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Effects of edge biasing on blob dynamics and associated transport in the edge of the J-TEXT tokamak

PLASMA PHYSICS AND CONTROLLED FUSION 2022年第3期64卷 035013-035013页

作者： Li, W. Xu, Y. Cheng, J. Liu, H. Chen, Z. P. Xu, J. Q. Wang, X. Q. Chen, Z. Y. Wang, N. C. Yang, Z. J. Ding, Y. H. Pan, Y. Southwest Jiaotong Univ Sch Phys Sci & Technol Inst Fus Sci Chengdu 610031 Sichuan Peoples R China Huazhong Univ Sci & Technol Sch Elect & Elect Engn Int Joint Res Lab Magnet Confinement Fus & Plasma State Key Lab Adv Electromagnet Engn & Technol Wuhan 430074 Peoples R China Southwestern Inst Phys POB 432 Chengdu 610041 Peoples R China

Effects of edge radial electric field E-r and E-r x B flow shear on edge turbulence and turbulent transport, in particular, on large-scale blobs and blobby transport have been investigated in the positive and negative biasing discharges in the J-TEXT tokamak. The results show that under certain conditions, the positive electrode biasing induces better plasma confinement than the negative biasing. Further studies reveal that in addition to flow shear effects on blob dynamics, the local radial electric field at the edge region plays a significant role in repulsion of the blobs and associated transport, leading to improvement of particle confinement when the outward motion of the blobs is blocked. The results are consistent with the existing theory on blob dynamics.

关键词： blobs biasing electric field turbulent transport

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Visual4DTracker: a tool to interact with 3D+t image stacks

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BMC BIOINFORMATICS 2021年第1期22卷 1-15页

作者： Cordelli, Ermanno Soda, Paolo Iannello, Giulio Univ Campus Biomed Roma Unit Comp Syst & Bioinformat Dept Engn Rome Italy

BackgroundBiological phenomena usually evolves over time and recent advances in high-throughput microscopy have made possible to collect multiple 3D images over time, generating 3D+t (or 4D) datasets. To extract useful information there is the need to extract spatial and temporal data on the particles that are in the images, but particle tracking and feature extraction need some kind of *** manuscript introduces our new freely downloadable toolbox, the Visual4DTracker. It is a MATLAB package implementing several useful functionalities to navigate, analyse and proof-read the track of each particle detected in any 3D+t stack. Furthermore, it allows users to proof-read and to evaluate the traces with respect to a given gold standard. The Visual4DTracker toolbox permits the users to visualize and save all the generated results through a user-friendly graphical user interface. This tool has been successfully used in three applicative examples. The first processes synthetic data to show all the software functionalities. The second shows how to process a 4D image stack showing the time-lapse growth of Drosophila cells in an embryo. The third example presents the quantitative analysis of insulin granules in living beta-cells, showing that such particles have two main dynamics that coexist inside the ***4DTracker is a software package for MATLAB to visualize, handle and manually track 3D+t stacks of microscopy images containing objects such cells, granules, etc.. With its unique set of functions, it remarkably permits the user to analyze and proof-read 4D data in a friendly 3D fashion. The tool is freely available at https://***/drive/folders/19AEn0TqP-2B8Z10kOavEAopTUxsKUV73?usp=sharing

关键词： Tracking Image proofreading blobs MATLAB package

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Strongly intermittent far scrape-off layer fluctuations in Alcator C-Mod plasmas close to the empirical discharge density limit

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PLASMA PHYSICS AND CONTROLLED FUSION 2023年第10期65卷 105008-105008页

作者： Ahmed, Sajidah Garcia, Odd Erik Kuang, Adam Labombard, Brian Terry, James Theodorsen, Audun UiT Arctic Univ Norway Dept Phys & Technol N-9037 Tromso Norway Commonwealth Fus Syst 117 Hosp Rd Devens MA 01434 USA MIT Plasma Sci & Fus Ctr Cambridge MA 02139 USA

Intermittent plasma fluctuations in the boundary region of the Alcator C-Mod device were comprehensively investigated using data time-series from gas puff imaging and mirror Langmuir probe diagnostics. Fluctuations were sampled during stationary plasma conditions in ohmically heated, lower single null diverted configurations with scans in both line-averaged density and plasma current, with Greenwald density fractions up to 0.85. Utilizing a stochastic model, we describe the plasma fluctuations as a super-position of uncorrelated pulses, with large-amplitude events corresponding to blob-like filaments moving through the scrape-off layer (SOL). A deconvolution method is used to estimate the pulse arrival times and amplitudes. The analysis reveals a significant increase of pulse amplitudes and waiting times as the line-averaged density approaches the empirical discharge density limit. Broadened and flattened average radial profiles are thus accompanied by strongly intermittent and large-amplitude fluctuations. Although these filaments are arriving less frequently at high line-averaged densities, we show that there are significant increases in radial far-SOL particle and heat fluxes which will further enhance plasma-wall interactions. The stochastic model has been used as a framework for study of the scalings in the intermittency parameter, flux and mean amplitude and waiting times, and is being used to inform predictive capability for the effects of filamentary transport as a function of Greenwald fraction.

