Model of Preformed Hole-Pairs in c-Axis Transport in Cuprate Superconductors

Model of hole-pairs in electrical transport along ab plane in cuprate superconductors has already been proposed. It has been found to be in the shape of 3dx2–y2 orbital of an electron in an atom. This time, model of hole-pairs in transport along c-axis in cuprate superconductors is proposed. In ab-plane, hole-pairs are formed along CuO2 plane;one hole-pair covering 9 - 10 two dimensional CuO2 unit cells in 3dx2–y2 configuration. In the investigation of c-axis hole-pairs, cuprate superconductors have been sub-divided into three categories depending on the number of CuO2 planes/formula unit. There is a little different treatment for finding out the order parameter in each category. Coherence lengths along ab-planes are of the order of a few tens of Angstroms, whereas along c-axis, they are less than even their a-, b-lattice constants. In cuprates with 2 or 3 CuO2 planes, the order parameter is of 3dz2–x2 type in zx-plane with lobes along both the axes much constrained. For cuprates with a single CuO2 layer, the order parameter is of 3dx2–y2 type, but its dimensions are less than a-, b-lattice constants.

Model of Preformed Hole-Pairs in Cuprate Superconductors

A model of preformed hole-pairs in cuprate superconductors has been proposed based on some experimental results i.e., 1) electron paramagnetic resonance spectra of quenched superconductors which show very frequently the fragment (CuO)4 broken off from the CuO2 layer in the structure, 2) 41 meV peak observed in neutron diffraction and nuclear magnetic resonance spectra of superconductors, 3) Heisenberg exchange interaction leading to ferromagnetism observed in CuO which is an essential ingredient of all superconductors and some generally accepted conclusions i.e., a) that the order parameter in superconductors has dx2–y2 symmetr and b) coherence length is of the order of 15 - 20 Angstrom. Heisenberg exchange interaction between two (CuO4) plaquettes each containing a lattice hole binds the two holes which are the charge carriers in the cuprate superconductors. It is not very clear whether the hole-pair is in the triplet or singlet state, but the triplet state is supported by the experimental observation of ferromagnetism in the parent material CuO. The proposed hole-pair singlet is different from Zhang-Rice singlet.

Insight into the preformed albumin corona on in vitro and in vivo performances of albumin-selective nanoparticles

Preformed albumin corona of albumin-nonselective nanoparticles(NPs)is widely exploited to inhibit the unavoidable protein adsorption upon intravenous administration.However,very few studies have concerned the preformed albumin corona of albumin-selective NPs.Herein,we report a novel type of albumin-selective NPs by decorating 6-maleimidocaproyl polyethylene glycol stearate(SA)onto PLGA NPs(SP NPs)surface,taking albuminnonselective PLGA NPs as control.PLGA NPs and SP NPs were prepared by emulsion-solvent evaporation method and the resultant NPs were in spherical shape with an average diameter around 180 nm.The corresponding albumin-coating PLGA NPs(PLGA@BSA NPs)and albumin-coating SP NPs(SP@BSA NPs)were formulated by incubating SP NPs or PLGA NPs with bovine serum albumin solution,respectively.The impact of albumin corona on particle characteristics,stability,photothermal effect,cytotoxicity,cell uptake,spheroid penetration and pharmacokinetics was investigated.In line with previous findings of preformed albumin coating,PLGA@BSA NPs exhibited higher stability,cytotoxicity,cell internalization and spheroid penetration performances in vitro,and longer blood circulation time in vivo than those of albumin-nonselective PLGA NPs,but albumin-selective SP NPs is capable of achieving a comparable in vitro and in vivo performances with both SP@BSA NPs and PLGA@BSA NPs.Our results demonstrate that SA decorated albumin-selective NPs pave a versatile avenue for optimizing nanoparticulate delivery without preformed albumin corona.

Spinel Castables for Steel Ladle Lining:In-Situ Versus Preformed

The paper discusses the difference in the formulation concepts of alumina - spinel （spinel containing ） and alumina - magnesia （ spin, el forming） castables and the influence on their physical properties. The individual property profile is discussed with respect to the requirements of refactory lining materials for the different zones of a steel ladle.

