Degradation Mechanism of Polyimide Film Under Square Impulse Voltages

Partial discharge (PD) under a sequence of high-repetition-rate square pulses is one of the key factors leading to premature failure of insulation systems of inverter-fed motors. Polyimide (PI) film is an important type of insulating material used in the inverter-fed motors. In this paper, micro-morphology and structure change of PI film aged by bipolar continuous square impulse voltage (BCSIV) with ampli- tude above partial discharge inception voltage (PDIV) are investigated by scanning electron microscope (SEM). The chemical bonds of PI chain are analyzed through Fourier transform infrared spectroscopy (FTIR). The results show that the degradation mechanism of PI film is the fracturing of chemical bonds caused by the erosion from PDs. Three layers are displayed in both 100 HN film and 100 CR film. The de- gradation path of PI film is initiated from surface and then gradually extends to the interior with continuous aging. Nano-fillers can retard the degradation of PI film and prolong its lifetime.

A preliminary study of the mechanism of compound hearing loss caused by ototoxic drugs combined with impulse noise

Background:Hearing loss(HL)is becoming increasingly common and is more commonly caused by noise,ototoxic substances,or a combination of ototoxic factors.However,so far,few studies have examined the mechanism by which compound factors cause HL.The only relevant study is about occupational ototoxic substances combined with environmental noise at 85-110 dB SPL.In this study,to address the shortcomings of existing research,we innovatively focused on HL induced by loud noise(impulse noise,>160 dB SPL)combined with common ototoxic drugs.The aim of this study was to establish and validate a mature animal model,and then to compare the characteristics of audiology,pathomorphology and molecular features,and to preliminarily predict pathogenesis in compound HL.Materials and Methods:We selected guinea pigs to construct in vivo HL model groups for different extents of exposure,including a blank control group,a single-drug group,a single-impulse noise group,and a compound group.The animal model of the mature compound HL group was established using gentamicin combined with impulse noise.We then performed audio-logical and pathological verification.We analyzed the auditory brainstem response(ABR),pathological morphology of the cochlea,and molecules(including important self-radicals,cytokines,and apoptosis signal trans-duction pathway proteins in the pathogenesis of drug-and noise-induced HL),compared the effect of different extents of exposure on HL,and preliminarily predict the pathogenic mechanism of compound HL.Results:Four groups of animal models were established successfully and verified by audiology and pathology.Regarding audiology,there were no sig-nificant differences in the ABR thresholds before exposure(p>0.05),but differences emerged among the groups after exposure.Notably,after 3,7,and 14 days of exposure,there were significant differences in the ABR thresholds between the compound group and both the drug and noise groups(p<0.01),and after 14 days,the HL of the compound group was much more severe(greater than the linear sum of single-factor HL group).Regarding the patho-morphology,compared with the control group,the cochleae were damaged to different degrees in the factor exposure groups.The drug group had the least severe HL,the noise group had serious HL(p<0.05),and the compound group had the most severe HL(p<0.01).The compound group's damage was greater than the linear sum of the single-factor group in many ways,such as the loss and damage of hair cells and cilia,disturbed morphology and arrangement of hair cells,protein metabolism,cell function,and structural defects on the epidermal plate(p<0.01).From a molecular perspective,the trend was similar to pathology and audiology,and the synergistic effect of ototoxic drugs and impulse noise significantly increased cytokine levels(IL-6,ICAM-1,8-OHDG,IL-1,and TNF-α),free radicals Malondialdehyde([MDA],▪OH,LPO,O•2ˉ),and the apoptosis signal transduction pathway protein.There were significant differences between the compound group and single-factor groups(p<0.05).Conclusion:Gentamicin,impulse noise,and compound factors were used to induce HL in animal models,which were verified by audiology and pathology,laying a foundation for future studies.After constructing the animal models,we found that 50 mg/kg of gentamicin for 10 days was a subinjury dose,and 50�impulse noise caused partial HL,but the two factors combined had a significant synergistic ototoxicity effect,which increased the level of oxidative stress and the waterfall response of inflammatory cytokines in the cochleae and enhanced the expression of apoptosis-related proteins,resulting in syn-ergistic pathomorphological and audiological injury.We preliminarily analyzed the pathogenic mechanism of compound HL,establishing the basis for further study of the mechanism,prevention,and treatment of this increasing global problem.

