Microstructure and texture evolution in titanium subjected to friction roll surface processing and subsequent annealing

Commercial purity and high purity titanium sheets were initially strained by a new technique, named as friction roll surface processing （FRSP）. Severe strain was imposed into the surface layer and strain gradient was formed through the thickness of the sheet. The microstructure and texture in as-strained state were investigated by optical microscopy and X-ray diffraction technique On the surface of the sheets, ultra-fine grains were found to have a sharp texture with a preferred orientation strongly related to the FRSP direction. The evolution of microstructure and crystallographic texture of FRSPed samples during recrystallization were also studied by electron back-scattered diffraction （EBSD） technique after being annealed at selected temperatures and time. The results indicated that the preferred orientations resulting from FRSP and annealing in the surface layer were formed during rolling and its recrystallization textures were reduced by FRSP. In addition, the texture evolved stably without change in main components during the annealing.

Progresses and future directions on yardangs

Background,aim,and scope Yardang is a kind of typical wind-eroded landform in arid zones both on Earth and other planets.Their geomorphic process records the surface changes and climate,which may play a vital role in exploring the coupled landform-atmosphere system in arid zones.Recently,significant progresses have been made in this research field,and a review is still absent,which is the aim of the paper.Materials and methods Previous studies on the distribution,composition,morphology,and climatic driving force of yardang landform were reviewed.Results Earth yardang’s three evolutionary models were generalized:morphology evolution model,altitude evolution model and climate driven evolution model.Extraterrestrial yardang and its evolution are also summarized:the morphology is dominated by long ridges on Venus and Titan,and three yardang evolution hypotheses and an indirect dating method based on stratigraphic contact have been studied on Mars.Discussion In this study,firstly,the definition and morphology of yardang were described to define its characteristics.Secondly,we argue that yardang evolution has two dimensions:short-term variation and longterm variation.In the short-term variation,the morphological evolution of yardang on earth can be divided into four stages:embryonic stage,juvenile stage,mature stage,and demise stage.In the long-term variation,the evolution of yardang on earth is climate-driven,i.e.,it is controlled by atmospheric circulation changes during glacial-interglacial periods.Thirdly,yardang research on extraterrestrial bodies was also summarized:yardang has been found on Mars,Venus,and Titan,and the research focus by far are on geomorphology only.Conclusions(1)Yardang landform is an erosion landform with alternating ridges and troughs,with main form of whale back shape and fluctuations in the range of aspect ratios;(2)the short-term variation of yardang is manifested in its morphological evolution and height change,while the long-term variation is climate-driven;(3)based on Earth yardang,extraterrestrial yardang research has been carried out on Mars,Venus,and Titan.Recommendations and perspectives We then proposed that:(1)yardang formation ages,due to the erosion characteristics,are difficult to constraint;(2)the wind erosion capacity in the yardang areas might have been severely underestimated,making it essential to re-evaluate the previous paleoclimate reconstruction in the closed basins with limited chronological data;(3)yardang evolution is driven by climate change,but the coupling relationship between the yardang geomorphy and the air circulation is still unclear.Finally,future research directions:(1)more chronological data are needed,as well as the wind erosion capacity for yardang initiation and development;(2)the co-evolution of mid-low latitude landforms involved in yardang long-term variation and its relationship with global atmospheric circulation.

Improved efficiency and stability of inverse perovskite solar cells via passivation cleaning

Amidst the global energy and environmental crisis,the quest for efficient solar energy utilization intensifies.Perovskite solar cells,with efficiencies over 26%and cost-effective production,are at the forefront of research.Yet,their stability remains a barrier to industrial application.This study introduces innovative strategies to enhance the stability of inverted perovskite solar cells.By bulk and surface passivation,defect density is reduced,followed by a"passivation cleaning"using Apacl amino acid salt and isopropyl alcohol to refine film surface quality.Employing X-ray diffraction(XRD),scanning electron microscope(SEM),and atomic force microscopy(AFM),we confirmed that this process effectively neutralizes surface defects and curbs non-radiative recombination,achieving 22.6%efficiency for perovskite solar cells with the composition Cs_(0.15)FA_(0.85)PbI_(3).Crucially,the stability of treated cells in long-term tests has been markedly enhanced,laying groundwork for industrial viability.

