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| 1 | CHARACTERISTICS OF ELECTROMECHANICAL COUPLING SELF-SYNCHRONIZATION OF A MULTI-MOTOR VIBRATION TRANSMISSION SYSTEM显示文摘Multi-motor vibratory transmission systems have been wide used in large vibratory machines, and four-motor linear vibratory machine is one typical equipment of them. Under non-forcible synchronization condition zero-phase synchronization of the machine is non-stationary and it-phase synchronization is stable. Under half-forcible synchronization condition in which only one motor is controlled being synchronous to another, only lag synchronization near zero-phase synchronization can be realized. Both of the characteristics have never been revealed with classical theory quantitatively. The problem is solved by means of establishing an electromechanical coupling mathematical model of the system and numerical analysis of the starting processes. | Xiong Wanli,Duan Zhishan (School of Mechanical and Electrical Engineering, Xi’ an University of Architecture and Technology) Wen Bangchun (Northeastern University) | 2001 | Chinese Journal of Mechanical Engineering2001，14，3： | 8 |
| 2 | Effects of gravel mulch on aeolian transport:a field wind tunnel simulation显示文摘The shape,size and coverage of gravels have significant impacts on aeolian sand transport.This study provided an understanding of aeolian transport over the gravel mulching surfaces at different wind velocities by means of a mobile wind tunnel simulation.The tested gravel coverage increased from 5% to 80%,with a progressive increment of 5%.The gravels used in the experiments have three sizes in diameter.Wind velocities were measured using 10 sand-proof pitot-static probes,and mean velocity fields were obtained and discussed.The results showed that mean velocity fields obtained over different gravel mulches were similar.The analysis of wind speed patterns revealed an inherent link between gravel mulches and mean airflow characteristics on the gravel surfaces.The optimal gravel coverage is considered to be the critical level above or below which aeolian transport characteristics differ strongly.According to the present study,the optimal gravel coverage was found to be around 30% or 40%.Threshold velocity linearly increased with gravel coverage.Sand transport rate first increased with height above the wind tunnel floor(Hf),reaching a peak at some midpoint,and then decreased. | KeCun ZHANG WeiMin ZHANG LiHai TAN ZhiShan AN Hao ZHANG | 2015 | Journal of Arid Land2015，7，3： | 5 |
| 3 | Quantitative analysis on the dynamic characteristics of megadunes around the Crescent Moon Spring, China显示文摘The Crescent Moon Spring is a precious natural heritage. However, the dynamic characteristics of megadunes around the Crescent Moon Spring are not well known. This paper quantitatively studied the character- istics and changes of megadunes around the Crescent Moon Spring by interpreting aerial photographs taken in 1985 and 2004 and analysing the dune crestlines and the wind data collected from 2011 to 2012. Results revealed that pyramid dunes were formed by a complex wind regime. The Crescent Moon Spring was not buried by shifting sands because of the stable wind regime and relative stability of pyramid dunes. The crestlines of the dunes around the spring moved northward between 1985 and 2004. The south-facing slip faces were also exposed to wind ero- sion, whereas the other faces were under deposition, thus indicating that the southerly wind was relatively en- hanced. Limiting the scale of tall windbreaks and architectures in the Dunhuang oasis at the north of the spring was necessary to maintain the dynamic equilibrium of the wind regime and sand transport. | YingJun PANG JianJun QU KeCun ZHANG ZhiShan AN QingHe NIU | 2014 | Journal of Arid Land2014，6，3： | 4 |
| 4 | Morphological variation of star dune and implications for dune management: a case study at the Crescent Moon Spring scenic spot of Dunhuang, China显示文摘Aerial photographs and 3-D laser scans of a 90-m high star dune at the Crescent Moon Spring scenic spot in Dunhuang,China,are used to investigate the changes in dune morphology on timescales from months to decades.The result revealed that relative-equilibrium airflow strength in three wind directions of northeast,west and south was an important condition for the stability of star dunes with limited migration.Transverse and longitudinal airflows exerted a crucial impact on variation processes of star dune morphology.Controlled by transverse airflows,the easterly winds,the east side was dominated by wind erosion;and strong deposition occurred on the south-south-east arm with a maximum deposition rate of 0.44 m/a in the 46-a monitoring period,causing the east side becoming steep and high.Controlled by longitudinal airflows,the westerly winds,the west-north-west side was mainly eroded and the north arm