Effect of initiation manners on the scattering characteristics of semi-preformed fragment warhead

The lethality of a semi-preformed fragment warhead is closely related to the expand velocity and spatial distribution of the fragments from ruptured metal casing. The topic of how to improve the utilization of charge of have been drawing great attention from researchers and designer in this filed. In present paper,in order to investigate the influence of charge initiation manners on the scattering characteristics of semi-preformed fragment warhead, the numerical simulations and experimental test are conducted.Firstly, the influence of grid density on numerical results is investigated, and a proper numerical model with relatively high accuracy and effectiveness is determined. Then. numerical simulations of three kinds of different initiation position of a semi-preformed fragment warhead are carried out. An experimental test of the explosion of a semi-preformed fragment warhead is carried out. By comparing and analyzing the numerical results and experimental data, it is found that the initiation manners have great influence on scattering characteristics of semi-preformed fragment warhead. The researcher work of this paper would provide an effective alternative method to optimize the design of warhead.

Reactivity of Human Preformed Natural Antibodies with Various Porcine Pancreatic Cells

The reactivity of human preformed natural antibodies (PNAbs) with various porcine pancreatic cells and its isotypes was investigated. Eighteen serum samples from patients with insulin dependent diabetes mellitus (IDDM) and 20 serum samples from healthy human subjects were collected. The frozen sections of the pig pancreas were incubated with these sera, and subsequently incubated with FITC conjugated goat antihuman IgG and IgM monoclonal antibodies. The reactivity of human PNAbs with various porcine pancreatic cells was determined by indirect immunofluorescence staining technique. The results showed that 55.6 % of IDDM patients and 55.0 % of healthy human individuals contained PNAbs against porcine endocrine cells. However, the percentage of strongly reacting sera in the patient group was significantly increased as compared with that in the control group. All used sera from IDDM patients and 95 % of sera from healthy controls could react to one or more of the various pancreatic cell types, including: endocrine cells, exocrine cells, vascular endothelial cells, ductal epithelial cells and macrophages. The isotypes of PNAbs contained both IgG and IgM. In view of strongly positive reactivity of PNAbs with various porcine pancreatic cells, pretransplantly cross matching test and graft pretreatment may be necessary for survival of islet transplants.

Degradable preformed particle gel as temporary plugging agent for low-temperature unconventional petroleum reservoirs:Effect of molecular weight of the cross-linking agent

The development of unconventional petroleum resources has gradually become an important succession for increasing oil production.However,the related engineers and researchers are paying more and more attention to the application of temporary plugging agents(TPAs)for their efficient development.TPAs can expand the stimulated reservoir volume(SRV)and facilitate the flow of oil and gas to the bottom of the well.Particle-gels used as temporary plugging agents have the characteristics of the simple injection process,good deformation,high plugging strength,and complete self-degradation performance,which have been widely applied in recent years.In this paper,five samples of DPPG polymerized by different molecular weights of cross-linking agents were prepared.In addition,infrared spectroscopy analysis,differential calorimetry scanning(DSC)analysis,static particle gel swelling and degradation performance evaluation experiments,and dynamic temporary plugging performance experiments in cores were conducted at 34°C.Results show that as the molecular weight of the cross-linking agent(at 0.01 g)in the DPPG molecule decreased from 1,000 to 200 Da,the fewer cross-linking sites of DPPG,the looser the microscopic three-dimensional mesh structure formed.The swelling ratio increased from 7 to 33 times.However,the complete degradation time increased from 40 to 210 min.Moreover,the DSC results confirmed that the higher the molecular weight of the cross-linking agent,the worse is chemical stability and the more prone it to self-degradation.DPPG samples had good temporary plugging performance in reservoir cores.DPPGs prepared by the cross-linking agent with smaller molecular weight has a stronger swelling ratio,higher gel strength,and greater plugging strength in the core permeabilities.Moreover,the degraded DPPG is less damaging to the cores.However,their slower degradation rates take a slightly longer times to reach complete degradation.The results of this paper can provide new ideas and a theoretical basis for the development of particle gel-type temporary plugging agents(TPA)with controllable degradation time in low-temperature reservoirs.It can help to expand the application range of existing DPPG reservoir conditions.

