变轴交角渐开线齿轮啮合理论和设计

为了提供合理的变轴交角渐开线齿轮传动设计方法,基于双自由度齿轮啮合理论,对这种传动进行了研究。在轴交角变动范围内,由相配齿轮2齿面无根切导出两轮支座摆动轴线位置和相配齿轮2工作齿宽的计算公式,得到支座摆动轴线与渐开线齿轮1轴线间距l1的许用最小值l1min和最大值l1max;得到不同轴交角 时的重合度计算公式;推导出啮合点瞬时接触椭圆参数的计算公式。研究表明：取l1接近l1max时,相配齿轮2工作齿宽最大;轴交角| |为最大时重合度ε最大,=0时ε最小;相配齿轮2中断面分度圆啮合点处的瞬时接触椭圆参数接近其余各点的平均值,可由该点来评价接触质量,使计算大为简化。为这种传动的几何设计,提供一套详尽的计算方法。     

Sensing Magnetic Field and Intermolecular Interactions in Diamagnetic Solution Using Residual Dipolar Couplings of Zephycandidine

An unusual residual dipolar coupling of methylene protons was recorded in NMR spectra because aromatic zephycandidine has preferential orientation at the external magnetic field. The observed splitting contains contribution from the dipole–dipole D-coupling and the anisotropic component of J-coupling. Absolute values of the anisotropy of magnetic susceptibility |Δχ_ax| are larger for protic solvents because of the hydrogen-bonding compared to aprotic solvents for which polar and dispersion forces are more important. The energy barrier for the reorientation due to hydrogen-bonding is 1.22 kJ/mol in methanol-d_4, 0.85 kJ/mol in ethanol-d₆ and 0.87 kJ/mol in acetic acid-d₆. In dimethyl sulfoxide-d₆, 1.08 kJ/mol corresponds to the interaction of solvent lone pair electrons with π-electrons of zephycandidine. This energy barrier decreases for acetone-d₆ which has smaller electric dipole moment. In acetonitrile-d₃, there is no energy barrier which suggests solvent ordering around the solute due to the solvent-solvent interactions. The largest absolute values of the magnetic anisotropy are observed for aromatic benezene-d₆ and tolune-d₈ which have their own preferential orientation and enhance the order in the solution. The magnetic anisotropy of “isolated” zephycandidine, not hindered by intermolecular interaction could be estimated from the correlation between Δχ_ax and cohesion energy density.     

Cu元素对AMS6308钢抗回火性能的影响

为研究Cu元素对AMS6308钢耐温性的影响,采用SEM、TEM、EBSD、相分析和力学性能测试等手段,研究了不同回火温度下,AMS6308钢(含2％Cu)与不含Cu对比试验钢的组织与力学性能,探讨AMS6308钢中Cu元素对提高抗回火性能的作用.结果 表明,随着回火温度提高,AMS6308钢强度先升后降,450℃出现...     

Synthesis of Lightweight Renewable Microwave-Absorbing Bio-Polyurethane/Fe3O4 Composite Foam: Structure Analysis and Absorption Mechanism

Sustainable renewable polymer foam used as a lightweight porous skeleton for microwave absorption is a novel strategy that can effectively solve the problems of the large surface density, high additive amount, and narrow absorbing band of absorbing materials. In this article, novel renewable microwave-absorbing foams were prepared using Sapiumse biferum kernel oil-based polyurethane foam (BPUF) as porous matrix and Fe₃O₄-nanoparticles as magnetic absorbents. The microstructure and the microwave absorption performance, the structural effects on the properties, and electromagnetic mechanism of the magnetic BPUF (mBPUF) were systematically characterized and analyzed. The results show that the mBPUF displayed a porous hierarchical structure and was multi-interfacial, which provided a skeleton and matching layer for the Fe₃O₄ nanoparticles. The effective reflection loss (RL ≤ −10 dB) frequency of the mBPUF was from 4.16 GHz to 18 GHz with only 9 wt% content of Fe₃O₄ nanoparticles at a thickness of 1.5~5 mm. The surface density of the mBPUF coatings was less than 0.5 kg/cm² at a thickness of 1.8 mm. The lightweight characteristics and broadband absorption were attributed to the porous hierarchical structures and the dielectric combined with the magnetic loss effect. It indicates that the mBPUF is a prospective broadband-absorbing material in the field of lightweight stealth materials.     

