Pedestal Temperature Model for Type III ELMy H-mode Plasma

International Nuclear Information System (INIS)

Buangam, W.; Suwanna, S.; Onjun, T.; Poolyarat, N.; Picha, R.; Singhsomroje, W.

2009-07-01

Full text: It is widely known that the improved performance of H-mode plasma results mainly from a formation of the pedestal, which is a narrow region of strong pressure gradient near the edge of plasma. A predictive capability for the conditions at the top of the pedestal is important, especially for predictive simulations of future experiments. New models for predicting the temperature values at the top of the pedestal for type III ELMy H-mode plasma are developed by using two different approaches: a theory-based approaches and an empirical approach. For a theory-based approach, a model is developed based on the calculation of thermal energy in the pedestal region and on accepted scaling laws of energy confinement time. For an empirical model, a scaling law for pedestal temperature in terms of plasma controlled parameters, such as plasma current, magnetic field, heating power, is deduced from experimental data. Predictions from these models are compared with experimental data from the Pedestal International Database. Statistical quantities, such as Root-Mean Square Error (RMSE) and offset values, are computed to quantify the predictive capability of the models. It is found that the theory-based model predicts the pedestal temperature values moderately well yielding RMSE between 30% and 40%. The IPB98(y,3) scaling law yields with best agreement with RMSE of 30.4%. The empirical model predicts the pedestal temperature value with better agreement, yield RMSE of 25.9%

Theory of Rapid Formation of Pedestal and Pedestal width due to Anomalous Particle Pinch in the Edge of H-mode Discharges

Energy Technology Data Exchange (ETDEWEB)

Kaw, P.K., E-mail: kaw@ipr.res.in [Institute for Plasma Research, Bhat (India); Singh, R. [Institute for Plasma Research, Bhat (India); ITER Organization, Saint Paul-lez-Durance [France; Nordman, H. [Chamlers Institute of Technology, Goteborg (Sweden); Garbet, X.; Bourdelle, C. [CEA, Saint Paul-lez-Durance (France); Campbell, D.; Loarte, A.; Bora, D. [ITER Organization, Saint Paul-lez-Durance (France)

2012-09-15

Full text: A theory based on a turbulent particle pinch is proposed to explain the rapid formation of sharp density gradients in tokamak edge plasmas, in particular the pedestal region. The inward radial particle flux in the pedestal results from the interaction between small scale electron temperature gradient driven (ETG) turbulence and self-consistently formed 'electron geodesic acoustic modes' (el-GAMs). To address this phenomenon, the el-GAM modulational instability driven by the ETG turbulence background is studied. The ETG level of fluctuations and particle pinch are estimated through the back reaction of eGAMs on ETG turbulence. It is found that the particle pinch is quite sensitive to magnetic shear, safety factor, ratio of electron to ion temperatures and atomic mass number. In the absence of particle source in the pedestal, the density gradient length scale, of the order of the pedestal width, is estimated. It is shown that it is proportional to the major radius, up to some dependence on the poloidal beta. Moreover it does not depend on the normalized gyro-radius. This scaling agrees with DIII-D and JET similarity experiments. This dependence is favorable when extrapolated to the pedestal width in ITER in spite of its low normalized gyro radius. It is also shown that the density scale length becomes sharper by increasing the magnetic shear. A new H-mode pedestal pressure scaling is derived assuming that the pressure gradient is limited by the ballooning instability. (author)

Differences in the H-mode pedestal width of temperature and density

International Nuclear Information System (INIS)

Schneider, P A; Wolfrum, E; Günter, S; Kurzan, B; Lackner, K; Zohm, H; Groebner, R J; Osborne, T H; Ferron, J R; Snyder, P B; Beurskens, M N A; Dunne, M G

2012-01-01

A pedestal database was built using data from type-I ELMy H-modes of ASDEX Upgrade, DIII-D and JET. ELM synchronized pedestal data were analysed with the two-line method. The two-line method is a bilinear fit which shows better reproducibility of pedestal parameters than a modified hyperbolic tangent fit. This was tested with simulated and experimental data. The influence of the equilibrium reconstruction on pedestal parameters was investigated with sophisticated reconstructions from CLISTE and EFIT including edge kinetic profiles. No systematic deviation between the codes could be observed. The flux coordinate system is influenced by machine size, poloidal field and plasma shape. This will change the representation of the width in different coordinates, in particular, the two normalized coordinates Ψ N and r/a show a very different dependence on the plasma shape. The scalings derived for the pedestal width, Δ, of all machines suggest a different scaling for the electron temperature and the electron density. Both cases show similar dependence with machine size, poloidal magnetic field and pedestal electron temperature and density. The influence of ion temperature and toroidal magnetic field is different on each of Δ T e and Δ n e . In dimensionless form the density pedestal width in Ψ N scales with ρ 0.6 i* , the temperature pedestal width with β p,ped 0.5 . Both widths also show a strong correlation with the plasma shape. The shape dependence originates from the coordinate transformation and is not visible in real space. The presented scalings predict that in ITER the temperature pedestal will be appreciably wider than the density pedestal. (paper)

Comparison of H-mode pedestals in different confinement regimes in DIII-D

Energy Technology Data Exchange (ETDEWEB)

Groebner, R J [General Atomics, PO Box 85608, San Diego, California, 92186-5608 (United States); Leonard, A W [General Atomics, PO Box 85608, San Diego, California, 92186-5608 (United States); Luce, T C [General Atomics, PO Box 85608, San Diego, California, 92186-5608 (United States); Fenstermacher, M E [Lawrence Livermore National Laboratory, Livermore, California (United States); Jackson, G L [General Atomics, PO Box 85608, San Diego, California, 92186-5608 (United States); Osborne, T H [General Atomics, PO Box 85608, San Diego, California, 92186-5608 (United States); Thomas, D M [General Atomics, PO Box 85608, San Diego, California, 92186-5608 (United States); Wade, M R [General Atomics, PO Box 85608, San Diego, California, 92186-5608 (United States)

2006-05-15

A survey of global performance parameters and their correlation with pedestal parameters is performed for standard H-mode, QH-mode and the enhanced confinement regimes of VH-mode, hybrid and advanced tokamak in the DIII-D tokamak. This study shows that there is a trend for global confinement quality or global beta to increase as the pedestal electron pressure or beta increases. However, there are also improvements in core confinement and beta, observed at fixed pedestal pressure or beta, which indicate that factors other than pedestal parameters also contribute to the best core performance. Several other pedestal structure parameters are found to be similar among these regimes. The scale lengths for electron pressure in the pedestal are in the range 0.8-1.6 cm at the outer midplane, most {eta}{sub e} values are in the range 1-3 in the middle of the T{sub e} pedestal and the T{sub e} and n{sub e} pedestals tend to penetrate the same distance into the plasma.

Scaling of H-mode pedestal characteristics in DIII-D and C-Mod

International Nuclear Information System (INIS)

Granetz, R.S.; Boivin, R.L.; Osborne, T.H.

1999-01-01

Since the H-mode edge pedestal effectively sets the boundary conditions for energy transport throughout the core, a better understanding of the pedestal region is necessary in order to fully predict H-mode performance. Pedestal characteristics in the DIII-D and Alcator C-Mod tokamaks are described, and scalings of the pedestal width with various plasma parameters are shown. The pedestal width in both tokamaks varies in an inverse sense with plasma current, and is independent of toroidal field. Other similarities, as well as differences, are discussed. It is also found that the pedestal widths of the various physical quantities involved (T e , T i , n e , n i ) may be different. (author)

Physics of the Tokamak Pedestal, and Implications for Magnetic Fusion Energy

Science.gov (United States)

Snyder, Philip

2017-10-01

High performance in tokamaks is achieved via the spontaneous formation of a transport barrier in the outer few percent of the confined plasma. This narrow insulating layer, referred to as a ``pedestal,'' typically results in a >30x increase in pressure across a 0.4-5cm layer. Predicted fusion power scales with the square of the pedestal top pressure (or ``pedestal height''), hence a fusion reactor strongly benefits from a high pedestal, provided this can be attained without large Edge Localized Modes (ELMs), which may erode plasma facing materials. The overlap of drift orbit, turbulence, and equilibrium scales across this narrow layer leads to rich and complex physics, and challenges traditional analytic and computational approaches. We review studies employing gyrokinetic, neoclassical, MHD, and other methods, which have explored how a range of instabilities, influenced by complex geometry, and strong ExB flows and bootstrap current, drive transport across the pedestal and guide its structure and dynamics. Development of high resolution diagnostics, and coordinated experiments on several tokamaks, have validated understanding of important aspects of the physics, while highlighting open issues. A predictive model (EPED) has proven capable of predicting the pedestal height and width to 20-25% accuracy in large statistical studies. This model was used to predict a new, high pedestal ``Super H-Mode'' regime, which was subsequently discovered on DIII-D, and motivated experiments on Alcator C-Mod which achieved world record, reactor relevant pedestal pressure. We review open issues including improved formalism, particle and momentum transport, the role of neutrals and impurities, ELM control, and pedestal formation. Finally we discuss coupling pedestal and core predictive models to enable more comprehensive optimization of the tokamak fusion concept. Supported by the US DOE under DE-FG02-95ER54309, FC02-06ER54873, DE-FC02-04ER54698, DE-FC02-99ER54512.

Contribution to the multi-machine pedestal scaling from the COMPASS tokamak

Science.gov (United States)

Komm, M.; Bílková, P.; Aftanas, M.; Berta, M.; Böhm, P.; Bogár, O.; Frassinetti, L.; Grover, O.; Háček, P.; Havlicek, J.; Hron, M.; Imríšek, M.; Krbec, J.; Mitošínková, K.; Naydenkova, D.; Pánek, R.; Peterka, M.; Snyder, P. B.; Stefanikova, E.; Stöckel, J.; Sos, M.; Urban, J.; Varju, J.; Vondráček, P.; Weinzettl, V.; the COMPASS Team

2017-05-01

First systematic measurements of pedestal structure during Ohmic and NBI-assisted Type I ELMy H-modes were performed on the COMPASS tokamak in two dedicated experimental campaigns during 2015 and 2016. By adjusting the NBI heating and a toroidal magnetic field, the electron pedestal temperature was increased from 200 eV up to 300 eV, which allowed reaching pedestal collisionality ν \\text{ped}\\ast   <  1 at q95 ~3. COMPASS has approached conditions for the Identity experiment done at JET & DIII-D, complementing the range of scanned ρ \\text{ped}\\ast . The pedestal pressure was successfully reproduced by the EPED model. The dependence of pedestal pressure width on ν \\text{ped}\\ast and β \\text{ped ~ }\\text{pol} is discussed.

Magnetic-flutter-induced pedestal plasma transport

International Nuclear Information System (INIS)

Callen, J.D.; Hegna, C.C.; Cole, A.J.

2013-01-01

Plasma toroidal rotation can limit reconnection of externally applied resonant magnetic perturbation (RMP) fields δB on rational magnetic flux surfaces. Hence it causes the induced radial perturbations δB ρ to be small there, thereby inhibiting magnetic island formation and stochasticity at the top of pedestals in high (H-mode) confinement tokamak plasmas. However, the δB ρ s induced by RMPs increase away from rational surfaces and are shown to induce significant sinusoidal radial motion (flutter) of magnetic field lines with a radial extent that varies linearly with δB ρ and inversely with distance from the rational surface because of the magnetic shear. This produces a radial electron thermal diffusivity that is (1/2)(δB ρ /B 0 ) 2 times a kinetically derived, electron-collision-induced, magnetic-shear-reduced, effective parallel electron thermal diffusivity in the absence of magnetic stochasticity. These low collisionality flutter-induced transport processes and thin magnetic island effects are shown to be highly peaked in the vicinity of rational surfaces at the top of low collisionality pedestals. However, the smaller but finite level of magnetic-flutter-induced electron heat transport midway between rational surfaces is the primary factor that determines the electron temperature difference between rational surfaces at the pedestal top. The magnetic-flutter-induced non-ambipolar electron density transport can be large enough to push the plasma toward an electron density transport root. Requiring ambipolar density transport is shown to determine the radial electric field, the plasma toroidal rotation (via radial force balance), a reduced electron thermal diffusivity and increased ambipolar density transport in the pedestal. At high collisionality the various flutter effects are less strongly peaked at rational surfaces and generally less significant. They are thus less likely to exhibit flutter-induced resonant behaviour and transition toward an

Magnetic-flutter-induced pedestal plasma transport

Science.gov (United States)

Callen, J. D.; Hegna, C. C.; Cole, A. J.

2013-11-01

Plasma toroidal rotation can limit reconnection of externally applied resonant magnetic perturbation (RMP) fields δB on rational magnetic flux surfaces. Hence it causes the induced radial perturbations δBρ to be small there, thereby inhibiting magnetic island formation and stochasticity at the top of pedestals in high (H-mode) confinement tokamak plasmas. However, the δBρs induced by RMPs increase away from rational surfaces and are shown to induce significant sinusoidal radial motion (flutter) of magnetic field lines with a radial extent that varies linearly with δBρ and inversely with distance from the rational surface because of the magnetic shear. This produces a radial electron thermal diffusivity that is (1/2)(δBρ/B0)2 times a kinetically derived, electron-collision-induced, magnetic-shear-reduced, effective parallel electron thermal diffusivity in the absence of magnetic stochasticity. These low collisionality flutter-induced transport processes and thin magnetic island effects are shown to be highly peaked in the vicinity of rational surfaces at the top of low collisionality pedestals. However, the smaller but finite level of magnetic-flutter-induced electron heat transport midway between rational surfaces is the primary factor that determines the electron temperature difference between rational surfaces at the pedestal top. The magnetic-flutter-induced non-ambipolar electron density transport can be large enough to push the plasma toward an electron density transport root. Requiring ambipolar density transport is shown to determine the radial electric field, the plasma toroidal rotation (via radial force balance), a reduced electron thermal diffusivity and increased ambipolar density transport in the pedestal. At high collisionality the various flutter effects are less strongly peaked at rational surfaces and generally less significant. They are thus less likely to exhibit flutter-induced resonant behaviour and transition toward an electron

The pinch of cold ions from recycling in the tokamak edge pedestal

International Nuclear Information System (INIS)

Wan Weigang; Parker, Scott E.; Chen Yang; Park, Gun-Young; Chang, Choong-Seock; Stotler, Daren

2011-01-01

We apply the ''natural fueling mechanism'' [W. Wan, S. E. Parker, Y. Chen, and F. W. Perkins, Phys. Plasmas 17, 040701 (2010)] to the edge pedestal. The natural fueling mechanism is where cold ions naturally pinch radially inward for a heat-flux dominated plasma. It is shown from neoclassical-neutral transport coupled simulations that the recycling neutrals and the associated source ions are colder than the main ions in the edge pedestal. These recycling source ions will pinch radially inward due to microturbulence. Gyrokinetic turbulence simulations indicate that near the top of the pedestal, the pinch velocity of the recycling source ions is much higher than the main ion outgoing flow velocity. The turbulent pinch of the recycling source ions may play a role in the edge pedestal transport and dynamics. The cold ion temperature significantly enhances the pinch velocity of the recycling source ions near to the pedestal top. Neoclassical calculations show a cold ion pinch in the pedestal as well.

Global performance enhancements via pedestal optimisation on ASDEX Upgrade

NARCIS (Netherlands)

Dunne, M.G.; Frassinetti, L.; Beurkens, M.N.A.; Cavedon, M.; Fietz, S.; Fischer, R.; Giannone, L.; Huijsmans, G.T.A.; Kurzan, B.; Laggner, F.; McCarhty, P.J.; McDermott, R.M.; Tardini, G.; Viezzer, E.; Willensdorfer, M.; Wolfrum, E.

2017-01-01

Results of experimental scans of heating power, plasma shape, and nitrogen content are presented, with a focus on global performance and pedestal alteration. In detailed scans at low triangularity, it is shown that the increase in stored energy due to nitrogen seeding stems from the pedestal. It is

A pedestal temperature model with self-consistent calculation of safety factor and magnetic shear

International Nuclear Information System (INIS)

Onjun, T; Siriburanon, T; Onjun, O

2008-01-01

A pedestal model based on theory-motivated models for the pedestal width and the pedestal pressure gradient is developed for the temperature at the top of the H-mode pedestal. The pedestal width model based on magnetic shear and flow shear stabilization is used in this study, where the pedestal pressure gradient is assumed to be limited by first stability of infinite n ballooning mode instability. This pedestal model is implemented in the 1.5D BALDUR integrated predictive modeling code, where the safety factor and magnetic shear are solved self-consistently in both core and pedestal regions. With the self-consistently approach for calculating safety factor and magnetic shear, the effect of bootstrap current can be correctly included in the pedestal model. The pedestal model is used to provide the boundary conditions in the simulations and the Multi-mode core transport model is used to describe the core transport. This new integrated modeling procedure of the BALDUR code is used to predict the temperature and density profiles of 26 H-mode discharges. Simulations are carried out for 13 discharges in the Joint European Torus and 13 discharges in the DIII-D tokamak. The average root-mean-square deviation between experimental data and the predicted profiles of the temperature and the density, normalized by their central values, is found to be about 14%

Structure, stability and ELM dynamics of the H-mode pedestal in DIII-D

International Nuclear Information System (INIS)

Fenstermacher, M.E.; Leonard, A.W.; Osborne, T.H.

2005-01-01

Experiments are described that have increased understanding of the transport and stability physics that set the H-mode edge pedestal width and height, determine the onset of Type-I edge localized modes (ELMs), and produce the nonlinear dynamics of the ELM perturbation in the pedestal and scrape-off layer (SOL). Predictive models now exist for the n e pedestal profile and the p e height at the onset of Type-I ELMs, and progress has been made toward predictive models of the T e pedestal width and nonlinear ELM evolution. Similarity experiments between DIII-D and JET suggested that neutral penetration physics dominates in the relationship between the width and height of the n e pedestal while plasma physics dominates in setting the T e pedestal width. Measured pedestal conditions including edge current at ELM onset agree with intermediate-n peeling-ballooning (P-B) stability predictions. Midplane ELM dynamics data show the predicted (P-B) structure at ELM onset, large rapid variations of the SOL parameters, and fast radial propagation in later phases, similar to features in nonlinear ELM simulations. (author)

Dynamics of the pedestal structure in the edge transport barrier in CHS

International Nuclear Information System (INIS)

Kado, S.; Oishi, T.; Tanaka, S.

2006-10-01

The dynamic behavior of the edge pedestal in the edge transport barrier (ETB) formation discharge (H-mode) in the compact helical system (CHS) is investigated. Edge Harmonic Oscillations (EHOs) having a fundamental frequency of 2-4.5 kHz, depending on the magnetic configuration, and their second harmonic are observed when the density gradient of the pedestal reaches a certain threshold. There are two groups of so-called EHOs in the CHS. One is located in the edge region where the ι=1 surface exists, and the other is in the core region (although we also call it EHO in this paper) around the half radius where the ι=0.5 surface exists. The magnetic probe signal is revealed to reflect the latter mode, showing the poloidal mode number of 2, while that for the edge BES channel is 1. The density build-up saturates simultaneously with the increase of EHOs in the edge BES channel, which suggests that to a considerable extend the mode increases the particle transport. (author)

Cost reduction for large turbine generator Pedestal in high seismic zone

International Nuclear Information System (INIS)

Sawhney, P.S.; Irani, P.; Pusheck, B.N.

1985-01-01

Turbine Generator Pedestals have generally been designed using reinforced concrete. For present day large turbine generators (1100 MWe class and above) with tall (about 80 feet) pedestals, the amount of reinforcing steel becomes quite large, especially for plants in high seismic zones. With the prime objective of cost reduction, an approach using steel/concrete composite design has been studied for a large BWR Turbine Generator pedestal with 0.3g peak ground acceleration. Large prefabricated steel modules were adopted for composite design and simplified construction. Design was based on the ACI and AISC codes. Costs and schedules were developed and compared with those for a conventionally designed reinforced concrete pedestal. Composite design was found to give considerable cost and schedule advantage over the conventional reinforced concrete design

Influence of air pressure on soliton formation in hollow-core photonic bandgap fibers

DEFF Research Database (Denmark)

Lægsgaard, Jesper; Roberts, Peter John

2009-01-01

Abstract Soliton formation during dispersive compression of chirped few-picosecond pulses at the microjoule level in a hollow-core photonic bandgap (HC-PBG) fiber is studied by numerical simulations. Long-pass filtering of the emerging frequency-shifted solitons is investigated with the objective...... of obtaining pedestal-free output pulses. Particular emphasis is placed on the influence of the air pressure in the HC-PBG fiber. It is found that a reduction in air pressure enables an increase in the fraction of power going into the most redshifted soliton and also improves the quality of the filtered pulse...

ELMs and constraints on the H-mode pedestal: A model based on peeling-ballooning modes

International Nuclear Information System (INIS)

Snyder, P.B.; Ferron, J.R.; Wilson, H.R.

2003-01-01

We propose a model for Edge Localized Modes (ELMs) and pedestal constraint based upon theoretical analysis of instabilities which can limit the pedestal height and drive ELMs. The sharp pressure gradients, and resulting bootstrap current, in the pedestal region provide free energy to drive peeling and ballooning modes. The interaction of peeling-ballooning coupling, ballooning mode second stability, and finite-Larmor-radius effects results in coupled peeling-ballooning modes of intermediate wavelength generally being the limiting instability. A highly efficient new MHD code, ELITE, is used to calculate quantitative stability constraints on the pedestal, including con straits on the pedestal height. Because of the impact of collisionality on the bootstrap current, these pedestal constraints are dependant on the density and temperature separately, rather than simply on the pressure. A model of various ELM types is developed, and quantitatively compared to data. A number of observations agree with predictions, including ELM onset times, ELM depth and variation in pedestal height with collisionality and discharge shape. Stability analysis of series of model equilibria are used both o predict and interpret pedestal trends in existing experiments and to project pedestal constraints for future burning plasma tokamak designs. (author)

ELMs and constraints on the H-mode pedestal: A model based on peeling-ballooning modes

International Nuclear Information System (INIS)

Snyder, P.B.

2002-01-01

Maximizing the pedestal height while maintaining acceptable ELMs is a key issue for optimizing tokamak performance. We present a model for ELMs and pedestal constraints based upon theoretical analysis of edge instabilities which can limit the pedestal height and drive ELMs. Sharp pedestal pressure gradients drive large bootstrap currents which play a complex dual role in the stability physics. Consequently, the dominant modes are often intermediate-n coupled 'peeling-ballooning' modes, driven both by current and the pressure gradient. A highly efficient new MHD code, ELITE, is used to study these modes, and calculate quantitative stability constraints on the pedestal, including direct constraints on the pedestal height. A model of various ELM types is developed, and quantitatively compared to data from several tokamaks. A number of observations agree with predictions, including ELM onset times, ELM depth, and variation in pedestal height with discharge shape. Projections of pedestal stability constraints for Next Step designs, and nonlinear simulations of peeling-ballooning modes using the BOUT code are also presented. (author)

Kinetic neoclassical transport in the H-mode pedestal

Energy Technology Data Exchange (ETDEWEB)

Battaglia, D. J.; Chang, C. S.; Ku, S.; Grierson, B. A. [Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey 08540 (United States); Burrell, K. H.; Grassie, J. S. de [General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States)

2014-07-15

Multi-species kinetic neoclassical transport through the QH-mode pedestal and scrape-off layer on DIII-D is calculated using XGC0, a 5D full-f particle-in-cell drift-kinetic solver with self-consistent neutral recycling and sheath potentials. Quantitative agreement between the flux-driven simulation and the experimental electron density, impurity density, and orthogonal measurements of impurity temperature and flow profiles is achieved by adding random-walk particle diffusion to the guiding-center drift motion. The radial electric field (E{sub r}) that maintains ambipolar transport across flux surfaces and to the wall is computed self-consistently on closed and open magnetic field lines and is in excellent agreement with experiment. The E{sub r} inside the separatrix is the unique solution that balances the outward flux of thermal tail deuterium ions against the outward neoclassical electron flux and inward pinch of impurity and colder deuterium ions. Particle transport in the pedestal is primarily due to anomalous transport, while the ion heat and momentum transport are primarily due to the neoclassical transport. The full-f treatment quantifies the non-Maxwellian energy distributions that describe a number of experimental observations in low-collisionallity pedestals on DIII-D, including intrinsic co-I{sub p} parallel flows in the pedestal, ion temperature anisotropy, and large impurity temperatures in the scrape-off layer.

Effect of pedestal fluctuation on ELM frequency in the EAST tokamak

Science.gov (United States)

Zhong, F. B.; Zhang, T.; Liu, Z. X.; Qu, H.; Liu, H. Q.; Li, G. Q.; Liu, Y.; Gao, W.; Duan, Y. M.; Yang, Y.; Zeng, L.; Xiang, H. M.; Geng, K. N.; Wen, F.; Zhang, S. B.; Gao, X.; the EAST Team

2018-05-01

The dependence of ELM frequency on heating power has been studied on the Experimental Advanced Superconducting Tokamak (EAST). It is found that the ELM frequency (f ELM) generally increases with the power through separatrix (P sep), indicating type-I ELM in these plasmas. However, there are two data points, named ‘abnormal ELM’ in the present paper, which have much lower f ELM than the ‘normal ELM’, while both types of ELM have similar ELM energy losses. The ‘abnormal ELM’ occurs at a phase with increased radiation power due to metal impurity influx events. The increased radiation power cannot explain the much lower f ELM for ‘abnormal ELM’, since the reduction of P sep is weaker than proportional to the observed reduction of the ELM frequency. The ‘abnormal ELM’ feature can be attributed to the enhanced amplitude of a coherent mode in the pedestal region. Comparing the pedestal evolutions for the two types of ELM with similar separatrix power P sep, it is actually found that the more pronounced pedestal coherent mode in the plasma with ‘abnormal ELM’ leads to a slower pressure pedestal recovery during the inter-ELM phase. This experimental result implies that the physical mechanism for ‘abnormal ELM’ is that the more pronounced pedestal fluctuation induces larger outward transport, slows down the pedestal evolution and leads to longer inter-ELM phase, i.e. lower ELM frequency.

Influence of the plasma pedestal parameters on ELM mitigation at low collisionality

Energy Technology Data Exchange (ETDEWEB)

Leuthold, Nils [Max-Planck-Institut fuer Plasmaphysik, Boltzmannstr. 2, 85748 Garching (Germany); Universitaet Bayreuth, Universitaetsstrasse 30, 95440 Bayreuth (Germany); Suttrop, Wolfgang [Max-Planck-Institut fuer Plasmaphysik, Boltzmannstr. 2, 85748 Garching (Germany)

2016-07-01

The control of Edge Localized Modes (ELMs) is of great importance for future fusion devices in order to provide longevity of the plasma facing components and a better overall plasma performance. In recent magnetic perturbation ELM mitigation experiments in ASDEX Upgrade at low pedestal collisionality, the dependence of ELM losses on pedestal parameters is investigated. It is found that the reduction of the stored energy loss associated with ELMs occurs in correlation with a reduction of edge density and edge pedestal pressure induced by the applied magnetic perturbation (''pedestal pump-out''). Significant ELM mitigation occurs at lowest densities, in a region of pedestal n-T parameter space that has not been accessible in ASDEX Upgrade without magnetic perturbations, and which is occupied by type-IV ELMs in DIII-D. The role of magnetic perturbations for ELM mitigation will be discussed in this context and attempts to counteract the confinement loss by increasing neutral beam injection power or pellet injection increases the ELM energy losses.

RMP-Flutter-Induced Pedestal Plasma Transport

Energy Technology Data Exchange (ETDEWEB)

Callen, J. D.; Hegna, C., E-mail: callen@engr.wisc.edu [University of Wisconsin, Madison (United States); Cole, A. J. [Columbia University, New York (United States)

2012-09-15

Full text: Plasma toroidal rotation can prevent or limit reconnection of externally applied resonant magnetic perturbation (RMP) fields {delta}B on rational magnetic flux surfaces. Hence, it causes the induced radial perturbations to vanish or be small there, and thereby inhibits magnetic island formation and stochasticity in the edge of high (H-mode) confinement tokamak plasmas. However, the radial component of the spatial magnetic flutter induced by RMP fields off rational surfaces causes a radial electron thermal diffusivity of (1/2)({delta}B{sub p}/B){sup 2} times a magnetic-shear-influenced effective parallel electron thermal diffusivity. The resultant RMP-flutter-induced electron thermal diffusivity can be comparable to experimentally inferred values at the top of H-mode pedestals. This process also causes a factor of about 3 smaller RMP-induced electron density diffusivity there. Because this electron density transport is non-ambipolar, it produces a toroidal torque on the plasma, which is usually in the co-current direction. Kinetic-based cylindrical screw-pinch and toroidal models of these RMP-flutter-induced plasma transport effects have been developed. The RMP-induced increases in these diffusive plasma transport processes are typically spatially inhomogeneous in that they are strongly peaked near the rational surfaces in low collisionality pedestals, which may lead to resonant sensitivities to the local safety factor q. The effects can be large enough to reduce the radially averaged gradients of the electron temperature and density at the top of H-mode edge pedestals, and modify the plasma toroidal rotation and radial electric field there. At high collisionality the various effects are less strongly peaked at rational surfaces and thus less likely to exhibit RMP-induced resonant behavior. These RMP-flutter-induced plasma transport processes provide a new paradigm for developing an understanding of how RMPs modify the pedestal structure to stabilize

Structural Modeling and Analysis on Dynamic Characteristics of Antenna Pedestal in Airborne SAR

Directory of Open Access Journals (Sweden)

He Li-ping

2012-06-01

Full Text Available Finite element modeling and structural dynamic characteristics of antenna pedestal in airborne SAR were studied in this paper. The Finite element model of antenna pedestal in airborne SAR was set up on the basis of structural dynamic theory, then, the key technologies of dynamic simulation were pointed out, and the modal analysis and transient analysis were carried out. Simulation results show that the dynamic characteristics of antenna pedestal in airborne SAR can meet the requirements of servo bandwidth and structural strength. The fast finite element modeling and simulation method proposed in this paper are of great significance to the weight reducing design of antenna pedestal in airborne SAR.

BURNING PLASMA PROJECTIONS USING DRIFT WAVE TRANSPORT MODELS AND SCALINGS FOR THE H-MODE PEDESTAL

International Nuclear Information System (INIS)

KINSEY, J.E.; ONJUN, T.; BATEMAN, G.; KRITZ, A.; PANKIN, A.; STAEBLER, G.M.; WALTZ, R.E.

2002-01-01

OAK-B135 The GLF23 and Multi-Mode (MM95) transport models are used along with a model for the H-mode pedestal to predict the fusion performance for the ITER, FIRE, and IGNITOR tokamak designs. The drift-wave predictive transport models reproduce the core profiles in a wide variety of tokamak discharges, yet they differ significantly in their response to temperature gradient (stiffness). Recent gyro-kinetic simulations of ITG/TEM and ETG modes motivate the renormalization of the GLF23 model. The normalizing coefficients for the ITG/TEM modes are reduced by a factor of 3.7 while the ETG mode coefficient is increased by a factor of 4.8 in comparison with the original model. A pedestal temperature model is developed for type I ELMy H-mode plasmas based on ballooning mode stability and a theory-motivated scaling for the pedestal width. In this pedestal model, the pedestal density is proportional to the line-averaged density and the pedestal temperature is inversely related to the pedestal density

Flux tube gyrokinetic simulations of the edge pedestal

Science.gov (United States)

Parker, Scott; Wan, Weigang; Chen, Yang

2011-10-01

The linear instabilities of DIII-D H-mode pedestal are studied with gyrokinetic micro-turbulence simulations. The simulation code GEM is an electromagnetic δf code with global tokamak geometry in the form of Miller equilibrium. Local flux tube simulations are carried out for multiple positions of two DIII-D profiles: shot #98889 and shot #131997. Near the top of the pedestal, the instability is clearly ITG. The dominant instability of the pedestal appears at the steep gradient region, and it is identified as a low frequency mode mostly driven by electron temperature gradient. The mode propagates along the electron diamagnetic direction for low n and may propagate along the ion direction for high n. At some positions near the steep gradient region, an ion instability is found which shows some characteristics of kinetic ballooning mode (KBM). These results will be compared to the results of E. Wang et al. and D. Fulton et al. in the same session. We thank R. Groebner and P. Snyder for providing experimental profiles and helpful discussions.

ELMs and constraints on the H-mode pedestal: peeling-ballooning stability calculation and comparison with experiment

International Nuclear Information System (INIS)

Snyder, P.B.; Ferron, J.R.; Wilson, H.R.

2004-01-01

We review and test the peeling-ballooning model for edge localized modes (ELMs) and pedestal constraints, a model based upon theoretical analysis of magnetohydrodynamic (MHD) instabilities that can limit the pedestal height and drive ELMs. A highly efficient MHD stability code, ELITE, is used to calculate quantitative stability constraints on the pedestal, including constraints on the pedestal height. Because of the impact of collisionality on the bootstrap current, these pedestal constraints are dependent on the density and temperature separately, rather than simply on the pressure. ELITE stability calculations are directly compared with experimental data for a series of plasmas in which the density is varied and ELM characteristics change. In addition, a technique is developed whereby peeling-ballooning pedestal constraints are calculated as a function of key equilibrium parameters via ELITE calculations using series of model equilibria. This technique is used to successfully compare the expected pedestal height as a function of density, triangularity and plasma current with experimental data. Furthermore, the technique can be applied for parameter ranges beyond the purview of present experiments, and we present a brief projection of peeling-ballooning pedestal constraints for burning plasma tokamak designs. (author)

Threshold for sweepout from pedestal region of Mark III containment

International Nuclear Information System (INIS)

Sienicki, J.J.; Spencer, B.W.

1984-01-01

The assessment of the consequences of highly unlikely severe accident sequences in boiling water reactors includes those sequences in which molten corium is postulated to meltthrough the reactor pressure vessel (RPV) lower head and enter the pedestal region beneath the vessel. If localized melt-through of the reactor vessel occurs at elevated primary system pressure, the ejection of molten corium from the vessel will be followed by a blowdown of steam and hydrogen. The gases flowing from the breached vessel constitute a source of driving forces capable of dispersing corium from the pedestal into other parts of the containment. The extent of the gas blowdown-driven sweepout process depends upon a number of factors including the primary system pressure at melt through, breach flow area, overall blowdown timescale, and the specific pedestal/containment geometry. A model is presented to predict whether or not the conditions of gas flow from the failed RPV are sufficient to cause sweepout of corium and/or water from the pedestal. The model is shown to predict the onset of sweepout in scale model, simulant material experiments and is applied to the investigation of sweepout in the full-size reactor system

Scaling studies of the H-mode pedestal

International Nuclear Information System (INIS)

Groebner, R.J.; Osborne, T.H.

1998-01-01

The structure and scaling of the H-mode pedestal are examined for discharges in the DIII-D tokamak. For typical conditions, the pedestal values of the ion and electron temperatures T i and T e are comparable. Measurements of main ion and C 6+ profiles indicate that the ion pressure gradient in the barrier is 50%--100% of the electron pressure gradient for deuterium plasmas. The magnitude of the pressure gradient in the barrier often exceeds the predictions of infinite-n ballooning mode theory by a factor of two. Moreover, via the bootstrap current, the finite pressure gradient acts to entirely remove ballooning stability limits for typical discharges. For a large dataset, the width of the pressure barrier δ is best described by the dimensionless scaling δ/R ∝ (β pol ped ) 0.4 where (β pol ped ) is the pedestal value of poloidal beta and R is the major radius. Scalings based on the poloidal ion gyroradius or the edge density gradient do not adequately describe overall trends in the data set and the propagation of the pressure barrier observed between edge-localized modes. The width of the T i barrier is quite variable and is not a good measure of the width of the pressure barrier

The stabilizing effect of core pressure on the edge pedestal in MAST plasmas

International Nuclear Information System (INIS)

Chapman, I.T.; Simpson, J.; Saarelma, S.; Kirk, A.; O'Gorman, T.; Scannell, R.

2015-01-01

The pedestal pressure measured in Mega Ampere Spherical Tokamak plasmas has been shown to increase as the global plasma pressure increases. By deliberately suppressing the transition into the high-confinement regime, the core plasma pressure was systematically altered at the time of the first edge localized mode. Stability analysis shows that the enhanced Shafranov shift at higher core pressure stabilizes the ballooning modes driven by the pedestal pressure gradient, consequently allowing the pedestal to reach higher pressures. (paper)

Improved understanding of physics processes in pedestal structure, leading to improved predictive capability for ITER

International Nuclear Information System (INIS)

Groebner, R.J.; Snyder, P.B.; Leonard, A.W.; Chang, C.S.; Maingi, R.; Boyle, D.P.; Diallo, A.; Hughes, J.W.; Davis, E.M.; Ernst, D.R.; Landreman, M.; Xu, X.Q.; Boedo, J.A.; Cziegler, I.; Diamond, P.H.; Eldon, D.P.; Callen, J.D.; Canik, J.M.; Elder, J.D.; Fulton, D.P.

2013-01-01

Joint experiment/theory/modelling research has led to increased confidence in predictions of the pedestal height in ITER. This work was performed as part of a US Department of Energy Joint Research Target in FY11 to identify physics processes that control the H-mode pedestal structure. The study included experiments on C-Mod, DIII-D and NSTX as well as interpretation of experimental data with theory-based modelling codes. This work provides increased confidence in the ability of models for peeling–ballooning stability, bootstrap current, pedestal width and pedestal height scaling to make correct predictions, with some areas needing further work also being identified. A model for pedestal pressure height has made good predictions in existing machines for a range in pressure of a factor of 20. This provides a solid basis for predicting the maximum pedestal pressure height in ITER, which is found to be an extrapolation of a factor of 3 beyond the existing data set. Models were studied for a number of processes that are proposed to play a role in the pedestal n e and T e profiles. These processes include neoclassical transport, paleoclassical transport, electron temperature gradient turbulence and neutral fuelling. All of these processes may be important, with the importance being dependent on the plasma regime. Studies with several electromagnetic gyrokinetic codes show that the gradients in and on top of the pedestal can drive a number of instabilities. (paper)

Pedestal width and ELM size identity studies in JET and DIII-D; implications for ITER

Energy Technology Data Exchange (ETDEWEB)

Beurskens, M N A; Lomas, P; Saarelma, S; Balboa, I; Flanagan, J; Giroud, C; Kempenaars, M [EURATOM/UKAEA Fusion Association, Culham Sc. Centre, Abingdon, OX14 3DB (United Kingdom); Osborne, T H; Groebner, R; Leonard, A; Snyder, P B; Bray, B [General Atomics, PO Box 85608, San Diego, CA 92186-5608 (United States); Horton, L D [JET-EFDA, Culham Science Centre, OX14 3DB, Abingdon (United Kingdom); Frassinetti, L [Association EURATOM-VR, Alfven Laboratory, School of Electrical Engineering, KTH, Stockholm (Sweden); Nunes, I [Centro de Fusao Nuclear, Associacao EURATOM-IST, Lisboa (Portugal); Crombe, K [Department of Applied Physics, Ghent University, Rozier 44, 9000 Gent (Belgium); Giovannozzi, E [Associazione EURATOM-ENEA Sulla Fusione, Consorzio RFX Padova (Italy); Kohen, N [Association EURATOM-CEA, CEA/DSM/DRFC-Cadarache 13108, St Paul Durance (France); Loarte, A [ITER Organization, CS 90 046, F-13067 Saint Paul lez Durance Cedex (France); Loennroth, J, E-mail: Marc.Beurskens@jet.u [Association EURATOM-Tekes, Helsinki University of Technology (Finland)

2009-12-15

The dependence of the H-mode edge transport barrier width on normalized ion gyroradius (rho* = rho/a) in discharges with type I ELMs was examined in experiments combining data for the JET and DIII-D tokamaks. The plasma configuration as well as the local normalized pressure (beta), collisionality (nu*), Mach number and the ratio of ion and electron temperature at the pedestal top were kept constant, while rho* was varied by a factor of four. The width of the steep gradient region of the electron temperature (T{sub e}) and density (n{sub e}) pedestals normalized to machine size showed no or only a weak trend with rho*. A rho{sup 1/2} or rho{sup 1} dependence of the pedestal width, given by some theoretical predictions, is not supported by the current experiments. This is encouraging for the pedestal scaling towards ITER as it operates at lower rho* than existing devices. Some differences in pedestal structure and ELM behaviour were, however, found between the devices; in the DIII-D discharges, the n{sub e} and T{sub e} pedestal were aligned at high rho* but the n{sub e} pedestal shifted outwards in radius relative to T{sub e} as rho* decreases, while on JET the profiles remained aligned while rho* was scanned by a factor of two. The energy loss at an ELM normalized to the pedestal energy increased from 10% to 40% as rho* increased by a factor of two in the DIII-D discharges but no such variation was observed in the case of JET. The measured pedestal pressures and widths were found to be consistent with the predictions from modelling based on peeling-ballooning stability theory, and are used to make projections towards ITER

Control of bootstrap current in the pedestal region of tokamaks

Energy Technology Data Exchange (ETDEWEB)

Shaing, K. C. [Institute for Space and Plasma Sciences, National Cheng Kung University, Tainan City 70101, Taiwan (China); Department of Engineering Physics, University of Wisconsin, Madison, Wisconsin 53796 (United States); Lai, A. L. [Institute for Space and Plasma Sciences, National Cheng Kung University, Tainan City 70101, Taiwan (China)

2013-12-15

The high confinement mode (H-mode) plasmas in the pedestal region of tokamaks are characterized by steep gradient of the radial electric field, and sonic poloidal U{sub p,m} flow that consists of poloidal components of the E×B flow and the plasma flow velocity that is parallel to the magnetic field B. Here, E is the electric field. The bootstrap current that is important for the equilibrium, and stability of the pedestal of H-mode plasmas is shown to have an expression different from that in the conventional theory. In the limit where ‖U{sub p,m}‖≫ 1, the bootstrap current is driven by the electron temperature gradient and inductive electric field fundamentally different from that in the conventional theory. The bootstrap current in the pedestal region can be controlled through manipulating U{sub p,m} and the gradient of the radial electric. This, in turn, can control plasma stability such as edge-localized modes. Quantitative evaluations of various coefficients are shown to illustrate that the bootstrap current remains finite when ‖U{sub p,m}‖ approaches infinite and to provide indications how to control the bootstrap current. Approximate analytic expressions for viscous coefficients that join results in the banana and plateau-Pfirsch-Schluter regimes are presented to facilitate bootstrap and neoclassical transport simulations in the pedestal region.

Arbitrary poloidal gyroradius effects in tokamak pedestals and transport barriers

International Nuclear Information System (INIS)

Kagan, Grigory; Catto, Peter J

2008-01-01

A technique is developed and applied for analyzing pedestal and internal transport barrier (ITB) regions in a tokamak by formulating a special version of gyrokinetics. In contrast to typical gyrokinetic treatments, canonical angular momentum is taken as the gyrokinetic radial variable rather than the radial guiding center location. Such an approach allows strong radial plasma gradients to be treated, while retaining zonal flow and neoclassical (including orbit squeezing) behavior and the effects of turbulence. The new, nonlinear gyrokinetic variables are constructed to higher order than is typically the case. The nonlinear gyrokinetic equation obtained is capable of handling such problems as collisional zonal flow damping with radial wavelengths comparable to the ion poloidal gyroradius, as well as zonal flow and neoclassical transport in the pedestal or ITB. This choice of gyrokinetic variables allows the toroidally rotating Maxwellian solution of the isothermal tokamak limit to be recovered. More importantly, we prove that a physically acceptable solution for the lowest order ion distribution function in the banana regime anywhere in a tokamak and, in particular, in the pedestal must be nearly this same isothermal Maxwellian solution. That is, the ion temperature variation scale must be much greater than the poloidal ion gyroradius. Consequently, in the banana regime the background radial ion temperature profile cannot have a pedestal similar to that of plasma density

MODEL OF THE TOKAMAK EDGE DENSITY PEDESTAL INCLUDING DIFFUSIVE NEUTRALS

International Nuclear Information System (INIS)

BURRELL, K.H.

2003-01-01

OAK-B135 Several previous analytic models of the tokamak edge density pedestal have been based on diffusive transport of plasma plus free-streaming of neutrals. This latter neutral model includes only the effect of ionization and neglects charge exchange. The present work models the edge density pedestal using diffusive transport for both the plasma and the neutrals. In contrast to the free-streaming model, a diffusion model for the neutrals includes the effect of both charge exchange and ionization and is valid when charge exchange is the dominant interaction. Surprisingly, the functional forms for the electron and neutral density profiles from the present calculation are identical to the results of the previous analytic models. There are some differences in the detailed definition of various parameters in the solution. For experimentally relevant cases where ionization and charge exchange rate are comparable, both models predict approximately the same width for the edge density pedestal

Advances in measurement and modeling of the high-confinement-mode pedestal on the Alcator C-Mod tokamak

International Nuclear Information System (INIS)

Hughes, J.W.; LaBombard, B.; Mossessian, D.A.; Hubbard, A.E.; Terry, J.; Biewer, T.

2006-01-01

Edge transport barrier (ETB) studies on the Alcator C-Mod tokamak [Phys. Plasmas 1, 1511 (1994)] investigate pedestal scalings and the radial transport of plasma and neutrals. Pedestal profiles show trends with plasma operational parameters such as total current I P . A ballooning-like I P 2 dependence is seen in the pressure gradient, despite calculated stability to ideal ballooning modes. A similar scaling is seen in the near scrape-off layer for both low-confinement (L-mode) and H-mode discharges, possibly due to electromagnetic fluid drift turbulence setting transport near the separatrix. Neutral density diagnosis allows an examination of D 0 fueling in H-modes, yielding profiles of effective particle diffusivity in the ETB, which vary as I P is changed. Edge neutral transport is studied using a one-dimensional kinetic treatment. In both experiment and modeling, the C-Mod density pedestal exhibits a weakly increasing pedestal density and a nearly invariant density pedestal width as the D 0 source rate increases. Identical modeling performed on pedestal profiles typical of DIII-D [Nucl. Fusion 42, 614 (2002)] reveal differences in pedestal scalings qualitatively similar to experimental results

Effect of PFC recycling conditions on JET pedestal density

International Nuclear Information System (INIS)

Wiesen, S.; Brezinsek, S.; Dittmar, T.; Matveev, D.; Harting, D.; De la Luna, E.; Schmid, K.

2016-01-01

There is experimental evidence that the pedestal dynamics in type-I ELMy H-mode discharges is significantly affected by a change in the recycling conditions at the tungsten plasma-facing components (W-PFCs) after an ELM event. The integrated code JINTRAC has been employed to assess the impact of recycling conditions during type-I ELMs in JET ITER-like wall H-mode discharges. By employing a heuristic approach, a model to mimic the physical processes leading to formation and release (i.e. outgassing) of finite near-surface fuel reservoirs in W-PFCs has been implemented into the EDGE2D-EIRENE plasma-wall interaction code being part of JINTRAC. As main result it is shown, that a delay in the density pedestal build-up after an ELM event can be provoked by reduced recycling induced by depleted W-PFC particle near-surface reservoirs. However the pedestal temperature evolution is barely affected by the change in recycling parameters suggesting that the presented model is incomplete. (copyright 2016 The Authors. Contributions to Plasma Physics published by Wiley-VCH Verlag GmbH and Co. KGaA Weinheim. This)

Initial results of H-mode edge pedestal turbulence evolution with quadrature reflectometer measurements on DIII-D

Energy Technology Data Exchange (ETDEWEB)

Wang, G. [University of California, Los Angeles, CA 90095 (United States)]. E-mail: wangg@fusion.gat.com; Peebles, W.A. [University of California, Los Angeles, CA 90095 (United States); Doyle, E.J. [University of California, Los Angeles, CA 90095 (United States); Rhodes, T.L. [University of California, Los Angeles, CA 90095 (United States); Zeng, L. [University of California, Los Angeles, CA 90095 (United States); Nguyen, X. [University of California, Los Angeles, CA 90095 (United States); Osborne, T.H. [General Atomics, San Diego, CA 92186-5608 (United States); Snyder, P.B. [General Atomics, San Diego, CA 92186-5608 (United States); Kramer, G.J. [Princeton Plasma Physics Laboratory, Princeton, NJ 08543 (United States); Nazikian, R. [Princeton Plasma Physics Laboratory, Princeton, NJ 08543 (United States); Groebner, R.J. [General Atomics, San Diego, CA 92186-5608 (United States); Burrell, K.H. [General Atomics, San Diego, CA 92186-5608 (United States); Leonard, A.W. [General Atomics, San Diego, CA 92186-5608 (United States); Fenstermacher, M.E. [Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); Strait, E.J. [General Atomics, San Diego, CA 92186-5608 (United States)

2007-06-15

High-resolution quadrature reflectometer measurements of density fluctuation levels have been obtained on DIII-D for H-mode edge pedestal studies. Initial results are presented from the L-H transition to the first ELM for two cases: (i) a low pedestal beta discharge, in which density turbulence in the pedestal has little change during the ELM-free phase, and (ii) a high pedestal beta discharge in which both density and magnetic turbulence are observed to increase before the first ELM. These high beta data are consistent with the existence of electromagnetic turbulence suggested by some transport models. During Type-I ELM cycles, when little magnetic turbulence can be observed, pedestal turbulence increases just after an ELM crash and then decreases before next ELM strikes, in contrast to a drop after ELM crash and then it re-grows when strong magnetic turbulence shows similar behavior. Clear ELM precursors are observed on {<=}20% of Type-I ELMs observed to date.

Development of new pedestal temperature models with self-consistent magnetic shear and safety factor in BALDUR and JETTO codes

International Nuclear Information System (INIS)

Suwanna, S.; Onjun, T.; Wongpan, P.; Parail, V.; Poolyarat, N.; Picha, R.

2009-01-01

Full text: A formation of a steep pressure gradient region near the plasma edge, called the pedestal, is a main reason for an improved performance in H-mode plasma. In this work, new pedestal temperature models are developed based on different theoretical-based width concepts: flow shear stabilization width concept, magnetic and flow shear stabilization width concept, and diamagnetic stabilization width concept. In the BALDUR code, each pedestal width model is combined with a ballooning mode pressure gradient model to predict the pedestal temperature, which is a boundary condition needed to predict plasma profiles. In the JETTO code, an anomalous transport is suppressed within the pedestal region, which results in a formation of a steep pressure gradient region. The pedestal width is predicted using these theoretically based width concepts. The plasma profiles in the pedestal region are limited by ELM crashes, which can be triggered either by ballooning modes or by peeling modes, depending on which instability is destabilized first. It is found in the BALDUR simulations that the simulated pedestal temperature profiles agree well with experimental data in the region close to the pedestal, but show larger deviation in the core region. In a preliminary investigation, these models agree reasonably well with experiments, yielding overall RMS less than 20%. Furthermore, the model based flow shear stabilization matches very well data from both DIII-D and JET, while the model based on magnetic and flow shear stabilization over-predicts results from JET and under-predicts those from DIII-D. Other statistical analyses such a calculation of offset values, ratios of predicted pedestal (resp. core) temperatures to those from experiments are performed. (author)

Characteristics of edge pedestals in LHW and NBI heated H-mode plasmas on EAST

Science.gov (United States)

Zang, Q.; Wang, T.; Liang, Y.; Sun, Y.; Chen, H.; Xiao, S.; Han, X.; Hu, A.; Hsieh, C.; Zhou, H.; Zhao, J.; Zhang, T.; Gong, X.; Hu, L.; Liu, F.; Hu, C.; Gao, X.; Wan, B.; the EAST Team

2016-10-01

By using the recently developed Thomson scattering diagnostic, the pedestal structure of the H-mode with neutral beam injection (NBI) or/and lower hybrid wave (LHW) heating on EAST (Experimental Advanced Superconducting Tokamak) is analyzed in detail. We find that a higher ratio of the power of the NBI to the total power of the NBI and the lower hybrid wave (LHW) will produce a large and regular different edge-localized mode (ELM), and a lower ratio will produce a small and irregular ELM. The experiments show that the mean pedestal width has good correlation with β \\text{p,\\text{ped}}0.5 , The pedestal width appears to be wider than that on other similar machines, which could be due to lithium coating. However, it is difficult to draw any conclusion of correlation between ρ * and the pedestal width for limited ρ * variation and scattered distribution. It is also found that T e/\

H-mode pedestal characteristics, ELMs, and energy confinement in ITER shape discharges on DIII-D

International Nuclear Information System (INIS)

Osborne, T.H.; Groebner, R.J.; Lao, L.L.; Leonard, A.W.; Miller, R.L.; Thomas, D.M.; Waltz, R.E.; Maingi, R.; Porter, G.D.

1997-12-01

The H-mode confinement enhancement factor, H, is found to be strongly correlated with the height of the edge pressure pedestal in ITER shape discharges. In discharges with Type I ELMs the pedestal pressure is set by the maximum pressure gradient before the ELM and the width of the H-mode transport barrier. The pressure gradient before Type I ELMs is found to scale as would be expected for a stability limit set by ideal ballooning modes, but with values significantly in excess of that predicted by stability code calculations. The width of the H-mode transport barrier is found to scale equally well with pedestal P(POL)(2/3) or B(POL)(1/2). The improved H value in high B(POL) discharges may be due to a larger edge pressure gradient and wider H-mode transport barrier consistent with their higher edge ballooning mode limit. Deuterium puffing is found to reduce H consistent with the smaller pedestal pressure which results from the reduced barrier width and critical pressure gradient. Type I ELM energy loss is found to be proportional to the change in the pedestal energy

Fabrication of polymeric hollow nanospheres, hollow nanocubes and hollow plates

Science.gov (United States)

Cheng, Daming; Xia, Haibing; Chan, Hardy Sze On

2006-03-01

A facile strategy for fabricating polypyrrole-chitosan (PPy-CS) hollow nanostructures with different shapes (sphere, cube and plate) and a wide range of sizes (from 35 to 600 nm) is described. These hollow structures have been fabricated using silver bromide as a single template material for polymer nucleation and growth. PPy-CS hollow nanostructures are formed by reaction with an etching agent to remove the core. These hollow nanostructures have been extensively characterized using various techniques such as TEM, FT-IR, UV-vis, and XRD.

Theory and theory-based models for the pedestal, edge stability and ELMs in tokamaks

International Nuclear Information System (INIS)

Guzdar, P.N.; Mahajan, S.M.; Yoshida, Z.; Dorland, W.; Rogers, B.N.; Bateman, G.; Kritz, A.H.; Pankin, A.; Voitsekhovitch, I.; Onjun, T.; Snyder, S.

2005-01-01

Theories for equilibrium and stability of H-modes, and models for use within integrated modeling codes with the objective of predicting the height, width and shape of the pedestal at the edge of H-mode plasmas in tokamaks, as well as the onset and frequency of Edge Localized Modes (ELMs), are developed. A theory model for relaxed plasma states with flow, which uses two-fluid Hall-MHD equations, predicts that the natural scale length of the pedestal is the ion skin depth and the pedestal width is larger than the ion poloidal gyro-radius, in agreement with experimental observations. Computations with the GS2 code are used to identify micro-instabilities, such as electron drift waves, that survive the strong flow shear, diamagnetic flows, and magnetic shear that are characteristic of the pedestal. Other instabilities on the pedestal and gyro-radius scale, such as the Kelvin-Helmholtz instability, are also investigated. Time-dependent integrated modeling simulations are used to follow the transition from L-mode to H-mode and the subsequent evolution of ELMs as the heating power is increased. The flow shear stabilization that produces the transport barrier at the edge of the plasma reduces different modes of anomalous transport and, consequently, different channels of transport at different rates. ELM crashes are triggered in the model by pressure-driven ballooning modes or by current-driven peeling modes. (author)

Hollow micro string based calorimeter device

DEFF Research Database (Denmark)

2014-01-01

positions so as to form a free released double clamped string in-between said two longitudinally distanced positions said micro-channel string comprising a microfluidic channel having a closed cross section and extending in the longitudinal direction of the hollow string, acoustical means adapted...

Influence of plasma pedestal profiles on access to ELM-free regimes in ITER

Energy Technology Data Exchange (ETDEWEB)

Medvedev, S. Yu., E-mail: medvedev@a5.kiam.ru; Ivanov, A. A., E-mail: aai@a5.kiam.ru; Martynov, A. A., E-mail: martynov@a5.kiam.ru; Poshekhonov, Yu. Yu., E-mail: naida@a5.kiam.ru [Russian Academy of Sciences, Keldysh Institute of Applied Mathematics (Russian Federation); Konovalov, S. V., E-mail: konoval-sv@nrcki.ru [National Research Nuclear University “MEPhI,” (Russian Federation); Polevoi, A. R., E-mail: alexei.polevoi@iter.org [ITER Organization (France)

2016-05-15

The influence of current density and pressure gradient profiles in the pedestal on the access to the regimes free from edge localized modes (ELMs) like quiescent H-mode in ITER is investigated. Using the simulator of MHD modes localized near plasma boundary based on the KINX code, calculations of the ELM stability were performed for the ITER plasma in scenarios 2 and 4 under variations of density and temperature profiles with the self-consistent bootstrap current in the pedestal. Low pressure gradient values at the separatrix, the same position of the density and temperature pedestals and high poloidal beta values facilitate reaching high current density in the pedestal and a potential transition into the regime with saturated large scale kink modes. New version of the localized MHD mode simulator allows one to compute the growth rates of ideal peeling-ballooning modes with different toroidal mode numbers and to determine the stability region taking into account diamagnetic stabilization. The edge stability diagrams computations and sensitivity studies of the stability limits to the value of diamagnetic frequency show that diamagnetic stabilization of the modes with high toroidal mode numbers can help to access the quiescent H-mode even with high plasma density but only with low pressure gradient values at the separatrix. The limiting pressure at the top of the pedestal increases for higher plasma density. With flat density profile the access to the quiescent H-mode is closed even with diamagnetic stabilization taken into account, while toroidal mode numbers of the most unstable peeling-ballooning mode decrease from n = 10−40 to n = 3−20.

The effect of plasma collisionality on pedestal current density formation in DIII-D

Energy Technology Data Exchange (ETDEWEB)

Thomas, D M; Leonard, A W; Osborne, T H; Groebner, R J; West, W P; Burrell, K H [General Atomics, PO Box 85608, San Diego, California 92186-5608 (United States)

2006-05-15

The evolution and performance limits for the pedestal in H-mode are dependent on the two main drive terms for instability: namely the edge pressure gradient and the edge current density. These terms are naturally coupled though neoclassical (Pfirsch-Schluter and bootstrap) effects. On DIII-D, local measurements of the edge current density are made using an injected lithium beam in conjunction with Zeeman polarimetry and compared with pressure profile measurements made with other diagnostics. These measurements have confirmed the close spatial and temporal correlation that exists between the measured current density and the edge pressure in H- and QH-mode pedestals, where substantial pressure gradients exist. In the present work we examine the changes in the measured edge current for DIII-D pedestals which have a range of values for the ion and electron collisionalities {l_brace}{upsilon}{sub i}*,{upsilon}{sub e}*{r_brace} due to fuelling effects. Such changes in the collisionality in the edge are expected to significantly alter the level of the bootstrap current from the value predicted from the collisionless limit and therefore should correspondingly alter the pedestal stability limits. We find a clear decrease in measured current as {nu} increases, even for discharges having similar edge pressure gradients.

Hyraulic pedestal for a mine support

Energy Technology Data Exchange (ETDEWEB)

Nikonov, V IK; Gusel' nikov, L M; Iudin, N I; Miller, V B

1981-04-30

The goal of this invention is to provide additional brace support to a hydraulic pedestal and to provide for its operation in a given condition with steady resistance. In order to achieve this goal, the hydraulic accumulator is equipped with an intake valve with a valve lifter; this valve is built with a choke mounted on its axis. The hydraulic accumulator is built with a removable sectional upper section with a variable volume.

Pedestal evolution physics in low triangularity JET tokamak discharges with ITER-like wall

Science.gov (United States)

Bowman, C.; Dickinson, D.; Horvath, L.; Lunniss, A. E.; Wilson, H. R.; Cziegler, I.; Frassinetti, L.; Gibson, K.; Kirk, A.; Lipschultz, B.; Maggi, C. F.; Roach, C. M.; Saarelma, S.; Snyder, P. B.; Thornton, A.; Wynn, A.; Contributors, JET

2018-01-01

The pressure gradient of the high confinement pedestal region at the edge of tokamak plasmas rapidly collapses during plasma eruptions called edge localised modes (ELMs), and then re-builds over a longer time scale before the next ELM. The physics that controls the evolution of the JET pedestal between ELMs is analysed for 1.4 MA, 1.7 T, low triangularity, δ  =  0.2, discharges with the ITER-like wall, finding that the pressure gradient typically tracks the ideal magneto-hydrodynamic ballooning limit, consistent with a role for the kinetic ballooning mode. Furthermore, the pedestal width is often influenced by the region of plasma that has second stability access to the ballooning mode, which can explain its sometimes complex evolution between ELMs. A local gyrokinetic analysis of a second stable flux surface reveals stability to kinetic ballooning modes; global effects are expected to provide a destabilising mechanism and need to be retained in such second stable situations. As well as an electron-scale electron temperature gradient mode, ion scale instabilities associated with this flux surface include an electro-magnetic trapped electron branch and two electrostatic branches propagating in the ion direction, one with high radial wavenumber. In these second stability situations, the ELM is triggered by a peeling-ballooning mode; otherwise the pedestal is somewhat below the peeling-ballooning mode marginal stability boundary at ELM onset. In this latter situation, there is evidence that higher frequency ELMs are paced by an oscillation in the plasma, causing a crash in the pedestal before the peeling-ballooning boundary is reached. A model is proposed in which the oscillation is associated with hot plasma filaments that are pushed out towards the plasma edge by a ballooning mode, draining their free energy into the cooler plasma there, and then relaxing back to repeat the process. The results suggest that avoiding the oscillation and maximising the region

ROLE OF NEUTRALS IN CORE FUELING AND PEDESTAL STRUCTURE IN H-MODE DIII-D DISCHARGES

International Nuclear Information System (INIS)

WOLF, NS; PETRIE, TW; PORTER, GD; ROGNLIEN, TD; GROEBNER, RJ; MAKOWSKI, MA

2002-01-01

OAK A271 ROLE OF NEUTRALS IN CORE FUELING AND PEDESTAL STRUCTURE IN H-MODE DIII-D DISCHARGES. The 2-D fluid code UEDGE was used to analyze DIII-D experiments to determine the role of neutrals in core fueling, core impurities, and also the H-mode pedestal structure. The authors compared the effects of divertor closure on the fueling rate and impurity density of high-triangularity, H-mode plasmas. UEDGE simulations indicate that the decrease in both deuterium core fueling (∼ 15%-20%) and core carbon density (∼ 15%-30%) with the closed divertor compared to the open divertor configuration is due to greater divertor screening of neutrals. They also compared UEDGE results with a simple analytic model of the H-mode pedestal structure. The model predicts both the width and gradient of the transport barrier in n e as a function of the pedestal density. The more sophisticated UEDGE simulations of H-mode discharges corroborate the simple analytic model, which is consistent with the hypothesis that fueling processes play a role in H-mode transport barrier formation

Isotope and mixture effects on neoclassical transport in the pedestal

Science.gov (United States)

Pusztai, Istvan; Buller, Stefan; Omotani, John T.; Newton, Sarah L.

2017-10-01

The isotope mass scaling of the energy confinement time in tokamak plasmas differs from gyro-Bohm estimates, with implications for the extrapolation from current experiments to D-T reactors. Differences in mass scaling in L-mode and various H-mode regimes suggest that the isotope effect may originate from the pedestal. In the pedestal, sharp gradients render local diffusive estimates invalid, and global effects due to orbit-width scale profile variations have to be taken into account. We calculate neoclassical cross-field fluxes from a radially global drift-kinetic equation using the PERFECT code, to study isotope composition effects in density pedestals. The relative reduction to the peak heat flux due to global effects as a function of the density scale length is found to saturate at an isotope-dependent value that is larger for heavier ions. We also consider D-T and H-D mixtures with a focus on isotope separation. The ability to reproduce the mixture results via single-species simulations with artificial ``DT'' and ``HD'' species has been considered. These computationally convenient single ion simulations give a good estimate of the total ion heat flux in corresponding mixtures. Funding received from the International Career Grant of Vetenskapsradet (VR) (330-2014-6313) with Marie Sklodowska Curie Actions, Cofund, Project INCA 600398, and Framework Grant for Strategic Energy Research of VR (2014-5392).

Development of hollow electron beams for proton and ion collimation

CERN Document Server

Stancari, G; Kuznetsov, G; Shiltsev, V; Still, D A; Valishev, A; Vorobiev, L G; Assmann, R; Kabantsev, A

2012-01-01

Magnetically confined hollow electron beams for controlled halo removal in high-energy colliders such as the Tevatron or the LHC may extend traditional collimation systems beyond the intensity limits imposed by tolerable material damage. They may also improve collimation performance by suppressing loss spikes due to beam jitter and by increasing capture efficiency. A hollow electron gun was designed and built. Its performance and stability were measured at the Fermilab test stand. The gun will be installed in one of the existing Tevatron electron lenses for preliminary tests of the hollow-beam collimator concept, addressing critical issues such as alignment and instabilities of the overlapping proton and electron beams.