Spatial Pattern of Chinese Tourism Development and Its Mechanism Based on Different Spatial-temporal Scales:Taking the Panel Data of China Mainland(1996-2010) for Example

By taking the panel data of China mainland from 1996 to 2010 for an example, this paper used ESDA, gravity center and standard deviation ellipse to analyze the spatial differences, combined with the impulse response function to propose the infl uence mechanism of spatial evolution. The results showed that the provincial tourism economy generally showed a random spatial distribution and the spatial differences had narrowed from 1996 to 2010. The differences of tourism development in east China are the largest, and differences of the middle China are the smallest. The gravity center of Chinese provincial tourism has shifted to the northwest, the HH district concentrated in the Yangtze River Delta and its surroundings, the LL district concentrated in west Chinese. The high-value areas of city tourism economy are broadly distributed in the right of line "Heihe–Tengchong", mainly concentrated in four plates. Compared with spatial differences of provincial tourism economy, those of city tourism economy were more signifi cant. Regional tourism resources and social economic factors are the two major factors that infl uence spatial differences of tourism economy, the objective rule and policy and institution also have a great impact on regional tourism development differences. Special events may have a certain impact on the pattern of the original; however, it cannot change the spatial pattern completely.

Dynamical behavior and optimal impulse control analysis of a stochastic rumor spreading model

The Internet era has brought great convenience to our life and communication.Meanwhile,it also makes a bunch of rumors propagate faster and causes even more harm to human life.Therefore,it is necessary to perform effective control mechanisms to minimize the negative social impact from rumors.Thereout,firstly,we formulate a rumor spreading model considering psychological factors and thinking time,then,we add white noise(i.e.,stochastic interference)and two pulse control strategies which denote education mechanism and refutation mechanism into the model.Secondly,we obtain the global positive solutions and demonstrate the global exponential stability of the unique positive periodic rumor-free solution.Thirdly,we discuss the extinction and persistence of rumor.Moreover,we use Pontriagin’s minimum principle to explore the optimal impulse control.Finally,several numerical simulations are carried out to verify the effectiveness and availability of the theoretical analysis.We conclude that the pulse control strategies have a great influence on controlling rumor spreading,and different control strategies should be adopted under different transmission scenarios.

A Device that can Produce Net Impulse Using Rotating Masses

This paper describes a device capable of producing net impulse, through two synchronized masses, which move along a figure-eight-shaped orbit. In addition to the detailed description of the mechanical components of this device, particular attention is paid to the theoretical treatment of the innovative principle on which the device is based. In more details, the mechanical system consists of two independent but simultaneous rotations, the former being related to the formation of the figure-eight-shaped path and the latter to an additional spinning. Based on the parametric equations of motion of the lumped masses, and considering semi-static tensile deformation of the connecting rods carrying them, it was found that the resultant impulse towards the direction of the spin vector includes a non-vanishing term that is linearly proportional to the time. In addition, reduced but encouraging experimental results are reported. These findings sustain the capability of the proposed mechanism to achieve propulsion.

A Review of Research on Catastrophic Formation and Evolutionary Mechanism of Deep High Stress Rock Mass under Impact Loading

With the exploitation of resources expanded to deep, the geological environment which is “three tenors one disturbance” of rock mass in great depth has been more complex, resulting in some new engineering geological disasters, such as rock burst, pressure bumping, large deformation of surrounding rock, brittle-ductile transition of rock and zonal disintegration of rock mass, which occur frequently in deep underground engineering rock mass. The impact load caused by collision, explosion, extrusion and outburst is the root cause of the dynamic instability of the deep rock mass. What should be emphasized is that high in-situ stress and blasting excavation disturbance complicate disaster developing mechanism of deep underground engineering rock mass and sharply increase the difficulty of controlling disaster. This paper is aimed at the research status and development trend, of which dynamic characteristics of deep high stress rock mass and its damage and failure effect each other under impact, and conduct analysis, in the later stage where I would discuss how to carry out the response law of the deep high-stress rock mass under the impact load and the mechanism of catastrophe developing, which is of great significance to build a model of instability and fracture evolution about deep rock mass under shock disturbance and to maintain its safety and stability.

