Granular behaviour under bi-directional shear with constant vertical stress and constant volume

This paper aims to investigate the role of bi-directional shear in the mechanical behaviour of granular materials and macro-micro relations by conducting experiments and discrete element method(DEM)modelling.The bi-directional shear consists of a static shear consolidation and subsequent shear under constant vertical stress and constant volume conditions.A side wall node loading method is used to exert bi-directional shear of various angles.The results show that bi-directional shear can significantly influence the mechanical behaviour of granular materials.However,the relationship between bidirectional shear and mechanical responses relies on loading conditions,i.e.constant vertical stress or constant volume conditions.The stress states induced by static shear consolidation are affected by loading angles,which are enlarged by subsequent shear,consistent with the relationship between bidirectional shear and principal stresses.It provides evidence for the dissipation of stresses accompanying static liquefaction of granular materials.The presence of bi-directional principal stress rotation(PSR)is demonstrated,which evidences why the bi-directional shear of loading angles with components in two directions results in faster dissipations of stresses with static liquefaction.Contant volume shearing leads to cross-anisotropic stress and fabric at micro-contacts,but constant vertical stress shearing leads to complete anisotropic stress and fabric at micro-contacts.It explains the differentiating relationship between stress-strain responses and fabric anisotropy under these two conditions.Micromechanical signatures such as the slip state of micro-contacts and coordination number are also examined,providing further insights into understanding granular behaviour under bi-directional shear.

Cenozoic Vertical-Axis Rotations of the Hoh Xil Basin, Central–Northern Tibet

Understanding the Cenozoic vertical-axis rotation in the Tibetan Plateau is crucial for continental dynamic evolution. Paleomagnetic and rock magnetic investigations were carried out for the Oligocene and Miocene continental rocks of the Hoh Xii basin in order to better understand the tectonic rotations of central Tibet. The study area was located in the Tongtianhe area located in the southern part of the Hoh Xil basin and northern margin of the Tanggula thrust system in central-northern Tibet. A total of 160 independently oriented paleomagnetic samples were drilled from the Tongtianhe section for this study. The magnetic properties of magnetite and hematite have been recognized by measurements of magnetic susceptibility vs. temperature curves and unbiocking temperatures. The mean directions of the Oligocene Yaxicuo Group in stratigraphic coordinates （Declination/Inclination = 354.9°/29.3°, k = 33.0, a9s = 13.5°, N =5 Sites） and of the Miocene Wudaoliang Group in stratigraphic coordinates （Declination/Inclination = 3.60/36.4°, k = 161.0, a9s = 9.7°, N =3 Sites） pass reversal tests, indicating the primary nature of the characteristic magnetizations. Our results suggested that the sampled areas in the Tuotuohe depression of the Hoh Xil basin have undergone no paleomagnetically detectable rotations under single thrusting from the Tanggula thrust system. Our findings, together with constraints from other tectonic characteristics reported by previous paleomagnetic studies, suggest tectonic rotations in the Cuoredejia and Wudaoliang depressions of the Hoh Xil basin were affected by strike-slip faulting of the Fenghuo Shan-Nangqian thrust systems. A closer examination of geological data and different vertical-axis rotation magnitudes suggest the tectonic history of the Hoh Xil basin may be controlled by thrust and strike-slip faulting since the Eocene.

Vertical rotation effect on turbulence characteristics in an open channel flow

This paper solves the three-dimensional Navier-Stokes equation by a fractional-step method with the Reynolds number Reτ=194 and the rotation number Nτ=0-0.12. When Nτ is less than 0.06, the turbulence statistics relevant to the spanwise velocity fluctuation are enhanced, but other statistics are suppressed. When Nτ is larger than 0.06, all the turbulence statistics decrease significantly. Reynolds stress budgets elucidate that turbulence kinetic energy in the vertical direction is transferred into the streamwise and spanwise directions. The flow structures exhibit that the bursting processes near the bottom wall are ejected toward the free surface. Evident change of near-surface streak structures of the velocity fluctuations are revealed.

