Study on the clogging mechanism of punching screen in sand control by the punching structure parameters

As an independent sand control unit or a common protective shell of a high-quality screen,the punching screen is the outermost sand retaining unit of the sand control pipe which is used in geothermal well or oil and gas well.However,most screens only consider the influence of the internal sand retaining medium parameters in the sand control performance design while ignoring the influence of the plugging of the punching screen on the overall sand retaining performance of the screen.To explore the clogging mechanism of the punching screen,this paper established the clogging mechanism calculation model of a single punching screen sand control unit by using the computational fluid mechanics-discrete element method(CFD-DEM)combined method.According to the combined motion of particles and fluids,the influence of the internal flow state on particle motion and accumulation was analyzed.The results showed that(1)the clogging process of the punching sand control unit is divided into three stages:initial clogging,aggravation of clogging and stability of clogging.In the initial stage of blockage,coarse particles form a loose bridge structure,and blockage often occurs preferentially at the streamline gathering place below chamfering inside the sand control unit.In the stage of blockage intensification,the particle mass develops into a relatively complete sand bridge,which develops from both ends of the opening to the center of the opening.In the stable plugging stage,the sand deposits show a“fan shape”and form a“V-shaped”gully inside the punching slot element.(2)Under a certain reservoir particle-size distribution,The slit length and opening height have a large influence on the permeability and blockage rate,while the slit width size has little influence on the permeability and blockage rate.The microscopic clogging mechanism and its law of the punching screen prevention unit are proposed in this study,which has some field guidance significance for the design of punching screen and sand prevention selection.

A Study on the Problem of Employee Punch Card Substitution in Enterprise Management:The Case of Jingdong Enterprise

With economic progress and the continuous advancement of science and technology,the issue of employees substituting punch cards has gradually become a significant challenge in enterprise management.The purpose of this paper is to discuss the causes,effects,and countermeasures of the employee punch card phenomenon,with the aim of providing effective management recommendations for Chinese enterprises.In practice,enterprises should flexibly apply the countermeasures proposed in this paper according to their specific circumstances to prevent substitute punch card incidents and improve overall management efficiency.

A simplified approach for negative skin friction calculation of special-shaped pile considering pile-soil interaction under surcharge

A simplified approach was proposed to analyze the negative skin friction calculation of special-shaped pile considering pile-soil interaction under surcharge. Based on the concentric cylinder shearing theory, considering the changes of pile shape(such as, taper angle and diameters of pile base, etc.), the load-transfer of special-shaped pile was built. The accuracy of the developed simplified approach was verified by numerical simulation model with the same condition. Then, the influence factors, such as, taper angles, the diameter of pile base, surcharge, and pile-soil interface parameters were analyzed and discussed. The results show that the developed simplified approach can calculate NSF of special-shaped pile under surcharge effectively. A limited parametric study indicates that in many practical situations special-shaped piles(such as belled wedge pile shown in this work) offer a design option that is more economical than traditional uniform cross-section piles.

Reduced power consumption in stirred vessel with high solid loading by equipping punched baffles

Solid-liquid suspension in stirred tank is a common operation in the chemical industry. The power consumption, flow pattern and flow field instability of three systems named as unbaffled stirred tank, traditional baffled stirred tank and punched baffled stirred tank(Pun-BST) were studied by using the computational fluid dynamic analysis. Results showed that perforating holes in the baffles could reduce power consumption of mixing. Meanwhile, the punched baffle system could maintain the solids in suspension as traditional baffle system. The results also showed that the baffles could increase the “effective flow” of stirred tank even though the whole velocity of the vessel is lower than un-baffled vessel. In addition, both the solid-liquid suspension and “effective flow” were related to instability of the flow field.Perfect solid-liquid suspension results always along with obvious instability of the flow field. But, the strengthening effect of punched baffle on flow field instability mainly happened in the near-wall area.It's because the collision and aggregation among sub-streams induced by holes intensified the unstable fluid flow. On the whole, the Pun-BST system provided much better mixing characteristics and recommended to apply in the industrial process.

Experimental Study on Seismic Behavior of Exterior Joints of Special-shaped Columns with Different Lengths of Limbs

Four exterior joints with special-shaped columns which have different lengths of limbs are tested under low cyclic loading. Speeial-shaped columns adopted are L- and T-shaped in section. It can be concluded that crack pattern, failure mode and shear strength of joints are affected by the length of limb, and that shear strength and ductility increase with the length of limb; the joints with the flexural failure of the beam have better seismic behavior than those with the shear failure of the joint core.

