Robust and real-time guidewire simulation based on Kirchhoff elastic rod for vascular intervention training

Virtual reality （VR） based vascular intervention training is a fascinating innovation, which helps trainees develop skills in safety remote from patients. The vascular intervention training involves the use of flexible tipped guidewires to advance diagnostic or therapeutic catheters into a patient＇s vascular anatomy. In this paper, a real-time physically-based modeling approach is proposed to simulate complicated behaviors of guidewires and catheters based on Kirchhoff elastic rod. The slender body of guidewire and catheter is simulated using more efficient special case of naturally straight, isotropic Kirchhoff rods, and the short flexible tip composed of straight or angled design is modeled using more complex generalized Kirchhoff rods. We derive the equations of motion for guidewire and catheter with continuous elastic energy~ and then they were discretized using a linear implicit scheme that guarantees stability and robustness. In addition, we apply a fast-projection method to enforce the inextensibility of guidewire and catheter, while an adaptive sampling algorithm is implemented to improve the simulation efficiency without reducing accuracy. Experimental results reveal that our guidewire simulation method is both robust and efficient in a real-time performance.     

过量空气系数和点火提前角对CNG发动机NOX排放性能的影响

试验研究了过量空气系数和点火提前角对稀燃电控调压器式天然气发动机的燃烧以及排放的影响。试验过程对全工况的排放和动力进行了稳态优化。研究结果表明,在其他影响参数不变的情况下,随着点火提前角的减小和过量空气系数的增加,扭矩和NOX排放均降低。在匹配氧化型催化转化器后,各工况选取适当的点火提前角和过量空气系数可以满足国Ⅴ的排放标准。     

城市轨道交通60 kg/m钢轨12号单开道岔设计研究

北京新机场线是时速160 km的城市轨道交通线路,相较于普通城市轨道交通线路,具有列车轴重大、速度高、通过地段复杂多样等特点,有必要对其道岔系统进行专门研究。研究的重点为道岔平面线型、结构构造、轨下基础及工电结合部等几个方面。研究结果:采用60AT2尖轨并设置轨底坡或轨顶坡,提高了列车经过岔区时的平稳性和旅客的乘座舒适度;采用镶嵌翼轨式合金钢组合辙叉提高了辙叉使用寿命,减小了养护维修量;采用不同刚度的板下弹性垫层,实现了城市轨道交通道岔岔区的刚度均匀化及整体低刚度化,有效降低了岔区的振动噪声。     

地下检票厅开挖对既有地铁换乘通道稳定性影响研究

为研究地下检票厅开挖过程中周边换乘通道的稳定性,建立地下检票厅开挖离散元数值模型,通过分析检票厅开挖后对换乘通道结构力学响应,揭示地下开挖对周边既有结构稳定性的影响。结果表明:检票厅开挖后将引起换乘通道产生附加位移,双洞室分别开挖的过程中,右侧洞室开挖对换乘通道的影响远远高于左侧洞室,左侧洞室开挖后其周边岩体的位移以左侧洞室为中心成对称分布,右侧洞室开挖后其周边岩体的位移大致以检票厅中柱为中心成对称分布;检票厅开挖后,换乘通道洞壁中心最大水平位移为1.9mm,顶板中心最大竖向位移为0.74mm,底板中心最大竖向位移为3.3mm。位移值在施工控制中均满足位移控制标准。     

反激变换器中RCD箝位电路参数设计

针对反激变换器在实际应用中由于变压器漏感而引起的开关管电压应力过大问题,对反激变换器的工作原理进行分析,推导出箝位电容、箝位电阻和箝位二极管的计算公式,设计了RCD箝位电路。结合测试电路的实验波形,验证了理论分析的正确性,并探讨了开关管寄生电容大小对电路谐振过程的影响。     

机载光电设备隔振装置设计开发与性能分析

飞机在飞行的过程中所产生的激励会对机载光电设备产生振动影响,为了保证设备的正常工作,需要安装隔振装置对设备进行隔振．运用有限元软件ABAQUS,建立橡胶隔振支座有限元模型,在外加激励的作用下,对隔振支座进行分析,得到相应的振动响应;同时在满足设计要求的情况下,建立多种型号的隔振支座,设定橡胶材料的阻尼系数并进行模拟,得到的振动响应与外加激励进行对比,在较保守的阻尼比为0．08的情况下,其减振效果能够超过80％,在阻尼比为0．10的情况下起隔振效果能够近似90％．     

挤压铸造计算机模拟软件前处理技术网格剖分的研究

对数值分析对象的(几何)模型进行网格剖分是前处理技术研究的核心内容,它直接关系到后续计算模块以及后处理模块功能的实现.文中以导入的STL文件为输入数据,通过有限差分的方法,将原有的线框模型划分为网格模型.针对网格剖分过程以及显示过程出现的问题,开发了用于自动处理STL文件孔洞以及奇异点问题的错误诊断与容错系统,提出了用于网格显示的表面网格和网格偏移算法.     

基于统计分析的城际铁路建设条件研究

采用基于描述统计学的社会经济统计学方法对我国建成及在建26条城际铁路沿线地区的多项社会经济指标进行归纳统计,进而采用聚类分析的方法对其综合分析,探索能够反映城际铁路建设条件的参考指标,为我国城际铁路的建设规划提供决策参考。     

Effect of oxygen content on structural and optical properties of single Cu2O film by reactive magnetron sputtering method

Cuprous oxide (Cu₂O) thin films have been deposited on glass substrate by reactive magnetron sputtering method using Cu target and argon oxygen gas atmosphere. Effect of oxygen flow rate on structural and optical properties of thin films has been discussed. The results of X-ray diffraction, ultraviolet-visible spectrophotometry and atomic force micrograph indicated that the condition window for single Cu₂O phase was about 3.8 to 4.4 cm³/min, and the optimum oxygen flow rate was 4.2 cm³/min. The optical band gap E _g of Cu₂O film was determined by using the data of transmittance versus wavelength, and slightly decreased from 2.46 to 2.40 eV with the increase of oxygen flow rate from 3.8 to 4.4 cm³/min. The Cu₂O film formed at the oxygen flow rate of 4.2 cm³/min had an optical band gap of 2.43 eV.     

Degradation of selected indoor air pollutants: Comparison study of photocatalytic,ozone-assisted photocatalytic and amine adsorption processes

Indoor air pollutants impact human health, comfort and productivity. The method of photocatalysis has been applied mainly in flow reactors and little information is available on indoor air pollutant removal in airtight reactors. In the paper, experiments were carried out to remove formaldehyde (HCHO), ammonia (NH₃) and volatile organic compounds (VOCs) in the airtight and ventilated chambers. Results demonstrated that 90.4% of HCHO, 92.3% of NH₃ and 57.9% of VOCs were removed in the amine adsorption process, while 67.5% (hereinbefore, these are the mass fraction) of HCHO, 60.0% of NH₃, and 61.2% of VOCs were removed in the photocatalytic process. However, ozone-assisted photocatalytic process showed great potential to degrade indoor air pollutants in the ventilated chamber. Factors and mechanisms of the photocatalytic degradation of HCHO, NH₃ and VOCs were also discussed.