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The phenomenon of multiple tones is a typical feature of high-lift configuration noise, and the underlying nonlinear and nonstationary features need to be revealed through time-frequency analysis. This paper introduces the Hilbert–Huang transform method to detect the inherent amplitude modulation and frequency modulation phenomena of multiple tones from 30P30N three-element high-lift configuration with both slat and flap completely stowed. The acoustic modes are extracted from the multiple tones firstly and then the variation features of amplitude and instantaneous frequency are analyzed. The results show that the acoustic energy concentrates on the primary mode with much larger amplitude. Moreover, both the amplitude and instantaneous frequency are periodically varied in time and the predicted modulation frequencies are equal to the frequency intervals between nearby tones, confirming that the inherent temporal features of multiple tones are amplitude modulation and frequency modulation. [ABSTRACT FROM AUTHOR]

For noise reduction at a low-to-moderate Reynolds number, airfoil trailing-edge tonal noise has multiple prominent tones. Among these tones, secondary tones are greatly influenced by external disturbances such as oscillations commonly in the environment. In previous experiments, the spatial movement of sources was found to be related to an inherent high-frequency oscillation. Therefore, the spatial influence of external low-frequency oscillations was investigated in this study. By using tripping tapes to construct different symmetry source regions on the pressure side with side secondary tones, a transient spatial analysis of an NACA0012 airfoil at 2 degrees was performed by microphone arrays when a 10 Hz pressure oscillation was significant at 24 m/s. Temporally, this 10 Hz periodic strength change became more intense at a broader frequency bandwidth for a longer source region. Furthermore, a substantial time delay, significantly larger than the sound propagating time difference between microphones, was observed exclusively along the spanwise direction. This delay led to a periodic directivity pattern, particularly when two 0.2 m source regions were separated by a 0.2 m or 0.4 m tripping region. This low-frequency oscillation introduces an asymmetric transient switching pattern for symmetric spanwise source regions. Consequently, the response of airfoils to external oscillations in field tests should be considered. [ABSTRACT FROM AUTHOR]

This paper investigates the impact of varying the part geometric complexity and 3D printing process setup on the resulting structural load bearing capacity of fiber composites. Three levels of geometric complexity are developed through 2.5D topology optimization, 3D topology optimization, and 3D topology optimization with directional material removal. The 3D topology optimization is performed with the SIMP method and accelerated by high-performance computing. The directional material removal is realized by incorporating the advection-diffusion partial differential equation-based filter to prevent interior void or undercut in certain directions. A set of 3D printing and mechanical performance tests are performed. It is interestingly found that, the printing direction affects significantly on the result performance and if subject to the uni direction, the load-bearing capacity increases from the 2.5D samples to the 3D samples with the increased complexity, but the load-bearing capacity further increases for the 3D simplified samples due to directional material removal. Hence, it is concluded that a restricted structural complexity is suitable for topology optimization of 3D-printed fiber composites, since large area cross-sections give more degrees of design freedom to the fiber path layout and also makes the inter-layer bond of the filaments firmer. [ABSTRACT FROM AUTHOR]

To study the far-field aerodynamic noise of the leading-edge slat of a high-lift airfoil configuration, an experimental investigation of the BANC-II/30P30N airfoil model was carried out in the D5 areo-acoustic wind tunnel at Beihang University. A novel Kevlar-walled closed test section design was applied, as a way of upgrading the capabilities of a conventional aerodynamic wind tunnel to include far-field acoustic measurements for larger models at real Reynolds numbers. After the flap was retracted and the slat was deployed to isolate slat noise from other possible sources, the surface pressure distribution and the far-field sound pressure signals under different operating conditions were obtained by varying flow speed and angle of attack. The slat noise spectrum characteristics and the dependence of far-field noise on free stream velocity and airfoil incidence angle were acquired by the fast Fourier transform. The joint time-frequency analysis methods (short-time Fourier transform and continuous Morlet wavelet transform) were employed to process the far-field unsteady acoustic signal to identify the inherent physical mechanisms involved in the generation of multiple low-frequency tonal peaks emerging from the broadband component of the slat noise spectra. Results of the short-time Fourier transform (STFT) and wavelet analysis clearly showed that the dominant acoustic energy of these tonal noise was shared between the primary modes through rapid switching in time. Furthermore, the analysis results also indicated that an amplitude-modulation phenomenon exists in the dominant modes. The joint probability density function method was introduced to quantify the mode-switching phenomenon, and the results provided strong evidence that mode-switching occurs between the dominant modes of these low-frequency tones. [ABSTRACT FROM AUTHOR]

The aim was to quantify macroscopic renal blood flow and renal cortical microcirculation in patients with septic acute kidney injury (AKI) using ultrasound and contrast-enhanced ultrasound. In this case–control study, patients in the intensive care unit diagnosed with septic AKI were divided into stages 1–3 based on the 2012 KDIGO (Kidney Disease: Improving Global Outcomes) AKI diagnostic criteria. The patients were categorized into mild (stage 1) and severe (stages 2 and 3) groups, while septic patients without AKI served as the control group. Ultrasound parameters such as macrovascular renal blood flow and time-averaged velocity, as well as cardiac function parameters such as cardiac output and cardiac index, were measured. The time–intensity curve in the microcirculation was analyzed through contrast-enhanced ultrasound imaging software to calculate imaging parameters such as peak time, rise time, fall half-time and mean transit time of the interlobar arteries in the renal cortex. In terms of macrocirculation, renal blood flow and time-averaged velocity decreased gradually with the progression of septic acute renal injury (p = 0.004, p < 0.001). There was no difference in cardiac output and cardiac index values among the three groups (p = 0.17 and p = 0.12). In terms of microcirculation, ultrasonic Doppler parameters of the renal cortical interlobular artery, such as peak intensity, risk index and ratio of peak systolic velocity to end-diastolic velocity, gradually increased (all p values <0.05). The temporal contrast-enhanced ultrasound parameters—time to peak, rise time, fall half-time and mean transit time—were prolonged in AKI groups when compared with the control group (p < 0.001, p = 0.003, p = 0.004 and p = 0.009, respectively). In patients with septic AKI, the renal blood flow and time average velocity of macrocirculation in the kidneys are reduced, while the time parameters of microcirculation such as time to peak, rise time, fall half-time and mean transit time are prolonged, especially in patients with severe AKI. These changes are not related to changes in cardiac output or cardiac index. [ABSTRACT FROM AUTHOR]

The recent development of the lattice Boltzmann method enables its widespread application in various industrial areas. However, in the simulation of complicated industrial problems, considerable grid numbers are required to achieve reasonable resolution in the near-wall region due to the lack of a local refinement method on the geometry. This study proposes a new hybrid grid refinement method, which comprises the reconstruction algorithm in refined near-wall nodes on the refinement interface and the in-domain interpolation multi-grid method to prevent the local distortion of the pseudo-wall among resolution levels. The proposed method is validated on a two-dimensional flat plate and NACA0012 airfoil at low and high Reynolds numbers. Furthermore, the aerodynamic and aeroacoustics of a pair of counter-rotating propellers are simulated with the proposed lattice Boltzmann method and compared with the results obtained using commercial software. [ABSTRACT FROM AUTHOR]

