Alfvén cascade eigenmodes above the TAE-frequency and localization of Alfvén modes in D- 3 He plasmas on JET

2021 ◽  
Author(s):  
Mykola Dreval ◽  
Sergei E Sharapov ◽  
Yevgen Kazakov ◽  
Jozef Ongena ◽  
Massimo Nocente ◽  
...  
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
High Energy ◽  
Negative Ion ◽  
Energetic Ions ◽  
Fast Ions ◽  
Alfven Eigenmodes ◽  
Different Types ◽  
Central Regions ◽  
High Frequency Ac

Abstract Various types of Alfvén Eigenmodes (AEs) have been destabilized by fast ions over a broad frequency range from ~80 kHz to ~700 kHz in a series of JET experiments in mixed D-3He plasmas heated with the three-ion ICRF scenario [M. Nocente et al., Nucl. Fusion 60, 124006 (2020)]. In this paper, we identify the radial localization of AEs using an X-mode reflectometer, a multiline interferometer and soft X-ray diagnostics. The analysis is focused on the most representative example of these measurements in JET pulse #95691, where two different types of Alfvén cascade (AC) eigenmodes were observed. These modes originate from the presence of a local minimum of the safety factor qmin. In addition to ACs with frequencies below the frequency of toroidal Alfvén eigenmodes (TAEs), ACs with frequencies above the TAE frequency were destabilized by energetic ions. Both low- (f ≈80-180 kHz) and high-frequency (f ≈ 330-450 kHz) ACs were localized in the central regions of the plasma. The characteristics of the high-frequency ACs are investigated in detail numerically using HELENA, CSCAS and MISHKA codes. The resonant conditions for the mode excitation are found to be determined by passing ions of rather high energy of several hundred keV and similar to those established in JT-60U with negative-ion-based NBI [M. Takechi et al., Phys. Plasmas 12, 082509 (2005)]. The computed radial mode structure is found to be consistent with the experimental measurements. In contrast to low-frequency ACs observed most often, the frequency of the high-frequency ACs decreases with time as the value of qmin decreases. This feature is in a qualitative agreement with the analytical model of the high-frequency ACs in [B.N. Breizman et al., Phys. Plasmas 10 3649 (2003)]. The high-frequency AC could be highly relevant for future ITER and fusion reactor plasmas dominated by ~ MeV energetic ions, including a significant population of passing fast ions.

A New Infrared Image Magnification and Enhancement Method Based on Wavelet Transform

2012 ◽  
Vol 198-199 ◽  
pp. 238-243 ◽  
Author(s):  
Wen Sheng Guo ◽  
Feng Chen ◽  
Zhao You Sun ◽  
Xi Jun Wang
Keyword(s):  
Wavelet Transform ◽  
High Frequency ◽  
Infrared Image ◽  
Low Frequency ◽  
High Energy ◽  
Low Energy ◽  
Image Magnification ◽  
Edge Profile ◽  
Enhancement Method ◽  
Image Edge

The traditional image magnify method usually have some defects on details. This paper gives a new infrared image magnification and enhancement method which is based on wavelet reconstruction and gradation segment. In this method, first of all, make wavelet transform on the image, get the high-frequency coefficient. Apply the Newton differential algorithm enhance the high-frequency coefficient as the high-frequency part of the magnified image, treat the original image as the low-frequency part , make the wavelet reconstruction ,then get the magnified image. To enhance the magnified image, according to the double gray threshold, segment the image into high gray segment corresponding to target, low gray segment corresponding to background, and middle gray segment corresponding to transition sector. Then, make linear extension to them respectively; the result is the magnified image. Experiments indicate, this method is effective on distinguishing high-energy target from low-energy target (the low-energy target is the primary one) and displaying the details of image(edge profile of the bomb).

scholarly journals Performance Evaluation of Scalar Multiplication in Elliptic Curve Cryptography Implementation using Different Multipliers Over Binary Field GF (2233)