Development of hollow electron beams for proton and ion collimation

CERN Document Server

Stancari, G.; Kuznetsov, G.; Shiltsev, V.; Still, D.A.; Valishev, A.; Vorobiev, L.G.; Assmann, R.; Kabantsev, A.

2010-01-01

Magnetically confined hollow electron beams for controlled halo removal in high-energy colliders such as the Tevatron or the LHC may extend traditional collimation systems beyond the intensity limits imposed by tolerable material damage. They may also improve collimation performance by suppressing loss spikes due to beam jitter and by increasing capture efficiency. A hollow electron gun was designed and built. Its performance and stability were measured at the Fermilab test stand. The gun will be installed in one of the existing Tevatron electron lenses for preliminary tests of the hollow-beam collimator concept, addressing critical issues such as alignment and instabilities of the overlapping proton and electron beams

Ion orbit loss and pedestal width of H-mode tokamak plasmas in limiter geometry

International Nuclear Information System (INIS)

Xiao Xiaotao; Liu Lei; Zhang Xiaodong; Wang Shaojie

2011-01-01

A simple analytical model is proposed to analyze the effects of ion orbit loss on the edge radial electric field in a tokamak with limiter configuration. The analytically predicted edge radial electric field is consistent with the H-mode experiments, including the width, the magnitude, and the well-like shape. This model provides an explanation to the H-mode pedestal structure. Scaling of the pedestal width based on this model is proposed.

Placed on a Pedestal: Famous Faces in Clay

Science.gov (United States)

Walkup, Nancy

2010-01-01

Artists have created portraits of people for thousands of years. In sculpture, a portrait of a person's face often includes the neck and part of the shoulders and chest. These artworks are called portrait busts. In this article, the author describes how her fifth-grade students created clay portrait busts on pedestal columns. The objectives are…

Correlations between quasi-coherent fluctuations and the pedestal evolution during the inter-edge localized modes phase on DIII-D

Energy Technology Data Exchange (ETDEWEB)

Diallo, A.; Battaglia, D. J.; Guttenfelder, W. [Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey 08543-0451 (United States); Groebner, R. J.; Osborne, T. H.; Snyder, P. B. [General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States); Rhodes, T. L. [Physics and Astronomy Department, P.O. Box 957099, Los Angeles, California 90095-7099 (United States); Smith, D. R. [Department of Engineering Physics, 1500 Engineering Dr., Madison, Wisconsin 53706 (United States); Canik, J. M. [Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831 (United States)

2015-05-15

Direct measurements of the pedestal recovery during an edge-localized mode cycle provide evidence that quasi-coherent fluctuations (QCFs) play a role in the inter-ELM pedestal dynamics. Using fast Thomson scattering measurements, the pedestal density and temperature evolutions are probed on sub-millisecond time scales to show a fast recovery of the density gradient compared to the temperature gradient. The temperature gradient appears to provide a drive for the onset of quasi-coherent fluctuations (as measured with the magnetic probe and the density diagnostics) localized in the pedestal. The amplitude evolution of these QCFs tracks the temperature gradient evolution including its saturation. Such correlation suggests that these QCFs play a key role in limiting the pedestal temperature gradient. The saturation of the QCFs coincides with the pressure gradient reaching the kinetic-ballooning mode (KBM) critical gradient as predicted by EPED1. Furthermore, linear microinstability analysis using GS2 indicates that the steep gradient is near the KBM threshold. Thus, the modeling and the observations together suggest that QCFs are consistent with dominant KBMs, although microtearing cannot be excluded as subdominant.

Correlations between quasi-coherent fluctuations and the pedestal evolution during the inter-edge localized modes phase on DIII-D

International Nuclear Information System (INIS)

Diallo, A.; Battaglia, D. J.; Guttenfelder, W.; Groebner, R. J.; Osborne, T. H.; Snyder, P. B.; Rhodes, T. L.; Smith, D. R.; Canik, J. M.

2015-01-01

Direct measurements of the pedestal recovery during an edge-localized mode cycle provide evidence that quasi-coherent fluctuations (QCFs) play a role in the inter-ELM pedestal dynamics. Using fast Thomson scattering measurements, the pedestal density and temperature evolutions are probed on sub-millisecond time scales to show a fast recovery of the density gradient compared to the temperature gradient. The temperature gradient appears to provide a drive for the onset of quasi-coherent fluctuations (as measured with the magnetic probe and the density diagnostics) localized in the pedestal. The amplitude evolution of these QCFs tracks the temperature gradient evolution including its saturation. Such correlation suggests that these QCFs play a key role in limiting the pedestal temperature gradient. The saturation of the QCFs coincides with the pressure gradient reaching the kinetic-ballooning mode (KBM) critical gradient as predicted by EPED1. Furthermore, linear microinstability analysis using GS2 indicates that the steep gradient is near the KBM threshold. Thus, the modeling and the observations together suggest that QCFs are consistent with dominant KBMs, although microtearing cannot be excluded as subdominant

Impact of impurity seeding and divertor conditions on transitions, pedestal structure and ELMs

Science.gov (United States)

Dunne, M. G.

2017-02-01

Future devices will require a high scrape-off later (SOL) density and impurity seeding to avoid high-Z sputtering. However, these operational parameters are not included in present-day scaling laws, making extrapolations to larger devices difficult. As such, understanding the physics of such effects is vital in order to design the operational scenarios most favorable to high fusion gain. This review presents the favorable lowering of L-H transition power by changing to metal walled devices and sumarises the effects currently thought to be responsible for how SOL geometry can play a role in determining this threshold. Experimental observations on changes to the pedestal structure with main ion fuelling and low-, medium-, and high-Z impurity seeding are presented. These results, from several devices, show that main ion fuelling or high density operation can result in a lower pedestal top pressure, and hence reduced stored energy, while impurity seeding can recover this lost pressure. Particular focus is given to nitrogen seeded discharges and the recovery of pedestal parameters (notably high {{T}\\text{e,\\text{ped}}} ) in JET and AUG since the changeover to metal walls in these devices. Lithium seeding is also emerging as a strong actuator in pedestal dynamics, with results ranging from a prolonged inter-ELM period to completely ELM-free scenarios on different devices. ELM dynamics are also presented in each section, with nitrogen seeding offering a probe into the structure of the ELM and demonstrating the difference between the initial ELM crash, likely due to a sharp MHD event, and a prolonged second phase, the origin of which remains unkown. Finally, modelling of the pedestal in impurity seeded scenarios reveals a common effect in the position of the density profile. Either through mode excitation near to the separatrix or an altered fuelling profile, seeding of impurities results in an inward shift of the density profile. This inward shift improves MHD stability

Experimental and computational evaluation of neutrals in the Alcator C-Mod edge pedestal

Science.gov (United States)

Hughes, J. W.; Mossessian, D.; Labombard, B.; Terry, J.

2004-11-01

Pedestal-forming edge transport barriers (ETBs) in tokamak plasmas and the physics governing them are linked to the enhancement of confinement obtained in H-mode plasmas. Studies on Alcator C-Mod employ experimental measurements and simple 1-D transport models in order to better understand ETB physics. We examine the influences of ionization and charge exchange on the pedestals in electron density and temperature. Routine measurements from edge Thomson scattering (ETS) give pedestal scalings with global plasma parameters, while individual ETS profiles are combined with scanning Langmuir probe data and optical D_α emissivity measurements to give atomic density profiles and the associated radial distribution of the ionization source rate. From H-mode profiles of these quantities a well in effective plasma diffusivity is calculated, and is shown to systematically vary as the confinement regime is varied from ELM-free to EDA. Experimental work is supplemented with modeling and computation of edge neutral transport via KN1D, a kinetic solver for atomic and molecular distribution functions in slab geometry. The level of agreement between experiment and model is encouraging.

DSS 13 phase 2 pedestal room microwave layout

Science.gov (United States)

Cwik, T.; Chen, J. C.

1991-01-01

The design and predicted performance is described of the microwave layout for three band operation of the beam waveguide antenna Deep Space Station 13. Three pedestal room microwave candidate layout designs were produced for simultaneous X/S and X/Ka band operation. One of the three designs was chosen based on given constraints, and for this design the microwave performance was estimated.

Kinetic neutral transport effects in the pedestal of H-mode discharges in the DIII-D tokamak

Energy Technology Data Exchange (ETDEWEB)

Owen, L.W. [Oak Ridge National Laboratory, Building 5700, MS-6169, Oak Ridge, TN 37831-8072 (United States)]. E-mail: owenlw@ornl.gov; Groebner, R.J. [General Atomics, P.O. Box 85608, San Diego, CA 92186-9784 (United States); Mahdavi, M.A. [General Atomics, P.O. Box 85608, San Diego, CA 92186-9784 (United States)

2005-03-01

A series of hydrogen and deuterium discharges are analyzed with fluid plasma and Monte Carlo neutrals codes. Comparison of poloidally averaged radial distributions of core neutral density and ionization with analytic solutions of 1-D plasma and neutrals continuity equations support the hypothesis that the width of the density pedestal is largely determined by the neutral source. The increased neutral penetration depth that arises from multiple charge exchange can be included in the analytic model with radially dependent scale lengths. The scale length in the analytic model depends on the neutral fluid velocity which increases across the divertor and pedestal as the neutral atoms charge exchange with the higher temperature background ions. The neutral penetration depth and corresponding density pedestal width depend sensitively on the neutral temperature and the degree of ion-neutral temperature equilibration.

Characterisation of the ELM synchronized H-mode edge pedestal in ASDEX upgrade and DIII-D

Energy Technology Data Exchange (ETDEWEB)

Schneider, Philip A.; Wolfrum, Elisabeth; Guenter, Sibylle; Kurzan, Bernd; Zohm, Hartmut [Max Planck Institut fuer Plasmaphysik, EURATOM Association, Garching (Germany); Groebner, Rich; Osborne, Tom H.; Ferron, John; Snyder, Philip B. [General Atomics, San Diego, CA (United States); Dunne, Mike G. [Department of Physics, University College Cork, Association Euratom-DCU, Cork (Ireland); Collaboration: ASDEX Upgrade Team; DIII-D Team

2011-07-01

The results of a large database of edge pedestal data from type-I ELMy H-mode discharges from ASDEX Upgrade and DIII-D are presented. The data from high resolution edge diagnostics of both devices is analysed with the same analysis code in order to avoid systematic differences. Furthermore, sophisticated equilibrium reconstructions are used to asses uncertainties which arise during mapping from 2D real space coordinates to 1D flux coordinates. ELM synchronization allows the study of the pedestal structure at the ELM stability boundary. The pedestal is characterized by its top value, the gradient and the width. A large parameter range is covered by the two devices. Over this parameter range the profile shape of edge electron density differs from that of the temperature, irrespective of the device. However, the resulting electron pressure profile shape remains similar for all analysed H-Mode discharges.

A two term model of the confinement in Elmy H-modes using the global confinement and pedestal databases

International Nuclear Information System (INIS)

2003-01-01

Two different physical models of the H-mode pedestal are tested against the joint pedestal-core database. These models are then combined with models for the core and shown to give a good fit to the ELMy H-mode database. Predictions are made for the next step tokamaks ITER and FIRE. (author)

Facile and green fabrication of organic single-crystal hollow micro/nanostructures

Energy Technology Data Exchange (ETDEWEB)

Yang Jun; Chen Yingzhi; Ou Xuemei; Zhang Xiaohong [Nano-organic Photoelectronic Laboratory and Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); Zhang Xiujuan, E-mail: xjzhang@suda.edu.cn, E-mail: xhzhang@mail.ipc.ac.cn [Functional Nano and Soft Materials Laboratory (FUNSOM) and Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University, Suzhou 215123 (China)

2011-07-15

Under high humidity and appropriate temperature, tris (8-hydroxyquinoline) aluminum (Alq3) solid micro/nanostructures may be etched into hollow structures and still retain their crystalline structures and surface morphologies. The shapes and sizes of the hollow structures are easily adjusted by varying the experimental parameters. Throughout the entire process, water is introduced into the system instead of organic or corrosive solvents, making this method convenient and environmentally friendly; it can also be extended to application in other materials such as TCNQ.

Automatic diameter control system applied to the laser heated pedestal growth technique

Directory of Open Access Journals (Sweden)

Andreeta M.R.B.

2003-01-01

Full Text Available We described an automatic diameter control system (ADC, for the laser heated pedestal growth technique, that reduces the diameter fluctuations in oxide fibers grown from unreacted and non-sinterized pedestals, to less than 2% of the average fiber diameter, and diminishes the average diameter fluctuation, over the entire length of the fiber, to less than 1%. The ADC apparatus is based on an artificial vision system that controls the pulling speed and the height of the molten zone within a precision of 30 mum. We also show that this system can be used for periodic in situ axial doping the fiber. Pure and Cr3+ doped LaAlO3 and pure LiNbO3 were usedas model materials.

Using LGI experiments to achieve better understanding of pedestal-edge coupling in NSTX-U

Energy Technology Data Exchange (ETDEWEB)

Wang, Zhehui [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2015-02-23

PowerPoint presentation. Latest advances in granule or dust injection technologies, fast and high-resolution imaging, together with micro-/nano-structured material fabrication, provide new opportunities to examine plasma-material interaction (PMI) in magnetic fusion environment. Some of our previous work in these areas is summarized. The upcoming LGI experiments in NSTX-U will shed new light on granular matter transport in the pedestal-edge region. In addition to particle control, these results can also be used for code validation and achieving better understanding of pedestal-edge coupling in fusion plasmas in both NSTX-U and others.

Helical variation of density profiles and fluctuations in the tokamak pedestal with applied 3D fields and implications for confinement

Science.gov (United States)

Wilcox, R. S.; Rhodes, T. L.; Shafer, M. W.; Sugiyama, L. E.; Ferraro, N. M.; Lyons, B. C.; McKee, G. R.; Paz-Soldan, C.; Wingen, A.; Zeng, L.

2018-05-01

Small 3D perturbations to the magnetic field in DIII-D ( δB /B ˜2 ×10-4 ) result in large modulations of density fluctuation amplitudes in the pedestal, which are shown using Doppler backscattering measurements to vary by a factor of 2. Helical perturbations of equilibrium density within flux surfaces have previously been observed in the pedestal of DIII-D plasmas when 3D fields are applied and were correlated with density fluctuation asymmetries in the pedestal. These intra-surface density and pressure variations are shown through two fluid MHD modeling studies using the M3D-C1 code to be due to the misalignment of the density and temperature equilibrium iso-surfaces in the pedestal region. This modeling demonstrates that the phase shift between the two iso-surfaces corresponds to the diamagnetic direction of the two species, with the mass density surfaces shifted in the ion diamagnetic direction relative to the temperature and magnetic flux iso-surfaces. The resulting pedestal density, potential, and turbulence asymmetries within flux surfaces near the separatrix may be at least partially responsible for several poorly understood phenomena that occur with the application of 3D fields in tokamaks, including density pump out and the increase in power required to transition from L- to H-mode.

Gyrokinetic neoclassical study of the bootstrap current in the tokamak edge pedestal with fully non-linear Coulomb collisions

Energy Technology Data Exchange (ETDEWEB)

Hager, Robert, E-mail: rhager@pppl.gov; Chang, C. S., E-mail: cschang@pppl.gov [Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey 08543 (United States)

2016-04-15

As a follow-up on the drift-kinetic study of the non-local bootstrap current in the steep edge pedestal of tokamak plasma by Koh et al. [Phys. Plasmas 19, 072505 (2012)], a gyrokinetic neoclassical study is performed with gyrokinetic ions and drift-kinetic electrons. Besides the gyrokinetic improvement of ion physics from the drift-kinetic treatment, a fully non-linear Fokker-Planck collision operator—that conserves mass, momentum, and energy—is used instead of Koh et al.'s linearized collision operator in consideration of the possibility that the ion distribution function is non-Maxwellian in the steep pedestal. An inaccuracy in Koh et al.'s result is found in the steep edge pedestal that originated from a small error in the collisional momentum conservation. The present study concludes that (1) the bootstrap current in the steep edge pedestal is generally smaller than what has been predicted from the small banana-width (local) approximation [e.g., Sauter et al., Phys. Plasmas 6, 2834 (1999) and Belli et al., Plasma Phys. Controlled Fusion 50, 095010 (2008)], (2) the plasma flow evaluated from the local approximation can significantly deviate from the non-local results, and (3) the bootstrap current in the edge pedestal, where the passing particle region is small, can be dominantly carried by the trapped particles in a broad trapped boundary layer. A new analytic formula based on numerous gyrokinetic simulations using various magnetic equilibria and plasma profiles with self-consistent Grad-Shafranov solutions is constructed.

L-H Power Threshold, Pedestal Stability and Confinement in JET with a Metallic Wall

Energy Technology Data Exchange (ETDEWEB)

Beurskens, M.; Alper, B.; Challis, C.; Flanagan, J.; Giroud, C.; Kempenaars, M.; Lomas, P.; Maslov, M.; Matthews, G.; Mayoral, M. L.; Snyder, P. B.; Saarelma, S., E-mail: marc.beurskens@ccfe.ac.uk [EURATOM /CCFE Fusion Association, Culham Science Centre, Abingdon (United Kingdom); Frassinetti, L. [Division of Fusion Plasma Physics, Association EURATOM-VR , Stockholm (Sweden); Maggi, C.; Angioni, C.; Hobirk, J.; Neu, R. [IPP Garching, Garching (Germany); Calabro, G.; Buratti, P.; Giovannozzi, E. [Associazione EURATOM-ENEA sulla Fusione, Frascati (Italy); Bourdelle, C.; Joffrin, E. [Association Euratom-CEA, IRFM, St-Paul-Lez-Durance (France); Brezinsek, S. [Forschungszentrum Juelich, Juelich (Germany); Groth, M. [Association EURATOM/Helsinki University of Technology, Espoo (Finland); Leyland, M. [Department of Physics, University of York, Heslington, York (United Kingdom); De la Luna, E. [Ciemat, Madrid (Spain); Mantica, P. [Istituto di Fisica del Plasma ' P. Caldirola' , Milano (Italy); Nunes, I. [Centro de Fusao Nuclear, Associacao EURATOM-IST, Lisboa (Portugal); Osborne, T. [General Atomics, San Diego (United States); De Vries, P. [FOM DIFFER, Nieuwegein (Netherlands)

2012-09-15

Full text: After the change-over from the Carbon-Fibre Composite (CFC) wall to an ITER-like metallic wall (ILW) the baseline type I ELMy H-mode scenario has been re-established in JET with the new plasma-facing materials Be and W. A key finding for ITER is that the power required to enter H-mode has reduced with respect to that in JET with the CFC wall. In JET with the ILW the power threshold to enter H-mode (P{sub L-H}) is below the international L-H power threshold scaling P{sub Martin-08}. The minimum threshold is P{sub L-H} = 1.8 MW compared to P{sub Martin-08} = 4 MW with a pedestal density of n{sub ped} = 2 x 10{sup 19} m{sup -3} in plasmas with I{sub p} = 2.0 MA, B{sub t} = 2.4 T. However the threshold depends strongly on density; using slow ion cyclotron heating (ICRH) power ramps P{sub L-H} varies from 1.8 to 4.5 MW in a range of lower and upper plasma triangularity ({delta}{sub L} = 0.32 - 0.4, {delta}{sub U} = 0.19 - 0.38). Stationary Type I ELMy H-mode operation has been re-established at both low and high triangularity with I{sub p} {<=} 2.5 MA, q{sub 95} = 2.8 - 3.6 and H{sub 98} {<=} 1. The achieved plasma collisionality is relatively high, in the range of 1 < v{sub eff} < 4 due to the required strong gas dosing. Stability analysis with the linear MHD stability code ELITE show that the pedestal is marginally unstable with respect to the Peeling Ballooning boundary. Due to the stabilising effect of the global pressure on the pedestal stability, a strong coupling between core and edge confinement is expected. Indeed in an H-mode profile database comparison with 119 CFC- (0.1 < v{sub eff} < 1) and 40 ILW-H-modes a strong coupling of the core versus edge confinement is found, independent of wall material. In addition, the pedestal predictions using the EPED predictive pedestal code coincide with the measured pedestal height over a wide range of normalised pressure 1.5 < {beta}{sub N} < 3.5. Due to the strong core-edge coupling, beneficial effects of core

Synthesis of Hollow CdS-TiO2 Microspheres with Enhanced Visible-Light Photocatalytic Activity

Directory of Open Access Journals (Sweden)

Yuning Huo

2012-01-01

Full Text Available CdS-TiO2 composite photocatalyst in the shape of hollow microsphere was successfully synthesized via the hard-template preparation with polystyrene microspheres followed by ion-exchange approach. The hollow CdS-TiO2 microspheres significantly extended the light adsorption into visible light region, comparing to TiO2 microspheres. It led to much higher photocatalytic activities of hollow CdS-TiO2 microspheres than that of TiO2 during the photodegradation of rhodamine B under visible light irradiations. Furthermore, the well-remained hollow structure could achieve light multireflection within the interior cavities and the separation of photo-induced electrons and holes is efficient in CdS-TiO2, which were facilitated to improving the photoactivity.

High-frequency coherent edge fluctuations in a high-pedestal-pressure quiescent H-mode plasma.

Science.gov (United States)

Yan, Z; McKee, G R; Groebner, R J; Snyder, P B; Osborne, T H; Burrell, K H

2011-07-29

A set of high frequency coherent (HFC) modes (f=80-250 kHz) is observed with beam emission spectroscopy measurements of density fluctuations in the pedestal of a strongly shaped quiescent H-mode plasma on DIII-D, with characteristics predicted for kinetic ballooning modes (KBM): propagation in the ion-diamagnetic drift direction; a frequency near 0.2-0.3 times the ion-diamagnetic frequency; inferred toroidal mode numbers of n∼10-25; poloidal wave numbers of k(θ)∼0.17-0.4 cm(-1); and high measured decorrelation rates (τ(c)(-1)∼ω(s)∼0.5×10(6) s(-1)). Their appearance correlates with saturation of the pedestal pressure. © 2011 American Physical Society

Storage containers for radioactive material

International Nuclear Information System (INIS)

Cassidy, D.A.; Dates, L.R.; Groh, E.F.

1981-01-01

A radioactive material storage system is disclosed for use in the laboratory. This system is composed of the following: a flat base plate with a groove in one surface thereof and a hollow pedestal extending perpendicularly away from the other surface thereof; a sealing gasket in the groove, a cover having a filter therein and an outwardly extending flange which fits over the plate; the groove and the gasket, and a clamp for maintaining the cover and the plate are sealed together, whereby the plate and the cover and the clamp cooperate to provide a storage area for radioactive material readily accessible for use or inventory. Wall mounts are provided to prevent accidental formation of critical masses during storage

Ultem®/ZIF-8 mixed matrix hollow fiber membranes for CO2/N2 separations

KAUST Repository

Dai, Ying

2012-05-01

Organic-inorganic hybrid (mixed matrix) membranes can potentially extend the separation performance of traditional polymeric materials while maintaining processing convenience. Although many dense films studies have been reported, there have been few reported cases of these materials being successfully extended to asymmetric hollow fibers. In this work we report the first successful production of mixed matrix asymmetric hollow fiber membranes containing metal-organic-framework (MOF) ZIF-8 fillers. Specifically, we have incorporated ZIF-8 into a polyetherimide (Ultem ® 1000) matrix and produced dual-layer asymmetric hollow fiber membranes via the dry jet-wet quench method. The outer separating layer of these composite fibers contains 13wt% (17vol%) of ZIF-8 filler. These membranes have been tested over a range of temperatures and pressures for a variety of gas pairs. An increase in separation performance for the CO 2/N 2 gas pairs was observed for both pure gas and mixed gas feeds. © 2012 Elsevier B.V.

Ultem®/ZIF-8 mixed matrix hollow fiber membranes for CO2/N2 separations

KAUST Repository

Dai, Ying; Johnson, J.R.; Karvan, Oğuz; Sholl, David S.; Koros, W.J.

2012-01-01

Organic-inorganic hybrid (mixed matrix) membranes can potentially extend the separation performance of traditional polymeric materials while maintaining processing convenience. Although many dense films studies have been reported, there have been few reported cases of these materials being successfully extended to asymmetric hollow fibers. In this work we report the first successful production of mixed matrix asymmetric hollow fiber membranes containing metal-organic-framework (MOF) ZIF-8 fillers. Specifically, we have incorporated ZIF-8 into a polyetherimide (Ultem ® 1000) matrix and produced dual-layer asymmetric hollow fiber membranes via the dry jet-wet quench method. The outer separating layer of these composite fibers contains 13wt% (17vol%) of ZIF-8 filler. These membranes have been tested over a range of temperatures and pressures for a variety of gas pairs. An increase in separation performance for the CO 2/N 2 gas pairs was observed for both pure gas and mixed gas feeds. © 2012 Elsevier B.V.

Hollow-in-Hollow Carbon Spheres for Lithium-ion Batteries with Superior Capacity and Cyclic Performance

International Nuclear Information System (INIS)

Zang, Jun; Ye, Jianchuan; Fang, Xiaoliang; Zhang, Xiangwu; Zheng, Mingsen; Dong, Quanfeng

2015-01-01

Highlights: • Hollow-in-hollow structured HIHCS was synthesized via a facile templating strategy. • The HCS core and hollow carbon shell constitute the hollow-in-hollow structure. • The HIHCS exhibited superior rate capability and cycle stability as anode material. • The excellent performance is attributed to the unique hollow-in-hollow structure. - Abstract: Hollow spheres structured materials have been intensively pursued due to their unique properties for energy storage. In this paper, hollow-in-hollow carbon spheres (HIHCS) with a multi-shelled structure were successfully synthesized using a facile hard-templating procedure. When evaluated as anode material for lithium-ion batteries, the resultant HIHCS anode exhibited superior capacity and cycling stability than HCS. It could deliver reversible capacities of 937, 481, 401, 304 and 236 mAh g −1 at current densities of 0.1 A g −1 , 1 A g −1 , 2 A g −1 , 5 A g −1 and 10 A g −1 , respectively. And capacity fading is not apparent in 500 cycles at 5 A g −1 . The excellent performance of the HIHCS anode is ascribed to its unique hollow-in-hollow structure and high specific surface area.

Semi-analytical study of the tokamak pedestal density profile in a single-null diverted plasma with puffing-recycling gas sources

Science.gov (United States)

Shi, Bingren

2010-10-01

The tokamak pedestal density structure is generally studied using a diffusion-dominant model. Recent investigations (Stacey and Groebner 2009 Phys. Plasmas 16 102504) from first principle based physics have shown a plausible existence of large inward convection in the pedestal region. The diffusion-convection equation with rapidly varying convection and diffusion coefficients in the near edge region and model puffing-recycling neutral particles is studied in this paper. A peculiar property of its solution for the existence of the large convection case is that the pedestal width of the density profile, qualitatively different from the diffusion-dominant case, depends mainly on the width of the inward convection and only weakly on the neutral penetration length and its injection position.

Semi-analytical study of the tokamak pedestal density profile in a single-null diverted plasma with puffing-recycling gas sources

Energy Technology Data Exchange (ETDEWEB)

Shi Bingren, E-mail: shibr@swip.ac.c [Southwestern Institute of Physics, PO Box 432, Chengdu, Sichuan 610041 (China)

2010-10-15

The tokamak pedestal density structure is generally studied using a diffusion-dominant model. Recent investigations (Stacey and Groebner 2009 Phys. Plasmas 16 102504) from first principle based physics have shown a plausible existence of large inward convection in the pedestal region. The diffusion-convection equation with rapidly varying convection and diffusion coefficients in the near edge region and model puffing-recycling neutral particles is studied in this paper. A peculiar property of its solution for the existence of the large convection case is that the pedestal width of the density profile, qualitatively different from the diffusion-dominant case, depends mainly on the width of the inward convection and only weakly on the neutral penetration length and its injection position.

Global gyrokinetic simulation of Tokamak edge pedestal instabilities.

Science.gov (United States)

Wan, Weigang; Parker, Scott E; Chen, Yang; Yan, Zheng; Groebner, Richard J; Snyder, Philip B

2012-11-02

Global electromagnetic gyrokinetic simulations show the existence of near threshold conditions for both a high-n kinetic ballooning mode (KBM) and an intermediate-n kinetic version of peeling-ballooning mode (KPBM) in the edge pedestal of two DIII-D H-mode discharges. When the magnetic shear is reduced in a narrow region of steep pressure gradient, the KPBM is significantly stabilized, while the KBM is weakly destabilized and hence becomes the most-unstable mode. Collisions decrease the KBM's critical β and increase the growth rate.

Application of a probabilistic model of rainfall-induced shallow landslides to complex hollows

Directory of Open Access Journals (Sweden)

A. Talebi

2008-07-01

Full Text Available Recently, D'Odorico and Fagherazzi (2003 proposed "A probabilistic model of rainfall-triggered shallow landslides in hollows" (Water Resour. Res., 39, 2003. Their model describes the long-term evolution of colluvial deposits through a probabilistic soil mass balance at a point. Further building blocks of the model are: an infinite-slope stability analysis; a steady-state kinematic wave model (KW of hollow groundwater hydrology; and a statistical model relating intensity, duration, and frequency of extreme precipitation. Here we extend the work of D'Odorico and Fagherazzi (2003 by incorporating a more realistic description of hollow hydrology (hillslope storage Boussinesq model, HSB such that this model can also be applied to more gentle slopes and hollows with different plan shapes. We show that results obtained using the KW and HSB models are significantly different as in the KW model the diffusion term is ignored. We generalize our results by examining the stability of several hollow types with different plan shapes (different convergence degree. For each hollow type, the minimum value of the landslide-triggering saturated depth corresponding to the triggering precipitation (critical recharge rate is computed for steep and gentle hollows. Long term analysis of shallow landslides by the presented model illustrates that all hollows show a quite different behavior from the stability view point. In hollows with more convergence, landslide occurrence is limited by the supply of deposits (supply limited regime or rainfall events (event limited regime while hollows with low convergence degree are unconditionally stable regardless of the soil thickness or rainfall intensity. Overall, our results show that in addition to the effect of slope angle, plan shape (convergence degree also controls the subsurface flow and this process affects the probability distribution of landslide occurrence in different hollows. Finally, we conclude that

A novel technique for real-time estimation of edge pedestal density gradients via reflectometer time delay data

Energy Technology Data Exchange (ETDEWEB)

Zeng, L., E-mail: zeng@fusion.gat.com; Doyle, E. J.; Rhodes, T. L.; Wang, G.; Sung, C.; Peebles, W. A. [Physics and Astronomy Department, University of California, Los Angeles, California 90095 (United States); Bobrek, M. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6006 (United States)

2016-11-15

A new model-based technique for fast estimation of the pedestal electron density gradient has been developed. The technique uses ordinary mode polarization profile reflectometer time delay data and does not require direct profile inversion. Because of its simple data processing, the technique can be readily implemented via a Field-Programmable Gate Array, so as to provide a real-time density gradient estimate, suitable for use in plasma control systems such as envisioned for ITER, and possibly for DIII-D and Experimental Advanced Superconducting Tokamak. The method is based on a simple edge plasma model with a linear pedestal density gradient and low scrape-off-layer density. By measuring reflectometer time delays for three adjacent frequencies, the pedestal density gradient can be estimated analytically via the new approach. Using existing DIII-D profile reflectometer data, the estimated density gradients obtained from the new technique are found to be in good agreement with the actual density gradients for a number of dynamic DIII-D plasma conditions.

Dimensionless scalings of confinement, heat transport and pedestal stability in JET-ILW and comparison with JET-C

Czech Academy of Sciences Publication Activity Database

Frassinetti, L.; Saarelma, S.; Lomas, P.; Nunes, I.; Rimini, F.; Beurskens, M.N.A.; Bílková, Petra; Boom, J.E.; De La Luna, E.; Delabie, E.; Drewelow, P.; Flanagan, J.; Garzotti, L.; Giroud, C.; Hawks, N.; Joffrin, E.; Kempenaars, M.; Kim, H.-T.; Kruezi, U.; Loarte, A.; Lomanowski, B.; Lupelli, I.; Meneses, L.; Maggi, C.F.; Menmuir, S.; Peterka, Matěj; Rachlew, E.; Romanelli, M.; Stefanikova, E.

2017-01-01

Roč. 59, č. 1 (2017), č. článku 014014. ISSN 0741-3335. [EPS 2016: Conference on Plasma Physics/43./. Leuven, 04.07.2016-08.07.2016] EU Projects: European Commission(XE) 633053 - EUROfusion Institutional support: RVO:61389021 Keywords : JET-ILW * dimensionless scaling * pedestal * confinement * pedestal stability * heat transport Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 2.392, year: 2016 http://dx.doi.org/10.1088/0741-3335/59/1/014014

H-Mode Turbulence, Power Threshold, ELM, and Pedestal Studies in NSTX

International Nuclear Information System (INIS)

Maingi, R.; Bush, C.E.; Fredrickson, E.D.; Gates, D.A.; Kaye, S.M.; LeBlanc, B.P.; Menard, J.E.; Meyer, H.; Mueller, D.; Nishino, N.; Roquemore, A.L.; Sabbagh, S.A.; Tritz, K.; Zweben, S.J.; Bell, M.G.; Bell, R.E.; Biewer, T.; Boedo, J.A.; Johnson, D.W.; Kaita, R.; Kugel, H.W.; Maqueda, R.J.; Munsat, T.; Raman, R.; Soukhanovskii, V.A.; Stevenson, T.; Stutman, D.

2004-01-01

High-confinement mode (H-mode) operation plays a crucial role in NSTX [National Spherical Torus Experiment] research, allowing higher beta limits due to reduced plasma pressure peaking, and long-pulse operation due to high bootstrap current fraction. Here, new results are presented in the areas of edge localized modes (ELMs), H-mode pedestal physics, L-H turbulence, and power threshold studies. ELMs of several other types (as observed in conventional aspect ratio tokamaks) are often observed: (1) large, Type I ELMs, (2) ''medium'' Type II/III ELMs, and (3) giant ELMs which can reduce stored energy by up to 30% in certain conditions. In addition, many high-performance discharges in NSTX have tiny ELMs (newly termed Type V), which have some differences as compared with ELM types in the published literature. The H-mode pedestal typically contains between 25-33% of the total stored energy, and the NSTX pedestal energy agrees reasonably well with a recent international multi-machine scaling. We find that the L-H transition occurs on a ∼100 (micro)sec timescale as viewed by a gas puff imaging diagnostic, and that intermittent quiescent periods precede the final transition. A power threshold identity experiment between NSTX and MAST shows comparable loss power at the L-H transition in balanced double-null discharges. Both machines require more power for the L-H transition as the balance is shifted toward lower single null. High field side gas fueling enables more reliable H-mode access, but does not always lead to a lower power threshold e.g., with a reduction of the duration of early heating. Finally the edge plasma parameters just before the L-H transition were compared with theories of the transition. It was found that while some theories can separate well-developed L- and H-mode data, they have little predictive value

The Influence of Slowly Varying Mass on Severity of Dynamics Nonlinearity of Bearing-Rotor Systems with Pedestal Looseness

Directory of Open Access Journals (Sweden)

Mian Jiang

2018-01-01

Full Text Available Nonlinearity measure is proposed to investigate the influence of slowly varying mass on severity of dynamics nonlinearity of bearing-rotor systems with pedestal looseness. A nonlinear mathematical model including the effect of slowly varying disk mass is developed for a bearing-rotor system with pedestal looseness. The varying of equivalent disk mass is described by a cosine function, and the amplitude coefficient is used as a control parameter. Then, nonlinearity measure is employed to quantify the severity of dynamics nonlinearity of bearing-rotor systems. With the increasing of looseness clearances, the curves that denote the trend of nonlinearity degree are plotted for each amplitude coefficient of mass varying. It can be concluded that larger amplitude coefficients of the disk mass varying will have more influence on the severity of dynamics nonlinearity and generation of chaotic behaviors in rotor systems with pedestal looseness.

Switching a Nanocluster Core from Hollow to Non-hollow

KAUST Repository

Bootharaju, Megalamane Siddaramappa

2016-03-24

Modulating the structure-property relationship in atomically precise nanoclusters (NCs) is vital for developing novel NC materials and advancing their applications. While promising biphasic ligand-exchange (LE) strategies have been developed primarily to attain novel NCs, understanding the mechanistic aspects involved in tuning the core and the ligand-shell of NCs in such biphasic processes is challenging. Here, we design a single phase LE process that enabled us to elucidate the mechanism of how a hollow NC (e.g., [Ag44(SR)30]4-, -SR: thiolate) converts into a non-hollow NC (e.g., [Ag25(SR)18]-), and vice versa. Our study reveals that the complete LE of the hollow [Ag44(SPhF)30]4- NCs (–SPhF: 4-fluorobenzenethiolate) with incoming 2,4-dimethylbenzenethiol (HSPhMe2) induced distortions in the Ag44 structure forming the non-hollow [Ag25(SPhMe2)18]- by a disproportionation mechanism. While the reverse reaction of [Ag25(SPhMe2)18]- with HSPhF prompted an unusual dimerization of Ag25, followed by a rearrangement step that reproduces the original [Ag44(SPhF)30]4-. Remarkably, both the forward and the backward reactions proceed through similar size intermediates that seem to be governed by the boundary conditions set by the thermodynamic and electronic stability of the hollow and non-hollow metal cores. Furthermore, the resizing of NCs highlights the surprisingly long-range effect of the ligands which are felt by atoms far deep in the metal core, thus opening a new path for controlling the structural evolution of nanoparticles.

Highly scalable ZIF-based mixed-matrix hollow fiber membranes for advanced hydrocarbon separations

KAUST Repository

Zhang, Chen

2014-05-29

ZIF-8/6FDA-DAM, a proven mixed-matrix material that demonstrated remarkably enhanced C3H6/C3H8 selectivity in dense film geometry, was extended to scalable hollow fiber geometry in the current work. We successfully formed dual-layer ZIF-8/6FDA-DAM mixed-matrix hollow fiber membranes with ZIF-8 nanoparticle loading up to 30 wt % using the conventional dry-jet/wet-quench fiber spinning technique. The mixed-matrix hollow fibers showed significantly enhanced C3H6/C3H8 selectivity that was consistent with mixed-matrix dense films. Critical variables controlling successful formation of mixed-matrix hollow fiber membranes with desirable morphology and attractive transport properties were discussed. Furthermore, the effects of coating materials on selectivity recovery of partially defective fibers were investigated. To our best knowledge, this is the first article reporting successful formation of high-loading mixed-matrix hollow fiber membranes with significantly enhanced selectivity for separation of condensable olefin/paraffin mixtures. Therefore, it represents a major step in the research area of advanced mixed-matrix membranes. © 2014 American Institute of Chemical Engineers.

Martian Low-Aspect-Ratio Layered Ejecta (LARLE) craters: Distribution, characteristics, and relationship to pedestal craters

Science.gov (United States)

Barlow, Nadine G.; Boyce, Joseph M.; Cornwall, Carin

2014-09-01

Low-Aspect-Ratio Layered Ejecta (LARLE) craters are a unique landform found on Mars. LARLE craters are characterized by a crater and normal layered ejecta pattern surrounded by an extensive but thin outer deposit which terminates in a sinuous, almost flame-like morphology. We have conducted a survey to identify all LARLE craters ⩾1-km-diameter within the ±75° latitude zone and to determine their morphologic and morphometric characteristics. The survey reveals 140 LARLE craters, with the majority (91%) located poleward of 40°S and 35°N and all occurring within thick mantles of fine-grained deposits which are likely ice-rich. LARLE craters range in diameter from the cut-off limit of 1 km up to 12.2 km, with 83% being smaller than 5 km. The radius of the outer LARLE deposit displays a linear trend with the crater radius and is greatest at higher polar latitudes. The LARLE deposit ranges in length between 2.56 and 14.81 crater radii in average extent, with maximum length extending up to 21.4 crater radii. The LARLE layer is very sinuous, with lobateness values ranging between 1.45 and 4.35. LARLE craters display a number of characteristics in common with pedestal craters and we propose that pedestal craters are eroded versions of LARLE craters. The distribution and characteristics of the LARLE craters lead us to propose that impact excavation into ice-rich fine-grained deposits produces a dusty base surge cloud (like those produced by explosion craters) that deposits dust and ice particles to create the LARLE layers. Salts emplaced by upward migration of water through the LARLE deposit produce a surficial duricrust layer which protects the deposit from immediate removal by eolian processes.

High-Precision Dispensing of Nanoliter Biofluids on Glass Pedestal Arrays for Ultrasensitive Biomolecule Detection.

Science.gov (United States)

Chen, Xiaoxiao; Liu, Yang; Xu, QianFeng; Zhu, Jing; Poget, Sébastien F; Lyons, Alan M

2016-05-04

Precise dispensing of nanoliter droplets is necessary for the development of sensitive and accurate assays, especially when the availability of the source solution is limited. Conventional approaches are limited by imprecise positioning, large shear forces, surface tension effects, and high costs. To address the need for precise and economical dispensing of nanoliter volumes, we developed a new approach where the dispensed volume is dependent on the size and shape of defined surface features, thus freeing the dispensing process from pumps and fine-gauge needles requiring accurate positioning. The surface we fabricated, called a nanoliter droplet virtual well microplate (nVWP), achieves high-precision dispensing (better than ±0.5 nL or ±1.6% at 32 nL) of 20-40 nL droplets using a small source drop (3-10 μL) on isolated hydrophilic glass pedestals (500 μm on a side) bonded to arrays of polydimethylsiloxane conical posts. The sharp 90° edge of the glass pedestal pins the solid-liquid-vapor triple contact line (TCL), averting the wetting of the glass sidewalls while the fluid is prevented from receding from the edge. This edge creates a sufficiently large energy barrier such that microliter water droplets can be poised on the glass pedestals, exhibiting contact angles greater >150°. This approach relieves the stringent mechanical alignment tolerances required for conventional dispensing techniques, shifting the control of dispensed volume to the area circumscribed by the glass edge. The effects of glass surface chemistry and dispense velocity on droplet volume were studied using optical microscopy and high-speed video. Functionalization of the glass pedestal surface enabled the selective adsorption of specific peptides and proteins from synthetic and natural biomolecule mixtures, such as venom. We further demonstrate how the nVWP dispensing platform can be used for a variety of assays, including sensitive detection of proteins and peptides by fluorescence

Edge stability and pedestal profile sensitivity of snowflake diverted equilibria in the TCV Tokamak

International Nuclear Information System (INIS)

Medvedev, S.Yu.; Ivanov, A.A.; Martynov, A.A.; Poshekhonov, Yu.Yu.; Behn, R.; Martin, Y.R.; Moret, J.M.; Piras, F.; Pitzschke, A.; Pochelon, A.; Sauter, O.; Villard, L.

2010-01-01

A second order null divertor (snowflake) has been successfully created and controlled in the TCV tokamak[1] (F. Piras et al., Plasma Phys. Control. Fusion, 2009). The results of ideal MHD edge stability computations show an enhancement of the edge stability properties of the snowflake equilibria compared to standard x-point configurations[2] (S. Yu. Medvedev et al., 36th EPS Conference on Plasma Physics, 2009). However, a sensitivity study of the stability limits to variations of the pedestal profiles is essential for making conclusions about possibilities of ELM control in snowflake plasmas. Variations of the edge stability and beta limits for several types of snowflake equilibria, different values of triangularity and various pedestal profiles are investigated (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Global and pedestal confinement in JET with a Be/W metallic wall

Czech Academy of Sciences Publication Activity Database

Beurskens, M.N.A.; Frassinetti, L.; Challis, C.; Giroud, C.; Saarelma, S.; Alper, B.; Angioni, C.; Bílková, Petra; Bourdelle, C.; Brezinsek, S.; Buratti, P.; Calabrò, G.; Eich, E.; Flanagan, J.; Giovannozzi, E.; Groth, M.; Hobirk, J.; Joffrin, E.; Leyland, M.J.; Lomas, P.; De La Luna, E.; Kempenaars, M.; Maddison, G.; Maggi, C.; Mantica, P.; Maslov, M.; Matthews, G.; Mayoral, M.-L.; Neu, R.; Nunes, I.; Osborne, T.; Rimini, F.; Scannell, R.; Solano, E.R.; Snyder, P.B.; Voitsekhovitch, I.; de Vries, P.

2014-01-01

Roč. 54, č. 4 (2014), 043001-043001 ISSN 0029-5515 Institutional support: RVO:61389021 Keywords : pedestal * confinement * nitrogen * radiation * tokamak * metal wall Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 3.062, year: 2014 http://iopscience.iop.org/0029-5515/54/4/043001/pdf/0029-5515_54_4_043001.pdf

Power exhaust by SOL and pedestal radiation at ASDEX Upgrade and JET

Directory of Open Access Journals (Sweden)

M. Bernert

2017-08-01

Applying these seed impurities for highly radiative scenarios impacts local plasma parameters and alters the impurity transport in the pedestal region. Thus, plasma confinement and stability can be affected. A proper understanding of the effects by these impurities is required in order to predict the applicability of such scenarios for future devices.

Square-lattice large-pitch hollow-core photonic crystal fiber

DEFF Research Database (Denmark)

Couny, F.; Roberts, John; Birks, T.A.

2008-01-01

We report on the design, fabrication and characterization of silica square-lattice hollow core photonic crystal fibers optimized for low loss guidance over an extended frequency range in the mid-IR region of the optical spectrum. The fiber's linear optical properties include an ultra-low group...... velocity dispersion and a polarization cross-coupling as low as -13.4dB over 10m of fiber....

Transformation from hollow carbon octahedra to compressed octahedra and their use in lithium-ion batteries

International Nuclear Information System (INIS)

Mei, Tao; Li, Na; Li, Qianwen; Xing, Zheng; Tang, Kaibin; Zhu, Yongchun; Qian, Yitai; Shen, Xiaoyan

2012-01-01

Graphical abstract: Schematic illustration of the transformation process from hollow carbon octahedra into deflated balloon-like compressed hollow carbon octahedra ▪. Highlights: ► We demonstrate the in situ template synthesis of hollow carbon octahedra. ► The shell thickness of hollow carbon octahedra is only 2.5 nm. ► Morphology transformation could be realized by extending of reaction time. ► The hollow structures show reversible capacity as 353 mAh g −1 after 100 cycles. -- Abstract: Hollow carbon octahedra with an average size of 300 nm and a shell thickness of 2.5 nm were prepared by a reaction starting from ferrocene and Mg(CH 3 COO) 2 ·4H 2 O at 700 °C for 10 h. They became compressed and turned into deflated balloon-like octahedra when the reaction time was increased to 16 h. It was proposed that the gas pressure generated during the reaction process induced the transformation from broken carbon hollow octahedra into deflated balloon-like compressed octahedra. X-ray powder diffraction and Raman spectroscopy indicate that the as-obtained carbon products possess a graphitic structure and high-resolution transmission electron microscopy images indicate that they have low crystallinity. Their application as an electrode shows reversible capacity of 353 mAh g −1 after 100 cycles in the charge/discharge experiments of secondary lithium ion batteries.

Hollow-Core Fiber Lamp

Science.gov (United States)

Yi, Lin (Inventor); Tjoelker, Robert L. (Inventor); Burt, Eric A. (Inventor); Huang, Shouhua (Inventor)

2016-01-01

Hollow-core capillary discharge lamps on the millimeter or sub-millimeter scale are provided. The hollow-core capillary discharge lamps achieve an increased light intensity ratio between 194 millimeters (useful) and 254 millimeters (useless) light than conventional lamps. The capillary discharge lamps may include a cone to increase light output. Hollow-core photonic crystal fiber (HCPCF) may also be used.

Integrated predictive modeling of high-mode tokamak plasmas using a combination of core and pedestal models

International Nuclear Information System (INIS)

Bateman, Glenn; Bandres, Miguel A.; Onjun, Thawatchai; Kritz, Arnold H.; Pankin, Alexei

2003-01-01

A new integrated modeling protocol is developed using a model for the temperature and density pedestal at the edge of high-mode (H-mode) plasmas [Onjun et al., Phys. Plasmas 9, 5018 (2002)] together with the Multi-Mode core transport model (MMM95) [Bateman et al., Phys. Plasmas 5, 1793 (1998)] in the BALDUR integrated modeling code to predict the temperature and density profiles of 33 H-mode discharges. The pedestal model is used to provide the boundary conditions in the simulations, once the heating power rises above the H-mode power threshold. Simulations are carried out for 20 discharges in the Joint European Torus and 13 discharges in the DIII-D tokamak. These discharges include systematic scans in normalized gyroradius, plasma pressure, collisionality, isotope mass, elongation, heating power, and plasma density. The average rms deviation between experimental data and the predicted profiles of temperature and density, normalized by central values, is found to be about 10%. It is found that the simulations tend to overpredict the temperature profiles in discharges with low heating power per plasma particle and to underpredict the temperature profiles in discharges with high heating power per particle. Variations of the pedestal model are used to test the sensitivity of the simulation results

A flexible platform for simulations of sputtering hollow cathode discharges for laser applications

NARCIS (Netherlands)

Mihailova, D.B.; Grozeva, M.; Hagelaar, G.J.M.; Dijk, van J.; Brok, W.J.M.; Mullen, van der J.J.A.M.

2008-01-01

The Plasimo modelling platform, extended with a cathode wall sputtering module is used to study the discharge processes and to optimise the design parameters of a sputtering hollow cathode discharge (HCD). We present Plasimo simulations of a HCD used for laser applications. A time dependent

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

Characterization and parametric dependencies of low wavenumber pedestal turbulence in the National Spherical Torus Experiment

Energy Technology Data Exchange (ETDEWEB)

Smith, D. R.; Fonck, R. J.; McKee, G. R.; Thompson, D. S. [Department of Engineering Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Bell, R. E.; Diallo, A.; Guttenfelder, W.; Kaye, S. M.; LeBlanc, B. P.; Podesta, M. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)

2013-05-15

The spherical torus edge region is among the most challenging regimes for plasma turbulence simulations. Here, we measure the spatial and temporal properties of ion-scale turbulence in the steep gradient region of H-mode pedestals during edge localized mode-free, MHD quiescent periods in the National Spherical Torus Experiment. Poloidal correlation lengths are about 10 ρ{sub i}, and decorrelation times are about 5 a/c{sub s}. Next, we introduce a model aggregation technique to identify parametric dependencies among turbulence quantities and transport-relevant plasma parameters. The parametric dependencies show the most agreement with transport driven by trapped-electron mode, kinetic ballooning mode, and microtearing mode turbulence, and the least agreement with ion temperature gradient turbulence. In addition, the parametric dependencies are consistent with turbulence regulation by flow shear and the empirical relationship between wider pedestals and larger turbulent structures.

Influence of gold nanoparticles on the 805 nm gain in Tm3+/Yb3+ codoped PbO-GeO2 pedestal waveguides

Science.gov (United States)

de Assumpção, T. A. A.; Camilo, M. E.; Alayo, M. I.; da Silva, D. M.; Kassab, L. R. P.

2017-10-01

The production and characterization of pedestal waveguides based on PbO-GeO2 amorphous thin films codoped with Tm3+/Yb3+, with and without gold nanoparticles (NPs), are reported. Pedestal structure was obtained by conventional photolithography and plasma etching. Tm3+/Yb3+ codoped PGO amorphous thin film was obtained by RF Magnetron Sputtering deposition and used as core layer in the pedestal optical waveguide. The minimum propagation losses in the waveguide were 3.6 dB/cm at 1068 nm. The internal gain at 805 nm was enhanced and increased to 8.67 dB due to the presence of gold NPs. These results demonstrate for the first time that Tm3+/Yb3+ codoped PbO-GeO2 waveguides are promising for first telecom window and integrated photonics, especially for applications on fiber network at short distances.

International workshop of the Confinement Database and Modelling Expert Group in collaboration with the Edge and Pedestal Physics Expert Group

International Nuclear Information System (INIS)

Cordey, J.; Kardaun, O.

2001-01-01

A Workshop of the Confinement Database and Modelling Expert Group (EG) was held on 2-6 April at the Plasma Physics Research Center of Lausanne (CRPP), Switzerland. Presentations were held on the present status of the plasma pedestal (temperature and energy) scalings from an empirical and theoretical perspective. An integrated approach to modelling tokamaks incorporating core transport, edge pedestal and SOL, together with a model for ELMs was presented by JCT. New experimental data on on global H-mode confinement were discussed and presentations on L-H threshold power were made

Acoustic transfer of protein crystals from agarose pedestals to micromeshes for high-throughput screening

International Nuclear Information System (INIS)

Cuttitta, Christina M.; Ericson, Daniel L.; Scalia, Alexander; Roessler, Christian G.; Teplitsky, Ella; Joshi, Karan; Campos, Olven; Agarwal, Rakhi; Allaire, Marc; Orville, Allen M.; Sweet, Robert M.; Soares, Alexei S.

2015-01-01

An acoustic high-throughput screening method is described for harvesting protein crystals and combining the protein crystals with chemicals such as a fragment library. Acoustic droplet ejection (ADE) is an emerging technology with broad applications in serial crystallography such as growing, improving and manipulating protein crystals. One application of this technology is to gently transfer crystals onto MiTeGen micromeshes with minimal solvent. Once mounted on a micromesh, each crystal can be combined with different chemicals such as crystal-improving additives or a fragment library. Acoustic crystal mounting is fast (2.33 transfers s −1 ) and all transfers occur in a sealed environment that is in vapor equilibrium with the mother liquor. Here, a system is presented to retain crystals near the ejection point and away from the inaccessible dead volume at the bottom of the well by placing the crystals on a concave agarose pedestal (CAP) with the same chemical composition as the crystal mother liquor. The bowl-shaped CAP is impenetrable to crystals. Consequently, gravity will gently move the crystals into the optimal location for acoustic ejection. It is demonstrated that an agarose pedestal of this type is compatible with most commercially available crystallization conditions and that protein crystals are readily transferred from the agarose pedestal onto micromeshes with no loss in diffraction quality. It is also shown that crystals can be grown directly on CAPs, which avoids the need to transfer the crystals from the hanging drop to a CAP. This technology has been used to combine thermolysin and lysozyme crystals with an assortment of anomalously scattering heavy atoms. The results point towards a fast nanolitre method for crystal mounting and high-throughput screening

Preparation of TiO2 hollow fibers using poly(vinylidene fluoride) hollow fiber microfiltration membrane as a template

International Nuclear Information System (INIS)

Lu Haiqiang; Zhang Lixiong; Xing Weihong; Wang Huanting; Xu Nanping

2005-01-01

TiO 2 hollow fibers were successfully prepared by using poly(vinylidene fluoride) hollow fiber microfiltration membrane as a template. The preparation procedure includes repeated impregnation of the TiO 2 precursor in the pores of the polymeric membrane, and calcination to burn off the template, producing the TiO 2 hollow fibers. The TiO 2 hollow fibers were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). TiO 2 hollow fibers with other structures, such as honeycomb monolith and spring, were also prepared by preshaping the polymeric membranes into the honeycomb structure and spring, respectively. The phase structure of the TiO 2 hollow fibers could be readily adjusted by changing the calcination temperature

Observation of ion scale fluctuations in the pedestal region during the edge-localized-mode cycle on the National Spherical Torus Experiment

Energy Technology Data Exchange (ETDEWEB)

Diallo, A.; Kramer, G. J.; Bell, R. E.; Guttenfelder, W.; LeBlanc, B. P.; Podesta, M. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540 (United States); Smith, D. R.; McKee, G. J. [Departments of Engineering Physics and Physics, University of Wisconsin, Madison, Wisconsin (United States); Maingi, R. [Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831 (United States); Fonck, R. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540 (United States); Departments of Engineering Physics and Physics, University of Wisconsin, Madison, Wisconsin (United States)

2013-01-15

Characterization of the spatial structure of turbulence fluctuations during the edge localized mode cycle in the pedestal region is reported. Using the beam emission spectroscopy and the correlation reflectometry systems, measurements show spatial structure-k{sub Up-Tack }{rho}{sub i}{sup ped}-ranging from 0.2 to 0.7 propagating in the ion diamagnetic drift direction at the pedestal top. These propagating spatial scales are found to be anisotropic and consistent with ion-scale microturbulence of the type ion temperature gradient and/or kinetic ballooning modes.

Impact of the pedestal plasma density on dynamics of edge localized mode crashes and energy loss scaling

Energy Technology Data Exchange (ETDEWEB)

Xu, X. Q., E-mail: xxu@llnl.gov [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Ma, J. F. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Institute for Fusion Studies, University of Texas, Austin, Texas 78712 (United States); Li, G. Q. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Institute of Plasma Physics, Chinese Academy of Sciences, Hefei (China)

2014-12-15

The latest BOUT++ studies show an emerging understanding of dynamics of edge localized mode (ELM) crashes and the consistent collisionality scaling of ELM energy losses with the world multi-tokamak database. A series of BOUT++ simulations are conducted to investigate the scaling characteristics of the ELM energy losses vs collisionality via a density scan. Linear results demonstrate that as the pedestal collisionality decreases, the growth rate of the peeling-ballooning modes decreases for high n but increases for low n (1 < n < 5), therefore the width of the growth rate spectrum γ(n) becomes narrower and the peak growth shifts to lower n. Nonlinear BOUT++ simulations show a two-stage process of ELM crash evolution of (i) initial bursts of pressure blob and void creation and (ii) inward void propagation. The inward void propagation stirs the top of pedestal plasma and yields an increasing ELM size with decreasing collisionality after a series of micro-bursts. The pedestal plasma density plays a major role in determining the ELM energy loss through its effect on the edge bootstrap current and ion diamagnetic stabilization. The critical trend emerges as a transition (1) linearly from ballooning-dominated states at high collisionality to peeling-dominated states at low collisionality with decreasing density and (2) nonlinearly from turbulence spreading dynamics at high collisionality into avalanche-like dynamics at low collisionality.

Hollow Micro-/Nanostructures: Synthesis and Applications

KAUST Repository

Lou, Xiong Wen (David)

2008-11-03

Hollow micro-nanostructures are of great interest in many current and emerging areas of technology. Perhaps the best-known example of the former is the use of fly-ash hollow particles generated from coal power plants as partial replacement for Portland cement, to produce concrete with enhanced strength and durability. This review is devoted to the progress made in the last decade in synthesis and applications of hollow micro-nanostructures. We present a comprehensive overview of synthetic strategies for hollow structures. These strategies are broadly categorized into four themes, which include well-established approaches, such as conventional hard-templating and soft-templating methods, as well as newly emerging methods based on sacrificial templating and template-free synthesis. Success in each has inspired multiple variations that continue to drive the rapid evolution of the field. The Review therefore focuses on the fundamentals of each process, pointing out advantages and disadvantages where appropriate. Strategies for generating more complex hollow structures, such as rattle-type and nonspherical hollow structures, are also discussed. Applications of hollow structures in lithium batteries, catalysis and sensing, and biomedical applications are reviewed. © 2008 WILEY-VCH Verlag GmbH & Co. KGaA,.

The L-H transition and the stability of the edge pedestal

International Nuclear Information System (INIS)

Rogers, B.N.; Drake, J.F.; Zeiler, A.

2001-01-01

Based on three-dimensional simulations of the Braginskii equations, we identify two main parameters which control transport in the edge of tokamaks: the MHD ballooning parameter and a diamagnetic parameter. The space defined by these parameters delineates regions where typical L-mode levels of transport arise, where the transport is catastrophically large (density limit) and where the plasma spontaneously forms a transport barrier (H-mode). Ion diamagnetic effects allow the edge pedestal to steepen well beyond the first ideal MHD stability boundary. (author)

SnO2@C@VO2 Composite Hollow Nanospheres as an Anode Material for Lithium-Ion Batteries.

Science.gov (United States)

Guo, Wenbin; Wang, Yong; Li, Qingyuan; Wang, Dongxia; Zhang, Fanchao; Yang, Yiqing; Yu, Yang

2018-05-02

Porous SnO 2 @C@VO 2 composite hollow nanospheres were ingeniously constructed through the combination of layer-by-layer deposition and redox reaction. Moreover, to optimize the electrochemical properties, SnO 2 @C@VO 2 composite hollow nanospheres with different contents of the external VO 2 were also studied. On the one hand, the elastic and conductive carbon as interlayer in the SnO 2 @C@VO 2 composite can not only buffer the huge volume variation during repetitive cycling but also effectively improve electronic conductivity and enhance the utilizing rate of SnO 2 and VO 2 with high theoretical capacity. On the other hand, hollow nanostructures of the composite can be consolidated by the multilayered nanocomponents, resulting in outstanding cyclic stability. In virtue of the above synergetic contribution from individual components, SnO 2 @C@VO 2 composite hollow nanospheres exhibit a large initial discharge capacity (1305.6 mAhg -1 ) and outstanding cyclic stability (765.1 mAhg -1 after 100 cycles). This design of composite hollow nanospheres may be extended to the synthesis of other nanomaterials for electrochemical energy storage.

Acoustic transfer of protein crystals from agarose pedestals to micromeshes for high-throughput screening

Energy Technology Data Exchange (ETDEWEB)

Cuttitta, Christina M. [Brookhaven National Laboratory, Upton, NY 11973-5000 (United States); The City University of New York, 2800 Victory Boulevard, Staten Island, NY 10314 (United States); Ericson, Daniel L. [Brookhaven National Laboratory, Upton, NY 11973-5000 (United States); University at Buffalo, SUNY, 12 Capen Hall, Buffalo, NY 14260 (United States); Scalia, Alexander [Brookhaven National Laboratory, Upton, NY 11973-5000 (United States); Binghamton University, 4400 Vestal Parkway East, Binghamton, NY 11973-5000 (United States); Roessler, Christian G. [Brookhaven National Laboratory, Upton, NY 11973-5000 (United States); Teplitsky, Ella [Brookhaven National Laboratory, Upton, NY 11973-5000 (United States); Stony Brook University, Stony Brook, NY 11794-5215 (United States); Joshi, Karan [Brookhaven National Laboratory, Upton, NY 11973-5000 (United States); PEC University of Technology, Chandigarh (India); Campos, Olven [Brookhaven National Laboratory, Upton, NY 11973-5000 (United States); Florida Atlantic University, 777 Glades Road, Boca Raton, FL 33414 (United States); Agarwal, Rakhi; Allaire, Marc [Brookhaven National Laboratory, Upton, NY 11973-5000 (United States); Orville, Allen M. [Brookhaven National Laboratory, Upton, NY 11973-5000 (United States); Brookhaven National Laboratory, Upton, NY 11973-5000 (United States); Sweet, Robert M.; Soares, Alexei S., E-mail: soares@bnl.gov [Brookhaven National Laboratory, Upton, NY 11973-5000 (United States)

2015-01-01

An acoustic high-throughput screening method is described for harvesting protein crystals and combining the protein crystals with chemicals such as a fragment library. Acoustic droplet ejection (ADE) is an emerging technology with broad applications in serial crystallography such as growing, improving and manipulating protein crystals. One application of this technology is to gently transfer crystals onto MiTeGen micromeshes with minimal solvent. Once mounted on a micromesh, each crystal can be combined with different chemicals such as crystal-improving additives or a fragment library. Acoustic crystal mounting is fast (2.33 transfers s{sup −1}) and all transfers occur in a sealed environment that is in vapor equilibrium with the mother liquor. Here, a system is presented to retain crystals near the ejection point and away from the inaccessible dead volume at the bottom of the well by placing the crystals on a concave agarose pedestal (CAP) with the same chemical composition as the crystal mother liquor. The bowl-shaped CAP is impenetrable to crystals. Consequently, gravity will gently move the crystals into the optimal location for acoustic ejection. It is demonstrated that an agarose pedestal of this type is compatible with most commercially available crystallization conditions and that protein crystals are readily transferred from the agarose pedestal onto micromeshes with no loss in diffraction quality. It is also shown that crystals can be grown directly on CAPs, which avoids the need to transfer the crystals from the hanging drop to a CAP. This technology has been used to combine thermolysin and lysozyme crystals with an assortment of anomalously scattering heavy atoms. The results point towards a fast nanolitre method for crystal mounting and high-throughput screening.

High-order harmonic and attosecond pulse generation for a few-cycle laser pulse in modulated hollow fibres

International Nuclear Information System (INIS)

Zhang Xiangyun; Sun Zhenrong; Wang Yufeng; Chen Guoliang; Wang Zugeng; Li Ruxin; Zeng Zhinan; Xu Zhizhan

2007-01-01

High harmonic generation from Ar and He atoms by a few-cycle laser pulse in periodic and chirped hollow fibres is investigated theoretically by a self-consistent model. Based on enhanced high harmonics in a periodic hollow fibre, a chirped hollow fibre is proposed to improve quasi-phase matching for the generated harmonics near the cutoff. The results show that the extended and enhanced harmonics near the cutoff are well phase-matched, and a single x-ray pulse with a duration of 279 as in Ar gas and 255 as in He gas can be achieved by frequency synthesizing of high harmonics in the well-selected cutoff bandwidth. The results show that this technique is a potential candidate to generate an intense isolated attosecond pulse in the 'water window' spectrum

Effect of soil-structure interaction on the seismic behaviour of pedestal-structure system in large dish antennas

Directory of Open Access Journals (Sweden)

Bahador Pourhatami

2017-12-01

Full Text Available Regarding the progressive improvement in the territory of Space Technology in all developed countries and consequently developing countries including Islamic Republic of Iran, the optimization of design and utilization of the communication equipment has been paid more attention today. For instance, considering recent highly innovative methods, specifically in communication field, developed for design, manufacturing and exploiting dish antenna for specific cases, cooperation of other science and technology experts, like civil engineers, is also necessary. In this way, more delicate design procedure in order to satisfy communication requirement, is achieved. So far, no specific investigation about aforementioned subject, especially the effect of soil-structure interaction (SSI in analysing the seismic behaviour of communication large dish antennas has been conducted in Iran. In this paper, with the aim of investigating the effect of SSI on seismic behavior of pedestal, first an acceptable range for antenna displacement – as the most important parameter in pedestal structure for antenna – in both operational and survival states, has been calculated numerically based on generic formula. Secondly, the modelling of the whole pedestal-structure system has been modelled subjected to the associated loads and other primary conditions. This procedure has been performed once without considering the SSI and once more with it. Comparison of the obtained results shows that considering the SSI would impress the output results with a difference rate more than 50% and 600% respectively at survival and operational condition.

