Effect of Nonlinear Geometric Behavior on Random Response of Rotational Shell

Aimed at the large deformation problem of industry cooling tower shell, the mathematical model for the random response of rotational shell under the external random excitation is established by statistic perturbation method. The effect of nonlinear geometric behavior on the response of rotational shell is analyzed.

Corrosion behavior of T2 copper in 3.5% sodium chloride solution treated by rotating electromagnetic field

Copper is susceptible to producing corrosion problems in corrosive environments, which leads to serious safety problems. Thus, investigating the corrosion behavior of copper is of great significance. The effects of rotating electromagnetic field on corrosion behavior of T2 copper in 3.5% sodium chloride solution with electrochemical measurements were investigated. The results showed that rotating electromagnetic field changed properties of 3.5% sodium chloride solution by increasing the values of temperature and pH and decreasing the values of conductivity and dissolved oxygen. The rotating electromagnetic field improved the corrosion resistance of T2 copper. The corrosion products of T2 copper in treated 3.5% sodium chloride solution were composed of Cu20 and CuCl. The low corrosion rate of T2 copper was resulted from the decrease of dissolved oxygen in 3.5% sodium chloride solution treated by rotating electromagnetic field.

Nonlinear Stochastic Response of Rotational Shell Under the Action of Stationary Strong Wind Loads

Based on the theoretical analysis of nonlinear random response of structure, for the engineering practical problem, that is, the large deformation of industry cooling tower shell structure under the action of strong wind loads, the statistic perturbation method is also used to analyze some statistic characteristics of the nonlinear random response of rotational shell with geometric nonlinearity and stationary strong wind load considered. Through computation, some average values of nornal displacements and the nonlinear effect factor of the cooling tower shell are given.

In-situ pressure-preserved coring for deep exploration:Insight into the rotation behavior of the valve cover of a pressure controller

In-situ pressure-preserved coring(IPP-Coring)is considered to be the most reliable and efficient method for the identification of the scale of oil and gas resources.During IPP-Coring,because the rotation behavior of the pressure controller valve cover in different medium environments is unclear,interference between the valve cover and inner pipe may occur and negatively affect the IPP-Coring success rate.To address this issue,we conducted a series of indoor experiments employing a high-speed camera to gain greater insights into the valve cover rotation behavior in different medium environments,e.g.,air,water,and simulated drilling fluids.The results indicated that the variation in the valve cover rotation angle in the air and fluid environments can be described by a one-phase exponential decay function with a constant time parameter and by biphasic dose response function,respectively.The rotation behavior in the fluid environments exhibited distinct elastic and gravitational acceleration zones.In the fluid environments,the density clearly impacted the valve cover closing time and rotation behavior,whereas the effect of viscosity was very slight.This can be attributed to the negligible influence of the fluid viscosity on the drag coefficient found in this study;meanwhile,the density can increase the buoyancy and the time period during which the valve cover experienced a high drag coefficient.Considering these results,control schemes for the valve cover rotation behavior during IPP-Coring were proposed for different layers and geological conditions in which the different drilling fluids should be used,e.g.,the use of a high-density valve cover in high-pore pressure layers.

A phenomenological model for plastic flow behavior of rotating band material with a large temperature range

The plastic flow behavior of the rotating band material is investigated in this paper. The rotating band material is processed from H96 brass alloy, which is hardened to a much higher yield strength compared to the annealed one. The dynamically uniaxial compression behavior of the material is tested using the split Hopkinson pressure bar(SHPB) with temperature and strain rate ranging from 297 to 1073 K and500 to 3000 s^(-1), respectively, and a phenomenological plastic flow stress model is developed to describe the mechanical behavior of the material. The material is found to present noticeable temperature sensitivity and weak strain-rate sensitivity. The construction of the plastic flow stress model has two steps. Firstly, three univariate stress functions, taking plastic strain, plastic strain rate and temperature as independent variable, respectively, are proposed by fixing the other two variables. Then, as the three univariate functions describe the special cases of flow stress behavior under various conditions, the principle of stress compatibility is adopted to obtain the complete flow stress function. The numerical results show that the proposed plastic flow stress model is more suitable for the rotating band material than the existing well-known models.

