Martensitic stabilization and defects induced by deformation in TiNi shape memory alloys

Martensitic stabilization caused by deformation in a TiNi shape memory alloy was studied.Special attention was paid to the deformed microstructures to identify the cause of martensitic stabilization.Martensitic stabilization was demonstrated by differential scanning calorimetry for the tensioned TiNi shape memory alloy.Transmission electron microscopy revealed that antiphase boundaries were formed because of the fourfold dissociation of [110]B19＇ super lattice dislocations and were preserved after reverse transformation due to the lattice correspondence.Martensitic stabilization was attributed to dislocations induced by deformation,which reduced the ordering degree of the microstructure,spoiled the reverse path from martensite to parent phase compared with thermoelastic transformation,and imposed resistance on phase transformation through the stress field.

Ultimate Load Capacity of Offshore Pipeline with Arbitrary Shape Corrosion Defects

A set of generalized solutions are proposed for estimating ultimate load capacity of pipeline with arbitrary corrosion shapes subjected to combined internal pressure, axial force and bending moment. Isotropic and anisotropic material characteristics in longitudinal and circumferential direction of pipeline are also considered in the proposed equations. Simplified numerical method is used to solve the generalized expressions. The comparisons of numerical results based generalized solutions and full-scale experimental results are carried out. The predicted results agree reasonably well with the experiment results. Meanwhile, the effects of corrosion shapes and locations on the ultimate load capacity are studied.

THE TYPE II DEFECT IN 18R MARTENSITE IN A Cu-Zn-Al ALLOY

Type H defect in 18R martensite in a Cu-Zn-Al alloy has been studied by high resolution electron microscopy. It was found that Type H defect is not fault internal to martensite plate; rather,it is a stack of plates A and C. The rare observation of Type H defect is considered to be due to the fact that thc slice is too thin to exist for self-accommodation.

Evidence of the Precipitates in the V-Shaped Defects of Undoped GaN

Precipitates in undoped GaN epilayers with specular surfaces grown on sapphire substrates were imaged by super high-resolution electron microscopy(HREM)and analyzed by energy-dispersive x-ray spectrometry(EDXS).The HREM images of the precipitates appeared more or less hexagonal intersection with several ten-nanometer large,which is the same as that of the V-shape defects.The EDXS spectra of the precipitates were mainly composed of the characteristic x-rays of oxygen,carbon,and gallium elements.The results suggest that the precipitates nucleate at the pinholes of the V-shape cavities and grow as the GaN growth.

Influences of the Shape of Rods in Two Dimension Photonic Crystals on Their Defect Eigenmodes

The cross section of photonic crystal fiber (PCF) is a two dimensional photonic crystal. The rods formed in PCF are not exact cylinders, the shape of rods will affect the eigenmode formed in two dimensional photonic crystals around a defect. Based on the relations between the defect eigenmodes and the radius of dielectric cylinders, the defect eigenmodes in photonic crystals in which the ellipse rods take the place of cylinders are studied by numerical calculation. The analysis of the relation between the eigenfrequency and the minor axis radius of ellipse rods show that the defect eigenfrequency is controlled by the cross section area of rods and the distribution of electromagnetic field around the defect is also affected by the cross section shape of rods. It provides a better way to modify the distribution of electromagnetic fields in photonic crystal and keeps the eigenfrequency unchanged.

Electronic and transport properties of V-shaped defect zigzag MoS_2 nanoribbons

Based on the nonequilibrium Green＇s function （NEGF） in combination with density functional theory （DFT） calcu- lations, we study the electronic structures and transport properties of zigzag MoS2 nanoribbons （ZMNRs） with V-shaped vacancy defects on the edge. The vacancy formation energy results show that the zigzag vacancy is easier to create on the edge of ZMNR than the armchair vacancy. Both of the defects can make the electronic band structures of ZMNRs change from metal to semiconductor. The calculations of electronic transport properties depict that the currents drop off clearly and rectification ratios increase in the defected systems. These effects would open up possibilities for their applications in novel nanoelectronic devices.

Mechanism underlying the formation of cloud-shaped defects in 304 stainless steel after hot-rolled annealing and pickling

It is highly imperative to understand the mechanism underlying the formation of cloud-shaped defects in stainless steel to reduce the defect incidences. This study investigated the defect microstructure by SEM, simulated pickling in the laboratory, and performed structure analysis of oxide scales after hot rolling. Results show that the cloud-shaped defects in 304 No. 1 surface （after hot-rolled annealing and pickling） cause the pickling chromatic aberration between the honeycomb-shaped grains of the Cr-depleted layer and the smooth grains of the stainless steel matrix, which is formed in the case of insufficient pickling. The chromatic aberration is related to the uneven oxide scales formed before pickling. With the improvement of pickling capacity, it is possible to completely pickle the Cr-depleted layer and eliminate the cloud-shaped defects.

