Effect of Bogie Cavity End Wall Inclination on Flow Field and Aerodynamic Noise in the Bogie Region of High-Speed Trains

Combining the detached eddy simulation(DES)method and Ffowcs Williams-Hawkings(FW-H)equation,the effect of bogie cavity end wall inclination on the flow field and aerodynamic noise in the bogie region is numerically studied.First,the simulation is conducted based on a simplified cavity-bogie model,including five cases with different inclination angles of the front and rear walls of the cavity.By comparing and analyzing the flow field and acoustic results of the five cases,the influence of the regularity and mechanism of the bogie cavity end wall inclination on the flow field and the aerodynamic noise of the bogie region are revealed.Then,the noise reduction strategy determined by the results of the simplified cavity-bogie model is applied to a three-car marshaling train model to verify its effectiveness when applied to the real train.The results reveal that the forward inclination of the cavity front wall enlarges the influence area of shear vortex structures formed at the leading edge of the cavity and intensifies the interaction between the vortex structures and the front wheelset,frontmotor,and front gearbox,resulting in the increase of the aerodynamic noise generated by the bogie itself.The backward inclination of the cavity rear wall is conducive to guiding the vortex structures flow out of the cavity and weakening the interaction between the shear vortex structures and the cavity rear wall,leading to the reduction of the aerodynamic noise generated by the bogie cavity.Inclining the rear end wall of the foremost bogie cavity of the head car is a feasible aerodynamic noise reduction measure for high-speed trains.

Chitosan/Sodium Alginate Multilayer pH-Sensitive Films Based on Layer-by-Layer Self-Assembly for Intelligent Packaging

The abuse of plastic food packaging has brought about severe white pollution issues around the world.Developing green and sustainable biomass packaging is an effective way to solve this problem.Hence,a chitosan/sodium alginate-based multilayer film is fabricated via a layer-by-layer(LBL)self-assembly method.With the help of superior interaction between the layers,the multilayer film possesses excellent mechanical properties(with a tensile strength of 50 MPa).Besides,the film displays outstanding water retention property(blocking moisture of 97.56%)and ultraviolet blocking property.Anthocyanin is introduced into the film to detect the food quality since it is one natural plant polyphenol that is sensitive to the pH changes ranging from 1 to 13 in food when spoilage occurs.It is noted that the film is also bacteriostatic which is desired for food packaging.This study describes a simple technique for the development of advanced multifunctional and fully biodegradable food packaging film and it is a sustainable alternative to plastic packaging.

Enabling high-efficiency ethanol oxidation on NiFe-LDH via deprotonation promotion and absorption inhibition

Nucleophile oxidation reaction(NOR), represented by ethanol oxidation reaction(EOR), is a promising pathway to replace oxygen evolution reaction(OER). EOR can effectively reduce the driving voltage of hydrogen production in direct water splitting. In this work, large current and high efficiency of EOR on a Ni, Fe layered double hydroxide(NiFe-LDH) catalyst were simultaneously achieved by a facile fluorination strategy. F in NiFe-LDH can reduce the activation energy of the dehydrogenation reaction, thus promoting the deprotonation process of NiFe-LDH to achieve a lower EOR onset potential. It also weakens the absorption of OH-and nucleophile electrooxidation products on the surface of NiFe-LDH at a higher potential, achieving a high current density and EOR selectivity, according to density functional theory calculations. Based on our experiment results, the optimized fluorinated NiFe-LDH catalyst achieves a low potential of 1.386 V to deliver a 10 mA cm^(-2)EOR. Moreover, the Faraday efficiency is greater than 95%, with a current density ranging from 10 to 250 mA cm^(-2). This work provides a promising pathway for an efficient and cost-effective NOR catalyst design for economic hydrogen production.

An integrated rice panicle phenotyping method based on X-ray and RGB scanning and deep learning

Rice panicle phenotyping is required in rice breeding for high yield and grain quality.To fully evaluate spikelet and kernel traits without threshing and hulling,using X-ray and RGB scanning,we developed an integrated rice panicle phenotyping system and a corresponding image analysis pipeline.We compared five methods of counting spikelets and found that Faster R-CNN achieved high accuracy(R~2 of 0.99)and speed.Faster R-CNN was also applied to indica and japonica classification and achieved 91%accuracy.The proposed integrated panicle phenotyping method offers benefit for rice functional genetics and breeding.