High-lift airfoil slat and passive control noise were studied experimentally. A serrated slat with different parameters was installed on the trailing edge. Far-field noise was measured in an aeroacoustic wind tunnel using a microphone array. The results showed that the generation mechanism of discrete noise in slat noise was closely related to the feedback loop in the slat cove. As the Mach number increased, the pure tone frequency moved to the right, and the peak value gradually increased, whereas the pure tone frequency was not affected by the angle of attack. Serrated slats with different sawtooth angles had different effects on the aerodynamic noise of the slat, and the frequency of discrete noise also changed. The serrated slat needed to reach a certain value in the sawtooth angle to have the effect of noise reduction. When the sawtooth angle was large, the effect of noise increase also occurred, and there was a phenomenon of mode switching. The selection of the dominant mode was also determined by the time of modal occurrence. The smaller the sawtooth angle, the more obvious the effect of slat noise. When the sawtooth angle reached a certain angle, the discrete noise disappeared, and the noise reduction effect was basically the same. The serrated slat had little effect on the lift coefficient at a low angle of attack. [ABSTRACT FROM AUTHOR]

In turboprop engines, the lip of the S-shaped intake is behind the propeller rotation plane, so the complex slipstream flowfield has a strong impact on the flowfield in the S-shaped intake and affects engine performance. The present work attempts to improve the flowfield in the S-shaped intake in turboprop engines by using vortex generators. The research was carried out by solving Reynolds-averaged Navier–Stokes equations employed SST k-ω turbulence model. An attempt was made to explore the vortex generators' effect on S-shaped intake performance in the propeller slipstream. The results show that the total pressure recovery coefficient and distortion coefficient change periodically with time for the S-shaped intake in the propeller slipstream. For S-shaped intake with vortex generators (s/sm=0.3 , 12-mm height, 18° with the incoming flow) in the propeller slipstream, the vortices induced by the vortex generators are coupled with the propeller slipstream, which effectively inhibits flow separation in the S-shaped intake for turboprop engine and improves air quality on the aerodynamic interface plane (AIP) section of the S-shaped intake. [ABSTRACT FROM AUTHOR]

During an aircraft taxiing on a water-contaminated runway, the worn tires with shallower grooves will significantly deteriorate the safety of take-off and landing. The hydrodynamics generated by the tire-water-pavement interaction is numerically studied using the coupling method of Smoothed Particle Hydrodynamics and Finite Element Method. By comparing a completely worn tire with a new tire, the effects of tire wear on water spray and water displacement drag are analyzed. With the increasing tire speed and water film depth, the water spray composed of bow wave and side plume increases, and the water displacement drag decomposed of wave- and film-generated components also increases. The effects of tire wear depend on the relative height of tire grooves to the water film depth. For the shallow water film with a depth smaller than the grooves height, the water spray and water displacement drag of new tire is much smaller than those of worn tire, because the groove drainage effect can work very well. While for the deep water film that completely floods the grooves, the water spray and water displacement drag of new tire are similar with those of worn tires, because the groove drainage effect cannot be fully utilized. [ABSTRACT FROM AUTHOR]

Background. Ewing's sarcoma (ES) is the most common malignant primary bone tumor in children and adolescents. This study is aimed at developing new prognostic markers and building a microRNA-mRNA network in the development of ES. Method. GSE80201 and GSE39262 were downloaded from the Gene Expression Omnibus (GEO) database. Bioinformatics analysis was used to download and process data. The coexpression of differentially expressed microRNAs (DEMs) and genes (DEGs) was selected by using R software. The FunRich database was utilized to perform cellular component (CC), molecular function (MF), and biological process (BP) enrichment analysis. Cytoscape and ClueGO were used to perform Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis and construct the mRNA-microRNA network. The Kaplan-Meier Plotter was used to perform prognosis analysis between the expression level of genes we selected and overall survival (OS) of patients with ES. Univariate analysis and multivariate analysis were carried out to research the prognostic value of identified mRNA expression in ES according to TCGA database. Results. By using bioinformatics analysis, 10 DEMs and 5 target mRNAs were identified. Based on the KmPlot software, COL1A2, COL3A1, and TGFBI were significantly related to the OS of patients with ES. High COL3A1 mRNA expression was correlated with distant metastasis, margin status, and poor overall survival of ES. Besides, multivariate analysis indicated that COL3A1 was an independent risk factor for ES patients. Conclusions. In conclusion, our results suggest that COL3A1 and its related molecules may be a potential diagnostic and prognostic biomarker for patients with ES. [ABSTRACT FROM AUTHOR]

• A fast and unified microstructure analyzer that computes mechanical properties based on asymptotic homogenization. • A mechanical property profile (MPP) for the microstructure that depicts five commonly used mechanical properties in a radar chart, in addition to the spatial distribution of effective Young's modulus surface and the worst-case von Mises stress distribution. • A joint reinforcement algorithm for enhancing the strength of truss-based microstructures. [Display omitted] Microstructure is the microscopic scale of a material, which can strongly influence physical properties, such as elasticity, strength, hardness, etc. Recently, many research efforts have been made to design the topology of microstructures carefully and govern their material properties according to the specific application of these materials in industrial practice. However, most works target specific properties that are tailored to particular applications. An integral image for one microstructure concerning multiple mechanical properties is in high demand. In this paper, we present a microstructure analyzer based on asymptotic homogenization. A mechanical property profile (MPP) is proposed to depict commonly used mechanical properties, including Young's modulus, shear modulus, Poisson's ratio, compressive strength, shear strength, the spatial distribution of effective Young's modulus surface, and the worst-case von Mises stress distribution. Specifically, we utilize a radar chart to visualize the five scalar properties to help with an intuitive understanding of the microstructure. Moreover, we apply joints reinforcement on truss-based microstructures to enhance their strength. The results show that our analyzer and MPPs have the potential to help users understand and select the desired microstructure from alternatives and help them improve specific microstructure properties in microstructural design. [ABSTRACT FROM AUTHOR]

To study the noise reduction effect of a variable-bend slat, both experimental and numerical investigations are carried out on a two-dimensional high-lift configuration with a stowed flap at varying angle of attack. With respect to the base configuration, the different geometrical settings of the variable-bend slat at varying bending angles of the trailing edge are described, and the gap between the slat and the main wing is completely sealed with a bending angle of 18°. At smaller bending angles, the slat noise is reduced, especially for tones generated from the self-excited oscillation within the leading-edge slat cove. With the increase of the bending angle, the tonal frequency in the same mode gradually decreases, which agrees well with the predicted formula proposed by Terrocal. Moreover, the noise reduction effect of the bending slats decreases with the increase of the angle of attack. To provide further understanding of the noise reduction effect on tones at varying bending angles, flow parameters related to the self-excited oscillation are extracted using numerical calculation results. It is found that change in self-excited oscillation is mainly a consequence of change of shear layer length Lv and average vortex convection velocity along the shear layer Uv. As the bending angle increases, the main mode of self-excited oscillation gradually switches to a higher mode, which agrees well with the relationship between the flow parameters and the main mode of traditional nondeformable slat. [ABSTRACT FROM AUTHOR]

