates which explain the spatial and temporal patterns of the R-factor for each month across Switzerland. The monthly R-factor is mapped by summarizing the predicted R-factor of the regression equation and the corresponding residues of the regression, which are interpolated by ordinary kriging (regression-kriging). As spatial covariates, a variety of precipitation indicator data has been included such as snow depths, a combination product of hourly precipitation measurements and radar observations (CombiPrecip), daily Alpine precipitation (EURO4M-APGD), and monthly precipitation sums (RhiresM). Topographic parameters (elevation, slope) were also significant explanatory variables for single months. The comparison of the 12 monthly rainfall erosivity maps showed a distinct seasonality with the highest rainfall erosivity in summer (June, July, and August) influenced by intense rainfall events. Winter months have the lowest rainfall erosivity. A proportion of 62 % of

Three procedures for estimating erosion from construction areas

International Nuclear Information System (INIS)

Abt, S.R.; Ruff, J.F.

1978-01-01

Erosion from many mining and construction sites can lead to serious environmental pollution problems. Therefore, erosion management plans must be developed in order that the engineer may implement measures to control or eliminate excessive soil losses. To properly implement a management program, it is necessary to estimate potential soil losses from the time the project begins to beyond project completion. Three methodologies are presented which project the estimated soil losses due to sheet or rill erosion of water and are applicable to mining and construction areas. Furthermore, the three methods described are intended as indicators of the state-of-the-art in water erosion prediction. The procedures herein do not account for gully erosion, snowmelt erosion, wind erosion, freeze-thaw erosion or extensive flooding

Erosion resistance comparison of alternative surface treatments

Science.gov (United States)

Česánek, Z.; Schubert, J.; Houdková, Š.

2017-05-01

Erosion is a process characterized by the particle separation and the damage of component functional surfaces. Thermal spraying technology HP/HVOF (High Pressure / High Velocity Oxygen Fuel) is commonly used for protection of component surfaces against erosive wear. Alloy as well as cermet based coatings meet the requirements for high erosion resistance. Wear resistance is in many cases the determining property of required component functioning. The application suitability of coating materials is particularly influenced by different hardness. This paper therefore presents an erosion resistance comparison of alloy and cermet based coatings. The coatings were applied on steel substrates and were subjected to the erosive test using the device for evaluation of material erosion resistance working on the principle of centrifugal erodent flow. Abrasive sand Al2O3 with grain size 212-250 μm was selected as an erosive material. For this purpose, the specimens were prepared by thermal spraying technology HP/HVOF using commercially available powders Stellite 6, NiCrBSi, Cr3C2-25%NiCr, Cr3C2-25%CoNiCrAlY, Hastelloy C-276 and experimental coating TiMoCN-29% Ni. Erosion resistance of evaluated coatings was compared with erosive resistance of 1.4923 high alloyed steel without nitridation and in nitrided state and further with surface treatment using technology PVD. According to the evaluation, the resulting erosive resistance depends not only on the selected erodent and surface protection, but also on the erodent impact angle.

The erosion and erosion products of tungsten and carbon based materials bombarded by high energy pulse electron beam

International Nuclear Information System (INIS)

Liu Xiang; Zhang Fu; Xu Zengyu; Liu Yong; Yoshida, N.; Noda, N.

2002-01-01

In this paper, the erosion behaviors and erosion products of tungsten and some carbon based materials, such as graphite, C/C composite and B 4 C/Cu functionally graded material, were investigated by using a pulse electron beam to simulate the vertical displacement events (VDE) process. The authors will focus on the forms and differences of erosion products among these testing materials, and make clear to their erosion mechanisms

Auto consolidated cohesive sediments erosion

International Nuclear Information System (INIS)

Ternat, F.

2007-02-01

Pollutants and suspended matters of a river can accumulate into the sedimentary column. Once deposited, they are submitted to self-weight consolidation processes, ageing and burying, leading to an increase of their erosion resistance. Pollutant fluxes can be related to sedimentary fluxes, determined by threshold laws. In this work, an erosion threshold model is suggested by introducing a cohesion force into the usual force balance. A model of cohesion is developed on the basis of interactions between argillaceous cohesive particles (clays), particularly the Van der Waals force, whose parameterization is ensured by means of granulometry and porosity. Artificial erosion experiments were performed in a recirculating erosion flume with natural cored sediments where critical shear stress measurements were performed. Other analyses provided granulometry and porosity. The results obtained constitute a good database for the literature. The model is then applied to the experimental conditions and gives good agreement with measurements. An example of the accounting for self-weight consolidation processes is finally suggested, before finishing on a Mohr like diagram dedicated to soft cohesive sediment erosion. (author)

Dynamic Analysis of Soil Erosion in Songhua River Watershed

Science.gov (United States)

Zhang, Yujuan; Li, Xiuhai; Wang, Qiang; Liu, Jiang; Liang, Xin; Li, Dan; Ni, Chundi; Liu, Yan

2018-01-01

In this paper, based on RS and GIS technology and Revised Universal Soil Loss Equation (RUSLE), the soil erosion dynamic changes during the two periods of 1990 and 2010 in Bin County was analyzed by using the Landsat TM data of the two periods, so as to reveal the soil erosion spatial distribution pattern and spatial and temporal dynamic evolution rule in the region. The results showed that: the overall patterns of soil erosion were basically the same in both periods, mainly featuring slight erosion and mild erosion, with the area proportions of 80.68% and 74.71% respectively. The slight and extremely intensive erosion changing rates showed a narrowing trend; mild, moderate and intensive erosion was increasing, with a trend of increased soil erosion; mild and intensive erosion were developing towards moderate erosion and moderate and extremely intensive erosion were progressing towards intensive erosion.

Implications of climate change on wind erosion of agricultural lands in the Columbia plateau

Directory of Open Access Journals (Sweden)

B.S. Sharratt

2015-12-01

Full Text Available Climate change may impact soil health and productivity as a result of accelerated or decelerated rates of erosion. Previous studies suggest a greater risk of wind erosion on arid and semi-arid lands due to loss of biomass under a future warmer climate. There have been no studies conducted to assess the impact of climate change on wind erosion in the Columbia Plateau of the Pacific Northwest United States where wind erosion of agricultural lands can cause exceedance of national air quality standards. The Wind Erosion Prediction System (WEPS was used to assess wind erosion and PM10 (particulate matter ≤10 µm in aerodynamic diameter emissions under a future climate projected by downscaling 18 Global Climate Models (GCM for a conservative emissions pathway. Wind erosion simulations were conducted at Lacrosse and Lind, WA and Moro, OR on a winter wheat-summer fallow (WW-SF rotation and at Lind on an additional winter wheat-camelina-summer fallow (WW-Cam-SF rotation. Each rotation was subject to conservation or conventional tillage practices for a baseline (1970–1999 and mid-21st century climate (2035–2064. A significant increase in temperature and nominal increases in precipitation were projected by an ensemble of climate models for the Columbia Plateau by the mid-21st century. Soil and PM10 losses were 25–84% lower for a mid-21st century climate, due in part to greater biomass production associated with CO2 fertilization and warmer temperatures. The reduction in soil and PM10 loss is projected to be more apparent for conservation tillage practices in the future. Soil and PM10 losses were greater from a WW-Cam-SF rotation than WW-SF rotation when conservation tillage practices were employed during the fallow phase of the rotations. Despite accounting for differences in the length of each rotation, annual soil and PM10 losses remained higher for the WW-Cam-SF rotation than the WW-SF rotation. Soil and PM10 losses were more variable across

Detection of soil erosion with Thematic Mapper (TM) satellite data within Pinyon-Juniper woodlands

Science.gov (United States)

Price, Kevin Paul

1987-01-01

Pinyon-Juniper woodlands dominate approximately 24.3 million hectares (60 million acres) in the western United States. The overall objective was to test the sensitivity of the LANDSAT Thematic Mapper (TM) spectral data for detecting varying degrees of soil erosion within the Pinyon-Juniper woodlands. A second objective was to assess the potential of the spectral data for assigning the Universal Soil Loss Equation (USLE) crop management (C) factor values to varying cover types within the woodland. Thematic Mapper digital data for June 2, 1984 on channels 2, 3, 4, and 5 were used. Digital data analysis was performed using the ELAS software package. Best results were achieved using CLUS, an unsupervised clustering algorithm. Fifteen of the 40 Pinyon-Juniper signatures were identified as being relatively pure Pinyon-Juniper woodland. Final analysis resulted in the grouping of the 15 signatures into three major groups. Ten study sites were selected from each of the three groups and located on the ground. At each site the following field measurements were taken: percent tree canopy and percent understory cover, soil texture, total soil loss, and soil erosion rate estimates. A technique for measuring soil erosion within Pinyon-Juniper woodlands was developed. A theoretical model of site degradation after Pinyon-Juniper invasion is presented.

Application of Plasma Waveguides to High Energy Accelerators

Energy Technology Data Exchange (ETDEWEB)

Milchberg, Howard M

2013-03-30

The eventual success of laser-plasma based acceleration schemes for high-energy particle physics will require the focusing and stable guiding of short intense laser pulses in reproducible plasma channels. For this goal to be realized, many scientific issues need to be addressed. These issues include an understanding of the basic physics of, and an exploration of various schemes for, plasma channel formation. In addition, the coupling of intense laser pulses to these channels and the stable propagation of pulses in the channels require study. Finally, new theoretical and computational tools need to be developed to aid in the design and analysis of experiments and future accelerators. Here we propose a 3-year renewal of our combined theoretical and experimental program on the applications of plasma waveguides to high-energy accelerators. During the past grant period we have made a number of significant advances in the science of laser-plasma based acceleration. We pioneered the development of clustered gases as a new highly efficient medium for plasma channel formation. Our contributions here include theoretical and experimental studies of the physics of cluster ionization, heating, explosion, and channel formation. We have demonstrated for the first time the generation of and guiding in a corrugated plasma waveguide. The fine structure demonstrated in these guides is only possible with cluster jet heating by lasers. The corrugated guide is a slow wave structure operable at arbitrarily high laser intensities, allowing direct laser acceleration, a process we have explored in detail with simulations. The development of these guides opens the possibility of direct laser acceleration, a true miniature analogue of the SLAC RF-based accelerator. Our theoretical studies during this period have also contributed to the further development of the simulation codes, Wake and QuickPIC, which can be used for both laser driven and beam driven plasma based acceleration schemes. We

High voltage, high power operation of the plasma erosion opening switch

International Nuclear Information System (INIS)

Neri, J.M.; Boller, J.R.; Ottinger, P.F.; Weber, B.V.; Young, F.C.

1987-01-01

A Plasma Erosion Opening Switch (PEOS) is used as the opening switch for a vacuum inductive storage system driven by a 1.8-MV, 1.6-TW pulsed power generator. A 135-nH vacuum inductor is current charged to ∼750 kA in 50 ns through the closed PEOS which then opens in <10 ns into an inverse ion diode load. Electrical diagnostics and nuclear activations from ions accelerated in the diode yield a peak load voltage (4.25 MV) and peak load power (2.8 TW) that are 2.4 and 1.8 times greater than ideal matched load values for the same generator pulse

Effects of rapid urbanization on streamflow, erosion, and sedimentation in a desert stream in the American Southwest

Science.gov (United States)

Whitney, John W.; Glancy, Patrick A.; Buckingham , Susan E.; Ehrenberg, Arthur C.

2015-01-01

Rapid urbanization has resulted in a series of sequential effects on a desert stream in the American Southwest. Lower Las Vegas Wash was a dry wash characterized by infrequent flood deposition when Las Vegas, Nevada was established in 1905. Wastewater effluent was discharged into the wash in low volumes for over 3 decades. Wastewater volumes increased commensurably with accelerated population growth during the late 20th century and created a sequence of feedback effects on the floodplain. Initially slow saturation of the valley fill created a desert oasis of dense floodplain vegetation and wetlands. Annual streamflow began in 1958 and erosion began a decade later with shallow incision in discontinuous channel segments. Increasing baseflow gradually enlarged channels; headcutting was active during the 1970s to 1984. The incised channels concentrated storm runoff, which accelerated local channel erosion, and in 1984 the headcuts were integrated during a series of monsoon floods. Wetlands were drained and most floodplain vegetation destroyed. Channel erosion continued unabated until engineering interventions began in the 21st century. No natural channel recovery occurred after initial urbanization effects because streamflow never stabilized in the late 20th century. A 6.6 M m3 sediment slug, eroded from the wash in ∼25 years, was deposited in Las Vegas Bay in Lake Mead. Falling reservoir levels during the 21st century are responsible for sediment redistribution and infilling of the bay. Close monitoring of impacts is recommended when urban wastewater and storm runoff are discharged on a desert wash. Channel interventions, when necessary, are advised in order to prevent costly engineering schemes of channel stabilization, flood control, and floodplain restoration.

Decreasing soil erosion rates with evolving land-use techniques in a central European catchment

Science.gov (United States)

Larsen, Annegret; Heckmann, Tobias; Hans-Rudolf, Bork; Alexander, Fuelling

2015-04-01

Agricultural societies around the world have caused accelerated soil erosion. Soil erosion and a decrease in soil fertility may also have caused the abandonment of entire landscapes and the collapse of civilizations. In central Europe, Medieval land-use is thought to have lead to the largest loss of top soil in history, which in turn lead to a malnutrition of the population and abandonment of agricultural land. However, this might be only part of the picture, as people are also able to adapt to changing environmental conditions, including the type of land-use they adopt. Within a catchment in the central European mountain belt, we were able to distinguish the evolution between three main types of land-use techniques between ~ 900 AD and 1950 AD: horticulture, agriculture and shifting cultivation. We were able to relate these techniques with different soil erosion rates, which differ by an order of magnitude, ranging from 0.83 ± 0.09 mm/yr to 1.62 ± 0.17 mm/yr. Using high-resolution surface data and chrono-stratigraphical methods in combination with soil charcoal analysis, we were able to reconstruct past land-use techniques on a local scale. This illustrates that less erosive and more sustainable techniques were developed through time, and hypothesize that people were able to adapt to the less favorable environmental conditions by changing the cultivation techniques. Although cultural adaptation to changing environmental conditions has been extensively discussed, this study is able to quantitatively demonstrate improved soil management with evolving land-use in central Europe.

Use of 137Cs and other fallout radionuclide in soil erosion investigations: progress, problems and prospects

International Nuclear Information System (INIS)

Walling, D.E.

1998-01-01

Accelerated erosion and soil degradation currently represent serious problems for the global environment. Against this background there is a need to assemble reliable information on the rates of soil loss involved. Existing techniques for documenting rates of soil loss possess many limitations and there is increasing interest in the potential for using fallout radionuclides, particularly 137 Cs, to obtain such information. An example of the application of the 137 Cs approach to a cultivated field at Rufford Forest Farm, Nottinghamshire, UK, is presented to illustrate its value. The key advantages of the approach are that it provides a means of assembling retrospective estimates of medium-term (ca. 40 years) rates of soil loss and the spatial pattern of erosion and deposition involved, on the basis of a single site visit. There are, however, currently a number of problems and uncertainties associated with the use of 137 Cs in soil erosion investigations, and these are reviewed and needs for further research identified. Potential developments of the approach, including the use of other fallout radionuclides such as unsupported 210 Pb and 7 Be are also considered. (author)

Soil Erosion. LC Science Tracer Bullet.

Science.gov (United States)

Buydos, John F., Comp.

Soil erosion is the detachment and movement of topsoil or soil material from the upper part of the soil profile. It may occur in the form of rill, gully, sheet, or wind erosion. Agents of erosion may be water, wind, glacial ice, agricultural implements, machinery, and animals. Soil conservation measures require a thorough understanding of the…

Comparison of Inconel 625 and Inconel 600 in resistance to cavitation erosion and jet impingement erosion

International Nuclear Information System (INIS)

Hu, H.X.; Zheng, Y.G.; Qin, C.P.

2010-01-01

Liquid droplet erosion (LDE), which often occurs in bellows made of nickel-based alloys, threatens the security operation of the nuclear power plant. As the candidate materials of the bellows, Inconel 600 and Inconel 625 were both tested for resistance to cavitation erosion (CE) and jet impingement erosion (JIE) through vibratory cavitation equipment and a jet apparatus for erosion-corrosion. Cumulative mass loss vs. exposure time was used to evaluate the erosion rate of the two alloys. The surface and cross-sectional morphologies before and after the erosion tests were observed by scanning electron microscopy (SEM), the inclusions were analyzed by an energy dispersive spectroscopy (EDS), and the surface roughness was also measured by surface roughness tester to illustrate the evolution of erosion process. The results show that the cumulative mass loss of CE of Inconel 625 is about 1/6 that of Inconel 600 and the CE incubation period of the Inconel 625 is 4 times as long as that of the Inconel 600. The micro-morphology evolution of CE process illustrates that the twinning and hardness of the Inconel 625 plays a significant role in CE. In addition, the cumulative mass loss of JIE of Inconel 625 is about 2/3 that of Inconel 600 at impacting angle of 90 o , and almost equal to that of the Inconel 600 at impacting angle of 30 o . Overall, the resistance to CE and JIE of Inconel 625 is much superior to that of Inconel 600.

Preventing erosion at pipeline crossings of watercourses

International Nuclear Information System (INIS)

Sawatsky, L.; Arnold, G.

1997-01-01

Watercourses are naturally vulnerable to erosion but the risk is particularly acute after sub-soil and armour materials have been disturbed by trenching and backfilling during construction. Various types of erosion (river scour, river bed, river channel bed and river bank ) and the progressive removal of pipeline cover resulting from erosion were discussed. Methods of estimating the risk of progressive erosion, river avulsions and beaver dam scour, and methods of mitigating erosion at pipeline crossings such as deep burial, proper siting, conventional armouring, and a combination of bank toe protection, and upper bank vegetation cover, were described

Accelerated relative sea-level rise and rapid coastal erosion: Testing a causal relationship for the Louisiana barrier islands

Science.gov (United States)

List, J.H.; Sallenger, A.H.; Hansen, M.E.; Jaffe, B.E.

1997-01-01

The role of relative sea-level rise as a cause for the rapid erosion of Louisiana's barrier island coast is investigated through a numerical implementation of a modified Bruun rule that accounts for the low percentage of sand-sized sediment in the eroding Louisiana shoreface. Shore-normal profiles from 150 km of coastline west of the Mississippi delta are derived from bathymetric surveys conducted during the 1880s. 1930s and 1980s. An RMS difference criterion is employed to test whether an equilibrium profile form is maintained between survey years. Only about half the studied profiles meet the equilibrium Criterion this represents a significant limitation on the potential applicability of the Bruun rule. The profiles meeting the equilibrium criterion, along with measured rates of relative sea-level rise, are used to hindcast shoreline retreat rates at 37 locations within the study area. Modeled and observed shoreline retreat rates show no significant correlation. Thus in terms of the Bruun approach relative sea-level rise has no power for hindcasting (and presumably forecasting) rates of coastal erosion for the Louisiana barrier islands.

Categorization of erosion control matting.

Science.gov (United States)

2012-05-29

Erosion control is a critical aspect of any Georgia Department of Transportation (GDOT) : construction project, with the extreme negative impacts of high sediment loads in natural : waterways having been well documented. A variety of erosion control ...

Erosion products in disruption simulation experiments

International Nuclear Information System (INIS)

Safronov, V.; Arkhipov, N.; Bakhtin, V.; Barsuk, V.; Kurkin, S.; Mironova, E.; Toporkov, D.; Vasenin, S.; Zhitlukhin, A.; Arkhipov, I.; Werle, H.; Wuerz, H.

1998-01-01

Erosion of divertor materials under tokamak disruption event presents a serious problem of ITER technology. Erosion restricts the divertor lifetime and leads to production of redeposited layers of the material retaining large amount of tritium, which is a major safety issue for future fusion reactor. Since ITER disruptive heat loads are not achievable in existing tokamaks, material erosion is studied in special simulation experiments. Till now the simulation experiments have focused mainly on investigation of shielding effect and measurement of erosion rate. In the present work the properties of eroded and redeposited graphite are studied under condition typical for hard ITER disruption. (author)

Erosive lichen planus: a therapeutic challenge.

Science.gov (United States)

Romero, Williams; Giesen, Laura; Navajas-Galimany, Lucas; Gonzalez, Sergio

2016-01-01

Erosive lichen planus is an uncommon variant of lichen planus. Chronic erosions of the soles, accompanied by intense and disabling pain, are some of its most characteristic manifestations. We present the case of a woman who developed oral and plantar erosive lichen planus associated with lichen planus pigmentosus and ungueal lichen planus that were diagnosed after several years. The patient failed to respond to multiple therapies requiring longstanding medication but remained refractory. Knowledge of the treatment options for erosive lichen planus is insufficient. Further research is required to clarify their effectiveness, ideally adopting an evidence-based methodology.

Wind and water erosion control on semiarid lands

International Nuclear Information System (INIS)

Siddoway, F.H.

1980-01-01

Commercial crop production on semiarid lands is difficult because insufficient water is often present to manage the system effectively. Erosion control presents the major management problem. The factors contributing to wind erosion and their interaction have been quantified into a wind erosion equation. The control of wind erosion through agronomic alteration of the various factors is discussed. The quantification and control of water erosion is also discussed with respect to the Universal Soil Loss Equation. Radioisotopes tracers have been used in conjunction with these erosion equations to measure soil losses. (author)

Erosion control works and the intensity of soil erosion in the upper part of the river Toplica drainage basin

International Nuclear Information System (INIS)

Kostadinov, S; Dragovic, N; Zlatic, M; Todosijevic, M

2008-01-01

Aiming at the protection of the future storage 'Selova' against erosion and sediment, and also to protect the settlements and roads in the drainage basin against torrential floods, erosion control works in the upper part of the river Toplica basin, upstream of the storage 'Selova', started in 1947. The works included building-technical works (check dams) and biological works (afforestation and grassing of bare lands and other erosion risk areas). Within the period 1947-2006, the following erosion control works were executed: afforestation of bare lands on the slopes 2,257.00 ha, grassing of bare lands 1,520.00 ha, and altogether 54 dams were constructed in the river Toplica tributaries. This caused the decrease of sediment transport in the main flow of the river Toplica. This paper, based on the field research conducted in two time periods: 1988 and in the period 2004-2007, presents the state of erosion in the basin before erosion control works; type and scope of erosion control works and their effect on the intensity of erosion in the river Toplica basin upstream of the future storage 'Selova'.

