Characterization of alpine meadow surface crack and its correlation with root-soil properties

Quantifying surface cracks in alpine meadows is a prerequisite and a key aspect in the study of grassland crack development.Crack characterization indices are crucial for the quantitative characterization of complex cracks,serving as vital factors in assessing the degree of cracking and the development morphology.So far,research on evaluating the degree of grassland degradation through crack characterization indices is rare,especially the quantitative analysis of the development of surface cracks in alpine meadows is relatively scarce.Therefore,based on the phenomenon of surface cracking during the degradation of alpine meadows in some regions of the Qinghai-Tibet Plateau,we selected the alpine meadow in the Huangcheng Mongolian Township,Menyuan Hui Autonomous County,Qinghai Province,China as the study area,used unmanned aerial vehicle(UAV)sensing technology to acquire low-altitude images of alpine meadow surface cracks at different degrees of degradation(light,medium,and heavy degradation),and analyzed the representative metrics characterizing the degree of crack development by interpreting the crack length,length density,branch angle,and burrow(rat hole)distribution density and combining them with in situ crack width and depth measurements.Finally,the correlations between the crack characterization indices and the soil and root parameters of sample plots at different degrees of degradation in the study area were analyzed using the grey relation analysis.The results revealed that with the increase of degradation,the physical and chemical properties of soil and the mechanical properties of root-soil composite changed significantly,the vegetation coverage reduced,and the root system aggregated in the surface layer of alpine meadow.As the degree of degradation increased,the fracture morphology developed from"linear"to"dendritic",and eventually to a complex and irregular"polygonal"pattern.The crack length,width,depth,and length density were identified as the crack characterization indices via analysis of variance.The results of grey relation analysis also revealed that the crack length,width,depth,and length density were all highly correlated with root length density,and as the degradation of alpine meadows intensified,the underground biomass increased dramatically,forming a dense layer of grass felt,which has a significant impact on the formation and expansion of cracks.

基于超椭球T-S故障树的储气库注采井可靠性分析

为克服传统故障树在系统可靠性分析中的局限性,提出将超椭球T-S故障树分析法引入到储气库注采井可靠性分析中。首先,应用证据理论获得底事件发生故障的证据区间,以解决统计数据缺乏的问题,并将此证据区间作为故障树分析的输入数据;其次,利用超椭球模型对证据区间加以约束,以解决计算结果相对保守的问题;再次,建立基于超椭球T-S故障树的仿真流程,并以某T-S故障树实例对仿真结果进行验证;最后,运用仿真流程对储气库注采井进行可靠性分析。结果表明:注采井发生半故障的失效概率区间是[5.2501×10^(-4),5.3125×10^(-4)],其失效等级为二级,即注采井发生半故障的事故描述是很少发生,注采井完全故障的失效概率区间是[2.1109×10^(-3),2.1361×10^(-3)],其失效等级为三级,即注采井发生完全故障的事故描述是偶尔发生;重要度分析表明当注采井处于半故障状态时,应优先关注盐岩蠕变过量、管材不耐蚀、注采气频繁等底事件;当其处于全故障状态时,应优先检修套管密封面泄漏、注采气频繁、水泥环密封泄漏等底事件。

Optimization of short-circuit transition parameters of Q235B steel GMAW based on orthogonal gray relational analysis

In gas metal arc welding(GMAW)process,the short-circuit transition was the most typical transition observed in molten metal droplets.This paper used orthogonal tests to explore the coupling effect law of welding process parameters on the quality of weld forming under short-circuit transition,the design of 3 factors and 3 levels of a total of 9 groups of orthogonal tests,welding current,welding voltage,welding speed as input parameters:effective area ratio,humps,actual linear power density,aspect ratio,Vickers hardness as output paramet-ers(response targets).Using range analysis and trend charts,we can visually depict the relationship between input parameters and a single output parameter,ultimately determining the optimal process parameters that impact the single output index.Then combined with gray the-ory to transform the three response targets into a single gray relational grade(GRG)for analysis,the optimal combination of the weld mor-phology parameters as follows:welding current 100 A,welding voltage 25 V,welding speed 30 cm/min.Finally,validation experiments were conducted,and the results showed that the error between the gray relational grade and the predicted value was 2.74%.It was observed that the effective area ratio of the response target significantly improved,validating the reliability of the orthogonal gray relational method.

