Numerical simulation of sand load applied on high-speed train in sand environment

High-speed train running in the sand environment is different from the general environment. In the former situation, there will be sand load applied on high-speed train(SLAHT) caused by sand particles hitting train surface. This will have a great impact on the train stability, running drag and surface corrosion. Numerical simulation method of SLAHT in sand environment is studied. The velocity and mass flow rate models of saltation and suspension sand particles and the calculation model of SLAHT caused by sand particles hitting train surface are established. The discrete phase method is adopted for numerical simulating the process of saltation and suspension sand particles moving to train surface and generating sand load. By comparison with the field tests, the numerical simulation reliability is analysed. The theoretical formula of SLAHT changing with cross-wind and train speed is proposed. SLAHT changing law is analyzed. Research results indicate that SLAHT changing with cross-wind and train speed is a quadratic relationship. When train speed is constant, SLAHT increases quadratically with cross-wind speed improvement. When cross-wind speed is constant, SLAHT increases quadratically with train speed improvement.

Energy Consumption and Erosion Mechanism of Polyester Fiber Reinforced Cement Composite in Wind-blown Sand Environments

Considering the economic and environmental benefits associated with the recycling of polyester(PET)fibres,it is vital to study the application of fibre-reinforced cement composites.According to the characteristics of the wind-blown sand environment in Inner Mongolia,the erosion resistance of the polyester fibre-reinforced cement composites(PETFRCC)with different PET fibre contents to various erosion angles,velocities and sand particle flows was investigated by the gas-blast method.Based on the actual conditions of sandstorms in Inner Mongolia,the sand erosion parameters required for testing were calculated by the similarity theory.The elastic-plastic model and rigid plastic model of PETFRCC and cement mortar were established,and the energy consumption mechanism of the model under particle impact was analyzed.The experimental results indicate that the microstructure of PETFRCC rafter hydration causes a spring-like buffering effect,and the deformation of PETFRCC under the same impact load is slightly smaller than that of cement mortar,and the damage mechanism of PETFRCC is mainly characterized by fiber deformation and slight brittle spalling of matrix.And under the most unfavorable conditions of the erosion,the erosion rate of 0.5PETFRCC is about 57.69%lower than that of cement mortar,showing better erosion resistance.

Abrasive Wear Map of Polymer Tapes in Sand Dust Environment

To make clear the wear conditions of ATM (Automatic Teller Machine) tribosystem when servicing in Chi- nese sand dust environment, abrasive wear of two kinds of polymer tapes specified for ATM, PI (Polyimide) and PEN (Polyethylene-2, 6-naphthalenedicarboxylate), was investigated in simulated sand dust environment with ATM tape-scraper tribosystem under various conditions of loads and sliding distances. The surface profiles of worn tape were measured with a surface profiler in order to calculating the wear cross-section areas and the wear volumes. The specific wear rates of polymer tapes were calculated under load conditions of 0.6, 1 and 1.5 N, and wear mechanisms were in- vestigated with optical topography photos. As main results, the specific wear rates show stage variations in the wear process and the wear resistance of polymer tape shows good relationship with the mechanical deformation factors. In consideration of the service life, four wear models are generalized according to the magnitude of specific wear rates, which include no wear, mild wear, normal wear and severe wear model and the corresponding wear mechanisms for the four wear models are discussed with typical worn topographies. Based on the wear models and corresponding wear mechanisms, the abrasive wear maps of two polymer tapes servicing in sand dust environments are concluded for its industrial applications.

S. E. M. analysis of quartz sand grains from selected Hong Kong and Chinese littoral environments

This pilot study attempts to demonstrate some underlying scanning electron microscopy themes of quartz grain surface textures. A variety of textural patterns and individual features are described for grains selected from various littoral environments. An attempt was made to differentiate samples on surface textures alone, but limitations of using this technique in sedimentological isolation were apparent. Statistical analysis of checklist data and photographic evidence revealed some of the more important feature combinations used in environmental diagnosis. The use of discriminant analysis provided quantitative sample separation.

Impact of Sand Mining and Sea Reclamation on the Environment and Socioeconomic Activities of Ikate and Ilubirin Coastal Low Income Communities in Lagos Metropolis, Southwestern Nigeria

Land reclamation is gradually posing negative impact on man due to unplanned urbanization. A study was carried out on impact of land reclamation through sand mining of coastal communities in Ikate and Ilubirin in Lagos, Nigeria. Ten waters (8 surface and 2 groundwater sources), 10 soil samples and air were collected and taken for analysis. Results of water revealed concentrations lower than WHO (2017) and SON (2007) standards. Soil/sediment with average crustal value revealed Pb and Cd above standard values, which is attributed to anthropogenic influence on soils. Quality of air in the study was mainly particulate matter arising from the sea and reclaimed land in the surroundings of the environment with the highest Total Suspended Particulate of 0.8 mg/m3 in sulfur dioxide. This explains corrosion found on the roofs of the communities. Therefore, in the development planning adequate precautions should be put in place to avert environmental degradation.

