WorldWideScience

Sample records for rippling moa johansson

  1. MOAS

    International Nuclear Information System (INIS)

    Kim, I.S.; Modarres, M.

    1987-01-01

    A real-time knowledge-based operator advisory system (Maryland Operator Advisory System; MOAS) is being developed at the University of Maryland using PICON (real-time expert system shell for process control). MOAS is an expert system designed to assist the plant operators during transient conditions initiated by the Condensate and Feed Water System (CFWS) of a pressurized water reactor. The MOAS performs (1) intelligent prealarming and alarming, (2) real-time sensor validation and sensor conflict resolution, (3) real-time hardware failure diagnosis, and (4) real-time corrective measure synthesis. The core of the MOAS knowledge base is constructed using an integrated deep-knowledge approach called Coal Tree-Success Tree (GTST). The process domain knowledge of the CFWS is completely and rigorously modeled in the GTST format, which is then used to build up the knowledge base of the expert system. This paper briefly describes the GTST model, design of the current MOAS and ongoing and future efforts

  2. Sinding-Larsen-Johansson syndrome

    African Journals Online (AJOL)

    with tenderness over the infrapatellar area in the region of the infrapatellar .... Johansson syndrome, which has a similar radiographic appearance but represents ... The mechanism of injury is similar in all three of the entities and is believed to ...

  3. Sinding-Larsen-Johansson syndrome

    African Journals Online (AJOL)

    dislocation, chondromalacia patellae and prepatellar bursitis.1. Imaging of Sinding-Larsen-Johansson syndrome may require a combination of radiographs, MRI and ultrasound. Lateral radiographs may reveal peripatellar soft-tissue swelling, patella-alta deformity and one or multiple tiny osseous fragments adjacent to.

  4. Stardust Blazes MOA Trail

    Science.gov (United States)

    Faris, Grant B.; Bryant, Larry W.

    2010-01-01

    Mission Operations Assurance (MOA) started at the Jet Propulsion Laboratory (JPL) with the Magellan and Galileo missions of the late 80's. It continued to develop and received a significant impetus with the failures of two successive missions to Mars in the late 90's. MOA continued to evolve with each successive project at JPL achieving its current maturity with the Stardust sample return to Earth.

  5. Ripple Communication.

    Science.gov (United States)

    Wilcox, R. Stimson

    1980-01-01

    Discusses how surface-dwelling animals use the water surface as a mode of communication by making ripple signals while they swim about. Provides information about surfaces and surface waves, ripple communication in water striders, ripple signal characteristics, sensing and orienting, other modes of communication, and evolution of ripple…

  6. Me seisame uue renessansi lävel / Frans Johansson ; interv. Endrik Randoja

    Index Scriptorium Estoniae

    Johansson, Frans

    2008-01-01

    Ilmunud ka: Delovõje Vedomosti 2. apr. lk. 28. Juhtimismõtleja ja raamatu "Medici efekt" autor Frans Johansson arutleb teemal, kuidas erinevate ideede, tegevusalade, kultuuride ja kompetentside ristamisel luuakse uusi turge ja ärivõimalusi. Lisa: Frans Johansson

  7. Rolling Ripple

    Science.gov (United States)

    2006-01-01

    NASA's Mars Exploration Rover Opportunity continues to cut southward across a plain marked by large sand ripples and a pavement of outcrop rock. The ripple in the center of the image shows a distinct pattern of banding, which the science team hopes to investigate more closely during the trek through this terrain. The banding and other features have inspired a hypothesis that Meridiani ripples are old features that are currently being eroded, and not transported, by wind. This navigation camera image was taken on Opportunity's sol 795, April 19, 2006.

  8. Defining the period of moa extinction

    International Nuclear Information System (INIS)

    Anderson, A.

    2000-01-01

    Few aspects of New Zealand's prehistory have engaged scientific and public attention so consistently as two interlinked questions of moa extinction; when did moas become extinct and why? Answers offered over the last 160 years have run the gamut from chronological antiquity by evolutionary senescence, to within the 19th century Maori and European disturbance. (author)

  9. Ripple Belt

    Science.gov (United States)

    2006-01-01

    16 July 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows windblown materials that have collected and been shaped into large ripples in a valley in the Auqakuh Vallis system in northeastern Arabia Terra, Mars. Location near: 29.1oN, 299.6oW Image width: 2 km (1.2 mi) Illumination from: lower left Season: Northern Winter

  10. Ripple Trap

    Science.gov (United States)

    2006-01-01

    3 April 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows the margin of a lava flow on a cratered plain in the Athabasca Vallis region of Mars. Remarkably, the cratered plain in this scene is essentially free of bright, windblown ripples. Conversely, the lava flow apparently acted as a trap for windblown materials, illustrated by the presence of the light-toned, wave-like texture over much of the flow. That the lava flow surface trapped windblown sand and granules better than the cratered plain indicates that the flow surface has a rougher texture at a scale too small to resolve in this image. Location near: 10.7oN, 204.5oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Winter

  11. U(1) decoupling, Kleiss-Kuijf and Bern-Carrasco-Johansson relations in N=4 super Yang-Mills

    International Nuclear Information System (INIS)

    Jia Yin; Huang Rijun; Liu Changyong

    2010-01-01

    By using the Britto-Cachazo-Feng-Witten recursion relation of N=4 super Yang-Mills theory, we proved the color reflection, U(1) decoupling, Kleiss-Kuijf and Bern-Carrasco-Johansson relations for color-ordered amplitudes of N=4 super Yang-Mills theory. This proof verified the conjectured Bern-Carrasco-Johansson relations of matter fields. The proof depended only on general properties of superamplitudes. We showed also that the color reflection relation and U(1)-decoupling relation are special cases of Kleiss-Kuijf relations.

  12. Electronic properties of rippled graphene

    International Nuclear Information System (INIS)

    Gui Gui; Ma Zhenqiang; Zhong Jianxin

    2012-01-01

    Short range periodic ripples in graphene have been modeled. The electronic properties of the rippled graphene have been investigated using first-principles calculations. Compared with flat graphene, there is a band gap opening in rippled graphene. Generally, the value of energy gaps increases as the height of ripples increase, but it decreases as the range of ripples enlarges. The maximum value of energy gaps in rippled graphene can reach several hundred meV, which turns rippled graphene into a good semiconductor. As a result, the magnitude of energy gaps can be tuned effectively by controlling the range and height of ripples in graphene.

  13. Determinant of Household Business Scale of Moa Buffaloes at Moa Island Southwest Maluku Regency

    Science.gov (United States)

    Lainsamputty, J.; Roessali, W.; Santosa, S. I.; Eddy, B. T.

    2018-02-01

    The objective of this research was to analyze factors that affect the business scale of Moa buffaloes at Moa Island, Regency of Southwest Maluku. The research used a survey method with multistage random sampling. The location chosen was the District of Moa Lakor at Moa Island based on its largest buffalo population. Respondents were randomly drawn in a total of 120 respondents. The variables measured were years of experience in rearing animals, costs of production, farmer’s participation in group activities, animal housing systems, farmer’s income and farmer’s age. The statistical test used was the multiple linear regressions. The results showed that the mean of business scale in the area of high density of buffaloes population was 12.6 AU, in the moderate was 12.4 AU and in the low was 11.0 AU. The average of production cost was IDR 1.893.536.00/year, the average of revenue was IDR14.083.333.00/year, while the average of income was IDR 12.189.797.00/year. The independent variables simultaneously influence the business scale (Pbusiness scale (P<0.01).

  14. Permeation through graphene ripples

    Science.gov (United States)

    Liang, Tao; He, Guangyu; Wu, Xu; Ren, Jindong; Guo, Hongxuan; Kong, Yuhan; Iwai, Hideo; Fujita, Daisuke; Gao, Hongjun; Guo, Haiming; Liu, Yingchun; Xu, Mingsheng

    2017-06-01

    Real graphene sheets show limited anti-permeation performance deviating from the ideally flat honeycomb carbon lattice that is impermeable to gases. Ripples in graphene are prevalent and they could significantly influence carrier transport. However, little attention has been paid to the role of ripples in the permeation properties of graphene. Here, we report that gases can permeate through graphene ripples at room temperature. The feasibility of gas permeation through graphene ripples is determined by detecting the initial oxidation sites of Cu surface covered with isolated graphene domain. Nudged elastic band (NEB) calculations demonstrate that the oxygen atom permeation occurs via the formation of C-O-C bond, in which process the energy barrier through the rippled graphene lattice is much smaller than that through a flat graphene lattice, rendering permeation through ripples more favorable. Combining with the recent advances in atoms intercalation between graphene and metal substrate for transfer-free and electrically insulated graphene, this discovery provides new perspectives regarding graphene’s limited anti-permeation performance and evokes for rational design of graphene-based encapsulation for barrier and selective gas separation applications through ripple engineering.

  15. Electronic ripple indicator

    Science.gov (United States)

    Davidson, J. K.; Houck, W. H.

    1971-01-01

    Electronic circuit for monitoring excessive ripple voltage on dc power lines senses voltage variations from few millivolts to maximum of 10 volts rms. Instrument is used wherever power supply fluctuations might endanger system operations or damage equipment. Device is inexpensive and easily packaged in small chassis.

  16. Containerless Ripple Turbulence

    Science.gov (United States)

    Putterman, Seth; Wright, William; Duval, Walter; Panzarella, Charles

    2002-11-01

    One of the longest standing unsolved problems in physics relates to the behavior of fluids that are driven far from equilibrium such as occurs when they become turbulent due to fast flow through a grid or tidal motions. In turbulent flows the distribution of vortex energy as a function of the inverse length scale [or wavenumber 'k'] of motion is proportional to 1/k5/3 which is the celebrated law of Kolmogorov. Although this law gives a good description of the average motion, fluctuations around the average are huge. This stands in contrast with thermally activated motion where large fluctuations around thermal equilibrium are highly unfavorable. The problem of turbulence is the problem of understanding why large fluctuations are so prevalent which is also called the problem of 'intermittency'. Turbulence is a remarkable problem in that its solution sits simultaneously at the forefront of physics, mathematics, engineering and computer science. A recent conference [March 2002] on 'Statistical Hydrodynamics' organized by the Los Alamos Laboratory Center for Nonlinear Studies brought together researchers in all of these fields. Although turbulence is generally thought to be described by the Navier-Stokes Equations of fluid mechanics the solution as well as its existence has eluded researchers for over 100 years. In fact proof of the existence of such a solution qualifies for a 1 M millennium prize. As part of our NASA funded research we have proposed building a bridge between vortex turbulence and wave turbulence. The latter occurs when high amplitude waves of various wavelengths are allowed to mutually interact in a fluid. In particular we have proposed measuring the interaction of ripples [capillary waves] that run around on the surface of a fluid sphere suspended in a microgravity environment. The problem of ripple turbulence poses similar mathematical challenges to the problem of vortex turbulence. The waves can have a high amplitude and a strong nonlinear

  17. Containerless Ripple Turbulence

    Science.gov (United States)

    Putterman, Seth; Wright, William; Duval, Walter; Panzarella, Charles

    2002-01-01

    One of the longest standing unsolved problems in physics relates to the behavior of fluids that are driven far from equilibrium such as occurs when they become turbulent due to fast flow through a grid or tidal motions. In turbulent flows the distribution of vortex energy as a function of the inverse length scale [or wavenumber 'k'] of motion is proportional to 1/k(sup 5/3) which is the celebrated law of Kolmogorov. Although this law gives a good description of the average motion, fluctuations around the average are huge. This stands in contrast with thermally activated motion where large fluctuations around thermal equilibrium are highly unfavorable. The problem of turbulence is the problem of understanding why large fluctuations are so prevalent which is also called the problem of 'intermittency'. Turbulence is a remarkable problem in that its solution sits simultaneously at the forefront of physics, mathematics, engineering and computer science. A recent conference [March 2002] on 'Statistical Hydrodynamics' organized by the Los Alamos Laboratory Center for Nonlinear Studies brought together researchers in all of these fields. Although turbulence is generally thought to be described by the Navier-Stokes Equations of fluid mechanics the solution as well as its existence has eluded researchers for over 100 years. In fact proof of the existence of such a solution qualifies for a 1 M$ millennium prize. As part of our NASA funded research we have proposed building a bridge between vortex turbulence and wave turbulence. The latter occurs when high amplitude waves of various wavelengths are allowed to mutually interact in a fluid. In particular we have proposed measuring the interaction of ripples [capillary waves] that run around on the surface of a fluid sphere suspended in a microgravity environment. The problem of ripple turbulence poses similar mathematical challenges to the problem of vortex turbulence. The waves can have a high amplitude and a strong nonlinear

  18. Shape and Dimensions of Ripples

    DEFF Research Database (Denmark)

    Jacobsen, Niels Gjøl

    and the general conclusion is that sharp crested ripples is thought unlikely to become stable under oscillatory flow due to the large increase in bed shear stresses because of the rapid contraction of the flow around the crest. Further, a dynamically moving ripple crest is investigated. The key focus...... are the recirculation zone and its penetration into the main flow. This will be compared to the period averaged bed shear stress. An analysis of the bed load transport, both as a transport capacity in the phase resolved space and an analysis of possible stable ripples is conducted. This leads to some stable ripples...

  19. Local knowledge of fishermen in weather prediction in Moa and ...

    African Journals Online (AJOL)

    This study investigated local knowledge of fishermen in weather prediction in Moa and Kwale coastal villages, Tanzania. Focus Group Discussions, Seasonal Calendars, Time line analysis, key informant interviews, questionnaire surveys and documentary reviews were used to gather data. The SPSS programme was used ...

  20. Mechanics of wind ripple stratigraphy.

    Science.gov (United States)

    Forrest, S B; Haff, P K

    1992-03-06

    Stratigraphic patterns preserved under translating surface undulations or ripples in a depositional eolian environment are computed on a grain by grain basis using physically based cellular automata models. The spontaneous appearance, growth, and motion of the simulated ripples correspond in many respects to the behavior of natural ripples. The simulations show that climbing strata can be produced by impact alone; direct action of fluid shear is unnecessary. The model provides a means for evaluating the connection between mechanical processes occurring in the paleoenvironment during deposition and the resulting stratigraphy preserved in the geologic column: vertical compression of small laminae above a planar surface indicates nascent ripple growth; supercritical laminae are associated with unusually intense deposition episodes; and a plane erosion surface separating sets of well-developed laminae is consistent with continued migration of mature ripples during a hiatus in deposition.

  1. Anisotropic Ripple Deformation in Phosphorene.

    Science.gov (United States)

    Kou, Liangzhi; Ma, Yandong; Smith, Sean C; Chen, Changfeng

    2015-05-07

    Two-dimensional materials tend to become crumpled according to the Mermin-Wagner theorem, and the resulting ripple deformation may significantly influence electronic properties as observed in graphene and MoS2. Here, we unveil by first-principles calculations a new, highly anisotropic ripple pattern in phosphorene, a monolayer black phosphorus, where compression-induced ripple deformation occurs only along the zigzag direction in the strain range up to 10%, but not the armchair direction. This direction-selective ripple deformation mode in phosphorene stems from its puckered structure with coupled hinge-like bonding configurations and the resulting anisotropic Poisson ratio. We also construct an analytical model using classical elasticity theory for ripple deformation in phosphorene under arbitrary strain. The present results offer new insights into the mechanisms governing the structural and electronic properties of phosphorene crucial to its device applications.

  2. A Stellar Ripple

    Science.gov (United States)

    2006-01-01

    This false-color composite image shows the Cartwheel galaxy as seen by the Galaxy Evolution Explorer's far ultraviolet detector (blue); the Hubble Space Telescope's wide field and planetary camera 2 in B-band visible light (green); the Spitzer Space Telescope's infrared array camera at 8 microns (red); and the Chandra X-ray Observatory's advanced CCD imaging spectrometer-S array instrument (purple). Approximately 100 million years ago, a smaller galaxy plunged through the heart of Cartwheel galaxy, creating ripples of brief star formation. In this image, the first ripple appears as an ultraviolet-bright blue outer ring. The blue outer ring is so powerful in the Galaxy Evolution Explorer observations that it indicates the Cartwheel is one of the most powerful UV-emitting galaxies in the nearby universe. The blue color reveals to astronomers that associations of stars 5 to 20 times as massive as our sun are forming in this region. The clumps of pink along the outer blue ring are regions where both X-rays and ultraviolet radiation are superimposed in the image. These X-ray point sources are very likely collections of binary star systems containing a blackhole (called massive X-ray binary systems). The X-ray sources seem to cluster around optical/ultraviolet-bright supermassive star clusters. The yellow-orange inner ring and nucleus at the center of the galaxy result from the combination of visible and infrared light, which is stronger towards the center. This region of the galaxy represents the second ripple, or ring wave, created in the collision, but has much less star formation activity than the first (outer) ring wave. The wisps of red spread throughout the interior of the galaxy are organic molecules that have been illuminated by nearby low-level star formation. Meanwhile, the tints of green are less massive, older visible-light stars. Although astronomers have not identified exactly which galaxy collided with the Cartwheel, two of three candidate galaxies can be

  3. "Ripples" in an Aluminum Pool?

    Science.gov (United States)

    Rohr, James; Wang, Si-Yin; Nesterenko, Vitali F.

    2018-05-01

    Our motivation for this article is for students to realize that opportunities for discovery are all around them. Discoveries that can still puzzle present day researchers. Here we explore an observation by a middle school student concerning the production of what appears to be water-like "ripples" produced in aluminum foil when placed between two colliding spheres. We both applaud and explore the student's reasoning that the ripples were formed in a melted aluminum pool.

  4. Recent activities in the development of the MOA thruster

    Science.gov (United States)

    Frischauf, Norbert; Hettmer, Manfred; Grassauer, Andreas; Bartusch, Tobias; Koudelka, Otto

    2008-07-01

    More than 60 years after the later Nobel laureate Hannes Alfvén had published a letter stating that oscillating magnetic fields can accelerate ionised matter via magneto-hydrodynamic interactions in a wave like fashion, the technical implementation of Alfvén waves for propulsive purposes has been proposed, patented and examined for the first time by a group of inventors. The name of the concept, utilising Alfvén waves to accelerate ionised matter for propulsive purposes, is MOA-magnetic field oscillating amplified thruster. Alfvén waves are generated by making use of two coils, one being permanently powered and serving also as magnetic nozzle, the other one being switched on and off in a cyclic way, deforming the field lines of the overall system. It is this deformation that generates Alfvén waves, which are in the next step used to transport and compress the propulsive medium, in theory leading to a propulsion system with a much higher performance than any other electric propulsion system. Based on computer simulations, which were conducted to get a first estimate on the performance of the system, MOA is a corrosion free and highly flexible propulsion system, whose performance parameters might easily be adapted in flight, by changing the mass flow and/or the power level. As such the system is capable to deliver a maximum specific impulse of 13 116 s (12.87 mN) at a power level of 11.16 kW, using Xe as propellant, but can also be attuned to provide a thrust of 236.5 mN (2411 s) at 6.15 kW of power. First tests-that are further described in this paper-have been conducted successfully and underline the feasibility of the concept. While space propulsion is expected to be the prime application for MOA and is supported by numerous applications such as Solar and/or Nuclear Electric Propulsion or even as an "afterburner system" for nuclear thermal propulsion, other terrestrial applications can be thought of as well, making the system highly suited for a common space

  5. 76 FR 5394 - Notice of Proposed Information Collection for Public Comment; Memorandum of Agreement (MOA) and...

    Science.gov (United States)

    2011-01-31

    ... Information Collection for Public Comment; Memorandum of Agreement (MOA) and Improvement Plan (IP) in... (this is not a toll-free number) or email Ms. Pollard at [email protected] . Persons with hearing...: Title of Proposal: Memorandum of Agreement (MOA), Progress Report and Improvement Plan (IP). OMB Control...

  6. Reducing Ripple In A Switching Voltage Regulator

    Science.gov (United States)

    Paulkovich, John; Rodriguez, G. Ernest

    1994-01-01

    Ripple voltage in output of switching voltage regulator reduced substantially by simple additional circuitry adding little to overall weight and size of regulator. Heretofore, additional filtering circuitry needed to obtain comparable reductions in ripple typically as large and heavy as original regulator. Current opposing ripple current injected into filter capacitor.

  7. Radiocarbon dating the end of moa-hunting in New Zealand prehistory

    International Nuclear Information System (INIS)

    Schmidt, M.

    2000-01-01

    For over 150 years, New Zealand scientists and prehistorians have investigated and debated when the last moa (Aves : Dinornithiformes) was hunted and killed by humans (see Anderson 1989). Prior to the introduction of radiocarbon dating into New Zealand archaeology in the mid-1950s, theories on when moa predation ended were based on Maori oral tradition, dubious eye witness accounts, moa bones found on the surface of the ground and arbitrary archaeological excavations of large culling sites. Radiocarbon dating provided an absolute chronological tool for determining when the remains of moa found in prehistoric context were deposited, meaning the activity of moa-hunting could be more easily attributed to a particular period in New Zealand prehistory. (author)

  8. Big birds and their brains: paleoneurology of the New Zealand moa.

    Science.gov (United States)

    Ashwell, K W S; Scofield, R P

    2008-01-01

    The moa (Dinornithiformes: Aves) are an extinct group of ratites from the North and South Islands of New Zealand. The ancestors of both the moa and the kiwi were isolated from other Gondwanan fauna as much as 80 million years ago and evolved in the absence of large mammalian predators. As such they represent a natural experiment in the removal of mammalian predation pressure on the encephalization of these two groups of ratites. We have used endocranial and skull morphometry in conjunction with high resolution CT scanning of the skulls of 8 species of moa to assess encephalization and brain morphology in moa and compare these features with extant ratites. Absolute brain size among the moa ranged from 17.0 ml for Euryapteryx curtus to 60.0 ml for female Dinornis giganteus. Values for encephalization quotients (EQ) of moa ranged from 0.205 for Euryapteryx gravis of the southern North Island to a mean (+/- SD) of 0.475 (+/- 0.026) for Anomalopteryx didiformis, partially overlapping values for extant non-New Zealand ratites (emu: 0.402 +/- 0.042; rhea: 0.496 +/- 0.016; ostrich: 0.474 +/- 0.084). Nevertheless, mean +/- SD EQ for all moa examined (0.379 +/- 0.065) was significantly lower than EQ for extant non-New Zealand ratites (0.539 +/- 0.141). Bending of the endocranial axis was much less among moa than either the kiwi or non-New Zealand ratites, consistent with the caudal position of the foramen magnum and the horizontal carriage of the head and upper neck during life. Endocranial morphology of the moa species examined was similar to that for non-New Zealand ratites, with proportionally similar sizes of the olfactory bulb, Wulst, vagal and maxillomandibular foramina, suggesting that the moa occupied similar diurnal niches with comparable sensory specializations to the emu, rhea and ostrich. No evidence of olfactory specialization (i.e., enlarged olfactory bulbs and increased surface area of the olfactory nasal cavity or cribriform plate) was evident in any of the

  9. A Simple Ripple Filter for FLUKA

    DEFF Research Database (Denmark)

    Bassler, Niels; Herrmann, Rochus

    In heavy ion radiotherapy, pristine C-12 beams are usually widened a few mm (FWHM) along the beam axis, before the actual spread out Bragg peak (SOBP) is build. The pristine beam widening is commonly performed with a ripple filter, known from the facility at GSI (Darmstadt) and at HIT (Heidelberg......). The ripple filter at GSI and HIT consists of several wedge like structures, which widens the Bragg-peak up to e.g. 3 mm. For Monte Carlo simulations of C-12 therapy, the exact setup, including the ripple filter needs to be simulated. In the Monte Carlo particle transport program FLUKA, the ripple filter can....... Since the ripple filter is a periodic geometry, one could use the LATTIC card with advantage, but here we shall take a Monte Carlo based approach istead. The advantage of this method is that our input file merely contains one body as the ripple filter, which can be a flat slab (or any other arbitrary...

  10. Numerical simulation of aeolian sand ripples

    International Nuclear Information System (INIS)

    Kang Liqiang; Guo Liejin

    2004-01-01

    With a new horizontal saltation displacement vector, a model is implemented to simulate the initiation and evolution of aeolian sand ripples. In the model, saltation distance considers the effects of surface height and slope. A linear stability analysis is also carried out for formation of sand ripples. The results show that, the model can be able to successfully reproduce sand ripples which can increase in scale by merging of small ripples. The linear stability analysis indicates that sand ripples appear when the relaxation rate parameter is below a threshold value and wind strength parameter is larger than a critical value. The results also verified that the formation of sand ripples is a self-organization process

  11. Cargas actuantes en túneles de Moa

    Directory of Open Access Journals (Sweden)

    Roberto Blanco-Torrens

    2000-03-01

    Full Text Available Para la confección del presente trabajo se realizó un estudio que abarcó 2 km de túneles del municipio Moa a los que se les hizo un análisis detallado del macizo rocoso que los circunda, y se determinaron las propiedades físico-mecánica de las rocas, agrietamiento, afluencia de agua y sus consecuencias, etc. Se valoró la estabilidad por varias metodologías (Barton, Bieniawsky, Bulichev y otras y fueron usados, por sus resultados, los valores obtenidos del empleo de la de Barton. Se estableció el mecanismo de acción de la presión minera y se caracterizó en dos casos típicos, a partir de los cuales se determinan los valores de las cargas estáticas que se pueden producir. Se consideró el macizo como un cuerpo elástico, homogéneo e isotrópico para establecer el estado tensional inicial y así calcular las cargas dinámicas que pueden actuar. Además se puntualizan los valores de las cargas considerados como críticos.

  12. Environmental impact assessment in Moa-Holguín Port

    Directory of Open Access Journals (Sweden)

    Rosa María Pérez Silva

    2015-07-01

    Full Text Available The operations of unloading ships the reception and distribution of products derivate of oil crude in the storage area, the movement of raw materials like coal anthracite, ammonia and sulphur, the load of lots of minerals as well as the maintenance of ships, direct leads to the appearance of hydrocarbons that affects the different ecosystems which he meets in once the contaminating source in the municipal Moa. It is present the characterization of ecosystems affected with oil's hydrocarbons, attending to environmental impacts identified by the expert group and the prior characterization of the area using assessment tools expert judgment using Delphi methodology. The environmental impact study was realized of qualitative form through matrix of cause-effect, valuation and importance of impact. The environmental factors of resulting surface/groundwater and health and hygiene the most attacked while impacts were more aggressive emissions (throwing to the ground hydrocarbons/ liberation to the midway air of gases, noises and materials in particles, throwing and contamination of the source for dragging of sediments, hydrocarbons and chemical substances and accumulation waste (creation of drains industrials.

  13. On the formation of current ripples

    DEFF Research Database (Denmark)

    Bartholdy, Jesper; Ernstsen, Verner Brandbyge; Flemming, Burg W.

    2015-01-01

    such an explanation based on a virtual boundary layer concept, and present a model predicting ripple height on the basis of grain size, current velocity and water depth. The model contradicts the conventional view of current ripples as bedforms not scaling with flow depth. Furthermore, it confirms the dependence...

  14. Molecular structure of the lecithin ripple phase

    NARCIS (Netherlands)

    de Vries, AH; Yefimov, S; Mark, AE; Marrink, SJ

    2005-01-01

    Molecular dynamics simulations of lecithin lipid bilayers in water as they are cooled from the liquid crystalline phase show the spontaneous formation of rippled bilayers. The ripple consists of two domains of different length and orientation, connected by a kink. The organization of the lipids in

  15. Pattern formation - Instabilities in sand ripples

    DEFF Research Database (Denmark)

    Hansen, J. L.; v. Hecke, M.; Haaning, A.

    2001-01-01

    Sand ripples are seen below shallow wavy water and are formed whenever water oscillates over a bed of sand. Here we analyse the instabilities that can upset this perfect patterning when the ripples are subjected to large changes in driving amplitude or frequency, causing them to deform both...

  16. Ripple induced trapped particle loss in tokamaks

    International Nuclear Information System (INIS)

    White, R.B.

    1996-05-01

    The threshold for stochastic transport of high energy trapped particles in a tokamak due to toroidal field ripple is calculated by explicit construction of primary resonances, and a numerical examination of the route to chaos. Critical field ripple amplitude is determined for loss. The expression is given in magnetic coordinates and makes no assumptions regarding shape or up-down symmetry. An algorithm is developed including the effects of prompt axisymmetric orbit loss, ripple trapping, convective banana flow, and stochastic ripple loss, which gives accurate ripple loss predictions for representative Tokamak Fusion Test Reactor and International Thermonuclear Experimental Reactor equilibria. The algorithm is extended to include the effects of collisions and drag, allowing rapid estimation of alpha particle loss in tokamaks

  17. Model of ripples in graphene

    Science.gov (United States)

    Bonilla, L. L.; Carpio, A.

    2012-11-01

    We propose a model of ripples in suspended graphene sheets based on plate equations that are made discrete with the periodicity of the honeycomb lattice and then periodized. In addition, the equation for the displacements with respect to the planar configuration contains a double-well site potential, a nonlinear friction, and a multiplicative white-noise term satisfying the fluctuation-dissipation theorem. The nonlinear friction terms agree with those proposed by Eichler [Nature Nanotech.1748-338710.1038/nnano.2011.71 6, 339 (2011)] to explain their experiments with a graphene resonator. The site double-well potential indicates that the carbon atoms at each lattice point have equal probability to move upward or downward off plane. For the considered parameter values, the relaxation time due to friction is much larger than the periods of membrane vibrations and the noise is quite small. Then ripples with no preferred orientation appear as long-lived metastable states for any temperature. Numerical solutions confirm this picture.

  18. Complex species status for extinct moa (Aves: Dinornithiformes from the genus Euryapteryx.

    Directory of Open Access Journals (Sweden)

    Leon Huynen

    Full Text Available The exact species status of New Zealand's extinct moa remains unknown. In particular, moa belonging to the genus Euryapteryx have been difficult to classify. We use the DNA barcoding sequence on a range of Euryapteryx samples in an attempt to resolve the species status for this genus. We obtained mitochondrial control region and the barcoding region from Cytochrome Oxidase Subunit I (COI from a number of new moa samples and use available sequences from previous moa phylogenies and eggshell data to try and clarify the species status of Euryapteryx. Using the COI barcoding region we show that species status in Euryapteryx is complex with no clear separation between various individuals. Eggshell, soil, and bone data suggests that a Euryapteryx subspecies likely exists on New Zealand's North Island and can be characterized by a single mitochondrial control region SNP. COI divergences between Euryapteryx individuals from the south of New Zealand's South Island and those from the Far North of the North Island exceed 1.6% and are likely to represent separate species. Individuals from other areas of New Zealand were unable to be clearly separated based on COI differences possibly as a result of repeated hybridisation events. Despite the accuracy of the COI barcoding region to determine species status in birds, including that for the other moa genera, for moa from the genus Euryapteryx, COI barcoding fails to provide a clear result, possibly as a consequence of repeated hybridisation events between these moa. A single control region SNP was identified however that segregates with the two general morphological variants determined for Euryapteryx; a smaller subspecies restricted to the North Island of New Zealand, and a larger subspecies, found on both New Zealand's North and South Island.

  19. Complex species status for extinct moa (Aves: Dinornithiformes) from the genus Euryapteryx.

    Science.gov (United States)

    Huynen, Leon; Lambert, David M

    2014-01-01

    The exact species status of New Zealand's extinct moa remains unknown. In particular, moa belonging to the genus Euryapteryx have been difficult to classify. We use the DNA barcoding sequence on a range of Euryapteryx samples in an attempt to resolve the species status for this genus. We obtained mitochondrial control region and the barcoding region from Cytochrome Oxidase Subunit I (COI) from a number of new moa samples and use available sequences from previous moa phylogenies and eggshell data to try and clarify the species status of Euryapteryx. Using the COI barcoding region we show that species status in Euryapteryx is complex with no clear separation between various individuals. Eggshell, soil, and bone data suggests that a Euryapteryx subspecies likely exists on New Zealand's North Island and can be characterized by a single mitochondrial control region SNP. COI divergences between Euryapteryx individuals from the south of New Zealand's South Island and those from the Far North of the North Island exceed 1.6% and are likely to represent separate species. Individuals from other areas of New Zealand were unable to be clearly separated based on COI differences possibly as a result of repeated hybridisation events. Despite the accuracy of the COI barcoding region to determine species status in birds, including that for the other moa genera, for moa from the genus Euryapteryx, COI barcoding fails to provide a clear result, possibly as a consequence of repeated hybridisation events between these moa. A single control region SNP was identified however that segregates with the two general morphological variants determined for Euryapteryx; a smaller subspecies restricted to the North Island of New Zealand, and a larger subspecies, found on both New Zealand's North and South Island.

  20. Ripple transport in a modular Helias

    International Nuclear Information System (INIS)

    Beidler, C.D.

    1989-01-01

    Neoclassical transport rates are determined for Helical-Axis Advanced Stellarators (Helias). Special emphasis is given to Wendelstein VII-X candidates, for which the magnetic field is produced by a large number of discrete non-planar coils. The investigation is concentrated on the long-mean-free-path regime where particles trapped in local ripple wells of the magnetic field make the dominant contribution to transport. For Wendelstein VII-X, such particles fall into two classes; those localized in the helical ripple common to all stellarator-type devices and those very-localized particles which are trapped in the modular ripples existing between the individual coils. Using analytical techniques it is shown that helical-ripple transport rates are substantially reduced for all Wendelstein VII-X candidates relative to classical stellarator/torsatron configurations. This reduction is most pronounced in the 1/ν regime - equivalent helical ripples of less than 1% lead to reduction factors of more than an order of magnitude - but is significant throughout the entire long-mean-free-path regime. Modular ripple transport in Wendelstein VII-X is calculated by analytically solving the appropriate bounce-averaged kinetic equation. This solution assumes a general magnetic field model and fully accounts for the deformation of modular ripples due to the presence of the other magnetic-field harmonics. Results indicate that 12 coils per field period are necessary if modular-ripple losses are to remain smaller than helical-ripple losses over the entire plasma cross section. (orig.)

  1. Emittance growth due to dipole ripple and sextupole

    International Nuclear Information System (INIS)

    Shih, H.J.; Ellison, J.A.; Syphers, M.J.; Newberger, B.S.

    1993-05-01

    Ripple in the power supplies for storage ring magnets can have adverse effects on the circulating beams: orbit distortion and emittance growth from dipole ripple, tune modulation and dynamic aperture reduction from quadrupole ripple, etc. In this paper, we study the effects of ripple in the horizontal bending field of the SSC in the presence of nonlinearity, in particular, the growth in beam emittance

  2. Parallelization of Reversible Ripple-carry Adders

    DEFF Research Database (Denmark)

    Thomsen, Michael Kirkedal; Axelsen, Holger Bock

    2009-01-01

    The design of fast arithmetic logic circuits is an important research topic for reversible and quantum computing. A special challenge in this setting is the computation of standard arithmetical functions without the generation of \\emph{garbage}. Here, we present a novel parallelization scheme...... wherein $m$ parallel $k$-bit reversible ripple-carry adders are combined to form a reversible $mk$-bit \\emph{ripple-block carry adder} with logic depth $\\mathcal{O}(m+k)$ for a \\emph{minimal} logic depth $\\mathcal{O}(\\sqrt{mk})$, thus improving on the $mk$-bit ripple-carry adder logic depth $\\mathcal...

  3. Toroidal field ripple effects in large tokamaks

    International Nuclear Information System (INIS)

    Uckan, N.A.; Tsang, K.T.; Callen, J.D.

    1975-01-01

    In an experimental power reactor, the ripple produced by the finite number of toroidal field coils destroys the ideal axisymmetry of the configuration and is responsible for additional particle trapping, loss regions and plasma transport. The effects of toroidal field ripple on the plasma transport coefficient, the loss of alpha particles and energetic injection ions, and the relaxation of toroidal flows are investigated in a new and systematic way. The relevant results are applied to the ORNL-EPR reference design; the maximum ripple there of about 2.2 percent at the outer edge of the plasma column is found to be tolerable from plasma physics considerations

  4. Implementation of MOAS II diagnosis system at the OECD Halden Reactor project

    International Nuclear Information System (INIS)

    Kim, I.S.; Grini, R.E.; Nilsen, S.

    1995-01-01

    MOAS II is a surveillance and diagnosis system that uses several techniques for knowledge acquisition and diagnostic reasoning, e.g., goal tree-success tree, simplified directed graphs, diagnosis trees, and detailed knowledge of the process, such as mass or energy balance. This new approach was used at the Halden Man-Machine Laboratory of the OECD Halden Reactor Project. The performance of MOAS II, developed in G2 real-time expert system shell for the high-pressure preheaters of the NORS process, was tested against a variety of transient scenarios, including failures of control valves and sensors, and leakage of tubes of the preheaters. These tests showed that MOAS II successfully carried out its intended functions, i.e., quickly recognizing an occurring disturbance, correctly diagnosing its cause, and presenting advice on its control to the operator. The insights gained during the implementation are discussed

  5. Listening to Whispers of Ripple: Linking Wallets and Deanonymizing Transactions in the Ripple Network

    OpenAIRE

    Moreno-Sanchez Pedro; Zafar Muhammad Bilal; Kate Aniket

    2016-01-01

    The decentralized I owe you (IOU) transaction network Ripple is gaining prominence as a fast, low-cost and efficient method for performing same and cross-currency payments. Ripple keeps track of IOU credit its users have granted to their business partners or friends, and settles transactions between two connected Ripple wallets by appropriately changing credit values on the connecting paths. Similar to cryptocurrencies such as Bitcoin, while the ownership of the wallets is implicitly pseudony...

  6. Youngest reported radiocarbon age of a moa (Aves : Dinornithiformes) dated from a natural site in New Zealand

    International Nuclear Information System (INIS)

    Rawlence, N.J.; Cooper, A.

    2013-01-01

    The extinction date of the giant flightless New Zealand ratite bird, the crested moa (Pachyornis australis), is of considerable interest because the youngest verified remains are dated to the Pleistocene–Holocene transition c. 10,000 yr BP, which was characterised by severe climatic and habitat change, and are considerably earlier than the late Holocene extinctions of the other eight moa species. Analysis of a partial crested moa skeleton (NMNZ S23569) from Castle Keep Entrance, Bulmer Cave System, Mount Owen, South Island, generated a radiocarbon date of 564±26 yr BP (544-508 cal yr BP; 95.4% AD 1396-1442). As a result the Bulmer Cave specimen represents the youngest moa yet found from a natural site in New Zealand. Combined with additional crested moa remains dated to the late Holocene from Cheops Cave (Mount Arthur) and Magnesite Quarry (Cobb Valley), this indicates that crested moa did not go extinct during the Pleistocene–Holocene transition but survived until after Polynesian colonisation in c. AD 1280. The new radiocarbon dates reported here have important implications for the timing of moa extinction and the late survival of moa in alpine areas of New Zealand. (author). 47 refs., 2 figs., 1 tab.

  7. Impact of Attitude: The Ripple Effect.

    Science.gov (United States)

    Bullen, Robert

    1983-01-01

    Describes the potential ripple effect of a principal's mercurial personality and poor interpersonal skills on teachers, students, families, and the community. Suggests effective personnel selection methods to enhance the chances of employing desirable principals. (SB)

  8. Ripple enhanced transport of suprathermal alpha particles

    International Nuclear Information System (INIS)

    Tani, K.; Takizuka, T.; Azumi, M.

    1986-01-01

    The ripple enhanced transport of suprathermal alpha particles has been studied by the newly developed Monte-Carlo code in which the motion of banana orbit in a toroidal field ripple is described by a mapping method. The existence of ripple-resonance diffusion has been confirmed numerically. We have developed another new code in which the radial displacement of banana orbit is given by the diffusion coefficients from the mapping code or the orbit following Monte-Carlo code. The ripple loss of α particles during slowing down has been estimated by the mapping model code as well as the diffusion model code. From the comparison of the results with those from the orbit-following Monte-Carlo code, it has been found that all of them agree very well. (author)

  9. Constrained ripple optimization of Tokamak bundle divertors

    International Nuclear Information System (INIS)

    Hively, L.M.; Rome, J.A.; Lynch, V.E.; Lyon, J.F.; Fowler, R.H.; Peng, Y-K.M.; Dory, R.A.

    1983-02-01

    Magnetic field ripple from a tokamak bundle divertor is localized to a small toroidal sector and must be treated differently from the usual (distributed) toroidal field (TF) coil ripple. Generally, in a tokamak with an unoptimized divertor design, all of the banana-trapped fast ions are quickly lost due to banana drift diffusion or to trapping between the 1/R variation in absolute value vector B ω B and local field maxima due to the divertor. A computer code has been written to optimize automatically on-axis ripple subject to these constraints, while varying up to nine design parameters. Optimum configurations have low on-axis ripple ( 0 ) are lost. However, because finite-sized TF coils have not been used in this study, the flux bundle is not expanded

  10. Cryptocurrency market making in the Ripple network

    OpenAIRE

    Brezigar, Jakob

    2016-01-01

    Market maker provides counterparty for buyers and sellers of financial instruments in transaction settlement. Market makers quote the bid price and the ask price at the same time. This price setting process is called market making. This thesis covers theoretical and practical basis for implementation of autonomous market making algorithm for a promising cryptocurrency market called Ripple. We summarize market making theory, how Ripple cryptocurrency protocol works and how price formation proc...

  11. Moa (Aves : Dinornithiformes) nesting material from rockshelters in the semi-arid interior of South Island, New Zealand

    International Nuclear Information System (INIS)

    Wood, J.R.

    2008-01-01

    The first descriptions of plant remains from the nests of extinct moa (Aves: Dinornithiformes) are presented. The samples of desiccated nesting material were collected during excavation of Holocene sediments within five rockshelters in semi-arid regions of southern South Island, New Zealand, between 1964 and 2006. The nesting materials were attributed to moa on the basis of associated moa coprolites, feathers and eggshell fragments. The nesting material includes short, clipped twigs from a range of locally available tree, shrub and liane species. These twig clippings show a size distribution similar to those recorded from moa gizzard content samples. Other nesting material from the sites includes longer twigs and fragments of bark. The plant materials suggest general similarities between the nests of moa and those of the extant Australasian ratites, emu (Dromaius novaehollandiae) and cassowary (Casuarius spp.). (author). 37 refs., 7 figs., 1 tab

  12. Structural basis of thermal stability of the tungsten cofactor synthesis protein MoaB from Pyrococcus furiosus.

    Directory of Open Access Journals (Sweden)

    Nastassia Havarushka

    Full Text Available Molybdenum and tungsten cofactors share a similar pterin-based scaffold, which hosts an ene-dithiolate function being essential for the coordination of either molybdenum or tungsten. The biosynthesis of both cofactors involves a multistep pathway, which ends with the activation of the metal binding pterin (MPT by adenylylation before the respective metal is incorporated. In the hyperthermophilic organism Pyrococcus furiosus, the hexameric protein MoaB (PfuMoaB has been shown to catalyse MPT-adenylylation. Here we determined the crystal structure of PfuMoaB at 2.5 Å resolution and identified key residues of α3-helix mediating hexamer formation. Given that PfuMoaB homologues from mesophilic organisms form trimers, we investigated the impact on PfuMoaB hexamerization on thermal stability and activity. Using structure-guided mutagenesis, we successfully disrupted the hexamer interface in PfuMoaB. The resulting PfuMoaB-H3 variant formed monomers, dimers and trimers as determined by size exclusion chromatography. Circular dichroism spectroscopy as well as chemical cross-linking coupled to mass spectrometry confirmed a wild-type-like fold of the protomers as well as inter-subunits contacts. The melting temperature of PfuMoaB-H3 was found to be reduced by more than 15 °C as determined by differential scanning calorimetry, thus demonstrating hexamerization as key determinant for PfuMoaB thermal stability. Remarkably, while a loss of activity at temperatures higher than 50 °C was observed in the PfuMoaB-H3 variant, at lower temperatures, we determined a significantly increased catalytic activity. The latter suggests a gain in conformational flexibility caused by the disruption of the hexamerization interface.

  13. Listening to Whispers of Ripple: Linking Wallets and Deanonymizing Transactions in the Ripple Network

    Directory of Open Access Journals (Sweden)

    Moreno-Sanchez Pedro

    2016-10-01

    Full Text Available The decentralized I owe you (IOU transaction network Ripple is gaining prominence as a fast, low-cost and efficient method for performing same and cross-currency payments. Ripple keeps track of IOU credit its users have granted to their business partners or friends, and settles transactions between two connected Ripple wallets by appropriately changing credit values on the connecting paths. Similar to cryptocurrencies such as Bitcoin, while the ownership of the wallets is implicitly pseudonymous in Ripple, IOU credit links and transaction flows between wallets are publicly available in an online ledger. In this paper, we present the first thorough study that analyzes this globally visible log and characterizes the privacy issues with the current Ripple network. In particular, we define two novel heuristics and perform heuristic clustering to group wallets based on observations on the Ripple network graph. We then propose reidentification mechanisms to deanonymize the operators of those clusters and show how to reconstruct the financial activities of deanonymized Ripple wallets. Our analysis motivates the need for better privacy-preserving payment mechanisms for Ripple and characterizes the privacy challenges faced by the emerging credit networks.

  14. The evolutionary history of the extinct ratite moa and New Zealand Neogene paleogeography

    DEFF Research Database (Denmark)

    Bunce, M; Worthy, T H; Phillips, M J

    2009-01-01

    The ratite moa (Aves: Dinornithiformes) were a speciose group of massive graviportal avian herbivores that dominated the New Zealand (NZ) ecosystem until their extinction approximately 600 years ago. The phylogeny and evolutionary history of this morphologically diverse order has remained controv...

  15. A particle model of rolling grain ripples under waves

    DEFF Research Database (Denmark)

    Andersen, Ken Haste

    2001-01-01

    A simple model for the formation of rolling grain ripples on a flat sand bed by the oscillatory flow generated by a surface wave is presented. An equation of motion is derived for the individual ripples, seen as "particles," on the otherwise flat bed. The model accounts for the initial appearance...... of the ripples, the subsequent coarsening of the ripples, and the final equilibrium state. The model is related to the physical parameters of the problem, and an analytical approximation for the equilibrium spacing of the ripples is developed. It is found that the spacing between the ripples scales...

  16. Age of North Island giant moa (Dinornis novaezealandiae) bones found on the forest floor in the Ruahine Range

    International Nuclear Information System (INIS)

    Wood, J.R.; Wilmshurst, J.M.

    2013-01-01

    During the nineteenth century, multiple discoveries of moa bones lying on the ground surface in exposed situations generated debate about the recentness of moa extinction. Subsequently, clearance of land for agricultural purposes has probably resulted in the destruction of many surface moa bones and such finds are now rare. The recent discovery of a pair of tibiotarsi from a North Island giant moa (Dinornis novaezealandiae) lying on the forest floor at Aorangi Awarua, Ruahine Range, has allowed the age of two surface moa bones to be tested. Both tibiotarsi were AMS radiocarbon dated and returned ages of 681±28 and 721±29 14C years BP. The 2σ calibrated ranges are statistically the same age and suggest that the bones are from one bird that died sometime between AD 1286 and 1390. Although the bones post-date human settlement of New Zealand, they are not anomalously recent. The results show that, given favourable environmental conditions, moa bones can persist in exposed situations for long periods, and do not necessarily reflect survival of moa into relatively recent times. (author)

  17. Cochlear implant users' spectral ripple resolution.

    Science.gov (United States)

    Jeon, Eun Kyung; Turner, Christopher W; Karsten, Sue A; Henry, Belinda A; Gantz, Bruce J

    2015-10-01

    This study revisits the issue of the spectral ripple resolution abilities of cochlear implant (CI) users. The spectral ripple resolution of recently implanted CI recipients (implanted during the last 10 years) were compared to those of CI recipients implanted 15 to 20 years ago, as well as those of normal-hearing and hearing-impaired listeners from previously published data from Henry, Turner, and Behrens [J. Acoust. Soc. Am. 118, 1111-1121 (2005)]. More recently, implanted CI recipients showed significantly better spectral ripple resolution. There is no significant difference in spectral ripple resolution for these recently implanted subjects compared to hearing-impaired (acoustic) listeners. The more recently implanted CI users had significantly better pre-operative speech perception than previously reported CI users. These better pre-operative speech perception scores in CI users from the current study may be related to better performance on the spectral ripple discrimination task; however, other possible factors such as improvements in internal and external devices cannot be excluded.

  18. Beamforming applied to surface EEG improves ripple visibility.

    Science.gov (United States)

    van Klink, Nicole; Mol, Arjen; Ferrier, Cyrille; Hillebrand, Arjan; Huiskamp, Geertjan; Zijlmans, Maeike

    2018-01-01

    Surface EEG can show epileptiform ripples in people with focal epilepsy, but identification is impeded by the low signal-to-noise ratio of the electrode recordings. We used beamformer-based virtual electrodes to improve ripple identification. We analyzed ten minutes of interictal EEG of nine patients with refractory focal epilepsy. EEGs with more than 60 channels and 20 spikes were included. We computed ∼79 virtual electrodes using a scalar beamformer and marked ripples (80-250 Hz) co-occurring with spikes in physical and virtual electrodes. Ripple numbers in physical and virtual electrodes were compared, and sensitivity and specificity of ripples for the region of interest (ROI; based on clinical information) were determined. Five patients had ripples in the physical electrodes and eight in the virtual electrodes, with more ripples in virtual than in physical electrodes (101 vs. 57, p = .007). Ripples in virtual electrodes predicted the ROI better than physical electrodes (AUC 0.65 vs. 0.56, p = .03). Beamforming increased ripple visibility in surface EEG. Virtual ripples predicted the ROI better than physical ripples, although sensitivity was still poor. Beamforming can facilitate ripple identification in EEG. Ripple localization needs to be improved to enable its use for presurgical evaluation in people with epilepsy. Copyright © 2017 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.

  19. Molecular structure of the lecithin ripple phase

    Science.gov (United States)

    de Vries, Alex H.; Yefimov, Serge; Mark, Alan E.; Marrink, Siewert J.

    2005-04-01

    Molecular dynamics simulations of lecithin lipid bilayers in water as they are cooled from the liquid crystalline phase show the spontaneous formation of rippled bilayers. The ripple consists of two domains of different length and orientation, connected by a kink. The organization of the lipids in one domain of the ripple is found to be that of a splayed gel; in the other domain the lipids are gel-like and fully interdigitated. In the concave part of the kink region between the domains the lipids are disordered. The results are consistent with the experimental information available and provide an atomic-level model that may be tested by further experiments. molecular dynamics simulation | structural model

  20. Rotation and neoclassical ripple transport in ITER

    Science.gov (United States)

    Paul, E. J.; Landreman, M.; Poli, F. M.; Spong, D. A.; Smith, H. M.; Dorland, W.

    2017-11-01

    Neoclassical transport in the presence of non-axisymmetric magnetic fields causes a toroidal torque known as neoclassical toroidal viscosity (NTV). The toroidal symmetry of ITER will be broken by the finite number of toroidal field coils and by test blanket modules (TBMs). The addition of ferritic inserts (FIs) will decrease the magnitude of the toroidal field ripple. 3D magnetic equilibria in the presence of toroidal field ripple and ferromagnetic structures are calculated for an ITER steady-state scenario using the variational moments equilibrium code (VMEC). Neoclassical transport quantities in the presence of these error fields are calculated using the stellarator Fokker-Planck iterative neoclassical conservative solver (SFINCS). These calculations fully account for E r , flux surface shaping, multiple species, magnitude of ripple, and collisionality rather than applying approximate analytic NTV formulae. As NTV is a complicated nonlinear function of E r , we study its behavior over a plausible range of E r . We estimate the toroidal flow, and hence E r , using a semi-analytic turbulent intrinsic rotation model and NUBEAM calculations of neutral beam torque. The NTV from the \\vert{n}\\vert = 18 ripple dominates that from lower n perturbations of the TBMs. With the inclusion of FIs, the magnitude of NTV torque is reduced by about 75% near the edge. We present comparisons of several models of tangential magnetic drifts, finding appreciable differences only for superbanana-plateau transport at small E r . We find the scaling of calculated NTV torque with ripple magnitude to indicate that ripple-trapping may be a significant mechanism for NTV in ITER. The computed NTV torque without ferritic components is comparable in magnitude to the NBI and intrinsic turbulent torques and will likely damp rotation, but the NTV torque is significantly reduced by the planned ferritic inserts.

  1. Origin of the two scales of wind ripples on Mars

    Science.gov (United States)

    Lapotre, M. G. A.; Ewing, R. C.; Lamb, M. P.; Fischer, W. W.; Grotzinger, J. P.; Rubin, D. M.; Lewis, K. W.; Ballard, M.; Day, M. D.; Gupta, S.; Banham, S.; Bridges, N.; Des Marais, D. J.; Fraeman, A. A.; Grant, J. A., III; Ming, D. W.; Mischna, M.; Rice, M. S.; Sumner, D. Y.; Vasavada, A. R.; Yingst, R. A.

    2016-12-01

    Earth's sandy deserts host two main types of bedforms - decimeter-scale ripples and larger dunes. Years of orbital observations on Mars also confirmed the existence of two modes of active eolian bedforms - meter-scale ripples, and dunes. By analogy to terrestrial ripples, which are thought to form from a grain mechanism, it was hypothesized that large martian ripples also formed from grain impacts, but spaced further apart due to elongated saltation trajectories from the lower martian gravity and different atmospheric properties. However, the Curiosity rover recently documented the coexistence of three scales of bedforms in Gale crater. Because a grain impact mechanism cannot readily explain two distinct and coeval ripple modes in similar sand sizes, a new mechanism seems to be required to explain one of the scales of ripples. Small ripples are most similar to Earth's impact ripples, with straight crests and subdued profiles. In contrast, large martian ripples are sinuous and asymmetric, with lee slopes dominated by grain flows and grainfall deposits. Thus, large martian ripples resemble current ripples formed underwater on Earth, suggesting that they may form from a fluid-drag mechanism. To test this hypothesis, we develop a scaling relation to predict the spacing of fluid-drag ripples from an extensive flume data compilation. The size of large martian ripples is predicted by our scaling relation when adjusted for martian atmospheric properties. Specifically, we propose that the wavelength of martian wind-drag ripples arises from the high kinematic viscosity of the low-density atmosphere. Because fluid density controls drag-ripple size, our scaling relation can help constrain paleoatmospheric density from wind-drag ripple stratification.

  2. Beam-ripple monitor with secondary electrons

    International Nuclear Information System (INIS)

    Sato, Shinji; Kanazawa, Mitsutaka; Noda, Koji; Takada, Eiichi; Komiyama, Akihito; Ichinohe, Ken-ichi; Sano, Yoshinobu

    1997-01-01

    To replace the scintillation-ripple monitor, we have developed a new monitor with a smaller destructive effect on the beam. In this monitor, we use secondary electrons emitted from an aluminum foil with a thickness of 2 μm. The signals of secondary electrons are amplified by an electron multiplier having a maximum gain of 10 6 . By using the new monitor, we could clearly observe the beam ripple with a beam intensity of 3.6x10 8 pps (particle per second). This monitor can also be used as an intensity monitor in the range of 10 4 - 10 9 pps. (author)

  3. Ripple Ring Basins on Ganymede and Callisto

    Science.gov (United States)

    Croft, S. K.

    1985-01-01

    The unusual morphology of the Valhalla multiple or ripple-ring basin in Callisto was totally unexpected in light of the morphologies of large impact structures on the terrestrial planets. Two other ripple-ring basins (RRB's), Asgard and a smaller structure near the crater Adlinda are also described. Several additional RRB's were found on Callisto, an example of which is shown. A previously unrecognized RRB on Ganymede was also found. An image and geologic sketch map of this RRB are shown. Morphometric and positional data for all known RRB's are given.

  4. Optimum geometry for torque ripple minimization of switched reluctance motors

    NARCIS (Netherlands)

    Sahin, F.; Ertan, H.B.; Leblebicioglu, K.

    2000-01-01

    For switched reluctance motors, one of the major problems is torque ripple which causes increased undesirable acoustic noise and possibly speed ripple. This paper describes an approach to determine optimum magnetic circuit parameters to minimize low speed torque ripple for such motors. The

  5. Dynamical models for sand ripples beneath surface waves

    DEFF Research Database (Denmark)

    Andersen, Ken Haste; Chabanol, M.-L.; v. Hecke, M.

    2001-01-01

    We introduce order parameter models for describing the dynamics of sand ripple patterns under oscillatory flow. A crucial ingredient of these models is the mass transport between adjacent ripples, which we obtain from detailed numerical simulations for a range of ripple sizes. Using this mass tra...

  6. Were moas really hunted to extinction in less than 100 years?

    International Nuclear Information System (INIS)

    Wilkes, O.

    2000-01-01

    Three months ago New Zealand archaeologists were surprised to read in their daily newspapers that moas had been eaten to extinction by Maori moahunters in less than 100 years. The claim had been made in the US journal 'Science' by Richard Holdaway, formerly with Canterbury University, and Chris Jacomb of Canterbury Museum. It seems to me there are a number of weaknesses in the original paper, which should have been thrashed out locally before going for prestigious exposure overseas. The rapid extinction claim is based first of all on a 'Leslie matrix model' of moa population dynamics, and secondly on some recent carbon dates of a single archaeological site, Monck's Cave, near Christchurch. 21 refs

  7. Evaluación y cartografiado del peligro por deslizamientos en el municipio de Moa

    Directory of Open Access Journals (Sweden)

    Yexenia Viltres-Milán

    2014-10-01

    Full Text Available La ocurrencia de deslizamientos en el municipio de Moa genera situaciones de amenaza a la industria, las comunidades, las actividades socio-económicas y al medio ambiente. El presente trabajo tuvo el propósito de evaluar y cartografiar, aplicando los Sistemas de Información Geográfica (SIG, el peligro por deslizamiento en el municipio. Como basamento metodológico se utilizó la guía para el estudio de peligro, vulnerabilidad y riesgo por deslizamientos del terreno, elaborada por el Grupo Nacional de Gestión de Riesgos, del año 2012. El resultado fue el mapa de peligrosidad total por deslizamiento del municipio de Moa, a escala 1: 100 000, el cual constituye una herramienta más de gestión y reducción del riesgo en el ordenamiento territorial

  8. A Biatrial Myxoma with Triple Ripples.

    Science.gov (United States)

    Barik, Ramachandra

    2018-01-01

    Cardiac myxoma is a benign tumor, but it is known for its space-occupying effect at the site of origin and frequent systemic embolization. This case report highlights a biatrial myxoma of interatrial septum who presented with significant tricuspid valve regurgitation, atrial fibrillation, and cardioembolic stroke of the left parietal lobe, i.e., a biatrial myxoma with triple ripples.

  9. The Ripple Tank: Management and Observation

    Science.gov (United States)

    Auty, Geoff

    2017-01-01

    This overview is intended to help colleagues achieve successful and satisfying observations using a ripple tank. There are many observations to consider that can effectively illustrate reflection, refraction, interference and diffraction, but the most important consideration is to make every effort to enable students to see the effects we want…

  10. Recording Images Observed Using Ripple Tanks

    Science.gov (United States)

    Auty, Geoff

    2018-01-01

    Diagrams and photographs (or computer simulations) should not replace effective observations of the wave properties that can be illustrated using a ripple tank, but they can provide support when discussing and revising what has been observed. This article explains and illustrates a route towards successful photography, which is much easier with…

  11. Measuring Social Capital Change Using Ripple Mapping

    Science.gov (United States)

    Baker, Barbara; Johannes, Elaine M.

    2013-01-01

    This article provides a detailed description of how to implement a ripple mapping activity to assess youth program effects on community capital and concludes with examples from Maine and Kansas. The maps lead to group reflection on project outcomes and further research and evaluation questions for group members. The results from five Maine…

  12. Implementation of an integrated on-line process surveillance and diagnostic system at the Halden reactor project: MOAS

    International Nuclear Information System (INIS)

    Kim, I.S.; Grini, R.-E.; Nilsen, S.

    2001-01-01

    MOAS is an integrated on-line process surveillance and diagnostic system that uses several different models for knowledge acquisition and diagnostic reasoning, such as goal-tree success-tree model, process monitor trees, and sensor failure diagnosis trees. Within these models, the knowledge of the process and its operation, including deep knowledge, like mass balance or controller algorithm, is incorporated. During an extensive review, made as part of the integrated diagnosis system project of the Halden reactor project, MOAS (Maryland Operator Advisory System) was identified as one of the most thorough systems developed thus far. MOAS encompasses diverse functional aspects that are required for an effective process disturbance management: (1) intelligent process monitoring and alarming, (2) on-line sensor data validation and sensor failure diagnosis, (3) on-line hardware (besides sensors) failure diagnosis, and (4) real-time corrective measure synthesis. The MOAS methodology was used for the NORS (Nokia Research Simulator) process at the Halden man-machine laboratory HAMMLAB of the OECD Halden reactor project. The performance tests of MOAS, implemented in G2 real-time expert system shell, show that MOAS successfully carries out its intended functions, i.e. quickly recognizing an occurring disturbance, correctly diagnosing its cause, and presenting advice on its control to the operator. The lessons learned and insights gained during the implementation and performance tests also are discussed

  13. Current-ripple effect on superconductive dc critical current measurements

    International Nuclear Information System (INIS)

    Goodrich, L.F.; Bray, S.L.; Clark, A.F.

    1988-01-01

    The effect of sample-current power-supply ripple on dc critical current measurement in multifilamentary NbTi superconductors was evaluated. In general the ripple in a current supply became more significant above 500 A because effective filtering was hard to achieve. Ripple also caused noise at the input of the voltmeter used for the measurements. The quantitative effect of current ripple was studied using a battery current supply modified to allow the creation of ripple current with variable frequency and amplitude. Problems common to all large-conductor critical current measurements are discussed

  14. Generalized ripple-banana transport in a tokamak

    International Nuclear Information System (INIS)

    Yushmanov, P.N.

    1983-01-01

    The paper considers the transport of banana particles in a rippled magnetic field over the entire energy range. It is shown that all familiar regimes of ripple transport - ripple-plateau, banana-drift and stochastic - can be described in a unified manner. The general expression obtained for the rippled fluxes of banana particles describes, apart from the already familiar regimes, also the as yet unstudied energy region between the drift and stochastic regimes. A generalized ripple-banana thermal conductivity coefficient, chisub(i)sup(RB), is calculated. (author)

  15. Mesopontine median raphe regulates hippocampal ripple oscillation and memory consolidation.

    Science.gov (United States)

    Wang, Dong V; Yau, Hau-Jie; Broker, Carl J; Tsou, Jen-Hui; Bonci, Antonello; Ikemoto, Satoshi

    2015-05-01

    Sharp wave-associated field oscillations (∼200 Hz) of the hippocampus, referred to as ripples, are believed to be important for consolidation of explicit memory. Little is known about how ripples are regulated by other brain regions. We found that the median raphe region (MnR) is important for regulating hippocampal ripple activity and memory consolidation. We performed in vivo simultaneous recording in the MnR and hippocampus of mice and found that, when a group of MnR neurons was active, ripples were absent. Consistently, optogenetic stimulation of MnR neurons suppressed ripple activity and inhibition of these neurons increased ripple activity. Notably, using a fear conditioning procedure, we found that photostimulation of MnR neurons interfered with memory consolidation. Our results demonstrate a critical role of the MnR in regulating ripples and memory consolidation.

  16. High-resolution coproecology: using coprolites to reconstruct the habits and habitats of New Zealand's extinct upland moa (Megalapteryx didinus.

    Directory of Open Access Journals (Sweden)

    Jamie R Wood

    Full Text Available Knowledge about the diet and ecology of extinct herbivores has important implications for understanding the evolution of plant defence structures, establishing the influences of herbivory on past plant community structure and composition, and identifying pollination and seed dispersal syndromes. The flightless ratite moa (Aves: Dinornithiformes were New Zealand's largest herbivores prior to their extinction soon after initial human settlement. Here we contribute to the knowledge of moa diet and ecology by reporting the results of a multidisciplinary study of 35 coprolites from a subalpine cave (Euphrates Cave on the South Island of New Zealand. Ancient DNA analysis and radiocarbon dating revealed the coprolites were deposited by the extinct upland moa (Megalapteryx didinus, and span from at least 6,368±31 until 694±30 (14C years BP; the approximate time of their extinction. Using pollen, plant macrofossil, and ancient DNA analyses, we identified at least 67 plant taxa from the coprolites, including the first evidence that moa fed on the nectar-rich flowers of New Zealand flax (Phormium and tree fuchsia (Fuchsia excorticata. The plant assemblage from the coprolites reflects a highly-generalist feeding ecology for upland moa, including browsing and grazing across the full range of locally available habitats (spanning southern beech (Nothofagus forest to tussock (Chionochloa grassland. Intact seeds in the coprolites indicate that upland moa may have been important dispersal agents for several plant taxa. Plant taxa with putative anti-browse adaptations were also identified in the coprolites. Clusters of coprolites (based on pollen assemblages, moa haplotypes, and radiocarbon dates, probably reflect specimens deposited at the same time by individual birds, and reveal the necessity of suitably large sample sizes in coprolite studies to overcome potential biases in diet interpretation.

  17. Rippled beam free electron laser amplifier

    Science.gov (United States)

    Carlsten, Bruce E.

    1999-01-01

    A free electron laser amplifier provides a scalloping annular electron beam that interacts with the axial electric field of a TM.sub.0n mode. A waveguide defines an axial centerline and, a solenoid arranged about the waveguide produces an axial constant magnetic field within the waveguide. An electron beam source outputs a annular electron beam that interacts with the axial magnetic field to have an equilibrium radius and a ripple radius component having a variable radius with a ripple period along the axial centerline. An rf source outputs an axial electric field that propagates within the waveguide coaxial with the electron beam and has a radial mode that interacts at the electron beam at the equilibrium radius component of the electron beam.

  18. CBA main magnet power supply ripple reduction

    International Nuclear Information System (INIS)

    Bagley, G.; Edwards, R.J.

    1983-01-01

    The preliminary results of a development program to minimize beam perturbation resulting from ripple current generated by the CBA Main Magnet Power Supply are presented. The assessment of the magnitude and causes of the ripple generated led to a modification of the SCR Gate Driver and the addition of a bandpass amplifier correction loop which gave significant improvement. A description of the changes made and the results obtained are included. A second design approach was developed in which the timing of the SCR gate pulses is directly determined by a VCO. The results reported with this VCO Loop indicate superior performance particularly at frequencies below 60 Hz. A shunt transistor regulator design is proposed to minimize higher SCR switching frequency harmonics

  19. Runaway-ripple interaction in Tokamaks

    International Nuclear Information System (INIS)

    Laurent, L.; Rax, J.M.

    1989-08-01

    Two approaches of the interaction between runaway electrons and the ripple field, in tokamaks, are discussed. The first approach considers the resonance effect as an intense cyclotron heating of the electrons, by the ripple field, in the guiding center frame of the fast particles. In the second approach, an Hamiltonian formalism is used. A criterion for the onset of chaotic behavior and the results are given. A new universal instability of the runaway population in tokamak configuration is found. When combined with cyclotron losses one of its major consequence is to act as an effective slowing down mechanism preventing the free fall acceleration toward the synchrotron limit. This configuration allows the explanation of some experimental results of Tore Supra and Textor

  20. Spectral Ripple Discrimination in Normal Hearing Infants

    Science.gov (United States)

    Horn, David L.; Won, Jong Ho; Rubinstein, Jay T.; Werner, Lynne A.

