Steady motion and spiral patterns in typhoon

By using the equations describing typhoons in the atmosphere, the steady three-dimensional stream fieldand the corresponding pressure and temperature fields are obtained. The three-dimensional velocity fields construct anonlinear autonomuos system in the physical space. It is shown that the center of typhoon is a local minimum pressurewith positive vertical vorticity and horizontal convergence in lower levels and a local maximum pressure with negativevertical vorticity and horizontal divergence in the upper levels. Because there exits two saddle-focus points in the autnomous system, there exist the spiral patterns, in which the winds blow spirally in and out of the center in the lowerand upper levels in the Northern Hemisphere and cause the ascending motion near the center and dascending motionnear the edge, respectively . All these are in fair conformity with the observations. It implies that the rotation of earthand the viscosity of air play an important role in the spiral structure of typhoons.

Evolution of spiral wave and pattern formation in a vortical polarized electric field

In this paper, the evolution of the pattern transition induced by the vortical electric field （VEF） is investigated. Firstly, a scheme is suggested to generate the VEF by changing the spatial magnetic field. Secondly, the VEF is imposed on the whole medium, and the evolutions of the spiral wave and the spatiotemporal chaos are investigated by using the numerical simulation. The result confirms that the drift and the breakup of the spiral wave and the new net-like pattern are observed when different polarized fields are imposed on the whole medium respectively. Finally, the pattern transition induced by the polarized field is discussed theoretically.

2D spiral pattern recognition based on neural network covering algorithm

The main aim for a 2D spiral recognition algorithm is to learn to discriminate between data distributed on two distinct strands in the x-y plane.This problem is of critical importance since it incorporates temporal characteristics often found in real-time applications.Previous work with this benchmark has witnessed poor results with statistical methods such as discriminant analysis and tedious procedures for better results with neural networks.This paper presents a max-density covering learning algorithm based on constructive neural networks which is efficient in terms of the recognition rate and the speed of recognition.The results show that it is possible to solve the spiral problem instantaneously(up to 100% correct classification on the test set).

Experimental Research on Gas-Liquid Two-Phase Spiral Flow in Horizontal Pipe

In view of the importance of gas-liquid two-phase spiral flow and the few research reports at home and abroad,the gas-liquid two-phase spiral flow patterns have been researched in a horizontal pipe with different parameters investigated by means of observation and a high-speed camera.Since the appearance of spiral flow makes the distribution of twophase flow more complicated,the flow patterns appearing in the experiments were divided into the Spiral Wavy Stratified Flow(SWS),the Spiral Bubble Flow(SB),the Spiral Slug Flow(SS),the Spiral Linear Flow(SL),the Spiral Axial Flow(SA),and the Spiral Dispersed Flow(SD) by the observations and with reference to the predecessors' research achievements.A flow pattern map has been drawn up.The influence of velocity,vane angle and vane area on flow pattern conversion boundary and pressure drop has been studied,with a solid foundation laid for the future research work.

Applying a global pulse disturbance to eliminate spiral waves in models of cardiac muscle

Removal of spiral waves in cardiac muscle is necessary because of their threat to life.Common methods for this removal are to apply a local disturbance to the media,such as a periodic forcing.However,most of these methods accelerate the beating of the cardiac muscle,resulting in the aggravation of the ventricular tachycardia,which directly threatens life.In the present study,in order to clear off spiral waves,a global pulse-disturbance is applied to the media based on three models of cardiac muscle.It is found that the spiral waves are eliminated and the frequency of the cardiac muscle is decreased in a short time,and finally,the state of the medium reaches the normal oscillation,which supports a target waves.Our method sheds light on the removal of spiral waves in cardiac muscle and can prevent the ventricular tachycardia as well as the ventricular fibrillation.