Pitting Corrosion Behavior of Stainless Steel 304 in Carbon Dioxide Environments

With a rotating cylinder electrode apparatus, the polarization behaviors of the mild steel and the stainless steel 0Cr18Ni9 in NaHCO 3 (0.5 M)+Na 2CO 3 (0.5 M) solution with and without erodent particles were investigated and compared. The results show that the rotation speed of cylinder hardly affects the polarization behavior of sample in solution without particles but exerts a great influence on that with particles. Increasing rotation speed, the free corrosion potential shifts to positive direction and the oxygen limiting current density increases. Both the mild steel and stainless steel 0Cr18Ni9 experience a significant increase of the mass loss by increasing erosion, and erosive wear was dominated by severe micro-plowing. The insufficient mechanical strength of both materials leads to a low resistance to particle removal. Increasing peripheral velocities of the rotating cylinder enhances the corrosion rate of the mild steel. The stainless steel 0Cr18Ni9, due to a high erosive wear, also suffers from similar erosion-corrosion damage, despite that its corrosion resistance is much higher than that of the mild steel.

Characteristics of Atmospheric Pressure Rotating Gliding Arc Plasmas

In this work, a novel direct current （DC） atmospheric pressure rotating gliding arc （RGA） plasma reactor has been developed for plasma-assisted chemical reactions. The influence of the gas composition and the gas flow rate on the arc dynamic behaviour and the formation of reactive species in the N2 and air gliding arc plasmas has been investigated by means of electrical signals, high speed photography, and optical emission spectroscopic diagnostics. Compared to conventional gliding arc reactors with knife-shaped electrodes which generally require a high flow rate （e.g., 10-20 L/min） to maintain a long arc length and reasonable plasma discharge zone, in this RGA system, a lower gas flow rate （e.g., 2 L/min） can also generate a larger effective plasma reaction zone with a longer arc length for chemical reactions. Two different motion patterns can be clearly observed in the N2 and air RGA plasmas. The time-resolved arc voltage signals show that three different arc dynamic modes, the arc restrike mode, takeover mode, and combined modes, can be clearly identified in the RGA plasmas. The occurrence of different motion and arc dynamic modes is strongly dependent on the composition of the working gas and gas flow rate.

Isomorphic 2D/3D Objects and Saccadic Characteristics in Mental Rotation

Mental rotation(MR)is an important aspect of cognitive processing in gaming since transformation andmanipulation of visuospatial information are necessary in order to execute a gaming task.This study provides insights on saccadic characteristics in gaming task performance that involves 2D and 3D isomorphic objects with varying angular disparity.Healthy participants(N=60)performedMR gaming task.Each participantwas tested individually in an acoustic treated lab environment.Gaze behavior data of all participants were recorded during task execution and analyzed to find the changes in spatiotemporal characteristics of saccades associated with the variation in angular disparity and dimensionality.There were four groups with unique combination of angular disparity and dimensionality,each with fifteen participants randomly assigned.Results indicate that the spatial characteristics of the object affect the temporal aspect of saccade(duration),whereas the spatial aspect of the saccade(amplitude)is influenced by the objects’dimension.A longer saccade duration indicates a prolonged suppression of spatial information processing during the MR tasks with objects at convex range angular disparities.Therefore,the MR tasks with convex angular disparity become more complex to process compared to the tasks with reflex angular disparity.MR process is faster and more accurate with 3D objects compared to the 2D objects.There is an interaction between angular disparity and dimensionality in terms of mental demand,such that theMR processing with 2Dobjects in reflex angular disparitywasmoremental demanding than that of convex angular disparity;however,this trend was absent in case of 3Dobjects.Hence,during the MR task,the longer saccade duration implies that the taskswith convex angular disparities become comparativelymore challenging.Also,the lower saccadic amplitude for 2D objects indicates difficulties in processing due to deficient visual features.The findings could help in framing the computer-based game(or videogame)concerningMRabilities for training or rehabilitation purposes.

