Effects of T-S wave amplitude on the control of boundary layer transition by streaks

The effects of streaks on boundary layer transition depend on the initial amplitude of T-S waves introduced to excite the transition. This problem was studied in a flat-plate boundary layer in water tunnel by using hydrogen bubble method. Three T-S wave initial amplitudes were tested. The results show that both narrow and wide-spacing streaks depress the transition excited by T-S waves with lower initial amplitude. However, when transition is excited by T-S waves of higher initial amplitude, the narrow-spacing streaks depress the transition, while the wide-spacing streaks promote the transition. Futrther the underlying mechanisms were also analyzed.

A new kind of hairpin-like vortical structure induced by cross-interaction of sinuous streaks in turbulent channel

This work is motivated by previous experimental and numerical studies which reveal that the hairpin vortex could be formed by the interaction between spanwise adjacent low-speed streaks. To prove that such an interaction mechanism is still applicable in the normal direction, two sinuous low-speed streaks with the same streamwise phase are set to be in the upper half and bottom half of a small size channel, respectively, and their evolution and interaction are investigated by direct numerical simulation. A new kind of hairpin-like vortical structure, distributed in the normal direction and straddled across both halves of the channel, is found during the cross-interaction process of the low-speed streaks. The influence of such a normal-distributed hairpin-like vortex （NHV） on the turbulent statistical regularity is also revealed. It is observed that the NHV can lead to a sudden surge of wall skin friction, but the value of the normal velocity as well as the streamwise and spanwise vorticity sharply decrease to zero in the center of the channel.

Choroidal neovascularization and angioid streaks in pseudoxanthoma elasticum

AIM: To report a case of pseudoxanthoma elasticum (PXE) in a 48 year old woman that presented with bilateral blurry vision. METHODS: A case report RESULTS: A 48-year-old woman presented with bilateral blurry vision and right eye metamorphopsia. The patient had a history of angioid streaks in the left eye ten years ago for which she had received laser surgery and had poor residual vision. Visual acuity was 20/60 in the right eye and count fingers at 6 feet in the left. Fundus examination showed subretinal hemorrhage and macular thickening on the right and a disciform macular scar with focal atrophic pigment epithelial lesions on the left. Both eyes had angioid streaks and peau d’orange pigmentary pattern of the retina. External examination showed several, yellow skin papules and plaques on the lateral and posterior neck, as well as prominent mental creases. Pathologic examination of skin biopsy confirmed the diagnosis of PXE, showing calcium deposition and fragmented, clumped elastic fibers in the deep reticular dermis. She responded well to intravitreal bevacizumab injections and visual acuity improved to 20/25 OD. Preventative care was emphasized and the patient was referred to cardiology, gastroenterology and human genetics for counseling. CONCLUSION: PXE is a multisystem disorder affecting the dermatologic, ocular, and cardiovascular systems. Ophthalmic findings of angioid streaks and choroidal neovascularization in the presence of stereotypical skin changes and prominent mental creases should prompt evaluation for PXE.

Angioid Streaks in Psuedoxanthoma Elasticum

Pseudoxanthoma elasticum (PXE) is a hereditary disorder that affects primarily the elastic tissues of skin, eyes and blood vessels. Its estimated prevalence is thought to be 1:25,000 - 100,000. PXE patients also carry an increased risk for cardiovascular and gastrointestinal diseases. Early diagnosis can play a crucial role in preventing early loss of vision and systemic complications in these patients however despite having characteristic clinical features;it is still to a large extent being under-diagnosed. Here we present two cases of PXE with reduced vision.

