PROMOTER FLOW ACTION OF SOLID-STATE LOW MELT POINT METAL ON THE POLYPROPYLENE

With the aid of a slip-disentanglemnt theory, a rheological equation has been deduced about the composite system of solid-state low melting point metal and polymer. By measuring some rheological properties of the composite system composed of low melt point metal and polypropylene (LMPM/PP), the results show that LMPM has a promoter flow action upon PP when using a small amount of LMPM and, if some coupled agents are added, the promoter flow action will be remarkable. Moreover, while LMPM being added into the composite, the temperature sensitivity of system will go rip. This indicates that the system's viscosity will drop further if its temperature is increased.

Generalized Mean-Flow Theory of Wave-Current-BottomInteractions

The interaction between waves, currents and bottoms in estuarine and coastal regions is ubiquitious, in particular the dynamic mechanism of waves on large-scale slowly varying currents. The wave action concept may be extended and applicated to the study of the mechanism. Considering the effects of moving bottoms and starting from the Navier-Stokes equation of motion of a vinous fluid including the Coriolis force, a generalized mean-flow medel theory for the nearshore region, that is, a set of mean-flow equations and their generalized wave action equation involving the three new kinds of actions termed respectively as the current wave action, the bottom wave action and the dissipative wave action which can be applied to arbitrary depth over moving bottoms and ambient currents with a typical vertical structure, is developed by vertical integration and time-averaglng over a wave peried, thus extending the classical concept, wave action, from the ideal averaged flow conservative system to the real averaged flow dissipative dynamical system, and having a large range of application.

Vertical Migration of Fine-Grained Sediments from Interior to Surface of Seabed Driven by Seepage Flows–‘Sub-Bottom Sediment Pump Action'

A scientific hypothesis is proposed and preliminarily verified in this paper: under the driving of seepage flows, there might be a vertical migration of fine-grained soil particles from interior to surface of seabed, which is defined as ‘sub-bottom sediment pump action' in this paper. Field experiments were performed twice on the intertidal flat of the Yellow River delta to study this process via both trapping the pumped materials and recording the pore pressures in the substrate. Experimental results are quite interesting as we did observe yellow slurry which is mainly composed of fine-grained soil particles appearing on the seabed surface; seepage gradients were also detected in the intertidal flat, under the action of tides and small wind waves. Preliminary conclusions are that ‘sediment pump' occurs when seepage force exceeds a certain threshold: firstly, it is big enough to disconnect the soil particles from the soil skeleton; secondly, the degree of seabed fluidization or bioturbation is big enough to provide preferred paths for the detached materials to migrate upwards. Then they would be firstly pumped from interior to the surface of seabed and then easily re-suspended into overlying water column. Influential factors of ‘sediment pump' are determined as hydrodynamics(wave energy), degree of consolidation, index of bioturbation(permeability) and content of fine-grained materials(sedimentary age). This new perspective of ‘sediment pump' may provide some implications for the mechanism interpretation of several unclear geological phenomena in the Yellow River delta area.

基于注意力机制和能量函数的动作识别算法

针对零样本动作识别(ZSAR)算法的框架缺乏结构性指导的问题,以基于能量的模型(EBM)指导框架设计,提出基于注意力机制和能量函数的动作识别算法(ARAAE)。首先,为了得到EBM的输入,设计了光流加3D卷积(C3D)架构的组合以提取视觉特征,从而达到空间去冗余的效果;其次,将视觉Transformer(ViT)用于视觉特征的提取以减少时间冗余,同时利用ViT配合光流加C3D架构的组合以减少空间冗余,从而获得非冗余视觉空间;最后,为度量视觉空间和语义空间的相关性,实现能量评分评估机制,设计联合损失函数来进行优化实验。采用6个经典ZSAR算法及近年文献里的算法在两个数据集HMDB51和UCF101进行实验的结果表明:相较于CAGE(Coupling Adversarial Graph Embedding)、Bi-dir GAN(Bi-directional Generative Adversarial Network)和ETSAN(Energy-based Temporal Summarized Attentive Network)等算法,在平均分组的HMDB51数据集上,ARAAE平均识别准确率提升至(22.1±1.8)%,均明显优于对比算法;在平均分组的UCF101数据集上,ARAAE的平均识别准确率提升至(22.4±1.6)%,略优于对比算法;在以81/20为分割方式的UCF101数据集上,ARAAE的平均识别准确率提升至(40.2±2.6)%,均大于对比算法。可见,ARAAE在ZSAR中能有效提高识别性能。

Action演算中动作内部数据流分析方法及其实现

针对Action演算的分子形式,提出分子语法结构树等概念,并且给出基于分子语法结构树的一个动作内部数据流分析方法及其实现.为深入研究Action演算的性质和应用提供了分析手段.

