Modeling and Investigation of the Wall Thickness Changes and Process Time in Thermo-Mechanical Tube Spinning Process Using Design of Experiments

Tube spinning technology is one of the effective methods of manufacturing large diameter thin-walled shapes. In this research, effects of major parameters of thermo mechanical tube spinning process such as preform's thickness, percentage of thickness reduction, mandrel rotational speed, feed rate, solution treatment time and aging treatment time on the wall thickness changes and process time in thermo-mechanical tube spinning process for fabrication of 2024 aluminum spun tubes using design of experiments (DOE), are studied. The statistical results are verified through some experiments. Results of experimental evaluation are analyzed by variance analysis and mathematic models are obtained. Finally using these models, input parameters for optimum production are achieved.

Effect of the Oxidation Time on Properties of Ceramic Coatings Produced on Ti-6Al-4V by Micro-Arc Oxidation

Ceramic coatings were prepared on Ti-6AI-4V alloy using ac micro-arc oxidation (MAO) in silicate-hypophosphate solution. Growth regularity and formation mechanism of ceramic coatings were discussed. It was found that during the first stage the growth rate of coatings toward the external surface was larger than that toward substrate and then the coating began to grow mainly towards Ti alloy. When the total coating thickness reaches a certain value, it would no longer increase. In addition, the variations of the composition and microstructure of ceramic coatings according to the depositing time were also investigated with X-ray diffraction (XRD) and scanning electron microscope (SEM). The amount of rutile TiO2 gradually increased, whereas the amounts of the anatase TiO2 and amorphous phases first increased and then decreased slightly.

Influence of Blade Thickness on Transient Flow Characteristics of Centrifugal Slurry Pump with Semi-open Impeller

As the critical component, the impellers of the slurry pumps usually have blades of a large thickness. The increasing excretion coefficient of the blades affects the flow in the impeller resulting in a relatively higher hydraulic loss, which is rarely reported. In order to investigate the influence of blade thickness on the transient flow characteristics of a centrifugal slurry pump with a semi-open impeller, transient numerical simulations were carried out on six impellers, of which the meridional blade thickness from the leading edge to trailing edge varied from 5-10 mm, 5-15 mm, 5-20 mm, 10-10 mm, 10-15 mm, and 10-20 mm, respectively. Then, two of the six impellers, namely cases 4 and 6, were manufactured and experimentally tested for hydraulic performance to verify the simulation results. Results of these tests agreed reasonably well with those of the numerical simulation. The results demonstrate that when blade thickness increases, pressure fluctuations at the outlet of the impeller become severe. Moreover, the standard deviation of the relative velocity in the middle portion of the suction sides of the blades decreases and that at the outlet of the impeller increases. Thus, the amplitude of the impeller head pulsation for each case increases. Meanwhile, the distribution of the time-averaged relative flow angle becomes less uniform and decreases at the outlet of the impeller. Hence, as the impeUer blade thickness increases, the pump head drops rapidly and the maximum efficiency point is offset to a lower flow rate condition. As the thickness of blade trailing edge increases by 10 mm, the head of the pump drops by approximately 5 m, which is approximately 10 % of the original pump head. Futhermore, it is for the first time that the time-averaged relative flow angle is being considered for the analysis of transient flow in centrifugal pump. The presented work could be a useful guideline in engineering practice when designing a centrifugal slurry pump with thick impeller blades.

Residence time distribution of high viscosity fluids falling film flow down outside of industrial-scale vertical wavy wall: Experimental investigation and CFD prediction

The flow behavior of gravity-driven falling film of non-conductive high viscosity polymer fluids on an industrial-scale vertical wavy wall was investigated in terms of film thickness and residence time distribution by numerical simulation and experiment.Falling film flow of high viscosity fluids was found to be steady on a vertical wavy wall in the presence of the large film thickness.The comparison between numerical simulation and experiment for the film thickness both in crest and trough of wavy wall showed good agreement.The simulation results of average residence time of falling film flow with different viscous fluids were also consistent with the experimental results.This work provides the initial insights of how to evaluate and optimize the falling film flow system of polymer fluid.

