Causal Analysis Between Rice Growth and Cadmium Accumulation and Transfer under Arbuscular Mycorrhizal Inoculation

Cadmium(Cd)contamination in rice has been a serious threat to human health.To investigate the effects of arbuscular mycorrhizal fungi(AMF)on the Cd translocation in rice,a controlled pot experiment was conducted.The results indicated that AMF significantly increased rice biomass,with an increase of up to 40.0%,particularly in root biomass by up to 68.4%.Notably,the number of prominent rice individuals also increased,and their plasticity was enhanced following AMF inoculation.AMF led to an increase in the net photosynthetic rate and antioxidant enzyme activity of rice.In the AMF treatment group,the Cd concentration in the rice roots was significantly higher(19.1%‒68.0%)compared with that in the control group.Conversely,the Cd concentration in the rice seeds was lower in the AMF treatment group,indicating that AMF facilitated the sequestration of Cd in rice roots and reduced Cd accumulation in the seeds.Path coefficients varied across different treatments,suggesting that AMF inoculation reduced the direct impact of soil Cd concentration on the total Cd accumulation in seeds.The translocation of Cd was consistently associated with simultaneous growth dilution and compensatory accumulation as a result of mycorrhizal effects.Our study quantitatively analyzed this process through path analysis and clarified the causal relationship between rice growth and Cd transfer under the influence of AMF.

Sound Source Localisation for a High-Speed Train and Its Transfer Path to Interior Noise

Noise is one of the key issues in the operation of high-speed railways, with sound source localisation and its transfer path as the two major aspects. This study investigates both the exterior and interior sound source distribution of a high-speed train and presents a method for performing the contribution analysis of airborne sound with regard to the interior noise. First, both exterior and interior sound source locations of the high-speed train are identified through in-situ measurements. Second, the sound source contribution for di erent regions of the train and the relationships between the exterior and interior noises are analysed. Third, a method for conducting the contribution analysis of airborne sound with regard to the interior noise of the high-speed train is described. Lastly, a case study on the sidewall area is carried out, and the contribution of airborne sound to the interior noise of this area is obtained. The results show that, when the high-speed train runs at 310 km/h, dominant exterior sound sources are located in the bogie and pantograph regions, while main interior sound sources are located at the sidewall and roof. The interior noise, the bogie area noise and the sound source at the middle of the coach exhibit very similar rates of increase with increasing train speed. For the selected sidewall area, structure-borne sound dominates in most of the 1/3 octave bands.

Transfer Path Contribution to Floor Vibration of Metro Vehicles Based on Operational Transfer Path Analysis Method

Operational transfer path analysis(OTPA)is an advanced vibration and noise transfer path identification and contribution evaluation method.However,the application of OTPA to rail transit vehicles considers only the excitation amplitude and ignores the influence of the excitation phase.This study considers the influence of the excitation amplitude and phase,and analyzes the contribution of the secondary suspension path to the floor vibration when the metro vehicle runs at 60 km/h,using an analysis based on the OTPA method.The results show that the vertical direction of the anti-rolling torsion bar area provides the maximum contribution to the floor vibration,with a contribution of 22.1%,followed by the longitudinal vibration of the air spring area,with a contribution of 17.1%.Based on the contribution analysis,a transfer path optimization scheme is proposed,which may provide a reference for the optimization of the transfer path of metro vehicles in the future.

Analysis of fluid vibration transfer path and parameter sensitivity of swash plate axial piston pump

Taking swash plate axial piston pump as the research object,the mechanism of fluid vibration and transfer rule are analyzed.The pump shell can be assumed as the ultimate recipient of vibration transmission,the path model and differential equations from the fluid to the shell are established.The parameters of the path model are determined by the simulation software,and the mathematical model is solved by the simulation software.And time/frequency domain analysis of vibration acceleration of shell is presented.Based on the different influence of various parameters in the transfer path model on transfer characteristics and vibrational recipients,the time-varying parameters are studied by using sensitivity analysis theory,and the influence of the structural parameters on the vibration characteristics of vibration subject is quantitatively analyzed.The research in the paper provides theoretical basis for vibration analysis and structure parameter optimization of axial piston pump.