Erosion Pressure on the Danish Coasts

DEFF Research Database (Denmark)

Sørensen, Carlo Sass; Sørensen, Per; Kroon, Aart

Coastlines around the world are receding due to coastal erosion.With rising sea levels and a potential climatic deterioration due to climate change, erosion rates are likely to increase at many locations in the future.Together with the current preference of people to settle near or directly...... by the ocean, coastal erosion issues become increasingly more important to the human values at risk. Along many Danish coastlines, hard structures already act as coastal protection in the form of groins, breakwaters, revetments etc. These eroding coasts however still lack sand and where the public, in general......, neglects the need for sand replenishment i.e. in the form of repeated sand nourishments. Here we present a conceptual model and method for dividing coastal erosion into acute and chronic erosion pressure, respectively. We focus on the model use for management and climate change adaptation purposes...

Quantifying erosion over timescales of one million years: A photogrammetric approach on the amount of Rhenish erosion in southwestern Germany

Science.gov (United States)

Strasser, Annette; Strasser, Marcel; Seyfried, Hartmut

2010-10-01

The Lein valley in southwestern Germany possesses well-preserved Pliocene to mid Pleistocene land surfaces featuring a gentle relief and sediments accumulated by former tributaries of the Danube. This ancient Danubian land surface was captured and incised by mid Pleistocene to Holocene tributaries of the River Rhine. In a photogrammetric approach we calculated the volume of material extracted by Rhenish erosion providing a first quantification of the effects of stream piracy on timescales of about 1 Ma. Using stereoscopic surface modelling software a DEM was generated with a resolution of 5 m. From borehole data, literature, geological maps, and own field observations we determined the morphometric parameters of the ancient Danubian Ur-Lein valley. The gradient was imported as a 3D-breakline into the model where it controls the reinterpolation of surrounding data points. The result is a high-resolution DEM of the valley of the Ur-Lein. Subtraction of the DEM of the actual landscape from the DEM of the ancient Ur-Lein valley yields a model representing the rock volume eroded by the Rhenish Lein which totals 1.39 km 3 and converts into a rate of erosion between 63 and 74 mm/ka over a period of 700 to 600 ka, respectively, in accordance with figures obtained elsewhere in Central Europe through cosmogenic nuclides. It reflects the dominance of frequent fluctuations in climate and is considered to be mainly a product of strong changes in temperature and related processes during the transitional times between mid to late Pleistocene warm and cold states. A filtering procedure applied to cold and transitional state erosion rates of the Middle and Late Pleistocene yielded peak values between 66 and 77 mm/ka, up to three times higher than the modern rate or the rate of warm-state episodes. An assessment of the contribution of Rhenish stream piracy on long-term mid Pleistocene denudation under changing climate conditions resulted in a maximum 4.9-fold acceleration.

The Progress of the HIRFL-CSR Project and the Commissioning of the Cluster Target

International Nuclear Information System (INIS)

Cai Xiaohong; Lu Rongchun; Shao Caojie; Ruan, Fangfang; Yu, Deyang; Li Mingsheng; Torpokov, D K; Shestakov, Yu V; Sadykov, Rs; Zevakov, S A; Xia Jiawen; Zhan Wenlong

2007-01-01

HIRFL-CSR, a new cooler-storage-ring project, is the post-acceleration system of the Heavy Ion Research Facility in Lanzhou (HIRFL) consisting of a main ring (CSRm) and an experimental ring (CSRe). The construction of the HIRFL-CSR complex is nearing completion. The stored beam in the CSRm has been observed. Recently, the stored beam was accelerated from 7 MeV/u to 30 MeV/u. The cluster target is located in one straight section of the CSRe providing cluster jet targets of inert gases and small molecular gases. The cluster target has been finished and the results of the test running are presented

Restorative Rehabilitation of a Patient with Dental Erosion

OpenAIRE

AlShahrani, Mohammed Thamer; Haralur, Satheesh B.; Alqarni, Mohammed

2017-01-01

Dental erosion is the chemical dissolution of the tooth structure. Factors like eating disorders and gastrointestinal diseases are recognized as intrinsic factors for dental erosion. Advanced stages of dental erosion extensively damage the tooth morphology, consequently affecting both esthetics and functions. Reports indicate the growing prevalence of erosion, and hence knowledge of restorative rehabilitation of tooth erosion is an integral part of the contemporary dental practice. This clini...

Erosion Modeling Analysis For Modified DWPF SME Tank

International Nuclear Information System (INIS)

LEE, SI

2004-01-01

In support of an erosion evaluation for the modified cooling coil guide and its supporting structure in the DWPF SME vessel, a computational model was developed to identify potential sites of high erosion using the same methodology established by previous work. The erosion mechanism identified in the previous work was applied to the evaluation of high erosion locations representative of the actual flow process in the modified coil guide of the SME vessel, abrasive erosion which occurs by high wall shear of viscous liquid. The results show that primary locations of the highest erosion due to the abrasive wall erosion are at the leading edge of the guide, external surface of the insert plate, the tank floor next to the insert plate of the coil guide support, and the upstream lead-in plate. The present modeling results show a good comparison between the original and the modified cases in terms of high erosion sites, as well as the degree of erosion and the calculated shear stress. Wall she ar of the tank floor is reduced by about 30 per cent because of the new coil support plate. Calculations for the impeller speed lower than 103 rpm in the SME showed similar erosion patterns but significantly reduced wall shear stresses and reduced overall erosion. Comparisons of the 103 rpm results with SME measurements indicated that no significant erosion of the tank floor in the SME is to be expected. Thus, it is recommended that the agitator speed of SME does not exceed 103 rpm

Dental erosion among 12 year-old Libyan schoolchildren.

Science.gov (United States)

Huew, R; Waterhouse, P J; Moynihan, P J; Maguire, A

2012-12-01

As there are limited data on dental erosion in Libya, the aim of this study was to assess the prevalence and severity of dental erosion in a sample of 12 year-old children in Benghazi, Libya. Cross-sectional observational study. Elementary schools in Benghazi, Libya. A random sample of 791 12 year-old children (397 boys and 394 girls) attending 36 schools. Clinical dental examination for erosion using UK National Diet and Nutrition Survey (2000) criteria and self-completion questionnaire. The area and depth of dental erosion affecting the labial and palatal surfaces of the upper permanent incisors and occlusal surfaces of the first permanent molars. Dental erosion was observed in 40.8% of subjects; into enamel affecting 32.5%, into dentine affecting 8.0% and into pulp affecting 0.3% of subjects. Based on area affected, 323 subjects (40.8%) exhibited dental erosion (code > 0), with 32.6% of these subjects having erosion affecting more than two thirds of one or more surfaces examined. Mean total scores for dental erosion for all surfaces per mouth by area and by depth were both 2.69 (sd 3.81). Of the 9492 tooth surfaces examined, 2128 surfaces (22.4%) had dental erosion. Girls had more experience of erosion than boys at all levels of severity (p = 0.001). In a cohort of 12 year-old Libyan schoolchildren, more than one third of children examined showed dental erosion, requiring clinical preventive counselling. Significantly more erosion occurred in girls than boys.

Spiking neural networks on high performance computer clusters

Science.gov (United States)

Chen, Chong; Taha, Tarek M.

2011-09-01

In this paper we examine the acceleration of two spiking neural network models on three clusters of multicore processors representing three categories of processors: x86, STI Cell, and NVIDIA GPGPUs. The x86 cluster utilized consists of 352 dualcore AMD Opterons, the Cell cluster consists of 320 Sony Playstation 3s, while the GPGPU cluster contains 32 NVIDIA Tesla S1070 systems. The results indicate that the GPGPU platform can dominate in performance compared to the Cell and x86 platforms examined. From a cost perspective, the GPGPU is more expensive in terms of neuron/s throughput. If the cost of GPGPUs go down in the future, this platform will become very cost effective for these models.

Erosion and stability of a mine soil

International Nuclear Information System (INIS)

Wu, T.H.; Stadler, A.T.; Low, C.

1996-01-01

Mine soils developed from mine spoils commonly have a wide range of particle size. The slopes of old spoil piles usually are marked by gullies due to years of uncontrolled erosion. These characteristics raise questions about applicability of available theories and models for estimating runoff and erosion. An investigation was made to determine whether available erosion models can work for mine soils and can account for gully erosion. The investigation at an abandoned surface mine consisted of measurement of soil and sediment properties, measurement of runoff and erosion, observations of armor by rock fragments on gully floor, and calculations with available theories of sediment transport and slope stability. The results at this site suggest that (1) predictions with the ANSWERS model have about the same accuracy as those made for agricultural lands; (2) armor provided by rock fragments are temporary as they are periodically removed by debris flows; (3) detachment by rainfall impact is the primary cause of erosion on short steep slopes; and (4) a simplified method can be used for estimating erosion on such slopes

Erosion and sedimentation caused by watercourse regulation

International Nuclear Information System (INIS)

Dahl, T.E.; Godtland, K.

1995-01-01

This report describes the observations made by SINTEF NHL in 1993 - 1994 on the development of erosion in three regulated lakes in Norway: Devdesjavri, Store Maalvatn and Gjevilvatnet. Surveys, profile levelling, water sample analyses, aerial photography etc were all used. Erosion was dramatic in all three magazines the first year of regulation and then slowed down. It has since remained relatively stable. However, there is a risk of further strong erosion connected with flooding tributaries, notably at low water such as usually occurs in spring. This is true in particular of the main river discharging into Devdesjavri, which is subject to landslides, wave and river erosion. In addition, ground water erosion may occur if the magazine is drained too fast. The report is lavishly illustrated with colour pictures of the effects of erosion. 21 refs., 15 figs., 13 tabs

Varioliform erosions in the stomach and duodenum

Energy Technology Data Exchange (ETDEWEB)

Lotz, W.; Schulz, D.; Munkel, G.

1984-04-01

One thousand five hundred and eighty-three patients who were x-rayed for dyspepsia showed varioliform erosions in 15.3%. Men had an incidence of 9.8%, almost twice as common as in women (5.5%). Mucosal polyps, usually of the hyperplastic type, occurred in 2.4%. 15% of patients with gastric ulcers and 16% of patients with duodenal ulcers had varioliform erosions. On the other hand, amongst patients with erosions, 11% had gastric ulcers and 8.3% duodenal ulcers. The definitions of erosion which have been given in the literature are partly contradictory, and are discussed. Varioliform erosions, also known as complete erosions, may be acute or chronic. They are the third most common cause of bleeding from the upper gastrointestinal tract. With modern radiological methods of examining the stomach, they are no longer a rare finding. 5 figs.

Varioliform erosions in the stomach and duodenum

International Nuclear Information System (INIS)

Lotz, W.; Schulz, D.; Munkel, G.

1984-01-01

One thousand five hundred and eighty-three patients who were x-rayed for dyspepsia showed varioliform erosions in 15.3%. Men had an incidence of 9.8%, almost twice as common as in women (5.5%). Mucosal polyps, usually of the hyperplastic type, occurred in 2.4%. 15% of patients with gastric ulcers and 16% of patients with duodenal ulcers had varioliform erosions. On the other hand, amongst patients with erosions, 11% had gastric ulcers and 8.3% duodenal ulcers. The definitions of erosion which have been given in the literature are partly contradictory, and are discussed. Varioliform erosions, also known as complete erosions, may be acute or chronic. They are the third most common cause of bleeding from the upper gastrointestinal tract. With modern radiological methods of examining the stomach, they are no longer a rare finding. (orig.) [de

Comparison of Inconel 625 and Inconel 600 in resistance to cavitation erosion and jet impingement erosion

Energy Technology Data Exchange (ETDEWEB)

Hu, H.X. [State Key Laboratory for Corrosion and Protection, Institute of Metal Research, Chinese Academy of Science, 62 Wencui Road, Shenyang 110016 (China); Zheng, Y.G., E-mail: ygzheng@imr.ac.c [State Key Laboratory for Corrosion and Protection, Institute of Metal Research, Chinese Academy of Science, 62 Wencui Road, Shenyang 110016 (China); Qin, C.P. [State Key Laboratory for Corrosion and Protection, Institute of Metal Research, Chinese Academy of Science, 62 Wencui Road, Shenyang 110016 (China)

2010-10-15

Liquid droplet erosion (LDE), which often occurs in bellows made of nickel-based alloys, threatens the security operation of the nuclear power plant. As the candidate materials of the bellows, Inconel 600 and Inconel 625 were both tested for resistance to cavitation erosion (CE) and jet impingement erosion (JIE) through vibratory cavitation equipment and a jet apparatus for erosion-corrosion. Cumulative mass loss vs. exposure time was used to evaluate the erosion rate of the two alloys. The surface and cross-sectional morphologies before and after the erosion tests were observed by scanning electron microscopy (SEM), the inclusions were analyzed by an energy dispersive spectroscopy (EDS), and the surface roughness was also measured by surface roughness tester to illustrate the evolution of erosion process. The results show that the cumulative mass loss of CE of Inconel 625 is about 1/6 that of Inconel 600 and the CE incubation period of the Inconel 625 is 4 times as long as that of the Inconel 600. The micro-morphology evolution of CE process illustrates that the twinning and hardness of the Inconel 625 plays a significant role in CE. In addition, the cumulative mass loss of JIE of Inconel 625 is about 2/3 that of Inconel 600 at impacting angle of 90{sup o}, and almost equal to that of the Inconel 600 at impacting angle of 30{sup o}. Overall, the resistance to CE and JIE of Inconel 625 is much superior to that of Inconel 600.

Satellite-based estimation of rainfall erosivity for Africa

NARCIS (Netherlands)

Vrieling, A.; Sterk, G.; Jong, S.M. de

2010-01-01

Rainfall erosivity is a measure for the erosive force of rainfall. Rainfall kinetic energy determines the erosivity and is in turn greatly dependent on rainfall intensity. Attempts for its large-scale mapping are rare. Most are based on interpolation of erosivity values derived from rain gauge

Probabilistic soil erosion modeling using the Erosion Risk Management Tool (ERMIT) after wildfires

Science.gov (United States)

P. R. Robichaud; W. J. Elliot; J. W. Wagenbrenner

2011-01-01

The decision of whether or not to apply post-fire hillslope erosion mitigation treatments, and if so, where these treatments are most needed, is a multi-step process. Land managers must assess the risk of damaging runoff and sediment delivery events occurring on the unrecovered burned hillslope. We developed the Erosion Risk Management Tool (ERMiT) to address this need...

The erosive potential of lollipops

NARCIS (Netherlands)

Brand, H.S.; Gambon, D.L.; Paap, A.; Bulthuis, M.S.; Veerman, E.C.I.; Nieuw Amerongen, A.V.

2009-01-01

Aim: To determine the erosive potential of several commercially available lollipops and the protective effect of saliva. Methods: The erosive potential of lollipops was determined in vitro by measuring the pH and neutralisable acidity. Subsequently, 10 healthy volunteers tested different types of

On the Material Characterisation of Wind Turbine Blade Coatings: The Effect of Interphase Coating–Laminate Adhesion on Rain Erosion Performance

Directory of Open Access Journals (Sweden)

Enrique Cortés

2017-09-01

Full Text Available Rain erosion damage, caused by repeated droplet impact on wind turbine blades, is a major cause for concern, even more so at offshore locations with larger blades and higher tip speeds. Due to the negative economic influence of blade erosion, all wind turbine Original Equipment Manufacturers (OEMs are actively seeking solutions. In most cases, since the surface coating plays a decisive role in the blade manufacture and overall performance, it has been identified as an area where a solution may be obtained. In this research, two main coating technologies have been considered: In-mould coatings (Gel coating applied during moulding on the entire blade surface and the post-mould coatings specifically developed for Leading Edge Protection (LEP. The coating adhesion and erosion is affected by the shock waves created by the collapsing water droplets on impact. The stress waves are reflected and transmitted to the laminate substrate, so microstructural discontinuities in coating layers and interfaces play a key role on its degradation and may accelerate erosion by delamination. Analytical and numerical models are commonly used to relate lifetime prediction and to identify suitable coating and composite substrate combinations based on their potential stress reduction on the interface. Nevertheless, in order to use them, it is necessary to measure the contact adhesion resistance of the multi-layered system interfaces. The rain erosion performance is assessed using an accelerated testing technique, whereby the test material is repeatedly impacted at high speed with water droplets in a Whirling Arm Rain Erosion Rig (WARER. The materials, specifically the coating–laminate interphase region and acoustic properties, are further characterised by several laboratory tests, including Differential Scanning Calorimetry (DSC, pull-off testing, peeling–adhesion testing and nanoindentation testing. This body of work includes a number of case studies. The first case

On the Material Characterisation of Wind Turbine Blade Coatings: The Effect of Interphase Coating–Laminate Adhesion on Rain Erosion Performance

Science.gov (United States)

Cortés, Enrique; Sánchez, Fernando; Madramany, Borja

2017-01-01

Rain erosion damage, caused by repeated droplet impact on wind turbine blades, is a major cause for concern, even more so at offshore locations with larger blades and higher tip speeds. Due to the negative economic influence of blade erosion, all wind turbine Original Equipment Manufacturers (OEMs) are actively seeking solutions. In most cases, since the surface coating plays a decisive role in the blade manufacture and overall performance, it has been identified as an area where a solution may be obtained. In this research, two main coating technologies have been considered: In-mould coatings (Gel coating) applied during moulding on the entire blade surface and the post-mould coatings specifically developed for Leading Edge Protection (LEP). The coating adhesion and erosion is affected by the shock waves created by the collapsing water droplets on impact. The stress waves are reflected and transmitted to the laminate substrate, so microstructural discontinuities in coating layers and interfaces play a key role on its degradation and may accelerate erosion by delamination. Analytical and numerical models are commonly used to relate lifetime prediction and to identify suitable coating and composite substrate combinations based on their potential stress reduction on the interface. Nevertheless, in order to use them, it is necessary to measure the contact adhesion resistance of the multi-layered system interfaces. The rain erosion performance is assessed using an accelerated testing technique, whereby the test material is repeatedly impacted at high speed with water droplets in a Whirling Arm Rain Erosion Rig (WARER). The materials, specifically the coating–laminate interphase region and acoustic properties, are further characterised by several laboratory tests, including Differential Scanning Calorimetry (DSC), pull-off testing, peeling–adhesion testing and nanoindentation testing. This body of work includes a number of case studies. The first case study compares

On the Material Characterisation of Wind Turbine Blade Coatings: The Effect of Interphase Coating-Laminate Adhesion on Rain Erosion Performance.

Science.gov (United States)

Cortés, Enrique; Sánchez, Fernando; O'Carroll, Anthony; Madramany, Borja; Hardiman, Mark; Young, Trevor M

2017-09-28

Rain erosion damage, caused by repeated droplet impact on wind turbine blades, is a major cause for concern, even more so at offshore locations with larger blades and higher tip speeds. Due to the negative economic influence of blade erosion, all wind turbine Original Equipment Manufacturers (OEMs) are actively seeking solutions. In most cases, since the surface coating plays a decisive role in the blade manufacture and overall performance, it has been identified as an area where a solution may be obtained. In this research, two main coating technologies have been considered: In-mould coatings (Gel coating) applied during moulding on the entire blade surface and the post-mould coatings specifically developed for Leading Edge Protection (LEP). The coating adhesion and erosion is affected by the shock waves created by the collapsing water droplets on impact. The stress waves are reflected and transmitted to the laminate substrate, so microstructural discontinuities in coating layers and interfaces play a key role on its degradation and may accelerate erosion by delamination. Analytical and numerical models are commonly used to relate lifetime prediction and to identify suitable coating and composite substrate combinations based on their potential stress reduction on the interface. Nevertheless, in order to use them, it is necessary to measure the contact adhesion resistance of the multi-layered system interfaces. The rain erosion performance is assessed using an accelerated testing technique, whereby the test material is repeatedly impacted at high speed with water droplets in a Whirling Arm Rain Erosion Rig (WARER). The materials, specifically the coating-laminate interphase region and acoustic properties, are further characterised by several laboratory tests, including Differential Scanning Calorimetry (DSC), pull-off testing, peeling-adhesion testing and nanoindentation testing. This body of work includes a number of case studies. The first case study compares two

Spatial bedrock erosion distribution in a natural gorge

Science.gov (United States)

Beer, A. R.; Turowski, J. M.; Kirchner, J. W.

2015-12-01

Quantitative analysis of morphological evolution both in terrestrial and planetary landscapes is of increasing interest in the geosciences. In mountainous regions, bedrock channel formation as a consequence of the interaction of uplift and erosion processes is fundamental for the entire surface evolution. Hence, the accurate description of bedrock channel development is important for landscape modelling. To verify existing concepts developed in the lab and to analyse how in situ channel erosion rates depend on the interrelations of discharge, sediment transport and topography, there is a need of highly resolved topographic field data. We analyse bedrock erosion over two years in a bedrock gorge downstream of the Gorner glacier above the town of Zermatt, Switzerland. At the study site, the Gornera stream cuts through a roche moutonnée in serpentine rock of 25m length, 5m width and 8m depth. We surveyed bedrock erosion rates using repeat terrestrial laser scanning (TLS) with an average point spacing of 5mm. Bedrock erosion rates in direction of the individual surface normals were studied directly on the scanned point clouds applying the M3C2 algorithm (Lague et al., 2013, ISPRS). The surveyed erosion patterns were compared to a simple stream erosivity visualisation obtained from painted bedrock sections at the study location. Spatially distributed erosion rates on bedrock surfaces based on millions of scan points allow deduction of millimeter-scale mean annual values of lateral erosion, incision and downstream erosion on protruding streambed surfaces. The erosion rate on a specific surface point is shown to depend on the position of this surface point in the channel's cross section, its height above the streambed and its spatial orientation to the streamflow. Abrasion by impacting bedload was likely the spatially dominant erosion process, as confirmed by the observed patterns along the painted bedrock sections. However, a single plucking event accounted for the half

Self-Assembled Gold Nano-Ripple Formation by Gas Cluster Ion Beam Bombardment.