An improved hollow fiber solvent-stir bar microextraction for the preconcentration of anabolic steroids in biological matrix with determination by gas chromatography-mass spectrometry.

Science.gov (United States)

Liu, Wei; Zhang, Lan; Fan, Liangbiao; Lin, Zian; Cai, Yimin; Wei, Zhenyi; Chen, Guonan

2012-04-13

In this paper, a convenient and self-assembled hollow fiber solvent-stir bar microextraction (HF-SSBME) device was developed, which could stir by itself. In the extraction process, the proposed device made the solvent "bar" not floating at the sample solution and exposing to air while organic solvents outside hollow fiber always wrapped with donor phase solvent, which reduced the vaporization of organic solvents. This design could improve the precisions and recoveries of experiments. For evaluating the device, seven anabolic steroids (prasterone, 5α-androstane-3α, 17β-diol, methandriol, 19-norandrostenediol, androstenediol, methyltestosterone and methandienone) were used as model analytes and extraction conditions such as type and volume of organic solvents, agitation speed, extraction time, extraction temperature and salt addition were studied in detail. Under the optimum conditions (15 μL toluene, 40 °C, stirring at 750 rpm for 30 min with 1.5 g sodium chloride addition in 20.0 mL donor phase), the linear ranges of anabolic steroids were 0.25-200 ng mL(-1) with gas chromatography-mass spectrometry. The limits of detection were lower than 0.10 ng mL(-1). The recoveries and precisions in spiked urine and hair samples were between 73.97-93.56% and 2.18-4.47% (n=5). HF-SSBME method combined the intrinsical merits of hollow fiber with the superiority of the proposed self-stirring device which can be developed to two-phase, three-phase and in situ derivatization modes with wide prospect of application. Besides, the pedestal of this proposed device can be converted to fix stir bar in stir bar sorptive extraction (SBSE) method. Copyright © 2012 Elsevier B.V. All rights reserved.

Method for the production of fabricated hollow microspheroids

Science.gov (United States)

Wickramanayake, Shan; Luebke, David R.

2015-06-09

The method relates to the fabrication of a polymer microspheres comprised of an asymmetric layer surrounding a hollow interior. The fabricated hollow microsphere is generated from a nascent hollow microsphere comprised of an inner core of core fluid surrounded by a dope layer of polymer dope, where the thickness of the dope layer is at least 10% and less than 50% of the diameter of the inner core. The nascent hollow microsphere is exposed to a gaseous environment, generating a vitrified hollow microsphere, which is subsequently immersed in a coagulation bath. Solvent exchange produces a fabricated hollow microsphere comprised of a densified outer skin surrounding a macroporous inner layer, which surrounds a hollow interior. In an embodiment, the polymer is a polyimide or a polyamide-imide, and the non-solvent in the core fluid and the coagulation bath is water. The fabricated hollow microspheres are particularly suited as solvent supports for gas separation processes.

Complex Hollow Nanostructures: Synthesis and Energy-Related Applications.

Science.gov (United States)

Yu, Le; Hu, Han; Wu, Hao Bin; Lou, Xiong Wen David

2017-04-01

Hollow nanostructures offer promising potential for advanced energy storage and conversion applications. In the past decade, considerable research efforts have been devoted to the design and synthesis of hollow nanostructures with high complexity by manipulating their geometric morphology, chemical composition, and building block and interior architecture to boost their electrochemical performance, fulfilling the increasing global demand for renewable and sustainable energy sources. In this Review, we present a comprehensive overview of the synthesis and energy-related applications of complex hollow nanostructures. After a brief classification, the design and synthesis of complex hollow nanostructures are described in detail, which include hierarchical hollow spheres, hierarchical tubular structures, hollow polyhedra, and multi-shelled hollow structures, as well as their hybrids with nanocarbon materials. Thereafter, we discuss their niche applications as electrode materials for lithium-ion batteries and hybrid supercapacitors, sulfur hosts for lithium-sulfur batteries, and electrocatalysts for oxygen- and hydrogen-involving energy conversion reactions. The potential superiorities of complex hollow nanostructures for these applications are particularly highlighted. Finally, we conclude this Review with urgent challenges and further research directions of complex hollow nanostructures for energy-related applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Evolution of edge pedestal transport between edge-localized modes in DIII-D

Energy Technology Data Exchange (ETDEWEB)

Floyd, J.-P.; Stacey, W. M.; Mellard, S. C. [Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Groebner, R. J. [General Atomics, San Diego, California 92186 (United States)

2015-02-15

Evolution of measured profiles of densities, temperatures, and velocities in the edge pedestal region between successive ELM (edge-localized mode) events are analyzed and interpreted in terms of the constraints imposed by particle, momentum and energy balance in order to gain insights regarding the underlying evolution of transport processes in the edge pedestal between ELMs in a series of DIII-D [J. Luxon, Nucl. Fusion 42, 614 (2002)] discharges. The data from successive inter-ELM periods during an otherwise steady-state phase of the discharges were combined into a composite inter-ELM period for the purpose of increasing the number of data points in the analysis. Variation of diffusive and non-diffusive (pinch) particle, momentum, and energy transport over the inter-ELM period are interpreted using the GTEDGE code for discharges with plasma currents from 0.5 to 1.5 MA and inter-ELM periods from 50 to 220 ms. Diffusive transport is dominant for ρ < 0.925, while non-diffusive and diffusive transport are very large and nearly balancing in the sharp gradient region 0.925 < ρ < 1.0. During the inter-ELM period, diffusive transport increases slightly more than non-diffusive transport, increasing total outward transport. Both diffusive and non-diffusive transport have a strong inverse correlation with plasma current.

Pedestal bifurcation and resonant field penetration at the threshold of edge-localized mode suppression in the DIII-D Tokamak.

Science.gov (United States)

Nazikian, R; Paz-Soldan, C; Callen, J D; deGrassie, J S; Eldon, D; Evans, T E; Ferraro, N M; Grierson, B A; Groebner, R J; Haskey, S R; Hegna, C C; King, J D; Logan, N C; McKee, G R; Moyer, R A; Okabayashi, M; Orlov, D M; Osborne, T H; Park, J-K; Rhodes, T L; Shafer, M W; Snyder, P B; Solomon, W M; Strait, E J; Wade, M R

2015-03-13

Rapid bifurcations in the plasma response to slowly varying n=2 magnetic fields are observed as the plasma transitions into and out of edge-localized mode (ELM) suppression. The rapid transition to ELM suppression is characterized by an increase in the toroidal rotation and a reduction in the electron pressure gradient at the top of the pedestal that reduces the perpendicular electron flow there to near zero. These events occur simultaneously with an increase in the inner-wall magnetic response. These observations are consistent with strong resonant field penetration of n=2 fields at the onset of ELM suppression, based on extended MHD simulations using measured plasma profiles. Spontaneous transitions into (and out of) ELM suppression with a static applied n=2 field indicate competing mechanisms of screening and penetration of resonant fields near threshold conditions. Magnetic measurements reveal evidence for the unlocking and rotation of tearinglike structures as the plasma transitions out of ELM suppression.

Global simulation of edge pedestal micro-instabilities

Science.gov (United States)

Wan, Weigang; Parker, Scott; Chen, Yang

2011-10-01

We study micro turbulence of the tokamak edge pedestal with global gyrokinetic particle simulations. The simulation code GEM is an electromagnetic δf code. Two sets of DIII-D experimental profiles, shot #131997 and shot #136051 are used. The dominant instabilities appear to be two kinds of modes both propagating in the electron diamagnetic direction, with comparable linear growth rates. The low n mode is at the Alfven frequency range and driven by density and ion temperature gradients. The high n mode is driven by electron temperature gradient and has a low real frequency. A β scan shows that the low n mode is electromagnetic. Frequency analysis shows that the high n mode is sometimes mixed with an ion instability. Experimental radial electric field is applied and its effects studied. We will also show some preliminary nonlinear results. We thank R. Groebner, P. Snyder and Y. Zheng for providing experimental profiles and helpful discussions.

Fluid and gyrokinetic modelling of particle transport in plasmas with hollow density profiles

International Nuclear Information System (INIS)

Tegnered, D; Oberparleiter, M; Nordman, H; Strand, P

2016-01-01

Hollow density profiles occur in connection with pellet fuelling and L to H transitions. A positive density gradient could potentially stabilize the turbulence or change the relation between convective and diffusive fluxes, thereby reducing the turbulent transport of particles towards the center, making the fuelling scheme inefficient. In the present work, the particle transport driven by ITG/TE mode turbulence in regions of hollow density profiles is studied by fluid as well as gyrokinetic simulations. The fluid model used, an extended version of the Weiland transport model, Extended Drift Wave Model (EDWM), incorporates an arbitrary number of ion species in a multi-fluid description, and an extended wavelength spectrum. The fluid model, which is fast and hence suitable for use in predictive simulations, is compared to gyrokinetic simulations using the code GENE. Typical tokamak parameters are used based on the Cyclone Base Case. Parameter scans in key plasma parameters like plasma β, R/L T , and magnetic shear are investigated. It is found that β in particular has a stabilizing effect in the negative R/L n region, both nonlinear GENE and EDWM show a decrease in inward flux for negative R/L n and a change of direction from inward to outward for positive R/L n . This might have serious consequences for pellet fuelling of high β plasmas. (paper)

Hollow bunches production

CERN Document Server

Hancock, S

2017-01-01

Hollow bunches address the issue of high-brightnessbeams suffering from transverse emittance growth in a strongspace charge regime. During the Proton Synchrotron (PS)injection plateau, the negative space charge tune shift canpush the beam onto theQy=6integer resonance. Modify-ing the longitudinal bunch profile in order to reduce the peakline charge density alleviates the detrimental impact of spacecharge. To this end we first produce longitudinally hollowphase space distributions in the PS Booster by exciting aparametric resonance with the phase loop feedback system.These inherently flat bunches are then transferred to the PS,where the beam becomes less prone to the emittance growthcaused by the integer resonance.During the late 2016 machine development sessions inthe PS Booster we profited from solved issues from 2015and managed to reliably extract hollow bunches of1.3eVsmatched longitudinal area. Furthermore, first results to cre-ate hollow bunches with larger longitudinal emittances to-wards the LHC Inject...

The role of the density profile in the ASDEX-Upgrade pedestal structure

Czech Academy of Sciences Publication Activity Database

Dunne, M.G.; Potzel, S.; Reimold, F.; Wischmeier, M.; Wolfrum, E.; Frassinetti, L.; Beurskens, M.; Bílková, Petra; Cavedon, M.; Fischer, R.; Kurzan, B.; Laggner, F.M.; McDermott, R.M.; Tardini, G.; Trier, E.; Viezzer, E.; Willensdorfer, M.

2017-01-01

Roč. 59, č. 1 (2017), č. článku 014017. ISSN 0741-3335. [EPS 2016: Conference on Plasma Physics/43./. Leuven, 04.07.2016-08.07.2016] EU Projects: European Commission(XE) 633053 - EUROfusion Institutional support: RVO:61389021 Keywords : pedestal * scrape-off layer * peeling-balooning * prediction Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 2.392, year: 2016 http://iopscience.iop.org/0741-3335/59/1/014017

Contribution to the multi-machine pedestal scaling from COMPASS tokamak

Czech Academy of Sciences Publication Activity Database

Komm, Michael; Bílková, Petra; Aftanas, Milan; Berta, Miklós; Böhm, Petr; Bogár, Ondrej; Frassinetti, L.; Grover, Ondřej; Háček, Pavel; Havlíček, Josef; Hron, Martin; Imríšek, Martin; Krbec, Jaroslav; Mitošinková, Klára; Naydenkova, Diana; Pánek, Radomír; Peterka, Matěj; Snyder, P.B.; Stefanikova, E.; Stöckel, Jan; Šos, Miroslav; Urban, Jakub; Varju, Jozef; Vondráček, Petr; Weinzettl, Vladimír

2017-01-01

Roč. 57, č. 5 (2017), č. článku 056041. ISSN 0029-5515. [IAEA Fusion Energy Conference (FEC 2016)/26./. Kyoto, 17.10.2016-22.10.2016] R&D Projects: GA ČR(CZ) GA14-35260S; GA ČR(CZ) GA16-14228S; GA MŠk(CZ) 8D15001 EU Projects: European Commission(XE) 633053 - EUROfusion Institutional support: RVO:61389021 Keywords : COMPASS * H-mode * pedestal * scaling * tokamak * HRTS Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 3.307, year: 2016 https://doi.org/10.1088/1741-4326/aa6659

Plasma current dependence of the edge pedestal height in JET ELM-free H-modes

International Nuclear Information System (INIS)

Nave, M.; Lomas, P.; Gowers, C.

2000-01-01

Models for the suppression of turbulence in the L to H transition, suggest that the width of the H-mode edge barrier is either proportional or is of the order of the ion poloidal Larmor radius. This would require that the width of the edge barrier should depend on the plasma current. This dependence has been clearly verified at JET in experiments designed to control the edge MHD stability of ELM-free hot-ion H-mode plasmas. The effects of isotopic mass and the applicability of several edge barrier models to the hot-ion H-mode plasmas were analysed in using a large database containing both Deuterium-only (DD) and Deuterium-Tritium (DT) plasmas. This database has now been enlarged to include discharges from a plasma shape scan, allowing to study the dependence of the pedestal height on the edge shear. In addition the range of plasma currents was extended up to 6 MA. It is shown that the edge data is best described by a model where the edge barrier width is determined by the fast ions weighted towards the components with largest poloidal Larmor radii. However, it is not possible to eliminate conclusively the thermal ion model. (author)

Method to fabricate hollow microneedle arrays

Energy Technology Data Exchange (ETDEWEB)

Kravitz, Stanley H [Placitas, NM; Ingersoll, David [Albuquerque, NM; Schmidt, Carrie [Los Lunas, NM; Flemming, Jeb [Albuquerque, NM

2006-11-07

An inexpensive and rapid method for fabricating arrays of hollow microneedles uses a photoetchable glass. Furthermore, the glass hollow microneedle array can be used to form a negative mold for replicating microneedles in biocompatible polymers or metals. These microneedle arrays can be used to extract fluids from plants or animals. Glucose transport through these hollow microneedles arrays has been found to be orders of magnitude more rapid than natural diffusion.

Evidence of fire resistance of hollow-core slabs

DEFF Research Database (Denmark)

Hertz, Kristian Dahl; Sørensen, Lars Schiøtt; Giuliani, Luisa

is therefore going on in the Netherlands about the fire resistance of hollow-core slabs. In 2014 the producers of hollow-core slabs have published a report of a project called Holcofire containing a collection of 162 fire tests on hollow-core slabs giving for the first time an overview of the fire tests made....... The present paper analyses the evidence now available for assessment of the fire resistance of extruded hollow-core slabs. The 162 fire tests from the Holcofire report are compared against the requirements for testing from the product standard for hollow-core slabs EN1168 and knowledge about the possible......Hollow-core slabs have during the past 50 years comprised a variety of different structures with different cross-sections and reinforcement. At present the extruded hollow-core slabs without cross-reinforcement in the bottom flange and usually round or oval longitudinal channels (holes...

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

The Electrospun Ceramic Hollow Nanofibers

Directory of Open Access Journals (Sweden)

Shahin Homaeigohar

2017-11-01

Full Text Available Hollow nanofibers are largely gaining interest from the scientific community for diverse applications in the fields of sensing, energy, health, and environment. The main reasons are: their extensive surface area that increases the possibilities of engineering, their larger accessible active area, their porosity, and their sensitivity. In particular, semiconductor ceramic hollow nanofibers show greater space charge modulation depth, higher electronic transport properties, and shorter ion or electron diffusion length (e.g., for an enhanced charging–discharging rate. In this review, we discuss and introduce the latest developments of ceramic hollow nanofiber materials in terms of synthesis approaches. Particularly, electrospinning derivatives will be highlighted. The electrospun ceramic hollow nanofibers will be reviewed with respect to their most widely studied components, i.e., metal oxides. These nanostructures have been mainly suggested for energy and environmental remediation. Despite the various advantages of such one dimensional (1D nanostructures, their fabrication strategies need to be improved to increase their practical use. The domain of nanofabrication is still advancing, and its predictable shortcomings and bottlenecks must be identified and addressed. Inconsistency of the hollow nanostructure with regard to their composition and dimensions could be one of such challenges. Moreover, their poor scalability hinders their wide applicability for commercialization and industrial use.

Evolution of nickel sulfide hollow spheres through topotactic transformation

Science.gov (United States)

Wei, Chengzhen; Lu, Qingyi; Sun, Jing; Gao, Feng

2013-11-01

In this study, a topotactic transformation route was proposed to synthesize single-crystalline β-NiS hollow spheres with uniform phase and morphology evolving from polycrystalline α-NiS hollow spheres. Uniform polycrystalline α-NiS hollow spheres were firstly prepared with thiourea and glutathione as sulfur sources under hydrothermal conditions through the Kirkendall effect. By increasing the reaction temperature the polycrystalline α-NiS hollow spheres were transformed to uniform β-NiS hollow spheres. The β-NiS crystals obtained through the topotactic transformation route not only have unchanged morphology of hollow spheres but are also single-crystalline in nature. The as-prepared NiS hollow spheres display a good ability to remove the organic pollutant Congo red from water, which makes them have application potential in water treatment.In this study, a topotactic transformation route was proposed to synthesize single-crystalline β-NiS hollow spheres with uniform phase and morphology evolving from polycrystalline α-NiS hollow spheres. Uniform polycrystalline α-NiS hollow spheres were firstly prepared with thiourea and glutathione as sulfur sources under hydrothermal conditions through the Kirkendall effect. By increasing the reaction temperature the polycrystalline α-NiS hollow spheres were transformed to uniform β-NiS hollow spheres. The β-NiS crystals obtained through the topotactic transformation route not only have unchanged morphology of hollow spheres but are also single-crystalline in nature. The as-prepared NiS hollow spheres display a good ability to remove the organic pollutant Congo red from water, which makes them have application potential in water treatment. Electronic supplementary information (ESI) available: XRD patterns; SEM images and TEM images. See DOI: 10.1039/c3nr03371f

Interpretation of changes in diffusive and non-diffusive transport in the edge plasma during pedestal buildup following a low-high transition in DIII-D

Energy Technology Data Exchange (ETDEWEB)

Stacey, W. M.; Sayer, M.-H.; Floyd, J.-P. [Georgia Tech, Atlanta, Georgia 30332 (United States); Groebner, R. J. [General Atomics, San Diego, California 92186 (United States)

2013-01-15

The evolution of diffusive and non-diffusive transport during pedestal buildup following a low-high (L-H) transition has been interpreted from a particle-momentum-energy balance analysis of the measured density, temperature, and rotation velocity profiles in the plasma edge (0.82<{rho}<1.0) of a DIII-D [Luxon, Nucl. Fusion 42, 614 (2002)] discharge. In the discharge examined, there was an edge-localized-mode-free period of more than 600 ms following the L-H transition, and the majority of edge pedestal development occurred within the first 100 ms following the L-H transition. There appears to be a spatio-temporal correlation among the measured toroidal and poloidal rotation, the formation of a negative well in the measured radial electric field, the creation of a large inward particle pinch, the calculated intrinsic rotation due to ion orbit loss, and the measured formation of steep gradients in density and temperature in the outer region ({rho}>0.95) of the edge pedestal.

Plasticization-resistant hollow fiber membranes for CO2/CH4 separation based on a thermally crosslinkable polyimide

KAUST Repository

Chen, Chien-Chiang

2011-10-01

Decarboxylation-induced thermal crosslinking has been demonstrated to be effective for stabilizing membranes against plasticization in dense films. This study extends this promising crosslinking approach from dense films to industrially relevant asymmetric hollow fiber membranes. Crosslinkable asymmetric hollow fiber membranes were spun from a carboxylic acid containing polyimide, 6FDA-DAM:DABA. Dope and spinning conditions were optimized to obtain fibers with a defect-free selective skin layer. It is found that slightly defective fibers suffered severe selectivity loss after thermal crosslinking, suggesting that defect-free property is essential to the performance of the resulting crosslinked hollow fiber membranes. The crosslinked fibers were tested for CO 2/CH 4 separation. The excellent plasticization resistance under high pressure feeds (with highest CO 2 partial pressure of 400psia) suggests that these robust membranes are promising for aggressive natural gas purification. © 2011 Elsevier B.V.

Plasticization-resistant hollow fiber membranes for CO2/CH4 separation based on a thermally crosslinkable polyimide

KAUST Repository

Chen, Chien-Chiang; Qiu, Wulin; Miller, Stephen J.; Koros, William J.

2011-01-01

Decarboxylation-induced thermal crosslinking has been demonstrated to be effective for stabilizing membranes against plasticization in dense films. This study extends this promising crosslinking approach from dense films to industrially relevant asymmetric hollow fiber membranes. Crosslinkable asymmetric hollow fiber membranes were spun from a carboxylic acid containing polyimide, 6FDA-DAM:DABA. Dope and spinning conditions were optimized to obtain fibers with a defect-free selective skin layer. It is found that slightly defective fibers suffered severe selectivity loss after thermal crosslinking, suggesting that defect-free property is essential to the performance of the resulting crosslinked hollow fiber membranes. The crosslinked fibers were tested for CO 2/CH 4 separation. The excellent plasticization resistance under high pressure feeds (with highest CO 2 partial pressure of 400psia) suggests that these robust membranes are promising for aggressive natural gas purification. © 2011 Elsevier B.V.

Hollow core plasma channel generation

International Nuclear Information System (INIS)

Quast, Heinrich Martin

2018-03-01

The use of a hollow plasma channel in plasma-based acceleration has beneficial properties for the acceleration of electron and positron bunches. In the scope of the FLASHForward facility at DESY, the generation of such a plasma structure is examined. Therefore, the generation of a ring-shaped laser intensity profile with different techniques is analyzed. From the obtained intensity profiles the electron density of a hollow plasma channel is simulated in the focal region. Different parameters are scanned to understand their influence on the electron density distribution - an important parameter being, for example, the radius of the central region of the channel. In addition to the simulations, experiments are presented, during which a laser pulse is transformed into a hollow beam with a spiral phase plate. Subsequently, it forms a plasma during the interaction with hydrogen, where the plasma is imaged with interferometry. For energies above 0.9 mJ a hollow plasma structure can be observed at the location of first plasma formation.

Edge localized linear ideal magnetohydrodynamic instability studies in an extended-magnetohydrodynamic code

International Nuclear Information System (INIS)

Burke, B. J.; Kruger, S. E.; Hegna, C. C.; Zhu, P.; Snyder, P. B.; Sovinec, C. R.; Howell, E. C.

2010-01-01

A linear benchmark between the linear ideal MHD stability codes ELITE [H. R. Wilson et al., Phys. Plasmas 9, 1277 (2002)], GATO [L. Bernard et al., Comput. Phys. Commun. 24, 377 (1981)], and the extended nonlinear magnetohydrodynamic (MHD) code, NIMROD [C. R. Sovinec et al.., J. Comput. Phys. 195, 355 (2004)] is undertaken for edge-localized (MHD) instabilities. Two ballooning-unstable, shifted-circle tokamak equilibria are compared where the stability characteristics are varied by changing the equilibrium plasma profiles. The equilibria model an H-mode plasma with a pedestal pressure profile and parallel edge currents. For both equilibria, NIMROD accurately reproduces the transition to instability (the marginally unstable mode), as well as the ideal growth spectrum for a large range of toroidal modes (n=1-20). The results use the compressible MHD model and depend on a precise representation of 'ideal-like' and 'vacuumlike' or 'halo' regions within the code. The halo region is modeled by the introduction of a Lundquist-value profile that transitions from a large to a small value at a flux surface location outside of the pedestal region. To model an ideal-like MHD response in the core and a vacuumlike response outside the transition, separate criteria on the plasma and halo Lundquist values are required. For the benchmarked equilibria the critical Lundquist values are 10 8 and 10 3 for the ideal-like and halo regions, respectively. Notably, this gives a ratio on the order of 10 5 , which is much larger than experimentally measured values using T e values associated with the top of the pedestal and separatrix. Excellent agreement with ELITE and GATO calculations are made when sharp boundary transitions in the resistivity are used and a small amount of physical dissipation is added for conditions very near and below marginal ideal stability.

Microanatomical Location of Hyaluronic Acid Gel Following Injection of the Temporal Hollows.

Science.gov (United States)

Chundury, Rao V; Weber, Adam C; McBride, Jennifer; Plesec, Thomas P; Perry, Julian D

2015-01-01

To examine the microanatomical location of hyaluronic acid gel injected within the temporal hollows of cadaver specimens. The temporal hollows were injected subcutaneously with hyaluronic acid gel in 6 fresh frozen human cadaver hemifaces. Temporal soft tissues were dissected to a preperiosteal plane and fixated in 95% alcohol. A soft tissue section extending from skin to temporal bone was obtained for each specimen. Histologic examination was performed using hematoxylin and eosin stain. In 5 of 6 specimens, at least 95% of the hyaluronic acid was located within the subcutaneous fat. In 1 of 6 specimens, approximately 35% of the material was located within the subcutaneous fat and 60% was located within the superficial temporal fascia. Two specimens had 5% located within the temporalis muscle. In 1 specimen, hyaluronic acid was found to encompass a superficial muscular artery within the superficial temporal fascia. This study elucidates the location of hyaluronic acid gel after subcutaneous injection within the temporal hollow. Histology confirmed consistent placement of the gel within the subcutaneous tissues, but it also showed that injection in this region may produce unintended deeper location of filler, and a significant perivascular collection of the material. The proximity of dense temporal fascial and muscle arterial networks in this region may pose risk for perivascular injection and associated complications.

Hollow rods for the oil producing industry

Energy Technology Data Exchange (ETDEWEB)

Khalimova, L M; Elyasheva, M A

1970-01-01

Hollow sucker rods have several advantages over conventional ones. The hollow rods actuate the well pump and at the same time conduct produced fluids to surface. When paraffin deposition occurs, it can be minimized by injecting steam, hot oil or hot water into the hollow rod. Other chemicals, such as demulsifiers, scale inhibitors, corrosion inhibitors, etc., can also be placed in the well through the hollow rods. This reduces cost of preventive treatments, reduces number of workovers, increases oil production, and reduces cost of oil. Because the internal area of the rod is small, the passing liquids have a high velocity and thereby carry sand and dirt out of the well. This reduces pump wear between the piston and the plunger. Specifications of hollow rods, their operating characteristics, and results obtained with such rods under various circumstances are described.

The Effect of Plasma Shape on H-Mode Pedestal Characteristics on DIII-D

International Nuclear Information System (INIS)

T.H. Osborne; J.R. Ferron; R.J. Groebner; L.L. Lao; A.W. Leonard; R. Maingi; R.L. Miller; A.D. Turnbull; M.R. Wade; J.G. Watkins

1999-01-01

The characteristics of the H-mode are studied in discharges with varying triangularity and squareness. The pressure at the top of the H-mode pedestal increases strongly with triangularity primarily due to an increase in the margin by which the edge pressure gradient exceeds the ideal ballooning mode first stability limit. Two models are considered for how the edge may exceed the ballooning mode limit. In one model [1], access to the ballooning mode second stable regime allows the edge pressure gradient and associated bootstrap current to continue to increase until an edge localized, low toroidal mode number, ideal kink mode is destabilized. In the second model [2], the finite width of the H-mode transport barrier, and diamagnetic effects raise the pressure gradient limit above the ballooning mode limit. We observe a weak inverse dependence of the width of the H-mode transport barrier, Δ, on triangularity relative to the previously obtained [3] scaling Δ ∞ (β P PED ) 1/2 . The energy loss for Type I ELMs increases with triangularity in proportion to the pedestal energy increase. The temperature profile is found to respond stiffly to changes in T PED at low temperature, while at high temperature the response is additive. The response of the density profile is also found to play a role in the response of the total stored energy to changes in the W PED

Transmission properties of hollow-core photonic bandgap fibers

DEFF Research Database (Denmark)

Falk, Charlotte Ijeoma; Hald, Jan; Petersen, Jan C.

2010-01-01

Variations in optical transmission of four types of hollow-core photonic bandgap fibers are measured as a function of laser frequency. These variations influence the potential accuracy of gas sensors based on molecular spectroscopy in hollow-core fibers.......Variations in optical transmission of four types of hollow-core photonic bandgap fibers are measured as a function of laser frequency. These variations influence the potential accuracy of gas sensors based on molecular spectroscopy in hollow-core fibers....

A novel synthesis of micrometer silica hollow sphere

International Nuclear Information System (INIS)

Pan Wen; Ye Junwei; Ning Guiling; Lin Yuan; Wang Jing

2009-01-01

Silica microcapsules (hollow spheres) were synthesized successfully by a novel CTAB-stabilized water/oil emulsion system mediated hydrothermal method. The addition of urea to a solution of aqueous phase was an essential step of the simple synthetic procedure of silica hollow spheres, which leads to the formation of silica hollow spheres with smooth shell during hydrothermal process. The intact hollow spheres were obtained by washing the as-synthesized solid products with distilled water to remove the organic components. A large amount of silanol groups were retained in the hollow spheres by this facile route without calcination. The morphologies and optical properties of the product were characterized by transmission electron microscopy, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy. Furthermore, on the basis of a series of SEM observations, phenomenological elucidation of a mechanism for the growth of the silica hollow spheres has been presented

Facile synthesis of hollow Sn-Co@PMMA nanospheres as high performance anodes for lithium-ion batteries via galvanic replacement reaction and in situ polymerization

Science.gov (United States)

Yu, Xiaohui; Jiang, Anni; Yang, Hongyan; Meng, Haowen; Dou, Peng; Ma, Daqian; Xu, Xinhua

2015-08-01

Polymethyl methacrylate (PMMA)-coated hollow Sn-Co nanospheres (Sn-Co@PMMA) with superior electrochemical performance had been synthesized via a facile galvanic replacement method followed by an in situ emulsion polymerization route. The properties were investigated in detail and results show that the hollow Sn-Co nanospheres were evenly coated with PMMA. Benefiting from the protection of the PMMA layers, the hollow Sn-Co@PMMA nanocomposite is capable of retaining a high capacity of 590 mAh g-1 after 100 cycles with a coulomb efficiency above 98%, revealing better electrochemical properties compared with hollow Sn-Co anodes. The PMMA coating could help accommodate the mechanical strain caused by volume expansion and stabilize the solid electrolyte interphase (SEI) film formed on the electrode. Such a facile process could be further extended to other anode materials for lithium-ion batteries.

Detailed analysis of hollow ions spectra from dense matter pumped by X-ray emission of relativistic laser plasma

International Nuclear Information System (INIS)

Hansen, S. B.; Colgan, J.; Abdallah, J.; Faenov, A. Ya.; Pikuz, S. A.; Skobelev, I. Yu.; Wagenaars, E.; Culfa, O.; Dance, R. J.; Tallents, G. J.; Rossall, A. K.; Woolsey, N. C.; Booth, N.; Lancaster, K. L.; Evans, R. G.; Gray, R. J.; McKenna, P.; Kaempfer, T.; Schulze, K. S.; Uschmann, I.

2014-01-01

X-ray emission from hollow ions offers new diagnostic opportunities for dense, strongly coupled plasma. We present extended modeling of the x-ray emission spectrum reported by Colgan et al. [Phys. Rev. Lett. 110, 125001 (2013)] based on two collisional-radiative codes: the hybrid-structure Spectroscopic Collisional-Radiative Atomic Model (SCRAM) and the mixed-unresolved transition arrays (MUTA) ATOMIC model. We show that both accuracy and completeness in the modeled energy level structure are critical for reliable diagnostics, investigate how emission changes with different treatments of ionization potential depression, and discuss two approaches to handling the extensive structure required for hollow-ion models with many multiply excited configurations

Plasma current dependence of the edge pedestal height in JET ELM-free H-modes

International Nuclear Information System (INIS)

Nave, M.F.F; Lomas, P.; Gowers, C.; Guo, H.; Hawkes, N.; Huysmans, G.T.A.; Jones, T.; Parail, V.V.; Rimini, F.; Schunke, B.

2000-01-01

Some models for the suppression of turbulence in the L to H transition, suggest that the width of the H-mode edge barrier is either proportional or is of the order of the thermal or the fast-ion poloidal Larmor radius. This would require that the width of the edge barrier should depend on the plasma current. This dependence has been clearly verified at JET in experiments designed to control the edge MHD stability of ELM-free hot-ion H-mode plasmas. The effects of isotopic mass and the applicability of several edge barrier models to the hot-ion H-mode plasmas were analysed in (Guo H Y et al 2000 Edge transport barrier in JET hot-ion H-modes Nucl. Fusion 40 69) using a large database containing both deuterium-only and deuterium-tritium plasmas. This database has now been enlarged to include discharges from a plasma shape scan, allowing one to study the dependence of the pedestal height on the edge shear. In addition, the range of plasma currents was extended up to 6 MA. It is shown that the edge data are best described by a model where the edge barrier width is determined by the fast ions weighted towards the components with largest poloidal Larmor radii. However, it is not possible to conclusively eliminate the thermal ion model. (author)

A unified treatment of kinetic effects in a tokamak pedestal

International Nuclear Information System (INIS)

Catto, Peter J; Landreman, Matt; Kagan, Grigory; Pusztai, Istvan

2011-01-01

We consider the effects of a finite pedestal radial electric field on ion orbits using a unified approach. We then employ these modified orbit results to retain finite E x B drift departures from flux surfaces in an improved drift-kinetic equation. The procedure allows us to make a clear distinction between transit averages and flux surface averages when solving this kinetic equation. The technique outlined here is intended to clarify and unify recent evaluations of the banana regime decrease and plateau regime alterations in the ion heat diffusivity; the reduction and possible reversal of the poloidal flow in the banana regime, and its augmentation in the plateau regime; the increase in the bootstrap current; and the enhancement of the residual zonal flow regulation of turbulence.

Hollow nanocrystals and method of making

Science.gov (United States)

Alivisatos, A Paul [Oakland, CA; Yin, Yadong [Moreno Valley, CA; Erdonmez, Can Kerem [Berkeley, CA

2011-07-05

Described herein are hollow nanocrystals having various shapes that can be produced by a simple chemical process. The hollow nanocrystals described herein may have a shell as thin as 0.5 nm and outside diameters that can be controlled by the process of making.

Single-crystal SrTiO3 fiber grown by laser heated pedestal growth method: influence of ceramic feed rod preparation in fiber quality

Directory of Open Access Journals (Sweden)

D. Reyes Ardila

1998-10-01

Full Text Available The rapidly spreading use of optical fiber as a transmission medium has created an interest in fiber-compatible optical devices and methods for growing them, such as the Laser Heated Pedestal Growth (LHPG. This paper reports on the influence of the ceramic feed rod treatment on fiber quality and optimization of ceramic pedestal processing that allows improvements to be made on the final quality in a simple manner. Using the LHPG technique, transparent crack-free colorless single crystal fibers of SrTiO3 (0.50 mm in diameter and 30-40 mm in length were grown directly from green-body feed rods, without using external oxygen atmosphere.

Formation of Uniform Hollow Silica microcapsules

Science.gov (United States)

Yan, Huan; Kim, Chanjoong

2013-03-01

Microcapsules are small containers with diameters in the range of 0.1 - 100 μm. Mesoporous microcapsules with hollow morphologies possess unique properties such as low-density and high encapsulation capacity, while allowing controlled release by permeating substances with a specific size and chemistry. Our process is a one-step fabrication of monodisperse hollow silica capsules with a hierarchical pore structure and high size uniformity using double emulsion templates obtained by the glass-capillary microfluidic technique to encapsulate various active ingredients. These hollow silica microcapsules can be used as biomedical applications such as drug delivery and controlled release.

Microring embedded hollow polymer fiber laser

Energy Technology Data Exchange (ETDEWEB)

Linslal, C. L., E-mail: linslal@gmail.com; Sebastian, S.; Mathew, S.; Radhakrishnan, P.; Nampoori, V. P. N.; Girijavallabhan, C. P.; Kailasnath, M. [International School of Photonics, Cochin University of Science and Technology, Cochin 22 (India)

2015-03-30

Strongly modulated laser emission has been observed from rhodamine B doped microring resonator embedded in a hollow polymer optical fiber by transverse optical pumping. The microring resonator is fabricated on the inner wall of a hollow polymer fiber. Highly sharp lasing lines, strong mode selection, and a collimated laser beam are observed from the fiber. Nearly single mode lasing with a side mode suppression ratio of up to 11.8 dB is obtained from the strongly modulated lasing spectrum. The microring embedded hollow polymer fiber laser has shown efficient lasing characteristics even at a propagation length of 1.5 m.

Radially global δf computation of neoclassical phenomena in a tokamak pedestal

International Nuclear Information System (INIS)

Landreman, Matt; Parra, Felix I; Catto, Peter J; Ernst, Darin R; Pusztai, Istvan

2014-01-01

Conventional radially-local neoclassical calculations become inadequate if the radial gradient scale lengths of the H-mode pedestal become as small as the poloidal ion gyroradius. Here, we describe a radially global δf continuum code that generalizes neoclassical calculations to allow for stronger gradients. As with conventional neoclassical calculations, the formulation is time-independent and requires only the solution of a single sparse linear system. We demonstrate precise agreement with an asymptotic analytic solution of the radially global kinetic equation in the appropriate limits of aspect ratio and collisionality. This agreement depends crucially on accurate treatment of finite orbit width effects. (paper)

Space Charge Mitigation With Longitudinally Hollow Bunches

CERN Multimedia

Oeftiger, Adrian; Rumolo, Giovanni

2016-01-01

Hollow longitudinal phase space distributions have a flat profile and hence reduce the impact of transverse space charge. Dipolar parametric excitation with the phase loop feedback systems provides such hollow distributions under reproducible conditions. We present a procedure to create hollow bunches during the acceleration ramp of CERN’s PS Booster machine with minimal changes to the operational cycle. The improvements during the injection plateau of the downstream Proton Synchrotron are assessed in comparison to standard parabolic bunches.

Hollow nanotubular toroidal polymer microrings.

Science.gov (United States)

Lee, Jiyeong; Baek, Kangkyun; Kim, Myungjin; Yun, Gyeongwon; Ko, Young Ho; Lee, Nam-Suk; Hwang, Ilha; Kim, Jeehong; Natarajan, Ramalingam; Park, Chan Gyung; Sung, Wokyung; Kim, Kimoon

2014-02-01

Despite the remarkable progress made in the self-assembly of nano- and microscale architectures with well-defined sizes and shapes, a self-organization-based synthesis of hollow toroids has, so far, proved to be elusive. Here, we report the synthesis of polymer microrings made from rectangular, flat and rigid-core monomers with anisotropically predisposed alkene groups, which are crosslinked with each other by dithiol linkers using thiol-ene photopolymerization. The resulting hollow toroidal structures are shape-persistent and mechanically robust in solution. In addition, their size can be tuned by controlling the initial monomer concentrations, an observation that is supported by a theoretical analysis. These hollow microrings can encapsulate guest molecules in the intratoroidal nanospace, and their peripheries can act as templates for circular arrays of metal nanoparticles.

Hollow spheres: crucial building blocks for novel nanostructures and nanophotonics

Directory of Open Access Journals (Sweden)

Zhong Kuo

2018-03-01

Full Text Available In this review, we summarize the latest developments in research specifically derived from the unique properties of hollow microspheres, in particular, hollow silica spheres with uniform shells. We focus on applications in nanosphere (colloidal lithography and nanophotonics. The lithography from a layer of hollow spheres can result in nanorings, from a multilayer in unique nano-architecture. In nanophotonics, disordered hollow spheres can result in antireflection coatings, while ordered colloidal crystals (CCs of hollow spheres exhibit unique refractive index enhancement upon infiltration, ideal for optical sensing. Furthermore, whispering gallery mode (WGM inside the shell of hollow spheres has also been demonstrated to enhance light absorption to improve the performance of solar cells. These applications differ from the classical applications of hollow spheres, based only on their low density and large surface area, such as catalysis and chemical sensing. We provide a brief overview of the synthesis and self-assembly approaches of the hollow spheres. We elaborate on their unique optical features leading to defect mode lasing, optomicrofluidics, and the existence of WGMs inside shell for light management. Finally, we provide a perspective on the direction towards which future research relevant to hollow spheres might be directed.

Hollow spheres: crucial building blocks for novel nanostructures and nanophotonics

Science.gov (United States)

Zhong, Kuo; Song, Kai; Clays, Koen

2018-03-01

In this review, we summarize the latest developments in research specifically derived from the unique properties of hollow microspheres, in particular, hollow silica spheres with uniform shells. We focus on applications in nanosphere (colloidal) lithography and nanophotonics. The lithography from a layer of hollow spheres can result in nanorings, from a multilayer in unique nano-architecture. In nanophotonics, disordered hollow spheres can result in antireflection coatings, while ordered colloidal crystals (CCs) of hollow spheres exhibit unique refractive index enhancement upon infiltration, ideal for optical sensing. Furthermore, whispering gallery mode (WGM) inside the shell of hollow spheres has also been demonstrated to enhance light absorption to improve the performance of solar cells. These applications differ from the classical applications of hollow spheres, based only on their low density and large surface area, such as catalysis and chemical sensing. We provide a brief overview of the synthesis and self-assembly approaches of the hollow spheres. We elaborate on their unique optical features leading to defect mode lasing, optomicrofluidics, and the existence of WGMs inside shell for light management. Finally, we provide a perspective on the direction towards which future research relevant to hollow spheres might be directed.

Edge localized modes and edge pedestal in NBI and ICRF heated H, D and T-plasmas in JET

International Nuclear Information System (INIS)

Bhatnagar, V.; Lingertat, J.; Barnsley, R.

1998-12-01

Based on experiments carried out in JET in D:T mixtures varying from 100:0 to 5:95 and those carried out in hydrogen plasmas, the isotopic mass dependence of ELM parameters and the edge pedestal pressure in neutral beam (NBI) and ion cyclotron resonance (ICRF) heated H-mode plasmas is presented. The ELM frequency is found to decrease with the atomic mass number both in ICRH and NBI discharges. However, the frequency in the case of ICRH is about 8 - 10 times higher than in the NBI case. Assuming that ELMs occur at a critical edge pressure gradient, limited by the ballooning instability, the scaling of the maximum edge pressure is most consistent with the assumption that the width of the transport barrier scales as the ion poloidal Larmor radius governed by the average energy of fast ions at the edge. The critical edge pressure in NBI heated discharges increases with the isotopic mass which. is consistent with the higher deduced width of the edge transport, barrier in tritium than in deuterium and hydrogen. The critical edge pressure in ICRH discharges is smaller, presumably, due to the smaller fast-ion contribution to the edge region. As a consequence of the edge pressure scaling with isotopic mass, the edge operational space in the n e - T e diagram increases with operation in tritium. If the evidence that the edge pedestal width is governed by the average energy of fast ions in the edge prevails, the pedestal in ITER would be controlled by the slowing down energy spectrum of α-particles in the edge. (author)

Development of tree hollows in pedunculate oak (Quercus robur)

OpenAIRE

Ranius, Thomas; Niklasson, Mats; Berg, Niclas

2009-01-01

Many invertebrates, birds and mammals are dependent on hollow trees. For landscape planning that aims at persistence of species inhabiting hollow trees it is crucial to understand the development of such trees. In this study we constructed an individual-based simulation model to predict diameter distribution and formation of hollows in oak tree populations. Based on tree-ring data from individual trees, we estimated the ages when hollow formation commences for pedunculate oak (Quercus robur) ...

Method for producing small hollow spheres

International Nuclear Information System (INIS)

Hendricks, C.D.

1979-01-01

A method is described for producing small hollow spheres of glass, metal or plastic, wherein the sphere material is mixed with or contains as part of the composition a blowing agent which decomposes at high temperature (T >approx. 600 0 C). As the temperature is quickly raised, the blowing agent decomposes and the resulting gas expands from within, thus forming a hollow sphere of controllable thickness. The thus produced hollow spheres (20 to 10 3 μm) have a variety of application, and are particularly useful in the fabrication of targets for laser implosion such as neutron sources, laser fusion physics studies, and laser initiated fusion power plants

Facile synthesis of hollow Sn–Co@PMMA nanospheres as high performance anodes for lithium-ion batteries via galvanic replacement reaction and in situ polymerization

Energy Technology Data Exchange (ETDEWEB)

Yu, Xiaohui; Jiang, Anni; Yang, Hongyan; Meng, Haowen; Dou, Peng; Ma, Daqian [School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China); Xu, Xinhua, E-mail: xhxutju@gmail.com [School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China); Tianjin Key Laboratory of Composite and Functional Materials, Tianjin 300072 (China)

2015-08-30

Highlights: • Hollow Sn–Co nanospheres were synthesized via a facile galvanic replacement method. • PMMA layers were uniform coated on the surface of Sn–Co composites via in situ emulsion polymerization. • The coating layers are beneficial to suppress the aggregation and stabilize the SEI formation on the surface. • Excellent cycling stability and rate capability were obtained by coating PMMA protective layers on the surface of hollow Sn–Co nanospheres. - Abstract: Polymethyl methacrylate (PMMA)-coated hollow Sn–Co nanospheres (Sn–Co@PMMA) with superior electrochemical performance had been synthesized via a facile galvanic replacement method followed by an in situ emulsion polymerization route. The properties were investigated in detail and results show that the hollow Sn–Co nanospheres were evenly coated with PMMA. Benefiting from the protection of the PMMA layers, the hollow Sn–Co@PMMA nanocomposite is capable of retaining a high capacity of 590 mAh g{sup −1} after 100 cycles with a coulomb efficiency above 98%, revealing better electrochemical properties compared with hollow Sn–Co anodes. The PMMA coating could help accommodate the mechanical strain caused by volume expansion and stabilize the solid electrolyte interphase (SEI) film formed on the electrode. Such a facile process could be further extended to other anode materials for lithium-ion batteries.

Facile synthesis of hollow Sn–Co@PMMA nanospheres as high performance anodes for lithium-ion batteries via galvanic replacement reaction and in situ polymerization

International Nuclear Information System (INIS)

Yu, Xiaohui; Jiang, Anni; Yang, Hongyan; Meng, Haowen; Dou, Peng; Ma, Daqian; Xu, Xinhua

2015-01-01

Highlights: • Hollow Sn–Co nanospheres were synthesized via a facile galvanic replacement method. • PMMA layers were uniform coated on the surface of Sn–Co composites via in situ emulsion polymerization. • The coating layers are beneficial to suppress the aggregation and stabilize the SEI formation on the surface. • Excellent cycling stability and rate capability were obtained by coating PMMA protective layers on the surface of hollow Sn–Co nanospheres. - Abstract: Polymethyl methacrylate (PMMA)-coated hollow Sn–Co nanospheres (Sn–Co@PMMA) with superior electrochemical performance had been synthesized via a facile galvanic replacement method followed by an in situ emulsion polymerization route. The properties were investigated in detail and results show that the hollow Sn–Co nanospheres were evenly coated with PMMA. Benefiting from the protection of the PMMA layers, the hollow Sn–Co@PMMA nanocomposite is capable of retaining a high capacity of 590 mAh g −1 after 100 cycles with a coulomb efficiency above 98%, revealing better electrochemical properties compared with hollow Sn–Co anodes. The PMMA coating could help accommodate the mechanical strain caused by volume expansion and stabilize the solid electrolyte interphase (SEI) film formed on the electrode. Such a facile process could be further extended to other anode materials for lithium-ion batteries

The Riddle of the Apparently Hollow Himalaya

Indian Academy of Sciences (India)

The Riddle of the Apparently Hollow Himalaya. Ramesh .... It was as if the Himalayas were hollow inside. ... block would be consistent with the ground elevation in such a ... Alternative models and possible preference: Many refinements of.

Theory-based model for the pedestal, edge stability and ELMs in tokamaks

International Nuclear Information System (INIS)

Pankin, A.Y.; Bateman, G.; Brennan, D.P.; Schnack, D.D.; Snyder, P.B.; Voitsekhovitch, I.; Kritz, A.H.; Janeschitz, G.; Kruger, S.; Onjun, T.; Pacher, G.W.; Pacher, H.D.

2006-01-01

An improved model for triggering edge localized mode (ELM) crashes is developed for use within integrated modelling simulations of the pedestal and ELM cycles at the edge of H-mode tokamak plasmas. The new model is developed by using the BALOO, DCON and ELITE ideal MHD stability codes to derive parametric expressions for the ELM triggering threshold. The whole toroidal mode number spectrum is studied with these codes. The DCON code applies to low mode numbers, while the BALOO code applies to only high mode numbers and the ELITE code applies to intermediate and high mode numbers. The variables used in the parametric stability expressions are the normalized pressure gradient and the parallel current density, which drive ballooning and peeling modes. Two equilibria motivated by DIII-D geometry with different plasma triangularities are studied. It is found that the stable region in the high triangularity discharge covers a much larger region of parameter space than the corresponding stability region in the low triangularity discharge. The new ELM trigger model is used together with a previously developed model for pedestal formation and ELM crashes in the ASTRA integrated modelling code to follow the time evolution of the temperature profiles during ELM cycles. The ELM frequencies obtained in the simulations of low and high triangularity discharges are observed to increase with increasing heating power. There is a transition from second stability to first ballooning mode stability as the heating power is increased in the high triangularity simulations. The results from the ideal MHD stability codes are compared with results from the resistive MHD stability code NIMROD

Hollow metal nanostructures for enhanced plasmonics (Conference Presentation)

Science.gov (United States)

Genç, Aziz; Patarroyo, Javier; Sancho-Parramon, Jordi; Duchamp, Martial; Gonzalez, Edgar; Bastus, Neus G.; Houben, Lothar; Dunin-Borkowski, Rafal; Puntes, Victor F.; Arbiol, Jordi

2016-03-01

Complex metal nanoparticles offer a great playground for plasmonic nanoengineering, where it is possible to cover plasmon resonances from ultraviolet to near infrared by modifying the morphologies from solid nanocubes to nanoframes, multiwalled hollow nanoboxes or even nanotubes with hybrid (alternating solid and hollow) structures. We experimentally show that structural modifications, i.e. void size and final morphology, are the dominant determinants for the final plasmonic properties, while compositional variations allow us to get a fine tuning. EELS mappings of localized surface plasmon resonances (LSPRs) reveal an enhanced plasmon field inside the voids of hollow AuAg nanostructures along with a more homogeneous distributions of the plasmon fields around the nanostructures. With the present methodology and the appropriate samples we are able to compare the effects of hybridization at the nanoscale in hollow nanostructures. Boundary element method (BEM) simulations also reveal the effects of structural nanoengineering on plasmonic properties of hollow metal nanostructures. Possibility of tuning the LSPR properties of hollow metal nanostructures in a wide range of energy by modifying the void size/shell thickness is shown by BEM simulations, which reveals that void size is the dominant factor for tuning the LSPRs. As a proof of concept for enhanced plasmonic properties, we show effective label free sensing of bovine serum albumin (BSA) with some of our hollow nanostructures. In addition, the different plasmonic modes observed have also been studied and mapped in 3D.

Ni hollow spheres as catalysts for methanol and ethanol electrooxidation

Energy Technology Data Exchange (ETDEWEB)

Xu, Changwei [Department of Chemistry and Institute of Nanochemistry, Jinan University, Guangzhou 510632 (China); School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Hu, Yonghong; Rong, Jianhua; Liu, Yingliang [Department of Chemistry and Institute of Nanochemistry, Jinan University, Guangzhou 510632 (China); Jiang, San Ping [School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798 (Singapore)

2007-08-15

In this paper, we successfully synthesized Ni hollow spheres consisting of needle-like nickel particles by using silica spheres as template with gold nanoparticles seeding method. The Ni hollow spheres are applied to methanol and ethanol electrooxidation in alkaline media. The results show that the Ni hollow spheres give a very high activity for alcohol electrooxidation at a very low nickel loading of 0.10 mg cm{sup -2}. The current on Ni hollow spheres is much higher than that on Ni particles. The onset potential and peak potential on Ni hollow spheres are more negative than that on Ni particles for methanol and ethanol electrooxidation. The Ni hollow spheres may be of great potential in alcohol sensor and direct alcohol fuel cells. (author)

Fabrication of Closed Hollow Bulb Obturator Using Thermoplastic Resin Material

Directory of Open Access Journals (Sweden)

Bidhan Shrestha

2015-01-01

Full Text Available Purpose. Closed hollow bulb obturators are used for the rehabilitation of postmaxillectomy patients. However, the time consuming process, complexity of fabrication, water leakage, and discoloration are notable disadvantages of this technique. This paper describes a clinical report of fabricating closed hollow bulb obturator using a single flask and one time processing method for an acquired maxillary defect. Hard thermoplastic resin sheet has been used for the fabrication of hollow bulb part of the obturator. Method. After fabrication of master cast conventionally, bulb and lid part of the defect were formed separately and joined by autopolymerizing acrylic resin to form one sized smaller hollow body. During packing procedure, the defect area was loaded with heat polymerizing acrylic resin and then previously fabricated smaller hollow body was adapted over it. The whole area was then loaded with heat cure acrylic. Further processes were carried out conventionally. Conclusion. This technique uses single flask which reduces laboratory time and makes the procedure simple. The thickness of hollow bulb can be controlled and light weight closed hollow bulb prosthesis can be fabricated. It also minimizes the disadvantages of closed hollow bulb obturator such as water leakage, bacterial infection, and discoloration.

Preparation and Application of Hollow Silica/magnetic Nanocomposite Particle

Science.gov (United States)

Wang, Cheng-Chien; Lin, Jing-Mo; Lin, Chun-Rong; Wang, Sheng-Chang

The hollow silica/cobalt ferrite (CoFe2O4) magnetic microsphere with amino-groups were successfully prepared via several steps, including preparing the chelating copolymer microparticles as template by soap-free emulsion polymerization, manufacturing the hollow cobalt ferrite magnetic microsphere by in-situ chemical co-precipitation following calcinations, and surface modifying of the hollow magnetic microsphere by 3-aminopropyltrime- thoxysilane via the sol-gel method. The average diameter of polymer microspheres was ca. 200 nm from transmission electron microscope (TEM) measurement. The structure of the hollow magnetic microsphere was characterized by using TEM and scanning electron microscope (SEM). The spinel-type lattice of CoFe2O4 shell layer was identified by using XRD measurement. The diameter of CoFe2O4 crystalline grains ranged from 54.1 nm to 8.5 nm which was estimated by Scherrer's equation. Additionally, the hollow silica/cobalt ferrite microsphere possesses superparamagnetic property after VSM measurement. The result of BET measurement reveals the hollow magnetic microsphere which has large surface areas (123.4m2/g). After glutaraldehyde modified, the maximum value of BSA immobilization capacity of the hollow magnetic microsphere was 33.8 mg/g at pH 5.0 buffer solution. For microwave absorption, when the hollow magnetic microsphere was compounded within epoxy resin, the maximum reflection loss of epoxy resins could reach -35dB at 5.4 GHz with 1.9 mm thickness.

Long-term evaluation of hollow screw and hollow cylinder dental implants : Clinical and radiographic results after 10 years

NARCIS (Netherlands)

Telleman, Gerdien; Meijer, Henny J. A.; Raghoebar, Gerry M.

Background: In 1988, an implant manufacturer offered a new dental implant system, with a wide choice of hollow cylinder (HC) and hollow screw (HS) implants. The purpose of this retrospective study of HS and HC implants was to evaluate clinical and radiographic parameters of peri-implant tissue and

X transport and its effect on H-mode and edge pedestal in tokamaks

International Nuclear Information System (INIS)

Chang, C.S.; Darrow, D.; White, R.; Lin, Z.; Lee, W.; Ku, S.H.; Weitzner, H.; Carlstrom, T.N.; Grassie, J.S. de

2001-01-01

A new classical non-ambipolar transport mechanism has been identified which can be a dominant source of strong Er and edge pedestal layer formation immediately inside the separatrix in a diverted tokamak. Due to vanishingly small poloidal B-field and grad-B drift toward x-point, plasma ions with small ν parallel in the X-region do not have confined single particle orbits. This leads to a non-ambipolar convective transport in the X-region (X-transport), either collisional or collisionless, inducing a strong negative Er-shear layer. The X-transport can provide basic understanding of many of the experimental observations. (author)

Synthesis of barium-strontium titanate hollow tubes using Kirkendall effect

Science.gov (United States)

Chen, Xuncai; Im, SangHyuk; Kim, Jinsoo; Kim, Woo-Sik

2018-02-01

(BaSr)TiO3 hexagonal hollow tubes was fabricated by a solid-state interfacial reaction including a Kirkendall diffusion. Using a co-precipitation and sol-gel process, a core@shell structure of (BaSr)CO3@TiO2 rods were prepared, and then converted to (BaSr)TiO3 hollow tubes at 750 °C. This was a first achievement of single-phase crystal hollow tube. Here, the inner diameter and wall thickness of hollow tube were about 700 nm and 130 nm, respectively. The fabrication of (BaSr)TiO3 hollow tubes was monitored with scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), transmission electron microscopy (TEM), and X-ray diffraction (XRD) to investigate their formation mechanism. The present synthetic approach would provide a new insight into the design and fabrication of hollow architectures of many perovskite oxides.

Pedestal characteristics and MHD stability of H-mode plasmas in TCV

International Nuclear Information System (INIS)

Pitzschke, A.

2011-01-01

temperature profile during the ELM cycle, the low repetition rate of the lasers used for Thomson scattering is a limiting. Although the system on TCV comprises 3 laser units that may be triggered in sequence with time separations down to 1 ms, time evolution over longer periods can only be reconstructed from repetitive events. In this context, an adjustment of the laser trigger to improve the synchronization with the ELM event is an advantage. A method was developed and implemented to generate a synchronizing trigger sequence, by a real-time monitoring of the D-alpha emission, which provides a marker for the ELM event. Recently, a ‘snowflake’ (SF) divertor configuration, proposed as a possible solution to reduce the plasma-wall interaction by changing the divertor’s poloidal magnetic field topology, was generated, for the first time, in TCV. A numerical code (KINX), based on a magnetohydrodynamic model (ideal MHD), was used to investigate the stability limits of this configuration under H-mode conditions and compare them with a similar standard single-null equilibrium. In a series of experiments, improved energy confinement was found and explained by improved stability of the edge region in the SF configuration. The influence of the pedestal structure in ELMy H-mode plasmas on the energy confinement and on ELM energy losses was investigated. The different ELM regimes found in TCV were analyzed, in particular the transition between type-III to type-I ELMs. The operational boundary of each ELM regime was characterized and verified by ideal MHD stability simulations for the ETB region. Recent studies on the scaling of the pedestal width with normalized poloidal pressure were confirmed. Using the capabilities of TCV, the influence of plasma shaping on pedestal parameters and MHD stability limits was investigated. In the past, models were developed to describe the onset of type-I ELMs, which are associated with modes in the ETB region arising from a coupling of pressure- and

Hollow porous-wall glass microspheres for hydrogen storage

Science.gov (United States)

Heung, Leung K.; Schumacher, Ray F.; Wicks, George G.

2010-02-23

A porous wall hollow glass microsphere is provided having a diameter range of between 1 to 200 microns, a density of between 1.0 to 2.0 gm/cc, a porous-wall structure having wall openings defining an average pore size of between 10 to 1000 angstroms, and which contains therein a hydrogen storage material. The porous-wall structure facilitates the introduction of a hydrogen storage material into the interior of the porous wall hollow glass microsphere. In this manner, the resulting hollow glass microsphere can provide a membrane for the selective transport of hydrogen through the porous walls of the microsphere, the small pore size preventing gaseous or liquid contaminants from entering the interior of the hollow glass microsphere.

H-mode pedestal and threshold studies over an expanded operating space on Alcator C-Moda)

Science.gov (United States)

Hubbard, A. E.; Hughes, J. W.; Bespamyatnov, I. O.; Biewer, T.; Cziegler, I.; LaBombard, B.; Lin, Y.; McDermott, R.; Rice, J. E.; Rowan, W. L.; Snipes, J. A.; Terry, J. L.; Wolfe, S. M.; Wukitch, S.

2007-05-01

This paper reports on studies of the edge transport barrier and transition threshold of the high confinement (H) mode of operation on the Alcator C-Mod tokamak [I. H. Hutchinson et al., Phys. Plasmas 1, 1511 (1994)], over a wide range of toroidal field (2.6-7.86T) and plasma current (0.4-1.7MA). The H-mode power threshold and edge temperature at the transition increase with field. Barrier widths, pressure limits, and confinement are nearly independent of field at constant current, but the operational space at high B shifts toward higher temperature and lower density and collisionality. Experiments with reversed field and current show that scrape-off-layer flows in the high-field side depend primarily on configuration. In configurations with the B ×∇B drift away from the active X-point, these flows lead to more countercurrent core rotation, which apparently contributes to higher H-mode thresholds. In the unfavorable case, edge temperature thresholds are higher, and slow evolution of profiles indicates a reduction in thermal transport prior to the transition in particle confinement. Pedestal temperatures in this case are also higher than in the favorable configuration. Both high-field and reversed-field results suggest that parameters at the L-H transition are influencing the evolution and parameters of the H-mode pedestal.

Hollow proppants and a process for their manufacture

Science.gov (United States)

Jones, A.H.; Cutler, R.A.

1985-10-15

Hollow, fine-grained ceramic proppants are less expensive and improve fracture control when compared to conventional proppants (dense alumina, mullite, bauxite, zirconia, etc.). Hollow proppants of the present invention have been fabricated by spray drying, followed by sintering in order to obtain a dense case and a hollow core. These proppants generally have high sphericity and roundness (Krumbein sphericity and roundness greater than 0.8), have diameters on average between 2,250 and 125 [mu]m, depending on proppant size required, and have strength equal to or greater than that of sand. The hollow core, the size of which can be controlled, permits better fracture control in hydraulic fracturing treatments since the proppant can be transported in lower viscosity fluids. Hollow proppants produced at the same cost/weight as conventional proppants also provide for lower costs, since less weight is required to fill the same volume. The fine-grained (preferably less than 5 [mu]m in diameter) ceramic case provides the strength necessary to withstand closure stresses and prevent crushing. 6 figs.

Fabrication of hollow-sphere films of wurtzite CuInS{sub 2} on copper substrate

Energy Technology Data Exchange (ETDEWEB)

Lei, Shuijin, E-mail: shjlei@ncu.edu.cn [School of Materials Science and Engineering, Nanchang University, Nanchang, Jiangxi 330031 (China); Wang, Chunying [School of Materials Science and Engineering, Nanchang University, Nanchang, Jiangxi 330031 (China); Huang, Qiang [School of Electromechanical Engineering, Nanchang University, Nanchang, Jiangxi 330031 (China); Liu, Lei; Ge, Yang; Tang, Qingliu; Cheng, Baochang; Xiao, Yanhe; Zhou, Lang [School of Materials Science and Engineering, Nanchang University, Nanchang, Jiangxi 330031 (China)

2013-12-16

As important semiconductors, I–III–VI{sub 2} compounds have attracted wide attention, among which the wurtzite structured CuInS{sub 2} has been the research focus due to its metastable phase. In this paper, the wurtzite CuInS{sub 2} hollow-sphere films have been successfully prepared on copper substrate in a self-designed solvothermal detached system. The films of Cu(OH){sub 2} one-dimensional nanostructure arrays and thioacetamide were used as the precursors and triethylene glycol was used as the solvent. Experiments showed that the amount of indium trichloride played a determinative role in the final morphology of the products. Meanwhile, the one-dimensional nanostructure arrays and the detached solvothermal system have great influences on the crystal shape as well. Based on the experimental results, a possible formation mechanism for the CuInS{sub 2} hollow spheres was also proposed. The UV–Vis absorption spectrum showed a broad absorption over the entire visible light and extending into the near-infrared region and presented the band gap of 1.53 eV for the as-prepared wurtzite CuInS{sub 2}, which indicates the potential applications in solar cells. - Highlights: • A self-designed detached system along with solvothermal treatment was developed. • Wurtzite CuInS{sub 2} hollow-sphere films were successfully fabricated on Cu substrate. • The detached system and InCl{sub 3} usage were crucial for the hollow spheres. • The broadband absorption and 1.53 eV band-gap indicates its potentials in PV.

