Numerical modelling of resonance mechanisms in jointed rocks using transfer functions

Resonance effects in parallel jointed rocks subject to stress waves are investigated using transfer functions,derived from signals generated through numerical modelling.Resonance is important for a range of engineering situations as it identifies the frequency of waves which will be favourably transmitted.Two different numerical methods are used for this study,adopting the finite difference method and the combined discrete element-finite difference method.The numerical models are validated by replicating results from previous studies.The two methods are found to behave similarly and show the same resonance effects;one operating at low frequency and the other operating at relatively high frequency.These resonance effects are interpreted in terms of simple physical systems and analytical equations are derived to predict the resonant frequencies of complex rock masses.Low frequency resonance is shown to be generated by a system synonymous with masses between springs,described as spring resonance,with an equal number of resonant frequencies as the number of blocks.High frequency resonance is generated through superposition of multiple reflected waves developing standing waves within intact blocks,described as superposition resonance.While resonance through superposition has previously been identified,resonance based on masses between springs has not been previously identified in jointed rocks.The findings of this study have implications for future analysis of multiple jointed rock masses,showing that a wave travelling through such materials can induce other modes of propagation of waves,i.e.spring resonance.

Joint transfer of time and frequency signals and multi-point synchronization via fiber network

A system of jointly transferring time signals with a rate of 1 pulse per second （PPS） and frequency signals of 10 MHz via a dense wavelength division multiplex-based （DWDM） fiber is demonstrated in this paper. The noises of the fiber links are suppressed and compensated for by a controlled fiber delay line. A method of calibrating and characterizing time is described. The 1PPS is synchronized by feed-forward calibrating the fiber delays precisely. The system is experimen- tally examined via a 110 km spooled fiber in laboratory. The frequency stabilities of the user end with compensation are 1.8x 10-14 at 1 s and 2.0x 10-17 at 104 s average time. The calculated uncertainty of time synchronization is 13.1 ps, whereas the direct measurement of the uncertainty is 12 ps. Next, the frequency and 1PPS are transferred via a metropoli- tan area optical fiber network from one central site to two remote sites with distances of 14 km and 110 km. The frequency stabilities of 14 km link reach 3.0x 10-14 averaged in 1 s and 1.4x 10-17 in 104 s respectively; and the stabilities of 110 km link are 8.3 x 10-14 and 1.7 x 10-17, respectively. The accuracies of synchronization are estimated to be 12.3 ps for the 14 km link and 13.1 ps for the 110 km link, respectively.

Is the Equity Transfer Agreement of a Chinese-Foreign Contractual Joint Venture Valid? A Case Comment on Xianyuan v.Zhongxin

Under Chinese law, when parties have signed an equity transfer agreement of the Chinese-Foreign contractual joint venture, they need to report to the examination and approval authority for approval. However, due to imperfection of and conflicts among laws and regulations as well as misunderstanding of the above system, it is always difficult for judges to determine the validity of such equity transfer agreement under the administrative approval system. Among the three categories of FIEs provided in Chinese law 1, scholars have had a comprehensive discussion over equity transfer agreement involving Sino-Foreign Equity Joint Venture Enterprises, but this case is concerned with the equity transfer agreement of a Chinese-Foreign contractual joint venture. In this case, the People's Supreme Court holds that the equity transfer agreement that has not undergone the approval procedures are not valid but not void. Furthermore, the parties that are bound to submit the agreement to the approval authority shall perform their duties of this kind.

Study on Relationship Between Arc Behavior and Joint Forming in Cold Metal Transfer Welding Technology with Polarity⁃Exchanging

Cold metal transfer with polarity⁃exchanging is a new integrated welding technology based on MIG.Due to the alternation of the positive and negative polarities of the wire,favorable control upon the deposition rate and the welding shape coefficient was obtained in order to meet the desired joint design,and the related controlling principles and joint characteristics were reported.Droplet transfer physical behavior exhibited strong dependability on the studied welding parameters,such as welding voltage,welding current,wire feeding speed,and polarity⁃exchanging.This welding technology provides a new way for the welding of body⁃in⁃white(BIW)thin sheet with special demands.Moreover,the typical quality defects of MIG were greatly improved.Our study provides important technical information from the perspective of industrial application of MIG and sheds light on the higher application level of MIG in BIW welding.