Oxidative Precipitation Synthesis of Calcium-Doped Manganese Ferrite Nanoparticles for Magnetic Hyperthermia

Superparamagnetic nanoparticles are of high interest for therapeutic applications. In this work, nanoparticles of calcium-doped manganese ferrites (Ca_xMn_1−xFe₂O₄) functionalized with citrate were synthesized through thermally assisted oxidative precipitation in aqueous media. The method provided well dispersed aqueous suspensions of nanoparticles through a one-pot synthesis, in which the temperature and Ca/Mn ratio were found to influence the particles microstructure and morphology. Consequently, changes were obtained in the optical and magnetic properties that were studied through UV-Vis absorption and SQUID, respectively. XRD and Raman spectroscopy studies were carried out to assess the microstructural changes associated with stoichiometry of the particles, and the stability in physiological pH was studied through DLS. The nanoparticles displayed high values of magnetization and heating efficiency for several alternating magnetic field conditions, compatible with biological applications. Hereby, the employed method provides a promising strategy for the development of particles with adequate properties for magnetic hyperthermia applications, such as drug delivery and cancer therapy.     

高 Q 值超低功耗谐振式磁传感器的设计与实现

针对现有谐振式磁传感器原理不能同时实现高品质因数(Q)和低功耗的缺点,利用双端固定石英音叉谐振器与铁镓磁致伸缩合金片复合,设计了一种隔离磁机阻尼的高Q值、数字频率输出的超低功耗谐振式磁传感器。利用音叉谐振器结构的解耦特性,设计应力耦合传递结构,隔离了磁致伸缩材料磁机阻尼,从而保证复合传感器Q值与音叉谐振器Q值相当。在磁场作用下,磁致伸缩力传递到音叉谐振器,由于音叉力敏感特性,实现磁-力-频率转换。制备了铁镓合金/石英音叉谐振器复合敏感结构,测试表明,在低气压封装条件下的品质因数约为16 764,门振荡电路功耗约为124.8μW,在线性区灵敏度为3.05 Hz/Oe,分辨率为6 mOe。     

建筑钢板件三点弯曲试验及磁记忆信号研究

为研究适用于钢结构建筑中以受弯为主的试件的损伤评价,通过对Q235钢板试件进行三点受弯试验,采集了试件加载阶段的磁记忆信号值Hp(y),引入多个磁记忆信号特征量,进行对钢结构损伤的表征研究.试验结果表明,通过磁记忆曲线的"波峰"和"波谷"现象以及磁记忆梯度曲线的"峰-峰值"现象,可以判断试件的应力集中区域.通过其余相关...     

管道漏磁内检测的管壁缺陷漏磁场解析模型

漏磁内检测技术是长输油气管道缺陷检测的主要手段,缺陷几何特征识别对管道安全运行评价具有重要意义。基于二维磁偶极子模型,建立管道内壁缺陷漏磁场空间分布的三维解析模型,对磁化方向垂直缺陷时磁荷产生漏磁场的变化规律进行研究;基于内壁解析模型,引入管壁退磁影响因子,对模型进行补偿,建立管道外壁缺陷漏磁场三维解析模型,得到了管道外壁不同缺陷漏磁场的分布特征。搭建漏磁检测实验平台,对所建模型有效性进行实验验证。结果表明,管壁对外壁缺陷漏磁场具有一定屏蔽作用,实验结果和理论分析具有很好的一致性,所建模型可有效描述管道内外壁缺陷漏磁场空间分布特性,对缺陷识别和定量评估具有一定工程指导意义。     

基于复合磁性槽楔的 PMLSM 推力波动抑制

永磁直线同步电机(permanent magnet linear synchronous motor,PMLSM)存在齿槽力,影响电机的控制性能。 本文提出一 种基于软磁、硬磁材料混搭的新型复合磁性槽楔结构(composite magnetic slot wedge,CMSW),能有效抑制 PMLSM 推力波动。 首 先,分析了单一磁性槽楔的材料、尺寸和空间位置分布对 PMLSM 输出推力和推力波动的变化规律。 然后,研究新型复合磁性 槽楔的软磁、硬磁材料配比和位置分布,对电机输出推力、推力波动和齿槽力等电磁性能的影响。 以最大推力和推力波动最小 为优化目标,利用正交优化法对复合磁性槽楔的尺寸进行优化。 研究表明,采用新型复合磁性槽楔可有效降低推力波动和损 耗,推力波动降低 79. 4%,而平均推力基本不变,为 PMLSM 推力波动抑制提供新的技术途径。     

基于 IAS 精确估计的太阳轮齿面剥落检测方法研究

瞬时角速度(instantaneous angular speed, IAS)信号的估计精度易受编码器自身误差影响,影响其故障检测结果。针对上述问题提出了一种局部多项式微分估计方法对IAS信号进行估计。首先通过局部多项式微分抑制编码器细分误差产生的锯齿状噪声和估计误差导致的信号不连续问题,实现了IAS信号的高精度获取,然后使用精确估计的IAS信号通过局部同步拟合技术提取太阳轮故障特征。通过实验和仿真说明,本文提出的局部多项式微分估计能较好地抑制编码器误差导致的IAS信号噪声,提高IAS信号的信号比,结合局部同步拟合能够有效地提取太阳轮齿面剥落故障特征。