Preliminary Results of Drift Instability by Fast Optical Images in KT-5D Toroidal Plasma

Drift instability in plasma generated by electron cyclotron resonance （ECR） in KT- 5D device was investigated by using a fast camera and Langmuir probes. The similarity between the distribution of light intensity from the images and the plasma pressure indicates a nearly linear relationship. The discharge images taken by the camera and the plasma parameters measured by the probes also indicate the existence of low frequency turbulent events with a time scale less than a few mini-seconds.

An improved fast converted-wave imaging method

The conventional fast converted-wave imaging method directly uses backward Pand converted S-wavefield to produce joint images. However, this image is accompanied by strong background noises, because the wavefi elds in all propagation directions contribute to it. Given this issue, we improve the conventional imaging method in the two aspects. First, the amplitude-preserved P-and S-wavef ield are obtained by using an improved space-domain wavef ield separation scheme to decouple the original elastic wavef ield. Second, a convertedwave imaging condition is constructed based on the directional-wavefield separation and only the wavefields propagating in the same directions used for cross-correlation imaging, resulting in effectively eliminating the imaging artifacts of the wavefields with different directions;Complex-wavefi eld extrapolation is adopted to decompose the decoupled P-and S-wavefield into directional-wavefields during backward propagation, this improves the eff iciency of the directional-wavef ield separation. Experiments on synthetic data show that the improved method generates more accurate converted-wave images than the conventional one. Moreover, the improved method has application potential in micro-seismic and passive-source exploration due to its source-independent characteristic.

Non-iterative image reconstruction from sparse magnetic resonance imaging radial data without priors

The state-of-the-art approaches for image reconstruction using under-sampled k-space data are compressed sensing based.They are iterative algorithms that optimize objective functions with spatial and/or temporal constraints.This paper proposes a non-iterative algorithm to estimate the un-measured data and then to reconstruct the image with the efficient filtered backprojection algorithm.The feasibility of the proposed method is demonstrated with a patient magnetic resonance imaging study.The proposed method is also compared with the state-of-the-art iterative compressed-sensing image reconstruction method using the total-variation optimization norm.

Ionization wave propagation and cathode sheath formation due to surface dielectric-barrier discharge sustained in pulsed mode

This work deals with the experimental study of a surface dielectric-barrier discharge,as a part of the ongoing interest in the control of plasma induced electro-fluid dynamic effects(e.g.plasma actuators).The discharge is generated using a plasma reactor consisting of a fused silica plate which is sandwiched between two printed circuit boards where the electrodes are developed.The reactor is driven by narrow high voltage square pulses of asymmetric rising(25 ns)and falling(2.5μs)parts,while the discharge evolution is considered in a temporarily and spatially resolved manner over these pulses.That is,conventional electrical and optical emission analyzes are combined with high resolution optical emission spectroscopy and ns-resolved imaging,unveiling main characteristics of the discharge with a special focus on its propagation along the dielectric-barrier surface.The voltage rising part leads to cathode-directed ionization waves,which propagate with a speed up to 105m s~(-1).The voltage falling part leads to cathode sheath formation on the driven electrode.Τhe polarization of the dielectric barrier appears critical for the discharge dynamics.

Fast processing of foreign fiber images by image blocking

In the textile industry,it is always the case that cotton products are constitutive of many types of foreign fibers which affect the overall quality of cotton products.As the foundation of the foreign fiber automated inspection,image process exerts a critical impact on the process of foreign fiber identification.This paper presents a new approach for the fast processing of foreign fiber images.This approach includes five main steps,image block,image predecision,image background extraction,image enhancement and segmentation,and image connection.At first,the captured color images were transformed into gray-scale images;followed by the inversion of gray-scale of the transformed images;then the whole image was divided into several blocks.Thereafter,the subsequent step is to judge which image block contains the target foreign fiber image through image pre-decision.Then we segment the image block via OSTU which possibly contains target images after background eradication and image strengthening.Finally,we connect those relevant segmented image blocks to get an intact and clear foreign fiber target image.The experimental result shows that this method of segmentation has the advantage of accuracy and speed over the other segmentation methods.On the other hand,this method also connects the target image that produce fractures therefore getting an intact and clear foreign fiber target image.

Fast Adaptive Wavelet for Remote Sensing Image Compression

Remote sensing images are hard to achieve high compression ratio because of their rich texture. By analyzing the influence of wavelet properties on image compression, this paper proposes wavelet construction rules and builds a new biorthogonal wavelet construction model with parameters. The model parameters are optimized by using genetic algorithm and adopting energy compaction as the optimization object function. In addition, in order to resolve the computation complexity problem of online construction, according to the image classification rule proposed in this paper we construct wavelets for different classes of images and implement the fast adaptive wavelet selection algorithm （FAWS）. Experimental results show wavelet bases of FAWS gain better compression performance than Daubechies9/7.