An investigation into high-speed train interior noise with operational transfer path analysis method

Passengers’demands for riding comfort have been getting higher and higher as the high-speed railway develops.Scientific methods to analyze the interior noise of the high-speed train are needed and the operational transfer path analysis(OTPA)method provides a theoretical basis and guidance for the noise control of the train and overcomes the shortcomings of the traditional method,which has high test efficiency and can be carried out during the working state of the targeted machine.The OTPA model is established from the aspects of“path reference point-target point”and“sound source reference point-target point”.As for the mechanism of the noise transmission path,an assumption is made that the direct sound propagation is ignored,and the symmetric sound source and the symmetric path are merged.Using the operational test data and the OTPA method,combined with the results of spherical array sound source identification,the path contribution and sound source contribution of the interior noise are analyzed,respectively,from aspects of the total value and spectrum.The results show that the OTPA conforms to the calculation results of the spherical array sound source identification.At low speed,the contribution of the floor path and the contribution of the bogie sources are dominant.When the speed is greater than 300 km/h,the contribution of the roof path is dominant.Moreover,for the carriage with a pantograph,the lifted pantograph is an obvious source.The noise from the exterior sources of the train transfer into the interior mainly through the form of structural excitation,and the contribution of air excitation is non-significant.Certain analyses of train parts provide guides for the interior noise control.

The Application Analysis of Concurrent Multipath Transfer over Broadband Network

In the network for data transmission using CMT,there are multiple paths to choose,and the time delay of each path is not the same,there is a certain issue packet out-of-order.This article studied and analyzed the packet transmission in the sender,for each path assigned specific packet sequence number,in order to reduce the random sequence problem,improve the efficiency of network transmission.In the network for data transmission using CMT,there are multiple paths to choose,and the time delay of each path is not the same,there is a certain issue packet out-of-order.This article studied and analyzed the packet transmission in the sender,for each path assigned specific packet sequence number,in order to reduce the random sequence problem,improve the efficiency of network transmission.

科技成果转化新路径和新模式的探索:国内外技术转移概念验证中心的建设启示

[研究目的]概念验证是技术转移机构核心职能之一,可弥补早期科技成果与可进行市场化成果之间的空白,提高科技成果转化效率。[研究方法]就概念验证在科技成果转化技术创新链中所处的位置、特点详细阐明,对国内代表性城市概念验证中心建设、发布政策情况开展梳理与研究。[研究结论]在借鉴国外概念验证中心建设的具体举措基础上,针对我国概念验证在科技成果转化链条中的薄弱点与瓶颈制约提出对策建议,以进一步促进科技成果向现实新质生产力转化、让创新成果更快更好落地。

科技论文视域下国际物理学科学中心与转移路径识别研究

综合科技多样化指数、科技专业化指数、社会网络分析法,构建国际物理学科学中心与转移路径识别模型,基于2003-2022年全球物理学领域代表性期刊论文数据,实现国际物理学科学中心及其转移路径识别。研究发现:(1)美国作为国际物理学科学中心具有绝对优势,但多中心格局或将成为大势所趋;(2)德国、英国、法国、瑞士、日本、中国等国家同美国的距离逐渐缩小,构成国际物理学研究的“一超多强”局面;(3)国际物理学科学中心呈现出从由美国向欧洲转移,再由欧洲向亚洲转移的态势。