Using Sports Wagering Markets to Evaluate and Compare Team Winning Streaks in Sports

Point spreads and money lines from sports wagering markets are used to evaluate the impressiveness of team streaks. Sports wagering data have previously been useful in assessing competitive balance in sports. Our approach was motivated by the amount of media scrutiny that accompanied the winning streak of the NBA’s Miami Heat and the point streak of the NHL’s Chicago Blackhawks which occurred simultaneously for the most part in 2013. The topic came to the forefront again with the 2014-2015 winning streak of the Atlanta Hawks. Three streaks are highlighted in our paper. The length of the streaks, the quality of the competition, injuries, and a variety of other factors were mentioned in the media but the discussion was limited to subjective opinions as no way of properly weighing relative influence of the factors was identified. Wagering markets provide an excellent source of information for making these judgments. Several complementary measures are described and the most impressive team streaks within and across professional baseball, basketball, football, and ice hockey are identified.

SOME CHARACTERISTICS OF LOW-SPEED STREAKS UNDER SHEARED AIR-WATER INTERFACES

The characteristics of low-speed fluid streaks occurring under sheared air-water interfaces were examined by means of hydrogen bubble visualization technique. A critical shear condition under which the streaky structure first appears was determined to be u(tau) approximate to 0.19 cm/s. The mean spanwise streak spacing increases with distance from the water surface owing to merging and bursting processes, and a linear relationship describing variation of non-dimensional spacing <(<lambda>+)over bar> versus y(+) was found essentially independent of shear stress on the interface. Values of <(<lambda>+)over bar>, however, are remarkably smaller than their counterparts in the near-wall region of turbulent boundary layers. Though low-speed streaks occur randomly in time and space, the streak spacing exhibits a lognormal probability distribution behavior. A tentative explanation concerning the formation of streaky structure is suggested, and the fact that <(<lambda>+)over bar> takes rather smaller values than that in wall turbulence is briefly discussed.

Numerical study on evolution of subharmonic varicose low-speed streaks in turbulent channel flow

The evolution of two spanwise-aligned low-speed streaks in a wall turbulent flow, triggered by the instability of the subharmonic varicose （SV） mode, is studied by a direct numerical simulation （DNS） method in a small spatial-periodic channel. The results show that the SV low-speed streaks are self-sustained at the early stage, and then transform into subharmonic sinuous （SS） low-speed streaks. Initially, the streamwise vortex sheets are formed by shearing, and then evolve into zigzag vortex sheets due to the mutual induction. As the intensification of the SV low-speed streaks becomes prominent, the tilted streamwise vortex tubes and the V-like streamwise vortex tubes can be formed simultaneously by increasing ＋~. When the SV low-speed streaks break down, new zigzag streamwise vortices will be generated, thus giving birth to the next sustaining cycle of the SV low-speed streaks. When the second breakdown happens, new secondary V-like streamwise vortices instead of zigzag streamwise vortices will be generated. Because of the sweep motion of the fluid induced by the secondary V-like streamwise vortices, each decayed low-speed streak can be divided into two parts, and each part combines with the part of another streak, finally leading to the formation of SS low-speed streaks.

Numerical simulation on evolution of subharmonic low-speed streaks in minimal channel turbulent flow

The evolution of low-speed streaks in the turbulent boundary layer of the minimum channel flow unit at a low Reynolds number is simulated by the direct numer- ical simulation （DNS） based on the standard Fourier-Chebyshev spectral method. The subharmonic sinuous （SS） mode for two spanwise-aligned low-speed streaks is excited by imposing the initial perturbations. The possibilities and the physical realities of the turbulent sustaining in the minimal channel unit are examined. Based on such a flow field environment, the evolution of the low-speed streaks during a cycle of turbulent sus- taining, including lift-up, oscillation, and breakdown, is investigated. The development of streamwise vortices and the dynamics of vortex structures are examined. The results show that the vortices generated from the same streak are staggered along the streamwise direction, while the vortices induced by different streaks tilt toward the normal direction due to the mutual induction effect. It is the spatial variations of the streamwise vortices that cause the lift-up of the streaks. By resolving the transport dynamics of enstrophy, the strength of the vortices is found to continuously grow in the logarithmic layer through the vortex stretching mechanism during the evolution of streaks. The enhancement of the vortices contributes to the spanwise oscillation and the following breakdown of the low-speed streaks.