migrated from west to east with a rate of 0.30 m/a,causing the dune slope becoming gentle and elongate.The local air circulation(southerly winds)exerted a significant impact on the development process of the star dune.Due to the influence of human activities,the south side present surface processes from a concave profile to a convex profile in 46 a,which is a potential threat to the Crescent Moon Spring.The results indicate that rehabilitating the airflow field at most is a crucial strategy to the protection of Crescent Moon Spring from burial.Opening up the passage of easterly,westerly and southerly winds through intermediately cutting the protection forest,demolishing the enclosed wall and changing the pavilion into a porous pattern have been suggested to protect the Crescent Moon Spring from burial. | ZHANG Weimin TAN Lihai AN Zhishan ZHANG Kecun GAO Yang NIU Qinghe | 2019 | Journal of Arid Land2019，11，3： | 1 |
| 5 | Aeolian processes on sandy desertification of an alpine meadow: A wind tunnel experiment显示文摘In recent years,the desertification of alpine meadows has become a serious ecological problem and has gradually become a threat to regional economic activities in Maqu County.To reveal the mechanism for sandy desertification of alpine meadows,we conducted wind tunnel experiments on aeolian processes over sandy alpine meadows.Results show that the sandflux profile of mix-sized sediment decays exponentially with increasing height.However,the profile pattern of a group of uniform-sized particles depends on the experimental wind speeds.The profile pattern of all the groups studied can be expressed by exponential decay functions when the wind speed is less than or equal to 16 m/s.while that for all the groups studied can be expressed by a Gaussian distribution function when the wind speed is above 16 m/s.The average saltation heights of mixed sands at wind speeds of 12 m/s,16 m/s,20 m/s,and 24 m/s were 2.74,4.19,5.28,and 6.12 cm,respectively.The mean grain size basically first decreases and then increases with increasing height under different wind speeds.The sorting improves with increasing wind speed,while the kurtosis and skewness show relationships with only the characteristics of the parent soil. | ZhiShan An KeCun Zhang LiHai Tan BaiCheng Niu YanPing Yu | 2020 | Research in Cold and Arid Regions2020，12，1： | 0 |
| 6 | Progress on research and mitigation of wind-blown sand risk in Dunhuang Singing Sand Mountain and Crescent Spring Scenic area,China显示文摘The Singing Sand Mountain and Crescent Spring Scenic Spot in Dunhuang,Northwest China is a world-renowned desert attraction that is also an integral component of the Dunhuang UNESCO Global Geopark.This scenic area underwent a 30-year transformation,i.e.,from a severe sand risk with spring water threatened by sand burial due to dune deformation,to restoration of the original sand flow field and mitigation of the sand burial problem.The current paper summarizes the research on the intensive monitoring of the dynamic change of star dunes near the spring,observation of wind and sand flow movement,and then restoring the harmonic vibration of the sand particles(singing sand)that were previously silenced.The existing and prospective impacts of anthropogenic and natural forces on the deformation of the sand dunes are investigated by integrated methods,guiding the implementation of mitigating measures with significant ameliorative effects.Contrast to common sand control practices that aim to reduce wind speed and stop blown sands,our research highlights the importance of maintaining the natural wind flow field in stabilizing surrounding dunes.These mitigation measures consist of removing excessive vegetation and newly constructed buildings to recover the original wind flow field and sand transport activity.Such research and mitigation efforts ensure the scientific protection and restoration of the special desert landform,and contribute to the mutual enhancement of the conservation and exploitation of this desert scenic spot and similar sites. | BenLi Liu KeCun Zhang JianJun Qu HaiJiang Li QingHe Niu ZhiShan An YingJun Pang LiHai Tan GenSheng Yang | 2023 | Research in Cold and Arid Regions2023，15，3： | 0 |