Science.gov (United States)

Tilakaratne, Buddhi P; Chen, Quark Y; Chu, Wei-Kan

2017-09-08

In this study, we used a 30 keV argon cluster ion beam bombardment to investigate the dynamic processes during nano-ripple formation on gold surfaces. Atomic force microscope analysis shows that the gold surface has maximum roughness at an incident angle of 60° from the surface normal; moreover, at this angle, and for an applied fluence of 3 × 10 16 clusters/cm², the aspect ratio of the nano-ripple pattern is in the range of ~50%. Rutherford backscattering spectrometry analysis reveals a formation of a surface gradient due to prolonged gas cluster ion bombardment, although the surface roughness remains consistent throughout the bombarded surface area. As a result, significant mass redistribution is triggered by gas cluster ion beam bombardment at room temperature. Where mass redistribution is responsible for nano-ripple formation, the surface erosion process refines the formed nano-ripple structures.

GALAXY CLUSTER RADIO RELICS IN ADAPTIVE MESH REFINEMENT COSMOLOGICAL SIMULATIONS: RELIC PROPERTIES AND SCALING RELATIONSHIPS

International Nuclear Information System (INIS)

Skillman, Samuel W.; Hallman, Eric J.; Burns, Jack O.; Smith, Britton D.; O'Shea, Brian W.; Turk, Matthew J.

2011-01-01

Cosmological shocks are a critical part of large-scale structure formation, and are responsible for heating the intracluster medium in galaxy clusters. In addition, they are capable of accelerating non-thermal electrons and protons. In this work, we focus on the acceleration of electrons at shock fronts, which is thought to be responsible for radio relics-extended radio features in the vicinity of merging galaxy clusters. By combining high-resolution adaptive mesh refinement/N-body cosmological simulations with an accurate shock-finding algorithm and a model for electron acceleration, we calculate the expected synchrotron emission resulting from cosmological structure formation. We produce synthetic radio maps of a large sample of galaxy clusters and present luminosity functions and scaling relationships. With upcoming long-wavelength radio telescopes, we expect to see an abundance of radio emission associated with merger shocks in the intracluster medium. By producing observationally motivated statistics, we provide predictions that can be compared with observations to further improve our understanding of magnetic fields and electron shock acceleration.

Cavitation erosion - scale effect and model investigations

Science.gov (United States)

Geiger, F.; Rutschmann, P.

2015-12-01

The experimental works presented in here contribute to the clarification of erosive effects of hydrodynamic cavitation. Comprehensive cavitation erosion test series were conducted for transient cloud cavitation in the shear layer of prismatic bodies. The erosion pattern and erosion rates were determined with a mineral based volume loss technique and with a metal based pit count system competitively. The results clarified the underlying scale effects and revealed a strong non-linear material dependency, which indicated significantly different damage processes for both material types. Furthermore, the size and dynamics of the cavitation clouds have been assessed by optical detection. The fluctuations of the cloud sizes showed a maximum value for those cavitation numbers related to maximum erosive aggressiveness. The finding suggests the suitability of a model approach which relates the erosion process to cavitation cloud dynamics. An enhanced experimental setup is projected to further clarify these issues.

Investigation of Erosion of Cement-Bentonite via Piping

Directory of Open Access Journals (Sweden)

Zijun Wang

2017-01-01

Full Text Available Cement-bentonite is one of the main materials used in the seepage barriers to protect earth dams and levees from water erosion. However, the current understanding of the erodibility of the cementitious materials and the interactions between cracked seepage barriers and the water flow is inadequate. Based on the laboratory pinhole erosion test, we first investigated the impacts of cement-bentonite treatments by using the ground granulated blast-furnace slag (GGBS as replacement on the erosion characteristics, compared with the original mixtures; the inclusion of GGBS highlighted a potential advantage against water erosion. In addition, we proposed to calculate the erosion percentage and establish the mathematical relationships between the erosion percentage and different regimes, that is, different curing period, erosion time, and sizes of initial holes. Results showed that enough curing period was critical to avoid the increases of hydraulic conductivity in the macrofabric of the barrier; meanwhile, the materials were eroded quickly at the beginning and slowed down with the erosion time, where the enlargement of the initial creaks would be stabilised at some point in time. Moreover, the sizes of initial holes may affect the erosion situation varying from the sample curing periods.

Monitoring bank erosion at the Locke Island Archaeological National Register District: Summary of 1996/1997 field activities

Energy Technology Data Exchange (ETDEWEB)

Nickens, P.R. [ed.; Bjornstad, B.N.; Nickens, P.R.; Cadoret, N.A.; Wright, M.K.

1998-08-01

Locke Island is located in the Columbia River in south-central Washington. The US Department of Energy (DOE) owns Locke Island as part of its Hanford Site. In the 1960s and 1970s, as a result of intensive irrigation developments on the inland shoreline to the east of the island, the White Bluffs, which form the eastern boundary of the Columbia River channel in this area, began to show geological failures as excess irrigation water seeped out along the bluffs. One of the largest such failures, known as the Locke Island Landslide, is located just east of Locke Island. By the early 1980s, this landslide mass had moved westward into the river channel toward the island and was diverting the current at the island`s eastern perimeter. Erosion of the bank in the center of the island accelerated, threatening the cultural resources. By the early 1990s, the erosion had exposed cultural features and artifacts along the bank, leading to the beginning of intermittent monitoring of the cutbank. In 1994, DOE initiated more scheduled, systematic monitoring of island erosion to better understand the physical processes involved as well as mitigate ongoing loss of the archaeological record.

Wind erosion processes and control

Science.gov (United States)

Wind erosion continues to threaten the sustainability of our nations' soil, air, and water resources. To effectively apply conservation systems to prevent wind driven soil loss, an understanding of the fundamental processes of wind erosion is necessary so that land managers can better recognize the ...

Anthropogenic Increase Of Soil Erosion In The Gangetic Plain Revealed By Geochemical Budget Of Erosion

Science.gov (United States)

Galy, V.; France-Lanord, C.; Galy, A.; Gaillardet, J.

2007-12-01

Tectonic and climatic factors are the key natural variables controlling the erosion through complex interactions. Nonetheless, over the last few hundred years, human activity also exerts a dominant control in response to extensive land use. The geochemical budget of erosion allows the balance between the different erosion processes to be quantified. The chemical composition of river sediment results from the chemical composition of the source rock modified by (1) weathering reactions occurring during erosion and (2) physical segregation during transport. If erosion is at steady state, the difference between the chemical composition of source rocks and that of river sediments must therefore be counterbalanced by the dissolved flux. However, climatic variations or anthropic impact can induce changes in the erosion distribution in a given basin resulting in non steady state erosion. Using a mass balance approach, the comparison of detailed geochemical data on river sediments with the current flux of dissolved elements allows the steady state hypothesis to be tested. In this study, we present a geochemical budget of weathering for the Ganga basin, one of the most densely populated basin in the world, based on detailed sampling of Himalayan rivers and of the Ganga in the delta. Sampling includes depth profile in the river, to assess the variability generated by transport processes. Himalayan river sediments are described by the dilution of an aluminous component (micas + clays + feldspars) by quartz. Ganga sediments on the other hand correspond to the mixing of bedload, similar to coarse Himalayan sediments, with an aluminous component highly depleted in alkaline elements. Compared with the dissolved flux, the depletion of alkaline elements in Ganga sediments shows that the alkaline weathering budget is imbalanced. This imbalance results from an overabundance of fine soil material in the Ganga sediment relative to other less weathered material directly derived from

Restorative Rehabilitation of a Patient with Dental Erosion.

Science.gov (United States)

AlShahrani, Mohammed Thamer; Haralur, Satheesh B; Alqarni, Mohammed

2017-01-01

Dental erosion is the chemical dissolution of the tooth structure. Factors like eating disorders and gastrointestinal diseases are recognized as intrinsic factors for dental erosion. Advanced stages of dental erosion extensively damage the tooth morphology, consequently affecting both esthetics and functions. Reports indicate the growing prevalence of erosion, and hence knowledge of restorative rehabilitation of tooth erosion is an integral part of the contemporary dental practice. This clinical report describes an adult patient with gastroesophageal reflux induced dental erosion involving the palatal surface of the maxillary anterior teeth. The extensive involvement of the palatal surfaces compromised the esthetics, incisal guidance, and functional occlusal efficiency. Indirect all-ceramic restorations were utilized to restore the esthetics and occlusal reconstruction. In conclusion, patients affected by severe dental erosion require prosthetic rehabilitation besides the management of the associated medical condition.

Restorative Rehabilitation of a Patient with Dental Erosion

Directory of Open Access Journals (Sweden)

Mohammed Thamer AlShahrani

2017-01-01

Full Text Available Dental erosion is the chemical dissolution of the tooth structure. Factors like eating disorders and gastrointestinal diseases are recognized as intrinsic factors for dental erosion. Advanced stages of dental erosion extensively damage the tooth morphology, consequently affecting both esthetics and functions. Reports indicate the growing prevalence of erosion, and hence knowledge of restorative rehabilitation of tooth erosion is an integral part of the contemporary dental practice. This clinical report describes an adult patient with gastroesophageal reflux induced dental erosion involving the palatal surface of the maxillary anterior teeth. The extensive involvement of the palatal surfaces compromised the esthetics, incisal guidance, and functional occlusal efficiency. Indirect all-ceramic restorations were utilized to restore the esthetics and occlusal reconstruction. In conclusion, patients affected by severe dental erosion require prosthetic rehabilitation besides the management of the associated medical condition.

Erosion of the first wall of Tokamaks

International Nuclear Information System (INIS)

Guseva, M.I.; Ionova, E.S.; Martynenko, Yu.V.

1980-01-01

An estimate of the rate of erosion of the wall due to sputtering and blistering requires knowledge of the fluxes and energies of the particles which go from the plasma to the wall, of the sputtering coefficients S, and of the erosion coefficients S* for blistering. The overall erosion coefficient is equal to the sum of the sputtering coefficient and the erosion coefficient for blistering. Here the T-20 Tokamak is examined as an example of a large-scale Tokamak. 18 refs

Protection From Dental Erosion: All Fluorides are Not Equal.

Science.gov (United States)

Faller, Robert V; Noble, Warden H

2018-03-01

All fluoride sources help strengthen teeth against bacterial acids that cause caries. However, excessive exposure to dietary acids, which can result in dental erosion, presents a more aggressive level of challenge compared to caries. Despite the fact that almost all toothpastes contain fluoride, both the incidence and prevalence of dental erosion appear to be on the rise. This article: (1) describes key differences between caries and dental erosion and the ability of different fluoride sources to help prevent erosion; (2) discusses the importance of the evaluation of patients for dental erosion at the earliest stages using the Basic Erosive Wear Examination scoring system to help assess and educate patients; and (3) provides evidence-based information for making specific recommendations to patients with dental erosion. The objective of this article is to assess the comparative ability of fluoride agents to protect against dental erosion. Though all fluorides are able to help strengthen teeth against cariogenic acids, not all available sources of fluoride provide the same level of erosion protection. Daily use of a stabilized stannous fluoride dentifrice has been shown to provide the most effective means of protecting teeth against the increasing risk of dental erosion and erosive tooth wear.

Three Gorges Reservoir Area: soil erosion under natural condition vs. soil erosion under current land use

Science.gov (United States)

Schönbrodt, Sarah; Behrens, Thorsten; Scholten, Thomas

2010-05-01

Apparently, the current most prominent human-induced example for large scale environmental impact is the Three Gorges Dam in China. The flooding alongside the Yangtze River, and its tributaries results in a vast loss of settlement and farmland area with productive, fertile valley soils. Due to the associated high land use dynamic on uphill-sites, the soil resources are underlying high land use pressure. Within our study, the soil erosion under natural conditions is compared to the soil erosion under current land use after the impoundment. Both were modeled using the empirical Universal Soil Loss Equation (USLE) which is able to predict long-term annual soil loss with limited data. The database consists of digital terrain data (45 m resolution DEM, erosive slope length based on Monte-Carlo-Aggregation according to Behrens et al. (2008)), field investigations of recent erosion forms, and literature studies. The natural disposition to soil erosion was calculated considering the USLE factors R, S, and K. The soil erosion under current land use was calculated taking into account all USLE factors. The study area is the catchment of the Xiangxi River in the Three Gorges Reservoir area. Within the Xiangxi Catchment (3,200 km²) the highly dynamic backwater area (580 km²), and two micro-scale study sites (Xiangjiaba with 2.8 km², and Quyuan with 88 km²) are considered more detailed as they are directly affected by the river impoundment. Central features of the Xiangxi Catchment are the subtropical monsoon climate, an extremely steep sloping relief (mean slope angle 39°, SD 22.8°) artificially fractured by farmland terraces, and a high soil erodibility (mean K factor 0.37, SD 0.13). On the catchment scale the natural disposition to soil erosion makes up to mean 518.0 t ha-1 a-1. The maximum potential soil loss of 1,730.1 t ha-1 a-1 under natural conditions is reached in the Quyuan site (mean 635.8 t ha-1 a-1) within the backwater area (mean 582.9 t ha-1 a-1). In the

SILTATION AND EROSION PROCESSES ON A TRIBUTARY OF LAKE ITAIPU DUE A DAM RESERVOIR

Directory of Open Access Journals (Sweden)

Cristiano Poleto

2012-12-01

Full Text Available It is known that sediments in the river have their origin from different sources. Therefore, the proportion that each source contributes to the mix varies over time and space, as a result of erosion processes that are ongoing in the basin of contribution. Within this context, both in human actions in urban and rural watersheds generate different rates of sediment production, but mainly with different characteristics or quality. Thus, the fluvial sedimentology should have a broad character within the study area and check all the possible influences of land use and soil. Hydrosedimentological processes are complex and include a disaggregation ("erosion" in the strict definition, transport, sedimentation, consolidation of sediments. Therefore, it is necessary more detailed studies of sediments and their interactions with the environment, considering it as a topic of interest to economic, social and ecological needs of a sustainable management, where they articulate an understanding of the physical and chemical properties of sediments with ecological and hydrological information of the water bodies receiver on a regional scale and thus evaluate the possible scenarios of pollution of water resources. This information will support in decision-making processes for managing the watershed and its water resources. Therefore, this project aims to determine the interference that a hydroelectric plant, together with the lack of proper management of the basin, can cause to the river morphology. The research is conducting a survey of sensitive areas to erode and the influence of a newly installed hydropower in a tributary of Lake Itaipu. Could notice that the removal of riparian vegetation is accelerating the erosion processes at various points of the river, but the agriculture system used in the rural area, without revolving of soil, has reduced the sediment load produced by this source. However, the retention of much of the coarse sediments by the new dam is

DENTAL EROSION IN PRIMARY DENTITION- A REVIEW

Directory of Open Access Journals (Sweden)

Rafi Shaik

2017-06-01

Full Text Available BACKGROUND The pattern of oral diseases has been influenced by ever changing human lifestyle. Tooth wear especially dental erosion has drawn increasing attention as risk factor for tooth damage or loss in recent years. It is a common condition in primary dentition compared to permanent dentition due to thinner and less mineralised enamel. However, it is more worrying, when this condition is being found in an alarming proportion among children. The presence of dental erosion in children is likely to be associated with a number of general health and dietary factors, but it is also aggravated by the relatively more rapid progression of erosion in the deciduous teeth. An understanding of the aetiologies and risk factors for erosion is important for early recognition of dental erosion to prevent serious irreversible damage to the dentition. This paper discusses the erosion in children with regard to its epidemiology, prevalence, clinical features, measurement and prevention.

Fundamental study on cavitation erosion in liquid metal. Effect of liquid parameter on cavitation erosion in liquid metals (Joint research)

International Nuclear Information System (INIS)

Hattori, Shuji; Kurachi, Hiroaki; Inoue, Fumitaka; Watashi, Katsumi; Tsukimori, Kazuyuki; Yada, Hiroki; Hashimoto, Takashi

2009-02-01

Cavitation erosion, which possibly occurs on the surfaces of fluid machineries and components contacting flowing liquid and causes sponge-like damage on the material surface, is important problem, since it may become the cause of performance deduction, life shortening, noise, vibration of mechanical components and moreover failure of machine. Research on cavitation erosion in liquid metal is very important to confirm the safety of fast breeder reactor using sodium coolant and to avoid serious damage of the target vessel of spallation neutron source containing liquid-mercury. But the research on cavitation erosion in liquid metal has been hardly performed because of its specially in comparison with that in water. In this study, a cavitation erosion test apparatus was developed to carry out the erosion tests in low-temperature liquid metals. Cavitation erosion tests were carried out in liquid lead-bismuth alloy and in deionized water. We discuss the effect of liquid parameters and temperature effects on the erosion rate. We reach to the following conclusions. The erosion rate was evaluated in terms of a relative temperature which was defind as the percentage between freezing and boiling points. At 14degC relative temperature, the erosion rate is 10 times in lead-bismuth alloy, and 2 to 5 times in sodium, compared with that in deionized water. At 14degC relative temperature, the erosion rate can be evaluated in terms of the following parameter. 1 / (1/ρ L /C L +1/ρ S C S )√ρ L . Where ρ is the material density and c is the velocity of sound, L and S denote liquid and solid. In the relative temperature between 14 and 30degC, the temperature dependence on the erosion rate is due to the increase in vapor pressure. (author)

New projectiles: multicharged metal clusters and biopolymers

International Nuclear Information System (INIS)

Della-Negra, S.; Gardes, D.; Le Beyec, Y.; Waast, B.

1991-01-01

Metal clusters and molecules are the one mean to realize simultaneous impacts of several atoms on a reduced surface(∼100A). The interaction characteristics is the non-linearity of energy deposition; the perturbation that the cluster produces, is above than the sum of the perturbation induced by its components, taken separately. The purpose of ORION project is to accelerate these new projectiles at ORSAY Tandem. The considered mass range is from 100 Daltons to 100 000 Daltons and energy range from MeV to GeV

Natural and anthropogenic rates of soil erosion

Science.gov (United States)

Regions of land that are brought into crop production from native vegetation typically undergo a period of soil erosion instability, and long term erosion rates are greater than for natural lands as long as the land continues being used for crop production. Average rates of soil erosion under natur...

Spatial distribution level of land erosion disposition based on the analysis of slope on Central Lematang sub basin

Science.gov (United States)

Putranto, Dinar Dwi Anugerah; Sarino, Yuono, Agus Lestari

2017-11-01

Soil erosion is a natural process that is influenced by the magnitude of rainfall intensity, land cover, slope, soil type and soil processing system. However, it is often accelerated by human activities, such as improper cultivation of agricultural land, clearing of forest land for mining activities, and changes in topographic area due to use for other purposes such as pile materials, mined pits and so on. The Central Lematang sub-basin is part of the Lematang sub basin, at the Musi River Region Unit, South Sumatra Province, in Indonesia, which has a topographic shape with varying types of slope and altitude. The critical condition of Central Lematang sub basin has been at an alarming rate, as more than 47.5% of topographic and land use changes are dominated by coal mining activities and forest encroachment by communities. The method used in predicting erosion is by USPED (Unit Stream Power Erosion and Disposition). This is because the USPED [1] method can predict not only sediment transport but also the value of peeling (detachment) and sediment deposition. From slope analysis result, it is found that the highest erosion potential value is found on slope (8-15%) and the sediment is carried on a steep slope (15-25%). Meanwhile, the high sediment deposition area is found in the waters of 5.226 tons / ha / year, the steeper area of 2.12 tons / ha / year.

Dietary assessment and counseling for dental erosion.

Science.gov (United States)

Marshall, Teresa A

2018-02-01

Dental erosion occurs after exposure to intrinsic or extrinsic acids. Exposure to intrinsic gastrointestinal acids is associated with anorexia nervosa, bulimia nervosa, rumination syndrome, or gastroesophageal reflux. Extrinsic dietary acids from foods or beverages also can cause erosion, particularly when exposure is prolonged by holding or swishing behaviors. Clinicians should screen patients exhibiting dental erosion for anorexia nervosa, bulimia nervosa, rumination syndrome, and gastroesophageal reflux disease. Clinicians should screen patients without a medical explanation for their erosion for exposure to acidic foods and beverages, particularly for habits that prolong exposure. Identification of intrinsic and extrinsic acid exposures and recommendations to minimize exposures are important to prevent erosion and maintain oral health. Copyright © 2018 American Dental Association. Published by Elsevier Inc. All rights reserved.

Local expansion flows of galaxies: quantifying acceleration effect of dark energy

Science.gov (United States)

Chernin, A. D.; Teerikorpi, P.

2013-08-01

The nearest expansion flow of galaxies observed around the Local group is studied as an archetypical example of the newly discovered local expansion flows around groups and clusters of galaxies in the nearby Universe. The flow is accelerating due to the antigravity produced by the universal dark energy background. We introduce a new acceleration measure of the flow which is the dimensionless ``acceleration parameter" Q (x) = x - x-2 depending on the normalized distance x only. The parameter is zero at the zero-gravity distance x = 1, and Q(x) ∝ x, when x ≫ 1. At the distance x = 3, the parameter Q = 2.9. Since the expansion flows have a self-similar structure in normalized variables, we expect that the result is valid as well for all the other expansion flows around groups and clusters of galaxies on the spatial scales from ˜ 1 to ˜ 10 Mpc everywhere in the Universe.