Extradural contralateral S1 nerve root transfer for spastic lower limb paralysis

The current study aims to ascertain the anatomical feasibility of transferring the contralateral S1 ventral root(VR)to the ipsilateral L5 VR for treating unilateral spastic lower limb paralysis.Six formalin-fixed(three males and three females)cadavers were used.The VR of the contralateral S1 was transferred to the VR of the ipsilateral L5.The sural nerve was selected as a bridge between the donor and recipient nerve.The number of axons,the cross-sectional areas and the pertinent distances between the donor and recipient nerves were measured.The extradural S1 VR and L5 VR could be separated based on anatomical markers of the dorsal root ganglion.The gross distance between the S1 nerve root and L5 nerve root was 31.31(±3.23)mm in the six cadavers,while that on the diffusion tensor imaging was 47.51(±3.23)mm in 60 patients without spinal diseases,and both distances were seperately greater than that between the outlet of S1 from the spinal cord and the ganglion.The numbers of axons in the S1 VRs and L5 VRs were 13414.20(±2890.30)and 10613.20(±2135.58),respectively.The cross-sectional areas of the S1 VR and L5 VR were 1.68(±0.26)mm2 and 1.08(±0.26)mm2,respectively.In conclusion,transfer of the contralateral S1 VR to the ipsilateral L5 VR may be an anatomically feasible treatment option for unilateral spastic lower limb paralysis.

论注册资本认缴制的兴利除弊:兼论期限利益与交易安全的动态平衡

肇端于2005年《公司法》的注册资本认缴制改革具有正当性与合理性。认缴制的核心是创设了股东延期实缴出资的期限利益,尊重与保护期限利益是一般原则,出资义务加速到期是例外规则。股东期限利益的得丧变更均不妨碍股权的自由转让。认缴制未根本否定资本制度,一旦公司丧失偿债能力,期限利益立即终止,出资义务加速到来。公司不能清偿到期债务的识别标准是执行失败主义,出资加速到期不以股东或公司存在主观过错为要件。有必要建立股东加速出资信息公示制度与敦促债权人及时申报债权的公示催告程序,以确保债权人平等保护。不少判例追究股东恶意转让未实缴出资股权时对公司债权人的赔偿责任,建议以2023年新修订的《中华人民共和国公司法》为基础,完善平衡对冲制度,兼顾公司资本信用与股权流转自由,细化股权转让链条中出资义务加速到期的责任在前后手之间的配置规则。信息披露、5年最长实缴出资期限与出资加速到期连带之债的良性互动,有助于遏制注册资本认缴制的道德风险外溢。

钢管输电塔挂线节点足尺模型失效模式与承载力提升分析

针对特高压钢管输电塔挂线位置节点在极端荷载下的安全性,提出了挂线节点双侧挂线板协同受力的构造改进措施,并对比研究两种挂线节点的极限承载力与失效模式。通过足尺挂线节点处的承载力试验与有限元分析,比较挂线节点在单侧板受力、双侧板受力情况下的应力分布与承载能力,分析传力螺母与挂线板之间的合理初始间距。结果表明:双侧受力时两侧挂线板均发生弯曲破坏,受力形式更加合理,节点板应力分布更加均匀,挂线点的屈服承载力可以提升一倍以上,传力螺母与挂线板之间的合理初始间隙为2~4 mm。

基于联合深度统计特征对齐的鱼类目标识别方法

水下鱼类目标识别技术是认识海洋、经略海洋、向海图强的重要技术之一.基于深度学习的水下目标识别技术已成为研究热点,但是针对水下鱼类数据小样本甚至零样本识别性能亟待提高.本文基于迁移学习,提出了联合深度统计特征对齐(Joint Deep Statistical Feature Alignment, JDSFA)方法,解决小样本下的鱼类目标识别问题.以ResNet-50作为骨干网络,将均方和协方差纳入权重选择算法用来构建自适应损失函数,对齐源域和目标域之间的特征分布,联合源域损失与领域间的自适应损失,设计全局损失函数,建立深度学习识别模型,实现鱼类目标识别任务.利用公开的水下鱼类数据集QUT进行实验验证,相比目前代表性的DADAN、PMTrans、DSAN方法,JDSFA方法的鱼类识别性能分别提升了3.59%、4.96%、5.91%,结果表明了本文JDSFA方法的有效性,并对鱼类目标识别具有良好的应用价值.