An Improved Parameters Extraction Method for Dumbbell-Shaped Defected Ground Structure

The paper presents an improved equivalent circuit parameters extraction method for the dumbbell-shaped defected ground structure (DGS). The new extraction parameters equations are obtained in closed-form expressions, which contain S11 and S21. The DGS unit with center frequency of 5 GHz is designed and fabricated on a TLX substrate with thickness of 1 mm and dielectric constant of 2.55. The circuit simulated results are in good agreement with the measured results. This parameters extraction method can be widely used for the design and analysis of DGS .

基于多种分析方法的岩质边坡稳定性研究

以某岩质高边坡为研究对象,采用楔形体滑动、圆弧滑动及离散元数值模拟等方法对边坡稳定性及治理方案进行综合分析研究。研究结果表明:按设计坡率为1∶0.3进行开挖后坡体主要发生楔形体滑动及圆弧滑动破坏,开挖完成后坡脚变形大,边坡治理工程措施不具备实施性;按边坡放坡坡率为1∶1进行分析,坡体稳定性系数满足规范要求,同时开挖完成后坡脚变形相对减小。最后基于边坡稳定性计算分析对边坡治理方案提出针对性建议。

V型折叠颏下皮瓣修复口腔缺损的临床应用

目的:口腔中小型缺损修复一直是一个难题,游离皮瓣和远位带蒂组织瓣难以满足临床需求,传统颏下皮瓣存在供区损伤风险。本研究旨在探讨V型折叠颏下皮瓣修复口腔中小型缺损的疗效。方法:回顾性分析2019年3月至2022年12月中南大学湘雅三医院口腔科收治的28例口腔黏膜病变患者的临床资料。根据颏下皮瓣手术方式的不同将患者分为V型折叠组(17例)和传统组(11例),V型折叠组采用V型折叠颏下皮瓣进行术后软组织修复,传统组采用传统颏下皮瓣进行修复,患者术后随访6~48个月。比较2组皮瓣存活情况、皮瓣修复时间以及皮瓣修复效果。结果:2组皮瓣存活率、皮瓣大小、制瓣时间、修复手术时间和术后住院时间差异均无统计学意义(均P>0.05)。术后6个月,V型折叠组无抬头困难和下唇外翻,无皮肤“猫耳”畸形,疤痕隐藏于下颌骨下缘处,创面美观度、功能评分均明显高于传统组(均P<0.05)。结论:V型折叠颏下皮瓣具有设计灵活、制备简单、血供可靠、保护供区等优点,可以有效维持颏部美观和避免功能障碍。

不同成形方式对WE43镁合金组织和力学性能的影响

采用激光选区熔化成形(SLM)、铸造及挤压方式制备了WE43镁合金试样,通过维氏硬度计、密度测试计、光学显微镜、扫描电镜以及拉伸试验机等设备分析了不同制备方式下WE43镁合金的宏微观组织和力学性能变化规律;设计了基于指数函数的模型对不同成形方式的WE43应力–应变曲线进行统一拟合,为WE43材料未来增材、减材以及等材工艺复合制造复杂零件打下基础。结果表明,SLM成形WE43有明显的各向异性,铸态和挤压态不明显。SLM成形WE43镁合金的强度最高,抗拉强度达到313 MPa,是铸态的183%;挤压态WE43镁合金塑性最好,伸长率达到10.2%,是铸态的232%;此外,SLM态镁合金密度只有1.731 g/cm^(3),仅为挤压态的85.7%和铸态的95.2%。在断裂特性上,SLM态和挤压态为韧性断裂,而铸造态为脆性断裂。在内部存在20μm左右孔洞形缺陷的情况下,SLM成形镁合金依然具有最高的强度,主要原因是SLM成形WE43镁合金平均晶粒尺寸仅为2.6μm,基体内存在大量的稀土相沉淀以及纳米级亚稳相。由此可知,通过进一步的后处理方法焊合SLM态镁合金内部孔洞形缺陷后,材料力学性能可以大幅提高。

细石叶技术的起源、二元分化及环境驱动因素

在亚洲东北部地区,细石叶技术是旧石器时代晚期人类适应气候和环境的最关键因素之一。学术界围绕细石叶技术产生很多讨论,其中起源、技术演变及技术类型的区域分布是被关注的几个关键问题。细石叶技术可分为初始、成熟、简约几个技术发展阶段,压制法的运用是细石叶技术成熟的关键,细小化的特点决定了各类细石叶使用功能上的区别并不显著。因而在实践层面上,细石叶技术的判定应重视石核和产品形态、技术生产流程、产品的使用意义、强调剥片策略分析,不应限定细石叶的剥制方法。末次盛冰期时,华北地区与中国东北地区、俄罗斯远东、日本北部等所构成的“北方区域”形成分别以船形石核、两面预制的楔形石核为主的二元分化格局,虽然出现过文化上的交叉融合,但是两个区存在以宽、窄楔形石核为主的现象,二元状态没有从根本上发生改变。细石叶技术的起源、成熟、分化与H3、H2、末次盛冰期几次冷事件间有较好的耦合关系,显示出环境驱动力仍然是导致史前人类生存策略变化的关键因素。

