Research progress in friction stir processing of magnesium alloys and their metal matrix surface composites: Evolution in the 21^(st )century

Rising concerns about climate change drive the demand for lightweight components.Magnesium(Mg)alloys are highly valued for their low weight,making them increasingly important in various industries.Researchers focusing on enhancing the characteristics of Mg alloys and developing their Metal Matrix Composites(MMCs)have gained significant attention worldwide over the past decade,driven by the global shift towards lightweight materials.Friction Stir Processing(FSP)has emerged as a promising technique to enhance the properties of Mg alloys and produce Mg-MMCs.Initially,FSP adapted to refine grain size from the micro to the nano level and accelerated the development of MMCs due to its solid-state nature and the synergistic effects of microstructure refinement and reinforcement,improving strength,hardness,ductility,wear resistance,corrosion resistance,and fatigue strength.However,producing defect-free and sound FSPed Mg and Mg-MMCs requires addressing several variables and their interdependencies,which opens up a broad range of practical applications.Despite existing reviews on individual FSP of Mg,its alloys,and MMCs,an attempt has been made to analyze the latest research on these three aspects collectively to enhance the understanding,application,and effectiveness of FSP for Mg and its derivatives.This review article discusses the literature,classifies the importance of Mg alloys,provides a historical background,and explores developments and potential applications of FSPed Mg alloys.It focuses on novel fabrication methods,reinforcement strategies,machine and tool design parameters,material characterization,and integration with other methods for enhanced properties.The influence of process parameters and the emergence of defects are examined,along with specific applications in mono and hybrid composites and their microstructure evolution.The study identifies promising reinforcement materials and highlights research gaps in FSP for Mg alloys and MMCs production.It concludes with significant recommendations for further exploration,reflecting ongoing advancements in this field.

Using a Modified Soil-Plant-Atmosphere Scheme(MSPAS)to Simulate the Interaction between Land Surface Processes and Atmospheric Boundary Layer in Semi-Arid Regions

This paper uses a Modified Soil-Plant-Atmosphere Scheme (MSPAS) to study the interaction between land surface and atmospheric boundary layer processes. The scheme is composed of two main parts: atmospheric boundary layer processes and land surface processes. Compared with SiB and BATS, which are famous for their detailed parameterizations of physical variables, this simplified model is more convenient and saves much more computation time. Though simple, the feasibility of the model is well proved in this paper. The numerical simulation results from MSPAS show good agreement with reality. The scheme is used to obtain reasonable simulations for diurnal variations of heat balance, potential temperature of boundary layer, and wind field, and spatial distributions of temperature, specific humidity, vertical velocity, turbulence kinetic energy, and turbulence exchange coefficient over desert and oasis. In addition, MSPAS is used to simulate the interaction between desert and oasis at night, and again it obtains reasonable results. This indicates that MSPAS can be used to study the interaction between land surface processes and the atmospheric boundary layer over various underlying surfaces and can be extended for regional climate and numerical weather prediction study.

Surface runoff processes and sustainable utilization of water resources in Manas River Basin, Xinjiang, China

Water is the important resource to guarantee the existence and development of oases in arid areas. To improve the utilization efficiency of water resources in Manas River Basin, this paper investigated the trends and periods of runoff based on the runoff and climate data for the past 50 years. Subsequently, with the socioeconomic and water resources data, we studied a comprehensive evaluation on the water security in this area. The results indicated that the stream flows in the three hydrological stations of Hongshanzui, Kensiwat and Bajiahu have sig- nificantly increased and undergone abrupt changes, with periods of 18 and 20 years. According to assessment, water security in the Manas River Basin was at an unsafe level in 2008. In criterion layer, the ecological security index and the index of supply-demand situation are both at the relatively secure level; the quantity index and so- cioeconomic index of water resources are at the unsafe level and basic security level, respectively. Therefore, in order to achieve sustainable economic and social development within the Manas River Basin, it is vital to take a series of effective measures to improve the status of water security.

Understanding the Interactions between Climate Change,Landscape Evolution,Surface Processes and Tectonics in the Earth System:What Can the Studies of Chinese Deserts Contribute?