脉冲控制下基于合作机制的多智能体系统分组一致性研究

针对在脉冲控制下非线性多智能体系统的分组一致性协同控制问题,本文基于复杂系统中智能体间的合作机制,提出了一种新颖的具有领导-跟随网络的分组一致性控制协议.该协议控制智能体仅在脉冲时刻接收来自邻居节点的信息并更新自己的状态,减少智能体因持续接收邻居信息更新自己状态而造成的网络开销.针对不同组之间智能体的信息交互,该协议具有防止组间干扰的机制,降低了不同组之间的通信干扰,提高系统鲁棒性.此外,本文还介绍了一种适用于非线性系统的方案,增强协议的适应性.基于实现分组一致性条件,构建了多智能体系统的动力学模型,并进行了协议的详细设计和理论推导.最后,通过仿真验证了协议的正确性和有效性.

表面涂覆提升氧化铝材料的冲压机械强度

为了有效提升氧化铝材料的冲压机械强度,通过表面涂覆的方式对该材料的孔道结构进行改性。利用DL-3型强度测试仪测试发现,表面涂覆氯化铝的氧化铝样品在100~1100℃的温度范围内焙烧后,冲压机械强度从35 MPa提升至51 MPa,表面涂覆铝基络合的氧化铝样品在相同条件下,冲压机械强度从21 MPa提升至46 MPa,相比较而言,无表面涂覆的氧化铝样品在相同条件下,冲压机械强度从17 MPa提升至39 MPa。结合扫描电镜和X射线衍射等表征发现:氯化铝和铝基络合物的表面涂覆对氧化铝材料晶体类型影响较小,但是能够有效填充氧化铝材料的基体孔道,增加载体的密实程度,进而有效提升氧化铝材料的冲压机械强度。另外,相对于表面涂覆铝基络合物的氧化铝样品,表面涂覆氯化铝的氧化铝材料经过高温焙烧后比表面积更大、孔径更小、孔径分布也更为集中。更为重要的是:表面涂覆氯化铝的氧化铝样品,经过高温焙烧后表面会形成利于稳定活性金属的粗糙形貌。

机械脉冲力脊椎矫正对腰椎间盘突出症患者主观疼痛、腰部活动度及躯干肌力的影响

目的 对比机械脉冲力脊椎矫正与物理因子治疗对机械性腰痛腰椎间盘突出症(LDH)患者主观疼痛、腰部活动度及躯干肌力的影响。方法 选取118例机械性腰痛LDH患者作为研究对象,分为对照组、观察组,每组各59例。对照组给予物理因子治疗,观察组给予机械脉冲力脊椎矫正治疗,比较2组临床疗效、疼痛程度视觉模拟评分法(VAS)、功能障碍(RDQ)评分、腰部活动度及躯干肌力。结果 观察组总有效率为93.22%,对照组为76.27%;治疗后观察组VAS、RDQ评分低于对照组(P<0.05);治疗后观察组屈曲、伸展、左侧屈度及右侧屈度均高于对照组(P<0.05);治疗后观察组屈肌、伸肌及旋转肌力优于对照组(P<0.05)。结论 机械脉冲力脊椎矫正较物理因子治疗机械性腰痛LDH疗效更佳,可帮助患者缓解疼痛,改善功能障碍,提高腰部活动度及躯干肌力。

Influence of air pressure on mechanical effect of laser plasma shock wave

The influence of air pressure on mechanical effect of laser plasma shock wave in a vacuum chamber produced by a Nd：YAG laser has been studied. The laser pulses with pulse width of 10ns and pulse energy of about 320mJ at 1.06μm wavelength is focused on the aluminium target mounted on a ballistic pendulum, and the air pressure in the chamber changes from 2.8 × 10^ 3 to 1.01 × 10^5pa. The experimental results show that the impulse coupling coefficient changes as the air pressure and the distance of the target from focus change. The mechanical effects of the plasma shock wave on the target are analysed at different distances from focus and the air pressure.

Bifurcation analysis of the logistic map via two periodic impulsive forces

The complex dynamics of the logistic map via two periodic impulsive forces is investigated in this paper. The influ- ences of the system parameter and the impulsive forces on the dynamics of the system are studied respectively. With the parameter varying, the system produces the phenomenon such as periodic solutions, chaotic solutions, and chaotic crisis. Furthermore, the system can evolve to chaos by a cascading of period-doubling bifurcations. The Poincar6 map of the logistic map via two periodic impulsive forces is constructed and its bifurcation is analyzed. Finally, the Floquet theory is extended to explore the bifurcation mechanism for the periodic solutions of this non-smooth map.