137Cs applicability to soil erosion assessment: theoretical and empirical model

International Nuclear Information System (INIS)

Andrello, Avacir Casanova

2004-02-01

The soil erosion processes acceleration and the increase of soil erosion rates due to anthropogenic perturbation in soil-weather-vegetation equilibrium has influenced in the soil quality and environment. So, the possibility to assess the amplitude and severity of soil erosion impact on the productivity and quality of soil is important so local scale as regional and global scale. Several models have been developed to assess the soil erosion so qualitative as quantitatively. 137 Cs, an anthropogenic radionuclide, have been very used to assess the superficial soil erosion process Empirical and theoretical models were developed on the basis of 137 Cs redistribution as indicative of soil movement by erosive process These models incorporate many parameters that can influence in the soil erosion rates quantification by 137 Cs redistribution. Statistical analysis was realized on the models recommended by IAEA to determinate the influence that each parameter generates in results of the soil redistribution. It was verified that the most important parameter is the 137 Cs redistribution, indicating the necessity of a good determination in the 137 Cs inventory values with a minimum deviation associated with these values. After this, it was associated a 10% deviation in the reference value of 137 Cs inventory and the 5% in the 137 Cs inventory of the sample and was determinate the deviation in results of the soil redistribution calculated by models. The results of soil redistribution was compared to verify if there was difference between the models, but there was not difference in the results determinate by models, unless above 70% of 137 Cs loss. Analyzing three native forests and an area of the undisturbed pasture in the Londrina region, can be verified that the 137 Cs spatial variability in local scale was 15%. Comparing the 137 Cs inventory values determinate in the three native forest with the 137 Cs inventory value determinate in the area of undisturbed pasture in the

Soil erosion in Slovene Istria

Directory of Open Access Journals (Sweden)

Matjaž Mikoš

2009-12-01

Full Text Available From the end of nineties of the 20th century, intense hydrologic and geomorphologic research is taking place in the Slovene Istria. As a part of this research also studies on soil erosion were undertaken in the period from 2005 to 2008. The field measurements were under taken onclosed 1m2 large erosion plots under three different land uses (on bare soils in an olive grove, on an overgrown meadow, in a forest, placed south of the Marezige village in the Rokava River basin.We show weekly measurements of surface erosion (interrill erosion for the period of 13 months (the end of March 2005 – the end of April 2006, as well as monthly and seasonal averages together with selected linear statistical correlations between soil erosion and weather parameters.From May 2005 to April 2006 the interrill erosion on bare soils in an olive grove with an inclination of 5.5° amounted to 9013 g/m2 (90 t/ha that corresponds to surface lowering rate of 8.5 mm/yr; on an overgrown meadow with an inclination of 9.4° it amounted to 168 g/m2 (1,68 t/ha that corresponds to surface lowering rate of 0.16 mm//yr; and in a forest with an inclination of 7.8° it amounted to 391 g/m2 (3,91 t/ha and in a forest with an inclination of 21.4° it amounted to 415 g/m2 (4,15 t/ha, respectively, that corresponds to surface lowering rate of 0.4 mm/yr.

Bentonite erosion. Final report

Energy Technology Data Exchange (ETDEWEB)

Birgersson, Martin; Boergesson, Lennart; Hedstroem, Magnus; Karnland, Ola; Nilsson, Ulf (Clay Technology AB, Lund (Sweden))

2009-12-15

Low saline water may reach KBS-3 repository depth, e.g. during periods of glaciation. Under such aqueous conditions, the montmorillonite part of the bentonite buffer might transform into a sol and thereby be transported away with flowing water in fractures. The primary aim with this report is to improve the understanding of the basic principles for this possible montmorillonite particle release. The report includes experimental and theoretical work performed at Clay Technology. Natural bentonite and ion-exchanged purified montmorillonite from three different geographical origins, Wyoming (U.S.), Milos (Greece) and Kutch (India) have been studied. Experimental and/or theoretical investigations have been performed with respect to: - Free swelling ability; - Rheological properties; - Rate of bentonite loss into fractures; - Filtering; - Ion exchange; - Sol formation ability; - Ion diffusion; - Mass loss due to erosion. The performed erosion experiments show that erosion does not occur in a mixed calcium/sodium montmorillonite with at least 20% calcium in exchange positions, when the external solution contains above 4 mM charge equivalents. This result is in agreement with the presented conceptual view of sol formation and measured equilibrium properties in mixed calcium/sodium montmorillonite. The findings imply that the buffer will be stable for non-glacial conditions. However, erosion due to sol formation cannot be ruled out for glacial conditions.

Bentonite erosion. Final report

International Nuclear Information System (INIS)

Birgersson, Martin; Boergesson, Lennart; Hedstroem, Magnus; Karnland, Ola; Nilsson, Ulf

2009-12-01

Low saline water may reach KBS-3 repository depth, e.g. during periods of glaciation. Under such aqueous conditions, the montmorillonite part of the bentonite buffer might transform into a sol and thereby be transported away with flowing water in fractures. The primary aim with this report is to improve the understanding of the basic principles for this possible montmorillonite particle release. The report includes experimental and theoretical work performed at Clay Technology. Natural bentonite and ion-exchanged purified montmorillonite from three different geographical origins, Wyoming (U.S.), Milos (Greece) and Kutch (India) have been studied. Experimental and/or theoretical investigations have been performed with respect to: - Free swelling ability; - Rheological properties; - Rate of bentonite loss into fractures; - Filtering; - Ion exchange; - Sol formation ability; - Ion diffusion; - Mass loss due to erosion. The performed erosion experiments show that erosion does not occur in a mixed calcium/sodium montmorillonite with at least 20% calcium in exchange positions, when the external solution contains above 4 mM charge equivalents. This result is in agreement with the presented conceptual view of sol formation and measured equilibrium properties in mixed calcium/sodium montmorillonite. The findings imply that the buffer will be stable for non-glacial conditions. However, erosion due to sol formation cannot be ruled out for glacial conditions.

PROBLEMS OF SOIL PROTECTION FROM EROSION

OpenAIRE

M. Voloshuk; Natalia Kiriak

2007-01-01

In this article the problems of soil protection from erosion in Moldova are considered. The history (evolution) of erosive processes is generalized, the first items of information on presence washed off soils are marked. Purposeful study of soil erosion, development of measures of struggle with it were begun in Moldova at the end of 40 years. In connection with transition to new economic methods of conducting economy (farmers, rent, privatization of land) before pedologist, the experts of des...

Soil erosion in humid regions: a review

Science.gov (United States)

Daniel J. Holz; Karl W.J. Williard; Pamela J. Edwards; Jon E. Schoonover

2015-01-01

Soil erosion has significant implications for land productivity and surface water quality, as sediment is the leading water pollutant worldwide. Here, erosion processes are defined. The dominant factors influencing soil erosion in humid areas are reviewed, with an emphasis on the roles of precipitation, soil moisture, soil porosity, slope steepness and length,...

Erosion prediction for alpine slopes: a symbiosis of remote sensing and a physical based erosion model

Science.gov (United States)

Kaiser, Andreas; Neugirg, Fabian; Haas, Florian; Schindewolf, Marcus; Schmidt, Jürgen

2014-05-01

As rainfall simulations represent an established tool for quantifying soil detachment on cultivated area in lowlands and low mountain ranges, they are rarely used on steep slopes high mountain ranges. Still this terrain represents productive sediment sources of high morphodynamic. A quantitative differentiation between gravitationally and fluvially relocated material reveals a major challenge in understanding erosion on steep slopes: does solifluction as a result of melting in spring or heavy convective rainstorms during summer cause the essential erosion processes? This paper aims to answer this question by separating gravitational mass movement (solifluction, landslides, mudflow and needle ice) and runoff-induced detachment. First simulated rainstorm experiments are used to assess the sediment production on bare soil on a strongly inclined plot (1 m², 42°) in the northern limestone Alps. Throughout precipitation experiments runoff and related suspended sediments were quantified. In order to enlarge slope length virtually to around 20 m a runoff feeding device is additionally implemented. Soil physical parameters were derived from on-site sampling. The generated data is introduced to the physically based and catchment-scaled erosion model EROSION 3D to upscale plot size to small watershed conditions. Thus infiltration, runoff, detachment, transport and finally deposition can be predicted for single rainstorm events and storm sequences. Secondly, in order to separate gravitational mass movements and water erosion, a LiDAR and structure-from-motion based monitoring approach is carried out to produce high-resolution digital elevation models. A time series analysis of detachment and deposition from different points in time is implemented. Absolute volume losses are then compared to sediment losses calculated by the erosion model as the latter only generates data that is connected to water induced hillside erosion. This methodology will be applied in other watersheds

Modelling rainfall erosion resulting from climate change

Science.gov (United States)

Kinnell, Peter

2016-04-01

It is well known that soil erosion leads to agricultural productivity decline and contributes to water quality decline. The current widely used models for determining soil erosion for management purposes in agriculture focus on long term (~20 years) average annual soil loss and are not well suited to determining variations that occur over short timespans and as a result of climate change. Soil loss resulting from rainfall erosion is directly dependent on the product of runoff and sediment concentration both of which are likely to be influenced by climate change. This presentation demonstrates the capacity of models like the USLE, USLE-M and WEPP to predict variations in runoff and erosion associated with rainfall events eroding bare fallow plots in the USA with a view to modelling rainfall erosion in areas subject to climate change.

Erosion by rain in the western Congo

International Nuclear Information System (INIS)

Ploey, J. de

1967-01-01

Vast expanses of the western part of central and southern Africa are covered with uniform, sandy formations of the Kalahari type. The topography of these areas and their present morphological characteristics are mainly the result of erosion by rain. Information on the hydrology of the surface waters in these areas is fairly limited and is insufficient to permit any conclusions regarding the way in which erosion by rain takes place. To obtain a better understanding of these phenomena, the author devised a series of experiments based on the use of 46 Sc-labelled radioactive sand. These experiments began at the beginning of the 1964/65 rainy season and are continuing. The experimental plot corresponds to convex and rectilinear portions of a hillside with a slope varying between 0 and 12 degrees. The vegetation consists of grassy savannah of substeppe appearance and secondary forests. Series of labelled samples were placed successively on the surface of the experimental plot and the erosive effect of rain was determined by measuring the residual concentrations after rainfall. Some samples were placed below a shield so as to eliminate the effects of splash and reveal the part played by runoff. Radiographic films were used to study the dispersion of labelled particles in the surrounding area. This radiographic method made it possible to determine the scale of erosion by splash for different rainfall conditions. The erosion diagrams obtained from these experiments show the correlations that exist between the intensity and duration of the rainfall and the erosion of the soil. Examination of the erosion diagrams and the shielded samples and analysis of the radiographs showed that erosion by rain on Kalahari ground covered with substeppe savannah is caused mainly by splash erosion and by dispersed, intermittent runoff. Sheet wash plays no part if the slope is less than 12 degrees. (author) [fr

Thermal activation in statistical clusters of magnetic nanoparticles

International Nuclear Information System (INIS)

Hovorka, O

2017-01-01

This article presents a kinetic Monte-Carlo study of thermally activated magnetisation dynamics in clusters of statistically distributed magnetic nanoparticles. The structure of clusters is assumed to be of fractal nature, consistently with recent observations of magnetic particle aggregation in cellular environments. The computed magnetisation relaxation decay and frequency-dependent hysteresis loops are seen to significantly depend on the fractal dimension of aggregates, leading to accelerated magnetisation relaxation and reduction in the size of hysteresis loops as the fractal dimension increases from one-dimensional-like to three-dimensional-like clusters. Discussed are implications for applications in nanomedicine, such as magnetic hyperthermia or magnetic particle imaging. (paper)

Rainfall erosivity factor estimation in Republic of Moldova

Science.gov (United States)

Castraveš, Tudor; Kuhn, Nikolaus

2017-04-01

Rainfall erosivity represents a measure of the erosive force of rainfall. Typically, it is expressed as variable such as the R factor in the Universal Soil Loss Equation (USLE) (Wischmeier and Smith, 1965, 1978) or its derivates. The rainfall erosivity index for a rainfall event (EI30) is calculated from the total kinetic energy and maximum 30 minutes intensity of individual events. However, these data are often unavailable for wide regions and countries. Usually, there are three issues regarding precipitation data: low temporal resolution, low spatial density and limited access to the data. This is especially true for some of postsoviet countries from Eastern Europe, such as Republic of Moldova, where soil erosion is a real and persistent problem (Summer, 2003) and where soils represents the main natural resource of the country. Consequently, researching and managing soil erosion is particularly important. The purpose of this study is to develop a model based on commonly available rainfall data, such as event, daily or monthly amounts, to calculate rainfall erosivity for the territory of Republic of Moldova. Rainfall data collected during 1994-2015 period at 15 meteorological stations in the Republic of Moldova, with 10 minutes temporal resolution, were used to develop and calibrate a model to generate an erosivity map of Moldova. References 1. Summer, W., (2003). Soil erosion in the Republic of Moldova — the importance of institutional arrangements. Erosion Prediction in Ungauged Basins: Integrating Methods and Techniques (Proceedings of symposium HS01 held during IUGG2003 at Sapporo. July 2003). IAHS Publ. no. 279. 2. Wischmeier, W.H., and Smith, D.D. (1965). Predicting rainfall-erosion losses from cropland east of the Rocky Mountains. Agr. Handbook No. 282, U.S. Dept. Agr., Washington, DC 3. Wischmeier, W.H., and Smith, D.D. (1978). Predicting rainfall erosion losses. Agr. handbook No. 537, U.S. Dept. of Agr., Science and Education Administration.

Restorative Management of Intrinsic and Extrinsic Dental Erosion.

Science.gov (United States)

Al-Salehi, Samira Kathryn

2014-12-01

The restorative management of tooth surface loss is highlighted through the presentation of two advanced cases of dental erosion. On presentation, the causes of the dental erosion in both patients had been previously diagnosed and stopped. The first patient was a 67 year old with intrinsic erosion and an element of attrition where a multidisciplinary approach was used. The other, a 17 year old patient with extrinsic erosion managed via adhesive restorations. Adhesive techniques are a relatively simple, effective and conservative method for the treatment of dental erosion. The two treatment modalities (conventional versus contemporary) are compared and discussed.

Definition of tolerable soil erosion values

Directory of Open Access Journals (Sweden)

G. Sparovek

1997-09-01

Full Text Available Although the criteria for defining erosion tolerance are well established, the limits generally used are not consistent with natural, economical and technological conditions. Rates greater than soil formation can be accepted only until a minimum of soil depth is reached, provided that they are not associated with environmental hazard or productivity losses. A sequence of equations is presented to calculate erosion tolerance rates through time. The selection of equation parameters permits the definition of erosion tolerance rates in agreement with environmental, social and technical needs. The soil depth change that is related to irreversible soil degradation can be calculated. The definition of soil erosion tolerance according to these equations can be used as a guideline for sustainable land use planning and is compatible with expert systems.

PROBLEMS OF SOIL PROTECTION FROM EROSION

Directory of Open Access Journals (Sweden)

M. Voloshuk

2007-10-01

Full Text Available In this article the problems of soil protection from erosion in Moldova are considered. The history (evolution of erosive processes is generalized, the first items of information on presence washed off soils are marked. Purposeful study of soil erosion, development of measures of struggle with it were begun in Moldova at the end of 40 years. In connection with transition to new economic methods of conducting economy (farmers, rent, privatization of land before pedologist, the experts of design organizations put forward the new requirements to study of erosive processes, development of soil protection, ecologo-adaptive systems of landscape agriculture. The tasks for improvement of a soil cover, restoration of fertility soil and their protection are put forward which are necessary for deciding in a near future.

Dental erosion: understanding this pervasive condition.

Science.gov (United States)

Almeida e Silva, Júnio S; Baratieri, Luiz Narciso; Araujo, Edson; Widmer, Nicolas

2011-08-01

Dental erosion is a contemporary disease, mostly because of the change of the eating patterns that currently exist in society. It is a "silent" and multifactorial disease, and is highly influenced by habits and lifestyles. The prevalence of dental erosion has considerably increased, with this condition currently standing as a great challenge for the clinician, regarding the diagnosis, identification of the etiological factors, prevention, and execution of an adequate treatment. This article presents a dental erosion review and a case report of a restorative treatment of dental erosion lesions using a combination of bonded ceramic overlays to reestablish vertical dimension and composite resin to restore the worn palatal and incisal surfaces of the anterior upper teeth. Adequate function and esthetics can be achieved with this approach. © 2011 Wiley Periodicals, Inc.

Dental erosion in groups of Yemeni children and adolescents and the modification of an erosion partial recording system.

Science.gov (United States)

Al-Ashtal, Amin; Johansson, Anders; Omar, Ridwaan; Johansson, Ann-Katrin

2017-07-01

The prevalence of dental erosion is rising especially among children and adolescents and its grading needs further investigation. To determine the prevalence and severity of dental erosion in groups of Yemeni children and adolescents, and to clinically compare an erosion partial recording system (EPRS) with a proposed modified-simplified version (EPRS-M). Of 6163 individuals aged 5-6, 13-14 and 18-19 years, 911 were randomly selected, of which 668 participated in the study. Dental erosion was graded using EPRS. EPRS-M was proposed, and its sensitivity and specificity was calculated in relation to EPRS. Prevalence of erosion extending into dentine on at least one tooth was 6.8% among 5- to 6-year-olds, 3.0% among 13- to 14-year-olds and 14.6% among 18- to 19-year olds. The highest prevalence was 19.2% among girls aged 18-19 years which was significantly higher than boys (10.4%) in the same age group (P = 0.044). Sensitivity and specificity for EPRS-M in relation to EPRS were 85.7% and 100% for primary teeth, and 84.1% and 100% for permanent teeth. Dental erosion was common among children and older teenagers and highest among older girls but less common among younger teenagers. The tested accuracy of EPRS-M qualifies it to be used as an initial quick detection tool in future dental erosion research. © 2016 The Authors. International Journal of Paediatric Dentistry published by BSPD, IAPD and John Wiley & Sons Ltd.

First evidence of diffuse ultra-steep-spectrum radio emission surrounding the cool core of a cluster

Science.gov (United States)

Savini, F.; Bonafede, A.; Brüggen, M.; van Weeren, R.; Brunetti, G.; Intema, H.; Botteon, A.; Shimwell, T.; Wilber, A.; Rafferty, D.; Giacintucci, S.; Cassano, R.; Cuciti, V.; de Gasperin, F.; Röttgering, H.; Hoeft, M.; White, G.

2018-05-01

Diffuse synchrotron radio emission from cosmic-ray electrons is observed at the center of a number of galaxy clusters. These sources can be classified either as giant radio halos, which occur in merging clusters, or as mini halos, which are found only in cool-core clusters. In this paper, we present the first discovery of a cool-core cluster with an associated mini halo that also shows ultra-steep-spectrum emission extending well beyond the core that resembles radio halo emission. The large-scale component is discovered thanks to LOFAR observations at 144 MHz. We also analyse GMRT observations at 610 MHz to characterise the spectrum of the radio emission. An X-ray analysis reveals that the cluster is slightly disturbed, and we suggest that the steep-spectrum radio emission outside the core could be produced by a minor merger that powers electron re-acceleration without disrupting the cool core. This discovery suggests that, under particular circumstances, both a mini and giant halo could co-exist in a single cluster, opening new perspectives for particle acceleration mechanisms in galaxy clusters.

Irradiation effects of Ar cluster ion beams on Si substrates

International Nuclear Information System (INIS)

Ishii, Masahiro; Sugahara, Gaku; Takaoka, G.H.; Yamada, Isao

1993-01-01

Gas-cluster ion beams can be applied to new surface modification techniques such as surface cleaning, low damage sputtering and shallow junction formation. The effects of energetic Ar cluster impacts on solid surface were studied for cluster energies of 10-30keV. Irradiation effects were studied by RBS. For Si(111) substrates, irradiated with Ar ≥500 clusters to a dose of 1x10 15 ion/cm 2 at acceleration voltage 15kV, 2x10 14 atoms/cm 2 implanted Ar atoms were detected. In this case, the energy per cluster atom was smaller than 30eV; at this energy, no significant implantation occurs in the case of monomer ions. Ar cluster implantation into Si substrates occurred due to the high energy density irradiation. (author)

Accelerated subcutaneous immunotherapy in pediatric population – Systematic review

Directory of Open Access Journals (Sweden)

R.A. Gomes dos Reis Pimentel

2018-05-01

Full Text Available Background: Accelerated subcutaneous immunotherapy (SCIT schedules represent an alternative to conventional SCIT, providing immunotherapy benefits in a shorter period of time. The objectives of this systematic review were to assess clinical and immunological efficacy as well as safety of accelerated SCIT build-up schedules for the treatment of respiratory allergy in pediatric patients. Methods: Studies were located by searching PubMed, using “immunotherapy” and “desensitization” as keywords. The selection of studies, published from January 1st, 2006, to December 31th, 2015, was performed in two stages: screening of titles and abstracts, and assessment of the full papers identified as relevant, considering the inclusion criteria. Data were extracted in a standardized way and synthesized qualitatively to assess efficacy and safety of accelerated schedules in respiratory allergy. Results: Eleven trials were included: two evaluated rush SCIT and nine assessed cluster SCIT. This review demonstrated that rush and cluster schedules are clinically and immunological efficacious, with faster effect than conventional schedules. No relevant difference with respect to clinical outcomes was noticed between subgroups (pediatric, adult and mixed populations. Regarding safety, most local adverse reactions were mild and there were neither life-threatening systemic reactions nor fatal events. No relevant differences in the incidence and severity of either local or systemic reactions between the accelerated schedule group and control group were registered. Conclusions: Accelerated SCIT build-up schedules are effective in the treatment of respiratory allergy in pediatric patients, representing a safe alternative to the conventional schedules with the advantage of achieving clinical effectiveness sooner. Keywords: Allergy, Immunotherapy, Pediatrics

Erosion testing of hard materials and coatings

Energy Technology Data Exchange (ETDEWEB)

Hawk, Jeffrey A.

2005-04-29

Erosion is the process by which unconstrained particles, usually hard, impact a surface, creating damage that leads to material removal and component failure. These particles are usually very small and entrained in fluid of some type, typically air. The damage that occurs as a result of erosion depends on the size of the particles, their physical characteristics, the velocity of the particle/fluid stream, and their angle of impact on the surface of interest. This talk will discuss the basics of jet erosion testing of hard materials, composites and coatings. The standard test methods will be discussed as well as alternative approaches to determining the erosion rate of materials. The damage that occurs will be characterized in genera1 terms, and examples will be presented for the erosion behavior of hard materials and coatings (both thick and thin).

Applicability of 239Pu as a tracer for soil erosion in the wet-dry tropics of northern Australia

International Nuclear Information System (INIS)

Lal, R.; Tims, S.G.; Fifield, L.K.; Wasson, R.J.; Howe, D.

2013-01-01

The technique of accelerator mass spectroscopy (AMS) has been employed to determine modern soil loss rates through the analysis of 239 Pu profiles in soil cores from the Daly basin in Northern Territory, Australia. In areas in which soil conservation banks were not present or were only added recently ( −1 a −1 . The measured rates are up to 5 times higher compared to agricultural and uncultivated areas within soil conservation banks in other parts of the catchment. High intensity seasonal rainfall combined with reduction in land cover due to grazing and episodic bush fires are primary factors influencing erosion although other impacts on the landscape such as tillage generated runoff and land clearing seem to be responsible for accelerated sediment production.

Building a cluster computer for the computing grid of tomorrow

International Nuclear Information System (INIS)

Wezel, J. van; Marten, H.

2004-01-01

The Grid Computing Centre Karlsruhe takes part in the development, test and deployment of hardware and cluster infrastructure, grid computing middleware, and applications for particle physics. The construction of a large cluster computer with thousands of nodes and several PB data storage capacity is a major task and focus of research. CERN based accelerator experiments will use GridKa, one of only 8 world wide Tier-1 computing centers, for its huge computer demands. Computing and storage is provided already for several other running physics experiments on the exponentially expanding cluster. (orig.)