Stabilizing Spiral and Spatiotemporal Chaos in External Centric Field

In this paper, a scheme of spatial perturbation is introduced into a class of excitable media, which are described by two-dimensional partial-differential equation models. Inertial acentric force （or centrlpetal force）, which is generated by circumgyrating the whole system vs. a right axis, is used to disturb the system. The whole system becomes homogeneous as soon as the spatial perturbation is imposed on even when the noise is in consideration. The principle of this scheme is confirmed based on the theory of hopf bifurcation and numerical simulation.

Slow Quasi-Periodic Curves and Spiral Cracks in Chalcogenide Glass Thin Films

In the paper,thin films(1.5÷2.5μm thick)of As2S3 and As2Se3 chalcogenide glasses were investigated.The propagation of slow curves cracks in real time was observed,as well as circular Hertz cracks,the growth of which is an increase in the diameter of the crack in time.All crack patterns known in the literature were observed.Research shows the spiral crack is a consequence of the superposition of the Hertz crack and the straight crack.The principle of coordination of stress relieving during the formation of patterns is formulated.Authors have done a lot of research work.And authors have drawn some meaningful conclusions.

Numerical and experimental study on the falling film flow characteristics with the effect of co-current gas flow in hydrogen liquefaction process

Liquid hydrogen storage and transportation is an effective method for large-scale transportation and utilization of hydrogen energy. Revealing the flow mechanism of cryogenic working fluid is the key to optimize heat exchanger structure and hydrogen liquefaction process(LH2). The methods of cryogenic visualization experiment, theoretical analysis and numerical simulation are conducted to study the falling film flow characteristics with the effect of co-current gas flow in LH2spiral wound heat exchanger.The results show that the flow rate of mixed refrigerant has a great influence on liquid film spreading process, falling film flow pattern and heat transfer performance. The liquid film of LH2mixed refrigerant with column flow pattern can not uniformly and completely cover the tube wall surface. As liquid flow rate increases, the falling film flow pattern evolves into sheet-column flow and sheet flow, and liquid film completely covers the surface of tube wall. With the increase of shear effect of gas-phase mixed refrigerant in the same direction, the liquid film gradually becomes unstable, and the flow pattern eventually evolves into a mist flow.

弧齿锥齿轮TCA接触印痕与传动误差协同求解方法研究

弧齿锥齿轮齿面接触分析(Tooth contact analysis,TCA)可以精确计算得到反映传动性能的重要评价指标接触印痕以及传递误差。然而由于存在强烈的非线性和数值耦合关系,导致求解精度差、效率低和稳定性差。因此,提出了一种同时考虑接触印痕与传动误差的TCA协同求解新方法。首先基于啮合原理进行齿面参数化表达,同时在三维坐标空间中利用旋转矩阵模拟齿轮副的啮合运动进行接触轨迹和传递误差求解;再根据数值齿面的曲率特征,进行接触印痕精确解析求解。算例结果验证了本文所提方法的可行性。

考虑安装误差的弧齿锥齿轮凹凸齿面印痕修正

弧齿锥齿轮作为重型燃气轮机中关键的动力传动部件,其双向传动的运行特点对齿轮凹凸齿面的接触印痕提出了更高的质量要求。为了满足实际需求,通过建立齿面啮合模型,利用考虑安装误差的齿轮接触分析(error tooth contact analysis, ETCA)技术研究了一对弧齿锥齿轮凹面和凸面均为工作面时,接触印痕随安装误差变化的数值规律。同时,以齿面印痕的中点位置、长轴倾角和面积作为印痕参数化处理后的特征值,优化齿轮安装误差调整值,修正印痕的不合理之处,实现凹凸齿面印痕的一致性和重叠性。滚检实验验证了模拟印痕的准确性,该修正规律可以为弧齿锥齿轮副的安装调整提供理论依据。

中华传统纹饰回形纹的嬗变研究

回形纹是中华民族共有共享的精神文化符号,蕴含着中华民族共有的美好生活诉求。文章在前人对回形纹的研究基础上,结合不同阶段的社会背景探究回形纹发展历程,揭示了不同历史时期思想、审美、文化、民族交流和经贸等因素对回形纹发展的影响,总结出回形纹在中华民族历史中所蕴含的文化基因。