Numerical Investigation of Contra Rotating Vertical-Axis Tidal-Current Turbine

In this study,the performance of a contra rotating vertical-axis tidal-current turbine was investigated.The incompressible unsteady Reynolds-averagedNavier-Stokes(U-RANS)equations were solved via two-dimensional(2D)numerical simulation using ANSYS Fluent computational fluid dynamics(CFD)code.An algorithm known as SIMPLE from the CFD code was used to calculate the pressure-velocity coupling and second-order finite-volume discretization for all the transport equations.The base turbine model was validated using the available experimental data.Three given scenarios for the contra rotating turbine were modeled.The contra rotating turbine performs better in a low tip speed ratio(TSR)than in a high TSR operation.In a high TSR operation,the contra rotating turbine inefficiently operates,surviving to rotate in the chaotic flow distribution.Thus,it is recommended to use contra rotating turbine as a part of new design to increase the performance of a vertical-axis tidal-current turbine with a lower TSR.

Numerical Simulations of Liquid-Solid Flows in A Vertical Pipe by MPS-DEM Coupling Method

In the process of deep-sea mining,the liquid-solid flows in the vertical transportation pipeline are very complex.In the present work,an in-house solver MPSDEM-SJTU based on the improved MPS and DEM is developed for the simulation of hydraulic conveying.Firstly,three examples including the multilayer cylinder collapse,the Poiseuille flow and two-phase dam-break are used to validate the precision of the DEM model,the pipe flow model and MPS-DEM coupling model,respectively.Then,the hydraulic conveying with coarse particles in a vertical pipe is simulated.The solid particle distribution is presented and investigated in detail.Finally,the coupling method is successfully applied for the simulation of the liquid-solid flows in a vertical pipe with rotating blades,which shows the stability of the solver under rotating boundary conditions.This fully Lagrangian model is expected to be a new approach for analyzing hydraulic conveying.

Variations of the Earth＇s rotation rate and cyclic processes in geodynamics

The authors analyzed the relationship between variations of the Earth＇s rotation rate and the geodynamic processes within the Earth＇s body, including seismic activity, The rotation rate of a planet determines its uniaxial compression along the axis of rotation and the areas of various surface elements of the body. The Earth＇s ellipticity variations, caused naturally by the rotation rate variations, are manifested in vertical components of precise GPS measurements. Comparative analysis of these variations is considered in view of modern theoretical ideas concerning the Earth＇s figure. The results justify further research that is of interest for improvement of space svstems and technologiesi.

Investigation of factors affecting vertical sag of stretched wire

To study vertical sag requirements and factors affecting the stretched wire alignment method,the vertical sag equation is first derived theoretically.Subsequently,the influencing factors(such as the hanging weight or tension,span length,temperature change,elastic deformation,and the Earth’s rotation)of the vertical sag are summarized,and their validity is verified through actual measurements.Finally,the essential factors affecting vertical sag,i.e.,the specific strength and length,are discussed.It is believed that the vertical sag of a stretched wire is proportional to the square of the length and inversely proportional to the specific strength of the material.

冬小麦-夏玉米轮作田沟金针虫垂直活动特征

基于河北固城农业气象国家野外科学观测研究站2019—2020年、2021—2022年冬小麦-夏玉米轮作田沟金针虫在土壤中分层调查数据,引入虫口重量指标,结合虫口密度指标,揭示沟金针虫在冬小麦-夏玉米轮作田为害-休眠动态变化,讨论沟金针虫在土壤中垂直活动特征、气象条件与其相关性以及对冬小麦产量影响。结果表明:沟金针虫在冬小麦-夏玉米轮作田存在3个为害期和3个休眠期,且交替出现。3个为害期出现在冬小麦返青-拔节期、夏玉米幼苗期、冬小麦秋苗期,3个休眠期出现在冬小麦越冬期、冬小麦成熟-收获期、夏玉米灌浆-成熟期,3个为害期中以冬小麦返青-拔节期最为严重。冬季偏暖及春季回暖早,沟金针虫表现出晚下早上特征,使得沟金针虫冬季休眠期缩短而为害活动期延长;土壤温度、湿度以及食源关系共同影响沟金针虫为害、休眠以及取食活动,其为害适宜土壤重量含水率约为15%~18%,适宜土壤温度为14~18℃。分析沟金针虫为害与冬小麦减产率可知,虫口密度每增加10 m^(-2)或虫口重量每增加1.0 g·m^(-2),可导致减产率增加5.1%。