Adiabatic Rearrangement of Hollow PV Towers

Directory of Open Access Journals (Sweden)

Eric A Hendricks

2010-10-01

Full Text Available Diabatic heating from deep moist convection in the hurricane eyewall produces a towering annular structure of elevated potential vorticity (PV. This structure has been referred to as a hollow PV tower. The sign reversal of the radial gradient of PV satisfies the Charney-Stern necessary condition for combined barotropic-baroclinic instability. For thin enough annular structures, small perturbations grow exponentially, extract energy from the mean flow, and lead to hollow tower breakdown, with significant vortex structural and intensity change. The three-dimensional adiabatic rearrangements of two prototypical hurricane-like hollow PV towers (one thick and one thin are examined in an idealized framework. For both hollow towers, dynamic instability causes air parcels with high PV to be mixed into the eye preferentially at lower levels, where unstable PV wave growth rates are the largest. Little or no mixing is found to occur at upper levels. The mixing at lower and middle levels is most rapid for the breakdown of the thin hollow tower, consistent with previous barotropic results. For both hollow towers, this advective rearrangement of PV affects the tropical cyclone structure and intensity in a number of ways. First, the minimum central pressure and maximum azimuthal mean velocity simultaneously decrease, consistent with previous barotropic results. Secondly, isosurfaces of absolute angular momentum preferentially shift inward at low levels, implying an adiabatic mechanism by which hurricane eyewall tilt can form. Thirdly, a PV bridge, similar to that previously found in full-physics hurricane simulations, develops as a result of mixing at the isentropic levels where unstable PV waves grow most rapidly. Finally, the balanced mass field resulting from the PV rearrangement is warmer in the eye between 900 and 700 hPa. The location of this warming is consistent with observed warm anomalies in the eye, indicating that in certain instances the hurricane

Recent progress in hollow sphere-based electrodes for high-performance supercapacitors

Science.gov (United States)

Zhao, Yan; Chen, Min; Wu, Limin

2016-08-01

Hollow spheres have drawn much attention in the area of energy storage and conversion, especially in high-performance supercapacitors owing to their well-defined morphologies, uniform size, low density and large surface area. And quite some significant breakthroughs have been made in advanced supercapacitor electrode materials with hollow sphere structures. In this review, we summarize and discuss the synthesis and application of hollow spheres with controllable structure and morphology as electrode materials for supercapacitors. First, we briefly introduce the fabrication strategies of hollow spheres for electrode materials. Then, we discuss in detail the recent advances in various hollow sphere-based electrode materials for supercapacitors, including single-shelled, yolk-shelled, urchin-like, double-shelled, multi-shelled, and mesoporous hollow structure-based symmetric and asymmetric supercapacitor devices. We conclude this review with some perspectives on the future research and development of the hollow sphere-based electrode materials.

Recent progress in hollow sphere-based electrodes for high-performance supercapacitors.

Science.gov (United States)

Zhao, Yan; Chen, Min; Wu, Limin

2016-08-26

Hollow spheres have drawn much attention in the area of energy storage and conversion, especially in high-performance supercapacitors owing to their well-defined morphologies, uniform size, low density and large surface area. And quite some significant breakthroughs have been made in advanced supercapacitor electrode materials with hollow sphere structures. In this review, we summarize and discuss the synthesis and application of hollow spheres with controllable structure and morphology as electrode materials for supercapacitors. First, we briefly introduce the fabrication strategies of hollow spheres for electrode materials. Then, we discuss in detail the recent advances in various hollow sphere-based electrode materials for supercapacitors, including single-shelled, yolk-shelled, urchin-like, double-shelled, multi-shelled, and mesoporous hollow structure-based symmetric and asymmetric supercapacitor devices. We conclude this review with some perspectives on the future research and development of the hollow sphere-based electrode materials.

Hollow-duct radiation delivery system investigation

Directory of Open Access Journals (Sweden)

Kramer D.

2013-05-01

Full Text Available Investigation of hollow-duct structure for high-power laser-diode-array radiation delivery into the end-pumped large-aperture gain media is reported. A ray tracing method has been used to evaluate the performance of the structure designed for maximum transmission efficiency and output beam profile homogeneity. Variable hollow-duct lengths as well as emanating angles of laser-diode-array have been taken into account.

Hollow fiber liquid supported membranes

International Nuclear Information System (INIS)

Violante, V.

1987-01-01

The hollow fiber system are well known and developed in the scientific literature because of their applicability in the process separation units. The authors approach to a mathematical model for a particular hollow fiber system, usin liquid membranes. The model has been developed in order to obtain a suitable tool for a sensitivy analysis and for a scaling-up. This kind of investigation is very usefull from an engineering point of view, to get a spread range of information to build up a pilot plant from the laboratory scale

Experimental study on hollow structural component by explosive welding

Energy Technology Data Exchange (ETDEWEB)

Duan, Mianjun, E-mail: dmjwl@163.com [PLA University of Science and Technology, Nanjing 210007 (China); Wei, Ling, E-mail: 386006087@qq.com [Tongda College, Nanjing University of Posts and Telecommunication, Nanjing 210007 (China); Hong, Jin [PLA University of Science and Technology, Nanjing 210007 (China); Ran, Hong [Southwestern Institute of Physics, Chengdu 610041 (China); Ma, Rui; Wang, Yaohua [PLA University of Science and Technology, Nanjing 210007 (China)

2014-12-15

Highlights: • This paper relates to a study on a thin double-layers hollow structural component by using an explosive welding technology. • This thin double-layer hollow structural component is an indispensable component required for certain core equipment of thermonuclear experimental reactor. • An adjusted explosive welding technology for manufacturing an inconel625 hollow structural component was developed which cannot be made by common technology. • The result shows that a metallurgical bonding was realized by the ribs and slabs of the hollow sheet. • The shearing strength of bonding interface exceeds that of the parent metal. - Abstract: A large thin-walled hollow structural component with sealed channels is required for the vacuum chamber of a thermonuclear experimental reactor, with inconel625 as its fabrication material. This hollow structural component is rarely manufactured by normal machining method, and its manufacture is also problematic in the field of explosive welding. With this in mind, we developed an adjusted explosive welding technology which involves a two-step design, setting and annealing technology. The joints were evaluated using optical microscope and scanning electron microscope, and a mechanical experiment was conducted, involving micro-hardness test, cold helium leak test and hydraulic pressure test. The results showed that a metallurgical bonding was realized by the ribs and slabs, and the shearing strength of the bonding interface exceeded that of the parent metal. Hence, the hollow structural component has a good comprehensive mechanical performance and sealing property.

Experimental study on hollow structural component by explosive welding

International Nuclear Information System (INIS)

Duan, Mianjun; Wei, Ling; Hong, Jin; Ran, Hong; Ma, Rui; Wang, Yaohua

2014-01-01

Highlights: • This paper relates to a study on a thin double-layers hollow structural component by using an explosive welding technology. • This thin double-layer hollow structural component is an indispensable component required for certain core equipment of thermonuclear experimental reactor. • An adjusted explosive welding technology for manufacturing an inconel625 hollow structural component was developed which cannot be made by common technology. • The result shows that a metallurgical bonding was realized by the ribs and slabs of the hollow sheet. • The shearing strength of bonding interface exceeds that of the parent metal. - Abstract: A large thin-walled hollow structural component with sealed channels is required for the vacuum chamber of a thermonuclear experimental reactor, with inconel625 as its fabrication material. This hollow structural component is rarely manufactured by normal machining method, and its manufacture is also problematic in the field of explosive welding. With this in mind, we developed an adjusted explosive welding technology which involves a two-step design, setting and annealing technology. The joints were evaluated using optical microscope and scanning electron microscope, and a mechanical experiment was conducted, involving micro-hardness test, cold helium leak test and hydraulic pressure test. The results showed that a metallurgical bonding was realized by the ribs and slabs, and the shearing strength of the bonding interface exceeded that of the parent metal. Hence, the hollow structural component has a good comprehensive mechanical performance and sealing property

Engineering Porous Polymer Hollow Fiber Microfluidic Reactors for Sustainable C-H Functionalization.

Science.gov (United States)

He, Yingxin; Rezaei, Fateme; Kapila, Shubhender; Rownaghi, Ali A

2017-05-17

Highly hydrophilic and solvent-stable porous polyamide-imide (PAI) hollow fibers were created by cross-linking of bare PAI hollow fibers with 3-aminopropyl trimethoxysilane (APS). The APS-grafted PAI hollow fibers were then functionalized with salicylic aldehyde for binding catalytically active Pd(II) ions through a covalent postmodification method. The catalytic activity of the composite hollow fiber microfluidic reactors (Pd(II) immobilized APS-grafted PAI hollow fibers) was tested via heterogeneous Heck coupling reaction of aryl halides under both batch and continuous-flow reactions in polar aprotic solvents at high temperature (120 °C) and low operating pressure. X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma (ICP) analyses of the starting and recycled composite hollow fibers indicated that the fibers contain very similar loadings of Pd(II), implying no degree of catalyst leaching from the hollow fibers during reaction. The composite hollow fiber microfluidic reactors showed long-term stability and strong control over the leaching of Pd species.

Review of Synthetic Methods to Form Hollow Polymer Nanocapsules

Energy Technology Data Exchange (ETDEWEB)

Barker, Madeline T. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2014-03-13

Syntactic foams have grown in interest due to the widened range of applications because of their mechanical strength and high damage tolerance. In the past, hollow glass or ceramic particles were used to create the pores. This paper reviews literature focused on the controlled synthesis of hollow polymer spheres with diameters ranging from 100 –200 nm. By using hollow polymer spheres, syntactic foams could reach ultra-low densities.

The Performance and Fouling Control of Submerged Hollow Fiber (HF Systems: A Review

Directory of Open Access Journals (Sweden)

Ebrahim Akhondi

2017-07-01

Full Text Available The submerged membrane filtration concept is well-established for low-pressure microfiltration (MF and ultrafiltration (UF applications in the water industry, and has become a mainstream technology for surface-water treatment, pretreatment prior to reverse osmosis (RO, and membrane bioreactors (MBRs. Compared to submerged flat sheet (FS membranes, submerged hollow fiber (HF membranes are more common due to their advantages of higher packing density, the ability to induce movement by mechanisms such as bubbling, and the feasibility of backwashing. In view of the importance of submerged HF processes, this review aims to provide a comprehensive landscape of the current state-of-the-art systems, to serve as a guide for further improvements in submerged HF membranes and their applications. The topics covered include recent developments in submerged hollow fiber membrane systems, the challenges and developments in fouling-control methods, and treatment protocols for membrane permeability recovery. The highlighted research opportunities include optimizing the various means to manipulate the hydrodynamics for fouling mitigation, developing online monitoring devices, and extending the submerged HF concept beyond filtration.

Hollow cathode for positive ion sources

International Nuclear Information System (INIS)

Schechter, D.E.; Kim, J.; Tsai, C.C.

1979-01-01

Development to incorporate hollow cathodes into high power ion sources for neutral beam injection systems is being pursued. Hollow tube LaB 6 -type cathodes, similar to a UCLA design, have been constructed and tested in several ORNL ion source configurations. Results of testing include arc discharge parameters of >1000 and 500 amps for 0.5 and 10 second pulse lengths, respectively. Details of cathode construction and additional performance results are discussed

Polyazole hollow fiber membranes for direct contact membrane distillation

KAUST Repository

Maab, Husnul; Alsaadi, Ahmad Salem; Francis, Lijo; Livazovic, Sara; Ghaffour, NorEddine; Amy, Gary L.; Nunes, Suzana Pereira

2013-01-01

Porous hollow fiber membranes were fabricated from fluorinated polyoxadiazole and polytriazole by a dry-wet spinning method for application in desalination of Red Sea water by direct contact membrane distillation (DCMD). The data were compared with commercially available hollow fiber MD membranes prepared from poly(vinylidene fluoride). The membranes were characterized by electron microscopy, liquid entry pressure (LEP), and pore diameter measurements. Finally, the hollow fiber membranes were tested for DCMD. Salt selectivity as high as 99.95% and water fluxes as high as 35 and 41 L m -2 h-1 were demonstrated, respectively, for polyoxadiazole and polytriazole hollow fiber membranes, operating at 80 C feed temperature and 20 C permeate. © 2013 American Chemical Society.

Polyazole hollow fiber membranes for direct contact membrane distillation

KAUST Repository

Maab, Husnul

2013-08-07

Porous hollow fiber membranes were fabricated from fluorinated polyoxadiazole and polytriazole by a dry-wet spinning method for application in desalination of Red Sea water by direct contact membrane distillation (DCMD). The data were compared with commercially available hollow fiber MD membranes prepared from poly(vinylidene fluoride). The membranes were characterized by electron microscopy, liquid entry pressure (LEP), and pore diameter measurements. Finally, the hollow fiber membranes were tested for DCMD. Salt selectivity as high as 99.95% and water fluxes as high as 35 and 41 L m -2 h-1 were demonstrated, respectively, for polyoxadiazole and polytriazole hollow fiber membranes, operating at 80 C feed temperature and 20 C permeate. © 2013 American Chemical Society.

Boron nitride hollow nanospheres: Synthesis, formation mechanism and dielectric property

Energy Technology Data Exchange (ETDEWEB)

Zhong, B.; Tang, X.H. [School of Materials Science and Engineering, Harbin Institute of Technology at Weihai, Weihai 264209 (China); Huang, X.X., E-mail: swliza@hit.edu.cn [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Xia, L. [School of Materials Science and Engineering, Harbin Institute of Technology at Weihai, Weihai 264209 (China); Zhang, X.D. [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Wang, C.J. [School of Materials Science and Engineering, Harbin Institute of Technology at Weihai, Weihai 264209 (China); Wen, G.W., E-mail: g.wen@hit.edu.cn [School of Materials Science and Engineering, Harbin Institute of Technology at Weihai, Weihai 264209 (China); School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China)

2015-04-15

Highlights: • BN hollow nanospheres are fabricated in large scale via a new CVD method. • Morphology and structure are elucidated by complementary analytical techniques. • Formation mechanism is proposed based on experimental observations. • Dielectric properties are investigated in the X-band microwave frequencies. • BN hollow nanospheres show lower dielectric loss than regular BN powders. - Abstract: Boron nitride (BN) hollow nanospheres have been successfully fabricated by pyrolyzing vapors decomposed from ammonia borane (NH{sub 3}BH{sub 3}) at 1300 °C. The final products have been extensively characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The BN hollow nanospheres were ranging from 100 to 300 nm in diameter and around 30–100 nm in thickness. The internal structure of the products was found dependent on the reaction temperatures. A possible formation mechanism of the BN hollow nanospheres was proposed on the basis of the experimental observations. Dielectric measurements in the X-band microwave frequencies (8–12 GHz) showed that the dielectric loss of the paraffin filled by the BN hollow nanospheres was lower than that filled by regular BN powders, which indicated that the BN hollow nanospheres could be potentially used as low-density fillers for microwave radomes.

High performance methanol-oxygen fuel cell with hollow fiber electrode

Science.gov (United States)

Lawson, Daniel D. (Inventor); Ingham, John D. (Inventor)

1983-01-01

A methanol/air-oxygen fuel cell including an electrode formed by open-ended ion-exchange hollow fibers having a layer of catalyst deposited on the inner surface thereof and a first current collector in contact with the catalyst layer. A second current collector external of said fibers is provided which is immersed along with the hollow fiber electrode in an aqueous electrolyte body. Upon passage of air or oxygen through the hollow fiber electrode and introduction of methanol into the aqueous electrolyte, a steady current output is obtained. Two embodiments of the fuel cell are disclosed. In the first embodiment the second metal electrode is displaced away from the hollow fiber in the electrolyte body while in the second embodiment a spiral-wrap electrode is provided about the outer surface of the hollow fiber electrode.

High-performance supercapacitors based on hollow polyaniline nanofibers by electrospinning.

Science.gov (United States)

Miao, Yue-E; Fan, Wei; Chen, Dan; Liu, Tianxi

2013-05-22

Hollow polyaniline (PANI) nanofibers with controllable wall thickness are fabricated by in situ polymerization of aniline using the electrospun poly(amic acid) fiber membrane as a template. A maximum specific capacitance of 601 F g(-1) has been achieved at 1 A g(-1), suggesting the potential application of hollow PANI nanofibers for supercapacitors. The superior electrochemical performance of the hollow nanofibers is attributed to their hollow structure, thin wall thickness, and orderly pore passages, which can drastically facilitate the ion diffusion and improve the utilization of the electroactive PANI during the charge-discharge processes. Furthermore, the high flexibility of the self-standing fiber membrane template provides possibilities for the facile construction and fabrication of conducting polymers with hollow nanostructures, which may find potential applications in various high-performance electrochemical devices.

Mercury - the hollow planet

Science.gov (United States)

Rothery, D. A.

2012-04-01

Mercury is turning out to be a planet characterized by various kinds of endogenous hole (discounting impact craters), which are compared here. These include volcanic vents and collapse features on horizontal scales of tens of km, and smaller scale depressions ('hollows') associated with bright crater-floor deposits (BCFD). The BCFD hollows are tens of metres deep and kilometres or less across and are characteristically flat-floored, with steep, scalloped walls. Their form suggests that they most likely result from removal of surface material by some kind of mass-wasting process, probably associated with volume-loss caused by removal (via sublimation?) of a volatile component. These do not appear to be primarily a result of undermining. Determining the composition of the high-albedo bluish surface coating in BCFDs will be a key goal for BepiColombo instruments such as MIXS (Mercury Imaging Xray Spectrometer). In contrast, collapse features are non-circular rimless pits, typically on crater floors (pit-floor craters), whose morphology suggests collapse into void spaces left by magma withdrawal. This could be by drainage of either erupted lava (or impact melt) or of shallowly-intruded magma. Unlike the much smaller-scale BCFD hollows, these 'collapse pit' features tend to lack extensive flat floors and instead tend to be close to triangular in cross-section with inward slopes near to the critical angle of repose. The different scale and morphology of BCFD hollows and collapse pits argues for quite different modes of origin. However, BCFD hollows adjacent to and within the collapse pit inside Scarlatti crater suggest that the volatile material whose loss was responsible for the growth of the hollows may have been emplaced in association with the magma whose drainage caused the main collapse. Another kind of volcanic collapse can be seen within a 25 km-wide volcanic vent outside the southern rim of the Caloris basin (22.5° N, 146.1° E), on a 28 m/pixel MDIS NAC image

[Study on Hollow Brick Wall's Surface Temperature with Infrared Thermal Imaging Method].

Science.gov (United States)

Tang, Ming-fang; Yin, Yi-hua

2015-05-01

To address the characteristic of uneven surface temperature of hollow brick wall, the present research adopts soft wares of both ThermaCAM P20 and ThermaCAM Reporter to test the application of infrared thermal image technique in measuring surface temperature of hollow brick wall, and further analyzes the thermal characteristics of hollow brick wall, and building material's impact on surface temperature distribution including hollow brick, masonry mortar, and so on. The research selects the construction site of a three-story-high residential, carries out the heat transfer experiment, and further examines the exterior wall constructed by 3 different hollow bricks including sintering shale hollow brick, masonry mortar and brick masonry. Infrared thermal image maps are collected, including 3 kinds of sintering shale hollow brick walls under indoor heating in winter; and temperature data of wall surface, and uniformity and frequency distribution are also collected for comparative analysis between 2 hollow bricks and 2 kinds of mortar masonry. The results show that improving heat preservation of hollow brick aid masonry mortar can effectively improve inner wall surface temperature and indoor thermal environment; non-uniformity of surface temperature decreases from 0. 6 to 0. 4 °C , and surface temperature frequency distribution changes from the asymmetric distribution into a normal distribution under the condition that energy-saving sintering shale hollow brick wall is constructed by thermal mortar replacing cement mortar masonry; frequency of average temperature increases as uniformity of surface temperature increases. This research provides a certain basis for promotion and optimization of hollow brick wall's thermal function.

Plasma generation using the hollow cathod

International Nuclear Information System (INIS)

Moon, K.J.

1983-01-01

A hollow cathode of tungsten was adapted to an University of California, Berkely, LBL bucket ion source to investigate ion density fluctuations at the extractior grid. Fluctuations in plasma ion density are observed to range between 100kHz to 2 MHz. The observed fluctuation frequencies of plasma ion density are found to be inversely proportional to the square root of ion masses. It is guessed that the plasma fluctuation are also correlated with the hollow cathode length. (Author)

Hollow density profile on electron cyclotron resonance heating JFT-2M plasma

International Nuclear Information System (INIS)

Yamauchi, Toshihiko; Hoshino, Katsumichi; Kawashima, Hisato; Ogawa, Toshihide; Kawakami, Tomohide; Shiina, Tomio; Ishige, Youichi

1998-01-01

The first hollow electron density profile in the central region on the JAERI Fusion Torus-2M (JFT-2M) is measured during electron cyclotron resonance heating (ECRH) with a TV Thomson scattering system (TVTS). The peripheral region is not hollow but is accumulated due to pump-out from the central region. The hollowness increases with time but is saturated at ∼40 ms and maintains a constant hollow ratio. The hollowness is strongly related to the steep temperature gradient of the heated zone. (author)

HOLLOW FIBRE MEMBRANE

NARCIS (Netherlands)

Wessling, Matthias; Stamatialis, Dimitrios; Kopec, K.K.; Dutczak, S.M.

2011-01-01

The present invention relates to a process for manufacturing a hollow fibre membrane having a supporting layer and a separating layer, said process comprising: (a)extruding a spinning composition comprising a first polymer and a solvent for the first polymer through an inner annular orifice of a

HOLLOW FIBRE MEMBRANE

NARCIS (Netherlands)

Wessling, Matthias; Stamatialis, Dimitrios; Kopec, K.K.; Dutczak, S.M.

2013-01-01

The present invention relates to a process for manufacturing a hollow fibre membrane having a supporting layer and a separating layer, said process comprising: (a) extruding a spinning composition comprising a first polymer and a solvent for the first polymer through an inner annular orifice of a

A novel approach to fabrication of superparamagnetite hollow silica/magnetic composite spheres

Energy Technology Data Exchange (ETDEWEB)

Yuan Junjie, E-mail: yuanjunjie@tongji.edu.c [School of Materials Science and Engineering, Tongji University, Shanghai 200092 (China); Key Laboratory of Molecular Engineering of Polymers, Fudan University, Shanghai 200433 (China); Zhang Xiong; Qian He [School of Materials Science and Engineering, Tongji University, Shanghai 200092 (China)

2010-08-15

We described a method for synthesizing hollow silica/magnetic composite spheres using sulfonic acid functionalized hollow silica spheres (SAFHSS) as templates. The Fe{sub 3}O{sub 4} nanoparticles were deposited on or imbedded in the hollow silica shell by a precipitation reaction. The morphologies, composition and properties of the hollow composite spheres were characterized by transmission electron microscopy, Fourier transform infrared analysis, X-ray diffraction measurement and vibrating-sample magnetometry measurement. The results indicated crystal sizes and amount of the Fe{sub 3}O{sub 4} nanoparticles on the SAFHSS. The magnetic properties of the hollow composite spheres were controlled by adjusting the proportion between Fe{sup 2+} and Fe{sup 3+} and iron ion total concentration. When appropriate loading species were added into the system, superparamagnetite hollow composite spheres were obtained. The method also could be applicable to prepare other superparamagnetite hollow silica/ferrite composite spheres.

Coprecipitation-assisted hydrothermal synthesis of PLZT hollow nanospheres

International Nuclear Information System (INIS)

Zhu, Renqiang; Zhu, Kongjun; Qiu, Jinhao; Bai, Lin; Ji, Hongli

2010-01-01

Lanthanum-modified lead zirconate titanate Pb 1-x La x (Zr 1-y Ti y )O 3 (PLZT) hollow nanospheres have been successfully prepared via a template-free hydrothermal method using the well-mixed coprecipitated precursors and the KOH mineralizer. The structure, composition, and morphology of the PLZT hollow nanospheres were characterized by XRD (X-ray diffraction), ICP (inductive coupled plasma emission spectrometer), FTIR (Fourier transform infrared spectra), TG/DTA (thermogravimetric analysis and differential thermal analysis), TEM (transmission electron microscopy) and SEAD (selected area diffraction). The results show that the composition and the morphology control of the PLZT products are determined by the KOH concentration. The PLZT hollow nanospheres with uniform size of about 4 nm were synthesized in the presence of 5 M KOH. The crystalline nanoparticles can be prepared at dilute KOH, in contrast to the amorphous powders prepared at concentrated KOH. Formation mechanisms of the PLZT hollow nanospheres are also discussed.

Performance of different hollow fiber membranes for seawater desalination using membrane distillation

KAUST Repository

Francis, Lijo; Ghaffour, NorEddine; Alsaadi, Ahmad Salem; Amy, Gary L.

2014-01-01

Membrane distillation requires a highly porous hydrophobic membrane with low surface energy. In this paper, we compare the direct contact membrane distillation (DCMD) performances of four different types of in-house fabricated hollow fiber membranes and two different commercially available hollow fiber membranes. Hollow fiber membranes are fabricated using wet-jet phase inversion technique and the polymeric matrices used for the fabrication are polyvinylidine fluoride (PVDF) and polyvinyl chloride (PVC). Commercial hollow fiber membrane materials are made of polytetrafluoroethylene (PTFE) and polypropylene (PP). PVDF hollow fibers showed a superior performance among all the hollow fibers tested in the DCMD process and gave a water vapor flux of 31 kg m-2h-1 at a feed and coolant inlet temperatures of 80 and 20°C, respectively. Under the same conditions, the water vapor flux observed for PP, PTFE, and PVC hollow fiber membranes are 13, 11, and 6 kg m-2h-1, respectively, with 99.99% salt rejection observed for all membranes used.

Performance of different hollow fiber membranes for seawater desalination using membrane distillation

KAUST Repository

Francis, Lijo

2014-08-11

Membrane distillation requires a highly porous hydrophobic membrane with low surface energy. In this paper, we compare the direct contact membrane distillation (DCMD) performances of four different types of in-house fabricated hollow fiber membranes and two different commercially available hollow fiber membranes. Hollow fiber membranes are fabricated using wet-jet phase inversion technique and the polymeric matrices used for the fabrication are polyvinylidine fluoride (PVDF) and polyvinyl chloride (PVC). Commercial hollow fiber membrane materials are made of polytetrafluoroethylene (PTFE) and polypropylene (PP). PVDF hollow fibers showed a superior performance among all the hollow fibers tested in the DCMD process and gave a water vapor flux of 31 kg m-2h-1 at a feed and coolant inlet temperatures of 80 and 20°C, respectively. Under the same conditions, the water vapor flux observed for PP, PTFE, and PVC hollow fiber membranes are 13, 11, and 6 kg m-2h-1, respectively, with 99.99% salt rejection observed for all membranes used.

Methodology for construction of hollow spheres for use in physical phantoms

International Nuclear Information System (INIS)

Oliveira, A.C.H.; Lima, F.R.A.; Oliveira, F.; Vieira, J.W.

2015-01-01

In positron emission tomography (PET), quantitative evaluation of spatial resolution/object size, attenuation and scatter effects is often performed using phantoms with hollow spheres. Fillable, plastic-walled spheres are commercially available in several sizes. Radioactive solutions in any concentration can be injected into the spheres. Hollow spheres have several desirable traits, including repeatable, consistent use, and standardization across measurements at different institutions, since identical items are distributed by a single manufacturer. The objective of this work is to describe a methodology for construction of hollow spheres using rapid prototyping. It was used the software SolidWork (2014) to create five 3D models of the hollow spheres with inner diameters of 10 mm, 13 mm, 17 mm, 22 mm, and 28 mm. These models were based on hollow spheres of NEMA/IEC PET body phantom. It was used a Cubex Duo 3D printer (3D Systems) to build the hollow spheres. The material used was the ABS (acrylonitrile butadiene styrene) resin. (authors)

Electro-magnetic properties of composites with aligned Fe-Co hollow fibers

Directory of Open Access Journals (Sweden)

Seungchan Cho

2016-05-01

Full Text Available A novel Fe-Co binary hollow fiber was synthesized by electroless plating using hydrolyzed polyester fiber and its anisotropy characteristic was investigated for electromagnetic wave absorbing materials. The hollow fibers in parallel with magnetic field show higher saturated magnetization of 202 emu/g at the applied magnetic field of 10 kOe and lower coercivity (27.658 Oe, compared with the random and vertical oriented hollow fibers. From complex permittivity measurement, the Fe-Co hollow fiber composites clearly display a single dielectric resonance, located at ∼14 GHz. The Fe-Co hollow fibers not only provide excellent EM properties in GHz frequency ranges, resulting mainly from the strong resonance, but also adjust the soft magnetic properties through fiber alignments. The cavitary structure of the Fe-Co hollow fibers, not only giving rise to a dielectric loss resonance and also adjusting its peak frequency, may be a pathway to useful EM wave absorptive devices in GHz frequency ranges.

Adsorption characteristics of activated carbon hollow fibers

Directory of Open Access Journals (Sweden)

B. V. Kaludjerović

2009-01-01

Full Text Available Carbon hollow fibers were prepared with regenerated cellulose or polysulfone hollow fibers by chemical activation using sodium phosphate dibasic followed by the carbonization process. The activation process increases the adsorption properties of fibers which is more prominent for active carbone fibers obtained from the cellulose precursor. Chemical activation with sodium phosphate dibasic produces an active carbon material with both mesopores and micropores.

Manufacturing hollow obturator with resilient denture liner on post hemimaxillectomy

Directory of Open Access Journals (Sweden)

Michael Josef Kridanto Kamadjaja

2006-03-01

Full Text Available A resilient denture liner is placed in the part of the hollow obturator base that contacts to post hemimaxillectomy mucosa. Replacing the resilient denture liner can makes the hollow obturator has an intimate contact with the mucosa, so it can prevents the mouth liquid enter to the cavum nasi and sinus, also eliminates painful because of using the hollow obturator. Resilient denture liner is a soft and resilient material that applied to the fitting surface of a denture in order to allow a more distribution of load. A case was reported about using the hollow obturator with resilient denture liner on post hemimaxillectomy to overcome these problems.

Hollow fiber membranes and methods for forming same

Science.gov (United States)

Bhandari, Dhaval Ajit; McCloskey, Patrick Joseph; Howson, Paul Edward; Narang, Kristi Jean; Koros, William

2016-03-22

The invention provides improved hollow fiber membranes having at least two layers, and methods for forming the same. The methods include co-extruding a first composition, a second composition, and a third composition to form a dual layer hollow fiber membrane. The first composition includes a glassy polymer; the second composition includes a polysiloxane; and the third composition includes a bore fluid. The dual layer hollow fiber membranes include a first layer and a second layer, the first layer being a porous layer which includes the glassy polymer of the first composition, and the second layer being a polysiloxane layer which includes the polysiloxane of the second composition.

Study of the hollow cathode plasma electron-gun

International Nuclear Information System (INIS)

Zhang Yonghui; Jiang Jinsheng; Chang Anbi

2003-01-01

For developing a novel high-current, long pulse width electron source, the theoretics and mechanism of the hollow cathode plasma electron-gun are analyzed in detail in this paper, the structure and the physical process of hollow cathode plasma electron-gun are also studied. This gun overcomes the limitations of most high-power microwave tubes, which employ either thermionic cathodes that produce low current-density beams because of the limitation of the space charge, or field-emission cathodes that offer high current density but provide only short pulse width because of plasma closure of the accelerating gap. In the theories studying on hollow cathode plasma electron-gun, the characteristic of the hollow-cathode discharge is introduced, the action during the forming of plasma of the stimulating electrode and the modulating anode are discussed, the movement of electrons and ions and the primary parameters are analyzed, and the formulas of the electric field, beam current density and the stabilization conditions of the beam current are also presented in this paper. The numerical simulation is carried out based on Poisson's equation, and the equations of current continuity and movement. And the optimized result is reported. On this basis, we have designed a hollow-cathode-plasma electron-gun, whose output pulse current is 2 kA, and pulse width is 1 microsecond

Fe2O3 hollow sphere nanocomposites for supercapacitor applications

Science.gov (United States)

Zhao, Yu; Wen, Yang; Xu, Bing; Lu, Lu; Ren, Reiming

2018-02-01

Nanomaterials have attracted increasing interest in electrochemical energy storage and conversion. Hollow sphere Fe2O3 nanocomposites were successfully prepared through facile low temperature water-bath method with carbon sphere as hard template. The morphology and microstructure of samples were characterized by X-ray diffraction (XRD) and Scanning electron microscope (SEM), respectively. Through hydrolysis mechanism, using ferric chloride direct hydrolysis, iron hydroxide coated on the surface of carbon sphere, after high temperature calcination can form the hollow spherical iron oxide materials. Electrochemical performances of the hollow sphere Fe2O3 nanocomposites electrodes were investigated by cyclic voltammery (CV) and galvanostatic charge/discharge. The Pure hollow sphere Fe2O3 nanocomposites achieves a specific capacitance of 125 F g-1 at the current density of 85 mA g-1. The results indicate that the uniform dispersion of hollow ball structure can effectively reduce the particle reunion in the process of charging and discharging.

Energy-dependent expansion of .177 caliber hollow-point air gun projectiles.

Science.gov (United States)

Werner, Ronald; Schultz, Benno; Bockholdt, Britta; Ekkernkamp, Axel; Frank, Matthias

2017-05-01

Amongst hundreds of different projectiles for air guns available on the market, hollow-point air gun pellets are of special interest. These pellets are characterized by a tip or a hollowed-out shape in their tip which, when fired, makes the projectiles expand to an increased diameter upon entering the target medium. This results in an increase in release of energy which, in turn, has the potential to cause more serious injuries than non-hollow-point projectiles. To the best of the authors' knowledge, reliable data on the terminal ballistic features of hollow-point air gun projectiles compared to standard diabolo pellets have not yet been published in the forensic literature. The terminal ballistic performance (energy-dependent expansion and penetration) of four different types of .177 caliber hollow-point pellets discharged at kinetic energy levels from approximately 3 J up to 30 J into water, ordnance gelatin, and ordnance gelatin covered with natural chamois as a skin simulant was the subject of this investigation. Energy-dependent expansion of the tested hollow-point pellets was observed after being shot into all investigated target media. While some hollow-point pellets require a minimum kinetic energy of approximately 10 J for sufficient expansion, there are also hollow-point pellets which expand at kinetic energy levels of less than 5 J. The ratio of expansion (RE, calculated by the cross-sectional area (A) after impact divided by the cross-sectional area (A 0 ) of the undeformed pellet) of hollow-point air gun pellets reached values up of to 2.2. The extent of expansion relates to the kinetic energy of the projectile with a peak for pellet expansion at the 15 to 20 J range. To conclude, this work demonstrates that the hollow-point principle, i.e., the design-related enlargement of the projectiles' frontal area upon impact into a medium, does work in air guns as claimed by the manufacturers.

Inflatable hollow obturator prostheses for patients undergoing an extensive maxillectomy: a case report

Science.gov (United States)

Hou, Yue-Zhong; Huang, Zhi; Ye, Hong-Qiang; Zhou, Yong-Sheng

2012-01-01

The presence of a large palatal or maxillary defect after partial or total maxillectomy for tumor, trauma or congenital deformation poses a challenge to prosthodontists, particularly when the use of an implant cannot be considered. This case report described the use of an air valve in a hollow silicone obturator to manufacture an inflatable obturator that could be extended further into undercut area to retain itself. The inflatable obturator exhibited adequate retention, stability and border sealing, thereby improving the masticatory, pronunciation and swallowing functions of patients. It may be a suitable alternative treatment option to an implant-retained obturator. PMID:22653550

Recovery of uranium from seawater using amidoxime hollow fibers

International Nuclear Information System (INIS)

Saito, K.; Uezu, K.; Hori, T.; Furusaki, S.; Sugo, T.; Okamoto, J.

1988-01-01

A novel amidoxime-group-containing adsorbent of hollow-fiber form (AO-H fiber) was prepared by radiation-induced graft polymerization of acrylonitrile onto a polyethylene hollow fiber, followed by chemical conversion of the produced cyano group to an amidoxime group. Distribution of the amidoxime group was uniform throughout hollow-fiber membrane. The fixed-bed adsorption column, 30 cm in length and charged with the bundle of AO-H fibers, was found to adsorb uranium from natural seawater at a sufficiently high rate: 0.66 mg uranium per g of adsorbent in 25 days

A hollow definitive obturator fabrication technique for management of partial maxillectomy.

Science.gov (United States)

Patil, Pravinkumar Gajanan; Patil, Smita Pravinkumar

2012-11-01

Maxillary obturator prosthesis is the most frequent treatment option for management of partial or total maxillectomy. Heavy weight of the obturators is often a dislocating factor. Hollowing the prosthesis to reduce its weight is the well established fact. The alternate technique to hollow-out the prosthesis has been described in this article which is a variation of previously described processing techniques. A pre-shaped wax-bolus was incorporated inside the flasks during packing of the heat-polymerized acrylic resin to automatically create the hollow space. The processing technique described is a single step flasking procedure to construct a closed-hollow-obturator prosthesis as a single unit. To best understand the technique, this article describes management of a patient who had undergone partial maxillectomy secondary to squamous cell carcinoma rehabilitated with a hollow-obturator prosthesis.

Preparation and surface encapsulation of hollow TiO nanoparticles for electrophoretic displays

International Nuclear Information System (INIS)

Zhao Qian; Tan Tingfeng; Qi Peng; Wang Shirong; Bian Shuguang; Li Xianggao; An Yong; Liu Zhaojun

2011-01-01

Hollow black TiO nanosparticles were obtained via deposition of inorganic coating on the surface of hollow core-shell polymer latex with Ti(OBu) 4 as precursor and subsequent calcination in ammonia gas. Hollow TiO particles were characterized by scanning electron microscope, transmission electronic microscopy, X-ray diffraction, and thermogravimetric analysis. Encapsulation of TiO via dispersion polymerization was promoved by pretreating the pigments with 3-(trimethoxysilyl) propyl methacrylate, making it possible to prepare hollow TiO-polymer particles. When St and DVB were used as polymerization monomer, hollow TiO-polymer core-shell particles came into being via dispersion polymerization, and the lipophilic degree is 28.57%. Glutin-arabic gum microcapsules containing TiO-polymer particles electrophoretic liquid were prepared using via complex coacervation. It was founded that hollow TiO-polymer particles had enough electrophoretic mobility after coating with polymer.

Hollow Nanospheres Array Fabrication via Nano-Conglutination Technology.

Science.gov (United States)

Zhang, Man; Deng, Qiling; Xia, Liangping; Shi, Lifang; Cao, Axiu; Pang, Hui; Hu, Song

2015-09-01

Hollow nanospheres array is a special nanostructure with great applications in photonics, electronics and biochemistry. The nanofabrication technique with high resolution is crucial to nanosciences and nano-technology. This paper presents a novel nonconventional nano-conglutination technology combining polystyrenes spheres (PSs) self-assembly, conglutination and a lift-off process to fabricate the hollow nanospheres array with nanoholes. A self-assembly monolayer of PSs was stuck off from the quartz wafer by the thiol-ene adhesive material, and then the PSs was removed via a lift-off process and the hollow nanospheres embedded into the thiol-ene substrate was obtained. Thiolene polymer is a UV-curable material via "click chemistry" reaction at ambient conditions without the oxygen inhibition, which has excellent chemical and physical properties to be attractive as the adhesive material in nano-conglutination technology. Using the technique, a hollow nanospheres array with the nanoholes at the diameter of 200 nm embedded into the rigid thiol-ene substrate was fabricated, which has great potential to serve as a reaction container, catalyst and surface enhanced Raman scattering substrate.

Biotemplate synthesis of monodispersed iron phosphate hollow microspheres

International Nuclear Information System (INIS)

Cao Feng; Li Dongxu

2010-01-01

Monodispersed iron phosphate hollow microspheres with a high degree of crystallization were prepared through a facile in situ deposition method using rape pollen grains as a biotemplate. The functional group on the surface of the pollen grains could adsorb Fe 3+ , which provided the nucleation sites for growth of iron phosphate nanoparticles. After being sintered at 600 deg. C for 10 h, the pollen grains were removed and iron phosphate hollow microspheres were obtained. A scanning electron microscope and x-ray diffraction were applied to characterize the morphology and crystalline structure of the pollen grains, iron phosphate-coated pollen grains and iron phosphate hollow microspheres. Differential scanning calorimetry and thermogravity analyses were performed to investigate the thermal behavior of the iron phosphate-coated pollen grains during the calcinations. Energy dispersive spectroscopy and Fourier transform infrared spectroscopy were utilized to investigate the interaction between the pollen grains and iron phosphate. The effect of the pollen wall on the surface morphology of these iron phosphate hollow microspheres was also proven in this work.

Biotemplate synthesis of monodispersed iron phosphate hollow microspheres

Energy Technology Data Exchange (ETDEWEB)

Cao Feng; Li Dongxu, E-mail: dongxuli@njut.edu.c [College of Materials Science and Engineering, Nanjing University of Technology, Jiangsu Nanjing 210009 (China)

2010-03-15

Monodispersed iron phosphate hollow microspheres with a high degree of crystallization were prepared through a facile in situ deposition method using rape pollen grains as a biotemplate. The functional group on the surface of the pollen grains could adsorb Fe{sup 3+}, which provided the nucleation sites for growth of iron phosphate nanoparticles. After being sintered at 600 deg. C for 10 h, the pollen grains were removed and iron phosphate hollow microspheres were obtained. A scanning electron microscope and x-ray diffraction were applied to characterize the morphology and crystalline structure of the pollen grains, iron phosphate-coated pollen grains and iron phosphate hollow microspheres. Differential scanning calorimetry and thermogravity analyses were performed to investigate the thermal behavior of the iron phosphate-coated pollen grains during the calcinations. Energy dispersive spectroscopy and Fourier transform infrared spectroscopy were utilized to investigate the interaction between the pollen grains and iron phosphate. The effect of the pollen wall on the surface morphology of these iron phosphate hollow microspheres was also proven in this work.

Fire resistance of extruded hollow-core slabs

DEFF Research Database (Denmark)

Hertz, Kristian Dahl; Sørensen, Lars Schiøtt; Giuliani, Luisa

2017-01-01

to the structural codes with data derived from a standard fire test and from a thorough examination of the comprehensive test documentation available on fire exposed hollow-core slabs. Findings – Mechanisms for loss of load-bearing capacity are clarified, and evidence of the fire resistance is found. Originality......Purpose – Prefabricated extruded hollow-core slabs are preferred building components for floor structures in several countries. It is therefore important to be able to document the fire resistance of these slabs proving fulfilment of standard fire resistance requirements of 60 and 120 min found...... in most national building regulations. The paper aims to present a detailed analysis of the mechanisms responsible for the loss of loadbearing capacity of hollow-core slabs when exposed to fire. Design/methodology/approach – Furthermore, it compares theoretica calculation and assessment according...

Method and apparatus for producing small hollow spheres

International Nuclear Information System (INIS)

Hendricks, C.D.

1979-01-01

A method and apparatus are described for producing small hollow spheres of glass, metal or plastic, wherein the sphere material is mixed with or contains as part of the composition a blowing agent which decomposes at high temperature (T greater than or equal to 600 0 C). As the temperature is quickly raised, the blowing agent decomposes and the resulting gas expands from within, thus forming a hollow sphere of controllable thickness. The thus produced hollow spheres (20 to 10 3 μm) have a variety of application, and are particularly useful in the fabrication of targets for laser implosion such as neutron sources, laser fusion physics studies, and laser initiated fusion power plants

Mercury's Hollows: New Information on Distribution and Morphology from MESSENGER Observations at Low Altitude

Science.gov (United States)

Blewett, D. T.; Stadermann, A. C.; Chabot, N. L.; Denevi, B. W.; Ernst, C. M.; Peplowski, P. N.

2014-12-01

MESSENGER's orbital mission at Mercury led to the discovery of an unusual landform not known from other airless rocky bodies of the Solar System. Hollows are irregularly shaped, shallow, rimless depressions, often occurring in clusters and with high-reflectance interiors and halos. The fresh appearance of hollows suggests that they are relatively young features. For example, hollows are uncratered, and talus aprons downslope of hollows in certain cases appear to be covering small impact craters (100-200 in diameter). Hence, some hollows may be actively forming at present. The characteristics of hollows are suggestive of formation via destruction of a volatile-bearing phase (possibly one or more sulfides) through solar heating, micrometeoroid bombardment, and/or ion impact. Previous analysis showed that hollows are associated with low-reflectance material (LRM), a color unit identified from global color images. The material hosting hollows has often been excavated from depth by basin or crater impacts. Hollows are small features (tens of meters to several kilometers), so their detection and characterization with MESSENGER's global maps have been limited. MESSENGER's low-altitude orbits provide opportunities for collection of images at high spatial resolutions, which reveal new occurrences of hollows and offer views of hollows with unprecedented detail. As of this writing, we have examined more than 21,000 images with pixel sizes Shadow-length measurements were made on 280 images, yielding the depths of 1343 individual hollows. The mean depth is 30 m, with a standard deviation of 17 m. We also explored correlations between the geographic locations of hollows and maps provided by the MESSENGER geochemical sensors (X-Ray, Gamma-Ray, and Neutron Spectrometers), including the abundances of Al/Si, Ca/Si, Fe/Si, K, Mg/Si, and S/Si, as well as total neutron cross-section. No clear compositional trends emerged; it is likely that any true compositional preference for terrain

Method of coating the interior surface of hollow objects with a diffusion coating

Science.gov (United States)

Knowles, Shawn D.; Senor, David J.; Forbes, Steven V.; Johnson, Roger N.; Hollenberg, Glenn W.

2005-03-15

A method for forming a diffusion coating on the interior of surface of a hollow object wherein a filament, extending through a hollow object and adjacent to the interior surface of the object, is provided, with a coating material, in a vacuum. An electrical current is then applied to the filament to resistively heat the filament to a temperature sufficient to transfer the coating material from the filament to the interior surface of the object. The filament is electrically isolated from the object while the filament is being resistively heated. Preferably, the filament is provided as a tungsten filament or molybdenum filament. Preferably, the coating materials are selected from the group consisting of Ag, Al, As, Au, Ba, Be, Bi, Ca, Cd, Co, Cr, Cu, Dy, Er, Eu, Fe, Ga, Ge, Hg, In, K, Li, Mg, Mn, Na, Ni P, Pb, Pd, Pr, S, Sb, Sc, Se, Si, Sn, Sr, Te, Tl, Y, Yb, Zn, and combinations thereof. The invention additionally allows for the formation of nitrides, hydrides, or carbides of all the possible coating materials, where such compounds exist, by providing a partial pressure of nitrogen, hydrogen, hydrocarbons, or combination thereof, within the vacuum.

Fundamental investigation on the impact strength of hollow fan blades

Energy Technology Data Exchange (ETDEWEB)

Ikeda, T; Miyachi, T; Sofue, Y

1985-01-01

Models of hollow fan blades were made and tested to prove that their strength is sufficient for use in real engines. The hollow blades were fabricated by diffusion bonding of two titanium alloy (6Al-4V-Ti) plates, one of which had three spanwise stiffners and the other being flat plate. The model as a nontwisted tapered blade. Impact tests were carried out on the hollow fan blade models in which the ingestion of a 1.5 pounds bird was simulated. Solid blades with the same external form were also tested by similar methods for comparison. The results of these tests show that properly designed hollow blades have sufficient stiffness and strength for use as fan blades in the turbo-fan engine.

One-pot formation of SnO2 hollow nanospheres and α-Fe2O3@SnO2 nanorattles with large void space and their lithium storage properties

KAUST Repository

Chen, Jun Song; Li, Chang Ming; Zhou, Wen Wen; Yan, Qing Yu; Archer, Lynden A.; Lou, Xiong Wen

2009-01-01

-out Ostwald ripening mechanism. More importantly, this facile one-pot process can be extended to fabricate rattle-type hollow structures using α-Fe2O3@SnO2 as an example. Furthermore, the electrochemical lithium storage properties have been investigated

The Nature of Mercury's Hollows, and Space Weathering Close to the Sun

Science.gov (United States)

Blewett, D. T.; Chabot, N. L.; Denevi, B. W.; Ernst, C. M.

2018-05-01

Hollows are a landform that appear to form by loss of a volatile-bearing phase from silicate rock. Hollows are very young and are likely to be forming in the present day. Hollows may be an analog for extreme weathering on near-Sun asteroids.

Generation and propagation characteristics of a localized hollow beam

Science.gov (United States)

Xia, Meng; Wang, Zhizhang; Yin, Yaling; Zhou, Qi; Xia, Yong; Yin, Jianping

2018-05-01

A succinct experimental scheme is demonstrated to generate a localized hollow beam by using a π-phase binary bitmap and a convergent thin lens. The experimental results show that the aspect ratio of the dark-spot size of the hollow beam can be effectively controlled by the focal length of the lens. The measured beam profiles in free space also agree with the theoretical modeling. The studies hold great promise that such a hollow beam can be used to cool trapped atoms (or molecules) by Sisyphus cooling and to achieve an optically-trapped Bose–Einstein condensate by optical-potential evaporative cooling.

Hydroxyapatite nanorod-assembled porous hollow polyhedra as drug/protein carriers.

Science.gov (United States)

Yu, Ya-Dong; Zhu, Ying-Jie; Qi, Chao; Jiang, Ying-Ying; Li, Heng; Wu, Jin

2017-06-15

Hydroxyapatite (HAP) with a porous hollow structure is an ideal biomaterial owing to its excellent biocompatibility and unique architecture. In this study, HAP nanorod-assembled porous hollow polyhedra, consisting of nanorod building blocks, have been successfully prepared at room temperature or under hydrothermal circumstances using a self-sacrificing Ca(OH) 2 template strategy. The hydrothermal treatment (at 180°C for 1h) can promote the HAP nanorods to be arranged with their axial direction normal to the polyhedron surface. The HAP nanorod-assembled porous hollow polyhedra have been explored for the potential application in drug/protein delivery, using ibuprofen (IBU) as a model drug and hemoglobin (Hb) as a model protein. The experimental results indicate that the HAP nanorod-assembled porous hollow polyhedra have a relatively high drug loading capacity and protein adsorption ability, and sustained drug and protein release. The HAP nanorod-assembled porous hollow polyhedra have promising applications in various biomedical fields such as the drug and protein delivery. Copyright © 2017 Elsevier Inc. All rights reserved.

CAISSON TYPE HOLLOW FLOOR SLABS OF MONOLITHIC MULTI-STOREYED BUILDINGS

Directory of Open Access Journals (Sweden)

Malakhova Anna Nikolaevna

2016-06-01

Full Text Available One of the disadvantages of building structures made of reinforced concrete is their considerable weight. One of the trends to decrease the weight of concrete structures, including floor slabs, is the arrangement of voids in the cross-sectional building structures. In Russian and foreign practice paper, cardboard and plastic tubes has been used for creation of voids in the construction of monolithic floor slabs. Lightweight concretes were also used for production of precast hollow core floor slabs. The article provides constructive solutions of precast hollow core floor slabs and solid monolithic slabs that were used in the construction of buildings before wide use of large precast hollow core floor slabs. The article considers the application of caisson hollow core floor slabs for modern monolithic multi-storeyed buildings. The design solutions of such floor slabs, experimental investigations and computer modeling of their operation under load were described in this article. The comparative analysis of the calculation results of computer models of a hollow slabs formed of rod or plastic elements showed the similarity of calculation results.

The crazy hollow formation (Eocene) of central Utah

Science.gov (United States)

Weiss, M.P.; Warner, K.N.

2001-01-01

The Late Eocene Crazy Hollow Formation is a fluviatile and lacustrine unit that was deposited locally in the southwest arm of Lake Uinta during and after the last stages of the lake the deposited the Green River Formation. Most exposures of the Crazy Hollow are located in Sanpete and Sevier Counties. The unit is characterized by a large variety of rock types, rapid facies changes within fairly short distances, and different lithofacies in the several areas where outcrops of the remnants of the formation are concentrated. Mudstone is dominant, volumetrically, but siltstone, shale, sandstone, conglomerate and several varieties of limestone are also present. The fine-grained rocks are mostly highly colored, especially in shades of yellow, orange and red. Sand grains, pebbles and small cobbles of well-rounded black chert are widespread, and "salt-and-pepper sandstone" is the conspicuous characteristic of the Crazy Hollow. The salt-and-pepper sandstone consists of grains of black chert, white chert, quartz and minor feldspar. The limestone beds and lenses are paludal and lacustrine in origin; some are fossiliferous, and contain the same fauna found in the Green River Formation. With trivial exceptions, the Crazy Hollow Formation lies on the upper, limestone member of the Green River Formation, and the beds of the two units are always accordant in attitude. The nature of the contact differs locally: at some sites there is gradation from the Green River to the Crazy Hollow; at others, rocks typical of the two units intertongue; elsewhere there is a disconformity between the two. A variety of bedrock units overlie the Crazy Hollow at different sites. In the southeasternmost districts it is overlain by the late Eocene formation of Aurora; in western Sevier County it is overlain by the Miocene-Pliocene Sevier River Formation; in northernmost Sanpete County it is overlain by the Oligocene volcanics of the Moroni Formation. At many sites bordering Sanpete and Sevier Valleys

Structural investigation of spherical hollow excipient Mannit Q by X-ray microtomography.

Science.gov (United States)

Kajihara, Ryusuke; Noguchi, Shuji; Iwao, Yasunori; Yasuda, Yuki; Segawa, Megumi; Itai, Shigeru

2015-11-10

The structure of Mannit Q particles, an excipient made by spray-drying a d-mannitol solution, and Mannit Q tablets were investigated by synchrotron X-ray microtomography. The Mannit Q particles had a spherical shape with a hollow core. The shells of the particles consisted of fine needle-shaped crystals, and columnar crystals were present in the hollows. These structural features suggested the following formation mechanism for the hollow particles:during the spray-drying process, the solvent rapidly evaporated from the droplet surface, resulting in the formation of shells made of fine needle-shaped crystals.Solvent remaining inside the shells then evaporated slowly and larger columnar crystals grew as the hollows formed. Although most of the Mannit Q particles were crushed on tableting, some of the particles retained their hollow structures, probably because the columnar crystals inside the hollows functioned as props. This demonstrated that the tablets with porous void spaces may be readily manufactured using Mannit Q. Copyright © 2015 Elsevier B.V. All rights reserved.

Analysis of ELM stability with extended MHD models in JET, JT-60U and future JT-60SA tokamak plasmas

Science.gov (United States)

Aiba, N.; Pamela, S.; Honda, M.; Urano, H.; Giroud, C.; Delabie, E.; Frassinetti, L.; Lupelli, I.; Hayashi, N.; Huijsmans, G.; JET Contributors, the; Research Unit, JT-60SA

2018-01-01

The stability with respect to a peeling-ballooning mode (PBM) was investigated numerically with extended MHD simulation codes in JET, JT-60U and future JT-60SA plasmas. The MINERVA-DI code was used to analyze the linear stability, including the effects of rotation and ion diamagnetic drift ({ω }* {{i}}), in JET-ILW and JT-60SA plasmas, and the JOREK code was used to simulate nonlinear dynamics with rotation, viscosity and resistivity in JT-60U plasmas. It was validated quantitatively that the ELM trigger condition in JET-ILW plasmas can be reasonably explained by taking into account both the rotation and {ω }* {{i}} effects in the numerical analysis. When deuterium poloidal rotation is evaluated based on neoclassical theory, an increase in the effective charge of plasma destabilizes the PBM because of an acceleration of rotation and a decrease in {ω }* {{i}}. The difference in the amount of ELM energy loss in JT-60U plasmas rotating in opposite directions was reproduced qualitatively with JOREK. By comparing the ELM affected areas with linear eigenfunctions, it was confirmed that the difference in the linear stability property, due not to the rotation direction but to the plasma density profile, is thought to be responsible for changing the ELM energy loss just after the ELM crash. A predictive study to determine the pedestal profiles in JT-60SA was performed by updating the EPED1 model to include the rotation and {ω }* {{i}} effects in the PBM stability analysis. It was shown that the plasma rotation predicted with the neoclassical toroidal viscosity degrades the pedestal performance by about 10% by destabilizing the PBM, but the pressure pedestal height will be high enough to achieve the target parameters required for the ITER-like shape inductive scenario in JT-60SA.

Emission mechanism in high current hollow cathode arcs

International Nuclear Information System (INIS)

Krishnan, M.

1976-01-01

Large (2 cm-diameter) hollow cathodes have been operated in a magnetoplasmadynamic (MPD) arc over wide ranges of current (0.25 to 17 kA) and mass flow (10 -3 to 8 g/sec), with orifice current densities and mass fluxes encompassing those encountered in low current steady-state hollow cathode arcs. Detailed cathode interior measurements of current and potential distributions show that maximum current penetration into the cathode is about one diameter axially upstream from the tip, with peak inner surface current attachment up to one cathode diameter upstream of the tip. The spontaneous attachment of peak current upstream of the cathode tip is suggested as a criterion for characteristic hollow cathode operation. This empirical criterion is verified by experiment

Evolution of ESR Technology and Equipment for Long Hollow Ingots Manufacture

Science.gov (United States)

Medovar, Lev; Stovpchenko, Ganna; Dudka, Grigory; Kozminskiy, Alexander; Fedorovskii, Borys; Lebid, Vitalii; Gusiev, Iaroslav

In this paper development of both ESR technology and equipment for hollow ingot manufacture review and analysis are presented. The real complications of hollow ingot manufacture and some tendentious issues which restrict process dissemination are discussed. An actual data of modern manufacture of as-cast pipes for heat and power engineering by traditional ESR with consumable electrode are given. Results of microstructure and nonmetal inclusion investigations have shown the high quality of as-cast ESR pipes. On the basis of these results the possibility to produce huge ESR hollows (up 5000 mm in dia) with final goal drastically to reduce setting ratio on forged shells and rings or even replace it by ESR hollows as-cast is grounded. Two new ESR technologies — consumable electrodes change and liquid metal usage — have passed pilot tests for heavy hollow production and shown very prospective results to be presented.

Hollow-core photonic band gap fibers for particle acceleration

Directory of Open Access Journals (Sweden)

Robert J. Noble

2011-12-01

Full Text Available Photonic band gap (PBG dielectric fibers with hollow cores are being studied both theoretically and experimentally for use as laser driven accelerator structures. The hollow core functions as both a longitudinal waveguide for the transverse-magnetic (TM accelerating fields and a channel for the charged particles. The dielectric surrounding the core is permeated by a periodic array of smaller holes to confine the mode, forming a photonic crystal fiber in which modes exist in frequency passbands, separated by band gaps. The hollow core acts as a defect which breaks the crystal symmetry, and so-called defect, or trapped modes having frequencies in the band gap will only propagate near the defect. We describe the design of 2D hollow-core PBG fibers to support TM defect modes with high longitudinal fields and high characteristic impedance. Using as-built dimensions of industrially made fibers, we perform a simulation analysis of prototype PBG fibers with dimensions appropriate for speed-of-light TM modes.

Method for selecting hollow microspheres for use in laser fusion targets

Science.gov (United States)

Farnum, Eugene H.; Fries, R. Jay; Havenhill, Jerry W.; Smith, Maurice Lee; Stoltz, Daniel L.

1976-01-01

Hollow microspheres having thin and very uniform wall thickness are useful as containers for the deuterium and tritium gas mixture used as a fuel in laser fusion targets. Hollow microspheres are commercially available; however, in commercial lots only a very small number meet the rigid requirements for use in laser fusion targets. Those meeting these requirements may be separated from the unsuitable ones by subjecting the commercial lot to size and density separations and then by subjecting those hollow microspheres thus separated to an external pressurization at which those which are aspherical or which have nonuniform walls are broken and separating the sound hollow microspheres from the broken ones.

Global gyrokinetic simulations of the H-mode tokamak edge pedestal

Energy Technology Data Exchange (ETDEWEB)

Wan, Weigang; Parker, Scott E.; Chen, Yang [Department of Physics, University of Colorado, Boulder, Colorado 80309 (United States); Groebner, Richard J. [General Atomics, Post Office Box 85068, San Diego, California 92186 (United States); Yan, Zheng [University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Pankin, Alexei Y.; Kruger, Scott E. [Tech-X Corporation, 5621 Arapahoe Ave., Boulder, Colorado 80305 (United States)

2013-05-15

Global gyrokinetic simulations of DIII-D H-mode edge pedestal show two types of instabilities may exist approaching the onset of edge localized modes: an intermediate-n, high frequency mode which we identify as the “kinetic peeling ballooning mode (KPBM),” and a high-n, low frequency mode. Our previous study [W. Wan et al., Phys. Rev. Lett. 109, 185004 (2012)] has shown that when the safety factor profile is flattened around the steep pressure gradient region, the high-n mode is clearly kinetic ballooning mode and becomes the dominant instability. Otherwise, the KPBM dominates. Here, the properties of the two instabilities are studied by varying the density and temperature profiles. It is found that the KPBM is destabilized by density and ion temperature gradient, and the high-n mode is mostly destabilized by electron temperature gradient. Nonlinear simulations with the KPBM saturate at high levels. The equilibrium radial electric field (E{sub r}) reduces the transport. The effect of the parallel equilibrium current is found to be weak.

Periodic organosilica hollow nanospheres as anode materials for lithium ion rechargeable batteries

Science.gov (United States)

Sasidharan, Manickam; Nakashima, Kenichi; Gunawardhana, Nanda; Yokoi, Toshiyuki; Ito, Masanori; Inoue, Masamichi; Yusa, Shin-Ichi; Yoshio, Masaki; Tatsumi, Takashi

2011-11-01

Polymeric micelles with core-shell-corona architecture have been found to be the efficient colloidal templates for synthesis of periodic organosilica hollow nanospheres over a broad pH range from acidic to alkaline media. In alkaline medium, poly (styrene-b-[3-(methacryloylamino)propyl] trimethylammonium chloride-b-ethylene oxide) (PS-PMAPTAC-PEO) micelles yield benzene-silica hollow nanospheres with molecular scale periodicity of benzene groups in the shell domain of hollow particles. Whereas, an acidic medium (pH 4) produces diverse hollow particles with benzene, ethylene, and a mixture of ethylene and dipropyldisulfide bridging functionalities using poly(styrene-b-2-vinyl pyridine-b-ethylene oxide) (PS-PVP-PEO) micelles. These hollow particles were thoroughly characterized by powder X-ray diffraction (XRD), dynamic light scattering (DLS), thermogravimetric analysis (TG/DTA), Fourier transformation infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), magic angle spinning-nuclear magnetic resonance (29Si MAS NMR and 13CP-MAS NMR), Raman spectroscopy, and nitrogen adsorption/desorption analyses. The benzene-silica hollow nanospheres with molecular scale periodicity in the shell domain exhibit higher cycling performance of up to 300 cycles in lithium ion rechargeable batteries compared with micron-sized dense benzene-silica particles.Polymeric micelles with core-shell-corona architecture have been found to be the efficient colloidal templates for synthesis of periodic organosilica hollow nanospheres over a broad pH range from acidic to alkaline media. In alkaline medium, poly (styrene-b-[3-(methacryloylamino)propyl] trimethylammonium chloride-b-ethylene oxide) (PS-PMAPTAC-PEO) micelles yield benzene-silica hollow nanospheres with molecular scale periodicity of benzene groups in the shell domain of hollow particles. Whereas, an acidic medium (pH 4) produces diverse hollow particles with benzene, ethylene, and a mixture of ethylene and

Bubble template synthesis of hollow gold nanoparticles and their applications as theranostic agents

Science.gov (United States)

Huang, Chienwen

Hollow gold nanoparticle with a sub-30nm polycrystalline shell and a 50 nm hollow core has been successfully synthesized through the reduction of sodium gold sulfite by electrochemically evolved hydrogen. Such hollow gold nanoparticles exhibit unique plasmonic properties. They strongly scatter and absorb near infrared light. In this thesis we seek to understand the formation mechanism of hollow gold nanoparticles in this new synthesis process and their plasmonic properties. Also, we explore their biomedical applications as theranostic agents (therapeutic and diagnostic imaging). A lithographically patterned electrode consisting of Ag stripes on a glass substrate was used to investigate the formation process of hollow gold nanoparticles. Ag stripes served as working electrode for electrochemically evolution of hydrogen, and adjacent glass areas provided supporting surface for hydrogen nanobubbles nucleation and growth. Hydrogen nanobubbles served as both templates and reducing agents to trigger the autocatalytic disproportionation reaction of sodium gold sulfite. The effects of applied potential and the additives in the electrolyte have been studied. It has been found that the size and size distribution of hollow gold nanoparticle are directly relative to the applied potential, i.e. the hydrogen evolution rate. It has also been found the addition of Ni2+ ions can greatly improve the size distribution of hollow gold nanoparticles that can be contributed to that the newly electrodeposited nickel metal can enhance the hydrogen evolution efficiency. Another additive, ethylenediamine (EDA) can suppress the autocatalytic reaction of gold sulfite to increase the stability of sodium gold sulfite electrolyte. To capture such electrochemically evolved hydrogen nanobubbles, and subsequently to generate hollow gold nanoparticles in large numbers, alumina membranes were placed on the top of the working electrode. Anodic alumina membrane consists of ~200 nm pores, which provides

Electromagnetic wave absorption properties of composites with ultrafine hollow magnetic fibers

Energy Technology Data Exchange (ETDEWEB)

Yi, Jin Woo [Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (BK21 Granted Program), 291 Daehak-ro, Yuseong-gu, Daejeon (Korea, Republic of); Composites Research Center, Korea Institute of Materials Science, 66 Sang-nam-dong, Changwon, Gyeongnam (Korea, Republic of); Lee, Sang Bok; Kim, Jin Bong; Lee, Sang Kwan [Composites Research Center, Korea Institute of Materials Science, 66 Sang-nam-dong, Changwon, Gyeongnam (Korea, Republic of); Park, O Ok, E-mail: oopark@kaist.ac.kr [Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (BK21 Granted Program), 291 Daehak-ro, Yuseong-gu, Daejeon (Korea, Republic of); Department of Energy Systems Engineering, Daegu Gyeongbuk Institute of Science and Technology (DGIST), 50-1, Sang-ri, Hyeongpung-myeon, Dalseong-gun, Daegu 711-873 (Korea, Republic of)

2014-06-01

Ultrafine hollow magnetic fibers were prepared by electroless plating using hydrolyzed polyester fiber as a sacrificial substrate. These hollow fibers can be served for lightweight and efficient electromagnetic (EM) absorbing materials. As observed from SEM and EDS analysis, hollow structures consisting of Ni inner layer and Fe or Fe–Co outer layer were obtained. By introducing Co onto Fe, oxidation of the Fe layer was successfully prevented making it possible to enhance the complex permeability compared to a case in which only Fe was used. Polymeric composites containing the hollow fibers with different weight fractions and fiber lengths were prepared by a simple mixing process. The electromagnetic wave properties of the composites were measured by a vector network analyzer and it was found that the hollow magnetic fibers show a clear resonance peak of the complex permittivity around the X-band range (8–12 GHz) and the resonance frequency strongly depends on the fiber concentration and length. A possible explanation for the unique resonance is that the hollow fibers possess relatively low electrical conductivity and a long mean free path due to their oxidized phase and hollow structure. The calculated EM wave absorption with the measured EM wave properties showed that the composite containing 30 wt% hollow Ni/Fe–Co (7:3) fibers in length of 180 μm exhibited multiple absorbance peaks resulting in a broad absorption bandwidth of 4.2 GHz. It is obvious that this multiple absorbance is attributed to the resonance characteristic of the composite. - Highlights: • The ultrafine hollow fibers consist of inner Ni layer (∼100 nm) and outer Fe or Fe–Co layer (500–700 nm). • Composites with the fibers show a high permittivity as well as permeability at low weight fractions (10–30 wt%). • The composites show a permittivity resonance and the resonance frequency can be controlled by fiber content and length. • The composite absorber exhibits a double

Porous-wall hollow glass microspheres as carriers for biomolecules

Science.gov (United States)

Li, Shuyi; Dynan, William S; Wicks, George; Serkiz, Steven

2013-09-17

The present invention includes compositions of porous-wall hollow glass microspheres and one or more biomolecules, wherein the one or more biomolecules are positioned within a void location within the hollow glass microsphere, and the use of such compositions for the diagnostic and/or therapeutic delivery of biomolecules.