Standardization of Winning Streaks in Sports

This research provides some metrics to better summarize streaks in sporting events with binary outcomes. In sporting events, information is often lost when “statistics” are presented regarding “streaks,” and whether or not certain teams or players have been recently been successful or unsuccessful. This usually leads to the presentation of metrics with no common baseline. This particular research effort provides statistics to capture the information regarding recent success or lack thereof, in a more standardized manner. To illustrate the presented metrics, data from the 2016 seasons for the American sports leagues National Basketball Association and Major League Baseball are used in an attempt to standardize streaks.

Attosecond ionization time delays in strong-field physics

Electronic processes within atoms and molecules reside on the timescale of attoseconds. Recent advances in the laserbased pump-probe interrogation techniques have made possible the temporal resolution of ultrafast electronic processes on the attosecond timescale, including photoionization and tunneling ionization. These interrogation techniques include the attosecond streak camera, the reconstruction of attosecond beating by interference of two-photon transitions, and the attoclock. While the former two are usually employed to study photoionization processes, the latter is typically used to investigate tunneling ionization. In this review, we briefly overview these timing techniques towards an attosecond temporal resolution of ionization processes in atoms and molecules under intense laser fields. In particular, we review the backpropagation method, which is a novel hybrid quantum-classical approach towards the full characterization of tunneling ionization dynamics. Continued advances in the interrogation techniques promise to pave the pathway towards the exploration of ever faster dynamical processes on an ever shorter timescale.

Investigation of influencing factors of hot streaks migration in high pressure stage of a vaneless counter-rotating turbine

Three-dimensional,viscous,and unsteady CFD simulations have been performed in order to reveal the influencing factors of hot streaks migration in high pressure stage of a vaneless counter-rotating turbine. Based on the numerical results,the comparison between the case with inlet hot streaks and case without inlet hot streaks is carried out,which shows that the effect of inlet hot streaks on the load distributions of high pressure turbine airfoils is not notable and the airfoil load distributions are directly related to the inlet pressure distributions. The predicted results also indicate that the circumferential and radial movements of the hot streaks were not observed in the high pressure turbine stator. This means that the combined effects of secondary flow and buoyancy are very weak in the high pres-sure turbine stator. The numerical results also prove that the circumferential flow angle effect at the inlet of the high pressure turbine rotor,secondary flow effect and buoyancy effect are the mainly influencing factors to directly affect the migration characteristics of the hot streaks in the high pressure turbine rotor.

基于CBAM-U-Net的全二维气相色谱streak目标分割

针对全二维气相色谱(GC×GC)图像中streak目标具有低对比度特点而难以分割的问题,提出了一种基于CBAM-U-Net的图像分割模型,所提出的模型在U-Net网络模型的基础上,通过在网络特征提取阶段嵌入CBAM注意力机制,来增强目标区域的特征信息,保留更多图像纹理。基于企业提供的全二维气相色谱数据集的实验结果表明,所提出方法的Acc、CPA、Dice系数等方面均有所提升,分别达到了98.80%、73.50%和71.73%,说明融合CBAM注意力机制的U-Net模型能够有效提升对streak目标区域的分割精度。

Ultrafast two-dimensional x-ray imager with temporal fiducial pulses for laser-produced plasmas

It is challenging to make an ultrafast diagnosis of the temporal evolution of small and short-lived plasma in two dimensions. To overcome this difficulty, we have developed a well-timed diagnostic utilizing an x-ray streak camera equipped with a row of multi-pinhole arrays. By processing multiple sets of one-dimensional streaked image data acquired from various pinholes, we are capable of reconstructing high-resolution two-dimensional images with a temporal resolution of 38 ps and a spatial resolution of 18 μm. The temporal fiducial pulses accessed from external sources can advance the precise timing and accurately determine the arrival time of the laser. Moreover, it can correct the nonlinear sweeping speed of the streak camera. The effectiveness of this diagnostic has been successfully verified at the Shenguang-II laser facility,providing an indispensable tool for observing complex physical phenomena, such as the implosion process of laser-fusion experiments.