For turboprop engine, the S-shaped intake affects the engine performance and the propeller is not far in front of the inlet of the S-shaped intake, so the slipstream inevitably affects the flow field in the S-shaped intake and the engine performance. Here, an S-shaped intake with/without propeller is studied by solving Reynolds-averaged Navier-Stokes equation employed SST k-ω turbulence model. The results are presented as time-averaged results and transient results. By comparing the flow field in S-shaped intake with/without propeller, the transient results show that total pressure recovery coefficient and distortion coefficient on the AIP section vary periodically with time. The time-averaged results show that the influence of propeller slipstream on the performance of S-shaped intake is mainly circumferential interference and streamwise interference. Circumferential interference mainly affects the secondary flow in the S-shaped intake and then affects the airflow uniformity; the streamwise interference mainly affects the streamwise flow separation in the S-shaped intake and then affects the total pressure recovery. The total pressure recovery coefficient on the AIP section for the S-shaped intake with propeller is 1%-2.5% higher than that for S-shaped intake without propeller, and the total pressure distortion coefficient on the AIP section for the S-shaped intake with propeller is 1%-12% higher than that for the S-shaped intake without propeller. However, compared with the free stream flow velocity (Ma = 0.527), the influence of the propeller slipstream belongs to the category of small disturbance, which is acceptable for engineering applications. [ABSTRACT FROM AUTHOR]

Experimental and numerical studies on noise radiated by flow past a rectangular two-dimensional deep cavity with passive control are conducted to research the mechanism of cavity noise reduction at low Mach numbers. The clean cavity has a depth-to-length ratio of 1.5 and a width-to-length ratio of 3. The passive control method is used by slanting the front and rear walls. Using acoustic microphones, both the surface noise and far-field noise are tested in an aeroacoustic wind tunnel. It is observed that the slanted rear wall can suppress the noise effectively, but for the slanted front wall, the tones will be enhanced at some velocities. Numerical simulation is conducted to reveal the mechanism. The results reveal that the slanted rear wall can reflect the unsteadiness back to the shear layer and break up the vortices in it. These vortexes will diffuse after impacting the rear wall and prevent the perturbation from moving deeper, which brings a stable flow field into the cavity. As for the slanted front wall, the vortices will be enlarged and become accelerated in the shear layer, which makes the impingement of it to the rear wall more intense, thus leading to an increase in the noise level. [ABSTRACT FROM AUTHOR]

The flow control effect of Gurney flaps on 50° swept delta wings during large-amplitude and high-frequency pitching were investigated both experimentally and numerically. Both force and velocity measurements were conducted and compared with the numerical simulation results. The lift hysteresis was found to be significantly affected by the Gurney flaps. It was found that the leading-edge Gurney flap (LG) acts to redistribute the vorticity over the suction surface of the wing during the upstroke process. The formation and development of the leading-edge vortex (LEV) on the suction surface was delayed by the LG, which was accompanied by enhancement of the lift at high angles of attack. The lower surface pressure can be altered with the flow velocity being slowed down by the trailing-edge Gurney flap (TG), which improves overall lift performance of the pitching wing at small to moderate angles of attack. [ABSTRACT FROM AUTHOR]

Air traffic has developed rapidly in the last decades. The noise generated from aircraft can impair the health of passengers and airport residents, so it is necessary to reduce aircraft noise and relieve the annoyance due to aircraft noise. As one important component of aircraft wings, the high-lift device is a barrier to the noise reduction of the large commercial civil aircraft in the next stage, especially during the approach and landing phases. When the slat and flap of the high-lift device are both stowed, some gaps and cavities will emerge and radiate strong noise. However, little attention has been paid to these geometric structures on real aircraft. This paper presents an experimental investigation on the far-field aeroacoustic characteristics of the stowed 30P30N high-lift configuration in the cruise condition, namely with slat and flap both stowed absolutely. The experiment of acoustic field measurements with a far-field microphone and acoustic microphone array shows that the gap between the main element and stowed flap on the pressure surface is the main noise source and can radiate tonal noise in the low-frequency range. The flow field measurement aided by a hot-wire anemometer reveals that the frequencies of the intense fluctuations near this gap are close to the tonal frequencies in the far-field noise spectra. Finally, with the applications of a gap cover and tripping device, the tonal noise of the stowed 30P30N high-lift configuration can be obviously suppressed because the feedback loop between the boundary layer instability upstream and the pressure wave from the flap–main element gap has been disturbed. [ABSTRACT FROM AUTHOR]

This paper studies the acoustic behavior inside the deep annular and cylindrical cavity at low Mach number. The turbulent shear layer above the cavity acts as a broadband noise source and drives resonant standing waves inside the cavity for various modes. According to previous investigation, those resonant standing waves inside the cavity play an important role in the aeroacoustic resonance of cavity noise, which gives perfect prediction of tonal frequency from the solution of wave equation. From the perspective of engineering application, it is more important to predict the spatial distribution of tonal intensity. It is needed to point out that the solution of the linear wave equation also provides the relative spatial distribution tonal intensity and the absolute value of tonal intensity can be determined from the acoustic experiments that is measured only at some locations. Based on this idea, a scheme is setup and validated to predict the amplitude spatial distribution of tonal intensity of aeroacoustic resonance. For example, an analytical model is established to provide the relative mode shape of aeroacoustic resonance in a simple geometry of cavity, which is realized by solving the wave equation with boundary conditions in a semi-closed space. This model considers the freestream velocity scaling and the depth correction factor varying with the Helmholtz number. The experimental aeroacoustic result is acquired by measuring the pressure fluctuation at some locations of cavity internal wall with the use of surface microphones. The experimental results are used to supplement and validate this analytical model. The amplitude spatial distribution at any freestream velocity (low Mach number) can be acquired by measuring the pressure fluctuation once at the leading edge or trailing edge of cavity bottom at an arbitrary Mach number, as the amplitude of most modes reaches its maximum here. [ABSTRACT FROM AUTHOR]

To provide further understanding of the low to mid frequency tonal noise characteristics of the leading-edge slat in the processes of take-off and landing, both experimental and numerical investigations are carried out on a two-dimensional high-lift configuration, with a stowed flap at varying incoming flow speeds (from 30 m/s to 60 m/s). The intensity variation of the low to mid frequency tonal noise is found to be closely related to the selection of the main mode of self-excited oscillation within the leading-edge slat cove. With increasing incoming flow speed, the main mode of the self-excited oscillation switches to a higher one. Meanwhile, the ratio of the self-excited oscillation period to the vortex shedding period is introduced to explain further the relationship between the main mode and incoming flow speed. As the incoming flow speed increases from 30 m/s to 60 m/s, the self-excited oscillation period is basically constant due to the flow similarity, whereas, the vortex shedding frequency is gradually increasing. The characteristic frequency of the shedding vortex near the cusp is found to be approximately proportional to 3/2 of the incoming flow speed power law. [ABSTRACT FROM AUTHOR]