Relationships between Artemisia ordosica communities and environmental factors following sand-dune stabilization in the Mu Us desert,northwest China

Artemisia ordosica is an excellent sand-fixing shrub for sand stabilization in northwestern China. Sand dune stabilization, a critically important process, leads changes in abiotic factors, such as soil structure and nutrient contents. However, the effects of factors on an A. ordosica community following sand stabilization remain unclear. In this study, we used canonical correspondence analysis （CCA） to examine the relationships between A. ordosica communities and environmental factors at three habitats： semi-fixed dune （SF）, fixed dune with low-cov- erage biological soil crust （F）, and fixed dune with high- coverage biological soil crust （FC） in Mu Us desert. The mean height and coverage of plants increased with sand stabilization, while species diversity and richness increased initially and then reduced significantly. Correlation analysis and CCA revealed that slope, soil organic carbon, and nutrient contents, proportion of fine soil particles, soil moisture, and thickness of biological soil crust were all highly correlated with vegetation characteristics. These environmental factors could explain 40.42 % of the vege- tation-environment relationships at the three habitats. The distribution of plant species was positively related to soil moisture in the SF dune. Soil moisture, soil nutrient, and fine-particle contents mainly affected plants distribution in the F dune. In the FC dune, distribution of plant species was positively and negatively correlated with the thickness of biological soil crust and soil moisture at a depth 0-20 cm, respectively. The dominance value of typical steppe species increased significantly following sand-dune stabilization and relations between species and samples in CCA ordination bi-plots showed that perennial grasses could invade the A. ordosica community on FC, indicating A. ordosica communities had a tendency to change into typical steppe vegetation with the further fixation. We conclude that the significant differentiation not only occurred in community characteristics, but also in the relationships between vegetation and environmental factors among the three stages of dune fixation. So, restoration of degraded dune ecosystems should be based on habitat conditions and ecological needs.

青海湖湖东地区近32 ka BP以来风沙沉积的粒度端元特征及环境意义

青海湖湖东地区出露典型的风成沉积,对气候变化响应敏感,为古气候环境的重建提供了良好研究窗口。本文选取湖东地区厚度10 m的风成砂-砂质古土壤剖面为对象,运用端元分析模型对沉积物粒度数据进行分析,提取对气候变化反映敏感的粒级组分,进一步结合粒度组分、磁化率指标,阐释各端元指示的环境意义以及近32 ka BP以来青海湖湖东地区的环境演化过程。结果表明,大水塘剖面粒度组成以砂粒物质为主,粉砂次之,黏粒最少。剖面的沉积物粒度组分可分解为3个端元:EM1是受冬季风影响的敏感粒径,指示冬季风的强弱变化;EM2指示的是区域环境受风沙作用的强弱,与EM1指示相反,但共同反映冬季风的强弱;EM3指示受区域性低空风系的影响,以尘暴的形式搬运沉积。青海湖湖东地区的环境演化过程可划分为4个阶段:(1)末次冰期间冰阶阶段(32~23.2 ka BP),气候整体较湿润,风沙活动较弱;(2)末次冰期冰盛期阶段(23.2~15.8 ka BP),气候冷偏干,风沙活动增强;(3)末次冰期冰消期阶段(15.8~9.5 ka BP),气候仍以冷偏干为主,冷暖波动,但存在小幅度升温;(4)全新世阶段(9.5 ka BP以来),早期转暖、中期最暖、晚期转凉,气候波动显著。

Effects of forest cover types and environmental factors on soil respiration dynamics in a coastal sand dune of subtropical China

Trees on sand dunes are more sensitive to environmental changes because sandy soils have extremely low water holding capacity and nutrient availability. We investigated the dynamics of soil respiration(Rs) for secondary natural Litsea forest and plantations of casuarina,pine, acacia and eucalyptus. Results show that significant diurnal variations of Rsoccurred in autumn for the eucalyptus species and in summer for the pine species, with higher mean soil respiration at night. However, significant seasonal variations of Rswere found in all five forest stands. Rschanged exponentially with soil temperatures at the 10-cm depth; the models explain 43.3–77.0% of Rs variations. Positive relationships between seasonal Rsand soil moisture varied with stands. The correlations were significant only in the secondary forest, and the eucalyptus and pine plantations. The temperature sensitivity parameter(Q10 value) of Rsranged from 1.64 in casuarina plantation to 2.32 the in secondary forest; annual Rswas highest in the secondary forest and lowest in the pine plantation. The results indicate that soil temperatures and moisture are the primary environmental controls of soil respiration and mainly act through a direct influence on roots and microbial activity. Differences in root biomass, quality of litter,and soil properties(pH, total N, available P, and exchangeable Mg) were also significant factors.