降低石墨微细鳞片含量的再磨工艺优化研究

对黑龙江某石墨粗精矿进行了立式搅拌磨机再磨试验。以陶瓷球为磨矿介质,研究了磨机转速、介质球直径、磨矿时间等工艺参数对石墨磨矿-浮选效果的影响。结果表明,石墨磨矿的优化工艺参数为:采用慢-快-慢交替的磨机转速,陶瓷介质球直径8~10 mm,磨矿时间5 min,在该优化条件下进行磨矿-浮选开路试验,获得了固定碳含量95.83%、-0.045 mm粒级含量24.51%、大鳞片(+0.15 mm)含量14.27%的石墨精矿。

基于扫描旋转同步运动的三维成像方法

为满足在役战机隐身性能的快速检测需求,提出了一种基于垂直扫描、方位旋转同步运动的三维成像方法。成像系统主要由射频收发设备、收发天线对、竖直方向导轨、转台和数据处理终端构成。天线发射频率步进信号时,对转台上的被测目标进行水平旋转,同时,收发天线对在垂直方向上扫描被测目标。以点目标组合为例,通过理论分析和仿真计算,确定该成像系统的参数配置,比较不同参数配置下系统的三维成像性能。仿真结果表明:采用垂直扫描、方位旋转同步运动方法能够实现三维成像,该方法与经典圆柱面扫描方法相比,扫描时间可缩短92%,同时保持11 dB峰值旁瓣比率。所提方法具有测试效率高、系统搭建简单、易于调节的特点,为服役阶段的隐身飞机散射源诊断提供了一种有效的测量方法选择。

吡罗昔康贴剂溶出度的测定及不同测定方法结果的评估

目的:采用桨碟法、转筒法、扩散池法测定吡罗昔康贴剂的溶出度,并对溶出结果进行评价,以期选择能更加准确反映吡罗昔康贴剂释药过程的测定方法,为科学准确评价药品质量提供参考。方法:建立检测吡罗昔康的液相色谱测定方法,分别使用桨碟法、转筒法、扩散池法考察吡罗昔康贴剂的24 h溶出曲线,分别使用f 1差异因子法、f 2相似因子法、Weibull模型拟合对溶出曲线进行比较,评估不同测定方法的结果。结果:吡罗昔康在1~150μg·mL^(-1)范围内线性关系良好(r=1.000),准确度100.9%(n=9),精密度1.7%(n=9),样品溶液在72 h内稳定。溶出曲线比较结果表明,吡罗昔康贴剂的溶出曲线更符合Weibull模型。在相同溶出介质和温度的条件下,桨碟法和转筒法差异不大,存在相互替代的可能性,扩散池法与其他2种方法均存在显著性差异。结论:扩散池法的装置更加符合吡罗昔康贴剂在实际使用中的溶出过程,为该药物的质量评价提供更多的参考。

宽式防旋墩环形堰竖井水力特性分析

目前许多拟建抽蓄工程泄洪洞的环形堰竖井入口设置了新型宽式防旋墩,以消除喉口处由不可控漩流引起的呛水等不利流态,而宽式防旋墩环形堰竖井的水气特性与以往采用起旋墩和窄式防旋墩的竖井存在较大差异,业内对其认识尚不清晰。以石台抽水蓄能电站下水库泄洪洞的竖井作为研究对象,采用物理模型试验与数值模拟相结合的手段,分析了流态、流速、压力、消能率等水力指标。研究结果表明:宽式防旋墩引导水流平顺进入竖井形成脱壁流,其尾部可形成顺畅的进气通道,空气经此通道可充分进入竖井以保持井内流态与压力的稳定;新型竖井过流能力满足要求,各部位流速、压力分布正常,总消能率达85%以上;宽式防旋墩可消除不可控漩流导致的呛水现象并引导水流在竖井内形成脱壁流态,使竖井壁面免于空蚀破坏;墩尾通气量足够时,可取消通气管及环形堰与竖井结合部突扩体型,简化工程布置。相关经验可供类似抽蓄电站工程的泄洪洞竖井设计参考。