An Overview of 3D Thin Shell Textile Preforms

The automobiles, aircraft, and lightweight industries continuously demand thin near-net-shape preforms just out-of-machine as close to the final shape. This study addresses the possibilities of 3D thin shell textile preform as the solution of lightweight reinforcement in various applications. Investigation into the development of 3D thin shells has led to different manufacturing processes. However, 3D thin shell preforms are mostly made by weaving and knitting, but nonwoven, winding, and/or layup techniques have been reported for over a decade. Owing to the complex thin shell manufacturing processes, they are not similar to the conventional methods. The different 3D thin shell preforms can extend the opportunities for new applications in various technical fields. This study presents existing research gaps and a few potential issues to be solved regarding 3D thin shell preforms in the near future.

An Overview of 3D Thin Shell Textile Preforms

The automobiles, aircraft, and lightweight industries continuously demand thin near-net-shape preforms just out-of-machine as close to the final shape. This study addresses the possibilities of 3D thin shell textile preform as the solution of lightweight reinforcement in various applications. Investigation into the development of 3D thin shells has led to different manufacturing processes. However, 3D thin shell preforms are mostly made by weaving and knitting, but nonwoven, winding, and/or layup techniques have been reported for over a decade. Owing to the complex thin shell manufacturing processes, they are not similar to the conventional methods. The different 3D thin shell preforms can extend the opportunities for new applications in various technical fields. This study presents existing research gaps and a few potential issues to be solved regarding 3D thin shell preforms in the near future.

双工位针刺机器人系统设计

针对单工位针刺成型系统中人和机器无法高效协同生产,预制体生产效率较低;现有的直线型双工位针刺机器人设备需要2个外部回转轴带动双工位参与织物针刺,系统编程难度较高,且工位切换时需要占据的空间大的问题。提出一种混合切换双工位针刺机器人系统,并开展了双工位针刺成形系统的机械结构设计、异型预制体模具和针刺工艺设计、控制系统设计、运动仿真以及预制体制备的实验验证。结果表明:系统成功实现了大尺寸异型曲面预制体的高效针刺成形,直线/旋转混合切换的双工位使得实现预制体的自动换装的同时又能保证系统空间占用量小;双工位中只有针刺工位上的外部回转轴与6关节机械臂联动,系统较为简单,编程方便;同时提高了数控回转工作台的承载力且将针刺末端执行器的布针数量增加至25针,满足了大尺寸预制体的针刺成形,并使得针刺成形效率直接提高2倍。本文系统可应用于批量化制备大尺寸异型曲面复材预制体。

三角形编织工艺数字化建模方法

三维旋转式编织工艺按角轮缺口数分为三角形、四角形和六角形编织工艺,其中三角形编织工艺研究较少。为探索基于三角形编织工艺的预制体结构,基于Python语言和CATIA开发编织工艺软件,获得预制体几何结构。角轮和交换轮交替旋转,驱动携纱器在底盘中运动,使纱线相互交织形成预制体。对角轮、交换轮、携纱器的编号和运动状态进行数字化编码,研究不同旋转状态下携纱器的交换规律。携纱器轨迹与编织节点高度共同确定了织物空间拓扑结构,采用三次B-spline曲线对纱线空间轨迹进行拟合,建立预制体的参数化几何模型。结果表明:采用三角形编织工艺获得的预制体结构紧凑,织物几何模型与试验样件一致性较好,验证了建模方法的精度。

用于三维机织物预成形变形预测的各向异性超弹性本构模型

随着三维机织物逐渐广泛应用在航空发动机叶片、机匣等复杂曲面结构的制造方面,预测三维碳纤维机织物在曲面结构制造的预成形过程中的复杂变形行为对提升纤维结构的成形质量具有重要意义。基于连续介质力学理论,本文提出一种各向异性超弹性本构模型描述三维机织物在成形过程中由于大变形所引起的各向异性力学变形行为。通过三维机织物的变形试验,建立了应变能密度函数,获取了三维机织物材料参数,并通过偏轴拉伸、半球冲压预成形有限元仿真与试验对比,验证了本文提出的超弹性本构模型的有效性。超弹性本构模型的提出可对三维机织物成形的有限元仿真模型与成形工艺优化设计起指导作用。