基于时空双流的矿井人员求救动作识别

当矿井人员遇险通过动作发出求救信号时,救援系统若能及时准确识别矿井人员求救动作,则能快速响应,实施救援,从而避免人员伤亡事故发生或降低事故严重程度。研究了煤矿井下视频中人员求救动作识别问题,提出了一种特征通道注意力及多空间注意力的时空双流动作识别解决方案,该方案的特点是融合了特征通道信息的差异性与空间中多个运动显著区域的特征,实验验证该方案的求救动作识别准确率达92.8%。

Characteristics of mining gas channel expansion in the remote overlying strata and its control of gas flow

The technology of pressure relief gas drainage is one of the most effective and economic for preventing gas emissions in underground mines.Based on current understanding of strata breakage and fracture development in overlying strata,the current study divides the overlying strata into the following three longitudinal zones in terms of the state of gas flow:a turbulent channel zone,a transitional circulation channel zone and a seepage channel zone.According to the key strata discrimination theory of controlling the overlying strata,the calculation method establishes that the step-type expansion of the mining gas channel corresponds to the advancing distance of working face,and this research also confrms the expanding rule that the mining gas channel in overlying strata follows the advancing distance of mining working face.Based on the geological conditions of Xinjing Coal Mine of Yangquan,this paper researches the expanding rule of mining gas channel as well as the control action of the channel acting on the pressure relief flow under the condition of the remote protective layer,and got the distance using inversion that the step-type expanding of mining gas channel is corresponding to the advancing distance of working face,which verifes the accuracy and feasibility of theoretical calculation method proposed in this study.The research provides the theoretical basis for choosing the technology of pressure relief gas drainage and designing the parameters of construction.

Gao's interacting shear flows( ISF) theory and its inferences and their applications

Gao＇s viscous/in-viscid interacting shear flows （ISF） theory, proposed by professor Gao Zhi in Institute of Mechanics, China Academy of Science, and its inferences and their applications in computational fluid dynamics （CFD） are reviewed and some subjects worthy to be studied are pro- posed in this paper. The flow-field and motion law of ISF, mathematics definition of strong viscous shear layer flow in ISF, ISF equations, wall-surface compatibility criteria （Gao＇s criteria ）, space scale variety law of strong viscous shear layer reveals flow mechanism and local space small scale triggered by strong interaction that cause some abnormal severe local pneumatic heating phenomenon in hypersonic flow. Gao＇s ISF theory was used in near wall flow, free ISF flow simulation and design of computing grids, Gao＇s wall-surface criteria were used to verify calculation reliability and accuracy of near wall flows, ISF theory approximate analytical result of shock waves-boundary layer interac- tion and ISF equations were used to obtain the numerical exact solution of local area flow （ such as stationary point flow）. Some new subjects, such as, improving near-wall turbulent models according to the turbulent flow simulation satisfying the wall-criteria and illustrating relation between grid-con- vergence based on the wall criteria and other convergence tactics, are suggested. The necessity of applying Gao＇s ISF theory and wall criteria is revealed. Difficulties and importance of hypersonic vis- cous/in-viscid interaction phenomenon were also emphasized.

基于阻力规律视角的水流能态区辨识

高、低水流能态区形成条件不同,其识别对于预测动床阻力具有重要意义。基于量纲一阻力方程推导了一个新的高、低水流能态区判别函数,包含悬浮数和水流作用数2个量纲一参数,提出了能态转变角和能态转移路径的概念,从流动阻力角度重新审视了水流能态区分问题。通过国内外4176组水槽和野外实测数据对该函数进行率定,确定了高、低能态区的临界方程。研究结果表明:该方法低能态区预测精度约为91%,高能态区约为85%,综合精度约为89%;在细沙河流中,随着水温的降低,更易发生水流低能态向高能态的转变。本文建立的判别函数不仅可高精度识别水流能态区,还可分析水温对能态区过渡的影响。

数字经济促进农村代际收入流动:作用机制与经验证据

根据数据经济与农村代际收入流动的理论分析,构建数字经济影响农村代际收入流动的双向固定效应模型,并利用中国家庭追踪调查CFPS2014年-2020年四年微观数据和数字经济发展指数实证分析数字经济对农村代际收入流动的影响路径及作用机制。研究发现,数字经济能够增强农村代际收入的流动性,并且该结论在通过多项稳健性检验之后依然成立。机制分析结果显示,数字经济通过子代人力资本投资、社会资本积累及增强金融可及性三种路径降低农村代际收入弹性,提高农村代际收入的流动性。异质性分析表明,在经济较为落后地区、低收入群体及高学历群体中,数字经济对农村代际收入流动性的提升效应更为显著。据此,提出加强农村数字基础设施建设、加强农村居民人力资本和社会资本积累并增强农村地区金融可及性、加强区域合作与联动等相关建议。