Evolution of windblown sand flux and dune field——Trans-scale modeling and simulation

Windblown sand flux and dune field evolving toward the oasis have been a common ecological and environmental threat confronted by many countries.Meanwhile,it is also a kind of complex dynamical process involving multiple temporal and spatial scales which is still out of accurate description through current field observations.Available models and reliable quantitative simulations are of significant value to predict the spreading rate of desertification and provide an optimal design for sand prevention.This paper presents a 'triple-jump' method to realize quantitative simulations to the formation and evolution of an aeolian dune field from an arbitrary initial configuration.Simulated results achieve a satisfactory agreement with observations qualitatively and quantitatively,which also reveal the characteristics and dynamical behaviors of dunes and dune field.Such a paradigm is of a good level of generality,which provides an exploratory probe into the subject of multi-scale physics.

中国式现代化视域下习近平生态文明思想整体系统观及其方法论

党的十八大以来,在推进中国式现代化建设的伟大征程中,以习近平同志为核心的党中央坚持系统观念,基于对西方现代化道路的深刻反思和对自然界作为有机系统整体的精准认识,赓续与拓新马克思主义和中华优秀传统文化关于人与自然真实图景的系统辩证思想,形成和确立了丰富完备、逻辑严密的习近平生态文明思想整体系统观。秉持山水林田湖草沙是生命共同体的系统理念,这一整体系统观锚定生态文明建设和环境治理的目标任务,坚持推进中国式现代化生态文明建设与环境治理的系统层级观,坚持共同体构架的国内外合作治理的系统联动机制,对其内核“是什么”的问题作了精要而又深邃的回答。习近平生态文明思想层层追问中国式现代化生态文明建设之道,彰显了其整体系统思维在回答生态文明建设根本性问题上的强大方法论功能;以系统工程方式“全方位全地域全过程”推进生态文明建设与环境治理的全面系统展开,立体呈现了习近平生态文明思想整体系统观鲜明的方法论特质,为中国式现代化新征程上全面推进美丽中国建设提供了科学思想方法,开拓了中国式现代化恢宏壮丽的生态篇章。

南昌市厚田沙地末次冰期风沙沉积的磁化率特征及其环境意义

鄱阳湖滨周围和赣江下游沿岸广泛分布着一系列风成砂山。为了探讨南方风沙沉积的磁化率特征及其环境意义,本研究对鄱阳湖南部之厚田剖面的古风沙沉积进行了光释光测年、磁化率、粒度和重矿物分析。结果表明:(1)沙丘砂层的磁化率整体较低,平均粒径(Mz)较粗,成熟度指数(ZTR)较低而风化指数(HW)较高,说明风化程度较低,形成于冬季风强盛、干燥寒冷的气候条件下;砂质古土壤层的磁化率较高,Mz较细,ZTR指数较高而HW指数较低,说明风化程度较高,形成于冬季风较弱、夏季风较强,温暖湿润的气候环境下。(2)厚田剖面第Ⅰ(77.0~57.1 ka)、Ⅲ(49.7~36.8 ka)、Ⅴ(29.7~14.9 ka)阶段依次对应深海氧同位素的MIS4、MIS3b、MIS2,指示为冷期,冬季风强盛,磁化率较低;第Ⅱ(57.1~49.7 ka)、Ⅳ(36.8~29.7 ka)阶段分别对应MIS3c和MIS3a,指示为暖期,夏季风强盛,磁化率较高。这些气候变化特征与黄土高原渭南剖面、深海氧同位素和中国亚热带洞穴石笋δ^(18)O记录具有良好的对比性。因此认为,磁化率在南方风沙沉积中可以有效揭示气候变化。

乡村振兴视域下新建机制砂场对生态环境影响评价研究

基于生态文明视角的乡村振兴,就是要转变传统以破坏生态环境换取经济发展水平提升的发展模式.强调经济建设与生态环境保护协调发展,建设项目的环境影响评价是保护生态环境的重要举措之一.以位于川东北乡村振兴重点发展地区之一——麻柳镇的达州双获建材新建机制砂场为例,评价砂场运营对乡村大气环境、地表水环境、声环境、生态环境等的影响,提出相应的环境问题防治措施和管理建议,对于探讨促进绿色经济的发展、建设生态友好型乡村方面有十分重要的现实意义.

