Chamfer Matching在CT和MRI图像匹配融合中的应用

医学影像中的CT和MRI图像的精确匹配融合能为临床提供全面、丰富的诊断信息。文中首先对CT图像正常脑组织边缘做距离变换 ,形成距离图像 ,然后利用MRI图像正常脑组织边缘作为模板 ,实现了CT和MRI图像的精确匹配。在此基础上完成了CT和MRI的信息融合。文中算法适用于CT和MRI的匹配 ,并对SPECT ,PET 。

Experimental Study on Wear Characteristics of PCBN Tool with Variable Chamfered Edge

Owing to heavy dynamic and thermal loads, PCBN tools are seriously worn during hard cutting, which largely constrains the improvement of their machining performance. Therein, the chamfered structure of a cutting edge has a notable influence on the tool wear. Thus, a comparative study was carried out on the wear morphology and wear mechanism of PCBN tools with either a variable chamfered edge or an invariable chamfered edge. The results indicate that, for a PCBN tool with a variable chamfered edge, the rake wear area is far from the cutting edge and slowly extends toward it. A shallow large-area crater wear occurs on the rake face, and the flank wear area has a long triangular shape with a smaller wear area and width, and the cutting edge remains in a good state during the cutting process. In contrast, for a PCBN tool with an invariable chamfered edge, a deep small-area crater appears on the rake face, and the wear area is close to the cutting edge and quickly extends toward it. Thus, it is easy for chips to accumulate in the crater, resulting in large-area and high-speed wear on the flank face. In addition, the tool shows a weak wear resistance. In the initial wear stage, the rake wear mechanism of the two cutting tools is a mixture of abrasive, oxidation, and other types of wear, whereas their flank wear mechanism is dominated by abrasive wear. With an aggravation of the tool wear, the oxidation and diffusion wear mechanism are both increasingly strengthened. The rake wear of the cutter with a variable chamfered edge showed an obvious increase in the oxidation and diffusion wear, as did the flank wear of the cutter with an invariable chamfered edge. This study revealed the wear mechanism of the PCBN tool with a variable chamfered edge and provided theoretical and technological support for its popularization and application in the machining of high-hardness materials.

Slenderness Ratio Effect on the Eccentric Compression Performance of Chamfered Laminated Bamboo Lumber Columns

Eccentric compression tests on 15 chamfered laminated bamboo lumber(LBL)columns with a height ranging from 600 to 3000 mm were conducted in order to study the eccentric mechanical performance.The failure of all specimens was caused by the crack of bamboo fiber in the tensile region.When the ultimate strength was reached,except specimens with a height of 600 mm,all other specimens could bear large deformation,showing good ductility.The lateral displacements of the specimens under eccentric compression were approximately para-bolic in the direction of column height.The ultimate bending moment of LBL columns with different slenderness ratios under compression with the same initial eccentricity was a fixed value.The relationship between ultimate capacity,axial displacement,lateral displacement,and slenderness ratio was analyzed based on test results.It was found that the plane section assumption could be used to express the stress and strain distribution of chamfered LBL columns under eccentric compression.A method for calculating the ultimate bearing capacity was proposed using a constitutive model based on the Ramberg-Osgood relation and the empirical formula for calculating the ultimate capacity was given on the basis of the former research as well as the test results in this paper.

Influence of the Hole Chamfer on the Characteristics of a Multi-hole Orifice Flowmeter

In order to analyze the influence of the hole chamfer on the metering performances of a Multi-hole Orifice Flowmeter and optimize the related orifice structure,a multi-hole orifice flowmeter with DN80 and throttle ratio of 0.45 was considered in the present study.The flow field characteristics were determined in the framework of a CFD technique.The results show that the multi-hole orifice flowmeter with filleting transition around the throttle orifice has higher accuracy in a wide range of the space of parameters,and is more suitable for accurate measurement of fluid in process control.