基于图像处理技术的太阳神鸟图几何结构分析

为揭示并破译太阳神鸟金箔图案可能存在的历史与文化内涵,利用图像处理技术对图案的几何结构进行定量研究和分析。首先,利用最小二乘法结合等角螺旋的数学表达式对图案内层弧形旋转芒纹进行拟合。其次,在猜想图案几何结构的基础上得到重构图形,利用弦点距离累积技术检测出图案所涉内、外两组角点,通过计算内、外圈角点到中心的径向距离相对于重构图形中两内切圆半径的误差平均值,定量验证相关猜想的合理性。实验结果显示:太阳神鸟图案内层的弧形旋转芒纹对应等角螺旋结构,内、外圈角点到中心的径向距离相对于重构图形中两内切圆半径的误差平均值都在5.3%以内,证明了图案与古代历法的关联性。

A flat-foldable equiangular spiral folding pattern inspired by sunflowers for deployable structures

Flasher origami pattern has been widely utilized to improve the stowage efficiency of deployable structures.Nevertheless,flasher origami cannot be folded fully flat,and they still have great potential for optimization in terms of storage volume and folding creases.In this paper,a flat foldable equiangular spiral folding pattern inspired by the sunflower disk is introduced.Then,a parametric design method for this equiangular spiral crease diagram is introduced in detail.Subsequently,a kinematic model of the equiangular spiral folding pattern is established based on the kinematic equivalence between rigid origami and spherical linkages.A simulation of the developed model demonstrates that the equiangular spiral folding pattern can be folded flat.Using the folded ratio as an evaluation index,the calculated results and experiments show that the equiangular spiral crease pattern can yield fewer creases and improve stowage efficiency in comparison to flasher origami pattern.Equiangular spiral folding pattern can save a considerable amount of space and provide a new approach to spatially deployable structures.

航空弧齿锥齿轮接触印痕主动设计与试验验证

以某航空发动机弧齿锥齿轮箱为研究对象,提出了一套锥齿轮接触印痕主动设计的方法。首先,基于弧齿锥齿轮宏观参数和GEMS软件,进行齿面设计,得到齿轮副精确齿面;其次,考虑传动系统受载变形、轴承游隙和加工误差等因素的影响,建立弧齿锥齿轮系统级接触印痕仿真分析模型,得到锥齿轮在工作状态下的接触印痕和振动响应;然后,将上述设计齿面应用于加工,设计试验,将试验得到的接触印痕和振动响应分析结果与理论分析进行对比,验证了仿真分析模型的可靠性;最后,基于该仿真分析模型对上述齿面进行接触印痕优化设计,得到了满足强度和动态性能要求的齿面,形成了弧齿锥齿轮接触印痕主动设计方法。

第3代新型低碳高合金钢弧齿锥齿轮失效分析

在中央传动调试试验中发生主动弧齿锥齿轮轮齿断裂故障,并连带其他部件产生不同程度损伤。主动弧齿锥齿轮整个圆周的接触印痕偏向小端一侧、靠近齿底,从动弧齿锥齿轮接触印痕分布在小端齿顶部位,印痕已不完整、局部超出工作面。为了排除15Cr14Co12Mo5Ni2钢弧齿锥齿轮试验中发生的断裂故障,对齿轮进行宏观检查、断口分析、组织检查、硬度测试、成分分析、啮合印痕仿真分析与验证,确定了故障齿轮断裂的性质和产生原因。结果表明:主动弧齿锥齿轮为高周疲劳断裂,疲劳起源于小端面与齿凸面根部转接棱角部位,与材质与冶金缺陷无关;在工作过程中存在异常咬合是导致该齿轮产生早期疲劳开裂的主要原因。建议优化齿面加工参数,提高齿轮工作过程中的咬合质量,从而避免此类故障再次发生。