Henry入路蝶形钢板内固定治疗桡骨远端双柱Die-punch骨折

目的:探讨Henry入路蝶形钢板切开复位内固定治疗桡骨远端双柱Die-punch骨折的临床疗效。方法:选择2018年1月至2021年6月采用Henry手术入路切开复位内固定治疗的26例桡骨远端双柱Die-punch骨折患者,男14例,女12例;年龄20~75(44.2±3.4)岁。观察术后并发症情况,术后12个月采用Gartland-Werley评分标准进行腕关节功能评价。结果:26例患者均获得随访,时间10~18(13.4±0.8)个月。所有骨折均获得骨性愈合,时间8.5~15.8(11.4±0.5)周。所有患者手术切口都Ⅰ期愈合,无伤口感染、血管神经损伤及内固定失效等病例。术后12个月GarthndWerley评分(3.65±0.36)分,优16例,良8例,可2例。结论:通过掌侧Henry入路,使用蝶形钢板切开复位内固定治疗桡骨远端双柱Die-punch骨折,可获得满意的临床疗效。

Design of Special-shaped Interchange between Expressway and Urban Road in Mountainous Cities

Driven by the rapid economic development,the development of transportation in China has begun to move towards mountainous areas.The climate environment,topography and landform of mountainous cities are different from those of plain areas.In mountainous cities,the area of opposite interchanges between expressways and urban roads is generally large,which has a certain contradiction with the topographic conditions of mountainous cities.Therefore,it is necessary to reasonably design the opposite interchanges between expressways and urban roads in mountainous cities.The author explores and analyzes the factors restricting the special-shaped interchange between expressway and urban road in mountainous cities and the main fbnns of special-shaped interchange,and puts forward a reasonable design scheme,hoping to make a smooth development of the special-shaped interchange in mountainous cities.

草莓移栽机控制系统设计与试验

针对草莓高起垄定向移栽农艺要求,设计一种机械打穴、人工识别草莓苗弓背方向后定向穴栽的移栽机。基于可编程控制器(PLC)设计整机控制系统,包括移栽机定速行走控制系统、前轮转向控制系统、打穴控制系统等任务模块。整机采用直流无刷电机作为底盘的驱动元件,根据电机自带编码器的输出值进行行走速度、栽植株距和打穴频率的协调控制,采用步进电机作为打穴机构的驱动元件,由接近开关对打穴机构进行定位,通过二者配合完成打穴过程,在人机协同作业下,完成草莓苗移栽。试验结果表明:当单行移栽效率为15株/min,株距为150 mm、200 mm、250 mm时,株距合格率、孔深合格率、孔径合格率均在95%以上,其变异系数均小于5%,打穴成功率均大于95%,符合移栽机行业标准,打穴移栽效果满足农艺要求。

钢筋混凝土板柱节点冲切性能研究进展

为提高板柱节点冲切性能从而促进其工程应用,比较了各类抗冲切元件的不同布置形式、形状尺寸、几何参数以及组合形式对节点抗冲切承载力的影响,概括了受损板柱节点修复与加固的研究现状,梳理了不同开洞尺寸、距离、数量、形状及偏心荷载作用下开洞板柱试件抗冲切性能的研究成果,归纳了有无抗冲切钢筋和配置型钢剪力架板柱节点的抗冲切承载力计算方法以及基于机器学习的板柱节点冲切承载力预测方法。结果表明:各类抗冲切元件可通过改变布置形式、形状尺寸、几何参数以及元件组合从而改善板柱节点的冲切性能;板件开洞的尺寸越大、距离越远、数量越多,对节点的抗冲切性能越不利;基于数值模拟和规范改进得出的冲切承载力计算公式仅对特定试验有较高的预测精度,尚未形成较为统一的承载力计算公式,而基于机器学习的冲切承载力预测模型是未来研究的重点;需进一步开展关于受损板柱节点修复与加固方法的研究,对完善板柱节点抗冲切性能研究理论体系具有重要意义。

机械完工尾项管理系统在FPSO建造项目的应用

在国际海洋工程建造项目中,机械完工被广泛采用。作为从施工到调试前的重要过渡阶段,机械完工是一种工程管理理念,也是项目精细化管理的体现。施工和检验人员在根据ITR执行机械完工检查的过程中会记录大量尾项,并形成尾项清单。如何快速高效地对完工尾项进行实时跟踪和管理是项目管理人员和现场检验人员关注的重点。基于以上需求,提出了一种解决方案,基于Django建立了一套机械完工尾项管理系统。在某FPSO项目的实际运行效果良好,其中的应用经验可供其他类似项目参考。

H13钢模具冲头早期断裂原因

在对某钻杆接头进行锻造加工时,H13钢模具冲头发生早期断裂现象。采用宏观观察、化学成分分析、扫描电镜分析、硬度测试、金相检验等方法分析其早期断裂原因,并结合实际工况,对断裂冲头进行有限元热模拟试验。结果表明:冲头断口呈塑性断裂特征,在接头冲模成型时,冲头在接头内部停留时间过长,使冲头温度超过700℃,内部组织发生了转变,强度急剧降低,最后导致冲头发生拉拔塑性断裂现象。

