STRONGLY CONVERGENT INERTIAL FORWARD-BACKWARD-FORWARD ALGORITHM WITHOUT ON-LINE RULE FOR VARIATIONAL INEQUALITIES

This paper studies a strongly convergent inertial forward-backward-forward algorithm for the variational inequality problem in Hilbert spaces.In our convergence analysis,we do not assume the on-line rule of the inertial parameters and the iterates,which have been assumed by several authors whenever a strongly convergent algorithm with an inertial extrapolation step is proposed for a variational inequality problem.Consequently,our proof arguments are different from what is obtainable in the relevant literature.Finally,we give numerical tests to confirm the theoretical analysis and show that our proposed algorithm is superior to related ones in the literature.

Linear and Non-Linear Dynamics of Inertial Waves in a Rotating Cylinder with Antiparallel Inclined Ends

This work is devoted to the experimental study of inertial wave regimes in a non-uniform rotating cylinder with antiparallel inclined ends.In this setting,the cross-section of the cylinder is divided into two regions where the fluid depth increases or decreases with radius.Three different regimes are found:inertial wave attractor,global oscillations(the cavity’s resonant modes)and regime of symmetric reflection of wave beams.In linear wave regimes,a steady single vortex elongated along the rotation axis is generated.The location of the wave’s interaction with the sloping ends determines the vortex position and the vorticity sign.In non-linear regimes several pairs of the triadic resonance subharmonics are detected simultaneously.The instability of triadic resonance is accompanied by the periodic generation of mean vortices drifting in the azimuthal direction.Moreover,the appearance frequency of the vortices is consistent with the low-frequency subharmonic of the triadic resonance.The experimental results shed light on the mechanisms of the inertial wave interaction with zonal flow and may be useful for the development of new methods of mixing.

4D-Flow MRI在肥厚型心肌病左室流出道血流评估中的价值探索

目的 探索四维血流(four-dimensional flow,4D-Flow)磁共振成像(magnetic resonance imaging,MRI)技术在左心室腔内应用的可行性。材料与方法 本研究为前瞻性、横断面研究,纳入2022年8月至2023年1月于我院接受心脏MRI检查的21例肥厚型心肌病患者,采用3.0 T MRI扫描仪进行二维血流(tow-dimensional flow,2D-Flow)及4D-Flow成像,收集患者一周内进行的超声心动图检查结果。采用组内相关系数(inter-class correlation coefficient,ICC)、变异系数(coefficients of variation,COV)及Bland-Altman分析比较2D-Flow、4D-Flow评估左室流出道峰值流速的可重复性及一致性,并通过Pearson相关性分析探究二者与超声心动图测量结果的关系。结果 2D-Flow和4D-Flow观察者内/观察者间的ICC分别为0.999/0.999和0.995/0.992,COV分别为0.5%/0.5%和2.4%/2.6%。4D-Flow与超声心动图的测量结果呈中度相关,相关系数r值为0.574(P=0.006),但一致性较差,ICC为0.375(P=0.013)。2D-Flow与4D-Flow和超声心动图间无显著的一致性及相关性。结论 4D-Flow技术能够可视化心腔内血流模式,对左室流出道峰值流速的测量具有高度可重复性,且与超声心动图的测量结果具有显著的一致性。

Research on a non-linear chaotic prediction model for urban traffic flow

In order to solve serious urban transport problems, according to the proved chaotic characteristic of traffic flow, a non linear chaotic model to analyze the time series of traffic flow is proposed. This model reconstructs the time series of traffic flow in the phase space firstly, and the correlative information in the traffic flow is extracted richly, on the basis of it, a predicted equation for the reconstructed information is established by using chaotic theory, and for the purpose of obtaining the optimal predicted results, recognition and optimization to the model parameters are done by using genetic algorithm. Practical prediction research of urban traffic flow shows that this model has famous predicted precision, and it can provide exact reference for urban traffic programming and control.