压裂液连续混配石油设备液压系统分析与优化

压裂液连续混配常规采用阀前负载敏感液压系统作为其液压动力系统,由于混配施工工艺不断改良细化,在大扭矩工况下多马达复合动作,液压系统流量饱和情况下流量优先向轻载分配。为解决这一问题,优选阀后负载敏感液压系统,在流量供给不足情况下,同比减少各负载流量供给,实现马达同步动作。基于AMESim仿真软件,分别搭建连续混配设备阀前及阀后负载敏感液压系统仿真模型,得到泵与马达压力、流量及功率变化曲线。仿真结果表明:阀后负载敏感系统中,负载敏感泵输出功率始终与负载所需功率相匹配;系统流量充足时,泵输出流量始终随着系统所需流量的变化而变化;系统流量不足时,阀后负载敏感阀可以实现流量共享,各马达负载同步动作。实验结果表明:仿真与实验数据差距小于3%,阀后负载敏感系统可以按照阀口开度比例分配各路负载流量,实现各负载平稳动作。

LUDV多路阀复合动作流量分配影响因素分析

以某阀后补偿流量共享型多路换向阀为对象,在不饱和流量状态下分析了复合动作中补偿阀芯的压力补偿功能,探明了补偿阀芯的补偿压力随负载动态变化的特性。通过分析不同过流面积下主阀芯和补偿阀芯对各动作流量的影响,提出了考虑补偿阀芯最小开口与主阀芯过流面积影响下的复合动作流量随负载变化理论计算公式。并通过多路阀复合动作试验进行了验证,通过误差分析确立了其具有一定准确性,为实际应用中多路阀流量分配设计提供了理论依据。

基于微水试验求解高渗透性承压含水层水文地质参数

为了提高高渗透性承压含水层渗透系数与储水率等水文地质参数的反演精度,科学解释井筒水位的非线性振荡现象,本研究建立了考虑表皮效应和非达西流效应耦合惯性力作用的微水试验模型。模型中表皮效应采用Robbin边界条件描述,非达西流效应采用Forchheimer方程刻画,惯性力作用采用动量平衡方程表达。利用Laplace变换法推导模型的解析解,基于现场试验数据,分析3种因素对反演水文地质参数的影响。结果表明表皮效应、非达西流效应与惯性力作用对参数反演结果的影响均不能忽视。无因次表皮因子(Sw)值、Forchheimer系数(γ)值与瞬时注水后井筒水位与承压含水层隔水顶板之间的垂直距离(l) 3个值越大,井筒水位恢复速度越慢;Sw值越大,井筒水位振荡幅度越小,而γ值和l值越大,井筒水位振荡幅度越大。忽略表皮效应、非达西流效应或惯性力作用均导致渗透系数与储水率的反演结果偏小。研究结果为裂隙承压含水层中水文地质参数的反演提供了一种合理的理论基础和技术依据。

水流作用下水利工程闸门的动力特性研究

在水利工程中,闸门用于控制水流和调节水位,但传统模型无法准确描述闸门的复杂响应。为此,研究利用流固耦合模型,分析水流作用下闸门的动力特性。结果显示,当开度为0.4时,振型云图表现出复杂的模式,闸门的下半部分呈现出更为明显的振动;与传统模型相比,研究模型在水深100 m时的最大拉应力在0.78~2.7 MPa之间,表明研究模型可为水利工程闸门的设计和优化提供重要的参考依据。

考虑变荷载与非达西渗流的软土一维非线性固结分析

为研究变荷载作用下软土的一维非线性固结特性,通过引入新的一维非线性压缩模型,推导出变荷载作用下考虑非达西渗流的饱和软土地基一维非线性固结方程。基于有限差分法求解,并通过与半解析解结果对比分析,验证了其合理性与可靠性。根据该固结方程的解答,详细讨论了非达西渗流参数(m和i 1)、土体初始压缩系数、压缩指数与渗透指数的比值以及加载速率与加载形式对土体固结的影响。结果表明:随着非达西参数(m和i 1)及压缩指数与渗透指数的比值的增大,土体的固结速率减慢;土体初始压缩系数越大,土体的固结速率越快;荷载的加载速率越快,土体的固结速率就越快;与已有模型相比,引入的新模型无需测量土体的初始有效应力,可更加方便地应用于工程中。