负压条件下球形爆炸容器内乳化炸药冲击波参数研究

为了探究负压条件下乳化炸药冲击波参数,在4m直径可调真空度球形爆炸容器内,开展不同负压和不同药量条件下的乳化炸药内爆实验,获得冲击波的超压时程曲线,重新拟合了乳化炸药在不同负压环境下的峰值超压公式和正压冲量公式。结果表明,乳化炸药质量每减少50g,峰值超压平均下降27%;环境压力每降低20kPa,峰值超压平均下降8.66%;乳化炸药在不同负压环境下的正压冲量约为单质炸药的81.3%;负压条件下的乳化炸药峰值超压和正压冲量实验值与传统经验公式相比误差均大于10%,而基于常压实验值拟合的公式与不同工况下的实验值误差均小于4%,能够精确预测不同负压环境下乳化炸药的冲击波参数。

圆柱壳结构水下爆炸冲击波毁伤的吸收冲量准则

为了准确评估水下爆炸冲击波对圆柱壳结构造成的破坏程度,考虑了冲击波与目标耦合过程中的冲量传递效率因素,给出了球面冲击波作用下圆柱壳吸收冲量的积分计算方法,并提出用其作为圆柱壳结构的毁伤准则威力参量。为了避免工程计算困难的问题,进一步给出了无需积分计算的近似简化算法。借助相关文献数据,对比分析了准则的准确度与适用性。结果表明,相对于冲击波峰压准则、比冲量准则以及能流密度准则,吸收冲量准则可以更准确地对比圆柱壳目标在不同工况下的毁伤效果,与圆柱壳结构毁伤程度具有更强的相关性,均方误差比其他准则降低76%以上;吸收冲量准则的简化计算方法可以准确逼近积分方法的结果,以文中工况为例,相对误差均在0.9%以内。所提出的毁伤准则具有良好的准确度和适用性,为准确评估水下爆炸冲击波对圆柱壳结构的毁伤效果提供了新的支撑。

装药埋深对地表空气冲击波影响的试验研究

为研究土壤中装药埋深对地表空气冲击波传播规律的影响,开展了5kg TNT的触地爆炸试验以及埋深分别为0.108、0.228、0.85m的爆炸试验,获得了多个比例距离处的冲击波峰值压力、冲量以及正压作用时间数据,分析了埋深对冲击波传播特性的影响。结果表明,冲击波峰值压力和冲量随着埋深的增加而减小,随着爆距的增大而减小;触地爆炸比例距离为4的测点处其峰值压力是比例距离为1处的3.24%,埋深为0.108m的爆炸试验比例距离为4处的测点其峰值压力是比例距离为1处的25.02%;埋深为0.108m时,比例距离为1处的峰值压力和冲量分别是触地爆炸对应值的8.7%和20.4%;并对两种工况的正压作用时间进行了分析,触地爆炸的正压作用时间随爆心距增加呈指数增加,埋深为0.85m的爆炸试验其正压作用时间呈对数增加。通过对试验数据的进一步分析,建立了冲击波峰值压力、冲量与埋深、比例距离的工程计算模型,可用于浅埋爆炸时弹药威力评价与毁伤效能预估。

35型齿轮长环形齿条抽油机传动机构力学分析

针对目前电潜泵深井开采存在作业周期短、能耗高等问题,以适用于深井开采的一种新型35型抽油机为研究对象,对其齿轮-长环形齿条传动机构进行了力学分析。建立了传动机构换向过程的力学模型,获得了换向过程中齿轮长环形齿条的受力变化规律;采用Adams对抽油机运行过程进行了动力学仿真,研究了传动机构及多组滚轮在抽油机整个运行过程中的动力学特性,并分析了动力对抽油机运行状态的影响。结果表明,换向过程中传动机构受力随齿轮位置发生变化;上下冲程过程中长环形齿条受力大小和方向不同;齿条箱存在绕自身x轴、y轴、z轴翻转的状况;气平衡配重7 t为抽油机最优配重。研究结果可为该抽油机零部件的进一步改进优化提供理论参考。