基于主动激励的掘进机回转台振动抑制研究

悬臂式掘进机截割过程由于煤岩形状、硬度分布的随机性,当截割到硬岩时截割头会产生无规则的剧烈振动,瞬时高强度的冲击对掘进机关键受力部件回转台影响最大,其动态可靠性和寿命影响着截割效率和截割稳定性,为减弱截割过程回转台的振动,首先,基于截割现场回转台易失效损坏现象,建立截割过程回转台力学模型,推导回转台力学方程,研究回转台受力随截割参数变化规律;通过搭建截割试验台,测试截割过程回转台振动响应,结合有限元进行回转台振动模态分析,求解回转台前6阶固有频率及振型,分析回转台剧烈振动的原因。其次,基于工况路径分析理论,建立截割过程回转台工况传递路径分析模型,模拟回转台合成振动,分析各激励点对回转台振动贡献量及贡献程度,准确找到回转台主要激振源。最后,通过施加外部主动激励的方式,分析不同激励频率加载下回转台振动情况,探寻能够降低截割过程回转台振动的激励频段。试验结果表明:外部激振频率处于20~60 Hz,回转台振动幅值降低明显,此频段激励频率对回转台振动控制效果良好,有益于提高回转台寿命,且激振频率为40 Hz时回转台振动最小,回转台振动抑制效果最佳。研究结果有益于丰富回转台振动相关研究理论,实现在不改变机械结构基础上,降低回转台受力与结构变形,可为掘进机回转台的振动问题提供理论参考。

池式钠冷快堆复杂空间内流动与传热特性三维数值模拟研究综述

钠冷快堆是第四代先进核能系统的重要堆型之一。池式钠冷快堆安全裕量大,但结构较为复杂,其堆内一回路循环流动呈多尺度、复杂空间、多路径、三维流动等特点,给池式钠冷快堆计算与实验带来一定困难。近年来,计算流体力学(CFD)的快速发展为解决上述问题提供了重要技术路径,本文对池式钠冷快堆复杂空间内流动与传热特性三维数值模拟研究进行综述。对于全堆一体化整体计算,获取池式钠冷快堆典型对称/非对称工况下的三维温度场分布及关键热工参数瞬态变化,评价其余热排出能力;对于局部部件或区域精细化计算,获取局部三维流动与传热特征参数,也为全堆一体化计算提供关键输入。相关研究为池式钠冷快堆安全稳定运行及设计优化提供重要支撑。

“路径”和“模式”的内涵辨析

“路径”“模式”作为基本概念,被广泛应用在各学科领域研究中,出现了各类混用、误用现象,并且这些现象仍在蔓延。厘清二者的内涵是一项基础性理论工作。总体上,“路径”是多条的、有范围的,由初始节点、关键节点和终结节点组成,节点之间按照一定次序连接。“模式”具有可复制属性,是相关要素按照一定规则形成的组织形式,且要素之间存在一定的内在关系。但是,“路径”“模式”的内涵在不同学科领域的研究中有不同的表达,尤其是“模式”表现得更加明显。

基于改进蚁群算法的AGV路径规划研究

路径规划是自动导引车(automated guided vehicle,AGV)实现自主能力的重要组成部分。针对传统蚁群算法收敛速度慢、易陷入局部最优等问题,提出一种改进蚁群算法的路径规划方法。该方法通过引入一种动态调节因子,以实现算法在收敛性和全局搜索能力方面的平衡作用;改进状态转移规则,以提高算法的搜索质量,避免陷入局部最优;提出了一种改进的信息素更新策略,有效提高了算法的收敛速度;通过对信息素挥发因子进行自适应调整,以提高算法的收敛速度和整体优化能力。最后,在改进算法所规划出的最优路径的基础上进行路径的二次优化,可以减少路径长度,降低能耗,提高AGV的工作效率。实验结果表明,将该方法应用在AGV的路径规划方面更具有效性和优越性。

