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.

Deformation and defects in hydroforming of Y-shaped tubes

Hydroforming process of a Y-shaped stainless steel tube was investigated through numerical simulation and experiments. The forming process and reasons of typical defects were analyzed with three different loading paths. Thickness distribution of formed Y-shaped tube was obtained. It is shown by numerical and experimental results that the transition regions are depressed in the forming condition of low inner pressure and wrinkles occur, while fracture occurs in the forming condition of high inner pressure. After forming, the thickness in left transition fillet region is the largest, that in right transition fillet region is thinner, and the thinnest thickness is at the top of the protrusion. The original thickness line is below the top of the protrusion. The thinning area occurs above this line, while the thickening area is below this line. The maximum thinning rate is significantly increased as the calibration pressure increases, while the maximum thickening rate remains almost 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 .

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.

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.

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。

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。

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。

激光功率对3/4H SUS301和SUS316异种不锈钢激光点焊成形特征及组织性能的影响

采用准连续激光器对测力传感器的3/4H SUS301弹性体和SUS316支撑体进行异种不锈钢激光焊接,探讨了激光功率对点焊接头成形特征和力学性能的影响。研究表明,采用准连续激光模式,在脉冲时间为2 ms、激光功率为180 W至270 W范围内,弹性体焊后的角变形量随着激光功率的增大而增大,激光功率为270 W时弹性体焊后的角变形远低于传感器容许的变形量。当激光功率为210W时,在焊接界面处产生气孔缺陷,焊接功率增大至270 W时,在匙孔底部形成严重的气孔缺陷。焊缝内部以胞状晶方式生长,从熔合区两侧向焊缝中心生长为粗大的柱状晶,焊缝中心为等轴状的树枝晶,随着激光功率的增大,等轴晶区域的宽度减小。焊缝区承受较高的焊接热量使得焊缝区内形变组织发生不完全再结晶,致使形变诱发马氏体相变被抑制,α'马氏体含量降低。点焊接头的剪切力随着激光功率先增大后减小,当激光功率为250 W时,接头的剪切力达到最大值0.49 kN,远高于行业要求。

2195铝锂合金贮箱球底充液拉深成形起皱缺陷演变规律数值模拟研究

为满足登月着陆器舱体高可靠性、轻量化制造需求,提出贮箱球底充液拉深成形方法。对于直径3350 mm的2195铝锂合金箱底,相对2219和5A06铝合金,材料塑性差,成形易开裂失效,且整底成形厚径比仅为2.5‰,易起皱失稳。针对上述问题,建立了整底充液拉深成形仿真模型,进行不同液室压力、压边力条件下的数值模拟,讨论整底充液拉深成形变形规律,分析整底成形缺陷形式及控制方法,优化整底充液拉深液室压力加载路径,获得球底壁厚分布规律。结果表明:拉深行程达0.24H(H为零件最终高度)时,球底悬空区域为典型的压缩应力状态,产生了沿母线方向的起皱缺陷环向均布12个,拉深行程0.79H时,环向起皱数量倍增;引入液室压力后使悬空区由压缩应力状态转变为拉伸应力状态,从而避免了悬空区起皱缺陷的发生;压边力和液室压力对悬空区应力状态影响显著,随着压边力增大,球底壁厚减薄趋势增大,而随着液室压力的增大,球底壁厚减薄趋势减弱;球底拉深试验对初始壁厚9.5 mm板材,采用2.5×107 N压边力、8 MPa液室压力加载路径时,壁厚最大减薄率为7.4%,壁厚分布均匀,无起皱缺陷。

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。

基于特征嵌入的小样本涡轮叶片缺陷识别研究

航空发动机涡轮叶片的缺陷,影响发动机可靠性与使用寿命,基于计算机视觉与深度学习技术进行叶片缺陷的自动化检测具有重要现实意义。但是,涡轮叶片图像采集环境的高度非结构化、缺陷形式高差异性,为准确的缺陷识别带来困难。针对上述问题,提出了深度特征嵌入先验网络,其核心通过引入缺陷形状先验的特征嵌入层,准确刻画缺陷的形状特征,提高模型在小样本情况下的分类准确率。实验结果表明,所提方法在小样本叶片缺陷识别问题上取得了优越性能。

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。

修复方式对不同面积楔状缺损抗折强度的影响

目的 研究不同修复方式对不同面积楔状缺损抗折强度的影响。方法 60颗下颌第一前磨牙随机分成6组,制备两种缺损面积的蝶形缺损,其中A1、B1组充填树脂作为对照,A2、A3和B2、B3按缺损面积在1/3以内、大于1/3小于轴角和桩核、桩核冠修复分组。进行10000次人工老化处理后,采用万能材料试验机垂直加载,记录最大载荷数值并分析折裂模式。结果 当缺损面积<1/3时,A1(935.24±50.21)N与A2(950.53±61.23)N、A3(943.35±23.48)N抗折强度差异无统计学意义,当缺损面积>1/3且小于轴角时,B1(867.38±45.79)N与B2(903.20±43.08)N,B3(920.52±82.98)N间差异有统计学意义,B2与B3间差异无统计学意义。除B2与B1、B3之间折裂模式有差异外,其余无差异。结论 当缺损面积<1/3时,直接树脂充填即可,当缺损面积>1/3小于轴角时,可增加纤维桩来进一步提高抗折强度。全冠修复可能会导致不可修复性折裂的发生,是否制作全冠应慎重决定。