    2016-01-01

    Objectives Spectral resolution is a correlate of open-set speech understanding in post-lingually deaf adults as well as pre-lingually deaf children who use cochlear implants (CIs). In order to apply measures of spectral resolution to assess device efficacy in younger CI users, it is necessary to understand how spectral resolution develops in NH children. In this study, spectral ripple discrimination (SRD) was used to measure listeners’ sensitivity to a shift in phase of the spectral envelope of a broadband noise. Both resolution of peak to peak location (frequency resolution) and peak to trough intensity (across-channel intensity resolution) are required for SRD. Design SRD was measured as the highest ripple density (in ripples per octave) for which a listener could discriminate a 90 degree shift in phase of the sinusoidally-modulated amplitude spectrum. A 2X3 between subjects design was used to assess the effects of age (7-month-old infants versus adults) and ripple peak/trough “depth” (10, 13, and 20 dB) on SRD in normal hearing listeners (Experiment 1). In Experiment 2, SRD thresholds in the same age groups were compared using a task in which ripple starting phases were randomized across trials to obscure within-channel intensity cues. In Experiment 3, the randomized starting phase method was used to measure SRD as a function of age (3-month-old infants, 7-month-old infants, and young adults) and ripple depth (10 and 20 dB in repeated measures design). Results In Experiment 1, there was a significant interaction between age and ripple depth. The Infant SRDs were significantly poorer than the adult SRDs at 10 and 13 dB ripple depths but adult-like at 20 dB depth. This result is consistent with immature across-channel intensity resolution. In contrast, the trajectory of SRD as a function of depth was steeper for infants than adults suggesting that frequency resolution was better in infants than adults. However, in Experiment 2 infant performance was

  1. Reduction of ripple voltage in a dynamitron

    International Nuclear Information System (INIS)

    Langsdorf, A. Jr.

    1982-01-01

    We determined that a precise neutralization of the RF ripple voltage on the high-voltage terminal of a Dynamitron has previously been prevented by a nonegligible phase shift of RF currents in the two halves of the approx. 100-kHz class C oscillator tank circuit, which is actually constituted of two slightly unequal high-Q coupled circuits because it has two ground points: the inescapable center-tap-ground in the capacitive legs and a center-tap-ground lead to the induction coil. The latter is needed to prevent damage by flashover transients; equivalent to its removal was the adjusting of RF ground return current to a null by aid of a current transformer on this lead and the suitable adjusting of trimmer capacitance. While the phase shift was thus held to a null, the actual ripple amplitude on the hv terminal was minimized by adjusting additional trimmer capacitances installed in the terminal of the machine. Then p/p 100-kHz ripple at 2-MV dc output was reduced to about 50V and RMS resolution by (p,#betta#) resonance threshold data near 1 MV was about 250 V. The limit to resolution has various causes including mechanical vibrations and unbalanced harmonics of the RF

  2. Comparing the force ripple during asynchronous and conventional stimulation.

    Science.gov (United States)

    Downey, Ryan J; Tate, Mark; Kawai, Hiroyuki; Dixon, Warren E

    2014-10-01

    Asynchronous stimulation has been shown to reduce fatigue during electrical stimulation; however, it may also exhibit a force ripple. We quantified the ripple during asynchronous and conventional single-channel transcutaneous stimulation across a range of stimulation frequencies. The ripple was measured during 5 asynchronous stimulation protocols, 2 conventional stimulation protocols, and 3 volitional contractions in 12 healthy individuals. Conventional 40 Hz and asynchronous 16 Hz stimulation were found to induce contractions that were as smooth as volitional contractions. Asynchronous 8, 10, and 12 Hz stimulation induced contractions with significant ripple. Lower stimulation frequencies can reduce fatigue; however, they may also lead to increased ripple. Future efforts should study the relationship between force ripple and the smoothness of the evoked movements in addition to the relationship between stimulation frequency and NMES-induced fatigue to elucidate an optimal stimulation frequency for asynchronous stimulation. © 2014 Wiley Periodicals, Inc.

  3. Automatic detection and visualisation of MEG ripple oscillations in epilepsy

    Directory of Open Access Journals (Sweden)

    Nicole van Klink

    2017-01-01

    Full Text Available High frequency oscillations (HFOs, 80–500 Hz in invasive EEG are a biomarker for the epileptic focus. Ripples (80–250 Hz have also been identified in non-invasive MEG, yet detection is impeded by noise, their low occurrence rates, and the workload of visual analysis. We propose a method that identifies ripples in MEG through noise reduction, beamforming and automatic detection with minimal user effort. We analysed 15 min of presurgical resting-state interictal MEG data of 25 patients with epilepsy. The MEG signal-to-noise was improved by using a cross-validation signal space separation method, and by calculating ~2400 beamformer-based virtual sensors in the grey matter. Ripples in these sensors were automatically detected by an algorithm optimized for MEG. A small subset of the identified ripples was visually checked. Ripple locations were compared with MEG spike dipole locations and the resection area if available. Running the automatic detection algorithm resulted in on average 905 ripples per patient, of which on average 148 ripples were visually reviewed. Reviewing took approximately 5 min per patient, and identified ripples in 16 out of 25 patients. In 14 patients the ripple locations showed good or moderate concordance with the MEG spikes. For six out of eight patients who had surgery, the ripple locations showed concordance with the resection area: 4/5 with good outcome and 2/3 with poor outcome. Automatic ripple detection in beamformer-based virtual sensors is a feasible non-invasive tool for the identification of ripples in MEG. Our method requires minimal user effort and is easily applicable in a clinical setting.

  4. PathShuffle: Credit Mixing and Anonymous Payments for Ripple

    OpenAIRE

    Moreno-Sanchez Pedro; Ruffing Tim; Kate Aniket

    2017-01-01

    The I owe you (IOU) credit network Ripple is one of the most prominent alternatives in the burgeoning field of decentralized payment systems. Ripple’s path-based transactions set it apart from cryptocurrencies such as Bitcoin. Its pseudonymous nature, while still maintaining some regulatory capabilities, has motivated several financial institutions across the world to use Ripple for processing their daily transactions. Nevertheless, with its public ledger, a credit network such as Ripple is n...

  5. MOA: Magnetic Field Oscillating Amplified Thruster and its Application for Nuclear Electric and Thermal Propulsion

    International Nuclear Information System (INIS)

    Frischauf, Norbert; Hettmer, Manfred; Grassauer, Andreas; Bartusch, Tobias; Koudelka, Otto

    2006-01-01

    More than 60 years after the later Nobel laureate Hannes Alfven had published a letter stating that oscillating magnetic fields can accelerate ionised matter via magneto-hydrodynamic interactions in a wave like fashion, the technical implementation of Alfven waves for propulsive purposes has been proposed, patented and examined for the first time by a group of inventors. The name of the concept, utilising Alfven waves to accelerate ionised matter for propulsive purposes, is MOA - Magnetic field Oscillating Amplified thruster. Alfven waves are generated by making use of two coils, one being permanently powered and serving also as magnetic nozzle, the other one being switched on and off in a cyclic way, deforming the field lines of the overall system. It is this deformation that generates Alfven waves, which are in the next step used to transport and compress the propulsive medium, in theory leading to a propulsion system with a much higher performance than any other electric propulsion system. Based on computer simulations, which were conducted to get a first estimate on the performance of the system, MOA is a highly flexible propulsion system, whose performance parameters might easily be adapted, by changing the mass flow and/or the power level. As such the system is capable to deliver a maximum specific impulse of 13116 s (12.87 mN) at a power level of 11.16 kW, using Xe as propellant, but can also be attuned to provide a thrust of 236.5 mN (2411 s) at 6.15 kW of power. While space propulsion is expected to be the prime application for MOA and is supported by numerous applications such as Solar and/or Nuclear Electric Propulsion or even as an 'afterburner system' for Nuclear Thermal Propulsion, other terrestrial applications can be thought of as well, making the system highly suited for a common space-terrestrial application research and utilisation strategy. (authors)

  6. The MOA thruster. A high performance plasma accelerator for nuclear power and propulsion applications

    International Nuclear Information System (INIS)

    Frischauf, Norbert; Hettmer, Manfred; Grassauer, Andreas; Bartusch, Tobias; Koudelka, Otto

    2009-01-01

    More than 60 years after the late Nobel laureate Hannes Alfven had published a letter stating that oscillating magnetic fields can accelerate ionised matter via magneto-hydrodynamic interactions in a wave like fashion, the technical implementation of Alfven waves for propulsive purposes has been proposed, patented and examined for the first time by a group of inventors. The name of the concept, utilising Alfven waves to accelerate ionised matter for propulsive purposes, is MOA - Magnetic field Oscillating Amplified thruster. Alfven waves are generated by making use of two coils, one being permanently powered and serving also as magnetic nozzle, the other one being switched on and off in a cyclic way, deforming the field lines of the overall system. It is this deformation that generates Alfven waves, which are in the next step used to transport and compress the propulsive medium, in theory leading to a propulsion system with a much higher performance than any other electric propulsion system. While space propulsion is expected to be the prime application for MOA and is supported by numerous applications such as Solar and/or Nuclear Electric Propulsion or even as an 'afterburner system' for Nuclear Thermal Propulsion, other, terrestrial applications, like coating, semiconductor implantation and manufacturing as well as steel cutting can be thought of as well, making the system highly suited for a common space-terrestrial application research and utilisation strategy. This paper presents the recent developments of the MOA Thruster R and D activities at QASAR, the company in Vienna, Austria, which has been set up to further develop and test the Alfven wave technology and its applications. (author)

  7. Ripple losses during ICRF heating in Tore Supra

    International Nuclear Information System (INIS)

    Basiuk, V.; Eriksson, L.-G.; Bergeaud, V.; Chantant, M.; Martin, G.; Nguyen, F.; Reichle, R.; Vallet, J.C.; Delpeche, L.; Surle, F.

    2004-01-01

    The toroidal field coils in Tore Supra are supra-conducting, and their number is restricted to 18. As a result, the ripple is fairly large, about 7% at the plasma boundary. Tore Supra has consequently been equipped with dedicated ripple loss diagnostics, which has allowed ripple loss studies. This paper reports on the measurements made with these diagnostics and provides an analysis of the experimental results, comparing them with theoretical expectations whenever possible. Furthermore, the main heating source accelerating ions in Tore Supra is ion cyclotron resonance range of frequency (ICRF) heating, and the paper provides new information on the ripple losses of ICRF accelerated ions. (author)

  8. The development of a modified spectral ripple test.

    Science.gov (United States)

    Aronoff, Justin M; Landsberger, David M

    2013-08-01

    Poor spectral resolution can be a limiting factor for hearing impaired listeners, particularly for complex listening tasks such as speech understanding in noise. Spectral ripple tests are commonly used to measure spectral resolution, but these tests contain a number of potential confounds that can make interpretation of the results difficult. To measure spectral resolution while avoiding those confounds, a modified spectral ripple test with dynamically changing ripples was created, referred to as the spectral-temporally modulated ripple test (SMRT). This paper describes the SMRT and provides evidence that it is sensitive to changes in spectral resolution.

  9. The crystal structure of escherichia coli MoaB suggests a probable role in molybdenum cofactor synthesis

    International Nuclear Information System (INIS)

    Sanishvili, R.; Beasley, S.; Skarina, T; Glesne, D; Joachimiak, A; Edwards, A; Savchenko, A.; Univ. Health Network; Univ. of Toronto

    2004-01-01

    The crystal structure of Escherichia coli MoaB was determined by multiwavelength anomalous diffraction phasing and refined at 1.6 Angstrom resolution. The molecule displayed a modified Rossman fold. MoaB is assembled into a hexamer composed of two trimers. The monomers have high structural similarity with two proteins, MogA and MoeA, from the molybdenum cofactor synthesis pathway in E. Coli, as well as with domains of mammalian gephyrin and plant Cnx1, which are also involved in molybdopterin synthesis. Structural comparison between these proteins and the amino acid conservation patterns revealed a putative active site in MoaB. The structural analysis of this site allowed to advance several hypothesis which can be tested in further studies

  10. Ripple-Triggered Stimulation of the Locus Coeruleus during Post-Learning Sleep Disrupts Ripple/Spindle Coupling and Impairs Memory Consolidation

    Science.gov (United States)

    Novitskaya, Yulia; Sara, Susan J.; Logothetis, Nikos K.; Eschenko, Oxana

    2016-01-01

    Experience-induced replay of neuronal ensembles occurs during hippocampal high-frequency oscillations, or ripples. Post-learning increase in ripple rate is predictive of memory recall, while ripple disruption impairs learning. Ripples may thus present a fundamental component of a neurophysiological mechanism of memory consolidation. In addition to…

  11. Gap junction networks can generate both ripple-like and fast ripple-like oscillations

    Science.gov (United States)

    Simon, Anna; Traub, Roger D.; Vladimirov, Nikita; Jenkins, Alistair; Nicholson, Claire; Whittaker, Roger G.; Schofield, Ian; Clowry, Gavin J.; Cunningham, Mark O.; Whittington, Miles A.

    2014-01-01

    Fast ripples (FRs) are network oscillations, defined variously as having frequencies of > 150 to > 250 Hz, with a controversial mechanism. FRs appear to indicate a propensity of cortical tissue to originate seizures. Here, we demonstrate field oscillations, at up to 400 Hz, in spontaneously epileptic human cortical tissue in vitro, and present a network model that could explain FRs themselves, and their relation to ‘ordinary’ (slower) ripples. We performed network simulations with model pyramidal neurons, having axons electrically coupled. Ripples ( 250 Hz, were sustained or interrupted, and had little jitter in the firing of individual axons. The form of model FR was similar to spontaneously occurring FRs in excised human epileptic tissue. In vitro, FRs were suppressed by a gap junction blocker. Our data suggest that a given network can produce ripples, FRs, or both, via gap junctions, and that FRs are favored by clusters of axonal gap junctions. If axonal gap junctions indeed occur in epileptic tissue, and are mediated by connexin 26 (recently shown to mediate coupling between immature neocortical pyramidal cells), then this prediction is testable. PMID:24118191

  12. Effects of spectral smearing on performance of the spectral ripple and spectro-temporal ripple tests.

    Science.gov (United States)

    Narne, Vijaya Kumar; Sharma, Mridula; Van Dun, Bram; Bansal, Shalini; Prabhu, Latika; Moore, Brian C J

    2016-12-01

    The main aim of this study was to use spectral smearing to evaluate the efficacy of a spectral ripple test (SRt) using stationary sounds and a recent variant with gliding ripples called the spectro-temporal ripple test (STRt) in measuring reduced spectral resolution. In experiment 1 the highest detectable ripple density was measured using four amounts of spectral smearing (unsmeared, mild, moderate, and severe). The thresholds worsened with increasing smearing and were similar for the SRt and the STRt across the three conditions with smearing. For unsmeared stimuli, thresholds were significantly higher (better) for the STRt than for the SRt. An amplitude fluctuation at the outputs of simulated (gammatone) auditory filters centered above 6400 Hz was identified as providing a potential detection cue for the STRt stimuli. Experiment 2 used notched noise with energy below and above the passband of the SRt and STRt stimuli to reduce confounding cues in the STRt. Thresholds were almost identical for the STRt and SRt for both unsmeared and smeared stimuli, indicating that the confounding cue for the STRt was eliminated by the notched noise. Thresholds obtained with notched noise present could be predicted reasonably accurately using an excitation-pattern model.

  13. Radiocarbon dates on desiccated moa (Dinornithiformes) flesh from inland Otago, New Zealand

    International Nuclear Information System (INIS)

    Anderson, A.; Rowe, L.; Petchey, F.; White, M.

    2010-01-01

    Remains of soft tissues from extinct moa (Dinornithiformes), mainly desiccated sinew, muscle, skin, and feathers have been recovered rather seldom but their distribution is distinctive. Of 22 records of such finds accumulated between 1864 and 1987, 15 came from inland Otago, west of Dunedin in the southern South Island. Most were found in the late nineteenth century in rockshelters, clefts or alluvial sediments and were regarded at the time as ev dence of the survival of moa up to about AD 1800. Improbable as this latter point is, it has not been tested by radiocarbon dating until now. Our particular impetus to do so, however, arises in another way. It is from research, again largely within inland Otago, on Maori artefacts which have also been made from various other kinds of soft tissues (flax, grasses, dog skin, bird skin, feathers etc.). A series of accelerator mass spectrometry (AMS) radiocarbon dates on these shows that they are exclusively late, post-AD 1650, which begs the question of why the age range does not extend across the full prehistoric period, beginning about AD 1300. (author). 6 refs., 2 figs., 1 tab.

  14. Structure of the ripple phase of phospholipid multibilayers

    International Nuclear Information System (INIS)

    Sengupta, Kheya; Raghunathan, V.A.; Katsaras, John

    2003-01-01

    We present electron density maps (EDMs) of the ripple phase formed by phosphorylcholine lipids such as dimyristoyl phosphatidylcholine (DMPC), palmitoyl-oleoyl phosphatidylcholine (POPC), dihexadecyl phosphatidylcholine, and dilauroyl phosphatidylcholine (DLPC). With the exception of DLPC, the rippled bilayers have a sawtooth shape in all the systems, with one arm being almost twice as long as the other. For DMPC and POPC bilayers, EDMs have been obtained at different temperatures at a fixed relative humidity, and the overall shape of the ripples and the ratio of the lengths of the two arms are found to be insensitive to temperature. EDMs of all the systems with saturated hydrocarbon chains suggest the existence of a mean chain tilt along the ripple wave vector. In the literature it is generally assumed that the asymmetry of the rippled bilayers (absence of a mirror plane normal to the ripple wave vector) arises from a sawtoothlike height profile. However, in the case of DLPC, the height profile is found to be almost symmetric and the asymmetry results mainly from different bilayer thicknesses in the two arms of the ripple. We also present EDMs of the metastable ripple phase of dipalmitoyl phosphatidylcholine, formed on cooling from the L α phase

  15. Vibrational resonances of nonrigid vehicles: Polygonization and ripple patterns

    NARCIS (Netherlands)

    Dekker, H.

    2009-01-01

    The well-known phenomenon of ripples on roads has its modern counterpart in ripple patterns on railroads and polygonization of wheels on state-of-the-art lightrail streetcars. Here we study an idealized mechanical suspension model for the vibrational frequency response of a buggy with a nonrigid

  16. Automatic Detection of Sand Ripple Features in Sidescan Sonar Imagery

    Science.gov (United States)

    2014-07-09

    Among the features used in forensic scientific fingerprint analysis are terminations or bifurcations of print ridges. Sidescan sonar imagery of ripple...always be pathological cases. The size of the blocks of pixels used in determining the ripple wavelength is evident in the output images on the right in

  17. Angular tuning of the magnetic birefringence in rippled cobalt films

    Energy Technology Data Exchange (ETDEWEB)

    Arranz, Miguel A., E-mail: MiguelAngel.Arranz@uclm.es [Facultad de Ciencias y Tecnologías Químicas, Universidad de Castilla-La Mancha, Avda. Camilo J. Cela 10, 13071 Ciudad Real (Spain); Colino, José M. [Instituto de Nanociencia, Nanotecnología y Materiales Moleculares, Universidad de Castilla-La Mancha, Campus de la Fábrica de Armas, 45071 Toledo (Spain)

    2015-06-22

    We report the measurement of magnetically induced birefringence in rippled Co films. For this purpose, the magneto-optical properties of ion beam eroded ferromagnetic films were studied using Kerr magnetometry and magnetic birefringence in the transmitted light intensity. Upon sufficient ion sculpting, these ripple surface nanostructures developed a defined uniaxial anisotropy in the in-plane magnetization, finely tuning the magnetic birefringence effect. We have studied its dependence on the relative orientation between the ripple direction and the magnetic field, and found this effect to be dramatically correlated with the capability to neatly distinguish the mechanisms for the in-plane magnetization reversal, i.e., rotation and nucleation. This double refraction corresponds univocally to the two magnetization axes, parallel and perpendicular to the ripples direction. We have also observed that tuned birefringence in stack assemblies of rippled Co films, which enables us to technically manipulate the number and direction of refraction axes.

  18. Large wind ripples on Mars: A record of atmospheric evolution

    Science.gov (United States)

    Lapotre, M. G. A.; Ewing, R. C.; Lamb, M. P.; Fischer, W. W.; Grotzinger, J. P.; Rubin, D. M.; Lewis, K. W.; Ballard, M. J.; Day, M.; Gupta, S.; Banham, S. G.; Bridges, N. T.; Des Marais, D. J.; Fraeman, A. A.; Grant, J. A.; Herkenhoff, K. E.; Ming, D. W.; Mischna, M. A.; Rice, M. S.; Sumner, D. A.; Vasavada, A. R.; Yingst, R. A.

    2016-07-01

    Wind blowing over sand on Earth produces decimeter-wavelength ripples and hundred-meter- to kilometer-wavelength dunes: bedforms of two distinct size modes. Observations from the Mars Science Laboratory Curiosity rover and the Mars Reconnaissance Orbiter reveal that Mars hosts a third stable wind-driven bedform, with meter-scale wavelengths. These bedforms are spatially uniform in size and typically have asymmetric profiles with angle-of-repose lee slopes and sinuous crest lines, making them unlike terrestrial wind ripples. Rather, these structures resemble fluid-drag ripples, which on Earth include water-worked current ripples, but on Mars instead form by wind because of the higher kinematic viscosity of the low-density atmosphere. A reevaluation of the wind-deposited strata in the Burns formation (about 3.7 billion years old or younger) identifies potential wind-drag ripple stratification formed under a thin atmosphere.

  19. Large wind ripples on Mars: A record of atmospheric evolution

    Science.gov (United States)

    Lapotre, M G; Ewing, R C; Lamb, M P; Fischer, W W; Grotzinger, J P; Rubin, D M; Lewis, K W; Ballard, M; Day, Mitch D.; Gupta, S.; Banham, S G; Bridges, N T; Des Marais, D J; Fraeman, A A; Grant, J A; Herkenhoff, Kenneth E.; Ming, D W; Mischna, M A; Rice, M S; Sumner, D A; Vasavada, A R; Yingst, R A

    2016-01-01

    Wind blowing over sand on Earth produces decimeter-wavelength ripples and hundred-meter– to kilometer-wavelength dunes: bedforms of two distinct size modes. Observations from the Mars Science Laboratory Curiosity rover and the Mars Reconnaissance Orbiter reveal that Mars hosts a third stable wind-driven bedform, with meter-scale wavelengths. These bedforms are spatially uniform in size and typically have asymmetric profiles with angle-of-repose lee slopes and sinuous crest lines, making them unlike terrestrial wind ripples. Rather, these structures resemble fluid-drag ripples, which on Earth include water-worked current ripples, but on Mars instead form by wind because of the higher kinematic viscosity of the low-density atmosphere. A reevaluation of the wind-deposited strata in the Burns formation (about 3.7 billion years old or younger) identifies potential wind-drag ripple stratification formed under a thin atmosphere.

  20. PathShuffle: Credit Mixing and Anonymous Payments for Ripple

    Directory of Open Access Journals (Sweden)

    Moreno-Sanchez Pedro

    2017-07-01

    Full Text Available The I owe you (IOU credit network Ripple is one of the most prominent alternatives in the burgeoning field of decentralized payment systems. Ripple’s path-based transactions set it apart from cryptocurrencies such as Bitcoin. Its pseudonymous nature, while still maintaining some regulatory capabilities, has motivated several financial institutions across the world to use Ripple for processing their daily transactions. Nevertheless, with its public ledger, a credit network such as Ripple is no different from a cryptocurrency in terms of weak privacy; recent demonstrative deanonymization attacks raise important concerns regarding the privacy of the Ripple users and their transactions. However, unlike for cryptocurrencies, there is no known privacy solution compatible with the existing credit networks such as Ripple.

  1. Angular tuning of the magnetic birefringence in rippled cobalt films

    International Nuclear Information System (INIS)

    Arranz, Miguel A.; Colino, José M.

    2015-01-01

    We report the measurement of magnetically induced birefringence in rippled Co films. For this purpose, the magneto-optical properties of ion beam eroded ferromagnetic films were studied using Kerr magnetometry and magnetic birefringence in the transmitted light intensity. Upon sufficient ion sculpting, these ripple surface nanostructures developed a defined uniaxial anisotropy in the in-plane magnetization, finely tuning the magnetic birefringence effect. We have studied its dependence on the relative orientation between the ripple direction and the magnetic field, and found this effect to be dramatically correlated with the capability to neatly distinguish the mechanisms for the in-plane magnetization reversal, i.e., rotation and nucleation. This double refraction corresponds univocally to the two magnetization axes, parallel and perpendicular to the ripples direction. We have also observed that tuned birefringence in stack assemblies of rippled Co films, which enables us to technically manipulate the number and direction of refraction axes

  2. Pyramidal cell-interneuron interactions underlie hippocampal ripple oscillations.

    Science.gov (United States)

    Stark, Eran; Roux, Lisa; Eichler, Ronny; Senzai, Yuta; Royer, Sebastien; Buzsáki, György

    2014-07-16

    High-frequency ripple oscillations, observed most prominently in the hippocampal CA1 pyramidal layer, are associated with memory consolidation. The cellular and network mechanisms underlying the generation, frequency control, and spatial coherence of the rhythm are poorly understood. Using multisite optogenetic manipulations in freely behaving rodents, we found that depolarization of a small group of nearby pyramidal cells was sufficient to induce high-frequency oscillations, whereas closed-loop silencing of pyramidal cells or activation of parvalbumin- (PV) or somatostatin-immunoreactive interneurons aborted spontaneously occurring ripples. Focal pharmacological blockade of GABAA receptors abolished ripples. Localized PV interneuron activation paced ensemble spiking, and simultaneous induction of high-frequency oscillations at multiple locations resulted in a temporally coherent pattern mediated by phase-locked interneuron spiking. These results constrain competing models of ripple generation and indicate that temporally precise local interactions between excitatory and inhibitory neurons support ripple generation in the intact hippocampus. Copyright © 2014 Elsevier Inc. All rights reserved.

  3. Ripple/Carcinoid pattern sebaceoma with apocrine differentiation.

    Science.gov (United States)

    Misago, Noriyuki; Narisawa, Yutaka

    2011-02-01

    Sebaceoma is a benign sebaceous neoplasm, which has been reported to show characteristic growth patterns, such as, ripple, labyrinthine/sinusoidal, and carcinoid-like patterns. Another recent finding regarding in sebaceoma is the observation of apocrine differentiation within the sebaceoma lesion. This report describes a case of carcinoid (a partial ripple and labyrinthine) pattern sebaceoma with apocrine differentiation with a literature review and immunohistochemical studies. The various characteristic growth patterns in sebaceoma were suggested to simply be variations of the same growth pattern arranged in cords, namely, a unified term "ripple/carcinoid pattern." The primitive sebaceous germinative cells in sebaceoma may still have the ability to undergo apocrine differentiation. Most of the reports so far on sebaceoma with apocrine differentiation, including the present case, describe a ripple/carcinoid pattern, thus suggesting that ripple/carcinoid pattern sebaceoma is composed of more primitive sebaceous germinative cells than conventional sebaceoma.

  4. Highly sensitive detection of a current ripple

    International Nuclear Information System (INIS)

    Aoki, Takashi; Gushiken, Tutomu; Nishikigouri, Kazutaka; Kumada, Masayuki.

    1996-01-01

    In the HIMAC, there are six thyristor-controlled power sources for driving two synchrotrons. These power sources are the three-output terminal power sources which are equipped with positive output, negative output and neutral point for the common mode countermeasures. As electromagnet circuits are connected to the three-output terminal power sources, those are three-line type. In the inside of the power source circuits controlled by thyristors, there is the oscillation peculiar to the power sources, and the variation of voltage induces current spikes. This time, in order to assess the results of the common mode countermeasures in the power source and electromagnet circuits, as one method of cross-check, it is considered that since electromagnet current flows being divided to the bridging resistance and the coil, if attention is paid to the current on bridging resistance side, the ripple components of common mode and normal mode can be detected with high sensitivity, and this was verified. The present state of heightening the performance of synchrotron power sources is explained. The cross-check of the method of assessing the performance of electromagnet power sources is reported. The method of measuring ripple current and the results of the measurement are reported. (K.I.)

  5. Quantum and classical ripples in graphene

    Science.gov (United States)

    Hašík, Juraj; Tosatti, Erio; MartoÅák, Roman

    2018-04-01

    Thermal ripples of graphene are well understood at room temperature, but their quantum counterparts at low temperatures are in need of a realistic quantitative description. Here we present atomistic path-integral Monte Carlo simulations of freestanding graphene, which show upon cooling a striking classical-quantum evolution of height and angular fluctuations. The crossover takes place at ever-decreasing temperatures for ever-increasing wavelengths so that a completely quantum regime is never attained. Zero-temperature quantum graphene is flatter and smoother than classical graphene at large scales yet rougher at short scales. The angular fluctuation distribution of the normals can be quantitatively described by coexistence of two Gaussians, one classical strongly T -dependent and one quantum about 2° wide, of zero-point character. The quantum evolution of ripple-induced height and angular spread should be observable in electron diffraction in graphene and other two-dimensional materials, such as MoS2, bilayer graphene, boron nitride, etc.

  6. Desgin of On-line Monitoring Device for MOA (Metal Oxide Arrestor Based on FPGA and C8051F

    Directory of Open Access Journals (Sweden)

    Xiaotong YAO

    2014-10-01

    Full Text Available Monitoring of metal oxide surge arresters (MOA due to aging, moisture and other components cause increased resistive current. Through a lot of practices, it has been proved that in the early days, MOA insulation damage and current increase is not obvious. The accurate working conditions of the MOA are also not obvious but it can reflect the aging or moisture of MOA. When the resistive current of the fundamental component increases, there is no increment in the harmonic components that is the general performance of a serious or moisture contamination. In the same way when the resistive current of harmonic components increases, the fundamental component is not increased and it is the general performance of aging. Therefore, this paper designed an experiment-based FPGA and C8051F-line monitoring device. This device uses resistive current as a detection target. The main monitoring parameters are the fundamental and peak value of resistive current, third harmonic content of the leakage current, phase angle difference and power consumption. Through laboratory tests, the device can be used with a network arrester line monitoring, maintenance, reduce the economic losses caused by power outages and improve the distribution network reliability.

  7. Ripples and ripples: from sandy deserts to ion-sputtered surfaces

    International Nuclear Information System (INIS)

    Aste, T; Valbusa, U

    2005-01-01

    We study the morphological evolution of surfaces during ion sputtering and we compare their dynamical corrugation with aeolian ripple formation in sandy deserts. We show that, although the two phenomena are physically different, they must obey similar geometrical constraints and therefore they can be described within the same theoretical framework. The present theory distinguishes between atoms that stay bounded in the bulk and others that are mobile on the surface. We describe the excavation mechanisms, the adsorption and the surface mobility by means of a continuous equation derived from the study of dune formation on sand. We explore the spontaneous development of ordered nanostructures and explain the different dynamical behaviours experimentally observed in metals or in semiconductors or in amorphous systems. We also show that this novel approach can describe the occurrence of rotation in the ripple direction and the formation of other kinds of self-organized patterns induced by changes in the sputtering incidence angle

  8. MOA-2013-BLG-220Lb: Massive planetary companion to galactic-disk host

    Energy Technology Data Exchange (ETDEWEB)

    Yee, J. C.; Gould, A.; Gaudi, B. S. [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Han, C.; Choi, J.-Y.; Hwang, K.-H.; Jung, Y. K. [Department of Physics, Chungbuk National University, Cheongju 361-763 (Korea, Republic of); Skowron, J.; Udalski, A. [Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland); Bond, I. A. [Institute of Information and Mathematical Sciences, Massey University, Private Bag 102-904, North Shore Mail Centre, Auckland (New Zealand); Hundertmark, M. [SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS (United Kingdom); Monard, L. A. G. [Klein Karoo Observatory, Centre for Backyard Astrophysics, Calitzdorp (South Africa); Porritt, I. [Turitea Observatory, Palmerston North (New Zealand); Nelson, P. [Ellinbank Observatory, Ellinbank, Victoria (Australia); Bozza, V. [Dipartimento di Fisica " E. R. Caianiello," Università degli Studi di Salerno, Via S. Allende, I-84081 Baronissi (Italy); Albrow, M. D. [Department of Physics and Astronomy, University of Canterbury, Private Bag 4800, Christchurch 8020 (New Zealand); Christie, G. W. [Auckland Observatory, Auckland (New Zealand); DePoy, D. L. [Department of Physics and Astronomy, Texas A and M University, College Station, TX 77843-4242 (United States); Lee, C.-U. [Korea Astronomy and Space Science Institute, 776 Daedukdae-ro, Yuseong-gu, Daejeon 305-348 (Korea, Republic of); McCormick, J. [Farm Cove Observatory, Centre for Backyard Astrophysics, Pakuranga, Auckland (New Zealand); Collaboration: μFUN Collaboration),; MOA Collaboration),; OGLE Collaboration),; RoboNet Collaboration),; and others

    2014-07-20

    We report the discovery of MOA-2013-BLG-220Lb, which has a super-Jupiter mass ratio q = 3.01 ± 0.02 × 10{sup –3} relative to its host. The proper motion, μ = 12.5 ± 1 mas yr{sup –1}, is one of the highest for microlensing planets yet discovered, implying that it will be possible to separately resolve the host within ∼7 yr. Two separate lines of evidence imply that the planet and host are in the Galactic disk. The planet could have been detected and characterized purely with follow-up data, which has important implications for microlensing surveys, both current and into the Large Synoptic Survey Telescope (LSST) era.

  9. Environmental impact of the minero-metallurgic industry on the marine ecosystem in Moa, Cuba

    International Nuclear Information System (INIS)

    Martinez Canals, M.; Pedro Garcia, L.

    1999-01-01

    One of the biggest nickel mineral deposits of the world is located in Moa; therefore two plants are installed for the extraction of this metal in the region, and another is in its construction phase. During the technological processes, residuals that contain great quantity of metallic elements, and high acidity level are discharged into the environment. The objectives of this research were to establish the levels of pollution of eleven metals, Al, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb and Zn in the superficial bottom sediments, sea water and organisms of the marine aquatorium (green and white sea urchins, blue crabs, oysters and mangrove leaves). The dynamics of pollution in superficial sediments was also determined in the course of a 9-year study. As complementary analyses, pH and salinity were determined for the supradjacent water to the marine bottom, as well as the content of organic carbon, and granulometry of the sediment

  10. MOA-2010-BLG-311: A PLANETARY CANDIDATE BELOW THE THRESHOLD OF RELIABLE DETECTION

    International Nuclear Information System (INIS)

    Yee, J. C.; Hung, L.-W.; Gould, A.; Gaudi, B. S.; Bond, I. A.; Allen, W.; Monard, L. A. G.; Albrow, M. D.; Fouqué, P.; Dominik, M.; Tsapras, Y.; Udalski, A.; Zellem, R.; Bos, M.; Christie, G. W.; DePoy, D. L.; Dong, Subo; Drummond, J.; Gorbikov, E.; Han, C.

    2013-01-01

    We analyze MOA-2010-BLG-311, a high magnification (A max > 600) microlensing event with complete data coverage over the peak, making it very sensitive to planetary signals. We fit this event with both a point lens and a two-body lens model and find that the two-body lens model is a better fit but with only Δχ 2 ∼ 80. The preferred mass ratio between the lens star and its companion is q = 10 –3.7±0.1 , placing the candidate companion in the planetary regime. Despite the formal significance of the planet, we show that because of systematics in the data the evidence for a planetary companion to the lens is too tenuous to claim a secure detection. When combined with analyses of other high-magnification events, this event helps empirically define the threshold for reliable planet detection in high-magnification events, which remains an open question.

  11. MOA-2010-BLG-311: A PLANETARY CANDIDATE BELOW THE THRESHOLD OF RELIABLE DETECTION

    Energy Technology Data Exchange (ETDEWEB)

    Yee, J. C.; Hung, L.-W.; Gould, A.; Gaudi, B. S. [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Bond, I. A. [Institute for Information and Mathematical Sciences, Massey University, Private Bag 102-904, Auckland 1330 (New Zealand); Allen, W. [Vintage Lane Observatory, Blenheim (New Zealand); Monard, L. A. G. [Bronberg Observatory, Centre for Backyard Astrophysics, Pretoria (South Africa); Albrow, M. D. [Department of Physics and Astronomy, University of Canterbury, Private Bag 4800, Christchurch 8020 (New Zealand); Fouque, P. [IRAP, CNRS, Universite de Toulouse, 14 avenue Edouard Belin, F-31400 Toulouse (France); Dominik, M. [SUPA, University of St. Andrews, School of Physics and Astronomy, North Haugh, St. Andrews, KY16 9SS (United Kingdom); Tsapras, Y. [Las Cumbres Observatory Global Telescope Network, 6740B Cortona Drive, Goleta, CA 93117 (United States); Udalski, A. [Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland); Zellem, R. [Department of Planetary Sciences/LPL, University of Arizona, 1629 East University Boulevard, Tucson, AZ 85721 (United States); Bos, M. [Molehill Astronomical Observatory, North Shore City, Auckland (New Zealand); Christie, G. W. [Auckland Observatory, P.O. Box 24-180, Auckland (New Zealand); DePoy, D. L. [Department of Physics, Texas A and M University, 4242 TAMU, College Station, TX 77843-4242 (United States); Dong, Subo [Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540 (United States); Drummond, J. [Possum Observatory, Patutahi (New Zealand); Gorbikov, E. [School of Physics and Astronomy, Raymond and Beverley Sackler Faculty of Exact Sciences, Tel-Aviv University, Tel Aviv 69978 (Israel); Han, C., E-mail: liweih@astro.ucla.edu, E-mail: rzellem@lpl.arizona.edu, E-mail: tim.natusch@aut.ac.nz [Department of Physics, Chungbuk National University, 410 Seongbong-Rho, Hungduk-Gu, Chongju 371-763 (Korea, Republic of); Collaboration: muFUN Collaboration; MOA Collaboration; OGLE Collaboration; PLANET Collaboration; RoboNet Collaboration; MiNDSTEp Consortium; and others

    2013-05-20

    We analyze MOA-2010-BLG-311, a high magnification (A{sub max} > 600) microlensing event with complete data coverage over the peak, making it very sensitive to planetary signals. We fit this event with both a point lens and a two-body lens model and find that the two-body lens model is a better fit but with only {Delta}{chi}{sup 2} {approx} 80. The preferred mass ratio between the lens star and its companion is q = 10{sup -3.7{+-}0.1}, placing the candidate companion in the planetary regime. Despite the formal significance of the planet, we show that because of systematics in the data the evidence for a planetary companion to the lens is too tenuous to claim a secure detection. When combined with analyses of other high-magnification events, this event helps empirically define the threshold for reliable planet detection in high-magnification events, which remains an open question.

  12. The molecular dynamics simulation of ion-induced ripple growth

    International Nuclear Information System (INIS)

    Suele, P.; Heinig, K.-H.

    2009-01-01

    The wavelength-dependence of ion-sputtering induced growth of repetitive nanostructures, such as ripples has been studied by molecular dynamics (MD) simulations in Si. The early stage of the ion erosion driven development of ripples has been simulated on prepatterned Si stripes with a wavy surface. The time evolution of the height function and amplitude of the sinusoidal surface profile has been followed by simulated ion-sputtering. According to Bradley-Harper (BH) theory, we expect correlation between the wavelength of ripples and the stability of them. However, we find that in the small ripple wavelength (λ) regime BH theory fails to reproduce the results obtained by molecular dynamics. We find that at short wavelengths (λ 35 nm is stabilized in accordance with the available experimental results. According to the simulations, few hundreds of ion impacts in λ long and few nanometers wide Si ripples are sufficient for reaching saturation in surface growth for for λ>35 nm ripples. In another words, ripples in the long wavelength limit seems to be stable against ion-sputtering. A qualitative comparison of our simulation results with recent experimental data on nanopatterning under irradiation is attempted.

  13. Facile characterization of ripple domains on exfoliated graphene.

    Science.gov (United States)

    Choi, Jin Sik; Kim, Jin-Soo; Byun, Ik-Su; Lee, Duk Hyun; Hwang, In Rok; Park, Bae Ho; Choi, Taekjib; Park, Jeong Young; Salmeron, Miquel

    2012-07-01

    Ripples in graphene monolayers deposited on SiO(2)/Si wafer substrates were recently shown to give rise to friction anisotropy. High friction appears when the AFM tip slides in a direction perpendicular to the ripple crests and low friction when parallel. The direction of the ripple crest is, however, hard to determine as it is not visible in topographic images and requires elaborate measurements of friction as a function of angle. Here we report a simple method to characterize ripple crests by measuring the cantilever torsion signal while scanning in the non-conventional longitudinal direction (i.e., along the cantilever axis, as opposed to the usual friction measurement). The longitudinal torsion signal provides a much clearer ripple domain contrast than the conventional friction signal, while both signals show respective rotation angle dependences that can be explained using the torsion component of the normal reaction force exerted by the graphene ripples. We can also determine the ripple direction by comparing the contrast in torsion images obtained in longitudinal and lateral scans without sample rotation or complicated normalization.

  14. Strategy of restraining ripple error on surface for optical fabrication.

    Science.gov (United States)

    Wang, Tan; Cheng, Haobo; Feng, Yunpeng; Tam, Honyuen

    2014-09-10

    The influence from the ripple error to the high imaging quality is effectively reduced by restraining the ripple height. A method based on the process parameters and the surface error distribution is designed to suppress the ripple height in this paper. The generating mechanism of the ripple error is analyzed by polishing theory with uniform removal character. The relation between the processing parameters (removal functions, pitch of path, and dwell time) and the ripple error is discussed through simulations. With these, the strategy for diminishing the error is presented. A final process is designed and demonstrated on K9 work-pieces using the optimizing strategy with magnetorheological jet polishing. The form error on the surface is decreased from 0.216λ PV (λ=632.8  nm) and 0.039λ RMS to 0.03λ PV and 0.004λ RMS. And the ripple error is restrained well at the same time, because the ripple height is less than 6 nm on the final surface. Results indicate that these strategies are suitable for high-precision optical manufacturing.

  15. Il museo di antropologia come museo culturale: il caso del MOA di Vancouver

    Directory of Open Access Journals (Sweden)

    Claudia Gualtieri

    2011-03-01

    Full Text Available This essay will examine anthropology museums as cultural museums from the methodological approach of Cultural Studies. Within this frame, the museum acts as a mode of conservation of material culture thus revealing its immaterial consequences. In the museum, historical memories are preserved and re-enacted to articulate cultural identities in the present, to shed light on the past, and to illuminate future communal practices. After a brief survey on collections in the epoch of European geographical discoveries and on the birth of anthropology as a science in colonial times, the essay will consider the exhibition of cultural artefacts belonging to the First Nations of British Columbia in the Museum of Anthropology (MOA in Vancouver. References to native land claims will help to understand the links between time and place, history and geography, cultural memory and land that are central to native re-constructions of identity. Through a critical reading of conventional ethnographic and anthropological criteria in museum displays, the codes of conservation and repatriation will be introduced in relation to the notion of native title and cultural property. The MOA will be used as a case in point to explore practices of negotiation with native peoples. The indigenous worldview regarding the use of objects and the performance of a living culture will be presented as opposed to the conventional aesthetic appreciation and exhibition of cultural objects. The essay will then illustrate how museums are produced and organised according to ideologically relevant standpoints in specific times and places, and how visitor-oriented practices should address a critical reading of dynamics of power and knowledge control in contemporary societies.

  16. Predictive ecotoxicity of MoA 1 of organic chemicals using in silico approaches.

    Science.gov (United States)

    de Morais E Silva, Luana; Alves, Mateus Feitosa; Scotti, Luciana; Lopes, Wilton Silva; Scotti, Marcus Tullius

    2018-05-30

    Persistent organic products are compounds used for various purposes, such as personal care products, surfactants, colorants, industrial additives, food, pesticides and pharmaceuticals. These substances are constantly introduced into the environment and many of these pollutants are difficult to degrade. Toxic compounds classified as MoA 1 (Mode of Action 1) are low toxicity compounds that comprise nonreactive chemicals. In silico methods such as Quantitative Structure-Activity Relationships (QSARs) have been used to develop important models for prediction in several areas of science, as well as aquatic toxicity studies. The aim of the present study was to build a QSAR model-based set of theoretical Volsurf molecular descriptors using the fish acute toxicity values of compounds defined as MoA 1 to identify the molecular properties related to this mechanism. The selected Partial Least Squares (PLS) results based on the values of cross-validation coefficients of determination (Q cv 2 ) show the following values: Q cv 2 = 0.793, coefficient of determination (R 2 ) = 0.823, explained variance in external prediction (Q ext 2 ) = 0.87. From the selected descriptors, not only the hydrophobicity is related to the toxicity as already mentioned in previously published studies but other physicochemical properties combined contribute to the activity of these compounds. The symmetric distribution of the hydrophobic moieties in the structure of the compounds as well as the shape, as branched chains, are important features that are related to the toxicity. This information from the model can be useful in predicting so as to minimize the toxicity of organic compounds. Copyright © 2018. Published by Elsevier Inc.

  17. Recent developments of the MOA thruster concerning its application for nuclear electric and thermal propulsion

    International Nuclear Information System (INIS)

    Frischauf, N.; Hettmer, M.; Grassauer, A.; Bartusch, T.; Koudelka, O.

    2007-01-01

    The name of the concept, utilising Alfven waves to accelerate ionised matter for propulsive purposes, is MOA for Magnetic field Oscillating Amplified thruster. Alfven waves are generated by making use of 2 coils, one being permanently powered and serving also as magnetic nozzle, the other one being switched on and off in a cyclic way, deforming the field lines of the overall system. It is this deformation that generates Alfven waves, which are in the next step used to transport and compress the propulsive medium, in theory leading to a propulsion system with a much higher performance than any other electric propulsion system. Based on computer simulations, which were conducted to get a first estimate on the performance of the system, MOA is a highly flexible propulsion system, whose performance parameters might easily be adapted, by changing the mass flow and/or the power level. As such the system is capable to deliver a maximum specific impulse of 13116 s (12.87 mN) at a power level of 11.16 kW, using Xe as propellant, but can also be attuned to provide a thrust of 236.5 mN (2411 s) at 6.15 kW of power. Several prototypes have been built and tested, the results that were obtained are promising: with an overall power consumption of 400 W, 6 to 11 mN of thrust could be obtained, leading on the average to a specific power of about 50 W/mN. Better results are expected for optimised prototypes in terms of power consumption

  18. Thermal ripples in model molybdenum disulfide monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Remsing, Richard C.; Klein, Michael L. [Institute for Computational Molecular Science, Center for the Computational, Design of Functional Layered Materials, and Department of Chemistry, Temple University, 1925 N. 12th St., 19122, Philadelphia, PA (United States); Waghmare, Umesh V. [Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, 560 064, Jakkur, Bangalore (India)

    2017-01-15

    Molybdenum disulfide (MoS{sub 2}) monolayers have the potential to revolutionize nanotechnology. To reach this potential, it will be necessary to understand the behavior of this two-dimensional (2D) material on large length scales and under thermal conditions. Herein, we use molecular dynamics (MD) simulations to investigate the nature of the rippling induced by thermal fluctuations in monolayers of the 2H and 1T phases of MoS{sub 2}. The 1T phase is found to be more rigid than the 2H phase. Both monolayer phases are predicted to follow long wavelength scaling behavior typical of systems with anharmonic coupling between vibrational modes as predicted by classic theories of membrane-like systems. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. Martian Dune Ripples as Indicators of Recent Surface Wind Patterns

    Science.gov (United States)

    Johnson, M.; Zimbelman, J. R.

    2015-12-01

    Sand dunes have been shown to preserve the most recent wind patterns in their ripple formations. This investigation continues the manual documentation of ripples on Martian dunes in order to assess surface wind flow. Study sites investigated must have clear HiRISE frames and be able to represent diverse locations across the surface, decided primarily by their spread of latitude and longitude values. Additionally, frames with stereo pairs are preferred because of their ability to create digital terrain models. This will assist in efforts to relate dune slopes and obstacles to ripple patterns. The search and analysis period resulted in 40 study sites with mapped ripples. Lines were drawn perpendicular to ripple crests across three adjacent ripples in order to document both ripple wavelength from line length and inferred wind direction from azimuth. It is not possible to infer a unique wind direction from ripple orientation alone and therefore these inferred directions have a 180 degree ambiguity. Initial results from all study sites support previous observations that the Martian surface has many dune types in areas with adequate sand supply. The complexity of ripple patterns varies greatly across sites as well as within individual sites. Some areas of uniform directionality for hundreds of kilometers suggest a unimodal wind regime while overlapping patterns suggest multiple dominant winds or seasonally varying winds. In most areas, form flow related to dune shape seems to have a large effect on orientation and must be considered along with the dune type. As long as the few steep slip faces on these small dunes are avoided, form flow can be considered the dominant cause of deviation from the regional wind direction. Regional results, wind roses, and comparisons to previous work will be presented for individual sites.

  20. Edge pedestal characteristics in JET and JT-60U tokamaks under variable toroidal field ripple

    NARCIS (Netherlands)

    Urano, H.; Saibene, G.; Oyama, N.; Parail, V.; P. de Vries,; Sartori, R.; Kamada, Y.; Kamiya, K.; Loarte, A.; Lonnroth, J.; Sakamoto, Y.; Salmi, A.; Shinohara, K.; Takenaga, H.; Yoshida, M.

    2011-01-01

    The effects of toroidal field (TF) ripple on the edge pedestal characteristics were examined in the TF ripple scan experiments at the plasma current I(p) of 1.1 MA in JET and JT-60U. The TF ripple amplitude delta(R) was defined as a value averaged over the existing ripple wells at the separatrix on

  1. Raman scattering in a nearly resonant density ripple

    International Nuclear Information System (INIS)

    Barr, H.C.; Chen, F.F.

    1987-01-01

    Stimulated Raman scattering of light waves by an underdense plasma is affected by the presence of a density ripple caused by a simultaneously occurring stimulated Brillouin instability. The problem is treated kinetically for the particularly interesting case where the ripple has nearly the same wavelength as the plasma wave. The ripple is found to reduce the growth rate of the usual Raman instability but allows other decay modes to occur. Numerical results for the frequencies, growth rates, and k spectra of these modes are obtained. A physical explanation is given for a baffling result of the calculation. The physical picture is also of interest to particle acceleration by plasma waves

  2. Immune-mediated rippling muscle disease and myasthenia gravis.

    Science.gov (United States)

    Bettini, Mariela; Gonorazky, Hernan; Chaves, Marcelo; Fulgenzi, Ernesto; Figueredo, Alejandra; Christiansen, Silvia; Cristiano, Edgardo; Bertini, Enrico S; Rugiero, Marcelo

    2016-10-15

    Cases of acquired rippling muscle disease in association with myasthenia gravis have been reported. We present three patients with iRMD (immune-mediated rippling muscle disease) and AChR-antibody positive myasthenia gravis. None of them had thymus pathology. They presented exercise-induced muscle rippling combined with generalized myasthenia gravis. One of them had muscle biopsy showing a myopathic pattern and a patchy immunostaining with caveolin antibodies. They were successfully treated steroids and azathioprine. The immune nature of this association is supported by the response to immunotherapies and the positivity of AChR-antibodies. Copyright © 2016 Elsevier B.V. All rights reserved.

  3. Analysis of Input and Output Ripples of PWM AC Choppers

    Directory of Open Access Journals (Sweden)

    Pekik Argo Dahono

    2008-11-01

    Full Text Available This paper presents an analysis of input and output ripples of PWM AC choppers. Expressions of input and output current and voltage ripples of single-phase PWM AC choppers are first derived. The derived expressions are then extended to three-phase PWM AC choppers. As input current and output voltage ripples specification alone cannot be used to determine the unique values of inductance and capacitance of the LC filters, an additional criterion based on the minimum reactive power is proposed. Experimental results are included in this paper to show the validity of the proposed analysis method.

  4. Analisis Ripple Masukan Dan Keluaran PWM AC Chopper 3-Fasa Pada Beban Motor Induksi 3-Fasa

    OpenAIRE

    Luthfi, Muhamad; Dachlan, Harry Soekotjo; Wijono, Wijono

    2013-01-01

    Penggunaan chopper dalam sistem kelistrikan akan menimbulkan ripple pada tegangan keluarannya. Kebanyakan ripple difahami terbangkit pada sisi output. Pada penelitian ini ripple pada sisi input juga dianalisis. Disamping ripple, penggunaan chopper akan membangkitkan harmonisa yang akan menimbulkan rugirugi. Untuk memperkecil rugi-rugi tersebut, pada sisi input maupun output perlu dipasang filter LC. Penentuan nilai komponen filter ini dipengaruhi oleh ripple yang timbul. Dengan mengetahui m...

  5. Climbing ripple structure and associated storm-lamination from a ...

    Indian Academy of Sciences (India)

    Pranhita–Godavari Valley, south India, displays well developed climbing ripple lamination and ... sedimentary environments, such as river flood .... Sediment, sequence and facies ..... tic Archaean Witwatersrand Supergroup, South Africa;.

  6. Oscillatory ripples, evaluation of ancient wave climates and ...

    African Journals Online (AJOL)

    Oscillatory ripples, evaluation of ancient wave climates and epierogeny in the Anambra ... conditions, epierogenic patterns and paleogeographic history of the basins. ... shallow and marked by low to moderate hydrodynamic energy conditions.

  7. Real time algorithms for sharp wave ripple detection.

    Science.gov (United States)

    Sethi, Ankit; Kemere, Caleb

    2014-01-01

    Neural activity during sharp wave ripples (SWR), short bursts of co-ordinated oscillatory activity in the CA1 region of the rodent hippocampus, is implicated in a variety of memory functions from consolidation to recall. Detection of these events in an algorithmic framework, has thus far relied on simple thresholding techniques with heuristically derived parameters. This study is an investigation into testing and improving the current methods for detection of SWR events in neural recordings. We propose and profile methods to reduce latency in ripple detection. Proposed algorithms are tested on simulated ripple data. The findings show that simple realtime algorithms can improve upon existing power thresholding methods and can detect ripple activity with latencies in the range of 10-20 ms.

  8. Design and Analysis of LT Codes with Decreasing Ripple Size

    DEFF Research Database (Denmark)

    Sørensen, Jesper Hemming; Popovski, Petar; Østergaard, Jan

    2012-01-01

    In this paper we propose a new design of LT codes, which decreases the amount of necessary overhead in comparison to existing designs. The design focuses on a parameter of the LT decoding process called the ripple size. This parameter was also a key element in the design proposed in the original...... work by Luby. Specifically, Luby argued that an LT code should provide a constant ripple size during decoding. In this work we show that the ripple size should decrease during decoding, in order to reduce the necessary overhead. Initially we motivate this claim by analytical results related...... to the redundancy within an LT code. We then propose a new design procedure, which can provide any desired achievable decreasing ripple size. The new design procedure is evaluated and compared to the current state of the art through simulations. This reveals a significant increase in performance with respect...

  9. Correlation between the ripple phase and stripe domains in membranes.

    Science.gov (United States)

    Bernchou, Uffe; Midtiby, Henrik; Ipsen, John Hjort; Simonsen, Adam Cohen

    2011-12-01

    We investigate the relationship between stripe domains and the ripple phase in membranes. These have previously been observed separately without being linked explicitly. Past results have demonstrated that solid and ripple phases exhibit rich textural patterns related to the orientational order of tilted lipids and the orientation of ripple corrugations. Here we reveal a highly complex network pattern of ripple and solid domains in DLPC, DPPC bilayers with structures covering length scales from 10 nm to 100 μm. Using spincoated double supported membranes we investigate domains by correlated AFM and fluorescence microscopy. Cooling experiments demonstrate the mode of nucleation and growth of stripe domains enriched in the fluorescent probe. Concurrent AFM imaging reveals that these stripe domains have a one-to-one correspondence with a rippled morphology running parallel to the stripe direction. Both thin and thick stripe domains are observed having ripple periods of 13.5±0.2 nm and 27.4±0.6 nm respectively. These are equivalent to previously observed asymmetric/equilibrium and symmetric/metastable ripple phases, respectively. Thin stripes grow from small solid domains and grow predominantly in length with a speed of ~3 times that of the thick stripes. Thick stripes grow by templating on the sides of thinner stripes or can emerge directly from the fluid phase. Bending and branching angles of stripes are in accordance with an underlying six fold lattice. We discuss mechanisms for the nucleation and growth of ripples and discuss a generic phase diagram that may partly rationalize the coexistence of metastable and stable phases. Copyright © 2011 Elsevier B.V. All rights reserved.

  10. MD 1691: Active halo control using tune ripple at injection

    CERN Document Server

    Garcia Morales, Hector; Bruce, Roderik; Redaelli, Stefano; Fitterer, Miriam; Fiascaris, Maria; Nisbet, David; Thiesen, Hugues; Valentino, Gianluca; Xu, Chen; CERN. Geneva. ATS Department

    2017-01-01

    In this MD we performed halo excitation through tune ripple. This consists in an excitation that introduces new resonance sidebands around the existing resonance lines. In presence of sufficient detuning with amplitude, these sidebands can in principle affect only the dynamics of the halo particles at large amplitudes. Tune ripple was induced through a current modulation of the warm trim quadrupoles in IR7. This is the first time this method is experimentally tested at the LHC.

  11. Uniting ripple-formation theory under water and winds: A universal scaling relation for the wavelength of fluid-drag ripples across fluids and planetary bodies

    Science.gov (United States)

    Lapotre, M. G. A.; Lamb, M. P.; Ewing, R. C.; McElroy, B. J.

    2016-12-01

    Current ripples form on riverbeds and on the seafloor from viscous drag exerted by water flow over sand and are thought to be absent in subaerial systems, where ripple formation is dominated by a mechanism involving the impacting and splashing of sand grains. A fluid-drag mechanism, however, is not precluded in subaerial conditions and was originally hypothesized by R. A. Bagnold. Despite decades of observations in the field and in the laboratory, no universal scaling relation exists to predict the size of fluid-drag ripples. We combine dimensional analysis and a new extensive data compilation to develop a relationship and predict the equilibrium wavelength of current ripples. Our analysis shows that ripples are spaced farther apart when formed by more viscous fluids, smaller bed shear velocities, in coarser grains, or for smaller sediment specific gravity. Our scaling relation also highlights the abrupt transition between current ripples and subaqueous dunes, and thus allows for a process-based segregation of ripples from dunes. When adjusting for subaerial conditions, we predict the formation of decimeter-scale wind-drag ripples on Earth and meter-scale wind-drag ripples on Mars. The latter are ubiquitous on the Red Planet, and are found to co-exist with smaller decimeter-scale ripples, which we interpret as impact ripples. Because the predicted scale of terrestrial wind-drag ripples overlaps with that of impact ripples, it is possible that wind-drag ripples exist on Earth too, but are not recognized as such. When preserved in rocks, fluid-drag ripple stratification records flow directions and fluid properties that are crucial to constrain paleo-environments. Our new theory allows for predictions of ripple size, perhaps in both fluvial and eolian settings, and thus potentially represents a powerful tool for paleo-environmental reconstructions on different planetary bodies.

  12. Multichannel Mars Organic Analyzer (McMOA): Microfluidic Networks for the Automated In Situ Microchip Electrophoretic Analysis of Organic Biomarkers on Mars

    Science.gov (United States)

    Chiesl, T. N.; Benhabib, M.; Stockton, A. M.; Mathies, R. A.

    2010-04-01

    We present the Multichannel Mars Organic Analyzer (McMOA) for the analysis of Amino Acids, PAHs, and Oxidized Carbon. Microfluidic architecures integrating automated metering, mixing, on chip reactions, and serial dilutions are also discussed.

  13. Deterministic ripple-spreading model for complex networks.

    Science.gov (United States)

    Hu, Xiao-Bing; Wang, Ming; Leeson, Mark S; Hines, Evor L; Di Paolo, Ezequiel

    2011-04-01

    This paper proposes a deterministic complex network model, which is inspired by the natural ripple-spreading phenomenon. The motivations and main advantages of the model are the following: (i) The establishment of many real-world networks is a dynamic process, where it is often observed that the influence of a few local events spreads out through nodes, and then largely determines the final network topology. Obviously, this dynamic process involves many spatial and temporal factors. By simulating the natural ripple-spreading process, this paper reports a very natural way to set up a spatial and temporal model for such complex networks. (ii) Existing relevant network models are all stochastic models, i.e., with a given input, they cannot output a unique topology. Differently, the proposed ripple-spreading model can uniquely determine the final network topology, and at the same time, the stochastic feature of complex networks is captured by randomly initializing ripple-spreading related parameters. (iii) The proposed model can use an easily manageable number of ripple-spreading related parameters to precisely describe a network topology, which is more memory efficient when compared with traditional adjacency matrix or similar memory-expensive data structures. (iv) The ripple-spreading model has a very good potential for both extensions and applications.

  14. Moa fossils and chronology of a Pleistocene terrace sequence, Tauweru, Wairarapa, New Zealand

    International Nuclear Information System (INIS)

    Collen, J.D.; Grapes, R.H.; Eager, S.H.

    2000-01-01

    The fortuitous preservation of bones of the medium-sized moa Euryapteryx geranoides (Owen) in Pleistocene colluvial sediments near Tauweru, Wairarapa, has allowed radiocarbon dating of a terrace sequence along the lower Tauweru River. The bones were in a shelly, conglomeratic sandstone on an erosion surface cut into mid-Pliocene (Waipipian) siltstone, and were overlain by loess and situated immediately adjacent to onlapping fluvial gravels. Most of the bones are from a single skeleton buried articulated and apparently nearly complete, and there is also a single left tibiotarsus from a slightly larger bird. Bone from the right femur gave a radiocarbon age of 14 262 +/- 87 yr BP by accelerator mass spectrometry. The material was slightly chalky and had a low collagen yield with a relatively large amount of humic material; contamination which would lower the measured age is thus possible. However, an amino acid profile characteristic of collagen makes it unlikely that high contaminant levels are present. The radiocarbon age for the bone is likely to be 14-18 ka (16-22 000 cal. yr) or possibly older, with the lower limit being set by the radiocarbon age and the upper limit inferred from the amount of humic contamination. This is thus the oldest moa skeleton reported from Wairarapa. Loess overlying the bones contains disseminated shards of clear rhyolitic glass with a composition identical to that of the 22.6 ka (24 500 cal. yr) Kawakawa Tephra, and gave an age by optical dating of 26 +/- 2 ka. A thicker tephra deposit within loess on a higher, deeply dissected surface may also be partly reworked; optical dating of a sample of loess from 2 m beneath it gave an age of 22 +/- 2 ka. Thermoluminescence dating of two samples of the conglomeratic deposits surrounding the bones gave ages of 52 +/- 13.2 and 102 +/- 18 ka, respectively, indicating redeposition of these sediments without resetting of the thermoluminescence signal. One of these samples was also dated by optical

  15. 4'-Methyl derivatives of 5-MOP and 5-MOA: synthesis, photoreactivity, and photobiological activity.

    Science.gov (United States)

    Gia, O; Anselmo, A; Conconi, M T; Antonello, C; Uriarte, E; Caffieri, S

    1996-10-25

    The synthesis and photobiological activity of four new 4'-methyl derivatives of 5-MOP (5-methoxypsoralen) and 5-MOA (5-methoxyangelicin), i.e., 4,4'-dimethyl-5-methoxypsoralen, 3,4'-dimethyl-5-methoxypsoralen, 4,4'-dimethyl-5-methoxyangelicin, and 3,4'-dimethyl-5-methoxyangelicin, are described. All these compounds photobind efficiently to DNA. The DNA-photobinding process was investigated using various nucleic acid structures such as double-helix DNA, bacterial DNA, and synthetic polydeoxyribonucleotides. Photoreaction experiments showed that, unlike 8-MOP (8-methoxypsoralen) and 5-MOP, both angular derivatives bind thymine and cytosine with the same efficiency. The principal nucleoside-psoralen monoadducts were isolated and characterized after enzymatic digestion or acid hydrolysis. Biological activity studies revealed a good correlation with the extent of covalent photoaddition. Moreover, the two angular derivatives and the 4,4'-dimethyl-5-methoxypsoralen were unable to induce skin erythema, in striking contrast with the reference drugs, 8-MOP and 5-MOP; only the 3,4'-dimethyl-5-methoxypsoralen caused erythema, although to a substantially lower extent than that induced by the two parent compounds.

  16. MOA-2010-BLG-328Lb: A sub-Neptune orbiting very late M dwarf?

    International Nuclear Information System (INIS)

    Furusawa, K.; Abe, F.; Itow, Y.; Masuda, K.; Matsubara, Y.; Udalski, A.; Sumi, T.; Bennett, D. P.; Bond, I. A.; Ling, C. H.; Gould, A.; Jørgensen, U. G.; Snodgrass, C.; Prester, D. Dominis; Albrow, M. D.; Botzler, C. S.; Freeman, M.; Chote, P.; Harris, P.; Fukui, A.

    2013-01-01

    We analyze the planetary microlensing event MOA-2010-BLG-328. The best fit yields host and planetary masses of M h = 0.11 ± 0.01 M ☉ and M p = 9.2 ± 2.2 M ⊕ , corresponding to a very late M dwarf and sub-Neptune-mass planet, respectively. The system lies at D L = 0.81 ± 0.10 kpc with projected separation r = 0.92 ± 0.16 AU. Because of the host's a priori unlikely close distance, as well as the unusual nature of the system, we consider the possibility that the microlens parallax signal, which determines the host mass and distance, is actually due to xallarap (source orbital motion) that is being misinterpreted as parallax. We show a result that favors the parallax solution, even given its close host distance. We show that future high-resolution astrometric measurements could decisively resolve the remaining ambiguity of these solutions

  17. MOA-2010-BLG-328Lb: A sub-Neptune orbiting very late M dwarf?

    Energy Technology Data Exchange (ETDEWEB)

    Furusawa, K.; Abe, F.; Itow, Y.; Masuda, K.; Matsubara, Y. [Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya 464-8601 (Japan); Udalski, A. [Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland); Sumi, T. [Department of Earth and Space Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043 (Japan); Bennett, D. P. [Department of Physics, 225 Nieuwland Science Hall, University of Notre Dame, Notre Dame, IN 46556 (United States); Bond, I. A.; Ling, C. H. [Institute for Information and Mathematical Sciences, Massey University, Private Bag 102-904, Auckland 1330 (New Zealand); Gould, A. [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Jørgensen, U. G. [Niels Bohr Institutet, Københavns Universitet, Juliane Maries Vej 30, 2100 Copenhagen (Denmark); Snodgrass, C. [Max Planck Institute for Solar System Research, Max-Planck-Str. 2, D-37191 Katlenburg-Lindau (Germany); Prester, D. Dominis [Department of Physics, University of Rijeka, Omladinska 14, 51000 Rijeka (Croatia); Albrow, M. D. [Department of Physics and Astronomy, University of Canterbury, Private Bag 4800, Christchurch 8020 (New Zealand); Botzler, C. S.; Freeman, M. [Department of Physics, University of Auckland, Private Bag 92-019, Auckland 1001 (New Zealand); Chote, P.; Harris, P. [School of Chemical and Physical Sciences, Victoria University, Wellington (New Zealand); Fukui, A., E-mail: furusawa@stelab.nagoya-u.ac.jp, E-mail: liweih@astro.ucla.edu, E-mail: tim.natusch@aut.ac.nz, E-mail: rzellem@lpl.arizona.edu [Okayama Astrophysical Observatory, National Astronomical Observatory of Japan, 3037-5 Honjo, Kamogata, Asakuchi, Okayama 719-0232 (Japan); Collaboration: MOA Collaboration; OGLE Collaboration; μFUN Collaboration; MiNDSTEp Consortium; RoboNet Collaboration; PLANET Collaboration; and others

    2013-12-20

    We analyze the planetary microlensing event MOA-2010-BLG-328. The best fit yields host and planetary masses of M {sub h} = 0.11 ± 0.01 M {sub ☉} and M {sub p} = 9.2 ± 2.2 M {sub ⊕}, corresponding to a very late M dwarf and sub-Neptune-mass planet, respectively. The system lies at D {sub L} = 0.81 ± 0.10 kpc with projected separation r = 0.92 ± 0.16 AU. Because of the host's a priori unlikely close distance, as well as the unusual nature of the system, we consider the possibility that the microlens parallax signal, which determines the host mass and distance, is actually due to xallarap (source orbital motion) that is being misinterpreted as parallax. We show a result that favors the parallax solution, even given its close host distance. We show that future high-resolution astrometric measurements could decisively resolve the remaining ambiguity of these solutions.