FRP筋混凝土双向板冲切强度公式评估

为评价现有FRP筋混凝土双向板冲切强度计算公式的精度,采用数理统计的方法对收集到的38组FRP筋混凝土双向板冲切强度试验数据进行评估。结果表明,影响FRP筋混凝土双向板冲切强度的主要因素有混凝土强度、临界冲切截面周长、有效板厚、FRP筋配筋率及其弹性模量、尺寸效应;在所评价的10个计算公式中,规范公式的预测结果大多比较保守,且其精度均低于文献公式;Ospina公式预测结果与试验结果最为接近,且精度最高,预测结果与试验结果比值的均值为1.03,标准差为16.04%,变异系数为15.53%。研究结果为FRP筋混凝土双向板冲切强度计算公式的进一步优化提供了参考。

基于小冲杆试验的纯钨韧脆转变温度测定及其变形特性

在不同温度(25,200,300,400,500℃)下对纯钨进行小冲杆试验,获得断裂能与温度之间的关系,拟合得到纯钨的韧脆转变温度;对不同温度小冲杆试验后的纯钨断口形貌进行观察,探究纯钨在小冲杆试验中的变形特性。结果表明:在25,200℃下纯钨处于完全脆性状态,在300℃下处于半脆性状态,而当温度达到400℃后,纯钨表现出良好的塑性;在250~400℃范围内纯钨的断裂能急剧升高,拟合得到的韧脆转变温度为(342±8)℃。当温度低于韧脆转变温度,纯钨断口存在沿轧制方向的长直裂纹,断裂特征随温度升高由沿晶断裂向穿晶断裂转变;当温度高于韧脆转变温度,断口出现帽形挤出形貌以及环形裂纹和短缺口裂纹,并且环形裂纹处存在大量韧窝,断裂特征为韧性断裂,且短缺口裂纹处出现钨分层现象。

基于正交试验的PE淋膜纸冲裁工艺参数优化

为了提高冲裁加工PE淋膜纸的断面质量,该文以冲裁速度、冲裁间隙、斜刃倾角三种工艺参数为影响因素,选择纸张毛刺高度作为评价指标,利用正交试验对工艺参数进行分析。结果表明:冲裁工艺参数对纸张毛刺高度的影响程度分别为:加工间隙>冲裁速度>斜刃倾角。冲裁速度的变化与纸张毛刺高度的变化呈负相关,斜刃倾角、加工间隙的变化与纸张毛刺高度的变化呈正相关。研究得出最优冲裁工艺参数组合为:冲裁速度为220 n·min^(-1),斜刃倾角为0.35°,加工间隙为20μm。该项实验研究结果对提高冲裁加工PE淋膜纸的断面质量和生产效率以及降低产品的加工成本具有重要参考价值,在实际生产中具有一定的实用性、经济性价值。

体育服饰用超细纤维合成革针刺非织造基布的力学性能表征

为有效解决开纤处理后海岛超细纤维针刺非织造基布致密性低且针刺痕迹等一系列问题,以促使其在体育服饰用超细纤维合成革中广泛应用,本文基于针刺法将高收缩聚酯纤维掺入海岛超细纤维合成革非织造基布,以制备生成了超细纤维合成革针刺非织造基布,并对其力学性能进行了测试表征。结果发现,随着高收缩聚酯纤维掺入量增加,超细纤维合成革针刺非织造基布断裂强度与撕裂强度皆逐渐增大;透湿性与吸湿性先降低后升高;热收缩率逐步增高;耐磨性逐渐提升,且基布均匀度较好;弯曲长度与弯曲刚度皆逐渐增大,柔软度随之降低;以针刺非织造基布为原料制成的体育服饰用超细纤维合成革表面平整且光滑,底面平整且粗糙度适中,致密性较好,且断裂强度、撕裂强度、透湿性与吸水性均表现优异。

基于CAD/CAE的异形凸模冲头工装设计与优化研究

异形凸模冲头是汽车锁头连接件模具的重要配件,其材料为冷作模具钢DC53,对汽车锁孔冲压有重要作用。传统加工中,加工质量无法保证,生产效率低。设计了专用工装,结合CAD/CAE软件,优化并改进工装结构设计。实际加工对比表明,该工装的设计与优化方案合理,改进工装后,凸模冲头零件生产效率和加工质量均显著提高。该研究对同类异型模具工装设计也具有参考价值。