Central Asia’s Foreign Relations:A Comparison Between the Soviet and Post-Soviet Era

Central Asia’s pivotal geographical position allowed it to play an essential role in relations among nations of Eurasia in the Middle Ages,as the bridge between China and Europe.Yet,during the Russian and then the Soviet rule on Central Asia,the region’s republics had no independent position in international community as foreign relations were formed and managed by central government in Moscow.The collapse of the Union of Soviet in 1991 made salient the geopolitical,economic,and cultural importance of the five former Soviet Central Asian republics.Accordingly,the republics reemerged as independent actors in the global interstate system and could play a role in international affairs during the last three decades.This paper aims to compare Central Asia’s foreign relations in the Soviet and Post-Soviet era.

车辆主动悬架自适应变论域T-S模糊控制研究

针对传统变论域模糊控制存在过度依赖专家经验、伸缩因子参数不能自适应调整的问题,提出一种车辆主动悬架自适应变论域T-S模糊控制策略,从而提高车辆的行驶平顺性。结合神经网络和T-S模糊推理建立基于自适应神经模糊推理的一阶T-S模糊控制器,利用神经网络的自学习特性产生完善的模糊规则,进而在传统函数型伸缩因子的基础上,将系统误差和误差变化率作为动态参数引入伸缩因子中,实现伸缩因子参数的自适应调整,解决了传统函数型伸缩因子因参数确定难度大导致控制效果差的问题。通过随机工况下的仿真分析和基于相似理论的缩尺实验,对所提出算法的有效性和工况自适应性进行了验证。结果表明,所提出的自适应变论域T-S模糊控制策略具有较强的工况适应性,在不同车速、路面激励下均可有效提高车辆的平顺性并保证轮胎接地安全性。

基于T-S模糊故障树的驱动电机冷却系统可靠性分析

车用驱动电机液压冷却系统存在故障机理不确定等问题。本文应用模糊数描述其故障概率和故障程度,建立驱动电机冷却系统的T-S模糊故障树模型,计算系统模糊可能性,分析各部件的概率重要度和关键重要度,找出影响系统可靠性的关键部件。

基于T-S模糊故障树与贝叶斯网络的作业风险评估

针对传统故障树分析法存在一定局限性的问题,提出一种基于T-S模糊故障树与贝叶斯网络的作业风险评估方法。构建工程作业风险评估T-S模糊故障树模型,引人四边形隶属函数表征底事件风险概率和风险程度;根据底事件与中间事件、中间事件与顶事件之间的逻辑关系确定T-S模糊门规则;然后,根据T-S模糊故障树模型向有向无环图转换规则建立贝叶斯网络模型,根据T-S模糊门规则确定节点之间的条件概率关系。最后,以安排导弹战备值班为例进行了作业风险评估分析。仿真结果表明:T-S模糊故障树计算结果与贝叶斯网络正向推理一致,验证了评估方法的准确性与合理性;诊断推理确定了顶事件发生严重风险、一般风险情况下各底事件出现相应风险的概率大小,从而为确定风险隐患优先排查对象和重点排查对象提供决策参考。

混合差分和多种群粒子群算法的T-S模糊模型辨识

为提高T-S模型的辨识精度,针对基本粒子群优化(particle swarm optimization,PSO)算法T-S模型全局优化辨识问题,提出混合差分和多种群粒子群算法的T-S模糊模型辨识方法,将T-S模型前件参数和后件参数整体编码进行全局优化辨识.为避免基本粒子群的早熟收敛和后期收敛速度慢的缺陷对T-S模型辨识精度和速度的影响,算法将种群分为若干个子群,每个子群根据粒子适应度值自适应调整惯性权重,平衡了算法的开发和探索能力,对子群最优粒子,进行差分操作以增强算法的全局搜索能力,采用全局最优粒子替代随机子群的最优粒子以加强子群间的信息交流,维持粒子多样性.典型非线性系统和混沌系统的仿真结果表明,采用混合差分和多种群粒子群算法辨识的T-S模型具有更高的辨识精度.