基于 Moldflow 的汽车中控台框架翘曲变形分析及优化

以某汽车中控台框架为研究对象,测量试模样品发现其翘曲变形量超过了装配要求。通过Moldflow软件模拟了该塑件实际的注塑过程,翘曲变形量的模拟值与实测平均值的最大误差为5.98%,发现该塑件翘曲变形的主要因素为冷却不均和收缩不均。本文在原物料中添加质量分数为25%的玻璃纤维以及优化工艺参数后,翘曲变形量的模拟值与初始方案相比降低了86.22%。试模验证表明,优化后的翘曲变形量模拟值与实测平均值的最大误差为4.35%,证明了Moldflow软件模拟分析的准确性。试模后各检测点的最大翘曲变形量降到了1.6 mm以下,较优化之前降低了80%以上,为类似大型复杂注塑件的翘曲变形分析及优化提供了思路。

基于Flow Simulation的某发动机涡轮压气机流场与效率分析

涡轮机内部流场对涡轮增压器的性能和效率有着重要影响,采用SolidWorks Flow Simulation模块对某发动机涡轮压气机侧流场和压气效率分析。在六种不同空气体积流量工况下,体积流量为0.29时,压气机效率最高,达到80%左右。模型的建模和流体分析均在SolidWorks环境下,分析效率高,为涡轮增压器设计和优化提供了支撑。

iFlow彩色血流编码成像技术在下肢动脉硬化闭塞症诊断中的应用价值

目的研究iFlow彩色血流编码成像技术在下肢动脉硬化闭塞症(LEASO)诊断中的应用价值。方法选择2022年3月至2023年10月期间确诊的106例LEASO患者作为本研究的LEASO组,以一般资料与LEASO组匹配且无动脉病变的80例志愿者作为对照组。两组受试者均进行数字减影血管造影(DSA)并采用iFlow彩色血流编码成像技术检测股骨头区域和踝关节区域达峰时间(TTP)、计算踝关节区域与股骨头区域TTP的差值,测量踝肱指数(ABI)。结果两组研究对象年龄、性别、体质量指数、吸烟史、高血压病史、糖尿病史、冠心病史、股骨头区域TTP的比较,差异无统计学意义(P>0.05);LEASO组踝关节区域TTP及TTP差值均高于对照组,差异有统计学意义(P<0.05);LEASO组中不同Rutherford分类患者股骨头区域TTP的比较以及左侧病变患者与右侧病变患者股骨头区域TTP、踝关节区域TTP、TTP差值的比较,差异无统计学意义(P>0.05),Rutherford分类越高,踝关节区域TTP及TTP差值越低(P<0.05);经Pearson检验,LEASO患者的踝关节区域TTP、TTP差值与ABI呈负相关(P<0.05);经受试者工作特征(ROC)曲线分析,踝关节区域TTP、TTP差值对LEASO具有诊断效能;经Delong检验,TTP差值诊断的ROC曲线下面积高于踝关节区域TTP(P<0.05)。结论iFlow彩色血流编码成像技术测定踝关节区TTP及TTP差值是诊断LEASO的量化指标。

袋型阻尼密封动力学特性双控制体Bulk Flow模型

为快速准确预测袋型阻尼密封泄漏特性和动力学特性,针对传统单控制体Bulk Flow模型预测精度低、无法预测交叉动力系数的问题,提出了袋型阻尼密封双控制体Bulk Flow模型和动力学特性数值预测方法,并开发了计算程序。首先,依据边界层理论,将袋型密封腔室划分为两个控制体,推导了控制体的连续性、周向动量和能量方程,引入Swamee-Jain和Takahashi方程,计算流体-壁面间和流体-流体间的周向黏性摩擦力;其次,采用牛顿-拉夫森算法和摄动分析法分别求解0阶和1阶控制方程,获得各刚度、阻尼动力特性系数;然后,通过与袋型阻尼密封泄漏量和动力特性系数的实验值、单控制体Bulk Flow模型和非定常计算流体动力学(CFD)数值结果进行比较,验证了模型和方法的准确性和可靠性;最后,研究了转子转速(10 000、15 000、20 000 r/min)和预旋比(0.067、0.724、0.997)对袋型阻尼密封动力学特性的影响。结果表明:所发展的模型和方法具有计算速度快、预测精度高(泄漏量预测误差小于6%,动力特性系数预测误差小于38%)的优点;转子转速和进口预旋的增大均会导致袋型阻尼密封有效阻尼显著减小,穿越频率显著增大,易诱发轴系失稳。