Mimics软件三维重建技术行钛网形态优化设计在颅骨成形术中的应用

目的探讨应用Mimics软件三维重建技术进行钛网形态优化设计在颅骨成形术中的应用效果。方法2017年5月至2022年5月前瞻性进行颅骨成形术60例,其中30例应用Mimics软件三维重建技术进行钛网形态优化设计(优化组),30例应用常规设计的钛网(对照组)。结果与对照组比较,优化组手术切口供血良好率明显增高(80.0%vs.53.3%;P=0.028),术后切口甲级愈合率明显增高(70.0%vs.40.0%;P=0.020),术后拆线时间明显缩短[(7.07±0.95)d vs.(7.83±1.12)d;P=0.006],术后大量硬膜外积液发生率明显降低(10.0%vs.36.7%;P=0.015)。优化组术后无颅内出血、钛网外露情况。结论应用Mimics软件三维重建技术对钛网形态进行优化设计,可有效降低颅骨成形术中切口缝合的张力,术后切口供血和愈合更佳,缩短术后拆线时间,降低大量硬膜外积液的发生率,有效减少颅内出血和钛网外露。

纤维桩、纳米复合树脂结合氧化锆烤瓷冠修复牙楔状缺损的效果及对龈沟液炎性介质水平、美学评分的影响

目的探究纤维桩、纳米复合树脂结合氧化锆烤瓷冠修复牙楔状缺损的效果及对龈沟液(GCF)炎性介质水平、美学评分的影响。方法选择2018年4月至2021年6月收治的96例牙楔状缺损患者为研究对象,以随机数字表法将其分为对照组和观察组,每组48例。对照组接受金属桩核结合金属烤瓷冠修复,观察组实施纤维桩、纳米复合树脂结合氧化锆烤瓷冠修复。比较两组的修复效果。结果观察组的口腔致病菌检出率低于对照组,修复成功率高于对照组(P<0.05)。修复后,观察组GCF中的神经激肽A(NKA)、组织基质金属蛋白酶抑制剂-1(TIMP-1)、基质金属蛋白酶-9(MMP-9)及白细胞介素-8(IL-8)水平均低于对照组(P<0.05)。修复后,观察组的红色美学指数(PES)、白色美学指数(WES)评分均高于对照组(P<0.05)。修复后,观察组的GCF量及碱性磷酸酶(ALP)、天冬氨酸转氨酶(AST)水平均低于对照组(P<0.05)。结论纤维桩、纳米复合树脂结合氧化锆烤瓷冠修复牙楔状缺损可改善GCF量及GCF中炎性介质、ALP、AST表达,提高修复成功率及美学评分。

纤维桩+复合树脂+氧化锆全瓷冠修复根管治疗后后牙楔状缺损的疗效分析

目的:探究纤维桩+复合树脂+氧化锆全瓷冠修复根管治疗后后牙楔状缺损患者的效果及美观满意度。方法:纳入2022年1月-2023年1月在笔者医院就诊的102例后牙楔状缺损患者,根据患者自主选择意愿分为研究组(n=50)和对照组(n=52),对照组行金属桩核+金属烤瓷冠修复,研究组行纤维桩+复合树脂+氧化锆全瓷冠修复。6个月后,对比两组临床疗效,观察两组牙周健康情况(牙龈指数、菌斑指数、龈沟出血指数),检测牙周炎症[肿瘤坏死因子-α(Tumor necrosis factor-α,TNF-α)、白细胞介素-4(Interleukin-4,IL-4)、白细胞介素-6(Interleukin-6,IL-6)],调查美观满意度[美国公共健康服务标准(United states public health service,USPHS)]和实用度(咀嚼功能、咬合情况、语言功能),比较两组并发症发生情况。结果:治疗后,研究组治疗有效率达92.00%,高于对照组的76.92%(P<0.05);两组牙周健康相关指数及TNF-α、IL-4、IL-6均较治疗前降低,且研究组降低幅度大于对照组(P<0.05);治疗后,研究组牙齿表面形态、色泽协调性、边缘着色满意度均高于对照组(P<0.05),两组咀嚼功能、咬合情况、语言功能均较治疗前提高,但差异无统计学意义(P>0.05);两组并发症发生率比较治疗组低于对照组(P<0.05)。结论:采用纤维桩+复合树脂+氧化锆全瓷冠修复根管治疗后后牙楔状缺损能够减轻炎症反应,提升患者牙周健康,增加美观满意度及实用度,疗效显著,安全性高。