The Effect of an External Magnetic Field on the Plume Expansion Dynamics of Laser-Induced Aluminum Plasma

In this work, we investigated the plasma morphology induced by a Nd：YAG laser with the aim of improving the understanding of the formation and dynamics of the plasma in two cases, with and without a magnetic field. Single laser pulse production of a plasma in the absence and presence of a magnetic field was performed with an aluminum target in air. A fast photography technique was employed to obtain information about the expansion dynamics and confinement of the aluminum plasma in each case. The generation of the laser plasma was allowed to expand at two locations with different magnetic field strengths, which correspond to the strength 0.58 T in the center of two magnetic poles and 0.83 T at a distance of 4 mm from the upper pole （N）. The plume showed lateral confinement at longer delays when the target was placed at the center of the two poles. When the target was placed at a distance of 4 mm from the upper pole it was observed that the plume was divided into two lobes at the initial stage and traveled towards the center of the magnetic field with further elapse of time.

MR-GUIDED PULSE OXIMETRY IMAGING OF BREAST IN VIVO

A near-infrared(NIR)tomography system with spectrally-encoded sources in two wavelength bands was built to quantify the temporal oxyhemoglobin and deoxyhemoglobin contrast in breast tissue at a 20 Hz bandwidth.The system was integrated into a 3T magnetic resonance(MR)imaging system through a customized breast coil interface for simultaneous optical and MRI acquisition.In this configuration,the MR images provide breast tissue structural information for NIR spectroscopy of adipose andfibro-glandular tissue in breast.Spectral characterization performance of the NIR system was verified through dynamic phantom experiments.Normal human subjects were imaged withfinger pulse oximeter(PO)plethysmogram synchronized to the NIR system to provide a frequency-locked reference.Both the raw data from the NIR system and the recovered absorption coefficients of the breast at two wavelengths showed the same frequency of about 1.3 Hz as the PO output.The frequency lock-in approach provided a practical platform for MR-localized recovery of small pulsatile variations of oxyhemoglobin and deoxyhemoglobin in the breast,which are related to the heartbeat and vascular resistance of the tissue.

Quantitative analysis of intraspinal cerebrospinal fluid flow in normal adults

The present study quantitatively analyzed intraspinal cerebrospinal fluid flow patterns in 19 normal adults using fast cine phase-contrast magnetic resonance imaging. Results showed increased downward flow velocity and volume compared with upward flow, and the average downward flow volume of intraspinal cerebrospinal fluid decreased from top to bottom at different intervertebral disc levels. Upward and downward cerebrospinal fluid flow velocity reached a peak at the thoracic intraspinal anterior region, and velocity reached a minimum at the posterior region. Overall measurements revealed that mean upward and downward flow volume positively correlated with the subarachnoid area. Upward peak flow velocity and volume positively correlated with spinal anteroposterior diameter. However, downward peak flow velocity and volume exhibited a negative correlation with spinal anteroposterior diameter. Further flow measurements showed that flow velocity in upward and downward directions was associated with subarachnoid anteroposterior diameter, respectively. The present experimental results showed that cerebrospinal fluid flow velocity and volume varied at different intraspinal regions and were affected by subarachnoid space area and anteroposterior diameter size.

Fast compression of computer-generated holographic images based on a GPU-accelerated skip-dimension vector quantization method

A method for fast and low bit-rate compression of digital holograms based on a new vector quantization （VQ） method known as the skip-dimension VQ （SDVQ） is proposed. Briefly, a complex hologram is converted into a real off-axis hologram, and partitioned into a set of image vectors. The image vectors are passed into a graphic processing unit （GPU）, and compressed through SDVQ into a set of code indices considerably smaller in data size than the source hologram. Experimental evaluation reveals that our scheme is capable of compressing a digital hologram to a compression ratio of over 500 times, in approximately 20-22 ms.

