基于普通模式和电子束减速模式的加速电压对FESEM图像的影响

为阐明加速电压对场发射扫描电子显微镜(FESEM)图像的影响,实验以4种典型材料为研究对象,比较了普通模式和电子束减速模式下不同加速电压的FESEM图像。结果表明:普通模式下,对低原子序数的样品进行FESEM表征时,宜选择较低的加速电压;对高原子序数样品或样品的内部相进行FESEM表征时,宜选择较高的加速电压。电子束减速模式在对不耐电子束的样品表征方面具有独特的优势。

行波磁场减速模式对板坯连铸结晶器内传输行为的影响

高拉速高质量连铸生产是当前钢铁冶金领域中绿色低碳发展的重要路径。基于汽车板生产用1000 mm×230 mm断面连铸板坯结晶器内的钢水传输行为研究,探究一种行波磁场减速模式(EMLS)对水口侧孔射流及其钢坯质量的影响。根据电磁热流体与凝固传输理论建立了三维耦合数值模型,利用电导率等效法测试装置测量电磁力校验了模型的准确性,并提出了电磁控流作用下的结晶器综合冶金性能评价依据。结果表明,EMLS电磁力在结晶器宽面两侧呈大小相等、方向相反分布,最佳工作频率为4 Hz,其电流强度对电磁力的影响起主导作用。指出,当前浇铸条件下EMLS的最佳减速电流为200 A。此时,电磁力方向具有指向水口两侧出钢口且略微向下的特征,可以较好地控制其侧孔射流对初凝坯壳的冲刷强度,同时也避免了电磁力作用下弯月面波动过大和钢液冲击深度加深的问题。综合表明,合理利用行波磁场减速控流有望较好地解决当前常见的结晶器液面卷渣和凝固钩对夹杂物与气泡的捕捉,从而有利于提高后续IF钢冷轧板的表面质量。

关于蓝牙减速呼吸模式的研究

文章阐述了减速呼吸模式(sniff subrating)引入的原因,它相对于普通呼吸模式的优点所在,着重说明了减速呼吸在蓝牙协议中的实现,以及发展前景。

导电性较差样品的扫描电镜优化观测条件

为解决扫描电镜测试中样品的荷电问题,采用场发射扫描电镜(FESEM),以导电性较差样品如介孔硅SBA-15粉末、介孔SiO2纳米球、聚苯乙烯球及SBA-15/W等为研究对象,比较不同测试条件下的FESEM图片。结果表明,影响FESEM图像质量的因素较多,其中工作距离和加速电压是影响图片质量的主要因素;较小的工作距离、较低的加速电压、一定量背散射电子信号的加入、下探测器的选用(放大倍数小于5万倍)、减速观察模式及线平均扫描模式,是导电性较差样品FESEM图片的优化观测条件。

玉米淀粉的扫描电镜分析方法

利用Regulus 8230型高分辨率扫描电镜对导电性能较差的玉米淀粉进行微观形貌观察,对比分析了试样分散方法、喷金处理及不同电压模式对玉米淀粉扫描电镜图像质量的影响。结果表明:超声波分散法可获得更加均匀的颗粒分布,有利于对玉米淀粉的微观形貌进行观察;对喷金处理后的玉米淀粉进行扫描电镜低倍观察时,荷电效应降低,图像质量得到改善;对喷金处理后的玉米淀粉进行扫描电镜高倍观察时,颗粒表面出现裂纹,因此不建议进行喷金处理;对未喷金处理的玉米淀粉采用电子束减速模式进行观察,可显著提升扫描电镜的图像质量。

Impact shock frequency components and attenuation in rearfoot and forefoot running

Background:The forefoot running footfall pattern has been suggested to reduce the risk of developing running related overuse injuries due to a reduction of impact related variables compared with the rearfoot running footfall pattern.However,only time-domain impact variables have been compared between footfall patterns.The frequency content of the impact shock and the degree to which it is attenuated may be of greater importance for injury risk and prevention than time-domain variables.Therefore,the purpose of this study was to determine the differences in head and tibial acceleration signal power and shock attenuation between rearfoot and forefoot running.Methods:Nineteen habitual rearfoot runners and 19 habitual forefoot runners ran on a treadmill at 3.5 m/s using their preferred footfall patterns while tibial and head acceleration data were collected.The magnitude of the first and second head acceleration peaks,and peak positive tibial acceleration were calculated.The power spectral density of each signal was calculated to transform the head and tibial accelerations in the frequency domain.Shock attenuation was calculated by a transfer function of the head signal relative to the tibia.Results:Peak positive tibial acceleration and signal power in the lower and higher ranges were significantly greater during rearfoot than forefoot running(/】 【 0.05).The first and second head acceleration peaks and head signal power were not statistically different between patterns(p 】 0.05).Rearfoot running resulted in significantly greater shock attenuation for the lower and higher frequency ranges as a result of greater tibial acceleration(p 【 0.05).Conclusion:The difference in impact shock frequency content between footfall patterns suggests that the primary mechanisms for attenuation may differ.The relationship between shock attenuation mechanisms and injury is not clear but given the differences in impact frequency content,neither footfall pattern may be more beneficial for injury,rather the type of injury sustained may vary with footfall pattern preference.

One-Dimensional Traffic Model to Consider Priority of the Stochastic Deceleration

A one-dimensional cellular automaton model of traffic flow is proposed to introduce the different delay probabilities in the steps of rules and the stochastic deceleration prior to the deterministic one when the anticipation velocity of vehicle is larger than the headway. The fundamental diagram shows the capacity of road more approaches to the observed data compared with that by the NaSch model. Moreover, the model is able to reproduce the complicated behavior of the real traffic, such as the metastability state, the separation of different phases and the effect of hysteresis.It is concluded that the order arrangement of the stochastic deceleration and deterministic acceleration has indeed remarkable effect on traffic flow and the modification presented in this paper is reasonable and realistic.

纤维状二氧化硅纳米球的扫描电镜形貌观察

利用场发射扫描电子显微镜(FESEM)研究了纤维状二氧化硅纳米球(KCC-1)的形貌,探讨了样品前处理方法、加速电压、工作距离、发射电流、减速模式对其FESEM图像的影响规律。结果表明,影响FESEM成像的因素较多,其中样品前处理方法、工作距离和加速电压是影响图片质量的主要因素;选择乙醇为溶剂、硅片为基底、较小的工作距离、较低的加速电压、高发射电流、减速观察模式的优化观测条件可获得理想的FESEM图像。