基于轻量化U-Net网络的果园垄间路径识别方法

针对目前果园垄间导航路径识别方法存在准确性与实时性难以同时兼顾、泛化能力弱等问题,本文在U-Net模型的基础上进行优化,采用MobileNet-v3 Large作为U-Net的主干特征提取网络,并在跳跃连接处引入坐标注意力机制(Coordinate attention,CA),构建轻量化路径识别模型。以该模型分割的垄间可行驶区域为基础,利用最小二乘法重塑可行驶区域边缘点,并进一步提取垄间导航线。首先采用数据增强的草莓垄间数据集进行模型训练,并进一步迁移到葡萄和蓝莓数据集上进行权重微调,以提高模型适应能力。最后在相应的验证集上进行导航路径识别,并通过可视化对比不同模型识别结果,以验证模型准确性。试验结果表明,网络模型在草莓、蓝莓和葡萄果园垄间路径识别的平均交并比分别为98.06%、97.36%和98.50%,平均像素准确度分别达到99.13%、98.75%和99.29%。模型处理RGB图像分割可行驶区域的理论推理速度可达19.23 f/s,满足导航实时性和准确性的要求。

基于中继保障的分布式海战补给路径优化

分布式海战是未来战争形态发展的必然趋势。与传统海战样式相比,分布式海战作战部署更加灵活,作战区域更广。分布式海战条件下的后勤保障区域分布范围广、保障半径大、分散程度高,传统伴随保障方式难以适应战争形态发展。依托中继保障基地进行递进保障,并运用补给舰编队进行物资转运的补给模式,更加适合分布式海战特点。考虑复杂多变的海洋天气对远距离物资投送带来的极大影响,首先基于不同地理位置的历史天气信息模拟有效波高,然后根据有效波高测算天气因素对舰船航速及补给开销的影响程度,最后触发优化模型与仿真模型之间的反馈并得到优化方案。将优化方案与未触发仿真模型的理想优化结果进行比较,以验证不同策略的性能表现,得到契合实际应用环境的优化方案,从而提高最优路径的鲁棒性,为分布式海战物资补给提供较好的决策支撑。

大倾角煤层覆岩应力非对称传递时空演化特征

【目的】大倾角煤层安全高效开采的关键是对围岩的有效控制,而发现并揭示覆岩应力传递路径的时空演化特征是围岩稳定性控制的基础。【方法】以新疆某矿25221工作面为例,采用现场实测、物理相似模拟实验和数值计算相结合的研究方法,在综合厘定工作面矿压显现特征、覆岩变形破坏规律基础之上,构建以切应力与正应力为主的应力特征量,研究覆岩应力传递路径时空演化特征。【结果和结论】结果显示:工作面回采过程中,顶板倾向围岩结构呈中上部垮落高度较大、下部垮落高度较小的非对称分布特征,顶板走向围岩结构则随工作面推进呈周期性演化规律。受此影响,顶板采动应力随工作面推进呈现倾向非对称、走向对称的传递演化特征。在工作面倾向与走向剖面内,顶板应力特征量以切应力分界线为界沿采空区四周煤体传递,其传递路径呈现出“m”形分布特征。随着工作面推进距离的增加,应力传递路径由“m”形向中部相连的双“n”形转变,采空区两侧煤体支承压力峰值呈现增大→稳定的演化趋势。在平行煤层剖面内,顶板应力分界线为“w”形分布特征,应力分界线至采空区中心处,顶板应力呈单向传递特征,分界线至煤壁处,顶板应力呈双向传递特征。且随着顶板层位的增加,应力分界线演化至“v”形,研究结果揭示了大倾角煤层顶板应力非对称传递时空演化特征,对丰富大倾角煤层岩层控制理论具有重要意义。

圆柱壳体瞬态辐射噪声评估试验验证与分析

基于自身振动数据实时测量进行水下结构体辐射噪声快速预报,对于掌握水下目标运行状况、保持隐蔽性具有重要意义。该文针对工况传递路径分析方法评估瞬态辐射噪声问题,在圆柱壳体(舱段模型)上开展验证试验,通过稳态工况下的振动信号和实测辐射噪声,利用基于广义交叉验证的正则化方法求解振-声传递函数,以此来评估瞬态激励下的辐射噪声,并与实测的瞬态辐射噪声进行对比,同时提出针对目标被探测性影响程度的加权平均误差来衡量评估误差。试验结果显示,在瞬态辐射噪声的特征频段(辐射噪声水平明显高于背景噪声),评估结果的加权平均误差在2 dB以内。该文验证了工况传递路径分析方法评估瞬态辐射噪声的有效性,为进一步在水下复杂结构上开展研究奠定了基础。

