An Improved Time-Domain Inverse Technique for Localization and Quantifcation of Rotating Sound Sources

The time-domain inverse technique based on the time-domain rotating equivalent source method has been proposed to localize and quantify rotating sound sources. However, this technique encounters two problems to be addressed: one is the time-consuming process of solving the transcendental equation at each time step, and the other is the difculty of controlling the instability problem due to the time-varying transfer matrix. In view of that, an improved technique is proposed in this paper to resolve these two problems. In the improved technique, a de-Dopplerization method in the time-domain rotating reference frame is frst applied to eliminate the Doppler efect caused by the source rotation in the measured pressure signals, and then the restored pressure signals without the Doppler efect are used as the inputs of the time-domain stationary equivalent source method to locate and quantify sound sources. Compared with the original technique, the improved technique can avoid solving the transcendental equation at each time step, and facilitate the treatment of the instability problem because the transfer matrix does not change with time. Numerical simulation and experimental results show that the improved technique can eliminate the Doppler efect efectively, and then localize and quantify the rotating nonstationary or broadband sources accurately. The results also demonstrate that the improved technique can guarantee a more stable reconstruction and compute more efciently than the original one.

Characteristics and Trends of Urban Waterfront Human Settlements Based on CiteSpace

Urban waterfront human settlements have gradually become a hot topic for research in recent years.Using CiteSpace,597 publications from 2017 to 2023 that were retrieved from the Web of Science were analyzed and sorted out,and the following characteristics were found:(1)The research hotspots transitioned from thermal comfort evaluation to the functional mechanism of water bodies,and then to the impact on the environment and residents’behavior.(2)The integration of disciplines has promoted the diversification of perspectives on urban waterfront human settlements,and the content has become more concentrated in interdisciplinary fields.Research on corresponding technology and methods of urban waterfront human settlement has improved,and so has the extensiveness of the experiments.(3)The research on urban waterfront human settlement from the perspective of ecology has been improving.The research focuses more on the harmonious coexistence of ecological and cultural values and human beings.

基于回流区特性的气雾化喷嘴设计及流场结构模拟

本文设计了一种laval喷管结构雾化器,并利用CFD软件模拟研究了雾化气压P、雾化气体温度T、气体喷口孔心距D、气体喷射角度α以及导流管伸出长度d五大因素对流场结构的影响。结果表明:laval喷管雾化流场结构与狭缝喷嘴不同,气流喷出后不发生膨胀,不形成闭涡结构;随着P的增大,流场速度增加,区域扩大,回流区静态压力Ps不随P变化而变化;增加气体温度T可以提升流场速度和流场温度;气体喷口孔心距D会影响回流区压力和流场速度;增大气体喷射角度α可以提升流场速度,同时会导致回流区压力升高;随着导流管伸出长度d的增加,回流区静压先下降后升高。

Axial compressive behavior of Moso Bamboo and its components with respect to fiber-reinforced composite structure

Bamboo is a unique fiber-reinforced bio-composite with fibers embedded into a parenchyma cell matrix.We conducted axial compression tests on bamboo blocks prepared from bottom to top,and from inner to outer portions of the culm.The apparent Young’s modulus and compressive strength of whole thickness bamboo blocks exhibited slight increases with increasing height along the culm,due to slight increases of fiber volume fraction(Vf)from 28.4 to 30.4%.Other blocks showed a significant increase in apparent Young’s modulus and strength from the inner to outer part of the culm wall,mainly owing to a sharp increase of Vf from 17.1 to 59.8%.With a decrease of fiber fraction volume there was a transition from relatively brittle behavior to very ductile behavior in bamboo blocks.Results indicated that stiffness and strength of bamboo was primarily due to fiber in compression,and ductility of bamboo was provided by the parenchyma cell matrix acting as a natural fiber-reinforced composite.

FeNiCrSiMoMnC合金气雾化熔滴的运动与传热行为模拟分析

气雾化过程中合金液流被高压气流破碎后,要飞行一段距离才开始冷却凝固,这称为熔滴的飞行过程。本文以重载耐磨耐腐蚀激光熔覆涂层用FeNiCrSiMoMnC合金为对象,通过建立熔滴飞行过程的模型,并对该过程进行数值模拟,计算讨论了雾化气体初始速率、熔滴直径对熔滴的速度、传热系数等参数的影响。结果表明,熔滴速度呈现先增大至最大值后逐渐减小的趋势,且随熔滴直径的增大,熔滴速度最大值点逐渐降低;传热系数与速度曲线相反,呈先下降后上升的趋势,极小值为2kg/d,熔滴直径越大,与气体速度差越小,传热系数越小;随气体初始速率的增大,熔滴最大速度点上移,同时传热系数也逐渐增大。