渤海湾西岸一次局地极端短时强降水事件的成因分析

2021年9月4日早晨,渤海湾西岸的天津滨海新区出现短时强降水,过程累计降雨量达224.2 mm,最大小时雨强为110.9 mm·h^(-1),均打破当地建站以来的历史纪录。利用加密自动气象观测站、风廓线雷达、多普勒雷达等观测资料,结合欧洲中期天气预报中心ERA5再分析资料,分析该事件成因及其与海陆环境的关系,探讨对流系统新生、组织化机制以及水汽输送特征等。结果表明:(1)对流单体在海岸线海水一侧新生后西移登陆,经多次与后向新生对流单体合并加强,最终发展为具有中γ尺度涡旋且位于线状中尺度对流系统前端的强降水系统。(2)对流单体新生地点与两条地面辐合线的相交点对应。一条南北向的风速辐合线位于海上,与水陆表面摩擦系数差异有关;另一条东西向的风向辐合线位于陆地,由东北残余冷空气与原有偏南风相遇而成。(3)由于清晨海面湿度比陆地大,湿空气被向岸偏东气流从渤海湾带到西岸,为对流系统的发生发展提供热力条件;而850 hPa持续存在暖性切变线,为多个对流系统线状组织排列提供了动力支持;值得关注的是,浅层残余弱冷空气在925 hPa造成明显的中尺度锋生。(4)次级垂直环流促进周围水汽汇集和垂直向上输送加强,而水汽垂直递减率的大小(水汽垂直辐合)对小时雨强有指示意义。分钟雨强很可能与中γ尺度涡旋有内在联系。

垂直深旋耕下有机物料改良酸性土壤及烤烟产质量的调控效应

为探明深旋耕配施有机物料改良烤烟根际土壤酸化特性和调控烤烟生长、产质量的效应。以烤烟品种‘NC102’为材料,在云南省石林县酸性红壤上,采用双因素裂区设计,研究耕作方式(垂直深旋耕和传统耕作)和施有机改土物料(不施改土物料、酸性有机肥、碱性有机肥和生物质炭)及其互作对烤烟根际土壤理化特性、烟株根系和植株生长形态及产质量的影响。结果表明:植烟土壤理化特性主要受耕作方式、有机改土物料及二者互作的影响,其中垂直深旋耕配施有机肥可显著降低土壤容重,提高土壤孔隙度及水解性氮、有效磷、速效钾、水溶性氯含量,尤其施碱性有机肥、生物质炭更有利于增加土壤速效钾含量,显著降低土壤交换性酸总量、土壤交换性氢(H+)和交换性铝(Al3+),提升土壤硅铝率、阳离子交换量和盐基饱和度,增强酸性土壤调酸效果。烤烟根冠形态及烟叶产量、产值性状主要受深旋耕和碱性改土物料的影响。耕作方式、有机改土物料及其互作对烟叶化学成分可用性指数影响较大,其中施碱性有机肥、生物质炭主要影响总糖、还原糖、钾及水溶性氯;垂直深旋耕显著影响烟叶6项常规化学指标。因此,在云南酸性土壤山地烟区,采用垂直深旋耕结合施碱性有机肥、生物质炭,可较好地协同改良土壤酸度及提升土壤肥力,促进烤烟地上和地下部生长,形成良好根冠关系,提高烟叶产量和产值,改善烟叶化学成分协调性。

ANALYSIS OF UN-COINCIDE COORDINATE ERROR IN SINGLE-AXIS ROTATING FIBER OPTIC STRAP-DOWN INERTIAL NAVIGATION SYSTEM

The un-coincide coordinate error in the single-axis rotating fiber optic strap-down inertial navigation system（SINS） is analyzed. Firstly, a rotating modulation technology is presented for SINS. The method provides the enhanced property of SINS when using the same-leveled inertial measurement units. Then, the rotating struc- ture modification is derived and augmented to resolve the un-modulated error-accumulated problem. As the insuf- ficient machine processing, the horizontal and the vertical errors on the machine surface are inevitable, and the in- volved coordinates are difficult to get the exact coincident. So, two major kinds of coordinate situation are stud- ied. The equivalent error models on gyro and acceleration outputs are built for each situation, and the impact is analyzed for compensation. The part of attitude and position error models caused by the built angle-rate error is established to calculate the un-eoincident impact. Considering these conditions of different gyro accuracy and mo- tion states simultaneously, numerical simulations are implemented. Results indicate that the SINS modulation ac- curacy is seriously affected by the combined factors on gyro accuracy and motion conditions.

