This study presents an experimental investigation of boundary-layer transition over a 7 degrees rotating cone at Mach 6, using infrared thermography, high-frequency pressure sensors, and focused laser differential interferometry. The cone rotated at 150 rpm, and the angle of attack was varied between 0 degrees and 6 degrees Spectral analysis, continuous wavelet transform, and bispectrum techniques were applied to characterize the instability mechanisms. For small angles of attack (0 degrees-1 degrees), the rotating boundary layer behaves similarly to the non-rotating case, with the second mode and its fundamental resonance dominating. At moderate angles of attack (2 degrees-3 degrees), the instability shifts to traveling crossflow vortices and their y-type and z-type secondary instabilities, accompanied by nonlinear interactions involving both the self-interaction of the secondary modes and their coupling with low-frequency traveling crossflow waves. For higher angles of attack (4 degrees-6 degrees), the second mode reappears and coexists with traveling crossflow vortices and secondary crossflow instabilities, with nonlinear interactions additionally involving second-mode self-interaction. Fluctuating-pressure measurements further reveal a significant azimuthal shift of the transition location: approximately 90 degrees clockwise at a 3 degrees angle of attack, reducing to about 45 degrees at 6 degrees

In this work, the effects of nose-tip temperature and bluntness on the crossflow instabilities and their secondary instability have been studied experimentally at Mach 6 by infrared thermography and high-frequency pulsating pressure sensors. The investigations are conducted within the boundary layer of a 7 degrees half-angle cone at a 6 degrees angle of attack, with nose-tip bluntness radii (R = 0.5, 2, and 5 mm) and wall temperature ratio (Tw/T0, the ratio of nose-tip temperature to total incoming temperature) ranging from 0.6 to 1.3. It is demonstrated that increasing the nose-tip temperature in the case of small bluntness reduces the amplitude of traveling crossflow waves while enhancing stationary crossflow vortices on the leeward side, resulting in a 16.2% increase in the maximum wave number. Increasing bluntness reduces the influence of nose-tip temperature on both traveling waves and stationary vortices, with a more pronounced effect on traveling waves. As bluntness increases, the high-frequency instability transitions from primarily secondary instability of traveling waves to secondary instability of stationary crossflow vortices. Additionally, the interaction between traveling and stationary waves transitions from initial suppression of traveling waves by stationary vortices to synchronous growth before being suppressed by the traveling waves.

In this paper, the influence of the nose-tip temperature on hypersonic crossflow instability is experimentally investigated using infrared thermal imaging and high-frequency pulsating pressure sensors at Mach 6 for a 7° semi-cone angle of 6° angle of attack. The wall temperature ratio (ratio of nose-tip temperature to total incoming temperature) Tw/T0 varies between 0.6 and 1.3. The experimental results show that the transition position gradually moves toward the tail of the cone as Tw/T0 increases. Wavelet analysis reveals stationary crossflow vortices with wave numbers ranging from 30 to 50, and the maximum wave number decreases as Tw/T0 increases. The pressure sensors are then used to detect the traveling crossflow waves of 15–50 kHz and the high frequency mode of 100–450 kHz. The high frequency mode is considered to be the secondary instability of the traveling crossflow waves. An increase in Tw/T0 stabilizes the traveling crossflow waves while weakening the secondary instability. The results of bispectral analysis show that an increase in nose-tip temperature weakens both the self-interaction of the secondary instabilities and the interaction between the traveling crossflow waves and their secondary instabilities.