Dynamic reconstruction of Ni-Zn alloy solid-electrolyte interface for highly stable Zn anode

Aqueous zinc ion batteries(AZIBs)are ideal candidates for large-scale battery storage,with a high theoretical specific capacity,ecological friendliness,and extremely low cost but are strongly hindered by zinc dendrite growth.Herein,Ni-Zn alloy is artificially constructed as a solid-electrolyte interface(SEI)for Zn anodes by electrodeposition and annealing.The Ni-Zn alloy layer acts as a dynamic shield at the electrode/electrolyte interface.Interestingly,the zinc atoms migrate out of the electrode body during zinc stripping while merging into the electrode body during the plating.In this way,the Ni-Zn alloy is able to guide the zinc deposition in the horizontal direction,thereby suppressing the formation of dendrite.Benefiting from those,the Ni-Zn alloy symmetric cell shows a greatly improved cycle life and is able to operate stably for 1,900 h at a current density of 0.5 mA·cm^(−2).The present study is a strategy for negative electrode protection of AZIBs.

Enabling a stable and dendrite-suppressed Zn anode via facile surface roughness engineering

The safety and cycle lifespan of zinc metal-based aqueous batteries are greatly restricted by zinc anode.The poor cycling performance of zinc metal anode is often considered to be impacted by the dendrite growth,surface passivation,zinc metal corrosion and hydrogen evolution reaction,while surface roughness is a matter that has often been ignored in past studies.Herein,a roughness gradient is constructed on the zinc anode surface by a simple grinding and pasting method.It has been found the modified zinc anodes with lower surface roughness exhibit the smaller zinc deposition overpotential and longer cycle life.Further,in situ optical microscopy photographs indicate that the zinc anode with an optimized roughness enables more uniform distribution of zinc precipitation and corrosion sites,which will facilitate a stable cycling performance of aqueous zinc ion batteries.The Zn anode dendrite-suppressing mechanism via surface roughness engineering was revealed through finite element computational simulation.These results emphasize the effectiveness of roughness engineering for tuning the surface physics of Zn anode and provide a facile strategy to develop better and safer aqueous zinc ion batteries.

Cathodic Zn underpotential deposition:an evitable degradation mechanism in aqueous zinc-ion batteries

Aqueous zinc-ion batteries(AZIBs)are promising for large-scale energy storage,but their development is plagued by inadequate cycle life.Here,for the first time,we reveal an unusual phenomenon of cathodic underpotential deposition(UPD)of Zn,which is highly irreversible and considered the origin of the inferior cycling stability of AZIBs.Combining experimental and theoretical simulation approaches,we propose that the UPD process agrees with a two-dimensional nucleation and growth model,following a thermodynamically feasible mechanism.Furthermore,the universality of Zn UPD is identified in systems,including VO_(2)//Zn,TiO_(2)//Zn,and SnO_(2)//Zn.In practice,we propose and successfully implement removing cathodic Zn UPD and substantially mitigate the degradation of the battery by controlling the end-ofdischarge voltage.This work provides new insights into AZIBs degradation and brings the cathodic UPD behavior of rechargeable batteries into the limelight.

Identification and genetic characterization of bovine hepacivirus in China:A large scale epidemiological study

Bovine hepacivirus(BovHepV)is a novel virus that was recently discovered in Ghana and Germany in 2015.Until now,this virus has been identified in cattle population worldwide and is classified into subtypes A-G.To fully understand the epidemic situation and genetic characteristic of BovHepV in China,a total of 612 cattle serum samples were collected from 20 farms in seven provinces and municipality in China between 2018 and 2020 and were tested for the presence of BovHepV RNA via semi-nested PCR.The results demonstrated that 49(8.0%)samples were BovHepV RNA-positive.It is noted that BovHepV infection in yak was confirmed for the first time.BovHepV was detected in all the seven provinces,with the positive rate ranging from 3.1%to 13.3%,which indicates a wide geographical distribution pattern of BovHepV in China.Sequencing results revealed that 5'UTR of the 49 field BovHepV strains have a nucleotide similarity of 96.3%-100%between each other and 93.9%-100%with previously reported BovHepV strains.In addition,genetic analysis identified five critical nucleotide sites in 5'UTR to distinguish different subtypes,which was further verified by genomic sequencing and nucleotide similarity analysis.All the 49 Chinese field BovHepV strains were classified into subtype G and this subtype is only determined in cattle in China currently.This study will provide insights for us to better understand the epidemiology and genetic diversity of BovHepV.