  18. Thermal dynamics of silver clusters grown on rippled silica surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Bhatnagar, Mukul, E-mail: mkbh10@gmail.com [FCIPT, Institute for Plasma Research, Gandhinagar, Gujarat (India); Nirma University, Ahmedabad, Gujarat (India); Ranjan, Mukesh [FCIPT, Institute for Plasma Research, Gandhinagar, Gujarat (India); Nirma University, Ahmedabad, Gujarat (India); Jolley, Kenny; Lloyd, Adam; Smith, Roger [Dept. of Mathematical Sciences, Loughborough University, Leicestershire LE11 3TU (United Kingdom); Mukherjee, Subroto [FCIPT, Institute for Plasma Research, Gandhinagar, Gujarat (India); Nirma University, Ahmedabad, Gujarat (India)

    2017-02-15

    Highlights: • Low energy oblique angle ion bombardment forms ripple pattern on silicon surface. • The ripple patterns have wavelengths between 20 and 45 nm and correspondingly low height. • Silver nanoparticles have been deposited at an angle of 70° on patterned silicon templates. • The as-deposited np are annealed in vacuo at temperature of 573 K for a time duration of 1 h. • MD simulation is used to model the process and compare the results to the experiment. • Results show that silver clusters grow preferentially along parallel to the rippled surface. • Mobility of silver atoms depends on the site to which they are bonded on this amorphous surface. • MD simulations show contour ordered coalescence which is dependent on ripple periodicity. - Abstract: Silver nanoparticles have been deposited on silicon rippled patterned templates at an angle of incidence of 70° to the surface normal. The templates are produced by oblique incidence argon ion bombardment and as the fluence increases, the periods and heights of the structures increase. Structures with periods of 20 nm, 35 nm and 45 nm have been produced. Moderate temperature vacuum annealing shows the phenomenon of cluster coalescence following the contour of the more exposed faces of the ripple for the case of 35 nm and 45 nm but not at 20 nm where the silver aggregates into larger randomly distributed clusters. In order to understand this effect, the morphological changes of silver nanoparticles deposited on an asymmetric rippled silica surface are investigated through the use of molecular dynamics simulations for different deposition angles of incidence between 0° and 70° and annealing temperatures between 500 K and 900 K. Near to normal incidence, clusters are observed to migrate over the entire surface but for deposition at 70°, a similar patterning is observed as in the experiment. The random distribution of clusters for the periodicity ≈ of 20 nm is linked to the geometry of the silica

  19. VHTR Construction Ripple Effect using Inter-Industry Analysis

    International Nuclear Information System (INIS)

    Lee, T. H.; Lee, K. Y.; Shin, Y. J.

    2015-01-01

    As a part of a VHTR economic analysis, we have studied the VHTR construction cost and operation and maintenance cost. However, it is somewhat difficult to expect the exact cost due to insufficient reference data and experience. As a result, we propose quantitative analysis techniques for ripple effects such as the production inducement effect, added value inducement effect, and employment inducement effect for VHTR 600MWt x 4 module construction and operation ripple effect based on NOAK. This paper presents a new method for the ripple effect and preliminary ripple effect consequence. We proposed a ripple effect analysis method using a time series and inter-industry table. As a result, we can predict that a 600MWth x 4 module VHTR reactor construction will bring about a 43771 employment effect, 24160 billion KRW production effect, and 4472 billion added value effect for 22 years. It is necessary to use the sub-account values of an inter-industry table to obtain a more precise effect result. However, the methodology can be applied with minor modification to another reactor type.

  20. VHTR Construction Ripple Effect using Inter-Industry Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Lee, T. H.; Lee, K. Y.; Shin, Y. J. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-10-15

    As a part of a VHTR economic analysis, we have studied the VHTR construction cost and operation and maintenance cost. However, it is somewhat difficult to expect the exact cost due to insufficient reference data and experience. As a result, we propose quantitative analysis techniques for ripple effects such as the production inducement effect, added value inducement effect, and employment inducement effect for VHTR 600MWt x 4 module construction and operation ripple effect based on NOAK. This paper presents a new method for the ripple effect and preliminary ripple effect consequence. We proposed a ripple effect analysis method using a time series and inter-industry table. As a result, we can predict that a 600MWth x 4 module VHTR reactor construction will bring about a 43771 employment effect, 24160 billion KRW production effect, and 4472 billion added value effect for 22 years. It is necessary to use the sub-account values of an inter-industry table to obtain a more precise effect result. However, the methodology can be applied with minor modification to another reactor type.

  1. Spontaneous ripple formation in phosphorene: electronic properties and possible applications.

    Science.gov (United States)

    Zhou, Yungang; Yang, Li; Zu, Xiaotao; Gao, Fei

    2016-06-09

    According to the Mermin-Wagner theorem and theory of elasticity, long-range order in two-dimensional (2D) crystals will be inevitably destroyed due to a thermal fluctuation. Thus, a 2D lattice prefers a corrugation meaning that a 2D crystal is easy to present a ripple. In this work, we, via employing ab initio molecular dynamics (AIMD) simulations, for the first time evidenced that the inherent dynamics of phosphorene would lead to a spontaneous formation of ripples at room temperature. The height of a ripple closely associates with the temperature and the width. Via density functional theory (DFT) calculations, we further demonstrated that the emergence of ripples would remarkably reduce the bandgap of phosphorene. Via the construction of the unique phosphorene structure, we finally found that such a rippled structure is expected to be used in the light-emitting field. These results give us further knowledge of phosphorene, which goes beyond the current scope of phosphorene limited to the flat lattice.

  2. Wave plus current over a ripple-covered bed

    DEFF Research Database (Denmark)

    Fredsøe, Jørgen; Andersen, Ken Haste; Sumer, B. Mutlu

    1999-01-01

    This paper concerns the combined wave and current boundary layer flow over a ripple-covered bed, The study comprises experiments as well as a numerical modelling study: the experimental part comprises laser Doppler anemometry (LDA) velocity and turbulence measurements, and a flow-visualization st......This paper concerns the combined wave and current boundary layer flow over a ripple-covered bed, The study comprises experiments as well as a numerical modelling study: the experimental part comprises laser Doppler anemometry (LDA) velocity and turbulence measurements, and a flow......-visualization study in the laboratory with ripples, 22 cm in length, and 3.5 cm in height. One wave-alone, three current-alone, and three combined waves and current tests were conducted. The wave-velocity-to-current-velocity ratio ranges from 1 to 2.4. The orbiral-amplitude-ro-ripple-length ratio (at the bed) is 0.......41. The effect of superimposing waves on a current is to displace the velocity profile to higher elevations. The velocity profiles exhibit two "logarithmic layers", one associated with the actual roughness of the bed (the actual ripple roughness), and the other with the apparent roughness induced by the waves...

  3. Mechanisms for Selective Single-Cell Reactivation during Offline Sharp-Wave Ripples and Their Distortion by Fast Ripples.

    Science.gov (United States)

    Valero, Manuel; Averkin, Robert G; Fernandez-Lamo, Ivan; Aguilar, Juan; Lopez-Pigozzi, Diego; Brotons-Mas, Jorge R; Cid, Elena; Tamas, Gabor; Menendez de la Prida, Liset

    2017-06-21

    Memory traces are reactivated selectively during sharp-wave ripples. The mechanisms of selective reactivation, and how degraded reactivation affects memory, are poorly understood. We evaluated hippocampal single-cell activity during physiological and pathological sharp-wave ripples using juxtacellular and intracellular recordings in normal and epileptic rats with different memory abilities. CA1 pyramidal cells participate selectively during physiological events but fired together during epileptic fast ripples. We found that firing selectivity was dominated by an event- and cell-specific synaptic drive, modulated in single cells by changes in the excitatory/inhibitory ratio measured intracellularly. This mechanism collapses during pathological fast ripples to exacerbate and randomize neuronal firing. Acute administration of a use- and cell-type-dependent sodium channel blocker reduced neuronal collapse and randomness and improved recall in epileptic rats. We propose that cell-specific synaptic inputs govern firing selectivity of CA1 pyramidal cells during sharp-wave ripples. Copyright © 2017 Elsevier Inc. All rights reserved.

  4. Output Current Ripple Reduction Algorithms for Home Energy Storage Systems

    Directory of Open Access Journals (Sweden)

    Jin-Hyuk Park

    2013-10-01

    Full Text Available This paper proposes an output current ripple reduction algorithm using a proportional-integral (PI controller for an energy storage system (ESS. In single-phase systems, the DC/AC inverter has a second-order harmonic at twice the grid frequency of a DC-link voltage caused by pulsation of the DC-link voltage. The output current of a DC/DC converter has a ripple component because of the ripple of the DC-link voltage. The second-order harmonic adversely affects the battery lifetime. The proposed algorithm has an advantage of reducing the second-order harmonic of the output current in the variable frequency system. The proposed algorithm is verified from the PSIM simulation and experiment with the 3 kW ESS model.

  5. Rippling modes in the edge of a tokamak plasma

    International Nuclear Information System (INIS)

    Carreras, B.A.; Callen, J.D.; Gaffney, P.W.; Hicks, H.R.

    1982-02-01

    A promising resistive magnetohydrodynamic candidate for the underlying cause of turbulence in the edge of a tokamak plasma is the rippling instability. In this paper we develop a computational model for these modes in the cylindrical tokamak approximation and explore the linear growth and single-helicity quasi-linear saturation phases of the rippling modes for parameters appropriate to the edge of a tokamak plasma. Large parallel heat conduction does not stabilize these modes; it only reduces their growth rate by a factor scaling as k/sub parallel//sup -4/3/. Nonlinearly, individual rippling modes are found to saturate by quasi-linear flattening of the resistivity profile. The saturated amplitude of the modes scales as m/sup -1/, and the radial extent of these modes grows linearly with time due to radial Vector E x Vector B 0 convection. This evolution is found to be terminated by parallel heat conduction

  6. Rippling modes in the edge of a tokamak plasma

    International Nuclear Information System (INIS)

    Carreras, B.A.; Gaffney, P.W.; Hicks, H.R.; Callan, J.D.

    1982-01-01

    A promising resistive magnetohydrodynamic candidate for the underlying cause of turbulence in the edge of a tokamak plasma is the rippling instability. In this paper a computational model for these modes in the cylindrical tokamak approximation was developed and the linear growth and single-helicity quasi-linear saturation phases of the rippling modes for parameters appropriate to the edge of a tokamak plasma were explored. Large parallel heat conduction does not stabilize these modes; it only reduces their growth rate by a factor sacling as K/sup -4/3//sub parallel/. Nonlinearly, individual rippling modes are found to saturate by quasi-linear flattening of the resistivity profile. The saturated amplitude of the modes scales as m -1 , and the radial extent of these modes grows linearly with time due to radial E x B 0 convection. This evolution is found to be terminated by parallel heat conduction

  7. Evolution of a Rippled Membrane during Phospholipase A2 Hydrolysis Studied by Time-Resolved AFM

    DEFF Research Database (Denmark)

    Leidy, Chad; Mouritsen, Ole G.; Jørgensen, Kent

    2004-01-01

    The sensitivity of phospholipase A2 (PLA2) for lipid membrane curvature is explored by monitoring, through time-resolved atomic force microscopy, the hydrolysis of supported double bilayers in the ripple phase. The ripple phase presents a corrugated morphology. PLA2 is shown to have higher activity...... toward the ripple phase compared to the gel phase in 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) membranes, indicating its preference for this highly curved membrane morphology. Hydrolysis of the stable and metastable ripple structures is monitored for equimolar DMPC/1,2-distearoyl- sn-glycero-3....... This is reflected in an increase in ripple spacing, followed by a sudden flattening of the lipid membrane during hydrolysis. Hydrolysis of the ripple phase results in anisotropic holes running parallel to the ripples, suggesting that the ripple phase has strip regions of higher sensitivity to enzymatic attack. Bulk...

  8. Helical ripple transport in stellarators at low collision frequency

    International Nuclear Information System (INIS)

    Beidler, C.D.

    1987-12-01

    Numerical and analytical techniques have been developed to investigate the plasma transport which is due to particles trapping/detrapping in the local helical ripple wells of a stellarator's magnetic field. This process is of considerable importance as it provides the dominant transport mechanism in a stellarator plasma at ''low'' collision frequency: that is, when the frequency with which a particle is collisionally detrapped from a local ripple well is less than the bounce frequency of the particle in that well. A form of the longitudinal adiabatic invariant, J, is constructed and shown to describe accurately the orbits of ripple trapped particles. Unlike previous expressions for J, the form derived here correctly accounts for the local toroidal variation of the magnetic field. The expression for J is incorporated into a rapid ''hybrid'' Monte Carlo simulation of ripple transport in stellarators. The simulation is a hybrid in the sense that particle orbits in the narrow region of phase space on either side of the ripple trapping/detrapping boundary are followed using guiding center equations of motion while orbits in the remainder of phase space are described using adiabatic invariants. An analytical expression for the distribution function of ripple trapped particles in a stellarator - valid at all low collision frequencies - has been obtained by series solution of the bounce - averaged kinetic equation. This solution has been applied to both 'standard' and a class of 'transport optimized' stellarator magnetic fields. Analytical estimates of the diffusion coefficient obtained from the series solution show excellent agreement with the numerical results of the hybrid Monte Carlo code in all cases studied. 55 refs., 30 figs

  9. Mechanisms of sharp wave initiation and ripple generation.

    Science.gov (United States)

    Schlingloff, Dániel; Káli, Szabolcs; Freund, Tamás F; Hájos, Norbert; Gulyás, Attila I

    2014-08-20

    Replay of neuronal activity during hippocampal sharp wave-ripples (SWRs) is essential in memory formation. To understand the mechanisms underlying the initiation of irregularly occurring SWRs and the generation of periodic ripples, we selectively manipulated different components of the CA3 network in mouse hippocampal slices. We recorded EPSCs and IPSCs to examine the buildup of neuronal activity preceding SWRs and analyzed the distribution of time intervals between subsequent SWR events. Our results suggest that SWRs are initiated through a combined refractory and stochastic mechanism. SWRs initiate when firing in a set of spontaneously active pyramidal cells triggers a gradual, exponential buildup of activity in the recurrent CA3 network. We showed that this tonic excitatory envelope drives reciprocally connected parvalbumin-positive basket cells, which start ripple-frequency spiking that is phase-locked through reciprocal inhibition. The synchronized GABA(A) receptor-mediated currents give rise to a major component of the ripple-frequency oscillation in the local field potential and organize the phase-locked spiking of pyramidal cells. Optogenetic stimulation of parvalbumin-positive cells evoked full SWRs and EPSC sequences in pyramidal cells. Even with excitation blocked, tonic driving of parvalbumin-positive cells evoked ripple oscillations. Conversely, optogenetic silencing of parvalbumin-positive cells interrupted the SWRs or inhibited their occurrence. Local drug applications and modeling experiments confirmed that the activity of parvalbumin-positive perisomatic inhibitory neurons is both necessary and sufficient for ripple-frequency current and rhythm generation. These interneurons are thus essential in organizing pyramidal cell activity not only during gamma oscillation, but, in a different configuration, during SWRs. Copyright © 2014 the authors 0270-6474/14/3411385-14$15.00/0.

  10. Effects of complex magnetic ripple on fast ions in JFT-2M ferritic insert experiments

    International Nuclear Information System (INIS)

    Shinohara, Kouji; Kawashima, H.; Tsuzuki, K.

    2003-01-01

    In JFT-2M, the ferritic steel plates (FPs) were installed inside the vacuum vessel all over vacuum vessel, which is named Ferritic Inside Wall (FIW), as the third step of the Advanced Material Tokamak Experiment (AMTEX) program. A toroidal field ripple was reduced, however the magnetic field structure has become the complex ripple structure with a non-periodic feature in the toroidal direction because of the existence of other components and ports that limit the periodic installation of FPs. Under the complex magnetic ripple, we investigated its effect on the heat flux to the first wall due to the fast ion loss. The small heat flux was observed as the result of the reduced magnetic ripple by FIW. Additional FPs were also installed outside the vacuum vessel to produce the localized larger ripple. The small ripple trapped loss was observed when the shallow ripple well exist in the poloidal cross section, and the large ripple trapped loss was observed when the ripple well hollow out the plasma region deeply. The experimental results were almost consistent with the newly developed Fully three Dimensional magnetic field Orbit-Following Monte-Carlo (F3D OFMC) code including the three dimensional complex structure of the toroidal field ripple and the non-axisymmetric first wall geometry. By using F3D OFMC, we investigated the effect on the ripple trapped loss of the localized larger ripple produced by FPs in detail. The ripple well structure, e.g. the thickness of the ripple well, is important for ripple trapped loss in complex magnetic ripple rather than the value defined at one position in a poloidal cross section. (author)

  11. Ion bombardment induced ripple topography on amorphous solids

    International Nuclear Information System (INIS)

    Carter, G.; Nobes, M.J.; Paton, F.; Williams, J.S.

    1977-01-01

    Earlier studies of the ion bombardment induced ripple morphology on the surfaces of amorphous solids when compared with geomorphological effects are shown to possess many similar features. The present study, with 40 keV Ar + ion bombarded Si suggests that analogies are incomplete, however, and that greater similarities with the process of macroscopic sandblasting (corrosion) exist. It is shown that the genesis of wave like structures on Si is from isolated features, which have the appearance of ripple trains, which are faceted. It is suggested that these features result from particle flux enhancement processes near surface dimples generated by stress induced surface lifting. (author)

  12. Buck supplies output voltage ripple reduction using fuzzy control

    Directory of Open Access Journals (Sweden)

    Nicu BIZON

    2007-12-01

    Full Text Available Using the PWM control for switching power supplies the peaks EMI noise appear at the switching frequency and its harmonics. Using randomize or chaotic PWM control techniques in these systems the power spectrum is spread out in all frequencies band spectral emissions, but with a bigger ripple in the output voltage. The proposed nonlinear feedback control method, which induces chaos, is based by fuzzy rules that minimize the output voltage ripple. The feasibility and effectiveness of this relative simple method is shown by simulation. A comparison with the previous control method is included, too.

  13. Gravitational-Like Lens Based on Graphene Ripple.

    Science.gov (United States)

    Liu, Daqing; Chen, Shuyue; Ma, Ning; Zhao, Xiang; Xu, Zhuo

    2015-10-01

    We conducted a semiclassical study on carrier movement in curved graphene. A previous attempt was made to show that curved graphene is a readily available and cheap laboratory material used to study general relativity effects, especially if the electron energies satisfy 4μeV ≪ |E| ≪ 3eV. Furthermore, a gravitational-like lens can be constructed based on a special graphene ripple; this lens has neither chromatic nor cometic aberration. One can design an ideal electron lens using a graphene ripple.

  14. Preliminary ripple effect analysis for HTR 350MWt 4 modules construction

    Energy Technology Data Exchange (ETDEWEB)

    Lee, T. H.; Lee, K. Y.; Shin, Y. J. [KAERI, Daejeon (Korea, Republic of)

    2016-05-15

    We propose quantitative analysis techniques for ripple effects such as the production inducement effect and employment inducement effect for HTR 350MWt x 4 module construction and operation ripple effect based on NOAK. It is known that APR1400 reactors export ripple effect is about 8,500 billion KRW. As a result, HTR construction has more effective effect than that of APR1400.

  15. MOA-2008-BLG-379Lb: A massive planet from a high magnification event with a faint source

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, D.; Sumi, T.; Fukagawa, M.; Shibai, H. [Department of Earth and Space Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043 (Japan); Udalski, A. [Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland); Bennett, D. P. [Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States); Bond, I. A.; Ling, C. H. [Institute of Information and Mathematical Sciences, Massey University, Private Bag 102-904, North Shore Mail Centre, Auckland (New Zealand); Abe, F.; Furusawa, K.; Itow, Y.; Masuda, K.; Matsubara, Y. [Solar-Terrestrial Environment Laboratory, Nagoya University, Furo-cho, Chikusa, Nagoya, Aichi 464-8601 (Japan); Botzler, C. S.; Freeman, M.; Rattenbury, N. [Department of Physics, University of Auckland, Private Bag 92019, Auckland (New Zealand); Fukui, A. [Okayama Astrophysical Observatory, National Astronomical Observatory, 3037-5 Honjo, Kamogata, Asakuchi, Okayama 719-0232 (Japan); Muraki, Y. [Department of Physics, Konan University, Nishiokamoto 8-9-1, Kobe 658-8501 (Japan); Ohnishi, K. [Nagano National College of Technology, Nagano 381-8550 (Japan); Saito, To. [Tokyo Metropolitan College of Industrial Technology, Tokyo 116-8523 (Japan); Collaboration: MOA Collaboration; OGLE Collaboration; and others

    2014-01-10

    We report on the analysis of the high microlensing event MOA-2008-BLG-379, which has a strong microlensing anomaly at its peak due to a massive planet with a mass ratio of q = 6.9 × 10{sup –3}. Because the faint source star crosses the large resonant caustic, the planetary signal dominates the light curve. This is unusual for planetary microlensing events, and as a result, the planetary nature of this light curve was not immediately noticed. The planetary nature of the event was found when the Microlensing Observations in Astrophysics (MOA) Collaboration conducted a systematic study of binary microlensing events previously identified by the MOA alert system. We have conducted a Bayesian analysis based on a standard Galactic model to estimate the physical parameters of the lens system. This yields a host star mass of M{sub L}=3.3{sub −1.2}{sup +1.7} M{sub ⊙} orbited by a planet of mass m{sub P}=0.56{sub −0.27}{sup +0.24} M{sub Jup} at an orbital separation of a=3.3{sub −1.2}{sup +1.3} AU at a distance of D{sub L}=4.1{sub −1.9}{sup +1.7} kpc. The faint source magnitude of I {sub S} = 21.30 and relatively high lens-source relative proper motion of μ{sub rel} = 7.6 ± 1.6 mas yr{sup –1} imply that high angular resolution adaptive optics or Hubble Space Telescope observations are likely to be able to detect the source star, which would determine the masses and distance of the planet and its host star.

  16. ALFIN-ORG: Sitio web para el desarrollo de habilidades informacionales en el Instituto Superior Metalúrgico de Moa

    Directory of Open Access Journals (Sweden)

    MSc. Miguel Ángel Fernández Marín

    2016-04-01

    Full Text Available En el Instituto Superior Minero Metalúrgico de Moa, no existe acceso pleno a todas las fuentes de información, no se le da el uso adecuado a las tecnologías, no hay cultura infor­macional de cómo aprovecharla y a la hora de determinar que es útil, no se toma la decisión correcta. Debido a esto, existe un cúmulo de información que no es aprovechada y tras el avance tecnológico crece cada día. Por estas ra­zones, es necesario que se pueda trabajar y asimilar toda la información de manera correcta, basado en el desarro­llo de estrategias de búsqueda mediante la utilización de los medios digitales. Para darle solución a la problemática anterior, se proyecta el objetivo de crear un sitio web que contribuya al desarrollo de habilidades informacionales en el Instituto Superior Minero Metalúrgico de Moa. Para la con­fección del sitio web se utilizó Hot Potatoes 6.3.0.3 para di­señar los sistemas de ejercicios de autoevaluación en el sitio web. Joomla 1.6.0 para el desarrollo del sitio web. Como len­guaje de programación PHP Script Language versión 5.2.6. Como gestor de Bases de Datos MySQL Database versión 5.0.51b. El resultado del trabajo constituye un sitio web que posee una estructura informativa-evaluativa para lograr las habilidades informacionales en el Instituto Superior Minero Metalúrgico de Moa.

  17. Recent developments of the MOA thruster, a high performance plasma accelerator for nuclear power and propulsion applications

    International Nuclear Information System (INIS)

    Frischauf, N.; Hettmer, M.; Grassauer, A.; Bartusch, T.; Koudelka, O.

    2008-01-01

    More than 60 years after the late Nobel laureate Hannes Alfven had published a letter stating that oscillating magnetic fields can accelerate ionised matter via magneto-hydrodynamic interactions in a wave like fashion, the technical implementation of Alfven waves for propulsive purposes has been proposed, patented and examined for the first time by a group of inventors. The name of the concept, utilising Alfven waves to accelerate ionised matter for propulsive purposes, is MOA -Magnetic field Oscillating Amplified thruster. Alfven waves are generated by making use of two coils, one being permanently powered and serving also as magnetic nozzle, the other one being switched on and off in a cyclic way, deforming the field lines of the overall system. It is this deformation that generates Alfven waves, which are in the next step used to transport and compress the propulsive medium, in theory leading to a propulsion system with a much higher performance than any other electric propulsion system. Based on computer simulations, which were conducted to get a first estimate on the performance of the system, MOA is a highly flexible propulsion system, whose performance parameters might easily be adapted, by changing the mass flow and/or the power level. As such the system is capable to deliver a maximum specific impulse of 13116 s (12.87 mN) at a power level of 11.16 kW, using Xe as propellant, but can also be attuned to provide a thrust of 236.5 mN (2411 s) at 6.15 kW of power. While space propulsion is expected to be the prime application for MOA and is supported by numerous applications such as Solar and/or Nuclear Electric Propulsion or even as an 'afterburner system' for Nuclear Thermal Propulsion, other terrestrial applications can be thought of as well, making the system highly suited for a common space-terrestrial application research and utilization strategy. This paper presents the recent developments of the MOA Thruster R and D activities at QASAR, the company in

  18. Plasma-filled rippled wall rectangular backward wave oscillator

    Indian Academy of Sciences (India)

    Performance of the backward wave oscillator (BWO) is greatly enhanced with the introduction of plasma. Linear theory of the dispersion relation and the growth rate have been derived and analysed numerically for plasma-filled rippled wall rectangular waveguide driven by sheet electron beam. To see the effect of plasma ...

  19. Wave Driven Fluid-Sediment Interactions over Rippled Beds

    Science.gov (United States)

    Foster, Diane; Nichols, Claire

    2008-11-01

    Empirical investigations relating vortex shedding over rippled beds to oscillatory flows date back to Darwin in 1883. Observations of the shedding induced by oscillating forcing over fixed beds have shown vortical structures to reach maximum strength at 90 degrees when the horizontal velocity is largest. The objective of this effort is to examine the vortex generation and ejection over movable rippled beds in a full-scale, free surface wave environment. Observations of the two-dimensional time-varying velocity field over a movable sediment bed were obtained with a submersible Particle Image Velocimetry (PIV) system in two wave flumes. One wave flume was full scale and had a natural sand bed and the other flume had an artificial sediment bed with a specific gravity of 1.6. Full scale observations over an irregularly rippled bed show that the vortices generated during offshore directed flow over the steeper bed form slope were regularly ejected into the water column and were consistent with conceptual models of the oscillatory flow over a backward facing step. The results also show that vortices remain coherent during ejection when the background flow stalls (i.e. both the velocity and acceleration temporarily approach zero). These results offer new insight into fluid sediment interaction over rippled beds.

  20. Analysis of ripple formation in single crystal spot welds

    Energy Technology Data Exchange (ETDEWEB)

    Rappaz, M. [Ecole Polytechnique Federale de Lausanne (Switzerland). Lab de Metallurgie Physique; Corrigan, D.; Boatner, L.A. [Oak Ridge National Lab., TN (United States). Solid State Div.

    1997-10-01

    Stationary spot welds have been made at the (001) surface of Fe-l5%Ni-15%Cr single crystals using a Gas Tungsten Arc (GTA). On the top surface of the spot welds, very regular and concentric ripples were observed after solidification by differential interference color microscopy. Their height (typically 1--5 {micro}m) and spacing (typically {approximately} 60 {micro}m) decreased with the radius of the pool. These ripples were successfully accounted for in terms of capillary-wave theory using the fundamental mode frequency f{sub 0} given by the first zero of the zero-order Bessel function. The spacing d between the ripples was then equated to v{sub s}/f{sub 0}, where v{sub s} is the solidification rate. From the measured ripple spacing, the velocity of the pool was deduced as a function of the radius, and this velocity was in good agreement with the results of a heat-flow simulation.

  1. Ripple distribution for nonlinear fiber-optic channels.

    Science.gov (United States)

    Sorokina, Mariia; Sygletos, Stylianos; Turitsyn, Sergei

    2017-02-06

    We demonstrate data rates above the threshold imposed by nonlinearity on conventional optical signals by applying novel probability distribution, which we call ripple distribution, adapted to the properties of the fiber channel. Our results offer a new direction for signal coding, modulation and practical nonlinear distortions compensation algorithms.

  2. A low-ripple chargepump circuit for high voltage applications

    NARCIS (Netherlands)

    Berkhout, M.; Berkhout, M.; van Steenwijk, G.; van Steenwijk, Gijs; van Tuijl, Adrianus Johannes Maria

    1995-01-01

    The subject of this paper is a fully integrated chargepump circuit with a very low output voltage ripple. At a supply voltage of 30V the chargepump can source 1mA at an output voltage of 40V. Two simple modifications to the classical chargepump circuit give a substantial reduction of the output

  3. Uncovering Transdisciplinary Team Project Outcomes through Ripple Effect Mapping

    Science.gov (United States)

    Daniels, Catherine H.; Chalker-Scott, Linda; Martini, Nicole

    2016-01-01

    The Garden Team at Washington State University is a transdisciplinary, geographically dispersed group of faculty and staff. As with many such teams, member retention requires effort, as busy individuals may not see the overall benefits of active team membership. Ripple effect mapping is a strategy that can illustrate the tangible and often…

  4. The WEBSIM FISHBANKS Simulation Laboratory: Analysis of Its Ripple Effects

    Science.gov (United States)

    Arantes do Amaral, João Alberto; Hess, Aurélio

    2018-01-01

    In this article, we discuss the ripple effects of the WEBSIM FISHBANKS Simulation Laboratory held at Federal University of Sao Paulo (UNIFESP) in 2014, held as a result of a partnership between the Sloan School of Management of the Massachusetts Institute of Technology, the UNIFESP, and the Brazilian Chapter of the System Dynamics Society of…

  5. Ripple design of LT codes for AWGN channel

    DEFF Research Database (Denmark)

    Sørensen, Jesper Hemming; Koike-Akino, Toshiaki; Orlik, Philip

    2012-01-01

    In this paper, we present an analytical framework for designing LT codes in additive white Gaussian noise (AWGN) channels. We show that some of analytical results from binary erasure channels (BEC) also hold in AWGN channels with slight modifications. This enables us to apply a ripple-based design...

  6. Ripple Design of LT Codes for BIAWGN Channels

    DEFF Research Database (Denmark)

    Sørensen, Jesper Hemming; Koike-Akino, Toshiaki; Orlik, Philip

    2014-01-01

    This paper presents a novel framework, which enables a design of rateless codes for binary input additive white Gaussian noise (BIAWGN) channels, using the ripple-based approach known from the works for the binary erasure channel (BEC). We reveal that several aspects of the analytical results from...

  7. Delayed ripple counter simplifies square-root computation

    Science.gov (United States)

    Cliff, R.

    1965-01-01

    Ripple subtract technique simplifies the logic circuitry required in a binary computing device to derive the square root of a number. Successively higher numbers are subtracted from a register containing the number out of which the square root is to be extracted. The last number subtracted will be the closest integer to the square root of the number.

  8. Ripple Effect Mapping: A "Radiant" Way to Capture Program Impacts

    Science.gov (United States)

    Kollock, Debra Hansen; Flage, Lynette; Chazdon, Scott; Paine, Nathan; Higgins, Lorie

    2012-01-01

    Learn more about a promising follow-up, participatory group process designed to document the results of Extension educational efforts within complex, real-life settings. The method, known as Ripple Effect Mapping, uses elements of Appreciative Inquiry, mind mapping, and qualitative data analysis to engage program participants and other community…

  9. Ripple coarsening on ion beam-eroded surfaces.

    Science.gov (United States)

    Teichmann, Marc; Lorbeer, Jan; Frost, Frank; Rauschenbach, Bernd

    2014-01-01

    The temporal evolution of ripple pattern on Ge, Si, Al 2 O 3, and SiO 2 by low-energy ion beam erosion with Xe (+) ions is studied. The experiments focus on the ripple dynamics in a fluence range from 1.1 × 10(17) cm(-2) to 1.3 × 10(19) cm(-2) at ion incidence angles of 65° and 75° and ion energies of 600 and 1,200 eV. At low fluences a short-wavelength ripple structure emerges on the surface that is superimposed and later on dominated by long wavelength structures for increasing fluences. The coarsening of short wavelength ripples depends on the material system and angle of incidence. These observations are associated with the influence of reflected primary ions and gradient-dependent sputtering. The investigations reveal that coarsening of the pattern is a universal behavior for all investigated materials, just at the earliest accessible stage of surface evolution.

  10. Relationship between behavioral and physiological spectral-ripple discrimination.

    Science.gov (United States)

    Won, Jong Ho; Clinard, Christopher G; Kwon, Seeyoun; Dasika, Vasant K; Nie, Kaibao; Drennan, Ward R; Tremblay, Kelly L; Rubinstein, Jay T

    2011-06-01

    Previous studies have found a significant correlation between spectral-ripple discrimination and speech and music perception in cochlear implant (CI) users. This relationship could be of use to clinicians and scientists who are interested in using spectral-ripple stimuli in the assessment and habilitation of CI users. However, previous psychoacoustic tasks used to assess spectral discrimination are not suitable for all populations, and it would be beneficial to develop methods that could be used to test all age ranges, including pediatric implant users. Additionally, it is important to understand how ripple stimuli are processed in the central auditory system and how their neural representation contributes to behavioral performance. For this reason, we developed a single-interval, yes/no paradigm that could potentially be used both behaviorally and electrophysiologically to estimate spectral-ripple threshold. In experiment 1, behavioral thresholds obtained using the single-interval method were compared to thresholds obtained using a previously established three-alternative forced-choice method. A significant correlation was found (r = 0.84, p = 0.0002) in 14 adult CI users. The spectral-ripple threshold obtained using the new method also correlated with speech perception in quiet and noise. In experiment 2, the effect of the number of vocoder-processing channels on the behavioral and physiological threshold in normal-hearing listeners was determined. Behavioral thresholds, using the new single-interval method, as well as cortical P1-N1-P2 responses changed as a function of the number of channels. Better behavioral and physiological performance (i.e., better discrimination ability at higher ripple densities) was observed as more channels added. In experiment 3, the relationship between behavioral and physiological data was examined. Amplitudes of the P1-N1-P2 "change" responses were significantly correlated with d' values from the single-interval behavioral

  11. Ripple formation in unilamellar-supported lipid bilayer revealed by FRAPP.

    Science.gov (United States)

    Harb, Frédéric; Simon, Anne; Tinland, Bernard

    2013-12-01

    The mechanisms of formation and conditions of the existence of the ripple phase are fundamental thermodynamic questions with practical implications for medicine and pharmaceuticals. We reveal a new case of ripple formation occurring in unilamellar-supported bilayers in water, which results solely from the bilayer/support interaction, without using lipid mixtures or specific ions. This ripple phase is detected by FRAPP using diffusion coefficient measurements as a function of temperature: a diffusivity plateau is observed. It occurs in the same temperature range where ripple phase existence has been observed using other methods. When AFM experiments are performed in the appropriate temperature range the ripple phase is confirmed.

  12. Effects of Resonant Helical Field on Toroidal Field Ripple in IR-T1 Tokamak

    Science.gov (United States)

    Mahdavipour, B.; Salar Elahi, A.; Ghoranneviss, M.

    2018-02-01

    The toroidal magnetic field which is created by toroidal coils has the ripple in torus space. This magnetic field ripple has an importance in plasma equilibrium and stability studies in tokamak. In this paper, we present the investigation of the interaction between the toroidal magnetic field ripple and resonant helical field (RHF). We have estimated the amplitude of toroidal field ripples without and with RHF (with different q = m/n) ( m = 2, m = 3, m = 4, m = 5, m = 2 & 3, n = 1) using “Comsol Multiphysics” software. The simulations show that RHF has effects on the toroidal ripples.

  13. SUB-SATURN PLANET MOA-2008-BLG-310Lb: LIKELY TO BE IN THE GALACTIC BULGE

    International Nuclear Information System (INIS)

    Janczak, Julia; Dong, Subo; Kozlowski, Szymon

    2010-01-01

    We report the detection of sub-Saturn-mass planet MOA-2008-BLG-310Lb and argue that it is the strongest candidate yet for a bulge planet. Deviations from the single-lens fit are smoothed out by finite-source effects and therefore are not immediately apparent from the light curve. Nevertheless, we find that a model in which the primary has a planetary companion is favored over the single-lens model by Δχ 2 ∼ 880 for an additional 3 degrees of freedom. Detailed analysis yields a planet/star mass ratio q = (3.3 ± 0.3) x 10 -4 and an angular separation between the planet and star within 10% of the angular Einstein radius. The small angular Einstein radius, θ E = 0.155 ± 0.011 mas, constrains the distance to the lens to be D L >6.0 kpc if it is a star (M L >0.08 M sun ). This is the only microlensing exoplanet host discovered so far that must be in the bulge if it is a star. By analyzing VLT NACO adaptive optics images taken near the baseline of the event, we detect additional blended light that is aligned to within 130 mas of the lensed source. This light is plausibly from the lens, but could also be due to a companion to the lens or source, or possibly an unassociated star. If the blended light is indeed due to the lens, we can estimate the mass of the lens, M L = 0.67 ± 0.14 M sun , planet mass m = 74 ± 17 M + , and projected separation between the planet and host, 1.25 ± 0.10 AU, putting it right on the 'snow line'. If not, then the planet has lower mass, is closer to its host and is colder. To distinguish among these possibilities on reasonable timescales would require obtaining Hubble Space Telescope images almost immediately, before the source-lens relative motion of μ= 5 mas yr -1 causes them to separate substantially.

  14. Spatial patterns of cyanobacterial mat growth on sand ripples

    Science.gov (United States)

    Mariotti, G.; Klepac-Ceraj, V.; Perron, J. T.; Bosak, T.

    2016-02-01

    Photosynthetic microbial mats produce organic matter, cycle nutrients, bind pollutants and stabilize sediment in sandy marine environments. Here, we investigate the influence of bedforms and wave motion on the growth rate, composition and spatial variability of microbial mats by growing cyanobacterial mats on a rippled bed of carbonate sand in a wave tank. The tank was forced with an oscillatory flow with velocities below the threshold for sediment motion yet able to induce a porewater flow within the sediment. Different spatial patterns developed in mats depending on the initial biochemistry of the water medium. When growing in a medium rich in nitrogen, phosphorous and micronutrients, mats grew faster on ripple troughs than on ripple crests. After two months, mats covered the bed surface uniformly, and the microbial communities on the crests and in the troughs had similar compositions. Differences in bed shear stress and nutrient availability between crests and troughs were not able to explain the faster growth in the troughs. We hypothesize that this growth pattern is due to a "strainer" effect, i.e. the suspended bacteria from the inoculum were preferentially delivered to troughs by the wave-induced porewater flow. In the experiments initiated in a medium previously used up by a microbial mat and thus depleted in nutrients, mats grew preferentially on the ripple crests. This spatial pattern persisted for nearly two years, and the microbial composition on troughs and crests was different. We attribute this pattern to the upwelling of porewater in the crests, which increased the delivery of nutrients from sediment to the cyanobacteria on the bed surface. Thus, the macroscopic patterns formed by photosynthetic microbial mats on sand ripples may be used to infer whether mats are nutrient-limited and whether they are recently colonized or older than a month.

  15. Modelación del geoide en presas de colas de la región minera de Moa

    Directory of Open Access Journals (Sweden)

    Yordanis Esteban Batista-Legrá

    2014-12-01

    Full Text Available El presente trabajo tuvo el propósito de determinar el modelo del geoide en las presas de colas de la región minera de Moa, con el fin de obtener las alturas de puntos sobre la superficie del terreno con la exactitud que requiere el movimiento de tierras, para lo cual fueron empleados los Sistemas de Posicionamiento Global (GPS. Se aplicaron métodos de Topografía Minera, Geodesia Física, Hidrografía, Oceanografía, Cartografía Digital y Modelación y se integraron diferentes softwares para procesar la información obtenida en los experimentos. Como resultado se ofrece un nuevo método para determinar el modelo del geoide, la implementación de un Sistema de Información Geográfica (SIG para la modelación y un estudio del nivel medio del mar en la costa de Moa

  16. The effect of biological cohesion on current ripple development

    Science.gov (United States)

    Malarkey, Jonathan; Baas, Jaco H.; Hope, Julie

    2014-05-01

    Results are presented from laboratory experiments examining the role of biological cohesion, associated with Extra Polymeric Substances, on the development of current ripples. The results demonstrate the importance of biological cohesion compared to the effect of physical cohesion associated with clays in an otherwise sandy bed. FURTHER INFORMATION In fluvial and marine environments sediment transport is mainly dependent on the nature of the bed surface (rippled or flat) and the nature of cohesion in the bed. Cohesion can be either physical, as a result of the presence of clays, or biological as a result of the presence of organisms. In the case of the latter, biological cohesion occurs as a result of the presence of Extra Polymeric Substances (EPS) secreted by microorganisms. While it is known that EPS can dramatically increase the threshold of motion (Grant and Gust, 1987), comparatively little is known about the effect of EPS on ripple formation and development. The experiments described here seek to fill this gap. They also allow the effect of biological cohesion to be compared with that of physical cohesion from previous experiments (Baas et al., 2013). The experiments, which were conducted in a 10m flume at Bangor University, involved a current over a bed made of fine sand, with a median diameter of 0.148mm, and various amounts of xanthan gum, a proxy for naturally occurring EPS (Vardy et al., 2007). The hydrodynamic experimental conditions were matched very closely to those of Baas et al. (2013). The ripple dimensions were recorded through the glass side wall of the tank using time lapse photography. In the physical cohesion experiments of Baas et al. (2013) for clay contents up to 12%, the clay was very quickly winnowed out of the bed, leaving essentially clay-free ripples that developed at more or less the same rate as clean sand ripples. The resulting equilibrium ripples were essentially the same length as the clean sand ripples but reduced in height. By

  17. Spectral Ripple Discrimination in Normal-Hearing Infants.

    Science.gov (United States)

    Horn, David L; Won, Jong Ho; Rubinstein, Jay T; Werner, Lynne A

    Spectral resolution is a correlate of open-set speech understanding in postlingually deaf adults and prelingually deaf children who use cochlear implants (CIs). To apply measures of spectral resolution to assess device efficacy in younger CI users, it is necessary to understand how spectral resolution develops in normal-hearing children. In this study, spectral ripple discrimination (SRD) was used to measure listeners' sensitivity to a shift in phase of the spectral envelope of a broadband noise. Both resolution of peak to peak location (frequency resolution) and peak to trough intensity (across-channel intensity resolution) are required for SRD. SRD was measured as the highest ripple density (in ripples per octave) for which a listener could discriminate a 90° shift in phase of the sinusoidally-modulated amplitude spectrum. A 2 × 3 between-subjects design was used to assess the effects of age (7-month-old infants versus adults) and ripple peak/trough "depth" (10, 13, and 20 dB) on SRD in normal-hearing listeners (experiment 1). In experiment 2, SRD thresholds in the same age groups were compared using a task in which ripple starting phases were randomized across trials to obscure within-channel intensity cues. In experiment 3, the randomized starting phase method was used to measure SRD as a function of age (3-month-old infants, 7-month-old infants, and young adults) and ripple depth (10 and 20 dB in repeated measures design). In experiment 1, there was a significant interaction between age and ripple depth. The infant SRDs were significantly poorer than the adult SRDs at 10 and 13 dB ripple depths but adult-like at 20 dB depth. This result is consistent with immature across-channel intensity resolution. In contrast, the trajectory of SRD as a function of depth was steeper for infants than adults suggesting that frequency resolution was better in infants than adults. However, in experiment 2 infant performance was significantly poorer than adults at 20 d

  18. Theory of the rippling instability in toroidal devices

    International Nuclear Information System (INIS)

    Rogister, A.

    1985-04-01

    The theory of the rippling instability is developed for axisymmetric toroidal plasmas including ion viscosity and parallel electron heat conduction, but assuming that the growth rate is small compared to the wave angular frequency. Parallel electron heat conduction is stabilizing but ion viscosity broadens the instability domain. Under certain conditions, an important top-bottom asymmetry of the density fluctuation spectrum may arise. (orig./GG)

  19. Periodic sediment shift in migrating ripples influences benthic microbial activity

    Science.gov (United States)

    Zlatanović, Sanja; Fabian, Jenny; Mendoza-Lera, Clara; Woodward, K. Benjamin; Premke, Katrin; Mutz, Michael

    2017-06-01

    Migrating bedforms have high levels of particulate organic matter and high rates of pore water exchange, causing them to be proposed as hot spots of carbon turnover in rivers. Yet, the shifting of sediments and associated mechanical disturbance within migrating bedforms, such as ripples, may stress and abrade microbial communities, reducing their activity. In a microcosm experiment, we replicated the mechanical disturbances caused by the periodic sediment shift within ripples under oligotrophic conditions. We assessed the effects on fungal and bacterial biomass ratio (F:B), microbial community respiration (CR), and bacterial production (BCP) and compared with stable undisturbed sediments. Interactions between periodic mechanical disturbance and sediment-associated particulate organic matter (POM) were tested by enriching sediments collected from migrating ripples with different qualities of POM (fish feces, leaf litter fragments and no addition treatments). F:B and BCP were affected by an interaction between mechanical disturbance and POM quality. Fish feces enriched sediments showed increased F:B and BCP compared to sediments with lower POM quality and responded with a decrease of F:B and BCP to sediment disturbance. In the other POM treatments F:B and BCP were not affected by disturbance. Microbial respiration was however reduced by mechanical disturbance to similar low activity levels regardless of POM qualities added, whereas fish feces enriched sediment showed short temporary boost of CR. With the worldwide proliferation of migrating sand ripples due to massive catchment erosion, suppressed mineralization of POM will increasingly affect stream metabolism, downstream transport of POM and carbon cycling from reach to catchment scale.

  20. Large wind ripples on Mars: A record of atmospheric evolution

    OpenAIRE

    Lapotre, M. G. A.; Ewing, R. C.; Lamb, M. P.; Fischer, W. W.; Grotzinger, J. P.; Rubin, D. M.; Lewis, K. W.; Ballard, M. J.; Daybell, M.; Gupta, S.; Banham, S. G.; Bridges, N. T.; Des Marais, D. J.; Fraeman, A. A.; Grant, J. A.

    2016-01-01

    Wind blowing over sand on Earth produces decimeter-wavelength ripples and hundred-meter– to kilometer-wavelength dunes: bedforms of two distinct size modes. Observations from the Mars Science Laboratory Curiosity rover and the Mars Reconnaissance Orbiter reveal that Mars hosts a third stable wind-driven bedform, with meter-scale wavelengths. These bedforms are spatially uniform in size and typically have asymmetric profiles with angle-of-repose lee slopes and sinuous crest lines, making them ...

  1. Ripple compensation for a class-D amplifier

    OpenAIRE

    Cox, Stephen M.; du Toit Mouton, Hendrik

    2015-01-01

    This paper presents the first detailed mathematical analysis of the ripple compensation technique for reducing audio distortion in a class-D amplifier with negative feedback. The amplifier converts a relatively low-frequency audio signal to a high-frequency train of rectangular pulses whose widths are slowly modulated according to the audio signal (pulse-width modulation, PWM). Distortion manifests itself through unwanted audio-frequency harmonics that arise in the output due to nonlinearitie...

  2. Oscillon dynamics and rogue wave generation in Faraday surface ripples.

    Science.gov (United States)

    Xia, H; Maimbourg, T; Punzmann, H; Shats, M

    2012-09-14

    We report new experimental results which suggest that the generation of extreme wave events in the Faraday surface ripples is related to the increase in the horizontal mobility of oscillating solitons (oscillons). The analysis of the oscillon trajectories in a horizontal plane shows that at higher vertical acceleration, oscillons move chaotically, merge and form enclosed areas on the water surface. The probability of the formation of such craters, which precede large wave events, increases with the increase in horizontal mobility.

  3. Reducing torque ripples in permanent magnet synchronous motor

    Directory of Open Access Journals (Sweden)

    Rihab Abdelmoula

    2017-09-01

    Full Text Available Permanent magnet synchronous motors (PMSMs are exceptionally promising thanks to their many advantages compared with other types of electrical machines. Indeed, PMSMs are characterized by their important torque density, light weight, high air gap flux density, high acceleration, high efficiency and strong power-to-weight ratio. A surface-mounted PMSM (SPMSM is used in this work. The SPMSM is built using a 2D finite element method (FEM. Cogging torque, torque ripples and back-EMF are examined during the design process in order to obtain sinusoidal back-EMF and to minimise torque ripples which are one of the major problems with PMSMs. Two procedures are used to reduce the cogging torque of SPMSM: the effect of slot opening and the influence of skewing the stator laminations. Cogging torque factor tc and the torque ripples factor tr have been calculated to compare the two configurations (open slots and closed slots. Then, the configuration with closed slots is utilised with skewing the stator laminations for different angle 0°, 10° and 15°.

  4. Ripple-Spreading Network Model Optimization by Genetic Algorithm

    Directory of Open Access Journals (Sweden)

    Xiao-Bing Hu

    2013-01-01

    Full Text Available Small-world and scale-free properties are widely acknowledged in many real-world complex network systems, and many network models have been developed to capture these network properties. The ripple-spreading network model (RSNM is a newly reported complex network model, which is inspired by the natural ripple-spreading phenomenon on clam water surface. The RSNM exhibits good potential for describing both spatial and temporal features in the development of many real-world networks where the influence of a few local events spreads out through nodes and then largely determines the final network topology. However, the relationships between ripple-spreading related parameters (RSRPs of RSNM and small-world and scale-free topologies are not as obvious or straightforward as in many other network models. This paper attempts to apply genetic algorithm (GA to tune the values of RSRPs, so that the RSNM may generate these two most important network topologies. The study demonstrates that, once RSRPs are properly tuned by GA, the RSNM is capable of generating both network topologies and therefore has a great flexibility to study many real-world complex network systems.

  5. West Point student drops out / Jorgen Johansson

    Index Scriptorium Estoniae

    Johansson, Jorgen

    2001-01-01

    Läti kohus mõistis välja kahjutasu Juris Matusevics'ilt, kes rikkus Läti kaitsejõududega sõlmitud kokkulepet, mis kohustas teda pärast USA West Pointi sõjaväeakadeemia lõpetamist teenima viis aastat Läti armees

  6. Validation of a clinical assessment of spectral-ripple resolution for cochlear implant users.

    Science.gov (United States)

    Drennan, Ward R; Anderson, Elizabeth S; Won, Jong Ho; Rubinstein, Jay T

    2014-01-01

    Nonspeech psychophysical tests of spectral resolution, such as the spectral-ripple discrimination task, have been shown to correlate with speech-recognition performance in cochlear implant (CI) users. However, these tests are best suited for use in the research laboratory setting and are impractical for clinical use. A test of spectral resolution that is quicker and could more easily be implemented in the clinical setting has been developed. The objectives of this study were (1) To determine whether this new clinical ripple test would yield individual results equivalent to the longer, adaptive version of the ripple-discrimination test; (2) To evaluate test-retest reliability for the clinical ripple measure; and (3) To examine the relationship between clinical ripple performance and monosyllabic word recognition in quiet for a group of CI listeners. Twenty-eight CI recipients participated in the study. Each subject was tested on both the adaptive and the clinical versions of spectral ripple discrimination, as well as consonant-nucleus-consonant word recognition in quiet. The adaptive version of spectral ripple used a two-up, one-down procedure for determining spectral ripple discrimination threshold. The clinical ripple test used a method of constant stimuli, with trials for each of 12 fixed ripple densities occurring six times in random order. Results from the clinical ripple test (proportion correct) were then compared with ripple-discrimination thresholds (in ripples per octave) from the adaptive test. The clinical ripple test showed strong concurrent validity, evidenced by a good correlation between clinical ripple and adaptive ripple results (r = 0.79), as well as a correlation with word recognition (r = 0.7). Excellent test-retest reliability was also demonstrated with a high test-retest correlation (r = 0.9). The clinical ripple test is a reliable nonlinguistic measure of spectral resolution, optimized for use with CI users in a clinical setting. The test

  7. VALIDATION OF A CLINICAL ASSESSMENT OF SPECTRAL RIPPLE RESOLUTION FOR COCHLEAR-IMPLANT USERS

    Science.gov (United States)

    Drennan, Ward. R.; Anderson, Elizabeth S.; Won, Jong Ho; Rubinstein, Jay T.

    2013-01-01

    Objectives Non-speech psychophysical tests of spectral resolution, such as the spectral-ripple discrimination task, have been shown to correlate with speech recognition performance in cochlear implant (CI) users (Henry et al., 2005; Won et al. 2007, 2011; Drennan et al. 2008; Anderson et al. 2011). However, these tests are best suited for use in the research laboratory setting and are impractical for clinical use. A test of spectral resolution that is quicker and could more easily be implemented in the clinical setting has been developed. The objectives of this study were 1) To determine if this new clinical ripple test would yield individual results equivalent to the longer, adaptive version of the ripple discrimination test; 2) To evaluate test-retest reliability for the clinical ripple measure; and 3) To examine the relationship between clinical ripple performance and monosyllabic word recognition in quiet for a group of CI listeners. Design Twenty-eight CI recipients participated in the study. Each subject was tested on both the adaptive and the clinical versions of spectral ripple discrimination, as well as CNC word recognition in quiet. The adaptive version of spectral ripple employed a 2-up, 1-down procedure for determining spectral ripple discrimination threshold. The clinical ripple test used a method of constant stimuli, with trials for each of 12 fixed ripple densities occurring six times in random order. Results from the clinical ripple test (proportion correct) were then compared to ripple discrimination thresholds (in ripples per octave) from the adaptive test. Results The clinical ripple test showed strong concurrent validity, evidenced by a good correlation between clinical ripple and adaptive ripple results (r=0.79), as well as a correlation with word recognition (r = 0.7). Excellent test-retest reliability was also demonstrated with a high test-retest correlation (r = 0.9). Conclusions The clinical ripple test is a reliable non-linguistic measure

  8. Effects of toroidal field ripple on suprathermal ions in tokamak plasmas

    International Nuclear Information System (INIS)

    Goldston, R.J.; Towner, H.H.

    1980-02-01

    Analytic calculations of three important effects of toroidal field ripple on suprathermal ions in tokamak plasmas are presented. In the first process, collisional ripple-trapping, beam ions become trapped in local magnetic wells near their banana tips due to pitch-angle scattering as they traverse the ripple on barely unripple-trapped orbits. In the second process, collisionless ripple-trapping, near-perpendicular untrapped ions are captured (again near a banana tip) due to their finite orbits, which carry them out into regions of higher ripple. In the third process, banana-drift diffusion, fast-ion banana orbits fail to close precisely, due to a ripple-induced variable lingering period near the banana tips. These three mechanisms lead to substantial radial transport of banana-trapped, neutral-beam-injected ions when the quantity α* identical with epsilon/sin theta/Nqdelta is of order unity or smaller

  9. Effects of toroidal field ripple on suprathermal ions in tokamak plasmas

    International Nuclear Information System (INIS)

    Goldston, R.J.; Towner, H.H.

    1981-01-01

    Analytic calculations of three important effects of toroidal field ripple on suprathermal ions in tokamak plasmas are presented. In the first process, collisional ripple-trapping, ions become trapped in local magnetic wells near their banana tips owing to pitch-angle scattering as they traverse the ripple on barely unripple-trapped orbits. In the second process, collisionless ripple-trapping, ions are captured (again near a banana tip) owing to their finite orbits, which carry them out into regions of higher ripple. In the third process, banana-drift diffusion, fast-ion banana orbits fail to close precisely, due to a ripple-induced 'variable lingering period' near the banana tips. These three mechanisms lead to substantial radial transport of banana-trapped, neutral-beam-injected ions when the quantity α* is identical with epsilonsinthetaNqdelta is of order unity or smaller. (author)

  10. Learning-enhanced coupling between ripple oscillations in association cortices and hippocampus.

    Science.gov (United States)

    Khodagholy, Dion; Gelinas, Jennifer N; Buzsáki, György

    2017-10-20

    Consolidation of declarative memories requires hippocampal-neocortical communication. Although experimental evidence supports the role of sharp-wave ripples in transferring hippocampal information to the neocortex, the exact cortical destinations and the physiological mechanisms of such transfer are not known. We used a conducting polymer-based conformable microelectrode array (NeuroGrid) to record local field potentials and neural spiking across the dorsal cortical surface of the rat brain, combined with silicon probe recordings in the hippocampus, to identify candidate physiological patterns. Parietal, midline, and prefrontal, but not primary cortical areas, displayed localized ripple (100 to 150 hertz) oscillations during sleep, concurrent with hippocampal ripples. Coupling between hippocampal and neocortical ripples was strengthened during sleep following learning. These findings suggest that ripple-ripple coupling supports hippocampal-association cortical transfer of memory traces. Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

  11. Evaluation of kaolinite clays of Moa for the production of cement based clinker-calcined clay-limestone (LC3

    Directory of Open Access Journals (Sweden)

    Roger S. Almenares-Reyes

    2016-12-01

    Full Text Available Clay materials from two outcrops of the Moa region were analyzed to determine their potential use as supplementary cementitious material in the production of ternary cements based on limestone-calcined clay. The clays were characterized by atomic absorption spectroscopy (EAA, X-ray diffraction (XRD, Fourier transform infrared spectroscopy (FTIR and thermogravimetric analysis (ATG. These methods revealed high aluminum in clays, moderate kaolinite content, a disordered structure and the presence of impurities. The solubility of aluminum and silicon in alkali and the compressive strength of LC3 systems is proportional to their content in clay, being higher for the one with higher kaolinite content and greater structural disorder (outcrop D1, although the clay of both outcrops may constitute supplementary cementitious materials in the production of ternary cements based clinker-calcined clay-limestone. The suitable thermal activation range for both clays is between 650 ° C and 850 ° C.

  12. Falla Moa: caracterización geodinámica y riesgos tectónicos asociados

    Directory of Open Access Journals (Sweden)

    José A. Batista-Rodríguez

    2007-03-01

    Full Text Available En el contexto geodinámico del noreste oriental de Cuba existen numerosas estructuras disyuntivas activas que se ponen de manifiesto a través de los movimientos lentos y pulsantes, y de la actividad sísmica. Dentro de esas estructuras se encuentra la Falla Moa, que se extiende de forma submeridional, cortando el macizo ofiolítico y atravesando importantes yacimientos e instalaciones de la localidad. La caracterización de esta falla partiendo de su génesis, sentido de desplazamiento de los bloques rocosos y elementos que facilitaron su interpretación y cartografiado son tratados en este artículo, donde además se propone la necesidad del monitoreo de dicha estructura a partir de la influencia de ella en el medio ambiente territorial.

  13. Reactive transport model of the formation of oxide-type Ni-laterite profiles (Punta Gorda, Moa Bay, Cuba)

    Science.gov (United States)

    Domènech, Cristina; Galí, Salvador; Villanova-de-Benavent, Cristina; Soler, Josep M.; Proenza, Joaquín A.

    2017-10-01

    Oxide-type Ni-laterite deposits are characterized by a dominant limonite zone with goethite as the economically most important Ni ore mineral and a thin zone of hydrous Mg silicate-rich saprolite beneath the magnesium discontinuity. Fe, less soluble, is mainly retained forming goethite, while Ni is redeposited at greater depth in a Fe(III) and Ni-rich serpentine (serpentine II) or in goethite, where it adsorbs or substitutes for Fe in the mineral structure. Here, a 1D reactive transport model, using CrunchFlow, of Punta Gorda oxide-type Ni-laterite deposit (Moa Bay, Cuba) formation is presented. The model reproduces the formation of the different laterite horizons in the profile from an initial, partially serpentinized peridotite, in 106 years, validating the conceptual model of the formation of this kind of deposits in which a narrow saprolite horizon rich in Ni-bearing serpentine is formed above peridotite parent rock and a thick limonite horizon is formed over saprolite. Results also confirm that sorption of Ni onto goethite can explain the weight percent of Ni found in the Moa goethite. Sensitivity analyses accounting for the effect of key parameters (composition, dissolution rate, carbonate concentration, quartz precipitation) on the model results are also presented. It is found that aqueous carbonate concentration and quartz precipitation significantly affects the laterization process rate, while the effect of the composition of secondary serpentine or of mineral dissolution rates is minor. The results of this reactive transport modeling have proven useful to validate the conceptual models derived from field observations.

  14. Limitations on current ripple of the power supplies for the SSC bending magnets

    International Nuclear Information System (INIS)

    Lebedev, V.A.

    1993-01-01

    Noise and ripple in the bending magnets of large proton collider cause the beam emittance growth and the luminosity degradation. The emittance growth due to voltage ripple of the bending magnets power supplies is studied. The role of the collider transverse feedback system is shown to be very important to facilitate the requirements to value of ripple. The longitudinal emittance growth due to slow variations of power supply current is studied as well. 9 refs.; 15 figs

  15. Minimization of torque ripple in ferrite-assisted synchronous reluctance motors by using asymmetric stator

    Science.gov (United States)

    Xu, Meimei; Liu, Guohai; Zhao, Wenxiang; Aamir, Nazir

    2018-05-01

    Torque ripple is one of the important issues for ferrite assisted synchronous reluctance motors (FASRMs). In this paper, an asymmetrical stator is proposed for the FASRM to reduce its torque ripple. In the proposed FASRM, an asymmetrical stator is designed by appropriately choosing the angle of the slot-opening shift. Meanwhile, its analytical torque expressions are derived. The results show that the proposed FASRM has an effective reduction in the cogging torque, reluctance torque ripple and total torque ripple. Moreover, it is easy to implement while the average torque is not sacrificed.

  16. Detailed Analysis of Torque Ripple in High Frequency Signal Injection based Sensor less PMSM Drives

    Directory of Open Access Journals (Sweden)

    Ravikumar Setty A.

    2017-01-01

    Full Text Available High Frequency Signal Injection based techniques are robust and well proven to estimate the rotor position from stand still to low speed. However, Injected high frequency signal introduces, high frequency harmonics in the motor phase currents and results in significant Output Torque ripple. There is no detailed analysis exist in the literature, to study the effect of injected signal frequency on Torque ripple. Objective of this work is to study the Torque Ripple resulting from High Frequency signal injection in PMSM motor drives. Detailed MATLAB/Simulink simulations are carried to quantify the Torque ripple at different Signal frequencies.

  17. Nonlocal theory of electromagnetic wave decay into two electromagnetic waves in a rippled density plasma channel

    International Nuclear Information System (INIS)

    Sati, Priti; Tripathi, V. K.

    2012-01-01

    Parametric decay of a large amplitude electromagnetic wave into two electromagnetic modes in a rippled density plasma channel is investigated. The channel is taken to possess step density profile besides a density ripple of axial wave vector. The density ripple accounts for the momentum mismatch between the interacting waves and facilitates nonlinear coupling. For a given pump wave frequency, the requisite ripple wave number varies only a little w.r.t. the frequency of the low frequency decay wave. The radial localization of electromagnetic wave reduces the growth rate of the parametric instability. The growth rate decreases with the frequency of low frequency electromagnetic wave.

  18. Effects of toroidal field ripple on injected deuterons in the FED device

    International Nuclear Information System (INIS)

    Fowler, R.H.; Rome, J.A.

    1981-07-01

    A Monte Carlo beam deposition and thermalization code is used to assess the effects of toroidal field (TF) ripple on injected fast deuterons in the Fusion Engineering Device (FED). The code uses realistic geometry for the beam, plasma equilibrium, TF ripple, and vacuum chamber. For injection at an angle of 35 0 (co) from perpendicular, no particles were ripple trapped and less than 1% of the injected power went to the wall and the limiter. However, due to the large amounts of computer time required by these programs, only 100 particles were followed in the rippled case and the results must be regarded as preliminary

  19. Age Is Associated with Reduced Sharp-Wave Ripple Frequency and Altered Patterns of Neuronal Variability.

    Science.gov (United States)

    Wiegand, Jean-Paul L; Gray, Daniel T; Schimanski, Lesley A; Lipa, Peter; Barnes, C A; Cowen, Stephen L

    2016-05-18

    Spatial and episodic memory performance declines with age, and the neural basis for this decline is not well understood. Sharp-wave ripples are brief (∼70 ms) high-frequency oscillatory events generated in the hippocampus and are associated with the consolidation of spatial memories. Given the connection between ripple oscillations and memory consolidation, we investigated whether the structure of ripple oscillations and ripple-triggered patterns of single-unit activity are altered in aged rats. Local field and single-unit activity surrounding sharp-wave ripple events were examined in the CA1 region of the hippocampus of old (n = 5) and young (n = 6) F344 rats during periods of rest preceding and following performance on a place-dependent eyeblink-conditioning task. Neural responses in aged rats differed from responses in young rats in several ways. First, compared with young rats, the rate of ripple occurrence (ripple density) is reduced in aged rats during postbehavior rest. Second, mean ripple frequency during prebehavior and postbehavior rest is lower in aged animals (aged: 132 Hz; young: 146 Hz). Third, single neurons in aged animals responded more consistently from ripple to ripple. Fourth, variability in interspike intervals was greater in aged rats. Finally, neurons were tuned to a narrower range of phases of the ripple oscillation relative to young animals. Together, these results suggest that the CA1 network in aged animals has a reduced "vocabulary" of available representational states. The hippocampus is a structure that is critical for the formation of episodic memories. Sharp-wave ripple events generated in the hippocampus have been implicated in memory consolidation processes critical to memory stabilization. We examine here whether these ripple oscillations are altered over the course of the life span, which could contribute to hippocampus-dependent memory deficits that occur during aging. This experiment used young and aged memory-impaired rats

  20. Diffraction analysis of sidelobe characteristics of optical elements with ripple error

    Science.gov (United States)

    Zhao, Lei; Luo, Yupeng; Bai, Jian; Zhou, Xiangdong; Du, Juan; Liu, Qun; Luo, Yujie

    2018-03-01

    The ripple errors of the lens lead to optical damage in high energy laser system. The analysis of sidelobe on the focal plane, caused by ripple error, provides a reference to evaluate the error and the imaging quality. In this paper, we analyze the diffraction characteristics of sidelobe of optical elements with ripple errors. First, we analyze the characteristics of ripple error and build relationship between ripple error and sidelobe. The sidelobe results from the diffraction of ripple errors. The ripple error tends to be periodic due to fabrication method on the optical surface. The simulated experiments are carried out based on angular spectrum method by characterizing ripple error as rotationally symmetric periodic structures. The influence of two major parameter of ripple including spatial frequency and peak-to-valley value to sidelobe is discussed. The results indicate that spatial frequency and peak-to-valley value both impact sidelobe at the image plane. The peak-tovalley value is the major factor to affect the energy proportion of the sidelobe. The spatial frequency is the major factor to affect the distribution of the sidelobe at the image plane.

  1. Differentiation of specific ripple patterns helps to identify epileptogenic areas for surgical procedures.

    Science.gov (United States)

    Kerber, Karolin; Dümpelmann, Matthias; Schelter, Björn; Le Van, Pierre; Korinthenberg, Rudolf; Schulze-Bonhage, Andreas; Jacobs, Julia

    2014-07-01

    High frequency oscillations (HFOs) at 80-500 Hz are promising markers of epileptic areas. Several retrospective studies reported that surgical removal of areas generating HFOs was associated with a good seizure outcome. Recent reports suggested that ripple (80-200 Hz) HFO patterns co-existed with different background EEG activities. We hypothesized that the coexisting background EEG pattern may distinguish physiological from epileptic ripples. Rates of HFOs were analyzed in intracranial EEG recordings of 22 patients. Additionally, ripple patterns were classified for each channel depending either as coexisting with a flat or oscillatory background activity. A multi-variate analysis was performed to determine whether removal of areas showing the above EEG markers correlated with seizure outcome. Removal of areas generating high rates of 'fast ripples (>200 Hz)' and 'ripples on a flat background activity' showed a significant correlation with a seizure-free outcome. In contrast, removal of high rates of 'ripples' or 'ripple patterns in a continuously oscillating background' was not significantly associated with seizure outcome. Ripples occurring in an oscillatory background activity may be suggestive of physiological activity, while those on a flat background reflect epileptic activity. Consideration of coexisting background patterns may improve the delineation of the epileptogenic areas using ripple oscillations. Copyright © 2013 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

  2. Rippling and drift instabilities in the straight cylinder tokamak

    International Nuclear Information System (INIS)

    Rogister, A.