Matching characteristics of magnetic field configuration and chamfered channel wall in a magnetically shielded Hall thruster

To date, the selection of the magnetic field line used to match the chamfered inner and outer channel walls in a magnetically shielded Hall thruster has not been quantitatively studied. Hence, an experimental study was conducted on a 1.35 k W magnetically shielded Hall thruster with a xenon propellant. Different magnetic field lines were chosen, and corresponding tangentially matched channel walls were manufactured and utilized. The results demonstrate that high performance and a qualified anti-sputtering effect cannot be achieved simultaneously. When the magnetic field lines that match the chamfered wall have a strength at the channel centerline of less than 12% of the maximum field strength, the channel wall can be adequately protected from ion sputtering. When the magnetic field lines have a strength ratio of 12%–20%, the thruster performance is high. These findings provide the first significant quantitative design reference for the match between the magnetic field line and chamfered channel wall in magnetically shielded Hall thrusters.

Experimental Evaluation on Grinding Texture on Flank Face in Chamfer Milling of Stainless Steel

The surface quality of chamfer milling of stainless steel is closed related to the products of 3 C(Computer, Communication and Consumer electronics), where a cutter is a major part to achieve that. Targeting a high-quality cutter,an experimental evaluation is carried out on the influence of grinding texture of cutter flank face on surface quality.The mathematic models of chamfer cutter are established, and they are validated by a numerical simulation. Also the grinding data are generated by the models and tested by a grinding simulation for safety reasons. Then, a set of chamfer cutting tools are machined in a five-axis CNC grinding machine, and consist of five angles between the cutting edge and the grinding texture on the 1 st flank faces, i.e., 0°, 15°, 30°, 45° and 60°. Furthermore, the machined cutting tools are tested in a series of milling experiments of chamfer hole of stainless steel, where cutting forces and surface morphologies are measured and observed. The results show that the best state of both surface quality and cutting force is archived by the tool with 45° grinding texture, which can provide a support for manufacturing of cutting tool used in chamfer milling.

基于改进Chamfer匹配的台标识别

已有电视台台标的识别技术多基于视频流处理,实时性较差,且对半透明台标识别效果不佳。为此,提出一种基于改进Chamfer匹配的台标识别方法。利用Canny算子提取台标边缘颜色及梯度方向,采用RANSAC算法对台标边缘进行优化,通过距离变换计算边缘梯度方向的距离图,并基于距离最短准则对其识别。实验结果表明,该方法能实现台标的单帧识别,克服半透明台标的识别难题,平均识别率达97.7%,平均识别时间为801 ms。

Y9420 Gear Chamfering Machine

Y9420 Gear Chamfering Machine is ahigh efficiency machine tool designedby the Chongqing Machine ToolsWorks to meet market demand. The machineemploys the principle of cool extrusion anduses a special chamfering tool which drivesthe work piece to rotate and achievechamfering. It features no tool tracks and noburr on the ends. Multiple cutters can beused to process cluster gears, and thechamfering can be realized on either oneside of the tooth or on both. It is an idealpiece of equipment for automobiles, machinetools and gears manufacture to chamfer anddeburr disk type gears, spur and helical shaftgears and cluster gears.

Experimental and numerical investigation of a Hall thruster with a chamfered channel wall

A discharge channel with a chamfered wall not only has application in the design of modern Hall thrusters, but also exists where the channel wall is eroded, and so is a common status for these units. In this paper, the laws and mechanisms that govern the effect of the chamfered wall on the performance of a Hall thruster are investigated. By applying both experimental measurement and particle-in-cell simulation, it is determined that there is a moderate chamfer angle that can further improve the optimal performance obtained with a straight channel. This is because the chamfering of the wall near the channel exit can enhance ion acceleration and effectively reduce ion recombination on the wall, which is favorable to the promotion of the thrust and efficiency. However, the chamfer angle should not be too large; otherwise, both the density of the propellant gas and the distribution of the plasma potential in the channel are influenced, which is undesirable for efficient propellant utilization and beam concentration. Therefore, it is suggested that the chamfer shape of the channel wall is an important factor that must be carefully considered in the design of Hall thrusters.