Highlights • The helical-cable technique is to reduce cylinder noise and tandem cylinder noise. • The method can suppress the vortex shedding process and noise radiation efficiency. • Control on the upstream cylinder is the key for the tandem cylinder noise reduction. Abstract Cylinder noise can be remarkably reduced when the surface is helically wrapped with cables along the cylinder span. In this paper, aeroacoustic and aerodynamic experiments are conducted to reveal the noise reduction mechanism of the helical-cable technique. With the application of helical cables on the single circular cylinder, three-dimensional flow is promoted into the cylinder near wake, leading to the suppression of two-dimensional vortex shedding process and flow fluctuations. Besides, the three-dimensional wake also destroys the in-phase relationship of flow fluctuations along the cylinder span, leading to the reduction of spanwise correlation length and noise radiation efficiency. These two effects together contribute to the cylinder noise reduction. Furthermore, this helical-cable technique is extended to tandem cylinders and the results show that it can also reduce the tandem cylinder noise effectively. Especially for the moderate and large spacing tandem cylinder configurations, the key of the noise reduction is the control on the upstream cylinder. [ABSTRACT FROM AUTHOR]

In an effort to understand the tonal noise characteristics of high-lift configurations, aero-acoustic experiments are conducted on a two-dimensional, three-element high-lift configuration model, with a stowed flap. As a less expensive aid to experimentation, the numerical simulation method is used to obtain flow parameters possibly related to tones. Experimental results show that the low-mid-frequency band tonal noise generated by the self-excited oscillation in the slat cove is the main far-field noise source. Based on the local flow field information obtained by numerical simulations, an improved empirical formula, as proposed by Terrocal, is adopted to predict the characteristic frequencies of self-excited oscillation within the slat cove, which agrees well with the tonal frequencies observed by wind tunnel testing at varying angles of attack. The intensity of these low to mid frequency band tones is also found to be dependent on the angle of attack, i.e., the primary tone of the self-excited oscillation switches from the second mode to the third mode, with increasing angles of attack. By investigating the local flow around the slat cove, the ratio of the shear layer length over the shear layer momentum thickness is determined, i.e., L v / θ plays an important role in this transition of tonal intensity. As the angle of attack increases, both L v and θ monotonous decrease, whereas L v / θ increases and gives rise to a switch in the main characteristic frequency of the self-excited oscillation and a clear reduction in the overall sound pressure level. [ABSTRACT FROM AUTHOR]

During the taxiing of an aircraft on a water-contaminated runway, the rolling tires impact water film resulting in a considerable water displacement drag and a large amount of spray, which will affect the safety of take-off and landing. The characteristics and flow mechanism of the water displacement drag generated by an elastic tire are numerically studied based on the coupling method of Smoothed Particle Hydrodynamics and Finite Element Method. The water displacement drag is divided into wave-generated drag and film-generated drag based on flow mechanism for the first time, and the former is much larger than the latter. The water displacement drag satisfies the Gaussian distribution along the rotation axis. The longitudinal grooves cause a significant increase in the wave-generated drag and a reduction in the film-generated drag. A simple potential flow model around a semi-infinite bluff body is proposed to reveal the flow physics of film-generated drag. Two drag formulas are proposed to quickly predict the wave-generated drag and film-generated drag. [ABSTRACT FROM AUTHOR]

• The energy conversion is proposed to study the crown evolution of the drop impact upon film. • The effects of both the ratio of initial kinetic energy to surface tension energy of the drop and the initial film thickness on the energy conversion during the impact process are analyzed in detail. • The crown evolution can be divided into five stages based on the energy conversion and flow characteristics. • The impact phenomenon can be divided into three types: the drop impacts on shallow, medium and deep films. • For all the film depths, the inertial force and surface tension both play important roles. The energy conversion is proposed to analyze the effects of inertial force, surface tension, gravitational force and viscous force during the crown evolution of the drop impact phenomena. The incompressible laminar Navier–Stokes equations coupled with the volume of fluid model are solved numerically in the axisymmetric frame to simulate the impact process. The influences of both the ratio of the initial kinetic energy to the surface tension energy of the drop as well as the initial film thickness on the energy conversion during the impact process are studied in detail. The ratio of the initial kinetic energy to the surface tension energy of the drop can affect the energy conversion at a very early stage of the impact process, thus it can affect the occurrence of prompt splash significantly; while the initial film thickness can affect the energy conversion process during the whole impact process, and it is related to the occurrence of delayed splash. The energy conversion process corresponds to the type of impact phenomena, which is affected by the film depth significantly. according to the differences in energy curves and flow characteristics, the impact phenomenon is divided into three types: the drop impacts on shallow, medium and deep films. A typical impact process of the medium film is analyzed in detail. The impact process is divided into five stages, namely, crown formation, crown growth, crown stabilization, crown collapse and central jet formation. In the crown formation and growth stages, inertial force promotes the deformation of the liquid-gas interface and surface tension prevents the deformation; while in the crown collapse stage, inertial force prevents the deformation and surface tension does the opposite effect. During the whole process, the viscous force plays a prevention effect. [ABSTRACT FROM AUTHOR]

The initial spray caused by a rolling aircraft elastic pneumatic tire is studied by Smoothed Particle Hydrodynamics method. The tire spray is divided into four types: bow wave, rooster tail, impact-generated side plume and wave-generated side plume. The distributions of the particles involved in the different types of spray in the initial unperturbed water film are studied, with the relationship between the momentum transfer, the relative position of water particles and the aircraft tire being proposed. The impact-generated side plume is caused by the direct impact of tire, while the wave-generated side plume is caused by the breakup of the wave developed by the tire. The particles involved in the wave-generated side plume all come from a parabolic region inside the strip of initial injected particles at a given time. The width of the parabolic region reduces with the increasing water depth. The strips and the kinematic characteristics of particles at any time are both similar. A model is developed to predict the direction and magnitude of the momentum transfer velocity in water film based on the similarity of the strips and the kinematic characteristics of the particles, which works well for the cases with small tire load and thick water film. [ABSTRACT FROM AUTHOR]

• The parameter R d is proposed to predict the dominant mode in the locked-on state. • The paper finds the law of variation of the phase lag term γ with velocity in the flow-driven cavity process. • The Rossiter formulation is modified to predict the frequency of the dominant mode in the locked-on state. • The validity of this prediction formulation is verified by different models. Rossiter resonance noise, which is flow driven cavity noise involving fluid dynamics processes, was investigated in a low-speed wind tunnel. The experiments include near-field and far-field acoustic field measurements of the rectangular cavity at different depths as well as velocity measurements of the shear layer. The rectangular cavity geometry was also designed to enable the Rossiter mode to interact with the first-order depth resonant mode in a locked-on state. The experimental results showed the variation of frequency and overall sound pressure level (OASPL) when the self-sustained oscillation was in the locked-on state. When the self-sustained oscillatory mode is in the unlocked state, the frequency of the self-sustained oscillatory mode can be predicted well by using the Rossiter formula, whereas the frequency of the dominant Rossiter mode in the locked-on state will be predicted inconsistently. Moreover, the corresponding selection of the dominant mode also depends on the resonant mode, and there are local variations in the OASPL. The results indicate that the ratio of the resonant mode frequency to the self-sustained oscillatory fundamental frequency, R d , plays a key role in the locked-on state. In this paper, the Rossiter model is modified using the parameter R d for the prediction of the dominant mode frequency in the locked-on state. The difference between the current formula and previous studies is that the variation of the phase delay coefficient γ with velocity is considered, and γ is related to R d. Finally, the accuracy of the formulation is verified with experimental data from different models. [ABSTRACT FROM AUTHOR]