Impact of wall materials and seeding gases on the pedestal and on core plasma performance

Directory of Open Access Journals (Sweden)

E. Wolfrum

2017-08-01

Full Text Available Plasmas in machines with all metal plasma facing components have a lower Zeff, less radiation cooling in the scrape-off layer and divertor regions and are prone to impurity accumulation in the core. Higher gas puff and the seeding of low-Z impurities are applied to prevent impurity accumulation, to increase the frequency of edge localised modes and to cool the divertor. A lower power threshold for the transition from low-confinement mode to high confinement mode has been found in all metal wall machines when compared to carbon wall machines. The application of lithium before or during discharges can lead to ELM free H-modes. The seeding of high-Z impurities increases core radiation, reduces the power flux across the separatrix and, if applied in the right amount, does not lead to deterioration of the confinement. All these effects have in common that they can often be explained by the shape or position of the density profile. Not only the peakedness of the density profile in the core but also the position of the edge pressure gradient influences global confinement. It is shown how (i ionisation in the pedestal region due to higher reflection of deuterium from high-Z walls, (ii reduced recycling in consequence of lithium wall conditioning, (iii the fostering of edge modes with lithium dropping, (iv increased gas puff and (v the cooling of the scrape-off layer by medium-Z impurities such as nitrogen affect the edge density profile. The consequence is a shift in the pressure profile relative to the separatrix, leading to improved pedestal stability of H-mode plasmas when the direction is inwards.

Morphology and performance of polyvinylidene fluoride/perfluoro sulphonic acid hollow fiber ultrafiltration blend membranes

International Nuclear Information System (INIS)

Yuan, Guo-Lin; Xu, Zhen-Liang; Wei, Yong-Ming; Yu, Li-Yun

2009-01-01

-perfluoro sulphonic acid hollow fibre membranes with different morphologies and performances were prepared by these two different routes. Meanwhile, the range of Polyvinylidene fluoride -perfluoro sulphonic acid hollow fibre blend membranes was extended.

Hollow fiber apparatus and use thereof for fluids separations and heat and mass transfers

Energy Technology Data Exchange (ETDEWEB)

Bikson, Benjamin; Etter, Stephen; Ching, Nathaniel

2017-04-18

A hollow fiber fluid separation device includes a hollow fiber cartridge, comprising a plurality of hollow fiber membranes arranged around a central tubular core, a first tubesheet and a second tubesheet encapsulating respective distal ends of the hollow fiber bundle. The tubesheets have boreholes in fluid communication with bores of the hollow fiber membrane. In at least one of the tubesheets, the boreholes are formed radially and are in communication with the central tubular core. The hollow fiber fluid separation device can be utilized in liquid separation applications such as ultrafiltration and in gas separation processes such as air separation. The design disclosed herein is light weight and compact and is particularly advantageous at high operating temperatures when the pressure of the feed fluid introduced into the bores of hollow fibers is higher than the pressure on the shell side of the device.

Axisymmetric Vibration of Piezo-Lemv Composite Hollow Multilayer Cylinder

Directory of Open Access Journals (Sweden)

E. S. Nehru

2012-01-01

Full Text Available Axisymmetric vibration of an infinite piezolaminated multilayer hollow cylinder made of piezoelectric layers of 6 mm class and an isotropic LEMV (Linear Elastic Materials with Voids layers is studied. The frequency equations are obtained for the traction free outer surface with continuity conditions at the interfaces. Numerical results are carried out for the inner, middle, and outer hollow piezoelectric layers bonded by LEMV (It is hypothetical material layers and the dispersion curves are compared with that of a similar 3-layer model and of 3 and 5 layer models with inner, middle, and outer hollow piezoelectric layers bonded by CFRP (Carbon fiber reinforced plastics.

Turbine airfoil with dual wall formed from inner and outer layers separated by a compliant structure

Science.gov (United States)

Campbell,; Christian X. , Morrison; Jay, A [Oviedo, FL

2011-12-20

A turbine airfoil usable in a turbine engine with a cooling system and a compliant dual wall configuration configured to enable thermal expansion between inner and outer layers while eliminating stress formation is disclosed. The compliant dual wall configuration may be formed a dual wall formed from inner and outer layers separated by a compliant structure. The compliant structure may be configured such that the outer layer may thermally expand without limitation by the inner layer. The compliant structure may be formed from a plurality of pedestals positioned generally parallel with each other. The pedestals may include a first foot attached to a first end of the pedestal and extending in a first direction aligned with the outer layer, and may include a second foot attached to a second end of the pedestal and extending in a second direction aligned with the inner layer.

Hollow Mill for Extraction of Stripped Titanium Screws: An Easy ...

African Journals Online (AJOL)

countries. The known alternative in such condition is ... Key words: Hollow mill, stripped screws, titanium locked plates ... used a locally manufactured stainless steel hollow mill, ... head ‑ plate hole” assembly as a mono‑block single unit. In.

Self-sacrifice Template Formation of Hollow Hetero-Ni7S6/Co3S4 Nanoboxes with Intriguing Pseudo-capacitance for High-performance Electrochemical Capacitors

Science.gov (United States)

Hua, Hui; Liu, Sijia; Chen, Zhiyi; Bao, Ruiqi; Shi, Yaoyao; Hou, Linrui; Pang, Gang; Hui, Kwun Nam; Zhang, Xiaogang; Yuan, Changzhou

2016-02-01

Herein, we report a simple yet efficient self-sacrifice template protocol to smartly fabricate hollow hetero-Ni7S6/Co3S4 nanoboxes (Ni-Co-S NBs). Uniform nickel cobalt carbonate nanocubes are first synthesized as the precursor via solvothermal strategy, and subsequently chemically sulfidized into hollow heter-Ni-Co-S NBs through anion-exchange process. When evaluated as electrode for electrochemical capacitors (ECs), the resultant hetero-Ni-Co-S NBs visually exhibit attractive pesudo-capacitance in KOH just after continuously cyclic voltammetry (CV) scanning for 100 cycles. New insights into the underlying energy-storage mechanism of the hollow hetero-Ni-Co-S electrode, based on physicochemical characterizations and electrochemical evaluation, are first put forward that the electrochemically induced phase transformation gradually occurrs during CV sweep from the hetero-Ni-Co-S to bi-component-active NiOOH and CoOOH, which are the intrinsic charge-storage phases for the appealing Faradaic capacitance (~677 F g-1 at 4 A g-1) of hollow Ni-Co-S NBs at high rates after cycling. When further coupled with negative activated carbon (AC), the AC//hetero-Ni-Co-S asymmetric device with extended electrochemical window of 1.5 V demonstrates high specific energy density of ~31 Wh kg-1. Of significance, we strongly envision that hollow design concept and new findings here hold great promise for enriching synthetic methodologies, and electrochemistry of complex metal sulfides for next-generation ECs.

Evolution of radiation resistant hollow fibers membranes for nuclear

International Nuclear Information System (INIS)

Neelam Kumari; Raut, D.R.; Bhardwaj, Y.K.; Mohapatra, P.K.

2014-01-01

We have evaluated hollow fiber supported liquid membrane (HFSLM) technique for the separation of actinides, fission products and other valuables from the nuclear waste solutions. In this technique, ligand responsible for separation of metal ion is held in tiny pores of membrane. Any drastic change as a consequence of irradiation, like change in pore size, change in hydrophobicity of polymeric material can be fatal for separation process as it may lead dislodging of carrier ligands from the pores. It was therefore needed to study the irradiation stability of hollow fibers. We have earlier showed that polypropylene fibers were stable up to 500 radiation dose and we therefore need to look into other options. In the present work, hollow fiber membranes made from polyether ether ketone (PEEK), polysulphone (PS). Polymers were evaluated for their radiation stability after exposing to varying absorbed dose of gamma radiation. The hollow fibers were irradiated to 100 KGy, 200 KGy, 500 KGy and 1000 KGy and its changes in hydrophobicity were measured using contact angle measurement studies

Polymer blends used to develop felodipine-loaded hollow microspheres for improved oral bioavailability.

Science.gov (United States)

Pi, Chao; Feng, Ting; Liang, Jing; Liu, Hao; Huang, Dongmei; Zhan, Chenglin; Yuan, Jiyuan; Lee, Robert J; Zhao, Ling; Wei, Yumeng

2018-06-01

Felodipine (FD) has been widely used in anti-hypertensive treatment. However, it has extremely low aqueous solubility and poor bioavailability. To address these problems, FD hollow microspheres as multiple-unit dosage forms were synthesized by a solvent diffusion evaporation method. Particle size of the hollow microspheres, types of ethylcellulose (EC), amounts of EC, polyvinyl pyrrolidone (PVP) and FD were investigated based on an orthogonal experiment of three factors and three levels. In addition, the release kinetics in vitro and pharmacokinetics in beagle dogs of the optimized FD hollow microspheres was investigated and compared with Plendil (commercial FD sustained-release tablets) as a single-unit dosage form. Results showed that the optimal formulation was composed of EC 10 cp :PVP:FD (0.9:0.16:0.36, w/w). The FD hollow microspheres were globular with a hollow structure and have high drug loading (17.69±0.44%) and floating rate (93.82±4.05%) in simulated human gastric fluid after 24h. Pharmacokinetic data showed that FD hollow microspheres exhibited sustained-release behavior and significantly improved relative bioavailability of FD compared with the control. Pharmacodynamic study showed that the FD hollow microspheres could effectively lower blood pressure. Therefore, these findings demonstrated that the hollow microspheres were an effective sustained-release delivery system for FD. Copyright © 2018 Elsevier B.V. All rights reserved.

Method for sizing hollow microspheres

Science.gov (United States)

Farnum, E.H.; Fries, R.J.

1975-10-29

Hollow Microspheres may be effectively sized by placing them beneath a screen stack completely immersed in an ultrasonic bath containing a liquid having a density at which the microspheres float and ultrasonically agitating the bath.

Pressure effects in hollow and solid iron oxide nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Silva, N.J.O., E-mail: nunojoao@ua.pt [Departamento de Física and CICECO, Universidade de Aveiro, 3810-193 Aveiro (Portugal); Saisho, S.; Mito, M. [Faculty of Engineering, Kyushu Institute of Technology, Kitakyushu 804-8550 (Japan); Millán, A.; Palacio, F. [Instituto de Ciencia de Materiales de Aragón, CSIC - Universidad de Zaragoza. Departamento de Física de la Materia Condensada, Facultad de Ciencias, 50009 Zaragoza (Spain); Cabot, A. [Universitat de Barcelona and Catalonia Energy Research Institute, Barcelona (Spain); Iglesias, Ò.; Labarta, A. [Departament de Física Fonamental, Universitat de Barcelona and Institut de Nanociència i Nanotecnologia, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona (Spain)

2013-06-15

We report a study on the pressure response of the anisotropy energy of hollow and solid maghemite nanoparticles. The differences between the maghemite samples are understood in terms of size, magnetic anisotropy and shape of the particles. In particular, the differences between hollow and solid samples are due to the different shape of the nanoparticles and by comparing both pressure responses it is possible to conclude that the shell has a larger pressure response when compared to the core. - Highlights: ► Study of the pressure response of core and shell magnetic anisotropy. ► Contrast between hollow and solid maghemite nanoparticles. ► Disentanglement of nanoparticles core and shell magnetic properties.

One-pot formation of SnO2 hollow nanospheres and α-Fe2O3@SnO2 nanorattles with large void space and their lithium storage properties

KAUST Repository

Chen, Jun Song

2009-01-01

In this work, uniform SnO2 hollow nanospheres with large void space have been synthesized by a modified facile method. The void space can be easily controlled by varying the reaction time. The formation of interior void space is based on an inside-out Ostwald ripening mechanism. More importantly, this facile one-pot process can be extended to fabricate rattle-type hollow structures using α-Fe2O3@SnO2 as an example. Furthermore, the electrochemical lithium storage properties have been investigated. It is found that α-Fe2O3@SnO 2 nanorattles manifest a much lower initial irreversible loss and higher reversible capacity compared to SnO2 hollow spheres. This interesting finding supports a general hypothesis that a synergistic effect between functional core and shell materials can lead to improved lithium storage capabilities. © The Royal Society of Chemistry 2009.

Theoretical prediction of low-density hexagonal ZnO hollow structures

Energy Technology Data Exchange (ETDEWEB)

Tuoc, Vu Ngoc, E-mail: tuoc.vungoc@hust.edu.vn [Institute of Engineering Physics, Hanoi University of Science and Technology, 1 Dai Co Viet Road, Hanoi (Viet Nam); Huan, Tran Doan [Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269-3136 (United States); Thao, Nguyen Thi [Institute of Engineering Physics, Hanoi University of Science and Technology, 1 Dai Co Viet Road, Hanoi (Viet Nam); Hong Duc University, 307 Le Lai, Thanh Hoa City (Viet Nam); Tuan, Le Manh [Hong Duc University, 307 Le Lai, Thanh Hoa City (Viet Nam)

2016-10-14

Along with wurtzite and zinc blende, zinc oxide (ZnO) has been found in a large number of polymorphs with substantially different properties and, hence, applications. Therefore, predicting and synthesizing new classes of ZnO polymorphs are of great significance and have been gaining considerable interest. Herein, we perform a density functional theory based tight-binding study, predicting several new series of ZnO hollow structures using the bottom-up approach. The geometry of the building blocks allows for obtaining a variety of hexagonal, low-density nanoporous, and flexible ZnO hollow structures. Their stability is discussed by means of the free energy computed within the lattice-dynamics approach. Our calculations also indicate that all the reported hollow structures are wide band gap semiconductors in the same fashion with bulk ZnO. The electronic band structures of the ZnO hollow structures are finally examined in detail.

Studies on pulsed hollow cathode capillary discharges

Energy Technology Data Exchange (ETDEWEB)

Choi, P; Dumitrescu-Zoita, C; Larour, J; Rous, J [Ecole Polytechnique, 91 - Palaiseau (France). Lab. de Physique des Milieux Ionises; Favre, M; Moreno, J; Chuaqui, H; Wyndham, E [Pontificia Univ. Catolica de Chile, Santiago (Chile). Facultad de Fisica; Zambra, M [Comision Chilena de Energia Nuclear, Santiago (Chile); Wong, C S [Univ. of Malaya, Kuala Lumpur (Malaysia). Plasma Research Lab

1997-12-31

Preliminary results on radiation characteristics of pulsed hollow cathode capillary discharges are presented. The device combines the on axis electron beam assisted ionization capabilities of the transient hollow cathode discharge with a novel high voltage low inductance geometrical design, which integrates the local energy storage into the electrode system. A nanosecond regime high temperature plasma is produced in a long, high aspect ratio capillary, with light emission in the UV to XUV region. The discharge is operated from near vacuum to pressure in the 1000 mTorr range. (author). 2 figs., 7 refs.

Biomolecule-assisted construction of cadmium sulfide hollow spheres with structure-dependent photocatalytic activity.

Science.gov (United States)

Wei, Chengzhen; Zang, Wenzhe; Yin, Jingzhou; Lu, Qingyi; Chen, Qun; Liu, Rongmei; Gao, Feng

2013-02-25

In this study, we report the synthesis of monodispersive solid and hollow CdS spheres with structure-dependent photocatalytic abilities for dye photodegradation. The monodispersive CdS nanospheres were constructed with the assistance of the soulcarboxymthyi chitosan biopolymer under hydrothermal conditions. The solid CdS spheres were corroded by ammonia to form hollow CdS nanospheres through a dissolution-reprecipitation mechanism. Their visible-light photocatalytic activities were investigated, and the results show that both the solid and the hollow CdS spheres have visible-light photocatalytic abilities for the photodegradation of dyes. The photocatalytic properties of the CdS spheres were demonstrated to be structure dependent. Although the nanoparticles comprising the hollow spheres have larger sizes than those comprising the solid spheres, the hollow CdS spheres have better photocatalytic performances than the solid CdS spheres, which can be attributed to the special hollow structure. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High resolution main-ion charge exchange spectroscopy in the DIII-D H-mode pedestal.

Science.gov (United States)

Grierson, B A; Burrell, K H; Chrystal, C; Groebner, R J; Haskey, S R; Kaplan, D H

2016-11-01

A new high spatial resolution main-ion (deuterium) charge-exchange spectroscopy system covering the tokamak boundary region has been installed on the DIII-D tokamak. Sixteen new edge main-ion charge-exchange recombination sightlines have been combined with nineteen impurity sightlines in a tangentially viewing geometry on the DIII-D midplane with an interleaving design that achieves 8 mm inter-channel radial resolution for detailed profiles of main-ion temperature, velocity, charge-exchange emission, and neutral beam emission. At the plasma boundary, we find a strong enhancement of the main-ion toroidal velocity that exceeds the impurity velocity by a factor of two. The unique combination of experimentally measured main-ion and impurity profiles provides a powerful quasi-neutrality constraint for reconstruction of tokamak H-mode pedestals.

Preparation of SnO 2 /Carbon Composite Hollow Spheres and Their Lithium Storage Properties

KAUST Repository

Lou, Xiong Wen; Deng, Da; Lee, Jim Yang; Archer, Lynden A.

2008-01-01

In this work, we present a novel concept of structural design for preparing functional composite hollow spheres and derived double-shelled hollow spheres. The approach involves two main steps: preparation of porous hollow spheres of one component and deposition of the other component onto both the interior and exterior surfaces of the shell as well as in the pores. We demonstrate the concept by preparing SnO2/carbon composite hollow spheres and evaluate them as potential anode materials for lithium-ion batteries. These SnO2/carbon hollow spheres are able to deliver a reversible Li storage capacity of 473 mA h g-1 after 50 cycles. Unusual double-shelled carbon hollow spheres are obtained by selective removal of the sandwiched porous SnO2 shells. © 2008 American Chemical Society.

Preparation of SnO 2 /Carbon Composite Hollow Spheres and Their Lithium Storage Properties

KAUST Repository

Lou, Xiong Wen

2008-10-28

In this work, we present a novel concept of structural design for preparing functional composite hollow spheres and derived double-shelled hollow spheres. The approach involves two main steps: preparation of porous hollow spheres of one component and deposition of the other component onto both the interior and exterior surfaces of the shell as well as in the pores. We demonstrate the concept by preparing SnO2/carbon composite hollow spheres and evaluate them as potential anode materials for lithium-ion batteries. These SnO2/carbon hollow spheres are able to deliver a reversible Li storage capacity of 473 mA h g-1 after 50 cycles. Unusual double-shelled carbon hollow spheres are obtained by selective removal of the sandwiched porous SnO2 shells. © 2008 American Chemical Society.

Size and thickness effect on magnetic structures of maghemite hollow magnetic nanoparticles

International Nuclear Information System (INIS)

Sayed, Fatima; Labaye, Yvan; Sayed Hassan, Rodaina; El Haj Hassan, Fouad; Yaacoub, Nader; Greneche, Jean-Marc

2016-01-01

The effect of surface anisotropy on the magnetic ground state of hollow maghemite nanoparticles is investigated using atomistic Monte Carlo simulation. The computer modeling is carried on hollow nanostructures as a function of size and shell thickness. It is found that the large contribution of the surface anisotropy imposes a “throttled” spin structure where the moments located at the outer surface tend to orient normal to the surface while those located at the inner surface appear to be more aligned. For increasing values of surface anisotropy in the frame of a radial model, the magnetic moments become radially oriented either inward or outward giving rise to a “hedgehog” configuration with nearly zero net magnetization. We also show the effect of the size of hollow nanoparticle on the spin behavior where the spin non-collinearity increases (for fixed value of surface anisotropy) as the diameter of the hollow nanoparticle increases due to the significant increase in surface-to-volume ratio, the thickness being constant. Moreover, the thickness of the hollow nanoparticle shell influences the spin configuration and thus the relation between surface anisotropy and the size or the thickness of the hollow nanoparticle is established.

Size and thickness effect on magnetic structures of maghemite hollow magnetic nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Sayed, Fatima; Labaye, Yvan, E-mail: yvan.labaye@univ-lemans.fr [Université du Maine, Institut des Molécules et Matériaux du Mans CNRS UMR-6283 (France); Sayed Hassan, Rodaina; El Haj Hassan, Fouad [Université Libanaise, Faculté des Sciences Section I, MPLAB (Lebanon); Yaacoub, Nader, E-mail: nader.yaacoub@univ-lemans.fr; Greneche, Jean-Marc [Université du Maine, Institut des Molécules et Matériaux du Mans CNRS UMR-6283 (France)

2016-09-15

The effect of surface anisotropy on the magnetic ground state of hollow maghemite nanoparticles is investigated using atomistic Monte Carlo simulation. The computer modeling is carried on hollow nanostructures as a function of size and shell thickness. It is found that the large contribution of the surface anisotropy imposes a “throttled” spin structure where the moments located at the outer surface tend to orient normal to the surface while those located at the inner surface appear to be more aligned. For increasing values of surface anisotropy in the frame of a radial model, the magnetic moments become radially oriented either inward or outward giving rise to a “hedgehog” configuration with nearly zero net magnetization. We also show the effect of the size of hollow nanoparticle on the spin behavior where the spin non-collinearity increases (for fixed value of surface anisotropy) as the diameter of the hollow nanoparticle increases due to the significant increase in surface-to-volume ratio, the thickness being constant. Moreover, the thickness of the hollow nanoparticle shell influences the spin configuration and thus the relation between surface anisotropy and the size or the thickness of the hollow nanoparticle is established.

Preparation and photocatalytic activity of hollow ZnSe microspheres via Ostwald ripening

International Nuclear Information System (INIS)

Zhang Lihui; Yang Heqing; Xie Xiaoli; Zhang Fenghua; Li Li

2009-01-01

Hollow ZnSe microspheres were prepared via a facile hydrothermal reaction of Zn(AC) 2 .2H 2 O with Na 2 SeO 3 and ethylene glycol in NaOH solution at 180 deg. C for 12 h. The products were characterized by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Raman spectrum. The hollow microspheres with the diameters of about 2 μm are constructed from ZnSe nanoparticles with the cubic zinc blende structure, the size of hollow interiors and constituent ZnSe nanodots can be tuned by changing the reaction time. The hollow microspheres are formed via an Ostwald ripening process. Photoluminescence and photocatalytic activity of the hollow ZnSe microspheres were studied at room temperature. The results indicate that the hollow microspheres constructed from ZnSe nanoparticles display a strong near-band edge emission at 479 nm and a very weak deep defect (DD) related emission at 556 nm and a high photocatalytic activity in the photodegradation of methyl orange. The photodegradation of methyl orange catalyzed by the ZnSe microspheres is a pseudo first-order reaction

Periodic organosilica hollow nanospheres as anode materials for lithium ion rechargeable batteries.

Science.gov (United States)

Sasidharan, Manickam; Nakashima, Kenichi; Gunawardhana, Nanda; Yokoi, Toshiyuki; Ito, Masanori; Inoue, Masamichi; Yusa, Shin-ichi; Yoshio, Masaki; Tatsumi, Takashi

2011-11-01

Polymeric micelles with core-shell-corona architecture have been found to be the efficient colloidal templates for synthesis of periodic organosilica hollow nanospheres over a broad pH range from acidic to alkaline media. In alkaline medium, poly (styrene-b-[3-(methacryloylamino)propyl] trimethylammonium chloride-b-ethylene oxide) (PS-PMAPTAC-PEO) micelles yield benzene-silica hollow nanospheres with molecular scale periodicity of benzene groups in the shell domain of hollow particles. Whereas, an acidic medium (pH 4) produces diverse hollow particles with benzene, ethylene, and a mixture of ethylene and dipropyldisulfide bridging functionalities using poly(styrene-b-2-vinyl pyridine-b-ethylene oxide) (PS-PVP-PEO) micelles. These hollow particles were thoroughly characterized by powder X-ray diffraction (XRD), dynamic light scattering (DLS), thermogravimetric analysis (TG/DTA), Fourier transformation infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), magic angle spinning-nuclear magnetic resonance ((29)Si MAS NMR and (13)CP-MAS NMR), Raman spectroscopy, and nitrogen adsorption/desorption analyses. The benzene-silica hollow nanospheres with molecular scale periodicity in the shell domain exhibit higher cycling performance of up to 300 cycles in lithium ion rechargeable batteries compared with micron-sized dense benzene-silica particles.

A simple approach to hollow maxillary complete denture fabrication: An innovative technique

Directory of Open Access Journals (Sweden)

Kathleen Manuela D'souza

2017-01-01

Full Text Available A severely atrophic maxillary arch exhibits reduced denture bearing area and increased inter-ridge distance, thus, affecting retention of the complete denture. Such clinical situations necessitate the fabrication of a hollow complete denture to reduce the weight of the prosthesis and increase retention. This article describes a simple technique to fabricate a hollow maxillary complete denture using salt and thermoplastic poly (methyl methacrylate sheet. The vacuum-formed thermoplastic matrix regulates the quantity of salt and determines its placement in the unpolymerized denture base material during the denture packing stage. The matrix lining the hollow cavity also aids to reinforce the hollow denture base.

Mesoscale cavities in hollow-core waveguides for quantum optics with atomic ensembles

Directory of Open Access Journals (Sweden)

Haapamaki C.M.

2016-08-01

Full Text Available Single-mode hollow-core waveguides loaded with atomic ensembles offer an excellent platform for light–matter interactions and nonlinear optics at low photon levels. We review and discuss possible approaches for incorporating mirrors, cavities, and Bragg gratings into these waveguides without obstructing their hollow cores. With these additional features controlling the light propagation in the hollow-core waveguides, one could potentially achieve optical nonlinearities controllable by single photons in systems with small footprints that can be integrated on a chip. We propose possible applications such as single-photon transistors and superradiant lasers that could be implemented in these enhanced hollow-core waveguides.

Synthesis and upconversion luminescence properties of YF{sub 3}:Yb{sup 3+}/Er{sup 3+} hollow nanofibers derived from Y{sub 2}O{sub 3}:Yb{sup 3+}/Er{sup 3+} hollow nanofibers

Energy Technology Data Exchange (ETDEWEB)

Li Dan; Dong Xiangting, E-mail: dongxiangting888@163.com; Yu Wensheng; Wang Jinxian; Liu Guixia [Changchun University of Science and Technology, Key Laboratory of Applied Chemistry and Nanotechnology at Universities of Jilin Province (China)

2013-06-15

YF{sub 3}:Yb{sup 3+}/Er{sup 3+} hollow nanofibers were successfully fabricated via fluorination of the relevant Y{sub 2}O{sub 3}:Yb{sup 3+}/Er{sup 3+} hollow nanofibers which were obtained by calcining the electrospun PVP/[Y(NO{sub 3}){sub 3} + Yb(NO{sub 3}){sub 3} + Er(NO{sub 3}){sub 3}] composite nanofibers. The morphology and properties of the products were investigated in detail by X-ray diffraction, scanning electron microscope, transmission electron microscope, and fluorescence spectrometer. YF{sub 3}:Yb{sup 3+}/Er{sup 3+} hollow nanofibers were pure orthorhombic phase with space group Pnma and were hollow-centered structure with mean diameter of 174 {+-} 22 nm, and YF{sub 3}:Yb{sup 3+}/Er{sup 3+} hollow nanofibers are composed of nanoparticles with size in the range of 30-60 nm. Upconversion emission spectrum analysis manifested that YF{sub 3}:Yb{sup 3+}/Er{sup 3+} hollow nanofibers emitted strong green and weak red upconversion emissions centering at 523, 545, and 654 nm, respectively. The green and red emissions were, respectively, originated from {sup 2}H{sub 11/2}/{sup 4}S{sub 3/2} {yields} {sup 4}I{sub 15/2} and {sup 4}F{sub 9/2} {yields} {sup 4}I{sub l5/2} energy levels transitions of the Er{sup 3+} ions. Moreover, the emitting colors of YF{sub 3}:Yb{sup 3+}/Er{sup 3+} hollow nanofibers were located in the green region in CIE chromaticity coordinates diagram. This preparation technique could be applied to prepare other rare earth fluoride upconversion luminescence hollow nanofibers.Graphical AbstractYF{sub 3}:Yb{sup 3+}/Er{sup 3+} hollow nanofibers with orthorhombic structure were synthesized by fluorination of the electrospun Y{sub 2}O{sub 3}:Yb{sup 3+}/Er{sup 3+} hollow nanofibers via a double-crucible method using NH{sub 4}HF{sub 2} as fluorinating agent. The mean diameter of YF{sub 3}:Yb{sup 3+}/Er{sup 3+} hollow nanofibers was 174 {+-} 22 nm. The fluorination method we proposed here has been proved to be an important method, as it can not only

An organosilane-directed growth-induced etching strategy for preparing hollow/yolk–shell mesoporous organosilica nanospheres with perpendicular mesochannels and amphiphilic frameworks

KAUST Repository

Zou, Houbing

2014-06-27

We have developed an organosilane-directed growth-induced etching strategy to prepare hollow periodic mesoporous organosilica (PMO) nanospheres with perpendicular mesoporous channels and a clear hollow interior as well as an amphiphilic framework. This facile strategy is simple, efficient, and highly controllable. Silica nanospheres were utilized as hard templates to obtain hollow PMO nanospheres through a one-step route, with the structure parameter highly controlled by adjusting the synthesis conditions. Different organosilanes were used to obtain bridged hollow PMO nanospheres of different organic groups and showed different directed capacities. The integrity of the bridged organic group was confirmed by Fourier-transform infrared (FT-IR) spectroscopy and solid-state 13C nuclear magnetic resonance (NMR) spectroscopy. Transmission electron microscopy (TEM) observations showed that the growth of the PMO shell and the dissolution of the silica nanosphere core occurred simultaneously for each nanosphere, while 29Si NMR spectra revealed that the dissolved silica species from the silica nanospheres transformed into PMO shells by co-condensation with hydrolyzed organosilane oligomers. As a result, the obtained hollow nanospheres were amphiphilic, which can even be used as a particle emulsifier for O-W or W-O emulsion in various systems. These materials can also be served as an efficient sorbent for removal of hydrophobic contaminants in water. Using the proposed formation mechanism, this strategy can be extended to transform silica-coated composite materials into yolk-shell structures with a functional interior core and a perpendicular mesoporous amphiphilic shell. As a nanoreactor, the -Ph- bridged amphiphilic shell showed a faster diffusion rate for organic reactants in water than the hydrophilic silica shell, and thus better catalytic activity for reduction of 4-nitrophenol. This journal is © the Partner Organisations 2014.

Mesoporous hollow spheres from soap bubbling.

Science.gov (United States)

Yu, Xianglin; Liang, Fuxin; Liu, Jiguang; Lu, Yunfeng; Yang, Zhenzhong

2012-02-01

The smaller and more stable bubbles can be generated from the large parent bubbles by rupture. In the presence of a bubble blowing agent, hollow spheres can be prepared by bubbling a silica sol. Herein, the trapped gas inside the bubble acts as a template. When the porogen, i.e., other surfactant, is introduced, a mesostructured shell forms by the co-assembly with the silica sol during sol-gel process. Morphological evolution emphasizes the prerequisite of an intermediate interior gas flow rate and high exterior gas flow rate for hollow spheres. The method is valid for many compositions from inorganic, polymer to their composites. Copyright © 2011 Elsevier Inc. All rights reserved.

Controllable Synthesis of Functional Hollow Carbon Nanostructures with Dopamine As Precursor for Supercapacitors.

Science.gov (United States)

Liu, Chao; Wang, Jing; Li, Jiansheng; Luo, Rui; Shen, Jinyou; Sun, Xiuyun; Han, Weiqing; Wang, Lianjun

2015-08-26

N-doped hollow carbon spheres (N-HCSs) are promising candidates as electrode material for supercapacitor application. In this work, we report a facile one-step synthesis of discrete and highly dispersible N-HCSs with dopamine (DA) as a carbon precursor and TEOS as a structure-assistant agent in a mixture containing water, ethanol, and ammonia. The architectures of resultant N-HCSs, including yolk-shell hollow carbon spheres (YS-HCSs), single-shell hollow carbon spheres (SS-HCSs), and double-shells hollow carbon spheres (DS-HCSs), can be efficiently controlled through the adjustment of the amount of ammonia. To explain the relation and formation mechanism of these hollow carbon structures, the samples during the different synthetic steps, including polymer/silica spheres, carbon/silica spheres and silica spheres by combustion in air, were characterized by TEM. Electrochemical measurements performed on YS-HCSs, SS-HCSs, and DS-HCSs showed high capacitance with 215, 280, and 381 F g(-1), respectively. Moreover, all the nitrogen-doped hollow carbon nanospheres showed a good cycling stability 97.0% capacitive retention after 3000 cycles. Notably, the highest capacitance of DS-HCSs up to 381 F g(-1) is higher than the capacitance reported so far for many carbon-based materials, which may be attributed to the high surface area, hollow structure, nitrogen functionalization, and double-shell architecture. These kinds of N-doped hollow-structured carbon spheres may show promising prospects as advanced energy storage materials and catalyst supports.

Innovative hydrogen storage in hollow glass-microspheres

Energy Technology Data Exchange (ETDEWEB)

Keding, M.; Schmid, G.; Tajmar, M. [Austrian Research Centers, Vienna (Austria)

2009-07-01

Hydrogen storage technologies are becoming increasingly important for a number of future applications. The Austrian Research Centers (ARC) are developing a unique hydrogen storage system that combines the advantages of both hollow glass microsphere and chemical compound hydrogen storage, but eliminates their respective drawbacks. Water is utilized as a functional liquid to carry the hollow glass microspheres that are loaded with up to 700 bar of hydrogen gas. Sodium borohydride (NaBH{sub 4}) is then injected together with the glass microspheres into a reaction chamber where the water reacts catalytically with the NaBH{sub 4} producing hydrogen and heat. The heat is then utilized to release the hydrogen from the hollow glass microspheres providing a double hydrogen generation process without any external energy or heat during storage or gas release. The paper described this hydrogen storage system with particular reference to microspheres, the coating process, the experimental facility and NaBH{sub 4} test results. It was concluded that hydrogen storage and production on demand is possible with microspheres and sodium borohydride solution. 9 refs., 16 figs.

Fabrication of Metallic Hollow Nanoparticles

Science.gov (United States)

Kim, Jae-Woo (Inventor); Choi, Sr., Sang H. (Inventor); Lillehei, Peter T. (Inventor); Chu, Sang-Hyon (Inventor); Park, Yeonjoon (Inventor); King, Glen C. (Inventor); Elliott, James R. (Inventor)

2016-01-01

Metal and semiconductor nanoshells, particularly transition metal nanoshells, are fabricated using dendrimer molecules. Metallic colloids, metallic ions or semiconductors are attached to amine groups on the dendrimer surface in stabilized solution for the surface seeding method and the surface seedless method, respectively. Subsequently, the process is repeated with additional metallic ions or semiconductor, a stabilizer, and NaBH.sub.4 to increase the wall thickness of the metallic or semiconductor lining on the dendrimer surface. Metallic or semiconductor ions are automatically reduced on the metallic or semiconductor nanoparticles causing the formation of hollow metallic or semiconductor nanoparticles. The void size of the formed hollow nanoparticles depends on the dendrimer generation. The thickness of the metallic or semiconductor thin film around the dendrimer depends on the repetition times and the size of initial metallic or semiconductor seeds.

A General Synthesis Strategy for Hierarchical Porous Metal Oxide Hollow Spheres

Directory of Open Access Journals (Sweden)

Huadong Fu

2015-01-01

Full Text Available The hierarchical porous TiO2 hollow spheres were successfully prepared by using the hydrothermally synthesized colloidal carbon spheres as templates and tetrabutyl titanate as inorganic precursors. The diameter and wall thickness of hollow TiO2 spheres were determined by the hard templates and concentration of tetrabutyl titanate. The particle size, dispersity, homogeneity, and surface state of the carbon spheres can be easily controlled by adjusting the hydrothermal conditions and adding certain amount of the surfactants. The prepared hollow spheres possessed the perfect spherical shape, monodispersity, and hierarchically pore structures, and the further experiment verified that the present approach can be used to prepare other metal oxide hollow spheres, which could be used as catalysis, fuel cells, lithium-air battery, gas sensor, and so on.

Sharp tipped plastic hollow microneedle array by microinjection moulding

Science.gov (United States)

Yung, K. L.; Xu, Yan; Kang, Chunlei; Liu, H.; Tam, K. F.; Ko, S. M.; Kwan, F. Y.; Lee, Thomas M. H.

2012-01-01

A method of producing sharp tipped plastic hollow microneedle arrays using microinjection moulding is presented in this paper. Unlike traditional approaches, three mould inserts were used to create the sharp tips of the microneedles. Mould inserts with low surface roughness were fabricated using a picosecond laser machine. Sharp tipped plastic hollow microneedles 500 µm in height were fabricated using a microinjection moulding machine developed by the authors’ group. In addition, the strength of the microneedle was studied by simulation and penetration experiments. Results show that the microneedles can penetrate into skin, delivering liquid successfully without any breakage or severe deformation. Techniques presented in this paper can be used to fabricate sharp tipped plastic hollow microneedle arrays massively with low cost.

Sharp tipped plastic hollow microneedle array by microinjection moulding

International Nuclear Information System (INIS)

Yung, K L; Xu, Yan; Kang, Chunlei; Liu, H; Tam, K F; Ko, S M; Kwan, F Y; Lee, Thomas M H

2012-01-01

A method of producing sharp tipped plastic hollow microneedle arrays using microinjection moulding is presented in this paper. Unlike traditional approaches, three mould inserts were used to create the sharp tips of the microneedles. Mould inserts with low surface roughness were fabricated using a picosecond laser machine. Sharp tipped plastic hollow microneedles 500 µm in height were fabricated using a microinjection moulding machine developed by the authors’ group. In addition, the strength of the microneedle was studied by simulation and penetration experiments. Results show that the microneedles can penetrate into skin, delivering liquid successfully without any breakage or severe deformation. Techniques presented in this paper can be used to fabricate sharp tipped plastic hollow microneedle arrays massively with low cost. (paper)

Forged hollows (alloy 617) for PNP-hot gas collectors

International Nuclear Information System (INIS)

Hofmann, F.

1984-01-01

When the partners in the PNP-Project decided to manufacture components, such as gas collectors, from material of type alloy 617, the problem arose that required semi-fabricated products, especially forged hollows weighing several tons each, were not available. As VDM (Vereinigte Deutsche Metallwerke AG) had already experience in production of other semi-fabricated products of this alloy, attempts were made based on this knowledge, to develop manufacturing methods for forged hollows. The aim was to produce hollows as long as possible, and to keep the welding cost minimum. Welded seams are always critical during fabrication, as well as during later inspection under actual operating conditions. The three stage plan used to perform the above task illustrates the development aims is described

Monodisperse Hollow Tricolor Pigment Particles for Electronic Paper

Directory of Open Access Journals (Sweden)

Meng Xianwei

2009-01-01

Full Text Available Abstract A general approach has been designed to blue, green, and red pigments by metal ions doping hollow TiO 2. The reaction involves initial formation of PS at TiO2 core–shell nanoparticles via a mixed-solvent method, and then mixing with metal ions solution containing PEG, followed calcining in the atmosphere. The as-prepared hollow pigments exhibit uniform size, bright color, and tunable density, which are fit for electronic paper display.

Three-dimensional assembly structure of anatase TiO2 hollow microspheres with enhanced photocatalytic performance

Science.gov (United States)

Tang, Yihao; Zhan, Shuai; Wang, Li; Zhang, Bin; Ding, Minghui

The pure anatase TiO2 hollow microspheres are synthesized by a one-step template-free hydrothermal route. By defining temperature and time limits, we produce TiO2 hollow microspheres with a fluoride-mediated self-transformation. The surface morphology of TiO2 hollow microspheres was studied by SEM. The hollow microspheres have diameters of about 800 nm and are remarkably uniform. The UV-light photocatalytic activity and the stability/multifunction of TiO2 hollow microspheres structure were evaluated by photocatalytic degradation of methylene blue and photocatalytic hydrogen evolution. The excellent photocatalytic activity is attributed to large specific surface area, more active sites, unique hollow structures, and improved light scattering.

Hollow-core fibers for high power pulse delivery

DEFF Research Database (Denmark)

Michieletto, Mattia; Lyngsø, Jens K.; Jakobsen, Christian

2016-01-01

We investigate hollow-core fibers for fiber delivery of high power ultrashort laser pulses. We use numerical techniques to design an anti-resonant hollow-core fiber having one layer of non-touching tubes to determine which structures offer the best optical properties for the delivery of high power...... picosecond pulses. A novel fiber with 7 tubes and a core of 30 mu m was fabricated and it is here described and characterized, showing remarkable low loss, low bend loss, and good mode quality. Its optical properties are compared to both a 10 mu m and a 18 mu m core diameter photonic band gap hollow......-core fiber. The three fibers are characterized experimentally for the delivery of 22 picosecond pulses at 1032nm. We demonstrate flexible, diffraction limited beam delivery with output average powers in excess of 70W. (C) 2016 Optical Society of America...

Enhanced lithium storage performances of hierarchical hollow MoS₂ nanoparticles assembled from nanosheets.

Science.gov (United States)

Wang, Meng; Li, Guangda; Xu, Huayun; Qian, Yitai; Yang, Jian

2013-02-01

MoS(2), because of its layered structure and high theoretical capacity, has been regarded as a potential candidate for electrode materials in lithium secondary batteries. But it suffers from the poor cycling stability and low rate capability. Here, hierarchical hollow nanoparticles of MoS(2) nanosheets with an increased interlayer distance are synthesized by a simple solvothermal reaction at a low temperature. The formation of hierarchical hollow nanoparticles is based on the intermediate, K(2)NaMoO(3)F(3), as a self-sacrificed template. These hollow nanoparticles exhibit a reversible capacity of 902 mA h g(-1) at 100 mA g(-1) after 80 cycles, much higher than the solid counterpart. At a current density of 1000 mA g(-1), the reversible capacity of the hierarchical hollow nanoparticles could be still maintained at 780 mAh g(-1). The enhanced lithium storage performances of the hierarchical hollow nanoparticles in reversible capacities, cycling stability and rate performances can be attributed to their hierarchical surface, hollow structure feature and increased layer distance of S-Mo-S. Hierarchical hollow nanoparticles as an ensemble of these features, could be applied to other electrode materials for the superior electrochemical performance.

Novel one-step route for synthesizing CdS/polystyrene nanocomposite hollow spheres.

Science.gov (United States)

Wu, Dazhen; Ge, Xuewu; Zhang, Zhicheng; Wang, Mozhen; Zhang, Songlin

2004-06-22

CdS/polystyrene nanocomposite hollow spheres with diameters between 240 and 500 nm were synthesized under ambient conditions by a novel microemulsion method in which the polymerization of styrene and the formation of CdS nanoparticles were initiated by gamma-irradiation. The product was characterized by transmission electron microscopy (TEM), field-emission scanning electron microscopy (FESEM), X-ray powder diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA), which show the walls of the hollow spheres are porous and composed of polystyrene containing homogeneously dispersed CdS nanoparticles. The quantum-confined effect of the CdS/polystyrene nanocomposite hollow spheres is confirmed by the ultraviolet-visible (UV-vis) and photoluminescent (PL) spectra. We propose that the walls of these nanocomposite hollow spheres originate from the simultaneous synthesis of polystyrene and CdS nanoparticles at the interface of microemulsion droplets. This novel method is expected to produce various inorganic/polymer nanocomposite hollow spheres with potential applications in the fields of materials science and biotechnology.

Hollow fiber liquid-phase microextraction of cadmium(II) using an ionic liquid as the extractant

International Nuclear Information System (INIS)

Chen, Hui; Wang, Yun; Hu, Yutao; Ni, Liang; Liu, Yingying; Kang, Wenbing; Liu, Yan; Han, Juan

2014-01-01

A method is presented for hollow fiber liquid-phase microextraction (HF-LPME) of cadmium(II), which is chelated with 1-(2-pyridylazo)-2-naphthol (PAN) to obtain a hydrophobic complex which then is extracted into a polypropylene hollow fiber containing an ionic liquid in its pores which acts as the membrane phase. EDTA is then injected into the lumen of the membrane as an acceptor phase to trap the analyte. The extraction time (20 min), agitation (400 rpm at 25 °C), pH value (10.0), and the concentrations of PAN (2.5 ng mL −1 ) and EDTA (250 ng mL −1 ) were optimized. With a sample volume of 50 mL and a stripping volume of 15 μL, the enrichment factor is 162. Cadmium(II) was then quantified by graphite furnace AAS. The limit of detection is 0.12 pg mL −1 , the relative standard deviation is 5.2 %, and the linear working range extends from 4 to 45 pg mL −1 . The method was successfully applied to the determination of Cd(II) in environmental and food samples. (author)

Hierarchical CuO hollow microspheres: Controlled synthesis for enhanced lithium storage performance

International Nuclear Information System (INIS)

Guan Xiangfeng; Li Liping; Li Guangshe; Fu Zhengwei; Zheng Jing; Yan Tingjiang

2011-01-01

Graphical abstract: Hierarchical CuO microspheres with hollow interiors were formed through self-wrapping of a single layer of radically oriented CuO nanorods, and these microspheres showed excellent cycle performance and enhanced lithium storage capacity. Display Omitted Research highlights: → Hierarchical CuO hollow microspheres were prepared by a hydrothermal method. → The CuO hollow microspheres were assembled from radically oriented nanorods. → The growth mechanism was proposed to proceed via self-assembly and Ostwald's ripening. → The microspheres showed good cycle performance and enhanced lithium storage capacity. → Hierarchical microstructures with hollow interiors promote electrochemical property. - Abstract: In this work, hierarchical CuO hollow microspheres were hydrothermally prepared without use of any surfactants or templates. By controlling the formation reaction conditions and monitoring the relevant reaction processes using time-dependent experiments, it is demonstrated that hierarchical CuO microspheres with hollow interiors were formed through self-wrapping of a single layer of radically oriented CuO nanorods, and that hierarchical spheres could be tuned to show different morphologies and microstructures. As a consequence, the formation mechanism was proposed to proceed via a combined process of self-assembly and Ostwald's ripening. Further, these hollow microspheres were initiated as the anode material in lithium ion batteries, which showed excellent cycle performance and enhanced lithium storage capacity, most likely because of the synergetic effect of small diffusion lengths in building blocks of nanorods and proper void space that buffers the volume expansion. The strategy reported in this work is reproducible, which may help to significantly improve the electrochemical performance of transition metal oxide-based anode materials via designing the hollow structures necessary for developing lithium ion batteries and the relevant

Administration of a Sol-Gel Formulation of Phenylephrine Using Low-Temperature Hollow Microneedle for Treatment of Intermittent Fecal Incontinence.

Science.gov (United States)

Lee, Hyunji; Park, Jung-Hwan; Park, Jung Ho

2017-12-01

A low temperature hollow microneedle system was devised to deliver sol-gel transition formulation near the surface of the skin for extended release and local delivery of drug by a non-invasive method. This new system can improve treatment of intermittent fecal incontinence. The low-temperature system was integrated with a hollow microneedle to maintain the low temperature of the sol formulation. Various sol-gel formulations using Pluronic F-127 (PF-127) and Hydroxy-propyl-methyl-cellulose (HPMC) were prepared, and their gelation temperature, flow property, and diffusion retardation were observed. Resting anal sphincter pressure in response to a phenylephrine (PE) sol-gel formulation was measured using an air-charged catheter. The biocompatibility of the sol-gel PE formulation was evaluated by observing the immunological response. When the PF-127 25%, HPMC 1% and PE formulation (PF25-HPMC1-PE) was injected through the peri-anal skin of the rat in vivo, the highest pressure on the anal sphincter muscle occurred at 6-8 h and anal pressure increased and lasted twice as long as with the phosphate-buffered saline (PBS)-PE formulation. There was no significant difference in the number of mast cells after administration into the rat in vivo between the PF25-HPMC1-PE formulation and the PBS-PE formulation. The combination of a low-pain hollow microneedle system and an injectable sol-gel formulation improved the efficacy of treatment of intermittent fecal incontinence. A low-temperature hollow microneedle system using a sol-gel formulation has many applications in medical treatments that require depot effect, local targeting, and pain control.

Microfabricated hollow microneedle array using ICP etcher

Science.gov (United States)

Ji, Jing; Tay, Francis E. H.; Miao, Jianmin

2006-04-01

This paper presents a developed process for fabrication of hollow silicon microneedle arrays. The inner hollow hole and the fluidic reservoir are fabricated in deep reactive ion etching. The profile of outside needles is achieved by the developed fabrication process, which combined isotropic etching and anisotropic etching with inductively coupled plasma (ICP) etcher. Using the combination of SF6/O2 isotropic etching chemistry and Bosch process, the high aspect ratio 3D and high density microneedle arrays are fabricated. The generated needle external geometry can be controlled by etching variables in the isotropic and anisotropic cases.

Microfabricated hollow microneedle array using ICP etcher

International Nuclear Information System (INIS)

Ji Jing; Tay, Francis E H; Miao Jianmin

2006-01-01

This paper presents a developed process for fabrication of hollow silicon microneedle arrays. The inner hollow hole and the fluidic reservoir are fabricated in deep reactive ion etching. The profile of outside needles is achieved by the developed fabrication process, which combined isotropic etching and anisotropic etching with inductively coupled plasma (ICP) etcher. Using the combination of SF 6 /O 2 isotropic etching chemistry and Bosch process, the high aspect ratio 3D and high density microneedle arrays are fabricated. The generated needle external geometry can be controlled by etching variables in the isotropic and anisotropic cases

Microfabricated hollow microneedle array using ICP etcher

Energy Technology Data Exchange (ETDEWEB)

Ji Jing [Mechanical Engineering National University of Singapore, 119260, Singapore (Singapore); Tay, Francis E H [Mechanical Engineering National University of Singapore, 119260, Singapore (Singapore); Miao Jianmin [MicroMachines Center, School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 (Singapore)

2006-04-01

This paper presents a developed process for fabrication of hollow silicon microneedle arrays. The inner hollow hole and the fluidic reservoir are fabricated in deep reactive ion etching. The profile of outside needles is achieved by the developed fabrication process, which combined isotropic etching and anisotropic etching with inductively coupled plasma (ICP) etcher. Using the combination of SF{sub 6}/O{sub 2} isotropic etching chemistry and Bosch process, the high aspect ratio 3D and high density microneedle arrays are fabricated. The generated needle external geometry can be controlled by etching variables in the isotropic and anisotropic cases.

Predicting hollow viscus injury in blunt abdominal trauma with computed tomography.

Science.gov (United States)

Bhagvan, Savitha; Turai, Matthew; Holden, Andrew; Ng, Alexander; Civil, Ian

2013-01-01

Evaluation of blunt abdominal trauma is controversial. Computed tomography (CT) of the abdomen is commonly used but has limitations, especially in excluding hollow viscus injury in the presence of solid organ injury. To determine whether CT reports alone could be used to direct operative treatment in abdominal trauma, this study was undertaken. The trauma database at Auckland City Hospital was accessed for patients who had abdominal CT and subsequent laparotomy during a five-year period. The CT scans were reevaluated by a consultant radiologist who was blinded to operative findings. The CT findings were correlated with the operative findings. Between January 2002 and December 2007, 1,250 patients were evaluated for blunt abdominal injury with CT. A subset of 78 patients underwent laparotomy, and this formed the study group. The sensitivity and specificity of CT scan in predicting hollow viscus injury was 55.33 and 92.06 % respectively. The positive and negative predictive values were 61.53 and 89.23 % respectively. Presence of free fluid in CT scan was sensitive in diagnosing hollow viscus injury (90 %). Specific findings for hollow viscus injuries on CT scan were free intraperitoneal air (93 %), retroperitoneal air (100 %), oral contrast extravasation (100 %), bowel wall defect (98 %), patchy bowel enhancement (97 %), and mesenteric abnormality (94 %). CT alone cannot be used as a screening tool for hollow viscus injury. The decision to operate in hollow viscus injury has to be based on mechanism of injury and clinical findings together with radiological evidence.

Guiding Properties of Silica/Air Hollow-Core Bragg Fibers

DEFF Research Database (Denmark)

Foroni, Matteo; Passaro, Davide; Poli, Federica

2008-01-01

The guiding properties of realistic silica/air hollow-core Bragg fibers have been investigated by calculating the dispersion curves, the confinement loss spectrum and the field distribution of the guided modes through a full-vector modal solver based on the finite element method. In particular, t...... the different possible applications, the feasibility of a DNA bio-sensor based on a hollow-core Bragg fiber has been demonstrated....

The effects of the pedestal/floor interface on the dynamic characteristics of the storage ring girder support assemblies

International Nuclear Information System (INIS)

Jendrzejczyk, J.A.; Chen, S.S.; Zhu, S.; Mangra, D.; Smith, R.K.

1993-05-01

To avoid unacceptable vibration of the storage ring quadrupoles, and to ensure that the established vibration criteria are satisfied, the philosophy from inception of the APS has been (1) to locate and design the machine to minimize motion of the storage ring basemat and, (2) following construction, to monitor machine operation and user experiments to ensure that vibration sources are not introduced. This report addresses the design of the storage ring girder support assemblies, and, specifically, the effect of the pedestal/floor interface on the dynamic characteristics (i.e., resonant frequencies, damping, and mode shape)

Synthesis of ZnS hollow nanoneedles via the nanoscale Kirkendall effect

International Nuclear Information System (INIS)

Sun Hongyu; Chen Yan; Wang Xiaoliang; Xie Yanwu; Li Wei; Zhang Xiangyi

2011-01-01

The facile synthesis of one-dimensional II–VI semiconductor hollow nanostructures with sharp tips is of particular interest for their applications in novel nanodevices. In this study, by employing ZnO nanoneedles with lower symmetry structures as self-sacrificed templates, ZnS hollow nanoneedles with homogeneous thickness have been synthesized by a low temperature hydrothermal route through in situ chemical conversion manner and the nanoscale Kirkendall effect. The hollow needlelike structures obtained in the present study can be used as starting materials to create fantastic nanoarchitectures and may have important applications in optoelectronic nanodevices.

Hollow waveguide cavity ringdown spectroscopy

Science.gov (United States)

Dreyer, Chris (Inventor); Mungas, Greg S. (Inventor)

2012-01-01

Laser light is confined in a hollow waveguide between two highly reflective mirrors. This waveguide cavity is used to conduct Cavity Ringdown Absorption Spectroscopy of loss mechanisms in the cavity including absorption or scattering by gases, liquid, solids, and/or optical elements.

Microstructured hollow fibers for ultrafiltration

NARCIS (Netherlands)

Culfaz, Pmar Zeynep; Culfaz, P.Z.; Rolevink, Hendrikus H.M.; van Rijn, C.J.M.; Lammertink, Rob G.H.; Wessling, Matthias

2010-01-01

Hollow fiber ultrafiltration membranes with a corrugated outer microstructure were prepared from a PES/PVP blend. The effect of spinning parameters such as air gap, take-up speed, polymer dope viscosity and coagulation value on the microstructure and membrane characteristics was investigated. Fibers

Report on the combined meeting of the core confinement and internal transport barrier expert group, confinement database and modeling expert group and edge pedestal expert group, 12-16 April 1999, Garching

International Nuclear Information System (INIS)

Janeschitz, G.; Connor, J.W.; Cordey, G.; Kardaun, O.; Mukhovatov, V.; Stambaugh, R.; Ryter, F.; Wakatani, M.

1999-01-01

This contribution to the ITER EDA Newsletter reports on the combined meeting of the core confinement and internal transport barrier expert group, confinement database and modeling expert group and edge pedestal expert group in Garching, Germany. This is the first workshop of its kind after the re-organisation of the expert groups. The new scheme of the meetings, namely to permit more interaction between groups by arranging them at the same time and location turned out to be very successful. The main issues discussed were for the Confinement Database: merging of edge pedestal and confinement data, improvement of the density- and magnetic shape parameters, addition of new dedicated threshold data, the effect of different divertors in JET; for the H-Mode Power Threshold Database: assembly of a new version of the database with about 650 time points from 10 tokamaks; for the 1-D Modelling Workshop: management of the database after the re-organisation of the Joint Central Team an ongoing efforts in plasma transport modelling; for the newly formed pedestal group: issues of the H-mode shear layer at the plasma edge. There was also an executive summary given of a recent USA workshop on internal transport barriers and regimes with weak or negative magnetic shear

Large-scale preparation of hollow graphitic carbon nanospheres

International Nuclear Information System (INIS)

Feng, Jun; Li, Fu; Bai, Yu-Jun; Han, Fu-Dong; Qi, Yong-Xin; Lun, Ning; Lu, Xi-Feng

2013-01-01

Hollow graphitic carbon nanospheres (HGCNSs) were synthesized on large scale by a simple reaction between glucose and Mg at 550 °C in an autoclave. Characterization by X-ray diffraction, Raman spectroscopy and transmission electron microscopy demonstrates the formation of HGCNSs with an average diameter of 10 nm or so and a wall thickness of a few graphenes. The HGCNSs exhibit a reversible capacity of 391 mAh g −1 after 60 cycles when used as anode materials for Li-ion batteries. -- Graphical abstract: Hollow graphitic carbon nanospheres could be prepared on large scale by the simple reaction between glucose and Mg at 550 °C, which exhibit superior electrochemical performance to graphite. Highlights: ► Hollow graphitic carbon nanospheres (HGCNSs) were prepared on large scale at 550 °C ► The preparation is simple, effective and eco-friendly. ► The in situ yielded MgO nanocrystals promote the graphitization. ► The HGCNSs exhibit superior electrochemical performance to graphite.

Laser-driven ion acceleration with hollow laser beams

International Nuclear Information System (INIS)

Brabetz, C.; Kester, O.; Busold, S.; Bagnoud, V.; Cowan, T.; Deppert, O.; Jahn, D.; Roth, M.; Schumacher, D.

2015-01-01

The laser-driven acceleration of protons from thin foils irradiated by hollow high-intensity laser beams in the regime of target normal sheath acceleration (TNSA) is reported for the first time. The use of hollow beams aims at reducing the initial emission solid angle of the TNSA source, due to a flattening of the electron sheath at the target rear side. The experiments were conducted at the PHELIX laser facility at the GSI Helmholtzzentrum für Schwerionenforschung GmbH with laser intensities in the range from 10 18  W cm −2 to 10 20  W cm −2 . We observed an average reduction of the half opening angle by (3.07±0.42)° or (13.2±2.0)% when the targets have a thickness between 12 μm and 14 μm. In addition, the highest proton energies were achieved with the hollow laser beam in comparison to the typical Gaussian focal spot

Laser-driven ion acceleration with hollow laser beams

Energy Technology Data Exchange (ETDEWEB)

Brabetz, C., E-mail: c.brabetz@gsi.de; Kester, O. [Goethe-Universität Frankfurt am Main, 60323 Frankfurt (Germany); GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt (Germany); Busold, S.; Bagnoud, V. [GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt (Germany); Helmholtz-Institut Jena, 07743 Jena (Germany); Cowan, T. [Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden (Germany); Technische Universität Dresden, 01069 Dresden (Germany); Deppert, O.; Jahn, D.; Roth, M. [Technische Universität Darmstadt, 64277 Darmstadt (Germany); Schumacher, D. [GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt (Germany)

2015-01-15

The laser-driven acceleration of protons from thin foils irradiated by hollow high-intensity laser beams in the regime of target normal sheath acceleration (TNSA) is reported for the first time. The use of hollow beams aims at reducing the initial emission solid angle of the TNSA source, due to a flattening of the electron sheath at the target rear side. The experiments were conducted at the PHELIX laser facility at the GSI Helmholtzzentrum für Schwerionenforschung GmbH with laser intensities in the range from 10{sup 18} W cm{sup −2} to 10{sup 20} W cm{sup −2}. We observed an average reduction of the half opening angle by (3.07±0.42)° or (13.2±2.0)% when the targets have a thickness between 12 μm and 14 μm. In addition, the highest proton energies were achieved with the hollow laser beam in comparison to the typical Gaussian focal spot.

Recent progress on the fabrication of hollow microspheres

International Nuclear Information System (INIS)

Wang Aijuan; Lu Yupeng; Sun Ruixue

2007-01-01

Hollow microspheres represent a special class of materials, on which intense interest has been paid in the fields of material science, medicine, chemistry and chromatography. Several methods, including templating method, emulsion processing, high temperature smelting and layer-by-layer self-assembly technique, have been used to produce this kind of materials. However, most of the current needs for hollow microspheres are limited because of the disadvantages of these fabricating methods, such as time-consuming and relatively complex fabricating process. Spray drying method, as a simple and feasible technology, has also been used to fabricate this kind of materials. This method can improve the efficiency and save the time to some extent, and thus gains more and more interest recently. The factors of influencing the product morphology, including inlet air temperature, atomized pressure, feed rate, initial slurry concentration, primary powders size and additives, are reviewed in this paper. In addition, several kinds of typical hollow microspheres fabricated by this method are also listed particularly

Hollow Au@Pd and Au@Pt core-shell nanoparticles as electrocatalysts for ethanol oxidation reactions

KAUST Repository

Song, Hyon Min

2012-09-27

Hybrid alloys among gold, palladium and platinum become a new category of catalysts primarily due to their enhanced catalytic effects. Enhancement means not only their effectiveness, but also their uniqueness as catalysts for the reactions that individual metals may not catalyze. Here, preparation of hollow Au@Pd and Au@Pt core-shell nanoparticles (NPs) and their use as electrocatalysts are reported. Galvanic displacement with Ag NPs is used to obtain hollow NPs, and higher reduction potential of Au compared to Ag, Pd, and Pt helps to produce hollow Au cores first, followed by Pd or Pt shell growth. Continuous and highly crystalline shell growth was observed in Au@Pd core-shell NPs, but the sporadic and porous-like structure was observed in Au@Pt core-shell NPs. Along with hollow core-shell NPs, hollow porous Pt and hollow Au NPs are also prepared from Ag seed NPs. Twin boundaries which are typically observed in large size (>20 nm) Au NPs were not observed in hollow Au NPs. This absence is believed to be due to the role of the hollows, which significantly reduce the strain energy of edges where the two lattice planes meet. In ethanol oxidation reactions in alkaline medium, hollow Au@Pd core-shell NPs show highest current density in forward scan. Hollow Au@Pt core-shell NPs maintain better catalytic activities than metallic Pt, which is thought to be due to the better crystallinity of Pt shells as well as the alloy effect of Au cores. © 2012 The Royal Society of Chemistry.

Thin-walled reinforcement lattice structure for hollow CMC buckets

Science.gov (United States)

de Diego, Peter

2017-06-27

A hollow ceramic matrix composite (CMC) turbine bucket with an internal reinforcement lattice structure has improved vibration properties and stiffness. The lattice structure is formed of thin-walled plies made of CMC. The wall structures are arranged and located according to high stress areas within the hollow bucket. After the melt infiltration process, the mandrels melt away, leaving the wall structure to become the internal lattice reinforcement structure of the bucket.