关键词： scrape-off layer intermittency filament blobs stochastic modeling turbulence plasma-wall interactions

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Cross-field and parallel dynamics of SOL filaments in TCV

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NUCLEAR FUSION 2022年第9期62卷 096014-096014页

作者： Offeddu, N. Han, W. Theiler, C. Golfinopoulos, T. Terry, J. L. Marmar, E. Wuthrich, C. Tsui, C. K. de Oliveira, H. Duval, B. P. Galassi, D. Oliveira, D. S. Mancini, D. Ecole Polytech Fed Lausanne EPFL Swiss Plasma Ctr SPC CH-1015 Lausanne Switzerland MIT Plasma Sci & Fus Ctr PSFC 77 Massachusetts Ave Cambridge MA 02139 USA UCSD Ctr Energy Res CER La Jolla CA 92093 USA Univ Tuscia Largo Univ Snc I-01100 Viterbo Italy

Using recently installed scrape-off layer diagnostics on the tokamak a configuration variable, we characterise the poloidal and parallel properties of turbulent filaments. We access both attached and detached divertor conditions across a wide range of core densities (f (G) is an element of [0.09, 0.66]) in diverted L-mode plasma configurations. With a gas puff imaging (GPI) diagnostic at the outer midplane we observed filaments with a monotonic increase in radial velocity (from 390 m s(-1) to 800 m s(-1)) and cross-field radii (from 8.5 mm to 13.4 mm) with increasing core density. Interpreting the filament behaviour in the context of the two-region model by Myra et al (2006 Phys. Plasmas 13 112502), we find that they populate the ideal-interchange regime (C (i)) in discharges at very low densities, and the resistive X (RX)-point regime for all other discharges. The scaling of filament velocity versus size shows good agreement with this interpretation. These results are discussed and compared with previous probe-based measurements for similar conditions, which mostly placed filaments in TCV in the resistive ballooning (RB) regime (Tsui et al 2018 Phys. Plasmas 25 072506). In addition, for the first time in TCV, the parallel filament extension is studied by magnetically aligning the GPI measurements at the outboard midplane with a reciprocating probe in the divertor. In agreement with the filaments being in the ideal-interchange and the RX-point regimes, they are found to extend beyond the X-point into the outer divertor leg.

关键词： filamentary turbulence SOL turbulence cross-field transport blobs two-region model turbulent transport regime parallel dynamics

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Dependency of the mobility of carboxymethylated cellulosic polyions on the nature of their counterions

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JOURNAL OF MOLECULAR LIQUIDS 2022年 353卷

作者： Ghazouani, Anis M'halla, Jalel Boughammoura, Sondes Univ Monastir Fac Sci Monastir Lab LPQS UR Electrolytes Monastir 5000 Tunisia

In this paper, we propose a new approach in order to interpret the dependency of the conductibility of carboxymethylated cellulosic polyelectrolytes XCMC1, XCMC2, XCMC3 in water at 25 degrees C, with their alkali counterions (X Li+, Na+ and K+) or ammonium counterions (X Et4N+ and Bu4N+). The 750 ring-blocks of each CMCi chain are randomly substituted by CH2COO groups, of electric charge (e alpha(x)), where alpha(x) is the degree of dissociation of the counterions X. It is found that for a given C-X <= 7 10(-3) mol.l(-1), the experimental equivalent conductivity lambda(P,X) of the polyion CMCi decreases as follows: lambda(+)(P,X) > lambda(+)(P,Na) >= lambda(+)(P,Li) > lambda(+)(P,Et4N) > lambda(+)(P,Bu4N). This behavior cannot be explained either by a specific ionic condensation, or in terms of hydrodynamic friction or ionic friction undergone by the polyion, or in terms of change of configuration of the polyions (ellipsoidal configuration). However, calculations taking into account the dielectric friction effect according to our new general formula, recently published, giving the dielectric friction coefficient, beta(df)(P), for pearl-necklace-like polyelectrolyte chains, allowed to obtain good convergence between experimental and theoretical results. This new approach improves the interpretations given by Manning and Vink in terms of electrophoretic effect only. (C) 2022 Elsevier B.V. All rights reserved.