不同补牙材料在充填楔状缺损治疗中的临床效果

目的分析不同补牙材料在充填楔状缺损治疗中的临床疗效。方法回顾性分析2021年2月—2022年10月在太仓市第三人民医院进行充填治疗的80例楔状缺损患者的临床资料。根据不同治疗方式分为观察组和对照组,每组40例。对照组患者选用玻璃离子作为补牙材料,观察组患者选用光固化复合树脂作为补牙材料。比较两组的治疗效果、并发症发生率等。结果观察组治疗有效率为97.50%,明显高于对照组的82.50%,差异有统计学意义(χ^(2)=5.000,P<0.05)。观察组并发症发生率低于对照组,差异有统计学意义(P<0.05)。治疗后,观察组饮食能力评分和美观度评分高于对照组,差异有统计学意义(P均<0.05)。结论在楔状缺损的临床治疗中,光固化复合树脂的整体价值高于玻璃离子,能更有效提升治疗效果,同时还能降低并发症发生率,改善患者饮食功能,保障患者健康。

不同材料修复牙颈部楔状缺损的美学效果及对微渗漏的影响

目的:探究不同材料修复牙颈部楔状缺损的美学效果及对微渗漏的影响。方法:回顾性分析2021年9月-2022年9月于笔者医院接受治疗的80例(80颗患牙)牙颈部楔状缺损患者临床资料,根据修复材料不同分为玻璃离子组(富士Ⅱ玻璃离子)39例(39颗患牙)和流动树脂组(Z350XT流动树脂)41例(41颗患牙)。修复3个月后,分析两组患者修复效果、微渗漏情况,比较修复前和修复3个月后两组患者美学效果[红色美学指数、白色美学指数]、牙周健康[龈沟出血指数、探诊深度、碱性磷酸酶(Alkaline phosphatase,ALP)、天门冬氨酸转氨酶(Aspartic transaminase,AST)]、炎症因子[白细胞介素-1β(Interleukin-1β,IL-1β)、白细胞介素-6(Interleukin-6,IL-6)、基质金属蛋白酶-2(Matrix metalloproteinase-2,MMP-2)]水平。结果:修复3个月后,两组患者修复效果、美学效果差异比较无统计学意义(P>0.05);流动树脂组微渗漏程度轻于玻璃离子组(P<0.05);两组患者龈沟出血指数、探诊深度均较修复前降低,且玻璃离子组低于流动树脂组(P<0.05);两组ALP、AST水平均较修复前升高,且流动树脂组高于玻璃离子组(P<0.05);两组IL-1β、IL-6、MMP-2水平均较修复前升高,且流动树脂组高于玻璃离子组(P<0.05)。结论:Z350XT流动树脂与富士Ⅱ玻璃离子在牙颈部楔状缺损中修复效果、美学效果相当,但Z350XT流动树脂修复后微渗漏较轻,富士Ⅱ玻璃离子修复后牙周较健康,龈沟炎症反应较轻。

纤维桩联合复合树脂及氧化锆烤瓷冠修复在根管治疗后后牙楔状缺损患者中的应用效果

目的探究纤维桩联合复合树脂及氧化锆烤瓷冠修复治疗根管治疗(RCT)后后牙楔状缺损(WSD)的效果。方法选取2019年8月—2022年8月在新乡市口腔医院治疗的300例(300牙)RCT后后牙WSD患者,按随机数字表法分成A组(n=150)、B组(n=150)。A组接受纤维桩联合复合树脂及氧化锆烤瓷冠修复治疗,B组接受金属烤瓷冠(PFM)联合金属桩核(MPC)修复治疗。对比2组修复成功率、修复效果、修复前后牙周健康指标[牙龈指数(GI)、菌斑指数(PLI)、牙周探诊深度(PD)]、龈沟液炎性因子[白细胞介素-6(IL-6)、白细胞介素-10(IL-10)、肿瘤坏死因子-α(TNF-α)]水平。结果A组修复成功率为97.33%(146/150),高于B组的87.33%(131/150)(P<0.05);A组边缘密合性、表面质地、颜色匹配均优于B组(P<0.05);修复6个月后A组GI、PLI、PD较B组低(P<0.05);修复1个月后A组龈沟液TNF-α、IL-6水平较B组低,IL-10水平较B组高(P<0.05)。结论与PFM联合MPC修复治疗RCT后后牙WSD患者相比,应用纤维桩联合复合树脂及氧化锆烤瓷冠修复治疗更有助于提升修复成功率及修复效果,改善牙周健康,且对组织产生创伤更小。