铝合金副车架环保型制芯工艺研究及应用

针对整体式铝合金副车架树脂砂芯体积大,浇注过程烟雾大、环境污染严重等难点,试制开发无机砂芯工艺。通过制芯设备选型、水平分模射芯方式确定,再对芯砂组份配比、混砂时间、芯盒温度、保存温度及湿度等工艺参数进一步试验研究。试验结果表明,整体式副车架铸造采用无机制芯工艺砂芯更容易成型,浇注过程中不仅没有明显的热分解产物、无任何凝聚物,还易溃散去砂效果好、发气量低等优点,有效降低气孔类缺陷提高产品质量,促进绿色低碳铸造技术发展。

雅江中游河谷典型山水林田湖草沙生态修复工程技术实践

通过对雅鲁藏布江中游河谷典型山水林田湖草沙生态修复工程实施效果调查,针对露天采矿、灌草地退化、土壤沙化等突出生态环境问题,基于自然的解决方案,系统梳理并形成了地形地貌重塑、土壤基质重构、防沙治沙、植被恢复四大工程技术措施,对西藏山水林田湖草沙生态修复相关工程的实施具有一定借鉴和指导意义。

Chronology of coastal aeolian deposition and its paleo-environmental implications on the Liuao Peninsula of South China

Coastal dunes are a common geomorphic type in sandy coastal zones.They are a record of the coupled evolutionary processes of the wind and ocean waves.Many coastal dune fields have developed on the east coast of Fujian China and now occur as widespread typical coastal aeolian sand landforms on the Liuao Peninsula,Gulei Peninsula and Dongshan Island,but it is difficult to evaluate the dynamic geomorphologic process of sandy coast due to the lack of systematic and accurate chronological data.In this study,we selected the Hutoushan(HTS)aeolian dune on the Liuao Peninsula as the research object.Optical dating and grain-size analysis were applied to sand samples from the aeolian sequence of a profile of the HTS dune.The results show that the ages of seven samples of this profile were in the range of 37.8–0.19 ka from 4.0 to 0.2 m deep.These correspond to the Marine Isotope Stage 3(MIS3),abrupt climatic change events of 4.2 and 1.1 ka and the Little Ice Age(LIA),respectively.These samples displayed evidence of a longer-term climate trend in this area.The period of formation of this coastal aeolian dune corresponds to a cold and arid climate associated with the East Asia Winter Monsoon(EAWM).Periods of dune fixation and rubification are evidence of a hot and humid climate.Mobilization and stabilization of the aeolian dune is an important characteristic of the coastal evolution in South China since the late Pleistocene.

Canonical Correlation Factors Causing the Formation of Accumulated Sand-belts along the Oasis Fringe in Hexi Corridor

Accumulated sand-belts refer to those formed along the oasis fringe,especially at the upwind location,due to the accumulation of sand blocked by farmland windbreak. In the 60 years since the foundation of new China,a lot of trees have been planted for desertification combating in northwest and north China,thus,accumulated sand-belts were formed at the upwind location. The formation and the ecological effects of the accumulated sand-belts along the oasis fringe is a new scientific concern. To study the formation causes of these belts in Hexi corridor,21 samples were selected,and the height / width of the belts,as well as the vegetation,soil,soil moisture and climatic factors were investigated. This paper analyzed the correlation between the height / width of the belts and the vegetation,soil,soil moisture and climatic factors using the methods of variance analysis,correlation analysis and canonical correlation analysis. The results indicate that: the accumulated sand-belts take a trend of being high and wide in the east whereas low and narrow in the west,and most of the parts tend to be stable; the species on the belts are dominated by Tamarix austromongolica,the vegetation cover and the pure vegetation cover of different dominant species on the leeward slope of the accumulated sand-belts vary significantly. The canonical correlation analysis shows that: the height and width of accumulated sand-belt is the interaction of precipitation,distance to the sand source,leeward vegetation cover and annual average wind speed. Moreover,the height of accumulated sand-belts are negatively correlated to the soil moisture at the depth of 30- 50 cm,air humidity and leeward vegetation cover,and the width of the belts is also negatively correlated with the distance to the sand source. The ecological effects of the accumulated sand-belts are both positive( stopping sands from moving into farmland,protective role as an obstacle)and negative( when the belts decay and activate one day,they will become the new sand sources). At present,there are no signs showing the negative effects of the belts. The ecological effects of the accumulated sand-belts are: firstly the protective role as an obstacle,and secondly to intercept and reduce the sands moving into farmlands.