Morphology conserving aminopropyl functionalization of hollow silica nanospheres in toluene

Science.gov (United States)

Dobó, Dorina G.; Berkesi, Dániel; Kukovecz, Ákos

2017-07-01

Inorganic nanostructures containing cavities of monodisperse diameter distribution find applications in e.g. catalysis, adsorption and drug delivery. One of their possible synthesis routes is the template assisted core-shell synthesis. We synthesized hollow silica spheres around polystyrene cores by the sol-gel method. The polystyrene template was removed by heat treatment leaving behind a hollow spherical shell structure. The surface of the spheres was then modified by adding aminopropyl groups. Here we present the first experimental evidence that toluene is a suitable alternative functionalization medium for the resulting thin shells, and report the comprehensive characterization of the amino-functionalized hollow silica spheres based on scanning electron microscopy, transmission electron microscopy, N2 adsorption, FT-IR spectroscopy, Raman spectroscopy and electrokinetic potential measurement. Both the presence of the amino groups and the preservation of the hollow spherical morphology were unambiguously proven. The introduction of the amine functionality adds amphoteric character to the shell as shown by the zeta potential vs. pH function. Unlike pristine silica particles, amino-functionalized nanosphere aqueous sols can be stable at both acidic and basic conditions.

Process for fabricating PBI hollow fiber asymmetric membranes for gas separation and liquid separation

Science.gov (United States)

Jayaweera, Indira; Krishnan, Gopala N.; Sanjurjo, Angel; Jayaweera, Palitha; Bhamidi, Srinivas

2016-04-26

The invention provides methods for preparing an asymmetric hollow fiber, the asymmetric hollow fibers prepared by such methods, and uses of the asymmetric hollow fibers. One method involves passing a polymeric solution through an outer annular orifice of a tube-in-orifice spinneret, passing a bore fluid though an inner tube of the spinneret, dropping the polymeric solution and bore fluid through an atmosphere over a dropping distance, and quenching the polymeric solution and bore fluid in a bath to form an asymmetric hollow fiber.

Study on Manufacturing Process of Hollow Main Shaft by Open Die Forging

International Nuclear Information System (INIS)

Kwon, Yong Chul; Kang, Jong Hun; Kim, Sang Sik

2016-01-01

The main shaft is one of the key components connecting the rotor hub and gear box of a wind power generator. Typically, main shafts are manufactured by open die forging method. However, the main shaft for large MW class wind generators is designed to be hollow in order to reduce the weight. Additionally, the main shafts are manufactured by a casting process. This study aims to develop a manufacturing process for hollow main shafts by the open die forging method. The design of a forging process for a solid main shaft and hollow shaft was prepared by an open die forging process design scheme. Finite element analyses were performed to obtain the flow stress by a hot compression test at different temperature and strain rates. The control parameters of each forging process, such as temperature and effective strain, were obtained and compared to predict the suitability of the hollow main shaft forging process. Finally, high productivity reflecting material utilization ratio, internal quality, shape, and dimension was verified by the prototypes manufactured by the proposed forging process for hollow main shafts

Study on Manufacturing Process of Hollow Main Shaft by Open Die Forging

Energy Technology Data Exchange (ETDEWEB)

Kwon, Yong Chul [Gyeongnam Technopark, Changwon (Korea, Republic of); Kang, Jong Hun [Jungwon Univ., Goisan (Korea, Republic of); Kim, Sang Sik [Gyeongsang Natiional Univ., Jinju (Korea, Republic of)

2016-02-15

The main shaft is one of the key components connecting the rotor hub and gear box of a wind power generator. Typically, main shafts are manufactured by open die forging method. However, the main shaft for large MW class wind generators is designed to be hollow in order to reduce the weight. Additionally, the main shafts are manufactured by a casting process. This study aims to develop a manufacturing process for hollow main shafts by the open die forging method. The design of a forging process for a solid main shaft and hollow shaft was prepared by an open die forging process design scheme. Finite element analyses were performed to obtain the flow stress by a hot compression test at different temperature and strain rates. The control parameters of each forging process, such as temperature and effective strain, were obtained and compared to predict the suitability of the hollow main shaft forging process. Finally, high productivity reflecting material utilization ratio, internal quality, shape, and dimension was verified by the prototypes manufactured by the proposed forging process for hollow main shafts.

Hydrothermal synthesis of lindgrenite with a hollow and prickly sphere-like architecture

International Nuclear Information System (INIS)

Xu Jiasheng; Xue Dongfeng

2007-01-01

Lindgrenite [Cu 3 (OH) 2 (MoO 4 ) 2 ] with a hollow and prickly sphere-like architecture has been synthesized via a simple and mild hydrothermal route in the absence of any external inorganic additives or organic structure-directing templates. The hierarchical lindgrenite particles are hollow and prickly spheres, which are comprised of numerous small crystal strips that are aligned perpendicularly to the spherical surface. Two factors are important for the formation of hollow and prickly architecture in the present process. One is the general phenomenon of Ostwald ripening in solution, which can be responsible for the hollow structure; the other is that lindgrenite crystals have a rhombic growth habit, which plays an important role in the formation of prickly surface. Furthermore, Cu 3 Mo 2 O 9 with the similar size and morphology can be easily obtained by a simple thermal treatment of the as-prepared lindgrenite in air atmosphere. - Graphical abstract: Lindgrenite [Cu 3 (OH) 2 (MoO 4 ) 2 ] with a hollow and prickly sphere-like architecture has been synthesized via a hydrothermal route. The hierarchical lindgrenite particles are hollow and prickly spheres, which are comprised of numerous crystal strips that are aligned perpendicularly to the spherical surface. Cu 3 Mo 2 O 9 with the similar size and morphology can be easily obtained by a thermal treatment of the as-prepared lindgrenite

Hierarchical Ag/AgCl-TiO{sub 2} hollow spheres with enhanced visible-light photocatalytic activity

Energy Technology Data Exchange (ETDEWEB)

Wang, Xu Long; Yin, Hao Yong [College of Materials Environment Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Nie, Qiu Lin, E-mail: nieqiulin@hdu.edu.cn [College of Materials Environment Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Wu, Wei Wei [College of Materials Environment Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Zhang, Yang; LiYuan, Qiu [College of Science, Hangzhou Dianzi University, Hangzhou 310018 (China)

2017-01-01

The hierarchical Ag/AgCl-TiO{sub 2} hollow spheres were synthesized by depositing Ag/AgCl nanoparticles on TiO{sub 2} hollow spheres via a precipitation photoreduction method, and they were further characterized using TGA, SEM, TEM, XRD, XPS, UV–vis DRS and photoelectric chemical analysis. The analysis showed that the hierarchical Ag/AgCl-TiO{sub 2} hollow spheres exhibited the highest photocatalytic activity, which was approximately 13 times higher than that of TiO{sub 2} hollow spheres. The high photocatalytic activity of the composites is due to efficient electron-hole pairs separation at the photocatalyst interfaces, and localized surface plasmon resonance of Ag nanoparticles formed on AgCl particles in the degradation reaction. - Highlights: • TiO{sub 2} hollow spheres were prepared by a sacrificial template method. • The hollow spheres were modified with Ag/AgCl to form the heterojunctions. • The modification may produce synergistic effect of LSPR and hollow structure. • Visible light photocatalytic activity was enhanced on this hollow catalyst. • The mechanism of the improved photocatalytic performance was discussed.

High performance micro-engineered hollow fiber membranes by smart spinneret design

NARCIS (Netherlands)

de Jong, J.; Nijdam, W.; van Rijn, C.J.M.; Visser, Tymen; Bolhuis-Versteeg, Lydia A.M.; Kapantaidakis, G.; Koops, G.H.; Wessling, Matthias

2005-01-01

Can hollow fiber membranes be produced in other geometries than circular? If so, are membrane properties maintained and what could be the possible benefits of other geometries? This article gives answers and describes the fabrication of micro-structured hollow fiber membranes using micro-fabricated

A method for manufacturing a hollow mems structure

DEFF Research Database (Denmark)

2017-01-01

The present invention relates to a method for manufacturing an at least partly hollow MEMS structure. In a first step one or more through-going openings is/are provided in core material. The one or more through-going openings is/are then covered by an etch-stop layer. After this step, a bottom...... further comprises the step of creating bottom and top conductors in the respective bottom and top layers. Finally, excess core material is removed in order to create the at least partly hollow MEMS structure which may include a MEMS inductor....

Control of Dispersion in Hollow Core Photonic Crystal Fibers

DEFF Research Database (Denmark)

Roberts, John

2007-01-01

The dispersion of hollow core photonic crystal fibers can be tailored by modifying a single ring of holes in the cladding. The dispersion can be lowered and flattened, or alternatively greatly increased, in a controlled manner.......The dispersion of hollow core photonic crystal fibers can be tailored by modifying a single ring of holes in the cladding. The dispersion can be lowered and flattened, or alternatively greatly increased, in a controlled manner....

Synthesis and characterization of hollow magnetic nanospheres modified with Au nanoparticles for bio-encapsulation

Energy Technology Data Exchange (ETDEWEB)

Seisno, Satoshi, E-mail: seino@mit.eng.osaka-u.ac.jp; Suga, Kent; Nakagawa, Takashi; Yamamoto, Takao A.

2017-04-01

Hollow magnetic nanospheres modified with Au nanoparticles were successfully synthesized. Au/SiO{sub 2} nanospheres fabricated by a radiochemical process were used as templates for ferrite templating. After the ferrite plating process, Au/SiO{sub 2} templates were fully coated with magnetite nanoparticles. Dissolution of the SiO{sub 2} core lead to the formation of hollow magnetic nanospheres with Au nanoparticles inside. The hollow magnetic nanospheres consisted of Fe{sub 3}O{sub 4} grains, with an average diameter of 60 nm, connected to form the sphere wall, inside which Au grains with an average diameter of 7.2 nm were encapsulated. The Au nanoparticles immobilized on the SiO{sub 2} templates contributed to the adsorption of the Fe ion precursor and/or Fe{sub 3}O{sub 4} seeds. These hollow magnetic nanospheres are proposed as a new type of nanocarrier, as the Au grains could specifically immobilize biomolecules inside the hollow sphere. - Highlights: • A procedure to synthesize hollow magnetic nanospheres with Au inside was reported. • The Au nanoparticles inside the hollow showed high Au-S binding affinity. • The nanospheres are expected to be suitable as a new magnetic carrier for DDS.

Synthesis and characterization of hollow spherical copper phosphide (Cu 3P) nanopowders

Science.gov (United States)

Liu, Shuling; Qian, Yitai; Xu, Liqiang

2009-03-01

In this paper, hollow spherical Cu 3P nanopowders were synthesized by using copper sulfate pentahydrate (CuSO 4ṡ5H 2O) and yellow phosphorus in a mixed solvent of glycol, ethanol and water at 140-180 ∘C for 12 h. X-ray powder diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), electron diffraction pattern (ED) and transmission electronic microscopy (TEM) studies show that the as-synthesized nanocrystal is pure hexagonal phase Cu 3P with a hollow spherical morphology. Based on the TEM observations, a possible aggregation growth mechanism was proposed for the formation of Cu 3P hollow structures. Meanwhile, the effects of some key factors such as solvents, reaction temperature and reaction time on the final formation of the Cu 3P hollow structure were also discussed.

Space Charge Mitigation by Hollow Bunches

CERN Multimedia

Oeftiger, AO

2014-01-01

To satisfy the requirements of the HL-LHC (High Luminosity Large Hadron Collider), the LHC injector chain will need to supply a higher brightness, i.e. deliver the same transverse beam emittances \\epsilon_{x,y} while providing a higher intensity N. However, a larger number of particles per bunch enhances space charge effects. One approach to mitigate the impact of space charge is to change the longitudinal phase space distribution: hollow bunches feature a depleted bunch centre and a densely populated periphery. Thus, the spatial line density maximum is depressed which ultimately decreases the tune spread imposed by space charge. Therefore, a higher intensity can be accepted while keeping the same overall space charge tune shift. 3 different methods to create hollow bunches in the PSBooster are simulated.

Evaluation of an inductively-coupled plasma with an extended-sleeve torch as an atomization cell for laser-excited fluorescence spectrometry.

Science.gov (United States)

Kosinski, M A; Uchida, H; Winefordner, J D

1983-05-01

An inductively-coupled plasma (ICP) with an extended-sleeve torch has been evaluated as an atomization cell for laser-excited fluorescence spectrometry. Limits of detection for 20 lines are given. The detection power is almost equivalent to that obtained by excitation with a hollow-cathode lamp. Interelement effects and spectral interferences are discussed.

Dual layer hollow fiber sorbents for trace H2S removal from gas streams

KAUST Repository

Bhandari, Dhaval A.; Bessho, Naoki; Koros, William J.

2013-01-01

Hollow fiber sorbents are pseudo monolithic materials with potential use in various adsorption based applications. Dual layer hollow fiber sorbents have the potential to allow thermal regeneration without direct contact of the regeneration fluid with the sorbent particles. This paper considers the application of dual layer hollow fiber sorbents for a case involving trace amounts of H2S removal from a simulated gas stream and offers a comparison with single layer hollow fiber sorbents. The effect of spin dope composition and core layer zeolite loading on the gas flux, H2S transient sorption capacity and pore structure are also studied. This work can be used as a guide to develop and optimize dual layer hollow fiber sorbent properties beyond the specific example considered here. © 2013 Elsevier Ltd.

Dual layer hollow fiber sorbents for trace H2S removal from gas streams

KAUST Repository

Bhandari, Dhaval A.

2013-05-01

Hollow fiber sorbents are pseudo monolithic materials with potential use in various adsorption based applications. Dual layer hollow fiber sorbents have the potential to allow thermal regeneration without direct contact of the regeneration fluid with the sorbent particles. This paper considers the application of dual layer hollow fiber sorbents for a case involving trace amounts of H2S removal from a simulated gas stream and offers a comparison with single layer hollow fiber sorbents. The effect of spin dope composition and core layer zeolite loading on the gas flux, H2S transient sorption capacity and pore structure are also studied. This work can be used as a guide to develop and optimize dual layer hollow fiber sorbent properties beyond the specific example considered here. © 2013 Elsevier Ltd.

Novel Ultrafine Fibrous Poly(tetrafluoroethylene Hollow Fiber Membrane Fabricated by Electrospinning

Directory of Open Access Journals (Sweden)

Qinglin Huang

2018-04-01

Full Text Available Novel poly(tetrafluoroethylene (PTFE hollow fiber membranes were successfully fabricated by electrospinning, with ultrafine fibrous PTFE membranes as separation layers, while a porous glassfiber braided tube served as the supporting matrix. During this process, PTFE/poly(vinylalcohol (PVA ultrafine fibrous membranes were electrospun while covering the porous glassfiber braided tube; then, the nascent PTFE/PVA hollow fiber membrane was obtained. In the following sintering process, the spinning carrier PVA decomposed; meanwhile, the ultrafine fibrous PTFE membrane shrank inward so as to further integrate with the supporting matrix. Therefore, the ultrafine fibrous PTFE membranes had excellent interface bonding strength with the supporting matrix. Moreover, the obtained ultrafine fibrous PTFE hollow fiber membrane exhibited superior performances in terms of strong hydrophobicity (CA > 140°, high porosity (>70%, and sharp pore size distribution. The comprehensive properties indicated that the ultrafine fibrous PTFE hollow fiber membranes could have potentially useful applications in membrane contactors (MC, especially membrane distillation (MD in harsh water environments.

Synthesis and gas-sensing characteristics of α-Fe2O3 hollow balls

Directory of Open Access Journals (Sweden)

Chu Manh Hung

2016-03-01

Full Text Available The synthesis of porous metal-oxide semiconductors for gas-sensing application is attracting increased interest. In this study, α-Fe2O3 hollow balls were synthesized using an inexpensive, scalable, and template-free hydrothermal method. The gas-sensing characteristics of the semiconductors were systematically investigated. Material characterization by XRD, SEM, HRTEM, and EDS reveals that single-phase α-Fe2O3 hollow balls with an average diameter of 1.5 μm were obtained. The hollow balls were formed by self assembly of α-Fe2O3 nanoparticles with an average diameter of 100 nm. The hollow structure and nanopores between the nanoparticles resulted in the significantly high response of the α-Fe2O3 hollow balls to ethanol at working temperatures ranging from 250 °C to 450 °C. The sensor also showed good selectivity over other gases, such as CO and NH3 promising significant application.

Mechanism of the formation of hollow spherical granules using a high shear granulator.

Science.gov (United States)

Asada, Takumi; Nishikawa, Mitsunori; Ochiai, Yasushi; Noguchi, Shuji; Kimura, Shin-Ichiro; Iwao, Yasunori; Itai, Shigeru

2018-05-30

Recently, we have developed a novel granulation technology to manufacture hollow spherical granules (HSGs) for controlled-release formulations; however, the mechanism of the granulation is still unclear. The aim of this study is to determine the mechanism of the formation of the HSGs using a high shear granulator. Samples of granulated material were collected at various times during granulation and were investigated using scanning electron microscope and X-ray computed tomography. It was observed that the granulation proceeded by drug layering to the polymer, followed by formation of a hollow in the granule. In addition, it was also found that generation of a crack in the adhered drug layer and air flow into the granules might be involved in forming the hollow in the structure. Observation of the granulation of formulations with different types of drugs and polymers indicated that negative pressure in the granules occurred and the granules caved in when the hollow was formed. The hollow-forming speed and the shell density of the hollow granules depended on the particular drug and polymer. Taken together, the granulation mechanism of HSGs was determined and this information will be valuable for HSGs technology development. Copyright © 2018 Elsevier B.V. All rights reserved.

Large-scale preparation of hollow graphitic carbon nanospheres

Energy Technology Data Exchange (ETDEWEB)

Feng, Jun; Li, Fu [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Jinan 250061 (China); Bai, Yu-Jun, E-mail: byj97@126.com [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Jinan 250061 (China); State Key laboratory of Crystal Materials, Shandong University, Jinan 250100 (China); Han, Fu-Dong; Qi, Yong-Xin; Lun, Ning [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Jinan 250061 (China); Lu, Xi-Feng [Lunan Institute of Coal Chemical Engineering, Jining 272000 (China)

2013-01-15

Hollow graphitic carbon nanospheres (HGCNSs) were synthesized on large scale by a simple reaction between glucose and Mg at 550 Degree-Sign C in an autoclave. Characterization by X-ray diffraction, Raman spectroscopy and transmission electron microscopy demonstrates the formation of HGCNSs with an average diameter of 10 nm or so and a wall thickness of a few graphenes. The HGCNSs exhibit a reversible capacity of 391 mAh g{sup -1} after 60 cycles when used as anode materials for Li-ion batteries. -- Graphical abstract: Hollow graphitic carbon nanospheres could be prepared on large scale by the simple reaction between glucose and Mg at 550 Degree-Sign C, which exhibit superior electrochemical performance to graphite. Highlights: Black-Right-Pointing-Pointer Hollow graphitic carbon nanospheres (HGCNSs) were prepared on large scale at 550 Degree-Sign C Black-Right-Pointing-Pointer The preparation is simple, effective and eco-friendly. Black-Right-Pointing-Pointer The in situ yielded MgO nanocrystals promote the graphitization. Black-Right-Pointing-Pointer The HGCNSs exhibit superior electrochemical performance to graphite.

Molecular beam sampling of a hollow cathode arc

International Nuclear Information System (INIS)

Theuws, P.

1981-01-01

This thesis deals with the description of the process of molecular beam sampling of a Hollow Cathode Arc. The aim of the study is twofold, i.e. investigation of the applicability of molecular beam sampling as a plasma diagnostic and the use of a Hollow Cathode Arc as a high intensity beam source for ground state atoms and metastable state atoms in the superthermal energy range. Suitable models are introduced, describing the process of molecular beam sampling of both ground state atoms and metastable state atoms. Fast ground state atoms produced by ion-atom collisions. The experimental facilities, i.e. the Hollow Cathode Arc, the time-of-flight machine and the dye laser system are described. And an alternative detection scheme for ground state atoms is presented and experimental results on the molecular beam sampling of a low density plasma (densities 10 19 -10 20 m -3 ) in the long arc configuration are reported. The results on the short arc configuration (densities 10 21 -10 22 m -3 ) are discussed. (Auth.)

Green and facile fabrication of hollow porous MnO/C microspheres from microalgaes for lithium-ion batteries.

Science.gov (United States)

Xia, Yang; Xiao, Zhen; Dou, Xiao; Huang, Hui; Lu, Xianghong; Yan, Rongjun; Gan, Yongping; Zhu, Wenjun; Tu, Jiangping; Zhang, Wenkui; Tao, Xinyong

2013-08-27

Hollow porous micro/nanostructures with high surface area and shell permeability have attracted tremendous attention. Particularly, the synthesis and structural tailoring of diverse hollow porous materials is regarded as a crucial step toward the realization of high-performance electrode materials, which has several advantages including a large contact area with electrolyte, a superior structural stability, and a short transport path for Li(+) ions. Meanwhile, owing to the inexpensive, abundant, environmentally benign, and renewable biological resources provided by nature, great efforts have been devoted to understand and practice the biotemplating technology, which has been considered as an effective strategy to achieve morphology-controllable materials with structural specialty, complexity, and related unique properties. Herein, we are inspired by the natural microalgae with its special features (easy availability, biological activity, and carbon sources) to develop a green and facile biotemplating method to fabricate monodisperse MnO/C microspheres for lithium-ion batteries. Due to the unique hollow porous structure in which MnO nanoparticles were tightly embedded into a porous carbon matrix and form a penetrative shell, MnO/C microspheres exhibited high reversible specific capacity of 700 mAh g(-1) at 0.1 A g(-1), excellent cycling stability with 94% capacity retention, and enhanced rate performance of 230 mAh g(-1) at 3 A g(-1). This green, sustainable, and economical strategy will extend the scope of biotemplating synthesis for exploring other functional materials in various structure-dependent applications such as catalysis, gas sensing, and energy storage.

Enhancement of acoustical performance of hollow tube sound absorber

International Nuclear Information System (INIS)

Putra, Azma; Khair, Fazlin Abd; Nor, Mohd Jailani Mohd

2016-01-01

This paper presents acoustical performance of hollow structures utilizing the recycled lollipop sticks as acoustic absorbers. The hollow cross section of the structures is arranged facing the sound incidence. The effects of different length of the sticks and air gap on the acoustical performance are studied. The absorption coefficient was measured using impedance tube method. Here it is found that improvement on the sound absorption performance is achieved by introducing natural kapok fiber inserted into the void between the hollow structures. Results reveal that by inserting the kapok fibers, both the absorption bandwidth and the absorption coefficient increase. For test sample backed by a rigid surface, best performance of sound absorption is obtained for fibers inserted at the front and back sides of the absorber. And for the case of test sample with air gap, this is achieved for fibers introduced only at the back side of the absorber.

Enhancement of acoustical performance of hollow tube sound absorber

Energy Technology Data Exchange (ETDEWEB)

Putra, Azma, E-mail: azma.putra@utem.edu.my; Khair, Fazlin Abd, E-mail: fazlinabdkhair@student.utem.edu.my; Nor, Mohd Jailani Mohd, E-mail: jai@utem.edu.my [Centre for Advanced Research on Energy, Universiti Teknikal Malaysia Melaka, Hang Tuah Jaya, Durian Tunggal Melaka 76100 Malaysia (Malaysia)

2016-03-29

This paper presents acoustical performance of hollow structures utilizing the recycled lollipop sticks as acoustic absorbers. The hollow cross section of the structures is arranged facing the sound incidence. The effects of different length of the sticks and air gap on the acoustical performance are studied. The absorption coefficient was measured using impedance tube method. Here it is found that improvement on the sound absorption performance is achieved by introducing natural kapok fiber inserted into the void between the hollow structures. Results reveal that by inserting the kapok fibers, both the absorption bandwidth and the absorption coefficient increase. For test sample backed by a rigid surface, best performance of sound absorption is obtained for fibers inserted at the front and back sides of the absorber. And for the case of test sample with air gap, this is achieved for fibers introduced only at the back side of the absorber.

Edge Pedestal Control in Quiescent H-Mode Discharges in DIII-D Using Co Plus Counter Neutral Beam Injection

International Nuclear Information System (INIS)

Burrell, K.H.; Osborne, T.H.; Snyder, P.B.; West, W.P.; Chu, M.S.; Fenstermacher, M.E.; Gohil, P.; Solomon, W.M.

2008-01-01

We have made two significant discoveries in our recent studies of quiescent H-mode (QH-mode) plasmas in DIII-D. First, we have found that we can control the edge pedestal density and pressure by altering the edge particle transport through changes in the edge toroidal rotation. This allows us to adjust the edge operating point to be close to, but below the ELM stability boundary, maintaining the ELM-free state while allowing up to a factor of two increase in edge pressure. The ELM boundary is significantly higher in more strongly shaped plasmas, which broadens the operating space available for QH-mode and leads to improved core performance. Second, for the first time on any tokamak, we have created QH-mode plasmas with strong edge co-rotation; previous QH-modes in all tokamaks had edge counter rotation. This result demonstrates that counter NBI and edge counter rotation are not essential conditions for QH-mode. Both these investigations benefited from the edge stability predictions based on peeling-ballooning mode theory. The broadening of the ELM-stable region with plasma shaping is predicted by that theory. The theory has also been extended to provide a model for the edge harmonic oscillation (EHO) that regulates edge transport in the QH-mode. Many of the features of that theory agree with the experimental results reported either previously or in the present paper. One notable example is the prediction that co-rotating QH-mode is possible provided sufficient shear in the edge rotation can be created

Computational predictions of zinc oxide hollow structures

Science.gov (United States)

Tuoc, Vu Ngoc; Huan, Tran Doan; Thao, Nguyen Thi

2018-03-01

Nanoporous materials are emerging as potential candidates for a wide range of technological applications in environment, electronic, and optoelectronics, to name just a few. Within this active research area, experimental works are predominant while theoretical/computational prediction and study of these materials face some intrinsic challenges, one of them is how to predict porous structures. We propose a computationally and technically feasible approach for predicting zinc oxide structures with hollows at the nano scale. The designed zinc oxide hollow structures are studied with computations using the density functional tight binding and conventional density functional theory methods, revealing a variety of promising mechanical and electronic properties, which can potentially find future realistic applications.

A dark hollow beam from a selectively liquid-filled photonic crystal fibre

International Nuclear Information System (INIS)

Mei-Yan, Zhang; Shu-Guang, Li; Yan-Yan, Yao; Bo, Fu; Lei, Zhang

2010-01-01

This paper reports that, based on the electromagnetic scattering theory of the multipole method, a high-quality hollow beam is produced through a selectively liquid-filled photonic crystal fibre. Instead of a doughnut shape, a typical hollow beam is produced by other methods; the mode-field images of the hollow-beam photonic crystal fibre satisfy sixth-order rotation symmetry, according to the symmetry of the photonic crystal fibre (PCF) structure. A dark spot size of the liquid-filled photonic crystal fibre-generated hollow beam can be tuned by inserting liquid into the cladding region and varying the photonic crystal fibre structure parameters. The liquid-filled PCF makes a convenient and flexible tool for the guiding and trapping of atoms and the creation of all-fibre optical tweezers. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

One-pot template-free synthesis of monodisperse hollow hydrogel microspheres and their resulting properties.

Science.gov (United States)

Lim, Hyung-Seok; Kwon, Eunji; Lee, Moonjoo; Moo Lee, Young; Suh, Kyung-Do

2013-08-01

Monodisperse poly(methacrylic acid/ethyleneglycoldimethacrylate) (MAA/EGDMA) hollow microcapsules, which exhibit pH-responsive behavior, are prepared by diffusion of cationic surfactants and hydrophobic interaction. During the association of the negatively charged hydrogel microspheres and an oppositely charged surfactant (cetyltrimethylammonium bromide, CTA(+)B), the hydrophobic polymer-surfactant complexes that form are separated from the internal water; consequently, a hollow structure can be formed. Confocal laser scanning microscopy, UV spectro-scopy and zeta potential are employed to study the formation of the hollow structure during the diffusion of the cationic surfactant. The controlled release behavior of methylene blue as a model drug from the as-prepared poly(MAA/EGDMA) microcapsules with a hollow structure is investigated under different pH conditions. The hollow structure can be retained, even during repetitive pH changes. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hollow Electron Beam Collimation for HL-LHC - Effects on the Beam Core

Energy Technology Data Exchange (ETDEWEB)

Fitterer, M. [Fermilab; Stancari, G. [Fermilab; Valishev, A. [Fermilab; Bruce, R. [CERN; Papotti, G [CERN; Redaelli, S. [CERN; Valentino, G. [Malta U.; Valentino, G. [CERN; Valuch, D. [CERN; Xu, C. [CERN

2017-06-13

Collimation with hollow electron beams is currently one of the most promising concepts for active halo control in the High Luminosity Large Hadron Collider (HL-LHC). To ensure the successful operation of the hollow beam collimator the unwanted effects on the beam core, which might arise from the operation with a pulsed electron beam, must be minimized. This paper gives a summary of the effect of hollow electron lenses on the beam core in terms of sources, provides estimates for HL-LHC and discusses the possible mitigation methods.

Fabrication of hollow silica–zirconia composite spheres and their activity for hydrolytic dehydrogenation of ammonia borane

Energy Technology Data Exchange (ETDEWEB)

Umegaki, Tetsuo, E-mail: umegaki.tetsuo@nihon-u.ac.jp [Department of Materials and Applied Chemistry, College of Science and Engineering, Nihon University, 1-8-14, Kanda-Surugadai, Chiyoda-Ku, Tokyo 101-8308 (Japan); Hosoya, Tatsuya; Toyama, Naoki [Department of Materials and Applied Chemistry, College of Science and Engineering, Nihon University, 1-8-14, Kanda-Surugadai, Chiyoda-Ku, Tokyo 101-8308 (Japan); Xu, Qiang [National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577 (Japan); Kojima, Yoshiyuki [Department of Materials and Applied Chemistry, College of Science and Engineering, Nihon University, 1-8-14, Kanda-Surugadai, Chiyoda-Ku, Tokyo 101-8308 (Japan)

2014-09-01

Highlights: • Hollow silica–zirconia composite spheres were fabricated on polystyrene templates by the sol–gel method. • We study the effect of preparation conditions on the activity for hydrolytic dehydrogenation of ammonia borane. • The activity of hollow silica–zirconia composite spheres depends on wall thickness. - Abstract: In this paper, we report fabrication of hollow silica–zirconia composite spheres by polystyrene (PS) template method and control of wall thickness of the hollow spheres in nanoscale. Both the hollow spheres before and after calcination were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), elemental analysis, and powder X-ray diffraction analysis (XRD). Morphology of the hollow spheres does not significantly change after calcination from the results of SEM and TEM images, while the amount of residual PS templates drastically decreases via the calcination procedure from the results of FTIR and elemental analysis. The sample after calcination mainly includes amorphous silica from the results of XRD, indicating that the hollow silica–zirconia composite spheres consist of amorphous phases and/or fine particles. Wall thicknesses of the samples after calcination are controlled by adjusting the amount of PS template suspension, and hollow silica–zirconia composite spheres with the wall thicknesses of 17.5, 15.0, 10.0, and 2.0 nm are obtained using the PS template suspension of 25.0, 33.5, 100.0, and 400.0 g, respectively. The activities of the hollow spheres for hydrolytic dehydrogenation of ammonia borane (NH{sub 3}BH{sub 3}) were compared. The evolutions of 2.0, 3.1, 5.0, and 8.0 mL hydrogen from aqueous NH{sub 3}BH{sub 3} solution were finished in about 4, 5, 3, and 7 min in the presence of the hollow spheres with wall thicknesses of 17.5, 15.0, 10.0, and 2.0 nm, respectively. The molar ratios of the hydrolytically generated hydrogen to

Hollow Micro-/Nanostructures: Synthesis and Applications

KAUST Repository

Lou, Xiong Wen (David); Archer, Lynden A.; Yang, Zichao

2008-01-01

for Portland cement, to produce concrete with enhanced strength and durability. This review is devoted to the progress made in the last decade in synthesis and applications of hollow micro-nanostructures. We present a comprehensive overview of synthetic

Tensile Strength of GFRP Reinforcing Bars with Hollow Section

Directory of Open Access Journals (Sweden)

Young-Jun You

2015-01-01

Full Text Available Fiber reinforced polymer (FRP has been proposed to replace steel as a reinforcing bar (rebar due to its high tensile strength and noncorrosive material properties. One obstacle in using FRP rebars is high price. Generally FRP is more expensive than conventional steel rebar. There are mainly two ways to reduce the cost. For example, one is making the price of each composition cost of FRP rebar (e.g., fibers, resin, etc. lower than steel rebar. Another is making an optimized design for cross section and reducing the material cost. The former approach is not easy because the steel price is very low in comparison with component materials of FRP. For the latter approach, the cost could be cut down by reducing the material cost. Therefore, an idea of making hollow section over the cross section of FRP rebar was proposed in this study by optimizing the cross section design with acceptable tensile performance in comparison with steel rebar. In this study, glass reinforced polymer (GFRP rebars with hollow section and 19 mm of outer diameter were manufactured and tested to evaluate the tensile performance in accordance with the hollowness ratio. From the test results, it was observed that the tensile strength decreased almost linearly with increase of hollowness ratio and the elastic modulus decreased nonlinearly.

Formation of hollow atoms above a surface

Science.gov (United States)

Briand, Jean Pierre; Phaneuf, Ronald; Terracol, Stephane; Xie, Zuqi

2012-06-01

Slow highly stripped ions approaching or penetrating surfaces are known to capture electrons into outer shells of the ions, leaving the innermost shells empty, and forming hollow atoms. Electron capture occurs above and below the surfaces. The existence of hollow atoms below surfaces e.g. Ar atoms whose K and L shells are empty, with all electrons lying in the M and N shells, was demonstrated in 1990 [1]. At nm above surfaces, the excited ions may not have enough time to decay before hitting the surfaces, and the formation of hollow atoms above surfaces has even been questioned [2]. To observe it, one must increase the time above the surface by decelerating the ions. We have for the first time decelerated O^7+ ions to energies as low as 1 eV/q, below the minimum energy gained by the ions due to the acceleration by their image charge. As expected, no ion backscattering (trampoline effect) above dielectric (Ge) was observed and at the lowest ion kinetic energies, most of the observed x-rays were found to be emitted by the ions after surface contact. [4pt] [1] J. P. Briand et al., Phys.Rev.Lett. 65(1990)159.[0pt] [2] J.P. Briand, AIP Conference Proceedings 215 (1990) 513.

H-mode pedestal characteristics in ITER shape discharges on DIII-D

International Nuclear Information System (INIS)

Osborne, T.H.; Burrell, K.H.; Groebner, R.J.

1998-09-01

Characteristics of the H-mode pedestal are studied in Type 1 ELM discharges with ITER cross-sectional shape and aspect ratio. The scaling of the width of the edge step gradient region, δ, which is most consistent with the data is with the normalized edge pressure, (β POL PED ) 0.4 . Fits of δ to a function of temperature, such as ρ POL , are ruled out in divertor pumping experiments. The edge pressure gradient is found to scale as would be expected from infinite n ballooning mode theory; however, the value of the pressure gradient exceeds the calculated first stable limit by more than a factor of 2 in some discharges. This high edge pressure gradient is consistent with access to the second stable regime for ideal ballooning for surfaces near the edge. In lower q discharges, including discharges at the ITER value of q, edge second stability requires significant edge current density. Transport simulations give edge bootstrap current of sufficient magnitude to open second stable access in these discharges. Ideal kink analysis using current density profiles including edge bootstrap current indicate that before the ELM these discharges may be unstable to low n, edge localized modes

Rotary compression process for producing toothed hollow shafts

Directory of Open Access Journals (Sweden)

J. Tomczak

2014-10-01

Full Text Available The paper presents the results of numerical analyses of the rotary compression process for hollow stepped shafts with herringbone teeth. The numerical simulations were performed by Finite Element Method (FEM, using commercial software package DEFORM-3D. The results of numerical modelling aimed at determining the effect of billet wall thickness on product shape and the rotary compression process are presented. The distributions of strains, temperatures, damage criterion and force parameters of the process determined in the simulations are given, too. The numerical results obtained confirm the possibility of producing hollow toothed shafts from tube billet by rotary compression methods.

Soliton formation in hollow-core photonic bandgap fibers

DEFF Research Database (Denmark)

Lægsgaard, Jesper

2009-01-01

of an approximate scaling relation is tested. It is concluded that compression of input pulses of several ps duration and sub-MW peak power can lead to a formation of solitons with ∼100 fs duration and multi-megawatt peak powers. The dispersion slope of realistic hollow-core fibers appears to be the main obstacle......The formation of solitons upon compression of linearly chirped pulses in hollow-core photonic bandgap fibers is investigated numerically. The dependence of soliton duration on the chirp and power of the input pulse and on the dispersion slope of the fiber is investigated, and the validity...

Antiresonant hollow core fiber with seven nested capillaries

DEFF Research Database (Denmark)

Antonio-Lopez, Jose E.; Habib, Selim; Van Newkirk, Amy

2016-01-01

We report an antiresonant hollow core fiber formed of 7 non-touching capillaries with inner tubes. The fiber has a core diameter of ∼33μm and a core wall of ∼780nm of thickness. We demonstrate robust single mode operation at 1064nm and broad transmission bandwidth.......We report an antiresonant hollow core fiber formed of 7 non-touching capillaries with inner tubes. The fiber has a core diameter of ∼33μm and a core wall of ∼780nm of thickness. We demonstrate robust single mode operation at 1064nm and broad transmission bandwidth....

Catalyst-Free Synthesis of Hollow-Sphere-Like ZnO and Its Photoluminescence Property

Directory of Open Access Journals (Sweden)

Junye Cheng

2014-01-01

Full Text Available Hollow-sphere-like ZnO was successfully prepared by a facile combustion route at 950°C, and no external catalysts or additives were introduced. The morphology and structure of the hollow-sphere-like ZnO were characterized by X-ray diffraction (XRD, scanning electron microscopy (SEM, high-resolution transmission electron microscopy (HRTEM, and energy dispersive spectrometer (EDS. The possible growth mechanism was discussed in detail. In addition, the as-obtained hollow-sphere-like ZnO exhibited a strong green emission at 518 nm and a weak UV emission at 385 nm. We believe that the hollow-sphere-like ZnO material may be a good candidate for application in optical devices and catalyst systems.

Enhancement of the predicted drug hepatotoxicity in gel entrapped hepatocytes within polysulfone-g-poly (ethylene glycol) modified hollow fiber

International Nuclear Information System (INIS)

Shen Chong; Zhang Guoliang; Meng Qin

2010-01-01

Collagen gel-based 3D cultures of hepatocytes have been proposed for evaluation of drug hepatotoxicity because of their more reliability than traditional monolayer culture. The collagen gel entrapment of hepatocytes in hollow fibers has been proven to well reflect the drug hepatotoxicity in vivo but was limited by adsorption of hydrophobic drugs onto hollow fibers. This study aimed to investigate the impact of hollow fibers on hepatocyte performance and drug hepatotoxicity. Polysulfone-g-poly (ethylene glycol) (PSf-g-PEG) hollow fiber was fabricated and applied for the first time to suppress the drug adsorption. Then, the impact of hollow fibers was evaluated by detecting the hepatotoxicity of eight selected drugs to gel entrapped hepatocytes within PSf and PSf-g-PEG hollow fibers, or without hollow fibers. The hepatocytes in PSf-g-PEG hollow fiber showed the highest sensitivity to drug hepatotoxicity, while those in PSf hollow fiber and cylindrical gel without hollow fiber underestimated the hepatotoxicity due to either drug adsorption or low hepatic functions. Therefore, the 3D culture of gel entrapped hepatocytes within PSf-g-PEG hollow fiber would be a promising tool for investigation of drug hepatotoxicity in vitro.

Synthesis of solid and hollow ATO spheres by carbothermal reduction of ATO nanoparticles

International Nuclear Information System (INIS)

Chai Chunfang; Huang Zaiyin; Liao Dankui; Tan Xuecai; Wu Jian; Yuan Aiqun

2007-01-01

Solid and hollow ATO spheres were fabricated by heating ATO nanoparticles and graphite mixture in a tube furnace. The as-synthesized samples were characterized by EDS, XRD, FE-SEM, TEM and HRTEM. The size of the solid spheres could be controlled by adjusting the rate of Ar flow and deposition positions. The hollow spheres were synthesized in an alumina tube system under conditions of a relatively high oxygen concentration. The growth mechanism of solid and hollow spheres was analysed

Construction of anatase/rutile TiO2 hollow boxes for highly efficient photocatalytic performance

Science.gov (United States)

Jia, Changchao; Zhang, Xiao; Yang, Ping

2018-02-01

Hollow TiO2 hierarchical boxes with suitable anatase and rutile ratios were designed for photocatalysis. The unique hierarchical structure was fabricated via a Topotactic synthetic method. CaTiO3 cubes were acted as the sacrificial templates to create TiO2 hollow hierarchical boxes with well-defined phase distribution. The phase composition of the hollow TiO2 hierarchical boxes is similar to that of TiO2 P25 nanoparticles (∼80% anatase, and 20% rutile). Compared with nanaoparticles, TiO2 hollow boxes with hierarchical structures exhibited an excellent performance in the photocatalytic degradation of methylene blue organic pollutant. Quantificationally, the degradation rate of the hollow boxes is higher than that of TiO2 P25 nanoparticles by a factor of 2.7. This is ascribed that hollow structure provide an opportunity for using incident light more efficiently. The surface hierarchical and well-organized porous structures are beneficial to supply more active sites and enough transport channels for reactant molecules. The boxes consist of single crystal anatase and rutile combined well with each other, which gives photon-generated carriers transfer efficiently.

Pt monolayer shell on hollow Pd core electrocatalysts: Scale up synthesis, structure, and activity for the oxygen reduction reaction

Directory of Open Access Journals (Sweden)

Vukmirovic Miomir B.

2013-01-01

Full Text Available We report on synthesis, characterization and the oxygen reduction reaction (ORR kinetics of Pt monolayer shell on Pd(hollow, or Pd-Au(hollow core electrocatalysts. Comparison between the ORR catalytic activity of the electrocatalysts with hollow cores and those of Pt solid and Pt hollow nanoparticles has been obtained using the rotating disk electrode technique. Hollow nanoparticles were made using Ni or Cu nanoparticles as sacrificial templates. The Pt ORR specific and mass activities of the electrocatalysts with hollow cores were found considerably higher than those of the electrocatalysts with the solid cores. We attribute this enhanced Pt activity to the smooth surface morphology and hollow-induced lattice contraction, in addition to the mass-saving geometry of hollow particles.

Space and Temporal Correlation between the Moving Virtual Anode and the Ionization Growth in a Transient Hollow Cathode Discharge

International Nuclear Information System (INIS)

Zambra, M.; Moreno, J.; Soto, L.; Silva, P.; Sylvester, G.; Alarcon, H.

2001-01-01

A Transient Hollow Cathode Discharge is a low-pressure high-voltage electric discharge between plane parallel electrodes with an axial hole in the cathode. There are essential ionization events which lead to final electrical breakdown, between them the enhanced ionization processes taking place inside the Hollow Cathode Region (HCR) and the virtual anode moving in the interelectrode region, which extends the anode potential to within the HCR. In previous works it was studied the virtual anode speed in the A-K gap and the temporal evolution of the ionization growth in the HCR separately. In this paper, the virtual anode speed has been studied temporal and space correlated with the ionization growth inside the HCR. The presence of the moving virtual anode and the ionization growth has been diagnosed by means of capacitive probes and observing the light emission at 656 nm (H-α) from a point behind the cathode aperture respectively. The discharge was operated in hydrogen gas, at pressure in the range 100-300 mTorr, with 5 mm cathode aperture and at 30 kV maximum voltage. (author)

L-cysteine-assisted synthesis of hierarchical NiS2 hollow spheres supported carbon nitride as photocatalysts with enhanced lifetime

Science.gov (United States)

Zhu, Chengzhang; Jiang, Zhifeng; Chen, Linlin; Qian, Kun; Xie, Jimin

2017-03-01

Novel hierarchical NiS2 hollow spheres modified by graphite-like carbon nitride were prepared using a facile L-cysteine-assisted solvothermal route. The NiS2/g-C3N4 composites exhibited excellent photocatalytic efficiency in rhodamine B, methyl orange and ciprofloxacin degradation as compared to single g-C3N4 and NiS2, which could be due to the synergistic effects of the unique hollow sphere-like structure, strong visible-light absorption and increased separation rate of the photoinduced electron-hole pairs at the intimate interface of heterojunctions. A suitable combination of g-C3N4 with NiS2 showed the best photocatalytic performance. In addition, an electron spin resonance and trapping experiment demonstrated that the photogenerated hydroxyl radicals and superoxide radicals were the two main photoactive species in photocatalysis. A possible photocatalytic mechanism of NiS2/g-C3N4 composites under visible light irradiation is also proposed. The strategy presented here can be extended to a general strategy for constructing 3D/2D heterostructured photocatalysts for broad applications in photocatalysis.

Facile synthesis and electrochemical performances of hollow graphene spheres as anode material for lithium-ion batteries

Science.gov (United States)

Yao, Ran-Ran; Zhao, Dong-Lin; Bai, Li-Zhong; Yao, Ning-Na; Xu, Li

2014-07-01

The hollow graphene oxide spheres have been successfully fabricated from graphene oxide nanosheets utilizing a water-in-oil emulsion technique, which were prepared from natural flake graphite by oxidation and ultrasonic treatment. The hollow graphene oxide spheres were reduced to hollow graphene spheres at 500°C for 3 h under an atmosphere of Ar(95%)/H2(5%). The first reversible specific capacity of the hollow graphene spheres was as high as 903 mAh g-1 at a current density of 50 mAh g-1. Even at a high current density of 500 mAh g-1, the reversible specific capacity remained at 502 mAh g-1. After 60 cycles, the reversible capacity was still kept at 652 mAh g-1 at the current density of 50 mAh g-1. These results indicate that the prepared hollow graphene spheres possess excellent electrochemical performances for lithium storage. The high rate performance of hollow graphene spheres thanks to the hollow structure, thin and porous shells consisting of graphene sheets.

A Hollow-Structured Manganese Oxide Cathode for Stable Zn-MnO₂ Batteries.

Science.gov (United States)

Guo, Xiaotong; Li, Jianming; Jin, Xu; Han, Yehu; Lin, Yue; Lei, Zhanwu; Wang, Shiyang; Qin, Lianjie; Jiao, Shuhong; Cao, Ruiguo

2018-05-05

Aqueous rechargeable zinc-manganese dioxide (Zn-MnO₂) batteries are considered as one of the most promising energy storage devices for large scale-energy storage systems due to their low cost, high safety, and environmental friendliness. However, only a few cathode materials have been demonstrated to achieve stable cycling for aqueous rechargeable Zn-MnO₂ batteries. Here, we report a new material consisting of hollow MnO₂ nanospheres, which can be used for aqueous Zn-MnO₂ batteries. The hollow MnO₂ nanospheres can achieve high specific capacity up to ~405 mAh g −1 at 0.5 C. More importantly, the hollow structure of birnessite-type MnO₂ enables long-term cycling stability for the aqueous Zn-MnO₂ batteries. The excellent performance of the hollow MnO₂ nanospheres should be due to their unique structural properties that enable the easy intercalation of zinc ions.

Two-stream sausage and hollowing instabilities in high-intensity particle beams

International Nuclear Information System (INIS)

Uhm, Han S.; Davidson, Ronald C.; Kaganovich, Igor

2001-01-01

Axisymmetric two-stream instabilities in high-intensity particle beams are investigated analytically by making use of the Vlasov-Maxwell equations in the smooth-focusing approximation. The eigenfunctions for the axisymmetric radial modes are calculated self-consistently in order to determine the dispersion relation describing collective stability properties. Stability properties for the sausage and hollowing modes, characterized by radial mode numbers n=1 and n=2, respectively, are investigated, and the dispersion relations are obtained for the complex eigenfrequency ω in terms of the axial wavenumber k and other system parameters. The eigenfunctions obtained self-consistently for the sausage and hollowing modes indicate that the perturbations exist only inside the beam. Therefore, the location of the conducting wall does not have an effect on stability behavior. The growth rates of the sausage and hollowing modes are of the same order of magnitude as that of the hose (dipole-mode) instability. Therefore, it is concluded that the axisymmetric sausage and hollowing instabilities may also be deleterious to intense ion beam propagation when a background component of electrons is presented

Sensitive Nonenzymatic Electrochemical Glucose Detection Based on Hollow Porous NiO

Science.gov (United States)

He, Gege; Tian, Liangliang; Cai, Yanhua; Wu, Shenping; Su, Yongyao; Yan, Hengqing; Pu, Wanrong; Zhang, Jinkun; Li, Lu

2018-01-01

Transition metal oxides (TMOs) have attracted extensive research attentions as promising electrocatalytic materials. Despite low cost and high stability, the electrocatalytic activity of TMOs still cannot satisfy the requirements of applications. Inspired by kinetics, the design of hollow porous structure is considered as a promising strategy to achieve superior electrocatalytic performance. In this work, cubic NiO hollow porous architecture (NiO HPA) was constructed through coordinating etching and precipitating (CEP) principle followed by post calcination. Being employed to detect glucose, NiO HPA electrode exhibits outstanding electrocatalytic activity in terms of high sensitivity (1323 μA mM-1 cm-2) and low detection limit (0.32 μM). The excellent electrocatalytic activity can be ascribed to large specific surface area (SSA), ordered diffusion channels, and accelerated electron transfer rate derived from the unique hollow porous features. The results demonstrate that the NiO HPA could have practical applications in the design of nonenzymatic glucose sensors. The construction of hollow porous architecture provides an effective nanoengineering strategy for high-performance electrocatalysts.

Highly efficient fluorescence sensing with hollow core photonic crystal fibers

DEFF Research Database (Denmark)

Smolka, Stephan; Barth, Michael; Benson, Oliver

2008-01-01

We investigate hollow core photonic crystal fibers for ultra-sensitive fluorescence detection by selectively infiltrating the central hole with fluorophores. Dye concentrations down to 10(-9) M can be detected using only nanoliter sample volumes.......We investigate hollow core photonic crystal fibers for ultra-sensitive fluorescence detection by selectively infiltrating the central hole with fluorophores. Dye concentrations down to 10(-9) M can be detected using only nanoliter sample volumes....

Porous hollow Co₃O₄ with rhombic dodecahedral structures for high-performance supercapacitors.

Science.gov (United States)

Zhang, Yi-Zhou; Wang, Yang; Xie, Ye-Lei; Cheng, Tao; Lai, Wen-Yong; Pang, Huan; Huang, Wei

2014-11-06

Porous hollow Co₃O₄ with rhombic dodecahedral structures were prepared by the calcination of ZIF-67 ([Co(mim)2; mim = 2-methylimidazolate]) rhombic dodecahedral microcrystals. A supercapacitor was successfully constructed by adopting the resulting porous hollow Co₃O₄ rhombic dodecahedral structure as the electrode material, which showed a large specific capacitance of 1100 F g(-1) and retained more than 95.1% of the specific capacitance after 6000 continuous charge-discharge cycles. The excellent capacitive properties and stability mark the porous hollow Co₃O₄ with the rhombic dodecahedral structure as one of the most promising electrode materials for high-performance supercapacitors.

Modeling of formation of binary-phase hollow nanospheres from metallic solid nanospheres

International Nuclear Information System (INIS)

Svoboda, J.; Fischer, F.D.; Vollath, D.

2009-01-01

Spontaneous formation of binary-phase hollow nanospheres by reaction of a metallic nanosphere with a non-metallic component in the surrounding atmosphere is observed for many systems. The kinetic model describing this phenomenon is derived by application of the thermodynamic extremal principle. The necessary condition of formation of the binary-phase hollow nanospheres is that the diffusion coefficient of the metallic component in the binary phase is higher than that of the non-metallic component (Kirkendall effect occurs in the correct direction). The model predictions of the time to formation of the binary-phase hollow nanospheres agree with the experimental observations

Synthesis of Hollow Silica by Stober Method with Double Polymers as Templates

International Nuclear Information System (INIS)

Nguyen, Anhthu; Park, Chang Woo; Kim, Sang Hern

2014-01-01

The hollow SiO 2 spheres with uniform size were synthesized by a modified stoeber method under the control of polyelectrolytes (PSS and PAA) as templates. This synthetic route includes the formation of spherical colloid micelle in ethanol solution, hydrolysis of TEOS under control of ammonia, and the removal of polyelectrolyte by washing or calcination. Hollow silica spheres with controllable core diameters between 100 and 270 nm and wall thickness between 15 and 50 nm have been synthesized. The influence of template solution concentration and solvent and dispersant on the formation of silica hollow spheres is studied and reported in detail

Fire resistance of extruded hollow-core slabs

DEFF Research Database (Denmark)

Hertz, Kristian Dahl; Giuliani, Luisa; Sørensen, Lars Schiøtt

2016-01-01

Prefabricated extruded hollow-core slabs are preferred building components for floor structures in several countries. It is therefore important to be able to document the fire resistance of these slabs proving fulfilment of standard fire resistance requirements of 60- and 120 minutes found in most...... a standard fire test and from a thorough examination of the comprehensive test documentation available on fire exposed hollow-core slabs. Mechanisms for loss of load-bearing capacity are clarified, and evidence of the fire resistance is found. For the first time the mechanisms responsible for loss of load......-bearing capacity are identified and test results and calculation approach are for the first time Applied in accordance with each other for assessment of fire resistance of the structure....

Gyrator transform of Gaussian beams with phase difference and generation of hollow beam

Science.gov (United States)

Xiao, Zhiyu; Xia, Hui; Yu, Tao; Xie, Ding; Xie, Wenke

2018-03-01

The optical expression of Gaussian beams with phase difference, which is caused by gyrator transform (GT), has been obtained. The intensity and phase distribution of transform Gaussian beams are analyzed. It is found that the circular hollow vortex beam can be obtained by overlapping two GT Gaussian beams with π phase difference. The effect of parameters on the intensity and phase distributions of the hollow vortex beam are discussed. The results show that the shape of intensity distribution is significantly influenced by GT angle α and propagation distance z. The size of the hollow vortex beam can be adjusted by waist width ω 0. Compared with previously reported results, the work shows that the hollow vortex beam can be obtained without any model conversion of the light source.

Modeling High Pressure Micro Hollow Cathode Discharges

National Research Council Canada - National Science Library

Boeuf, Jean-Pierre; Pitchford, Leanne

2004-01-01

This report results from a contract tasking CPAT as follows: The Grantee will perform theoretical modeling of point, surface, and volume high-pressure plasmas created using Micro Hollow Cathode Discharge sources...

optimizing compressive strength characteristics of hollow building

African Journals Online (AJOL)

eobe

Keywords: hollow building Blocks, granite dust, sand, partial replacement, compressive strength. 1. INTRODUCTION ... exposed to extreme climate. The physical ... Sridharan et al [13] conducted shear strength studies on soil-quarry dust.

Fabrication and Characterization of Nanoenergetic Hollow Spherical Hexanitrostibene (HNS Derivatives

Directory of Open Access Journals (Sweden)

Xiong Cao

2018-05-01

Full Text Available The spherization of nanoenergetic materials is the best way to improve the sensitivity and increase loading densities and detonation properties for weapons and ammunition, but the preparation of spherical nanoenergetic materials with high regularization, uniform size and monodispersity is still a challenge. In this paper, nanoenergetic hollow spherical hexanitrostibene (HNS derivatives were fabricated via a one-pot copolymerization strategy, which is based on the reaction of HNS and piperazine in acetonitrile solution. Characterization results indicated the as-prepared reaction nanoenergetic products were HNS-derived oligomers, where a free radical copolymerization reaction process was inferred. The hollow sphere structure of the HNS derivatives was characterized by scanning electron microscopy (SEM, transmission electron microscope (TEM, and synchrotron radiation X-ray imaging technology. The properties of the nanoenergetic hollow spherical derivatives, including thermal decomposition and sensitivity are discussed in detail. Sensitivity studies showed that the nanoenergetic derivatives exhibited lower impact, friction and spark sensitivity than raw HNS. Thermogravimetric-differential scanning calorimeter (TG-DSC results showed that continuous exothermic decomposition occurred in the whole temperature range, which indicated that nanoenergetic derivatives have a unique role in thermal applications. Therefore, nanoenergetic hollow spherical HNS derivatives could provide a new way to modify the properties of certain energetic compounds and fabricate spherical nanomaterials to improve the charge configuration.

Silicon-Encapsulated Hollow Carbon Nanofiber Networks as Binder-Free Anodes for Lithium Ion Battery

Directory of Open Access Journals (Sweden)

Ding Nan

2014-01-01

Full Text Available Silicon-encapsulated hollow carbon nanofiber networks with ample space around the Si nanoparticles (hollow Si/C composites were successfully synthesized by dip-coating phenolic resin onto the surface of electrospun Si/PVA nanofibers along with the subsequent solidification and carbonization. More importantly, the structure and Si content of hollow Si/C composite nanofibers can be effectively tuned by merely varying the concentration of dip solution. As-synthesized hollow Si/C composites show excellent electrochemical performance when they are used as binder-free anodes for Li-ion batteries (LIBs. In particular, when the concentration of resol/ethanol solution is 3.0%, the product exhibits a large capacity of 841 mAh g−1 in the first cycle, prominent cycling stability, and good rate capability. The discharge capacity retention of it was ~90%, with 745 mAh g−1 after 50 cycles. The results demonstrate that the hollow Si/C composites are very promising as alternative anode candidates for high-performance LIBs.

Nanosized aluminum nitride hollow spheres formed through a self-templating solid-gas interface reaction

International Nuclear Information System (INIS)

Zheng Jie; Song Xubo; Zhang Yaohua; Li Yan; Li Xingguo; Pu Yikang

2007-01-01

Nanosized aluminum nitride hollow spheres were synthesized by simply heating aluminum nanoparticles in ammonia at 1000 deg. C. The as-synthesized sphere shells are polycrystalline with cavity diameters ranging from 15 to 100 nm and shell thickness from 5 to 15 nm. The formation mechanism can be explained by the nanoscale Kirkendall effect, which results from the difference in diffusion rates between aluminum and nitrogen. The Al nanoparticles served as both reactant and templates for the hollow sphere formation. The effects of precursor particle size and temperature were also investigated in terms of product morphology. Room temperature cathode luminescence spectrum of the nanosized hollow spheres showed a broad emission band centered at 415 nm, which is originated from oxygen related luminescence centers. The hollow structure survived a 4-h heat treatment at 1200 deg. C, exhibiting excellent thermal stability. - Graphical abstract: Nanosized aluminum nitride hollow spheres were synthesized by nitridation of aluminum nanoparticles at 1000 deg. C using ammonia

Metallic double shell hollow nanocages: the challenges of their synthetic techniques.

Science.gov (United States)

Mahmoud, M A; El-Sayed, M A

2012-03-06

Hollow metallic nanoparticles have been attracting the attention of many researchers in the past five years due to their new properties and potential applications. The unique structure of the hollow nanoparticles; presence of two surfaces (internal and external), and the presence of both cavities and pores in the wall surfaces of these nanoparticles are responsible for their unique properties and applications. Here the galvanic replacement technique is used to prepare nanocages made of gold, platinum, and palladium. In addition, hollow double shell nanoparticles are made of two metal shells like Au-Pt, Pt-Au, Au-Pd, Pd-Au, Pd-Pt, and Pt-Pd. Silver nanocubes are used as templates during the synthesis of hollow nanoparticles with single metal shell or double shell nanocages. Most of the problems that could affect the synthesis of solid Silver nanocubes used as template as well as the double shell nanocages and their possible solutions are discussed in a detail. The sizes and shapes of the single-shell and double-shell nanocages were characterized by a regular and high-resolution TEM. A SEM mapping technique is also used to image the surface atoms for the double shell hollow nanoparticles in order to determine the thickness of the two metal shells. In addition, optical studies are used to monitor the effect of the dielectric properties of the other metals on the plasmonic properties of the gold nanoshell in these mixed nanoparticles.

Hollow volcanic tumulus caves of Kilauea Caldera, Hawaii County, Hawaii

Directory of Open Access Journals (Sweden)

William R. Halliday

1998-01-01

Full Text Available In addition to lava tube caves with commonly noted features, sizable subcrustal spaces of several types exist on the floor of Kilauea Caldera. Most of these are formed by drainage of partially stabilized volcanic structures enlarged or formed by injection of very fluid lava beneath a plastic crust. Most conspicuous are hollow tumuli, possibly first described by Walker in 1991. Walker mapped and described the outer chamber of Tumulus E-I Cave. Further exploration has revealed that it has a hyperthermic inner room beneath an adjoining tumulus with no connection evident on the surface. Two lengthy, sinuous hollow tumuli also are present in this part of the caldera. These findings support Walkers conclusions that hollow tumuli provide valuable insights into tumulus-forming mechanisms, and provide information about the processes of emplacement of pahoehoe sheet flows.

Nb2O5 hollow nanospheres as anode material for enhanced performance in lithium ion batteries

International Nuclear Information System (INIS)

Sasidharan, Manickam; Gunawardhana, Nanda; Yoshio, Masaki; Nakashima, Kenichi

2012-01-01

Graphical abstract: Nb 2 O 5 hollow nanosphere constructed electrode delivers high capacity of 172 mAh g −1 after 250 cycles and maintains structural integrity and excellent cycling stability. Highlights: ► Nb 2 O 5 hollow nanospheres synthesis was synthesized by soft-template. ► Nb 2 O 5 hollow nanospheres were investigated as anode material in Li-ion battery. ► Nanostructured electrode delivers high capacity of 172 mAh g −1 after 250 cycles. ► The electrode maintains the structural integrity and excellent cycling stability. ► Nanosized shell domain facilitates fast lithium intercalation/deintercalation. -- Abstract: Nb 2 O 5 hollow nanospheres of average diameter ca. ∼29 nm and hollow cavity size ca. 17 nm were synthesized using polymeric micelles with core–shell–corona architecture under mild conditions. The hollow particles were thoroughly characterized by transmission electron microscope (TEM), X-ray diffraction (XRD), infrared spectroscopy (FTIR), thermal (TG/DTA) and nitrogen adsorption analyses. Thus obtained Nb 2 O 5 hollow nanospheres were investigated as anode materials for lithium ion rechargeable batteries for the first time. The nanostructured electrode delivers high capacity of 172 mAh g −1 after 250 cycles of charge/discharge at a rate of 0.5 C. More importantly, the hollow particles based electrodes maintains the structural integrity and excellent cycling stability even after exposing to high current density 6.25 A g −1 . The enhanced electrochemical behavior is ascribed to hollow cavity coupled with nanosized Nb 2 O 5 shell domain that facilitates fast lithium intercalation/deintercalation kinetics.

Low-Loss Hollow-Core Anti-Resonant Fibers With Semi-Circular Nested Tubes

DEFF Research Database (Denmark)

Habib, Selim; Bang, Ole; Bache, Morten

2016-01-01

Hollow-core fibers with a single ring of circular antiresonant tubes as the cladding provide a simple way of getting a negative-curvature hollow core, resulting in broadband low-loss transmission with little power overlap in the glass. These fibers show a significant improvement in loss performan...

Sweep gas membrane distillation in a membrane contactor with metallic hollow fibers

NARCIS (Netherlands)

Shukla, Sushumna; Benes, Nieck Edwin; Vankelecom, I.F.J.; Mericq, J.P.; Belleville, M.P.; Hengl, N.; Sanchez Marcano, Jose

2015-01-01

This work revolves around the use of porous metal hollow fibers in membrane distillation. Various stages are covered, starting from membrane synthesis up to the testing of a pilot scale membrane module. Mechanically stable metal hollow fibers have been synthesized by phase inversion of a stainless

The Legend of Sleepy Hollow

Institute of Scientific and Technical Information of China (English)

Washington; Irving

1987-01-01

Part Ⅰ On the Eastern shore of the Hudson River there was a little valley, among high hills, which was one of the quietest places in the whole world. This little valley had long been known by the name of SIeepy Hollow. Many strange stories about ghosts were told and retold in the village situated there.

Numerical simulation of the sustaining discharge in radio frequency hollow cathode discharge in argon

Energy Technology Data Exchange (ETDEWEB)

Jiang, Xin-Xian; He, Feng, E-mail: hefeng@bit.edu.cn; Ouyang, Ji-Ting [School of Physics, Beijing Institute of Technology, Beijing 100081 (China); Chen, Qiang, E-mail: lppmchenqiang@hotmail.com; Ge, Teng [Laboratory of Plasma Physics and Materials, Beijing Institute of Graphic Communication, Beijing 10081 (China)

2014-03-15

In this paper, a two-dimensional fluid model was developed to study the radio frequency (RF) hollow cathode discharge (HCD) in argon at 1 Torr. The evolutions of the particle density distribution and the ionization rate distribution in RF HCD at 13.56 MHz indicate that the discharge mainly occurs inside the hollow cathode. The spatio-temporal distributions of the ionization rate and the power deposition within the hollow cathode imply that sheath oscillation heating is the primary mechanism to sustain the RF HCD, whereas secondary electron emission plays a negligible role. However, as driving frequency decreases, secondary electron heating becomes a dominant mechanism to sustain the discharge in RF hollow cathode.