Minimum critical thickness of dike for ore-bearing fluid injection:A new approach applied to the Shihu gold deposit,Hebei Province,North China

According to the metallogenic theory by transmagmatic fluid （TMF）, one magmatic intrusion is a channel of ore-bearing fluids, but not their source. Therefore, it is possible to use TMF＇s ability for injection into and for escaping t^om the magmatic intrusion to evaluate its ore-forming potential. As the ore-bearing fluids cannot effectively inject into the magmatic intrusion when the magma fully crystal- lized, the cooling time and rates viscosity varied can be used to estimate the minimum critical thickness of the intrusion. One dimensional heat transfer model is used to determine the cooling time for three representative dikes of different composition （granite porphyry, quartz diorite and diabase） in the Shihu gold deposit. It also estimated the rates viscosity varied in these time interval. We took the thickness of dike at the intersection of the cooling time -- thickness curve and the rates viscosity varied versus thick- ness curve as the minimum critical thickness. For the ore-bearing fluids effectively injecting into the magma, the minimum critical thicknesses for the three representative dikes are 33.45 m for granite porphyry, 8.22 m for quartz diorite and 1.02 m for diabase, indicating that ore-bearing dikes must be thicker than each value. These results are consistent with the occurrence of ore bodies, and thus they could be applied in practice. Based on the statistical relationship between the length and the width of dikes, these critical thicknesses are used to compute critical areas： 0.0003--0.0016 km2 for diabase, 0.014--0.068 km2 for quartz diorite and 0.011-0.034 km2 for granite porphyry. This implies that ore- bearing minor intrusions have varied areas corresponding to their composition. The numerical simulation has provided the theoretical threshold of exposed thickness and area of the ore-bearing intrusion. These values can be used to determine the ore-forming potentials of dikes.

A borehole stability study by newly designed laboratory tests on thick-walled hollow cylinders

At several mineral exploration drilling sites in Australia, weakly consolidated formations mainly consistof sand particles that are poorly bonded by cementing agents such as clay, iron oxide cement or calcite.These formations are being encountered when drilling boreholes to the depth of up to 2 0 0 m. To studythe behaviour of these materials, thick-walled hollow cylinder （TWHC） and solid cylindrical syntheticspecimens were designed and prepared by adding Portland cement and water to sand grains. The effectsof different parameters such as water and cement contents, grain size distribution and mixture curingtime on the characteristics of the samples were studied to identify the mixture closely resembling theformation at the drilling site. The Hoek triaxia! cell was modified to allow the visual monitoring of graindebonding and borehole breakout processes during the laboratory tests. The results showed the significanceof real-time visual monitoring in determining the initiation of the borehole breakout. The sizescaleeffect study on TWHC specimens revealed that with the increasing borehole size, the ductility ofthe specimen decreases, however, the axial and lateral stiffnesses of the TWHC specimen remain unchanged.Under different confining pressures the lateral strain at the initiation point of boreholebreakout is considerably lower in a larger size borehole （2 0 mm） compared to that in a smaller one（10 mm）. Also, it was observed that the level of peak strength increment in TWHC specimens decreaseswith the increasing confining pressure.

Comparison and interchangeability of macular thickness measured with Cirrus OCT and Stratus OCT in myopic eyes

AIMTo investigate the difference of macular thickness measurements between stratus optical coherence tomography (OCT) and Cirrus OCT (Carl Zeiss Meditec, Dublin, CA, USA) in the same myopic patient and to develop a conversion equation to interchange macular thickness obtained with these two OCT devices.METHODSEighty-nine healthy Chinese adults with spherical equivalent (SE) ranging from -1.13 D to -9.63 D were recruited. The macular thickness was measured by Cirrus OCT and Stratus OCT. The correlation between macular thickness and axial length and the agreement between two OCT measurements were evaluated. A formula was generated to interchange macular thickness obtained with two OCT devices.RESULTSAverage macular thickness measured with Stratus OCT (r=-0.280, P=0.008) and Cirrus OCT (r=-0.224, P=0.034) were found to be negatively correlated with axial length. No statistically significant correlation was found between axial length and central subfield macular thickness (CMT) measured with Stratus OCT (r=0.191, P=0.073) and Cirrus OCT (r=0.169, P=0.113). The mean CMT measured with Cirrus OCT was 53.63±7.94 µm thicker than with Stratus OCT. The formula CMTCirrus OCT=78.328+0.874×CMTStratus OCT was generated to interchange macular thickness obtained with two OCT devices.CONCLUSIONMacular thickness measured with Cirrus OCT were thicker than with Stratus OCT in myopic eyes. A formula can be used to interchange macular thickness measured with two OCT devices in myopic eyes. Studies with different OCT devices and larger samples are warranted to enable the comparison of macular values measured with different OCT devices.