基于T-S模糊逻辑的混合储能孤岛直流微电网功率分配控制

在含混合储能的直流微电网中,传统阻容下垂控制无法解决由线路电阻和负荷功率波动导致的系统功率分配失衡问题。为此,提出一种基于Takagi-Sugeno(T-S)模糊逻辑的自适应阻容下垂控制方法以实现混合储能的分频分配。根据蓄电池和超级电容的物理特性,建立单个蓄电池支路输出电压、蓄电池组间输出功率差额和阻性下垂系数之间的T-S模糊逻辑关系,以及单个超级电容支路输出功率及其变化率、超级电容组间功率差额和容性下垂系数之间的T-S模糊逻辑关系,并由此构建基于T-S模糊逻辑的阻容下垂控制器。推导含混合储能的直流微电网中各部分的平均阻抗模型,并采用阻抗比分析法对微电网的小信号稳定性进行研究。MATLAB/Simulink仿真结果表明,基于T-S模糊逻辑的阻容下垂控制可保证在线路电阻和负荷功率波动情况下系统功率的合理分配。

基于J2EE的O/R(Object-Relation)映射方案研究

对象模型和关系模型是两种完全不同的模式,在开发中如何实现对象到关系的映射是一个关键的问题,分析了对象关系映射不匹配的各个方面,以及当前的各种持久化解决方案,并重点分析了透明对象关系映射的特点,最后对如何实现对象关系映射的关键技术进行了研究。

Tunable dispersion relations manipulated by strain in skyrmion-based magnonic crystals

We theoretically investigate the propagation characteristics of spin waves in skyrmion-based magnonic crystals. It is found that the dispersion relation can be manipulated by strains through magneto-elastic coupling. Especially, the allowed bands and forbidden bands in dispersion relations shift to higher frequency with strain changing from compressive to tensile,while shifting to lower frequency with strain changing from tensile to compressive. We also confirm that the spin wave with specific frequency can pass the magnonic crystal or be blocked by tuning the strains. The result provides an advanced platform for studying the tunable skyrmion-based spin wave devices.

基于T-S模糊故障树和剩余寿命的离心泵健康评估方法

针对现有离心泵健康评估方法只考虑单部件,无法客观反映离心泵真实健康状态的问题,提出了一种考虑多部件的基于T-S模糊故障树和剩余寿命的离心泵健康评估方法。首先,对离心泵故障进行了T-S模糊故障树建模,在故障树中用T-S门连接了部件与离心泵,用T-S门规则表征了部件失效概率与离心泵失效概率的影响关系;然后,根据部件的劣化可监测性,采用了基于Wiener过程或Weibull分布的寿命预测方法,根据部件的状态监测数据或历史失效记录,计算了部件的失效概率;最后,根据部件失效概率和T-S门算法,计算了离心泵失效概率和健康因子,得到了离心泵健康状态及其使用和维修建议,并将该健康评估方法应用于离心泵试验台数据集、西安交通大学和SY公司合作开发的(XJTU-SY)数据集。研究结果表明:离心泵试验台中离心泵健康因子为0.789,健康状态为比较健康,该方法综合考虑多部件对离心泵进行状态评估;采用XJTU-SY数据集进行验证可知,相较于基于单部件的健康评估方法,该方法评估健康因子始终低于0.6,且降至0.4的时间明显提前于基于单部件的健康评估方法,评估结果更准确。该方法可为离心泵健康评估方法的改进提供参考。

Relationship of Ambient Humidity with Cardiovascular Diseases:A Prospective Study of 24,510 Adults in a General Population