Hollow-Fiber Spacesuit Water Membrane Evaporator

Science.gov (United States)

Bue, Grant; Trevino, Luis; Tsioulos, Gus; Mitchell, Keith; Settles, Joseph

2013-01-01

The hollow-fiber spacesuit water membrane evaporator (HoFi SWME) is being developed to perform the thermal control function for advanced spacesuits and spacecraft to take advantage of recent advances in micropore membrane technology in providing a robust, heat-rejection device that is less sensitive to contamination than is the sublimator. After recent contamination tests, a commercial-off-the-shelf (COTS) micro porous hollow-fiber membrane was selected for prototype development as the most suitable candidate among commercial hollow-fiber evaporator alternatives. An innovative design that grouped the fiber layers into stacks, which were separated by small spaces and packaged into a cylindrical shape, was developed into a full-scale prototype for the spacesuit application. Vacuum chamber testing has been performed to characterize heat rejection as a function of inlet water temperature and water vapor back-pressure, and to show contamination resistance to the constituents expected to be found in potable water produced by the wastewater reclamation distillation processes. Other tests showed tolerance to freezing and suitability to reject heat in a Mars pressure environment. In summary, HoFi SWME is a lightweight, compact evaporator for heat rejection in the spacesuit that is robust, contamination- insensitive, freeze-tolerant, and able to reject the required heat of spacewalks in microgravity, lunar, and Martian environments. The HoFi is packaged to reject 810 W of heat through 800 hours of use in a vacuum environment, and 370 W in a Mars environment. The device also eliminates free gas and dissolved gas from the coolant loop.

New Strategies for Constructing Polymeric Micelles and Hollow Spheres Via Self-Assembly

Institute of Scientific and Technical Information of China (English)

Ming Jiang

2005-01-01

@@ 1Introduction In recent years, self-assembly of block copolymers leading to micelles in selective solvents, which dissolve only one of the blocks, has developed rapidly because the micelles are very strong candidates for potential applications in advanced technologies. The micelles usually have core-shell structure which are connected by covalent bonds. Based on our long-term research on interpolymer complexation due to hydrogen bonding, where we noticed that the complexation often led to the formation of irregular aggregates, we succeeded recently in developing a series of new approaches to polymeric micelles and hollow spheres via specific intermolecular interactions. As in these approaches, a variety of polymers with interacting groups i.e. homopolymers, random copolymers, graft copolymers as well as low mass compounds (LMC), can be used as building blocks, our research strategies have substantially extended the field of self-assembly.

Optical trapping and control of nanoparticles inside evacuated hollow core photonic crystal fibers

Energy Technology Data Exchange (ETDEWEB)

Grass, David, E-mail: david.grass@univie.ac.at; Fesel, Julian; Hofer, Sebastian G.; Kiesel, Nikolai; Aspelmeyer, Markus, E-mail: markus.aspelmeyer@univie.ac.at [Vienna Center for Quantum Science and Technology (VCQ), Faculty of Physics, University of Vienna, A-1090 Vienna (Austria)

2016-05-30

We demonstrate an optical conveyor belt for levitated nanoparticles over several centimeters inside both air-filled and evacuated hollow-core photonic crystal fibers (HCPCF). Detection of the transmitted light field allows three-dimensional read-out of the particle center-of-mass motion. An additional laser enables axial radiation pressure based feedback cooling over the full fiber length. We show that the particle dynamics is a sensitive local probe for characterizing the optical intensity profile inside the fiber as well as the pressure distribution along the fiber axis. In contrast to some theoretical predictions, we find a linear pressure dependence inside the HCPCF, extending over three orders of magnitude from 0.2 mbar to 100 mbar. A targeted application is the controlled delivery of nanoparticles from ambient pressure into medium vacuum.

Hollow organ perforation in blunt abdominal trauma: the role of diagnostic peritoneal lavage.

Science.gov (United States)

Wang, Yu-Chun; Hsieh, Chi-Hsun; Fu, Chih-Yuan; Yeh, Chun-Chieh; Wu, Shih-Chi; Chen, Ray-Jade

2012-05-01

With recent advances in radiologic diagnostic procedures, the use of diagnostic peritoneal lavage (DPL) has markedly declined. In this study, we reviewed data to reevaluate the role of DPL in the diagnosis of hollow organ perforation in patients with blunt abdominal trauma. Adult patients who had sustained blunt abdominal trauma and who were hemodynamically stable after initial resuscitation underwent an abdominal computed tomographic (CT) scan. Diagnostic peritoneal lavage was performed for patients who were indicated to receive nonoperative management and where hollow organ perforation could not be ruled out. During a 60-month period, 64 patients who had received abdominal CT scanning underwent DPL. Nineteen patients were diagnosed as having a positive DPL based on cell count ratio of 1 or higher. There were 4 patients who sustained small bowel perforation. The sensitivity and specificity of the cell count ratio for a hollow organ perforation in this study were 100% and 75%, respectively. No missed hollow organ perforations were detected. For patients with blunt abdominal trauma and hemoperitoneum who plan to receive nonoperative management, DPL is still a useful tool to exclude hollow organ perforation that is undetected by CT. Copyright © 2012 Elsevier Inc. All rights reserved.

MoS2 coated hollow carbon spheres for anodes of lithium ion batteries

International Nuclear Information System (INIS)

Zhang, Yufei; Wang, Ye; Shi, Wenhui; Yang, Huiying; Yang, Jun; Huang, Wei; Dong, Xiaochen

2016-01-01

With the assistance of resorcinol–formaldehyde, MoS 2 coated hollow carbon spheres (C@MoS 2 ) were synthesized through a facile hydrothermal route followed by heat and alkali treatments. The measurements indicate that the hollow carbon spheres with an average diameter of 300 nm and shell thickness of 20 nm. And the hollow core are uniformly covered by ultrathin MoS 2 nanosheets with a length increased to 400 nm. The unique hollow structure and the synergistic effect between carbon layer and MoS 2 nanosheets significantly enhance the rate capability and electrochemical stability of C@MoS 2 spheres as anode material of lithium-ion battery. The synthesized C@MoS 2 delivered a capacity of 750 mAh g −1 at a current density of 100 mA g −1 . More importantly, the C@MoS 2 maintained a reversible capacity of 533 mAh g −1 even at a high current density of 1000 mA g −1 . The study indicated that MoS 2 coated hollow carbon spheres can be promising anode material for next generation high-performance lithium-ion batteries. (paper)

Study on surface adhesion of Plasma modified Polytetrafluoroethylene hollow fiber membrane

Science.gov (United States)

Chen, Jiangrong; Zhang, Huifeng; Liu, Guochang; Guo, Chungang; Lv, Jinglie; Zhangb, Yushan

2018-01-01

Polytetrafluoroethylene (PTFE) is popular membrane material because of its excellent thermal stability, chemical stability and mechanical stability. However, the low surface energy and non-sticky property of PTFE present challenges for modification. In the present study, plasma treatment was performed to improve the surface adhesion of PTFE hollow fiber membrane. The effect of discharge voltage, treatment time on the adhesion of PTFE hollow fiber membrane was symmetrically evaluated. Results showed that the plasma treatment method contributed to improve the surface activity and roughness of PTFE hollow fiber membrane, and the adhesion strength depend significantly on discharge voltage, which was beneficial to seepage pressure of PTFE hollow fiber membrane module. The adhesion strength of PTFE membrane by plasma treated at 220V for 3min reached as high as 86.2 N, far surpassing the adhesion strength 12.7 N of pristine membrane. Furthermore, improvement of content of free radical and composition analysis changes of the plasma modified PTFE membrane were investigated. The seepage pressure of PTFE membrane by plasma treated at 220V for 3min was 0.375 MPa, which means that the plasma treatment is an effective technique to improve the adhesion strength of membrane.

Surface functionalized hollow silica particles and composites

KAUST Repository

Rodionov, Valentin

2017-05-26

Composition comprising hollow spherical silica particles having outside particle walls and inside particle walls, wherein the particles have an average particle size of about 10 nm to about 500 nm and an average wall thickness of about 10 nm to about 50 nm; and wherein the particles are functionalized with at least one organic functional group on the outside particle wall, on the inside particle wall, or on both the outside and inside particle walls, wherein the organic functional group is in a reacted or unreacted form. The organic functional group can be epoxy. The particles can be mixed with polymer precursor or a polymer material such as epoxy to form a prepreg or a nanocomposite. Lightweight but strong materials can be formed. Low loadings of hollow particles can be used.

Surface functionalized hollow silica particles and composites

KAUST Repository

Rodionov, Valentin; Khanh, Vu Bao

2017-01-01

Composition comprising hollow spherical silica particles having outside particle walls and inside particle walls, wherein the particles have an average particle size of about 10 nm to about 500 nm and an average wall thickness of about 10 nm to about 50 nm; and wherein the particles are functionalized with at least one organic functional group on the outside particle wall, on the inside particle wall, or on both the outside and inside particle walls, wherein the organic functional group is in a reacted or unreacted form. The organic functional group can be epoxy. The particles can be mixed with polymer precursor or a polymer material such as epoxy to form a prepreg or a nanocomposite. Lightweight but strong materials can be formed. Low loadings of hollow particles can be used.

Low Loss and Highly Birefringent Hollow-Core Photonic Crystal Fiber

DEFF Research Database (Denmark)

Roberts, P. John; Williams, D.P.; Mangan, Brian J.

2006-01-01

A hollow-core photonic crystal fiber design is proposed which enables both low-loss and polarization-maintained signal propagation. The design relies on an arrangement of antiresonant features positioned on the glass ring that surrounds the air core.......A hollow-core photonic crystal fiber design is proposed which enables both low-loss and polarization-maintained signal propagation. The design relies on an arrangement of antiresonant features positioned on the glass ring that surrounds the air core....

All-Silica Hollow-Core Microstructured Bragg Fibers for Biosensor Application

DEFF Research Database (Denmark)

Passaro, Davide; Foroni, Matteo; Poli, Federica

2008-01-01

The possibility to exploit all-silica hollow-core-microstructured Bragg fibers to realize a biosensor useful to detect the DNA hybridization process has been investigated. A Bragg fiber recently fabricated has been considered for the analysis performed by means of a full-vector modal solver based...... layer on the inner surface of the fiber holes can modify the fundamental mode properties. The numerical analysis results have successfully demonstrated the DNA bio-sensor feasibility in hollow-core Bragg fibers....

Fabrication and characterization of functionally graded poly(vinylidine fluoride)-silver nanocomposite hollow fibers for sustainable water recovery

KAUST Repository

Francis, Lijo

2014-12-01

Poly(vinylidine fluoride) (PVDF) asymmetric hydrophobic hollow fibers were fabricated successfully using dryjet wet spinning. Hydrophobic silver nanoparticles were synthesized and impregnated into the PVDF polymer matrix and functionally graded PVDF-silver nanocomposite hollow fibers are fabricated and tested in the direct contact membrane distillation (DCMD) process. The as-synthesized silver nanoparticles were characterized for Transmission Electron Microscopy (TEM), particle size distribution (PSD) and Ultra Violet (UV) visible spectroscopy. Both the PVDF and PVDF-silver nanocomposite asymmetric hollow fibers were characterized for their morphology, water contact angle and mechanical strength. Addition of hydrophobic silver nanoparticles was found to enhance the hydrophobicity and ~ 2.5 fold increase the mechanical strength of the hollow fibers. A water vapor flux of 31.9kg m-2 h-1 was observed at a feed inlet temperature of 80 °C and at a permeate temperature of 20 °C in the case of hollow fiber membrane modules fabricated using PVDF hollow fibers; the water vapor flux was found to be increased by about 8% and to reach 34.6kg m-2 h-1 for the hollow fiber membrane modules fabricated from the PVDF-silver nanocomposite hollow fibers at the same operating conditions with 99.99% salt rejection.

Management of maxillectomy defect with a hybrid hollow bulb obturator

Science.gov (United States)

Singh, Kamleshwar; Singh, Saumyendra V; Mishra, Niraj; Agrawal, Kaushal Kishor

2013-01-01

A woman having already undergone maxillectomy came to the department complaining of difficulty in eating and speech. During the construction of an obturator, the bulb area should be hollowed to reduce weight so that the teeth and supporting tissues are not stressed unnecessarily. The conventional open design drains fluid from the adjacent mucosa, possibly increasing the weight of the prosthesis, and is difficult to clean. The closed bulb design does not drain secretions and may cause obstruction and susceptibility to infection in the paranasal and pharyngeal regions, though it is easier to maintain. An alternative to the two designs, combining their advantages, is presented in this report. As the open hollow part of the obturator was shallow, it was easy to clean. Making the inferior part of the bulb hollow and closed led to a reduction in the overall weight of the prosthesis while increasing its resonance. PMID:23436886

Template free fabrication of hollow hematite spheres via a one-pot polyoxometalate-assisted hydrolysis process

International Nuclear Information System (INIS)

Mao Baodong; Kang Zhenhui; Wang Enbo; Tian Chungui; Zhang Zhiming; Wang Chunlei; Song Yanli; Li Meiye

2007-01-01

Uniform hollow hematite (α-Fe 2 O 3 ) spheres with diameter of about 600-700 nm and shell thickness lower than 100 nm are obtained by direct hydrothermal treatment of dilute FeCl 3 and tungstophosphoric acid H 3 PW 12 O 40 solution at 180 deg. C. The hollow spheres are composed of robust shells with small nanoparticles standing out of the surface and present a high-surface area and a weak ferromagnetic behavior at room temperature. The effect of concentration of H 3 PW 12 O 40 , reaction time and temperature for the formation of the hollow spheres are investigated in series of experiments. The formation of the hollow spheres may be ascribed to a polyoxometalte-assisted forced hydrolysis and dissolution process. - Graphical abstract: Uniform hollow hematite (α-Fe 2 O 3 ) spheres with diameter of about 600-700 nm and shell thickness lower than 100 nm are obtained by direct hydrothermal treatment of dilute FeCl 3 and tungstophosphoric acid H 3 PW 12 O 40 solution at 180 deg. C. The hollow spheres present a high surface area and weak ferromagnetic behavior at room temperature

Formation and characterization of magnetic barium ferrite hollow fibers with low coercivity via co-electrospun

Energy Technology Data Exchange (ETDEWEB)

Liu, Gui-fang, E-mail: guifang777@163.com; Zhang, Zi-dong, E-mail: 1986zzd@163.com; Dang, Feng, E-mail: dangfeng@sdu.edu.cn; Cheng, Chuan-bing, E-mail: 807033063@qq.com; Hou, Chuan-xin, E-mail: 710313782@qq.com; Liu, Si-da, E-mail: superliustar@hotmail.com

2016-08-15

BaFe{sub 12}O{sub 19} fibers and hollow fibers were successfully prepared by electrospun and co-electrospun. A very interesting result appeared in this study that hollow fibers made by co-electrospun showed low coercivity values of a few hundred oersteds, compared with the coercivity values of more than thousand oersteds for the fibers made by electrospun. So the hollow fibers with high saturation magnetization (M{sub s}) and while comparatively low coercivity (H{sub c}) exhibited strong magnetism and basically showed soft character. And this character for hollow fibers will lead to increase of the permeability for the samples which is favorable for impedance matching in microwave absorption. So these hollow fibers are promised to have use in a number of applications, such as switching and sensing applications, electromagnetic materials, microwave absorber. - Highlights: • BaFe{sub 12}O{sub 19} fibers were prepared via electrospinning successfully. • The coercivity has a value of a few hundred oersteds for the hollow fibers made by coaxial electrospun. • BaFe{sub 12}O{sub 19} with high saturation magnetization and low coercivity shows great potential in microwave absorbing application.

Emission characteristics of laser ablation-hollow cathode glow discharge spectral source

Directory of Open Access Journals (Sweden)

Karatodorov Stefan

2014-11-01

Full Text Available The emission characteristics of a scheme combining laser ablation as sample introduction source and hollow cathode discharge as excitation source are presented. The spatial separation of the sample material introduction by laser ablation and hollow cathode excitation is achieved by optimizing the gas pressure and the sample-cathode gap length. At these conditions the discharge current is maximized to enhance the analytical lines intensity.

THE NATURAL ENVIRONMENT OF THE UBSUNUR HOLLOW AND ITS ANTHROPOGENIC CONDITIONALITY

Directory of Open Access Journals (Sweden)

T. N. Prudnikova

2017-06-01

Full Text Available Research of the early historical epochs anthropogenic activity impact on the environment proves its influence on ecosystems dynamics and its substantial role in changing natural and climatic conditions. Methods and results. With the help of remote sensing (deciphering space images (Google resources, free access and landscape observations on the area of Ubsunur Hollow, one of the largest arid hollows of Central Asia, in the neighbourhood of the Agar-Dag range numerous tracks of irrigation agriculture have been found. The absence of fresh water continuous supply in the area of ancient irrigation presupposes milder climatic conditions and the presence of forest flora maintaining the level of ground waters in the past. The presence of forest steppe landscapes on arid areas of Ubsunur Hollow in the recent past has been proved by the results of paleobotanic research on ancient agroirrigation landscapes to the south-west of Lake Shara Nur in the Upper Naryin Gol River. Conclusion. A big number of land allotments found in north-eastern part of Ubsunur Hollow near the Agar-Dag range (Lake Shara Nur allows us to speak about significant water reserves (and forestry area of this territory as well as about a big number of people living there in early epochs and who needed fuel, wood as a source of construction materials, etc., consequently forests were destroyed. They were also being destroyed during numerous wars: Central Asia is the region of constant battles between western and eastern civilizations. The conducted research proves the presence of forest flora (spruce-larch-grass-sedge communities, steppificated pine forests in the Late Quaternary period in the central part of Ubsunur Hollow on the area which is now deserted. The most probable reason of desertisation of the area is destruction of the forest. Forest devastation is the major reason of landscape degradation not only of Ubsunur Hollow but also of the whole steppe Asian belt.

Compact and Robust Refilling and Connectorization of Hollow Core Photonic Crystal Fiber Gas Reference Cells

Science.gov (United States)

Poberezhskiy, Ilya Y.; Meras, Patrick; Chang, Daniel H.; Spiers, Gary D.

2007-01-01

This slide presentation reviews a method for refilling and connectorization of hollow core photonic crystal fiber gas reference cells. Thees hollow-core photonic crystal fiber allow optical propagation in air or vacuum and are for use as gas reference cell is proposed and demonstrated. It relies on torch-sealing a quartz filling tube connected to a mechanical splice between regular and hollow-core fibers.

Solvent-free synthesis of nanosized hierarchical sodalite zeolite with a multi-hollow polycrystalline structure

KAUST Repository

Zeng, Shangjing; Wang, Runwei; Li, Ang; Huang, Weiwei; Zhang, Zongtao; Qiu, Shilun

2016-01-01

A solvent-free route is developed for preparing nanoscale sodalite zeolite with a multi-hollow structure. Furthermore, the synthesis of nanosized hollow sodalite polycrystalline aggregates with a mesoporous structure and high crystallinity

Porous hollow Co3O4 with rhombic dodecahedral structures for high-performance supercapacitors

Science.gov (United States)

Zhang, Yi-Zhou; Wang, Yang; Xie, Ye-Lei; Cheng, Tao; Lai, Wen-Yong; Pang, Huan; Huang, Wei

2014-11-01

Porous hollow Co3O4 with rhombic dodecahedral structures were prepared by the calcination of ZIF-67 ([Co(mim)2; mim = 2-methylimidazolate]) rhombic dodecahedral microcrystals. A supercapacitor was successfully constructed by adopting the resulting porous hollow Co3O4 rhombic dodecahedral structure as the electrode material, which showed a large specific capacitance of 1100 F g-1 and retained more than 95.1% of the specific capacitance after 6000 continuous charge-discharge cycles. The excellent capacitive properties and stability mark the porous hollow Co3O4 with the rhombic dodecahedral structure as one of the most promising electrode materials for high-performance supercapacitors.Porous hollow Co3O4 with rhombic dodecahedral structures were prepared by the calcination of ZIF-67 ([Co(mim)2; mim = 2-methylimidazolate]) rhombic dodecahedral microcrystals. A supercapacitor was successfully constructed by adopting the resulting porous hollow Co3O4 rhombic dodecahedral structure as the electrode material, which showed a large specific capacitance of 1100 F g-1 and retained more than 95.1% of the specific capacitance after 6000 continuous charge-discharge cycles. The excellent capacitive properties and stability mark the porous hollow Co3O4 with the rhombic dodecahedral structure as one of the most promising electrode materials for high-performance supercapacitors. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr04782f

Electrodepositing of Au on hollow PS micro-spheres

International Nuclear Information System (INIS)

Sun Jingyuan; Zhang Yunwang; Du Kai; Wan Xiaobo; Xiao Jiang; Zhang Wei; Zhang Lin; Chen Jing

2010-01-01

Using the self-regulating new micro-sphere electrodepositing device, the techniques of electrodepositing gold on hollow PS micro-spheres were established. The experiment was carried out under the following conditions: voltage was about 0.7 ∼ 0.8 V, current density was 2.0 mA · cm -2 , the temperature was 45 degree C, cathode rotating rate was 250 r · min -1 , flow rate of the solution was 7 mL · min -1 · cm -2 . Hollow gold-plated micro-spheres were prepared with well spherical symmetry, uniform thickness and surface smoothness under 500 nm. The speed of the gold depositing was 6 μm · h -1 . (authors)

Molecular motor transport through hollow nanowires

DEFF Research Database (Denmark)

Lard, Mercy; Ten Siethoff, Lasse; Generosi, Johanna

2014-01-01

-driven motion of fluorescent probes (actin filaments) through 80 nm wide, Al2O 3 hollow nanowires of micrometer length. The motor-driven transport is orders of magnitude faster than would be possible by passive diffusion. The system represents a necessary element for advanced devices based on gliding assays...

Nanotubes within transition metal silicate hollow spheres: Facile preparation and superior lithium storage performances

Energy Technology Data Exchange (ETDEWEB)

Zhang, Fan; An, Yongling; Zhai, Wei; Gao, Xueping [Key Laboratory for Liquid–Solid Structural Evolution & Processing of Materials (Ministry of Education), Jinan 250100 (China); Feng, Jinkui, E-mail: jinkui@sdu.edu.cn [Key Laboratory for Liquid–Solid Structural Evolution & Processing of Materials (Ministry of Education), Jinan 250100 (China); Ci, Lijie [Key Laboratory for Liquid–Solid Structural Evolution & Processing of Materials (Ministry of Education), Jinan 250100 (China); Xiong, Shenglin [School of Materials Science and Engineering, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100 (China)

2015-10-15

Highlights: • The hollow Co{sub 2}SiO{sub 4}, MnSiO{sub 3} and CuSiO{sub 3} were successfully prepared by a facile hydrothermal method using SiO{sub 2} nanosphere. • The hollow Co{sub 2}SiO{sub 4}, MnSiO{sub 3} and CuSiO{sub 3} were tested as anode materials for lithium batteries. • The hollow Co{sub 2}SiO{sub 4}, MnSiO{sub 3} and CuSiO{sub 3} delivered superior electrochemical performance. • The lithium storage mechanism is probe via cyclic voltammetry and XPS. - Abstract: A series of transition metal silicate hollow spheres, including cobalt silicate (Co{sub 2}SiO{sub 4}), manganese silicate (MnSiO{sub 3}) and copper silicate (CuSiO{sub 3}.2H{sub 2}O, CuSiO{sub 3} as abbreviation in the text) were prepared via a simple and economic hydrothermal method by using silica spheres as chemical template. Time-dependent experiments confirmed that the resultants formed a novel type of hierarchical structure, hollow spheres assembled by numerous one-dimensional (1D) nanotubes building blocks. For the first time, the transition metal silicate hollow spheres were characterized as novel anode materials of Li-ion battery, which presented superior lithium storage capacities, cycle performance and rate performance. The 1D nanotubes assembly and hollow interior endow this kind of material facilitate fast lithium ion and electron transport and accommodate the big volume change during the conversion reactions. Our study shows that low-cost transition metal silicate with rationally designed nanostructures can be promising anode materials for high capacity lithium-ion battery.

3D hollow nanostructures as building blocks for multifunctional plasmonics

KAUST Repository

De Angelis, Francesco De; Malerba, Mario; Patrini, Maddalena; Miele, Ermanno; Das, Gobind; Toma, Andrea; Proietti Zaccaria, Remo; Di Fabrizio, Enzo M.

2013-01-01

We present an advanced and robust technology to realize 3D hollow plasmonic nanostructures which are tunable in size, shape, and layout. The presented architectures offer new and unconventional properties such as the realization of 3D plasmonic hollow nanocavities with high electric field confinement and enhancement, finely structured extinction profiles, and broad band optical absorption. The 3D nature of the devices can overcome intrinsic difficulties related to conventional architectures in a wide range of multidisciplinary applications. © 2013 American Chemical Society.

3D hollow nanostructures as building blocks for multifunctional plasmonics

KAUST Repository

De Angelis, Francesco De

2013-08-14

We present an advanced and robust technology to realize 3D hollow plasmonic nanostructures which are tunable in size, shape, and layout. The presented architectures offer new and unconventional properties such as the realization of 3D plasmonic hollow nanocavities with high electric field confinement and enhancement, finely structured extinction profiles, and broad band optical absorption. The 3D nature of the devices can overcome intrinsic difficulties related to conventional architectures in a wide range of multidisciplinary applications. © 2013 American Chemical Society.

Breaking the glass ceiling: hollow OmniGuide fibers

Science.gov (United States)

Johnson, Steven G.; Ibanescu, Mihai; Skorobogatiy, Maksim A.; Weisberg, Ori; Engeness, Torkel D.; Soljacic, Marin; Jacobs, Steven A.; Joannopoulos, John D.; Fink, Yoel

2002-04-01

We argue that OmniGuide fibers, which guide light within a hollow core by concentric multilayer films having the property of omnidirectional reflection, have the potential to lift several physical limitations of silica fibers. We show how the strong confinement in OmniGuide fibers greatly suppresses the properties of the cladding materials: even if highly lossy and nonlinear materials are employed, both the intrinsic losses and nonlinearities of silica fibers can be surpassed by orders of magnitude. This feat, impossible to duplicate in an index-guided fiber with existing materials, would open up new regimes for long-distance propagation and dense wavelength-division multiplexing (DWDM). The OmniGuide-fiber modes bear a strong analogy to those of hollow metallic waveguides; from this analogy, we are able to derive several general scaling laws with core radius. Moreover, there is strong loss discrimination between guided modes, depending upon their degree of confinement in the hollow core: this allows large, ostensibly multi-mode cores to be used, with the lowest-loss TE01 mode propagating in an effectively single-mode fashion. Finally, because this TE01 mode is a cylindrically symmetrical ('azimuthally' polarized) singlet state, it is immune to polarization-mode dispersion (PMD), unlike the doubly-degenerate linearly-polarized modes in silica fibers that are vulnerable to birefringence.

Determination of corrosion potential of coated hollow spheres

International Nuclear Information System (INIS)

Fedorkova, Andrea; Orinakova, Renata; Orinak, Andrej; Dudrova, Eva; Kupkova, Miriam; Kalavsky, Frantisek

2008-01-01

Copper hollow spheres were created on porous iron particles by electro-less deposition. The consequent Ni plating was applied to improve the mechanical properties of copper hollow micro-particles. Corrosion properties of coated hollow spheres were investigated using potentiodynamic polarisation method in 1 mol dm -3 NaCl solution. Surface morphology and composition were studied by scanning electron microscopy (SEM), light microscopy (LM) and energy-dispersive X-ray spectroscopy (EDX). Original iron particles, uncoated copper spheres and iron particles coated with nickel were studied as the reference materials. The effect of particle composition, particularly Ni content on the corrosion potential value was investigated. The results indicated that an increase in the amount of Ni coating layer deteriorated corrosion resistivity of coated copper spheres. Amount of Ni coating layer depended on conditions of Ni electrolysis, mainly on electrolysis time and current intensity. Corrosion behaviour of sintered particles was also explored by potentiodynamic polarisation experiments for the sake of comparison. Formation of iron rich micro-volumes on the particle surface during sintering caused the corrosion potential shift towards more negative values. A detailed study of the morphological changes between non-sintered and sintered micro-particles provided explanation of differences in corrosion potential (E corr )

Fabrication of Polyacrylonitrile Hollow Fiber Membranes from Ionic Liquid Solutions

KAUST Repository

Kim, Dooli; Moreno Chaparro, Nicolas; Nunes, Suzana Pereira

2015-01-01

The interest in green processes and products has increased to reduce the negative impact of many industrial processes to the environment. Solvents, which play a crucial role in the fabrication of membranes, need to be replaced by sustainable and less toxic solvent alternatives for commonly used polymers. The purpose of this study is the fabrication of greener hollow fiber membranes based on polyacrylonitrile (PAN), substituting dimethylformamide (DMF) by less toxic mixtures of ionic liquids (IL) and dimethylsulfoxide (DMSO). A thermodynamic analysis was conducted, estimating the Gibbs free energy of mixing to find the most convenient solution compositions. Hollow fiber membranes were manufactured and optimized. As a result, a uniform pattern and high porosity were observed in the inner surface of the membranes prepared from the ionic liquid solutions. The membranes were coated with a polyamide layer by interfacial polymerization the hollow fiber membranes were applied in forward osmosis experiments by using sucrose solutions as draw solution.

Hierarchical VOOH hollow spheres for symmetrical and asymmetrical supercapacitor devices

Science.gov (United States)

Jing, Xuyang; Wang, Cong; Feng, Wenjing; Xing, Na; Jiang, Hanmei; Lu, Xiangyu; Zhang, Yifu; Meng, Changgong

2018-01-01

Hierarchical VOOH hollow spheres with low crystallinity composed of nanoparticles were prepared by a facile and template-free method, which involved a precipitation of precursor microspheres in aqueous solution at room temperature and subsequent hydrothermal reaction. Quasi-solid-state symmetric and asymmetric supercapacitor (SSC and ASC) devices were fabricated using hierarchical VOOH hollow spheres as the electrodes, and the electrochemical properties of the VOOH//VOOH SSC device and the VOOH//AC ASC device were studied by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS). Results demonstrated that the electrochemical performance of the VOOH//AC ASC device was better than that of the VOOH//VOOH SSC device. After 3000 cycles, the specific capacitance of the VOOH//AC ASC device retains 83% of the initial capacitance, while the VOOH//VOOH SSC device retains only 7.7%. Findings in this work proved that hierarchical VOOH hollow spheres could be a promising candidate as an ideal electrode material for supercapacitor devices.

Fabrication of Polyacrylonitrile Hollow Fiber Membranes from Ionic Liquid Solutions

KAUST Repository

Kim, Dooli

2015-10-08

The interest in green processes and products has increased to reduce the negative impact of many industrial processes to the environment. Solvents, which play a crucial role in the fabrication of membranes, need to be replaced by sustainable and less toxic solvent alternatives for commonly used polymers. The purpose of this study is the fabrication of greener hollow fiber membranes based on polyacrylonitrile (PAN), substituting dimethylformamide (DMF) by less toxic mixtures of ionic liquids (IL) and dimethylsulfoxide (DMSO). A thermodynamic analysis was conducted, estimating the Gibbs free energy of mixing to find the most convenient solution compositions. Hollow fiber membranes were manufactured and optimized. As a result, a uniform pattern and high porosity were observed in the inner surface of the membranes prepared from the ionic liquid solutions. The membranes were coated with a polyamide layer by interfacial polymerization the hollow fiber membranes were applied in forward osmosis experiments by using sucrose solutions as draw solution.

High-power picosecond pulse delivery through hollow core photonic band gap fibers

DEFF Research Database (Denmark)

Michieletto, Mattia; Johansen, Mette Marie; Lyngsø, Jens Kristian

2015-01-01

We demonstrated robust and bend insensitive fiber delivery of high power pulsed laser with diffraction limited beam quality for two different kind of hollow core photonic band gap fibers......We demonstrated robust and bend insensitive fiber delivery of high power pulsed laser with diffraction limited beam quality for two different kind of hollow core photonic band gap fibers...

Multilayered pyramidal dissolving microneedle patches with flexible pedestals for improving effective drug delivery.

Science.gov (United States)

Lau, Shinying; Fei, Jie; Liu, Haoran; Chen, Weixing; Liu, Ran

2017-11-10

Dissolving microneedles have been employed as a safe and convenient transdermal delivery system for drugs and vaccines. To improve effective drug delivery, a multilayered pyramidal dissolving microneedle patch, composed of silk fibroin tips with the ability of robust mechanical strength, rapid dissolution and drug release supported on a flexible polyvinyl alcohol (PVA) pedestal is reported. To show the utility of this approach the ability of the fabricated microneedles to deliver insulin is demonstrated. The dissolving microneedles have sufficient mechanical strength to be inserted into abdomen skin of mice to a depth of approximately 150μm, and release their encapsulated insulin into the skin to cause a hypoglycemic effect. The fabrication of microneedles avoids high temperature which benefits storage stability at room temperature for 20d. This result indicates >99.4% of insulin remained in the microneedles. In comparison to traditional needle-based administration, the proposed multilayered pyramidal dissolving microneedle patches enable self-administration, miniaturization, pain-free administration, drug delivery and drug stability, all being important features in needle free drug delivery. Copyright © 2016 Elsevier B.V. All rights reserved.

Ag/α-Fe2O3 hollow microspheres: Preparation and application for hydrogen peroxide detection

Science.gov (United States)

Kang, Xinyuan; Wu, Zhiping; Liao, Fang; Zhang, Tingting; Guo, Tingting

2015-09-01

In this paper, we demonstrated a simple approach for preparing α-Fe2O3 hollow spheres by mixing ferric nitrate aqueous and glucose in 180 °C. The glucose was found to act as a soft template in the process of α-Fe2O3 hollow spheres formation. Ag/α-Fe2O3 hollow nanocomposite was obtained under UV irradiation without additional reducing agents or initiators. Synthesized Ag/α-Fe2O3 hollow composites exhibited remarkable catalytic performance toward H2O2 reduction. The electrocatalytic activity mechanism of Ag/α-Fe2O3/GCE were discussed toward the reduction of H2O2 in this paper.

Preparation of carbon nanotubes/epoxy resin composites by using hollow glass beads as the carrier

International Nuclear Information System (INIS)

Wu, X.F.; Zhao, Y.K.; Zhang, D.; Chen, T.B.; Ma, L.Y.

2012-01-01

Hollow glass beads had been utilized as the carrier to assist dispersion of carbon nanotubes in epoxy resin. Hollow glass beads were firstly aminated with gamma-aminopropyl-triethoxysilane, sencondly reacted with carboxyl-functionalized carbon nanotubes via an amidation reaction and susequently mixed with epoxy resin and hardener. The experimental results showed that carbon nanotubes could be loaded on the surfaces of hollow glass beads and approximately a monolayer of carbon nanotubes was formed when the weight ratio of hollow glass beads to carbon nanotubes was 100:5. Moreover, the dispersity of carbon nanotubes in the matrix was improved as compared to the control samples prepared by using a conventional mixing method. (author)

Testing and performance analysis of a hollow fiber-based core for evaporative cooling and liquid desiccant dehumidification

DEFF Research Database (Denmark)

Jradi, Muhyiddine; Riffat, Saffa

2016-01-01

In this study, an innovative heat and mass transfer core is proposed to provide thermal comfort and humidity control using a hollow fiber contactor with multiple bundles of micro-porous hollow fibers. The hollow fiberbased core utilizes 12 bundles aligned vertically, each with 1,000 packed...

Hollow Microtube Resonators via Silicon Self-Assembly toward Subattogram Mass Sensing Applications.

Science.gov (United States)

Kim, Joohyun; Song, Jungki; Kim, Kwangseok; Kim, Seokbeom; Song, Jihwan; Kim, Namsu; Khan, M Faheem; Zhang, Linan; Sader, John E; Park, Keunhan; Kim, Dongchoul; Thundat, Thomas; Lee, Jungchul

2016-03-09

Fluidic resonators with integrated microchannels (hollow resonators) are attractive for mass, density, and volume measurements of single micro/nanoparticles and cells, yet their widespread use is limited by the complexity of their fabrication. Here we report a simple and cost-effective approach for fabricating hollow microtube resonators. A prestructured silicon wafer is annealed at high temperature under a controlled atmosphere to form self-assembled buried cavities. The interiors of these cavities are oxidized to produce thin oxide tubes, following which the surrounding silicon material is selectively etched away to suspend the oxide tubes. This simple three-step process easily produces hollow microtube resonators. We report another innovation in the capping glass wafer where we integrate fluidic access channels and getter materials along with residual gas suction channels. Combined together, only five photolithographic steps and one bonding step are required to fabricate vacuum-packaged hollow microtube resonators that exhibit quality factors as high as ∼ 13,000. We take one step further to explore additionally attractive features including the ability to tune the device responsivity, changing the resonator material, and scaling down the resonator size. The resonator wall thickness of ∼ 120 nm and the channel hydraulic diameter of ∼ 60 nm are demonstrated solely by conventional microfabrication approaches. The unique characteristics of this new fabrication process facilitate the widespread use of hollow microtube resonators, their translation between diverse research fields, and the production of commercially viable devices.

Ultra-large bandwidth hollow-core guiding in all-silica bragg fibers with nano-supports

DEFF Research Database (Denmark)

Vienne, Guillaume; Xu, Yong; Jakobsen, Christian

2004-01-01

We demonstrate a new class of hollow-core Bragg fibers that are composed of concentric cylindrical silica rings separated by nanoscale support bridges. We theoretically predict and experimentally observe hollow-core confinement over an octave frequency range. The bandwidth of bandgap guiding in t...... in this new class of Bragg fibers exceeds that of other hollow-core fibers reported in the literature. With only three rings of silica cladding layers, these Bragg fibers achieve propagation loss of the order of 1 dB/m....

Etched glass self-assembles into micron-size hollow platonic solids

KAUST Repository

Boukhalfa, Sofiane

2012-10-03

The interaction between the spreading of a hydrofluoric acid-based drop on a glass surface and its etching rate gives rise to hollow crystals of various shapes, including cubes, triangles, and icosahedra. These geometries are dependent on their position with respect to the contact line, where a rim forms by agglutination, similar to the formation of a coffee stain. Atomic force microscopy indentation and transmission electron microscopy observations revealed that these crystals are hollow ammonium-fluosilicate-based cryptohalite shells. © 2012 American Chemical Society.

Etched glass self-assembles into micron-size hollow platonic solids

KAUST Repository

Boukhalfa, Sofiane; Chaieb, Saharoui

2012-01-01

The interaction between the spreading of a hydrofluoric acid-based drop on a glass surface and its etching rate gives rise to hollow crystals of various shapes, including cubes, triangles, and icosahedra. These geometries are dependent on their position with respect to the contact line, where a rim forms by agglutination, similar to the formation of a coffee stain. Atomic force microscopy indentation and transmission electron microscopy observations revealed that these crystals are hollow ammonium-fluosilicate-based cryptohalite shells. © 2012 American Chemical Society.

Hollow Fiber Space Suit Water Membrane Evaporator Development for Lunar Missions

Science.gov (United States)

Bue, Grant C.; Trevino, Luis A.; Hanford, Anthony J.; Mitchell, Keith

2009-01-01

The Space Suit Water Membrane Evaporator (SWME) is the baseline heat rejection technology selected for development for the Constellation lunar suit. The Hollow Fiber (HoFi) SWME is being considered for service in the Constellation Space Suit Element (CSSE) Portable Life Support Subsystem (PLSS) to provide cooling to the thermal loop through water evaporation to the vacuum of space. Previous work described the test methodology and planning to compare the test performance of three commercially available hollow fiber materials as alternatives to the sheet membrane prototype for SWME: 1) porous hydrophobic polypropylene, 2) porous hydrophobic polysulfone, and 3) ion exchange through nonporous hydrophilic modified Nafion. Contamination tests were performed to probe for sensitivities of the candidate SWME elements to organics and non-volative inorganics expected to be found in the target feedwater source, i.e., potable water provided by the vehicle. The resulting presence of precipitate in the coolant water could plug pores and tube channels and affect the SWME performance. From this prior work, a commercial porous hydrophobic hollow fiber was selected to satisfy both the sensitivity question and the need to provide 800 W of heat rejection. This paper describes the trade studies, the design methodology, and the hollow fiber test data used to design a full

Simple Synthesis of Molybdenum Disulfide/Reduced Graphene Oxide Composite Hollow Microspheres as Supercapacitor Electrode Material.

Science.gov (United States)

Xiao, Wei; Zhou, Wenjie; Feng, Tong; Zhang, Yanhua; Liu, Hongdong; Tian, Liangliang

2016-09-20

MoS₂/RGO composite hollow microspheres were hydrothermally synthesized by using SiO₂/GO microspheres as a template, which were obtained via the sonication-assisted interfacial self-assembly of tiny GO sheets on positively charged SiO₂ microspheres. The structure, morphology, phase, and chemical composition of MoS₂/RGO hollow microspheres were systematically investigated by a series of techniques such as FE-SEM, TEM, XRD, TGA, BET, and Raman characterizations, meanwhile, their electrochemical properties were carefully evaluated by CV, GCD, and EIS measurements. It was found that MoS₂/RGO hollow microspheres possessed unique porous hollow architecture with high-level hierarchy and large specific surface area up to 63.7 m²·g -1 . When used as supercapacitor electrode material, MoS₂/RGO hollow microspheres delivered a maximum specific capacitance of 218.1 F·g -1 at the current density of 1 A·g -1 , which was much higher than that of contrastive bare MoS₂ microspheres developed in the present work and most of other reported MoS₂-based materials. The enhancement of supercapacitive behaviors of MoS₂/RGO hollow microspheres was likely due to the improved conductivity together with their distinct structure and morphology, which not only promoted the charge transport but also facilitated the electrolyte diffusion. Moreover, MoS₂/RGO hollow microsphere electrode displayed satisfactory long-term stability with 91.8% retention of the initial capacitance after 1000 charge/discharge cycles at the current density of 3 A·g -1 , showing excellent application potential.

Simple Synthesis of Molybdenum Disulfide/Reduced Graphene Oxide Composite Hollow Microspheres as Supercapacitor Electrode Material

Directory of Open Access Journals (Sweden)

Wei Xiao

2016-09-01

Full Text Available MoS2/RGO composite hollow microspheres were hydrothermally synthesized by using SiO2/GO microspheres as a template, which were obtained via the sonication-assisted interfacial self-assembly of tiny GO sheets on positively charged SiO2 microspheres. The structure, morphology, phase, and chemical composition of MoS2/RGO hollow microspheres were systematically investigated by a series of techniques such as FE-SEM, TEM, XRD, TGA, BET, and Raman characterizations, meanwhile, their electrochemical properties were carefully evaluated by CV, GCD, and EIS measurements. It was found that MoS2/RGO hollow microspheres possessed unique porous hollow architecture with high-level hierarchy and large specific surface area up to 63.7 m2·g−1. When used as supercapacitor electrode material, MoS2/RGO hollow microspheres delivered a maximum specific capacitance of 218.1 F·g−1 at the current density of 1 A·g−1, which was much higher than that of contrastive bare MoS2 microspheres developed in the present work and most of other reported MoS2-based materials. The enhancement of supercapacitive behaviors of MoS2/RGO hollow microspheres was likely due to the improved conductivity together with their distinct structure and morphology, which not only promoted the charge transport but also facilitated the electrolyte diffusion. Moreover, MoS2/RGO hollow microsphere electrode displayed satisfactory long-term stability with 91.8% retention of the initial capacitance after 1000 charge/discharge cycles at the current density of 3 A·g−1, showing excellent application potential.

Surface extended x-ray absorption fine structure of low-Z absorbates using fluorescence detection

International Nuclear Information System (INIS)

Stoehr, J.; Kollin, E.B.; Fischer, D.A.; Hastings, J.B.; Zaera, F.; Sette, F.

1985-05-01

Comparison of x-ray fluorescence yield (FY) and electron yield surface extended x-ray absorption fine structure spectra above the S K-edge for c(2 x 2) S on Ni(100) reveals an order of magnitude higher sensitivity of the FY technique. Using FY detection, thiophene (C 4 H 4 S) chemisorption on Ni(100) is studied with S coverages down to 0.08 monolayer. The molecule dissociates at temperatures as low as 100K by interaction with fourfold hollow Ni sites. Blocking of these sites by oxygen leaves the molecule intact

Southern Appalachian hillslope erosion rates measured by soil and detrital radiocarbon in hollows

Science.gov (United States)

T.C. Hales; K.M. Scharer; R.M. Wooten

2012-01-01

Understanding the dynamics of sediment generation and transport on hillslopes provides important constraints on the rate of sediment output from orogenic systems. Hillslope sediment fluxes are recorded by organic material found in the deposits infilling unchanneled convergent topographic features called hollows. This study describes the first hollow infilling rates...

Synergistic effects of hollow structure and surface fluorination on the photocatalytic activity of titania

International Nuclear Information System (INIS)

Lv Kangle; Yu Jiaguo; Deng Kejian; Sun Jie; Zhao Yanxi; Du Dongyun; Li Mei

2010-01-01

To study the synergistic effects of hollow structure and surface fluorination on the photoactivity of TiO 2 , TiO 2 hollow microspheres were synthesized by a hydrolysis-precipitate method using sulfonated polystyrene (PS) as templates and tetrabutylorthotitanate (TBOT) as precursor, and then calcined at 500 o C for 2 h. The calcined samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and N 2 sorption. Photocatalytic activity was evaluated using reactive brilliant red X3B, an anionic organic dye, as a model pollutant in water. The results show that the photocatalytic activity of TiO 2 hollow microspheres is significantly higher than that of TiO 2 nanoparticles prepared in the same experimental conditions. At pH 7 and 3, the apparent rate constants of the former exceed that of the latter by a factor of 3.38 and 3.15, respectively. After surface fluorination at pH 3, the photoactivity of hollow microspheres and nanoparticles further increases for another 1.61 and 2.19 times, respectively. The synergistic effect of surface fluorination and hollow structure can also be used to prepare other highly efficient photocatalyst.

Hollow ZSM-5 encapsulated Pt nanoparticles for selective catalytic reduction of NO by hydrogen

Science.gov (United States)

Hong, Zhe; Wang, Zhong; Chen, Dan; Sun, Qiang; Li, Xuebing

2018-05-01

Pt nanoparticles were successfully encapsulated in hollow ZSM-5 single crystals by tetrapropylammonium hydroxide (TPAOH) hydrothermal treatment with an "dissolution-recrystallization" process. The prepared Pt/hollow ZSM-5 (Pt/h-ZSM-5re) sample exhibited the best activity and a maximum NO conversion of 84% can be achieved at 90 °C with N2 selectivity of 92% (GHSV = 50,000 h-1). Meanwhile, Pt/h-ZSM-5re catalyst exhibited excellent SO2, H2O resistance and durability, which was related to the stabilization of Pt active sites by hollow structure during H2-SCR. It was found that the increase of NO2 concentration in the feed gas mixture led to an activity decline. In addition, the H2-SCR reaction routes over Pt/hollow ZSM-5 catalyst at different temperature were investigated.

Hollow MEMS

DEFF Research Database (Denmark)

Larsen, Peter Emil

Miniaturization of electro mechanical sensor systems to the micro range and beyond has shown impressive sensitivities measuring sample properties like mass, viscosity, acceleration, pressure and force just to name a few applications. In order to enable these kinds of measurements on liquid samples...... a hollow MEMS sensor has been designed, fabricated and tested. Combined density, viscosity, buoyant mass spectrometry and IR absorption spectroscopy are possible on liquid samples and micron sized suspended particles (e.g. single cells). Measurements are based on changes in the resonant behavior...... of these sensors. Optimization of the microfabrication process has led to a process yield of almost 100% .This is achieved despite the fact, that the process still offers a high degree of flexibility. By simple modifications the Sensor shape can be optimized for different size ranges and sensitivities...

Evolution of transverse instability in a hollow cylindrical weakly-ionized plasma column

International Nuclear Information System (INIS)

Kuedyan, H.M.

1978-01-01

Having observed formation of plasma striations in an Electron Cyclotron Resonance Heating (ECRH) device, we have studied the conditions under which the hollow cylindrical plasma columns would develop into striations. We first present the observed conditions of the hollow cylindrical plasma which would develop into plasma striations, the measured characteristics of the transverse oscillations and a simple small signal model for a transverse instability in a weakly-ionized hollow cylindrical plasma. This linearized model, which assumes flowing cold ion fluid (T/sub i/ approximately < 0.1 eV) in warm electron fluid (T/sub e/ approximately 1 eV) and background neutrals, reveals a transverse flute-type electrostatic instability whose characteristics are in qualitative and quantitative agreement with the measured values of the oscillations in our experiment

Fabrication of porous silver/titania composite hollow spheres with enhanced photocatalytic performance

International Nuclear Information System (INIS)

Li, Sa; Halperin, Shakked O.; Wang, Chang-An

2015-01-01

Silver/titania composite hollow spheres were first synthesized through an in-situ chemical reaction using functional-grouped carbon spheres as the template in this study. The prepared samples were characterized through an X-ray diffraction, N 2 adsorption–desorption, scanning electron microscopy, transmission electron microscopy and UV–Vis spectrophotometer. The photocatalytic activity of as-prepared samples was evaluated by photocatalytic decolorization of Methyl orange (MO) aqueous solution at ambient temperature under UV light. We found a structure with an optimal Ag:TiO 2 composition that exhibited a photodecomposition rate constant more than twice as high as titania hollow spheres lacking silver, and over three times higher than a commercial photocatalyst. - Highlights: • Ag/silver composites. • Hollow spheres. • Photocatalysis enhancement

SU-8 hollow cantilevers for AFM cell adhesion studies

Science.gov (United States)

Martinez, Vincent; Behr, Pascal; Drechsler, Ute; Polesel-Maris, Jérôme; Potthoff, Eva; Vörös, Janos; Zambelli, Tomaso

2016-05-01

A novel fabrication method was established to produce flexible, transparent, and robust tipless hollow atomic force microscopy (AFM) cantilevers made entirely from SU-8. Channels of 3 μm thickness and several millimeters length were integrated into 12 μm thick and 40 μm wide cantilevers. Connected to a pressure controller, the devices showed high sealing performance with no leakage up to 6 bars. Changing the cantilever lengths from 100 μm to 500 μm among the same wafer allowed the targeting of various spring constants ranging from 0.5 to 80 N m-1 within a single fabrication run. These hollow polymeric AFM cantilevers were operated in the optical beam deflection configuration. To demonstrate the performance of the device, single-cell force spectroscopy experiments were performed with a single probe detaching in a serial protocol more than 100 Saccharomyces cerevisiae yeast cells from plain glass and glass coated with polydopamine while measuring adhesion forces in the sub-nanoNewton range. SU-8 now offers a new alternative to conventional silicon-based hollow cantilevers with more flexibility in terms of complex geometric design and surface chemistry modification.

SU-8 hollow cantilevers for AFM cell adhesion studies

International Nuclear Information System (INIS)

Martinez, Vincent; Behr, Pascal; Vörös, Janos; Zambelli, Tomaso; Drechsler, Ute; Polesel-Maris, Jérôme; Potthoff, Eva

2016-01-01

A novel fabrication method was established to produce flexible, transparent, and robust tipless hollow atomic force microscopy (AFM) cantilevers made entirely from SU-8. Channels of 3 μm thickness and several millimeters length were integrated into 12 μm thick and 40 μm wide cantilevers. Connected to a pressure controller, the devices showed high sealing performance with no leakage up to 6 bars. Changing the cantilever lengths from 100 μm to 500 μm among the same wafer allowed the targeting of various spring constants ranging from 0.5 to 80 N m −1 within a single fabrication run. These hollow polymeric AFM cantilevers were operated in the optical beam deflection configuration. To demonstrate the performance of the device, single-cell force spectroscopy experiments were performed with a single probe detaching in a serial protocol more than 100 Saccharomyces cerevisiae yeast cells from plain glass and glass coated with polydopamine while measuring adhesion forces in the sub-nanoNewton range. SU-8 now offers a new alternative to conventional silicon-based hollow cantilevers with more flexibility in terms of complex geometric design and surface chemistry modification. (paper)

Template-directed synthesis of MS (M=Cd, Zn) hollow microsphere via hydrothermal method

Science.gov (United States)

Wang, Shi-Ming; Wang, Qiong-Sheng; Wan, Qing-Li

2008-05-01

CdS, ZnS hollow microspheres were prepared with chitosan as the synthesis template at 140 and 150 °C, respectively, by hydrothermal method. The resultant products were characterized by X-ray diffraction (XRD) measurements in order to determine the crystalline phase of the products. The structural and morphological features of the nanoparticles were investigated by transmission electron microscopy (TEM) and ultraviolet-visible diffuse reflection spectroscopy (DRS). The experimental results indicated that all the nanoparticles aggregated into hollow microspheres and chitosan as a template played an important role in the formation of hollow microspheres. In addition, an intermediate complex structure-controlling possible reaction mechanism was proposed in this paper.

Air Separation Using Hollow Fiber Membranes

Science.gov (United States)

Huang, Stephen E.

2004-01-01

The NASA Glenn Research Center in partnership with the Ohio Aerospace Institute provides internship programs for high school and college students in the areas of science, engineering, professional administrative, and other technical areas. During the summer of 2004, I worked with Dr. Clarence T. Chang at NASA Glenn Research Center s combustion branch on air separation using hollow fiber membrane technology. . In light of the accident of Trans World Airline s flight 800, FAA has mandated that a suitable solution be created to prevent the ignition of fuel tanks in aircrafts. In order for any type of fuel to ignite, three important things are needed: fuel vapor, oxygen, and an energy source. Two different ways to make fuel tanks less likely to ignite are reformulating the fuel to obtain a lower vapor pressure for the fuel and or using an On Board Inert Gas Generating System (OBIGGS) to inert the Central Wing Tank. goal is to accomplish the mission, which means that the Air Separation Module (ASM) tends to be bulky and heavy. The primary goal for commercial aviation companies is to transport as much as they can with the least amount of cost and fuel per person, therefore the ASM must be compact and light as possible. The plan is to take bleed air from the aircraft s engines to pass air through a filter first to remove particulates and then pass the air through the ASM containing hollow fiber membranes. In the lab, there will be a heating element provided to simulate the temperature of the bleed air that will be entering the ASM and analysis of the separated air will be analyzed by a Gas Chromatograph/Mass Spectrometer (GC/MS). The GUMS will separate the different compounds in the exit streams of the ASM and provide information on the performance of hollow fiber membranes. Hopefully I can develop ways to improve efficiency of the ASM. different types of jet fuel were analyzed and data was well represented on SAE Paper 982485. Data consisted of the concentrations of over

High-frequency and microwave heating as a pretreatment to kiln drying of hollowed-out timber

International Nuclear Information System (INIS)

Yamada, N.; Okumura, S.; Taniguchi, Y.

2001-01-01

To dry hollowed-out timber without V-shaped drying checks, its inner part should be dried faster than the outer part. The feasibility of high frequency heating and microwave heating as a pretreatment of kiln drying of hollow timber was examined. During high frequency heating, the top and bottom parts of the timber were dried faster than the right and left parts because the central hollow acts as an air-gap. The outer part dried faster than the inner part during microwave heating, probably because of insufficient penetration of microwave energy into the inner part. The uneven heating of hollowed timber was improved by turning the specimen around its axis during high frequency heating and by setting the specimen upright in the microwave oven

Fabricating process of hollow out-of-plane Ni microneedle arrays and properties of the integrated microfluidic device

Science.gov (United States)

Zhu, Jun; Cao, Ying; Wang, Hong; Li, Yigui; Chen, Xiang; Chen, Di

2013-07-01

Although microfluidic devices that integrate microfluidic chips with hollow out-of-plane microneedle arrays have many advantages in transdermal drug delivery applications, difficulties exist in their fabrication due to the special three-dimensional structures of hollow out-of-plane microneedles. A new, cost-effective process for the fabrication of a hollow out-of-plane Ni microneedle array is presented. The integration of PDMS microchips with the Ni hollow microneedle array and the properties of microfluidic devices are also presented. The integrated microfluidic devices provide a new approach for transdermal drug delivery.

Preparation and Electrochemical Properties of Silver Doped Hollow Carbon Nanofibers

Directory of Open Access Journals (Sweden)

LI Fu

2016-11-01

Full Text Available Silver doped PAN-based hollow carbon nanofibers were prepared combining co-electrospinning with in situ reduction technique subsequently heat treatment to improve the electrochemical performances of carbon based supercapacitor electrodes. The morphology, structure and electrochemical performances of the resulted nanofiber were studied. The results show that the silver nanoparticles can be doped on the surface of hollow carbon nanofibers and the addition of silver favors the improvement of the electrochemical performances, exhibiting the enhanced reversibility of electrode reaction and the capacitance and the reduced charge transfer impedance.

Ultrasonic/surfactant assisted of CdS nano hollow sphere synthesis and characterization

International Nuclear Information System (INIS)

Rafati, Amir Abbas; Borujeni, Ahmad Reza Afraz; Najafi, Mojgan; Bagheri, Ahmad

2011-01-01

CdS hollow nanospheres with diameters ranging from 40 to 150 nm have been synthesized by a surfactant-assisted sonochemical route. The successful vesicle templating indicates that the outer leaflet of the bilayer is the receptive surface in the controlled growth of CdS nanoparticles which provide the unique reactor for the nucleation and mineralization growth of CdS nanoparticles. The CdS nanostructures obtained were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, ultraviolet-visible spectroscopy and photoluminescence spectroscopy. Structural characterization of hollow CdS nanospheres indicates that these products packed with square subunits having sizes between 5 and 7 nm in diameter. The formation of the hollow nanostructure was explained by a vesicle template mechanism, in which sonication and surfactant play important roles. The band-edge emission and surface luminescence of the CdS nanoparticles were observed. -Research Highlights: → CdS hollow nanospheres with diameters of 40-150 nm were synthesized. → Nanoparticles were characterized by UV/Vis and photoluminescence. → Nanospheres are composed of smaller nanocrystals with the average size of 6.8 nm. → The band gap energy of the CdS nanoparticles is higher than its bulk value.

Three-dimensional interconnected cobalt oxide-carbon hollow spheres arrays as cathode materials for hybrid batteries

Directory of Open Access Journals (Sweden)

Jiye Zhan

2016-06-01

Full Text Available Hierarchical porous metal oxides arrays is critical for development of advanced energy storage devices. Herein, we report a facile template-assisted electro-deposition plus glucose decomposition method for synthesis of multilayer CoO/C hollow spheres arrays. The CoO/C arrays consist of multilayer interconnected hollow composite spheres with diameters of ∼350 nm as well as thin walls of ∼20 nm. Hierarchical hollow spheres architecture with 3D porous networks are achieved. As cathode of high-rate hybrid batteries, the multilayer CoO/C hollow sphere arrays exhibit impressive enhanced performances with a high capacity (73.5 mAh g−1 at 2 A g−1, and stable high-rate cycling life (70 mAh g−1 after 12,500 cycles at 2 A g−1. The improved electrochemical performance is owing to the composite hollow-sphere architecture with high contact area between the active materials and electrolyte as well as fast ion/electron transportation path.

Hollow reduced graphene oxide microspheres as a high-performance anode material for Li-ion batteries

International Nuclear Information System (INIS)

Mei, Riguo; Song, Xiaorui; Hu, Yan; Yang, Yanfeng; Zhang, Jingjie

2015-01-01

Hollow reduced graphene oxide (RGO) microspheres are successfully synthesized in large quantities through spray-drying suspension of graphene oxide (GO) nanosheets and subsequent carbothermal reduction. With this new procedure, blighted-microspherical GO precursor is synthesized through the process of spray drying, afterwards the GO precursor is subsequently calcined at 800 °C for 5 h to obtain hollow RGO microspheres. A series of analyses, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and Fourier transform infrared spectroscopy (FTIR) are performed to characterize the structure and morphology of intermediates and as-obtained product. The as-obtained hollow RGO microspheres provide a high specific surface area (175.5 m 2 g −1 ) and excellent electronic conductivity (6.3 S cm −1 ), and facilitated high electrochemical performance as anode material for Li-ion batteries (LIBs). Compared with the RGO nanosheets, the as-obtained hollow RGO microspheres exhibit superior specific capacity and outstanding cyclability. In addition, this spray drying and carbothermal reduction (SDCTR) method provided a facile route to prepare hollow RGO microspheres in large quantities

Comparison of NiS2 and α-NiS hollow spheres for supercapacitors, non-enzymatic glucose sensors and water treatment.

Science.gov (United States)

Wei, Chengzhen; Cheng, Cheng; Cheng, Yanyan; Wang, Yan; Xu, Yazhou; Du, Weimin; Pang, Huan

2015-10-21

NiS2 hollow spheres are successfully prepared by a one-step template free method. Meanwhile, α-NiS hollow spheres can also be synthesized via the calcination of the pre-obtained NiS2 hollow spheres at 400 °C for 1 h in air. The electrochemical performances of the as-prepared NiS2 and α-NiS hollow sphere products are evaluated. When used for supercapacitors, compared with NiS2 hollow spheres, the α-NiS hollow sphere electrode shows a large specific capacitance of 717.3 F g(-1) at 0.6 A g(-1) and a good cycle life. Furthermore, NiS2 and α-NiS hollow spheres are successfully applied to fabricate non-enzymatic glucose sensors. In particular, the α-NiS hollow spheres exhibit good catalytic activity for the oxidation of glucose, a fast amperometric response time of less than 5 s, and the detection limit is estimated to be 0.08 μM. More importantly, compared with other normally co-existing interfering species, such as ascorbic acid, uric acid and dopamine, the electrode modified with α-NiS hollow spheres shows good selectivity. Moreover, the α-NiS hollow spheres also present good capacity to remove Congo red organic pollutants from wastewater by their surface adsorption ability.

Comparison of hollow cathode discharge plasma configurations

International Nuclear Information System (INIS)

Farnell, Casey C; Farnell, Cody C; Williams, John D

2011-01-01

Hollow cathodes used in plasma contactor and electric propulsion devices provide electrons for sustaining plasma discharges and enabling plasma bridge neutralization. Life tests show erosion on hollow cathodes exposed to the plasma environment produced in the region downstream of these devices. To explain the observed erosion, plasma flow field measurements are presented for hollow cathode generated plasmas using both directly immersed probes and remotely located plasma diagnostics. Measurements on two cathode discharge configurations are presented: (1) an open, no magnetic field configuration and (2) a setup simulating the discharge chamber environment of an ion thruster. In the open cathode configuration, large amplitude plasma potential oscillations, ranging from 20 to 85 V within a 34 V discharge, were observed using a fast response emissive probe. These oscillations were observed over a dc potential profile that included a well-defined potential hill structure. A remotely located electrostatic analyzer (ESA) was used to measure the energy of ions produced within the plasma, and energies were detected that met, and in some cases exceeded, the peak oscillatory plasma potentials detected by the emissive probe. In the ion thruster discharge chamber configuration, plasma potentials from the emissive probe again agreed with ion energies recorded by the remotely located ESA; however, much lower ion energies were detected compared with the open configuration. A simplified ion-transit model that uses temporal and spatial plasma property measurements is presented and used to predict far-field plasma streaming properties. Comparisons between the model and remote measurements are presented.

Synthesis of CdS hollow/solid nanospheres and their chain-structures by membrane technique

International Nuclear Information System (INIS)

Duan Shumin; Wu Qingsheng; Jia Runping; Liu Xinbo

2008-01-01

CdS hollow/solid nanospheres and their chain-structures were successfully synthesized through supporting liquid membrane (SLM) system with bio-membrane. X-ray powder diffraction (XRD), transmission electron microscopy (TEM), UV-Vis spectroscopy, and photoluminescence (PL) spectroscopy have been used for the characterization of the products. The average diameters of CdS solid/hollow spheres are about 10, 40 nm, respectively. The wall of the hollow spheres is about 5 nm. CdS products are all cubic face-centered structure with the cell constant a = 5.830 A. We also explore the morphology, structure and possible synthesis mechanism. A possible template mechanism has been proposed for the production of the hollow CdS nanocrystals, that is, CdS nanoparticles grow along the non-soakage interface between CHCl3 and reactant solution. During this process, the organic functional groups were crucial to the control of crystal morphologies

Masking functions and fixed-signal functions for low-level 1000-Hz tones.

Science.gov (United States)

Shepherd, Daniel; Hautus, Michael J; Jesteadt, Walt

2013-06-01

Masking functions and fixed-signal functions were constructed using a narrow range of pedestal intensities for 10-ms, 1000-Hz gated tones. Data from three experiments agreed with previously reported data, clearly demonstrating negative masking and the pedestal effect. The data extend earlier findings by showing (1) the resilience of the pedestal effect when a background noise masker is introduced; (2) a possible indifference of the fixed-signal function to stimulus duration; (3) the ability of a set of psychometric functions to produce both masking and fixed-signal functions; (4) depending on method, the impact of unit choice on the interpretation of both the pedestal effect and negative masking data. Results are discussed in relation to current psychophysical models, and suggest that accounting for the auditory system's sensitivity to differences in low-level sounds remains a challenge.