Erosive Lichen Planus.

Science.gov (United States)

Mauskar, Melissa

2017-09-01

Lichen planus is an inflammatory mucocutaneous condition with a myriad of clinical manifestations. There are 3 forms of lichen planus that effect the vulva: papulosquamous, hypertrophic, and erosive. Erosive lichen planus can progress to vulvar scaring, vaginal stenosis, and squamous cell carcinoma; these long-term sequelae cause sexual distress, depression, and decreased quality of life for patients. Diagnosis is often delayed because of patient embarrassment or clinician misdiagnosis. Early recognition and treatment is essential to decreasing the morbidity of this condition. Multimodal treatment, along with a multidisciplinary approach, will improve outcomes and further clinical advances in studying this condition. Copyright © 2017 Elsevier Inc. All rights reserved.

The amount of glacial erosion of the bedrock

International Nuclear Information System (INIS)

Paasse, Tore

2004-11-01

The purpose of this study is to estimate an upper bound for the average erosion of fresh bedrock that can reasonably be expected during a glacial period or a single glaciation. The study is based on the assumption that classic sediments, formed by Scandinavian ice erosion during the Quaternary period, still exist within the formerly glaciated area or its periphery. The volume of these sediments thus constitutes the maximum average glacial erosion of bedrock within this area. This volume is calculated by estimating the thickness of the minerogenic Quaternary from well data in Sweden and Denmark and from seismic measurements in adjacent sea areas. The average thickness of the Quaternary deposits and other reogolith in the investigated area was estimated to 16 m. Assuming that the whole volume is the result of glacial erosion of fresh bedrock this corresponds to 12 m depth. However, a great part of the sediments may consist of glacially redistributed Tertiary regolith. As the amount of Tertiary regolith is uncertain the estimated maximum average glacial erosion rate in fresh bedrock is uncertain, and assuming that the total sediment volume is the result of glacial erosion leads to an overestimation of the glacial erosion depth. Considering this, the average glacial erosion during a full glacial period has been estimated to between 0.2 m and 4 m. If the extremes in the made assumptions are excluded the glacial erosion during a glacial cycle can be estimated to about 1 m

The amount of glacial erosion of the bedrock

Energy Technology Data Exchange (ETDEWEB)

Paasse, Tore [Geological Survey of Sweden, Uppsala (Sweden)

2004-11-01

The purpose of this study is to estimate an upper bound for the average erosion of fresh bedrock that can reasonably be expected during a glacial period or a single glaciation. The study is based on the assumption that classic sediments, formed by Scandinavian ice erosion during the Quaternary period, still exist within the formerly glaciated area or its periphery. The volume of these sediments thus constitutes the maximum average glacial erosion of bedrock within this area. This volume is calculated by estimating the thickness of the minerogenic Quaternary from well data in Sweden and Denmark and from seismic measurements in adjacent sea areas. The average thickness of the Quaternary deposits and other reogolith in the investigated area was estimated to 16 m. Assuming that the whole volume is the result of glacial erosion of fresh bedrock this corresponds to 12 m depth. However, a great part of the sediments may consist of glacially redistributed Tertiary regolith. As the amount of Tertiary regolith is uncertain the estimated maximum average glacial erosion rate in fresh bedrock is uncertain, and assuming that the total sediment volume is the result of glacial erosion leads to an overestimation of the glacial erosion depth. Considering this, the average glacial erosion during a full glacial period has been estimated to between 0.2 m and 4 m. If the extremes in the made assumptions are excluded the glacial erosion during a glacial cycle can be estimated to about 1 m.

Parallel hyperbolic PDE simulation on clusters: Cell versus GPU

Science.gov (United States)

Rostrup, Scott; De Sterck, Hans

2010-12-01

Increasingly, high-performance computing is looking towards data-parallel computational devices to enhance computational performance. Two technologies that have received significant attention are IBM's Cell Processor and NVIDIA's CUDA programming model for graphics processing unit (GPU) computing. In this paper we investigate the acceleration of parallel hyperbolic partial differential equation simulation on structured grids with explicit time integration on clusters with Cell and GPU backends. The message passing interface (MPI) is used for communication between nodes at the coarsest level of parallelism. Optimizations of the simulation code at the several finer levels of parallelism that the data-parallel devices provide are described in terms of data layout, data flow and data-parallel instructions. Optimized Cell and GPU performance are compared with reference code performance on a single x86 central processing unit (CPU) core in single and double precision. We further compare the CPU, Cell and GPU platforms on a chip-to-chip basis, and compare performance on single cluster nodes with two CPUs, two Cell processors or two GPUs in a shared memory configuration (without MPI). We finally compare performance on clusters with 32 CPUs, 32 Cell processors, and 32 GPUs using MPI. Our GPU cluster results use NVIDIA Tesla GPUs with GT200 architecture, but some preliminary results on recently introduced NVIDIA GPUs with the next-generation Fermi architecture are also included. This paper provides computational scientists and engineers who are considering porting their codes to accelerator environments with insight into how structured grid based explicit algorithms can be optimized for clusters with Cell and GPU accelerators. It also provides insight into the speed-up that may be gained on current and future accelerator architectures for this class of applications. Program summaryProgram title: SWsolver Catalogue identifier: AEGY_v1_0 Program summary URL

A Zoo of Radio Relics: Cluster Cores to Filaments Ruta Kale1,2 ...

Indian Academy of Sciences (India)

Abstract. Radio relics in galaxy clusters can be electrons accelerated at cluster merger shocks or adiabatically compressed fossil radio cocoons or dying radio galaxies. The spectral evolution of radio relics is affected by the surrounding thermal plasma. We present a low frequency study of three radio relics representing ...

Photogrammetric techniques for across-scale soil erosion assessment

OpenAIRE

Eltner, Anette

2016-01-01

Soil erosion is a complex geomorphological process with varying influences of different impacts at different spatio-temporal scales. To date, measurement of soil erosion is predominantly realisable at specific scales, thereby detecting separate processes, e.g. interrill erosion contrary to rill erosion. It is difficult to survey soil surface changes at larger areal coverage such as field scale with high spatial resolution. Either net changes at the system outlet or remaining traces after the ...

Low-energy irradiation effects of gas cluster ion beams

International Nuclear Information System (INIS)

Houzumi, Shingo; Takeshima, Keigo; Mochiji, Kozo; Toyoda, Noriaki; Yamada, Isao

2007-01-01

A cluster-ion irradiation system with cluster-size selection has been developed to study the effects of the cluster size for surface processes using cluster ions. A permanent magnet with a magnetic field of 1.2 T is installed for size separation of large cluster ions. Trace formations at HOPG surface by the irradiation with size-selected Ar-cluster ions under acceleration energy of 30 keV were investigated by a scanning tunneling microscopy. Generation behavior of the crater-like traces is strongly affected by the number of constituent atoms (cluster size) of the irradiating cluster ion. When the incident cluster ion is composed of 100-3000 atoms, crater-like traces are observed on the irradiated surfaces. In contrast, such traces are not observed at all with the irradiation of the cluster-ions composed of over 5000 atoms. Such the behavior is discussed on the basis of the kinetic energy per constituent atom of the cluster ion. To study GCIB irradiation effects against macromolecule, GCIB was irradiated on DNA molecules absorbed on graphite surface. By the GCIB irradiation, much more DNA molecules was sputtered away as compared with the monomer-ion irradiation. (author)

Effects of erosive, cariogenic or combined erosive/cariogenic challenges on human enamel: an in situ/ex vivo study.

Science.gov (United States)

Honório, H M; Rios, D; Santos, C F; Magalhães, A C; Buzalaf, M A R; Machado, M A A M

2008-01-01

Individuals with cariogenic diet can also consume erosive beverages. Thus, it seems necessary to investigate a possible caries/erosion interaction. To test in situ/ex vivo a combination of these challenges, 11 subjects wore intraoral appliances containing four enamel blocks randomly assigned. In the first 2-week phase, the appliances were immersed in a cola drink 3 times/day. Two blocks were free of plaque (erosion only: EO) and two blocks were covered with plaque (erosion + plaque: EP). In the second 2-week phase, four new blocks were all covered with plaque and subjected to a sucrose solution 8 times/day. Among the four new blocks, two were also subjected to the cola drink 3 times/day (erosion + caries: EC) while the other two were not (caries only: CO). Thus, in EO, the specimens were fixed at the intraoral appliance level. In EP, EC and CO they were fixed 1.0 mm under the appliance level and covered with plastic meshes for dental plaque accumulation. Changes in wear and hardness were measured. Data were tested using ANOVA and Tukey's test (p cariogenic challenges showed less enamel alterations when compared to erosive or cariogenic challenges only. (c) 2008 S. Karger AG, Basel.

TURBULENT COSMIC-RAY REACCELERATION AT RADIO RELICS AND HALOS IN CLUSTERS OF GALAXIES

International Nuclear Information System (INIS)

Fujita, Yutaka; Takizawa, Motokazu; Yamazaki, Ryo; Akamatsu, Hiroki; Ohno, Hiroshi

2015-01-01

Radio relics are synchrotron emission found on the periphery of galaxy clusters. From the position and the morphology, it is often believed that the relics are generated by cosmic-ray (CR) electrons accelerated at shocks through a diffusive shock acceleration (DSA) mechanism. However, some radio relics have harder spectra than the prediction of the standard DSA model. One example is observed in the cluster 1RXS J0603.3+4214, which is often called the “Toothbrush Cluster.” Interestingly, the position of the relic is shifted from that of a possible shock. In this study, we show that these discrepancies in the spectrum and the position can be solved if turbulent (re)acceleration is very effective behind the shock. This means that for some relics turbulent reacceleration may be the main mechanism to produce high-energy electrons, contrary to the common belief that it is the DSA. Moreover, we show that for efficient reacceleration, the effective mean free path of the electrons has to be much smaller than their Coulomb mean free path. We also study the merging cluster 1E 0657−56, or the “Bullet Cluster,” in which a radio relic has not been found at the position of the prominent shock ahead of the bullet. We indicate that a possible relic at the shock is obscured by the observed large radio halo that is generated by strong turbulence behind the shock. We propose a simple explanation of the morphological differences of radio emission among the Toothbrush, the Bullet, and the Sausage (CIZA J2242.8+5301) Clusters

Numerical study of impact erosion of multiple solid particle

Science.gov (United States)

Zheng, Chao; Liu, Yonghong; Chen, Cheng; Qin, Jie; Ji, Renjie; Cai, Baoping

2017-11-01

Material erosion caused by continuous particle impingement during hydraulic fracturing results in significant economic loss and increased production risks. The erosion process is complex and has not been clearly explained through physical experiments. To address this problem, a multiple particle model in a 3D configuration was proposed to investigate the dynamic erosion process. This approach can significantly reduce experiment costs. The numerical model considered material damping and elastic-plastic material behavior of target material. The effects of impact parameters on erosion characteristics, such as plastic deformation, contact time, and energy loss rate, were investigated. Based on comprehensive studies, the dynamic erosion mechanism and geometry evolution of eroded crater was obtained. These findings can provide a detailed erosion process of target material and insights into the material erosion caused by multiple particle impingement.

Soil erosion assessment - Mind the gap

Science.gov (United States)

Kim, Jongho; Ivanov, Valeriy Y.; Fatichi, Simone

2016-12-01

Accurate assessment of erosion rates remains an elusive problem because soil loss is strongly nonunique with respect to the main drivers. In addressing the mechanistic causes of erosion responses, we discriminate between macroscale effects of external factors - long studied and referred to as "geomorphic external variability", and microscale effects, introduced as "geomorphic internal variability." The latter source of erosion variations represents the knowledge gap, an overlooked but vital element of geomorphic response, significantly impacting the low predictability skill of deterministic models at field-catchment scales. This is corroborated with experiments using a comprehensive physical model that dynamically updates the soil mass and particle composition. As complete knowledge of microscale conditions for arbitrary location and time is infeasible, we propose that new predictive frameworks of soil erosion should embed stochastic components in deterministic assessments of external and internal types of geomorphic variability.

Erosion of Earthen Levees by Wave Action

Science.gov (United States)

Ozeren, Y.; Wren, D. G.; Reba, M. L.

2016-02-01

Earthen levees of aquaculture and irrigation reservoirs in the United States often experience significant erosion due to wind-generated waves. Typically constructed using local soils, unprotected levees are subjected to rapid erosion and retreat due to wind generated waves and surface runoff. Only a limited amount of published work addresses the erosion rates for unprotected levees, and producers who rely on irrigation reservoirs need an economic basis for selecting a protection method for vulnerable levees. This, in turn, means that a relationship between wave energy and erosion of cohesive soils is needed. In this study, laboratory experiments were carried out in order to quantify wave induced levee erosion and retreat. A model erodible bank was packed using a soil consisting of approximately 14% sand, 73% silt, and 13% clay in a 20.6 m long 0.7 m wide and 1.2 m deep wave tank at the USDA-ARS, National Sedimentation Laboratory in Oxford MS. The geometry of the levee face was monitored by digital camera and the waves were measured by means of 6 capacitance wave staffs. Relationships were established between levee erosion, edge and retreat rates, and incident wave energy.

Centrifugal acceleration in the magnetotail lobes

Directory of Open Access Journals (Sweden)

H. Nilsson

2010-02-01

Full Text Available Combined Cluster EFW and EDI measurements have shown that cold ion outflow in the magnetospheric lobes dominates the hydrogen ion outflow from the Earth's atmosphere. The ions have too low kinetic energy to be measurable with particle instruments, at least for the typical spacecraft potential of a sunlit spacecraft in the tenuous lobe plasmas outside a few R_E. The measurement technique yields both density and bulk velocity, which can be combined with magnetic field measurements to estimate the centrifugal acceleration experienced by these particles. We present a quantitative estimate of the centrifugal acceleration, and the velocity change with distance which we would expect due to centrifugal acceleration. It is found that the centrifugal acceleration is on average outward with an average value of about of 5 m s⁻². This is small, but acting during long transport times and over long distances the cumulative effect is significant, while still consistent with the relatively low velocities estimated using the combination of EFW and EDI data. The centrifugal acceleration should accelerate any oxygen ions in the lobes to energies observable by particle spectrometers. The data set also put constraints on the effectiveness of any other acceleration mechanisms acting in the lobes, where the total velocity increase between 5 and 19 R_E geocentric distance is less than 5 km s⁻¹.

Dental erosion in groups of Yemeni children and adolescents and the modification of an erosion partial recording system

OpenAIRE

Al-Ashtal, Amin Mohsen Saleh; Johansson, Anders; Ridwaan, Omar; Johansson, Ann-Katrin

2016-01-01

Background: Dental erosion is a multifactorial oral health problem with an increasing prevalence among children and adolescents in many countries. Awareness of the condition among lay people is generally lacking, and methods for its clinical grading also need further improvements. Aim: The aims of this thesis was to investigate various aspects of dental erosion including prevalence and risk indicators, to evaluate the recording system used, and to assess the awareness of dental erosion in ...

Reduction of surface erosion in fusion reactors

International Nuclear Information System (INIS)

Rossing, T.D.; Das, S.K.; Kaminsky, M.

1976-01-01

Some of the major processes leading to surface erosion in fusion reactors are reviewed briefly, including blistering by implanted gas, sputtering by ions, atoms, and neutrons, and vaporization by local heating. Surface erosion affects the structural integrity and limits the lifetime of reactor components exposed to plasma radiation. In addition, some of the processes leading to surface erosion also cause the release of plasma contaminants. Methods proposed to reduce surface erosion have included control of surface temperature, selection of materials with a favorable microstructure, chemical and mechanical treatment of surfaces, and employment of protective surface coatings, wall liners, and divertors. The advantages and disadvantages of some of these methods are discussed

Label-free colorimetric detection of mercury via Hg2+ ions-accelerated structural transformation of nanoscale metal-oxo clusters

Science.gov (United States)

Chen, Kun; She, Shan; Zhang, Jiangwei; Bayaguud, Aruuhan; Wei, Yongge

2015-11-01

Mercury and its compounds are known to be extremely toxic but widely distributed in environment. Although many works have been reported to efficiently detect mercury, development of simple and convenient sensors is still longed for quick analyzing mercury in water. In this work, a nanoscale metal-oxo cluster, (n-Bu4N)2[Mo5NaO13(OCH3)4(NO)], (MLPOM), organically-derivatized from monolacunary Lindqvist-type polyoxomolybdate, is found to specifically react with Hg2+ in methanol/water via structural transformation. The MLPOM methanol solution displays a color change from purple to brown within seconds after being mixed with an aqueous solution containing Hg2+. By comparing the structure of polyoxomolybdate before and after reaction, the color change is revealed to be the essentially structural transformation of MLPOM accelerated by Hg2+. Based on this discovery, MLPOM could be utilized as a colorimetric sensor to sense the existence of Hg2+, and a simple and label-free method is developed to selectively detect aqueous Hg2+. Furthermore, the colorimetric sensor has been applied to indicating mercury contamination in industrial sewage.

Soil carbon and nitrogen erosion in forested catchments: implications for erosion-induced terrestrial carbon sequestration

Science.gov (United States)

E. M. Stacy; S. C. Hart; C. T. Hunsaker; D. W. Johnson; A. A. Berhe

2015-01-01

Lateral movement of organic matter (OM) due to erosion is now considered an important flux term in terrestrial carbon (C) and nitrogen (N) budgets, yet most published studies on the role of erosion focus on agricultural or grassland ecosystems. To date, little information is available on the rate and nature of OM eroded from forest ecosystems. We present annual...

Soil erosion as a driver of land-use change

NARCIS (Netherlands)

Bakker, M.M.; Govers, G.; Kosmas, C.; VanAcker, H.; Oost, van K.; Rounsevell, M.

2005-01-01

Although much research has been carried out on the crop productivity response to soil erosion, little is known about the role of soil erosion as a driver of land-use change. Given, however, the some-times large erosion-induced reductions in crop yields, it appears likely that erosion has a strong

Long-term predictive capability of erosion models

Science.gov (United States)

Veerabhadra, P.; Buckley, D. H.

1983-01-01

A brief overview of long-term cavitation and liquid impingement erosion and modeling methods proposed by different investigators, including the curve-fit approach is presented. A table was prepared to highlight the number of variables necessary for each model in order to compute the erosion-versus-time curves. A power law relation based on the average erosion rate is suggested which may solve several modeling problems.

Erosion and corrosion of nuclear power plant materials

International Nuclear Information System (INIS)

1994-01-01

This conference is composed of 23 papers, grouped in 3 sessions which main themes are: analysis of corrosion and erosion damages of nuclear power plant equipment and influence of water chemistry, temperature, irradiations, metallurgical and electrochemical factors, flow assisted cracking, stress cracking; monitoring and control of erosion and corrosion in nuclear power plants; susceptibility of structural materials to erosion and corrosion and ways to improve the resistance of materials, steels, coatings, etc. to erosion, corrosion and cracking

Comparison Between Bandage Contact Lenses and Pressure Patching on the Erosion Area and Pain Scale in Patients With Corneal Erosion.

Science.gov (United States)

Triharpini, Ni Nyoman; Gede Jayanegara, I Wayan; Handayani, Ariesanti Tri; Widiana, I Gde Raka

2015-01-01

Corneal erosion is common in eye emergency cases. Extensive corneal erosions result in severe pain and prolonged healing time. This study aimed to compare bandage contact lenses with pressure patching in terms of reducing the size of the erosion area, pain scale in patients with corneal erosion and its complications. A randomized open-label clinical trial was conducted. Subjects with mechanical corneal erosion were selected to use either bandage contact lenses or pressure patching. All subjects received antibiotic eye drops and 0.5% tropicamide eye drops. Evaluations were done 24 and 72 hours after treatment. The size of the corneal erosion area, pain scale, and complications were assessed. A total of 32 eyes (16 eyes in each group) were studied. The change in the size of the corneal erosion area was greater in the bandage contact lens group than in the pressure patching group, although there was no significant difference. In the bandage contact lens group, 56.25% of the eyes were healed at 24 hours and 43.75% were healed at 72 hours. In the pressure patching group, 62.50% were healed at 24 hours and 12.50% were healed at 72 hours. The change in pain scale was significantly greater in the bandage contact lens group than in the pressure patching group. No complications were found in both groups. Bandage contact lenses are an effective alternative to treating mechanical corneal erosion because of their effect in reducing pain without causing any complications.

Evaluating the new soil erosion map of Hungary

Science.gov (United States)

Waltner, István; Centeri, Csaba; Takács, Katalin; Pirkó, Béla; Koós, Sándor; László, Péter; Pásztor, László

2017-04-01

With growing concerns on the effects of climate change and land use practices on our soil resources, soil erosion by water is becoming a significant issue internationally. Since the 1964 publication of the first soil erosion map of Hungary, there have been several attempts to provide a countrywide assessment of erosion susceptibility. However, there has been no up-to-date map produced in the last decade. In 2016, a new, 1:100 000 scale soil erosion map was published, based on available soil, elevation, land use and meteorological data for the extremely wet year of 2010. The map utilized combined outputs for two spatially explicit methods: the widely used empirical Universal Soil Loss Equation (USLE) and the process-based Pan-European Soil Erosion Risk Assessment (PESERA) models. The present study aims to provide a detailed analysis of the model results. In lieu of available national monitoring data, information from other sources were used. The Soil Degradation Subsystem (TDR) of the National Environmental Information System (OKIR) is a digital database based on a soil survey and farm dairy data collected from representative farms in Hungary. During the survey all kind of degradation forms - including soil erosion - were considered. Agricultural and demographic data was obtained from the Hungarian Central Statistical Office (KSH). Data from an interview-based survey was also used in an attempt to assess public awareness of soil erosion risks. Point-based evaluation of the model results was complemented with cross-regional assessment of soil erosion estimates. This, combined with available demographic information provides us with an opportunity to address soil erosion on a community level, with the identification of regions with the highest risk of being affected by soil erosion.

