In vivo remineralization of acid-etched enamel in non-brushing areas as influenced by fluoridated orthodontic adhesive and toothpaste

This study aimed to evaluate the in vivo remineralization of acid-etched enamel in non-brushing areas as influenced by fluoridated orthodontic adhesive and toothpaste. One hundred and twenty teeth from 30 volunteers were selected. The teeth were assigned to four treatments: no treatment (negative control); 37% phosphoric acid-etching (PAE) (positive control); PAE + resin-modified glass ionomer cement (RMGIC); and, PAE + composite resin. Patients brushed teeth with fluoridated (n = 15) or non-fluoridated (n = 15) toothpastes, so that etched enamel was protected with screens and it was not in contact with the brush bristles. Remineralization was evaluated by means of laser fluorescence (LF), environmental scanning electronic microscopy, and energy dispersive spectrometry after extraction. The LF means were compared by means of Wilcoxon and Mann Whitney tests. Environmental scanning electron microscopy scores were compared among the groups using a Kruskal Wallis test, whereas the Ca/P ratio was evaluated by means of an Analysis of Variance with subparcels (treatments) and Tukey's post-hoc test. There were no statistically significant differences between the tooth pastes and between the orthodontic adhesives evaluated. Most teeth presented only partial enamel remineralization. Therefore, the fluoride released by the RMGIC was not enough to cause increased crystal regrowth in the acid-etched enamel. The use of fluoridated toothpaste did not provide positive additional effect.     

On the temperature and specific energy during electrodischarge diamond grinding (EDDG)

Electrodischarge diamond grinding (EDDG) is a hybrid machining process comprising conventional grinding and electrodischarge machining (EDM) as its constituent processes. It has the potential of shaping advanced engineering materials. Temperature of the workpiece and material removal rate are chosen as responses in full factorial (3³) design with current, pulse-on time, and wheel speed as process parameters. Specific energy is a vital consideration for any machining process. EDM is known for its inefficiency. Experiments were conducted with a specially fabricated bronze disk as tool electrode to evaluate specific energy in EDM, and the results were compared with that of EDDG. It has been found that specific energy required in EDDG is less than that in EDM with a rotating disk electrode.     

EPS快速转向性能对ESC性能影响的分析

目前,ESC系统基本成为汽车的标准配置,ECE R140规定了ESC的性能要求。测试方法中的过度转向干涉正弦延迟测试对方向盘的转速要求较高,EPS在方向盘高转速下的性能对ESC性能测试的影响较大,而在EPS设计时对此和ESC性能的考虑较少。基于此,详细分析ESC的测试性能要求和EPS性能的相关性,对ESC和EPS系统的联合开发及测试提供参考。     

轿车后轮轴承磨粒磨损失效特性与产生机理

通过对 2 0 0余套早期失效的轿车后轮轴承失效统计分析发现 ,磨粒磨损及烧伤是后轮轴承主要的失效形式 ,该失效形式占所有轴承失效率的 6 0 %。根据轿车后桥半轴的结构、后轮轴承装配状况、及轿车后轮的动力学特性 ,本文提出了轿车后轮发生磨粒磨损及烧伤损坏的失效模型 :(1)在惯性载荷作用下 ,轴承内圈与轴颈接触部位的切向蠕动形成粘着磨损颗粒 ;(2 )半轴轴端螺纹防松键槽侵入轴颈与轴承内孔配合段 ,导致键槽锐边在轴承内孔刮研 ,产生切削微屑 ;(3)蠕动及刮研作用产生的磨损颗粒进入轴承滚道表面 ,与滚动体形成三体磨粒磨损。(4)在制动鼓的维修过程中 ,磨损颗粒的异常侵入 ,同样会导致轴承发生磨粒磨损失效。本文提出 ,防止轿车后轮轴承发生早期磨粒磨损失效的有效途径是 :(1)尽量避免与轴承配合的轴颈圆柱表面受到结构或工艺性的损害。(2 )提高轴颈与轴承内孔表面的光洁度和配合精度 ,以降低蠕动造成的磨损颗粒大小和数量。(3)通过密封等防范措施 ,防止磨损颗粒的侵入。     

异齿宽齿轮泵的研究

概述了直齿轮泵和斜齿轮泵的困油特性及目前解决困油问题的方法。通过对齿轮泵的结构调整，得出消除齿轮泵的困油现象的新方法。通过与卸荷槽法进行比较，总结出异齿宽齿轮泵的优点及其技术要点，并给出了轴套的结构尺寸。     

基于LAPIC并联机器人的群钻外刃的锥面刃磨法

在LAPIC并联机器人的特殊坐标系中，采用坐标变换法推导建立了群钻外刃的数学模型，分析了锥面刃磨原理，用矢量变换表示了在虚轴机床上实现刃磨群钻圆锥面外刃的运动方程。     

采用径向射流冲击与钎焊砂轮解决磨削烧伤的研究

在分析高效磨削烧伤机理的基础上，提出了两项对策：一是采用高压径向射流冲击强化磨削弧区换热，以最大限度地疏导已经产生的积聚在弧区的磨削热；二是采用钎焊超硬磨料砂轮取代传统电镀砂轮，以提高砂轮的锋利度降低磨削比能，减少磨削热的产生。缓进给断续磨削试验结果表明，该两项对策对解决难加工材料磨削烧伤问题效果十分明显，具有广阔的应用前景。     

22CrMnMo大模数齿轮磨削裂纹的原因与控制措施

从磨削过程中磨削热、磨削力、齿面应力状态及磨削之前的渗碳淬火工序所得的显微组织等方面，阐述裂纹产生的原因．并提出从磨削工艺上降低磨削温度、从淬火处理上改善齿轮表面应力状态等措施，可有效控制和防止该齿轮的磨削裂纹的产生。     

超高速数控精密磨床磁浮轴承主轴单元设计

本文介绍了磁浮轴承的优点，并提出了磁浮轴承作为磨床主轴轴承的设计方法。同时，首次提出了超高速数控精密外圆磨床磁浮轴承主轴单元设计方法和设计过程。并针对一台300m／s超高速数控精密外圆磨床磁浮轴承主轴单元进行了设计。经过实验证明，提出的设计方法是正确的。同时，应用了该技术的超高速数控精密磨床，虽然初期投资成本高，但其优越的使用性能使其综合效益高。     

基于NUM的磨齿机数控系统的开发

以NUM数控系统为平台，设计了系统显示界面和控制界面，建立了用户数据库，实现了图形界面和数控系统的联系和通讯。