Longitudinal corner crack of chamfered slab and optimization of mould

Chamfered mould has gradually become a new technology equipment to eliminate transverse corner crack.However,longitudinal corner crack ratio of chamfered slab was very high.Solidification microstructure was detected in the area where the longitudinal corner crack occurred.Effect of narrow face shape and taper distribution of mould copper plate on longitudinal corner crack was studied by industrial tests.Water velocity distribution in the narrow copper plate was studied by numerical simulation.On the premise of preventing cooling water from nuclear boiling,improvement measures of mould cooling process and water seam structure were put forward through heat transfer calculation.The results showed that local taper of the meniscus region of mould should be increased to prevent generation of longitudinal corner crack.Chamfering slope length of narrow copper plate should be controlled within 55 mm,and chamfering angle should be controlled at about 30°.Average water velocity should be more than 7.0 m/s.The flat and chamfering regions of narrow copper plate working face should be designed as double taper and funnel structure,respectively.The water seam in the chamfering region should preferentially choose the combined cooling structure with two holes and one slot.In order to prevent the extension of longitudinal corner crack,chamfered narrow face foot roller should be used.

并列切角方柱风致干扰效应的大涡模拟研究

针对并列切角高层建筑间的干扰影响问题,本文采用大涡模拟方法研究雷诺数22 000的均匀流场下并列切角(切角率10%)方柱的干扰效应。基于模型的网格收敛性分析及模型准确性验证,对比分析不同间距比下并列切角方柱的气动干扰效应和流场分布,并探寻风压干扰效应的影响规律和形成机理。结果表明:对于并列切角方柱,平均阻力系数主要呈放大效应,脉动升力系数主要呈减小效应。在并列切角方柱处于小间距(B/L=1.2)时,由于风与壁面的相互作用,产生风压力,风压力与方柱表面力叠加,对正压区域产生加强效果,表现为放大效应,对负压区域进行削弱,出现减小效应;当B/L=1.5时,结构干扰最剧烈,其中相邻立面后流场的切角处放大效明显,干扰因子最大值为2.58;当B/L≥4.0时,除相邻立面外的其他立面与切角干扰效应趋于消失;当B/L=8.0时,相邻立面仍然存在28%的放大效应。

小倒角结晶器窄面铜板角部冷却结构优化

为解决某钢厂板坯小倒角结晶器高拉速生产时铸坯角部纵裂纹比例增大问题,在原型倒角分叉槽冷却结构基础上,提出不同圆孔直径和圆孔位置的1孔1槽方案。建立窄面铜板和冷却水三维传热耦合模型,并通过工业实测热电偶温度和冷却水进出口水温差进行验证,计算了优化前后不同方案的窄面铜板和冷却水温度和速度场。对比分析不同方案的铜板热面温度值大小和均匀性后发现,相比于分叉槽结构,圆孔直径D=8 mm和圆孔位置H=26 mm的1孔1槽冷却结构:弯月面铜板倒角热面温度降低幅度最大为14.4~17.6 K;螺栓截面铜板倒角热面温度降低幅度最大为10.9~12.3 K;圆孔内冷却水流速达到8.4 m/s,保证了对倒角面和倒角顶点铜板的冷却;螺栓两侧水槽冷却水流速达10.0 m/s,增强了螺栓周围铜板冷却均匀性。

基于COMSOL的电化学去除微小孔毛刺研究

微细钻削加工微小孔时产生的孔口毛刺,影响工件表面质量。并且微小孔毛刺难以去除,为此建立了电化学去毛刺仿真模型,分析了毛刺去除过程中的电流密度变化规律及其与材料去除速率间的对应关系,探究了孔口倒角的产生机理。结果表明:毛刺表面电流密度大小表征了电化学对材料去除能力的强弱,毛刺尖端部位电流密度大加工速度快,随着加工进行毛刺逐步变得更平滑电流密度开始分散毛刺尖端部位加工速度逐渐变慢。此外,增加阴极直径会提高加工速度,但也会导致倒角增大;而增高电极高度,有助于降低倒角,但加工时间也变得更久。在U=4V,C=12%,d=400μm,Z=150μm时加工效果较好,毛刺去除后得到的孔口倒角深度为21μm。

Three-dimensional temperature prediction in cylindrical turning with large-chamfer insert based on a modified slip-line field approach