Due to large deserts on Earth surface a thorough understanding of climate change, landscape evolution and geomorphological processes having occurred in deserts is crucial for Earth System Science. The landscapes in deserts are, however, diverse and different over the globe with regard to their geomorphological nature, human activities and geological histories. In the last decades a great number of efforts have been put to the investigation of the initial timing of the occurrence of arid climate, e. g. in northwestern China. Silty sediments in the downwind directions have been used to deduce the histories of deserts. In general, there is a lack of knowledge about processes and landscapes in Chinese drylands between the initial Miocene silt sedimentation at desert margins and the late Quaternary multiple occurrences of wetter climate with assumed large lakes in many of the deserts in northern China. The geomorphological concept of three primary triggering factors, i.e., the sediment supply, sediment availability and transport capacity of wind, and additionally the underground geology need to be fully considered for a better understanding of the environmental histories of sand seas which should not be viewed as equivalent for deserts because sand seas cover between 〈 1% and ca. 45% of the desert areas in various continents dependent on a complex interaction between various processes of both exogenous and endogenous origins.

An overview of the spatial patterns of land surface processes over arid and semiarid regions

With data from the project Collaborative Observation of Semi-arid/Arid Regions in North China, collected during July and September 2008, the spatial patterns of land surface processes over arid and semiarid regions have been investigated based on the ordinary Kriging interpolation approach. Generally, for the radiation processes, downward and upward short-wave radiation have a uniformly increasing trend with latitude, but the spatial patterns of long-wave radiation present notable regional differences: both upward and downward long-wave radiation increase with latitude in the west of North China, while in the east they vary inversely with latitude, suggesting surface temperature and clouds respectively have feedbacks to the long-wave radiation in the west and east of North China. The surface net radiation basically has a negative latitudinal trend. Long-wave radiation budget plays an important role in the spatial pattern of surface net radiation, particularly in the east of North China, although short-wave radiation budget largely determines the magnitude of surface net radiation. For the energy processes, latent and sensible heat flux varies conversely with latitude: more available land surface energy is consumed by evaporating soil water at lower latitudes while more is used for heating the atmosphere at higher latitudes. A soil heat flux maximum and minimum are found in Loess Plateau and Qinghai Plateau respectively, and a maximum is seen in the northeast China.

Intermolecular and Surface Interactions in Engineering Processes

Interactions involving chemical reagents,solid particles,gas bubbles,liquid droplets,and solid surfaces in complex fluids play a vital role in many engineering processes,such as froth flotation,emulsion and foam formation,adsorption,and fouling and anti-fouling phenomena.These interactions at the molecular,nano-,and micro scale significantly influence and determine the macroscopic performance and efficiency of related engineering processes.Understanding the intermolecular and surface interactions in engineering processes is of both fundamental and practical importance,which not only improves production technologies,but also provides valuable insights into the development of new materials.In this review,the typical intermolecular and surface interactions involved in various engineering processes,including Derjaguin–Landau–Verwey–Overbeek(DLVO)interactions(i.e.,van der Waals and electrical doublelayer interactions)and non-DLVO interactions,such as steric and hydrophobic interactions,are first introduced.Nanomechanical techniques such as atomic force microscopy and surface forces apparatus for quantifying the interaction forces of molecules and surfaces in complex fluids are briefly introduced.Our recent progress on characterizing the intermolecular and surface interactions in several engineering systems are reviewed,including mineral flotation,petroleum engineering,wastewater treatment,and energy storage materials.The correlation of these fundamental interaction mechanisms with practical applications in resolving engineering challenges and the perspectives of the research field have also been discussed.

Surface Rainfall Processes during the Genesis Period of Tropical Cyclone Durian(2001)