Beautiful Flow Plus与FUjiⅨ玻璃离子水门汀在牙颈部楔状缺损治疗中的应用效果比较

目的:比较Beautiful Flow Plus与FUjiⅨ玻璃离子水门汀在牙颈部楔状缺损治疗中的应用效果。方法:选取牙颈部楔状缺损患者198例(567颗患牙),根据修复时充填材料不同将患者分为观察组101例289颗患牙(Beautiful Flow Plus修复治疗)和对照组97例278颗患牙(FUjiⅨ玻璃离子水门汀修复治疗)。比较两组患者治疗后1、2年填充体状态及修复成功率。比较两组患者治疗后2年咀嚼功能、美观度评分。记录治疗期间和治疗后2年内患者不良事件发生情况。结果:两组治疗后1年患牙填充体状态良好率及修复成功率比较差异无统计学意义(均P>0.05)。治疗后2年,观察组色泽协调性良好及无边缘着色的牙齿比例高于对照组(均P<0.05)。两组其余充填体状态良好率及修复成功率比较差异无统计学意义(均P>0.05)。治疗后2年,两组干燥咀嚼物X50数值较治疗前降低,且观察组低于对照组(均P<0.05)。治疗后2年,两组患者和医生美观度评分较治疗前升高,且观察组高于对照组(均P<0.05)。在治疗期间和治疗后2年内,两组不良事件总发生率比较差异无统计学意义(P<0.05)。结论:与FUjiⅨ玻璃离子水门汀比较,Beautiful Flow Plus在牙颈部楔状缺损治疗中具有较好的远期美学效果,且有助于改善患者咀嚼功能。

多盘连续可变工作间隙磁流变制动器仿真与验证

为提高磁流变制动器制动能效,提出一种多盘连续可变磁流变液工作间隙结构的磁流变制动器。在ANSYS workbench环境下完成不同电流、间隙状态下的三维静态磁场仿真,对磁场沿工作间隙分布状况进行分析,通过试验台架对制动器性能进行测试。结果表明,磁流变液工作区域磁矢量分布相对均匀,无明显积聚现象,磁路设计合理。理论与实验结果变化趋势基本吻合,但在电流较大时,两者之间误差呈逐渐增大趋势。制动力矩在0~2.5 A电流变化区间增速较快,而在2.5~4.0 A区间明显放缓,最大力矩达到146.4 N·m,较间隙未改变状态增加25.80%。设计的制动器TVR值达到48.81 kN·m/m^(3),较传统磁流变制动器结构更紧凑,力矩调节范围更广,设计思路及实验结论对磁流变制动器结构的进一步研究具有借鉴意义。

流体树脂充填楔状缺损成功率的临床观察

纳入符合标准的楔状缺损患者90例(251颗患牙),随机分为研究组(45例125颗患牙,流体树脂充填缺损)和对照组(45例126颗患牙,复合树脂充填缺损),比较两组的成功率,结果表明流体树脂充填楔状缺损与复合树脂充填相比成功率基本相同,临床操作时间更短。

轴向柱塞泵配流副油膜温度特性

柱塞泵配流副油膜温度分布影响配流副油膜润滑、泄漏与摩擦。为了探究轴向柱塞泵配流副油膜的温度分布,搭建了配流副三点油膜厚度与多点温度测试平台。根据采集的配流副油膜三点膜厚试验数据,建立了配流副楔形油膜模型;考虑了柱塞腔、配流副油膜对缸体的静压力、配流副表面微凸体间作用力,建立了缸体轴向力平衡方程;考虑了配流副油膜的能量损失、热传导以及油液黏温特性,建立了配流副油膜热平衡模型。结果表明,配流副油膜最高温度值随着压力和斜盘倾角的增大而增大,最高温度点位置保持在高压腰型槽对称线两侧-20°~20°的区域内;最高温度理论与试验结果的相对误差小于8%。

铝合金双面焊对接接头内部缺陷扩展行为分析

基于ABAQUS和FRANC3D联合仿真方法分析了铝合金双面焊对接接头中内部缺陷在疲劳荷载作用下的裂纹扩展行为。对比接头全模型中不同裂纹深度a下裂纹尖端应力强度因子K及疲劳寿命N,验证了对称模型的准确性,进而基于对称模型分析了不同形状比(深度a/长度2c)下初始缺陷的疲劳扩展规律。结果表明:当椭圆形缺陷的深度a不变而长度2c逐渐增大时,初始应力强度也随之增加,试件的疲劳寿命显著降低,当长轴长度增加3倍时,疲劳寿命降低了50%;随着裂纹的扩展,a/c的比值逐渐趋近于1,即形状趋近于圆形。