OsBLS6.2:A rice bacterial leaf streak resistance gene identified by GWAS and RNA-seq

Bacterial leaf streak(BLS),caused by Xanthomonas oryzae pv.oryzicola(Xoc),is a bacterial disease affecting rice production in Asia and Africa,whose severity is expected to increase with climate change.Identification of new quantitative-trait loci(QTL)or resistance genes for BLS resistance is essential for developing resistant rice.A genome-wide association study to identify QTL associated with BLS resistance was conducted using phenotypic and genotypic data from 429 rice accessions.Of 47 QTL identified,45 were novel and two co-localized with previously reported QTL or genes conferring BLS resistance.qBLS6.2 on chromosome 6 explained the greatest phenotypic variation.Combined analysis of differential expression and annotations of predicted genes near qBLS6.2 based on haplotype and disease phenotype identified OsBLS6.2(LOC_Os06g02960)as a candidate gene for qBLS6.2.OsBLS6.2 knockout plants showed higher resistance to Xoc than wild-type plants.Many other candidate genes for resistance to Xoc were identified.

Prevalence and Spatial Distribution of Badnavirus in the Banana (Musa spp) Major Growing Areas in Burkina Faso

Banana streak virus (BSV) and Sugarcane bacilliform virus (SCBV) are two badnaviruses commonly found in all banana growing areas of the world. It is a threat to the production and improvement of Musa germplasm. In Burkina Faso, the presence of badnaviruses was reported in banana producing regions. The objective of this study was to determine the prevalence of BSV and SCBV in banana production areas of Burkina Faso. A survey followed by a symptomatologic study was conducted in banana plantations in 27 localities of the nine main banana producing regions from July to October 2018 and September to December 2020. In all, 251 leaf samples were collected and analysed for BSV and SCBV infection by Indirect Antigen Coated Plate Assay-ELISA followed by amplification of the RT/RNase H region using Polymerase chain reaction with Badna FP/RP and SCBV F/R primers, respectively. A variety of symptoms were observed on almost all plant organs which were revealed due to BSV by symptomatologic study. The results of serological and molecular diagnosis revealed a high overall prevalence of BSV in 80.48% of the samples tested. BSV was distributed in seven survey regions out of nine with prevalence ranging from 10% to 100% in North, Centre, Centre West, Hauts Bassins, Cascades, Centre East and Boucle of Mouhoun regions. Very low prevalence was recorded for SCBV in Cascades and East Centre region with 4.35 and 12.5%, respectively. Species detection using specific primers to each species revealed three main species: Banana streak Obino l’ewaï virus (BSOLV), Goldfinger virus (BSGFV) and Imové virus (BSIMV) in the samples tested, respectively in the proportions of 23%, 8% and 0.8%. Co-infection between BSV species was also detected.

Genetic Diversity Analysis of Badnaviruses Infecting Banana in Burkina Faso

Badnaviruses are serious plant pararetroviruses affecting banana and causes serious economic losses to banana production worldwide. This study aims to examine the variability of BSV and SCBV nature infecting banana in Burkina Faso. Polymerase Chain Reaction (PCR) used the Badna FP/RP specific primers for the RT/RNase H regions present in badnaviruses. The PCR yielded about 579 bp amplicons from banana infected by BSV and SCBV. The 38 BSV isolates recorded low nucleotide identity ranging from 58.9% - 98.1%. Based on percentage nucleotide sequence identity and phylogenetic analyse, BSV isolates were categorized into four groups: 1, 2, 3 and 4. Group 4 shared 76.9% - 100% identity with BSOL species. However, Groups 1 and 3 recorded a low identity ranging, from 76.8% - 79.2%, 68.8% - 79.7% with BSCV, and 72.8% - 79.0% between Group 2 and BSOLV. Groups 1, 2 and 3 were assigned to a potentially new BSV species. The two SCBV isolates recorded a low nucleotide identity of 68% among themselves indicating high diversity. In addition, SCBV_Cd and SCBV_CE showed high nucleotide identity 91.3% and 58.7% with SCBV_C and SCBV, when they were compared to all published SCBV genotypes. In addition, phylogenetic analysis revealed the segregation of SCBV isolates into two genotypes, SCBV_Cd in C and SCBV_CE segregated in a new genotype namely Z. Recombination analyses showed weak signatures of recombination among some of the BSV and SCBV sequences.