    1984-01-01

    It is shown that the electron and ion diamagnetic drifts stabilize the rippling mode in the straigth cylindrical tokamak model. Parallel electron heat conduction is further stabilizing if the parameter etasub(e) = dlnTsub(e)/dlnN is positive. This has a consequence that the mode does not survive at temperatures exceeding, typically, 50 eV for standard values of magnetic field and density. The collisional drift wave is found to be always stable even when the effect of the tokamak current is included in the calculation. (orig.)

  3. Rippled cosmological dark matter from a damped oscillating Newton constant

    International Nuclear Information System (INIS)

    Davidson, Aharon

    2005-01-01

    Let the reciprocal Newton 'constant' be an apparently non-dynamical Brans-Dicke scalar field damped oscillating towards its general relativistic VEV. We show, without introducing additional matter fields or dust, that the corresponding cosmological evolution averagely resembles, in the Jordan frame, the familiar dark radiation → dark matter → dark energy domination sequence. The fingerprints of our theory are fine ripples, hopefully testable, in the FRW scale factor; they die away at the general relativity limit. The possibility that the Brans-Dicke scalar also serves as the inflaton is favourably examined

  4. Rippled shock front solutions for testing hydrodynamic stability simulations

    International Nuclear Information System (INIS)

    Munro, D.H.

    1989-01-01

    The response of a shock front to arbitrary small perturbations can be calculated analytically. Such rippled shock front solutions are useful for determining the accuracy of hydrodynamic simulation codes such as LASNEX [Comments Plasma Phys. Controlled Fusion 2, 51 (1977)], which are used to compute perturbation growth in inertial fusion targets. The LASNEX fractional errors are of order κ 2 L 2 , where κ is the transverse wavenumber of the perturbation, and L is the largest zone dimension. Numerical errors are about 25% for a calculation using 26 zones per transverse wavelength

  5. Temperature-controlled structure and kinetics of ripple phases in one- and two-component supported lipid bilayers

    DEFF Research Database (Denmark)

    Kaasgaard, Thomas; Leidy, Chad; Crowe, J.H.

    2003-01-01

    Temperature-controlled atomic force microscopy (AFM) has been used to visualize and study the structure and kinetics of ripple phases in one-component dipalmitoylphosphaticlylcholine (DPPC) and two-component dimyristoylphosphatidylcholine-distearoylphosphatidylcholine (DMPC-DSPC) lipid bilayers....... The lipid bilayers are mica-supported double bilayers in which ripple-phase formation occurs in the top bilayer. In one-component DPPC lipid bilayers, the stable and metastable ripple phases were observed. In addition, a third ripple structure with approximately twice the wavelength of the metastable...... ripples was seen. From height profiles of the AFM images, estimates of the amplitudes of the different ripple phases are reported. To elucidate the processes of ripple formation and disappearance, a ripple-phase DPPC lipid bilayer was taken through the pretransition in the cooling and the heating...

  6. Missing lynx and trophic cascades in food webs: A reply to Ripple et al.

    Science.gov (United States)

    John R. Squires; Nicholas J. DeCesare; Mark Hebblewhite; Joel Berger

    2012-01-01

    Ripple et al. (2011) proposed a hypothesis that the recovery of gray wolves (Canis lupus) may positively affect the viability of threatened Canada lynx (Lynx canadensis) populations in the contiguous United States through indirect species interactions. Ripple et al. (2011) proposed 2 key trophic linkages connecting wolf restoration with lynx recovery. First, recovering...

  7. Radial electric field in JET advanced tokamak scenarios with toroidal field ripple

    NARCIS (Netherlands)

    Crombe, K.; Andrew, Y.; Biewer, T. M.; Blanco, E.; de Vries, P. C.; Giroud, C.; Hawkes, N. C.; Meigs, A.; Tala, T.; von Hellermann, M.; Zastrow, K. D.

    2009-01-01

    A dedicated campaign has been run on JET to study the effect of toroidal field (TF) ripple on plasma performance. Radial electric field measurements from experiments on a series of plasmas with internal transport barriers (ITBs) and different levels of ripple amplitude are presented. They have been

  8. Reynolds Number Effect on Spatial Development of Viscous Flow Induced by Wave Propagation Over Bed Ripples

    Science.gov (United States)

    Dimas, Athanassios A.; Kolokythas, Gerasimos A.

    Numerical simulations of the free-surface flow, developing by the propagation of nonlinear water waves over a rippled bottom, are performed assuming that the corresponding flow is two-dimensional, incompressible and viscous. The simulations are based on the numerical solution of the Navier-Stokes equations subject to the fully-nonlinear free-surface boundary conditions and appropriate bottom, inflow and outflow boundary conditions. The equations are properly transformed so that the computational domain becomes time-independent. For the spatial discretization, a hybrid scheme is used where central finite-differences, in the horizontal direction, and a pseudo-spectral approximation method with Chebyshev polynomials, in the vertical direction, are applied. A fractional time-step scheme is used for the temporal discretization. Over the rippled bed, the wave boundary layer thickness increases significantly, in comparison to the one over flat bed, due to flow separation at the ripple crests, which generates alternating circulation regions. The amplitude of the wall shear stress over the ripples increases with increasing ripple height or decreasing Reynolds number, while the corresponding friction force is insensitive to the ripple height change. The amplitude of the form drag forces due to dynamic and hydrostatic pressures increase with increasing ripple height but is insensitive to the Reynolds number change, therefore, the percentage of friction in the total drag force decreases with increasing ripple height or increasing Reynolds number.

  9. Evidence of across-channel processing for spectral-ripple discrimination in cochlear implant listeners a

    Science.gov (United States)

    Ho Won, Jong; Jones, Gary L.; Drennan, Ward R.; Jameyson, Elyse M.; Rubinstein, Jay T.

    2011-01-01

    Spectral-ripple discrimination has been used widely for psychoacoustical studies in normal-hearing, hearing-impaired, and cochlear implant listeners. The present study investigated the perceptual mechanism for spectral-ripple discrimination in cochlear implant listeners. The main goal of this study was to determine whether cochlear implant listeners use a local intensity cue or global spectral shape for spectral-ripple discrimination. The effect of electrode separation on spectral-ripple discrimination was also evaluated. Results showed that it is highly unlikely that cochlear implant listeners depend on a local intensity cue for spectral-ripple discrimination. A phenomenological model of spectral-ripple discrimination, as an “ideal observer,” showed that a perceptual mechanism based on discrimination of a single intensity difference cannot account for performance of cochlear implant listeners. Spectral modulation depth and electrode separation were found to significantly affect spectral-ripple discrimination. The evidence supports the hypothesis that spectral-ripple discrimination involves integrating information from multiple channels. PMID:21973363

  10. Effect of buck driver ripple on BER performance in visible light communication using LED

    NARCIS (Netherlands)

    Deng, X.; Linnartz, J.P.M.G.; Arulandu, K.; Zhou, G.; Wu, Y.

    2015-01-01

    This paper analyses the communication performance for visible light communication (VLC) with Manchester encoded amplitude modulation. In particular, it considers the ripple generated by the LED driver as an important noise contribution for VLC. The ripple depends on the oscillation frequency of the

  11. New possibility of magnetic ripple shielding for specific heat measurements in hybrid magnets

    NARCIS (Netherlands)

    Tarnawski, Z.; Meulen, der, H. van; Franse, J.J.M.; Kadowaki, K.; Veenhuizen, P.A.; Klaasse, J.

    1988-01-01

    A test of the new high Tc superconducting materials for magnetic ripple shielding has been carried out. It was found that magnetic ripples of 0.0009 T (peak-to-peak) in the frequency range below 20 kHz can be completely shielded in high static fields by a 2 mm thick Y-Ba-Cu-O screen.

  12. Asynchronous ripple oscillations between left and right hippocampi during slow-wave sleep.

    Science.gov (United States)

    Villalobos, Claudio; Maldonado, Pedro E; Valdés, José L

    2017-01-01

    Spatial memory, among many other brain processes, shows hemispheric lateralization. Most of the published evidence suggests that the right hippocampus plays a leading role in the manipulation of spatial information. Concurrently in the hippocampus, memory consolidation during sleep periods is one of the key steps in the formation of newly acquired spatial memory traces. One of the most characteristic oscillatory patterns in the hippocampus are sharp-wave ripple (SWR) complexes. Within this complex, fast-field oscillations or ripples have been demonstrated to be instrumental in the memory consolidation process. Since these ripples are relevant for the consolidation of memory traces associated with spatial navigation, and this process appears to be lateralized, we hypothesize that ripple events between both hippocampi would exhibit different temporal dynamics. We tested this idea by using a modified "split-hyperdrive" that allows us to record simultaneous LFPs from both right and left hippocampi of Sprague-Dawley rats during sleep. We detected individual events and found that during sleep periods these ripples exhibited a different occurrence patterns between hemispheres. Most ripple events were synchronous between intra- rather than inter-hemispherical recordings, suggesting that ripples in the hippocampus are independently generated and locally propagated within a specific hemisphere. In this study, we propose the ripples' lack of synchrony between left and right hippocampi as the putative physiological mechanism underlying lateralization of spatial memory.

  13. Evidence of across-channel processing for spectral-ripple discrimination in cochlear implant listeners.

    Science.gov (United States)

    Won, Jong Ho; Jones, Gary L; Drennan, Ward R; Jameyson, Elyse M; Rubinstein, Jay T

    2011-10-01

    Spectral-ripple discrimination has been used widely for psychoacoustical studies in normal-hearing, hearing-impaired, and cochlear implant listeners. The present study investigated the perceptual mechanism for spectral-ripple discrimination in cochlear implant listeners. The main goal of this study was to determine whether cochlear implant listeners use a local intensity cue or global spectral shape for spectral-ripple discrimination. The effect of electrode separation on spectral-ripple discrimination was also evaluated. Results showed that it is highly unlikely that cochlear implant listeners depend on a local intensity cue for spectral-ripple discrimination. A phenomenological model of spectral-ripple discrimination, as an "ideal observer," showed that a perceptual mechanism based on discrimination of a single intensity difference cannot account for performance of cochlear implant listeners. Spectral modulation depth and electrode separation were found to significantly affect spectral-ripple discrimination. The evidence supports the hypothesis that spectral-ripple discrimination involves integrating information from multiple channels. © 2011 Acoustical Society of America

  14. Unique parasite aDNA in moa coprolites from New Zealand suggests mass parasite extinctions followed human-induced megafauna extinctions

    Science.gov (United States)

    Lafferty, Kevin D.; Hopkins, Skylar R.

    2018-01-01

    Having split early from Gondwana, Zealandia (now modern New Zealand) escaped discovery until the late 13th century, and therefore remains an important glimpse into a human-free world. Without humans or other land mammals, diverse and peculiar birds evolved in isolation, including several flightless moa species, the giant pouakai eagle (Harpagornis moorei), the kiwi (Apteryx mantelli), and the kakapo parrot (Strigops habroptila). This unique community has fascinated paleoecologists, who have spent almost two centuries devising new ways to glean information from ancient bird remains. In PNAS, Boast et al. (1) apply one recent technological advance, ancient DNA (aDNA) metabarcoding, to confirm previous discoveries and report new details about moa and kakapo diets, parasites, and niches. Their efforts confirm Zealandia was a lot different before humans arrived.

  15. Computational studies of the effect of magnetic field ''ripple'' on neutral beam heating of ZEPHYR

    International Nuclear Information System (INIS)

    Lister, G.G.; Gruber, O.

    1981-01-01

    The results of computations to estimate the heating efficiency of neutral injection in the proposed ZEPHYR experiment are presented. A suitably modified version of the Monte-Carlo neutral deposition and orbit following code FREYA was used for these calculations, in which particular emphasis has been placed on the effects of toroidal field ripple. We find that the ripple associated with the preliminary design of the experiment (+-6%) would result in intolerable energy losses due to ''ripple trapping'' of the fast ions produced by the neutral beam and insufficient heating of the central plasma. The necessary conditions for ignition can be obtained with a total heating power of 25 MW provided the ripple can be reduced to +-1%, in which case energy losses could be kept below 30%. These results are compatible with those found from transport code calculations of the losses to be expected due to ripple enhanced thermal conduction in the plasma

  16. Real-time observation of FIB-created dots and ripples on GaAs

    International Nuclear Information System (INIS)

    Rose, F; Fujita, H; Kawakatsu, H

    2008-01-01

    We report a phenomenological study of Ga dots and ripples created by a focused ion beam (FIB) on the GaAs(001) surface. Real-time observation of dot diffusion and ripple formation was made possible by recording FIB movies. In the case of FIB irradiation with a 40 nA current of Ga + ions accelerated under 40 kV with an incidence angle of θ = 30 0 , increasing ion dose gives rise to three different regimes. In Regime 1, dots with lateral sizes in the range 50-460 nm are formed. Dots diffuse under continuous sputtering. In Regime 2, dots self-assemble into Bradley and Harper (BH) type ripples with a pseudo-period of λ = 1150 ± 25 nm. In Regime 3, ripples are eroded and the surface topology evolves into microplanes. In the case of normal incidence, FIB sputtering leads only to the formation of dots, without surface rippling

  17. Ion peak narrowing by applying additional AC voltage (ripple voltage) to FAIMS extractor electrode.

    Science.gov (United States)

    Pervukhin, Viktor V; Sheven, Dmitriy G

    2010-01-01

    The use of a non-uniform electric field in a high-field asymmetric waveform ion mobility spectrometry (FAIMS) analyzer increases sensitivity but decreases resolution. The application of an additional AC voltage to the extractor electrode ("ripple" voltage, U(ripple)) can overcome this effect, which decreases the FAIMS peak width. In this approach, the diffusion ion loss remains minimal in the non-uniform electric field in the cylindrical part of the device, and all ion losses under U(ripple) occur in a short portion of their path. Application of the ripple voltage to the extractor electrode is twice as efficient as the applying of U(ripple) along the total length of the device. 2010 American Society for Mass Spectrometry. Published by Elsevier Inc. All rights reserved.

  18. High speed non-latching squid binary ripple counter

    International Nuclear Information System (INIS)

    Silver, A.H.; Phillips, R.R.; Sandell, R.D.

    1985-01-01

    High speed, single flux quantum (SFQ) binary scalers are important components in superconducting analog-to-digital converters (ADC). This paper reviews the concept for a SQUID ADC and the design of an SFQ binary ripple counter, and reports the simulation of key components, and fabrication and performance of non-latching SQUID scalers and SFQ binary ripple counters. The SQUIDs were fabricated with Nb/Nb 2 O 5 /PbIn junctions and interconnected by monolithic superconducting transmission lines and isolation resistors. Each SQUID functioned as a bistable flip-flop with the input connected to the center of the device and the output across one junction. All junctions were critically damped to optimize the pulse response. Operation was verified by observing the dc I-V curves of successive SQUIDs driven by a cw pulse train generated on the same chip. Each SQUID exhibited constant-voltage current steps at 1/2 the voltage of the preceding device as expected from the Josephson voltage-to-frequency relation. Steps were observed only for the same voltage polarity of successive devices and for proper phase bias of the SQUID. Binary frequency division was recorded up to 40GHz for devices designed to operate to 28GHz

  19. Permanent magnet working point ripple in synchronous generators

    Directory of Open Access Journals (Sweden)

    Stefan Sjökvist

    2017-04-01

    Full Text Available Permanent magnets (PMs are today widely used in electrical machines of all sorts. With their increase in popularity, the amount of research has increased as well. In this study, the magnetic flux density ripple of the working point of the PMs in a 100 kW PM synchronous generator has been investigated for three different load cases: no load, AC load, and DC load. The PMs will be subjected to a shift in working point as a consequence of the characteristics of the electrical loading. This study is based on finite element method simulations where the ripple of the magnetic flux density in the PMs was recorded at three positions within a PM. The slot harmonic of 7.5 times the electrical frequency (f(el was present in the results for all load cases, but mainly at the surface of the PM, as expected. Results showed an unexpected harmonic of 1.5 f(el, assumed to be an undertone of the slot harmonics. The 6f(el harmonic for the DC load case was significantly higher than for the AC load case and is caused by the current fluctuation during passive rectification. For the studied machine, the added harmonics in the magnetic field due to passive rectification are less than the slot-related harmonics.

  20. Ion flow ripples in the Earth's plasma sheet

    Science.gov (United States)

    De Spiegeleer, Alexandre; Hamrin, Maria; Pitkänen, Timo; Norqvist, Patrik; Mann, Ingrid

    2016-04-01

    For a long time, magnetotail flows were considered rather smooth and laminar, and primarily dominated by a simple convection flow pattern. However, in the early 90's, high speed bursty bulk flows (BBFs) were discovered and found to commonly perturb the underlying convection flows. In addition, there are other disturbances complicating the magnetotail flow pattern. Instabilities such as the Kelvin-Helmholz instability and the kink instability can cause different types of magnetic field oscillations, such as field line resonances. It is expected that ions will follow these oscillations if the typical time and length scales are larger than the gyroperiod and gyroradius of the ions. Though low-velocity sloshing and ripple disturbances of the average magnetotail convection flows have been observed, their connection with magnetic field oscillations is not fully understood. Furthermore, when studying BFFs, these "Ion Flow Ripples" (IFRs) are often neglected, dismissed as noise or can even erroneously be identified as BBFs. It is therefore of utter importance to find out and understand the role of IFRs in magnetotail dynamics. In a statistical investigation, we use several years of Cluster plasma sheet data to study the low-speed flows in the magnetotail. We investigate different types of IFRs, study their occurrence, and discuss their possible causes.

  1. Final Environmental Assessment for Proposed Airspace Changes for Paradise East and Paradise West Military Operations Areas (MOAs) at Mountain Home Air Force Base (MHAFB) Idaho

    Science.gov (United States)

    2010-03-29

    Force requires that installations associated with MOAs prepare Mid-Air Collision Avoidance ( MACA ) programs and encourages the installations to brief...civilian pilots on this information. MHAFB participates in MACA briefings at local area airports within 100 NM of the Mountain Home Range Complex...MHAFB has developed Wing MACA Plan 9601-05, updated every 18 months, a 23-page MACA pamphlet, and a two-page MACA handout. The March 2006 issue of

  2. Wave-induced ripple development in mixed clay-sand substrates

    Science.gov (United States)

    Wu, Xuxu; Parsons, Daniel; Baas, Jaco H.; Mouazé, Dominique; McLelland, Stuart; Amoudry, Laurent; Eggenhuisen, Jorris; Cartigny, Matthieu; Ruessink, Gerben

    2016-04-01

    This paper reports on a series of experiments that aim to provide a fuller understanding of ripple development within clay-sand mixture substrates under oscillatory flow conditions. The work was conducted in the Total Environment Simulator at the University of Hull and constituted 6 separate runs, in which 5 runs were conducted under identical sets of regular waves (an additional run was conducted under irregular waves, but is not discussed in present paper). The bed content was systematically varied in its composition ranging from a pure sand bed through to a bed comprising 7.4% clay. A series of state-of-the-art measurements were employed to quantify interactions of near-bed hydrodynamics, sediment transport, and turbulence over rippled beds formed by wave action, during and after, each run. The experimental results demonstrate the significant influence of the amount of cohesive clay materials in the substrate on ripple evolution under waves. Most importantly, addition of clay in the bed dramatically slowed down the rate of ripple development and evolution. The equilibrium time of each run increased exponentially from 30 minutes under the control conditions of a pure sand bed, rising to ~350 minutes for the bed with the highest fraction of clay. The paper discusses the slower ripple growth rates with higher cohesive fractions, via an influence on critical shear, but highlights that the end equilibrium size of ripples is found to be independent of increasing substrate clay fraction. The suspended particles mass (SPM) concentration indicates that clay particles were suspended and winnowed by wave action. Additionally, laser granulometry of the final substrates verified that ripple crests were composed of pure sand layers that were absent at ripple troughs, reflecting a relatively higher winnowing efficiency at wave ripples crest. The winnowing process and its efficiency is inexorably linked to wave ripple development and evolution. The implications of the results

  3. Comparing auditory filter bandwidths, spectral ripple modulation detection, spectral ripple discrimination, and speech recognition: Normal and impaired hearing.

    Science.gov (United States)

    Davies-Venn, Evelyn; Nelson, Peggy; Souza, Pamela

    2015-07-01

    Some listeners with hearing loss show poor speech recognition scores in spite of using amplification that optimizes audibility. Beyond audibility, studies have suggested that suprathreshold abilities such as spectral and temporal processing may explain differences in amplified speech recognition scores. A variety of different methods has been used to measure spectral processing. However, the relationship between spectral processing and speech recognition is still inconclusive. This study evaluated the relationship between spectral processing and speech recognition in listeners with normal hearing and with hearing loss. Narrowband spectral resolution was assessed using auditory filter bandwidths estimated from simultaneous notched-noise masking. Broadband spectral processing was measured using the spectral ripple discrimination (SRD) task and the spectral ripple depth detection (SMD) task. Three different measures were used to assess unamplified and amplified speech recognition in quiet and noise. Stepwise multiple linear regression revealed that SMD at 2.0 cycles per octave (cpo) significantly predicted speech scores for amplified and unamplified speech in quiet and noise. Commonality analyses revealed that SMD at 2.0 cpo combined with SRD and equivalent rectangular bandwidth measures to explain most of the variance captured by the regression model. Results suggest that SMD and SRD may be promising clinical tools for diagnostic evaluation and predicting amplification outcomes.

  4. Comparing auditory filter bandwidths, spectral ripple modulation detection, spectral ripple discrimination, and speech recognition: Normal and impaired hearinga)

    Science.gov (United States)

    Davies-Venn, Evelyn; Nelson, Peggy; Souza, Pamela

    2015-01-01

    Some listeners with hearing loss show poor speech recognition scores in spite of using amplification that optimizes audibility. Beyond audibility, studies have suggested that suprathreshold abilities such as spectral and temporal processing may explain differences in amplified speech recognition scores. A variety of different methods has been used to measure spectral processing. However, the relationship between spectral processing and speech recognition is still inconclusive. This study evaluated the relationship between spectral processing and speech recognition in listeners with normal hearing and with hearing loss. Narrowband spectral resolution was assessed using auditory filter bandwidths estimated from simultaneous notched-noise masking. Broadband spectral processing was measured using the spectral ripple discrimination (SRD) task and the spectral ripple depth detection (SMD) task. Three different measures were used to assess unamplified and amplified speech recognition in quiet and noise. Stepwise multiple linear regression revealed that SMD at 2.0 cycles per octave (cpo) significantly predicted speech scores for amplified and unamplified speech in quiet and noise. Commonality analyses revealed that SMD at 2.0 cpo combined with SRD and equivalent rectangular bandwidth measures to explain most of the variance captured by the regression model. Results suggest that SMD and SRD may be promising clinical tools for diagnostic evaluation and predicting amplification outcomes. PMID:26233047

  5. Distribución fraccional de metales y minerales en la laterita de balance del yacimiento Punta Gorda, Moa, Cuba

    Directory of Open Access Journals (Sweden)

    Alberto Hernández-Flores

    2010-03-01

    Full Text Available Laterita de balance es la denominación tecnológica de la mena procesada para la obtención de níquel en Moa mediante proceso Caron, para la cual se ha establecido un contenido de Fe superior a 35 % y no menor del 1% de Ni. El propósito de la investigación fue determinar en la laterita de balance del yacimiento Punta Gorda, la composición química y mineralógica de las clases granulométricas comprendidas en el rango entre 8 y 0,045 mm. Se emplearon técnicas de separación granulométrica por vía húmeda según la serie de Taylor, métodos de difracción y de fluorescencia de rayos X y el análisis térmico diferencial. Se llega a establecer que la laterita de balance es esencialmente ferrosa, y que la mayoría de los minerales en ella contenidos presentan una granulometría específica de concentración, de manera que en los granos minerales mayores de 2 mm se concentran los silicatos de magnesio (olivino y serpentina y el hidróxido de aluminio (gibbsita, en cambio los óxidos de hierro (goethita se concentran en los granos menores de 0,071 mm.

  6. Back-flow ripples in troughs downstream of unit bars: Formation, preservation and value for interpreting flow conditions

    OpenAIRE

    Herbert, Christopher; Alexander, Jan; Martinez De Alvaro, Maria

    2015-01-01

    Back-flow ripples are bedforms created within the lee-side eddy of a larger bedform with migration directions opposed or oblique to that of the host bedform. In the flume experiments described in this article, back-flow ripples formed in the trough downstream of a unit bar and changed with mean flow velocity; varying from small incipient back-flow ripples at low velocities, to well-formed back-flow ripples with greater velocity, to rapidly migrating transient back-flow ripples formed at the g...

  7. Emission spectra from super-critical rippled plasma density profiles illuminated by intense laser pulses

    International Nuclear Information System (INIS)

    Ondarza R, R.; Boyd, T.J.M.

    2000-01-01

    High-order harmonic emission from the interaction of intense femtosecond laser pulses with super-critical plasmas characterized by a rippled density profile at the vacuum-plasma interface has been observed from particle-in-cell (PIC) simulations. A plasma simulation box several laser wavelengths in extent was prepared with a rippled density of a fraction of a laser wavelength. Emission spectra at the very initial stage of the interaction were recorded with spectral characteristics dissimilar to those previously reported in the literature. The reflected light spectra were characterized by a strong emission at the plasma line and by a series of harmonics at multiples of the ripple frequency. Harmonic spectra were obtained for different values of the plasma ripple frequency. In all cases the harmonics were emitted at the precise multiple harmonic number of the ripple frequency. Another important feature apparent from the simulations was that the emission peaks appeared to havea complex structure as compared with those for unrippled plasmas. For the cases when the plasma was rippled the peaks that corresponded to the multiples of the rippled density typically showed a double peak for the first few harmonics. The reflected emission plots for the main laser pulse showed strong emission at the plasma frequency and at multiples of that frequency as reported by the authors in the literature. (Author)

  8. Effect of ripple loads on sustained-load cracking in titanium alloys

    International Nuclear Information System (INIS)

    Pao, P.S.; Meyn, D.A.; Bayles, R.A.; Feng, C.R.; Yoder, G.R.

    1995-01-01

    In the present paper, the authors have extended their study on the effect of the ripple loads on the sustained-load cracking (SLC) behavior of two titanium alloys, Ti-6Al-4V (an α-β alloy) and Ti-15V-3Cr-3Al-3Sn (a β-α alloy), in an ambient air environment. The methodology which has been used successfully to treat ripple effects on stress-corrosion cracking (SCC) is employed again to address the influence of ripple loads on sustained-load cracking. Ripple loads can significantly reduce the apparent sustained load cracking resistance of titanium alloys in a relatively benign environment such as ambient air. For a ripple-load amplitude equal to 5% of the sustained load, the ripple-load cracking thresholds (K IRLC ) of beta-annealed Ti-6Al-4V and Ti-15V-3Cr-3al-3Sn are less than half of the respective sustained-load cracking thresholds (K ISLC ). The extent of ripple-load degradation for these alloys in ambient air -- relative to K ISLC , were found comparable to those observed in a much more aggressive 3.5% NaCl aqueous solution

  9. Seasonal and local time variability of ripples from airglow imager observations in US and Japan

    Directory of Open Access Journals (Sweden)

    J. Yue

    2010-07-01

    Full Text Available Ripples as seen in airglow imagers are small wavy structures with short horizontal wavelengths (<15 km. Ripples are thought to form as the result of local instabilities, which are believed to occur when the amplitude of gravity waves becomes large enough. We have investigated ripple formation based on years of airglow imager observations located at Fort Collins, Colorado (41° N, 105° W and Misato Observatory, Japan (34° N, 135° E/Shigaraki MU Observatory (35° N, 136° E. Na temperature-wind lidar observations are employed to detect convective and dynamic instabilities in the mesosphere and lower thermosphere (MLT region over Fort Collins, Colorado. Seasonal variation of the ripple occurrence in Colorado is compared to that of the lidar-measured instability. The occurrence frequency of ripples varies semiannually, with maxima occurring during solstices and minima during equinoxes in both Colorado and Japan. However, the probability of convective and dynamic instabilities varies annually with a peak in Colorado winter. The seasonal variation of the occurrence frequency of ripples correlates with that of the gravity wave variances in the MLT. Ripple occurrence over Colorado also shows strong local time dependence, but it bears little resemblance to the local time dependence of instability probability.

  10. Comparing spatial tuning curves, spectral ripple resolution, and speech perception in cochlear implant users.

    Science.gov (United States)

    Anderson, Elizabeth S; Nelson, David A; Kreft, Heather; Nelson, Peggy B; Oxenham, Andrew J

    2011-07-01

    Spectral ripple discrimination thresholds were measured in 15 cochlear-implant users with broadband (350-5600 Hz) and octave-band noise stimuli. The results were compared with spatial tuning curve (STC) bandwidths previously obtained from the same subjects. Spatial tuning curve bandwidths did not correlate significantly with broadband spectral ripple discrimination thresholds but did correlate significantly with ripple discrimination thresholds when the rippled noise was confined to an octave-wide passband, centered on the STC's probe electrode frequency allocation. Ripple discrimination thresholds were also measured for octave-band stimuli in four contiguous octaves, with center frequencies from 500 Hz to 4000 Hz. Substantial variations in thresholds with center frequency were found in individuals, but no general trends of increasing or decreasing resolution from apex to base were observed in the pooled data. Neither ripple nor STC measures correlated consistently with speech measures in noise and quiet in the sample of subjects in this study. Overall, the results suggest that spectral ripple discrimination measures provide a reasonable measure of spectral resolution that correlates well with more direct, but more time-consuming, measures of spectral resolution, but that such measures do not always provide a clear and robust predictor of performance in speech perception tasks. © 2011 Acoustical Society of America

  11. Extracellular calcium controls the expression of two different forms of ripple-like hippocampal oscillations.

    Science.gov (United States)

    Aivar, Paloma; Valero, Manuel; Bellistri, Elisa; Menendez de la Prida, Liset

    2014-02-19

    Hippocampal high-frequency oscillations (HFOs) are prominent in physiological and pathological conditions. During physiological ripples (100-200 Hz), few pyramidal cells fire together coordinated by rhythmic inhibitory potentials. In the epileptic hippocampus, fast ripples (>200 Hz) reflect population spikes (PSs) from clusters of bursting cells, but HFOs in the ripple and the fast ripple range are vastly intermixed. What is the meaning of this frequency range? What determines the expression of different HFOs? Here, we used different concentrations of Ca(2+) in a physiological range (1-3 mM) to record local field potentials and single cells in hippocampal slices from normal rats. Surprisingly, we found that this sole manipulation results in the emergence of two forms of HFOs reminiscent of ripples and fast ripples recorded in vivo from normal and epileptic rats, respectively. We scrutinized the cellular correlates and mechanisms underlying the emergence of these two forms of HFOs by combining multisite, single-cell and paired-cell recordings in slices prepared from a rat reporter line that facilitates identification of GABAergic cells. We found a major effect of extracellular Ca(2+) in modulating intrinsic excitability and disynaptic inhibition, two critical factors shaping network dynamics. Moreover, locally modulating the extracellular Ca(2+) concentration in an in vivo environment had a similar effect on disynaptic inhibition, pyramidal cell excitability, and ripple dynamics. Therefore, the HFO frequency band reflects a range of firing dynamics of hippocampal networks.

  12. The Ripple Effect: Citation Chain Reactions of a Nobel Prize

    DEFF Research Database (Denmark)

    Faber Frandsen, Tove; Nicolaisen, Jeppe

    2013-01-01

    This paper explores the possible citation chain reactions of a Nobel Prize using the mathematician Robert J. Aumann as a case example. The results show that the award of the Nobel Prize in 2005 affected not only the citations to his work, but also affected the citations to the references in his s...... citation network. The effect is discussed using innovation decision process theory as a point of departure to identify the factors that created a bandwagon effect leading to the reported observations....... scientific oeuvre. The results indicate that the spillover effect is almost as powerful as the effect itself. We are consequently able to document a ripple effect in which the awarding of the Nobel Prize ignites a citation chain reaction to Aumann's scientific ouvre and to the references in its nearest...

  13. The Ripple Pond: Enabling Spiking Networks to See

    Directory of Open Access Journals (Sweden)

    Saeed eAfshar

    2013-11-01

    Full Text Available We present the biologically inspired Ripple Pond Network (RPN, a simply connected spiking neural network which performs a transformation converting two dimensional images to one dimensional temporal patterns suitable for recognition by temporal coding learning and memory networks. The RPN has been developed as a hardware solution linking previously implemented neuromorphic vision and memory structures such as frameless vision sensors and neuromorphic temporal coding spiking neural networks. Working together such systems are potentially capable of delivering end-to-end high-speed, low-power and low-resolution recognition for mobile and autonomous applications where slow, highly sophisticated and power hungry signal processing solutions are ineffective. Key aspects in the proposed approach include utilising the spatial properties of physically embedded neural networks and propagating waves of activity therein for information processing, using dimensional collapse of imagery information into amenable temporal patterns and the use of asynchronous frames for information binding.

  14. The ripple pond: enabling spiking networks to see.

    Science.gov (United States)

    Afshar, Saeed; Cohen, Gregory K; Wang, Runchun M; Van Schaik, André; Tapson, Jonathan; Lehmann, Torsten; Hamilton, Tara J

    2013-01-01

    We present the biologically inspired Ripple Pond Network (RPN), a simply connected spiking neural network which performs a transformation converting two dimensional images to one dimensional temporal patterns (TP) suitable for recognition by temporal coding learning and memory networks. The RPN has been developed as a hardware solution linking previously implemented neuromorphic vision and memory structures such as frameless vision sensors and neuromorphic temporal coding spiking neural networks. Working together such systems are potentially capable of delivering end-to-end high-speed, low-power and low-resolution recognition for mobile and autonomous applications where slow, highly sophisticated and power hungry signal processing solutions are ineffective. Key aspects in the proposed approach include utilizing the spatial properties of physically embedded neural networks and propagating waves of activity therein for information processing, using dimensional collapse of imagery information into amenable TP and the use of asynchronous frames for information binding.

  15. Emulating porphyrins with a rippled multivacancy graphene system

    Science.gov (United States)

    Mombrú, Dominique; Faccio, Ricardo; Mombrú, Alvaro W.

    2018-04-01

    The interaction between a complex porphyrin-like system formed by an iron atom and multivacant graphene layer and O2, CO and CO2 molecules is studied, using Density Functional Theory (DFT) calculations. The multivacancy graphene system used for this study, consists in the removal of a 1,4-dimethybenzene-like moiety, in a 6 × 6 supercell. This removal and the structural optimization subsequently performed, yield to a biaxial vacancy, where the location of an iron atom embedded in it, lead to a system with resemblance to iron-porphyrin systems. This similar structure could be used to form complexes where gas molecules are allowed to interact with these iron-octavacant graphene systems. The study focuses on the structure of the system and the net magnetic moment for different gas molecules: O2, CO2 and CO. Rippling in the vacant graphene is enhanced through this interaction.

  16. Direct measurements of mean Reynolds stress and ripple roughness in the presence of energetic forcing by surface waves

    Science.gov (United States)

    Scully, Malcolm; Trowbridge, John; Sherwood, Christopher R.; Jones, Katie R.; Traykovski, Peter A.

    2018-01-01

    Direct covariance observations of the mean flow Reynolds stress and sonar images of the seafloor collected on a wave‐exposed inner continental shelf demonstrate that the drag exerted by the seabed on the overlying flow is consistent with boundary layer models for wave‐current interaction, provided that the orientation and anisotropy of the bed roughness are appropriately quantified. Large spatial and temporal variations in drag result from nonequilibrium ripple dynamics, ripple anisotropy, and the orientation of the ripples relative to the current. At a location in coarse sand characterized by large two‐dimensional orbital ripples, the observed drag shows a strong dependence on the relative orientation of the mean current to the ripple crests. At a contrasting location in fine sand, where more isotropic sub‐orbital ripples are observed, the sensitivity of the current to the orientation of the ripples is reduced. Further, at the coarse site under conditions when the currents are parallel to the ripple crests and the wave orbital diameter is smaller than the wavelength of the relic orbital ripples, the flow becomes hydraulically smooth. This transition is not observed at the fine site, where the observed wave orbital diameter is always greater than the wavelength of the observed sub‐orbital ripples. Paradoxically, the dominant along‐shelf flows often experience lower drag at the coarse site than at the fine site, despite the larger ripples, highlighting the complex dynamics controlling drag in wave‐exposed environments with heterogeneous roughness.

  17. Ripples on spikes show increased phase-amplitude coupling in mesial temporal lobe epilepsy seizure onset zones

    Science.gov (United States)

    Weiss, Shennan A; Orosz, Iren; Salamon, Noriko; Moy, Stephanie; Wei, Linqing; Van ’t Klooster, Maryse A; Knight, Robert T; Harper, Ronald M; Bragin, Anatol; Fried, Itzhak; Engel, Jerome; Staba, Richard J

    2016-01-01

    Objective Ripples (80–150 Hz) recorded from clinical macroelectrodes have been shown to be an accurate biomarker of epileptogenic brain tissue. We investigated coupling between epileptiform spike phase and ripple amplitude to better understand the mechanisms that generate this type of pathological ripple (pRipple) event. Methods We quantified phase amplitude coupling (PAC) between epileptiform EEG spike phase and ripple amplitude recorded from intracranial depth macroelectrodes during episodes of sleep in 12 patients with mesial temporal lobe epilepsy. PAC was determined by 1) a phasor transform that corresponds to the strength and rate of ripples coupled with spikes, and a 2) ripple-triggered average to measure the strength, morphology, and spectral frequency of the modulating and modulated signals. Coupling strength was evaluated in relation to recording sites within and outside the seizure onset zone (SOZ). Results Both the phasor transform and ripple-triggered averaging methods showed ripple amplitude was often robustly coupled with epileptiform EEG spike phase. Coupling was more regularly found inside than outside the SOZ, and coupling strength correlated with the likelihood a macroelectrode’s location was within the SOZ (pripples coupled with EEG spikes inside the SOZ to rates of coupled ripples in non-SOZ was greater than the ratio of rates of ripples on spikes detected irrespective of coupling (pripple amplitude (pripple spectral frequency (pripple amplitude. The changes in excitability reflected as epileptiform spikes may also cause clusters of pathologically interconnected bursting neurons to grow and synchronize into aberrantly large neuronal assemblies. PMID:27723936

  18. Surface ripple evolution by argon ion irradiation in polymers

    International Nuclear Information System (INIS)

    Goyal, Meetika; Aggarwal, Sanjeev; Sharma, Annu

    2016-01-01

    In this report, an attempt has been made to investigate the morphological evolution of nanoscale surface ripples on aliphatic (polypropylene, PP) and aromatic (polyethylene terephthalate, PET) polymeric substrates irradiated with 50 keV Ar"+ ions. The specimens were sputtered at off normal incidence of 30° with 5 × 10"1"6 Ar"+ cm"−"2. The topographical features and structural behavior of the specimens were studied using Atomic Force Microscopy (AFM) and UV-Visible spectroscopy techniques, respectively. The Stopping and Range of Ions in Matter simulations were performed to calculate sputtering yield of irradiated PP and PET polymers. Sputtering yield of carbon atoms has been found to be smaller for PP (0.40) as compared to PET (0.73), which is attributed to the different structures of two polymers. AFM analysis demonstrates the evolution of ripple like features with amplitude (2.50 nm) and wavelength (690 nm) on PET while that of lower amplitude (1.50 nm) and higher wavelength (980 nm) on PP specimen. The disorder parameter (Urbach energy) has been found to increase significantly from 0.30 eV to 1.67 eV in case of PP as compared to a lesser increase from 0.35 eV to 0.72 eV in case of PET as revealed by UV-Visible characterization. A mutual correlation between ion beam sputtering induced topographical variations with that of enhancement in the disorder parameter of the specimens has been discussed.

  19. FLOC: Field Line and Orbit Code for the study of ripple beam injection into tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Fowler, R. H.; Lee, D. K.; Gaffney, P. W.; Rome, J. A.

    1978-06-01

    The computer code described is used to study ripple beam injection into a tokamak plasma. The collisionless guiding center equations of motion are integrated to find the orbits of single particles in realistic magnetic fields for ripple injection. In order to determine if the ripple is detrimental to the plasma, the magnetic flux surfaces are constructed by integration of the field line equations. The numerical techniques are described, and use of the code is outlined. A program listing is provided, and the results of sample cases are presented.

  20. Advanced RF-KO slow-extraction method for the reduction of spill ripple

    CERN Document Server

    Noda, K; Shibuya, S; Uesugi, T; Muramatsu, M; Kanazawa, M; Takada, E; Yamada, S

    2002-01-01

    Two advanced RF-knockout (RF-KO) slow-extraction methods have been developed at HIMAC in order to reduce the spill ripple for accurate heavy-ion cancer therapy: the dual frequency modulation (FM) method and the separated function method. As a result of simulations and experiments, it was verified that the spill ripple could be considerably reduced using these advanced methods, compared with the ordinary RF-KO method. The dual FM method and the separated function method bring about a low spill ripple within standard deviations of around 25% and of 15% during beam extraction within around 2 s, respectively, which are in good agreement with the simulation results.

  1. Adaptive feedforward of estimated ripple improves the closed loop system performance significantly

    International Nuclear Information System (INIS)

    Kwon, S.; Regan, A.; Wang, Y.M.; Rohlev, A.S.

    1998-01-01

    The Low Energy Demonstration Accelerator (LEDA) being constructed at Los Alamos National Laboratory will serve as the prototype for the low energy section of Acceleration Production of Tritium (APT) accelerator. This paper addresses the problem of LLRF control system for LEDA. The authors propose an estimator of the ripple and its time derivative and a control law which is based on PID control and adaptive feedforward of estimated ripple. The control law reduces the effect of the deterministic cathode ripple that is due to high voltage power supply and achieves tracking of desired set points

  2. Online high voltage power supply ripple estimation and feedforward in LEDA

    International Nuclear Information System (INIS)

    Kwon, S.; Regan, A.; Wang, Y.M.; Rohlev, T.

    1999-01-01

    The Low Energy Demonstration Accelerator (LEDA) being constructed at Los Alamos National Laboratory will serve as the prototype for the low energy section of Acceleration Production of Tritium (APT) accelerator. This paper addresses the problem of LLRF control system for LEDA. They propose an estimator of the ripple and its time derivative and a control law which is based on PID control and adaptive feedforward of estimated ripple. The control law reduces the effect of the deterministic cathode ripple that is due to high voltage power supply and achieves tracking of desired set points

  3. Final Report: Mechanisms of sputter ripple formation: coupling among energetic ions, surface kinetics, stress and composition

    Energy Technology Data Exchange (ETDEWEB)

    Chason, Eric; Shenoy, Vivek

    2013-01-22

    Self-organized pattern formation enables the creation of nanoscale surface structures over large areas based on fundamental physical processes rather than an applied template. Low energy ion bombardment is one such method that induces the spontaneous formation of a wide variety of interesting morphological features (e.g., sputter ripples and/or quantum dots). This program focused on the processes controlling sputter ripple formation and the kinetics controlling the evolution of surfaces and nanostructures in high flux environments. This was done by using systematic, quantitative experiments to measure ripple formation under a variety of processing conditions coupled with modeling to interpret the results.

  4. A New Switched Reluctance Motor Design to Reduce Torque Ripple using Finite Element Fuzzy Optimization

    Directory of Open Access Journals (Sweden)

    S. R. Mousavi-Aghdam

    2012-03-01

    Full Text Available This paper presents a new design to reduce torque ripple in Switched Reluctance Motors (SRM. Although SRM possesses many advantages in terms of motor structure, it suffers from large torque ripple that causes problems such as vibration and acoustic noise. The paper describes new rotor and stator pole shapes with a non-uniform air gap profile to reduce torque ripple while retaining its average value. An optimization using fuzzy strategy is successfully performed after sensitivity analysis. The two dimensional (2-D finite element method (FEM results, have demonstrated validity of the proposed new design.

  5. Magnetic ripple and the modeling of lower-hybrid current drive in tokamaks

    International Nuclear Information System (INIS)

    Peysson, Y.; Arslanbekov, R.; Basiuk, V.; Carrasco, J.; Litaudon, X.; Moreau, D.; Bizarro, J.P.

    1996-01-01

    Using ray-tracing, a detailed investigation of the lower hybrid (LH) wave propagation in presence of toroidal magnetic field ripple is presented. By coupling ray tracing with a one-dimensional relativistic Fokker-Planck code, simulations of LH experiments have been performed for the Tore Supra tokamak. Taking into account magnetic ripple in LH simulations, a better agreement is found between numerical predictions and experimental observations, such as non-thermal Bremsstrahlung emission, current profile, ripple-induced power losses in local magnetic mirrors, when plasma conditions correspond to the ' 'few passes' regime. (author)

  6. FLOC: Field Line and Orbit Code for the study of ripple beam injection into tokamaks

    International Nuclear Information System (INIS)

    Fowler, R.H.; Lee, D.K.; Gaffney, P.W.; Rome, J.A.

    1978-06-01

    The computer code described is used to study ripple beam injection into a tokamak plasma. The collisionless guiding center equations of motion are integrated to find the orbits of single particles in realistic magnetic fields for ripple injection. In order to determine if the ripple is detrimental to the plasma, the magnetic flux surfaces are constructed by integration of the field line equations. The numerical techniques are described, and use of the code is outlined. A program listing is provided, and the results of sample cases are presented

  7. The wave plus current flow over vortex ripples at an arbitrary angle

    DEFF Research Database (Denmark)

    Andersen, Ken Haste; Faraci, C

    2003-01-01

    This work concerns the wave plus current flow over a sand bed covered by vortex ripples, with the current and the waves coming from different angles. Experiments were performed in a basin, where current and waves were perpendicular, in order to determine the conditions (current strength) leading...... to a regular ripple pattern formation. Numerical simulations were conducted changing the direction between the waves and the current from 0degrees to 90degrees and the ratio between the current strength and the wave orbital velocity from 0.2 to 1.5. Close to the bed, the current aligns parallel to the ripple...

  8. Pattern dynamics of vortex ripples in sand: Nonlinear modeling and experimental validation

    DEFF Research Database (Denmark)

    Andersen, Ken Haste; Abel, M.; Krug, J.

    2002-01-01

    Vortex ripples in sand are studied experimentally in a one-dimensional setup with periodic boundary conditions. The nonlinear evolution, far from the onset of instability, is analyzed in the framework of a simple model developed for homogeneous patterns. The interaction function describing the mass...... transport between neighboring ripples is extracted from experimental runs using a recently proposed method for data analysis, and the predictions of the model are compared to the experiment. An analytic explanation of the wavelength selection mechanism in the model is provided, and the width of the stable...... band of ripples is measured....

  9. Stable carbon and nitrogen isotope signatures indicate recovery of marine biota from sewage pollution at Moa Point, New Zealand

    International Nuclear Information System (INIS)

    Rogers, Karyne M.

    2003-01-01

    Stable carbon and nitrogen isotopes have been used to assess sewage contamination of a sewage outfall, discharging milli-screened effluent into Moa Point Bay, New Zealand, and monitor the recovery of flora and fauna after the outfall's closure. An initial study characterising the extent of the discharge and the effects on seaweed (Ulva lactuca L.), blue mussels (Mytilus galloprovincialis) and limpets (Cellana denticulata) from the area, showed effects of the sewage discharge on flora and fauna were localised within in the bay. The immediate area surrounding the discharge area was found to contain limited biodiversity, with an abundance of Ulva lactuca, a bright green lettuce-like seaweed, typically found in areas with high nutrient input, limpets and small blue mussels. The nitrogen isotopic signature (δ 15 N) is shown to be a good tracer of sewage pollution in seaweed and associated grazers (i.e. limpets) as a result of the increased contribution of urea and ammonia to seawater nitrogen derived from the effluent. The carbon isotopic signature (δ 13 C) is suggested as a more appropriate sewage tracer for mussels, which filter feed the effluent's particulate organic matter from the water. Lower carbon:nitrogen ratios were found in Ulva lactuca sampled from around the outfall region compared to uncontaminated control sites. However carbon:nitrogen ratios do not vary significantly amongst shellfish species. After closure, monitoring continued for 9 months and showed that the carbon and nitrogen isotopic signatures of algae (Ulva lactuca L.) returned to similar control site levels within 3 months. Limpet and blue mussels (Cellana denticulata and Mytilus galloprovincialis) showed slower recovery times than the Ulva lactuca, with detectable levels of the sewage-derived carbon and nitrogen remaining in the animal's tissue for up to 9 months

  10. Stable carbon and nitrogen isotope signatures indicate recovery of marine biota from sewage pollution at Moa Point, New Zealand

    Energy Technology Data Exchange (ETDEWEB)

    Rogers, Karyne M

    2003-07-01

    Stable carbon and nitrogen isotopes have been used to assess sewage contamination of a sewage outfall, discharging milli-screened effluent into Moa Point Bay, New Zealand, and monitor the recovery of flora and fauna after the outfall's closure. An initial study characterising the extent of the discharge and the effects on seaweed (Ulva lactuca L.), blue mussels (Mytilus galloprovincialis) and limpets (Cellana denticulata) from the area, showed effects of the sewage discharge on flora and fauna were localised within in the bay. The immediate area surrounding the discharge area was found to contain limited biodiversity, with an abundance of Ulva lactuca, a bright green lettuce-like seaweed, typically found in areas with high nutrient input, limpets and small blue mussels. The nitrogen isotopic signature ({delta}{sup 15}N) is shown to be a good tracer of sewage pollution in seaweed and associated grazers (i.e. limpets) as a result of the increased contribution of urea and ammonia to seawater nitrogen derived from the effluent. The carbon isotopic signature ({delta}{sup 13}C) is suggested as a more appropriate sewage tracer for mussels, which filter feed the effluent's particulate organic matter from the water. Lower carbon:nitrogen ratios were found in Ulva lactuca sampled from around the outfall region compared to uncontaminated control sites. However carbon:nitrogen ratios do not vary significantly amongst shellfish species. After closure, monitoring continued for 9 months and showed that the carbon and nitrogen isotopic signatures of algae (Ulva lactuca L.) returned to similar control site levels within 3 months. Limpet and blue mussels (Cellana denticulata and Mytilus galloprovincialis) showed slower recovery times than the Ulva lactuca, with detectable levels of the sewage-derived carbon and nitrogen remaining in the animal's tissue for up to 9 months.

  11. Control of surface ripple amplitude in ion beam sputtered polycrystalline cobalt films

    Energy Technology Data Exchange (ETDEWEB)

    Colino, Jose M., E-mail: josemiguel.colino@uclm.es [Institute of Nanoscience, Nanotechnology and Molecular Materials, University of Castilla-La Mancha, Campus de la Fabrica de Armas, Toledo 45071 (Spain); Arranz, Miguel A. [Facultad de Ciencias Quimicas, University of Castilla-La Mancha, Ciudad Real 13071 (Spain)

    2011-02-15

    We have grown both polycrystalline and partially textured cobalt films by magnetron sputter deposition in the range of thickness (50-200 nm). Kinetic roughening of the growing film leads to a controlled rms surface roughness values (1-6 nm) increasing with the as-grown film thickness. Ion erosion of a low energy 1 keV Ar+ beam at glancing incidence (80{sup o}) on the cobalt film changes the surface morphology to a ripple pattern of nanometric wavelength. The wavelength evolution at relatively low fluency is strongly dependent on the initial surface topography (a wavelength selection mechanism hereby confirmed in polycrystalline rough surfaces and based on the shadowing instability). At sufficiently large fluency, the ripple wavelength steadily increases on a coarsening regime and does not recall the virgin surface morphology. Remarkably, the use of a rough virgin surface makes the ripple amplitude in the final pattern can be controllably increased without affecting the ripple wavelength.

  12. Plasma waves generated by rippled magnetically focused electron beams surrounded by tenuous plasmas

    International Nuclear Information System (INIS)

    Cuperman, S.; Petran, F.

    1982-01-01

    This chapter investigates the electrostatic instability and the corresponding unstable wave spectrum of magnetically focused neutralized rippled electron beams under spacelike conditions. Topics considered include general equations and equilibrium, the derivation of the dispersion relation, and the solution of the dispersion relation (long wavelength perturbations, short wavelength perturbations, the rippled beam). The results indicate that in the long wavelength limit two types of instability (extending over different frequency ranges) exist. An instability of the beam-plasma type occurs due to the interaction between the beam electrons and the surrounding plasm electrons at the beam-plasma interface. A parametric type instability is produced by the coupling of a fast forward wave and a fast backward wave due to the rippling (modulation) of the beam. It is demonstrated that in the short wavelength limit, surface waves which are stable for the laminar beam may become unstable in the rippled beam case

  13. Implementation of vertically asymmetric toroidal-field ripple for beam heating of tokamak reactor plasmas

    International Nuclear Information System (INIS)

    Jassby, D.L.; Sheffield, G.V.; Towner, H.H.; Weissenburger, D.W.

    1976-10-01

    The neutral-beam energy required for adequate penetration of tokamak plasmas of high opacity can be reduced by a large factor if the beam is injected vertically into a region of large TF (toroidal-field) ripple. Energetic ions are trapped in local magnetic wells and drift vertically toward the midplane (z = 0). If the ripple is made very small on the opposite side of the midplane, drifting ions are detrapped and thermalized in the central plasma region. This paper discusses design considerations for establishing the required vertically asymmetric ripple. Examples are given of special TF-coil configurations, and of the use of auxiliary coil windings to create the prescribed ripple profiles

  14. Roles of effective helical ripple rates in nonlinear stability of externally induced magnetic islands

    Energy Technology Data Exchange (ETDEWEB)

    Nishimura, Seiya, E-mail: n-seiya@kobe-kosen.ac.jp [Kobe City College of Technology, Kobe, Hyogo 651-2194 (Japan)

    2015-02-15

    Magnetic islands are externally produced by resonant magnetic perturbations (RMPs) in toroidal plasmas. Spontaneous annihilation of RMP-induced magnetic islands called self-healing has been observed in helical systems. A possible mechanism of the self-healing is shielding of RMP penetration by helical ripple-induced neoclassical flows, which give rise to neoclassical viscous torques. In this study, effective helical ripple rates in multi-helicity helical systems are revisited, and a multi-helicity effect on the self-healing is investigated, based on a theoretical model of rotating magnetic islands. It is confirmed that effective helical ripple rates are sensitive to magnetic axis positions. It is newly found that self-healing thresholds also strongly depend on magnetic axis positions, which is due to dependence of neoclassical viscous torques on effective helical ripple rates.

  15. Effect of toroidal field ripple on the formation of internal transport barriers

    Energy Technology Data Exchange (ETDEWEB)

    Vries, P C de; Hawkes, N C; Challis, C D; Andrew, Y; Beurskens, M; Brix, M; Giroud, C; Zastrow, K-D [EURATOM/UKAEA Fusion Association, Culham Science Centre, Abingdon, OX14 3DB (United Kingdom); Joffrin, E [EFDA-JET CSU, Culham Science Centre, Abingdon, Oxfordshire, OX14 3DB (United Kingdom); Litaudon, X [Association EURATOM-CEA, DSM/DFRC, CEA Cadarache, 13108, St Paul lez Durance (France); Brzozowski, J; Johnson, T [Association EURATOM-VR, Fusion Plasma Physics, EES, KTH, Stockholm (Sweden); Crombe, K [Department of Applied Physics, Ghent University, Ghent (Belgium); Hobirk, J [Max-Planck-Institut fuer Plasmaphysik, Euratom Association, 85748 Garching (Germany); Loennroth, J; Salmi, A [Association Euratom-Tekes, Helsinki University of Technology, PO Box 4100, 02015 TKK (Finland); Tala, T [Association Euratom-Tekes, VTT, PO Box 1000, 02044 VTT (Finland); Yavorskij, V [Institute for Theoretical Physics, Association EURATOM-OEAW, University of Innsbruck (Austria)], E-mail: Peter.de.Vries@jet.uk

    2008-06-15

    The effect of a toroidal field (TF) ripple on the formation and performance of internal transport barriers (ITBs) has been studied in JET. It was found that the TF ripple had a profound effect on the toroidal plasma rotation. An increased TF ripple up to {delta} = 1% led to a lower rotation and reduced the rotational shear in the region where the ITBs were formed. ITB triggering events were observed in all cases and it is thought that the rotational shear may be less important for this process than, for example, the q-profile. However, the increase in the pressure gradient following the ITB trigger was reduced in discharges with a larger TF ripple and consequently a lower rotational shear. This suggests that toroidal rotation and its shear play a role in the growth of the ITB once it has been triggered.

  16. A High Power Density Single-Phase PWM Rectifier With Active Ripple Energy Storage

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Ruxi [Virginia Polytechnic Institute and State University (Virginia Tech); Wang, Fei [ORNL; Boroyevich, Dushan [Virginia Polytechnic Institute and State University (Virginia Tech); Burgos, Rolando [ABB; Lai, Rixin [General Electric; Ning, Puqi [ORNL; Rajashekara, Kaushik [Rolls Royce

    2011-01-01

    It is well known that single-phase pulse width modulation rectifiers have second-order harmonic currents and corresponding ripple voltages on the dc bus. The low-frequency harmonic current is normally filtered using a bulk capacitor in the bus, which results in low power density. However, pursuing high power density in converter design is a very important goal in the aerospace applications. This paper studies methods for reducing the energy storage capacitor for single-phase rectifiers. The minimum ripple energy storage requirement is derived independently of a specific topology. Based on theminimum ripple energy requirement, the feasibility of the active capacitor s reduction schemes is verified. Then, we propose a bidirectional buck boost converter as the ripple energy storage circuit, which can effectively reduce the energy storage capacitance. The analysis and design are validated by simulation and experimental results.

  17. 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.

  18. A high voltage ratio and low ripple interleaved DC-DC converter for fuel cell applications.

    Science.gov (United States)

    Chang, Long-Yi; Chao, Kuei-Hsiang; Chang, Tsang-Chih

    2012-01-01

    This paper proposes a high voltage ratio and low ripple interleaved boost DC-DC converter, which can be used to reduce the output voltage ripple. This converter transfers the low DC voltage of fuel cell to high DC voltage in DC link. The structure of the converter is parallel with two voltage-doubler boost converters by interleaving their output voltages to reduce the voltage ripple ratio. Besides, it can lower the current stress for the switches and inductors in the system. First, the PSIM software was used to establish a proton exchange membrane fuel cell and a converter circuit model. The simulated and measured results of the fuel cell output characteristic curve are made to verify the correctness of the established simulation model. In addition, some experimental results are made to validate the effectiveness in improving output voltage ripple of the proposed high voltage ratio interleaved boost DC-DC converters.

  19. Studies of suprathermal electron loss in the magnetic ripple of Tore Supra

    International Nuclear Information System (INIS)

    Basiuk, V.; Lipa, M.; Martin, G.; Chantant, M.; Guilhem, D.; Imbeaux, F.; Mitteau, R.; Peysson, Y.; Surle, F.

    2000-01-01

    A new prototype of protection against fast electron trapped in the magnetic ripple was installed on Tore-Supra in 1998. It was designed to support the high flux of fast electron generated by lower hybrid in the CIEL project (up to 6 MW/m 2 ) during steady state experiments. So it is actively cooled and allows a direct measurement of the energy lost in the ripple. (author)

  20. Surface magnetization and the role of pattern defects in various types of ripple patterned films

    International Nuclear Information System (INIS)

    Colino, Jose M; Arranz, Miguel A; Barbero, Antonio J; Bollero, A; Camarero, J

    2016-01-01

    We present a detailed study of the magnetic properties of cobalt films with wide-area nanoscale ripple patterns, either on their surface only, or on both the film surface and substrate interface. Angular dependence vectorial-resolved magnetometry measurements and magnetic force microscopy with in situ magnetic field have been used to determine the magnetization reversal processes to correlate them to the different patterned nanostructures. All the samples show well-defined uniaxial magnetic anisotropy with the anisotropy axis lying along the ripple direction. Atomic force microscopy of the different types of pattern reveals various pattern defects: height corrugation and breaks of continuity along the ripple direction, and overlapping ripples and Y-shaped defects (pattern dislocation) across the pattern. In spite of the existence of such customary defects of erosive-regime patterns, the type of low-amplitude, surface-patterned films remarkably behave as a macrospin over almost the whole in-plane angular range (340°), with negligible spread of anisotropy axis or energy. In turn, it is found that high-amplitude surface-patterned films develop an angular distribution of anisotropy axes, probably related to the large distribution of amplitudes in a pattern of short ripples, and a significant distribution of anisotropy fields ΔH k /H k up to 15%. On the other hand, films grow on pre-patterned silicon with a significantly longer mean ripple length, and develop a larger anisotropy energy with H k up to 110 mT, probably because of the double interface effect. The switching fields close to the magnetization easy axis of all types of ripple pattern are not well reproduced by the macrospin approximation, but the observed pattern defects seem to be not responsible for the domain wall pinning that occurs with the field applied along the ripple direction. (paper)

  1. Simulation of Alpha Particles in Rotating Plasma Interacting with a Stationary Ripple

    International Nuclear Information System (INIS)

    Fetterman, Abraham J.; Fisch, Nathaniel J.

    2011-01-01

    Superthermal ExB rotation can provide magnetohydrodynamic (MHD) stability and enhanced confinement to axisymmetric mirrors. However, the rotation speed has been limited by phenomena at end electrodes. A new prediction is that rotation might instead be produced using a magnetic ripple and alpha particle kinetic energy, in an extension of the alpha channeling concept. The interaction of alpha particles with the ripple results in visually interesting and practically useful orbits.

  2. Temperature-Controlled High-Speed AFM: Real-Time Observation of Ripple Phase Transitions.

    Science.gov (United States)

    Takahashi, Hirohide; Miyagi, Atsushi; Redondo-Morata, Lorena; Scheuring, Simon

    2016-11-01

    With nanometer lateral and Angstrom vertical resolution, atomic force microscopy (AFM) has contributed unique data improving the understanding of lipid bilayers. Lipid bilayers are found in several different temperature-dependent states, termed phases; the main phases are solid and fluid phases. The transition temperature between solid and fluid phases is lipid composition specific. Under certain conditions some lipid bilayers adopt a so-called ripple phase, a structure where solid and fluid phase domains alternate with constant periodicity. Because of its narrow regime of existence and heterogeneity ripple phase and its transition dynamics remain poorly understood. Here, a temperature control device to high-speed atomic force microscopy (HS-AFM) to observe dynamics of phase transition from ripple phase to fluid phase reversibly in real time is developed and integrated. Based on HS-AFM imaging, the phase transition processes from ripple phase to fluid phase and from ripple phase to metastable ripple phase to fluid phase could be reversibly, phenomenologically, and quantitatively studied. The results here show phase transition hysteresis in fast cooling and heating processes, while both melting and condensation occur at 24.15 °C in quasi-steady state situation. A second metastable ripple phase with larger periodicity is formed at the ripple phase to fluid phase transition when the buffer contains Ca 2+ . The presented temperature-controlled HS-AFM is a new unique experimental system to observe dynamics of temperature-sensitive processes at the nanoscopic level. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Assessing the role of spectral and intensity cues in spectral ripple detection and discrimination in cochlear-implant users.

    Science.gov (United States)

    Anderson, Elizabeth S; Oxenham, Andrew J; Nelson, Peggy B; Nelson, David A

    2012-12-01

    Measures of spectral ripple resolution have become widely used psychophysical tools for assessing spectral resolution in cochlear-implant (CI) listeners. The objective of this study was to compare spectral ripple discrimination and detection in the same group of CI listeners. Ripple detection thresholds were measured over a range of ripple frequencies and were compared to spectral ripple discrimination thresholds previously obtained from the same CI listeners. The data showed that performance on the two measures was correlated, but that individual subjects' thresholds (at a constant spectral modulation depth) for the two tasks were not equivalent. In addition, spectral ripple detection was often found to be possible at higher rates than expected based on the available spectral cues, making it likely that temporal-envelope cues played a role at higher ripple rates. Finally, spectral ripple detection thresholds were compared to previously obtained speech-perception measures. Results confirmed earlier reports of a robust relationship between detection of widely spaced ripples and measures of speech recognition. In contrast, intensity difference limens for broadband noise did not correlate with spectral ripple detection measures, suggesting a dissociation between the ability to detect small changes in intensity across frequency and across time.

  4. Metal Accumulation in Surface Sediment of the Urban and Industrial Coastal Area of the Municipality of Moa (Cuba: Distribution and Pollution Assessment

    Directory of Open Access Journals (Sweden)

    Yosbanis Cervantes-Guerra

    2017-04-01

    Full Text Available The investigation is to evaluate the accumulation of ten elements (Al, Cr, Fe, Mn, Ni, Co, As, Cu, Pb and Zn in surface sediments from the urban and industrial coastal area of Moa. Human activity has influenced the region, which has been developing in one of the most important mining regions of Cuba since the middle of the past century. Two methods were used to assess the contamination of the sediments: the estimation of metal enrichment by calculating the index of geo-accumulation (Igeo and the interpretation of the data obtained based on quality criteria. The overall range of concentrations is 15.7 - 83.5 mg g-1 for aluminum, 1.4 – 17.9 mg g-1 for chromium, 22.8 - 379.5 mg g-1 for iron, 1.5 - 56.2 mg g-1 for manganese, 0.9 – 6.2 mg g-1 for nickel, 56 - 1094 µg g-1 for cobalt, 6 - 126 µg g-1 for arsenic, 17 to 146 µg g-1 for copper, 6 - 66 µg g-1 for lead, and 64 - 576 µg g-1 for zinc. The results obtained from the studied coastal zone show a high level of pollution in surface sediments. The spatial distribution of the elements varied according to the analyzed elements: Al, Cr, Fe and Ni showed high levels of concentration throughout the studied zone; Mn, Co, Cu, As and Zn are in a higher proportion in Moa Bay Cay. In the case of As and Pb, higher concentrations were located at the deltas of Moa and Cayo Guam rivers and also in some areas in the west of the bay.

  5. Toroidal ripple transport of beam ions in the mega-ampère spherical tokamak

    International Nuclear Information System (INIS)

    McClements, K. G.; Hole, M. J.

    2012-01-01

    The transport of injected beam ions due to toroidal magnetic field ripple in the mega-ampère spherical tokamak (MAST) is quantified using a full orbit particle tracking code, with collisional slowing-down and pitch-angle scattering by electrons and bulk ions taken into account. It is shown that the level of ripple losses is generally rather low, although it depends sensitively on the major radius of the outer midplane plasma edge; for typical values of this parameter in MAST plasmas, the reduction in beam heating power due specifically to ripple transport is less than 1%, and the ripple contribution to beam ion diffusivity is of the order of 0.1 m 2 s –1 or less. It is concluded that ripple effects make only a small contribution to anomalous transport rates that have been invoked to account for measured neutron rates and plasma stored energies in some MAST discharges. Delayed (non-prompt) losses are shown to occur close to the outer midplane, suggesting that banana-drift diffusion is the most likely cause of the ripple-induced losses.

  6. A High Power Density Integrated Charger for Electric Vehicles with Active Ripple Compensation

    Directory of Open Access Journals (Sweden)

    Liwen Pan

    2015-01-01

    Full Text Available This paper suggests a high power density on-board integrated charger with active ripple compensation circuit for electric vehicles. To obtain a high power density and high efficiency, silicon carbide devices are reported to meet the requirement of high-switching-frequency operation. An integrated bidirectional converter is proposed to function as AC/DC battery charger and to transfer energy between battery pack and motor drive of the traction system. In addition, the conventional H-bridge circuit suffers from ripple power pulsating at second-order line frequency, and a scheme of active ripple compensation circuit has been explored to solve this second-order ripple problem, in which a pair of power switches shared traction mode, a ripple energy storage capacitor, and an energy transfer inductor. Simulation results in MATLAB/Simulink validated the eligibility of the proposed topology. The integrated charger can work as a 70 kW motor drive circuit or a converter with an active ripple compensation circuit for 3 kW charging the battery. The impact of the proposed topology and control strategy on the integrated charger power losses, efficiency, power density, and thermal performance has also been analysed and simulated.