Microscale deformation behavior of sandstone mineral particles based on XCT scanning

This work aimed to quantify the physical and mechanical behavior of three-dimensional microstructures in rocks under uniaxial compression.A high-precision in situ XCT(X-ray transmission computed tomography)technology was applied to investigating the behavior of mineral grains in sandstone:the movement,the rotation deformation,and the principal strains between fault zone and non-fault zone.The results indicate that after unloading,the shear strain of mineral grains is periodic in the radial direction,the strain of mineral grains in the fracture zone is about 30 times of the macro strain of the specimen,which is about 5 times in the non-fracture zone,and the shear strain near the fault zone is larger than the compressive strain,and there is the shear stress concentration feature.

Undrained response of reconstituted clay to cyclic pure principal stress rotation

A series of monotonic and rotational shearing tests are carried out on reconstituted clay using a hollow cylinder apparatus under undrained condition. In the rotational shearing tests, the principal stress axes rotate cyclically with the magnitudes of the principal stresses keeping constant. The anisotropy of the reconstituted clay is analyzed from the monotonic shearing tests. Obvious pore pressure is induced by the principal stress rotation alone even with shear stress q0=5 k Pa. Strain components also accumulate with increasing the number of cycles and increases suddenly at the onset of failure. The deviatoric shear strain of 7.5% can be taken as the failure criterion for clay subjected to the pure cyclic principal stress rotation. The intermediate principal stress parameter b plays a significant role in the development of pore pressure and strain. Specimens are weakened by cyclic rotational shearing as the shear modulus decreases with increasing the number of cycles, and the shear modulus reduces more quickly with larger b. Clear deviation between the directions of the principal plastic strain increment and the principal stress is observed during pure principal stress rotation. Both the coaxial and non-coaxial plastic mechanisms should be taken into consideration to simulate the deformation behavior of clay under pure principal stress rotation. The mechanism of the soil response to the pure principal stress rotation is discussed based on the experimental observations.

Sensitivity analysis for axis rotation diagrid structural systems according to brace angle changes

General regular shaped diagrid structures can express diverse shapes because braces are installed along the exterior faces of the structures and the structures have no columns. However, since irregular shaped structures have diverse variables, studies to assess behaviors resulting from various variables are continuously required to supplement the imperfections related to such variables. In the present study, materials elastic modulus and yield strength were selected as variables for strength that would be applied to diagrid structural systems in the form of Twisters among the irregular shaped buildings classified by Vollers and that affect the structural design of these structural systems. The purpose of this study is to conduct sensitivity analysis for axial rotation diagrid structural systems according to changes in brace angles in order to identify the design variables that have relatively larger effects and the tendencies of the sensitivity of the structures according to changes in brace angles and axial rotation angles.

Analysis of the Orbitation and Rotation of Celestial Bodies

We have developed a structure of dynamic knowledge for non-inertial systems, the so-called Theory of Dynamic Interactions (TDI) as a part of non-inertial dynamic knowledge, which incorporates a causal demonstration of phenomena accelerated by rotation, which would complement Classical Mechanics. We believe that the TDI mathematical model that we propose is of great conceptual importance. In addition, we think that it is not only necessary to understand the dynamics of rotating bodies, but also to understand the dynamics of the cosmos, with bodies that orbit and with constantly recurring movements, which make possible systems that have been in dynamic equilibrium for centuries and are not in a process of unlimited expansion. We even believe that this new dynamic theory allows us a better understanding of our universe, and the matter from which it is made.

User Preference Survey on Staircase Rotation

Staircase is an important means of vertical transportation. Staircase design exerts a great influence on the aesthetics, transportation efficiency, user comfort and experience level. In this paper, a survey on the staircase rotation preference was conducted, based on the environment behavior studies. Different user frequencies of a pair of scissors stairs in the 2nd teaching building of North China University of Technology were analyzed. The psychological effect was evaluated and quantified, and the user preference on the two staircase rotations was then withdrawn. The survey found that the type of staircase with clockwise upstairs was much more preferred （78%） than the other staircase rotation anti-clock upstairs. Considering different genders, the female shows a 66% higher preference inclination of this type of staircase rotation than the male. To improve the transportation efficiency of the staircase in case of fire, the result of this paper can be very constructive for the evacuation staircase rotation choice for the high-rise buildings.