考虑载荷模拟作用的高压弯头冲蚀数值仿真

在水力压裂过程中,地面高压管汇在管内复杂固液两相流冲击和管体恶劣载荷的耦合作用下,弯头、三通及接头等薄弱部件长期遭受严重的冲蚀磨损,极易导致管件发生断裂破坏,对现场人员及设备构成严重威胁。开展载荷作用下的高压管汇典型材料冲蚀磨损试验,根据试验结果,基于E/CRC冲蚀模型构建一种考虑应力状态影响的新型冲蚀数学模型,所构建的新模型与冲蚀试验数据之间的准确度可达95%以上。采用计算流体力学离散相模型(CFD-DPM),开展高压管汇件冲蚀性能的三维数值模拟,考察高压弯头在不同压裂工况下的冲蚀磨损程度及空间分布情况。结果表明:在固液两相流冲击下,主要冲蚀区位于靠近弯头出口处的弯头外侧,且管件的最大冲蚀率也位于该处;在弯头内侧二次流涡流的影响下,部分颗粒在流经弯头后会在下游直管内侧积聚,从而在这个区域造成次要冲蚀区;随着流动颗粒斯托克斯系数增加,主要冲蚀区面积增大,次要冲蚀区面积减小;此外,在嵌入新型冲蚀数学模型后,可观察到随着操作压力增大,高压管汇弯头部位的冲蚀磨损率明显增加。

加温加湿经鼻高流量氧疗对难治性哮喘病人支气管热成形术后的应用及机制研究

目的探讨加温加湿经鼻高流量氧疗对难治性哮喘病人支气管热成形术(BT)后的应用及机制。方法选择2021年1月至2022年10月在中国科学院大学深圳医院(光明)拟行BT的哮喘病人118例进行研究。采用随机数字表法将病人分为两组,每组各59例。两组均行BT治疗,术后对照组病人给予常规鼻导管吸氧,观察组则行经鼻高流量氧疗(HFNC)。比较两组病人临床疗效、痰液黏稠度、舒适度、生活质量、炎症因子、呼出气一氧化氮(FeNO)、血气分析指标及疗程结束后3周内并发症发生情况。结果观察组病人显效率、总有效率分别为64.41%、96.61%,高于对照组的38.98%、86.44%(P<0.05)。治疗后两组Ⅲ度黏痰占比、ACQ得分、TNF-α、FeNO及二氧化碳分压均低于治疗前,但观察组低于对照组;治疗后两组CQC得分、AQLQ得分、ACT得分、IL-10、氧分压均高于治疗前,但观察组高于对照组(P<0.05)。治疗后两组均高于治疗前,但观察组高于对照组(P<0.05)。两组治疗前后pH均差异无统计学意义(P>0.05)。对照组共出现16例(27.12%)并发症,高于观察组的6例(10.16%)并发症(P<0.05)。结论难治性哮喘病人BT后HFNC较常规鼻导管吸氧可有效提高临床疗效,提高病人舒适度与生活质量,降低痰液黏稠度;其机制可能与HFNC可改善炎症水平和血气分析指标、降低FeNO水平有关。

液压快换接头压力降-流量特性试验台的设计及不确定度分析

为测试不同流体介质、流量等工况下液压快换接头的流通能力,设计一套液压快换接头压力降-流量特性试验台,完成配套测试处理软件的开发。该试验台可采用46号液压油或水作为试验介质,其流量测试范围为40~1000 L/min,被测快换接头的进、出口压力降测量范围为0~5.0 MPa,被测快换接头的适用公称通径范围为12.5~51 mm。在此基础上,依据ISO 9110-1:2020和ISO 9110-2:2020标准,建立被测快换接头压降值测量的数学模型,并分别计算得到了使用46号液压油或水作为试验介质时的合成不确定度。该试验台的技术参数符合GB/T 5861—2003,也可用于测量快换接头的流量系数和流阻系数。

血流限制训练运动表现效果及作用机制研究进展

本文主要运用文献资料法、归纳总结法等研究方法,对血流限制训练(BFRT)在运动表现效果及作用机制方面的成果进行综述与分析,探讨BFRT现阶段的研究进展。结果显示,BFRT能显著增加肌肉质量与力量、改善有氧代谢能力、提高运动表现成绩,并对康复治疗效果有积极影响,但BFRT的具体作用机制仍不明确,可能涉及代谢激素、信号通路、血管生长因子和肌纤维募集等方面因素。鉴于此,在未来的研究中应注重不同个体之间的差异,在确保安全性的前提下,进一步探索BFRT的作用机制和最佳训练方案,以期为运动训练和康复治疗等方面提供新的路径。

山区乡村房屋模型水流作用试验

通过山区乡村房屋模型在水流槽中进行模拟山洪水流作用的试验,研究山区洪水对村镇房屋的作用,了解不同地形地貌条件下,不同墙体开洞率的山区乡村房屋在山洪作用下的作用机理和作用特性.根据试验结果得出各片墙体所受水流力的分布规律为水平方向中间大两头小,竖直方向随高度的增加而减小,模型沿水流方向所受总合力随着开洞率的增大而逐渐减小,依据此规律,山区乡村房屋在设计和建造时应考虑满足适当的开洞率,以降低所受到的水流作用力.