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Factorial Design-of-Experiment analyses were applied for conventional and beam oscillation fiber laser cutting of 10 mm thick AISI 304 stainless steel. Considered factors in case of the conventional process with a static beam involve both laser and cutting gas parameters, in particular the laser power, the focal plane position, the cutting gas pressure, the nozzle stand-off distance as well as the nozzle diameter. The conducted trials were evaluated with respect to the achievable cutting speed, the cut kerf geometry and the cut edge roughness. Noticeable correlations between cut edge roughness and cut kerf geometry stimulated the development of a corresponding Computational Fluid Dynamics (CFD) model of the cutting gas flow through the kerf. A specific approach of data synchronization revealed that the experimentally determined roughness values do well correlate with numerically computed values of the backward directed component of the gas-induced shear stress and that the cut kerf geometry as internal process-inherent boundary condition influences relevant cutting characteristics more than controllable external cutting gas parameters. Finally, effects of circular beam oscillation were investigated by an additional factorial analysis considering the laser power, the focal plane position, the oscillation frequency and the oscillation amplitude as factors. The results demonstrate the potential of beam oscillation techniques for quality improvements in laser cutting. 相似文献
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《The British journal of oral & maxillofacial surgery》2020,58(5):590-596
The aim of this retrospective study was to use computer-aided design and manufacturing (CAD/CAM) patient-specific plates and cutting guides for the waferless positioning and fixation of the maxilla after bimaxillary osteotomies in cases of hemifacial microsomia with condylar dysplasia or absence of the temporomandibular joint (TMJ), and to compare the results with the CAD/CAM fabricated surgical wafer by 3-dimensional analysis. Eighteen patients were selected from the hospital database, preoperative surgical planning and simulation were done on 3-dimensional computed tomographic models for all patients, and they were divided into Group I – in which CAD/CAM patient-specific cutting guides and plates were used; and Group II – in which CAD/CAM fabricated surgical wafers were used. Finally, the outcome was evaluated by comparing planned with postoperative outcomes. The largest discrepancies of the Le Fort I segment were 0.50 (0.18) mm in the anteroposterior direction and 0.82 (0.60)° in the yaw orientation with Group I. The largest discrepancies of the Le Fort I segment were 1.32 (1.40) mm in superioinferior direction and 8.48 (7.73)° in the yaw orientation with Group II. The CAD/CAM patient-specific cutting guides and plates proved to be reliable and have great value in improving the accuracy in repositioning the Le Fort I segment and in the efficacy of orthognathic treatment of hemifacial microsomia with condylar dysplasia or no TMJ. The CAD/CAM patient-specific cutting guides and plates are therefore a useful alternative to the wafer technique. 相似文献
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Chen S Duan B Liu Z Wu X Wei F Qian X Ye F Fang W Hu Z Tamari I Chen H 《中华医学杂志(英文版)》2002,115(2):166-169
目的 研究切割球囊对支架内再狭窄的即刻和 6个月内随访效果。方法 6 9例支架内再狭窄患者随机分配到切割球囊和普通球囊治疗组。切割球囊组 38例。球囊扩张前及扩张后即刻在定量冠状动脉造影和冠状动脉内超声下 ,测定相关参数。随访 6个月内临床改善及冠状动脉造影结果。研究终点包括出现心肌梗塞 ,需要冠状动脉搭桥或再介入治疗。结果 两组的手术成功率为 10 0 %。切割球囊组 1例患者扩张后在支架的远端出现夹层。平均随访 6 7± 2 3月。切割球囊组于术后 3和 6个月时的再狭窄率显著低于普通球囊组 (15 %VS 38%及 18%VS 4 3%,P均小于0 0 0 1)。扩张后即刻血管直径获得值在切割球囊组和普通球囊组分别为 1 72± 0 5 2mm和 1 15± 0 5 4mm ,而随访终点时切割球囊组的血管直径晚期丢失为 0 2 6± 0 0 5mm(3个月 )及 0 38± 0 0 6mm ,同时的普通球囊组丢失值为 0 78± 0 19mm(3个月 )及 0 89± 0 16mm。对于支架体部狭窄 ,普通球囊难以固定 ,扩张时移动明显 ,而切割球囊较易于固定 ,扩张时罕见移动。结论 切割球囊治疗支架内再狭窄效果可靠 ,安全 ,容易操作。再狭窄率低 ,手术费用相对易于患者接受 ,是一个较有前途的治疗手段。 相似文献
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目的 优选人参Panax ginseng趁鲜切制饮片工艺,比较分析趁鲜切制与传统切制人参饮片的质量,为人参趁鲜切制的合理性提供数据支持。方法 考察切片厚度、烘干温度、烘干时间等因素优选人参趁鲜切制饮片最佳制备工艺;建立指纹图谱结合化学计量法评价2种炮制工艺人参饮片质量差异性;并定量分析2种人参饮片中指标性成分人参皂苷含量差异。结果 人参趁鲜切制饮片的最佳制备工艺为人参鲜药材含水量65%,烘干温度50℃、烘干时间8 h、切片厚度1.5 mm;指纹图谱分别确定了人参趁鲜切制饮片和传统切制工艺饮片22个共有峰,指认了其中7个共有峰,2种炮制工艺所得人参饮片指纹图谱相似度分别在0.983~0.992、0.948~0.996。趁鲜切制与传统切制工艺饮片之间的指纹图谱相似度为0.960~0.993,相似度良好;主成分分析(principal component analysis,PCA)将人参趁鲜切制饮片和传统切制饮片归为2类,正交偏最小二乘法-判别分析(orthogonal partial least squares-discriminant analysis,OPLS-DA)确定2种炮制工艺项... 相似文献
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Occupational asthma caused by ethanolamines 总被引:2,自引:0,他引:2
Amino alcohols are used in various industries, often as minor constituents of compounds to modify the properties of the compound. Generally, they are considered to be safe, but they have been known to cause local skin irritation at higher concentrations in solutions. We report on three cases of occupational asthma caused by ethanolamines: two metal workers exposed to a cutting fluid containing triethanolamine, and one cleaner exposed to a detergent containing monoethanolamine. The diagnosis was based on work-related symptoms and on a chamber challenge with the suspected agent. Persistence of the symptoms after exposure ended was a common feature of the three cases. 相似文献