大跨度公铁合建斜拉桥钢混板-桁组合梁关键节点空间受力特性

针对大跨度公铁合建斜拉桥—主跨808 m洪奇沥特大桥新型钢混板-桁组合梁的关键节点—辅助墩顶钢混节点,采用ANSYS软件建立钢桁-混凝土板组合梁部分节段细化的全桥多尺度有限元模型,分析边跨组合梁节点在受力最不利工况下的受力规律及传力特性,并讨论下弦杆等杆件截面等结构参数变化对节点受力、传力的影响规律。结果表明:最不利组合工况下,边跨组合梁辅助墩顶钢混节点处钢结构最不利Mises应力为265.9 MPa,混凝土局部最大名义拉应力为9.2 MPa,导致局部开裂而受力转移至钢结构;在辅助墩顶局部负弯矩影响下,内外节点板处应力总体呈“倒V”形分布,混凝土顶面及底面分别呈“鞍形”及“倒鞍”形分布;节点处下弦杆(含管内混凝土)、竖杆分别传递77.86%和40.15%荷载,为纵向、竖向主要传力构件;混凝土桥面厚度变化对自身应力影响明显,其厚度和下弦杆截面面积对纵向传力比影响大,竖杆截面面积对自身竖向传力影响相对明显;混凝土厚度及下弦杆、斜腹杆、竖杆截面为节点受力、传力的主要影响因素,其系数在0.8~1.1时,组合梁关键节点各构件应力及传力比均较为合理。

模块化公交系统车辆单元动态编组方案优化

为研究基于模块化公交系统的车辆单元路段运行动态编组方案优化问题,首先,构建车辆单元方向分配与位置调整的两阶段联合优化模型。第1阶段,构建以乘客换乘次数最少为目标的整数线性规划模型,实现车辆单元最佳方向分配与增补车辆单元数计算;第2阶段,构建以位置调整时间最小和车内换乘时间最小的双目标混合整数非线性规划模型,实现车辆单元动态编组方案优化。其次,构建模型的求解算法,利用CPLEX求解器求解第1阶段车辆单元分配模型,设计非支配排序遗传算法(NSGA-Ⅱ)求解第2阶段车辆编队位置调整模型。最后,算例验证构建模型及求解算法的有效性,并定量探究不同车辆单元容量下的车辆单元动态编组效率与公交载客率变化。算例结果表明:在模块化公交车辆单元容量一定增幅内,模块化公交车辆单元动态编组效率会随着车辆单元容量的增加而提高;而车辆单元容量增幅太大,不仅不会提高动态编组效率,反而会降低车辆编队的载客率,造成模块化公交车辆编队运力过剩。

双智能反射面辅助的上行链路通信调度分析

本文旨在研究一种基于双智能反射面(Intelligent Reflecting Surface,IRS)辅助的上行链路多用户通信方案,以提高用户的信息传输速率。研究提出了一种合作式被动波束成形技术,作为新型的IRS反射波束成形技术。与传统的被动波束成形技术不同的是,合作式被动波束成形技术允许不同的IRS之间进行协作,能够进一步提高系统性能。通过联合优化基站(Base Station,BS)处的接收波束成形和两个分布式IRS(分别部署在BS和用户附近)处的合作式反射波束成形,本研究能够最大化用户的信息传输速率。仿真实验的结果展示了基于双IRS辅助的多用户调度通信系统在最大化信息传输速率方面的显著优势。此外,本文量化比较了我们的方案与现有类似方案的性能改进。仿真结果表明,相较于现有方案,本系统在提高信息传输速率方面有显著的性能提升。特别是在用户数量较大时,双IRS合作系统可以更好地克服路径损耗和多路径干扰,进一步提高系统的性能表现。本研究的创新点总结如下:1)提出了合作式被动波束成形技术作为一种新型的IRS反射波束成形技术,具有重要的理论和实用价值;2)通过联合优化基站处的接收波束成形和两个分布式IRS处的合作式反射波束成形,实现了多用户通信系统的性能最大化;3)在仿真实验中展示了基于双IRS辅助的多用户调度通信系统在最大化信息传输速率方面的显著优越性。本研究不仅为IRS辅助通信技术的推广提供了有益的参考,也为未来智能无线通信系统的发展提供了重要的支持。同时,也为IRS辅助用户调度技术的发展提供了新的思路和方法。

从整体到局部优化的文本风格迁移模型

提出一种从整体到局部优化的风格迁移(global-local based style transfer,G-LST)模型.首先,利用广泛的源端数据进行迭代优化来自动构建高质量的伪平行数据,并通过联合训练来提升模型对整体风格的语义感知;随后,利用常识性知识修正词级的细粒度风格来增强局部风格的表现,同时兼顾整体与局部风格,提高风格转换的准确度.基于GYAFC数据集的实验结果表明,相较于目前表现最佳的文本风格迁移模型,G-LST模型在E&M与F&R两个领域数据上的风格转换准确率分别提高了2.70%和4.47%,内容保留与风格准确率的综合指标分别提升了1.18%和1.95%.