关键词： Carboxymethylated cellulosic polyelectrolytes Ammonium counterions Dielectric friction blobs Pearl necklace

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Turbulent filament properties in L and H-mode regime in the RFX-mod operating as a tokamak

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NUCLEAR FUSION 2020年第12期60卷

作者： Grenfell, G. Spolaore, M. Abate, D. Carraro, L. Marrelli, L. Predebon, I. Spagnolo, S. Veranda, M. Agostini, M. van Milligen, B. Ph. Cavazzana, R. Cordaro, L. De Masi, G. Franz, P. Hidalgo, C. Martines, E. Momo, B. Puiatti, M. E. Scarin, P. Vianello, N. Zaniol, B. Zuin, M. Univ Padua Acciaierie Venete SpA CNR Consorzio RFXENEAINFN Cso Stati Uniti 4 I-35127 Padua Italy CIEMAT Natl Fus Lab Avda Complutense 40 Madrid 28040 Spain Max Planck Inst Plasma Phys Boltzmannstr 2 Garching Germany

The dynamics of turbulent filaments in L and ELM-free H-mode in the RFX-mod device operating as a tokamak is discussed in the present work. L-H transition and sustained H-mode have been achieved in the RFX-mod with the aid of an external electrode biasing (Spolaoreet al 2017 Nucl. Fusion57116039). Through advanced statistical techniques, turbulent filaments are detected and tracked from the edge to the scrape-off layer (SOL) in a two-dimension floating potential map (measured with a 2D array of Langmuir probes) related with extreme events of a fixed ion saturation current signal in the SOL. While in L-mode filaments travel almost freely, their motion becomes restricted to the near SOL during the induced biasing H-mode. In this region, the background shear decorrelation time becomes shorter than the convective filament time, favouring its suppression. However, the experimental observation of a nearly 'trapped' monopole potential points out the possible role of the vortex selection mechanism. The sign and magnitude of the turbulent parallel vorticity are consistent with theE x Bbackground vorticity in the SOL in this regime, while in L-mode, the inferred turbulent vorticity is always above the background one. The sparse filamentary transport in the far SOL during H-mode is further confirmed from the measurements of a poloidally symmetric array of electrostatic sensors on the wall. Lastly, the radial velocity of filaments in both regimes was discussed in the framework of analytical scalings. Filaments in L-mode exhibit a reasonable agreement with the sheath-limited regime in the cold ion approximation, with a non-negligible associated parallel current density measured with a set of 3-axial pick-up coils installed in the probe head. In H-mode, the collisionality increases near the separatrix while filaments seem to follow the inertial regime before become trapped.

关键词： turbulence biasing H-mode blobs filaments vorticity magnetic fluctuations

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Autonomous localization of the best depth blob using TOPSIS: application on forage plants for the Sharjah pastures project 14

Autonomous localization of the best depth blob using TOPSIS:...

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14th International Conference on Developments in eSystems Engineering (DeSE)

作者： Sani, Radhwan Cheaitou, Ali Rabie, Tamer Univ Sharjah Coll Engn Dept Ind Engn & Engn Management Sharjah U Arab Emirates Univ Sharjah Coll Comp & Informat Dept Comp Engn Sharjah U Arab Emirates

ISBN: (纸本)9781665408882

This research constitutes a building block in a larger decision support system, which combines computer vision and multi-criteria decision making, to identify indigenous forage plants in close-range aerial images. Such a system enables managing the open pastures project of the Emirate of Sharjah, United Arab Emirates (UAE). The system aims at the identification of forage plants through the detection of plant inflorescences in depth images, and applying TOPSIS, to select and localize the best plant inflorescence.

关键词： Decision Support System DSS TOPSIS Plant Identification Decision Making Process Computer Vision Depth blobs Cenchrus ciliaris Pennisetum divisum forage

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Parametric decay instabilities near the second-harmonic upper hybrid resonance in fusion plasmas

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NUCLEAR FUSION 2020年第10期60卷

作者： Hansen, S. K. Nielsen, S. K. Stober, J. Rasmussen, J. Stejner, M. Hoelzl, M. Jensen, T. MIT Plasma Sci & Fus Ctr 77 Massachusetts Ave Cambridge MA 02139 USA Tech Univ Denmark Dept Phys DK-2800 Lyngby Denmark Max Planck Inst Plasma Phys D-85748 Garching Germany