变厚度CFRP超声缺陷自动成像的相关性算法研究

针对变厚度碳纤维增强聚合物复合材料(carbon fiber reinforced polymer,CFRP)超声缺陷成像工序繁琐的问题,提出了一种基于相关性的自动成像算法。试验预埋夹杂缺陷,使用超声相控阵检测获取数据,首先依据离散序列互相关理论,对不同厚度CFRP的超声A扫描信号进行底波时移处理,之后利用自相关理论从无缺陷区域生成必要的参考信号。通过相关计算结果,利用欧氏距离区分缺陷信号和非缺陷信号,并依据欧式距离进行颜色编码绘图。最后通过基于机器视觉以及Hough圆变换的边缘检测算法来对缺陷尺寸进行统计测量,总体均值误差率小于7%,最大误差率为16.25%,最小误差率为0.25%。结果表明该算法可广泛应用于变厚度CFRP自动化超声检测。

不同时间添加蚯蚓对矸石覆土生理生态的影响

为探究不同时间添加蚯蚓对矸石覆土中香根草(Vetiveria zizanioides)生理生态的影响,采用土柱试验,设置两种覆土厚度[30 cm(M)、50 cm(N)],每组覆土分别设4个处理组:单独种植香根草(CK)、接种蚯蚓20 d后添加香根草(A)、同时接种蚯蚓和添加香根草(B)、添加香根草20 d后接种蚯蚓(C)处理,分析覆土理化性质及香根草生理生态指标变化特征。结果显示:与CK相比,A、B和C处理均能使覆土pH显著降低趋向中性(P<0.05),提升覆土电导率(EC)、有机质(OM)、全氮(TN)和全磷(TP)含量。与CK相比,不同时间接种蚯蚓均能增加香根草发芽率、总重和叶绿素a含量,其中B处理光合色素(叶绿素a、叶绿素b、类胡萝卜素)含量、A处理叶绿素b含量和C处理根系总长较CK均显著提高(P<0.05)。与CK相比,B处理降低香根草可溶性蛋白和脯氨酸含量效果较强,30和50 cm厚度覆土下B处理香根草可溶性蛋白较CK分别降低9.34%和4.69%(P<0.05),50 cm厚度覆土下脯氨酸含量较CK降低了5.55%(P<0.05),而A处理能显著提高香根草丙二醛含量。同一覆土厚度下,A处理仅在30 cm条件下显著降低香根草过氧化氢酶活性;B、C处理香根草超氧化物歧化酶、过氧化物酶活性较CK相比均无显著差异(P>0.05)。冗余分析和相关性分析表明:A、C处理中覆土OM、TN是影响香根草生理生态特性主要环境因子,而B处理中覆土OM、TP是影响香根草生理生态特性的主要环境因子。研究结果可为蚯蚓-香根草联合应用于复垦土壤修复提供理论依据。