Partial Discharge Measurement of OCP-Tapes in Rotating Electrical Machines

Nowadays, PD （partial discharge） measurements are a crucial part of the preventive maintenance of electrical equipment within high voltage engineering. Especially for electrical machines, both the supplier and the user are interested in the results of PD measurements. However, PDs hardly represent the cause of the failure, more likely they are claimed as the outcome of a failure. This paper deals with the insulation of a 6 kV electrical machine, whereas PD measurements were carried out at a single stator from wound coils. During manufacturing, these coils were equipped with different materials for the OCP （outer corona protection）. Using different PD measurement systems and different bandwidths, investigations of the PD behavior of the coils were carried out. Additionally, the surface resistivity of the corona protection was determined. As a result, conclusions for the correlations between the resistance of the OCP as well as the PD behavior are stated. Furthermore, the influence of using different measurement systems, different measuring circuits, and different bandwidths is shown.

不同水平足球运动员空间知觉能力差异:基于行为学和fNIRS的研究

空间知觉能力是决定足球运动员运动技能的关键,更是提升运动员竞技表现的核心因素。选取20名国家一级足球运动员(专家组)和20名高校足球俱乐部的体教专业大学生(新手组),采用功能性近红外光谱成像技术(fNIRS),探讨心理旋转任务下行为绩效、前额叶脑血氧(Oxy-Hb)激活以及脑功能连接的组间差异。结果显示:(1)专家组心理旋转任务正确率显著高于新手组(P<0.05),反应时显著短于新手组(P<0.01)。(2)专家组左右侧背外侧前额叶、额极区和右腹外侧前额叶激活低于新手组(P<0.05),并且脑间功能连接协同更强。研究认为,长期足球训练能够改变运动员的空间知觉加工模式,提高神经资源的利用效率,有利于大脑网络连接性,对认知功能的改善起到重要作用。

双阶受力干式装配梁-柱节点抗震性能试验研究

研究提出了一种双阶受力干式装配梁-柱节点(DADBJ)。该节点的关键组件是摩擦铰(RFH)和预设缝防屈曲钢板(SBRSP),具备2个受力工作阶段和损伤集中易修复的特性。为了验证DADBJ构造的合理性,揭示其双阶段受力工作机理,设计加工了DADBJ试件,以SBRSP的预设缝隙宽度作为试验变量,进行了2个工况的低周往复拟静力试验。结果表明:提出的DADBJ构造实现了预期的双阶段受力特性,第一阶段由RFH提供节点的力学性能,第二阶段由RFH和SBRSP共同提供节点的力学性能;DADBJ的损伤集中于芯板,通过更换SBRSP芯板对节点快速修复,节点的性能可恢复到初始状态;SBRSP的预设缝隙宽度可直接决定DADBJ第二阶段的启动位移;提出的DADBJ双阶屈服荷载理论公式和二阶启动位移理论公式精确度好。该研究可为装配式框架结构和多阶受力型结构的设计和研究提供参考。

空间机器人关节高转速下摩擦行为试验研究

针对典型基于谐波减速器的空间机器人关节,研究其在高低温真空环境下高速正驱和反驱摩擦行为。关节采用XBS-60-120双圆弧齿形谐波减速器,柔性轴承及齿面采用DLC+LW-YZ-5空间润滑脂,试验温度覆盖-40℃至+120℃,电机端转速提高至2520 r/min。试验结果表明:正驱模式下,关节内部摩擦阻力矩随温度的逐渐降低而显著增加,且输出端载荷越大,摩擦阻力越大,但效率提升也较为明显。输出端速度越高,摩擦力矩越大,效率呈下降趋势;反驱模式下,关节摩擦阻力同样随温度的降低而显著增加,且相同输出端载荷和转速情况下,反驱模式的传动效率显著低于正驱模式。