| 7 | Wind dynamic environment and wind-sand erosion and deposition processes on different surfaces along the Dunhuang–Golmud railway,China显示文摘The Dunhuang–Golmud railway passes through different deserts in arid areas,especially drifting-sand desert and sandy-gravel Gobi.The near-surface wind environment and wind-sand transport process vary due to different external factors,such as topography,vegetation,and regional climate,resulting in evident spatial differences in surface erosion and deposition.Consequently,the measures for preventing wind-sand hazards will differ.However,the mechanism and control theory of sand damage remain poorly understood.In this study,we used meteorological observation,three-dimensional(3D)laser scanning,and grain-size analysis to compare and evaluate the spatial distribution of wind conditions,sand erosion and deposition patterns,and grain composition in the drifting-sand desert and sandy-gravel Gobi along the Dunhuang–Golmud railway in China.Results show that the annual mean wind speed,the frequency of sand-driving wind,and the drift potential of sandy-gravel Gobi are higher than those of drifting-sand desert,indicating a greater wind strength in the sandy-gravel Gobi,which exhibits spatial heterogeneity in wind conditions.The major sediment components in sandy-gravel Gobi are very fine sand,fine sand,and medium sand,and that in drifting-sand desert are very fine sand and fine sand.We found that the sediment in the sandy-gravel Gobi is coarser than that in the drifting-sand desert based on mean grain size and sediment component.The spatial distributions of sand erosion and deposition in the sandy-gravel Gobi and drifting-sand desert are consistent,with sand deposition mainly on the west side of the railway and sand erosion on the east side of the railway.The area of sand deposition in the drifting-sand desert accounts for 75.83%of the total area,with a mean deposition thickness of 0.032 m;while the area of sand deposition in the sandy-gravel Gobi accounts for 65.31%of the total area,with a mean deposition thickness of 0.028 m,indicating greater deposition amounts in the drifting-sand desert due to the presence of more fine sediment components.However,the sand deposition is more concentrated with a greater thickness on the embankment and track in the sandy-gravel Gobi and is dispersed with a uniform thickness in the drifting-sand desert.The sand deposition on the track of the sandy-gravel Gobi mainly comes from the east side of the railway.The results of this study are helpful in developing the preventive measures and determining appropriate selection and layout measures for sand control. | ZHANG Hongxue ZHANG Kecun AN Zhishan YU Yanping | 2023 | Journal of Arid Land2023，15，4： | 0 |
| 8 | Genesis of the Nuri Cu-W-Mo Deposit,Tibet,China:Constraints from in situ Trace Elements and Sr Isotopic Analysis of Scheelite显示文摘The Nuri deposit is the only Cu-W-Mo polymetallic deposit with large-scale WO3 resources in the eastern section of the Gangdese metallogenic belt,Tibet,China.However,the genetic type of this deposit has been controversial since its discovery.Based on a study of the geological characteristics of the deposit,this study presents mineralization stages,focusing on the oxide stage and the quartz-sulfide stage where scheelite is mainly formed,referred to as Sch-A and Sch-B,respectively.Through LA-ICP-MS trace element and Sr isotope analyses,the origin,evolutionary process of the oreforming fluid and genesis of the ore deposit are investigated.Scanning Electron Microscope-Cathodoluminescence(SEMCL)observations reveal that Sch-A consists of three generations,with dark gray homogenous Sch-A1 being replaced by relatively lighter and homogeneous Sch-A2 and Sch-A3,with Sch-A2 displaying a gray CL image color with vague and uneven growth bands and Sch-A3 has a light gray CL image color with hardly any growth band.In contrast,Sch-B exhibits a‘core-rim’structure,with the core part(Sch-B1)being dark gray and displaying a uniform growth band,while the rim part(Sch-B2)is light gray and homogeneous.The normalized distribution pattern of rare earth elements in scheelite and Sr isotope data suggest that the early ore-forming fluid in the Nuri deposit originated from granodiorite porphyry and,later on,some country rock material was mixed in,due to strong water-rock interaction.Combining the O-H isotope data further indicates that the ore-forming fluid in the Nuri deposit originated from magmatic-hydrothermal sources,with contributions from metamorphic water caused by water-rock interaction during the mineralization process,as well as later meteoric water.The intense water-rock interaction likely played a crucial role in the precipitation of scheelite,leading to varying Eu anomalies in different generations of scheelite from the oxide stage to the quartz-sulfide stage,while also causing a gradual decrease in oxygen fugacity(fO2)and a slow rise in pH value.Additionally,the high Mo and low Sr contents in the scheelite are consistent with typical characteristics of magmatic-hydrothermal scheelite.Therefore,considering the geological features of the deposit,the geochemical characteristics of scheelite and the O-H isotope data published previously,it can be concluded that the genesis of the Nuri deposit belongs to porphyry-skarn deposit. | WANG Yiyun WU Zhishan CHEN Wenqing DU Qing’an TANG Liwei SHI Hongzhao MA Guotao ZHANG Zhi LIANG Wei WU Bo MIAO Hengyi | 2024 | Acta Geologica Sinica(English Edition)2024，98，1： | 0 |
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