直锥圆截面结构的展开方法

介绍了直锥圆截面结构的三种展开方法,并指出各种方法的优缺点。

大型圆弧齿螺旋锥齿轮螺旋角近似测量方法

针对大型圆弧齿螺旋锥齿轮的螺旋角难以精确测量的问题,根据该类齿轮加工原理图,推导了节锥圆与齿面交线的弦长与螺旋角的关系,寻找到一种较便捷且相对准确的螺旋角测量方法,实例计算表明角度误差小于0.25°。该方法便于实现加工过程中对螺旋角在线测量,且较滚印法准确性有较大提高。

线源圆轨道锥束扫描三维CT重建算法

基于点X射线源圆轨道锥束扫描的FDK近似3D-CT重建算法重建速度快,在10°锥角内重建精度高,因此在工程上得到广泛应用。但是,这种算法不能满足线X射线源圆轨道锥束扫描的情况。为此,将上述点源FDK近似原理拓展到线源情况,推导了线源圆轨道锥束扫描3D-CT重建算法。计算机仿真结果证明了该算法的正确性。利用这种算法,对圆轨道锥束大视场扫描3D-CT实验数据进行重建,获得了正确的图像。

关于带有倒锥凸起圆盖注射模的设计与改进

带有倒锥凸起圆盖注塑件的模具设计在现实生产中存在着很多问题,尤其是在脱模取件方面。为此,以化妆品盒配件注射模具的设计为例,在控制成本、提高生产效率、实现安全操作的前提下,对原有模具进行了脱模取件困难缺陷的改进。该改进设计主要是在定模部分增加型芯,并将一次分型改成二次分型,再使倒锥部分实现强制脱模。通过试模,验证了该改进方案的合理、可行性。

浅圆仓锥斗“危大”模板支撑工程方案设计及施工工艺介绍

超过一定规模的危险性较大的分部分项工程具有施工规模大、作业危险性高的特点,为贯彻安全第一、预防为主的生产方针,针对此类工程需制定针对性强、有效性高的专项施工方案。本文介绍了济宁江北现代粮食物流园项目浅圆仓锥斗模板支撑工程专项施工方案和施工工艺。

晶体电光调制实验中常见“故障”诊断

为了加深操作者对实验的理解,并通过实验学会对偏振光和非线性光学等知识的应用,从实验的原理入手,揭示了晶体电光调制实验中经常出现的“故障”原因,并提出解决方案。第一,实验中输出信号出现的绝大部分问题,都可以归结为光路没有达到最佳状态。此时可以通过观察干涉圆环图样进行初步判断,再用“两平行一正交”的法则对光路进行调节。第二,输出电压增量ΔV与入射光强I_(0)成正比例变化,和调制信号幅度成反比例变化。据此可以有效地将输出电压的增量控制在合理范围内,保证实验的成效。第三,当起偏器和检偏器平行时,增加偏压后输出电压不增反降。

锥束准三代三维工业CT成像方法研究

基于FDK(Feldkamp,Davis and Kress)重建算法的圆轨道锥束扫描方式,因为算法的简洁性和工程实现的可行性,成为目前主要的三维工业计算机X射线断层摄影术(3D-ICT)成像技术。但受探测器长度的限制,该种技术的扫描视场小,可检构件尺寸受到限制。为解决较大尺寸构件3D-ICT检测问题,讨论了一种扫描锥束偏转的准三代3D-ICT成像方法,推导了它基于FDK原理的滤波反投影(FBP)重建算法。计算机仿真验证了该方法的正确性。分析表明,在扫描锥束偏转两次情况下,其有效扫描视野比圆轨道扫描方式提高1.4倍以上。

模锻弧齿锥齿圈工艺

在空气锤上采用镦粗、冲孔、扩孔、整形的自由锻工艺锻造弧齿锥齿圈,存在劳动强度大、火次多、生产效率低(班产量仅达100件左右)、质量难以保证、安全性差等问题。在中、大批量生产中,这种工艺已被淘汰了。由于没有扩孔机,经过一段时间的摸索试验,我们开发了在6300kN摩擦压力机上模锻弧齿锥齿圈的工艺,供大家参考。 1.工艺分析 弧齿锥齿圈零件图如图1所示。