The rainfall processes during the formation of tropical cyclone(TC) Durian(2001) were investigated quantitatively using the three-dimensional(3 D) WRF-based precipitation equation. The rain rate(PS) decreased slightly as the TC approached to formation, and then increased as Durian began to intensify. The rate of moisture-related processes(QWV) in the equation contributed around 80% to PSbefore TC genesis, and made more contribution during and after TC genesis. The rate of hydrometeor-related processes(QCM) contributed about 20% before TC formation, followed by less contribution during and after TC formation. QWVwere dominated by the 3 D moisture flux advection rate(QWVA), while the surface evaporation rate(QWVE) also played an important role. Just before TC genesis, moisture from QWVAand QWVEhelped the local atmosphere moisten(negative QWVL). QCMwere determined by the 3 D hydrometeor advection rates(QCLAand QCIA) and the local change rates of hydrometeors(QCLLand QCIL). During TC formation, QCMlargely decreased and then reactivated as Durian began to intensify, accompanied by the development of TC cloud. Both the height and the strength of the net latent heating center associated with microphysical processes generally lowered before and during TC genesis, resulting mainly from lessening deposition and condensation. The downward shift of the net latent heating center induced a more bottom-heavy upward mass flux profile, suggesting to promote lower-tropospheric convergence in a shallower layer, vorticity amplification and TC spin-up.

A CLOUD-RESOLVING MODELING STUDY OF SURFACE RAINFALL PROCESSES ASSOCIATED WITH LANDFALLING TYPHOON KAEMI(2006)

The detailed surface rainfall processes associated with landfalling typhoon Kaemi（2006） are investigated based on hourly data from a two-dimensional cloud-resolving model simulation. The model is integrated for 6 days with imposed large-scale vertical velocity, zonal wind, horizontal temperature and vapor advection from National Center for Environmental Prediction （NCEP） / Global Data Assimilation System （GDAS） data. The simulation data are validated with observations in terms of surface rain rate. The Root-Mean-Squared （RMS） difference in surface rain rate between the simulation and the gauge observations is 0.660 mm h^-1, which is smaller than the standard deviations of both the simulated rain rate （0.753 mm h^-1） and the observed rain rate （0.833 mm h^-1）. The simulation data are then used to study the physical causes associated with the detailed surface rainfall processes during the landfall. The results show that time averaged and model domain-mean Ps mainly comes from large-scale convergence （QWVF） and local vapor loss （positive QWVT）. Large underestimation （about 15%） of Ps will occur if QWVT and QCM （cloud source/sink） are not considered as contributors to Ps ,QWVF accounts for the variation of P during most of the integration time, while it is not always a contributor to Ps,Sometimes surface rainfall could occur when divergence is dominant with local vapor loss to be a contributor to Ps - Surface rainfall is a result ofmulti-timescale interactions. QWVE possesses the longest time scale and the lowest frequeney the second and QCM of variation with time and may exert impact on P on longer time scales. QWVF possesses longest time scale and lowest frequency and can explain most of the variation of Ps. QWVT possess shorter time scales and higher frequencies, which can explain more detailed variations in Ps. Partitioning analysis shows that stratiform rainfall is dominant from the morning of 26 July till the late night of 27 July. After that, convective rainfall dominates till about 1000 LST 28 July. Before 28 July, the variations of QWVT in rainfall-free regions contribute less to that of the domain-mean QWVT while after that they contribute much, which is consistent to the corresponding variations in their fractional coverage. The variations of QWVF in rainfall regions are the main contributors to that of the domain-mean QWVF, then the main contributors to the surface rain rate before the afternoon of 28 July.

Surface modification of magnesium alloys using thermal and solid-state cold spray processes:Challenges and latest progresses

Potential engineering applications of magnesium(Mg)and Mg-based alloys,as the lightest structural metal,have made them a popular subject of study.However,the inferior corrosion and wear characteristics significantly limit their application range.It is widely recognized that surface treatment is the most commonly utilized technique for remarkably improving a substrate’s surface characteristics.Numerous methods have been introduced for the surface treatment of Mg and Mg-based alloys to improve their corrosion behavior and tribological performance.Among these,thermal spray(TS)technology provides several methods for deposition of various functional metallic,ceramic,cermet,or other coatings tailored to particular conditions.Recent researches have shown the tremendous potential for thermal spray coated Mg alloys for biomedical and industrial applications.In this context,the cold spray(CS)method,as a comparatively new TS coating technique,can generate the coating layer using kinetic energy rather than combined thermal and kinetic energies,like the high-velocity oxy-fuel(HVOF)spray method.Moreover,the CS process,as a revolutionary method,is able to repair and refurbish with a faster turnaround time;it also provides solutions that do not require dealing with the thermal stresses that are part of the other repair processes,such as welding or other TS processes using a high-temperature flame.In this review paper,the recently designed coatings that are specifically applied to Mg alloys(primarily for industrial applications)employing various coating processes are reviewed.Because of the increased utilization of CS technology for both 3D printed(additively manufactured)coatings and repair of structurally critical components,the most recent CS methods for the surface treatment,repair,and refurbishment of Mg alloys as well as their benefits and restrictions are then discussed and reviewed in detail.Lastly,the prospects of this field of study are briefly discussed,along with a summary of the presented work.