  7. IDENTIFIKASI PENYAKIT PADA TERUMBU KARANG MENGGUNAKAN RIPPLE DOWN RULES

    Directory of Open Access Journals (Sweden)

    Agus Cahyo Nugroho

    2018-01-01

    Full Text Available Along with the development of technology, people developed a system that capable of adopting processes and human thinking as an expert system that contains specific knowledge so that everyone can use it to solve a specific problem, namely the diagnosis of coral reef disease. The purpose of this study is to develop an expert system for diagnosing coral reef disease  in the form of websites using PHP with a MySQL database. Expert system for diagnosing coral reef disease problem is using Ripple Down Rules (RDR method has a goal to discover symptoms that appear in the form of questions that can diagnose the coral reef disease based on website. Web based expert system is able to recognize types of coral reef disease after consultation by answering a few questions that are displayed by the application of expert systems and can infer some types of coral  reef disease. Data coral reef disease that already known adapt to rules which are made for matching the symptoms of coral reef disease.

  8. Mathematical Relationship Between Particle Reynolds Number and Ripple Factor using Tapi River Data, India.

    Directory of Open Access Journals (Sweden)

    S. M. Yadav

    2011-02-01

    Full Text Available The computation of bed load allows for the fact that only part of the shear stress is used for transport of sediments and some of the shear stress is wasted in overcoming the resistance due to bed forms therefore the total shear stress developed in the open channel requires correction in the form of correction factor called ripple factor. Different methods have been followed for correcting the actual shear stress in order to compute the sediment load. Correction factors are based on particular characteristics grain size of particle. In the present paper the ripple factor has been obtained for non uniform bed material considering the various variables like discharge, hydraulic mean depth, flow velocity, bed slope, average diameter of particle etc. by collecting the field data of Tapi river for 15 years for a particular gauging station. The ripple factor is obtained using Meyer Peter and Muller formula, Einstein Formula, Kalinske’s formula, Du Boy’s formula, Shield’s formula, Bagnold’s formula, average of six formulae and multiple regression analysis. The variation of ripple factor with particle Reynolds Number is studied. The ripple factor obtained by different approaches are further analyzed using Origin software and carrying out multiple regression on the 15 years of data with more than 10 parameters, ripple factor by multiple regression has been obtained. These values are further analysed and giving statistical mean to the parameters a relationship of power form has been developed. The ripple factor increases with the increase in the value of Particle Reynolds number. The large deviation is observed in case of Kalinske’s approach when compare with other approaches

  9. Two different mechanisms associated with ripple-like oscillations (100-250 Hz) in the human epileptic subiculum in vitro

    Science.gov (United States)

    Alvarado-Rojas, C; Huberfeld, G; Baulac, M; Clemenceau, S; Charpier, S; Miles, R; Menendez de la Prida, L; Le Van Quyen, M

    2015-01-01

    Transient high-frequency oscillations (150-600 Hz) in local field potential generated by human hippocampal and parahippocampal areas have been related to both physiological and pathological processes. The cellular basis and effects of normal and abnormal forms of high-frequency oscillations (HFO) has been controversial. Here, we searched for HFOs in slices of the subiculum prepared from human hippocampal tissue resected for treatment of pharmacoresistant epilepsy. HFOs occurred spontaneously in extracellular field potentials during interictal discharges (IID) and also during pharmacologically induced preictal discharges (PID) preceding ictal-like events. While most of these events might be considered pathological since they invaded the fast ripple band (>250 Hz), others were spectrally similar to physiological ripples (150-250 Hz). Do similar cellular mechanisms underly IID-ripples and PID-ripples? Are ripple-like oscillations a valid proxy of epileptogenesis in human TLE? With combined intra- or juxta-cellular and extracellular recordings, we showed that, despite overlapping spectral components, ripple-like IID and PID oscillations were associated with different cellular and synaptic mechanisms. IID-ripples were associated with rhythmic GABAergic and glutamatergic synaptic potentials with moderate neuronal firing. In contrast, PID-ripples were associated with depolarizing synaptic inputs frequently reaching the threshold for bursting in most cells. Thus ripple-like oscillations (100-250 Hz) in the human epileptic hippocampus are associated with different mechanisms for synchrony reflecting distinct dynamic changes in inhibition and excitation during interictal and pre-ictal states. PMID:25448920

  10. Dynamics of Neural Responses in Ferret Primary Auditory Cortex: I. Spectro-Temporal Response Field Characterization by Dynamic Ripple Spectra

    National Research Council Canada - National Science Library

    Depireux, Didier A; Simon, Jonathan Z; Klein, David J; Shamma, Shihab A

    1999-01-01

    .... It is calculated here from the responses to elementary 'ripples,' a family of sounds with drifting, sinusoidal, spectral envelopes - the complex spectrotemporal envelope of any broadband, dynamic...

  11. Assessment of Estimation Methods ForStage-Discharge Rating Curve in Rippled Bed Rivers

    Directory of Open Access Journals (Sweden)

    P. Maleki

    2016-02-01

    Full Text Available Introduction: Interactionbetweenwater flow characteristics andthe bed erodibilityplays an important role in sediment transport process. In order to reach stability, rivers with deposition or bottom erosion make a different bed form in the riverbed. One way to identify thebehavior of therivers is to study the structure and formation of bed forms within them. Ripples are the smallest of the bed forms. The longitudinal cross section of ripples are usually not symmetrical. The upstream face is long and has a gentle slope, and the downstream face is short and steep. The height of ripples is usually between 0.5 cm and 2 cm; the height ripple is not more than 5 cm. The wave lengths normally do not exceed 30cm, and they are usually within the range of 1 cm to 15 cm. Their occurrence is the result of the unstable viscous layer near the boundary. They can form in both shallow and deep water.With an increase of the flow velocity, the plan form of the ripples gradually develops form straight line to curves and then to a pattern like fish scales, symmetrical or unsymmetrical, as shown in Fig 1. Figure1-The patterndevelopment oftheripple Raudkivi (1966 was the first person that, the flow structure over ripples was investigated experimentally.Hethenestablishseveraldifferent conditionsonthemovingsandbedinanlaboratorychannelconsisted of a rectangular cross-section with base width of 70cm, wasable toform arow ofripples , he wassucceed toform arow ofripples.JafariMianaei and Keshavarzi(2008,studied the turbulentflow betweentwoartificialripples for investigate the change of kinetic energyandshearstress on overripples. The stage- discharge rating curve is one of the most important tools in the hydraulic studies. In alluvial rivers,bed rippled are formed and significantly affect the stage- discharge rating curve. In this research, the effects of two different type of ripples (parallel and flakeshape onthe hydraulic characteristicsof flow were experimentally studied

  12. The ripple electromagnetic calculation: accuracy demand and possible responses

    International Nuclear Information System (INIS)

    Cocilovo, V.; Ramogida, G.; Formisano, A.; Martone, R.; Portone, A.; Roccella, M.; Roccella, R.

    2006-01-01

    Due to a number of causes (the finite number of toroidal field coils or the presence of concentrate blocks of magnetic materials, as the neutral beam shielding) the actual magnetic configuration in a Tokamak differs from the desired one. For example, a ripple is added to the ideal axisymmetric toroidal field, impacting the equilibrium and stability of the plasma column; as a further example the magnetic field out of plasma affects the operation of a number of critical components, included the diagnostic system and the neutral beam. Therefore the actual magnetic field has to be suitably calculated and his shape controlled within the required limits. Due to the complexity of its design, the problem is quite critical for the ITER project. In this paper the problem is discussed both from mathematical and numerical point of view. In particular, a complete formulation is proposed, taking into account both the presence of the non linear magnetic materials and the fully 3D geometry. Then the quality level requirements are discussed, included the accuracy of calculations and the spatial resolution. As a consequence, the numerical tools able to fulfil the quality needs while requiring reasonable computer burden are considered. In particular possible tools based on numerical FEM scheme are considered; in addition, in spite of the presence of non linear materials, the practical possibility to use Biot-Savart based approaches, as cross check tools, is also discussed. The paper also analyses the possible geometrical simplifications of the geometry able to make possible the actual calculation while guarantying the required accuracy. Finally the characteristics required for a correction system able to effectively counteract the magnetic field degradation are presented. Of course a number of examples will be also reported and commented. (author)

  13. Dynamic and photometric evolutionary models of tidal tails and ripples

    International Nuclear Information System (INIS)

    Wallin, J.F.

    1989-01-01

    An investigation into the causes of star formation in tidal tails has been conducted using a restricted three-body dynamical model in conjunction with a broad-band photometric evolutionary code. In these models, regions of compression form inside the disk and along the tidal tail and tidal bridge. The effects these density changes have on the colors of the tidal features are examined with a broad-band photometric evolutionary code. A spiral galaxy population is synthesized and the effects of modest changes in the star formation rate are explored. Limits on the density changes needed to make detectable changes in the colors are calculated using a Schmidt (1959) law. These models suggest that the blue colors and knotty features observed in the tidal features of some galaxies result from increased rates of star formation induced by tidally produced density increases. Limitations of this model are discussed along with photometric evolutionary models based on the density evolution in the tails. The Lynds and Toomre (1976) interpretation of ring galaxies as the natural result of a nearly head-on collision between a disk galaxy and a companion galaxy has become widely accepted. Similarly, Quinn's (1984) interpretation of the shells in elliptical galaxies as the aftermath of the cannibalization of a low-mass companion has been quite successful in accounting for the observations. Restricted three-body calculations of high inclination, low impact parameter encounters demonstrate that the shell-like ripples observed in a number of disk galaxies can also be produced as collisional artifacts from internal oscillations much as in ring galaxies

  14. Turbulence and sediment transport over sand dunes and ripples

    Science.gov (United States)

    Bennis, A.; Le Bot, S.; lafite, R.; Bonneton, P.; Ardhuin, F.

    2013-12-01

    Several bedforms are present near to the surfzone of natural beaches. Dunes and ripples are frequently observed. Understanding the turbulence over these forms is essential for the sediment transport. The turbulent flow and the suspended sand particles interact with each other. At the moment, the modelling strategy for turbulence is still a challenge. According to the spatial scales, some different methods to model the turbulence are employed, in particular the RANS (Reynolds Averaged Navier-Stokes) and the LES (Large Eddy Simulation). A hybrid method combining both RANS and LES is set up here. We have adapted this method, initially developed for atmospheric flow, to the oceanic flow. This new method is implemented inside the 3D hydrodynamic model, MARS 3D, which is forced by waves. LES is currently the best way to simulate turbulent flow but its higher cost prevents it from being used for large scale applications. So, here we use RANS near the bottom while LES is set elsewhere. It allows us minimize the computational cost and ensure a better accuracy of the results than with a fully RANS model. In the case of megaripples, the validation step was performed with two sets of field data (Sandy Duck'97 and Forsoms'13) but also with the data from Dune2D model which uses only RANS for turbulence. The main findings are: a) the vertical profiles of the velocity are similar throughout the data b) the turbulent kinetic energy, which was underestimated by Dune2D, is in line with the observations c) the concentration of the suspended sediment is simulated with a better accuracy than with Dune2D but this remains lower than the observations.

  15. Serotonin dependent masking of hippocampal sharp wave ripples.

    Science.gov (United States)

    ul Haq, Rizwan; Anderson, Marlene L; Hollnagel, Jan-Oliver; Worschech, Franziska; Sherkheli, Muhammad Azahr; Behrens, Christoph J; Heinemann, Uwe

    2016-02-01

    Sharp wave ripples (SPW-Rs) are thought to play an important role in memory consolidation. By rapid replay of previously stored information during slow wave sleep and consummatory behavior, they result from the formation of neural ensembles during a learning period. Serotonin (5-HT), suggested to be able to modify SPW-Rs, can affect many neurons simultaneously by volume transmission and alter network functions in an orchestrated fashion. In acute slices from dorsal hippocampus, SPW-Rs can be induced by repeated high frequency stimulation that induces long-lasting LTP. We used this model to study SPW-R appearance and modulation by 5-HT. Although stimulation in presence of 5-HT permitted LTP induction, SPW-Rs were "masked"--but appeared after 5-HT wash-out. This SPW-R masking was dose dependent with 100 nM 5-HT being sufficient--if the 5-HT re-uptake inhibitor citalopram was present. Fenfluramine, a serotonin releaser, could also mask SPW-Rs. Masking was due to 5-HT1A and 5-HT2A/C receptor activation. Neither membrane potential nor membrane conductance changes in pyramidal cells caused SPW-R blockade since both remained unaffected by combining 5-HT and citalopram. Moreover, 10 and 30 μM 5-HT mediated SPW-R masking preceded neuronal hyperpolarization and involved reduced presynaptic transmitter release. 5-HT, as well as a 5-HT1A agonist, augmented paired pulse facilitation and affected the coefficient of variance. Spontaneous SPW-Rs in mice hippocampal slices were also masked by 5-HT and fenfluramine. While neuronal ensembles can acquire long lasting LTP during higher 5-HT levels, lower 5-HT levels enable neural ensembles to replay previously stored information and thereby permit memory consolidation memory. Copyright © 2015 Elsevier Ltd. All rights reserved.

  16. Hurricane Sandy's Fingerprint: Ripple Bedforms at an Inner Continental Shelf Sorted Bedform Field Site

    Science.gov (United States)

    DuVal, C.; Trembanis, A. C.; Beaudoin, J. D.; Schmidt, V. E.; Mayer, L. A.

    2013-12-01

    The hydrodynamics and seabed morphodynamics on the inner continental shelf and near shore environments have increasing relevance with continued development of near shore structures, offshore energy technologies and artificial reef construction. Characterizing the stresses on and response of the seabed near and around seabed objects will inform best practices for structural design, seabed mine and unexploded ordnance detection, and archaeological and benthic habitat studies. As part of an ONR funded project, Delaware's Redbird Reef is being studied for object scour and sorted bedform morphodynamics (Trembanis et al., in press). Central to this study are the effects of large storm events, such as Hurricane Sandy, which have had significant impact on the seafloor. Previous studies of inner shelf bedform dynamics have typically focused on near bed currents and bed stressors (e.g. Trembanis et al., 2004), sorted bedforms (e.g. Green et al., 2004) and object scour (e.g. Quinn, 2006; Trembanis et al., 2007; Mayer et al., 2007), but our understanding of the direct effects of objects and object scour on bedform morphodynamics is still incomplete. With prominent sorted bedform ripple fields, the Delaware Redbird artificial reef site, composed of 997 former New York City subway cars, as well as various military vehicles, tugboats, barges and ballasted tires, has made an ideal study location (Raineault et al., 2013 and 2011). Acoustic mapping of the Redbird reef three days prior to Sandy and two days after the following nor'easter, captured the extensive effects of the storms to the site, while acoustic Doppler current profilers characterized both the waves and bottom currents generated by the storm events. Results of the post-Sandy survey support the theory of sorted bedform evolution proposed by Murray and Thieler (2004). Acoustic imagery analysis indicates a highly energized and mobile bed during the storms, leading to self-organization of bedforms and creation of large

  17. Effect of ripple-induced transport on H-mode performance in tokamaks

    International Nuclear Information System (INIS)

    Parail, V.; Vries, P. de; Lonnroth, J.; Kiviniemi, T.; Johnson, T.; Loarte, A.; Saibene, G.; Hatae, T.; Kamada, Y.; Konovalov, S.; Oyama, N.; Shinohara, K.; Tobita, K.; Urano, H.

    2005-01-01

    A number of experiments have shown that ripple-induced transport influences performance of ELMy H-modes in the tokamak. A noticeable difference in confinement, ELM frequency and amplitude was found between JET (with ripple amplitude δ∼0.1%) and JT-60U (with δ∼1%) in otherwise identical discharges. It was previously shown in JET experiments with enhanced ripple that a gradual increase in the ripple amplitude first leads to a modest improvement in plasma confinement, which is followed by the degradation of edge pedestal and further transition to the L-mode regime if δ increases further. The DIII-D team recently reported a marginal increase in confinement in experiments with an edge transport enhanced by the externally driven resonant magnetic perturbation. Numerical predictive modelling of the dynamics of ELMy H-mode JET plasma relevant to a JET/JT-60U similarity experiment has been conducted taking into account ripple-induced ion transport, which was computed using the orbit following code ASCOT. This predictive modelling reveals that, depending on plasma parameters, ripple amplitude and localisation (the latter depending on the toroidal coil design), this additional transport can either improve global plasma confinement or reduce it. These controlled ripple losses might be used as an effective tool for ELM mitigation and may provide an explanation for the difference between JET and JT-60U observed in the similarity experiments. A detailed comparison between ripple- induced transport and the alternative method of ELM mitigation by an externally driven edge magnetic perturbation is discussed. The fact that ripple losses mainly increase ion transport, while a stochastic magnetic layer increases electron transport indicates that it might be beneficial to use a combination of both methods in future experiments. This work was funded partly by the United Kingdom Engineering and Physical Sciences Research Council and by the European Communities under the contract of

  18. Energy-separated sequential irradiation for ripple pattern tailoring on silicon surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Tanuj [Department of Physics, Central University of Haryana, Jant-Pali, Mahendergarh 1123029 (India); Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India); Kumar, Manish, E-mail: manishbharadwaj@gmail.com [Department of Physics, Central University of Rajasthan, Kishangarh 305801 (India); Panchal, Vandana [Department of Physics, National Institute of Technology, Kurukshetra 136119 (India); Sahoo, P.K. [School of Physical Sciences, National Institute of Science Education and Research, Bhubaneswar 751005 (India); Kanjilal, D. [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India)

    2015-12-01

    Highlights: • A new process for controlling the near-surface amorphization of ripples on Si surfaces. • Ripples generation by 100 KeV Ar{sup +} and amorphization control by 60 KeV Ar{sup +} irradiation. • Advantage of energy-separated irradiation demonstrated by detailed RBS and AFM studies. • Relevant mechanism is presented on the basis of DAMAGE and SIMNRA simulations. • Key role of solid flow towards the amorphous/crystalline interface is demonstrated. - Abstract: Nanoscale ripples on semiconductor surfaces have potential application in biosensing and optoelectronics, but suffer from uncontrolled surface-amorphization when prepared by conventional ion-irradiation methods. A two-step, energy-separated sequential-irradiation enables simultaneous control of surface-amorphization and ripple-dimensions on Si(1 0 0). The evolution of ripples using 100 keV Ar{sup +} bombardment and further tuning of the patterns using a sequential-irradiation by 60 keV Ar{sup +} at different fluences are demonstrated. The advantage of this approach as opposed to increased fluence at the same energy is clarified by atomic force microscopy and Rutherford backscattering spectroscopy investigations. The explanation of our findings is presented through DAMAGE simulation.

  19. Dune and ripple migration along Curiosity's traverse in Gale Crater on Mars

    Science.gov (United States)

    Silvestro, S.; Vaz, D.; Ewing, R. C.; Fenton, L. K.; Michaels, T. I.; Ayoub, F.; Bridges, N. T.

    2013-12-01

    The NASA Mars Science Laboratory (MSL) rover, Curiosity, has safely landed near a 35-km-long dark dune field in Gale Crater on Mars. This dune field lies along Curiosity's traverse to Aeolis Mons (Mt. Sharp). Here we present new evidence of aeolian activity and further estimate wind directions within the dune field through analysis of ripple migration with the COSI-Corr technique, which provides precise measurements of ripple displacement at the sub-pixel scale.The area analyzed is located ~10 km southwest of rover Curiosity's current position and ~4 km SW of its selected path through Aeolis Mons (Mt. Sharp) (Fig. 1a). Here barchan dunes with elongated horns and seif dunes coexist with more typical barchan and dome dunes (Fig. 1a, b), with slopes sculpted by two intersecting ripple crestline orientations trending at 45° and 330°. The range of dune types and ripple orientations indicate the dune field morphology is influenced by at least two winds from the NW and the NE. The direction of migration is toward the SW, suggesting the most recent sand transporting winds were from the NE (Fig. 1c). These results match previous predictions and can be used to forecast the wind conditions close to the entry point to Mt. Sharp. Fig. 1: a-b) Study area c) Ripple migration direction computed using the COSI-Corr technique

  20. Hippocampal sharp wave/ripples during sleep for consolidation of associative memory.

    Directory of Open Access Journals (Sweden)

    Wiâm Ramadan

    Full Text Available The beneficial effect of sleep on memory has been well-established by extensive research on humans, but the neurophysiological mechanisms remain a matter of speculation. This study addresses the hypothesis that the fast oscillations known as ripples recorded in the CA1 region of the hippocampus during slow wave sleep (SWS may provide a physiological substrate for long term memory consolidation. We trained rats in a spatial discrimination task to retrieve palatable reward in three fixed locations. Hippocampal local field potentials and cortical EEG were recorded for 2 h after each daily training session. There was an increase in ripple density during SWS after early training sessions, in both trained rats and in rats randomly rewarded for exploring the maze. In rats learning the place -reward association, there was a striking further significant increase in ripple density correlated with subsequent improvements in behavioral performance as the rat learned the spatial discrimination aspect of the task. The results corroborate others showing an experience-dependent increase in ripple activity and associated ensemble replay after exploratory activity, but in addition, for the first time, reveal a clear further increase in ripple activity related to associative learning based on spatial discrimination.

  1. Adhesion modification of neural stem cells induced by nanoscale ripple patterns

    International Nuclear Information System (INIS)

    Pedraz, P; Casado, S; Rodriguez, V; Ayuso-Sacido, A; Gnecco, E; Giordano, M C; Mongeot, F Buatier de

    2016-01-01

    We have studied the influence of anisotropic nanopatterns (ripples) on the adhesion and morphology of mouse neural stem cells (C17.2) on glass substrates using cell viability assay, optical microscopy and atomic force microscopy. The ripples were produced by defocused ion beam sputtering with inert Ar ions, which physically remove atoms from the surface at the energy of 800 eV. The ripple periodicity (∼200 nm) is comparable to the thickness of the cytoplasmatic microspikes (filopodia) which link the stem cells to the substrate. All methods show that the cell adhesion is significantly lowered compared to the same type of cells on flat glass surfaces. Furthermore, the AFM analysis reveals that the filopodia tend to be trapped parallel or perpendicular to the ripples, which limits the spreading of the stem cell on the rippled substrate. This opens the perspective of controlling the micro-adhesion of stem cells and the orientation of their filopodia by tuning the anisotropic substrate morphology without chemical reactions occurring at the surface. (paper)

  2. Hierarchical thermoplastic rippled nanostructures regulate Schwann cell adhesion, morphology and spatial organization.

    Science.gov (United States)

    Masciullo, Cecilia; Dell'Anna, Rossana; Tonazzini, Ilaria; Böettger, Roman; Pepponi, Giancarlo; Cecchini, Marco

    2017-10-12

    Periodic ripples are a variety of anisotropic nanostructures that can be realized by ion beam irradiation on a wide range of solid surfaces. Only a few authors have investigated these surfaces for tuning the response of biological systems, probably because it is challenging to directly produce them in materials that well sustain long-term cellular cultures. Here, hierarchical rippled nanotopographies with a lateral periodicity of ∼300 nm are produced from a gold-irradiated germanium mold in polyethylene terephthalate (PET), a biocompatible polymer approved by the US Food and Drug Administration for clinical applications, by a novel three-step embossing process. The effects of nano-ripples on Schwann Cells (SCs) are studied in view of their possible use for nerve-repair applications. The data demonstrate that nano-ripples can enhance short-term SC adhesion and proliferation (3-24 h after seeding), drive their actin cytoskeleton spatial organization and sustain long-term cell growth. Notably, SCs are oriented perpendicularly with respect to the nanopattern lines. These results provide information about the possible use of hierarchical nano-rippled elements for nerve-regeneration protocols.

  3. Direct imaging of atomic-scale ripples in few-layer graphene.

    Science.gov (United States)

    Wang, Wei L; Bhandari, Sagar; Yi, Wei; Bell, David C; Westervelt, Robert; Kaxiras, Efthimios

    2012-05-09

    Graphene has been touted as the prototypical two-dimensional solid of extraordinary stability and strength. However, its very existence relies on out-of-plane ripples as predicted by theory and confirmed by experiments. Evidence of the intrinsic ripples has been reported in the form of broadened diffraction spots in reciprocal space, in which all spatial information is lost. Here we show direct real-space images of the ripples in a few-layer graphene (FLG) membrane resolved at the atomic scale using monochromated aberration-corrected transmission electron microscopy (TEM). The thickness of FLG amplifies the weak local effects of the ripples, resulting in spatially varying TEM contrast that is unique up to inversion symmetry. We compare the characteristic TEM contrast with simulated images based on accurate first-principles calculations of the scattering potential. Our results characterize the ripples in real space and suggest that such features are likely common in ultrathin materials, even in the nanometer-thickness range.

  4. Diversity of sharp-wave–ripple LFP signatures reveals differentiated brain-wide dynamical events

    Science.gov (United States)

    Ramirez-Villegas, Juan F.; Logothetis, Nikos K.; Besserve, Michel

    2015-01-01

    Sharp-wave–ripple (SPW-R) complexes are believed to mediate memory reactivation, transfer, and consolidation. However, their underlying neuronal dynamics at multiple scales remains poorly understood. Using concurrent hippocampal local field potential (LFP) recordings and functional MRI (fMRI), we study local changes in neuronal activity during SPW-R episodes and their brain-wide correlates. Analysis of the temporal alignment between SPW and ripple components reveals well-differentiated SPW-R subtypes in the CA1 LFP. SPW-R–triggered fMRI maps show that ripples aligned to the positive peak of their SPWs have enhanced neocortical metabolic up-regulation. In contrast, ripples occurring at the trough of their SPWs relate to weaker neocortical up-regulation and absent subcortical down-regulation, indicating differentiated involvement of neuromodulatory pathways in the ripple phenomenon mediated by long-range interactions. To our knowledge, this study provides the first evidence for the existence of SPW-R subtypes with differentiated CA1 activity and metabolic correlates in related brain areas, possibly serving different memory functions. PMID:26540729

  5. A ripple-spreading genetic algorithm for the aircraft sequencing problem.

    Science.gov (United States)

    Hu, Xiao-Bing; Di Paolo, Ezequiel A

    2011-01-01

    When genetic algorithms (GAs) are applied to combinatorial problems, permutation representations are usually adopted. As a result, such GAs are often confronted with feasibility and memory-efficiency problems. With the aircraft sequencing problem (ASP) as a study case, this paper reports on a novel binary-representation-based GA scheme for combinatorial problems. Unlike existing GAs for the ASP, which typically use permutation representations based on aircraft landing order, the new GA introduces a novel ripple-spreading model which transforms the original landing-order-based ASP solutions into value-based ones. In the new scheme, arriving aircraft are projected as points into an artificial space. A deterministic method inspired by the natural phenomenon of ripple-spreading on liquid surfaces is developed, which uses a few parameters as input to connect points on this space to form a landing sequence. A traditional GA, free of feasibility and memory-efficiency problems, can then be used to evolve the ripple-spreading related parameters in order to find an optimal sequence. Since the ripple-spreading model is the centerpiece of the new algorithm, it is called the ripple-spreading GA (RSGA). The advantages of the proposed RSGA are illustrated by extensive comparative studies for the case of the ASP.

  6. Ripple artifact reduction using slice overlap in slice encoding for metal artifact correction.

    Science.gov (United States)

    den Harder, J Chiel; van Yperen, Gert H; Blume, Ulrike A; Bos, Clemens

    2015-01-01

    Multispectral imaging (MSI) significantly reduces metal artifacts. Yet, especially in techniques that use gradient selection, such as slice encoding for metal artifact correction (SEMAC), a residual ripple artifact may be prominent. Here, an analysis is presented of the ripple artifact and of slice overlap as an approach to reduce the artifact. The ripple artifact was analyzed theoretically to clarify its cause. Slice overlap, conceptually similar to spectral bin overlap in multi-acquisition with variable resonances image combination (MAVRIC), was achieved by reducing the selection gradient and, thus, increasing the slice profile width. Time domain simulations and phantom experiments were performed to validate the analyses and proposed solution. Discontinuities between slices are aggravated by signal displacement in the frequency encoding direction in areas with deviating B0. Specifically, it was demonstrated that ripple artifacts appear only where B0 varies both in-plane and through-plane. Simulations and phantom studies of metal implants confirmed the efficacy of slice overlap to reduce the artifact. The ripple artifact is an important limitation of gradient selection based MSI techniques, and can be understood using the presented simulations. At a scan-time penalty, slice overlap effectively addressed the artifact, thereby improving image quality near metal implants. © 2014 Wiley Periodicals, Inc.

  7. Diversity of sharp-wave-ripple LFP signatures reveals differentiated brain-wide dynamical events.

    Science.gov (United States)

    Ramirez-Villegas, Juan F; Logothetis, Nikos K; Besserve, Michel

    2015-11-17

    Sharp-wave-ripple (SPW-R) complexes are believed to mediate memory reactivation, transfer, and consolidation. However, their underlying neuronal dynamics at multiple scales remains poorly understood. Using concurrent hippocampal local field potential (LFP) recordings and functional MRI (fMRI), we study local changes in neuronal activity during SPW-R episodes and their brain-wide correlates. Analysis of the temporal alignment between SPW and ripple components reveals well-differentiated SPW-R subtypes in the CA1 LFP. SPW-R-triggered fMRI maps show that ripples aligned to the positive peak of their SPWs have enhanced neocortical metabolic up-regulation. In contrast, ripples occurring at the trough of their SPWs relate to weaker neocortical up-regulation and absent subcortical down-regulation, indicating differentiated involvement of neuromodulatory pathways in the ripple phenomenon mediated by long-range interactions. To our knowledge, this study provides the first evidence for the existence of SPW-R subtypes with differentiated CA1 activity and metabolic correlates in related brain areas, possibly serving different memory functions.

  8. Deciphering the role of CA1 inhibitory circuits in sharp wave-ripple complexes.

    Science.gov (United States)

    Cutsuridis, Vassilis; Taxidis, Jiannis

    2013-01-01

    Sharp wave-ripples (SWRs) are population oscillatory patterns in hippocampal LFPs during deep sleep and immobility, involved in the replay of memories acquired during wakefulness. SWRs have been extensively studied, but their exact generation mechanism is still unknown. A computational model has suggested that fast perisomatic inhibition may generate the high frequency ripples (~200 Hz). Another model showed how replay of memories can be controlled by various classes of inhibitory interneurons targeting specific parts of pyramidal cells (PC) and firing at particular SWR phases. Optogenetic studies revealed new roles for interneuronal classes and rich dynamic interplays between them, shedding new light in their potential role in SWRs. Here, we integrate these findings in a conceptual model of how dendritic and somatic inhibition may collectively contribute to the SWR generation. We suggest that sharp wave excitation and basket cell (BC) recurrent inhibition synchronises BC spiking in ripple frequencies. This rhythm is imposed on bistratified cells which prevent pyramidal bursting. Axo-axonic and stratum lacunosum/moleculare interneurons are silenced by inhibitory inputs originating in the medial septum. PCs receiving rippling inhibition in both dendritic and perisomatic areas and excitation in their apical dendrites, exhibit sparse ripple phase-locked spiking.

  9. Computational study of ammonia adsorption on the perfect and rippled graphene sheet

    International Nuclear Information System (INIS)

    Seyed-Talebi, Seyedeh Mozhgan; Beheshtian, Javad

    2013-01-01

    Adsorption of an ammonia molecule onto perfect and rippled graphene is studied using molecular mechanics calculations. The most stable orientation of an ammonia molecule and equilibrium distance of this molecule over graphene surface (motivated by the recent realization of graphene sensors to detect individual gas molecules) is determined using DFT calculation. This result is in agreement with the predicted molecular mechanics calculation result. It also has been found that (i) the ammonia molecule is weakly adsorbed onto the graphene sheet; (ii) the periodic nature of the potential energy stored between ammonia and perfect graphene is altered due to the sinusoidal ripples; and (iii) the effect of amplitude and wavelength of the one-dimensional created ripple on different energy modes is reported

  10. Low cost concepts to reduce the voltage ripple of the DC power supply

    International Nuclear Information System (INIS)

    Cheng, Y.; Liu, K.B.

    1993-01-01

    If the gain of current feedback is low, the short term stability of magnet power supply will be affected by a soft power line. Typically, the step-charge and the imbalance of the three phase power line cause the most serious voltage ripple. Usually, the voltage feedback with a coupling transformer is considered to reduce the voltage ripple. However, for the high current power supply, the space and cooling problem of the coupling transformer become inconvenient. In this paper, the authors suggest to use the toroidal core with the compensation winding, working like a DCCT, as the coupling transformer. Then, a high speed detector of the AC line level is developed. It restricts the voltage ripple passing to the coupling transformer. These methods have the advantage of small size, low power consumption and low cost

  11. Use of field ripple for burn phase control in short-pulse tokamak reactors

    International Nuclear Information System (INIS)

    Davidson, J.N.; Stacey, W.M. Jr.

    1979-05-01

    The possible use of toroidal field ripple to control temperature excursions was investigated. In particular, the magnitude of the power savings necessary to control the ion temperature for about 120 seconds during the burn phase of an ETF tokamak was determined through the use of a global dynamics code. Then the amount of field ripple necessary to effect that control was calculated for each case. In the next section the basic properties of the simulation code are given and the various plasma cases investigated are described in some detail. There follows a discussion of the field ripple control mechanisms and their application to the problem at hand. Finally, the results of the study are presented along with the conclusions drawn from them

  12. Computational study of ammonia adsorption on the perfect and rippled graphene sheet

    Energy Technology Data Exchange (ETDEWEB)

    Seyed-Talebi, Seyedeh Mozhgan [Department of Physics, Shahid Rajaee Teacher Training University, Tehran (Iran, Islamic Republic of); Beheshtian, Javad, E-mail: J.Beheshtian@Srttu.edu [Department of Chemistry, Shahid Rajaee Teacher Training University, Tehran (Iran, Islamic Republic of)

    2013-11-15

    Adsorption of an ammonia molecule onto perfect and rippled graphene is studied using molecular mechanics calculations. The most stable orientation of an ammonia molecule and equilibrium distance of this molecule over graphene surface (motivated by the recent realization of graphene sensors to detect individual gas molecules) is determined using DFT calculation. This result is in agreement with the predicted molecular mechanics calculation result. It also has been found that (i) the ammonia molecule is weakly adsorbed onto the graphene sheet; (ii) the periodic nature of the potential energy stored between ammonia and perfect graphene is altered due to the sinusoidal ripples; and (iii) the effect of amplitude and wavelength of the one-dimensional created ripple on different energy modes is reported.

  13. Reducing Torque Ripples of the Axial Flux PM Motors by Magnet Stepping and Shifting

    Directory of Open Access Journals (Sweden)

    E. Cetin

    2018-02-01

    Full Text Available Higher efficiency on electric machines is the research goal of many studies. An example is the axial flux permanent magnet machines. These machines have some advantages like their watt/kg efficiency and torque density. This study aims to develop the performance characteristics of the axial flux permanent magnet machines. A new rotor magnet poles design in axial flux machines is suggested to mitigate the torque ripples. The method of stepping and shifting of the magnets is used. Two different designs are compared to verify the proposed approach. 3D finite element analysis is used for simulations. Torque ripple and back electromotive force waveforms are obtained from computer analysis. As a conclusion, the suggested method is found to be useable and mitigates the torque ripples. In addition to that, back EMF waveforms are turned to sinusoidal by the suggested design.

  14. Xe ion beam induced rippled structures on differently oriented single-crystalline Si surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Hanisch, Antje; Grenzer, Joerg; Facsko, Stefan [Forschungszentrum Dresden-Rossendorf, Institut fuer Ionenstrahlphysik und Materialforschung, PO Box 510119, 01314 Dresden (Germany); Biermanns, Andreas; Pietsch, Ullrich, E-mail: A.Hanisch@fzd.d [Universitaet Siegen, Festkoerperphysik, 57068 Siegen (Germany)

    2010-03-24

    We report on Xe{sup +} induced ripple formation at medium energy on single-crystalline silicon surfaces of different orientations using substrates with an intentional miscut from the [0 0 1] direction and a [1 1 1] oriented wafer. The ion beam incidence angle with respect to the surface normal was kept fixed at 65{sup 0} and the ion beam projection was parallel or perpendicular to the [1 1 0] direction. By a combination of atomic force microscopy, x-ray diffraction and high-resolution transmission electron microscopy we found that the features of the surface and subsurface rippled structures such as ripple wavelength and amplitude and the degree of order do not depend on the surface orientation as assumed in recent models of pattern formation for semiconductor surfaces. (fast track communication)

  15. Ripple structures on surfaces and underlying crystalline layers in ion beam irradiated Si wafers

    Energy Technology Data Exchange (ETDEWEB)

    Grenzer, J.; Muecklich, A. [Forschungszentrum Rossendorf, Institut fuer Ionenstrahlphysik und Materialforschung, Dresden (Germany); Biermanns, A.; Grigorian, S.A.; Pietsch, U. [Institute of Physics, University of Siegen (Germany)

    2009-08-15

    We report on the formation of ion beam induced ripples in Si(001) wafers when bombarded with Ar+ ions at an energy of 60 keV. A set of samples varying incidence and azimuthal angles of the ion beam with respect to the crystalline surface orientation was studied by two complementary near surface sensitive techniques, namely atomic force microscopy and depth-resolved X-ray grazing incidence diffraction (GID). Additionally, cross-section TEM investigations were carried out. The ripple-like structures are formed at the sample surface as well as at the buried amorphous-crystalline interface. Best quality of the ripple pattern was found when the irradiating ion beam was aligned parallel to the (111) planes. The quality decreases rapidly if the direction of the ion beam deviates from (111). (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  16. Effect of impurities and ripple upon power regulation in self-sustained tokamaks

    International Nuclear Information System (INIS)

    Bromberg, L.; Cohn, D.R.

    1981-01-01

    Tokamak power reactors will likely operate in a self sustained heating mode where additional power losses are introduced to permit higher levels of alpha particle heating (and thus higher levels of total fusion power) at thermal equilibrium. Illustrative 0-dimensional calculations are made to assess requirements for power regulation of self sustained tokamak plasmas by the use of impurity radiation. Effects of impurities upon allowable fuel density and thermal stability are determined. Requirements are calculated for passive thermal stability control by temperature driven radial motion in the presence of ripple transport losses; it appears that stability might be attained over a relatively wide temperature range with a small amount of ripple transport loss. Requirements for power regulation by the use of ripple transport are also determined

  17. High Ripples Reduction in DTC of Induction Motor by Using a New Reduced Switching Table

    Science.gov (United States)

    Mokhtari, Bachir; Benkhoris, Mohamed F.

    2016-05-01

    The direct torque and flux control (DTC) of electrical motors is characterized by ripples of torque and flux. Among the many solutions proposed to reduce them is to use modified switching tables which is very advantageous; because its implementation is easy and requires no additional cost compared to other solutions. This paper proposes a new reduced switching table (RST) to improve the DTC by reducing harmful ripples of torque and flux. This new switching table is smaller than the conventional one (CST) and depends principally at the flux error. This solution is studied by simulation under Matlab/Simulink and experimentally validated on a testbed with DSPACE1103. The results obtained of a DTC with RST applied to a three-phase induction motor (IM) show a good improvement and an effectiveness of proposed solution, the torque ripple decreases about 47% and 3% for the stator flux compared with a basic DTC.

  18. An Analysis of Ripple and Error Fields Induced by a Blanket in the CFETR

    Science.gov (United States)

    Yu, Guanying; Liu, Xufeng; Liu, Songlin

    2016-10-01

    The Chinese Fusion Engineering Tokamak Reactor (CFETR) is an important intermediate device between ITER and DEMO. The Water Cooled Ceramic Breeder (WCCB) blanket whose structural material is mainly made of Reduced Activation Ferritic/Martensitic (RAFM) steel, is one of the candidate conceptual blanket design. An analysis of ripple and error field induced by RAFM steel in WCCB is evaluated with the method of static magnetic analysis in the ANSYS code. Significant additional magnetic field is produced by blanket and it leads to an increased ripple field. Maximum ripple along the separatrix line reaches 0.53% which is higher than 0.5% of the acceptable design value. Simultaneously, one blanket module is taken out for heating purpose and the resulting error field is calculated to be seriously against the requirement. supported by National Natural Science Foundation of China (No. 11175207) and the National Magnetic Confinement Fusion Program of China (No. 2013GB108004)

  19. Temperature dependence of rippled corrugations induced on the Rh(1 1 0) surface via ion sputtering

    International Nuclear Information System (INIS)

    Molle, Alessandro; Buatier de Mongeot, F.; Granone, F.; Buzio, R.; Firpo, G.; Boragno, C.; Valbusa, U.

    2005-01-01

    Metal surfaces can be easily nanopatterned via ion sputtering: mounds or ripples can be created depending on the surface symmetry and temperature. However, in many cases these structures are unstable at room temperature and above, due to the adatom fast diffusion. This fact prevents the use of such systems as substrate or nanostamps for a technological implementation. In this paper we present a spot profile analysis low energy electron diffraction (SPA-LEED) study on the nanopatterning of a Rh(1 1 0) single crystal. Like the other (1 1 0) metal surfaces, previously investigated, also Rh(1 1 0) shows for increasing temperatures a transition between different rippled morphologies. The main advantage of this system is its stability at room temperature. From SPA-LEED data we can measure the structural features (average periodicity and local faceting) of the observed rippled structures

  20. Torque ripple reduction of brushless DC motor based on adaptive input-output feedback linearization.

    Science.gov (United States)

    Shirvani Boroujeni, M; Markadeh, G R Arab; Soltani, J

    2017-09-01

    Torque ripple reduction of Brushless DC Motors (BLDCs) is an interesting subject in variable speed AC drives. In this paper at first, a mathematical expression for torque ripple harmonics is obtained. Then for a non-ideal BLDC motor with known harmonic contents of back-EMF, calculation of desired reference current amplitudes, which are required to eliminate some selected harmonics of torque ripple, are reviewed. In order to inject the reference harmonic currents to the motor windings, an Adaptive Input-Output Feedback Linearization (AIOFBL) control is proposed, which generates the reference voltages for three phases voltage source inverter in stationary reference frame. Experimental results are presented to show the capability and validity of the proposed control method and are compared with the vector control in Multi-Reference Frame (MRF) and Pseudo-Vector Control (P-VC) method results. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

  1. Lacosamide and Levetiracetam Have No Effect on Sharp-Wave Ripple Rate.

    Science.gov (United States)

    Kudlacek, Jan; Chvojka, Jan; Posusta, Antonin; Kovacova, Lubica; Hong, Seung Bong; Weiss, Shennan; Volna, Kamila; Marusic, Petr; Otahal, Jakub; Jiruska, Premysl

    2017-01-01

    Pathological high-frequency oscillations are a novel marker used to improve the delineation of epileptogenic tissue and, hence, the outcome of epilepsy surgery. Their practical clinical utilization is curtailed by the inability to discriminate them from physiological oscillations due to frequency overlap. Although it is well documented that pathological HFOs are suppressed by antiepileptic drugs (AEDs), the effect of AEDs on normal HFOs is not well known. In this experimental study, we have explored whether physiological HFOs (sharp-wave ripples) of hippocampal origin respond to AED treatment. The results show that application of a single dose of levetiracetam or lacosamide does not reduce the rate of sharp-wave ripples. In addition, it seems that these new generation drugs do not negatively affect the cellular and network mechanisms involved in sharp-wave ripple generation, which may provide a plausible explanation for the absence of significant negative effects on cognitive functions of these drugs, particularly on memory.

  2. A Zero Input Current Ripple ZVS/ZCS Boost Converter with Boundary-Mode Control

    Directory of Open Access Journals (Sweden)

    Ching-Ming Lai

    2014-10-01

    Full Text Available In this paper, in order to achieve zero ripple conditions, the use of a ripple mirror (RM circuit for the boost converter is proposed. The operation modes are studied and steady-state analyses performed to show the merits of the proposed converter. It is found that the proposed RM circuit technique can provide much better flexibility than the two-phase interleaved boost converter for locating the zero ripple operating point in the design stage. In addition, the choice of using a boundary-mode control is mainly based on the consideration of achieving both ZVS (zero voltage switching/ZCS (zero current switching soft-switching and constant on-time control for the converter. To verify the performance of the proposed converter, a 48 V input and 200 W/200 V output prototype is constructed. Experimental results verify the effectiveness of the proposed converter.

  3. Metales traza en sedimentos de la Bahía de Cayo Moa (Cuba. Una evaluación de la contaminación

    Directory of Open Access Journals (Sweden)

    Yosbanis M. Cervantes-Guerra

    2011-12-01

    Full Text Available En este artículo se evalúan los niveles de cuatro elementos traza: arsénico (As, cobre (Cu, plomo (Pb y zinc (Zn en sedimentos superficiales de la bahía de Cayo Moa, en la cual la actividad humana ha incidido desde mediados del pasado siglo, paralelamente al desarrollo de una de las regiones mineras más importante de Cuba. Para evaluar el grado de contaminación de los sedimentos se utilizaron tres métodos fundamentales: la comparación con otros ecosistemas marinos, la determinación del nivel de enriquecimiento metálico mediante el cálculo del Factor de Contaminación, y la interpretación de los datos obtenidos con base en criterios de calidad. El rango de concentraciones varió entre 7-153 µgg-1 para As, 18-175 µgg-1 para Cu, 5-62 µgg-1 para Pb y de 46-527 µgg-1 para el Zn. La distribución espacial de las concentraciones mostró valores altos en toda la bahía y zonas aledañas, con variaciones según el elemento analizado; los mayores niveles de As se encontraron en las desembocaduras de los ríos Moa y Cayo Guam. El Cu, Pb y Zn están en mayor proporción en el interior de la bahía, específicamente en el punto P5, aunque en los puntos ubicados en el sur de Cayo Moa Grande los valores de estos contaminantes fueron también elevados. Los resultados muestran una elevada concentración de As, Cu, Pb y Zn; los niveles de contaminación revelados en este estudio permiten clasificar algunos puntos analizados como altamente contaminados o con un potencial de riesgo biológico alto.

  4. Utilization of reduced fuelling ripple set in ROP detector layout optimization

    International Nuclear Information System (INIS)

    Kastanya, Doddy

    2012-01-01

    Highlights: ► ADORE is an ROP detect layout optimization algorithm in CANDU reactors. ► The effect of using reduced set of fuelling ripples in ADORE is assessed. ► Significant speedup can be realized by adopting this approach. ► The quality of the results is comparable to results from full set of ripples. - Abstract: The ADORE (Alternative Detector layout Optimization for REgional overpower protection system) algorithm for performing the optimization of regional overpower protection (ROP) for CANDU® reactors has been recently developed. This algorithm utilizes the simulated annealing (SA) stochastic optimization technique to come up with an optimized detector layout for the ROP systems. For each history in the SA iteration where a particular detector layout is evaluated, the goodness of this detector layout is measured in terms of its trip set point value which is obtained by performing a probabilistic trip set point calculation using the ROVER-F code. Since during each optimization execution thousands of candidate detector layouts are evaluated, the overall optimization process is time consuming. Since for each ROVER-F evaluation the number of fuelling ripples controls the execution time, reducing the number of fuelling ripples will reduce the overall execution time. This approach has been investigated and the results are presented in this paper. The challenge is to construct a set of representative fuelling ripples which will significantly speedup the optimization process while guaranteeing that the resulting detector layout has similar quality to the ones produced when the complete set of fuelling ripples is employed.

  5. A unifying model for planform straightness of ripples and dunes in air and water

    Science.gov (United States)

    Rubin, David M.

    2012-01-01

    Geologists, physicists, and mathematicians have studied ripples and dunes for more than a century, but despite considerable effort, no general model has been proposed to explain perhaps the most fundamental property of their morphology: why are some bedforms straight, continuous, parallel, and uniform in planform geometry (i.e. two-dimensional) whereas others are irregular (three-dimensional)? Here we argue that physical coupling along the crest of a bedform is required to produce straight crests and that along-crest flow and sand transport provide effective physical mechanisms for that coupling. Ripples and dunes with the straightest and most continuous crests include longitudinal and oblique dunes in unidirectional flows, wave ripples, dunes in reversing flows, wind ripples, and ripples migrating along a slope. At first glance, these bedforms appear quite different (ripples and dunes; air and water; transverse, oblique, and longitudinal orientations relative to the net sand-transport direction), but they all have one property in common: a process that increases the amount of along-crest sand transport (that lengthens and straightens their crests) relative to the across-crest transport (that makes them migrate and take the more typical and more three-dimensional planform geometry). In unidirectional flows that produce straight bedforms, along-crest transport of sand is caused by along-crest flow (non-transverse bedform orientation), gravitational transport along an inclined crest, or ballistic splash in air. Bedforms in reversing flows tend to be straighter than their unidirectional counterparts, because reverse transport across the bedform crest reduces the net across-crest transport (that causes the more typical irregular geometry) relative to the along-crest transport (that smoothes and straightens planform geometry).

  6. Intelligent measurement and compensation of linear motor force ripple: a projection-based learning approach in the presence of noise

    Science.gov (United States)

    Liu, Yang; Song, Fazhi; Yang, Xiaofeng; Dong, Yue; Tan, Jiubin

    2018-06-01

    Due to their structural simplicity, linear motors are increasingly receiving attention for use in high velocity and high precision applications. The force ripple, as a space-periodic disturbance, however, would deteriorate the achievable dynamic performance. Conventional force ripple measurement approaches are time-consuming and have high requirements on the experimental conditions. In this paper, a novel learning identification algorithm is proposed for force ripple intelligent measurement and compensation. Existing identification schemes always use all the error signals to update the parameters in the force ripple. However, the error induced by noise is non-effective for force ripple identification, and even deteriorates the identification process. In this paper only the most pertinent information in the error signal is utilized for force ripple identification. Firstly, the effective error signals caused by the reference trajectory and the force ripple are extracted by projecting the overall error signals onto a subspace spanned by the physical model of the linear motor as well as the sinusoidal model of the force ripple. The time delay in the linear motor is compensated in the basis functions. Then, a data-driven approach is proposed to design the learning gain. It balances the trade-off between convergence speed and robustness against noise. Simulation and experimental results validate the proposed method and confirm its effectiveness and superiority.

  7. Higher-order paraxial theory of the propagation of ring rippled laser beam in plasma: Relativistic ponderomotive regime

    International Nuclear Information System (INIS)

    Purohit, Gunjan; Rawat, Priyanka; Chauhan, Prashant; Mahmoud, Saleh T.

    2015-01-01

    This article presents higher-order paraxial theory (non-paraxial theory) for the ring ripple formation on an intense Gaussian laser beam and its propagation in plasma, taking into account the relativistic-ponderomotive nonlinearity. The intensity dependent dielectric constant of the plasma has been determined for the main laser beam and ring ripple superimposed on the main laser beam. The dielectric constant of the plasma is modified due to the contribution of the electric field vector of ring ripple. Nonlinear differential equations have been formulated to examine the growth of ring ripple in plasma, self focusing of main laser beam, and ring rippled laser beam in plasma using higher-order paraxial theory. These equations have been solved numerically for different laser intensities and plasma frequencies. The well established experimental laser and plasma parameters are used in numerical calculation. It is observed that the focusing of the laser beams (main and ring rippled) becomes fast in the nonparaxial region by expanding the eikonal and other relevant quantities up to the fourth power of r. The splitted profile of laser beam in the plasma is observed due to uneven focusing/defocusing of the axial and off-axial rays. The growths of ring ripple increase when the laser beam intensity increases. Furthermore, the intensity profile of ring rippled laser beam gets modified due to the contribution of growth rate

  8. A comprehensive study and analysis of second order harmonic ripple in DC microgrid feeding single phase PWM inverter loads

    DEFF Research Database (Denmark)

    Gautam, Aditya R.; Fulwani, Deepak; Guerrero, Josep M.

    2016-01-01

    The paper presents a detailed analysis of second order harmonic ripple in a DC microgrid. A boost converter feeding PWM inverter load is considered and equivalent circuit is proposed. The effect of the size of input capacitor, output capacitor and inductor of boost converter, on this ripple has...

  9. Ripples and the formation of anisotropic lipid domains: Imaging two-component double bilayers by atomic force microscopy_copy_03

    DEFF Research Database (Denmark)

    Leidy, C.; Kaasgaard, Thomas; Crowe, J.H.

    2002-01-01

    by atomic force microscopy, we investigated the origin of these anisotropic lipid domain patterns, and found that ripple phase formation is directly responsible for the anisotropic nature of these domains. The nucleation and growth of fluid-phase domains are found to be directed by the presence of ripples....... In particular, the fluid-phase domains elongate parallel to the ripples. The results show that ripple phase formation may have implications for domain formation in biological systems....

  10. Tuning the shape and damage in ion-beam induced ripples on silicon

    Energy Technology Data Exchange (ETDEWEB)

    Biermanns, Andreas; Pietsch, Ullrich [Universitaet Siegen, Festkoerperphysik, 57068 Siegen (Germany); Hanisch, Antje; Grenzer, Joerg [Helmholtz-Zentrum Dresden-Rossendorf, Institut fuer Ionenstrahlphysik und Materialforschung, P.O. Box 510119, 01314 Dresden (Germany); Metzger, Till Hartmut [ESRF, 6 rue Jules Horowitz, BP220, 38043 Grenoble Cedex (France)

    2011-11-15

    We investigate the influence of ion beam parameters on the ripple formation on Si(001) surfaces after bombardment with Xe{sup +} ions of 25 keV kinetic energy using a scanning ion beam system. By combining grazing incidence X-ray diffraction, small angle scattering and X-ray reflectivity, we show that during ion irradiation with 70 off-normal angle of incidence, changing the size of the irradiated area leads to an increased number of defects at the interface towards crystalline material. At 65 angle of incidence, the ripple amplitude grows. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  11. The effect of toroidal field ripple on confined alphas in TFTR D-T plasmas

    International Nuclear Information System (INIS)

    Duong, H.H.; Medley, S.S.

    1996-05-01

    The Pellet Charge Exchange (PCX) diagnostic on the Tokamak Fusion Test Reactor (TFTR) presently measures trapped alpha distribution functions with very small pitch angle (v parallel /v ∼ 0.05) at the midplane. The measured PCX alpha signal exhibits a depletion region near the outboard region. Results of the alpha energy spectra and radial profile suggest stochastic ripple diffusion is the cause of the depletion. Comparison of the ripple stochastization boundary with Goldston-White-Boozer theory also shows the correct functional dependence on alpha energy and q-profile

  12. On ripples and rafts: Curvature induced nanoscale structures in lipid membranes

    International Nuclear Information System (INIS)

    Schmid, Friederike; Dolezel, Stefan; Meinhardt, Sebastian; Lenz, Olaf

    2014-01-01

    We develop an elastic theory that predicts the spontaneous formation of nanoscale structures in lipid bilayers which locally phase separate between two phases with different spontaneous monolayer curvature. The theory rationalizes in a unified manner the observation of a variety of nanoscale structures in lipid membranes: Rippled states in one-component membranes, lipid rafts in multicomponent membranes. Furthermore, we report on recent observations of rippled states and rafts in simulations of a simple coarse-grained model for lipid bilayers, which are compatible with experimental observations and with our elastic model

  13. Impacts of Ripple Current to the Loading and Lifetime of Power Semiconductor Device

    DEFF Research Database (Denmark)

    Ma, Ke; Choi, Uimin; Blaabjerg, Frede

    2017-01-01

    The thermal loading of power electronics devices is determined by many factors and has being a crucial design consideration because it is closely related to the reliability and cost of the converter system. In this paper the impacts of the ripple current to the loss and thermal loading, as well...... as reliability performances of power devices are comprehensively investigated and tested. It is concluded that the amplitude of ripple current may modify the loss and thermal loading of the power devices, especially under the conditions of converter with low power output, and thus the lifetime of devices could...

  14. Reduction of torque ripple in DTC induction motor drive with discrete voltage vectors

    Directory of Open Access Journals (Sweden)

    Rosić Marko

    2014-01-01

    Full Text Available This paper presents а practical implementation of direct torque control (DTC of an induction machine on MSK2812 DSP platform, and the analysis of possibilities for reduction of torque ripple. Basic theoretical background relating the DTC was primarily set and the obtained experimental results have been given. It is shown that the torque ripple can be reduced by adjusting the intensity of voltage vectors and by modification of hysteresis comparator, while the simplicity of the basic DTC algorithm has been maintained. [Projekat Ministarstva nauke Republike Srbije, br. TR33016

  15. Observing trans-Planckian ripples in the primordial power spectrum with future large scale structure probes

    DEFF Research Database (Denmark)

    Hamann, Jan; Hannestad, Steen; Sloth, Martin Snoager

    2008-01-01

    We revisit the issue of ripples in the primordial power spectra caused by trans-Planckian physics, and the potential for their detection by future cosmological probes. We find that for reasonably large values of the first slow-roll parameter epsilon (> 0.001), a positive detection of trans......-Planckian ripples can be made even if the amplitude is as low as 10^-4. Data from the Large Synoptic Survey Telescope (LSST) and the proposed future 21 cm survey with the Fast Fourier Transform Telescope (FFTT) will be particularly useful in this regard. If the scale of inflation is close to its present upper bound...

  16. Hippocampal Ripple Oscillations and Inhibition-First Network Models: Frequency Dynamics and Response to GABA Modulators.

    Science.gov (United States)

    Donoso, José R; Schmitz, Dietmar; Maier, Nikolaus; Kempter, Richard

    2018-03-21

    Hippocampal ripples are involved in memory consolidation, but the mechanisms underlying their generation remain unclear. Models relying on interneuron networks in the CA1 region disagree on the predominant source of excitation to interneurons: either "direct," via the Schaffer collaterals that provide feedforward input from CA3 to CA1, or "indirect," via the local pyramidal cells in CA1, which are embedded in a recurrent excitatory-inhibitory network. Here, we used physiologically constrained computational models of basket-cell networks to investigate how they respond to different conditions of transient, noisy excitation. We found that direct excitation of interneurons could evoke ripples (140-220 Hz) that exhibited intraripple frequency accommodation and were frequency-insensitive to GABA modulators, as previously shown in in vitro experiments. In addition, the indirect excitation of the basket-cell network enabled the expression of intraripple frequency accommodation in the fast-gamma range (90-140 Hz), as in vivo In our model, intraripple frequency accommodation results from a hysteresis phenomenon in which the frequency responds differentially to the rising and descending phases of the transient excitation. Such a phenomenon predicts a maximum oscillation frequency occurring several milliseconds before the peak of excitation. We confirmed this prediction for ripples in brain slices from male mice. These results suggest that ripple and fast-gamma episodes are produced by the same interneuron network that is recruited via different excitatory input pathways, which could be supported by the previously reported intralaminar connectivity bias between basket cells and functionally distinct subpopulations of pyramidal cells in CA1. Together, our findings unify competing inhibition-first models of rhythm generation in the hippocampus. SIGNIFICANCE STATEMENT The hippocampus is a part of the brain of humans and other mammals that is critical for the acquisition and

  17. Vzdrževanje likvidnosti kriptovalutnega trga v omrežju Ripple

    OpenAIRE

    BREZIGAR, JAKOB

    2017-01-01

    Vzdrževalec likvidnosti zagotavlja prodajalcem in kupcem finančnih inštrumentov nasprotno stranko pri sklepanju transakcij. Izvajanju nakupnega in prodajnega naročila hkrati pravimo vzdrževanje likvidnosti. Diplomsko delo obsega teoretično in praktično osnovo za izdelavo algoritma za samodejno vzdrževanje likvidnosti na enem izmed perspektivnih kriptovalutnih trgov Ripple. V diplomskem delu povzamemo teoretične osnove vzdrževanja likvidnosti, delovanje kriptovalutnega protokola Ripple in proc...

  18. Were Viking Dry-dock methods in the Americas used earlier to Build Pyramids, with Outflow Eroding the Sphinx, and were Stonehenge, the Obelisks, and Moas Similarly Erected?

    Science.gov (United States)

    McLeod, Edward; McLeod, Roger

    2006-03-01

    Chisel-quarried recycled granite in MA is datable by runes to 1069 CE; it could corroborate dating by a LIDAR. Associated sites, possibly used by Vikings to dry-dock their ships, could have exploited lock-like controls, possibly a continued technology. Site-leveling at the Giza Pyramids proves water was used. `Locks' and body-immersion worked for building, moving, erecting, or watering, at sites like Stonehenge, The Hanging Gardens at Babylon, the Moas of Easter Island, or The Pyramids, where the eroding water discharge was deliberately flushed over the Sphinx complex. It enhance the electromagnetically excited blue light signals we can detect, especially at sites frequented by Molocket of ME. Information, as at America's Stonehenge, in NH, and constructions at Acton MA, at Giza or at Rumford ME proves that the Pyramids and Sphinx were engineered and built about 4500 BP.

  19. Particularidades geológicas del complejo ofiolítico de Moa a partir de los datos aeromagnéticos 1:50 000

    Directory of Open Access Journals (Sweden)

    Alina Rodríguez-Infante

    2000-03-01

    Full Text Available En este artículo se presentan los resultados obtenidos de la interpretación de los datos aeromagnéticos a escala 1:50000 de la secuencia ofiolítica de la región de Moa.Los datos fueron reducidos al polo, lo que permitió obtener un mapa de anomalías magnéticas más sencillo y representativo de las heterogeneidades geológicas presentes en el área de estudio. A partir de esta interpretación se ubicaron las zonas de posible desarrollo de alteraciones hidrotermales, se establecieron las variaciones espaciales de los diferentes tipos litológicos y de los espesores de las rocas ultrabásicas serpentinizadas, se delimitaron los posibles frentes de escamas de cabalgamientos y se aportaron nuevos elementos a considerar durante la prospección de cromita.

  20. Identificación mineralógica de los óxidos de manganeso del yacimiento laterítico Punta Gorda, Moa, Cuba

    OpenAIRE

    Arturo L. Rojas-Purón; Rómulo Simoes-Angélica; Gerardo Orozco-Melgar

    2012-01-01

    Estudios recientes revelaron contenidos atípicos de manganeso en los depósitos lateríticos ferroniquelíferos de Moa. Muestras enriquecidas de dos perfiles del yacimiento Punta Gorda se investigaron con el propósito de determinar las formas mineralógicas en que aparecen los óxidos de manganeso en este depósito. Mediante la aplicación de técnicas de Difracción de Rayos–X, Análisis Térmico Diferencial, Fluorescencia de Rayos–X, Microscopía Electrónica de Barrido y Espectroscopía Infrarroja se pu...

  1. Effects of sewage contamination on macro-algae and shellfish at Moa Point, New Zealand, using stable carbon and nitrogen isotopes

    International Nuclear Information System (INIS)

    Rogers, K.M.

    1999-01-01

    Stable carbon and nitrogen isotopes have been used to characterise sewage discharge and effects on seaweed (Ulva lactuca L.), blue mussels (Mytilus galloprovincialis), and limpets (Cellana denticulata) from Moa Point Bay, New Zealand. The nitrogen ( 15 N / 14 N) ratio is shown to be a good tracer of sewage pollution in Ulva lactuca and associated grazers (Cellana denticulata) as a result of the increased contribution of urea and ammonia to the surrounding marine environment from the sewage outfall. The carbon ( 13 C / 12 C) ratio is suggested as a more appropriate sewer tracer for mussels (Mytilus galloprovincialis), which filter feed the particulate organic matter from the effluent. Lower carbon : nitrogen ratios were found in U. lactuca sampled from the outfall region, compared to uncontaminated control sites, however carbon : nitrogen ratios do not vary significantly amongst shellfish species. (author). 18 refs., 4 figs., 2 tabs

  2. Utilization of independent component analysis for accurate pathological ripple detection in intracranial EEG recordings recorded extra- and intra-operatively.

    Science.gov (United States)

    Shimamoto, Shoichi; Waldman, Zachary J; Orosz, Iren; Song, Inkyung; Bragin, Anatol; Fried, Itzhak; Engel, Jerome; Staba, Richard; Sharan, Ashwini; Wu, Chengyuan; Sperling, Michael R; Weiss, Shennan A

    2018-01-01

    To develop and validate a detector that identifies ripple (80-200 Hz) events in intracranial EEG (iEEG) recordings in a referential montage and utilizes independent component analysis (ICA) to eliminate or reduce high-frequency artifact contamination. Also, investigate the correspondence of detected ripples and the seizure onset zone (SOZ). iEEG recordings from 16 patients were first band-pass filtered (80-600 Hz) and Infomax ICA was next applied to derive the first independent component (IC1). IC1 was subsequently pruned, and an artifact index was derived to reduce the identification of high-frequency events introduced by the reference electrode signal. A Hilbert detector identified ripple events in the processed iEEG recordings using amplitude and duration criteria. The identified ripple events were further classified and characterized as true or false ripple on spikes, or ripples on oscillations by utilizing a topographical analysis to their time-frequency plot, and confirmed by visual inspection. The signal to noise ratio was improved by pruning IC1. The precision of the detector for ripple events was 91.27 ± 4.3%, and the sensitivity of the detector was 79.4 ± 3.0% (N = 16 patients, 5842 ripple events). The sensitivity and precision of the detector was equivalent in iEEG recordings obtained during sleep or intra-operatively. Across all the patients, true ripple on spike rates and also the rates of false ripple on spikes, that were generated due to filter ringing, classified the seizure onset zone (SOZ) with an area under the receiver operating curve (AUROC) of >76%. The magnitude and spectral content of true ripple on spikes generated in the SOZ was distinct as compared with the ripples generated in the NSOZ (p ripple rates and properties defined using this approach may accurately delineate the seizure onset zone. Strategies to improve the spatial resolution of intracranial EEG and reduce artifact can help improve the clinical utility of

  3. Ripple reduction activities in the MG room at the Bevatron, August 1991 to August 1992

    International Nuclear Information System (INIS)

    Blasbalg, M.; Bennett, M.

    1992-08-01

    This report discusses the following topics: magnet - voltage dividers temperature ampersand voltage influence error calculation; magnet filters summarized data table; magnet transfer function measurement setup and connection diagrams; response of existing magnet system including ripple reduction filters - Dec 1991; magnet filters - mutual inductance problem; and damping the magnet filters

  4. Density ripples in expanding low-dimensional gases as a probe of correlations

    DEFF Research Database (Denmark)

    Imambekov, A.; Mazets, I. E.; Petrov, D. S.

    2009-01-01

    fluctuations. For the case of free ballistic expansion relevant to current experiments, we present simple analytical relations between the spectrum of "density ripples" and the correlation functions of the original confined systems. We analyze several physical regimes, including weakly and strongly interacting...

  5. A non-unity torque sharing function for torque ripple minimization of switched reluctance generators

    DEFF Research Database (Denmark)

    Park, Kiwoo; Liu, Xiao; Chen, Zhe

    2013-01-01

    This paper presents a new torque ripple minimization technique for a Switched Reluctance Generator (SRG). Although the SRG has many advantageous characteristics as a generator, it has not been widely employed in the industry. One of the most notorious disadvantages of the SRG is its high torque...

  6. Relation Between Observed Micromagnetic Ripple and FMR Width in Ultrasoft Magnetic Films

    NARCIS (Netherlands)

    Chechenin, N.G.; Craus, C.B.; Chezan, A.R.; Vystavel, T.; Boerma, D.O.; Hosson, J.Th.M. De; Niesen, L.