铝酸盐体系中氧化时间对碳化硅颗粒增强铝基复合材料微弧氧化膜层的影响

[目的]探究氧化时间对碳化硅颗粒增强铝基(SiC_(p)/Al)复合材料微弧氧化膜层的影响。[方法]选用铝酸盐体系作为电解液,对SiC_(p)/Al复合材料进行微弧氧化处理,分析氧化时间对膜层组织结构、物相、厚度、粗糙度、结合力、电绝缘性及耐蚀性的影响。[结果]随着氧化时间延长,膜层逐渐变得连续均匀,厚度增加。若氧化时间过长,膜层会出现层叠现象,形成大尺寸微孔及裂纹,且生长速率越来越低。膜层结合力随氧化时间延长先增大后减小,在60 min时最大,达到39.85 N。氧化时间为10 min时,膜层的电绝缘性及耐蚀性最优,100 V和500 V电压下的绝缘电阻分别达到3.11×10^(12)Ω和1.41×10^(12)Ω,腐蚀电位为-0.6298 V,腐蚀电流密度为1.332×10^(-7)A/cm^(2)。[结论]SiC_(p)/Al复合材料表面微弧氧化膜层的连续性、均匀性及生长速率均与氧化时间有关。需选择合适的氧化时间,才能制备出连续、均匀且综合性能优异的膜层。

基于时序LSTM-MLP模型的输电线路非平稳型覆冰厚度预测

在“两微”环境中,电力系统中输电线路受到严重覆冰的威胁,对电网运行的稳定性构成潜在风险。为提高事前预警运维效率,以经典输电线路的覆冰厚度监测时间序列为研究对象,创新地提出多变量长短期记忆-多层感知机(long short-term memory-multilayer perceptron, LSTM-MLP)模型,旨在建立合理可靠的覆冰厚度预测方法,以更好地捕捉输电线路覆冰监测数据的大范围波动。为此,使用LSTM-MLP模型分别对不同数据容量的导线运维数据进行预测并对比分析。模型使用导线覆冰量的时间序列数据对覆冰厚度进行预测,并引入温度、湿度、风力等多种覆冰控制因素提升模型在波动数据上的预测能力。为进一步提升模型性能,引入灰狼算法对模型超参数进行优化处理。结果显示:优化后的多变量LSTM-MLP模型对12个测试数据地覆冰厚度预测具有较低的均方根误差(root mean square error, RMSE)、平均绝对误差值(mean absolute error, MAE)和较高的决定系数(R~2),分别为1.076 5、0.745 5和0.889 3。对30个测试数据的预测结果,RMSE、MAE和R~2分别为0.881 4、0.523 8和0.931 5。这一系列结果相对于单变量LSTM-MLP模型更接近实际监测值,从而验证了多变量LSTM-MLP模型的高精度和可靠性。综上所述,多变量LSTM-MLP模型能够较好地捕捉输电线路覆冰数据的波动性,为非平稳型覆冰厚度的预测和预警提供了一种创新且高效的解决方案。

采后冷敏果蔬低温逆境下电解质外渗率测定的影响因素

冷敏果蔬在不良贮藏环境中遭受损伤,最先影响细胞膜结构与功能,破坏其选择透过性,损伤严重程度影响果蔬货架期间表观品质劣变速度,从而影响其商品价值。果蔬遭受逆境损伤程度与细胞膜透性紧密相关,而细胞膜透性的大小,通常以电解质外渗率进行表征。本研究就渗透提取剂及浓度、振荡时间、组织圆片厚度、不同组织部位等测定影响因素,采用典型冷敏果蔬“申青”黄瓜、“绿丰”西葫芦以及“甜杂”青圆椒作为研究对象选取展开试验,得出0.2 mol·L^(–1)甘露醇溶液为果蔬组织圆片(黄瓜、西葫芦、青圆椒)等渗浓度提取剂,在电解质外渗率测定时选取振荡时间范围90~240 min,组织圆片厚度0.7~2 mm的中果皮作为合适的取样组织进行测定。该研究结果可以更好反映采后果蔬低温逆境下受冷害后细胞膜透性改变的规律。