Simulation Experiments of Land Surface Physical Processes and Ecological Effect over Different Underlying Surface

Based on the existing Land Surface Physical Process Models(Deardorff, Dickinson, LIU, Noilhan, Seller, ZHAO), a Comprehensive Land Surface Physical Process Model (CLSPPM) is developed by considering the different physical processes of the earth's surface-vegetation-atmosphere system more completely. Compared with SiB and BATS, which are famous for their detailed parameterizations of physical variables, this simplified model is more convenient and saves much more computation time. Though simple, the feas...

A Modeling Study of Surface Rainfall Processes Associated with a Torrential Rainfall Event over Hubei,China,during July 2007

The surface rainfall processes associated with the torrential rainfall event over Hubei,China,during July 2007 were investigated using a two-dimensional cloud-resolving model.The model integrated the large-scale vertical velocity and zonal wind data from National Centers for Environmental Prediction（NCEP）/Global Data Assimilation System（GDAS） for 5 days.The time and model domain mean surface rain rate was used to identify the onset,mature,and decay periods of rainfall.During the onset period,the descending motion data imposed in the lower troposphere led to a large contribution of stratiform rainfall to the model domain mean surface rainfall.The local atmospheric drying and transport of rain from convective regions mainly contributes to the stratiform rainfall.During the mature periods,the ascending motion data integrated into the model was so strong that water vapor convergence was the dominant process for both convective and stratiform rainfall.Both convective and stratiform rainfalls made important contributions to the model domain mean surface rainfall.During the decay period,descending motion data input into the model prevailed,making stratiform rainfall dominant.Stratiform rainfall was mainly caused by the water vapor convergence over raining stratiform regions.

Surface metal-matrix composites based on AZ91 magnesium alloy via friction stir processing:A review

This monograph presents an overview of friction stir processing(FSP)of surface metal-matrix composites(MMCs)using the AZ91 magnesium alloy.The reported results in relation to various reinforcing particles,including silicon carbide(SiC),alumina(Al_(2)O_(3)),quartz(SiO_(2)),boron carbide(B_(4)C),titanium carbide(TiC),carbon fiber,hydroxyapatite(HA),in-situ formed phases,and hybrid reinforcements are summarized.AZ91 composite fabricating methods based on FSP are explained,including groove filling(grooving),drilled hole filling,sandwich method,stir casting followed by FSP,and formation of in-situ particles.The effects of introducing second-phase particles and FSP process parameters(e.g.,tool rotation rate,traverse speed,and the number of passes)on the microstructural modification,grain refinement,homogeneity in the distribution of particles,inhibition of grain growth,mechanical properties,strength–ductility trade-off,wear/tribological behavior,and corrosion resistance are discussed.Finally,useful suggestions for future work are proposed,including focusing on the superplasticity and superplastic forming,metal additive manufacturing processes based on friction stir engineering(such as additive friction stir deposition),direct FSP,stationary shoulder FSP,correlation of the dynamic recrystallization(DRX)grain size with the Zener–Hollomon parameter similar to hot deformation studies,process parameters(such as the particle volume fraction and external cooling),and common reinforcing phases such as zirconia(ZrO_(2))and carbon nanotubes(CNTs).

Joint Operation of Atomic Force Microscope and Advanced Laser Confocal Microscope for Observing Surface Processes in a Protein Crystal

We demonstrated the insitu observation of a moving atomic force microscope (AFM) cantilever using a laser confocal microscope combined with a differential interference microscope (LCM-DIM). The AFM cantilever scanned or indented the {110} surface of a hen egg-white lysozyme crystal in a supersaturated solution. Using a soft cantilever, we could observe the step growth with high time resolution by LCM-DIM and perform quantitative measurements of the step height by AFM simultaneously. In addition, a hard cantilever was used with LCM-DIM to observe the dynamics of crystal surface scratching and indentation. In the supersaturated solution, the small steps generated from the scratched line aggregated to macro steps, and subsequently flattened the surface.