Cone-shaped source characteristics and inductance effect of transient electromagnetic method

Small multi-turn coil devices are used with the transient electromagnetic method （TEM） in areas with limited space, particularly in underground environments such as coal mines roadways and engineering tunnels, and for detecting shallow geological targets in environmental and engineering fields. However, the equipment involved has strong mutual inductance coupling, which causes a lengthy turn-off time and a deep “blind zone”. This study proposes a new transmitter device with a conical-shape source and derives the radius formula of each coil and the mutual inductance coefficient of the cone. According to primary field characteristics, results of the two fields created, calculation of the conical-shaped source in a uniform medium using theoretical analysis, and a comparison of the inductance of the new device with that of the multi-turn coil, show that inductance of the multi-turn coil is nine times greater than that of the conical source with the same equivalent magnetic moment of 926.1 A·m2. This indicates that the new source leads to a much shallower “blind zone.” Furthermore, increasing the bottom radius and turn of the cone creates a larger mutual inductance but increasing the cone height results in a lower mutual inductance. Using the superposition principle, the primary and secondary magnetic fields for a conical source in a homogeneous medium are calculated; results indicate that the magnetic behavior of the cone is the same as that of the multi-turn coils, but the transient responses of the secondary field and the total field are more stronger than those of the multi-turn coils. To study the transient response characteristics using a cone-shaped source in a layered earth, a numerical filtering algorithm is then developed using the fast Hankel transform and the improved cosine transform, again using the superposition principle. During development, an average apparent resistivity inverted from the induced electromotive force using each coil is defined to represent the comprehensive resistivity of the conical source. To verify the forward calculation method, the transient responses of H type models and KH type models are calculated, and data are inverted using a “smoke ring” inversion. The results of inversion have good agreement with original models and show that the forward calculation method is effective. The results of this study provide an option for solving the problem of a deep “blind zone” and also provide a theoretical indicator for further research.

Determination of undrained shear strength using piezocone penetration test in clayey soil for bridge foundation

In order to obtain the reasonable undrained shear strength Su for geotechnical analyses of bridge foundations in Yangtze River floodplain clayey soils, a site-specific study is conducted using the imported piezocone penetration test （CPTu） with dissipation phases at the Fourth Nanjing Yangtze River Bridge construction sites. Taking the values of Su from laboratory tests as references, several existing Su-predicted methods based on CPTu are compared and evaluated. To verify the presented cone factor Nk, additional test sites are selected and examined. The results show that the values of cone factors such as Nkt, Nke, and Nau, depend on the shear test mode and disturbance. Generally, the values of Nke show more scattering than those of Nkt and N△u. For the stratified and layered sediments of the Yangtze River floodplain, it is recommended using the net cone resistance qT to estimate Su and the preliminary cone factor values Nkt are from 7 to 16, with an average of 11. It is also confirmed that the CPTu test, as a new technique in site characterization, can present reasonable parameters for bridge foundations.

COUPLED DYNAMIC CHARACTERISTICS AND CONTROL OF ROTOR-CONICAL MAGNETIC BEARING SYSTEM

The coupled dynamic characteristics of the conical electromagnetic bearing are presented and their definitions are given. On the basis of the analyses of the characteristics, the dynamic model of five degrees of freedom (five-DOF) rotor-conical electromagnetic bearing system is made, and the influence of the coupled characteristics on the system optimal controller is analyzed.

An approach to improving maneuver performance of coning algorithm

Aiming to improve the maneuver performance of the strapdown inertial navigation attitude coning algorithm a new coning correction structure is constructed by adding a sample to the traditional compressed coning correction structure. According to the given definition of classical coning motion the residual coning correction error based on the new coning correction structure is derived. On the basis of the new structure the frequency Taylor series method is used for designing a coning correction structure coefficient and then a new coning algorithm is obtained.Two types of error models are defined for the coning algorithm performance evaluation under coning environments and maneuver environments respectively.Simulation results indicate that the maneuver accuracy of the new 4-sample coning algorithm is almost double that of the traditional compressed 4-sample coning algorithm. The new coning algorithm has an improved maneuver performance while maintaining coning performance compared to the traditional compressed coning algorithm.