    2002-01-01

    Using Lorentz transmission electron microscopy, the micromagnetic structure was observed and the periodicity and angular spread of the in-plane magnetization were estimated for Fe–Zr–N films sputter-deposited on different substrates. The influence of the micromagnetic ripple on the ferromagnetic

  7. Directional excitation of Rg due to ripple-fired explosions: 2-Dimensional finite-difference simulations

    International Nuclear Information System (INIS)

    Jih, Rong-Song

    1993-01-01

    A major issue for the Non-Proliferation Treaty is the discrimination of large chemical explosions from possible clandestine or small nuclear tests. Unless discrimination is possible, the numerous mining blasts could give ample opportunity for concealing clandestine tests. Ripple-fired explosions are commonly used to fragment rocks during quarry and open-pit mining. The periodicity inherent in the ripple firing could produce a seismic reinforcement at the frequency of the delay between shots or rows. It has been suggested that the convolution of a single explosion with a comb function of variable spacing and variable amplitude can be used to model the distinctive signature of ripple firing. Baumgardt and Ziegler (1988) delicately demonstrated that the incoherent array-stack spectra can be used to identify some multiple shots recorded at NORSAR. By superpositioning the waveform due to a single shot with proper time delay, they were able to model the source multiplicity under the assumption that the spatial spreading of the shots is negligible with respect to the distance to the receiver. The work by Stump et al. successfully characterized the major features of the wavefield due to ripple firings at near-source ranges

  8. Formation of two ripple modes on Si by ion erosion with simultaneous Fe incorporation

    International Nuclear Information System (INIS)

    Cornejo, Marina; Ziberi, Bashkim; Meinecke, Christoph; Frost, Frank

    2011-01-01

    This report focuses on the self organized nanostructure formation on Si (0 0 1) by erosion with low energy Kr + ions with simultaneous incorporation of metallic atoms, in particular Fe. The incorporation of Fe is thought to play an important role in the formation of some features. In the experimental set-up used here the Fe atoms come from the sputtering of a cylindrical stainless steel target situated between the source and the sample holder. It is demonstrated how the Fe flux can be regulated by operational parameters of the ion source. It is shown that two different ripple modes, one perpendicular to the ion beam projection on the surface and the other parallel, were formed at near normal incidence (α = 20 o ) with ion energy between 300 eV and 2000 eV and a fluence of 6.7 x 10 18 cm -2 . The perpendicular mode ripples dominated the topography when E ion = 2000 eV, while the parallel mode ripples were the main features observed when E ion = 300 eV. The correlation of Fe concentration with ion sources parameters and resulting topography is analyzed. It is demonstrated that a certain Fe concentration is necessary for the formation of ripples that are oriented perpendicular to the ion beam and that the Fe concentration alone does not determine the evolving topography.

  9. Direct writing of sub-wavelength ripples on silicon using femtosecond laser at high repetition rate

    International Nuclear Information System (INIS)

    Xie, Changxin; Li, Xiaohong; Liu, Kaijun; Zhu, Min; Qiu, Rong; Zhou, Qiang

    2016-01-01

    Graphical abstract: - Highlights: • The NSRs and DSRs are obtained on silicon surface. • With increasing direct writing speed, the NSRs suddenly changes and becomes the DSRs. • We develop a Sipe–Drude interference theory by considering the thermal excitation. - Abstract: The near sub-wavelength and deep sub-wavelength ripples on monocrystalline silicon were formed in air by using linearly polarized and high repetition rate femtosecond laser pulses (f = 76 MHz, λ = 800 nm, τ = 50 fs). The effects of laser pulse energy, direct writing speed and laser polarization on silicon surface morphology are studied. When the laser pulse energy is 2 nJ/pulse and the direct writing speed varies from 10 to 25 mm/s, the near sub-wavelength ripples (NSRs) with orientation perpendicular to the laser polarization are generated. While the direct writing speed reaches 30 mm/s, the direction of the obtained deep sub-wavelength ripples (DSRs) suddenly changes and becomes parallel to the laser polarization, rarely reported so far for femtosecond laser irradiation of silicon. Meanwhile, we extend the Sipe–Drude interference theory by considering the thermal excitation, and numerically calculate the efficacy factor for silicon irradiated by femtosecond laser pulses. The revised Sipe–Drude interference theoretical results show good agreement with the periods and orientations of sub-wavelength ripples.

  10. High energy Xe{sup +} ion beam induced ripple structures on silicon

    Energy Technology Data Exchange (ETDEWEB)

    Hanisch, Antje; Grenzer, Joerg; Facsko, Stefan; Winkler, Ingolf [Forschungszentrum Dresden-Rossendorf, Institute for Ion Beam Physics and Materials Research, Dresden (Germany); Biermanns, Andreas; Grigorian, Souren; Pietsch, Ullrich [University of Siegen (Germany). Institute of Physics

    2008-07-01

    Ion beam bombardment on semiconductor surfaces leads to well-defined morphological structures in the nanoscale range. Due to the impact of ions a self-organized wave-like surface structure develops. Ion bombardment causes an amorphization of a surface-adjacent layer of several nanometers and creates a periodical structure on the surface as well as at the amorphous-crystalline interface. We investigate the dependence of the periodicity on the crystallography of (100) silicon bombarded with Xe{sup +} ions, the ion beam incidence and the azimutal angle of the sample surface. So far we found that the ripple wavelength scales with the ion energy in a range of 5 to 70 keV. In order to understand the initiation of the ripple formation we also ask the question which role the initial surface structure plays. Therefore we investigate the formation of ripples on pre-structured and rough surfaces such as wafers with an intentional miscut. Therefore, we not only introduce a certain initial roughness but also vary the orientation of the (100) lattice plane in respect to the surface. We distinguish between ion beam induced surface effects (sputter erosion) and the influence of the crystalline Si lattice (strain) on the ripple formation.

  11. Spatial variability of the wave bottom boundary layer over movable rippled beds

    NARCIS (Netherlands)

    Rodriguez-Abudo, S.; Foster, D.L.; Henriquez, M.

    2013-01-01

    Observations of the spatially dependent velocity field over movable bed forms subjected to slightly skewed and asymmetric regular wave forcing were collected. The dynamics between the ripple elements is dominated by coherent vortices, characterized by the swirling strength, and evidenced in the

  12. Highly-stabilized power supply for synchrotron accelerators. High speed, low ripple power supply

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Kenji [Osaka Univ., Ibaraki (Japan). Research Center for Nuclear Physics; Kumada, Masayuki; Fukami, Kenji; Koseki, Shoichiro; Kubo, Hiroshi; Kanazawa, Toru

    1997-02-01

    In synchrotron accelerators, in order to utilize high energy beam effectively, those are operated by repeating acceleration and taking-out at short period. In order to accelerate by maintaining beam track stable, the tracking performance with the error less than 10{sup -3} in the follow-up of current is required for the power supply. Further, in order to maintain the intensity and uniformity of beam when it is taken out, very low ripple is required for output current. The power supply having such characteristics has been developed, and applied to the HIMAC and the SPring-8. As the examples of the application of synchrotrons, the accelerators for medical treatment and the generation of synchrotron radiation are described. As to the power supply for the deflection magnets and quadrupole magnets of synchrotron accelerators, the specifications of the main power supply, the method of reducing ripple, the method of improving tracking, and active filter control are reported. As to the test results, the measurement of current ripple and tracking error is shown. The lowering of ripple was enabled by common mode filter and the symmetrical connection of electromagnets, and high speed response was realized by the compensation for delay with active filter. (K.I.)

  13. Analysis of dc-Link Voltage Switching Ripple in Three-Phase PWM Inverters

    Directory of Open Access Journals (Sweden)

    Marija Vujacic

    2018-02-01

    Full Text Available The three-phase voltage source inverter (VSI is de facto standard in power conversion systems. To realize high power density systems, one of the items to be correctly addressed is the design and selection of the dc-link capacitor in relation to the voltage switching ripple. In this paper, effective formulas for designing the dc-link capacitor as a function of the switching voltage ripple amplitude are obtained, considering the operating conditions such as the modulation index and the output current amplitude. The calculations are obtained considering the requirements and restrictions referring to the high (switching-frequency dc-link voltage ripple component. Analyses have been performed considering the dc source impedance (non-ideal dc voltage source at the switching frequency and a balanced load. Analytical expressions are derived for the dc-link voltage switching ripple amplitude and its maximum value over the fundamental period. Different values of modulation index and output phase angle have been considered and different diagrams are presented. Analytical results were validated both by simulations and comprehensive experimental tests.

  14. Modelling and measurements of sand transport processes over full-scale ripples in oscillatory flow

    NARCIS (Netherlands)

    van der Werf, Jebbe J.; Ribberink, Jan S.; O'Donoghue, Tom; Doucette, Jeffrey C.

    2006-01-01

    A new series of laboratory experiments was performed in the Aberdeen Oscillatory Flow Tunnel (AOFT) and the Large Oscillating Water Tunnel (LOWT) to investigate time-averaged suspended sand concentrations and transport rates over rippled beds in regular and irregular oscillatory flow. The

  15. Restrictions on TWT Helix Voltage Ripple for Acceptable Notch Filter Performance

    Energy Technology Data Exchange (ETDEWEB)

    Hyslop, B.

    1984-12-01

    An ac ripple on the helix voltage of the 1-2 GHz TWT's creates FM sidebands that cause amplitude and phase modulation of the microwave TWT output signal. A limit of 16 volts peak-to-peak is required for acceptable superconducting notch filter performance.

  16. Amplitude equation and long-range interactions in underwater sand ripples in one dimension

    DEFF Research Database (Denmark)

    Schnipper, Teis; Mertens, Keith; Ellegaard, Clive

    2008-01-01

    We present an amplitude equation for sand ripples under oscillatory flow in a situation where the sand is moving in a narrow channel and the height profile is practically one dimensional. The equation has the form h(t)=epsilon-(h-(h) over bar) + ((h(x))(2)-1)h(xx)-h(xxxx) + delta((h(x))(2))(xx...

  17. Analysis and minimization of Torque Ripple for variable Flux reluctance machines

    NARCIS (Netherlands)

    Bao, J.; Gysen, B.L.J.; Boynov, K.; Paulides, J.J.H.; Lomonova, E.A.

    2017-01-01

    Variable flux reluctance machines (VFRMs) are permanent-magnet-free three-phase machines and are promising candidates for applications requiring low cost and robustness. This paper studies the torque ripple and minimization methods for 12-stator VFRMs. Starting with the analysis of harmonics in the

  18. Torque ripple minimization in a doubly salient permanent magnet motors by skewing the rotor teeth

    International Nuclear Information System (INIS)

    Sheth, N.K.; Sekharbabu, A.R.C.; Rajagopal, K.R.

    2006-01-01

    This paper presents the effects of skewing the rotor teeth on the performance of an 8/6 doubly salient permanent magnet motor using a simple method, which utilizes the results obtained from the 2-D FE analysis. The optimum skewing angle is obtained as 12-15 o for the least ripple torque without much reduction in the back-emf

  19. Analysis of transient state in HTS tapes under ripple DC load current

    Science.gov (United States)

    Stepien, M.; Grzesik, B.

    2014-05-01

    The paper concerns the analysis of transient state (quench transition) in HTS tapes loaded with the current having DC component together with a ripple component. Two shapes of the ripple were taken into account: sinusoidal and triangular. Very often HTS tape connected to a power electronic current supply (i.e. superconducting coil for SMES) that delivers DC current with ripples and it needs to be examined under such conditions. Additionally, measurements of electrical (and thermal) parameters under such ripple excitation is useful to tape characterization in broad range of load currents. The results presented in the paper were obtained using test bench which contains programmable DC supply and National Instruments data acquisition system. Voltage drops and load currents were measured vs. time. Analysis of measured parameters as a function of the current was used to tape description with quench dynamics taken into account. Results of measurements were also used to comparison with the results of numerical modelling based on FEM. Presented provisional results show possibility to use results of measurements in transient state to prepare inverse models of superconductors and their detailed numerical modelling.

  20. Disrupting neural activity related to awake-state sharp wave-ripple complexes prevents hippocampal learning.

    Science.gov (United States)

    Nokia, Miriam S; Mikkonen, Jarno E; Penttonen, Markku; Wikgren, Jan

    2012-01-01

    Oscillations in hippocampal local-field potentials (LFPs) reflect the crucial involvement of the hippocampus in memory trace formation: theta (4-8 Hz) oscillations and ripples (~200 Hz) occurring during sharp waves are thought to mediate encoding and consolidation, respectively. During sharp wave-ripple complexes (SPW-Rs), hippocampal cell firing closely follows the pattern that took place during the initial experience, most likely reflecting replay of that event. Disrupting hippocampal ripples using electrical stimulation either during training in awake animals or during sleep after training retards spatial learning. Here, adult rabbits were trained in trace eyeblink conditioning, a hippocampus-dependent associative learning task. A bright light was presented to the animals during the inter-trial interval (ITI), when awake, either during SPW-Rs or irrespective of their neural state. Learning was particularly poor when the light was presented following SPW-Rs. While the light did not disrupt the ripple itself, it elicited a theta-band oscillation, a state that does not usually coincide with SPW-Rs. Thus, it seems that consolidation depends on neuronal activity within and beyond the hippocampus taking place immediately after, but by no means limited to, hippocampal SPW-Rs.

  1. Relationship between channel interaction and spectral-ripple discrimination in cochlear implant users.

    Science.gov (United States)

    Jones, Gary L; Won, Jong Ho; Drennan, Ward R; Rubinstein, Jay T

    2013-01-01

    Cochlear implant (CI) users can achieve remarkable speech understanding, but there is great variability in outcomes that is only partially accounted for by age, residual hearing, and duration of deafness. Results might be improved with the use of psychophysical tests to predict which sound processing strategies offer the best potential outcomes. In particular, the spectral-ripple discrimination test offers a time-efficient, nonlinguistic measure that is correlated with perception of both speech and music by CI users. Features that make this "one-point" test time-efficient, and thus potentially clinically useful, are also connected to controversy within the CI field about what the test measures. The current work examined the relationship between thresholds in the one-point spectral-ripple test, in which stimuli are presented acoustically, and interaction indices measured under the controlled conditions afforded by direct stimulation with a research processor. Results of these studies include the following: (1) within individual subjects there were large variations in the interaction index along the electrode array, (2) interaction indices generally decreased with increasing electrode separation, and (3) spectral-ripple discrimination improved with decreasing mean interaction index at electrode separations of one, three, and five electrodes. These results indicate that spectral-ripple discrimination thresholds can provide a useful metric of the spectral resolution of CI users.

  2. Ripple Effects: Budgets Grow Modestly, but Energy Costs Cloud the Horizon

    Science.gov (United States)

    Oder, Norman

    2006-01-01

    In this article, the author reports the ripple effects of the energy squeeze due to Hurricane Katrina and other factors that sent energy costs skyrocketing. Energy costs are a good part of why budget growth, which has been steady over the past five years, has been slowing down. The projected change from FY2005 to FY2006 is only 3.3%, compared to…

  3. Correlation between micrometer-scale ripple alignment and atomic-scale crystallographic orientation of monolayer graphene.

    Science.gov (United States)

    Choi, Jin Sik; Chang, Young Jun; Woo, Sungjong; Son, Young-Woo; Park, Yeonggu; Lee, Mi Jung; Byun, Ik-Su; Kim, Jin-Soo; Choi, Choon-Gi; Bostwick, Aaron; Rotenberg, Eli; Park, Bae Ho

    2014-12-01

    Deformation normal to the surface is intrinsic in two-dimensional materials due to phononic thermal fluctuations at finite temperatures. Graphene's negative thermal expansion coefficient is generally explained by such an intrinsic property. Recently, friction measurements on graphene exfoliated on a silicon oxide surface revealed an anomalous anisotropy whose origin was believed to be the formation of ripple domains. Here, we uncover the atomistic origin of the observed friction domains using a cantilever torsion microscopy in conjunction with angle-resolved photoemission spectroscopy. We experimentally demonstrate that ripples on graphene are formed along the zigzag direction of the hexagonal lattice. The formation of zigzag directional ripple is consistent with our theoretical model that takes account of the atomic-scale bending stiffness of carbon-carbon bonds and the interaction of graphene with the substrate. The correlation between micrometer-scale ripple alignment and atomic-scale arrangement of exfoliated monolayer graphene is first discovered and suggests a practical tool for measuring lattice orientation of graphene.

  4. Synchrony, waves and ripple in spatially coupled Kuramoto oscillators with Mexican hat connectivity.

    Science.gov (United States)

    Heitmann, Stewart; Ermentrout, G Bard

    2015-06-01

    Spatiotemporal waves of synchronized activity are known to arise in oscillatory neural networks with lateral inhibitory coupling. How such patterns respond to dynamic changes in coupling strength is largely unexplored. The present study uses analysis and simulation to investigate the evolution of wave patterns when the strength of lateral inhibition is varied dynamically. Neural synchronization was modeled by a spatial ring of Kuramoto oscillators with Mexican hat lateral coupling. Broad bands of coexisting stable wave solutions were observed at all levels of inhibition. The stability of these waves was formally analyzed in both the infinite ring and the finite ring. The broad range of multi-stability predicted hysteresis in transitions between neighboring wave solutions when inhibition is slowly varied. Numerical simulation confirmed the predicted transitions when inhibition was ramped down from a high initial value. However, non-wave solutions emerged from the uniform solution when inhibition was ramped upward from zero. These solutions correspond to spatially periodic deviations of phase that we call ripple states. Numerical continuation showed that stable ripple states emerge from synchrony via a supercritical pitchfork bifurcation. The normal form of this bifurcation was derived analytically, and its predictions compared against the numerical results. Ripple states were also found to bifurcate from wave solutions, but these were locally unstable. Simulation also confirmed the existence of hysteresis and ripple states in two spatial dimensions. Our findings show that spatial synchronization patterns can remain structurally stable despite substantial changes in network connectivity.

  5. New Experiments on Wave Physics with a Simply Modified Ripple Tank

    Science.gov (United States)

    Logiurato, Fabrizio

    2014-01-01

    The ripple tank is one of the physics education devices most appreciated by teachers and students. It allows one to visualize various phenomena related to wave physics in an effective and enthralling way. Usually this apparatus consists of a tank with a transparent bottom that is filled with a thin layer of water. A source of light illuminates the…

  6. A Method of Sky Ripple Residual Nonuniformity Reduction for a Cooled Infrared Imager and Hardware Implementation.

    Science.gov (United States)

    Li, Yiyang; Jin, Weiqi; Li, Shuo; Zhang, Xu; Zhu, Jin

    2017-05-08

    Cooled infrared detector arrays always suffer from undesired ripple residual nonuniformity (RNU) in sky scene observations. The ripple residual nonuniformity seriously affects the imaging quality, especially for small target detection. It is difficult to eliminate it using the calibration-based techniques and the current scene-based nonuniformity algorithms. In this paper, we present a modified temporal high-pass nonuniformity correction algorithm using fuzzy scene classification. The fuzzy scene classification is designed to control the correction threshold so that the algorithm can remove ripple RNU without degrading the scene details. We test the algorithm on a real infrared sequence by comparing it to several well-established methods. The result shows that the algorithm has obvious advantages compared with the tested methods in terms of detail conservation and convergence speed for ripple RNU correction. Furthermore, we display our architecture with a prototype built on a Xilinx Virtex-5 XC5VLX50T field-programmable gate array (FPGA), which has two advantages: (1) low resources consumption; and (2) small hardware delay (less than 10 image rows). It has been successfully applied in an actual system.

  7. On the limits of uniaxial magnetic anisotropy tuning by a ripple surface pattern

    Energy Technology Data Exchange (ETDEWEB)

    Arranz, Miguel A. [Facultad de Ciencias Químicas, Universidad de Castilla-La Mancha, Avda. Camilo J. Cela 10, 13071 Ciudad Real (Spain); Colino, Jose M., E-mail: josemiguel.colino@uclm.es [Instituto de Nanociencia, Nanotecnología y Materiales Moleculares, Universidad de Castilla-La Mancha, Campus de la Fábrica de Armas, 45071 Toledo (Spain); Palomares, Francisco J. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, c/ Sor Juana Inés de la Cruz 3, 28049 Madrid (Spain)

    2014-05-14

    Ion beam patterning of a nanoscale ripple surface has emerged as a versatile method of imprinting uniaxial magnetic anisotropy (UMA) on a desired in-plane direction in magnetic films. In the case of ripple patterned thick films, dipolar interactions around the top and/or bottom interfaces are generally assumed to drive this effect following Schlömann's calculations for demagnetizing fields of an ideally sinusoidal surface [E. Schlömann, J. Appl. Phys. 41, 1617 (1970)]. We have explored the validity of his predictions and the limits of ion beam sputtering to induce UMA in a ferromagnetic system where other relevant sources of magnetic anisotropy are neglected: ripple films not displaying any evidence of volume uniaxial anisotropy and where magnetocrystalline contributions average out in a fine grain polycrystal structure. To this purpose, the surface of 100 nm cobalt films grown on flat substrates has been irradiated at fixed ion energy, fixed ion fluency but different ion densities to make the ripple pattern at the top surface with wavelength Λ and selected, large amplitudes (ω) up to 20 nm so that stray dipolar fields are enhanced, while the residual film thickness t = 35–50 nm is sufficiently large to preserve the continuous morphology in most cases. The film-substrate interface has been studied with X-ray photoemission spectroscopy depth profiles and is found that there is a graded silicon-rich cobalt silicide, presumably formed during the film growth. This graded interface is of uncertain small thickness but the range of compositions clearly makes it a magnetically dead layer. On the other hand, the ripple surface rules both the magnetic coercivity and the uniaxial anisotropy as these are found to correlate with the pattern dimensions. Remarkably, the saturation fields in the hard axis of uniaxial continuous films are measured up to values as high as 0.80 kG and obey a linear dependence on the parameter ω{sup 2}/Λ/t in quantitative

  8. Effect of ripple taper on band-gap overlap in a coaxial Bragg structure operating at terahertz frequency

    International Nuclear Information System (INIS)

    Ding Xueyong; Li Hongfan; Lv Zhensu

    2012-01-01

    Based on the mode-coupling method, numerical analysis is presented to demonstrate the influence of ripple taper on band-gap overlap in a coaxial Bragg structure operating at terahertz frequency. Results show that the interval between the band-gaps of the competing mode and the desired working mode is narrowed by use of positive-taper ripples, but is expanded if negative-taper ripples are employed, and the influence of the negative-taper ripples is obviously more advantageous than the positive-taper ripples; the band-gap overlap of modes can be efficiently separated by use of negative-taper ripples. The residual side-lobes of the frequency response in a coaxial Bragg structure with ripple taper also can be effectively suppressed by employing the windowing-function technique. These peculiarities provide potential advantage in constructing a coaxial Bragg cavity with high quality factor for single higher-order-mode operation of a high-power free-electron maser in the terahertz frequency range.

  9. A simple overlap angle control strategy for reducing commutation torque ripple in a brushless DC motor drive

    Directory of Open Access Journals (Sweden)

    Chetan K. Lad

    2017-08-01

    Full Text Available A commutation torque ripple is generated in a brushless DC motor due to a finite time taken for current transfer between outgoing phase and incoming phase due to the phase inductance. The effect of commutation ripple will be more severe for low voltage high current BLDC drives used for automotive applications. Direct Torque Control (DTC techniques are used to reduce the torque ripple. Two phase conduction with six voltage space vectors and three phase conduction with twelve voltage space vectors with DTC are used to reduce the torque ripple. Twelve Step DTC (TSDTC is capable of reducing torque ripple considerably but at the cost of increased inverter and winding losses. In Six Step DTC (SSDTC the torque ripple is higher than that of TSDTC but with reduced winding and inverter losses. In this paper an attempt has been made to strike a balance between torque ripple and losses. A novel Direct Torque Control with twelve voltage space vector with overlap angle control has been proposed. The proposed method is validated through simulation and experimental results.

  10. [SPECIFIC DIAGNOSTIC SIGNIFICANCE OF "RIPPLE SIGN" OF MEDIAL FEMORAL CONDYLE UNDER ARTHROSCOPE IN MEDIAL LONGITUDINAL MENISCAL TEARS].

    Science.gov (United States)

    Ren Shiyou; Sun, Limang; Chen, Guofei; Jiang, Changqing; Zhang, Xintao; Zhang Wentao

    2015-01-01

    To investigate the reliability of the "ripple sign" on the upper surface of the medial femoral condyle in the diagnosis of medial longitudinal meniscal tears under arthroscope. Between June 2013 and June 2014, 56 patients with knee injuries were included. There were 35 males and 21 females with an average age of 22.2 years (range, 12-38 years). The causes of injury were sports in 40 cases, falling in 10 cases, and traffic accident in 6 cases. The injury was located at the left knee in 22 cases and at the right knee in 34 cases. The disease duration was 10-40 days (mean, 20.2 days). Of 56 patients, 15 cases had simple medial meniscal injury; 41 cases had combined injuries, including anterior cruciate ligament injury in 38 cases, posterior cruciate ligament injury in 2 cases, and patellar dislocation in 1 case. The "ripple sign" was observed under arthroscope before operation. Repair of medial meniscal injury and reconstruction of cruciate ligament were performed. The positive "ripple sign" was seen under arthroscope in all patients, who were diagnosed to have longitudinal meniscal tears, including 23 cases of mild "ripple sign" , 28 cases of moderate "ripple sign", and 5 cases of severe "ripple sign". The "ripple sign" on the upper surface of the medial femoral condyle is a reliable diagnostic evidence of medial longitudinal meniscal tears.

  11. Analysis and Minimization of Output Current Ripple for Discontinuous Pulse-Width Modulation Techniques in Three-Phase Inverters

    Directory of Open Access Journals (Sweden)

    Gabriele Grandi

    2016-05-01

    Full Text Available This paper gives the complete analysis of the output current ripple in three-phase voltage source inverters considering the different discontinuous pulse-width modulation (DPWM strategies. In particular, peak-to-peak current ripple amplitude is analytically evaluated over the fundamental period and compared among the most used DPWMs, including positive and negative clamped (DPWM+ and DPWM−, and the four possible combinations between them, usually named as DPWM0, DPWM1, DPWM2, and DPWM3. The maximum and the average values of peak-to-peak current ripple are estimated, and a simple method to correlate the ripple envelope with the ripple rms is proposed and verified. Furthermore, all the results obtained by DPWMs are compared to the centered pulse-width modulation (CPWM, equivalent to the space vector modulation to identify the optimal pulse-width modulation (PWM strategy as a function of the modulation index, taking into account the different average switching frequency. In this way, the PWM technique providing for the minimum output current ripple is identified over the whole modulation range. The analytical developments and the main results are experimentally verified by current ripple measurements with a three-phase PWM inverter prototype supplying an induction motor load.

  12. Seabed ripple morphology and surficial sediment size at the SAX04 experiments near Fort Walton Beach, Florida, fall 2004

    Science.gov (United States)

    Hanes, Daniel M.; Erikson, Li H.; Lescinski, Jamie M.R.; Harney, Jodi N.; Carter, Carissa L.; Hatcher, Gerry A.; Lacy, Jessica R.; Rubin, David M.

    2007-01-01

    Data presented in this report originates from measurements obtained off the Florida coast (fig. 1) as part of the Sediment Acoustics Experiment (SAX04) and Ripples Department Research Initiative (DRI) (Office of Naval Research (ONR), Critical Benthic Environmental Processes and Modeling, Long Range BAA 04-001, Sept. 10, 2003). The aim of this document is to present methods employed to extract data and the resulting measured ripple characteristics (ripple height, wavelength, and orientation) and seabed grain sizes. Application and analysis of the data with respect to hydro- and morphodynamics will be addressed in subsequent reports. Sediment transport in the coastal region is a complex process involving interactions between flow dynamics, sediments, and bedforms. Sediment type and bed geometry directly influence entrainment of sediments into suspension, and at sites where ripples occur (sand formations on the order of several cm high and less than two meter long wavelengths), the understanding of ripple dynamics is an essential component in improving sediment transport models. To gain a better understanding and ability to predict sediment transport, a field study was undertaken to investigate morphology, orientation, and dynamics of ripples on the seafloor. The data obtained from the field campaign also supports an on-going effort to study the effects of ripples on low grazing acoustic penetration into sandy marine sediments for the detection of objects, such as mines (Jackson and others, 2002).

  13. High frequency vibration characteristics of electric wheel system under in-wheel motor torque ripple

    Science.gov (United States)

    Mao, Yu; Zuo, Shuguang; Wu, Xudong; Duan, Xianglei

    2017-07-01

    With the introduction of in-wheel motor, the electric wheel system encounters new vibration problems brought by motor torque ripple excitation. In order to analyze new vibration characteristics of electric wheel system, torque ripple of in-wheel motor based on motor module and vector control system is primarily analyzed, and frequency/order features of the torque ripple are discussed. Then quarter vehicle-electric wheel system (QV-EWS) dynamics model based on the rigid ring tire assumption is established and the main parameters of the model are identified according to tire free modal test. Modal characteristics of the model are further analyzed. The analysis indicates that torque excitation of in-wheel motor is prone to arouse horizontal vibration, in which in-phase rotational, anti-phase rotational and horizontal translational modes of electric wheel system mainly participate. Based on the model, vibration responses of the QV-EWS under torque ripple are simulated. The results show that unlike vertical low frequency (lower than 20 Hz) vibration excited by road roughness, broadband torque ripple will arouse horizontal high frequency (50-100 Hz) vibration of electric wheel system due to participation of the three aforementioned modes. To verify the theoretical analysis, the bench experiment of electric wheel system is conducted and vibration responses are acquired. The experiment demonstrates the high frequency vibration phenomenon of electric wheel system and the measured order features as well as main resonant frequencies agree with simulation results. Through theoretical modeling, analysis and experiments this paper reveals and explains the high frequency vibration characteristics of electric wheel system, providing references for the dynamic analysis, optimal design of QV-EWS.

  14. Pre-compression volume on flow ripple reduction of a piston pump

    Science.gov (United States)

    Xu, Bing; Song, Yuechao; Yang, Huayong

    2013-11-01

    Axial piston pump with pre-compression volume(PCV) has lower flow ripple in large scale of operating condition than the traditional one. However, there is lack of precise simulation model of the axial piston pump with PCV, so the parameters of PCV are difficult to be determined. A finite element simulation model for piston pump with PCV is built by considering the piston movement, the fluid characteristic(including fluid compressibility and viscosity) and the leakage flow rate. Then a test of the pump flow ripple called the secondary source method is implemented to validate the simulation model. Thirdly, by comparing results among the simulation results, test results and results from other publications at the same operating condition, the simulation model is validated and used in optimizing the axial piston pump with PCV. According to the pump flow ripples obtained by the simulation model with different PCV parameters, the flow ripple is the smallest when the PCV angle is 13°, the PCV volume is 1.3×10-4 m3 at such operating condition that the pump suction pressure is 2 MPa, the pump delivery pressure 15 MPa, the pump speed 1 000 r/min, the swash plate angle 13°. At the same time, the flow ripple can be reduced when the pump suction pressure is 2 MPa, the pump delivery pressure is 5 MPa,15 MPa, 22 MPa, pump speed is 400 r/min, 1 000 r/min, 1 500 r/min, the swash plate angle is 11°, 13°, 15° and 17°, respectively. The finite element simulation model proposed provides a method for optimizing the PCV structure and guiding for designing a quieter axial piston pump.

  15. Lamina-specific contribution of glutamatergic and GABAergic potentials to hippocampal sharp wave-ripple complexes.

    Science.gov (United States)

    Schönberger, Jan; Draguhn, Andreas; Both, Martin

    2014-01-01

    The mammalian hippocampus expresses highly organized patterns of neuronal activity which form a neuronal correlate of spatial memories. These memory-encoding neuronal ensembles form on top of different network oscillations which entrain neurons in a state- and experience-dependent manner. The mechanisms underlying activation, timing and selection of participating neurons are incompletely understood. Here we studied the synaptic mechanisms underlying one prominent network pattern called sharp wave-ripple complexes (SPW-R) which are involved in memory consolidation during sleep. We recorded SPW-R with extracellular electrodes along the different layers of area CA1 in mouse hippocampal slices. Contribution of glutamatergic excitation and GABAergic inhibition, respectively, was probed by local application of receptor antagonists into s. radiatum, pyramidale and oriens. Laminar profiles of field potentials show that GABAergic potentials contribute substantially to sharp waves and superimposed ripple oscillations in s. pyramidale. Inhibitory inputs to s. pyramidale and s. oriens are crucial for action potential timing by ripple oscillations, as revealed by multiunit-recordings in the pyramidal cell layer. Glutamatergic afferents, on the other hand, contribute to sharp waves in s. radiatum where they also evoke a fast oscillation at ~200 Hz. Surprisingly, field ripples in s. radiatum are slightly slower than ripples in s. pyramidale, resulting in a systematic shift between dendritic and somatic oscillations. This complex interplay between dendritic excitation and perisomatic inhibition may be responsible for the precise timing of discharge probability during the time course of SPW-R. Together, our data illustrate a complementary role of spatially confined excitatory and inhibitory transmission during highly ordered network patterns in the hippocampus.

  16. Las nuevas casas de la Inquisición en Santiago de Compostela: del palacio de Monterrey a la sede de Porta da Mámoa

    Directory of Open Access Journals (Sweden)

    Pita Galán, Paula

    2012-12-01

    Full Text Available In 1726 the Inquisition decided to rebuild its building: the Palace of Monterrey, in Santiago de Compostela. This intervention should have been made according to a project of Fernando de Casas but caused the moving of the Santo Oficio to a new building known as Casa Grande del Horreo or de Calo, in front of Porta da Mámoa. Thanks to unknown documents and the collection of plates of the Inquisition conserved at Archivo Histórico Universitario de Santiago, we will analized the circumstances that caused the change of building as well as propose an hypothetical reconstruction of the Casa de Calo from the testimonies of those who knew it before of the deep removal, directed by the master mason of San Martín Pinario fray Francisco Velasco that transform it into a Palace of the Inquisition.

    En 1726 el Tribunal de la Inquisición se propuso remodelar sus instalaciones en el Palacio de Monterrey, en Santiago de Compostela. Dicha intervención, que debía realizarse según un proyecto de Fernando de Casas, determinó el traslado del Santo Oficio a un nuevo inmueble: la Casa Grande del Hórreo o de Calo, frente a la Porta da Mámoa. A partir de documentación inédita y del estudio de la colección de planos de la Inquisición que conserva el Archivo Histórico Universitario de Santiago, analizaremos las circunstancias que motivaron el cambio de sede, y reconstruiremos la Casa de Calo según los testimonios de quienes la conocieron antes de que una profunda remoción dirigida por fray Francisco Velasco, maestro de obras de San Martín Pinario, la transformase en un palacio de la Inquisición. [gl] En 1726 o Tribunal da Inquisición propúxose remodelar a súas instalacións no Pazo de Monterrey, en Santiago de Compostela. Dita intervención, que debíase realizar seguindo un proxecto de Fernando de Casas, determinou o traslado do Santo Ofi cio a un novo inmoble: a Casa Grande do Hórreo ou de Calo, frente a Porta da Mámoa. A partir de

  17. Toxicological studies for adults and children of insecticide residues with common mode of action (MoA) in pome, stone, berries and other small fruit

    Energy Technology Data Exchange (ETDEWEB)

    Lozowicka, B., E-mail: B.Lozowicka@iorpib.poznan.pl [Plant Protection Institute - National Research Institute, Laboratory of Pesticide Residues, Chelmonskiego 22, 15-195 Bialystok (Poland); Mojsak, P.; Jankowska, M.; Kaczynski, P.; Hrynko, I.; Rutkowska, E.; Szabunko, J. [Plant Protection Institute - National Research Institute, Laboratory of Pesticide Residues, Chelmonskiego 22, 15-195 Bialystok (Poland); Borusiewicz, A. [Department of Agronomy, The Academy of Agrobusiness in Łomza (Poland)

    2016-10-01

    The presence of pesticide residues in fruit is a serious health concern. This paper for the first time demonstrated the Hazard Index (HI) method to carry out acute, chronic and cumulative health risk assessment to the 14 groups of insecticides for three subpopulations. The challenge of this study was to present results from a long period of research (years 2005–2014) with toxicological aspects, especially in multiresidue samples. Near 1000 fresh pome, stone, berries and small fruit were prepared by two accredited MSPD and QuEChERS methods followed by liquid and gas chromatography analyses with various systems of detection ECD/NPD/MS/MS. Twenty percent of the fruit samples contained 16 insecticide residues in the range of 0.01–0.81 mg/kg and 3% over MRL. The class of pesticide with the highest contribution to the ADI was found to be OPPs: dimethoate and diazinon for adults 48% and 66% of the ADI whereas for infants 144% and 294% of the ADI. The highest contributions of the cHQ to common MoA pesticides were AChE inhibitors: 135% for adults and 528% for infants, sodium channel modulators 4.9% and 20%, nicotic acetylocholine receptor < 2.9% and < 10.6% for adults and infants, respectively. The fruit with the highest contribution to the ADI were found to be apples (316%, 58%), cherries (96%, 37%) and pears (129%, 33%) for infants and adults. The study findings indicated that dietary exposures to insecticide residues in fruit would be unlikely to pose unacceptable health risks for the infants, toddlers and adults. - Highlights: • Health risk assessment of insecticide via dietary intake of fruit was estimated. • Sixteen residues in pome, stone, berries and small fruit ranged from 0.01 to 0.8 mg/kg. • Organophosphates were the most frequently occurring group with common MoA. • Dietary exposures for adults and children were below the safety reference values. • Toxicological study provided important date of human health.

  18. Toxicological studies for adults and children of insecticide residues with common mode of action (MoA) in pome, stone, berries and other small fruit

    International Nuclear Information System (INIS)

    Lozowicka, B.; Mojsak, P.; Jankowska, M.; Kaczynski, P.; Hrynko, I.; Rutkowska, E.; Szabunko, J.; Borusiewicz, A.

    2016-01-01

    The presence of pesticide residues in fruit is a serious health concern. This paper for the first time demonstrated the Hazard Index (HI) method to carry out acute, chronic and cumulative health risk assessment to the 14 groups of insecticides for three subpopulations. The challenge of this study was to present results from a long period of research (years 2005–2014) with toxicological aspects, especially in multiresidue samples. Near 1000 fresh pome, stone, berries and small fruit were prepared by two accredited MSPD and QuEChERS methods followed by liquid and gas chromatography analyses with various systems of detection ECD/NPD/MS/MS. Twenty percent of the fruit samples contained 16 insecticide residues in the range of 0.01–0.81 mg/kg and 3% over MRL. The class of pesticide with the highest contribution to the ADI was found to be OPPs: dimethoate and diazinon for adults 48% and 66% of the ADI whereas for infants 144% and 294% of the ADI. The highest contributions of the cHQ to common MoA pesticides were AChE inhibitors: 135% for adults and 528% for infants, sodium channel modulators 4.9% and 20%, nicotic acetylocholine receptor < 2.9% and < 10.6% for adults and infants, respectively. The fruit with the highest contribution to the ADI were found to be apples (316%, 58%), cherries (96%, 37%) and pears (129%, 33%) for infants and adults. The study findings indicated that dietary exposures to insecticide residues in fruit would be unlikely to pose unacceptable health risks for the infants, toddlers and adults. - Highlights: • Health risk assessment of insecticide via dietary intake of fruit was estimated. • Sixteen residues in pome, stone, berries and small fruit ranged from 0.01 to 0.8 mg/kg. • Organophosphates were the most frequently occurring group with common MoA. • Dietary exposures for adults and children were below the safety reference values. • Toxicological study provided important date of human health.

  19. Persistence at low temperature of the P beta' ripple in dipalmitoylphosphatidylcholine multilamellar vesicles containing either glycosphingolipids or cholesterol.

    Science.gov (United States)

    Rock, P; Thompson, T E; Tillack, T W

    1989-03-13

    The disappearance and reappearance of the P beta' ripple in multilamellar liposomes of dipalmitoylphosphatidylcholine (DPPC) has been examined by freeze-etch electron microscopy. The presence of less than 10 mol% of various glycosphingolipids or cholesterol in the liposomes markedly increases the time required for ripple disappearance when the vesicles are cooled from 38 degrees C to 30 degrees C, as compared to the pure phospholipid. Once the ripples have begun to disappear in the two-component vesicles, they do not uniformly reappear until the system is heated above the main transition of DPPC and allowed to cool into the pretransition region. These results suggest that the long time for ripple disappearance in the two-component systems reflects a slow molecular reorganization process which occurs when the systems are forced to change from the P beta' gel to the L beta' gel by a temperature downshift.

  20. Equalization of FBG-induced group-delay ripples penalties using a coherent receiver and digital signal processing

    NARCIS (Netherlands)

    Veljanovski, V.; Al Fiad, M.S.A.S.; Borne, van den D.; Jansen, S.L.; Wuth, T.

    2009-01-01

    We show the mitigation of fiber Bragg gratings induced group delay ripple penalties through the use of coherent detection and electronic equalizer. For 111-Gb/s POLMUX-RZDQPSK only a negligible penalty is observed after 10 cascaded FBGs.

  1. Modulations of anisotropic optical transmission on alumina-doped zinc oxide surface by femtosecond laser induced ripples

    Science.gov (United States)

    Lu, Yanhui; Jiang, Lan; Sun, Jingya; Cao, Qiang; Wang, Qingsong; Han, Weina; Lu, Yongfeng

    2018-04-01

    This study demonstrated that femtosecond-laser-induced ripples on an alumina-doped zinc oxide (AZO) film with space intervals of approximately 340 and 660 nm exhibit modulations of anisotropic optical transmission. At low laser fluence, ripples can not affect the original absorption peak of AZO film, but at higher laser fluence, the absorption peak of AZO film is disappeared due to the modulation by femtosecond laser induced ripples. Moreover, the relationship between the anisotropic optical transmission and the features of nanostructures is discussed. Ripples with a space interval of approximately 660 nm have a higher ability to block light than nanostructures with a space interval of approximately 340 nm. These observations indicate that anisotropic optical transmission has potential applications in the field of optoelectronics.

  2. Evaluation of beam delivery and ripple filter design for non-isocentric proton and carbon ion therapy.

    Science.gov (United States)

    Grevillot, L; Stock, M; Vatnitsky, S

    2015-10-21

    This study aims at selecting and evaluating a ripple filter design compatible with non-isocentric proton and carbon ion scanning beam treatment delivery for a compact nozzle. The use of non-isocentric treatments when the patient is shifted as close as possible towards the nozzle exit allows for a reduction in the air gap and thus an improvement in the quality of scanning proton beam treatment delivery. Reducing the air gap is less important for scanning carbon ions, but ripple filters are still necessary for scanning carbon ion beams to reduce the number of energy steps required to deliver homogeneous SOBP. The proper selection of ripple filters also allows a reduction in the possible transverse and depth-dose inhomogeneities that could appear in non-isocentric conditions in particular. A thorough review of existing ripple filter designs over the past 16 years is performed and a design for non-isocentric treatment delivery is presented. A unique ripple filter quality index (QIRiFi) independent of the particle type and energy and representative of the ratio between energy modulation and induced scattering is proposed. The Bragg peak width evaluated at the 80% dose level (BPW80) is proposed to relate the energy modulation of the delivered Bragg peaks and the energy layer step size allowing the production of homogeneous SOBP. Gate/Geant4 Monte Carlo simulations have been validated for carbon ion and ripple filter simulations based on measurements performed at CNAO and subsequently used for a detailed analysis of the proposed ripple filter design. A combination of two ripple filters in a series has been validated for non-isocentric delivery and did not show significant transverse and depth-dose inhomogeneities. Non-isocentric conditions allow a significant reduction in the spot size at the patient entrance (up to 350% and 200% for protons and carbon ions with range shifter, respectively), and therefore in the lateral penumbra in the patients.

  3. Reduction of toroidal magnetic field ripple in the advanced material tokamak experiment on JFT-2M

    International Nuclear Information System (INIS)

    Sato, M.; Miura, Y.; Kimura, H.; Yamamoto, M.; Koike, T.; Nakayama, T.; Hasegawa, M.; Urata, K.

    1998-01-01

    In order to reduce fast ion losses due to the toroidal field ripple, the reduction of ripple amplitude (δ) by inserting ferritic steel is studied, taking its toroidal mode number into account. The guideline of the design for reduction is wider and thicker ferritic board (FB) is located at further position from VV. The δ depends on the toroidal magnetic field. The value of B r21 /B t in the case of displacement of few cm is about 1 x 10 -5 which is one order smaller than the critical value. The offsetting of FB is not a problem for locked mode. Preliminary experiments with insertion of one or two FB's indicate no adverse effect on global plasma parameters. (author)

  4. Reduction of toroidal magnetic field ripple in the advanced material tokamak experiment on JFT-2M

    Energy Technology Data Exchange (ETDEWEB)

    Sato, M.; Miura, Y.; Kimura, H.; Yamamoto, M.; Koike, T. [Japan Atomic Energy Research Inst. (Japan); Nakayama, T. [Hitachi Ltd. (Japan); Hasegawa, M. [Mitsubishi Electric Corp. (Japan); Urata, K. [Mitsubishi Heavy Industries Ltd. (Japan)

    1998-07-01

    In order to reduce fast ion losses due to the toroidal field ripple, the reduction of ripple amplitude ({delta}) by inserting ferritic steel is studied, taking its toroidal mode number into account. The guideline of the design for reduction is wider and thicker ferritic board (FB) is located at further position from VV. The {delta} depends on the toroidal magnetic field. The value of B{sub r21} /B{sub t} in the case of displacement of few cm is about 1 x 10{sup -5} which is one order smaller than the critical value. The offsetting of FB is not a problem for locked mode. Preliminary experiments with insertion of one or two FB's indicate no adverse effect on global plasma parameters. (author)

  5. First row transition metal atoms embedded in multivacancies in a rippled graphene system

    Science.gov (United States)

    Mombrú, Dominique; Faccio, Ricardo; Mombrú, Alvaro W.

    2018-03-01

    Ab-initio calculations based on density functional theory (DFT) have been performed to study systems where a first row transition metal atom is embedded in a rippled graphene due to the existence of an 8-order multivacancy. In addition to these cases, also the inclusion of a zinc atom, with a 3d10 electron configuration, was also studied. Structural distortions and magnetic response for each system were studied. A correlation was found for the magnitude of the rippling and the distortion in the vacancy. Variation in the trends was found for Cu and Zn cases, which were explained on the basis of the filling of the 3dx2-y2 orbital. All the systems exhibit lower magnetic moment in comparison to the metal-less system. The quenching of the magnetic moment due to the carbon atoms in the vacancy is observed for Sc and Cu.

  6. The resonance between runaway electrons and magnetic ripple in HT-7 Tokamak

    International Nuclear Information System (INIS)

    Zhou Ruijie; Hu Liqun; Lu Hongwei; Lin Shiyao; Zhong Guoqiang; Xu Ping; Zhang Jizong

    2011-01-01

    For suppressing the energy of runaway electrons in tokamak plasma, we analyzed the X-ray energy spectra by runaway electrons in different discharges of the HT-7 tokamak experiment performed in the autumn of 2009. The resonant phenomenon between runaway electrons and magnetic ripple was found. Although, the energy of runaway electrons in the plasma core can be as high as several tens of MeV, but when they are transported to the edge, the electron energy are limited to a certain range by resonance with the magnetic ripple of different harmonic numbers. The runaway electrons under high loop voltage resonate with low step magnetic perturbations, with high energy gain; whereas the runaway electrons under low loop voltage resonate with high level magnetic perturbations, with low energy gain. Using this mechanism, the energy of runaway electrons can be restricted to a low level, and this will significantly mitigate the damage effect on the equipment caused by runaway electrons. (authors)

  7. Harmonic Analysis on Torque Ripple of Brushless DC Motor Based on Advanced Commutation Control

    Directory of Open Access Journals (Sweden)

    Yanpeng Ji

    2018-01-01

    Full Text Available This paper investigates the relationship between current, back electromotive force (back-EMF, and torque for permanent-magnet brushless DC (PM BLDC motors under advanced commutation control from the perspective of harmonics. Considering that the phase current is the influencing factor of both torque and torque ripple, this paper firstly analyzes the effects of advanced commutation on phase current and current harmonics. And then, based on the harmonics of the phase current and back-EMF, the torque harmonic expressions are deduced. The expressions reveal the relationship of harmonic order between the torque, phase current, and back-EMF and highlight the different contribution of individual torque harmonic to the total torque ripple. Finally, the proposed harmonic analysis method is verified by the experiments with different speed and load conditions.

  8. Comparison of Output Current Ripple in Single and Dual Three-Phase Inverters for Electric Vehicle Motor Drives

    Directory of Open Access Journals (Sweden)

    Jelena Loncarski

    2015-04-01

    Full Text Available The standard solution for the traction system in battery powered electric vehicles (EVs is a two-level (2L inverter feeding a three-phase motor. A simple and effective way to achieve a three-level (3L inverter in battery-supplied electric vehicles consists of using two standard three-phase 2L inverters with the open-end winding connection of standard three-phase ac motors. The 3L inverter solution can be usefully adopted in EVs since it combines several benefits such as current ripple reduction, increment of phase motor voltage with limited voltage ratings of the two battery banks, improvement in system reliability, etc. The reduction in current ripple amplitude is particularly relevant since it is a source of electromagnetic interference and audio noise from the inverter-motor power connection cables and from the motor itself. By increasing the inverter switching frequency the ripple amplitude is reduced, but the drive efficiency decreases due to the proportionally increased switching losses. In this paper the peak-to-peak ripple amplitude of the dual-2L inverter is evaluated and compared with the corresponding ripple of the single-2L inverter, considering the same voltage and power motor ratings. The ripple analysis is carried out as a function of the modulation index to cover the whole modulation range of the inverter, and the theoretical results are verified with experimental tests carried out by an inverter-motor drive prototype.

  9. Configuration of ripple domains and their topological defects formed under local mechanical stress on hexagonal monolayer graphene.

    Science.gov (United States)

    Park, Yeonggu; Choi, Jin Sik; Choi, Taekjib; Lee, Mi Jung; Jia, Quanxi; Park, Minwoo; Lee, Hoonkyung; Park, Bae Ho

    2015-03-24

    Ripples in graphene are extensively investigated because they ensure the mechanical stability of two-dimensional graphene and affect its electronic properties. They arise from spontaneous symmetry breaking and are usually manifested in the form of domains with long-range order. It is expected that topological defects accompany a material exhibiting long-range order, whose functionality depends on characteristics of domains and topological defects. However, there remains a lack of understanding regarding ripple domains and their topological defects formed on monolayer graphene. Here we explore configuration of ripple domains and their topological defects in exfoliated monolayer graphenes on SiO2/Si substrates using transverse shear microscope. We observe three-color domains with three different ripple directions, which meet at a core. Furthermore, the closed domain is surrounded by an even number of cores connected together by domain boundaries, similar to topological vortex and anti-vortex pairs. In addition, we have found that axisymmetric three-color domains can be induced around nanoparticles underneath the graphene. This fascinating configuration of ripple domains may result from the intrinsic hexagonal symmetry of two-dimensional graphene, which is supported by theoretical simulation using molecular dynamics. Our findings are expected to play a key role in understanding of ripple physics in graphene and other two-dimensional materials.

  10. Objective assessment of spectral ripple discrimination in cochlear implant listeners using cortical evoked responses to an oddball paradigm.

    Science.gov (United States)

    Lopez Valdes, Alejandro; Mc Laughlin, Myles; Viani, Laura; Walshe, Peter; Smith, Jaclyn; Zeng, Fan-Gang; Reilly, Richard B

    2014-01-01

    Cochlear implants (CIs) can partially restore functional hearing in deaf individuals. However, multiple factors affect CI listener's speech perception, resulting in large performance differences. Non-speech based tests, such as spectral ripple discrimination, measure acoustic processing capabilities that are highly correlated with speech perception. Currently spectral ripple discrimination is measured using standard psychoacoustic methods, which require attentive listening and active response that can be difficult or even impossible in special patient populations. Here, a completely objective cortical evoked potential based method is developed and validated to assess spectral ripple discrimination in CI listeners. In 19 CI listeners, using an oddball paradigm, cortical evoked potential responses to standard and inverted spectrally rippled stimuli were measured. In the same subjects, psychoacoustic spectral ripple discrimination thresholds were also measured. A neural discrimination threshold was determined by systematically increasing the number of ripples per octave and determining the point at which there was no longer a significant difference between the evoked potential response to the standard and inverted stimuli. A correlation was found between the neural and the psychoacoustic discrimination thresholds (R2=0.60, p<0.01). This method can objectively assess CI spectral resolution performance, providing a potential tool for the evaluation and follow-up of CI listeners who have difficulty performing psychoacoustic tests, such as pediatric or new users.

  11. Laterally structured ripple and square phases with one and two dimensional thickness modulations in a model bilayer system.

    Science.gov (United States)

    Debnath, Ananya; Thakkar, Foram M; Maiti, Prabal K; Kumaran, V; Ayappa, K G

    2014-10-14

    Molecular dynamics simulations of bilayers in a surfactant/co-surfactant/water system with explicit solvent molecules show formation of topologically distinct gel phases depending upon the bilayer composition. At low temperatures, the bilayers transform from the tilted gel phase, Lβ', to the one dimensional (1D) rippled, Pβ' phase as the surfactant concentration is increased. More interestingly, we observe a two dimensional (2D) square phase at higher surfactant concentration which, upon heating, transforms to the gel Lβ' phase. The thickness modulations in the 1D rippled and square phases are asymmetric in two surfactant leaflets and the bilayer thickness varies by a factor of ∼2 between maximum and minimum. The 1D ripple consists of a thinner interdigitated region of smaller extent alternating with a thicker non-interdigitated region. The 2D ripple phase is made up of two superimposed square lattices of maximum and minimum thicknesses with molecules of high tilt forming a square lattice translated from the lattice formed with the thickness minima. Using Voronoi diagrams we analyze the intricate interplay between the area-per-head-group, height modulations and chain tilt for the different ripple symmetries. Our simulations indicate that composition plays an important role in controlling the formation of low temperature gel phase symmetries and rippling accommodates the increased area-per-head-group of the surfactant molecules.

  12. A Minimization of Speed Ripple of Sensorless DTC for controlled Induction Motors used in Electric Vehicles

    OpenAIRE

    Khoucha , Farid; Marouani , Khoudir; Kheloui , Abdelaziz; Benbouzid , Mohamed

    2006-01-01

    International audience; The main theme of this paper is to present different switching techniques in DTC induction motor drives for electric vehicle applications, witch insert zero-voltage vector and/or more non zero-voltage vectors to the conventional switching table associated to full adaptive flux and speed observer. Those techniques are quite effective in reducing the torque pulsation and the speed ripples of the motors, as demonstrated in experimental results.

  13. Removal of Direct Current Link Harmonic Ripple in Single Phase Voltage Source Inverter Systems Using Supercapacitors

    Science.gov (United States)

    2016-09-01

    Khaligh, “Optimization of sizing and battery cycle life in battery/ultracapacitor hybrid energy storage systems for electric vehicle applications...depth cycling operation in photovoltaic system ,” in 22nd International Conference “Mixed Design of Integrated Circuits and Systems ,” Toruń, Poland...CURRENT LINK HARMONIC RIPPLE IN SINGLE-PHASE VOLTAGE SOURCE INVERTER SYSTEMS USING SUPERCAPACITORS by Gabriel D. Hernandez September 2016

  14. Impact of cognitive stimulation on ripples within human epileptic and non-epileptic hippocampus

    Czech Academy of Sciences Publication Activity Database

    Brázdil, M.; Cimbálník, J.; Roman, R.; Shaw, D. J.; Stead, M.; Daniel, P.; Jurák, Pavel; Halámek, Josef

    2015-01-01

    Roč. 16, JULY 25 (2015), 47:1-9 ISSN 1471-2202 R&D Projects: GA ČR GAP103/11/0933; GA MŠk ED0017/01/01; GA MŠk(CZ) LO1212 Institutional support: RVO:68081731 Keywords : high-frequency oscillations * hippocampal ripples * epilepsy * human cognition Subject RIV: FH - Neurology Impact factor: 2.304, year: 2015

  15. A High Power Density Integrated Charger for Electric Vehicles with Active Ripple Compensation

    OpenAIRE

    Pan, Liwen; Zhang, Chengning

    2015-01-01

    This paper suggests a high power density on-board integrated charger with active ripple compensation circuit for electric vehicles. To obtain a high power density and high efficiency, silicon carbide devices are reported to meet the requirement of high-switching-frequency operation. An integrated bidirectional converter is proposed to function as AC/DC battery charger and to transfer energy between battery pack and motor drive of the traction system. In addition, the conventional H-bridge cir...

  16. The active filter voltage ripple correction system of the Brookhaven AGS main magnet power supply

    International Nuclear Information System (INIS)

    Marneris, I.; Bonati, R.; Geller, J.; Sandberg, J.N.; Soukas, A.

    1995-01-01

    This paper, and a companion paper, describe the improvements to the Main Magnet Power Supply (MMPS) so that it enables a more flexible operation of the AGS, enhances its reliability, and also improves the MMPS's ultimate performance specifications. One of the major areas for the latter is the fixed target program operating off the AGS slow extracted beam lines. The active filter, by improving the MMPS output ripple, is instrumental in the improvement of the ultimate duty factor of the extraction beam spill

  17. Assessing spectral and temporal processing in children and adults using temporal modulation transfer function (TMTF), Iterated Ripple Noise (IRN) perception, and spectral ripple discrimination (SRD).

    Science.gov (United States)

    Peter, Varghese; Wong, Kogo; Narne, Vijaya Kumar; Sharma, Mridula; Purdy, Suzanne C; McMahon, Catherine

    2014-02-01

    There are many clinically available tests for the assessment of auditory processing skills in children and adults. However, there is limited data available on the maturational effects on the performance on these tests. The current study investigated maturational effects on auditory processing abilities using three psychophysical measures: temporal modulation transfer function (TMTF), iterated ripple noise (IRN) perception, and spectral ripple discrimination (SRD). A cross-sectional study. Three groups of subjects were tested: 10 adults (18-30 yr), 10 older children (12-18 yr), and 10 young children (8-11 yr) Temporal envelope processing was measured by obtaining thresholds for amplitude modulation detection as a function of modulation frequency (TMTF; 4, 8, 16, 32, 64, and 128 Hz). Temporal fine structure processing was measured using IRN, and spectral processing was measured using SRD. The results showed that young children had significantly higher modulation thresholds at 4 Hz (TMTF) compared to the other two groups and poorer SRD scores compared to adults. The results on IRN did not differ across groups. The results suggest that different aspects of auditory processing mature at different age periods and these maturational effects need to be considered while assessing auditory processing in children. American Academy of Audiology.

  18. Identificación mineralógica de los óxidos de manganeso del yacimiento laterítico Punta Gorda, Moa, Cuba

    Directory of Open Access Journals (Sweden)

    Arturo L. Rojas-Purón

    2012-03-01

    Full Text Available Estudios recientes revelaron contenidos atípicos de manganeso en los depósitos lateríticos ferroniquelíferos de Moa. Muestras enriquecidas de dos perfiles del yacimiento Punta Gorda se investigaron con el propósito de determinar las formas mineralógicas en que aparecen los óxidos de manganeso en este depósito. Mediante la aplicación de técnicas de Difracción de Rayos–X, Análisis Térmico Diferencial, Fluorescencia de Rayos–X, Microscopía Electrónica de Barrido y Espectroscopía Infrarroja se pudo establecer que la forma mineralógica principal de los óxidos de manganeso en Punta Gorda es la litioforita; el mineral fue revelado por sus reflejos difractométricos y por sus características macroscópicas (grano de color negro, brillo semimetálico, no magnético y su aspecto botroidal o masivo. Las bandas de absorción de los espectros infrarrojos a los 467 y 1019 cm-1 corroboran este resultado y la presencia de picos endotérmicos inferiores a los 500 oC evidencian la baja cristalinidad de la litioforita en este depósito.

  19. Determinación del coeficiente conjunto de curvatura y refracción en yacimientos lateríticos de Moa

    Directory of Open Access Journals (Sweden)

    Walkis Herrera-Blanco

    2015-10-01

    Full Text Available En este trabajo se analizaron factores meteorológicos, así como la densidad de la capa de aire, la diferencia de altura sobre el nivel del mar, la variación de las condiciones atmosféricas en diferentes horas del día y la presión atmosférica. Se realizaron mediciones experimentales a partir de los trabajos organizativos, instrumentos utilizados y la red topográfica empleada. Para determinar el coeficiente conjunto de curvatura y refracción en estos yacimientos se usó el método de centración forzada. Se obtuvo un coeficiente conjunto de curvatura y refracción para los yacimientos lateríticos del municipio de Moa de 0,20 m, el cual difiere del valor aplicado nacionalmente (0,14 m. Se verifica que al aplicar el valor obtenido a las mediciones topográficas experimentales, las alturas de los puntos se aproximan más al valor real que cuando se calculan con 0,14 m.

  20. Sterile Acellular Dermal Collagen as a Treatment for Rippling Deformity of Breast

    Directory of Open Access Journals (Sweden)

    Brittany Busse

    2014-01-01

    Full Text Available Prosthetic implants are frequently used for breast augmentation and breast reconstruction following mastectomy. Unfortunately, long-term aesthetic results of prosthetic breast restoration may be hindered by complications such as rippling, capsular contracture, and implant malposition. The advent of use of acellular dermal matrices has greatly improved the outcomes of prosthetic breast reconstruction. We describe a case of rippling deformity of breast that was treated using an acellular dermal matrix product, AlloMax. The patient presented with visible rippling of bilateral prosthetic breast implants as well as significant asymmetry of the breasts after multiple excisional biopsies for right breast ductal carcinoma in situ. A 6×10 cm piece of AlloMax was placed on the medial aspect of each breast between the implant and the skin flap. Follow-up was performed at 1 week, 3 months, and 1 year following the procedure. The patient recovered well from the surgery and there were no complications. At her first postoperative follow-up the patient was extremely satisfied with the result. At her 3-month and 1-year follow-up she had no recurrence of her previous deformity and no new deformity.

  1. Ripple-modulated electronic structure of a 3D topological insulator.

    Science.gov (United States)

    Okada, Yoshinori; Zhou, Wenwen; Walkup, D; Dhital, Chetan; Wilson, Stephen D; Madhavan, V

    2012-01-01

    Three-dimensional topological insulators host linearly dispersing states with unique properties and a strong potential for applications. An important ingredient in realizing some of the more exotic states in topological insulators is the ability to manipulate local electronic properties. Direct analogy to the Dirac material graphene suggests that a possible avenue for controlling local properties is via a controlled structural deformation such as the formation of ripples. However, the influence of such ripples on topological insulators is yet to be explored. Here we use scanning tunnelling microscopy to determine the effects of one-dimensional buckling on the electronic properties of Bi(2)Te(3.) By tracking spatial variations of the interference patterns generated by the Dirac electrons we show that buckling imposes a periodic potential, which locally modulates the surface-state dispersion. This suggests that forming one- and two-dimensional ripples is a viable method for creating nanoscale potential landscapes that can be used to control the properties of Dirac electrons in topological insulators.

  2. Stimulated Raman scattering by an intense relativistic electron beam in a long rippled magnetic field

    International Nuclear Information System (INIS)

    Efthimion, P.C.; Schlesinger, S.P.

    1977-01-01

    For the first time, the parametric coupling of the negative-energy cyclotron and space-charge modes to a fast coaxial waveguide structure is observed. The coaxial waveguide smooth center conductor is internally loaded to maintain a 5% ripple of 1.4-, 1.6-, or 2.0-cm periods on the background axial magnetic field throughout the interaction region of 70 cm. The parametric coupling may be considered a stimulated scattering process with the rippled magnetic field of zero frequency in the lab frame appearing as an electromagnetic pump wave in the beam frame, with 30-MW/cm 2 power density imparting to the electrons a quiver velocity V/sub os/ approx. = 0.1c. As predicted by theory, the frequency of the microwave radiation generated by the negative-energy cyclotron mode decreases with increasing magnetic field while remaining constant for the negative-energy space-charge mode. Power levels from 1 to 5 MW have been measured at mm and cm wavelengths. Radiation at frequencies of 2γ 2 V/L, where V and L are the beam velocity and ripple period, respectively, has been observed at high magnetic fields with an exponential-growth rate consistent with parametric coupling theory. This mechanism could be employed as a tunable generator of millimeter and submillimeter wavelength radiation

  3. Stimulated Raman scattering by an intense relativistic electron beam in a long rippled magnetic field

    International Nuclear Information System (INIS)

    Efthimion, P.C.

    1977-01-01

    For the first time, the parametric coupling of the negative energy cyclotron and space-charge modes to a fast coaxial waveguide structure is observed. The coaxial waveguide smooth center conductor is internally loaded to maintain a 5% ripple of 1.4, 1.6, or 2.0 cm periods on the background axial magnetic field throughout the interaction region of 70 cm. The parametric coupling may be considered a stimulated scattering process with the rippled magnetic field of zero frequency in the laboratory frame appearing as an electromagnetic pump wave in the beam frame, with 30 MW/cm 2 power density imparting to the electrons a quiver velocity V/sub os/ = 0.1 c. As predicted by theory, the frequency of the microwave radiation generated by the negative energy cyclotron mode decreases with increasing magnetic field while remaining constant for the negative energy space-charge mode. Power levels from 1 to 5 MW have been measured at mm and cm wavelengths. Radiation at frequencies 2γ 2 V/L, where V and L are the beam velocity and ripple period respectively, has been observed at high magnetic fields with an exponential growth rate consistent with parametric coupling theory. This mechanism could be employed as a tunable generator of submillimeter and infrared wavelength radiation

  4. Ripple FPN reduced algorithm based on temporal high-pass filter and hardware implementation

    Science.gov (United States)

    Li, Yiyang; Li, Shuo; Zhang, Zhipeng; Jin, Weiqi; Wu, Lei; Jin, Minglei

    2016-11-01

    Cooled infrared detector arrays always suffer from undesired Ripple Fixed-Pattern Noise (FPN) when observe the scene of sky. The Ripple Fixed-Pattern Noise seriously affect the imaging quality of thermal imager, especially for small target detection and tracking. It is hard to eliminate the FPN by the Calibration based techniques and the current scene-based nonuniformity algorithms. In this paper, we present a modified space low-pass and temporal high-pass nonuniformity correction algorithm using adaptive time domain threshold (THP&GM). The threshold is designed to significantly reduce ghosting artifacts. We test the algorithm on real infrared in comparison to several previously published methods. This algorithm not only can effectively correct common FPN such as Stripe, but also has obviously advantage compared with the current methods in terms of detail protection and convergence speed, especially for Ripple FPN correction. Furthermore, we display our architecture with a prototype built on a Xilinx Virtex-5 XC5VLX50T field-programmable gate array (FPGA). The hardware implementation of the algorithm based on FPGA has two advantages: (1) low resources consumption, and (2) small hardware delay (less than 20 lines). The hardware has been successfully applied in actual system.

  5. Simulated near-field mapping of ripple pattern supported metal nanoparticles arrays for SERS optimization

    Science.gov (United States)

    Arya, Mahima; Bhatnagar, Mukul; Ranjan, Mukesh; Mukherjee, Subroto; Nath, Rabinder; Mitra, Anirban

    2017-11-01

    An analytical model has been developed using a modified Yamaguchi model along with the wavelength dependent plasmon line-width correction. The model has been used to calculate the near-field response of random nanoparticles on the plane surface, elongated and spherical silver nanoparticle arrays supported on ion beam produced ripple patterned templates. The calculated near-field mapping for elongated nanoparticles arrays on the ripple patterned surface shows maximum number of hot-spots with a higher near-field enhancement (NFE) as compared to the spherical nanoparticle arrays and randomly distributed nanoparticles on the plane surface. The results from the simulations show a similar trend for the NFE when compared to the far field reflection spectra. The nature of the wavelength dependent NFE is also found to be in agreement with the observed experimental results from surface enhanced Raman spectroscopy (SERS). The calculated and the measured optical response unambiguously reveal the importance of interparticle gap and ordering, where a high intensity Raman signal is obtained for ordered elongated nanoparticles arrays case as against non-ordered and the aligned configuration of spherical nanoparticles on the rippled surface.

