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RISS 인기검색어
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- 저자 : Dendy, R.O. (검색결과 4 건)
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Performance of Pico Scale Turgo Turbine in Difference the Nozzle Diameter
Dendy Adanta,Imam Syofii,Dewi Puspita Sari,Apri Wiyono 한국유체기계학회 2022 International journal of fluid machinery and syste Vol.15 No.1
Pico scale Turgo turbine (PSTT) is proper as a power plant to be applied for remote areas because of its simple construction, cheap investment cost, and good performance above 35%. However, the design of PSTT is still based on estimation because the wheel diameter and nozzle diameter (D/d) ratio are not yet in reasonable agreement. Furthermore, the literature on D/d affects PSTT performance has not been comprehensive. Accordingly, this study investigates the relation of D/d on PSTT performance and its effect on the U/Vjet. Based on experimental results, the relation of D/d and U/Vjet to PSTT performance is parabolic (expressed by polynomial quadratic); the maximum configuration of D/d of 22, and U/Vjet between 0.42 to 0.47.
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Chapman, B.,Dendy, R.O.,Chapman, S.C.,McClements, K.G.,Yun, G.S.,Thatipamula, S.G.,Kim, M.H. International Atomic Energy Agency 2018 Nuclear fusion Vol.58 No.9
<P>The radio frequency detection system on the KSTAR tokamak has exceptionally high spectral and temporal resolution. This enables measurement of previously undetected fast plasma phenomena in the ion cyclotron range of frequencies. Here we report and analyse a novel spectrally structured ion cyclotron emission (ICE) feature in the range 500 MHz to 900 MHz, which exhibits chirping on sub-microsecond timescales. Its spectral peaks correspond to harmonics <I>l</I> of the proton cyclotron frequency <I>f</I> <SUB>cp</SUB> at the outer midplane edge, where <I>l</I> = 20–36. This frequency range exceeds estimates of the local lower hybrid frequency <I>f</I> <SUB>LH</SUB> in the KSTAR deuterium plasma. The new feature is time-shifted with respect to a brighter lower-frequency chirping ICE feature in the range 200 MHz (8<I>f</I> <SUB>cp</SUB>) to 500 MHz (20<I>f</I> <SUB>cp</SUB>), which is probably driven (Chapman <I>et al</I> 2017 <I>Nucl. Fusion</I> <B>57</B> 124004) by 3 MeV fusion-born protons undergoing collective relaxation by the magnetoacoustic cyclotron instability (MCI). Here we show that the new, fainter, higher-frequency chirping ICE feature is driven by nonlinear wave coupling between different neighbouring spectral peaks in the lower-frequency ICE feature. This follows from bispectral analysis of the measured KSTAR fields, and of the field amplitudes output from particle-in-cell (PIC) simulations of the KSTAR edge plasma containing fusion-born protons. This reinforces the identification of the MCI as the plasma physics process underlying proton harmonic ICE from KSTAR, while providing a novel instance of nonlinear wave coupling on very fast timescales.</P>
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Chapman, B.,Dendy, R.O.,McClements, K.G.,Chapman, S.C.,Yun, G.S.,Thatipamula, S.G.,Kim, M.H. International Atomic Energy Agency 2017 Nuclear fusion Vol.57 No.12
<P>During edge localised mode (ELM) crashes in KSTAR deuterium plasmas, bursts of spectrally structured ion cyclotron emission (ICE) are detected. Usually the ICE spectrum chirps downwards during an ELM crash, on sub-microsecond timescales. For KSTAR ICE where the separation of spectral peak frequencies is close to the proton cyclotron frequency <img ALIGN='MIDDLE' ALT='$\Omega_{\rm cp}$ ' SRC='http://ej.iop.org/images/0029-5515/57/12/124004/nfaa8e09ieqn001.gif'/> at the outer plasma edge, we show that the driving population of energetic ions is likely to be a subset of the 3 MeV fusion protons, born centrally on deeply passing orbits which drift from the core to the edge plasma. We report first principles modelling of this scenario using a particle-in-cell code, which evolves the full orbit dynamics of large numbers of energetic protons, thermal deuterons, and electrons self-consistently with the electric and magnetic fields. The Fourier transform of the excited fields in the nonlinear saturated regime of the simulations is the theoretical counterpart to the measured ICE spectra. Multiple simulation runs for different, adjacent, values of the plasma density under KSTAR edge conditions enable us to infer the theoretical dependence of ICE spectral structure on the local electron number density. By matching this density dependence to the observed time-dependence of chirping ICE spectra in KSTAR, we obtain sub-microsecond time resolution of the evolving local electron number density during the ELM crash.</P>
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The cages, dynamics, and structuring of incipient methane clathrate hydrates
Walsh, Matthew R.,Rainey, J. Daniel,Lafond, Patrick G.,Park, Da-Hye,Beckham, Gregg T.,Jones, Michael D.,Lee, Kun-Hong,Koh, Carolyn A.,Sloan, E. Dendy,Wu, David T.,Sum, Amadeu K. Royal Society of Chemistry 2011 Physical chemistry chemical physics Vol.13 No.44
<P>Interest in describing clathrate hydrate formation mechanisms spans multiple fields of science and technical applications. Here, we report findings from multiple molecular dynamics simulations of spontaneous methane clathrate hydrate nucleation and growth from fully demixed and disordered two-phase fluid systems of methane and water. Across a range of thermodynamic conditions and simulation geometries and sizes, a set of seven cage types comprises approximately 95% of all cages formed in the nucleated solids. This set includes the ubiquitous 5<SUP>12</SUP> cage, the 5<SUP>12</SUP>6<SUP><I>n</I></SUP> subset (where <I>n</I> ranges from 2–4), and the 4<SUP>1</SUP>5<SUP>10</SUP>6<SUP><I>n</I></SUP> subset (where <I>n</I> also ranges from 2–4). Transformations among these cages occur <I>via</I> water pair insertions/removals and rotations, and may elucidate the mechanisms of solid–solid structural rearrangements observed experimentally. Some consistency is observed in the relative abundance of cages among all nucleation trajectories. 5<SUP>12</SUP> cages are always among the two most abundant cage types in the nucleated solids and are usually the most abundant cage type. In all simulations, the 5<SUP>12</SUP>6<SUP><I>n</I></SUP> cages outnumber their 4<SUP>1</SUP>5<SUP>10</SUP>6<SUP><I>n</I></SUP> counterparts with the same number of water molecules. Within these consistent features, some stochasticity is observed in certain cage ratios and in the long-range ordering of the nucleated solids. Even when comparing simulations performed at the same conditions, some trajectories yield swaths of multiple adjacent sI unit cells and long-range order over 5 nm, while others yield only isolated sI unit cells and little long-range order. The nucleated solids containing long-range order have higher 5<SUP>12</SUP>6<SUP>2</SUP>/5<SUP>12</SUP> and 5<SUP>12</SUP>6<SUP>3</SUP>/4<SUP>1</SUP>5<SUP>10</SUP>6<SUP>2</SUP> cage ratios when compared to systems that nucleate with little long-range order. The formation of multiple adjacent unit cells of sI hydrate at high driving forces suggests an alternative or addition to the prevailing hydrate nucleation hypotheses which involve formation through amorphous intermediates.</P> <P>Graphic Abstract</P><P>The dominant cages of clathrates are classified and the formation of multiple sI unit cells is reported from large-scale simulations. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c1cp21899a'> </P>
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