基于Flow-3D的桩林坝不同布置形式对坝基的冲刷侵蚀

桩林坝是一种以桩为基础的竖向格子坝,既有良好的受力条件,又相对节约材料,同时拥有“拦粗排细”的功效,现有桩林坝的研究,多在冲击荷载、拦截固源和调控泥石流性能等方面构建不同布置形式的桩林坝模型。以杨家沟为例,通过野外现场踏勘和数值仿真计算,基于Flow-3D软件开展数值模拟研究,建立不同布置形式(单排桩、双排桩、桩间距、排间距)的桩林坝模型,探讨不同影响因素下桩林坝坝基冲刷侵蚀规律。结果表明:桩林坝的整体设计中桩林不宜过密,桩间距和排间距以2.5 m为宜;单排桩的稳定性较弱,在泥石流冲击下极易发生剪切破坏,且对上游的“固源”作用远不如多排桩,但单排桩的冲刷深度及侵蚀规模均小于多排桩。研究成果对桩林坝的布置形式及冲刷机制提供数据支撑,并为震后泥石流防治工程设计提供参考。

肝硬化患者4D flow MRI血流动力学参数与中医证型的相关性研究

目的探讨肝硬化患者4D flow MRI血流动力学参数与中医证型的相关性。方法将118例肝硬化患者依据中医辨证分为肝气郁结证、湿热蕴结证、肝肾阴虚证、脾肾阳虚证、瘀血阻络证5个证型,所有患者均行门静脉4D flow MRI检查,统计不同证型肝硬化患者分布情况,观察门静脉系统(门静脉主干、脾静脉、肠系膜上静脉)的血流动力学参数,包括血流量、流速、壁剪切力等,比较不同证型患者门静脉血流动力学参数差异。结果肝硬化代偿期以肝气郁结证、湿热蕴结证为主,肝硬化失代偿期以脾肾阳虚、瘀血络阻证为主;A级以肝气郁结证、湿热蕴结证为主,B、C级以瘀血络阻证为主。瘀血络阻证肝硬化患者门静脉主干及脾静脉血流量明显高于肝气郁结证、湿热蕴结证患者(P<0.05);脾肾阳虚证门静脉主干血流量明显高于肝气郁结证肝硬化患者(P<0.05);瘀血络阻证肝硬化患者门静脉主干流速及剪切力较肝气郁结证和湿热蕴结证低。结论肝硬化患者中医辨证分型与门静脉血流动力学参数具有一定相关性,4D flow MRI可为肝硬化的中医辨证提供血流动力学参考。

One-step Eco-friendly Fabrication of Antibacterial Polyester Via On-line Amination Reaction by Melt Coextrusion

The work is dedicated to develop a one-step eco-friendly method to prepare antibacterial polyethylene terephthalate(PET).We report a one-step eco-friendly method to manufacture antibacterial PET via on-line amination reaction by melt coextrusion.Beside evenly mixing of poly(hexamethylene guanidine)(PHMG)and PET in the melt coextrusion procedure,the amination reaction also occurred between PHMG and PET under high temperature(230-270℃).The antibacterial ability of composite PET showed obvious PHMG concentration dependence,and antibacterial activity reached more than 99%when PHMG content was 2.5 wt%.Moreover,LIVE/DEAD fluorescence test further confirmed that the composite PET could kill bacteria quickly and efiectively(within 30 min);while negligible cytotoxicity was observed to HSF and HUVEC cells.Onestep eco-friendly fabrication of composite antibacterial PET was accomplished by on-line melt coextrusion.The composite antibacterial PET has potential use in multiple fields to combat with pathogenic including textiles,packaging materials,decoration materials and biomedical devices,etc.

Numerical and experimental study on the falling film flow characteristics with the effect of co-current gas flow in hydrogen liquefaction process

Liquid hydrogen storage and transportation is an effective method for large-scale transportation and utilization of hydrogen energy. Revealing the flow mechanism of cryogenic working fluid is the key to optimize heat exchanger structure and hydrogen liquefaction process(LH2). The methods of cryogenic visualization experiment, theoretical analysis and numerical simulation are conducted to study the falling film flow characteristics with the effect of co-current gas flow in LH2spiral wound heat exchanger.The results show that the flow rate of mixed refrigerant has a great influence on liquid film spreading process, falling film flow pattern and heat transfer performance. The liquid film of LH2mixed refrigerant with column flow pattern can not uniformly and completely cover the tube wall surface. As liquid flow rate increases, the falling film flow pattern evolves into sheet-column flow and sheet flow, and liquid film completely covers the surface of tube wall. With the increase of shear effect of gas-phase mixed refrigerant in the same direction, the liquid film gradually becomes unstable, and the flow pattern eventually evolves into a mist flow.