2020 ◽  
Vol 26 (9) ◽  
pp. 45-64
Author(s):  
Alaa Mohammed Abdul-Hadi ◽  
Yousraa Abdul-sahib Saif-aldeen ◽  
Firas Ghanim Tawfeeq
Keyword(s):  
Elliptic Curve Cryptography ◽  
Performance Index ◽  
High Frequency ◽  
Low Frequency ◽  
Scalar Multiplication ◽  
Maximum Frequency ◽  
Binary Field ◽  
Point Multiplication ◽  
Additional Layer ◽  
Different Types

This paper presents a point multiplication processor over the binary field GF (2233) with internal registers integrated within the point-addition architecture to enhance the Performance Index (PI) of scalar multiplication. The proposed design uses one of two types of finite field multipliers, either the Montgomery multiplier or the interleaved multiplier supported by the additional layer of internal registers. Lopez Dahab coordinates are used for the computation of point multiplication on Koblitz Curve (K-233bit). In contrast, the metric used for comparison of the implementations of the design on different types of FPGA platforms is the Performance Index. The first approach attains a performance index of approximately 0.217610202 when its realization is over Virtex-6 (6vlx130tff1156-3). It uses an interleaved multiplier with 3077 register slices, 4064 lookup tables (LUTs), 2837 flip-flops (FFs) at a maximum frequency of 221.6Mhz. This makes it more suitable for high-frequency applications. The second approach, which uses the Montgomery multiplier, produces a PI of approximately 0.2228157 when its implementation is on Virtex-4 (6vlx130tff1156-3). This approach utilizes 3543 slices, 2985 LUTs, 3691 FFs at a maximum frequency of 190.47MHz. Thus, it is found that the implementation of the second approach on Virtex-4 is more suitable for applications with a low frequency of about 86.4Mhz and a total number of slices of about 12305.

A Note on the Masking of Pictures

Perception ◽  
1982 ◽  
Vol 11 (3) ◽  
pp. 319-324 ◽  
Author(s):  
Peter M Forster
Keyword(s):  
Information Processing ◽  
High Frequency ◽  
Visual Information ◽  
Random Noise ◽  
Low Frequency ◽  
Pattern Mask ◽  
Type B ◽  
General Applicability ◽  
Everyday Objects ◽  
Different Types

An experiment is described in which photographs of everyday objects were masked by frequency-filtered random visual noise. The masking functions obtained were of the same type as those obtained by masking letters and words with random noise or a pattern mask. That is, the high-frequency mask produced a type A function while the low-frequency mask produced a type B function. This result is discussed in terms of the general applicability of models of visual information processing constructed on the basis of experiments with letter or word stimuli. It is suggested that spatial-frequency concepts may usefully be employed to describe the relevant features of different types of mask.

A Distinction Between Different Types of Stall in a Centrifugal Compressor Stage

1986 ◽  
Vol 108 (1) ◽  
pp. 83-92 ◽  
Author(s):  
N. Ka¨mmer ◽  
M. Rautenberg
Keyword(s):  
Energy Transfer ◽  
Centrifugal Compressor ◽  
High Frequency ◽  
Low Frequency ◽  
Rotating Stall ◽  
Compressor Stage ◽  
Vaneless Diffuser ◽  
Pressure Transducers ◽  
Different Types ◽  
Probe Measurements

The flow at the stall line of a centrifugal compressor with vaneless diffuser was investigated at different speeds. A distinction between three kinds of stall phenomena could be made. One type of stall with regurgitation of fluid at the impeller inlet was of a nonperiodic character, whereas two different types of periodic stall appeared at higher speeds. The rotating nature of these two types of stall was verified from a comparison of signals of peripherally spaced pressure transducers. The low-frequency rotating stall exhibited features of diffuser generated stall and a lobe number of three was measured. From a detailed investigation of the high-frequency rotating stall, which included unsteady probe measurements upstream and downstream of the impeller, it can be shown that this type of rotating stall is generated in the impeller by a periodic breakdown of energy transfer from the rotor to the flow. This conclusion is supported by the distribution of shroud static pressures.