流固耦合作用下泵站大体积混凝土结构振动特性分析

在泵站运行过程中,由转轮和导叶之间水体的动静干扰所引起的压力脉动是引起泵站混凝土结构及机组振动的主要原因。现有关于泵站及水电站厂房的研究中,仅以数值参数形式表达脉动,并未真实反映流体与导叶间的相互水力干涉。采用有限元软件ADINA建立泵站混凝土结构、流道和流体的耦合三维模型,特别将机架、轴流泵等金属结构建入模型中,真实反映流体与固定导叶间的相互水力干涉,模拟脉动传递路径。分析了泵站大体积混凝土结构的振动特性,并对泵站运行安全性作出评价分析。研究结果可为工程实践提供参考。

基于改进积分梯度的黑盒迁移攻击算法

对抗样本可以轻易攻击深度神经网络,影响模型的使用安全。虽然白盒攻击方法有优秀的成功率,但是在黑盒迁移攻击时通常表现出较差的效果。目前最先进的TAIG算法基于积分梯度,可以提升对抗样本的迁移性。但研究发现其积分路径缺失到饱和区的有效信息,并且使用不恰当的基线和梯度计算,限制了算法攻击成功率的上限。改进了积分梯度并提出了IIGA攻击算法(improved integrated gradients attack)。改进积分梯度将有限路径扩展为无限路径,融合输入到真实饱和区的梯度累计,可以表征每个分量更准确的重要性;并提出信息熵基线,确保基线相对于模型不含任何信息。IIGA将生成的改进积分梯度进行平滑处理作为攻击的反向优化方向,平滑操作过滤因神经网络在小范围偏导剧烈跳动而产生的大量噪点,使梯度信息集中于视觉特征,并在迭代过程中加入动量信息稳定梯度方向。在ImageNet数据集上进行的大量实验表明IIGA不仅在白盒攻击下优于FGSM、C&W等算法,在黑盒迁移攻击模式下也大大超过了SI-NI、VMI、AOA和TAIG等先进的算法。

基于孔隙尺度的大豆粮堆热湿耦合传递的研究

开展通风干燥过程中粮堆孔隙结构分布以及热湿耦合传递规律的研究,可为安全储粮以及干燥系统的设计提供理论依据。以大豆填充床为研究对象,基于局部质量和热量的非平衡原理,建立了大豆填充床通风干燥过程双扩散热湿传递模型。采用离散元法-有限容积法数值模拟了干燥条件下填充床内孔隙率、气流路径分布以及温度和水分耦合传递规律。结果表明:填充床的径向孔隙率呈振荡分布,近壁面孔隙率较大而填充床中轴线附近孔隙率较小,会使气流路径迂曲度呈现不规则分布;填充床的干燥速率主要受干燥空气温度和大豆颗粒含水量的影响;在干燥空气的相对湿度为17%及温度分别为35、45、55和65℃的条件下,前20 min填充床的干燥速率分别为0.077%/min、0.083%/min、0.089%/min和0.096%/min。

某乘用车加速工况车内轰鸣声诊断分析及控制方法

该文针对某乘用车加速工况出现的轰鸣声进行诊断分析与控制。首先通过主观评价确定问题工况,通过实车测试发现2400 r/min左右车内存在明显轰鸣声。利用阶次分析、模态分析及错频验证可知,发动机激励经悬置传递副车架,引起副车架的共振,进而传递到车内引起轰鸣声。最后通过传递分析及柔性连接点导纳法,优化副车架橡胶衬套结构。结果表明,优化后在2400 r/min声压总级与2阶声压差值为7.5 dB(A);声压总级较原状态降低2 dB(A),2阶噪声降低7.8 dB(A),声压总级和2阶噪声声压差值增大,轰鸣声明显减小,主观评价可接受。