从知识导向到素养立意:生成论视域下的作业评价变革

受预成论哲学的影响,我国中小学作业评价长期陷于知识导向的评价困局,学生发展的全面性、过程性和生活性难以得到充分彰显。区别于传统的预成论哲学,生成论哲学以主张生成性、强调主体间性和注重现实生活性为显著特征,可为突破当下知识导向的作业评价困局提供有益的变革思路和可鉴的变革行动。在生成论视域下,素养立意是当下作业评价变革的主要方向。为了促进学生核心素养的培育与发展,中小学的作业评价需要调整作业评价目的,确立以素养立意的作业评价理念;革新作业评价过程,强调协同共生的多元主体共同参与;改革作业评价方式,注重分层分类的现实情境评价。

乳切牙树脂预成冠的数字化设计方法及初步应用

目的:本研究旨在探索乳切牙树脂预成冠的数字化设计和制作方法,并初步评价其临床适合性。方法:应用牙颌模型扫描仪获取儿童乳牙牙列教学模型4颗上颌乳切牙临床牙冠的三维数据,应用逆向工程软件Geomagic Wrap 2021,参考王慧芸教授对中国儿童乳牙外形的测量和统计数据,对上述上颌乳切牙三维扫描数据进行尺寸比例和三维形态的调整,以切端0.8 mm厚度和唇腭面0.3 mm厚度的牙冠设计参数,构建乳切牙预成冠标准尺寸数字模型。参考儿童口腔科临床常用的上颌乳切牙透明树脂冠各型号间的尺寸比例关系,设计出4个牙位(51、52、61、62)3个型号的乳切牙预成冠数字模型,通过五轴数控切削技术制作出临时冠桥树脂材质的乳切牙预成冠,进行临床病例试戴评价。结果:完成了上颌乳切牙(4个牙位)树脂预成冠的数字化设计和制作方法,并初步进行了临床病例应用,儿科高年资专家对本研究乳切牙树脂预成冠的应用评价显示,其在外观、颜色和强度等方面均可满足口腔儿科临床的应用需求。结论:本研究采用数字化方法设计和制作的乳切牙树脂预成冠,针对儿科临床乳切牙大范围龋损修复的病例,相比传统乳切牙透明树脂冠充填修复技术具有更好的牙冠解剖外形恢复和更佳的美观修复效果,并且该技术可以实现更便捷的临床操作流程,有较好的儿科临床应用前景。

Bending properties and fracture mechanism of C/C composites with high density preform

C/C composites with banded structure pyrocarbon were fabricated by fast chemical vapor infiltration（CVI）,with C3H6 as carbon source,N2 as carrier gas,and three-dimensional（3D） 12K PAN-based carbon fabric with high density of 0.94 g/cm3 as preform.Experimental results indicated that the fracture characteristics of C/C composites were closely related to the frequency of high-temperature treatment（HTT） at the break of CVI process.According to the load？displacement curves,C/C composites showed a pseudoplastic fracture after twice of HTT.After three times of HTT,load？displacement curves tended to be stable with a decreasing bending strength at 177.5 MPa.Delamination failure and intrastratal fiber fracture were observed at the cross-section of C/C composites by scanning electronic microscope.Because the content of pyrocarbon and fibers has a different distribution in layers,the C/C composites show different fracture characteristics at various regions,which leads to good toughness and bending strength.

基于改进人工势场法的机织机器人避障路径规划

针对机织机器人自动化作业时的避障问题,提出基于改进人工势场法的三维避障路径规划算法。利用改进人工势场法中斥力势场函数,引入修正系数,在机织机器人陷入局部极小值点时增加虚拟障碍物,破坏其在虚拟力下的平衡状态,解决了人工势场法无法到达目标位置和局部极小值点的问题。通过体素化网格方法和快速凸包算法处理障碍物点云数据,重建实际障碍物模型,提高了碰撞检测效率。仿真结果表明,以点云数据重建障碍物模型并采用改进人工势场算法规划出的避障路径使机织机器人成功到达目标位置,末端位置精度平均提高37%,并避免陷入局部极小值点。