新型外包钢板-自攻螺钉连接胶合竹梁柱节点转动性能

针对胶合竹材不易预开槽和预开孔以及节点转动时竹材易发生横纹劈裂的问题,研究了新型外包钢板-自攻螺钉连接节点的转动性能。对T形外包钢板-自攻螺钉连接节点和双L形外包钢板-自攻螺钉连接节点共5个试件进行了单调加载试验,分析了节点的破坏模式、初始刚度、极限承载力、变形能力和延性系数。试验发现,T形外包钢板-自攻螺钉连接节点相较双L形外包钢板-自攻螺钉连接节点,各项受力性能参数均较优。布置直径小但数量多的自攻螺钉时,节点(T8×8-M)的破坏表现为钢板和自攻螺钉的受拉断裂以及与胶合竹柱连接的自攻螺钉受拉断裂,布置直径较大但数量少的自攻螺钉时,节点(T6×10-M)的破坏则表现为竹材的横纹劈裂和自攻螺钉的剪切破坏。横纹方向采用自攻螺丝加强,可改善节点的受力性能,对T形外包钢板-自攻螺钉连接节点改善更明显。现行《工程竹结构设计标准》(T/CECS 1101—2022)提供的节点设计方法偏于安全地预测胶合竹自攻螺钉连接梁柱节点的抗弯承载力。

Effects of shore-normal coastal structure on medium-to long-term embayed shoreline evolution

Based on high-tide shoreline data extracted from 87 Landsat satellite images from 1986 to 2019 as well as using the linear regression rate and performing a Mann-Kendall(M–K)trend test,this study analyzes the linear characteristics and nonlinear behavior of the medium-to long-term shoreline evolution of Jinghai Bay,eastern Guangdong Province.In particular,shoreline rotation caused by a shore-normal coastal structure is emphasized.The results show that the overall shoreline evolution over the past 30 years is characterized by erosion on the southwest beach,with an average erosion rate of 3.1 m/a,and significant accretion on the northeast beach,with an average accretion rate of 5.6 m/a.Results of the M–K trend test indicate that significant shoreline changes occurred in early 2006,which can be attributed to shore-normal engineering.Prior to that engineering construction,the shorelines are slightly eroded,where the average erosion rate is 0.7 m/a.However,after shore-normal engineering is performed,the shoreline is characterized by significant erosion(3.2 m/a)on the southwest beach and significant accretion(8.5 m/a)on the northeast beach,thus indicating that the shore-normal engineering at the updrift headland contributes to clockwise shoreline rotation.Further analysis shows that the clockwise shoreline rotation is promoted not only by longshore sediment transport processes from southwest to northeast,but also by cross-shore sediment transport processes.These findings are crucial for beach erosion risk management,coastal disaster zoning,regional sediment budget assessments,and further observations and predictions of beach morphodynamics.

双幅整体转体跨铁路刚构桥主墩设计方案比选

广西滨海公路长坜桥主桥为2×79 m连续刚构桥,桥宽39.4 m,主梁为双幅单箱三室箱梁,左、右幅箱梁共用一个箱式双肢薄壁墩,墩高5.22 m。该桥采用先平行铁路双幅整体支架现浇后转体跨越铁路的施工方法,转体重量3.6万吨,球铰直径6.0 m。根据桥墩较矮、桥宽较宽、转体T构悬臂较大、转体吨位大、上承台受力较大的构造和结构受力特点,提出双肢薄壁墩、墙式墩、箱形空心墩3种主墩方案,从构造、结构受力、抗推刚度等方面进行综合比选。结果表明:双肢薄壁墩抗弯刚度大,可提高大悬臂转体施工状态下的结构安全性,对梁体主墩处的负弯矩起削峰作用;其抗推刚度小,可降低墩梁刚度比,改善梁体和桥墩的受力,故选择双肢薄壁墩方案。为进一步减小上承台厚度,解决矮墩身、分幅梁体、中心转铰带来的墩身受力问题,在常规整体式双肢薄壁墩的墩顶设置预应力混凝土系梁,形成箱式双肢薄壁墩。经计算,相较于整体式双肢薄壁墩,箱式双肢薄壁墩能有效减小上承台厚度,且能极大地降低主墩和上承台的应力,使结构受力更优,因此该桥最终采用箱式双肢薄壁墩方案。