Ship hull plate processing surface fairing with constraints based on B-spline

The problem of ship hull plate processing surface fairing with constraints based on B-spline is solved in this paper. The algorithm for B-spline curve fairing with constraints is one of the most common methods in plane curve fairing. The algorithm can be applied to global and local curve fairing. It can constrain the perturbation range of the control points and the shape variation of the curve, and get a better fairing result in plane curves. In this paper, a new fairing algorithm with constraints for curves and surfaces in space is presented. Then this method is applied to the experiments of ship hull plate processing surface. Finally numerical results are obtained to show the efficiency of this method.

Nanocrystallization of Cementite in 0.4C-1Cr Steel During High-Power Surface Processing

The microstructures of the nanocrystalline surface layer of a quenched and high temperature tempered 0. 4C- 1Cr steel induced by high-power surface processing （HPSP） technique were characterized by scan- ning eleetron microscopy and transmission electron microscopy. The results indicate that a nanocrystalline layer was fabricated on the surface of the steel 19 using HPSP treatment. The mean grain size in the surface layer is about 11 nm. The nanocrystallization of cementite is prior to that of the matrix phase, ferrite.

ACQUIREMENT AND COMPUTER PROCESSING OF 3-D SURFACE SHAPE DATA

The laser scanning and CCD image-transmitting measurement method and principle on acquiring 3-D curved surface shape data are discussed. Computer processing technique of 3-D curved surface shape(be called“ 3 - D surface shape”for short) data is analysed. This technique in- cludes these concrete methods and principles such as data smoothing, fitting, reconstructing ,elimi- nating and so on. The example and result about computer processing of 3- D surface shape data are given .

The Characteristics and Controlling Factors of Water and Heat Exchanges over the Alpine Wetland in the East of the Qinghai–Tibet Plateau

Alpine wetland is one of the typical underlying surfaces on the Qinghai–Tibet Plateau.It plays a crucial role in runoff regulation.Investigations on the mechanisms of water and heat exchanges are necessary to understand the land surface processes over the alpine wetland.This study explores the characteristics of hydro-meteorological factors with in situ observations and uses the Community Land Model 5 to identify the main factors controlling water and heat exchanges.Latent heat flux and thermal roughness length were found to be greater in the warm season(June–August)than in the cold season(December–February),with a frozen depth of 20–40 cm over the alpine wetland.The transfers of heat fluxes were mainly controlled by longwave radiation and air temperature and affected by root distribution.Air pressure and stomatal conductance were also important to latent heat flux,and soil solid water content was important to sensible heat flux.Soil temperature was dominated by longwave radiation and air temperature,with crucial surface parameters of initial soil liquid water content and total water content.The atmospheric control factors transitioned to precipitation and air temperature for soil moisture,especially at the shallow layer(5 cm).Meanwhile,the more influential surface parameters were root distribution and stomatal conductance in the warm season and initial soil liquid water content and total water content in the cold season.This work contributes to the research on the land surface processes over the alpine wetland and is helpful to wetland protection.

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.

A Modeling Study of Land Surface Process Impacts on Inland Behavior of Typhoon Rananim(2004)

On 12 August 2004, Typhoon Rananim （0414） moved inland over China and stagnated over the Poyang Lake area, resulting in torrential rainfall and severe geologic hazards. The Advanced Weather Research and Forecasting （ARW-WRF） model and its different land surface models （LSMs） were employed to study the impacts of land surface process on the inland behavior of Typhoon Rananim. Results show that simulations, coupled with LSMs or not, have no significant differences in predicting typhoon track, intensity, and largescale circulation. However, the simulations of mesoscale structure, rainfall rate, and rainfall distribution of typhoon are more reasonable with LSMs than without LSMs. Although differences are slight among LSMs, NOAH is better than the others. Based on outputs using the NOAH scheme, the interaction between land surtace and typhoon was explored in this study. Notably, typhoon rainfall and cloud cover can cool land surface, but rainfall expands the underlying saturated wetland area, which exacerbates the asymmetric distribution of surface heat fluxes. Accordingly, an energy frontal zone may form in the lower troposphere that enhances ascending motion and local convection, resulting in heavier rainfall. Moreover, the expanded underlying saturated wetlands provide plentiful moisture and unstable energy for the maintenance of Typhoon Rananim and increased rainfall in return.