Water Impingement Erosion of Deep-Rolled Ti64

Directory of Open Access Journals (Sweden)

Dina Ma

2015-08-01

Full Text Available In this work, the Liquid Impingement Erosion (LIE performances of deep-rolling (DR treated and non-treated Ti64 were investigated. Various erosion stages, from the incubation to the terminal erosion stages, could be observed. A full factorial design of experiments was used to study the effect of DR process parameters (Feed Rate, Spindle Velocity, Number of Passes, Pressure on the residual stress distribution, microhardness and surface roughness of the treated Ti64 specimens. The DR-treated Ti64 specimens exhibited improved surface microhardness, surface roughness, and large magnitude of compressive residual stresses, which were attributed to the amount of cold work induced by the DR process. Although DR improved the mechanical properties of the Ti64, the results showed that the treatment has little or no effect on the LIE performance of Ti64 but different damage modes were observed in these two cases. Evolution of the erosion stages was described based on water-hammer pressure, stress waves, radial wall jetting, and hydraulic penetration modes. The initial erosion stages were mainly influenced by water-hammer pressure and stress waves, whereas the intermediate erosion stages were influenced by the combination of the four modes together. The final erosion stages contain the four modes, however the erosion was greatly driven by the radial jetting and hydraulic penetration modes, where more material was removed. The failure mechanism of the final stages of the LIE test of both DR-treated and non-treated Ti64 was characterized as fatigue fracture. However, a brittle fracture behavior was observed in the initial and intermediate erosion stages of the DR-treated Ti64, whereas a ductile fracture behavior was observed in the non-treated Ti64. This was concluded from the micrographs of the LIE damage through different erosion stages.

Understanding Soil Erosion in Irrigated Agriculture

OpenAIRE

O' Schwankl, Lawrence J

2006-01-01

A soil's physical and chemical properties determine whether it is vulnerable to erosion, which can reduce soil quality and cause other problems besides. Learn the basics of identifying what type of erosion is affecting your land and what's causing it.

Erosion and the limits to planetesimal growth

Science.gov (United States)

Krijt, S.; Ormel, C. W.; Dominik, C.; Tielens, A. G. G. M.

2015-02-01

Context. The coagulation of microscopic dust into planetesimals is the first step towards the formation of planets. The composition, size, and shape of the growing aggregates determine the efficiency of this early growth. In particular, it has been proposed that fluffy ice aggregates can grow very efficiently in protoplanetary disks, suffering less from the bouncing and radial drift barriers. Aims: While the collision velocity between icy aggregates of similar size is thought to stay below the fragmentation threshold, they may nonetheless lose mass from collisions with much smaller projectiles. As a result, erosive collisions have the potential to terminate the growth of pre-planetesimal bodies. We investigate the effect of these erosive collisions on the ability of porous ice aggregates to cross the radial drift barrier. Methods: We develop a Monte Carlo code that calculates the evolution of the masses and porosities of growing aggregates, while resolving the entire mass distribution at all times. The aggregate's porosity is treated independently of its mass, and is determined by collisional compaction, gas compaction, and eventually self-gravity compaction. We include erosive collisions and study the effect of the erosion threshold velocity on aggregate growth. Results: For erosion threshold velocities of 20-40 m s-1, high-velocity collisions with small projectiles prevent the largest aggregates from growing when they start to drift. In these cases, our local simulations result in a steady-state distribution, with most of the dust mass in particles with Stokes numbers close to unity. Only for the highest erosion threshold considered (60 m s-1) do porous aggregates manage to cross the radial drift barrier in the inner 10 AU of MMSN-like disks. Conclusions: Erosive collisions are more effective in limiting the growth than fragmentary collisions between similar-size particles. Conceivably, erosion limits the growth before the radial drift barrier, although the

On the Disruption of Star Clusters in a Hierarchical Interstellar Medium

Science.gov (United States)

Elmegreen, Bruce G.; Hunter, Deidre A.

2010-03-01

The distribution of the number of clusters as a function of mass M and age T suggests that clusters get eroded or dispersed in a regular way over time, such that the cluster number decreases inversely as an approximate power law with T within each fixed interval of M. This power law is inconsistent with standard dispersal mechanisms such as cluster evaporation and cloud collisions. In the conventional interpretation, it requires the unlikely situation where diverse mechanisms stitch together over time in a way that is independent of environment or M. Here, we consider another model in which the large-scale distribution of gas in each star-forming region plays an important role. We note that star clusters form with positional and temporal correlations in giant cloud complexes, and suggest that these complexes dominate the tidal force and collisional influence on a cluster during its first several hundred million years. Because the cloud complex density decreases regularly with position from the cluster birth site, the harassment and collision rates between the cluster and the cloud pieces decrease regularly with age as the cluster drifts. This decrease is typically a power law of the form required to explain the mass-age distribution. We reproduce this distribution for a variety of cases, including rapid disruption, slow erosion, combinations of these two, cluster-cloud collisions, cluster disruption by hierarchical disassembly, and partial cluster disruption. We also consider apparent cluster mass loss by fading below the surface brightness limit of a survey. In all cases, the observed log M-log T diagram can be reproduced under reasonable assumptions.

ON THE DISRUPTION OF STAR CLUSTERS IN A HIERARCHICAL INTERSTELLAR MEDIUM

International Nuclear Information System (INIS)

Elmegreen, Bruce G.; Hunter, Deidre A.

2010-01-01

The distribution of the number of clusters as a function of mass M and age T suggests that clusters get eroded or dispersed in a regular way over time, such that the cluster number decreases inversely as an approximate power law with T within each fixed interval of M. This power law is inconsistent with standard dispersal mechanisms such as cluster evaporation and cloud collisions. In the conventional interpretation, it requires the unlikely situation where diverse mechanisms stitch together over time in a way that is independent of environment or M. Here, we consider another model in which the large-scale distribution of gas in each star-forming region plays an important role. We note that star clusters form with positional and temporal correlations in giant cloud complexes, and suggest that these complexes dominate the tidal force and collisional influence on a cluster during its first several hundred million years. Because the cloud complex density decreases regularly with position from the cluster birth site, the harassment and collision rates between the cluster and the cloud pieces decrease regularly with age as the cluster drifts. This decrease is typically a power law of the form required to explain the mass-age distribution. We reproduce this distribution for a variety of cases, including rapid disruption, slow erosion, combinations of these two, cluster-cloud collisions, cluster disruption by hierarchical disassembly, and partial cluster disruption. We also consider apparent cluster mass loss by fading below the surface brightness limit of a survey. In all cases, the observed log M-log T diagram can be reproduced under reasonable assumptions.

Combining Landsat TM multispectral satellite imagery and different modelling approaches for mapping post-fire erosion changes in a Mediterranean site

Science.gov (United States)

Petropoulos, George P.; Kairis, Orestis; Karamesouti, Mina; Papanikolaou, Ioannis D.; Kosmas, Constantinos

2013-04-01

South European countries are naturally vulnerable to wildfires. Their natural resources such as soil, vegetation and water may be severely affected by wildfires, causing an imminent environmental deterioration due to the complex interdependence among biophysical components. Soil surface water erosion is a natural process essential for soil formation that is affected by such interdependences. Accelerated erosion due to wildfires, constitutes a major restrictive factor for ecosystem sustainability. In 2007, South European countries were severely affected by wildfires, with more than 500,000 hectares of land burnt in that year alone, well above the average of the last 30 years. The present work examines the changes in spatial variability of soil erosion rates as a result of a wildfire event that took place in Greece in 2007, one of the most devastating years in terms of wildfire hazards. Regional estimates of soil erosion rates before and after the fire outbreak were derived from the Revised Universal Soil Loss Equation (RUSLE, Renard et al. 1991) and the Pan-European Soil Erosion Risk Assessment model (PESERA, Kirkby, 1999; Kirkby et al., 2000). Inputs for both models included climatic, land-use, soil type, topography and land use management data. Where appropriate, both models were also fed with input data derived from the analysis of LANDSAT TM satellite imagery available in our study area, acquired before and shortly after the fire suppression. Our study was compiled and performed in a GIS environment. In overall, the loss of vegetation from the fire outbreak caused a substantial increase of soil erosion rates in the affected area, particularly towards the steep slopes. Both tested models were compared to each other and noticeable differences were observed in the soil erosion predictions before and after the fire event. These are attributed to the different parameterization requirements of the 2 models. This quantification of sediment supply through the river

Variability of Rainfall Erosivity and Erosivity Density in the Ganjiang River Catchment, China: Characteristics and Influences of Climate Change

Directory of Open Access Journals (Sweden)

Xianghu Li

2018-02-01

Full Text Available Soil erosion is one of the most critical environmental hazards in the world. Understanding the changes in rainfall erosivity (RE and erosivity density (ED, as well as their affecting factors, at local and catchment scales in the context of climate warming is an important prerequisite of soil erosion prevention and soil loss risk assessment. The present study identified the variability and trends of RE and ED in terms of both time and space in the Ganjiang River catchment over the period of 1960–2012, and also analyzed and discussed the impact of climate change. The results show that RE and ED in the catchment had great monthly variations and high year-to-year variability. Both presented long-term increasing trends over the entire study period. The highest RE and ED were observed in June and in the eastern and northeast parts of the catchment, which indicated that June was the most susceptible month for soil erosion in this area and the lower reaches of the Ganjiang River was the riskiest area for soil erosion. Finally, the East Asian summer monsoon and climate change were highly correlated with changes in RE and ED.

Soft drinks and in vitro dental erosion.

Science.gov (United States)

Gravelle, Brent L; Hagen Ii, Ted W; Mayhew, Susan L; Crumpton, Brooks; Sanders, Tyler; Horne, Victoria

2015-01-01

The purpose of this investigation was to determine to what extent the in vitro exposure of healthy teeth to various commonly consumed carbonated soft drinks may precipitate dental erosion. Forty-two healthy, extracted, previously unerupted human molars were weighed prior to, during, and after suspension in various sugared and diet or zero-calorie carbonated beverages for 20 days; the specimens were stored at room temperature while being stirred at 275 rpm. The percentage decrease in tooth weight from before to after exposure represented the weight loss due to enamel erosion; values in the experimental groups varied from 3.22% to 44.52% after 20 days' exposure. Data were subjected to analysis of variance and post hoc Scheffe testing at a level of α = 0.05. Nonsugared drinks (diet and zero-calorie) as a whole were more erosive than sugared beverages. A significant positive correlation was found between the amount of titratable acid and percentage of tooth erosion, while a significant negative correlation was revealed between the beverage pH and percentage of tooth erosion. No significant correlations were found between calcium or phosphate ion concentrations and the amount of erosion. It appears that enamel erosion is dependent on not only the beverage flow rate, pH, and amount of titratable acid, but also whether the soft drink is of the diet or zero-calorie variety, which reflects the type of artificial sweetener present.

Acoustic measurements of soil-pipeflow and internal erosion

Science.gov (United States)

Internal erosion of soil pipes can lead to embankment failures, landslides, and gully erosion. Therefore, non-intrusive methods are needed to detect and monitor soil pipeflow and the resulting internal erosion. This paper presents a laboratory study using both active and passive acoustic techniques ...

Dental Erosion in Children with Gastroesophageal Reflux Disease.

Science.gov (United States)

De Oliveira, Patricia Alves Drummond; Paiva, Saul Martins; De Abreu, Mauro Henrique Nogueira Guimarães; Auad, Sheyla Márcia

2016-01-01

The purpose of this study was to investigate the impact of gastroesophageal reflux disease (GERD) on dental erosion (DE) in children and analyze the association between dental erosion and diet, oral hygiene, and sociodemographic characteristics. This case-control study encompassed 43 two- to 14-year-olds diagnosed positive for GERD by the 24-hour pH monitoring, paired by age group with 136 healthy controls, in Belo Horizonte, Minas Gerais, Brazil. DE was assessed by one calibrated examiner using the O'Sullivan index. A questionnaire was self-administered by parents collecting information regarding sociodemographics, oral hygiene, and dietary habits. Dental erosion experience was compared between the groups, and a stratified analysis was performed (PDental erosion was diagnosed in 10.6 percent (N equals 19) of all the children; 25.6 percent (N equals 11) of GERD children and 5.9 percent (N equals eight) of children without GERD, P=0.001). Dental erosion was not associated with dietary consumption or sociodemographic characteristics in both groups (P≥0.05). Children who used adult toothpaste had a 5.79 higher chance of having dental erosion in the group with GERD. Children diagnosed with gastroesophageal reflux disease were at an increased risk of having dental erosion when compared to healthy subjects; among the GERD children, dental erosion was associated with the use of adult toothpaste.

Diagnosis of the Accelerated Soil Erosion in São Paulo State (Brazil by the Soil Lifetime Index Methodology

Directory of Open Access Journals (Sweden)

Grasiela de Oliveira Rodrigues Medeiros

Full Text Available ABSTRACT: The soil is a key component of the Earth System, and is currently under high pressure, due to the increasing global demands for food, energy and fiber. Moreover, the management of agricultural systems is often inadequate and ignores the agricultural suitability of lands, and particularly the vulnerability of soils. This paper demonstrates the application of the concept of the Soil Lifetime Index (SLtI for the entire state of São Paulo, at a spatial resolution of 30 m. The SLtI methodology represents a tolerance criterion and a diagnostic tool to assess the level of soil degradation by water erosion, based on estimated soil loss rates and on an average soil renewal rate. Two approaches were applied to determine: i the remaining time (years until the solum (horizons A + B is removed by water erosion to a critical depth of 1.0 m (original approach; ii the remaining time (years until the top 0.25 m of the nutrient-rich soil surface is removed by water erosion (new approach. Several areas in the state have reached a very critical soil depletion level, due to the predominance of consolidated agricultural activities, mainly of sugarcane and livestock production (as in the mesoregions of Ribeirão Preto, Bauru, Assis, Itapetininga and Araraquara. Only 35 % of the study area is in conserved state; 65 % of the study area is in the state of resource degradation, requiring intervention to diminish soil loss rates - and of this total, SLtI is zero in 1 and 0.25 % of the study area, respectively, for the original (critical depth of 1 m and the new approach (0.25 m. It was estimated that at the current soil loss rates, within 100 years, 20,000 km2 of the total area of the state of São Paulo (248,209 km2 will have reached the critical depth of 1.0 m, and the top 0.25 m of the soil surface from an area of approximately 76,000 km2 will have been completely removed if the current pace of resource exploitation is maintained.

Dental erosion: prevalence, incidence, and distribution

NARCIS (Netherlands)

Jager, D.H.J.; Amaechi, B.T.

2015-01-01

Dental erosion is one of the most common dental diseases and it is a growing problem. Numerous epidemiological studies have investigated the prevalence of dental erosion. For these studies different cross sections of the population are investigated. Large differences were found between countries,

Natural and anthropogenic rates of soil erosion

Directory of Open Access Journals (Sweden)

Mark A. Nearing

2017-06-01

Full Text Available Regions of land that are brought into crop production from native vegetation typically undergo a period of soil erosion instability, and long term erosion rates are greater than for natural lands as long as the land continues being used for crop production. Average rates of soil erosion under natural, non-cropped conditions have been documented to be less than 2 Mg ha−1 yr−1. On-site rates of erosion of lands under cultivation over large cropland areas, such as in the United States, have been documented to be on the order of 6 Mg ha−1 yr−1 or more. In northeastern China, lands that were brought into production during the last century are thought to have average rates of erosion over this large area of as much as 15 Mg ha−1 yr−1 or more. Broadly applied soil conservation practices, and in particular conservation tillage and no-till cropping, have been found to be effective in reducing rates of erosion, as was seen in the United States when the average rates of erosion on cropped lands decreased from on the order of 9 Mg ha−1 yr−1 to 6 or 7 Mg ha−1 yr−1 between 1982 and 2002, coincident with the widespread adoption of new conservation tillage and residue management practices. Taking cropped lands out of production and restoring them to perennial plant cover, as was done in areas of the United States under the Conservation Reserve Program, is thought to reduce average erosion rates to approximately 1 Mg ha−1 yr−1 or less on those lands.

Advancements in Hydrology and Erosion Process Understanding and Post-Fire Hydrologic and Erosion Model Development for Semi-Arid Landscapes

Science.gov (United States)

Williams, C. Jason; Pierson, Frederick B.; Al-Hamdan, Osama Z.; Robichaud, Peter R.; Nearing, Mark A.; Hernandez, Mariano; Weltz, Mark A.; Spaeth, Kenneth E.; Goodrich, David C.

2017-04-01

Fire activity continues to increase in semi-arid regions around the globe. Private and governmental land management entities are challenged with predicting and mitigating post-fire hydrologic and erosion responses on these landscapes. For more than a decade, a team of scientists with the US Department of Agriculture has collaborated on extensive post-fire hydrologic field research and the application of field research to development of post-fire hydrology and erosion predictive technologies. Experiments funded through this research investigated the impacts of fire on vegetation and soils and the effects of these fire-induced changes on infiltration, runoff generation, erodibility, and soil erosion processes. The distribution of study sites spans diverse topography across grassland, shrubland, and woodland landscapes throughout the western United States. Knowledge gleaned from the extensive field experiments was applied to develop and enhance physically-based models for hillslope- to watershed-scale runoff and erosion prediction. Our field research and subsequent data syntheses have identified key knowledge gaps and challenges regarding post-fire hydrology and erosion modeling. Our presentation details some consistent trends across a diverse domain and varying landscape conditions based on our extensive field campaigns. We demonstrate how field data have advanced our understanding of post-fire hydrology and erosion for semi-arid landscapes and highlight remaining key knowledge gaps. Lastly, we briefly show how our well-replicated experimental methodologies have contributed to advancements in hydrologic and erosion model development for the post-fire environment.

Development of an Integrated Water and Wind Erosion Model

Science.gov (United States)

Flanagan, D. C.; Ascough, J. C.; Wagner, L. E.; Geter, W. F.

2006-12-01

Prediction technologies for soil erosion by the forces of wind or water have largely been developed independently from one another, especially within the United States. Much of this has been due to the initial creation of equations and models which were empirical in nature (i.e., Universal Soil Loss Equation, Wind Erosion Equation) and based upon separate water erosion or wind erosion plot and field measurements. Additionally, institutional organizations in place typically divided research efforts and funding to unique wind or water erosion research and modeling projects. However, during the past 20 years computer technologies and erosion modeling have progressed to the point where it is now possible to merge physical process-based computer simulation models into an integrated water and wind erosion prediction system. In a physically- based model, many of the processes which must be simulated for wind and water erosion computations are the same, e.g., climate, water balance, runoff, plant growth, etc. Model components which specifically deal with the wind or water detachment, transport and deposition processes are those that must differ, as well as any necessary parameterization of input variables (e.g., adjusted soil erodibilities, critical shear stresses, etc.) for those components. This presentation describes current efforts towards development of a combined wind and water erosion model, based in part upon technologies present in the Water Erosion Prediction Project (WEPP) and the Wind Erosion Prediction System (WEPS) models. Initial efforts during the past two years have resulted in modular modeling components that allow for prediction of infiltration, surface runoff, and water erosion at a hillslope scale within an Object Modeling System. Additional components currently in development include wind detachment at a single field point, continuous water balance, and unified plant growth. Challenges in this project are many, and include adequate field

Erosion scenarios for Wellenberg

International Nuclear Information System (INIS)

Klemenz, W.

1993-09-01

The proposed Wellenberg site for a radioactive waste repository is located between Altzellen in the Engelberger valley and the Oberrickenbach valley, in a thick Valanginian marl series. The marl is generally overlaid with unconsolidated rocks but reaches to the surface in some places. In contrast to the situation in the Oberbauenstock region this marl complex is not protected by an overlying erosion resistant series and exhibits a marked relief. The question therefore arises with respect to the Wellenberg site, to what extent will the marl (i.e. the repository host rock formation) be removed by erosion processes during the 100,000 years interval under consideration and what overburden will remain at the end of this period. This report presents the results of an investigation of the longterm behaviour of the proposed site in respect of those processes of erosion and deposition which can lead to changes in the terrain surface and its location relative to the repository. A wide range of possible scenarios encompassing different developments of climatic conditions during the 100,000 year period of interest, was investigated. In addition to the continuation of the present climate and the occurrence of a new ice age on the scale of the Wuerm glaciation the consequences of altered climatic conditions on erosion removal of the repository overburden were considered. Within the 100,000 year period of interest none of the scenarios considered leads to the exposure of the repository. (author) figs., tabs, refs

Intuitional experiment and numerical analysis of flow characteristics affected by flow accelerated corrosion in elbow pipe system

Energy Technology Data Exchange (ETDEWEB)

Kim, Hyung Joon [School of Mechanical and Aerospace Engineering, Seoul National University, Gwanak-gu, Seoul 151-744 (Korea, Republic of); Kim, Kyung Hoon, E-mail: kimkh@khu.ac.kr [Department of Mechanical Engineering, Kyung Hee University, Seochun 1, Yongin, Gyeonggi 446-701 (Korea, Republic of)

2016-05-15

Highlights: • Wall-thinning erosion of pipelines in plants leads to fatal accidents unexpectedly. • Flow Acceleration Corrosion (FAC) is a main reason of wall-thinning. • For industrial safety, it is necessary to verify the tendency of FAC. • We focused on local wall thinning by FAC with intuitional visualization experiment and numerical analysis in elbow pipe.

A longitudinal study of tooth erosion in adolescents.

NARCIS (Netherlands)

El Aidi, H.; Bronkhorst, E.M.; Truin, G.J.

2008-01-01

Incidence studies on tooth erosion among adolescents are scarce. This longitudinal study aimed at estimating the prevalence, incidence, progression, and distribution of erosion in young adolescents over a 1.5-year period. Erosion at baseline was present in 32.2% of the 622 children (mean age, 11.9

How does slope form affect erosion in CATFLOW-SED?

Science.gov (United States)

Gabelmann, Petra; Wienhöfer, Jan; Zehe, Erwin

2016-04-01

Erosion is a severe environmental problem in agro-ecosystems with highly erodible loess soils. It is controlled by various factors, e.g. rainfall intensity, initial wetness conditions, soil type, land use and tillage practice. Furthermore slope form and gradient have been shown to influence erosion amounts to a large extent. Within the last fifty years, various erosion models have been developed to describe the erosion process, estimate erosion amounts and identify erosion-prone areas. These models differ in terms of complexity, the processes which are considered, and the data required for model calibration and they can be categorised into empirical or statistical, conceptual, and physically-based models. CATFLOW-SED is a process-based hydrology and erosion model that can operate on catchment and hillslope scales. Soil water dynamics are described by the Richards equation including effective approaches for preferential flow. Evapotranspiration is simulated using an approach based on the Penman-Monteith equation. The model simulates overland flow using the diffusion wave equation. Soil detachment is related to the attacking forces of rainfall and overland flow, and the erosion resistance of soil. Sediment transport capacity and sediment deposition are related to overland flow velocity using the equation of Engelund and Hansen and the sinking velocity of grain sizes respectively. We performed a study to analyse the erosion process on different virtual hillslopes, with varying slope gradient and slope form, using the CATFLOW-SED model. We explored the role of landform on erosion and sedimentation, particularly we look for forms that either maximise or minimise erosion. Results indicate the importance to performing the process implementation within physically meaningful limits and choose appropriate model parameters respectively.