In a propeller blade optimization, both aerodynamic and aeroacoustic performance were considered simultaneously. A multi-fidelity sampling scheme was adopted by Transfer Learning (TL) to improve the overall optimization efficiency. A Deep Neural Network (DNN) was selected to map the non-linear relationship between the blade parameters and the aerodynamic/aeroacoustic performance, with the optimization being achieved by implementing a deep reinforcement learning algorithm, namely, Deep Deterministic Policy Gradient (DDPG), upon which a Multi-fidelity DNN based surrogate model (TL-MFDNN) was introduced with Transfer Learning between pre-trained and retrained processes. It was found that, by comparing the TL-MFDNN surrogate model based optimization with DDPG optimization using direct CFD simulation, the overall computing cost can be saved up to 77.3% and the optimized propeller has maximum noise reduction of up to 1.69 dB, with a negligible penalty on propulsive performance. [ABSTRACT FROM AUTHOR]

Aerodynamic and aeroacoustic experiments of 30P30N three-element high-lift configuration are conducted in D5 aeroacoustic wind tunnel at Beihang University. The test section is composed of Kevlar and perforated plate which can measure aerodynamic features with less jet shear layer interference and aeroacoustic characteristics with good sound transmission simultaneously. Aiming at the research of high-lift configurations during the aircraft approach and landing, Mach number and angle of attack vary from 0.09 to 0.17 and 3 ° to 8 ° , respectively. The measured surface pressure distributions in D5 agree well with the results of JAXA-LWT2 and computational fluid dynamics predictions. Consistent with previous investigations, the far-field noise spectra obtained by 1/2 in. free-field microphones nearly decrease with a slope proportional to f - 2 in a wide frequency range and scale with Ma 4.5 . Moreover, all mid-frequency peaks are observed in the range of 1 < St < 5 with one maximum within St = 1 - 3 . The tonal frequencies and noise spectral shape seem less sensitive to the tested angles of attack, except that the tonal intensity decreases with increasing angles of attack. Noise source maps for 1/3 octave band obtained from data processed by conventional beamforming with the far-field noise spectra indicate that the slat cove and slat-main element region is the main noise source that can radiate narrow-band peaks. [ABSTRACT FROM AUTHOR]

During the take-off and landing of aircrafts from/on water-contaminated runways, the tire-generated water spray can endanger flight safety, such as engine spray ingestion and spray impingement drag. In this paper, the flow physics and chine control of the spray generated by an aircraft rigid tire are studied by the Smoothed Particle Hydrodynamics (SPH) method. The SPH method is validated by a NASA experiment. The forming and developing progresses of the front and side sprays are described in detail. It is found that the parabolic stripe of initial ejected particles at a given time is the boundary between the spray source region and the non-disturbed region in water film, and the stripes at any time are similar. The effects of tire speed and water film depth on spray angles are evaluated. The chines can effectively control the spray angles by reducing the vertical velocity component of the ejected particles and increasing the lateral component. The arc chines are more effective in controlling the spray than the linear chines. [ABSTRACT FROM AUTHOR]

This paper introduces the continuous wavelet transform method to analyze different multiple tonal phenomena of the high-lift configurations, aiming at revealing the time-frequency information of these multiple tones simultaneously. Two types of multiple tones can be respectively observed in the far-field noise spectra at landing and cruise configurations, but their inherent physical mechanisms are different. Two wavelet functions are applied in this paper. The Morlet function as a complex wavelet function returns both amplitude and phase information for capturing oscillatory behaviors, so that it can clearly distinguish the mode switching mechanism and the amplitude modulation mechanism of different multiple tonal phenomena. While the Mexihat function as a real wavelet function returns only amplitude information, so that it is usually to isolate peaks or discontinuities of signals and cannot reveal the mechanisms of different multiple tonal phenomena. In summary, the Morlet function is more appropriate to analyze the periodical oscillatory acoustic tonal signals from multiple tonal phenomena. [ABSTRACT FROM AUTHOR]

Both aerodynamic and aeroacoustic measurements in wind tunnels are necessary for the study of high-lift devices. The existing wind tunnels have difficulties in simultaneously measuring aerodynamic features in a stable condition with less flow interference and aeroacoustic characteristics in a non-reflecting environment with good sound transmission. The test section in D5 aeroacoustic wind tunnel at Beihang University is recently upgraded for the aeroacoustic measurement of 30P30N high-lift configuration. The sidewall on the suction side consists of internal Kevlar cloth tensioned by a perforated plate and the other sidewall on the pressure side only consists of Kevlar cloth. Both aerodynamic and aeroacoustic features are measured to validate the performance of this test section. The surface static pressure distributions measured in D5 are similar to JAXA's results, verifying the similarity of flow field and the reliability of experiments. For acoustic field, noise spectral shape, tonal frequency and noise source location all agree well with aeroacoustic characteristics of high-lift configurations in previous investigations and numerical simulations. Thus, the test section overcomes the limitations and disadvantages of open and closed hard-wall test sections and can be applied for aerodynamic and aeroacoustic measurements of high-lift devices in aeroacoustic wind tunnels, especially for small scale wind tunnels. [ABSTRACT FROM AUTHOR]

The aerodynamics and flow physics of a close-coupled canard configuration W40C60 (the sweep angles of the wing and canard are 40° and 60°, respectively) with sharp leading edge at the angle of attack of 12.0° in static ground effect are investigated by the Delayed Detached Eddy Simulation grounded on Spalart–Allmaras turbulence model. With the ride height decreasing, the lift, drag, nose-down pitching moment and lift to drag ratio of W40C60 increase nonlinearly. In the unbounded flow field, both the canard lift increment and the wing lift decrement due to Wing/Canard Interference (WCI) stem mainly from the leeward surface. With the ride height decreasing, the canard lift increment due to WCI will increase and the wing lift decrement due to WCI will decrease, which is because both the canard and wing windward surface lift increments due to WCI increase significantly with the decreasing ride height. The windward surface lift behaviors are also interpreted as that the windward surface pressure increment of canard and wing of W40C60 due to ground effect is larger than that of the canard alone and the wing alone, respectively. This is because the WCI increases the effective chord length so that the effective dimensionless ride height of W40C60 is smaller than those of the canard alone and the wing alone at the same nominal dimensionless ride height. [ABSTRACT FROM AUTHOR]