A simulation study of a high-resolution fast neutron imaging detector based on liquid scintillator loaded capillaries

Background At present,the highest spatial resolution of a fast neutron imaging detector,mainly determined by the range of secondary particles generated by fast neutrons,is about hundreds of microns.In view of the above inherent spatial resolution limitation,a capillary-based scintillation detector that can improve the spatial resolution of fast neutron imaging by recording and reconstructing the recoil proton track was developed.Purpose The purpose of this paper is to develop a detector for recognizing recoil proton events,reconstructing particle track and improving the position resolution with track reconstruction method to reconstruct the position of interaction.Methods The proposed detector consists of a 1000×1000 array of glass capillaries loaded with a high refractive index liquid scintillator.Each glass capillary was 10μm in diameter and 5 cm in length.The recoil protons generated by the incident neutrons move within the detector and produce scintillation light within each capillary that they traverse.The light emitted from the capillary array can be recorded by employing an intensified CCD camera.We used Geant4 to simulate the detector performance and CERN ROOT analysis framework to record physical information of recoil proton,including position,energy deposition in each capillary and track length.Based on Hough transform,a rapid,computerized and efficient proton track reconstruction procedure was developed.Conclusion The recoil proton events display a continuous extended structure.The track reconstruction algorithms can reconstruct individual track precisely,and when the counting rate was relatively low,the track reconstruction results were in good agreement with simulation data.Moreover,for intensive overlap conditions,this algorithm also reconstructs periphery tracks with high rate of accuracy.

Backprojection by Multiorientation Simultaneous Computation Scheme for CT Image Reconstruction

Based on the geometrical relationships between image pixels and projection rays at different viewing angles,a Multiorientation Simultaneous Back Projection (MSBP) approach is proposed in this papar for two-dimensional (2-D) parallel and fan beam CT systems. In this scheme, backprojections for eight views, 6, π/2 - θ, π/2 + 6, π- θ, π+ θ, 3π/2 - θ, 3π/2 + θ, and 2π- θ, are implemented at the same time,while the locating operation of pixels for interpolation and computation of weighting parameters are only required for one of them when one half of the number of thaws is even. Implementation remits on an Intel 80386 hosed computer show that the proposed method has a notable computational gain,compared with the conventional implementation of backprojection.

Holographic laser fabrication of 3D artificial compound μ-eyes

The demand for fast optical image acquisition without movable optical elements(e.g.,for self-driving car technology)can be met using bioinspired 3D compound eyes.3D laser processing strategies enable designable 3D structuring but suffer from low fabrication efficiency,which significantly limits their applications in producing complex 3D optical devices.Herein,we demonstrate a versatile yet simple wet-etching-assisted holographic laser fabrication method for the development of 3D compound eyes.Artificial compoundμ-eyes can be readily fabricated by programming a 3D spot array for the parallel ablation of a curved fused silica surface,followed by controllable etching in a hydrofluoric(HF)acid solution.A 3D-concave-lens array made on a curved surface over an area of 100μm cross-section with each lenslet of 10μm radius was fabricated with high fidelity and excellent imaging/focusing quality.The resultant 3D-concave-lens can serve as a hard template for the mass production of soft compound eyes through soft lithography.Additionally,using a generative adversarial network(GAN)-based deep learning algorithm,image restoration was conducted for each lenslet,which retained a large field of view and significantly improved image quality.This method provides a simple solution to the requirements of compoundμ-eyes required by Industry 4.0.

Compact MPPC-based coded aperture imaging camera for dual-particle detection

Purpose Fast neutrons and gamma-ray imaging detection is an effective way to detect and identify radioactive material in the field of nuclear security.A compact coded aperture imaging(CAI)camera was designed to be sensitive to both gamma and neutron radiation based on plastic scintillators and multi-pixel photon counters(MPPC).Methods MPPCs coupling with the 13×13 pixelated plastic scintillators one-to-one were utilized to reduce the scale of the CAI system while maintaining good positional performance.The symmetric charge division(SCD)circuit was adopted to reduce the 169 signals output from the MPPC array to 26.Each waveform was collected and processed with four Domino Ring Sampler 4(DRS4)chips and two 16-channel analog-to-digital converter(ADC)modules.As the pulse shapes of fast neutrons would be broadened after elastic scattering multiple times in the scintillators,the Anger-Logic method was applied to eliminate multiple elastic scattering events so that good pulse shape discrimination(PSD)performance can be achieved.Results The imaging and detection ability of the camerawas evaluated using the 241Am-Be(5.9×10^(5) n/s)neutron source and 137Cs(370 MBq)gammasource.The camera can be used to detect fast neutrons(0.5–10 MeV)and gammarays(0.2–2.5MeV).Furthermore,it can implement efficient neutron/gamma PSD capabilities in the mixed-field environment.The figure of merit(FOM)of the camera calculated at 400keVee energy cut is 0.93.Conclusion A compact MPPC-based CAI camera was designed to detect and discriminate fast neutrons and gamma rays.Its good PSD performance was well suited to distinguish fast neutrons from gamma rays in a dual-particle environment.The portable design makes it promising for complex monitoring scenarios in nuclear security.