EFFECT OF INITIAL PERTURBATION OF LAND SURFACE PROCESSES ON TROPICAL CYCLONE FORECAST

Many studies have explored the importance and influence of planetary boundary layer processes on tropical cyclones (TCs). However, few studies have focused on the influence of land surface processes on the activity of TCs. To test the effect of initial perturbations of land surface processes on TCs, a land surface process perturbation module is built in a global ensemble prediction system. Ensemble experiments for the TCs that occurred from 12 UTC 22 August to 18 UTC 24 November, 2006 show that consideration of the uncertainties within the land surface process could increase the predictability of the global ensemble prediction system. Detailed analysis on TC Xangsane (2006) indicates that the perturbation of land surface processes may increase the variation of sensible heat flux and latent heat flux. Meanwhile, the effect from land surface perturbation can be transferred to the upper atmosphere, which leads to better TC forecasts.

Key regions where land surface processes shape the East Asian climate

Land-atmosphere interaction,as one of the key processes affecting the atmosphere and climate over East Asia,has drawn increasing attention during the past few decades.However,the current level of understanding regarding the mechanisms through which land surface processes impact the East Asian climate needs to be improved.Based on existing studies,six key regions where land surface processes affect the East Asian climate are proposed in this study,which can provide a valuable reference for future research into land-atmosphere interaction in East Asia.

Embedded System Development for Detection of Railway Track Surface Deformation Using Contour Feature Algorithm

Derailment of trains is not unusual all around the world,especially in developing countries,due to unidentified track or rolling stock faults that cause massive casualties each year.For this purpose,a proper condition monitoring system is essential to avoid accidents and heavy losses.Generally,the detection and classification of railway track surface faults in real-time requires massive computational processing and memory resources and is prone to a noisy environment.Therefore,in this paper,we present the development of a novel embedded system prototype for condition monitoring of railway track.The proposed prototype system works in real-time by acquiring railway track surface images and performing two tasks a)detect deformation(i.e.,faults)like squats,shelling,and spalling using the contour feature algorithm and b)the vibration signature on that faulty spot by synchronizing acceleration and image data.A new illumination scheme is also proposed to avoid the sunlight reflection that badly affects the image acquisition process.The contour detection algorithm is applied here to detect the uneven shapes and discontinuities in the geometrical structure of the railway track surface,which ultimately detects unhealthy regions.It works by converting Red,Green,and Blue(RGB)images into binary images,which distinguishes the unhealthy regions by making them white color while the healthy regions in black color.We have used the multiprocessing technique to overcome the massive processing and memory issues.This embedded system is developed on Raspberry Pi by interfacing a vision camera,an accelerometer,a proximity sensor,and a Global Positioning System(GPS)sensors(i.e.,multi-sensors).The developed embedded system prototype is tested in real-time onsite by installing it on a Railway Inspection Trolley(RIT),which runs at an average speed of 15 km/h.The functional verification of the proposed system is done successfully by detecting and recording the various railway track surface faults.An unhealthy frame’s onsite detection processing time was recorded at approximately 25.6ms.The proposed system can synchronize the acceleration data on specific railway track deformation.The proposed novel embedded system may be beneficial for detecting faults to overcome the conventional manual railway track condition monitoring,which is still being practiced in various developing or underdeveloped countries.

Impressive strides in amelioration of corrosion behavior of Mg-based alloys through the PEO process combined with surface laser process: A review

The unsatisfactory corrosion properties of Mg-based alloys pose a significant obstacle to their widespread application. Plasma electrolytic oxidation(PEO) is a prevalent and effective coating method that produces a ceramic-like oxide coating on the surface of Mg-based alloys,enhancing their resistance to corrosion. Research has demonstrated that PEO treatment can substantially improve the corrosion performance of alloys based on magnesium in the short term. In an effort to enhance the corrosion resistance of PEO coatings over an extended period of time, researchers have turned their attention to the use of laser processes as both pre-and post-treatments in conjunction with the PEO process. Various laser processes, such as laser shock melting(LSM), laser shock adhesion(LSA), laser shock texturing(LST), and laser shock peening(LSP), have been investigated for their potential to improve PEO coatings on Mg substrates and their alloys. These laser melting processes can homogenize and alter the microstructure of Mg-based alloys while leaving the bulk material unchanged, thereby modifying the substrate surface. However, the porous and rough structure of PEO coatings, with their open and interconnected pore structure, can reduce their long-term corrosion resistance. As such, various laser processes are well-suited for surface modification of these coatings. This study will first examine the PEO process and the various types of laser processes used in this process, before investigating the corrosion behavior of PEO coatings in conjunction with laser pre-and post-treatment processes.