  6. Ripple formation on Si surfaces during plasma etching in Cl2

    Science.gov (United States)

    Nakazaki, Nobuya; Matsumoto, Haruka; Sonobe, Soma; Hatsuse, Takumi; Tsuda, Hirotaka; Takao, Yoshinori; Eriguchi, Koji; Ono, Kouichi

    2018-05-01

    Nanoscale surface roughening and ripple formation in response to ion incidence angle has been investigated during inductively coupled plasma etching of Si in Cl2, using sheath control plates to achieve the off-normal ion incidence on blank substrate surfaces. The sheath control plate consisted of an array of inclined trenches, being set into place on the rf-biased electrode, where their widths and depths were chosen in such a way that the sheath edge was pushed out of the trenches. The distortion of potential distributions and the consequent deflection of ion trajectories above and in the trenches were then analyzed based on electrostatic particle-in-cell simulations of the plasma sheath, to evaluate the angular distributions of ion fluxes incident on substrates pasted on sidewalls and/or at the bottom of the trenches. Experiments showed well-defined periodic sawtooth-like ripples with their wave vector oriented parallel to the direction of ion incidence at intermediate off-normal angles, while relatively weak corrugations or ripplelike structures with the wave vector perpendicular to it at high off-normal angles. Possible mechanisms for the formation of surface ripples during plasma etching are discussed with the help of Monte Carlo simulations of plasma-surface interactions and feature profile evolution. The results indicate the possibility of providing an alternative to ion beam sputtering for self-organized formation of ordered surface nanostructures.

  7. Wave Tank Studies of Strong Modulation of Wind Ripples Due To Long Waves

    Science.gov (United States)

    Ermakov, S.; Sergievskaya, I.; Shchegolkov, Yu.

    Modulation of wind capillary-gravity ripples due to long waves has been studied in wave tank experiment at low wind speeds using Ka-band radar. The experiments were carried out both for clean water and the water surface covered with surfactant films. It is obtained that the modulation of radar signals is quite strong and can increase with surfactant concentration and fetch. It is shown that the hydrodynamic Modulation Transfer Function (MTF) calculated for free wind ripples and taking into account the kinematic (straining) effect, variations of the wind stress and variations of surfactant concentration strongly underestimates experimental MTF-values. The effect of strong modulation is assumed to be connected with nonlinear harmonics of longer dm-cm- scale waves - bound waves ("parasitic ripples"). The intensity of bound waves depends strongly on the amplitude of decimetre-scale waves, therefore even weak modulation of the dm-scale waves due to long waves results to strong ("cascade") modulation of bound waves. Modulation of the system of "free/bound waves" is estimated using results of wave tank studies of bound waves generation and is shown to be in quali- tative agreement with experiment. This work was supported by MOD, UK via DERA Winfrith (Project ISTC 1774P) and by RFBR (Project 02-05-65102).

  8. Ripple scalings in geothermal facilities, a key to understand the scaling process

    Science.gov (United States)

    Köhl, Bernhard; Grundy, James; Baumann, Thomas

    2017-04-01

    Scalings are a widespread problem among geothermal plants which exploit the Malm Aquifer in the Bavarian Molasse Zone. They effect the technical and economic efficiency of geothermal plants. The majority of the scalings observed at geothermal facilities exploring the Malm aquifer in the Bavarian Molasse Basin are carbonates. They are formed due to a disruption of the lime-carbonic-acid equilibrium during production caused by degassing of CO2. These scalings are found in the production pipes, at the pumps and at filters and can nicely be described using existing hydrogeochemical models. This study proposes a second mechanism for the formation of scalings in ground-level facilities. We investigated scalings which accumulated at the inlet to the heat exchanger. Interestingly, the scalings were recovered after the ground level facilities had been cleaned. The scalings showed distinct ripple structures, which is likely a result of solid particle deposition. From the ripple features the the flow conditions during their formation were calculated based on empirical equations (Soulsby, 2012). The calculations suggest that the deposits were formed during maintenance works. Thin section images of the sediments indicate a two-step process: deposition of sediment grains, followed by stabilization with a calcite layer. The latter likely occured during maintenance. To prevent this type of scalings blocking the heat exchangers, the maintenance procedure has to be revised. References: Soulsby, R. L.; Whitehouse, R. J. S.; Marten, K. V.: Prediction of time-evolving sand ripples in shelf seas. Continental Shelf Research 2012, 38, 47-62

  9. Oriented gold ripple-like structures on poly-L-lactic acid

    Energy Technology Data Exchange (ETDEWEB)

    Juřík, Petr, E-mail: petr.jurik@gmail.com [Department of Solid State Engineering, Institute of Chemical Technology, Prague (Czech Republic); Slepička, Petr [Department of Solid State Engineering, Institute of Chemical Technology, Prague (Czech Republic); Mistrík, Jan; Janíček, Petr [Department of Applied Physics and Mathematics, University of Pardubice (Czech Republic); Rimpelová, Silvie [Department of Biochemistry and Microbiology, Institute of Chemical Technology, Prague (Czech Republic); Kolská, Zdeňka [Faculty of Science, University of J. E. Purkyně, Ústí nad Labem (Czech Republic); Švorčík, Václav [Department of Solid State Engineering, Institute of Chemical Technology, Prague (Czech Republic)

    2014-12-01

    Highlights: • We prepared oriented ripple-like structures on polymer surface with thin gold layer. • These structures show preferential orientation over large areas which is unusual for heat induced wrinkling. • Significant electrical and optical anisotropy was observed. • Zeta-potential, XPS, goniometry and ellipsometry suggest formation of gold lines separated by polymer gaps. • Increase in cell growth in comparison with poly-styrene mock was observed. - Abstract: In this paper chemical, morphological, electrical and biological properties of poly-L-lactic acid thin films with gold nanolayers were studied. These samples were examined as-sputtered and annealed at glass transition temperature. Morphological changes of poly-L-lactic films introduced by annealing were studied by means of atomic force microscopy. This method showed formation of oriented ripple-like structures on the surface of the film. X-ray photoelectron spectroscopy, goniometry, ellipsometry, sheet resistance measurement and electrokinetic analysis were used to determine distribution of gold on the surface. Combined data suggests that these ripple-like structures were formed by gold lines with insulating polymer gaps in between. These lines show preferential orientation over large areas and under proper conditions offer simple way to form electrically anisotropic material on large scale. Also cytocompatibility was studied showing increased cell adhesion and proliferation of mouse embryonic fibroblasts offering another use for these easily formed structures.

  10. Suppression of Gain Ripples in Superconducting Traveling-Wave Kinetic Inductance Amplifiers

    Science.gov (United States)

    Bal, Mustafa; Erickson, Robert P.; Ku, Hsiang Sheng; Wu, Xian; Pappas, David P.

    Superconducting traveling-wave kinetic inductance (KIT) amplifiers demonstrated gain over a wide bandwidth with high dynamic range and low noise. However, the gain curve exhibits ripples. Impedance mismatch at the input and output ports of the KIT amplifier as wells as split ground planes of the coplanar waveguide (CPW) geometry are potential contributors to the ripple in the gain curve. Here we study the origin of these ripples in KIT amplifiers configured in CPW geometry using approximately 20 nm thick NbTiN films grown by reactive co-sputtering of NbN and TiN. Our NbTiN films have non-linear kinetic inductance as a function of current, described by L =L0 (1 +(I /I*) 2) , where I* = 15 . 96 +/- 0 . 11 mA measured by time domain reflectometry. We report the results of implementing an impedance taper that takes into account a significantly reduced phase velocity as it narrows, adding Au onto the CPW split grounds, as well as employing different designs of dispersion engineering. Qubit Measurements using KIT amplifiers will also be reported.

  11. X-ray scattering and diffraction from Xe-induced ripples in crystalline silicon

    Energy Technology Data Exchange (ETDEWEB)

    Biermanns, Andreas; Pietsch, Ullrich; Grigorian, Souren [Universitaet Siegen (Germany); Grenzer, Joerg; Facsko, Stefan; Hanisch, Antje [Foschungszentrum Dresden-Rossendorf (Germany); Carbone, Dina; Metzger, Hartmut [ID Beamline, ESRF (France)

    2008-07-01

    The formation of surface-nanostructures with a characteristic size ranging from several nanometer up to microns has attracted significant interest in the last decades in the context of fabrication of novel opto-electronic and storage devices. One kind of those nanostructures are wave-like patterns (ripples) produced by an interplay between a roughening process caused by ion beam erosion (sputtering) of the surface and smoothening processes caused by surface diffusion. In this contribution we report on investigations of patterned Si(001) surfaces after irradiation with Xe{sup +}-ions using ion-energies up to 40 keV. During the sputtering, an amorphous surface-layer is formed followed by a rather sharp interface towards crystalline material, showing the same morphology as the surface. The structures of the amorphous layer and the amorphous-crystalline interface were studied by means of grazing-incidence-small angle scattering (GISAXS) and diffraction (GID) using synchrotron-radiation. We found that the crystal structure at the interface is expanded along the ripples, caused by the creation of defects inside the surface region, whereas this expansion is strongly reduced across the ripples. This different relaxation may play a driving role in pattern formation at the interface.

  12. Xe{sup +} ion beam induced rippled structures on Si miscut wafers

    Energy Technology Data Exchange (ETDEWEB)

    Hanisch, Antje; Grenzer, Joerg [Forschungszentrum Dresden-Rossendorf, Dresden (Germany); Biermanns, Andreas; Pietsch, Ullrich [Institute of Physics, University of Siegen (Germany)

    2009-07-01

    We report on the influence of the initial roughness and crystallography of the substrate on the formation of self-organized ripple structures on semiconductors surfaces by noble gas ion bombardment. The Bradley-Harper theory predicts that an initial roughness is most important for starting the sputtering process which in the ends leads to the evolution of regular patterns. We produced periodic structures with intermediate Xe{sup +} ion energies (5-70 keV) at different incidence and azimuthal angles which lead to the assumption that also crystallography plays a role at the beginning of ripple evolution. Most of the previous investigations started from the original roughness of a polished silicon wafer. We used (001) silicon wafers with a miscut angle of 1 , 5 and 10 towards[110]. We studied the ripple formation keeping the ion beam parallel to the[111],[-1-11] or[-111] direction, i.e. parallel, antiparallel or perpendicular to the miscut direction[110]. The parallel and antiparallel case implies a variation of the incidence angle with increased roughness over the surface step terraces. The perpendicular orientation means almost no roughness. The results were compared to normal Si(001) and Si(111) wafers.

  13. Radial electric field in JET advanced tokamak scenarios with toroidal field ripple

    Energy Technology Data Exchange (ETDEWEB)

    Crombe, K [Postdoctoral Fellow of the Research Foundation - Flanders (FWO), Department of Applied Physics, Ghent University, Rozier 44, B-9000 Gent (Belgium); Andrew, Y; De Vries, P C; Giroud, C; Hawkes, N C; Meigs, A; Zastrow, K-D [EURATOM/UKAEA Fusion Association, Culham Science Centre, Abingdon, Oxon, OX14 3DB (United Kingdom); Biewer, T M [Oak Ridge National Laboratory, Oak Ridge, TN 37831-6169, TN (United States); Blanco, E [Laboratorio Nacional de Fusion, Asociacion EURATOM-CIEMAT, Madrid (Spain); Tala, T [VTT Technical Research Centre of Finland, Association EURATOM-Tekes, PO Box 1000, FIN-02044 VTT (Finland); Von Hellermann, M [FOM Institute for Plasma Physics Rijnhuizen, Association EURATOM-FOM, Trilateral Euregio Cluster, PO Box 1207, 3430 BE Nieuwegein (Netherlands)], E-mail: Kristel.Crombe@jet.uk

    2009-05-15

    A dedicated campaign has been run on JET to study the effect of toroidal field (TF) ripple on plasma performance. Radial electric field measurements from experiments on a series of plasmas with internal transport barriers (ITBs) and different levels of ripple amplitude are presented. They have been calculated from charge exchange measurements of impurity ion temperature, density and rotation velocity profiles, using the force balance equation. The ion temperature and the toroidal and poloidal rotation velocities are compared in plasmas with both reversed and optimized magnetic shear profiles. Poloidal rotation velocity (v{sub {theta}}) in the ITB region is measured to be of the order of a few tens of km s{sup -1}, significantly larger than the neoclassical predictions. Increasing levels of the TF ripple are found to decrease the ion temperature gradient in the ITB region, a measure for the quality of the ITB, and the maximum value of v{sub {theta}} is reduced. The poloidal rotation term dominates in the calculations of the total radial electric field (E{sub r}), with the largest gradient in E{sub r} measured in the radial region coinciding with the ITB.

  14. Oriented gold ripple-like structures on poly-L-lactic acid

    International Nuclear Information System (INIS)

    Juřík, Petr; Slepička, Petr; Mistrík, Jan; Janíček, Petr; Rimpelová, Silvie; Kolská, Zdeňka; Švorčík, Václav

    2014-01-01

    Highlights: • We prepared oriented ripple-like structures on polymer surface with thin gold layer. • These structures show preferential orientation over large areas which is unusual for heat induced wrinkling. • Significant electrical and optical anisotropy was observed. • Zeta-potential, XPS, goniometry and ellipsometry suggest formation of gold lines separated by polymer gaps. • Increase in cell growth in comparison with poly-styrene mock was observed. - Abstract: In this paper chemical, morphological, electrical and biological properties of poly-L-lactic acid thin films with gold nanolayers were studied. These samples were examined as-sputtered and annealed at glass transition temperature. Morphological changes of poly-L-lactic films introduced by annealing were studied by means of atomic force microscopy. This method showed formation of oriented ripple-like structures on the surface of the film. X-ray photoelectron spectroscopy, goniometry, ellipsometry, sheet resistance measurement and electrokinetic analysis were used to determine distribution of gold on the surface. Combined data suggests that these ripple-like structures were formed by gold lines with insulating polymer gaps in between. These lines show preferential orientation over large areas and under proper conditions offer simple way to form electrically anisotropic material on large scale. Also cytocompatibility was studied showing increased cell adhesion and proliferation of mouse embryonic fibroblasts offering another use for these easily formed structures

  15. Torque Ripple Minimization and Performance Investigation of an In-Wheel Permanent Magnet Motor

    Directory of Open Access Journals (Sweden)

    A. Mansouri

    2016-06-01

    Full Text Available Recently, electric vehicle motoring has become a topic of interest, due to the several problems caused by thermal engines such as pollution and high oil prices. Thus, electric motors are increasingly applied in vehicle’ applications and relevant research about these motors and their applications has been performed. Of particular interest are the improvements regarding torque production capability, the minimization of torque ripple and iron losses. The present work deals with the optimum design and the performance investigation of an outer rotor permanent magnet motor for in-wheel electric vehicle application. At first, and in order to find the optimum motor design, a new based particle-swarm multi-objective optimization procedure is applied. Three objective functions are used: efficiency maximization, weight and ripple torque minimization. Secondly, the effects of the permanent magnets segmentation, the stator slots opening, and the separation of adjacent magnets by air are outlined. The aim of the paper is the design of a topology with smooth output torque, low ripple torque, low iron losses and mechanical robustness.

  16. A diagnostic algorithm to optimize data collection and interpretation of Ripple Maps in atrial tachycardias.

    Science.gov (United States)

    Koa-Wing, Michael; Nakagawa, Hiroshi; Luther, Vishal; Jamil-Copley, Shahnaz; Linton, Nick; Sandler, Belinda; Qureshi, Norman; Peters, Nicholas S; Davies, D Wyn; Francis, Darrel P; Jackman, Warren; Kanagaratnam, Prapa

    2015-11-15

    Ripple Mapping (RM) is designed to overcome the limitations of existing isochronal 3D mapping systems by representing the intracardiac electrogram as a dynamic bar on a surface bipolar voltage map that changes in height according to the electrogram voltage-time relationship, relative to a fiduciary point. We tested the hypothesis that standard approaches to atrial tachycardia CARTO™ activation maps were inadequate for RM creation and interpretation. From the results, we aimed to develop an algorithm to optimize RMs for future prospective testing on a clinical RM platform. CARTO-XP™ activation maps from atrial tachycardia ablations were reviewed by two blinded assessors on an off-line RM workstation. Ripple Maps were graded according to a diagnostic confidence scale (Grade I - high confidence with clear pattern of activation through to Grade IV - non-diagnostic). The RM-based diagnoses were corroborated against the clinical diagnoses. 43 RMs from 14 patients were classified as Grade I (5 [11.5%]); Grade II (17 [39.5%]); Grade III (9 [21%]) and Grade IV (12 [28%]). Causes of low gradings/errors included the following: insufficient chamber point density; window-of-interestRipple Maps in atrial tachycardias. This algorithm requires prospective testing on a real-time clinical platform. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  17. Interaction of rippled shock wave with flat fast-slow interface

    Science.gov (United States)

    Zhai, Zhigang; Liang, Yu; Liu, Lili; Ding, Juchun; Luo, Xisheng; Zou, Liyong

    2018-04-01

    The evolution of a flat air/sulfur-hexafluoride interface subjected to a rippled shock wave is investigated. Experimentally, the rippled shock wave is produced by diffracting a planar shock wave around solid cylinder(s), and the effects of the cylinder number and the spacing between cylinders on the interface evolution are considered. The flat interface is created by a soap film technique. The postshock flow and the evolution of the shocked interface are captured by a schlieren technique combined with a high-speed video camera. Numerical simulations are performed to provide more details of flows. The wave patterns of a planar shock wave diffracting around one cylinder or two cylinders are studied. The shock stability problem is analytically discussed, and the effects of the spacing between cylinders on shock stability are highlighted. The relationship between the amplitudes of the rippled shock wave and the shocked interface is determined in the single cylinder case. Subsequently, the interface morphologies and growth rates under different cases are obtained. The results show that the shock-shock interactions caused by multiple cylinders have significant influence on the interface evolution. Finally, a modified impulsive theory is proposed to predict the perturbation growth when multiple solid cylinders are present.

  18. Hippocampal sharp wave‐ripple: A cognitive biomarker for episodic memory and planning

    Science.gov (United States)

    2015-01-01

    ABSTRACT Sharp wave ripples (SPW‐Rs) represent the most synchronous population pattern in the mammalian brain. Their excitatory output affects a wide area of the cortex and several subcortical nuclei. SPW‐Rs occur during “off‐line” states of the brain, associated with consummatory behaviors and non‐REM sleep, and are influenced by numerous neurotransmitters and neuromodulators. They arise from the excitatory recurrent system of the CA3 region and the SPW‐induced excitation brings about a fast network oscillation (ripple) in CA1. The spike content of SPW‐Rs is temporally and spatially coordinated by a consortium of interneurons to replay fragments of waking neuronal sequences in a compressed format. SPW‐Rs assist in transferring this compressed hippocampal representation to distributed circuits to support memory consolidation; selective disruption of SPW‐Rs interferes with memory. Recently acquired and pre‐existing information are combined during SPW‐R replay to influence decisions, plan actions and, potentially, allow for creative thoughts. In addition to the widely studied contribution to memory, SPW‐Rs may also affect endocrine function via activation of hypothalamic circuits. Alteration of the physiological mechanisms supporting SPW‐Rs leads to their pathological conversion, “p‐ripples,” which are a marker of epileptogenic tissue and can be observed in rodent models of schizophrenia and Alzheimer's Disease. Mechanisms for SPW‐R genesis and function are discussed in this review. © 2015 The Authors Hippocampus Published by Wiley Periodicals, Inc. PMID:26135716

  19. Kuula. Kuu artist Scarlett Johansson. Kuu plaat / Mart Juur

    Index Scriptorium Estoniae

    Juur, Mart, 1964-

    2008-01-01

    Näitlejast ja lauljast Scarlett Johanssonist. Heliplaatidest: Madonna "Hard Candy", Vaiko Eplik ja Eliit "3: Kosmoseodüsseia", Pia Fraus "After Summer", HU? "Film", Enrique Iglesias "95/08 Exitos", Pendulum "In Silico", Mariah Carey "E=MC2"

  20. Baltic companies prepare for stiff competition / Jorgen Johansson

    Index Scriptorium Estoniae

    Johansson, Jorgen

    2001-01-01

    "Baltic Sea Partenariat 2001" on Rootsi valitsuse toetatav projekt ärisidemete arendamiseks Rootsi ja Baltimaade ettevõtete vahel ning aitamaks läänemeremaade väikeettevõtetel valmistuda konkurentsiks EL-i turul

  1. A Prospective Study of Ripple Mapping the Post-Infarct Ventricular Scar to Guide Substrate Ablation for Ventricular Tachycardia.

    Science.gov (United States)

    Luther, Vishal; Linton, Nick W F; Jamil-Copley, Shahnaz; Koa-Wing, Michael; Lim, Phang Boon; Qureshi, Norman; Ng, Fu Siong; Hayat, Sajad; Whinnett, Zachary; Davies, D Wyn; Peters, Nicholas S; Kanagaratnam, Prapa

    2016-06-01

    Post-infarct ventricular tachycardia is associated with channels of surviving myocardium within scar characterized by fractionated and low-amplitude signals usually occurring late during sinus rhythm. Conventional automated algorithms for 3-dimensional electro-anatomic mapping cannot differentiate the delayed local signal of conduction within the scar from the initial far-field signal generated by surrounding healthy tissue. Ripple mapping displays every deflection of an electrogram, thereby providing fully informative activation sequences. We prospectively used CARTO-based ripple maps to identify conducting channels as a target for ablation. High-density bipolar left ventricular endocardial electrograms were collected using CARTO3v4 in sinus rhythm or ventricular pacing and reviewed for ripple mapping conducting channel identification. Fifteen consecutive patients (median age 68 years, left ventricular ejection fraction 30%) were studied (6 month preprocedural implantable cardioverter defibrillator therapies: median 19 ATP events [Q1-Q3=4-93] and 1 shock [Q1-Q3=0-3]). Scar (ripple mapping conducting channels were seen within each scar (length 60 mm; initial component 0.44 mV; delayed component 0.20 mV; conduction 55 cm/s). Ablation was performed along all identified ripple mapping conducting channels (median 18 lesions) and any presumed interconnected late-activating sites (median 6 lesions; Q1-Q3=2-12). The diastolic isthmus in ventricular tachycardia was mapped in 3 patients and colocated within the ripple mapping conducting channels identified. Ventricular tachycardia was noninducible in 85% of patients post ablation, and 71% remain free of ventricular tachycardia recurrence at 6-month median follow-up. Ripple mapping can be used to identify conduction channels within scar to guide functional substrate ablation. © 2016 American Heart Association, Inc.

  2. Space Vector Modulation for DC-Link Current Ripple Reduction in Back-To-Back Current Source Converters for Microgrid Applications

    DEFF Research Database (Denmark)

    Guo, Xiaoqiang; Xu, David; Guerrero, Josep M.

    2015-01-01

    Back-to-back converters have been typically used to interconnect the microgrids. For a back-to-back current source converter, the dc-link current ripple is one of the important parameters. A large ripple will cause the electromagnetic interference, undesirable high-frequency losses, and system...... instability. Conventionally, with a given switching frequency and rated voltage, the current ripple can be reduced by increasing the dc-link inductor, but it leads to bulky size, high cost and slow dynamic response. In order to solve this problem, this paper reveals that the current ripple can...

  3. Presencia de rodingitas en las rocas de dique asociadas a gabros de la zona de Yaguaneque, Moa, Holguín

    Directory of Open Access Journals (Sweden)

    Alianna Corona Rodríguez

    2014-07-01

    Full Text Available En la zona de Yaguaneque abundan las rocas ofiolíticas como parte del macizo Moa-Baracoa. En el interior de los cuerpos básicos (gabros afloran rocas de diques con tremolita-actinolita, clorita, epidota, clinocloro y zoisita, pertenecientes a la facies de esquistos verdes, indicadores de la existencia de procesos metasomáticos en las rocas básicas y metamorfismo retrógrado. Asociadas a los gabros se reportan rodingitas, en forma de lentes o como diques de color claro, con espesores que varían entre 30 cm y 70 cm y longitud de hasta un metro. La composición mineralógica es: clinocloro, anfíboles cálcicos (tremolita actinolita, zoisita, epidota y clorita. Se interpreta que estas rocas son producto de un metasomatismo cálcico, contemporáneo a la serpentinización de las rocas ultrabásicas en dos eventos: el primero asociado a un metamorfismo hidrotermal evidenciado por la preservación de texturas magmáticas; el segundo, durante el emplazamiento tectónico, bajo condiciones de P-T correspondientes a la facies esquistos verdes, que dio lugar a un metamorfismo retrógrado que supuestamente transformó los granates en cloritas. Los gabros constituyen la roca de caja y su composición mineralógica es: plagioclasa (anortita, clinopiroxenos (diópsido y, subordinadamente,olivino en forma de granos relícticos con un borde de alteración a clorita

  4. A New Adaptive Self-Tuning Fourier Coefficients Algorithm for Periodic Torque Ripple Minimization in Permanent Magnet Synchronous Motors (PMSM

    Directory of Open Access Journals (Sweden)

    Gilberto Herrera-Ruíz

    2013-03-01

    Full Text Available A New Adaptive Self-Tuning Fourier Coefficients Algorithm for Periodic Torque Ripple Minimization in Permanent Magnet Synchronous Motors (PMSM Torque ripple occurs in Permanent Magnet Synchronous Motors (PMSMs due to the non-sinusoidal flux density distribution around the air-gap and variable magnetic reluctance of the air-gap due to the stator slots distribution. These torque ripples change periodically with rotor position and are apparent as speed variations, which degrade the PMSM drive performance, particularly at low speeds, because of low inertial filtering. In this paper, a new self-tuning algorithm is developed for determining the Fourier Series Controller coefficients with the aim of reducing the torque ripple in a PMSM, thus allowing for a smoother operation. This algorithm adjusts the controller parameters based on the component’s harmonic distortion in time domain of the compensation signal. Experimental evaluation is performed on a DSP-controlled PMSM evaluation platform. Test results obtained validate the effectiveness of the proposed self-tuning algorithm, with the Fourier series expansion scheme, in reducing the torque ripple.

  5. A new adaptive self-tuning Fourier coefficients algorithm for periodic torque ripple minimization in permanent magnet synchronous motors (PMSM).

    Science.gov (United States)

    Gómez-Espinosa, Alfonso; Hernández-Guzmán, Víctor M; Bandala-Sánchez, Manuel; Jiménez-Hernández, Hugo; Rivas-Araiza, Edgar A; Rodríguez-Reséndiz, Juvenal; Herrera-Ruíz, Gilberto

    2013-03-19

    A New Adaptive Self-Tuning Fourier Coefficients Algorithm for Periodic Torque Ripple Minimization in Permanent Magnet Synchronous Motors (PMSM) Torque ripple occurs in Permanent Magnet Synchronous Motors (PMSMs) due to the non-sinusoidal flux density distribution around the air-gap and variable magnetic reluctance of the air-gap due to the stator slots distribution. These torque ripples change periodically with rotor position and are apparent as speed variations, which degrade the PMSM drive performance, particularly at low speeds, because of low inertial filtering. In this paper, a new self-tuning algorithm is developed for determining the Fourier Series Controller coefficients with the aim of reducing the torque ripple in a PMSM, thus allowing for a smoother operation. This algorithm adjusts the controller parameters based on the component's harmonic distortion in time domain of the compensation signal. Experimental evaluation is performed on a DSP-controlled PMSM evaluation platform. Test results obtained validate the effectiveness of the proposed self-tuning algorithm, with the Fourier series expansion scheme, in reducing the torque ripple.

  6. Climate Forcing of Ripple Migration and Crest Alignment in the Last 400 kyr in Meridiani Planum, Mars

    Science.gov (United States)

    Fenton, Lori K.; Carson, Helen C.; Michaels, Timothy I.

    2018-04-01

    The plains ripples of Meridiani Planum are the first paleo-aeolian bedforms on Mars to have had their last migration episode constrained in time (to 50-200 ka). Here we test how variations in orbital configuration, air pressure, and atmospheric dust loading over the past 400 kyr affect bedform mobility and crest alignment. Using the National Aeronautics and Space Administration Ames Mars Global Climate Model, we ran a series of sensitivity tests under a number of different conditions, seeking changes in wind patterns relative to those modeled for present-day conditions. Results indicate that enhanced sand drift potential in Meridiani Planum correlates with (1) high axial obliquity, (2) a longitude of perihelion (Lp) near southern summer solstice, and (3) a greater air pressure. The last pulse of westward plains ripple migration likely occurred during the most recent obliquity (relative) maximum, from 111 to 86 ka. At Lp coinciding with southern summer solstice, the Mars Global Climate Model produced a westward resultant drift direction, consistent with the observed north-south plains ripple crest alignment. However, smaller superposed ripples, aligned NNE-SSW, are consistent with a strengthened northern summer Hadley return flow, occurring when Lp coincided with northern summer solstice. The superposed NNE-SSW ripples likely formed as the axial obliquity decreased during the last relative maximum and Lp swung toward northern summer, from 86 to 72 ka. The timeline of bedform activity supports the proposed sequence of CO2 sequestration in the south polar residual cap over the past 400 kyr.

  7. Ripple filter for the 10,000A superconducting magnet test stand at the magnet test facility

    Energy Technology Data Exchange (ETDEWEB)

    Drennan, E.

    1991-11-01

    The new 10,000A dumpswitch (1) and dumpresistor (2) system at MTF required a 720Hz filter to eliminate power supply ripple from the load. The new filter, shown in Figure 1, had two requirements: (1) Less then 1/2 Ap-p ripple current with a load current of 10,000A; (2) No or minimal overshoot when the current reaches flattop after it is ramped to 10,000A. MFT magnets are ramped to their final current values at different ramp rates depending on the inductance and type of the magnet under test. The filter design was done with the help of PSPICE simulations. Most of the simulations that will be shown in this write-up were done using a 50mH magnet and a ramprate of 200A/s. In order to study this filter with SPICE, two different simulations had to be done. Due to the relatively high frequency of the ripple when compared with the ramping times, if the ripple current was studied together with the overshoot, the simulations would have taken a very long time to run. Therefore the voltage ripple and the current overshoot were studied separately.

  8. Analysis of Peak-to-Peak Current Ripple Amplitude in Seven-Phase PWM Voltage Source Inverters

    Directory of Open Access Journals (Sweden)

    Gabriele Grandi

    2013-08-01

    Full Text Available Multiphase systems are nowadays considered for various industrial applications. Numerous pulse width modulation (PWM schemes for multiphase voltage source inverters with sinusoidal outputs have been developed, but no detailed analysis of the impact of these modulation schemes on the output peak-to-peak current ripple amplitude has been reported. Determination of current ripple in multiphase PWM voltage source inverters is important for both design and control purposes. This paper gives the complete analysis of the peak-to-peak current ripple distribution over a fundamental period for multiphase inverters, with particular reference to seven-phase VSIs. In particular, peak-to-peak current ripple amplitude is analytically determined as a function of the modulation index, and a simplified expression to get its maximum value is carried out. Although reference is made to the centered symmetrical PWM, being the most simple and effective solution to maximize the DC bus utilization, leading to a nearly-optimal modulation to minimize the RMS of the current ripple, the analysis can be readily extended to either discontinuous or asymmetrical modulations, both carrier-based and space vector PWM. A similar approach can be usefully applied to any phase number. The analytical developments for all different sub-cases are verified by numerical simulations.

  9. Observations of plan-view sand ripple behavior and spectral wave climate on the inner shelf of San Pedro Bay, California

    Science.gov (United States)

    Xu, J. P.

    2005-01-01

    Concurrent video images of sand ripples and current meter measurements of directional wave spectra are analyzed to study the relations between waves and wave-generated sand ripples. The data were collected on the inner shelf off Huntington Beach, California, at 15 m water depth, where the sea floor is comprised of well-sorted very fine sands (D50=92 ??m), during the winter of 2002. The wave climate, which was controlled by southerly swells (12-18 s period) and westerly wind waves (5-10 s period), included three wave types: (A) uni-modal, swells only; (B) bi-modal, swells dominant; and (C) bi-modal, wind-wave dominant. Each wave type has distinct relations with the plan-view shapes of ripples that are classified into five types: (1) sharp-crested, two-dimensional (2-D) ripples; (2) sharp-crested, brick-pattern, 3-D ripples; (3) bifurcated, 3-D ripples; (4) round-crested, shallow, 3-D ripples; and (5) flat bed. The ripple spacing is very small and varies between 4.5 and 7.5 cm. These ripples are anorbital as ripples in many field studies. Ripple orientation is only correlated with wave directions during strong storms (wave type C). In a poly-modal, multi-directional spectral wave environment, the use of the peak parameters (frequency, direction), a common practice when spectral wave measurements are unavailable, may lead to significant errors in boundary layer and sediment transport calculations. ?? 2004 Elsevier Ltd. All rights reserved.

  10. Physiological Ripples (± 100 Hz) in Spike-Free Scalp EEGs of Children With and Without Epilepsy.

    Science.gov (United States)

    Mooij, Anne H; Raijmann, Renee C M A; Jansen, Floor E; Braun, Kees P J; Zijlmans, Maeike

    2017-11-01

    Pathological high frequency oscillations (HFOs, >80 Hz) are considered new biomarkers for epilepsy. They have mostly been recorded invasively, but pathological ripples (80-250 Hz) can also be found in scalp EEGs with frequent epileptiform spikes. Physiological HFOs also exist. They have been recorded invasively in hippocampus and neocortex. There are no reports of spontaneously occurring physiological HFOs recorded with scalp EEG. We aimed to study ripples in spike-free scalp EEGs. We included 23 children (6 with, 17 without epilepsy) who had an EEG without interictal epileptiform spikes recorded during sleep. We differentiated true ripples from spurious ripples such as filtering effects of sharp artifacts and high frequency components of muscle artifacts by viewing ripples simultaneously in bipolar and average montage and double-checking the unfiltered signal. We calculated mean frequency, duration and root mean square amplitude of the ripples, and studied their shape and distribution. We found ripples in EEGs of 20 out of 23 children (4 with, 16 without epilepsy). Ripples had a regular shape and occurred mostly on central and midline channels. Mean frequency was 102 Hz, mean duration 70 ms, mean root mean square amplitude 0.95 µV. Ripples occurring in normal EEGs of children without epilepsy were considered physiological; the similarity in appearance suggested that the ripples occurring in normal EEGs of children with epilepsy were also physiological. The finding that it is possible to study physiological neocortical ripples in scalp EEG paves the way for investigating their occurrence during brain development and their relation with cognitive functioning.

  11. Confinement of ripple-trapped slowing-down ions by a radial electric field

    International Nuclear Information System (INIS)

    Herrmann, W.

    1998-03-01

    Weakly collisional ions trapped in the toroidal field ripples at the outer plasma edge can be prevented to escape the plasma due to grad B-drift by a counteracting radial electric field. This leads to an increase in the density of ripple-trapped ions, which can be monitored by the analysis of charge exchange neutrals. The minimum radial electric field E r necessary to confine ions with energy E and charge q (q=-1: charge of the electron) is E r = -E/(q * R), where R is the major radius at the measuring point. Slowing-down ions from neutral injection are usually in the right energy range to be sufficiently collisionless in the plasma edge and show the confinement by radial electric fields in the range of tens of kV/m. The density of banana ions is almost unaffected by the radial electric field. Neither in L/H- nor in H/L-transitions does the density of ripple-trapped ions and, hence, the neutral particle fluxes, show jumps in times shorter than 1 ms. According to [1,2] the response time of the density and the fluxes to a sudden jump in the radial electric field is less than 200 μs, if the halfwidth of the electric field is larger or about 2 cm. This would exclude rapid jumps in the radial electric field at the transition. Whether the halfwidth of the electric field is that large during transition cannot be decided from the measurement of the fluxes alone. (orig.)

  12. Computational analysis of network activity and spatial reach of sharp wave-ripples.

    Directory of Open Access Journals (Sweden)

    Sadullah Canakci

    Full Text Available Network oscillations of different frequencies, durations and amplitudes are hypothesized to coordinate information processing and transfer across brain areas. Among these oscillations, hippocampal sharp wave-ripple complexes (SPW-Rs are one of the most prominent. SPW-Rs occurring in the hippocampus are suggested to play essential roles in memory consolidation as well as information transfer to the neocortex. To-date, most of the knowledge about SPW-Rs comes from experimental studies averaging responses from neuronal populations monitored by conventional microelectrodes. In this work, we investigate spatiotemporal characteristics of SPW-Rs and how microelectrode size and distance influence SPW-R recordings using a biophysical model of hippocampus. We also explore contributions from neuronal spikes and synaptic potentials to SPW-Rs based on two different types of network activity. Our study suggests that neuronal spikes from pyramidal cells contribute significantly to ripples while high amplitude sharp waves mainly arise from synaptic activity. Our simulations on spatial reach of SPW-Rs show that the amplitudes of sharp waves and ripples exhibit a steep decrease with distance from the network and this effect is more prominent for smaller area electrodes. Furthermore, the amplitude of the signal decreases strongly with increasing electrode surface area as a result of averaging. The relative decrease is more pronounced when the recording electrode is closer to the source of the activity. Through simulations of field potentials across a high-density microelectrode array, we demonstrate the importance of finding the ideal spatial resolution for capturing SPW-Rs with great sensitivity. Our work provides insights on contributions from spikes and synaptic potentials to SPW-Rs and describes the effect of measurement configuration on LFPs to guide experimental studies towards improved SPW-R recordings.

  13. The effects of high frequency current ripple on electric vehicle battery performance

    International Nuclear Information System (INIS)

    Uddin, Kotub; Moore, Andrew D.; Barai, Anup; Marco, James

    2016-01-01

    Highlights: • Experimental study into the impact of current ripple on li-ion battery degradation. • 15 cells exercised with 1200 cycles coupled AC–DC signals, at 5 frequencies. • Results highlight a greater spread of degradation for cells exposed to AC excitation. • Implications for BMS control, thermal management and system integration. - Abstract: The power electronic subsystems within electric vehicle (EV) powertrains are required to manage both the energy flows within the vehicle and the delivery of torque by the electrical machine. Such systems are known to generate undesired electrical noise on the high voltage bus. High frequency current oscillations, or ripple, if unhindered will enter the vehicle’s battery system. Real-world measurements of the current on the high voltage bus of a series hybrid electric vehicle (HEV) show that significant current perturbations ranging from 10 Hz to in excess of 10 kHz are present. Little is reported within the academic literature about the potential impact on battery system performance and the rate of degradation associated with exposing the battery to coupled direct current (DC) and alternating currents (AC). This paper documents an experimental investigation that studies the long-term impact of current ripple on battery performance degradation. Initial results highlight that both capacity fade and impedance rise progressively increase as the frequency of the superimposed AC current increases. A further conclusion is that the spread of degradation for cells cycled with a coupled AC–DC signal is considerably more than for cells exercised with a traditional DC waveform. The underlying causality for this degradation is not yet understood. However, this has important implications for the battery management system (BMS). Increased variations in cell capacity and impedance will cause differential current flows and heat generation within the battery pack that if not properly managed will further reduce battery life

  14. Sharp wave/ripple network oscillations and learning-associated hippocampal maps.

    Science.gov (United States)

    Csicsvari, Jozsef; Dupret, David

    2014-02-05

    Sharp wave/ripple (SWR, 150-250 Hz) hippocampal events have long been postulated to be involved in memory consolidation. However, more recent work has investigated SWRs that occur during active waking behaviour: findings that suggest that SWRs may also play a role in cell assembly strengthening or spatial working memory. Do such theories of SWR function apply to animal learning? This review discusses how general theories linking SWRs to memory-related function may explain circuit mechanisms related to rodent spatial learning and to the associated stabilization of new cognitive maps.

  15. Current ripple in the coils of the TJ-II Spanish stellarator

    Energy Technology Data Exchange (ETDEWEB)

    Perez, A.; Acero, J.; Alberdi, B.; Del Rio, J.M. [JEMA SA, Lasarte-Oria (Spain); Almoguera, L.; Blaumoser, M.; Kirpitchev, I.; Mendez, P. [Asociacion EURATOM-CIEMAT para Fusion, Madrid (Spain)

    1995-12-31

    High precision coil current control, stability and ripple content are very important aspects for a stellarator design. The TJ-II coils will be supplied by network commutated current converters and therefore the coil currents will contain harmonics which have to be kept to a very low level. An analytical investigation as well as numerous simulations with EMTP, SABER{reg_sign} and other softwares, have been done in order to predict the harmonic currents and to verify the completion with the specified maximum levels. The calculations and the results are presented.

  16. Design and Implement of Low Ripple and Quasi-digital Power Supply

    Science.gov (United States)

    Xiangli, Li; Yanjun, Wei; Hanhong, Qi; Yan, Ma

    A switch linearity hybrid power supply based on single chip microcomputer is designed which merged the merits of the switching and linear power supply. Main circuit includes pre-regulator which works in switching mode and series regulator which works in linear mode. Two-stage regulation mode was adopted in the main circuit of the power. A single chip computer (SCM) and high resolution of series D/A and A/D converters are applied to control and measurement which achieved continuous adjustable and low ripple constant current or voltage power supply

  17. Analysis of the Torque Ripples in Designing a Disk Type Brushless Direct Current Motor

    Directory of Open Access Journals (Sweden)

    A. V. Stepanov

    2015-01-01

    Full Text Available This paper investigates the torque ripples of disk-type low-power brushless direct current motor (BDCM with permanent magnets. In spite of numerous studies on designing of valve engines this issue is understudied as yet. The torque ripples cause noise and vibration and can significantly limit accuracy when used in instrumentation, computer technology.We consider a motor that includes a power unit consisting of a rotor and a stator. There are ferrite elements of sensor on the rotor, and the nonmagnetic disk, bonded to it, contains permanent magnets. The rotor is mounted on a rotating shaft. The stator consists of a steel casing and bonded to it non-magnetic, non-conductive disk with holes. In the disk holes from both sides are mounted armature coils. The armature winding consists of two sections each of which has 6 coils. Each adjacent coil in section has an opposite direction of winding. The coils are arranged circumferentially and are shifted relative to each other; the displacement angle between the coils of one section is equal to 2π/6 (rad. Sections are also shifted relative to each other; the angular shift is π/6 (rad. Sections are connected to the output terminals of the electronic switch. Sections of motor windings have the reverse full-wave power.The paper has investigated the steady operation at four-stroke switching and under constant load (torque. In this case, the electromagnetic torque and rotor speed are periodical functions of the rotor rotation angle. The dependencies of the averaged torque on the rotation speed have been obtained. The spectral distribution of the torque ripples at various rotor speeds of rotation has been calculated. The dependencies of the torque on the speed were studied both at constant speed and taking into account the uneven speed. Based on the research findings of disk type BDCM was computed a level of ripples amounted to 0.8 - 5%, which is quite acceptable for use in a drive. The results are useful for

  18. Aspects Concerning the Torque Ripple Control of the Brushless DC Motor

    Directory of Open Access Journals (Sweden)

    BALUTA, G.

    2013-05-01

    Full Text Available This paper deals with two advanced numerical structures to control the electromagnetic torque ripple of Brushless Direct Current Motors (BLDCM, indirectly achieved by phase currents control and directly by the Direct Torque Control (DTC technique. In DTC there was implemented an observer to increase the rudimentary transducer resolution, containing three Hall Effect sensors. The experimental results describe the evolution of torque in both situations of control and are obtained by applying a control strategy for an electric drive system with BLDCM with trapezoidal Back-EMF in Two-Phase Mode.

  19. Current ripple in the coils of the TJ-II Spanish stellarator

    International Nuclear Information System (INIS)

    Perez, A.; Acero, J.; Alberdi, B.; Del Rio, J.M.; Almoguera, L.; Blaumoser, M.; Kirpitchev, I.; Mendez, P.

    1995-01-01

    High precision coil current control, stability and ripple content are very important aspects for a stellarator design. The TJ-II coils will be supplied by network commutated current converters and therefore the coil currents will contain harmonics which have to be kept to a very low level. An analytical investigation as well as numerous simulations with EMTP, SABER reg-sign and other softwares, have been done in order to predict the harmonic currents and to verify the completion with the specified maximum levels. The calculations and the results are presented

  20. Amplification mechanism of ion-ripple lasers and its possible application

    International Nuclear Information System (INIS)

    Chen, K.R.; Dawson, J.M.

    1992-05-01

    The IRL is an advanced scheme for generating coherent high-power radiation, in which a relativistic electron beam propagates obliquely through an ion ripple in a plasma. Its amplification mechanism is described by a low gain theory while the linear growth rate is given by the dispersion relation. The efficiency of the lasing is determined by the nonlinear saturation mechanism discussed. By proper choice of device parameters, sources of microwaves, optical, and perhaps even x-rays can be made. The availability of tunable sources for wide wavelength regimes, coherence and high-power, as well as lower cost and simplicity of equipment are emphasized

  1. Lacosamide and Levetiracetam Have No Effect on Sharp-Wave Ripple Rate

    Czech Academy of Sciences Publication Activity Database

    Kudláček, Jan; Chvojka, Jan; Pošusta, Antonín; Kováčová, Ľubica; Hong, S.B.; Weiss, S.; Volná, K.; Marusič, P.; Otáhal, Jakub; Jiruška, Přemysl

    2017-01-01

    Roč. 8, Dec 21 (2017), č. článku 687. ISSN 1664-2295 R&D Projects: GA ČR(CZ) GA14-02634S; GA ČR(CZ) GA15-08565S; GA MZd(CZ) NV15-29835A; GA MZd(CZ) NV17-28427A Institutional support: RVO:67985823 Keywords : high-frequency oscillations * sharp-wave ripples * levetiracetam * lacosamide * antiepileptic drugs Subject RIV: FH - Neurology OBOR OECD: Neurosciences (including psychophysiology Impact factor: 3.552, year: 2016

  2. Phase lag control of tidally reversing mega-ripple geometry and bed stress in tidal inlets

    Science.gov (United States)

    Traykovski, P.

    2016-02-01

    Recent observations in the Columbia River Mouth, New River Inlet, and Wasque Shoals have shown that tidally reversing mega-ripples are an ubiquitous bedform morphology in energetic tidal inlets. As the name implies, these bedforms reverse asymmetry and migration direction in each half tidal cycle. With wavelengths of 2 to 5 m and heights of 0.2 to 0.5 m, these bedforms are larger than current formed ripples, but smaller than dunes. Unlike dunes which have a depth dependent geometry, observations indicate the tidally reversing mega-ripples geometry is related to the time dependent tidal flow and independent of depth. Previous empirical relations for predicting the geometry of ripples or dunes do not successfully predict the geometry of these features. A time dependent geometric model was developed that accounts for the reversal of migration and asymmetry to successfully predict bedform geometry. The model requires sufficient sediment transport in each half tidal cycle to reverse the asymmetry before the bedforms begin to grow. Both the observations and model indicate that the complete reversal of asymmetry and development of a steep lee face occurs near or after maximum flow in each half tidal cycle. This phase lag in bedform response to tidal forcing also has important implications for bed stress in tidal inlets. Observations of frictional drag in the Columbia River mouth based on a tidal momentum balance of surface slope over 10 km regressed against quadratic near bed velocity show drag coefficients that fall off as CD U-1.4. Reynolds stress measurements performed using the dual ADV differencing technique show similar relations. The Reynolds stress measurements also show a dramatic asymmetry between accelerating flows and decelerating flows with a factor of 5 increase during deceleration. Pulse coherent Doppler profiles of near bed turbulence indicate that the turbulence is dominated by energetic fluctuations in separation zones downstream of steep lee faces. The

  3. Tooth shape optimization of brushless permanent magnet motors for reducing torque ripples

    International Nuclear Information System (INIS)

    Hsu, L.-Y.; Tsai, M.-C.

    2004-01-01

    This paper presents a tooth shape optimization method based on a generic algorithm to reduce the torque ripple of brushless permanent magnet motors under two different magnetization directions. The analysis of this design method mainly focuses on magnetic saturation and cogging torque and the computation of the optimization process is based on an equivalent magnetic network circuit. The simulation results, obtained from the finite element analysis, are used to confirm the accuracy and performance. Finite element analysis results from different tooth shapes are compared to show the effectiveness of the proposed method

  4. Capacitor voltage ripple reduction and arm energy balancing in MMC-HVDC

    DEFF Research Database (Denmark)

    Parikh, Harsh; Martin-Loeches, Ruben Sánches; Tsolaridis, Georgios

    2016-01-01

    Modular Multilevel Converters are emerging and widely used in HVDC applications. However, the submodule capacitors are still large and the energy balancing under unbalanced conditions is a challenge. In this paper, an analytical model focusing on the energy stored in the capacitors and voltage...... variations is utilized in order to achieve better performance. By injecting a second order harmonic component into the circulating current, the energy variation and consequently the capacitor voltage ripple is reduced allowing for a capacitor size reduction. At the same time, an arm energy balancing...

  5. A study on the pressure ripple characteristics in a bent-axis type oil hydraulic piston pump

    International Nuclear Information System (INIS)

    Cho, Ihn Sung; Jung, Jae Youn

    2013-01-01

    To improve the performance of a bent-axis type axial piston pump driven by tapered pistons, it is necessary to know the pressure ripple characteristics. The purpose of this paper is to understand the effect on the pressure ripple characteristics, and to predict by comparing experimental and theoretical analysis results. The simulation model of a bent-axis type axial piston pump is developed in the AMESim environment using the geometrical dimension, and the driving mechanism of the piston pump, such as the stroke of pump, the velocity of piston, the instantaneous volumetric flow, the overlap area of valve plate opening to cylinder bore, the angle of notch, and so on. The results show that theoretical analysis results of the bent-axis type axial piston pump by using the AMESim approximate the pressure ripple characteristic of the test pump, and through this, simulations can be obtained that predict the performance characteristics of a bentaxis type axial piston pump.

  6. Effect of self-focusing on resonant third harmonic generation of laser in a rippled density plasma

    International Nuclear Information System (INIS)

    Kaur, Sukhdeep; Sharma, A. K.; Yadav, Sushila

    2010-01-01

    Resonant third harmonic generation by a Gaussian laser beam in a rippled density plasma is studied. The laser ponderomotive force induces second harmonic longitudinal velocity on electrons that couples with the static density ripple to produce a density perturbation at 2ω,2k+q, where ω and k are the frequency and wave number of the laser and q is the ripple wave number of the laser. This density perturbation beats with electron oscillatory velocity at ω,k-vector to produce a nonlinear current driving the third harmonic generation. In the regime of quadratic nonlinearity, the self-focusing of the laser enhances the third harmonic power. However, at higher intensity, plasma density is significantly reduced on the axis, detuning the third harmonic resonance and weakening the harmonic yield. Self-focusing causes enhancement in the efficiency of harmonic generation.

  7. Input-parallel output-parallel (IPOP) three-level (TL) DC/DC converters with minimized capacitor ripple currents

    DEFF Research Database (Denmark)

    Liu, Dong; Deng, Fujin; Zhang, Qi

    2016-01-01

    , the component current stresses in the proposed converters are reduced. More significantly, the combination of the proposed IPOP TL circuit structure and the interleaving control strategy can largely reduce the ripple currents on the two input capacitors not only by doubling the frequencies of the ripple...... currents on two input capacitors but also by counteracting part of these ripple currents according to the operation principle of the proposed converters. Therefore, the proposed IPOP TL DC/DC converters with the interleaving control strategy can improve the performances of the converters in increasing...... the lifetimes of the input capacitors and minimizing the sizes of the input capacitors. Finally, the simulation and experimental results are presented to verify the effectiveness and feasibility of the proposed converters combined with the interleaving control strategy....

  8. Controlling the ripple density and heights: a new way to improve the electrical performance of CVD-grown graphene.

    Science.gov (United States)

    Park, Won-Hwa; Jo, Insu; Hong, Byung Hee; Cheong, Hyeonsik

    2016-05-14

    We report a new way to enhance the electrical performances of large area CVD-grown graphene through controlling the ripple density and heights after transfer onto SiO2/Si substrates by employing different cooling rates during fabrication. We find that graphene films prepared with a high cooling rate have reduced ripple density and heights and improved electrical characteristics such as higher electron/hole mobilities as well as reduced sheet resistance. The corresponding Raman analysis also shows a significant decrease of the defects when a higher cooling rate is employed. We suggest a model that explains the improved morphology of the graphene film obtained with higher cooling rates. From these points of view, we can suggest a new pathway toward a relatively lower density and heights of ripples in order to reduce the flexural phonon-electron scattering effect, leading to higher lateral carrier mobilities.

  9. Real time implementation of viable torque and flux controllers and torque ripple minimization algorithm for induction motor drive

    International Nuclear Information System (INIS)

    Vasudevan, M.; Arumugam, R.; Paramasivam, S.

    2006-01-01

    Field oriented control (FOC) and direct torque control (DTC) are becoming the industrial standards for induction motors torque and flux control. This paper aims to give a contribution for a detailed comparison between these two control techniques, emphasizing their advantages and disadvantages. The performance of these two control schemes is evaluated in terms of torque and flux ripple and their transient response to step variations of the torque command. Moreover, a new torque and flux ripple minimization technique is also proposed to improve the performance of the DTC drive. Based on the experimental results, the analysis has been presented

  10. Novel MSVPWM to reduce the inductor current ripple for Z-source inverter in electric vehicle applications.

    Science.gov (United States)

    Zhang, Qianfan; Dong, Shuai; Xue, Ping; Zhou, Chaowei; Cheng, ShuKang

    2014-01-01

    A novel modified space vector pulse width modulation (MSVPWM) strategy for Z-Source inverter is presented. By rearranging the position of shoot-through states, the frequency of inductor current ripple is kept constant. Compared with existing MSVPWM strategies, the proposed approach can reduce the maximum inductor current ripple. So the volume of Z-source network inductor can be designed smaller, which brings the beneficial effect on the miniaturization of the electric vehicle controller. Theoretical findings in the novel MSVPWM for Z-Source inverter have been verified by experiment results.

  11. Second Ripple Current Suppression by Two Bandpass Filters and Current Sharing Method for Energy Storage Converters in DC Microgrid

    DEFF Research Database (Denmark)

    Yang, Ling; Chen, Yandong; Luo, An

    2017-01-01

    With the increasing of AC loads injected into DC microgird (MG) through the inverters, the second ripple current (SRC) in the front-end energy storage converter (ESC) and circulating current among the ESCs in DC MG become more and more serious. In this paper, the SRC suppression method by introdu......With the increasing of AC loads injected into DC microgird (MG) through the inverters, the second ripple current (SRC) in the front-end energy storage converter (ESC) and circulating current among the ESCs in DC MG become more and more serious. In this paper, the SRC suppression method...

  12. Anomalous behavior in temporal evolution of ripple wavelength under medium energy Ar{sup +}-ion bombardment on Si: A case of initial wavelength selection

    Energy Technology Data Exchange (ETDEWEB)

    Garg, Sandeep Kumar [Institute of Physics, Sachivalaya Marg, Bhubaneswar 751 005 (India); Inter-University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110 067 (India); Cuerno, Rodolfo [Departamento de Matematicas and Grupo Interdisciplinar de Sistemas Complejos (GISC), Universidad Carlos III de Madrid, 28911 Leganes (Spain); Kanjilal, Dinakar [Inter-University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110 067 (India); Som, Tapobrata, E-mail: tsom@iopb.res.in [Institute of Physics, Sachivalaya Marg, Bhubaneswar 751 005 (India)

    2016-06-14

    We have studied the early stage dynamics of ripple patterns on Si surfaces, in the fluence range of 1–3 × 10{sup 18} ions cm{sup −2}, as induced by medium energy Ar{sup +}-ion irradiation at room temperature. Under our experimental conditions, the ripple evolution is found to be in the linear regime, while a clear decreasing trend in the ripple wavelength is observed up to a certain time (fluence). Numerical simulations of a continuum model of ion-sputtered surfaces suggest that this anomalous behavior is due to the relaxation of the surface features of the experimental pristine surface during the initial stage of pattern formation. The observation of this hitherto unobserved behavior of the ripple wavelength seems to have been enabled by the use of medium energy ions, where the ripple wavelengths are found to be order(s) of magnitude larger than those at lower ion energies.

  13. Quantum mechanical rippling of a MoS2 monolayer controlled by interlayer bilayer coupling.

    Science.gov (United States)

    Zheng, Yi; Chen, Jianyi; Ng, M-F; Xu, Hai; Liu, Yan Peng; Li, Ang; O'Shea, Sean J; Dumitrică, T; Loh, Kian Ping

    2015-02-13

    Nanoscale corrugations are of great importance in determining the physical properties of two-dimensional crystals. However, the mechanical behavior of atomically thin films under strain is not fully understood. In this Letter, we show a layer-dependent mechanical response of molybdenum disulfide (MoS(2)) subject to atomistic-precision strain induced by 2H-bilayer island epitaxy. Dimensional crossover in the mechanical properties is evidenced by the formation of star-shaped nanoripple arrays in the first monolayer, while rippling instability is completely suppressed in the bilayer. Microscopic-level quantum mechanical simulations reveal that the nanoscale rippling is realized by the twisting of neighboring Mo-S bonds without modifying the chemical bond length, and thus invalidates the classical continuum mechanics. The formation of nanoripple arrays significantly changes the electronic and nanotribological properties of monolayer MoS(2). Our results suggest that quantum mechanical behavior is not unique for sp(2) bonding but general for atomic membranes under strain.

  14. Inactivation of Stigmatella aurantiaca CsgA gene impares rippling formation

    Directory of Open Access Journals (Sweden)

    Milosevic-Đeric Ana

    2015-01-01

    Full Text Available Stigmatella aurantiaca fruiting body development depends on cell-cell interactions. One type of the signaling molecule stigmolone isolated from S. aurantiaca cells acts to help cells to stay together in the aggregation phase. Another gene product involved in intercellular signaling in S. aurantiaca is the csgA homolog of Myxococcus xanthus. In close relative M. xanthus C signal the product of the csgA gene is required for rippling, aggregation and sporulation. Isolation of homologous gene in S. aurantiaca implicates a probable role of CsgA in intercellular communication. Inactivation of the gene by insertion mutagenesis caused alterations in S. aurantiaca fruiting. The motility behavior of the cells during development was changed as well as their ability to stay more closely together in the early stages of development. Inactivation of the csgA gene completely abolished rippling of the cells. This indicates the crucial role of the CsgA protein in regulating this rhythmic behavior.

  15. Striped aeolian bedforms: a novel longitudinal pattern observed in ripples and megaripples on Earth and Mars

    Science.gov (United States)

    Gough, T. R.; Hugenholtz, C.; Barchyn, T.; Martin, R. L.

    2017-12-01

    Striped aeolian bedforms (SABs) are a previously undocumented longitudinal pattern consisting of streamwise corridors of ripples or megaripples separated by corridors containing smaller bedforms. Similar patterns of spanwise variations in bed texture and/or bed topography are observed in water flumes. SABs have been observed in satellite imagery at sites in Peru, Iran, California, the Puna region of northwestern Argentina, and on Mars. The spanwise periodicity varies from automated image-based grain size analysis, we found that median grain size was larger on the ripples and megaripples than on the intervening corridors containing smaller bedforms. This result is consistent with fluvial stripes, for which it is suggested that instability-driven streamwise vortices produce lateral sediment transport and sorting. We found no consistent evidence upwind of the SAB patterns to indicate topographic seeding is necessary. Therefore, we hypothesize that SABs are a self-organized bedform pattern that develops from secondary (lateral) transport of sediment in mixed sediment deposits. We also hypothesize that the development and maintenance of SABs requires unimodal wind regimes.

  16. Intrinsic rippling enhances static non-reciprocity in a graphene metamaterial.

    Science.gov (United States)

    Ho, Duc Tam; Park, Harold S; Kim, Sung Youb

    2018-01-18

    In mechanical systems, Maxwell-Betti reciprocity means that the displacement at point B in response to a force at point A is the same as the displacement at point A in response to the same force applied at point B. Because the notion of reciprocity is general, fundamental, and is operant for other physical systems like electromagnetics, acoustics, and optics, there is significant interest in understanding systems that are not reciprocal, or exhibit non-reciprocity. However, most studies on non-reciprocity have occurred in bulk-scale structures for dynamic problems involving time reversal symmetry. As a result, little is known about the mechanisms governing static non-reciprocal responses, particularly in atomically-thin two-dimensional materials like graphene. Here, we use classical atomistic simulations to demonstrate that out-of-plane ripples, which are intrinsic to graphene, enable significant, multiple orders of magnitude enhancements in the statically non-reciprocal response of graphene metamaterials. Specifically, we find that a striking interplay between the ripples and the stress fields that are induced in the metamaterials due to their geometry impacts the displacements that are transmitted by the metamaterial, thus leading to a significantly enhanced static non-reciprocal response. This study thus demonstrates the potential of two-dimensional mechanical metamaterials for symmetry-breaking applications.

  17. Grey Wolf based control for speed ripple reduction at low speed operation of PMSM drives.

    Science.gov (United States)

    Djerioui, Ali; Houari, Azeddine; Ait-Ahmed, Mourad; Benkhoris, Mohamed-Fouad; Chouder, Aissa; Machmoum, Mohamed

    2018-03-01

    Speed ripple at low speed-high torque operation of Permanent Magnet Synchronous Machine (PMSM) drives is considered as one of the major issues to be treated. The presented work proposes an efficient PMSM speed controller based on Grey Wolf (GW) algorithm to ensure a high-performance control for speed ripple reduction at low speed operation. The main idea of the proposed control algorithm is to propose a specific objective function in order to incorporate the advantage of fast optimization process of the GW optimizer. The role of GW optimizer is to find the optimal input controls that satisfy the speed tracking requirements. The synthesis methodology of the proposed control algorithm is detailed and the feasibility and performances of the proposed speed controller is confirmed by simulation and experimental results. The GW algorithm is a model-free controller and the parameters of its objective function are easy to be tuned. The GW controller is compared to PI one on real test bench. Then, the superiority of the first algorithm is highlighted. Copyright © 2018 ISA. Published by Elsevier Ltd. All rights reserved.

  18. MOA-2011-BLG-262Lb: A sub-Earth-mass moon orbiting a gas giant primary or a high velocity planetary system in the galactic Bulge

    Energy Technology Data Exchange (ETDEWEB)

    Bennett, D. P. [Department of Physics, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN 46556 (United States); Batista, V. [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Bond, I. A.; Ling, C. H. [Institute of Natural and Mathematical Sciences, Massey University, Auckland 0745 (New Zealand); Bennett, C. S. [Department of Physics, Massachussets Institute of Technology, Cambridge, MA 02139 (United States); Suzuki, D.; Koshimoto, N. [Department of Earth and Space Science, Osaka University, Osaka 560-0043 (Japan); Beaulieu, J.-P. [UPMC-CNRS, UMR 7095, Institut d' Astrophysique de Paris, 98bis Boulevard Arago, F-75014 Paris (France); Udalski, A. [Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland); Donatowicz, J. [Technische Universität Wien, Wieder Hauptst. 8-10, A-1040 Vienna (Austria); Bozza, V. [Dipartimento di Fisica, Università di Salerno, Via Ponte Don Melillo 132, I-84084 Fisciano (Italy); Abe, F.; Fukunaga, D.; Itow, Y.; Masuda, K.; Matsubara, Y.; Muraki, Y. [Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya 464-8601 (Japan); Botzler, C. S.; Freeman, M. [Department of Physics, University of Auckland, Private Bag 92-019, Auckland 1001 (New Zealand); Fukui, A., E-mail: bennett@nd.edu [Okayama Astrophysical Observatory, National Astronomical Observatory of Japan, Okayama 719-0232 (Japan); Collaboration: MOA Collaboration; PLANET Collaboration; μFUN Collaboration; OGLE Collaboration; RoboNet Collaboration; and others

    2014-04-20

    We present the first microlensing candidate for a free-floating exoplanet-exomoon system, MOA-2011-BLG-262, with a primary lens mass of M {sub host} ∼ 4 Jupiter masses hosting a sub-Earth mass moon. The argument for an exomoon hinges on the system being relatively close to the Sun. The data constrain the product M{sub L} π{sub rel} where M{sub L} is the lens system mass and π{sub rel} is the lens-source relative parallax. If the lens system is nearby (large π{sub rel}), then M{sub L} is small (a few Jupiter masses) and the companion is a sub-Earth-mass exomoon. The best-fit solution has a large lens-source relative proper motion, μ{sub rel} = 19.6 ± 1.6 mas yr{sup –1}, which would rule out a distant lens system unless the source star has an unusually high proper motion. However, data from the OGLE collaboration nearly rule out a high source proper motion, so the exoplanet+exomoon model is the favored interpretation for the best fit model. However, there is an alternate solution that has a lower proper motion and fits the data almost as well. This solution is compatible with a distant (so stellar) host. A Bayesian analysis does not favor the exoplanet+exomoon interpretation, so Occam's razor favors a lens system in the bulge with host and companion masses of M{sub host}=0.12{sub −0.06}{sup +0.19} M{sub ⊙} and m{sub comp}=18{sub −10}{sup +28} M{sub ⊕}, at a projected separation of a{sub ⊥}=0.84{sub −0.14}{sup +0.25} AU. The existence of this degeneracy is an unlucky accident, so current microlensing experiments are in principle sensitive to exomoons. In some circumstances, it will be possible to definitively establish the mass of such lens systems through the microlensing parallax effect. Future experiments will be sensitive to less extreme exomoons.

  19. Ripple Effects

    Science.gov (United States)

    Birkenholz, Robert J.

    2013-01-01

    Dr. Robert J. Birkenholz is a Professor of Agricultural and Extension Education in the Department of Agricultural Communication, Education, and Leadership (ACEL) at The Ohio State University. In 2002, he was appointed Chair of the department and served in that administrative role for two terms. In 2009, Dr. Birkenholz returned to a full-time…

  20. MOA-2009-BLG-387Lb

    DEFF Research Database (Denmark)

    Batista...[], V.; Gould, A.; Dieters, S.

    2011-01-01

    parameters. One of these, the angular Einstein radius \\theta_E = 0.31 +- 0.03 mas, is very well measured, but the other (the microlens parallax \\pi_E, which is due to the Earth's orbital motion) is highly degenate with the orbital motion of the planet. We statistically resolve the degeneracy between Earth...... and planet orbital effects by imposing priors from a Galactic model that specifies the positions and velocities of lenses and sources and a Kepler model of orbits. The 90% confidence intervals for the distance, semi-major axis, and period of the planet are 3.5 kpc AU AU, and 3...

  1. Ripple Mitigation with Improved Line-Load Transients Response in Two-Stage DC-DC-AC Converter

    DEFF Research Database (Denmark)

    Gautam, Aditya R.; Gaurav, Kumar; Guerrero, Josep M.

    2018-01-01

    . The front-end boost converter in the considered two-stage converter interfaces a battery bank and single phase inverter fed loads. The control shapes the output impedance of boost converter to reduce the ripple component at battery input. Secondly, the proposed controller achieves good dynamic performance...