Gastroesophageal reflux is not associated with dental erosion in children.

Science.gov (United States)

Wild, Yvette K; Heyman, Melvin B; Vittinghoff, Eric; Dalal, Deepal H; Wojcicki, Janet M; Clark, Ann L; Rechmann, Beate; Rechmann, Peter

2011-11-01

Dental erosion is a complication of gastroesophageal reflux (GER) in adults; in children, it is not clear if GER has a role in dental pathologic conditions. Dietary intake, oral hygiene, high bacterial load, and decreased salivary flow might contribute independently to GER development or dental erosion, but their potential involvement in dental erosion from GER is not understood. We investigated the prevalence of dental erosion among children with and without GER symptoms, and whether salivary flow rate or bacterial load contribute to location-specific dental erosion. We performed a cross-sectional study of 59 children (ages, 9-17 y) with symptoms of GER and 20 asymptomatic children (controls); all completed a questionnaire on dietary exposure. Permanent teeth were examined for erosion into dentin, erosion locations, and affected surfaces. The dentist was not aware of GER status, and the gastroenterologist was not aware of dental status. Stimulated salivary flow was measured and salivary bacterial load was calculated for total bacteria, Streptococcus mutans, and Lactobacilli. Controlling for age, dietary intake, and oral hygiene, there was no association between GER symptoms and dental erosion by tooth location or affected surface. Salivary flow did not correlate with GER symptoms or erosion. Erosion location and surface were independent of total bacteria and levels of Streptococcus mutans and Lactobacilli. Location-specific dental erosion is not associated with GER, salivary flow, or bacterial load. Prospective studies are required to determine the pathogenesis of GER-associated dental erosion and the relationship between dental caries to GER and dental erosion. Copyright © 2011 AGA Institute. Published by Elsevier Inc. All rights reserved.

Mechanisms of erosion of atherosclerotic plaques.

Science.gov (United States)

Quillard, Thibaut; Franck, Grégory; Mawson, Thomas; Folco, Eduardo; Libby, Peter

2017-10-01

The present review explores the mechanisms of superficial intimal erosion, a common cause of thrombotic complications of atherosclerosis. Human coronary artery atheroma that give rise to thrombosis because of erosion differ diametrically from those associated with fibrous cap rupture. Eroded lesions characteristically contain few inflammatory cells, abundant extracellular matrix, and neutrophil extracellular traps (NETs). Innate immune mechanisms such as engagement of Toll-like receptor 2 (TLR2) on cultured endothelial cells can impair their viability, attachment, and ability to recover a wound. Hyaluronan fragments may serve as endogenous TLR2 ligands. Mouse experiments demonstrate that flow disturbance in arteries with neointimas tailored to resemble features of human eroded plaques disturbs endothelial cell barrier function, impairs endothelial cell viability, recruits neutrophils, and provokes endothelial cells desquamation, NET formation, and thrombosis in a TLR2-dependent manner. Mechanisms of erosion have received much less attention than those that provoke plaque rupture. Intensive statin treatment changes the characteristic of plaques that render them less susceptible to rupture. Thus, erosion may contribute importantly to the current residual burden of risk. Understanding the mechanisms of erosion may inform the development and deployment of novel therapies to combat the remaining atherothrombotic risk in the statin era.

Application of NAA in study of rill erosion process

International Nuclear Information System (INIS)

Li Mian; Li Zhanbin; Ding Wenfeng

2003-01-01

Based on the principle and method of rare earth elements (REE) tracer and NAA for the study of soil erosion, the changeable process of rill erosion on loess sloping surface was researched in runoff scouring experiments. The results showed that the REE tracer and NAA method can be used not only quantitatively to determine soil erosion amounts on different slope sections, but also to reveal the changeable trend of relative erosion amounts. The relative errors are mostly less than ±20% for the tracing elements, which is considered satisfactory in the soil erosion studies

Illuminating wildfire erosion and deposition patterns with repeat terrestrial lidar

Science.gov (United States)

Rengers, Francis K.; Tucker, G.E.; Moody, J.A.; Ebel, Brian

2016-01-01

Erosion following a wildfire is much greater than background erosion in forests because of wildfire-induced changes to soil erodibility and water infiltration. While many previous studies have documented post-wildfire erosion with point and small plot-scale measurements, the spatial distribution of post-fire erosion patterns at the watershed scale remains largely unexplored. In this study lidar surveys were collected periodically in a small, first-order drainage basin over a period of 2 years following a wildfire. The study site was relatively steep with slopes ranging from 17° to > 30°. During the study period, several different types of rain storms occurred on the site including low-intensity frontal storms (2.4 mm h−1) and high-intensity convective thunderstorms (79 mm h−1). These storms were the dominant drivers of erosion. Erosion resulting from dry ravel and debris flows was notably absent at the site. Successive lidar surveys were subtracted from one another to obtain digital maps of topographic change between surveys. The results show an evolution in geomorphic response, such that the erosional response after rain storms was strongly influenced by the previous erosional events and pre-fire site morphology. Hillslope and channel roughness increased over time, and the watershed armored as coarse cobbles and boulders were exposed. The erosional response was spatially nonuniform; shallow erosion from hillslopes (87% of the study area) contributed 3 times more sediment volume than erosion from convergent areas (13% of the study area). However, the total normalized erosion depth (volume/area) was highest in convergent areas. From a detailed understanding of the spatial locations of erosion, we made inferences regarding the processes driving erosion. It appears that hillslope erosion is controlled by rain splash (for detachment) and overland flow (for transport and quasi-channelized erosion), with the sites of highest erosion corresponding to locations

Giant Radio Halos in Galaxy Clusters as Probes of Particle ...

Indian Academy of Sciences (India)

scenario still remain poorly understood. ... to test models with future observations. ... A popular scenario for the origin of radio halos assumes that relativis- ..... based on particle acceleration by merger-driven turbulence in galaxy clusters shows.

Olive Cultivation, its Impact on Soil Erosion and its Progression into Yield Impacts in Southern Spain in the Past as a Key to a Future of Increasing Climate Uncertainty

Directory of Open Access Journals (Sweden)

José A. Gómez

2014-06-01

Full Text Available This article is intended as a review of the current situation regarding the impact of olive cultivation in Southern Spain (Andalusia on soil degradation processes and its progression into yield impacts, due to diminishing soil profile depth and climate change in the sloping areas where it is usually cultivated. Finally, it explores the possible implications in the regional agricultural policy these results might have. It tries to show how the expansion and intensification of olive cultivation in Andalusia, especially since the late 18th century, had as a consequence an acceleration of erosion processes that can be identified by several indicators and techniques. Experimental and model analysis indicates that the rate of soil erosion accelerated since the expansion of mechanization in the late 1950s. In addition, that unsustainable erosion rates have prevailed in the region since the shift to a more intense olive cultivation systems by the end of the 17th Century. Although agroenvironmental measures implemented since the early 2000s have reduced erosion rates, they are still unsustainably high in a large fraction of the olive area in the region. In the case of olive orchards located in steeper areas with soils of lower water-holding capacity (due to coarse texture and stone content, cumulative erosion has already had a high impact on reducing their potential productivity. This is one of the factors that contributes towards increasing the gap between these less intensified orchards in the mountainous areas and those in the hilly areas with more gentle slopes, such as for instance the lower stretches of the Guadalquivir River Valley. In the case of olive orchards in the hilly areas with better soils, easier access to irrigation and lower production costs per unit, the efforts on soil conservation should be oriented towards limiting off-site damage, since the soil water-storage function of these soils may be preserved in the medium term even at the

The erosive potential of candy sprays

NARCIS (Netherlands)

Gambon, D.L.; Brand, H.S.; Nieuw Amerongen, A.V.

2009-01-01

Objective To determine the erosive potential of seven different commercially available candy sprays in vitro and in vivo. Material and methods The erosive potential was determined in vitro by measuring the pH and neutralisable acidity. The salivary pH and flow rate were measured in healthy

Enhanced sediment loading facilitates point bar growth and accelerates bank erosion along a modelled meander bend on the Sacramento River, USA

Science.gov (United States)

Ahmed, J.; Constantine, J. A.; Hales, T. C.

2017-12-01

Meandering channels provide a conduit through which sediment and water is routed from the uplands to the sea. Alluvial material is periodically stored and transported through the channel network as permitted by the prevailing hydrologic conditions. The lowlands are typically characterised by accumulations of sediment attached to the inner banks of meander bends (point bars). These bedforms have been identified as important for facilitating a link between in-stream sediment supplies and channel dynamism. A 2D curvilinear hydrodynamic model (MIKE 21C) was used to perform a number of experiments in which the sediment load was adjusted to investigate how changes in alluvial material fluxes affect the development of point bars and the resultant patterns of bank erosion. A doubling of the sediment load caused a longitudinal increase in the bar in the upstream direction and caused a coeval doubling of the transverse channel slope at the meander apex. The upstream growth of the point bar was accompanied by an increase in length over which lateral migration took place at the outer bank. The magnitude of outer bank erosion was 9-times greater for the high-sediment simulation. These results suggest that enhanced sediment loads (potentially the result of changes in land use or climate) can trigger greater rates of bank erosion and channel change through the sequestration of alluvial material on point bars, which encourage high-velocity fluid deflection towards the outer bank of the meander. This controls riparian habitat development and exchanges of sediment and nutrients across the channel-floodplain interface.

Annual report of the Tandem Accelerator Center, University of Tsukuba. April 1, 1995 - March 31, 1996

International Nuclear Information System (INIS)

1996-10-01

This annual report includes the research activities from April, 1995 to March, 1996. The 12 UD Pelletron tandem accelerator has been operated successfully to provide sufficient beam time for experiments. The stable operation of the accelerator brought out steady advances in many investigations continued as long range projects. Those are polarization phenomena in nuclear reactions, the nonresonant breakup of Li-7, further refinement of continuum discretized coupled channels theory, fusion and fission in heavy ion reactions, nuclear structure physics by means of in-beam γ ray spectroscopy, solid state physics using fast ion beams, Moessbauer effect, NMR, and the application of accelerated ion beams to PIXE and accelerator mass spectrometry. As the new developments of experimental instruments, an ion source for micro-cluster beams and a pulsing system for low velocity cluster ions have been successfully constructed. A beam line producing proton micro-beam has been constructed. In this report, the accelerator and experimental facilities, the experiments and theories of nuclear physics, atomic and solid state physics, ion beam applications, publications, theses and seminars, and personnel are reported. (K.I.)

Riparian erosion vulnerability model based on environmental features.

Science.gov (United States)

Botero-Acosta, Alejandra; Chu, Maria L; Guzman, Jorge A; Starks, Patrick J; Moriasi, Daniel N

2017-12-01

Riparian erosion is one of the major causes of sediment and contaminant load to streams, degradation of riparian wildlife habitats, and land loss hazards. Land and soil management practices are implemented as conservation and restoration measures to mitigate the environmental problems brought about by riparian erosion. This, however, requires the identification of vulnerable areas to soil erosion. Because of the complex interactions between the different mechanisms that govern soil erosion and the inherent uncertainties involved in quantifying these processes, assessing erosion vulnerability at the watershed scale is challenging. The main objective of this study was to develop a methodology to identify areas along the riparian zone that are susceptible to erosion. The methodology was developed by integrating the physically-based watershed model MIKE-SHE, to simulate water movement, and a habitat suitability model, MaxEnt, to quantify the probability of presences of elevation changes (i.e., erosion) across the watershed. The presences of elevation changes were estimated based on two LiDAR-based elevation datasets taken in 2009 and 2012. The changes in elevation were grouped into four categories: low (0.5 - 0.7 m), medium (0.7 - 1.0 m), high (1.0 - 1.7 m) and very high (1.7 - 5.9 m), considering each category as a studied "species". The categories' locations were then used as "species location" map in MaxEnt. The environmental features used as constraints to the presence of erosion were land cover, soil, stream power index, overland flow, lateral inflow, and discharge. The modeling framework was evaluated in the Fort Cobb Reservoir Experimental watershed in southcentral Oklahoma. Results showed that the most vulnerable areas for erosion were located at the upper riparian zones of the Cobb and Lake sub-watersheds. The main waterways of these sub-watersheds were also found to be prone to streambank erosion. Approximatively 80% of the riparian zone (streambank

Erosion of soil organic carbon: implications for carbon sequestration

Science.gov (United States)

Van Oost, Kristof; Van Hemelryck, Hendrik; Harden, Jennifer W.; McPherson, B.J.; Sundquist, E.T.

2009-01-01

Agricultural activities have substantially increased rates of soil erosion and deposition, and these processes have a significant impact on carbon (C) mineralization and burial. Here, we present a synthesis of erosion effects on carbon dynamics and discuss the implications of soil erosion for carbon sequestration strategies. We demonstrate that for a range of data-based parameters from the literature, soil erosion results in increased C storage onto land, an effect that is heterogeneous on the landscape and is variable on various timescales. We argue that the magnitude of the erosion term and soil carbon residence time, both strongly influenced by soil management, largely control the strength of the erosion-induced sink. In order to evaluate fully the effects of soil management strategies that promote carbon sequestration, a full carbon account must be made that considers the impact of erosion-enhanced disequilibrium between carbon inputs and decomposition, including effects on net primary productivity and decomposition rates.

The water erosion processes in the retreat erosive of cliff on soft rocks in the province of Cadiz (Spain); Los procesos de erosion hidrica en el retroceso erosivo de acantilados sobre rocas blandas en la provincia de Cadiz

Energy Technology Data Exchange (ETDEWEB)

Rendon Aragon, J. J.; Gracia Prieto, F. J.; Rio Rodriguez, L. del

2009-07-01

The littoral cliffs on soft materials of the Atlantic Cadiz coast show an important activity of the fresh water erosion processes, sometimes even more significant than the marine erosion processes. The connection of the lower cliffs with sandy beaches favours aeolian sand invasion, which fills previous rills and reduces the water erosion intensity by increasing infiltration. Cliff retreat and rill erosion measurement by using erosion sticks has shown very variables values, most of them higher than the estimated error of the employed methods. This indicates the existence of other factors influencing the distribution of water erosion processes along these cliffs, which have to be studied through different techniques. (Author) 5 refs.

Experimental study of the cavitation erosion in centrifugal pump impeller

International Nuclear Information System (INIS)

Rayan, M.A.

1985-01-01

Research on cavitation damage scale effects show that the damage rate is increased with size and velocity. It seems that for constant velocity there is no clear trend for the variation of erosion with cavitation number. Research on the time effects on damage rate show similarity between cavitation and impingement erosion. The cumulative weight loss versus time curve is of a ''S'' shaped type characterized by an incubation period followed by a period of increasing erosion rate, then a maximum erosion rate, and finally a period of decreasing erosion rate. The objective of this investigation is to present a prototype cavitation erosion experiment in order to clarify the time dependency of the erosive wear

Numerical Modelling and Prediction of Erosion Induced by Hydrodynamic Cavitation

Science.gov (United States)

Peters, A.; Lantermann, U.; el Moctar, O.

2015-12-01

The present work aims to predict cavitation erosion using a numerical flow solver together with a new developed erosion model. The erosion model is based on the hypothesis that collapses of single cavitation bubbles near solid boundaries form high velocity microjets, which cause sonic impacts with high pressure amplitudes damaging the surface. The erosion model uses information from a numerical Euler-Euler flow simulation to predict erosion sensitive areas and assess the erosion aggressiveness of the flow. The obtained numerical results were compared to experimental results from tests of an axisymmetric nozzle.

IN SITU MEASUREMENT OF BEDROCK EROSION

Directory of Open Access Journals (Sweden)

D. H. Rieke-Zapp

2012-07-01

Full Text Available While long term erosion rates of bedrock material may be estimated by dating methods, current day erosion rates are – if at all available – based on rough estimates or on point measurements. Precise quantification of short term erosion rates are required to improve our understanding of short term processes, for input in landscape evolution models, as well as for studying the mechanics and efficiency of different erosion processes in varying geomorphological settings. Typical current day erosion rates in the European Alps range from sub-millimetre to several millimetres per year depending on the dominant erosion processes. The level of surveying accuracy required for recurring sub-millimetre to millimetre measurements in the field is demanding. A novel surveying setup for in-situ measurement of bedrock erosion was tested recently in three different locations in Switzerland. Natural bedrock was investigated in the Gornera gorge close to Zermatt. Further on, bedrock samples were installed in exposed locations in the Erlenbach research watershed close to Einsiedeln, and in the Illgraben debris flow channel, located in the Canton Schwyz and Valais, respectively. A twofold measurement approach was chosen for all locations. For the first setup control points providing an absolute reference frame for recurrent measurements were embedded close to the area of interest. Close range photogrammetry was applied to measure surface changes on the bedrock samples. The precision for surface measurements in the field was 0.1 mm (1 σ and thus suitable for the application. The equipment needed for the surveys can easily be carried to the field. At one field site a structured light scanner was used along with the photogrammetric setup. Although the current generation of structured light scanners appeared less suitable for field application, data acquisition was much faster and checking the data for completeness in the field was straight forward. The latest

In Situ Measurement of Bedrock Erosion

Science.gov (United States)

Rieke-Zapp, D. H.; Beer, A.; Turowski, J. M.; Campana, L.

2012-07-01

While long term erosion rates of bedrock material may be estimated by dating methods, current day erosion rates are - if at all available - based on rough estimates or on point measurements. Precise quantification of short term erosion rates are required to improve our understanding of short term processes, for input in landscape evolution models, as well as for studying the mechanics and efficiency of different erosion processes in varying geomorphological settings. Typical current day erosion rates in the European Alps range from sub-millimetre to several millimetres per year depending on the dominant erosion processes. The level of surveying accuracy required for recurring sub-millimetre to millimetre measurements in the field is demanding. A novel surveying setup for in-situ measurement of bedrock erosion was tested recently in three different locations in Switzerland. Natural bedrock was investigated in the Gornera gorge close to Zermatt. Further on, bedrock samples were installed in exposed locations in the Erlenbach research watershed close to Einsiedeln, and in the Illgraben debris flow channel, located in the Canton Schwyz and Valais, respectively. A twofold measurement approach was chosen for all locations. For the first setup control points providing an absolute reference frame for recurrent measurements were embedded close to the area of interest. Close range photogrammetry was applied to measure surface changes on the bedrock samples. The precision for surface measurements in the field was 0.1 mm (1 σ) and thus suitable for the application. The equipment needed for the surveys can easily be carried to the field. At one field site a structured light scanner was used along with the photogrammetric setup. Although the current generation of structured light scanners appeared less suitable for field application, data acquisition was much faster and checking the data for completeness in the field was straight forward. The latest generation of compact

Annual report of the Tandem Accelerator Center, University of Tsukuba. April 1, 1996 - March 31, 1997

Energy Technology Data Exchange (ETDEWEB)

NONE

1997-06-01

The 12 UD Pelletron tandem accelerator has been operated successfully from April, 1996 to January, 1997. Although the operation of the accelerator became unstable in the middle of January, it was a short period. The research in the Tandem Accelerator Center covers wide fields, that is, polarization phenomena in nuclear reactions, the nonresonant breakup of Li-7, the further refinement of the CDCC theory, fusion and fission in heavy ion reactions, nuclear structure physics by means of in-beam {gamma} ray spectroscopy, solid state physics using fast ion bemas, Moessbauer effect, NMR, the application of accelerated ion beams to PIXE, and accelerator mass spectrometry. In addition, two major installations were carried out in this academic year. One is a small tandem accelerator which was moved from Electrotechnical Laboratory in Tsukuba, and the other is a system for the production and analysis of atomic clusters. The research activities at the accelerator and experimental facilities and on experimental nuclear physics, theoretical nuclear physics, atomic and solid state physics, cluster science, and ion beam application are reported in this book. Also the list of the publications by these groups is given. Ph. D. and M. Sc. theses are listed, and the speakers and the titles of seminars are reported. (K.I.)

Annual report of the Tandem Accelerator Center, University of Tsukuba. April 1, 1996 - March 31, 1997

International Nuclear Information System (INIS)

1997-06-01

The 12 UD Pelletron tandem accelerator has been operated successfully from April, 1996 to January, 1997. Although the operation of the accelerator became unstable in the middle of January, it was a short period. The research in the Tandem Accelerator Center covers wide fields, that is, polarization phenomena in nuclear reactions, the nonresonant breakup of Li-7, the further refinement of the CDCC theory, fusion and fission in heavy ion reactions, nuclear structure physics by means of in-beam γ ray spectroscopy, solid state physics using fast ion bemas, Moessbauer effect, NMR, the application of accelerated ion beams to PIXE, and accelerator mass spectrometry. In addition, two major installations were carried out in this academic year. One is a small tandem accelerator which was moved from Electrotechnical Laboratory in Tsukuba, and the other is a system for the production and analysis of atomic clusters. The research activities at the accelerator and experimental facilities and on experimental nuclear physics, theoretical nuclear physics, atomic and solid state physics, cluster science, and ion beam application are reported in this book. Also the list of the publications by these groups is given. Ph. D. and M. Sc. theses are listed, and the speakers and the titles of seminars are reported. (K.I.)

[Research progress on wind erosion control with polyacrylamide (PAM).

Science.gov (United States)

Li, Yuan Yuan; Wang, Zhan Li

2016-03-01

Soil wind erosion is one of the main reasons for soil degradation in the northwest region of China. Polyacrylamide (PAM), as an efficient soil amendment, has gained extensive attention in recent years since it is effective in improving the structure of surface soil due to its special physical and chemical properties. This paper introduced the physical and chemical properties of PAM, reviewed the effects of PAM on soil wind erosion amount and threshold wind velocity, as well as the effect differences of PAM in soil wind erosion control under conditions of various methods and doses. Its effect was proved by comparing with other materials in detail. Furthermore, we analyzed the mecha-nism of wind erosion control with PAM according to its influence on soil physical characteristics. Comprehensive analysis showed that, although some problems existed in wind erosion control with (PAM), PAM as a sand fixation agent, can not only enhance the capacity of the soil resis-tance to wind erosion, but also improve soil physical properties to form better soil conditions. Besides, we proposed that combination of PAM and plant growth would increase the survival rate of plants greatly, control soil wind erosion in wind-erosive areas, and improve the quality of the ecological environment construction. Thus, PAM has practically important significance and wide application prospect in controlling soil wind erosion.