Parametric decay instabilities (PDIs) lead to the generation of strong frequency-shifted radiation when powerful X-mode polarized microwaves, injected for electron cyclotron resonance heating (ECRH) of fusion plasmas, cross a region of non-monotonic electron density near the second-harmonic upper hybrid resonance (UHR). For the standard second-harmonic X-mode ECRH scenarios used at the ASDEX Upgrade tokamak, the second-harmonic UHR occurs near the plasma edge, meaning that PDIs occur in connection with phenomena leading to non-monotonic edge electron density profiles, e.g. blobs, edge-localized modes (ELMs), and inter-ELM modes. We present the first study of strong signals near half the ECRH frequency in fusion-relevant plasmas and demonstrate their PDI-like features, such as an ECRH power threshold required for their occurrence, through analog modulations of the ECRH power. The signals near half the ECRH frequency are found to be far more prevalent than expected based on previous theories, and we hence present a qualitative explanation of their origin, in terms of cross-polarized microwaves generated through non-linear interactions of the waves involved in the PDIs, which captures the basic features of the experimental observations. We additionally present examples of the PDI-related microwave signals just below the ECRH frequency which indicate the location of the microwave source. Furthermore, based on a non-linear magnetohydrodynamics simulation of an ELM crash in ASDEX Upgrade, performed using the JOREK code, the duration of the PDI-like microwave spikes observed in connection with ELMs is shown to match the transit time of an ELM filament though an ECRH beam. Finally, the PDI power threshold expected theoretically, calculated using the electron density and temperature profiles from the JOREK simulation, is shown to match the experimentally observed values.

关键词： parametric decay instability ECRH upper hybrid waves wave trapping microwave diagnostics ELMs blobs

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J-TEXT托卡马克装置间歇性爆发事件的实验研究

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能源研究与管理 2024年第1期16卷 96-103页

作者：杨宇赵开君谢耀禹陈志鹏陈忠勇高丽王能超丁肖冠胡莹欣温思宇东华理工大学核科学与工程学院南昌330013 华中科技大学电气与电子工程学院磁约束聚变与等离子体国际合作联合实验室强电磁技术全国重点实验室武汉430074

为研究密度对J-TEXT托卡马克边缘湍流及间歇性爆发事件的影响,采用往复式朗缪尔静电探针测量边缘等离子体参数,采用概率分布函数以及条件平均等分析方法,详细比较了不同线积分密度情况下边缘等离子体电子温度、密度、电位和径向电场等... 详细信息

为研究密度对J-TEXT托卡马克边缘湍流及间歇性爆发事件的影响,采用往复式朗缪尔静电探针测量边缘等离子体参数,采用概率分布函数以及条件平均等分析方法,详细比较了不同线积分密度情况下边缘等离子体电子温度、密度、电位和径向电场等径向分布及涨落特征。结果表明:随着等离子体密度的增加,边缘电子温度降低,在最后闭合磁面附近的E×B剪切流减弱;密度涨落在刮削层(SOL)具有更大的正偏度与峰度,涨落幅度>1.5倍标准差的气泡(blobs)所引起的粒子输运占总输运的占比从25%上升到45%;但blobs爆发的时间间隔不依赖于积分密度,保持在35μs左右。因此,随着密度增加,blobs对边缘输运的影响更大。

关键词：托卡马克 blobs 径向输运剪切流静电探针

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Translational dielectric friction on a pearl-necklace-like polyelectrolyte chain

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JOURNAL OF MOLECULAR LIQUIDS 2021年 326卷

作者： M'halla, Jalel Boughammoura, Sondes Ghazouani, Anis Univ Monastir Fac Sci Monastir Lab LPQS UR Electrolytes Monastir 5000 Tunisia

Translational dielectric friction effect on polyions is ignored by the literature. However, its contribution to the polyion conductibility is very sensitive to the configuration of the polyion chain, so that transition from coiled configurations to completely stretched configuration gives generally rise to a gap of the dielectric friction coefficient, beta(df)(P). In the present work we analyze in details this effect in the case of slowly moving Pearl-Necklace-like Polyelectrolyte Chain of structural charge Z(S)e, and length L less than the structural length L-S = vertical bar Z(S)vertical bar b(S), constituted by N-b beads separated alternatively by (N-b- 1) strings enclosing N-g groups (or small thermal blobs). The obtained practical results make possible, by comparing the experimental dielectric friction coefficient with its different possible theoretical values, to predict the chain conformation of the concerned polyelectrolyte. (C) 2020 Elsevier B.V. All rights reserved.

关键词： Polyelectrolyte Ionic condensation Dielectric friction blobs Pearl Necklace

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