  2. Robust low frequency current ripple elimination algorithm for grid-connected fuel cell systems with power balancing technique

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jong-Soo; Choe, Gyu-Yeong; Lee, Byoung-Kuk [School of Information and Communication Engineering, Sungkyunkwan University, 300 Cheoncheon-dong, Jangan-gu, Suwon, Gyeonggi-do 440-746 (Korea, Republic of); Kang, Hyun-Soo [R and D Center, Advanced Drive Technology (ADT) Company, 689-26 Geumjeong-dong, Gunpo-si, Gyeonggi-do 435-862 (Korea, Republic of)

    2011-05-15

    The low frequency current ripple in grid-connected fuel cell systems is generated from dc-ac inverter operation, which generates 60 Hz fundamental component, and gives harmful effects on fuel cell stack itself, such as making cathode surface responses slower, causing an increase of more than 10% in the fuel consumption, creating oxygen starvation, causing a reduction in the operating lifetime, and incurring a nuisance tripping such as overload situation. With these reasons, low frequency current ripple makes fuel cell system unstable and lifetime of fuel cell stack itself short. This paper presents a fast and robust control algorithm to eliminate low frequency current ripple in grid-connected fuel cell systems. Compared with the conventional methods, in the proposed control algorithm, dc link voltage controller is shifted from dc-dc converter to dc-ac inverter, resulting that dc-ac inverter handles dc link voltage control and output current control simultaneously with help of power balancing technique. The results indicate that the proposed algorithm can not only completely eliminate current ripple but also significantly reduce the overshoot or undershoot during transient states without any extra hardware. The validity of the proposed algorithm is verified by computer simulations and also by experiments with a 1 kW laboratory prototype. (author)

  3. Influence of the ion distribution on shape and damage in Xe-induced ripple formation on Si

    Energy Technology Data Exchange (ETDEWEB)

    Biermanns, Andreas; Pietsch, Ullrich [Universitaet Siegen (Germany); Hanisch, Antje; Grenzer, Joerg; Facsko, Stefan [Foschungszentrum Dresden-Rossendorf (Germany); Metzger, Hartmut [ID01 beamline, ESRF (France)

    2009-07-01

    In recent years, the creation of surface-nanostructures due to ion-beam sputtering has gained much interest due to the possibility to pattern large surface areas with tunable morphologies in a short time. One kind of those nanostructures are wave-like patterns (ripples) produced by an interplay between a roughening process caused by ion beam erosion (sputtering) of the surface and smoothening processes caused by surface diffusion. For the creation of such ripple patterns with medium energy ions, the ion beam has to be inclined with respect to the surface normal of the target by an angle between 60 {sup circle} and 80 {sup circle}. In this presentation we show that the resulting inhomogeneity within the irradiated sample area is essential for the ripple formation. We report on investigations of the ion distribution on ripple formation on Si (001) surfaces after irradiation with medium-energy Xe{sup +}-ions. We studied the change of average surface morphology and the damage imposed to the crystal by means of grazing-incidence - small angle scattering (GISAXS) and diffraction (GID) using synchrotron-radiation. We show that changing the asymmetry of the ion distribution changes both morphology and degree of damage of the crystalline material.

  4. Ripple characteristic of the main ring magnet power supply for the KEK 12 GeV PS

    International Nuclear Information System (INIS)

    Sato, Hikaru; Sueno, Tuyosi; Mikawa, Katsuhiko

    1995-01-01

    First of all, general description of the main ring magnet power supply for the KEK 12 GeV PS will be described. The main power supply consists of thyristor rectifiers, DC filters, reactive power compensators, AC harmonic filters and control systems. Devices and control systems for suppressing ripple component of magnet field will be described. (author)

  5. Anne K. Bang: Islamic Sufi Networks in the Western Indian Ocean (c. 1880-1940. Ripples of Reform.

    Directory of Open Access Journals (Sweden)

    Angelika Brodersen

    2015-03-01

    Full Text Available This contribution offers a review of Anne K. Bang's book: Islamic Sufi Networks in the Western Indian Ocean (c. 1880-1940. Ripples of Reform. Islam in Africa, Volume 16. Leiden: Brill 2014. xiv + 227 pages, € 104.00, ISBN 978-900-425-1342.

  6. Spontaneous ripples in the hippocampus correlate with epileptogenicity and not memory function in patients with refractory epilepsy

    NARCIS (Netherlands)

    Jacobs, Julia; Banks, Sarah; Zelmann, Rina; Zijlmans, Maeike; Jones-Gotman, Marilyn; Gotman, Jean

    2016-01-01

    Introduction High-frequency oscillations (HFOs, 80–500 Hz) are newly-described EEG markers of epileptogenicity. The proportion of physiological and pathological HFOs is unclear, as frequency analysis is insufficient for separating the two types of events. For instance, ripples (80–250 Hz) also occur

  7. Source of spill ripple in the RF-KO slow-extraction method with FM and AM

    International Nuclear Information System (INIS)

    Noda, K.; Furukawa, T.; Shibuya, S.; Muramatsu, M.; Uesugi, T.; Kanazawa, M.; Torikoshi, M.; Takada, E.; Yamada, S.

    2002-01-01

    The RF-knockout (RF-KO) slow-extraction method with frequency modulation (FM) and amplitude modulation (AM) has brought high-accuracy irradiation to the treatment of a cancer tumor moving with respiration, because of a quick response to beam start/stop. However, a beam spill extracted from a synchrotron ring through RF-KO slow-extraction has a huge ripple with a frequency of around 1 kHz related to the FM. The spill ripple will disturb the lateral dose distribution in the beam scanning methods. Thus, the source of the spill ripple has been investigated through experiments and simulations. There are two tune regions for the extraction process through the RF-KO method: the extraction region and the diffusion region. The particles in the extraction region can be extracted due to amplitude growth through the transverse RF field, only when its frequency matches with the tune in the extraction region. For a large chromaticity, however, the particles in the extraction region can be extracted through the synchrotron oscillation, even when the frequency does not match with the tune in the extraction region. Thus, the spill structure during one period of the FM strongly depends on the horizontal chromaticity. They are repeated with the repetition frequency of the FM, which is the very source of the spill ripple in the RF-KO method

  8. Using Ripple Effect Mapping to Evaluate Program Impact: Choosing or Combining the Methods That Work Best for You

    Science.gov (United States)

    Emery, Mary; Higgins, Lorie; Chazdon, Scott; Hansen, Debra

    2015-01-01

    A mind mapping approach to evaluation called Ripple Effects Mapping (REM) has been developed and used by a number of Extension faculty across the country recently. This article describes three approaches to REM, as well as key differences and similarities. The authors, each from different land-grant institutions, believe REM is an effective way to…

  9. Torque ripple reduction of brushless DC motor with harmonic current injection based on integral terminal sliding mode control

    DEFF Research Database (Denmark)

    Boroujeni, Mojtaba Shirvani; Markadeh, Gholamreza Arab; Soltani, Jafar

    2018-01-01

    Brushless Harmonic current injection to the stator windings is one of the most effective methods for torque ripple reduction of brushless DC motors. Because of multi harmonic contents of the stator currents, the conventional methods based on rotational reference frame cannot be used to calculate...

  10. Fluence inhomogeneities due to a ripple filter induced Moiré effect.

    Science.gov (United States)

    Ringbæk, Toke Printz; Brons, Stephan; Naumann, Jakob; Ackermann, Benjamin; Horn, Julian; Latzel, Harald; Scheloske, Stefan; Galonska, Michael; Bassler, Niels; Zink, Klemens; Weber, Uli

    2015-02-07

    At particle therapy facilities with pencil beam scanning, the implementation of a ripple filter (RiFi) broadens the Bragg peak, so fewer energy steps from the accelerator are required for a homogeneous dose coverage of the planning target volume (PTV). However, sharply focusing the scanned pencil beams at the RiFi plane by ion optical settings can lead to a Moiré effect, causing fluence inhomogeneities at the isocenter. This has been experimentally proven at the Heidelberg Ionenstrahl-Therapiezentrum (HIT), Universitätsklinikum Heidelberg, Germany. 150 MeV u(-1) carbon-12 ions are used for irradiation with a 3 mm thick RiFi. The beam is focused in front of and as close to the RiFi plane as possible. The pencil beam width is estimated to be 0.78 mm at a 93 mm distance from the RiFi. Radiographic films are used to obtain the fluence profile 30 mm in front of the isocenter, 930 mm from the RiFi. The Monte Carlo (MC) code SHIELD-HIT12A is used to determine the RiFi-induced inhomogeneities in the fluence distribution at the isocenter for a similar setup, pencil beam widths at the RiFi plane ranging from σχ(RiFi to 1.2 mm and for scanning step sizes ranging from 1.5 to 3.7 mm. The beam application and monitoring system (BAMS) used at HIT is modelled and simulated. When the width of the pencil beams at the RiFi plane is much smaller than the scanning step size, the resulting inhomogeneous fluence distribution at the RiFi plane interfers with the inhomogeneous RiFi mass distribution and fluence inhomogeneity can be observed at the isocenter as large as an 8% deviation from the mean fluence. The inverse of the fluence ripple period at the isocenter is found to be the difference between the inverse of the RiFi period and the inverse of the scanning step size. We have been able to use MC simulations to reproduce the spacing of the ripple stripes seen in films irradiated at HIT. Our findings clearly indicate that pencil beams sharply focused near the RiFi plane result in

  11. The H-mode pedestal, ELMs and TF ripple effects in JT-60U/JET dimensionless identity experiments

    International Nuclear Information System (INIS)

    Saibene, G.; Oyama, N.; Loennroth, J.; Andrew, Y.; Luna, E. de la; Giroud, C.; Huysmans, G.T.A.; Kamada, Y.; Kempenaars, M.A.H.; Loarte, A.; Donald, D. Mc; Nave, M.M.F.; Meiggs, A.; Parail, V.; Sartori, R.; Sharapov, S.; Stober, J.; Suzuki, T.; Takechi, M.; Toi, K.; Urano, H.

    2007-01-01

    This paper summarizes results of dimensionless identity experiments in JT-60U and JET, aimed at the comparison of the H-mode pedestal and ELM behaviour in the two devices. Given their similar size, dimensionless matched plasmas are also similar in their dimensional parameters (in particular, the plasma minor radius a is the same in JET and JT-60U). Power and density scans were carried out at two values of I p , providing a q scan (q 95 = 3.1 and 5.1) with fixed (and matched) toroidal field. Contrary to initial expectations, a dimensionless match between the two devices was quite difficult to achieve. In general, p ped in JT-60U is lower than in JET and, at low q, the pedestal pressure of JT-60U with a Type I ELMy edge is matched in JET only in the Type III ELM regime. At q 95 = 5.1, a dimensionless match in ρ*, ν* and β p,ped is obtained with Type I ELMs, but only with low power JET H-modes. These results motivated a closer investigation of experimental conditions in the two devices, to identify possible 'hidden' physics that prevents obtaining a good match of pedestal values over a large range of plasmas parameters. Ripple-induced ion losses of the medium bore plasma used in JT-60U for the similarity experiments are identified as the main difference with JET. The magnitude of the JT-60U ripple losses is sufficient to induce counter-toroidal rotation in co-injected plasma. The influence of ripple losses was demonstrated at q 95 = 5.1: reducing ripple losses by ∼2 (from 4.3 to 1.9 MW) by replacing positive with negative neutral beam injection at approximately constant P in resulted in an increased p ped in JT-60U, providing a good match to full power JET H-modes. At the same time, the counter-toroidal rotation decreased. Physics mechanisms relating ripple losses to pedestal performance are not yet identified, and the possible role of velocity shear in the pedestal stability, as well as the possible influence of ripple on thermal ion transport are briefly

  12. Pole-shape optimization of permanent-magnet linear synchronous motor for reduction of thrust ripple

    Energy Technology Data Exchange (ETDEWEB)

    Tavana, Nariman Roshandel, E-mail: nroshandel@ee.iust.ac.i [Department of Electrical Engineering, Iran University of Science and Technology, Narmak, Tehran 16846-13114 (Iran, Islamic Republic of); Shoulaie, Abbas, E-mail: shoulaie@iust.ac.i [Department of Electrical Engineering, Iran University of Science and Technology, Narmak, Tehran 16846-13114 (Iran, Islamic Republic of)

    2011-01-15

    In this paper, we have used magnet arc shaping technique in order to improve the performance of permanent-magnet linear synchronous motor (PMLSM). At first, a detailed analytical modeling based on Maxwell equations is presented for the analysis and design of PMLSM with the arc-shaped magnetic poles (ASMPs). Then the accuracy of presented method is verified by finite-element method. Very close agreement between the analytical and finite-element results shows the effectiveness of the proposed method. Finally, a magnet shape design is carried out based on the analytical method to enhance the motor developed thrust. Pertinent evaluations on the optimal design performance demonstrate that shape optimization leads to a design with extra low thrust ripple.

  13. The 'ripple effect': Towards researching improvisational music therapy in dementia care homes.

    Science.gov (United States)

    Pavlicevic, Mercédès; Tsiris, Giorgos; Wood, Stuart; Powell, Harriet; Graham, Janet; Sanderson, Richard; Millman, Rachel; Gibson, Jane

    2015-09-01

    Increased interest in, and demand for, music therapy provision for persons with dementia prompted this study's exploration of music therapists' strategies for creating musical communities in dementia care settings, considering the needs and resources of people affected by dementia. Focus group discussions and detailed iterative study of improvisational music therapy work by six experienced practitioners clarify the contextual immediacy and socio-musical complexities of music therapy in dementia care homes. Music therapy's 'ripple effect', with resonances from micro (person-to-person musicking), to meso (musicking beyond 'session time') and macro level (within the care home and beyond), implies that all who are part of the dementia care ecology need opportunities for flourishing, shared participation, and for expanded self-identities; beyond 'staff', 'residents', or 'being in distress'. On such basis, managers and funders might consider an extended brief for music therapists' roles, to include generating and maintaining musical wellbeing throughout residential care settings. © The Author(s) 2013.

  14. The development of enhanced ripple-fire identification methods using high frequency data from Pinedale

    Energy Technology Data Exchange (ETDEWEB)

    Carr, D.; Garbin, H.D.

    1996-01-01

    A technique called ripple fire used in quarry blasts produces modulations in the spectra of these events. The Deployable Seismic Verification System (DSVS) was installed at the Pinedale Seismic Research Facility in Wyoming, an area with a lot of mining activity. DSVS records at frequencies up to 50 Hz and these data provides us with a unique opportunity to determine how well we can discriminate quarry blasts and if there are operational benefits from using high frequency (>20 Hz) data. We have collected a database of 646 events consisting of known earthquakes, known quarry blasts and unknown signals. We have started to calculate preliminary spectrograms if we get the time-independent banding from the quarry blasts, and at what frequencies the banning occurs. We also detail what we hope to accomplish in FY 1996.

  15. Ripples Make Waves: Binding Structured Activity and Plasticity in Hippocampal Networks

    Directory of Open Access Journals (Sweden)

    Josef H. L. P. Sadowski

    2011-01-01

    Full Text Available Establishing novel episodic memories and stable spatial representations depends on an exquisitely choreographed, multistage process involving the online encoding and offline consolidation of sensory information, a process that is largely dependent on the hippocampus. Each step is influenced by distinct neural network states that influence the pattern of activation across cellular assemblies. In recent years, the occurrence of hippocampal sharp wave ripple (SWR oscillations has emerged as a potentially vital network phenomenon mediating the steps between encoding and consolidation, both at a cellular and network level by promoting the rapid replay and reactivation of recent activity patterns. Such events facilitate memory formation by optimising the conditions for synaptic plasticity to occur between contingent neural elements. In this paper, we explore the ways in which SWRs and other network events can bridge the gap between spatiomnemonic processing at cellular/synaptic and network levels in the hippocampus.

  16. Microgrid Restraining Strategy Based on Improved DC Grid Connected DFIG Torque Ripple

    Science.gov (United States)

    Fei, Xia; Yang, Zhixiong; Zongze, Xia

    2017-05-01

    Aiming to the voltage of the stator side is generated by the modulation of the SSC in the improved topology, especially under the circumstance with the asymmTeric fault of stator side, DFIG’s electromagnTeic torque, amplifies ripple of grid-connected power for the grid side. The novel control mTehod suitable to stator side converter and rotor side converter based on reduced-order resonant controller (RORC) is proposed in this thesis, DFIG’s torque and output power performance are improved. Under the RORC control conditions the transfer functions of stator current and torque control system are established, the amplitude characteristic and the system stability of RORC control are analysed. The simulation results in Matlab/Simulink verify the correctness and validity of the proposed mTehod.

  17. Pierce gain analysis for a sheet beam in a rippled waveguide traveling-wave tube

    International Nuclear Information System (INIS)

    Carlsten, Bruce E.

    2001-01-01

    A Pierce-type mode analysis is presented for a planar electron beam in a rippled planar waveguide. This analysis describes the gain of a traveling-wave tube consisting of that geometry. The dispersion relation is given by the determinant of a matrix based on the coupling of different free-space modes through the boundary conditions. For the case of high-frequency, low-power amplifiers, the dispersion relation reduces to a simple cubic expression for the Compton regime, leading to three roots analogous to the Pierce solution of a standard traveling-wave tube. The analysis shows that this type of traveling-wave tube is capable of very high gain at extremely high frequencies

  18. Quantifying denitrification in rippled permeable sands through combined flume experiments and modeling

    DEFF Research Database (Denmark)

    Kessler, Adam J.; Glud, Ronnie N.; Cardenas, M. Bayani

    2012-01-01

    We measured denitrification in permeable sediments in a sealed flume tank with environmentally representative fluid flow and solute transport behavior using novel measurements. Numerical flow and reactive transport models representing the flume experiments were implemented to provide mechanistic...... insight into the coupled hydrodynamic and biogeochemical processes. There was broad agreement between the model results and experimental data. The model showed that the coupling between nitrification and denitrification was relatively weak in comparison to that in cohesive sediments. This was due...... of permeable sediments with nonmigratory ripples to remove bioavailable nitrogen from coastal ecosystems is lower than that of cohesive sediments. We conclude that while experimental measurements provide a good starting point for constraining key parameters, reactive transport models with realistic kinetic...

  19. Using Transcendental Phenomenology to Explore the “Ripple Effect” in a Leadership Mentoring Program

    Directory of Open Access Journals (Sweden)

    Tammy Moerer-Urdahl

    2004-06-01

    Full Text Available Several approaches exist for organizing and analyzing data in a phenomenological qualitative study. Transcendental phenomenology, based on principles identified by Husserl (1931 and translated into a qualitative method by Moustakas (1994, holds promise as a viable procedure for phenomenological research. However, to best understand the approach to transcendental phenomenology, the procedures need to be illustrated by a qualitative study that employs this approach. This article first discusses the procedures for organizing and analyzing data according to Moustakas (1994. Then it illustrates each step in the data analysis procedure of transcendental phenomenology using a study of reinvestment or the “ripple effect” for nine individuals who have participated in a youth leadership mentoring program from the 1970s to the present. Transcendental phenomenology works well for this study as this methodology provides logical, systematic, and coherent design elements that lead to an essential description of the experience.

  20. Pole-shape optimization of permanent-magnet linear synchronous motor for reduction of thrust ripple

    International Nuclear Information System (INIS)

    Tavana, Nariman Roshandel; Shoulaie, Abbas

    2011-01-01

    In this paper, we have used magnet arc shaping technique in order to improve the performance of permanent-magnet linear synchronous motor (PMLSM). At first, a detailed analytical modeling based on Maxwell equations is presented for the analysis and design of PMLSM with the arc-shaped magnetic poles (ASMPs). Then the accuracy of presented method is verified by finite-element method. Very close agreement between the analytical and finite-element results shows the effectiveness of the proposed method. Finally, a magnet shape design is carried out based on the analytical method to enhance the motor developed thrust. Pertinent evaluations on the optimal design performance demonstrate that shape optimization leads to a design with extra low thrust ripple.

  1. Spatial potential ripples of azimuthal surface modes in topological insulator Bi2Te3 nanowires.

    Science.gov (United States)

    Muñoz Rojo, Miguel; Zhang, Yingjie; Manzano, Cristina V; Alvaro, Raquel; Gooth, Johannes; Salmeron, Miquel; Martin-Gonzalez, Marisol

    2016-01-11

    Topological insulators (TI) nanowires (NW) are an emerging class of structures, promising both novel quantum effects and potential applications in low-power electronics, thermoelectrics and spintronics. However, investigating the electronic states of TI NWs is complicated, due to their small lateral size, especially at room temperature. Here, we perform scanning probe based nanoscale imaging to resolve the local surface potential landscapes of Bi2Te3 nanowires (NWs) at 300 K. We found equipotential rings around the NWs perimeter that we attribute to azimuthal 1D modes. Along the NW axis, these modes are altered, forming potential ripples in the local density of states, due to intrinsic disturbances. Potential mapping of electrically biased NWs enabled us to accurately determine their conductivity which was found to increase with the decrease of NW diameter, consistent with surface dominated transport. Our results demonstrate that TI NWs can pave the way to both exotic quantum states and novel electronic devices.

  2. A PIPO Boost Converter with Low Ripple and Medium Current Application

    Science.gov (United States)

    Bandri, S.; Sofian, A.; Ismail, F.

    2018-04-01

    This paper presents a Parallel Input Parallel Output (PIPO) boost converter is proposed to gain power ability of converter, and reduce current inductors. The proposed technique will distribute current for n-parallel inductor and switching component. Four parallel boost converters implement on input voltage 20.5Vdc to generate output voltage 28.8Vdc. The PIPO boost converter applied phase shift pulse width modulation which will compare with conventional PIPO boost converters by using a similar pulse for every switching component. The current ripple reduction shows an advantage PIPO boost converter then conventional boost converter. Varies loads and duty cycle will be simulated and analyzed to verify the performance of PIPO boost converter. Finally, the unbalance of current inductor is able to be verified on four area of duty cycle in less than 0.6.

  3. Neural mechanisms of mental schema: a triplet of delta, low beta/spindle and ripple oscillations.

    Science.gov (United States)

    Ohki, Takefumi; Takei, Yuichi

    2018-02-06

    Schemas are higher-level knowledge structures that integrate and organise lower-level representations. As internal templates, schemas are formed according to how events are perceived, interpreted and remembered. Although these higher-level units are assumed to play a fundamental role in our daily life from an early age, the neuronal basis and mechanisms of schema formation and use remain largely unknown. It is important to elucidate how the brain constructs and maintains these higher-level units. In order to examine the possible neural underpinnings of schema, we recapitulate previous work and discuss their findings related to schemas as the brain template. We specifically focused on low beta/spindle oscillations, which are assumed to be the key components of schemas, and propose that the brain template is implemented with a triplet of neural oscillations, that is delta, low beta/spindle and ripple oscillations. © 2018 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

  4. Ripple gate drive circuit for fast operation of series connected IGBTs

    Science.gov (United States)

    Rockot, Joseph H.; Murray, Thomas W.; Bass, Kevin C.

    2005-09-20

    A ripple gate drive circuit includes a plurality of transistors having their power terminals connected in series across an electrical potential. A plurality of control circuits, each associated with one of the transistors, is provided. Each control circuit is responsive to a control signal and an optical signal received from at least one other control circuit for controlling the conduction of electrical current through the power terminals of the associated transistor. The control circuits are responsive to a first state of the control circuit for causing each transistor in series to turn on sequentially and responsive to a second state of the control signal for causing each transistor in series to turn off sequentially.

  5. An Analytical Time–Domain Expression for the Net Ripple Produced by Parallel Interleaved Converters

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Brian B.; Krein, Philip T.

    2017-03-01

    We apply modular arithmetic and Fourier series to analyze the superposition of N interleaved triangular waveforms with identical amplitudes and duty-ratios. Here, interleaving refers to the condition when a collection of periodic waveforms with identical periods are each uniformly phase-shifted across one period. The main result is a time-domain expression which provides an exact representation of the summed and interleaved triangular waveforms, where the peak amplitude and parameters of the time-periodic component are all specified in closed-form. Analysis is general and can be used to study various applications in multi-converter systems. This model is unique not only in that it reveals a simple and intuitive expression for the net ripple, but its derivation via modular arithmetic and Fourier series is distinct from prior approaches. The analytical framework is experimentally validated with a system of three parallel converters under time-varying operating conditions.

  6. On nonstationarity and rippling of the quasiperpendicular zone of the Earth bow shock: Cluster observations

    Directory of Open Access Journals (Sweden)

    V. V. Lobzin

    2008-09-01

    Full Text Available A new method for remote sensing of the quasiperpendicular part of the bow shock surface is presented. The method is based on analysis of high frequency electric field fluctuations corresponding to Langmuir, upshifted, and downshifted oscillations in the electron foreshock. Langmuir waves usually have maximum intensity at the upstream boundary of this region. All these waves are generated by energetic electrons accelerated by quasiperpendicular zone of the shock front. Nonstationary behavior of the shock, in particular due to rippling, should result in modulation of energetic electron fluxes, thereby giving rise to variations of Langmuir waves intensity. For upshifted and downshifted oscillations, the variations of both intensity and central frequency can be observed. For the present study, WHISPER measurements of electric field spectra obtained aboard Cluster spacecraft are used to choose 48 crossings of the electron foreshock boundary with dominating Langmuir waves and to perform for the first time a statistical analysis of nonstationary behavior of quasiperpendicular zone of the Earth's bow shock. Analysis of hidden periodicities in plasma wave energy reveals shock front nonstationarity in the frequency range 0.33 fBiBi, where fBi is the proton gyrofrequency upstream of the shock, and shows that the probability to observe such a nonstationarity increases with Mach number. The profiles observed aboard different spacecraft and the dominating frequencies of the periodicities are usually different. Hence nonstationarity and/or rippling seem to be rather irregular both in space and time rather than resembling a quasiregular wave propagating on the shock surface.

  7. On nonstationarity and rippling of the quasiperpendicular zone of the Earth bow shock: Cluster observations

    Directory of Open Access Journals (Sweden)

    V. V. Lobzin

    2008-09-01

    Full Text Available A new method for remote sensing of the quasiperpendicular part of the bow shock surface is presented. The method is based on analysis of high frequency electric field fluctuations corresponding to Langmuir, upshifted, and downshifted oscillations in the electron foreshock. Langmuir waves usually have maximum intensity at the upstream boundary of this region. All these waves are generated by energetic electrons accelerated by quasiperpendicular zone of the shock front. Nonstationary behavior of the shock, in particular due to rippling, should result in modulation of energetic electron fluxes, thereby giving rise to variations of Langmuir waves intensity. For upshifted and downshifted oscillations, the variations of both intensity and central frequency can be observed. For the present study, WHISPER measurements of electric field spectra obtained aboard Cluster spacecraft are used to choose 48 crossings of the electron foreshock boundary with dominating Langmuir waves and to perform for the first time a statistical analysis of nonstationary behavior of quasiperpendicular zone of the Earth's bow shock. Analysis of hidden periodicities in plasma wave energy reveals shock front nonstationarity in the frequency range 0.33 fBirippling seem to be rather irregular both in space and time rather than resembling a quasiregular wave propagating on the shock surface.

  8. A Single-Phase Multilevel PV Generation System with an Improved Ripple Correlation Control MPPT Algorithm

    Directory of Open Access Journals (Sweden)

    Manel Hammami

    2017-12-01

    Full Text Available The implementation of maximum power point tracking (MPPT schemes by the ripple correlation control (RCC algorithm is presented in this paper. A reference is made to single-phase single-stage multilevel photovoltaic (PV generation systems, when the inverter input variables (PV voltage and PV current have multiple low-frequency (ripple harmonics. The harmonic analysis is carried out with reference to a multilevel configuration consisting of an H-bridge inverter and level doubling network (LDN cell, leading to the multilevel inverter having double the output voltage levels as compared to the basic H-bridge inverter topology (i.e., five levels vs. three levels. The LDN cell is basically a half-bridge fed by a floating capacitor, with self-balancing voltage capability. The multilevel configuration introduces additional PV voltage and current low-frequency harmonics, perturbing the basic implementation of the RCC scheme (based on the second harmonic component, leading to malfunctioning. The proposed RCC algorithm employs the PV current and voltage harmonics at a specific frequency for the estimation of the voltage derivative of power dP/dV (or dI/dV, driving the PV operating point toward the maximum power point (MPP in a faster and more precise manner. The steady-state and transient performances of the proposed RCC-MPPT schemes have been preliminarily tested and compared using MATLAB/Simulink. Results have been verified by experimental tests considering the whole multilevel PV generation system, including real PV modules, multilevel insulated-gate bipolar transistor (IGBT inverters, and utility grids.

  9. Energy measurement of fast ions trapped in the toroidal field ripple of Tore Supra

    International Nuclear Information System (INIS)

    Basiuk, V.; Becoulet, A.; Hutter, T.; Martin, G.; Pecquet, A.L.; Saoutic, B.

    1993-09-01

    During additional heating in Tore Supra (ICRF or NBI) fast ion losses due to the toroidal field ripple were clearly measured by a set of graphite probes. This diagnostic collects the flow of fast ions entering a vertical port and usually shows a maximum flux for ions originating from the vicinity of surface δ * = 0. During the monster sawteeth regime, achieved with ICRF, a remarkable phenomenon was observed: the ejection of fast ions, not correlated with any measured MHD activity. The radial distribution of these ions is quite different from that usually observed exhibiting a peak located in the central section of the plasma. In order to measure the energy distribution of these ions, from 80 keV (energy of the neutral beam injected in Tore Supra) up to 1 MeV (expected during ICRF), a new diagnostic is under construction. The principle of the diagnostic is to discriminate the ions in energy using their Larmor radius (p = 1.3 cm for 100 keV → p = 3.6 cm for 700 keV, B = 4T). The detector is made of a hollow graphite cylinder with a small entrance slot, located in a vertical port on the ion drift side. An array of six metallic collectors placed inside the graphite cylinder intercepts the ions. The current on each collector was estimated at 10 → 100 nA, during ICRF heating. The energy resolution of this diagnostic is expected to be about 20 keV for the lowest energy range and 100 keV for the highest. This type of ruggedized detector might be extrapolated for the measurements of alpha particle losses in future DT experiments. It should also be suitable for the studies of stochastic ripple diffusion. (authors). 3 refs., 9 figs

  10. Choline-mediated modulation of hippocampal sharp wave-ripple complexes in vitro.

    Science.gov (United States)

    Fischer, Viktoria; Both, Martin; Draguhn, Andreas; Egorov, Alexei V

    2014-06-01

    The cholinergic system is critically involved in the modulation of cognitive functions, including learning and memory. Acetylcholine acts through muscarinic (mAChRs) and nicotinic receptors (nAChRs), which are both abundantly expressed in the hippocampus. Previous evidence indicates that choline, the precursor and degradation product of Acetylcholine, can itself activate nAChRs and thereby affects intrinsic and synaptic neuronal functions. Here, we asked whether the cellular actions of choline directly affect hippocampal network activity. Using mouse hippocampal slices we found that choline efficiently suppresses spontaneously occurring sharp wave-ripple complexes (SPW-R) and can induce gamma oscillations. In addition, choline reduces synaptic transmission between hippocampal subfields CA3 and CA1. Surprisingly, these effects are mediated by activation of both mAChRs and α7-containing nAChRs. Most nicotinic effects became only apparent after local, fast application of choline, indicating rapid desensitization kinetics of nAChRs. Effects were still present following block of choline uptake and are, therefore, likely because of direct actions of choline at the respective receptors. Together, choline turns out to be a potent regulator of patterned network activity within the hippocampus. These actions may be of importance for understanding state transitions in normal and pathologically altered neuronal networks. In this study we asked whether choline, the precursor and degradation product of acetylcholine, directly affects hippocampal network activity. Using mouse hippocampal slices we found that choline efficiently suppresses spontaneously occurring sharp wave-ripple complexes (SPW-R). In addition, choline reduces synaptic transmission between hippocampal subfields. These effects are mediated by direct activation of muscarinic as well as nicotinic cholinergic pathways. Together, choline turns out to be a potent regulator of patterned activity within hippocampal

  11. Disruption of perineuronal nets increases the frequency of sharp wave ripple events.

    Science.gov (United States)

    Sun, Zhi Yong; Bozzelli, P Lorenzo; Caccavano, Adam; Allen, Megan; Balmuth, Jason; Vicini, Stefano; Wu, Jian-Young; Conant, Katherine

    2018-01-01

    Hippocampal sharp wave ripples (SWRs) represent irregularly occurring synchronous neuronal population events that are observed during phases of rest and slow wave sleep. SWR activity that follows learning involves sequential replay of training-associated neuronal assemblies and is critical for systems level memory consolidation. SWRs are initiated by CA2 or CA3 pyramidal cells (PCs) and require initial excitation of CA1 PCs as well as participation of parvalbumin (PV) expressing fast spiking (FS) inhibitory interneurons. These interneurons are relatively unique in that they represent the major neuronal cell type known to be surrounded by perineuronal nets (PNNs), lattice like structures composed of a hyaluronin backbone that surround the cell soma and proximal dendrites. Though the function of the PNN is not completely understood, previous studies suggest it may serve to localize glutamatergic input to synaptic contacts and thus influence the activity of ensheathed cells. Noting that FS PV interneurons impact the activity of PCs thought to initiate SWRs, and that their activity is critical to ripple expression, we examine the effects of PNN integrity on SWR activity in the hippocampus. Extracellular recordings from the stratum radiatum of horizontal murine hippocampal hemisections demonstrate SWRs that occur spontaneously in CA1. As compared with vehicle, pre-treatment (120 min) of paired hemislices with hyaluronidase, which cleaves the hyaluronin backbone of the PNN, decreases PNN integrity and increases SWR frequency. Pre-treatment with chondroitinase, which cleaves PNN side chains, also increases SWR frequency. Together, these data contribute to an emerging appreciation of extracellular matrix as a regulator of neuronal plasticity and suggest that one function of mature perineuronal nets could be to modulate the frequency of SWR events. © 2017 Wiley Periodicals, Inc.

  12. Uniform nano-ripples on the sidewall of silicon carbide micro-hole fabricated by femtosecond laser irradiation and acid etching

    Energy Technology Data Exchange (ETDEWEB)

    Khuat, Vanthanh [Key Laboratory for Physical Electronics and Devices of the Ministry of Education and Collaborative Innovation Center of Suzhou Nano Science and Technology, School of Electronics and Information Engineering, Xi' an Jiaotong University, No. 28, Xianning West Road, Xi' an 710049 (China); Le Quy Don Technical University, No. 100, Hoang Quoc Viet Street, Hanoi 7EN-248 (Viet Nam); Chen, Tao; Gao, Bo; Si, Jinhai, E-mail: jinhaisi@mail.xjtu.edu.cn; Ma, Yuncan; Hou, Xun [Key Laboratory for Physical Electronics and Devices of the Ministry of Education and Collaborative Innovation Center of Suzhou Nano Science and Technology, School of Electronics and Information Engineering, Xi' an Jiaotong University, No. 28, Xianning West Road, Xi' an 710049 (China)

    2014-06-16

    Uniform nano-ripples were observed on the sidewall of micro-holes in silicon carbide fabricated by 800-nm femtosecond laser and chemical selective etching. The morphology of the ripple was analyzed using scanning electronic microscopy. The formation mechanism of the micro-holes was attributed to the chemical reaction of the laser affected zone with mixed solution of hydrofluoric acid and nitric acid. The formation of nano-ripples on the sidewall of the holes could be attributed to the standing wave generated in z direction due to the interference between the incident wave and the reflected wave.

  13. A dual mode operated boost inverter and its control strategy for ripple current reduction in single-phase uninterruptible power supplies

    DEFF Research Database (Denmark)

    Tang, Y.; Yao, W.; Blaabjerg, Frede

    2015-01-01

    In single-phase uninterruptible power supply (UPS) applications, it is well known that the AC side instantaneous power is not constant by nature. The resulting input current from the DC source side will inevitably contain low frequency ripple components that may largely deteriorate the system...... as active power conversion, while its CM operation is controlled in such a way that the low frequency ripple current on the DC side can be maintained in a minimum level. The proposed ripple current reduction method may not only work with linear loads, but also nonlinear loads, where more sophisticated...

  14. Flow ripple reduction of an axial piston pump by a combination of cross-angle and pressure relief grooves: Analysis and optimization

    International Nuclear Information System (INIS)

    Xu, Bing; Ye, Shaogan; Zhang, Junhui; Zhang, Chunfeng

    2016-01-01

    This paper investigates the potential of flow ripple reduction of an axial piston pump by a combination of cross-angle and pressure relief grooves. A dynamic model is developed to analyze the pumping dynamics of the pump and validated by experimental results. The effects of cross-angle on the flow ripples in the outlet and inlet ports, and the piston chamber pressure are investigated. The effects of pressure relief grooves on the optimal solutions obtained by a multi-objective optimization method are identified. A sensitivity analysis is performed to investigate the sensitivity of cross-angle to different working conditions. The results reveal that the flow ripples from the optimal solutions are smaller using the cross-angle and pressure relief grooves than those using the cross-angle and ordinary precompression and decompression angles and the cross-angle can be smaller. In addition, when the optimal design is used, the outlet flow ripples sensitivity can be reduced significantly.

  15. Analysis and Speed Ripple Mitigation of a Space Vector Pulse Width Modulation-Based Permanent Magnet Synchronous Motor with a Particle Swarm Optimization Algorithm

    Directory of Open Access Journals (Sweden)

    Xing Liu

    2016-11-01

    Full Text Available A method is proposed for reducing speed ripple of permanent magnet synchronous motors (PMSMs controlled by space vector pulse width modulation (SVPWM. A flux graph and mathematics are used to analyze the speed ripple characteristics of the PMSM. Analysis indicates that the 6P (P refers to pole pairs of the PMSM time harmonic of rotor mechanical speed is the main harmonic component in the SVPWM control PMSM system. To reduce PMSM speed ripple, harmonics are superposed on a SVPWM reference signal. A particle swarm optimization (PSO algorithm is proposed to determine the optimal phase and multiplier coefficient of the superposed harmonics. The results of a Fourier decomposition and an optimized simulation model verified the accuracy of the analysis as well as the effectiveness of the speed ripple reduction methods, respectively.

  16. Características físico-químicas de las dunitas serpentinizadas de la región de Moa-Baracoa (zonas Amores y Miraflores

    Directory of Open Access Journals (Sweden)

    María C. Ramírez-Pérez

    2000-03-01

    Full Text Available Los principales resultados de la caracterización físico-química y mineralógica de las dunitas serpentinizadas de las zonas de Amores y Miraflores en la región de Moa-Baracoa, se exponen en este trabajo. Se demuestra la presencia de minerales del grupo de la serpentina, principalmente antigorita, debido al proceso de serpentinización que ha afectado a estas rocas, y su transformación en fase forsterita luego de su calentamiento. Estos aspectos revisten especial importancia para las investigaciones que en la actualidad se realizan con estas litologías para su empleo como material refractario

  17. Impact of typical steady-state conditions and transient conditions on flow ripple and its test accuracy for axial piston pump

    Science.gov (United States)

    Xu, Bing; Hu, Min; Zhang, Junhui

    2015-09-01

    The current research about the flow ripple of axial piston pump mainly focuses on the effect of the structure of parts on the flow ripple. Therein, the structure of parts are usually designed and optimized at rated working conditions. However, the pump usually has to work in large-scale and time-variant working conditions. Therefore, the flow ripple characteristics of pump and analysis for its test accuracy with respect to variant steady-state conditions and transient conditions in a wide range of operating parameters are focused in this paper. First, a simulation model has been constructed, which takes the kinematics of oil film within friction pairs into account for higher accuracy. Afterwards, a test bed which adopts Secondary Source Method is built to verify the model. The simulation and tests results show that the angular position of the piston, corresponding to the position where the peak flow ripple is produced, varies with the different pressure. The pulsating amplitude and pulsation rate of flow ripple increase with the rise of pressure and the variation rate of pressure. For the pump working at a constant speed, the flow pulsation rate decreases dramatically with the increasing speed when the speed is less than 27.78% of the maximum speed, subsequently presents a small decrease tendency with the speed further increasing. With the rise of the variation rate of speed, the pulsating amplitude and pulsation rate of flow ripple increase. As the swash plate angle augments, the pulsating amplitude of flow ripple increases, nevertheless the flow pulsation rate decreases. In contrast with the effect of the variation of pressure, the test accuracy of flow ripple is more sensitive to the variation of speed. It makes the test accuracy above 96.20% available for the pulsating amplitude of pressure deviating within a range of ±6% from the mean pressure. However, with a variation of speed deviating within a range of ±2% from the mean speed, the attainable test

  18. Ripple Field AC Losses in 10-MW Wind Turbine Generators With a MgB2 Superconducting Field Winding

    DEFF Research Database (Denmark)

    Liu, Dong; Polinder, Henk; Magnusson, Niklas

    2016-01-01

    Superconducting (SC) synchronous generators are proposed as a promising candidate for 10-20-MW direct-drive wind turbines because they can have low weights and small sizes. A common way of designing an SC machine is to use SC wires with high current-carrying capability in the dc field winding...... and the ac armature winding is made with copper conductors. In such generators, the dc field winding is exposed to ac magnetic field ripples due to space harmonics from the armature. In generator design phases, the ac loss caused by these ripple fields needs to be evaluated to avoid local overheating...... and an excessive cooling budget. To determine the applicability of different design solutions in terms of ac losses, this paper estimates the ac loss level of 10-MW wind generator designs employing a MgB2 SC field winding. The effects on ac losses are compared between nonmagnetic and ferromagnetic teeth...

  19. Multiphase soft switched DC/DC converter and active control technique for fuel cell ripple current elimination

    Science.gov (United States)

    Lai, Jih-Sheng; Liu, Changrong; Ridenour, Amy

    2009-04-14

    DC/DC converter has a transformer having primary coils connected to an input side and secondary coils connected to an output side. Each primary coil connects a full-bridge circuit comprising two switches on two legs, the primary coil being connected between the switches on each leg, each full-bridge circuit being connected in parallel wherein each leg is disposed parallel to one another, and the secondary coils connected to a rectifying circuit. An outer loop control circuit that reduces ripple in a voltage reference has a first resistor connected in series with a second resistor connected in series with a first capacitor which are connected in parallel with a second capacitor. An inner loop control circuit that reduces ripple in a current reference has a third resistor connected in series with a fourth resistor connected in series with a third capacitor which are connected in parallel with a fourth capacitor.

  20. A new technique to detect antibody-antigen reaction (biological interactions) on a localized surface plasmon resonance (LSPR) based nano ripple gold chip

    Energy Technology Data Exchange (ETDEWEB)

    Saleem, Iram, E-mail: iiram.qau@gmail.com [Department of Physics and Texas Center for Superconductivity, University of Houston, Houston, TX 77204 (United States); Widger, William, E-mail: widger@uh.edu [Department of Biology and Biochemistry and Texas Center for Superconductivity, University of Houston, Houston, TX 77204 (United States); Chu, Wei-Kan, E-mail: wkchu@uh.edu [Department of Physics and Texas Center for Superconductivity, University of Houston, Houston, TX 77204 (United States)

    2017-07-31

    Highlights: • The nano ripple LSPR chip has monolayer molecule-coating sensitivity and specific selectivity. • Gold nano-ripple sensing chip is a low cost, and a label-free method for detecting the antibody-antigen reaction. • The plasmonic resonance shift depends upon the concentration of the biomolecules attached on the surface of the nano ripple pattern. - Abstract: We demonstrate that the gold nano-ripple localized surface plasmon resonance (LSPR) chip is a low cost and a label-free method for detecting the presence of an antigen. A uniform stable layer of an antibody was coated on the surface of a nano-ripple gold pattern chip followed by the addition of different concentrations of the antigen. A red shift was observed in the LSPR spectral peak caused by the change in the local refractive index in the vicinity of the nanostructure. The LSPR chip was fabricated using oblique gas cluster ion beam (GCIB) irradiation. The plasmon-resonance intensity of the scattered light was measured by a simple optical spectroscope. The gold nano ripple chip shows monolayer scale sensitivity and high selectivity. The LSPR substrate was used to detect antibody-antigen reaction of rabbit X-DENTT antibody and DENTT blocking peptide (antigen).

  1. Theoretical study of flow ripple for an aviation axial-piston pump with damping holes in the valve plate

    OpenAIRE

    Guan, Changbin; Jiao, Zongxia; He, Shouzhan

    2014-01-01

    Based on the structure of a certain type of aviation axial-piston pump’s valve plate which adopts a pre-pressurization fluid path (consisting a damping hole, a buffer chamber, and an orifice) to reduce flow ripple, a single-piston model of the aviation axial-piston pump is presented. This single-piston model comprehensively considers fluid compressibility, orifice restriction effect, fluid resistance in the capillary tube, and the leakage flow. Besides, the instantaneous discharge areas used ...

  2. Measurements of the ripple effect and geometric distribution of switched gradient fields inside a magnetic resonance scanner.

    Science.gov (United States)

    Sundström, Henrik; Mild, Kjell Hansson; Wilén, Jonna

    2015-02-01

    Knowledge of patient exposure during magnetic resonance imaging (MRI) procedures is limited, and the need for such knowledge has been demonstrated in recent in vitro and in vivo studies of the genotoxic effects of MRI. This study focuses on the dB/dt of the switched gradient field (SGF) and its geometric distribution. These values were characterized by measuring the peak dB/dt generated by a programmed gradient current of alternating triangles inside a 1.5T MR scanner. The maximum dB/dt exposure to the gradient field was 6-14 T/s, and this occurred at the edges of the field of view (FOV) 20-25 cm from the isocenter in the longitudinal direction. The dB/dt exposure dropped off to roughly half the maximum (3-7 T/s) at the edge of the bore. It was found that the dB/dt of the SGF was distorted by a 200 kHz ripple arising from the amplifier. The ripple is small in terms of B-field, but the high frequency content contributes to a peak dB/dt up to 18 times larger than that predicted by the slew rate (4 T/s m) and the distance from the isocenter. Measurements on a 3 T MRI scanner, however, revealed a much smaller filtered ripple of 100 kHz in dB/dt. These findings suggest that the gradient current to each coil together with information on the geometrical distribution of the gradient field and ripple effects could be used to assess the SGF exposure within an MRI bore. © 2014 Wiley Periodicals, Inc.

  3. Comparison of the Spectral-Temporally Modulated Ripple Test With the Arizona Biomedical Institute Sentence Test in Cochlear Implant Users.

    Science.gov (United States)

    Lawler, Marshall; Yu, Jeffrey; Aronoff, Justin M

    Although speech perception is the gold standard for measuring cochlear implant (CI) users' performance, speech perception tests often require extensive adaptation to obtain accurate results, particularly after large changes in maps. Spectral ripple tests, which measure spectral resolution, are an alternate measure that has been shown to correlate with speech perception. A modified spectral ripple test, the spectral-temporally modulated ripple test (SMRT) has recently been developed, and the objective of this study was to compare speech perception and performance on the SMRT for a heterogeneous population of unilateral CI users, bilateral CI users, and bimodal users. Twenty-five CI users (eight using unilateral CIs, nine using bilateral CIs, and eight using a CI and a hearing aid) were tested on the Arizona Biomedical Institute Sentence Test (AzBio) with a +8 dB signal to noise ratio, and on the SMRT. All participants were tested with their clinical programs. There was a significant correlation between SMRT and AzBio performance. After a practice block, an improvement of one ripple per octave for SMRT corresponded to an improvement of 12.1% for AzBio. Additionally, there was no significant difference in slope or intercept between any of the CI populations. The results indicate that performance on the SMRT correlates with speech recognition in noise when measured across unilateral, bilateral, and bimodal CI populations. These results suggest that SMRT scores are strongly associated with speech recognition in noise ability in experienced CI users. Further studies should focus on increasing both the size and diversity of the tested participants, and on determining whether the SMRT technique can be used for early predictions of long-term speech scores, or for evaluating differences among different stimulation strategies or parameter settings.

  4. Intra- and interregional cortical interactions related to sharp-wave ripples and dentate spikes.

    Science.gov (United States)

    Headley, Drew B; Kanta, Vasiliki; Paré, Denis

    2017-02-01

    The hippocampus generates population events termed sharp-wave ripples (SWRs) and dentate spikes (DSs). While little is known about DSs, SWR-related hippocampal discharges during sleep are thought to replay prior waking activity, reactivating the cortical networks that encoded the initial experience. During slow-wave sleep, such reactivations likely occur during up-states, when most cortical neurons are depolarized. However, most studies have examined the relationship between SWRs and up-states measured in single neocortical regions. As a result, it is currently unclear whether SWRs are associated with particular patterns of widely distributed cortical activity. Additionally, no such investigation has been carried out for DSs. The present study addressed these questions by recording SWRs and DSs from the dorsal hippocampus simultaneously with prefrontal, sensory (visual and auditory), perirhinal, and entorhinal cortices in naturally sleeping rats. We found that SWRs and DSs were associated with up-states in all cortical regions. Up-states coinciding with DSs and SWRs exhibited increased unit activity, power in the gamma band, and intraregional gamma coherence. Unexpectedly, interregional gamma coherence rose much more strongly in relation to DSs than to SWRs. Whereas the increase in gamma coherence was time locked to DSs, that seen in relation to SWRs was not. These observations suggest that SWRs are related to the strength of up-state activation within individual regions throughout the neocortex but not so much to gamma coherence between different regions. Perhaps more importantly, DSs coincided with stronger periods of interregional gamma coherence, suggesting that they play a more important role than previously assumed. Off-line cortico-hippocampal interactions are thought to support memory consolidation. We surveyed the relationship between hippocampal sharp-wave ripples (SWRs) and dentate spikes (DSs) with up-states across multiple cortical regions. SWRs and

  5. Speed control with torque ripple reduction of switched reluctance motor by Hybrid Many Optimizing Liaison Gravitational Search technique

    Directory of Open Access Journals (Sweden)

    Nutan Saha

    2017-06-01

    Full Text Available This paper presents a control scheme for simultaneous control of the speed of Switched Reluctance Motor (SRM and minimizing the torque ripple employing Hybrid Many Optimizing Liaison Gravitational Search Algorithm (Hybrid MOLGSA technique. The control mechanism includes two controlling loops, the outer loop is governed for speed control and a current controller for the inner loop, intelligent selection of turn on and turn off angle for a 60 KW, 3-phase 6/8 SRM. It is noticed that the torque ripple coefficient, ISE of speed & current are reduced by 12.81%, 38.60%, 16.74% respectively by Hybrid MOLGSA algorithm compared to Gravitational Search Algorithm (GSA algorithm. It is also observed that the settling times for the controller using the parameter values for obtaining best values of torque ripple, Integral square error of speed and current are reduced by 51.25%, 58.04% and 59.375% by proposed Hybrid MOLGSA algorithm compared to the GSA algorithm.

  6. Source of spill ripple in the RF-KO slow-extraction method with FM and AM

    CERN Document Server

    Noda, K; Shibuya, S; Muramatsu, M; Uesugi, T; Kanazawa, M; Torikoshi, M; Takada, E; Yamada, S

    2002-01-01

    The RF-knockout (RF-KO) slow-extraction method with frequency modulation (FM) and amplitude modulation (AM) has brought high-accuracy irradiation to the treatment of a cancer tumor moving with respiration, because of a quick response to beam start/stop. However, a beam spill extracted from a synchrotron ring through RF-KO slow-extraction has a huge ripple with a frequency of around 1 kHz related to the FM. The spill ripple will disturb the lateral dose distribution in the beam scanning methods. Thus, the source of the spill ripple has been investigated through experiments and simulations. There are two tune regions for the extraction process through the RF-KO method: the extraction region and the diffusion region. The particles in the extraction region can be extracted due to amplitude growth through the transverse RF field, only when its frequency matches with the tune in the extraction region. For a large chromaticity, however, the particles in the extraction region can be extracted through the synchrotron ...

  7. FUeW opts for wireless centralised ripple control systems; Das FUeW entscheidet sich fuer Funk-Rundsteuerung

    Energy Technology Data Exchange (ETDEWEB)

    Fuchs, G [Fraenkische Ueberlandwerk AG, Nuernberg (Germany); Saupe, R [EFR Europaeische Funk-Rundsteuerung GmbH, Berlin (Germany)

    1996-01-15

    After extensive trials in the course of a project study Fraenkische Ueberlandwerk AG (FUeW) has decided to introduce a wireless centralised ripple control system for its entire service area. The system will initially be used for synchronising and parameterising multiple tariff meters. Ripple control receivers are to take over the function formerly perfomed by switch clocks of switching between night and day tariff. FUeW`s decision was essentially motivated by the proven reliability of wireless centralised ripple control systems and by the economic advantages of this modern technology. (orig.) [Deutsch] Die Fraenkische Ueberlandwerk AG (FUeW), Nuernberg, hat nach umfangreichen Versuchen im Rahmen einer Projektstudie entschieden, die Funk-Rundsteuerung flaechendeckend im Versorgungsgebiet einzusetzen. Das System wird zunaechst zur Synchronisierung und Parametrierung von Mehrtarifzaehlern angewendet. Wurde bisher die HT/NT-Umschaltung der Zaehler durch Schaltuhren durchgefuehrt, so wird kuenftig ein Funk-Rundsteuerempfaenger diese Aufgabe uebernehmen. Wesentlich fuer die Entscheidung des FUeW waren die bewiesene Funktionssicherheit der Funk-Rundsteuerung und die wirtschaftlichen Vorteile, die sich durch den Einsatz dieser modernen Technik ergeben. (orig.)

  8. A Controlled Design of Ripple-Like Polyamide-6 Nanofiber/Nets Membrane for High-Efficiency Air Filter.

    Science.gov (United States)

    Zhang, Shichao; Liu, Hui; Zuo, Fenglei; Yin, Xia; Yu, Jianyong; Ding, Bin

    2017-03-01

    The filtration capacity of fibrous media for airborne particles is restricted by their thick diameter, low porosity, and limited frontal area. The ability to solve this problem would have broad technological implications for various air filtration applications; despite many past efforts, it remains a great challenge to achieve. Herein, a facile and scalable strategy to fabricate the ripple-like polyamide-6 nanofiber/nets (PA-6 NF/N) air filter via combining electrospinning/netting technique with receiving substrate design is demonstrated. This proposed approach allows the scaffold filaments to orderly embed into 2D PA-6 nanonets layer with Steiner-tree structures and nanoscale diameter of ≈20 nm, resulting in the ripple-like membrane with extremely small pore size, highly porous structure, and hugely extended frontal surface, by facilely adjusting its pleat span and pleat pitch. These unique structural advantages enable the ripple-like PA-6 NF/N filter to filtrate the ultrafine particles with high removal efficiency of 99.996%, low air resistance of 95 Pa, and robust quality factor of >0.11 Pa -1 ; using its superlight weight of 0.9 g m -2 and physical sieving manner. This approach has the potentialities to give rise to a novel generation of filter media displaying enhanced filtration capacity for various applications thanks to their nanoscale features and designed macrostructures. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Bi-frontal transcranial alternating current stimulation in the ripple range reduced overnight forgetting

    Directory of Open Access Journals (Sweden)

    Géza Gergely eAmbrus

    2015-09-01

    Full Text Available High frequency oscillations in the hippocampal structures recorded during sleep have been proved to be essential for long-term episodic memory consolidation in both animals and in humans. The aim of this study was to test if transcranial Alternating Current Stimulation (tACS of the dorsolateral prefrontal cortex (DLPFC in the hippocampal ripple range, applied bi-frontally during encoding, could modulate declarative memory performance, measured immediately after encoding, and after a night’s sleep. An associative word-pair learning test, taken from Marshall and colleagues, was used. During an evening encoding phase, participants received 1 mA 140 Hz tACS or sham stimulation over both DLPFCs for 10 minutes while being presented twice with a list of word-pairs. Cued recall performance was investigated 10 minutes after training and the morning following the training session. Forgetting from evening to morning was observed in the sham condition, but not in the 140 Hz stimulation condition. 140 Hz tACS during encoding may have an effect on the consolidation of declarative material.

  10. Ripple transport in helical-axis advanced stellarators - a comparison with classical stellarator/torsatrons

    International Nuclear Information System (INIS)

    Beidler, C.D.; Hitchon, W.N.G.

    1993-08-01

    Calculations of the neoclassical transport rates due to particles trapped in the helical ripples of a stellarator's magnetic field are carried out, based on solutions of the bounce-averaged kinetic equation. These calculations employ a model for the magnetic field strength, B, which is an accurate approximation to the actual B for a wide variety of stellarator-type devices, among which are Helical-Axis Advanced Stellarators (Helias) as well as conventional stellarators and torsatrons. Comparisons are carried out in which it is shown that the Helias concept leads to significant reductions in neoclassical transport rates throughout the entire long-mean-free-path regime, with the reduction being particularly dramatic in the ν -1 regime. These findings are confirmed by numerical simulations. Further, it is shown that the behavior of deeply trapped particles in Helias can be fundamentally different from that in classical stellarator/torsatrons; as a consequence, the beneficial effects of a radial electric field on the transport make themselves felt at lower collision frequency than is usual. (orig.)

  11. Edge plasma physics modifications due to magnetic ripple in RFX-mod

    International Nuclear Information System (INIS)

    Scarin, P.; Agostini, M.; Carraro, L.; Cavazzana, R.; Ciaccio, G.; De Masi, G.; Spizzo, G.; Spolaore, M.; Vianello, N.

    2015-01-01

    The edge of the RFX-mod (R = 2 m, a = 0.46 m) Reversed Field Pinch is characterized by weak magnetic chaos affecting ion and electron diffusion. Edge particle transport is strongly influenced by a toroidal asymmetry caused by magnetic islands. An ambipolar radial electric field ensures local neutrality and possesses the same symmetry as the parent magnetic ripple: the result is the modulation of the perpendicular flow, with a slowing-down at the island X-point. In this paper we present a complete statistical analysis, over a large database of RFX-mod discharges, of the edge properties as they are modified by the magnetic topology: the plasma wall footprint follows the helical shape of the dominant central mode (m/n = 1/7), with an increase of H α emission and electron density corresponding to the O-point of the inner magnetic island. Edge turbulence is modified by the magnetic topology, being generated in the O-point region and damped near the X-point

  12. The ripples of "The Big (agricultural) Bang": the spread of early wheat cultivation.

    Science.gov (United States)

    Abbo, Shahal; Gopher, Avi; Peleg, Zvi; Saranga, Yehoshua; Fahima, Tzion; Salamini, Francesco; Lev-Yadun, Simcha

    2006-08-01

    Demographic expansion and (or) migrations leave their mark in the pattern of DNA polymorphisms of the respective populations. Likewise, the spread of cultural phenomena can be traced by dating archaeological finds and reconstructing their direction and pace. A similar course of events is likely to have taken place following the "Big Bang" of the agricultural spread in the Neolithic Near East from its core area in southeastern Turkey. Thus far, no attempts have been made to track the movement of the founder genetic stocks of the first crop plants from their core area based on the genetic structure of living plants. In this minireview, we re-interpret recent wheat DNA polymorphism data to detect the genetic ripples left by the early wave of advance of Neolithic wheat farming from its core area. This methodology may help to suggest a model charting the spread of the first farming phase prior to the emergence of truly domesticated wheat types (and other such crops), thereby increasing our resolution power in studying this revolutionary period of human cultural, demographic, and social evolution.

  13. Efficiency improvement and torque ripple minimization of Switched Reluctance Motor using FEM and Seeker Optimization Algorithm

    International Nuclear Information System (INIS)

    Navardi, Mohammad Javad; Babaghorbani, Behnaz; Ketabi, Abbas

    2014-01-01

    Highlights: • This paper proposes a new method to optimize a Switched Reluctance Motor (SRM). • A combination of SOA and GA with Finite Element Method (FEM) analysis is employed to solve the SRM design optimization. • The results show that optimized SRM obtains higher average torque and higher efficiency. - Abstract: In this paper, performance optimization of Switched Reluctance Motor (SRM) was determined using Seeker Optimization Algorithm (SOA). The most efficient aim of the algorithm was found for maximum torque value at a minimum mass of the entire construction, following changing the geometric parameters. The optimization process was carried out using a combination of Seeker Optimization Algorithm and Finite Element Method (FEM). Fitness value was calculated by FEM analysis using COMSOL3.4, and the SOA was realized by MATLAB. The proposed method has been applied for a case study and it has been also compared with Genetic Algorithm (GA). The results show that the optimized motor using SOA had higher torque value and efficiency with lower mass and torque ripple, exhibiting the validity of this methodology for SRM design

  14. A third-order class-D amplifier with and without ripple compensation

    Science.gov (United States)

    Cox, Stephen M.; du Toit Mouton, H.

    2018-06-01

    We analyse the nonlinear behaviour of a third-order class-D amplifier, and demonstrate the remarkable effectiveness of the recently introduced ripple compensation (RC) technique in reducing the audio distortion of the device. The amplifier converts an input audio signal to a high-frequency train of rectangular pulses, whose widths are modulated according to the input signal (pulse-width modulation) and employs negative feedback. After determining the steady-state operating point for constant input and calculating its stability, we derive a small-signal model (SSM), which yields in closed form the transfer function relating (infinitesimal) input and output disturbances. This SSM shows how the RC technique is able to linearise the small-signal response of the device. We extend this SSM through a fully nonlinear perturbation calculation of the dynamics of the amplifier, based on the disparity in time scales between the pulse train and the audio signal. We obtain the nonlinear response of the amplifier to a general audio signal, avoiding the linearisation inherent in the SSM; we thereby more precisely quantify the reduction in distortion achieved through RC. Finally, simulations corroborate our theoretical predictions and illustrate the dramatic deterioration in performance that occurs when the amplifier is operated in an unstable regime. The perturbation calculation is rather general, and may be adapted to quantify the way in which other nonlinear negative-feedback pulse-modulated devices track a time-varying input signal that slowly modulates the system parameters.

  15. Air Entrainment and Surface Ripples in a Turbulent Ship Hull Boundary Layer

    Science.gov (United States)

    Masnadi, Naeem; Erinin, Martin; Duncan, James H.

    2017-11-01

    The air entrainment and free-surface fluctuations caused by the interaction of a free surface and the turbulent boundary layer of a vertical surface-piercing plate is studied experimentally. In this experiment, a meter-wide stainless steel belt travels horizontally in a loop around two rollers with vertically oriented axes. This belt device is mounted inside a large water tank with the water level set just below the top edge of the belt. The belt, rollers, and supporting frame are contained within a sheet metal box to keep the device dry except for one 6-meter-long straight test section. The belt is accelerated suddenly from rest until reaching constant speed in order to create a temporally evolving boundary layer analogous to the spatially evolving boundary layer that would exist along a surface-piercing towed flat plate. Surface ripples are measured using a cinematic laser-induced fluorescence technique with the laser sheet oriented parallel or normal to the belt surface. Air entrainment events and bubble motions are recorded from underneath the water surface using a stereo imaging system. Measurements of small bubbles, that tend to stay submerged for a longer time, are planned via a high-speed digital in-line holographic system. The support of the Office of Naval Research is gratefully acknowledged.

  16. Screening conditions in a magnetized plasma with electron beam, with application to ripple trapped electron losses

    Energy Technology Data Exchange (ETDEWEB)

    Faudot, E.; Heuraux, S. [Nancy-1 Univ. Henri Poincare, LPMIA, UMR CNRS 7040, 54 (France); Colas, L.; Saint-Laurent, F.; Martin, G.; Basiuk, V. [Association Euratom-CEA Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee

    2004-07-01

    In Tore Supra, electrons are accelerated by lower hybrid waves in the direction parallel to the confinement magnetic field, in order to drive non-inductive current. But electrons have also on increase of their perpendicular velocity, then 10% of the most energetic electrons get trapped in the magnetic ripple between 2 adjacent toroidal coils, thus forming a beam. The electron beam follows a banana trajectory, the 20 mm wide protection represented by a cooled copper tube is assumed to protect the VP entrance from this energetic flux. Nevertheless, this beam is able to go beyond the copper tube and creates a hot spot on the steel panel edge able to melt the metal. Heat fluxes deposition on the vertical port (VP) can be understood with a beam+sheath theory including the fact that the sheaths can be obstructed when their length becomes greater than flux tube length. By this way, we identify 4 deposition regimes: 2 free sheath regimes and 2 obstructed sheath regimes. Beam flux deposits either at the entrance of the VP along first 2 cm behind the copper tube or until the end of the VP when beam flux is high and for free sheath. Obstructed sheaths make the repulsive, potential for electrons decrease and so accelerate the flux deposition. (authors)

  17. Ferritic insertion for reduction of toroidal magnetic field ripple on JT-60U

    International Nuclear Information System (INIS)

    Shinohara, K.; Sakurai, S.; Ishikawa, M.; Tsuzuki, K.; Suzuki, Y.; Masaki, K.; Naito, O.; Kurihara, K.; Suzuki, T.; Koide, Y.; Fujita, T.; Miura, Y.

    2007-01-01

    Ferritic steel tiles (FSTs) have been installed to improve the energetic ion confinement by reducing a toroidal magnetic field ripple. Aiming at cost-effective installation, orbit-following calculations of energetic ions were carried out for a design of the installation of ferritic steel on the JT-60U by using the fully three dimensional magnetic field orbit-following Monte-Carlo (F3D OFMC) code, which had been developed for ferritic insert experiments on the JFT-2M and can treat the complex magnetic field structure produced by ferritic inserts. The installed FSTs add a non-linear magnetic field on magnetic sensors for plasma control and an equilibrium calculation. The code for real-time control has been modified to take into account the magnetic field by the FSTs. The plasma operation was successfully resumed after usual conditioning processes and real-time plasma control was successfully carried out. The heat load measurement indicates the improved confinement of energetic ions. These results are important for practical application of the ferritic steel, which is a leading candidate of a structural material on a DEMO reactor

  18. Frequency-Controlled Current-Fed Resonant Converter with No Input Ripple Current

    Directory of Open Access Journals (Sweden)

    Bor-Ren Lin

    2018-02-01

    Full Text Available This paper studies a frequency-controlled current-fed resonant circuit. The adopted direct current (DC-to-DC converter contains two boost circuits and a resonant circuit on the primary side. First, two boost circuits are connected in parallel to achieve voltage step-up and reduce input ripple current by using interleaved pulse-width modulation. Therefore, the size and current rating of boost inductors are decreased in the proposed converter. Second, the boost voltage is connected to the resonant circuit to realize the mechanism of the zero-voltage switching of all active switches and zero-current switching of all diodes. Two boost circuits and a resonant circuit use the same power devices in order to lessen the switch counts. The voltage doubler topology is adopted on the secondary side (high-voltage side. Therefore, the voltage rating of diodes on the high-voltage side is clamped at output voltage. The feasibility of the studied circuit is confirmed by the experimental tests with a 1 kW prototype circuit.

  19. Anthropogenic halo disturbances alter landscape and plant richness: a ripple effect.

    Science.gov (United States)

    Liu, Bingliang; Su, Jinbao; Chen, Jianwei; Cui, Guofa; Ma, Jianzhang

    2013-01-01

    Although anthropogenic landscape fragmentation is often considered as the primary threat to biodiversity, other factors such as immediate human disturbances may also simultaneously threaten species persistence in various ways. In this paper, we introduce a conceptual framework applied to recreation landscapes (RLs), with an aim to provide insight into the composite influences of landscape alteration accompanying immediate human disturbances on plant richness dynamics. These impacts largely occur at patch-edges. They can not only alter patch-edge structure and environment, but also permeate into surrounding natural matrices/patches affecting species persistence-here we term these "Halo disturbance effects" (HDEs). We categorized species into groups based on seed or pollen dispersal mode (animal- vs. wind-dispersed) as they can be associated with species richness dynamics. We evaluated the richness of the two groups and total species in our experimental landscapes by considering the distance from patch-edge, the size of RLs and the intensity of human use over a six-year period. Our results show that animal-dispersed species decreased considerably, whereas wind-dispersed species increased while their richness presented diverse dynamics at different distances from patch-edges. Our findings clearly demonstrate that anthropogenic HDEs produce ripple effects on plant, providing an experimental interpretation for the diverse responses of species to anthropogenic disturbances. This study highlights the importance of incorporating these composite threats into conservation and management strategies.

  20. Anthropogenic halo disturbances alter landscape and plant richness: a ripple effect.

    Directory of Open Access Journals (Sweden)

    Bingliang Liu

    Full Text Available Although anthropogenic landscape fragmentation is often considered as the primary threat to biodiversity, other factors such as immediate human disturbances may also simultaneously threaten species persistence in various ways. In this paper, we introduce a conceptual framework applied to recreation landscapes (RLs, with an aim to provide insight into the composite influences of landscape alteration accompanying immediate human disturbances on plant richness dynamics. These impacts largely occur at patch-edges. They can not only alter patch-edge structure and environment, but also permeate into surrounding natural matrices/patches affecting species persistence-here we term these "Halo disturbance effects" (HDEs. We categorized species into groups based on seed or pollen dispersal mode (animal- vs. wind-dispersed as they can be associated with species richness dynamics. We evaluated the richness of the two groups and total species in our experimental landscapes by considering the distance from patch-edge, the size of RLs and the intensity of human use over a six-year period. Our results show that animal-dispersed species decreased considerably, whereas wind-dispersed species increased while their richness presented diverse dynamics at different distances from patch-edges. Our findings clearly demonstrate that anthropogenic HDEs produce ripple effects on plant, providing an experimental interpretation for the diverse responses of species to anthropogenic disturbances. This study highlights the importance of incorporating these composite threats into conservation and management strategies.