In this paper, the wind tunnel experiment and parabolic stability equation (PSE) have been used to study the effect of porous surface on hypersonic boundary layer transition over the sharp cone at a 6 degrees angle of attack. Infrared thermography was employed to visualize streak structures induced by stationary crossflow vortices on both the smooth and porous surfaces. Compared to the solid wall, the porous surface slightly enhances the intensity of the stationary crossflow vortices. However, it significantly suppresses high-frequency instabilities while stimulating the low-frequency instabilities, especially the traveling crossflow vortices in the yawed cone boundary layer. The PSE results demonstrate that the high-frequency oblique modes have a higher growth rate than the Mack modes of a sharp cone at a 6 degrees angle of attack. The continuous wavelet transform analysis reveals two high-frequency unstable modes (y-mode and z-mode) on the solid wall, while only one is present on the porous surface. Through bispectrum analysis, it is found that the porous surface exhibits stronger interactions between high-frequency and low-frequency unstable modes, with no observed self-interactions among high-frequency modes.

In this work, the crossflow instability modes on a 7 degrees half-angle cone with 6 degrees angle of attack at Mach 6 have been experimentally studied. To begin with, the complete laminar-to-turbulence transition process is acquired by infrared thermography, and the heat flux streaks caused by the stationary crossflow vortices are distinct over the areas of leeward side. Further wavelet analysis reveals a dominant wavenumber of the stationary crossflow vortices, which is centered at about k = 50. Subsequently, the spatial distribution characteristics of the traveling crossflow instability (f = 20-50 kHz) and high-frequency instabilities (f = 100-500 kHz) are acquired between the azimuthal angle phi = 90 degrees -150 degrees (windside to leeside) through wall mounted pressure sensors. The results of spectral and wavelet analysis indicate that the two types of instability are the traveling crossflow instability and its secondary instability, respectively. Further bispectral analysis is used to show that these high-frequency waves undergo several quadratic phase-coupled interactions with themselves to produce harmonics, as well interact with low-frequency waves that results in spectral broadening.

Abstract Spinning vehicles achieve gyroscopic effects by rotating around their axis. However, transition significantly influences the stability of flight. In this work, a study of instability on the unstable modes in boundary layers over a rotating cone with a 7° half-apex angle in hypersonic flows is presented with linear instability analysis (LST). To quantify the effect of compressibility, Mach numbers (5-10) are considered, and a higher rotational velocity is considered for analysis of centrifugal mode. MMM, CFM, and CM shift towards low frequency, low streamwise, and circumferential wavenumbers. Also, the maximum amplification rate of MMM, CFM, and CM decreases with Mach number, suggesting a stabilizing effect of compressibility on the boundary layer over a spinning cone in hypersonic flows.

In this work, a virtual body-fitted grid-based immersed boundary method (IBM) combined with the thermal lattice Boltzmann flux solver (TLBFS) is proposed to efficiently simulate thermal flows with Dirichlet and Neumann boundary conditions. The method involves generating a virtual body-fitted grid along the immersed boundary and implementing the boundary conditions using a fractional step technique. In the prediction step, the finite-volume TLBFS is used to obtain the predicted flow field on the Eulerian mesh without considering the immersed boundary, while in the correction step, the correction process of the flow field is conducted on the virtual grid. Thus, the effect of the boundary is transferred to the fluid domain through the virtual grid indirectly. For Dirichlet boundary conditions, such as the no-slip condition and the specified temperature condition, the velocity and temperature corrections are considered unknowns and solved through a matrix system formed from enforcing the boundary conditions. As for the Neumann boundary condition, such as the specified heat flux condition, the temperatures at virtual layers inside the immersed body are regarded as unknowns and computed from those at virtual layers outside the wall according to the quadratic distribution. Several benchmark cases including natural, forced, and mixed convection problems are well simulated to validate the method. The numerical results are in good agreement with reference data, demonstrating the capacity of the present method to simulate thermal flows with Dirichlet and Neumann boundary conditions while requiring fewer Lagrangian points and achieving higher computational efficiency.