The spatial-temporal evolution of coherent structures in log law region of turbulent boundary layer

The spatial-temporal evolution of coherent structures （CS） is significant for turbulence control and drag re- duction. Among the CS, low and high speed streak structures show typical burst phenomena. The analysis was based on a time series of three-dimensional and three-component （3D-3C） velocity fields of the flat plate turbulent boundary layer （TBL） measured by a Tomographic and Time-resolved PIV （Tomo TRPIV） system. Using multi-resolution wavelet transform and conditional sampling method, we extracted the intrinsic topologies and found that the streak structures appear in bar-like patterns. Furthermore, we seized locations and velocity information of transient CS, and then calculated the propagation velocity of CS based on spatial-temporal cross-correlation scanning. This laid a foundation for further studies on relevant dynamics properties.

R2N: A Novel Deep Learning Architecture for Rain Removal from Single Image

Visual degradation of captured images caused by rainy streaks under rainy weather can adversely affect the performance of many open-air vision systems.Hence,it is necessary to address the problem of eliminating rain streaks from the individual rainy image.In this work,a deep convolution neural network(CNN)based method is introduced,called Rain-Removal Net(R2N),to solve the single image de-raining issue.Firstly,we decomposed the rainy image into its high-frequency detail layer and lowfrequency base layer.Then,we used the high-frequency detail layer to input the carefully designed CNN architecture to learn the mapping between it and its corresponding derained high-frequency detail layer.The CNN architecture consists of four convolution layers and four deconvolution layers,as well as three skip connections.The experiments on synthetic and real-world rainy images show that the performance of our architecture outperforms the compared state-of-the-art de-raining models with respects to the quality of de-rained images and computing efficiency.

Eddy Kinetic Energy Study of the Snowstorm over Southern China in January 2008

The energetics of the third stage of a snowstorm over China was analyzed using ECWMF data.The analysis of the energy budget for the Middle East trough and the western Pacific trough that developed toward China on 25-28 January 2008 showed the advection of the geopotential by the ageostrophic wind to be both a crucial source and the primary sink of the eddy kinetic energy centers associated with the troughs.The magnitudes of the energy conversion terms,interaction kinetic energy conversion and baroclinic conversion,were too small to explain the development of the energy centers and the jet streaks.The energy centers gained energy at their entrance regions via the convergence of the ageostrophic geopotential fluxes,and then lost energy at their exit regions by the same fluxes.At the entrance regions,the fluxes converged,increasing the geopotential gradient,which generated a stronger geostrophic wind and higher kinetic energy,resulting in an ascending motion in this area.When the troughs moved to China,the ascending motion caused by the convergence of the fluxes at entrance region intensified the snowstorms over central and southern China.

VISUALIZATION OF FLOW STRUCTURES IN A TURBULENT BOUNDARY LAYER USING A NEW TECHNIQUE

In this paper, an experimental investigation on the flow structures in a turbulent bounda- ry layer employing a special laser light sheet-Hydrogen bubble flow visualization technique is described. It is observed that the high/low speed streaks are directly related to the hairpin or horseshoe-like vortices. This observation can give a better understanding of the physical mechanism in the turbulent boundary layer.