基于太赫兹时域光谱技术的CFRP薄涂层厚度检测方法

针对碳纤维增强复合材料(CFRP)上的薄涂层测厚存在的基底各向异性、多重反射、回波重叠、环境噪声等问题,提出基于太赫兹时域光谱技术与稀疏分解的涂层测厚方法,并在仿真波形和实际样品上成功验证。CFRP通常由碳纤维与环氧基体牢固结合并多层复合而成,具有各向异性特点,在光学性质上表现为CFRP上同一位置不同入射方向、同一入射方向不同位置的反射波形均存在差别。这致使基于理论模型的优化算法用于其上涂层测厚时精度有待提高。另外,在涂层较薄时,受噪声与多重反射等因素的干扰,无法直接在时域根据反射波形区分涂层界面,即直接使用飞行时间法(TOF)难以获得涂层厚度。为此,使用稀疏分解法来定位薄涂层的分界面,再结合TOF法计算CFRP上薄涂层的厚度。首先,分析了多层结构上的太赫兹反射信号与信号稀疏分解模型之间的联系,并利用参考信号构成稀疏字典。然后,鉴于太赫兹信号的传播路径只在分界面发生改变这一先验知识,即涂层层数决定了信号稀疏分解后非零脉冲个数,使用前向正交匹配追踪算法(LAOMP)求解太赫兹反射信号的稀疏表示。LAOMP算法可直接指定稀疏度,便于选择稀疏脉冲定位涂层分界面。获得对应于各涂层界面的脉冲后,使用TOF法求得涂层的厚度。最后,在总厚度分别为102和66μm的双涂层仿真数据与实际样品上验证方法的性能,并与经典基于L1范数的谱投影梯度算法(SPGL1)进行了对比。结果表明:在相邻涂层折射率差别较小的情况下,LAOMP算法可以有效检测CFRP上35μm的薄涂层。在总厚度为66μm的双涂层样件上,检测误差在11%以内,具有调参简单、结果稳定的优点。

杭州湾富浅层气区工程超前排气井井距优化研究

对遭遇浅层气灾害地质的工程,一般防治措施多为建设前期布设超前排气井进行控制性排气。深入了解排气过程中气藏内部的气水运移规律,对于排气井井距的设计和高效率排气有重要意义。基于非饱和土两相渗流原理和杭州湾富浅层气区的典型概化地质模型,利用数值模拟方法研究了有控排气条件下气藏内部气水界面运移过程,探讨了影响超前排气井布设的因素,提出一种井距优化方法,并在实际工程中应用。结果表明:不同井口排气速率下,气藏内部气水分布形态与气体排放效果显著不同;工程超前排气井井距的设置可以淹井时间最长和剩余气藏厚度最小进行优化;原始气藏压力是影响井距优化的最显著因素,而储气层下部渗水系数、气藏厚度等并不影响最优井距的确定;调节井距对改善竖向排气井的排气效果随原始气藏压力系数减小而减弱;原始气藏压力系数大,井距适当减小,反之,可适度增加;对于气藏压力系数小的工程,建议发展水平排气井布设技术,以改善排气效果。此外,工程超前排气井的井距设置还应考虑与建(构)筑物的合理安全距离,达到高效、安全和避免投资浪费的目的。

“帕纳斯的进阶”——“活的当下”的初始规定及其三个解释模型

从胡塞尔早期开始考察“活的当下”,是准确把握其系统性地位的必要步骤。通过重构性分析1893—1905年文本,我们发现:胡塞尔在亚里士多德-奥古斯丁争执和迈农-斯特恩争执中的态度表明,“活的当下”一开始就被规定为具有“厚度”的当下;作为对具有“厚度”之当下的第一个正面解释,心理学模型具有相对主义和循环论证的根本缺陷;形式化模型作为第二个解释虽然避免相对主义,但也只是论证了一种必然的可能性;第三个解释,即清新回忆模型,试图描述“活的当下”的现实被给予性,但其“内容-立义”模式使得它无法说明时间意识的直接性和连续性。因此,“活的当下”在此一阶段还在“帕纳斯的进阶”途中。

基于时域卷积网络的精轧出口厚度预测

以精轧过程为研究对象,引入时域卷积网络算法,构建了基于时域卷积网络的精轧出口厚度预测模型。利用时域卷积网络模型提取精轧过程时序数据的特征信息,通过优化模型结构和参数,提升精轧出口厚度预测性能。实际钢种数据集仿真实验结果表明,相较于传统方法,本文所提出的时域卷积网络算法在均方根误差、平均绝对百分比误差及决定系数等评价指标方面存在较大优势,可为现场工程师提供重要的决策信息。