Chamfered inserts have found broader applications in metal cutting process especially in high-performance machining of hard-to-cut materials for their excellent edge resistance and cutting toughness.However,excessive heat generation and resulting high cutting temperature eventually cause severe tool wear and poor surface integrity,which simultaneously limits the optimal selection of machining parameters.In the present study,an analytical thermal–mechanical model is proposed for the prediction of the three-dimensional(3-D)temperature field in cylindrical turning with chamfered round insert based on a modified slip-line field approach.First,an innovative discretization method is introduced in a general 3-D coordinate system to provide a comprehensive demonstration of the irregular cutting geometry and heat generation zones.Then,a plasticity-theory-based slip-line field model is developed and employed to determine the intensities and geometries of every elementary heat sources in Primary Deformation Zones(PDZ),Secondary Deformation Zones(SDZ)and Dead Metal Zones(DMZ).At last,a 3-D analytical model is suggested to calculate the temperature increases caused by the entire heat sources and associated images.The maximum cutting temperature region predicted is found existing upon the chip-tool contact area rather than the tool edge.Moreover,the rationalities of cutting parameters employed are analyzed along with theoretical material removal rates and ensuing maximum cutting temperatures.The results indicate that the cutting conditions with large depth of cut and high cutting speed are more desirable than those with high feed rates.The proposed models are respectively verified through a series of 3-D Finite Element(FE)simulations and dry cutting experiments of Inconel 718 with chamfered round insert.Satisfactory agreement has been reached between the predictions and simulations as well as the measurements,which confirms the correctness and effectiveness of the presented analytical model.

制造工艺对飞机铝锂合金结构细节疲劳性能影响研究

研究制造工艺(铣圆转速、孔边倒角、干涉量等)对飞机铝锂合金结构细节疲劳性能DFR的影响。结果表明:在一定铣圆转速范围内,存在最优铣圆转速;孔边倒角可以有效减轻应力集中现象,提高疲劳性能;干涉配合铆接在孔壁引入残余压应力,对孔连接具有一定强化作用,通过增加干涉量可使连接达到与整体材料相当的疲劳寿命,不再是铆接件中最薄弱“环节”。

碳环密封泄漏超标的探讨及安装优化

介绍碳环密封装置在二氧化碳压缩机的应用及出现的泄漏超标异常现象,经研究其结构特点及对现场检修安装过程的观察分析,找到了碳环密封泄漏超标的原因。通过重新设计安装专用工具及优化安装方案,解决了泄漏超标故障,保障了设备安全运行。

Influence of the Chamfer on the Flexural Properties of Beetle Elytron Plates

To improve the flexural properties of Beetle Elytron Plates(BEPs)and clarify the effect of the transition arcs(chamfers)between the skins and the trabeculae,the chamfers were set in BEPs,and then the influence of the chamfer on BEPs'mechanical properties was investigated via experimentation and the Finite Elemnent Method simulation(FEM).The results indicate that the influence of the chamfer on the flexural properties and ductility was most obvious in the Trabecular Beetle Elytron Plates(TBEPs),less obvious in the Honeycomb Plates(HPs)and basically no efiect was observed on End-trabecular Beetle Elytron Plates(EBEPs).The chamfer can improve the mechanical stability of EBEPSs.As the chamfer diameter increased in the BEPs,the length of the residual trabecular root on the skin increased when failure occurred in the TBEPs.The crack position in the honeycomb wallsof the HPs gradually shifted from the skin to the center.The EBEPs continued to exhibit oblique cracks.From the perspective of the force characteristics of these BEPs.combined with numerical simulation,the influence mechanism of the chamfer on their flcxural propertics was investigated.

不完整螺纹形成机理分析及应用

以普通螺纹为例,分析典型工况下不完整螺纹产生的原因,提出应用场景解决方案。

新型电缆外半导电层切割倒角器的研制

配网电缆附件制作施工中剥离外半导电屏蔽层、外半导电屏蔽层断口和绝缘层断口倒角时,施工人员一般依靠感觉和经验,难以控制切割的深浅度和平稳度,无法保证电缆的断口和倒角光滑平整,不能与冷缩主体(应力锥)紧密搭接,易造成尖端放电效应,留下严重安全隐患。文章旨在开发一种用于配网电缆切割外半导电屏蔽层环切和纵切、外半导电屏蔽层断口和绝缘层断口倒角的三合一专用刀具。该研究能够显著提高电缆的断口和倒角的光滑度和平整度,提升工作效率,降低电缆头绝缘损坏的隐患风险。