井筒内气液两相流流型对气测数据影响规律的实验分析

气测录井技术是目前钻探现场快速、准确判断油气层的重要方法之一,但气测数据受影响因素众多,导致气测录井数据的准确性有所降低。现阶段已有很多针对气测数据影响因素的研究,但鲜有井筒内气液两相流流型变化对气测数据影响的研究。为此,专门设计了一种利用螺旋管代替直管的气测实验装置,并验证了该实验装置的可行性;然后,基于Fluent软件建立了与气测实验装置相同参数的螺旋管数值模型,并据此模型给出了气测实验中各流型(泡状流、弹状流、段塞流、环状流和雾状流)的产生条件;最后,基于气测实验装置及各流型产生条件,开展了气液两相流流型变化对气测影响的实验。结果表明(:1)全烃检测值随流型变化(泡状流→弹状流→段塞流→环状流→雾状流)而增大,且不同流型转变引起的全烃检测值变化仍有较大差异(;2)不同流型下全烃检测值均随钻井液密度增大而减小,且钻井液密度对气测数据的影响程度随流型变化而降低(;3)不同流型下全烃检测值均随钻井液粘度增大而先增大后减小,且钻井液粘度对气测数据的影响灵敏度随流型变化而降低。通过研究气液两相流流型对气测数据的影响,进一步提高了气测录井数据的校正精度。

基于改进ResNet-18模型的弧齿锥齿轮安装位置偏差分类识别方法研究

针对现有的弧齿锥齿轮安装位置偏差分类识别效率低的问题,使用改进的ResNet-18神经网络构建轻量级弧齿锥齿轮安装位置偏差分类识别模型,改进的网络修改了ResNet-18网络第一卷积层,并引入了通道与空间注意力机制。实验结果表明,改进ResNet-18较原网络对于齿面接触印痕图像的分类准确率提高了3.23%,损失值降低了0.04。该方法为齿轮安装偏差识别提供了新路径,对弧齿锥齿轮总成的安装调整作业提供了一定的指导。

介质阻挡流光放电中的螺旋波与靶波

采用双水电极实验装置,对大气压氩气介质阻挡放电中的靶波与螺旋波斑图进行了观察测量.实验发现靶波与螺旋波可以互相转变,且有2种不同的转变路径:靶波→单臂螺旋波→靶波→单臂螺旋波;靶波→单臂螺旋波→双臂螺旋波→靶波.

弧齿锥齿轮的齿面主动设计

齿面印痕和传动误差对齿轮传动的性能起着决定作用,针对齿面印痕和传动误差,提出弧齿锥齿轮点啮合齿面主动设计的方法。该方法突破了传统齿轮设计的局限性,采用'局部共轭原理'和'局部综合法',并依据弧齿锥齿轮的加工原理,使齿轮设计人员能够按照要求的传动性能来设计齿面的形状,并可在摇台结构的铣齿机进行加工。齿面主动设计能保证齿面在整个啮合过程中满足预先设计的传动误差和齿面接触路径的要求,从而达到对齿面啮合质量的全程控制,它为弧齿锥齿轮副设计提供新的方法和途径,这对于高速和重载齿轮以及有特殊要求的齿轮的设计具有十分重要的意义。

基于齿面印痕控制的弧齿锥齿轮公差优化设计

应用基于特征变动的三维公差建模理论和传递矩阵累积方法,建立了系统综合安装误差与弧齿锥齿轮4个当量错位量的关系。给出了考虑安装误差的齿面接触分析算法,并对齿面印痕数字化特征完成了定义。以齿面啮合印痕相对于安装误差的敏感度为优化目标函数,在满足传动性能要求和成本限制的情况下,应用遗传算法对零部件精度进行优化。以弧齿锥齿轮为例,通过对优化前后啮合印痕、传动误差的比较,验证了该公差优化方法的可行性。