Low-frequency global Alfvén eigenmodes in low-shear tokamaks with trapped energetic ions

2009 ◽  
Vol 16 (9) ◽  
pp. 092502 ◽  
Author(s):  
V. S. Marchenko ◽  
Ya. I. Kolesnichenko ◽  
S. N. Reznik
Keyword(s):  
Low Frequency ◽  
Energetic Ions ◽  
Alfven Eigenmodes ◽  
Low Shear

scholarly journals Radiation Effects in Nuclear Ceramics

2012 ◽  
Vol 2012 ◽  
pp. 1-13 ◽  
Author(s):  
L. Thomé ◽  
S. Moll ◽  
A. Debelle ◽  
F. Garrido ◽  
G. Sattonnay ◽  
...  
Keyword(s):  
Radiation Effects ◽  
Electronic Excitation ◽  
High Energy ◽  
Radiation Stability ◽  
Nuclear Materials ◽  
Energetic Ions ◽  
Slowing Down ◽  
Different Types ◽  
Fission Reactors ◽  
Actinide Transmutation

Due to outstanding physicochemical properties, ceramics are key engineering materials in many industrial domains. The evaluation of the damage created in ceramics employed in radiative media is a challenging problem for electronic, space, and nuclear industries. In this latter field, ceramics can be used as immobilization forms for radioactive wastes, inert fuel matrices for actinide transmutation, cladding materials for gas-cooled fission reactors, and structural components for fusion reactors. Information on the radiation stability of nuclear materials may be obtained by simulating the different types of interactions involved during the slowing down of energetic particles with ion beams delivered by various types of accelerators. This paper presents a review of the radiation effects occurring in nuclear ceramics, with an emphasis on recent results concerning the damage accumulation processes. Energetic ions in the KeV-GeV range are used to explore the nuclear collision (at low energy) and electronic excitation (at high energy) regimes. The recovery by electronic excitation of the damage created by ballistic collisions (SHIBIEC process) is also addressed.

scholarly journals Warp-knitted Fabric Defect Segmentation Based on the Shearlet Transform

2017 ◽  
Vol 25 (0) ◽  
pp. 87-94
Author(s):  
Zhijia Dong ◽  
Dong Xia ◽  
Pibo Ma ◽  
Gaoming Jiang
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Curvelet Transform ◽  
High Energy ◽  
Knitted Fabric ◽  
Threshold Method ◽  
Shearlet Transform ◽  
Fabric Defect ◽  
Polar Grid ◽  
Warp Knitted Fabric

The Shearlet transform has been a burgeoning method applied in the area of image processing recently which, differing from the Wavelet transform, has excellent properties in processing singularities for multidimensional signals. Not only is it similar to the performance of the Curvelet transform, it also overcomes the disadvantage of the Curvelet transform with respect to discretization. In this paper, the Shearlet transform with segmented threshold de-nosing is proposed to segment a warp-knitted fabric defect. Firstly a warp-knitted fabric image of size 512*512 is filtered by the Laplacian Pyramid transform and decomposed into low frequency and high frequency coefficients. Secondly the high frequency coefficients are operated with a pseudo-polar grid and then convoluted by the window function. Thirdly the shearlet coefficients will be obtained through redefining the Cartesian coordinates from the pseudo-polar grid coordinates and de-noised by the segmented threshold method. Then the coefficients which have high energy are selected for reconstruction in an inverse way using the previous steps. Finally the iterative threshold method and object operation based on morphology are applied to segment out the defect profile. The experiment’s result states that the Shearlet transform shows excellent performance in segmenting a common warp-knitted fabric defect, indicating that the segment results can be applied for further defect automatic recognition.