Numerical Investigation on the Aerodynamic Noise Generated by a Simplified Double-Strip Pantograph

In order to understand the mechanism by which a pantograph can generate aerodynamic noise and grasp its farfield characteristics,a simplified double-strip pantograph is analyzed numerically.Firstly,the unsteady flow field around the pantograph is simulated in the frame of a large eddy simulation(LES)technique.Then the location of the main noise source is determined using surface fluctuating pressure data and the vortex structures in the pantograph flow field are analyzed by means of the Q-criterion.Based on this,the relationship between the wake vortex and the intensity of the aerodynamic sound source on the pantograph surface is discussed.Finally,the far-field aerodynamic noise is calculated by means of the Ffowcs Williams-Hawkings(FW-H)equation,and the contribution of each component to total noise and the frequency spectrum characteristics are analyzed.The results show that on the pantograph surface where vortex shedding or interaction with the wake of upstream components occurs,the pressure fluctuation is more intense,resulting in strong dipole sources.The far-field aerodynamic noise energy of the pantograph is mainly concentrated in the frequency band below 1500 Hz.The peaks in the frequency spectrum are mainly generated by the base frame,balance arm and the rear strip,which are also the main contributors to the aerodynamic noise.

Ascorbate peroxidase 1 confers resistance to southern corn leaf blight in maize

Southern corn leaf blight (SCLB), caused by Bipolarismaydis, is one of the most devastatingdiseases affecting maize production. However,only one SLCB resistance gene, conferring partialresistance, is currently known, underscoring theimportance of isolating new SCLB resistancerelatedgenes. Here, we performed a comparativeproteomic analysis and identified 258 proteinsshowing differential abundance during the maizeresponse to B. maydis. These proteins included anascorbate peroxidase (Zea mays ascorbate peroxidase1 (ZmAPX1)) encoded by a gene locatedwithin the mapping interval of a previously identifiedquantitative trait locus associated with SCLBresistance. ZmAPX1 overexpression resulted inlower H_(2)O_(2) accumulation and enhanced resistanceagainst B. maydis. Jasmonic acid (JA)contents and transcript levels for JA biosynthesisand responsive genes increased in ZmAPX1-overexpressing plants infected with B. maydis,whereas Zmapx1 mutants showed the oppositeeffects. We further determined that low levels of H_(2)O_(2) are accompanied by an accumulation of JAthat enhances SCLB resistance. These resultsdemonstrate that ZmAPX1 positively regulatesSCLB resistance by decreasing H_(2)O_(2) accumulationand activating the JA-mediated defensesignaling pathway. This study identified ZmAPX1as a potentially useful gene for increasing SCLBresistance. Furthermore, the generated datamay be relevant for clarifying the functions ofplant APXs.

High-energy all-fiber gain-switched thulium-doped fiber laser for volumetric photoacoustic imaging of lipids

We demonstrate a high-energy all-fiber short wavelength gain-switched thulium-doped fiber laser for volumetric photoacoustic(PA)imaging of lipids.The laser cavity is constructed by embedding a short piece of gain fiber between a pair of fiber Bragg gratings(FBGs).Through using three pairs of FBGs with operation wavelengths at1700,1725,and 1750 nm,three similar lasers are realized with a cavity length of around 25 cm.Under a maximum pump energy of 300μJ at 1560 nm,laser pulse energies of 58.2,66.8,and 75.3μJ are,respectively,achieved with a minimum pulse width of<16.7 ns at a repetition rate of 10 kHz.Volumetric imaging of lipids is validated through scanning a fat beef slice with a PA microscopy system incorporated with the newly developed source,and a lateral resolution of 18.8μm and an axial resolution of 172.9μm are achieved.Moreover,the higher shooting speed of the developed source can potentially allow for increasing at twice the frame rate of current intravascular PA imaging.