V Flow技术测量颈动脉壁面剪应力的一致性研究

目的评价血流向量成像(V Flow)技术在测量健康成年人颈动脉壁面剪应力(WSS)中的一致性。方法于2021年2月至2021年3月招募健康成年志愿者20人,由2名不同年资的超声医师使用配备V Flow功能的Mindray Resona 7超声仪和3~9 MHz线阵探头进行双侧颈动脉扫查,分别采集双侧颈总动脉远段、颈总动脉分叉至颈内动脉起始部两段动脉的动态V Flow图像,测量两侧颈总动脉远段的近心端、远心端、分叉处及颈内动脉起始部的前、后壁的WSS,使用组内相关系数(ICC)和Bland-Altman图评估组内一致性及组间一致性。结果双侧颈动脉前、后壁的4个不同节段之间WSS值差异均有统计学意义(P<0.05)。高年资超声医师2次测量结果的一致性结果显示,左侧颈总动脉远段的远心端一致性极好(ICC 0.779),右侧颈总动脉远段的近心端(ICC 0.605)、远心端(ICC 0.585)、颈内动脉起始部(ICC 0.457)、左侧颈总动脉分叉处(ICC 0.606)及颈内动脉起始部(ICC 0.702)一致性均较好;不同年资超声医师的测量结果显示,仅右侧颈总动脉分叉处(ICC 0.486)及左侧颈总动脉远段的远心端(ICC 0.576)一致性较好。结论V Flow技术可显示不同位点间颈动脉WSS之间的差异,其组内一致性较好,但在不同年资超声医师间存在一定的差异。

Flow-Injection Microcolumn on-Line Preconcentration for theDetermination of Chromium(Ⅵ)

A rapid and sensitive on-line preconcentration method for spectrophotometric determination of chromium (VI) in nature water is described. Preconcentration and determination are based on (i) the quantitative and fast adsorption of chromium (VI) on the high surface area nanometer-size TiO2 (anatase) powders, which prepared by a sol-gel method from hydrolysis of TiCI4 and (ii) the quantitative and reproducible elution of Cr (VI) by 2. 0 mol. L-1 HCI. A mini-column system for preconcentration is developed, Cr(VI)on the mini-column is eluted and merged with a stream water and DPCB (1, 5-diphenylcarbazide ) as the chromogenic reagent. The Proposed system permits throughputs of 6 sample h--l (0. 001 μg mL-1 Cr(VI) ) or 20 sample h-1 (0. 1 μg mL-1Cr (VI) . The preconcentration factor is 55. The detection limit is 0. 8 ng·mL-1 Cr(VI). The reproducibility is satisfactory with a relative standard deviation of less than 3. 35% (0. Of μg'mL-1Cr (VI), n = 5).

An On-line Galvanic Cell Generated Electrochemiluminescence and Flow Injection Determination of Calcium in Milk and Vegetable

An on-line Ag/Al galvanic cell is investigated and employed to generate electrochemiluminescence (ECL). The potential of the galvanic cell could be adjusted by varying the components of flow reagent. The cell performed perfect capability of supplying a stable potential for ECL generation. Based on the weak ECL of calcein blue could be greatly sensitized by the presence of calcium in alkaline solution, calcium contents in milk samples and in cabbage were assayed and the results were compared with those from ICP-AES method.

In vivo label-free measurement of blood flow velocity symmetry based on dual line scanning third-harmonic generation microscopy excited at the 1700 nm window

Measurement of bloodflow velocity is key to understanding physiology and pathology in vivo.While most measurements are performed at the middle of the blood vessel,little research has been done on characterizing the instantaneous bloodflow velocity distribution.This is mainly due to the lack of measurement technology with high spatial and temporal resolution.Here,we tackle this problem with our recently developed dual-wavelength line-scan third-harmonic generation(THG)imaging technology.Simultaneous acquisition of dual-wavelength THG line-scanning signals enables measurement of bloodflow velocities at two radially symmetric positions in both venules and arterioles in mouse brain in vivo.Our results clearly show that the instantaneous bloodflow velocity is not symmetric under general conditions.

Evaluating the stability and volumetric flowback rate of proppant packs in hydraulic fractures using the lattice Boltzmann-discrete element coupling method

The stability and mobility of proppant packs in hydraulic fractures during hydrocarbon production are numerically investigated by the lattice Boltzmann-discrete element coupling method(LB-DEM).This study starts with a preliminary proppant settling test,from which a solid volume fraction of 0.575 is calibrated for the proppant pack in the fracture.In the established workflow to investigate proppant flowback,a displacement is applied to the fracture surfaces to compact the generated proppant pack as well as further mimicking proppant embedment under closure stress.When a pressure gradient is applied to drive the fluid-particle flow,a critical aperture-to-diameter ratio of 4 is observed,above which the proppant pack would collapse.The results also show that the volumetric proppant flowback rate increases quadratically with the fracture aperture,while a linear variation between the particle flux and the pressure gradient is exhibited for a fixed fracture aperture.The research outcome contributes towards an improved understanding of proppant flowback in hydraulic fractures,which also supports an optimised proppant size selection for hydraulic fracturing operations.