scholarly journals Vibroacoustic Monitoring Features of Radiation-Beam Technologies by the Case Study of Laser, Electrical Discharge, and Electron-Beam Machining

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1117
Author(s):  
Sergey N. Grigoriev ◽  
Mikhail P. Kozochkin ◽  
Marina A. Volosova ◽  
Anna A. Okunkova ◽  
Sergey V. Fedorov
Keyword(s):  
Electron Beam ◽  
Chemical Reactions ◽  
High Frequency ◽  
Short Circuit ◽  
Low Frequency ◽  
Signal Amplitude ◽  
High Energy ◽  
Radiation Beam ◽  
Vibroacoustic Signal ◽  
The Impact

A feature of radiation-beam technologies is similar processes associated with phase transformations and chemical reactions that cause changes in the volume of matter, accompanied by the vibroacoustic energy release distributed through the equipment flexible system in a wide frequency range (up to 40 kHz and high for 150 ms). The vibroacoustic signal amplitude accompanying radiation-beam technologies depends on the power density and process performance. The accelerated growth of the high-frequency components of the vibroacoustic signal is associated with the activation of the processes of volumetric boiling and evaporation/sublimation of the material. The Kf parameter, introduced as the ratio of the effective amplitudes of the low-frequency and high-frequency ranges of the vibroacoustic signal, monitors the results of high-energy flows’ impact on the material in the direction of vaporization/sublimation. The Kf parameter decrease tendency shows an increase in the proportion of the substance evaporated during laser treatment. The Kf parameter control allows the indication of the short-circuit approach in electric discharge machining, which allows increased productivity and reliability of processing. The monitoring of the Kf parameter helps to select rational processing modes, preventing excessive evaporation, providing the necessary intensity of the impact power to trigger the necessary chemical reactions in surface electron-beam alloying.

scholarly journals Heart rhythm variation during affective pictures viewing in women in different phases of the menstrual cycle

2020 ◽  
Vol 80 (1) ◽  
pp. 35-40
Author(s):  
V. Kravchenko ◽  
K. Demidova
Keyword(s):  
Menstrual Cycle ◽  
High Frequency ◽  
Luteal Phase ◽  
Cardiac Rhythm ◽  
Low Frequency ◽  
Heart Rhythm ◽  
Follicular Phase ◽  
Activity Level ◽  
Spectral Indices ◽  
Different Types

The peculiarities of the dynamics of the spectral indices of cardiac rhythm variability in 32 women 17-23 years of age while viewing emotional IAPS (International affective picture system) images in different phases of the menstrual cycle were studied. It is shown that the differences in the regulation of the heart rhythm associated with viewing emotional images of different types are manifested mainly in the follicular phase of the menstrual cycle. During this period, significant differences in viewing emotional images of different types were found in the absolute and relative power of the very low-frequency (VLF) and high-frequency (HF) component of the spectrum. In the ovulation phase, emotion-sensitive markerwas a lowfrequency spectrum component (LF), reflecting the effect of the sympathetic nervous system on cardiac rhythm. This indicator was significantly higher when viewing unpleasant images compared to pleasant and erotic visual stimuli.The contribution of the sympathetic division to the regulation of cardiac rhythm was observed during viewing of negative and neutral images, and only the viewing of erotic images was characterized by an increase in parasympathetic activity, which was accompaniedwith the increased power of the high-frequency component of the spectrum (HF) reducing the proportion of LF/HF and respiratory rate. The study shows that during the menstrual cycle, the autonomic balance shifts toward the predominance of sympathetic regulation of the heart rhythm, which reaches a maximum in the luteal phase. In this regard, the activity level of the sympathetic link recorded by the power of the low-frequency (LF) component while viewing unpleasant images was the lowest in the follicular phase and the highest in the luteal one. No significant differences were found between the spectral indices of cardio-interval variability when viewing emotional images in the luteal phase, indicating that this period of the cycle was low informative to assess the characteristics of women's emotional response based on heart rate analysis.

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