This paper presents a parametric study on the far-field noise control effect of a circular cylinder with helical cables wrapping along cylinder span, aiming at finding an optimal operation condition for this treatment. Experimental results reveal that the noise control efficiency of this treatment is highly dependent on the non-dimensional thread pitch and cable density. The noise control efficiency gradually increases with the non-dimensional thread pitch and cable density increasing when both values are smaller than critical values. Further increasing the values of the two parameters, the control efficiency cannot increase any more. By choosing the optimal parameters of helical cables, both tonal and broadband noise can be remarkably suppressed, and the overall sound pressure level can be reduced by as large as 17 dB. [ABSTRACT FROM AUTHOR]

The D5 aeroacoustic wind tunnel at Beihang University is a newly commissioned small-scale closed-circuit wind tunnel with low turbulence intensity and low background noise. The wind tunnel is built to study both aerodynamic and aeroacoustic performance of aircraft components or scaled models. The wind tunnel has two types of test sections, the closed type test section is used for aerodynamic tests while the open type test section is mainly used for aeroacoustic experiments. Both types of test section are 1 m in height and 1 m in width, and the maximum wind velocity in the test section can be up to 80 m/s. An anechoic chamber is built surrounding the test section to provide the non-reflecting condition. This paper provides an overview of design criteria and performance of the small-scale wind tunnel. The layout of the wind tunnel and some critical design treatments to improve aerodynamic and acoustic performance are discussed in detail. Some experiments are conducted to verify the performance of D5 wind tunnel, results confirm that the turbulence intensity is less than 0.08% in the core of test section and the background noise is comparable with other aeroacoustic wind tunnels. A scaled simplified nose landing gear model is also measured as a benchmark test, results reveal that noise radiated from the model is adequately higher than the background noise for a wide frequency range and remarkably consistent with other results from literatures. [ABSTRACT FROM AUTHOR]

The slamming and transition stages are the most important for the water entry of wedges, in which the wedges experience the main hydrodynamic forces. The slamming stage is fully investigated by analytical methods, while there are few formulations for the transition stage where the spray root exceeds the top of wedge. Motivated by that, this paper numerically studies the transition stage of the water entry of linear wedges with constant and varying speeds, with assumptions that the fluid is incompressible, inviscid and with negligible effects of gravity and surface tension, and the flow is irrotational. For the constant speed impact, the similitude of the declining forces between different deadrise angles in the transition stage is found by scaling the differences between the maximum values in the slamming stage and the results of steady supercavitating flow. The hydrodynamic force is formulated based on the similitude of the declining forces in the transition stage together with the linear increasing forces in the slamming stage. For the varying speed impact, the hydrodynamic force component caused by the acceleration effect in the transition stage is formulated by an added mass coefficient with an average increase of 27.13% compared with that of slamming stage. Finally, a general expression of the hydrodynamic forces in both the slamming and transition stages is thus proposed and has good predictions in the range of deadrise angles from 5° to 70° for both the constant and varying speed impacts. [ABSTRACT FROM AUTHOR]

With the aim of investigating noise characteristics of tonal noise generated from a Krueger storage cavity, aero-acoustic experiments on a two-dimensional, Krueger flap configuration with an open or closed gap were conducted in the D5 aero-acoustic wind tunnel at Beihang University. The angles of attack are from 4° to 8°, and the free-stream velocities are from 45 m/s to 60 m/s. To study further the noise temporal characteristics and generation mechanism, experimental results were analyzed using a band-pass filtering method. The results show that low-frequency noise generated by the Krueger storage flow is dominant when the Krueger flap is deployed without a gap. For the Krueger configuration with a closed gap, low-frequency multiple tones observed at a free-stream velocity above 45 m/s are generated by self-excited oscillation within the storage cavity. The frequencies corresponding to these tonal noises have an octave relationship and satisfy the Strouhal number related scaling law. Filtering results reveal further that these low-frequency tones are intermittently and alternately excited in time and satisfy the oscillation mode switching mechanism. [ABSTRACT FROM AUTHOR]

The recent development of the Lattice Boltzmann Method has been widely applied in various industrial fields. In the application of rotor machinery simulation, the sliding mesh method with grid refinement becomes particularly important for the scenario of large-scale rotating flow computation. A new sliding mesh method based on the extrapolation boundary condition, with only first order interpolation across the interface, is proposed in the current study, which achieved a second order solving precision in two dimensional cases of Taylor-Couette flow and flow over a rotating elliptical cylinder. In the simulation of flow over a rotating propeller, both aerodynamic loads and far-field tonal noise were predicted and matched well with the experimental results. [ABSTRACT FROM AUTHOR]

• Aeroacoustic experiment and wavelet analysis are conductedon the 30P30N model. • Time-frequency characteristicsof differentslat and flap configurations. • Multiple tonesof flap noiseis satisfied withamplitude modulation phenomenon. • Multiple tones of slat noise is satisfied withmode switching phenomenon. High-lift device installed on modern large aircraft is a major noise source during the approach and landing phases. For high-lift device, slat and flap parameters such as gap, overlap and deflection angle have strong effect on aerodynamic and aeroacoustic characteristics. However, the research about time–frequency characteristics of high-lift device noise affected by slat and flap parameters is lacking. This paper presents an investigation on 30P30N model to reveal the effect of different slat and flap geometrical configurations on the aeroacoustic time–frequency characteristics with experimental measurement and wavelet analysis. The results show that the multiple tones at small flap and slat deflection angles are mainly generated from the flap gap region. The time–frequency characteristic of the tones is satisfied with the amplitude modulation phenomenon, namely that the acoustic energy concentrates on the primary tone and the other tones are generated from the modulation process of the primary tone. While the multiple tones at large slat deflection angles are generated from the slat cove and slat gap regions. The time–frequency characteristic of the tones is satisfied with the mode switching phenomenon, namely that the dominant noise energy temporally switches from one mode to another in time and these multiple tones cannot coexist independent of one another. [ABSTRACT FROM AUTHOR]

The experiments were conducted in a water tunnel facility and were aimed at investigating the merging process of co-rotating wake vortices in ground effect. A corresponding two-dimensional analytical model was also introduced based on experimental results. The two like-sign vortices were generated with equal size and strength above the ground plane. The evolution of vortex pair was attained by using particle image velocimetry at a series of downstream locations. The main finding is that the ground effect promotes the merging process and accelerates the vortices' rotation around one another. Vertical movements, known as vortex rebound, and lateral movements are observed. The ground effect also leads to the emergence of a secondary vortex ( SV ), which adds to the complexity of the vortex system. Prediction of the modified potential model, which takes vortex decay, viscous drag and the evolution of the SV into account, is compared with the experimental data. The results show that the vortex merging and rebound of a co-rotating vortex pair is successfully predicted and the prediction of vortex orientation and lateral motion are also improved by this model. [ABSTRACT FROM AUTHOR]