乳磨牙牙髓切断术后预成冠修复的疗效评价

目的 探讨金属预成冠(PMC)与全瓷预成冠(ZC)在儿童乳磨牙龋损中的修复疗效以及对牙周健康的影响,分析其可能的影响因素。方法 本研究采用队列研究方法,收集2021年10月—2021年12月于深圳市儿童医院口腔科就诊的3~8岁患儿,下颌第一乳磨牙因龋损行牙髓切断术后进行PMC、ZC修复,共192例,包括PMC组96例(96颗龋齿),ZC组96例(96颗龋齿),分别于治疗后3个月、1年和2年进行临床检查,观察PMC组和ZC组的临床修复效果以及牙周状况,记录修复体是否完整、牙龈指数(GI)、探诊出血指数(BI)、菌斑指数(PLI)和世界牙科联盟(FDI)修复体各项性能评价指标。结果 PMC组与ZC组在修复后3个月、1年、2年的牙周健康指标差异无统计学意义(P>0.05);经修复3个月、1年、2年后,PMC组GI、BI、PLI高于ZC组,差异有统计学意义(P<0.05);而FDI修复体各项性能评分差异无统计学意义(P>0.05)。不同性别患儿在2组修复后,GI、BI、PLI差异均无统计学意义(P>0.05)。不同性别患儿在PMC修复后的FDI修复体各项性能评分差异无统计学意义(P>0.05);在ZC修复后的FDI修复体各项性能评分中,女童评分高于男童,差异有统计学意义(P<0.05)。Pearson相关分析显示,PMC组年龄与GI、BI、PLI、FDI修复体各项性能评分均呈负相关,存在显著相关性(P<0.01),ZC组年龄与GI、BI、PLI、FDI修复体各项性能评分均无显著相关性(P>0.05)。结论 PMC与ZC可为乳磨牙龋损患儿提供较理想的修复手段。两种预成冠修复后的牙周健康状况趋于稳定,乳牙ZC组牙周健康状况优于PMC。患儿的年龄越大,PMC组牙周状况越好。

碳纤维三维编织预制体渗透特性实验研究

针对航空发动机风扇机匣用碳纤维三维编织复合材料,开展了预制体材料渗透特性的实验研究。实验模具为厚度可调的长方体中空结构。通过分析液体在厚度和孔隙率不同的4种三维编织预制体内的渗透过程,结果表明,所有预制体在面内的渗透主向与编织的轴/横向平行,且轴向渗透率约为横向渗透率值的3.2倍。液体在A预制体内的渗透性最好,其轴向、横向和厚度方向的渗透率值分别为1.136×10^(-10)、4.259×10^(-11)和5.900×10^(-12)m^(2),厚度方向上的渗透率远小于面内渗透率,差距在1~2个数量级。液体在预制体内3个方向上的渗透是相互影响的过程,预制体厚度方向上的渗透特性影响了面内的渗透特性。

基于机器视觉的PET瓶坯缺陷检测系统设计

针对PET瓶坯缺陷人工检测工作强度大、效率低等问题,基于机器视觉技术设计一套由检测组件、控制组件、输送机构组件以及剔除机构组件等组成的PET瓶坯检测系统。通过Halcon软件对采集的PET瓶坯图像采用中值滤波降噪、自适应阈值方法提取检测区域,并使用改进Canny算法进行缺陷检测。试验结果表明:PET瓶坯检测系统可完成对PET瓶表面黑点、划痕类缺陷检测,试验检测准确率可达97.4%,可以稳定识别不合格瓶坯。

高压渗流法制备中高体积分数SiCp/Al复合材料的研究现状

高压渗流法制备SiCp/Al复合材料因其适应性广、操作简单、易于实现中高体积分数SiCp/Al复合材料的生产等特点而受到广大科研工作者的关注与广泛应用。本文详细阐述了中高体积分数SiCp/Al复合材料的高压渗流工艺,包括预制体的制备和高压渗流过程两方面,并对预制体制备过程中颗粒粒径、添加剂等因素以及高压渗流过程中压力、温度等工艺参数对复合材料性能的影响进行了分析;简述了SiCp/Al界面润湿性的改善策略及其对复合材料性能的影响,以及热处理对复合材料组织与性能的影响;最后介绍了中高体积分数SiCp/Al复合材料的应用,并展望了高压渗流法制备中高体积分数SiCp/Al复合材料的发展前景。