金婺大桥桥塔竖向转体施工关键技术

金婺大桥主桥为(85+143+37)m独塔斜拉桥,采用塔墩梁固结体系,桥面以上塔柱高82.404 m,包括钢塔段(T1~T11)和3 m长钢-混结合段(T0)。钢塔采用整体竖向转体方式施工,总转体重量为2530 t,转动角度90°。由于钢塔较高、重量较大,钢塔在桥面上拼装后采用二次接力牵引竖转的方案施工,设置大、小压杆,首先由小压杆牵拉大压杆到一定角度,再由大压杆起扳钢塔。大、小压杆均采用门式空间桁架结构;钢塔转铰由上、下铰座和销轴组成,设置在T0与T1节段分节处。施工时,在桥面上分别以0°、13°、30°的倾角卧拼钢塔、大压杆、小压杆;通过小压杆和压杆牵引索牵拉大压杆到60°的倾斜位置,拆除小压杆进行体系转换;通过大压杆和钢塔牵引索牵拉钢塔从水平位置竖向转动到竖直位置,顺利完成钢塔竖向转体施工。

上承式拱桥立柱及盖梁平吊竖转施工工艺的创新

针对上承式拱桥拱上钢立柱及盖梁传统吊装方案存在的吊装节段多、施工周期长、高空焊接量大、安全风险高和施工成本高的缺点,提出了上承式拱桥立柱及盖梁平吊竖转施工新技术。分析了平吊竖转主要影响因素,提出了平吊竖转立柱尺寸需要满足的条件,并对立柱、立柱-盖梁组合体吊具设计方案进行了优化。通过工程实践证明,平吊竖转新技术,不仅有力地保障了施工质量,还节约工期72 d,降低高空作业安全风险66%,节约施工成本932万元,可以在类似工程中推广应用。

华东稻麦轮作区立旋自走电驱动式定角度清秸机设计与试验

传统卧旋式清秸装置动土量较大,且湿黏土壤抛起时易黏附在机器上,导致作业质量下降、油耗增加,影响装置作业稳定性,针对这一问题,设计一种立旋式定角度清秸机,通过结构设计与分析实现清秸刀齿恒定角度作业,避免秸秆二次带回种床,通过对清秸刀齿切土迹距分析确定装置关键结构参数,应用三因素三水平正交试验方法,以作业速度、迹距系数和入土深度为试验因素,清秸率和单位面积作业功耗为试验评价指标,对影响清秸机作业性能的相关参数进行试验与优化。试验结果表明,当参数组合为作业速度4~8 km/h、迹距系数2和入土深度10 mm时,清秸率不小于89.7%、单位面积作业功耗不大于1.84 W·h/m^(2),整个作业过程均未发生土壤黏附现象。研究结果可突破湿黏土壤环境下播种装备作业局限,为稻麦轮作全程机械化提供技术支撑。

面向9%Ni钢大型储罐的旋转电弧窄间隙立焊装备

提出一种面向9%钢大型LNG储罐的旋转电弧窄间隙立焊装备,旨在解决LNG储罐立缝位置的焊接难题。采用窄间隙TIG旋转电弧焊接新工艺,将钨极打磨成非轴对称的尖端,通过电机控制钨极旋转,使电弧周期性加热窄间隙坡口两侧,有效解决了侧壁熔合问题。为配合该工艺,设计了新型窄间隙TIG旋转电弧焊枪,具备无线回转导电、自动送丝和双路气保护功能。同时,提出了一套适用于LNG储罐立缝位置的自动焊接设备,包括真空吸附的挂壁小车和焊接小车。在实验室搭建了全套试验装备,包括焊接小车、全自动送丝机、焊接电源等,控制焊枪立缝位置的焊接行走,防止9%Ni钢磁化,同时保证焊接过程的稳定。对24 mm厚9%Ni钢进行单层单道的焊接试验和窄间隙坡口对接试验,验证了新工艺能够解决厚板窄间隙焊接中侧壁熔合的问题,并且由于电弧循环旋转,对熔池具有搅拌作用,焊缝表面成形平滑美观。该研究为LNG储罐立缝的自动高效焊接提供了技术和装备支持。

基于TEOS源LPCVD设备的设计开发

在以TEOS源为SiO_(2)薄膜淀积源的低压化学气相沉积(LPCVD)工艺过程中,频繁出现薄膜厚度均匀性差、表面颗粒度高、设备维护周期短的问题。针对这个问题,设计并开发出一种适用于半导体工艺中的立式LPCVD设备。在设备结构上,工艺腔采用双管式结构,以提高气氛场均匀性;在晶舟系统中,增加自旋转功能,以提高晶圆表面气体含量的均匀性;为延长设备维护周期,并降低工艺颗粒度,排气管道增加伴热带和冷阱装置。基于此,通过工艺验证,有效提高了设备在线生产应用的可靠性。