基于机液联合仿真模型的闸门启闭机故障注入及诊断研究

为了对含故障特征的弧形闸门系统运行信号进行评估和故障诊断研究,基于某弧形闸门试验平台检测数据,建立弧形闸门启闭机构的机液联合仿真模型,进行模型相似度分析和修正。通过基于闸门实时开度反馈信号闸门状态控制策略对闸门进行工作状态的控制,提高了仿真效率和稳定性,获得更符合实际的状态特征。在模型中注入液压系统与机械系统故障,分析故障对闸门运行信号产生的影响。为了充分体现故障特征信息,选取多个信号进行融合并调整权重分配,基于加权多通道数据融合方法解决了故障识别精度波动大的问题,为了提高网络模型的泛化能力,在网络模型中加入残差结构进行优化,基于迁移学习的卷积神经网络解决了故障识别精度低的问题。结果表明,构建的模型可以表现出弧形闸门工作过程中重要信号比如压力、流量、振动等信号特征的动态变化;使用改进后的加权多通道数据融合的基于残差结构优化的神经网络准确率达到了97.17%。

钢塔-组合塔混合结构结合部承载性能试验研究

针对新型钢塔-组合塔混合结构结合部构造,开展了局部缩尺模型轴压试验,并建立了非线性有限元模型与试验结果进行比较。研究了钢塔-组合塔结合部的极限承载力以及破坏形式,探究了钢板应变分布规律和焊钉受力分布规律,并对传力路径和荷载分担比例进行了变参数分析。研究结果表明:新型钢塔-组合塔混合结构结合部的承载力符合设计要求;结合部的破坏形式表现为承压板下方钢壁板达到屈服并发生鼓曲变形;承压板为结合部的核心传力构件,增大板厚可以提高结合部承载力以及承压板所传递的荷载,其厚度宜与外壁钢板厚度相近;焊钉和开孔板连接件是保证结合部钢和混凝土共同受力的关键构造,在钢壁板屈服前以受竖向剪力为主,在钢壁板屈服后以受拉拔力为主。

结合深度强化学习与变形五次多项式的搬运机器人关节轨迹规划

针对在生产节拍固定的情况下搬运机器人各关节的运动轨迹及时间分配问题,构建基于深度强化学习与变形五次多项式相结合的搬运机器人关节轨迹时间分配模型;设计以节拍要求、速度约束和加速度约束为目标的奖励函数,搭建神经网络,利用MATLAB/Simulink软件,得到满足生产节拍和运动学约束的时间序列,并利用单臂四自由度搬运机器人仿真实验,验证所构建模型的可行性和有效性。结果表明:单臂四自由度搬运机器人各关节的运行时间均为5.89 s,其中平移关节1、 3的最大速度分别为2 597.84、 1 697.97 mm/s,最大加速度分别为19 532.11、 31 302.61 mm/s^(2);旋转关节2、 4的速度大小相等且方向相反,最大角速度均为137.53 (°)/s,最大角加速度均为1 180.51 (°)/s^(2),均未超过运动学约束;所构建的模型可以解决在指定生产节拍下搬运机器人关节轨迹时间分配问题,实现搬运机器人搬运过程中各关节的运动均衡,改善搬运机器人运行的稳定性和有效性。

基于跨语言迁移学习及联合训练的泰语语音合成

随着深度学习和神经网络的快速发展,基于深度神经网络的端到端语音合成系统因性能优异成为主流。然而近年来,泰语语音合成相关研究还不充分,主要原因是大规模泰语数据集稀缺且该语言拼写方式有其特殊性。为此,在低资源前提下基于FastSpeech2声学模型和StyleMelGAN声码器研究泰语语音合成。针对基线系统中存在的问题,提出了3个改进方法以进一步提高泰语合成语音的质量。(1)在泰语语言专家指导下,结合泰语语言学相关知识设计泰语G2P模型,旨在处理泰语文本中存在的特殊拼写方式;(2)根据所设计的泰语G2P模型转换的国际音标表示的音素,选择拥有相似音素输入单元且数据集丰富的语言进行跨语言迁移学习来解决泰语训练数据不足的问题;(3)采用FastSpeech2和StyleMelGAN声码器联合训练的方法解决声学特征失配的问题。为了验证所提方法的有效性,从注意力对齐图、客观评测MCD和主观评测MOS评分3方面进行测评。实验结果表明,使用所提泰语G2P模型可以获得更好的对齐效果进而得到更准确的音素持续时间,采用“所提泰语G2P模型+联合训练+迁移学习”方法的系统可以获得最好的语音合成质量,合成语音的MCD和MOS评分分别为7.43±0.82分和4.53分,明显优于基线系统的9.47±0.54分和1.14分。