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.

Inter-Comparison of 10-year Precipitation Simulated by Several RCMs for Asia

In phase Ⅱ of the Regional Climate Model Inter-comparison Project （RMIP） for Asia, the regional climate has been simulated for July 1988 through December 1998 by five regional climate models and one global variable resolution model. Comparison of the 10-year simulated precipitation with the observations was carried out. The results show that most models have the capacity to reproduce the basic spatial pattern of precipitation for Asia, and the main rainbelt can be reproduced by most models, but there are distinctions in the location and the intensity. Most models overestimate the precipitation over most continental regions. Interannual variability of the precipitation can also be basically simulated, while differences exist between various models and the observations. The biases in the stream field are important reasons behind the simulation errors of the Regional Climate Models （RCMs）. The cumulus scheme and land surface process have large influences on the precipitation simulation. Generally, the Grell cumulus scheme produces more precipitation than the Kuo scheme.

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.

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.

Land Surface Hydrology Parameterization over Heterogeneous Surface for the Study of Regional Mean Runoff Ratio with Its Simulations

An analytical expression for subgrid–scale inhomogeneous runoff ratios generated by heterogeneous soil moisture content and climatic precipitation forcing is presented based on physical mechanisms for land surface hydrology and theory of statistical probability distribution. Thereby the commonly used mosaic parameterization of subgrid runoff ratio was integrated into a statistical–dynamic scheme with the bulk heterogeneity of a grid area included. Furthermore, a series of numerical experiments evaluating the reliability of the parameterization were conducted using the data generated by the emulated simulation method. All the experimental results demonstrate that the proposed scheme is feasible and practical.

Influence of Ultrasonic Surface Rolling Process and Shot Peening on Fretting Fatigue Performance of Ti-6Al-4V

At present,there are many studies on the residual stress field and plastic strain field introduced by surface strengthening,which can well hinder the initiation of early fatigue cracks and delay the propagation of fatigue cracks.However,there are few studies on the effects of these key factors on fretting wear.In the paper,shot-peening(SP)and ultrasonic surface rolling process(USRP)were performed on Ti-6Al-4V plate specimens.The surface hardness and residual stresses of the material were tested by vickers indenter and X-ray diffraction residual stress analyzer.Microhardness were measured by HXD-1000MC/CD micro Vickers hardness tester.The effects of different surface strengthening on its fretting fatigue properties were verified by fretting fatigue experiments.The fretting fatigue fracture surface and wear morphology of the specimens were studied and analyzed by means of microscopic observation,and the mechanism of improving fretting fatigue life by surface strengthening process was further explained.After USRP treatment,the surface roughness of Ti-6Al-4V is significantly improved.In addition,the microhardness of the specimen after SP reaches the maximum at 80μm from the surface,which is about 123%higher than that of the AsR specimen.After USRP,it reaches the maximum at 150μm from the surface,which is about 128%higher than that of AsR specimen.It is also found that the residual compressive stress of the specimens treated by USRP and SP increases first and then decreases with the depth direction,and the residual stress reaches the maximum on the sub surface.The USRP specimen reaches the maximum value at 0.18 mm,about−550 MPa,while the SP specimen reaches the maximum value at 0.1 mm,about−380 MPa.The fretting fatigue life of Ti-6Al-4V effectively improved after USRP and SP.The surface integrity of specimens after USRP is the best,which has deeper residual compressive stress layer and more refined grain.In this paper,a fretting wear device is designed to carry out fretting fatigue experiments on specimens with different surface strengthening.

