主应力轴旋转对软土塑性变形影响分析

在姜洪伟所提出的软土各向异性弹塑性本构关系基础上，考虑类似于砂土的Ｒ－旋转试验条件，计算了软土由于主应力轴旋转所产生的塑性变形，对不同中主应力比情况下的变形规律进行分析，解释忽略主应力轴旋转影响将使设计偏于不安全的原因。     

基于近红外频域自适应分析法的电煤发热量模型研究（英文）

目前由于部分电站锅炉所用到的燃煤大多为配煤,在有些情况下,其复杂的物理化学特性导致难以获得高精确度的常规近红外定量分析模型,这给电煤发热量的在线检测带来了一定困难。针对该问题,深入研究了电煤近红外光谱时域和频域特征,提出一种能够通过全局优化策略自动在频域内建立最优近红外定量分析模型的新方法—频域自适应分析法。该方法首先将时域近红外光谱通过快速傅里叶变换转换为频域近红外信号;然后采用有效光谱能量率得到合适的频域信息范围;接着根据近红外光谱频域下的相关系数谱图、方差谱图以及谐波在频域中的坐标合理构建了频域信息量评价参数,利用该参数对模型输入变量的种群位置进行初始化;最后采用频域分区搜索和综合性能评价函数得到最佳建模方案。与此同时,结合电煤煤粉近红外图谱的特性,并以其发热量为待测目标对该方法进行了验证,取得相对较好实验效果,与传统方法主成分回归、偏最小二乘回归、反向传播神经网络以及基于遗传算法的偏最小二乘回归和支持向量机回归相比,该方法预测精度更高,并且有效避免了频域随机搜索潜在的过拟合和虚假有效模型的弊端,具有良好的应用前景。此外,该方法也可推广用于其他类型的光谱定量分析。     

超光谱成像技术应用于神经分类的研究

在外科神经修复手术中, 断端神经束性质的识别成为良好修复的关键。现有的一些神经束识别的方法不太理想。分子超光谱成像技术同时提供生物组织图像和光谱两方面的信息, 对检测目标可进行定性、定量和定位的描述, 可对不同的生物组织从光谱特性的角度识别、分类并在图像上定位;相比较于其他医学成像技术, 具有独特的优势。本研究把超光谱成像技术应用于神经束的识别和分类研究中, 以期通过不同神经束的特征光谱来识别并分类神经束, 并借助图像光谱信息确定神经束在图像中的定位, 以便更好的辅助外科手术人员开展神经修复手术。研究意义在于: 提出一种全新的神经束识别和定位的方法, 辅助外科人员提高神经修复的疗效;储备超光谱成像技术应用于生物组织的定性定量定位分析和研究的技术, 加快超光谱成像技术向实用阶段进展的步伐。     

On ultrasound waves guided by bones with coupled soft tissues: A mechanism study and in vitro calibration

The influence of soft tissues coupled with cortical bones on precision of quantitative ultrasound (QUS) has been an issue in the clinical bone assessment in conjunction with the use of ultrasound. In this study, the effect arising from soft tissues on propagation characteristics of guided ultrasound waves in bones was investigated using tubular Sawbones phantoms covered with a layer of mimicked soft tissue of different thicknesses and elastic moduli, and an in vitro porcine femur in terms of the axial transmission measurement. Results revealed that presence of soft tissues can exert significant influence on the propagation of ultrasound waves in bones, leading to reduced propagation velocities and attenuated wave magnitudes compared with the counterparts in a free bone in the absence of soft tissues. However such an effect is not phenomenally dependent on the variations in thickness and elastic modulus of the coupled soft tissues, making it possible to compensate for the coupling effect regardless of the difference in properties of the soft tissues. Based on an in vitro calibration, this study proposed quantitative compensation for the effect of soft tissues on ultrasound waves in bones, facilitating development of high-precision QUS.     

The preliminary evaluation of a 1 MHz ultrasound probe for measuring the elastic anisotropy of human cortical bone

Our objective is to evaluate an ultrasound probe for measurements of velocity and anisotropy in human cortical bone (tibia). The anisotropy of cortical bone is a known and mechanically relevant property in the context of osteoporotic fracture risk. Current in vivo quantitative ultrasound devices measuring the velocity of ultrasound in long bones can only be applied in the axial direction. For anisotropy measurements a second direction for velocity measurements preferably perpendicular to the axial direction is necessary. We developed a new ultrasound probe which permits axial transmission measurements with a simultaneous second perpendicular direction (tangential). Anisotropy measurements were performed on isotropic and anisotropic phantoms and two excised human female tibiae (age 63 and 82). Anisotropy ratios (AI; ratio of squared ultrasound velocities in the two directions) were for the isotropic phantom 1.06 ± 0.01 and for the anisotropic phantom 1.14 ± 0.03 (mean ± standard deviation). AI was 1.83 ± 0.29 in the tibia from the older donor and 1.37 ± 0.18 in the tibia from the younger donor. The AIs were in the expected range and differed significantly (p < 0.05, t-test) between the tibiae. Measured sound velocities were reproducible (mean standard deviation of short time precision of both channels for phantom measurements 31 m/s) and in agreement with reported velocities of the phantom material. Our results document the feasibility of anisotropy measurements at long bones using a single probe. Further improvements in the design of the probe and tests in vivo are warranted. If this approach can be evaluated in vivo an additional tool for assessing the bone status is available for clinical use.     