Intelligent Reflecting Surface Assisted Transmission Optimization Strategies in Wireless Networks

Wireless Power Transfer(WPT)technology can provide real-time power for many terminal devices in Internet of Things(IoT)through millimeterWave(mmWave)to support applications with large capacity and low latency.Although the intelligent reflecting surface(IRS)can be adopted to create effective virtual links to address the mmWave blockage problem,the conventional solutions only adopt IRS in the downlink from the Base Station(BS)to the users to enhance the received signal strength.In practice,the reflection of IRS is also applicable to the uplink to improve the spectral efficiency.It is a challenging to jointly optimize IRS beamforming and system resource allocation for wireless energy acquisition and information transmission.In this paper,we first design a Low-Energy Adaptive Clustering Hierarchy(LEACH)clustering protocol for clustering and data collection.Then,the problem of maximizing the minimum system spectral efficiency is constructed by jointly optimizing the transmit power of sensor devices,the uplink and downlink transmission times,the active beamforming at the BS,and the IRS dynamic beamforming.To solve this non-convex optimization problem,we propose an alternating optimization(AO)-based joint solution algorithm.Simulation results show that the use of IRS dynamic beamforming can significantly improve the spectral efficiency of the system,and ensure the reliability of equipment communication and the sustainability of energy supply under NLOS link.

基于联合特征分布匹配的跨项目缺陷预测

为解决跨项目软件缺陷预测研究中存在的特征不完备和分类边界模糊问题,提出一种基于联合特征的双编码器分布匹配方法(DeDM-JF)。利用卷积神经网络提取代码中与缺陷有关的结构语义特征,将其与人为选取的Handcrafted特征结合,形成联合特征;在此基础上,构建包含分布差异匹配层的双自编码器,学习跨项目全局和局部可迁移特征用于训练缺陷预测模型。面向软件缺陷数据仓库中的798对跨项目缺陷预测任务开展实验,与相关的跨项目缺陷预测方法比较,DeDM-JF方法预测的F-measure和MCC指标有明显提升。

道基不均匀分布下通用机型轮载对机场道面力学性能影响研究

为研究道基水平方向不均匀分布对机场道面板力学性能的影响,建立飞机荷载-道面结构-不均匀道基三维模型,采用数值模拟方法分析多板协同受力模式下基顶反应模量变化对道面板弯拉应力影响,探讨通用机型(空客A320和波音B737-800)轮载作用时基顶反应模量变化和道面板厚度对道面板力学性能以及接缝传荷系数的影响,同时基于缩尺试验对数值模拟结果进行验证。研究结果表明:对于A320机型,当道基水平不均匀分布时混凝土板弯拉应力增大,基顶反应模量变化率由0%增加至65.46%时,轮载作用于传力杆接缝板边时道面板弯拉应力由4.06 MPa增加至5.73 MPa,超过极限弯拉应力;增加板厚能够有效地提升刚性道面板受力安全时基顶反应模量变化率的取值范围;道面板接缝传荷系数随着基顶反应模量变化率的增加而增大,基顶反应模量变化率从6.84%增加至56.30%时,道面板传荷系数增加2.44%;室内缩尺试验验证了道基不均匀分布对传荷系数的影响规律。在道面板设计时,应充分考虑道基水平方向不均匀分布对道面板力学性能的影响,避免在服役期间过早出现结构破坏。

管片接缝对地铁振动源强影响现场测试研究

地铁振动源强的选取是开展环境振动评估的核心环节。目前,地铁盾构隧道普遍采用管片拼接方式,在进行振动源强测试时存在跨越管片接缝和不跨管片接缝2种情况,文章通过现场行车测试和锤击试验,研究管片接缝对振动源强的影响效果和振动传递特征。结果表明:对于最大Z振级评价,全天车次最大Z振级差值统计结果的平均值为0.77 dB,最大值为2.22 dB;对于典型工况分频最大振级评价,Z计权前分频最大振级在200 Hz频率处,测点1和测点2的差值为3.44 dB,Z计权后分频最大振级在50 Hz频率处,测点1和测点2的差值为0.45 dB;管片接缝在141~346 Hz和410~502 Hz频率段具有振动减小作用。相关研究可为地铁振动源强测点选择提供参考。