Investigations of physicochemical properties of dusts generated in mechanical reclamation process of spent moulding sands with alkaline resins

Mechanical reclamation processes of spent moulding sands generate large amounts of postreclamation dusts mainly containing rubbed spent binding agents and quartz dusts. The amount of postreclamation dusts, depending in the reclamation system effi ciency and the reclaim dedusting system, can reach 5%-10% in relation to the total reclaimed spent moulding sand. The proper utilization of such material is a big problem facing foundries these days. This study presents the results of investigations of physicochemical properties of post- reclamation dusts. All tested dusts originated from various Polish cast steel plants applying the mechanical reclamation process of moulding sands with alkaline resins, obtained from different producers. Different dusts, delivered from foundries, were tested to determine their chemical composition, granular characterization, physicochemical and energetic properties. Presented results confi rmed assumptions that it is possible to utilize dusts generated during mechanical reclamation of used sands with organic resins as a source of energy.

利用微胶囊包覆技术提高耐碱树脂砂的环境适应性——以大庆油田为例

大庆油田三元复合驱常出现压裂裂缝内支撑剂移动现象,通常采用压裂后尾追树脂砂的工艺来延长压裂有效期,但目前适用于三元复合驱的耐碱树脂砂存在高温储存易胶结的难题。利用微胶囊包覆技术,以耐碱树脂砂为囊芯,以明胶等组分制作囊壁,开展耐碱树脂砂的环境适应性研究。结果表明,有覆膜的耐碱树脂砂有效保存周期在2 a以上,强碱浸泡72 h后抗压强度为3.1 MPa。先期试验3口井,未发现支撑剂运移现象,固砂有效期长达814 d且仍有效,平均单井累计增油4057 t,具有良好的固砂增油效果,在三元复合驱区块具有良好的应用前景。

Effects of Different Gravel Mulched Years on Soil Microbial Flora and Physical and Chemical Properties in Gravelsand Mulched Fields

Soil microbial flora and influencing factors of soil microbes in soil and gravel-sand mixed layer（ SGSML）,roots denseness layer（ RDL）,eluviate layer（ EL） and calcium accumulation layer（ CAL） in gravel-sand mulched fields（ GSMFs） with different gravel mulched years（ 1,6,12,19 and 25 years） were studied. The results showed that in the composition of soil microbes in the GSMFs,the quantity of bacteria was the largest,followed by actinomycetes,while the number of fungi was the smallest. The total quantity of soil microorganisms in the GSMFs dropped rapidly with the increase of soil depth,which was related to the sudden decrease in the quantity of bacteria. The number of microbes in the RDL was larger than that in the SGSML with few roots due to the effects of root distribution. The number of bacteria and actinomycete in the growing season was larger than that in the non-growing season,while the quantity of fungi in the growing season was smaller than that in the non-growing season. The quantity of bacteria and fungi was the largest in the GSMFs which had been mulched with gravel for 6-12 years. With the increase of mulching time,the GSMFs aged gradually,so their quantity reduced gradually. The quantity of actinomycetes was the smallest in the GSMFs which had been mulched with gravel for 6-12 years and increased with the increase of mulching time. The number of soil microbes in the GSMFs had a good correlation with soil moisture content,p H and mulching time. Soil total carbon content was an important factor restricting the quantity of soil microbes in the GSMFs.

地震与水平环境荷载下风电单桩基础动力响应分析

为探究复杂环境荷载和地震共同作用下饱和场地中单桩基础的动力响应,文中采用有限差分整体时程数值分析方法,对饱和砂土场地中海上风电单桩基础在水平环境荷载与地震荷载联合作用下的动力响应进行了非线性分析。通过与离心机试验结果对比,验证了所建立的数值分析模型的合理性与有效性。基于数值计算结果,对地震单独作用和水平环境荷载-地震联合作用2种工况下海上风电单桩基础的动力响应规律差异进行探讨,并进一步分析了上部结构质量、埋深等对联合荷载作用下单桩基础动力响应的影响。研究结果表明,在海上风电单桩基础结构设计中应考虑水平环境荷载与地震联合作用的影响,且应将桩的埋深作为重要设计参数加以考虑,而结构质量对联合荷载作用下海上风电单桩基础结构体系响应的影响较小。