Controlled synthesis of ZnO hollow microspheres via precursor-template method and its gas sensing property

International Nuclear Information System (INIS)

Tian, Yu; Li, Jinchai; Xiong, Hui; Dai, Jiangnan

2012-01-01

Highlights: ► Zn powder as precursor template for synthesis ZnO hollow spheres. ► Different precursor templates result in different ZnO nanostructures. ► Different experimental conditions enable growth of different surface morphologies of ZnO sphere. ► ZnO hollow sphere materials have good gas sensing performance for detecting ethanol gas. - Abstract: Using Zn powder as precursor templates, ZnO hollow microspheres were successfully prepared by thermal evaporation method and characterized by X-ray diffraction analysis, scanning electron microscope and transmission electron microscope. It was found that different size and shape of precursor resulted in different ZnO nanostructures. When varying experimental conditions, such as air flow rate and working pressure, ZnO hollow spheres with different surface morphologies could be obtained. The advantages of the present synthetic technology are simple, relatively low cost, and high reproducibility. A gas sensor was fabricated from the as-prepared ZnO hollow microspheres and tested to the ethanol gas at different operating temperatures.

Hollow NiO nanofibers modified by citric acid and the performances as supercapacitor electrode

International Nuclear Information System (INIS)

Ren, Bo; Fan, Meiqing; Liu, Qi; Wang, Jun; Song, Dalei; Bai, Xuefeng

2013-01-01

Graphical abstract: The possible formation process of NiO nanofibers without citric acid (a), and modified by citric acid (b). When the nanofibers is modified by citric acid, the nickel citrate is produced by complexing action of citric acid and nickel nitrate. Because of the larger space steric hindrance, the structure is limited by the molecular geometry. Under high temperature, the hollow nanofibers composed of NiO slices formed after the removal of PVP. Highlights: ► The method of obtaining hollow nanofibers is raised for the first time. ► The prepared NiO nanofibers are hollow tube and comprised of many NiO sheets. ► The hollow structure facilitated the electrolyte penetration. ► The hollow NiO nanofibers have good electrochemical properties. -- Abstract: NiO nanofibers modified by citric acid (NiO/CA) for supercapacitor material have been fabricated by electrospinning process. The characterizations of the nanofibers are investigated by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Electrochemical properties are characterized by cyclic voltammetry, galvanostatic charge/discharge measurements, and electrochemical impedance spectroscopy. Results show that the NiO/CA nanofibers are hollow tube and comprised of many NiO sheets. Furthermore, the NiO/CA nanofibers have good electrochemical reversibility and display superior capacitive performance with large capacitance (336 F g −1 ), which is 2.5 times of NiO electrodes. Moreover, the NiO/CA nanofibers show excellent cyclic performance after 1000 cycles

The rheological responds of the superparamagnetic fluid based on Fe{sub 3}O{sub 4} hollow nanospheres

Energy Technology Data Exchange (ETDEWEB)

Ruan, Xiaohui; Pei, Lei; Xuan, Shouhu, E-mail: xuansh@ustc.edu.cn; Yan, Qifan; Gong, Xinglong, E-mail: gongxl@ustc.edu.cn

2017-05-01

In this work, a superparamagnetic fluid based on Fe{sub 3}O{sub 4} hollow nanospheres was developed and the influence of the particle structure on the rheological properties was investigated. The Fe{sub 3}O{sub 4} hollow nanospheres which were prepared by using the hydrothermal method presented the superparamagnetic characteristic, and the magnetic fluid thereof showed well magnetorheological (MR) effect. The stable magnetic fluid had a high yield stress even at low shear rate and its maximal yield stress was dramatically influenced by the measurement gap. In comparison to the Fe{sub 3}O{sub 4} nanoparticles based magnetic fluid (MF), the Fe{sub 3}O{sub 4} hollow nanospheres based MF exhibited better MR effect and higher stability since the unique hollow nanostructure. The shear stress of the hollow nanospheres is about 1.85 times larger than the nanoparticles based MF because it formed stronger chains structure under applying a magnetic field. To further investigate the enhancing mechanism, a molecule dynamic simulation was conducted to analyze the shear stress and the structure evolution of the Fe{sub 3}O{sub 4} hollow nanospheres based MF and the simulation matched well with the experimental results. - Highlights: • A superparamagnetic fluid based on Fe{sub 3}O{sub 4} hollow nanospheres was investigated. • The stable magnetic fluid had a high yield stress even at low shear rate. • The shear stress of the hollow nanospheres is large. • A molecule dynamic simulation was conducted to analyze the shear stress.

Synthesis of single-crystalline hollow β-FeOOH nanorods via a controlled incomplete-reaction course

International Nuclear Information System (INIS)

Yu Haiyun; Song Xinyu; Yin Zhilei; Fan Weiliu; Tan Xuejie; Fan Chunhua; Sun Sixiu

2007-01-01

The single-crystalline β-FeOOH hollow nanorods with a diameter ranging from 20∼30 nm and length in the range of 70-110 nm have been successfully synthesized through a two-step route in the solution. The phase transformation and the morphologies of the hollow β-FeOOH nanorods were investigated with X-ray powdered diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electric diffraction (SAED), high-resolution transmission electron microscopy (HRTEM), infrared spectrum (IR) and thermo-gravimetric analysis (TGA). These studies indicate that the first step is an incomplete-reaction course. Furthermore, The formation mechanism of the hollow nanorods has been discussed. It is found that the mixed system including chitosan and n-propanol is essential for the final formation of the hollow β-FeOOH nanorods

Ultraviolet Generation by Atmospheric Micro-Hollow Cathode Discharges

National Research Council Canada - National Science Library

Cooper, J

2004-01-01

Report developed under STTR contract for topic AFO3TOl9. This report documents the program objectives, work performed, results obtained, and future plans for a program to develop micro-hollow cathode discharge (MHCD...

Block copolymer hollow fiber membranes with catalytic activity and pH-response

KAUST Repository

Hilke, Roland

2013-08-14

We fabricated block copolymer hollow fiber membranes with self-assembled, shell-side, uniform pore structures. The fibers in these membranes combined pores able to respond to pH and acting as chemical gates that opened above pH 4, and catalytic activity, achieved by the incorporation of gold nanoparticles. We used a dry/wet spinning process to produce the asymmetric hollow fibers and determined the conditions under which the hollow fibers were optimized to create the desired pore morphology and the necessary mechanical stability. To induce ordered micelle assembly in the doped solution, we identified an ideal solvent mixture as confirmed by small-angle X-ray scattering. We then reduced p-nitrophenol with a gold-loaded fiber to confirm the catalytic performance of the membranes. © 2013 American Chemical Society.

Block copolymer hollow fiber membranes with catalytic activity and pH-response

KAUST Repository

Hilke, Roland; Neelakanda, Pradeep; Madhavan, Poornima; Vainio, Ulla; Behzad, Ali Reza; Sougrat, Rachid; Nunes, Suzana Pereira; Peinemann, Klaus-Viktor

2013-01-01

We fabricated block copolymer hollow fiber membranes with self-assembled, shell-side, uniform pore structures. The fibers in these membranes combined pores able to respond to pH and acting as chemical gates that opened above pH 4, and catalytic activity, achieved by the incorporation of gold nanoparticles. We used a dry/wet spinning process to produce the asymmetric hollow fibers and determined the conditions under which the hollow fibers were optimized to create the desired pore morphology and the necessary mechanical stability. To induce ordered micelle assembly in the doped solution, we identified an ideal solvent mixture as confirmed by small-angle X-ray scattering. We then reduced p-nitrophenol with a gold-loaded fiber to confirm the catalytic performance of the membranes. © 2013 American Chemical Society.

Solvent-free synthesis of nanosized hierarchical sodalite zeolite with a multi-hollow polycrystalline structure

KAUST Repository

Zeng, Shangjing

2016-08-03

A solvent-free route is developed for preparing nanoscale sodalite zeolite with a multi-hollow structure. Furthermore, the synthesis of nanosized hollow sodalite polycrystalline aggregates with a mesoporous structure and high crystallinity is investigated by adding an organosilane surfactant as a mesopore-generating agent.

Photocatalytic action of cerium molybdate and iron-titanium oxide hollow nanospheres on Escherichia coli

Energy Technology Data Exchange (ETDEWEB)

Kartsonakis, I. A., E-mail: ikartsonakis@ims.demokritos.gr; Kontogiani, P.; Pappas, G. S.; Kordas, G. [NCSR ' DEMOKRITOS' , Sol-Gel Laboratory, Institute of Advanced Materials, Physicochemical Processes, Nanotechnology and Microsystems (Greece)

2013-06-15

This study is focused on the production of hollow nanospheres that reveal antibacterial action. Cerium molybdate and iron-titanium oxide hollow nanospheres with a diameter of 175 {+-} 15 and 221 {+-} 10 nm, respectively, were synthesized using emulsion polymerization and the sol-gel process. Their morphology characterization was accomplished using scanning electron microscopy. Their antibacterial action was examined on pure culture of Escherichia coli considering the loss of their viability. Both hollow nanospheres presented photocatalytic action after illumination with blue-black light, but those of cerium molybdate also demonstrated photocatalytic action in the dark. Therefore, the produced nanospheres can be used for antibacterial applications.

Hollow viscus injury in children: Starship Hospital experience

Directory of Open Access Journals (Sweden)

Upadhyay Vipul

2007-06-01

Full Text Available Abstract Starship Children's Hospital in Auckland, New Zealand, serves a population of 1.2 million people and is a tertiary institution for pediatric trauma. This study is designed to review all cases of abdominal injury (blunt and penetrating that resulted in injury of a hollow abdominal viscus including the stomach, duodenum, small intestine, large intestine and urinary bladder. The mechanism of injury; diagnosis and outcome were studied. This was done by retrospective chart review of patients admitted from January 1995 to December 2001. Thirty two injuries were found in 29 children. The age ranged from 7 months to 15 years with boys represented more commonly. Small bowel was the most frequently injured hollow viscus. Computerized Tomography (CT scan is an extremely useful tool for the diagnosis of HVI.

Spectroscopy of Rb atoms in hollow-core fibers

International Nuclear Information System (INIS)

Slepkov, Aaron D.; Bhagwat, Amar R.; Venkataraman, Vivek; Londero, Pablo; Gaeta, Alexander L.

2010-01-01

Recent demonstrations of light-matter interactions with atoms and molecules confined to hollow waveguides offer great promise for ultralow-light-level applications. The use of waveguides allows for tight optical confinement over interaction lengths much greater than what could be achieved in bulk geometries. However, the combination of strong atom-photon interactions and nonuniformity of guided light modes gives rise to spectroscopic features that must be understood in order to take full advantage of the properties of such systems. We use light-induced atomic desorption to generate an optically dense Rb vapor at room temperature inside a hollow-core photonic band-gap fiber. Saturable-absorption spectroscopy and passive slow-light experiments reveal large ac Stark shifts, power broadening, and transit-time broadening, that are present in this system even at nanowatt powers.

Biocompatible magnetic and molecular dual-targeting polyelectrolyte hybrid hollow microspheres for controlled drug release.

Science.gov (United States)

Du, Pengcheng; Zeng, Jin; Mu, Bin; Liu, Peng

2013-05-06

Well-defined biocompatible magnetic and molecular dual-targeting polyelectrolyte hybrid hollow microspheres have been accomplished via the layer-by-layer (LbL) self-assembly technique. The hybrid shell was fabricated by the electrostatic interaction between the polyelectrolyte cation, chitosan (CS), and the hybrid anion, citrate modified ferroferric oxide nanoparticles (Fe3O4-CA), onto the uniform polystyrene sulfonate microsphere templates. Then the magnetic hybrid core/shell composite particles were modified with a linear, functional poly(ethylene glycol) (PEG) monoterminated with a biotargeting molecule (folic acid (FA)). Afterward the dual targeting hybrid hollow microspheres were obtained after etching the templates by dialysis. The dual targeting hybrid hollow microspheres exhibit exciting pH response and stability in high salt-concentration media. Their pH-dependent controlled release of the drug molecule (anticancer drug, doxorubicin (DOX)) was also investigated in different human body fluids. As expected, the cell viability of the HepG2 cells which decreased more rapidly was treated by the FA modified hybrid hollow microspheres rather than the unmodified one in the in vitro study. The dual-targeting hybrid hollow microspheres demonstrate selective killing of the tumor cells. The precise magnetic and molecular targeting properties and pH-dependent controlled release offers promise for cancer treatment.

Self-assembly of hollow MoS{sub 2} microflakes by one-pot hydrothermal synthesis for efficient electrocatalytic hydrogen evolution

Energy Technology Data Exchange (ETDEWEB)

Chen, Aishi; Cui, Renjie; He, Yanna; Wang, Qi [Key Laboratory for Organic Electronics and Information Displays & Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing University of Posts & Telecommunications, Nanjing 210023 (China); Zhang, Jian, E-mail: iamjzhang@njupt.edu.cn [Key Laboratory for Organic Electronics and Information Displays & Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing University of Posts & Telecommunications, Nanjing 210023 (China); Yang, Jianping [School of Science, Nanjing University of Posts and Telecommunications (NUPT), Nanjing 210023 (China); Li, Xing’ao, E-mail: lxahbmy@126.com [Key Laboratory for Organic Electronics and Information Displays & Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing University of Posts & Telecommunications, Nanjing 210023 (China); School of Science, Nanjing University of Posts and Telecommunications (NUPT), Nanjing 210023 (China)

2017-07-31

Highlights: • A new hollow MoS{sub 2} microflakes are prepared by hydrothermal synthesis firstly. • SEM and TEM study show the structural nature of hollow microflakes in depth. • The unique hollow structures have large surface area owing to the cavity. • The hollow microflakes show better HER performance than their solid counterparts. - Abstract: Molybdenum disulfide (MoS{sub 2}) has emerged as a promising non-precious metal catalyst for hydrogen evolution reaction (HER) in recent years. Some strategies including nanotechnology as well as atom doping have been employed in the preparing of electrocatalysts for high-activity and stability. To the best of our knowledge, hollow MoS{sub 2} microflakes assembled from ultrathin nanosheets have not been prepared previously. In this work, a simple, facile and environmentally friendly hydrothermal synthesis was utilized for the fabrication of hollow MoS{sub 2} microflakes for the first time. The unique hollow structures have fascinating properties, such as the large surface and low density. The morphology and structure of MoS{sub 2} microflakes were confirmed by XRD, SEM, TEM and Raman. The composition of these materials was identified by the X-ray photoelectron spectroscopy. Notably, the as-prepared hollow MoS{sub 2} microflakes showed better electrocatalytic activity than other samples. The hollow flake-like structure can not only increase the active edge sites owing to the large specific surface area, but also enhance the electron transport to improve the electrocatalytic activity. Benefiting from these factors, the hollow MoS{sub 2} microflakes exhibited electrocatalytic activity and excellent stability with a low overpotential about 85 mV and a Tafel slope of 59 mV per decade.

Electrochemical performance of Ni/TiO_2 hollow sphere in proton exchange membrane water electrolyzers system

International Nuclear Information System (INIS)

Chattopadhyay, Jayeeta; Srivastava, Rohit; Srivastava, Prem Kumar

2013-01-01

This work presents the electrocatalytic evaluation of Ni/TiO_2 hollow sphere materials in PEM water electrolysis cell. All the electrocatalysts have shown remarkably enhanced electrocatalytic properties in comparison with their performance in aqueous electrolysis cell. According to cyclic voltammetric results, 0.36 A cm"−"2 peak current density has been exhibited in hydrogen evolution reaction (HER) from 30 wt% Ni/TiO_2 electrocatalyst. 15 wt% Ni-doped titania sample has shown the best result in oxygen evolution reaction (OER) with the anodic peak current density of 0.3 A cm"−"2. In the anodic polarization curves, the performance of 15 wt% Ni/TiO_2 hollow sphere electrocatalyst was evaluated up to 140 mA cm"−"2 at comparatively lower over-potential value. 20 wt% Ni/TiO_2 hollow sphere electrocatalyst has also shown electrochemical stability in PEM water electrolyzer for 48 h long analysis. The comparative electrocatalytic behavior of hollow spherical materials with non-sphericals is also presented, which clearly shows the influence of hollow spherical structure in greater electrocatalytic activity of the materials. The physical characterization of all the hollow spherical materials is presented in this work, which has confirmed their better electrochemical behavior in PEM water electrolyzer

Droplets Behavior of Hollow-Cone Spray in a Non-Condensable Environment

International Nuclear Information System (INIS)

Minoru Takahashi; Shin-ichi Kitagawa; Suizheng Qiu

2002-01-01

The characteristics of droplets in a water hollow-cone spray from nozzles 1.1 mm and 3.6 mm in diameter in an air environment have been investigated experimentally. The dual phase Doppler anemometry (PDA) system was used to measure the size and two velocity components of individual spherical particles. The liquid spray geometry, including spray breakup length and spray angle were also obtained experimentally. The mechanism and the influence of these parameters on a hollow cone spray flow were described. (authors)

Controlled synthesis and characterization of hollow flower-like silver nanostructures

Directory of Open Access Journals (Sweden)

Eid KAM

2012-03-01

Full Text Available Kamel AM Eid, Hassan ME AzzazyNovel Diagnostics and Therapeutics Group, Yousef Jameel Science and Technology Research Center, School of Sciences and Engineering, The American University in Cairo, New Cairo, EgyptBackground: The synthesis of anisotropic silver nanoparticles is a time-consuming process and involves the use of expensive toxic chemicals and specialized laboratory equipment. The presence of toxic chemicals in the prepared anisotropic silver nanostructures hindered their medical application. The authors have developed a fast and inexpensive method for the synthesis of three-dimensional hollow flower-like silver nanostructures without the use of toxic chemicals.Methods: In this method, silver nitrate was reduced using dextrose in presence of trisodium citrate as a capping agent. Sodium hydroxide was added to enhance reduction efficacy of dextrose and reduce time of synthesis. The effects of all four agents on the shape and size of silver nanostructures were investigated.Results: Robust hollow flower-like silver nanostructures were successfully synthesized and ranged in size from 0.2 µm to 5.0 µm with surface area between 25–240 m2/g. Changing the concentration of silver nitrate, dextrose, sodium hydroxide, and trisodium citrate affected the size and shape of the synthesized structures, while changing temperature had no effect.Conclusion: The proposed method is simple, safe, and allows controlled synthesis of anisotropic silver nanostructures, which may represent promising tools as effective antimicrobial agents and for in vitro diagnostics. The synthesized hollow nanostructures may be used for enhanced drug encapsulation and sustained release.Keywords: silver nanoparticles, 3D hollow, flower-like, green synthesis

Spray Modeling for Outwardly-Opening Hollow-Cone Injector

KAUST Repository

Sim, Jaeheon; Badra, Jihad; Elwardani, Ahmed Elsaid; Im, Hong G.

2016-01-01

linear instability sheet atomization (LISA) model was originally developed for pressure swirl hollow-cone injectors with moderate spray angle and toroidal ligament breakups. Therefore, it is not appropriate for the outwardly-opening injectors having wide

CNT-embedded hollow TiO{sub 2} nanofibers with high adsorption and photocatalytic activity under UV irradiation

Energy Technology Data Exchange (ETDEWEB)

Jung, Jin-Young; Lee, Dayoung; Lee, Young-Seak, E-mail: youngslee@cnu.ac.kr

2015-02-15

Highlights: • CNT-embedded hollow TiO{sub 2} nanofibers were successfully fabricated via electrospinning, impregnation, and calcination. • The highest degradation ratio achieved using the CNT-embedded hollow TiO{sub 2} nanofibers. • Incorporation of embedded CNTs both increased the adsorption capability and enhanced the photodegradation activity. - Abstract: Hollow TiO{sub 2} nanofibers with embedded carbon nanotubes (CNTs) were prepared for use as photocatalysts through electrospinning, impregnation, and calcination using multiwalled CNTs (MWCNTs) with various ratios of titanium tetraisopropoxide (TTIP), and further characterized by SEM, TGA, BET and XRD. The results demonstrated the successful fabrication of hollow TiO{sub 2} nanofibers with embedded CNTs. The CNT-embedded hollow TiO{sub 2} nanofibers prepared in this study exhibited improved photocatalytic activity compared to plain hollow TiO{sub 2} nanofibers based on the conversion of methylene blue (MB) in aqueous solution under UV irradiation. The highest degradation ratio produced by the CNT-embedded hollow TiO{sub 2} nanofibers was approximately 62% after 70 min, which represented an increase of more than 80% over that of TiO{sub 2}. It was found that the enhanced efficiency of MB removal could be attributed not only to the adsorption capability of the CNTs but also to electron transfer between the CNTs and the TiO{sub 2}.

Ionization processes in a transient hollow cathode discharge before electric breakdown: statistical distribution

International Nuclear Information System (INIS)

Zambra, M.; Favre, M.; Moreno, J.; Wyndham, E.; Chuaqui, H.; Choi, P.

1998-01-01

The charge formation processes in a hollow cathode region (HCR) of transient hollow cathode discharge have been studied at the final phase. The statistical distribution that describe different processes of ionization have been represented by Gaussian distributions. Nevertheless, was observed a better representation of these distributions when the pressure is near a minimum value, just before breakdown

Hollow fibre supported liquid membrane extraction of ...

African Journals Online (AJOL)

A simple sample pre-treatment method utilizing hollow fibre supported liquid membrane (HFSLM) was carried out on pharmaceuticals samples comprising of cough syrups (CS1 and CS2) and an anti-inflammatory product (AI). The active ingredients targeted in the extraction process were diphenylhydramine (DPH), ...

Nb{sub 2}O{sub 5} hollow nanospheres as anode material for enhanced performance in lithium ion batteries

Energy Technology Data Exchange (ETDEWEB)

Sasidharan, Manickam [Department of Chemistry, Faculty of Science and Engineering, Saga University, 1 Honjo-machi, Saga 840-8502 (Japan); Gunawardhana, Nanda [Advanced Research Center, Saga University, 1341 Yoga-machi, Saga 840-0047 (Japan); Yoshio, Masaki, E-mail: yoshio@cc.saga-u.ac.jp [Advanced Research Center, Saga University, 1341 Yoga-machi, Saga 840-0047 (Japan); Nakashima, Kenichi, E-mail: nakashik@cc.saga-u.ac.jp [Department of Chemistry, Faculty of Science and Engineering, Saga University, 1 Honjo-machi, Saga 840-8502 (Japan)

2012-09-15

Graphical abstract: Nb{sub 2}O{sub 5} hollow nanosphere constructed electrode delivers high capacity of 172 mAh g{sup −1} after 250 cycles and maintains structural integrity and excellent cycling stability. Highlights: ► Nb{sub 2}O{sub 5} hollow nanospheres synthesis was synthesized by soft-template. ► Nb{sub 2}O{sub 5} hollow nanospheres were investigated as anode material in Li-ion battery. ► Nanostructured electrode delivers high capacity of 172 mAh g{sup −1} after 250 cycles. ► The electrode maintains the structural integrity and excellent cycling stability. ► Nanosized shell domain facilitates fast lithium intercalation/deintercalation. -- Abstract: Nb{sub 2}O{sub 5} hollow nanospheres of average diameter ca. ∼29 nm and hollow cavity size ca. 17 nm were synthesized using polymeric micelles with core–shell–corona architecture under mild conditions. The hollow particles were thoroughly characterized by transmission electron microscope (TEM), X-ray diffraction (XRD), infrared spectroscopy (FTIR), thermal (TG/DTA) and nitrogen adsorption analyses. Thus obtained Nb{sub 2}O{sub 5} hollow nanospheres were investigated as anode materials for lithium ion rechargeable batteries for the first time. The nanostructured electrode delivers high capacity of 172 mAh g{sup −1} after 250 cycles of charge/discharge at a rate of 0.5 C. More importantly, the hollow particles based electrodes maintains the structural integrity and excellent cycling stability even after exposing to high current density 6.25 A g{sup −1}. The enhanced electrochemical behavior is ascribed to hollow cavity coupled with nanosized Nb{sub 2}O{sub 5} shell domain that facilitates fast lithium intercalation/deintercalation kinetics.

Self-assembly of calcium phosphate nanoparticles into hollow spheres induced by dissolved amino acids

NARCIS (Netherlands)

Hagmeyer, D.; Ganesan, K.; Ruesing, J.; Schunk, D.; Mayer, C.; Dey, A.; Sommerdijk, N.A.J.M.; Epple, M.

2011-01-01

Nanoparticles of calcium phosphate assemble spontaneously within a few seconds into hollow spheres with a diameter around 200–300 nm in the presence of dissolved amino acids and dipeptides. The process of formation was followed by cryo-transmission electron microscopy (cryoTEM), proving their hollow

Facile synthesis of hollow dendritic Ag/Pt alloy nanoparticles for enhanced methanol oxidation efficiency.

Science.gov (United States)

Sui, Ning; Wang, Ke; Shan, Xinyao; Bai, Qiang; Wang, Lina; Xiao, Hailian; Liu, Manhong; Colvin, Vicki L; Yu, William W

2017-11-14

Hollow dendritic Ag/Pt alloy nanoparticles were synthesized by a double template method: Ag nanoparticles as the hard template to obtain hollow spheres by a galvanic replacement reaction between PtCl 6 2- and metallic Ag and surfactant micelles (Brij58) as the soft template to generate porous dendrites. The formation of a Ag/Pt alloy phase was confirmed by XRD and HRTEM. Elemental mapping and line scanning revealed the formation of the hollow architecture. We studied the effects of the Ag/Pt ratio, surfactant and reaction temperature on the morphology. In addition, we explored the formation process of hollow dendritic Ag/Pt nanoparticles by tracking the morphologies of the nanostructures formed at different stages. In order to improve the electrocatalytic property, we controlled the size of the nanoparticles and the thickness of the shell by adjusting the amount of the precursor. We found that these Ag/Pt alloy nanoparticles exhibited high activity (440 mA mg -1 ) and stability as an electrocatalyst for catalyzing methanol oxidation.

3D-printed PMMA Preform for Hollow-core POF Drawing

DEFF Research Database (Denmark)

Zubel, M. G.; Fasano, Andrea; Woyessa, Getinet

2016-01-01

In this paper we report the first, to our knowledge, 3D-printed hollow-core poly(methyl methacrylate) (PMMA) preform for polymer optical fibre drawing. It was printed of commercial PMMA by means of fused deposition modelling technique. The preform was drawn to cane, proving good enough quality...... of drawing process and the PMMA molecular weight to be appropriate for drawing. This ascertains that the manufacturing process provides preforms suitable for hollow-core fibre drawing. The paper focuses on maximisation of transparency of PMMA 3D printouts by optimising printing process parameters: nozzle...... temperature, printing speed and infill...

Rapid Temperature Swing Adsorption using Polymeric/Supported Amine Hollow Fibers

Energy Technology Data Exchange (ETDEWEB)

Chance, Ronald [Georgia Tech Research Corporation, Atlanta, GA (United States); Chen, Grace [Georgia Tech Research Corporation, Atlanta, GA (United States); Dai, Ying [Georgia Tech Research Corporation, Atlanta, GA (United States); Fan, Yanfang [Georgia Tech Research Corporation, Atlanta, GA (United States); Jones, Christopher [Georgia Tech Research Corporation, Atlanta, GA (United States); Kalyanaraman, Jayashree [Georgia Tech Research Corporation, Atlanta, GA (United States); Kawajiri, Yoshiaki [Georgia Tech Research Corporation, Atlanta, GA (United States); Koros, William [Georgia Tech Research Corporation, Atlanta, GA (United States); Lively, Ryan [Georgia Tech Research Corporation, Atlanta, GA (United States); McCool, Benjamin [Georgia Tech Research Corporation, Atlanta, GA (United States); Pang, Simon [Georgia Tech Research Corporation, Atlanta, GA (United States); Realff, Matthew [Georgia Tech Research Corporation, Atlanta, GA (United States); Rezaei, Fateme [Georgia Tech Research Corporation, Atlanta, GA (United States); Searcy, Katherine [Georgia Tech Research Corporation, Atlanta, GA (United States); Sholl, David [Georgia Tech Research Corporation, Atlanta, GA (United States); Subramanian, Swernath [Georgia Tech Research Corporation, Atlanta, GA (United States); Pang, Simon [Georgia Tech Research Corporation, Atlanta, GA (United States)

2015-03-31

This project is a bench-scale, post-combustion capture project carried out at Georgia Tech (GT) with support and collaboration with GE, Algenol Biofuels, Southern Company and subcontract to Trimeric Corporation. The focus of the project is to develop a process based on composite amine-functionalized oxide / polymer hollow fibers for use as contactors in a rapid temperature swing adsorption post-combustion carbon dioxide capture process. The hollow fiber morphology allows coupling of efficient heat transfer with effective gas contacting, potentially giving lower parasitic loads on the power plant compared to traditional contacting strategies using solid sorbents.

Hollow TiO2 modified reduced graphene oxide microspheres encapsulating hemoglobin for a mediator-free biosensor.

Science.gov (United States)

Liu, Hui; Guo, Kai; Duan, Congyue; Dong, Xiaonan; Gao, Jiaojiao

2017-01-15

Hollow TiO 2 modified reduced graphene oxide microspheres (hollow TiO 2 -rGO microspheres or H-TiO 2 -rGO MS) have been synthesized and then be used to immobilize hemoglobin (Hb) to fabricate a mediator-free biosensor. The morphology and structure of hollow TiO 2 -rGO microspheres were characterized by scanning electron microscopy, transmission electronic microscopy and X-ray diffraction. Results of spectroscopy and electrochemistry tests revealed that hollow TiO 2 -rGO microsphere is an excellent immobilization matrix with biocompatibility for redox protein, affording good protein bioactivity and stability. The hollow TiO 2 -rGO microspheres with special structure and component enhance the immobilization efficiency of proteins and facilitate the direct electron transfer, which result in the better H 2 O 2 detection performance-the wide linear range of 0.1-360μM for H 2 O 2 (sensitivity of 417.6 μA mM -1 cm -2 ) and the extremely low detection limit of 10nM for H 2 O 2 . Moreover, the hollow microsphere can provide a protective microenvironment for Hb to make the as-prepared biosensor improve long-term stability. The as-prepared biosensor retains 95.4% of the initial response to H 2 O 2 after 60-d storage. Hence, this work suggests that if can be fabricated a mediator-free biosensor, hollow TiO 2 -rGO microspheres will find wide potential applications in environmental analysis and biomedical detection. Copyright © 2016 Elsevier B.V. All rights reserved.

Block copolymer/homopolymer dual-layer hollow fiber membranes

KAUST Repository

Hilke, Roland; Neelakanda, Pradeep; Behzad, Ali Reza; Nunes, Suzana Pereira; Peinemann, Klaus-Viktor

2014-01-01

We manufactured the first time block copolymer dual-layer hollow fiber membranes and dual layer flat sheet membranes manufactured by double solution casting and phase inversion in water. The support porous layer was based on polystyrene

Intensity-gradient induced Sisyphus cooling of a single atom in a localized hollow-beam trap

International Nuclear Information System (INIS)

Yin, Yaling; Xia, Yong; Ren, Ruimin; Du, Xiangli; Yin, Jianping

2015-01-01

In order to realize a convenient and efficient laser cooling of a single atom, we propose a simple and promising scheme to cool a single neutral atom in a blue-detuned localized hollow-beam trap by intensity-gradient induced Sisyphus cooling, and study the dynamic process of the intensity-gradient cooling of a single 87 Rb atom in the localized hollow-beam trap by using Monte-Carlo simulations. Our study shows that a single 87 Rb atom with a temperature of 120 μK from a magneto-optical trap (MOT) can be directly cooled to a final temperature of 4.64 μK in our proposed scheme. We also investigate the dependences of the cooling results on the laser detuning δ of the localized hollow-beam, the power RP 0 of the re-pumping laser beam, the sizes of both the localized hollow-beam and the re-pumping beam, and find that there is a pair of optimal cooling parameters (δ and RP 0 ) for an expected lowest temperature, and the cooling results strongly depend on the size of the re-pumping beam, but weakly depend on the size of the localized hollow-beam. Finally, we further study the cooling potential of our localized hollow-beam trap for the initial temperature of a single atom, and find that a single 87 Rb atom with an initial temperature of higher than 1 mK can also be cooled directly to about 6.6 μK. (paper)

Photonic bandgap narrowing in conical hollow core Bragg fibers

Energy Technology Data Exchange (ETDEWEB)

Ozturk, Fahri Emre; Yildirim, Adem; Kanik, Mehmet [UNAM-National Nanotechnology Research Center, Bilkent University, 06800 Ankara (Turkey); Institute of Materials Science and Nanotechnology, Bilkent University, 06800 Ankara (Turkey); Bayindir, Mehmet, E-mail: bayindir@nano.org.tr [UNAM-National Nanotechnology Research Center, Bilkent University, 06800 Ankara (Turkey); Institute of Materials Science and Nanotechnology, Bilkent University, 06800 Ankara (Turkey); Department of Physics, Bilkent University, 06800 Ankara (Turkey)

2014-08-18

We report the photonic bandgap engineering of Bragg fibers by controlling the thickness profile of the fiber during the thermal drawing. Conical hollow core Bragg fibers were produced by thermal drawing under a rapidly alternating load, which was applied by introducing steep changes to the fiber drawing speed. In conventional cylindrical Bragg fibers, light is guided by omnidirectional reflections from interior dielectric mirrors with a single quarter wave stack period. In conical fibers, the diameter reduction introduced a gradient of the quarter wave stack period along the length of the fiber. Therefore, the light guided within the fiber encountered slightly smaller dielectric layer thicknesses at each reflection, resulting in a progressive blueshift of the reflectance spectrum. As the reflectance spectrum shifts, longer wavelengths of the initial bandgap cease to be omnidirectionally reflected and exit through the cladding, which narrows the photonic bandgap. A narrow transmission bandwidth is particularly desirable in hollow waveguide mid-infrared sensing schemes, where broadband light is coupled to the fiber and the analyte vapor is introduced into the hollow core to measure infrared absorption. We carried out sensing simulations using the absorption spectrum of isopropyl alcohol vapor to demonstrate the importance of narrow bandgap fibers in chemical sensing applications.

Synthesis and characterization of ZnO and TiO2 hollow spheres with enhanced photoreactivity

International Nuclear Information System (INIS)

Li Xiaofang; Lv Kangle; Deng Kejian; Tang Junfeng; Su Rong; Sun Jie; Chen Lianqing

2009-01-01

To study the relationship between the morphology and the photoreactivity of the catalyst, hollow spheres of two semiconductors of ZnO and TiO 2 were synthesized by using sulfonated polystyrene (PS) as template. The catalyst samples were then characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), diffuse reflectance spectra (DRS), transmission electron microscopy (TEM) and N 2 sorption. Reactive brilliant red X3B, an anionic organic dye, was used in this study as a model chemical with the aim of organic pollutants control. The results show that, whatever the catalyst was, both the adsorptive ability and photoreactivity of the hollow spheres were much higher than that of nanoparticles. The adsorption and photoreactivity of ZnO hollow spheres increased by a factor of 7.36 and 4.66, respectively compared with ZnO nanoparticles, while 3.74 times increased in adsorption and 3.41 times increased in photoreactivity for TiO 2 hollow spheres compared with TiO 2 nanoparticles. Correlations between adsorption and photoreactivity reflected the importance of adsorption in the enhanced photoreactivity of ZnO and TiO 2 hollow spheres

Synthesis of Dispersible Mesoporous Nitrogen-Doped Hollow Carbon Nanoplates with Uniform Hexagonal Morphologies for Supercapacitors.

Science.gov (United States)

Cao, Jie; Jafta, Charl J; Gong, Jiang; Ran, Qidi; Lin, Xianzhong; Félix, Roberto; Wilks, Regan G; Bär, Marcus; Yuan, Jiayin; Ballauff, Matthias; Lu, Yan

2016-11-02

In this study, dispersible mesoporous nitrogen-doped hollow carbon nanoplates have been synthesized as a new anisotropic carbon nanostructure using gibbsite nanoplates as templates. The gibbsite-silica core-shell nanoplates were first prepared before the gibbsite core was etched away. Dopamine as carbon precursor was self-polymerized on the hollow silica nanoplates surface assisted by sonification, which not only favors a homogeneous polymer coating on the nanoplates but also prevents their aggregation during the polymerization. Individual silica-polydopamine core-shell nanoplates were immobilized in a silica gel in an insulated state via a silica nanocasting technique. After pyrolysis in a nanoconfine environment and elimination of silica, discrete and dispersible hollow carbon nanoplates are obtained. The resulted hollow carbon nanoplates bear uniform hexagonal morphology with specific surface area of 460 m 2 ·g -1 and fairly accessible small mesopores (∼3.8 nm). They show excellent colloidal stability in aqueous media and are applied as electrode materials for symmetric supercapacitors. When using polyvinylimidazolium-based nanoparticles as a binder in electrodes, the hollow carbon nanoplates present superior performance in parallel to polyvinylidene fluoride (PVDF) binder.

Hollow magnetic nano-CO3O4/polystyrene microspheres synthesized through radiation induced interfacial polymerization

International Nuclear Information System (INIS)

Zhang Wei; Wang Mozhen; Wang Shufeng; Zhang Zhicheng

2010-01-01

Co 3 O 4 nanoparticles (around 8 nm) were synthesized hydrothermally by dissolving Co 2+ in the mixture of ethanol and water, and then decorated with oleic acid to endow them with hydrophobic surface nature. After that, nano-particles were added into emulsion which consisted by sodium dodecyl sulfate, water, styrene and cetyl alcohol. Hollow magnetic composite spheres were prepared by irradiated the emulsion with γ-rays. The final products are thoroughly characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), field-emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) techniques, which showed the formation of hollow magnetic composite spheres. The influence of addition dosage of nano-particles, sodium dodecyl sulfate and the types of nano-particles on the average size and shape of hollow composites were studied. The effects of nano-particles to the polymerization of styrene were studied by kinetics. Nano-particles are capsulated by polystyrene to form hollow composites, which confirmed by XPS results. Finally, magnetic property of hollow composites is compared with pure nano-Co 3 O 4 . (authors)

One-Step Synthesis of Hollow Titanate (Sr/Ba Ceramic Fibers for Detoxification of Nerve Agents

Directory of Open Access Journals (Sweden)

Satya R. Agarwal

2012-01-01

Full Text Available Poly(vinyl pyrrolidone(PVP/(strontium/barium acetate/titanium isopropoxide composite fibers were prepared by electrospinning technique via sol-gel process. Diameters of fibers prepared by calcinations of PVP composite fibers were 80–140 nm (solid and 1.2-2.2 μm (hollow fibers prepared by core-shell method. These fibers were characterized using scanning electron microscope (SEM, X-ray diffraction (XRD, and transmission electron microscope (TEM analytical techniques. XRD results showed better crystalline nature of the materials when calcined at higher temperatures. SEM and TEM results clearly showed the formation of hollow submicrometer tubes. The surface area of the samples determined by BET analysis indicated that hollow fibers have ~20% higher surface area than solid fibers. The UV studies indicate better detoxification properties of the hollow fibers compared to solid fibers.

Charge exchange induced X-ray transitions of hollow ions in laser field ionized plasmas

International Nuclear Information System (INIS)

Rosmej, F.B.; Hoffmann, D.H.H.; Faenov, A. Ya.; Pikuz, T.A.; Magunov, A.I.; Skobelev, I.Yu.; Auguste, T.; D'Oliveira, P.; Hulin, S.; Monot, P.

2000-01-01

Double electron charge exchange is proposed for the formation of hollow He-like ions when laser field ionized nuclei penetrate into the residual gas. Using transitions from different configurations in hollow ions a method for the determination of the electron temperature in the long lasting recombination phase is developed

Optofluidic in-fiber interferometer based on hollow optical fiber with two cores.

Science.gov (United States)

Yuan, Tingting; Yang, Xinghua; Liu, Zhihai; Yang, Jun; Li, Song; Kong, Depeng; Qi, Xiuxiu; Yu, Wenting; Long, Qunlong; Yuan, Libo

2017-07-24

We demonstrate a novel integrated optical fiber interferometer for in-fiber optofluidic detection. It is composed of a specially designed hollow optical fiber with a micro-channel and two cores. One core on the inner surface of the micro-channel is served as sensing arm and the other core in the annular cladding is served as reference arm. Fusion-and-tapering method is employed to couple light from a single mode fiber to the hollow optical fiber in this device. Sampling is realized by side opening a microhole on the surface of the hollow optical fiber. Under differential pressure between the end of the hollow fiber and the microhole, the liquids can form steady microflows in the micro-channel. Simultaneously, the interference spectrum of the interferometer device shifts with the variation of the concentration of the microfluid in the channel. The optofluidic in-fiber interferometer has a sensitivity of refractive index around 2508 nm/RIU for NaCl. For medicine concentration detection, its sensitivity is 0.076 nm/mmolL -1 for ascorbic acid. Significantly, this work presents a compact microfluidic in-fiber interferometer with a micro-channel which can be integrated with chip devices without spatial optical coupling and without complex manufacturing procedure of the waveguide on the chips.

Synthesis, characterization, and photocatalytic properties of Ni12P5 hollow microspheres

Science.gov (United States)

Liu, Shuling; Han, Xiaoli; Zhang, Hongzhe; Liu, Hui

2017-05-01

Ni12P5 hollow microspheres were prepared by a simple mixed cetyltrimethyl ammonium bromide/sodium dodecyl sulfate surfactant-assisted hydrothermal route. The as-prepared Ni12P5 microstructures were characterized by X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). It was interesting to find that cetyltrimethyl ammonium bromide/sodium dodecyl sulfate could form a micro-reactor by the mixed micelles in the aqueous solution, which served as a soft template for Ni12P5 hollow microspheres with a diameter of 2 6 μm. Moreover, the as-prepared Ni12P5 hollow microspheres exhibited a good photocatalytic degradation activity for some organic dyes (such as Rhodamine B, Methylene Blue, Pyronine B, and Safranine T), and the degradation ratio could achieve more than 80%.

Analytical approach of laser beam propagation in the hollow polygonal light pipe.

Science.gov (United States)

Zhu, Guangzhi; Zhu, Xiao; Zhu, Changhong

2013-08-10

An analytical method of researching the light distribution properties on the output end of a hollow n-sided polygonal light pipe and a light source with a Gaussian distribution is developed. The mirror transformation matrices and a special algorithm of removing void virtual images are created to acquire the location and direction vector of each effective virtual image on the entrance plane. The analytical method is demonstrated by Monte Carlo ray tracing. At the same time, four typical cases are discussed. The analytical results indicate that the uniformity of light distribution varies with the structural and optical parameters of the hollow n-sided polygonal light pipe and light source with a Gaussian distribution. The analytical approach will be useful to design and choose the hollow n-sided polygonal light pipe, especially for high-power laser beam homogenization techniques.

Protesa Maksilofasial Thermoplastic Nylon (Valplast dengan Hollow Bulb (Klas III Aramany palate schisis hereditary

Directory of Open Access Journals (Sweden)

A. Azhindra

2012-06-01

Full Text Available Latar Belakang: pada penderita palato schisis (celah langit-langityang disebkan hereditary atau bawaan lahir terlihat defect yang menyebabkan gangguan bicara (sengau, penelanan, pengunyahan, estetik, dan psikologis. Untuk dapat mencapai fungsi bicara, fungsi mengunyah dan fungsi estetika diperlukan protesa untuk menutup celah tersebut. Tujuan: untuk meninformasikan cara rehabilitas defect atau cacat pada wajah dengan protesa maksilofasial thermoplastic nylon dengan hollow buib yang berguna untuk mengembalikan fungsi bicara, penelanan, pengunyahan, estetik dan psikologis penderita. Kasus dan penanganan: pasien pria berusia 46 tahun dating ke RSGM Prof. Soedomo atas rujukan dari poli RS. Dr. Sardjito. Saat datang pasien terganggu berbicara, menguyah dan menelan disebkan adanya celah langit-langit terbuka dan merupakan kelainan bawaan. Pasien kehilangan banyak gigi terutama pada gigi posterior pada rahang atas dan ingin dibuatkan gigi tiruan. Obturator ini dibuat segera dengan mempertimbangkan penutupan celah langit-langit, menggunakan bahan yang lebih ringan (menggunakan hoolow bulb agar keluhan pasien dapat diatasi didesain alat yang mempunyai retensi maksimal dan mengembalikan pengunyahan, fungsi bicara, penelanan, estetis dan psikologis sehingga pasien akan akan mempunyai bentuk wajah yang mendekati normal. Hollow bulb adalah rongga yang dibuat pada protesa maksilofasial untuk menutup rongga mulut, rongga hidung dan defect. Pada waktu insersi diperiksa retensi, stabilisasi, oklusi, estetik dan pengucapan. Kontrol dilakukan 1 minggu dan 1 bulan setelah pemakaian. Hasil pemeriksaan dan evaluasi setelah 1 minggu dan 1 bulan setelah pemakaian protesa maksilofasial hollow bulb didapatkan hasil dengan retensi, stabilisasi, olusi dan pengucapan lebih baik. Kesimpulan: setelah menggunakan protesa maksilofasial thermoplastic nylon dengan hollow buib pada penderita palato scisis, pasien dapat berbicara dan mengunyah dengan normal. Protesa maksilofasial

A fluid model for the edge pressure pedestal height and width in tokamaks based on the transport constraint of particle, energy, and momentum balance

Energy Technology Data Exchange (ETDEWEB)

Stacey, W. M., E-mail: weston.stacey@nre.gatech.edu [Georgia Institute of Technology, Atlanta, Georgia 30332 (United States)

2016-06-15

A fluid model for the tokamak edge pressure profile required by the conservation of particles, momentum and energy in the presence of specified heating and fueling sources and electromagnetic and geometric parameters has been developed. Kinetics effects of ion orbit loss are incorporated into the model. The use of this model as a “transport” constraint together with a “Peeling-Ballooning (P-B)” instability constraint to achieve a prediction of edge pressure pedestal heights and widths in future tokamaks is discussed.

Photocatalytic action of cerium molybdate and iron-titanium oxide hollow nanospheres on Escherichia coli

International Nuclear Information System (INIS)

Kartsonakis, I. A.; Kontogiani, P.; Pappas, G. S.; Kordas, G.

2013-01-01

This study is focused on the production of hollow nanospheres that reveal antibacterial action. Cerium molybdate and iron-titanium oxide hollow nanospheres with a diameter of 175 ± 15 and 221 ± 10 nm, respectively, were synthesized using emulsion polymerization and the sol–gel process. Their morphology characterization was accomplished using scanning electron microscopy. Their antibacterial action was examined on pure culture of Escherichia coli considering the loss of their viability. Both hollow nanospheres presented photocatalytic action after illumination with blue–black light, but those of cerium molybdate also demonstrated photocatalytic action in the dark. Therefore, the produced nanospheres can be used for antibacterial applications.

Investigation of concrete mixtures incorporating hollow plastic microspheres.

Science.gov (United States)

1981-01-01

This study investigated the potential of hollow plastic microspheres, HPM, for providing non-air-entrained portland cement concrete resistance to damage from cycles of freezing and thawing. In the study, a mixture with an air-entraining agent (vinsol...

Realization of low loss and polarization maintaining hollow core photonic crystal fibers

DEFF Research Database (Denmark)

Mangan, Brian Joseph; Lyngsøe, Jens Kristian; Roberts, John

2008-01-01

Antiresonant core wals in 7-cell hollow core fibers are used to reduce the attenuation to 9.3dB/km and create an intentionally hightly birefringent fiber with a beatlength as low as 0.2mm......Antiresonant core wals in 7-cell hollow core fibers are used to reduce the attenuation to 9.3dB/km and create an intentionally hightly birefringent fiber with a beatlength as low as 0.2mm...

Interconnected Silicon Hollow Nanospheres for Lithium-Ion Battery Anodes with Long Cycle Life

KAUST Repository

Yao, Yan

2011-07-13

Silicon is a promising candidate for the anode material in lithium-ion batteries due to its high theoretical specific capacity. However, volume changes during cycling cause pulverization and capacity fade, and improving cycle life is a major research challenge. Here, we report a novel interconnected Si hollow nanosphere electrode that is capable of accommodating large volume changes without pulverization during cycling. We achieved the high initial discharge capacity of 2725 mAh g-1 with less than 8% capacity degradation every hundred cycles for 700 total cycles. Si hollow sphere electrodes also show a Coulombic efficiency of 99.5% in later cycles. Superior rate capability is demonstrated and attributed to fast lithium diffusion in the interconnected Si hollow structure. © 2011 American Chemical Society.

Calculation of shear strength of prestressed hollow core slabs by use of plastic theory

DEFF Research Database (Denmark)

Hoang, Linh Cao; Jørgensen, H.G.; Nielsen, Mogens Peter

2014-01-01

Th is paper deals with calculations of the shear capacity of precast, prestressed hollow core slabs. Such slabs are often used as floor systems in building structures. A common way to produce hollow core slabs is to use the extrusion technique where long strips of slabs are extruded and thereafter...

Block copolymer/homopolymer dual-layer hollow fiber membranes

KAUST Repository

Hilke, Roland

2014-12-01

We manufactured the first time block copolymer dual-layer hollow fiber membranes and dual layer flat sheet membranes manufactured by double solution casting and phase inversion in water. The support porous layer was based on polystyrene and the selective layer with isopores was formed by micelle assembly of polystyrene-. b-poly-4-vinyl pyridine. The dual layers had an excellent interfacial adhesion and pore interconnectivity. The dual membranes showed pH response behavior like single layer block copolymer membranes with a low flux for pH values less than 3, a fast increase between pH4 and pH6 and a constant high flux level for pH values above 7. The dry/wet spinning process was optimized to produce dual layer hollow fiber membranes with polystyrene internal support layer and a shell block copolymer selective layer.

Motion Control of Urea-Powered Biocompatible Hollow Microcapsules.

Science.gov (United States)

Ma, Xing; Wang, Xu; Hahn, Kersten; Sánchez, Samuel

2016-03-22

The quest for biocompatible microswimmers powered by compatible fuel and with full motion control over their self-propulsion is a long-standing challenge in the field of active matter and microrobotics. Here, we present an active hybrid microcapsule motor based on Janus hollow mesoporous silica microparticles powered by the biocatalytic decomposition of urea at physiological concentrations. The directional self-propelled motion lasts longer than 10 min with an average velocity of up to 5 body lengths per second. Additionally, we control the velocity of the micromotor by chemically inhibiting and reactivating the enzymatic activity of urease. The incorporation of magnetic material within the Janus structure provides remote magnetic control on the movement direction. Furthermore, the mesoporous/hollow structure can load both small molecules and larger particles up to hundreds of nanometers, making the hybrid micromotor an active and controllable drug delivery microsystem.

3D hollow framework of GeOx with ultrathin shell for improved anode performance in lithium-ion batteries

International Nuclear Information System (INIS)

Fang, Zhen; Qiang, Tingting; Fang, Jiaxin; Song, Yixuan; Ma, Qiuyang; Ye, Ming; Qiang, Feiqiang; Geng, Baoyou

2015-01-01

Highlights: • 3D hollow framework of GeO x was synthesized using hydrothermal procedure. • The obtained GeO x 3D hollow framework has large surface area and porous thin shell. • The structure improved the cycle and rate performances. - Abstract: In this paper, 3D hollow framework of GeO x is synthesized using a bubble-template hydrothermal procedure. The as-obtained hollow structure exhibits excellent cycling performance and rate capability in comparison with GeO x nanoparticles when used as an anode material in lithium ion batteries. The GeO x 3D hollow framework shows a high capacity of up to 1480 mAh·g −1 and 1109 mAh·g −1 at 80 mA·g −1 and 1600 mA·g −1 current density, respectively. The excellent lithium storage performance can be attributed to the unique 3D hollow framework. The framework not only acts as the buffer layer to alleviate the strain during lithiation, but also facilitates the electron transfer during the charge/discharge processes

Reflection From Hollow Armour Units / by Fritz Büsching. - COPEDEC V, Cape Town, South Africa, 19-23 April 1999

OpenAIRE

Büsching, Fritz

1999-01-01

Model investigations are carried out in using irregular and monochromatic waves synchronously acting on 2 sloping structures 1:n = 1:2 in order to demonstrate the advantages of a new designed structure composed from hollow armour units (“Hollow Cubes”) versus a conventional smooth sloping structure. The energy of the water level deflections in front of the hollow armour units piled up to form a stepped-face hollow seawall structure appears to be reduced by about -65% with refer-ence to a smoo...

Electrochemical properties of CuO hollow nanopowders prepared from formless Cu–C composite via nanoscale Kirkendall diffusion process

Energy Technology Data Exchange (ETDEWEB)

Won, Jong Min [Department of Materials Science and Engineering, Korea University, Anam-Dong, Seongbuk-Gu, Seoul 136-713 (Korea, Republic of); Kim, Jong Hwa [Daegu Center, Korea Basic Science Institute, 80 Daehakro Bukgu, Daegu 702-701 (Korea, Republic of); Choi, Yun Ju [Suncheon Center, Korea Basic Science Institute, Suncheon 540-742 (Korea, Republic of); Cho, Jung Sang [Department of Materials Science and Engineering, Korea University, Anam-Dong, Seongbuk-Gu, Seoul 136-713 (Korea, Republic of); Kang, Yun Chan, E-mail: yckang@korea.ac.kr [Department of Materials Science and Engineering, Korea University, Anam-Dong, Seongbuk-Gu, Seoul 136-713 (Korea, Republic of)

2016-06-25

Hollow CuO nanopowders are prepared using a simple spray drying process that relied on nanoscale Kirkendall diffusion; these nanopowders have potential applications in lithium-ion batteries. Citric acid is used as both the carbon source material and chelating agent and plays a key role in the preparation of the hollow nanopowders. The formless Cu–C composite that formed as an intermediate product transforms into slightly aggregated CuO hollow nanopowders after post-treatment at 300 and 400 °C under an air atmosphere. The CuO hollow nanopowders exhibit higher initial discharge capacities and better cycling performances than those of the filled-structured CuO nanopowders, which are prepared at a post-treatment temperature of 500 °C under an air atmosphere. The discharge capacities of the CuO nanopowders post-treated at 300, 400, and 500 °C for the 150{sup th} cycle at a current density of 1 A g{sup −1} are 793, 632, and 464 mA h g{sup −1}, respectively, and their capacity retentions calculated from the maximum discharge capacities are 88, 80, and 73%, respectively. The CuO nanopowders with hollow structures exhibit better structural stability for repeated lithium insertion and desertion processes than those with filled structures. - Highlights: • Hollow CuO nanopowders are prepared using a simple spray drying process. • Cu–C composite transforms into CuO hollow nanopowders by Kirkendall diffusion. • Hollow CuO nanopowders show good electrochemical properties for lithium-ion storage.

A facile one-pot hydrothermal method to prepare europium-doped titania hollow phosphors and their sensitized luminescence properties

Energy Technology Data Exchange (ETDEWEB)

Feng Xuan; Yang Ling; Zhang Nianchun [Department of Chemistry and Institute of Nanochemistry, Jinan University, 601 Western Huangpu Road, Guangzhou 510632 (China); Liu Yingliang, E-mail: tliuyl@jnu.edu.c [Department of Chemistry and Institute of Nanochemistry, Jinan University, 601 Western Huangpu Road, Guangzhou 510632 (China)

2010-09-17

Research highlights: {yields} The strongest emission intensity was observed with TiO{sub 2}:Eu{sub 0.2} hollow spheres and TiO{sub 2}:Eu{sub 0.2} hollow spheres calcining at 550 {sup o}C. Moreover, the strongest excitation of TiO{sub 2}:Eu{sub 0.2} hollow spheres transferred from 400 to 500 {sup o}C and the effective nonradiative energy transfer from the TiO{sub 2} hollow spheres host matrix to Eu{sup 3+} ions crystal field states was realized due to changes of crystalline field in the environment around Eu{sup 3+} ions occupying Ti{sup 4+} sites. The proposed energy transfer mechanism was that UV light is absorbed in the band of TiO{sub 2} hollow spheres crystal and then the energy is relaxed to the defect states of TiO{sub 2} host. The energy can transfer to the crystal states of Eu{sup 3+} ions ({sup 7}F{sub j}, j = 0, 1, 2, 3 and 4), which results in efficient photoluminescence. The fluorescent intensity of TiO{sub 2}:Eu{sub 0.2} hollow spheres was 2.2 times as strong as that of TiO{sub 2}:Eu{sub 0.2} bulk material. - Abstract: Monodisperse europium-activated titania hollow phosphors had been synthesized by a facile one-pot hydrothermal method using carbon spheres as hard templates. Samples were characterized by X-ray powder diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, energy dispersive spectrometer and photoluminescence spectrum. The strongest emission intensity was observed with TiO{sub 2}:Eu{sub 0.2} hollow spheres and TiO{sub 2}:Eu{sub 0.2} hollow spheres calcining at 550 {sup o}C. Moreover, the strongest excitation of TiO{sub 2}:Eu{sub 0.2} hollow spheres transferred from 400 to 500 {sup o}C and the effective nonradiative energy transfer from the TiO{sub 2} hollow spheres host matrix to Eu{sup 3+} ions crystal field states was realized due to changes of crystalline field in the environment around Eu{sup 3+} ions occupying Ti{sup 4+} sites. The proposed energy transfer mechanism was that UV light is absorbed in the band

Determination of thermal characteristics of standard and improved hollow concrete blocks using different measurement techniques

DEFF Research Database (Denmark)

Caruana, C.; Yousif, C.; Bacher, Peder

2017-01-01

The lighter weight, improved thermal properties and better acoustic insulation of hollow-core concrete blocks are few of the characteristics that one encounters when comparing them to traditional Maltese globigerina limestone solid blocks. As a result, hollow concrete blocks have recently been...

Hollow Au@Pd and Au@Pt core-shell nanoparticles as electrocatalysts for ethanol oxidation reactions

KAUST Repository

Song, Hyon Min; Anjum, Dalaver H.; Sougrat, Rachid; Hedhili, Mohamed N.; Khashab, Niveen M.

2012-01-01

that individual metals may not catalyze. Here, preparation of hollow Au@Pd and Au@Pt core-shell nanoparticles (NPs) and their use as electrocatalysts are reported. Galvanic displacement with Ag NPs is used to obtain hollow NPs, and higher reduction potential of Au

Solvothermal synthesis and electrochemical performance of hollow LiFePO{sub 4} nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Zheng, Zhenmiao [School of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China); Pang, Wei Kong [Institute for Superconducting and Electronic Materials, University of Wollongong, Wollongong, NSW 2522 (Australia); Australian Nuclear Science and Technology Organization, Locked Bag 2001, Kirrawee DC, NSW 2232 (Australia); Tang, Xincun, E-mail: tangxincun@163.com [School of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China); Jia, Dianzeng; Huang, Yudai [Institute of Applied Chemistry, Xinjiang University, Urumqi 840046 (China); Guo, Zaiping [Institute for Superconducting and Electronic Materials, University of Wollongong, Wollongong, NSW 2522 (Australia)

2015-08-15

Highlights: • Hollow LiFePO{sub 4} nanoparticles were successfully synthesized via solvothermal method. • The shorter b lattice parameter allows the shorter diffusion path of lithium ion. • Hollow LiFePO{sub 4} nanoparticles show better rate capability than solid LiFePO{sub 4}. - Abstract: Hollow LiFePO{sub 4} nanoparticles were synthesized via a solvothermal technique, using ammonium tartrate as additive and carbon source, and ethylene glycol/water as solvent. The as-prepared samples were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, Raman spectroscopy, scanning and transmission electron microscopies, and Brunauer–Emmett–Teller specific surface area measurements. The electrochemical properties of the LiFePO{sub 4} cathode were examined in coin-type cell configuration and the cathode exhibited excellent rate capability (i.e., discharge capacity of 120.9 mA h g{sup −1} at 10 C) and cycling performance (i.e., >98% of capacity retention rate after 50 cycles). It is believed that the enhanced performance is correlated to the hollow structure, small crystallite and particle sizes, and relatively shorter lattice parameter b.

Hollow carbon nanospheres using an asymmetric triblock copolymer structure directing agent.

Science.gov (United States)

Li, Yunqi; Tan, Haibo; Salunkhe, Rahul R; Tang, Jing; Shrestha, Lok Kumar; Bastakoti, Bishnu Prasad; Rong, Hongpan; Takei, Toshiaki; Henzie, Joel; Yamauchi, Yusuke; Ariga, Katsuhiko

2016-12-20

We introduce a simple method to prepare hollow carbon nanospheres (HCNs) by using triblock copolymer poly(styrene-b-2-vinylpyridine-b-ethylene oxide) (PS-b-P2VP-b-PEO) micelles as a new class of soft-templates. Simply by changing the solvent we can prepare ultra-small sized micelles of the triblock copolymer PS-b-P2VP-b-PEO soft template to obtain HCNs with ultra-small diameters (43 nm) and hollow cores (19 nm). Furthermore, we use these HCNs to make electric double-layer capacitors (EDLCs) that exhibit superior performance.

Development of Novel ECTFE Coated PP Composite Hollow-Fiber Membranes

Directory of Open Access Journals (Sweden)

Sergio Santoro

2016-09-01

Full Text Available In this work composite hollow-fibers were prepared by dip-coating of commercial polypropylene (PP with a thin layer of ethylene–chlorotrifluoroethylene copolymer (ECTFE. The employment of N-methyl pyrrolidone (NMP as solvent improved the polymer processability favoring dip-coating at lower temperature (135 °C. Scanning electron microscopy (SEM analyses showed that after dip-coating the PP support maintained its microstructure, whereas a thin coated layer of ECTFE on the external surface of the PP hollow-fiber was clearly distinguishable. Membrane characterization evidenced the effects of the concentration of ECTFE in the dope-solution and the time of dip-coating on the thickness of ECTFE layer and membrane properties (i.e., contact angle and pore size. ECTFE coating decreased the surface roughness reducing, as a consequence, the hydrophobicity of the membrane. Moreover, increasing the ECTFE concentration and dip-coating time enabled the preparation of a thicker layer of ECTFE with low and narrow pore size that negatively affected the water transport. On the basis of the superior chemical resistance of ECTFE, ECTFE/PP composite hollow fibers could be considered as very promising candidates to be employed in membrane processes involving harsh conditions.

Hybrid welding of hollow section beams for a telescopic lifter

Science.gov (United States)

Jernstroem, Petteri

2003-03-01

Modern lifting equipment is normally constructed using hollow section beams in a telescopic arrangement. Telescopic lifters are used in a variety number of applications including e.g. construction and building maintenance. Also rescue sector is one large application field. It is very important in such applications to use a lightweight and stable beam construction, which gives a high degree of flexibility in working high and width. To ensure a high weld quality of hollow section beams, high efficiency and minimal distortion, a welding process with a high power density is needed. The alternatives, in practice, which fulfill these requirements, are laser welding and hybrid welding. In this paper, the use of hybrid welding process (combination of CO2 laser welding and GMAW) in welding of hollow section beam structure is presented. Compared to laser welding, hybrid welding allows wider joint tolerances, which enables joints to be prepared and fit-up less accurately, aving time and manufacturing costs. A prerequisite for quality and effective use of hybrid welding is, however, a complete understanding of the process and its capabilities, which must be taken into account during both product design and manufacture.

Sputter deposition of BSCCO films from a hollow cathode

International Nuclear Information System (INIS)

Lanagan, M.T.; Kampwirth, R.T.; Doyle, K.; Kowalski, S.; Miller, D.; Gray, K.E.

1991-01-01

High-T c superconducting thin films were deposited onto MgO single crystal substrates from a hollow cathode onto ceramic targets with the nominal composition of Bi 2 Sr 2 CaCu 2 O x . Films similar in composition to those used for the targets were deposited on MgO substrates by rf sputtering. The effects of sputtering time, rf power, and post-annealing on film microstructure and properties were studied in detail. Substrate temperature was found to have a significant influence on the film characteristics. Initial results show that deposition rates from a hollow cathode are an order of magnitude higher than those of a planar magnetron source at equivalent power levels. Large deposition rates allow for the coating of long lengths of wire

Hollow-core infrared fiber incorporating metal-wire metamaterial

DEFF Research Database (Denmark)

Yan, Min; Mortensen, Asger

2009-01-01

Infrared (IR) light is considered important for short-range wireless communication, thermal sensing, spectroscopy, material processing, medical surgery, astronomy etc. However, IR light is in general much harder to transport than optical light or microwave radiation. Existing hollow-core IR...

Method of altering the effective bulk density of solid material and the resulting product: hollow polymeric particles

International Nuclear Information System (INIS)

Kool, L.B.; Nolen, R.L.; Solomon, D.E.

1981-01-01

Hollow spherical particles are made by spraying a mixture of powdered solid material with a solution of a film-forming polymer in a solvent therefor into a heated chamber where the solvent evaporates. The powder is thereby captured in the wall of the hollow polymer particles formed. Such particles are used to form a suspension in a fluid material. The hollow particles are of such size and wall thickness, in relation to the bulk density of the powdered solid material, that the bulk density of each hollow spherical particle is commensurate with the density of the fluid material. The particles thereby remain in suspension over a substantial period of time with little or no agitation of the fluid. (author)

Difference-frequency laser spectroscopy of molecular ions with a hollow-cathode cell: extended analysis of the ν1 band of H2D+

International Nuclear Information System (INIS)

Amano, T.

1985-01-01

A cooled hollow-cathode cell was used for observation of the infrared spectra of positive ions in the 3-μm region with a difference-frequency laser as a radiation source. About an order-of-magnitude enhancement of the signal intensity was attained, compared with the similar signals obtained with our previous glow-discharge cell. Ten more weaker lines of the ν 1 fundamental band of H 2 D + , which could not be observed in our previous experiment [J. Chem. Phys. 81, 2869 (1984)] were measured. Improved molecular constants were obtained from a least-squares fit including the infrared lines and the two millimeter-and submillimeter-wave lines in the ground state