大型斗轮取料机斗轮体制作方法

大型斗轮取料机斗轮体外形尺寸大、焊接要求高、装配关系复杂,为解决斗轮结构在机加工和安装过程中存在的问题,需要采取措施有效控制斗轮体制作质量。文中介绍的斗轮体制作方法,实践证明效果明显,具有很好的指导作用和可操作性。

火力发电厂主厂房油箱水喷雾灭火系统的优化

通过对水喷雾灭火系统设计要素分析,合理选择相关参数,选择的喷头在水雾喷头有效射程内实现喷头曲线全覆盖被保护对象表面,并达到规范所要求的喷雾强度。提出水喷雾灭火系统的优化原则,实现对主厂房油箱水喷雾灭火系统的优化,做到水量节约、经济安全。

Excited-State Proton Transfer and Decay in Hydrogen-Bonded Oxazole System： MS-CASPT2//CASSCF Study

Herein we have employed high-level multi-reference CASSCF and MS-CASPT2 electronic structure methods to systematically study the photochemical mechanism of intramolecularly hydrogen-bonded 2-（2＇-hydroxyphenyl）-4-methyloxazole. At the CASSCF level, we have optimized minima, conical intersections, minimum-energy reaction paths relevant to the excited-state intramolecular proton transfer （ESIPT）, rotation, photoisomerization, and the excited-state deactivation pathways. The energies of all structures and paths are refined by the MS-CASPT2 method. On the basis of the present results, we found that the ESIPT process in a conformer with the OH... N hydrogen bond is essentially barrierless process; whereas, the ESIPT process is inhibited in the other conformer with the OH... O hydrogen bond. The central single-bond rotation of the S1 enol species is energetically unfavorable due to a large barrier. In addition, the excited-state deactivation of the S1 keto species, as a result of the ultrafast ESIPT, is very efficient because of the existence of two easily-approached keto S1/S0 conical intersections. In stark contrast to the S1 keto species, the decay of the S1 enol species is almostly blocked. The present theoretical study contributes valuable knowledge to the understanding of photochemistry of similar intramolecularly hydrogen-bonded molecular and biological systems.

Design of a Tapered Lens for Semiconductor Laser to Single-Mode Fiber Coupling

The theoretical investigation of the coupling efficiency of a laser diode to a single mode fiber via a hemispherical lens on the tip of the tapered fiber in the presence of possible transverse offset and angular mismatch is reported.Without the misalignment,coupling efficiency increases with the decreasing of taper length.With the misalignment,this relation is that the coupling efficiency decreases with each kind of offset.

Simulation of Variable Viscosity and Jeffrey Fluid Model for Blood Flow Through a Tapered Artery with a Stenosis

Non-Newtonian fluid model for blood flow through a tapered artery with a stenosis and variable viscosity by modeling blood as Jeffrey fluid has been studied in this paper. The Jeffrey fluid has two parameters, the relaxation time A1 and retardation time A2. The governing equations are simplified using the case of mild stenosis. Perturbation method is used to solve the resulting equations. The effects of non-Newtonian nature of blood on velocity profile, temperature profile, wall shear stress, shearing stress at the stenotsis throat and impedance of the artery are discussed. The results for Newtonian fluid are obtained as special case from this model.

Effect of Cultural Measures on Nutrient Contellts in Rice Plants with Erect Panicles

Field experiments were carried out with rice variety of Shennong 91 of short culms and erect panicles to study nutrient contents in high-yielding rice plants and to increase rice yield by appropriate fertilization.Nitrogen, phosphorus, potassium, magnesium, zinc, manganese, iron and copper contents in rice plants varied with different treatment factors. The relationship between the nutrient contents and treatment factors could be simulated using a multiple quadratic equation. The nutrient contents in plants should be appropriate for high-yielding rice. If the mean nutrient content in rice plants producing 11 t ha-1 or more of grain (μj) was set as the standard value and the standard deviation (σj) was set as the range of variation, the nutrient content in high-yielding rice plants should be μj±1.99σj. Rice leaves were sensitive to the nutrient elements. Heavy nitrogen dressing increased the content of nitrogen in rice plants. Sparse transplanting also increased nitrogen content. Improper application of nitrogen, phosphorus and potassium could affect the nutrient contents and decrease the grain yield.