Evaluating the Capabilities of Soil Enthalpy, Soil Moisture and Soil Temperature in Predicting Seasonal Precipitation

Soil enthalpy （H） contains the combined effects of both soil moisture （w） and soil temperature （T） in the land surface hydrothermal process. In this study, the sensitivities of H to w and T are investigated using the multi-linear regression method. Results indicate that T generally makes positive contributions to H, while w exhibits different （positive or negative） impacts due to soil ice effects. For example, w negatively contributes to H if soil contains more ice; however, after soil ice melts, w exerts positive contributions. In particular, due to lower w interannual variabilities in the deep soil layer （i.e., the fifth layer）, H is more sensitive to T than to w. Moreover, to compare the potential capabilities of H, w and T in precipitation （P） prediction, the Huanghe-Huaihe Basin （HHB） and Southeast China （SEC）, with similar sensitivities of H to w and T, are selected. Analyses show that, despite similar spatial distributions of H-P and T-P correlation coefficients, the former values are always higher than the latter ones. Furthermore, H provides the most effective signals for P prediction over HHB and SEC, i.e., a significant leading correlation between May H and early summer （June） P. In summary, H, which integrates the effects of T and w as an independent variable, has greater capabilities in monitoring land surface heating and improving seasonal P prediction relative to individual land surface factors （e.g., T and w）.

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.

The Interannual Variability and Predictability in a Global Climate Model

The interannual variabilities of the climatological simulation (V1) and the AMIP (Atmospheric Model Intercomparison Project) simulation (V2) by the IAP 9-Level Atmospheric General Circulation Model are studied and discussed in this paper. Based on the analysis of ratio of variability (R) of above two simulations the predictability of the model on the interannual climate variation are studied as well. Results show that V2 is bigger than V1 generally and V2 is more comparable to the real variability of the atmosphere, the major difference of V1 and V2 is in the tropics, for temperature and geopotential height the predictability is higher in the tropics while in the extra-tropics there is almost no predictability and the predictability is bigger in higher level than in lower level. The predictability for precipitation is generally low in the globe, and generally the predictability is high in the tropical eastern Pacific for the lower level. This study suggests that the possible way of increasing the model predictability is the improvement of land surface process modelling and the inclusion of the interannual variations of the land surface conditions (snow cover, albedo, soil moisture, etc.) as the forcing factor for climate modelling and prediction.

The Sensitivity of Ground Surface Temperature Prediction to Soil Thermal Properties Using the Simple Biosphere Model(SiB2)

Using the Simple Biosphere Model （SiB2）, soil thermal properties （STP） were examined in a Tibetan prairie during the monsoon period to investigate ground surface temperature prediction. We improved the SiB2 model by incorporating a revised force-restore method （FRM） to take the vertical heterogeneity of soil thermal diffusivity （k） into account. The results indicate that （1） the revised FRM alleviates daytime overestimation and nighttime underestimation in modeled ground surface temperature （Tg）, and （2） its role in little rainfall events is significant because the vertical gradient of k increases with increasing surface evaporation. Since the original formula of thermal conductivity （A） in the SiB2 greatly underestimates soil thermal conductivity, we compared five Mgorithms of A involving soil moisture to investigate the cause of overestimation during the day and underestimation at night on the basis of the revised FRM. The results show that （1） the five algorithms significantly improve Tg prediction, especially in daytime, and （2） taking one of these five algorithms as an example, the simulated Tg values in the daytime are closer to the field measurements than those in the nighttime. The differences between modeled Tg and field measurements are mostly within the margin of error of -4-2 K during 3 August to 4 September 1998.

Uranium comminution age responds to erosion rate semiquantitatively

Here we present(^(234)U/^(238)U)data from river sediments collected on the Tibetan Plateau.The(^(234)U/^(238)U)ratios of a specific grain size fraction show good correlation with erosion rates,which were determined by in-situ–produced cosmogenic nuclides.This correlation has previously been observed in a wide range of geomorphic settings,suggesting that(^(234)U/^(238)U)ratios of fluvial sediments have great potential to quantify erosion rates.