Orientation relationship between α-Fe precipitate and α-Al2O3 matrix in iron-implanted sapphire

Fe ions were implanted into α-Al₂O₃ single crystals (sapphire) at room temperature and annealed in a reducing atmosphere. The orientation relationships (ORs) between α-Fe particles and sapphire matrix were investigated using transmission electron microscopy (TEM). All the α-Fe particles have the orientation relationship (OR) of (1 1 1)_α-Fe || (0 0 0 1)_sapphire and ${[1\overline{1}0]}_{\alpha \text{-Fe}}\left|\right|{[11\overline{2}0]}_{\text{sapphire}}$ with sapphire. This OR is predicted precisely by the coincidence of reciprocal lattice points (CRLP) method. The other OR of (1 1 0)_α-Fe || (0 0 0 1)_sapphire and ${[111]}_{\alpha \text{-Fe}}\left|\right|{[5\overline{1}\overline{4}0]}_{\text{sapphire}}$ reported before is confirmed by the same method to be one of the secondary preferred orientation relationships in the α-Fe/sapphire system.     

Kinetics of alkaline hydrolysis of p‐substituted benzylidenemalononitriles in 50% aqueous acetonitrile: substituent effects and quantification of the electrophilic reactivity

The rate constants of the reaction of p‐X‐substituted benzylidenemalononitriles 1a , 1b , 1c , 1d , 1e , 1f , 1g , 1h with hydroxide ion were measured in 50% water–50% acetonitrile at 20 °C. The experimental kinetic data reveal that the points pertaining to electron donating substituted compounds (X = Me, OMe and NMe₂) exhibit negative deviations from the Hammett plot. However, the Yukawa–Tsuno plot for the same rate constants resulted in a good straight line with an excellent correlation coefficient (r² = 0.9916) and an r value of 1.15. Possible ground‐state stabilization through resonance interactions has been suggested to explain the origin of the nonlinear Hammett plot. On the basis of the relationship between E and σ_p⁺, the electrophilicity parameter E of some benzylidenemalononitriles 1c and 1e , 1f , 1g , 1h has been evaluated. More importantly, the three compounds 1f (E = ?7.90), 1g (E = ?7.80) and 1h (E = ?7.55) exhibit high electrophilicities that compare well with that of 4,6‐dinitrobenzoselenadiazole (E = ?7.40), a compound which has a general behaviour representative for the superelectrophilic dimension. We have shown that the second‐order rate constants calculated from Mayr's approach for the reaction of 1a , 1b , 1c , 1d , 1e , 1f , 1g , 1h with hydroxide ion do not agree with the available experimental data. On the other hand, a good linear correlation between log k_exp and log k_calc has been observed and discussed. Copyright © 2014 John Wiley & Sons, Ltd.     

A self-method for resolving the problem of apparent LWIR emissivity for quantitative thermography up to 130 °C

In a previous work, we succeeded in connecting normal LWIR apparent emissivity to the spectral one of an aluminum nitride ceramic plate. The key problem was the knowledge of the effective spectral bandwidth in use in the system. Hence we have developed an analyzer which permits to identify the spectral bandwidth of IR system using only its raw data. It proceeds by minimizing the dispersion from linearity of the characteristic thermosignals/integrated radiance over a temperature range of the IR system. The capacities of the analyzer are tested for five commercial cameras. Each of these systems exhibits a similar formatting process implemented during the thermogram recording. The effective spectral bandwidth shows plausible values. It varies significantly from one model to the other and the residual non-linearity is connected to the NETD of the IR system. The robustness of the apparent emissivity measurements is also tested with the aid of emissivity reference of 0.5. The overall accuracy of the method is less than 1%, depending on the specular or diffuse part of the reflected irradiation. Applied in field situation, the method is suitable to detect absolute variation of emissivity of less than 6 ⋅ 10⁻³. We use the analyzer to determine the spectral bandwidth of a commercial 320 × 240 microbolometer uncooled IRFPA camera which had already served to characterize the normal LWIR apparent emissivity of the aluminum nitride ceramic plate. By using the spectral response of the two major microbolometer sensor technologies, the general formulation of apparent emissivity matches our apparent emissivity measurements. An agreement better than 0.6% in absolute value and a less than 6 ⋅ 10⁻³%/°C dispersion are found over the entire temperature range [40–130 °C].     

基于LabVIEW的机械密封模糊控制系统软件设计

机械密封的泄漏特性和摩擦特性相悖,为了提高机械密封的可靠性、延长使用寿命,必须对机械密封进行可控性研究,使机械密封工作在最佳工况。机械密封的泄漏率和端面摩擦扭矩之间无法建立精确的数学模型,因此在研制测控装置时使用基于模糊集合理论的模糊控制方式。目前大部分模糊控制类论文仅仅停留在论述模糊控制器的设计原理及流程上,本文结合实际应用完整的阐述了基于LabVIEW设计模糊控制软件的过程。     

基于迟滞应力应变关系的非线性声学检测理论与方法研究

本文将传统PM(Preisach-Mayergoyz)模型由一维介质拓展到二维介质,引入迟滞细观弹性单元概念,得到迟滞变化的应力应变关系.并采用一阶有限差分方程进行了声场计算和分析,发现空间声场中含有明显的高阶奇次谐波成分.对接收到的全波信号进行滤波、放大、时间反转后加载到接收换能器对应阵元上再进行发射,观察到高次谐波在微损伤区域实现聚焦.这为利用非线性高次谐波检测微损伤提供了可能的途径,也为疲劳损伤等缺陷的早期检测提供了理论和方法依据.