Breathing dissipative soliton explosions in a bidirectional ultrafast fiber laser

Soliton explosions,among the most exotic dynamics,have been extensively studied on parameter invariant stationary solitons.However,the explosion dynamics are still largcly unexplored in breathing dissipative solitons as a dynamic solution to many nonlincar systems.Here,we report on the first observation of a breathing dissipative soliton explosion in a nct-normal-dispersion bidirectional ultrafast fiber lascr.The breathing soliton explos ionscould be stimulated by the soliton buildup process or alteration of polarization settings.Transient breathing soliton pairs with intensive repulsion that is sensitive to initial conditions can also be triggered by multiple soliton explosions in the soliton buildup process instead of being triggered by varying polarization settings.The high bchavior similarity also exists in the breathing soliton buildup and explosion process owing to the common gain and loss modulation.In addition,dissipative rogue waves were detected in the breathing soliton explosion,and the collision of breathing soliton significantly enhanced the amplitude of rogue waves,which is characteristic of the breathing solitons in a bidirectional fiber laser.These results shed new insights into complex dissipative soliton dynamics.

Hybrid optical parametrically-oscillating emitter at 1930 nm for volumetric photoacoustic imaging of water content

Water plays a vital role in biological metabolism and it would be essential to trace the water content non-invasively,such as leveraging the vibrational absorption peak of the O-H bond.However,due to the lack of an efficient laser source,it was challenging to image the water content in the deep tissue with micron-level spatial resolution.To address this problem,we develop a high-power hybrid optical parametrically-oscillating emitter(HOPE)at 1930 nm,at which the vibrational absorption peak of the O-H bond locates.The maximum pulse energy is over 1.74μJ with a pulse repetition rate of 50 kHz and a pulse width of 15 ns.We employ this laser source in the optical-resolution photoacoustic microscopy(OR-PAM)system to image the water content in the phantom and the biological tissue in vitro.Our 1930-nm OR-PAM could map the water content in the complex tissue environment at high spatial resolution,deep penetration depth,improved sensitivity,and suppressed artifact signal of the lipid.

Experimental and computational models for tissue-engineered heart valves:a narrative review

Valvular heart disease is currently a common problem which causes high morbidity and mortality worldwide.Prosthetic valve replacements are widely needed to correct narrowing or backflow through the valvular orifice.Compared to mechanical valves and biological valves,tissue-engineered heart valves can be an ideal substitute because they have a low risk of thromboembolism and calcification,and the potential for remodelling,regeneration,and growth.In order to test the performance of these heart valves,various animal models and other models are needed to optimise the structure and function of tissue-engineered heart valves,which may provide a potential mechanism responsible for substantial enhancement in tissue-engineered heart valves.Choosing the appropriate model for evaluating the performance of the tissue-engineered valve is important,as different models have their own advantages and disadvantages.In this review,we summarise the current state-of-the-art animal models,bioreactors,and computational simulation models with the aim of creating more strategies for better development of tissue-engineered heart valves.This review provides an overview of major factors that influence the selection and design of a model for tissue-engineered heart valve.Continued efforts in improving and testing models for valve regeneration remain crucial in basic science and translational researches.Future research should focus on finding the right animal model and developing better in vitro testing systems for tissue-engineered heart valve.

A Novel Method to Improve the Physical Property and Biocompatibility of Decellularized Heart Valve Scaffold with Sericin and Polydopamine

Cardiac valve replacement is an effective method to treat valvular heart disease.Artificial valves used routinely in clinic still have defects.In our study,we explored a novel method to modify the performance of Decellularized Heart Valve(DHV)scaffold.The decellularized porcine aortic valve was prepared using sequential hydrophile and lipophile solubilization method.The sericin was extracted from silk fibroin-deficient silkworm cocoon by lithium bromide method.First,DHV was immersed in sericin solution to produce the sericin–DHV composite scaffold.Then,we modified the DHV by making a Polydopamine(PDA)coating on the DHV first and then binding the sericin.The physical properties and biological compatibility of our composite scaffold were assessed in vitro and in vivo.Sericin were successfully prepared,combined to DHV and improved its biocompatibility.PDA coating further promoted the combination of sericin on DHV and improved the physical properties of scaffolds.The decay rate of our modified valve scaffold was decreased in vivo and it showed good compatibility with blood.In conclusion,our modification improved the physical properties and biocompatibility of the valve scaffold.The combination of PDA and sericin promoted the recellularization of decellularized valves,showing great potential to be a novel artificial valve.

Current progress on scaffolds of tissue engineering heart valves

Tissue engineering heart valves(TEHV)may be the most promising valve substitute,but the study has been relatively stagnant in the recent five years due to the special position,function and mechanical property of heart valves.It is one of the key factors to select an ideal scaffold material in the construction of TEHV.And this article will briefly review the current research and progress on the scaffolds of TEHV,especially based on Chinese works.