高性能厚板多段轧制工艺研究

对高性能S420ML钢分别进行模拟两段和多段轧制。检测了不同工艺轧制的钢板的CCT曲线、显微组织和力学性能。结果表明:在多段轧制工艺过程中,钢板的待温厚度从120 mm增加至140 mm并增加未再结晶区的910℃轧制过程,能提高钢板未再结晶奥氏体的晶界能和位错能,钢板中具有更多的形核质点和更大的相变驱动力,从而组织细化、大角度晶界增多;大角度晶界增多使裂纹难以扩展,从而明显改善钢板的低温韧性,钢板1/4厚度处的-40℃冲击吸收能量提高了108 J;与普通两段轧制工艺相比,多段轧制工艺能提高中厚板的生产率。

基于LMS自适应时延估计的高精度超声测厚系统

针对现有超声测厚系统精度较低的问题,研制基于最小均方(Least Mean Square,LMS)自适应时间延迟估计的高精度超声测厚系统。设计超声发射及接收电路,研发基于现场可编程门阵列(Field Programmable Gate Array,FPGA)的高速数据采集及传输系统,开发基于MATLAB的上位机信号处理软件,通过LMS自适应时间延迟估计算法准确、高效地计算超声飞行时间(Time of Flight,TOF),从而实现高精度厚度测量。开展模拟回波仿真实验,结果显示:相较峰值法、包络法和相关法,LMS法在时间延迟估计方面更具优势。搭建基于LMS自适应时延估计的超声测厚系统,以量块为对象进行测厚实验,结果表明:该系统测厚相对误差小于3.77%,重复实验标准差不高于0.2μm,最大相对不确定度为1.4%。基于LMS自适应时延估计的超声测厚系统可应用于板材厚度测量等领域,有利于推动高精度超声测厚技术发展,具有重要技术借鉴价值。

基于改进广义S变换时频分析的“板状”断控油藏油柱高度预测

塔里木盆地北部坳陷碳酸盐岩断控领域油气资源丰富。断控“板状”油藏油水界面的识别是该类油藏效益开发的关键工作。钻井探测油藏油水界面的成本高、工程实现难度大,而采用地球物理的方法识别油水界面是一种高效措施。文章提出一种基于广义S变换时频分析的应用方法,通过大量过井地震道时频分析结果与开发动态分析数据联合分析,发现地震资料主频随深度/时间的变化与油层厚度具有正相关关系,提出采用地震道时频道集能量包络异常拐点判别油水界面的思路。实验表明,针对“板状”油藏,当油柱厚度OCH<120 m时,分析结果存在不确定性;当120≤OCH≤250 m时,分析结果基本可靠;当OCH>250 m时,油层厚度可靠。应用表明,在富满油田某区某断裂破碎带预测油层厚度主体为200~520 m,与当地开发实际相符,可指导开发实践。

围绝经期异常子宫出血合并子宫内膜病变的影响因素探究

目的:探讨围绝经期异常子宫出血合并子宫内膜病变的影响因素。方法:选取2021年5月至2023年5月期间在本院妇产科诊治的128例围绝经期异常子宫出血患者的临床资料进行回顾性分析。全部患者均接受诊刮术以获取子宫内膜组织进行病理学诊断。根据患者子宫内膜病变情况的病理学诊断结果将发生子宫内膜病变的患者分为病变组,其他未发生子宫内膜病变的患者分为正常组。查阅患者资料,分析围绝经期异常子宫出血合并子宫内膜病变的影响因素。结果:所有患者中合并子宫内膜病变93例(72.66%);单因素与多因素Logistic回归分析检验结果显示:年龄、子宫内膜厚度、出血时间均可能是围绝经期异常子宫出血患者合并子宫内膜病变的影响因素,其均是风险因素(OR>1,P<0.05)。结论:年龄大、子宫内膜厚度≥7 mm、出血时间≥3 m均可能会导致围绝经期异常子宫出血患者合并子宫内膜病变,应引起临床重视。