Brucellosis is a zoonotic infectious disease caused by Brucella spp, which could cause serious economic losses to animal husbandry and threaten human public health. Ingestion of contaminated animal products is a common way to acquire Brucella infection in humans, while research on effect of oral Brucella infection on host gut microbiota and the gene expression in intestinal tissues is limited. In the present study, 16S rRNA sequencing and RNA sequencing were conducted to explore gut microbiota and expression profiles of mRNAs in the colon of BALB/c mice, which were infected by Brucella abortus 2308. The fecal samples were collected at 7 and 28 days post infection to observe changes in the gut microbiota during Brucella infection. In the alpha diversity analysis, significantly increased Chao 1 index was observed at 28 days after Brucella infection. The Bray-Curtis distancebased principal coordinate analysis indicated that the WT group showed a separation from the Brucella infection groups. In addition, analysis of composition of microbes revealed that Prevotellaceae_NK3B31_group were more abundant in 1 week and 4 week infection groups, while Turicibacter was only more abundant in 4 week infection group. Based on the RNA-seq assay, a total of 45 differentially expressed genes were detected between Brucella abortus infection group and control group. Furthermore, KEGG pathway enrichment analysis showed that protein processing in endoplasmic reticulum, Legionellosis, Spliceosome, Hippo signaling pathway and Influenza A were significantly enriched in response to Brucella abortus infection. Our finding will help to improve the knowledge of the mechanisms underlying Brucella infection and may provide novel targets for future treatment of this pathogen infection.

Experimental and linear stability theory (LST) investigation of boundary layer transition on a flat plate was conducted with a flow of Mach number 5. The temperature distributions and second-mode disturbances on the flat plate surface at different unit Reynolds number (Reunit) values were captured by infrared thermography and PCB technology, respectively, which revealed the transition location of the flat-plate boundary layer. The PCB sensors successfully captured the second-mode disturbances within the boundary layer initially at a frequency of about 100 kHz, with a gradually expanding frequency range as the distance travelled downstream increased. The evolution characteristics of the second-mode instabilities were also investigated by LST and obtained for the second mode, ranging from 100 to 250 kHz. The amplitude amplification factor (N-factor) of the second-mode instabilities was calculated by the eN method. The N-factor of the transition location in the wind tunnel experiment predicted by LST is about 0.98 and 1.25 for Reunit = 6.38 × 106 and 8.20 × 106, respectively.

The process of intracellular proteolysis through ATP-dependent proteases is a biologically conserved phenomenon. The stress responses and bacterial virulence of various pathogenic bacteria are associated with the ATP-dependent Clp protease. In this study, a Brucella abortus 2308 strain, Δ clpP , was constructed to characterize the function of ClpP peptidase. The growth of the Δ clpP mutant strain was significantly impaired in the TSB medium. The results showed that the Δ clpP mutant was sensitive to acidic pH stress, oxidative stress, high temperature, detergents, high osmotic environment, and iron deficient environment. Additionally, the deletion of clpP significantly affected Brucella virulence in macrophage and mouse infection models. Integrated transcriptomic and proteomic analyses of the Δ clpP strain showed that 1965 genes were significantly affected at the mRNA and/or protein levels. The RNA-seq analysis indicated that the Δ clpP strain exhibited distinct gene expression patterns related to energy production and conversion, cell wall/membrane/envelope biogenesis, carbohydrate transport, and metabolism. The iTRAQ analysis revealed that the differentially expressed proteins primarily participated in amino acid transport and metabolism, energy production and conversion, and secondary metabolites biosynthesis, transport and catabolism. This study provided insights into the preliminary molecular mechanism between Clp protease to bacterial growth, stress response, and bacterial virulence in Brucella strains.

传统离散速度方法在求解跨流域流动问题时,通常只求解动理学模型方程,即Boltzmann-BGK方程.与传统方法不同,改进离散速度方法同步求解了动理学模型方程和相应的宏观伴随方程.通过这种方式,可以将分子碰撞影响考虑到宏观伴随方程的通量计算中,同时宏观方程预估得到的结果可以用于预估平衡态,从而实现Boltzmann-BGK方程的全隐式离散.这两点改进可以有效克服传统方法在连续和近连续流区域计算效率低、计算精度差的缺陷.为了进一步减少速度空间的网格量和避免数值求积时的Runge现象,采用了非结构网格结合矩形律来离散速度空间并引进守恒修正来强制满足相容性条件.算例测试表明,采用速度空间非结构网格和守恒修正可以有效减少改进离散速度方法的计算量和内存花销.