During takeoff and landing processes, the aerodynamic characteristics of a delta wing configuration aircraft are influenced by the dynamic ground effect (DGE). In this paper, the DGE during the landing process of a 65° sweep delta wing (VFE-2) with sharp leading edge is numerically studied at AOA = 23°. The unsteady compressible Reynolds-Averaged Navier–Stokes equations and Spalart–Allmaras turbulence model are discretized using the finite volume method. With the ride height decreasing, the lift, drag and nose-down pitching moment increase nonlinearly, and the increments become larger with the sink velocity increasing. The DGE can be divided into three regions based on the aerodynamics and flow physics. In the large ride height region, the aerodynamic forces in DGE remain unchanged with the ride height decreasing, and they are equal to those in static ground effect (SGE) as long as the angles of attack (AOAs) are equal; the ground effect (GE) can be neglected. In the medium ride height region, the aerodynamic forces in DGE increase slowly with the ride height decreasing, and they are still equal to those in SGE as long as the AOAs are equal; SGE governs the flow. In the small ride height region, the aerodynamic forces in DGE increase significantly with the ride height decreasing, and they are much larger than those in SGE although the AOAs are equal; SGE and compression work effect govern the flow together. Among them, SGE stagnates the airflow under the delta wing, increasing the pressure on the windward surface; simultaneously, it enhances the primary vortex strength, promotes its breakdown and drives it outward along the span. The compression work effect further increases the pressure on the windward surface; however, it has little influence on the airflow over the delta wing. [ABSTRACT FROM AUTHOR]

Leading edge droop nose devices have been adopted into the high-lift systems of A380 and A350 in order to reduce the takeoff drag as well as the noise emission. In this paper, the commercial code FLUENT is employed to investigate the aerodynamic characteristics of the two-element airfoil with droop nose based on the British NHLP 2-D L1T2 three-element airfoil with slat. Numerical results show that the three-element airfoil with slat has a higher C L at the tail-scrape angle as well as a much higher C Lmax than the two-element airfoil with droop nose. On the other hand, the two-element airfoil with droop nose has a much higher L/D when C L = C Lmax /1.13 2 than the three-element airfoil with slat. In order to improve the aerodynamic characteristics of the two-element airfoil with droop nose, three ways of deflecting the Fowler flap and the spoiler are utilized: 1) deflecting the Fowler flap only; 2) deflecting the spoiler only; 3) deflecting both of the Fowler flap and the spoiler. Through analysis and comparisons, deflecting both of the Fowler flap and the spoiler demonstrates the best overall aerodynamic characteristics among these three ways. The final two-element airfoil with droop nose has a much higher C L at the tail-scrape angle as well as a much higher L/D when C L = C Lmax /1.13 2 than the three-element airfoil with slat. On the contrary, the three-element airfoil with slat still has a much higher C Lmax than the final two-element airfoil with droop nose, due to a much larger stall angle of attack. Furthermore, both of the baseline two-element airfoil with droop nose and the final two-element airfoil with droop nose have a larger nose down moment than the three-element airfoil with slat. [ABSTRACT FROM AUTHOR]

Phytophthora capsici is an oomycete plant pathogen that infects peppers, tomatoes, and other agronomic and ornamental crops of the Solanaceae and Cucurbitaceae families worldwide. Early and accurate detection of P. capsici is essential for controlling this disease in the field. The internal transcribed spacer (ITS) regions of nuclear-encoded ribosomal DNA genes are widely used to detect Phytophthora nicotianae, Pythium helicoides and Peronospora variabilis. In this study, a novel and highly sensitive loop-mediated isothermal amplification (LAMP) assay was developed for the specific detection of P. capsici using calcein as a fluorescent indicator. Four LAMP primers were designed based on the ITS sequence of P. capsici. A total of 23 isolates of P. capsici from geographically distinct counties in China yielded positive results in the LAMP assay. No cross-reaction was observed with other oomycetes or fungal pathogens. The detection limit of P. capsici by LAMP was 100 fg genomic DNA per 25 μL reaction. The LAMP assay developed in this study is simple, fast, sensitive and specific, and can be used in the field to detect P. capsici in infected plant tissue. [ABSTRACT FROM AUTHOR]

Phytophthora nicotianae is an important soilborne plant pathogen. It causes black shank in tobacco and other commercially important crop diseases. Early and accurate detection of P. nicotianae is essential for controlling these diseases. In this study, primers based on the Ras-related protein gene (Yptl) of P. nicotianae were tested for their specific detection of the pathogen using nested PCR and LAMP assays. For specificity testing, DNA extracts from 47 P. nicotianae isolates, 45 isolates of 16 different oomycetes and 25 isolates of other fungal species were used;no cross-reaction with other pathogens was observed. The sensitivity assay showed that the nested PCR and LAMP assays had detection limits of 100 fg and 10 fg genomic DNA per 25-il reaction, respectively. Furthermore, the nested PCR and LAMP assays were used for the detection of DNA from naturally P. nicotianae-infected tobacco tissues and soil. Our results suggest that the LAMP assay has the greatest potential for the specific detection of P. nicotianae in regions that are at risk of contracting tobacco black shank disease and that the Yptl gene is a novel and effective target of P. nicotianae LAMP visual detection. [ABSTRACT FROM AUTHOR]

Aspergillus flavus is a common filamentous fungus that produces aflatoxins and presents a major threat to agriculture and human health. Previous studies focused mainly on the detection of A. flavus or aflatoxin separately. Here, we developed internal transcribed spacer (ITS)- and aflP-based rapid detection of A. flavus in food samples using the loop-mediated isothermal amplification (LAMP) method. The ITS1-5.8S-ITS2 rDNA region of A. flavus and the aflatoxin-encoding gene aflP were used as target regions. The detection limits of A. flavus and aflP were 10 fg and 1 pg pure DNA, respectively, which allows aflatoxin-contaminated samples to be differentiated from infected samples and reduces false-negative or false-positive results. For specificity testing, DNA extracted from 7 A. flavus, 5 different Aspergillus spp., and 21 other fungi were used, and our results showed that A. flavus strains are detected by ITS-based detection and aflatoxigenic A. flavus strains are detected by aflP-based detection. Furthermore, the ITS- and aflP-based LAMP assays were used for detection analysis of DNA from food samples artificially and naturally contaminated with A. flavus. Our results showed that the detection rate of A. flavus based on the multi-ITS-based LAMP detection is 100% and that the aflatoxigenic strains in all A. flavus are detected by the aflP-based LAMP assay. The LAMP protocol described in our study represents a rapid and highly specific and sensitive diagnostic method for A. flavus detection, which can be used as a diagnostic tool that simplifies A. flavus monitoring and guarantees the quality and safety of foods. [ABSTRACT FROM AUTHOR]

The computational fluid dynamics is the main method to evaluate the aerodynamic performance for the optimization of high-lift devices. Currently, the direct three-dimensional (3D) optimization requires significant computational resources. Additionally, the commonly used heuristic algorithms can not extract the experience of two-dimensional (2D) optimization to accelerate the 3D optimization process. In order to resolve these issues, a novel 2D-to-3D optimization method based on the coupling of Deep Reinforcement Learning (DRL) and Transfer Learning (TL) is proposed to conduct the aerodynamic optimization of the 3D high-lift devices and tested on the NASA Trap Wing model. The 2D optimization is first carried out, and then its neural networks in DRL and the optimal configuration are extracted by TL to turn into the 3D optimization. Compared with the direct 3D optimization, the proposed 2D-to-3D optimization method can result in improved aerodynamic performance for the same computational cost, or can save 51%-81% of the computational cost to obtain a similar performance. [ABSTRACT FROM AUTHOR]