不同配筋率下钢筋混凝土板柱节点抗冲切承载力试验研究

为研究纵筋配筋率对普通钢筋混凝土板柱节点抗冲切承载力的影响,制作了4个配筋率分别为0.3%、0.7%、1.2%及1.8%的无腹筋板柱中节点并进行冲切试验,试验结果表明:随着配筋率的增加,板柱节点的初始刚度和极限承载力明显增加,试件的延性降低,破坏模式由弯曲破坏逐渐向冲切破坏转变;收集并整理了国内外269个板柱节点冲切试验的数据,通过与采用中国规范、美国规范、欧洲规范和日本规范抗冲切承载力计算公式计算结果的对比分析,进一步说明了在冲切承载力计算公式中考虑纵筋配筋率的必要性;通过对试验数据的回归分析,考虑包含纵筋配筋率在内的主要影响因素,建立了适用于钢筋混凝土无腹筋板柱抗冲切承载力的计算公式。

中重度牙周炎患者维护期应用PDCA循环管理模式联合脉冲式冲牙器的临床疗效

目的:观察中重度牙周炎患者维护期应用质量控制(PDCA)循环管理模式联合脉冲式冲牙器的临床效果,为PDCA循环管理模式在牙周炎患者中的应用提供理论依据。方法:通过预定的试验纳入标准、排除标准和剔除标准选取50例中重度牙周炎患者,随机分为实验组(n=25)和对照组(n=25),实验组患者通过脉冲式冲牙器联合巴氏(BASS)刷牙法维护,对照组患者单纯通过BASS刷牙法维护。2组患者均采用PDCA循环管理模式,在自我维护2、4、8和12周分别要求患者复诊,通过患者菌斑堆积量进行个性化纠正和指导,在自我维护4和12周时观察并记录2组患者牙周临床检查指标,包括菌斑指数(PLI)、探诊深度(PD)和出血指数(BI),检测龈沟液中肿瘤坏死因子α(TNF-α)和白细胞介素17(IL-17)水平。结果:经过4和12周自我维护,与对照组比较,实验组患者PLI、PD和BI明显降低(P<0.01);与基线时比较,自我维护4和12周时2组患者PLI、PD和BI均明显升高(P<0.05或P<0.01);与自我维护4周时比较,自我维护12周时2组患者PLI、PD和BI值明显升高(P<0.01)。经过4和12周自我维护,与对照组比较,实验组患者龈沟液中TNF-α和IL-17水平明显降低(P<0.01);与基线时比较,自我维护4和12周时2组患者龈沟液中TNF-α和IL-17水平均明显升高(P<0.01)。结论:在PDCA循环管理模式下应用脉冲式冲牙器可明显降低中重度牙周炎患者的PLI、PD、BI和龈沟液中炎症因子水平,有效抑制菌斑的形成并控制牙龈炎症状态,有利于中重度牙周炎患者治疗效果的维护。

配置抗冲切钢筋的RC板柱节点受冲切承载力计算

为计算配有常用抗冲切钢筋(箍筋和栓钉)的钢筋混凝土(RC)板柱节点的受冲切承载力,结合梁斜拉破坏机理和修正压力场理论(MCFT)提出一种配有抗冲切钢筋的RC板柱节点的受冲切承载计算方法.首先根据MCFT推导出配有抗冲切钢筋的RC板柱节点的临界斜裂缝倾角计算式;然后,假定冲切破坏时临界截面周长范围内的抗冲切钢筋达到屈服强度,将临界斜裂缝倾角代入MCFT推导出板柱节点的受冲切承载力计算方法;最后,使用该方法和美国规范(ACI 318-19)方法计算62个配有抗冲切钢筋的RC板柱节点试验的冲切承载力,并分析了混凝土强度、板有效厚度、柱截面边长、抗弯钢筋配筋率及抗冲切钢筋配筋率对节点抗冲切承载力的影响.结果表明:由MCFT推导出的节点受冲切承载力计算值与试验值吻合较好,均值为0.96,变异系数为0.20;节点的冲切承载力与上述影响因素呈非线性正相关.该方法可用于配有抗冲切钢筋的RC板柱节点的受冲切承载力计算.

在线激光打孔参数对中支卷烟理化指标的影响

[目的]明确在线激光打孔参数对中支卷烟理化指标的影响,为中支卷烟激光打孔参数的设置提供借鉴。[方法]以物理指标、常规烟气成分释放量和感官质量为衡量指标,分析不同在线激光打孔参数对中支卷烟质量的影响。[结果]激光打孔数量与中支卷烟吸阻呈现负相关关系(P<0.01),与滤嘴通风率、总通风率呈现正相关关系(P<0.01),与TPM、水分、焦油释放量均呈现二次回归关系。激光脉冲时间与中支卷烟吸阻、滤嘴通风率、总通风率均呈现二次回归关系,但其对常规烟气成分释放量无显著影响。激光打孔数量对中支卷烟理化指标的影响程度大于激光脉冲时间,在线激光打孔参数主要影响中支卷烟的香气量、刺激性和协调性。[结论]得到一套在线激光打孔参数和中支卷烟理化指标关系的数学模型,可应用于中支卷烟开发和产品维护中激光打孔参数的设置。