As an active flow control technology, the opposing jet has become a research hotspot due to its broad prospect in reducing aerodynamic heat. In order to explore the heat flux reduction law and related mechanism of opposing jet flow control for hypersonic vehicles, a hemispherical bluff body model was studied by numerical simulations and wind tunnel experiments under different freestream and opposing jet conditions. The flow field and Stanton number distribution on the model surface were obtained, and both numerical and experimental data were verified against each other. The results suggest that, the heat flux reduction effect of the opposing jet is the consequence of a combined action of the jet backflow and the jet pushing away the front shockwave from the head. At a fixed Mach number, the heat flux reduction effect of opposing jet becomes more obvious with the increase of the jet pressure ratio; while under the condition of a similar jet pressure ratio, better heat flux reduction effect by the opposing jet can be achieved at higher Mach numbers.

The effect of hydrodynamic interactions on the collective locomotion of fish schools is still poorly understood. In this paper, the flow-mediated organization of two tandem flapping foils, which are free in both the longitudinal and lateral directions, is numerically studied. It is found that the tandem formation is unstable for two foils when they can self-propel in both the longitudinal and lateral directions. Three types of resultant regular formations are observed, i.e. semi-tandem formation, staggered formation and transitional formation. Which type of regular formation occurs depends on the flapping parameters and the initial longitudinal distance between the two foils. Moreover, there is a threshold value of the cycle-averaged longitudinal distance (which is approximately 0.55) below which both velocity enhancement and efficiency augmentation can be achieved by two foils in regular formations. The results obtained here may shed some light on understanding the emergence of regular formations of fish schools.

It is widely acknowledged that pseudogenes play important roles in bacterial diversification and evolution and participate in gene regulation and RNA interference (RNAi). However, the function of most pseudogenes in Brucella spp remains poorly understood, warranting further studies.To comprehensively analyze the function of the pseudogenes BMEA_B0173 in Brucella melitensis strain 63/9, a BMEA_B0173 in-frame deleted mutant strain was constructed. Then, the phenotypes of the mutant strain, such as growth characteristics and bacterial virulence, were assessed in mice infection models. Finally, iTRAQ analysis was performed to investigate the gene expression profile affected by the pseudogenes BMEA_B0173. In this study, we found that BMEA_B0173 deletion exhibited increased agglutination with M monospecific sera. In a mouse model of chronic infection, the BMEA_B0173 deletion strain displayed increased colonization in the spleen compared to the wild-type pathogen. The iTRAQ assay revealed that 252 proteins were differentially expressed between the BMEA_B0173 deletion and the wild-type strains. In addition, deletion of BMEA_B0173 significantly increased the expression of proteins involved in the denitrification pathway, iron metabolism, and several transcriptional regulators, which might cause increased virulence of the mutant strain. In conclusion, this study preliminary uncovered the function of the pseudogene BMEA_B0173 in Brucella melitensis 63/9 and provided novel insights for studying the pathogenesis of Brucella strains.

The study of brain science is vital to human health. The application of hyperspectral imaging in biomedical fields has grown dramatically in recent years due to their unique optical imaging method and multidimensional information acquisition. Hyperspectral imaging technology can acquire two-dimensional spatial information and one-dimensional spectral information of biological samples simultaneously, covering the ultraviolet, visible and infrared spectral ranges with high spectral resolution, which can provide diagnostic information about the physiological, morphological and biochemical components of tissues and organs. This technology also presents finer spectral features for brain imaging studies, and further provides more auxiliary information for cerebral disease research. This paper reviews the recent advance of hyperspectral imaging in cerebral diagnosis. Firstly, the experimental setup, image acquisition and pre-processing, and analysis methods of hyperspectral technology were introduced. Secondly, the latest research progress and applications of hyperspectral imaging in brain tissue metabolism, hemodynamics, and brain cancer diagnosis in recent years were summarized briefly. Finally, the limitations of the application of hyperspectral imaging in cerebral disease diagnosis field were analyzed, and the future development direction was proposed.