Perillaldehyde (PAE) is a natural compound used to control post-harvest fungal disease. Ethylenediaminetetraacetic acid (EDTA) also has anti-fungal effects, but its synergistic effects on the anti-fungal mechanisms of PAE against Aspergillus flavus (A. flavus) are unexplored. Therefore, we examined A. flavus mycelial growth, conidial formation, and pathogenicity, as well as the mechanisms, with EDTA and PAE treatment. EDTA was found to accelerate PAE-suppressed mycelial growth and conidial formation. These effects coincided with an increase in membrane permeability, autophagy, and apoptosis. Accordingly, the expression of pathogenicity-associated genes was dramatically decreased with PAE + EDTA treatment. In addition, the levels of the antioxidants vitamin C, total thiols, and total phenols, and the total antioxidant capacity and radical-scavenging capacity were increased with EDTA + PAE. Thus, the findings indicate that EDTA enhances PAE-mediated control of post-harvest A. flavus via autophagy, apoptosis, antioxidant, and membrane permeability mechanisms, making it suitable for global application in the food industry to attenuate A. flavus from post-harvest crops and improve antioxidant nutrient accumulation. • EDTA enhances perillaldehyde-inhibited mycelium growth, conidia, and pathogenicity. • Mycelium inhibition involves apoptosis and membrane permeability pathways. • EDTA enhances perillaldehyde-induced increase in the antioxidant levels in peanuts. • EDTA enhances perillaldehyde-induced inhibition of aflatoxin and pathogenicity genes. [ABSTRACT FROM AUTHOR]

Abstract: Background: Our previous studies demonstrated that berberine could improve the renal function in rats and mice with diabetic nephropathy (DN) and inhibit extracellular matrix (ECM) component, fibronectin (FN) expression in rat mesangial cells (MCs) cultured under high glucose. However, the molecular mechanisms have not been fully elucidated. Objective: To explore the potential mechanisms of berberine in the treatment of DN, we investigated the effects of berberine on lipopolysaccharide (LPS)-induced nuclear factor-kappa B (NF-κB) activation and its downstream inflammatory mediators, such as intercellular adhesion molecule-1 (ICAM-1), transforming growth factor-beta 1 (TGF-β1), inducible nitric oxide synthase (iNOS) and fibronectin (FN) protein expression in rat MCs. Method: Cell proliferation was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). The activation of NF-κB was detected by Western blot and confocal microscopy. The protein levels of ICAM-1, TGF-β1, iNOS and FN in rat MCs were detected by Western blot. Results: Our results revealed that berberine significantly suppressed LPS-induced cell proliferation and inhibited LPS-induced NF-κB nuclear translocation in MCs, as well as protein expression of ICAM-1, TGF-β1, iNOS and FN. Conclusion: Berberine significantly repressed LPS-induced cell proliferation and FN expression in rat MCs through inhibiting the activation of NF-κB signaling pathway and protein expression of its downstream inflammatory mediators. The ameliorative effects of berberine on DN might be associated with this inhibition effect on NF-κB signaling pathway which was independent of its hypoglycemic effect. [ABSTRACT FROM AUTHOR]

Abstract: Ethylene response factors (ERFs) constitute a transcription factor family that contains at least 65 members in Arabidopsis. However, only a few ERFs have been characterized that function in plant defense responses. In the present study, we determined if RAP2.6L, an ERF transcription factor, plays a role in Arabidopsis resistance to DC3000, a virulent strain of the bacterial pathogen Pseudomonas syringae pathovar tomato [(Okabe) Young, Dye & Wilkie]. Expression of the RAP2.6L gene was induced by DC3000 inoculation in wild-type Arabidopsis and in mutants exhibiting defects in basal defense pathways. The RAP2.6L protein localized to the nuclei of onion epidermal cells and functioned as a transcriptional activator in yeast. Genetic disruption of RAP2.6L substantially impacted Arabidopsis response to DC3000. Results showed inhibition of bacterial multiplication, reduced severity of necrosis symptoms caused by the pathogen, and an increased defense response in the RAP2.6L-discrupted mutants compared to the wild-type plants. These changes accompanied DC3000-induced and RAP2.6L-dependent expression of several defense-related genes. [Copyright &y& Elsevier]

SUMMARY: Uncovering the function of phytopathogen effectors is crucial for understanding mechanisms of pathogen pathogenicity and for improving our ability to protect plants from diseases. An increasing number of effectors have been predicted in various plant pathogens. Functional characterization of these effectors has become a major focus in the study of plant–pathogen interactions. In this study, we designed a novel screening system that combines the TMV (tobacco mosaic virus)‐GFP vector and Agrobacterium‐mediated transient expression in the model plant Nicotiana benthamiana. This system enables the rapid identification of effectors that interfere with plant immunity. The biological function of these effectors can be easily evaluated by observing the GFP fluorescence signal using a UV lamp within just a few days. To evaluate the TMV‐GFP system, we initially tested it with well‐described virulence and avirulence type III effectors from the bacterial pathogen Ralstonia solanacearum. After proving the accuracy and efficiency of the TMV‐GFP system, we successfully screened a novel virulence effector, RipS1, using this approach. Furthermore, using the TMV‐GFP system, we reproduced consistent results with previously known cytoplasmic effectors from a diverse array of pathogens. Additionally, we demonstrated the effectiveness of the TMV‐GFP system in identifying apoplastic effectors. The easy operation, time‐saving nature, broad effectiveness, and low technical requirements of the TMV‐GFP system make it a promising approach for high‐throughput screening of effectors with immune interference activity from various pathogens. Significance Statement: The development of a robust high‐throughput functional screening assay for pathogen effectors will facilitate the study in plant‐pathogen interactions. We established a novel screening system using the TMV‐GFP vector, enabling the rapid identification of effectors that interfere with plant immunity by observing GFP fluorescence under a UV lamp within a few days. The TMV‐GFP system is a promising approach for high‐throughput screening of effectors from diverse pathogens. [ABSTRACT FROM AUTHOR]

Discrete tones exist in the airframe noise spectra. For landing gear components, some cavities may generate multiple tones. The tonal frequencies can be accurately predicted and two different tonal noise generation mechanisms have been already proposed, namely fluid-acoustic feedback loop and acoustic resonance. However, the inherent temporal features and the relationships between multiple tones are rarely researched. This paper introduces the continuous wavelet transform method to analyze the acoustic signals from a simplified nose landing gear model and a ring cavity model, aiming at revealing the temporal features and excitation rules of these multiple tones. For the landing gear model, the wavelet analysis results show the mid-high frequency tones generated from the acoustic resonance phenomenon are randomly excited in time and the excitation states are independent of one another. For the ring cavity model, the low frequency tones generated from fluid-acoustic feedback loop are excited alternately and the primary acoustic energy switches from one to another in time, namely the mode switching mechanism. While among the high frequency tones generated from acoustic resonance, the second to the fourth tones satisfy the amplitude modulation mechanism and the other tones are randomly excited. [ABSTRACT FROM AUTHOR]