Objective This study aimed to explore the association between humidity exposure and the risk of cardiovascular disease(CVD),utilizing follow-up data and relative humidity(RH)metric assessments.Methods We extracted the baseline data from the China Hypertension Survey(CHS)of 24,510 enrolled participants aged≥35 years without a history of CVD between 2012 and 2015 and followed them up from 2018 to 2019.The National Meteorological Information Center(NMIC)of the China Meteorological Administration(CMA)provided the quality-controlled relative humidity(RH)datasets.Cox proportional hazards models were used to estimate hazard ratios(HRs)for CVD in relation to RH.Results During the follow-up period(2018-2019),973 patients with CVD were identified.The HR of CVD risk was 1.17(95%CI:1.04-1.31)per 10%increase in summer mean RH.Compared with participants in the 3rd quintile group,those in the 1st and 5th quintiles of RH had a higher risk of CVD.For summer mean RH,the HRs(95%CIs)for the 1st and 5th quintiles were 1.34(1.04-1.71)and 1.44(1.14-1.83),respectively.The relationship(“U”shape)between summer mean RH and the risk of CVD was nonlinear.Stratified analyses indicated that the risk of CVD was substantially influenced by the summer mean RH in female,older individuals,and those in southern China.Conclusion Unsuitable(too high or low)humidity environments affect the risk of CVD.Our study highlights those future policies for adapting to climate change should consider the humidity-CVD relationship.

基于T-S模糊模型的PLZT驱动器的本构建模及伺服驱动控制

针对目前ON-OFF控制策略在PLZT驱动器光致应变位移的闭环伺服控制系统中的缺点,提出了一种基于T-S模糊模型的PLZT驱动器应变位移的动态模型及预测控制方法。首先,建立了PLZT驱动器光致应变位移的T-S模糊模型,该模型利用基于减法聚类的模糊C均值聚类算法进行前件辨识,并利用奇异值分解(singular value decomposition, SVD)算法进行后件辨识,所建立模型的有效性通过拟合度仿真加以验证。随后,在所建立的T-S模糊模型的基础上结合预测控制方法对PLZT驱动器的光致应变位移进行闭环控制,并对该算法进行仿真验证。仿真结果显示,在PLZT驱动器微位移的控制中,该文控制算法减小了基于ON-OFF控制策略下的抖振,且具有更好的控制效果。

Understanding the Relationship Between Shrinking Cities and Land Prices:Spatial Pattern,Effectiveness,and Policy Implications

Urban shrinkage has emerged as a widespread phenomenon globally and has a significant impact on land,particularly in terms of land use and price.This study focuses on 2851 county-level cities in China in 2005–2018(excluding Hong Kong,Macao,Taiwan,and‘no data’areas in Qinhai-Tibet Plateau)as the fundamental units of analysis.By employing nighttime light(NTL)data to identify shrinking cities,the propensity score matching(PSM)model was used to quantitatively examine the impact of shrinking cities on land prices,and evaluate the magnitude of this influence.The findings demonstrate the following:1)there were 613 shrinking cities in China,with moderate shrinkage being the most prevalent and severe shrinkage being the least.2)Regional disparities are evident in the spatial distribution of shrinking cities,especially in areas with diverse terrain.3)The spatial pattern of land price exhibits a significant correlated to the economic and administrative levels.4)Shrinking cities significantly negatively impact on the overall land price(ATT=–0.1241,P<0.05).However,the extent of the effect varies significantly among different spatial regions.This study contributes novel insights into the investigation of land prices and shrinking cities,ultimately serving as a foundation for government efforts to promote the sustainable development of urban areas.

System Reliability Analysis Method Based on T-S FTA and HE-BN

For high-reliability systems in military,aerospace,and railway fields,the challenges of reliability analysis lie in dealing with unclear failure mechanisms,complex fault relationships,lack of fault data,and uncertainty of fault states.To overcome these problems,this paper proposes a reliability analysismethod based on T-S fault tree analysis(T-S FTA)and Hyper-ellipsoidal Bayesian network(HE-BN).The method describes the connection between the various systemfault events by T-S fuzzy gates and translates them into a Bayesian network(BN)model.Combining the advantages of T-S fault tree modeling with the advantages of Bayesian network computation,a reliability modeling method is proposed that can fully reflect the fault characteristics of complex systems.Experts describe the degree of failure of the event in the form of interval numbers.The knowledge and experience of experts are fused with the D-S evidence theory to obtain the initial failure probability interval of the BN root node.Then,the Hyper-ellipsoidal model(HM)constrains the initial failure probability interval and constructs a HE-BN for the system.A reliability analysismethod is proposed to solve the problem of insufficient failure data and uncertainty in the degree of failure.The failure probability of the system is further calculated and the key components that affect the system’s reliability are identified.The proposedmethod accounts for the uncertainty and incompleteness of the failure data in complex multi-state systems and establishes an easily computable reliability model that fully reflects the characteristics of complex faults and accurately identifies system weaknesses.The feasibility and accuracy of the method are further verified by conducting case studies.