This Review summarizes the progress in research on the flow structure and aerodynamic characteristics of an airfoil at a low Reynolds number encountered by near-space low-speed aircrafts and micro-air vehicles. The structures of several kinds of laminar separation bubbles and their effect are discussed by drawing on experimental and numerical results reported in the past few decades. The transition process in the separation bubble is detailed from various perspectives, including the receptive, primary instability, secondary instability, and break-down stage. The process of evolution of a coherent vortex structure that may affect the transition is discussed by analyzing the vortex dynamics in the separation bubble. Combined with the flow characteristics at a low Reynolds number and data on the airfoil, aerodynamic characteristics of the airfoil, such as the nonlinear effect and static hysteresis effect at a low angle of attack, are discussed.

The transcriptional regulator MucR is related to normal growth, stress responses and Brucella virulence, and affects the expression of various virulence-related genes in smooth-type Brucella strains. However, the function of MucR in the rough-type Brucella canis remains unknown. In this study, we discovered that MucR protein was involved in resistance to heat stress, iron-limitation, and various antibiotics in B . canis . In addition, the expression level of various bacterial flagellum-related genes was altered in mucR mutant strain. Deletion of this transcriptional regulator in B. canis significantly affected Brucella virulence in RAW264.7 macrophage and mice infection model. To gain insight into the genetic basis for distinctive phenotypic properties exhibited by mucR mutant strain, RNA-seq was performed and the result showed that various genes involved in translation, ribosomal structure and biogenesis, signal transduction mechanisms, energy production, and conversion were significantly differently expressed in Δ mucR strain. Overall, these studies have not only discovered the phenotype of mucR mutant strain but also preliminarily uncovered the molecular mechanism between the transcriptional regulator MucR, stress response and bacterial virulence in B . canis .

Roughness element induced hypersonic boundary layer transition on a flat plate is investigated using infrared thermography at Ma = 5 and 6 flow condition. Surface Stanton number is acquired to analyze the effect of roughness element shape and height on the transition process. The correlation between the vortex structure induced by roughness element and the wall heat streaks is established. The results indicate that higher roughness element would induce stronger streamwise heat flux streaks, lead to transition advance in streamwise centerline and increase the width of spanwise wake. Moreover, for low roughness element, the effect of the shape is not obvious, and the height plays a leading role in the transition; for tall roughness element, the effect on accelerating transition for the diamond roughness element is the best, the square is the worst, and the shape plays a leading role in the transition.

The upper surface blowing (USB) technology is considered to be an effective active control technology, which can improve the aerodynamic performances of vehicle. In this paper, numerical simulation is used to investigate the aerodynamic interaction of electric ducted fan on airfoil. It is observed that the electric ducted fan jet on the upper wing leads to pronounced improvements on the aerodynami...

BACKGROUND:Porcine circovirus type 3 (PCV3) has been an emerging porcine virus spread around the world. The conserved DNA sequence of PCV3 enabled good performance in molecular biological assays.RESULT:In this study, we developed a real-time fluorescence PCR assay for the detection of PCV3. The conserved region within Capsid genome of PCV3 was selected for the design of primer pairs and probes. After optimizing, a primer pair and probe was screened, providing high sensitivity (10 copies/μL) and specificity (no cross reaction with other porcine viruses or common bacterium). In addition, this method was applied in the detection of 110 clinical samples, and the performance was compared with other previously reported PCR and real-time PCR methods. This method provided higher detection rate.CONCLUSION:A real-time fluorescence PCR assay has been developed for the detection of PCV3, with high sensitivity and specificity, exhibiting good performance in detecting clinical samples.