硅掺杂无氢非晶碳膜的HiPIMS/DCMS共沉积制备及其高温摩擦学性能

采用高功率脉冲磁控溅射(HiPIMS)和直流磁控溅射(DCMS)共沉积技术制备了不同硅原子含量的无氢Si-DLC薄膜,利用高温摩擦试验机对比考察了不同Si原子含量的Si-DLC(硅掺杂类金刚石)薄膜在25~500℃下的摩擦学性能,并通过Raman及XPS等测试方法分析了Si原子含量对薄膜微观结构的影响以及摩擦前后薄膜化学组成和结构变化.探讨了Si-DLC在高温下的摩擦磨损机理.结果表明:Si-DLC薄膜呈现出致密的非晶结构.随着Si原子含量的增加,薄膜中sp3-C的含量增加.掺入的Si形成C-Si-O与C-Si-C键.Si-C键的形成使薄膜的内应力降低,薄膜的膜基结合力增加.摩擦测试表明:室温下,转移膜的形成有助于降低Si-DLC薄膜的摩擦系数.高温下,Si-C键增加了薄膜的高温稳定性,摩擦区域部分Si-C键氧化为Si-O-C键,使薄膜的摩擦系数与磨损率同时降低.

非高斯脉冲干扰下MIMO系统频谱智能感知方法

智能频谱感知是未来电磁频谱管控的关键支撑技术.针对现有多输入多输出系统(multiple-input mulitiple-output,MIMO)频谱感知方法提取特征能力有限,且无法适应非高斯脉冲干扰等问题,提出一种基于注意力机制的协作频谱智能感知方法.通过引入非线性变换器抑制非高斯脉冲干扰,并利用广义协方差矩阵表征MIMO信号统计特性,将其作为后续网络的输入.基于Transformer模型构建特征提取网络,通过其自注意力机制挖掘不同的深层特征.采用随机样本对网络进行训练,并利用网络输出特征向量设计二元假设检验方法实现MIMO系统的频谱智能感知.仿真结果表明,所提方法在高斯噪声和非高斯脉冲干扰下可以有效实现MIMO系统频谱感知,且在低信干比条件下具有较高的感知性能.

髌股关节疼痛对老年人楼梯行走时髌股关节力学特征的影响

目的:观察髌股关节疼痛(PFP)对老年人楼梯行走时髌股关节力学特征的影响,为PFP老年人制定合理的干预治疗策略提供理论支撑。方法:随机招募健康老年人和PFP老年人各22名,采用Qualisys红外动作捕捉系统和AMTI三维测力台同步采集两组受试者楼梯行走时的运动学和动力学数据,利用髌股关节接触力及冲量、髌股关节应力及冲量对老年人楼梯行走时的髌股关节力学特征进行量化评定。结果:与健康组相比,PFP组在上楼梯时表现出较小的髌股关节接触力冲量(P=0.030)、髌股关节应力(P=0.024)及冲量(P=0.004),在下楼梯时表现出较大的屈膝角度峰值(P=0.022)及较小的髌股关节应力冲量(P=0.067),其余指标未见显著性差异(P>0.05)。结论:PFP老年人在楼梯行走尤其是上楼梯过程中表现出较小的髌股关节力学特征,这可能是PFP老年人为提供足够的下肢支撑能力、降低髌股关节负荷而主动采取的自我保护策略。建议:PFP老年人注重下肢肌肉尤其是股四头肌的锻炼,同时采用更灵敏的髌股关节接触力冲量及应力冲量评价楼梯行走时的髌股关节负荷。

考虑结构变化的架空地线雷击机械损伤建模与分析

针对铝包钢地线遭受雷击后发生损伤乃至断股、断线的机理,国内外已开展多项针对雷击造成地线热烧蚀损伤的研究,但地线的损伤是热烧蚀损伤和机械损伤共同作用的结果,因此有必要对地线在雷击过程中的机械损伤进行分析。首先根据实际雷击地线的物理过程,利用COMSOL软件搭建一个考虑结构动态演变的地线机械损伤评估模型,该模型可以实现地线在雷击过程中存在的结构演变的模拟;接着利用试验数据验证该模型的准确性;最后使用该模型,对地线在各种参数的脉冲分量、持续分量作用下的机械损伤进行计算并评估其损伤结果,确定机械力对地线雷击损伤的影响。研究结果表明:相比于脉冲分量作用阶段,在持续分量作用下,机械力会对地线造成更加明显的损伤;雷击过程中冲击力和电磁力不会对地线造成损伤,但是热应力和轴向拉力的存在会明显加剧地线的损伤,因此在进行地线在雷击作用下的损伤分析时,机械力的作用不可忽略。