Optimization of Solid-state Fermentation Conditions of Sophora japonica cv.jinhuai by Response Surface Methodology

[Objectives]To optimize the solid-state fermentation process of Flos Sophorae Immaturus by Penicillium with Sophora japonica cv.jinhuai as raw material.[Methods]The fermentation conditions were optimized by single factor experiment and response surface methodology with quercetin content as the dependent variable.[Results]According to the established model,the optimal fermentation process of Flos Sophorae Immaturus was obtained as follows:temperature 29.97℃,time 6.88 d,rotation speed 180.86 rpm,inoculation amount 3.93 mL,and the expected content of quercetin was 34.8053 mg/g.Based on this,the fermentation parameters were adjusted,and the actual content was 33.67 mg/g,which was close to the predicted value.[Conclusions]The optimization of fermentation process of Flos Sophorae Immaturus by response surface methodology provides a reference for the development and utilization of this medicinal material.

超疏水表面加工技术及耐磨性能研究进展

当前制备的超疏水表面耐磨性能普遍较差,因而其在各领域的应用受到限制。研究表明微纳结构和低表面能是实现功能表面超疏水性能的关键因素,因此,首先基于超疏水表面作用机制,对超疏水表面织构进行了归纳,旨在通过优化表面织构来解决微纳结构易磨损难题;然后对超疏水表面加工技术进行了梳理总结,从成本和效率两个方面分析了降低表面能的措施,为拓展超疏水表面加工体系提供思路;进而详细总结了超疏水表面耐磨性的分析手段,并阐述了提高超疏水表面耐磨性的方法;最后,展望了耐磨性超疏水表面的未来发展前景,以期推动超疏水表面在工程中的大规模应用。

华南晚中生代大陆变形、深部过程及动力学

受控古太平洋板块俯冲及后撤作用,华南晚中生代经历了强烈大陆再造,并伴随幕式岩浆活动,是研究活动大陆边缘构造-岩浆作用、壳幔过程和板块俯冲动力学的天然实验室。本文系统综述了近年来发表的构造变形、岩浆作用和深部结构等多学科成果,以构造解析为主线,深-浅结合,在华南识别出与古太平洋板块俯冲相关的中晚侏罗世弧背缩短和白垩纪弧后伸展系统,厘定了二者的时空格架和叠加改造关系。弧背缩短系统以扬子中部的隔档-隔槽式褶皱、深部多层滑脱和双重逆冲推覆构造为特征,具SE向NW的逆冲扩展变形规律,与古太平洋板块的前进式俯冲有关。白垩纪主体以大陆伸展为主,经历了伸展和挤压变形交替,并伴随着岩浆活动的爆发、迁移和停止,其可能与板片俯冲动力学变化有关。在此基础上,我们分析了白垩纪岩石圈长距离伸展的深部过程及浅表响应,提出了岩石圈随深度变化的分层差异伸展模式。自下而上,从岩石圈地幔到上地壳,应变近一致地表现为(W)NW-(E)SE伸展,反映了垂向变形一致性。可能的垂向应力传播过程:板片后撤诱发长距离地幔流,其在岩石圈底部形成剪切牵引应力,促进下岩石圈地幔被动拉伸;上岩石圈地幔局部发育强应变剪切带,作为应力传播构造,其可有效加强壳-幔间剪切,促进下地壳韧性拉伸,将下地壳和岩石圈地幔的变形关联。我们认为岩石圈伸展、板片后撤和地幔流形成了三位一体的动力学耦合系统,将华南岩石圈长距离伸展的驱动力归结为:(1)古太平洋俯冲带海沟后撤和板片回卷诱发的远程效应,和(2)地幔流在岩石圈底部施加的剪切牵引应力。