Attention-relation network for mobile phone screen defect classification via a few samples

How to use a few defect samples to complete the defect classification is a key challenge in the production of mobile phone screens.An attention-relation network for the mobile phone screen defect classification is proposed in this paper.The architecture of the attention-relation network contains two modules:a feature extract module and a feature metric module.Different from other few-shot models,an attention mechanism is applied to metric learning in our model to measure the distance between features,so as to pay attention to the correlation between features and suppress unwanted information.Besides,we combine dilated convolution and skip connection to extract more feature information for follow-up processing.We validate attention-relation network on the mobile phone screen defect dataset.The experimental results show that the classification accuracy of the attentionrelation network is 0.9486 under the 5-way 1-shot training strategy and 0.9039 under the 5-way 5-shot setting.It achieves the excellent effect of classification for mobile phone screen defects and outperforms with dominant advantages.

基于T-S MPC的车辆自适应巡航控制策略研究

针对于汽车自适应巡航系统面对复杂工况时自适应性不强的问题,提出了一种基于T-S模糊变权重模型预测控制(Takagi-Sugeno fuzzy model predictive control,T-S MPC)的自适应巡航分层控制策略。首先上层控制器基于安全距离模型将自适应巡航系统划分为定速巡航模式、多目标优化控制的跟随模式和紧急制动模式;下层控制器基于车辆逆动力学模型,将上层控制器输出的期望加速度转变为节气门开度或制动压力;其次考虑到权重系数对控制精度的影响,建立基于T-S模糊控制的变权重模型预测控制器;最后搭建Carsim Simulink联合仿真平台,验证控制策略的准确性、适应性和跟踪响应速度。结果表明,在定速巡航工况时,T-S MPC控制方法跟踪响应时间为1.54 s,较PID和传统MPC控制跟踪响应快;在跟随和混合工况时,T-S MPC控制方法均方根误差为分别为0.3073、2.775,均低于PID、PID+LQR和传统MPC控制的均方根误差、并且自适应性好,有效提高了跟车性能与安全性。

基于改进T-S模糊模型的弧焊机器人轨迹实时跟踪

针对弧焊机器人在实际作业中受到诸多不确定因素的影响,导致弧焊机器人焊接轨迹偏离预期轨迹的问题,提出一种基于改进T-S(Takagi-Sugeno)模糊模型的弧焊机器人轨迹实时跟踪方法。采用图像识别技术识别并定位焊缝,通过坐标转换,确定焊缝中心线在机器人坐标系中的位置坐标。利用蚁群算法根据焊缝中心线在机器人坐标系中的坐标,搜索从起始位置到目标位置的最优焊接路径。设计了一种改进区间二型T-S模糊模型,通过视觉传感器实时获取新的焊缝信息,计算轨迹误差,以此为输入,利用改进T-S模糊模型对机器人的运动轨迹进行实时调整。实验结果表明,采用改进T-S模糊模型后,机器人轨迹跟踪离散度均降至1 mm以下,弧焊机器人轨迹与预期轨迹高度重合,比传统方法跟踪离散度大大降低。

TWO PRIVACY-PRESERVING PROTOCOLS FOR POINT-CURVE RELATION

Numerous privacy-preserving issues have emerged along with the fast development of Internet, both in theory and in real-life applications. To settle the privacy-preserving problems, secure multi-party computation is essential and critical. In this paper, we have solved two problems regarding to how to determine the position relation between points and curves without revealing any private information. Two protocols have been proposed in order to solve the problems in different conditions. In addition, some building blocks have been developed, such as scalar product protocol, so that we can take advantage of them to settle the privacy-preserving computational geometry problems which are a kind of special secure multi-party computation problems. Moreover, oblivious transfer and power series expansion serve as significant parts in our protocols. Analyses and proofs have also been given to argue our conclusion.