A semi-analytical model for coupled flow in stress-sensitive multi-scale shale reservoirs with fractal characteristics

A large number of nanopores and complex fracture structures in shale reservoirs results in multi-scale flow of oil. With the development of shale oil reservoirs, the permeability of multi-scale media undergoes changes due to stress sensitivity, which plays a crucial role in controlling pressure propagation and oil flow. This paper proposes a multi-scale coupled flow mathematical model of matrix nanopores, induced fractures, and hydraulic fractures. In this model, the micro-scale effects of shale oil flow in fractal nanopores, fractal induced fracture network, and stress sensitivity of multi-scale media are considered. We solved the model iteratively using Pedrosa transform, semi-analytic Segmented Bessel function, Laplace transform. The results of this model exhibit good agreement with the numerical solution and field production data, confirming the high accuracy of the model. As well, the influence of stress sensitivity on permeability, pressure and production is analyzed. It is shown that the permeability and production decrease significantly when induced fractures are weakly supported. Closed induced fractures can inhibit interporosity flow in the stimulated reservoir volume (SRV). It has been shown in sensitivity analysis that hydraulic fractures are beneficial to early production, and induced fractures in SRV are beneficial to middle production. The model can characterize multi-scale flow characteristics of shale oil, providing theoretical guidance for rapid productivity evaluation.

基于Moldflow软件对薄壁件某塑料喷嘴的注塑方案优化研究

喷嘴注塑产品的质量和性能很大程度上由注塑方案和工艺参数所决定,不当的注塑方案和工艺参数会导致充填不足、熔接线过多、翘曲变形量大等问题。为了可以减少生产周期,节约生产成本,利用三维软件UG对喷嘴进行建模,基于模流分析软件Moldflow软件对喷嘴注塑产品进行分析和优化,通过比较点浇口和侧浇口两种方案的分析结果,最终确定该产品点浇口的方案更好。并通过设计正交实验,得到优化后的工艺参数。

Investigation of pore geometry influence on fluid flow in heterogeneous porous media:A pore-scale study

Brazilian pre-salt reservoirs are renowned for their intricate pore networks and vuggy nature,posing significant challenges in modeling and simulating fluid flow within these carbonate reservoirs.Despite possessing excellent petrophysical properties,such as high porosity and permeability,these reservoirs typically exhibit a notably low recovery factor,sometimes falling below 10%.Previous research has indicated that various enhanced oil recovery(EOR)methods,such as water alternating gas(WAG),can substantially augment the recovery factor in pre-salt reservoirs,resulting in improvements of up to 20%.Nevertheless,the fluid flow mechanism within Brazilian carbonate reservoirs,characterized by complex pore geometry,remains unclear.Our study examines the behavior of fluid flow in a similar heterogeneous porous material,utilizing a plug sample obtained from a vugular segment of a Brazilian stromatolite outcrop,known to share analogies with certain pre-salt reservoirs.We conducted single-phase and multi-phase core flooding experiments,complemented by medical-CT scanning,to generate flow streamlines and evaluate the efficiency of water flooding.Subsequently,micro-CT scanning of the core sample was performed,and two cross-sections from horizontal and vertical plates were constructed.These cross-sections were then employed as geometries in a numerical simulator,enabling us to investigate the impact of pore geometry on fluid flow.Analysis of the pore-scale modeling and experimental data unveiled that the presence of dead-end pores and vugs results in a significant portion of the fluid remaining stagnant within these regions.Consequently,the injected fluid exhibits channeling-like behavior,leading to rapid breakthrough and low areal swept efficiency.Additionally,the numerical simulation results demonstrated that,irrespective of the size of the dead-end regions,the pressure variation within the dead-end vugs and pores is negligible.Despite the stromatolite's favorable petrophysical properties,including relatively high porosity and permeability,as well as the presence of interconnected large vugs,the recovery factor during water flooding remained low due to early breakthrough.These findings align with field data obtained from pre-salt reservoirs,providing an explanation for the observed low recovery factor during water flooding in such reservoirs.