Temporal and spatial variations of rainfall erosivity in Southern Taiwan

Science.gov (United States)

Lee, Ming-Hsi; Lin, Huan-Hsuan; Chu, Chun-Kuang

2014-05-01

Soil erosion models are essential in developing effective soil and water resource conservation strategies. Soil erosion is generally evaluated using the Universal Soil Loss Equation (USLE) with an appropriate regional scale description. Among factors in the USLE model, the rainfall erosivity index (R) provides one of the clearest indications of the effects of climate change. Accurate estimation of rainfall erosivity requires continuous rainfall data; however, such data rarely demonstrate good spatial and temporal coverage. The data set consisted of 9240 storm events for the period 1993 to 2011, monitored by 27 rainfall stations of the Central Weather Bureau (CWB) in southern Taiwan, was used to analyze the temporal-spatial variations of rainfall erosivity. The spatial distribution map was plotted based on rainfall erosivity by the Kriging interpolation method. Results indicated that rainfall erosivity is mainly concentrated in rainy season from June to November typically contributed 90% of the yearly R factor. The temporal variations of monthly rainfall erosivity during June to November and annual rainfall erosivity have increasing trend from 1993 to 2011. There is an increasing trend from southwest to northeast in spatial distribution of rainfall erosivity in southern Taiwan. The results further indicated that there is a higher relationship between elevation and rainfall erosivity. The method developed in this study may also be useful for sediment disasters on Climate Change.

Rainfall erosivity in Brazil: A Review

Science.gov (United States)

In this paper, we review the erosivity studies conducted in Brazil to verify the quality and representativeness of the results generated and to provide a greater understanding of the rainfall erosivity (R-factor) in Brazil. We searched the ISI Web of Science, Scopus, SciELO, and Google Scholar datab...

Backward erosion piping : Initiation and progression

NARCIS (Netherlands)

Van Beek, V.M.

2015-01-01

Backward erosion piping is an internal erosion mechanism during which shallow pipes are formed in the direction opposite to the flow underneath water-retaining structures as a result of the gradual removal of sandy material by the action of water. It is an important failure mechanism in both dikes

Modeling of technical soil-erosion control measures and its impact on soil erosion off-site effects within urban areas

Science.gov (United States)

Dostal, Tomas; Devaty, Jan

2013-04-01

The paper presents results of surface runoff, soil erosion and sediment transport modeling using Erosion 3D software - physically based mathematical simulation model, event oriented, fully distributed. Various methods to simulate technical soil-erosion conservation measures were tested, using alternative digital elevation models of different precision and resolution. Ditches and baulks were simulated by three different approaches, (i) by change of the land-cover parameters to increase infiltration and decrease flow velocity, (ii) by change of the land-cover parameters to completely infiltrate the surface runoff and (iii) by adjusting the height of the digital elevation model by "burning in" the channels of the ditches. Results show advantages and disadvantages of each approach and conclude suitable methods for combinations of particular digital elevation model and purpose of the simulations. Further on a set of simulations was carried out to model situations before and after technical soil-erosion conservation measures application within a small catchment of 4 km2. These simulations were focused on quantitative and qualitative assessment of technical soil-erosion control measures impact on soil erosion off-site effects within urban areas located downstream of intensively used agricultural fields. The scenarios were built upon a raster digital elevation model with spatial resolution of 3 meters derived from LiDAR 5G vector point elevation data. Use of this high-resolution elevation model allowed simulating the technical soil-erosion control measures by direct terrain elevation adjustment. Also the structures within the settlements were emulated by direct change in the elevation of the terrain model. The buildings were lifted up to simulate complicated flow behavior of the surface runoff within urban areas, using approach of Arévalo (Arévalo, 2011) but focusing on the use of commonly available data without extensive detailed editing. Application of the technical

A clinical index for evaluating and monitoring dental erosion

DEFF Research Database (Denmark)

Larsen, I B; Westergaard, J; Stoltze, K

2000-01-01

This study describes a new fine-scaled system for classifying initial and advanced dental erosions. The system includes the use of study casts of the teeth in an epoxy resin with an accurate surface reproduction. The severity of erosion on each tooth surface is scored according to six grades...... of severity. In addition, the presence of a Class V restoration and dental erosion on the same surface increases the erosion score, as it is assumed that the need for restorative treatment can be caused by the erosion. A high inter-examiner agreement was found when the present scoring system was used by two...... of the oral cavity and are furthermore suitable for data analysis. The system is thereby well-suited for determining etiologic factors and monitoring the progression of erosion over time....

Seasonal variation and climate change impact in Rainfall Erosivity across Europe

Science.gov (United States)

Panagos, Panos; Borrelli, Pasquale; Meusburger, Katrin; Alewell, Christine; Ballabio, Cristiano

2017-04-01

Rainfall erosivity quantifies the climatic effect on water erosion and is of high importance for soil scientists, land use planners, agronomists, hydrologists and environmental scientists in general. The rainfall erosivity combines the influence of rainfall duration, magnitude, frequency and intensity. Rainfall erosivity is calculated from a series of single storm events by multiplying the total storm kinetic energy with the measured maximum 30-minute rainfall intensity. This estimation requests high temporal resolution (e.g. 30 minutes) rainfall data for sufficiently long time periods (i.e. 20 years). The European Commission's Joint Research Centr(JRC) in collaboration with national/regional meteorological services and Environmental Institutions made an extensive data collection of high resolution rainfall data in the 28 Member States of the European Union plus Switzerland to estimate rainfall erosivity in Europe. This resulted in the Rainfall Erosivity Database on the European Scale (REDES) which included 1,675 stations. The interpolation of those point erosivity values with a Gaussian Process Regression (GPR) model has resulted in the first Rainfall Erosivity map of Europe (Science of the Total Environment, 511: 801-815). In 2016, REDES extended with a monthly component, which allowed developing monthly and seasonal erosivity maps and assessing rainfall erosivity both spatially and temporally for European Union and Switzerland. The monthly erosivity maps have been used to develop composite indicators that map both intra-annual variability and concentration of erosive events (Science of the Total Environment, 579: 1298-1315). Consequently, spatio-temporal mapping of rainfall erosivity permits to identify the months and the areas with highest risk of soil loss where conservation measures should be applied in different seasons of the year. Finally, the identification of the most erosive month allows recommending certain agricultural management practices (crop

Accelerated 3D-OSEM image reconstruction using a Beowulf PC cluster for pinhole SPECT

International Nuclear Information System (INIS)

Zeniya, Tsutomu; Watabe, Hiroshi; Sohlberg, Antti; Iida, Hidehiro

2007-01-01

A conventional pinhole single-photon emission computed tomography (SPECT) with a single circular orbit has limitations associated with non-uniform spatial resolution or axial blurring. Recently, we demonstrated that three-dimensional (3D) images with uniform spatial resolution and no blurring can be obtained by complete data acquired using two-circular orbit, combined with the 3D ordered subsets expectation maximization (OSEM) reconstruction method. However, a long computation time is required to obtain the reconstruction image, because of the fact that 3D-OSEM is an iterative method and two-orbit acquisition doubles the size of the projection data. To reduce the long reconstruction time, we parallelized the two-orbit pinhole 3D-OSEM reconstruction process by using a Beowulf personal computer (PC) cluster. The Beowulf PC cluster consists of seven PCs connected to Gbit Ethernet switches. Message passing interface protocol was utilized for parallelizing the reconstruction process. The projection data in a subset are distributed to each PC. The partial image forward-and back-projected in each PC is transferred to all PCs. The current image estimate on each PC is updated after summing the partial images. The performance of parallelization on the PC cluster was evaluated using two independent projection data sets acquired by a pinhole SPECT system with two different circular orbits. Parallelization using the PC cluster improved the reconstruction time with increasing number of PCs. The reconstruction time of 54 min by the single PC was decreased to 10 min when six or seven PCs were used. The speed-up factor was 5.4. The reconstruction image by the PC cluster was virtually identical with that by the single PC. Parallelization of 3D-OSEM reconstruction for pinhole SPECT using the PC cluster can significantly reduce the computation time, whereas its implementation is simple and inexpensive. (author)

Validation of a probabilistic post-fire erosion model

Science.gov (United States)

Pete Robichaud; William J. Elliot; Sarah A. Lewis; Mary Ellen Miller

2016-01-01

Post-fire increases of runoff and erosion often occur and land managers need tools to be able to project the increased risk. The Erosion Risk Management Tool (ERMiT) uses the Water Erosion Prediction Project (WEPP) model as the underlying processor. ERMiT predicts the probability of a given amount of hillslope sediment delivery from a single rainfall or...

Development Of Rainfall Erosivity Map For Nigeria | Ogedengbe ...

African Journals Online (AJOL)

The indices were used to develop a rainfall erosivity map or Nigeria. The map reveals that Nigeria may be broadly divided into five major erosion risk zones. The south-western part is generally in the low erosion zone, with the exception of the coastal portion of Lagos, Ondo, Edo and Delta states. The south-east and central ...

Erosivity of rainfall in Lages, Santa Catarina, Brazil

Directory of Open Access Journals (Sweden)

Jefferson Schick

2014-12-01

Full Text Available The erosive capacity of rainfall can be expressed by an index and knowing it allows recommendation of soil management and conservation practices to reduce water erosion. The objective of this study was to calculate various indices of rainfall erosivity in Lages, Santa Catarina, Brazil, identify the best one, and discover its temporal distribution. The study was conducted at the Center of Agricultural and Veterinary Sciences, Lages, Santa Catarina, using daily rainfall charts from 1989 to 2012. Using the computer program Chuveros , 107 erosivity indices were obtained, which were based on maximum intensity in 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 70, 80, 90, 100, 110, 120, 135, 150, 165, 180, 210, and 240 min of duration and on the combination of these intensities with the kinetic energy obtained by the equations of Brown & Foster, Wagner & Massambani, and Wischmeier & Smith. The indices of the time period from 1993 to 2012 were correlated with the respective soil losses from the standard plot of the Universal Soil Loss Equation (USLE in order to select the erosivity index for the region. Erosive rainfall accounted for 83 % of the mean annual total volume of 1,533 mm. The erosivity index (R factor of rainfall recommended for Lages is the EI30, whose mean annual value is 5,033 MJ mm ha-1 h-1, and of this value, 66 % occurs from September to February. Mean annual erosivity has a return period estimated at two years with a 50 % probability of occurrence.

Acquired pellicle as a modulator for dental erosion.

Science.gov (United States)

Vukosavljevic, Dusa; Custodio, William; Buzalaf, Marilia A R; Hara, Anderson T; Siqueira, Walter L

2014-06-01

Dental erosion is a multifactorial condition that can result in the loss of tooth structure and function, potentially increasing tooth sensitivity. The exposure of enamel to acids from non-bacterial sources is responsible for the progression of erosion. These erosive challenges are counteracted by the anti-erosive properties of the acquired pellicle (AP), an integument formed in vivo as a result of selective adsorption of salivary proteins on the tooth surface, containing also lipids and glycoproteins. This review provides an in-depth discussion regarding how the physical structure of the AP, along with its composition, contributes to AP anti-erosive properties. The physical properties that contribute to AP protective nature include pellicle thickness, maturation time, and site of development. The pellicle contains salivary proteins embedded within its structure that demonstrate anti-erosive properties; however, rather than individual proteins, protein-protein interactions play a fundamental role in the protective nature of the AP. In addition, dietary and synthetic proteins can modify the pellicle, enhancing its protective efficiency against dental erosion. The salivary composition of the AP and its corresponding protein-profile may be employed as a diagnostic tool, since it likely contains salivary biomarkers for oral diseases that initiate at the enamel surface, including dental erosion. Finally, by modifying the composition and structure of the AP, this protein integument has the potential to be used as a target-specific treatment option for oral diseases related to tooth demineralization. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

Soil erosion under multiple time-varying rainfall events

Science.gov (United States)

Heng, B. C. Peter; Barry, D. Andrew; Jomaa, Seifeddine; Sander, Graham C.

2010-05-01

Soil erosion is a function of many factors and process interactions. An erosion event produces changes in surface soil properties such as texture and hydraulic conductivity. These changes in turn alter the erosion response to subsequent events. Laboratory-scale soil erosion studies have typically focused on single independent rainfall events with constant rainfall intensities. This study investigates the effect of multiple time-varying rainfall events on soil erosion using the EPFL erosion flume. The rainfall simulator comprises ten Veejet nozzles mounted on oscillating bars 3 m above a 6 m × 2 m flume. Spray from the nozzles is applied onto the soil surface in sweeps; rainfall intensity is thus controlled by varying the sweeping frequency. Freshly-prepared soil with a uniform slope was subjected to five rainfall events at daily intervals. In each 3-h event, rainfall intensity was ramped up linearly to a maximum of 60 mm/h and then stepped down to zero. Runoff samples were collected and analysed for particle size distribution (PSD) as well as total sediment concentration. We investigate whether there is a hysteretic relationship between sediment concentration and discharge within each event and how this relationship changes from event to event. Trends in the PSD of the eroded sediment are discussed and correlated with changes in sediment concentration. Close-up imagery of the soil surface following each event highlight changes in surface soil structure with time. This study enhances our understanding of erosion processes in the field, with corresponding implications for soil erosion modelling.

Ash particle erosion on steam boiler convective section

Energy Technology Data Exchange (ETDEWEB)

Meuronen, V

1998-12-31

In this study, equations for the calculation of erosion wear caused by ash particles on convective heat exchanger tubes of steam boilers are presented. A new, three-dimensional test arrangement was used in the testing of the erosion wear of convective heat exchanger tubes of steam boilers. When using the sleeve-method, three different tube materials and three tube constructions could be tested. New results were obtained from the analyses. The main mechanisms of erosion wear phenomena and erosion wear as a function of collision conditions and material properties have been studied. Properties of fossil fuels have also been presented. When burning solid fuels, such as pulverized coal and peat in steam boilers, most of the ash is entrained by the flue gas in the furnace. In bubbling and circulating fluidized bed boilers, particle concentration in the flue gas is high because of bed material entrained in the flue gas. Hard particles, such as sharp edged quartz crystals, cause erosion wear when colliding on convective heat exchanger tubes and on the rear wall of the steam boiler. The most important ways to reduce erosion wear in steam boilers is to keep the velocity of the flue gas moderate and prevent channelling of the ash flow in a certain part of the cross section of the flue gas channel, especially near the back wall. One can do this by constructing the boiler with the following components. Screen plates can be used to make the velocity and ash flow distributions more even at the cross-section of the channel. Shield plates and plate type constructions in superheaters can also be used. Erosion testing was conducted with three types of tube constructions: a one tube row, an in- line tube bank with six tube rows, and a staggered tube bark with six tube rows. Three flow velocities and two particle concentrations were used in the tests, which were carried out at room temperature. Three particle materials were used: quartz, coal ash and peat ash particles. Mass loss

Effect of mechanical properties on erosion resistance of ductile materials

Science.gov (United States)

Levin, Boris Feliksovih

Solid particle erosion (SPE) resistance of ductile Fe, Ni, and Co-based alloys as well as commercially pure Ni and Cu was studied. A model for SPE behavior of ductile materials is presented. The model incorporates the mechanical properties of the materials at the deformation conditions associated with SPE process, as well as the evolution of these properties during the erosion induced deformation. An erosion parameter was formulated based on consideration of the energy loss during erosion, and incorporates the material's hardness and toughness at high strain rates. The erosion model predicts that materials combining high hardness and toughness can exhibit good erosion resistance. To measure mechanical properties of materials, high strain rate compression tests using Hopkinson bar technique were conducted at strain rates similar to those during erosion. From these tests, failure strength and strain during erosion were estimated and used to calculate toughness of the materials. The proposed erosion parameter shows good correlation with experimentally measured erosion rates for all tested materials. To analyze subsurface deformation during erosion, microhardness and nanoindentation tests were performed on the cross-sections of the eroded materials and the size of the plastically deformed zone and the increase in materials hardness due to erosion were determined. A nanoindentation method was developed to estimate the restitution coefficient within plastically deformed regions of the eroded samples which provides a measure of the rebounding ability of a material during particle impact. An increase in hardness near the eroded surface led to an increase in restitution coefficient. Also, the stress rates imposed below the eroded surface were comparable to those measured during high strain-rate compression tests (10sp3-10sp4 ssp{-1}). A new parameter, "area under the microhardness curve" was developed that represents the ability of a material to absorb impact energy. By

Observational probes of cosmic acceleration

International Nuclear Information System (INIS)

Weinberg, David H.; Mortonson, Michael J.; Eisenstein, Daniel J.; Hirata, Christopher; Riess, Adam G.; Rozo, Eduardo

2013-01-01

The accelerating expansion of the universe is the most surprising cosmological discovery in many decades, implying that the universe is dominated by some form of “dark energy” with exotic physical properties, or that Einstein’s theory of gravity breaks down on cosmological scales. The profound implications of cosmic acceleration have inspired ambitious efforts to understand its origin, with experiments that aim to measure the history of expansion and growth of structure with percent-level precision or higher. We review in detail the four most well established methods for making such measurements: Type Ia supernovae, baryon acoustic oscillations (BAO), weak gravitational lensing, and the abundance of galaxy clusters. We pay particular attention to the systematic uncertainties in these techniques and to strategies for controlling them at the level needed to exploit “Stage IV” dark energy facilities such as BigBOSS, LSST, Euclid, and WFIRST. We briefly review a number of other approaches including redshift-space distortions, the Alcock–Paczynski effect, and direct measurements of the Hubble constant H 0 . We present extensive forecasts for constraints on the dark energy equation of state and parameterized deviations from General Relativity, achievable with Stage III and Stage IV experimental programs that incorporate supernovae, BAO, weak lensing, and cosmic microwave background data. We also show the level of precision required for clusters or other methods to provide constraints competitive with those of these fiducial programs. We emphasize the value of a balanced program that employs several of the most powerful methods in combination, both to cross-check systematic uncertainties and to take advantage of complementary information. Surveys to probe cosmic acceleration produce data sets that support a wide range of scientific investigations, and they continue the longstanding astronomical tradition of mapping the universe in ever greater detail over ever

Observational probes of cosmic acceleration

Energy Technology Data Exchange (ETDEWEB)

Weinberg, David H., E-mail: dhw@astronomy.ohio-state.edu [Department of Astronomy, Ohio State University, Columbus, OH (United States); Center for Cosmology and Astro-Particle Physics, Ohio State University, Columbus, OH (United States); Mortonson, Michael J. [Center for Cosmology and Astro-Particle Physics, Ohio State University, Columbus, OH (United States); Eisenstein, Daniel J. [Steward Observatory, University of Arizona, Tucson, AZ (United States); Harvard College Observatory, Cambridge, MA (United States); Hirata, Christopher [California Institute of Technology, Pasadena, CA (United States); Riess, Adam G. [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD (United States); Rozo, Eduardo [Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL (United States)

2013-09-10

The accelerating expansion of the universe is the most surprising cosmological discovery in many decades, implying that the universe is dominated by some form of “dark energy” with exotic physical properties, or that Einstein’s theory of gravity breaks down on cosmological scales. The profound implications of cosmic acceleration have inspired ambitious efforts to understand its origin, with experiments that aim to measure the history of expansion and growth of structure with percent-level precision or higher. We review in detail the four most well established methods for making such measurements: Type Ia supernovae, baryon acoustic oscillations (BAO), weak gravitational lensing, and the abundance of galaxy clusters. We pay particular attention to the systematic uncertainties in these techniques and to strategies for controlling them at the level needed to exploit “Stage IV” dark energy facilities such as BigBOSS, LSST, Euclid, and WFIRST. We briefly review a number of other approaches including redshift-space distortions, the Alcock–Paczynski effect, and direct measurements of the Hubble constant H{sub 0}. We present extensive forecasts for constraints on the dark energy equation of state and parameterized deviations from General Relativity, achievable with Stage III and Stage IV experimental programs that incorporate supernovae, BAO, weak lensing, and cosmic microwave background data. We also show the level of precision required for clusters or other methods to provide constraints competitive with those of these fiducial programs. We emphasize the value of a balanced program that employs several of the most powerful methods in combination, both to cross-check systematic uncertainties and to take advantage of complementary information. Surveys to probe cosmic acceleration produce data sets that support a wide range of scientific investigations, and they continue the longstanding astronomical tradition of mapping the universe in ever greater detail over

Polymers Erosion and Contamination Experiment Being Developed

Science.gov (United States)

deGroh, Kim K.; Banks, Bruce A.; Barney-Barton, Elyse A.; Sechkar, Edward; Hunt, Patricia

1999-01-01

The Polymers Erosion and Contamination Experiment (PEACE) is currently being developed at the NASA Lewis Research Center by the Electro-Physics Branch in conjunction with students and faculty from Hathaway Brown School in Cleveland. The experiment is a Get Away Special Canister shuttle flight experiment sponsored by the American Chemical Society. The two goals of this experiment are (1) to measure ram atomic oxygen erosion rates of approximately 40 polymers that have potential use in space applications and (2) to validate a method for identifying sources of silicone contamination that occur in the shuttle bay. Equipment to be used in this flight experiment is shown in the schematic diagram. Spacecraft materials subjected to attack by atomic oxygen in the space environment experience significant degradation over the span of a typical mission. Therefore, learning the rates of atomic oxygen erosion of a wide variety of polymers would be of great benefit to future missions. PEACE will use two independent techniques to determine the atomic oxygen erosion rates of polymers. Large (1-in.-diameter) samples will be used for obtaining mass loss. Preflight and postflight dehydrated masses will be obtained, and the mass lost during flight will be determined. Small (0.5-in.-diameter) samples will be protected with isolated particles (such as NaCl crystals) and then exposed to the space environment. After flight, the protective particles will be removed (washed off) and atomic force microscopy (AFM) will be used to measure the erosion depth from protected mesas. Erosion depth measurements are more sensitive than traditional mass measurements and are very useful for materials with low erosion yields or with very low fluence missions.